Les dèmes, circonscriptions administratives de la cité d’Athènes, constituent un observatoire privilégié pour l’étude des sociétés antiques. La petite échelle qu’ils représentent donne la possibilité ...à l’historien d’appréhender les aspects les plus divers de la vie de leurs habitants et de leurs ressortissants. Ce livre propose de pénétrer au plus près du quotidien des anciens Athéniens à travers l’étude d’Aixônè, l’un des dèmes les plus peuplés et les mieux documentés. Par une exploitation minutieuse des sources disponibles – inscriptions, structures archéologiques, auteurs antiques, récits de voyageurs modernes et contemporains –, un éclairage nouveau est apporté sur la topographie et le fonctionnement institutionnel d’un dème, sur les activités politiques, économiques et religieuses qui s’y déroulaient. Les résultats de cette enquête dépassent cependant largement le niveau local. Divinités nouvelles ou méconnues, magistratures inédites, pratiques religieuses, économiques, juridiques et institutionnelles mal documentées ou incomprises jusqu’ici, c’est tout un pan de l’histoire grecque qui se révèle dans cette microhistoire d’Athènes.
The delivery of therapeutic levels of electrical current to neural tissue is a well-established treatment for numerous indications such as Parkinson's disease and chronic pain. While the ...neuromodulation medical device industry has experienced steady clinical growth over the last two decades, much of the core technology underlying implanted pulse generators remain unchanged. In this study we propose some new methods for achieving increased energy-efficiency during neural stimulation. The first method exploits the biophysical features of excitable tissue through the use of a centered-triangular stimulation waveform. Neural activation with this waveform is achieved with a statistically significant reduction in energy compared to traditional rectangular waveforms. The second method demonstrates energy savings that could be achieved by advanced circuitry design. We show that the traditional practice of using a fixed compliance voltage for constant-current stimulation results in substantial energy loss. A portion of this energy can be recuperated by adjusting the compliance voltage to real-time requirements. Lastly, we demonstrate the potential impact of axon fiber diameter on defining the energy-optimal pulse-width for stimulation. When designing implantable pulse generators for energy efficiency, we propose that the future combination of a variable compliance system, a centered-triangular stimulus waveform, and an axon diameter specific stimulation pulse-width has great potential to reduce energy consumption and prolong battery life in neuromodulation devices.
We present the first structure determination by surface x-ray diffraction during the restructuring of a model catalyst under reaction conditions, i.e., at high pressure and high temperature, and ...correlate the restructuring with a change in catalytic activity. We have analyzed the Pt(110) surface during CO oxidation at pressures up to 0.5 bar and temperatures up to 625 K. Depending on the pressure ratio, we find three well-defined structures: namely, (i) the bulk-terminated Pt(110) surface, (ii) a thin, commensurate oxide, and (iii) a thin, incommensurate oxide. The commensurate oxide only appears under reaction conditions, i.e., when both and CO are present and at sufficiently high temperatures. Density functional theory calculations indicate that the commensurate oxide is stabilized by carbonate ions (CO3(2-)). Both oxides have a substantially higher catalytic activity than the bulk-terminated Pt surface.
•The block inception time for kiloHertz frequency alternating current nerve block has not been measured previously.•A novel method was created to extract the block inception time from muscle force ...measurements.•The block inception time was found to be on average 5 ms to 10 ms, with the most rapid inception being 2.5 ms to 5 ms.•Block inception times for KHFAC nerve block were significant more rapid than previously estimated.
Kilohertz frequency alternating currents (KHFAC) produce rapid nerve conduction block of mammalian peripheral nerves and have potential clinical applications in reducing nerve hyperactivity. However, there are no experimental measurements of the block inception time (BIT) for the complete block of mammalian motor axons, i.e. the time from the start of delivery of the KHFAC to the axons reaching a fully blocked state.
