Simulation of alnico coercivity

Micromagnetic simulations of alnico show substantial deviations from Stoner-Wohlfarth behavior due to the unique size and spatial distribution of the rod-like Fe-Co phase formed during spinodal decomposition in an external magnetic field. The maximum coercivity is limited by single-rod effects, especially deviations from ellipsoidal shape, and by interactions between the rods. Both the exchange interaction between connected rods and magnetostatic interaction between rods are considered, and the results of our calculations show good agreement with recent experiments. Unlike systems dominated by magnetocrystalline anisotropy, coercivity in alnico is highly dependent on size, shape, and geometric distribution of the Fe-Co phase, all factors that can be tuned with appropriate chemistry and thermal-magnetic annealing

Fibronectin and Cyclic Strain Improve Cardiac Progenitor Cell Regenerative Potential In Vitro.

Cardiac progenitor cells (CPCs) have rapidly advanced to clinical trials, yet little is known regarding their interaction with the microenvironment. Signaling cues present in the microenvironment change with development and disease. This work aims to assess the influence of two distinct signaling moieties on CPCs: cyclic biaxial strain and extracellular matrix. We evaluate four endpoints for improving CPC therapy: paracrine signaling, proliferation, connexin43 expression, and alignment. Vascular endothelial growth factor A (about 900 pg/mL) was secreted by CPCs cultured on fibronectin and collagen I. The application of mechanical strain increased vascular endothelial growth factor A secretion 2-4-fold for CPCs cultured on poly-L-lysine, laminin, or a naturally derived cardiac extracellular matrix. CPC proliferation was at least 25% higher on fibronectin than that on other matrices, especially for lower strain magnitudes. At 5% strain, connexin43 expression was highest on fibronectin. With increasing strain magnitude, connexin43 expression decreased by as much as 60% in CPCs cultured on collagen I and a naturally derived cardiac extracellular matrix. Cyclic mechanical strain induced the strongest CPC alignment when cultured on fibronectin or collagen I. This study demonstrates that culturing CPCs on fibronectin with 5% strain magnitude is optimal for their vascular endothelial growth factor A secretion, proliferation, connexin43 expression, and alignment

Extracellular Matrix Hydrogel Promotes Tissue Remodeling, Arteriogenesis, and Perfusion in a Rat Hindlimb Ischemia Model.

ObjectiveThis study aimed to examine acellular extracellular matrix based hydrogels as potential therapies for treating peripheral artery disease (PAD). We tested the efficacy of using a tissue specific injectable hydrogel, derived from decellularized porcine skeletal muscle (SKM), compared to a new human umbilical cord derived matrix (hUC) hydrogel, which could have greater potential for tissue regeneration because of its young tissue source age.BackgroundThe prevalence of PAD is increasing and can lead to critical limb ischemia (CLI) with potential limb amputation. Currently there are no therapies for PAD that effectively treat all of the underlying pathologies, including reduced tissue perfusion and muscle atrophy.MethodsIn a rodent hindlimb ischemia model both hydrogels were injected 1-week post-surgery and perfusion was regularly monitored with laser speckle contrast analysis (LASCA) to 35 days post-injection. Histology and immunohistochemistry were used to assess neovascularization and muscle health. Whole transcriptome analysis was further conducted on SKM injected animals on 3 and 10 days post-injection.ResultsSignificant improvements in hindlimb tissue perfusion and perfusion kinetics were observed with both biomaterials. End point histology indicated this was a result of arteriogenesis, rather than angiogenesis, and that the materials were biocompatible. Skeletal muscle fiber morphology analysis indicated that the muscle treated with the tissue specific, SKM hydrogel more closely matched healthy tissue morphology. Short term histology also indicated arteriogenesis rather than angiogenesis, as well as improved recruitment of skeletal muscle progenitors. Whole transcriptome analysis indicated that the SKM hydrogel caused a shift in the inflammatory response, decreased cell death, and increased blood vessel and muscle development.ConclusionThese results show the efficacy of an injectable ECM hydrogel alone as a potential therapy for treating patients with PAD. Our results indicate that the SKM hydrogel improved functional outcomes through stimulation of arteriogenesis and muscle progenitor cell recruitment

Rabi oscillations between ground and Rydberg states with dipole-dipole atomic interactions

We demonstrate Rabi oscillations of small numbers of 87Rb atoms between ground and Rydberg states with n≤43. Coherent population oscillations are observed for single atoms, while the presence of two or more atoms decoheres the oscillations. We show that these observations are consistent with van der Waals interactions of Rydberg atoms

Fast ground state manipulation of neutral atoms in microscopic optical traps

We demonstrate Rabi flopping at MHz rates between ground hyperfine states of neutral 87Rb atoms that are trapped in two micron sized optical traps. Using tightly focused laser beams we demonstrate high fidelity, site specific Rabi rotations with cross talk on neighboring sites separated by 8  μm at the level of 10−3. Ramsey spectroscopy is used to measure a dephasing time of 870  μs, which is ≈5000  times longer than the time for a π/2 pulse

