Eletrização de dielétricos: novas propostas para resolver velhos problemas

Electrostatic phenomena were discovered long ago but their interpretation according to well-established atomic-molecular theory is still lacking. As a result, electrostatic phenomena are often irreproducible and uncontrolled, causing serious practical problems. Highly reproducible recent experimental results on electrostatic charging from this and other laboratories are reviewed in this work, together with a description of the relevant but not so usual Kelvin probe and Faraday cup techniques. These results support a new model for electrostatic charging of dielectrics and insulated metals, based on the role of moist atmosphere as a charge reservoir.

Hábitos e costumes de mulheres universitárias quanto ao uso de roupas íntimas, adornos genitais, depilação e práticas sexuais

OBJETIVO: Descrever as práticas e cuidados com a área genital de mulheres universitárias. MÉTODOS: Estudo analítico descritivo, que analisou os hábitos e costumes de 364 estudantes de uma universidade pública do Estado de São Paulo quanto ao uso de roupas íntimas, piercings corporais, tatuagens, depilação e práticas sexuais. Um questionário com 42 perguntas avaliou as práticas habituais mais comuns das universitárias. Todas as perguntas foram autorrespondidas e os questionários, sem qualquer identificação, foram colocados em urnas lacradas para garantir o sigilo das informações. As respostas foram tabuladas em planilha Microsoft® Excel 2007 para obtenção de análise univariável. RESULTADOS: A média de idade das universitárias estudadas foi de 21 anos (DP±2,7), sendo 84% brancas. Participaram do estudo voluntárias das áreas de biológicas (50%), exatas (29%) e humanas (21%). Observou-se que 61,8% das entrevistadas usam calcinhas de algodão, porém, ao mesmo tempo, 75,4% usam calças jeans apertadas, e que somente 18,4% deixam de usar calcinha para dormir. Apenas uma participante relatou ter piercing genital e nenhuma tinha tatuagem. A maioria das universitárias faz depilação genital, sendo que aproximadamente um terço delas o faz de forma completa. Após depilar, dois terços usam produtos como anti-inflamatórios e/ou hidratantes na região. Apenas 62% usam camisinha masculina e 17,6% lubrificante na relação sexual. Metade pratica sexo oral receptor; 17,9% sexo anal e 26,6% delas relatam ter dor no ato sexual. Corrimento vaginal foi relatado após a relação sexual em 25,6% dos casos. CONCLUSÃO:Mulheres jovens de universidade pública brasileira têm muitos hábitos inadequados de cuidados relacionados à sua área genital. Não costumam usar piercings ou tatuagens genitais, mas relatam ter dor no ato sexual e corrimento vaginal após o sexo em um grande número de casos.

Partially folded intermediates during trypsinogen denaturation

The equilibrium unfolding of bovine trypsinogen was studied by circular dichroism, differential spectra and size exclusion HPLC. The change in free energy of denaturation was = 6.99 ± 1.40 kcal/mol for guanidine hydrochloride and = 6.37 ± 0.57 kcal/mol for urea. Satisfactory fits of equilibrium unfolding transitions required a three-state model involving an intermediate in addition to the native and unfolded forms. Size exclusion HPLC allowed the detection of an intermediate population of trypsinogen whose Stokes radii varied from 24.1 ± 0.4 Å to 26.0 ± 0.3 Å for 1.5 M and 2.5 M guanidine hydrochloride, respectively. During urea denaturation, the range of Stokes radii varied from 23.9 ± 0.3 Å to 25.7 ± 0.6 Å for 4.0 M and 6.0 M urea, respectively. Maximal intrinsic fluorescence was observed at about 3.8 M urea with 8-aniline-1-naphthalene sulfonate (ANS) binding. These experimental data indicate that the unfolding of bovine trypsinogen is not a simple transition and suggest that the equilibrium intermediate population comprises one intermediate that may be characterized as a molten globule. To obtain further insight by studying intermediates representing different stages of unfolding, we hope to gain a better understanding of the complex interrelations between protein conformation and energetics.

Breathing disorders in congestive heart failure: gender, etiology and mortality

We investigated the relationship between sleep-disordered breathing (SDB) and Cheyne-Stokes respiration (CSR) while awake as well as mortality. Eighty-nine consecutive outpatients (29 females) with congestive heart failure (CHF; left ventricular ejection fraction, LVEF <45%) were prospectively evaluated. The presence of SDB and of CSR while awake before sleep onset was investigated by polysomnography. SDB prevalence was 81 and 56%, using apnea-hypopnea index cutoffs >5 and >15, respectively. CHF etiologies were similar according to the prevalence of SDB and sleep pattern. Males and females were similar in age, body mass index, and LVEF. Males presented more SDB (P = 0.01), higher apnea-hypopnea index (P = 0.04), more light sleep (stages 1 and 2; P < 0.05), and less deep sleep (P < 0.001) than females. During follow-up (25 ± 10 months), 27% of the population died. Non-survivors had lower LVEF (P = 0.01), worse New York Heart Association (NYHA) functional classification (P = 0.03), and higher CSR while awake (P < 0.001) than survivors. As determined by Cox proportional model, NYHA class IV (RR = 3.95, 95%CI = 1.37-11.38, P = 0.011) and CSR while awake with a marginal significance (RR = 2.96, 95%CI = 0.94-9.33, P = 0.064) were associated with mortality. In conclusion, the prevalence of SDB and sleep pattern of patients with Chagas' disease were similar to that of patients with CHF due to other etiologies. Males presented more frequent and more severe SDB and worse sleep quality than females. The presence of CSR while awake, but not during sleep, may be associated with a poor prognosis in patients with CHF.

Rheological behavior of corn and soy mix as feed ingredients

Foods behave as non-Newtonian fluids, but little is known about how corn and soybean mix behave under viscometric flow. In order to characterize the rheological behavior of animal feed under viscometric flow, a 70:30 (mass:mass) mixture of ground corn and soybean grains was submitted to a capillary rheometer at 3 different temperatures (80, 120, and 160 °C), different moisture levels (26.5 ± 0.08; 30.4 ± 0.31, and 33.4 ± 0.05%), and 4 shear rates (30.4; 72.9; 304.3, and 728.6/second). Different strain rates and die dimensions were used to obtain the target shear rates. The resulting data were fitted to Power Law, Casson, and Bingham models. Based on experimental data, water content, mass temperature, and the effects of shear rate on the apparent shear viscosity of corn-soy mix were fitted to a single expression (p < 0.001, R² = 0.93): η = 18,769.7 (y)-0.86 e (-9.34 U + 935 T), where y is shear rate, U is sample moisture, and T is sample temperature in Kelvin scale. As expected, such mixture presented a pseudoplastic (shear-thinning) behavior.