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Sample records for aquaglyceroporin aqp9 null

  1. Expression and localization of aqua-glyceroporins AQP3 and AQP9 in rat oral epithelia.

    Science.gov (United States)

    Poveda, Marlene; Hashimoto, Sadamitsu; Enokiya, Yasunobu; Matsuki-Fukushima, Miwako; Sasaki, Hodaka; Sakurai, Kaoru; Shimono, Masaki

    2014-01-01

    Aquaporins (AQPs) are a family of small integral membrane proteins made up of 6 hydrophobic, a-helical, membrane-spanning domains surrounding a highly selective aqueous pore. AQP3, AQP7, and AQP9, termed aqua-glyceroporins, are known to be involved in the transport of water, glycerol, and other small molecules. In this study, we investigated the expression and localization of aqua-glyceroporins in rat oral stratified squamous epithelia of the palate, the buccal mucosa, the inferior aspect of the tongue, and the oral floor by using RT-PCR, immunofluorescence, and immunogold electron microscopy. AQP3 and AQP9 mRNAs were expressed in whole oral epithelium. Immunostaining for AQP3 was recognized in each type of epithelium. The results suggest that AQP3 synthesis begins predominantly in the cytoplasm of the basal cells. During the process of epithelial cell differentiation, AQP3 protein appears to accumulate and be transported to the plasma membrane, from where it is incorporated into the cornified or surface layers. The intracellular localization of AQP3 appears to correlate with the differentiation of keratinocytes, suggesting that it acts as an enhancer of the physiological permeability barrier together with membrane coating granules. The distribution pattern of AQP9 was limited to the marginal areas of the basal and suprabasal layers, which was different from that of AQP3. This difference in distribution between AQP3 and AQP9 suggests that AQP9 in rat oral epithelia acts as a channel by facilitating glycerol uptake from the blood through the endothelial cells of the capillary vessels to the oral stratified squamous epithelium. AQP3 and AQP9 facilitate both transcellular osmotic water flow and glycerol transport as pore-like passive transporters in the keratinocytes of oral epithelia, and may play a key role in not only hydration and the permeability barrier, but also cell proliferation, differentiation, migration, development, and wound healing by generating ATP.

  2. Analysis of mice with targeted deletion of AQP9 gene provides conclusive evidence for expression of AQP9 in neurons

    DEFF Research Database (Denmark)

    Mylonakou, Maria N; Petersen, Petur H; Rinvik, Eric;

    2009-01-01

    AQP9 is an aquaglyceroporin that serves important functions in peripheral organs, including the liver. Reflecting the lack of AQP9 knockout mice, uncertainties still prevail regarding the localization and roles of AQP9 in the central nervous system. Here we present a comprehensive analysis of AQP9...... and mouse liver, the organ with the highest level of AQP9. By blue native gel analysis it could be demonstrated that the brain contains tetrameric AQP9, corresponding to the functional form of AQP9. The band corresponding to the AQP9 tetramer was absent in AQP9 knockout brain and liver. Immunocytochemistry...... and in situ hybridization analyses with AQP9 knockout controls show that subpopulations of nigral neurons express AQP9 both at the mRNA and at the protein levels and that populations of cortical cells (including hilar neurons in the hippocampus) contain AQP9 mRNA but no detectable AQP9 immunosignal...

  3. Pentavalent methylated arsenicals are substrates of human AQP9.

    Science.gov (United States)

    McDermott, Joseph R; Jiang, Xuan; Beene, Lauren C; Rosen, Barry P; Liu, Zijuan

    2010-02-01

    Liver aquaglyceroporin AQP9 facilitates movement of trivalent inorganic arsenite (As(III)) and organic monomethylarsonous acid (MAs(III)). However, the transport pathway for the two major pentavalent arsenic cellular metabolites, MAs(V) and DMAs(V), remains unknown in mammals. These products of arsenic metabolism, in particular DMAs(V), are the major arsenicals excreted in the urine of mammals. In this study, we examined the uptake of the two pentavalent organic arsenicals by human AQP9 in Xenopus laevis oocytes. Xenopus laevis oocytes microinjected with AQP9 cRNA exhibited uptake of both MAs(V) and DMAs(V) in a pH-dependent manner. The rate of transport was much higher at acidic pH (pH5.5) than at neutral pH. Hg(II), an aquaporin inhibitor, inhibited transport of As(III), MAs(III), MAs(V) and DMAs(V) via AQP9. However, phloretin, which inhibits water and glycerol permeation via AQP9, can only inhibit transport of pentavalent MAs(V) and DMAs(V) but not trivalent As(III) and MAs(III), indicating the translocation mechanisms of these arsenic species are not exactly the same. Reagents such as FCCP, valinomycin and nigericin that dissipate transmembrane proton potential or change the transmemebrane pH gradient did not significantly inhibit all arsenic transport via AQP9, suggesting the transport of pentavalent arsenic is not proton coupled. The results suggest that in addition to the initial uptake of trivalent inorganic As(III) inside cells, AQP9 plays a dual role in the detoxification of arsenic metabolites by facilitating efflux from cells.

  4. SL7207/pEGFP-N1-AQP9及SL7207/pshRNA-AQP9重组沙门菌的构建及表达%Construction and expression of recombinant Salmonella SL7207/pEGFP-N1-AQP9 and SL7207/pshRNA-AQP9

    Institute of Scientific and Technical Information of China (English)

    王川; 亢渝俊; 姜政; 王丕龙

    2012-01-01

    Objective To transform human aquaglyceroporin 9(AQP9) recombinant eukaryotic expression plasmid pEGFP Nl AQP9 and interference plasmid pshRNA AQP9 into attenuated Salmonella strain SL7207 by electroporation and detect their ex pression,in order to lay the foundation for elucidating the human AQP9 in pathogenesis of nonalcoholic fatty liver disease (NAFLD). Methods AQP9 gene was obtained by RT PCR from human hepatic tissue and cloned into pEGFP Nl vector,recombi nant eukaryotic expression plasmid pEGFP Nl AQP9 was constructed,designed and synthesized human AQP9 SiRNA,annealed to double stranded ShRNA, inserted to pGenesil 1 plasmid, interference plasmid pshRNA AQP9 was constructed, and then trans formed into attenuated Salmonella strain SL7207 by electroporation,the expression were detected by PCR and Western Blot,and we detected their stability. Results Recombinant plasmid pEGFP Nl AQP9 and pshRNA AQP9 were constructed, transformed into attenuated Salmonella strain SL7207,after transformed into SL7207,could express in recombinant Salmonella. Conclusion Recom binant Salmonella SL7207/pEGFP Nl AQP9 and SL7207/pshRNA AQP9 are successfully constructed,lay the foundation for fur ther study on the gene therapy of NAFLD with AQP9.%目的 将人水甘油通道蛋白9(AQP9)真核表达质粒pEGFP-N1-AQP9及干扰质粒pshRNA-AQP9通过电穿孔转化减毒沙门菌株SL7207,并验证其表达情况,为阐明AQP9在非酒精性脂肪肝病(NAFLD)中的作用奠定基础.方法 从人肝脏组织中通过RT-PCR获得AQP9基因,克隆到载体pEGFP-N1上,构建真核表达质粒pEGFP-N1-AQP9,设计合成针对人AQP9的siRNA,退火形成双链shRNA,并插入pGenesil-1质粒中,构建干扰质粒pshRNA-AQP9,电穿孔转化减毒沙门菌株SL7207,通过PCR、Western blot验证其表达情况,并检测其稳定性.结果 成功构建pEGFP-N1-AQP9及pshRNA-AQP9重组质粒,将其转化SL7207后,能在重组沙门菌中表达.结论 成功构建SL7207/pEGFP-N1-AQP9及SL7207/pshRNA-AQP

  5. Aquaglyceroporins serve as metabolic gateways in adiposity and insulin resistance control

    OpenAIRE

    Rodriguez, A.; Catalan, V.; Gomez-Ambrosi, J.; Frühbeck, G.

    2011-01-01

    Aquaglyceroporins (AQP3, AQP7, AQP9 and AQP10) encompass a subfamily of aquaporins that allow the movement of water and other small solutes, especially glycerol, through cell membranes. Adipose tissue constitutes a major source of glycerol via AQP7. We have recently reported that, in addition to the well-known expression of AQP7 in adipose tissue, AQP3 and AQP9 are also expressed in omental and subcutaneous fat depots. Moreover, insulin and leptin act as regulators of aquaglyceroporins throug...

