RESUMO
A tissue equivalent proportional counter designed to measure the linear energy transfer spectra (LET) in the range 0.2-1250 keV/micrometer was flown in the Kvant module on the Mir orbital station during September 1994. The spacecraft was in a 51.65 degrees inclination, elliptical (390 x 402 km) orbit. This is nearly the lower limit of its flight altitude. The total absorbed dose rate measured was 411.3 +/- 4.41 microGy/day with an average quality factor of 2.44. The galactic cosmic radiation (GCR) dose rate was 133.6 microGy/day with a quality factor of 3.35. The trapped radiation belt dose rate was 277.7 microGy/day with an average quality factor of 1.94. The peak rate through the South Atlantic Anomaly was approximately 12 microGy/min and nearly constant from one pass to another. A detailed comparison of the measured LET spectra has been made with radiation transport models. The GCR results are in good agreement with model calculations; however, this is not the case for radiation belt particles and again points to the need for improving the AP8 omni-directional trapped proton models.
Assuntos
Radiação Cósmica , Transferência Linear de Energia , Modelos Teóricos , Prótons , Atividade Solar , Voo Espacial/instrumentação , Brasil , Nêutrons , Doses de Radiação , Monitoramento de Radiação/instrumentação , Radiometria/instrumentaçãoRESUMO
Measurements of the energy spectra of secondary particles produced by galactic cosmic rays and trapped protons due to the nuclear interactions of these particles with the Shuttle shielding provide a powerful tool for validating radiation transport codes. A code validated in this way can be used to better estimate the dose and dose equivalent to body organs, measurements that cannot be made directly. The principal cause of single event upsets in electronic devices in the region of the South Atlantic Anomaly is secondary particles, and even in the region of galactic cosmic radiation a significant fraction is produced by secondary particles. In this paper, we describe the first direct measurements of the energy spectra of secondary protons, deuterons, tritons, 3He and 4He produced by galactic cosmic rays inside the Space Shuttle using a charged particle spectrometer. A comparison of these spectra with radiation transport code HZETRN showed reasonably good agreement for secondary protons. However, the code seriously underestimated the flux of all other light ions. The code has been modified to include pick-up and knock-on processes. The modified code leads to good agreement for deuterons and 3He but not for other light ions. This revised code leads to about 10% higher dose equivalent than the original code under moderate shielding, if we assume that higher charge ion fluxes are correctly predicted by the model.
Assuntos
Radiação Cósmica , Interações de Partículas Elementares , Monitoramento de Radiação/instrumentação , Atividade Solar , Voo Espacial/instrumentação , Astronave/instrumentação , Oceano Atlântico , Deutério , Processamento Eletrônico de Dados , Desenho de Equipamento , Meio Ambiente Extraterreno , Hélio , Transferência Linear de Energia , Modelos Teóricos , Prótons , América do SulRESUMO
SSc is an autoimmune connective tissue disease in which strong HLA associations have not been described. Anti-topo I antibodies are recognized, in general, in SSc patients with diffuse cutaneous involvement, whereas anti-ACAs are found in individuals with limited cutaneous involvement. We studied 95 Caucasian SSc patients, 44 with anti-topo I antibodies and 51 with neither anti-topo I nor ACA, for HLA-DR associations by using DNA typing techniques. We analyzed 181 normal Caucasian individuals in the same fashion. A significant association was observed in the anti-topo-I-positive patients with DRw11 (p = 1.7 x 10(-6), RR 4.2). The distribution of DRw11 alleles in these patients was significantly different from that observed in controls and could be accounted for by an increase in the frequency of the DRB1*1104 allele (p = 1.2 x 10(-9), RR 9.5). The DRw11 alleles were also associated with SSc with more tendon friction rubs (p = 0.006), which is a marker of more severe disease. In addition, a strong association was observed with anti-topo I antibodies and a particular sequence (aa 71-77) of the DQB1 chain (p = 0.02, RR 2.2). HLA associations in the case of SSc patients with anti-topo I antibodies are complex and involve at least two genes: HLA-DRw11, which appears to play a major role in determining the severity of the disease, and a DQ sequence, which associates with the development of the anti-topo I antibodies.
Assuntos
Autoanticorpos/imunologia , DNA Topoisomerases Tipo I/imunologia , Antígenos HLA-DQ/genética , Antígenos HLA-DR/genética , Escleroderma Sistêmico/genética , Escleroderma Sistêmico/imunologia , Adulto , Alelos , Feminino , Frequência do Gene , Humanos , Masculino , Pessoa de Meia-IdadeRESUMO
Patients with allergic rhinitis (AR), compared with nonallergic persons, have been reported to respond differently to a variety of stimuli, some of which are immunologic in nature. This study compared the systemic cellular immune responses to experimental rhinovirus (RV) 39 challenge in RV-39-seronegative AR (n = 20) and nonallergic (n = 18) subjects. Peripheral blood was obtained before, 4 or 7 days after, and 23 days after RV-39 intranasal challenge and assayed for the number and function of various white blood cells. All subjects were infected, as manifested by viral shedding in nasal secretions or seroconversion. RV-39 induced marked changes from baseline values in both immune cell number and functions. Compared with nonallergic subjects, AR subjects manifested different responses for the following parameters: (1) numbers of total white blood cells and lymphocytes (smaller increases on day 4), (2) helper/suppressor T cell ratio (absence of an increase on day 7 and presence of an increase on day 23), (3) number of IL-2 receptor-positive suppressor T cells (presence of a decrease on day 7), (4) natural killer (NK) cell numbers (absence of an increase on day 4 and presence of increases on days 7 and 23), (5) NK/T cell ratio (absence of an increase on day 4 and a decrease on day 7), (6) NK cell activity (a blunted decrease on day 7 and absence of a decrease on day 23), and (7) RV-39-induced lymphocyte proliferation (exaggerated increase on day 4). The results show that intranasal challenge with RV-39 induced RV-39-specific and nonspecific systemic cellular immune responses and a unique immunologic response pattern in AR subjects.