Radu Hristu

Radu Hristu
Polytechnic University of Bucharest | UPB · Center for Microscopy-Microanalysis and Information Processing

PhD

About

105
Publications
9,821
Reads
How we measure 'reads'
A 'read' is counted each time someone views a publication summary (such as the title, abstract, and list of authors), clicks on a figure, or views or downloads the full-text. Learn more
1,020
Citations
Citations since 2016
56 Research Items
732 Citations
2016201720182019202020212022050100150
2016201720182019202020212022050100150
2016201720182019202020212022050100150
2016201720182019202020212022050100150
Introduction
Education
October 2007 - July 2012
Polytechnic University of Bucharest
Field of study
  • Electronics
October 2002 - June 2007
Polytechnic University of Bucharest
Field of study
  • Electronics

Publications

Publications (105)
Article
Second harmonic generation microscopy (SHG) is generally acknowledged as a powerful tool for the label-free three-dimensional visualization of tissues and advanced materials, with one of its most popular applications being collagen imaging. Despite the great need, progress in super-resolved SHG imaging lags behind the developments reported over the...
Preprint
Full-text available
Investigation techniques based on tip-enhanced optical effects, capable to yield spatial resolutions down to nanometers level, have enabled a wide palette of important discoveries over the past twenty years. Recently, their underlying optical setups are beginning to emerge as useful tools to modify and manipulate matter with nanoscale spatial resol...
Preprint
Full-text available
Chromium Nitride thin films are known for their good mechanical properties. We present the characteristics of ultrathin Chromium Nitride films under 400 nm thickness deposited on silicon substrates by direct current and high-power impulse magnetron sputtering techniques. The methods of investigation of the CrN films were scanning electron microscop...
Preprint
Full-text available
When the cornea becomes hydrated above its physiologic level it begins to significantly scatter light, loosing transparency and thus impairing eyesight. This condition, known as corneal edema, can be associated with different causes, such as corneal scarring, corneal infection, corneal inflammation, and others, making it difficult to diagnose and q...
Article
Full-text available
In the present study, we report the development and characterization of composite layers (by spin coating) based on magnesium-doped hydroxyapatite in a chitosan matrix, (Ca10−xMgx(PO4)6(OH)2; xMg = 0, 0.08 and 0.3; HApCh, 8MgHApCh and 30MgHApCh). The MgHApCh composite layers were investigated using scanning electron microscopy (SEM), energy-dispers...
Preprint
Full-text available
Second Harmonic Generation Microscopy (SHG) is generally acknowledged as a powerful tool for the label-free 3D visualization of tissues and advanced materials, with one of its most popular applications being collagen imaging. Although the great need, progress in super-resolved SHG imaging lags behind the developments reported over the past years in...
Article
Full-text available
Second harmonic generation (SHG) microscopy is acknowledged as an established imaging technique capable to provide information on the collagen architecture in tissues that is highly valuable for the diagnostics of various pathologies. The polarization-resolved extension of SHG (PSHG) microscopy, together with associated image processing methods, re...
Article
Full-text available
Scattering-type scanning near-field optical microscopy (s-SNOM) has emerged over the past years as a powerful characterization tool that can probe important properties of advanced materials and biological samples in a label-free manner, with spatial resolutions lying in the nanoscale realm. In this work, we explore such usefulness in relationship w...
Article
Full-text available
Two-photon microscopy techniques are non-linear optical imaging methods which are gaining momentum in the investigation of fixed tissue sections, fresh tissue or even for in vivo experiments. Two-photon excited fluorescence and second harmonic generation are two non-linear optical contrast mechanisms which can be simultaneously used for offering co...
Conference Paper
The local refractive index of polymethyl methacrylate is modified due to low power femtosecond laser exposure in the proximity of a sharp metallic tip. Such modified nanoscale-sized regions can be used for photonic crystals creation.
Article
The spread of Acinetobacter baumannii in clinical settings is a great concern at the time being, given the epidemic potential and the capacity to elude the effects of drugs of this bacterial species. How A. baumannii achieves its resistance determinants is not yet exactly understood, hence the need for new studies aimed at resolving its structu...
Article
Second harmonic generation (SHG) microscopy has emerged over the past two decades as a powerful tool for tissue characterization and diagnostics. Its main applications in medicine are related to mapping the collagen architecture of in-vivo, ex-vivo and fixed tissues based on endogenous contrast. In this work we present how H&E staining of excised a...
Article
Full-text available
Hydroxyapatite Ca10(PO4)6(OH)2 (HAp) is an important bioactive material for bone tissue reconstruction, due to its highly thermodynamic stability at a physiological pH without bio-resorption. In the present study, the Ag:HAp and the corresponding Ag:HAp + D3 thin films (~200 nm) coating were obtained by vacuum deposition method on Ti substrate. The...
Article
Full-text available
Background In recent years, a variety of imaging techniques operating at nanoscale resolution have been reported. These techniques have the potential to enrich our understanding of bacterial species relevant to human health, such as antibiotic-resistant pathogens. However, owing to the novelty of these techniques, their use is still confined to add...
