1,150 research outputs found
Supersymmetric effects in top quark decay into polarized W-boson
We investigate the one-loop supersymmetric QCD (SUSY-QCD) and electroweak
(SUSY-EW) corrections to the top quark decay into a b-quark and a longitudinal
or transverse W-boson. The corrections are presented in terms of the
longitudinal ratio \Gamma(t-->W_L b)/\Gamma(t--> W b) and the transverse ratio
\Gamma(t-->W_- b)/\Gamma(t--> W b). In most of the parameter space, both
SUSY-QCD and SUSY-EW corrections to these ratios are found to be less than 1%
in magnitude and they tend to have opposite signs. The corrections to the total
width \Gamma(t-->W b) are also presented for comparison with the existing
results in the literature. We find that our SUSY-EW corrections to the total
width differ significantly from previous studies: the previous studies give a
large correction of more than 10% in magnitude for a large part of the
parameter space while our results reach only few percent at most.Comment: Version in PRD (explanation and refs added
Helicity Analysis of Semileptonic Hyperon Decays Including Lepton Mass Effects
Using the helicity method we derive complete formulas for the joint angular
decay distributions occurring in semileptonic hyperon decays including lepton
mass and polarization effects. Compared to the traditional covariant
calculation the helicity method allows one to organize the calculation of the
angular decay distributions in a very compact and efficient way. In the
helicity method the angular analysis is of cascade type, i.e. each decay in the
decay chain is analyzed in the respective rest system of that particle. Such an
approach is ideally suited as input for a Monte Carlo event generation program.
As a specific example we take the decay () followed by the nonleptonic decay for which we show a few examples of decay distributions which are
generated from a Monte Carlo program based on the formulas presented in this
paper. All the results of this paper are also applicable to the semileptonic
and nonleptonic decays of ground state charm and bottom baryons, and to the
decays of the top quark.Comment: Published version. 40 pages, 11 figures included in the text. Typos
corrected, comments added, references added and update
Protecting the primordial baryon asymmetry in the seesaw model compatible with WMAP and KamLAND
We require that the primordial baryon asymmetry is not washed out in the
seesaw model compatible with the recent results of WMAP and the neutrino
oscillation experiments including the first results of KamLAND. We find that
only the case of the normal neutrino mass hierarchy with an approximate
-symmetry satisfies the requirement. We further derive, depending on the
signs of neutrino mass eigenvalues, three types of neutrino mass matrixes,
where the values of each element are rather precisely fixed.Comment: 21pages; added reference
An action for the exact string black hole
A local action is constructed describing the exact string black hole
discovered by Dijkgraaf, Verlinde and Verlinde in 1992. It turns out to be a
special 2D Maxwell-dilaton gravity theory, linear in curvature and field
strength. Two constants of motion exist: mass M>1, determined by the level k,
and U(1)-charge Q>0, determined by the value of the dilaton at the origin. ADM
mass, Hawking temperature T_H \propto \sqrt{1-1/M} and Bekenstein-Hawking
entropy are derived and studied in detail. Winding/momentum mode duality
implies the existence of a similar action, arising from a branch ambiguity,
which describes the exact string naked singularity. In the strong coupling
limit the solution dual to AdS_2 is found to be the 5D Schwarzschild black
hole. Some applications to black hole thermodynamics and 2D string theory are
discussed and generalizations - supersymmetric extension, coupling to matter
and critical collapse, quantization - are pointed out.Comment: 41 pages, 2 eps figures, dedicated to Wolfgang Kummer on occasion of
his Emeritierung; v2: added ref; v3: extended discussion in sections 3.2, 3.3
and at the end of 5.3 by adding 2 pages of clarifying text; updated refs;
corrected typo
Improved detection by next-generation sequencing of pyrazinamide resistance in mycobacterium tuberculosis isolates
Technical limitations of common tests used for detecting pyrazinamide (PZA) resistance in
Mycobacterium tuberculosis (MTB) isolates pose challenges for comprehensive and accurate
descriptions of drug resistance in patients with multi-drug resistant tuberculosis (MDR-TB) . In
this study, a 606 base pair fragment (comprising the pncA coding region plus promoter) was
sequenced using Ion Torrent next generation sequencing (NGS) for detecting associated PZA
resistance mutations in 90 re-cultured, MDR-TB isolates from an archived series collected in
2001. These 90 isolates were previously Sanger sequenced, with 55 (62%) designated as carrying
wild type pncA gene and 33 (38%) showing mutations. Also earlier, PZA susceptibility of the isolates was determined using the Bactec 460 TB system and the Wayne test. In this study,
isolates were re-cultured and susceptibility testing performed in Bactec 960 MGIT. Concordance
between NGS and MGIT results was 87% (n = 90), and with the Bactec 460, Wayne test, and
pncA gene Sanger sequencing, 82% (n = 88), 83% (n = 88), and 89% (n = 88), respectively.
