The Ardennes Offensive 1944

The abstract The presented bachelor's thesis examines the Ardennes Offensive undertaken in the end of the year of 1944 during the World War II. Based on the study of monographs related to this subject as well as examination of relevant historical sources, the aim of this thesis is to describe the planning, preparation and key military aspects of this operation. The final chapter analyses the causes of the German failure

Czechoslovak-US Relations during the 20th Years of the 20th Century

The aim of this thesis is to examine the foreign relations between Czechoslovakia and the United States of America during the second decade of the twentieth century. Particular attention is focused on the Czechoslovak effort to build a close relationship with the United States, an endeavor which resulted from the previous generous support, as many contemporaries believed, the United States provided to the Czechoslovak movement for independency during the World War I. The major objective of this study is thus to present evidence that Czechoslovak diplomacy intentionally pursued the vision of a stronger, above average bond with the United States. Furthermore, it attempts to assess to which extent was the Czechoslovak policy successful and which limitations it had to face. In this effort, the thesis mainly draws on extensive study of the archive materials from the Ministry of Foreign Affairs

Challenging aspects of contemporary cochlear implant electrode array design

Objective: A design comparison of current perimodiolar and lateral wall electrode arrays of the cochlear implant (CI) is provided. The focus is on functional features such as acoustic frequency coverage and tonotopic mapping, battery consumption and dynamic range. A traumacity of their insertion is also evaluated. Methods: Review of up-to-date literature. Results: Perimodiolar electrode arrays are positioned in the basal turn of the cochlea near the modiolus. They are designed to initiate the action potential in the proximity to the neural soma located in spiral ganglion. On the other hand, lateral wall electrode arrays can be inserted deeper inside the cochlea, as they are located along the lateral wall and such insertion trajectory is less traumatic. This class of arrays targets primarily surviving neural peripheral processes. Due to their larger insertion depth, lateral wall arrays can deliver lower acoustic frequencies in manner better corresponding to cochlear tonotopicity. In fact, spiral ganglion sections containing auditory nerve fibres tuned to low acoustic frequencies are located deeper than 1 and half turn inside the cochlea. For this reason, a significant frequency mismatch might be occurring for apical electrodes in perimodiolar arrays, detrimental to speech perception. Tonal languages such as Mandarin might be therefore better treated with lateral wall arrays. On the other hand, closer proximity to target tissue results in lower psychophysical threshold levels for perimodiolar arrays. However, the maximal comfort level is also lower, paradoxically resulting in narrower dynamic range than that of lateral wall arrays. Battery consumption is comparable for both types of arrays. Conclusions: Lateral wall arrays are less likely to cause trauma to cochlear structures. As the current trend in cochlear implantation is the maximal protection of residual acoustic hearing, the lateral wall arrays seem more suitable for hearing preservation CI surgeries. Future development could focus on combining the advantages of both types: perimodiolar location in the basal turn extended to lateral wall location for higher turn locations. Keyword: Cochlear implan

Three-dimensional current flow in a large-scale model of the cochlea and the mechanism of amplification of sound

The mammalian inner ear uses its sensory hair cells to detect and amplify incoming sound. It is unclear whether cochlear amplification arises uniquely from a voltage-dependent mechanism (electromotility) associated with outer hair cells (OHCs) or whether other mechanisms are necessary, for the voltage response of OHCs is apparently attenuated excessively by the membrane electrical filter. The cochlea contains many thousands of hair cells organized in extensive arrays, embedded in an electrically coupled system of supporting cells. We have therefore constructed a multi-element, large-scale computational model of cochlear sound transduction to study the underlying potassium (K+) recirculation. We have included experimentally determined parameters of cochlear macromechanics, which govern sound transduction, and data on hair cells' electrical parameters including tonotopical variation in the membrane conductance of OHCs. In agreement with the experiment, the model predicts an exponential decay of extracellular longitudinal K+ current spread. In contrast to the predictions from isolated cells, it also predicts low attenuation of the OHC transmembrane receptor potential (−5 dB per decade) in the 0.2–30 kHz range. This suggests that OHC electromotility could be driven by the transmembrane potential. Furthermore, the OHC electromotility could serve as a single amplification mechanism over the entire hearing range

