Using the Fundamental Plane to Estimate the Total Binding Mass in A2626

We use fundamental plane (FP) distance estimates to the components of the double cluster A2626 (cz~17,500 km/s) to constrain cluster kinematics and estimate total binding mass. The FP coefficients for a sample of 24 early type and S0 cluster members (alpha=1.30+/-0.36 and beta=0.31+/-0.06) are consistent with others reported in the literature. We examine the Mg_b distributions within both subclusters and find them to be indistinguishable. Lacking evidence for stellar population differences, we interpret the FP zeropoint offset (\log(D_B/D_A)=-0.037+/-0.046, where D_{cl} is distance to subcluster cl) as a measure of the distance difference. This measurement is consistent with the subclusters being at the same distance, and it rules out the Hubble flow hypothesis (distances proportional to velocity) with 99% confidence; analysis of the subcluster galaxy magnitude distributions rules out Hubble flow at 93% confidence. Both results favor a kinematic model where the subclusters are bound and infalling. We estimate the total cluster binding mass by modelling the subcluster merger as radial infall. The minimum possible total binding mass is 1.65 times higher than the sum of the standard virial masses, a difference statistically significant at the ~3sigma level. We discuss explanations for the inconsistency including (1) biases in the standard virial mass estimator, (2) biases in our radial infall mass estimate, and (3) mass beyond the virialized cluster region; if the standard virial mass is significantly in error, the cluster has an unusually high mass to light ratio (~1000h). Because observational signatures of departures from radial infall are absent, we explore the implications of mass beyond the virialized, core regions. (abridged)Comment: 14 pages and 5 figures, Latex, Accepted for publication in A

Modified Kolsky Formulas for an Increased Measurement Duration of SHPB Systems

International audienceThe so-called incident, reflected and transmitted strain histories are typically recorded during standard Split Hopkinson Pressure Bar (SHPB) experiments. Subsequently, the stress-strain curve for the specimen material is determined based on these recordings. Unless wave deconvolution techniques are employed, the reliable measurement of the reflected wave requires an input bar which is at least twice as long as the striker bar (of equal impedance). The present brief technical note elucidates the advantages of a simple alternative configuration which has only been seldom used in the past. Based on the assumption of quasi-static equilibrium at the specimen level, we present a modification of Kolsky's formulas such that the stress-strain curve for the specimen material can be obtained from the measurement of the incident and transmitted strain histories only. As a result, the measurement of the reflected wave may be omitted and a much shorter input bar can be chosen. Conversely, a much longer striker bar may be used for a given input bar length, thereby increasing the valid duration of standard SHPB experiments by up to 100% through the use of the modified Kolky formulas. An example experiment is shown where the duration of valid measurements has been increased by more than 70%

Wireless Magnetothermal Deep Brain Stimulation

Wireless deep brain stimulation of well-defined neuronal populations could facilitate the study of intact brain circuits and the treatment of neurological disorders. Here we demonstrate minimally-invasive and remote neural excitation through the activation of the heat-sensitive capsaicin receptor TRPV1 by magnetic nanoparticles. When exposed to alternating magnetic fields, the nanoparticles dissipate heat generated by hysteresis, triggering widespread and reversible firing of TRPV1+ neurons. Wireless magnetothermal stimulation in the ventral tegmental area of mice evoked excitation in subpopulations of neurons in the targeted brain region and in structures receiving excitatory projections. The nanoparticles persisted in the brain for over a month, allowing for chronic stimulation without the need for implants and connectors.United States. Defense Advanced Research Projects Agency (Young Faculty Award D13AP00043)McGovern Institute for Brain Research at MITNational Science Foundation (U.S.) (CAREER Award CBET-1253890)National Science Foundation (U.S.). Graduate Research FellowshipAmerican Society for Engineering Education. National Defense Science and Engineering Graduate Fellowshi