NGS confirmed the majority of pncA mutations detected by Sanger sequencing, but revealed
several new and mixed-strain mutations that resolved discordancy in other phenotypic results.
Importantly, in 53% (18/34) of these isolates, pncA mutations were located in the 151-360
region, and warrants further exploration. In these isolates, with known resistance to rifampicin,
NGS of pncA improved PZA resistance detection sensitivity to 97% and specificity to 94% using
NGS as the gold standard, and helped to resolve discordant results from conventional
methodologies.University of Pretoria, the South African Medical Research Council, and the National Research Foundation of South Africa.http://jcm.asm.org2016-06-30hb201
TEM-EELS study of low-friction superlattice TiAlN/VN coating: the wear mechanisms
A 20-50 nm thick tribofilm was generated on the worn surface of a multilayer coating TiAlN/VN after dry sliding test against an alumina counterpart. The tribofilm was characterized by applying analytical transmission electron microscopy techniques with emphasis on detailed electron energy loss spectrometry and energy loss near edge structure analysis. Pronounced oxygen in the tribofilm indicated a predominant tribo-oxidation wear. Structural changes in the inner-shell ionization edges of N, Ti and V suggested decomposition of nitride fragments
Molecular detection of Mycobacterium tuberculosis from sputum transported in PrimeStore(®) from rural settings
SETTING : Mopani District, South Africa.
OBJECTIVE : To explore remote, molecular detection of
Mycobacterium tuberculosis from sputum transported
using PrimeStorew Molecular Transport Medium (PSMTM)
compared to settings where microscopy or
Xpertw MTB/RIF is used as the baseline test.
DESIGN : Two sputum specimens were collected from
patients with cough of72 weeks at clinics in rural South
Africa. Shortly after expectoration and before processing
using Xpert, microscopy and liquid culture, a flocked
swab was swirled in each of these specimens and placed
in PS-MTM. Swabs were stored and transported to the
United States at ambient temperature for real-time
PrimeMixw polymerase chain reaction (PM-PCR).
RESULTS : Of 132 patients, 23 (17%) were positive on
microscopy, 39 (30%) on Xpert and 44 (33%) by PSMTM/PSMTM/
PM-PCR. Concordance of PS-MTM/PM-PCR
with positive microscopy and Xpert was respectively
96% and 85%. Of 107 microscopy-negative samples, 22
(21%) were positive using PS-MTM/PM-PCR, while
11/91 (12%) Xpert-negative samples were PS-MTM/
PM-PCR-positive. PS-MTM/PM-PCR positivity was
significantly higher than smear microscopy positivity
(P , 0.001), but similar to Xpert (P ¼ 0.33).
CONCLUSION: PCR testing of specimens transported in
PS-MTM would enhance TB diagnosis in settings where
smear microscopy is the baseline diagnostic test, and
could provide an alternative in settings where Xpert
testing is not available.http://www.ingentaconnect.comcontent/iuatld/ijtld2015-11-30hb201
Multi- and extensively drug resistant mycobacterium tuberculosis in South Africa : a molecular analysis of historical isolates
Modern advances in genomics provide an opportunity to reinterpret historical bacterial culture collections. In this study, genotypic antibiotic resistance profiles of Mycobacterium tuberculosis isolates from a historical 20-year-old multidrug-resistant tuberculosis (MDR-TB) culture collection in South Africa are described. DNA samples extracted from the phenotypically MDR-TB isolates (n = 240) were assayed by Hain line probe assay (LPA) for the confirmation of MDR-TB and by Illumina Miseq whole-genome sequencing (WGS) for the characterization of mutations in eight genes (rpoB, katG, inhA, rpsL, pncA, embB, gyrA, and rrs) that are known to code for resistance to commonly used anti-TB agents. LPA identified 71.3% of the TB isolates as MDR-TB, 18.3% as rifampin (RIF) monoresistant, 2% as isoniazid (INH) monoresistant, and 8.3% as susceptible to both RIF and INH (RIF+INH). In a subset of 42 randomly selected isolates designated as RIF+INH resistant by Löwenstein-Jensen (LJ) culture in 1993, LPA and WGS results confirmed MDR-TB. In all five INH-monoresistant isolates by LPA and in all but one (the wild type) of the 34 successfully sequenced RIF-monoresistant isolates, WGS revealed matching mutations. Only 26% of isolates designated as susceptible by LPA, however, were found to be wild type by WGS. Novel mutations were found in the rpoB (Thr480Ala, Gln253Arg, Val249Met, Val251Tyr, Val251Phe), katG (Trp477STOP, Gln88STOP, Trp198STOP, Trp412STOP), embB (Thr11Xaa, Gln59Pro), and pncA (Thr100Ile, Thr159Ala, Ala134Arg, Val163Ala, Thr153Ile, DelGpos7, Phe106Ser) genes. Three MDR-TB isolates showed mutations in both the gyrA and rrs genes, suggesting that extensively drug-resistant tuberculosis existed in South Africa well before its formal recognition in 2006.The Global Infectious Diseases Research Training Fogarty Fellowship, the University of Pretoria; the South African Medical Research Council and the National Research Foundation of South Africa.http://jcm.asm.org2018-10-31hj2018Medical Microbiolog
