744 research outputs found
Phonon-induced dephasing of singlet-triplet superpositions in double quantum dots without spin-orbit coupling
We show that singlet-triplet superpositions of two-electron spin states in a
double quantum dot undergo a phonon-induced pure dephasing which relies only on
the tunnel coupling between the dots and on the Pauli exclusion principle. As
such, this dephasing process is independent of spin-orbit coupling or hyperfine
interactions. The physical mechanism behind the dephasing is elastic phonon
scattering, which persists to much lower temperatures than real phonon-induced
transitions. Quantitative calculations performed for a lateral GaAs/AlGaAs
gate-defined double quantum dot yield micro-second dephasing times at
sub-Kelvin temperatures, which is consistent with experimental observations.Comment: Extended versio
Sudden death of effective entanglement
Sudden death of entanglement is a well-known effect resulting from the finite
volume of separable states. We study the case when the observer has a limited
measurement capability and analyse the effective entanglement, i.e.
entanglement minimized over the output data. We show that in the well defined
system of two quantum dots monitored by single electron transistors, one may
observe a sudden death of effective entanglement when real, physical
entanglement is still alive. For certain measurement setups, this occurs even
for initial states for which sudden death of physical entanglement is not
possible at all. The principles of the analysis may be applied to other
analogous scenarios, such as etimation of the parameters arising from quantum
process tomography.Comment: final version, 5 pages, 3 figure
Complete disentanglement by partial pure dephasing
We study the effect of pure dephasing on the entanglement of a pair of
two-level subsystems (qubits). We show that partial dephasing induced by a
super-Ohmic reservoir, corresponding to well-established properties of confined
charge states and phonons in semiconductors, may lead to complete
disentanglement. We show also that the disentanglement effect increases with
growing distance between the two subsystems.Comment: Final, considerably extended version, 6 pages, 4 figure
Monocyte Chemoattractant Protein-1− 2518 A/G Single Nucleotide Polymorphism Might Be Associated with Renal Disease and Thrombocytopenia of SLE
There is conflicting evidence on the contribution of the MCP-1 −2518 A>G (rs 1024611) polymorphism to SLE incidence and clinical manifestations.
We examined the prevalence of the MCP-1 −2518 A>G polymorphism in SLE patients (n = 199) and controls (n = 250) in Poland. We did not observe a significant difference in the distribution of MCP-1 −2518 A>G polymorphic variants in patients with SLE and healthy individuals. However, we found an association between the GG versus AG and AA genotypes as well as the AG and GG versus AA genotypes with renal manifestations of SLE OR = 3.614 (1.123–11.631, P = 0.0345) and OR = 2.297 (1.301–4.057, P = 0.0046), respectively. We also observed that the MCP-1 AG and GG -genotypes contribute to the occurrence of thrombocytopenia in SLE patients OR = 2.618 (1.280–5.352, P = 0.0089). Our observations indicate that either MCP-1 −2518 G variant can be associated with some clinical findings in patients with SLE
Phonon-induced decoherence for a quantum dot spin qubit operated by Raman passage
We study single-qubit gates performed via stimulated Raman adiabatic passage
(STIRAP) on a spin qubit implemented in a quantum dot system in the presence of
phonons. We analyze the interplay of various kinds of errors resulting from the
carrier-phonon interaction as well as from quantum jumps related to
nonadiabaticity and calculate the fidelity as a function of the pulse
parameters. We give quantitative estimates for an InAs/GaAs system and identify
the parameter values for which the error is considerably minimized, even to
values below per operation.Comment: Final version; considerable extensions; 18 pages, 7 figure
Calculated conformer energies for organic molecules with multiple polar functionalities are method dependent: Taxol (case study)
BACKGROUND: Molecular mechanics (MM) and quantum chemical (QM) calculations are widely applied and powerful tools for the stereochemical and conformational investigations of molecules. The same methods have been extensively used to probe the conformational profile of Taxol (Figure 1) both in solution and at the β-tubulin protein binding site. RESULTS: In the present work, the relative energies of seven conformations of Taxol derived from NMR and X-ray analyses were compared with a set of widely used force fields and semiempirical MO methods coupled to a continuum solvent treatment. The procedures not only diverge significantly in their assessment of relative conformational energies, but none of them provide satisfactory agreement with experiment. CONCLUSIONS: For Taxol, molecular mechanics and semiempirical QM methods are unable to provide a consistent energetic ranking of side-chain conformations. For similar highly polar organic structures, "energy-free" conformational search methods are advised
