The Validity of The VmaxPro during Countermovement Jump and Back Squat Performance

Background: Advances in technology have resulted in an increase in the utilization of velocity-based training in the strength and conditioning field while utilization of inertia measurement units (IMUs) shows promise. Methods: Recreationally trained participants (N=25, 28.3 ± 2.9 years) were recruited to determine the validity of the VmaxPro device for measuring performance variables in the back squat and countermovement jump (CMJ) against a gold standard force plate. Squat variables assessed included mean concentric velocity (MCV), mean concentric power (MCP), depth, and duration while CMJ variables assessed included MCV, MCP, depth, duration, and jump height. Squat variables were assessed across 3 conditions: BW, 50% BW, and 100% BW. Results: MCV demonstrated strong correlations in the BW, 50% and 100% conditions (r= 0.965; r=.907; r= 0.827, pp pConclusion:The VmaxPro is a reasonably valid device for assessing duration and jump height when assessing CMJ performance as compared to the force plate while demonstrating overestimation bias. For back squat performance variables, the VmaxPro proves as a reasonably valid device for assessing MCV, MCP, depth, and duration while demonstrating overestimation bias in MCV and MCP

The Magnetic Field of the Irregular Galaxy NGC 4214

We examine the magnetic field in NGC 4214, a nearby irregular galaxy, using multi-wavelength radio continuum polarization data from the Very Large Array. We find that the global radio continuum spectrum shows signs that free-free absorption and/or synchrotron losses may be important. The 3cm radio continuum morphology is similar to that of the Halpha, while the 20cm emission is more diffuse. We estimate that 50% of the radio continuum emission in the center of the galaxy is thermal. Our estimate of the magnetic field strength is $30\pm 9.5$ \uG\ in the center and $10\pm3$ \uG\ at the edges. We find that the hot gas, magnetic, and the gravitational pressures are all the same order of magnitude. Inside the central star forming regions, we find that the thermal and turbulent pressures of the HII regions dominate the pressure balance. We do not detect any significant polarization on size scales greater than 200 pc. We place an upper limit of 8 \uG\ on the uniform field strength in this galaxy. We suggest that the diffuse synchrotron region, seen to the north of the main body of emission at 20cm, is elongated due to a uniform magnetic field with a maximum field strength of 7.6 \uG. We find that, while the shear in NGC 4214 is comparable to that of the Milky Way, the supernova rate is half that of the Milky Way and suggest that the star formation episode in NGC 4214 needs additional time to build up enough turbulence to drive an $\alpha-\omega$ dynamo.Comment: Accepted by ApJ. Version with high resolution figures at http://www.astro.virginia.edu/~aak8t/data/n4214/ms.pd

Associations Between Visceral Adipose Tissue Estimates Produced By Near-Infrared Spectroscopy, Mobile Anthropometrics, and Traditional Body Composition Assessments and Estimates Derived From Dual-Energy X-Ray Absorptiometry

Assessments of visceral adipose tissue (VAT) are critical in preventing metabolic disorders; however, there are limited measurement methods that are accurate and accessible for VAT. The purpose of this cross-sectional study was to evaluate the association between VAT estimates from consumer-grade devices and traditional anthropometrics and VAT and subcutaneous adipose tissue (SAT) from dual-energy X-ray absorptiometry (DXA). Data were collected from 182 participants (female = 114; White = 127; Black/African-American (BAA) = 48) which included anthropometrics and indices of VAT produced by near-infrared reactance spectroscopy (NIRS), visual body composition (VBC) and multifrequency BIA (MFBIA). VAT and SAT were collected using DXA. Bivariate and partial correlations were calculated between DXAVAT and DXASAT and other VAT estimates. All VAT indices had positive moderate–strong correlations with VAT (all P \u3c 0·001) and SAT (all P \u3c 0·001). Only waist:hip (r = 0·69), VATVBC (r = 0·84), and VATMFBIA (r = 0·86) had stronger associations with VAT than SAT (P \u3c 0·001). Partial associations between VATVBC and VATMFBIA were only stronger for VAT than SAT in White participants (r = 0·67, P \u3c 0·001) but not female, male, or BAA participants individually. Partial correlations for waist:hip were stronger for VAT than SAT, but only for male (r = 0·40, P \u3c 0·010) or White participants (r = 0·48, P \u3c 0·001). NIRS was amongst the weakest predictors of VAT which was highest in male participants (r = 0·39, P \u3c 0·010) but non-existent in BAA participants (r = –0·02, P \u3e 0·050) after adjusting for SAT. Both anthropometric and consumer-grade VAT indices are consistently better predictors of SAT than VAT. These data highlight the need for a standardised, but convenient, VAT estimation protocol that can account for the relationship between SAT and VAT that differs by sex/race