Struktura a optické vlastnosti amorfních tenkých vrstev podél linie As40S60 - MoS3 připravené rotačním nanášením

The extremely high melting point of Mo, W and their sulfides acts as a barrier to the synthesis of chalcogenide glasses modified with these transition metal elements. Here, we demonstrate the preparation of amorphous thin films along the pseudobinary As40S60 MoS3 tie-line by spin-coating. Using 0.02 M stock solutions, the limiting As40S60 : MoS3 molar ratio was found to be 1 : 3 for the deposition of highly transparent, very smooth and compact defect-free amorphous thin films. The spectral analysis of optical constants revealed that both the refractive index and extinction coefficient decrease with increasing MoS3 content. On the other hand, the contribution of absorption tails was observed starting from the ratio 2 : 1 and they gradually become more intense and red-shifted with increasing MoS3. Using Raman and infrared spectroscopies (ATR), we confirmed that As40S60 and MoS3 reacted chemically in solution and all thin layers contained only residual amounts of organic ammonium salts after annealing at 200 degrees C. Our results demonstrate that the sol-gel method can be a feasible and cost-effective strategy for the preparation of amorphous chalcogenide thin films containing transition metals.Extrémně vysoký bod tání Mo, W a jejich sulfidů působí jako bariéra pro syntézu chalkogenidových skel modifikovaných těmito prvky přechodných kovů. Zde demonstrujeme přípravu amorfních tenkých vrstev podél pseudobinární linie As40S60 - MoS3 metodou rotačního nanášení. Použitím 0,02 M zásobních roztoků byl zjištěn limitní molární poměr As40S60 : MoS3 1 : 3 pro depozici vysoce transparentních, velmi hladkých a kompaktních amorfních tenkých vrstev bez defektů. Spektrální analýza optických konstant odhalila, že jak index lomu, tak i extinkční koeficient klesají s rostoucím obsahem MoS3. Na druhou stranu byl pozorován příspěvek absorpčních chvostů od poměru 2 : 1, které se postupně stávají intenzivnějšími a posouvají se k nižším energiím s rostoucím obsahem MoS3. Pomocí Ramanovy a infračervené spektroskopie (ATR) jsme potvrdili, že As40S60 a MoS3 chemicky reagovaly v roztoku a všechny tenké vrstvy po žíhání při 200 ∘ C obsahovaly pouze zbytková množství organických amonných solí. Naše výsledky ukazují, že metoda sol-gel může být proveditelná a nákladově efektivní strategii pro přípravu tenkých amorfních chalkogenidových filmů obsahujících přechodný kov

Effect of plasma composition on nanocrystalline diamond layers deposited by a microwave linear antenna plasma-enhanced chemical vapour deposition system

International audienceThe addition of CO2 into the process gas has a significant impact on the quality and the incorporation of boron in CVD diamond layers. In this report we study the effect of CO2 addition in the gas phase on the properties of boron doped nano‐crystalline diamond (BNCD) layers grown at low substrate temperatures (450–500 °C) using a microwave linear antenna plasma‐enhanced chemical vapour deposition apparatus (MW‐LA‐PECVD). Experimental results show an increase in the layers' conductivity with a reduction in CO2 concentration, which is consistent with the variation in the atomic boron emission line intensity measured by optical emission spectroscopy (OES). At CO2 concentrations close to zero, we observed the formation of a smooth, transparent and highly resistive layer on unseeded substrates. This layer has been identified as silicon carbide (SiC) by transmission electron microscopy and X‐ray photoelectron microscopy. The presence of silicon in the plasma is confirmed by OES and it is attributed to quartz tube etching. In this specific deposition condition, diamond growth is in competition with SiC growth

