Applied Sciences

Published by MDPI

Online ISSN: 2076-3417

Articles


Figure 1. 
Table 1
Figure 2. 
Figure 3. 
Radiosynthesis and in Vivo Evaluation of Two PET Radioligands for Imaging α-Synuclein
  • Article
  • Full-text available

March 2014

·

382 Reads

·

·

·

[...]

·

Two α-synuclein ligands, 3-methoxy-7-nitro-10H-phenothiazine (2a, Ki = 32.1 ± 1.3 nM) and 3-(2-fluoroethoxy)-7-nitro-10H-phenothiazine (2b, Ki = 49.0 ± 4.9 nM), were radiolabeled as potential PET imaging agents by respectively introducing (11)C and (18)F. The syntheses of [(11)C]2a and [(18)F]2b were accomplished in a good yield with high specific activity. Ex vivo biodistribution studies in rats revealed that both [(11)C]2a and [(18)F]2b crossed the blood-brain barrier (BBB) and demonstrated good brain uptake 5 min post-injection. MicroPET imaging of [(11)C]2a in a non-human primate (NHP) confirmed that the tracer was able to cross the BBB with rapid washout kinetics from brain regions of a healthy macaque. The initial studies suggested that further structural optimization of [(11)C]2a and [(18)F]2b is necessary in order to identify a highly specific positron emission tomography (PET) radioligand for in vivo imaging of α-synuclein aggregation in the central nervous system (CNS).
Download
Share

Ion Acceleration by Short Chirped Laser Pulses

February 2015

·

198 Reads

Direct laser acceleration of ions by short frequency-chirped laser pulses is investigated theoretically. We demonstrate that intense beams of ions with a kinetic energy broadening of about 1 % can be generated. The chirping of the laser pulse allows the particles to gain kinetic energies of hundreds of MeVs, which is required for hadron cancer therapy, from pulses of energies of the order of 100 J. It is shown that few-cycle chirped pulses can accelerate ions more efficiently than long ones, i.e. higher ion kinetic energies are reached with the same amount of total electromagnetic pulse energy.

Practical quantum oblivious transfer and bit commitment protocols

January 2015

·

115 Reads

Oblivious transfer (OT) and bit commitment (BC) are two-party cryptographic protocols which play crucial roles in the construction of various cryptographic protocols. We propose three practical quantum cryptographic protocols in this paper. We first construct a practical quantum random oblivious transfer (R-OT) protocol based on the fact that non-orthogonal states cannot be reliably distinguished. Then, we construct a fault-tolerant one-out-of-two oblivious transfer ( O T 1 2 ) protocol based on the quantum R-OT protocol. Afterwards, we propose a quantum bit commitment (QBC) protocol which executes the fault-tolerant O T 1 2 several times. Mayers, Lo and Chau (MLC) no-go theorem proves that QBC protocol cannot be unconditionally secure. However, we find that computing the unitary transformation of no-go theorem attack needs so many resources that it is not realistically implementable. We give a definition of physical security for QBC protocols and prove that the practical QBC we proposed is physically secure and can be implemented in the real world.

A Review of Cavity Design for Kerr Lens Mode-Locked Solid-State Lasers

January 2015

·

3,584 Reads

We provide a critical review of the fundamental concepts of Kerr lens mode-locking (KLM), along with a detailed description of the experimental considerations involved in the realization of a mode-locked oscillator. In addition, we review recent developments that overcome inherent limitations and disadvantages in standard KLM lasers. Our review is aimed mainly at readers who wish to realize/maintain such an oscillator or for those who wish to better understand this major experimental tool.

Attosecond Hard X-ray Free Electron Laser

March 2013

·

424 Reads

For a real, meaningful pump-probe experiment with attosecond temporal resolution, an isolated attosecond pulse is in demand. In this vein we report the generation of an isolated ~ 148 attosecond pulse duration radiation pulse at 0.1 angstrom wavelength using current enhanced self-amplified spontaneous emission free electron laser. We consider the 10-GeV PAL-XFEL e-beam for enhanced self-amplified spontaneous emission (ESASE) scheme. In ESASE, X-ray SASE FEL is combined with a femtosecond laser system. An 800 nm wavelength, 5 fs FWHM carrier envelope phase stabilized laser was employed in ESASE scheme.

Hybrid Coded Excitation of the Torsional Guided Wave Mode T(0,1) for Oil and Gas Pipeline Inspection

January 2022

·

91 Reads

Ultrasonic guided wave testing is an essential technique in non-destructive testing for structural integrity of oil and gas pipelines. This technique, based on the pulse-echo method, is often used for the long-range detection of pipelines at any location. However, guided waves suffer from high attenuation when they propagate in attenuative material structures and multiple wave modes due to the excitation, which reduces the power of echo signals and induces corruption caused by coherent noise. In this paper, a developed hybrid coded excitation method that uses the convolution of a Barker code and Golay code pair is proposed and applied for an ultrasonic guided wave testing system to excite the torsional guided wave mode T(0,1) in a steel pipe. The proposed method combines the advantages of these two coding methods and increases the flexibility of code lengths. The performance is evaluated by signal to noise ratio and peak sidelobe level of the processed signal. Both theoretical simulations and experiments have investigated using the proposed codes composed of Barker codes and Golay code pairs of different lengths and combinations. The experimental results show the significant improvement of the signal to noise ratio and the peak sidelobe level due to the proposed hybrid code usage for the excitation of guided waves. The values are further improved to around 32 dB and around −24 dB, respectively. Overall, the proposed hybrid coded method for improving the echo SNR can benefit from guided wave testing to reduce coherent and random noise levels and many other potential applications.

Figure 1. Dispersion curves of axisymmetric UGWs: (a) phase velocity, (b) group velocity and (c) normalized displacement distribution.
Figure 7. (a) Noisy UGW signals, sparse signals processed by (b) ISSP-PT and (c) ISSP-PTM.
Figure 13. Schematic diagram of magnetostrictive UGW testing.
SNRG, DNRG, and misjudgments of N/PUS signals processed by ISSP, EWISSP, and VWISSP.
Resolution Enhancement Method of L(0,2) Ultrasonic Guided Wave Signal Based on Variational Mode Decomposition, Wavelet Transform and Improved Split Spectrum Processing

January 2023

·

58 Reads

Pipeline systems are prone to defects due to the harsh service conditions, which may induce catastrophic failure if found not in time. Ultrasonic guided wave (UGW) testing provides a convenient option for pipeline detection, showing high-efficiency, non-contact, long-distance and large-scale capabilities. To address the problem that UGW signals suffer from poor signal resolution that is mainly related to the coherent noise caused by the dispersion, multi-mode and mode conversion, an advanced signal processing method called VWISSP, based on variational mode decomposition (VMD), wavelet transform (WT), and improved split spectrum processing (ISSP) was proposed, of which SSP was improved by replacing the Gaussian filter bank with cosine filters of constant frequency-to-bandwidth and frequency-to-filter spacing ratios. Compared with ISSP, VWISSP shows better higher accuracy and resolution processing effects to noisy multi-defect UGW signals, which is manifested through the improvement of both the signal-to-noise ratio gain and the defect-to-noise gain. Only feature signals (defects and pipe end) are retained, whereas noise signals are eliminated completely.

Figure 3. Dispersion curves of the zero-order axisymmetric UGWs: (a) phase velocity, (b) group velocity and dispersion curves of the asymmetric UGWs: (c) phase velocity, (d) group velocity.
Figure 4. Normalized (a) axial, (b) circumferential and (c) radial displacement distributions of the L(0,1), F(n,1), L(0,2) and F(n,3) UGWs (1 ≤ n ≤ 4) at 110 kHz.
Figure 9. Effects of filter parameters: (a) Bf, (b) Bt, (c) Δf and (d) Br on SNRG and DCRG of the s thesized UGW signals processed by FBR-RC-SSP.
Figure 17. Experimental UGW signals before and after applying GS-SSP and FBR-RC-SSP (1 ≤ defect number ≤ 3, 60° ≤ α ≤ 300°).
Split-Spectrum Processing with Raised Cosine Filters of Constant Frequency-to-Bandwidth Ratio for L(0,2) Ultrasonic Guided Wave Testing in a Pipeline

July 2022

·

99 Reads

Ultrasonic guided wave (UGW) nondestructive testing suffers from poor signal interpretation accuracy caused by the coherent noise that is related to dispersion, multi-mode and mode conversion. In order to split the L(0,2) UGW from the coherent noise, split-spectrum processing with raised cosine filters of constant frequency-to-bandwidth ratio (FBR-RC-SSP) is proposed. With the advantages of time domain resolution and frequency domain split, FBR-RC-SSP is studied based on time-frequency analysis using the chirplet transform, and the effects of filter parameters on signal-to-noise ratio gain (SNRG) and defect-to-coherent noise gain (DCRG) are explained. The excellent effects of eliminating the coherent noise and improving the signal resolution in FBR-RC-SSP are reported by the validation of synthesized, simulated and experimental UGW signals, of which the average SNRG and DCRG are 22.92% and 23.71% higher than those of traditional SSP using Gaussian filters, and it has the potential to locate and characterize defects in further UGW testing research.

