Studies of the optical properties of laser plasmas produced by irradiating spherical targets

Results are presented from studies of the spectral characteristics of a glowing plasma object that forms behind a shock wave propagating in a background gas at a pressure of 1 Torr after laser irradiation of a spherical organic target in the MKV-4 device (a component of the Iskra-5 facility). The experimental data are compared to the results of calculations.     

Improving spatial and temporal resolution in evoked EEG responses using surface Laplacians

Spline generated surface Laplacian temporal wave forms are presented as a method to improve both spatial and temporal resolution of evoked EEG responses. Middle latency and the N1 components of the auditory evoked response were used to compare potential-based methods with surface Laplacian methods in the time domain. Results indicate that surface Laplacians provide better estimates of underlying cortical activity than do potential wave forms. Spatial discrimination among electrode sites was markedly better with surface Laplacian than with potential wave forms. Differences in the number and latencies of peaks, and their topographic distributions, were observed for surface Laplacian, particularly during the time period encompassing the middle latency responses. Focal activities were observed in surface Laplacian wave forms and topographic maps which were in agreement with previous findings from auditory evoked response studies. Methodological issues surrounding the application of spline methods to the time domain are also discussed. Surface Laplacian methods in the time domain appear to provide an improved way for studying evoked EEG responses by increasing temporal and spatial resolution of component characteristics.     

An experimental study of the forms of complexly organized nonautomatized activities in cats in free behavior

Modification is proposed of the method of "pair presentations with transfer" for the purpose of studying of some forms of animals complex behaviour in chronic experiment. The experiments were conducted on cats in the apparatus, the limited size of which make possible simultaneous recording of electrophysiological characteristics of the brain activity. On the basis of experimental data it is postulated that "reflex to relation" is one of the most complex reflexes of the animal including, alongside with conditioned component, elements of non-automatized behaviour. The proposed method can be used in neurophysiological, electrophysiological and neuropharmacological experiments on animals.     

The role of scent marking in Lemur catta agonistic behavior

Certain forms of marking behavior in Lemur catta have been considered to be aggressive in nature but had not been analyzed specifically in this respect. This study examines the relationship between the occurrence of all forms of marking behavior displayed by a captive group of lemurs and their physical and nonphysical aggressive interactions. All forms of marking behavior, especially males' tail mark and tail wave displays, were found to correlate with aggressive behavior including female-instigated agonism. In comparison, allogrooming, a behavior thought not to have an agonistic component, was not significantly correlated with any marking nor agonistic category. The data suggest that in intersexual interactions male marking behavior is an aggressive but nonphysical substitute for physical aggression toward females who have generally been regarded as dominant to males in this species.     

The use of principal component analysis to resolve the spectra and kinetics of cytochrome c oxidase reduction by 5,10-dihydro-5-methyl phenazine.

The method of principal component analysis (PCA) was applied to the absorption-wavelength-time surfaces generated by rapid scanning stopped-flow spectrophotometry (RSSFS). The method was used to resolve the absorption surfaces generated during the reduction of cytochrome c oxidase by 5,10-dihydro-5-methyl phenazine (MPH) into the individual spectral shapes and time courses of the component chromophores. Two forms of resting cytochrome oxidase were used in these analyses: one that has its maximum absorption in the Soret region at 418 nm (418-nm species) and the other has its absorption maximum at 424 nm (424-nm species). A weighting scheme suitable for RSSFS data was developed. The optical absorption spectra obtained by W.H. Vanneste (1966, Biochemistry, 5:838-848) for the oxidase components were found to fit adequately as components of the experimental surfaces. Among these spectra were the oxidized forms of cytochromes a and a3 in the wavelength region 330-520 nm for the 418-nm species. Vanneste's spectral shape for the oxidized cytochrome a3 did not fit as a component in the spectrum of the 424-nm species. After accounting for the spectral shape of all components present, PCA provided a straightforward method for determining the separate time courses of each chromophore. We have found for both forms used that cytochrome a is reduced by MPH in the initial stages of the reaction, while cytochrome a3 is reduced in subsequent, slow phases. An important aspect of PCA is that it provided confirmation of the spectra of the various oxidase components without requiring the use of inhibitors or the use of simplifying mechanistic assumptions. The resolution of time profiles of strongly overlapping chromophores is also demonstrated.     

alpha-Helical solenoid model for the human involucrin

Involucrin is a key component of the cross-linked envelope of terminally differentiated keratinocytes. The human molecule largely consists of 10 residue repeats and forms a thin 460 A long rod. Summarized experimental data and a detailed stereochemical analysis made with computer modeling resulted in a structural model for the involucrin molecule. The suggested structure is a left-handed alpha-helical solenoid built of a tandem array of helix-turn-helix folds. The structure enables us to explain the whole set of experimental data and residue conservations within the repeats. It is ideally suited to serve as a scaffold for cell envelope assembly and proposes a possible mode of the intermolecular interactions of involucrin during cell cornification.     

