Modeling the spontaneous initiation of the polymerization of methyl methacrylate

The mechanism of the spontaneous initiation of the polymerization of methyl methacrylate (MMA) was investigated theoretically. The six minimum energy paths (MEP) of the possible reactions were calculated using the density functional theory (DFT) in conjunction with the B3LYP functional and 6-31G* basis set. The Diels-Alder initiation mechanism (path (I) and path (II)) with remarkably high energy barriers is not applicable to MMA. Four favorable paths were found (path (III), path (IV), path (V) and path (VI)), which are supporting the Flory mechanism. Path (V) has the lowest active energy. Therefore this path is considered as the main path for the spontaneous polymerization of MMA. Figure The mechanism of the spontaneous initiation of the polymerization of methyl methacrylate (MMA) was investigated theoretically. The six minimum energy paths (MEP) of the possible reactions were calculated using the density functional theory (DFT) in conjunction with the B3LYP functional and 6-31G* basis set.     

Mortality of vertebrates on a road crossing the Biebrza Valley (NE Poland)

Mortality of vertebrates was monitored on a local road running across Poland’s Biebrza River Valley during 2 years (August 2005–July 2006). On the basis of distance from the river and surrounding habitats, the road (of total length 2,510 m) was divided into three stretches. The road was monitored on foot by two people every month, over a few consecutive days. A total of 1,892 road kills representing at least 47 species were found. Of these, 90.7% were amphibians, 4.2% mammals, 3.1% birds and 2.0% reptiles. Most (70%) of the amphibians were anurans, with the common toad, common frog and moor frog among them together accounting for 82% of the total. Mortality among amphibians differed between months, most anurans dying in May and August, while a majority of Urodela are lost in October. The peaks in mortality were connected with the migration of adult amphibians in spring and juveniles in summer and autumn. The number of amphibians killed was greatest on the (wettest) stretch adjacent to the river and decreased with distance from it. Mortality among birds was highest in July—probably in association with the dispersal of young individuals. Among recorded mammalian road kills, there was a prevalence of small rodents (mainly voles) and insectivores (mainly shrews). Medium-sized mammals were found only accidentally. Mortality in general was conditioned by the number of anurans killed.     

Toward an Integrated Understanding of Pesticide Use Intensity in Costa Rican Vegetable Farming

Understanding the factors that influence the adoption of synthetic pesticides has to date overshadowed explanations of variation in pesticide intensity. I conducted a survey of vegetable farmers in Northern Cartago and the Ujarrás Valley, Costa Rica, in 2003–2004 with the goal of explaining differences in pesticide intensity with reference to socioeconomic, political economic, and agroecological characteristics and relationships. Using ordinary least squares regression models, this paper explores the factors that influence pesticide use intensity in potato and squash production. Results indicate that many variables strongly influence pesticide intensity, including variables related to the farmer, farm household, political-economic relationships, the biophysical environment, and agroecological relationships. Conclusions discuss the need for an integrated approach to adequately understand pesticide intensity and potential policy interventions including agroecological education and extension, increased enforcement of pesticide residue limits in the national market, and land reform to allow for longer fallow periods.

Müller Glia as an Active Compartment Modulating Nervous Activity in the Vertebrate Retina: Neurotransmitters and Trophic Factors

Müller cells represent the main type of glia present in the retina interacting with most, if not all neurons in this tissue. Müller cells have been claimed to function as optic fibers in the retina delivering light to photoreceptors with minimal distortion and low loss [Franze et al (2007) Proc Natl Acad Sci 104:8287–8292]. Most of the mediators found in the brain are also detected in the retinal tissue, and glia cells are active players in the synthesis, release, signaling and uptake of major mediators of synaptic function. Müller glia trophic factors may regulate many different aspects of neuronal circuitry during synaptogenesis, differentiation, neuroprotection and survival of photoreceptors, Retinal Ganglion Cells (RGCs) and other targets in the retina. Here we review the role of several transmitters and trophic factors that participate in the neuron-glia loop in the retina. Special issue article in honor of Dr. Ricardo Tapia.     

The liquid-ordered phase in sphingomyelincholesterol membranes as detected by the discrimination by oxygen transport (DOT) method

Membranes made from binary mixtures of egg sphingomyelin (ESM) and cholesterol were investigated using conventional and saturation-recovery EPR observations of the 5-doxylstearic acid spin label (5-SASL). The effects of cholesterol on membrane order and the oxygen transport parameter (bimolecular collision rate of molecular oxygen with the nitroxide spin label) were monitored at the depth of the fifth carbon in fluid- and gel-phase ESM membranes. The saturation-recovery EPR discrimination by oxygen transport (DOT) method allowed the discrimination of the liquid-ordered (l _o), liquid-disordered (l _d), and solid-ordered (s _o) phases because the bimolecular collision rates of the molecular oxygen with the nitroxide spin label differ in these phases. Additionally, oxygen collision rates (the oxygen transport parameter) were obtained in coexisting phases without the need for their separation, which provides information about the internal dynamics of each phase. The addition of cholesterol causes a dramatic decrease in the oxygen transport parameter around the nitroxide moiety of 5-SASL in the l _o phase, which at 50 mol% cholesterol becomes ∼5 times smaller than in the pure ESM membrane in the l _d phase, and ∼2 times smaller than in the pure ESM membrane in the s _o phase. The overall change in the oxygen transport parameter is as large as ∼20-fold. Conventional EPR spectra show that 5-SASL is maximally immobilized at the phase boundary between regions with coexisting l _d and l _o phases or s _o and l _o phases and the region with a single l _o phase. The obtained results all _owed for the construction of a phase diagram for the ESM-cholesterol membrane.     

