Yuri Dekhtyar

Riga Technical University | RTU · Institute of Biomedical Engineering and Nanotechnologies

Insulin and immunoglobulin therapy is commonly administered through injections that are invasive and painful. They cannot be taken orally because digestive enzymes break them down. To protect against enzymes, drug molecules may be “packed”, which decreases interaction of the active surface of the molecule with the environment. Silica nanoparticles...

Nanolayered coatings are proposed for use in microelectronic devices where the size/performance ratio is becoming increasingly important, with the aim to achieve existing quality requirements while reducing the size of the devices and improving their ability to perform stably over multiple cycles. Si-SiO2-W structures have been proposed as a potent...

This study examines the electrical properties and layer quality of field emission microtriodes that have planar electrode geometry and are based on tungsten (W) and silicon dioxide (SiO2). Two types of microtriodes were analyzed: one with a multi-tip cathode fabricated using photolithography (PL) and the other with a single-tip cathode fabricated u...

For the past few decades, many researches have been devoted to study and develop new biocompatible materials for medical implants. MgCa1 and TiAl6V4 are examples of such materials. It is possible to adjust their physical and chemical parameters by coating the surface with calcium phosphates (CaP). In turn, exposing materials to UV radiation influen...

Diamond is among the best solid-state dosimeters for measuring ionising radiation. Diamond nanoparticles (DNPs) could be used to estimate doses at nanovolumes, which is desirable for determining ionising radiation absorption by a single structural nanounit of DNA. However, there is no research aimed at verifying the possibility of exploiting DNP fo...

Cell attachment is of paramount importance in implant design, bioreactor design, tissue engineering and the design of non-fouling surfaces. Surface roughness is a significant factor that affects cell attachment. To explore the impact of roughness characteristics, micromachining approaches can be used to fabricate surfaces with controlled microscale...

Thermally stimulated exo-electron emission (TSEE) and thermally stimulated desorption (TSD) methods were employed to characterize interactions in the surface of thin films of Lu2O3 doped by Eu3+ fabricated by pulsed laser deposition. Samples with 1 and 3% doped europium were selected. Pulsed laser annealing (PLA) was performed to modify surfaces. T...

An interesting development of biotechnology has linked microbial cell immobilisation with nanoparticles. The main task of our research was to reveal the possible influences of differently electrically charged diamond nanoparticles upon physiological characteristics of the yeast Saccharomyces cerevisiae. It was revealed that the adverse impact of th...

Physical vapor deposition (PVD) of metallic thin films is used extensively in the fabrication of semiconductor technology devices - use as of lately for them have grown. Tungsten (W) is a low resistivity, refractory metal, that is often deposited by PVD methods for use as a gate contact to semiconductor devices and due to the low work function and...

In the divertor of the tokamak type fusion reactors tungsten and tungsten-covered plasma facing materials are currently among the selected materials. However, metallic, high-Z plasma facing materials require plasma mitigation. Recent researches show, that mitigation with boron can be used for optimizing plasma operations, while the interactions bet...

Spiral‐shaped aluminum nanowires grow from scratches and abrasions on the surface of black aluminum film after heating the film in a vacuum. The growth of nanowires is driven by the stress‐induced migration of aluminum atoms. The mechanism of nanowire growth is studied in article number 2100467 by Marina Romanova and co‐workers. – This article belo...

Thermal stability of black aluminum (Black Al) films deposited on unheated fused silica substrates by pulsed DC magnetron sputtering has been investigated. The deposited films have porous moth-eye morphology and a relatively soft surface that can be easily damaged mechanically. Photothermally stimulated exoelectron emission (PTSE) spectra of the fi...

Thin films of black aluminum (B–Al) were prepared by pulsed DC magnetron sputtering in a mixture of argon + nitrogen (Ar + N2) gases with concentration of nitrogen 6%. At this concentration the process of anti-reflective surface (UV to near IR diffuse reflectance below 4%) formation is favored. The properties of such layers have been investigated u...

The aim of the study was to investigate how cerebral vasospasm, vasodilation and haemorrhage under artificial circulation conditions during cardiopulmonary bypass affect transcranial duplex ultrasonography measurements. A description of transcranial duplex ultrasonography and phantom development is provided. Measurements were made using a commercia...

