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Sample records for asymmetric post-natal development

  1. Characterisation of microRNA expression in post-natal mouse mammary gland development

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    Karagavriilidou Konstantina

    2009-11-01

    Full Text Available Abstract Background The differential expression pattern of microRNAs (miRNAs during mammary gland development might provide insights into their role in regulating the homeostasis of the mammary epithelium. Our aim was to analyse these regulatory functions by deriving a comprehensive tissue-specific combined miRNA and mRNA expression profile of post-natal mouse mammary gland development. We measured the expression of 318 individual murine miRNAs by bead-based flow-cytometric profiling of whole mouse mammary glands throughout a 16-point developmental time course, including juvenile, puberty, mature virgin, gestation, lactation, and involution stages. In parallel whole-genome mRNA expression data were obtained. Results One third (n = 102 of all murine miRNAs analysed were detected during mammary gland development. MicroRNAs were represented in seven temporally co-expressed clusters, which were enriched for both miRNAs belonging to the same family and breast cancer-associated miRNAs. Global miRNA and mRNA expression was significantly reduced during lactation and the early stages of involution after weaning. For most detected miRNA families we did not observe systematic changes in the expression of predicted targets. For miRNA families whose targets did show changes, we observed inverse patterns of miRNA and target expression. The data sets are made publicly available and the combined expression profiles represent an important community resource for mammary gland biology research. Conclusion MicroRNAs were expressed in likely co-regulated clusters during mammary gland development. Breast cancer-associated miRNAs were significantly enriched in these clusters. The mechanism and functional consequences of this miRNA co-regulation provide new avenues for research into mammary gland biology and generate candidates for functional validation.

  2. Indian hedgehog roles in post-natal TMJ development and organization.

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    Ochiai, T; Shibukawa, Y; Nagayama, M; Mundy, C; Yasuda, T; Okabe, T; Shimono, K; Kanyama, M; Hasegawa, H; Maeda, Y; Lanske, B; Pacifici, M; Koyama, E

    2010-04-01

    Indian hedgehog (Ihh) is essential for embryonic mandibular condylar growth and disc primordium formation. To determine whether it regulates those processes during post-natal life, we ablated Ihh in cartilage of neonatal mice and assessed the consequences on temporomandibular joint (TMJ) growth and organization over age. Ihh deficiency caused condylar disorganization and growth retardation and reduced polymorphic cell layer proliferation. Expression of Sox9, Runx2, and Osterix was low, as was that of collagen II, collagen I, and aggrecan, thus altering the fibrocartilaginous nature of the condyle. Though a disc formed, it exhibited morphological defects, partial fusion with the glenoid bone surface, reduced synovial cavity space, and, unexpectedly, higher lubricin expression. Analysis of the data shows, for the first time, that continuous Ihh action is required for completion of post-natal TMJ growth and organization. Lubricin overexpression in mutants may represent a compensatory response to sustain TMJ movement and function.

  3. Dynamics of Notch pathway expression during mouse testis post-natal development and along the spermatogenic cycle.

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    Murta, Daniel; Batista, Marta; Silva, Elisabete; Trindade, Alexandre; Henrique, Domingos; Duarte, António; Lopes-da-Costa, Luís

    2013-01-01

    The transcription and expression patterns of Notch pathway components (Notch 1-3, Delta1 and 4, Jagged1) and effectors (Hes1, Hes2, Hes5 and Nrarp) were evaluated (through RT-PCR and IHC) in the mouse testis at key moments of post-natal development, and along the adult spermatogenic cycle. Notch pathway components and effectors are transcribed in the testis and expressed in germ, Sertoli and Leydig cells, and each Notch component shows a specific cell-type and time-window expression pattern. This expression at key testis developmental events prompt for a role of Notch signaling in pre-pubertal spermatogonia quiescence, onset of spermatogenesis, and regulation of the spermatogenic cycle.

  4. Brain acetylcholinesterase and its molecular forms in a precocial murid, Acomys cahirinus, and rat during post-natal development.

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    Michalek, H; Pintor, A; Fortuna, S; Bisso, G M

    1984-01-01

    Brain acetylcholinesterase (AChE) and its molecular forms of a precocial murid, Acomys cahirinus, characterized by a large hippocampus, were measured during post-natal development and compared with rat. The activity of soluble AChE in Acomys increased slightly up to 4 weeks after birth. The total AChE activity increased somewhat more but, in rats, this increase was still greater. Three main molecular forms of AChE were separated by 7.5% polyacrylamide gel electrophoresis. Their close similarity to the rat AChE forms was assessed by gradient polyacrylamide gel electrophoresis and electrofocusing. Maturation of these forms, i.e., conversion of simple into more complex forms in the soluble fraction of AChE was, however, considerably delayed reaching only after 4 weeks the pattern comparable to that of rat.

  5. Characterization and comparison of post-natal rat Achilles tendon-derived stem cells at different development stages.

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    Chen, Jialin; Zhang, Wei; Liu, Zeyu; Zhu, Ting; Shen, Weiliang; Ran, Jisheng; Tang, Qiaomei; Gong, Xiaonan; Backman, Ludvig J; Chen, Xiao; Chen, Xiaowen; Wen, Feiqiu; Ouyang, Hongwei

    2016-03-14

    Tendon stem/progenitor cells (TSPCs) are a potential cell source for tendon tissue engineering. The striking morphological and structural changes of tendon tissue during development indicate the complexity of TSPCs at different stages. This study aims to characterize and compare post-natal rat Achilles tendon tissue and TSPCs at different stages of development. The tendon tissue showed distinct differences during development: the tissue structure became denser and more regular, the nuclei became spindle-shaped and the cell number decreased with time. TSPCs derived from 7 day Achilles tendon tissue showed the highest self-renewal ability, cell proliferation, and differentiation potential towards mesenchymal lineage, compared to TSPCs derived from 1 day and 56 day tissue. Microarray data showed up-regulation of several groups of genes in TSPCs derived from 7 day Achilles tendon tissue, which may account for the unique cell characteristics during this specific stage of development. Our results indicate that TSPCs derived from 7 day Achilles tendon tissue is a superior cell source as compared to TSPCs derived from 1 day and 56 day tissue, demonstrating the importance of choosing a suitable stem cell source for effective tendon tissue engineering and regeneration.

  6. Long-Term Supplementation with Beta Serum Concentrate (BSC), a Complex of Milk Lipids, during Post-Natal Brain Development Improves Memory in Rats.

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    Guan, Jian; MacGibbon, Alastair; Fong, Bertram; Zhang, Rong; Liu, Karen; Rowan, Angela; McJarrow, Paul

    2015-06-05

    We have previously reported that the supplementation of ganglioside-enriched complex-milk-lipids improves cognitive function and that a phospholipid-enriched complex-milk-lipid prevents age-related cognitive decline in rats. This current study evaluated the effects of post-natal supplementation of ganglioside- and phospholipid-enriched complex-milk-lipids beta serum concentrate (BSC) on cognitive function in young rats. The diet of male rats was supplemented with either gels formulated BSC (n = 16) or blank gels (n = 16) from post-natal day 10 to day 70. Memory and anxiety-like behaviors were evaluated using the Morris water maze, dark-light boxes, and elevated plus maze tests. Neuroplasticity and white matter were measured using immunohistochemical staining. The overall performance in seven-day acquisition trials was similar between the groups. Compared with the control group, BSC supplementation reduced the latency to the platform during day one of the acquisition tests. Supplementation improved memory by showing reduced latency and improved path efficiency to the platform quadrant, and smaller initial heading error from the platform zone. Supplemented rats showed an increase in striatal dopamine terminals and hippocampal glutamate receptors. Thus BSC supplementation during post-natal brain development improved learning and memory, independent from anxiety. The moderately enhanced neuroplasticity in dopamine and glutamate may be biological changes underlying the improved cognitive function.

  7. Long-Term Supplementation with Beta Serum Concentrate (BSC, a Complex of Milk Lipids, during Post-Natal Brain Development Improves Memory in Rats

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    Jian Guan

    2015-06-01

    Full Text Available We have previously reported that the supplementation of ganglioside-enriched complex-milk-lipids improves cognitive function and that a phospholipid-enriched complex-milk-lipid prevents age-related cognitive decline in rats. This current study evaluated the effects of post-natal supplementation of ganglioside- and phospholipid-enriched complex-milk-lipids beta serum concentrate (BSC on cognitive function in young rats. The diet of male rats was supplemented with either gels formulated BSC (n = 16 or blank gels (n = 16 from post-natal day 10 to day 70. Memory and anxiety-like behaviors were evaluated using the Morris water maze, dark–light boxes, and elevated plus maze tests. Neuroplasticity and white matter were measured using immunohistochemical staining. The overall performance in seven-day acquisition trials was similar between the groups. Compared with the control group, BSC supplementation reduced the latency to the platform during day one of the acquisition tests. Supplementation improved memory by showing reduced latency and improved path efficiency to the platform quadrant, and smaller initial heading error from the platform zone. Supplemented rats showed an increase in striatal dopamine terminals and hippocampal glutamate receptors. Thus BSC supplementation during post-natal brain development improved learning and memory, independent from anxiety. The moderately enhanced neuroplasticity in dopamine and glutamate may be biological changes underlying the improved cognitive function.

  8. Parathyroid hormone-related protein is not required for normal ductal or alveolar development in the post-natal mammary gland.

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    Kata Boras-Granic

    Full Text Available PTHrP is necessary for the formation of the embryonic mammary gland and, in its absence, the embryonic mammary bud fails to form the neonatal duct system. In addition, PTHrP is produced by the breast during lactation and contributes to the regulation of maternal calcium homeostasis during milk production. In this study, we examined the role of PTHrP during post-natal mammary development. Using a PTHrP-lacZ transgenic mouse, we surveyed the expression of PTHrP in the developing post-natal mouse mammary gland. We found that PTHrP expression is restricted to the basal cells of the gland during pubertal development and becomes expressed in milk secreting alveolar cells during pregnancy and lactation. Based on the previous findings that overexpression of PTHrP in cap and myoepithelial cells inhibited ductal elongation during puberty, we predicted that ablation of native PTHrP expression in the post-natal gland would result in accelerated ductal development. To address this hypothesis, we generated two conditional models of PTHrP-deficiency specifically targeted to the postnatal mammary gland. We used the MMTV-Cre transgene to ablate the floxed PTHrP gene in both luminal and myoepithelial cells and a tetracycline-regulated K14-tTA;tetO-Cre transgene to target PTHrP expression in just myoepithelial and cap cells. In both models of PTHrP ablation, we found that mammary development proceeds normally despite the absence of PTHrP. We conclude that PTHrP signaling is not required for normal ductal or alveolar development.

  9. Elk3 deficiency causes transient impairment in post-natal retinal vascular development and formation of tortuous arteries in adult murine retinae.

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    Christine Weinl

    Full Text Available Serum Response Factor (SRF fulfills essential roles in post-natal retinal angiogenesis and adult neovascularization. These functions have been attributed to the recruitment by SRF of the cofactors Myocardin-Related Transcription Factors MRTF-A and -B, but not the Ternary Complex Factors (TCFs Elk1 and Elk4. The role of the third TCF, Elk3, remained unknown. We generated a new Elk3 knockout mouse line and showed that Elk3 had specific, non-redundant functions in the retinal vasculature. In Elk3(-/- mice, post-natal retinal angiogenesis was transiently delayed until P8, after which it proceeded normally. Interestingly, tortuous arteries developed in Elk3(-/- mice from the age of four weeks, and persisted into late adulthood. Tortuous vessels have been observed in human pathologies, e.g. in ROP and FEVR. These human disorders were linked to altered activities of vascular endothelial growth factor (VEGF in the affected eyes. However, in Elk3(-/- mice, we did not observe any changes in VEGF or several other potential confounding factors, including mural cell coverage and blood pressure. Instead, concurrent with the post-natal transient delay of radial outgrowth and the formation of adult tortuous arteries, Elk3-dependent effects on the expression of Angiopoietin/Tie-signalling components were observed. Moreover, in vitro microvessel sprouting and microtube formation from P10 and adult aortic ring explants were reduced. Collectively, these results indicate that Elk3 has distinct roles in maintaining retinal artery integrity. The Elk3 knockout mouse is presented as a new animal model to study retinal artery tortuousity in mice and human patients.

  10. Unbiased cell quantification reveals a continued increase in the number of neocortical neurones during early post-natal development in mice

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    Lyck, Lise; Krøigård, Thomas; Finsen, Bente

    2007-01-01

    The post-natal growth spurt of the mammalian neocortex has been attributed to maturation of dendritic arborizations, growth and myelination of axons, and addition of glia. It is unclear whether this growth may also involve recruitment of additional neurones. Using stereological methods, we analysed...

  11. Long-Term Supplementation with Beta Serum Concentrate (BSC), a Complex of Milk Lipids, during Post-Natal Brain Development Improves Memory in Rats

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    GUAN, JIAN; MacGibbon, Alastair; Fong, Bertram; Zhang, Rong; Liu, Karen; Rowan, Angela; McJarrow, Paul

    2015-01-01

    We have previously reported that the supplementation of ganglioside-enriched complex-milk-lipids improves cognitive function and that a phospholipid-enriched complex-milk-lipid prevents age-related cognitive decline in rats. This current study evaluated the effects of post-natal supplementation of ganglioside- and phospholipid-enriched complex-milk-lipids beta serum concentrate (BSC) on cognitive function in young rats. The diet of male rats was supplemented with either gels formulated BSC (n...

  12. miR-200c affects the mRNA expression of E-cadherin by regulating the mRNA level of TCF8 during post-natal epididymal development in juvenile rats

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    Junfeng Wang; Kangcheng Ruan

    2010-01-01

    The unique temporal expression pattern of miR-200c in epididymis during post-natal development in juvenile rats was revealed by our home-made miRNA microarray in this paper.It was found that miR-200c expressed in the lowest level at Day 7 and then increased to the highest at Day 36 followed by a dramatic decrease.The pattern was exactly inverse to that of mRNA expression of transcrip tion factor 8(TCF8)revealed by quantitative real-time polymerase chain reaction(qRT-PCR),providing an extra evidence that TCF8 is one degradation target of miR-200c even in epididymis.Moreover,the qRT-PCR study on expression of E-cadherin and interleukin-2 indicated that miR-200c does exert an obvious effect on the mRNA expression of E-cadherin by directly regulating the mRNA level of TCF8,although the effect on interleukin-2 is not obvious as on E-cadherin,which implicates that interleukin-2 may be also regulated by other factors besides TCF8 in rat epididymis.

  13. Connexins, E-cadherin, Claudin-7 and β-catenin transiently form junctional nexuses during the post-natal mammary gland development.

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    Dianati, Elham; Poiraud, Jérémy; Weber-Ouellette, Anne; Plante, Isabelle

    2016-08-01

    Gap junctions are intercellular channels made of connexins (Cxs) that allow direct communication between adjacent cells. Modulation of Cxs has been associated with abnormal development and function of the mammary gland and breast cancer. However, the mechanisms underlying their expression during normal mammary gland are not yet known. Cxs interact with components of tight and adherens junctions. Thus, we hypothesized that the expression levels of Cxs vary during mammary gland development and are regulated through stage-dependent interactions with members of the tight and adherens junctions. Our specific objectives were to: 1) determine the expression of Cxs and tight and adherens junction proteins throughout development and 2) characterize Cxs interactions with components of tight and adherens junctions. Murine mammary glands were sampled at various developmental stages (pre-pubescent to post-weaning). RT-qPCR and western-blot analyses demonstrated differential expression patterns for all gap (Cx43, Cx32, Cx26, Cx30), tight (Claudin-1, -3, -4, -7) and adherens (β-catenin, E- and P-cadherins) junctions throughout development. Interestingly, co-immunoprecipitation demonstrated interactions between these different types of junctions. Cx30 interacted with Cx26 just at the late pregnancy stage. While Cx43 showed a persistent interaction with β-catenin from virginity to post-weaning, its interactions with E-cadherin and Claudin-7 were transient. Cx32 interacted with Cx26, E-cadherin and β-catenin during lactation. Immunofluorescence results confirmed the existence of a junctional nexus that remodeled during mammary gland development. Together, our results confirm that the expression levels of Cxs vary concomitantly and that Cxs form junctional nexuses with tight and adherens junctions, suggesting the existence of common regulatory pathways.

  14. Does Pain in the Neonatal Period Influence Motor and Sensory Functions in a Similar Way for Males and Females During Post-Natal Development in Rats?

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    Carmo, Elisabete de Cássia do; Sanada, Luciana Sayuri; Machado, Nathalia Leilane Berto; Fazan, Valéria Paula Sassoli

    2016-08-01

    OBJECTIVE : Early pain experiences can lead to disruption in the long-term responses to pain and in abnormal development and behavior in rodents. We evaluated the sensory and motor development of Wistar rats after exposure to painful stimulation (repetitive needle prickling) immediately after birth. METHODS : Male and female rats were followed up to 6 months of life, and sensory and motor functions were investigated by testing paw withdrawal with von Frey filaments, calibrated forceps (CF), and grip strength (GS) tests. RESULTS : Body weight increased with age and tended to be smaller in pain groups compared with their controls of the same sex. GS values also increased with age in controls but were stable and even decreased in pain groups from 120 up to 180 days. The von Frey filaments test showed higher values on the nonstimulated paws in male and female pain groups, with no differences between sides on the controls. The CF test showed smaller values on the stimulated paws in the pain group, with no differences between sides on the controls. CONCLUSIONS : Pain in the neonatal period influences sensory and motor functions negatively during development in male and female rats, even long term after the painful stimulus is ceased. The neonatal injury-induced hypersensitivity is persistent, and male and female rats respond similarly to the stimulus.

  15. Post-natal development of rats` offspring treated with the ethanol extract of Neem leaves (Azadirachta indica A. Juss during pregnancy and lactation

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    Vanessa Carla Lima da Silva

    2015-08-01

    Full Text Available Teratogenicity and developmental abnormalities in the offspring of female rats that ingested ethanol extract of Neem plants during pregnancy and lactation period were assessed. Twenty-four female Wistar rats were randomly distributed in control group and in three experimental groups and treated during the 4th, 5th, and 6th day of pregnancy. After birth, the lactating females received, by gavage, 65, 135 and 200 mg kg-1 of Neem ethanol extract, during 15 days. Results show, there was no significant difference in body mass index of neonatal rats in the 4 groups evaluated, whereas mean rate of offspring survival was 79.4%. Hair growth, incisor teeth eruption, ear detachment, eyelid opening, and spontaneous ambulation were similar for all groups. Likewise, physical development and development of motor activity, ambulation, and postural reflexes were similar for all groups. The administration of Neem ethanol extract did not cause any reproductive or systemic toxicity in animals. Results show that, Neem ethanol extract safe at doses 65, 135 and 200 mg kg-1 in pregnant or lactating rats.

  16. Brain choline acetyltransferase and muscarinic receptor sites, brain and liver cholinesterases in precocial Acomys cahirinus and altricial rat during post-natal development.

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    Michalek, H; Pintor, A; Fortuna, S; Bisso, G M

    1988-01-01

    Brain choline acetyltransferase, acetylcholinesterase with its molecular forms, and muscarinic receptor sites, as well as liver total cholinesterases were evaluated during the first postnatal month in pups of a precocial (Acomys cahirinus) and altricial (rat) murid species. At birth the levels of brain cholinergic markers were higher in the Acomys than in the rat, but in adulthood the differences were smaller or even reversed. The postnatal increase up in the markers to weaning was considerably more pronounced in the rat. However, substantial variations in the patterns of development of the three cholinergic markers within and between species were observed. Liver cholinesterases were considerably higher in Acomys than in rats at all ages investigated. These and literature data are discussed in relation to postnatal, post-conception and post-organogenesis age of pups belonging to the two species. The variability of the ontogenetic patterns between the enzymes suggests that there is some biological control of individual rates of maturation and that it is necessary to be careful in broadly interpreting growth patterns across organs within the same species and across species.

  17. Post-natal growth in the rat pineal gland: a stereological study.

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    Erbagci, H; Kizilkan, N; Ozbag, D; Erkilic, S; Kervancioglu, P; Canan, S; Gumusburun, E

    2012-10-01

    The purpose was to observe the changes in a rat pineal gland using stereological techniques during lactation and post-weaning periods. Thirty Wistar albino rats were studied during different post-natal periods using light microscopy. Pineal gland volume was estimated using the Cavalieri Method. Additionally, the total number of pinealocytes was estimated using the optical fractionator technique. Pineal gland volume displayed statistically significant changes between lactation and after weaning periods. A significant increase in pineal gland volume was observed from post-natal day 10 to post-natal day 90. The numerical density of pinealocytes became stabilized during lactation and decreased rapidly after weaning. However, the total number of pinealocytes continuously increased during post-natal life of all rats in the study. However, this increment was not statistically significant when comparing the lactation and after weaning periods. The increase in post-natal pineal gland volume may depend on increment of immunoreactive fibres, capsule thickness or new synaptic bodies.

  18. Cannabinoids modulate Olig2 and polysialylated neural cell adhesion molecule expression in the subventricular zone of post-natal rats through cannabinoid receptor 1 and cannabinoid receptor 2.

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    Arévalo-Martín, Angel; García-Ovejero, Daniel; Rubio-Araiz, Ana; Gómez, Oscar; Molina-Holgado, Francisco; Molina-Holgado, Eduardo

    2007-09-01

    The subventricular zone (SVZ) is a source of post-natal glial precursors that can migrate to the overlying white matter, where they may differentiate into oligodendrocytes. We showed that, in the post-natal SVZ ependymocytes, radial glia and astrocyte-like cells express cannabinoid receptor 1 (CB1), whereas cannabinoid receptor 2 (CB2) is found in cells expressing the polysialylated neural cell adhesion molecule. To study CB1 and CB2 function, post-natal rats were exposed to selective CB1 or CB2 agonists (arachidonyl-2-chloroethylamide and JWH-056, respectively) for 15 days. Accordingly, we found that CB1 activation increases the number of Olig2-positive cells in the dorsolateral SVZ, whereas CB2 activation increases polysialylated neural cell adhesion molecule expression in this region. As intense myelination occurs during the first weeks of post-natal development, we examined how modulating these factors affected the expression of myelin basic protein. Pharmacological administration of agonists and antagonists of CB1 and CB2 showed that the activation of both receptors is needed to augment the expression of myelin basic protein in the subcortical white matter.

  19. Effects of environmental temperature on oxygen diffusion capacity during post-natal development in the altricial rodent, Phyllotis darwini Efectos de la temperatura ambiental sobre la capacidad de difusión de oxígeno durante el desarrollo postnatal en el roedor altricial Phyllotis darwini

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    MAURICIO CANALS

    2009-03-01

    Full Text Available In this contribution we studied the developmental phenotypic plasticity of respiratory structures involved in the exchange of gases in an altricial rodent, the leaf-eared mouse {Phyllotis darwini. We studied morphological pulmonary parameters of warm (30 °C and cold acclimated animals 15 °C at different developmental stages. We found that acclimation treatments did not affect neither lung volume, the alveolo-capillary barrier thickness nor the respiratory surface density. In consequence the oxygen diffusion capacity was not affected. Although Phyllotis darwini exhibited structural respiratory changes expected by its ontogenetic development, these structures were not affected by thermal acclimation during the post-natal development.Estudiamos la plasticidad fenotípica del desarrollo de las estructuras respiratorias responsables del intercambio de oxígeno en el roedor altricial Phyllotis darwini. Investigamos los parámetros morfológicos del pulmón en animales aclimatados a alta temperatura (bajo requerimiento energético de termorregulación: 30 °C y a baja temperatura (alto requerimiento: 15 °C en diferentes etapas del desarrollo. Encontramos que la temperatura ambiental no afectó el volumen pulmonar, el grosor de la barrera alvéolo-capilar ni la densidad de superficie alveolar. Y en consecuencia, tampoco la capacidad de difusión de oxígeno. Aun cuando Phyllotis darwini mostró los cambios respiratorios esperados de acuerdo a su desarrollo ontogénico, las estructuras evaluadas no fueron afectadas por la aclimatación térmica durante el desarrollo postnatal.

  20. Reversibilitas kalsifikasi tulang akibat kekurangan protein pre dan post natal (Reversibility of bone calcification on pre and post natal protein deficiency

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    Pinandi Sri Pudyani

    2005-09-01

    Full Text Available The growth and development play an important role in orthodontics mainly in bone, because it can determine the maturity of the bone. Bone maturity evaluation is very important in orthodontic treatment, because there are many individual variations in growth and development such as time, duration and velocity of the growth. Nutritional status during pregnancy and infant period will influence the growth and the development of bone. Protein diet is an important factor, which will determine the optimal calcification during bone growth and development stages. Bone calcification, in orthodontics, can be used to estimate the bone maturity for diagnosis and treatment planning. The purpose of this study was to recognize ones ability to surpass calcium and phosphor deficiency because of pre and postnatal protein deficiency. There were three groups of samples of Rattus norvegicus rats. The first group was the control group with standard diet, the second was the infant group with pre and postnatal protein deficiency, and the third group was young rat at weaning age with pre and postnatal protein deficiency supplemented with enough protein in the diet. Bone calcification stage was analyzed: 1 Histologically by measuring epiphyseal width on right femur; 2 by measuring calcium and phosphor concentration on left femur with Spectrophotometry Atomic Absorption and spectroscopy ultra light visible. The data were analyzed by one way ANOVA continued by t test. The result showed that: 1 there was significant (p < 0.01 epiphyseal width difference between group I and II, I and III (p < 0,01 but there was not significant difference between group II & III (p > 0.05; 2 there was significant calcium and phosphor concentration on bone between group I, II and III (p < 0.01. It was concluded that bone calcification damage because of pre and post natal protein deficiency was an irreversible process. Protein supplement after bone calcification could not restore the condition.

  1. Estudo longitudinal do desenvolvimento de crianças nascidas pré-termo no primeiro ano pós-natal Longitudinal study of the development of children born preterm in the first year of post-natal age

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    Fabíola Dantas Andréz Nobre

    2009-01-01

    Full Text Available O objetivo do estudo foi avaliar indicadores de desenvolvimento de crianças nascidas pré-termo e comparar o desempenho nas faixas de 5 a 7 e 10 a 14 meses de idade corrigida. Foram relacionados indicadores do desenvolvimento com variáveis neonatais e do ambiente familiar e sexo. Trinta crianças foram avaliadas pelo Denver-II. As cuidadoras responderam à entrevista e o prontuário médico foi analisado. Na faixa de 5 a 7 meses, 20 % das crianças apresentaram risco para problemas de desenvolvimento e 27% de 10 a 14 meses. Houve diferença significativa entre as fases com mais risco na linguagem na faixa de 10 a 14 meses. As crianças nascidas com menor peso e idade gestacional, que permaneceram mais tempo hospitalizadas e com situações familiares adversas apresentaram mais problemas de desenvolvimento.The aim of the study was to assess the development of children born preterm and to compare the performance in the ranges of 5-7 and 10-14 months of corrected age. The children's development indicators and the variables of neonatal period and familial environment were correlated. Thirty children were assessed by Denver-II. The caregivers were interviewed and the medical chart was examined. Twenty per cent of children presented risk for developmental problems at 5-7 months, and 27% at 10-14 months. There was statistical significant difference between ages in language, with high risk at 10-14. The children with lower birthweight, lower gestational age, longer time stay in the hospital, and with adverse family situations showed higher risk for developmental problems.

  2. Comparative study of the effects of pre and post natal administration of a thyroid drug on testicular activity in adult rat.

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    F Hadj-Bekkouche

    2008-04-01

    Full Text Available Thyroid hormone is known to play a critical role in growth and development of rat testes with a specific effect on the differentiation of Sertoli cells leading to a normal evolution of germ cells. In the present study, we aimed to compare the effect of induced hypothyroidism during fetal and post-natal life on the structure and function of the testis in adult. Pregnant or lactating mothers were treated with 6-propyl-2-thiouracil (PTU during 21 days and weight gain of pups was steady until adult age. Plasma hormonal levels were determined by RIA and morphology of testis was studied on sections stained with Masson's trichrome. Pre and early post natal hypothyroidism resulted in an impairment of body development and a diminution of thyroid hormone levels of treated rats. No significant effect on testicular development has been observed when hypothyroidism is induced in fetal life while it was associated with reduction in testis weight, diameter of seminiferous tubules and hormonal levels and delay in maturation of germ cells, when induced during early post natal life.

  3. The rabbit as an animal model for post-natal vitreous matrix differentiation and degeneration

    NARCIS (Netherlands)

    Los, L. I.

    2008-01-01

    Purpose This study evaluates whether rabbits are a suitable animal model to study post-natal vitreous differentiation and degeneration. Methods Human and rabbit eyes of various ages were studied by complementary anatomical techniques, light microscopy, and transmission electron microscopy. Results T

  4. Early meiotic-specific protein expression in post-natal rat ovaries.

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    Zhang, P; Lv, L X; Xing, W J

    2010-12-01

    Recent studies in mice challenged the basic doctrine that most mammalian females lose neo-oogenesis in post-natal ovaries. In order to provide more information in other species, we examined post-natal rat ovaries by histological sections and detected the germline cell marker protein RVLG (rat vasa-like gene), BrdU (5-bromodeoxyuridine) incorporation in RVLG-expressing cells, for identification of germline cells undergoing mitosis and meiosis in the ovarian surface epithelium (OSE). We also detected the expression of early meiotic-specific proteins disruption of meiotic control 1 (DMC1), stimulated by retinoic acid gene 8 (STRA8) and synaptonemal complex protein 3 (SCP3) by immunohistochemical analysis and Western blotting, and the transcript of SCP1, SCP3 and Sporulation-specific protein 11 (SPO11) by RT-PCR in the post-natal ovarian cortex. However we failed in detecting large ovoid cells in the OSE, which may represent the putative germline stem cells (GSCs) that are supposed to sustain neo-oogenesis, and the transcription of the meiotic-specific genes SCP1, SCP3 and SPO11 by RT-PCR as well as the translation of DMC1, STRA8 and SCP3 by Western blotting. Our data support the postulation that there is no neo-oogenesis occurring in the OSE of rat post-natal ovary through meiosis of GSCs.

  5. Placental abnormalities associated with post-natal mortality in sheep somatic cell clones.

    Science.gov (United States)

    Loi, Pasqualino; Clinton, Michael; Vackova, Irena; Fulka, Josef; Feil, Robert; Palmieri, Chiara; Della Salda, Leonardo; Ptak, Grazyna

    2006-04-01

    We report on cloning experiments designed to explore the causes of peri- and post-natal mortality of cloned lambs. A total of 93 blastocysts obtained by nuclear transfer of somatic cells (granulosa cells) were transferred into 41 recipient ewes, and pregnancies were monitored by ultrasound scanning. In vitro derived, fertilized embryos (IVF, n=123) were also transferred to assess oocyte competence, and naturally mated ewes (n=120) were analysed as well. Cloned embryos developed to the blastocyst stage and implanted at the same rate as IVF embryos. After day 30 of gestation, however, dramatic losses occurred, and only 12 out of 93 (13%) clones reached full-term development, compared to 51 out of 123 (41.6%) lambs born from the IVF control embryos. Three full-term lamb clones were delivered stillborn, as a result of placental degeneration. A further five clone recipients developed hydroallantois. Their lambs died within 24h following delivery by caesarian section, and displayed degenerative lesions in liver and kidney resulting from the severe hydroallantois. One set of twins was delivered by assisted parturition at day 150, but died 24h later due to respiratory distress syndrome. The remaining two clone recipients underwent caesarian section, and the corresponding two lambs displayed signs of respiratory dysfunction and died at approximately 1 month of age due to a bacterial complication. Blood samples collected from the cloned lambs after birth revealed a wide range of abnormalities indicative of kidney and liver dysfunction. Macroscopical and histopathological examination of the placentae revealed a marked reduction in vascularization, particularly at the apex of the villous processes, as well as a loss of differentiation of the trophoblastic epithelium. Our results strongly suggest that post-mortality in cloned lambs is mainly caused by placental abnormalities.

  6. Erk1/2 but not PI3K pathway is required for neurotrophin 3-induced oligodendrocyte differentiation of post-natal neural stem cells

    Institute of Scientific and Technical Information of China (English)

    XinhuaHu; LuJin; LinyinFeng

    2005-01-01

    Neurotrophin 3 (NT3) induces mouse cortical stem cells to an asymmetric division from a symmetric division, suggesting that NT3 may work as an early differentiative signal for neural stem cells (NSCs). Here, using cultured post-natal hippocampal stem cells as a model, we demonstrated that NT3-stimulation causes NSCs to differentiate into oligodendrocyte precursors (OLPs) through an extracellular signal-related kinasel/2 (Erkl/2)-dependent pathway. Following the treatment of NT3 for 24h, NSCs differentiated into more OLPs and fewer neurons, whereas the proliferation and survival of OLPs were not affected. NT3 induced a series of intracellular responses including enhancement of phosphorylation of Erk 1/2 or Akt and increase of expression of oligodendrocyte lineage gene (Olig)-1, a transcriptional factor known to participate in oligodendrocyte development. Application of U0126, a specific inhibitor of MEK1/2 which are upstream to Erk1/2, blocked the phosphorylation of Erk1/2, suppressed the expression of Olig-1 and prevented NSC differentiation into OLPs in response to NT3 stimulation. Blockade of TrkC also inhibited the differentiation of NSCs to OLPs induced by NT3. However,administration of LY294002, an inhibitor of phosphatidylinositol 3 kinase (PI3K), blocked the phosphorylation of Akt but did not affect the effect of NT3 on the expression of Olig-1 and on NSC differentiation into OLPs. Taken together, these results suggest that NT3 induce NSCs to differentiate into OLPs by enhancing the expression of Olig-1 through an Erk1/2-dependent pathway.

  7. Myostatin shows a specific expression pattern in pig skeletal and extraocular muscles during pre- and post-natal growth.

    Science.gov (United States)

    Patruno, Marco; Caliaro, Francesca; Maccatrozzo, Lisa; Sacchetto, Roberta; Martinello, Tiziana; Toniolo, Luana; Reggiani, Carlo; Mascarello, Francesco

    2008-02-01

    Myogenesis is driven by an extraordinary array of cellular signals that follow a common expression pattern among different animal phyla. Myostatin (mstn) is a secreted growth factor that plays a pivotal role in skeletal muscle mass regulation. The aim of the present study was to investigate mstn expression in a large mammal (the pig) in order to ascertain whether distinct expression changes of this factor might be linked to the fiber-type composition of the muscle examined and/or to specific developmental stages. To assess the expression pattern of mstn in relation to myogenic proliferative (Pax7 and MyoD) and differentiative (myogenin) markers, we evaluated muscles with different myosin heavy-chain compositions sampled during pre- and post-natal development and on myogenic cells isolated from the same muscles. Skeletal muscles showed higher levels of mRNA for mstn and all other genes examined during fetal development than after birth. The wide distribution of mstn was also confirmed by immunohistochemistry experiments supporting evidence for cytoplasmic staining in early fetal periods as well as the localization in type 1 fibers at the end of the gestation period. Extraocular muscles, in contrast, did not exhibit decreasing mRNA levels for mstn or other genes even in adult samples and expressed higher levels of both mstn mRNA and protein compared with skeletal muscles. Experiments carried out on myogenic cells showed that mstn mRNA levels decreased when myoblasts entered the differentiation program and that cells isolated at early post-natal stages maintained a high level of Pax7 expression. Our results showed that mstn had a specific expression pattern whose variations depended on the muscle type examined, thus supporting the hypothesis that at birth, porcine myogenic cells continue to be influenced by hyperplastic/proliferative mechanisms.

  8. Challenges in the prenatal and post-natal diagnosis of mediastinal cystic hygroma: a case report

    Directory of Open Access Journals (Sweden)

    Nazir Sarfraz

    2008-08-01

    Full Text Available Abstract Introduction Cystic hygroma is a benign congenital neoplasm that mostly presents as a soft-tissue mass in the posterior triangle of the neck. Pure mediastinal lesions are uncommon; the vast majority are asymptomatic and are an incidental finding in adulthood. The diagnosis is often made intra- or postoperatively. Prenatal identification is exceptional and post-natal diagnosis also proves challenging. Case presentation We report one such case that was mistaken for other entities in both the prenatal and immediate post-natal period. Initial and follow-up antenatal ultrasound scans demonstrated a multicystic lesion in the left chest, and the mother was counselled about the possibility of her baby having a congenital diaphragmatic hernia. Initial post-natal chest radiographs were reported as normal. An echocardiogram and thoracic computed tomography scan confirmed a complex multiloculated cystic mediastinal mass. The working diagnoses were of a mediastinal teratoma or congenital cystic adenomatous malformation. At operation, the lesion was compressed by the left lung and was found to be close to the left phrenic nerve, which was carefully identified and preserved. After excision, histopathological examination of the mass confirmed the diagnosis of cystic hygroma. Postoperative dyspnoea was observed secondary to paradoxical movement of the left hemidiaphragm and probable left phrenic neuropraxia. This settled conservatively with excellent recovery. Conclusion Despite the fact that isolated intrathoracic cystic hygroma is a rare entity, it needs to be considered in the differential diagnosis of foetal and neonatal mediastinal masses, particularly for juxtadiaphragmatic lesions. The phrenic nerve is not identifiable on prenatal ultrasound imaging, and it is therefore understandable that a mass close to the diaphragm may be mistaken for a congenital diaphragmatic hernia because of the location, morphology and potential phrenic nerve compression

  9. Metabolism correlates with variation in post-natal growth rate among songbirds at three latitudes

    Science.gov (United States)

    Ton, Riccardo; Martin, Thomas E.

    2016-01-01

    1. Variation in post-natal growth rates is substantial among organisms and especially strong among latitudes because tropical and south temperate species typically have slower growth than north temperate relatives. Metabolic rate is thought to be a critical mechanism underlying growth rates after accounting for allometric effects of body mass. However, comparative tests on a large spatial scale are lacking, and the importance of metabolism for growth rates remains unclear both within and particularly across latitudes.

  10. Post-natal growth of the gastrointestinal tract of the Siberian hamster: morphometric analysis.

    Science.gov (United States)

    Wołczuk, K; Kobak, J

    2014-12-01

    Post-natal growth of the gastrointestinal tract of the Siberian hamster was studied in newborn and 3-, 7-, 14-, 21-, 42- and 90-day-old animals. Morphometric measurements and calculations were carried out: length and internal surface of gastrointestinal tract segments, size (height, width, surface) and density of villi as well as allometric growth rate of the length and internal surface of the segments with respect to the body mass. The fastest growth rate of the gastrointestinal tract segments was noticed during the first 3 days of the post-natal life. Nevertheless, significant regional differences in their growth rate were found. The increase in the length and internal surface of the large intestine was fastest, while the smallest increase was observed in the oesophagus. All segments of the gastrointestinal tract except oesophagus exhibited a positive allometric relationship to the body mass from birth till final weaning, whereas during the post-weaning period, the increase was isometric. Thus, at birth, the gastrointestinal tract segments were relatively smaller compared with those observed in adults, but then, the gastrointestinal tract grew faster than the rest of the body and reached its adult proportions just before the transition to solid food. Most probably, reaching the adult structure of the gastrointestinal tract before the final weaning is an essential condition for the proper growth of an organism after the weaning.

  11. Role of Nanog in the maintenance of marrow stromal stem cells during post natal bone regeneration

    Energy Technology Data Exchange (ETDEWEB)

    Bais, Manish V.; Shabin, Zabrina M.; Young, Megan; Einhorn, Thomas A. [Orthopaedic Research Laboratory, Department of Orthopedic Surgery, Boston University School of Medicine, Boston, MA 02118 (United States); Kotton, Darrell N. [Pulmonary Center, Boston University School of Medicine, Boston, MA 02118 (United States); Gerstnefeld, Louis C., E-mail: lgersten@bu.edu [Orthopaedic Research Laboratory, Department of Orthopedic Surgery, Boston University School of Medicine, Boston, MA 02118 (United States)

    2012-01-06

    Highlights: Black-Right-Pointing-Pointer Nanog is related to marrow stromal stem cell maintenance. Black-Right-Pointing-Pointer Increasing Nanog expression is seen during post natal surgical bone repair. Black-Right-Pointing-Pointer Nanog knockdown decreases post surgical bone regeneration. -- Abstract: Post natal bone repair elicits a regenerative mechanism that restores the injured tissue to its pre-injury cellular composition and structure and is believed to recapitulate the embryological processes of bone formation. Prior studies showed that Nanog, a central epigenetic regulator associated with the maintenance of embryonic stem cells (ESC) was transiently expressed during fracture healing, Bais et al. . In this study, we show that murine bone marrow stromal cells (MSCs) before they are induced to undergo osteogenic differentiation express {approx}50 Multiplication-Sign the background levels of Nanog seen in murine embryonic fibroblasts (MEFs) and the W20-17 murine marrow stromal cell line stably expresses Nanog at {approx}80 Multiplication-Sign the MEF levels. Nanog expression in this cell line was inhibited by BMP7 treatment and Nanog lentivrial shRNA knockdown induced the expression of the terminal osteogenic gene osteocalcin. Lentivrial shRNA knockdown or lentiviral overexpression of Nanog in bone MSCs had inverse effects on proliferation, with knockdown decreasing and overexpression increasing MSC cell proliferation. Surgical marrow ablation of mouse tibia by medullary reaming led to a {approx}3-fold increase in Nanog that preceded osteogenic differentiation during intramembranous bone formation. Lentiviral shRNA knockdown of Nanog after surgical ablation led to an initial overexpression of osteogenic gene expression with no initial effect on bone formation but during subsequent remodeling of the newly formed bone a {approx}50% decrease was seen in the expression of terminal osteogenic gene expression and a {approx}50% loss in trabecular bone mass. This

  12. Production of fat-1 transgenic rats using a post-natal female germline stem cell line.

    Science.gov (United States)

    Zhou, Li; Wang, Lei; Kang, Jing X; Xie, Wenhai; Li, Xiaoyong; Wu, Changqing; Xu, Bo; Wu, Ji

    2014-03-01

    Germline stem cell lines possess the abilities of self-renewal and differentiation, and have been established from both mouse and human ovaries. Here, we established a new female germline stem cell (FGSC) line from post-natal rats by immunomagnetic sorting for Fragilis, which showed a normal karyotype, high telomerase activity, and a consistent gene expression pattern of primordial germ cells after 1 year of culture. Using an in vitro differentiation system, the FGSC line could differentiate into oocytes. After liposome-based transfection with green fluorescent protein (GFP) or fat-1 vectors, the FGSCs were transplanted into the ovaries of infertile rats. The transplanted FGSCs underwent oogenesis, and the rats produced offspring carrying the GFP or fat-1 transgene after mating with wild-type male rats. The efficiency of gene transfer was 27.86-28.00%, and 2 months was needed to produce transgenic rats. These findings have implications in biomedical research and potential applications in biotechnology.

  13. Late gestation over- and undernutrition predispose for visceral adiposity in response to a post-natal obesogenic diet, but with differential impacts on glucose-insulin adaptations during fasting in lambs

    DEFF Research Database (Denmark)

    Khanal, Prabhat; Husted, Sanne Vinter; Axel, Anne Marie Dixen;

    2014-01-01

    of subcutaneous adipose tissue and induced differential physiological adaptations to fasting. This study does not suggest that exposure to gestational overnutrition will provide a protective effect against development of hyperglycaemia later in life. © 2013 Scandinavian Physiological Society.......Aim: To investigate if late gestation under- or overnutrition has similar adverse impacts on visceral adiposity, metabolic and endocrine function in sheep, and if subsequent exposure to a high-fat diet in early post-natal life exaggerates the prenatal programming outcomes later in life. Methods......, cholesterol, non-esterified fatty acids, triglyceride and lactate combined with abdominal obesity. Peri-renal fat appeared to be a particular target of a high-fat diet post-natally. Conclusion: Both prenatal under- and overnutrition predisposed for abdominal adiposity, apparently by reducing the expandability...

  14. Brain-derived neurotrophic factor (BDNF) and TrkB in the piglet brainstem after post-natal nicotine and intermittent hypercapnic hypoxia.

    Science.gov (United States)

    Tang, Samantha; Machaalani, Rita; Waters, Karen A

    2008-09-26

    Brain-derived neurotrophic factor (BDNF) and its receptor TrkB play a significant role in the regulation of cell growth, survival and death during central nervous system development. The expression of BDNF and TrkB is affected by noxious insults. Two insults during the early post-natal period that are of interest to our laboratory are exposure to nicotine and to intermittent hypercapnic hypoxia (IHH). Piglet models were used to mimic the conditions associated with the risk factors for the sudden infant death syndrome (SIDS) including post-natal cigarette smoke exposure (nicotine model) and prone sleeping where the infant is subjected to re-breathing of expired gases (IHH model). We aimed to determine the effects of nicotine and IHH, alone or in combination, on pro- and rhBDNF and TrkB expression in the developing piglet brainstem. Four piglet groups were studied, with equal gender ratios in each: control (n=14), nicotine (n=14), IHH (n=10) and nic+IHH (n=14). Applying immunohistochemistry, and studying six nuclei of the caudal medulla, we found that compared to controls, TrkB was the only protein significantly decreased after nicotine and nic+IHH exposure regardless of gender. For pro-BDNF and rhBDNF however, observed changes were more evident in males than females exposed to nicotine and nic+IHH. The implications of these findings are that a prior nicotine exposure makes the developing brainstem susceptible to greater changes in the neurotrophic effects of BDNF and its receptor TrkB in the face of a hypoxic insult, and that the effects are greater in males than females.

  15. Lubricin is Required for the Structural Integrity and Post-natal Maintenance of TMJ.

    Science.gov (United States)

    Koyama, E; Saunders, C; Salhab, I; Decker, R S; Chen, I; Um, H; Pacifici, M; Nah, H D

    2014-07-01

    The Proteoglycan 4 (Prg4) product lubricin plays essential roles in boundary lubrication and movement in limb synovial joints, but its roles in temporomandibular joint (TMJ) are unclear. Thus, we characterized the TMJ phenotype in wild-type and Prg4(-/-) mouse littermates over age. As early as 2 weeks of age, mutant mice exhibited hyperplasia in the glenoid fossa articular cartilage, articular disc, and synovial membrane. By 1 month of age, there were fewer condylar superficial tenascin-C/Col1-positive cells and more numerous apoptotic condylar apical cells, while chondroprogenitors displayed higher mitotic activity, and Sox9-, Col2-, and ColX-expressing chondrocyte zones were significantly expanded. Mutant subchondral bone contained numerous Catepsin K-expressing osteoclasts at the chondro-osseous junction, increased invasive marrow cavities, and suboptimal subchondral bone. Mutant glenoid fossa, disc, synovial cells, and condyles displayed higher Hyaluronan synthase 2 expression. Mutant discs also lost their characteristic concave shape, exhibited ectopic chondrocyte differentiation, and occasionally adhered to condylar surfaces. A fibrinoid substance of unclear origin often covered the condylar surface. By 6 months of age, mutant condyles displayed osteoarthritic degradation with apical/mid-zone separation. In sum, lubricin exerts multiple essential direct and indirect roles to preserve TMJ structural and cellular integrity over post-natal life.

  16. Evaluation of the Edinburgh Post Natal Depression Scale using Rasch analysis

    Directory of Open Access Journals (Sweden)

    Tennant Alan

    2006-06-01

    Full Text Available Abstract Background The Edinburgh Postnatal Depression Scale (EPDS is a 10 item self-rating post-natal depression scale which has seen widespread use in epidemiological and clinical studies. Concern has been raised over the validity of the EPDS as a single summed scale, with suggestions that it measures two separate aspects, one of depressive feelings, the other of anxiety. Methods As part of a larger cross-sectional study conducted in Melbourne, Australia, a community sample (324 women, ranging in age from 18 to 44 years: mean = 32 yrs, SD = 4.6, was obtained by inviting primiparous women to participate voluntarily in this study. Data from the EPDS were fitted to the Rasch measurement model and tested for appropriate category ordering, for item bias through Differential Item Functioning (DIF analysis, and for unidimensionality through tests of the assumption of local independence. Results Rasch analysis of the data from the ten item scale initially demonstrated a lack of fit to the model with a significant Item-Trait Interaction total chi-square (chi Square = 82.8, df = 40; p Conclusion The results of this study suggest that EPDS, in its original 10 item form, is not a viable scale for the unidimensional measurement of depression. Rasch analysis suggests that a revised eight item version (EPDS-8 would provide a more psychometrically robust scale. The revised cut points of 7/8 and 9/10 for the EPDS-8 show high levels of agreement with the original case identification for the EPDS-10.

  17. Inherent plasticity of brown adipogenesis in white fat of mice allows for recovery from effects of post-natal malnutrition.

    Directory of Open Access Journals (Sweden)

    Leslie P Kozak

    Full Text Available Interscapular brown adipose tissue (iBAT is formed during fetal development and stable for the life span of the mouse. In addition, brown adipocytes also appear in white fat depots (wBAT between 10 and 21 days of age in mice maintained at a room temperature of 23 °C. However, this expression is transient. By 60 days of age the brown adipocytes have disappeared, but they can re-emerge if the adult mouse is exposed to the cold (5 °C or treated with β3-adrenergic agonists. Since the number of brown adipocytes that can be induced in white fat influences the capacity of the mouse to resist the obese state, we determined the effects of the nutritional conditions on post-natal development (birth to 21 days of wBAT and its long-term effects on diet-induced obesity (DIO. Under-nutrition caused essentially complete suppression of wBAT in inguinal fat at 21 days of age, as indicated by expression of Ucp1 and genes of mitochondrial structure and function based upon microarray and qRT-PCR analysis, whereas over-nutrition had no discernible effects on wBAT induction. Surprisingly, the suppression of wBAT at 21 days of age did not affect DIO in adult mice maintained at 23 °C, nor did it affect the reduction in obesity or cold tolerance when DIO mice were exposed to the cold at 5 °C for one week. Gene expression analysis indicated that mice raised under conditions that suppressed wBAT at 21 days of age were able to normally induce wBAT as adults. Therefore, neither severe hypoleptinemia nor hypoinsulinemia during suckling permanently impaired brown adipogenesis in white fat. In addition, energy balance studies of DIO mice exposed to cold indicates that mice with reduced adipose stores preferentially increased food intake, whereas those with larger adipose tissue depots preferred to utilize energy from their adipose stores.

  18. Development of the asymmetric human

    Science.gov (United States)

    Wolpert, Lewis

    2005-10-01

    Symmetry across the midline is present in many animals, together with the left/right asymmetry of several organs, such as the heart in vertebrates. The development of such asymmetries during embryonic development requires first the specification of the midline and then specification of left/right. One model proposes the transfer of molecular asymmetry to the multicellular level. Nodal expression on the left side in mammals and chicks is a key event, and is due to the release of calcium on the left possibly involving an ion pump and the Notch pathway

  19. High uptake of exclusive breastfeeding and reduced early post-natal HIV transmission.

    Directory of Open Access Journals (Sweden)

    Louise Kuhn

    Full Text Available BACKGROUND: Empirical data showing the clear benefits of exclusive breastfeeding (EBF for HIV prevention are needed to encourage implementation of lactation support programs for HIV-infected women in low resource settings among whom replacement feeding is unsafe. We conducted a prospective, observational study in Lusaka, Zambia, to test the hypothesis that EBF is associated with a lower risk of postnatal HIV transmission than non-EBF. METHODS AND RESULTS: As part of a randomized trial of early weaning, 958 HIV-infected women and their infants were recruited and all were encouraged to breastfeed exclusively to 4 months. Single-dose nevirapine was provided to prevent transmission. Regular samples were collected from infants to 24 months of age and tested by PCR. Detailed measurements of actual feeding behaviors were collected to examine, in an observational analysis, associations between feeding practices and postnatal HIV transmission. Uptake of EBF was high with 84% of women reporting only EBF cumulatively to 4 months. Post-natal HIV transmission before 4 months was significantly lower (p = 0.004 among EBF (0.040 95% CI: 0.024-0.055 than non-EBF infants (0.102 95% CI: 0.047-0.157; time-dependent Relative Hazard (RH of transmission due to non-EBF = 3.48 (95% CI: 1.71-7.08. There were no significant differences in the severity of disease between EBF and non-EBF mothers and the association remained significant (RH = 2.68 95% CI: 1.28-5.62 after adjusting for maternal CD4 count, plasma viral load, syphilis screening results and low birth weight. CONCLUSIONS: Non-EBF more than doubles the risk of early postnatal HIV transmission. Programs to support EBF should be expanded universally in low resource settings. EBF is an affordable, feasible, acceptable, safe and sustainable practice that also reduces HIV transmission providing HIV-infected women with a means to protect their children's lives. TRIAL REGISTRATION: ClinicalTrials.gov NCT00310726.

  20. [Development of new methods in asymmetric reactions and their applications].

    Science.gov (United States)

    Node, Manabu

    2002-01-01

    Several novel methods using chiral reagents and biocatalysts for asymmetric reactions are described. Among those reactions, asymmetric reduction via a novel tandem Michael addition/Meerwein-Ponndorf-Verley reduction of acyclic alpha,beta-unsaturated ketones using a chiral mercapto alcohol, asymmetric synthesis of allene-1,3-dicarboxylate via crystallization induced asymmetric transformation, and improved asymmetric nitroolefination of lactones and lactames at alpha-carbon using new chiral reagents were developed. In the reactions using biocatalysts, asymmetric dealkoxycarbonylation of bicyclic beta-keto diesters having sigma-symmetry with lipase or esterase to give optically active beta-keto esters, the asymmetric reduction of bicyclic 1,3-diketones having sigma-symmetry with Baker's yeast to give optically active keto alcohols, and the asymmetric aldol reaction of glycine with threonine aldolase were also developed. The above mentioned products were effectively utilized as chiral building blocks for the asymmetric synthesis of natural products and drugs.

  1. [Germ cells and post-natal development of testicular function: in vitro studies].

    Science.gov (United States)

    Jégou, B; Le Magueresse, B; Pineau, C; Sharpe, R M

    1991-03-01

    Studies in recent years have clearly established that, in addition to the well known endocrine regulation by gonadotrophin hormones, spermatogenesis is under the modulatory control of a complex set of paracrine regulators. Whereas the role of Leydig cells (testosterone) and of Sertoli cells (nurce cells of germ cells) in spermatogenesis has focused most of the attention, until recently little was known about the contribution of germ cells in the spermatogenetic process. This was the aim of the present experiments. We have used, in vitro, 3 complementary approaches; 1) we measured the influence of the removal of germ cells contaminating Sertoli cell cultures by a hypotonic treatment; 2) in coculture, we examined to what extend isolated germ cells could affect Sertoli cell function; 3) we investigated the effects of germ cell conditioned media on Sertoli cell cultures. Our results indicate that germ cells are able to modulate Sertoli cell function in vitro. This germ cell influence varies according to: 1) the germ cell fraction tested (pachytene spermatocytes, early spermatids or cytoplast from elongated spermatids/residual bodies); 2) the parameter of Sertoli cell function studied (inhibition of oestradiol; stimulation of androgen-binding protein, transferrin...); 3) the age of the Sertoli cell donors; 4) the hormonal environment (+/- FSH). Furthermore we wave demonstrated that germ cell effects were partly at least mediated via proteinaceous factor(s) detected in germ cell spent media. Taking into account previous in vivo studies and these in vitro results, we have hypothesized that germ cells, in conjunction with hormones (LH, FSH, testosterone) play an important role in the ontogenesis of Sertoli cells and therefore in spermatogenesis.

  2. Post-natal development of the median eminence of the guinea pig.

    Science.gov (United States)

    Silverman, A J; Desnoyers, P

    1975-11-01

    The ultrastructure of the median eminence of neonatal (newborn) 1-, 3-, 5-, and 10-day old) and adult guinea pigs was studied to determine the dynamic changes occurring in this structure during early life. At birth the portal vasculature consists of the Mantelplexus and a few, non-fenestrated capillary loops. The number of ansae and the degree of fenestration increase rapidly after birth. The abundance of cytoplasmic and ciliary projections into the ventricular recess and the large numbers of organelles indicate that the ependymal cells are more active in the neonatal period than in the adult male. Moreover, the ependymal endfeet cover most of the surface area of the primary portal plexus during this time. The neuronal layers of the median eminence are difficult to distinguish at birth due to the lack of myelinated fibers in the zona interna. Significant myelination appears on day 3 but is not complete until day 10. There is a progressive increase in the numbers of Herring bodies and large neuro-secretory granules (1,500-1,700 A) during this same time period. In the zona externa, few nerve terminals abut on the perivascular space until day 3. Increases in numbers of granules per axon profile were noted for each day after birth. Despite the relatively long gestation period of the guinea pig (68-72 days), the morphologic appearance of the median eminence at birth suggests that the neurovascular link controlling anterior pituitary function is not yet complete.

  3. [Effect of pre and post natal undernutrition on components of metabolic syndrome later in life; systematic review].

    Science.gov (United States)

    Bacardí Gascón, Montserrat; Jiménez Morán, Elsa; Santillana Marín, Ernestina; Jimenez Cruz, Arturo

    2014-05-01

    Antecedentes: Un entorno intrauterino o una infancia temprana con desnutrición, pueden convertirse en factores de riesgo que aumentan la susceptibilidad de enfermedades crónicas degenerativas en etapas posteriores de la vida. La programación fetal significa que durante la etapa embrionaria pueden presentarse condiciones adversas del entorno que generan cambios en los parámetros fisiológicos que a su vez aumentan la susceptibilidad a cambios metabólicos en etapas posteriores de la vida. Objetivo: El propósito de este estudio fue analizar el efecto de la desnutrición pre y post natal en la presentación de obesidad y componentes del síndrome metabólico (SM) en etapas posteriores de la vida. Metodología: Se realizó una búsqueda electrónica de la literatura en las bases de datos de PubMed y EBSCO con el siguiente término: “Undernutrition in early life and obesity” de artículos publicados de noviembre de 1997 a enero del 2014. Se identificaron siete estudios y se anexaron seis obtenidos de otras referencias. Resultados: Se analizaron trece publicaciones de seis estudios realizados en seis países de Asia, África, Europa y Latinoamérica. Diez de los trece estudios fueron de tipo retrospectivo y la edad de la población que participó al final del estudio osciló de los 11 a los 70 años. En todos los estudios se observó una asociación entre la desnutrición pre y postnatal y la aparición de varios componentes del SM. Conclusión: En esta revisión se observó una consistente asociación entre la desnutrición pre y post natal con algún componente del SM en etapas posteriores de la vida.

  4. Mice Deficient in NF-κB p50 and p52 or RANK Have Defective Growth Plate Formation and Post-natal Dwarfism

    Institute of Scientific and Technical Information of China (English)

    Lianping Xing; Di Chen; Brendan F.Boyce

    2013-01-01

    NF-κBp50/p52 double knockout (dKO) and RANK KO mice have no osteoclasts and develop severe osteopetrosis associated with dwarfism. In contrast, Op/Op mice, which form few osteoclasts, and Src KO mice, which have osteoclasts with defective resorptive function, are osteopetrotic, but they are not dwarfed. Here, we compared the morphologic features of long bones from p50/p52 dKO, RANK KO, Op/Op and Src KO mice to attempt to explain the differences in their long bone lengths. We found that growth plates in p50/p52 dKO and RANK KO mice are significantly thicker than those in WT mice due to a 2-3-fold increase in the hypertrophic chondrocyte zone associated with normal a proliferative chondrocyte zone. This growth plate abnormality disappears when animals become older, but their dwarfism persists. Op/Op or Src KO mice have relatively normal growth plate morphology. In-situ hybridization study of long bones from p50/p52 dKO mice showed marked thickening of the growth plate region containing type 10 collagen-expressing chondrocytes. Treatment of micro-mass chondrocyte cultures with RANKL did not affect expression levels of type 2 collagen and Sox9, markers for proliferative chondrocytes, but RANKL reduced the number of type 10 collagen-expressing hypertrophic chondrocytes. Thus, RANK/NF-κB signaling plays a regulatory role in post-natal endochondral ossification that maintains hypertrophic conversion and prevents dwarfism in normal mice.

  5. Post-natal cardiomyocytes can generate iPS cells with an enhanced capacity toward cardiomyogenic re-differentation.

    Science.gov (United States)

    Rizzi, R; Di Pasquale, E; Portararo, P; Papait, R; Cattaneo, P; Latronico, M V G; Altomare, C; Sala, L; Zaza, A; Hirsch, E; Naldini, L; Condorelli, G; Bearzi, C

    2012-07-01

    Adult mammalian cells can be reprogrammed to a pluripotent state by forcing the expression of a few embryonic transcription factors. The resulting induced pluripotent stem (iPS) cells can differentiate into cells of all three germ layers. It is well known that post-natal cardiomyocytes (CMs) lack the capacity to proliferate. Here, we report that neonatal CMs can be reprogrammed to generate iPS cells that express embryonic-specific markers and feature gene-expression profiles similar to those of mouse embryonic stem (mES) cell and cardiac fibroblast (CF)-derived iPS cell populations. CM-derived iPS cells are able to generate chimeric mice and, moreover, re-differentiate toward CMs more efficiently then either CF-derived iPS cells or mES cells. The increased differentiation capacity is possibly related to CM-derived iPS cells retaining an epigenetic memory of the phenotype of their founder cell. CM-derived iPS cells may thus lead to new information on differentiation processes underlying cardiac differentiation and proliferation.

  6. Epigenetic and phenotypic changes result from a continuous pre and post natal dietary exposure to phytoestrogens in an experimental population of mice

    OpenAIRE

    Sabat Pablo; Guerrero-Bosagna Carlos M; Valdovinos Fernanda S; Valladares Luis E; Clark Susan J

    2008-01-01

    Abstract Background Developmental effects of exposure to endocrine disruptors can influence adult characters in mammals, but could also have evolutionary consequences. The aim of this study was to simulate an environmental exposure of an experimental population of mice to high amounts of nutritional phytoestrogens and to evaluate parameters of relevance for evolutionary change in the offspring. The effect of a continuous pre- and post-natal exposure to high levels of dietary isoflavones was e...

  7. The Asymmetric Impact of Growth Fluctuation on Human Development

    OpenAIRE

    Serap Bedir

    2015-01-01

    In this paper, we re-examine the impact of economic growth fluctuation on human development indicators. Using the per capita growth rate and human development indicators for 131 countries between 1974 and 2007, we find that growth acceleration and deceleration have significant impact on the human development indicators. We also find that the effects are asymmetric. This asymmetric effect is valid both in terms of acceleration and deceleration periods and countries which are classified accordi...

  8. Role of the pre- and post-natal environment in developmental programming of health and productivity.

    Science.gov (United States)

    Reynolds, Lawrence P; Caton, Joel S

    2012-05-06

    The concept that developmental insults (for example, poor pre- or postnatal nutrition) can have long-term consequences on health and well-being of the offspring has been termed developmental programming. In livestock, developmental programming affects production traits, including growth, body composition, and reproduction. Although low birth weight was used as a proxy for compromised fetal development in the initial epidemiological studies, based on controlled studies using livestock and other animal models in the last two decades we now know that developmental programming can occur independently of any effects on birth weight. Studies in humans, rodents, and livestock also have confirmed the critical role of the placenta in developmental programming. In addition, the central role of epigenetic regulation in developmental programming has been confirmed. Lastly, relatively simple therapeutic/management strategies designed to 'rescue' placental development and function are being developed to minimize the effects of developmental programming on health and productivity of humans, livestock, and other mammals.