Figure 3. SEM top view of the multicomponent ferroelectric hybrid films. (a,c,e,g,i) are the ferroelectric films formed by [C 6 N 2 H 18 ]BiI 5 and [C 6 N 2 H 18 ]SbI 5 mixing ratios of 0.8:0.2, 0.6:0.4, 0.5:0.5, 0.4:0.6 and 0.2:0.8, in that order. (b,d,f,h,j) are enlarged views of (a,c,e,g,i), respectively.
Figure 5. Plot of (ahV) 1/2 ~hV for a multicomponent ferroelectric film.
Figure 6. Theoretical calculated bandgap diagram of multicomponent ferroelectric films.
Effect of Doping on the Bandgap of the Organic–Inorganic Hybrid Ferroelectric Material [C6N2H18]Bi1−xSbxI5 (0.0 < x < 1.0)

October 2022

·

35 Reads

The rapidly developing organic–inorganic hybrid chalcogenide solar cells have now become a hot topic of interest. However, the bandgap of inorganic ferroelectric materials with a typical chalcogenide structure is too wide to match the solar spectrum, while the ferroelectricity of organic-inorganic hybrid chalcogenide materials with a narrow bandgap, meth amide–lead–iodine, is not obvious, and the lead element causes environmental pollution. The recently discovered organic–inorganic hybrid material [C6N2H18]BiI5 with good ferroelectricity and the narrowest bandgap of molecular ferroelectrics can absorb visible light in the range of 380 nm to 660 nm, and compound [C6N2H18]SbI5 with the Bi cognate element Sb was also synthesized. In this paper, we designed the first experiment to prepare thin films by mixing and doping the above two materials in five different molar ratios, and we comparatively studied the changes in crystal structure, surface morphology, and photophysical properties of the prepared multicomponent hybrid films according to the mixing ratio. A theoretical model was developed to calculate and analyze the bandgap of the hybrid doped compounds and compare it with the experimental values. It was found that the absorption spectra of the multicomponent hybrid films were red-shifted relative to the original material, indicating that the forbidden bandwidth was reduced to absorb a wider range of visible light, and the reason for this was thought to be the narrowing of the bandgap due to doping. When the mixing ratio was 0.4:0.6, the bandgap was the narrowest and the light absorption was the best; the highest quality of the film was obtained when the mixing ratio was 0.5:0.5.

Figure 4. Cylindrical pipe tests (constant heat flux). Nusselt numbers from different experimental data in Equations (40)-(45) as a function of the Peclet number.
Figure 5. Cylindrical pipe tests. Nusselt number values for the simulations performed for fluids with Pr = 0.025 and Pr = 0.01 with the KLW and Kays [13] models. The values are compared with the Kirillov [33] and Cheng [4] correlations.
Physical properties used in the simulation for Pr = 0.025 and 0.01.
Cylindrical pipe tests. Numerical comparison of the KLW and Kays [13] models with Kirillov [33] and Cheng [4] correlations for Pr = 0.025 and 0.01.
A Logarithmic Turbulent Heat Transfer Model in Applications with Liquid Metals for Pr = 0.01–0.025

June 2020

·

263 Reads

The study of turbulent heat transfer in liquid metal flows has gained interest because of applications in several industrial fields. The common assumption of similarity between the dynamical and thermal turbulence, namely, the Reynolds analogy, has been proven to be invalid for these fluids. Many methods have been proposed in order to overcome the difficulties encountered in a proper definition of the turbulent heat flux, such as global or local correlations for the turbulent Prandtl number and four parameter turbulence models. In this work we assess a four parameter logarithmic turbulence model for liquid metals based on the Reynolds Averaged Navier-Stokes (RAN) approach. Several simulation results considering fluids with P r = 0 . 01 and P r = 0 . 025 are reported in order to show the validity of this approach. The Kays turbulence model is also assessed and compared with integral heat transfer correlations for a wide range of Peclet numbers.

Figure 1. Flow diagram of the exclusion and research steps.
Figure 2. The relative periodontitis and caries risk scores after 4 weeks of dexamethasone treatment. (**: Wilcoxon signed-rank test significance level at 0.01; CR-score, relative caries risk score; PR-score, relative periodontitis risk score).
Demographic information and qualitative changes in the oral bacterial species of the oral lichen planus patients before and after the treatment with dexamethasone gargle.
Absolute quantitative changes in the oral microbial species of oral lichen planus patients before and after treatment with dexamethasone gargle.
The Effect of Mouthrinse with 0.05% Dexamethasone Solution on the Oral Bacterial Community of Oral Lichen Planus Patients: Prospective Pilot Study

July 2021

·

418 Reads

Few studies have already been performed to assess oral bacteria during steroid therapy for oral lichen planus (OLP). Thus, the aim of our study was to analyze the effect of dexamethasone mouthrinse treatment on the oral bacteria of OLP patients. This prospective study was conducted on patients who were diagnosed with OLP and treated with 0.05% dexamethasone mouthrinse twice per day for 4 weeks. Using unstimulated saliva of the patients before and after treatment, the qualitative and quantitative changes in oral bacteria were analyzed using quantitative real-time polymerase chain reaction (qPCR). The qPCR results were analyzed using Wilcoxon signed-rank test to the quantitative changes with dexamethasone mouthrinse. The statistical significance was considered at a level of 0.05. In total, 20 patients were enrolled in this study, wherein all were noted to show improved symptoms of OLP. Fifteen patients (75%) had a qualitative change in the oral microbial species and an improved relative periodontitis risk score (from 26.1 ± 10.7 to 20.9 ± 9.2; p = 0.008). However, quantitative changes in all species were determined to be not statistically different before and after the treatment. Most OLP patients had a changed microbial community composition after 0.05% dexamethasone mouthrinse for 4 weeks. In particular, the composition of the periodontopathic bacteria was improved after the treatment.

Figure 7. Thickness of the interfacial IMC layers (IMLs) aged at 150 °C. (a): Thickness of Cu6Sn5 + Cu3Sn layer; (b): Thickness of Cu3Sn layer; (c): The computing process of IMC layer's thickness.
Thickness of IMC layers in the interface of solder/Cu during the aging process.
EDS results of spot A and spot B.
The Enhanced Mechanism of 0.05 wt. % Nd Addition on High Temperature Reliability of Sn-3.8Ag-0.7Cu/Cu Solder Joint

December 2020

·

82 Reads

In this study, the effect of appropriate Nd addition on improving the high-temperature reliability of Sn-3.8Ag-0.7Cu (SAC387)/Cu solder joint after aging treatment was investigated. The interfacial microstructure of solder joint was refined with proper addition of Nd. This phenomenon could be explained as the adsorbing-hindering effect of surface-active Nd atoms which blocked the growth of brittle intermetallic compounds (IMCs) in the solder joint. Theoretical analysis indicated that 0.05 wt. % addition of Nd could distinctly decrease the growth constant of Cu6Sn5 IMCs and slightly decrease the growth constant of Cu3Sn IMCs respectively. The shear force of SAC387-0.05Nd/Cu solder joint was evidently improved compared with the origin solder joint. In addition, SAC387-0.05Nd/Cu solder joint maintained excellent mechanical property compared with SAC387/Cu solder joint even after 1440 h aging treatment.

Figure 2. Cont.
Figure 3. Schematic diagram of the experimental setup.
Figure 4. Instruments used: (a) AM-THz source with Gunn diode and attached horn antenna, (b) AM-THz source and lens holder, (c) Sensor PCB, and (d) Sensor PCB holder with linear motor.
Position Sensing with a Compact 0.1 THz Amplitude Modulated Source

January 2022

·

75 Reads

Position determination is an important manufacturing process in many modern industries. The objective of this paper is to present an affordable measurement system that can replace optical position measurement with a laser beam in an opaque environment that prevents the laser beam from penetrating through the fog of gases or other materials that are opaque to optical light. THz waves are a good example of replacing a laser beam, as shown in this article. It is known that THz rays can penetrate fabrics, wood, Styrofoam, etc. The triangulation method using an amplitude modulated THz source proved to be a cost-effective solution for position determination in opaque environments.

