2,143 research outputs found
Bose-Einstein Condensation of an Ytterbium Isotope
We report the observation of a Bose Einstein condensate in a bosonic isotope
of ytterbium (170Yb). More than 10^6 atoms are trapped in a crossed optical
dipole trap and cooled by evaporation. Condensates of approximately 10^4 atoms
have been obtained. From an expansion of the condensate, we have extracted the
scattering length a=3.6(9) nm.Comment: 4 pages, 3 figure
Room-temperature Coulomb oscillation of Ni-Nb-Zr-H glassy alloys with nanoscale size clusters
Tipping the balance both ways: drug resistance and virulence in Candida glabrata
Among existing fungal pathogens, Candida glabrata is outstanding in its capacity to rapidly develop resistance to currently used antifungal agents. Resistance to the class of azoles, which are still widely used agents, varies in proportion (from 5 to 20%) depending on geographical area. Moreover, resistance to the class of echinocandins, which was introduced in the late 1990s, is rising in several institutions. The recent emergence of isolates with acquired resistance to both classes of agents is a major concern since alternative therapeutic options are scarce. Although considered less pathogenic than C. albicans, C. glabrata has still evolved specific virulence traits enabling its survival and propagation in colonized and infected hosts. Development of drug resistance is usually associated with fitness costs, and this notion is documented across several microbial species. Interestingly, azole resistance in C. glabrata has revealed the opposite. Experimental models of infection showed enhanced virulence of azole-resistant isolates. Moreover, azole resistance could be associated with specific changes in adherence properties to epithelial cells or innate immunity cells (macrophages), both of which contribute to virulence changes. Here we will summarize the current knowledge on C. glabrata drug resistance and also discuss the consequences of drug resistance acquisition on the balance between C. glabrata and its host
Simulations of Protoplanetary Disk Dispersal: Stellar Mass Dependence of the Disk Lifetime
Recent infrared and submillimeter observations suggest that the
protoplanetary disk lifetime depends on the central stellar mass. The disk
dispersal is thought to be driven by viscous accretion, magneto-hydrodynamics
(MHD) winds, and photoevaporation by the central star. We perform a set of
one-dimensional simulations of long-term disk evolution that include all the
three processes. We vary the stellar mass in the range of 0.5-7M, and
study the mass dependence of the disk evolution. We show that a significant
fraction of the disk gas is lost by MHD winds in the early stage, but the later
disk evolution is mainly governed by photoevaporation. The disk radius
decreases as photoevaporation clears out the gas in the outer disk efficiently.
The qualitative evolutionary trends of the disk mass are remarkably similar for
the wide range of the central stellar mass we consider, and the time evolution
of the disk mass can be well fitted by a simple function. The dispersal time is
approximately ten million years for low mass stars with weak mass dependence,
but gets as short as two million years around a 7M star. In the
latter case, a prominent inner hole is formed by the combined effect of
accretion and MHD winds within about one million years. The strength of the MHD
wind and viscous accretion controls the overall mass-loss rate, but does not
alter the dependence of the dispersal timescale on the central stellar mass.Comment: 14 pages, 10 figures, 1 tabl
2-D Heat Transfer Model of A Horizontal U-Tube
Paying attention to the shallow ground heat inside a tunnel, a Horizontal U-Tube (HUT) road heating system was introduced for the first time in Japan in order to prevent winter traffic accidents associated with road freezing at the west side mouth of Nanaori-Toge tunnel, Aizu-bange, Fukushima Prefecture. Horizontal U-tubes were buried at a depth of 1.2 m in the ground of the central part of the tunnel. The ground heat extracted by the HUT is injected into the anti-freezing pavement at the tunnel mouth. In this study, attempts were made to propose a simplified heat transfer model of HUT system. The proposed model consists of the energy balance equations of the fluid circulating in the HUT and the surrounding ground. Solving these two equations simultaneously, the extracted ground heat could be calculated as well as the fluid and ground temperatures. The model could also lead the overall heat transfer coefficient between the fluid and the surrounding ground. The validity of the model was accepted from the comparison with indoor experimental results using a miniature HUT
2-D Heat Transfer Model of A Horizontal U-Tube
Paying attention to the shallow ground heat inside a tunnel, a Horizontal U-Tube (HUT) road heating system was introduced for the first time in Japan in order to prevent winter traffic accidents associated with road freezing at the west side mouth of Nanaori-Toge tunnel, Aizu-bange, Fukushima Prefecture. Horizontal U-tubes were buried at a depth of 1.2 m in the ground of the central part of the tunnel. The ground heat extracted by the HUT is injected into the anti-freezing pavement at the tunnel mouth. In this study, attempts were made to propose a simplified heat transfer model of HUT system. The proposed model consists of the energy balance equations of the fluid circulating in the HUT and the surrounding ground. Solving these two equations simultaneously, the extracted ground heat could be calculated as well as the fluid and ground temperatures. The model could also lead the overall heat transfer coefficient between the fluid and the surrounding ground. The validity of the model was accepted from the comparison with indoor experimental results using a miniature HUT
A practice-related risk score (PRS): a DOPPS-derived aggregate quality index for haemodialysis facilities
Background. The Dialysis Outcomes and Practice Patterns Study (DOPPS) database was used to develop and validate a practice-related risk score (PRS) based on modifiable practices to help facilities assess potential areas for improving patient care.
