Rapid and efficient computation of cell trajectories during ultrasonic focusing

This biophysical analysis explores the first-principles physics of movement of white blood cell sized particles, suspended in an aqueous fluid and experiencing progressive or standing waves of acoustic pressure. In many current applications the cells are gradually nudged or herded toward the antinodes of the standing wave, providing a degree of acoustic focusing and concentration of the cells in layers perpendicular to the direction of sound propagation. Here the underlying biomechanics of this phenomenon are analyzed specifically for the viscous regime of water--as opposed to air--and for small diameter microscopic spheroids such as living cells--as opposed to large diameter, macroscopic spheroids such as suspended polystyrene beads or levitated ping-pong balls. The resulting mathematical model leads to a single algebraic expression for the creep or drift velocity as a function of sound frequency, amplitude, wavelength, fluid viscosity, boundary dimensions, and boundary reflectivity. This expression can be integrated numerically by a very simple and fast computer algorithm to demonstrate net movement of particles as a function of time, providing a guide to optimization in a variety of emerging applications of ultrasonic cell focusing

Small solid renal masses: Characterization by diffusion-weighted MRI at 3 T

AIM: To describe the appearance of small solid renal lesions ( 643 cm) on diffusion-weighted magnetic resonance imaging (MRI) and to determine whether ADC measurements may help to differentiate benign from malignant small solid renal masses. METHODS AND MATERIALS: Thirty-five patients with 47 small renal masses (23 malignant, 24 benign) who underwent 3 T MRI of the kidney using diffusion-weighted sequences (b values of 0 and 1000 s/mm(2)) were retrospectively evaluated. Qualitative and quantitative analysis of diffusion-weighted images was performed. RESULTS: Most lesions were hyperintense to kidney on high b-value diffusion-weighted images and hypointense on apparent diffusion coefficient (ADC) map. The mean ADC of the lesions was significantly lower than that of kidney (1.22 \ub1 0.3 versus 1.85 \ub1 0.12 mm(2)/s; p < 0.005). The mean ADC was significantly different between renal cell carcinomas (1.2 \ub1 0.01 mm(2)/s), metastases (1.25 \ub1 0.04 mm(2)/s), angiomyolipoma (1.07 \ub1 0.3 mm(2)/s) and oncocytomas (1.56 \ub1 0.08 mm(2)/s; p < 0.05). The mean ADC of clear cell renal cell carcinomas was significantly different from that of non-clear cell renal cell carcinomas (1.38 \ub1 0.34 versus 0.83 \ub1 0.34 mm(2)/s; p < 0.005). No significant difference was found between mean ADC of fat containing and minimal fat angiomyolipomas (1.06 \ub1 0.48 versus 1.11 \ub1 0.33 mm(2)/s). CONCLUSION: Small solid renal masses are hyperintense on high b value and have different ADC values

Prescription drug monitoring and drug overdose mortality

Background: Abuse of prescription drugs, particularly opioid analgesics, has become a major source of injury mortality and morbidity in the United States. To prevent the diversion and misuse of controlled substances, many states have implemented prescription drug monitoring programs (PDMPs). This study assessed the impact of state PDMPs on drug overdose mortality. Methods: We analyzed demographic and drug overdose mortality data for state-quarters with and without PDMPs in 50 states and the District of Columbia during 1999–2008, and estimated adjusted risk ratios (aRRs) and 95% confidence intervals (CIs) of drug overdose mortality associated with the implementation of state PDMPs through multivariable negative bionomial regression modeling. ResultsL During the study period, annual national death rates from drug overdose increased by 96%, from 5.7 deaths per 100,000 population in 1999 to 11.2 in 2008. The impact of PDMPs on drug overdose mortality varied greatly across states, ranging from a 35% decrease in Michigan (aRR = 0.65; 95% CI = 0.54–0.77) to a more than 3-fold increase in Nevada (aRR = 3.37; 95% CI = 2.48–4.59). Overall, implementation of PDMPs was associated with an 11% increase in drug overdose mortality (aRR = 1.11; 95% CI = 1.02–1.21). Conclusions: Implementation of PDMPs did not reduce drug overdose mortality in most states through 2008. Program enhancement that facilitates the access and use of prescription drug monitoring data systems by healthcare practitioners is needed

