Sequential photoisomerisation dynamics of the push-pull azobenzene Disperse Red 1

The ultrafast dynamics of the push-pull azobenzene Disperse Red 1 following photoexcitation at λ(pump) = 475 nm in solution in 2-fluorotoluene have been probed by broadband transient absorption spectroscopy and fluorescence up-conversion spectroscopy. The measured two-dimensional spectro-temporal absorption map features a remarkable "fast" excited-state absorption (ESA) band at λ ≈ 570 nm appearing directly with the excitation laser pulse and showing a sub-100 fs lifetime with a rapid spectral blue-shift. Moreover, its ultrafast decay is paralleled by rising distinctive ESA at other wavelengths. Global fits to the absorption-time profiles using a consecutive kinetic model yielded three time constants, τ(1) = 0.08 ± 0.03 ps, τ(2) = 0.99 ± 0.02 ps, and τ(3) = 6.0 ± 0.1 ps. Fluorescence-time profiles were biexponential with time constants τ(1)' = 0.12 ± 0.06 ps and τ(2)' = 0.70 ± 0.10 ps, close to the absorption results. Based on the temporal evolution of the transient spectra, especially the "fast" excited-state absorption band at λ ≈ 570 nm, and on the global kinetic analysis of the time profiles, τ(1) is assigned to an ultrafast transformation of the optically excited ππ* state to an intermediate state, which may be the nπ* state, τ(2) to the subsequent isomerisation and radiationless deactivation time to the S(0) electronic ground state, and τ(3) to the eventual vibrational cooling of the internally "hot" S(0) molecules.     

Incorporation of a high potential quinone reveals that electron transfer in Photosystem I becomes highly asymmetric at low temperature

Photosystem I (PS I) has two nearly identical branches of electron-transfer co-factors. Based on point mutation studies, there is general agreement that both branches are active at ambient temperature but that the majority of electron-transfer events occur in the A-branch. At low temperature, reversible electron transfer between P(700) and A(1A) occurs in the A-branch. However, it has been postulated that irreversible electron transfer from P(700) through A(1B) to the terminal iron-sulfur clusters F(A) and F(B) occurs via the B-branch. Thus, to study the directionality of electron transfer at low temperature, electron transfer to the iron-sulfur clusters must be blocked. Because the geometries of the donor-acceptor radical pairs formed by electron transfer in the A- and B-branch differ, they have different spin-polarized EPR spectra and echo-modulation decay curves. Hence, time-resolved, multiple-frequency EPR spectroscopy, both in the direct-detection and pulse mode, can be used to probe the use of the two branches if electron transfer to the iron-sulfur clusters is blocked. Here, we use the PS I variant from the menB deletion mutant strain of Synechocyctis sp. PCC 6803, which is unable to synthesize phylloquinone, to incorporate 2,3-dichloro-1,4-naphthoquinone (Cl(2)NQ) into the A(1A) and A(1B) binding sites. The reduction midpoint potential of Cl(2)NQ is approximately 400 mV more positive than that of phylloquinone and is unable to transfer electrons to the iron-sulfur clusters. In contrast to previous studies, in which the iron-sulfur clusters were chemically reduced and/or point mutations were used to prevent electron transfer past the quinones, we find no evidence for radical-pair formation in the B-branch. The implications of this result for the directionality of electron transfer in PS I are discussed.     

Removing ECG contamination from EMG recordings: a comparison of ICA-based and other filtering procedures

Trunk muscle electromyography (EMG) is often contaminated by the electrocardiogram (ECG), which hampers data analysis and potentially yields misinterpretations. We propose the use of independent component analysis (ICA) for removing ECG contamination and compared it with other procedures previously developed to decontaminate EMG. To mimic realistic contamination while having uncontaminated reference signals, we employed EMG recordings from peripheral muscles with different activation patterns and superimposed distinct ECG signals that were recorded during rest at conventional locations for trunk muscle EMG. ICA decomposition was performed with and without a separately collected ECG signal as part of the data set and contaminated ICA modes representing ECG were identified automatically. Root mean squared relative errors and correlations between the linear envelopes of uncontaminated and contaminated EMG were calculated to assess filtering effects on EMG amplitude. Changes in spectral content were quantified via mean power frequencies. ICA-based filtering largely preserved the EMG's spectral content. Performance on amplitude measures was especially successful when a separate ECG recording was included. That is, the ICA-based filtering can produce excellent results when EMG and ECG are indeed statistically independent and when mode selection is flexibly adjusted to the data set under study.     

Catapult effect in pole vaulting: Is muscle coordination determinant?

This study focused on the phase between the time of straightened pole and the maximum height (HP) of vaulter and aimed at determining the catapult effect in pole vaulting on HP. Seven experienced vaulters performed 5-10 vaults recorded by two video cameras, while the surface electromyography (sEMG) activity of 10 upper limbs muscles was recorded. HP was compared with an estimated maximum height (HP_est) allowing the computation of a push-off index. Muscle synergies were extracted from the sEMG activity profiles using a non-negative matrix factorization algorithm. No significant difference (p > 0.47) was found between HP_est (4.64 ± 0.21 m) and HP (4.69 ± 0.23 m). Despite a high inter-individual variability in sEMG profiles, two muscle synergies were extracted for all the subjects which accounted for 96.1 ± 2.9% of the total variance. While, the synergy activation coefficients were very similar across subjects, a higher variability was found in the muscle synergy vectors. Consequently, whatever the push-off index among the pole vaulters, the athletes used different muscle groupings (i.e., muscle synergy vectors) which were activated in a similar fashion (i.e., synergy activation coefficients). Overall, these results suggested that muscle coordination adopted between the time of straightened pole and the maximum height does not have a major influence on HP.     