  6. Roles of vertebrate aquaglyceroporins in arsenic transport and detoxification.

    Science.gov (United States)

    Liu, Zijuan

    2010-01-01

    Aquaporins are important channel proteins that are responsible for the balance of cellular osmolarity and nutrient transport in vertebrates. Recently, new functions of these ancient channels have been found in the conduction of metalloid arsenic (As). Chronic As exposure through contaminated water and food sources is associated with multiple human diseases and endangers millions of people's health worldwide. Therefore, identification of the As transport pathways is necessary to elucidate the mechanisms of As carcinogenesis. Arsenic detoxification systems have been studied in multiple vertebrates such as mammalian mouse, rat, humans and nonmammalian vertebrates. Multiple transporters and enzymes have been shown to be involved in As translocation and cellular transformation. In these vertebrates, members ofaquaglyceroporins, which include AQP7 in kidney and AQP9 in liver, catalyze uptake of inorganic trivalent arsenite [As(III)]. AQP9, the major liver aquaglyceroporin, conducts both inorganic As(III) and organic monomethylarsonous acid [MMA(III)], an intermediate that is generated during the cellular methylation. As a channel that facilitates a downhill movement of substances dependent on the concentration gradient, AQP9 may play an important role in the simultaneous influx of inorganic As(III) from blood to liver and efflux of As metabolite MMA(III) from liver to blood. In this chapter, we will discuss the function ofaquaglyceroporins ofvertebrates in uptake and detoxification of the metalloid As.

  7. Expression and clinical significance of aquaglyceroporins in human hepatocellular carcinoma.

    Science.gov (United States)

    Chen, Xiao-Feng; Li, Chuan-Fei; Lü, Lin; Mei, Zhe-Chuan

    2016-06-01

    Aquaglyceroporins (AQPs) are a subset of the aquaporin family, and are permeable to water and glycerol. The aim of the present study was to determine the expression and clinical significance of three AQPs, AQP3, 7 and 9 in hepatocellular carcinoma (HCC). Fresh HCC and adjacent non‑tumorous liver tissues were collected from 68 patients diagnosed with HCC. The expression levels of AQP3, 7 and 9 were detected by reverse transcription‑quantitative polymerase chain reaction, western blotting and immunohistochemical analysis. The association between the expression of AQPs and clinicopathological parameters of HCC were investigated. Compared with non‑tumorous liver tissue, HCC tissues exhibited a significant (P<0.05) increase in the expression of AQP3 and a concomitant reduction in the expression levels of AQP7 and AQP9, at both the mRNA and protein levels. Immunohistochemistry revealed that AQP9 was dominantly localized on the plasma membrane of hepatocytes, while AQP3 and AQP7 exhibited a predominantly cytoplasmic and nuclear distribution. High expression of AQP3 was significantly (P<0.05) associated with low expression levels of AQP7 and AQP9. High expression of AQP3 was correlated with tumor grade (P=0.017), tumor stage (P=0.010) and lymphatic metastasis (P=0.031). Low expression of AQP7 was correlated with tumor grade (P=0.043). AQP3 was upregulated, and AQP7 and AQP9 were downregulated in HCC. A high expression of AQP3 and low expression of AQP7 was significantly associated with the aggressive features of HCC. PMID:27121567

  8. Hepatic AQP9 expression in male rats is reduced in response to PPARα agonist treatment.

    Science.gov (United States)

    Lebeck, Janne; Cheema, Muhammad Umar; Skowronski, Mariusz T; Nielsen, Søren; Praetorius, Jeppe

    2015-02-01

    The peroxisome proliferator receptor α (PPARα) is a key regulator of the hepatic response to fasting with effects on both lipid and carbohydrate metabolism. A role in hepatic glycerol metabolism has also been found; however, the results are somewhat contradictive. Aquaporin 9 (AQP9) is a pore-forming transmembrane protein that facilitates hepatic uptake of glycerol. Its expression is inversely regulated by insulin in male rodents, with increased expression during fasting. Previous results indicate that PPARα plays a crucial role in the induction of AQP9 mRNA during fasting. In the present study, we use PPARα agonists to explore the effect of PPARα activation on hepatic AQP9 expression and on the abundance of enzymes involved in glycerol metabolism using both in vivo and in vitro systems. In male rats with free access to food, treatment with the PPARα agonist WY 14643 (3 mg·kg(-1)·day(-1)) caused a 50% reduction in hepatic AQP9 abundance with the effect being restricted to AQP9 expressed in periportal hepatocytes. The pharmacological activation of PPARα had no effect on the abundance of GlyK, whereas it caused an increased expression of hepatic GPD1, GPAT1, and L-FABP protein. In WIF-B9 and HepG2 hepatocytes, both WY 14643 and another PPARα agonist GW 7647 reduced the abundance of AQP9 protein. In conclusion, pharmacological PPARα activation results in a marked reduction in the abundance of AQP9 in periportal hepatocytes. Together with the effect on the enzymatic apparatus for glycerol metabolism, our results suggest that PPARα activation in the fed state directs glycerol into glycerolipid synthesis rather than into de novo synthesis of glucose. PMID:25477377

  9. Charakterisierung des Burkholderia cenocepacia Aquaglyceroporins

    OpenAIRE

    Wree, Dorothea

    2010-01-01

    In der vorliegenden Arbeit wurde ein Aquaglyceroporin des Krankenhausproblemkeims Burkholderia cenocepacia, BccGlpF, charakterisiert. Unter besonderer Beobachtung stand die Struktur-Funktionsbeziehung der eigentlich kochkonservierten NPA-Motive.

  10. Mammalian aquaglyceroporin function in metabolism.

    Science.gov (United States)

    Laforenza, Umberto; Bottino, Cinzia; Gastaldi, Giulia

    2016-01-01

    Aquaglyceroporins are integral membrane proteins that are permeable to glycerol as well as water. The movement of glycerol from a tissue/organ to the plasma and vice versa requires the presence of different aquaglyceroporins that can regulate the entrance or the exit of glycerol across the plasma membrane. Actually, different aquaglyceroporins have been discovered in the adipose tissue, small intestine, liver, kidney, heart, skeletal muscle, endocrine pancreas and capillary endothelium, and their differential expression could be related to obesity and the type 2 diabetes. Here we describe the expression and function of different aquaglyceroporins in physiological condition and in obesity and type 2 diabetes, suggesting they are potential therapeutic targets for metabolic disorders. PMID:26456554

  11. Aquaglyceroporins: ancient channels for metalloids

    OpenAIRE

    Bhattacharjee, Hiranmoy; Mukhopadhyay, Rita; Thiyagarajan, Saravanamuthu; Rosen, Barry P.

    2008-01-01

    The identification of aquaglyceroporins as uptake channels for arsenic and antimony shows how these toxic elements can enter the food chain, and suggests that food plants could be genetically modified to exclude arsenic while still accumulating boron and silicon.

  12. Deletion of glycerol channel aquaporin-9 (Aqp9) impairs long-term blood glucose control in C57BL/6 leptin receptor-deficient (db/db) obese mice

    DEFF Research Database (Denmark)

    Spegel, Peter; Chawade, Aakash; Nielsen, Søren;

    2015-01-01

    profiling did not detect differential gene expression between genotypes. Metabolite profiling revealed a sex independent increase in plasma glycerol (+55%) and glucose (+24%), and reduction in threonate (all at q < 0.1) in Aqp9(-/-) db/db mice compared to controls. Metabolite profiling thus confirms a role......Deletion of the glycerol channel aquaporin-9 (Aqp9) reduces postprandial blood glucose levels in leptin receptor-deficient (db/db) obese mice on a C57BL/6 × C57BLKS mixed genetic background. Furthermore, shRNA-mediated reduction of Aqp9 expression reduces liver triacylglycerol (TAG) accumulation in...... observed elevated plasma glucose in Aqp9(-/-) db/db mice (+1.1 mmol/L, life-time average), while plasma insulin concentration was reduced at the time of death. Glucose levels changed similarly in pentobarbital anesthetized, glucagon challenged Aqp9(wt) db/db and Aqp9(-/-) db/db mice. Liver transcriptional...

  13. Trypanosoma Brucei Aquaglyceroporins Facilitate the Uptake of Arsenite and Antimonite in a pH Dependent Way

    Directory of Open Access Journals (Sweden)

    Néstor L. Uzcátegui

    2013-09-01

    Full Text Available Background: Trypanosoma brucei is a primitive parasitic protozoan that thrives in diverse environments such as the midgut of the tsetse fly and the blood of a mammalian host. For an adequate adaptation to these environments, the parasite´s aquaglyceroporins play an important role. Methods and Results: In order to test their ability to transport trivalent arsenic and antimony, we expressed the three known Trypanosoma brucei aquaglyceroporins (TbAQPs in the heterologous systems of yeast null aquaporin mutant and Xenopus laevis oocytes. For both expression systems, we found a pH dependent intracellular accumulation of As(III or Sb(III mediated by all of the three TbAQPs, with the exception of TbAQP1-As(III uptake. Additionally, we observed that Trypanosoma brucei aquaglyceroporins allow the passage of As(III in both directions. Conclusion: Taken together, these results demonstrated that T. brucei aquaglyceroporins can serve as entry routes for As(III and Sb(III into the parasitic cell, and that this uptake is pH sensitive. Therefore, aquaporins of protozoan parasites may be considered useful as a vehicle for drug delivery.

