Universal Quantum Viscosity in a Unitary Fermi Gas

A Fermi gas of atoms with resonant interactions is predicted to obey universal hydrodynamics, where the shear viscosity and other transport coefficients are universal functions of the density and temperature. At low temperatures, the viscosity has a universal quantum scale $\hbar n$ where $n$ is the density, while at high temperatures the natural scale is $p_T^3/\hbar^2$ where $p_T$ is the thermal momentum. We employ breathing mode damping to measure the shear viscosity at low temperature. At high temperature $T$, we employ anisotropic expansion of the cloud to find the viscosity, which exhibits precise $T^{3/2}$ scaling. In both experiments, universal hydrodynamic equations including friction and heating are used to extract the viscosity. We estimate the ratio of the shear viscosity to the entropy density and compare to that of a perfect fluid.Comment: 13 pages, 3 figure

Revealing the Superfluid Lambda Transition in the Universal Thermodynamics of a Unitary Fermi Gas

We have observed the superfluid phase transition in a strongly interacting Fermi gas via high-precision measurements of the local compressibility, density and pressure down to near-zero entropy. Our data completely determine the universal thermodynamics of strongly interacting fermions without any fit or external thermometer. The onset of superfluidity is observed in the compressibility, the chemical potential, the entropy, and the heat capacity. In particular, the heat capacity displays a characteristic lambda-like feature at the critical temperature of $T_c/T_F = 0.167(13)$. This is the first clear thermodynamic signature of the superfluid transition in a spin-balanced atomic Fermi gas. Our measurements provide a benchmark for many-body theories on strongly interacting fermions, relevant for problems ranging from high-temperature superconductivity to the equation of state of neutron stars.Comment: 11 pages, 8 figure

Phase II study of S-1, a novel oral fluoropyrimidine derivative, in patients with metastatic colorectal carcinoma

This study set out to evaluate, in patients with metastatic colorectal carcinoma, the efficacy and toxicity of S-1, which contains tegafur, 5-chloro-2,4-dihydroxypyridine (CDHP) and potassium oxonate, based on a biochemical modulation of 5-fluorouracil (5-FU) targeted at inhibition of dihydropyrimidine dehydrogenase (DPD). Sixty-three patients with measurable metastatic colorectal carcinoma were enrolled into the study. None of the patients had received prior chemotherapy except for adjuvant setting. S-1 was administered orally twice daily at a standard dose of 80 mg m–2day–1for 28 days followed by a 14-day rest. This agent is continued until disease progression, unaccepted toxicity, or patient refusal. Twenty-two (35%) of the 62 eligible patients achieved PR with a 95% confidence interval of 25–48%. Five of the 10 patients with a history of adjuvant chemotherapy achieved partial remission. The median survival time was 12 months. Major adverse reactions included myelosuppressive and gastrointestinal toxicities, though their incidence of grade 3 or 4 being 13% in neutropenia and less than 10% in the others. None of the 53 patients treated as outpatients required hospitalization due to adverse reactions: These results suggest that S-1 achieves similar responses to those of infusional 5-FU plus leucovorin and shows the potential of another biochemical modulation with easily manageable toxicity. © 2000 Cancer Research Campaig

Cerebrospinal fluid leakage after radioisotope cisternography is not influenced by needle size at lumbar puncture in patients with intracranial hypotension

<p>Abstract</p> <p>Background</p> <p>Radioisotope (RI) cisternography is considered to be the most important examination for the final diagnosis of intracranial hypotension, typically indicating cerebrospinal fluid (CSF) leakage as RI parathecal activity. Early bladder filling (EBF) of RI is another important finding. However, whether EBF without parathecal activity represents real CSF leakage due to intracranial hypotension or only an epiphenomenon of lumbar puncture causing CSF leak through a needle hole has been questioned.</p> <p>Methods</p> <p>To address this issue, we performed quantitative analysis of RI cisternography on 171 patients with suspected intracranial hypotension using different needle sizes (22 G, 23 G and 25 G) and compared RI residual activity in the CSF at different time points after injection. We also analyzed occurrence of early bladder filling and post-lumbar puncture headache.</p> <p>Results</p> <p>No significant difference in RI residual activity was identified between the 22 G, 23 G and 25 G groups. The incidence of parathecal activity and early bladder filling was not significantly different between groups. The 22 G and 23 G groups had a higher but non-significant incidence of post lumbar headache.</p> <p>Conclusion</p> <p>The results suggest that needle size, at least for 22–25 G, does not affect the results of RI cisternographic diagnostic tests for CSF leakage and bladder filling in intracranial hypotension.</p

Measurement of the cosmic-ray antiproton spectrum at solar minimum with a long-duration balloon flight over Antarctica

The energy spectrum of cosmic-ray antiprotons from 0.17 to 3.5 GeV has been measured using 7886 antiprotons detected by BESS-Polar II during a long-duration flight over Antarctica near solar minimum in December 2007 and January 2008. This shows good consistency with secondary antiproton calculations. Cosmologically primary antiprotons have been investigated by comparing measured and calculated antiproton spectra. BESS-Polar II data show no evidence of primary antiprotons from evaporation of primordial black holes.Comment: 4 pages, 4 figures, submitted to Physical Review Letter

Novel diffusion mechanism on the GaAs(001) surface: the role of adatom-dimer interaction

Employing first principles total energy calculations we have studied the behavior of Ga and Al adatoms on the GaAs(001)-beta2 surface. The adsorption site and two relevant diffusion channels are identified. The channels are characterized by different adatom-surface dimer interaction. Both affect in a novel way the adatom migration: in one channel the diffusing adatom jumps across the surface dimers and leaves the dimer bonds intact, in the other one the surface dimer bonds are broken. The two channels are taken into account to derive effective adatom diffusion barriers. From the diffusion barriers we conclude a strong diffusion anisotropy for both Al and Ga adatoms with the direction of fastest diffusion parallel to the surface dimers. In agreement with experimental observations we find higher diffusion barriers for Al than for Ga.Comment: 4 pages, 2 figures, Phys. Rev. Lett. 79 (1997). Other related publications can be found at http://www.rz-berlin.mpg.de/th/paper.htm