  9. The post-natal fate of supernumerary ribs in rat teratogenicity studies.

    Science.gov (United States)

    Wickramaratne, G A

    1988-04-01

    A common occurrence in rat teratology studies, supernumerary ribs, have been considered to be indicative of teratogenicity by some authors but not to be so indicative by others. As a teratogenic event is, by definition a permanent change, a study to follow the fate of supernumerary ribs in the development of adulthood of the rat was undertaken. An established teratogen in the rat, aspirin, was used to increase the frequency of supernumerary ribs. Even though aspirin treatment of the dams doubled the initial frequency of supernumerary ribs the results show that over the first 60 days post-partum their frequency in both control and treated groups decline to essentially zero. This decline in frequency of supernumerary ribs is complemented by an increase in the proportion of foetuses with a fully developed transverse process on the first lumbar vertebra. The proposal that supernumerary ribs in the rat are a result of developmental delays in a labile region of the axial skeleton and not a manifestation of a teratogenic event is presented.

  10. Infants' Peripheral Blood Lymphocyte Composition Reflects Both Maternal and Post-Natal Infection with Plasmodium falciparum.

    Directory of Open Access Journals (Sweden)

    Odilon Nouatin

    Full Text Available Maternal parasitoses modulate fetal immune development, manifesting as altered cellular immunological activity in cord blood that may be linked to enhanced susceptibility to infections in early life. Plasmodium falciparum typifies such infections, with distinct placental infection-related changes in cord blood exemplified by expanded populations of parasite antigen-specific regulatory T cells. Here we addressed whether such early-onset cellular immunological alterations persist through infancy. Specifically, in order to assess the potential impacts of P. falciparum infections either during pregnancy or during infancy, we quantified lymphocyte subsets in cord blood and in infants' peripheral blood during the first year of life. The principal age-related changes observed, independent of infection status, concerned decreases in the frequencies of CD4+, NKdim and NKT cells, whilst CD8+, Treg and Teff cells' frequencies increased from birth to 12 months of age. P. falciparum infections present at delivery, but not those earlier in gestation, were associated with increased frequencies of Treg and CD8+ T cells but fewer CD4+ and NKT cells during infancy, thus accentuating the observed age-related patterns. Overall, P. falciparum infections arising during infancy were associated with a reversal of the trends associated with maternal infection i.e. with more CD4+ cells, with fewer Treg and CD8+ cells. We conclude that maternal P. falciparum infection at delivery has significant and, in some cases, year-long effects on the composition of infants' peripheral blood lymphocyte populations. Those effects are superimposed on separate and independent age- as well as infant infection-related alterations that, respectively, either match or run counter to them.

  11. Post-natal stress-induced endocrine and metabolic alterations in mice at adulthood involve different pro-opiomelanocortin-derived peptides.

    Science.gov (United States)

    Loizzo, Stefano; Campana, Gabriele; Vella, Stefano; Fortuna, Andrea; Galietta, Gabriella; Guarino, Irene; Costa, Loredana; Capasso, Anna; Renzi, Paolo; Frajese, Giovanni V; Franconi, Flavia; Loizzo, Alberto; Spampinato, Santi

    2010-11-01

    In previous investigations we added a physical stress (mild pain) to the "classical" post-natal psychological stress in male mice, and we found that this combination produced a series of dysmetabolic signs very similar to mild human type-2 diabetes. Here, for the first time we demonstrate that within this diabetes model at least two groups of signs depend on the unbalance of two different endogenous systems. Newborn male mice were daily exposed to stressful procedures for 21 days (brief mother separation plus sham injection). Other groups underwent the same procedure, and also received naloxone (Na) to block μ-δ endogenous receptors, or a phosphorothioate antisense oligonucleotide (AS) directed against pro-opiomelanocortin (POMC)-mRNA [to block adrenocorticotropin (ACTH)- and POMC-derived opioid peptides]. Adult mice which received only post-natal stress increased body weight (+7.5%), abdominal overweight (+74%), fasting glycemia (+43%), plasma corticosterone (+110%), plasma (+169%) and pituitary (+153%) ACTH levels. Conversely, hypothalamic ACTH and corticotropin-releasing hormone (CRH) were reduced (-70% and -75%, respectively). Neonatal AS administration reverted all parameters to control values. Neonatal naloxone had little or no influence on glucose, corticosterone, ACTH, CRH levels, whereas it prevented body overweight and abdominal overweight. We conclude that, within this type-2 diabetes model in male mice at least two endocrino-neurohumoral systems are damaged, one concerning the opioid system, and the other concerning HPA hormones. The use of the two drugs was of primary importance to demonstrate this statement, and to demonstrate that these two groups of signs could be defined as "separate entities" following our complex post-natal stress model.

  12. Developing a Practical Chiral Toolbox for Asymmetric Catalytic Reactions

    Institute of Scientific and Technical Information of China (English)

    ZHANG XuMu

    2001-01-01

    @@ Chiral Quest's Toolbox Approach: During the last several decades, chemists have made major progress in discovering man-made catalysts to perform challenging asymmetric transformations. However, there is no universal chiral ligand or catalyst for solving problems in enantioselective transformations. The focus of Chiral Quest's research is to develop a useful chiral toolbox for strategically important asymmetric catalytic reactions by inventing a diverse set of novel chiral ligands and combining them with transition metals as effective enantioselective catalysts. The toolbox approach addresses significant problems in organic stereochemistry and has resulted in practical methods for the synthesis of chiral pharmaceuticals and agrochemicals

  13. Developing a Practical Chiral Toolbox for Asymmetric Catalytic Reactions

    Institute of Scientific and Technical Information of China (English)

    ZHANG; XuMu

    2001-01-01

    Chiral Quest's Toolbox Approach: During the last several decades, chemists have made major progress in discovering man-made catalysts to perform challenging asymmetric transformations. However, there is no universal chiral ligand or catalyst for solving problems in enantioselective transformations. The focus of Chiral Quest's research is to develop a useful chiral toolbox for strategically important asymmetric catalytic reactions by inventing a diverse set of novel chiral ligands and combining them with transition metals as effective enantioselective catalysts. The toolbox approach addresses significant problems in organic stereochemistry and has resulted in practical methods for the synthesis of chiral pharmaceuticals and agrochemicals  ……

  14. Development of chiral sulfoxide ligands for asymmetric catalysis.

    Science.gov (United States)

    Trost, Barry M; Rao, Meera

    2015-04-20

    Nitrogen-, phosphorus-, and oxygen-based ligands with chiral backbones have been the historic workhorses of asymmetric transition-metal-catalyzed reactions. On the contrary, sulfoxides containing chirality at the sulfur atom have mainly been used as chiral auxiliaries for diastereoselective reactions. Despite several distinct advantages over traditional ligand scaffolds, such as the proximity of the chiral information to the metal center and the ability to switch between S and O coordination, these compounds have only recently emerged as a versatile class of chiral ligands. In this Review, we detail the history of the development of chiral sulfoxide ligands for asymmetric catalysis. We also provide brief descriptions of metal-sulfoxide bonding and strategies for the synthesis of enantiopure sulfoxides. Finally, insights into the future development of this underutilized ligand class are discussed.

  15. Lactational exposure to atypical antipsychotic drugs disrupts the pituitary-testicular axis in mice neonates during post-natal development.

    Science.gov (United States)

    Mishra, Akash C; Mohanty, Banalata

    2010-07-01

    Olanzapine (OLNZ) and risperidone (RISP), two widely prescribed drugs for post-partum psychosis, transfer through milk to the neonates. Hence, neonates are susceptible to their adverse side effects. In the present study, the pituitary-testicular axis of lactationally exposed mice neonates (PND 28) was examined to evaluate the reproductive adverse effects. Testicular histopathology, immunocytochemistry and morphometric analysis of pituitary PRL (prolactin) and LH (luteinizing hormone) cells and plasma hormonal (PRL, LH and testosterone) levels were the various end points studied. Significantly regressed testes, reduced seminiferous tubules with disrupted germ-cell alignment, spermatogonial exfoliation into the tubule lumens and sparse sperms in the lumens were observed. PRL-immunointensity and plasma levels were elevated, whereas immunoreactivity and plasma levels of LH were decreased. Plasma testosterone levels were also decreased. The hypogonadism thus observed might be mediated by drug-induced hyperprolactinemia, which further inhibited secretions of LH and testosterone. Age may be the factor which made the neonates vulnerable to the PRL elevation by OLNZ which otherwise causes transient elevation in adults and is considered safe. The adverse impact was persistent until adulthood with higher doses of both of the drugs as evident by the analysis of testicular weight, histology and hormonal profiles of post-pubertal mice (PND 63) lactationally exposed as neonates.

  16. Late gestation under- and overnutrition have differential impacts when combined with a post-natal obesogenic diet on glucose-lactate-insulin adaptations during metabolic challenges in adolescent sheep

    DEFF Research Database (Denmark)

    Khanal, Prabhat; Axel, Anne Marie Dixen; Kongsted, Anna Hauntoft

    2015-01-01

    AIM: To determine whether late gestation under- and overnutrition programme metabolic plasticity in a similar way, and whether metabolic responses to an obesogenic diet in early post-natal life depend on the foetal nutrition history. METHODS: In a 3 × 2 factorial design, twin-pregnant ewes were f...

  17. The Asymmetric Impact of Growth Fluctuation on Human Development

    Directory of Open Access Journals (Sweden)

    Serap Bedir

    2015-07-01

    Full Text Available In this paper, we re-examine the impact of economic growth fluctuation on human development indicators. Using the per capita growth rate and human development indicators for 131 countries between 1974 and 2007, we find that growth acceleration and deceleration have significant impact on the human development indicators. We also find that the effects are asymmetric. This asymmetric effect is valid both in terms of acceleration and deceleration periods and countries which are classified according to human development. Namely, the negative impact of economic deceleration on human development outcomes is greater than the positive impact of economic acceleration for all countries. The same is true for medium and low human development countries. The positive impact of economic acceleration and negative impact of economic deceleration are greater than the impacts on very high and high development countries. Therefore, economic growth must be provided, which will reach everyone and ensure everyone's utilization of economic opportunities in order to achieve the 2023 Millennium Goals.

  18. Parental mood during pregnancy and post-natally is associated with offspring risk of Tourette syndrome or chronic tics: prospective data from the Avon Longitudinal Study of Parents and Children (ALSPAC).

    Science.gov (United States)

    Ben-Shlomo, Y; Scharf, J M; Miller, L L; Mathews, C A

    2016-04-01

    Little is known about risk factors for Tourette syndrome (TS) and chronic tic disorders (CT) but maternal psychological morbidity in pregnancy may be associated with TS/CT. We examined whether pre- and post-natal parental anxiety and/or depression are associated with risk of TS/CT in the Avon Longitudinal Study of Parents and Children. We compared self-reported anxiety and depression measures collected prospectively at four time points (18 and 32 weeks prenatally, and 8 weeks and 8 months post-natally) among parents of children who subsequently met criteria for TS/CT at 13 years of age as compared to other children from the cohort. We adjusted for various socioeconomic measures and tested both for time period-specific exposure and chronic exposure using multivariable logistic regression models. 122 children had TS/CT (50 TS, 72 CT) and 5968 children had no tics. In crude analyses, both pre- and post-natal maternal anxiety and depression, but only post-natal paternal depression at 8 months, showed associations with TS/CT. In the final, adjusted multivariable models, chronic maternal anxiety (odds ratio 2.17, 95% CI 1.23, 3.84, p = 0.007) and pre-natal maternal depression (odds ratio 1.86, 95% CI 1.02, 3.39, p = 0.04) showed associations with TS/CT though the latter was consistent with chance (p = 0.07) after adjustment for past maternal depression. We find associations between maternal psychological morbidity pre- and post-natally and risk of future TS/CT in offspring. These associations may reflect either shared genetic susceptibility or a pre-natal exposure. Further work is required to see if these findings can be replicated in larger datasets.

  19. Asymmetric cell division during T cell development controls downstream fate

    Science.gov (United States)

    Pham, Kim; Shimoni, Raz; Charnley, Mirren; Ludford-Menting, Mandy J.; Hawkins, Edwin D.; Ramsbottom, Kelly; Oliaro, Jane; Izon, David; Ting, Stephen B.; Reynolds, Joseph; Lythe, Grant; Molina-Paris, Carmen; Melichar, Heather; Robey, Ellen; Humbert, Patrick O.; Gu, Min

    2015-01-01

    During mammalian T cell development, the requirement for expansion of many individual T cell clones, rather than merely expansion of the entire T cell population, suggests a possible role for asymmetric cell division (ACD). We show that ACD of developing T cells controls cell fate through differential inheritance of cell fate determinants Numb and α-Adaptin. ACD occurs specifically during the β-selection stage of T cell development, and subsequent divisions are predominantly symmetric. ACD is controlled by interaction with stromal cells and chemokine receptor signaling and uses a conserved network of polarity regulators. The disruption of polarity by deletion of the polarity regulator, Scribble, or the altered inheritance of fate determinants impacts subsequent fate decisions to influence the numbers of DN4 cells arising after the β-selection checkpoint. These findings indicate that ACD enables the thymic microenvironment to orchestrate fate decisions related to differentiation and self-renewal. PMID:26370500

  20. Study of post-natal effect of chemopreventive agents on ethylnitrosourea-induced transplacental carcinogenesis in rats. III. Inhibitory action of indomethacin, voltaren, theophylline and epsilon-aminocaproic acid.

    Science.gov (United States)

    Alexandrov, V A; Bespalov, V G; Petrov, A S; Troyan, D N; Lidaks MYu

    1996-09-01

    The influence of the arachidonic acid metabolism inhibitors, indomethacin and voltaren; an inhibitor of phosphodiesterase activity, theophylline and the protease inhibitor epsilonaminocaproic acid (EACA) on N-ethyl-N-nitrosourea (ENU)-induced transplacental carcinogenesis was studied in rats. ENU was given to pregnant rats as a single i.v. exposure at a dose of 75 mg/kg body weight on the 21st day after conception. Indomethacin and voltaren (20 p.p.m. in drinking water), theophylline (0.01% in diet) and EACA (1000 p.p.m. in drinking water) were given to the offspring throughout their post-natal life until all survivors were killed at 12 months. In the ENU-only control groups, 100% of the offspring developed tumors of brain, spinal cord, peripheral nervous system or kidneys, with a total average number of 3.1 tumors per rat. The most marked inhibitory effect was exerted by theophylline, which significantly decreased the incidence and multiplicity of total tumors, and at all main sites selectively (brain, spinal cord, peripheral nerves and kidneys). It also prolonged average survival time of the offspring. Indomethacin and voltaren significantly decreased total tumor incidence and multiplicity and brain tumor incidence and multiplicity. Indomethacin also decreased kidney tumor multiplicity and voltaren diminished spinal cord tumor multiplicity. EACA decreased multiplicities of total, brain, peripheral nerve and kidney tumors, and diminished the incidence of brain tumors. These chemopreventive agents decreased tumor incidences 20-33% and tumor multiplicities 1.4-2.7 times, compared with the ENU-only controls.

  1. Effect of a low glycaemic index diet in gestational diabetes mellitus on post-natal outcomes after 3 months of birth: a pilot follow-up study.

    Science.gov (United States)

    Louie, Jimmy Chun Yu; Markovic, Tania P; Ross, Glynis P; Foote, Deborah; Brand-Miller, Jennie C

    2015-07-01

    A low glycaemic index (LGI) diet during pregnancy complicated by gestational diabetes mellitus (GDM) may offer benefits to the mother and infant pair beyond those during pregnancy. We aimed to investigate the effect of an LGI diet during pregnancy complicated with GDM on early post-natal outcomes. Fifty-eight women (age: 23-41 years; mean ± SD pre-pregnancy body mass index: 24.5 ± 5.6 kg m(-2) ) who had GDM and followed either an LGI diet (n = 33) or a conventional high-fibre diet (HF; n = 25) during pregnancy had a 75-g oral glucose tolerance test and blood lipid tests at 3 months post-partum. Anthropometric assessments were conducted for 55 mother-infant pairs. The glycaemic index of the antenatal diets differed modestly (mean ± SD: 46.8 ± 5.4 vs. 52.4 ± 4.4; P diet during pregnancy complicated by GDM has outcomes similar to those of a conventional healthy diet. Adequately powered studies should explore the potential beneficial effects of LGI diet on risk factors for chronic disease.

  2. The effect of contraceptive counselling in the pre and post-natal period on contraceptive use at three months after delivery among Italian and immigrant women

    Directory of Open Access Journals (Sweden)

    Laura Lauria

    2014-03-01

    Full Text Available INTRODUCTION: Contraceptive counselling in the pre and post-natal period may be important for the use of postpartum contraception and prevention of induced abortion. This paper evaluates the use of postpartum contraceptives and the factors associated with it in a sample of Italian and immigrant women. MATERIALS AND METHODS: Data are drawn from two population-based follow-up surveys conducted to evaluate the quality of maternal care in 25 Italian Local Health Units in 2008/9 and 2010/1. Descriptive analyses and logistic regression models for complex survey data were used. RESULTS: The use of effective contraceptives in the postpartum period is similar between Italians and immigrants (65%. Fifty-nine percent of Italians and 63% of immigrants received contraceptive counselling by natal care services. Women who received counselling are more likely to use effective contraceptives (Italians OR = 2.55 95% CI 2.06 - 3.14; immigrants OR = 4.01 95% CI 2.40 - 6.70. CONCLUSIONS: This study supports the notion that health professionals should take every opportunity during pregnancy, childbirth and puerperium to provide information and counselling to improve knowledge and awareness of contraception.

  3. Rational Asymmetric Development, Piketty and Poverty in Africa

    Directory of Open Access Journals (Sweden)

    Simplice A. Asongu

    2016-12-01

    Full Text Available An April 2015 World Bank report on the Millennium Development Goal poverty target has revealed that extreme poverty has been decreasing in all regions of the world with the exception of Africa. This study extends the implications of Thomas Piketty’s celebrated literature from developed countries to the nexus between developed nations and African countries by building on responses from Rogoff (2014 and Stiglitz (2014, post Washington Consensus paradigms and underpinnings from SolowSwan and Boyce-Fofack-Ndikumana. The central argument presented is that the inequality problem is at the heart of rational asymmetric development between rich and poor countries. Piketty has shown that inequality increases when the return on capital is higher than the growth rate, because the poor cannot catch-up with the rich. We argue that when the return on political economy (or capitalism fuelled illicit capital flight is higher than the growth rate in African countries, inequality in development increases and Africa may not catch-up with the developed world. As an ideal solution, Piketty has proposed progressive income taxation based on automatic exchange of bank information. The ideal analogy proposed in tackling the spirit of African poverty is a comprehensive commitment to fighting illicit capital flight based on this. Hence, contrary to theoretical underpinnings of exogenous growth models, catch-up may not be so apparent. Implications for the corresponding upward bias in endogenous development and catch-up literature are discussed.

  4. Self-help groups can improve utilization of post-natal care by HIV-positive mothers

    NARCIS (Netherlands)

    T.A. Nguyen; P. Oosterhoff; P.N. Yen; P. Wright; A. Hardon

    2009-01-01

    HIV prevention within maternal-child health services has increased in many developing countries, but many HIV-infected women in developing countries still receive insufficient postnatal care. This study explored the experience of 30 HIV-infected women in Vietnam in accessing HIV-related postnatal ca

  5. Incidence of pre-, peri-, and post-natal birth and developmental problems of children with sensory processing disorder and children with autism spectrum disorder

    Directory of Open Access Journals (Sweden)

    Teresa A May-Benson

    2009-11-01

    Full Text Available As the diagnosis of sensory processing disorder (SPD is advanced, it is important to investigate potential contributing factors to this disorder as well as early diagnostic signs. An exploratory descriptive study, utilizing retrospective chart review, was conducted to investigate the incidence of pre-, peri- and post-natal, birth and developmental problems in a sample of 1000 children with SPD and of 467 children with autism spectrum disorder (ASD, who also had SPD. This study revealed that although no one factor was strongly associated with SPD or ASD, an average of seven events for children with SPD and eight events for children with ASD occurred across categories. These included: one pre-natal/pregnancy problem, delivery complication, assisted delivery, gestational or birth-related injury/illness; one or more early childhood illnesses or injuries; two or more infancy/early childhood developmental problems; and one or more delayed early childhood developmental milestones. When comparing results to national studies of the typical population, most remarkable was the incidence of jaundice, three to four times higher in both the SPD and ASD groups than in typical children. In addition, rates of breech position, cord wrap/ prolapse, assisted delivery methods (particularly forceps and suction deliveries, and high birth-weight were greater in both groups. Incidence of premature birth was higher in the ASD although not significantly different from the SPD group. Also of note was a high frequency of absent or brief crawling phase, and high percentages of problems with ear infections, allergies, and maternal stresses during pregnancy.

  6. Isolation and characterization of primary microglia from post-natal murine brain tissues: a comparison of two methods.

    Science.gov (United States)

    Jose, Shinsmon; Tan, Shi Wei; Tong, Chih Kong; Vidyadaran, Sharmili

    2015-12-01

    Microglia are resident macrophages of the central nervous system (CNS). Apart from playing vital roles as sentinel cells, they are crucial in physiological processes such as synaptic pruning during brain development. CNS disorders require an understanding of the contribution of each cellular compartment to the pathogenesis. Elucidating the role of microglia in disease development and progression in the intricate CNS environment is technically challenging and requires the establishment of reliable, reproducible techniques to isolate and culture microglia. A number of different protocols have been developed for isolation of neonatal microglia and here we compare two widely used methods, namely, mild trypsinization and EasySep® magnetic separation. EasySep® magnetic separation provided higher microglia yield, and flow cytometric evaluation of CD11b and F4/80 markers revealed that EasySep® separation method also produced significantly higher purity compared to mild trypsinization. Microglia isolated using EasySep® separation method were functional, as demonstrated by the generation of nitric oxide, IL-6, TNF-α, and MCP-1 in response to lipopolysaccharide stimulation. In summary, this study has revealed that magnetic separation is superior to mild trypsinization in terms of yield and purity of microglia.

  7. Unique molecular signatures influencing the biological function and fate of post-natal stem cells isolated from different sources.

    Science.gov (United States)

    Abu Kasim, Noor Hayaty; Govindasamy, Vijayendran; Gnanasegaran, Nareshwaran; Musa, Sabri; Pradeep, Padmaja Jayaprasad; Srijaya, Thekkeparambil Chandrabose; Aziz, Zeti Adura Che Ab

    2015-12-01

    The discovery of mesenchymal stem cells (MSCs) from a myriad of tissues has triggered the initiative of establishing tailor-made stem cells for disease-specific therapy. Nevertheless, lack of understanding on the inherent differential propensities of these cells may restrict their clinical outcome. Therefore, a comprehensive study was done to compare the proliferation, differentiation, expression of cell surface markers and gene profiling of stem cells isolated from different sources, viz. bone marrow, Wharton's jelly, adipose tissue and dental pulp. We found that although all MSCs were phenotypically similar to each other, Wharton's jelly (WJ) MSCs and dental pulp stem cells (DPSCs) were highly proliferative as compared to bone marrow (BM) MSCs and adipose tissue (AD) MSCs. Moreover, indistinguishable cell surface characteristics and differentiation capacity were confirmed to be similar among all cell types. Based on gene expression profiling, we postulate that BM-MSCs constitutively expressed genes related to inflammation and immunodulation, whereas genes implicated in tissue development were highly expressed in AD-MSCs. Furthermore, the transcriptome profiling of WJ-MSCs and DPSCs revealed an inherent bias towards the neuro-ectoderm lineage. Based on our findings, we believe that there is no unique master mesenchymal stem cell that is appropriate to treat all target diseases. More precisely, MSCs from different sources exhibit distinct and unique gene expression signatures that make them competent to give rise to specific lineages rather than others. Therefore, stem cells should be subjected to rigorous characterization and utmost vigilance needs to be adopted in order to choose the best cellular source for a particular disease.

  8. En escolares de México la presión arterial se relacionó con la masa corporal, pero no con el crecimiento pre- y post-natal

    OpenAIRE

    Cruz Ángeles,Laura Isabel; Ortiz-Hernández,Luis

    2006-01-01

    Objetivos: 1) Conocer la prevalencia de desnutrición y valores elevados de presión arterial en escolares de la Delegación Xochimilco. 2) Analizar la asociación del crecimiento pre- y post-natal y la masa corporal con los valores altos de presión arterial. Material y métodos: Estudio transversal, observacional y analítico. Se evaluaron 972 escolares de la Delegación Xochimilco, durante el año lectivo 2003-2004. Las variables independientes fueron edad, sexo, crecimiento prenatal e infantil, ma...

  9. Recent Developments in the Area of Asymmetric Transfer Hydrogenation

    Directory of Open Access Journals (Sweden)

    Tim Walsgrove

    2001-01-01

    Full Text Available The use of an enantiomerically pure amino alcohol, coupled to a transfer hydrogenation process, in the asymmetric catalysis of the reduction of ketones to alcohols, is described. The process works well for unfunctionalised ketones, affording e.e.s of up to 98%, and excellent conversions. We have recently extended, for the first time in this application, the scope of the methodology to the reductions of a-heteroatom substituted substrates, through the use of the appropriate protecting groups on each atom.

  10. Investigate the Affect of Post-natal Care Intervention on Breastfeeding Rates and Duration%浅谈进行产后护理干预对母乳喂养率及持续时间的影响

    Institute of Scientific and Technical Information of China (English)

    付雅铭

    2015-01-01

    目的:探讨产后护理干预对母乳喂养率及持续时间的影响效果。方法收集我院2013年1月~2014年6月收治的1600例产妇按是否愿意接受产后护理干预分为两组。对照组产妇给予常规护理,实验组产妇加施产后护理,比较两组产妇母乳喂养率、母乳喂养持续时间与自信心情况等。结果实验组产妇母乳喂养率高于对照组,差异具有统计学意义(P<0.01);实验组产妇母乳喂养持续时间与BSES评分高于对照组,差异具有统计学意义(P<0.01)。结论产后护理干预对母乳喂养率及持续时间的影响效果显著。%Objective Investigate the affect of post-natal care intervention on breastfeeding rates and duration.MethodsColected in our hospital from January 2013 to June 2014 were treated 1 600 cases of maternal press are wiling to accept post-natal care interventions into two groups. Control groups were given routine care,the experimental groups were applied on post-natal care,maternal breastfeeding rates between the two groups,duration of breastfeeding and self-confidence and so on.ResultsExperimental groups were significantly higher than the rate of breastfeeding,there was a significant difference statisticaly significant(P< 0.01),the experimental groups were breastfeeding duration and BSES score significantly higher,there was a significant difference,statisticaly significant(P< 0.01).Conclusion Postpartum care intervention on breastfeeding rates and duration affect the results significantly.

  11. Cell chirality: its origin and roles in left-right asymmetric development.

    Science.gov (United States)

    Inaki, Mikiko; Liu, Jingyang; Matsuno, Kenji

    2016-12-19

    An item is chiral if it cannot be superimposed on its mirror image. Most biological molecules are chiral. The homochirality of amino acids ensures that proteins are chiral, which is essential for their functions. Chirality also occurs at the whole-cell level, which was first studied mostly in ciliates, single-celled protozoans. Ciliates show chirality in their cortical structures, which is not determined by genetics, but by 'cortical inheritance'. These studies suggested that molecular chirality directs whole-cell chirality. Intriguingly, chirality in cellular structures and functions is also found in metazoans. In Drosophila, intrinsic cell chirality is observed in various left-right (LR) asymmetric tissues, and appears to be responsible for their LR asymmetric morphogenesis. In other invertebrates, such as snails and Caenorhabditis elegans, blastomere chirality is responsible for subsequent LR asymmetric development. Various cultured cells of vertebrates also show intrinsic chirality in their cellular behaviours and intracellular structural dynamics. Thus, cell chirality may be a general property of eukaryotic cells. In Drosophila, cell chirality drives the LR asymmetric development of individual organs, without establishing the LR axis of the whole embryo. Considering that organ-intrinsic LR asymmetry is also reported in vertebrates, this mechanism may contribute to LR asymmetric development across phyla.This article is part of the themed issue 'Provocative questions in left-right asymmetry'.

  12. Cell chirality: its origin and roles in left–right asymmetric development

    Science.gov (United States)

    Inaki, Mikiko; Liu, Jingyang

    2016-01-01

    An item is chiral if it cannot be superimposed on its mirror image. Most biological molecules are chiral. The homochirality of amino acids ensures that proteins are chiral, which is essential for their functions. Chirality also occurs at the whole-cell level, which was first studied mostly in ciliates, single-celled protozoans. Ciliates show chirality in their cortical structures, which is not determined by genetics, but by ‘cortical inheritance’. These studies suggested that molecular chirality directs whole-cell chirality. Intriguingly, chirality in cellular structures and functions is also found in metazoans. In Drosophila, intrinsic cell chirality is observed in various left–right (LR) asymmetric tissues, and appears to be responsible for their LR asymmetric morphogenesis. In other invertebrates, such as snails and Caenorhabditis elegans, blastomere chirality is responsible for subsequent LR asymmetric development. Various cultured cells of vertebrates also show intrinsic chirality in their cellular behaviours and intracellular structural dynamics. Thus, cell chirality may be a general property of eukaryotic cells. In Drosophila, cell chirality drives the LR asymmetric development of individual organs, without establishing the LR axis of the whole embryo. Considering that organ-intrinsic LR asymmetry is also reported in vertebrates, this mechanism may contribute to LR asymmetric development across phyla. This article is part of the themed issue ‘Provocative questions in left–right asymmetry’. PMID:27821533

  13. Development of Asymmetric Hydrogenation Catalysts via High Throughput Experimentation

    NARCIS (Netherlands)

    Vries, J.G. de; Lefort, L.

    2013-01-01

    The dynamics of drugs discovery imposes severe time constraints on the development chemist in charge of implementing the large scale production of a new Active Pharmaceutical Ingredient (API). This results in the use of well-established and robust transformations at the expense of the cost-efficienc

  14. OBSERVATIONS OF THE CRAB NEBULA'S ASYMMETRICAL DEVELOPMENT

    Energy Technology Data Exchange (ETDEWEB)

    Loll, A. M.; Desch, S. J.; Scowen, P. A. [School of Earth and Space Exploration, Arizona State University, P.O. Box 871404, Tempe, AZ 85287 (United States); Foy, J. P., E-mail: allison.loll@asu.edu [Barrett, The Honors College, Arizona State University, P.O. Box 871612, Tempe, AZ 85287 (United States)

    2013-03-10

    We present the first Hubble Space Telescope Wide Field Planetary Camera-2 imaging survey of the entire Crab Nebula, in the filters F502N ([O III] emission), F673N ([S II]), F631N ([O I]), and F547M (continuum). We use our mosaics to characterize the pulsar wind nebula (PWN) and its three-dimensional structure, the ionizational structure in the filaments forming at its periphery, the speed of the shock driven by the PWN into surrounding ejecta (by inferring the cooling rates behind the shock), and the morphology and ionizational structure of the Rayleigh-Taylor (R-T) fingers. We quantify a number of asymmetries between the northwest (NW) and southeast (SE) quadrants of the Crab Nebula. The lack of observed filaments in the NW, and our observations of the spatial extent of [O III] emission lead us to conclude that cooling rates are slower, and therefore the shock speeds are greater, in the NW quadrant of the nebula, compared with the SE. We conclude that R-T fingers are longer, more ionizationally stratified, and apparently more massive in the NW than in the SE, and the R-T instability appears more fully developed in the NW.

  15. Plasticity in the development of handedness: evidence from normal development and early asymmetric brain injury.

    Science.gov (United States)

    Corbetta, Daniela; Williams, Joshua; Snapp-Childs, Winona

    2006-09-01

    Previous research revealed that shifting patterns of hand preference in the first year of life are linked to infants' sensory-motor experiences as they learn to sit, creep, and walk. In this report, we examine whether new and different forms of locomotion and sensory-motor experiences similarly contribute to alter patterns of hand preference in early development. We examined the cases of three infants with unique developmental histories. Two infants adopted distinctive forms of locomotion in lieu of typical hands-and-knees crawling. One infant scooted using both hands and legs in a coupled fashion, while the other infant performed an asymmetrical, left-biased belly-crawl using only one arm to drag his body. The third infant suffered damage to his left-brain hemisphere shortly after birth and received intense physical therapy to his right arm as a result of it. We followed all three infants on a weekly basis and tracked changes in their reaching behavior, mode of locomotion, and postural achievements. The two infants with unique locomotor patterns displayed changes in hand preference that reciprocated the arm patterns that they used during locomotion. The infant who coupled his body for scooting began to reach bimanually, while the infant who adopted the left-biased belly-crawl developed a strong unimanual, right-hand, preference. The infant with left-hemisphere damage initially displayed a right-hand preference, then a temporary decline in preferred hand use as he began to cruise and walk, and ultimately resumed a right-hand preference in the 2nd year of life. This data is consistent with previous work showing that the development of hand preference in the 1st year of life is highly malleable and sensitive to a variety of new sensory-motor experiences.

  16. Development of asymmetric membrane capsules of metformin hydrochloride for oral osmotic controlled drug delivery

    Directory of Open Access Journals (Sweden)

    Venkatesh Teja Banala

    2014-01-01

    Full Text Available Asymmetric membrane capsules are one of the novel osmotic delivery devices which offer the delivery of a wide range of drugs in a controlled manner. In the present work, we developed a semi-automatic process by fabricating a hydraulic assisted mechanical robotic arm for the manufacturing of asymmetric membrane capsules and the process was validated in comparison with the manual procedure of manufacturing. The capsule walls were made by dip coating phase inversion process using cellulose acetate butyrate as polymer and propylene glycol as plasticizer/pore forming agent. The comparative examination of physical parameters in manual and semi-automatic process confirmed the consistency, reproducibility and efficiency of the semi-automatic process over manual procedure. The resulting asymmetric membrane wall was evaluated by scanning electron microscopy studies revealed the thin dense region supported on a thicker porous region. Fourier transform infrared studies showed phase inversion of the asymmetric membrane as compared to plain membrane. Osmotic release study and in vitro behavior was studied for controlled delivery of metformin hydrochloride as a model drug. In vitro release studies of the formulations showed that drug release was dependent on the concentration of pore forming agent, level of osmogents and independent of the media pH and agitation. The effect of the process variables on the drug release was optimized using 2 3 full factorial design and the release kinetics of the optimized formulation confirmed zero order kinetics with a controlled drug delivery of 13 h and the mechanism of drug release was found to be super case II transport.

  17. Animal studies of the functional consequences of suboptimal polyunsaturated fatty acid status during pregnancy, lactation and early post-natal life.

    Science.gov (United States)

    Brenna, J Thomas

    2011-04-01

    Scores of animal studies demonstrate that seed oils replete with linoleic acid and very low in linolenic acid fed as the exclusive source of fat through pregnancy and lactation result in visual, cognitive, and behavioural deficits in the offspring. Commodity peanut, sunflower, and safflower oils fed to mother rats, guinea pigs, rhesus monkeys, and baboons induce predictable changes in tissue polyunsaturated fatty acid composition that are abnormal in free-living land mammals as well as changes in neurotransmitter levels, catecholamines, and signalling compounds compared with animals with a supply of ω3 polyunsaturated fatty acid. These diets consistently induce functional deficits in electroretinograms, reflex responses, reward or avoidance induced learning, maze learning, behaviour, and motor development compared with ω3 replete groups. Boosting neural tissue docosahexaenoic acid (DHA) by feeding preformed DHA enhances visual and cognitive function. Though no human randomized controlled trials on minimal ω3 requirements in pregnancy and lactation have been conducted, the weight of animal evidence compellingly shows that randomizing pregnant or lactating humans to diets that include high linoleate oils as the sole source of fat would be frankly unethical because they would result in suboptimal child development. Increasing use of commodity ω3-deficient oils in developing countries, many in the name of heart health, will limit brain development of the next generation and can be easily corrected at minimal expense by substituting high oleic acid versions of these same oils, in many cases blended with small amounts of α-linolenic acid oils like flax or perilla oil. Inclusion of DHA in these diets is likely to further enhance visual and neural development.

  18. Time asymmetric spacetimes near null and spatial infinity: I. Expansions of developments of conformally flat data

    Science.gov (United States)

    Valiente Kroon, Juan Antonio

    2004-12-01

    The conformal Einstein equations and the representation of spatial infinity as a cylinder introduced by Friedrich are used to analyse the behaviour of the gravitational field near null and spatial infinity for the development of data which are asymptotically Euclidean, conformally flat and time asymmetric. Our analysis allows for initial data whose second fundamental form is more general than the one given by the standard Bowen York ansatz. The conformal Einstein equations imply, upon evaluation on the cylinder at spatial infinity, a hierarchy of transport equations which can be used to calculate asymptotic expansions for the gravitational field in a recursive way. It is found that the solutions to these transport equations develop logarithmic divergences at the critical sets where null infinity meets spatial infinity. Associated with these, there is a series of quantities expressible in terms of the initial data (obstructions), which if zero, preclude the appearance of some of the logarithmic divergences. The obstructions are, in general, time asymmetric. That is, the obstructions at the intersection of future null infinity with spatial infinity are in general different from those obtained at the intersection of past null infinity with spatial infinity. The latter allows for the possibility of having spacetimes where future and past null infinity have different degrees of smoothness. Finally, it is shown that if both sets of obstructions vanish up to a certain order, then the initial data have to be asymptotically Schwarzschildean in a certain sense.

  19. Effects of combined pre-and post-natal protein deprivation on the myenteric plexus of the esophagus of weanling rats:A histochemical, quantitative and ultrastructural study

    Institute of Scientific and Technical Information of China (English)

    Edson A Liberti; Ricardo BV Fontes; Verginia M Fuggi; Laura BM Maifrino; Romeu R Souza

    2007-01-01

    AIM: To evaluate the effects of protein deprivation on the myenteric plexus of the esophagus of weanling rats.METHODS: Pregnant female Wistar rats were divided into 2 groups: nourished (N), receiving normal diet,and undernourished (D), receiving a protein-deprived diet, which continued after birth. At twenty-one days of age, 13 esophagi from each group were submitted to light microscopy and morphometrical analysis employing the NADH diaphorase, NADPH diaphorase and acetylcholinesterase techniques. Three other esophagi from each group were evaluated with transmission electron microscopy (TEM).RESULTS: In both the NADH- and the NADPH-reactive mounts, the neurons of the N mounts were more intensely stained, while in the D esophagi only the larger neurons were reactive. Many myenteric neurons of N were intensely reactive for AChE activity but only a few neurons of D exhibited these aspects. Ultrastructural analysis revealed that the granular reticulum of N showed large numbers of ribosomes aligned on the outer surface of its regularly arranged membrane while the ribosomes of D were disposed in clusters. The chromatin was more homogeneously scattered inside the neuron nucleus of N as well as the granular component of the nucleolus was evidently more developed in this group.Statistically significant differences between N and D groups were detected in the total estimated number of neurons stained by the NADPH technique.CONCLUSION: The morphological and quantitative data shows that feeding with protein-deprived diet in 21-d old rats induces a delay in the development of the myenteric neurons of the esophagus.

  20. Post-natal size and morphology of the sella turcica. Longitudinal cephalometric standards for Norwegians between 6 and 21 years of age.

    Science.gov (United States)

    Axelsson, Stefan; Storhaug, Kari; Kjaer, Inger

    2004-12-01

    The purpose of this study was to establish normative longitudinal cephalometric standards of size and to describe the morphology of the sella turcica in Norwegian males and females between 6 and 21 years of age using standardized lateral radiographic cephalograms. The subjects comprised 35 males and 37 females from the Oslo University Craniofacial Growth Archive. All were healthy Caucasians, with an Angle Class I molar and canine relationship with no apparent facial disharmony. None had undergone orthodontic therapy. The length, depth, and diameter of the sella turcica was measured and the mean values were analysed longitudinally. Comparisons between the dimensions of the sella turcica of males and females in each age group were performed using a Student's t-test. The length of the sella turcica was almost constant throughout the observation period and the depth and diameter increased with age. No differences between males and females were detected for the depth and diameter of the sella turcica, but the length was larger in males throughout the observation period. The morphology of the sella turcica was assessed and five different morphological aberration types were identified: oblique anterior wall, sella turcica bridging, double contour of the floor, irregularity (notching) in the posterior part of the dorsum sellae, and pyramidal shape of the dorsum sellae. The female subjects had slightly more sella turcicas with aberrant morphology. These reference standards for the dimensions of the sella turcica can be used in the study of growth and development of individuals with craniofacial aberrations and syndromes.

  1. Effect of different contents of extruded linseed in the sow diet on piglet fatty acid composition and hepatic desaturase expression during the post-natal period.

    Science.gov (United States)

    de Quelen, F; Boudry, G; Mourot, J

    2013-10-01

    n-3 polyunsaturated fatty acids (n-3 PUFA) contribute to the normal growth and development of numerous organs in the piglet. The fatty acid composition of piglet tissues is linked to the fatty acid composition of sow milk and, consequently, to the composition of sow diet during the gestation and lactation period. In this study, we investigated the impact of different contents of extruded linseed in the sow diet on the fatty acid composition and desaturase gene expression of piglets. Sows received a diet containing either sunflower oil (low 18:3n-3 with 18:3n-3 representing 3% of total fatty acids) or a mixture of extruded linseed and sunflower oil (medium 18:3n-3 with 9% of 18:3n-3) or extruded linseed (high 18:3n-3 with 27% of 18:3n-3) during gestation and lactation. Fatty acid composition was evaluated on sow milk and on different piglet tissues at days 0, 7, 14, 21 and 28. The postnatal evolution of delta5 (D5D) and delta6 (D6D) desaturase mRNA expression was also measured in the liver of low 18:3n-3 and high 18:3n-3 piglets. The milk of high 18:3n-3 sows had higher proportions of n-3PUFA than that of low 18:3n-3 and medium 18:3n-3 sows. Piglets suckling the high 18:3n-3 sows had greater proportions of 18:3n-3, 20:5n-3, 22:5n-3 and 22:6n-3 in the liver, and of 22:5n-3 and 22:6n-3 in the brain than low 18:3n-3 and medium 18:3n-3 piglets. D5D and D6D mRNA expressions in piglet liver were not affected by the maternal diet at any age. In conclusion, extruded linseed in the sow diet modifies the n-3PUFA status of piglets during the postnatal period. However, a minimal content of 18:3n-3 in the sow diet is necessary to increase the n-3PUFA level in piglet liver and brain. Moreover, modifications in the n-3PUFA fatty acid composition of piglet tissue seem linked to the availability of 18:3n-3 in maternal milk and not to desaturase enzyme expression.

  2. Development and Optimization of Osmotically Controlled Asymmetric Membrane Capsules for Delivery of Solid Dispersion of Lycopene

    Directory of Open Access Journals (Sweden)

    Nitin Jain

    2014-01-01

    Full Text Available The aim of the present investigation is to develop and statistically optimize the osmotically controlled asymmetric membrane capsules of solid dispersion of lycopene. Solid dispersions of lycopene with β-cyclodextrin in different ratios were prepared using solvent evaporation method. Solubility studies showed that the solid dispersion with 1 : 5 (lycopene : β-cyclodextrin exhibited optimum solubility (56.25 mg/mL for osmotic controlled delivery. Asymmetric membrane capsules (AMCs were prepared on glass mold pins via dip coating method. Membrane characterization by scanning electron microscopy showed inner porous region and outer dense region. Central composite design response surface methodology was applied for the optimization of AMCs. The independent variables were ethyl cellulose (X1, glycerol (X2, and NaCl (X3 which were varied at different levels to analyze the effect on dependent variables (percentage of cumulative drug release (Y1 and correlation coefficient of drug release (Y2. The effect of independent variables on the response was significantly influential. The F18 was selected as optimized formulation based on percentage of CDR (cumulative drug release of 85.63% and correlation coefficient of 0.9994. The optimized formulation was subjected to analyze the effect of osmotic pressure and agitational intensity on percentage of CDR. The drug release was independent of agitational intensity but was dependent on osmotic pressure of dissolution medium.

  3. BCL11B regulates epithelial proliferation and asymmetric development of the mouse mandibular incisor.

    Directory of Open Access Journals (Sweden)

    Kateryna Kyrylkova

    Full Text Available Mouse incisors grow continuously throughout life with enamel deposition uniquely on the outer, or labial, side of the tooth. Asymmetric enamel deposition is due to the presence of enamel-secreting ameloblasts exclusively within the labial epithelium of the incisor. We have previously shown that mice lacking the transcription factor BCL11B/CTIP2 (BCL11B hereafter exhibit severely disrupted ameloblast formation in the developing incisor. We now report that BCL11B is a key factor controlling epithelial proliferation and overall developmental asymmetry of the mouse incisor: BCL11B is necessary for proliferation of the labial epithelium and development of the epithelial stem cell niche, which gives rise to ameloblasts; conversely, BCL11B suppresses epithelial proliferation, and development of stem cells and ameloblasts on the inner, or lingual, side of the incisor. This bidirectional action of BCL11B in the incisor epithelia appears responsible for the asymmetry of ameloblast localization in developing incisor. Underlying these spatio-specific functions of BCL11B in incisor development is the regulation of a large gene network comprised of genes encoding several members of the FGF and TGFβ superfamilies, Sprouty proteins, and Sonic hedgehog. Our data integrate BCL11B into these pathways during incisor development and reveal the molecular mechanisms that underlie phenotypes of both Bcl11b(-/- and Sprouty mutant mice.

  4. 分娩预演对初产妇自我效能和产后抑郁情绪的影响%Effect of early maternal childbirth rehearsal on self-efficacy and post-natal depression for primipara

    Institute of Scientific and Technical Information of China (English)

    吕连玉; 孙莉娟

    2015-01-01

    目的:研究分娩预演健康教育对初产妇自我效能和产后抑郁情绪的影响,以期降低临床剖宫产率,提高初产妇的生活质量。方法选取2013年1—12月入院定期产检,且无剖宫产指征的初产妇120名。根据随机数字表法随机分为观察组60名和对照组60名。对照组初产妇接受常规产前健康教育培训,观察组在其基础上应用分娩预演健康教育培训。比较两组初产妇培训前后的自我效能感(GSES)评分、分娩方式及产后抑郁情况。结果两组初产妇培训前GSES评分差异无统计学意义(P>0.05),培训后观察组为(30.13±4.10)分,高于对照组的(26.18±5.69)分,差异有统计学意义( t=2.978,P<0.05)。观察组自然分娩50名占83.33%,剖宫产10名占16.67%;与对照组比较差异有统计学意义(χ2值分别为2.316,2.334;P<0.05)。产前1个月两组产后抑郁评分差异无统计学意义( P>0.05),观察组产后1个月为(12.1±2.4)分,产后6个月为(9.7±1.6)分,分别低于对照组,差异有统计学意义( t值分别为2.297,5.497;P<0.05)。结论分娩预演健康教育可提高初产妇的自我效能感,提高自然分娩率、降低社会因素剖宫产率,并可有效改善产后抑郁,可为临床指导初产妇生产提供一定参考。%Objective To study the impact of early maternal childbirth rehearsal on self-efficacy and post-natal depression , in order to reduce the rate of cesarean section and improve the quality of life in primipara . Methods From January to December in 2013, totals of 120 cases without the evidence of maternal cesarean section were selected as the research subjects .They were randomly divided into experimental group (60 cases) and control group (60 cases) according to the random table method .The control group received routine prenatal maternal health education

  5. Asymmetric development of dorsal and ventral attention networks in the human brain

    Directory of Open Access Journals (Sweden)

    Kristafor Farrant

    2015-04-01

    Full Text Available Two neural systems for goal-directed and stimulus-driven attention have been described in the adult human brain; the dorsal attention network (DAN centered in the frontal eye fields (FEF and intraparietal sulcus (IPS, and the ventral attention network (VAN anchored in the temporoparietal junction (TPJ and ventral frontal cortex (VFC. Little is known regarding the processes governing typical development of these attention networks in the brain. Here we use resting state functional MRI data collected from thirty 7 to 12 year-old children and thirty 18 to 31 year-old adults to examine two key regions of interest from the dorsal and ventral attention networks. We found that for the DAN nodes (IPS and FEF, children showed greater functional connectivity with regions within the network compared with adults, whereas adults showed greater functional connectivity between the FEF and extra-network regions including the posterior cingulate cortex. For the VAN nodes (TPJ and VFC, adults showed greater functional connectivity with regions within the network compared with children. Children showed greater functional connectivity between VFC and nodes of the salience network. This asymmetric pattern of development of attention networks may be a neural signature of the shift from over-representation of bottom-up attention mechanisms to greater top-down attentional capacities with development.

  6. An Asymmetrical Network: National and International Dimensions of the Development of Mexican Physiology.

    Science.gov (United States)

    Cueto, Marcos

    2016-01-01

    This article examines the history of Mexican physiology during the period 1910-60 when two noted investigators, José J. Izquierdo, first, and Arturo Rosenblueth, second, inscribed their work into an international network of medical research. The network had at its center the laboratory of Walter B. Cannon at Harvard University. The Rockefeller Foundation was its main supporter. Rosenblueth was quite familiar with the network because he worked with Cannon at Harvard for over ten years before returning to Mexico in the early 1940s. Izquierdo and Rosenblueth developed different strategies to face adverse conditions such as insufficient laboratory equipment, inadequate library resources, a small scientific community, and ephemeral political support. Both acquired local influence and international prestige, but the sources of financial and academic power remained in the United States. This case study provides insight into the circulation of scientific ideas and practices in an important Latin American country and suggests that the world's circulation of science among industrial and developing nations during the mid-twentieth century was intrinsically asymmetric but opened temporary opportunities for talented individuals and groups of researchers.

  7. Recent developments in the catalytic asymmetric synthesis of alpha- and beta-amino acids.

    Science.gov (United States)

    Ma, Jun-An

    2003-09-22

    The stereoselective synthesis of amino acids is of great importance for the construction of optically active natural products and pharmaceuticals. Apart from enzymes, a broad repertoire of chiral reagents, auxiliaries, and catalysts can be used for the formation of amino acids. Asymmetric reactions using catalytic amounts of chiral molecules provide efficient methods for the generation of optically active proteinogenic and nonproteinogenic amino acids. This minireview collects recent work on catalytic asymmetric synthesis of alpha- and beta-amino acids.

  8. Development of Ar-BINMOL-Derived Atropisomeric Ligands with Matched Axial and sp(3) Central Chirality for Catalytic Asymmetric Transformations.

    Science.gov (United States)

    Xu, Zheng; Xu, Li-Wen

    2015-10-01

    Recently, academic chemists have renewed their interest in the development of 1,1'-binaphthalene-2,2'-diol (BINOL)-derived chiral ligands. Six years ago, a working hypothesis, that the chirality matching of hybrid chirality on a ligand could probably lead to high levels of stereoselective induction, prompted us to use the axial chirality of BINOL derivatives to generate new stereogenic centers within the same molecule with high stereoselectivity, obtaining as a result sterically favorable ligands for applications in asymmetric catalysis. This Personal Account describes our laboratory's efforts toward the development of a novel class of BINOL-derived atropisomers bearing both axial and sp(3) central chirality, the so-called Ar-BINMOLs, for asymmetric synthesis. Furthermore, on the basis of the successful application of Ar-BINMOLs and their derivatives in asymmetric catalysis, the search for highly efficient and enantioselective processes also compelled us to give special attention to the BINOL-derived multifunctional ligands with multiple stereogenic centers for use in catalytic asymmetric reactions.

  9. Study of different routes to develop asymmetric double decker silsesquioxane (DDSQ)

    Science.gov (United States)

    Attanayake, Gayanthi Kumari

    on studies of different routes to an asymmetric DDSQ cage. DDSQ molecules possess a higher symmetry. Breaking the symmetry and selective functionalization of the DDSQ molecule would be highly desirable to fine tune the physical properties. Different routes were studied to develop an asymmetric DDSQ cage. One route is monoprotection of a hydroxyl group from four symmetrical hydroxyl groups present in the DDSQ cage using McDougal chemistry. This chemistry was applied to DDSQ cage, DDSQ(Me)(OH) and DDSQ(Me)(Hydroxypropyl)(carbinol system). The second attempt was hindering one side of the DDSQ cage using an immobilized surface. Different surface immobilized reagents such as "Red-Sil" (Reducing Silica) and Merrifield resinwere analyzed in this project as screening surfaces.

  10. Development of chiral metal amides as highly reactive catalysts for asymmetric [3 + 2] cycloadditions

    Science.gov (United States)

    Yamashita, Yasuhiro; Yoshimoto, Susumu; Dutton, Mark J

    2016-01-01

    Summary Highly efficient catalytic asymmetric [3 + 2] cycloadditions using a chiral copper amide are reported. Compared with the chiral CuOTf/Et3N system, the CuHMDS system showed higher reactivity, and the desired reactions proceeded in high yields and high selectivities with catalyst loadings as low as 0.01 mol %. PMID:27559396

  11. Role of FGF1, FGF2 and FGF7 in the development of the pancreas from control and streptozotocin-treated hamsters.

    Science.gov (United States)

    Inchovska, M; Ogneva, V; Martinova, Y

    2006-12-01

    Although progress has been made with respect to the growth and transcription factors implicated in pancreatic development, many questions remain unsolved. It has been established that during embryonic life, both endocrine and acinar cells are derived from pancreatic epithelial precursor cells. Growth factors control the proliferation of precursor cells and their ability to differentiate into mature cells, both in pre-natal and in early post-natal life. Pancreatic development during the early post-natal period is an area of great interest for many scientists. In this study we have examined the structure characteristics, functional and proliferative activity of control and diabetic hamster pancreatic ductal, exocrine and beta cells, following treatment with FGFs 1, 2 and 7 in vitro. Light and electron microscopic studies indicated active synthetic processes in these cells under the influence of the investigated FGFs. In our experimental model of diabetes, the labelling index of the cells was significantly higher than in corresponding control groups of hamsters. We established that FGF2 at a concentration of 10 ng/l was responsible for the most prominent effect on ductal cells and beta cells in the diabetic groups. FGF1 at a concentration of 10 ng/l displayed the highest stimulatory effect on exocrine cells in the diabetic groups at post-natal day 10. Taken together these data strongly suggest that FGF1 and FGF2 induce proliferation of pancreatic epithelial cells during the early post-natal period whereas FGF7 is not strictly specific for pancreatic cell proliferation.

  12. Asymmetrical interhemispheric connections develop in cat visual cortex after early unilateral convergent strabismus: Anatomy, physiology and mechanisms

    Directory of Open Access Journals (Sweden)

    Emmanuel eBui Quoc

    2012-01-01

    Full Text Available In the mammalian primary visual cortex, the corpus callosum contributes to the unification of the visual hemifields that project to the two hemispheres. Its development depends on visual experience. When the latter is abnormal, callosal connections must undergo dramatic anatomical and physiological changes. However, such data are sparse and incomplete. Thus, little is known about the consequences of abnormal postnatal visual experience on the development of callosal connections and their role in unifying representation of the two hemifields. Here, the effects of early unilateral convergent strabismus (a model of abnormal visual experience were fully characterized with respect to the development of the callosal connections in cat visual cortex, an experimental model for humans. Electrophysiological responses and 3D reconstruction of single callosal axons show that abnormally asymmetrical callosal connections develop after unilateral convergent strabismus, resulting from an extension of axonal branches of specific orders in the hemisphere ipsilateral to the deviated eye and a decreased number of nodes and terminals in the other (ipsilateral to the non deviated eye. Furthermore this asymmetrical organization prevents the establishment of a unifying representation of the two visual hemifields. As a general rule, we suggest that crossed and uncrossed retino-geniculo-cortical pathways contribute in succession to the development of the callosal maps in visual cortex.

  13. Mechanism-guided development of VO(salen)X complexes as catalysts for the asymmetric synthesis of cyanohydrin trimethylsilyl ethers.

    Science.gov (United States)

    Belokon, Yuri N; Clegg, William; Harrington, Ross W; Maleev, Victor I; North, Michael; Pujol, Marta Omedes; Usanov, Dmitry L; Young, Carl

    2009-01-01

    Catalyze this! Detailed study of the mechanism of asymmetric cyanohydrin synthesis catalyzed by VO(salen)X complexes (see figure) led to the development of VO(salen)NCS, as the most active vanadium-based catalyst yet developed for this reaction.The mechanism by which oxovanadium(V)(salen) complexes(1) VO(salen)X catalyze the asymmetric addition of trimethylsilyl cyanide to benzaldehyde has been studied. The reaction kinetics indicated that the structure of the counterion (X) had a significant influence on the rate, but not on the enantioselectivity of the reaction. The less coordinating the counterion, the lower the catalytic activity; a trend that was confirmed by a Hammett analysis. Variable temperature kinetics allowed the enthalpies and entropies of activation to be determined for some catalysts, and showed that, for others, the overall reaction order changes from second order to zero order as the temperature is reduced. The order with respect to the catalyst was determined for nine of the VO(salen)X complexes and showed that the less active catalysts were active predominantly as mononuclear species whilst the more active catalysts were active predominantly as dinuclear species. Mass spectrometry confirmed the formation of dinuclear species in situ from all of the VO(salen)X complexes and indicated that the dinuclear complexes contained one vanadium(V) and one vanadium(IV) ion. The latter conclusion was supported by cyclic voltammetry of the complexes, by fluorescence measurements and by the fact that catalyst deactivation occurs when reactions are carried out under an inert atmosphere. Based on this evidence, it has been deduced that the catalysis involves two catalytic cycles: one for catalysis by mononuclear VO(salen)X species and the other for catalysis by dinuclear species. The catalytic cycle involving dinuclear species involves activation of both the cyanide and aldehyde, whereas the catalytic cycle involving mononuclear species activates only the

  14. Stress-induced alterations in the programmed natural cycles of post-natal lymphoid organ development in C57BL/6 mice: Evidence for a regulatory feedback relationship between bone marrow and thymus.

    Science.gov (United States)

    Domínguez-Gerpe, Lourdes

    2007-01-01

    This study investigated some effects of weaning and immobilization stress in C57BL/6 mice aged 22-68 days, i.e., over a period including activation of the hypothalamus-pituitary-adrenal (HPA) axis and puberty. Specifically, the study evaluated the evolution, over the referred age interval, of a set of variables (body, thymus, spleen and axillary lymph nodes weights, the proportion of lymphoid cells in the bone marrow, the relative chemoattraction capacity of thymic supernatants for lymphoid cells and the migratory capacity of bone marrow lymphoid cells) in either weaned mice or weaned mice subjected to immobilization stress, compared to "non-stressed" unweaned mice. Cyclic patterns, observed for most variables in unweaned mice, were especially pronounced in two cases: the relative migratory capacity of bone marrow lymphoid cells collected at different ages towards neonatal thymic supernatant, and the relative chemoattraction capacity of thymic supernatants of different ages as tested against a sample of bone marrow lymphoid cells from mice aged 35 days. Weaning stress tended to intensify the involution stages of the cycles in thymus, spleen and lymph node weight, but increased the relative proportion of lymphoid cells in the bone marrow cell population. Both types of exogenous stress tended to affect cycle phase, i.e., cycle peaks and troughs were shifted in time. Correlations were observed between patterns seen in the thymus and bone marrow, suggesting the existence of an autoregulatory feedback loop governing pre-T cell migration and bone marrow/thymus homeostasis. These results also suggest that exogenous stress acts as a non-programmed regulator, modulating the naturally programmed cyclic patterns.

  15. THE NEXUS BETWEEN ENERGY CONSUMPTION AND FINANCIAL DEVELOPMENT WITH ASYMMETRIC CAUSALITY TEST: NEW EVIDENCE FROM NEWLY INDUSTRIALIZED COUNTRIES

    Directory of Open Access Journals (Sweden)

    Feyyaz Zeren

    2014-01-01

    Full Text Available In this study, the relationship between energy consumption and financial development is investigated via Hatemi-J asymmetric causality test (2012 which is able to separate positive and negative shocks in analysis. In order to determine different dimensions of financial system, deposit money bank assets to GDP (dbagdp, financial system deposits to GDP (fdgdp and private credit to GDP (pcrdbgdp were used as three different indicators. As a result of this study on Newly Industrialized 7 Countries spanning the period 1971 till 2010, both positive and negative shocks existed for Malaysia and Mexico, causality from energy consumption to financial developments emerged for Philippines in only negative shocks. While two-way causality occurred for India, Turkey and Thailand, there was not for South Africa.

  16. Development of the titanium–TADDOLate-catalyzed asymmetric fluorination of β-ketoesters

    Directory of Open Access Journals (Sweden)

    Lukas Hintermann

    2011-10-01

    Full Text Available Titanium-based Lewis acids catalyze the α-fluorination of β-ketoesters by electrophilic N–F-fluorinating reagents. Asymmetric catalysis with TADDOLato–titanium(IV dichloride (TADDOL = α,α,α',α'-tetraaryl-(1,3-dioxolane-4,5-diyl-dimethanol Lewis acids produces enantiomerically enriched α-fluorinated β-ketoesters in up to 91% enantiomeric excess, with either F–TEDA (1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate in acetonitrile solution or NFSI (N-fluorobenzenesulfonimide in dichloromethane solution as fluorinating reagents. The effects of various reaction parameters and of the TADDOL ligand structure on the catalytic activity and enantioselectivity were investigated. The absolute configuration of several fluorination products was assigned through correlation. Evidence for ionization of the catalyst complex by chloride dissociation, followed by generation of titanium β-ketoenolates as key reaction intermediates, was obtained. Based on the experimental findings, a general mechanistic sketch and a steric model of induction are proposed.

  17. Development, validation and application of multi-point kinetics model in RELAP5 for analysis of asymmetric nuclear transients

    Energy Technology Data Exchange (ETDEWEB)

    Pradhan, Santosh K., E-mail: santosh@aerb.gov.in [Nuclear Safety Analysis Division, Atomic Energy Regulatory Board, Mumbai 400094 (India); Obaidurrahman, K. [Nuclear Safety Analysis Division, Atomic Energy Regulatory Board, Mumbai 400094 (India); Iyer, Kannan N. [Department of Mechanical Engineering, IIT Bombay, Mumbai 400076 (India); Gaikwad, Avinash J. [Nuclear Safety Analysis Division, Atomic Energy Regulatory Board, Mumbai 400094 (India)

    2016-04-15

    Highlights: • A multi-point kinetics model is developed for RELAP5 system thermal hydraulics code. • Model is validated against extensive 3D kinetics code. • RELAP5 multi-point kinetics formulation is used to investigate critical break for LOCA in PHWR. - Abstract: Point kinetics approach in system code RELAP5 limits its use for many of the reactivity induced transients, which involve asymmetric core behaviour. Development of fully coupled 3D core kinetics code with system thermal-hydraulics is the ultimate requirement in this regard; however coupling and validation of 3D kinetics module with system code is cumbersome and it also requires access to source code. An intermediate approach with multi-point kinetics is appropriate and relatively easy to implement for analysis of several asymmetric transients for large cores. Multi-point kinetics formulation is based on dividing the entire core into several regions and solving ODEs describing kinetics in each region. These regions are interconnected by spatial coupling coefficients which are estimated from diffusion theory approximation. This model offers an advantage that associated ordinary differential equations (ODEs) governing multi-point kinetics formulation can be solved using numerical methods to the desired level of accuracy and thus allows formulation based on user defined control variables, i.e., without disturbing the source code and hence also avoiding associated coupling issues. Euler's method has been used in the present formulation to solve several coupled ODEs internally at each time step. The results have been verified against inbuilt point-kinetics models of RELAP5 and validated against 3D kinetics code TRIKIN. The model was used to identify the critical break in RIH of a typical large PHWR core. The neutronic asymmetry produced in the core due to the system induced transient was effectively handled by the multi-point kinetics model overcoming the limitation of in-built point kinetics model

  18. The Asymmetric Cell Division Regulators Par3, Scribble and Pins/Gpsm2 Are Not Essential for Erythroid Development or Enucleation

    Science.gov (United States)

    Wölwer, Christina B.; Gödde, Nathan; Pase, Luke B.; Elsum, Imogen A.; Lim, Krystle Y. B.; Sacirbegovic, Faruk; Walkley, Carl R.; Ellis, Sarah; Ohno, Shigeo; Matsuzaki, Fumio; Russell, Sarah M.; Humbert, Patrick O.