  14. Glycerol inhibits water permeation through Plasmodium falciparum aquaglyceroporin.

    Science.gov (United States)

    Chen, Liao Y

    2013-01-01

    Plasmodium falciparum aquaglyceroporin (PfAQP) is a multifunctional membrane protein in the plasma membrane of P. falciparum, the parasite that causes the most severe form of malaria. The current literature has established the science of PfAQP's structure, functions, and hydrogen-bonding interactions but left unanswered the following fundamental question: does glycerol modulate water permeation through aquaglyceroporin that conducts both glycerol and water? This paper provides an affirmative answer to this question of essential importance to the protein's functions. On the basis of the chemical-potential profile of glycerol from the extracellular bulk region, throughout PfAQP's conducting channel, to the cytoplasmic bulk region, this study shows the existence of a bound state of glycerol inside aquaglyceroporin's permeation pore, from which the dissociation constant is approximately 14μM. A glycerol molecule occupying the bound state occludes the conducting pore through which permeating molecules line up in single file by hydrogen-bonding with one another and with the luminal residues of aquaglyceroporin. In this way, glycerol inhibits permeation of water and other permeants through aquaglyceroporin. The biological implications of this theory are discussed and shown to agree with the existent in vitro data. It turns out that the structure of aquaglyceroporin is perfect for the van der Waals interactions between the protein and glycerol to cause the existence of the bound state deep inside the conducting pore and, thus to play an unexpected but significant role in aquaglyceroporin's functions.

  15. Expression of aquaporin-9 in the brain tissue of rats with infectious brain edema%AQP-9在大鼠感染性脑水肿脑组织中的表达及意义

    Institute of Scientific and Technical Information of China (English)

    田培超; 王怀立; 罗强; 禚志红

    2008-01-01

    Objective To investigate the expression of aquaporin-9(AQP-9)in the brain tissue of rats with infectious brain edema and explore the role of AQP-9 in the oecurrgnce and progression of the brain edema. Methods A total of 128 normal 1-month-old SD rats weighing 70-100 g of either sex were randomly divided into two equal groups, namely the normal saline(NS) group and lipopolysaecharide(LPS)group.Acute infectious brain edema was induced in rats in the LPS group by injecting LPS via the left internal carotid artery,and the rats in the NS groups received NS injection.At 6,12,24 and 48 h after the injection,the brain tissue was taken from the rats to observe the histopathology by Hernatoxylin-Eosin Stain and lneasure the brain water content(BWC).The permeability of the blood-brain barrier of the rats was tested using Evans blue(EB)method.The expressions of AQP-9 protein and mRNA in the brain tissue Were detected using immunohistochemistry and RT-PCR,respectively. Results InLPS group,the space around the blood vessels was obviously broadened in the brain tissue,where inflammatory cell infiltration,glioeyte swelling,vacuolar degeneration of the neurons and neuronal nuclear shrinkage were seen.At 6,12,24,and 48 h following LPS or NS injection,the BWC,EB content,and expressions of AQP-9 protein and mRNA in the LPS group were all significantly higher than those in the NS group(P<0.05),In the LPS group,positive correlations were found between BWC and EB content,AQP-9 protein expression and BWC,AQP一9 mRNA and BWC,AQP-9mR.NA and EBcontent,and between AQP-9 protein andmRNA.Conclusion AQP-9 might participate in occurrcnce and development of infectious brain edema in rats,it might be positive correlation.%目的 探讨水通道蛋白-9(AQP-9)在内毒素脂多糖(LPS)致大鼠感染性脑水肿脑组织中的表达及意义. 方法 1月龄普通级SD大鼠128只采用随机数字表法分为生理盐水(NS)组(64只)和LPS组(64只),采用颈内动脉注射LPS制作大鼠感染

  16. Aquaglyceroporins in the kidney: present state of knowledge and prospects.

    Science.gov (United States)

    Michalek, K

    2016-04-01

    Aquaporins belong to a family of small, transmembrane proteins that form channels selectively permeable for water. Some of them known as aquaglyceroporins also enable transportation of other small molecules such as glycerol, urea or ammonia. To date, 13 isoforms of aquaporins has been discovered in mammals (AQP0 - AQP12), 9 of which is localized in different parts of the renal tubular epithelium. In recent years, particular interest has been paid to aquaporins selectively permeable only to water molecules, determination of their localization and expression allowed to define the role of these proteins in renal excretion of water and their importance in the development of diseases. Alas, thus far the role in the physiological processes of the aquaglyceroporins localized in the kidneys has not been fully determined. This review summarizes our current knowledge on additional transport functions of renal AQPs (AQP3, AQP6, AQP7 and AQP8). On the basis of the information gathered and the opinions by many authors, it has been found that aquaglyceroporins are most probably the key element in the renal regulation of nitrogen balance and maintenance of the correct pH of body fluids. Elucidating additional transport functions of AQPs in the kidney will improve our understanding of the renal function in heath and diseases. The presented in this article prospect on renal aquaglyceroporin hopefully will stimulate future research in both basic and clinical fields. PMID:27226178

  17. Comparative analysis of sequences, polymorphisms and topology of yeasts aquaporins and aquaglyceroporins.

    Science.gov (United States)

    Sabir, Farzana; Loureiro-Dias, Maria C; Prista, Catarina

    2016-05-01

    Efficient homeostasis of water and glycerol is a prerequisite for osmoregulation and other aspects of yeasts life. The cellular status of these molecules is often associated with functional presence of aquaporins and aquaglyceroporins. The present study provides a detailed updated analysis of aquaporins and aquaglyceroporins in 47 yeast species. A comprehensive analysis of aquaporins and aquaglyceroporins in 38 strains of Saccharomyces cerevisiae from different ecological niches is also presented. The functionality of specific aquaporins in yeasts has been associated with their adaptation requirements in different environmental conditions. In the present study, various inactivating mutations in aquaporin sequences were found in strains of S. cerevisiae Likewise, several new interesting polymorphisms in aquaglyceroporin sequences of some commercial wine and brewing strains, vineyard and bakery strains were also observed. Conceivably, both in the case of aquaporins and aquaglyceroporins inactivating mutations resulted in competitive advantage in selected environments. Topology and conservation of important regulatory residues within all sequences are also analyzed. We expect that the present review may contribute to establish the functional relevance of aquaporins/aquaglyceroporins for various aspects of yeasts physiology. PMID:27001976

  18. Metalloid transport by aquaglyceroporins: consequences in the treatment of human diseases.

    Science.gov (United States)

    Mukhopadhyay, Rita; Beitz, Eric

    2010-01-01

    Metalloids can severely harm human physiology in a toxicological sense if taken up from the environment in acute high doses or chronically. However, arsenic or antimony containing drugs are still being used as treatment and are often the sole regime for certain forms of cancer, mainly types of leukemia and diseases caused by parasites, such as sleeping sickness or leishmaniasis. In this chapter, we give an outline of the positive effects of arsenicals and antimonials against such diseases, we summarize data on uptake pathways through human and parasite aquaglyceroporins and we discuss the progress and options in the development of therapeutic aquaporin and aquaglyceroporin inhibitor compounds.

  19. Pentamidine Is Not a Permeant but a Nanomolar Inhibitor of the Trypanosoma brucei Aquaglyceroporin-2.

    Directory of Open Access Journals (Sweden)

    Jie Song

    2016-02-01

    Full Text Available The chemotherapeutic arsenal against human African trypanosomiasis, sleeping sickness, is limited and can cause severe, often fatal, side effects. One of the classic and most widely used drugs is pentamidine, an aromatic diamidine compound introduced in the 1940s. Recently, a genome-wide loss-of-function screen and a subsequently generated trypanosome knockout strain revealed a specific aquaglyceroporin, TbAQP2, to be required for high-affinity uptake of pentamidine. Yet, the underlying mechanism remained unclear. Here, we show that TbAQP2 is not a direct transporter for the di-basic, positively charged pentamidine. Even though one of the two common cation filters of aquaglyceroporins, i.e. the aromatic/arginine selectivity filter, is unconventional in TbAQP2, positively charged compounds are still excluded from passing the channel. We found, instead, that the unique selectivity filter layout renders pentamidine a nanomolar inhibitor of TbAQP2 glycerol permeability. Full, non-covalent inhibition of an aqua(glyceroporin in the nanomolar range has not been achieved before. The remarkable affinity derives from an electrostatic interaction with Asp265 and shielding from water as shown by structure-function evaluation and point mutation of Asp265. Exchange of the preceding Leu264 to arginine abolished pentamidine-binding and parasites expressing this mutant were pentamidine-resistant. Our results indicate that TbAQP2 is a high-affinity receptor for pentamidine. Taken together with localization of TbAQP2 in the flagellar pocket of bloodstream trypanosomes, we propose that pentamidine uptake is by endocytosis.

