Pre-saccadic perception: separate time courses for enhancement and spatial pooling at the saccade target

We interact with complex scenes using eye movements to select targets of interest. Studies have shown that the future target of a saccadic eye movement is processed differently by the visual system. A number of effects have been reported, including a benefit for perceptual performance at the target (“enhancement”), reduced influences of backward masking (“unmasking”), reduced crowding (“un-crowding”) and spatial compression towards the saccade target. We investigated the time course of these effects by measuring orientation discrimination for targets that were spatially crowded or temporally masked. In four experiments, we varied the target-flanker distance, the presence of forward/backward masks, the orientation of the flankers and whether participants made a saccade. Masking and randomizing flanker orientation reduced performance in both fixation and saccade trials. We found a small improvement in performance on saccade trials, compared to fixation trials, with a time course that was consistent with a general enhancement at the saccade target. In addition, a decrement in performance (reporting the average flanker orientation, rather than the target) was found in the time bins nearest saccade onset when random oriented flankers were used, consistent with spatial pooling around the saccade target. We did not find strong evidence for un-crowding. Overall, our pattern of results was consistent with both an early, general enhancement at the saccade target and a later, peri-saccadic compression/pooling towards the saccade target

Towards Dead Time Inclusion in Neuronal Modeling

A mathematical description of the refractoriness period in neuronal diffusion modeling is given and its moments are explicitly obtained in a form that is suitable for quantitative evaluations. Then, for the Wiener, Ornstein-Uhlenbeck and Feller neuronal models, an analysis of the features exhibited by the mean and variance of the first passage time and of refractoriness period is performed.Comment: 12 pages, 1 figur

A stochastic model for the stepwise motion in actomyosin dynamics

A jump-diffusion process is proposed to describe the displacements performed by single myosin heads along actin filaments during the rising phases. The process consists of the superposition of a Wiener and a jump process, with jumps originated by sequences of Poisson-distributed energy-supplying pulses. In a previous paper, the amplitude of the jumps was described by a mixture of two Gaussian distributions. To embody the effects of ATP hydrolysis, we now refine such a model by assuming that the jumps' amplitude is described by a mixture of three Gaussian distributions. This model has been inspired by the experimental data of T. Yanagida and his co-workers concerning observations at single molecule processes level.Comment: 9 pages, 4 figure

A chemically driven fluctuating ratchet model for actomyosin interaction

With reference to the experimental observations by T. Yanagida and his co-workers on actomyosin interaction, a Brownian motor of fluctuating ratchet kind is designed with the aim to describe the interaction between a Myosin II head and a neighboring actin filament. Our motor combines the dynamics of the myosin head with a chemical external system related to the ATP cycle, whose role is to provide the energy supply necessary to bias the motion. Analytical expressions for the duration of the ATP cycle, for the Gibbs free energy and for the net displacement of the myosin head are obtained. Finally, by exploiting a method due to Sekimoto (1997, J. Phys. Soc. Jpn., 66, 1234), a formula is worked out for the amount of energy consumed during the ATP cycle.Comment: 15 pages. 1 figur

On Myosin II dynamics in the presence of external loads

We address the controversial hot question concerning the validity of the loose coupling versus the lever-arm theories in the actomyosin dynamics by re-interpreting and extending the phenomenological washboard potential model proposed by some of us in a previous paper. In this new model a Brownian motion harnessing thermal energy is assumed to co-exist with the deterministic swing of the lever-arm, to yield an excellent fit of the set of data obtained by some of us on the sliding of Myosin II heads on immobilized actin filaments under various load conditions. Our theoretical arguments are complemented by accurate numerical simulations, and the robustness of the model is tested via different choices of parameters and potential profiles.Comment: 6 figures, 8 tables, to appear on Biosystem

Lipid oxidation of a meat product packaged with poly (lactic acid)/clay nanocomposites

