Search

We use in situ high-pressure neutron powder diffraction to study elastic properties of Fe3O4 magnetite nanoparticles of different sizes. It is found that nanoparticles are elastically softer than the bulk. Apart from the smallest nanoparticle of diameter 8 nm, the atomic and magnetic structures do not change significantly with nanoparticle size or pressure. The 8 nm sample appears to take a disordered spinel structure instead of the inverse spinel structure of the bulk and larger nanoparticles, as seen in bond lengths and magnetic structures. Synchrotron x-ray total scattering was used to support this interpretation. Furthermore, this study suggests that the influence of magnetic disorder at the nanoparticle surface is significant for the size of 8 nm. [ABSTRACT FROM AUTHOR]

Nanocrystalline Ge films were prepared by isotropic chemical etching on single-crystalline Ge substrates with 100 and 111 orientations. The structural and optical properties have been investigated by transmission electron microscopy (TEM), electron diffraction (ED), Raman photoluminescence (PL), and infrared spectroscopy. The average size of nanocrystals (NCs) was estimated by fitting of the Raman spectra using a phonon-confinement model developed for spherical semiconductor NCs. Considered collectively TEM, ED, and Raman results indicate that all films contain high density of 3–4 nm diameter, diamond-structured Ge NCs with disordered surfaces. There are indications that surface of nanoparticles is mainly hydrogen terminated even for air-stabilized samples. Red PL is observed at room temperature upon excitation by 1.96 eV with peak energy of ∼1.55 eV and correlates well with recent theoretical calculations of the enlarged optical gap in Ge NCs of similar size. [ABSTRACT FROM AUTHOR]

The influence of high pressure in the range of 0–15 GPa on the linewidth and the position of the Raman G band is investigated for graphene‐based materials with controlled crystallite sizes, La, obtained from pitch‐based cokes by increasing annealing temperature. It is observed that the linewidth of the G band increases significantly above the critical pressure, Pc ≈ 10 GPa, for all samples, whereas at atmospheric pressure, the linewidth neither depends on variation in the measurement temperature (<400 K) nor on excitation wavelengths. The crystallite size (varied using different annealing temperatures) is found not to influence the critical pressure associated with the modification of carbon hybridization. At the same time, the G band linewidth increases significantly for smaller crystallite sizes depending on the annealing temperature at atmospheric pressure due to the merging of the D′ and G phonon bands. This merging of the bands can be explained by a single phonon involved in two physical Raman processes, which cannot be discriminated. [ABSTRACT FROM AUTHOR]

Carbon nanoparticles are relatively new and promising area of research receiving increasingly growing attention. They are small, cheap to produce, and do not contain potentially toxic components while showing bright and tunable light emission. They can thus potentially replace inorganic quantum dots in applications such as bioimaging, solar cells, photocatalysis and sensor applications. Units of nanometer size carbon dots (CDs) stable in aqueous solutions with photoluminescence in visible range can be obtained in one-step synthesis from variety of available materials. Currently, application of CDs is restricted by the lack of understanding of fundamental relationship between synthesis routes (and ingredients including raw materials), CDs' structure and CDs' properties. This review is focused on evaluating recent trends in CDs research and application, including CDs synthesis, understanding of their photoluminescent properties. We also discuss the principles, perspectives and current limitations in CDs applications. [ABSTRACT FROM AUTHOR]

The rotational dynamics of microparticles in liquids have a wide range of applications, including chemical microreactors, biotechnologies, microfluidic devices, tunable heat and mass transfer, and fundamental understanding of chiral active soft matter which refers to systems composed of particles that exhibit a handedness in their rotation, breaking mirror symmetry at the microscopic level. Here, we report on the study of two effects in colloids in rotating electric fields: (i) the rotation of individual colloidal particles in rotating electric field and related to that (ii) precession of pairs of particles. We show that the mechanism responsible for the rotation of individual particles is related to the time lag between the external field applied to the particle and the particle polarization. Using numerical simulations and experiments with silica particles in a water-based solvent, we prove that the observed rotation of particle pairs and triplets is governed by the tunable rotation of individual particles and can be explained and described by the action of hydrodynamic forces. Our findings demonstrate that colloidal suspensions in rotating electric fields, under some conditions, represent a novel class of chiral soft active matter—tunable colloidal spinners. The experiments and the corresponding theoretical framework we developed open novel prospects for future studies of these systems and for their potential applications. [ABSTRACT FROM AUTHOR]

The article suggests that science and technology in the U.S., England, the Union of Soviet Socialist Republics (U.S.S.R.), and France was influenced by Nazi Germany. It states that Germany's intention to dominate the world led them to concentrate their research and engineering potential from 1938 to 1943 to developing military weapons including jet fighters, missiles, and nuclear submarines. Germany's defeat gave the technologies to the Allied powers who improved on them after the war.