A “counted cycles” method (CCM) was designed to exploit characteristics of the onset response, which is typical of KHFAC block, to measure the BIT with a millisecond time resolution. Randomized and repeated experiments were conducted in an in-vivo rodent model, using trains of KHFAC over a range of complete cycle counts at three frequencies (10, 20, and 40 kHz).
Complete motor nerve conduction block was obtained in the rat sciatic nerve (N = 4) with an average BIT range of 5 ms–10 ms. The fastest BIT measured was 2.5 ms–5 ms. There was no statistical difference between the block inception times for the three frequencies tested.
There are no comparable methods to measure the KHFAC BIT.
The KHFAC BIT is faster than previously estimated. KHFAC motor nerve block is established in milliseconds. These results may assist in the design of methods to eliminate the onset response produced by KHFAC nerve block.
Isomers in superheavy nuclei Ackermann, D.; Antalic, S.; Heßberger, F. P.
The European physical journal. ST, Special topics,
2024/6, Volume:
233, Issue:
5
Journal Article
Peer reviewed
Open access
Isomeric states in atomic nuclei are a well-known phenomenon all over the complete chart of nuclei. Their properties deliver valuable information on the structure of the nuclei. A region of specific ...interest are the very heavy and superheavy nuclei, where the occurrence and properties of isomeric states will have an impact on the prediction of localization and strength of the spherical superheavy proton and neutron shells. In this review, an overview of the present situation is given. Some specific features are discussed for selected examples.
Zeolites and mesoporous materials were systematically modified by ion exchange and impregnation with hygroscopic salts to improve their storage capacity in thermochemical storage of heat. The ...sorption properties of those potential storage materials against water were investigated with physico-chemical methods such as thermogravimetry, differential scanning calorimetry, microcalorimetry and isotherm measurements confirming the improvement of the storage properties. Selected materials were pelleted and investigated in a lab-scaled storage to prove the performance of the modified storage materials. Two zeolite based materials with a charging temperature of approximately 450 K but a high temperature lift and an improved storage density of up to 576 kJ/L were found. Impregnated mesoporous materials show a much lower temperature lift, however, they offer a potential storage density of about 864 kJ/L at a charging temperature of about 390 K.
Atomic steps at the surface of a catalyst play an important role in heterogeneous catalysis, for example as special sites with increased catalytic activity. Exposure to reactants can cause entirely ...new structures to form at the catalyst surface, and these may dramatically influence the reaction by 'poisoning' it or by acting as the catalytically active phase. For example, thin metal oxide films have been identified as highly active structures that form spontaneously on metal surfaces during the catalytic oxidation of carbon monoxide. Here, we present operando X-ray diffraction experiments on a palladium surface during this reaction. They reveal that a high density of steps strongly alters the stability of the thin, catalytically active palladium oxide film. We show that stabilization of the metal, caused by the steps and consequent destabilization of the oxide, is at the heart of the well-known reaction rate oscillations exhibited during CO oxidation at atmospheric pressure.
Kilohertz frequency alternating current (KHFAC) waveforms reversibly block conduction in mammalian peripheral nerves. The initiation of the KHFAC produces nerve activation, called the onset response, ...before complete block occurs. An amplitude ramp, starting from zero amplitude, is ineffective in eliminating this onset activity. We postulated that initiating the ramp from a non-zero amplitude would produce a different effect on the onset.
Experiments were conducted in an in vivo rat model. KHFAC was applied at supra block threshold amplitudes and then reduced to a lower sub block amplitude (25, 50, 75 and 90% of the block threshold amplitude). The amplitude was then increased again to the original supra block threshold amplitude with an amplitude ramp. This ramp time was varied for each of the amplitude levels tested.
The amplitude ramp was successful in eliminating a second onset. This was always possible for the ramps up from 75 and 90% block threshold amplitude, usually from 50% but never from 25% of the block threshold amplitude.
This maneuver can potentially be used to initiate complete nerve block, transition to partial block and then resume complete block without producing further onset responses.
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