4,036 research outputs found
The fraction of Bose-Einstein condensed triplons in TlCuCl3 from magnetization M(T,H)-data
In this study we calculate the fraction of condensed magnetic quasiparticles
of TlCuCl3 from magnetization M(T,H)-data. It is independent of the direction
of the magnetic field and slightly decreases with increasing magnetic field.Comment: 8 pages, 10 figure
Defect propagation in one-, two-, and three-dimensional compounds doped by magnetic atoms
Inelastic neutron scattering experiments were performed to study
manganese(II) dimer excitations in the diluted one-, two-, and
three-dimensional compounds CsMn(x)Mg(1-x)Br(3), K(2)Mn(x)Zn(1-x)F(4), and
KMn(x)Zn(1-x)F(3) (x<0.10), respectively. The transitions from the ground-state
singlet to the excited triplet, split into a doublet and a singlet due to the
single-ion anisotropy, exhibit remarkable fine structures. These unusual
features are attributed to local structural inhomogeneities induced by the
dopant Mn atoms which act like lattice defects. Statistical models support the
theoretically predicted decay of atomic displacements according to 1/r**2, 1/r,
and constant (for three-, two-, and one-dimensional compounds, respectively)
where r denotes the distance of the displaced atoms from the defect. The
observed fine structures allow a direct determination of the local exchange
interactions J, and the local intradimer distances R can be derived through the
linear law dJ/dR.Comment: 22 pages, 5 figures, 2 table
Enzyme-linked immunosorbent assay for urinary albumin at low concentrations
We describe an enzyme-linked immunosorbent assay (ELISA) for urinary albumin. It requires only commercially available reagents, can detect as little as 16 micrograms of albumin per liter, and analytical recovery ranges from 92 to 116%. The assay is simple, rapid, and inexpensive. Albumin excretion was 6.2 (SD 4.1) mg/24 h in healthy subjects (n = 40), 14.7 (SD 7.2) mg/24 h in albumin-test-strip-negative Type I diabetics (n = 11), and 19.7 (SD 16.2) mg/24 h in patients with essential hypertension (n = 12)
Hemodynamic and inotropic effects of endothelin-1 in vivo
Endothelin-1 (ET-1) is known to have strong vasoactive properties. Contradictory results have been reported with regard to its inotropic effects. This study examined the dose-dependent (500, 1000, 2500, 5000 and 10,000 ng ET-1/kg vs. NaCl controls) hemodynamic and inotropic effects of ET-1 in 53 open-chest rats during and after a 7-min infusion. Besides measurements in the intact circulation the myocardial function was examined by isovolumic registrations independent of peripheral vascular effects. A transient ET-1 induced (500, 1000, 2500, 5000 ng ET-1/kg) decrease of the left ventricular systolic pressure (LVSP) and the mean aortic pressure (AoPmean) was followed by a dose-related rise of these pressures (LVSP: -1%, -1%, +8%, +16% vs. preinfusion values; AoPmean: -11%, +9%, +39%, +52%). Heart rate (HR) was not influenced by ET-1. Due to the dose-dependent decrease of the stroke volume (SV) the cardiac output (CO) was reduced (CO: -8%, -23%, -40%, -50%). After an initial vasodilatation ET-1 elevates the total peripheral resistance (TPR: -1%, +49%, +139%, +215%) dose-dependently. 10,000 ng ET-1/kg was a lethal dose resulting in cardiac failure within minutes (low output). Since the maximum of the isovolumic LVSP (peak LVSP) and the corresponding dP/dtmax (peak dP/dtmax) were unchanged under ET-1, the isovolumic measurements do not indicate a positive inotropic effect of ET-1 in vivo in contrast to published results of in vitro experiments. It may be possible that a direct positive inotropic effect of ET-1 observed in in vitro studies is counterbalanced in vivo by an indirect negative inotropic effect due to the coronary-constrictive effect of ET-1
Bounds on R-parity violating supersymmetric couplings from leptonic and semi-leptonic meson decays
We present a comprehensive update of the bounds on R-Parity violating
supersymmetric couplings from lepton-flavour- and lepton-number-violating decay
processes. We consider tau and mu decays as well as leptonic and semi-leptonic
decays of mesons. We present several new bounds resulting from tau, eta and
Kaon decays and correct some results in the literature concerning B-meson
decays.Comment: 30 pages; changed title, updated some bounds from the literature from
different references, added reference
Supersymmetric NLO QCD Corrections to Resonant Slepton Production and Signals at the Tevatron and the LHC
