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© 2008 IOP Publishing Ltd. This work was supported by MEC (Project MAT2006-01259)., Sn doped GeO_2 nanowires and microwires have been grown by an evaporation-deposition method, using a mixture of Ge and SnO_2 powders as precursors. Comparison with undoped GeO_2 nanowires grown by the same method shows that the presence of Sn prevents the formation of sharp bends, which makes the wires more suitable for waveguiding applications. Incorporation of about 0.5 at.% of Sn into the wires influences their morphology and gives rise to wires showing two different cross-sectional dimensions along the growth axis. Sn does not influence the luminescence spectra in the visible range but causes the appearance of emission bands in the near-infrared range. The waveguiding behavior of the Sn doped wires for green and red laser light has been demonstrated., MEC, Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

Sintering behavior of micron-sized combusted iron powder is studied in a packed bed reactor, at various temperatures under inert (nitrogen) and reducing (hydrogen) conditions. Compression tests are subsequently used to quantify the degree of sintering. A sintering model, based on the formation of a solid bridge through solid state surface diffusion of iron atoms, matches the experimental results. Sintering of combusted iron occurs at temperatures C in both nitrogen and hydrogen atmospheres and increases exponentially with temperature. The observed decrease in reduction rate at high temperatures is not caused by the sintering process but by the formation of wüstite as an intermediate species, leading to the formation of a dense iron layer. Iron whiskers form at high temperatures (C) in combination with low reduction rates (vol% H2), leading to the production of sub-micron fines., Sintering behavior of micron-sized combusted iron powder is studied in a packed bed reactor, at various temperatures under inert (nitrogen) and reducing (hydrogen) conditions. Compression tests are subsequently used to quantify the degree of sintering. A sintering model, based on the formation of a solid bridge through solid state surface diffusion of iron atoms, matches the experimental results. Sintering of combusted iron occurs at temperatures ≥575°C in both nitrogen and hydrogen atmospheres and increases exponentially with temperature. The observed decrease in reduction rate at high temperatures is not caused by the sintering process but by the formation of wüstite as an intermediate species, leading to the formation of a dense iron layer. Iron whiskers form at high temperatures (≥700°C) in combination with low reduction rates (≤25 vol% H 2), leading to the production of sub-micron fines.

Diese aus drei verschiedenen Studien bestehende Arbeit trägt mittels Verknüpfung von Anatomie (Struktur) und Physiologie oder Verhalten (Funktion) zu einem besseren Verständnis von somatosensorischer Informationsverarbeitung bei. In der ersten Studie untersuchten wir wie das Nervensystem der Ratte sich an das kontinuierliche Nachwachsen und Ausfallen der Tasthaare anpasst. Unsere Ergebnisse zeigen, dass Barrel-Kortex Neurone nach Auslenkung von sowohl jungen oder alten Tasthaaren ähnliche neuronale Antworten aufweisen. Wir konnten auch beobachten, dass junge und alte Tasthaare gemeinsam im Follikel innerviert werden und im Kortex nicht separat topologisch repräsentiert sind. Diese Ergebnisse könnten erklären wie die Stabilität von Wahrnehmung während fortlaufenden körperlich-sensorischen Veränderungen gewährleistet wird. In der zweiten Studie identifizierten wir Details der kortikalen Nasen Repräsentation und konnten zeigen, dass die Organisation von Schicht 4 im Somatosensorischen Kortex in Nagetieren konserviert ist. Wir fanden auch eine Kopplung von Nervenzellaktivität mit der Atmung, was für eine koordinierte Verarbeitung von Tastsinn und Atmung im Nasen-Somatosensorischen Kortex spricht. In der dritten Studie charakterisierten wir die kortikale Repräsentation der Schnauze im Hausschwein und konnten zeigen, dass dessen makroskopische, drei-dimensionale Erscheinung viele Details aufweist, die auch bei der tatsächlichen Schnauze zu finden sind. Ähnlich wie bei unseren histologischen Beobachtungen im Nasen- Somatosensorischen Kortex von Nagern konnten wir im Hausschwein Kortex eine Verjüngung von Schicht 4 der mutmaßlichen Repräsentation des Nasenlochs beobachten. Zusammengefasst zeigt diese Arbeit i) einen potentiellen Mechanismus für Kontinuität der Wahrnehmung während körperlichen Veränderungen ii) Details der kortikalen Nasen-Repräsentation und dessen Verhältnis zur Atmung und iii) isomorphe Eigenschaften der kortikalen Schnauzen-Repräsentation im Hausschwein., Topological mapping of body part representations in the brain have long been studied in neuroscience. In this thesis, three separate studies investigate such somatosensory representations by relating anatomy (structure) to physiology or behavior (function). In the first study we investigated whether and how the rat nervous system adapts to whiskers regrowth. We found that barrel cortex neurons displayed similar response properties to young and old whisker deflection and that both whiskers share their peripheral innervation in the same follicle. Our results further suggest that young and old whiskers do not form topologically distinct representations in the cortex. Such findings illuminate how perceptual stability is maintained despite the constant change of bodies and sensory structures. In the second study we identified the rodent nose somatosensory cortex and found that its tangential layer 4 organization is conserved across rodents. We also found significant respiration locked neural activity in the rat nose somatosensory cortex, suggesting coordinated processing of touch and respiration. In the third study we characterized the pig rostrum somatosensory cortex and found that its three-dimensional, gross organization matches the detailed structure of the actual rostrum appearance. We also found that layer 4 appears thinner in the putative nostril, similar to our results in the rodent nose somatosensory cortex. Collectively, our data i) reveal potential mechanisms for perceptual stability during bodily changes ii) identify the rodent nose somatosensory cortex and its relationship to respiration and iii) a striking isomorphism of the pig cortical rostrum representation with the pig snout.

