NonQCD contributions to heavy quark masses and sensitivity to Higgs mass

We find that if the Higgs mass is close to its present experimental lower limit (100 GeV),Yukawa interactions in the quark-Higgs sector can make substantial contributions to the heavy quark MS masses.Comment: 16 pages, 1 figure. Fixed a few typos (eqs (7),(34)

Characterization of swimming motility in a marine unicellular cyanobacterium

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution April 1988The structural mechanism, behavior, energetics and functional significance of the unique swimming motility displayed by some oceanic isolates of the cyanobacterium Synechococcus was investigated. A variety of analytical techniques confirmed that these strains swam through liquids without flagella or flagellar-like appendages. No extracellular structures were observed in a broad range of cell preparations examined by transmission electron microscopy (TEM), or by high-intensity dark field microscopy. The possibility that a structure might be present that eluded visualization was eliminated by the lack of motility-dependent amplitude spectra, the absence of discrete circulation of microspheres around the cell body and the inability of shearing forces to arrest motility. TEM and gel electrophoretic analysis of spheroplasts, cell wall-enriched fractions from motile and nonmotile strains, and cell material collected following the application of a flagellar hook-basal body complex isolation technique to a motile Synechococcus strain provided no further evidence of a structure or protein unique to motile strains. The motile Synechococcus strains represent the only cyanobacterium reported to date capable of swimming rather than gliding motility. Swimming behavior was characterized by several features: between 50 - 80% of cells were actively motile during loyarithmic phase of growth, with speeds that ranged from 5 - 40 um s-1 the average speed was 13 um s-1. Swimming patterns were entirely random, consistent with the absence of bacterial flagella. Synechococcus motility resembled flagellar-mediated motility in that thrust (forward motion) was accompanied by torque (cell rotation) as demonstrated by i) dividing cells which swam with the daughter cells at an angle, ii) individual cells that were sometimes seen to rotate end over end at a rate of 3 to 5 rev s-1, iii) polystyrene beads attached to the cell body served as a point of reference as the cell rotated concomitant with translocation and iv) cells attached to the coverslip or slide spun about one pole at an average rate of 1 rev s-1. When observed in the same plane of focus, 50% of the cells spun clockwise and 50% spun counterclockwise, but unlike flagellated cells, Synechococcus was never seen to change direction of rotation, as would be predicted if the cell body were rotating as a single unit and the motility apparatus were incapable of reversing direction of rotation. This motility apparatus appeared to operate at a constant torque, as indicated by the relationship between swimming speeds and the fluidity of the surrounding medium. Investigation of the energetics of motility in Synechococcus WH8ll3 demonstrated that swimming was sodium coupled. There was a specific sodium requirement such that cells were immotile at external sodium concentrations below 10 mM, with speeds increasing with increasing sodium to a maximum speed at 150 to 250mM sodium, pH 8.0 to 8.5. The sodium motive force increased similarly, but other energetic parameters including proton motive force, electrical potential, and the proton and sodium diffusion gradients lacked correlation to levels of motility. When components of the sodium motive force were diminished by monensin or carbonyl cyanide m-chlorophenyl-hydrazone, motility was arrested. Motility was independent of the magnitude of internal ATP pools, which were depleted to 2% of control values without affecting cell motility. These results suggest that the direct source of energy for Synechococcus motility is a sodium motive force, and that the devise driving motility is located in the cytoplasmic membrane, as is the case for flagellated bacteria. The ecological role of Synechococcus motility was explored and several lines of evidence indicated that cells lacked behavioral photoresponses but were able to detect and respond to very low concentrations of simple nitrogenous compounds. When 23 compounds were tested in spatial gradients established in blind well chemotaxis chambers, cells displayed positive chemoresponses only when placed in gradients of NH4Cl, NaN03, urea, glycine and alanine. Cells also failed to respond in chambers which lacked gradients due to the presence of only seawater or an equal distribution of chemoeffector, demonstrating that a gradient was required to elicit a response. The apparent threshold levels of 10-10 M - 10-9 M for Synechococcus chemoresponses are 4 to 5 orders of magnitude lower than those for most other bacteria and place them in the range of ecological significance. The presence of chemotaxis in this oceanic cyanobacterium may help support the notion that nutrient enriched microaggregates may play an important role in picoplankton nutrient dynamics

