854 research outputs found
Bayesian approach and Naturalness in MSSM analyses for the LHC
The start of LHC has motivated an effort to determine the relative
probability of the different regions of the MSSM parameter space, taking into
account the present, theoretical and experimental, wisdom about the model.
Since the present experimental data are not powerful enough to select a small
region of the MSSM parameter space, the choice of a judicious prior probability
for the parameters becomes most relevant. Previous studies have proposed
theoretical priors that incorporate some (conventional) measure of the
fine-tuning, to penalize unnatural possibilities. However, we show that such
penalization arises from the Bayesian analysis itself (with no ad hoc
assumptions), upon the marginalization of the mu-parameter. Furthermore the
resulting effective prior contains precisely the Barbieri-Giudice measure,
which is very satisfactory. On the other hand we carry on a rigorous treatment
of the Yukawa couplings, showing in particular that the usual practice of
taking the Yukawas "as required", approximately corresponds to taking
logarithmically flat priors in the Yukawa couplings. Finally, we use an
efficient set of variables to scan the MSSM parameter space, trading in
particular B by tan beta, giving the effective prior in the new parameters.
Beside the numerical results, we give accurate analytic expressions for the
effective priors in all cases. Whatever experimental information one may use in
the future, it is to be weighted by the Bayesian factors worked out here.Comment: LaTeX, 19 pages, 3 figure
Mitochondria do not play a major role in landomycin E-induced ROS burst and circumvention of multiple drug resistance in HL-60 leukemia cells
Aim. To study the molecular mechanisms of reactive oxygen species (ROS) involvement in circumventing the cancer drug resistance by novel angucycline antibiotic landomycin E in HL-60 human leukemia cells and its drug-resistant sublines HL-60/adr and HL-60/vinc. Methods. MTT assay, trypan blue exclusion test, DCFDA and JC-1 staining of cells. Results. Landomycin E (LE) leads to a massive hydrogen peroxide production in HL-60 cell line already 1h after the drug addition to the cell culture, while depolarization of mitochondria is observed only at 6–12h, which indicates on the extra-mitochondrial ROS production by LE. The drug-resistant cells of HL-60/vinc (P-gp+) despite 100-fold resistance to doxorubicin (Dx) action, demonstrated no difference in the resistance to LE compared to the parental cell line, while HL-60/adr line (MRP-1+), which was found to be 200-fold resistant to Dx action, had shown a weak (2-fold) decrease in sensitivity to LE. Circumvention of drug resistance by LE in HL-60/adr cells was accompanied by a 2-fold higher level of H2O2 compared to the wild-type cells, but the mitochondrial respiratory chain inhibitors had no impact on this phenomenon. Conclusions. LE-induced cell death is accompanied by massive hydrogen peroxide production, consisting of two peaks – major one at 1h and secondary at 12h after drug treatment. The highest ROS production was observed in HL-60/adr cells, which have shown a 2-fold increase of resistance to LE compared to parental cells. However, mitochondria seem to play secondary role in this process, due to the fact that the use of specific inhibitors of mitochondrial respiratory chain did not affect the early ROS burst, induced by LE in tumor cells.