Vibratory Stimulus Reduces In Vitro Biofilm Formation On Tracheoesophageal Voice Prostheses

Objectives/Hypothesis Demonstrate that biofilm formation will be reduced on tracheoesophageal prostheses when vibratory stimulus is applied, compared to controls receiving no vibratory stimulus, in a dynamic in vitro model of biofilm accumulation simulating the interface across the tracheoesophageal puncture site. Study Design Prospective, randomized, controlled, crossover in university laboratory. Methods Ex vivo tracheoesophageal prostheses were obtained from university-affiliated speech language pathologists at Indiana University School of Medicine, Indianapolis. Prostheses demonstrating physical integrity and an absence of gross biofilm accumulation were utilized. Sixteen prostheses were cleansed and sterilized prior to random placement by length in two modified Robbins devices arranged in parallel. Each device was seeded with a polymicrobial oral flora on day 1 and received basal artificial salivary flow continuously with three growth medium meals daily. One device was randomly selected for vibratory stimulus, and 2 minutes of vibration was applied to each prosthesis before and after meals for 5 days. The prostheses were explanted and sonicated, and the biofilm cultured for enumeration. This process was repeated after study arm crossover. Results Tracheoesophageal prostheses in the dynamic model receiving vibratory stimulus demonstrated reduced gross biofilm accumulation and a significant biofilm colony forming unit per milliliter reduction of 5.56-fold compared to nonvibratory controls (P < 0.001). Significant reductions were observed within length subgroups. Conclusion Application of vibratory stimulus around meal times significantly reduces biofilm accumulation on tracheoesophageal prostheses in a dynamic in vitro model. Further research using this vibratory stimulus method in vivo will be required to determine if reduced biofilm accumulation correlates with longer device lifespan

Anxiogenic CO2 Stimulus Elicits Exacerbated Hot Flash-like Responses in a Rat Menopause Model and Hot Flashes in Menopausal Women

Objective Since longitudinal studies determined that anxiety is a strong risk factor for hot flashes, we hypothesized that an anxiogenic stimulus that signals air hunger (hypercapnic, normoxic gas) would trigger an exacerbated hot flash-associated increase in tail skin temperature (TST) in a rat ovariectomy (OVEX) model of surgical menopause and hot flashes in symptomatic menopausal women. We also assessed TST responses in OVEX serotonin transporter (SERT)+/− rats that models a common polymorphism that is associated with increased climacteric symptoms in menopausal women and increases in anxiety traits. Methods OVEX and sham-OVEX rats (initial experiment) and wildtype and SERT+/− OVEX rats (subsequent experiment) were exposed to a 5 min infusion of 20%CO2 normoxic gas while measuring TST. Menopausal women were given brief 20% and 35%CO2 challenges, and hot flashes were self-reported and objectively verified. Results Compared to controls, OVEX rats had exacerbated increases in TST, and SERT+/− OVEX rats had prolonged TST increases following CO2. Most women reported mild/moderate hot flashes after CO2 challenges, and the hot flash severity to CO2 was positively correlated with daily hot flash frequency. Conclusions The studies demonstrate that this anxiogenic stimulus is capable of inducing cutaneous vasomotor responses in OVEX rats, and eliciting hot flashes in menopausal women. In rats, the severity of the response was mediated by loss of ovarian function and increased anxiety traits (SERT+/−), and, in women, by daily hot flash frequency. These findings may provide insights into anxiety related triggers and genetic risk factors for hot flashes in thermoneutral environments

Ultraviolet through Infrared Spectral Energy Distributions from 1000 SDSS Galaxies: Dust Attenuation

The meaningful comparison of models of galaxy evolution to observations is critically dependent on the accurate treatment of dust attenuation. To investigate dust absorption and emission in galaxies we have assembled a sample of ~1000 galaxies with ultraviolet (UV) through infrared (IR) photometry from GALEX, SDSS, and Spitzer and optical spectroscopy from SDSS. The ratio of IR to UV emission (IRX) is used to constrain the dust attenuation in galaxies. We use the 4000A break as a robust and useful, although coarse, indicator of star formation history (SFH). We examine the relationship between IRX and the UV spectral slope (a common attenuation indicator at high-redshift) and find little dependence of the scatter on 4000A break strength. We construct average UV through far-IR spectral energy distributions (SEDs) for different ranges of IRX, 4000A break strength, and stellar mass (M_*) to show the variation of the entire SED with these parameters. When binned simultaneously by IRX, 4000A break strength, and M_* these SEDs allow us to determine a low resolution average attenuation curve for different ranges of M_*. The attenuation curves thus derived are consistent with a lambda^{-0.7} attenuation law, and we find no significant variations with M_*. Finally, we show the relationship between IRX and the global stellar mass surface density and gas-phase-metallicity. Among star forming galaxies we find a strong correlation between IRX and stellar mass surface density, even at constant metallicity, a result that is closely linked to the well-known correlation between IRX and star-formation rate.Comment: 12 pages, 8 figures, 2 tables, appearing in the Dec 2007 GALEX special issue of ApJ Supp (29 papers