    2017-01-01

    Erythroid enucleation is the process by which the future red blood cell disposes of its nucleus prior to entering the blood stream. This key event during red blood cell development has been likened to an asymmetric cell division (ACD), by which the enucleating erythroblast divides into two very different daughter cells of alternate molecular composition, a nucleated cell that will be removed by associated macrophages, and the reticulocyte that will mature to the definitive erythrocyte. Here we investigated gene expression of members of the Par, Scribble and Pins/Gpsm2 asymmetric cell division complexes in erythroid cells, and functionally tested their role in erythroid enucleation in vivo and ex vivo. Despite their roles in regulating ACD in other contexts, we found that these polarity regulators are not essential for erythroid enucleation, nor for erythroid development in vivo. Together our results put into question a role for cell polarity and asymmetric cell division in erythroid enucleation. PMID:28095473

  19. Fat3 and Ena/VASP proteins influence the emergence of asymmetric cell morphology in the developing retina.

    Science.gov (United States)

    Krol, Alexandra; Henle, Steven J; Goodrich, Lisa V

    2016-06-15

    Neurons exhibit asymmetric morphologies throughout development - from migration to the elaboration of axons and dendrites - that are correctly oriented for the flow of information. For instance, retinal amacrine cells migrate towards the inner plexiform layer (IPL) and then retract their trailing processes, thereby acquiring a unipolar morphology with a single dendritic arbor restricted to the IPL. Here, we provide evidence that the Fat-like cadherin Fat3 acts during multiple stages of amacrine cell development in mice to orient overall changes in cell shape towards the IPL. Using a time-lapse imaging assay, we found that developing amacrine cells are less directed towards the IPL in the absence of Fat3, during both migration and retraction. Consistent with its predicted role as a cell-surface receptor, Fat3 functions cell-autonomously and is able to influence the cytoskeleton directly through its intracellular domain, which can bind and localize Ena/VASP family actin regulators. Indeed, a change in Ena/VASP protein distribution is sufficient to recapitulate the Fat3 mutant amacrine cell phenotype. Thus, Fat-like proteins might control the polarized development of tissues by sculpting the cytoskeleton of individual cells.

  20. Targeting on Asymmetric Dimethylarginine-Related Nitric Oxide-Reactive Oxygen Species Imbalance to Reprogram the Development of Hypertension

    Directory of Open Access Journals (Sweden)

    You-Lin Tain

    2016-12-01

    Full Text Available Adult-onset diseases, including hypertension, can originate from early life, known as the developmental origins of health and disease (DOHaD. Because the developing kidney is vulnerable to early-life insults, renal programming is considered key in the developmental programming of hypertension. Asymmetric dimethylarginine (ADMA, an endogenous nitric oxide (NO synthase inhibitor, can regulate the NO–reactive oxygen species (ROS balance, and is involved in the development of hypertension. Reprogramming interventions aimed at NO-ROS balance can be protective in both genetic and developmentally programmed hypertension. Here we review several emergent themes of the DOHaD approach regarding the impact of ADMA-related NO-ROS imbalance on programmed hypertension. We focus on the kidney in the following areas: mechanistic insights to interpret programmed hypertension; the impact of ADMA-related NO-ROS imbalance in both genetic and acquired animal models of hypertension; alterations of the renal transcriptome in response to ADMA in the developing kidney; and reprogramming strategies targeting ADMA-related NO-ROS balance to prevent programmed hypertension.

  1. Targeting on Asymmetric Dimethylarginine-Related Nitric Oxide-Reactive Oxygen Species Imbalance to Reprogram the Development of Hypertension.

    Science.gov (United States)

    Tain, You-Lin; Hsu, Chien-Ning

    2016-12-02

    Adult-onset diseases, including hypertension, can originate from early life, known as the developmental origins of health and disease (DOHaD). Because the developing kidney is vulnerable to early-life insults, renal programming is considered key in the developmental programming of hypertension. Asymmetric dimethylarginine (ADMA), an endogenous nitric oxide (NO) synthase inhibitor, can regulate the NO-reactive oxygen species (ROS) balance, and is involved in the development of hypertension. Reprogramming interventions aimed at NO-ROS balance can be protective in both genetic and developmentally programmed hypertension. Here we review several emergent themes of the DOHaD approach regarding the impact of ADMA-related NO-ROS imbalance on programmed hypertension. We focus on the kidney in the following areas: mechanistic insights to interpret programmed hypertension; the impact of ADMA-related NO-ROS imbalance in both genetic and acquired animal models of hypertension; alterations of the renal transcriptome in response to ADMA in the developing kidney; and reprogramming strategies targeting ADMA-related NO-ROS balance to prevent programmed hypertension.

  2. Neuropsychological development in preschool children born with asymmetrical intrauterine growth restriction and impact of postnatal head growth.

    Science.gov (United States)

    Klaric, Andrea Simić; Galić, Slavka; Kolundzić, Zdravko; Bosnjak, Vlatka Mejaski

    2013-07-01

    Neuropsychological development and the impact of postnatal head growth were studied in preschool children with asymmetrical intrauterine growth restriction. Examinees born at term with a birth weight below the 10th percentile were matched to the control group according to chronological and gestational age, gender, and maternal education. Fifty children were in each group, with a mean age of 6 years, 4 months. The Touwen neurological examination, the Čuturić developmental test, an imitative hand positions test, and a visual attention test were performed. There were significant differences (Pmotor variables, the developmental quotient, and the imitative hand positions test. Fine motor skills had the most discriminative power. Relative growth of the head in relation to weight gain was positively correlated to neurocognitive outcome. Intrauterine growth-restricted children with a current head circumference ≤10th percentile had poorer outcomes. Conclusively, intrauterine growth restriction has a negative impact on neurocognitive development. Slow postnatal head growth is correlated with a poorer neuropsychological outcome.

  3. The World Bank, Support for Universities, and Asymmetrical Power Relations in International Development

    Science.gov (United States)

    Collins, Christopher S.; Rhoads, Robert A.

    2010-01-01

    This article examines the role of the World Bank in advancing higher education sectors in the developing world, considering in particular the increasing power and strength of a global knowledge-based economy. Given the powerful role that intergovernmental organizations such as the World Bank play in shaping global economic policies, the authors…

  4. Magnetically Modified Asymmetric Supercapacitors Project

    Data.gov (United States)

    National Aeronautics and Space Administration — This Small Business Innovation Research Phase I project is for the development of an asymmetric supercapacitor that will have improved energy density and cycle life....

  5. Cyclodextrins in Asymmetric and Stereospecific Synthesis

    Directory of Open Access Journals (Sweden)

    Fliur Macaev

    2015-09-01

    Full Text Available Since their discovery, cyclodextrins have widely been used as green and easily available alternatives to promoters or catalysts of different chemical reactions in water. This review covers the research and application of cyclodextrins and their derivatives in asymmetric and stereospecific syntheses, with their division into three main groups: (1 cyclodextrins promoting asymmetric and stereospecific catalysis in water; (2 cyclodextrins’ complexes with transition metals as asymmetric and stereospecific catalysts; and (3 cyclodextrins’ non-metallic derivatives as asymmetric and stereospecific catalysts. The scope of this review is to systematize existing information on the contribution of cyclodextrins to asymmetric and stereospecific synthesis and, thus, to facilitate further development in this direction.

  6. Development of high power and energy density microsphere silicon carbide-MnO2 nanoneedles and thermally oxidized activated carbon asymmetric electrochemical supercapacitors.

    Science.gov (United States)

    Kim, Myeongjin; Kim, Jooheon

    2014-06-21

    In order to achieve high energy and power densities, a high-voltage asymmetric electrochemical supercapacitor has been developed, with activated carbon (AC) as the negative electrode and a silicon carbide-MnO2 nanoneedle (SiC-N-MnO2) composite as the positive electrode. A neutral aqueous Na2SO4 solution was used as the electrolyte. SiC-N-MnO2 was prepared by packing growing MnO2 nanoneedle crystal species in only one direction on the silicon carbide surface. AC was oxidized by thermal treatment in order to introduce oxygen-containing functional groups. Owing to the high capacitance and excellent rate performance of SiC-N-MnO2 and AC, as well as the synergistic effects of the two electrodes, a constructed asymmetric supercapacitor exhibited superior electrochemical performance. The optimized asymmetric supercapacitor could be cycled reversibly in the voltage range from 0 to 1.9 V, and it exhibited a specific capacitance of 59.9 F g(-1) at a scan rate of 2 mV s(-1) and excellent energy density and power density (30.06 W h kg(-1) and 113.92 W kg(-1), respectively) with a specific capacitance loss of less than 3.1% after 1000 charge-discharge cycles, indicating excellent electrochemical stability. These encouraging results show great potential in terms of developing energy storage devices with high energy and power densities for practical applications.

  7. Asymmetric Evolutionary Games.

    Directory of Open Access Journals (Sweden)

    Alex McAvoy

    2015-08-01

    Full Text Available Evolutionary game theory is a powerful framework for studying evolution in populations of interacting individuals. A common assumption in evolutionary game theory is that interactions are symmetric, which means that the players are distinguished by only their strategies. In nature, however, the microscopic interactions between players are nearly always asymmetric due to environmental effects, differing baseline characteristics, and other possible sources of heterogeneity. To model these phenomena, we introduce into evolutionary game theory two broad classes of asymmetric interactions: ecological and genotypic. Ecological asymmetry results from variation in the environments of the players, while genotypic asymmetry is a consequence of the players having differing baseline genotypes. We develop a theory of these forms of asymmetry for games in structured populations and use the classical social dilemmas, the Prisoner's Dilemma and the Snowdrift Game, for illustrations. Interestingly, asymmetric games reveal essential differences between models of genetic evolution based on reproduction and models of cultural evolution based on imitation that are not apparent in symmetric games.

  8. Development of a Novel, Oxidatively Activated, Safety-Catch Linker for Solid-Phase Asymmetric Organic Synthesis (SPOS)

    Institute of Scientific and Technical Information of China (English)

    LIN,Jun; Hjalmar Skarphedinsson; Stepehen G.Davies

    2004-01-01

    @@ Solid-phase asymmetric organic synthesis has become a very important synthetic strategy within the organic chemistry community.[1] Critical to success in SPOS is a linking strategy which allows both the substrate to be loaded and the product released efficiently from the polymeric support. A safety catch linker[2] (SCL) is in principle a linking molecule orthogonal to the reaction conditions of the library synthesis, which can be easily activated by a simple chemical transformation to allow efficient cleavage of the products from the polymer under mild conditions. In order to introduce the SuperQuat chiral auxiliaries[3] for SOPS, we report herein design and synthesis of a novel safety catch linker for asymmetric conjugate addition reactions.

  9. Review of Composite Asymmetric Spur Gear

    OpenAIRE

    Sandeep C. Dhaduti; Dr. S. G. Sarganachari

    2015-01-01

    Gears made from composite materials are widely used in many power and motion transmission applications. Due to lower weight to stiffness ratio, composite gears may be replaced by conventional material gears in power transmission systems. Design of gears with asymmetric teeth enables to increase load capacity, reduce weight, size and vibration level. This article includes a summary of asymmetric gear design parameters, new developments of asymmetric spur gear and their ...

  10. Asymmetric Ashes

    Science.gov (United States)

    2006-11-01

    that oscillate in certain directions. Reflection or scattering of light favours certain orientations of the electric and magnetic fields over others. This is why polarising sunglasses can filter out the glint of sunlight reflected off a pond. When light scatters through the expanding debris of a supernova, it retains information about the orientation of the scattering layers. If the supernova is spherically symmetric, all orientations will be present equally and will average out, so there will be no net polarisation. If, however, the gas shell is not round, a slight net polarisation will be imprinted on the light. This is what broad-band polarimetry can accomplish. If additional spectral information is available ('spectro-polarimetry'), one can determine whether the asymmetry is in the continuum light or in some spectral lines. In the case of the Type Ia supernovae, the astronomers found that the continuum polarisation is very small so that the overall shape of the explosion is crudely spherical. But the much larger polarization in strongly blue-shifted spectral lines evidences the presence, in the outer regions, of fast moving clumps with peculiar chemical composition. "Our study reveals that explosions of Type Ia supernovae are really three-dimensional phenomena," says Dietrich Baade. "The outer regions of the blast cloud is asymmetric, with different materials found in 'clumps', while the inner regions are smooth." "This study was possible because polarimetry could unfold its full strength thanks to the light-collecting power of the Very Large Telescope and the very precise calibration of the FORS instrument," he adds. The research team first spotted this asymmetry in 2003, as part of the same observational campaign (ESO PR 23/03 and ESO PR Photo 26/05). The new, more extensive results show that the degree of polarisation and, hence, the asphericity, correlates with the intrinsic brightness of the explosion. The brighter the supernova, the smoother, or less clumpy

  11. Asymmetric catalysis in Brazil: development and potential for advancement of Brazilian chemical industry; Catalise assimetrica no Brasil: desenvolvimento e potencialidades para o avanco da industria quimica brasileira

    Energy Technology Data Exchange (ETDEWEB)

    Braga, Antonio Luiz, E-mail: braga.antonio@ufsc.br [Universidade Federal de Santa Catarina (UFSC), Florianopolis, SC (Brazil). Departamento de Quimica; Luedtke, Diogo Seibert; Schneider, Paulo Henrique [Universidade Federal do Rio Grande do Sul (UFRS), Porto Alegre, RS (Brazil). Instituto de Quimica; Andrade, Leandro Helgueira [Universidade de Sao Paulo (USP), SP (Brazil). Instituto de Quimica; Paixao, Marcio Weber [Universidade Federal de Sao Carlos (UFSCar), SP (Brazil). Departamento de Quimica

    2013-07-01

    The preparation of enantiomerically pure or enriched substances is of fundamental importance to pharmaceutical, food, agrochemical, and cosmetics industries and involves a growing market of hundreds of billions of dollars. However, most chemical processes used for their production are not environmentally friendly because in most cases, stoichiometric amounts of chiral inductors are used and substantial waste is produced. In this context, asymmetric catalysis has emerged as an efficient tool for the synthesis of enantiomerically enriched compounds using chiral catalysts. More specifically, considering the current scenario in the Brazilian chemical industry, especially that of pharmaceuticals, the immediate prospect for the use of synthetic routes developed in Brazil in an enantioselective fashion or even the discovery of new drugs is practically null. Currently, the industrial production of drugs in Brazil is primarily focused on the production of generic drugs and is basically supported by imports of intermediates from China and India. In order to change this panorama and move forward toward the gradual incorporation of genuinely Brazilian synthetic routes, strong incentive policies, especially those related to continuous funding, will be needed. These incentives could be a breakthrough once we establish several research groups working in the area of organic synthesis and on the development and application of chiral organocatalysts and ligands in asymmetric catalysis, thus contributing to boost the development of the Brazilian chemical industry. Considering these circumstances, Brazil can benefit from this opportunity because we have a wide biodiversity and a large pool of natural resources that can be used as starting materials for the production of new chiral catalysts and are creating competence in asymmetric catalysis and related areas. This may decisively contribute to the growth of chemistry in our country. (author)

  12. Developing a biomimetic tooth bud model.

    Science.gov (United States)

    Smith, Elizabeth E; Zhang, Weibo; Schiele, Nathan R; Khademhosseini, Ali; Kuo, Catherine K; Yelick, Pamela C

    2017-01-08

    A long-term goal is to bioengineer, fully functional, living teeth for regenerative medicine and dentistry applications. Biologically based replacement teeth would avoid insufficiencies of the currently used dental implants. Using natural tooth development as a guide, a model was fabricated using post-natal porcine dental epithelial (pDE), porcine dental mesenchymal (pDM) progenitor cells, and human umbilical vein endothelial cells (HUVEC) encapsulated within gelatin methacrylate (GelMA) hydrogels. Previous publications have shown that post-natal DE and DM cells seeded onto synthetic scaffolds exhibited mineralized tooth crowns composed of dentin and enamel. However, these tooth structures were small and formed within the pores of the scaffolds. The present study shows that dental cell-encapsulated GelMA constructs can support mineralized dental tissue formation of predictable size and shape. Individually encapsulated pDE or pDM cell GelMA constructs were analysed to identify formulas that supported pDE and pDM cell attachment, spreading, metabolic activity, and neo-vasculature formation with co-seeded endothelial cells (HUVECs). GelMa constructs consisting of pDE-HUVECS in 3% GelMA and pDM-HUVECs within 5% GelMA supported dental cell differentiation and vascular mineralized dental tissue formation in vivo. These studies are the first to demonstrate the use of GelMA hydrogels to support the formation of post-natal dental progenitor cell-derived mineralized and functionally vascularized tissues of specified size and shape. These results introduce a novel three-dimensional biomimetic tooth bud model for eventual bioengineered tooth replacement teeth in humans. Copyright © 2017 John Wiley & Sons, Ltd.

  13. The Catalytic Asymmetric Intramolecular Stetter Reaction.

    Science.gov (United States)

    de Alaniz, Javier Read; Rovis, Tomislav

    2009-05-01

    This account chronicles our efforts at the development of a catalytic asymmetric Stetter reaction using chiral triazolium salts as small molecule organic catalysts. Advances in the mechanistically related azolium-catalyzed asymmetric benzoin reaction are discussed, particularly as they apply to catalyst design. A chronological treatise of reaction discovery, catalyst optimization and reactivity extension follows.

  14. Escala de Depressão Pós-natal de Edimburgo para triagem no sistema público de saúde Escala de Depresión Post-natal de Edimburgo para tamizage en el sistema público de salud Edinburgh Postnatal Depression Scale for screening in the public health system

    Directory of Open Access Journals (Sweden)

    Patrícia Figueira

    2009-08-01

    Full Text Available OBJETIVO: Avaliar a utilização da Escala de Depressão Pós-natal de Edimburgo como instrumento de triagem no sistema público de saúde. MÉTODOS: A Escala foi administrada entre o 40º e 90º dia do pós-parto, a 245 mulheres que tiveram parto em uma maternidade privada no município de Belo Horizonte (MG, entre 2005 e 2006. As participantes foram submetidas a uma entrevista psiquiátrica estruturada (Mini-Plus 5.0 utilizada como padrão-ouro para diagnóstico de depressão. Foram calculadas sensibilidade e especificidade da escala e utilizou-se a curva ROC para achar o melhor ponto de corte. Foi utilizado o teste t de Student para comparação das variáveis numéricas e o qui-quadrado para as variáveis categóricas. A confiabilidade foi aferida pelo coeficiente de consistência interna á de Cronbach. RESULTADOS: Foram diagnosticadas 66 mulheres com o quadro depressivo pós-parto (26,9% da amostra. Não houve diferença entre as mulheres com e sem depressão pós-parto em relação à idade, escolaridade, número de partos anteriores e estado civil. Utilizando-se o ponto de corte de 10, a sensibilidade da escala foi 86,4, a especificidade 91,1 e o valor preditivo positivo 0,78. CONCLUSÕES: As propriedades psicométricas da Escala a caracterizam como um bom instrumento de triagem da depressão pós-parto e seu uso disseminado no Sistema Único de Saúde poderia repercutir positivamente com aumento significativo na taxa de reconhecimento, diagnóstico, e tratamento da depressão pós parto.OBJETIVO: Evaluar la utilización de la Escala de Depresión Post-natal de Edimburgo como instrumento de tamizage en el sistema público de salud. MÉTODOS: La Escala fue administrada entre el 40º y 90º día de post-parto, a 245 mujeres que tuvieron parto en una maternidad privada en el municipio de Bello Horizonte (MG, entre 2005 y 2006. Las participantes fueron sometidas a una entrevista psiquiátrica estructurada (Mini-Plus 5.0 utilizada como patr

  15. Asymmetric stem cell division: lessons from Drosophila.

    Science.gov (United States)

    Wu, Pao-Shu; Egger, Boris; Brand, Andrea H

    2008-06-01

    Asymmetric cell division is an important and conserved strategy in the generation of cellular diversity during animal development. Many of our insights into the underlying mechanisms of asymmetric cell division have been gained from Drosophila, including the establishment of polarity, orientation of mitotic spindles and segregation of cell fate determinants. Recent studies are also beginning to reveal the connection between the misregulation of asymmetric cell division and cancer. What we are learning from Drosophila as a model system has implication both for stem cell biology and also cancer research.

  16. On-chip asymmetric microcavity optomechanics.

    Science.gov (United States)

    Soltani, Soheil; Hudnut, Alexa W; Armani, Andrea M

    2016-12-26

    High quality factor (Q) optical resonators have enabled rapid growth in the field of cavity-enhanced, radiation pressure-induced optomechanics. However, because research has focused on axisymmetric devices, the observed regenerative excited mechanical modes are similar. In the present work, a strategy for fabricating high-Q whispering gallery mode microcavities with varying degrees of asymmetry is developed and demonstrated. Due to the combination of high optical Q and asymmetric device design, two previously unobserved modes, the asymmetric cantilever and asymmetric crown mode, are demonstrated with sub-mW thresholds for onset of oscillations. The experimental results are in good agreement with computational modeling predictions.

  17. Enantiopure sulfoxides: recent applications in asymmetric synthesis.

    Science.gov (United States)

    Carreño, M Carmen; Hernández-Torres, Gloria; Ribagorda, María; Urbano, Antonio

    2009-11-07

    Sulfoxides are nowadays recognised as powerful chiral auxiliaries that may participate in a wide range of asymmetric reactions. Their high configurational stability, the existence of several efficient methods allowing the access to both configurations as well as their synthetic versatility are characteristic features offering a tremendous potential to develop new applications. Significant recent advances leading to high asymmetric inductions in carbon-carbon and carbon-oxygen bond forming reactions, and applications of homochiral sulfoxides to atroposelective synthesis and asymmetric catalysis are discussed. New uses of sulfoxides in the design of chiroptical switches are also shown.

  18. The development of the chicken small intestine: a scanning electron microscopy study.

    Science.gov (United States)

    Sabatakou, O; Paraskevakou, E; Tseleni-Balafouta, S; Athanasiadis, A; Fasseas, K

    2003-07-01

    The surface pattern of the small intestine of the chicken was studied using SEM in stages ranging from 11th day of foetal development to 60 days of post-natal life. The definite villi of the small intestine were preceded by the development of the previllous ridges. The villi were finger like and of unequal length during incubation. After hatching, gradually, the villi were longer, well formed with furrows along their sides. Respectively, the crypts, being present at late incubation, increased with age. Columnar epithelial cells with dense microvilli lined the luminal surface of the intestine with obvious goblet cells openings among them.

  19. Trace level impurity method development with high-field asymmetric waveform ion mobility spectrometry: systematic study of factors affecting the performance.

    Science.gov (United States)

    Champarnaud, Elodie; Laures, Alice M-F; Borman, Phil J; Chatfield, Marion J; Kapron, James T; Harrison, Mark; Wolff, Jean-Claude

    2009-01-01

    For the determination of trace level impurities, analytical chemists are confronted with complex mixtures and difficult separations. New technologies such as high-field asymmetric waveform ion mobility spectrometry (FAIMS) have been developed to make their work easier; however, efficient method development and troubleshooting can be quite challenging if little prior knowledge of the factors or their settings is available. We present the results of an investigation performed in order to obtain a better understanding of the FAIMS technology. The influence of eight factors (polarity of dispersion voltage, outer bias voltage, total gas flow rate, composition of the carrier gas (e.g. %He), outer electrode temperature, ratio between the temperatures of the inner and outer electrodes, flow rate and composition of the make-up mobile phase) was assessed. Five types of responses were monitored: value of the compensation voltage (CV), intensity, width and asymmetry of the compensation voltage peak, and resolution between two peaks. Three types of studies were performed using different test mixtures and various ionisation modes to assess whether the same conclusions could be drawn across these conditions for a number of different types of compounds. To extract the maximum information from as few experiments as possible, a Design of Experiment (DoE) approach was used. The results presented in this work provide detailed information on the factors affecting FAIMS separations and therefore should enable the user to troubleshoot more effectively and to develop efficient methods.

  20. Mapping the global mRNA transcriptome during development of the murine first molar

    Directory of Open Access Journals (Sweden)

    Maria A. eLandin

    2015-02-01

    Full Text Available The main objective of this study was to map global gene expression in order to provide information about the populations of mRNA species participating in murine tooth development at 24 h intervals, starting at the eleventh embryonic day (E11.5 up to the seventh post-natal day (P7. The levels of RNA species expressed during murine tooth development were mesured using a total of 58 deoxyoligonucleotide microarrays. Microarray data was validated using real-time RT-PCR. Differentially expressed genes (p<0.05 were subjected to bioinformatic analysis to identify cellular activities significantly associated with these genes. Using ANOVA the microarray data yielded 4362 genes as being differentially expressed from the elleventh embryonic day (E11.5 up to seven days post-natal (P7, 1921 of these being genes without known functions. The remaining 2441 genes were subjected to further statistical analysis using a supervised procedure.Bioinformatic analysis results for each time-point studied suggests that the main molecular functions associated with genes expressed at the early pre-natal stages (E12.5-E18.5 studied were cell cycle progression, cell morphology, lipid metabolism, cellular growth, proliferation, senescence and apoptosis, whereas most genes expressed at post-natal and secretory stages (P0- P7 were significantly associated with regulation of cell migration, biosynthesis, differentiation, oxidative stress, polarization and cell death. Differentially expressed genes (DE not described earlier during murine tooth development; Inositol 1, 4, 5-triphosphate receptor 3 (Itpr3, metallothionein 1(Mt1, cyclin-dependent kinase 4 (Cdk4, cathepsin D (Ctsd, keratin complex 2, basic, gene 6a (Krt2-6a, cofilin 1, non-muscle (Cfl1, cyclin 2 (Ccnd2, were verified by real-time RT-PCR.

  1. Temporal dynamics of the developing lung transcriptome in three common inbred strains of laboratory mice reveals multiple stages of postnatal alveolar development

    OpenAIRE

    Beauchemin, Kyle J.; Julie M. Wells; Kho, Alvin T.; Philip, Vivek M.; Kamir, Daniela; Kohane, Isaac S; Graber, Joel H.; Bult, Carol J.

    2016-01-01

    To characterize temporal patterns of transcriptional activity during normal lung development, we generated genome wide gene expression data for 26 pre- and post-natal time points in three common inbred strains of laboratory mice (C57BL/6J, A/J, and C3H/HeJ). Using Principal Component Analysis and least squares regression modeling, we identified both strain-independent and strain-dependent patterns of gene expression. The 4,683 genes contributing to the strain-independent expression patterns w...

  2. Terahertz metamaterial with asymmetric transmission

    CERN Document Server

    Singh, R; Menzel, C; Rockstuhl, C; Azad, A K; Cheville, R A; Lederer, F; Zhang, W; Zheludev, N I

    2009-01-01

    We show for the first time that a planar metamaterial, an array of coupled metal split-ring resonators with a unit cell lacking mirror symmetry, exhibits asymmetric transmission of terahertz radiation propagating through it in opposite directions. This intriguing effect, that is compatible with Lorentz reciprocity and time-reversal, depends on a directional difference in conversion efficiency of the incident circularly polarized wave into one of opposite handedness, that is only possible in lossy low-symmetry planar chiral metamaterials. We show that asymmetric transmission is linked to excitation of enantiomerically sensitive plasmons, these are induced charge-field excitations that depend on the mutual handedness of incident wave and metamaterial pattern. Various bands of positive, negative and zero phase and group velocities have been identified indicating the opportunity to develop polarization sensitive negative index and slow light media based on such metamaterials.

  3. Time asymmetric spacetimes near null and spatial infinity. II. Expansions of developments of initial data sets with non-smooth conformal metrics

    CERN Document Server

    Kroon, J A V

    2004-01-01

    This article uses the conformal Einstein equations and the conformal representation of spatial infinity introduced by Friedrich to analyse the behaviour of the gravitational field near null and spatial infinity for the development of initial data which are, in principle, non-conformally flat and time asymmetric. This article is the continuation of the investigation started in Class. Quantum Grav. 21 (2004) 5457-5492, where only conformally flat initial data sets were considered. For the purposes of this investigation, the conformal metric of the initial hypersurface is assumed to have a very particular type of non-smoothness at infinity in order to allow for the presence of non-Schwarzschildean initial data sets in the class under study. The calculation of asymptotic expansions of the development of these initial data sets reveals --as in the conformally flat case-- the existence of a hierarchy of obstructions to the smoothness of null infinity which are expressible in terms of the initial data. This allows f...

  4. Chiral nonracemic late-transition-metal organometallics with a metal-bonded stereogenic carbon atom: development of new tools for asymmetric organic synthesis.

    Science.gov (United States)

    Malinakova, Helena C

    2004-06-07

    Transition-metal-catalyzed cross-coupling reactions and the Heck reaction have evolved into powerful tools for the construction of carbon-carbon bonds. In most cases, the reactive organometallic intermediates feature a carbon-transition-metal sigma bond between a sp(2)-hybridized carbon atom and the transition metal (Csp(2)--TM). New, and potentially more powerful approach to transition-metal-catalyzed asymmetric organic synthesis would arise if catalytic chiral nonracemic organometallic intermediates with a stereogenic sp(3)-hybridized carbon atoms directly bonded to the transition metal (C*sp(3)--TM bond) could be formed from racemic or achiral organic substrates, and subsequently participate in the formation of a new carbon-carbon bond (C*sp(3)-C) with retention of the stereochemical information. To date, only a few catalytic processes that are based on this concept, have been developed. In this account, both "classical" and recent studies on preparation and reactivity of stable chiral nonracemic organometallics with a metal-bonded stereogenic carbon, which provide the foundation for the future design of new synthetic transformations exploiting the outlined concept, are discussed, along with examples of relevant catalytic processes.

  5. THE ANALYSIS OF THE ASYMMETRICAL RISK IN TOURISM FOR THE DEVELOPMENT AND PROMOTION OF A LASTING REGIONAL TOURISM IDENTITY

    Directory of Open Access Journals (Sweden)

    Alexandru NEDELEA

    2009-06-01

    Full Text Available In order to establish an adequate balance between tourists' welfare, the needs of the natural and cultural environment, as well as to develop tourist destinations and organizations' competitiveness, it is necessary to carry out a global and integrated approach, where all interested parties share the same goals regarding the durability of tourism and the approached challenges. The purpose of this work is to identify the factors of reduced risk having a major impact over the sustainability of the tourist region under analysis and to highlight the risk factors' connections and impact in order to minimize and eliminate them, with direct effects over the awareness of tourist industry's values. The identification of lasting development's indicators will take into account all these three aspects of the durable development of tourism, namely ecological, economical and social factors, that play a part in highlighting the real performance of a tourist destination. All these aspects are absolutely necessary for the promotion of the Danube's tourist potential, achievable through the emphasis of the relevant values from the tourist patrimony of the county of Galati. The promotion of the Danube' tourist potential presupposes a series of objectives that are subordinated to the general direction that is marked at the national level, respectively Romania's transformation into a qualitative tourist destination based on its natural and cultural patrimony, in order to correspond to the European Union standards. The new policy regarding tourism proposed by the European Commission aims at offering constant support for this industry to be able to face different challenges, by promoting also competitiveness in general.

  6. A review of new developments in the Friedel–Crafts alkylation – From green chemistry to asymmetric catalysis

    Science.gov (United States)

    2010-01-01

    Summary The development of efficient Friedel–Crafts alkylations of arenes and heteroarenes using only catalytic amounts of a Lewis acid has gained much attention over the last decade. The new catalytic approaches described in this review are favoured over classical Friedel–Crafts conditions as benzyl-, propargyl- and allyl alcohols, or styrenes, can be used instead of toxic benzyl halides. Additionally, only low catalyst loadings are needed to provide a wide range of products. Following a short introduction about the origin and classical definition of the Friedel–Crafts reaction, the review will describe the different environmentally benign substrates which can be applied today as an approach towards greener processes. Additionally, the first diastereoselective and enantioselective Friedel–Crafts-type alkylations will be highlighted. PMID:20485588

  7. A review of new developments in the Friedel–Crafts alkylation – From green chemistry to asymmetric catalysis

    Directory of Open Access Journals (Sweden)

    Magnus Rueping

    2010-01-01

    Full Text Available The development of efficient Friedel–Crafts alkylations of arenes and heteroarenes using only catalytic amounts of a Lewis acid has gained much attention over the last decade. The new catalytic approaches described in this review are favoured over classical Friedel–Crafts conditions as benzyl-, propargyl- and allyl alcohols, or styrenes, can be used instead of toxic benzyl halides. Additionally, only low catalyst loadings are needed to provide a wide range of products. Following a short introduction about the origin and classical definition of the Friedel–Crafts reaction, the review will describe the different environmentally benign substrates which can be applied today as an approach towards greener processes. Additionally, the first diastereoselective and enantioselective Friedel–Crafts-type alkylations will be highlighted.

  8. Laminins and retinal vascular development.

    Science.gov (United States)

    Edwards, Malia M; Lefebvre, Olivier

    2013-01-01

    The mechanisms controlling vascular development, both normal and pathological, are not yet fully understood. Many diseases, including cancer and diabetic retinopathy, involve abnormal blood vessel formation. Therefore, increasing knowledge of these mechanisms may help develop novel therapeutic targets. The identification of novel proteins or cells involved in this process would be particularly useful. The retina is an ideal model for studying vascular development because it is easy to access, particularly in rodents where this process occurs post-natally. Recent studies have suggested potential roles for laminin chains in vascular development of the retina. This review will provide an overview of these studies, demonstrating the importance of further research into the involvement of laminins in retinal blood vessel formation.

  9. Asymmetrical field emitter

    Science.gov (United States)

    Fleming, J.G.; Smith, B.K.

    1995-10-10

    A method is disclosed for providing a field emitter with an asymmetrical emitter structure having a very sharp tip in close proximity to its gate. One preferred embodiment of the present invention includes an asymmetrical emitter and a gate. The emitter having a tip and a side is coupled to a substrate. The gate is connected to a step in the substrate. The step has a top surface and a side wall that is substantially parallel to the side of the emitter. The tip of the emitter is in close proximity to the gate. The emitter is at an emitter potential, and the gate is at a gate potential such that with the two potentials at appropriate values, electrons are emitted from the emitter. In one embodiment, the gate is separated from the emitter by an oxide layer, and the emitter is etched anisotropically to form its tip and its asymmetrical structure. 17 figs.

  10. Asymmetrical international attitudes

    NARCIS (Netherlands)

    Van Oudenhoven, JP; Askevis-Leherpeux, F; Hannover, B; Jaarsma, R; Dardenne, B

    2002-01-01

    In general, attitudes towards nations have a fair amount of reciprocity: nations either like each other are relatively indifferent to each other or dislike each other Sometimes, however international attitudes are asymmetrical. In this study, we use social identity theory in order to explain asymmet

  11. Asymmetric reactions in continuous flow

    Directory of Open Access Journals (Sweden)

    Xiao Yin Mak

    2009-04-01

    Full Text Available An overview of asymmetric synthesis in continuous flow and microreactors is presented in this review. Applications of homogeneous and heterogeneous asymmetric catalysis as well as biocatalysis in flow are discussed.

  12. Asymmetric catalysis with helical polymers

    NARCIS (Netherlands)

    Megens, Rik P.; Roelfes, Gerard

    2011-01-01

    Inspired by nature, the use of helical biopolymer catalysts has emerged over the last years as a new approach to asymmetric catalysis. In this Concept article the various approaches and designs and their application in asymmetric catalysis will be discussed.

  13. Cytokine-like factor 1 (CLF1): life after development?

    Science.gov (United States)

    Kass, Daniel J

    2011-09-01

    Cytokine-like factor 1 (CLF1) is a secreted receptor belonging to the interleukin-6 family of cytokines. CLF1 and its physiologic partner, cardiotrophin-like cytokine (CLC) are secreted as a heterodimer and engage the tripartite signaling complex of ciliary neurotrophic factor receptor (CNTFR), leukemia inhibitory factor (LIFR) and gp130. Ligation of this receptor complex leads to activation of the STAT3 and MAPK pathways and mediates survival pathways in neurons. Mutations in CLF1, CLC, or CNTFR in mice lead to the birth of mice that die on post-natal day 1 because of an inability to nurse. These animals exhibit significant decreases in the number of motor neurons in the facial nucleus and the spinal cord. CLF1 or CLC deficiency is associated with the development of the human cold-induced sweating syndromes. A growing body of research suggests that CLF1 expression may be associated with several post-natal disease processes. In this review, we summarize the current understanding of CLF1 expression and suggest future studies to understand the potentially important role of CLF1 in postnatal life and disease.

  14. Asymmetric information and economics

    Science.gov (United States)

    Frieden, B. Roy; Hawkins, Raymond J.

    2010-01-01

    We present an expression of the economic concept of asymmetric information with which it is possible to derive the dynamical laws of an economy. To illustrate the utility of this approach we show how the assumption of optimal information flow leads to a general class of investment strategies including the well-known Q theory of Tobin. Novel consequences of this formalism include a natural definition of market efficiency and an uncertainty principle relating capital stock and investment flow.

  15. Asymmetric extractions in orthodontics

    OpenAIRE

    Camilo Aquino Melgaço; Mônica Tirre de Souza Araújo

    2012-01-01

    INTRODUCTION: Extraction decisions are extremely important in during treatment planning. In addition to the extraction decision orthodontists have to choose what tooth should be extracted for the best solution of the problem and the esthetic/functional benefit of the patient. OBJECTIVE: This article aims at reviewing the literature relating the advantages, disadvantages and clinical implications of asymmetric extractions to orthodontics. METHODS: Keywords were selected in English and Portugue...

  16. The Role of Maternal Dietary Proteins in Development of Metabolic Syndrome in Offspring

    Directory of Open Access Journals (Sweden)

    Alireza Jahan-Mihan

    2015-11-01

    Full Text Available The prevalence of metabolic syndrome and obesity has been increasing. Pre-natal environment has been suggested as a factor influencing the risk of metabolic syndrome in adulthood. Both observational and experimental studies showed that maternal diet is a major modifier of the development of regulatory systems in the offspring in utero and post-natally. Both protein content and source in maternal diet influence pre- and early post-natal development. High and low protein dams’ diets have detrimental effect on body weight, blood pressure191 and metabolic and intake regulatory systems in the offspring. Moreover, the role of the source of protein in a nutritionally adequate maternal diet in programming of food intake regulatory system, body weight, glucose metabolism and blood pressure in offspring is studied. However, underlying mechanisms are still elusive. The purpose of this review is to examine the current literature related to the role of proteins in maternal diets in development of characteristics of the metabolic syndrome in offspring.

  17. Control of apoptosis by asymmetric cell division.

    Directory of Open Access Journals (Sweden)

    Julia Hatzold

    2008-04-01

    Full Text Available Asymmetric cell division and apoptosis (programmed cell death are two fundamental processes that are important for the development and function of multicellular organisms. We have found that the processes of asymmetric cell division and apoptosis can be functionally linked. Specifically, we show that asymmetric cell division in the nematode Caenorhabditis elegans is mediated by a pathway involving three genes, dnj-11 MIDA1, ces-2 HLF, and ces-1 Snail, that directly control the enzymatic machinery responsible for apoptosis. Interestingly, the MIDA1-like protein GlsA of the alga Volvox carteri, as well as the Snail-related proteins Snail, Escargot, and Worniu of Drosophila melanogaster, have previously been implicated in asymmetric cell division. Therefore, C. elegans dnj-11 MIDA1, ces-2 HLF, and ces-1 Snail may be components of a pathway involved in asymmetric cell division that is conserved throughout the plant and animal kingdoms. Furthermore, based on our results, we propose that this pathway directly controls the apoptotic fate in C. elegans, and possibly other animals as well.

  18. Asymmetric extractions in orthodontics

    Directory of Open Access Journals (Sweden)

    Camilo Aquino Melgaço

    2012-04-01

    Full Text Available INTRODUCTION: Extraction decisions are extremely important in during treatment planning. In addition to the extraction decision orthodontists have to choose what tooth should be extracted for the best solution of the problem and the esthetic/functional benefit of the patient. OBJECTIVE: This article aims at reviewing the literature relating the advantages, disadvantages and clinical implications of asymmetric extractions to orthodontics. METHODS: Keywords were selected in English and Portuguese and the EndNote 9 program was used for data base search in PubMed, Web of Science (WSc and LILACS. The selected articles were case reports, original articles and prospective or retrospective case-control studies concerning asymmetrical extractions of permanent teeth for the treatment of malocclusions. CONCLUSION: According to the literature reviewed asymmetric extractions can make some specific treatment mechanics easier. Cases finished with first permanent molars in Class II or III relationship in one or both sides seem not to cause esthetic or functional problems. However, diagnosis knowledge and mechanics control are essential for treatment success.

  19. Homogeneous asymmetric catalysis in fragrance chemistry.

    Science.gov (United States)

    Ciappa, Alessandra; Bovo, Sara; Bertoldini, Matteo; Scrivanti, Alberto; Matteoli, Ugo

    2008-06-01

    Opposite enantiomers of a chiral fragrance may exhibit different olfactory activities making a synthesis in high enantiomeric purity commercially and scientifically interesting. Accordingly, the asymmetric synthesis of four chiral odorants, Fixolide, Phenoxanol, Citralis, and Citralis Nitrile, has been investigated with the aim to develop practically feasible processes. In the devised synthetic schemes, the key step that leads to the formation of the stereogenic center is the homogeneous asymmetric hydrogenation of a prochiral olefin. By an appropriate choice of the catalyst and the reaction conditions, Phenoxanol, Citralis, and Citralis Nitrile were obtained in high enantiomeric purity, and odor profiles of the single enantiomers were determined.

  20. Asymmetric catalysis with short-chain peptides.

    Science.gov (United States)

    Lewandowski, Bartosz; Wennemers, Helma

    2014-10-01

    Within this review article we describe recent developments in asymmetric catalysis with peptides. Numerous peptides have been established in the past two decades that catalyze a wide variety of transformations with high stereoselectivities and yields, as well as broad substrate scope. We highlight here catalytically active peptides, which have addressed challenges that had thus far remained elusive in asymmetric catalysis: enantioselective synthesis of atropoisomers and quaternary stereogenic centers, regioselective transformations of polyfunctional substrates, chemoselective transformations, catalysis in-flow and reactions in aqueous environments.

  1. Dynamic Conditional Correlations for Asymmetric Processes

    NARCIS (Netherlands)

    M. Asai (Manabu); M.J. McAleer (Michael)

    2010-01-01

    textabstractThe paper develops two Dynamic Conditional Correlation (DCC) models, namely the Wishart DCC (WDCC) model and the Matrix-Exponential Conditional Correlation (MECC) model. The paper applies the WDCC approach to the exponential GARCH (EGARCH) and GJR models to propose asymmetric DCC models.

  2. Asymmetric synthesis v.4

    CERN Document Server

    Morrison, James

    1984-01-01

    Asymmetric Synthesis, Volume 4: The Chiral Carbon Pool and Chiral Sulfur, Nitrogen, Phosphorus, and Silicon Centers describes the practical methods of obtaining chiral fragments. Divided into five chapters, this book specifically examines initial chiral transmission and extension. The opening chapter describes the so-called chiral carbon pool, the readily available chiral carbon fragments used as building blocks in synthesis. This chapter also provides a list of 375 chiral building blocks, along with their commercial sources, approximate prices, and methods of synthesis. Schemes involving

  3. Asymmetric flow networks

    OpenAIRE

    Olaizola Ortega, María Norma; Valenciano Llovera, Federico

    2012-01-01

    This paper provides a new model of network formation that bridges the gap between the two benchmark models by Bala and Goyal, the one-way flow model, and the two-way flow model, and includes both as particular extreme cases. As in both benchmark models, in what we call an "asymmetric flow" network a link can be initiated unilaterally by any player with any other, and the flow through a link towards the player who supports it is perfect. Unlike those models, in the opposite direction there is ...

  4. Synthesis of 3,3-Disubstituted Oxindoles by Palladium-Catalyzed Asymmetric Intramolecular α-Arylation of Amides: Reaction Development and Mechanistic Studies.

    Science.gov (United States)

    Katayev, Dmitry; Jia, Yi-Xia; Sharma, Akhilesh K; Banerjee, Dipshikha; Besnard, Céline; Sunoj, Raghavan B; Kündig, E Peter

    2013-09-02

    Palladium complexes incorporating chiral N-heterocyclic carbene (NHC) ligands catalyze the asymmetric intramolecular α-arylation of amides producing 3,3-disubstituted oxindoles. Comprehensive DFT studies have been performed to gain insight into the mechanism of this transformation. Oxidative addition is shown to be rate-determining and reductive elimination to be enantioselectivity-determining. The synthesis of seven new NHC ligands is detailed and their performance is compared. One of them, L8, containing a tBu and a 1-naphthyl group at the stereogenic centre, proved superior and was very efficient in the asymmetric synthesis of fifteen new spiro-oxindoles and three azaspiro-oxindoles often in high yields (up to 99 %) and enantioselectivities (up to 97 % ee; ee=enantiomeric excess). Three palladacycle intermediates resulting from the oxidative addition of [Pd(NHC)] into the aryl halide bond were isolated and structurally characterized (X-ray). Using these intermediates as catalysts showed alkene additives to play an important role in increasing turnover number and frequency.

  5. Early life exposure to 2.45GHz WiFi-like signals: effects on development and maturation of the immune system.

    Science.gov (United States)

    Sambucci, Manolo; Laudisi, Federica; Nasta, Francesca; Pinto, Rosanna; Lodato, Rossella; Lopresto, Vanni; Altavista, Pierluigi; Marino, Carmela; Pioli, Claudio

    2011-12-01

    The development of the immune system begins during embryogenesis, continues throughout fetal life, and completes its maturation during infancy. Exposure to immune-toxic compounds at levels producing limited/transient effects in adults, results in long-lasting or permanent immune deficits when it occurs during perinatal life. Potentially harmful radiofrequency (RF) exposure has been investigated mainly in adult animals or with cells from adult subjects, with most of the studies showing no effects. Is the developing immune system more susceptible to the effects of RF exposure? To address this question, newborn mice were exposed to WiFi signals at constant specific absorption rates (SAR) of 0.08 or 4 W/kg, 2h/day, 5 days/week, for 5 consecutive weeks, starting the day after birth. The experiments were performed with a blind procedure using sham-exposed groups as controls. No differences in body weight and development among the groups were found in mice of both sexes. For the immunological analyses, results on female and male newborn mice exposed during early post-natal life did not show any effects on all the investigated parameters with one exception: a reduced IFN-γ production in spleen cells from microwaves (MW)-exposed (SAR 4 W/kg) male (not in female) mice compared with sham-exposed mice. Altogether our findings do not support the hypothesis that early post-natal life exposure to WiFi signals induces detrimental effects on the developing immune system.

  6. Additive Effects on Asymmetric Catalysis.

    Science.gov (United States)

    Hong, Liang; Sun, Wangsheng; Yang, Dongxu; Li, Guofeng; Wang, Rui

    2016-03-23

    This review highlights a number of additives that can be used to make asymmetric reactions perfect. Without changing other reaction conditions, simply adding additives can lead to improved asymmetric catalysis, such as reduced reaction time, improved yield, or/and increased selectivity.

  7. The asymmetric sandwich theorem

    CERN Document Server

    Simons, Stephen

    2011-01-01

    We discuss the asymmetric sandwich theorem, a generalization of the Hahn-Banach theorem. As applications, we derive various results on the existence of linear functionals that include bivariate, trivariate and quadrivariate generalizations of the Fenchel duality theorem. Most of the results are about affine functions defined on convex subsets of vector spaces, rather than linear functions defined on vector spaces. We consider both results that use a simple boundedness hypothesis (as in Rockafellar's version of the Fenchel duality theorem) and also results that use Baire's theorem (as in the Robinson-Attouch-Brezis version of the Fenchel duality theorem). This paper also contains some new results about metrizable topological vector spaces that are not necessarily locally convex.

  8. Asymmetric black dyonic holes

    Directory of Open Access Journals (Sweden)

    I. Cabrera-Munguia

    2015-04-01

    Full Text Available A 6-parametric asymptotically flat exact solution, describing a two-body system of asymmetric black dyons, is studied. The system consists of two unequal counterrotating Kerr–Newman black holes, endowed with electric and magnetic charges which are equal but opposite in sign, separated by a massless strut. The Smarr formula is generalized in order to take into account their contribution to the mass. The expressions for the horizon half-length parameters σ1 and σ2, as functions of the Komar parameters and of the coordinate distance, are displayed, and the thermodynamic properties of the two-body system are studied. Furthermore, the seven physical parameters satisfy a simple algebraic relation which can be understood as a dynamical scenario, in which the physical properties of one body are affected by the ones of the other body.

  9. Loss Aversion and the Asymmetric Transmission of Monetary Policy

    DEFF Research Database (Denmark)

    Santoro, Emiliano; Petrella, Ivan; Pfajfar, Damjan

    2014-01-01

    There is widespread evidence that monetary policy exerts asymmetric effects on output over contractions and expansions in economic activity, while price responses display no sizeable asymmetry. To rationalize these facts we develop a dynamic general equilibrium model where households’ utility...

  10. Venture Capital Contracting Under Asymmetric Information

    OpenAIRE

    Jeffrey Trester

    1993-01-01

    The author develops a model of venture capital contracting in which the entrepreneur and venture capitalist contract under symmetric information. A condition of asymmetric information may arise subsequent to the first contract. The author shows that this condition makes debt contracts infeasible and leads to the use of preferred equity contracts. The author notes that discussions of the relation between venture capital and capital structure are rare. This paper expands the literature by addre...

  11. Fluorous Mixture Synthesis of Asymmetric Dendrimers

    Science.gov (United States)

    Jiang, Zhong-Xing; Yu, Yihua Bruce

    2010-01-01

    A divergent fluorous mixture synthesis (FMS) of asymmetric fluorinated dendrimers has been developed. Four generations of fluorinated dendrimers with the same fluorinated moiety were prepared with high efficiency, yield and purity. Comparison of the physicochemical properties of these dendrimers provided valuable information for their application and future optimization. This strategy has not only provided a practical method for the synthesis and purification of dendrimers, but also established the possibility of utilizing the same fluorinated moiety for FMS. PMID:20170088

  12. Asymmetric Gepner Models (Revisited)

    CERN Document Server

    Gato-Rivera, B

    2010-01-01

    We reconsider a class of heterotic string theories studied in 1989, based on tensor products of N=2 minimal models with asymmetric simple current invariants. We extend this analysis from (2,2) and (1,2) spectra to (0,2) spectra with SO(10) broken to the Standard Model. In the latter case the spectrum must contain fractionally charged particles. We find that in nearly all cases at least some of them are massless. However, we identify a large subclass where the fractional charges are at worst half-integer, and often vector-like. The number of families is very often reduced in comparison to the 1989 results, but there are no new tensor combinations yielding three families. All tensor combinations turn out to fall into two classes: those where the number of families is always divisible by three, and those where it is never divisible by three. We find an empirical rule to determine the class, which appears to extend beyond minimal N=2 tensor products. We observe that distributions of physical quantities such as th...

  13. Multicatalyst system in asymmetric catalysis

    CERN Document Server

    Zhou, Jian

    2014-01-01

    This book introduces multi-catalyst systems by describing their mechanism and advantages in asymmetric catalysis.  Helps organic chemists perform more efficient catalysis with step-by-step methods  Overviews new concepts and progress for greener and economic catalytic reactions  Covers topics of interest in asymmetric catalysis including bifunctional catalysis, cooperative catalysis, multimetallic catalysis, and novel tandem reactions   Has applications for pharmaceuticals, agrochemicals, materials, and flavour and fragrance

  14. On Asymmetric Quantum MDS Codes

    CERN Document Server

    Ezerman, Martianus Frederic; Ling, San

    2010-01-01

    Assuming the validity of the MDS Conjecture, the weight distribution of all MDS codes is known. Using a recently-established characterization of asymmetric quantum error-correcting codes, linear MDS codes can be used to construct asymmetric quantum MDS codes with $d_{z} \\geq d_{x}\\geq 2$ for all possible values of length $n$ for which linear MDS codes over $\\F_{q}$ are known to exist.

  15. Asymmetric cation-binding catalysis

    DEFF Research Database (Denmark)

    Oliveira, Maria Teresa; Lee, Jiwoong

    2017-01-01

    and KCN, are selectively bound to the catalyst, providing exceptionally high enantioselectivities for kinetic resolutions, elimination reactions (fluoride base), and Strecker synthesis (cyanide nucleophile). Asymmetric cation-binding catalysis was recently expanded to silicon-based reagents, enabling...... solvents, thus increasing their applicability in synthesis. The expansion of this concept to chiral polyethers led to the emergence of asymmetric cation-binding catalysis, where chiral counter anions are generated from metal salts, particularly using BINOL-based polyethers. Alkali metal salts, namely KF...

  16. Cosmological signatures of time-asymmetric gravity

    CERN Document Server

    Cortês, Marina; Smolin, Lee

    2016-01-01

    We develop the model proposed by Cort\\^es, Gomes & Smolin, to predict cosmological signatures of time-asymmetric extensions of general relativity they proposed recently. Within this class of models the equation of motion of chiral fermions is modified by a torsion term. This term leads to a dispersion law for neutrinos that associates a new time-varying energy with each particle. We find a new neutrino contribution to the Friedmann equation resulting from the torsion term in the Ashtekar connection. In this note we explore the phenomenology of this term and observational consequences for cosmological evolution. We show that constraints on the critical energy density will ordinarily render this term unobservably small, a maximum of order $10^{-25}$ of the neutrino energy density today. However, if the time-asymmetric dark energy is tuned to cancel the cosmological constant, the torsion effect may be a dark matter candidate.

  17. Asymmetric total synthesis of vindoline.

    Science.gov (United States)

    Kato, Daisuke; Sasaki, Yoshikazu; Boger, Dale L

    2010-03-24

    A concise asymmetric total synthesis of (-)-vindoline (1) is detailed based on a tandem intramolecular [4+2]/[3+2] cycloaddition cascade of a 1,3,4-oxadiazole inspired by the natural product structure, in which the tether linking the initiating dienophile and oxadiazole bears a chiral substituent that controls the facial selectivity of the initiating Diels-Alder reaction and sets absolute stereochemistry of the remaining six stereocenters in the cascade cycloadduct. This key reaction introduces three rings and four C-C bonds central to the pentacyclic ring system setting all six stereocenters and introducing essentially all the functionality found in the natural product in a single step. Implementation of the approach also required the development of a unique ring expansion reaction to provide a six-membered ring suitably functionalized for introduction of the Delta (6, 7)-double bond found in the core structure of vindoline and defined our use of a protected hydroxymethyl group as the substituent used to control the stereochemical course of the cycloaddition cascade.

  18. De novo synthesis of natural products via the asymmetric hydration of polyenes.

    Science.gov (United States)

    Wang, Yanping; Xing, Yalan; Zhang, Qi; O'Doherty, George A

    2011-08-14

    For the last ten years our group has been working toward the development of an asymmetric hydration approach to polyketide natural products based on the regioselective hydration of di- and tri-enoates. Key to the success of this approach is the recognition that both high regiocontrol and asymmetric induction could be obtained by the use of a Sharpless asymmetric dihydroxylation reaction. Herein we describe the development of the method and its application to natural product total synthesis.

  19. Vínculo materno-fetal: implicaciones en el desarrollo psicológico y propuesta de intervención en atención temprana (Maternal-foetal bonding: implications for psychological development and proposal for early intervention

    Directory of Open Access Journals (Sweden)

    Claudia Patricia Roncallo

    2015-09-01

    Full Text Available Health research has identified maternal-foetal bonding as a significant antecedent of post-natal bonding between mother and baby. Maternal-foetal bonding is associated with the emotional and cognitive aspects that allow the foetus to be recreated as another human being. This bond is expressed in health practices aimed at the protection and welfare of the foetus. It has been observed that the psychological state of the mother affects the foetus at the neurobehavioral level and influences the appearance of developmental disorders that also manifest in the post-natal period, thereby significantly affecting the mother-baby relationship. Thus, early intervention practices could be extended to the prenatal period as a prevention strategy to favourably impact the health of the child and mother. To address this issue, we present an interdisciplinary intervention model, which focuses on maternal-foetal bonding as a protective factor for bonding during the postnatal period, and as an enhancer of positive parenting practices that promote healthy psychological development.

  20. Asymmetric threat data mining and knowledge discovery

    Science.gov (United States)

    Gilmore, John F.; Pagels, Michael A.; Palk, Justin

    2001-03-01

    Asymmetric threats differ from the conventional force-on- force military encounters that the Defense Department has historically been trained to engage. Terrorism by its nature is now an operational activity that is neither easily detected or countered as its very existence depends on small covert attacks exploiting the element of surprise. But terrorism does have defined forms, motivations, tactics and organizational structure. Exploiting a terrorism taxonomy provides the opportunity to discover and assess knowledge of terrorist operations. This paper describes the Asymmetric Threat Terrorist Assessment, Countering, and Knowledge (ATTACK) system. ATTACK has been developed to (a) data mine open source intelligence (OSINT) information from web-based newspaper sources, video news web casts, and actual terrorist web sites, (b) evaluate this information against a terrorism taxonomy, (c) exploit country/region specific social, economic, political, and religious knowledge, and (d) discover and predict potential terrorist activities and association links. Details of the asymmetric threat structure and the ATTACK system architecture are presented with results of an actual terrorist data mining and knowledge discovery test case shown.

  1. SPECT using asymmetric pinholes with truncated projections

    Energy Technology Data Exchange (ETDEWEB)

    Lin Jianyu; Meikle, Steven R, E-mail: jianyu.lin@curtin.edu.au [Ramaciotti Imaging Centre, Brain and Mind Research Institute, University of Sydney (Australia)

    2011-07-07

    Tomographic systems employing truncated projections have been developed for parallel and fan beam collimation and for cone beam CT but the idea has not been extensively explored in pinhole single photon emission computed tomography (SPECT). In this paper, we explore the sampling requirements and system performance of SPECT systems with asymmetric pinhole collimators and truncated projections. We demonstrate that complete 3D sampling can be achieved by using multiple detectors with truncated asymmetric pinholes, offset axially from each other, and a spiral orbit. The use of truncated projections can be exploited in the design of pinhole SPECT systems by moving the pinholes closer to the subject, resulting in increased sensitivity and improved spatial resolution. Truncated and untruncated pinhole systems were evaluated using the contrast-to-noise ratio (CNR) calculated from the linearized local impulse response as a figure of merit. The CNR for the truncated pinhole system was up to 60% greater than that for the untruncated system at matched resolution for a source voxel near the centre of a uniform phantom and 30% greater at the edge. We conclude that an object can be reconstructed from asymmetric pinholes with truncated projections, which leads to potentially important design considerations and applications in single- and multi-pinhole SPECT.

  2. Nonlinear effects in asymmetric catalysis.

    Science.gov (United States)

    Satyanarayana, Tummanapalli; Abraham, Susan; Kagan, Henri B

    2009-01-01

    There is a need for the preparation of enantiomerically pure compounds for various applications. An efficient approach to achieve this goal is asymmetric catalysis. The chiral catalyst is usually prepared from a chiral auxiliary, which itself is derived from a natural product or by resolution of a racemic precursor. The use of non-enantiopure chiral auxiliaries in asymmetric catalysis seems unattractive to preparative chemists, since the anticipated enantiomeric excess (ee) of the reaction product should be proportional to the ee value of the chiral auxiliary (linearity). In fact, some deviation from linearity may arise. Such nonlinear effects can be rich in mechanistic information and can be synthetically useful (asymmetric amplification). This Review documents the advances made during the last decade in the use of nonlinear effects in the area of organometallic and organic catalysis.

  3. Asymmetric distances for binary embeddings.

    Science.gov (United States)

    Gordo, Albert; Perronnin, Florent; Gong, Yunchao; Lazebnik, Svetlana

    2014-01-01

    In large-scale query-by-example retrieval, embedding image signatures in a binary space offers two benefits: data compression and search efficiency. While most embedding algorithms binarize both query and database signatures, it has been noted that this is not strictly a requirement. Indeed, asymmetric schemes that binarize the database signatures but not the query still enjoy the same two benefits but may provide superior accuracy. In this work, we propose two general asymmetric distances that are applicable to a wide variety of embedding techniques including locality sensitive hashing (LSH), locality sensitive binary codes (LSBC), spectral hashing (SH), PCA embedding (PCAE), PCAE with random rotations (PCAE-RR), and PCAE with iterative quantization (PCAE-ITQ). We experiment on four public benchmarks containing up to 1M images and show that the proposed asymmetric distances consistently lead to large improvements over the symmetric Hamming distance for all binary embedding techniques.

  4. Extrahepatic biliary atresia with choledochal cyst: Prenatal MRI predicted and post natally confirmed: A case report

    Directory of Open Access Journals (Sweden)

    Madhavi Nori

    2013-01-01

    Full Text Available Extrahepatic biliary atresia (EHBA is an uncommon cause of neonatal jaundice. Antenatal Magnetic Resonance Imaging (MRI diagnosis of EHBA has not been published to the best of our knowledge till date. EHBA with cystic component is likely to be mistaken for choledochal cyst. A case that was antenatally predicted and postnatally confirmed by surgery and histopathology is being reported. All imaging signs are analyzed herewith. Imaging helps in the prediction of EHBA and also helps in early postnatal surgical referral which in turn improves the results of Kasai′s portoenterostomy.

  5. Persuade Mothers in Post Natal Ward for Timely Initiation of Breastfeeding

    Directory of Open Access Journals (Sweden)

    Mamtarani, Ratan K Srivastava, B.Divakar

    2011-01-01

    Full Text Available Objective: Timely initiation of breast feeding has been an important issue since last many decades. However, encouragement and early initiation of breast feeding gained momentum since last 20 years. The traditional wisdom and scientific research have proved that mother’s milk is the best. Design: It is a Cross sectional study conducted in urban tertiary care teaching hospital. Methods: a pretested semi-structured questionnaire was used to interview hospitalised mothers. This paper is the result of the interview of 600 women who delivered babies in the hospital. Their Details of socio-demographic features were enquired in addition to the questions related to their initiation of breast feeding after the birth of baby. Timely initiation of breast-feeding was calculated in this paper as percent of infants (0 - <12 months who were put to the breast within one hour of delivery. Results: Out of all deliveries, breast feeding was timely initiated with in one hour only by 1.0 percent of mothers. However 30 percent mothers initiated breast feeding within two hours. Conclusion: The observations of the present study supports that the health functionaries must utilise the opportunity to persuade mothers in the postnatal ward after delivery of their babies for early initiation of breast feeding.

  6. Pre and post-natal risk and determination of factors for child obesity

    Science.gov (United States)

    Trandafir, LM; Temneanu, OR

    2016-01-01

    Obesity is considered a condition presenting a complex, multi-factorial etiology that implies genetic and non-genetic factors. The way the available information should be efficiently and strategically used in the obesity and overweight prohylaxisprogrammes for children all over the world is still unclear for most of the risk factors. Mothers’ pre-conception weight and weight gain during pregnancy are two of the most important prenatal determinants of childhood obesity. Maternal obesity and gestational weight gain are associated with foetal macrosomia and childhood obesity, and this effect extends into adulthood. Obesity and the metabolic syndrome in children originate in intrauterine life. The current obesity epidemic is probably the result of our evolutive inheritance associated with the consumption of highly processed food with an increased calorific value. The determination of risk factors involved in child obesity are: genetic predisposition, diet, sedentary behaviors, socioeconomic position, ethnic origin, microbiota, iatrogenic, endocrine diseases, congenital and acquired hypothalamic defects, usage of medications affecting appetite. However, the vast majority of patients will not have any of these identifiable conditions. Regardless of the aetiology, all the patients should be considered for modifiable lifestyle risk factors and screened for the complications of obesity. PMID:27928443

  7. Pre and post natal drivers of childhood intelligence: Evidence from Singapore

    OpenAIRE

    Gail Pacheco; Mary Hedges; Chris Schilling; Susan Morton

    2011-01-01

    In this study, we seek to investigate what influences children’s intelligence in early childhood. The Singapore Cohort Study of the Risk Factors of Myopia (SCORM) is used in to assess determinants of childhood IQ and changes in IQ. This longitudinal data set, collected from 1999, includes a wealth of demographic, socioeconomic, and prenatal characteristics. The richness of the data allows us to employ various econometric approaches including the use of ordered and multinomial logit analysis. ...