Мета. Молекулярні механізми участі активних форм кисню (АФК) в доланні множинної лікарської стійкості злоякісних клітин новим ангуцикліновим антибіотиком ландоміцином E в лейкозних клітинах людини лінії HL-60 і її сублініях HL-60/adr і HL-60/vinc, резистетних до хіміотерапії. Методи. МТТ тест, тест на життєздатність клітин з трипановим синім, фарбування клітин флуоресцентними барвниками DCFDA і JC-1. Результати. Ландоміцин Е (ЛЕ) призводить до значного зростання продукції пероксиду водню в клітинах лінії HL-60 вже на 1 год після додавання препарату до культури клітин, в той час як деполяризация мітохондрій спостерігаються тільки на 6-12 год, що вказує на позамітохондріальне джерело АФК за дії цього антибіотика. Клітини лінії HL-60/vinc (P-глікопротеїн +), незважаючи на 100-кратне зростання стійкості до доксорубіцину (Dx), продемонстрували ідентичну чутливість до ЛЕ в порівнянні з вихідною клітинною лінією, в той час як клітини лінії HL-60/adr (MRP- 1+), які проявляли 200-кратне зростання стійкості до дії Dx, показали слабке (в 2 рази) зниження чутливості до ЛЕ. Долання стійкості до ліків ландоміцином Е у клітинах лінії HL-60/adr супроводжувалося 2-кратним зростанням рівня Н2О2 в порівнянні з клітинами дикого типу, але мітохондріальні інгібітори дихального ланцюга не проявляли ніякого впливу на це явище. Висновки. ЛЕ-індукована загибель пухлинних клітин супроводжується масовим виробництвом перекису водню, що складається з двох піків – основного (1 год) і вторинного (на 12 год дії препарату). Найвища продукція АФК спостерігалася в клітинах лінії HL-60/adr, які показали 2-кратне збільшення стійкості до ЛЕ в порівнянні з вихідною лінією HL-60. Мітохондрії, очевидно, відіграють вторинну роль в цьому процесі, оскільки використання специфічних інгібіторів дихального ланцюга мітохондрій ніяк не вплинуло на ранню індукцію АФК за дії ЛЕ в пухлинних клітинах.Цель. Молекулярные механизмы участия активных форм кислорода (АФК) в преодолении множественной лекарственной устойчивости злокачественных клеток новым ангуциклиновым антибиотиком ландомицином E в лейкозных клетках человека линии HL-60 и ее сублиниях HL-60/adr и HL-60/vinc, резистентных к химиотерапии. Методы. МТТ тест, тест на жизнеспособность клеток с трипановым синим, окраска клеток флуоресцентными красителями DCFDA и JC-1. Результаты. Ландомицин Е (ЛЕ) приводит к значительному росту продукции пероксида водорода в клетках линии HL-60 уже на 1 ч после добавления препарата к культуре клеток, в то время как деполяризация митохондрий наблюдаются только на 6–12 ч, что указывает на внемитохондриальный источник АФК происхождения при действии этого антибиотика. Клетки линии HL-60 vinc (P-гликопротеин+), несмотря на 100-кратный рост устойчивости к доксорубицину (Dx), продемонстрировали идентичную чувствительность к ЛЕ по сравнению с исходной клеточной линией, в то время как клетки линии HL-60/adr (MRP-1+), которые проявляли 200-кратный рост устойчивости к действию Dx, показали слабое (в 2 раза) снижение чувствительности к ЛЕ. Преодоление устойчивости к лекарствам ландомицином Е в клетках линии HL-60/adr сопровождалось 2-кратным ростом уровня Н2О2 по сравнению с клетками дикого типа, но митохондриальные ингибиторы дыхательной цепи не проявляли никакого влияния на это явление. Выводы. ЛЕ-индуцированная гибель опухолевых клеток сопровождается массовым производством перекиси водорода, состоящей из двух пиков – основного (1 час) и вторичного (на 12 ч действия препарата). Самая высокая продукция АФК наблюдалась в клетках линии HL-60/adr, которые показали 2-кратное увеличение устойчивости к ЛЕ по сравнению с исходной линией HL-60. Митохондрии, очевидно, играют вторичную роль в этом процессе, поскольку использование специфических ингибиторов митохондриальной дыхательной цепи никак не повлияло на раннюю индукцию АФК при действии ЛЕ на опухолевые клетки
Strengthening Altitude Knowledge: A Delphi Study to Define Minimum Knowledge of Altitude Illness for Laypersons Traveling to High Altitude.
