494 research outputs found
Exotic polarizations of D2 branes and oblique vacua of (S)YM
We investigate the oblique vacua in the perturbed 2+1 dimensional gauge
theory living on D2 branes. The string theory dual of these vacua is expected
to correspond to polarizations of the D2 branes into NS5 branes with D4 brane
charge. We perturb the gauge theory by adding fermions masses. In the
nonsupersymmetric case, we also consider the effect of slight variations of the
masses of the scalars. For certain ranges of scalar masses we find oblique
vacua.
We show that D4 charge is an essential ingredient in understanding D2 -> NS5
polarizations. We find that some of the polarization states which appear as
metastable vacua when D4 charge is not considered are in fact unstable. They
decay by acquiring D4 charge, tilting and shrinking to zero size.Comment: 15 pages, 3 figures, LaTe
NMR Chemical Shifts of Trace Impurities: Common Laboratory Solvents, Organics, and Gases in Deuterated Solvents Relevant to the Organometallic Chemist
Tables of ^1H and ^(13)C NMR chemical shifts have been compiled for common organic compounds often used as reagents or found as products or contaminants in deuterated organic solvents. Building upon the work of Gottlieb, Kotlyar, and Nudelman in the Journal of Organic Chemistry, signals for common impurities are now reported in additional NMR solvents (tetrahydrofuran-d_8, toluene-d_8, dichloromethane-d_2, chlorobenzene-d_5, and 2,2,2-trifluoroethanol-d_3) which are frequently used in organometallic laboratories. Chemical shifts for other organics which are often used as reagents or internal standards or are found as products in organometallic chemistry are also reported for all the listed solvents
Controlling Internal Pore Sizes in Bicontinuous Polymeric Nanospheres
Complex polymeric nanospheres were formed in water from comb-like amphiphilic block copolymers. Their internal morphology was determined by three-dimensional cryo-electron tomographic analysis. Varying the polymer molecular weight (MW) and the hydrophilic block weight content allowed for fine control over the internal structure. Construction of a partial phase diagram allowed us to determine the criteria for the formation of bicontinuous polymer nanosphere (BPN), namely for copolymers with MW of up to 17?kDa and hydrophilic weight fractions of ?0.25; and varying the organic solvent to water ratio used in their preparation allowed for control over nanosphere diameters from 70 to 460?nm. Significantly, altering the block copolymer hydrophilicâhydrophobic balance enabled control of the internal pore diameter of the BPNs from 10 to 19?nm
A lathe system for micrometre-sized cylindrical sample preparation at room and cryogenic temperatures
A simple two-spindle based lathe system for the preparation of cylindrical samples intended for X-ray tomography is presented. The setup can operate at room temperature as well as under cryogenic conditions, allowing the preparation of samples down to 20 and 50â
”m in diameter, respectively, within minutes. Case studies are presented involving the preparation of a brittle biomineral brachiopod shell and cryogenically fixed soft brain tissue, and their examination by means of ptychographic X-ray computed tomography reveals the preparation method to be mainly free from causing artefacts. Since this lathe system easily yields near-cylindrical samples ideal for tomography, a usage for a wide variety of otherwise challenging specimens is anticipated, in addition to potential use as a time- and cost-saving tool prior to focused ion-beam milling. Fast sample preparation becomes especially important in relation to shorter measurement times expected in next-generation synchrotron sources
Disordered Filaments Mediate the Fibrillogenesis of Type I Collagen in Solution
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Telomere length associations with cognition depend on Alzheimer's disease biomarkers
Introduction
While telomere shortening, a marker of cellular aging, may impact the progression of ageârelated neurodegenerative diseases, its association with cognition is unclear, particularly in the context of Alzheimer's disease (AD) pathology.
Methods
Telomere, cognitive, and CSF data from 482 participants in the AD Neuroimaging Initiative (148 cognitively normal, 283 mild cognitive impairment, 51 AD) was leveraged to assess telomere length associations with cognition (measured by memory and executive function) and interactions with CSF amyloidâÎČ, tau, and APOEâΔ4. Secondary analyses assessed brain volume and thickness outcomes.
Results
Longer telomeres at baseline were associated with faster executive function decline. AmyloidâÎČ and tau interacted with telomere length on cognition, with longer telomeres related to faster decline among biomarkerâpositive individuals.
Discussion
Telomere associations with cognition shift with AD progression, with longer telomeres related to worse outcomes as pathology increases, highlighting the need for further investigation of telomere length along the AD neuropathological cascade
Warping and vacua of
We use dielectric branes to find non singular string theory duals of a
perturbed 2+1 dimensional gauge theory living on D2 branes. By adding fermion
masses we obtain theories with reduced supersymmetry. The Higgs vacua of the
perturbed theory correspond to polarization of the D2 branes into D4 branes.
The confining vacua correspond to polarization of the D2 branes into NS5
branes. We consider different mass perturbations. Adding three equal masses
preserves N=2 supersymmetry. In this case there are no confining vacua. By
adding a fourth fermion mass we break all the supersymmetry, and find confining
vacua. We also obtain duals for domain walls, condensates, baryon vertices,
glueballs and flux tubes. We comment on the Kahler potentials for the Higgs and
confining phases. In the course of the calculations we also find a nontrivial
consistency check of the NS5 brane action in a D2 brane background.Comment: 33 pages, 2 figures, LaTeX. A factor in the last term of (67) and
some typos are corrected, references adde
Cerebral Perfusion and Gray Matter Changes Associated With Chemotherapy-Induced Peripheral Neuropathy
PURPOSE:
To investigate the longitudinal relationship between chemotherapy-induced peripheral neuropathy (CIPN) symptoms (sx) and brain perfusion changes in patients with breast cancer. Interaction of CIPN-sx perfusion effects with known chemotherapy-associated gray matter density decrease was also assessed to elucidate the relationship between CIPN and previously reported cancer treatment-related brain structural changes.
METHODS:
Patients with breast cancer treated with (n = 24) or without (n = 23) chemotherapy underwent clinical examination and brain magnetic resonance imaging at the following three time points: before treatment (baseline), 1 month after treatment completion, and 1 year after the 1-month assessment. CIPN-sx were evaluated with the self-reported Functional Assessment of Cancer Therapy/Gynecologic Oncology Group-Neurotoxicity four-item sensory-specific scale. Perfusion and gray matter density were assessed using voxel-based pulsed arterial spin labeling and morphometric analyses and tested for association with CIPN-sx in the patients who received chemotherapy.
RESULTS:
Patients who received chemotherapy reported significantly increased CIPN-sx from baseline to 1 month, with partial recovery by 1 year (P < .001). CIPN-sx increase from baseline to 1 month was significantly greater for patients who received chemotherapy compared with those who did not (P = .001). At 1 month, neuroimaging showed that for the group that received chemotherapy, CIPN-sx were positively associated with cerebral perfusion in the right superior frontal gyrus and cingulate gyrus, regions associated with pain processing (P < .001). Longitudinal magnetic resonance imaging analysis in the group receiving chemotherapy indicated that CIPN-sx and associated perfusion changes from baseline to 1 month were also positively correlated with gray matter density change (P < .005).
CONCLUSION:
Peripheral neuropathy symptoms after systemic chemotherapy for breast cancer are associated with changes in cerebral perfusion and gray matter. The specific mechanisms warrant further investigation given the potential diagnostic and therapeutic implications
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