778 research outputs found
General Relativity as Classical Limit of Evolutionary Quantum Gravity
We analyze the dynamics of the gravitational field when the covariance is
restricted to a synchronous gauge. In the spirit of the Noether theorem, we
determine the conservation law associated to the Lagrangian invariance and we
outline that a non-vanishing behavior of the Hamiltonian comes out. We then
interpret such resulting non-zero ``energy'' of the gravitational field in
terms of a dust fluid. This new matter contribution is co-moving to the slicing
and it accounts for the ``materialization'' of a synchronous reference from the
corresponding gauge condition. Further, we analyze the quantum dynamics of a
generic inhomogeneous Universe as described by this evolutionary scheme,
asymptotically to the singularity. We show how the phenomenology of such a
model overlaps the corresponding Wheeler-DeWitt picture. Finally, we study the
possibility of a Schr\"odinger dynamics of the gravitational field as a
consequence of the correspondence inferred between the ensemble dynamics of
stochastic systems and the WKB limit of their quantum evolution. We demonstrate
that the time dependence of the ensemble distribution is associated with the
first order correction in to the WKB expansion of the energy spectrum.Comment: 23 pages, to appear on Class. Quant. Gra
Integrin-mediated Tyrosine Phosphorylation and Cytokine Message Induction in Monocytic Cells: A POSSIBLE SIGNALING ROLE FOR THE Syk TYROSINE KINASE
Activation of cytoplasmic tyrosine kinases is an important aspect of signal transduction mediated by integrins. In the human monocytic cell line THP-1, either integrin-dependent cell adhesion to fibronectin or ligation of beta 1 integrins with antibodies causes a rapid and intense tyrosine phosphorylation of two sets of proteins of about 65-75 and 120-125 kDa. In addition, integrin ligation leads to nuclear translocation of the p50 and p65 subunits of the NF-kappa B transcription factor, to activation of a reporter gene driven by a promoter containing NF-kappa B sites, and to increased levels of mRNAs for immediate-early genes, including the cytokine interleukin (IL)-1 beta. The tyrosine kinase inhibitors genistein and herbimycin A block both integrin-mediated tyrosine phosphorylation and increases in IL-1 beta message levels, indicating a causal relationship between the two events. The components tyrosine phosphorylated subsequent to cell adhesion include paxillin, pp125FAK, and the SH2 domain containing tyrosine kinase Syk. In contrast, integrin ligation with antibodies induces tyrosine phosphorylation of Syk but not of FAK or paxillin. In adhering cells, pre-treatment with cytochalasin D suppresses tyrosine phosphorylation of FAK and paxillin but not of Syk, while IL-1 beta message induction is unaffected. These observations indicate that the Syk tyrosine kinase may be an important component of an integrin signaling pathway in monocytic cells, leading to activation of NF-kappa B and to increased levels of cytokine messages
Quantum Gravitational Corrections to the Real Klein-Gordon Field in the Presence of a Minimal Length
The (D+1)-dimensional -two-parameter Lorentz-covariant
deformed algebra introduced by Quesne and Tkachuk [C. Quesne and V. M. Tkachuk,
J. Phys. A: Math. Gen. \textbf {39}, 10909 (2006).], leads to a nonzero minimal
uncertainty in position (minimal length). The Klein-Gordon equation in a
(3+1)-dimensional space-time described by Quesne-Tkachuk Lorentz-covariant
deformed algebra is studied in the case where up to first order
over deformation parameter . It is shown that the modified Klein-Gordon
equation which contains fourth-order derivative of the wave function describes
two massive particles with different masses. We have shown that physically
acceptable mass states can only exist for which
leads to an isotropic minimal length in the interval . Finally, we have shown that the above estimation of
minimal length is in good agreement with the results obtained in previous
investigations.Comment: 10 pages, no figur
String-inspired cosmology: Late time transition from scaling matter era to dark energy universe caused by a Gauss-Bonnet coupling
The Gauss-Bonnet (GB) curvature invariant coupled to a scalar field
can lead to an exit from a scaling matter-dominated epoch to a late-time
accelerated expansion, which is attractive to alleviate the coincident problem
of dark energy. We derive the condition for the existence of cosmological
scaling solutions in the presence of the GB coupling for a general scalar-field
Lagrangian density , where is a kinematic
term of the scalar field. The GB coupling and the Lagrangian density are
restricted to be in the form and , respectively, where is a constant and is an
arbitrary function. We also derive fixed points for such a scaling Lagrangian
with a GB coupling and clarify the conditions
under which the scaling matter era is followed by a de-Sitter solution which
can appear in the presence of the GB coupling. Among scaling models proposed in
the current literature, we find that the models which allow such a cosmological
evolution are an ordinary scalar field with an exponential potential and a
tachyon field with an inverse square potential, although the latter requires a
coupling between dark energy and dark matter.Comment: 18 pages, 4 figures, version to appear in JCA
On (Cosmological) Singularity Avoidance in Loop Quantum Gravity
Loop Quantum Cosmology (LQC), mainly due to Bojowald, is not the cosmological
sector of Loop Quantum Gravity (LQG). Rather, LQC consists of a truncation of
the phase space of classical General Relativity to spatially homogeneous
situations which is then quantized by the methods of LQG. Thus, LQC is a
quantum mechanical toy model (finite number of degrees of freedom) for LQG(a
genuine QFT with an infinite number of degrees of freedom) which provides
important consistency checks. However, it is a non trivial question whether the
predictions of LQC are robust after switching on the inhomogeneous fluctuations
present in full LQG. Two of the most spectacular findings of LQC are that 1.
