Thin sections techniques in fossil remains of mammals impregnated with asphalt

Paleohistological studies of vertebrates are based on the analysis and interpretation of bone microstructure of petrographic thin sections. These sections are mainly performed following standard techniques; however, the methodology can vary according to the particular characteristics of the sample (e.g. skeletal element, type of preservation) or the purpose of the work. As part of a paleohistological study on Equus occidentalis recovered from a Late Pleistocene asphalt seep ("tar pit"), Rancho La Brea (California, United States), in this contribution we describe the technique used to make thin sections of fossils impregnated with asphalt. The hydrocarbons act as a release agent, which causes the resins commonly used for glued or embedding not to adhere to the fossil remains. For chip preparation (=block) the sample were embedded in a large volume of low-viscosity epoxy resin, which generated a higher shrinkage and prevented the separation of the chip components (resin / fossil). The chip must be mounted on the glass slide using UV acrylic resin, which, unlike epoxy resins, does not require heat application, optimizes adhesion, and reduces the curing time, offering the possibility of cutting and polishing quickly after mounting. During polishing, it was necessary to reduce the cleaning time with ultrasound to avoid peeling and loss of portions of the sample. Based on the results obtained, we consider that this variant of the traditional methodology is optimal to work with fossils preserved in this particular context, as it allows making complete thin sections without altering the original osteohistological features.Fil: Garrone, Mariana Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Instituto Geológico del Sur. Universidad Nacional del Sur. Departamento de Geología. Instituto Geológico del Sur; ArgentinaFil: Ortiz, Herácleo O.. Universidad Nacional del Sur. Departamento de Geología; ArgentinaFil: Prado, José L.. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Investigaciones Arqueológicas y Paleontológicas del Cuaternario Pampeano. Universidad Nacional del Centro de la Provincia de Buenos Aires. Investigaciones Arqueológicas y Paleontológicas del Cuaternario Pampeano; Argentina2nd Palaeontological Virtual CongressEspañaPalaeontological Virtual Congres

Porous Sulfonated PVA Microspheres for Controlled Molecules Delivery: A Methylene Blue Study

 Functionalized PVA microspheres are commonly used as drug carriers in the fields of pharmacy and medicine. With this aim, we obtained and test novel PVA-PVAc-AMPS sulfonated microspheres by free radical suspension polymerization of vinyl acetate (VAc) and 2-acrylamido-2-methyl-1-propanesulfonic sodium salt acid (AMPS), followed by saponification. The microspheres exhibited a porous core-shell structure with excellent sphericity, a mean size of 171 µm, and elasticity modulus comparable with commercial particles currently used in medical applications. Methylene blue (MB) which has shown similar adherence properties as the cytostatic drug doxorubicin was used as a model drug to study the drug loading/release characteristics of the sulfonated microspheres prepared in this work. 20.7 mg g-1 MB per gram of microspheres was the maximum adsorption capacity in two hours using UV-Vis absorption spectroscopy. The experimental data on adsorption were well described by the pseudo-second order kinetic model. The in vitro release profile of loaded MB microspheres showed rapid desorption in the first hour followed by slower MB release, reaching 8.6% elution at four hours. The diffusion process was found to be dominant in the MB desorption from the PVA-PVAc-AMPS microspheres

Análise comparativa entre sondas multiparamétricas para avaliação da qualidade da água para fins agroambientais.

Perante a situação atual de degradação dos corpos hídricos, principalmente nas áreas mais populosas do país, fica evidente a necessidade de um monitoramento eficaz da qualidade das águas dos rios, lagos e outros, que no presente estudo está conectado aos impactos das atividades antrópicas, com destaque às agropecuárias na qualidade da água. Neste sentido, as sondas multiparamétricas tem grande aplicação, uma vez que podem ser instaladas em campo permitindo um monitoramento contínuo e eficaz, poupando-se tempo e recursos. Visando contribuir na identificação da sonda mais adequada para o tipo de monitoramento que se pretende e recursos disponíveis, foi proposto o presente estudo, que tem por objetivo fazer um levantamento e análise comparativa das sondas multiparamétricas para avaliação da qualidade da água disponíveis no mercado. Destaca-se que há uma escassez de trabalhos publicados na literatura que façam este tipo de análise. Especificamente foi feita uma análise comparativa para as principais sondas disponíveis no mercado em relação à quantidade de parâmetros que analisam, o seu custo-benefício, as oportunidades de assistências técnicas no Brasil em relação a cada uma delas, a capacidade de comunicação não só com programas específicos, mas também com Dataloggers (coletores de dados), alimentação energética das sondas, a facilidade de manutenção e calibração, dentre outros fatores. Os resultados mostram os parâmetros mais usados no monitoramento da qualidade da água, as vantagens e desvantagens em se utilizar sondas multiparamétricas e os principais cuidados que se devem tomar quando se está utilizando estas sondas.SIAGRO 2014