Figure 5. Cell viability (%) of extracts of calcium alginate (at 100% v/v) and calcium alginate/CNFs films (at 100% and 10% v/v), culture medium (negative control), and 1000 µM zinc chloride cytotoxic solution (positive control) in human keratinocyte HaCaT cells. Only significant statistical differences were found with the negative control. *** p > 0.001; ns: not significant.
Enhancement of Antimicrobial Activity of Alginate Films with a Low Amount of Carbon Nanofibers (0.1% w/w)

March 2021

·

95 Reads

The World Health Organization has called for new effective and affordable alternative antimicrobial materials for the prevention and treatment of microbial infections. In this regard, calcium alginate has previously been shown to possess antiviral activity against the enveloped double-stranded DNA herpes simplex virus type 1. However, non-enveloped viruses are more resistant to inactivation than enveloped ones. Thus, the viral inhibition capacity of calcium alginate and the effect of adding a low amount of carbon nanofibers (0.1% w/w) were explored here against a non-enveloped double-stranded DNA virus model for the first time. The results of this study showed that neat calcium alginate films partly inactivated this type of non-enveloped virus and that including that extremely low percentage of carbon nanofibers (CNFs) significantly enhanced its antiviral activity. These calcium alginate/CNFs composite materials also showed antibacterial properties against the Gram-positive Staphylococcus aureus bacterial model and no cytotoxic effects in human keratinocyte HaCaT cells. Since alginate-based materials have also shown antiviral activity against four types of enveloped positive-sense single-stranded RNA viruses similar to SARS-CoV-2 in previous studies, these novel calcium alginate/carbon nanofibers composites are promising as broad-spectrum antimicrobial biomaterials for the current COVID-19 pandemic.

Figure 4. Temporal dependence of the photoinduced OD change (∆OD) at 70 K (closed black circles). The excitation conditions are 1.56 eV, E || stack polarization, and 7.00 × 10 15 photons/cm 2. The probe photon energy is 0.27 eV with the E ⊥ stack polarization direction. The thin red line indicates the results of the fitting analysis using function (1). The pink, blue, and green dashed lines represent the temporal dependences of each component of fitting function (1).
Optical Study of Electronic Structure and Photoinduced Dynamics in the Organic Alloy System [(EDO-TTF)0.89(MeEDO-TTF)0.11]2PF6

March 2019

·

240 Reads

Over the past two decades (EDO-TTF)2PF6 (EDO-TTF = 4,5-ethylenedioxytetrathiafulvalene), which exhibits a metal–insulator (M–I) phase transition with charge–ordering (CO), has been investigated energetically because of attractive characteristics that include ultrafast and massive photoinduced spectral and structural changes. In contrast, while its crystal structure has much in common with the (EDO-TTF)2PF6 crystal, the organic alloy system of [(EDO-TTF)0.89(MeEDO-TTF)0.11]2PF6 (MeEDO-TTF = 4,5-ethylenedioxy-4′-methyltetrathiafulvalene) exhibits a quite different type of M–I phase transition that is attributed to Peierls instability. Here, an optical study of the static absorption spectra and the time-resolved changes in the absorption spectra of [(EDO-TTF)0.89(MeEDO-TTF)0.11]2PF6 are reported. The observed absorption spectra related to the electronic structure are highly anisotropic. With a reduction in temperature (T), the opening of a small optical gap and a small shift in the center frequency of the C=C stretching mode are observed along with the M–I phase transition. Additionally, photoinduced transient states have been assigned based on their relaxation processes and transient intramolecular vibrational spectra. Reflecting small valence and structural changes and weak donor–anion interactions, a photoinduced transient state that is similar to the thermal-equilibrium high-T metallic phase appears more rapidly in the alloy system than that in (EDO-TTF)2PF6.

Figure 1. Typical schematic view of PDD calculation for a linear accelerator photon beam in a water phantom. The different parts of the head Linac and the voxels used to score the dose within the box are shown.
Figure 2. Comparison of Geant4-simulated (based on IAEA phase space file) and experimental PDD data for a 6 MV photon beam (field size of 3 × 3 cm 2 ) within water.
Figure 3. Geant4-simulated PDD of adipose, cortical bone, fat, lung and muscle tissues for a 10 × 10 cm 2 field size of a 6 MV photon beam.
Figure 4. Buildup factor for adipose tissue as a function of: (left side) photon energy for fixed depths between 0.5 and 40 mfp and (right side) depth for a fixed photon energy between 0.15 and 15 MeV.
Buildup Factor Computation and Percentage Depth Dose Simulation of Tissue Mimicking Materials for an External Photon Beam (0.15–15 MeV)

April 2022

·

178 Reads

Nowadays, the use of tissue mimicking material (TMM) is widespread in both diagnostic and therapeutic medicine, as well as for quality assurance and control. For example, patient exposure evaluation during therapeutic tests has been commonly measured using TMMs. However, only a few materials have been developed for research use at the megavoltage photon energy encountered in medical radiology. In this paper, we extended our previous work to cover the photon energy range of 0.15–15 MeV for five human tissues (adipose, cortical bone, fat, lung and muscle). As a selection criterion for TMM, other than the attenuation coefficient, we introduced the computation of the buildup factor (BUF) for a given couple of energy and depth based on the geometric progression fitting method. Hence, we developed a C++ program able to compute BUF for depths up to 40 mean free path. Moreover, we simulated the percentage depth dose (PDD) of a 6 MV photon beam through each tissue and their equivalent materials using the Geant4 Monte Carlo toolkit (version 10.5). After the comparison of a set of parameters (mass attenuation and mass energy absorption coefficients, BUF, equivalent and effective atomic numbers, electron density, superficial and maximal dose and dose at 10 and 20 cm depths), we found that SB3 (a mixture of epoxy and calcium carbonate) and MS15 (a mixture of epoxy, phenol, polyethylene and aluminum oxide) accurately imitate cortical bone and muscle tissues, respectively. AP6 (a mixture of epoxy, phenol, polyethylene and teflon), glycerol trioleate and LN1 (a mixture of polyurethane and aluminum oxide) are also suitable TMMs for adipose, fat and lung tissues, respectively. Therefore, this work can be useful to physician researchers in dosimetry and radiological diagnosis.

Figure 7. Interstage matching: (a) AC equivalent circuit of the amplifier; (b) first interstage matching at 42 GHz; (c) second interstage matching at 26 GHz.
Figure 8. Chip micrograph of the full Ka-band amplifier.
Design parameter values of the full Ka-band amplifier.
Performance comparison with previous CMOS-based Ka-band amplifiers.
A Full Ka-Band CMOS Amplifier Using Inductive Neutralization with a Flat Gain of 13 ± 0.2 dB

May 2022

·

86 Reads

This paper presents a CMOS wideband amplifier operating in the full Ka-band, with a low gain variation. An inductive neutralization is applied to the amplifier to compensate for the gain roll-off in the high-frequency region. Neutralization inductance is carefully determined considering the tradeoff between stability and gain. To achieve a low gain variation over the full Ka-band, the amplifier employs the frequency staggering technique in which impedance matching for three gain stages is performed at different frequencies of 26, 34, and 42 GHz. The experimental results show that a peak gain of 13.2 dB is achieved at 39.2 GHz. The 3 dB bandwidth is from 23.5 to 41.7 GHz, which fully covers the Ka-band. Especially, the gain ripple of the amplifier is only 13 ± 0.2 dB over a wide bandwidth from 26.2 to 40.2 GHz. The input and output return loss values are better than −10 dB from 26.3 to 40.1 GHz and from 25.3 to 50 GHz, respectively. The DC power consumption is 18.6 mW.

Evaluation of new Seawater-based Mouth Rinse Versus Chlorhexidine 0.2% Reducing Plaque and Gingivitis Indexes. A Randomized Controlled Pilot Study

February 2020

·

370 Reads

For a long time, Chlorhexidine digluconate (CHX) has been considered the most used mouth-rinse for reducing plaque and gingivitis. Sea4® Encias is a new seawater-based mouth rinse with a similar action to CHX. Its prolonged use produces fewer side effects. This study compared the effects of two oral rinses: Chlorhexidine 0.20% and Sea 4® Encias (seawater) for reducing plaque and gingivitis indices. This double-blind crossover study recruited and monitored 93 volunteer dental students, hygienists and doctors from the Universidad Católica de Murcia (UCAM), for 1 month, and compared the efficacy of Chlorhexidine 0.20% (Group A); Sea4® Encías (Group B); and a placebo saline solution (Group C) mouth-rinses for reducing plaque and gingivitis indices. Plaque and gingival inflammation (Löe and Silness test) were evaluated at baseline and after each study stage. Group A reduced plaque growth and gingivitis significantly compared with Groups B and C; Group B was more effective than Group C. The mean P.I. decreased similarly in groups A and B. However, Group A showed the statistically significant value compared with other groups. Group A and group B, showed greater reduction in Gingival Indexes compared with group C. The Sea4 mouthwash showed better inhibitory activity on plaque (1.32 ± 0.22) compared with CHX (1.97 ± 0.34) and saline (2.78 ± 0.11). Sea4 Encias and Chlorhexidine 0.20% mouth-rinses significantly reduce plaque growth and G.I. compared with saline mouth-rinse; Sea4 Encías mouth-rinse is more effective against plaque regrowth than Chlorhexidine in this pilot study.

