Determination of Local Experimental Heat-Transfer Coefficients on Combustion Side of an Ammonia-Oxygen Rocket

Local experimental heat-transfer coefficients were measured in the chamber and throat of a 2400-pound-thrust ammonia-oxygen rocket engine with a nominal chamber pressure of 600 pounds per square inch absolute. Three injector configurations were used. The rocket engine was run over a range of oxidant-fuel ratio and chamber pressure. The injector that achieved the best performance also produced the highest rates of heat flux at design conditions. The heat-transfer data from the best-performing injector agreed well with the simplified equation developed by Bartz at the throat region. A large spread of data was observed for the chamber. This spread was attributed generally to the variations of combustion processes. The spread was least evident, however, with the best-performing injector

Heat flux measurements on ceramics with thin film thermocouples

Two methods were devised to measure heat flux through a thick ceramic using thin film thermocouples. The thermocouples were deposited on the front and back face of a flat ceramic substrate. The heat flux was applied to the front surface of the ceramic using an arc lamp Heat Flux Calibration Facility. Silicon nitride and mullite ceramics were used; two thicknesses of each material was tested, with ceramic temperatures to 1500 C. Heat flux ranged from 0.05-2.5 MW/m2(sup 2). One method for heat flux determination used an approximation technique to calculate instantaneous values of heat flux vs time; the other method used an extrapolation technique to determine the steady state heat flux from a record of transient data. Neither method measures heat flux in real time but the techniques may easily be adapted for quasi-real time measurement. In cases where a significant portion of the transient heat flux data is available, the calculated transient heat flux is seen to approach the extrapolated steady state heat flux value as expected

Photodynamic inactivation of SARS-CoV-2 infectivity and antiviral treatment effects in vitro

Despite available vaccines, antibodies and antiviral agents, the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) pandemic still continues to cause severe disease and death. Current treatment options are limited, and emerging new mutations are a challenge. Thus, novel treatments and measures for prevention of viral infections are urgently required. Photodynamic inactivation (PDI) is a potential treatment for infections by a broad variety of critical pathogens, including viruses. We explored the infectiousness of clinical SARS-CoV-2 isolates in Vero cell cultures after PDI-treatment, using the photosensitizer Tetrahydroporphyrin-tetratosylate (THPTS) and near-infrared light. Replication of viral RNA (qPCR), viral cytopathic effects (microscopy) and mitochondrial activity were assessed. PDI of virus suspension with 1 µM THPTS before infection resulted in a reduction of detectable viral RNA by 3 log levels at day 3 and 6 after infection to similar levels as in previously heat-inactivated virions (<99.9%; p < 0.05). Mitochondrial activity, which was significantly reduced by viral infection, was markedly increased by PDI to levels similar to uninfected cell cultures. When applying THPTS-based PDI after infection, a single treatment had a virus load-reducing effect only at a higher concentration (3 µM) and reduced cell viability in terms of PDI-induced toxicity. Repeated PDI with 0.3 µM THPTS every 4 h for 3 d after infection reduced the viral load by more than 99.9% (p < 0.05), while cell viability was maintained. Our data demonstrate that THPTS-based antiviral PDI might constitute a promising approach for inactivation of SARS-CoV-2. Further testing will demonstrate if THPTS is also suitable to reduce the viral load in vivo

Search for variations in circular-polarization spectra of the magnetic white dwarf LP790-29

We present highly time resolved circular-polarization and flux spectra of the magnetic white dwarf LP790-29 taken with the VLT UT1 in order to test the hypothesis that LP790-29 is a fast rotator with a period of the order of seconds to minutes. Due to low time resolution of former observations this might have been overlooked -- leading to the conclusion that LP790-29 has a rotational period of over 100 years. The optical spectrum exhibits one prominent absorption feature with minima at about 4500, 4950, and 5350 A, which are most likely C2 Swan-bands shifted by about 180 A in a magnetic field between 50MG and 200MG. At the position of the absorption structures the degree of circular polarization varies between -1% and +1%, whereas it amounts to +8 to +10% in the blue and red continuum. With this very high degree of polarization lp790-29 is very well suited to a search for short time variations, since a variation of several percent in the polarization can be expected for a magnetic field oblique to the rotational axis. From our analysis we conclude that variations on time scales from 50 to 2500 seconds must have amplitudes <0.7% in the continuum and <2% in the strongest absorption feature at 4950A. While no short-term variations could be found a careful comparison of our polarization data of LP790-29 with those in the literatures indicates significant variations on time scales of decades with a possible period of about 24-28 years.Comment: 5 pages, 4 figures. Astronomy and Astrophysics, in pres

A Hot DQ White Dwarf in the Open Star Cluster M35

We report the discovery of a hot DQ white dwarf, NGC 2168:LAWDS 28, that is a likely member of the 150-Myr old cluster NGC 2168 (Messier 35). The spectrum of the white dwarf is dominated by CII features. The effective temperature is difficult to estimate but likely > 20,000 K based on the temperatures of hot DQs with similar spectra. NGC2168:LAWDS 28 provides further evidence that hot DQs may be the ``missing'' high-mass helium-atmosphere white dwarfs. Based on published studies, we find that the DBA WD LP 475-242 is likely a member of the Hyades open cluster, as often assumed. These two white dwarfs are the entire sample of known He-atmosphere white dwarfs in open clusters with turnoff masses >2 solar masses. Based on the number of known cluster DA white dwarfs and a redetermination of the H-atmosphere:He-atmosphere ratio, commonly known as the DA:DB ratio, we re-examine the hypothesis that the H- to He-atmosphere ratio in open clusters is the same as the ratio in the field. Under this hypothesis, we calculate that five He-atmosphere WDs are expected to have been discovered, with a probability of finding fewer than three He-atmosphere white dwarfs of 0.08, or at the ~ 2-sigma level.Comment: 9 pages with 2 figures, uses LaTeX/AASTeX 5.2. Accepted for publications in ApJ Letter