Testing the Evolutionary Sequence of High Mass Protostars with CARMA

We present 1" resolution CARMA observations of the 3mm continuum and 95 GHz methanol masers toward 14 candidate high mass protostellar objects (HMPOs). Dust continuum emission is detected toward seven HMPOs, and methanol masers toward 5 sources. The 3mm continuum sources have diameters < 2x10^4 AU, masses between 21 and 1200 M_sun, and volume densities > 10^8 cm^-3. Most of the 3mm continuum sources are spatially coincident with compact HII regions and/or water masers, and are presumed to be formation sites of massive stars. A strong correlation exists between the presence of 3mm continuum emission, 22 GHz water masers, and 95 GHz methanol masers. However, no 3mm continuum emission is detected toward ultracompact HII regions lacking maser emission. These results are consistent with the hypothesis that 22 GHz water masers and methanol masers are signposts of an early phase in the evolution of an HMPO before an expanding HII region destroys the accretion disk.Comment: accepted to Ap

Gas, Stars, and Star Formation in ALFALFA Dwarf Galaxies

We examine the global properties of the stellar and H I components of 229 low H_I mass dwarf galaxies extracted from the ALFALFA survey, including a complete sample of 176 galaxies with H_I masses <10^(7.7) M_☉ and H_I line widths <80 km s^(–1). Sloan Digital Sky Survey (SDSS) data are combined with photometric properties derived from Galaxy Evolution Explorer to derive stellar masses (M_*) and star formation rates (SFRs) by fitting their UV-optical spectral energy distributions (SEDs). In optical images, many of the ALFALFA dwarfs are faint and of low surface brightness; only 56% of those within the SDSS footprint have a counterpart in the SDSS spectroscopic survey. A large fraction of the dwarfs have high specific star formation rates (SSFRs), and estimates of their SFRs and M_* obtained by SED fitting are systematically smaller than ones derived via standard formulae assuming a constant SFR. The increased dispersion of the SSFR distribution at M_* ≲ 10^8 M_☉ is driven by a set of dwarf galaxies that have low gas fractions and SSFRs; some of these are dE/dSphs in the Virgo Cluster. The imposition of an upper H_I mass limit yields the selection of a sample with lower gas fractions for their M_* than found for the overall ALFALFA population. Many of the ALFALFA dwarfs, particularly the Virgo members, have H_I depletion timescales shorter than a Hubble time. An examination of the dwarf galaxies within the full ALFALFA population in the context of global star formation (SF) laws is consistent with the general assumptions that gas-rich galaxies have lower SF efficiencies than do optically selected populations and that H_I disks are more extended than stellar ones

Molecular gas in late-type galaxies

We present $^{12}$CO(J=1--0) line observations of 22 low-luminosity spiral galaxies in the Virgo cluster. These data, together with 244 others available in the literature, allow us to build a large sample that we use to study the molecular gas properties of galaxies spanning a large range of morphological types and luminosities and belonging to different environments (clusters - field). The molecular gas content of the target galaxies is estimated using a luminosity-dependent X = $N(H_2)/I(CO)$ conversion factor that has been calibrated on a sample of nearby galaxies. $X$ spans from $\sim$ 10$^{20}$ mol cm$^{-2}$ (K km s$^{-1})^{-1}$ in giant spirals to $\sim$ 10$^{21}$ mol cm$^{-2}$ (K km s$^{-1})^{-1}$ in dwarf irregulars. The value of the $X$ conversion factor is found consistent with a value derived independently from dust masses estimated from FIR fluxes, with a metallicity-dependent dust to gas ratio. The relationships between X and the UV radiation field (as traced by the $H\alpha+[NII] E.W.$), the metallicity and the H band luminosity are analysed. We show that the molecular gas contained in molecular clouds or complexes is of the order of 15% of the total gas on average whatever the luminosity or the Hubble type of the galaxies. We discuss the relation between the star formation rate and the molecular gas content and estimate the average star formation efficiency of late-type galaxies.Comment: accepted for publication on Astronomy and Astrophysic

