Water entry of a flat elastic plate at high horizontal speed

The two-dimensional problem of an elastic-plate impact onto an undisturbed surface of water of infinite depth is analysed. The plate is forced to move with a constant horizontal velocity component which is much larger than the vertical velocity component of penetration. The small angle of attack of the plate and its vertical velocity vary in time, and are determined as part of the solution, together with the elastic deflection of the plate and the hydrodynamic loads within the potential flow theory. The boundary conditions on the free surface and on the wetted part of the plate are linearized and imposed on the initial equilibrium position of the liquid surface. The wetted part of the plate depends on the plate motion and its elastic deflection. To determine the length of the wetted part we assume that the spray jet in front of the advancing plate is negligible. A smooth separation of the free-surface flow from the trailing edge is imposed. The wake behind the moving body is included in the model. The plate deflection is governed by Euler’s beam equation, subject to free–free boundary conditions. Four different regimes of plate motion are distinguished depending on the impact conditions: (a) the plate becomes fully wetted; (b) the leading edge of the plate touches the water surface and traps an air cavity; (c) the free surface at the forward contact point starts to separate from the plate; (d) the plate exits the water. We could not detect any impact conditions which lead to steady planing of the free plate after the impact. It is shown that a large part of the total energy in the fluid–plate interaction leaves the main bulk of the liquid with the spray jet. It is demonstrated that the flexibility of the plate may increase the hydrodynamic loads acting on it. The impact loads can cause large bending stresses, which may exceed the yield stress of the plate material. The elastic vibrations of the plate are shown to have a significant effect on the fluid flow in the wake

Polyion Detection via All‐solid‐contact Paper‐based Polyion‐sensitive Polymeric Membrane Electrodes

The first all‐solid‐contact paper‐based single‐use polyion‐sensitive ion‐selective electrodes (ISEs) are described. These polyion‐sensitive ISEs are fabricated using cellulose filter paper coated with a carbon ink conductive layer. A polyanion sensing membrane is cast on a section of the coated paper and the sensor is insulated, resulting in a disposable, single‐use device. Various polyanions are shown to yield large negative potentiometric responses when using these disposable devices for direct polyanion detection. These new sensors are further demonstrated to be useful in indirect polycation detection when polycations (i. e., polyquaterniums (PQs)) are titrated with polyanionic dextran sulfate (DS). Titrations monitored using these paper‐based, all‐solid‐contact devices yield endpoints proportional to the given PQ concentration present in the test sample.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/151253/1/elan201900155.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/151253/2/elan201900155_am.pd

Association of Superoxide Dismutase 2 (SOD2) Genotype with Gray Matter Volume Shrinkage in Chronic Alcohol Users: Replication and Further Evaluation of an Addiction Gene Panel.

BackgroundReduction in brain volume, especially gray matter volume, has been shown to be one of the many deleterious effects of prolonged alcohol consumption. High variance in the degree of gray matter tissue shrinkage among alcohol-dependent individuals and a previous neuroimaging genetics report suggest the involvement of environmental and/or genetic factors, such as superoxide dismutase 2 (SOD2). Identification of such underlying factors will help in the clinical management of alcohol dependence.MethodsWe analyzed quantitative magnetic resonance imaging and genotype data from 103 alcohol users, including both light drinkers and treatment-seeking alcohol-dependent individuals. Genotyping was performed using a custom gene array that included genes selected from 8 pathways relevant to chronic alcohol-related brain volume loss.ResultsWe replicated a significant association of a functional SOD2 single nucleotide polymorphism with normalized gray matter volume, which had been reported previously in an independent smaller sample of alcohol-dependent individuals. The SOD2-related genetic protection was observed only at the cohort's lower drinking range. Additional associations between normalized gray matter volume and other candidate genes such as alcohol dehydrogenase gene cluster (ADH), GCLC, NOS3, and SYT1 were observed across the entire sample but did not survive corrections for multiple comparisons.ConclusionConverging independent evidence for a SOD2 gene association with gray matter volume shrinkage in chronic alcohol users suggests that SOD2 genetic variants predict differential brain volume loss mediated by free radicals. This study also provides the first catalog of genetic variations relevant to gray matter loss in chronic alcohol users. The identified gene-brain structure relationships are functionally pertinent and merit replication