  8. Maternal post natal hospital readmission-trends and association with mode of delivery.

    LENUS (Irish Health Repository)

    Ade-Conde, J A

    2012-02-01

    The aim of this study is to examine the trend in maternal postnatal readmission within six weeks of discharge from childbirth hospitalisation. It is a retrospective review of the maternity computer records system, patient\\'s clinical notes and HIPE data base. All women who delivered babies weighing > 500 g and\\/ > or = 24 weeks gestational age at Our Lady of Lourdes Hospital, Drogheda, Ireland from 1st January 2005 to 31st December 2008 who were re-hospitalised within six weeks of discharge from hospital following child birth were included in the study. A total of 15782 women were delivered over the four year study period. Of these, 236 were readmitted. A series of chi-square analysis were conducted to assess the difference in readmission rates between the year 2008 86 (2.03%) and the years 2005-51(1.46%), 2006-39 (1.01%) and 2007-60 (1.42%). The readmission rate was found to be significantly higher in 2008 compared with the three preceding years. Complications of Caesarean section and secondary postpartum haemorrhage following spontaneous vaginal delivery constitute the major indications for readmission.

  9. Pre and post-natal risk and determination of factors for child obesity

    OpenAIRE

    LM, Trandafir; OR, Temneanu

    2016-01-01

    Obesity is considered a condition presenting a complex, multi-factorial etiology that implies genetic and non-genetic factors. The way the available information should be efficiently and strategically used in the obesity and overweight prohylaxisprogrammes for children all over the world is still unclear for most of the risk factors. Mothers’ pre-conception weight and weight gain during pregnancy are two of the most important prenatal determinants of childhood obesity. Maternal obesity and ge...

  10. Pre- and post-natal exposure of children to EMF generated by domestic induction cookers

    Energy Technology Data Exchange (ETDEWEB)

    Kos, Bor; Miklavcic, Damijan; Kotnik, Tadej [Laboratory of Biocybernetics, Faculty of Electrical Engineering, University of Ljubljana, Trzaska 25, SI-1000 Ljubljana (Slovenia); Valic, Blaz; Gajsek, Peter, E-mail: bor.kos@fe.uni-lj.si, E-mail: damijan.miklavcic@fe.uni-lj.si, E-mail: tadej.kotnik@fe.uni-lj.si, E-mail: blaz.valic@inis.si, E-mail: p.gajsek@inis.si [Institute of Non-Ionizing Radiation, Pohorskega Bataljona 215, SI-1000 Ljubljana (Slovenia)

    2011-10-07

    Induction cookers are a type of cooking appliance that uses an intermediate-frequency magnetic field to heat the cooking vessel. The magnetic flux density produced by an induction cooker during operation was measured according to the EN 62233 standard, and the measured values were below the limits set in the standard. The measurements were used to validate a numerical model consisting of three vertically displaced coaxial current loops at 35 kHz. The numerical model was then used to compute the electric field (E) and induced current (J) in 26 and 30 weeks pregnant women and 6 and 11 year old children. Both E and J were found to be below the basic restrictions of the 2010 low-frequency and 1998 ICNRIP guidelines. The maximum computed E fields in the whole body were 0.11 and 0.66 V m{sup -1} in the 26 and 30 weeks pregnant women and 0.28 and 2.28 V m{sup -1} in the 6 and 11 year old children (ICNIRP basic restriction 4.25 V m{sup -1}). The maximum computed J fields in the whole body were 46 and 42 mA m{sup -2} in the 26 and 30 weeks pregnant women and 27 and 16 mA m{sup -2} in the 6 and 11 year old children (ICNIRP basic restriction 70 mA m{sup -2}).

  11. Pre- and post-natal exposure of children to EMF generated by domestic induction cookers

    Science.gov (United States)

    Kos, Bor; Valič, Blaž; Miklavčič, Damijan; Kotnik, Tadej; Gajšek, Peter

    2011-10-01

    Induction cookers are a type of cooking appliance that uses an intermediate-frequency magnetic field to heat the cooking vessel. The magnetic flux density produced by an induction cooker during operation was measured according to the EN 62233 standard, and the measured values were below the limits set in the standard. The measurements were used to validate a numerical model consisting of three vertically displaced coaxial current loops at 35 kHz. The numerical model was then used to compute the electric field (E) and induced current (J) in 26 and 30 weeks pregnant women and 6 and 11 year old children. Both E and J were found to be below the basic restrictions of the 2010 low-frequency and 1998 ICNRIP guidelines. The maximum computed E fields in the whole body were 0.11 and 0.66 V m-1 in the 26 and 30 weeks pregnant women and 0.28 and 2.28 V m-1 in the 6 and 11 year old children (ICNIRP basic restriction 4.25 V m-1). The maximum computed J fields in the whole body were 46 and 42 mA m-2 in the 26 and 30 weeks pregnant women and 27 and 16 mA m-2 in the 6 and 11 year old children (ICNIRP basic restriction 70 mA m-2).

  12. Post-natal size and morphology of the sella turcica in Williams syndrome.

    Science.gov (United States)

    Axelsson, Stefan; Storhaug, Kari; Kjaer, Inger

    2004-12-01

    Williams syndrome (WS) is a rare congenital disorder with distinctive craniofacial features, cardiovascular abnormalities, mental retardation, and behaviour characteristics. The purpose of this study was to investigate the size and morphology of the sella turcica on profile cephalograms in a group of individuals with WS. The material consisted of radiographic cephalograms of 62 Norwegian children, adolescents, and adults with an age range of 4.7-44.4 years. The length, depth, and diameter of the sella turcica were measured and the mean values were compared with normal reference material from the Oslo University Craniofacial Growth Archive. In total, the two-dimensional size of the sella turcica in the WS group was smaller in length, depth, and diameter compared with the control group, but only occasionally reached a significance level of 5 per cent (Student's t-test). The morphology of the sella turcica was assessed and five different morphological types were identified; oblique anterior wall, extremely low sella turcica, sella turcica bridging, irregularity (notching) in the posterior part of the dorsum sellae, and pyramidal shape of the dorsum sellae. The occurrence of these morphological types was more frequent in the WS subjects compared with the reference material, except for sella turcica bridging, which was equally frequent. The females with WS had more dysmorphic sella turcicas than males. This study has demonstrated morphological aberrations in the sella turcica in Norwegian individuals with WS, which should be further elucidated in future research and combined with neurological andendocrinological investigations.

  13. Asymmetric Synthesis via Chiral Aziridines

    DEFF Research Database (Denmark)

    Tanner, David Ackland; Harden, Adrian; Wyatt, Paul

    1996-01-01

    A series of chiral bis(aziridines) has been synthesised and evaluated as chelating ligands for a variety of asymmetric transformations mediated by metals [Os (dihydroxylation), Pd (allylic alkylation) Cu (cyclopropanation and aziridination, Li (1,2-addition of organolithiums to imines)]. In the b......A series of chiral bis(aziridines) has been synthesised and evaluated as chelating ligands for a variety of asymmetric transformations mediated by metals [Os (dihydroxylation), Pd (allylic alkylation) Cu (cyclopropanation and aziridination, Li (1,2-addition of organolithiums to imines...

  14. Recent advances in catalytic asymmetric hydrogenation:Renaissance of the monodentate phosphorus ligands

    Institute of Scientific and Technical Information of China (English)

    GUO Hongchao; DING Kuiling; DAI Lixin

    2004-01-01

    The history for the development of chiral phosphorus ligands in catalytic asymmetric hydrogenation is briefly highlighted. This review focuses on the recent advances in the synthesis of the monodentate phosphorus ligands and their applications in catalytic asymmetric hydrogenation. The examples highlighted in this article clearly demonstrated the importance and advantages of monodentate phosphorus ligands, which had been ignored for 30 a and experienced a renaissance at the very beginning of this millennium, particularly in the area of asymmetric hydrogenation.

  15. Synthesis of Asymmetric Propanetriol Analogues

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    From natural tartaric acid, (R)-2-benzyloxy-3-(2-tetrahydropyranyloxy) propanol 3 was designed and synthesized, and (R)-2-benzyloxy-3-(4-methoxybenzyloxy) propanol 7 was prepared in a new method. They can be used as chiral synthons of lysophosphatidic acid and other compounds with asymmetric propanetriol backbone.

  16. Catalytic Asymmetric Bromocyclization of Polyenes.

    Science.gov (United States)

    Samanta, Ramesh C; Yamamoto, Hisashi

    2017-02-01

    The first catalytic asymmetric bromonium ion-induced polyene cyclization has been achieved by using a chiral BINOL-derived thiophosphoramide catalyst and 1,3-dibromo-5,5-dimethylhydantoin as an electrophilic bromine source. Bromocyclization products are obtained in high yields, with good enantiomeric ratios and high diastereoselectivity, and are abundantly found as scaffolds in natural products.

  17. Dynamic Conditional Correlations for Asymmetric Processes

    OpenAIRE

    Asai, Manabu; McAleer, Michael

    2011-01-01

    The paper develops two Dynamic Conditional Correlation (DCC) models, namely the Wishart DCC (wDCC) model. The paper applies the wDCC approach to the exponential GARCH (EGARCH) and GJR models to propose asymmetric DCC models. We use the standardized multivariate t-distribution to accommodate heavy-tailed errors. The paper presents an empirical example using the trivariate data of the Nikkei 225, Hang Seng and Straits Times Indices for estimating and forecasting the wDCC-EGARCH and wDCC-GJR mod...

  18. Analysis of Asymmetric Piezoelectric Composite Beam

    CERN Document Server

    Chen, J -S; Wu, K -C

    2008-01-01

    This paper deals with the vibration analysis of an asymmetric composite beam composed of glass a piezoelectric material. The Bernoulli's beam theory is adopted for mechanical deformations, and the electric potential field of the piezoelectric material is assumed such that the divergence-free requirement of the electrical displacements is satisfied. The accuracy of the analytic model is assessed by comparing the resonance frequencies obtained by the analytic model with those obtained by the finite element method. The model developed can be used as a tool for designing piezoelectric actuators such as micro-pumps.

  19. Neuronal Alignment On Asymmetric Textured Surfaces

    CERN Document Server

    Beighley, Ross; Sekeroglu, Koray; Atherton, Timothy; Demirel, Melik C; Staii, Cristian

    2013-01-01

    Axonal growth and the formation of synaptic connections are key steps in the development of the nervous system. Here we present experimental and theoretical results on axonal growth and interconnectivity in order to elucidate some of the basic rules that neuronal cells use for functional connections with one another. We demonstrate that a unidirectional nanotextured surface can bias axonal growth. We perform a systematic investigation of neuronal processes on asymmetric surfaces and quantify the role that biomechanical surface cues play in neuronal growth. These results represent an important step towards engineering directed axonal growth for neuro-regeneration studies.

  20. Scanning electron microscopic observations of the development of the chicken caecum.

    Science.gov (United States)

    Sabatakou, O; Paraskevakou, E; Tseleni-Balafouta, S; Athanasiadis, A; Fasseas, C

    2003-10-01

    The surface pattern of the caeca of the chicken was examined using the scanning electron microscope (SEM) in stages ranging from 11th day of foetal development to 60 days of post-natal life. During incubation the proximal region (basis) of the caecum presented a few irregular elevations, which were later regarded as villi and after hatching, gradually, became longer and wider. These structures were found to be similar to those of the small intestine. The middle (corpus) and distal (apex) regions of caecum presented ridges/folds with short and blunt villi that were even shorter in the apex. The ridges/folds were running longitudinally the inner surface of the corpus while those of the apex were not so well developed.

  1. Laminin-511 and integrin beta-1 in hair follicle development and basal cell carcinoma formation

    Directory of Open Access Journals (Sweden)

    Williams Samantha

    2010-11-01

    Full Text Available Abstract Background Initiation of the hair follicle placode and its subsequent growth, maturation and cycling in post-natal skin requires signaling interactions between epithelial cells and adjacent dermal cells and involves Shh signaling via the primary cilium. Previous reports have implicated laminins in hair follicle epithelial invagination. Results Here we use a human BCC model system and mouse mutants to re-evaluate the role of laminin-511 in epithelial invagination in the skin. Blocking laminin 511 and 332 in BCCs maintains primary cilia and Shh signalling, but prevents invagination. Similarly, in laminin-511 and dermal beta-1 integrin mutants, dermal papilla development and primary cilia formation are normal. Dermal beta-1 integrin mutants have normal hair follicle development. Conclusions Our data provides support for a primary role of laminin-511 promoting hair follicle epithelial downgrowth without affecting dermal primary cilia and Shh target gene induction.

  2. Is HCMV vaccine an unmet need? The state of art of vaccine development.

    Science.gov (United States)

    Chiurchiu, S; Calo Carducci, F I; Rocchi, F; Simonetti, A; Bonatti, G; Salmaso, S; Melchiorri, D; Pani, L; Rossi, P

    2013-01-01

    Congenital HCMV infection is the most frequent congenital infection, with an incidence of 0.2- 2.5 percent among all live births. About 11 percent of infected newborns show symptoms at birth, including hepato-splenomegaly, thrombocytopenia, neurologic involvement, hearing impairment and visual deficit. Moreover, 5-25 percent of the asymptomatic congenital HCMV-infected neonates will develop sequelae over months or even years. The relevant social burden, the economic costs of pre-natal screening, post-natal diagnosis, follow-up and possible therapy, although still limited, are the major factors to be considered. Several types of vaccines have been explored in order to develop an effective and safe HCMV vaccine: live attenuated, subunit, vectored, peptide, DNA, and subviral ones, but none are available for use. This review illustrates the different vaccine types studied to date, focusing on the possible vaccination strategy to be implemented once the HCMV vaccine is available, in terms of target population.

  3. ASYMMETRIC VORTICES FLOW OVER SLENDER BODY AND ITS ACTIVE CONTROL AT HIGH ANGLE OF ATTACK

    Institute of Scientific and Technical Information of China (English)

    DENG Xueying; WANG Yankui

    2004-01-01

    The studies of asymmetric vortices flow over slender body and its active control at high angles of attack have significant importance for both academic field and engineering area. This paper attempts to provide an update state of art to the investigations on the fields of forebody asymmetric vortices. This review emphasizes the correlation between micro-perturbation on the model nose and its response and evolution behaviors of the asymmetric vortices. The critical issues are discussed,which include the formation and evolution mechanism of asymmetric multi-vortices; main behaviors of asymmetric vortices flow including its deterministic feature and vortices flow structure; the evolution and development of asymmetric vortices under the perturbation on the model nose; forebody vortex active control especially discussed micro-perturbation active control concept and technique in more detail. However present understanding in this area is still very limited and this paper tries to identify the key unknown problems in the concluding remarks.

  4. Long non-coding RNA expression profiling of mouse testis during postnatal development.

    Directory of Open Access Journals (Sweden)

    Jin Sun

    Full Text Available Mammalian testis development and spermatogenesis play critical roles in male fertility and continuation of a species. Previous research into the molecular mechanisms of testis development and spermatogenesis has largely focused on the role of protein-coding genes and small non-coding RNAs, such as microRNAs and piRNAs. Recently, it has become apparent that large numbers of long (>200 nt non-coding RNAs (lncRNAs are transcribed from mammalian genomes and that lncRNAs perform important regulatory functions in various developmental processes. However, the expression of lncRNAs and their biological functions in post-natal testis development remain unknown. In this study, we employed microarray technology to examine lncRNA expression profiles of neonatal (6-day-old and adult (8-week-old mouse testes. We found that 8,265 lncRNAs were expressed above background levels during post-natal testis development, of which 3,025 were differentially expressed. Candidate lncRNAs were identified for further characterization by an integrated examination of genomic context, gene ontology (GO enrichment of their associated protein-coding genes, promoter analysis for epigenetic modification, and evolutionary conservation of elements. Many lncRNAs overlapped or were adjacent to key transcription factors and other genes involved in spermatogenesis, such as Ovol1, Ovol2, Lhx1, Sox3, Sox9, Plzf, c-Kit, Wt1, Sycp2, Prm1 and Prm2. Most differentially expressed lncRNAs exhibited epigenetic modification marks similar to protein-coding genes and tend to be expressed in a tissue-specific manner. In addition, the majority of differentially expressed lncRNAs harbored evolutionary conserved elements. Taken together, our findings represent the first systematic investigation of lncRNA expression in the mammalian testis and provide a solid foundation for further research into the molecular mechanisms of lncRNAs function in mammalian testis development and spermatogenesis.

  5. 水电站非对称月牙肋岔管体型生成系统开发%System Development of Somatotype Generation for Hydropower Station Asymmetric Crescent-Rib Reinforced Branch Pipe

    Institute of Scientific and Technical Information of China (English)

    李斌; 宋海亭; 白正雄

    2016-01-01

    针对水电站非对称月牙肋岔管结构体型、空间关系复杂,手算方法设计工作量大、设计效率不高的问题,根据新的水电站压力钢管设计规范对岔管体型提出的要求,从程序开发的角度出发,从各圆锥的几何关系入手,重新推导了相关公式,解决了体型生成中的关键问题;应用C++语言编制非对称月牙肋岔管的体型生成程序,采用VTK图形库实现了系统的三维可视化功能。工程应用实例表明,该系统数据输入简单,人机交互性和可操作性好,输出体型方案齐全,能够将岔管体形设计和绘制设计图很好地结合起来,为月牙肋岔管的设计提供了一个方便可靠的工具。%For the complicated issues of somatotype of hydropower station asymmetric crescent⁃rib reinforced branch pipe, rather difficult spatial relationship to be imagined, huge design workload by means of manual computation and lower design efficiency, it had been re⁃deduced the relevant formula to solve key problems during the somatotype generation, from the angle of program development, which matched the requirements for branch pipe somatotype from the new design criterion of hydropower station pressure steel tube and began with the geometric relation of various tapers;it had been accomplished the somatotype development program of asymmetric crescent⁃rib reinforced branch pipe by employing C++Language and produced the 3D systematic visual function by employing the VTK graphic library. According to the engineering application examples, the system data input is simple, with perfect human computer interaction and good operability, and the output somatotype plan is complete enough to provide a convenient reliable tool for designing the crescent⁃rib reinforced branch pipe, which can wonderfully combine the branch pipe somatotype design with the drawing design figure.

  6. Recent advances in cooperative bimetallic asymmetric catalysis: dinuclear Schiff base complexes.

    Science.gov (United States)

    Matsunaga, Shigeki; Shibasaki, Masakatsu

    2014-02-04

    Cooperative catalysis has proven to be a powerful strategy for realizing high reactivity and selectivity in asymmetric transformations. A variety of cooperative asymmetric catalysts have been developed over the last two decades. In this feature article, recent advances from our research on cooperative asymmetric catalysis, focusing on dinuclear Schiff base catalysis, are described. Design of dinuclear Schiff base catalysts and their applications in several asymmetric C-C and C-N bond-forming reactions under simple proton transfer conditions with perfect atom-economy are discussed in detail.

  7. Asymmetric photoredox transition-metal catalysis activated by visible light

    Science.gov (United States)

    Huo, Haohua; Shen, Xiaodong; Wang, Chuanyong; Zhang, Lilu; Röse, Philipp; Chen, Liang-An; Harms, Klaus; Marsch, Michael; Hilt, Gerhard; Meggers, Eric

    2014-11-01

    Asymmetric catalysis is seen as one of the most economical strategies to satisfy the growing demand for enantiomerically pure small molecules in the fine chemical and pharmaceutical industries. And visible light has been recognized as an environmentally friendly and sustainable form of energy for triggering chemical transformations and catalytic chemical processes. For these reasons, visible-light-driven catalytic asymmetric chemistry is a subject of enormous current interest. Photoredox catalysis provides the opportunity to generate highly reactive radical ion intermediates with often unusual or unconventional reactivities under surprisingly mild reaction conditions. In such systems, photoactivated sensitizers initiate a single electron transfer from (or to) a closed-shell organic molecule to produce radical cations or radical anions whose reactivities are then exploited for interesting or unusual chemical transformations. However, the high reactivity of photoexcited substrates, intermediate radical ions or radicals, and the low activation barriers for follow-up reactions provide significant hurdles for the development of efficient catalytic photochemical processes that work under stereochemical control and provide chiral molecules in an asymmetric fashion. Here we report a highly efficient asymmetric catalyst that uses visible light for the necessary molecular activation, thereby combining asymmetric catalysis and photocatalysis. We show that a chiral iridium complex can serve as a sensitizer for photoredox catalysis and at the same time provide very effective asymmetric induction for the enantioselective alkylation of 2-acyl imidazoles. This new asymmetric photoredox catalyst, in which the metal centre simultaneously serves as the exclusive source of chirality, the catalytically active Lewis acid centre, and the photoredox centre, offers new opportunities for the `green' synthesis of non-racemic chiral molecules.

  8. Asymmetric Multilevel Diversity Coding and Asymmetric Gaussian Multiple Descriptions

    CERN Document Server

    Mohajer, Soheil; Diggavi, Suhas N

    2009-01-01

    We consider the asymmetric multilevel diversity (A-MLD) coding problem, where a set of $2^K-1$ information sources, ordered in a decreasing level of importance, is encoded into $K$ messages (or descriptions). There are $2^K-1$ decoders, each of which has access to a non-empty subset of the encoded messages. Each decoder is required to reproduce the information sources up to a certain importance level depending on the combination of descriptions available to it. We obtain a single letter characterization of the achievable rate region for the 3-description problem. In contrast to symmetric multilevel diversity coding, source-separation coding is not sufficient in the asymmetric case, and ideas akin to network coding need to be used strategically. Based on the intuitions gained in treating the A-MLD problem, we derive inner and outer bounds for the rate region of the asymmetric Gaussian multiple description (MD) problem with three descriptions. Both the inner and outer bounds have a similar geometric structure t...

  9. Modelling asymmetric growth in crowded plant communities

    DEFF Research Database (Denmark)

    Damgaard, Christian

    2010-01-01

    A class of models that may be used to quantify the effect of size-asymmetric competition in crowded plant communities by estimating a community specific degree of size-asymmetric growth for each species in the community is suggested. The model consists of two parts: an individual size-asymmetric ......A class of models that may be used to quantify the effect of size-asymmetric competition in crowded plant communities by estimating a community specific degree of size-asymmetric growth for each species in the community is suggested. The model consists of two parts: an individual size...

  10. Development of the permanent mandibular cheek teeth in fallow deer (Dama dama).

    Science.gov (United States)

    Kierdorf, H; Hommelsheim, S; Kierdorf, U

    2012-12-01

    The study describes crown and root formation of the permanent mandibular cheek teeth of fallow deer from a gestational age of 22-23 weeks up to a post-natal age of 33 months. Tooth development was recorded using a scoring scheme based on morphological criteria ranging from crypt formation to completion of root growth. The morphological appearance of the enamel surface during three different stages (secretory-stage enamel, maturation-stage enamel and mature enamel) was described, and the approximate age at termination of the secretory stage of amelogenesis in the deciduous and permanent mandibular cheek teeth was determined. The data enable an age estimation of fallow deer up to 3 years of age and provide a basis for assessing the timing of stress episodes that affect tooth crown formation. This information is useful for the management of the species as well as in bioarchaeological and bioindication studies.

  11. Asymmetric tandem organic solar cells

    Science.gov (United States)

    Howells, Thomas J.

    Organic photovoltaics (OPVs) is an area that has attracted much attention recently as a potential low cost, sustainable source of energy with a good potential for full-scale commercialisation. Understanding the factors that determine the efficiency of such cells is therefore a high priority, as well as developing ways to boost efficiency to commercially-useful levels. In addition to an intensive search for new materials, significant effort has been spent on ways to squeeze more performance out of existing materials, such as multijunction cells. This thesis investigates double junction tandem cells in the context of small molecule organic materials. . Two different organic electron donor materials, boron subphthalocyanine chloride (SubPc) and aluminium phthalocyanine chloride (ClAlPc) were used as donors in heterojunctions with C60 to create tandem cells for this thesis. These materials have been previously used for solar cells and the absorption spectra of the donor materials complement each other, making them good candidates for tandem cell architectures. The design of the recombination layer between the cells is considered first, with silver nanoparticles demonstrated to work well as recombination centres for charges from the front and back sub-cells, necessary to avoid a charge build-up at the interface. The growth conditions for the nanoparticles are optimised, with the tandem cells outperforming the single heterojunction architecture. Optical modelling is considered as a method to improve the understanding of thin film solar cells, where interference effects from the reflective aluminium electrode are important in determining the magnitude of absorption a cell can achieve. The use of such modelling is first demonstrated in hybrid solar cells based on a SubPc donor with a titanium oxide (TiOx) acceptor; this system is ideal for observing the effects of interference as only the SubPc layer has significant absorption. The modelling is then applied to tandem cells

  12. Asymmetric information and macroeconomic dynamics

    Science.gov (United States)

    Hawkins, Raymond J.; Aoki, Masanao; Roy Frieden, B.

    2010-09-01

    We show how macroeconomic dynamics can be derived from asymmetric information. As an illustration of the utility of this approach we derive the equilibrium density, non-equilibrium densities and the equation of motion for the response to a demand shock for productivity in a simple economy. Novel consequences of this approach include a natural incorporation of time dependence into macroeconomics and a common information-theoretic basis for economics and other fields seeking to link micro-dynamics and macro-observables.

  13. Asymmetrical Γ-Source Inverters

    DEFF Research Database (Denmark)

    Wei, Mo; Poh Chiang, Loh; Blaabjerg, Frede

    2014-01-01

    , inverters with coupled transformers have been introduced, but they usually lead to high turns ratio, and hence many winding turns, at high gain. An alternative would then be the asymmetrical Γ-source inverters proposed in this paper, whose gain is raised by lowering their turns ratio toward unity. The input...... current drawn by the proposed inverters is smoother and, hence, more adaptable by the source. Theories and experimental results have been presented in this paper for validating the concepts proposed....

  14. Success Factors of Asymmetric Connections - Example of Large Slovenian Enterprises

    Directory of Open Access Journals (Sweden)

    Viktor Vračar

    2014-11-01

    Full Text Available More and more companies realize the fact that networking or partner collaborations, which are based on partner relations between companies, are essential for their long-term existence. In today’s global competitive environment each company is included at least in some different connections. Very common connections occur between large and smaller enterprises, where the so called asymmetric connections occur, which may be understood as the ability of one organisation to establish power, influence and control over the other organisation and its resources. According to numerous statements, the connections between enterprises are very frequently uneffectivenessful, with opinions on the optimal nature of asymmetric connections being quite common as well, whereby it is, as a rule, a synergic complementing of missing content for both partners. To verify the thesis, that companies achieve more competitiveness and effectiveness through connections, whereby the so called asymmetric connections are common, a structural model of the evolution of asymmetric connection has been developed, which connects the theoretically identified factors and all dependent concepts of competitiveness, efficiency and effectiveness. The empirical research also attempts to further expose the factors of asymmetric connections, which affect efficiency and effectiveness of the connected enterprises.

  15. Up-down asymmetric tokamaks

    CERN Document Server

    Ball, Justin

    2016-01-01

    Bulk toroidal rotation has proven capable of stabilising both dangerous MHD modes and turbulence. In this thesis, we explore a method to drive rotation in large tokamaks: up-down asymmetry in the magnetic equilibrium. We seek to maximise this rotation by finding optimal up-down asymmetric flux surface shapes. First, we use the ideal MHD model to show that low order external shaping (e.g. elongation) is best for creating up-down asymmetric flux surfaces throughout the device. Then, we calculate realistic up-down asymmetric equilibria for input into nonlinear gyrokinetic turbulence analysis. Analytic gyrokinetics shows that, in the limit of fast shaping effects, a poloidal tilt of the flux surface shaping has little effect on turbulent transport. Since up-down symmetric surfaces do not transport momentum, this invariance to tilt implies that devices with mirror symmetry about any line in the poloidal plane will drive minimal rotation. Accordingly, further analytic investigation suggests that non-mirror symmetri...

  16. The Development of Chiral Catalysis in Asymmetric Synthesis%手性催化在不对称合成中的发展

    Institute of Scientific and Technical Information of China (English)

    杨晓刚; 黄蓓

    2012-01-01

    介绍了手性化合物的重要性及其发展情况,从手性分子的制备、手性有机小分子催化的应用等方面总结了手性分子的研究进展,指出了手性分子的发展方向。%The importance and devopment of chiral compounds are introduced, from the preparation of chiral molecule, the application of chiral organic small molecular catalyst, the research progress of chiral molealle are summarized, the development direction of chiral molecule are pointed out.

  17. Asymmetric condensed dark matter

    CERN Document Server

    Aguirre, Anthony

    2015-01-01

    We explore the viability of a boson dark matter candidate with an asymmetry between the number densities of particles and antiparticles. A simple thermal field theory analysis confirms that, under certain general conditions, this component would develop a Bose-Einstein condensate in the early universe that, for appropriate model parameters, could survive the ensuing cosmological evolution until now. The condensation of a dark matter component in equilibrium with the thermal plasma is a relativistic process, hence the amount of matter dictated by the charge asymmetry is complemented by a hot relic density frozen out at the time of decoupling. Contrary to the case of ordinary WIMPs, dark matter particles in a condensate can be very light, $10^{-22}\\,{\\rm eV} \\lesssim m \\lesssim 10^2\\,{\\rm eV}$; the lower limit arises from constraints on small-scale structure formation, while the upper bound ensures that the density from thermal relics is not too large. Big-Bang nucleosynthesis constrains the temperature of deco...

  18. Asymmetric condensed dark matter

    Science.gov (United States)

    Aguirre, Anthony; Diez-Tejedor, Alberto

    2016-04-01

    We explore the viability of a boson dark matter candidate with an asymmetry between the number densities of particles and antiparticles. A simple thermal field theory analysis confirms that, under certain general conditions, this component would develop a Bose-Einstein condensate in the early universe that, for appropriate model parameters, could survive the ensuing cosmological evolution until now. The condensation of a dark matter component in equilibrium with the thermal plasma is a relativistic process, hence the amount of matter dictated by the charge asymmetry is complemented by a hot relic density frozen out at the time of decoupling. Contrary to the case of ordinary WIMPs, dark matter particles in a condensate must be lighter than a few tens of eV so that the density from thermal relics is not too large. Big-Bang nucleosynthesis constrains the temperature of decoupling to the scale of the QCD phase transition or above. This requires large dark matter-to-photon ratios and very weak interactions with standard model particles.

  19. Effect of stress hormone antagonists on ovarian follicular development in pre-pubertal rat

    Directory of Open Access Journals (Sweden)

    Kalid Hamood Abdullah

    2012-08-01

    Full Text Available Effect of stress on pre-pubertal ovarian follicular development was studied. Fifteen day old female rats were administered under stress (exposed to maternal separation; 6 hours/day from post-natal day 15 to 21 for 7 days, and appropriate controls were maintained. The time of exposure was randomly changed every day during light phase (7AM to 7 PM of the day to avoid habituation. There was a significant decrease in serum estrogen levels on post-natal day 21 in stress group rats compared to controls indicating stress response in these rats. However, mean number of healthy follicles in all categories of follicles were significantly lower in stressed rats compared to controls. Concomitant with these changes, mean number of atreitic follicles showed an increase over control values in stressed rats. In contrast administration of Naltrexone (5μg NTX/rat/day, Mifepristone (1 μg MP/rat/day, FSH (10 IU FSH/rat/day with stressed the significant increases in the relative weight of ovary, uterus, fallopian tube, body weight and the mean number of healthy follicles in the ovary compared to the controls. In the ovary treatment of stressed did not affect primordial follicles. Primordial follicles were reduced in number significantly in the ovary of controls and treated groups when compared with the initial controls whereas there was no significant variation among the controls and the treated groups. The results indicate that stress dose not interfere with the progress of pre-pubertal follicular development. However, it causes increased loss of follicles by atretia.

  20. Gravity-induced asymmetric distribution of a plant growth hormone

    Science.gov (United States)

    Bandurski, R. S.; Schulze, A.; Momonoki, Y.

    1984-01-01

    Dolk (1936) demonstrated that gravistimulation induced an asymmetric distribution of auxin in a horizontally-placed shoot. An attempt is made to determine where and how that asymmetry arises, and to demonstrate that the endogenous auxin, indole-3-acetic acid, becomes asymmetrically distributed in the cortical cells of the Zea mays mesocotyl during 3 min of geostimulation. Further, indole-3-acetic acid derived by hydrolysis of an applied transport form of the hormone, indole-3-acetyl-myo-inositol, becomes asymmetrically distributed within 15 min of geostimulus time. From these and prior data is developed a working theory that the gravitational stimulus induces a selective leakage, or secretion, of the hormone from the vascular tissue to the cortical cells of the mesocotyl.

  1. Data analysis of asymmetric structures advanced approaches in computational statistics

    CERN Document Server

    Saito, Takayuki

    2004-01-01

    Data Analysis of Asymmetric Structures provides a comprehensive presentation of a variety of models and theories for the analysis of asymmetry and its applications and provides a wealth of new approaches in every section. It meets both the practical and theoretical needs of research professionals across a wide range of disciplines and  considers data analysis in fields such as psychology, sociology, social science, ecology, and marketing. In seven comprehensive chapters this guide details theories, methods, and models for the analysis of asymmetric structures in a variety of disciplines and presents future opportunities and challenges affecting research developments and business applications.

  2. Preview-based Asymmetric Load Reduction of Wind Turbines

    DEFF Research Database (Denmark)

    Madsen, Mathias; Filsø, Jakob; Soltani, Mohsen

    2012-01-01

    Fatigue loads on wind turbines caused by an asymmetric wind field become an increasing concern when the scale of wind turbines increases. This paper presents a model based predictive approach to reduce asymmetric loads by using Light Detection And Ranging (LIDAR) measurements. The Model Predictive...... Controller (MPC) developed is based on a model with individual blade pitching to utilize the LIDAR measurements. The MPC must also maintain a given power reference while satisfying a set of actuator constraints. The designed controller was tested on a 5 MW wind turbine in the FAST simulator and compared...

  3. Instability of asymmetric continuous shaft system

    Science.gov (United States)

    Srinath, R.; Sarkar, Abhijit; Sekhar, A. S.

    2016-11-01

    In this work, the governing equation of asymmetric continuous shaft in inertial frame of reference is studied. In particular, determination of the parameter ranges for the stability or instability of the shaft response is the focus of the present work. The governing equations are a fourth-order coupled partial differential equations containing time dependent coefficients. The equations are non-dimensionalized in terms of two parameters related to the average moment of inertia and the difference of moments of inertia about the principal axes. Using the latter as the asymptotic parameter and employing modal superposition, a formal methodology based on perturbation methods is developed to ascertain the stability and instability characteristics. The methodology is applicable to shafts subjected to some of the classical boundary conditions viz. simply supported, cantilever, and fixed-fixed. Similar stability curves are obtained for each mode for these different boundary conditions. The novel non-dimensionalization scheme chosen leads to the stability boundaries as well as the loci of varying speeds to be in the form of straight lines. The intersection of these lines determine the stable and unstable speed ranges of different asymmetric shafts. The results are generalized for different material and geometric properties of the shaft.

  4. Development of Asymmetric Hydrogenation Catalysts via High Throughput Experimentation Développement de catalyseurs d’hydrogénation asymétrique par criblage haut débit

    Directory of Open Access Journals (Sweden)

    de Vries J. G.

    2013-02-01

    Full Text Available The dynamics of drugs discovery imposes severe time constraints on the development chemist in charge of implementing the large scale production of a new Active Pharmaceutical Ingredient (API. This results in the use of well-established and robust transformations at the expense of the cost-efficiency and the sustainability of the process. In order to cope with the short development time and allow the implementation of new more efficient production technologies such as asymmetric hydrogenation, we have turned towards the use of high throughput experimentation for the discovery of new catalysts. The protocol for the preparation of a library of chiral ligands and its application to real-life pharmaceutical molecules is described in this article. La découverte de nouvelles molécules pharmaceutiques a sa propre dynamique qui impose des contraintes temporelles très strictes au chimiste en charge de développer la production du principe actif à large échelle. En conséquence, ce dernier va se tourner vers l’utilisation de technologies éprouvées et robustes quitte à rendre le procédé plus coûteux ou plus polluant. Afin de pouvoir faire face à des temps de développement très courts et d’introduire en production des technologies modernes et non polluantes comme l’hydrogénation asymétrique, nous avons développé une plateforme de criblage haut débit pour la découverte de nouveaux catalyseurs. Dans cet article, nous décrivons une des facettes de cette plateforme qui est la synthèse de librairies de ligands chiraux et leur application au cas réel d’une molécule pharmaceutique.

  5. Rh-Catalyzed Asymmetric Hydrogenation of 1,2-Dicyanoalkenes.

    Science.gov (United States)

    Li, Meina; Kong, Duanyang; Zi, Guofu; Hou, Guohua

    2017-01-06

    A highly efficient enantioselective hydrogenation of 1,2-dicyanoalkenes catalyzed by the complex of rhodium and f-spiroPhos has been developed. A series of 1,2-dicyanoalkenes were successfully hydrogenated to the corresponding chiral 1,2-dicyanoalkanes under mild conditions with excellent enantioselectivities (up to 98% ee). This methodology provides efficient access to the asymmetric synthesis of chiral diamines.

  6. Recent advances in rhodium-catalyzed asymmetric synthesis of heterocycles.

    Science.gov (United States)

    Chen, Wen-Wen; Xu, Ming-Hua

    2017-02-01

    Heterocycles are crucial structural motifs that are ubiquitously present in biologically active natural products and pharmaceutically important compounds. Over the past few decades, great attention has been paid to develop efficient methodologies for the construction of diverse enantioenriched heterocyclic frameworks. This review focuses on the recent impressive progress and advances in the asymmetric synthesis of heterocycles under rhodium catalysis.

  7. Asymmetric Schiff bases derived from diaminomaleonitrile and their metal complexes

    Science.gov (United States)

    Yang, Jianjie; Shi, Rufei; Zhou, Pei; Qiu, Qiming; Li, Hui

    2016-02-01

    Asymmetric Schiff bases, due to its asymmetric structure, can be used as asymmetric catalyst, antibacterial, and mimic molecules during simulate biological processes, etc. In recent years, research on synthesis and properties of asymmetric Schiff bases have become an increase interest of chemists. This review summarizes asymmetric Schiff bases derived from diaminomaleonitrile (DAMN) and DAMN-based asymmetric Schiff bases metal complexes. Applications of DAMN-based asymmetric Schiff bases are also discussed in this review.

  8. Investigation of roles for LRR-RLKs PNL1 and PNL2 in asymmetric cell division in Arabidopsis thaliana

    OpenAIRE

    Rodriguez, Maiti Celina

    2008-01-01

    Asymmetric cell division is a vital component of plant development. It enables cell differentiation and cell diversity. A key component of asymmetric cell division is cell signaling. Signals are believed to control polarization and orientation of asymmetric divisions during stomatal development. The findings of this report suggest that PNL1 and PNL2, two LRR-RLKs found in Arabidopsis and closely related to maize PAN1 LRR-RLK, are possibly involved in the signaling events occurring during the ...

  9. Spontaneous baryogenesis from asymmetric inflaton

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Fuminobu [Tohoku Univ., Sendai (Japan). Dept. of Physics; Tokyo Univ., Chiba (Japan). Kavli IPMU (WPI), UTIAS; Yamada, Masaki [Tokyo Univ., Chiba (Japan). Kavli IPMU (WPI), UTIAS; Tokyo Univ., Chiba (Japan). Inst. for Cosmic Ray Research; DESY Hamburg (Germany)

    2015-10-15

    We propose a variant scenario of spontaneous baryogenesis from asymmetric inflaton based on current-current interactions between the inflaton and matter fields with a non-zero B-L charge. When the inflaton starts to oscillate around the minimum after inflation, it may lead to excitation of a CP-odd component, which induces an effective chemical potential for the B-L number through the current-current interactions. We study concrete inflation models and show that the spontaneous baryogenesis scenario can be naturally implemented in the chaotic inflation in supergravity.

  10. The asymmetric Goos-H\\"anchen effect

    OpenAIRE

    Araujo, Manoel P.; Carvalho, Silvânia A.; De Leo, Stefano

    2013-01-01

    We show in which conditions optical gaussian beams, propagating throughout an homogeneous dielectric right angle prism, present an asymmetric Goos-H\\"anchen (GH) effect. This asymmetric behavior is seen for incidence at critical angles and happens in the propagation direction of the outgoing beam. The asymmetric GH effect can be also seen as an amplification of the standard GH shift. Due to the fact that it only depends on the ratio between the wavelength and the minimal waist size of the inc...

  11. The asymmetric Goos-H\\"anchen effect

    CERN Document Server

    Araujo, Manoel P; De Leo, Stefano

    2014-01-01

    We show in which conditions optical gaussian beams, propagating throughout an homogeneous dielectric right angle prism, present an asymmetric Goos-H\\"anchen (GH) effect. This asymmetric behavior is seen for incidence at critical angles and happens in the propagation direction of the outgoing beam. The asymmetric GH effect can be also seen as an amplification of the standard GH shift. Due to the fact that it only depends on the ratio between the wavelength and the minimal waist size of the incoming gaussian beam, it can be also used to determine one of these parameters. Multiple peaks interference is an additional phenomenon seen in the presence of such asymmetric effects.

  12. Thin lenses of asymmetric power

    Directory of Open Access Journals (Sweden)

    W. F. Harris

    2009-12-01

    Full Text Available It is generally supposed that thin systems, including refracting surfaces and thin lenses, have powers that are necessarily symmetric.  In other words they have powers which can be represented assymmetric dioptric power matrices and in the familar spherocylindrical form used in optometry and ophthalmology.  This paper shows that this is not correct and that it is indeed possible for a thin system to have a power that is not symmetric and which cannot be expressed in spherocylindrical form.  Thin systems of asymmetric power are illustratedby means of a thin lens that is modelled with small prisms and is chosen to have a dioptric power ma-trix that is antisymmetric.  Similar models can be devised for a thin system whose dioptric power matrix is any  2 2 ×  matrix.  Thus any power, symmetric, asymmetric or antisymmetric, is possible for a thin system.  In this sense our understanding of the power of thin systems is now complete.

  13. Excitons in asymmetric quantum wells

    Science.gov (United States)

    Grigoryev, P. S.; Kurdyubov, A. S.; Kuznetsova, M. S.; Ignatiev, I. V.; Efimov, Yu. P.; Eliseev, S. A.; Petrov, V. V.; Lovtcius, V. A.; Shapochkin, P. Yu.

    2016-09-01

    Resonance dielectric response of excitons is studied for the high-quality InGaAs/GaAs heterostructures with wide asymmetric quantum wells (QWs). To highlight effects of the QW asymmetry, we have grown and studied several heterostructures with nominally square QWs as well as with triangle-like QWs. Several quantum confined exciton states are experimentally observed as narrow exciton resonances. A standard approach for the phenomenological analysis of the profiles is generalized by introducing different phase shifts for the light waves reflected from the QWs at different exciton resonances. Good agreement of the phenomenological fit to the experimentally observed exciton spectra for high-quality structures allowed us to reliably obtain parameters of the exciton resonances: the exciton transition energies, the radiative broadenings, and the phase shifts. A direct numerical solution of the Schrödinger equation for the heavy-hole excitons in asymmetric QWs is used for microscopic modeling of the exciton resonances. Remarkable agreement with the experiment is achieved when the effect of indium segregation is taken into account. The segregation results in a modification of the potential profile, in particular, in an asymmetry of the nominally square QWs.

  14. Asymmetric Laguerre-Gaussian beams

    Science.gov (United States)

    Kovalev, A. A.; Kotlyar, V. V.; Porfirev, A. P.

    2016-06-01

    We introduce a family of asymmetric Laguerre-Gaussian (aLG) laser beams. The beams have been derived via a complex-valued shift of conventional LG beams in the Cartesian plane. While propagating in a uniform medium, the first bright ring of the aLG beam becomes less asymmetric and the energy is redistributed toward peripheral diffraction rings. The projection of the orbital angular momentum (OAM) onto the optical axis is calculated. The OAM is shown to grow quadratically with increasing asymmetry parameter of the aLG beam, which equals the ratio of the shift to the waist radius. Conditions for the OAM becoming equal to the topological charge have been derived. For aLG beams with zero radial index, we have deduced an expression to define the intensity maximum coordinates and shown the crescent-shaped intensity pattern to rotate during propagation. Results of the experimental generation and rotation of aLG beams agree well with theoretical predictions.

  15. Neurons derive from the more apical daughter in asymmetric divisions in the zebrafish neural tube.

    Science.gov (United States)

    Alexandre, Paula; Reugels, Alexander M; Barker, David; Blanc, Eric; Clarke, Jonathan D W

    2010-06-01

    In the developing CNS, asymmetric cell division is critical for maintaining the balanced production of differentiating neurons while renewing the population of neural progenitors. In invertebrates, this process depends on asymmetric inheritance of fate determinants during progenitor divisions. A similar mechanism is widely believed to underlie asymmetrically fated divisions in vertebrates, but compelling evidence for this is missing. We used live imaging of individual progenitors in the intact zebrafish embryo CNS to test this hypothesis. We found that asymmetric inheritance of a subcellular domain is strongly correlated with asymmetric daughter fates and our results reveal an unexpected feature of this process. The daughter cell destined to become a neuron was derived from the more apical of the two daughters, whereas the more basal daughter inherited the basal process and replenished the apical progenitor pool.

  16. Asymmetric catalysis : ligand design and microwave acceleration

    OpenAIRE

    Bremberg, Ulf

    2000-01-01

    This thesis deals partly with the design and synthesis ofligands for use in asymmetric catalysis, and partly with theapplication of microwave heating on metal-based asymmetriccatalytic reactions. Enantiomerically pure pyridyl alcohols and bipyridylalcohols were synthesized from the chiral pool for future usein asymmetric catalysis. Lithiated pyridines were reacted withseveral chiral electrophiles, yielding diastereomeric mixturesthat could be separated without the use of resolutiontechniques....

  17. Worst Asymmetrical Short-Circuit Current

    DEFF Research Database (Denmark)

    Arana Aristi, Iván; Holmstrøm, O; Grastrup, L

    2010-01-01

    In a typical power plant, the production scenario and the short-circuit time were found for the worst asymmetrical short-circuit current. Then, a sensitivity analysis on the missing generator values was realized in order to minimize the uncertainty of the results. Afterward the worst asymmetrical...

  18. Renewable resource management under asymmetric information

    DEFF Research Database (Denmark)

    Jensen, Frank; Andersen, Peder; Nielsen, Max

    2013-01-01

    Asymmetric information between fishermen and the regulator is important within fisheries. The regulator may have less information about stock sizes, prices, costs, effort, productivity and catches than fishermen. With asymmetric information, a strong analytical tool is principal-agent analysis. I...

  19. The interaction of glutathione S-transferase M1-null variants with tobacco smoke exposure and the development of childhood asthma

    DEFF Research Database (Denmark)

    Rogers, A J; Brasch-Andersen, C; Ionita-Laza, I;

    2009-01-01

    : To explore the joint interactive effects of GSTM1 copy number and tobacco smoke exposure on the development of asthma and asthma-related phenotypes in a family-based cohort of childhood asthmatics. METHODS: We performed quantitative PCR-based genotyping for GSTM1 copy number in children of self......BACKGROUND: The glutathione S-transferase M1 (GSTM1)-null variant is a common copy number variant associated with adverse pulmonary outcomes, including asthma and airflow obstruction, with evidence of important gene-by-environment interactions with exposures to oxidative stress. OBJECTIVE......-reported white ancestry with mild to moderate asthma in the Childhood Asthma Management Program. Questionnaire data regarding intrauterine (IUS) and post-natal, longitudinal smoke exposure were available. We performed both family-based and population-based tests of association for the interaction between GSTM1...

  20. Research on the Design and Modification of Asymmetric Spur Gear

    Directory of Open Access Journals (Sweden)

    Xiaohe Deng

    2015-01-01

    Full Text Available A design method for the geometric shape and modification of asymmetric spur gear was proposed, in which the geometric shape and modification of the gear can be obtained directly according to the rack-cutter profile. In the geometric design process of the gear, a rack-cutter with different pressure angles and fillet radius in the driving side and coast side was selected, and the generated asymmetric spur gear profiles also had different pressure angles and fillets accordingly. In the modification design of the gear, the pressure angle modification of rack-cutter was conducted firstly and then the corresponding modified involute gear profile was obtained. The geometric model of spur gears was developed using computer-aided design, and the meshing process was analyzed using finite element simulation method. Furthermore, the transmission error and load sharing ratio of unmodified and modified asymmetric spur gears were investigated. Research results showed that the proposed gear design method was feasible and desired spur gear can be obtained through one time rapid machining by the method. Asymmetric spur gear with better transmission characteristic can be obtained via involute modification.

  1. Design of activated carbon/activated carbon asymmetric capacitors

    Directory of Open Access Journals (Sweden)

    Isabel ePiñeiro-Prado

    2016-03-01

    Full Text Available Supercapacitors are energy storage devices that offer a high power density and a low energy density in comparison with batteries. Their limited energy density can be overcome by using asymmetric configuration in mass electrodes, where each electrode works within their maximum available potential window, rendering the maximum voltage output of the system. Such asymmetric capacitors must be optimized through careful electrochemical characterization of the electrodes for accurate determination of the capacitance and the potential stability limits. The results of the characterization are then used for optimizing mass ratio of the electrodes from the balance of stored charge. The reliability of the design largely depends on the approach taken for the electrochemical characterization. Therefore, the performance could be lower than expected and even the system could break down, if a well thought out procedure is not followed.In this work, a procedure for the development of asymmetric supercapacitors based on activated carbons is detailed. Three activated carbon materials with different textural properties and surface chemistry have been systematically characterized in neutral aqueous electrolyte. The asymmetric configuration of the masses of both electrodes in the supercapacitor has allowed to cover a higher potential window, resulting in an increase of the energy density of the three devices studied when compared with the symmetric systems, and an improved cycle life.

  2. Quality Prediction of Asymmetrically Distorted Stereoscopic 3D Images.

    Science.gov (United States)

    Wang, Jiheng; Rehman, Abdul; Zeng, Kai; Wang, Shiqi; Wang, Zhou

    2015-11-01

    Objective quality assessment of distorted stereoscopic images is a challenging problem, especially when the distortions in the left and right views are asymmetric. Existing studies suggest that simply averaging the quality of the left and right views well predicts the quality of symmetrically distorted stereoscopic images, but generates substantial prediction bias when applied to asymmetrically distorted stereoscopic images. In this paper, we first build a database that contains both single-view and symmetrically and asymmetrically distorted stereoscopic images. We then carry out a subjective test, where we find that the quality prediction bias of the asymmetrically distorted images could lean toward opposite directions (overestimate or underestimate), depending on the distortion types and levels. Our subjective test also suggests that eye dominance effect does not have strong impact on the visual quality decisions of stereoscopic images. Furthermore, we develop an information content and divisive normalization-based pooling scheme that improves upon structural similarity in estimating the quality of single-view images. Finally, we propose a binocular rivalry-inspired multi-scale model to predict the quality of stereoscopic images from that of the single-view images. Our results show that the proposed model, without explicitly identifying image distortion types, successfully eliminates the prediction bias, leading to significantly improved quality prediction of the stereoscopic images.

  3. Condensation on Slippery Asymmetric Bumps

    CERN Document Server

    Park, Kyoo-Chul; He, Neil; Aizenberg, Joanna

    2015-01-01

    Bumps are omnipresent from human skin to the geological structures on planets, which offer distinct advantages in numerous phenomena including structural color, drag reduction, and extreme wettability. Although the topographical parameters of bumps such as radius of curvature of convex regions significantly influence various phenomena including anti-reflective structures and contact time of impacting droplets, the effect of the detailed bump topography on growth and transport of condensates have not been clearly understood. Inspired by the millimetric bumps of the Namib Desert beetle, here we report the identified role of radius of curvature and width of bumps with homogeneous surface wettability in growth rate, coalescence and transport of water droplets. Further rational design of asymmetric convex topography and synergetic combination with slippery coating simultaneously enable self-transport, leading to unseen five-fold higher growth rate and an order of magnitude faster shedding time of droplets compared...

  4. Direct asymmetric aldol reaction using MBHA resin-supported peptide containing L-proline unit

    Institute of Scientific and Technical Information of China (English)

    Liang Zhang; Wen Bo Ding; Yong Ping Yu; Hong Bin Zou

    2009-01-01

    MBHA resin-supported tripeptide catalyst system containing L-proline unit has been developed for use in the direct asymmetric aldol reaction of acetone and aldehydes,which afford the corresponding products with satisfactory isolated yields and enantiomeric excesses.

  5. Asymmetric desymmetrization of meso-diols by C2-symmetric chiral 4-pyrrolidinopyridines

    Directory of Open Access Journals (Sweden)

    Hartmut Schedel

    2012-10-01

    Full Text Available In this work we developed C2-symmetric chiral nucleophilic catalysts which possess a pyrrolidinopyridine framework as a catalytic site. Some of these organocatalysts effectively promoted asymmetric desymmetrization of meso-diols via enantioselective acylation.

  6. Asymmetric septal hypertrophy - a marker of hypertension in aortic stenosis (a SEAS substudy)

    DEFF Research Database (Denmark)

    Tuseth, Nora; Cramariuc, Dana; Rieck, Ashild E

    2010-01-01

    Some patients with aortic stenosis develop asymmetric septal hypertrophy (ASH) that may influence the surgical approach and is associated with higher perioperative morbidity. The aim of this analysis was to characterize further this subtype of aortic stenosis patients....

  7. Asymmetric septal hypertrophy - a marker of hypertension in aortic stenosis (a SEAS substudy)

    DEFF Research Database (Denmark)

    Tuseth, Nora; Cramariuc, Dana; Rieck, Ashild E

    2010-01-01

    Some patients with aortic stenosis develop asymmetric septal hypertrophy (ASH) that may influence the surgical approach and is associated with higher perioperative morbidity. The aim of this analysis was to characterize further this subtype of aortic stenosis patients.......Some patients with aortic stenosis develop asymmetric septal hypertrophy (ASH) that may influence the surgical approach and is associated with higher perioperative morbidity. The aim of this analysis was to characterize further this subtype of aortic stenosis patients....

  8. Asymmetric Facial Bone Fragmentation Mirrors Asymmetric Distribution of Cranial Neuromasts in Blind Mexican Cavefish.

    Science.gov (United States)

    Gross, Joshua B; Gangidine, Andrew; Powers, Amanda K

    2016-11-01

    Craniofacial asymmetry is a convergent trait widely distributed across animals that colonize the extreme cave environment. Although craniofacial asymmetry can be discerned easily, other complex phenotypes (such as sensory organ position and numerical variation) are challenging to score and compare. Certain bones of the craniofacial complex demonstrate substantial asymmetry, and co-localize to regions harboring dramatically expanded numbers of mechanosensory neuromasts. To determine if a relationship exists between this expansion and bone fragmentation in cavefish, we developed a quantitative measure of positional symmetry across the left-right axis. We found that three different cave-dwelling populations were significantly more asymmetric compared to surface-dwelling fish. Moreover, cave populations did not differ in the degree of neuromast asymmetry. This work establishes a method for quantifying symmetry of a complex phenotype, and demonstrates that facial bone fragmentation mirrors the asymmetric distribution of neuromasts in different cavefish populations. Further developmental studies will provide a clearer picture of the developmental and cellular changes that accompany this extreme phenotype, and help illuminate the genetic basis for facial asymmetry in vertebrates.

  9. Preparation and Reactions of Amino Acid Ester Sulfones as New Remote Asymmetrical Induced Reagents

    Institute of Scientific and Technical Information of China (English)

    ZHOU,Cheng-He; BAI,Xue; LI,Tan-Qing; WU,Jun; Alfred Hassner

    2004-01-01

    @@ The development of chiral auxiliary-controlled asymmetric synthesis has been receiving increasing interest in recent yearsfi,2] Various chiral auxiliary reagents have been observed[3] and a lot of results showed that variation of the chiral auxiliary could influence asymmetric induction. Recently, it has been reported the reaction of the aminated sulfones as a remote chiral auxiliary with α,β-unsaturated carbonyl compounds.[4] Here we would like to report the preparation of amino acid ester sulfones as new remote asymmetrical induced reagents and their reactions with α,β-unsaturated esters.

  10. Regenerating a symmetry in asymmetric dark matter.

    Science.gov (United States)

    Buckley, Matthew R; Profumo, Stefano

    2012-01-06

    Asymmetric dark matter theories generically allow for mass terms that lead to particle-antiparticle mixing. Over the age of the Universe, dark matter can thus oscillate from a purely asymmetric configuration into a symmetric mix of particles and antiparticles, allowing for pair-annihilation processes. Additionally, requiring efficient depletion of the primordial thermal (symmetric) component generically entails large annihilation rates. We show that unless some symmetry completely forbids dark matter particle-antiparticle mixing, asymmetric dark matter is effectively ruled out for a large range of masses, for almost any oscillation time scale shorter than the age of the Universe.

  11. Absolute Asymmetric Synthesis Using A Cocrystal Approach

    Institute of Scientific and Technical Information of China (English)

    H.Koshima

    2007-01-01

    1 Results Absolute asymmetric synthesis by means of solid-state reaction of chiral crystals self-assembled from achiral molecules is an attractive and promising methodology for asymmetric synthesis because it is not necessary to employ any external chiral source like a chiral catalyst.In order to design reliably absolute asymmetric syntheses in the solid state,it is inevitable to prepare and predict the formation of chiral crystals from achiral compounds.We have prepared a number of chiral cocrystals co...

  12. Asymmetric dark matter in braneworld cosmology

    Energy Technology Data Exchange (ETDEWEB)

    Meehan, Michael T.; Whittingham, Ian B., E-mail: Michael.Meehan@my.jcu.edu.au, E-mail: Ian.Whittingham@jcu.edu.au [School of Engineering and Physical Sciences, James Cook University, Townsville, 4811 Australia (Australia)

    2014-06-01

    We investigate the effect of a braneworld expansion era on the relic density of asymmetric dark matter. We find that the enhanced expansion rate in the early universe predicted by the Randall-Sundrum II (RSII) model leads to earlier particle freeze-out and an enhanced relic density. This effect has been observed previously by Okada and Seto (2004) for symmetric dark matter models and here we extend their results to the case of asymmetric dark matter. We also discuss the enhanced asymmetric annihilation rate in the braneworld scenario and its implications for indirect detection experiments.

  13. Asymmetric Organocatalytic Reactions of α,β-Unsaturated Cyclic Ketones

    Directory of Open Access Journals (Sweden)

    Giuseppe Bartoli

    2011-03-01

    Full Text Available The 1,4-conjugate addition of nucleophiles to α,β-unsaturated carbonyl compounds represents one fundamental bond-forming reaction in organic synthesis. The development of effective organocatalysts for the enantioselective conjugate addition of malonate, nitroalkane and other carbon and heteroatom nucleophiles to cycloenones constitutes an important research field and has been explored in recent years. At the same time, asymmetric Diels-Alder reactions have been developed and often a mechanism has been demonstrated to be a double addition rather than synchronous. This review aims to cover literature up to the end of 2010, describing all the different organocatalytic asymmetric 1,4-conjugate additions even if they are listed as transfer hydrogenation, cycloadditions or desymmetrization of aromatic compounds.

  14. NONLINEAR EXTENSION OF ASYMMETRIC GARCH MODEL WITHIN NEURAL NETWORK FRAMEWORK

    Directory of Open Access Journals (Sweden)

    Josip Arnerić

    2016-05-01

    Full Text Available The importance of volatility for all market participants has led to the development and application of various econometric models. The most popular models in modelling volatility are GARCH type models because they can account excess kurtosis and asymmetric effects of financial time series. Since standard GARCH(1,1 model usually indicate high persistence in the conditional variance, the empirical researches turned to GJR-GARCH model and reveal its superiority in fitting the asymmetric heteroscedasticity in the data. In order to capture both asymmetry and nonlinearity in data, the goal of this paper is to develop a parsimonious NN model as an extension to GJR-GARCH model and to determine if GJR-GARCH-NN outperforms the GJR-GARCH model.

  15. Mechanistic Insights into Homogeneous and Heterogeneous Asymmetric Iron Catalysis

    Science.gov (United States)

    Sonnenberg, Jessica

    Our group has been focused on replacing toxic and expensive precious metal catalysts with iron for the synthesis of enantiopure compounds for industrial applications. During an investigation into the mechanism of asymmetric transfer hydrogenation with our first generation iron-(P-N-N-P) catalysts we found substantial evidence for zero-valent iron nanoparticles coated in chiral ligand acting as the active site. Extensive experimental and computational experiments were undertaken which included NMR, DFT, reaction profile analysis, substoichiometric poisoning, electron microscope imaging, XPS and multiphasic analysis, all of which supported the fact that NPs were the active species in catalysis. Reversibility of this asymmetric reaction on the nanoparticle surface was then probed using oxidative kinetic resolution of racemic alcohols, yielding modest enantiopurity and high turnover frequencies (TOF) for a range of aromatic alcohols. Efficient dehydrogenation of ammonia-borane for hydrogen evolution and the formation of B-N oligomers was also shown using the NP system, yielding highly active systems, with a maximum TOF of 3.66 H2/s-1 . We have also begun to focus on the development of iron catalysts for asymmetric direct hydrogenation of ketones using hydrogen gas. New chiral iron-(P-N-P) catalysts were developed and shown to be quite active and selective for a wide range of substrates. Mechanistic investigations primarily using NMR and DFT indicated that a highly active trans-dihydride species was being formed during catalyst activation. Lastly, a new library of chiral P-N-P and P-NH-P ligands were developed, as well as their corresponding iron complexes, some of which show promise for the development of future generations of active asymmetric direct hydrogenation catalysts.

  16. Kinematics and Dynamics of an Asymmetrical Parallel Robotic Wrist

    DEFF Research Database (Denmark)

    Wu, Guanglei

    2014-01-01

    This paper introduces an asymmetrical parallel robotic wrist, which can generate a decoupled unlimited-torsion motion and achieve high positioning accuracy. The kinematics, dexterity, and singularities of the manipulator are investigated to visualize the performance contours of the manipulator....... Using the method of Lagrange multipliers and considering all the mobile components, the equations of motion of the manipulator are derived to investigate the dynamic characteristics efficiently. The developed dynamic model is numerically illustrated and compared with its simplified formulation to show...

  17. Reflection-asymmetric nuclear deformations within the Density Functional Theory

    CERN Document Server

    Olsen, E; Nazarewicz, W; Stoitsov, M; 10.1088/1742-6596/402/1/012034

    2013-01-01

    Within the nuclear density functional theory (DFT) we study the effect of reflection-asymmetric shapes on ground-state binding energies and binding energy differences. To this end, we developed the new DFT solver AxialHFB that uses an approximate second-order gradient to solve the Hartree-Fock-Bogoliubov equations of superconducting DFT with the quasi-local Skyrme energy density functionals. Illustrative calculations are carried out for even-even isotopes of radium and thorium.

