White dwarfs are compact stars, similar in size to Earth but approximately 200,000 times more massive. Isolated white dwarfs emit most of their power from ultraviolet to near-infrared wavelengths, ...but when in close orbits with less dense stars, white dwarfs can strip material from their companions and the resulting mass transfer can generate atomic line and X-ray emission, as well as near- and mid-infrared radiation if the white dwarf is magnetic. However, even in binaries, white dwarfs are rarely detected at far-infrared or radio frequencies. Here we report the discovery of a white dwarf/cool star binary that emits from X-ray to radio wavelengths. The star, AR Scorpii (henceforth AR Sco), was classified in the early 1970s as a δ-Scuti star, a common variety of periodic variable star. Our observations reveal instead a 3.56-hour period close binary, pulsing in brightness on a period of 1.97 minutes. The pulses are so intense that AR Sco's optical flux can increase by a factor of four within 30 seconds, and they are also detectable at radio frequencies. They reflect the spin of a magnetic white dwarf, which we find to be slowing down on a 10
-year timescale. The spin-down power is an order of magnitude larger than that seen in electromagnetic radiation, which, together with an absence of obvious signs of accretion, suggests that AR Sco is primarily spin-powered. Although the pulsations are driven by the white dwarf's spin, they mainly originate from the cool star. AR Sco's broadband spectrum is characteristic of synchrotron radiation, requiring relativistic electrons. These must either originate from near the white dwarf or be generated in situ at the M star through direct interaction with the white dwarf's magnetosphere.
A novel, simple geometry for high throughput electrospinning from a bowl edge is presented that utilizes a vessel filled with a polymer solution and a concentric cylindrical collector. Successful ...fiber formation is presented for two different polymer systems with differing solution viscosity and solvent volatility. The process of jet initiation, resultant fiber morphology and fiber production rate are discussed for this unconfined feed approach. Under high voltage initiation, the jets spontaneously form directly on the fluid surface and rearrange along the circumference of the bowl to provide approximately equal spacing between spinning sites. Nanofibers currently produced from bowl electrospinning are identical in quality to those fabricated by traditional needle electrospinning (TNE) with a demonstrated ∼ 40 times increase in the production rate for a single batch of solution due primarily to the presence of many simultaneous jets. In the bowl electrospinning geometry, the electric field pattern and subsequent effective feed rate are very similar to those parameters found under optimized TNE experiments. Consequently, the electrospinning process per jet is directly analogous to that in TNE and thereby results in the same quality of nanofibers.
Metal nanoparticles incorporated at low concentration into epoxy systems enable in situ curing via photothermal heating. In the process of nanoparticle-mediated photothermal heating, light interacts ...specifically with particles embedded within a liquid or solid material and this energy is transformed into heat, resulting in significant temperature increase local to each particle with minimal warming of surroundings. The ability to use such internal heating to transform the mechanical properties of a material (e.g., from liquid to rigid solid) without application of damaging heat to the surrounding environment represents a powerful tool for a variety of scientific applications, particularly within the biomedical sector. Uniform particle dispersion is achieved by placing the nanoparticles within solvent miscible with the desired epoxy resin, demonstrating a strategy utilizable for a wide range of materials without requiring chemical modification of the particles or epoxy. Mechanical and thermal properties (storage modulus, Tg, and degradation behavior) of the cured epoxy are equivalent to those obtained under traditional heating methods. Selective curing of a shape is demonstrated within a liquid bath of epoxy, where the solid form is generated by rastering a spatially confined, photothermal-driving light beam. The non-irradiated regions are largely unaffected and the solid part is easily removed from the remaining liquid. Temperature profiles showing minimal heating outside the irradiated zone are presented and discussed.
Dramatically raising the conductivity of a polymer solution by using a salt additive allows control over the electric field-induced jet feed rate when electrospinning from an unconfined fluid without ...altering the applied voltage. As the solution conductivity increases, the flow rate drops by an order of magnitude. At a high voltage level and fluid conductivity value, the jets undergo a whipping instability over almost the entire path from the source to the collector experiencing only a negligibly short linear region which, along with the flow rate data, indicates that the jet narrows due to the high conductivity. Under these conditions, even while possessing relatively large individual jet feed rates, thin diameter nanofibers (200–300 nm) are readily produced. In contrast with other approaches to obtain narrow fibers from unconfined fluids (e.g., voltage reduction to control feed rate), here the fiber forming jets are present indefinitely. Continuous, scaled up nanofiber production rate of >125× over the traditional single needle electrospinning method is observed from the presence of multiple jets, each possessing a relatively high solution feed rate. These fundamental experiments reveal new pathways for exploring novel electrospinning configurations where the jet feed rate can be controlled by manipulating the solution conductivity.
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•Stable electrospinning when utilizing highly conductive solutions is demonstrated.•The jets exhibit a negligible linear region and a greatly enhanced whipping region.•High quality nanofibers are formed using unusually large jet solution feed rates.•In unconfined electrospinning, many parallel jets provide an enhanced fiber production rate.