Different subcellular localizations and functions of Arabidopsis myosin VIII

Background  

Myosins are actin-activated ATPases that use energy to generate force and move along actin filaments, dragging with their tails different cargos. Plant myosins belong to the group of unconventional myosins and Arabidopsis myosin VIII gene family contains four members: ATM1, ATM2, myosin VIIIA and myosin VIIIB.     

Novel splice variants derived from the receptor tyrosine kinase superfamily are potential therapeutics for rheumatoid arthritis

Introduction  

Despite the advent of biological therapies for the treatment of rheumatoid arthritis, there is a compelling need to develop alternative therapeutic targets for nonresponders to existing treatments. Soluble receptors occur naturally in vivo, such as the splice variant of the cell surface receptor for vascular endothelial growth factor (VEGF) – a key regulator of angiogenesis in rheumatoid arthritis. Bioinformatics analyses predict that the majority of human genes undergo alternative splicing, generating proteins – many of which may have regulatory functions. The objective of the present study was to identify alternative splice variants (ASV) from cell surface receptor genes, and to determine whether the novel proteins encoded exert therapeutic activity in an in vivo model of arthritis.     

Expression of novel extracellular sulfatases Sulf-1 and Sulf-2 in normal and osteoarthritic articular cartilage

Introduction  

Changes in sulfation of cartilage glycosaminoglycans as mediated by sulfatases can regulate growth factor signaling. The aim of this study was to analyze expression patterns of recently identified extracellular sulfatases Sulf-1 and Sulf-2 in articular cartilage and chondrocytes.     

Ecology of seed germination of eight non-pioneer tree species from a tropical seasonal rain forest in southwest China

We compared various aspects of the seed biology of eight non-pioneer tree species from a tropical seasonal rain forest in Xishuangbanna, SW China, that differ in time of dispersal, size and fresh seed moisture content (MC). Seeds were tested for germination under laboratory conditions after dehydration to different moisture levels and under 3.5, 10 and 30% solar irradiances in neutral-shade houses. For six species, germination was also compared in forest understory (3.5% light) and center of a forest gap (32.5% light). Under continuous dehydration over activated silica gel, 100% of seeds of four species had lost the ability to germinate after 48 h, and those of all species except Castanopsis hystrix (decreased from >90 to 30% germination) had lost the ability to germinate after 120 h. Four species did not differ in final germination percentages at the three irradiances (i.e. uniform germination). However, final germination percentages of Horsfieldia pandurifolia and Litsea pierrei var. szemaois were significantly lower in 30% than in 10 or 3.5% light, and seeds of Antiaris toxicaria and C. hystrix germinated to higher percentages in 30 and 10% than in 3.5% light. Mean time to germination (MTG) of the eight species (forest and shade house data combined) ranged from 5–5 days for Pometia tomentosa to 72–207days for L. pierrei; MTG for four species was ≤21 days. There was no obvious relationship between relative desiccation resistance and either time of dispersal, MTG or uniformity of germination at the three light levels, or between seed size and MC or MTG. However, the relationship between seed MC at maturity (25–60% fresh mass basis) and MC at 50% loss of seed viability (12.4–42.5%) was significant. Seven of the species fit Garwood’s (Ecol Monogr 53:159–181, 1983) rapid-rainy germination syndrome and one, L. pierrei, either her delayed-rainy or intermediate-dry germination syndrome. However, fresh, non-dehydrated seeds of all eight species germinated in ≤30 days at constant 30°C in light.     

Fisheries management in practice: review of 13 commercially important fish stocks

This paper comparatively reviews several commercially important fish stocks, their state and their management in various regions of the world including Japanese anchovy, Bay of Biscay anchovy, North Sea sandeel, North Sea herring, Icelandic cod, Barents Sea cod, South African cape hakes, sockeye salmon, chinook salmon, southern bluefin tuna, Pacific halibut, Greenland halibut and Patagonian toothfish. The reviewed fish stocks are systemized in three categories: (1) stock properties and status; (2) management structure and objectives; and (3) management advice. We gather evidence to outline qualities of management regimes that are recommended and highlight those that most often fail. Robust management, biological limits (reference points), implementation and consensus are critical points that separate successful and unsuccessful management regimes. We evaluate each fish stock’s management performance relative to its management objectives and current conservation issues. Furthermore, we point out the importance of stakeholder involvement in fisheries management as well as the problems that international fisheries commissions face through examples from the case studies. Management successes tended to be single-nation and single-stock fisheries with capacity control and clear stakeholder involvement. Fisheries with fleet overcapacity, unclear objectives and illegal activity characterized the case studies with management problems.