ABSTRACT
The hydrogen (H) dimer structures formed upon room-temperature H adsorption on single layer graphene (SLG) grown on SiC(0001) are addressed using a combined theoretical-experimental approach. Our study includes density functional theory (DFT) calculations for the full (6â3 × 6â3)R30° unit cell of the SLG/SiC(0001) substrate and atomically resolved scanning tunneling microscopy images determining simultaneously the graphene lattice and the internal structure of the H adsorbates. We show that H atoms normally group in chemisorbed coupled structures of different sizes and orientations. We make an atomic scale determination of the most stable experimental geometries, the small dimers and ellipsoid-shaped features, and we assign them to hydrogen adsorbed in para dimers and ortho dimers configuration, respectively, through comparison with the theory.
Subject(s)
Graphite/chemistry , Hydrogen/chemistry , Quantum Theory , Dimerization , Microscopy, Scanning TunnelingABSTRACT
BACKGROUND: The study aimed to identify factors associated with the survival of patients receiving antiretroviral therapy. METHODS: A historic cohort of HIV patients from two major hospitals in Goma (Democratic Republic of Congo) was followed from 2004 to 2012. The Kaplan-Meier method was used to describe the probability of survival as a function of time since inclusion into the cohort. The log-rank test was used to compare survival curves based on determinants. The Cox regression model identified the determinants of survival since treatment induction. RESULTS: The median follow-up time was 3.56 years (IQR=2.22-5.39). The mortality rate was 40 deaths per 1000 person-years. Male gender (RR: 2.56; 95 %CI 1.66-4.83), advanced clinical stage (RR: 2.12; 95 %CI 1.15-3.90), low CD4 count (CD4 < 50) (RR: 2.05; 95 %CI : 1.22-3.45), anemia (RR: 3.95; 95 %CI 2.60-6.01), chemoprophylaxis with cotrimoxazole (RR: 4.29, 95 % CI 2.69-6.86) and period of treatment initiation (2010-2011) (RR: 3.34; 95 %CI 1.24-8.98) were statistically associated with short survival. CONCLUSION: Initiation of treatment at an early stage of the disease with use of less toxic molecules and an increased surveillance especially of male patients are recommended to reduce mortality.
Subject(s)
Antiretroviral Therapy, Highly Active , HIV Infections/drug therapy , HIV Infections/mortality , Adult , Antiretroviral Therapy, Highly Active/statistics & numerical data , Cohort Studies , Democratic Republic of the Congo/epidemiology , Epidemiologic Factors , Female , HIV-1 , Humans , Lost to Follow-Up , Male , Middle Aged , Survival RateABSTRACT
Friction between two objects can be understood by the making, stretching, and breaking of thousands of atomic-scale asperities. We have probed single atoms in a nonisotropic surface [the H-terminated Si(100) surface] with a lateral force microscope operating in noncontact mode. We show that these forces are measurably different, depending upon the direction. Experimentally, these differences are observable in both the line profiles and the maximum stiffnesses. Density functional theory calculations show a concerted motion of the whole Si dimer during the tip-sample interaction. These results demonstrate that on an asperity-by-asperity basis, the surface atomic structure plays a strong role in the directional dependence of friction.
ABSTRACT
AIM: Polymorphisms in uncoupling protein (UCP) genes have been strongly associated with energy expenditure and obesity. This study aimed at investigating the effects of UCP gene polymorphisms (UCP1 -3826A/G, UCP2A/V, UCP2 I/D, and UCP3 -55C/T) on change in body mass index (BMI) during a lifestyle modification program in Japanese subjects. RESULTS: Intervention induced a significant decrease in energy intake (-8.6% ± 17.0%) and a significant increase in energy expenditure (7.7% ± 7.4%). As a result, participants experienced a significant decrease in their BMI of -1.8% ± 2.7%. In a multivariate regression analysis, only UCP2 D/I among the selected UCP gene polymorphisms was associated with a change in BMI independent of the effects of gender, age, baseline BMI, changes in energy intake, and expenditure. Further regression analysis revealed that, in contrast to the DD genotype group, the DI+II genotype group showed no significant association between weight loss and change in energy expenditure suggesting this polymorphism altered the effects of this parameter on change in BMI. CONCLUSION: The study found UCP2 D/I to be associated with change in BMI by altering the effect of change in energy expenditure on change in BMI.