We compute the total cross section and the transverse momentum distribution
for single charged slepton and sneutrino production at hadronic colliders
including NLO supersymmetric and non-supersymmetric QCD corrections. The
supersymmetric QCD corrections can be substantial. We also resum the gluon
transverse momentum distribution and compare our results with two Monte Carlo
generators. We compute branching ratios of the supersymmetric decays of the
slepton and determine event rates for the like-sign dimuon final state at the
Tevatron and at the LHC.Comment: 14 pages, LaTeX, 8 figures, uses REVTex
Dimensional reduction by pressure in the magnetic framework material CuF(DO)pyz: from spin-wave to spinon excitations
Metal organic magnets have enormous potential to host a variety of electronic
and magnetic phases that originate from a strong interplay between the spin,
orbital and lattice degrees of freedom. We control this interplay in the
quantum magnet CuF(DO)pyz by using high pressure to drive the
system through a structural and magnetic phase transition. Using neutron
scattering, we show that the low pressure state, which hosts a two-dimensional
square lattice with spin-wave excitations and a dominant exchange coupling of
0.89 meV, transforms at high pressure into a one-dimensional spin-chain
hallmarked by a spinon continuum and a reduced exchange interaction of 0.43
meV. This direct microscopic observation of a magnetic dimensional crossover as
a function of pressure opens up new possibilities for studying the evolution of
fractionalised excitations in low dimensional quantum magnets and eventually
pressure-controlled metal--insulator transitions
Probing the Top-Quark Electric Dipole Moment at a Photon Linear Collider
We probe the top-quark electric dipole moment (EDM) in top-quark pair
production via photon-photon fusion at a photon linear collider. We show how
linearly-polarized photon beams can be used to extract information on the
top-quark EDM without the use of complicated angular correlations of top-quark
decay products. If the luminosity of the laser back-scattered photon-photon
collisions is comparable to that of the collisions, then the
measurement of the top-quark EDM obtained by counting top-quark-production
events in photon fusion can be as accurate as the measurement obtained by
studying the decay correlations in collisions using a
perfect detector.Comment: Latex, 11 pages, 1 figure (not included). One compressed postscript
file of the paper available at
ftp://ftp.kek.jp/kek/preprints/TH/TH-443/kekth443.ps.g
High-resolution wide-band Fast Fourier Transform spectrometers
We describe the performance of our latest generations of sensitive wide-band
high-resolution digital Fast Fourier Transform Spectrometer (FFTS). Their
design, optimized for a wide range of radio astronomical applications, is
presented. Developed for operation with the GREAT far infrared heterodyne
spectrometer on-board SOFIA, the eXtended bandwidth FFTS (XFFTS) offers a high
instantaneous bandwidth of 2.5 GHz with 88.5 kHz spectral resolution and has
been in routine operation during SOFIA's Basic Science since July 2011. We
discuss the advanced field programmable gate array (FPGA) signal processing
pipeline, with an optimized multi-tap polyphase filter bank algorithm that
provides a nearly loss-less time-to-frequency data conversion with
significantly reduced frequency scallop and fast sidelobe fall-off. Our digital
spectrometers have been proven to be extremely reliable and robust, even under
the harsh environmental conditions of an airborne observatory, with
Allan-variance stability times of several 1000 seconds. An enhancement of the
present 2.5 GHz XFFTS will duplicate the number of spectral channels (64k),
offering spectroscopy with even better resolution during Cycle 1 observations.Comment: Accepted for publication in A&A (SOFIA/GREAT special issue
Dependence of the BEC transition temperature on interaction strength: a perturbative analysis
We compute the critical temperature T_c of a weakly interacting uniform Bose
gas in the canonical ensemble, extending the criterion of condensation provided
by the counting statistics for the uniform ideal gas. Using ordinary
perturbation theory, we find in first order , where T_c^0 is the transition temperature of the corresponding
ideal Bose gas, a is the scattering length, and is the particle number
density.Comment: 14 pages (RevTeX
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