Proton irradiation of plastic scintillator bars for POLAR-2

POLAR-2, a plastic scintillator based Compton polarimeter, is currently under development and planned for a launch to the China Space Station in 2025. It is intended to shed a new light on our understanding of Gamma-Ray Bursts by performing high precision polarization measurements of their prompt emission. The instrument will be orbiting at an average altitude of 383 km with an inclination of 42° and will be subject to background radiation from cosmic rays and solar events. In this work, we tested the performance of plastic scintillation bars, EJ-200 and EJ-248M from Eljen Technology, under space-like conditions, that were chosen as possible candidates for POLAR-2. Both scintillator types were irradiated with 58 MeV protons at several doses from 1.89 Gy(corresponding to about 13 years in space for POLAR-2) up to 18.7 Gy, that goes far beyond the expected POLAR-2 life time. Their respective properties, expressed in terms of light yield, emission and absorption spectra, and activation analysis due to proton irradiation are discussed. Scintillators activation analyses showed a dominant contribution of β + decay with a typical for this process gamma-ray energy line of 511 keV.

Proton irradiation of SiPM arrays for POLAR-2

POLAR-2 is a space-borne polarimeter, built to investigate the polarization of Gamma-Ray Bursts and help elucidate their mechanisms. The instrument is targeted for launch in 2024 or 2025 aboard the China Space Station and is being developed by a collaboration between institutes from Switzerland, Germany, Poland and China. The instrument will orbit at altitudes between 340km and 450km with an inclination of 42 ∘ and will be subjected to background radiation from cosmic rays and solar events. It is therefore pertinent to better understand the performance of sensitive devices under space-like conditions. In this paper we focus on the radiation damage of the silicon photomultiplier arrays S13361-6075NE-04 and S14161-6050HS-04 from Hamamatsu. The S13361 are irradiated with 58MeV protons at several doses up to 4.96Gy, whereas the newer series S14161 are irradiated at doses of 0.254Gy and 2.31Gy. Their respective performance degradation due to radiation damage are discussed. The equivalent exposure time in space for silicon photomultipliers inside POLAR-2 with a dose of 4.96Gy is 62.9years (or 1.78years when disregarding the shielding from the instrument). Primary characteristics of the I-V curves are an increase in the dark current and dark counts, mostly through cross-talk events. Annealing processes at 25 ∘ C were observed but not studied in further detail. Biasing channels while being irradiated have not resulted in any significant impact. Activation analyses showed a dominant contribution of β + particles around 511 keV. These resulted primarily from copper and carbon, mostly with decay times shorter than the orbital period.

Efficacy of venom immunotherapy in beekeepers

INTRODUCTION

We previously found that some beekeepers continue beekeeping even after experiencing systemic allergic reactions. The present study was performed to collect data on the experience of beekeepers who underwent desensitization and continued beekeeping. The results are important for future counseling in this group of patients, and they show the effectiveness of desensitization under real conditions.

METHODS

With the help of German and American beekeeping journals, we asked beekeepers who had undergone desensitization to participate. Data were obtained using a newly developed questionnaire and supplemented by reports obtained from the physicians who treated the allergy.

RESULTS

We sent a questionnaire to each of the 73 beekeepers who responded to our call, and 63 (86.3%) questionnaires were returned. The vast majority of participants were hobby beekeepers who developed signs of allergy after a median of 2 years' beekeeping (mean, 4.27 years) and a median of 15 stings (mean, 51 stings). Additional allergies were reported by 35 beekeepers. Forty-three beekeepers were evaluated to determine the effectiveness of desensitization. The average number of bee stings after desensitization was 107 (median 18). All but one reported no longer having allergic responses; however, in the case of those that did, the severity of the allergic symptoms improved significantly.

CONCLUSION

To our knowledge, this study is the first to provide data on the experience of beekeepers who continue their activity after desensitization. Our results show that desensitization can result in a complete absence of symptoms after re-exposure to bee stings.

Polarized photoacoustic, absorption and fluorescence spectra of chloroplasts and thylakoids oriented in polyvinyl alcohol films

The polarized photoacoustic, absorption and fluorescence spectra of chloroplasts and thylakoids in unstretched and stretched polyvinyl alcohol films were measured. The intensity ratios of fluorescence bands at 674 nm, 700 nm, 730 nm and 750 nm, and the polarized fluorescence excitation spectra are strongly dependent on light polarization and film stretching. In stretched films, thylakoids exhibit predominantly 674 nm emission. The ratio of photoacoustic signal to absorption is different for light polarized parallel and perpendicular to film stretching. This difference is large in the region of chlorophyll a and carotenoids absorption in which the fluorescence excitation spectra are also strongly dependent on light polarization and film stretching. The observed spectral changes are explained by reorientation of pigment molecules influencing the yield of excitation transfer between different pigments.