  18. Metal and organo-catalysed asymmetric hydroaminomethylation of styrenes

    Institute of Scientific and Technical Information of China (English)

    Barbara Villa-Marcos; Jianliang Xiao

    2015-01-01

    A new protocol that enables asymmetric hydroaminomethylation of styrenes to afford chiral amines has been developed. Catalysed by an Rh‐phosphine species and a chiral phosphoric acid, styrenes are converted intoβ‐chiral amines with good enantioselectivities under syngas in the presence of an amine and Hantzsch ester. The reaction involves two key steps, hydroformylation and reductive amination, with the former catalysed by the Rh species whilst the latter by the phosphoric acid.

  19. Asymmetric dark matter bound state

    Science.gov (United States)

    Bi, Xiao-Jun; Kang, Zhaofeng; Ko, P.; Li, Jinmian; Li, Tianjun

    2017-02-01

    We propose an interesting framework for asymmetric scalar dark matter (ADM), which has novel collider phenomenology in terms of an unstable ADM bound state (ADMonium) produced via Higgs portals. ADMonium is a natural consequence of the basic features of ADM: the (complex scalar) ADM is charged under a dark local U (1 )d symmetry which is broken at a low scale and provides a light gauge boson X . The dark gauge coupling is strong and then ADM can annihilate away into X -pair effectively. Therefore, the ADM can form a bound state due to its large self-interaction via X mediation. To explore the collider signature of ADMonium, we propose that ADM has a two-Higgs doublet portal. The ADMonium can have a sizable mixing with the heavier Higgs boson, which admits a large cross section of ADMonium production associated with b b ¯. The resulting signature at the LHC depends on the decays of X . In this paper we consider a case of particular interest: p p →b b ¯ +ADMonium followed by ADMonium→2 X →2 e+e- where the electrons are identified as (un)converted photons. It may provide a competitive explanation to heavy di-photon resonance searches at the LHC.

  20. Twin Higgs Asymmetric Dark Matter.

    Science.gov (United States)

    García García, Isabel; Lasenby, Robert; March-Russell, John

    2015-09-18

    We study asymmetric dark matter (ADM) in the context of the minimal (fraternal) twin Higgs solution to the little hierarchy problem, with a twin sector with gauged SU(3)^{'}×SU(2)^{'}, a twin Higgs doublet, and only third-generation twin fermions. Naturalness requires the QCD^{'} scale Λ_{QCD}^{'}≃0.5-20  GeV, and that t^{'} is heavy. We focus on the light b^{'} quark regime, m_{b^{'}}≲Λ_{QCD}^{'}, where QCD^{'} is characterized by a single scale Λ_{QCD}^{'} with no light pions. A twin baryon number asymmetry leads to a successful dark matter (DM) candidate: the spin-3/2 twin baryon, Δ^{'}∼b^{'}b^{'}b^{'}, with a dynamically determined mass (∼5Λ_{QCD}^{'}) in the preferred range for the DM-to-baryon ratio Ω_{DM}/Ω_{baryon}≃5. Gauging the U(1)^{'} group leads to twin atoms (Δ^{'}-τ^{'}[over ¯] bound states) that are successful ADM candidates in significant regions of parameter space, sometimes with observable changes to DM halo properties. Direct detection signatures satisfy current bounds, at times modified by dark form factors.

  1. Force on an Asymmetric Capacitor

    CERN Document Server

    Bahder, T B; Bahder, Thomas B.; Fazi, Chris

    2002-01-01

    When a high voltage (~30 kV) is applied to a capacitor whose electrodes have different physical dimensions, the capacitor experiences a net force toward the smaller electrode (Biefeld-Brown effect). We have verified this effect by building four capacitors of different shapes. The effect may have applications to vehicle propulsion and dielectric pumps. We review the history of this effect briefly through the history of patents by Thomas Townsend Brown. At present, the physical basis for the Biefeld-Brown effect is not understood. The order of magnitude of the net force on the asymmetric capacitor is estimated assuming two different mechanisms of charge conduction between its electrodes: ballistic ionic wind and ionic drift. The calculations indicate that ionic wind is at least three orders of magnitude too small to explain the magnitude of the observed force on the capacitor. The ionic drift transport assumption leads to the correct order of magnitude for the force, however, it is difficult to see how ionic dr...

  2. A novel asymmetric synthesis of cinacalcet hydrochloride

    OpenAIRE

    Arava, Veera R; Laxminarasimhulu Gorentla; Pramod K. Dubey

    2012-01-01

    A novel route to asymmetric synthesis of cinacalcet hydrochloride by the application of (R)-tert-butanesulfinamide and regioselective N-alkylation of the naphthyl ethyl sulfinamide intermediate is described.

  3. A novel asymmetric synthesis of cinacalcet hydrochloride

    Directory of Open Access Journals (Sweden)

    Veera R. Arava

    2012-08-01

    Full Text Available A novel route to asymmetric synthesis of cinacalcet hydrochloride by the application of (R-tert-butanesulfinamide and regioselective N-alkylation of the naphthyl ethyl sulfinamide intermediate is described.

  4. A novel asymmetric synthesis of cinacalcet hydrochloride

    Science.gov (United States)

    Gorentla, Laxminarasimhulu; Dubey, Pramod K

    2012-01-01

    Summary A novel route to asymmetric synthesis of cinacalcet hydrochloride by the application of (R)-tert-butanesulfinamide and regioselective N-alkylation of the naphthyl ethyl sulfinamide intermediate is described. PMID:23019473

  5. Catalytic Asymmetric Synthesis of Phosphine Boronates

    NARCIS (Netherlands)

    Hornillos, Valentin; Vila, Carlos; Otten, Edwin; Feringa, Ben L.

    2015-01-01

    The first catalytic enantioselective synthesis of ambiphilic phosphine boronate esters is presented. The asymmetric boration of ,-unsaturated phosphine oxides catalyzed by a copper bisphosphine complex affords optically active organoboronate esters that bear a vicinal phosphine oxide group in good y

  6. Asymmetric Swiss-cheese brane-worlds

    CERN Document Server

    Gergely, L A; K\\'{e}p\\'{\\i}r\\'{o}, Ibolya

    2006-01-01

    We consider Swiss-cheese brane universes embedded asymmetrically into the bulk. Neither the junction conditions between the Schwarzschild spheres and the sorrounding Friedmann brane regions with cosmological constant $\\Lambda $, nor the evolution of the scale factor are changed with respect to the symmetric case. The universe expands and decelerates forever. The asymmetry however has a drastic influence on the evolution of the cosmological fluid. Instead of the two branches of the symmetric case, in the asymmetric case four branches emerge. Moreover, the future pressure singularity arising in the symmetric case only for huge values of $\\Lambda $ becomes quite generic in the asymmetric case. Such pressure singularities emerge also when $\\Lambda=0$ is set. Then they are due entirely to the asymmetric embedding. For generic values of $\\Lambda $ we introduce a critical value of a suitably defined asymmetry parameter, which separates Swiss-cheese cosmologies with and without pressure singularities.

  7. Congenital asymmetric crying face: a case report

    Directory of Open Access Journals (Sweden)

    Semra Kara

    2011-12-01

    Full Text Available Congenital asymmetric crying face is an anomalia caused by unilateral absence or weakness of depressor anguli oris muscle The major finding of the disease is the absence or weakness in the outer and lower movement of the commissure during crying. The other expression muscles are normal and the face is symmetric at rest. The asymmetry in congenital asymmetric crying face is most evident during infancy but decreases by age. Congenital asymmetric crying face can be associated with cervicofacial, musclebone, respiratory, genitourinary and central nervous system anomalia. It is diagnosed by physical examination. This paper presents a six days old infant with Congenital asymmetric crying face and discusses the case in terms of diagnosis and disease features.

  8. Asymmetric cryptography based on wavefront sensing.

    Science.gov (United States)

    Peng, Xiang; Wei, Hengzheng; Zhang, Peng

    2006-12-15

    A system of asymmetric cryptography based on wavefront sensing (ACWS) is proposed for the first time to our knowledge. One of the most significant features of the asymmetric cryptography is that a trapdoor one-way function is required and constructed by analogy to wavefront sensing, in which the public key may be derived from optical parameters, such as the wavelength or the focal length, while the private key may be obtained from a kind of regular point array. The ciphertext is generated by the encoded wavefront and represented with an irregular array. In such an ACWS system, the encryption key is not identical to the decryption key, which is another important feature of an asymmetric cryptographic system. The processes of asymmetric encryption and decryption are formulized mathematically and demonstrated with a set of numerical experiments.

  9. DOES VOLATILITY RESPOND ASYMMETRIC TO PAST SHOCKS?

    OpenAIRE

    Claudiu Botoc

    2014-01-01

    The main aim of the paper is to examine if the stock market volatility exhibits asymmetric or an asymmetric response to past shocks, for certain CEE countries (Romania,Hungary, Bulgaria, Poland) over the period May 2004 - September 2014. For the stock marketsfrom East Europe the results are in line with the symmetric volatility, i.e. volatility is similaraffected by both positive and negative returns with the same magnitude. For the stock marketsfrom Central Europe the results are consistent ...

  10. Exchange-rate forecasts and asymmetric loss: empirical evidence for the yen/dollar exchange rate

    DEFF Research Database (Denmark)

    Stadtmann, Georg; Pierdzioch; Rülke

    2012-01-01

    We used the yen/dollar exchange-rate forecasts of the Wall Street Journal (WSJ) poll to analyse whether exchange-rate forecasters have an asymmetric loss function. To this end, we applied an approach recently developed by Elliott et al. (2005). We found that only few forecasters seem to form...... forecasts under an asymmetric loss function. For some forecasters, accounting for the asymmetry of their loss function makes their forecasts look rational....

  11. Profile of asymmetrical retinopathy of prematurity in twins

    Directory of Open Access Journals (Sweden)

    Azad Rajvardhan

    2010-01-01

    Full Text Available Background: In twin births, both babies have the same gestational age and pre-natal conditions. However, twins may develop a varied retinopathy of prematurity (ROP course depending on birth weight and other systemic factors. Objective: To study the profile of asymmetric ROP in twins Design: Retrospective study Setting: Tertiary ROP referral eye hospital. Materials and Methods: The profile of 56 pairs of twins with ROP were studied and analyzed for differences in zone or need for treatment, while studying possible causes for the varied outcome. Results: In 45 pairs of twins (80% the disease progressed identically in both eyes, while in 11 pairs (20% the ROP showed differences in zone or need for treatment. Four of these pairs were discordant. In 3 of these 4 pairs, the heavier birth weight twin had a more severe ROP course. Conclusions: Twins can present with asymmetric ROP course, and it is therefore essential to examine both twins as per screening protocols.

  12. Asymmetric excitation of surface plasmons by dark mode coupling

    KAUST Repository

    Zhang, X.

    2016-02-19

    Control over surface plasmons (SPs) is essential in a variety of cutting-edge applications, such as highly integrated photonic signal processing systems, deep-subwavelength lasing, high-resolution imaging, and ultrasensitive biomedical detection. Recently, asymmetric excitation of SPs has attracted enormous interest. In free space, the analog of electromagnetically induced transparency (EIT) in metamaterials has been widely investigated to uniquely manipulate the electromagnetic waves. In the near field, we show that the dark mode coupling mechanism of the classical EIT effect enables an exotic and straightforward excitation of SPs in a metasurface system. This leads to not only resonant excitation of asymmetric SPs but also controllable exotic SP focusing by the use of the Huygens-Fresnel principle. Our experimental findings manifest the potential of developing plasmonic metadevices with unique functionalities.

  13. Asymmetric trienamine catalysis: new opportunities in amine catalysis.

    Science.gov (United States)

    Kumar, Indresh; Ramaraju, Panduga; Mir, Nisar A

    2013-02-07

    Amine catalysis, through HOMO-activating enamine and LUMO-activating iminium-ion formation, is receiving increasing attention among other organocatalytic strategies, for the activation of unmodified carbonyl compounds. Particularly, the HOMO-raising activation concept has been applied to the greatest number of asymmetric transformations through enamine, dienamine, and SOMO-activation strategies. Recently, trienamine catalysis, an extension of amine catalysis, has emerged as a powerful tool for synthetic chemists with a novel activation strategy for polyenals/polyenones. In this review article, we discuss the initial developments of trienamine catalysis for highly asymmetric Diels-Alder reactions with different dienophiles and emerging opportunities for other types of cycloadditions and cascade reactions.

  14. Asymmetric excitation of surface plasmons by dark mode coupling.

    Science.gov (United States)

    Zhang, Xueqian; Xu, Quan; Li, Quan; Xu, Yuehong; Gu, Jianqiang; Tian, Zhen; Ouyang, Chunmei; Liu, Yongmin; Zhang, Shuang; Zhang, Xixiang; Han, Jiaguang; Zhang, Weili

    2016-02-01

    Control over surface plasmons (SPs) is essential in a variety of cutting-edge applications, such as highly integrated photonic signal processing systems, deep-subwavelength lasing, high-resolution imaging, and ultrasensitive biomedical detection. Recently, asymmetric excitation of SPs has attracted enormous interest. In free space, the analog of electromagnetically induced transparency (EIT) in metamaterials has been widely investigated to uniquely manipulate the electromagnetic waves. In the near field, we show that the dark mode coupling mechanism of the classical EIT effect enables an exotic and straightforward excitation of SPs in a metasurface system. This leads to not only resonant excitation of asymmetric SPs but also controllable exotic SP focusing by the use of the Huygens-Fresnel principle. Our experimental findings manifest the potential of developing plasmonic metadevices with unique functionalities.

  15. Asymmetric aminocatalysis--gold rush in organic chemistry.

    Science.gov (United States)

    Melchiorre, Paolo; Marigo, Mauro; Carlone, Armando; Bartoli, Giuseppe

    2008-01-01

    Catalysis with chiral secondary amines (asymmetric aminocatalysis) has become a well-established and powerful synthetic tool for the chemo- and enantioselective functionalization of carbonyl compounds. In the last eight years alone, this field has grown at such an extraordinary pace that it is now recognized as an independent area of synthetic chemistry, where the goal is the preparation of any chiral molecule in an efficient, rapid, and stereoselective manner. This has been made possible by the impressive level of scientific competition and high quality research generated in this area. This Review describes this "Asymmetric Aminocatalysis Gold Rush" and charts the milestones in its development. As in all areas of science, progress depends on human effort.

  16. Advanced materials for aqueous supercapacitors in the asymmetric design

    Directory of Open Access Journals (Sweden)

    Muniyandi Rajkumar

    2015-12-01

    Full Text Available Supercapacitors have been recognized as one of the promising energy storage devices in the future energy technology. In this perspective, rapid progress is made in the development of fundamental and applied aspects of supercapacitors. Various techniques have been developed specifically to estimate the specific capacitance. Numerous efforts have been made in the literature to increase the specific capacitance of electrode materials. Recently, researchers pay more attention on designing supercapacitors of asymmetric type with extending cell voltage and dissimilar materials with complementary working potentials. Researchers try to increase the specific energy of asymmetric supercapacitors (ASCs. Conversely, it is still a challenge to find a suitable operation conditions for ASCs in various designs, especially for the one with battery type electrode. In this review, we describe our recent research works and other reports on the preparation of various nanostructured electrode materials and the performances of both symmetric and asymmetric supercapacitors. Finally, we demonstrate effects of charge balance on the capacitive performances of ASCs which consist of one electrode material of the battery type and one capacitive material. We also demonstrate how to evaluate the charge capacities of both positive and negative electrode materials for this ASC application.

  17. Magmatism, Hydrothermal Cooling and Asymmetric Accretion at Slow-spreading Ridges

    Science.gov (United States)

    Bai, H.; Montesi, L.

    2014-12-01

    Mid-Atlantic Ridge that hydrothermal activities are closely associated with asymmetric segments. In addition, Lavier and Buck [2002] showed that efficient cooling of the lithosphere favors the development of large offset detachments and therefore asymmetric spreading.

  18. High-Voltage, Asymmetric-Waveform Generator

    Science.gov (United States)

    Beegle, Luther W.; Duong, Tuan A.; Duong, Vu A.; Kanik, Isik

    2008-01-01

    The shapes of waveforms generated by commercially available analytical separation devices, such as some types of mass spectrometers and differential mobility spectrometers are, in general, inadequate and result in resolution degradation in output spectra. A waveform generator was designed that would be able to circumvent these shortcomings. It is capable of generating an asymmetric waveform, having a peak amplitude as large as 2 kV and frequency of several megahertz, which can be applied to a capacitive load. In the original intended application, the capacitive load would consist of the drift plates in a differential-mobility spectrometer. The main advantage to be gained by developing the proposed generator is that the shape of the waveform is made nearly optimum for various analytical devices requiring asymmetric-waveform such as differential-mobility spectrometers. In addition, this waveform generator could easily be adjusted to modify the waveform in accordance with changed operational requirements for differential-mobility spectrometers. The capacitive nature of the load is an important consideration in the design of the proposed waveform generator. For example, the design provision for shaping the output waveform is based partly on the principle that (1) the potential (V) on a capacitor is given by V=q/C, where C is the capacitance and q is the charge stored in the capacitor; and, hence (2) the rate of increase or decrease of the potential is similarly proportional to the charging or discharging current. The proposed waveform generator would comprise four functional blocks: a sine-wave generator, a buffer, a voltage shifter, and a high-voltage switch (see Figure 1). The sine-wave generator would include a pair of operational amplifiers in a feedback configuration, the parameters of which would be chosen to obtain a sinusoidal timing signal of the desired frequency. The buffer would introduce a slight delay (approximately equal to 20 ns) but would otherwise

  19. Distinct characteristics of asymmetric magnetic reconnections: Observational results from the exhaust region at the dayside magnetopause

    Science.gov (United States)

    Zhang, Y. C.

    2016-01-01

    Magnetic reconnection plays a key role in the conversion of magnetic energy into the thermal and kinetic energy of plasma. On either side of the diffusion region in space plasma, the conditions for the occurrence of reconnections are usually not symmetric. Previous theoretical studies have predicted that reconnections under asymmetric conditions will bear different features compared with those of symmetric reconnections, and numerical simulations have verified these distinct features. However, to date, the features of asymmetric reconnections have not been thoroughly investigated using in situ observations; thus, some results from theoretical studies and simulations have not been tested with observations sufficiently well. Here, spacecraft observations are used in a statistical investigation of asymmetric magnetic reconnection exhaust at the dayside magnetopause. The resulting observational features are consistent with the theoretical predictions. The results presented here advance our understanding of the development of reconnections under asymmetric conditions. PMID:27270685

  20. Asymmetric ion track nanopores for sensor technology. Reconstruction of pore profile from conductometric measurements

    Science.gov (United States)

    Apel, Pavel Yu; Blonskaya, Irina V.; Orelovitch, Oleg L.; Sartowska, Bozena A.; Spohr, Reimar

    2012-06-01

    We reconstruct the profile of asymmetric ion track nanopores from an algorithm developed for conductometric measurements of symmetric nanopores. The validity of the reconstruction is supported by FESEM observations. Our analysis reveals that asymmetric pores fabricated by one-sided etching are funnel-like and not conical. The analysis provides the constriction diameter and the pore profile as a function of etching time. The reconstruction of the pore profile defines the starting conditions of asymmetric nanopores at breakthrough. The deviation from the conical shape is most pronounced at the pore tip. This critical zone dominates transport properties relevant to ion conductance, selectivity, current rectification, resistive pulse sensing and biosensors. The classical cone approximation used until now underestimates the tip diameter by a factor of two. As transport processes in nanopores depend in a highly nonlinear way on the constriction diameter the presented reconstruction must be taken into account when studying ionic and molecular transport processes in asymmetric pores.

  1. Asymmetric logistic peak as a suitable function for the resolution of highly asymmetric voltammograms in non-bilinear systems.

    Science.gov (United States)

    Kooshki, Mojtaba; Díaz-Cruz, José Manuel; Abdollahi, Hamid; Ariño, Cristina; Esteban, Miquel

    2011-11-21

    The asymmetric logistic peak is tested as a new function for the parametric signal fitting (PSF) of highly asymmetric electrochemical signals in non-bilinear datasets, such as those obtained in linear sweep voltammetry (LSV) or in the presence of irreversible electrochemical processes. This new multivariate curve resolution strategy (PSF-ALPA) is successfully applied to LS voltammograms measured for the Cd(II)-glutathione system with a hanging mercury drop electrode, where Cd(II) is reversibly reduced, and to differential pulse voltammograms (DPV) measured at a glassy carbon electrode, where Cd(II) reduction becomes irreversible. Matrix augmentation by using LS voltammograms measured at different scan rates provides good results and encourages the development of ALPA methodology for third order data.

  2. Magnetohydrodynamic Waves in an Asymmetric Magnetic Slab

    Science.gov (United States)

    Allcock, Matthew; Erdélyi, Robert

    2017-02-01

    Analytical models of solar atmospheric magnetic structures have been crucial for our understanding of magnetohydrodynamic (MHD) wave behaviour and in the development of the field of solar magneto-seismology. Here, an analytical approach is used to derive the dispersion relation for MHD waves in a magnetic slab of homogeneous plasma enclosed on its two sides by non-magnetic, semi-infinite plasma with different densities and temperatures. This generalises the classic magnetic slab model, which is symmetric about the slab. The dispersion relation, unlike that governing a symmetric slab, cannot be decoupled into the well-known sausage and kink modes, i.e. the modes have mixed properties. The eigenmodes of an asymmetric magnetic slab are better labelled as quasi-sausage and quasi-kink modes. Given that the solar atmosphere is highly inhomogeneous, this has implications for MHD mode identification in a range of solar structures. A parametric analysis of how the mode properties (in particular the phase speed, eigenfrequencies, and amplitudes) vary in terms of the introduced asymmetry is conducted. In particular, avoided crossings occur between quasi-sausage and quasi-kink surface modes, allowing modes to adopt different properties for different parameters in the external region.

  3. Asymmetric Electrostatic Radiation Shielding for Spacecraft

    Science.gov (United States)

    Metzger, Philip T.; Youngquist, Robert C.; Lane, John E.

    2005-01-01

    A paper describes the types, sources, and adverse effects of energetic-particle radiation in interplanetary space, and explores a concept of using asymmetric electrostatic shielding to reduce the amount of such radiation impinging on spacecraft. Typically, such shielding would include a system of multiple inflatable, electrically conductive spheres deployed in clusters in the vicinity of a spacecraft on lightweight structures that would maintain the spheres in a predetermined multipole geometry. High-voltage generators would maintain the spheres at potential differences chosen in conjunction with the multipole geometry so that the resulting multipole field would gradually divert approaching energetic atomic nuclei from a central region occupied by the spacecraft. The spheres nearest the center would be the most positive, so as to repel the positively charged impinging nuclei from the center. At the same time, the monopole potential of the overall spacecraft-and-shielding system would be made negative so as to repel thermal electrons. The paper presents results of computational simulations of energetic-particle trajectories and shield efficiency for a trial system of 21 spheres arranged in three clusters in an overall linear quadrupole configuration. Further development would be necessary to make this shielding concept practical.

  4. Dc SQUIDs with asymmetric shunt resistors

    Energy Technology Data Exchange (ETDEWEB)

    Rudolph, Matthias; Nagel, Joachim; Kemmler, Matthias; Koelle, Dieter; Kleiner, Reinhold [Physikalisches Institut - Experimentalphysik II and Center for Collective Quantum Phenomena in LISAplus, Universitaet Tuebingen (Germany); Meckbach, Johannes Maximilian; Ilin, Konstantin; Siegel, Michael [Institut fuer Mikro- und Nanoelektronische Systeme, Karlsruhe Institute of Technology, Karlsruhe (Germany)

    2013-07-01

    We have investigated asymmetrically shunted Nb/Al-AlO{sub x}/Nb dc SQUIDs. Simulations based on the coupled Langevin equations predict that the optimum energy resolution ε, and thus also the noise performance of such an asymmetric SQUID, can be 3-4 times better than that of its symmetric counterpart. While keeping the total resistance R identical to a comparable symmetric SQUID with R{sup -1} = R{sub 1}{sup -1} + R{sub 2}{sup -1}, we shunted only one of the two Josephson junctions with R = R{sub 1,2}/2. Both types of SQUIDs were characterized with respect to their transport and noise properties at temperature T = 4.2 K, and we compared the experimental results with numerical simulations. Experiments yielded ε ∼ 32 ℎ for an asymmetric SQUID with an inductance L = 22 pH, whereas a comparable symmetric device achieved ε = 110 ℎ.

  5. GENERATION OF ASYMMETRIC F-v CHARACTERISTICS FOR SYMMETRIC MR DAMPERS

    Institute of Scientific and Technical Information of China (English)

    WANG Enrong; YE Biaoming; MA Xiaoqing; SU Chunyi; RAKHEJA Subhash

    2006-01-01

    An asymmetric damping force generation algorithm is originally proposed to yield the asymmetric force-velocity characteristics for the symmetric magneto-rheological (MR) dampers. The command current is formulated in an asymmetric manner to excite the symmetric MR dampers by employing the "on-off" control law in response to the direction of velocity, and a smooth modulation function is developed without phase shift to suppress strong transients in the damping forces caused by the current-switching discontinuity. The effectiveness of the proposed algorithm is evaluated by analyzing the dynamic responses of a quarter-vehicle suspension system with a symmetric MR-damper by modulating the command current into the asymmetric manner. The simulation results show that the proposed algorithm could achieve a better compromise between the conflicting requirements of the asymmetric damping force ratio and the force-velocity curve smoothness, and the asymmetric damping MR-suspension design can ideally improve the road holding and ride performances of vehicle motion. The proposed algorithm can be generally incorporated with a controller synthesis to realize an intelligent vehicle suspension design with the symmetric MR dampers.

  6. Asymmetric gear rectifies random robot motion

    Science.gov (United States)

    Li, He; Zhang, H. P.

    2013-06-01

    We experimentally study the dynamics of centimetric robots and their interactions with rotary gears through inelastic collisions. Under the impacts of self-propelled robots, a gear with symmetric teeth diffuses with no preferred direction of motion. An asymmetric gear, however, rectifies random motion of nearby robots which, in return, exert a torque on the gear and drive it into unidirectional motion. Rectification efficiency increases with the degree of gear asymmetry. Our work demonstrates that asymmetric environments can be used to rectify and extract energy from random motion of macroscopic self-propelled particles.

  7. Asymmetric acoustic transmission in multiple frequency bands

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Hong-xiang, E-mail: jsdxshx@ujs.edu.cn [Research Center of Fluid Machinery Engineering and Technology, Jiangsu University, Zhenjiang 212013 (China); Laboratory of Modern Acoustics, Institute of Acoustics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China); State Key Laboratory of Acoustics, Institute of Acoustics, Chinese Academy of Sciences, Beijing 100190 (China); Yuan, Shou-qi, E-mail: Shouqiy@ujs.edu.cn [Research Center of Fluid Machinery Engineering and Technology, Jiangsu University, Zhenjiang 212013 (China); Zhang, Shu-yi [Laboratory of Modern Acoustics, Institute of Acoustics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China)

    2015-11-23

    We report both experimentally and numerically that the multi-band device of the asymmetric acoustic transmission is realized by placing two periodic gratings with different periods on both sides of two brass plates immersed in water. The asymmetric acoustic transmission can exist in four frequency bands below 1500 kHz, which arises from the interaction between various diffractions from the two gratings and Lamb modes in the brass plates immersed in water. The results indicate that the device has the advantages of multiple band, broader bandwidth, and simpler structure. Our finding should have great potential applications in ultrasonic devices.

  8. Integrated asymmetric vertical coupler pressure sensors

    Science.gov (United States)

    Kiyat, Isa; Kocabas, Askin; Akcag, Imran; Aydinli, Atilla

    2004-08-01

    Design and analysis of a novel pressure sensor based on a silicon-on-insulator asymmetric integrated vertical coupler is presented. The coupler is composed of a single mode low index waveguide and a thin silicon slab. Wavelength selective optical modulation of asymmetric vertical coupler is examined in detail. Its potential for sensing applications is highlighted as an integrated optical pressure sensor which can be realized by standard silicon micro-fabrication. Sensitivity of transmission of such couplers on refractive index change of silicon slab ensures that they are good candidates for applications requiring high sensitivities.

  9. Asymmetric localization in disordered Landau bands

    Energy Technology Data Exchange (ETDEWEB)

    Nita, M [Institute of Physics and Technology of Materials, PO Box MG7, Bucharest-Magurele (Romania); Aldea, A [Institute of Physics and Technology of Materials, PO Box MG7, Bucharest-Magurele (Romania); Zittartz, J [Institute of Theoretical Physics, Cologne University, 50937 Cologne (Germany)

    2007-06-06

    We show that, due to band mixing, the eigenstate localization within the disordered Landau bands gets an asymmetric structure: the degree of localization increases in the lower part of the band and decreases in the upper one. The calculation is performed for a two-dimensional lattice with the Anderson disorder potential and we prove that this effect is related to the upper shift of the extended states within the band and is enhanced by the disorder strength. The asymmetric localization and the energy shift disappear when the interband coupling is switched off.

  10. Asymmetric multiscale behavior in PM2.5 time series: Based on asymmetric MS-DFA

    Science.gov (United States)

    Zhang, Chen; Ni, Zhiwei; Ni, Liping

    2016-11-01

    Particulate matter with an aerodynamic diameter of 2.5 mm or less (PM2.5) is one of the most serious air pollution, considered most harmful for people by World Health Organisation. In this paper, we utilized the asymmetric multiscale detrended fluctuation analysis (A-MSDFA) method to explore the existence of asymmetric correlation properties for PM2.5 daily average concentration in two USA cities (Fresno and Los Angeles) and two Chinese cities (Hong Kong and Shanghai), and to assess the properties of these asymmetric correlations. The results show the existences of asymmetric correlations, and the degree of asymmetric for two USA cities is stronger than that of two Chinese cities. Further, most of the local exponent β(n) are smaller than 0.5, which indicates the existence of anti-persistent long-range correlation for PM2.5 time series in four cities. In addition, we reanalyze the asymmetric correlation by the A-MSDFA method with secant rolling windows of different sizes, which can investigate dynamic changes in the multiscale correlation for PM2.5 time series with changing window size. Whatever window sizes, the correlations are asymmetric and display smaller asymmetries at small scales and larger asymmetries at large scales. Moreover, the asymmetries become increasingly weaker with the increase of window sizes.

  11. Assessment of telomere length during post-natal period in offspring produced by a bull and its fibroblast derived clone

    Institute of Scientific and Technical Information of China (English)

    RobertoPuglisi; AndreaGalli; AnnaPozzi; RobertaVanni; DonatellaBalduzzi; Irina Lagutina; Silvia Colleoni; GiovannaLazzari; CesareGalli; GraziellaBongioni

    2014-01-01

    Objective:To investigate the telomere length in bovine offspring produced by a cloned and control bull, and the telomerase activity in embryos produced with the same technology. Methods:Five daughters of a control and five daughters of a bull cloned using a fibroblast of the control were produced byIVF using sperm of the two bulls.Blood samples of the offspring were collected at2,6, and12 months of age andthe relative telomere length(RTL) was assessed by flow cytometry.At same time the body growth, hematological profile, and clinical biochemistry of the same progeny was extensively surveyed, and results have been reported in a previous work.Thereafter, the telomerase activity was assessed using a real timePCR quantitative assay in groups of embryos produced with the same technology.Results:The offspring of the clone exhibited a modest, but significant(P<0.05), shortening of the telomeres(21.36%,20.56% and 20.56%) compared to that of the control(23.78%,23.53% and22.43%) as mean values determined at2,6 and12 months, respectively.Shortening of telomeres in respect to the age was not significant. No statistical difference was reported between telomerase activity assessed in144 cloned (3.4-03±2.4-03 amoles/μL) and80 control(2.1-03±1.8-03 amoles/μL) embryos.Conclusions:The results have revealed a moderate shortening of telomeres in the offspring of the clone with respect to control.However, this study did not evidence differences in the two progenies that suggest welfare problems during the first year of life.

  12. Assessment of telomere length during post-natal period in offspring produced by a bull and its fibroblast derived clone

    Directory of Open Access Journals (Sweden)

    Roberto Puglisi

    2014-03-01

    Conclusions: The results have revealed a moderate shortening of telomeres in the offspring of the clone with respect to control. However, this study did not evidence differences in the two progenies that suggest welfare problems during the first year of life.

  13. The role of routine post-natal abdominal ultrasound for newborns in a resource-poor setting: a longitudinal study

    Directory of Open Access Journals (Sweden)

    Omokhodion Samuel I

    2011-07-01

    Full Text Available Abstract Background- Neonatal abdominal ultrasound is usually performed in Nigeria to investigate neonatal symptoms rather than as a follow up to evaluate fetal abnormalities which were detected on prenatal ultrasound. The role of routine obstetric ultrasonography in the monitoring of pregnancy and identification of fetal malformations has partly contributed to lowering of fetal mortality rates. In Nigeria which has a high maternal and fetal mortality rate, many pregnant women do not have ante-natal care and not infrequently, women also deliver their babies at home and only bring the newborns to the clinics for immunization. Even when performed, most routine obstetric scans are not targeted towards the detection of fetal abnormalities. The aim of the present study is to evaluate the benefit of routinely performing abdominal scans on newborns with a view to detecting possible abnormalities which may have been missed ante-natally. Methods- This was a longitudinal study of 202 consecutive, apparently normal newborns. Routine clinical examination and abdominal ultrasound scans were performed on the babies by their mother's bedside, before discharge. Neonates with abnormal initial scans had follow-up scans. Results- There were 108 males and 94 females. There were 12 (5.9% abnormal scans seen in five male and seven female neonates. Eleven of the twelve abnormalities were in the kidneys, six on the left and five on the right. Three of the four major renal anomalies- absent kidney, ectopic/pelvic kidney and two cases of severe hydronephrosis were however on the left side. There was one suprarenal abnormality on the right suspected to be a possible infected adrenal haemorrage. Nine of the abnormal cases reported for follow- up and of these, two cases had persistent severe abnormalities. Conclusions- This study demonstrated a 5.9% incidence of genito urinary anomalies on routine neonatal abdominal ultrasound in this small population. Routine obstetric USS is very useful but inadequate availability of skilled personnel and cost implications create great challenges in poor resource settings like Nigeria. However, awareness should be created so that parents who can afford such investigations can make informed decisions.

  14. Preconception, prenatal and post-natal cares%孕前、孕期和产后保健

    Institute of Scientific and Technical Information of China (English)

    郁君; 周健

    2013-01-01

    ABSTRACT World Health Organization puts forward the tertiary prevention strategies of birth defects in order to reduce its occurrence. Among them, primary prevention refers to comprehensive intervention to prevent the birth defects in the preconception stage. The secondary prevention refers to screening in pregnancy and prenatal diagnosis to early find and intervene the serious fetal birth defects. This article describes the measures of preconception, prenatal and postpartum cares in detail.%  世界卫生组织提出出生缺陷的“三级预防”策略,以减少出生缺陷的发生,其中一级预防指的是孕前阶段综合干预预防出生缺陷,二级预防通过孕期筛查和产前诊断早期发现和早期干预胎儿严重的先天缺陷。该文详细描述了孕前和孕期保健的措施,对产后不可忽略的保健问题提出建议。

  15. Posibilidad regenerativa y reparadora de estructuras dentarias de células mesenquimáticas post natales

    OpenAIRE

    2014-01-01

    Objetivos: Presentar evidencias clínicas de la capacidad reparativa y de la formación de nuevos tejidos mineralizados en dientes con apices incompletamente desarrollados y diagnóstico de necrosis pulpar. Ha sido demostrado que las células pulpares adultas y las del ligamento periodontal presentan un comportamiento similar en su morfología y que la superficie cellular responde positivamente a marcadores de hueso, tejido adiposo, músculos y al estroma de tejido conectivo. La posibilid...

  16. The role of ghrelin, leptin and insulin in foetal development

    Directory of Open Access Journals (Sweden)

    Magdalena Warchoł

    2014-06-01

    Full Text Available introduction and objective. The growing epidemic of childhood obesity has forced scientists to search for methods to prevent feeding disorders. Increasing interest in appetite regulating hormones has revealed their influence on energy homeostasis after birth or even in[i] utero[/i]. state of knowledge. The presence of ghrelin in the stomach of human foetuses and the distinctive production in the pancreas of neonates suggests the role of ghrelin in pre- and post-natal development. The neonatal period appears to be a critical time for the formation of adipose tissue-hypothalamus circuits, thus the amount of adipocytes in foetal life may be a major regulator of food intake. Insulin’s orexigenic effect in the arcuate nucleus of the hypothalamus can be a major modulator of foetal development. objective. This review, based on available literature, aims to analyses the role of appetite regulating hormones in foetal development. summary. Different concentrations of hormones, such as ghrelin, leptin and insulin during foetal life raises the question whether or not they can be modulated, thereby avoiding obesity before birth. Children with pancreas agenesis showed smaller body size at birth, which emphasises the probable role of insulin in foetal growth. Study of sheep foetuses with IUGR confirmed these finding. Appetite-regulating hormones show different roles in foetal development and seem to be essential in the perinatal period.

  17. Chilly dark sectors and asymmetric reheating

    Science.gov (United States)

    Adshead, Peter; Cui, Yanou; Shelton, Jessie

    2016-06-01

    In a broad class of theories, the relic abundance of dark matter is determined by interactions internal to a thermalized dark sector, with no direct involvement of the Standard Model (SM). We point out that these theories raise an immediate cosmological question: how was the dark sector initially populated in the early universe? Motivated in part by the difficulty of accommodating large amounts of entropy carried in dark radiation with cosmic microwave background measurements of the effective number of relativistic species at recombination, N eff , we aim to establish which admissible cosmological histories can populate a thermal dark sector that never reaches thermal equilibrium with the SM. The minimal cosmological origin for such a dark sector is asymmetric reheating, when the same mechanism that populates the SM in the early universe also populates the dark sector at a lower temperature. Here we demonstrate that the resulting inevitable inflaton-mediated scattering between the dark sector and the SM can wash out a would-be temperature asymmetry, and establish the regions of parameter space where temperature asymmetries can be generated in minimal reheating scenarios. Thus obtaining a temperature asymmetry of a given size either restricts possible inflaton masses and couplings or necessitates a non-minimal cosmology for one or both sectors. As a side benefit, we develop techniques for evaluating collision terms in the relativistic Boltzmann equation when the full dependence on Bose-Einstein or Fermi-Dirac phase space distributions must be retained, and present several new results on relativistic thermal averages in an appendix.

  18. THz operation of asymmetric-nanochannel devices

    NARCIS (Netherlands)

    Balocco, C.; Halsall, M.; Vinh, N. Q.; Song, A. M.

    2008-01-01

    The THz spectrum lies between microwaves and the mid-infrared, a region that remains largely unexplored mainly due to the bottleneck issue of lacking compact, solid state, emitters and detectors. Here, we report on a novel asymmetric-nanochannel device, known as the self-switching device, which can

  19. Asymmetric conditional volatility in international stock markets

    Science.gov (United States)

    Ferreira, Nuno B.; Menezes, Rui; Mendes, Diana A.

    2007-08-01

    Recent studies show that a negative shock in stock prices will generate more volatility than a positive shock of similar magnitude. The aim of this paper is to appraise the hypothesis under which the conditional mean and the conditional variance of stock returns are asymmetric functions of past information. We compare the results for the Portuguese Stock Market Index PSI 20 with six other Stock Market Indices, namely the SP 500, FTSE 100, DAX 30, CAC 40, ASE 20, and IBEX 35. In order to assess asymmetric volatility we use autoregressive conditional heteroskedasticity specifications known as TARCH and EGARCH. We also test for asymmetry after controlling for the effect of macroeconomic factors on stock market returns using TAR and M-TAR specifications within a VAR framework. Our results show that the conditional variance is an asymmetric function of past innovations raising proportionately more during market declines, a phenomenon known as the leverage effect. However, when we control for the effect of changes in macroeconomic variables, we find no significant evidence of asymmetric behaviour of the stock market returns. There are some signs that the Portuguese Stock Market tends to show somewhat less market efficiency than other markets since the effect of the shocks appear to take a longer time to dissipate.

  20. Weak chaos in the asymmetric heavy top

    CERN Document Server

    Barrientos, M; Ranada, A F

    1995-01-01

    We consider the dynamics of the slightly asymmetric heavy top, a non-integrable system obtained from the Lagrange top by breaking the symmetry of its inertia tensor. It shows signs of weak chaos, which we study numerically. We argue that it is a good example for introducing students to non-integrability and chaos. (author)

  1. Catalytic Asymmetric Synthesis of Phosphine Boronates.

    Science.gov (United States)

    Hornillos, Valentín; Vila, Carlos; Otten, Edwin; Feringa, Ben L

    2015-06-26

    The first catalytic enantioselective synthesis of ambiphilic phosphine boronate esters is presented. The asymmetric boration of α,β-unsaturated phosphine oxides catalyzed by a copper bisphosphine complex affords optically active organoboronate esters that bear a vicinal phosphine oxide group in good yields and high enantiomeric excess. The synthetic utility of the products is demonstrated through stereospecific transformations into multifunctional optically active compounds.

  2. Beam-beam issues in asymmetric colliders

    Energy Technology Data Exchange (ETDEWEB)

    Furman, M.A.

    1992-07-01

    We discuss generic beam-beam issues for proposed asymmetric e{sup +}- e{sup -} colliders. We illustrate the issues by choosing, as examples, the proposals by Cornell University (CESR-B), KEK, and SLAC/LBL/LLNL (PEP-II).

  3. Three dimensional force balance of asymmetric droplets

    Science.gov (United States)

    Kim, Yeseul; Lim, Su Jin; Cho, Kun; Weon, Byung Mook

    2016-11-01

    An equilibrium contact angle of a droplet is determined by a horizontal force balance among vapor, liquid, and solid, which is known as Young's law. Conventional wetting law is valid only for axis-symmetric droplets, whereas real droplets are often asymmetric. Here we show that three-dimensional geometry must be considered for a force balance for asymmetric droplets. By visualizing asymmetric droplets placed on a free-standing membrane in air with X-ray microscopy, we are able to identify that force balances in one side and in other side control pinning behaviors during evaporation of droplets. We find that X-ray microscopy is powerful for realizing the three-dimensional force balance, which would be essential in interpretation and manipulation of wetting, spreading, and drying dynamics for asymmetric droplets. This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2016R1D1A1B01007133).

  4. Asymmetric Hydrogenation of 3-Substituted Pyridinium Salts

    NARCIS (Netherlands)

    Renom-Carrasco, Marc; Gajewski, Piotr; Pignataro, Luca; de Vries, Johannes G.; Piarulli, Umberto; Gennari, Cesare; Lefort, Laurent

    2016-01-01

    The use of an equivalent amount of an organic base leads to high enantiomeric excess in the asymmetric hydrogenation of N-benzylated 3-substituted pyridinium salts into the corresponding piperidines. Indeed, in the presence of Et3N, a Rh-JosiPhos catalyst reduced a range of pyridinium salts with ee

  5. Nucleation Process in Asymmetric Nuclear Matter

    CERN Document Server

    Peres-Menezes, D

    1998-01-01

    An extended version of the non linear Walecka model, with rho mesons and eletromagnetic field is used to investigate the possibility of phase transitions in hot (warm) nuclear matter, giving rise to droplet formation. Surface properties of asymmetric nuclear matter as the droplet surface energy and its thickness are also examined.

  6. Integrated Optical Asymmetric Coupler Pressure Sensor

    Science.gov (United States)

    Kiyat, Isa; Kocabas, Coskun; Aydinli, Atilla

    2004-05-01

    Analysis of a novel pressure sensor based on a silicon-on-insulator (SOI) asymmetric vertical coupler is presented. The integrated optical component is a coupler composed of a single mode (SM) low index waveguide and a thin silicon slab. High sensitivities of about 0.14 rad.kPa-1 should be achieved.

  7. Asymmetric relationships between proteins shape genome evolution.

    NARCIS (Netherlands)

    Notebaart, R.A.; Kensche, P.R.; Huynen, M.A.; Dutilh, B.E.

    2009-01-01

    BACKGROUND: The relationships between proteins are often asymmetric: one protein (A) depends for its function on another protein (B), but the second protein does not depend on the first. In metabolic networks there are multiple pathways that converge into one central pathway. The enzymes in the conv

  8. Standards vs. labels with imperfect competition and asymmetric information

    DEFF Research Database (Denmark)

    Baltzer, Kenneth Thomas

    2012-01-01

    I demonstrate that providing information about product quality is not necessarily the best way to address asymmetric information problems when markets are imperfectly competitive. In a vertical differentiation model I show that a Minimum Quality Standard, which retains asymmetric information...

  9. Standards vs. labels with imperfect competition and asymmetric information

    DEFF Research Database (Denmark)

    Baltzer, Kenneth Thomas

    I demonstrate that providing information about product quality is not necessarily the best way to address asymmetric information problems when markets are imperfectly competitive. In a vertical dierentiation model I show that a Minimum Quality Standard, which retains asymmetric information...

  10. Charge Asymmetric Cosmic Rays as a probe of Flavor Violating Asymmetric Dark Matter

    DEFF Research Database (Denmark)

    Masina, Isabella; Sannino, Francesco

    2011-01-01

    The recently introduced cosmic sum rules combine the data from PAMELA and Fermi-LAT cosmic ray experiments in a way that permits to neatly investigate whether the experimentally observed lepton excesses violate charge symmetry. One can in a simple way determine universal properties of the unknown...... component of the cosmic rays. Here we attribute a potential charge asymmetry to the dark sector. In particular we provide models of asymmetric dark matter able to produce charge asymmetric cosmic rays. We consider spin zero, spin one and spin one-half decaying dark matter candidates. We show that lepton...... flavor violation and asymmetric dark matter are both required to have a charge asymmetry in the cosmic ray lepton excesses. Therefore, an experimental evidence of charge asymmetry in the cosmic ray lepton excesses implies that dark matter is asymmetric....

  11. Asymmetric and Moving-Frame Approaches to MHD Equations

    Institute of Scientific and Technical Information of China (English)

    Bin Tao CAO

    2012-01-01

    The magnetohydrodynamic (MHD) equations of incompressible viscous fluids with finite electrical conductivity describe the motion of viscous electrically conducting fluids in a magnetic field.In this paper,we find eight families of solutions of these equations by Xu's asymmetric and moving frame methods.A family of singular solutions may reflect basic characteristics of vortices.The other solutions are globally analytic with respect to the spacial variables.Our solutions may help engineers to develop more effective algorithms to find physical numeric solutions to practical models.

  12. Direct asymmetric aldol reactions catalyzed by lipase from porcine pancreas.

    Science.gov (United States)

    Zheng, Jing; Xie, Bang-Hua; Chen, Yan-Li; Cao, Jian-Fei; Yang, Yang; Guan, Zhi; He, Yan-Hong

    2014-01-01

    Porcine pancreas lipase type II (PPL II) exhibited unnatural catalytic activity in direct asymmetric aldol reactions between cyclic ketones and aromatic or heteroaromatic aldehydes in acetonitrile in the presence of phosphate buffer. A wide range of substrates was accepted by the enzyme to afford the corresponding aldol products in low to high yields (10-98%), with moderate to excellent enantioselectivities (53-94% ee, for anti-isomers) and low to moderate diastereoselectivities (48/52-87/13 dr, anti/syn). This methodology expands the application of PPL II, and it might be developed into a potentially valuable method for sustainable organic synthesis.

  13. Asymmetric de Finetti Theorem for Infinite-dimensional Quantum Systems

    CERN Document Server

    Niu, Murphy Yuezhen

    2016-01-01

    The de Finetti representation theorem for continuous variable quantum system is first developed to approximate an N-partite continuous variable quantum state with a convex combination of independent and identical subsystems, which requires the original state to obey permutation symmetry conditioned on successful experimental verification on k of N subsystems. We generalize the de Finetti theorem to include asymmetric bounds on the variance of canonical observables and biased basis selection during the verification step. Our result thereby enables application of infinite-dimensional de Finetti theorem to situations where two conjugate measurements obey different statistics, such as the security analysis of quantum key distribution protocols based on squeezed state against coherent attack.

  14. Adaptive synchronization in an array of asymmetric coupled neural networks

    Institute of Scientific and Technical Information of China (English)

    Gao Ming; Cui Bao-Tong

    2009-01-01

    This paper investigates the global synchronization in an array of linearly coupled neural networks with constant and delayed coupling. By a simple combination of adaptive control and linear feedback with the updated laws, some sufficient conditions are derived for global synchronization of the coupled neural networks. The coupling configuration matrix is assumed to be asymmetric, which is more coincident with the realistic network. It is shown that the approaches developed here extend and improve the earlier works. Finally, numerical simulations are presented to demonstrate the effectiveness of the theoretical results.

  15. Clinical implementation of 4-dihydroxyborylphenylalanine synthesised by an asymmetric pathway.

    Science.gov (United States)

    Kulvik, Martti; Vähätalo, Jyrki; Buchar, Evzen; Färkkilä, Markus; Järviluoma, Eija; Jääskeläinen, Juha; Kriz, Otomar; Laakso, Juha; Rasilainen, Merja; Ruokonen, Inkeri; Kallio, Merja

    2003-02-01

    Boron neutron capture therapy (BNCT) is an experimental therapeutic modality combining a boron pharmaceutical with neutron irradiation. 4-Dihydroxyborylphenylalanine (L-BPA) synthesised via the asymmetric pathway by Malan and Morin [Synlett. 167-168 (1996)] was developed to be the boron containing pharmaceutical in the first series of Finnish BNCT clinical trials. The final product was >98.5% chemically pure L-BPA with L-phenylalanine and L-tyrosine as the residual impurities. The solubility of L-BPA was enhanced by complex formation with fructose (BPA-F). The pH and osmolarity of the BPA-F preparation is in the physiological range. Careful attention was given to the pharmaceutical quality of the BPA-F preparations. Prior to starting clinical trials the acute toxicity of L-BPA was studied in male albino Sprague-Dawley rats. In accordance with earlier studies no adverse effects were observed. After completion of the development work L-BPA solution was administered to brain tumour patients in conjunction with clinical studies for development and testing of BPA-based BNCT. No clinically significant adverse events attributable to the L-BPA i.v. infusions were observed. We conclude that our synthesis development, complementary preclinical and clinical observations justify the safe use of L-BPA up to clinical phase III studies with L-BPA produced by the asymmetric pathway, originally presented by Malan and Morin in 1996.

  16. Prenatal pharmacotherapy rescues brain development in a Down's syndrome mouse model.

    Science.gov (United States)

    Guidi, Sandra; Stagni, Fiorenza; Bianchi, Patrizia; Ciani, Elisabetta; Giacomini, Andrea; De Franceschi, Marianna; Moldrich, Randal; Kurniawan, Nyoman; Mardon, Karine; Giuliani, Alessandro; Calzà, Laura; Bartesaghi, Renata

    2014-02-01

    Intellectual impairment is a strongly disabling feature of Down's syndrome, a genetic disorder of high prevalence (1 in 700-1000 live births) caused by trisomy of chromosome 21. Accumulating evidence shows that widespread neurogenesis impairment is a major determinant of abnormal brain development and, hence, of intellectual disability in Down's syndrome. This defect is worsened by dendritic hypotrophy and connectivity alterations. Most of the pharmacotherapies designed to improve cognitive performance in Down's syndrome have been attempted in Down's syndrome mouse models during adult life stages. Yet, as neurogenesis is mainly a prenatal event, treatments aimed at correcting neurogenesis failure in Down's syndrome should be administered during pregnancy. Correction of neurogenesis during the very first stages of brain formation may, in turn, rescue improper brain wiring. The aim of our study was to establish whether it is possible to rescue the neurodevelopmental alterations that characterize the trisomic brain with a prenatal pharmacotherapy with fluoxetine, a drug that is able to restore post-natal hippocampal neurogenesis in the Ts65Dn mouse model of Down's syndrome. Pregnant Ts65Dn females were treated with fluoxetine from embryonic Day 10 until delivery. On post-natal Day 2 the pups received an injection of 5-bromo-2-deoxyuridine and were sacrificed after either 2 h or after 43 days (at the age of 45 days). Untreated 2-day-old Ts65Dn mice exhibited a severe neurogenesis reduction and hypocellularity throughout the forebrain (subventricular zone, subgranular zone, neocortex, striatum, thalamus and hypothalamus), midbrain (mesencephalon) and hindbrain (cerebellum and pons). In embryonically treated 2-day-old Ts65Dn mice, precursor proliferation and cellularity were fully restored throughout all brain regions. The recovery of proliferation potency and cellularity was still present in treated Ts65Dn 45-day-old mice. Moreover, embryonic treatment restored

  17. Type-Based Automated Verification of Authenticity in Asymmetric Cryptographic Protocols

    DEFF Research Database (Denmark)

    Dahl, Morten; Kobayashi, Naoki; Sun, Yunde

    2011-01-01

    Gordon and Jeffrey developed a type system for verification of asymmetric and symmetric cryptographic protocols. We propose a modified version of Gordon and Jeffrey's type system and develop a type inference algorithm for it, so that protocols can be verified automatically as they are, without any...

  18. A case of asymmetrical monocephalus dipygus (tetrapus dibrachius) in a male Holstein calf in Iran

    Science.gov (United States)

    Marzban Abbasabadi, Behrokh; Ahmadzadeh, Aliakbar; Ramezanpour, Shahab; Hajati Ziabari, Amir Reza

    2016-01-01

    Dipygus is a teratological fetus with a double pelvis, genitals, and extremities. Congenital duplications in cattle are rare. Caudal duplication is more common in sheep and pigs while cranial duplications seem to be predominant in cattle. Asymmetric or parasitic conjoined twins consisting of an incomplete twin (parasite) attached to the body of a fully-developed twin (autosite). This report deals with a male Holstein calf with two extra limbs, in the pelvic region which were directed ventrally between the two normal hind limbs. The extra limbs were completely developed in one side and in other side just a bony mass were observed. So classification has been made as asymmetrical attached twins. The genital system was not affected and just one extra kidney-like structure was found. To the authors’ best knowledge, this is the first report of asymmetrical monocephalus dipygus (tetrapus dibrachius) in a male Holstein calf in Iran. PMID:27482365

  19. Comparative transcriptional analysis reveals differential gene expression between asymmetric and symmetric zygotic divisions in tobacco.

    Directory of Open Access Journals (Sweden)

    Tian-Xiang Hu

    Full Text Available Asymmetric cell divisions occur widely during many developmental processes in plants. In most angiosperms, the first zygotic cell division is asymmetric resulting in two daughter cells of unequal size and with distinct fates. However, the critical molecular mechanisms regulating this division remain unknown. Previously we showed that treatment of tobacco zygotes with beta-glucosyl Yariv (βGlcY could dramatically alter the first zygotic asymmetric division to produce symmetric two-celled proembryos. In the present study, we isolated zygotes and two-celled asymmetric proembryos in vivo by micromanipulation, and obtained symmetric, two-celled proembryos by in vitro cell cultures. Using suppression-subtractive hybridization (SSH and macroarray analysis differential gene expression between the zygote and the asymmetric and symmetric two-celled proembryos was investigated. After sequencing of the differentially expressed clones, a total of 1610 EST clones representing 685 non-redundant transcripts were obtained. Gene ontology (GO term analysis revealed that these transcripts include those involved in physiological processes such as response to stimulus, regulation of gene expression, and localization and formation of anatomical structures. A homology search against known genes from Arabidopsis indicated that some of the above transcripts are involved in asymmetric cell division and embryogenesis. Quantitative real-time PCR confirmed the up- or down-regulation of the selected candidate transcripts during zygotic division. A few of these transcripts were expressed exclusively in the zygote, or in either type of the two-celled proembryos. Expression analyses of select genes in different tissues and organs also revealed potential roles of these transcripts in fertilization, seed maturation and organ development. The putative roles of few of the identified transcripts in the regulation of zygotic division are discussed. Further functional work on these

  20. Asymmetric catalysis: An enabling science

    OpenAIRE

    Trost, Barry M.

    2004-01-01

    Chirality of organic molecules plays an enormous role in areas ranging from medicine to material science, yet the synthesis of such entities in one enantiomeric form is one of the most difficult challenges. The advances being made stem from the convergence of a broader understanding of theory and how structure begets function, the developments in the interface between organic and inorganic chemistry and, most notably, the organic chemistry of the transition metals, and the continuing advancem...

  1. An Asymmetric Coevolutionary Voter Model

    CERN Document Server

    Wieland, Stefan

    2013-01-01

    We consider a modification of the coevolutionary voter model inspired by the idea of letting opinion dynamics reflect different strategies to promote consensus. This extension of the classic voter model breaks the symmetry of the two competing opinions, giving rise to more complex behaviour. A description of the phase diagram of the system is given, and the performance of the pair approximation is analyzed. The stochastic properties of the active phase are studied, and the applicability of analytic approximations developed for the coevolutionary voter model is discussed.

  2. Asymmetric interaction will facilitate the evolution of cooperation

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Explaining the evolution of cooperation remains one of the greatest problems for both biology and social science. The classical theories of cooperation suggest that cooperation equilibrium or evolutionary stable strategy between partners can be maintained through genetic similarity or reciprocity relatedness. These classical theories are based on an assumption that partners interact symmetrically with equal payoffs in a game of cooperation interaction. However, the payoff between partners is usually not equal and therefore they often interact asymmetrically in real cooperative systems. With the Hawk–Dove model, we find that the probability of cooperation between cooperative partners will depend closely on the payoff ratio. The higher the payoff ratio between recipients and cooperative actors, the greater will be the probability of cooperation interaction between involved partners. The greatest probability of conflict between cooperative partners will occur when the payoff between partners is equal. The results show that this asymmetric relationship is one of the key dynamics of the evolution of cooperation, and that pure cooperation strategy (i.e., Nash equilibrium) does not exist in asymmetrical cooperation systems, which well explains the direct conflict observed in almost all of the well documented cooperation systems. The model developed here shows that the cost-to-benefit ratio of cooperation is also negatively correlated with the probability of cooperation interaction. A smaller cost-to-benefit ratio of cooperation might be created by the limited dispersal ability or exit cost of the partners involved, and it will make the punishment of the non-cooperative individuals by the recipient more credible, and therefore make it more possible to maintain stable cooperation interaction.

  3. Asymmetric catalysis in organic synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Reilly, S.D.; Click, D.R.; Grumbine, S.K.; Scott, B.L.; Watkins, J.G.

    1998-11-01

    This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The goal of the project was to prepare new catalyst systems, which would perform chemical reactions in an enantioselective manner so as to produce only one of the possible optical isomers of the product molecule. The authors have investigated the use of lanthanide metals bearing both diolate and Schiff-base ligands as catalysts for the enantioselective reduction of prochiral ketones to secondary alcohols. The ligands were prepared from cheap, readily available starting materials, and their synthesis was performed in a ''modular'' manner such that tailoring of specific groups within the ligand could be carried out without repeating the entire synthetic procedure. In addition, they have developed a new ligand system for Group IV and lanthanide-based olefin polymerization catalysts. The ligand system is easily prepared from readily available starting materials and offers the opportunity to rapidly prepare a wide range of closely related ligands that differ only in their substitution patterns at an aromatic ring. When attached to a metal center, the ligand system has the potential to carry out polymerization reactions in a stereocontrolled manner.

  4. Enhancing molecule fluorescence with asymmetrical plasmonic antennas.

    Science.gov (United States)

    Lu, Guowei; Liu, Jie; Zhang, Tianyue; Shen, Hongming; Perriat, Pascal; Martini, Matteo; Tillement, Olivier; Gu, Ying; He, Yingbo; Wang, Yuwei; Gong, Qihuang

    2013-07-21

    We propose and justify by the finite-difference time-domain method an efficient strategy to enhance the spontaneous emission of a fluorophore with a multi-resonance plasmonic antenna. The custom-designed asymmetrical antenna consists of two plasmonic nanoparticles with different sizes and is able to couple efficiently to free space light through multiple localized surface plasmon resonances. This design simultaneously permits a large near-field excitation near the antenna as well as a high quantum efficiency, which results in an unusual and significant enhancement of the fluorescence of a single emitter. Such an asymmetrical antenna presents intrinsic advantages over single particle or dimer based antennas made using two identical nanostructures. This promising concept can be exploited in the large domain of light-matter interaction processes involving multiple frequencies.

  5. Design of Asymmetric Peptide Bilayer Membranes.

    Science.gov (United States)

    Li, Sha; Mehta, Anil K; Sidorov, Anton N; Orlando, Thomas M; Jiang, Zhigang; Anthony, Neil R; Lynn, David G

    2016-03-16

    Energetic insights emerging from the structural characterization of peptide cross-β assemblies have enabled the design and construction of robust asymmetric bilayer peptide membranes. Two peptides differing only in their N-terminal residue, phosphotyrosine vs lysine, coassemble as stacks of antiparallel β-sheets with precisely patterned charged lattices stabilizing the bilayer leaflet interface. Either homogeneous or mixed leaflet composition is possible, and both create nanotubes with dense negative external and positive internal solvent exposed surfaces. Cross-seeding peptide solutions with a preassembled peptide nanotube seed leads to domains of different leaflet architecture within single nanotubes. Architectural control over these cross-β assemblies, both across the bilayer membrane and along the nanotube length, provides access to highly ordered asymmetric membranes for the further construction of functional mesoscale assemblies.

  6. Asymmetric dark matter models in SO(10)

    Science.gov (United States)

    Nagata, Natsumi; Olive, Keith A.; Zheng, Jiaming

    2017-02-01

    We systematically study the possibilities for asymmetric dark matter in the context of non-supersymmetric SO(10) models of grand unification. Dark matter stability in SO(10) is guaranteed by a remnant Z2 symmetry which is preserved when the intermediate scale gauge subgroup of SO(10) is broken by a {126} dimensional representation. The asymmetry in the dark matter states is directly generated through the out-of-equilibrium decay of particles around the intermediate scale, or transferred from the baryon/lepton asymmetry generated in the Standard Model sector by leptogenesis. We systematically classify possible asymmetric dark matter candidates in terms of their quantum numbers, and derive the conditions for each case that the observed dark matter density is (mostly) explained by the asymmetry of dark matter particles.

  7. Asymmetric Dark Matter Models in SO(10)

    CERN Document Server

    Nagata, Natsumi; Zheng, Jiaming

    2016-01-01

    We systematically study the possibilities for asymmetric dark matter in the context of non-supersymmetric SO(10) models of grand unification. Dark matter stability in SO(10) is guaranteed by a remnant $\\mathbb{Z}_2$ symmetry which is preserved when the intermediate scale gauge subgroup of SO(10) is broken by a ${\\bf 126}$ dimensional representation. The asymmetry in the dark matter states is directly generated through the out-of-equilibrium decay of particles around the intermediate scale, or transferred from the baryon/lepton asymmetry generated in the Standard Model sector by leptogenesis. We systematically classify possible asymmetric dark matter candidates in terms of their quantum numbers, and derive the conditions for each case that the observed dark matter density is (mostly) explained by the asymmetry of dark matter particles.

  8. Asymmetric k-Center with Minimum Coverage

    DEFF Research Database (Denmark)

    Gørtz, Inge Li

    2008-01-01

    In this paper we give approximation algorithms and inapproximability results for various asymmetric k-center with minimum coverage problems. In the k-center with minimum coverage problem, each center is required to serve a minimum number of clients. These problems have been studied by Lim et al. [A....... Lim, B. Rodrigues, F. Wang, Z. Xu, k-center problems with minimum coverage, Theoret. Comput. Sci. 332 (1–3) (2005) 1–17] in the symmetric setting....

