181 research outputs found

    Interpretación de la solubilidad diferencial del Poli(etilentereftalato) en función de la temperatura.

    Get PDF
    Se ha procedido a la determinación de la solubilidad diferencial del PET en una mezcla fenol/tetracloroetano a diversas temperaturas. De las correspondientes fracciones solubles e insolubles ha sido determinado el peso molecular medio por cromatografía de exclusión (GPC). Los resultados obtenidos permiten indicar que el aumento de solubilidad de la fibra de poliéster que tiene lugar al aumentar la temperatura del ensayo de solubilidad diferencial no parece corresponder a materia de mayor peso molecular, sino a materia localizada en zonas más compactas de la fibra, las cuales se van haciendo más accesibles a la mezcla disolvente a medida que va aumentando la temperatura.On a procédé à la determination de la solubilité différentielle du PET dans un mélange phénol/tétrachloréthane a diverses températures. Des correspondantes fractions solubles et insolubles, on a déterminé le poids moyen moléculaire par chromatographie d'exclusion (GPC). Les résultats obtenus permettent d'indiquer que l'augmentation de la solubilité de la fibre de polyester qui a lieu lorsque la température de l'essai de solubilité différentielle augmente, ne semble pas correspondre a une matière a un poids moléculaire supérieur, mais à une matière localisée dans des zones plus compactes de la fibre, lesquelles deviennent plus accessibles au mélange solvant, au fur et à mesure que la temperature augmente.The determination of the differential solubility of PET in a mixture phenol/tetrachloroetane has been performed at different temperatures. Of the soluble and non-soluble fractions, the average molecular weight has been measured by exclusion chromatography (GPC). The results show that the increase of solubility of the polyester fibre experienced on increasing the temperature in the differential solubility test does not seem correspond to the matter with higher molecular weight but to some matter located in more compacted areas of the fibre, which become more accesible to the solvent mixture as temperature increases.Peer Reviewe

    Relationship Experiences of Long-Term Partners of Individuals with Narcissistic Traits

    Get PDF
    The phenomenon of narcissism is well-documented and has garnered much attention from the scientific community. However, a facet of this subject that has been largely unstudied involves the consequences that narcissistic relationships have on intimates. Typically, an individual with narcissistic traits (INT) most negatively affects the romantic partner. Still, there has been very little in the way of academic knowledge, understanding of partner experiences, or how to help from a mental health standpoint. Research has implied that partnering with an INT entails distinct forms of emotional abuse (EA), resulting in the development of unique psychological distress. This qualitative narrative study was designed to explore the experiences of and give voice to 29 former long-term partners of INTs, focusing on the course of the relationships and recovery, evolving self-views during that time, and meaning-making around relationship longevity. Data were collected via semi structured interviews and examined using thematic narrative analysis. Findings were informed by two associated models, that of investment and affect theories of social exchange, owing to the interactional nature of a romantic dyad. Results revealed five themes related to these distinctive relationship trajectories: intense foundation building, unveiling INT façades, cyclical EA and wooing phases, coping and recovery, followed by hindsight wisdom. Increased understanding of the partners’ experiences promotes positive social change by creating awareness and visibility of the impact on partners, contributing to the knowledge pool for psychological educators and clinicians, allowing the possibility of development and implementation of targeted clinical interventions, and providing future directions for study

    A study of the management problems and possible solutions in state-aided schools

    Get PDF
    The problems concerning the future management of state-aided (Model C) schools fall into two main categories, namely problems intrinsic to the Model C schools and the problem of giving substance to the stated vision of the ANC. Model C schools were seen as a South African model of school self-management. A study of the literature relating to school self-management in general, and how it is practised in various countries, was made and the management of state-aided (Model C) schools was analyzed. A impirical investigation was conducted to ascertain the perceptions of various role-players in school management about their duties and responsibilities in this regard. A model for the self-management of state-aided schools, based on the Caldwell and Spinks' s model, and conforming to various criteria, is proposed. The proposed model is, in the opinion of the researcher, applicable not only to State-aided schools, but to all schools in South Africa as it allows individual schools to accept as much or as little self-management as is consistent with the capacity of their communities to provide effective and efficient service. It also allows schools to accept increases in self-management as their communities gain in management skills and expertise.Educational StudiesD.Ed. (Educational Management