Tungsten (W) and tungsten diboride (WB2) materials can be used to fabricate electron emission layers in field emission microelectronic devices. The characterization and quality assurance of synthesized films is crucial for the good performance of the devices. W and WB2 nanofilms with a thickness of 150 nm and 200 nm were deposited on the Si-SiO2 su...

The ability of cells to adhere to substrates is an important factor for the effectiveness of biotechnologies and bioimplants. This research demonstrates that the statistical distribution of the sizes of the cells (Saccharomyces cerevisiae) attached to the substrate surface correlates with the statistical distribution of electrical potential on the...

The effect of 6 MeV gamma photons on thermally stimulated exoelectron emission (TSEE) spectra of MgO films was studied. The films were fabricated on Si/SiO 2 substrates using the extraction-pyrolytic method. The crystalline structure and surface morphology of the films were characterized by X-ray diffraction (XRD) and atomic force microscopy (AFM)....

It is more common to perform non-invasive examination during general anaesthesia to ensure effective perioperative patient care. To achieve these results, researchers and clinicians are seeking out different technologies and developing new equipment. One such apparatus is a cerebral oximeter, which is used during cardiac surgery with cardiopulmonar...

The paper deals with the evolution of the microstructure of AlSi10Mg alloy obtained by laser powder bed fusion (LPBF), as a function of the post-processing heat treatment temperature. This was approached by complementary methods including FE-scanning electron microscopy, scanning Kelvin probe force microscopy and exo-electron emission techniques. T...

The setup for measuring the effects of light stimulation on the surface charge kinetics using an atomic force microscope with KPFM measurement capacity is demonstrated.

Due to complex nature of 21st century battlefield, soldiers must perform multiple tasks to protect nations while maintaining their own safety. Advances in techno-logical innovations are critical to support such functionalities to enhance safety and security. Using nexus of electrospinning and additive processing, we present how recent developments...

This article belongs to a three-part series dedicated to the simultaneous measurements of thermally stimulated exo-electron emission (TSEE), desorption (TSD) and luminescence (TSL). These works aim is to verify the ability of the applied experimental setup to characterize and analyze at the same time all the three above-mentioned stimulated process...

Bio-Derived Polymers exist in abundance and display diverse chemical compositions, tunable properties, processability, excellent biocompatibility and biodegradability as well as nontoxicity. This feature provides capability for futuristic ubiquitous networked wearable and tactile electronics membranes and devices to efficiently scavenge and store o...

Potassium bromide (KBr) is a material with many potential uses in various branches of physics and technology (in scintillators, for a Fourier spectrometer, electro-optical elements such as IR laser windows, sensors and optical fibers). We conducted a series of combined measurements of thermally stimulated exo-electron emission (TSEE) and thermally...

The results of simultaneous measurements of three thermally stimulated phenomena (TSP) are presented as functions of temperature: thermally stimulated exo-electron emission (TSEE), thermally stimulated luminescence (TSL) and thermally stimulated desorption (TSD). These phenomena can be described by similar mathematical relationships. The measuremen...

This article is focusing on electrical functionalization of biomaterial’s surface to enhance its biocompatibility. It is an overview of previously unpublished results from a series of experiments concerning the effects surface electrical functionalization can have on biological systems. Saccharomyces cerevisiae cells were used for biological experi...

Single-layered and multi-layered 20–60 nm thick silicon nitride (Si3N4) dielectric nanofilms were fabricated using a low-pressure chemical vapour deposition (LPCVD) method. The X-ray photoelectron spectroscopy (XPS) confirmed less oxygen content in the multi-layered nanofilms. The capacitors with Si3N4 multilayer demonstrated a tendency to a higher...

The diversity of polymers and the versatility of their properties have transformed our everyday life. While their widespread use, including for disposable aspects was anticipated, some of the recent reports associated with the extent of nano/microplastics environmental pollution was not articulated. Presence of microplastics in treated tap and bott...

An electron irradiation assisted photoelectron emission technique was developed to study charge traps for nanolayered Si3N4 and SiO2. Sharp emission peaks were induced by electron irradiation, with characteristic energies revealing their microscopic origins. Trap energies, originating from SiO2, were observed to shift depending on the electron irra...