Effects of handling and short-term captivity: a multi-behaviour approach using red sea urchins, Mesocentrotus franciscanus
Understanding the effects of captivity-induced stress on wild-caught animals after their release back into the wild is critical for the long-term success of relocation and reintroduction programs. To date, most of the research on captivity stress has focused on vertebrates, with far less attention paid to invertebrates. Here, we examine the effect of short-term captivity (i.e., up to four days) on self-righting, aggregation, and predator-escape behaviours in wild-caught red sea urchins, Mesocentrotus franciscanus, after their release back into the wild. Aggregation behaviour, which has been linked to feeding in sea urchins, was not affected by handling or captivity. In contrast, the sea urchins that had been handled and released immediately, as well as those that were handled and held captive, took longer to right themselves and were poorer at fleeing from predators than wild, unhandled sea urchins. These results indicate that handling rather than captivity impaired these behaviours in the short term. The duration of captivity did not influence the sea urchin behaviours examined. Longer-term monitoring is needed to establish what the fitness consequences of these short-term behavioural changes might be. Our study nevertheless highlights the importance of considering a suite of responses when examining the effects of capture and captivity. Our findings, which are based on a locally abundant species, can inform translocation efforts aimed at bolstering populations of ecologically similar but depleted invertebrate species to retain or restore important ecosystem functions
TIGIT blockade repolarizes AML-associated TIGIT(+) M2 macrophages to an M1 phenotype and increases CD47-mediated phagocytosis
BACKGROUND: Leukemia-associated macrophages (LAMs) represent an important cell population within the tumor microenvironment, but little is known about the phenotype, function, and plasticity of these cells. The present study provides an extensive characterization of macrophages in patients with acute myeloid leukemia (AML). METHODS: The phenotype and expression of coregulatory markers were assessed on bone marrow (BM)-derived LAM populations, using multiparametric flow cytometry. BM and blood aspirates were obtained from patients with newly diagnosed acute myeloid leukemia (pAML, n=59), patients in long-term remission (lrAML, n=8), patients with relapsed acute myeloid leukemia (rAML, n=7) and monocyte-derived macrophages of the blood from healthy donors (HD, n=17). LAM subpopulations were correlated with clinical parameters. Using a blocking anti-T-cell immunoreceptor with Ig and ITIM domains (TIGIT) antibody or mouse IgG2a isotype control, we investigated polarization, secretion of cytokines, and phagocytosis on LAMs and healthy monocyte-derived macrophages in vitro. RESULTS: In pAML and rAML, M1 LAMs were reduced and the predominant macrophage population consisted of immunosuppressive M2 LAMs defined by expression of CD163, CD204, CD206, and CD86. M2 LAMs in active AML highly expressed inhibitory receptors such as TIGIT, T-cell immunoglobulin and mucin-domain containing-3 protein (TIM-3), and lymphocyte-activation gene 3 (LAG-3). High expression of CD163 was associated with a poor overall survival (OS). In addition, increased frequencies of TIGIT(+) M2 LAMs were associated with an intermediate or adverse risk according to the European Leukemia Network criteria and the FLT3 ITD mutation. In vitro blockade of TIGIT shifted the polarization of primary LAMs or peripheral blood-derived M2 macrophages toward the M1 phenotype and increased secretion of M1-associated cytokines and chemokines. Moreover, the blockade of TIGIT augmented the anti-CD47-mediated phagocytosis of AML cell lines and primary AML cells. CONCLUSION: Our findings suggest that immunosuppressive TIGIT(+) M2 LAMs can be redirected into an efficient effector population that may be of direct clinical relevance in the near future
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