Obscurin acts as a variable force resistor

Obscurin (800-900 kDa) is a giant cytoskeletal protein important to muscle cell maintenance and organization. One of its functions is to connect distal regions within the cell. The protein architecture suggests this role; obscurin consists of dozens of individually-folded domains linked together. Given obscurin’s shape and position in the cell, it likely responds to cell motion and stretch by itself stretching and compressing. One outstanding question is how obscurin accomplishes this. Here, we begin to probe the molecular mechanism and outcomes of obscurin stretch resistance. We hypothesize that obscurin could either act like a rope, only resisting stretch when fully extended, or it could act as a spring, resisting stretch regardless of how extended it is. By studying a collection of representative obscurin domains and tandem domains, using nuclear magnetic resonance (NMR) and small angle X-ray diffraction (SAXS) techniques, we gain insight into obscurin’s shape and self-interactions. Using computational techniques, we supplement our wet lab data and gain increased understanding of how obscurin resists external force. Our data suggest that different tandem domains, with unique linker sequences (but not lengths) variably react to stretch. As all of these domains are within one obscurin molecule, these results show obscurin to be a nonuniform force resistor; different regions resist force to different magnitudes

Standard Model stability bounds for new physics within LHC reach

We analyse the stability lower bounds on the Standard Model Higgs mass by carefully controlling the scale independence of the effective potential. We include resummed leading and next-to-leading-log corrections, and physical pole masses for the Higgs boson, M_H, and the top-quark, M_t. Particular attention is devoted to the cases where the scale of new physics \Lambda is within LHC reach, i.e. \Lambda\leq 10 TeV, which have been the object of recent controversial results. We clarify the origin of discrepancies and confirm our earlier results within the error of our previous estimate. In particular for \Lambda=1 TeV we find that M_H[GeV]>52+0.64(M_t[GeV]-175)-0.50\frac{\alpha_s(M_Z)-0.118}{0.006}. For fixed values of M_t and \alpha_s(M_Z), the error from higher effects, as the lack of exact scale invariance of the effective potential and higher-order radiative corrections, is conservatively estimated to be \simlt 5 GeV.Comment: 17 pages, latex + psfig.sty, 4 figure

Soil availability, plant uptake and soil to plant transfer of 99Tc - A review

The fission yield of 99Tc from 239Pu and 235U is similar to that of 137Cs or 90Sr and it is therefore an important component of nuclear weapons fall-out, nuclear waste and releases from nuclear facilities. There is particular current interest in 99Tc transfer from soil to plants for: (a) environmental impact assessments for terrestrial nuclear waste repositories, and (b) assessments of the potential for phytoextraction of radionuclides from contaminated effluent and soil. Vascular plants have a high 99Tc uptake capacity, a strong tendency to transport it to shoot material and accumulate it in vegetative rather than reproductive structures. The mechanisms that control 99Tc entry to plants have not been identified and there has been little discussion of the potential for phytoextraction of 99Tc contaminated effluents or soil. Here we review soil availability, plant uptake mechanisms and soil to plant transfer of 99Tc in the light of recent advances in soil science, plant molecular biology and phytoextraction technologies. We conclude that 99Tc might not be highly available in the long term from up to 50% of soils worldwide, and that no single mechanism that might be easily targeted by recombinant DNA technologies controls 99Tc uptake by plants. Overall, we suggest that Tc might be less available in terrestrial ecosystems than is often assumed but that nevertheless the potential of phytoextraction as a decontamination strategy is probably greater for 99Tc than for any other nuclide of radioecological interest. © 2002 Elsevier Science Ltd. All rights reserved

