5,005 research outputs found
Does ohmic heating influence the flow field in thin-layer electrodeposition?
In thin-layer electrodeposition the dissipated electrical energy leads to a
substantial heating of the ion solution. We measured the resulting temperature
field by means of an infrared camera. The properties of the temperature field
correspond closely with the development of the concentration field. In
particular we find, that the thermal gradients at the electrodes act like a
weak additional driving force to the convection rolls driven by concentration
gradients.Comment: minor changes: correct estimation of concentration at the anode,
added Journal-re
The Present and Future of Planetary Nebula Research. A White Paper by the IAU Planetary Nebula Working Group
We present a summary of current research on planetary nebulae and their
central stars, and related subjects such as atomic processes in ionized
nebulae, AGB and post-AGB evolution. Future advances are discussed that will be
essential to substantial improvements in our knowledge in the field.Comment: accepted for publication in RMxAA; 37 page
Experimental investigation of the initial regime in fingering electrodeposition: dispersion relation and velocity measurements
Recently a fingering morphology, resembling the hydrodynamic Saffman-Taylor
instability, was identified in the quasi-two-dimensional electrodeposition of
copper. We present here measurements of the dispersion relation of the growing
front. The instability is accompanied by gravity-driven convection rolls at the
electrodes, which are examined using particle image velocimetry. While at the
anode the theory presented by Chazalviel et al. describes the convection roll,
the flow field at the cathode is more complicated because of the growing
deposit. In particular, the analysis of the orientation of the velocity vectors
reveals some lag of the development of the convection roll compared to the
finger envelope.Comment: 11 pages, 15 figures, REVTEX 4; reference adde
Multiparticle Biased DLA with surface diffusion: a comprehensive model of electrodeposition
We present a complete study of the Multiparticle Biased Diffusion-Limited
Aggregation (MBDLA) model supplemented with surface difussion (SD), focusing on
the relevance and effects of the latter transport mechanism. By comparing
different algorithms, we show that MBDLA+SD is a very good qualitative model
for electrodeposition in practically all the range of current intensities {\em
provided} one introduces SD in the model in the proper fashion: We have found
that the correct procedure involves simultaneous bulk diffusion and SD,
introducing a time scale arising from the ratio of the rates of both processes.
We discuss in detail the different morphologies obtained and compare them to
the available experimental data with very satisfactory results. We also
characterize the aggregates thus obtained by means of the dynamic scaling
exponents of the interface height, allowing us to distinguish several regimes
in the mentioned interface growth. Our asymptotic scaling exponents are again
in good agreement with recent experiments. We conclude by discussing a global
picture of the influence and consequences of SD in electrodeposition.Comment: 15 pages, 20 figures, accepted for publication in Physical Review
Mesoscopic rings with Spin-Orbit interactions
A didactic description of charge and spin equilibrium currents on mesoscopic
rings in the presence of Spin-Orbit interaction is presented. Emphasis is made
on the non trivial construction of the correct Hamiltonian in polar
coordinates, the calculation of eigenvalues and eigenfunctions and the
symmetries of the ground state properties. Spin currents are derived following
an intuitive definition and then a more thorough derivation is built upon the
canonical Lagrangian formulation that emphasizes the SU(2) gauge structure of
the transport problem of spin 1/2 fermions in spin-orbit active media. The
quantization conditions that follow from the constraint of single-valued Pauli
spinors are also discussed. The targeted students are those of a graduate
Condensed Matter Physics course
Phenotypic profile of expanded NK cells in chronic lymphoproliferative disorders: a surrogate marker for NK-cell clonality
Currently, the lack of a universal and specific marker of clonality hampers the diagnosis and classification of chronic expansions of natural killer (NK) cells. Here we investigated the utility of flow cytometric detection of aberrant/altered NK-cell phenotypes as a surrogate marker for clonality, in the diagnostic work-up of chronic lymphoproliferative disorders of NK cells (CLPD-NK). For this purpose, a large panel of markers was evaluated by multiparametric flow cytometry on peripheral blood (PB) CD56low NK cells from 60 patients, including 23 subjects with predefined clonal (n = 9) and polyclonal (n = 14) CD56low NK-cell expansions, and 37 with CLPD-NK of undetermined clonality; also, PB samples from 10 healthy adults were included. Clonality was established using the human androgen receptor (HUMARA) assay. Clonal NK cells were found to show decreased expression of CD7, CD11b and CD38, and higher CD2, CD94 and HLADR levels vs. normal NK cells, together with a restricted repertoire of expression of the CD158a, CD158b and CD161 killer-associated receptors. In turn, NK cells from both clonal and polyclonal CLPD-NK showed similar/overlapping phenotypic profiles, except for high and more homogeneous expression of CD94 and HLADR, which was restricted to clonal CLPD-NK. We conclude that the CD94hi/HLADR+ phenotypic profile proved to be a useful surrogate marker for NK-cell clonality