Methods. Relative risks (RRs) from a multivariable Cox mortality model, based on observational haemodialysis (HD) patient data from DOPPS I (1996-2001, seven countries), were used. The four practices were the percent of patients with Kt/V >= 1.2, haemoglobin >= 11 g/dl (110 g/l), albumin >= 4.0 g/dl (40g/l) and catheter use, and were significantly related to mortality when modelled together. DOPPS II data (2002-2004, 12 countries) were used to evaluate the relationship between PRS and mortality risk using Cox regression.
Results. For facilities in DOPPS I and II, changes in PRS over time were significantly correlated with changes in the standardized mortality ratio (SMR). The PRS ranged from 1.0 to 2.1. Overall, the adjusted RR of death was 1.05 per 0.1 points higher PRS (P < 0.0001). For facilities in both DOPPS I and II (N = 119), a 0.2 decrease in PRS was associated with a 0.19 decrease in SMR (P = 0.005). On average, facilities that improved PRS practices showed significantly reduced mortality over the same time frame.
Conclusions. The PRS assesses modifiable HD practices that are linked to improved patient survival. Further refinements might lead to improvements in the PRS and will address regional variations in the PRS/mortality relationship
Specific Heat Study of Non-Fermi Liquid Behavior in CeNi_2Ge_2: Anomalous Peak in Quasi-Particle Density-of-States
To investigate the non-Fermi liquid (NFL) behavior in a nonalloyed system
CeNi_2Ge_2, we have measured the temperature and field dependences of the
specific heat C on a CeNi_2Ge_2 single crystal. The distinctive temperature
dependence of C/T (~a-b*T^(1/2)) is destroyed in almost the same manner for
both field directions of B//c-axis and B//a-axis. The overall behavior of
C(T,B) and the low-temperature upturn in magnetic susceptibility can be
reproduced, assuming an anomalous peak of the quasi-particle-band
density-of-states (DOS) at the Fermi energy possessing (epsilon)^(1/2) energy
dependence. Absence of residual entropy around T=0 K in B~0 T has been
confirmed by the magnetocaloric effect measurements, which are consistent with
the present model. The present model can also be applied to the NFL behavior in
CeCu_{5.9}Au_{0.1} using a ln(epsilon)-dependent peak in the DOS. Possible
origins of the peak in the DOS are discussed.Comment: 4 pages, LaTeX, using jpsj.sty, to be published in J. Phys. Soc. Jpn.
66 No. 10 (1997), 7 figures available at
http://494-475.phys.metro-u.ac.jp/ao/ceni2ge2.htm
Simulation of the many-body dynamical quantum Hall effect in an optical lattice
We propose an experimental scheme to simulate the many-body dynamical quantum
Hall effect with ultra-cold bosonic atoms in a one-dimensional optical lattice.
We first show that the required model Hamiltonian of a spin-1/2 Heisenberg
chain with an effective magnetic field and tunable parameters can be realized
in this system. For dynamical response to ramping the external fields, the
quantized plateaus emerge in the Berry curvature of the interacting atomic spin
chain as a function of the effective spin-exchange interaction. The
quantization of this response in the parameter space with the
interaction-induced topological transition characterizes the many-body
dynamical quantum Hall effect. Furthermore, we demonstrate that this phenomenon
can be observed in practical cold-atom experiments with numerical simulations.Comment: 8 pages, 3 figures; accepted in Quantum Information Processin
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