An Optical and X-Ray Study of Abell 576, a Galaxy Cluster with a Cold Core

We analyze the galaxy population and dynamics of the galaxy cluster A576; the observational constraints include 281 redshifts (230 new), R- band CCD galaxy photometry over a 2 h^-1^ Mpc x 2 h^-1^ Mpc region centered on the cluster, an Einstein IPC X-ray image, and an Einstein MPC X-ray spectrum. We focus on an 86% complete magnitude-limited sample (R_23.5_ \u3c 17) of 169 cluster galaxies. The cluster galaxies with emission lines in their spectra have a larger velocity dispersion and are significantly less clustered on this 2 h^-1^ Mpc scale than galaxies without emission lines. We show that excluding the emission-line galaxies from the cluster sample decreases the velocity dispersion by 18% and the virial mass estimate by a factor of 2. The central cluster region contains a nonemission galaxy population and an intracluster medium which is significantly cooler (σ_core_ = 387_-105_^+250^ km s^-1^ and T_x_ = 1.6_-0.3_^+0.4^ keV at 90% confidence) than the global populations (σ = 977_-96_^+124^ km s^- 1^ for the nonemission population and T_X_ \u3e 4 keV at 90% confidence). Because (1) the low-dispersion galaxy population is no more luminous than the global population and (2) the evidence for a cooling flow is weak, we suggest that the core of A576 may contain the remnants of a lower mass subcluster. We examine the cluster mass, baryon fraction, and luminosity function. The cluster virial mass varies significantly depending on the galaxy sample used. Consistency between the hydrostatic and virial estimators can be achieved if (1) the gas temperature at r~1 h^-1^ Mpc is T_X_ ~ 8 keV (the best-fit value) and (2) several velocity outliers are excluded from the virial calculation. Although the best-fit Schechter function parameters and the ratio of galaxy to gas mass in A576 are typical of other clusters, the baryon fraction is relatively low. Using the consistent cluster binding mass, we show that the gas mass fraction is ~3 h^-3/2^% and the baryon fraction is ~6%

A Photometric and Kinematic Study of AWM 7

We have measured redshifts and Kron-Cousins R-band magnitudes for a sample of galaxies in the poor cluster AWM 7. We have measured redshifts for 172 galaxies; 106 of these are cluster members. We determine the luminosity function from a photometric survey of the central 1.2 h^{-1} x 1.2 h^{-1} Mpc. The LF has a bump at the bright end and a faint-end slope of \alpha = -1.37+-0.16, populated almost exclusively by absorption-line galaxies. The cluster velocity dispersion is lower in the core (\sim 530 km/s) than at the outskirts (\sim 680 km/s), consistent with the cooling flow seen in the X-ray. The cold core extends \sim 150 h^{-1} kpc from the cluster center. The Kron-Cousins R-band mass-to-light ratio of the system is 650+-170 h M_\odot/L_\odot, substantially lower than previous optical determinations, but consistent with most previous X-ray determinations. We adopt H_0 = 100 h km/s/Mpc throughout this paper; at the mean cluster redshift, (5247+-76 km/s), 1 h^{-1} Mpc subtends 65\farcm5.Comment: 37 pages, LaTeX, including 12 Figures and 1 Table. Accepted for publication in the Astronomical Journa

Wildlife habitat conservation needs in Florida: updated recommendations for strategic habitat conservation areas

In 1994, researchers from the Florida Fish and Wildlife Conservation Commission (FWC) completed a report, entitled Closing the Gaps in Florida’s Wildlife Habitat Conservation System, assessing the security of rare and imperiled species on existing conservation lands in Florida. The biologists that authored this report used species occurrence data, habitat data, and the analytical capabilities of Geographic Information Systems (GIS) to assess the protection afforded to 62 focal species on lands managed for conservation and to identify important habitat areas in Florida that have no conservation protection. These areas, known as Strategic Habitat Conservation Areas (SHCA), depict areas needed for protection and serve as a foundation for conservation planning in Florida. Since 1994, landscape-level habitat changes, transfer of land from private to public ownership, and changes in land use have reduced the appropriateness of using the findings from the 1994 report to accurately assess Florida’s current biodiversity and wildlife conservation status. Advances in technological capabilities, revised habitat data, and more extensive species-occurrence data allowed us to reassess Florida’s biodiversity protection status. Additionally, advances in population-viability modeling techniques allowed us to examine the security of species given their current distribution, habitat needs, and the amount and distribution of habitats currently protected. We identified SHCA for a new selection of focal species, including many species that were in the original report. This project will help determine how habitat-protection needs have changed since 1994 and where protection efforts should be focused to ensure the long-term conservation of Florida’s wildlife