Neutral Hydrogen and Optical Observations of Edge-on Galaxies: Hunting for Warps

We present 21-cm HI line and optical R-band observations for a sample of 26 edge-on galaxies. The HI observations were obtained with the Westerbork Synthesis Radio Telescope, and are part of the WHISP database (Westerbork HI Survey of Spiral and Irregular Galaxies). We present HI maps, optical images, and radial HI density profiles. We have also derived the rotation curves and studied the warping and lopsidedness of the HI disks. 20 out of the 26 galaxies of our sample are warped, confirming that warping of the HI disks is a very common phenomenon in disk galaxies. Indeed, we find that all galaxies that have an extended HI disk with respect to the optical are warped. The warping usually starts around the edge of the optical disk. The degree of warping varies considerably from galaxy to galaxy. Furthermore, many warps are asymmetric, as they show up in only one side of the disk or exhibit large differences in amplitude in the approaching and receding sides of the galaxy. These asymmetries are more pronounced in rich environments, which may indicate that tidal interactions are a source of warp asymmetry. A rich environment tends to produce larger warps as well. The presence of lopsidedness seems to be related to the presence of nearby companions.Comment: To appear in Astronomy & Astrophysic

Optical BVI Imaging and HI Synthesis Observations of the Dwarf Irregular Galaxy ESO 364-G 029

As part of an effort to enlarge the number of well-studied Magellanic-type galaxies, we obtained broadband optical imaging and neutral hydrogen radio synthesis observations of the dwarf irregular galaxy ESO 364-G 029. The optical morphology characteristically shows a bar-like main body with a one-sided spiral arm, an approximately exponential light distribution, and offset photometric and kinematic centers. The HI distribution is mildly asymmetric and, although slightly offset from the photometric center, roughly follows the optical brightness distribution, extending to over 1.2 Holmberg radii (where mu_B = 26.5 mag/arcsec^2). In particular, the highest HI column densities closely follow the bar, one-arm spiral, and a third optical extension. The rotation is solid-body in the inner parts but flattens outside of the optical extent. The total HI flux F_HI = 23.1 pm 1.2 Jy km/s, yielding a total HI mass M_HI= (6.4 pm 1.7) x 10^8 Msun (for a distance D = 10.8 pm 1.4 Mpc) and a total HI mass-to-blue-luminosity ratio M_HI/L_B = (0.96 pm 0.14) Msun / Lsun,B (distance independent). The HI data suggest a very complex small-scale HI structure, with evidence of large shells and/or holes, but deeper observations are required for a detailed study. Follow-up observations are also desirable for a proper comparison with the Large Magellanic Cloud, where despite an optical morphology very similar to ESO 364-G 029 the HI bears little resemblance to the optical.Comment: 10 pages, 11 figures, accepted by A&

The Stellar and Gaseous Contents of the Orion Dwarf Galaxy

We present new KPNO 0.9-m optical and VLA HI spectral line observations of the Orion dwarf galaxy. This nearby (D ~ 5.4 Mpc), intermediate-mass (M_dyn = 1.1x10^10 Solar masses) dwarf displays a wealth of structure in its neutral ISM, including three prominent "hole/depression" features in the inner HI disk. We explore the rich gas kinematics, where solid-body rotation dominates and the rotation curve is flat out to the observed edge of the HI disk (~6.8 kpc). The Orion dwarf contains a substantial fraction of dark matter throughout its disk: comparing the 4.7x10^8 Solar masses of detected neutral gas with estimates of the stellar mass from optical and near-infrared imaging (3.7x10^8 Solar masses) implies a mass-to-light ratio of ~13. New H alpha observations show only modest-strength current star formation (~0.04 Solar masses per year); this star formation rate is consistent with our 1.4 GHz radio continuum non-detection.Comment: Astronomical Journal, in press. Full-resolution version available from http://www.macalester.edu/~jcannon/pubs.htm