Point-contact spectroscopy on URuSi
Tunnel and point contact experiments have been made in a URuSi single
crystal along the c-axis. The experiments were performed changing temperature
and contact size in a low temperature scanning tunneling microscope. A
resonance develops at the Fermi level at K. This resonance splits
and becomes asymmetric when the 17.5 K phase transition is crossed. These
results are consistent with the existence of Kondo like bound states of the
U ionic configurations and the conduction electrons. Below the
transition, these configurations are split by the development of quadrupolar
ordering. The peak separation can be interpreted as a direct measurement of the
order parameter. Measurements on a policrystalline UAu_2Si_2$ sample are also
reported, with a comparative study of the behavior of both materials.Comment: 4 pages (Latex) + 2 postscript figure
Remarks on Semileptonic B and D Decays into Orbitally Excited Mesons
We have obtained the differential decay rate and calculated the branching
ratios of the exclusive semileptonic decays , where is a
p-wave meson, using the nonrelativistic ISGW quark model. Our results are
compared with the predictions of the ISGW2 model. We have computed some
branching ratios that were not reported or were reported with 0.00 in this
model. For example, we find that , and , which seems to be
at the reach of forthcoming experiments. Furthermore, we have classified the
decays in two groups and compared the semileptonic and
nonleptonic decays including a tensor meson in the final state.Comment: 11 pages, LaTe
A possible hadronic excess in psi(2S) decay and rho-pi puzzle
We examine the so-called rho-pi puzzle of the psi(2S) decay by incorporating
two inputs: One is the relative phase between the one-photon and the gluon
decay amplitude, and the other is a possible anomaly in the inclusive
nonelectromagnetic decay rate of psi(2S). We propose the possibility that in
the psi(2S) decay a hadronic decay process of long distance origin is important
in addition to the short-distance decay process. The amplitude of this
additional process should nearly cancel the three-gluon amplitude in the
exclusive psi(2S)---> 1-0- and turn the sum dominantly real in contrast to the
J/psi decay. We present general consequences of this mechanism and then briefly
look into two models which possibly explain the course of this additional
amplitude.Comment: 14 pages, 2 Tables, and 3 eps figures. Replaces the original version
with a minor change in the title and inclusion of more references. The
version to appear in Phys. Rev.
Impact of Implementing a Dyslipidemia Management Guideline on Cholesterol Control for Secondary Prevention of Ischemic Heart Disease in Primary Care
Cardiovascular diseases (CVD) are the main cause of death worldwide. The control of CVD risk factors, such as dyslipidemia, reduces their mortality rate. Nonetheless, fewer than 50% of patients with ischemic heart disease (IHD) have good cholesterol control. Our objective is to assess whether the level of participation of general practitioners (GPs) in activities to implement a dyslipidemia management guideline, and the characteristics of the patient and physician are associated with cholesterol control in IHD patients. We undertook a quasi-experimental, uncontrolled, before-and-after study of 1151 patients. The intervention was carried out during 2010 and 2011, and consisted of a face-to-face training and online course phase (Phase 1), and another of face-to-face feedback (Phase 2). The main outcome variable was the low-density lipoprotein cholesterol (LDL-C) control, whereby values of <100 mg/dL (2.6 mmol/L) were set as a good level of control, according to the recommendations of the guidelines in force in 2009. After Phase 1, 6.7% more patients demonstrated good cholesterol control. With respect to patient characteristics, being female and being older were found to be risk factors of poor control. Being diabetic and having suffered a stroke were protective factors. Of the GPs' characteristics, being tutor in a teaching center for GP residents and having completed the online course were found to be protective factors. We concluded that cholesterol control in IHD patients was influenced by the type of training activity undertook by physicians during the implementation of the GPC, and patient and physician characteristics. We highlight that if we apply the recent targets of the European guideline, which establish a lower level of LDL-C control, the percentage of good control could be worse than the observed in this study
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