An investigation is presented of the preparation of calcium sulphate hemihydrate whiskers using either pure gypsum (CaSO4.2H2O) or complex jarosite waste (gypsum and ammonium jarosite) from a zinc hydrometallurgical process as raw materials. The samples are analysed by X-ray diffraction, X-ray fluorescence, scanning electron microscopy and Raman spectroscopy. Under autoclaved hydrothermal conditions, the effects on calcium sulphate hemihydrate morphology of using pure gypsum alone or in combination with Fe3+ or (NH4)+ impurity ions are described. The results show that pure gypsum alone produces calcium sulphate hemihydrate crystals with a high aspect ratio (50); the diameter of the crystals increases and the aspect ratio of the calcium sulphate hemihydrate decreases with increasing addition of Fe3+ or (NH4)+ ions. Calcified jarosite sediment containing mostly gypsum and ferric hydroxide is prepared by reacting complex jarosite waste with calcium oxide and washing with water. Treatment of the calcified jarosite sediment at 140 degrees C for 6 h in pH 5 solution under hydrothermal conditions provides calcium sulphate hemihydrate whiskers with a high aspect ratio (10-60), large diameter (1-4 micrometres) and smooth surface., An investigation is presented of the preparation of calcium sulphate hemihydrate whiskers using either pure gypsum (CaSO4.2H2O) or complex jarosite waste (gypsum and ammonium jarosite) from a zinc hydrometallurgical process as raw materials. The samples are analysed by X-ray diffraction, X-ray fluorescence, scanning electron microscopy and Raman spectroscopy. Under autoclaved hydrothermal conditions, the effects on calcium sulphate hemihydrate morphology of using pure gypsum alone or in combination with Fe3+ or (NH4)+ impurity ions are described. The results show that pure gypsum alone produces calcium sulphate hemihydrate crystals with a high aspect ratio (50); the diameter of the crystals increases and the aspect ratio of the calcium sulphate hemihydrate decreases with increasing addition of Fe3+ or (NH4)+ ions. Calcified jarosite sediment containing mostly gypsum and ferric hydroxide is prepared by reacting complex jarosite waste with calcium oxide and washing with water. Treatment of the calcified jarosite sediment at 140 degrees C for 6 h in pH 5 solution under hydrothermal conditions provides calcium sulphate hemihydrate whiskers with a high aspect ratio (10-60), large diameter (1-4 micrometres) and smooth surface.

Rodents engage in active touch using their facial whiskers: they explore their environment by making rapid back-and-forth movements. The fast nature of whisker movements, during which whiskers often cross each other, makes it notoriously difficult to track individual whiskers of the intact whisker field. We present here a novel algorithm, WhiskEras, for tracking of whisker movements in high-speed videos of untrimmed mice, without requiring labeled data. WhiskEras consists of a pipeline of image-processing steps: first, the points that form the whisker centerlines are detected with sub-pixel accuracy. Then, these points are clustered in order to distinguish individual whiskers. Subsequently, the whiskers are parameterized so that a single whisker can be described by four parameters. The last step consists of tracking individual whiskers over time. We describe that WhiskEras performs better than other whisker-tracking algorithms on several metrics. On our four video segments, WhiskEras detected more whiskers per frame than the Biotact Whisker Tracking Tool. The signal-to-noise ratio of the output of WhiskEras was higher than that of Janelia Whisk. As a result, the correlation between reflexive whisker movements and cerebellar Purkinje cell activity appeared to be stronger than previously found using other tracking algorithms. We conclude that WhiskEras facilitates the study of sensorimotor integration by markedly improving the accuracy of whisker tracking in untrimmed mice.

Rodents engage in active touch using their facial whiskers: they explore their environment by making rapid back-and-forth movements. The fast nature of whisker movements, during which whiskers often cross each other, makes it notoriously difficult to track individual whiskers of the intact whisker field. We present here a novel algorithm, WhiskEras, for tracking of whisker movements in high-speed videos of untrimmed mice, without requiring labeled data. WhiskEras consists of a pipeline of image-processing steps: first, the points that form the whisker centerlines are detected with sub-pixel accuracy. Then, these points are clustered in order to distinguish individual whiskers. Subsequently, the whiskers are parameterized so that a single whisker can be described by four parameters. The last step consists of tracking individual whiskers over time. We describe that WhiskEras performs better than other whisker-tracking algorithms on several metrics. On our four video segments, WhiskEras detected more whiskers per frame than the Biotact Whisker Tracking Tool. The signal-to-noise ratio of the output of WhiskEras was higher than that of Janelia Whisk. As a result, the correlation between reflexive whisker movements and cerebellar Purkinje cell activity appeared to be stronger than previously found using other tracking algorithms. We conclude that WhiskEras facilitates the study of sensorimotor integration by markedly improving the accuracy of whisker tracking in untrimmed mice., Computer Engineering, Bio-Electronics

