Coarse-grained simulations of flow-induced nucleation in semi-crystalline polymers

We perform kinetic Monte Carlo simulations of flow-induced nucleation in polymer melts with an algorithm that is tractable even at low undercooling. The configuration of the non-crystallized chains under flow is computed with a recent non-linear tube model. Our simulations predict both enhanced nucleation and the growth of shish-like elongated nuclei for sufficiently fast flows. The simulations predict several experimental phenomena and theoretically justify a previously empirical result for the flow-enhanced nucleation rate. The simulations are highly pertinent to both the fundamental understanding and process modeling of flow-induced crystallization in polymer melts.Comment: 17 pages, 6 eps figure

Cultivar-Dependent Expression of a Maize Lipoxygenase Responsive to Seed Infesting Fungi

Maize kernels are highly susceptible to Aspergillus spp. infection and aflatoxin (AF) contamination. Fatty acid signaling molecules appear to mediate the plant–fungal interaction by affecting the growth, development, and AF production of the fungus. In particular, fatty acid derivatives of the plant lipoxygenase (LOX) pathway are implicated in the Aspergillus spp.-seed interaction. The 9(S)-hydroperoxide derivative of linoleic acid promotes transcription of AF genes, whereas the 13(S)-hydroperoxide derivative decreases AF gene expression and production; both are sporulation factors. Our goal was to identify LOX genes responsive to Aspergillus spp. colonization and determine their specificities, 9(S)- or 13(S)-. Screening maize LOX expressed sequence tags (ESTs) identified one clone, cssap 92, which is highly expressed in Aspergillus spp.-infected seed susceptible to AF contamination and repressed in lines with resistance to AF contamination. The accumulation of cssap 92 transcript was similar during Fusarium spp. infection. The cDNA clone has 94% identity to the previously described L2 LOX gene from maize. Product-specificity analysis of the CSSAP 92 protein shows that it preferentially adds oxygen to carbon 9 of linoleic acid. Because 9(S)-hydroperoxy linoleic acid has been implicated as an aflatoxin-signaling molecule, it is possible that cssap 92 could be used as a biomarker that is indicative of AF resistance in maize lines

Cultivar-Dependent Expression of a Maize Lipoxygenase Responsive to Seed Infesting Fungi

Maize kernels are highly susceptible to Aspergillus spp. infection and aflatoxin (AF) contamination. Fatty acid signaling molecules appear to mediate the plant–fungal interaction by affecting the growth, development, and AF production of the fungus. In particular, fatty acid derivatives of the plant lipoxygenase (LOX) pathway are implicated in the Aspergillus spp.-seed interaction. The 9(S)-hydroperoxide derivative of linoleic acid promotes transcription of AF genes, whereas the 13(S)-hydroperoxide derivative decreases AF gene expression and production; both are sporulation factors. Our goal was to identify LOX genes responsive to Aspergillus spp. colonization and determine their specificities, 9(S)- or 13(S)-. Screening maize LOX expressed sequence tags (ESTs) identified one clone, cssap 92, which is highly expressed in Aspergillus spp.-infected seed susceptible to AF contamination and repressed in lines with resistance to AF contamination. The accumulation of cssap 92 transcript was similar during Fusarium spp. infection. The cDNA clone has 94% identity to the previously described L2 LOX gene from maize. Product-specificity analysis of the CSSAP 92 protein shows that it preferentially adds oxygen to carbon 9 of linoleic acid. Because 9(S)-hydroperoxy linoleic acid has been implicated as an aflatoxin-signaling molecule, it is possible that cssap 92 could be used as a biomarker that is indicative of AF resistance in maize lines

The distribution of Dishevelled in convergently extending mesoderm

Convergent extension (CE) is a conserved morphogenetic movement that drives axial lengthening of the primary body axis and depends on the planar cell polarity (PCP) pathway. In Drosophila epithelia, a polarised subcellular accumulation of PCP core components, such as Dishevelled (Dvl) protein, is associated with PCP function. Dvl has long been thought to accumulate in the mediolateral protrusions in Xenopus chordamesoderm cells undergoing CE. Here we present a quantitative analysis of Dvl intracellular localisation in Xenopus chordamesoderm cells. We find that, surprisingly, accumulations previously observed at mediolateral protrusions of chordamesodermal cells are not protrusion-specific but reflect yolk-free cytoplasm and are quantitatively matched by the distribution of the cytoplasm-filling lineage marker dextran. However, separating cell cortex-associated from bulk Dvl signal reveals a statistical enrichment of Dvl in notochord–somite boundary-(NSB)-directed protrusions, which is dependent upon NSB proximity. Dvl puncta were also observed, but only upon elevated overexpression. These puncta showed no statistically significant spatial bias, in contrast to the strongly posteriorly-enriched GFP-Dvl puncta previously reported in zebrafish. We propose that Dvl distribution is more subtle and dynamic than previously appreciated and that in vertebrate mesoderm it reflects processes other than protrusion as such

