Random sequential adsorption and diffusion of dimers and k-mers on a square lattice

We have performed extensive simulations of random sequential adsorption and diffusion of $k$-mers, up to $k=5$ in two dimensions with particular attention to the case $k=2$. We focus on the behavior of the coverage and of vacancy dynamics as a function of time. We observe that for $k=2,3$ a complete coverage of the lattice is never reached, because of the existence of frozen configurations that prevent isolated vacancies in the lattice to join. From this result we argue that complete coverage is never attained for any value of $k$. The long time behavior of the coverage is not mean field and nonanalytic, with $t^{-1/2}$ as leading term. Long time coverage regimes are independent of the initial conditions while strongly depend on the diffusion probability and deposition rate and, in particular, different values of these parameters lead to different final values of the coverage. The geometrical complexity of these systems is also highlighted through an investigation of the vacancy population dynamics.Comment: 9 pages, 9 figures, to be published in the Journal of Chemical Physic

Circadian Organization in Hemimetabolous Insects

The circadian system of hemimetabolous insects is reviewed in respect to the locus of the circadian clock and multioscillatory organization. Because of relatively easy access to the nervous system, the neuronal organization of the clock system in hemimetabolous insects has been studied, yielding identification of the compound eye as the major photoreceptor for entrainment and the optic lobe for the circadian clock locus. The clock site within the optic lobe is inconsistent among reported species; in cockroaches the lobula was previously thought to be a most likely clock locus but accessory medulla is recently stressed to be a clock center, while more distal part of the optic lobe including the lamina and the outer medulla area for the cricket. Identification of the clock cells needs further critical studies. Although each optic lobe clock seems functionally identical, in respect to photic entrainment and generation of the rhythm, the bilaterally paired clocks form a functional unit. They interact to produce a stable time structure within individual insects by exchanging photic and temporal information through neural pathways, in which serotonin and pigment-dispersing factor (PDF) are involved as chemical messengers. The mutual interaction also plays an important role in seasonal adaptation of the rhythm

Statistical properties of acoustic emission signals from metal cutting processes

Acoustic Emission (AE) data from single point turning machining are analysed in this paper in order to gain a greater insight of the signal statistical properties for Tool Condition Monitoring (TCM) applications. A statistical analysis of the time series data amplitude and root mean square (RMS) value at various tool wear levels are performed, �nding that ageing features can be revealed in all cases from the observed experimental histograms. In particular, AE data amplitudes are shown to be distributed with a power-law behaviour above a cross-over value. An analytic model for the RMS values probability density function (pdf) is obtained resorting to the Jaynes' maximum entropy principle (MEp); novel technique of constraining the modelling function under few fractional moments, instead of a greater amount of ordinary moments, leads to well-tailored functions for experimental histograms.Comment: 16 pages, 7 figure

Mining ancient microbiomes using selective enrichment of damaged DNA molecules

The identification of bona fide microbial taxa in microbiomes derived from ancient and historical samples is complicated by the unavoidable mixture between DNA from ante- and post-mortem microbial colonizers. One possibility to distinguish between these sources of microbial DNA is querying for the presence of age-associated degradation patterns typical of ancient DNA (aDNA). The presence of uracils, resulting from cytosine deamination, has been detected ubiquitously in aDNA retrieved from diverse sources, and used as an authentication criterion. Here, we employ a library preparation method that separates molecules that carry uracils from those that do not for a set of samples that includes Neandertal remains, herbarium specimens and archaeological plant remains

Long-term social restrictions and lack of work activities during the COVID-19 pandemic:Impact on the daily lives of people with intellectual disabilities

Purpose:  Lockdowns due to the Covid-19 pandemic may have had a disproportionate impact on the daily lives of people with intellectual disabilities. Many of them had to deal with limited social contacts for an extended period. This study explores in depth how people with intellectual disabilities in the Netherlands experienced their daily lives, in particular due to lack of access to regular work activities.  Materials and methods:  Eight participants with intellectual disabilities were interviewed. Interpretative Phenomenological Analysis (IPA) was employed in conducting and analysing interviews.  Results and conclusions:  Analysis yielded three overarching themes that are conceptually linked. Participants experienced a prolonged lack of social connections that resulted in experiences of social isolation and feelings of loneliness. This led to different kinds of struggles: either internal struggles involving negative thoughts or depressive feelings, or a perceived threat to their autonomous position in society. Meanwhile participants had to sustain their sense of self-worth in the absence of work activities. The findings emphasise the importance of social opportunities through the access to work activities for people with intellectual disabilities. Interventions are suggested to help reverse the increased social inequalities and enhance rehabilitation via work activities for people with intellectual disabilities. Implications for rehabilitation: More awareness may be raised among authorities, employers and the general public about the significant value people with intellectual disabilities attribute to meaningful social connections, in particular through work activities. Also, more awareness may be raised about the potential adverse effects of the loss of work activities and social connections on the quality of life of people with intellectual disabilities. Providing social support to others may help people with intellectual disabilities to construct social valued roles, either in or outside the work situation. Professionals and employers can support people with intellectual disabilities to find opportunities to provide social support to others. It is important to invest in sustainable and innovative post-pandemic community participation initiatives and particularly in accessible post-pandemic employment support, for example by organising paid in-company training placements. It is essential that professionals support people with intellectual disabilities to enhance their sources of resilience and coping strategies, that may have diminished as a result of the pandemic