Analysis of longitudinal metabolomics data

MOTIVATION: Metabolomics datasets are generally large and complex. Using principal component analysis (PCA), a simplified view of the variation in the data is obtained. The PCA model can be interpreted and the processes underlying the variation in the data can be analysed. In metabolomics, often a priori information is present about the data. Various forms of this information can be used in an unsupervised data analysis with weighted PCA (WPCA). A WPCA model will give a view on the data that is different from the view obtained using PCA, and it will add to the interpretation of the information in a metabolomics dataset. RESULTS: A method is presented to translate spectra of repeated measurements into weights describing the experimental error. These weights are used in the data analysis with WPCA. The WPCA model will give a view on the data where the non-uniform experimental error is accounted for. Therefore, the WPCA model will focus more on the natural variation in the data. AVAILABILITY: M-files for MATLAB for the algorithm used in this research are available at http://www-its.chem.uva.nl/research/pac/Software/pcaw.zip.     

Recycle hollow fiber enzyme reactor with flow swing

The hollow fiber enzyme reactor with pulsation developed by Kim and Chang (1983) was operated in a differential mode by recycling a substrate solution, in order to assess the efficiency of ultrafiltration swing. The rates of lactose conversion by beta-galactosidase contained in the shell side of the reactor were measured to determine the effects of recirculation rate, pulsation period, and amplitude. The conversion increased with the increase of recirculation flow rate and the amplitude while variation in period affected the conversion relatively little. The maximum increase of 113% in the activity was observed in the reactor with pulsation as compared to that without pulsation. The two-compartment model well described the experimental data obtained in this study. Square-wave pulsation was theoretically more effective in increasing conversion than sine wave pulsation. However, in experimental operation the damping effect of the hollow fiber wall narrowed the difference between these two wave forms.     

Redox properties of b-type cytochromes in Escherichia coli and rat liver mitochondria and techniques for their analysis

We describe here apparatus and procedures for conducting potentiometric titrations and for analyzing the collected data in terms of the number of components present, their amounts and their midpoint potentials. Using these procedures we have determined the presence of three forms of cytochrome b₁ in Escherichia coli with midpoint potentials at pH 7.1 of about ?50, +110 and +220 mV. We were not able to demonstrate a change in any of these potentials by the addition of phosphate, ATP, or 2,4-dinitrophenol. We have been able to confirm the presence of two forms of cytochrome b in non-energized mitochondria and the apparent conversion of the low-potential component to a new high potential component upon energization of the mitochondria. However we cite further experimental data that question the actual conversion of one form of cytochrome b to another. An alternative interpretation based on our analysis suggests that the high voltage component may be present in a masked form in the non-energized mitochondria.     

The influence of vessel wall elasticity and peripheral resistance on the carotid artery flow wave form: a CFD model compared to in vivo ultrasound measurements

The Doppler flow wave form and its derived measures such as the pulsatility index provide clinically important tools for the investigation of arterial disease. The typical shape of Doppler flow wave forms is physiologically known to be largely determined by both peripheral resistance and elastic properties of the arterial wall. In the present study we systematically investigate the influence of both vessel wall elasticity and peripheral resistance on the flow wave form obtained from a CFD-simulation of blood flow in the carotid bifurcation. Numerical results are compared to in vivo ultrasound measurements. The in vivo measurement provides a realistic geometry, local elasticities and an input flow wave form for the numerical experiment. Numerical and experimental results are compared at three different sites in the carotid branches. Peripheral resistance has a profoundly decreasing effect on velocities in the external carotid artery. If elasticity is taken into account, the computed peak systolic velocities are considerably lower and a more realistic smoothing of the flow wave form is found. Together, the results indicate that only if both vessel wall elasticity and positive peripheral resistance are taken into account, experimentally obtained Doppler flow wave forms can be reproduced numerically.     