    Relationship Experiences of Long-Term Partners of Individuals with Narcissistic Traits

    Get PDF
    The phenomenon of narcissism is well-documented and has garnered much attention from the scientific community. However, a facet of this subject that has been largely unstudied involves the consequences that narcissistic relationships have on intimates. Typically, an individual with narcissistic traits (INT) most negatively affects the romantic partner. Still, there has been very little in the way of academic knowledge, understanding of partner experiences, or how to help from a mental health standpoint. Research has implied that partnering with an INT entails distinct forms of emotional abuse (EA), resulting in the development of unique psychological distress. This qualitative narrative study was designed to explore the experiences of and give voice to 29 former long-term partners of INTs, focusing on the course of the relationships and recovery, evolving self-views during that time, and meaning-making around relationship longevity. Data were collected via semi structured interviews and examined using thematic narrative analysis. Findings were informed by two associated models, that of investment and affect theories of social exchange, owing to the interactional nature of a romantic dyad. Results revealed five themes related to these distinctive relationship trajectories: intense foundation building, unveiling INT façades, cyclical EA and wooing phases, coping and recovery, followed by hindsight wisdom. Increased understanding of the partners’ experiences promotes positive social change by creating awareness and visibility of the impact on partners, contributing to the knowledge pool for psychological educators and clinicians, allowing the possibility of development and implementation of targeted clinical interventions, and providing future directions for study

    Diversity of cortico-descending projections: histological and diffusion MRI characterization in the monkey

    Get PDF
    The axonal composition of cortical projections originating in premotor, supplementary motor (SMA), primary motor (a4), somatosensory and parietal areas and descending towards the brain stem and spinal cord was characterized in the monkey with histological tract tracing, electron microscopy (EM) and diffusion MRI (dMRI). These 3 approaches provided complementary information. Histology provided accurate assessment of axonal diameters and size of synaptic boutons. dMRI revealed the topography of the projections (tractography), notably in the internal capsule. From measurements of axon diameters axonal conduction velocities were computed. Each area communicates with different diameter axons and this generates a hierarchy of conduction delays in this order: a4 (the shortest), SMA, premotor (F7), parietal, somatosensory, premotor F4 (the longest). We provide new interpretations for i) the well-known different anatomical and electrophysiological estimates of conduction velocity; ii) why conduction delays are probably an essential component of the cortical motor command; and iii) how histological and dMRI tractography can be integrated

    Bioanalytical tools for the quantification of in-process and final product samples of a rotavirus vaccine

    Get PDF
    Rotavirus A infection is a global leading cause of severe acute gastroenteritis associated with most of life-threatening diarrhoea episodes in infants and young children. However, the disease burden is being reduced namely due to wider access to rotavirus vaccines and their inclusion into National Immunization Programs of several countries. Besides being live-saving, rotavirus vaccination has an important economic impact, being cost-effective or even cost-saving in some countries. Nevertheless, vaccines are not yet routinely available in all countries. There is a demand to expand the rotavirus vaccination programs and improved analytical tools for high-throughput in-process product quality control and vaccine manufacturing will be important in this context. Moreover, this can be also useful for current marketed vaccines to support their life cycle. In this work, we present the development of two analytical tools for the quantification of rotavirus particles contained in a licensed vaccine. In-process and drug product samples were evaluated using biolayer interferometry analysis, applied on an Octet platform, and flow cytometry, respectively. Please click Download on the upper right corner to see the full abstract

