1,705 research outputs found
High T(c) superconductors: Technical and commercial challenge
Some basic questions of the way which leads from the discovery of high-T(c) superconductors to their applications is surveyed. The influence of high-T(c) superconducting technology on the industrial and social development is also briefly analyzed
Resummation of double logarithms in electroweak high energy processes
At future linear collider experiments in the TeV range, Sudakov
double logarithms originating from massive boson exchange can lead to
significant corrections to the cross sections of the observable processes.
These effects are important for the high precision objectives of the Next
Linear Collider. We use the infrared evolution equation, based on a gauge
invariant dispersive method, to obtain double logarithmic asymptotics of
scattering amplitudes and discuss how it can be applied, in the case of broken
gauge symmetry, to the Standard Model of electroweak processes. We discuss the
double logarithmic effects to both non-radiative processes and to processes
accompanied by soft gauge boson emission. In all cases the Sudakov double
logarithms are found to exponentiate. We also discuss double logarithmic
effects of a non-Sudakov type which appear in Regge-like processes.Comment: 26 pages, 3 figures, Latex2
Double-logs, Gribov-Lipatov reciprocity and wrapping
We study analytical properties of the five-loop anomalous dimension of
twist-2 operators at negative even values of Lorentz spin. Following L. N.
Lipatov and A. I. Onishchenko, we have found two possible generalizations of
double-logarithmic equation, which allow to predict a lot of poles of anomalous
dimension of twist-2 operators at all orders of perturbative theory from the
known results. Second generalization is related with the reciprocity-respecting
function, which is a single-logarithmic function in this case. We have found,
that the knowledge of first orders of the reciprocity-respecting function gives
all-loop predictions for the highest poles. Obtained predictions can be used
for the reconstruction of a general form of the wrapping corrections for
twist-2 operators.Comment: 17 pages, references adde
Symmetry Properties of the Effective Action for High-Energy Scattering in QCD
We study the effective action describing high-energy scattering processes in
the multi-Regge limit of QCD, which should provide the starting point for a new
attempt to overcome the limitations of the leading logarithmic and the eikonal
approximations. The action can be obtained via simple graphical rules or by
integrating in the QCD functional integral over momentum modes of gluon and
quark fields that do not appear explicitely as scattering or exchanged
particles in the considered processes. The supersymmetry is used to obtain the
terms in the action involving quarks fields from the pure gluonic ones. We
observe a Weizs\"acker - Williams type relations between terms describing
scattering and production of particles.Comment: 37 pages LATEX, 1 Table and 7 figures using package FEYNMA
Asymptotic high energy behavior of the deeply virtual Compton scattering amplitude
We compute the deeply virtual Compton scattering (DVCS) amplitude for forward
and backward scattering in the asymptotic limit. Since this calculation does
not assume ordering of the transverse momenta, it includes important
logarithmic contributions that are beyond those summed by the DGLAP evolution.
These contributions lead to a power-like behavior for the forward DVCS
amplitude.Comment: Latex, 22 pages, 5 Figures; references enhanced; typos correcte
Factorization and high-energy effective action
I demonstrate that the amplitude for high-energy scattering can be factorized
as a convolution of the contributions due to fast and slow fields. The fast and
slow fields interact by means of Wilson-line operators -- infinite gauge
factors ordered along the straight line. The resulting factorization formula
gives a starting point for a new approach to the effective action for
high-energy scattering in QCD.Comment: 34 pages, Latex, 13 postscript figures, submitted to PR
Hematological Changes in Women and Infants Exposed to an AZT-Containing Regimen for Prevention of Mother-to-child-transmission of HIV in Tanzania.