Article
Full-text available
Polarization-resolved second harmonic generation microscopy is used to provide pixel-level angular distribution of collagen in thyroid nodule capsules. The pixel-level angular distribution is combined with textural analysis to quantify the collagen distribution in follicular adenoma (benign) and papillary thyroid carcinoma (malignant). Three second...
Article
Papillary carcinoma is the most prevalent type of thyroid cancer. Its diagnosis requires accurate and subjective analyses from expert pathologists. Here we propose a method based on the Hough transform (HT) to detect and objectively quantify local structural differences in collagen thyroid nodule capsules. Second harmonic generation (SHG) microscop...
Article
Super‐resolution microscopy techniques can provide answers to still pending questions on prokaryotic organisms but are yet to be employed at their full potential for this purpose. To address this, we evaluate the ability of the rhodamine‐like KK114 dye to label various types of bacteria, to enable imaging of fine structural details with Stimulated...
Article
Placed at the junction of laser-scanning and probe-scanning techniques, scattering scanning near-field optical microscopy (s-SNOM) is a promising tool for the optical investigation of surfaces at nanoscale resolution. In this work we expand the current possibilities of representing s-SNOM data by coupling typical s-SNOM results (amplitude and phase...
Article
Scattering-type Scanning Near Field Optical Microscopy (s-SNOM) is currently regarded as a powerful tool for exploring important optical properties at nanoscale resolutions depending only on the size of a sharp tip that is scanned across the sample surface while being excited with a focused laser beam. Recently, it was shown that, among others, s-S...
Article
Full-text available
Histopathological image analysis performed by a trained expert is currently regarded as the gold-standard for the diagnostics of many pathologies, including cancers. However, such approaches are laborious, time consuming and contain a risk for bias or human error. There is thus a clear need for faster, less intrusive and more accurate diagnostic so...
Article
Full-text available
In this study, the results about the influence of the surface morphology of layers based on montmorillonite (MMT) and silver (Ag) on antimicrobial properties are reported. The coating depositions were performed in the plasma of a radio frequency (RF) magnetron sputtering discharge. The studied layers were single montmorillonite layers (MMT) and sil...
Article
Full-text available
Despite intense research on high entropy films, the mechanism of film growth and the influence of key factors remain incompletely understood. In this study, high entropy films consisting of five elements (FeCoNiCrAl) with columnar and nanometer-scale grains were prepared by magnetron sputtering. The high entropy film growth mechanism, including the...
Article
Full-text available
Quantitative second harmonic generation microscopy methods that provide an estimate for the molecular structure of collagen in tissues by fitting theoretical models with experimental data at pixellevel are gaining increasing momentum. Such methods offer reliable diagnostic-relevant information that complement traditional histology procedures. We pr...
Preprint
Full-text available
Histopathological image analysis performed by a trained expert is currently regarded as the gold-standard in the case of many pathologies, including cancers. However, such approaches are laborious, time consuming and contain a risk for bias or human error. There is thus a clear need for faster, less intrusive and more accurate diagnostic solutions,...
Article
Full-text available
Quantitative second harmonic generation microscopy was used to investigate collagen organization in the fibrillar capsules of human benign and malignant thyroid nodules. We demonstrate that the combination of texture analysis and second harmonic generation images of collagen can be used to differentiate between capsules surrounding the thyroid foll...
Article
Full-text available
A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has not been fixed in the paper.
Conference Paper
We discuss an imaging approach that allows a better understanding of nanoscale datasets collected with Apertureless Scanning Near-Field Optical Microscopy, based on a multimodal system that incorporates multiple ASNOM and far-field Laser Scanning Microscopy variants.
Article
Full-text available
Apertureless scanning near-field optical microscopy (ASNOM) has attracted considerable interest over the past years as a result of its valuable contrast mechanisms and capabilities for optical resolutions in the nanoscale range. However, at this moment the intersections between ASNOM and the realm of bioimaging are scarce, mainly due to data interp...
Article
Full-text available
Second harmonic generation (SHG) microscopy represents a very powerful tool for tissue characterization. Polarization-resolved SHG (PSHG) microscopy extends the potential of SHG, by exploiting the dependence of SHG signals on the polarization state of the excitation beam. Among others, this dependence translates to the fact that SHG images collecte...
Article
We present a novel method for nanoscale reconstruction of complex refractive index by using scattering-type Scanning Near-field Optical Microscopy (s-SNOM). Our method relies on correlating s-SNOM experimental image data with computational data obtained through simulation of the classical oscillating point-dipole model. This results in assigning a...
Article
Full-text available
Although silicon carbide is a highly promising crystalline material for a wide range of electronic devices, extended and point defects which perturb the lattice periodicity hold deep implications with respect to device reliability. There is thus a great need for developing new methods that can detect silicon carbide defects which are detrimental to...
