1,350 research outputs found
Planar diagrams in light-cone gauge
We consider the open string vacuum amplitude determining the interaction
between a stack of N D3-branes and a single probe brane. When using light cone
gauge, it is clear that the sum of planar diagrams (relevant in the large-N
limit) is described by the free propagation of a closed string. A naive
calculation suggests that the Hamiltonian of the closed string is of the form H
= H0 - (g_s N) P. The same form of the Hamiltonian follows from considering the
bosonic part of the closed string action propagating in the full D3-brane
background suggesting the naive calculation captures the correct information.
Further, we compute explicitly P from the open string side in the bosonic
sector and show that, in a certain limit, the result agrees with the closed
string expectations up to extra terms due to the fact that we ignored the
fermionic sector. We briefly discuss extensions of the results to the
superstring and to the sum of planar diagrams in field theory. In particular we
argue that the calculations seem valid whenever one can define a sigma tau
dual Hamiltonian in the world-sheet which in principle does not require the
existence of a string action. This seems more generic than the existence of a
string dual in the large-N limit.Comment: 42 pages, 7 figures, LaTeX. v2: references added. v3: typos and minor
corrections. Small change of conventions in fermionic secto
Moments of the Virtual Photon Structure Function
The photon structure function is a useful testing ground for QCD. It is
perturbatively computable apart from a contribution from what is usually called
the hadronic component of the photon. There have been many proposals for this
nonperturbative part of the real photon structure function. By studying moments
of the virtual photon structure function, we explore the extent to which these
proposed nonperturbative contributions can be identified experimentally.Comment: LaTeX, 16 pages + 14 compressed and uuencoded postscript figures,
UMN-TH-1111/9
Truthmakers and modality
This paper attempts to locate, within an actualist ontology, truthmakers for modal truths: truths of the form or . In section 1 I motivate the demand for substantial truthmakers for modal truths. In section 2 I criticise Armstrongâs account of truthmakers for modal truths. In section 3 I examine essentialism and defend an account of what makes essentialist attributions true, but I argue that this does not solve the problem of modal truth in general. In section 4 I discuss, and dismiss, a theistic account of the source of modal truth proposed by Alexander Pruss. In section 5 I offer a means of (dis)solving the problem
Diet quality in a weight gain prevention trial of reproductive aged women: a secondary analysis of a cluster randomized controlled trial
Reproductive-aged women are at high risk for obesity development. Limited research exploring weight gain prevention initiatives and associated modifiable risk factors, including diet quality exists. In a secondary analysis of a 12 month, cluster randomized controlled trial for weight gain prevention in reproductive-aged women, we evaluated change in diet quality, macronutrient and micronutrient intake, predictors of change and associations with weight change at follow-up. Forty-one rural towns in Victoria, Australia were randomized to a healthy lifestyle intervention (n = 21) or control (n = 20). Women aged 18â»50, of any body mass index and without conditions known to affect weight, were recruited. Diet quality was assessed by the Dietary Guideline Index (DGI) and energy, macronutrient, and micronutrient intake as well as anthropometrics (weight; kg) were measured at baseline and 12 months. Results were adjusted for group (intervention/control), town cluster, and baseline values of interest. Of 409 women with matched data at baseline and follow-up, 220 women were included for final analysis after accounting for plausible energy intake. At 12 months, diet quality had improved by 6.2% following the intervention, compared to no change observed in the controls (p < 0.001). Significant association was found between a change in weight and a change in diet quality score over time ÎČ -0.66 (95%CI -1.2, -0.12) p = 0.02. The percentage of energy from protein (%) 0.009 (95%CI 0.002, 0.15) p = 0.01 and glycemic index -1.2 (95%CI -2.1, -0.24) p = 0.02 were also improved following the intervention, compared to the control group. Overall, a low-intensity lifestyle intervention effectively improves diet quality, with associated weight gain preventions, in women of reproductive age.Julie C. Martin, Lisa J. Moran, Helena J. Teede, Sanjeeva Ranasinha, Catherine B. Lombard and Cheryce L. Harriso
Control of Autophagosome Axonal Retrograde Flux by Presynaptic Activity Unveiled Using Botulinum Neurotoxin Type A
Botulinum neurotoxin type A (BoNT/A) is a highly potent neurotoxin that elicits flaccid paralysis by enzymatic cleavage of the exocytic machinery component SNAP25 in motor nerve terminals. However, recent evidence suggests that the neurotoxic activity of BoNT/A is not restricted to the periphery, but also reaches the CNS after retrograde axonal transport. Because BoNT/A is internalized in recycling synaptic vesicles, it is unclear which compartment facilitates this transport. Using live-cell confocal and single-molecule imaging of rat hippocampal neurons cultured in microfluidic devices, we show that the activity-dependent uptake of the binding domain of the BoNT/A heavy chain (BoNT/A-Hc) is followed by a delayed increase in retrograde axonal transport of BoNT/A-Hc carriers. Consistent with a role of presynaptic activity in initiating transport of the active toxin, activity-dependent uptake of BoNT/A in the terminal led to a significant increase in SNAP25 cleavage detected in the soma chamber compared with nonstimulated neurons. Surprisingly, most endocytosed BoNT/A-Hc was incorporated into LC3-positive autophagosomes generated in the nerve terminals, which then underwent retrograde transport to the cell soma, where they fused with lysosomes both in vitro and in vivo. Blocking autophagosome formation or acidification with wortmannin or bafilomycin A1, respectively, inhibited the activity-dependent retrograde trafficking of BoNT/A-Hc. Our data demonstrate that both the presynaptic formation of autophagosomes and the initiation of their retrograde trafficking are tightly regulated by presynaptic activity
An amplitude analysis of the reaction
A simple partial wave amplitude analysis of has been performed for data in the range p_{\sl lab} = 360 -- 1000
MeV/c. Remarkably few partial waves are required to fit the data, while the
number of required values barely changes over this energy range. However,
the resulting set of partial wave amplitudes is not unique. We discuss possible
measurements with polarized beam and target which will severely restrict and
help resolve the present analysis ambiguities. New data from the reaction
alone, are insufficient for that
purpose.Comment: 16 pages (revtex), 8 figures available on request, submitted to Phys.
Rev.
and from QCD sum rules
and are calculated using a QCD sum rule
motivated method used by Reinders, Rubinstein and Yazaki to extract Hadron
couplings to goldstone bosons. The SU(3) symmetry breaking effects are taken
into account by including the contributions from the strange quark mass and
assuming different values for the strange and the up down quark condensates. We
find and Comment: 14 pages (REVTeX) and 2 PS figure
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