  20. Pentamidine Is Not a Permeant but a Nanomolar Inhibitor of the Trypanosoma brucei Aquaglyceroporin-2.

    Science.gov (United States)

    Song, Jie; Baker, Nicola; Rothert, Monja; Henke, Björn; Jeacock, Laura; Horn, David; Beitz, Eric

    2016-02-01

    The chemotherapeutic arsenal against human African trypanosomiasis, sleeping sickness, is limited and can cause severe, often fatal, side effects. One of the classic and most widely used drugs is pentamidine, an aromatic diamidine compound introduced in the 1940s. Recently, a genome-wide loss-of-function screen and a subsequently generated trypanosome knockout strain revealed a specific aquaglyceroporin, TbAQP2, to be required for high-affinity uptake of pentamidine. Yet, the underlying mechanism remained unclear. Here, we show that TbAQP2 is not a direct transporter for the di-basic, positively charged pentamidine. Even though one of the two common cation filters of aquaglyceroporins, i.e. the aromatic/arginine selectivity filter, is unconventional in TbAQP2, positively charged compounds are still excluded from passing the channel. We found, instead, that the unique selectivity filter layout renders pentamidine a nanomolar inhibitor of TbAQP2 glycerol permeability. Full, non-covalent inhibition of an aqua(glycero)porin in the nanomolar range has not been achieved before. The remarkable affinity derives from an electrostatic interaction with Asp265 and shielding from water as shown by structure-function evaluation and point mutation of Asp265. Exchange of the preceding Leu264 to arginine abolished pentamidine-binding and parasites expressing this mutant were pentamidine-resistant. Our results indicate that TbAQP2 is a high-affinity receptor for pentamidine. Taken together with localization of TbAQP2 in the flagellar pocket of bloodstream trypanosomes, we propose that pentamidine uptake is by endocytosis. PMID:26828608

  1. Verified Null-Move Pruning

    CERN Document Server

    David-Tabibi, Omid

    2008-01-01

    In this article we review standard null-move pruning and introduce our extended version of it, which we call verified null-move pruning. In verified null-move pruning, whenever the shallow null-move search indicates a fail-high, instead of cutting off the search from the current node, the search is continued with reduced depth. Our experiments with verified null-move pruning show that on average, it constructs a smaller search tree with greater tactical strength in comparison to standard null-move pruning. Moreover, unlike standard null-move pruning, which fails badly in zugzwang positions, verified null-move pruning manages to detect most zugzwangs and in such cases conducts a re-search to obtain the correct result. In addition, verified null-move pruning is very easy to implement, and any standard null-move pruning program can use verified null-move pruning by modifying only a few lines of code.

  2. Null twisted geometries

    CERN Document Server

    Speziale, Simone

    2013-01-01

    We define and investigate a quantisation of null hypersurfaces in the context of loop quantum gravity on a fixed graph. The main tool we use is the parametrisation of the theory in terms of twistors, which has already proved useful in discussing the interpretation of spin networks as the quantization of twisted geometries. The classical formalism can be extended in a natural way to null hypersurfaces, with the Euclidean polyhedra replaced by null polyhedra with space-like faces, and SU(2) by the little group ISO(2). The main difference is that the simplicity constraints present in the formalims are all first class, and the symplectic reduction selects only the helicity subgroup of the little group. As a consequence, information on the shapes of the polyhedra is lost, and the result is a much simpler, abelian geometric picture. It can be described by an Euclidean singular structure on the 2-dimensional space-like surface defined by a foliation of space-time by null hypersurfaces. This geometric structure is na...

  3. Gravitational action with null boundaries

    CERN Document Server

    Lehner, Luis; Poisson, Eric; Sorkin, Rafael D

    2016-01-01

    We present a complete discussion of the boundary term in the action functional of general relativity when the boundary includes null segments in addition to the more usual timelike and spacelike segments. We confirm that ambiguities appear in the contribution from a null segment, because it depends on an arbitrary choice of parametrization for the generators. We also show that similar ambiguities appear in the contribution from a codimension-two surface at which a null segment is joined to another (spacelike, timelike, or null) segment. The parametrization ambiguity can be tamed by insisting that the null generators be affinely parametrized; this forces each null contribution to the boundary action to vanish, but leaves intact the fredom to rescale the affine parameter by a constant factor on each generator. Once a choice of parametrization is made, the ambiguity in the joint contributions can be eliminated by formulating well-motivated rules that ensure the additivity of the gravitational action. Enforcing t...

  4. Modulation of activity of the adipocyte aquaglyceroporin channel by plant extracts.

    Science.gov (United States)

    Cals-Grierson, M-M

    2007-02-01

    The plasma membrane protein, aquaglyceroporin-7 (AQP7) is exclusively expressed in adipocytes and appears to be a channel for glycerol entry and exit. It is possible that by facilitating the opening of these channels, the loss of intracellular glycerol could be encouraged and thus reduce the size of the lipid reservoir. Human preadipocytes and mouse 3T3-L1 preadipocytes were induced to develop an adipocytic phenotype by culture in a semi-defined medium. After 7 days, the expression of AQP7 message had increased by 37-fold, a level which could be further up-regulated by troglitazone or retinoic acid or down-regulated by insulin. The mature adipocytes also expressed immunoreactive aquaporin (AQP) channel protein as assessed by immunocytochemistry and Western blot. The addition of adrenaline to the culture medium stimulated the release of glycerol (blockable by HgCl(2)). Plant extracts, with potential anti-cellulite properties, were tested for their effect on glycerol elimination. These included wild yam root (Dioscorea opposita), cocoa bean (Theobroma cacao), horse chestnut tree (Aesculus hippocastanum) seed and bark and tomato (Solanum lycopersicum). Of these, D. opposita appeared to induce a dose-dependent glycerol release. The results show that our assay can help to identify modulators of AQP7 channel expression and activation in adipocytes. PMID:18489306

  5. Aquaglyceroporins are involved in uptake of arsenite into murine gastrointestinal tissues.

    Science.gov (United States)

    Wang, Chun; Chen, Gang; Jiang, Junkang; Qiu, Lianglin; Hosoi, Kazuo; Yao, Chenjuan

    2009-01-01

    Aquaglyceroporins (AQGPs) are members of aquaporin (AQP) family and belong to a subgroup of this water channel family; they are transmembrane proteins that transport water as well as glycerol and other solutes of small molecules. Recent studies have also identified that AQGPs are important transporters of trivalent metalloid in some mammalian cells. However, the uptake routes of arsenite in mammals are still less defined. In this study, to understand the routes of arsenite intake in mammals, mice were treated with Hg(II), glycerol, and As(III) and uptake of As(III) into the gastrointestinal tissues was measured. The level of inorganic arsenic (iAs) in gastrointestinal tissues after As(III) stimulation was much higher than Hg(II) +As(III) or glycerol+As(III) group. RT-PCR results showed that AQGPs were extensively expressed in gastrointestinal tissues of mice. We also treated Caco-2 cells with Hg(II) and As(III); the level of iAs in a group treated with Hg(II)+As(III) decreased compared with As(III)-treated group. Our results suggested that AQGPs could be important transporters in arsenite uptake into gastrointestinal tissues of mice, but more data are need to prove if AQGPs is the only pathway involved in As transport in mammals or just one of them.

  6. On Spinors and Null Vectors

    CERN Document Server

    Budinich, Marco

    2014-01-01

    We investigate the relations between spinors and null vectors in Clifford algebra with particular emphasis on the conditions that a spinor must satisfy to be simple (also: pure). In particular we prove: i) a new property for null vectors: each of them bisects spinor space into two parts of equal size; ii) that simple spinors form one-dimensional subspaces of spinor space; iii) a necessary and sufficient condition for a spinor to be simple that generalizes a theorem of Cartan and Chevalley that appears now as a corollary of this result. We also show how to write down easily the most general spinor with a given associated totally null plane.

  7. Identification of key residues involved in Si transport by the aquaglyceroporins.

    Science.gov (United States)

    Carpentier, Gabriel A; Garneau, Alexandre P; Marcoux, Andrée-Anne; Noël, Micheline; Frenette-Cotton, Rachelle; Isenring, Paul

    2016-09-01

    We recently demonstrated that the aquaglyceroporins (AQGPs) could act as potent transporters for orthosilicic acid (H4SiO4). Although interesting, this finding raised the question of whether water and H4SiO4, the transportable form of Si, permeate AQGPs by interacting with the same region of the pore, especially in view of the difference in molecular radius between the two substrates. Here, our goal was to identify residues that endow the AQGPs with the ability to facilitate Si diffusion by examining the transport characteristics of mutants in which residues were interchanged between a water-permeable but Si-impermeable channel (aquaporin 1 [AQP1]) and a Si-permeable but water-impermeable channel (AQP10). Our results indicate that the composition of the arginine filter (XX/R), known to include three residues that play an important role in water transport, may also be involved in Si selectivity. Interchanging the identities of the nonarginine residues within this filter causes Si transport to increase by approximately sevenfold in AQP1 and to decrease by approximately threefold in AQP10, whereas water transport and channel expression remain unaffected. Our results further indicate that two additional residues in the AQP arginine filter may be involved in substrate selectivity: replacing one of the residues has a profound effect on water permeability, and replacing the other has a profound effect on Si permeability. This study has thus led to the identification of residues that could play a key role in Si transport by the AQGPs and shown that substrate selectivity is likely ensured by more than one checkpoint within or near the pore.