A2B-COVID: A Tool for Rapidly Evaluating Potential SARS-CoV-2 Transmission Events

Identifying linked cases of infection is a critical component of the public health response to viral infectious diseases. In a clinical context, there is a need to make rapid assessments of whether cases of infection have arrived independently onto a ward, or are potentially linked via direct transmission. Viral genome sequence data are of great value in making these assessments, but are often not the only form of data available. Here, we describe A2B-COVID, a method for the rapid identification of potentially linked cases of COVID-19 infection designed for clinical settings. Our method combines knowledge about infection dynamics, data describing the movements of individuals, and evolutionary analysis of genome sequences to assess whether data collected from cases of infection are consistent or inconsistent with linkage via direct transmission. A retrospective analysis of data from two wards at Cambridge University Hospitals NHS Foundation Trust during the first wave of the pandemic showed qualitatively different patterns of linkage between cases on designated COVID-19 and non-COVID-19 wards. The subsequent real-time application of our method to data from the second epidemic wave highlights its value for monitoring cases of infection in a clinical context.     

Review on parasitic and non-parasitic forms of the arctic lamprey Lethenteron camtschaticum (Petromyzontiformes, Petromyzontidae) in the Eurasian arctic

Arctic lamprey Lethenteron camtschaticum is an important and poorly studied component of the aquatic ecosystems in the Northern part of Eurasia. In this region, the species has two life history forms: anadromous and resident, which are very closely related genetically. In this review data on morphology, distribution, ecology, abundance, economic value and preservation of these two forms from the basins of the Barents, White, Kara, Laptev, East Siberian, Chukchi and Bering Seas are presented (over 70 rivers in 9 Russian watershed districts). For the first time, rigorous amounts of previously published and authors’ own experimental data, observations and Russian historical documents, normally unobtainable for English speaking researchers, have been comprehensively analyzed. The review leads to the understanding of the forms belonging to the same species.     

Dynamic reconstruction of the fish locomotor wave

Theoretical modeling substantiates the bionic solution of an optimal wave propulsor for water transport, which must have the amplitude and phase characteristics of the fish bending locomotor waves. Use is made of a computer model of multilink chain bending waves where arbitrary distributions can be set for amplitudes and phases of separate segments. With the linear increase in the amplitude of segmental oscillations, a numerical experiment determines the optimal phasing whereby each segment provides a maximal longitudinal component of the motive force. Two versions of hydrodynamic interaction of the segments with water are compared, implying (i) linear and (ii) quadratic drag: the optimal phasing of the transverse and longitudinal oscillations proves to be (i) orthogonal and (ii) nearly orthogonal. The computed bending wave shapes corresponding to dynamic optimization are consistent with the experimental data.     

Traveling waves in a simple population model involving growth and death

The structure of solutions to a simple spatially dependent population model involving growth and death is investigated. Two forms of motility of the population are considered: (1) random motion only modeled by a Fickian law, and (2) a directed component of motion (chemotaxis), included in addition to the random motion. Under certain growth conditions a traveling wave of constant speed is approached. This speed can be increased by the addition of the chemotaxis with a corresponding increase in the asymptotic population. Development of initial conditions into a wave is illustrated numerically.     

A non-parametric method for the reconstruction of age- and time-dependent incidence from the prevalence data of irreversible diseases with differential mortality.

A method is proposed for reconstructing the time and age dependence of incidence rates from successive age-prevalence cross sections taken from the sentinel surveys of irreversible diseases when there is an important difference in mortality between the infected and susceptible subpopulations. The prevalence information at different time-age points is used to generate a surface; the time-age variations along the life line profiles of this surface and the difference in mortality rates are used to reconstruct the time and age dependence of the incidence rate. Past attempts were based on specified parametric forms for the incidence or on the hypothesis of time-invariant forms for the age-prevalence cross sections. The proposed method makes no such assumptions and is thus capable of coping with rapidly evolving prevalence situations. In the simulations carried out, it is found to be resilient to important random noise components added to a prescribed incidence rate input. The method is also tested on a real data set of successive HIV age-prevalence cross sections from Burundi coupled to differential mortality data on HIV(+) and HIV(-) individuals. The often-made assumption that the incidence rate can be written as the product of a calendar time component and an age component is also examined. In this case, a pooling procedure is proposed to estimate the time and the age profiles of the incidence rate using the reconstructed incidence rates at all time-age points.     