The star 1SWASP J024743.37−251549.2 was recently discovered to be a binary star in which an A-type dwarf star eclipses the remnant of a disrupted red giant star (WASP 0247−25 B). The remnant is in a ...rarely observed state evolving to higher effective temperatures at nearly constant luminosity prior to becoming a very low mass white dwarf composed almost entirely of helium, i.e. it is a pre-helium white dwarf (pre-He-WD). We have used the photometric database from the Wide Angle Search for Planets (WASP) to find 17 eclipsing binary stars with orbital periods P = 0.7-2.2 d with similar light curves to 1SWASP J024743.37−251549.2. The only star in this group previously identified as a variable star is the brightest one, EL CVn, which we adopt as the prototype for this class of eclipsing binary star. The characteristic light curves of EL CVn-type stars show a total eclipse by an A-type dwarf star of a smaller, hotter star and a secondary eclipse of comparable depth to the primary eclipse. We have used new spectroscopic observations for six of these systems to confirm that the companions to the A-type stars in these binaries have very low masses (
). This includes the companion to EL CVn which was not previously known to be a pre-He-WD. EL CVn-type binary star systems will enable us to study the formation of very low mass white dwarfs in great detail, particularly in those cases where the pre-He-WD star shows non-radial pulsations similar to those recently discovered in WASP0247−25 B.
We report bunching, slowing, and acceleration of a supersonically cooled beam of diatomic hydroxyl radicals (OH). In situ observation of laser-induced fluorescence along the beam propagation path ...allows for detailed characterization of longitudinal phase-space manipulation of OH molecules through the Stark effect by precisely sequenced inhomogeneous electric fields.
We present high-speed, three-colour photometry of the eclipsing dwarf nova PHL 1445, which, with an orbital period of 76.3 min, lies just below the period minimum of ∼82 min for cataclysmic variable ...stars (CVs). Averaging four eclipses reveals resolved eclipses of the white dwarf and bright spot. We determined the system parameters by fitting a parametrized eclipse model to the averaged light curve. We obtain a mass ratio of q = 0.087 ± 0.006 and inclination i = 85
$_{.}^{\circ}$
2 ± 0
$_{.}^{\circ}$
9. The primary and donor masses were found to be M
w = 0.73 ± 0.03 M⊙ and M
d = 0.064 ± 0.005 M⊙, respectively. Through multicolour photometry a temperature of the white dwarf of T
w = 13 200 ± 700 K and a distance of 220 ± 50 pc were determined. The evolutionary state of PHL 1445 is uncertain. We are able to rule out a significantly evolved donor, but not one that is slightly evolved. Formation with a brown dwarf donor is plausible, though the brown dwarf would need to be no older than 600 Myr at the start of mass transfer, requiring an extremely low mass ratio (q = 0.025) progenitor system. PHL 1445 joins SDSS 1433 as a sub-period minimum CV with a substellar donor. The existence of two such systems raises an alternative possibility that current estimates for the intrinsic scatter and/or position of the period minimum may be in error.
OBJECTIVE
To test the hypothesis that an intracavernosal injection with brain‐derived neurotrophin factor (BDNF) and vascular endothelial growth factor (VEGF) can facilitate nerve regeneration and ...recovery of erectile function after cavernosal nerve injury.
MATERIALS AND METHODS
The study included 25 Sprague‐Dawley rats; four had a sham operation, seven bilateral nerve crushing with no further intervention, and 14 bilateral nerve crushing with either an immediate (seven) or delayed for 1 month (seven) intracavernosal injection with BDNF+VEGF. Erectile function was assessed by cavernosal nerve electrostimulation at 3 months, and neural regeneration by NADPH‐diaphorase staining and tyrosine hydroxylase (TH) staining of penile tissue and major pelvic ganglia (MPG).
RESULTS
After nerve crushing, the functional evaluation at 3 months showed a lower mean (sd) intracavernosal pressure (ICP) with cavernosal nerve stimulation, at 33.9 (15.3) cmH2O, than in the sham group, at 107.8 (18.1) cmH2O. With an immediate injection with BDNF+VEGF the ICP was significantly higher than in the controls, at 67.8 (38.5) cmH2O. Even delayed injection with BDNF+VEGF improved the ICP, to 78.0 (21.8) cmH2O. Histological analysis of specimens stained for NADPH and TH showed a significant change in the morphology of terminal branches of the cavernosal and dorsal nerves, and the staining quality of the neurones in the MPG. The number of positively stained nerve fibres tended to revert to normal after treatment with BDNF+VEGF.
CONCLUSION
An intracavernosal injection with BDNF+VEGF appears to both prevent degeneration and facilitate regeneration of neurones containing neuronal nitric oxide synthase in the MPG, dorsal nerve and intracavernosal tissue. Therefore it might have therapeutic potential for enhancing the recovery of erectile function after radical pelvic surgery.
We present three newly discovered sub-Jupiter mass planets from the SuperWASP survey: WASP-54b is a heavily bloated planet of mass 0.636+0.025-0.024MJ and radius 1.653+0.090-0.083RJ. It orbits a F9 ...star, evolving off the main sequence, every 3.69 days. Our MCMC fit of the system yields a slightly eccentric orbit (e = 0.067+0.033-0.025) for WASP-54b. We investigated further the veracity of our detection of the eccentric orbit for WASP-54b, and we find that it could be real. However, given the brightness of WASP-54 V = 10.42 mag, we encourage observations of a secondary eclipse to draw robust conclusions on both the orbital eccentricity and the thermal structure of the planet. WASP-56b and WASP-57b have masses of 0.571+0.034-0.035MJ and 0.672+0.049-0.046MJ, respectively; and radii of 1.092+0.035-0.033RJ for WASP-56b and 0.916+0.017-0.014RJ for WASP-57b. They orbit main sequence stars of spectral type G6 every 4.67 and 2.84 days, respectively. WASP-56b and WASP-57b show no radius anomaly and a high density possibly implying a large core of heavy elements; possibly as high as ~50 M⊕ in the case of WASP-57b. However,the composition of the deep interior of exoplanets remains still undetermined. Thus, more exoplanet discoveries such as the ones presented in this paper, are needed to understand and constrain giant planets’ physical properties.
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