197 research outputs found
Characterization of an inertial micro gripper based on adhesion forces
Adhesive forces become predominant in the micro world comparing to the gravity effect implying the development of new micro manipulation strategies. This paper presents the design and conception of a gripper that use the inertial principle for the release (applying a high acceleration, in the order of 10’000g) and the adhesion for catching a micro part of 50μm with the goal of precisely control the position after release. Experiments were conducted and showed a positioning repeatability of 2μm to 6μm depending on the relative humidity with a success rate of more than 90%
Cyclosporine A reduces microvascular obstruction and preserves left ventricular function deterioration following myocardial ischemia and reperfusion
Postconditioning and cyclosporine A prevent
mitochondrial permeability transition pore opening providing
cardioprotection during ischemia/reperfusion.
Whether microvascular obstruction is affected by these
interventions is largely unknown. Pigs subjected to coronary
occlusion for 1 h followed by 3 h of reperfusion were
assigned to control (n = 8), postconditioning (n = 9) or
cyclosporine A intravenous infusion 10-15 min before the
end of ischemia (n = 8). Postconditioning was induced by
8 cycles of repeated 30-s balloon inflation and deflation.
After 3 h of reperfusion magnetic resonance imaging,
triphenyltetrazolium chloride/Evans blue staining and histopathology
were performed. Microvascular obstruction
(MVO, percentage of gadolinium-hyperenhanced area) was
measured early (3 min) and late (12 min) after contrast
injection. Infarct size with double staining was smaller in
cyclosporine (46.2 ± 3.1 %, P = 0.016) and postconditioning
pigs (47.6 ± 3.9 %, P = 0.008) versus controls
(53.8 ± 4.1 %). Late MVO was significantly reduced by
cyclosporine (13.9 ± 9.6 %, P = 0.047) but not postconditioning
(23.6 ± 11.7 %, P = 0.66) when compared with
controls (32.0 ± 16.9 %). Myocardial blood flow in the
late MVO was improved with cyclosporine versus controls
(0.30 ± 0.06 vs 0.21 ± 0.03 ml/g/min, P = 0.002) and
was inversely correlated with late-MVO extent ( = 0.93,
P\0.0001). Deterioration of left ventricular ejection
fraction (LVEF) between baseline and 3 h of reperfusion
was smaller with cyclosporine (-7.9 ± 2.4 %, P = 0.008)
but not postconditioning (-12.0 ± 5.5 %, P = 0.22) when
compared with controls (-16.4 ± 5.5 %). In the three
groups, infarct size (\beta = -0.69, P\0.001) and late MVO
(\beta = -0.33, P = 0.02) were independent predictors of
LVEF deterioration following ischemia/reperfusion
(R^{2} = 0.73, P\0.001). Despite both cyclosporine A and
postconditioning reduce infarct size, only cyclosporine A
infusion had a beneficial effect on microvascular damage
and was associated with better preserved LV function when
compared with controls
Testing J/psi Production and Decay Properties in Hadronic Collisions
The polar and azimuthal angular distributions for the lepton pair arising
from the decay of a J/psi meson produced at transverse momentum p_T balanced by
a photon [or gluon] in hadronic collisions are calculated in the color singlet
model (CSM). It is shown that the general structure of the decay lepton
distribution is controlled by four invariant structure functions, which are
functions of the transverse momentum and the rapidity of the J/psi. We found
that two of these structure functions [the longitudinal and transverse
interference structure functions] are identical in the CSM. Analytical and
numerical results are given in the Collins-Soper and in the Gottfried-Jackson
frame. We present a Monte Carlo study of the effect of acceptance cuts applied
to the leptons and the photon for J/psi+ gamma production at the Tevatron.Comment: 22 pages (LaTeX) plus 11 postscript figures, MAD/PH/822, YUMS94-11.
Figures are available from the authors or as a compressed tar file via
anonymous ftp at phenom.physics.wisc.edu in directory
{}~pub/preprints/madph-94-822-figs.tar.
Probing scalar-pseudoscalar mixing in the CP violating MSSM at high-energy colliders
We study the production processes , and
in the context of the CP violating MSSM. In a given
channel we show that the cross-section for all i (=1,2,3) can be above 0.1 fb
provided M_{H_{2,3}}\la 300 GeV. This should be detectable at a Next Linear
Collider and would provide evidence for scalar-pseudoscalar mixing.Comment: 17 pages, RevTex, 4 ps figures, figure 4 changed, minor modifications
to text, version to appear in PR
Resumming the color-octet contribution to e+ e- -> J/psi + X
Recent observations of the spectrum of J/psi produced in e+ e- collisions at
the Upsilon(4S) resonance are in conflict with fixed-order calculations using
the Non-Relativistic QCD (NRQCD) effective field theory. One problem is that
leading order color-octet mechanisms predict an enhancement of the cross
section for J/psi with maximal energy that is not observed in the data.