Rodents engage in active touch using their facial whiskers: they explore their environment by making rapid back-and-forth movements. The fast nature of whisker movements, during which whiskers often cross each other, makes it notoriously difficult to track individual whiskers of the intact whisker field. We present here a novel algorithm, WhiskEras, for tracking of whisker movements in high-speed videos of untrimmed mice, without requiring labeled data. WhiskEras consists of a pipeline of image-processing steps: first, the points that form the whisker centerlines are detected with sub-pixel accuracy. Then, these points are clustered in order to distinguish individual whiskers. Subsequently, the whiskers are parameterized so that a single whisker can be described by four parameters. The last step consists of tracking individual whiskers over time. We describe that WhiskEras performs better than other whisker-tracking algorithms on several metrics. On our four video segments, WhiskEras detected more whiskers per frame than the Biotact Whisker Tracking Tool. The signal-to-noise ratio of the output of WhiskEras was higher than that of Janelia Whisk. As a result, the correlation between reflexive whisker movements and cerebellar Purkinje cell activity appeared to be stronger than previously found using other tracking algorithms. We conclude that WhiskEras facilitates the study of sensorimotor integration by markedly improving the accuracy of whisker tracking in untrimmed mice., Computer Engineering, Bio-Electronics

The movement of whiskers in head-fixed mice is of high interest for neurological research, as it allows scientists to learn more about learning processes during active touch. However, manual tracking of whiskers in thousands of frames is not feasible, and reliable tracking of individual whiskers is not possible with the best current software available. In this work, a new system for the automatic tracking of whiskers in top-view videos of untrimmed, head-fixed mice is presented. The design of this system is based on a variety of image processing and computer vision algorithms. For each step, several alternatives have been considered and assessed. The best options have been combined and implemented in MATLAB. This new system, the Full-Whisker Tracking System (FWTS), detects the centerline of whiskers on each frame along their whole length with sub-pixel accuracy. The whiskers are defined by their angle, position, shape and length. FWTS uses these features to track and recognize whiskers over multiple frames in video segments with a frame rate of 1000 Hz. The system was tested on representative, challenging video segments from two experiments using different mice, and showed itself superior to the pre-existing system BWTT, by detecting on average 21.2% more whiskers, and with twice as much precision. In contrast to earlier systems, FWTS has been demonstrated reliably track individual whiskers in untrimmed mice. Furthermore, FWTS's processing time is on average 41.7% lower than that of BWTT. This thesis work shows that it is possible to track whiskers in untrimmed mice, even in the face of partial occlusions, and makes it possible to study the functioning of the intact whisker system of mice in unprecedented detail.

The movement of whiskers in head-fixed mice is of high interest for neurological research, as it allows scientists to learn more about learning processes during active touch. However, manual tracking of whiskers in thousands of frames is not feasible, and reliable tracking of individual whiskers is not possible with the best current software available. In this work, a new system for the automatic tracking of whiskers in top-view videos of untrimmed, head-fixed mice is presented. The design of this system is based on a variety of image processing and computer vision algorithms. For each step, several alternatives have been considered and assessed. The best options have been combined and implemented in MATLAB. This new system, the Full-Whisker Tracking System (FWTS), detects the centerline of whiskers on each frame along their whole length with sub-pixel accuracy. The whiskers are defined by their angle, position, shape and length. FWTS uses these features to track and recognize whiskers over multiple frames in video segments with a frame rate of 1000 Hz. The system was tested on representative, challenging video segments from two experiments using different mice, and showed itself superior to the pre-existing system BWTT, by detecting on average 21.2% more whiskers, and with twice as much precision. In contrast to earlier systems, FWTS has been demonstrated reliably track individual whiskers in untrimmed mice. Furthermore, FWTS's processing time is on average 41.7% lower than that of BWTT. This thesis work shows that it is possible to track whiskers in untrimmed mice, even in the face of partial occlusions, and makes it possible to study the functioning of the intact whisker system of mice in unprecedented detail.