Orbital Magnetism in Ensembles of Parabolic Potentials

We study the magnetic susceptibility of an ensemble of non-interacting electrons confined by parabolic potentials and subjected to a perpendicular magnetic field at finite temperatures. We show that the behavior of the average susceptibility is qualitatively different from that of billiards. When averaged over the Fermi energy the susceptibility exhibits a large paramagnetic response only at certain special field values, corresponding to comensurate classical frequencies, being negligible elsewhere. We derive approximate analytical formulae for the susceptibility and compare the results with numerical calculations.Comment: 4 pages, 4 figures, REVTE

The use of body weight support on ground level: an alternative strategy for gait training of individuals with stroke

<p>Abstract</p> <p>Background</p> <p>Body weight support (BWS) systems on treadmill have been proposed as a strategy for gait training of subjects with stroke. Considering that ground level is the most common locomotion surface and that there is little information about individuals with stroke walking with BWS on ground level, it is important to investigate the use of BWS on ground level in these individuals as a possible alternative strategy for gait training.</p> <p>Methods</p> <p>Thirteen individuals with chronic stroke (four women and nine men; mean age 54.46 years) were videotaped walking on ground level in three experimental conditions: with no harness, with harness bearing full body weight, and with harness bearing 30% of full body weight. Measurements were recorded for mean walking speed, cadence, stride length, stride speed, durations of initial and terminal double stance, single limb support, swing period, and range of motion of ankle, knee, and hip joints; and foot, shank, thigh, and trunk segments.</p> <p>Results</p> <p>The use of BWS system leads to changes in stride length and speed, but not in stance and swing period duration. Only the hip joint was influenced by the BWS system in the 30% BWS condition. Shank and thigh segments presented less range of motion in the 30% BWS condition than in the other conditions, and the trunk was held straighter in the 30% BWS condition than in the other conditions.</p> <p>Conclusion</p> <p>Individuals with stroke using BWS system on ground level walked slower and with shorter stride length than with no harness. BWS also led to reduction of hip, shank, and thigh range of motion. However, this system did not change walking temporal organization and body side asymmetry of individuals with stroke. On the other hand, the BWS system enabled individuals with chronic stroke to walk safely and without physical assistance. In interventions, the physical therapist can watch and correct gait pattern in patients' performance without the need to provide physical assistance.</p

Gait training with partial body weight support during overground walking for individuals with chronic stroke: a pilot study

<p>Abstract</p> <p>Background</p> <p>It is not yet established if the use of body weight support (BWS) systems for gait training is effective <it>per se </it>or if it is the combination of BWS and treadmill that improves the locomotion of individuals with gait impairment. This study investigated the effects of gait training on ground level with partial BWS in individuals with stroke during overground walking with no BWS.</p> <p>Methods</p> <p>Twelve individuals with chronic stroke (53.17 ± 7.52 years old) participated of a gait training program with BWS during overground walking, and were evaluated before and after the gait training period. In both evaluations, individuals were videotaped walking at a self-selected comfortable speed with no BWS. Measurements were obtained for mean walking speed, step length, stride length and speed, toe-clearance, durations of total double stance and single-limb support, and minimum and maximum foot, shank, thigh, and trunk segmental angles.</p> <p>Results</p> <p>After gait training, individuals walked faster, with symmetrical steps, longer and faster strides, and increased toe-clearance. Also, they displayed increased rotation of foot, shank, thigh, and trunk segmental angles on both sides of the body. However, the duration of single-limb support remained asymmetrical between each side of the body after gait training.</p> <p>Conclusions</p> <p>Gait training individuals with chronic stroke with BWS during overground walking improved walking in terms of temporal-spatial parameters and segmental angles. This training strategy might be adopted as a safe, specific and promising strategy for gait rehabilitation after stroke.</p

Short-range interactions in a two-electron system: energy levels and magnetic properties

The problem of two electrons in a square billiard interacting via a finite-range repulsive Yukawa potential and subjected to a constant magnetic field is considered. We compute the energy spectrum for both singlet and triplet states, and for all symmetry classes, as a function of the strength and range of the interaction and of the magnetic field. We show that the short-range nature of the potential suppresses the formation of ``Wigner molecule'' states for the ground state, even in the strong interaction limit. The magnetic susceptibility $\chi(B)$ shows low-temperature paramagnetic peaks due to exchange induced singlet-triplet oscillations. The position, number and intensity of these peaks depend on the range and strength of the interaction. The contribution of the interaction to the susceptibility displays paramagnetic and diamagnetic phases as a function of $T$.Comment: 12 pages,6 figures; to appear in Phys. Rev.