Berendsen, Remco R., Peter Bärtsch, Buddha Basnyat, Marc Moritz Berger, Peter Hackett, Andrew M. Luks, Jean-Paul Richalet, Ken Zafren, Bengt Kayser, and the STAK Plenary Group. Strengthening altitude knowledge: a Delphi study to define minimum knowledge of altitude illness for laypersons traveling to high altitude. High Alt Med Biol. 00:000-000, 2022. Introduction: A lack of knowledge among laypersons about the hazards of high-altitude exposure contributes to morbidity and mortality from acute mountain sickness (AMS), high-altitude cerebral edema (HACE), and high-altitude pulmonary edema (HAPE) among high-altitude travelers. There are guidelines regarding the recognition, prevention, and treatment of acute-altitude illness for experts, but essential knowledge for laypersons traveling to high altitudes has not been defined. We sought expert consensus on the essential knowledge required for people planning to travel to high altitudes. Methods: The Delphi method was used. The panel consisted of two moderators, a core expert group and a plenary expert group. The moderators made a preliminary list of statements defining the desired minimum knowledge for laypersons traveling to high altitudes, based on the relevant literature. These preliminary statements were then reviewed, supplemented, and modified by a core expert group. A list of 33 statements was then presented to a plenary group of experts in successive rounds. Results: It took three rounds to reach a consensus. Of the 10 core experts invited, 7 completed all the rounds. Of the 76 plenary experts, 41 (54%) participated in Round 1, and of these 41 a total of 32 (78%) experts completed all three rounds. The final list contained 28 statements in 5 categories (altitude physiology, sleeping at altitude, AMS, HACE, and HAPE). This list represents an expert consensus on the desired minimum knowledge for laypersons planning high-altitude travel. Conclusion: Using the Delphi method, the STrengthening Altitude Knowledge initiative yielded a set of 28 statements representing essential learning objectives for laypersons who plan to travel to high altitudes. This list could be used to develop educational interventions
Statefinder Parameter for Varying G in Three Fluid System
In this work, we have considered variable G in flat FRW universe filled with
the mixture of dark energy, dark matter and radiation. If there is no
interaction between the three fluids, the deceleration parameter and
statefinder parameters have been calculated in terms of dimensionless density
parameters which can be fixed by observational data. Also the interaction
between three fluids has been analyzed due to constant . The statefinder
parameters also calculated in two cases: pressure is constant and pressure is
variable.Comment: 5 pages, Accepted for publication in "Astrophysics and Space Science
Heart of Darkness: The Significance of the Zeptobarn Scale for Neutralino Direct Detection
The direct detection of dark matter through its elastic scattering off
nucleons is among the most promising methods for establishing the particle
identity of dark matter. The current bound on the spin-independent scattering
cross section is sigma^SI < 10 zb for dark matter masses m_chi ~ 100 GeV, with
improved sensitivities expected soon. We examine the implications of this
progress for neutralino dark matter. We work in a supersymmetric framework
well-suited to dark matter studies that is simple and transparent, with models
defined in terms of four weak-scale parameters. We first show that robust
constraints on electric dipole moments motivate large sfermion masses mtilde >
1 TeV, effectively decoupling squarks and sleptons from neutralino dark matter
phenomenology. In this case, we find characteristic cross sections in the
narrow range 1 zb 70 GeV. As sfermion masses are
lowered to near their experimental limit mtilde ~ 400 GeV, the upper and lower
limits of this range are extended, but only by factors of around two, and the
lower limit is not significantly altered by relaxing many particle physics
assumptions, varying the strange quark content of the nucleon, including the
effects of galactic small-scale structure, or assuming other components of dark
matter. Experiments are therefore rapidly entering the heart of dark
matter-favored supersymmetry parameter space. If no signal is seen,
supersymmetric models must contain some level of fine-tuning, and we identify
and analyze several possibilities. Barring large cancellations, however, in a
large and generic class of models, if thermal relic neutralinos are a
significant component of dark matter, experiments will discover them as they
probe down to the zeptobarn scale.Comment: 35 pages, 11 figures; v2: references added, figures extended to 2 TeV
neutralino masses, XENON100 results included, published versio
Constraining the MSSM with universal gaugino masses and implication for searches at the LHC