  8. Channel-mediated lactic acid transport: a novel function for aquaglyceroporins in bacteria.

    Science.gov (United States)

    Bienert, Gerd P; Desguin, Benoît; Chaumont, François; Hols, Pascal

    2013-09-15

    MIPs (major intrinsic proteins), also known as aquaporins, are membrane proteins that channel water and/or uncharged solutes across membranes in all kingdoms of life. Considering the enormous number of different bacteria on earth, functional information on bacterial MIPs is scarce. In the present study, six MIPs [glpF1 (glycerol facilitator 1)-glpF6] were identified in the genome of the Gram-positive lactic acid bacterium Lactobacillus plantarum. Heterologous expression in Xenopus laevis oocytes revealed that GlpF2, GlpF3 and GlpF4 each facilitated the transmembrane diffusion of water, dihydroxyacetone and glycerol. As several lactic acid bacteria have GlpFs in their lactate racemization operon (GlpF1/F4 phylogenetic group), their ability to transport this organic acid was tested. Both GlpF1 and GlpF4 facilitated the diffusion of D/L-lactic acid. Deletion of glpF1 and/or glpF4 in Lb. plantarum showed that both genes were involved in the racemization of lactic acid and, in addition, the double glpF1 glpF4 mutant showed a growth delay under conditions of mild lactic acid stress. This provides further evidence that GlpFs contribute to lactic acid metabolism in this species. This lactic acid transport capacity was shown to be conserved in the GlpF1/F4 group of Lactobacillales. In conclusion, we have functionally analysed the largest set of bacterial MIPs and demonstrated that the lactic acid membrane permeability of bacteria can be regulated by aquaglyceroporins.

  9. Identification of key residues involved in Si transport by the aquaglyceroporins.

    Science.gov (United States)

    Carpentier, Gabriel A; Garneau, Alexandre P; Marcoux, Andrée-Anne; Noël, Micheline; Frenette-Cotton, Rachelle; Isenring, Paul

    2016-09-01

    We recently demonstrated that the aquaglyceroporins (AQGPs) could act as potent transporters for orthosilicic acid (H4SiO4). Although interesting, this finding raised the question of whether water and H4SiO4, the transportable form of Si, permeate AQGPs by interacting with the same region of the pore, especially in view of the difference in molecular radius between the two substrates. Here, our goal was to identify residues that endow the AQGPs with the ability to facilitate Si diffusion by examining the transport characteristics of mutants in which residues were interchanged between a water-permeable but Si-impermeable channel (aquaporin 1 [AQP1]) and a Si-permeable but water-impermeable channel (AQP10). Our results indicate that the composition of the arginine filter (XX/R), known to include three residues that play an important role in water transport, may also be involved in Si selectivity. Interchanging the identities of the nonarginine residues within this filter causes Si transport to increase by approximately sevenfold in AQP1 and to decrease by approximately threefold in AQP10, whereas water transport and channel expression remain unaffected. Our results further indicate that two additional residues in the AQP arginine filter may be involved in substrate selectivity: replacing one of the residues has a profound effect on water permeability, and replacing the other has a profound effect on Si permeability. This study has thus led to the identification of residues that could play a key role in Si transport by the AQGPs and shown that substrate selectivity is likely ensured by more than one checkpoint within or near the pore. PMID:27527099

  10. Null distance on a spacetime

    CERN Document Server

    Sormani, Christina

    2015-01-01

    Given a time function $\\tau$ on a spacetime $M$, we define a `null distance function', $\\hat{d}_\\tau$, built from and closely related to the causal structure of $M$. In basic models with timelike $\

  11. Preparative scale production and functional reconstitution of a human aquaglyceroporin (AQP3) using a cell free expression system.

    Science.gov (United States)

    Müller-Lucks, Annika; Gena, Patrizia; Frascaria, Daniele; Altamura, Nicola; Svelto, Maria; Beitz, Eric; Calamita, Giuseppe

    2013-06-25

    Understanding the selectivity of aquaporin (AQP) membrane channels and exploiting their biotechnological potential will require structural and functional studies of wild type and modified proteins; however, expression systems have not previously yielded AQPs in the necessary milligrams quantities. Cell free (CF) systems have emerged in recent years as fast, efficient and versatile technologies for the production of high quality membrane proteins. Here, we establish a convenient method to synthesize large amounts of functional human aquaglyceroporin 3 protein (AQP3), an AQP of physiological relevance conducting glycerol and some small neutral solutes besides water. Milligram amounts of AQP3 were produced as a histidine-tagged protein (hAQP3-6His) in an Escherichia coli extract-based CF system in the presence of the non-ionic detergent Brij-98. The recombinant AQP3 was purified by affinity chromatography, incorporated into liposomes and evaluated functionally by stopped-flow light scattering. Correct protein folding was indicated by the high glycerol and water permeability exhibited by the hAQP3-6His proteoliposomes as compared to empty control liposomes. Functionality of hAQP3-6His was further confirmed by the strong inhibition of the glycerol and water permeability by phloretin and HgCl2, respectively, two blockers of AQP3. Fast and convenient CF production of functional AQP3 may serve as basis for further structural/functional assessment of aquaglyceroporins and help boosting the AQP-based biomimetic technologies. PMID:23541697

  12. Phase-Occultation Nulling Coronagraphy

    CERN Document Server

    Lyon, Richard G; Clampin, Mark; Petrone, Peter

    2015-01-01

    The search for life via characterization of earth-like planets in the habitable zone is one of the key scientific objectives in Astronomy. We describe a new phase-occulting (PO) interferometric nulling coronagraphy (NC) approach. The PO-NC approach employs beamwalk and freeform optical surfaces internal to the interferometer cavity to introduce a radially dependent plate scale difference between each interferometer arm (optical path) that nulls the central star at high contrast while transmitting the off-axis field. The design is readily implemented on segmented-mirror telescope architectures, utilizing a single nulling interferometer to achieve high throughput, a small inner working angle (IWA), sixth-order or higher starlight suppression, and full off-axis discovery space, a combination of features that other coronagraph designs generally must trade. Unlike previous NC approaches, the PO-NC approach does not require pupil shearing; this increases throughput and renders it less sensitive to on-axis common-mo...

  13. Bootstrapping Null Polygon Wilson Loops

    OpenAIRE

    Gaiotto, Davide; Maldacena, Juan; Sever, Amit; Vieira, Pedro

    2010-01-01

    We derive the two loop expressions for polygonal Wilson loops by starting from the one loop expressions and applying an operator product expansion. We do this for polygonal Wilson loops in R^{1,1} and find a result in agreement with previous computations. We also discuss the spectrum of excitations around flux tube that connects two null Wilson lines.

  14. Distinct transport selectivity of two structural subclasses of the nodulin-like intrinsic protein family of plant aquaglyceroporin channels.

    Science.gov (United States)

    Wallace, Ian S; Roberts, Daniel M

    2005-12-27

    Major intrinsic proteins (MIPs) are a diverse class of integral membrane proteins that facilitate the transport of water and some small solutes across cellular membranes. X-ray structures of MIPs indicate that a tetrad of residues (the ar/R region) form a narrow pore constriction that constitutes the selectivity filter. In comparison with mammalian and microbial species, plants have a greater number and diversity of MIPs with greater than 30 genes encoding four phylogenetic subfamilies with eight different classes of ar/R sequences. The nodulin 26-like intrinsic protein (NIP) subfamily in Arabidopsis can be subdivided into two ar/R subgroups: the NIP subgroup I, which resembles the archetype of the family, soybean nodulin 26, and the NIP subgroup II, which is represented by the Arabidopsis protein AtNIP6;1. These two NIPs differ principally by the substitution of a conserved alanine (NIP subgroup II) for a conserved tryptophan (NIP subgroup I) in the helix 2 position (H2) of the ar/R filter. A comparison of the water and solute tranport properties of the two proteins was performed by expression in Xenopus laevis oocytes. Nodulin 26 is an aquaglyceroporin with a modest osmotic water permeability (P(f)) and the ability to transport uncharged solutes such as glycerol and formamide. In constrast, AtNIP6;1 showed no measurable water permeability but transported glycerol, formamide, as well as larger solutes that were impermeable to nodulin 26. By site-directed mutagenesis, we show that the H2 position is the crucial determinant that confers these transport behaviors. A comparison of the NIPs and tonoplast-intrinsic proteins (TIP) shows that the H2 residue can predict the transport profile for water and glycerol with histidine found in TIP-like aquaporins, tryptophan found in aquaglyceroporins (NIP I), and alanine found in water-impermeable glyceroporins (AtNIP6;1). PMID:16363796

  15. Balloon Exoplanet Nulling Interferometer (BENI)

    Science.gov (United States)

    Lyon, Richard G.; Clampin, Mark; Woodruff, Robert A.; Vasudevan, Gopal; Ford, Holland; Petro, Larry; Herman, Jay; Rinehart, Stephen; Carpenter, Kenneth; Marzouk, Joe

    2009-01-01

    We evaluate the feasibility of using a balloon-borne nulling interferometer to detect and characterize exosolar planets and debris disks. The existing instrument consists of a 3-telescope Fizeau imaging interferometer with 3 fast steering mirrors and 3 delay lines operating at 800 Hz for closed-loop control of wavefront errors and fine pointing. A compact visible nulling interferometer is under development which when coupled to the imaging interferometer would in-principle allow deep suppression of starlight. We have conducted atmospheric simulations of the environment above 100,000 feet and believe balloons are a feasible path forward towards detection and characterization of a limited set of exoplanets and their debris disks. Herein we will discuss the BENI instrument, the balloon environment and the feasibility of such as mission.