Raman excitation and emission spectra for the radial breathing mode (RBM) are reported, together with a preliminary analysis. From the position of the peaks on the two-dimensional plot of excitation resonance energy against Raman shift, the chiral indices (m, n) for each peak are identified. Peaks shift from their positions in air when different pressure media are added – water, hexane, sulphuric acid – and when the nanotubes are unbundled in water with surfactant and sonication. The shift is about 2–3 cm−1 in RBM frequency, but unexpectedly large in resonance energy, being spread over up to 100 meV for a given peak. This contrasts with the effect of pressure. The shift of the peaks of semiconducting nanotubes in water under pressure is orthogonal to the shift from air to water. This permits the separation of the effects of the pressure medium and the pressure, and will enable the true pressure coefficients of the RBM and the other Raman peaks for each (m, n) to be established unambiguously. [ABSTRACT FROM PUBLISHER]

This article describes heat-resistant thermally insulating concrete mixtures and products with phosphate and aluminate binders, their properties, and the main processes used to make them. The thermophysical properties required of thermal insulation are obtained together with an increase in its strength thanks to the production of denser but less heat-conducting concretes with fillers composed of aluminum microspheres. [ABSTRACT FROM AUTHOR]

Abstract: We present a scanning electron microscopy study of interaction of porous silicon prepared by stain etching with rat hippocampal neurons (B50, immortalised line). Porous Si has been prepared by stain etching both from crystalline and polycrystalline substrates. Two types of patterns have been examined: (i) 100μm square pads separated by 100μm of untreated space and (ii) 30μm and 100μm stripes separated by 300μm of untreated surface. In all cases cells show clear preference in adhesion to porous Si over untreated surface. We observe a much closer attachment of the cell to the surface of porous Si than has been anticipated before with the gap between a cell and porous surface of no more than 20nm. This study demonstrates the influence of surface topology on proliferation of a neuron network, thus suggesting that a degree of control over cell growth pattern can be achieved using porous material alone. We show that the network pattern on porous Si is influenced by a single neuron response to the surface nature and topology. [Copyright &y& Elsevier]

Camera‐based super‐resolution approaches surpass the diffraction limit of conventional optical microscopy by relying on the stochastic activation and precise localization of fluorescent molecules. However, traditional probes such as organic dyes and quantum dots present challenges such as photobleaching and blinking variability, which limit their application in super‐resolution imaging, particularly in non‐liquid environments. Herein, the study demonstrates the potential of gold nanoparticles as a promising alternative for localization‐based super‐resolution imaging. The study specifically investigates how different surface functionalizations and states (aggregated vs isolated) of gold nanoparticles impact their photoluminescence properties, including fluorescence intensity, lifetime, and blinking behavior. By leveraging the intrinsic photoluminescence of gold nanoparticles, their capability is demonstrated as probes to achieve super‐resolution imaging of nano‐sized structures, at a resolution down to 100 nm, without the need for conventional imaging buffers. These proof‐of‐concept applications, which include imaging of silica nanosized wrinkles and logos, reveal that gold nanoparticles exhibit superior photophysical properties compared to common organic fluorophores, offering a promising alternative for super‐resolution imaging. This work paves the way for the application of super‐resolution fluorescence microscopy in materials science where non‐liquid environments often restrict the use of traditional probes. [ABSTRACT FROM AUTHOR]

A zinc oxide (ZnO) nanorod array exhibiting an intense deep-level emission (DLE) was probed at the Zn K edge (9659 eV) using extended x-ray absorption fine structure (EXAFS) analysis. X-ray excited optical luminescence was used to obtain site-specific information around the absorbing Zn atom using optically detected EXAFS (ODXAS). The visible-emission corresponds to defects in ZnO crystal lattice introduced during growth. A comparative study between red (660 nm) and green (500 nm) DLE was conducted by collecting specific wavelength emissions of the optically detected x-ray absorption spectra. It was shown that red emission primarily originates from the nanorod surface, and green emission was linked to disorder occurring on Zn sites. We show that ODXAS can distinguish between two emission regions and provides a platform to link defect emission with specific crystal structures. [ABSTRACT FROM AUTHOR]

Apoptosis signal-regulating kinase 1 (ASK1) has recently emerged as an attractive molecular target for pharmaceutical intervention. Several classes of small-molecular ASK1 inhibitors have been identified. In this article, we analysed the binding of small-molecular inhibitors from different chemotypes with ASK1 using molecular dynamic simulations. The umbrella sampling technique was used to calculate the binding free energy (ΔG) for these compounds with ASK1 ATP-binding pocket. According to the obtained results, umbrella sampling gave correct ranking of the binding affinities for investigated inhibitors relative to their experimental pIC50 values and can be useful for further structure-based design of ASK1 inhibitors to accelerate lead optimisation. Trial registration: ClinicalTrials.gov identifier: NCT02466516.. [ABSTRACT FROM AUTHOR]

Nowadays luminescent carbon-based nanoparticles can be synthesized by a wide range of physical and chemical methods from a large variety of carbon-based sources. However, in most of the cases the product of synthesis is a complex mixture of compounds, which results in significant challenges in understanding the structure and optical properties of the reaction products. Consequently, a number of separation and purification methodologies have been developed to alleviate these challenges. In this review, we provide a detailed analysis of the current state of the art for methods of luminescent carbon nanoparticles separation and purification. We specifically target such methods as sucrose density gradient centrifugation, chromatography techniques, and electrophoresis because of their ability for fine separation of the reaction products with into a number of fractions. The aim of our comparative analysis is to help development of future strategies for reaction product separation and purification leading to a better understanding of carbon nanoparticles structure and luminescent mechanism as well as to underpin their applications. Unlabelled Image • None of the methods for CNPs' synthesis allow obtaining nanoparticles with uniform size and properties. • Centrifugation and filtration are widely used for removing larger fragments such as soot from CNPs' suspensions. • Dialysis allows addressing the problem of CNPs solution purification from smaller molecules and substances. • Techniques for fine separation will allow isolating CNPs with uniform charge, mass, size, hydrophobic or hydrophilic nature. [ABSTRACT FROM AUTHOR]

