RESUMO
We investigate the effect of inter-mode coupling on the vibrational relaxation dynamics of molecules in weak dissipative environments. The simulations are performed within the reduced density matrix formalism in the Markovian regime, assuming a Lindblad form for the system-bath interaction. The prototypical two-dimensional model system representing two CO molecules approaching a Cu(100) surface is adapted from an ab initio potential, while the diatom-diatom vibrational coupling strength is systematically varied. In the weak system-bath coupling limit and at low temperatures, only first order non-adiabatic uni-modal coupling terms contribute to surface-mediated vibrational relaxation. Since dissipative dynamics is non-unitary, the choice of representation will affect the evolution of the reduced density matrix. Two alternative representations for computing the relaxation rates and the associated operators are thus compared: the fully coupled spectral basis, and a factorizable ansatz. The former is well-established and serves as a benchmark for the solution of Liouville-von Neumann equation. In the latter, a contracted grid basis of potential-optimized discrete variable representation is tailored to incorporate most of the inter-mode coupling, while the Lindblad operators are represented as tensor products of one-dimensional operators, for consistency. This procedure results in a marked reduction of the grid size and in a much more advantageous scaling of the computational cost with respect to the increase of the dimensionality of the system. The factorizable method is found to provide an accurate description of the dissipative quantum dynamics of the model system, specifically of the time evolution of the state populations and of the probability density distribution of the molecular wave packet. The influence of intra-molecular vibrational energy redistribution appears to be properly taken into account by the new model on the whole range of coupling strengths. It demontrates that most of the mode mixing during relaxation is due to the potential part of the Hamiltonian and not to the coupling among relaxation operators.
RESUMO
Recent studies from several groups have indicated that abnormal or ectopic expression and function of adrenal receptors for various hormones may regulate cortisol production in ACTH-independent hypercortisolism. Gastric inhibitory polypeptide (GIP)-dependent Cushing's syndrome has been described in patients with either unilateral adenoma or bilateral macronodular adrenal hyperplasia; this syndrome results from the large adrenal overexpression of the GIP receptor without any activating mutation. We have conducted a systematic in vivo evaluation of patients with adrenal Cushing's syndrome in order to identify the presence of abnormal hormone receptors. In macronodular adrenal hyperplasia, we have identified, in addition to GIP-dependent Cushing's syndrome, other patients in whom cortisol production was regulated abnormally by vasopressin, ss-adrenergic receptor agonists, hCG/LH, or serotonin 5HT-4 receptor agonists. In patients with unilateral adrenal adenoma, the abnormal expression or function of GIP or vasopressin receptor has been found, but the presence of ectopic or abnormal hormone receptors appears to be less prevalent than in macronodular adrenal hyperplasia. The identification of the presence of an abnormal adrenal receptor offers the possibility of a new pharmacological approach to control hypercortisolism by suppressing the endogenous ligands or by using specific antagonists for the abnormal receptors.