    Egg activation events are regulated by the duration of a sustained [Ca2+]cyt signal in the mouse

    Get PDF
    AbstractAlthough the dynamics of oscillations of cytosolic Ca2+ concentration ([Ca2+]cyt) play important roles in early mammalian development, the impact of the duration when [Ca2+]cyt is elevated is not known. To determine the sensitivity of fertilization-associated responses [i.e., cortical granule exocytosis, resumption of the cell cycle, Ca2+/calmodulin-dependent protein kinase II (CaMKII) activity, recruitment of maternal mRNAs] and developmental competence of the parthenotes to the duration of a [Ca2+]cyt transient, unfertilized mouse eggs were subjected to a prolonged [Ca2+]cyt change for 15, 25, or 50 min by means of repetitive Ca2+ electropermeabilization at 2-min intervals. The initiation and completion of fertilization-associated responses are correlated with the duration of time in which the [Ca2+]cyt is elevated, with the exception that autonomous CaMKII activity is down-regulated with prolonged elevated [Ca2+]cyt. Activated eggs from 25- or 50-min treatments readily develop to the blastocyst stage with no sign of apoptosis or necrosis and some implant. Ca2+ influx into unfertilized eggs causes neither Ca2+ release from intracellular stores nor rapid removal of cytosolic Ca2+. Thus, the total Ca2+ signal input appears to be an important regulatory parameter that ensures completion of fertilization-associated events and oocytes have a surprising degree of tolerance for a prolonged change in [Ca2+]cyt

    Nigrostriatal overabundance of α-synuclein leads to decreased vesicle density and deficits in dopamine release that correlate with reduced motor activity

    Get PDF
    α-Synuclein (α-syn) is a presynaptic protein present at most nerve terminals, but its function remains largely unknown. The familial forms of Parkinson's disease associated with multiplications of the α-syn gene locus indicate that overabundance of this protein might have a detrimental effect on dopaminergic transmission. To investigate this hypothesis, we use adeno-associated viral (AAV) vectors to overexpress human α-syn in the rat substantia nigra. Moderate overexpression of either wild-type (WT) or A30P α-syn differs in the motor phenotypes induced, with only the WT form generating hemiparkinsonian impairments. Wild-type α-syn causes a reduction of dopamine release in the striatum that exceeds the loss of dopaminergic neurons, axonal fibers, and the reduction in total dopamine. At the ultrastructural level, the reduced dopamine release corresponds to a decreased density of dopaminergic vesicles and synaptic contacts in striatal terminals. Interestingly, the membrane-binding-deficient A30P mutant does neither notably reduce dopamine release nor it cause ultrastructural changes in dopaminergic axons, showing that α-syn's membrane-binding properties are critically involved in the presynaptic defects. To further determine if the affinity of the protein for membranes determines the extent of motor defects, we compare three forms of α-syn in conditions leading to pronounced degeneration. While membrane-binding α-syns (wild-type and A53T) induce severe motor impairments, an N-terminal deleted form with attenuated affinity for membranes is inefficient in inducing motor defects. Overall, these results demonstrate that α-syn overabundance is detrimental to dopamine neurotransmission at early stages of the degeneration of nigrostriatal dopaminergic axon

    A fast algorithm for estimating transmission probabilities in QTL detection designs with dense maps

    Get PDF
    <p>Abstract</p> <p>Background</p> <p>In the case of an autosomal locus, four transmission events from the parents to progeny are possible, specified by the grand parental origin of the alleles inherited by this individual. Computing the probabilities of these transmission events is essential to perform QTL detection methods.</p> <p>Results</p> <p>A fast algorithm for the estimation of these probabilities conditional to parental phases has been developed. It is adapted to classical QTL detection designs applied to outbred populations, in particular to designs composed of half and/or full sib families. It assumes the absence of interference.</p> <p>Conclusion</p> <p>The theory is fully developed and an example is given.</p
    corecore