ZnO nanorods synthesised using an aqueous pH 11 solution are shown to exhibit surface-sensitive morphology post-annealing in oxygen, air, and nitrogen as shown by scanning electron microscopy and transmission electron microscopy analysis. Raman analysis confirms the nanorods were nitrogen-doped and that nitrogen incorporation takes place during the synthesis procedure in the form of N-Hx. A strong green photoluminescence is observed post-annealing for all samples, the intensity of which is dependent on the atmosphere of anneal. This luminescence is linked to zinc vacancies as recent reports have indicated that these defects are energetically favoured with the annealing conditions used herein. ZnO-nanorod/CuSCN diodes are fabricated to examine the effect of material properties on photodetector device performance. The devices exhibit a photocurrent at zero bias, creating a self-powered photodetector. A photocurrent response of 30 μA (at 6 mW cm-2 irradiance) is measured, with a rise time of ∼25 ns, and sensitivity to both UV and visible light (475-525 nm). [ABSTRACT FROM AUTHOR]

Presents an obituary for British physicist Susan Caroline Bayliss.

Accurate analysis of pair correlations in condensed matter allows us to establish relations between structures and thermodynamic properties and, thus, is of high importance for a wide range of systems, from solids to colloidal suspensions. Recently, the interpolation method (IM) that describes satisfactorily the shape of pair correlation peaks at short and at long distances has been elaborated theoretically and using molecular dynamics simulations, but it has not been verified experimentally as yet. Here, we test the IM by particle-resolved studies with colloidal suspensions and with complex (dusty) plasmas and demonstrate that, owing to its high accuracy, the IM can be used to experimentally measure parameters that describe interaction between particles in these systems. We used three- and two-dimensional colloidal crystals and monolayer complex (dusty) plasma crystals to explore suitability of the IM in systems with soft to hard-sphere-like repulsion between particles. In addition to the systems with pairwise interactions, if many-body interactions can be mapped to the pairwise ones with some effective (e.g., density-dependent) parameters, the IM could be used to obtain these parameters. The results reliably show that the IM can be effectively used for analysis of pair correlations and interactions in a wide variety of systems and therefore is of broad interest in condensed matter, complex plasma, chemical physics, physical chemistry, materials science, and soft matter. [ABSTRACT FROM AUTHOR]

Abstract: Excimer laser ablation at 308nm has been used to texture the surfaces of a variety of materials of interest for optoelectronic and biotechnological applications. Using a range of pre- and post-processing methods, we are able to produce nano-, micro- and meso-scale features over large areas rapidly in materials such as crystalline Si, porous silicon and TiO2. Texturing of porous silicon leads to the growth of crystalline dendritic structures, which distinguishes them dramatically from the conical pillars formed from crystalline silicon. Regular arrays of Si microdots are formed by irradiating a Si surface pre-covered with a Cr thin film grating. Nano-crystalline porous TiO2 films are easily ablated or compacted with laser irradiation. However, at low enough laser fluence, surface roughening without complete loss of porosity is possible. [Copyright &y& Elsevier]

[Display omitted] Many-body forces play a prominent role in structure and dynamics of matter, but their role is not well understood in many cases due to experimental challenges. Here, we demonstrate that a novel experimental system based on rotating electric fields can be utilised to deliver unprecedented degree of control over many-body interactions between colloidal silica particles in water. We further show that we can decompose interparticle interactions explicitly into the leading terms and study their specific effects on phase behaviour. We found that three-body interactions exert critical influence over the phase diagram domain boundaries, including liquid-gas binodal, critical and triple points. Phase transitions are shown to be reversible and fully controlled by the magnitude of external rotating electric field governing the tunable interactions. Our results demonstrate that colloidal systems in rotating electric fields are a unique laboratory to study the role of many-body interactions in physics of phase transitions and in applications, such as self-assembly, offering exciting opportunities for studying generic phenomena inherent to liquids and solids, from atomic to protein and colloidal systems. [ABSTRACT FROM AUTHOR]

In this study, with the aid of Raman measurements, we have observed transformations in small (∼3 nm and ∼10 nm) free-standing Ge nanoparticles under laser light exposure. The nanoparticles were obtained by the chemical stain etching of a monocrystalline Ge wafer and of Ge powder and by colloidal synthesis route. We found that the transformation path depends on laser power and exposure time. At relatively low values of the laser power (2 mW) over a period of 100 min, the Raman signal indicates transformation of the sample from a nanocrystaline to bulk-like state, followed by partial oxidation and finally a conversion of the entire sample into alpha-quartz type GeO2. However, when the laser power is set at 60mW, we observed a heat release during an explosive crystallization of the nanocrystalline material into bulk Ge without noticeable signs of oxidation. Together with the transmission electron microscopy measurements, these results suggest that the chemical stain etching method for the preparation of porous Ge may not be a top-down process as has been widely considered, but a bottom up one. Systematic studies of the laser exposure on Ge nanoparticles prepared by colloidal synthesis results in the fact that the explosive crystallisation is common for H-terminated and partially disordered Ge nanoparticles regardless of its particle size. We suggest possible bio-medical applications for the observed phenomena. [ABSTRACT FROM AUTHOR]

