1,188 research outputs found
Quantum phase gate with a selective interaction
We present a proposal for implementing quantum phase gates using selective
interactions. We analize selectivity and the possibility to implement these
gates in two particular systems, namely, trapped ions and Cavity QED.Comment: Four pages of TEX file and two EPS figures. Submitted for publicatio
Implementation of a two-qubit controlled-U gate based on unconventional geometric phase with a constant gating time
We propose an alternative scheme to implement a two-qubits Controlled-U gate
in the hybrid system atom- (coupled cavities array). Our scheme results in
a constant gating time and, with an adjustable qubit-bus coupling
(atom-resonator), one can specify a particular transformation on the target
qubit. We believe that this proposal may open promising perspectives for
networking quantum information processors and implementing distributed and
scalable quantum computation.Comment: 4 pages, 1 figure, APS format, an extended version is in progress
with some improvement
Universal quantum computation by holonomic and nonlocal gates with imperfections
We present a nonlocal construction of universal gates by means of holonomic
(geometric) quantum teleportation. The effect of the errors from imperfect
control of the classical parameters, the looping variation of which builds up
holonomic gates, is investigated. Additionally, the influence of quantum
decoherence on holonomic teleportation used as a computational primitive is
studied. Advantages of the holonomic implementation with respect to control
errors and dissipation are presented.Comment: 5 pages, 2 figures, REVTEX, title changed, typos correcte
NP7 protects from cell death induced by oxidative stress in neuronal and glial midbrain cultures from parkin null mice
AbstractParkin mutations produce Parkinson’s disease (PD) in humans and nigrostriatal dopamine lesions related to increased free radicals in mice. We examined the effects of NP7, a synthetic, marine derived, free radical scavenger which enters the brain, on H2O2 toxicity in cultured neurons and glia from wild-type (WT) and parkin null mice (PK-KO).NP7, 5–10μM, prevented the H2O2 induced apoptosis and necrosis of midbrain neuronal and glial cultures from WT and PK-KO mice. NP7 suppressed microglial activation and the H2O2 induced drop-out of dopamine neurons. Furthermore, NP7 prevented the increased phosphorylation of ERK and AKT induced by H2O2. NP7 may be a promising neuroprotector against oxidative stress in PD
Fatores prognósticos da infeção respiratória aguda baixa grave em crianças menores de 5 años na Colômbia
Introduction: Acute lower respiratory infection (alri: community acquired and/or bronchiolitis) is one of the main public health issues for children under five years of age. The main purpose of this research was to describe the epidemiological profile, associated factors, and prognosis of alri in two hospitals in Popayan, Colombia. Materials and Methods: This was a cohort study. We included children from 2 months to 5 years of age with diagnoses of severe alri. Sociodemographic profiles, clinical features, and prognostic factors were collected. The main outcomes under study were mortality, admission to icu, and length of stay. Multivariable analyses were performed to establish the independent contributions of prognostic factors. Results: 121 patients were included. Incidence of alri was 4% ci95% [3,3-4,7] during 6 months of follow-up. Mortality during follow-up was 0,8% (ci95% 0,l-4,4) (one patient). Thirty three percent of children required admission to icu. Median length of stay was 5 days and length of stay in icu was 4 days. Preterm birth was independently associated with icu admission (or=5,1 ci95% [l,3-20] p=0,0l9). Discussion: The incidence of severe alri was 4%. Mortality was low and length of stay was short. Factors related to the diagnosis of alri in this cohort are consistent with those reported in the national and international literature, and the only independent prognostic factor for admission to icu was preterm birth
New explanation of the strange baryon rapidity distributions in ultra-relativistic nucleus-nucleus collisions
A model of multiparticle production in hadronic collisions at