The studies of piezoresistance of boron doped p-type silicon whiskers with [111] crystallographic orientation mounted on the spring elements, fabricated of the invar alloy, were carried out in the wide ranges of strains ε = ±1.26×10-3 rel. units and temperatures 4.2–300 K. The measurements were carried out in a helium cryostat. There were investigated silicon whiskers with different types of boron doping: 1) heavily doped crystals with metallic conductivity; 2) in the vicinity of metal-insulator transition (MIT) from the metallic side of MIT and 3) in the vicinity of MIT from the insulating side of MIT. Resistance vs. strain (tensile and compressive) dependences at fixed temperatures: 4.2 K, 77 K and 300 K for Si were measured fo whiskers, mounted on in the tempereture range 4.2-300 K for the heavily doped silicon whiskers in the whole temperature range. The classic piezoresistance was observed. Non-classic piezoresistance at helium temperatures was revealed In Si whiskers with definite boron concentration in the vicinity of MIT. Gauge factor of Si whiskers with boron concentration presencefrom the insulating side of MIT achieves at 4.2 K the magnitude GF 4,2К≈–10000 at compressive strain and GF 4,2К≥8000 at the tensile strain. Obtained characteristics of p-type Si whiskers mounted on the spring elements allowed to forecast the performance of piezoresistive mechanical sensors characteristics on their basis. The possibility of construction of the mechanical parameters sensors (strain gages, pressure sensors etc.) of two types was shown: sensors based on heavily doped p-type Si whiskers for the wide temperature range 4.2–300 K and high-sensitive sensors based on Si crystals with boron concentration in the vicinity of MIT for control and signaling systems at cryogenic temperatures., Проведено дослідження п’єзоопору ниткоподібних кристалів (НК) кремнію р-типу з кристалографічною орієнтацією [111], легованих бором, на пружних елементах з інварного сплаву в широкому діапазоні деформацій ε=±1,26×10-3 відн. од. і температур 4,2–300 К. Вимірювання проводились в гелієвому кріостаті. Досліджувались НК кремнію з різною концентрацією бору: 1) сильно леговані кристали з металевою провідністю; 2) поблизу переходу метал-діелектрик (ПМД) з металевого боку; 3) поблизу ПМД з діелектричного боку. Визначалися залежності відносної зміни опору НК р-Si, закріплених на балках з інвару, від деформації розтягу і стиску при фіксованих температурах: 4,2 К, 77 К і 300 К, а також температурні залежності коефіцієнта тензочутливості цих кристалів у діапазоні температур 4,2–300 К. В сильно легованих НК р-Si у всьому діапазоні температур спостерігався класичний п’єзорезистивний ефект. В НК Si з концентрацією бору поблизу переходу метал-ізолятор при гелієвих температурах був виявлений некласичний п’єзоопір. Величина коефіцієнта тензочутливості в НК Si з концентрацією бору, що відповідає діелектричному боку ПМД, при 4,2 К досягала значень К 4,2К≈–10000 при деформації стиску і К4,2К≥8000 при деформації розтягу. Отримані характеристики НК кремнію р-типу, закріплених на пружних елементах, дозволяють прогнозувати характеристики п’єзорезистивних сенсорів механічних величин на їх основі. Показано можливість створення на основі цих кристалів сенсорів механічних величин (деформації, тиску та ін.) двох типів: для широкого діапазо- ну температур 4,2–300 К на основі сильно легованих НК Si p-типу і високочутливих сенсорів на основі кристалів кремнію з концентрацією бору поблизу ПМД для систем контролю і сигналізації при кріогенних температурах., Проведены исследования пьезосопротивления нитевидных кристаллов (НК) кремния р-типа с кристаллографической ориентацией [111], легированных бором, на упругих элементах из инварного сплава в широком диапазоне деформаций ε=±1,26×10-3 отн. ед. и температур 4,2–300 К. Измерения проводились в гелиевом криостате. Исследовались НК кремния с различной концентрацией бора: 1) сильно легированные кристаллы с металлической проводимостью; 2) вблизи перехода металл-изолятор (ПМИ) с металлической стороны; 3) вблизи ПМИ с изолирующей стороны. Определялись зависимости относительного изменения сопротивления НК р-Si, закрепленных на балках из инвара, от деформации растяжения и сжатия при фиксированных температурах: 4,2 К, 77 К и 300 К, а также температурные зависимости коэффициента тензочувствительности этих кристаллов в диапазоне температур 4,2–300 К. В сильно легированных НК р-Si во всём диапазоне температур наблюдался классический пьезорезистивный эффект. В НК Si с концентрацией бора вблизи перехода металл-изолятор при гелиевых температурах обнаружено неклассическое пьезосопротивление. Величина коэффициента тензочувствительности в НК Si c концентрацией бора, соответствующей изолирующей стороне ПМИ, при 4,2 К достигала значений К 4,2К≈–10000 при деформации сжатия и К4,2К≥8000 при деформации растяжения. Полученные характеристики НК кремния р-типа, закреплённых на упругих элементах, позволяют прогнозировать характеристики пьезорезистивных сенсоров механических величин на их основе. Показана возможность создания на основе этих кристаллов сенсоров механических величин (деформации, давления и др.) двух типов: для широкого диапазона температур 4,2–300 К на основе сильно легированных НК Si p-типа и высокочувствительных сенсоров на основе кристаллов кремния с концентрацией бора вблизи ПМИ для систем контроля и сигнализации при криогенных температурах.

Adaptation of neural responses due to the history of sensory input has been observed across all sensory modalities. However, the computational role of adaptation is not fully understood, especially when one considers neural coding problems in which adaptation increases the ambiguity of the neural responses to simple stimuli. To address this, we quantified the impact of adaptation on the information conveyed by thalamic neurons about paired whisker stimuli in male rat. At the single neuron level, although paired-pulse adaptation reduces the information about the present stimulus, the information per spike increases. Moreover, the adapted response can convey significant amounts of information about whether, when and where a previous stimulus occurred. At the population level, ambiguity of the adapted responses about the present stimulus can be compensated for by large numbers of neurons. Therefore, paired-pulse adaptation does not reduce the discriminability of simple stimuli. It provides information about the spatiotemporal context of stimulus history.SIGNIFICANCE STATEMENT The present work provides a computational framework that demonstrates how adaptation allows neurons to encode spatiotemporal dynamics of stimulus history.

In this study a largely available lignocellulose feedstock hemp (Cannabis sativa), obtained as an industrial waste, was used for cellulose extraction. The extraction of cellulose microfibres from hemp biomass was conducted by alkaline treatment and an acidification process. The extracted cellulose microfibres were characterised using Fourier-transformed infrared spectroscopy (FTIR), Scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and X-ray diffraction (XRD).The viability of the study was determined by growing human fibroblasts on the preparation which resulted in being non-toxic; indicating its potential in preparing biological scaffolds. Upon enzymatic hydrolysis of the cellulose microfibre using cellulase from Trichoderma reesei, a maximum of 909 mg/g of reducing sugars were obtained, which endorses its suitability for biofuel production.

