991 research outputs found
Physical modelling of backward erosion piping in foundation beneath levee
Centrifuge model tests are performed to observe piping progression in foundation beneath levee and to examine influence of repeated seepage and thickness of foundation ground on piping progression. Once the pipe is formed beneath the levee, hydraulic gradient upstream of the pipe tip becomes larger while that along the pipe becomes rather small. Shift of this large hydraulic gradient position to the upstream with rise of the flood water level leads to the large subsidence of the slope in the protected side and marked increase in flow rate. Repeated seepage and thickness of the permeable foundation layer have influence on stability of levee against piping. Repeated seepage makes the piping progression faster and levee vulnerable to the piping formation. With the thinner permeable foundation layer beneath the levee, the levee is at higher risk to cause brittle failure while the required hydraulic gradient to cause piping is larger
Purification and In Vitro Growth of Human Epidermal Basal Keratinocytes Using a Monoclonal Antibody
We have made a new monoclonal antibody, EL-2, and used it with an immunorosetting procedure combined with Ficoll-Hypaque gradient centrifugation to purify and culture basal keratinocytes. Immunofluorescence of cell suspensions and immunoperoxidase staining of tissue sections demonstrate that EL-2 reacts with malignant cell lines, activated lymphocytes and monocytes, and basal keratinocytes. Sequential immunoprecipitation studies demonstrate that monoclonal antibodies EL-2 and 4F2 detect the same membrane protein. However, we have extended previous studies by making the new observation that both EL-2 and 4F2 react with cultured melanocytes. Basal keratinocytes were purified from single-cell epidermal suspensions by incubation with EL-2 followed by rosetting with rabbit antimouse IgG antibodies covalently linked to bovine red blood cells. Rosetting (basal) keratinocytes were separated from EL-2 negative cells by Ficoll gradient centrifugation. We obtained basal keratinocyte populations of >90% purity as assessed by reactivity with EL-2 and another basal keratinocyte-specific monoclonal antibody, HCl. Langerhans cell, fibroblast, and melanocyte contamination was negligible. Cultures of basal keratinocytes were enriched in EL-2-reactive cells throughout the entire 19 days of culture studied. EL-2 is being used to characterize disorders of keratinocyte proliferation; EL-2 reacted with both squamous and basal cell carcinomas. EL-2 stained only the basal layer of lesional skin from patients with psoriasis, pityriasis rubra pilaris, and Darier's disease. Purification of basal keratinocytes will be important in biochemical and functional studies of normal skin and in establishing long-term keratinocyte lines from normal cells
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
Feynman diagrams versus Fermi-gas Feynman emulator
Precise understanding of strongly interacting fermions, from electrons in
modern materials to nuclear matter, presents a major goal in modern physics.
However, the theoretical description of interacting Fermi systems is usually
plagued by the intricate quantum statistics at play. Here we present a
cross-validation between a new theoretical approach, Bold Diagrammatic Monte
Carlo (BDMC), and precision experiments on ultra-cold atoms. Specifically, we
compute and measure with unprecedented accuracy the normal-state equation of
state of the unitary gas, a prototypical example of a strongly correlated
fermionic system. Excellent agreement demonstrates that a series of Feynman
diagrams can be controllably resummed in a non-perturbative regime using BDMC.
This opens the door to the solution of some of the most challenging problems
across many areas of physics
Pair excitations and parameters of state of imbalanced Fermi gases at finite temperatures
The spectra of low-lying pair excitations for an imbalanced two-component
superfluid Fermi gas are analytically derived within the path-integral
formalism taking into account Gaussian fluctuations about the saddle point. The
spectra are obtained for nonzero temperatures, both with and without imbalance,
and for arbitrary interaction strength. On the basis of the pair excitation
spectrum, we have calculated the thermodynamic parameters of state of cold
fermions and the first and second sound velocities. The parameters of pair
excitations show a remarkable agreement with the Monte Carlo data and with
experiment.Comment: 14 pages, 5 figure
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
Exploring the Thermodynamics of a Universal Fermi Gas
From sand piles to electrons in metals, one of the greatest challenges in
modern physics is to understand the behavior of an ensemble of strongly
interacting particles. A class of quantum many-body systems such as neutron
matter and cold Fermi gases share the same universal thermodynamic properties
when interactions reach the maximum effective value allowed by quantum
mechanics, the so-called unitary limit [1,2]. It is then possible to simulate
some astrophysical phenomena inside the highly controlled environment of an
atomic physics laboratory. Previous work on the thermodynamics of a
two-component Fermi gas led to thermodynamic quantities averaged over the trap
[3-5], making it difficult to compare with many-body theories developed for
uniform gases. Here we develop a general method that provides for the first
time the equation of state of a uniform gas, as well as a detailed comparison
with existing theories [6,14]. The precision of our equation of state leads to
new physical insights on the unitary gas. For the unpolarized gas, we prove
that the low-temperature thermodynamics of the strongly interacting normal
phase is well described by Fermi liquid theory and we localize the superfluid
transition. For a spin-polarized system, our equation of state at zero
temperature has a 2% accuracy and it extends the work of [15] on the phase
diagram to a new regime of precision. We show in particular that, despite
strong correlations, the normal phase behaves as a mixture of two ideal gases:
a Fermi gas of bare majority atoms and a non-interacting gas of dressed
quasi-particles, the fermionic polarons [10,16-18].Comment: 8 pages, 5 figure
Interlayer Coherence in the and Bilayer Quantum Hall States
We have measured the Hall-plateau width and the activation energy of the
bilayer quantum Hall (BLQH) states at the Landau-level filling factor
and 2 by tilting the sample and simultaneously changing the electron density in
each quantum well. The phase transition between the commensurate and
incommensurate states are confirmed at and discovered at . In
particular, three different BLQH states are identified; the compound
state, the coherent commensurate state, and the coherent incommensurate state.Comment: 4 pages including 5 figure
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