  9. New electric field in asymmetric magnetic reconnection.

    Science.gov (United States)

    Malakit, K; Shay, M A; Cassak, P A; Ruffolo, D

    2013-09-27

    We present a theory and numerical evidence for the existence of a previously unexplored in-plane electric field in collisionless asymmetric magnetic reconnection. This electric field, dubbed the "Larmor electric field," is associated with finite Larmor radius effects and is distinct from the known Hall electric field. Potentially, it could be an important indicator for the upcoming Magnetospheric Multiscale mission to locate reconnection sites as we expect it to appear on the magnetospheric side, pointing earthward, at the dayside magnetopause reconnection site.

  10. Asymmetric Information – Adverse Selection Problem

    Directory of Open Access Journals (Sweden)

    Dumitru MARIN

    2007-01-01

    Full Text Available The present paper makes an introduction in the contract theory starting with the definitions of asymmetric information and some of the problems that generate: moral hazard and adverse selection. We provide an insight of the latest empirical studies in adverse selection in different markets. An adverse selection model, based on Rothchild and Stiglitz is also present to give a perspective of the theoretical framework.

  11. Asymmetrically Compressed Stereoscopic 3D Videos: Quality Assessment and Rate-Distortion Performance Evaluation.

    Science.gov (United States)

    Wang, Jiheng; Wang, Shiqi; Wang, Zhou

    2017-03-01

    Objective quality assessment of stereoscopic 3D video is challenging but highly desirable, especially in the application of stereoscopic video compression and transmission, where useful quality models are missing, that can guide the critical decision making steps in the selection of mixed-resolution coding, asymmetric quantization, and pre- and post-processing schemes. Here we first carry out subjective quality assessment experiments on two databases that contain various asymmetrically compressed stereoscopic 3D videos obtained from mixed-resolution coding, asymmetric transform-domain quantization coding, their combinations, and the multiple choices of postprocessing techniques. We compare these asymmetric stereoscopic video coding schemes with symmetric coding methods and verify their potential coding gains. We observe a strong systematic bias when using direct averaging of 2D video quality of both views to predict 3D video quality. We then apply a binocular rivalry inspired model to account for the prediction bias, leading to a significantly improved full reference quality prediction model of stereoscopic videos. The model allows us to quantitatively predict the coding gain of different variations of asymmetric video compression, and provides new insight on the development of high efficiency 3D video coding schemes.

  12. Asymmetric Conditional Volatility in International Stock Markets

    CERN Document Server

    Ferreira, N B; Menezes, R; Ferreira, Nuno B.; Mendes, Diana A.; Menezes, Rui

    2006-01-01

    Recent studies show that a negative shock in stock prices will generate more volatility than a positive shock of similar magnitude. The aim of this paper is to appraise the hypothesis under which the conditional mean and the conditional variance of stock returns are asymmetric functions of past information. We compare the results for the Portuguese Stock Market Index PSI 20 with six other Stock Market Indices, namely the S&P 500, FTSE100, DAX 30, CAC 40, ASE 20, and IBEX 35. In order to assess asymmetric volatility we use autoregressive conditional heteroskedasticity specifications known as TARCH and EGARCH. We also test for asymmetry after controlling for the effect of macroeconomic factors on stock market returns using TAR and M-TAR specifications within a VAR framework. Our results show that the conditional variance is an asymmetric function of past innovations raising proportionately more during market declines, a phenomenon known as the leverage effect. However, when we control for the effect of chan...

  13. Multiple Traveling Salesmen in Asymmetric Metrics

    CERN Document Server

    Friggstad, Zachary

    2011-01-01

    We consider some generalizations of the Asymmetric Traveling Salesman Path problem. Suppose we have an asymmetric metric G = (V,A) with two distinguished nodes s,t. We are also given a positive integer k. The goal is to find k paths of minimum total cost from s to t whose union spans all nodes. We call this the k-Person Asymmetric Traveling Salesmen Path problem (k-ATSPP). Our main result for k-ATSPP is a bicriteria approximation that, for some parameter b >= 1 we may choose, finds between k and k + k/b paths of total length O(b log |V|) times the optimum value of an LP relaxation based on the Held-Karp relaxation for the Traveling Salesman problem. On one extreme this is an O(log |V|)-approximation that uses up to 2k paths and on the other it is an O(k log |V|)-approximation that uses exactly k paths. Next, we consider the case where we have k pairs of nodes (s_1,t_1), ..., (s_k,t_k). The goal is to find an s_i-t_i path for every pair such that each node of G lies on at least one of these paths. Simple appro...

  14. Traceless Synthesis of Asymmetrically Modified Bivalent Nucleosomes.

    Science.gov (United States)

    Lechner, Carolin C; Agashe, Ninad D; Fierz, Beat

    2016-02-18

    Nucleosomes carry extensive post-translational modifications (PTMs), which results in complex modification patterns that are involved in epigenetic signaling. Although two copies of each histone coexist in a nucleosome, they may not carry the same PTMs and are often differently modified (asymmetric). In bivalent domains, a chromatin signature prevalent in embryonic stem cells (ESCs), namely H3 methylated at lysine 4 (H3K4me3), coexists with H3K27me3 in asymmetric nucleosomes. We report a general, modular, and traceless method for producing asymmetrically modified nucleosomes. We further show that in bivalent nucleosomes, H3K4me3 inhibits the activity of the H3K27-specific lysine methyltransferase (KMT) polycomb repressive complex 2 (PRC2) solely on the same histone tail, whereas H3K27me3 stimulates PRC2 activity across tails, thereby partially overriding the H3K4me3-mediated repressive effect. To maintain bivalent domains in ESCs, PRC2 activity must thus be locally restricted or reversed.

  15. TMJ development and growth require primary cilia function.

    Science.gov (United States)

    Kinumatsu, T; Shibukawa, Y; Yasuda, T; Nagayama, M; Yamada, S; Serra, R; Pacifici, M; Koyama, E

    2011-08-01

    Primary cilia regulate limb and axial skeletal formation and hedgehog signaling, but their roles in temporomandibular joint (TMJ) development are unknown. Thus, we created conditional mouse mutants deficient in ciliary transport protein Kif3a in cartilage. In post-natal wild-type mice, primary cilia were occasionally observed on the superior, inferior, or lateral side of condylar cells. Cilia were barely detectable in mutant chondrocytes but were evident in surrounding tissues, attesting to the specificity of chondrocyte Kif3a ablation. Mutant condyles from 3-month-old mice were narrow and flat along their antero-posterior and medio-lateral axes, were often fused with the articular disc, and displayed an irregular bony surface. The polymorphic layer in P15 mutants contained fewer Sox9-expressing chondroprogenitor cells because of reduced mitotic activity, and newly differentiated chondrocytes underwent precocious hypertrophic enlargement accompanied by early activation of Indian hedgehog (Ihh). Interestingly, there was excessive intramembranous ossification along the perichondrium, accompanied by local expression of the hedgehog receptor Patched-1 and up-regulation of Osterix and Collagen I. In summary, Kif3a and primary cilia are required for coordination of chondrocyte maturation, intramembranous bone formation, and chondrogenic condylar growth. Defects in these processes in Kif3a condylar cartilage are likely to reflect abnormal hedgehog signaling topography and dysfunction.

  16. Asymmetric Explosions of Thermonuclear Supernovae

    CERN Document Server

    Ghezzi, C R; Horváth, J E

    2004-01-01

    A type Ia supernova explosion starts in a white dwarf as a laminar deflagration at the center of the star and soon several hydrodynamic instabilities (in particular, the Rayleigh-Taylor (R-T) instability) begin to act. In previous work (Ghezzi, de Gouveia Dal Pino, & Horvath 2001), we addressed the propagation of an initially laminar thermonuclear flame in presence of a magnetic field assumed to be dipolar. We were able to show that, within the framework of a fractal model for the flame velocity, the front is affected by the field through the quenching of the R-T instability growth in the direction perpendicular to the field lines. As a consequence, an asymmetry develops between the magnetic polar and the equatorial axis that gives a prolate shape to the burning front. We have here computed numerically the total integrated asymmetry as the flame front propagates outward through the expanding shells of decreasing density of the magnetized white dwarf progenitor, for several chemical compositions, and found...

  17. Optical color image encryption based on an asymmetric cryptosystem in the Fresnel domain

    Science.gov (United States)

    Chen, Wen; Chen, Xudong

    2011-08-01

    In recent years, optical color image encryption has attracted much attention in the information security field. Some approaches, such as digital holography, have been proposed to encrypt color images, but the previously proposed methods are developed based on optical symmetric cryptographic strategies. In this paper, we apply an optical asymmetric cryptosystem for the color image encryption instead of conventional symmetric cryptosystems. A phase-truncated strategy is applied in the Fresnel domain, and multiple-wavelength and indexed image methods are further employed. The security of optical asymmetric cryptosystem is also analyzed during the decryption. Numerical results are presented to demonstrate the feasibility and effectiveness of the proposed optical asymmetric cryptosystem for color image encryption.

  18. A numerical strategy for finite element modeling of frictionless asymmetric vocal fold collision

    DEFF Research Database (Denmark)

    Granados, Alba; Misztal, Marek Krzysztof; Brunskog, Jonas;

    2016-01-01

    Analysis of voice pathologies may require vocal fold models that include relevant features such as vocal fold asymmetric collision. The present study numerically addresses the problem of frictionless asymmetric collision in a self-sustained three-dimensional continuum model of the vocal folds....... Theoretical background and numerical analysis of the finite-element position-based contact model are presented, along with validation. A novel contact detection mechanism capable to detect collision in asymmetric oscillations is developed. The effect of inexact contact constraint enforcement on vocal fold...... dynamics is examined by different variational methods for inequality constrained minimization problems, namely the Lagrange multiplier method and the penalty method. In contrast to the penalty solution, which is related to classical spring-like contact forces, numerical examples show that the parameter...

  19. Asymmetric transmission of acoustic waves in a layer thickness distribution gradient structure using metamaterials

    Science.gov (United States)

    Chen, Jung-San; Chang, I.-Ling; Huang, Wan-Ting; Chen, Lien-Wen; Huang, Guan-Hua

    2016-09-01

    This research presents an innovative asymmetric transmission design using alternate layers of water and metamaterial with complex mass density. The directional transmission behavior of acoustic waves is observed numerically inside the composite structure with gradient layer thickness distribution and the rectifying performance of the present design is evaluated. The layer thickness distributions with arithmetic and geometric gradients are considered and the effect of gradient thickness on asymmetric wave propagation is systematically investigated using finite element simulation. The numerical results indicate that the maximum pressure density and transmission through the proposed structure are significantly influenced by the wave propagation direction over a wide range of audible frequencies. Tailoring the thickness of the layered structure enables the manipulation of asymmetric wave propagation within the desired frequency range. In conclusion, the proposed design offers a new possibility for developing directional-dependent acoustic devices.

  20. A New Asymmetric α-Amido-hydroxyalkylation Mediated by SmI2

    Institute of Scientific and Technical Information of China (English)

    ZHENG Xiao; FENG Chen-Guo; HUNG Pei-Qiang

    2004-01-01

    Polyhydroxylated indolizidine alkaloids, such as castanospermine (Ⅰ) and swainsonine (H)are of longstanding interest due to their powerful glycosidase inhibitory activity. Asymmetric hydroxyatkylation via α-amido carbanions to form C-C bands would provide a convenient approach to these compounds.In continuation of our efforts in developing asyrmmetric o-amido-hydroxyalkylation method,1 we report a new SmI2 mediated flexible asymmetric α-amido-hydroxyalkylation method. Starting from the known (S)-3-hydroxy-2-pyrrolidinone 1,2 sulfide 2 and 3 were prepared. SmI2-mediated reductive metallation of these sulfides followed by reaction with ketones or aldehydes under Barbier conditions provided C2 hydroxyalkylated products 4 in yields ranged from 30% to 83%. High C2/C3 trans diastereoselectivity and mediocre diastereoselectivity at newly formed carbinolic center have been observed. The present method will open an avenue for the asymmetric synthesis of polyhydroxylated indolizidine alkaloids.

  1. Measurement and understanding of single-molecule break junction rectification caused by asymmetric contacts.

    Science.gov (United States)

    Wang, Kun; Zhou, Jianfeng; Hamill, Joseph M; Xu, Bingqian

    2014-08-01

    The contact effects of single-molecule break junctions on rectification behaviors were experimentally explored by a systematic control of anchoring groups of 1,4-disubstituted benzene molecular junctions. Single-molecule conductance and I-V characteristic measurements reveal a strong correlation between rectifying effects and the asymmetry in contacts. Analysis using energy band models and I-V calculations suggested that the rectification behavior is mainly caused by asymmetric coupling strengths at the two contact interfaces. Fitting of the rectification ratio by a modified Simmons model we developed suggests asymmetry in potential drop across the asymmetric anchoring groups as the mechanism of rectifying I-V behavior. This study provides direct experimental evidence and sheds light on the mechanisms of rectification behavior induced simply by contact asymmetry, which serves as an aid to interpret future single-molecule electronic behavior involved with asymmetric contact conformation.

  2. Direct Asymmetric Aldol Type Reaction with Ethyl Diazoacetate: Stereoselective Synthesis of α, β-Dihydroxy Esters

    Institute of Scientific and Technical Information of China (English)

    LIAO Ming-Yi; YAO Wen-Gang; FENG Hai-Tao; WANG Jian-Bo

    2003-01-01

    @@ Enantioselective aldol condensation under catalytic condition remains a challenging task in modern organic synthesis, and numerous efforts have been directed to this area. In particular, the direct catalytic asymmetric aldol reaction is very attractive considering the requirement of atom efficiency. This has been studied only recently, and several very practical processes have been developed. We have recently initiated a study on the direct asymmetric aldol type reaction with ethyl diazoacetate as nucleophile. Moderate enantioselectivities (65% ~91% ee ) were achieved in the condensation of aldehydes with ethyl diazoacetate catalyzed by the chiral complex of BINOL derivatives-Zr (OBu- t )4. [1

  3. Analysis of Rolling Pressure in Asymmetrical Rolling Process by Slab Method

    Institute of Scientific and Technical Information of China (English)

    TIAN Yong; GUO Yan-hui; WANG Zhao-dong; WANG Guo-dong

    2009-01-01

    The plane strain asymmetrical rolling was analyzed using slab method. The contact arc was replaced by parabola, and the constant surface friction status was adopted during the analysis. The deformation area was divided into three zones according to the direction of the friction. Then, the three zones were studied, respectively. A rolling force model and a rolling torque model were developed based on the analysis, and they were used to analyze the influence of asymmetrical rolling factors on deformation area and unit pressure if they had good precision which was determined by comparing the calculated results with the measured ones.

  4. High Order Centrifugal Distortion Corrections to Energy Levels of Asymmetric Top Molecules

    Institute of Scientific and Technical Information of China (English)

    LIU Yu-Yan; LIU Xiao-Yong; LIU Hong-Ping; GUO Yuan-Qing; HUANG Guang-Ming; LIN Jie-Li; GAO Hui

    2000-01-01

    High order centrifugal distortion terms have been derived and added to the effective Hamiltonian of asymmetric top molecules. Based on this Hamiltonian, a program in Fortran 77 has been developed for spectral analysis of asymmetric top molecules. The high order centrifugal distortion terms are found to be non-negligible even for the low-lying rotational transitions of molecules, such as Ha 18O, subjected to severe centrifugal distortion effect,and for the high-lying rotational transitions of molecules, such as 14N16O2 subjected to the moderate centrifugal distortion effect.

  5. Tunable magnetoresistance in an asymmetrically coupled single-molecule junction

    Science.gov (United States)

    Warner, Ben; El Hallak, Fadi; Prüser, Henning; Sharp, John; Persson, Mats; Fisher, Andrew J.; Hirjibehedin, Cyrus F.

    2015-03-01

    Phenomena that are highly sensitive to magnetic fields can be exploited in sensors and non-volatile memories. The scaling of such phenomena down to the single-molecule level may enable novel spintronic devices. Here, we report magnetoresistance in a single-molecule junction arising from negative differential resistance that shifts in a magnetic field at a rate two orders of magnitude larger than Zeeman shifts. This sensitivity to the magnetic field produces two voltage-tunable forms of magnetoresistance, which can be selected via the applied bias. The negative differential resistance is caused by transient charging of an iron phthalocyanine (FePc) molecule on a single layer of copper nitride (Cu2N) on a Cu(001) surface, and occurs at voltages corresponding to the alignment of sharp resonances in the filled and empty molecular states with the Cu(001) Fermi energy. An asymmetric voltage-divider effect enhances the apparent voltage shift of the negative differential resistance with magnetic field, which inherently is on the scale of the Zeeman energy. These results illustrate the impact that asymmetric coupling to metallic electrodes can have on transport through molecules, and highlight how this coupling can be used to develop molecular spintronic applications.

  6. Light-Induced Charge Transport within a Single Asymmetric Nanowire

    Energy Technology Data Exchange (ETDEWEB)

    LIU, CHONG; HWANG, YUN YEONG; JEONG, HOON EIU; YANG, PEIDONG

    2011-01-21

    Artificial photosynthetic systems using semiconductor materials have been explored for more than three decades in order to store solar energy in chemical fuels such as hydrogen. By mimicking biological photosynthesis with two light-absorbing centers that relay excited electrons in a nanoscopic space, a dual-band gap photoelectrochemical (PEC) system is expected to have higher theoretical energy conversion efficiency than a single band gap system. This work demonstrates the vectorial charge transport of photo-generated electrons and holes within a single asymmetric Si/TiO2 nanowire using Kelvin probe force microscopy (KPFM). Under UV illumination, higher surface potential was observed on the n-TiO₂ side, relative to the potential of the p-Si side, as a result of majority carriers’ recombination at the Si/TiO₂ interface. These results demonstrate a new approach to investigate charge separation and transport in a PEC system. This asymmetric nanowire heterostructure, with a dual band gap configuration and simultaneously exposed anode and cathode surfaces represents an ideal platform for the development of technologies for the generation of solar fuels, although better photoanode materials remain to be discovered.

  7. Micro/nanofluidic Diode using Asymmetric Ion Concentration Polarization Layer

    Science.gov (United States)

    Sohn, Seoyun; Cho, Inhee; Kim, Sung Jae

    2016-11-01

    Recent developments of ion concentration polarization (ICP) theory would suggest that an over-limiting conductance (OLC) of the device is subject to the morphology of ICP layer and a micro-structure is able to alter the morphology. In this study, we demonstrated an ion rectification resulted only from asymmetric microscale structures, while conventional nanofluidic diode applications have usually employed a nanoscale asymmetry which requires sophisticate and expensive fabrication processes. We designed two dead-end microchannels incorporated with the nanoporous membrane. The difference in width of the microchannels was designed to yield asymmetry to the device. Cyclic voltammetry measurement was conducted to investigate the OLC behaviors on both forward and reverse bias. The diodic characteristics on I-V responses were observed at various ratio of the different microchannel width. In addition, we experimentally verified the logarithmical linearity between the ratios and the rectification ratios of OLC. This quantitative analysis would guide the further application utilizing microscale asymmetric diode device that now can be realized with minimum fabrication endeavors.

  8. The effects of the apoE4 genotype on the developing mouse retina.

    Science.gov (United States)

    Maharshak, Idit; Salomon-Zimri, Shiran; Antes, Ran; Liraz, Ori; Nisgav, Yael; Livnat, Tami; Weinberger, Dov; Colton, Carol A; Solomon, Arieh S; Michaelson, Daniel M

    2016-04-01

    Apolipoprotein E4 (apoE4), the most prevalent genetic risk factor for Alzheimer's disease (AD), is associated with neuronal and vascular impairments. The retina, which is as an extension of the central nervous system (CNS), is a particularly suitable model for studying developmental and functional aspects of the neuronal and vascular systems. This study investigates the apoE4-dependent developmental effects on the retinal vasculature and neuronal systems and on the levels of apoE and the vascular endothelial growth factor (VEGF) in the retina. This was performed utilizing retinas of 4, 7, 12, and of 120-day-old human-apoE4-targeted replacement mice and of corresponding mice that express the AD benign isoform, apoE3. The results obtained revealed retinal vascular pathology in the apoE4 mice, which started on the early post-natal days. This includes transient increase in vascular branching, and vascular buds which are round vascular elements representing sprouting or retracting vessels. These effects peaked and ended during the neonatal period. Examination of the synaptic system utilizing the pre-synaptic marker synaptophysin revealed a significant decrease of retinal synaptic density in the apoE4 mice, which was detectable by post-natal day 12 (P12). These morphological changes are associated with neonatal age-dependent elevation in the apoE levels in both apoE3 and apoE4 retinas which is more profound in the apoE4 mice and a corresponding increase in VEGF levels, which is less profound in the apoE4 mice. Additionally, we observed lower levels of retinal VEGF in the apoE4 mice compared to the apoE3 mice retinas on P12. These results show that apoE4 has a transient vascular effect during retinal development that ends in the neonatal period, which is accompanied by a synaptic effect that begins at the end of the neonatal period. These findings show that the apoE4 genotype can have distinct developmental effects on both the retinal vasculature and on neurons and

  9. Msx2 -/- transgenic mice develop compound amelogenesis imperfecta, dentinogenesis imperfecta and periodental osteopetrosis.

    Science.gov (United States)

    Aïoub, M; Lézot, F; Molla, M; Castaneda, B; Robert, B; Goubin, G; Néfussi, J R; Berdal, A

    2007-11-01

    The physiological function of the transcription factor Msx2 in tooth and alveolar bone was analysed using a knock-in transgenic mouse line. In this mouse line, the beta-galactosidase gene was used to disrupt Msx2: thus, beta-galactosidase expression was driven by the Msx2 promoter, but Msx2 was not produced. This allowed to monitor Msx2 expression using a beta-galactosidase assay. Msx2 transgenic mice ubiquitously and continuously expressed the mutated Msx2-nlacZ gene in cells of the complex formed by tooth and alveolar bone. Msx2 -/- homozygous mice displayed a wide spectrum of alterations in tooth eruption and morphology as well as dental and periodontal defects from the first post-natal weeks up to 6 months. These defects culminated with the formation of an odontogenic tumour at the mandibular third molar site. This study suggests that bone resorption is a functional target of Msx2 in the alveolar compartment, since Msx2 was expressed in osteoclasts, with the highest expression levels found in the active sites of bone modelling associated with tooth eruption and root elongation. The RANK osteoclast differentiation pathway was affected in microdissected Msx2 -/- mouse alveolar bone (as inferred by RANK ligand mRNA levels) compared to basal bone and wild-type controls. Decreased alveolar osteoclast activity was observed in Msx2 -/- mice, similar to that seen in osteopetrosis, another condition in which osteoclast activity is impaired and odontogenic tumours form. These data suggest a pleiotropic role for Msx2 in oral bone growth from birth until adult homeostasis. RANK pathway appeared to be modulated by Msx2, in addition to the previously reported modulations of BMP4 and laminin5alpha3 in early tooth development. Non-overlapping Msx1 and Msx2 expression patterns suggested that these two homeogenes play non-redundant roles in skeletal growth, with Msx1 targeting basal bone and Msx2 targeting alveolar bone. This study provides a detailed analysis of the phenotype

  10. Minimization of erase-band in shingled PMR with asymmetric writer

    Science.gov (United States)

    Tagawa, Ikuya; Urakami, Yosuke; Maeda, Maki; Maruyama, Youji; Kudo, Kazue; Shiina, Hiromi; Mochizuki, Masafumi

    2012-02-01

    To make the write-field much stronger with sharper cross-track field gradient in Shingled perpendicular Magnetic Recording (SMR), we have successfully developed asymmetric SMR heads with one-side shield design. Using these heads, higher track density capability on the shielded-side was demonstrated, which came from narrower erase-band width at shielded side.

  11. Rhodium-catalyzed Asymmetric Ring Opening Reaction of Oxabenzo-norbornadiene with Substituted Phenolic Nucleophiles

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    We have developed an asymmetric ring opening reaction of oxabenzonorbornadienes with substituted phenolic nucleophiles. Under the reaction conditions ( [Rh(COD)Cl]2 (1 mol%),(S)-(R)-PPF-ptBu2 (2 mol%), THF, reflux), the reaction products were obtained with high yield and enantiomeric excesses ( up to 99% ee).

  12. Rhodium-catalyzed asymmetric ring opening of azabenzonorbornadiene with substituted piperazine nucleophiles

    Institute of Scientific and Technical Information of China (English)

    Lei Xie; Ding Qiao Yang; Shuang Qi Zhao; Huan Wang; Li Hua Liang; Ren Shi Luo

    2007-01-01

    We have developed an asymmetric ring opening reaction of azabenzonorbornadiene with substituted piperazine. By increasing the amount of catalyst (from 2.5 to 5%) and ligands (5 to 10%) as well as addition of ammonium iodide, the products can be obtained in high yield and the reaction time shortened dramatically, but the ee values were rather low.

  13. A kinetic and structural investigation of DNA-Based asymmetric catalysis using first-generation ligands

    NARCIS (Netherlands)

    Rosati, Fiora; Boersma, Arnold J.; Klijn, Jaap E.; Meetsma, Auke; Feringa, Ben L.; Roelfes, Gerard

    2009-01-01

    The recently developed concept of DNA-based asymmetric catalysis involves the transfer of chirality from the DNA double helix in reactions using a noncovalently bound catalyst. To date, two generations of DNA-based catalysts have been reported that differ in the design of the ligand for the metal. H

  14. A Convenient Method to Construct Chroman Skeleton: Asymmetric Synthesis of (-)-4'-Hydroxy-7-methoxyflavane

    Institute of Scientific and Technical Information of China (English)

    XU, Boyan; XUE, Jijun; ZHANG, Huabing; LI, Ying

    2009-01-01

    The first enantioselective synthesis of a naturally occurring 4'-hydroxy-7-methoxyflavane was developed by an asymmetric reduction and a microwave-assistant aromatic C-O bond formation to construct the benzopyran skele- ton. Key features of this method include its brevity, its preserved stereochemical integrity and two different syn- thetic routes to choose.

  15. A nordehydroabietyl amide-containing chiral diene for rhodium-catalysed asymmetric arylation to nitroolefins.

    Science.gov (United States)

    Li, Ruikun; Wen, Zhongqing; Wu, Na

    2016-11-29

    A highly enantioselective rhodium catalysed asymmetric arylation (RCAA) of nitroolefins with arylboronic acids is presented using a newly developed, C1-symmetric, non-covalent interacted, phellandrene derived, nordehydroabietyl amide-containing chiral diene under mild conditions. Stereoelectronic effects were studied, suggesting an activation of the bound substrate through the secondary amide as a hydrogen-bond donor.

  16. Recent approaches towards the asymmetric synthesis of α,α-disubstituted α-amino acids

    DEFF Research Database (Denmark)

    Vogt, Henning; Brase, S.

    2007-01-01

    The class of alpha,alpha-disubstituted alpha-amino acids has gained considerable attention in the past decades and continues doing so. The ongoing interest in biological and chemical properties of the substance class has inspired the development of many new methodologies for their asymmetric...

  17. Enantioconvergent synthesis by sequential asymmetric Horner-Wadsworth-Emmons and palladium-catalyzed allylic substitution reactions

    DEFF Research Database (Denmark)

    Pedersen, Torben Møller; Hansen, E. Louise; Kane, John

    2001-01-01

    A new method for enantioconvergent synthesis has been developed. The strategy relies on the combination of an asymmetric Horner-Wadsworth-Emmons (HWE) reaction and a palladium-catalyzed allylic substitution. Different $alpha@-oxygen-substituted, racemic aldehydes were initially transformed...

  18. Asymmetric Reprogramming Capacity of Parental Pronuclei in Mouse Zygotes

    Directory of Open Access Journals (Sweden)

    Wenqiang Liu

    2014-03-01

    Full Text Available It has been demonstrated that reprogramming factors are sequestered in the pronuclei of zygotes after fertilization, because zygotes enucleated at the M phase instead of interphase of the first mitosis can support the development of cloned embryos. However, the contribution of the parental pronucleus derived from either the sperm or the oocyte in reprogramming remains elusive. Here, we demonstrate that the parental pronuclei have asymmetric reprogramming capacities and that the reprogramming factors reside predominantly in the male pronucleus. As a result, only female pronucleus-depleted (FPD mouse zygotes can reprogram somatic cells to a pluripotent state and support the full-term development of cloned embryos; male pronucleus-depleted (MPD zygotes fail to support somatic cell reprogramming. We further demonstrate that fusion of an additional male pronucleus into a zygote greatly enhances reprogramming efficiency. Our data provide a clue to further identify critical reprogramming factors in the male pronucleus.

  19. Ofd1 controls dorso-ventral patterning and axoneme elongation during embryonic brain development.

    Directory of Open Access Journals (Sweden)

    Anna D'Angelo

    Full Text Available Oral-facial-digital type I syndrome (OFDI is a human X-linked dominant-male-lethal developmental disorder caused by mutations in the OFD1 gene. Similar to other inherited disorders associated to ciliary dysfunction OFD type I patients display neurological abnormalities. We characterized the neuronal phenotype that results from Ofd1 inactivation in early phases of mouse embryonic development and at post-natal stages. We determined that Ofd1 plays a crucial role in forebrain development, and in particular, in the control of dorso-ventral patterning and early corticogenesis. We observed abnormal activation of Sonic hedgehog (Shh, a major pathway modulating brain development. Ultrastructural studies demonstrated that early Ofd1 inactivation results in the absence of ciliary axonemes despite the presence of mature basal bodies that are correctly orientated and docked. Ofd1 inducible-mediated inactivation at birth does not affect ciliogenesis in the cortex, suggesting a developmental stage-dependent role for a basal body protein in ciliogenesis. Moreover, we showed defects in cytoskeletal organization and apical-basal polarity in Ofd1 mutant embryos, most likely due to lack of ciliary axonemes. Thus, the present study identifies Ofd1 as a developmental disease gene that is critical for forebrain development and ciliogenesis in embryonic life, and indicates that Ofd1 functions after docking and before elaboration of the axoneme in vivo.

  20. Neonatal Imitation in Context: Sensory-Motor Development in the Perinatal Period.

    Science.gov (United States)

    Keven, Nazim; Akins, Kathleen A

    2016-07-14

    Over 35 years ago, Meltzoff and Moore (1977) published their famous article 'Imitation of facial and manual gestures by human neonates'. Their central conclusion, that neonates can imitate, was and continues to be controversial. Here we focus on an often neglected aspect of this debate, namely on neonatal spontaneous behaviors themselves. We present a case study of a paradigmatic orofacial 'gesture', namely tongue protrusion and retraction (TP/R). Against the background of new research on mammalian aerodigestive development, we ask: How does the human aerodigestive system develop and what role does TP/R play in the neonate's emerging system of aerodigestion? We show that mammalian aerodigestion develops in two phases: (1) from the onset of isolated orofacial movements in utero to the post-natal mastery of suckling at 4 months after birth, and; (2) thereafter, from preparation to the mastery of mastication and deglutition of solid foods. Like other orofacial stereotypies, TP/R emerges in the first phase and vanishes prior to the second. Based upon recent advances in activity-driven early neural development, we suggest a sequence of three developmental events in which TP/R might participate: the acquisition of tongue control, the integration of the central pattern generator for TP/R with other aerodigestive CPGs, and the formation of connections within the cortical maps of S1 and M1. If correct, orofacial stereotypies are crucial to the maturation of aerodigestion in the neonatal period but also unlikely to co-occur with imitative behavior.

  1. Asymmetric-Structure Analysis of Carbon and Energy Markets

    Science.gov (United States)

    Xu, Wei; Cao, Guangxi

    2016-02-01

    This study aimed to investigate the asymmetric structure between the carbon and energy markets from two aspects of different trends (up or down) and volatility-transmission direction using asymmetric detrended cross-correlation analysis (DCCA) cross-correlation coefficient test, multifractal asymmetric DCCA (MF-ADCCA) method, asymmetric volatility-constrained correlation metric and time rate of information-flow approach. We sampled 1283 observations from January 2008 to December 2012 among pairs of carbon and energy markets for analysis. Empirical results show that the (1) asymmetric characteristic from the cross-correlation between carbon and returns in the energy markets is significant, (2) asymmetric cross-correlation between carbon and energy market price returns is persistent and multifractral and (3) volatility of the base assets of energy market returns is more influential to the base asset of the carbon market than that of the energy market.

  2. Effect of asymmetric strain relaxation on dislocation relaxation processes in heteroepitaxial semiconductors

    Science.gov (United States)

    Andersen, D.; Hull, R.

    2017-02-01

    The effect of asymmetric interfacial strain configurations upon the generation of misfit dislocation arrays in lattice mismatched epitaxy is considered. For example, elastic strain relaxation for Si1-xGex/Si(110) films is uniaxial, assuming glide on {111} planes as expected for the diamond cubic system, which leads to asymmetric strain relief. Here, we extend our previously developed relaxation model for generation of dislocation arrays in SiGe/Si, by accounting for how the different energetics of asymmetrically strained films affect the kinetics of the relaxation process. Similarly, non-polar III-nitride epitaxial films have asymmetric strain from the outset of growth due to the different c/a lattice parameter ratios. In both systems, the asymmetric strain is represented by an additional term in the misfit dislocation applied stress equation. In SiGe/Si(110), a simple elasticity analysis of the strain produced by the uniaxial array of dislocations predicts that the relaxation orthogonal to the dislocation line direction occurs at a faster rate than predicted by purely biaxial strain relief due to the contributions of the strain parallel to the dislocations. This difference is because the strain parallel to the dislocation line directions continues to resolve stress onto the misfit dislocations even as the orthogonal strain is minimized. As a result, the minimum strain energy is predicted to occur for a dislocation spacing, which produces tensile layer strain in the orthogonal direction. Such tensile strain may modify the (opto)electronic properties of a Si, Ge, or GeSi epilayer but is only predicted to occur for advanced stages of relaxation. These asymmetric derivations are applicable to any thin film system where strain is not strictly biaxial.

  3. Quantum optics of lossy asymmetric beam splitters

    Science.gov (United States)

    Uppu, Ravitej; Wolterink, Tom A. W.; Tentrup, Tristan B. H.; Pinkse, Pepijn W. H.

    2016-07-01

    We theoretically investigate quantum interference of two single photons at a lossy asymmetric beam splitter, the most general passive 2$\\times$2 optical circuit. The losses in the circuit result in a non-unitary scattering matrix with a non-trivial set of constraints on the elements of the scattering matrix. Our analysis using the noise operator formalism shows that the loss allows tunability of quantum interference to an extent not possible with a lossless beam splitter. Our theoretical studies support the experimental demonstrations of programmable quantum interference in highly multimodal systems such as opaque scattering media and multimode fibers.

  4. Improved DFIG Capability during Asymmetrical Grid Faults

    DEFF Research Database (Denmark)

    Zhou, Dao; Blaabjerg, Frede

    2015-01-01

    the natural component of the Doubly-Fed Induction Generator (DFIG) stator flux during the fault period, their effects on the rotor voltage can be investigated. It is concluded that the phase-to-phase fault has the worst scenario due to its highest introduction of the negative stator flux. Afterwards......, the capability of a 2 MW DFIG to ride through asymmetrical grid faults can be estimated at the existing design of the power electronics converter. Finally, a control scheme aimed to improve the DFIG capability is proposed and the simulation results validate its feasibility....

  5. Resonance phenomena for asymmetric weakly nonlinear oscillator

    Institute of Scientific and Technical Information of China (English)

    钱定边

    2002-01-01

    We establish the coexistence of periodic solution and unbounded solution, the infinity of largeamplitude subharmonics for asymmetric weakly nonlinear oscillator x" + a2x+ - b2x- + h(x) = p(t) with h(±∞) - 0 and xh(x) → +∞(x →∞), assuming that M(τ ) has zeros which are all simple and M(τ ) 0respectively, where M(τ ) is a function related to the piecewise linear equation x" + a2x+ - b2x- = p(t).``

  6. On asymmetric causal relationships in Petropolitics

    Directory of Open Access Journals (Sweden)

    Balan Feyza

    2016-01-01

    Full Text Available The aim of this paper is to examine whether the First Law of Petropolitics denominated by Friedman in 2006 is valid for OPEC countries. To do this, this paper analyses the relationship between political risk and oil supply by applying the asymmetric panel causality test suggested by Hatemi-J (2011 to these countries for the period 1984-2014. The results show that the First Law of Petropolitics is valid for Angola, Iraq, Kuwait, Libya, Nigeria, Qatar, Saudi Arabia, and the UAE, given that positive oil supply shocks significantly lead to negative political stability shocks, and negative oil supply shocks significantly lead to positive shocks in political stability.

  7. Quantum optics of lossy asymmetric beam splitters

    CERN Document Server

    Uppu, Ravitej; Tentrup, Tristan B H; Pinkse, Pepijn W H

    2016-01-01

    We theoretically investigate quantum interference of two single photons at a lossy asymmetric beam splitter, the most general passive 2$\\times$2 optical circuit. The losses in the circuit result in a non-unitary scattering matrix with a non-trivial set of constraints on the elements of the scattering matrix. Our analysis using the noise operator formalism shows that the loss allows tunability of quantum interference to an extent not possible with a lossless beam splitter. Our theoretical studies support the experimental demonstrations of programmable quantum interference in highly multimodal systems such as opaque scattering media and multimode fibers.

  8. Asymmetric chemical reactions by polarized quantum beams

    Science.gov (United States)

    Takahashi, Jun-Ichi; Kobayashi, Kensei

    One of the most attractive hypothesis for the origin of homochirality in terrestrial bio-organic compounds (L-amino acid and D-sugar dominant) is nominated as "Cosmic Scenario"; a chiral impulse from asymmetric excitation sources in space triggered asymmetric reactions on the surfaces of such space materials as meteorites or interstellar dusts prior to the existence of terrestrial life. 1) Effective asymmetric excitation sources in space are proposed as polarized quantum beams, such as circularly polarized light and spin polarized electrons. Circularly polarized light is emitted as synchrotron radiation from tightly captured electrons by intense magnetic field around neutron stars. In this case, either left-or right-handed polarized light can be observed depending on the direction of observation. On the other hand, spin polarized electrons is emitted as beta-ray in beta decay from radioactive nuclei or neutron fireballs in supernova explosion. 2) The spin of beta-ray electrons is longitudinally polarized due to parity non-conservation in the weak interaction. The helicity (the the projection of the spin onto the direction of kinetic momentum) of beta-ray electrons is universally negative (left-handed). For the purpose of verifying the asymmetric structure emergence in bio-organic compounds by polarized quantum beams, we are now carrying out laboratory simulations using circularly polarized light from synchrotron radiation facility or spin polarized electron beam from beta-ray radiation source. 3,4) The target samples are solid film or aqueous solution of racemic amino acids. 1) K.Kobayashi, K.Kaneko, J.Takahashi, Y.Takano, in Astrobiology: from simple molecules to primitive life; Ed. V.Basiuk; American Scientific Publisher: Valencia, 2008. 2) G.A.Gusev, T.Saito, V.A.Tsarev, A.V.Uryson, Origins Life Evol. Biosphere. 37, 259 (2007). 3) J.Takahashi, H.Shinojima, M.Seyama, Y.Ueno, T.Kaneko, K.Kobayashi, H.Mita, M.Adachi, M.Hosaka, M.Katoh, Int. J. Mol. Sci. 10, 3044

  9. RHIC operation with asymmetric collisions in 2015

    Energy Technology Data Exchange (ETDEWEB)

    Liu, C. [Brookhaven National Lab. (BNL), Upton, NY (United States); Aschenauer, C. [Brookhaven National Lab. (BNL), Upton, NY (United States); Atoian, G. [Brookhaven National Lab. (BNL), Upton, NY (United States); Blaskiewicz, M. [Brookhaven National Lab. (BNL), Upton, NY (United States); Brown, K. A. [Brookhaven National Lab. (BNL), Upton, NY (United States); Bruno, D. [Brookhaven National Lab. (BNL), Upton, NY (United States); Connolly, R. [Brookhaven National Lab. (BNL), Upton, NY (United States); Ottavio, T. D. [Brookhaven National Lab. (BNL), Upton, NY (United States); Drees, K. A. [Brookhaven National Lab. (BNL), Upton, NY (United States); Fischer, W. [Brookhaven National Lab. (BNL), Upton, NY (United States); Gardner, C. J. [Brookhaven National Lab. (BNL), Upton, NY (United States); Gu, X. [Brookhaven National Lab. (BNL), Upton, NY (United States); Hayes, T. [Brookhaven National Lab. (BNL), Upton, NY (United States); Huang, H. [Brookhaven National Lab. (BNL), Upton, NY (United States); Laster, J. S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Luo, Y. [Brookhaven National Lab. (BNL), Upton, NY (United States); Makdisi, Y. [Brookhaven National Lab. (BNL), Upton, NY (United States); Marr, G. [Brookhaven National Lab. (BNL), Upton, NY (United States); Marusic, A. [Brookhaven National Lab. (BNL), Upton, NY (United States); Meot, F. [Brookhaven National Lab. (BNL), Upton, NY (United States); Mernick, K. [Brookhaven National Lab. (BNL), Upton, NY (United States); Michnoff, R. [Brookhaven National Lab. (BNL), Upton, NY (United States); Minty, M. [Brookhaven National Lab. (BNL), Upton, NY (United States); Montag, C. [Brookhaven National Lab. (BNL), Upton, NY (United States); Morris, J. [Brookhaven National Lab. (BNL), Upton, NY (United States); Narayan, G. [Brookhaven National Lab. (BNL), Upton, NY (United States); Nayak, S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Nemesure, S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Pile, P. [Brookhaven National Lab. (BNL), Upton, NY (United States); Poblaguev, A. [Brookhaven National Lab. (BNL), Upton, NY (United States); Ranjbar, V. [Brookhaven National Lab. (BNL), Upton, NY (United States); Robert-Demolaize, G. [Brookhaven National Lab. (BNL), Upton, NY (United States); Roser, T. [Brookhaven National Lab. (BNL), Upton, NY (United States); Schmidke, B. [Brookhaven National Lab. (BNL), Upton, NY (United States); Schoefer, V. [Brookhaven National Lab. (BNL), Upton, NY (United States); Severino, F. [Brookhaven National Lab. (BNL), Upton, NY (United States); Shrey, T. [Brookhaven National Lab. (BNL), Upton, NY (United States); Smith, K. [Brookhaven National Lab. (BNL), Upton, NY (United States); Steski, D. [Brookhaven National Lab. (BNL), Upton, NY (United States); Tepikian, S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Trbojevic, D. [Brookhaven National Lab. (BNL), Upton, NY (United States); Tsoupas, N. [Brookhaven National Lab. (BNL), Upton, NY (United States); Wang, G. [Brookhaven National Lab. (BNL), Upton, NY (United States); White, S. [Brookhaven National Lab. (BNL), Upton, NY (United States); Yip, K. [Brookhaven National Lab. (BNL), Upton, NY (United States); Zaltsman, A. [Brookhaven National Lab. (BNL), Upton, NY (United States); Zeno, K. [Brookhaven National Lab. (BNL), Upton, NY (United States); Zhang, S. Y. [Brookhaven National Lab. (BNL), Upton, NY (United States)

    2015-08-07

    To study low-x shadowing/saturation physics as well as other nuclear effects [1], [2], proton-gold (p-Au, for 5 weeks) and proton-Aluminum (p-Al, for 2 weeks) collisions were provided for experiments in 2015 at the Relativistic Heavy Ion Collider (RHIC), with polarized proton beam in the Blue ring and Au/Al beam in the Yellow ring. The special features of the asymmetric run in 2015 will be introduced. The operation experience will be reviewed as well in the report.

  10. Photoresponse of silicon with asymmetric area contacts

    Science.gov (United States)

    Rabbani, M. Golam; Sundararajan, Jency P.; Verma, Amit; Nekovei, Reza; Khader, Mahmoud M.; Darling, R. B.; Patil, Sunil R.

    2017-01-01

    We report on high performance metal-semiconductor-metal (MSM) photosensors based on asymmetric metal pad areas. The reported devices require a single-step metal deposition, and exhibit large photo response even under zero-bias. Moreover the devices offer fast and stable light switching behavior. Device fabrication and electrical characterization results are presented that are further analyzed with TCAD modeling and simulation. Device simulations show that contact asymmetry along with surface recombination and barrier lowering plays an important role in the MSM I-V characteristics.

  11. Chiral Diamine-catalyzed Asymmetric Aldol Reaction

    Institute of Scientific and Technical Information of China (English)

    LI Hui; XU Da-zhen; WU Lu-lu; WANG Yong-mei

    2012-01-01

    A highly efficient catalytic system composed of a simple and commercially available chiral primary diamine (1R,2R)-cyclohexane-1,2-diamine(6) and trifluoroacetic acid(TFA) was employed for asymmetric Aldol reaction in i-PrOH at room temperature.A loading of 10%(molar fraction) catalyst 6 with TFA as a cocatalyst could catalyze the Aldol reactions of various ketones or aldehydes with a series of aromatic aldehydes,furnishing Aldol products in moderate to high yields(up to >99%) with enantioselectivities of up to >99% and diastereoselectivities of up to 99:1.

  12. Asymmetric Synthesis of Both Enantiomers of Disparlure

    Institute of Scientific and Technical Information of China (English)

    王志刚; 郑剑峰; 黄培强

    2012-01-01

    Starting from propargyl alcohol (12), and on the basis of Zhou's modified Sharpless asymmetric epoxidation, the sex pheromone of the Gypsy moth, disparlure (+)-8 and its enantiomer (-)-8 have been synthesized, each in six steps, with overall yields of 29% for (+)-8 and 27% for (-)-8 (ee〉98%). The use of the sequential coupling tactic renders the method flexible, which is applicable to the synthesis of other cis-epoxy pheromones.

  13. Nanotribology of Symmetric and Asymmetric Liquid Lubricants

    Directory of Open Access Journals (Sweden)

    Shinji Yamada

    2010-03-01

    Full Text Available When liquid molecules are confined in a narrow gap between smooth surfaces, their dynamic properties are completely different from those of the bulk. The molecular motions are highly restricted and the system exhibits solid-like responses when sheared slowly. This solidification behavior is very dependent on the molecular geometry (shape of liquids because the solidification is induced by the packing of molecules into ordered structures in confinement. This paper reviews the measurements of confined structures and friction of symmetric and asymmetric liquid lubricants using the surface forces apparatus. The results show subtle and complex friction mechanisms at the molecular scale.

  14. Asymmetric acoustic transmission in graded beam

    Science.gov (United States)

    Jing, Li; Wu, Jiu Hui; Guan, Dong; Lu, Kuan; Gao, Nansha; Songhua, Cao

    2016-12-01

    We demonstrate the dynamic effective material parameters and vibration performance of a graded beam. The structure of the beam was composed of several unit cells with different fill factors. The dispersion relations and energy band structures of each unit cell were calculated using the finite element method (FEM). The dynamic effective material parameters in each unit cell of the graded beam were determined by the dispersion relations and energy band structures. Longitudinal wave propagation was investigated using a numerical method and FEM. The results show that the graded beam allows asymmetric acoustic transmission over a wide range of frequencies.

  15. An Asymmetric Block Dynamic Conditional Correlation Multivariate GARCH Model

    OpenAIRE

    Vargas, Gregorio A.

    2006-01-01

    The Block DCC model for determining dynamic correlations within and between groups of financial asset returns is extended to account for asymmetric effects. Simulation results show that the Asymmetric Block DCC model is competitive in in-sample forecasting and performs better than alternative DCC models in out-of-sample forecasting of conditional correlation in the presence of asymmetric effect between blocks of asset returns. Empirical results demonstrate that the model is able to capture ...

  16. Asymmetric joint multifractal analysis in Chinese stock markets

    Science.gov (United States)

    Chen, Yuwen; Zheng, Tingting

    2017-04-01

    In this paper, the asymmetric joint multifractal analysis method based on statistical physics is proposed to explore the asymmetric correlation between daily returns and trading volumes in Chinese stock markets. The result shows asymmetric multifractal correlations exist between return and trading volume in Chinese stock markets. Moreover, when the stock indexes are upward, the fluctuations of returns are always weaker than when they are downward, whether the trading volumes are more or less.

  17. Asymmetric Campaigning as a Rational Choice: Planning Considerations

    Science.gov (United States)

    2006-06-01

    Maslow identified five levels: survival, safety, belonging, esteem, and self-actualization. He presented his theory as a pyramid with five layers...to be sustained by actions of the asymmetric opponent. For the media-fed frenzy over constraints and protraction to continue, the asymmetric...lot of people. The reason for this is twofold. First, the actor needs sufficient support to exist and to sustain an asymmetric campaign. Second, the

  18. Asymmetric transmission: a generic property of lossy periodic interfaces

    CERN Document Server

    Plum, E; Zheludev, N I

    2010-01-01

    Asymmetric transmission of circularly polarized waves is a well-established property of lossy, anisotropic, two-dimensionally chiral patterns. Here we show that asymmetric transmission can be observed for oblique incidence onto any lossy periodically structured plane. Our results greatly expand the range of natural and artificial materials in which directionally asymmetric transmission can be expected making it a cornerstone electromagnetic effect rather than a curiosity of planar chiral metamaterials. Prime candidates for asymmetric transmission at oblique incidence are rectangular arrays of plasmonic spheres or semiconductor quantum dots, lossy double-periodic gratings and planar metamaterial structures.

  19. Quantity Discount Scheme in Supply Chain under Asymmetric Information

    Institute of Scientific and Technical Information of China (English)

    LI Ji-bin; PENG Zuo-he

    2007-01-01

    Quantity discount scheme plays an important role in supply chain management. The different quantity discount schemes under symmetric (full) information and asymmetric information, are analyzed by using principal-agent and optimal control theory. As a result, the research reveals that the optimal quantity discount solution under symmetric information is a special case of that under asymmetric information. At the same price, the critical value of quantity discount under asymmetric information is much lower than that under asymmetric information. Therefore, this leads to less cost for retailers and smaller profit for their supplier.

  20. Asymmetric and axisymmetric dynamics of tropical cyclones

    Directory of Open Access Journals (Sweden)

    J. Persing

    2013-05-01

    into annular rings, the azimuthally-averaged heating rate and radial gradient thereof is considerably less than that in the AX model. This lack of organization results broadly in a slower intensification rate in the 3-D model and leads ultimately to a weaker mature vortex after 12 days of model integration. While axisymmetric heating rates in the 3-D model are weaker than those in the AX model, local heating rates in the 3-D model exceed those in the AX model and at times the vortex in the 3-D model intensifies more rapidly than AX. Analyses of the 3-D model output do not support a recent hypothesis concerning the key role of small-scale vertical mixing processes in the upper-tropospheric outflow in controlling the intensification process. In the 3-D model, surface drag plays a particularly important role in the intensification process for the prototype intensification problem on meteorologically relevant time scales by helping foster the organization of convection in azimuth. There is a radical difference in the behaviour of the 3-D and AX simulations when the surface drag is reduced or increased from realistic values. Borrowing from ideas developed in a recent paper, we give a partial explanation for this difference in behaviour. Our results provide new qualitative and quantitative insight into the differences between the asymmetric and symmetric dynamics of tropical cyclones and would appear to have important consequences for the formulation of a fluid dynamical theory of tropical cyclone intensification and mature intensity. In particular, the results point to some fundamental limitations of strict axisymmetric theory and modelling for representing the azimuthally-averaged behaviour of tropical cyclones in three dimensions.

  1. Asymmetric disassembly and robustness in declining networks.

    Science.gov (United States)

    Saavedra, Serguei; Reed-Tsochas, Felix; Uzzi, Brian

    2008-10-28

    Mechanisms that enable declining networks to avert structural collapse and performance degradation are not well understood. This knowledge gap reflects a shortage of data on declining networks and an emphasis on models of network growth. Analyzing >700,000 transactions between firms in the New York garment industry over 19 years, we tracked this network's decline and measured how its topology and global performance evolved. We find that favoring asymmetric (disassortative) links is key to preserving the topology and functionality of the declining network. Based on our findings, we tested a model of network decline that combines an asymmetric disassembly process for contraction with a preferential attachment process for regrowth. Our simulation results indicate that the model can explain robustness under decline even if the total population of nodes contracts by more than an order of magnitude, in line with our observations for the empirical network. These findings suggest that disassembly mechanisms are not simply assembly mechanisms in reverse and that our model is relevant to understanding the process of decline and collapse in a broad range of biological, technological, and financial networks.

  2. Algebraic Davis Decomposition and Asymmetric Doob Inequalities

    Science.gov (United States)

    Hong, Guixiang; Junge, Marius; Parcet, Javier

    2016-09-01

    In this paper we investigate asymmetric forms of Doob maximal inequality. The asymmetry is imposed by noncommutativity. Let {({M}, τ)} be a noncommutative probability space equipped with a filtration of von Neumann subalgebras {({M}_n)_{n ≥ 1}}, whose union {bigcup_{n≥1}{M}_n} is weak-* dense in {{M}}. Let {{E}_n} denote the corresponding family of conditional expectations. As an illustration for an asymmetric result, we prove that for {1 spaces {{H}_p^r({M})} and {{H}_p^c({M})} respectively. In particular, this solves a problem posed by the Defant and Junge in 2004. In the case p = 1, our results establish a noncommutative form of the Davis celebrated theorem on the relation betwe en martingale maximal and square functions in L 1, whose noncommutative form has remained open for quite some time. Given {1 ≤ p ≤ 2}, we also provide new weak type maximal estimates, which imply in turn left/right almost uniform convergence of {{E}_n(x)} in row/column Hardy spaces. This improves the bilateral convergence known so far. Our approach is based on new forms of Davis martingale decomposition which are of independent interest, and an algebraic atomic description for the involved Hardy spaces. The latter results are new even for commutative von Neumann algebras.

  3. Asymmetric DSL Technology of Signal Transmission

    Directory of Open Access Journals (Sweden)

    Dražen Kovačević

    2005-05-01

    Full Text Available Asymmetric flow of information is the key feature of theADSL (Asymmetric Digital Subscriber Loop technology, i.e.higher data transmission rate towards the user than from theuser towards the network. Characteristic is the short messagesending by the user with a certain request to the se!Ver. These!Ver responds to the request by a significantly longer messageof various electronic forms (data, digitized speech, pictures orvideo. Therefore, this technology is most often used by smalland medium users. ADSL is currently the only commerciallyavailable DSL technology which is still experiencing the breakthroughon the seiVice market. It enables faster access to theInternet, LAN (Local Area Network, videoconferencing, VoD(Video on Demand and interactive multimedia. In order tostandardize such se/Vices, the !TU (International TelecommunicationsUnion G. 992.1 (standardized DMT-discrete multi-tone line coding technology and ANSJ (American NationalStandards Institution Tl.413-95!98 are used for ADSL. DMT(Discrete Multi Tone, as the more popular one, uses the linecoding technique, which splits a certain frequency range intoseveral sub-channels. Most of these sub-channels are used forupstream and downstream transmission of speech and data,whereas some are used as pilot signals or kept in rese/Ve. Suchmodulation technique expands the frequency spectrum, allowingthe usage ofbroadband se/Vices per one pair of wires. In thisway the sharing of speech and data se/Vice transmission is realized.

  4. An asymmetric B factory based on PEP

    Energy Technology Data Exchange (ETDEWEB)

    1991-02-01

    In this report we describe a design for a high-luminosity Asymmetric B Factory to be built in the PEP tunnel on the SLAC site. This proposal, a collaborative effort SLAC, LBL, and LLNL, is the culmination of more than two years of effort aimed at the design and construction of an asymmetric e{sup +}e{sup {minus}} collider capable of achieving a luminosity of L = 3 {times} 10{sup 33} cm{sup {minus}2} s{sup {minus}1}. The configuration adopted utilizes two storage rings, and electron ring operating at 9 GeV and a positron ring at 3.1 GeV, each with a circumference of 2200 m. The high-energy ring is an upgrade of the PEP storage ring at SLAC; all PEP magnets and most power supplies will be reused. The upgrade consists primarily of replacing the PEP vacuum chamber and RF system with newly designed versions optimized for the high-current environment of the B Factory. The low-energy ring will be newly constructed and will be situated atop the high-energy ring in the PEP tunnel. Utilities already installed in the PEP tunnel are largely sufficient to operate the two B Factory storage rings.

  5. Evolutionary stability in the asymmetric volunteer's dilemma.

    Directory of Open Access Journals (Sweden)

    Jun-Zhou He

    Full Text Available It is often assumed that in public goods games, contributors are either strong or weak players and each individual has an equal probability of exhibiting cooperation. It is difficult to explain why the public good is produced by strong individuals in some cooperation systems, and by weak individuals in others. Viewing the asymmetric volunteer's dilemma game as an evolutionary game, we find that whether the strong or the weak players produce the public good depends on the initial condition (i.e., phenotype or initial strategy of individuals. These different evolutionarily stable strategies (ESS associated with different initial conditions, can be interpreted as the production modes of public goods of different cooperation systems. A further analysis revealed that the strong player adopts a pure strategy but mixed strategies for the weak players to produce the public good, and that the probability of volunteering by weak players decreases with increasing group size or decreasing cost-benefit ratio. Our model shows that the defection probability of a "strong" player is greater than the "weak" players in the model of Diekmann (1993. This contradicts Selten's (1980 model that public goods can only be produced by a strong player, is not an evolutionarily stable strategy, and will therefore disappear over evolutionary time. Our public good model with ESS has thus extended previous interpretations that the public good can only be produced by strong players in an asymmetric game.

  6. At Low SNR Asymmetric Quantizers Are Better

    CERN Document Server

    Koch, Tobias

    2012-01-01

    We study the capacity of the discrete-time Gaussian channel when its output is quantized with a one-bit quantizer. We focus on the low signal-to-noise ratio (SNR) regime, where communication at very low spectral efficiencies takes place. In this regime a symmetric threshold quantizer is known to reduce channel capacity by 2/pi, i.e., to cause an asymptotic power loss of approximately two decibels. Here it is shown that this power loss can be entirely avoided by using asymmetric threshold quantizers and asymmetric signaling constellations. We prove that in order to avoid this power loss flash-signaling input-distributions are essential. Consequently, one-bit output quantization of the Gaussian channel reduces spectral efficiency. Threshold quantizers are not only asymptotically optimal: as we prove, at every fixed SNR, a threshold quantizer maximizes capacity among all one-bit output quantizers. The picture changes on the Rayleigh-fading channel. In the noncoherent case we show that a one-bit output quantizer ...

  7. Asymmetric transition disks: Vorticity or eccentricity?

    CERN Document Server

    Zsom, A; Ghanbari, J

    2013-01-01

    Context. Transition disks typically appear in resolved millimeter observations as giant dust rings surrounding their young host stars. More accurate observations with ALMA have shown several of these rings to be in fact asymmetric: they have lopsided shapes. It has been speculated that these rings act as dust traps, which would make them important laboratories for studying planet formation. It has been shown that an elongated giant vortex produced in a disk with a strong viscosity jump strikingly resembles the observed asymmetric rings. Aims. We aim to study a similar behavior for a disk in which a giant planet is embedded. However, a giant planet can induce two kinds of asymmetries: (1) a giant vortex, and (2) an eccentric disk. We studied under which conditions each of these can appear, and how one can observationally distinguish between them. This is important because only a vortex can trap particles both radially and azimuthally, while the eccentric ring can only trap particles in radial direction. Method...

  8. Properties of asymmetrically evolved community networks

    Institute of Scientific and Technical Information of China (English)

    Cui Di; Gao Zi-You; Zheng Jian-Feng

    2009-01-01

    This paper studies a simple asymmetrically evolved community network with a combination of preferential at-tachment and random properties. An important issue about community networks is to discover the different utility increments of two nodes, where the utility is introduced to investigate the asymmetrical effect of connecting two nodes. On the other hand, the connection of two nodes in community networks can be classified as two nodes belonging to the same or to different communities. The simulation results show that the model can reproduce a power-law utility distribution P(u)~ u-σ,σ=2+ 1/p, which can be obtained by using mean-field approximation methods. Furthermore, the model exhibits exponential behaviour with respect to small values of a parameter denoting the random effect in our model at the low-utility region and a power-law feature with respect to big values of this parameter at the high-utility region, which is in good agreement with theoretical analysis. This kind of community network can reproduce a unique utility distribution by theoretical and numerical analysis.

  9. Survey of Reflection-Asymmetric Nuclear Deformations

    Science.gov (United States)

    Olsen, Erik; Cao, Yuchen; Nazarewicz, Witold; Schunck, Nicolas

    2016-09-01

    Due to spontaneous symmetry breaking it is possible for a nucleus to have a deformed shape in its ground state. It is theorized that atoms whose nuclei have reflection-asymmetric or pear-like deformations could have non-zero electric dipole moments (EDMs). Such a trait would be evidence of CP-violation, a feature that goes beyond the Standard Model of Physics. It is the purpose of this project to predict which nuclei exhibit a reflection-asymmetric deformation and which of those would be the best candidates for an EDM measuring experiment. Using nuclear Density Functional Theory along with the new computer code AxialHFB and massively parallel computing we calculated ground state nuclear properties for thousands of even-even nuclei across the nuclear chart: from light to superheavy and from stable to short-lived systems. Six different Energy Density Functionals (EDFs) were used to assess systematic errors in our calculations. These results are to be added to the website Massexplorer (http://massexplorer.frib.msu.edu/) which contains results from earlier mass table calculations and information on single quasiparticle energies.

  10. Collocation method for the solution of the neutron transport equation with both symmetric and asymmetric scattering

    Energy Technology Data Exchange (ETDEWEB)

    Morel, J.E.

    1981-01-01

    A collocation method is developed for the solution of the one-dimensional neutron transport equation in slab geometry with both symmetric and polarly asymmetric scattering. For the symmetric scattering case, it is found that the collocation method offers a combination of some of the best characteristics of the finite-element and discrete-ordinates methods. For the asymmetric scattering case, it is found that the computational cost of cross-section data processing under the collocation approach can be significantly less than that associated with the discrete-ordinates approach. A general diffusion equation treating both symmetric and asymmetric scattering is developed and used in a synthetic acceleration algorithm to accelerate the iterative convergence of collocation solutions. It is shown that a certain type of asymmetric scattering can radically alter the asymptotic behavior of the transport solution and is mathematically equivalent within the diffusion approximation to particle transport under the influence of an electric field. The method is easily extended to other geometries and higher dimensions. Applications exist in the areas of neutron transport with highly anisotropic scattering (such as that associated with hydrogenous media), charged-particle transport, and particle transport in controlled-fusion plasmas. 23 figures, 6 tables.

  11. Asymmetric-shell ignition capsule design to tune the low-mode asymmetry during the peak drive

    Science.gov (United States)

    Gu, Jianfa; Dai, Zhensheng; Song, Peng; Zou, Shiyang; Ye, Wenhua; Zheng, Wudi; Gu, Peijun; Wang, Jianguo; Zhu, Shaoping

    2016-08-01

    The low-mode radiation flux asymmetry in the hohlraum is a main source of performance degradation in the National Ignition Facility (NIF) implosion experiments. To counteract the deleterious effects of the large positive P2 flux asymmetry during the peak drive, this paper develops a new tuning method called asymmetric-shell ignition capsule design which adopts the intentionally asymmetric CH ablator layer or deuterium-tritium (DT) ice layer. A series of two-dimensional implosion simulations have been performed, and the results show that the intentionally asymmetric DT ice layer can significantly improve the fuel ρR symmetry, hot spot shape, hot spot internal energy, and the final neutron yield compared to the spherical capsule. This indicates that the DT asymmetric-shell capsule design is an effective tuning method, while the CH ablator asymmetric-shell capsule could not correct the fuel ρR asymmetry, and it is not as effective as the DT asymmetric-shell capsule design.

  12. [Dynamics of symmetric and asymmetric mitosis and cytokinesis].