Melting is one of the most studied phase transitions important for atomic, molecular, colloidal, and protein systems. However, there is currently no microscopic experimentally accessible criteria that can be used to reliably track a system evolution across the transition, while providing insights into melting nucleation and melting front evolution. To address this, we developed a theoretical mean-field framework with the normalised mean-square displacement between particles in neighbouring Voronoi cells serving as the local order parameter, measurable experimentally. We tested the framework in a number of colloidal and in silico particle-resolved experiments against systems with significantly different (Brownian and Newtonian) dynamic regimes and found that it provides excellent description of system evolution across melting point. This new approach suggests a broad scope for application in diverse areas of science from materials through to biology and beyond. Consequently, the results of this work provide a new guidance for nucleation theory of melting and are of broad interest in condensed matter, chemical physics, physical chemistry, materials science, and soft matter. [ABSTRACT FROM AUTHOR]

Variations in the hardness of a poly (ether ether ketone) beam electrically modified with multiwalled carbon nanotubes (MWCNT, 0.5%-3%) are investigated. It is shown that both rupture and hardness variations correlate with the changes in carbon nanotube concentration when using micro indentation and extended Raman imaging. Statistical analysis of the relative spectral intensities in the Raman image is used to estimate local tube concentration and polymer crystallinity. We show that the histogram of the Raman D band across the image provides information about the amount of MWCNTs and the dispersion of MWCNTs in the composite. We speculate that we have observed a local modification of the ordering between pure and modified polymer. This is partially supported by small angle neutron scattering measurements, which indicate that the agglomeration state of the MWCNTs is the same at the concentrations studied. [ABSTRACT FROM AUTHOR]

The change in dispersion of high-frequency excitations in fluids, from an oscillating solidlike to a monotonic gaslike one, is shown for the first time to affect thermal behavior of heat capacity and the q-gap width in reciprocal space. With in silico study of liquified noble gases, liquid iron, liquid mercury, and model fluids, we established universal bilinear dependence of heat capacity on q-gap width, whereas the crossover precisely corresponds to the change in the excitation spectra. The results open novel prospects for studies of various fluids, from simple to molecular liquids and melts. [ABSTRACT FROM AUTHOR]

Newton's third law--the action-reaction symmetry--can be violated for effective interbody forces in open and nonequilibrium systems that are ubiquitous in areas as diverse as complex plasmas, colloidal suspensions, active and living soft matter, and social behavior. While studying monolayer complex plasma (confined charged particles in an ionized gas) with nonreciprocal interactions mediated by plasma flows, in silico we found that an interplay between melting and thermal activation drastically transforms the collective dynamics: the order-disorder transition modifies the system's thermal steady state so that the crystal tends to melt, whereas the fluid tends to freeze, jumping chaotically between the two states. We identified this collective chaotic behavior as strange attractors formed in a monolayer complex plasma and link the strange attractor behavior to the specifics of interparticle interactions. [ABSTRACT FROM AUTHOR]

A composition in the form of liquid polymer substance intended for embolization procedures was studied in in vivo experiment. The preparation was injected to rabbits into the femoral artery and abdominal aorta. The polymer composition exhibited properties previously demonstrated in vitro: strong adhesion to the vascular wall, high plasticity sufficient for embolization of the blood vessels, distal distribution, and the absence of toxic effects. The contrast substance remained in the embolus, which simplified its further localization. The agent underwent nether resorption nor organization. Injection of the agent in a volume of 0.1 ml was sufficient for embolization of an artery with a diameter of 0.1 cm. The polymer composition completely obstructed the vessel without inducing perforation of its wall. During the first day of the experiment, a slight infiltration of surrounding tissues with lymphoid cells was observed. By day 7, total dry necrosis of pelvic limb distal to the injection site was diagnosed. Inflammation of the surrounding tissues was shown histologically and was considered as the body response to impaired circulation and necrosis. [ABSTRACT FROM AUTHOR]

Aim. To identify novel putative drug targets of methicillin-resistant S. aureus (MRSA) through subtractive proteome analysis. Methods. Identification of non-homologous proteins in the human proteome, search of MRSA essential genes and evaluation of drug target novelty were performed using a protein BLAST server. Unique metabolic pathways identi- fication was carried out using data and tools from KEGG (Kyoto Encyclopedia of Genes and Genomes). Prediction of sub-cellular proteins localization was performed using combination of PSORT v. 3.0.2, CELLO v. 2.5, iLoc-Gpos, and Pred-Lipo tools. Homology modeling was performed using SWISS-MODEL, Phyre2, I-TASSER web-servers and the MODELLER software. Results. Proteomes of six annotated methicillin-resistant strains : MRSA ATCC BAA-1680, H-EMRSA-15, LA MRSA ST398, MRSA 252, MRSA ST772, UTSW MRSA 55 were initially analyzed. The proteome analysis of the MRSA strains in several consequent steps allowed to identify two molecular targets: diadenylate cyclase and D-alanyl-lipoteichoic acid biosynthesis (DltB) protein which meet the requirements of being essential, membrane-bound, non-homologous to human proteome, involved in unique metabolic pathways and new in terms of not having approved drugs. Using the homology modeling approach, we have built three-dimensional structures of these proteins and predicted their ligand-binding sites. Conclusions. We used classical bioinformatics approaches to identify two molecular targets of MRSA :diadenylate cyclase and DltB which can be used for further rational drug design in order to find novel therapeutic agents for treatment of multidrug resistant staphylococcal infection. [ABSTRACT FROM AUTHOR]