Changes in motor activity with age and the effects of pharmacologic treatment

In a previous study the decline in the motor performance of old rats was determined to be differential. In this study, whether, and to what extent, this decline can be pharmacologically influenced was tested. Therefore, 27 month old rats were orally treated with several nootropics and d-amphetamine for six weeks. Food and water intake were determined. The rats were tested on spontaneous activity and on the tilting plane, climbing, and rotarod tests. The results showed that the nootropics only effected pronounced improvements on complex motor tasks such as on the rotarod test. In contrast, amphetamine treatment caused rather negative effects. This could be observed in the motor performance as well as in the food and water intake. Young rats did not have this sort of reaction to amphetamine. The nootropics were all well tolerated. Additionally, it was obvious that the untreated rats also showed a slight improvement in motor performance due to repeated practice.

Inability to detect hepatitis B surface antigen (HBsAg) in the duodenum of HBsAg-positive persons

Incubation of hepatitis B surface antigen (HBsAg)-positive serum with duodenal fluid (DF) of normal persons results in marked reduction of immunoreactivity. This was shown to be caused by: (1) interference with radioimmunoassay (RIA) system and (2) actual destruction of HBsAg. The interference in the RIA system could be counteracted by addition of bovine serum and a reproducible detection system of HBsAg in DF was established. DF of HBsAg-positive persons was negative for HBsAg. One HBsAg carrier who had a partial pancreatectomy for an insulinoma had separate cannulae in his bile and pancreatic ducts. Whereas HBsAg could be detected in bile, it was undetectable in pancreatic juice. Incubation of his pancreatic juice with his bile resulted in disappearance of HBsAg. It appears that a factor present in pancreatic juice, or resulting from the interaction of pancreatic juice and bile, results in disappearance of HBsAg immunoreactivity.

Hepatitis non-A, non-B

Evidence for the existence of hepatitis non-A, non-B includes epidemiologic data and results of transmission studies indicating the presence of hepatitis that could not be explained by known causative agents. The diagnosis is suggested in patients who have multiple episodes of acute hepatitis or who contract hepatitis after transfusion, hemodialysis or drug abuse. Sporadic cases are common. Three such cases are described to illustrate that the disease is clinically indistinguishable from hepatitis A or B. The diagnosis is based on the absence of serologic markers of hepatitis A and B and of infection by Epstein-Barr virus and cytomegalovirus, or on serologic evidence of previous infection with hepatitis A and B.

Dichroism and polarized fluorescence of chlorophyll a, chlorophyll c and bacteriochlorophyll a dissolved in liquid crystals

Three photosynthetic pigments were studied: chlorophyll a, chlorophyll c and bacteriochlorcphyll a in nematic liquid crystal matrixes. The polarized absorption and fluorescence spectra as a function of the electric field have been measured. From the polarized components of the absorption A( parallel) and A( perpendicular) of the pigments in liquid crystals two reduced components A(x) and A(y) are calculated (x and y are the direction of the axis which is going through the second, fourth pyrrol rings, and the first, third rings, respectively). From these results the orientation of chlorophylls in liquid crystals and the configuration of the transition moments in the skeleton of the pigment molecules were determined.

Failure to detect hepatitis B surface antigen (HBsAg) in feces of HBsAg-positive persons

Since previous studies did not provide conclusive data regarding the presence of hepatitis B surface antigen (HBsAg) in the feces of HBsAg carriers, the feces of 20 HBsAg carriers and six patients with HBsAg-positive active liver disease were examined with use of a reproducible method for concentrating and detecting HBsAg in feces in which bovine serum, which has been shown to protect HBsAg destruction by fecal components, was added to the fecal specimens. HBsAg was not detected in 66 fecal specimens from the 26 HBs-Ag-positive persons. Furthermore, HBsAg could not be detected in the feces of a carrier who had ingested 4 ml of his own serum. This finding suggests that there are factors in the gastrointestinal tract that interfere with the immunoreactivity of the HBsAg and possibly destroy the hepatitis B virus. These findings explain why oral/fecal spread does not play a major role in the transmission of hepatitis B virus.

Hepatitis and hepatitis B surface antigen and antibody in dentists

Dentists were surveyed regarding a history of hepatitis and the presence in the blood of hepatitis B surface antigen (HBsAg) and antibody (anti-HBs) to determine whether they were at high risk of exposure to hepatitis B virus. Of 288 Canadian dentists 5.2% gave a history of hepatitis after graduation. This proportion is similar to that for 1462 Ontario dentists (6.3%) and that for 3162 accountants (5.1%) who had previously completed a mailed questionnaire. One dentist (0.3%) was HBsAg-positive and 42 (14.6%) were anti-HBs-positive. Of 210 healthy volunteer blood donors matched for age, sex and ethnic origin with the group of dentists none was HBsAg-positive and 2.9% significantly fewer (P less than 0.005), were anti-HBs-positive. Among Ontario blood donors 0.3% were HBsAg-positive and 3% were anti-HBs-positive. Thus, in Canada, dentists are not at increased risk of acquiring clinical hepatitis or becoming carriers, but they are more likely than other groups to have anti-HBs in the blood. Among dentists from outside Canada a higher proportion had a history of hepatitis (10.3%) and were HBsAg-positive (1.6%), but approximately the same proportion were anti-HBs-positive (15.9%).