    Science.gov (United States)

    Kaczanowska, Janina; Kaczanowski, Andrzej

    2010-01-01

    During cell division the bipolar microtubular mitotic spindle ensures faithful segregation of daughter chromosomes and appearance of the cytokinetic membrane in an equatorial area separating genetically identical daughter cells. This process proceeds in consecutive morphological stages of prophase, metaphase, anaphase and cytokinesis. The progress in embryology and oncology concerns the new data about intervening mechanisms of rotation of a bipolar spindle in prophase and the change of the position of a mitotic spindle in anaphase that result in an asymmetric and differential mitoses. The aim of this review is a discussion of some of molecular and signaling mechanisms which regulate position of mitotic spindles in different types of cells. It turns out that the knowledge of receptor-dependent and receptor-independent molecular mechanisms controlling geometry and localization of cytokinesis in some human cells and in early stages of development of C. elegans opens the new important research fields.

  13. A model for asymmetric magnetoimpedance effect in multilayered bimagnetic films

    Science.gov (United States)

    Buznikov, N. A.; Antonov, A. S.

    2016-12-01

    The magnetoimpedance in three-layered bimagnetic film structure is studied theoretically. The structure consists of the soft and hard magnetic films separated by highly conductive non-magnetic layer. A model to describe the magnetoimpedance effect in the film structure based on a simultaneous solution of linearized Maxwell equations and Landau-Lifshitz equation is proposed. It is shown that magnetostatic coupling between the magnetic layers results in the asymmetry in the field dependence of the film impedance. The magnetostatic coupling is described in terms of an effective bias field appearing in the soft magnetic layer. The calculated field and frequency dependences of the film impedance are shown to be in a qualitative agreement with previous results of experimental studies of the asymmetric magnetoimpedance in NiFe/Cu/Co film structures. The results obtained may be useful for development of weak magnetic-field sensors.

  14. Very-short-pulse modulator using asymmetric thyristors

    Science.gov (United States)

    Perol, P.

    1984-09-01

    The development of a semiconductor delay-line modulator for a 40-nsec/pulse 10-kHz-repetition-rate coaxial magnetron radar used to monitor airport runway traffic is reported and illustrated with circuit diagrams, output spectra, and photographs. The problems presented by the design specifications are indicated, and the solutions adopted (asymmetric press-packed thyristors and ferrite pulse transformer) are explained. Pulse widths and peak powers with 16 nf of delay line and a 2.5-kV charge at the level of the modulator are found to be 120 nsec and 58 kW without truncation and 40 nsec and 50-51 kW with truncation, the latter corresponding to an efficiency of 17 percent. The pulse leading edges have dI/dt at the transformer primary = 1.8 kA/microsec and dV/dt at the magnetron = 160 kV/microsec.

  15. Asymmetric Supercapacitor for Long-Duration Power Storage

    Science.gov (United States)

    Rangan, Krishnaswamy K.; Sudarshan, Tirumalai S.

    2012-01-01

    A document discusses a project in which a series of novel hybrid positive electrode materials was developed and tested in asymmetric capacitors with carbon negative electrodes. The electrochemical performance of the hybrid capacitors was characterized by cyclic voltammetry and a DC charge/discharge test. The hybrid capacitor exhibited ideal capacitor behavior with an extended operating voltage of 1.6 V in aqueous electrolyte, and energy density higher than activated carbon-based supercapacitors. Nanostructured MnO2 is a promising material for electrochemical capacitors (ECS) because of its low cost, environmentally friendly nature, and reasonably high specific capacitance. The charge capacity of the capacitors can be further improved by increasing the specific surface area of the MnO2 electrode material. The power density and space radiation stability of the capacitors can be enhanced by coating the MnO2 nanoparticles with conducting polymers. The conducting polymer coating also helps in radiation-hardening the ECS.

  16. Biomimetically inspired asymmetric total synthesis of (+)-19-dehydroxyl arisandilactone A

    Science.gov (United States)

    Han, Yi-Xin; Jiang, Yan-Long; Li, Yong; Yu, Hai-Xin; Tong, Bing-Qi; Niu, Zhe; Zhou, Shi-Jie; Liu, Song; Lan, Yu; Chen, Jia-Hua; Yang, Zhen

    2017-01-01

    Complex natural products are a proven and rich source of disease-modulating drugs and of efficient tools for the study of chemical biology and drug discovery. The architectures of complex natural products are generally considered to represent significant barriers to efficient chemical synthesis. Here we describe a concise and efficient asymmetric synthesis of 19-dehydroxyl arisandilactone A--which belongs to a family of architecturally unique, highly oxygenated nortriterpenoids isolated from the medicinal plant Schisandra arisanensis. This synthesis takes place by means of a homo-Michael reaction, a tandem retro-Michael/Michael reaction, and Cu-catalysed intramolecular cyclopropanation as key steps. The proposed mechanisms for the homo-Michael and tandem retro-Michael/Michael reactions are supported by density functional theory (DFT) calculation. The developed chemistry may find application for the synthesis of its other family members of Schisandraceae nortriterpenoids.

  17. Turbulent mixed convection in asymmetrically heated vertical channel

    Directory of Open Access Journals (Sweden)

    Mokni Ameni

    2012-01-01

    Full Text Available In this paper an investigation of mixed convection from vertical heated channel is undertaken. The aim is to explore the heat transfer obtained by adding a forced flow, issued from a flat nozzle located in the entry section of a channel, to the up-going fluid along its walls. Forced and free convection are combined studied in order to increase the cooling requirements. The study deals with both symmetrically and asymmetrically heated channel. The Reynolds number based on the nozzle width and the jet velocity is assumed to be 3 103 and 2.104; whereas, the Rayleigh number based on the channel length and the wall temperature difference varies from 2.57 1010 to 5.15 1012. The heating asymmetry effect on the flow development including the mean velocity and temperature the local Nusselt number, the mass flow rate and heat transfer are examined.

  18. Biomimetically inspired asymmetric total synthesis of (+)-19-dehydroxyl arisandilactone A

    Science.gov (United States)

    Han, Yi-Xin; Jiang, Yan-Long; Li, Yong; Yu, Hai-Xin; Tong, Bing-Qi; Niu, Zhe; Zhou, Shi-Jie; Liu, Song; Lan, Yu; Chen, Jia-Hua; Yang, Zhen

    2017-01-01

    Complex natural products are a proven and rich source of disease-modulating drugs and of efficient tools for the study of chemical biology and drug discovery. The architectures of complex natural products are generally considered to represent significant barriers to efficient chemical synthesis. Here we describe a concise and efficient asymmetric synthesis of 19-dehydroxyl arisandilactone A—which belongs to a family of architecturally unique, highly oxygenated nortriterpenoids isolated from the medicinal plant Schisandra arisanensis. This synthesis takes place by means of a homo-Michael reaction, a tandem retro-Michael/Michael reaction, and Cu-catalysed intramolecular cyclopropanation as key steps. The proposed mechanisms for the homo-Michael and tandem retro-Michael/Michael reactions are supported by density functional theory (DFT) calculation. The developed chemistry may find application for the synthesis of its other family members of Schisandraceae nortriterpenoids. PMID:28139648

  19. The early development of brain white matter: a review of imaging studies in fetuses, newborns and infants.

    Science.gov (United States)

    Dubois, J; Dehaene-Lambertz, G; Kulikova, S; Poupon, C; Hüppi, P S; Hertz-Pannier, L

    2014-09-12

    Studying how the healthy human brain develops is important to understand early pathological mechanisms and to assess the influence of fetal or perinatal events on later life. Brain development relies on complex and intermingled mechanisms especially during gestation and first post-natal months, with intense interactions between genetic, epigenetic and environmental factors. Although the baby's brain is organized early on, it is not a miniature adult brain: regional brain changes are asynchronous and protracted, i.e. sensory-motor regions develop early and quickly, whereas associative regions develop later and slowly over decades. Concurrently, the infant/child gradually achieves new performances, but how brain maturation relates to changes in behavior is poorly understood, requiring non-invasive in vivo imaging studies such as magnetic resonance imaging (MRI). Two main processes of early white matter development are reviewed: (1) establishment of connections between brain regions within functional networks, leading to adult-like organization during the last trimester of gestation, (2) maturation (myelination) of these connections during infancy to provide efficient transfers of information. Current knowledge from post-mortem descriptions and in vivo MRI studies is summed up, focusing on T1- and T2-weighted imaging, diffusion tensor imaging, and quantitative mapping of T1/T2 relaxation times, myelin water fraction and magnetization transfer ratio.

  20. Effects of Space Flight-Associated Stimuli on Development of Murine and Medaka Sensory-Motor Systems

    Science.gov (United States)

    Wolgemuth, Debra J.

    1999-01-01

    The major goal of these studies was to continue investigations into the influence of altered gravitational fields on the development and function of the vertebrate brain and nervous system. Of major focus during the 18-month finding period of this award was the maintenance of the animals used in the experimental mouse and medaka model paradigms. The experiments focused on characterization of stress-sensitive periods in neural development and immediate or delayed effects on gene expression, physiology and behavior. The hypothesis under investigation was that the environment of space will have biologically significant effects on the development and function of the vertebrate nervous system. We have postulated that these effects will be more significant on certain neural compartments, such as the vestibular-motor system, and that these effects will have greater impact at particular stages of embryonic and post-natal development of the animal. Development of the central nervous system is well known for its vulnerability and sensitivity to environmental stimuli, although the effects of gravitational influences are poorly understood. The long-term goals of this research effort, initiated previously and continued in limited capacity during this interim period, were to provide important new information on the effects of altered environments during these critical periods.

  1. Renal Development and Blood Pressure in Offspring from Dams Submitted to High-Sodium Intake during Pregnancy and Lactation

    Directory of Open Access Journals (Sweden)

    Terezila M. Coimbra

    2012-01-01

    Full Text Available Exposure to an adverse environment in utero appears to programme physiology and metabolism permanently, with long-term consequences for health of the fetus or offspring. It was observed that the offspring from dams submitted to high-sodium intake during pregnancy present disturbances in renal development and in blood pressure. These alterations were associated with lower plasma levels of angiotensin II (AII and changes in renal AII receptor I (AT1 and mitogen-activated protein kinase (MAPK expressions during post natal kidney development. Clinical and experimental evidence show that the renin-angiotensin system (RAS participates in renal development. Many effects of AII are mediated through MAPK pathways. Extracellular signal-regulated protein kinases (ERKs play a pivotal role in cellular proliferation and differentiation. In conclusion, high-sodium intake during pregnancy and lactation can provoke disturbances in renal development in offspring leading to functional and structural alterations that persist in adult life. These changes can be related at least in part with the decrease in RAS activity considering that this system has an important role in renal development.

  2. Renal Development and Blood Pressure in Offspring from Dams Submitted to High-Sodium Intake during Pregnancy and Lactation.

    Science.gov (United States)

    Coimbra, Terezila M; Francescato, Heloísa D C; Balbi, Ana Paula C; Marin, Evelyn C S; Costa, Roberto S

    2012-01-01

    Exposure to an adverse environment in utero appears to programme physiology and metabolism permanently, with long-term consequences for health of the fetus or offspring. It was observed that the offspring from dams submitted to high-sodium intake during pregnancy present disturbances in renal development and in blood pressure. These alterations were associated with lower plasma levels of angiotensin II (AII) and changes in renal AII receptor I (AT(1)) and mitogen-activated protein kinase (MAPK) expressions during post natal kidney development. Clinical and experimental evidence show that the renin-angiotensin system (RAS) participates in renal development. Many effects of AII are mediated through MAPK pathways. Extracellular signal-regulated protein kinases (ERKs) play a pivotal role in cellular proliferation and differentiation. In conclusion, high-sodium intake during pregnancy and lactation can provoke disturbances in renal development in offspring leading to functional and structural alterations that persist in adult life. These changes can be related at least in part with the decrease in RAS activity considering that this system has an important role in renal development.

  3. Asymmetric Synthesis of (+)-(11 R,12S)-Mefloquine Hydrochloride

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The asymmetric synthesis of (+)-(11R,12S)-mefloquine hydrochloride, an antimalarial drug, was accomplished from commercially available 2-trifluoromethylaniline, ethyl 4,4,4-trifluoroacetoacetate and cyclopentanone in 7 steps with a 14% overall yield. The key steps were proline-catalyzed asymmetric direct aldol reaction and Beck-mann rearrangement. The absolute configuration was assigned by a Mosher's method.

  4. ASYMMETRIC HYDROSILYLATION CATALYZED BY POLYMER—SUPPORTED THIAZOLIDINE RHODIUM CATALYSTS

    Institute of Scientific and Technical Information of China (English)

    LEIYanohui; LIHong; 等

    1999-01-01

    Asymmetric hydrisilylation catalyzed by polymeric thiazolidine rhodium catalysts was conducted.Almost the same optical yields have been obtained when comb-shaped polymeric ligands and their corresponding monomer complexed rhodium cataltysts were used to asymmetric hydrosilylation of acetophenone.Optical yield of chiral 1-methylbenzyl alcohol reaches as high as 71.5%.Temperature dependence of enantioselective hydrosilylation of acetophenone was discussed.

  5. Extensive Taguchi's Quality Loss Function Based On Asymmetric tolerances

    Institute of Scientific and Technical Information of China (English)

    ZHU Wei; LI Yuan-sheng; LIU Feng

    2004-01-01

    If specification interval is asymmetric, basic specification is the target value of quality characteristics. In this paper Taguchi's quality loss function is applied to describe quality loss based on asymmetric tolerances. The measurement of quality loss which is caused by the deviation of quality characteristics from basic specification is further presented.

  6. Asymmetric Catalytic Reactions Catalyzed by Chiral Titanium Complexes

    Institute of Scientific and Technical Information of China (English)

    FENG XiaoMing

    2001-01-01

    @@ Chiral titanium complexes is very importance catalyst to asymmetric catalytic reactions. A series of catalytic systems based on titanium-chiral ligands complexes has been reported. This presentation will discuss some of our recent progress on asymmetric catalytic reactions catalyzed by chiral titanium complexes.

  7. Asymmetric Catalytic Reactions Catalyzed by Chiral Titanium Complexes

    Institute of Scientific and Technical Information of China (English)

    FENG; XiaoMing

    2001-01-01

    Chiral titanium complexes is very importance catalyst to asymmetric catalytic reactions. A series of catalytic systems based on titanium-chiral ligands complexes has been reported. This presentation will discuss some of our recent progress on asymmetric catalytic reactions catalyzed by chiral titanium complexes.  ……

  8. A new convenient asymmetric approach to herbarumin Ⅲ

    Institute of Scientific and Technical Information of China (English)

    Xue Song Chen; Shi Jun Da; Li Hong Yang; Bo Yan Xu; Zhi Xiang Xie; Ying Li

    2007-01-01

    The asymmetric total synthesis of herbarumin Ⅲ 3, a naturally occurred phytotoxin, along with 8-epi-herbarumin Ⅲ 22, was succeeded in 12 steps from n-butyraldehyde based on Brown's asymmetric allylation, taking modified Julia olefination and Yamaguchi's macro-lactonization as key steps.

  9. Asymmetric catalytic synthesis of the proposed structure of trocheliophorolide B.

    Science.gov (United States)

    Trost, Barry M; Quintard, Adrien

    2012-09-01

    A concise catalytic asymmetric synthesis of the proposed structure of trocheliophorolide B is reported. The synthetic sequence notably features an asymmetric acetaldehyde alkynylation, a Ru-catalyzed alder-ene reaction, and a Zn-ProPhenol ynone aldol condensation. Comparison with the reported data suggests a misassignment of the natural product structure.

  10. Asymmetric group loans, non-assortative matching and adverse selection

    NARCIS (Netherlands)

    Gangopadhyay, Shubhashis; Lensink, Robert

    2014-01-01

    This paper shows that an asymmetric group debt contract, where one borrower co-signs for another, but not vice versa, leads to heterogeneous matching. The analysis suggests that micro finance organizations can achieve the first best by offering asymmetric group contracts. (C) 2014 Elsevier B.V. All

  11. Effect of asymmetric auxin application on Helianthus hypocotyl curvature

    Science.gov (United States)

    Migliaccio, F.; Rayle, D. L.

    1989-01-01

    Indole-3-acetic acid was applied asymmetrically to the hypocotyls of sunflower (Helianthus annuus L.) seedlings. After 5 hours on a clinostat, auxin gradients as small as 1 to 1.3 produced substantial (more than 60 degrees) hypocotyl curvature. This result suggests the asymmetric growth underlying hypocotyl gravitropism can be explained by lateral auxin redistribution.

  12. Computational simulations of asymmetric fluxes of large molecules through gap junction channel pores.

    Science.gov (United States)

    Mondal, Abhijit; Appadurai, Daniel A; Akoum, Nazem W; Sachse, Frank B; Moreno, Alonso P

    2017-01-07

    Gap junction channels are formed out of connexin isoforms, which enable molecule and ion selective diffusion amongst neighboring cells. HeLa cells expressing distinct connexins (Cx) allow the formation of heterotypic channels, where we observed a molecular charge-independent preferential flux of large fluorescent molecules in the Cx45 to Cx43 direction. We hypothesize that the pore's shape is a significant factor along-side charge and transjunctional voltages for this asymmetric flux. To test this hypothesis, we developed a 3D computational model simulating Brownian diffusion of large molecules in a gap junction channel pore. The basic pore contour was derived from x-ray crystallographic structures of Cx43 and Cx26 and approximated using basic geometric shapes. Lucifer yellow dye molecules and cesium counter-ions were modeled as spheres using their respective Stokes radii. Our simulation results from simple diffusion and constant concentration gradient experiments showed that only charged particles yield asymmetric fluxes in heterotypic pores. While increasing the inner mouth size resulted in a near-quadratic rise in flux, the rise was asymptotic for outer mouth radii increase. Probability maps and average force per particle per pore section explain the asymmetric flux with variation in pore shape. Furthermore, the simulation results are in agreement with our in vitro experimental results with HeLa cells in Cx43-Cx45 heterotypic configurations. The presence of asymmetric fluxes can help us to understand effects of the molecular structure of the pore and predict potential differences in vivo.

  13. Two-stage solar concentrators based on parabolic troughs: asymmetric versus symmetric designs.

    Science.gov (United States)

    Schmitz, Max; Cooper, Thomas; Ambrosetti, Gianluca; Steinfeld, Aldo

    2015-11-20

    While nonimaging concentrators can approach the thermodynamic limit of concentration, they generally suffer from poor compactness when designed for small acceptance angles, e.g., to capture direct solar irradiation. Symmetric two-stage systems utilizing an image-forming primary parabolic concentrator in tandem with a nonimaging secondary concentrator partially overcome this compactness problem, but their achievable concentration ratio is ultimately limited by the central obstruction caused by the secondary. Significant improvements can be realized by two-stage systems having asymmetric cross-sections, particularly for 2D line-focus trough designs. We therefore present a detailed analysis of two-stage line-focus asymmetric concentrators for flat receiver geometries and compare them to their symmetric counterparts. Exemplary designs are examined in terms of the key optical performance metrics, namely, geometric concentration ratio, acceptance angle, concentration-acceptance product, aspect ratio, active area fraction, and average number of reflections. Notably, we show that asymmetric designs can achieve significantly higher overall concentrations and are always more compact than symmetric systems designed for the same concentration ratio. Using this analysis as a basis, we develop novel asymmetric designs, including two-wing and nested configurations, which surpass the optical performance of two-mirror aplanats and are comparable with the best reported 2D simultaneous multiple surface designs for both hollow and dielectric-filled secondaries.

  14. Polyimides Derived from Novel Asymmetric Benzophenone Dianhydrides

    Science.gov (United States)

    Chuang, Chun-Hua (Inventor)

    2015-01-01

    This invention relates to the composition and processes for preparing thermoset polyimides derived from an asymmetric dianhydride, namely 2,3,3',4'-benzophenone dianhydride (a-BTDA) with at least one diamine, and a monofunctional terminal endcaps. The monofunctional terminating groups include 4-phenylethynylphthalic anhydride ester-acid derivatives, phenylethyl trimellitic anhydride (PETA) and its ester derivatives as well as 3-phenylethynylaniline. The process of polyimide composite comprises impregnating monomer reactants of dianhydride or its ester-acid derivatives, diamine and with monofunctional reactive endcaps into glass, carbon, quartz or synthetic fibers and fabrics, and then stack up into laminates and subsequently heated to between 150-375.degree. C. either at atmosphere or under pressure to promote the curing and crosslinking of the reactive endcaps to form a network of thermoset polyimides.

  15. Asymmetric quantum dialogue in noisy environment

    Science.gov (United States)

    Banerjee, Anindita; Shukla, Chitra; Thapliyal, Kishore; Pathak, Anirban; Panigrahi, Prasanta K.

    2017-02-01

    A notion of asymmetric quantum dialogue (AQD) is introduced. Conventional protocols of quantum dialogue are essentially symmetric as the users (Alice and Bob) can encode the same amount of classical information. In contrast, the proposed scheme for AQD provides different amount of communication powers to Alice and Bob. The proposed scheme offers an architecture, where the entangled state to be used and the encoding scheme to be shared between Alice and Bob depend on the amount of classical information they want to exchange with each other. The general structure for the AQD scheme has been obtained using a group theoretic structure of the operators introduced in Shukla et al. (Phys Lett A 377:518, 2013). The effect of different types of noises (e.g., amplitude damping and phase damping noise) on the proposed scheme is investigated, and it is shown that the proposed scheme for AQD is robust and it uses an optimized amount of quantum resources.

  16. Asymmetric Ferromagnet-Superconductor-Ferromagnet Switch

    Energy Technology Data Exchange (ETDEWEB)

    Cadden-Zimansky, P.; Bazaliy, Ya.B.; Litvak, L.M.; Jiang, J.S.; Pearson, J.; Gu, J.Y.; You, Chun-Yeol; Beasley, M.R.; Bader, S.D.

    2011-11-04

    In layered ferromagnet-superconductor-ferromagnet F{sub 1} /S/F{sub 2} structures, the critical temperature T{sub c} of the superconductors depends on the magnetic orientation of the ferromagnetic layers F{sub 1} and F{sub 2} relative to each other. So far, the experimentally observed magnitude of change in T{sub c} for structures utilizing weak ferromagnets has been 2 orders of magnitude smaller than is expected from calculations. We theoretically show that such a discrepancy can result from the asymmetry of F/S boundaries, and we test this possibility by performing experiments on structures where F{sub 1} and F{sub 2} are independently varied. Our experimental results indicate that asymmetric boundaries are not the source of the discrepancy. If boundary asymmetry is causing the suppressed magnitude of T{sub c} changes, it may only be possible to detect in structures with thinner ferromagnetic layers.

  17. Distributed Function Computation in Asymmetric Communication Scenarios

    CERN Document Server

    Agnihotri, Samar

    2009-01-01

    We consider the distributed function computation problem in asymmetric communication scenarios, where the sink computes some deterministic function of the data split among N correlated informants. The distributed function computation problem is addressed as a generalization of distributed source coding (DSC) problem. We are mainly interested in minimizing the number of informant bits required, in the worst-case, to allow the sink to exactly compute the function. We provide a constructive solution for this in terms of an interactive communication protocol and prove its optimality. The proposed protocol also allows us to compute the worst-case achievable rate-region for the computation of any function. We define two classes of functions: lossy and lossless. We show that, in general, the lossy functions can be computed at the sink with fewer number of informant bits than the DSC problem, while computation of the lossless functions requires as many informant bits as the DSC problem.

  18. Universality in freezing of an asymmetric drop

    Science.gov (United States)

    Ismail, Md Farhad; Waghmare, Prashant R.

    2016-12-01

    We present the evidence of universality in conical tip formation during the freezing of arbitrary-shaped sessile droplets. The focus is to demonstrate the relationship between this universality and the liquid drop shape. We observe that, in the case of asymmetric drops, this universal shape is achieved when the tip reconfigures by changing its location, which subsequently alters the frozen drop shape. The proposed "two-triangle" model quantifies the change in the tip configuration as a function of the asymmetry of the drop that shows a good agreement with the experimental evidence. Finally, based on the experimental and theoretical exercise, we propose the scaling dependence between the variations in the tip configuration and the asymmetry of the drop.

  19. Activation of carboxylic acids in asymmetric organocatalysis.

    Science.gov (United States)

    Monaco, Mattia Riccardo; Poladura, Belén; Diaz de Los Bernardos, Miriam; Leutzsch, Markus; Goddard, Richard; List, Benjamin

    2014-07-01

    Organocatalysis, catalysis using small organic molecules, has recently evolved into a general approach for asymmetric synthesis, complementing both metal catalysis and biocatalysis. Its success relies to a large extent upon the introduction of novel and generic activation modes. Remarkably though, while carboxylic acids have been used as catalyst directing groups in supramolecular transition-metal catalysis, a general and well-defined activation mode for this useful and abundant substance class is still lacking. Herein we propose the heterodimeric association of carboxylic acids with chiral phosphoric acid catalysts as a new activation principle for organocatalysis. This self-assembly increases both the acidity of the phosphoric acid catalyst and the reactivity of the carboxylic acid. To illustrate this principle, we apply our concept in a general and highly enantioselective catalytic aziridine-opening reaction with carboxylic acids as nucleophiles.

  20. THz operation of asymmetric-nanochannel devices

    Science.gov (United States)

    Balocco, C.; Halsall, M.; Vinh, N. Q.; Song, A. M.

    2008-09-01

    The THz spectrum lies between microwaves and the mid-infrared, a region that remains largely unexplored mainly due to the bottleneck issue of lacking compact, solid state, emitters and detectors. Here, we report on a novel asymmetric-nanochannel device, known as the self-switching device, which can operate at frequencies up to 2.5 THz for temperature up to 150 K. This is, to our knowledge, not only the simplest diode but also the quickest acting electronic nanodevice reported to date. The radiation was generated by the free electron laser FELIX (Netherlands). The dependences of the device efficiency as a function of the electric bias, radiation intensity, radiation frequency and temperature are reported.

  1. Isospin dependent properties of asymmetric nuclear matter

    CERN Document Server

    Chowdhury, P Roy; Samanta, C

    2009-01-01

    The density dependence of nuclear symmetry energy is determined from a systematic study of the isospin dependent bulk properties of asymmetric nuclear matter using the isoscalar and the isovector components of density dependent M3Y interaction. The incompressibility $K_\\infty$ for the symmetric nuclear matter, the isospin dependent part $K_{asy}$ of the isobaric incompressibility and the slope $L$ are all in excellent agreement with the constraints recently extracted from measured isotopic dependence of the giant monopole resonances in even-A Sn isotopes, from the neutron skin thickness of nuclei and from analyses of experimental data on isospin diffusion and isotopic scaling in intermediate energy heavy-ion collisions. This work provides a fundamental basis for the understanding of nuclear matter under extreme conditions, and validates the important empirical constraints obtained from recent experimental data.

  2. Chilly Dark Sectors and Asymmetric Reheating

    CERN Document Server

    Adshead, Peter; Shelton, Jessie

    2016-01-01

    In a broad class of theories, the relic abundance of dark matter is determined by interactions internal to a thermalized dark sector, with no direct involvement of the Standard Model (SM). We point out that these theories raise an immediate cosmological question: how was the dark sector initially populated in the early universe? Motivated in part by the difficulty of accommodating large amounts of entropy carried in dark radiation with cosmic microwave background measurements of the effective number of relativistic species at recombination, $N_{\\mathrm{eff}}$, we aim to establish which admissible cosmological histories can populate a thermal dark sector that never reaches thermal equilibrium with the SM. The minimal cosmological origin for such a dark sector is asymmetric reheating, when the same mechanism that populates the SM in the early universe also populates the dark sector at a lower temperature. Here we demonstrate that the resulting inevitable inflaton-mediated scattering between the dark sector and ...

  3. Spectral measurements of asymmetrically irradiated capsule backlighters

    Science.gov (United States)

    Keiter, P. A.; Drake, R. P.

    2016-11-01

    Capsule backlighters provide a quasi-continuum x-ray spectrum over a wide range of photon energies [J. F. Hansen et al., Rev. Sci. Instrum. 79, 013504 (2008)]. Ideally one irradiates the capsule backlighter symmetrically, however, in complex experimental geometries, this is not always possible. In recent experiments we irradiated capsule backlighters asymmetrically and measured the x-ray spectrum from multiple directions. We will present time-integrated spectra over the photon energy range of 2-13 keV and time-resolved spectra over the photon energy range of 2-3 keV. We will compare the spectra from different lines of sight to determine if the laser asymmetry results in an angular dependence in the x-ray emission.

  4. Magnetoresistive system with concentric ferromagnetic asymmetric nanorings

    Energy Technology Data Exchange (ETDEWEB)

    Avila, J. I., E-mail: javila@ulg.ac.be; Tumelero, M. A.; Pasa, A. A.; Viegas, A. D. C. [Laboratório de Filmes Finos e Superfícies (LFFS), Departamento de Física, Universidade Federal de Santa Catarina, CP 476 Florianópolis (Brazil)

    2015-03-14

    A structure consisting of two concentric asymmetric nanorings, each displaying vortex remanent states, is studied with micromagnetic calculations. By orienting in suitable directions, both the asymmetry of the rings and a uniform magnetic field, the vortices chiralities can be switched from parallel to antiparallel, obtaining in this way the analogue of the ferromagnetic and antiferromagnetic configurations found in bar magnets pairs. Conditions on the thickness of single rings to obtain vortex states, as well as formulas for their remanent magnetization are given. The concentric ring structure enables the creation of magnetoresistive systems comprising the qualities of magnetic nanorings, such as low stray fields and high stability. A possible application is as contacts in spin injection in semiconductors, and estimations obtained here of magnetoresistance change for a cylindrical spin injection based device show significant variations comparable to linear geometries.

  5. Asymmetric Beam Combination for Optical Interferometry

    CERN Document Server

    Monnier, J D

    2001-01-01

    Optical interferometers increasingly use single-mode fibers as spatial filters to convert varying wavefront distortion into intensity fluctuations which can be monitored for accurate calibration of fringe amplitudes. Here I propose using an asymmetric coupler to allow the photometric intensities of each telescope beam to be measured at the same time as the fringe visibility, but without the need for dedicated photometric outputs, which reduce the light throughput in the interferometric channels. In the read-noise limited case often encountered in the infrared, I show that a 53% improvement in signal-to-noise ratio for the visibility amplitude measurement is achievable, when compared to a balanced coupler setup with 50% photometric taps (e.g., the FLUOR experiment). In the Poisson-noise limit appropriate for visible light, the improvement is reduced to only ~8%. This scheme also reduces the cost and complexity of the beam combination since fewer components and detectors are required, and can be extended to mor...

  6. Asymmetric EPR entanglement in continuous variable systems

    CERN Document Server

    Wagner, Katherine; Armstrong, Seiji; Morizur, Jean-Francois; Lam, Ping Koy; Bachor, Hans-Albert

    2012-01-01

    Continuous variable entanglement can be produced in nonlinear systems or via interference of squeezed states. In many of optical systems, such as parametric down conversion or interference of optical squeezed states, production of two perfectly symmetric subsystems is usually used for demonstrating the existence of entanglement. This symmetry simplifies the description of the concept of entanglement. However, asymmetry in entanglement may arise naturally in a real experiment, or be intentionally introduced in a given quantum information protocol. These asymmetries can emerge from having the output beams experience different losses and environmental contamination, or from the availability of non-identical input quantum states in quantum communication protocols. In this paper, we present a visualisation of entanglement using quadrature amplitude plots of the twin beams. We quantitatively discuss the strength of asymmetric entanglement using EPR and inseparability criteria and theoretically show that the optimal...

  7. Scaffold of Asymmetric Organic Compounds - Magnetite Plaquettes

    Science.gov (United States)

    Chan, Q. H. S.; Zolensky, M. E.; Martinez, J.

    2015-01-01

    Life on Earth shows preference towards the set of organics with particular spatial configurations, this 'selectivity' is a crucial criterion for life. With only rare exceptions, life prefers the left- (L-) form over the right- (D-) form of amino acids, resulting in an L-enantiomeric excess (L-ee). Recent studies have shown Lee for alpha-methyl amino acids in some chondrites. Since these amino acids have limited terrestrial occurrence, the origin of their stereoselectivity is nonbiological, and it seems appropriate to conclude that chiral asymmetry, the molecular characteristic that is common to all terrestrial life form, has an abiotic origin. A possible abiotic mechanism that can produce chiral asymmetry in meteoritic amino acids is their formation with the presence of asymmetric catalysts, as mineral crystallization can produce spatially asymmetric structures. Magnetite is shown to be an effective catalyst for the formation of amino acids that are commonly found in chondrites. Magnetite 'plaquettes' (or 'platelets'), first described by Jedwab, show an interesting morphology of barrel-shaped stacks of magnetite disks with an apparent dislocation-induced spiral growth that seem to be connected at the center. A recent study by Singh et al. has shown that magnetites can self-assemble into helical superstructures. Such molecular asymmetry could be inherited by adsorbed organic molecules. In order to understand the distribution of 'spiral' magnetites in different meteorite classes, as well as to investigate their apparent spiral configurations and possible correlation to molecular asymmetry, we observed polished sections of carbonaceous chondrites (CC) using scanning electron microscope (SEM) imaging. The sections were also studied by electron backscattered diffraction (EBSD) in order to reconstruct the crystal orientation along the stack of magnetite disks.

  8. The evolution of cooperation in asymmetric systems

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Explaining the "Tragedy of the Commons" of the evolution of cooperation remains one of the greatest problems for both biology and social science.Asymmetrical interaction,which is one of the most important characteristics of cooperative systems,has not been sufficiently considered in the existing models of the evolution of cooperation.Considering the inequality in the number and payoff between the cooperative actors and recipients in cooperation systems,discriminative density-dependent interference competition will occur in limited dispersal systems.Our model and simulation show that the local but not the global stability of a cooperative interaction can be maintained if the utilization of common resource remains unsaturated,which can be achieved by density-dependent restraint or competition among the cooperative actors.More intense density dependent interference competition among the cooperative actors and the ready availability of the common resource,with a higher intrinsic contribution ratio of a cooperative actor to the recipient,will increase the probability of cooperation.The cooperation between the recipient and the cooperative actors can be transformed into conflict and,it oscillates chaotically with variations of the affecting factors under different environmental or ecological conditions.The higher initial relatedness(i.e.similar to kin or reciprocity relatedness),which is equivalent to intrinsic contribution ratio of a cooperative actor to the recipient,can be selected for by penalizing less cooperative or cheating actors but rewarding cooperative individuals in asymmetric systems.The initial relatedness is a pivot but not the aim of evolution of cooperation.This explains well the direct conflict observed in almost all cooperative systems.

  9. Childhood asymmetrical labium majus enlargement sonographic and MR imaging appearances

    Energy Technology Data Exchange (ETDEWEB)

    Gokli, Ami; Neuman, Jeremy; Lukse, Ruby; Koshy, June [Staten Island University Hospital, Department of Radiology, Staten Island, NY (United States); Kong, Fanyi [Staten Island University Hospital, Department of Pathology, Staten Island, NY (United States); Laor, Tal [Cincinnati Children' s Hospital Medical Center, Department of Radiology, Cincinnati, OH (United States)

    2016-05-15

    Childhood asymmetrical labium majus enlargement (CALME) has been described sparsely in recent surgery, pathology, pediatric and gynecology literature; however, no comprehensive description from a radiology perspective has been developed. The purpose of this case series is to describe the imaging findings of CALME and to review the current understanding of this recently described clinical entity with regard to clinical presentation, pathophysiology, differential diagnosis and treatment options. This is a retrospective analysis of 3 girls, ages 5-7 years, who presented for imaging evaluation with subsequent pathologically proven CALME. Each child's clinical history, length of symptoms, imaging appearance and pathological findings were reviewed. All three girls presented with unilateral enlargement of the labium majus (two right-side, one left-side) with no history of trauma or other inciting cause. Two girls had painless labial enlargement that was recognized for weeks, and one had similar symptoms for 1 year prior to presentation. One girl was evaluated initially with sonography, and all three children underwent MR imaging. Sonographic evaluation showed asymmetrical labial enlargement without a definable mass. In each girl, the MR imaging findings were characterized by relatively ill-defined T1-weighted hypointense signal, T2-weighted hypo- to isointense signal with interspersed hyperintense septae, and heterogeneous patchy and feathery strands of enhancement on post-contrast imaging. Biopsy from each child showed benign fibrous tissue with intervening mature fibroadipose tissue, vessels and nerves without findings of inflammation or neoplasia. The MR imaging appearance of CALME is consistent. Recognition and appreciation of this unique pediatric entity by the radiologist may be essential for appropriate diagnosis and can help to guide therapy. Current preferred treatment approach is conservative. (orig.)

  10. On the wake flow of asymmetrically beveled trailing edges

    Science.gov (United States)

    Guan, Yaoyi; Pröbsting, Stefan; Stephens, David; Gupta, Abhineet; Morris, Scott C.

    2016-05-01

    Trailing edge and wake flows are of interest for a wide range of applications. Small changes in the design of asymmetrically beveled or semi-rounded trailing edges can result in significant difference in flow features which are relevant for the aerodynamic performance, flow-induced structural vibration and aerodynamically generated sound. The present study describes in detail the flow field characteristics around a family of asymmetrically beveled trailing edges with an enclosed trailing-edge angle of 25° and variable radius of curvature R. The flow fields over the beveled trailing edges are described using data obtained by particle image velocimetry (PIV) experiments. The flow topology for different trailing edges was found to be strongly dependent on the radius of curvature R, with flow separation occurring further downstream as R increases. This variation in the location of flow separation influences the aerodynamic force coefficients, which were evaluated from the PIV data using a control volume approach. Two-point correlations of the in-plane velocity components are considered to assess the structure in the flow field. The analysis shows large-scale coherent motions in the far wake, which are associated with vortex shedding. The wake thickness parameter yf is confirmed as an appropriate length scale to characterize this large-scale roll-up motion in the wake. The development in the very near wake was found to be critically dependent on R. In addition, high-speed PIV measurements provide insight into the spectral characteristics of the turbulent fluctuations. Based on the time-resolved flow field data, the frequency range associated with the shedding of coherent vortex pairs in the wake is identified. By means of time-correlation of the velocity components, turbulent structures are found to convect from the attached or separated shear layers without distinct separation point into the wake.

  11. Special Issue of "Asymmetric Synthesis"%Special Issue of "Asymmetric Synthesis"

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    Organic chemistry exploring the world at a molecu- lar level remains essential for our society in the 21st century. Asymmetric synthesis, particularly those em- ploying catalytic approach, is one of the most important research fields in organic synthesis providing chiral compounds in an enantiopure form. The latter is critical since the two enantiomers of one chiral compound, in many cases, have a different response in biological sys- tems. The huge markets of non-racemic chiral com- pounds as synthetic intermediates, pharmaceuticals,

  12. Axially chiral imidodiphosphoric Acid catalyst for asymmetric sulfoxidation reaction: insights on asymmetric induction.

    Science.gov (United States)

    Jindal, Garima; Sunoj, Raghavan B

    2014-04-22

    Insights into chiral induction for an asymmetric sulfoxidation reaction involving a single oxygen atom transfer are gained through analyzing the stereocontrolling transition states. The fitting of the substrate into the chiral cavity of a new class of imidodiphosphoric Brønsted acids, as well as weak CH⋅⋅⋅π and CH⋅⋅⋅O noncovalent interactions, are identified as responsible for the observed chiral induction.

  13. The development and characterisation of complex ovine neuron cultures from fresh and frozen foetal neurons.

    Science.gov (United States)

    Kay, Graham W; Oswald, Manfred J; Palmer, David N

    2006-07-15

    Cultures of ovine cerebral and cerebellar neurons from mid-term sheep foetal brains, 9-15 weeks old, have been established for the first time. These foetal brains are relatively mature, being at similar stages of development as peri and post-natal rodent brains. Cultures were routinely maintained for 3-4 weeks, and longer. Nearly all the cells from the younger foetuses adhered as neurons. The proportion of glial cells increased with age, as did the risk of cultures being overtaken by glial cells. Cultured neurons were bipolar, tripolar and multipolar, similar to the morphologies of neurons in vivo. Older foetuses also yield more complex neurons, notably giant cells. Other properties of the cultured neurons also mimic in vivo observations, including neurite beading, complexity in neurotransmitter class (GABAergic and glutamatergic) and calcium binding protein (calbindin and calretinin) content. Single cell divisions of neurons were observed in younger cultures by time-lapse photography and the occurrence of telophase nuclei. The advantage of the high yield of genetically identical cells obtained from a single sheep foetus, 150 million, was extended by cryopreservation of neurons after snap freezing, and later culture. These cultures showed the same characteristics as cultures from the freshly plated cells.

  14. Examining the Cultural Leadership Behaviors of Schoo l Principal s within the Context of Symmetric and Asymmetric School Culture

    Directory of Open Access Journals (Sweden)

    Betül BALKAR

    2015-08-01

    Full Text Available The aim of this study is to determine the opinions of teachers on contributions of school principals’ cultural leadership behaviors to forming symmetric and asymmetric culture. The participants of the study consisted of 27 secondary school teachers working in Gaziantep province. Data of the study were collected through semi - structured interviews and analyzed through content analysis. Contributions of each cultural leader ship behavior to symmetric and asymmetric culture types were determined by taking relations between cultural leadership behaviors and symmetric and asymmetric cultures into consideration in the process of content analysis. According to the findings of the study ; supporting development of teachers and reflecting developments and innovations on schools are among the cultural leadership behaviors contributing to forming asymmetric culture at schools. Interpreting tasks and missions of school and ensuring neces sary environment for keeping social values alive at schools are among the cultural leadership behaviors contributing to forming symmetric culture at schools. Based on the results of the study, it is suggested that school principals should follow developmen ts in educational issues and transfer these developments into school practices. They should place more importance on supporting innovative behaviors of teachers in order to create asymmetric culture at schools.

  15. Phosphorylation of the Polarity Protein BASL Differentiates Asymmetric Cell Fate through MAPKs and SPCH.

    Science.gov (United States)

    Zhang, Ying; Guo, Xiaoyu; Dong, Juan

    2016-11-07

    Cell polarization is commonly used for the regulation of stem cell asymmetric division in both animals and plants. Stomatal development in Arabidopsis, a process that produces breathing pores in the epidermis, requires asymmetric cell division to differentiate highly specialized guard cells while maintaining a stem cell population [1, 2]. The BREAKING OF ASYMMETRY IN THE STOMATAL LINEAGE (BASL) protein exhibits a polarized localization pattern in the cell and is required for differential cell fates resulting from asymmetric cell division [3]. The polarization of BASL is made possible by a positive feedback loop with a canonical mitogen-activated protein kinase (MAPK) pathway that recruits the MAPKK kinase YODA (YDA) and MAPK 6 (MPK6) to the cortical polarity site [4]. Here, we study BASL intracellular dynamics and show that the membrane-associated BASL is slowly replenished at the cortical polarity site and that the mobility is tightly linked to its phosphorylation status. Because BASL polarity is only exhibited by one daughter cell after an asymmetric cell division, we study how BASL differentially functions in the two daughter cells. The YDA MAPK cascade transduces upstream ligand-receptor signaling [5-13] to the transcription factor SPEECHLESS (SPCH), which controls stomatal initiation and is directly suppressed by MPK3/6-mediated phosphorylation [14, 15]. We show that BASL polarization leads to elevated nuclear MPK6 signaling and lowered SPCH abundance in one of the two daughter cells. Therefore, two daughter cells are differentiated by BASL polarity-mediated differential suppression of SPCH, which may provide developmental plasticity in plant stem cell asymmetric cell division (ACD).

  16. Dysregulation of dimethylargininedimethylaminohydrolase/asymmetric dimethylarginine pathway in rat type II diabetic nephropathy.

    Science.gov (United States)

    Lai, Ying-Ling; Aoyama, Sae; Ohata, Miyuki; Otsuka, Nami; Shiokawa, Hidemi; Tomono, Susumu; Fujiwara, Yukio; Kanazawa, Hiroaki; Miyoshi, Noriyuki; Ohshima, Hiroshi

    2012-09-01

    An impaired generation of nitric oxide has been associated with diabetic renal disease. In order to elucidate the underlying molecular mechanisms into how nitric oxide synthesis is impaired in diabetic renal disease, we examined changes in activities and expressions of some renal enzymes involved in nitric oxide production during the development of diabetic nephropathy in type II diabetic Otsuka Long-Evans Tokushima Fatty rats. Ten-week old Otsuka Long-Evans Tokushima Fatty (n = 40) and control Long-Evans Tokushima Otsuka rats (n = 20) were given drinking water containing 20% sucrose to accelerate the development of diabetic nephropathy. Otsuka Long-Evans Tokushima Fatty rats developed diabetic nephropathy in an age-dependent manner. Renal nitric oxide synthase activities in Otsuka Long-Evans Tokushima Fatty rats gradually declined with the progression of diabetic mellitus and were significantly lower than those of age-matched Long-Evans Tokushima Otsuka rats after 22 weeks of age. The lower activities of renal nitric oxide synthase in Otsuka Long-Evans Tokushima Fatty rats were correlated with relatively higher levels of renal free asymmetric dimethylarginine, an endogenous nitric oxide synthase inhibitor, and were also correlated with decreased activities of dimethylargininedimethylaminohydrolase which metabolizes asymmetric dimethylarginine to citrulline. These results imply that dimethylargininedimethylaminohydrolase dysregulation may play an important role in the development of diabetic nephropathy by increasing asymmetric dimethylarginine levels, which leads to inhibition of renal nitric oxide synthesis.

  17. Dysregulation of dimethylargininedimethylaminohydrolase/asymmetric dimethylarginine pathway in rat type II diabetic nephropathy

    Science.gov (United States)

    Lai, Ying-Ling; Aoyama, Sae; Ohata, Miyuki; Otsuka, Nami; Shiokawa, Hidemi; Tomono, Susumu; Fujiwara, Yukio; Kanazawa, Hiroaki; Miyoshi, Noriyuki; Ohshima, Hiroshi

    2012-01-01

    An impaired generation of nitric oxide has been associated with diabetic renal disease. In order to elucidate the underlying molecular mechanisms into how nitric oxide synthesis is impaired in diabetic renal disease, we examined changes in activities and expressions of some renal enzymes involved in nitric oxide production during the development of diabetic nephropathy in type II diabetic Otsuka Long-Evans Tokushima Fatty rats. Ten-week old Otsuka Long-Evans Tokushima Fatty (n = 40) and control Long-Evans Tokushima Otsuka rats (n = 20) were given drinking water containing 20% sucrose to accelerate the development of diabetic nephropathy. Otsuka Long-Evans Tokushima Fatty rats developed diabetic nephropathy in an age-dependent manner. Renal nitric oxide synthase activities in Otsuka Long-Evans Tokushima Fatty rats gradually declined with the progression of diabetic mellitus and were significantly lower than those of age-matched Long-Evans Tokushima Otsuka rats after 22 weeks of age. The lower activities of renal nitric oxide synthase in Otsuka Long-Evans Tokushima Fatty rats were correlated with relatively higher levels of renal free asymmetric dimethylarginine, an endogenous nitric oxide synthase inhibitor, and were also correlated with decreased activities of dimethylargininedimethylaminohydrolase which metabolizes asymmetric dimethylarginine to citrulline. These results imply that dimethylargininedimethylaminohydrolase dysregulation may play an important role in the development of diabetic nephropathy by increasing asymmetric dimethylarginine levels, which leads to inhibition of renal nitric oxide synthesis. PMID:22962534

  18. Simulation of Chaos in Asymmetric Nonlinear Chua's Circuit

    Institute of Scientific and Technical Information of China (English)

    WANG Yu-fei; QIAO Shu-tong; JIANG Jian-guo

    2008-01-01

    In order to describe practical chaotic systems exactly, we presented a simple modified Chua's circuit,which contains an asymmetric nonlinear resistive element. Mathematical analysis was made, and simulation study was performed by MATLAB. By varying the value of linear resistor in the circuit, rich variety dynamical behaviors were observed, such as DC equilibrium point, Hopf bifurcation, period-doubling bifurcation,single-scroll strange attractor, periodic windows, and asymmetric double-scroll strange attractor. The extreme sensitivity in the state trajectory with respect to the initial conditions was exhibited; the special characteristic of asymmetric nonlinear Chua's circuit was found also.

  19. The Dualism of Asymmetric Information in Agricultural Insurance

    Directory of Open Access Journals (Sweden)

    Xuemei Yang

    2013-07-01

    Full Text Available Asymmetric information objectively exists in the insurance market, especially in agricultural insurance, which has a great impact on the insurance contract and market operation. This paper designs two game models to analyse the dualism of asymmetric information in agricultural insurance and its reasons of forming. We find that, the particularity of agricultural production, the agricultural risk diversification and the benefits’ spillover of the agricultural insurance are the main causes of asymmetric information. Therefore, this paper puts forward that establishment of appropriate agricultural insurance mode, optimization of insurance policy design and increasing investment in science and technology, increasing farmers’ insurance consciousness and establishing supervision system

  20. Asymmetric Orbifolds, Noncommutative Geometry and Type I String Vacua

    CERN Document Server

    Blumenhagen, R; Körs, B; Lüst, Dieter; Blumenhagen, Ralph; Goerlich, Lars; Kors, Boris; Lust, Dieter

    2000-01-01

    We investigate the D-brane contents of asymmetric orbifolds. Using T-dualitywe find that the consistent description of open strings in asymmetric orbifoldsrequires to turn on background gauge fields on the D-branes. Hence open stringsand D-branes in generic asymmetric orbifolds necessarily lead to noncommutativegeometry. We derive the corresponding noncommutative geometry arising on suchD-branes with mixed Neumann-Dirichlet boundary conditions by applying anasymmetric rotation to ordinary D-branes with pure Dirichlet boundaryconditions. As a concrete application of our results we construct asymmetrictype I vacua requiring open strings with mixed boundary conditions for tadpolecancellation.

  1. Mechanisms of asymmetric cell divisions in Drosophila melanogaster neuroblasts

    Directory of Open Access Journals (Sweden)

    X Jiang

    2014-04-01

    Full Text Available Stem cells possess the properties of self-renewal and differentiation, and mainly rely on two strategies for division, including symmetric and asymmetric cell divisions. In this review, we summarize the latest progress on asymmetric cell divisions in Drosophila melanogaster neuroblasts (NBs, which focus on the establishment of cell polarity, mitotic spindle orientation, the asymmetric segregation of cell fate determinants as well as cell-cycle control. Here we also introduce five major cell fate determinants, including Numb, Prospero, Brat, Miranda, and Pon, which are thought to be unequally segregated to the ganglion mother cells (GMCs and play an important role in the formation of stem cell-derived tumors

  2. Generic approach for synthesizing asymmetric nanoparticles and nanoassemblies

    Science.gov (United States)

    Sun, Yugang; Hu, Yongxing

    2015-05-26

    A generic route for synthesis of asymmetric nanostructures. This approach utilizes submicron magnetic particles (Fe.sub.3O.sub.4--SiO.sub.2) as recyclable solid substrates for the assembly of asymmetric nanostructures and purification of the final product. Importantly, an additional SiO.sub.2 layer is employed as a mediation layer to allow for selective modification of target nanoparticles. The partially patched nanoparticles are used as building blocks for different kinds of complex asymmetric nanostructures that cannot be fabricated by conventional approaches. The potential applications such as ultra-sensitive substrates for surface enhanced Raman scattering (SERS) have been included.

  3. The experimental study of acoustic field in an asymmetric borehole

    Institute of Scientific and Technical Information of China (English)

    LINWeijun; ZHANGChengyu; ZHANGHailan; WANGXiuming

    2003-01-01

    The acoustic field in an asymmetric borehole was investigated by recording and comparing the waveforms with different offset in both axial symmetric borehole and axial asymmetric borehole. The two-dimensional spectrum in wave-number and frequency domain was also calculated and compared with the result of numeric simulation with 2.5-D finite difference method, and a consistent result was obtained. This work provides an accurate verification of our investigation of asymmetric borehole with 2.5-D finite difference method.

  4. Monte Carlo analysis of Gunn oscillations in narrow and wide band-gap asymmetric nanodiodes

    Science.gov (United States)

    González, T.; Iñiguez-de-la Torre, I.; Pardo, D.; Mateos, J.; Song, A. M.

    2009-11-01

    By means of Monte Carlo simulations we show the feasibility of asymmetric nonlinear planar nanodiodes for the development of Gunn oscillations. For channel lengths about 1 μm, oscillation frequencies around 100 GHz are predicted in InGaAs diodes, being significantly higher, around 400 GHz, in the case of GaN structures. The DC to AC conversion efficiency is found to be higher than 1% for the fundamental and second harmonic frequencies in GaN diodes.

  5. Mo-catalyzed asymmetric olefin metathesis in target-oriented synthesis: Enantioselective synthesis of (+)-africanol

    Science.gov (United States)

    Weatherhead, Gabriel S.; Cortez, G. A.; Schrock, Richard R.; Hoveyda, Amir H.

    2004-01-01

    Catalytic asymmetric ring-opening metathesis (AROM) provides an efficient method for the synthesis of a variety of optically enriched small organic molecules that cannot be easily prepared by alternative methods. The development of Mo-catalyzed AROM transformations that occur in tandem with ring-closing metathesis are described. The utility of the Mo-catalyzed AROM/ring-closing metathesis is demonstrated through an enantioselective approach to the synthesis of (+)-africanol. PMID:15056762

  6. Optimization and evaluation of asymmetric flow field-flow fractionation of silver nanoparticles

    OpenAIRE

    Loeschner, Katrin; Navratilova, Jana; Legros, Samuel; Wagner, Stephan; Grombe, Ringo; Snell, James; von der Kammer, Frank; Larsen, Erik H

    2013-01-01

    Asymmetric flow field-flow fractionation (AF4) in combination with on-line optical detection and mass spectrometry is one of the most promising methods for separation and quantification of nanoparticles (NPs) in complex matrices including food. However, to obtain meaningful results regarding especially the NP size distribution a number of parameters influencing the separation need to be optimized. This paper describes the development of a separation method for polyvinylpyrrolidone-stabilized ...

  7. Monofunctional primary amine: A new class of organocatalyst for asymmetric Aldol reaction

    Indian Academy of Sciences (India)

    KHIANGTE VANLALDINPUIA; PORAG BORA; GHANASHYAM BEZ

    2017-03-01

    A new class of organocatalysts involving a primary amine as the only functional group is developed for catalytic asymmetric aldol reaction of cyclohexanone/ cyclopentanone with various aryl aldehydes in thepresence of benzoic acid as an additive at −10◦C. In an unexpected observation, the primary amine catalyzed reactions gave excellent yield and good to excellent stereoselectivity, while secondary amines were found to have little or no reactivity under similar reaction conditions.

  8. Asymmetric Synthesis of Optically Active Spirocyclic Indoline Scaffolds through an Enantioselective Reduction of Indoles

    KAUST Repository

    Borrmann, Ruediger

    2016-11-30

    An enantioselective synthesis of spirocyclic indoline scaffolds was achieved by applying an asymmetric iridium-catalyzed hydrogenation of 3H-indoles. Low catalyst loadings and mild reaction conditions provide a broad range of differently substituted products with excellent yields and enantioselectivities. The developed methodology allows an efficient synthesis of this important spirocyclic structural motif, which is present in numerous biologically active molecules and privileged structures in medicinal chemistry.

  9. Fault-tolerant quantum computation with asymmetric Bacon-Shor codes

    Science.gov (United States)

    Brooks, Peter; Preskill, John

    2013-03-01

    We develop a scheme for fault-tolerant quantum computation based on asymmetric Bacon-Shor codes, which works effectively against highly biased noise dominated by dephasing. We find the optimal Bacon-Shor block size as a function of the noise strength and the noise bias, and estimate the logical error rate and overhead cost achieved by this optimal code. Our fault-tolerant gadgets, based on gate teleportation, are well suited for hardware platforms with geometrically local gates in two dimensions.

  10. An optimization-based design procedure for asymmetric bidirectional associative memories.

    Science.gov (United States)

    Park, J; Kwon, C H; Park, D

    2001-01-01

    In this letter, we consider the problem of designing asymmetric bidirectional associative memories (ABAM). Based on a newly derived theorem for the ABAM model, we propose an optimization-based design procedure for obtaining an ABAM that can store given bipolar vector pairs with certain error correction properties. Our design procedure consists of generalized eigenvalue problems, which can be efficiently solved by recently developed interior point methods. The validity of the proposed method is illustrated by a design example.

  11. Evacuation dynamics of asymmetrically coupled pedestrian pairs

    CERN Document Server

    Müller, Frank

    2016-01-01

    We propose and analyze extended floor field cellular automaton models for evacuation dynamics of inhomogeneous pedestrian pairs which are coupled by asymmetric group interactions. Such pairs consist of a leader, who mainly determines the couple's motion and a follower, who has a defined tendency to follow the leader. Examples for such pairs are mother and child or two siblings of different age. We examine the system properties and compare them to the case of a homogeneous crowd. We find a strong impact on evacuation times for the regime of strong pair coupling due to the occurrence of a clogging phenomenon. In addition we obtain a non-trivial dependence of evacuation times on the followers' coupling to the static floor field, which carries the information of the shortest way to the exit location. In particular we find that systems with fully passive followers, who are solely coupled to their leaders, show lower evacuation times than homogeneous systems where all pedestrians have an equal tendency to move towa...

  12. Asymmetric vector mesons produced in nuclear collisions

    CERN Document Server

    Dremin, I M

    2016-01-01

    It is argued that the experimentally observed phenomenon of asymmetric shapes of vector mesons produced in nuclear media during high energy nucleus-nucleus collisions can be explained as Fano-Feshbach resonances. It has been observed that the mass distributions of lepton pairs created at meson decays decline from the traditional Breit-Wigner shape with some excess in the low-mass wing of the resonance. It is clear that the whole phenomenon is related to some interaction with the nuclear medium. Moreover, it can be further detalized in quantum mechanics as the interference of direct and continuum states in Fano-Feshbach effect. To reveal the nature of the interaction it is proposed to use a phenomenological model of the additional contribution due to Cherenkov gluons. They can be created because of the excess of the refractivity index over 1 just in the low-mass wing as required by the classical Cherenkov treatment. In quantum mechanics, this requirement is related to the positive real part of the interaction ...

  13. ADMonium: Asymmetric Dark Matter Bound State

    CERN Document Server

    Bi, Xiao-Jun; Ko, P; Li, Jinmian; Li, Tianjun

    2016-01-01

    We propose a novel framework for asymmetric scalar dark matter (ADM), which has interesting collider phenomenology in terms of an unstable ADM bound state (ADMonium) produced via Higgs portals. ADMonium is a natural consequence of the basic features of ADM: the (complex scalar) ADM is charged under a dark local $U(1)_d$ symmetry which is broken at a low scale and provides a light gauge boson $X$. The dark gauge coupling is strong and then ADM can annihilate away into $X$-pair effectively. Therefore, the ADM can form bound state due to its large self-interaction via $X$ mediation. To explore the collider signature of ADMonium, we propose that ADM has a two-Higgs doublet portal. The ADMonium can have a sizable mixing with the heavier Higgs boson, which admits a large cross section of ADMonium production associated with $b\\bar b$. Of particular interest, our setup nicely explains the recent di-photon anomaly at 750 GeV via the events from ${\\rm ADMonium}\\ra 2X(\\ra e^+e^-)$, where the electrons are identified as ...

  14. Asymmetric vector mesons produced in nuclear collisions

    Science.gov (United States)

    Dremin, I. M.; Nechitailo, V. A.

    2016-09-01

    It is argued that the experimentally observed phenomenon of asymmetric shapes of vector mesons produced in nuclear media during high-energy nucleus-nucleus collisions can be explained as Fano-Feshbach resonances. It has been observed that the mass distributions of lepton pairs created at meson decays decline from the traditional Breit-Wigner shape with some excess in the low-mass wing of the resonance. It is clear that the whole phenomenon is related to some interaction with the nuclear medium. Moreover, it can be further described in quantum mechanics as the interference of direct and continuum states in the Fano-Feshbach effect. To reveal the nature of the interaction it is proposed to use a phenomenological model of the additional contribution due to Cherenkov gluons. They can be created because of the excess of the refractivity index over 1 just in the low-mass wing as required by the classical Cherenkov treatment. In quantum mechanics, this requirement is related to the positive real part of the interaction amplitude in this wing. The corresponding parameters are found from the comparison with ρ-meson data and admit reasonable explanation.

  15. Barbed congruence of the asymmetric chi calculus

    Institute of Scientific and Technical Information of China (English)

    DONG Xiao-ju; FU Yu-xi

    2006-01-01

    The chi calculus is a model of mobile processes. It has evolved from the pi-calculus with motivations from simplification and communication-as-cut-elimination. This paper studies the chi calculus in the framework incorporating asymmetric communication. The major feature of the calculus is the identification of two actions:x/x and τ. The investigation on the barbed bisimilarity shows how the property affects the observational theory.Based on the definition of the barbed bisimilarity, the simulation properties of the barbed bisimilarity are studied. It shows that the algebraic properties of the barbed bisimilarity have changed greatly compared with the chi calculus. Although the definition of the barbed bisimilarity is very simple, the property of closeness under contexts makes it difficult to understand the barbed bisimilarity directly. Therefore an open style definition of the barbed bisimilarity is given, which is a context free description of barbed bisimilarity. Its definition is complex,but it is a well-behaved relation for it coincides with the barbed bisimilarity. It also helps to build an axiomatization system for the barbed congruence. Besides the axioms for the strong barbed bisimilarity, the paper proposes a new tau law and four new update laws for the barbed congruence. Both the operational and algebraic properties of the enriched calculus improve the understanding of the bisimulation behaviors of the model.

  16. Asymmetric vector mesons produced in nuclear collisions

    Energy Technology Data Exchange (ETDEWEB)

    Dremin, I.M.; Nechitailo, V.A. [Lebedev Physical Institute, Moscow (Russian Federation); National Research Nuclear University ' ' MEPhI' ' , Moscow (Russian Federation)

    2016-09-15

    It is argued that the experimentally observed phenomenon of asymmetric shapes of vector mesons produced in nuclear media during high-energy nucleus-nucleus collisions can be explained as Fano-Feshbach resonances. It has been observed that the mass distributions of lepton pairs created at meson decays decline from the traditional Breit-Wigner shape with some excess in the low-mass wing of the resonance. It is clear that the whole phenomenon is related to some interaction with the nuclear medium. Moreover, it can be further described in quantum mechanics as the interference of direct and continuum states in the Fano-Feshbach effect. To reveal the nature of the interaction it is proposed to use a phenomenological model of the additional contribution due to Cherenkov gluons. They can be created because of the excess of the refractivity index over 1 just in the low-mass wing as required by the classical Cherenkov treatment. In quantum mechanics, this requirement is related to the positive real part of the interaction amplitude in this wing. The corresponding parameters are found from the comparison with ρ-meson data and admit reasonable explanation. (orig.)

  17. Asymmetric Swiss-cheese brane-worlds

    Science.gov (United States)

    Gergely, László Á.; Képíró, Ibolya

    2007-07-01

    We study a brane-world cosmological scenario with local inhomogeneities represented by black holes. The brane is asymmetrically embedded into the bulk. The black strings/cigars penetrating the Friedmann brane generate a Swiss-cheese-type structure. This universe forever expands and decelerates, as its general relativistic analogue. The evolution of the cosmological fluid, however, can proceed along four branches, two allowed to have positive energy density, and one of them having the symmetric embedding limit. On this branch a future pressure singularity can arise for either (a) a difference in the cosmological constants of the cosmological and black hole brane regions or (b) a difference in the left and right bulk cosmological constants. While behaviour (a) can be avoided by a redefinition of the fluid variables, (b) establishes a critical value of the asymmetry over which the pressure singularity occurs. We introduce the pressure singularity censorship which bounds the degree of asymmetry in the bulk cosmological constant. We also show as a model-independent generic feature that the asymmetry source term due to the bulk cosmological constant increases in the early universe. In order to obey the nucleosynthesis constraints, the brane tension should be constrained therefore both from below and from above. With the maximal degree of asymmetry obeying the pressure singularity censorship, the higher limit is ten times the lower limit. The degree of asymmetry allowed by present cosmological observations is, however, much less, pushing the upper limit to infinity.

