Xenogeneic, extracorporeal liver perfusion in primates improves the ratio of branched-chain amino acids to aromatic amino acids (Fischer's ratio)

In fulminant hepatic failure (FHF), the development of hepatic encephalopathy is associated with grossly abnormal concentrations of plasma amino acids (PAA). Normalization of the ratio of branched-chain amino acids to aromatic amino acids (Fischer's ratio) correlates with clinical improvement. This study evaluated changes in PAA metabolism during 4 h of isolated, normothermic extracorporeal liver perfusion using a newly designed system containing human blood and a rhesus monkey liver. Bile and urea production were within the physiological range. Release of the transaminases AST, ALT and LDH were minimal. The ratio of branched (valine, leucine, isoleucine) to aromatic (tyrosine, phenylalanine) amino acids increased significantly. These results indicate that a xenogeneic extracorporeal liver perfusion system is capable of significantly increasing Fischer's ratio and may play a role in treating and bridging patients in FHF in the future

Test of Lorentz Symmetry by using a 3He/129Xe Co-Magnetometer

To test Lorentz symmetry we used a 3He/129Xe co-magnetometer. We will give a short summary of our experimental setup and the results of our latest measurements. We obtained preliminary results for the equatorial component of the background field interacting with the spin of the bound neutron: b_n < 3.72 x 10^(-32) GeV (95 C.L.).Comment: Presented at the Fifth Meeting on CPT and Lorentz Symmetry, Bloomington, Indiana, June 28 - July 2, 201

Limit on Lorentz and CPT violation of the bound Neutron Using a Free Precession 3He/129Xe co-magnetometer

We report on the search for Lorentz violating sidereal variations of the frequency difference of co-located spin-species while the Earth and hence the laboratory reference frame rotates with respect to a relic background field. The co-magnetometer used is based on the detection of freely precessing nuclear spins from polarized 3He and 129Xe gas samples using SQUIDs as low-noise magnetic flux detectors. As result we can determine the limit for the equatorial component of the background field interacting with the spin of the bound neutron to be bn < 3.7 x 10^{-32} GeV (95 C.L.).Comment: 5 pages, 4 figure

Glacial melt under a porous debris layer

In this paper we undertake a quantitative analysis of the dynamic process by which ice underneath a dry porous debris layer melts. We show that the incorporation of debris-layer airflow into a theoretical model of glacial melting can capture the empirically observed features of the so-called Østrem curve (a plot of the melt rate as a function of debris depth). Specifically, we show that the turning point in the Østrem curve can be caused by two distinct mechanisms: the increase in the proportion of ice that is debris-covered and/or a reduction in the evaporative heat flux as the debris layer thickens. This second effect causes an increased melt rate because the reduction in (latent) energy used for evaporation increases the amount of energy available for melting. Our model provides an explicit prediction for the melt rate and the temperature distribution within the debris layer, and provides insight into the relative importance of the two effects responsible for the maximum in the Østrem curve. We use the data of Nicholson and Benn (2006) to show that our model is consistent with existing empirical measurements

Comparison of ultracold neutron sources for fundamental physics measurements

Ultracold neutrons (UCNs) are key for precision studies of fundamental parameters of the neutron and in searches for new CP violating processes or exotic interactions beyond the Standard Model of particle physics. The most prominent example is the search for a permanent electric dipole moment of the neutron (nEDM). We have performed an experimental comparison of the leading UCN sources currently operating. We have used a 'standard' UCN storage bottle with a volume of 32 liters, comparable in size to nEDM experiments, which allows us to compare the UCN density available at a given beam port.Comment: 20 pages, 30 Figure

Synchronized dynamics of cortical neurons with time-delay feedback

The dynamics of three mutually coupled cortical neurons with time delays in the coupling are explored numerically and analytically. The neurons are coupled in a line, with the middle neuron sending a somewhat stronger projection to the outer neurons than the feedback it receives, to model for instance the relay of a signal from primary to higher cortical areas. For a given coupling architecture, the delays introduce correlations in the time series at the time-scale of the delay. It was found that the middle neuron leads the outer ones by the delay time, while the outer neurons are synchronized with zero lag times. Synchronization is found to be highly dependent on the synaptic time constant, with faster synapses increasing both the degree of synchronization and the firing rate. Analysis shows that presynaptic input during the interspike interval stabilizes the synchronous state, even for arbitrarily weak coupling, and independent of the initial phase. The finding may be of significance to synchronization of large groups of cells in the cortex that are spatially distanced from each other.Comment: 21 pages, 11 figure