Assuntos
Síndrome de Cushing/metabolismo , Hidrocortisona/metabolismo , Receptores de Superfície Celular/sangue , Hormônio Adrenocorticotrópico/metabolismo , Hormônio Adrenocorticotrópico/fisiologia , Catecolaminas/sangue , Catecolaminas/metabolismo , Catecolaminas/fisiologia , Síndrome de Cushing/tratamento farmacológico , Síndrome de Cushing/etiologia , Feminino , Polipeptídeo Inibidor Gástrico/sangue , Polipeptídeo Inibidor Gástrico/metabolismo , Polipeptídeo Inibidor Gástrico/fisiologia , Humanos , Masculino , Gravidez , Vasopressinas/sangue , Vasopressinas/metabolismo , Vasopressinas/fisiologiaRESUMO
The objectives of the study were to determine knowledge levels regarding AIDS and its modes of transmission, and to describe sexual behaviour of Montrealers of Haitian origin. A serial cross-sectional study was conducted in three phases between 1987 and 1990. A questionnaire was administered in a face-to-face interview with the exception of the section concerning sexual practices which was self-administered for those respondents who were literate in French. The study was conducted among 775 men and women residing in the metropolitan Montreal region. These individuals were aged 15 to 39, were born in Haiti or had at least one parent born in Haiti. Knowledge levels were high except for misconceptions about HIV transmission through casual contact and mosquito bites. There was a significant association between high risk sexual behaviour and marital status with the odds of having had multiple partners significantly raised for previously married individuals (OR = 5.96, 95% CI = 3.09; 11.50). High risk behaviour was also associated with being under 25 years of age (OR = 2.83, 95% CI = 1.40; 5.74), knowing someone with HIV/AIDS (OR = 1.88, 95% CI = 1.05; 3.37), being male (OR = 6.81, 95% CI = 3.99; 11.60) and earlier year of interview. Montrealers of Haitian origin, with their specific AIDS-related socio-cultural characteristics, constitute a community which is intermediate between their country of origin, Haiti, and their host country, Canada.
Assuntos
Síndrome da Imunodeficiência Adquirida/psicologia , Etnicidade , Conhecimentos, Atitudes e Prática em Saúde , Síndrome da Imunodeficiência Adquirida/transmissão , Adolescente , Adulto , Intervalos de Confiança , Estudos Transversais , Demografia , Emigração e Imigração , Feminino , Haiti/etnologia , Humanos , Masculino , Razão de Chances , Quebeque , Comportamento Sexual/etnologia , Parceiros Sexuais , Inquéritos e QuestionáriosRESUMO
To determine attitudes and beliefs related to AIDS among the population of metropolitan Montreal of Haitian origin, we conducted serial cross-sectional surveys between 1987 and 1990 among a random sample of 777 men and women aged 15 to 39. Data on perceived risk of AIDS and attitudes towards HIV testing were collected in home settings using a combination of face-to-face structured interviews and a self-administered questionnaire. Multivariate analysis was conducted to determine predictors of attitudes towards people with HIV. The fear of being infected with HIV is great in this population. The social representation of illness in this community is very much influenced by religious beliefs. Scores for the five-item scale suggest only moderately favourable attitudes towards persons with HIV compared to Montrealers in general. Attitudes towards persons with AIDS were positively associated with years of schooling and a higher perceived risk of getting infected (p < or = 0.01).
Assuntos
Síndrome da Imunodeficiência Adquirida/prevenção & controle , Conhecimentos, Atitudes e Prática em Saúde , Síndrome da Imunodeficiência Adquirida/epidemiologia , Síndrome da Imunodeficiência Adquirida/transmissão , Adolescente , Adulto , Estudos Transversais , Escolaridade , Medo , Feminino , Haiti/etnologia , Humanos , Masculino , Análise Multivariada , Quebeque/epidemiologia , Distribuição Aleatória , Religião e Psicologia , Projetos de Pesquisa , Fatores de Risco , Percepção SocialRESUMO
In Montreal the acquired immune deficiency syndrome (AIDS) was seen in eight Haitian immigrants and one Caucasian woman who had lived with Haitian immigrants for 3 years before the onset of her illness. AIDS was characterized by opportunistic infections alone in seven patients, by opportunistic infection and Kaposi's sarcoma in one patient and by chronic generalized lymphadenopathy in one patient. Five of the patients had presented with Mycobacterium tuberculosis infections 1 to 12 months before the onset of opportunistic infections. All nine patients were found to have recall anergy by skin testing for delayed hypersensitivity. Enumeration of the lymphocyte subpopulations in three patients showed a marked inversion of the ratio of helper to suppressor T lymphocytes. Six of the patients died as a result of the opportunistic infections; autopsies showed no recognizable causes of immunodeficiency. Thus, there is in Montreal a third clustering of AIDS cases in North America related to Haitian immigrants.