Using a Markov chain Monte Carlo approach, we find the allowed parameter
space of a MSSM model with seven free parameters. In this model universality
conditions at the GUT scale are imposed on the gaugino sector. We require in
particular that the relic density of dark matter saturates the value extracted
from cosmological measurements assuming a standard cosmological scenario. We
characterize the parameter space of the model that satisfies experimental
constraints and illustrate the complementarity of the LHC searches, B-physics
observables and direct dark matter searches for further probing the parameter
space of the model. We also explore the different decay chains expected for the
coloured particles that would be produced at LHC.Comment: 29 pages, 11 figure
Interacting Generalised Cosmic Chaplygin gas in Loop quantum cosmology: A singularity free universe
In this work we investigate the background dynamics when dark energy is
coupled to dark matter with a suitable interaction in the universe described by
Loop quantum cosmology. Dark energy in the form of Generalised Cosmic Chaplygin
gas is considered. A suitable interaction between dark energy and dark matter
is taken into account in order to at least alleviate (if not solve) the cosmic
coincidence problem. The dynamical system of equations is solved numerically
and a stable scaling solution is obtained. A significant attempt towards the
solution of the cosmic coincidence problem is taken. The statefinder parameters
are also calculated to classify the dark energy model. Graphs and phase
diagrams are drawn to study the variations of these parameters. It is seen that
the background dynamics of Generalised Cosmic Chaplygin gas is completely
consistent with the notion of an accelerated expansion in the late universe.
From the graphs, generalised cosmic Chaplygin gas is identified as a dark fluid
with a lesser negative pressure compared to Modified Chaplygin gas, thus
supporting a 'No Big Rip' cosmology. It has also been shown that in this model
the universe follows the power law form of expansion around the critical point,
which is consistent with the known results. Future singularities that may be
formed in this model as an ultimate fate of the universe has been studied in
detail. It was found that the model is completely free from any types of future
singularities.Comment: 10 pages, 10 figures. arXiv admin note: text overlap with
arXiv:1109.1481, arXiv:1102.275
Supersymmetry Without Prejudice
We begin an exploration of the physics associated with the general
CP-conserving MSSM with Minimal Flavor Violation, the pMSSM. The 19 soft SUSY
breaking parameters in this scenario are chosen so as to satisfy all existing
experimental and theoretical constraints assuming that the WIMP is a
conventional thermal relic, ie, the lightest neutralino. We scan this parameter
space twice using both flat and log priors for the soft SUSY breaking mass
parameters and compare the results which yield similar conclusions. Detailed
constraints from both LEP and the Tevatron searches play a particularly
important role in obtaining our final model samples. We find that the pMSSM
leads to a much broader set of predictions for the properties of the SUSY
partners as well as for a number of experimental observables than those found
in any of the conventional SUSY breaking scenarios such as mSUGRA. This set of
models can easily lead to atypical expectations for SUSY signals at the LHC.Comment: 61 pages, 24 figs. Refs., figs, and text added, typos fixed; This
version has reduced/bitmapped figs. For a version with better figs please go
to http://www.slac.stanford.edu/~rizz
Persistent Spin Currents in Helimagnets
We demonstrate that weak external magnetic fields generate dissipationless
spin currents in the ground state of systems with spiral magnetic order. Our
conclusions are based on phenomenological considerations and on microscopic
mean-field theory calculations for an illustrative toy model. We speculate on
possible applications of this effect in spintronic devices.Comment: 9 pages, 6 figures, updated version as published, Journal referenc
Superdeformed rotational bands in the Mercury region; A Cranked Skyrme-Hartree-Fock-Bogoliubov study
A study of rotational properties of the ground superdeformed bands in \Hg{0},
\Hg{2}, \Hg{4}, and \Pb{4} is presented. We use the cranked
Hartree-Fock-Bogoliubov method with the {\skm} parametrization of the Skyrme
force in the particle-hole channel and a seniority interaction in the pairing
channel. An approximate particle number projection is performed by means of the
Lipkin-Nogami prescription. We analyze the proton and neutron quasiparticle
routhians in connection with the present information on about thirty presently
observed superdeformed bands in nuclei close neighbours of \Hg{2}.Comment: 26 LaTeX pages, 14 uuencoded postscript figures included, Preprint
IPN-TH 93-6
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