Solution of the kinetic equations governing trap filling. Consequences concerning dose dependence and dose-rate effects

The equations governing the traffic of charge carriers during the filling, by ionizing radiation, of traps and luminescence centers in an insulator are numerically solved. The numerical solution is that of a set of four simultaneous differential equations governing the time-dependent functions of concentrations of electrons and holes in the conduction and valence bands and in traps and centers. The results are more general and accurate than those reported previously since no assumptions concerning the proximity to equilibrium have to be made. Moreover, all previous calculations took into account the accumulated concentrations at the end of the irradiation, whereas we have considered an additional period of time after the excitation which allows for the relaxation of carriers in the bands. This simulates the experimental conditions more accurately because during this time any charge carriers which may have accumulated in the conduction and valence bands will relax into the traps and centers and, in doing so, will contribute to the final concentration of trapped charge. In our calculations we have allowed for this by letting the charge in the bands decay for a period of time T following the cessation of the irradiation (which occurs at time t). Thus, the level of trapped charge n is calculated at time t+ T and this is taken to be a better representation of the trapped charge density. Results were obtained for very high and very low dose rates (intensities) of the radiation. Experimental findings of the dose dependence of thermoluminescence (TL) are susceptible to analysis by the approach developed by us. By adding a competing trapping level and changing the set of equations appropriately, we get a set of five simultaneous differential equations. In this way we can test the previous approximative results yielding a superlinear filling of one of the traps. It is found that, under an appropriate choice of parameters, superlinearity emerges, although the results are not identical to those of the previous approximations. In addition, an important result to emerge from the analysis is the possible dependence of TL output on the dose rate for a constant total dose. Recent experimental results of such a dependence on TL in quartz are shown to be in general accord with the numerical results.Peer reviewedPhysic

A VLT spectroscopic study of the ultracompact HII region G29.96-0.02

A high quality, medium-resolution K-band spectrum has been obtained of the ultracompact HII region G29.96-0.02 with the Very Large Telescope (VLT). The slit was positioned along the symmetry axis of the cometary shaped nebula. Besides the spectrum of the embedded ionizing O star, the long-slit observation revealed the rich emission-line spectrum produced by the ionized nebula with sub-arcsec spatial resolution. The nebular spectrum includes Br$\gamma$, several helium emission lines and a molecular hydrogen line. A detailed analysis is presented of the variation in strength, velocity and width of the nebular emission lines along the slit. The results are consistent with previous observations, but the much better spatial resolution allows a critical evaluation of models explaining the cometary shape of the nebula. Our observations support neither the wind bow shock model nor the champagne flow model. The measured line ratios of the nebular hydrogen and helium lines are compared to predictions from case B recombination-line theory. The results indicate an electron temperature between 6400 and 7500 K, in good agreement with other determinations and the Galactocentric distance of 4.6 kpc. The He$^{+}$/H$^{+}$ ratio is practically constant over the slit; we argue that He is singly ionized throughout the nebula. We review the various observational constraints on the effective temperature of the ionizing star and show that these are in agreement with its K-band spectral type of O5-O6V.Comment: 15 pages including 11 figures and 2 tables, LaTex, A&A style. Accepted for publication in A&

Prevalence of human papillomavirus infection in women in Benin, West Africa

<p>Abstract</p> <p>Background</p> <p>Cervical cancer ranks as the first most frequent cancer among women in Benin. The major cause of cervical cancer now recognized is persistent infection of Human Papillomavirus (HPV). In Benin there is a lack of screening programs for prevention of cervical cancer and little information exists regarding HPV genotype distribution.</p> <p>Methods</p> <p>Cervical cells from 725 women were examined for the presence of viral DNA by means of a polymerase chain reaction (PCR) multiplex-based assay with the amplification of a fragment of L1 region and of E6/E7 region of the HPV genome, and of abnormal cytology by Papanicolaou method. The association between HPV status and Pap test reports was evaluated. Socio-demographic and reproductive characteristics were also related.</p> <p>Results</p> <p>A total of 18 different HPV types were identified, with a prevalence of 33.2% overall, and 52% and 26.7% among women with and without cervical lesions, respectively. Multiple HPV infections were observed in 40.2% of HPV-infected women. In the HPV-testing group, the odds ratio for the detection of abnormal cytology was 2.98 (95% CI, 1.83-4.84) for HPV positive in comparison to HPV negative women. High risk types were involved in 88% of infections, most notably HPV-59, HPV-35, HPV-16, HPV-18, HPV-58 and HPV-45. In multiple infections of women with cytological abnormalities HPV-45 predominated.</p> <p>Conclusions</p> <p>This study provides the first estimates of the prevalence of HPV and type-specific distribution among women from Benin and demonstrates that the epidemiology of HPV infection in Benin is different from that of other world regions. Specific area vaccinations may be needed to prevent cervical cancer and the other HPV-related diseases.</p

Measurement of isotopic separation of argon with the prototype of the cryogenic distillation plant Aria for dark matter searches

The Aria cryogenic distillation plant, located in Sardinia, Italy, is a key component of the DarkSide-20k experimental program for WIMP dark matter searches at the INFN Laboratori Nazionali del Gran Sasso, Italy. Aria is designed to purify the argon, extracted from underground wells in Colorado, USA, and used as the DarkSide-20k target material, to detector-grade quality. In this paper, we report the first measurement of argon isotopic separation by distillation with the 26&nbsp;m tall Aria prototype. We discuss the measurement of the operating parameters of the column and the observation of the simultaneous separation of the three stable argon isotopes: 36Ar , 38Ar , and 40Ar . We also provide a detailed comparison of the experimental results with commercial process simulation software. This measurement of isotopic separation of argon is a significant achievement for the project, building on the success of the initial demonstration of isotopic separation of nitrogen using the same equipment in 2019

Diurnal variation of semen quality in human males.

The possibility of a diurnal variation in semen quality was tested in 54 human males attending our infertility clinic. Of the enrolled subjects, 24 were normozoospermic and 30 were suffering from oligo- and/or asthenozoospermia. Seminal fluid was collected by masturbation twice by each subject, once in the morning (7:00-7:30 a.m.) and once in the afternoon (5:00-5:30 p.m.). Abstinence from sexual intercourse for 3-4 days before each of the two collections was requested. Semen parameters were evaluated independently by two biologists before and after pellet swim-up. Beside similar macroscopic parameters, specimens collected in the afternoon showed a higher number (P < 0.01) and concentration (P < 0.01) of spermatozoa. Also, immediately (P < 0.05), and at 1 h (P < 0.02) and 2 h (P < 0.01) after pellet swim-up, the number of spermatozoa with progressive linear motility was higher in the afternoon than in the morning. These data are the first documenting a diurnal rhythm in sperm quality which may contribute to the reported variability in semen parameters, and may prove useful for spontaneous and assisted conceptions