Cytoskeletal remodelling and slow dynamics in the living cell

The cytoskeleton (CSK) is a crowded network of structural proteins that stabilizes cell shape and drives cell motions. Recent studies on the dynamics of the CSK have established that a wide variety of cell types exhibit rheology in which responses are not tied to any particular relaxation times and are thus scale-free. Scale-free rheology is often found in a class of materials called soft glasses, but not all materials expressing scale-free rheology are glassy (see plastics, wood, concrete or some metals for example). As such, the extent to which dynamics of the CSK might be regarded as glassy remained an open question. Here we report both forced and spontaneous motions of microbeads tightly bound to the CSK of human muscle cells. Large oscillatory shear fluidized the CSK matrix, which was followed by slow scale-free recovery of rheological properties (aging). Spontaneous bead motions were subdiffusive at short times but superdiffusive at longer times; intermittent motions reflecting nanoscale CSK rearrangements depended on both the approach to kinetic arrest and energy release due to ATP hydrolysis. Aging, intermittency, and approach to kinetic arrest establish a striking analogy between the behaviour of the living CSK and that of inert non-equilibrium systems, including soft glasses, but with important differences that are highly ATP-dependent. These mesoscale dynamics link integrative CSK functions to underlying molecular events, and represent an important intersection of topical issues in condensed matter physics and systems biology.     

Implementation of polynomial multi-objective optimization in Mathematica

We describe implementation of main methods for solving polynomial multi-objective optimization problems by means of symbolic processing available in the programming language MATHEMATICA. Symbolic transformations of unevaluated expressions, representing objective functions and constraints, into the corresponding representation of the single-objective constrained problem are especially emphasized. We also describe a function for the verification of Pareto optimality conditions and a function for graphical illustration of Pareto optimal points and given constraint set.     

Time-resolved momentum imaging system for molecular dynamics studies using a tabletop ultrafast extreme-ultraviolet light source

We describe a momentum imaging setup for direct time-resolved studies of ionization-induced molecular dynamics. This system uses a tabletop ultrafast extreme-ultraviolet (EUV) light source based on high harmonic upconversion of a femtosecond laser. The high photon energy (around 42 eV) allows access to inner-valence states of a variety of small molecules via single photon excitation, while the sub--10-fs pulse duration makes it possible to follow the resulting dynamics in real time. To obtain a complete picture of molecular dynamics following EUV induced photofragmentation, we apply the versatile cold target recoil ion momentum spectroscopy reaction microscope technique, which makes use of coincident three-dimensional momentum imaging of fragments resulting from photoexcitation. This system is capable of pump-probe spectroscopy by using a combination of EUV and IR laser pulses with either beam as a pump or probe pulse. We report several experiments performed using this system.     

Influence of the complex formation on the morphology of lead powder particles produced by the electrodeposition processes

The processes of lead electrodeposition from the basic (nitrate) and complex (acetate) electrolytes were mutually compared by the analysis of their polarization characteristics and by the scanning electron microscopic (SEM) analysis of the morphology of formed deposits. Although the polarization characteristics of lead recorded from these two electrolytes were relatively similar to each other, the shape of formed dendrites strongly depended on the type of electrolyte. The dendrites composed of stalk and weak developed primary branches (the primary (P) type) were predominantly formed from the basic electrolyte. On the other hand, the very branchy dendrites composed of stalk and of both primary and secondary branches (the secondary (S) type) were mainly electrodeposited from the complex electrolyte. Considering the fact that the application of lead powder in many technologies is closely related with its surface morphology, the special attention was given to the analysis of the type of electrolytes on formation of the different dendritic forms. It was shown that formation of more branchy dendrites from the acetate electrolyte can be ascribed to the lower exchange current density (or to the lower rate of electrochemical process) for this electrolyte than for the nitrate one due to the process of complex formation.     

Evaluation of measurement uncertainty using mixed distribution for conducted emission measurements

For evaluation of measurement uncertainty for conducted emission measurements, we propose a new model which uses mixed distribution. Namely, evaluation of probability density function (PDF) for the measurand has been done using a Monte Carlo method and a modified least-squares method. As the Monte Carlo method required numerical calculation of approximate PDF values, pseudorandom number generator (PRNG) was developed for these requirements. For illustration, this work presents mixed distributions of two normal distributions, normal and rectangular distributions, and normal and also triangular distributions in case of conducted emission measurements. The results obtained by the Monte Carlo method and the modified least-squares method are compared to the corresponding results when applying the standard Guide to the Expression of Uncertainty in Measurement (GUM) procedure.     

