M-Theory Through the Looking Glass: Tachyon Condensation in the E_8 Heterotic String

We study the spacetime decay to nothing in string theory and M-theory. First we recall a nonsupersymmetric version of heterotic M-theory, in which bubbles of nothing -- connecting the two E_8 boundaries by a throat -- are expected to be nucleated. We argue that the fate of this system should be addressed at weak string coupling, where the nonperturbative instanton instability is expected to turn into a perturbative tachyonic one. We identify the unique string theory that could describe this process: The heterotic model with one E_8 gauge group and a singlet tachyon. We then use worldsheet methods to study the tachyon condensation in the NSR formulation of this model, and show that it induces a worldsheet super-Higgs effect. The main theme of our analysis is the possibility of making meaningful alternative gauge choices for worldsheet supersymmetry, in place of the conventional superconformal gauge. We show in a version of unitary gauge how the worldsheet gravitino assimilates the goldstino and becomes dynamical. This picture clarifies recent results of Hellerman and Swanson. We also present analogs of R_\xi gauges, and note the importance of logarithmic CFT in the context of tachyon condensation.Comment: 36 pages, 1 figur

The Interaction of Goal Orientation and Stage of Change on Exercise Behavior in College Students

The purpose of this study was to develop and examine the reliability and validity of the Perceptions of Success Questionnaire for Exercise (POSQ-E), and to link goal orientations to self-reported physical activity patterns and perceptions. The final sample consisted of 569 recreation center participants who utilized the facility 3.77 days a week (SD = 1.94) and were active for an average of 70.18 minutes (SD = 33.3) per session. Sixty-three percent of respondents (n = 358) self-reported meeting adult guidelines for regular exercise (150 minutes per week). Using a single-item ladder, participants were assigned across the five stages of exercise readiness respectively: precontemplation (6.8%); contemplation (4.9%); preparation (26.2%); action (23.8%); and maintenance (38.3%). Task scores were shown to increase across the stages of change while ego scores decreased slightly. An extreme median split of the goal orientation scores yielded a sub-sample of 235 participants with 76 (32.3%) in the high task/high ego, 49 (20.9%) in the high task/low ego, 47 (20%) in the high ego/low task, and 63 (26.8%) in the low ego/low task group. The POSQ-E was shown to have good internal reliability, factor validity and convergent validity. Convergent validity linking the transtheoretical model and self-reported physical activity behavior with goal orientation theory may provide a new direction for applied research in exercise behavior

Sequence Requirements for the Nuclear Localization of the Murine Cytomegalovirus M44 Gene Product pp50

AbstractThe murine cytomegalovirus (MCMV) M44 gene product pp50 is normally present in the nuclei of virus-infected cells. During transient expression of pp50 in COS-1 cells, the phosphoprotein was readily detectable in the nuclei, indicating that it possesses a nuclear localization signal (NLS). Studies on the subcellular locations of N- and C-terminal deletion mutants of pp50 suggested that alterations in both the C terminus and the highly conserved N-terminal domains of pp50 affect nuclear localization. In particular, the C-terminal 11 amino acids of pp50, which includes a “KKQK” motif, were able to mediate the import of a β-galactosidase fusion protein into the nucleus. The pair of lysine residues in this motif constitutes an essential element of the C-terminal NLS as mutation of this motif to AAQK directly affected the nuclear localization of either pp50 or β-galactosidase fusion proteins containing the C-terminal portion of pp50. Furthermore our results indicated that the functionality of the C-terminal NLS is dependent on the structural integrity of the highly conserved N-terminal portion of the molecule, as deletion of amino acids 157–201 alone adversely affected nuclear localization. In the absence of a functional C-terminal NLS, the subcellular localization of pp50 is sensitive to potential conformational changes induced by mutations within the N-terminal half of the molecule. Under those circumstances, mutation of the YK residues at position 22–23 or deletion of amino acids 267–283 was sufficient to produce a protein that was impaired in nuclear import or retention

β\beta-NMR of Isolated 8^{8}Li+^{+} Implanted into a Thin Copper Film

Depth-controlled $\beta$-NMR was used to study highly spin-polarized $^8$Li in a Cu film of thickness 100 nm deposited onto a MgO substrate. The positive Knight Shifts and spin relaxation data show that $^8$Li occupies two sites at low temperatures, assigned to be the substitutional ($S$) and octahedral ($O$) interstitial sites. Between 50 to 100 K, there is a site change from $O$ to $S$. The temperature dependence of the Knight shifts and spin-lattice relaxation rates at high temperatures, i.e. when all the Li are in the $S$ site, is consistent with the Korringa Law for a simple metal.Comment: Accepted for publication in Phys. Rev.

Impact of enteral protein supplementation in premature infants

David M Barrus1, Joann Romano-Keeler2, Christopher Carr3, Kira Segebarth4, Betty Claxton2, William F Walsh2, Paul J Flakoll51Department of Neonatology, Saint Francis Hospital–Bartlett, Memphis, TN, 2Department of Pediatrics, Vanderbilt Medical Center, Nashville, TN, 3Department of Surgery, Naval Hospital Bremerton, Bremerton, WA, 4Pediatric and Diabetes Specialists, Carolinas Medical Center, Charlotte, NC, 5Department of Surgery, Vanderbilt Medical Center, Nashville, TN, USAObjective: The quantity of enteral protein supplementation required by premature infants to optimize growth has not been determined. This study compares the growth of premature infants fed the current standard intake of protein (3.5 g/kg/day) with the growth of those fed a higher amount (4.0 g/kg/day).Study design: Fifty-two infants <1500 g and <33 weeks gestational age participated in a blinded, single-center, prospective randomized control trial to compare growth between two groups of different protein-intake levels. Primary outcomes were average daily weight gain (g/kg/day), head-circumference (cm/kg/week) and linear growth velocity (cm/kg/week). Secondary outcomes were serum indices of protein tolerance and plasma amino acid concentrations.Results: Infants receiving higher amounts of protein had higher rates of growth for body weight (18.2 ± 0.7 versus 16.2 ± 1.0 g/kg/day; P < 0.05) and head circumference (0.87 ± 0.08 versus 0.62 ± 0.07 cm/kg/week; P < 0.05), with no differences in blood protein or plasma amino acid concentrations. Length of hospital stay was 14 days shorter for the higher-protein group (51.4 ± 4.0 versus 65.9 ± 6.3 days).Conclusion: Increasing premature infant enteral protein supplementation from a calculated intake of 3.5–4.0 g/kg/day improved growth in a safe manner.Keywords: human milk, human milk fortifier, growth, low birth weigh