The velocity modulation of galaxy properties in and near clusters: quantifying the decrease in star formation in backsplash galaxies

The efficiency of recent star formation (SF) in galaxies increases with increasing projected distance from the centre of a cluster out to several times its virial radius (R_v). Using a complete sample of galaxies in 268 clusters from the SDSS DR4, we investigate how, at a given projected radius from the cluster centre, M* and SF properties of a galaxy depend on its absolute line-of-sight velocity in the cluster rest frame, |v_LOS|. We find that for R<0.5 R_v, the fraction of high mass non-BCG galaxies increases towards the centre for low |v_LOS|. At a given projected radius, the fraction of Galaxies with Ongoing or Recent (<1-3 Gyr) Efficient Star Formation (GORES, with EW(H_delta)>2 ang & D_4000>1.5) is slightly but significantly lower for low |v_LOS| galaxies than for their high velocity counterparts. We study these observational trends with the help of a dark matter (DM) cosmological simulation. We find that the backsplash particles account for at least one-third (half) of all particles at projected radii slightly greater than the virial radius and |v_LOS|<sigma_v. The deprojection of the GORES fraction leads to a saturated linear increase with radius. We fit simple models of the fraction of GORES as a function of class only or class and distance to the cluster centre (as in our deprojected fraction). In our best-fitting model GORES account for 13% of galaxies within the virial sphere, 11% of the virial population, 34% of the distant (for projected radii R<2 R_v) infall population and 19% of the backsplash galaxies. Given the 1-3 Gyr lookback time of our GORES indicators, these results suggest that SF in a galaxy is almost completely quenched in a single passage through the cluster.Comment: 22 pages, 17 figures, MNRAS, 416, 2882, Labels for Figure 14 revise

Physical and mental health comorbidity is common in people with multiple sclerosis: nationally representative cross-sectional population database analysis

&lt;b&gt;Background&lt;/b&gt; Comorbidity in Multiple Sclerosis (MS) is associated with worse health and higher mortality. This study aims to describe clinician recorded comorbidities in people with MS. &lt;p&gt;&lt;/p&gt; &lt;b&gt;Methods&lt;/b&gt; 39 comorbidities in 3826 people with MS aged ≥25 years were compared against 1,268,859 controls. Results were analysed by age, gender, and socioeconomic status, with unadjusted and adjusted Odds Ratios (ORs) calculated using logistic regression. &lt;p&gt;&lt;/p&gt; &lt;b&gt;Results&lt;/b&gt; People with MS were more likely to have one (OR 2.44; 95% CI 2.26-2.64), two (OR 1.49; 95% CI 1.38-1.62), three (OR 1.86; 95% CI 1.69-2.04), four or more (OR 1.61; 95% CI 1.47-1.77) non-MS chronic conditions than controls, and greater mental health comorbidity (OR 2.94; 95% CI 2.75-3.14), which increased as the number of physical comorbidities rose. Cardiovascular conditions, including atrial fibrillation (OR 0.49; 95% CI 0.36-0.67), chronic kidney disease (OR 0.51; 95% CI 0.40-0.65), heart failure (OR 0.62; 95% CI 0.45-0.85), coronary heart disease (OR 0.64; 95% CI 0.52-0.71), and hypertension (OR 0.65; 95% CI 0.59-0.72) were significantly less common in people with MS. &lt;p&gt;&lt;/p&gt; &lt;b&gt;Conclusion&lt;/b&gt; People with MS have excess multiple chronic conditions, with associated increased mental health comorbidity. The low recorded cardiovascular comorbidity warrants further investigation