  16. Parasitic interference in nulling interferometry

    CERN Document Server

    Matter, Alexis; Danchi, William C; Lopez, Bruno; Absil, Olivier

    2013-01-01

    Nulling interferometry aims to detect faint objects close to bright stars. Its principle is to produce a destructive interference along the line-of-sight so that the stellar flux is rejected, while the flux of the off-axis source can be transmitted. In practice, various instrumental perturbations can degrade the nulling performance. Any imperfection in phase, amplitude, or polarization produces a spurious flux that leaks to the interferometer output and corrupts the transmitted off-axis flux. One of these instrumental pertubations is the crosstalk phenomenon, which occurs because of multiple parasitic reflections inside transmitting optics, and/or diffraction effects related to beam propagation along finite size optics. It can include a crosstalk of a beam with itself, and a mutual crosstalk between different beams. This can create a parasitic interference pattern, which degrades the intrinsic transmission map - or intensity response - of the interferometer. In this context, we describe how this instrumental ...

  17. Areas and volumes for null cones

    CERN Document Server

    Grant, James D E

    2010-01-01

    Motivated by recent work of Choquet-Bruhat, Chrusciel, and Martin-Garcia, we prove monotonicity properties and comparison results for the area of slices of the null cone of a point in a Lorentzian manifold. We also prove volume comparison results for subsets of the null cone analogous to the Bishop-Gromov relative volume monotonicity theorem and Guenther's volume comparison theorem. We briefly discuss how these estimates may be used to control the null second fundamental form of slices of the null cone in Ricci-flat Lorentzian four-manifolds with null curvature bounded above.

  18. Visible Nulling Coronagraph Testbed Results

    Science.gov (United States)

    Lyon, Richard G.; Clampin, Mark; Melnick, Gary; Tolls, Volker; Woodruff, Robert; Vasudevan, Gopal; Rizzo, Maxime; Thompson, Patrick

    2009-01-01

    The Extrasolar Planetary Imaging Coronagraph (EPIC) is a NASA Astrophysics Strategic Mission Concept study and a proposed NASA Discovery mission to image and characterize extrasolar giant planets in orbits with semi-major axes between 2 and 10 AU. EPIC would provide insights into the physical nature of a variety of planets in other solar systems complimenting radial velocity (RV) and astrometric planet searches. It will detect and characterize the atmospheres of planets identified by radial velocity surveys, determine orbital inclinations and masses, characterize the atmospheres around A and F stars, observed the inner spatial structure and colors of inner Spitzer selected debris disks. EPIC would be launched to heliocentric Earth trailing drift-away orbit, with a 5-year mission lifetime. The starlight suppression approach consists of a visible nulling coronagraph (VNC) that enables starlight suppression in broadband light from 480-960 nm. To demonstrate the VNC approach and advance it's technology readiness we have developed a laboratory VNC and have demonstrated white light nulling. We will discuss our ongoing VNC work and show the latest results from the VNC testbed.

  19. On the Penrose inequality along null hypersurfaces

    CERN Document Server

    Mars, Marc

    2015-01-01

    The null Penrose inequality, i.e. the Penrose inequality in terms of the Bondi energy, is studied by introducing a funtional on surfaces and studying its properties along a null hypersurface $\\Omega$ extending to past null infinity. We prove a general Penrose-type inequality which involves the limit at infinity of the Hawking energy along a specific class of geodesic foliations called Geodesic Asymptotic Bondi (GAB), which are shown to always exist. Whenever, this foliation approaches large spheres, this inequality becomes the null Penrose inequality and we recover the results of Ludvigsen-Vickers and Bergqvist. By exploiting further properties of the functional along general geodesic foliations, we introduce an approach to the null Penrose inequality called Renormalized Area Method and find a set of two conditions which implies the validity of the null Penrose inequality. One of the conditions involves a limit at infinity and the other a condition on the spacetime curvature along the flow. We investigate the...

  20. Role of aquaporin 9 in cellular accumulation of arsenic and its cytotoxicity in primary mouse hepatocytes.

    Science.gov (United States)

    Shinkai, Yasuhiro; Sumi, Daigo; Toyama, Takashi; Kaji, Toshiyuki; Kumagai, Yoshito

    2009-06-01

    Aquaporin (AQP) 9 is a member of the aquaglyceroporin subfamily of AQPs in the transfer of water and small solutes such as glycerol and arsenite. It is well recognized that arsenic toxicity is associated with intracellular accumulation of this metalloid. In the present study, we examined the contribution of AQP9 to the uptake of inorganic arsenite, thereby increasing arsenic-induced cytotoxicity in primary mouse hepatocytes. Pretreatment with sorbitol as a competitive inhibitor of AQP9 and siRNA-mediated knockdown of AQP9 resulted in a significant decrease of arsenite uptake in the cell and its cytotoxicity. Furthermore, overexpression of AQP9 in HEK293 cells led to the enhancement of intracellular arsenic concentration, resulting in enhanced cytotoxicity after arsenite exposure. These results suggest that AQP9 is a channel to define arsenite sensitivity in primary mouse hepatocytes.

  1. Causal cells: spacetime polytopes with null hyperfaces

    CERN Document Server

    Neiman, Yasha

    2012-01-01

    We consider polyhedra and 4-polytopes in Minkowski spacetime - in particular, null polyhedra with zero volume, and 4-polytopes that have such polyhedra as their hyperfaces. We present the basic properties of several classes of null-faced 4-polytopes: 4-simplices, "tetrahedral diamonds" and 4-parallelotopes. We propose a "most regular" representative of each class. The most-regular parallelotope is of particular interest: its edges, faces and hyperfaces are all congruent, and it features both null hyperplanes and null segments. A tiling of spacetime with copies of this polytope can be viewed alternatively as a lattice with null edges, such that each point is at the intersection of four lightrays in a tetrahedral pattern. We speculate on the relevance of this construct for discretizations of curved spacetime and for quantum gravity.

  2. Conformal symmetry inheritance in null fluid spacetimes

    CERN Document Server

    Tupper, B O J; Hall, G S; Coley, Alan A; Carot, J

    2003-01-01

    We define inheriting conformal Killing vectors for null fluid spacetimes and find the maximum dimension of the associated inheriting Lie algebra. We show that for non-conformally flat null fluid spacetimes, the maximum dimension of the inheriting algebra is seven and for conformally flat null fluid spacetimes the maximum dimension is eight. In addition, it is shown that there are two distinct classes of non-conformally flat generalized plane wave spacetimes which possess the maximum dimension, and one class in the conformally flat case.

  3. Conformal symmetry inheritance in null fluid spacetimes

    Energy Technology Data Exchange (ETDEWEB)

    Tupper, B O J [Department of Mathematics and Statistics, University of New Brunswick, Fredericton, New Brunswick E3B 5A3 (Canada); Keane, A J [Department of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom); Hall, G S [Department of Mathematical Sciences, University of Aberdeen, Dunbar Street, Aberdeen AB24 3UE (United Kingdom); Coley, A A [Department of Mathematics and Statistics, Dalhousie University, Halifax, Nova Scotia B3H 3J5 (Canada); Carot, J [Department de Fisica, Universitat de les Illes Balears, E-07071 Palma de Mallorca (Spain)

    2003-03-07

    We define inheriting conformal Killing vectors for null fluid spacetimes and find the maximum dimension of the associated inheriting Lie algebra. We show that for non-conformally flat null fluid spacetimes, the maximum dimension of the inheriting algebra is seven and for conformally flat null fluid spacetimes the maximum dimension is eight. In addition, it is shown that there are two distinct classes of non-conformally flat generalized plane wave spacetimes which possess the maximum dimension, and one class in the conformally flat case.