However, in this region of phase space large perturbative corrections (Sudakov
logarithms) as well as enhanced nonperturbative effects are important. In this
paper we use the newly developed Soft-Collinear Effective Theory (SCET) to
systematically include these effects. We find that these corrections
significantly broaden the color-octet contribution to the J/psi spectrum. Our
calculation employs a one-stage renormalization group evolution rather than the
two-stage evolution used in previous SCET calculations. We give a simple
argument for why the two methods yield identical results to lowest order in the
SCET power counting.Comment: 27 pages, 7 figure
Color-Singlet Production at Colliders
We calculate in closed form the complete
color-singlet differential cross section for
scattering. The cross section reduces at high energies to a heavy quark
fragmentation form. We find that the energy scale at which the approximate
fragmentation result becomes reliable exceeds the mass by more than an
order of magnitude. We also discuss the color-singlet model's predictions for
direct angular and energy distributions at CLEO.Comment: 17 pages RevTeX, 5 embedded ps/eps figure
Implementing statically typed object-oriented programming languages
A paraîtreInternational audienceObject-oriented programming languages represent an original implementation issue due to the mechanism known as late binding, aka message sending. The underlying principle is that the address of the actually called procedure is not statically determined, at compile-time, but depends on the dynamic type of a distinguished parameter known as the receiver. In statically typed languages, the point is that the receiver's dynamic type may be a subtype of its static type. A similar issue arises with attributes, because their position in the object layout may depends on the object's dynamic type. Furthermore, subtyping introduces another original feature, i.e. subtype checks. All three mechanisms need specific implementations, data structures and algorithms. In statically typed languages, late binding is generally implemented with tables, called virtual function tables in C++ jargon. These tables reduce method calls to pointers to functions, through a small fixed number of extra indirections. It follows that object-oriented programming yields some overhead, as compared to usual procedural languages. The different techniques and their resulting overhead depend on several parameters. Firstly, inheritance and subtyping may be single or multiple and a mixing is even possible, as in JAVA, which presents single inheritance for classes and multiple subtyping for interfaces. Multiple inheritance is a well known complication. Secondly, the production of executable programs may involve various schemes, from global compilation frameworks, where the whole program is known at compile time, to separate compilation and dynamic loading, where each program unit---usually a class in an object-oriented context---is compiled and loaded independently of any usage. Global compilation is well known to facilitate optimization. In this paper, we review the various implementation schemes available in the context of static typing and in the three cases of single inheritance, multiple inheritance, and single inheritance but with multiple subtyping, e.g. JAVA. The survey focuses on separate compilation and dynamic loading, as it is the most commonly used framework and the most demanding. However, many works have been recently undertaken in the global compilation framework, mostly for dynamically typed languages but also applied to the EIFFEL language in the SMARTEIFFEL compiler. Hence, we examine global techniques and how they can improve implementation efficiency. Finally, a mixed framework is considered, where separate compilation is followed by a global step, similar to linking, which uses global techniques, as well for implementation, with coloring, as for optimization, with type analysis. An application to dynamic loading is sketched
Subanesthetic ketamine treatment promotes abnormal interactions between neural subsystems and alters the properties of functional brain networks
Acute treatment with subanesthetic ketamine, a non-competitive N-methyl-D-aspartic acid (NMDA) receptor antagonist, is widely utilized as a translational model for schizophrenia. However, how acute NMDA receptor blockade impacts on brain functioning at a systems level, to elicit translationally relevant symptomatology and behavioral deficits, has not yet been determined. Here, for the first time, we apply established and recently validated topological measures from network science to brain imaging data gained from ketamine-treated mice to elucidate how acute NMDA receptor blockade impacts on the properties of functional brain networks. We show that the effects of acute ketamine treatment on the global properties of these networks are divergent from those widely reported in schizophrenia. Where acute NMDA receptor blockade promotes hyperconnectivity in functional brain networks, pronounced dysconnectivity is found in schizophrenia. We also show that acute ketamine treatment increases the connectivity and importance of prefrontal and thalamic brain regions in brain networks, a finding also divergent to alterations seen in schizophrenia. In addition, we characterize how ketamine impacts on bipartite functional interactions between neural subsystems. A key feature includes the enhancement of prefrontal cortex (PFC)-neuromodulatory subsystem connectivity in ketamine-treated animals, a finding consistent with the known effects of ketamine on PFC neurotransmitter levels. Overall, our data suggest that, at a systems level, acute ketamine-induced alterations in brain network connectivity do not parallel those seen in chronic schizophrenia. Hence, the mechanisms through which acute ketamine treatment induces translationally relevant symptomatology may differ from those in chronic schizophrenia. Future effort should therefore be dedicated to resolve the conflicting observations between this putative translational model and schizophrenia
Analysis of age-related left ventricular collagen remodeling in living donors: Implications in arrhythmogenesis
Age-related fibrosis in the left ventricle (LV) has been mainly studied in animals by assessing collagen content. Using second-harmonic generation microscopy and image processing, we evaluated amount, aggregation and spatial distribution of LV collagen in young to old pigs, and middle-age and elder living donors. All collagen features increased when comparing adult and old pigs with young ones, but not when comparing adult with old pigs or middle-age with elder individuals. Remarkably, all collagen parameters strongly correlated with lipofuscin, a biological age marker, in humans. By building patient-specific models of human ventricular tissue electrophysiology, we confirmed that amount and organization of fibrosis modulated arrhythmia vulnerability, and that distribution should be accounted for arrhythmia risk assessment. In conclusion, we characterize the age-associated changes in LV collagen and its potential implications for ventricular arrhythmia development. Consistency between pig and human results substantiate the pig as a relevant model of age-related LV collagen dynamics. © 2022 The Author(s
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