Introduction: Polylactic acid or polylactide (PLA, Poly) is a biodegradable thermoplastic aliphatic polyester derived from renewable resources, such as corn starch, tapioca roots, chips or starch, or sugarcane. Biopolymer nanocomposites are of great interest to the packaging industry as they can overcome the limitations of biopolymers compared to synthetic polymers. In the last two decades, the nanocomposites have been studied intensively, once the addition of fillers such as organoclays, in particular, montmorillonite (MMT), can improve rheological, thermal and mechanical properties of the biopolymers (Jollands M. et al. 2010). The presence of MMT can lead to materials which generally exhibit great property enhancements, mainly due to its intercalation or exfoliation into the polymer chains. In this work, PLA was incorporated with 5% (w/w) Cloisite Na+ prepared through a two-step process: first extrusion of pellets and secondly melted matter was pressed. The nanocomposite was used to pack a model food (salami) in order to evaluate of the ability of the new packaging to inhibit lipid oxidation. Thiobarbituric Acid Reactive Substances (TBARS) assay was used to evaluate the lipid oxidation stage. This assay allows to measure malondialdehyde (MDA) content, which is formed in the lipid oxidation of polyunsaturated fatty acids. Material and Methods: Packaged salami was homogenized with trichloroacetic acid (10 %) in 0.02 M of orthophosphoric acid and the solution was filtered. The filtered solution was homogenized with thiobarbituric acid aqueous solution (0.02 M) and heated at 100 °C for 40 min. Solutions were cooled down and absorbance was measured at 530 nm. Results were expressed as mg MDA per kg of salami. Results and Discussion: Salami slices were packaged with a control film and with the nanocomposite and analysed at initial time and after 15, 30, 60 and 90 days of contact. Results showed that salami packaged with the nanocomposite presented lower amount of MDA after all contact periods, except after 60 days, where there were no differences between control and nanofilm. Conclusion: Although the results showed that the new nanocomposite tends to reduce the production of MDA, further studies should be carried out to confirm the inhibition of lipid oxidation, such as the peroxide index, p-anisidine value, or the monitorization of a lipid oxidation indicator like hexanal.Project “Development of methodologies for the evaluation of polymeric food packaging components and determination of their structural and mechanical properties” (2016DAN 1289)N/

Longitudinal analysis of the developing rhesus monkey brain using magnetic resonance imaging: birth to adulthood.

We have longitudinally assessed normative brain growth patterns in naturalistically reared Macaca mulatta monkeys. Postnatal to early adulthood brain development in two cohorts of rhesus monkeys was analyzed using magnetic resonance imaging. Cohort A consisted of 24 rhesus monkeys (12 male, 12 female) and cohort B of 21 monkeys (11 male, 10 female). All subjects were scanned at 1, 4, 8, 13, 26, 39, and 52 weeks; cohort A had additional scans at 156 weeks (3 years) and 260 weeks (5 years). Age-specific segmentation templates were developed for automated volumetric analyses of the T1-weighted magnetic resonance imaging scans. Trajectories of total brain size as well as cerebral and subcortical subdivisions were evaluated over this period. Total brain volume was about 64 % of adult estimates in the 1-week-old monkey. Brain volume of the male subjects was always, on average, larger than the female subjects. While brain volume generally increased between any two imaging time points, there was a transient plateau of brain growth between 26 and 39 weeks in both cohorts of monkeys. The trajectory of enlargement differed across cortical regions with the occipital cortex demonstrating the most idiosyncratic pattern of maturation and the frontal and temporal lobes showing the greatest and most protracted growth. A variety of allometric measurements were also acquired and body weight gain was most closely associated with the rate of brain growth. These findings provide a valuable baseline for the effects of fetal and early postnatal manipulations on the pattern of abnormal brain growth related to neurodevelopmental disorders

Mortality-based damages per ton due to the on-road mobile sector in the Northeastern and Mid-Atlantic U.S. by region, vehicle class and precursor

A new study that quantifies the total and interstate deaths from transportation-related air pollution from five vehicle types in 12 states and Washington, D.C. has been published in Environmental Research Letters. The research was led by researchers at the University of North Carolina at Chapel Hill with the Center for Climate, Health, and the Global Environment at Harvard T.H Chan School of Public Health.The study is part of the Transportation, Equity, Climate, and Health project (TRECH), a multi-university research team from Harvard T.H. Chan School of Public Health, Boston University, University of North Carolina, and Columbia University, which analyzes policy scenarios to address carbon pollution from the transportation sector.Key TakeawaysOzone and fine particulate matter from vehicle emissions in 2016 led to an estimated 7,100 deaths in the Northeast and Mid-Atlantic regions of the U.S., and pollution from tailpipe emissions is also traveling across state lines, harming the health of people living in cities and states downwind.Region wide, light-duty trucks, which include SUVs, were responsible for the largest number of premature deaths at 2,463 followed by light-duty passenger vehicles (1,881) and heavy-duty trucks (1,465)All states experienced substantial health impacts from vehicle emissions and can gain health benefits from local action.New York, Pennsylvania, and New Jersey were hardest hit with health damages at $21 billion,$13 billion, and $12 billion, respectively, in 2016 (the most recent data available from EPA).Many states are heavily impacted by out-of-state emissions and some states cause more deaths out-of-state than in-state, including PA and NJ, highlighting the importance of region-wide action to reduce vehicle emissions.On a ton for ton basis, buses in the New York-Newark-Jersey City metropolitan area had the largest health damages at$4 million for every ton of particulate matter emitted.Ammonia emissions play a stronger relative role in causing health damages compared to oxides of nitrogen. Regionally, ammonia emissions from vehicles were responsible for 740 premature deaths in 2016, more than 10% of the total deaths. Ammonia emissions from vehicles are an unintended by-product of catalytic converters and are unregulated in the U.S., and their role in urban air pollution has been generally under appreciated