Immunohistochemical localization of transforming growth factor β1 and β2 in mouse testes during postnatal development

We examined age-related changes in the expression of transforming growth factor-β(1) (TGF-β(1)) and transforming growth factor-β(2) in mouse testes. The mice were assigned to three age groups: 35, 50, and 75 days old. Paraffin embedded testis sections were processed for the standard streptavidin biotin peroxidase complex immunohistochemistry method. TGF-β(1) expression increased in aging round spermatids over the time studied. There was no expression in 35-day-old Leydig cells, whereas strong expression of TGF-β(1) was observed in 50-day-old Leydig cells. Expression decreased in 75-day-old Leydig cells. TGF-β(2) expression was weak in 35- and 50-day-old mouse spermatids, but expression was greater in 75-day-old elongated spermatids. In Leydig cells, TGF-β(2) expression was strong in both 35- and 50-day-old mice, whereas the expression of TGF-β(2) was less in 75-day-old Leydig cells. Our results suggest that TGF-β(1) and TGF-β(2) may play significant roles in testicular functions and germ cell development in mice.     

Effect of cervical spine position on upper limb myoelectric activity during pre-manipulative stretch for Mills manipulation: a new model, relations to peripheral nerve biomechanics and specificity of Mills manipulation

Objectives(A) Describe a new method of investigation of the possible muscular effects of the commonly practiced Mills manipulation for lateral elbow pain (epicondylalgia), (B) ascertain if myoelectric activity is influenced during the pre-manipulative stretch for Mills manipulation, (C) establish whether muscle responses are influenced by ipsilateral lateral flexion of the cervical spine which reduces mechanical tension in the peripheral nerves of the upper limb.SampleEight asymptomatic subjects were tested bilaterally (N = 16).MethodsMyoelectric measurements – EMG signals were recorded with a 16 channel pocket EMG patient unit and processed off-line. Measurement of joint positions-three CCD adjustable cameras sensitive to 10 mm reflective passive markers applied at specific locations on the subjects’ bodies were used to reconstruct and verify accuracy of body movements and were correlated with EMG recordings.ResultsCompared with the standard (anatomical) position of the cervical spine in which Mills manipulation is typically performed, cervical spine ipsilateral lateral flexion produced significantly reduced activity in muscles that restrain the manipulation movement (elbow extension), namely biceps brachii (P = 0.018) and brachioradialis (P = 0.000). The affected muscles may therefore produce protective effects during the manipulation.ConclusionsChanges in myoelectric activity were in a pattern that suggests that muscle and neural mechanisms may be an integral part of the Mills manipulation. Cervical spine ipsilateral lateral flexion may be used to reduce mechanical stresses in the peripheral nerves and extraneous muscle activity, making Mills’ manipulation potentially safer and more specific.     

Blood meal analysis, flavivirus screening, and influence of meteorological variables on the dynamics of potential mosquito vectors of West Nile virus in northern Italy

An extended area of northern Italy has experienced several West Nile virus (WNV) outbreaks and the emergence of Usutu virus (USUV) during previous years. Our aim was to study some of the factors that could explain disease patterns in the Trentino region, where circulation was detected in human sera and sentinel chickens, but no human or equine cases were reported. We collected Culex species (Diptera: Culicidae) in peridomestic environments. The collected specimens were analyzed for feeding behavior, the influence of temperature and rainfall on the abundance of mosquitoes, and the occurrence of flaviviruses. Analysis of blood meals showed that Culex pipiens fed mainly on blackbirds (Turdus merula) and house sparrows (Passer domesticus), while Culex hortensis fed strictly on lizards. The abundance of Cx. pipiens females correlated positively with mean temperature and negatively with rainfall (one to four weeks before capture). This negative relationship could be due to the direct effect of the flushing of habitats together with an indirect effect of oviposition repellency. The mean weekly temperature influenced the abundance of Cx. hortensis. No flaviviruses were detected in the analyzed Culex mosquitoes. These data suggest a silent cycle at low enzootic transmission levels in the area. Furthermore, we present the first contribution to understanding the transmission role of Cx. pipiens mosquitoes in Italy by identifying vertebrate hosts to species level.     

新疆赛里木湖国家湿地公园生态旅游资源综合评价

湿地生态旅游是要在保护的前提下对湿地进行合理利用, 因此开发湿地生态旅游对湿地保护具有重要的现实意义。通过对新疆赛里木湖的实地考察与资料收集, 确定湖泊湿地生态旅游资源评价指标, 采用层次分析法(AHP)对赛里木湖国家湿地公园生态旅游资源进行综合评价, 得分66.88 分。结果表明: 赛里木湖湿地生态旅游资源属三级旅游资源, 适宜加大旅游开发投入, 且生态环境与旅游资源价值是赛里木湖生态旅游发展的关键点。