• A new one-step facile method for in-situ GNPs biofunctionalization is described. • Functionalization was performed using hydrothermal treatment of folate and GNPs suspension. • Hydrothermal treatment increases the light emission from the pterin moiety of folate. • Successful functionalization of GNPs with folate is confirmed by binding with specific antibody. A new fundamental concept for one-step in-situ functionalization of gold nanoparticles (GNPs) with folic acid using hydrothermal treatment is described. Hydrothermal treatment has been tuned to increase the light emission from the pterin moiety of folic acid molecule, while retain its structure and functionality, thus providing a simple route to multimodal tags for a variety of in vitro and in vivo biomedical applications. Successful functionalization of GNPs with the biological ligand is confirmed by specific binding with anti-folic acid antibody. [ABSTRACT FROM AUTHOR]

Persistent pain remains a major health issue: common treatments relying on either repeated local injections or systemic drug administration are prone to concomitant side-effects. It is thought that an alternative could be a multifunctional cargo system to deliver medicine to the target site and release it over a prolonged time window. We nano-engineered microcapsules equipped with adjustable cargo release properties and encapsulated the sodium-channel blocker QX-314 using the layer-by-layer (LbL) technology. First, we employed single-cell electrophysiology to establish in vitro that microcapsule application can dampen neuronal excitability in a controlled fashion. Secondly, we used two-photon excitation imaging to monitor and adjust long-lasting release of encapsulated cargo in target tissue in situ. Finally, we explored an established peripheral inflammation model in rodents to find that a single local injection of QX-314-containing microcapsules could provide robust pain relief lasting for over a week. This was accompanied by a recovery of the locomotive deficit and the amelioration of anxiety in animals with persistent inflammation. Post hoc immunohistology confirmed biodegradation of microcapsules over a period of several weeks. The overall remedial effect lasted 10-20 times longer than that of a single focal drug injection. It depended on the QX-314 encapsulation levels, involved TRPV1-channel-dependent cell permeability of QX-314, and showed no detectable side-effects. Our data suggest that nano-engineered encapsulation provides local drug delivery suitable for prolonged pain relief, which could be highly advantageous compared to existing treatments. [ABSTRACT FROM AUTHOR]

We report an effective and simple method for separation of carbon nanodots (CNDs) by size-exclusion chromatography that yields CNDs fractions with different sizes and luminescent properties. As a result, three major types of CNDs with spectrally distinct luminescent centers were identified. The first type of luminescent particles has emission maxima at about 400–440 nm, the highest size and luminescence intensity. CNDs of the second type have a middle size and the lowest luminescence intensity with emission maxima in the range 450–470 nm. The distinctive feature of these two fractions is the excitation-dependent shift of the emission maxima to longer wavelengths. The third type of CNDs has luminescence around 520 nm with no emission shift upon the increase of excitation wavelength and the smallest size. The observed spectral variations in different fractions correlate with a change in average particle size as seen in TEM images. Size fractionation of CNDs mixture is very important to many fields, mostly for bioimaging and medicine applications because it leads to CNDs' unified distribution and behavior. Dilution of CNDs in water suspension leads to the increase of emission intensity and shifts the PL spectra to shorter wavelengths providing evidence for concentration quenching effect in CNDs. [ABSTRACT FROM AUTHOR]

Persistent pain remains a major health issue: common treatments relying on either repeated local injections or systemic drug administration are prone to concomitant side-effects. It is thought that an alternative could be a multifunctional cargo system to deliver medicine to the target site and release it over a prolonged time window. We nano-engineered microcapsules equipped with adjustable cargo release properties and encapsulated the sodium-channel blocker QX-314 using the layer-by-layer (LbL) technology. First, we employed single-cell electrophysiology to establish in vitro that microcapsule application can dampen neuronal excitability in a controlled fashion. Secondly, we used two-photon excitation imaging to monitor and adjust long-lasting release of encapsulated cargo in target tissue in situ. Finally, we explored an established peripheral inflammation model in rodents to find that a single local injection of QX-314-containing microcapsules could provide robust pain relief lasting for over a week. This was accompanied by a recovery of the locomotive deficit and the amelioration of anxiety in animals with persistent inflammation. Post hoc immunohistology confirmed biodegradation of microcapsules over a period of several weeks. The overall remedial effect lasted 10-20 times longer than that of a single focal drug injection. It depended on the QX-314 encapsulation levels, involved TRPV1-channel-dependent cell permeability of QX-314, and showed no detectable side-effects. Our data suggest that nano-engineered encapsulation provides local drug delivery suitable for prolonged pain relief, which could be highly advantageous compared to existing treatments. [ABSTRACT FROM AUTHOR]

Aim. To search for new CK2 inhibitors by virtual screening. Methods. Virtual screening of a small organic compounds library was performed by molecular docking using the Autodock 4.2.6 package and pharmacophore screening with the “PharmDeveloper” program. The compound activity was determined by in vitro biochemical tests using γ-P32 ATP. Results. 298 compounds were selected for biochemical testing according to the results of virtual screening. In vitro experiments showed that 18 compounds have inhibitory activity against CK2 with IC50 in the range of 1.4 to 20 μM. The active compounds belonged to 15 chemical classes. Conclusions. A number of effective CK2 inhibitors were found using molecular modeling and biochemical testing methods. LE values of these compounds were higher than 0.3 that makes these compounds excellent candidates for further drug development. [ABSTRACT FROM AUTHOR]