The effect of gamma irradiation on Gd2O3 films was studied using the thermostimulated exoelectron emission (TSEE) technique. The films were deposited on a glass and Si/SiO2 substrates using an extraction-pyrolytic method. Crystalline structure, chemical composition, film thickness and surface morphology were characterized by means of X-ray diffract...

Modern semiconductor sensors which are used for gas detection are based on an MOS (metal–oxide–semiconductor) structure, but the usage of such sensors is limited due to its working principles. Over the last decade, MOS sensors have been combined with a UV-radiation source, but the sensing capabilities of a low gas concentration for those sensors ar...

Modern semiconductor sensors are based on an MOS (metal–oxide–semiconductor) structure and their further development is tending to combine them together with UV irradiation. In this paper, a system is presented that can pave the way towards gas analyzers that rely on visible spectrum light. The article presents a semiconductor gas sensor induced wi...

The report is directed to nanostructured hydroxyapatite (HA) electrically functionalized costing aimed to enhance biocompatibility of the HA originated implants. The reader will be guided from necessity and prerequisites for HA electrical functionalization to its computed designing, characterization technique, fabrication, and biological properties...

The article is aimed to engineer strength and elastic modulus of a polymer composite material embedded with electrically charged silica nanoparticles. Ultraviolet radiation was in use to induct an electrical charge at surfaces of the nanoparticles. The specimens were tested under mechanical loading (tensile test). An electron emission by the loaded...

Silicon nitride (Si 3 N 4 ) due to its good mechanical and electrical properties is a promising material for wide range of applications, including exploitation under action of ionizing radiation. For estimating the changes of chemical bonds in silicon nitride nanolayers under action of ionizing radiation single and multi-layer silicon nitride nanol...

Mesenchymal stem cells (MSCs) and osteoblasts respond to the surface electrical charge and topography of biomaterials. This work focuses on the connection between the roughness of calcium phosphate (CP) surfaces and their electrical potential (EP) at the micro- and nanoscales and the possible role of these parameters in jointly affecting human MSC...

In previous studies the possibility to use optically induced semiconductors to sense acetone vapors was demonstrated [1]. One of the studies demonstrated the possibility to sense and determine various solvent gases, where acetone vapor showed the highest signal increase [2]. In this study, two optical irradiation types (continuous and cyclical) are...

Summer school Nonlinear life 2018 https://www.rtu.lv/en/internationalization/international-events/summer-schools/nonlinearlife

Hydroxyapatite (HAp) has structural features that define its basic physical properties, which have an important role at the surface, and it is one of the most used materials in bone implants. In this work, we present a density functional modeling (DFT) study of HAp both as bulk and with special HAp models with various defects, especially oxygen vac...

Nanostructured hydroxyapatite (HAP) and its nanoparticles are widely used for implantation into the human organism. The biocompatibility of the implants depends very much on the interaction between the implant and the cells regenerating tissue to be connected to the implant. An implant surface electrical charged density plays an important role in t...

In the current study, we have examined the possibility to improve the biocompatibility of the (TiZrNbTaHf)C through replacement of either Ti or Ta by Si. The coatings were deposited on Si and 316L stainless steel substrates by magnetron sputtering in an Ar+CH4 mixed atmosphere and were examined for elemental composition, chemical bonds, surface top...

It is known that there is a number of VOC (volatile organic compounds) in exhaled human breath that can be used as biomarkers [1, 2]. To reach screening of the patients the exhalation gas sensor should be light, cheap and sensitive. Semiconductor gas sensors can offer advantages in size, but they are characterized with a long response time, short l...

The purpose of this study is to describe the spectrometer and the technology that is used to investigate the influence of X-ray radiation on exo-electron emission (EEE) on bone specimens. This paper addresses an approach to detect radiation-induced modifications in bone structure using method of exo-electron emission (EEE). The bone specimens were...

The unique biological properties of amber are well known. Amber particles that penetrate into the cellular matrix can potentially be used as markers of plant cell biological activity by identification of living cells in flow cytometry. However, there have been no studies on effect of amber particles on plant cells. The aim of this study was to dete...