Article
Full-text available
The goal of this paper was to investigate the antifungal activity of Enamel layers deposited on titanium substrate (Ti-Enamel) and Enamel layers deposited on titanium substrate previously coated with a vinyl polydimethylsiloxane layer (Ti-PDMS-Enamel). The physicochemical properties were also investigated. The Candida albicans biofilm development o...
Article
Imaging tissue samples by polarization‐resolved second harmonic generation microscopy provides both qualitative and quantitative insights into collagen organization in a label‐free manner. Polarization‐resolved second harmonic generation microscopy goes beyond simple intensity‐based imaging by adding the laser beam polarization component and applyi...
Article
This study investigates the morphology, composition and corrosion resistance of hot dip galvanized (HDG) steel panels treated by immersion in NaCl solution in the presence of six protective compounds: 8-hydroxyquinoline, 2-mercaptobenzothiazole, 5-amino-1,3,4-thiadiazole-2-thiol, calcium phosphate, cerium nitrate and sodium molybdate. The results r...
Article
Scattering scanning near-field optical microscopy has become in the past decade a powerful tool for high-resolution optical investigations. However, a deeper understanding of the signal detection, demodulation and reconstruction techniques is still required. In this paper we use the mathematical concept that forms the base for modulation/demodulati...
Article
Nano-engineered polyelectrolyte capsules (NPCs) were investigated using a multimodal approach based on Confocal Laser Scanning Microscopy, scattering-type Scanning Near-Field Optical Microscopy and Atomic Force Microscopy. Our experiment demonstrates that correlating optical information collected with far-field and near-field techniques and topogra...
Conference Paper
In our work we present some investigations on biological samples at micro and nanoscale by using nonlinear effects in laser scanning microscopy techniques. We developed an integrated multimodal system that allows for the simultaneous image acquisition from multiple optical imaging modalities. Our system includes several microscopy techniques workin...
Article
Full-text available
Nonlinear Laser Scanning Microscopy (NLSM) techniques have been demonstrated in the past two decades as powerful imaging tools for disease diagnostics (DD). Currently, in most DD related experiments the interpretation of NLSM data sets is performed by trained specialists. Such approaches are both time consuming and prone to errors due to inter- and...
Article
Full-text available
Laser Scanning Microscopy Techniques such as Confocal Microscopy, Two Photon Excitation Microscopy, Second Harmonic Generation Microscopy or Fluorescence Lifetime Imaging have been successfully employed to date for imaging skin cancer. However, the resolution that such techniques can provide is limited by diffraction, which prevents accurately imag...
Article
Complementary laser scanning microscopy micrographs are considered as pairs consisting in a master image (MI) and a slave image (SI), the latter with potential for facilitating the interpretation of the MI. We propose a strategy based on reversible watermarking for embedding a lossy compressed version of the SI into the MI. The use of reversible wa...
Article
Complementary laser scanning microscopy micrographs are considered as pairs consisting in a master image (MI) and a slave image (SI), the latter with potential for facilitating the interpretation of the MI. We propose a strategy based on reversible watermarking for embedding a lossy compressed version of the SI into the MI. The use of reversible wa...
Article
Scattering scanning near-field optical microscopy (s-SNOM) has been demonstrated as a valuable tool for mapping the optical and optoelectronic properties of materials with nanoscale resolution. Here we report experimental evidence that trapped electric charges injected by an electron beam at the surface of dielectric samples affect the sample-dipol...
Article
Full-text available
The goal of this study was the preparation, physicochemical characterization, and microbiological evaluation of novel hydroxyapatite doped with silver/polydimethylsiloxane (Ag:HAp-PDMS) composite layers. In the first stage, the deposition of polydimethylsiloxane (PDMS) polymer layer on commercially pure Si disks has been produced in atmospheric pre...
Article
Full-text available
A new composite matrix was developed for a cutting tool based on tungsten carbide ligated with cobalt (WC-Co) using sintering technique. The admixtures of niobium carbide, tantalum carbide, and titanium carbide with the WC-Co matrix aim to inhibit the grain growth of WC and to promote covalent bonding at the interface. The modified WC-Co tools were...
Article
Electron beam irradiation which is considered a reliable method for tailoring the surface charge of hydroxyapatite is hindered by carbon contamination. Separating the effects of the carbon contamination from those of irradiation-induced trapped charge is important for a wide range of biological applications. In this work we focus on the understandi...
Article
The Bag-of-Features (BoF) paradigm has been introduced to the field of computer vision about a decade ago. Since then, its potential for image classification and retrieval tasks has been demonstrated in numerous experiments, which contributed to BoF approaches becoming well-established in the field. The BoF methods reported to date use mainly spati...
Article
This study evaluates the corrosion inhibitive abilities of ammonium phosphate dibasic, 8-hydroxyquinoline, calcium fluoride, sodium fluoride, sodium dodecylbenzenesulfonate and zinc nitrate with respect to the protection of the magnesium ZK30 alloy to NaCl solution. A set of characterization assays addressing morphology, composition and structural...