MCAT Preparation Guide

Competition for admission to American medical schools has always been intense. Now, with more than 40,000 pre-med students applying for the few available slots each year, scoring well on the Medical College Admission Test (MCAT) is more critical than ever. The MCAT Preparation Guide offers students a systematic, sensible way to improve MCAT test scores. It recognizes their need to understand not only the subject areas covered but also the way the MCAT is structured and what test scorers look for. Extensively field tested at the University of Chicago, Tulane University, Howard University, and the University of Kentucky, this Guide has already helped hundreds of students to boost their MCAT scores significantly. With this edition, the Guide becomes available nationwide for the first time. One excellent feature is the chapter on preparing writing samples, a section of the MCAT often omitted or slighted in other guides. Here is a step-by step process for attacking writing sample prompts to produce superior essays. Miriam S. Willey and Barbara M. Jarecky are well-known specialists in teaching exam-taking and study skills to medical students and undergraduates.https://uknowledge.uky.edu/upk_medicine_and_health_sciences/1010/thumbnail.jp

Quality Control Methods for Optimal BCR-ABL1 Clinical Testing in Human Whole Blood Samples

Reliable breakpoint cluster region (BCR)–Abelson (ABL) 1 measurement is essential for optimal management of chronic myelogenous leukemia. There is a need to optimize quality control, sensitivity, and reliability of methods used to measure a major molecular response and/or treatment failure. The effects of room temperature storage time, different primers, and RNA input in the reverse transcription (RT) reaction on BCR-ABL1 and β-glucuronidase (GUSB) cDNA yield were assessed in whole blood samples mixed with K562 cells. BCR-ABL1 was measured relative to GUSB to control for sample loading, and each gene was measured relative to known numbers of respective internal standard molecules to control for variation in quality and quantity of reagents, thermal cycler conditions, and presence of PCR inhibitors. Clinical sample and reference material measurements with this test were concordant with results reported by other laboratories. BCR-ABL1 per 103 GUSB values were significantly reduced (P = 0.004) after 48-hour storage. Gene-specific primers yielded more BCR-ABL1 cDNA than random hexamers at each RNA input. In addition, increasing RNA inhibited the RT reaction with random hexamers but not with gene-specific primers. Consequently, the yield of BCR-ABL1 was higher with gene-specific RT primers at all RNA inputs tested, increasing to as much as 158-fold. We conclude that optimal measurement of BCR-ABL1 per 103 GUSB in whole blood is obtained when gene-specific primers are used in RT and samples are analyzed within 24 hours after blood collection

Linear Self-Motion Cues Support the Spatial Distribution and Stability of Hippocampal Place Cells

The vestibular system provides a crucial component of place-cell and head-direction cell activity [1-7]. Otolith signals are necessary for head-direction signal stability and associated behavior [8, 9], and the head-direction signal's contribution to parahippocampal spatial representations [10-14] suggests that place cells may also require otolithic information. Here, we demonstrate that self-movement information from the otolith organs is necessary for the development of stable place fields within and across sessions. Place cells in otoconia-deficient tilted mice showed reduced spatial coherence and formed place fields that were located closer to environmental boundaries, relative to those of control mice. These differences reveal an important otolithic contribution to place-cell functioning and provide insight into the cognitive deficits associated with otolith dysfunction

Variation in the transfer of radionuclide to freshwater fish: phylogeny or feeding strategy?

For both terrestrial vascular plants and marine organisms if has been demonstrated the differences in radionuclide transfer between species can be related to their evolutionary history or phylogeny. Relationships between phylogeny and radionuclide transfer offer a potential approach to help to derive best estimate values if data for a given species-radionuclide are not available. In this paper we describe the analyses of data for radionuclide transfer to freshwater fish from a data base recently compiled to support activities of both the IAEA and ICRP. There are sufficient data in the database to test the hypothesis that radionuclide transfer can be related to the evolutionary of freshwater fish for caesium, strontium and uranium. For instance, the database contains 750 entries for caesium considering nearly 70 species of fish. Initial results indicate that phylogeny does explain some of the variation in radionuclide transfer between species of fish. However, feeding strategy also explains variation in radionuclide transfer between species. In this paper we will compare our results to establish if phylogeny or feeding strategy is the most useful predictor of radionuclide transfer to freshwater fish