A semi-analytical solution for viscothermal wave propagation in narrow gaps with arbitrary boundary conditions.

Previous research has shown that viscothermal wave propagation in narrow gaps can efficiently be described by means of the low reduced frequency model. For simple geometries and boundary conditions, analytical solutions are available. For example, Beltman [4] gives the acoustic pressure in the gap between an oscillating, rigid, rectangular plate and a rigid surface. Assuming a pressure release boundary condition at the circumference of the plate, excellent agreement with experiments was obtained. In many engineering applications however, the boundary conditions may vary along the circumference of the plate. For instance, the vibrating membranes in hearing aid receivers are attached to complex structures and a simple pressure release (p = 0) or zero velocity boundary condition (dp=dn = 0) is only valid at some parts of the circumference of the vibrating structure. One can use numerical methods, like FEM or BEM, but often a large number of degrees of freedom is needed to obtain accurate results. Furthermore, a thorough understanding of the various phenomena can only be gained through a large number of calculations. In this paper a semi-analytical solution is presented for the viscothermal wave propagation in the gap between an oscillating, rigid, circular plate and a rigid surface for the boundary conditions just mentioned. The pressure in the gap is written as a series expansion of solutions satisfying the differential equations in the interior domain. Subsequently, either the pressure release or the zero velocity boundary condition is imposed on different parts of the circumference. The unknown constants in the series expansion are determined using a weak form of the boundary conditions. It is shown that only a limited number of terms is needed to accurately describe the total acoustic force on the plate. The solution is validated by means of a finite element calculation

Einzelmolekül-Experimente an Nanoporen mit der Optischen Pinzette

Spiering A. Einzelmolekül-Experimente an Nanoporen mit der Optischen Pinzette. Bielefeld: Universität Bielefeld; 2014

Does preappointment gabapentin affect neurological examination findings? a prospective, randomized and blinded study in healthy cats

Objectives The aim of this study was to evaluate the influence of a preappointment oral dose of gabapentin on the neurological examination of cats. Methods A prospective, randomized and blinded clinical trial was conducted in 35 client-owned healthy cats. Cats were scheduled for two appointments and randomly assigned to receive either a placebo or a 100 mg gabapentin capsule prior to the second veterinary visit. A neurological examination was performed during each visit, and the results were compared between groups. Normal/abnormal response rates for each test were based on the number of cats that allowed the test to be performed. Results Gabapentin was administered to 17 cats. Gait and postural reactions were significantly affected in the gabapentin group. Comparing the gabapentin with the placebo groups, proprioceptive ataxia was identified in 4/17(23.5%) vs 0/18 cats (P=0.0288); paw placement deficits were seen in 10/11(90.9%) vs 1/4(25%) cats; table tactile placement deficits were identified in 13/17(76.5%) vs 0/18 cats (P<0.0001); hopping deficits were seen in 5/17(29.4%) vs 0/16 cats (P=0.0185); and abnormalities on wheelbarrowing and extensor postural thrust were reported in 5/17(29.4%) vs 0/18 cats (P=0.0129). These results had no correlation with age or dose/kg received. No significant difference was noted in the assessment of level and content of consciousness, posture, cranial nerves and spinal nerves. No significant differences were noted in test compliance or examination duration. Conclusions and relevance Gabapentin significantly altered gait analyses and postural reactions in this group of healthy cats. The administration of gabapentin could lead to false–positive results and, possibly, an incorrect identification of neurological lesions. In contrast, gabapentin did not impair the assessment of cranial nerves and spinal reflexes, which can be assessed in patients receiving the drug

Search for non-relativistic Magnetic Monopoles with IceCube

The IceCube Neutrino Observatory is a large Cherenkov detector instrumenting $1\,\mathrm{km}^3$ of Antarctic ice. The detector can be used to search for signatures of particle physics beyond the Standard Model. Here, we describe the search for non-relativistic, magnetic monopoles as remnants of the GUT (Grand Unified Theory) era shortly after the Big Bang. These monopoles may catalyze the decay of nucleons via the Rubakov-Callan effect with a cross section suggested to be in the range of $10^{-27}\,\mathrm{cm^2}$ to $10^{-21}\,\mathrm{cm^2}$. In IceCube, the Cherenkov light from nucleon decays along the monopole trajectory would produce a characteristic hit pattern. This paper presents the results of an analysis of first data taken from May 2011 until May 2012 with a dedicated slow-particle trigger for DeepCore, a subdetector of IceCube. A second analysis provides better sensitivity for the brightest non-relativistic monopoles using data taken from May 2009 until May 2010. In both analyses no monopole signal was observed. For catalysis cross sections of $10^{-22}\,(10^{-24})\,\mathrm{cm^2}$ the flux of non-relativistic GUT monopoles is constrained up to a level of $\Phi_{90} \le 10^{-18}\,(10^{-17})\,\mathrm{cm^{-2}s^{-1}sr^{-1}}$ at a 90% confidence level, which is three orders of magnitude below the Parker bound. The limits assume a dominant decay of the proton into a positron and a neutral pion. These results improve the current best experimental limits by one to two orders of magnitude, for a wide range of assumed speeds and catalysis cross sections.Comment: 20 pages, 20 figure

