An HI interstellar bubble surrounding WR85 and RCW118

We analyze the distribution of the interstellar matter in the environs of the Wolf-Rayet star LSS3982 (= WR85, WN6+OB?) linked to the optical ring nebula RCW118. Our study is based on neutral hydrogen 21cm-line data belonging to the Southern Galactic Plane Survey (SGPS). The analysis of the HI data allowed the identification of a neutral hydrogen interstellar bubble related to WR 85 and the 25' diameter ring nebula RCW118. The HI bubble was detected at a systemic velocity of -21.5 km/s, corresponding to a kinematical distance of 2.8+/-1.1 kpc, compatible with the stellar distance. The neutral stucture is about 25' in radius or 21+/-8 pc, and is expanding at 9+/-2 km/s. The associated ionized and neutral masses amount to 3000 Mo. The CO emission distribution depicts a region lacking CO coincident in position and velocity with the HI structure. The 9'.3 diameter inner optical nebula appears to be related to the approaching part of the neutral atomic shell. The HI void and shell are the neutral gas counterparts of the optical bubble and have very probably originated in the action of the strong stellar wind of the central star during the O-type and WR phases on the surrounding interstellar medium. The HI bubble appears to be in the momentun conserving stage.Comment: 9 pages, 7 figures, accepted in MNRA

Exact charged black-hole solutions in D-dimensional f(T) gravity: torsion vs curvature analysis

We extract exact charged black-hole solutions with flat transverse sections in the framework of D-dimensional Maxwell-f(T) gravity, and we analyze the singularities and horizons based on both torsion and curvature invariants. Interestingly enough, we find that in some particular solution subclasses there appear more singularities in the curvature scalars than in the torsion ones. This difference disappears in the uncharged case, or in the case where f(T) gravity becomes the usual linear-in-T teleparallel gravity, that is General Relativity. Curvature and torsion invariants behave very differently when matter fields are present, and thus f(R) gravity and f(T) gravity exhibit different features and cannot be directly re-casted each other.Comment: 24 pages, 3 figures. arXiv admin note: text overlap with arXiv:1110.402

DBI equations and holographic DC conductivity

We provide a simple method for writing the Dirac-Born-Infeld (DBI) equations of a Dp-brane in an arbitrary static background whose metric depends only on the holographic radial coordinate z. Using this method we revisit the Karch-O'Bannon's procedure to calculate the DC conductivity in the presence of constant electric and magnetic fields for backgrounds where the boundary is four or three dimensional and satisfies homogeneity and isotropy. We find a frame-independent expression for the DC conductivity tensor. For particular backgrounds we recover previous results on holographic metals and strange metals.Comment: 1+21 pages; v2 : references added, minor typos correcte

Source amplitudes for active exterior cloaking

The active cloak comprises a discrete set of multipole sources that destructively interfere with an incident time harmonic scalar wave to produce zero total field over a finite spatial region. For a given number of sources and their positions in two dimensions it is shown that the multipole amplitudes can be expressed as infinite sums of the coefficients of the incident wave decomposed into regular Bessel functions. The field generated by the active sources vanishes in the infinite region exterior to a set of circles defined by the relative positions of the sources. The results provide a direct solution to the inverse problem of determining the source amplitudes. They also define a broad class of non-radiating discrete sources.Comment: 21 pages, 17 figure

Menstrual Phase Symptoms and Perceived Musculoskeletal Strength and Flexibility Among NCAA Collegiate Athletes

Previous findings suggest that the associations among menstrual hormones, symptoms and human performance are inconsistent and lacking. Earlier research has measured hormonal fluctuations and symptoms from each of the four menstrual phases (menstrual, follicular, ovulation, and luteal), but their physiological effects on perceived musculoskeletal strength and perceived flexibility remain unclear, particularly among college athletes. PURPOSE: To measure the prevalence and associations among self-reported menstrual symptoms, perceived overall strength and perceived flexibility in NCAA female athletes during each of the four menstrual phases. METHODS: In the Fall of 2020, a survey consisting of demographic questions and questions of perceived strength, flexibility, and menstrual symptoms was emailed to 99 female athletes at a NCAA Division III University. RESULTS: Twenty-five participants (M age= 19.76 years, SD= 1.01 years) representing 6 NCAA sports (softball N=11, volleyball N=5, soccer N=4, basketball N=2, cross country/track & field N=2, and tennis N=1) voluntarily responded. Eighty-eight percent of participants reported suffering from premenstrual and/or menstrual symptoms that included cramps, headaches, bloating, mood swings, back pain, cravings, decrease in physical activity, and breast aches. Most participants (56%) reported feeling the weakest during the menstruation phase, and only 29% felt no difference in strength throughout the phases. Less than half of participants (44%) felt the least amount of flexibility in the menstruation phase, but most participants (52%) reported no difference for flexibility throughout the phases. Further, bivariate analyses suggested statistical significance between the presence of premenstrual and/or menstrual symptoms and self-reported strength (r=.478, p=.018). CONCLUSION: Results suggest that perceived strength and flexibility can vary among the four menstrual phases and that the presence of symptoms and self-reported strength are correlated. Clinicians, trainers and coaches could consider symptom treatments, injury prevention programs, timing of competitions and appropriate strength training techniques to address perceived strength fluctuations among their female athletes