Hydroxyapatite (HAp) was studied from a first principle approach using the local density approximation (LDA) method in AIMPRO code, in combination with various quantum mechanical (QM) and molecular mechanical (MM) methods from HypemChem 7.5/8.0. The data obtained were used for studies of HAp structures, the physical properties of HAp (density of el...

First principle modeling and calculations of hydroxyapatite both native and surface modified and having various defects (OH vacancies, H inter-nodes) were performed. Local Density Approximation method used with calculations of Density of States allows us to analyze the experimental obtained work function data. Molecular modeling was confirmed by ph...

Lead sulfide (PbS) nanoparticles embedded in a thin-film matrix of zirconium oxide (ZrO2), ZrO2:PbS nanofilms, were studied for application in nanodosimetry of ionizing radiation. Readout of the delivered dose was carried out by measurements of photoelectron emission (PE) current from ZrO2:PbS nanofilms. PE emission was excited by UV photons having...

Breath analysis is in use since a long history as a part of medical diagnostics. Idea that some of the diseases are characterised by a specific odour was already known since the Hippocrates time. Modern breath analysis has significantly developed comparing to the discovery of the several hundred different VOCs in the common human breath [1] to more...

Work was studied in the composite material (tungsten and ceresin composite material) absorption and scattering characteristics as well as comparison with until now used Bi-Sn-Pb compound. the hypothesis is that this type of composite material can be used as a substitute for metal alloy in radiation therapy. The aim is to determine the absorption an...

Compact device of high sensitivity for measurement of the refractive indices of both stationary and flowing liquids has been developed. This device can be used to analyse a variety of biomedical liquids: urine, serum protein. The refractive index (RI) is determined by measuring the deviation of a laser beam passing through a cylindrical cell contai...

Advances in nanotechnology and nanomaterials have facilitated the development of silicon dioxide, or Silica, particles as a promising immunological adjuvant for the generation of novel prophylactic and therapeutic vaccines. In the present study, we have compared the adjuvanting potential of commercially available Silica nanoparticles (initial parti...

Rapid development of nanomaterials opens a wide horizon for their applications, medicine being one of them. Nanomaterials and nanodevices are in use both in the human body and as medical nanosensors. Reliable employment of materials requires trustworthy detection of their properties. Characterization of both the nanomaterials and nanosensors should...

Modern radiation therapy (RI) technologies and the needs of molecular and micro radiobiology have necessitated the detection of radiation absorbed by micro/nano volumes. The possibility of developing a nano/micro-scale dosimeter is demonstrated via the use of prethreshold photoelectron and exoelectron emission from solid-state nanolayers (Si, bone)...

The results are based on the first principal modeling and calculations for HAP nanostructures as native as well surface modified, charged and having various defects (H and OH vacancies, H inter-nodes). HAP structures were studied using Local Density Approximation (LOA) method with calculations of Density of States (DOS) allow us analyzes the experi...

Photoelectron (PE) and thermostimulated exoelectron (TE) emission spectroscopies were explored for gas sensing and electron radiation nanodosimetry. Silicon substrates were in use as the working matter for benzene and isopentane sensing. PbS nanocrystals embedded in ZrO2 thin-films were employed to absorb electron radiation. Both PE and TE influenc...

Nowadays in eye prosthetics and eye lenses produc-tion mostly poly methyl metha acrylate (PMMA) is used be-cause the material excellently fulfills biomedical and aesthetic functions. Peculiarities of PMMA material determines that under influence of mechanical impact (wind, sand, eye lid movements) and degradation in time, surface properties alter a...

The results of computational modeling for Hydroxyapatite (HAP) nanostructures and surface interactions properties are presented in this work. HAP were studied from first principles approaches using Local Density Approximation (LDA) method in combination with various quantum-chemical (QM), including Density Functional Theory (DFT) methods, and molec...

Changes in surface electric potential of P(VDF-TrFE 70:30) films deposited on glass substrate under influence of UV radiation were investigated. It was found that after 6 minutes of UV irradiation surface electric potential of the films decreased and no changes were observed further increasing irradiation time. Surface electric potential exponentially...

The general adhesion theory is the fundament to explain cell attachment to a bioimlplant surface in a human body. Electrical potential of the surface could be employed to control attachment. The paper demonstrates that the electrical potential may be engineered due to hydrogenation of hydroxyapatite. Such the procedure enhance attachment of osteobl...

