Comparative photophysical investigation of oxygen and sulfur as covalent linkers on octaalkylamino substituted zinc(II) phthalocyanines.

This work describes a systematic comparison of oxygen and sulfur as covalent linkers on octasubstituted zinc(II) phthalocyaninates. Most photophysical parameters that make phthalocyanines technologically relevant, e.g. molar absorption coefficients, fluorescence, triplet and singlet oxygen quantum yields, are essentially unaffected by the substitution. The energy content of the first triplet state was observed to be close to the first singlet state of molecular oxygen for both spacers, as follows from photoacoustic determinations. Nonetheless, a bathochromic shift of 30 nm in the absorption and emission maxima, and of 60 nm in the triplet-triplet absorption spectra were observed when alkyloxyl and alkylsulfanyl moieties were alternatively present. Fluorescence quantum yields proved to be much more sensitive towards aggregation than the absorption spectra. Therefore, a novel fluorescence data analysis provided aggregation parameters and photophysical properties of the monomeric species. It was observed that the tendency towards dimerization is slightly higher with sulfur linkers. These results set a foundation for the rational design of conveniently substituted phthalocyaninates with different connectors between the macrocycle and the side chains.     

Biomechanical analysis of the three-dimensional foot structure during gait: a basic tool for clinical applications

A novel three-dimensional numerical model of the foot, incorporating, for the first time in the literature, realistic geometric and material properties of both skeletal and soft tissue components of the foot, was developed for biomechanical analysis of its structural behavior during gait. A system of experimental methods, integrating the optical Contact Pressure Display (CPD) method for plantar pressure measurements and a Digital Radiographic Fluoroscopy (DRF) instrument for acquisition of skeletal motion during gait, was also developed in this study and subsequently used to build the foot model and validate its predictions. Using a Finite Element solver, the stress distribution within the foot structure was obtained and regions of elevated stresses for six subphases of the stance (initial-contact, heel-strike, midstance, forefoot-contact, push-off, and toe-off) were located. For each of these subphases, the model was adapted according to the corresponding fluoroscopic data, skeletal dynamics, and active muscle force loading. Validation of the stress state was achieved by comparing model predictions of contact stress distribution with respective CPD measurements. The presently developed measurement and numerical analysis tools open new approaches for clinical applications, from simulation of the development mechanisms of common foot disorders to pre- and post-interventional evaluation of their treatment.     

Effects of stimuli shape and polarization in evoking deimatic patterns in the European cuttlefish, Sepia officinalis, under varying turbidity conditions

Cuttlefish possess the complex ability to identify approaching threats and then to selectively express the appropriate defense. We examined the visual cues used by Sepia officinalis cuttlefish during predator detection and the responses they selected. Using computer-generated stimuli, we set out to quantitate the deimatic responses to artificial looming stimuli of different shapes and contrasts. Defensive behavior gradually intensified as geometrical shapes resembled an image of a fish. Therefore, in addition to an object’s size or its sudden increase in size, cuttlefish use form recognition to identify a threat. Cuttlefish demonstrated equal performance in predator detection trough clear water when presented with intensity versus polarization contrasts. However, when the water turbidity increased, the cuttlefish still detected looming fish shapes based on polarization contrast even when intensity information alone did not suffice. These results demonstrate the interplay between intensity and polarization information transmission and processing in the spatial domain. As nectobenthic organisms, cuttlefish probably experience low visibility conditions on a regular basis. The ability to see further into turbid water and to better detect an approaching object would be beneficial for their survival.     

Effect of Sodium Alginate on Staphylococcus aureus During Mild Heating and Freezing

The effects of sodium alginate on Staphyiococcus aureus 196 exposed to mild heating or to freezing at -21 C were studied. The addition of sodium alginate to a diluent appeared to confer some protection of viable cells during mild heating. The effect of the presence of sodium alginate in the suspending media during freezing was less clear. There was a slight trend, not statistically significant, for greater reduction in numbers of viable cells at the low temperature when 4% alginate was present in phosphate buffer. Results indicated that the value of sodium alginate in controlling this food-poisoning microorganism in frozen food is questionable.     

Molecular understanding of sterically controlled compound release through an engineered channel protein (FhuA)

Background  

Recently we reported a nanocontainer based reduction triggered release system through an engineered transmembrane channel (FhuA Δ1-160; Onaca et al., 2008). Compound fluxes within the FhuA Δ1-160 channel protein are controlled sterically through labeled lysine residues (label: 3-(2-pyridyldithio)propionic-acid-N-hydroxysuccinimide-ester). Quantifying the sterical contribution of each labeled lysine would open up an opportunity for designing compound specific drug release systems.     

Repeated assessments of informed consent comprehension among HIV-infected participants of a three-year clinical trial in Botswana

Background

Informed consent (IC) has been an international standard for decades for the ethical conduct of clinical trials. Yet frequently study participants have incomplete understanding of key issues, a problem exacerbated by language barriers or lack of familiarity with research concepts. Few investigators measure participant comprehension of IC, while even fewer conduct interim assessments once a trial is underway.