We report a facile aqueous procedure to create multivalent displays of sulfonated ligands on CNCs for future applications as viral inhibitors. CNCs were decorated with model compounds containing sulfonate groups via reactions of epoxides and isothiocyanates with amines under alkaline conditions. At first, surface sulfate groups of CNCs were hydrolytically cleaved by alkaline hydrolysis to increase the number of available surface hydroxyls. Success of desulfation was confirmed via dynamic light scattering (DLS), zeta potential measurements and thermogravimetric analysis (TGA). CNC surface hydroxyl groups were then activated with epichlorohydrin before subsequent reactions. As proof of concept toward aqueous pathways for functionalizing nanoparticles with sulfonated ligands, 3-chloro-2-hydroxy-1-propanesulfonic acid sodium salt hydrate (CPSA) and 4-sulfophenyl isothiocyanate sodium salt monohydrate (4-SPITC) were chosen as model compounds to react with homobifunctional 2,2'-(ethylenedioxy)bis(ethylamine) (EBEA) molecular spacer. The approaches presented are not only applicable to polysaccharide nanocrystals, but also other classes of polymeric and inorganic substrates presenting surface hydroxyl groups, as in the case of poly(2-hydroxyethyl methacrylate) (PHEMA), silica or glass. CNCs carrying sulfonated ligands were characterized by ATR-FTIR and UV–vis spectroscopy. Surface chemical compositions of desired elements were determined via X-ray photoelectron spectroscopy (XPS). We anticipate that with these facile aqueous procedures as the proof of concept, a diverse library of target-specific functionalities can be conjugated to CNCs for applications in nanomedicine, especially related to viral inhibition, Peer Reviewed, Postprint (author's final draft)

Despite a sufficiently large number of conducted studies, the analysis of literature sources has shown that the development of plastic deformation in whiskers has a number of problem-specific features. A literature review of the research problem has been proposed in the paper and such an important property of whiskers, as plastic deformation, has been studied more thoroughly. Herewith, on the basis of studying the results of previously conducted experiments the influence of this property on the fracture degree of crystals, and also on several other characteristics, has been shown.The research results from the point of view of the future use of whiskers have been analyzed in the paper, the principles of influence of deformation tests on the lattice structure and properties of whiskers have been considered in-depth., В статье рассмотрено такое достаточно важное свойство нитевидных кристаллов как пластическая деформация. На основании анализа результатов ранее проведенных экспериментов показано влияние свойства на степень разрушения кристаллов и сформулирована нерешенная часть научной проблемы изучения роста, структуры и свойств нитевидных кристаллов, возникшей в связи с необходимостью решения ряда практических задач, У статті розглянута така досить важлива властивість ниткоподібних кристалів як пластична деформація. На підставі аналізу результатів раніше проведених експериментів показано вплив властивості на ступінь руйнування кристалів і сформульована невирішена частина наукової проблеми вивчення росту, структури і властивостей ниткоподібних кристалів, що виникла у зв'язку з необхідністю вирішення ряду практичних завдань

Applying the hydrothermal reactions for synthesizing whiskers of alkali metal titanates is considered in the paper. Some results of our research in this field are presented. The main purpose of this research is to study the mechanisms of the hydrothermal synthesis process and to obtain kinetic models of whisker growth. The idea of the mechanisms of crystal synthesis is considered and the influence of pressure, temperature, degree of the autoclave filling and other process parameters is estimated. As a result of experimental studies, the possibility of synthesizing potassium titanate whiskers under hydrothermal conditions in obtaining high-quality fibrous crystal structure, corresponding to potassium hexatitanite, the maximum yield of which can be achieved by the degree of filling the reactor by 60% and a pressure of 50 MPa. Based on the studies of the process mechanisms the kinetic models are constructed. They can be used for analyzing the process and selecting the rational parameters of synthesizing potassium hexatitanite crystals. The results of theoretical and experimental studies allow estimating the measurements of the various process properties on the hydrothermal treatment and identifying the factors of controlling either the processes of batch mixture dissolution in the autoclave or the crystal growth processes, which can be applied in the development and design of reactors for performing hydrothermal reactions in obtaining whiskers., Проанализировано влияние физико-химических параметров процесса в автоклаве на образование нитевидных кристаллов гексатитаната калия. Результаты экспериментальных исследований подтверждают возможность синтеза вискеров титанатов калия в гидротермальных условиях с получением высококачественной волокнистой кристаллической структурой. Установлено, что максимальный выход длинноволокнистого продукта можно получить при степени заполнения реактора на 60 % и давлении 50 МПа., Проаналізовано вплив фізико-хімічних параметрів процесу в автоклаві на утворення ниткоподібних кристалів гексатитанату калію. Результати експериментальних досліджень підтверджують можливість синтезу віскерів титанатів калію в гідротермальних умовах з отриманням високоякісної волокнистої кристалічної структури. Встановлено, що максимальний вихід довговолокнистого продукту можна одержати при ступені заповнення реактора на 60% і тиску 50 МПа.

На основі експериментальних досліджень встановлено, що деформовані стиском мікрокристали Si1-хGeх (х = 0,01÷0,03) з питомим опором ρ300 = 0,016 Ом см можуть бути використані як чутливі елементи сенсорів механічних величин, працездатні за кріогенних температур. Створено вимірювальну систему з використанням чутливих елементів сенсорів на основі нитчастих кристалів Si1-xGex із одночасною корекцію їх температурних залежностей, що дозволить враховувати температурну залежність коефіцієнта тензочутливості при зміні температури середовища.