Theoretical Study of a 0.22 THz Backward Wave Oscillator Based on a Dual-Gridded, Carbon-Nanotube Cold Cathode

December 2018

·

138 Reads

The carbon nanotube (CNT) cold cathode is an attractive choice for millimeter and terahertz vacuum electronic devices owning to its unique instant switch-on and high emission current density. A novel, dual-gridded, field emission architecture based on a CNT cold cathode is proposed here. CNTs are synthesized directly on the cathode surface. The first separating grid is attached to the CNT cathode surface to shape the CNT cathode array. The second separating grid is responsible for controlled extraction of electrons from the CNT emitters. The cathode surface electric field distribution has been improved drastically compared to conventional planar devices. Furthermore, a high-compression-ratio, dual-gridded, CNT-based electron gun has been designed to further increase the current density, and a 21 kV/50 mA electron beam has been obtained with beam transparency of nearly 100%, along with a compression ratio of 39. A 0.22 THz disk-loaded waveguide backward wave oscillator (BWO) based on this electron gun architecture has been realized theoretically with output power of 32 W. The results indicate that higher output power and higher frequency terahertz BWOs can be made using advanced, nanomaterial-based cold cathodes.

Figure 5. Microphotograph of the S/C/X-band 4-bit GaN digital step attenuator MMIC and test module.
Figure 6. Measured (a) S21, and (b) normalized attenuation of the GaN digital step attenuator MMIC.
Component values of T-type resistive attenuators.
Performance comparison of the relevant digital control step attenuators.
An S/C/X-Band 4-Bit Digital Step Attenuator MMIC with 0.25 μm GaN HEMT Technology

May 2022

·

99 Reads

In this paper, a 4-bit digital step attenuator using 0.25 μm GaN HEMT technology for wideband radar systems is presented. A switched-path attenuator topology with resistive T-type attenuators and double-pole double-throw (DPDT) switches was used to achieve both low insertion loss and phase/amplitude error. The measured insertion loss of the reference state is 2.8–8.3 dB at DC-12 GHz. The input and output return loss are less than 12 dB at DC-12 GHz. An attenuation coverage of 30 dB with a least significant bit of 2 dB was achieved at DC-12 GHz. A root mean square (RMS) amplitude error of 1dB and a phase error of 8.5° were achieved, respectively. The attenuator chip size is 2.45 mm × 1.75 mm including pads. To the best of the authors’ knowledge, this is the first demonstration of a GaN-based digital step attenuator.

A 0.3 V, Rail-to-Rail, Ultralow-Power, Non-Tailed, Body-Driven, Sub-Threshold Amplifier

March 2021

·

430 Reads

A novel, inverter-based, fully differential, body-driven, rail-to-rail, input stage topology is proposed in this paper. The input stage exploits a replica bias control loop to set the common mode current and a common mode feed-forward strategy to set its output common mode voltage. This novel cell is used to build an ultralow voltage (ULV), ultralow-power (ULP), two-stage, unbuffered operational amplifier. A dual path compensation strategy is exploited to improve the frequency response of the circuit. The amplifier has been designed in a commercial 130 nm CMOS technology from STMicroelectronics and is able to operate with a nominal supply voltage of 0.3 V and a power consumption as low as 11.4 nW, while showing about 65 dB gain, a gain bandwidth product around 3.6 kHz with a 50 pF load capacitance and a common mode rejection ratio (CMRR) in excess of 60 dB. Transistor-level simulations show that the proposed circuit outperforms most of the state of the art amplifiers in terms of the main figures of merit. The results of extensive parametric and Monte Carlo simulations have demonstrated the robustness of the proposed circuit to PVT and mismatch variations.

Development of 0.34 THz Sub-Harmonic Mixer Combining Two-Stage Reduced Matching Technology with an Improved Active Circuit Model

December 2022

·

90 Reads

In this paper, a high-performance 0.34 THz sub-harmonic mixer combining two-stage reduced matching technology with an improved active circuit model is established and analyzed. The mixer’s improved active circuit model is realized by decomposing passive functional models into basic transmission line units and their impedance matching and filtering are realized through automatic optimization. The improved active circuit model takes out the RF (radio frequency) transition model separately to set an optimization goal instead of operating directly in the mixing circuit. Compared with traditional active circuit models in the SDM (subdivision design method) and GDM (global design method), it provides a massive optimization space, larger working bandwidth, and better results. In the RF frequency range of 320–360 GHz, the SSB (single sideband) conversion loss of the 0.34 THz sub-harmonic mixer is below 9.5 dB and the RF return loss is less than 12 dB.

A 0.38 V Fully Differential K-Band LNA with Transformer-Based Matching Networks
  • New
  • Article
  • Full-text available

April 2023

·

33 Reads

The implementation of a 0.38 V K-band low-power fully differential low-noise amplifier (LNA) in a 45 nm silicon-on-insulator (SOI) process is presented. The proposed architecture employs a two-stage approach with transformer-based interstage matching networks to minimize circuit area. The proposed LNA covers the frequency range from 20.3 to 24.1 GHz, it achieves a noise figure (NF) as low as 2.2 dB, and a gain of 12.9 dB, with a power consumption of 11.7 mW from a 0.38 V DC supply in a very compact area (0.15 mm2) excluding pads. Non-linearity simulations show the proposed circuit achieves a Po1dB of −7.3 dBm, and an OIP3 (Output Third Order Intercept) of 7 dBm. The transformers allow improved area use since they are simultaneously used as matching networks, RF chokes to bias the active devices, baluns at the input and output terminals to convert the single-ended signal into differential mode, and vice versa, and facilitates the interconnection with the upcoming stages. We used a state-of-the-art tool that generates the desired inductances to perform impedance matching for a given frequency and coupling factor value. A comparison with similar works proves the proposed LNA achieves a very low NF and the lowest power consumption reported in a differential circuit.

Maximum distance from TS with a 250 kVA transformer to SU when PTL wires are of different cross-sections.
Allocation of 0.4 kV PTL Sectionalizing Units under Criteria of Sensitivity Limits and Power Supply Reliability

December 2021

·

138 Reads

Sectionalizing 0.4 kV power transmission lines (PTL) improves power supply reliability and reduces electricity undersupply through the prevention of energy disconnection of consumers in the event of a short circuit in the power line behind the sectionalizing unit (SU). This research examines the impact of sectionalizing on power supply reliability and reviews the literature on sectionalizing unit allocation strategies in electrical networks. This paper describes the experience of the use of sectionalizing units with listing strengths and weaknesses of adopted technical solutions and describes the new structure of sectionalizing units. A new methodology is proposed, whereby there are two criteria for allocating SU in 0.4 kV power transmission lines. The first criterion is the sensitivity limits against single-phase short circuits used for calculating the maximum distance at which SU can be installed. The second criterion is power supply reliability improvement, evaluating the cost-effectiveness of installing sectionalizing equipment by reducing power supply outage time. The established methodology was put to the test on an actual electrical system (Mezenka village, Orel area, Russia), which demonstrated that the installation of a sectionalizing unit paid off.

Figure 1. Optical images of samples: (a) Mg-0.5Ca-0.5Gd; (b) Mg-0.5Ca-1Gd; (c) M (d) Mg-0.5Ca-2Gd; (e) Mg-0.5Ca-3Gd.
Figure 4. XRD pattern of Mg-0.5Ca-xGd samples.
Magnesium and Mg-based master alloy weight percentages [41,42].
Initial materials masses used formetal charges in order to obtain the experimental samples.
Lattice parameters of Mg-0.5Ca-xGd alloy phases.
Microstructural, Electrochemical and In Vitro Analysis of Mg-0.5Ca-xGd Biodegradable Alloys

January 2021

·

143 Reads

The subject of Mg-based biodegradable materials, used for medical applications, has been extensively studied throughout the years. It is a known fact that alloying Mg with biocompatible and non-toxic elements improves the biodegradability of the alloys that are being used in the field of surgical applications. The aim of this research is to investigate the aspects concerning the microstructure, electrochemical response (corrosion resistance) and in vitro cytocompatibility of a new experimental Mg-based biodegradable alloy—Mg–0.5%Ca with controlled addition of Gd as follows: 0.5, 1.0, 1.5, 2.0 and 3.0 wt.%—in order to establish improved biocompatibility with the human hard and soft tissues at a stable biodegradable rate. For this purpose, scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), light microscopy (LM) and X-ray diffraction (XRD) were used for determining the microstructure and chemical composition of the studied alloy and the linear polarization resistance (LPR) method was used to calculate the corrosion rate for the biodegradability rate assessment. The cellular response was evaluated using the 3-(4,5-dimethyltiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) test followed by fluorescence microscopy observation. The research led to the discovery of a dendritic α-Mg solid solution, as well as a lamellar Mg2Ca and a Mg5Gd intermetallic compound. The in vivo tests revealed 73–80% viability of the cells registered at 3 days and between 77 and 100% for 5 days, a fact that leads us to believe that the experimental studied alloys do not have a cytotoxic character and are suitable for medical applications.