the inverse scale factor is bounded from above on zero volume eigenstates which
hints at the avoidance of the local curvature singularity and 2. that the
Quantum Einstein Equations are non -- singular which hints at the avoidance of
the global initial singularity. We display the result of a calculation for LQG
which proves that the (analogon of the) inverse scale factor, while densely
defined, is {\it not} bounded from above on zero volume eigenstates. Thus, in
full LQG, if curvature singularity avoidance is realized, then not in this
simple way. In fact, it turns out that the boundedness of the inverse scale
factor is neither necessary nor sufficient for curvature singularity avoidance
and that non -- singular evolution equations are neither necessary nor
sufficient for initial singularity avoidance because none of these criteria are
formulated in terms of observable quantities.After outlining what would be
required, we present the results of a calculation for LQG which could be a
first indication that our criteria at least for curvature singularity avoidance
are satisfied in LQG.Comment: 34 pages, 16 figure
Integration of cell of origin into the clinical CNS International Prognostic Index improves CNS relapse prediction in DLBCL
Central nervous system (CNS) relapse carries a poor prognosis in diffuse large B-cell lymphoma (DLBCL). Integrating biomarkers into the CNS-International Prognostic Index (CNS-IPI) risk model may improve identification of patients at high risk for developing secondary CNS disease. CNS relapse was analyzed in 1418 DLBCL patients treated with obinutuzumab or rituximab plus cyclophosphamide, doxorubicin, vincristine, prednisone chemotherapy in the phase 3 GOYA study. Cell of origin (COO) was assessed using gene-expression profiling. BCL2 and MYC protein expression was analyzed by immunohistochemistry. The impact of CNS-IPI, COO, and BCL2/MYC dual-expression status on CNS relapse was assessed using a multivariate Cox regression model (data available in n = 1418, n = 933, and n = 688, respectively). High CNS-IPI score (hazard ratio [HR], 4.0; 95% confidence interval [CI], 1.3-12.3; P = .02) and activated B-cell\u2012like (ABC) (HR, 5.2; 95% CI, 2.1-12.9; P = .0004) or unclassified COO subtypes (HR, 4.2; 95% CI, 1.5-11.7; P = .006) were independently associated with CNS relapse. BCL2/MYC dual-expression status did not impact CNS relapse risk. Three risk subgroups were identified based on the presence of high CNS-IPI score and/or ABC/unclassified COO (CNS-IPI-C model): low risk (no risk factors, n = 450 [48.2%]), intermediate risk (1 factor, n = 408 [43.7%]), and high risk (both factors, n = 75 [8.0%]). Two-year CNS relapse rates were 0.5%, 4.4%, and 15.2% in the respective risk subgroups. Combining high CNS-IPI and ABC/unclassified COO improved CNS relapse prediction and identified a patient subgroup at high risk for developing CNS relapse. The study was registered at www.clinicaltrials.gov as #NCT01287741
Capturing the personal through the lens of the professional: The use of external data sources in autoethnography
This article shows how external data sources can be utilised in autoethnographic research. Beginning with an account of a critical incident that examines the incompatibility of private and professional identities, I show how, through the collection of data sources, I capture the impact of homophobic and heteronormative discursive practices on health, wellbeing and identity. In the critical incident, I explore how I prospered as a teacher at a British village school for almost 10 years by censoring my sexuality and carefully managing the intersection between my private and professional identities. However, when a malicious and homophobic neighbour and parent of children at the school exposed my sexuality to the Headteacher, I learned the extent to which the rural school community privileged and protected the heteronormative discourse. A poststructuralist theoretical framework underpins this article. My experience of being a subject is understood as the outcome of discursive practices. Sexual identity, teacher identity and autoethnographer identity are understood to be fluid, and constantly produced and reproduced in response to social, cultural and political influences. The article describes how email correspondence, medical records and notes from a course of cognitive behaviour therapy were deployed to augment my personal recollection and give a depth and richness to the narrative. As the critical incident became a police matter, examination takes place of how I sought to obtain and utilise data from the police national computer in the research. Attempts to collect data from the police and Crown Prosecution Service were problematic and provided an unexpected development in the research and offered additional insight into the nature of the British rural community and its police force
Measurement of the Charged Multiplicities in b, c and Light Quark Events from Z0 Decays
Average charged multiplicities have been measured separately in , and
light quark () events from decays measured in the SLD experiment.
Impact parameters of charged tracks were used to select enriched samples of
and light quark events, and reconstructed charmed mesons were used to select
quark events. We measured the charged multiplicities:
,
, from
which we derived the differences between the total average charged
multiplicities of or quark events and light quark events: and . We compared
these measurements with those at lower center-of-mass energies and with
perturbative QCD predictions. These combined results are in agreement with the
QCD expectations and disfavor the hypothesis of flavor-independent
fragmentation.Comment: 19 pages LaTex, 4 EPS figures, to appear in Physics Letters
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