Bending Properties of Nickel Electrodes for Nickel-Hydrogen Batteries

Recent changes in manufacturing have resulted in nickel-hydrogen batteries that fail prematurely by electrical shorting, This failure is believed to be a result of a blistering problem in the nickel electrodes. In this study the bending properties of nickel electrodes are investigated in an attempt to correlate the bending properties of the electrode with its propensity to blister. Nickel electrodes from three different batches of material were tested in both the as-received and impregnated forms. The effects of specimen curvature and position within the electrode on the bending strength were studied, and within-electrode and batch-to-batch variations were addressed. Two color-imaging techniques were employed to differentiate between the phases within the electrodes. These techniques aided in distinguishing the relative amounts of nickel hyroxide surface loading on each electrode, thereby relating surface loading to bend strength. Bend strength was found to increase with the amount of surface loading

Transition-Transversion Bias Is Not Universal: A Counter Example from Grasshopper Pseudogenes

Comparisons of the DNA sequences of metazoa show an excess of transitional over transversional substitutions. Part of this bias is due to the relatively high rate of mutation of methylated cytosines to thymine. Postmutation processes also introduce a bias, particularly selection for codon-usage bias in coding regions. It is generally assumed, however, that there is a universal bias in favour of transitions over transversions, possibly as a result of the underlying chemistry of mutation. Surprisingly, this underlying trend has been evaluated only in two types of metazoan, namely Drosophila and the Mammalia. Here, we investigate a third group, and find no such bias. We characterize the point substitution spectrum in Podisma pedestris, a grasshopper species with a very large genome. The accumulation of mutations was surveyed in two pseudogene families, nuclear mitochondrial and ribosomal DNA sequences. The cytosine-guanine (CpG) dinucleotides exhibit the high transition frequencies expected of methylated sites. The transition rate at other cytosine residues is significantly lower. After accounting for this methylation effect, there is no significant difference between transition and transversion rates. These results contrast with reports from other taxa and lead us to reject the hypothesis of a universal transition/transversion bias. Instead we suggest fundamental interspecific differences in point substitution processes

Stump appendicitis.

Stump appendicitis is a rare and late complication following appendectomy and can often be overlooked. Our case details a 42-year-old male who presented to the Emergency Department with right-sided lower abdominal pain, nausea, and vomiting. A computed tomography scan of his abdomen and pelvis demonstrated a tubular, fluid-filled structure with surrounding inflammatory changes at the level of the patient\u27s appendectomy clips with a 2.3-cm calcified intraluminal stone. Findings were concerning for stump appendicitis with appendicolith. He was admitted and taken to the operating room for a laparoscopic stump appendectomy. Stump appendicitis should always be considered in the differential diagnosis to prevent potentially serious complications

Вплив різних видів анестезіологічного забезпечення на неспецифічну ланку імунітету вагітних під час кесарева розтину

Компоненты хирургической операции – операционная травма, стресс, общая анестезия, кровопотеря, антибактериальная – терапия приводят к снижению защиты иммунной системы и развитию вторичной иммунной недостаточности. В результате операционно-анестезиологического стресса в организме больного возникает состояние иммунодепрессии, которое необходимо нивелировать путем выбора анестетиков, минимально угнетающих иммунные реакции. Такой подход дает возможность разработать и внедрить в клиническую практику оптимальные методы анестезии у беременных. Проведенное исследование показало, что операционный стресс негативно влияет на неспецифический иммунитет беременных. В зависимости от вида анестезии проявления негативного влияния будет различным. Установлено, что спинальная анестезия сопровождается минимальным влиянием на фагоцитарную активность лейкоцитов, а общая анестезия имеет депрессивное влияние, которое сопровождается более пяти дней.Components surgery . surgical trauma, stress, general anesthesia, blood loss, antibiotic . therapy leads to a decrease in defense of the immune system and the development of secondary immune deficiency. As a result of operational and anesthetic stress in the patient.s body a state of immunosuppression, which is necessary to level by selecting the anesthetic minimally depressing the immune response. This approach provides an opportunity to develop and introduce into clinical practice the best methods of anesthesia in pregnant women. The study showed that operational stress affects the nonspecific immunity of pregnant women. Depending on the type of anesthesia, manifestations of the negative impact will be different. Established that spinal anesthesia with a minimum influence on the phagocytic activity of leukocytes and general anesthesia has a depressive effect which is accompanied by more than five days

Rapid Interhemispheric Switching during Vocal Production in a Songbird

To generate complex bilateral motor patterns such as those underlying birdsong, neural activity must be highly coordinated across the two cerebral hemispheres. However, it remains largely elusive how this coordination is achieved given that interhemispheric communication between song-control areas in the avian cerebrum is restricted to projections received from bilaterally connecting areas in the mid- and hindbrain. By electrically stimulating cerebral premotor areas in zebra finches, we find that behavioral effectiveness of stimulation rapidly switches between hemispheres. In time intervals in which stimulation in one hemisphere tends to distort songs, stimulation in the other hemisphere is mostly ineffective, revealing an idiosyncratic form of motor dominance that bounces back and forth between hemispheres like a virtual ping-pong ball. The intervals of lateralized effectiveness are broadly distributed and are unrelated to simple spectral and temporal song features. Such interhemispheric switching could be an important dynamical aspect of neural coordination that may have evolved from simpler pattern generator circuits