Development of 1.3 GHz Medium-β (β = 0.634) Disk-Loaded Deflecting Cavity for 150 keV Electron Beam

September 2022

·

69 Reads

A miniaturized 150 kV DC photocathode gun is developed at Peking University to generate electron beam which can be manipulated in temporal and spatial distribution as requirements freely. To measure the bunch length which is an important temporal parameter of the low energy electron beam from the DC photocathode gun, a 1.3 GHz medium-β disk-loaded deflecting cavity is adopted. In this paper we present the design of the deflecting cavity which involves the microwave design including the geometry optimization and the separation of the orthogonal dipole modes as well as the power coupling, the mechanical design including the determination of the cavity wall thickness and the tuning as well as brazing structure, and the thermodynamic analysis. Particle tracking simulation shows that the best resolution of 190 fs can be achieved for the 150 keV electron beam by using the deflecting cavity. Its fabrication is completed and the RF measurements are carried out with a vector network analyzer. It is shown the measured values of the RF physical parameters are in good agreement with the simulation design ones.

Figure 3. Cont. 
Figure 3. Experimental response at RT (symbols) plotted as R (blue) and G (black) peaks, together with the reconstructed spectra after parameter determination by iterative analysis (continuous lines), for: (A) planar and (B) thickness resonance modes of a thickness-poled, thin disk of BNBT6 (t = 1.91 mm and D = 10.60 mm); and for a shear resonance of a thickness-poled, thin plate of BNBT6 (9.53 × 9.43 mm): (C) with t = 0.89, with strong coupling of modes and not fitted for parameters determination; and (D) with t = 0.83 mm, virtually uncoupled. The regression factor of the reconstructed to the experimental spectra (R 2 ) is shown for each analyzed resonance. 
Figure 4. Sensitivity analysis for the real part of the elastic constants. Each curve shows the evolution of a resonance using the conductivity G. Each parameter is changed over a range ±50% from the initial value. 
Figure 7. Thermal evolution of the imaginary part of the elastic, dielectric, and piezoelectric parameters. Parameters related with the thickness mode (high sensitivity) are represented in red. Those related with the radial modes are represented in black, and those related with the complex resonances C 1 and C 2 in blue. 
Electromechanical Anisotropy at the Ferroelectric to Relaxor Transition of (Bi0.5Na0.5)0.94Ba0.06TiO3 Ceramics from the Thermal Evolution of Resonance Curves

January 2018

·

110 Reads

(Bi0.5Na0.5)0.94Ba0.06TiO3 dense ceramics were obtained from autocombustion sol-gel synthesized nanopowders and sintered at 1050 °C for 1-2 h for the study of the electromechanical anisotropy. Measurement of the complex impedance spectrum was carried out on thin ceramic disks, thickness-poled, as a function of the temperature from 16 °C up to the vanishing of the electromechanical resonances at the ferroelectric to relaxor transition near 100 °C. The spectrum comprises the fundamental radial extensional mode and three overtones of this, together with the fundamental thickness extensional mode, coupled with other complex modes. Thermal evolution of the spectrum shows anisotropic behavior. Piezoelectric, elastic, and dielectric material coefficients, including all losses, were determined from iterative analysis of the complex impedance curves at the planar, thickness, and shear virtually monomodal resonances of disks and shear plates, thickness-poled. d33 was measured quasi-statically at 100 Hz. This set of data was used as the initial condition for the optimization of the numerical calculation by finite elements of the full spectrum of the disk, from 100 kHz to 1.9 MHz, to determine the thermal evolution of the material coefficients. An appropriate measurement strategy to study electromechanical anisotropy of piezoelectric ceramics has been developed.

A Deeper Insight on the Stability of Water-Induced Reconstruction of Anatase (001) Surface

December 2018

·

185 Reads

TiO 2 anatase (001) surface has been indicated for many years as a potential system for water dissociation and hydrogen production. Surface reconstruction periodicity of TiO 2 anatase (001) in water is revised on the basis of the new water induced reconstruction model that accounts for dissociative water adsorption in the first monolayer and self-assembling of surface hydroxyls. The study has been performed in the context of first principles total energy calculations on the basis of state of the art Density Functional Theory. Different surface periodical structures have been studied and compared in terms of residual surface stress and surface reactivity. While a preference seems to emerge for the (2 × 3) surface reconstruction, there are indications that this configuration might not occur spontaneously in bulk water.

Figure 1. Schematic diagram of the c-ZrO2(001)/α-Al2O3(11 02) interfacial shear simulation. The red, pink, and blue spheres represent O, Al, and Zr atoms, respectively. To better demonstrate the system, the model has been duplicated in the horizontal direction.
Figure 3. The energy Φ as a function of the shear displacement δ of the c-ZrO2(001)/α-Al2O3 (11 02) interface models.
Figure 4. The evolution of the atomic structures at the c-ZrO2(001)/α-Al2O3(11 02) interfaces during the shearing process: (a) O-<11 01>, (b) O-<112 0>, (c) 2O-<11 01>, (d) 2O-<112 0>, (e) Zr-<11 01>, and (f) Zr-<112 0>. The red, grey, and green spheres represent O, Al, and Zr atoms, respectively.
First-Principles Investigation of the Shear Properties and Sliding Characteristics of c-ZrO2(001)/α-Al2O3(\({1\overline{1}02}\)) Interfaces

September 2022

·

60 Reads

The ideal mechanical shear properties and sliding characteristics of c-ZrO2(001)/α-Al2O3(11¯02) interfaces are examined through simulated shear deformations using first-principles calculations. We investigate three types of interface models, abbreviated as O-, 2O-, and Zr- models, when shear displacements are applied along the <11¯01> and <112¯0> directions of their Al2O3 lattice. The theoretical shear strength and unstable stacking energy of the ZrO2/Al2O3 interfaces are discussed. In the process of the ZrO2/Al2O3 interfacial shear deformation, we find that the sliding of the ZrO2 atomic layers, accompanied by the shifting of Zr atoms and Al atoms near the interface, plays a dominant role; in addition, the ZrO2/Al2O3 interfaces fail within the ZrO2 atomic layer. Among the three models, the O- model exhibits the strongest shear resistance; whereas the Zr- model is the most prone to slip. Furthermore, their tensile and shear strengths are compared; moreover, their potential applications are provided.

A Theoretical Study of the Energetic Stability and Geometry of Silicon-Vacancy Color Centers in Diamond (001) Surfaces

December 2019

·

291 Reads

Single neutral silicon-vacancy ( SiV 0 ) color centers under H-, O-, or N-terminated diamond (001) surfaces were investigated using density functional theory. The formation energy calculation indicated that it is generally easier for SiV 0 to be embedded in an O-terminated diamond (001) surface as compared with H- and N-terminated surfaces, which were effected above the fifth C layer. The effects of the surface termination species on inner diamond atoms decay to be negligible below the fifth C layer. The binding energy results indicated that SiV centers exhibited rather high energetic stability once formed. Additionally, it was revealed that these three surface-terminating species had contracting or expanding effects on inner surface atoms. The calculation for density of states showed that the N-terminated diamond (001) surface served as a suitable medium for single SiV 0 to function as a single-photon source.

NumericalStudy of Turbulent Flows over a NACA 0012 Airfoil: Insights into Its Performance and the Addition of a Slotted Flap

July 2023

·

85 Reads

This work provides a comprehensive overview of various aspects of airfoil CFD simulations. The airflow around a 2D NACA 0012 airfoil at various angles of attack is simulated using the RANS SST turbulent flow model and compared to experimental data. The airfoil is then modified with a slotted flap and additionally the angle of the flap is altered. The flow model is subsequently coupled to a heat transfer model to compare the isothermal versus non-isothermal performance. The airfoil with the slotted flap shows increased CL and CD values compared to the standard NACA 0012. Larger flap angles further increase the CL and CD. The lift and drag coefficients show no difference in the non-isothermal model compared to the isothermal model, indicating the isothermal model is sufficient for this system. The 3D model without wingtips shows a similar CL to the 2D model as it effectively has an infinite span. Adding a wingtip reduces the lift coefficient, as the air can flow around the wingtip, increasing the pressure on top of the wing. Overall, these results match the behavior expected from wing theory well, showing how CFD can be effectively applied in the development and optimization of wings, flaps, and wingtips.