We examined sensitivity of the x-ray absorption near edge structure (XANES) to the local atomic arrangements in amorphous GaSb and nanoscale Ge. We demonstrate that XANES can be reliably used to obtain information about the local symmetry in these systems where lack of periodicity precludes the use of powerful diffraction methods. We used well-studied bulk amorphous GaSb as a reference to verify our approach and then extended it to matrix-free Ge nanoparticles. We show that in small (~ 4 nm) Ge nanoparticles prepared by colloidal synthesis where there is evidence for structural disorder, the local tetrahedral (diamond-type) symmetry is still preserved out to the second coordination shell on average. We find the XANES data collected in transmission and optical detection modes for Ge nanoparticles show distinctive differences with the bulk samples and attribute this to particles size and surface effects. This approach is thus capable of delivering structural information on local symmetry, structure and morphology in nanoscale systems. [ABSTRACT FROM AUTHOR]

The sensitivity of X-ray absorption near-edge structure (XANES) to the local symmetry has been investigated in small (∼4 nm) matrix-free Ge quantum dots. The FDMNES package was used to calculate the theoretical XANES spectra that were compared with the experimental data of as-prepared and annealed nanoparticles. It was found that XANES data for an as-prepared sample can only be adequately described if the second coordination shell of the diamond-type structural model is included in the FDMNES calculations. This is in contrast to the extended X-ray absorption fine-structure data that show only the first-shell signal. These results suggest that, despite the high degree of disorder and a large surface-to-volume ratio, as-prepared small Ge quantum dots retain the diamond-type symmetry beyond the first shell. Furthermore, we utilized this sensitivity of XANES to the local symmetry to study annealed Ge quantum dots and found evidence for significant structural distortion which we attribute to the existence of surface disorder in the annealed oxygen-free Ge quantum dots. [ABSTRACT FROM AUTHOR]

Over the last two decades, it hasbeen demonstrated that size effects have significant consequencesfor the atomic arrangements and phase behavior of matter under extremepressure. Furthermore, it has been shown that an understanding ofhow size affects critical pressure–temperature conditions providesvital guidance in the search for materials with novel properties.Here, we report on the remarkable behavior of small (under ∼5nm) matrix-free Ge nanoparticles under hydrostatic compression thatis drastically different from both larger nanoparticles and bulk Ge.We discover that the application of pressure drives surface-inducedamorphization leading to Ge–Ge bond overcompression and eventuallyto a polyamorphic semiconductor-to-metal transformation. A combinationof spectroscopic techniques together with ab initio simulations wereemployed to reveal the details of the transformation mechanism intoa new high density phaseamorphous metallic Ge. [ABSTRACT FROM AUTHOR]

The slow flow of a viscous liquid is a thought-provoking experiment that challenges students, academics and the public to think about some fundamental questions in modern science. In the Queensland demonstration—the world's longest-running experiment, which has earned the Ig Nobel prize—one drop of pitch takes about ten years to fall, leading to problems for actually observing the drops. Here, we describe our recent demonstration of slowly-flowing bitumen where appreciable flow is observed on the timescale of months. The experiment is free from dissipative heating effects and has the potential to improve the accuracy of measurement. Bitumen viscosity was calculated by undergraduate students during the summer project. Worldwide access to the experiment, as it runs, is provided by webcams uploading the images to a dedicated website, enhancing the student education experience and promotion of science. This demonstration serves as an attractive student education exercise and stimulates the discussion of fundamental concepts and hotly debated ideas in modern physics research: the difference between solids and liquids, the nature of the liquid–glass transition, the emergence of long timescales in a physical process and the conflict between human intuition and physical reality. [ABSTRACT FROM AUTHOR]

The structure of small (2-5 nm) Ge quantum dots prepared by the colloidal synthesis route is examined. Samples were synthesized using either GeO2 or GeCl4 as precursor. As-prepared samples were further annealed under Ar or H2/Ar atmosphere at different temperatures in order to understand the effect of annealing on their structure. It was found that as-prepared samples possess distinctly different structures depending on their synthesis route as indicated by their long-range ordering. An appreciable amount of oxygen was found to be bound to Ge in samples prepared with GeO2 as a precursor; however, not for GeCl4. Based on combined transmission electron microscope, Raman, X-ray diffraction and X-ray absorption measurements, it is suggested that as-prepared samples are best described by the core-shell model with a small nano-crystalline core and an amorphous outer layer terminated either with oxygen or hydrogen depending on the synthesis route. Annealing in an H2Ar atmosphere leads to sample crystallization and further nanoparticle growth, while at the same time reducing the Ge-O bonding. X-ray diffraction measurements for as-prepared and annealed samples indicate that diamond-type and metastable phases are present. [ABSTRACT FROM AUTHOR]