Introduction. The paper deals with investigation of impedance spectroscopy of Si whiskers with doping concentration in the vicinity to metal-insulator transition in the region of low (4,2 – 70 K) temperature and frequency range 0,01 – 250x103 Hz. Experimental results. The silicon whiskers were grown by chemical vapour deposition method in closed bromine system. The whiskers of 40x10-6 m in diameter have boron concentration from 2×1018 to 2×1019 сm-3. The impedance spectroscopy of Si whiskers was investigated with use of Lock-in amplifier in the region of low (4,2 – 70 K) temperature and frequency range 0,01 – 250 x 103 Hz. The investigations showed that in the range of zone conductance (T= 30 – 70 K) the whisker impedance has inductive character, while at the range of impurity conductance (T = 4,2 – 20 K) impedance changes to capacity character. The reduction of impurity concentration at dielectric side of metal-insulator transition leads to decrease of the whisker capacity in the range of low temperatures. Discussion. An inductive character of whisker impedance is explained skin-effect of conductance in thin whisker, while capacity character of the whisker impedance is connected with hopping conductance on impurity band. Conclusions. Character of changes of Si whisker impedance conductance is discussed in the frame of hopping conductance on impurity band, which takes place at low temperatures.

Reinforcement of polyvinyl alcohol (PVA) hydrogels was achieved by direct chemical cross-linking of surface modified microcrystalline cellulose (MCC) whiskers with PVA. In order to produce hydrogels, the MCC whiskers were first obtained by TEMPO-mediated oxidation of the cellulose substrate and ultrasonication followed by direct cross-linking to PVA (Mw 98,000) via forming acetal bonds and freeze-thawing. The viscoelastic properties of the produced hydrogels were clearly improved following the chemical cross-linking, featuring values for viscous and elastic moduli G' and GaEuro(3) on the order of 10 kPa, which is particularly interesting for biomedical orthopedic applications.

Introduction. The paper deals with investigation of electrophysical performances of Si1-xGex whiskers as strain sensors, operating at harsh conditions, in particular at liquid helium temperatures, and development of measurable system for signal treatment from the sensors. Experimental results. It was found that compression strained Si1-xGex (x = 0,01 ÷ 0,03) microcrystals with a resistivity ρ300 =1,6*10-4 Om*m can be used as sensitive elements of sensors of mechanical quantities operating at cryogenic temperatures. It was elaborated a measuring system using sensing elements based on Si1-xGex microcrystals with simultaneous correction of their temperature dependences, which will take into account the temperature dependence of the coefficient tensosensibility on environment temperature. Discussion. A low temperature whisker conductance is explained by Mott law and hopping conductance on twice occupied states of boron impurity. Conclusions. Gauge factor of Si-Ge whiskers was shown to have a very high value at low temperatures (of about 51000 at 4,2 K). that has been used for high sensitivity strain sensors and measuring system elaboration.

This study investigated the effect of shape, size, and surface modification of hydroxyapatite (HAP) fillers on the degree of conversion (DC) and mechanical properties of a model BisGMA/TEGDMA composite initially and after 4 weeks of storage. Ten percent of conventional glass fillers were replaced by HAP spheres (Sph), silicon-doped spheres (Sph(Si)), whiskers (Wh), silicon-doped whiskers (Wh(Si)), and nanosized HAP particles (Nano). Spheres were specifically structured agglomerates consisting of a central void and radially orientated primary particles, whereas whiskers were compact monocrystals. DC, Vickers hardness (HV), flexural strength (Fs), flexural modulus (Ef), compressive strength (Cs), and compressive modulus (Ec) were tested. There were no significant differences in the DC between all tested groups. HV decreased by 5.4-17% with the addition of HAP, while Fs increased by 13.9-29% except in Nano group (decrease by 13%). After storage, Sph and Sph(Si) groups showed similar HV, Ef, Cs and Ec and higher Fs than the control. The fracture mode of HAP spheres was through the central void whereas whiskers showed longitudinal delamination, transverse, and mixed fractures. HAP spheres with or without silicon- doping have a potential to be part of the filler content of dental composites.

Perovskite piezoelectric compositions near the morphotropic phase boundary (MPB) are known to exhibit high piezoelectric response. In lead-based ABO(3) compound with B-site disorder, the origin of this enhancement has been associated with the presence of an intermediate monoclinic/orthorhombic state that bridges the adjacent ferroelectric rhombohedral and tetragonal phases. However, the origin of high piezoelectric response in lead-free ABO(3) compounds with A-site disorder has not been conclusively established. We describe a microscopic model derived from comparative analyses of high resolution transmission electron microscopy and neutron diffraction that explains the origin of high piezoelectric response in lead-free MPB compositions of 0.93(Na0.5Bi0.5)TiO3-0.07BaTiO3. Direct observation of nanotwins with monoclinic symmetry confirmed the presence of an intermediate bridging phase that facilitates a pathway for polarization reorientation. Monoclinic distortions of an average rhombohedral phase are attributed to localized displacements of atoms along the non-polar directions. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4792729]