  4. Null Subjects in European and Brazilian Portuguese

    OpenAIRE

    Barbosa, Pilar; Duarte, Maria Eugênia L.; Kato, Mary Aizawa

    2005-01-01

    The goals of this paper are twofold: a) to provide a structural account of the effects of the informal ‘Avoid Pronoun Principle’, proposed in Chomsky (1981: 65) for the Null Subject Languages (NSLs), and b) to compare, in European and Brazilian Portuguese (EP and BP), the distribution of the third person pronouns in its full and null forms, to check whether in written corpora BP incorporates signs of the ongoing loss of the null subject, largely attested in its contemporary spoken language. T...

  5. Null geodesics in brane world universe

    International Nuclear Information System (INIS)

    We study null bulk geodesic motion in the brane world cosmology in the RS2 scenario and in the static universe in the bulk of the charged topological AdS black hole. We obtain equations describing the null bulk geodesic motion as observed in one lower dimensions. We find that the null geodesic motion in the bulk of the brane world cosmology in the RS2 scenario is observed to be under the additional influence of extra non-gravitational force by the observer on the three-brane, if the brane universe does not possess the Z2 symmetry. As for the null geodesic motion in the static universe in the bulk of the charged AdS black hole, the extra force is realized even when the brane universe has the Z2 symmetry. (author)

  6. Latex allergy and filaggrin null mutations

    DEFF Research Database (Denmark)

    Carlsen, Berit C; Meldgaard, Michael; Hamann, Dathan;

    2011-01-01

    Objectives Natural rubber latex (NRL) contains over 200 proteins of which 13 have been identified as allergens and the cause of type I latex allergy. Health care workers share a high occupational risk for developing latex allergy. Filaggrin null mutations increase the risk of type I sensitizations...... to aeroallergens and it is possible that filaggrin null mutations also increase the risk of latex allergy. The aim of this paper was to examine the association between filaggrin null mutations and type I latex allergy. Methods Twenty latex allergic and 24 non-latex allergic dentists and dental assistants......, occupationally exposed to latex, were genotyped for filaggrin null mutations R501X and 2282del4. Latex allergy was determined by a positive reaction or a historical positive reaction to a skin prick test with NRL. Results 41 individuals were successfully genotyped. Three individuals were filaggrin mutation...

  7. High-contrast Nulling Interferometry Techniques Project

    Data.gov (United States)

    National Aeronautics and Space Administration — "We are developing rotating-baseline nulling-interferometry techniques and algorithms on the single-aperture Hale and Keck telescopes at near-infrared wavelengths,...

  8. Null-sissemakse - eraisikule riskantne / Tõnu Tramm

    Index Scriptorium Estoniae

    Tramm, Tõnu, 1968-

    2005-01-01

    Ilmunud ka: Delovõje Vedomosti 20. apr. lk. 26. Hansaliising ja Ühisliising käivitasid kampaania, mille käigus pakutakse uusi kuni 250 000 krooni maksvaid autosid null-sissemaksega. Kommenteerib ASi SEB Ühisliising arendusdirektor Ove Muuk. Tabel: Null-sissemaksega auto tuleb kallim. Lisad: Kuidas saavutada võimalikult väike kuumakse?; Kuidas maksta võimalikult vähe intressi? Vt. samas: Argo Rebane: Liisingufirmast saab parema hinna

  9. Faddeev Null Plane Model of Proton

    CERN Document Server

    D'Araújo, W R B; Frederico, T

    1998-01-01

    The proton is formulated as a relativistic system of three constituent quarks interacting via a zero-range two-body force in the null-plane. The covariance of the null-plane Faddeev-like equation under kinematical front-form boosts is discussed. A simplified three-boson model of the nucleon wave-function is obtained numerically. The proton electric form-factor reproduces the experimental data for low momentum transfers and qualitatively describes the asymptotic region.

  10. On the Penrose inequality along null hypersurfaces

    Science.gov (United States)

    Mars, Marc; Soria, Alberto

    2016-06-01

    The null Penrose inequality, i.e. the Penrose inequality in terms of the Bondi energy, is studied by introducing a functional on surfaces and studying its properties along a null hypersurface Ω extending to past null infinity. We prove a general Penrose-type inequality which involves the limit at infinity of the Hawking energy along a specific class of geodesic foliations called Geodesic Asymptotically Bondi (GAB), which are shown to always exist. Whenever this foliation approaches large spheres, this inequality becomes the null Penrose inequality and we recover the results of Ludvigsen-Vickers (1983 J. Phys. A: Math. Gen. 16 3349-53) and Bergqvist (1997 Class. Quantum Grav. 14 2577-83). By exploiting further properties of the functional along general geodesic foliations, we introduce an approach to the null Penrose inequality called the Renormalized Area Method and find a set of two conditions which imply the validity of the null Penrose inequality. One of the conditions involves a limit at infinity and the other a restriction on the spacetime curvature along the flow. We investigate their range of applicability in two particular but interesting cases, namely the shear-free and vacuum case, where the null Penrose inequality is known to hold from the results by Sauter (2008 PhD Thesis Zürich ETH), and the case of null shells propagating in the Minkowski spacetime. Finally, a general inequality bounding the area of the quasi-local black hole in terms of an asymptotic quantity intrinsic of Ω is derived.

  11. Analysis of aquaporin 9 expression in human epidermis and cultured keratinocytes

    Directory of Open Access Journals (Sweden)

    Yoshinori Sugiyama

    2014-01-01

    Full Text Available Aquaporin 9 (AQP9 is a member of the aquaglyceroporin family that transports glycerol, urea and other small solutes as well as water. Compared to the expression and function in epidermal keratinocytes of AQP3, another aquaglyceroporin, our knowledge of epidermal AQP9 remains elusive. In this study, we investigated the expression of AQP9 in the human epidermis and cultured keratinocytes. Immunofluorescence studies revealed that AQP9 expression is highly restricted to the stratum granulosum of the human epidermis, where occludin is also expressed at the tight junctions. Interestingly, the AQP3 staining decreased sharply below the cell layers in which AQP9 is expressed. In cultured normal human epidermal keratinocytes (NHEK, knock-down of AQP9 expression in the differentiated cells induced by RNA interference reduced glycerol uptake, which was not as pronounced as was the case with AQP3 knock-down cells. In contrast, similar reduction of urea uptake was detected in AQP9 and AQP3 knock-down cells. These findings suggested that AQP9 expression in NHEK facilitates at least the transport of glycerol and urea. Finally, we analyzed the effect of retinoic acid (RA, a potent stimulator of keratinocyte proliferation, on AQP3 and AQP9 mRNA expression in differentiated NHEK. Stimulation with RA at 1 μM for 24 h augmented AQP3 expression and down-regulated AQP9 expression. Collectively, these results indicate that AQP9 expression in epidermal keratinocytes is regulated in a different manner from that of AQP3.

  12. Null structure groups in eleven dimensions

    CERN Document Server

    Cariglia, M; Conamhna, Oisin A. P. Mac

    2004-01-01

    We classify all the structure groups which arise as subgroups of the isotropy group, $(Spin(7)\\ltimes\\mathbb{R}^8)\\times\\mathbb{R}$, of a single null Killing spinor in eleven dimensions. We construct the spaces of spinors fixed by these groups. We determine the conditions under which structure subgroups of the maximal null strucuture group $(Spin(7)\\ltimes\\mathbb{R}^8)\\times\\mathbb{R}$ may also be embedded in SU(5), and hence the conditions under which supersymmetric spacetime admits only null, or both timelike and null, Killing spinors. This concludes, for spacetimes admitting at least one null Killing spinor, the first, purely algebraic, phase of the refined G-structure classification of supersymmetric spacetimes in eleven dimensions, the objective of which is the derivation of the general local bosonic solution of the Killing spinor equation of eleven dimensional supergravity. Finally, we discuss how the second phase of the classification, involving the direct analysis of the Killing spinor equation, may b...

  13. Two Roads to the Null Energy Condition

    CERN Document Server

    Parikh, Maulik

    2015-01-01

    The null energy condition has sweeping consequences in general relativity. I argue here that it has been misunderstood as a property exclusively of matter, when in fact it arises only in a theory of both matter and gravity. I then derive an equivalent geometric formulation of the null energy condition from worldsheet string theory, where it arises beautifully as simply Einstein's equations in two dimensions. But further, I show that this condition also has a thermodynamic origin, following from a local version of the second law of thermodynamics, applied to gravitational entropy. Thus, far from being an incidental property of matter, the validity of the null energy condition hints at the deep dual origins of gravity.