We used a combination of optically-detected x-ray absorption spectroscopy with molecular dynamics simulations to explore the origins of light emission in small (5 nm to 9 nim) Ge nanoparticles. Two sets of nanoparticles were studied, with oxygen and hydrogen terminated surfaces.Weshow that optically-detected x-ray absorption spectroscopy shows sufficient sensitivity to reveal the different origins of light emission in these two sets of samples. We found that in oxygen terminated nanoparticles its the oxide-rich regions that are responsible for the light emission. In hydrogen terminated nanoparticles we established that structurally disordered Ge regions contribute to the luminescence. Using a combination of molecular dynamics simulations and optically-detected x-ray absorption spectroscopy we show that these disordered regions correspond to the disordered layer a few Å thick at the surface of the simulated nanoparticle [ABSTRACT FROM AUTHOR]

We use 488 and 568 nm laser Raman spectroscopy under high pressure to selectively follow evolution of Raman G-mode signals of single-walled carbon nanotubes (SWCNTs) of selected diameters and chiralities ((6, 5) and (6, 4)). The G-mode pressure coefficients of tubes from our previous work are consistent with the thick-wall tube model. Here we report the observation of well-resolved G-minus peaks in the Raman spectrum of SWCNTs in a diamond-anvil cell. The pressure coefficients of these identified tubes in water, however, are unexpected, having the high value of over 9 cm−1 GPa−1for the G-plus and the G-minus, and surprisingly the shift rates of the same tubes in hexane have clearly lower values. We also report an abrupt increase of G-minus peak width at about 4 GPa superposed on a continuous peak broadening with pressure. [ABSTRACT FROM PUBLISHER]

Modern telecommunications rely on the transmission and manipulation of optical signals. Optical amplification plays a vital part in this technology, as all components in a real telecommunications system produce some loss. The two main issues with present amplifiers, which rely on erbium ions in a glass matrix, are the difficulty in integration onto a single substrate and the need of high pump power densities to produce gain. Here we show a potential organic optical amplifier material that demonstrates population inversion when pumped from above using low-power visible light. This system is integrated into an organic light-emitting diode demonstrating that electrical pumping can be achieved. This opens the possibility of direct electrically driven optical amplifiers and optical circuits. Our results provide an alternative approach to producing low-cost integrated optics that is compatible with existing silicon photonics and a different route to an effective integrated optics technology. [ABSTRACT FROM AUTHOR]

Abstract: Human protein kinase CK2 is one of the most intriguing enzymes, which functional role still remains unclear despite of decades of studying. At present there is abundant evidence pointing to the fact that inhibitors of CK2 could be used as pharmaceutical agents to treat cancer, viral infections and inflammatory diseases. Here we report novel synthetic flavone inhibitors, 4′-hydroxyflavones, possessing high activity towards CK2. These compounds were identified with receptor-based virtual screening and then chemically optimized on the base of rationale derived from biochemical screening and molecular modeling. It has been demonstrated that synthetic flavone derivatives are much more potent CK2 inhibitors than the natural ones, and we believe that their further examination will be helpful for studying biological role of CK2 as well as for development of new kinase-oriented drugs. [Copyright &y& Elsevier]

he spontaneous interaction between sulfuric acid and carbon nanotubes is studied using Raman spectroscopy. We are able to determine the charge transfer without any additional parameter using the spectral signature of inner and outer walls of double-wall carbon nanotubes. While for the outer wall both the lattice contraction and the nonadiabatic effects contribute to the phonon shift, only the lattice contraction contributes for the inner nanotube. For the outer nanotube, we are able to separate these two contributions of the Raman G-band shift as a function of the charge transfer. We have carried out density functional theory calculations on graphene to see how different chemical species (HSO4-, H2SO4, H+) affect the electronic band structure and electron-phonon coupling. The Raman G-band shift for the outer nanotube, Δω, as a function of hole charge transfer per carbon atom, fC, is found to be Δω(cm-1)=(350±20)fC+(101±8)√fC. [ABSTRACT FROM AUTHOR]

Studies of the mechanical properties of single-walled carbon nanotubes are hindered by their availability only as ensembles of tubes with a range of diameters. However, tunable Raman spectroscopy is capable of identifying individual tubes from such ensembles. Interestingly, both the radial breathing mode and, surprisingly, the G-mode pressure coefficients exhibit strong environmental effects, which are largely independent of the nature of the environment. We show that the G-mode pressure coefficient varies with diameter, consistent with the thick-wall tube model. Reappraisal of literature data for graphene and graphite suggests revision of both the G-mode Griineisen parameter y and the shear deformation parameter/3 toward the value of 1.34. [ABSTRACT FROM AUTHOR]

The structure and the electrical and magnetic properties of Mn-implanted Si, which exhibits ferromagnetic ordering at room temperature, are studied. Single-crystal n- and p-type Si wafers with high and low electrical resistivities are implanted by manganese ions to a dose of 5 × 1016 cm−2. After implantation and subsequent vacuum annealing at 850°C, the implanted samples are examined by various methods. The Mn impurity that exhibits an electric activity and is incorporated into the Si lattice in interstitial sites is found to account for only a few percent of the total Mn content. The main part of Mn is fixed in Mn15Si26 nanoprecipitates in the Si matrix. The magnetization of implanted Si is found to be independent of the electrical resistivity and the conductivity type of silicon and the type of implanted impurity. The magnetization of implanted Si increases slightly upon short-term postimplantation annealing and disappears completely upon vacuum annealing at 1000°C for 5 h. The Mn impurity in Si is shown to have no significant magnetic moment at room temperature. These results indicate that the room temperature ferromagnetism in Mn-implanted Si is likely to be caused by implantation-induced defects in the silicon lattice rather than by a Mn impurity. [ABSTRACT FROM AUTHOR]