X‐Ray Diffraction Camera for the Alignment of Large Single Crystals

A back-reflection Laue camera with three rotation axes and three orthogonal translation axes is described. This camera allows the alignment of large single crystals with a precision of plus or minus 0.25 deg . The degree of single crystallinity of a specimen may be examined. In addition it is possible to accurately mark a crystal for subsequent utilization. (auth

Social preferences for adaptation measures to conserve Australian birds threatened by climate change

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.Debate about climate change adaptation for biodiversity, and the ethics and consequences of assisted colonization in particular, has polarized professional opinion but the views of the wider community are unknown. We tested four hypotheses about the acceptability of adaptation strategies among a sample of the Australian general public using a combination of direct questions and a choice experiment. We found that (1) among the 80% who wanted extinction avoided, increased in situ management of wild populations was preferred to captive breeding or assisted colonization, (2) preferences for adaptation strategies were not explained by gender, income, education or knowledge about birds, (3) genetically distinctive taxa were not actively preferred, (4) > 60% of respondents were content for conservation managers to make decisions about strategies rather than local communities or the general public. The results provide Australian policy makers with a mandate to bolster efforts to retain existing populations but suggest that assisted colonization and captive breeding could be accepted if essential

Instanton Contribution to the Proton and Neutron Electric Form Factors

We study the instanton contribution to the proton and neutron electric form factors. Using the single instanton approximation, we perform the calculations in a mixed time-momentum representation in order to obtain the form factors directly in momentum space. We find good agreement with the experimentally measured electric form factor of the proton. For the neutron, our result falls short of the experimental data. We argue that this discrepancy is due to the fact that we neglect the contribution of the sea quarks. We compare to lattice calculations and a relativistic version of the quark-diquark model.Comment: 8 pages, 5 figures, updated references, to appear in Phys. Lett.

Decoupling Inflation From the String Scale

When Inflation is embedded in a fundamental theory, such as string theory, it typically begins when the Universe is already substantially larger than the fundamental scale [such as the one defined by the string length scale]. This is naturally explained by postulating a pre-inflationary era, during which the size of the Universe grew from the fundamental scale to the initial inflationary scale. The problem then arises of maintaining the [presumed] initial spatial homogeneity throughout this era, so that, when it terminates, Inflation is able to begin in its potential-dominated state. Linde has proposed that a spacetime with compact negatively curved spatial sections can achieve this, by means of chaotic mixing. Such a compactification will however lead to a Casimir energy, which can lead to effects that defeat the purpose unless the coupling to gravity is suppressed. We estimate the value of this coupling required by the proposal, and use it to show that the pre-inflationary spacetime is stable, despite the violation of the Null Energy Condition entailed by the Casimir energy.Comment: 24 pages, 5 eps figures, references added, stylistic changes, version to appear in Classical and Quantum Gravit

Response properties, applications and limitations of carbonate-selective polymer membrane electrodes

The preparation and response characteristics of a carbonate-selective polymer membrane electrode are reported. The electrode is prepared by incorporating Aliquat 336, trifluoroacetyl-p-butylbenzene and di-2-ethylhexyl sebacate or dioctyl phthalate in a poly(vinylchloride) membrane matrix. The effect of membrane composition and electrode response in various buffer systems are examined. Under buffer conditions appropriate for practical measurements, potentiometric data yield the following selectivity pattern: ClO4- = salicylate> total carbon dioxide species> I- > NO3- > acetate> Cl- > Br-. The electrode can be readily fabricated in tubular form and utilized within a very simple flow-injection arrangement to determine total carbon dioxide species. The possible applications of the electrode to serum CO2 measurements as well as within newly devised gas-sensing arrangements for dissolved CO2 are also examined.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23870/1/0000109.pd