Adsorption of CO on a Platinum (111) surface - a study within a four-component relativistic density functional approach
We report on results of a theoretical study of the adsorption process of a
single carbon oxide molecule on a Platinum (111) surface. A four-component
relativistic density functional method was applied to account for a proper
description of the strong relativistic effects. A limited number of atoms in
the framework of a cluster approach is used to describe the surface. Different
adsorption sites are investigated. We found that CO is preferably adsorbed at
the top position.Comment: 23 Pages with 4 figure
XRCC2 R188H (rs3218536), XRCC3 T241M (rs861539) and R243H (rs77381814) single nucleotide polymorphisms in cervical cancer risk
Human Papillomavirus (HPV) is the main cause of cervical cancer and its precursor lesions. Transformation may be induced by several mechanisms, including oncogene activation and genome instability. Individual differences in DNA damage recognition and repair have been hypothesized to influence cervical cancer risk. The aim of this study was to evaluate whether the double strand break gene polymorphisms XRCC2 R188H G>A (rs3218536), XRCC3 T241M C>T (rs861539) and R243H G>A (rs77381814) are associated to cervical cancer in Argentine women. A case control study consisting of 322 samples (205 cases and 117 controls) was carried out. HPV DNA detection was performed by PCR and genotyping of positive samples by EIA (enzyme immunoassay). XRCC2 and 3 polymorphisms were determined by pyrosequencing. The HPV-adjusted odds ratio (OR) of XRCC2 188 GG/AG genotypes was OR = 2.4 (CI = 1.1-4.9, p = 0.02) for cervical cancer. In contrast, there was no increased risk for cervical cancer with XRCC3 241 TT/CC genotypes (OR = 0.48; CI = 0.2-1; p = 0.1) or XRCC3 241 CT/CC (OR = 0.87; CI = 0.52-1.4; p = 0.6). Regarding XRCC3 R243H, the G allele was almost fixed in the population studied. In conclusion, although the sample size was modest, the present data indicate a statistical association between cervical cancer and XRCC2 R188H polymorphism. Future studies are needed to confirm these findings.Fil: Perez, Luis Orlando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico CONICET- La Plata. Instituto de Genética Veterinaria "Ing. Fernando Noel Dulout". Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias. Instituto de Genética Veterinaria; ArgentinaFil: Crivaro, Andrea Natalia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico CONICET- La Plata. Instituto de Genética Veterinaria "Ing. Fernando Noel Dulout". Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias. Instituto de Genética Veterinaria; ArgentinaFil: Barbisan, Gisela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico CONICET- La Plata. Instituto de Genética Veterinaria "Ing. Fernando Noel Dulout". Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias. Instituto de Genética Veterinaria; ArgentinaFil: Poleri, Lucía Belén. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico CONICET- La Plata. Instituto de Genética Veterinaria "Ing. Fernando Noel Dulout". Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias. Instituto de Genética Veterinaria; ArgentinaFil: Golijow, Carlos Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico CONICET- La Plata. Instituto de Genética Veterinaria "Ing. Fernando Noel Dulout". Universidad Nacional de La Plata. Facultad de Ciencias Veterinarias. Instituto de Genética Veterinaria; Argentin
Zeros and the functional equation of the quadrilateral zeta function
In this paper, we show that all real zeros of the bilateral Hurwitz zeta
function with are on
only the non-positive even integers exactly same as in the case of . We also prove that all real zeros of the bilateral periodic zeta
function
with are on only the negative even integers just like
. Moreover, we show that all real zeros of the quadrilateral zeta
function with are on only the
negative even integers. On the other hand, we prove that , and
have at least one real zero in when is sufficiently
small. The complex zeros of these zeta functions are also discussed when is rational or transcendental. As a corollary, we show that
with rational or does not satisfy the
analogue of the Riemann hypothesis even though satisfies the
functional equation that appeared in Hamburger's or Hecke's theorem and all
real zeros of are located at only the negative even integers again as
in the case of .Comment: 12 pages. We changed the title. Some typos are correcte
6,11-Dihydrodibenz[b,e]oxepin-11-one
In the title compound, C14H10O2, the seven-membered oxepine ring adopts a twist-boat conformation with a dihedral angle between the mean planes of the two fused benzene rings of 42.0 (1)°. In the crystal, molecules are linked into chains propagating along the c axis by intermolecular C—H⋯O hydrogen bonds and the chains are arranged in layers parallel to (100)
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