Abstract: The features of electrochemical formation process of porous silicon (PS) at the temperatures above the room temperature have been studied. It was found that besides electrochemical dissolution, chemical etching takes part in the formation process of PS even for concentrated HF electrolyte. The role of chemical etching increases with temperature causing an increase of the porosity and the crater depth. The temperature dependence of chemical etching rate has been established. Obtained results enable to conclude that OH− ions play a major role in the chemical etching. Electrochemical etching allows to fabricate PS with good surface quality at the temperatures at least below 65°C provided that HF electrolyte is concentrated. [Copyright &y& Elsevier]

Porous silicon (PS) is an excellent material to be used as a sacrificial layer (SL) for the fabrication of membranes, bridges, cantilevers and other complicated micro-sensor structures. Major advantages of this material are its smooth surface and large area of pores that provide a high rate of PS SL removal. In this work, electrochemical and chemical etching processes of porous silicon formation from polycrystalline silicon deposited on insulating substrates have been studied. It was shown that a sufficiently thick (about 2 µm), uniform PS with a smooth surface and high etching rate in buffered HF solution can be made by both electrochemical and chemical etching from low resistive p-type poly-Si only. Finally, the obtained PS layers have been used as sacrificial layers in a fabrication process of microbolometer array. [ABSTRACT FROM AUTHOR]

We report a detailed study of Vicker's hardness and ultrasonic elastic moduli for carbon phases prepared by heating fullerite C[sub 60] at pressures of 3.5, 5, and 8 GPa. It is shown that the transformation of two-dimensional C[sub 60] polymers into graphite-like amorphous carbon is accompanied by an increase in hardness of 100-200 times, as well as an increase in bulk and shear moduli by 4-5 and 2-3 times, respectively, with no density jump taking place. It is proposed that the high hardness (up to 40 GPa) of the disordered phases synthesized is caused by the three-dimensional ordering of sp[sup 2]-based network. It was found that, in the 3.5-8 GPa interval, the mechanical properties of the phases obtained depend basically on the temperature rather than on the pressure of synthesis. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We show that application of the non-hydrostatic pressure to the cluster-based molecular material, like fullerite C60, provides a new opportunity to create elastically and structurally anisotropic carbon materials, including 2D polymerized rhombohedral C60 and graphite-type (sp2) disordered atomic-based phases. The elastic anisotropy, detected by the difference in the ultrasound velocities propagating along and across the loading axis, is directly confirmed by the results of x-ray diffraction. [ABSTRACT FROM AUTHOR]

The photoluminescence (PL) at ∼2.2–2.3 eV from Ge-based nanocrystalline materials is described in the literature as nanocrystal size-independent. We have observed visible luminescence from two different types of stain-etched Ge samples, one prepared after Sendova-Vassileva et al. (Thin Solid Films 255 (1995) 282) in a solution of H2O2:HF at 50:1 volume ratio, and the other in a solution of HF:H3PO4:H2O2 at 34:17:1 volume ratio. Energy dispersive X-ray analysis (EDX), Raman and FTIR spectroscopy, and the near edge X-ray absorption structure (XANES), indicate that the chemically etched Ge layers of the former type of samples are composed of non-stoichometric Ge oxides, i.e. GeOx (0

The results of an investigation of the transformation of C[sub 60] fullerite to diamond under pressure through intermediate three-dimensionally polymerized and amorphous phases are reported. It is found that treatment of fullerite C[sub 60] at pressures 12–14 GPa and temperatures ∼1400 °C produces a nanocrystalline graphite–diamond composite with a concentration of the diamond component exceeding 50%. At lower temperatures (700–1200 °C) nanocomposites consisting of diamondlike (sp[sup 3]) and graphitic (sp[sup 2]) amorphous phases are formed. The nanocomposites obtained have extremely high mechanical characteristics: hardness comparable to that of best diamond single crystals and fracture resistance two times greater than that of diamond. Mechanisms leading to the transformation of C[sub 60] fullerite into diamond-based nanocomposites and the reasons for the high mechanical characteristics of these nanocomposites are discussed. © 1999 American Institute of Physics. [ABSTRACT FROM AUTHOR]

• Photodegradation of folic acid water colloid results in high-fluorescence water-soluble product. • Pterin moiety optical properties prevalent after photodergadation. • UV-exposed folic acid retains biological functions and promotes division of cancer cells. Folic acid (FA) is a natural body component essential for normal cell growth and division. Uptake of FA into cells is mediated by the folate receptors with particularly large amount of folate receptors found on the surface of cancer cells. This feature traditionally is used for selective drug delivery systems targeting in cancer cells or visualization of the border between healthy and tumor tissue based on FA-modified fluorescent labels. However, preparation of FA-conjugates can be an elaborate procedure, while FA itself shows low photostability under illumination. Here we use photodegradation of FA colloid to produce high fluorescent product and compare its effects on the cells grows and division with the ones of FA. It was found UV-irradiation of FA colloid for 60 min allows obtaining water soluble fluorophore with quantum yield 30 ± 2 %. We also show that the resulting fluorescent product retained FA biological activity in relation to cell growth and division, comparable to native FA. [ABSTRACT FROM AUTHOR]