This study investigated the effect of shape, size, and surface modification of hydroxyapatite (HAP) fillers on the degree of conversion (DC) and mechanical properties of a model BisGMA/TEGDMA composite initially and after 4 weeks of storage. Ten percent of conventional glass fillers were replaced by HAP spheres (Sph), silicon-doped spheres (Sph(Si)), whiskers (Wh), silicon-doped whiskers (Wh(Si)), and nanosized HAP particles (Nano). Spheres were specifically structured agglomerates consisting of a central void and radially orientated primary particles, whereas whiskers were compact monocrystals. DC, Vickers hardness (HV), flexural strength (Fs), flexural modulus (Ef), compressive strength (Cs), and compressive modulus (Ec) were tested. There were no significant differences in the DC between all tested groups. HV decreased by 5.4-17% with the addition of HAP, while Fs increased by 13.9-29% except in Nano group (decrease by 13%). After storage, Sph and Sph(Si) groups showed similar HV, Ef, Cs and Ec and higher Fs than the control. The fracture mode of HAP spheres was through the central void whereas whiskers showed longitudinal delamination, transverse, and mixed fractures. HAP spheres with or without silicon- doping have a potential to be part of the filler content of dental composites. (c) 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 101B: 1469-1476, 2013.

This work compiles a revision of the more relevant xork done on the field of nanocrystalline cellulose (CNC). Including manufacture methods and a variety of material sources for its production, CNC properties and their effect on selected applications are presented. Several approaches on CNC surface modification are discussed, as a tool towards enhanced performance in relevant applications. Finally, self-assembly of CNC behaviour is discussed, together with its implications on rheology and stability of CNC dispersions, as well as optical properties.

This work compiles a revision of the more relevant xork done on the field of nanocrystalline cellulose (CNC). Including manufacture methods and a variety of material sources for its production, CNC properties and their effect on selected applications are presented. Several approaches on CNC surface modification are discussed, as a tool towards enhanced performance in relevant applications. Finally, self-assembly of CNC behaviour is discussed, together with its implications on rheology and stability of CNC dispersions, as well as optical properties.

Perovskite piezoelectric compositions near the morphotropic phase boundary (MPB) are known to exhibit high piezoelectric response. In lead-based ABO(3) compound with B-site disorder, the origin of this enhancement has been associated with the presence of an intermediate monoclinic/orthorhombic state that bridges the adjacent ferroelectric rhombohedral and tetragonal phases. However, the origin of high piezoelectric response in lead-free ABO(3) compounds with A-site disorder has not been conclusively established. We describe a microscopic model derived from comparative analyses of high resolution transmission electron microscopy and neutron diffraction that explains the origin of high piezoelectric response in lead-free MPB compositions of 0.93(Na0.5Bi0.5)TiO3-0.07BaTiO3. Direct observation of nanotwins with monoclinic symmetry confirmed the presence of an intermediate bridging phase that facilitates a pathway for polarization reorientation. Monoclinic distortions of an average rhombohedral phase are attributed to localized displacements of atoms along the non-polar directions. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4792729]

This study investigated the effect of shape, size, and surface modification of hydroxyapatite (HAP) fillers on the degree of conversion (DC) and mechanical properties of a model BisGMA/TEGDMA composite initially and after 4 weeks of storage. Ten percent of conventional glass fillers were replaced by HAP spheres (Sph), silicon-doped spheres (Sph(Si)), whiskers (Wh), silicon-doped whiskers (Wh(Si)), and nanosized HAP particles (Nano). Spheres were specifically structured agglomerates consisting of a central void and radially orientated primary particles, whereas whiskers were compact monocrystals. DC, Vickers hardness (HV), flexural strength (Fs), flexural modulus (Ef), compressive strength (Cs), and compressive modulus (Ec) were tested. There were no significant differences in the DC between all tested groups. HV decreased by 5.4-17% with the addition of HAP, while Fs increased by 13.9-29% except in Nano group (decrease by 13%). After storage, Sph and Sph(Si) groups showed similar HV, Ef, Cs and Ec and higher Fs than the control. The fracture mode of HAP spheres was through the central void whereas whiskers showed longitudinal delamination, transverse, and mixed fractures. HAP spheres with or without silicon- doping have a potential to be part of the filler content of dental composites. (c) 2013 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 101B: 1469-1476, 2013.

This study investigated the effect of shape, size, and surface modification of hydroxyapatite (HAP) fillers on the degree of conversion (DC) and mechanical properties of a model BisGMA/TEGDMA composite initially and after 4 weeks of storage. Ten percent of conventional glass fillers were replaced by HAP spheres (Sph), silicon-doped spheres (Sph(Si)), whiskers (Wh), silicon-doped whiskers (Wh(Si)), and nanosized HAP particles (Nano). Spheres were specifically structured agglomerates consisting of a central void and radially orientated primary particles, whereas whiskers were compact monocrystals. DC, Vickers hardness (HV), flexural strength (Fs), flexural modulus (Ef), compressive strength (Cs), and compressive modulus (Ec) were tested. There were no significant differences in the DC between all tested groups. HV decreased by 5.4-17% with the addition of HAP, while Fs increased by 13.9-29% except in Nano group (decrease by 13%). After storage, Sph and Sph(Si) groups showed similar HV, Ef, Cs and Ec and higher Fs than the control. The fracture mode of HAP spheres was through the central void whereas whiskers showed longitudinal delamination, transverse, and mixed fractures. HAP spheres with or without silicon- doping have a potential to be part of the filler content of dental composites.