  18. The Asymmetric Pupil Fourier Wavefront Sensor

    CERN Document Server

    Martinache, Frantz

    2013-01-01

    This paper introduces a novel wavefront sensing approach that relies on the Fourier analysis of a single conventional direct image. In the high Strehl ratio regime, the relation between the phase measured in the Fourier plane and the wavefront errors in the pupil can be linearized, as was shown in a previous work that introduced the notion of generalized closure-phase, or kernel-phase. The technique, to be usable as presented requires two conditions to be met: (1) the wavefront errors must be kept small (of the order of one radian or less) and (2) the pupil must include some asymmetry, that can be introduced with a mask, for the problem to become solvable. Simulations show that this asymmetric pupil Fourier wavefront sensing or APF-WFS technique can improve the Strehl ratio from 50 to over 90 % in just a few iterations, with excellent photon noise sensitivity properties, suggesting that on-sky close loop APF-WFS is possible with an extreme adaptive optics system.

  19. Asymmetric translation between multiple representations in chemistry

    Science.gov (United States)

    Lin, Yulan I.; Son, Ji Y.; Rudd, James A., II

    2016-03-01

    Experts are more proficient in manipulating and translating between multiple representations (MRs) of a given concept than novices. Studies have shown that instruction using MR can increase student understanding of MR, and one model for MR instruction in chemistry is the chemistry triplet proposed by Johnstone. Concreteness fading theory suggests that presenting concrete representations before abstract representations can increase the effectiveness of MR instruction; however, little work has been conducted on varying the order of different representations during instruction and the role of concreteness in assessment. In this study, we investigated the application of concreteness fading to MR instruction and assessment in teaching chemistry. In two experiments, undergraduate students in either introductory psychology courses or general chemistry courses were given MR instruction on phase changes using different orders of presentation and MR assessment questions based on the representations in the chemistry triplet. Our findings indicate that the order of presentation based on levels of concreteness in MR chemistry instruction is less important than implementation of comprehensive MR assessments. Even after MR instruction, students display an asymmetric understanding of the chemical phenomenon on the MR assessments. Greater emphasis on MR assessments may be an important component in MR instruction that effectively moves novices toward more expert MR understanding.

  20. Polyimides Derived from Novel Asymmetric Dianhydrides

    Science.gov (United States)

    Chuang, Chun-Hua (Inventor)

    2012-01-01

    This invention relates to the compositions and processes for preparing thermoset and thermoplastic polyimides derived from novel asymmetrical dianhydrides: specifically 2,3,3',4' benzophenone dianhydride (a-BTDA), and 3,4'-(hexafluoroisopropylidene)diphthalic anhydride (a-6FDA). The a-BTDA anhydride is prepared by Suzuki coupling with catalysts from a mixed anhydride of 3,4-dimethylbenzoic acid or 2,3-dimethylbenzoic acid with 2,3-dimethylphenylboronic acid or 3,4-dimethylphenylboronic acid respectively, to form 2,3,3',4'-tetramethylbenzophenone which is oxidized to form 2,3,3',4'-benzophenonetetracarboxylic acid followed by cyclodehydration to obtain a-BTDA. The a-6FDA is prepared by nucleophilic triflouoromethylation of 2,3,3',4'-tetramethylbenzophenone with trifluoromethyltrimethylsilane to form 3,4'-(trifluoromethylmethanol)-bis(o-xylene) which is converted to 3,4'-(hexafluoroisopropylidene-bis(o-xylene). The 3,4'-(hexafluoroisopropylidene)-bis(o-xylene) is oxidized to the corresponding tetraacid followed by cyclodehydration to yield a-6FDA.

  1. Magnetic Field and Force Calculations for ATLAS Asymmetrical Structure

    CERN Document Server

    Nessi, Marzio

    2001-01-01

    Magnetic field distortion in the assymetrical ATLAS structure are calculated. Magnetic forces in the system are estimated. 3D magnetic field simulation by the Opera3D code for symmetrical and asymmetrical systems is used.

  2. Asymmetric H-D exchange reactions of fluorinated aromatic ketones

    KAUST Repository

    Zhao, Yujun

    2012-01-01

    Chiral bicyclic guanidine catalyzes the asymmetric H-D exchange reactions. Up to 30% ee was achieved. DFT calculations were employed to elucidate and explain the origin of the reaction\\'s stereoselectivity. © 2012 The Royal Society of Chemistry.

  3. Asymmetric Intramolecular Cyclopropanation Induced by (β-Diketone)-copper Complex

    Institute of Scientific and Technical Information of China (English)

    Qing Fang CHENG; Xing You XU; Wei Xing MA; Tian Pa YOU

    2005-01-01

    Asymmetric intramolecular cyclopropanation of allylic diazoacetate was investigated using a chiral (β-diketone)-copper complex as catalyst, excellent yield and enantioselectivity were achieved. Some factors influencing enantioselectivity were discussed.

  4. Salt supply to and significance of asymmetric salt diapirs

    DEFF Research Database (Denmark)

    Koyi, H.; Burliga, S.; Chemia, Zurab

    2012-01-01

    Salt diapirs can be asymmetric both internally and externally reflecting their evolution history. As such, this asymmetry bear a significant amount of information about the differential loading (± lateral forces) and in turn the salt supply that have shaped the diapir. In two dimensions......, In this study we compare results of analogue and numerical models of diapirs with two natural salt diapris (Klodawa and Gorleben diapirs) to explain their salt supply and asymmetric evolution. In a NW-SE section, the Gorleben salt diapir possesses an asymmetric external geometry represented by a large...... southeastern overhang due to salt extrusion during Middle Cretaceous followed by its burial in Tertiary. This external asymmetry is also reflected in the internal configuration of the diapir which shows different rates of salt flow on the two halves of the structure. The asymmetric external and internal...

  5. Asymmetric Dark Matter in the shear-dominated universe

    Science.gov (United States)

    Iminniyaz, Hoernisa

    2017-02-01

    We explore the relic abundance of asymmetric Dark Matter in shear-dominated universe in which it is assumed the universe is expanded anisotropically. The modified expansion rate leaves its imprint on the relic density of asymmetric Dark Matter particles if the asymmetric Dark Matter particles are decoupled in shear dominated era. We found the relic abundances for particle and anti-particle are increased. The particle and anti-particle abundances are almost in the same amount for the larger value of the shear factor xe which makes the indirect detection possible for asymmetric Dark Matter. We use the present day Dark Matter density from the observation to find the constraints on the parameter space in this model.

  6. Asymmetric periflexural exanthema: A report in an adult patient

    Directory of Open Access Journals (Sweden)

    Zawar V

    2003-11-01

    Full Text Available Asymmetric periflexural exanthem (APE is a distinctive exanthem, probably viral in origin. It is largely a disease of childhood and is uncommon in adults. We report an adult man presenting with the typical clinical findings of APE.

  7. Vertical Control and Parallel Trade under Asymmetric Information

    Directory of Open Access Journals (Sweden)

    Alessandro Avenali

    2015-05-01

    profits from the manufacturer to the wholesaler. Therefore, in R&D-intensive industries, such as pharmaceuticals, policy makers should anticipate the likely consequences of PT under asymmetric information on the long-run incentives to innovate.

  8. Abundance of Asymmetric Dark Matter in Brane World Cosmology

    Science.gov (United States)

    Abdusattar, Haximjan; Iminniyaz, Hoernisa

    2016-09-01

    Relic abundance of asymmetric Dark Matter particles in brane world cosmological scenario is investigated in this article. Hubble expansion rate is enhanced in brane world cosmology and it affects the relic abundance of asymmetric Dark Matter particles. We analyze how the relic abundance of asymmetric Dark Matter is changed in this model. We show that in such kind of nonstandard cosmological scenario, indirect detection of asymmetric Dark Matter is possible if the cross section is small enough which let the anti-particle abundance kept in the same amount with the particle. We show the indirect detection signal constraints can be used to such model only when the cross section and the 5-dimensional Planck mass scale are in appropriate values. Supported by the National Natural Science Foundation of China under Grant No. 11365022

  9. Asymptotic Theory for Extended Asymmetric Multivariate GARCH Processes

    NARCIS (Netherlands)

    M. Asai (Manabu); M.J. McAleer (Michael)

    2016-01-01

    textabstractThe paper considers various extended asymmetric multivariate conditional volatility models, and derives appropriate regularity conditions and associated asymptotic theory. This enables checking of internal consistency and allows valid statistical inferences to be drawn based on empirical

  10. Polarization dependent switching of asymmetric nanorings with a circular field

    Directory of Open Access Journals (Sweden)

    Nihar R. Pradhan

    2016-01-01

    Full Text Available We experimentally investigated the switching from onion to vortex states in asymmetric cobalt nanorings by an applied circular field. An in-plane field is applied along the symmetric or asymmetric axis of the ring to establish domain walls (DWs with symmetric or asymmetric polarization. A circular field is then applied to switch from the onion state to the vortex state, moving the DWs in the process. The asymmetry of the ring leads to different switching fields depending on the location of the DWs and direction of applied field. For polarization along the asymmetric axis, the field required to move the DWs to the narrow side of the ring is smaller than the field required to move the DWs to the larger side of the ring. For polarization along the symmetric axis, establishing one DW in the narrow side and one on the wide side, the field required to switch to the vortex state is an intermediate value.

  11. Asymmetric dynamic phase holographic grating in nematic liquid crystal

    Science.gov (United States)

    Ren, Chang-Yu; Shi, Hong-Xin; Ai, Yan-Bao; Yin, Xiang-Bao; Wang, Feng; Ding, Hong-Wei

    2016-09-01

    A new scheme for recording a dynamic phase grating with an asymmetric profile in C60-doped homeotropically aligned nematic liquid crystal (NLC) was presented. An oblique incidence beam was used to record the thin asymmetric dynamic phase holographic grating. The diffraction efficiency we achieved is more than 40%, exceeding the theoretical limit for symmetric profile gratings. Both facts can be explained by assuming that a grating with an asymmetric saw-tooth profile is formed in the NLC. Finally, physical mechanism and mathematical model for characterizing the asymmetric phase holographic grating were presented, based on the photo-refractive-like (PR-like) effect. Project supported by the Science and Technology Programs of the Educational Committee of Heilongjiang Province, China (Grant No. 12541730) and the National Natural Science Foundation of China (Grant No. 61405057).

  12. Results of investigations into coal cutting by asymmetric disks

    Energy Technology Data Exchange (ETDEWEB)

    Krauze, K.

    1985-02-01

    Effects are analyzed of design and specifications of asymmetric disk cutters on coal cutting by a shearer loader with disk cutters on helical cutting drums. Effects of disk diameter, wedge angle, cutting depth and chip thickness on cutting resistance were analyzed under operational conditions (a coal seam was cut by asymmetric disk cutters). On the basis of analysis of coal resistance to cutting by asymmetric cutting disks, regression equations were derived which describe coal cutting. Effects of disk parameters and cutting conditions on cutting resistance were determined. Analyses show that replacing radial cutting tools with asymmetric disk cutters would cause an increase in energy consumption of cutting and increase coal resistance to cutting. 1 reference.

  13. Reduced densities of parvalbumin- and somatostatin-expressing interneurons in experimental cortical dysplasia and heterotopia in early postnatal development.

    Science.gov (United States)

    Akakin, Dilek; Martinez-Diaz, Hildabelis; Chen, Huan-Xin; Roper, Steven N

    2013-05-01

    Cortical dysplasia (CD) is strongly associated with intractable epilepsy, probably due to hyperexcitability of neuronal networks. However, the underlying mechanisms are not completely understood. GABAergic interneurons provide major inhibitory function in the CNS and have different subtypes, but it is not clear how each subtype is affected in CD during early post-natal development. We have examined the developmental alterations of the densities of two major subtypes of interneurons, parvalbumin (PV)- and somatostatin (SS)-expressing interneurons in an animal model of CD, in utero irradiation, using immunocytochemistry. We found that the density of PV- and SS-positive interneurons increases significantly in CD and controls during the first three weeks of postnatal life. However, compared to controls, the densities of both subtypes are significantly decreased in CD and heterotopia at all age groups although the time of onset for both PV and SS expression remained unchanged. Our results indicate that the densities of both PV- and SS-positive interneurons are significantly decreased in CD and heterotopia, which may be one important mechanism leading to hyperexcitability of CD.

  14. Asymmetric Mid-Ocean ridges: Interplay Between Plate and Mantle Processes and Consequences for Melting

    Science.gov (United States)

    Montesi, L.; Bai, H.

    2014-12-01

    Mid-ocean ridges constitute a fundamental component of the global plate tectonic system. The classical view of ridges is of symmetric system, where plates diverge, generating a mostly passive upwelling immediately underneath the ridge axis. However, observations of mid-ocean ridges draw quite a different picture. At the Southern East Pacific Rise, plate subsidence (related to plate age) occurs at different rates on the Pacific and Nazca plates, implying different rates of accretion on each side of the ridge. At greater depth, the melting region extends much further beneath the Pacific plate than the Nazca plate. Asymmetry is also evident in slow spreading center. For examples, at the 13°N segment of the Mid-Atlantic Ridge, isochrons are more widely spaced on the American side than the European side. Core complexes along the axis are another manifestation of asymmetric accretion at that location. In this contribution, we seek to understand how is the melting system affected by ridge asymmetry. First, we discuss the different ways that an asymmetric ridge may develop. We present an analytical solution of mantle flow in the mantle underneath spreading centers that considers 1) different rates of accretion in on the two plates; 2) migration of the ridge system with respect to the underlying mantle (Couette flow in the asthenosphere); 3) mantle wind (Poiseuille flow in the asthenosphere); 4) different slopes of the lithosphere underneath each plate; and 5) any combination of the above. These solutions assume an isoviscous mantle underneath the lithosphere. Asymmetry in mantle flow is observed in each case. The temperature field associated with each case implies that melting is suppressed by the asymmetric accretion, although deeper processes have little effect on melting. As asymmetric accretion is thought to develop when melt flux to the axis is reduced, there is the possibility of a positive feedback that forces segments to switch between symmetric and asymmetric

  15. The evolution of Sf. Gheorghe (Danube asymmetric deltaic lobe

    Directory of Open Access Journals (Sweden)

    Alfred VESPREMEANU-STROE

    2014-11-01

    Full Text Available The wave asymmetric Sf. Gheorghe lobe is the only active in the Danube delta where river mouth bar (and the associated barrier islands and spits continuously deployed a cyclic development for almost two millennia. During first stage, the Sf. Gheorghe distributary had a small discharge (with an order of magnitude lower than present which after that experienced a rapid increase in consequence of the successive avulsions of Împuţita (southern distributary of Sulina arm and Dunavăţ distributaries. Our morphological analyses together with the newly obtained chronology, revealed the multiple ridgesets structure of Sf. Gheorghe deltaic lobe. In fact, all ridgesets (10 follow a common morphodynamic pattern characterized by the cyclic succession of three stages: i subaqueous mouth bar development, ii barrier island emergence, iii barrier spit phase with several secondary spits derived from an updrift trunk ridge. The size of each ridgeset increased exponentially with every new cycle due to the constant lengthening of the coastline as the downdrift side of the lobe advances seaward through a series of progressively larger similar quadrilaterals, yielding to a constant enlargment of the delta front size. 

  16. Research on the Design and Modification of Asymmetric Spur Gear

    OpenAIRE

    Xiaohe Deng; Lin Hua; Xinghui Han

    2015-01-01

    A design method for the geometric shape and modification of asymmetric spur gear was proposed, in which the geometric shape and modification of the gear can be obtained directly according to the rack-cutter profile. In the geometric design process of the gear, a rack-cutter with different pressure angles and fillet radius in the driving side and coast side was selected, and the generated asymmetric spur gear profiles also had different pressure angles and fillets accordingly. In the modificat...

  17. Catalytic Methods in Asymmetric Synthesis Advanced Materials, Techniques, and Applications

    CERN Document Server

    Gruttadauria, Michelangelo

    2011-01-01

    This book covers advances in the methods of catalytic asymmetric synthesis and their applications. Coverage moves from new materials and technologies to homogeneous metal-free catalysts and homogeneous metal catalysts. The applications of several methodologies for the synthesis of biologically active molecules are discussed. Part I addresses recent advances in new materials and technologies such as supported catalysts, supports, self-supported catalysts, chiral ionic liquids, supercritical fluids, flow reactors and microwaves related to asymmetric catalysis. Part II covers advances and milesto

  18. Cooperative Mechanism of Supply Chain Under Asymmetric Information

    Institute of Scientific and Technical Information of China (English)

    郭敏; 王红卫; 瞿坦

    2003-01-01

    The cooperative mechanism is one main issue in the decentralized supply chain system, especially in an asymmetric information structure. We analyze the non-cooperative game behavior of a 2-echelon distribution supply chain, compare the results with the system optimal solution, and give the supplier dominated cooperative mechanisms. We also analyze the validity of our contract under the asymmetric retailers' holding cost information and give some useful conclusions.

  19. Asymmetric zygote division: A mystery starting point of embryogenesis.

    Science.gov (United States)

    Zhao, Jing; Sun, Meng-Xiang

    2016-10-02

    In angiosperm, asymmetric zygote division is critical for embryogenesis. The molecular mechanism underlying this process has gained a great attention recently. Some players involve in the control of both accurate position and correct orientation of zygote division plane have been found, which provide useful clues for the extensive investigations. It is getting clear that both internal and external factors are involved in this complex regulatory mechanism and the asymmetric zygote division seems with great impact in cell fate determination and embryo pattern formation.

  20. Reduction of contact stresses using involute gears with asymmetric teeth

    OpenAIRE

    2015-01-01

    Asymmetrical involute gears have a different value of the operating pressure angle for right and left side of the gear. These teeth are suitable for one direction of rotation. Such teeth enable to change the length of the generating line. They enable to improve the value of reduced radii of curvature. Asymmetrical teeth allow reducing the values of Hertz's pressures, especially on the root of the teeth. Hertz pressures are directly related to the asymmetry.

  1. The upside of downsizing: asymmetric trifunctional organocatalysts as small enzyme mimics for cooperative enhancement of both rate and enantioselectivity with regulation.

    Science.gov (United States)

    Liu, Fei

    2013-11-01

    Small molecule organic catalysts (organocatalysts) are widely used in asymmetric catalysis and synthesis. Compared to their enzymatic and transition-metal counterparts, organocatalysts have advantages in catalytic scope and efficiency but are more limited in proficiency. Chiral trifunctional organocatalysts, in which multiple catalytic motifs act cooperatively on a chiral scaffold, are an emerging class of organocatalysts with improved proficiency. Cooperativity design that enables both enantioselectivity and rate enhancement is essential to developing future generations of organocatalysts in biomimetic asymmetric catalysis.

  2. 1H-Imidazol-4(5H)-ones and thiazol-4(5H)-ones as emerging pronucleophiles in asymmetric catalysis

    Science.gov (United States)

    Mielgo, Antonia

    2016-01-01

    Summary Asymmetric catalysis represents a very powerful tool for the synthesis of enantiopure compounds. In this context the main focus has been directed not only to the search for new efficient chiral catalysts, but also to the development of efficient pronucleophiles. This review highlights the utility and first examples of 1H-imidazol-4(5H)-ones and thiazol-4(5H)-ones as pronucleophiles in catalytic asymmetric reactions. PMID:27340482

  3. Asymmetric neuroimaging in Creutzfeldt-Jakob disease: a ruse.

    Science.gov (United States)

    Bavis, James; Reynolds, Patrick; Tegeler, Charles; Clark, Paige

    2003-10-01

    Creutzfeldt-Jakob disease (CJD) causes diffuse neurological symptoms, but asymmetric lesions have been found on conventional magnetic resonance imaging (MRI) and diffusion-weighted imaging (DWI). Less often, position emission tomography (PET) scanning can also reveal asymmetric lesions in patients with CJD. Such imaging may mislead clinicians. The authors present a case of a woman with CJD who was diagnosed as having suffered a stroke because she had asymmetric T2-weighted imaging (T2WI) MRI abnormalities that were interpreted as a stroke. It was noted that the patient had clinical features consistent with CJD, including rapidly progressive dementia, myoclonus, cerebellar dysfunction, and pyramidal and extrapyramidal signs. This diagnosis was supported by periodic epileptiform discharges on the electroencephalogram (EEG) and by elevated 14-3-3 protein in the cerebrospinal fluid. MRI T2WI and DWI showed dramatically asymmetric abnormalities involving the left cortex. A PET study found decreased metabolism in the left cerebral and right cerebellar hemispheres. The patient's clinical, EEG, and laboratory data were all consistent with CJD, not other diseases, but the MRI and PET had atypical, asymmetric findings. This case demonstrates that CJD should be considered in the differential diagnosis of patients with rapidly progressive neurological decline, even if they have asymmetric imaging findings.

  4. Asymmetric nucleosomes flank promoters in the budding yeast genome.

    Science.gov (United States)

    Ramachandran, Srinivas; Zentner, Gabriel E; Henikoff, Steven

    2015-03-01

    Nucleosomes in active chromatin are dynamic, but whether they have distinct structural conformations is unknown. To identify nucleosomes with alternative structures genome-wide, we used H4S47C-anchored cleavage mapping, which revealed that 5% of budding yeast (Saccharomyces cerevisiae) nucleosome positions have asymmetric histone-DNA interactions. These asymmetric interactions are enriched at nucleosome positions that flank promoters. Micrococcal nuclease (MNase) sequence-based profiles of asymmetric nucleosome positions revealed a corresponding asymmetry in MNase protection near the dyad axis, suggesting that the loss of DNA contacts around H4S47 is accompanied by protection of the DNA from MNase. Chromatin immunoprecipitation mapping of selected nucleosome remodelers indicated that asymmetric nucleosomes are bound by the RSC chromatin remodeling complex, which is required for maintaining nucleosomes at asymmetric positions. These results imply that the asymmetric nucleosome-RSC complex is a metastable intermediate representing partial unwrapping and protection of nucleosomal DNA on one side of the dyad axis during chromatin remodeling.

  5. Orientation- and position-controlled alignment of asymmetric silicon microrod on a substrate with asymmetric electrodes

    Science.gov (United States)

    Shibata, Akihide; Watanabe, Keiji; Sato, Takuya; Kotaki, Hiroshi; Schuele, Paul J.; Crowder, Mark A.; Zhan, Changqing; Hartzell, John W.; Nakatani, Ryoichi

    2014-03-01

    In this paper, we demonstrate the orientation-controlled alignment of asymmetric Si microrods on a glass substrate with an asymmetric pair of electrodes. The Si microrods have the shape of a paddle with a blade and a shaft part, and the pair of electrodes consists of a narrow electrode and a wide electrode. By applying AC bias to the electrodes, the Si microrods suspended in a fluid align in such a way to settle across the electrode pair, and over 80% of the aligned Si microrods have an orientation with the blade and the shaft of the paddle on the wide and the narrow electrodes, respectively. When Si microrods have a shell of dielectric film and its thickness on the top face is thicker than that on the bottom face, 97.8% of the Si microrods are aligned with the top face facing upwards. This technique is useful for orientation-controlled alignment of nano- and microsized devices that have polarity or a distinction between the top and bottom faces.

  6. Asymmetric Actuator Backlash Compensation in Quantized Adaptive Control of Uncertain Networked Nonlinear Systems.

    Science.gov (United States)

    Lai, Guanyu; Liu, Zhi; Zhang, Yun; Chen, Chun Lung Philip; Xie, Shengli

    2015-12-24

    This paper mainly aims at the problem of adaptive quantized control for a class of uncertain nonlinear systems preceded by asymmetric actuator backlash. One challenging problem that blocks the construction of our control scheme is that the real control signal is wrapped in the coupling of quantization effect and nonsmooth backlash nonlinearity. To resolve this challenge, this paper presents a two-stage separation approach established on two new technical components, which are the approximate asymmetric backlash model and the nonlinear decomposition of quantizer, respectively. Then the real control is successfully separated from the coupling dynamics. Furthermore, by employing the neural networks and adaptation method in control design, a quantized controller is developed to guarantee the asymptotic convergence of tracking error to an adjustable region of zero and uniform ultimate boundedness of all closed-loop signals. Eventually, simulations are conducted to support our theoretical results.

  7. Stability characteristics of the open channel flow above the asymmetrical irregular sand ripples

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Sandy bed cannot keep its original smoothness as the flows pass. With the increase of the flow intensity, the bed forms will appear as sand ripples and dune in turn. Among these morphologies, the sand ripple scale is the smallest, which is generally symmetrical when it just appears, but as time goes on, the asymmetrical form gradually develops. Just because of this sand ripples asymmetry, it manifests the influence of the flow on the bed morphology and also the impact on the laminar flow dynamical process, especially the stability characteristics. The stability features of laminar flow on open channels with the asymmetrical sand ripples are discussed, and also the results on the symmetrical sand ripples are compared in detail.

  8. GENERALIZED ASYMMETRIC HYSTERESIS MODEL OF CONTROLLABLE MAGNETORHEOLOGICAL DAMPER FOR VEHICLE SUSPENSION ATTENUATION

    Institute of Scientific and Technical Information of China (English)

    Wang Enrong; Ma Xiaoqing; Su Chunyi; Rakheja Subhash

    2004-01-01

    A generalized model is synthesized to characterize the asymmetric hysteresis force-velocity (F-v) properties of the magneto-rheological (MR) fluids damper.The model is represented as a function of the command current,excitation frequency,and displacement amplitude,based on the symmetric and asymmetric sigmoid functions.The symmetric hysteresis damping properties of the controllable MR-damper and properties of the conventional passive hydraulic damper can also be described by the proposed model.The validity of the model is verified by experiments,which show that the results calculated from the model are consistent with the measured data.In addition,it is shown that the model applies to a wide vibration frequency range.The proposed model has potential application in vehicle suspension design employing the symmetry MR-damper,and also in developing the asymmetry MR-damper especially for the vehicle suspension attenuation.

  9. Tunable hard X-ray spectrometer utilizing asymmetric planes of a quartz transmission crystal.

    Science.gov (United States)

    Seely, John F; Henins, Albert; Feldman, Uri

    2016-05-01

    A Cauchois type hard x-ray spectrometer was developed that utilizes the (301) diffraction planes at an asymmetric angle of 23.51° to the normal to the surface of a cylindrically curved quartz transmission crystal. The energy coverage is tunable by rotating the crystal and the detector arm, and spectra were recorded in the 8 keV to 20 keV range with greater than 2000 resolving power. The high resolution results from low aberrations enabled by the nearly perpendicular angle of the diffracted rays with the back surface of the crystal. By using other asymmetric planes of the same crystal and rotating to selected angles, the spectrometer can operate with high resolution up to 50 keV.

  10. Application of spherical Ni(OH)2/CNTs composite electrode in asymmetric supercapacitor

    Institute of Scientific and Technical Information of China (English)

    WANG Xiao-feng; RUAN Dian-bo; YOU Zheng

    2006-01-01

    The composite electrodes consisting of carbon nanotubes and spherical Ni(OH)2 are developed by mixing nickel hydroxide, carbon nanotubes and carbonyl nickel powder together in 8-1-1 ratio. A maximum capacitance of 311 F/g is obtained for an electrode prepared with the precipitation process. In order to enhance energy density, an asymmetric type pseudo-capacitor/electric double layer capacitor is considered and its electrochemical properties are investigated. Values for the specific energy and maximum specific power of 25.8 W-h/kg and 2.8 kW/kg, respectively, are demonstrated for a cell voltage between 0 and 1.6 V. By using the modified cathode of a Ni(OH)2/carbon nanotube composite electrode, the asymmetric supercapacitor exhibits high energy density and stable power characteristics.

  11. A carbon nanotube confinement strategy to implement homogeneous asymmetric catalysis in the solid phase.

    Science.gov (United States)

    Hashimoto, Kazuki; Kumagai, Naoya; Shibasaki, Masakatsu

    2015-03-09

    A readily recyclable asymmetric catalyst has been developed based on the self-assembly of a homogeneous catalyst in a fibrous network of multiwalled carbon nanotubes (MWNTs). Dimerization of an amide-based chiral ligand with a suitable spacer allows for the efficient formation of a heterogeneous catalyst by self-assembly on addition of Er(OiPr)3. The self-assembly proceeds in the MWNT fibrous network and small clusters of assembled catalyst are confined in the MWNTs, producing an easily handled solid-phase catalyst. The resulting MWNT-confined catalyst exhibits a good catalytic performance in a catalytic asymmetric Mannich-type reaction, which can be conducted in a repeated batch system and in a continuous-flow platform.

  12. Construction of an Asymmetric Quaternary Carbon Center via Allylation of Hydrazones

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jin Bum; Satyender, Apuri; Jang, Doo Ok [Yonsei Univ., Wonju (Korea, Republic of)

    2013-11-15

    Asymmetric indium-mediated allylation of imine derivatives bearing a chiral auxiliary is a reliable strategy for the synthesis of chiral homoallylic amines. Various techniques for indium-mediated stereoselective allylation of imines bearing a chiral auxiliary have been reported. In 1997 Loh and co-workers reported indium-mediated allylation with imines derived from L-valine methyl ester. Since then, many forms of indium-mediated allylation bearing a chiral auxiliary have been reported, including imines derived from (S)-valinol, (R)-phenylglycinol, uracil, (R)-phenylglycinol methyl ester, N-tert-butanesufinamide, and (1R,2S)-1-amino-2-indanol. However, the synthesis of chiral auxiliaries often involves a laborious multi-step synthesis with expensive reagents. Therefore, the development of readily accessible chiral auxiliaries for asymmetric indium-mediated all-ylation is in high demand.

  13. Effect of Asymmetrical Edge Disconnection on Equivalent Series Resistance of Metalized Polypropylene Capacitors

    Directory of Open Access Journals (Sweden)

    J. Sivakumar

    2014-01-01

    Full Text Available In order to investigate the effect of asymmetrical partial edge disconnection on the Equivalent Series Resistance (ESR of Metalized polypropylene capacitors an experimental study has been made. Theoretical analysis made using PSPICE simulation package reveals that electrode resistance of individual turn rises from 10 to 30% depending on the location of the turn. This rise is not measureable at all the frequencies as ESR is frequency dependent and it includes resistance due to electrodes and dielectric losses. Metalized polypropylene capacitors were made with partial edge disconnection at one end (asymmetrical with different magnitudes of edge disconnection by masking during the process of zinc spraying. Measurements of ESR have been made in a wide range of frequencies from 20 Hz to 50 MHz and the theoretical results are validated through the experimental data. A short time step stress test was conducted on the capacitors, which can be further developed as a type test to identify the capacitors with partial edge disconnection.

  14. Hemispherical anomaly from asymmetric initial states

    Science.gov (United States)

    Ashoorioon, Amjad; Koivisto, Tomi

    2016-08-01

    We investigate if the hemispherical asymmetry in the CMB is produced from "asymmetric" excited initial conditions. We show that in the limit where the deviations from the Bunch-Davies vacuum are large and the scale of new physics is maximally separated from the inflationary Hubble parameter, the primordial power spectrum is modulated only by position-dependent dipole and quadrupole terms. Requiring the dipole contribution in the power spectrum to account for the observed power asymmetry, A =0.07 ±0.022 , we show that the amount of quadrupole terms is roughly equal to A2. The mean local bispectrum, which gets enhanced for the excited initial state, is within the 1 σ bound of Planck 2015 results for a large field model, fNL≃4.17 , but is reachable by future CMB experiments. The amplitude of the local non-Gaussianity modulates around this mean value, depending on the angle that the correlated patches on the 2d CMB surface make with the preferred direction. The amount of variation is minimized for the configuration in which the short and long wavelength modes are around the preferred pole and |k→3|≈|k→l ≈10|≪|k→1|≈|k→2|≈|k→l ≈2500| with fNLmin≈3.64 . The maximum occurs when these modes are at the antipode of the preferred pole, fNLmax≈4.81 . The difference of non-Gaussianity between these two configurations is as large as ≃1.17 , which can be used to distinguish this scenario from other scenarios that try to explain the observed hemispherical asymmetry.

  15. Asymmetric transfer of auditory perceptual learning

    Directory of Open Access Journals (Sweden)

    Sygal eAmitay

    2012-11-01

    Full Text Available Perceptual skills can improve dramatically even with minimal practice. A major and practical benefit of learning, however, is in transferring the improvement on the trained task to untrained tasks or stimuli, yet the mechanisms underlying this process are still poorly understood. Reduction of internal noise has been proposed as a mechanism of perceptual learning, and while we have evidence that frequency discrimination (FD learning is due to a reduction of internal noise, the source of that noise was not determined. In this study, we examined whether reducing the noise associated with neural phase locking to tones can explain the observed improvement in behavioural thresholds. We compared FD training between two tone durations (15 and 100 ms that straddled the temporal integration window of auditory nerve fibers upon which computational modeling of phase locking noise was based. Training on short tones resulted in improved FD on probe tests of both the long and short tones. Training on long tones resulted in improvement only on the long tones. Simulations of FD learning, based on the computational model and on signal detection theory, were compared with the behavioral FD data. We found that improved fidelity of phase locking accurately predicted transfer of learning from short to long tones, but also predicted transfer from long to short tones. The observed lack of transfer from long to short tones suggests the involvement of a second mechanism. Training may have increased the temporal integration window which could not transfer because integration time for the short tone is limited by its duration. Current learning models assume complex relationships between neural populations that represent the trained stimuli. In contrast, we propose that training-induced enhancement of the signal-to-noise ratio offers a parsimonious explanation of learning and transfer that easily accounts for asymmetric transfer of learning.

  16. Asymmetric inhibitory treatment effects in multilingual aphasia.

    Science.gov (United States)

    Goral, Mira; Naghibolhosseini, Maryam; Conner, Peggy S

    2013-01-01

    Findings from recent psycholinguistic studies of bilingual processing support the hypothesis that both languages of a bilingual are always active and that bilinguals continually engage in processes of language selection. This view aligns with the convergence hypothesis of bilingual language representation. Furthermore, it is hypothesized that when bilinguals perform a task in one language they need to inhibit their other, nontarget language(s) and that stronger inhibition is required when the task is performed in the weaker language than in the stronger one. The study of multilingual individuals who acquire aphasia resulting from a focal brain lesion offers a unique opportunity to test the convergence hypothesis and the inhibition asymmetry. We report on a trilingual person with chronic nonfluent aphasia who at the time of testing demonstrated greater impairment in her first acquired language (Persian) than in her third, later learned language (English). She received treatment in English followed by treatment in Persian. An examination of her connected language production revealed improvement in her grammatical skills in each language following intervention in that language, but decreased grammatical accuracy in English following treatment in Persian. The increased error rate was evident in structures that are used differently in the two languages (e.g., auxiliary verbs). The results support the prediction that greater inhibition is applied to the stronger language than to the weaker language, regardless of their age of acquisition. We interpret the findings as consistent with convergence theories that posit overlapping neuronal representation and simultaneous activation of multiple languages and with proficiency-dependent asymmetric inhibition in multilinguals.

  17. Numerical study of asymmetrical modes in a vortex ring impacting a conical surface

    Science.gov (United States)

    Trejo Gutierrez, Jose Antonio; Lopez Sanchez, Erick Javier; Hernandez Zapata, Sergio; Ruiz Chavarria, Gerardo

    2016-11-01

    In this work we investigate the impact of an annular vortex on a conical surface when their symmetry axes are parallel but they do not coincide. For this purpose we solve the Navier-Stokes and continuity equations in cylindrical coordinates. We use a finite difference scheme for r and z coordinates whereas for the angular coordinate we use a Fourier spectral method. We study the development of asymmetrical modes when the vortex approaches the inner surface of the cone. The presence of the vortex ring induces the formation of a boundary layer which detaches and leads to the formation of a secondary vortex of opposite sign which moves away the cone. This secondary vortex also exhibits asymmetrical modes, which are attenuated as it moves. We present some results as the trajectories of the primary and the secondary vortices, their circulations as a function of time, the development of asymmetrical modes and the dependence of these properties on the Reynolds number and the distance between both symmetry axes. Finally we made a comparison of primary and secondary vortices with a free vortex. Authors acknowledge DGAPA-UNAM by support under project IN115315 "Ondas y estructuras coherentes en dinamica de fluidos".

  18. Impact and Use of the Asymmetric Property in Bi-directional Cooperative Relaying under Asymmetric Traffic Conditions

    Science.gov (United States)

    Saeki, Takaaki; Yamamoto, Koji; Murata, Hidekazu; Yoshida, Susumu

    Cooperative relaying (CR) is a promising technique to provide spatial diversity by combining multiple signals from source and relay stations. In the present paper, the impact and use of the asymmetric property in bi-directional CR under asymmetric traffic conditions are discussed assuming that CR involves one communication pair and one relay station in a time division duplex (TDD) system. The asymmetric property means that the average communication quality differs for each transmission direction because of the difference in signal power between the combined signals for each direction. First, numerical results show the asymmetric property of bi-directional CR. Next, in order to evaluate the impact of the asymmetric property, the optimal relay position and resource allocation are compared to those in simple multi-hop relaying, which does not have the asymmetric property. Numerical results show that, in order to maximize the overall quality of bi-directional communication, the optimal relay position in CR depends on the offered traffic ratio, which is defined as the traffic ratio of each transmission direction, while the offered traffic ratio does not affect the optimal relay position in multi-hop relaying. Finally, the asymmetric property is used to enhance the overall quality. Specifically, a high overall quality can be achieved by, for example, opportunistically switching to the transmission direction with higher quality. Under asymmetric traffic conditions, weighted proportionally fair scheduling (WPFS), which is proposed in the context of downlink scheduling in a cellular network, is applied to transmission direction switching. Numerical results reveal that WPFS provides a high overall quality and that the quality ratio is similar to the offered traffic ratio.

  19. Asymmetric ion transport through ion-channel-mimetic solid-state nanopores.

    Science.gov (United States)

    Guo, Wei; Tian, Ye; Jiang, Lei

    2013-12-17

    different environmental conditions in the electrolyte solutions on either side of the nanochannel. The novel and well-controlled nanofluidic phenomena have become the foundation for many promising applications, and we have highlighted several representative examples. Inspired by the electrogenic cell of the electric eel, we have demonstrated a proof-of-concept nanofluidic reverse electrodialysis system (NREDS) that converts salinity gradient energy into electricity by means of net diffusion current. We have also constructed chirality analysis systems into nanofluidic architectures and monitored these sensing events as the change in the degree of ionic current rectification. Moreover, we have developed a biohybrid nanosystem, in which we reconstituted the F0F1-ATPase on a liposome-coated, solid-state nanoporous membrane. By applying a transmembrane proton concentration gradient, the biohybrid nanodevice can synthesize ATP in vitro. These findings have improved our understanding of the asymmetric ion transport phenomena in synthetic nanofluidic systems and offer innovative insights into the design of functional nanofluidic devices.

  20. Ru/Me-BIPAM-Catalyzed Asymmetric Addition of Arylboronic Acids to Aliphatic Aldehydes and α-Ketoesters

    Directory of Open Access Journals (Sweden)

    Momoko Watanabe

    2011-06-01

    Full Text Available A ruthenium-catalyzed asymmetric arylation of aliphatic aldehydes and α-ketoesters with arylboronic acids has been developed, giving chiral alkyl(arylmethanols and α-hydroxy esters in good yields. The use of a chiral bidentate phosphoramidite ligand (Me-BIPAM achieved excellent enantioselectivities.

  1. A highly efficient and recoverable bi-cinchona alkaloid ligand for the catalytic asymmetric aminohydroxylation of olefins

    Directory of Open Access Journals (Sweden)

    SHENGYONG ZHANG

    2006-10-01

    Full Text Available A new freely recyclable bi-cinchona alkaloid ligand has been developed for the homogeneous catalytic asymmetric aminohydroxylation (AA of olefins. It can be easily recovered by precipitation and reused for 5 times without any significant loss in its catalytic efficiency in AA reactions.

  2. An Asymmetric Synthetic Approach to the A-ring of the Taxol Family of Anti-Cancer Compounds

    Directory of Open Access Journals (Sweden)

    M. L. Marin

    1998-02-01

    Full Text Available A synthetic route developed for the preparation of the A-ring of Taxol family of molecules is reported. By means of an intramolecular Diels-Alder reaction an asymmetric approach to this ring has been accomplished. Also, initial studies to prepare the A ring using an intramolecular Diels-Alder reaction have been successful.

  3. Ru/Me-BIPAM-catalyzed asymmetric addition of arylboronic acids to aliphatic aldehydes and α-ketoesters.

    Science.gov (United States)

    Yamamoto, Yasunori; Shirai, Tomohiko; Watanabe, Momoko; Kurihara, Kazunori; Miyaura, Norio

    2011-06-17

    A ruthenium-catalyzed asymmetric arylation of aliphatic aldehydes and α-ketoesters with arylboronic acids has been developed, giving chiral alkyl(aryl)methanols and α-hydroxy esters in good yields. The use of a chiral bidentate phosphoramidite ligand (Me-BIPAM) achieved excellent enantioselectivities.

  4. Asymmetric three-component domino reaction: an original access to chiral nonracemic 1,3-thiazin-2-ones.

    Science.gov (United States)

    Peudru, Flavie; Le Cavelier, Fabien; Lohier, Jean-François; Gulea, Mihaela; Reboul, Vincent

    2013-11-15

    A new asymmetric three-component domino process, based on a diastereoselective hetero-Diels-Alder reaction, involving an aldehyde, an alkene, and a chiral thiocarbamate was developed. The chiral auxiliary is directly removed during this process, leading to enantioenriched 2H-1,3-thiazin-2-ones with up to 96% ee.

  5. Voltage-Sharing Converter to Supply Single-Phase Asymmetrical Four-Level Diode-Clamped Inverter With High Power Factor Loads

    DEFF Research Database (Denmark)

    Boora, Arash A.; Nami, Alireza; Zare, Firuz

    2010-01-01

    The output voltage quality of some of the single-phase multilevel inverters can be improved when their dc-link voltages are regulated asymmetrically. Symmetrical and asymmetrical multilevel diode-clamped inverters have the problem of dc-link capacitor voltage balancing, especially when power factor...... of the load is close to unity. In this paper, a new single-inductor multi-output dc/dc converter is proposed that can control the dc-link voltages of a single-phase diode-clamped inverter asymmetrically to achieve voltage quality enhancement. The circuit of the presented converter is explained and the main...... equations are developed. A control strategy is proposed and explained in details. To validate the versatility of the proposed combination of the suggested dc–dc converter and the asymmetrical four-level diode-clamped inverter (ADCI), simulations and experiments have been directed. It is concluded...

  6. Optical asymmetric watermarking using modified wavelet fusion and diffractive imaging

    Science.gov (United States)

    Mehra, Isha; Nishchal, Naveen K.

    2015-05-01

    In most of the existing image encryption algorithms the generated keys are in the form of a noise like distribution with a uniform distributed histogram. However, the noise like distribution is an apparent sign indicating the presence of the keys. If the keys are to be transferred through some communication channels, then this may lead to a security problem. This is because; the noise like features may easily catch people's attention and bring more attacks. To address this problem it is required to transfer the keys to some other meaningful images to disguise the attackers. The watermarking schemes are complementary to image encryption schemes. In most of the iterative encryption schemes, support constraints play an important role of the keys in order to decrypt the meaningful data. In this article, we have transferred the support constraints which are generated by axial translation of CCD camera using amplitude-, and phase- truncation approach, into different meaningful images. This has been done by developing modified fusion technique in wavelet transform domain. The second issue is, in case, the meaningful images are caught by the attacker then how to solve the copyright protection. To resolve this issue, watermark detection plays a crucial role. For this purpose, it is necessary to recover the original image using the retrieved watermarks/support constraints. To address this issue, four asymmetric keys have been generated corresponding to each watermarked image to retrieve the watermarks. For decryption, an iterative phase retrieval algorithm is applied to extract the plain-texts from corresponding retrieved watermarks.

  7. Asymmetric Zinc Phthalocyanines as Dye-Sensitized Solar Cells

    Science.gov (United States)

    Tunc, Gulenay; Yavuz, Yunus; Gurek, Aysegul; Canimkurbey, Betul; Kosemen, Arif; San, Sait Eren; Ahsen, Vefa

    Dye-sensitized solar cells (DSSCs) have received increasing attention due to their high incident to photon efficiency, easy fabrication and low production cost . Tremendous research efforts have been devoted to the development of new and efficient sensitizers suitable for practical use. In TiO2-based DSSCs, efficiencies of up to 11.4% under simulated sunlight have been obtained with rutheniumepolypyridyl complexes. However, the main drawback of ruthenium complexes is the lack of absorption in the red region of the visible light and the high cost. For this reason, dyes with large and stable p-conjugated systems such as porphyrins and phthalocyanines are important classes of potential sensitizers for highly efficient DSSCs. Phthalocyanines (Pcs) have been widely used as sensitizers because of their improved light-harvesting properties in the far red- and near-IR spectral regions and their extraordinary robustness [1]. In this work, a series of asymmetric Zn(II) Pcs bearing a carboxylic acid group and six hexylthia groups either at the peripheral or non-peripheral positions have been designed and synthesized to investigate the influence of the COOH group and the positions of hexylthia groups on the dye-sensitized solar cell (DSSC) performance.

  8. Dcc regulates asymmetric outgrowth of forebrain neurons in zebrafish.

    Directory of Open Access Journals (Sweden)

    Jingxia Gao

    Full Text Available The guidance receptor DCC (deleted in colorectal cancer ortholog UNC-40 regulates neuronal asymmetry development in Caenorhabditis elegans, but it is not known whether DCC plays a role in the specification of neuronal polarity in vertebrates. To examine the roles of DCC in neuronal asymmetry regulation in vertebrates, we studied zebrafish anterior dorsal telencephalon (ADt neuronal axons. We generated transgenic zebrafish animals expressing the photo-convertible fluorescent protein Kaede in ADt neurons and then photo-converted Kaede to label specifically the ADt neuron axons. We found that ADt axons normally project ventrally. Knock down of Dcc function by injecting antisense morpholino oligonucleotides caused the ADt neurons to project axons dorsally. To examine the axon projection pattern of individual ADt neurons, we labeled single ADt neurons using a forebrain-specific promoter to drive fluorescent protein expression. We found that individual ADt neurons projected axons dorsally or formed multiple processes after morpholino knock down of Dcc function. We further found that knock down of the Dcc ligand, Netrin1, also caused ADt neurons to project axons dorsally. Knockdown of Neogenin1, a guidance receptor closely related to Dcc, enhanced the formation of aberrant dorsal axons in embryos injected with Dcc morpholino. These experiments provide the first evidence that Dcc regulates polarized axon initiation and asymmetric outgrowth of forebrain neurons in vertebrates.

  9. Structural and functional insights into asymmetric enzymatic dehydration of alkenols.

    Science.gov (United States)

    Nestl, Bettina M; Geinitz, Christopher; Popa, Stephanie; Rizek, Sari; Haselbeck, Robert J; Stephen, Rosary; Noble, Michael A; Fischer, Max-Philipp; Ralph, Erik C; Hau, Hoi Ting; Man, Henry; Omar, Muhiadin; Turkenburg, Johan P; van Dien, Stephen; Culler, Stephanie J; Grogan, Gideon; Hauer, Bernhard

    2017-03-01

    The asymmetric dehydration of alcohols is an important process for the direct synthesis of alkenes. We report the structure and substrate specificity of the bifunctional linalool dehydratase isomerase (LinD) from the bacterium Castellaniella defragrans that catalyzes in nature the hydration of β-myrcene to linalool and the subsequent isomerization to geraniol. Enzymatic kinetic resolutions of truncated and elongated aromatic and aliphatic tertiary alcohols (C5-C15) that contain a specific signature motif demonstrate the broad substrate specificity of LinD. The three-dimensional structure of LinD from Castellaniella defragrans revealed a pentamer with active sites at the protomer interfaces. Furthermore, the structure of LinD in complex with the product geraniol provides initial mechanistic insights into this bifunctional enzyme. Site-directed mutagenesis confirmed active site amino acid residues essential for its dehydration and isomerization activity. These structural and mechanistic insights facilitate the development of hydrating catalysts, enriching the toolbox for novel bond-forming biocatalysis.

  10. The dynamics and control of large flexible asymmetric spacecraft

    Science.gov (United States)

    Humphries, T. T.

    1991-02-01

    This thesis develops the equations of motion for a large flexible asymmetric Earth observation satellite and finds the characteristics of its motion under the influence of control forces. The mathematical model of the structure is produced using analytical methods. The equations of motion are formed using an expanded momentum technique which accounts for translational motion of the spacecraft hub and employs orthogonality relations between appendage and vehicle modes. The controllability and observability conditions of the full spacecraft motions using force and torque actuators are defined. A three axis reaction wheel control system is implemented for both slewing the spacecraft and controlling its resulting motions. From minor slew results it is shown that the lowest frequency elastic mode of the spacecraft is more important than higher frequency modes, when considering the effects of elastic motion on instrument pointing from the hub. Minor slews of the spacecraft configurations considered produce elastic deflections resulting in rotational attitude motions large enough to contravene pointing accuracy requirements of instruments aboard the spacecraft hub. Active vibration damping is required to reduce these hub motions to acceptable bounds in sufficiently small time. A comparison between hub mounted collocated and hub/appendage mounted non-collocated control systems verifies that provided the non-collocated system is stable, it can more effectively damp elastic modes whilst maintaining adequate damping of rigid modes. Analysis undertaken shows that the reaction wheel controller could be replaced by a thruster control system which decouples the modes of the spacecraft motion, enabling them to be individually damped.

  11. Is the HD 15115 circumstellar disk really asymmetrical?

    Science.gov (United States)

    Mazoyer, J.; Boccaletti, A.; Augereau, J.-C.; Lagrange, A.-M.; Galicher, R.; Baudoz, P.

    2014-09-01

    Similarly to beta Pictoris, HD 15115 is a young and nearby (45.2 pc) star that hosts a debris disk. This debris disk was first imaged in 2007 (Kalas et al., 2007) in visible using HST and in H band using the Keck observatory. The disk appeared edge-on and showed an asymmetry between its west and east parts. This detection was later observed in J band using HST / Nicmos data (Debes et al., 2008) and in Ks and L' using LBT (Rodigas et al. 2012). These observations confirmed the asymmetric nature of HD 15115 debris disk. We present here the results of the analysis of data from the Gemini / NICI archival system from 2009 and 2011 in H and K bands. We use newly developed differential treatment algorithms on these data (ADI, LOCI, KLIP) to subtract the light of the star and image the disk up to 1 arc second (30 AU). From this analysis, we find an inclination of 86 (confirming previous conclusions about HD 15115). We derive the disk position angle and spine and photometry and only find a brightness asymmetry in these elements. We also present evidence of an ring at 2 arc seconds (60 AU), with a rather sharp inner edge, and no sign of an asymmetry. With this radius and inclination, we create disk models (Augereau et al. 1999) and put constraints on the disk parameters, using either the position angle, spine and photometry or forward modeling.

  12. The asymmetric impact of natural disasters on China's bilateral trade

    Science.gov (United States)

    Meng, Y.; Yang, S.; Shi, P.; Jeager, C. C.

    2015-10-01

    Globalization and technological revolutions are making the world more interconnected. International trade is an important approach linking the world. Since the 2011 Tohoku earthquake and tsunami in Japan shocked the global supply chain, more attention has been paid to the global impact of large-scale disasters. China is the second largest trader in the world and faces frequent natural disasters. Therefore, this study proposes a gravity model for China's bilateral trade tailored to national circumstances and estimates the impact of natural disasters in China and trading partner countries on Chinese imports and exports. We analyzed Chinese and trading partner statistical data from 1980 to 2012. Study results show the following: (1) China's natural disasters have a positive impact on exports but have no significant impact on imports; (2) trading partner countries' natural disasters reduce Chinese imports and exports; (3) both development level and land area of the partners are important in determining the intensity of natural disaster impacts on China's bilateral trade. The above findings suggest that the impact of natural disasters on trade is asymmetric and significantly affected by other factors, which demand further study.

  13. Asymmetric Transfer Hydrogenation of ω -Bromo Acetophenones in Aqueous Media

    Institute of Scientific and Technical Information of China (English)

    Wang Fei; Liu Hui; Cui Xin; Cun Linfeng; Zhu Jin; Deng Jingen; Jiang Yaozhong

    2004-01-01

    Optical active ω-bromophenylethanols are useful building blocks for synthesis of various pharmaceuticals such as α 1-, β 2-, and β 3- adrenergic receptor agonists, which are always obtained though a biotransformative pathway and using boron reagent with rigorous conditions [1]. To our knowledge, the metal-catalysed transfer hydrogenation is seldom applied in this reaction. Recently we have developed a water-soluble chiral Ru-complex and applied successfully in transfer hydrogenation of ω-bromo acetophenones in aqueous media [2], which can not be performed in homogeneous system with HCOOH/NEt3 as hydrogen donor[3] .In this paper, we will report that asymmetric transfer hydrogenation of ω-bromo acetophenones was successfully performed in aqueous media by employing hydrophobic Rh-amido complex (TsDPEN-Rh) as catalyst and HCOONa as hydrogen donor. Moreover, marked increasing of activity and high enantioselectivity (up to 98%) of ω-bromo acetophenone 1a was found in the presence of different micelles or vesicles. This method was also applied successfully in preparation of the important chiral medicinal intermediates, such as the precursor of salbutamol, 2b and fermoterol, 2c with high enantioselectivity.

  14. Asymmetrical reinforcement and Wolbachia infection in Drosophila.

    Directory of Open Access Journals (Sweden)

    John Jaenike

    2006-10-01

    Full Text Available Reinforcement refers to the evolution of increased mating discrimination against heterospecific individuals in zones of geographic overlap and can be considered a final stage in the speciation process. One the factors that may affect reinforcement is the degree to which hybrid matings result in the permanent loss of genes from a species' gene pool. Matings between females of Drosophila subquinaria and males of D. recens result in high levels of offspring mortality, due to interspecific cytoplasmic incompatibility caused by Wolbachia infection of D. recens. Such hybrid inviability is not manifested in matings between D. recens females and D. subquinaria males. Here we ask whether the asymmetrical hybrid inviability is associated with a corresponding asymmetry in the level of reinforcement. The geographic ranges of D. recens and D. subquinaria were found to overlap across a broad belt of boreal forest in central Canada. Females of D. subquinaria from the zone of sympatry exhibit much stronger levels of discrimination against males of D. recens than do females from allopatric populations. In contrast, such reproductive character displacement is not evident in D. recens, consistent with the expected effects of unidirectional cytoplasmic incompatibility. Furthermore, there is substantial behavioral isolation within D. subquinaria, because females from populations sympatric with D. recens discriminate against allopatric conspecific males, whereas females from populations allopatric with D. recens show no discrimination against any conspecific males. Patterns of general genetic differentiation among populations are not consistent with patterns of behavioral discrimination, which suggests that the behavioral isolation within D. subquinaria results from selection against mating with Wolbachia-infected D. recens. Interspecific cytoplasmic incompatibility may contribute not only to post-mating isolation, an effect already widely recognized, but also to

  15. Rh(I)–Bisphosphine-Catalyzed Asymmetric, Intermolecular Hydroheteroarylation of α-Substituted Acrylate Derivatives

    Science.gov (United States)

    2015-01-01

    Asymmetric hydroheteroarylation of alkenes represents a convenient entry to elaborated heterocyclic motifs. While chiral acids are known to mediate asymmetric addition of electron-rich heteroarenes to Michael acceptors, very few methods exploit transition metals to catalyze alkylation of heterocycles with olefins via a C–H activation, migratory insertion sequence. Herein, we describe the development of an asymmetric, intermolecular hydroheteroarylation reaction of α-substituted acrylates with benzoxazoles. The reaction provides 2-substitued benzoxazoles in moderate to excellent yields and good to excellent enantioselectivities. Notably, a series of mechanistic studies appears to contradict a pathway involving enantioselective protonation of a Rh(I)–enolate, despite the fact that such a mechanism is invoked almost unanimously in the related addition of aryl boronic acids to methacrylate derivatives. Evidence suggests instead that migratory insertion or beta-hydride elimination is enantiodetermining and that isomerization of a Rh(I)–enolate to a Rh(I)–heterobenzyl species insulates the resultant α-stereocenter from epimerization. A bulky ligand, CTH-(R)-Xylyl-P-Phos, is crucial for reactivity and enantioselectivity, as it likely discourages undesired ligation of benzoxazole substrates or intermediates to on- or off-cycle rhodium complexes and attenuates coordination-promoted product epimerization. PMID:25545834

  16. Interactions and Translational Dynamics of Phosphatidylinositol Bisphosphate (PIP2) Lipids in Asymmetric Lipid Bilayers.

    Science.gov (United States)

    Shi, Xiaojun; Kohram, Maryam; Zhuang, Xiaodong; Smith, Adam W

    2016-02-23

    Phosphatidylinositol phosphate (PIP) lipids are critical to many cell signaling pathways, in part by acting as molecular beacons that recruit peripheral membrane proteins to specific locations within the plasma membrane. Understanding the biophysics of PIP-protein interactions is critical to developing a chemically detailed model of cell communication. Resolving such interactions is challenging, even in model membrane systems, because of the difficulty in preparing PIP-containing membranes with high fluidity and integrity. Here we report on a simple, vesicle-based protocol for preparing asymmetric supported lipid bilayers in which fluorescent PIP lipid analogues are found only on the top leaflet of the supported membrane facing the bulk solution. With this asymmetric distribution of lipids between the leaflets, the fluorescent signal from the PIP lipid analogue reports directly on interactions between the peripheral molecules and the top leaflet of the membrane. Asymmetric PIP-containing bilayers are an ideal platform to investigate the interaction of PIP with peripheral membrane proteins using fluorescence-based imaging approaches. We demonstrate their usefulness here with a combined fluorescence correlation spectroscopy and single particle tracking study of the interaction between PIP2 lipids and a polycationic polymer, quaternized polyvinylpyridine (QPVP). With this approach we are able to quantify the microscopic features of the mobility coupling between PIP2 lipids and polybasic QPVP. With single particle tracking we observe individual PIP2 lipids switch from Brownian to intermittent motion as they become transiently trapped by QPVP.

  17. Asymmetric resonance frequency analysis of in-plane electrothermal silicon cantilevers for nanoparticle sensors

    Science.gov (United States)

    Bertke, Maik; Hamdana, Gerry; Wu, Wenze; Marks, Markus; Suryo Wasisto, Hutomo; Peiner, Erwin

    2016-10-01

    The asymmetric resonance frequency analysis of silicon cantilevers for a low-cost wearable airborne nanoparticle detector (Cantor) is described in this paper. The cantilevers, which are operated in the fundamental in-plane resonance mode, are used as a mass-sensitive microbalance. They are manufactured out of bulk silicon, containing a full piezoresistive Wheatstone bridge and an integrated thermal heater for reading the measurement output signal and stimulating the in-plane excitation, respectively. To optimize the sensor performance, cantilevers with different cantilever geometries are designed, fabricated and characterized. Besides the resonance frequency, the quality factor (Q) of the resonance curve has a high influence concerning the sensor sensitivity. Because of an asymmetric resonance behaviour, a novel fitting function and method to extract the Q is created, different from that of the simple harmonic oscillator (SHO). For testing the sensor in a long-term frequency analysis, a phase- locked loop (PLL) circuit is employed, yielding a frequency stability of up to 0.753 Hz at an Allan variance of 3.77 × 10-6. This proposed asymmetric resonance frequency analysis method is expected to be further used in the process development of the next-generation Cantor.

  18. Flexible, transparent and high-power triboelectric generator with asymmetric graphene/ITO electrodes

    Science.gov (United States)

    Song, Xinbo; Chen, Yuanfu; Li, Pingjian; Liu, Jingbo; Qi, Fei; Zheng, Binjie; Zhou, Jinhao; Hao, Xin; Zhang, Wanli

    2016-07-01

    The reported flexible and transparent triboelectric generator (FTTG) can only output ultralow power density (˜2 μW cm-2), which has seriously hindered its further development and application. The low power density of FTTG is mainly limited by the transparent material and the electrode structure. Herein, for the first time, a FTTG with a superior power density of 60.7 μW cm-2 has been fabricated by designing asymmetric electrodes where graphene and indium tin oxide (ITO) act as top and bottom electrodes respectively. Moreover, the performance of FTTG with graphene/ITO (G/I) asymmetric electrodes (GI-FTTG) almost remains unchanged even after 700 cycles, indicating excellent mechanical stability. The excellent performance of GI-FTTG can be attributed to the suitable materials and unique asymmetric electrode structure: the extraordinary flexibility of the graphene top electrode ensures the GI-FTTG excellent mechanical robustness and stability even after longer cycles, and the bottom electrode with very low sheet resistance guarantees lower internal resistance and higher production rate of induction charges to obtain higher output power density. It shows that light-emitting diodes (LED) can be easily powered by GI-FTTG, which demonstrates that the GI-FTTG is very promising for harvesting electrical energy from human activities by using flexible and transparent devices.

  19. Hollow silica capsules with well-defined asymmetric windows in the shell.

    Science.gov (United States)

    Zhao, Bo; Collinson, Maryanne M

    2012-05-15

    A straightforward and effective approach to fabricate porous silica capsules with well-defined asymmetric windows in the shell using raspberry-like templates has been developed. This process begins with the formation of a hierarchical template by chemically coupling a large polystyrene sphere to an ensemble of small, polystyrene latex spheres. The hierarchical template in conjunction with a hard templating method and spin-coating leads to silica capsules with well-defined, asymmetric pores (windows) in the outer shell. Proof-of-principle of this approach has been demonstrated using a 1500/110 nm hierarchical template. The silica capsules thus produced were characterized with scanning electron microscopy and STEM. The diameter of the capsules was ~1400 nm, and the outer opening of the windows was ~100 nm in size, consistent with the diameters of the core and satellite spheres considering the shrinkage due to the calcination. The inner opening was ~30 nm, which gives rise to an asymmetry factor, defined as the diameter of the outer window to the diameter of the inner window, of ~3. In another example, surface-bound capsules with an asymmetry factor of ~1 were made. Collectively, these windows can provide efficient pathways to connect the inside of the capsule to the outside and have potential for asymmetric diffusion and rectification.

  20. Asymmetric segregation of damaged cellular components in spatially structured multicellular organisms.

    Directory of Open Access Journals (Sweden)

    Charlotte Strandkvist

    Full Text Available The asymmetric distribution of damaged cellular components has been observed in species ranging from fission yeast to humans. To study the potential advantages of damage segregation, we have developed a mathematical model describing ageing mammalian tissue, that is, a multicellular system of somatic cells that do not rejuvenate at cell division. To illustrate the applicability of the model, we specifically consider damage incurred by mutations to mitochondrial DNA, which are thought to be implicated in the mammalian ageing process. We show analytically that the asymmetric distribution of damaged cellular components reduces the overall damage level and increases the longevity of the cell population. Motivated by the experimental reports of damage segregation in human embryonic stem cells, dividing symmetrically with respect to cell-fate, we extend the model to consider spatially structured systems of cells. Imposing spatial structure reduces, but does not eliminate, the advantage of asymmetric division over symmetric division. The results suggest that damage partitioning could be a common strategy for reducing the accumulation of damage in a wider range of cell types than previously thought.