The Defensive Role of Volatile Emission and Extrafloral Nectar Secretion for Lima Bean in Nature

Lima bean (Phaseolus lunatus) features two indirect anti-herbivore defenses—emission of volatile organic compounds (VOCs) and secretion of extrafloral nectar (EFN)—which are both inducible upon herbivore damage. In a previous field study, Lima bean benefited from the simultaneous induction of the two defenses, yet it remained unclear whether both had contributed to plant protection. Our experimental approach aimed at studying the defensive role of both indirect defenses simultaneously. Tendrils were sprayed with jasmonic acid (JA) to induce both defenses, and performance was compared to that of others that were treated with a synthetic blend of either EFN or VOCs. Confirming earlier results, JA treatment and application of the VOC mixture induced EFN secretion in treated tendrils in quantitatively similar amounts. The composition of the applied synthetic blend of EFN was adjusted to match the concentration of EFN secreted from JA- and VOC-treated tendrils. Repeated application of either enhanced the performance of several fitness-relevant plant parameters such as growth rate and flower production. Tendrils treated with JA showed a similar trend, yet some fitness-related parameters responded less to this treatment. This suggests a minor importance of any putative JA-dependent direct defense traits or higher costs of JA-elicited responses as compared to VOCS and EFN, as otherwise JA-treated tendrils should have outperformed VOC- and EFN-treated tendrils. Moreover, the beneficial effect of applying synthetic EFN alone equaled or exceeded that of VOCs and JA. Ants were by far the dominant group among the arthropods that was attracted to JA-, VOC-, or EFN-treated tendrils. The results suggest that EFN plays a more important role as an indirect defense of lima bean than VOCs or any other JA-responsive trait

Ultra-sensitive magnetometry based on free precession of nuclear spins

We discuss the design and performance of a very sensitive low-field magnetometer based on the detection of free spin precession of gaseous, nuclear polarized 3He or 129Xe samples with a SQUID as magnetic flux detector. The device will be employed to control fluctuating magnetic fields and gradients in a new experiment searching for a permanent electric dipole moment of the neutron as well as in a new type of 3He/129Xe clock comparison experiment which should be sensitive to a sidereal variation of the relative spin precession frequency. Characteristic spin precession times T_2 of up to 60h could be measured. In combination with a signal-to-noise ratio of > 5000:1, this leads to a sensitivity level of deltaB= 1fT after an integration time of 220s and to deltaB= 10^(-4)fT after one day. Even in that sensitivity range, the magnetometer performance is statistically limited, and noise sources inherent to the magnetometer are not limiting. The reason is that free precessing 3He (129Xe) nuclear spins are almost completely decoupled from the environment. That makes this type of magnetometer in particular attractive for precision field measurements where a long-term stability is required

Low-lying continuum structures in B8 and Li8 in a microscopic model

We search for low-lying resonances in the B8 and Li8 nuclei using a microscopic cluster model and a variational scattering method, which is analytically continued to complex energies. After fine-tuning the nucleon-nucleon interaction to get the known 1+ state of B8 at the right energy, we reproduce the known spectra of the studied nuclei. In addition, our model predicts a 1+ state at 1.3 MeV in B8, relative to the Be7+p threshold, whose corresponding pair is situated right at the Li7+n threshold in Li8. Lacking any experimental evidence for the existence of such states, it is presently uncertain whether these structures really exist or they are spurious resonances in our model. We demonstrate that the predicted state in B8, if it exists, would have important consequences for the understanding of the astrophysically important Be7(p,gamma)B8 reaction.Comment: 6 pages with 1 figure. The postscript file and more information are available at http://nova.elte.hu/~csot

Global Study of Electron-Quark Contact Interactions

We perform a global fit of data relevant to $eeqq$ contact interactions, including deep inelastic scattering at high $Q^2$ from ZEUS and H1, atomic physics parity violation in Cesium from JILA, polarized $e^-$ on nuclei scattering experiments at SLAC, Mainz and Bates, Drell-Yan production at the Tevatron, the total hadronic cross section $\sigma_{had}$ at LEP, and neutrino-nucleon scattering from CCFR. With only the new HERA data, the presence of contact interactions improves the fit compared to the Standard Model. When other data sets are included, the size of the contact contributions is reduced and the overall fit represents no real improvement over the Standard Model.Comment: 26 pages (now single-spaced), Revtex, 2 eps figures, uses epsf.sty. Some clarifications, minor corrections, 2 new references, also 3 new tables which present 95% CL bounds on the contact interaction scales Lambd