The SPLASH Survey: Kinematics of Andromeda's Inner Spheroid

The combination of large size, high stellar density, high metallicity, and Sersic surface brightness profile of the spheroidal component of the Andromeda galaxy (M31) within R_proj ~ 20 kpc suggest that it is unlike any subcomponent of the Milky Way. In this work we capitalize on our proximity to and external view of M31 to probe the kinematical properties of this "inner spheroid." We employ a Markov chain Monte Carlo (MCMC) analysis of resolved stellar kinematics from Keck/DEIMOS spectra of 5651 red giant branch stars to disentangle M31's inner spheroid from its stellar disk. We measure the mean velocity and dispersion of the spheroid in each of five spatial bins after accounting for a locally cold stellar disk as well as the Giant Southern Stream and associated tidal debris. For the first time, we detect significant spheroid rotation (v_rot ~ 50 km/s) beyond R_proj ~ 5 kpc. The velocity dispersion decreases from about 140 km/s at R_proj = 7 kpc to 120 km/s at R_proj = 14 kpc, consistent to 2 sigma with existing measurements and models. We calculate the probability that a given star is a member of the spheroid and find that the spheroid has a significant presence throughout the spatial extent of our sample. Lastly, we show that the flattening of the spheroid is due to velocity anisotropy in addition to rotation. Though this suggests that the inner spheroid of M31 more closely resembles an elliptical galaxy than a typical spiral galaxy bulge, it should be cautioned that our measurements are much farther out (2 - 14 r_eff) than for the comparison samples.Comment: Accepted for publication in Ap

Rough droplet model for spherical metal clusters

We study the thermally activated oscillations, or capillary waves, of a neutral metal cluster within the liquid drop model. These deformations correspond to a surface roughness which we characterize by a single parameter $\Delta$. We derive a simple analytic approximate expression determining $\Delta$ as a function of temperature and cluster size. We then estimate the induced effects on shell structure by means of a periodic orbit analysis and compare with recent data for shell energy of sodium clusters in the size range $50 < N < 250$. A small surface roughness $\Delta\simeq 0.6$ \AA~ is seen to give a reasonable account of the decrease of amplitude of the shell structure observed in experiment. Moreover -- contrary to usual Jahn-Teller type of deformations -- roughness correctly reproduces the shape of the shell energy in the domain of sizes considered in experiment.Comment: 20 pages, 4 figures, important modifications of the presentation, to appear in Phys. Rev.

Quantum phase transitions of light

Recently, condensed matter and atomic experiments have reached a length-scale and temperature regime where new quantum collective phenomena emerge. Finding such physics in systems of photons, however, is problematic, as photons typically do not interact with each other and can be created or destroyed at will. Here, we introduce a physical system of photons that exhibits strongly correlated dynamics on a meso-scale. By adding photons to a two-dimensional array of coupled optical cavities each containing a single two-level atom in the photon-blockade regime, we form dressed states, or polaritons, that are both long-lived and strongly interacting. Our zero temperature results predict that this photonic system will undergo a characteristic Mott insulator (excitations localised on each site) to superfluid (excitations delocalised across the lattice) quantum phase transition. Each cavity's impressive photon out-coupling potential may lead to actual devices based on these quantum many-body effects, as well as observable, tunable quantum simulators. We explicitly show that such phenomena may be observable in micro-machined diamond containing nitrogen-vacancy colour centres and superconducting microwave strip-line resonators.Comment: 11 pages, 5 figures (2 in colour

