Stretching of BDT-gold molecular junctions: thiol or thiolate termination?

It is often assumed that the hydrogen atoms in the thiol groups of a benzene-1,4-dithiol dissociate when Au-benzene-1,4-dithiol-Au junctions are formed. We demonstrate, by stability and transport property calculations, that this assumption cannot be made. We show that the dissociative adsorption of methanethiol and benzene-1,4-dithiol molecules on a flat Au(111) surface is energetically unfavorable and that the activation barrier for this reaction is as high as 1 eV. For the molecule in the junction, our results show, for all electrode geometries studied, that the thiol junctions are energetically more stable than their thiolate counterparts. Due to the fact that density functional theory (DFT) within the local density approximation (LDA) underestimates the energy difference between the lowest unoccupied molecular orbital and the highest occupied molecular orbital by several electron-volts, and that it does not capture the renormalization of the energy levels due to the image charge effect, the conductance of the Au-benzene-1,4-dithiol-Au junctions is overestimated. After taking into account corrections due to image charge effects by means of constrained-DFT calculations and electrostatic classical models, we apply a scissor operator to correct the DFT energy level positions, and calculate the transport properties of the thiol and thiolate molecular junctions as a function of the electrode separation. For the thiol junctions, we show that the conductance decreases as the electrode separation increases, whereas the opposite trend is found for the thiolate junctions. Both behaviors have been observed in experiments, therefore pointing to the possible coexistence of both thiol and thiolate junctions. Moreover, the corrected conductance values, for both thiol and thiolate, are up to two orders of magnitude smaller than those calculated with DFT-LDA. This brings the theoretical results in quantitatively good agreement with experimental data.

Benefits of kinesiotherapy and aquatic rehabilitation on sickle cell anemia. A case report

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

A single bout of exercise with a flexible pole induces significant cardiac autonomic responses in healthy men

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Treatment of Dyslipidemia with Statins and Physical Exercises: Recent Findings of Skeletal Muscle Responses

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Electromyographic validation of the trapezius and serratus anterior muscles in military press exercises with open grip

It was studied the trapezius muscle and serratus anterior muscle in 24 male volunteers using a 2-channel TECA TE 4 electromyograph and Hewlett Packard surface electrodes, during the execution of four different modalities of military press exercises with open grip. The results showed that TS acted significantly in the modalities standing and sitting press behind neck, while SI acted in all the modalities, i.e., standing and sitting press behind neck and forward, justifying their inclusion as basic exercises for physical conditioning programmes.

Long duration exercise program in individuals with parkinson´s disease: effects on functional capacity

The aim of this study was to investigate the effects of long duration exercise program on physical fitness components of functional capacity in individuals with Parkinson disease (PD) and to evaluate ongoing effects of exercise after 8 to 10-week follow-up without exercise. Twenty-four individuals with PD were randomly assigned to two groups: generalized exercise program and stretching exercise program (control group). The generalized exercise program provided training in physical fitness components of functional capacity. The stretching exercise program was characterized by low intensity and volume, mainly with static exercises. Both groups were evaluated before (BI) and after the 4-month (AI) exercise program. In addition, the individuals of generalized exercise program were also evaluated after 8-month exercise program and after 8 to 10- week follow-up without exercise. The generalized exercise program improved flexibility (BI - 38.50±12.42 cm; AI - 44.00±12.74 cm) and agility (BI - 30.59±7.54 s; AI - 28.56±8.20 s) while the stretching exercise program worsened coordination (BI - 23.27±6.58 s; AI - 28.06±7.37 s) and aerobic resistance (BI- 13.64±3.76 min; AI - 17.27±5.15 min) and improved balance (BI - 44.00±7.79 pts; AI - 46.57±6.53 pts). Lower-limb strength and UPDRS-motor scale scores were better at 8 months (14.75±2.92 rep and 26.25±13.97 pts, respectively) compared to baseline (13.13±2.59 rep and 31.63±12.82 pts, respectively) and 4 months (13.50±1.93 rep and 30.38±14.52 pts, respectively) for generalized exercise program. However, the benefits of 8 months of exercise were lost after 8 to 10-week follow-up without exercise (lower-limb strength - 12.43±3.15 rep and UPDRS-motor scale - 32.57±14.05 pts). In conclusion, generalized exercise program improved the functional capacity in individuals with PD, differently of stretching exercise program. In addition, a long duration exercise program promoted benefits for functional capacity and disease progression in individuals with PD. However, benefits were lost after a short period without exercise.