Seismic Data Interpretation and Petrophysical Analysis of Kabirwala Area Tola (01) Well, Central Indus Basin, Pakistan

March 2021

·

435 Reads

Well logging is a significant procedure that assists geophysicists and geologists with making predictions regarding boreholes and efficiently utilizing and optimizing the drilling process. The current study area is positioned in the Punjab Territory of Pakistan, and the geographic coordinates are 30020′10 N and 70043′30 E. The objective of the current research work was to interpret the subsurface structure and reservoir characteristics of the Kabirwala area Tola (01) well, which is located in the Punjab platform, Central Indus Basin, utilizing 2D seismic and well log data. Formation evaluation for hydrocarbon potential using the reservoir properties is performed in this study. For the marked zone of interest, the study also focuses on evaluating the average water saturation, average total porosity, average effective porosity, and net pay thickness. The results of the study show a spotted horizon stone with respect to time and depth as follows: Dunghan formation, 0.9 s and 1080.46 m; Cretaceous Samana Suk formation, 0.96 s and 1174.05 m; Datta formation, 1.08 s and 1400 m; and Warcha formation, 1.24 s and 1810 m. Based on the interpretation of well logs, the purpose of petrophysical analysis was to identify hydrocarbon-bearing zones in the study area. Gamma ray, spontaneous potential, resistivity, neutron, and density log data were utilized. The high zone present in the east–west part of the contour maps may be a possible location of hydrocarbon entrapment, which is further confirmed by the presence of the Tola-01 well.

Extraction of City Roads Using Luojia 1-01 Nighttime Light Data

October 2021

·

63 Reads

The extraction of a road network is critical for city planning and has been widely studied in previous research using high resolution images, whereas the high cost of high-resolution remote sensing data and the complexity of its analysis also cause huge challenges for the extraction. The successful launch of a high resolution (130 m) nighttime remote sensing satellite, Luojia 1-01, provides great potential in the study of urban issues. This study attempted to extract city roads using a Luojia 1-01 nighttime lighting image. The urban regions were firstly distinguished through a threshold method. Then, an unsupervised PCNN (pulse coupled neural network) was established to extract the road networks in urban regions. A series of optimizing methods was proposed to enhance the image contrast and eliminate the residential regions along the roads. The final extraction results after optimizing were compared with OSM (OpenStreetMap) data, showing the high precision of the proposed approach with the accuracy rate reaching 83.2%. We also found the precision of city centers to be lower than suburban regions due to the influence of intensive human activities. Our study confirms the potential of Luojia 1-01 data in the extraction of city roads and provides new thought for more complex and microscopic study of city issues.

Clinical status of LCL161 for cancer treatment.
Clinical status of birinapant (TL32711) for cancer treatment.
An Updated Review of Smac Mimetics, LCL161, Birinapant, and GDC-0152 in Cancer Treatment

December 2020

·

169 Reads

Inhibitor of apoptosis proteins (IAPs) are suggested as therapeutic targets for cancer treatment. Smac/DIABLO is a natural IAP antagonist in cells; therefore, Smac mimetics have been developed for cancer treatment in the past decade. In this article, we review the anti-cancer potency and novel molecular targets of LCL161, birinapant, and GDC-0152. Preclinical studies demonstrated that Smac mimetics not only induce apoptosis but also arrest cell cycle, induce necroptosis, and induce immune storm in vitro and in vivo. The safety and tolerance of Smac mimetics are evaluated in phase 1 and phase 2 clinical trials. In addition, the combination of Smac mimetics and chemotherapeutic compounds was reported to improve anti-cancer effects. Interestingly, the novel anti-cancer molecular mechanism of action of Smac mimetics was reported in recent studies, suggesting that many unknown functions of Smac mimetics still need to be revealed. Exploring these currently unknown signaling pathways is important to provide hints for the modification and combination therapy of further compounds.

Automatic Matching of Multi-Source Satellite Images: A Case Study on ZY-1-02C and ETM+

October 2017

·

274 Reads

The ever-growing number of applications for satellites is being compromised by their poor direct positioning precision. Existing orthoimages, such as enhanced thematic mapper (ETM+) orthoimages, can provide georeferences or improve the geo-referencing accuracy of satellite images, such ZY-1-02C images that have unsatisfactory positioning precision, thus enhancing their processing efficiency and application. In this paper, a feasible image matching approach using multi-source satellite images is proposed on the basis of an experiment carried out with ZY-1-02C Level 1 images and ETM+ orthoimages. The proposed approach overcame differences in rotation angle, scale, and translation between images. The rotation and scale variances were evaluated on the basis of rational polynomial coefficients. The translation vectors were generated after blocking the overall phase correlation. Then, normalized cross-correlation and least-squares matching were applied for matching. Finally, the gross errors of the corresponding points were eliminated by local statistic vectors in a TIN structure. Experimental results showed a matching precision of less than two pixels (root-mean-square error), and comparison results indicated that the proposed method outperforms Scale-Invariant Feature Transform (SIFT), Speeded Up Robust Features (SURF), and Affine-Scale Invariant Feature Transform (A-SIFT) in terms of reliability and efficiency.

Conformance testing of SGSF-064-1 using CANoe

November 2015

·

1,932 Reads

In this paper, the authors describe a conformance testing system for SGSF-064-1, the communication protocol between electric vehicles and conductive DC (direct current) chargers in Korea. Since the SGSF-064-1 is based on CAN (controller area network), the testing system was developed by CANoe. The DC charger known as EVSE (electric vehicle supply equipment) is the system being tested and the developed system implemented in PC (personal computer). The developed system performs as a tester to ensure that the DC chargers from various manufactures can conform to the communication protocol in SGSF-064-1. The testing system contains four testing modes which also consist of several test cases.

0D/1D Thermo-Fluid Dynamic Modeling Tools for the Simulation of Driving Cycles and the Optimization of IC Engine Performances and Emissions

September 2021

·

298 Reads

The prediction of internal combustion engine performance and emissions in real driving conditions is getting more and more important due to the upcoming stricter regulations. This work aims at introducing and validating a new transient simulation methodology of an ICE coupled to a hybrid architecture vehicle, getting closer to real-time calculations. A one-dimensional computational fluid dynamic software has been used and suitably coupled to a vehicle dynamics model in a user function framework integrated within a Simulink® environment. A six-cylinder diesel engine has been modeled by means of the 1D tool and cylinder-out emissions have been compared to experimental data. The measurements available have been used also to calibrate the combustion model. The developed 1D engine model has been then used to perform driving cycle simulations considering the vehicle dynamics and the coupling with the energy storage unit in the hybrid mode. The map-based approach along with the vehicle simulation tool has also been used to perform the same simulation and the two results are compared to evaluate the accuracy of each approach. In this framework, to achieve the best simulation performance in terms of computational time over simulated time ratio, the 1D engine model has been used in a configuration with a very coarse mesh. Results have shown that despite the high mesh spacing used the accuracy of the wave dynamics prediction was not affected in a significant way, whereas a remarkable speed-up factor was achieved. This means that a crank angle resolution approach to the vehicle simulation is a viable and accurate strategy to predict the engine emission during any driving cycle with a computation effort compatible with the tight schedule of a design process.

Figure 4. The first and last snapshots in the first simulations systems (a); the most populated structures of L-Phes and D-Phes in the first simulations (b). Tail groups of DMPC membrane were omitted for the clarity.
Figure 5. The last snapshots of the third type of simulations of L-(left) and D-Phes (right). Water molecules and ions were omitted for the clarity. Charged and three-phenylalanine residues are shown by licorice model. Orange balls show phosphorus atoms of DMPC membrane. Green and yellow balls represent the sodium and chloride ions, respectively. Appl. Sci. 2019, 9, x FOR PEER REVIEW 9 of 16
Figure 6. Secondary structure profiles during the third type of simulations (MD3). Figure 6. Secondary structure profiles during the third type of simulations (MD3).
Information of simulation systems.
Average tilt angle in the last 100 ns simulations (MD3).
A Comparative Study on Interactions of Antimicrobial Peptides L- and D-phenylseptin with 1,2-dimyristoyl-sn-glycero-3-phosphocholine

June 2019

·

163 Reads

L-phenylseptin (L-Phes) and D-phenylseptin (D-Phes) are amphibian antimicrobial peptides isolated from the skin secretion of Hypsiboas punctatus. In the N-termini, L-Phes and D-Phes contain three consecutive phenylalanine residues, l-Phe-l-Phe-l-Phe and l-Phe-d-Phe-l-Phe, respectively. They are known to exhibit antimicrobial activity against Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Xanthomonas axonopodis pv. Glycines. However, their mechanism of action and the role of the D-amino acid residue have not been elucidated yet. In this study, the interactions of both peptides with 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) were investigated by means of quartz crystal microbalance, circular dichroism, vibrational circular dichroism, 31P solid-state NMR, and molecular dynamics simulation. Both peptides have similar binding constants to the DMPC lipid bilayers, in the order of 106 M−1, and form an α-helix structure in the DMPC lipid bilayers. Both the peptides induce similar changes in the dynamics of DMPC lipids. Thus, in spite of the difference in the conformations caused by the chirality at the N-terminus, the peptides showed similar behavior in the membrane-bound state, experimentally and computationally.