The filamentation instability driven by warm electron beams: Statistics and electric field generation

The filamentation instability of counterpropagating symmetric beams of electrons is examined with 1D and 2D particle-in-cell (PIC) simulations, which are oriented orthogonally to the beam velocity vector. The beams are uniform, warm and their relative speed is mildly relativistic. The dynamics of the filaments is examined in 2D and it is confirmed that their characteristic size increases linearly in time. Currents orthogonal to the beam velocity vector are driven through the magnetic and electric fields in the simulation plane. The fields are tied to the filament boundaries and the scale size of the flow-aligned and the perpendicular currents are thus equal. It is confirmed that the electrostatic and the magnetic forces are equally important, when the filamentation instability saturates in 1D. Their balance is apparently the saturation mechanism of the filamentation instability for our initial conditions. The electric force is relatively weaker but not negligible in the 2D simulation, where the electron temperature is set higher to reduce the computational cost. The magnetic pressure gradient is the principal source of the electrostatic field, when and after the instability saturates in the 1D simulation and in the 2D simulation.Comment: 10 pages, 6 figures, accepted by the Plasma Physics and Controlled Fusion (Special Issue EPS 2009

Competitive adsorption of wellbores corrosion inhibitor onto steel, esmectite and sandstone

A commercial corrosion inhibitor used in petroleum production was characterized by means of infrared spectroscopy and energy dispersive spectroscopy (EDS). Predicting the adsorption behavior of corrosion inhibitor onto steel, sandstone and esmectite is the key to improve working conditions. In this study, the adsorption kinetics of inhibitor formulations in HCl 15% or in Mud Acid (HCl 13,5% and ammonium bifluoride) onto steel, sandstone and esmectite was determined by means of spectrophotometry. Kinetic parameters indicated that adsorption of inhibitor in the presence of bifluoride was favored. Moreover, the adsorption constant rate was the largest when the substrate was esmectite.FAPESPCNP

Induction of senescence and foliar abscission in apple trees with the use of abscisic acid.

Aims: Evaluate the effects of different concentrations of abscisic acid (ABA) on adult plants of productive age of ?Daiane? and ?Fuji Suprema?, to follow the ecophysiological effects and their efficiency in inducing leaf senescence, sprouting and productivity, in the Midwestern region of the state of Santa Catarina. Study Design: The experiment was arranged in a randomized block design with six replications. Place and Duration of Study: The experiment was carried out in the municipality of Caçador, Brazil (latitude 26º50?07? S, longitude 50º58?32? W, altitude 969 meters), during the growing seasons of 2013/2014 and 2014/2015. Methodology: The apple fruit tree were submitted to the following treatments: 1) Control (without treatment), 2) abscisic acid 750 mg L-1 , 3) abscisic acid 750 + 750 mg L-1 , 4) abscisic acid 1500 mg L-1 and 5) abscisic acid 1500 + 1500 mg L-1 . ABA applications in the first year were carried out on May 2, 2013 in treatments 2, 3, 4, and 5, and after 11 days (05/13/13) the plants of treatments 3 and 5 were sprayed again. In the second year, ABA applications were carried out on May 6 and 15, 2014, following the same application methodology described for the first year. As the source of abscisic acid (ABA) the commercial product ProTone® (20% i.a.) was used, without the use of adjuvant. The exogenous application of ABA was effective in promoting the senescence and leaf fall of the ?Daiane? and ?Fuji Suprema? cultivars. In the 2013/2014 season, the concentration of 750 mg L-1 was enough to induce 100% leaf fall in 'Daiane' plants. However, a difference was observed between the concentrations of ABA used. There was a difference between concentrations and number of applications. Lower concentrations were efficient and deflated as much as the higher concentration. The application of ABA induces the abscission of apple leaves in early autumn in 'Daiane' and 'Fuji Suprema' apple plants. The ABA does not affect shoots of axillary buds and anticipates the beginning of shoots

Stretched exponential relaxation in a diffusive lattice model

We studied the single dimer dynamics in a lattice diffusive model as a function of particle density in the high densification regime. The mean square displacement is found to be subdiffusive both in one and two dimensions. The spatial dependence of the self part of the van Hove correlation function displays as function of $r$ a single peak and signals a dramatic slow down of the system for high density. The self intermediate scattering function is fitted to the Kohlrausch-Williams-Watts law. The exponent $\beta$ extracted from the fits is density independent while the relaxation time $\tau$ follows a scaling law with an exponent 2.5.Comment: 5 pages, 3 figures, to be published in Phys. Rev.