Relaxation of thermo-remanent magnetization in Fe-Cr GMR multilayers

The time decay of the thermo-remanent magnetization (TRM) in Fe-Cr giant magnetoresistive (GMR) multilayers has been investigated. The magnetization in these multilayers relaxes as a function of time after being cooled in a small magnetic field of 100 Oe to a low temperature and then the magnetic field is switched off. Low-field ($<$ 500 Oe) magnetization studies of these samples have shown hysteresis. This spin-glass-like behavior may originate from structural imperfections at the interfaces and in the bulk. We find that the magnetization relaxation is logarithmic. Here the magnetic viscosity is found to increase first with increasing temperature, then it reaches a maximum around T$_g$, and then it decreases with increasing temperature. This behavior is different from that of conventional spin glasses where the logarithmic creep rate is observed to increase with temperature. Power law also gives good fits and it is better than the logarithmic fit at higher temperatures. The dynamical effects of these multilayers are related to the relaxation of thermally blocked superparamagnetic grains and magnetic domains in the film layers.Comment: 19 page

On search for new Higgs physics in CDF at the Tevatron

We discuss the Higgs boson mass sum rules in the Minimal Supersymmetric Standard Model in order to estimate the upper limits on the masses of stop quarks as well as the lower bounds on the masses of the scalar Higgs boson state. The bounds on the scale of quark-lepton compositeness derived from the CDF Collaboration (Fermilab Tevatron) data and applied to new extra gauge boson search is taken into account. These extra gauge bosons are considered in the framework of the extended SU(2)_h \times SU(2)_l model. In addition, we discuss the physics of rare decays of the MSSM Higgs bosons in both CP-even and CP-odd sectors and also some extra gauge bosons.Comment: 24 pages, LaTeX, 8 figure

The Ricci flow on noncommutative two-tori

In this paper we construct a version of Ricci flow for noncommutative 2-tori, based on a spectral formulation in terms of the eigenvalues and eigenfunction of the Laplacian and recent results on the Gauss-Bonnet theorem for noncommutative tori.Comment: 18 pages, LaTe

Thermally assisted magnetization reversal in the presence of a spin-transfer torque

We propose a generalized stochastic Landau-Lifshitz equation and its corresponding Fokker-Planck equation for the magnetization dynamics in the presence of spin transfer torques. Since the spin transfer torque can pump a magnetic energy into the magnetic system, the equilibrium temperature of the magnetic system is ill-defined. We introduce an effective temperature based on a stationary solution of the Fokker-Planck equation. In the limit of high energy barriers, the law of thermal agitation is derived. We find that the N\'{e}el-Brown relaxation formula remains valid as long as we replace the temperature by an effective one that is linearly dependent of the spin torque. We carry out the numerical integration of the stochastic Landau-Lifshitz equation to support our theory. Our results agree with existing experimental data.Comment: 5 figure

Towards a global analysis of polarized parton distributions

We present a technique for implementing in a fast way, and without any approximations, higher-order calculations of partonic cross sections into global analyses of parton distribution functions. The approach, which is set up in Mellin-moment space, is particularly suited for analyses of future data from polarized proton-proton collisions, but not limited to this case. The usefulness and practicability of this method is demonstrated for the semi-inclusive production of hadrons in deep-inelastic scattering and the transverse momentum distribution of ``prompt'' photons in pp collisions, and a case study for a future global analysis of polarized parton densities is presented.Comment: 20 pages, LaTeX, 6 eps figures, final version to appear in PRD (minor changes

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

Restenosis, reocclusion and adverse cardiovascular events after successful balloon angioplasty of occluded versus nonoccluded coronary arteries: Results from the multicenter american research trial with cilazapril after angioplasty to prevent transluminal coronary obstruction and restenosis (MARCATOR)

OBJECTIVES: This study sought to compare the frequency of restenosis, reocclusion and adverse cardiovascular events after angioplasty of occluded versus nonoccluded coronary arteries. BACKGROUND: Angioplasty of chronically occluded coronary arteries is believed to be associated with a higher frequency of restenosis and reocclusion than angioplasty of subtotal stenoses. Whether this leads to adverse cardiovascular events is unknown. METHODS: The Multicenter American Research Trial With Cilazapril After Angioplasty to Prevent Restenosis (MARCATOR) was a placebo-controlled trial with angiographic follow-up to determine the effect of the angiotensin-converting enzyme inhibitor cilazapril on the frequency of restenosis. In this trial, restenosis was defined as 1) angiographic reduction of minimal lumen diameter > or = 0.72 mm between angioplasty and the follow-up visit; and 2) > 50% diameter stenosis on the follow-up angiogram. We identified

Equivalence Theorem and Probing the Electroweak Symmetry Breaking Sector

We examine the Lorentz non-invariance ambiguity in longitudinal weak-boson scatterings and the precise conditions for the validity of the Equivalence Theorem (ET). {\it Safe} Lorentz frames for applying the ET are defined, and the intrinsic connection between the longitudinal weak-boson scatterings and probing the symmetry breaking sector is analyzed. A universal precise formulation of the ET is presented for both the Standard Model and the Chiral Lagrangian formulated Electro-Weak Theories. It is shown that in electroweak theories with strongly interacting symmetry breaking sector, the longitudinal weak-boson scattering amplitude {\it under proper conditions} can be replaced by the corresponding Goldstone-boson scattering amplitude in which all the internal weak-boson lines and fermion loops are ignored.Comment: 20 pages, in LaTeX, to appear in Phys. Rev. D (1995). A few minor corrections were made to clarify our viewpoint of the Equivalence Theorem and compare our conclusion with those in the literatur

Running into New Territory in SUSY Parameter Space

The LEP-II bound on the light Higgs mass rules out the vast majority of parameter space left to the Minimal Supersymmetric Standard Model (MSSM) with weak-scale soft-masses. This suggests the importance of exploring extensions of the MSSM with non-minimal Higgs physics. In this article, we explore a theory with an additional singlet superfield and an extended gauge sector. The theory has a number of novel features compared to both the MSSM and Next-to-MSSM, including easily realizing a light CP-even Higgs mass consistent with LEP-II limits, tan(beta) < 1, and a lightest Higgs which is charged. These features are achieved while remaining consistent with perturbative unification and without large stop-masses. Discovery modes at the Tevatron and LHC are discussed.Comment: 15 pages, 5 figures; Typo in equation (4.5) corrected; submitted to JHE