Methods and Findings

We assessed comprehension of IC using a 20-question true/false quiz administered in 6-month intervals in the context of a placebo-controlled, randomized trial for the prevention of tuberculosis among HIV-infected adults in Botswana (2004–2009). Quizzes were offered in both Setswana and English. To enroll in the TB trial, participants were required to have ≥16/20 correct responses. We examined concepts understood and the degree to which understanding changed over three-years. We analyzed 5,555 quizzes from 1,835 participants. The participants'' highest education levels were: 28% primary, 59% secondary, 9% tertiary and 7% no formal education. Eighty percent of participants passed the enrollment quiz (Quiz1) on their first attempt and the remainder passed on their second attempt. Those having higher than primary education and those who took the quiz in English were more likely to receive a passing score on their first attempt (adjusted odds ratios and 95% confidence intervals, 3.1 (2.4–4.0) and 1.5 (1.2, 1.9), respectively). The trial''s purpose or procedures were understood by 90–100% of participants, while 44–77% understood randomization, placebos, or risks. Participants who failed Quiz1 on their initial attempt were more likely to fail quizzes later in the trial. Pass rates improved with quiz re-administration in subsequent years.

Conclusions

Administration of a comprehension quiz at enrollment and during follow-up was feasible in a large, international collaboration and efficiently determined IC comprehension by trial participants. Strategies to improve understanding of concepts like placebos and randomization are needed. Comprehension assessments throughout a study may reinforce key concepts.     

Proteomic studies of diauxic lag in the differentiating prokaryote Streptomyces coelicolor reveal a regulatory network of stress-induced proteins and central metabolic enzymes

Bacteria typically undergo intermittent periods of starvation and adaptation, emulated as diauxic growth in the laboratory. In association with growth arrest elicited by metabolic stress, the differentiating eubacterium Streptomyces coelicolor not only adapts its primary metabolism, but can also activate developmental programmes leading to morphogenesis and antibiotic biosynthesis. Here, we report combined proteomic and metabolomic data of S. coelicolor used to analyse global changes in gene expression during diauxic growth in a defined liquid medium. Cultures initially grew on glutamate, providing the nitrogen source and feeding carbon (as 2-oxoglutarate) into the TCA cycle, followed by a diauxic delay allowing reorientation of metabolism and a second round of growth supported by NH4+, formed during prediauxic phase, and maltose, a glycolytic substrate. Cultures finally entered stationary phase as a result of nitrogen starvation. These four physiological states had previously been defined statistically by their distinct patterns of protein synthesis and heat shock responses. Together, these data demonstrated that the rates of synthesis of heat shock proteins are determined not only by temperature increase but also by the patterns and rates of metabolic flux in certain pathways. Synthesis profiles for metabolic- and stress-induced proteins can now be interpreted by the identification of 204 spots (SWICZ database presented at http://proteom.biomed.cas.cz). Cluster analysis showed that the activity of central metabolic enzymes involved in glycolysis, the TCA cycle, starvation or proteolysis each displayed identifiable patterns of synthesis that logically underlie the metabolic state of the culture. Diauxic lag was accompanied by a structured regulatory programme involving the sequential activation of heat-, salt-, cold- and bacteriostatic antibiotic (pristinamycin I, PI)-induced stimulons. Although stress stimulons presumably provide protection during environmental- or starvation-induced stress, their identities did not reveal any coherent adaptive or developmental functions. These studies revealed interactive regulation of metabolic and stress response systems including some proteins known to support developmental programmes in S. coelicolor.     

Modeling the human body/seat system in a vibration environment

The vibration environment is a common man-made artificial surrounding with which humans have a limited tolerance to cope due to their body dynamics. This research studied the dynamic characteristics of a seated human body/seat system in a vibration environment. The main result is a multi degrees of freedom lumped parameter model that synthesizes two basic dynamics: (i) global human dynamics, the apparent mass phenomenon, including a systematic set of the model parameters for simulating various conditions like body posture, backrest, footrest, muscle tension, and vibration directions, and (ii) the local human dynamics, represented by the human pelvis/vibrating seat contact, using a cushioning interface. The model and its selected parameters successfully described the main effects of the apparent mass phenomenon compared to experimental data documented in the literature. The model provided an analytical tool for human body dynamics research. It also enabled a primary tool for seat and cushioning design. The model was further used to develop design guidelines for a composite cushion using the principle of quasi-uniform body/seat contact force distribution. In terms of evenly distributing the contact forces, the best result for the different materials and cushion geometries simulated in the current study was achieved using a two layer shaped geometry cushion built from three materials. Combining the geometry and the mechanical characteristics of a structure under large deformation into a lumped parameter model enables successful analysis of the human/seat interface system and provides practical results for body protection in dynamic environment.