Most of diagnostic radiography today is digital. Therefore there is a great possibility to make an express check of an x-ray beam quality using digital approach. The flux of the x-ray photons detected is governed by the Poisson statistics. The deviation of the radiating technique modes leads from the Poisson statistics. Because the single element o...

Preliminary diagnosis of human diseases such as cancer and diabetes is possible via the detection of violate organic compounds (VOCs) contained in exhaled breath gases. A pre-threshold electron emission yield from a solid emitter depends on the gas molecules adhered to the emitter, if the electron work function is influenced. The paper demonstrates...

An affect of relief features and quantitative variables of artificial surfaces on structural-functional status of human lung prenatal stromal cells (HLPSC) and remodeling of Balb/c mice bone/bone marrow system have been studied. Implants with rough (Ra>2 μm) calcium phosphate micro-arc coatings have structural-functional sites (micro-regions) named...

Photoelectron (PE) and thermostimulated exoelectron (TE) emission spectroscopies were explored for gas sensing and electron radiation nanodosimetry. Silicon substrates were in use as the working matter for benzene and isopentane sensing. PbS nanocrystals embedded in ZrO2 thin-films were employed to absorb electron radiation. Both PE and TE influenc...

Modern dental X-ray examinations are essential for diagnosis. The goal of this paper is to demonstrate time dependent behavior of dose providing parameters, which help to determine equipment’s age effects on the x-ray machine parameters. Also the comparisons between two different dental X-ray generator equipment types half-period and high frequency...

To characterize nanoobjects, a non-contact technique is preferable. Low energy electron has a mean free path on in a solid that is on order of nanoscale. Emission of these electrons from a solid is considered to characterize nanoobjects for sensing applications. This paper considers applications and limitations of weak electron emission for chemica...

PbS nanodots embedded in a zirconium oxide nanofilm were explored as possible ultraviolet (UV) sensors for nanodosimetry purposes. The nanodots were excited by ultraviolet photons to get emission of weak electrons. The emitted charge correlated to UV exposure indicates that PbS nanodots have potential for use as UV sensors for nanodosimetry.

Poly methyl metha acrylate (PMMA) is widely used for eye prostheses and contact lenses. These devices are worn outdoors and, therefore, exposed to the ultraviolet radia-tion of Sun. This may cause changes in PMMA properties and bring discomfort to the patient, for instance, because of poly-mer surface wettability alteration. Namely, alteration of w...

Ultraviolet (UV) radiation is able to cause biological changes at the cellular and molecular level. To study biological effects of UV radiation, UV detector is required. 10 monolayer thick ferroelectric P(VDF-TrFE) films consisting of 70% vinylidene fluoride (VDF) and 30% trifluoroethylene (TrFE), or P(VDF-TrFE 70:30), were investigated as a possib...

The electronic structure and self-polarization of P(VDF-TrFE) Langmuir-Blodgett nanofilms were analyzed under temperature-driven phase transitions, according to their thickness, composition, and structural conformation. Both thermo-stimulated exoelectron emission (TSEE) spectroscopy and computational simulation, including quantum-chemical calculati...

Virus like particles (VLP) are used to transport immune response-modulating agents to target cells to treat them. In order to deliver a high concentration of VLP to the cell, a number of VLP can be attached to a nanoparticle to be used as a nanolorry. In this study, SiO2 nanoparticles were attached to Hepatitis B VLP. Spectrophotometry measurements...

Poly methyl metha acrylate (PMMA) is widely used for eye prostheses and contact lenses. These devices are worn outdoors and, therefore, exposed to the ultraviolet radiation of Sun. This may cause changes in PMMA properties and bring discomfort to the patient, for instance, because of polymer surface wettability alteration. Namely, alteration of wet...

The influence of hydrogenation on the biocompatibility of different hydroxyapatite (HAP) materials was tested. Materials consisted of pure HAP, HAP substituted with manganese (Mn+2) and with magnesium (Mg+2) - all axially pressed and conventionally sintered for 2 h at 1200 °C pure HAP isostatic pressed and sintered by a microwave technique for 15 m...