Biogenic amines content in traditional dry fermented sausage Petrovská klobása as possible indicator of good manufacturing practice

The aim of this study was to determine the content of nine biogenic amines (tryptamine, phenylethylamine, putrescine, cadaverine, histamine, serotonin, tyramin, spermidine and spermine) and total biogenic amines in traditional dry fermented sausage Petrovská klobása at the end of drying period, as possible indicators of good manufacturing practice (GMP).Chromatographic separation of dansyl chloride derivatizated amines was completed in 8 min. Analyses were performed by HPLC-DAD on Eclipse XDB-C18 column. Tryptamine and spermine were determined in all analyzed samples, while histamine, serotonin and spermidine were not detected in any samples. Average content of individual biogenic amine ranged from 5.54 mg/kg (putrescin) to 75.1 mg/kg (tryptamine) and total content of biogenic amines varied from 77.8 mg/kg to 174 mg/kg.The results obtained in this study provided no evidence for deviations from good manufacturing practice in Petrovská klobása production.     

Experimentally observable transitions between dynamical states in complex reaction systems

Identification of trends and their correspondence with dynamical state transitions are briefly discussed on several reaction network models. The influence of different threshold values on the trend analysis and dynamical state analysis results is examined. Both methods are applied here to the results of the numerical simulation. For this purpose the models of three reaction systems are used: simple model of consecutive, first order, equilibrium reactions, partial oxidation of cyclohexane, and model of the oscillatory reaction Bray Liebhafsky.Detailed kinetic analysis confirmed that transient dynamical states may be identified through the symbolic representation of the sequence of trend episodes in experimentally obtainable time series. Stoichiometric Network Analysis of possible dynamical states was used to identify reaction pathways responsible for the sequences of trend episodes. Some technical problems were also addressed, connected with selection of the threshold value and dynamical state notion.     

Influence of traffic enforcement on the attitudes and behavior of drivers

Traditionally, traffic enforcement has been an important means of improving traffic safety. Many studies have provided evidence of connections between the level of police enforcement and both driving behavior and the number of traffic accidents. In Northern Kosovo, there has been little, if any, traffic enforcement during the last 13 years. This situation has created a very rare research opportunity – it is now possible to directly study the influence of traffic enforcement on the attitudes and behavior of drivers by comparing two regions, one with traffic enforcement and one without it (Serbia vs. Northern Kosovo). The sample in the present study consisted of 424 drivers (204 from Serbia and 220 from Northern Kosovo). Questionnaires included items about the behaviors of the drivers (e.g., speeding, seat belt, drunk driving) and their attitudes. We also conducted field observations of driving behavior. The results indicated that the lack of enforcement affects almost every type of behavior that we examined. Compared with drivers in Serbia, drivers in Northern Kosovo drive faster, exceed speed limits more frequently, use seat belts less frequently, drive after exceeding the legal limit for alcohol more often, commit aggressive and ordinary violations more frequently and are generally involved in more risky situations.     

Sensory,physical and chemical characteristics of cooked ham manufactured from rapidly chilled and earlier deboned M. semimembranosus

Effects of rapid chilling of carcasses (at − 31 °C in the first 3 h of chilling, and then at 2–4 °C) and earlier deboning (8 h post-mortem), compared to rapid (till 24 h post-mortem) and conventional chilling (at 2–4 °C, till 24 h post-mortem), on quality characteristics of pork M. semimebranosus and cooked ham were investigated. Quality measurements included pH value, colour (CIEL*a*b* values) and total aerobic count of M. semimebranosus, as well as sensory (colour, juiciness, texture, and flavour), physical (pH value, colour – CIEL*a*b* values and texture – Warner–Bratzler shear and penetration forces) and chemical (protein, total fat, and moisture content) characteristics of cooked ham. The cooked ham was manufactured from pieces of M. semimebranosus with ultimate lightness (CIEL* value) lower than 50. Rapid chilling and earlier deboning significantly increased quantity of M. semimebranosus desirable for cooked ham manufacturing. Earlier start of pork fabrication did not affect important quality characteristics of cooked ham.     

Simple and Rapid Method for the Simultaneous Determination of Cholesterol and Retinol in Meat Using Normal-Phase HPLC Technique

A direct saponification and normal-phase high-performance liquid chromatography (NP-HPLC) procedure was developed for simultaneous determination of cholesterol and retinol in meat. A normal-phase silica column fitted with diode array detection at 208 nm for cholesterol and fluorescence detection (λ-excitation 344 nm/λ-emission 472 nm) for retinol, with mobile phase consisting of 2% (v/v) 2-propanol in n-hexane was used. Cholesterol was eluted at 10 min and retinol at 12.66 min. High linearity (R ² > 0.9996 for both compounds) in calibration range was obtained. The LOD and LOQ values show the high sensitivity of the developed methodology for simultaneous determination of cholesterol and retinol in meat. Recovery results obtained in this study (98.67–102.14% for cholesterol and 91.72–98.27% for retinol) were between AOAC recommendations to validated method and were comparable to most recent studies in precision and accuracy. In addition, the present method showed high repeatability and reproducibility. As a general conclusion, the results indicate that the direct saponification, extraction, and HPLC analysis is an adequate method for cholesterol and retinol analysis in meat samples.