Word Length Perturbations in Certain Symmetric Presentations of Dihedral Groups

Given a finite group with a generating subset there is a well-established notion of length for a group element given in terms of its minimal length expression as a product of elements from the generating set. Recently, certain quantities called $\lambda_{1}$ and $\lambda_{2}$ have been defined that allow for a precise measure of how stable a group is under certain types of small perturbations in the generating expressions for the elements of the group. These quantities provide a means to measure differences among all possible paths in a Cayley graph for a group, establish a group theoretic analog for the notion of stability in nonlinear dynamical systems, and play an important role in the application of groups to computational genomics. In this paper, we further expose the fundamental properties of $\lambda_{1}$ and $\lambda_{2}$ by establishing their bounds when the underlying group is a dihedral group. An essential step in our approach is to completely characterize so-called symmetric presentations of the dihedral groups, providing insight into the manner in which $\lambda_{1}$ and $\lambda_{2}$ interact with finite group presentations. This is of interest independent of the study of the quantities $\lambda_{1},\; \lambda_{2}$. Finally, we discuss several conjectures and open questions for future consideration

Effects of lattice distortion and Jahn–Teller coupling on the magnetoresistance of La0.7Ca0.3MnO3 and La0.5Ca0.5CoO3 epitaxial films

Studies of La0.7Ca0.3MnO3 epitaxial films on substrates with a range of lattice constants reveal two dominant contributions to the occurrence of colossal negative magnetoresistance (CMR) in these manganites: at high temperatures (T → TC, TC being the Curie temperature), the magnetotransport properties are predominantly determined by the conduction of lattice polarons, while at low temperatures (T ≪ TC/, the residual negative magnetoresistance is correlated with the substrate-induced lattice distortion which incurs excess magnetic domain wall scattering. The importance of lattice polaron conduction associated with the presence of Jahn–Teller coupling in the manganites is further verified by comparing the manganites with epitaxial films of another ferromagnetic perovskite, La0.5Ca0.5CoO3. Regardless of the differences in the substrate-induced lattice distortion, the cobaltite films exhibit much smaller negative magnetoresistance, which may be attributed to the absence of Jahn–Teller coupling and the high electron mobility that prevents the formation of lattice polarons. We therefore suggest that lattice polaron conduction associated with the Jahn–Teller coupling is essential for the occurrence of CMR, and that lattice distortion further enhances the CMR effects in the manganites

870 micron continuum observations of the bubble-shaped nebula Gum 31

We are presenting here a study of the cold dust in the infrared ring nebula Gum 31. We aim at deriving the physical properties of the molecular gas and dust associated with the nebula, and investigating its correlation with the star formation in the region, that was probably triggered by the expansion of the ionization front. We use 870 micron data obtained with LABOCA to map the dust emission. The obtained LABOCA image was compared to archival IR,radio continuum, and optical images. The 870 micron emission follows the 8 micron (Spitzer), 250 micron, and 500 micron (Herschel) emission distributions showing the classical morphology of a spherical shell. We use the 870 micron and 250 micron images to identify 60 dust clumps in the collected layers of molecular gas using the Gaussclumps algorithm. The clumps have effective deconvolved radii between 0.16 pc and 1.35 pc, masses between 70 Mo and 2800 Mo, and volume densities between 1.1x10^3 cm^-3 and 2.04x10^5 cm^-3. The total mass of the clumps is 37600 Mo. The dust temperature of the clumps is in the range from 21 K to 32 K, while inside the HII region reaches ~ 40 K. The clump mass distribution is well-fitted by a power law dN/dlog(M/Mo) proportional to M^(-alpha), with alpha=0.93+/-0.28. The slope differs from those obtained for the stellar IMF in the solar neighborhood, suggesting that the clumps are not direct progenitors of single stars/protostars. The mass-radius relationship for the 41 clumps detected in the 870 microns emission shows that only 37% of them lie in or above the high-mass star formation threshold, most of them having candidate YSOs projected inside. A comparison of the dynamical age of the HII region with the fragmentation time, allowed us to conclude that the collect and collapse mechanism may be important for the star formation at the edge of Gum 31, although other processes may also be acting.Comment: 15 pages, 10 figures. Accepted for publication in A&