All-sky search for time-integrated neutrino emission from astrophysical sources with 7 years of IceCube data

Since the recent detection of an astrophysical flux of high energy neutrinos, the question of its origin has not yet fully been answered. Much of what is known about this flux comes from a small event sample of high neutrino purity, good energy resolution, but large angular uncertainties. In searches for point-like sources, on the other hand, the best performance is given by using large statistics and good angular reconstructions. Track-like muon events produced in neutrino interactions satisfy these requirements. We present here the results of searches for point-like sources with neutrinos using data acquired by the IceCube detector over seven years from 2008--2015. The discovery potential of the analysis in the northern sky is now significantly below $E_\nu^2d\phi/dE_\nu=10^{-12}\:\mathrm{TeV\,cm^{-2}\,s^{-1}}$, on average $38\%$ lower than the sensitivity of the previously published analysis of four years exposure. No significant clustering of neutrinos above background expectation was observed, and implications for prominent neutrino source candidates are discussed.Comment: 19 pages, 17 figures, 3 tables; ; submitted to The Astrophysical Journa

The IceCube Neutrino Observatory - Contributions to ICRC 2015 Part II: Atmospheric and Astrophysical Diffuse Neutrino Searches of All Flavors

Papers on atmospheric and astrophysical diffuse neutrino searches of all flavors submitted to the 34th International Cosmic Ray Conference (ICRC 2015, The Hague) by the IceCube Collaboration.Comment: 66 pages, 36 figures, Papers submitted to the 34th International Cosmic Ray Conference, The Hague 2015, v2 has a corrected author lis

Flavor Ratio of Astrophysical Neutrinos above 35 TeV in IceCube

A diffuse flux of astrophysical neutrinos above $100\,\mathrm{TeV}$ has been observed at the IceCube Neutrino Observatory. Here we extend this analysis to probe the astrophysical flux down to $35\,\mathrm{TeV}$ and analyze its flavor composition by classifying events as showers or tracks. Taking advantage of lower atmospheric backgrounds for shower-like events, we obtain a shower-biased sample containing 129 showers and 8 tracks collected in three years from 2010 to 2013. We demonstrate consistency with the $(f_e:f_{\mu}:f_\tau)_\oplus\approx(1:1:1)_\oplus$ flavor ratio at Earth commonly expected from the averaged oscillations of neutrinos produced by pion decay in distant astrophysical sources. Limits are placed on non-standard flavor compositions that cannot be produced by averaged neutrino oscillations but could arise in exotic physics scenarios. A maximally track-like composition of $(0:1:0)_\oplus$ is excluded at $3.3\sigma$, and a purely shower-like composition of $(1:0:0)_\oplus$ is excluded at $2.3\sigma$.Comment: 8 pages, 3 figures. Submitted to PR

A combined maximum-likelihood analysis of the high-energy astrophysical neutrino flux measured with IceCube

Evidence for an extraterrestrial flux of high-energy neutrinos has now been found in multiple searches with the IceCube detector. The first solid evidence was provided by a search for neutrino events with deposited energies $\gtrsim30$ TeV and interaction vertices inside the instrumented volume. Recent analyses suggest that the extraterrestrial flux extends to lower energies and is also visible with throughgoing, $\nu_\mu$-induced tracks from the Northern hemisphere. Here, we combine the results from six different IceCube searches for astrophysical neutrinos in a maximum-likelihood analysis. The combined event sample features high-statistics samples of shower-like and track-like events. The data are fit in up to three observables: energy, zenith angle and event topology. Assuming the astrophysical neutrino flux to be isotropic and to consist of equal flavors at Earth, the all-flavor spectrum with neutrino energies between 25 TeV and 2.8 PeV is well described by an unbroken power law with best-fit spectral index $-2.50\pm0.09$ and a flux at 100 TeV of $\left(6.7_{-1.2}^{+1.1}\right)\cdot10^{-18}\,\mathrm{GeV}^{-1}\mathrm{s}^{-1}\mathrm{sr}^{-1}\mathrm{cm}^{-2}$. Under the same assumptions, an unbroken power law with index $-2$ is disfavored with a significance of 3.8 $\sigma$ ($p=0.0066\%$) with respect to the best fit. This significance is reduced to 2.1 $\sigma$ ($p=1.7\%$) if instead we compare the best fit to a spectrum with index $-2$ that has an exponential cut-off at high energies. Allowing the electron neutrino flux to deviate from the other two flavors, we find a $\nu_e$ fraction of $0.18\pm0.11$ at Earth. The sole production of electron neutrinos, which would be characteristic of neutron-decay dominated sources, is rejected with a significance of 3.6 $\sigma$ ($p=0.014\%$).Comment: 16 pages, 10 figures; accepted for publication in The Astrophysical Journal; updated one referenc