ultra-relativistic energies, based on the assumption of independent string
fragmentation, reproduces the rapidity spectra of and
in sulphur-sulphur collisions reported by the NA35 Collaboration. This is
achieved after a reconsideration of the intermediate multi-string states and
the structure of the diquarks. Nuclear stopping power is also studied through
the computation of the rapidity spectra.Comment: Final version as it will appear in Nucl. Phys. A. It contains 27
pages including 12 figure
Taphonomic and spatial analyses from the Early Pleistocene site of Venta Micena 4 (Orce, Guadix-Baza Basin, southern Spain)
Venta Micena is an area containing several palaeontological sites marking the beginning of the Calabrian stage (Early Pleistocene). The richness of the fossil accumulation including species of Asian, African and European origin, makes Venta Micena a key site for the the palaeoecological and palaeoenvironmental study of southern Europe during the Early Pleistocene. Thus, research has been focused on Venta Micena 3, which was originally interpreted as a single palaeosurface associated with a marshy context, in which most of the fauna was accumulated by Pachycrocuta brevirostris. Recent excavations have unearthed a new site, Venta Micena 4, located in the same stratigraphic unit (Unit C) and in close proximity to Venta Micena 3. Here we show the first analyses regarding the taphonomic and spatial nature of this new site, defining two stratigraphic boundaries corresponding to two different depositional events. Furthermore, the taphonomic analyses of fossil remains seem to indicate a different accumulative agent than Pachycrocuta, thus adding more complexity to the palaeobiological interpretation of the Venta Micena area. These results contribute to the discussion of traditional interpretations made from Venta Micena 3. © 2021, The Author(s)
Branching Fractions for D0 -> K+K- and D0 -> pi+pi-, and a Search for CP Violation in D0 Decays
Using the large hadroproduced charm sample collected in experiment E791 at
Fermilab, we have measured ratios of branching fractions for the two-body
singly-Cabibbo-suppressed charged decays of the D0:
(D0 -> KK)/(D0 -> Kpi) = 0.109 +- 0.003 +- 0.003,
(D0 -> pipi)/(D0 -> Kpi) = 0.040 +- 0.002 +- 0.003, and
(D0 -> KK)/(D0 -> pipi) = 2.75 +- 0.15 +- 0.16. We have looked for
differences in the decay rates of D0 and D0bar to the CP eigenstates K+K- and
pi+pi-, and have measured the CP asymmetry parameters
A_CP(K+K-) = -0.010 +- 0.049 +- 0.012 and
A_CP(pi+pi-) = -0.049 +- 0.078 +- 0.030, both consistent with zero.Comment: 10 Postscript pages, including 2 figures. Submitted to Phys. Lett.
Search for Rare and Forbidden Dilepton Decays of the D+, Ds, and D0 Charmed Mesons
We report the results of a search for flavor-changing neutral current,
lepton-flavor violating, and lepton-number violating decays of D+, Ds, and D0
mesons (and their antiparticles) into modes containing muons and electrons.
Using data from Fermilab charm hadroproduction experiment E791, we examine the
pi,l,l and K,l,l decay modes of D+ and Ds and the l+l- decay modes of D0. No
evidence for any of these decays is found. Therefore, we present
branching-fraction upper limits at 90% confidence level for the 24 decay modes
examined. Eight of these modes have no previously reported limits, and fourteen
are reported with significant improvements over previously published results.Comment: 12 pages, 3 figures, LaTeX, elsart.cls, epsf.sty, amsmath.sty
Submitted to Physics Letters
Measurement of the form-factor ratios for D+ --> K* l nu
The form factor ratios rv=V(0)/A1(0), r2=A2(0)/A1(0) and r3=A3(0)/A1(0) in
the decay D+ --> K* l nu, K* -->K-pi+ have been measured using data from charm
hadroproduction experiment E791 at Fermilab. From 3034 (595) signal
(background) events in the muon channel, we obtain rv=1.84+-0.11+-0.09,
r2=0.75+-0.08+-0.09 and, as a first measurement of r3, we find 0.04+-0.33
+-0.29. The values of the form factor ratios rv and r2 measured for the muon
channel are combined with the values of rv and r2 that we have measured in the
electron channel. The combined E791 results for the muon and electron channels
are rv=1.87+-0.08+-0.07 and r2=0.73+-0.06+-0.08.Comment: 9 pages + 3 figures ; submitted to PL
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