This study investigated the effect of shape, size, and surface modification of hydroxyapatite (HAP) fillers on the degree of conversion (DC) and mechanical properties of a model BisGMA/TEGDMA composite initially and after 4 weeks of storage. Ten percent of conventional glass fillers were replaced by HAP spheres (Sph), silicon-doped spheres (Sph(Si)), whiskers (Wh), silicon-doped whiskers (Wh(Si)), and nanosized HAP particles (Nano). Spheres were specifically structured agglomerates consisting of a central void and radially orientated primary particles, whereas whiskers were compact monocrystals. DC, Vickers hardness (HV), flexural strength (Fs), flexural modulus (Ef), compressive strength (Cs), and compressive modulus (Ec) were tested. There were no significant differences in the DC between all tested groups. HV decreased by 5.4-17% with the addition of HAP, while Fs increased by 13.9-29% except in Nano group (decrease by 13%). After storage, Sph and Sph(Si) groups showed similar HV, Ef, Cs and Ec and higher Fs than the control. The fracture mode of HAP spheres was through the central void whereas whiskers showed longitudinal delamination, transverse, and mixed fractures. HAP spheres with or without silicon- doping have a potential to be part of the filler content of dental composites.

Nonwoven membranes based on electrospun, fibers are of great interest in applications such as biomedical, filtering, and protective clothing.. The poor, mechanical performance is a limitation, as is some of the electrospinning Solvents. To address these problems, porous nonwoven membranes based on nanofibrillated cellulose (NFC) modified by a hydroxyethyl cellulose (HEC) polymer coating. are prepared. NFC/HEC aqueous suspensions are subjected to simple vacuum filtration: in a Paper-making fashion,, followed by supercritical CO2. drying., These nonwoven nanocomposite membranes are truly nanostructured and exhibit a nanoporous, network structure with high specific surface area, as analyzed by nitrogen adsorption and FE-SEM. Mechanical properties by tensile tests show high strength combined with remarkable high strain to failure up to 55%. XRD analysis revealed significant fibril realignment during tensile stretching. After postdrawing of the random mats, the modulus and strength are strongly increased. The present preparation route uses components from renewable resources, is environmentally friendly, and results in permeable membranes of exceptional imechanical performance., QC 20130107

An environmentally friendly procedure in aqueous solution for the surface modification of cellulose nanocrystals (CNCs) using quaternary ammonium salts via adsorption is developed as inspired by organomodified layered silicates. CNCs with a high carboxylate content of 1.5 mmol g(-1) were prepared by a new route, direct hydrochloric acid hydrolysis of 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO)-oxidized nanofibrillated cellulose from a softwood pulp, and characterized by atomic force microscopy (AFM) and X-ray diffraction (XRD). Four quaternary ammonium cation surfactants bearing long alkyl, phenyl, glycidyl, and diallyl groups were successfully used to modify CNCs carrying carboxylic acid groups as characterized by Fourier transform infrared spectroscopy (FTIR). The modified CNCs can be redispersed and individualized in an organic solvent such as toluene as observed by scanning transmission electron microscopy (STEM). One may envision removing excess surfactant to obtain CNC with a monolayer of surfactant. The toluene suspension of the modified CNCs showed strong birefringence under crossed polars but no further chiral- nematic ordering was observed. The model surface prepared by the CNCs modified with quaternary ammonium salts bearing C18 alkyl chains showed a significant increase in water contact angle (71 degrees) compared to that of unmodified CNCs (12 degrees). This new series of modified CNCs can be dried from solvent and have the potential to form well-dispersed nanocomposites with non-polar polymers., QC 20121109. Updated from manuscript to article in journal.

Conductance and magnetoresistance of Si whiskers with diameters 5-40 mkm doped with B impurity were investigated in temperature range 4,2÷300 К, frequency range 1÷1106 Hz and magnetic fields with intensity up to 14 Т by method of impedance spectroscopy. Impedance investigations showed that dopingconcentration in the crystals are становлять 3,61018 сm-3 and 5,21018 сm-3 which is correspondent to metal dielecric transition. Hopping conductance on impurity states was shown to be realized in the crystals in low temperature region which leads to appearance of negative magnetoresistance, Исследовано электропроводность и магнетосопротивление нитевидных кристаллов Si диаметром 5-40 мкм в температурном интервале 4,2 ÷300 К, в частотном диапазоне 1÷1106 Гц и в сильных магнитных полях до 14 Тл методом импедансной спектроскопии. На основе исследования импеданса определены концентрации примесей в кристаллах, которые составляют 3,6 1018 см-3 и 5,2 1018 см-3 и соответствуют переходу металл-диэлектрик. Показано, что в данных кристаллах в интервале низких темпрератур имеет место прыжковая проводимость по примесной зоне, которая приводит квозникновению отрицательного магнитосопротивления., Досліджено електропровідність та магнетоопір ниткоподібних кристалів Si діаметром 5–40 мкм у температурному інтервалі 4,2÷300 К, частотному діапазоні 1÷1106 Гц та сильних магнітних полях до 14 Тл методом імпедансної спектроскопії. На основі дослідження імпедансу визначені концентрації домішок у кристалах, які становлять 3,61018 см-3 і 5,21018 см-3 і відповідають переходу метал-діелектрик. Показано, що у даних кристалах в інтервалі низьких темпрератур має місце стрибкова провідність по домішковій зоні, яка приводить до виникнення від’ємного магнітоопору.