Functional Morphology and Neural Control of Neck Muscles in Mammals

SYNOPSIS. Although the data described in this paper are froma traditional experimental animal, the cat, the problem addressedis applicable to many forms of motor control in a broad rangeof species. In general, we are trying to understand how themusculo-skeletal structure of a body component imposes constraintson how that component is controlled by the central nervous system.Our approach to this problem has been to develop a theoreticalmodel of sensory-motor integration in complex systems wheremovement is produced by a large number of muscles and then totest whether that model can predict the patterns of neck muscleactivity that underlie head movements. The resulting theoreticalinterpretation of physiological data sheds light on the organizationof head movement control in the cat and also reveals a numberof fundamental principles that must be considered in tryingto characterize and understand any sensory-motor system.     

Effects of electroporation pulse wave on the incorporation of viral RNA into tobacco protoplasts

The uptake and expression of cucumber mosaic viral (CMV) RNA by tobacco protoplasts was examined using both square wave and exponential wave electroporation pulses. These electropulses, when supplied at sufficient field strength for a critical duration, enabled RNA to be incorporated and expressed in more than 60% of the surviving protoplasts. The results of experiments using these two electroporation wave forms showed significant differences in RNA uptake and expression. The number of viable protoplasts and cells showing expression of RNA was higher over a much broader range of experimental conditions using the square rather than exponential wave generator, even when both machines were optimized for maximal performance. However, at a narrow range of low field strengths the exponential wave pulse generated a higher percentage of transformants than did the square wave pulse. It was shown that after an electroporation pulse from either wave form, there were viable cells which expressed foreign RNA at predictable levels.     

Linear and Nonlinear Regression Analyses for Binary Sorption Kinetics of Methylene Blue and Safranin onto Pretreated Rice Husk

This article extends the study of the comparison between linear and nonlinear forms of the two widely used kinetic models, namely, pseudo-first-order and pseudo-second-order, by considering the binary biosorption of the basic dyes methylene blue and safranin onto pretreated rice husk in a batch system. The present investigation showed that nonlinear forms of pseudo-first-order and pseudo-second-order models were more suitable than the linear forms for fitting the experimental data. The sorption process was found to follow the pseudo-second-order kinetics. The results suggest that it is not appropriate to use the linear method in determining the kinetic parameters of a particular kinetic model. The nonlinear method is a better way to obtain the kinetic parameters than the linear method and thus it should be primarily adopted to determine the kinetic parameters.     

Breath-by-breath analysis of expiratory gas concentration in chickens

Expiratory oxygen and carbon-dioxide concentration were analysed breath by breath in order to examine their wave forms in adult awake hens restrained in various postural positions, including supine, prone and sitting positions. Expired gas was collected at the nostril in almost all the hens. In the sitting position free from vocalization, feeding, drinking, panting, and restlessness, hens showed various forms of stable pattern of oxygen-gas curves. These forms were classified into three types, or the ascending, flat and descending types, with respect to the plateau inclination. The waves of carbon-dioxide were not always a mirror image of those of oxygen. The rate of occurrence of each type varied with the hen's postural position. The wave form was altered with the experimental body-rotation of the hen. When placed between the deflections of stable pattern, the episodes of wave deformation resembling that seen at the time of uneven pulmonary ventilation in mammals could frequently be observed in any hen's posture examined. Cardiogenic oscillation appeared on the plateau of expired-gas curves.     

Effects of waves on the early growth of Vallisneria americana

1. The impacts of 0.15-m waves on the survival and short-term growth and development of young Vallisneria americana plants were studied in experimental raceways. Young plants were planted at three depths within both wave and control raceways. Wave events were designed to simulate wave disturbances caused by boat traffic and were generated five or six times each day during the 67-day experimental growth period. The 0.15-m waves generated produced a maximum shear velocity of about 1.4 m s⁻¹ as they swept over the plants. 2. All plants survived at all depths in both treatments. However, plants exposed to the waves accumulated significantly less total mass than controls. The total mass accumulation of wave-exposed plants was only 50% of that of undisturbed plants. In addition, the plants experiencing the waves had significantly shorter leaves and produced significantly fewer daughter plants. 3. While plants under both wave and no wave treatments had a similar relative growth rate and both showed a net positive growth over the experimental period, those exposed to frequent wave energy developed more slowly due to continuous leaf loss caused by the waves. Plants exposed to even modest wave energy may spread more slowly and be less resilient to recovery from other forms of disturbance.