The Effect of Addition of Antioxidant 1,2-dihydro-2,2,4-trimethyl-quinoline on Characteristics of Crepe Rubber Modified Asphalt in Short Term Aging and Long Term Aging Conditions

October 2020

·

202 Reads

The use of natural rubber to resist bitumen is usually prone to degradation and aging. One method to overcome this problem is the addition of antioxidants. This study aims to determine the effect of the addition of antioxidants 1,2-dihydro-2,2,4-trimethyl-quinoline (TMQ) on natural rubber modified asphalt crepe rubber and its performance in short-term and long-term aging conditions. The modified rubber asphalt mixture’s manufacture begins by melting the crepe rubber at 200 °C before being mixed in asphalt at 165 °C. Addition of antioxidant TMQ during the stirring process of the mixture of asphalt and melted rubber. The crepe rubber content was 8, 10, and 12% w/w, while the TMQ content was 1, 2, and 3% w/w of the total sample weight. The modified asphalt samples’ characterization included penetration, softening point, weight loss after a rolling thin film oven test (RTFOT), penetration after RTFOT, and Marshall test. Review of the performance of asphalt under short-term aging conditions using a dynamic shear rheometer (DSR). Evaluation of asphalt performance under long-term aging conditions using Fourier-transform infrared spectroscopy (FTIR). The results showed that the fact that the best-modified asphalt product was the addition of 10% crepe rubber and 2% TMQ. The best-modified asphalt characteristics have penetration 68.70 dmm, softening point 55.45 °C, weight loss only 0.0579%, penetration after RTFOT 59.60, Marshall stability 1403.96 kg with optimum asphalt content of 5.50%, and rutting factor (G*/Sinδ) 6.91 kPa and 16.1 kPa before and after RTFOT. Overall, the modified crepe rubber asphalt can improve the performance of the asphalt in terms of durability. Simultaneously, the antioxidant TMQ works very well in increasing the resistance of bitumen to aging in the conditions of short-term aging and long-term aging.

A Systematical Comparison of Catalytic Behavior of NM/γ-Al2O3 (NM = Ru, Rh, Pt, Pd, Au, Ir) on 1,2-Dichloroethane Oxidation: Distributions of By-Products and Reaction Mechanism

December 2022

·

55 Reads

Understanding the reaction path and mechanism of chlorinated volatile organic compound (CVOC) destruction is important for designing efficient catalysts, especially for the application of noble metal-based materials. Herein, several typical noble metals, Ru, Rh, Pt, Pd, Au, and Ir, supported on γ-Al2O3 catalysts were synthesized by the hydrazine hydrate reduction method for 1,2-dichloroethane (1,2-DCE) elimination. Various character measurements were conducted, and the results suggest that the high-valence state of noble metals is beneficial for the 1,2-DCE reaction as it enables the enhancement of the mobility of the surficial active oxygen species of catalysts. Among the noble metals, Ru/γ-Al2O3 expresses superior catalytic reactivity, with a 90% pollutant conversion rate at 337 °C, and competitive CO2 selectivity, 99.15% at the temperature of total oxidation. The distribution of by-products and the degradation routes were analyzed online by GC-ECD and in situ diffuse reflectance infrared spectroscopy, which may provide helpful insight for the future application of noble metal-based catalysts for CVOC elimination in industrial fields.

Scheme 9. I2/CuCl2 mediated catalysis for the construction of thiadiazoles (53).
Scheme 9. I 2 /CuCl 2 mediated catalysis for the construction of thiadiazoles (53).
Scheme 10. Synthesis of acrylamide derivatives of thiadiazoles (59).
Synthetic Transformations and Medicinal Significance of 1,2,3-Thiadiazoles Derivatives: An Update

June 2021

·

157 Reads

The 1,2,3-thiadiazole moiety occupies a significant and prominent position among privileged heterocyclic templates in the field of medicine, pharmacology and pharmaceutics due to its broad spectrum of biological activities. The 1,2,3-thiadiazole hybrid structures showed myriad biomedical activities such as antifungal, antiviral, insecticidal, antiamoebic, anticancer and plant activators, etc. In the present review, various synthetic transformations and approaches are highlighted to furnish 1,2,3-thiadiazole scaffolds along with different pharmaceutical and pharmacological activities by virtue of the presence of the 1,2,3-thiadiazole framework on the basis of structure–activity relationship (SAR). The discussion in this review article will attract the attention of synthetic and medicinal researchers to explore 1,2,3-thiadiazole structural motifs for future therapeutic agents.

Figure 6. Optimized structures of the molecules considered for study: 3-mercaptopropyl-5-amino-1H-1,2,4-triazole (a), 3-mercaptobutyl-5-amino-1H-1,2,4-triazole (b) and 3-mercapto (3-methylbutyl)-5-amino-1H-1,2,4-triazole (c).
Open circuit potential E corr , polarization resistance R p , corrosion current density i corr , and degree of protection of brass Z i , in 10 mM NaCl solutions with various 3-mercaptoalkyl derivatives of 5-amino-1H-1,2,4-triazole.
Registered time of first corrosion attacks during the salt spray testing (τ corr , hours).
Elemental surface composition (at. %) of the brass electrode.
Calculated energies of HOMO, LUMO, HOMO LUMO gap (HLG), Ionization Potential (IP), Electron Affinity (EA), Electronegativity (χ), Absolute Hardness (η) and Softness (σ) in eV at B3LYP/6-311 + G (d, p) level.
Corrosion of α-Brass in Solutions Containing Chloride Ions and 3-Mercaptoalkyl-5-amino-1H-1,2,4-triazoles

July 2019

·

460 Reads

The protective effect of 3-mercaptoalkyl derivatives of 5-amino-1H-1,2,4-triazole against corrosion of α-brass in a chloride media was studied using polarization curves, electrochemical impedance spectroscopy, and full-scale corrosion testing. The brass electrode remains passive up to the activation potential, which is much higher than in solutions without organic additives, and it increases with the concentration of the inhibitor. The protection degree of all the studied inhibitors reaches its maximum of over 99% in solutions with the concentration of the inhibitor Cinh ≥ 0.10 mM. The protective effect increases with the length of the alkyl chain. All the studied derivatives are effective against atmospheric corrosion of α-brass. A protective film is formed on the brass surface, and it most probably includes oxides as well as complex compounds of zinc and copper with the molecules of the inhibitors. The impedance spectroscopy demonstrated that the presence of the inhibitor results in a decrease in the double-layer capacitance and an increase in the polarization resistance, which proves that the protective film actually forms on the brass surface. The quantum chemical analysis of the optimized molecular structures demonstrates that all the studied inhibitors should have a similar protective effect, which agrees with the experimental results.

Microwave-Assisted Synthesis and Antifungal Activity of Some Novel Thioethers Containing 1,2,4-Triazole Moiety

November 2015

·

130 Reads

A series of novel thioether derivatives containing 1,2,4-triazole moiety were designed and synthesized from 4-chlorophenol and ethyl 2-chloroacetate as starting materials by multi-step reactions under microwave irradiation, and their structures were characterized by 1H-NMR, MS and elemental analysis. The antifungal activity of title compounds was determined. The results indicated that some of title compounds exhibited moderate antifungal activity.

Scheme 2. Synthetic route through which 3,5 dialkyloxy-phenyl-1,2,4 triazolium trifluoromethanesulfonate was obtained.
Scheme 3. Proposed mechanism for the ANRORC rearrangements [30].
Shaping 1,2,4-Triazolium Fluorinated Ionic Liquid Crystals

February 2023

·

39 Reads

The synthesis and thermotropic behaviour of some di-alkyloxy-phenyl-1,2,4-triazolium trifluoromethane-sulfonate salts bearing a seven-carbon atom perfluoroalkyl chain on the cation is herein described. The fluorinated salts presenting a 1,2,4-triazole as a core and differing in the length of two alkyloxy chains on the phenyl ring demonstrated a typical liquid crystalline behaviour. The mesomorphic properties of this set of salts were studied by differential scanning calorimetry and polarized optical microscopy. The thermotropic properties are discussed on the grounds of the tuneable structures of the salts. The results showed the existence of a monotropic, columnar, liquid crystalline phase for the salts tested. An increase in the temperature mesophase range and the presence of two enantiotropic mesophases for the sixteen-atom alkyloxy chain salt can be observed by increasing the length of the alkyloxy chain on the phenyl ring.

Chiral Pyrazolo[4,3-e][1,2,4]triazine Sulfonamides—Their Biological Activity, Lipophilicity, Protein Affinity, and Metabolic Transformations

March 2021

·

102 Reads

Referring to our previous laboratory results related to the tyrosinase and urease inhibition by pyrazolo[4,3-e][1,2,4]triazine sulfonamides, we examined here in silico the mechanism of action at the molecular level of the investigated pyrazolotriazine sulfonamides by the molecular docking method. The studied compounds being evaluated for their cytotoxic effect against cancer cell lines (MCF-7, K-562) and for recombinant Abl and CDK2/E kinase inhibitory potency turned out to be inactive in these tests. The pyrazolotriazines were also investigated with respect to their lipophilicity and plasma protein binding using HPLC chromatography in isocratic conditions. The observed small affinity for plasma proteins could be advantageous in the potential in vivo studies. Moreover, the compounds were sensitive to metabolic transformations with phase I enzymes, which led to the hydroxylation and dealkylation products, whereas phase II transformations did not occur.