Fine control of drug delivery for cochlear implant applications

Cochlear implants are neuroprostheses that are inserted into the inner ear to directly electrically stimulate the auditory nerve, thus replacing lost cochlear receptors, the hair cells. The reduction of the gap between electrodes and nerve cells will contribute to technological solutions simultaneously increasing the frequency resolution, the sound quality and the amplification of the signal. Recent findings indicate that neurotrophins (NTs) such as brain derived neurotrophic factor (BDNF) stimulate the neurite outgrowth of auditory nerve cells by activating Trk receptors on the cellular surface (1–3). Furthermore, small-size TrkB receptor agonists such as di-hydroxyflavone (DHF) are now available, which activate the TrkB receptor with similar efficiency as BDNF, but are much more stable (4). Experimentally, such molecules are currently used to attract nerve cells towards, for example, the electrodes of cochlear implants. This paper analyses the scenarios of low dose aspects of controlled release of small-size Trk receptor agonists from the coated CI electrode array into the inner ear. The control must first ensure a sufficient dose for the onset of neurite growth. Secondly, a gradient in concentration needs to be maintained to allow directive growth of neurites through the perilymph-filled gap towards the electrodes of the implant. We used fluorescein as a test molecule for its molecular size similarity to DHF and investigated two different transport mechanisms of drug dispensing, which both have the potential to fulfil controlled low-throughput drug-deliverable requirements. The first is based on the release of aqueous fluorescein into water through well-defined 60-μm size holes arrays in a membrane by pure osmosis. The release was both simulated using the software COMSOL and observed experimentally. In the second approach, solid fluorescein crystals were encapsulated in a thin layer of parylene (PPX), hence creating random nanometer-sized pinholes. In this approach, the release occurred due to subsequent water diffusion through the pinholes, dissolution of the fluorescein and then release by out-diffusion. Surprisingly, the release rate of solid fluorescein through the nanoscopic scale holes was found to be in the same order of magnitude as for liquid fluorescein release through microscopic holes

Pore topology of the hyperpolarization-activated cyclic nucleotide-gated channel from sea urchin sperm.

The current flow through hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, referred to as I(h), plays a major role in several fundamental biological processes. The sequence of the presumed pore region of HCN channels is reminiscent of that of most known K(+)-selective channels. In the present work, the pore topology of an HCN channel from sea urchin sperm, called SpHCN, was investigated by means of the substituted-cysteine accessibility method (SCAM). The I(h) current in the wild-type (w.t.) SpHCN channel was irreversibly blocked by intracellular Cd(2+). This blockage was not observed in mutant C428S. Extracellular Cd(2+) did not cause any inhibition of the I(h) current in the w.t. SpHCN channel, but blocked the current in mutant channels K433C and F434C. Large extracellular anions blocked the current both in the w.t. and K433Q mutant channel. These results suggest that 1) cysteine in position 428 faces the intracellular medium; 2) lysine and phenylalanine in position 433 and 434, respectively, face the extracellular side of the membrane; and 3) lysine 433 does not mediate the anion blockade. Additionally, our study confirms that the K(+) channel signature sequence GYG also forms the inner pore in HCN channels

Reduced Electromotility of Outer Hair Cells Associated with Connexin-Related Forms of Deafness: An In silico Study of a Cochlear Network Mechanism

Mutations in the GJB2 gene encoding for the connexin 26 (Cx26) protein are the most common source of nonsyndromic forms of deafness. Cx26 is a building block of gap junctions (GJs) which establish electrical connectivity in distinct cochlear compartments by allowing intercellular ionic (and metabolic) exchange. Animal models of the Cx26 deficiency in the organ of Corti seem to suggest that the hearing loss and the degeneration of outer hair cells (OHCs) and inner hair cells is due to failed K+ and metabolite homeostasis. However, OHCs can develop normally in some mutants, suggesting that the hair cells death is not the universal mechanism. In search for alternatives, we have developed an in silico large scale three-dimensional model of electrical current flow in the cochlea in the small signal, linearised, regime. The effect of mutations was analysed by varying the magnitude of resistive components representing the GJ network in the organ of Corti. The simulations indeed show that reduced GJ conductivity increases the attenuation of the OHC transmembrane potential at frequencies above 5 kHz from 6.1 dB/decade in the wild-type to 14.2 dB/decade. As a consequence of increased GJ electrical filtering, the OHC transmembrane potential is reduced by up to 35 dB at frequencies >10 kHz. OHC electromotility, driven by this potential, is crucial for sound amplification, cochlear sensitivity and frequency selectivity. Therefore, we conclude that reduced OHC electromotility may represent an additional mechanism underlying deafness in the presence of Cx26 mutations and may explain lowered OHC functionality in particular reported Cx26 mutants