Deep Broadband Observations of the Distant Gamma-ray Blazar PKS 1424+240

We present deep VERITAS observations of the blazar PKS 1424+240, along with contemporaneous Fermi Large Area Telescope, Swift X-ray Telescope and Swift UV Optical Telescope data between 2009 February 19 and 2013 June 8. This blazar resides at a redshift of $z\ge0.6035$, displaying a significantly attenuated gamma-ray flux above 100 GeV due to photon absorption via pair-production with the extragalactic background light. We present more than 100 hours of VERITAS observations from three years, a multiwavelength light curve and the contemporaneous spectral energy distributions. The source shows a higher flux of (2.1$\pm0.3$)$\times10^{-7}$ ph m$^{-2}$s$^{-1}$ above 120 GeV in 2009 and 2011 as compared to the flux measured in 2013, corresponding to (1.02$\pm0.08$)$\times10^{-7}$ ph m$^{-2}$s$^{-1}$ above 120 GeV. The measured differential very high energy (VHE; $E\ge100$ GeV) spectral indices are $\Gamma=$3.8$\pm$0.3, 4.3$\pm$0.6 and 4.5$\pm$0.2 in 2009, 2011 and 2013, respectively. No significant spectral change across the observation epochs is detected. We find no evidence for variability at gamma-ray opacities of greater than $\tau=2$, where it is postulated that any variability would be small and occur on longer than year timescales if hadronic cosmic-ray interactions with extragalactic photon fields provide a secondary VHE photon flux. The data cannot rule out such variability due to low statistics.Comment: ApJL accepted March 17, 201

Assessment of Medical Students’ Shared Decision-Making in Standardized Patient Encounters

BackgroundShared decision-making, in which physicians and patients openly explore beliefs, exchange information, and reach explicit closure, may represent optimal physician-patient communication. There are currently no universally accepted methods to assess medical students' competence in shared decision-making.ObjectiveTo characterize medical students' shared decision-making with standardized patients (SPs) and determine if students' use of shared decision-making correlates with SP ratings of their communication.DesignRetrospective study of medical students' performance with four SPs.ParticipantsSixty fourth-year medical students.MeasurementsObjective blinded coding of shared decision-making quantified as decision moments (exploration/articulation of perspective, information sharing, explicit closure for a particular decision); SP scoring of communication skills using a validated checklist.ResultsOf 779 decision moments generated in 240 encounters, 312 (40%) met criteria for shared decision-making. All students engaged in shared decision-making in at least two of the four cases, although in two cases 5% and 12% of students engaged in no shared decision-making. The most commonly discussed decision moment topics were medications (n = 98, 31%), follow-up visits (71, 23%), and diagnostic testing (44, 14%). Correlations between the number of decision moments in a case and students' communication scores were low (rho = 0.07 to 0.37).ConclusionsAlthough all students engaged in some shared decision-making, particularly regarding medical interventions, there was no correlation between shared decision-making and overall communication competence rated by the SPs. These findings suggest that SP ratings of students' communication skill cannot be used to infer students' use of shared decision-making. Tools to determine students' skill in shared decision-making are needed

Delayed Recovery of Skeletal Muscle Mass following Hindlimb Immobilization in mTOR Heterozygous Mice

The present study addressed the hypothesis that reducing mTOR, as seen in mTOR heterozygous (+/−) mice, would exaggerate the changes in protein synthesis and degradation observed during hindlimb immobilization as well as impair normal muscle regrowth during the recovery period. Atrophy was produced by unilateral hindlimb immobilization and data compared to the contralateral gastrocnemius. In wild-type (WT) mice, the gradual loss of muscle mass plateaued by day 7. This response was associated with a reduction in basal protein synthesis and development of leucine resistance. Proteasome activity was consistently elevated, but atrogin-1 and MuRF1 mRNAs were only transiently increased returning to basal values by day 7. When assessed 7 days after immobilization, the decreased muscle mass and protein synthesis and increased proteasome activity did not differ between WT and mTOR+/− mice. Moreover, the muscle inflammatory cytokine response did not differ between groups. After 10 days of recovery, WT mice showed no decrement in muscle mass, and this accretion resulted from a sustained increase in protein synthesis and a normalization of proteasome activity. In contrast, mTOR+/− mice failed to fully replete muscle mass at this time, a defect caused by the lack of a compensatory increase in protein synthesis. The delayed muscle regrowth of the previously immobilized muscle in the mTOR+/− mice was associated with a decreased raptor•4EBP1 and increased raptor•Deptor binding. Slowed regrowth was also associated with a sustained inflammatory response (e.g., increased TNFα and CD45 mRNA) during the recovery period and a failure of IGF-I to increase as in WT mice. These data suggest mTOR is relatively more important in regulating the accretion of muscle mass during recovery than the loss of muscle during the atrophy phase, and that protein synthesis is more sensitive than degradation to the reduction in mTOR during muscle regrowth