3-Sulphinyl-5-Amino-1H-1,2,4-Triazoles as Inhibitors of Copper Corrosion

November 2019

·

751 Reads

A set of electrochemical and full-scale corrosion testing methods demonstrates that 3-sulphinylalkyl-5-amino-1H-1,2,4-triazoles can be used as inhibitors of copper corrosion in neutral chloride solutions and under atmospheric corrosion. It was shown that the inhibition effect of 3-sulphinylalkyl derivatives of 5-amino-1H-1,2,4-triazole increases with the growth of the chain of the additive. By means of the impedance spectroscopy method, the authors determined that the polarisation resistance and the Warburg impedance increases whereas the double-layer capacitance decreased with the growth of the inhibitor chain and the concentration of the inhibitor. In addition, the period when the first signs of corrosion attack appear on the copper plates in the salt spray chamber increased with the growth of the inhibitor chain and its concentrations. The lowest value of this period was measured for 3-sulphinylpropyl derivatives. However, it is still 12 times higher that this value measured without any inhibitors. Full-scale testing in 1% HCl solution showed that the corrosion rate slows down by 10–20 times upon the introduction of the derivatives of 3-sulphinylbutyl and 3-sulphinylpentyl at a concentration of ≥5.00 mM. If the concentration of 3-phenethylsulphinyl is equal to or higher than 1.00 mM, then the protection level is about 85%.

Synthesis and Physical and Chemical Properties of Hypergolic Chemicals such as N,N,N-Trimethylhydrazinium and 1-Ethyl-4-Methyl-1,2,4-Triazolium Salts

December 2015

·

507 Reads

Hypergolic chemicals N,N,N-trimethylhydrazinium iodide, [TMH](+)[I](-), and 1-ethyl-4-methyl-1,2,4-triazolium iodide, [EMT](+)[I](-) were firstly synthesized by nucleophilic substitution (SN2). The successful synthesis of hypergolic chemicals [TMH](+)[I](-) and [EMT](+)[I](-) was confirmed by IR and H-1-NMR spectroscopy and, GC-mass spectrometry. Subsequently the hypergolic chemicals [TMH](+)[X](-) (X = CN-, N-3(-), NO3-, NO2-, ClO4-, AlCl4-) were prepared via an ion exchange reaction from [TMH](+)[I](-) and [EMT](+)[I](-), respectively. After that, a mixture of hypergolic chemicals was prepared by dissolving the synthesized hypergolic chemicals in 2-hydroxyethylhydrazine (HOCH2CH2NHNH2). The physical and chemical properties of the mixture such as decomposition temperature (T-d), density (d), viscosity (eta), and decomposition energy (Delta Hd) was then evaluated to determine suitability for use as liquid rocket fuels. The ignition delay (ID) time of the mixture of hypergolic chemicals with [TMH](+)[N-3](-) and [TMH](+)[CN](-) using H2O2 as an oxidizer was determined as 55.6 ms and 97.4 ms; respectively. The ID time of the mixture of hypergolic chemicals with [EMT](+)[N-3]-; [EMT](+)[CN](-); [EMT](+)[AlCl4](-); and [EMT](+)[I](-) using H2O2 as an oxidizer was also determined as 18.0 ms; 32.6 ms; 27.6 ms; and 7.96 ms; respectively. The synthesized mixture of hypergolic chemicals could thus be used as a rocket propellant liquid fuel.

Figure 5. Atomic force microscope (AFM) scanned images: (a) PBA-1,3-BDO, (b) PBA-1,4-BDO, (c) PTMG-1,3-BDO, (d) PTMG-1,4-BDO.
The types of polyol used in synthesizing thermoplastic polyurethanes (TPUs).
Formula structures and [NCO]/[OH] ratios of thermoplastic polyurethanes.
Number-average molecular weight (Mn), weight-average molecular weight (Mw), and polydispersity index (PDI) of the TPUs synthesized in this study.
Thermal Behavior and Morphology of Thermoplastic Polyurethane Derived from Different Chain Extenders of 1,3- and 1,4-Butanediol

January 2021

·

449 Reads

In this study, when deriving thermoplastic polyurethane (TPU), the researchers replaced 1,4-butanediol (1,4-BDO) with 1,3-butanediol (1,3-BDO) as a chain extender and examined how the structure of the chain extender affected the final polymers. Regarding the raw materials for polymerization, three types of commercial polyols with the same molecular weight (Mn = 1000 g/mol), namely, poly (butyl acrylate) (PBA), poly (tetramethylene ether) glycol (PTMG), and polycarbonate diol (PCDL) were used. These polyols were used in conjunction with butanediol and 4,4’-methylene diphenyl diisocyanate. Three groups of TPUs were successfully synthesized using one-shot solvent-free bulk polymerization. Compared with TPUs polymerized using 1,4-BDO, materials polymerized using 1,3-BDO are more transparent and viscous. Structural analysis revealed that no substantial differences between the final structures of the TPUs were present when different chain extenders were used. Thermal analysis indicated that compared with TPUs polymerized using 1,4-BDO, the glass transition temperature of those with 1,3-BDO was 15 °C higher. Examination of microphase separation in the structure by using morphological analysis revealed that compared with TPUs synthesized using 1,4-BDO, PBA, and PTMG synthesized using 1,3-BDO were relatively separated. PCDL synthesized using 1,3-BDO exhibited no morphological difference. Rheological analysis indicated PCDL synthesized using either 1,4-BDO or 1,3-BDO did not exhibit any obvious differences. In conclusion, TPUs synthesized using PCDL and 1,3-BDO exhibited thermal plasticity at room temperature (15–20 °C). Their basic application could be extended to the development of smart materials. In terms of further application, they could be used in shape memory and temperature-sensitive high molecular polymers.

Effect of Impregnation with Maltodextrin and 1,3-Dimethylol-4,5-Dihydroxyethyleneurea on the Conventional Drying Characteristics of Poplar Wood

January 2019

·

145 Reads

The drying characteristics of poplar wood (Populus adenopoda Maxim) under three treatments were investigated with the aim of improving the drying quality of the impregnated wood. Untreated materials, impregnated materials with 10% initial moisture content (MC), and impregnated materials with 20% initial MC—denoted as T1, T2, and T3, respectively—were examined during conventional drying. Relative to that of T1, the average drying rate of T2 was reduced by 46%, and that of T3 was reduced by 37%. The anti-swelling efficiency of T2 sharply increased, whereas that of T3 only slightly increased in width and thickness. The drying defects of T2 were markedly less than those of T1 and T3, attributed to the reduced residual stress and fixation of the modifier. Scanning electron microscopy indicated that large amounts of modifiers were deposited inside the cell cavity of T2, whereas small amounts of modifiers were deposited in the cell cavity of T3. The impregnation treatment generally reduced the average drying rate and MC uniformity and delayed the decrease in residual stress; however, it reduced the number of defects in the wood and considerably improved the dimensional stability of the wood. Meanwhile, impregnation treatment with increased initial MC could potentially lead to more drying defects and increase production cost.

The chemical structures and purities (%) of the tested compounds.Table 1. The chemical structures and purities (%) of the tested compounds.
The MIC and MBIC values (µg/mL) measured for compounds 1d-f; 2a-f; 3a; 4a; 6i,j; and 6p against the tested microbial strains.
The probability (Pa) for the compounds to produce biological effects related to antibacterial action as predicted by the PASS application.
Descriptive statistics for the molecular descriptors.
In Silico and In Vitro Assessment of Antimicrobial and Antibiofilm Activity of Some 1,3-Oxazole-Based Compounds and Their Isosteric Analogues

May 2022

·

91 Reads

In this paper, we report on the antimicrobial activity assessment of 49 compounds previously synthesized as derivatives of alanine or phenylalanine that incorporate a 4-(4-X-phenylsulfonyl)phenyl fragment (X = H, Cl, or Br), namely 21 acyclic compounds (6 × N-acyl-α-amino acids, 1 × N-acyl-α-amino acid ester, and 14 × N-acyl-α-amino ketones) and 28 pentatomic heterocycles from the oxazole-based compound class (6 × 4H-1,3-oxazol-5-ones, 16 × 5-aryl-1,3-oxazoles, and 6 × ethyl 1,3-oxazol-5-yl carbonates). Both in silico and in vitro qualitative and quantitative assays were used to investigate the antimicrobial potential of these derivatives against planktonic and biofilm-embedded microbial strains. Some of the tested compounds showed promising antimicrobial and antibiofilm activity depending on their chemical scaffold and lipophilic character.

Top-cited authors