The stiff-man syndrome

In 1956 Moersch and Woltman first recorded a state of 'progressive fluctuating rigidity and spasm', for which they coined the term 'stiff-man syndrome', signifying that the aetiology and pathogenesis of the condition were unknown. At the time of writing only 16 cases have been described. It. is suggested that the case under consideration falls into this syndrome, although there are a number of features at variance with the published cases

Anisotropically Inflating Universes

We show that in theories of gravity that add quadratic curvature invariants to the Einstein-Hilbert action there exist expanding vacuum cosmologies with positive cosmological constant which do not approach the de Sitter universe. Exact solutions are found which inflate anisotropically. This behaviour is driven by the Ricci curvature invariant and has no counterpart in the general relativistic limit. These examples show that the cosmic no-hair theorem does not hold in these higher-order extensions of general relativity and raises new questions about the ubiquity of inflation in the very early universe and the thermodynamics of gravitational fields.Comment: 5 pages, further discussion and references adde

Thermodynamic Properties of the Spin-1/2 Antiferromagnetic ladder Cu2(C2H12N2)2Cl4 under Magnetic Field

Specific heat ($C_V$) measurements in the spin-1/2 Cu$_2$(C$_2$H$_{12}$N$_2$)$_2$Cl$_4$ system under a magnetic field up to $H=8.25 T$ are reported and compared to the results of numerical calculations based on the 2-leg antiferromagnetic Heisenberg ladder. While the temperature dependences of both the susceptibility and the low field specific heat are accurately reproduced by this model, deviations are observed below the critical field $H_{C1}$ at which the spin gap closes. In this Quantum High Field phase, the contribution of the low-energy quantum fluctuations are stronger than in the Heisenberg ladder model. We argue that this enhancement can be attributed to dynamical lattice fluctuations. Finally, we show that such a Heisenberg ladder, for $H>H_{C1}$, is unstable, when coupled to the 3D lattice, against a lattice distortion. These results provide an alternative explanation for the observed low temperature ($T_C\sim 0.5K$ -- $0.8K$) phase (previously interpreted as a 3D magnetic ordering) as a new type of incommensurate gapped state.Comment: Minor changes, list of authors complete

IMPACTS OF POLICY REFORMS ON THE SUPPLY OF MEXICAN LABOR TO U.S. FARMS: NEW EVIDENCE FROM MEXICO

The availability of immigrant farmworkers from Mexico critically shapes fruit, vegetable, and horticultural (FVH) production in the United States. We test the impact of recent policy reforms on the supply of Mexican labor to U.S. farms, using a 2-way fixed effects model and new data from rural Mexico.Labor and Human Capital,

VIRUS-INDUCED DIABETES MELLITUS : I. HYPERGLYCEMIA AND HYPOINSULINEMIA IN MICE INFECTED WITH ENCEPHALOMYOCARDITIS VIRUS

Infection of DBA/2N male mice with encephalomyocarditis virus resulted in a diabeteslike syndrome characterized by hyperglycemia, glycosuria, hypoinsulinemia, polydipsia, and polyphagia. Blood glucose levels were elevated within 4 days after infection and reached a maximum mean level of 320 mg/100 ml within 12 days. Approximately 60–80% of the animals developed a transient hyperglycemia while 10–15% of the animals remained hyperglycemic for well over 6 mo. The remaining animals failed to become hyperglycemic but many had abnormal glucose tolerance curves. Hyperglycemia was most pronounced when animals were allowed free access to food, and the incidence of byperglycemia was related both to the strain and sex of the animals, with few females developing hyperglycemia. The amount of immunoreactive insulin in the plasma of infected hyperglycemic mice was significantly lower than in appropriate controls, and injection of exogenous insulin resulted in a rapid drop in the blood glucose levels. Despite the fact that certain animals were hyperglycemic for many months, virus could not be recovered from the pancreas after the first 10 days of the infection

Electrostatic Properties of Polymers Subjected to Atmospheric Pressure Plasma Treatment; Correlation of Experimental Results with Atomistic Modeling

this study, PE, PTFE, PS and PMMA were exposed to a He+O2, APGD and pre and post treatment surface chemistries were analyzed by X-ray photoelectron spectroscopy and contact angle measurements. Semi-empirical and ab-initio calculations were performed to correlate the experimental results with sonic plausible molecular and electronic structure features of the oxidation process. For the PE and PS, significant surface oxidation showing C-O, C=O, and O-C=O bonding, and a decrease in the surface contact angles was observed. For the PTFE and PM MA, little change in the surface composition was observed. The molecular modeling calculations were performed on single and multiple oligomers and showed regardless of oxidation mechanism, e.g. -OH, =O or a combination thereof, experimentally observed levels of surface oxidation were unlikely to lead to a significant change in the electronic structure of PE and PS, and that the increased hydrophilic properties are the primary reason for the observed changes in its electrostatic behavior. Calculations for PTFE and PMMA argue strongly against significant oxidation of those materials, as confirmed by the XPS results

Stable Isotropic Cosmological Singularities in Quadratic Gravity

We show that, in quadratic lagrangian theories of gravity, isotropic cosmological singularities are stable to the presence of small scalar, vector and tensor inhomogeneities. Unlike in general relativity, a particular exact isotropic solution is shown to be the stable attractor on approach to the initial cosmological singularity. This solution is also known to act as an attractor in Bianchi universes of types I, II and IX, and the results of this paper reinforce the hypothesis that small inhomogeneous and anisotropic perturbations of this attractor form part of the general cosmological solution to the field equations of quadratic gravity. Implications for the existence of a 'gravitational entropy' are also discussed.Comment: 18 pages, no figure

Amp\`ere-Class Pulsed Field Emission from Carbon-Nanotube Cathodes in a Radiofrequency Resonator

Pulsed field emission from cold carbon-nanotube cathodes placed in a radiofrequency resonant cavity was observed. The cathodes were located on the backplate of a conventional $1+\frac{1}{2}$-cell resonant cavity operating at 1.3-GHz and resulted in the production of bunch train with maximum average current close to 0.7 Amp\`ere. The measured Fowler-Nordheim characteristic, transverse emittance, and pulse duration are presented and, when possible, compared to numerical simulations. The implications of our results to high-average-current electron sources are briefly discussed.Comment: 5 pages, 6 figures; submitted to Applied Physics Letter