An Initial Survey of White Dwarfs in the Sloan Digital Sky Survey

An initial assessment is made of white dwarf and hot subdwarf stars observed in the Sloan Digital Sky Survey. In a small area of sky (190 square degrees), observed much like the full survey will be, 269 white dwarfs and 56 hot subdwarfs are identified spectroscopically where only 44 white dwarfs and 5 hot subdwarfs were known previously. Most are ordinary DA (hydrogen atmosphere) and DB (helium) types. In addition, in the full survey to date, a number of WDs have been found with uncommon spectral types. Among these are blue DQ stars displaying lines of atomic carbon; red DQ stars showing molecular bands of C_2 with a wide variety of strengths; DZ stars where Ca and occasionally Mg, Na, and/or Fe lines are detected; and magnetic WDs with a wide range of magnetic field strengths in DA, DB, DQ, and (probably) DZ spectral types. Photometry alone allows identification of stars hotter than 12000 K, and the density of these stars for 15<g<20 is found to be ~2.2 deg^{-2} at Galactic latitudes 29-62 deg. Spectra are obtained for roughly half of these hot stars. The spectra show that, for 15<g<17, 40% of hot stars are WDs and the fraction of WDs rises to ~90% at g=20. The remainder are hot sdB and sdO stars.Comment: Accepted for AJ; 43 pages, including 12 figures and 5 table

Unrelated Helpers in a Primitively Eusocial Wasp: Is Helping Tailored Towards Direct Fitness?

The paper wasp Polistes dominulus is unique among the social insects in that nearly one-third of co-foundresses are completely unrelated to the dominant individual whose offspring they help to rear and yet reproductive skew is high. These unrelated subordinates stand to gain direct fitness through nest inheritance, raising the question of whether their behaviour is adaptively tailored towards maximizing inheritance prospects. Unusually, in this species, a wealth of theory and empirical data allows us to predict how unrelated subordinates should behave. Based on these predictions, here we compare helping in subordinates that are unrelated or related to the dominant wasp across an extensive range of field-based behavioural contexts. We find no differences in foraging effort, defense behaviour, aggression or inheritance rank between unrelated helpers and their related counterparts. Our study provides no evidence, across a number of behavioural scenarios, that the behaviour of unrelated subordinates is adaptively modified to promote direct fitness interests

Hepatic abscess in a pre-existed simple hepatic cyst as a late complication of sigmoid colon ruptured diverticula: a case report

<p>Abstract</p> <p>Introduction</p> <p>Hepatic abscesses have been reported as a rare complication of diverticulitis of the bowel. This complication is recognized more commonly at the time of the diagnosis of diverticulitis, or ruptured diverticula, but also can be diagnosed prior to surgery, or postoperatively.</p> <p>Case presentation</p> <p>This report describes a man who developed an hepatic abscess within a simple hepatic cyst, two months after operation for ruptured diverticula of the sigmoid colon. The abscess was drained surgically and the patient made a complete recovery.</p> <p>Conclusion</p> <p>The development of an hepatic abscess in a pre-existing hepatic cyst, secondary to diverticulitis, is a rare complication. A high degree of clinical suspicion is required for immediate diagnosis and treatment.</p

Performance assessment of time-domain optical brain imagers, part 1: basic instrumental performance protocol

open21siAbstract.  Performance assessment of instruments devised for clinical applications is of key importance for validation and quality assurance. Two new protocols were developed and applied to facilitate the design and optimization of instruments for time-domain optical brain imaging within the European project nEUROPt. Here, we present the “Basic Instrumental Performance” protocol for direct measurement of relevant characteristics. Two tests are discussed in detail. First, the responsivity of the detection system is a measure of the overall efficiency to detect light emerging from tissue. For the related test, dedicated solid slab phantoms were developed and quantitatively spectrally characterized to provide sources of known radiance with nearly Lambertian angular characteristics. The responsivity of four time-domain optical brain imagers was found to be of the order of 0.1  m2 sr. The relevance of the responsivity measure is demonstrated by simulations of diffuse reflectance as a function of source-detector separation and optical properties. Second, the temporal instrument response function (IRF) is a critically important factor in determining the performance of time-domain systems. Measurements of the IRF for various instruments were combined with simulations to illustrate the impact of the width and shape of the IRF on contrast for a deep absorption change mimicking brain activation.H. Wabnitz; D. R. Taubert; M. Mazurenka; O. Steinkellner; A. Jelzow;R. Macdonald;D. Milej;P. Sawosz;M. Kacprzak;A. Liebert;R. Cooper;J. Hebden;A. Pifferi;A. Farina;I. Bargigia;D. Contini;M. Caffini;L. Zucchelli;L. Spinelli;R. Cubeddu;A. TorricelliH., Wabnitz; D. R., Taubert; M., Mazurenka; O., Steinkellner; A., Jelzow; R., Macdonald; D., Milej; P., Sawosz; M., Kacprzak; A., Liebert; R., Cooper; J., Hebden; Pifferi, ANTONIO GIOVANNI; Farina, Andrea; Bargigia, Ilaria; Contini, Davide; Caffini, Matteo; Zucchelli, LUCIA MARIA GRAZIA; Spinelli, Lorenzo; Cubeddu, Rinaldo; Torricelli, Alessandr