Tanzanian guidelines for prevention of mother-to-child-transmission of HIV (PMTCT) recommend an antiretroviral combination regimen involving zidovudine (AZT) during pregnancy, single-dosed nevirapine at labor onset, AZT plus Lamivudine (3TC) during delivery, and AZT/3TC for 1-4 weeks postpartum. As drug toxicities are a relevant concern, we assessed hematological alterations in AZT-exposed women and their infants. A cohort of HIV-positive women, either with AZT intake (n = 82, group 1) or without AZT intake (n = 62, group 2) for PMTCT during pregnancy, was established at Kyela District Hospital, Tanzania. The cohort also included the infants of group 1 with an in-utero AZT exposure ≥4 weeks, receiving AZT for 1 week postpartum (n = 41), and infants of group 2 without in-utero AZT exposure, receiving a prolonged 4-week AZT tail (n = 58). Complete blood counts were evaluated during pregnancy, birth, weeks 4-6 and 12. For women of group 1 with antenatal AZT intake, we found a statistically significant decrease in hemoglobin level, red blood cells, white blood cells, granulocytes, as well as an increase in red cell distribution width and platelet count. At delivery, the median red blood cell count was significantly lower and the median platelet count was significantly higher in women of group 1 compared to group 2. At birth, infants from group 1 showed a lower median hemoglobin level and granulocyte count and a higher frequency of anemia and granulocytopenia. At 4-6 weeks postpartum, the mean neutrophil granulocyte count was significantly lower and neutropenia was significantly more frequent in infants of group 2. AZT exposure during pregnancy as well as after birth resulted in significant hematological alterations for women and their newborns, although these changes were mostly mild and transient in nature. Research involving larger cohorts is needed to further analyze the impact of AZT-containing regimens on maternal and infant health
Designing electronic collaborative learning environments
Electronic collaborative learning environments for learning and working are in vogue. Designers design them according to their own constructivist interpretations of what collaborative learning is and what it should achieve. Educators employ them with different educational approaches and in diverse situations to achieve different ends. Students use them, sometimes very enthusiastically, but often in a perfunctory way. Finally, researchers study them and—as is usually the case when apples and oranges are compared—find no conclusive evidence as to whether or not they work, where they do or do not work, when they do or do not work and, most importantly, why, they do or do not work. This contribution presents an affordance framework for such collaborative learning environments; an interaction design procedure for designing, developing, and implementing them; and an educational affordance approach to the use of tasks in those environments. It also presents the results of three projects dealing with these three issues
KCa1.1, a calcium-activated potassium channel subunit alpha 1, is targeted by miR-17-5p and modulates cell migration in malignant pleural mesothelioma
© 2016 Lin et al. Background: Malignant pleural mesothelioma (MPM) is an aggressive, locally invasive, cancer elicited by asbestos exposure and almost invariably a fatal diagnosis. To date, we are one of the leading laboratory that compared microRNA expression profiles in MPM and normal mesothelium samples in order to identify dysregulated microRNAs with functional roles in mesothelioma. We interrogated a significant collection of MPM tumors and normal pleural samples in our biobank in search for novel therapeutic targets. Methods: Utilizing mRNA-microRNA correlations based on differential gene expression using Gene Set Enrichment Analysis (GSEA), we systematically combined publicly available gene expression datasets with our own MPM data in order to identify candidate targets for MPM therapy. Results: We identified enrichment of target binding sites for the miR-17 and miR-30 families in both MPM tumors and cell lines. RT-qPCR revealed that members of both families were significantly downregulated in MPM tumors and cell lines. Interestingly, lower expression of miR-17-5p (P = 0.022) and miR-20a-5p (P = 0.026) was clearly associated with epithelioid histology. We interrogated the predicted targets of these differentially expressed microRNA families in MPM cell lines, and identified KCa1.1, a calcium-activated potassium channel subunit alpha 1 encoded by the KCNMA1 gene, as a target of miR-17-5p. KCa1.1 was overexpressed in MPM cells compared to the (normal) mesothelial line MeT-5A, and was also upregulated in patient tumor samples compared to normal mesothelium. Transfection of MPM cells with a miR-17-5p mimic or KCNMA1-specific siRNAs reduced mRNA expression of KCa1.1 and inhibited MPM cell migration. Similarly, treatment with paxilline, a small molecule inhibitor of KCa1.1, resulted in suppression of MPM cell migration. Conclusion: These functional data implicating KCa1.1 in MPM cell migration support our integrative approach using MPM gene expression datasets to identify novel and potentially druggable targets
The Physics of a Sextet Quark Sector
Electroweak symmetry breaking may be a consequence of color sextet quark
chiral symmetry breaking. A special solution of QCD is involved, with a
high-energy S-Matrix that can be constructed ``semi-perturbatively'' via the
chiral anomaly and reggeon diagrams. An infra-red fixed point and color
superconductivity are crucial components of the construction. Infinite momentum
physical states contain both quarks and a universal ``anomalous wee gluon''
component, and the spectrum is more limited than is required by confinement and
chiral symmetry breaking. The pomeron is approximately a regge pole and the
Critical Pomeron describes asymptotic cross-sections.
The strong coupling of the pomeron to the electroweak sector could produce
large and events at HERA, and vector boson pairs at Fermilab. Further
evidence for the sextet sector at Fermilab would be a large jet excess,
due in part to the non-evolution of , and other phenomena related
to the possibility that top quark production is due to the .
The sextet proton and neutron are the only new baryonic states. Sextet states
dominate high energy hadronic cross-sections and stable sextet neutrons could
produce both dark matter and ultra high energy cosmic rays. The cosmic ray
spectrum knee suggests the effective sextet threshold is between Fermilab and
LHC energies, with large cross-section effects expected at the LHC. Jet and
vector boson cross-sections will be very much larger than expected, and sextet
baryons should also be produced. Double pomeron produced states could provide
definitive evidence for the existence of the sextet sector in the initial low
luminosity running.Comment: Version to be publishe
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