  14. Supersymmteric Null-like Holographic Cosmologies

    OpenAIRE

    Lin, Feng-Li; Wen, Wen-Yu

    2006-01-01

    We construct a new class of 1/4-BPS time dependent domain-wall solutions with null-like metric and dilaton in type II supergravities, which admit a null-like big bang singularity. Based on the domain-wall/QFT correspondence, these solutions are dual to 1/4-supersymmetric quantum field theories living on a boundary cosmological background with time dependent coupling constant and UV cutoff. In particular we evaluate the holographic $c$ function for the 2-dimensional dual field theory living on...

  15. The Null Energy Condition and its violation

    OpenAIRE

    Rubakov, V. A.

    2014-01-01

    We give a mini-review of scalar field theories with second-derivative Lagrangians, whose field equations are second order. Some of these theories admit solutions violating the Null Energy Condition and having no obvious pathologies. We give a few examples of using these theories in cosmological setting and also in the context of the creation of a universe in the laboratory.

  16. Polarization nulling interferometry for exoplanet detection

    NARCIS (Netherlands)

    Spronck, J.; Pereira, S.F.; Braat, J.J.M.

    2006-01-01

    We introduce a new concept of nulling interferometer without any achromatic device, using polarization properties of light. This type of interferometer should enable a high rejection ratio in a theoretically unlimited spectral band. We analyze several consequences of the proposed design, notably, th

  17. A Philosophical Critique of Null Hypothesis Testing.

    Science.gov (United States)

    Orey III, Michael A.; And Others

    1989-01-01

    An attempt is made to clarify the philosophical foundations of the debate over research methodology appropriate for psychology in particular and the utility of null hypothesis testing in general. The article also relates the debate to education and suggests that the debate is far from settled. (IAH)

  18. Gravitational collapse of a cylindrical null shell in vacuum

    Directory of Open Access Journals (Sweden)

    S. Khakshournia

    2008-03-01

    Full Text Available   Barrabès-Israel null shell formalism is used to study the gravitational collapse of a thin cylindrical null shell in vacuum. In general the lightlike matter shell whose history coincides with a null hypersurface is characterized by a surface energy density. In addition, a gravitational impulsive wave is present on this null hypersurface whose generators admit both the shear and expansion. In the case of imposing the cylindrical flatness the surface energy-momentum tensor of the matter shell on the null hypersurface vanishes and the null hyper- surface is just the history of the gravitational wave .

  19. Broadband nulling behaviour of PSR B2319+60

    CERN Document Server

    Gajjar, Vishal; Kramer, M

    2012-01-01

    Pulse nulling is one of many single pulse phenomena exhibited by radio pulsars. The broadband nature of this phenomena remained unexplained due to lack of coordinated observations. We are reporting broadband nulling behaviour of a well known nulling pulsar PSR B2319+60. The simultaneous observations were carried out at four different frequencies using the Giant Meterwave Radio telescope (325 and 610 MHz), the Westerbork Synthesis Radio Telescope (1420 MHz) and the Effelsberg radio telescope (5100 MHz). The nulling fractions were estimated at all four observed frequencies, which suggest similar degree of nulling across these frequencies. To comment on the broadband behaviour of pulse nulling, we calculated the Pearson cross-correlation coefficients for the occurrence of null and burst pulses between all four frequencies. We conclude that nulling is largely a broadband phenomenon for this pulsar and it points towards a global failure of the magnetospheric currents which produces radio emission at these frequenc...

  20. Strings vs Spins on the Null Orbifold

    CERN Document Server

    Kiran, K Surya; Saurabh, Ayush; Simon, Joan

    2014-01-01

    We study the null orbifold singularity in 2+1 d flat space higher spin theory as well as string theory. Using the Chern-Simons formulation of 2+1 d Einstein gravity, we first observe that despite the singular nature of this geometry, the eigenvalues of its Chern-Simons holonomy are trivial. Next, we construct a resolution of the singularity in higher spin theory: a Kundt spacetime with vanishing scalar curvature invariants. We also point out that the UV divergences previously observed in the 2-to-2 tachyon tree level string amplitude on the null orbifold do not arise in the $\\alpha^\\prime\\to \\infty$ limit. We find all the divergences of the amplitude and demonstrate that the ones remaining in the tensionless limit are physical IR-type divergences. We conclude with a discussion on the meaning and limitations of higher spin (cosmological) singularity resolution and its potential connection to string theory.

  1. Collapse and bounce of null fluids

    CERN Document Server

    Creelman, Bradley

    2016-01-01

    Exact solutions describing the spherical collapse of null fluids can contain regions which violate the energy conditions. Physically the violations occur when the infalling matter continues to move inwards even when non-gravitational repulsive forces become stronger than gravity. In 1991 Ori proposed a resolution for these violations: spacetime surgery should be used to replace the energy condition violating region with an outgoing solution. The matter bounces. We revisit and implement this proposal for the more general Husain null fluids. We find that: 1) generically there is a thin shell discontinuity along the junction surface between ingoing and outgoing solutions, 2) there are special cases where the shell vanishes and 3) these conclusions also apply to charged Vaidya (the original paper argued that there were no shells at the junctions). Along the way we note an apparent error in the standard classification of energy condition violations for Type II stress-energy tensors.

  2. On the null origin of the ambitwistor string

    OpenAIRE

    Casali, Eduardo; Tourkine, Piotr

    2016-01-01

    In this paper we present the null string origin of the ambitwistor string. Classically, the null string is the tensionless limit of string theory, and so too is the Ambitwistor string. Both have as constraint algebra the Galilean Conformal Algebra in two dimensions. But something interesting happens in the quantum theory since there is an ambiguity in quantizing the null string. We show that, given a particular choice of quantization scheme and a particular gauge, the null string coincides wi...

  3. Motion Behavior of Null Space in Redundant Robotic Manipulators

    OpenAIRE

    Shibata, Tsuyoshi; Murakami, Toshiyuki

    2008-01-01

    This chapter shows the control design of null space motion by PID controller. When the work space observer is emplyed in work space controller, work space and null space motion are determined independently. Then the PD based work space controller makes work space motion stable, but global stability of null space motion is not always guranteed. To improve the stability and the robustness of null space motion, PID controller considering passivity is useful and the design strategy of PID control...

  4. Renormalization of null Wilson lines in EQCD

    International Nuclear Information System (INIS)

    Radiation and energy loss of a light, high-energy parton in a perturbative Quark-Gluon Plasma is controlled by transverse momentum exchange. The troublesome infrared contributions to transverse momentum exchange can be computed on the lattice using dimensional reduction to EQCD. However a novel extended operator, the Null Wilson Line of EQCD, is involved. We compute the renormalization properties of this object’s lattice implementation to next-to-leading order, which should facilitate its efficient calculation on the lattice

  5. PHASE CLOSURE NULLING: THEORY AND PRACTICE

    Directory of Open Access Journals (Sweden)

    A. Chelli

    2009-01-01

    Full Text Available We provide a complete theory of the phase closure of a binary system in which a small, feeble, and unresolved companion acts as a perturbing parameter on the spatial frequency spectrum of a dominant, bright, resolved source. We demonstrate that the in uence of the companion can be measured with precision by measuring the phase closure of the system near the nulls of the primary visibility function. In these regions of phase closure nulling, frequency intervals always exist where the phase closure signature of the companion is larger than any systematic error and can thus be measured. We show that this technique allows retrieval of many astrophysically relevant properties of faint and close companions such as ux, position, and in favorable cases, spectrum. As a proof of concept, using the AMBER/VLTI instrument with 3 auxiliary telescopes of 1.8 m and only 15 minutes of on-sky integration, we detected the ve magnitudes fainter companion of HD 59717 at only 3.5 stellar radii distance from the primary. This is one of the highest contrast detected by interferometry between a companion and its parent star. We conclude by a rapid study of the potentialities of phase closure nulling observations with current interferometers and explore the requirements for a new type of dedicated instrument.

  6. Null conformal Killing-Yano tensors and Birkhoff theorem

    CERN Document Server

    Ferrando, Joan Josep

    2015-01-01

    We study the space-times admitting a null conformal Killing-Yano tensor whose divergence defines a Killing vector. We analyze the similitudes and differences with the recently studied non null case (Gen. Relativ. Grav. (2015) {\\bf 47} 1911). The results by Barnes concerning the Birkhoff theorem for the case of null orbits are analyzed and generalized.

  7. A Conformal Extension Theorem based on Null Conformal Geodesics

    CERN Document Server

    Lübbe, Christian

    2008-01-01

    In this article we describe the formulation of null geodesics as null conformal geodesics and their description in the tractor formalism. A conformal extension theorem through an isotropic singularity is proven by requiring the boundedness of the tractor curvature and its derivatives to sufficient order along a congruence of null conformal geodesic. This article extends earlier work by Tod and Luebbe.

  8. Real null coframes in general relativity and GPS type coordinates

    CERN Document Server

    Blagojevic, M; Hehl, F W; Obukhov, Yu N; Obukhov, Yu.N.

    2002-01-01

    Some time ago, D. Finkelstein defined a `symmetric' null frame with {\\it four real null vectors}. We discuss this Finkelstein frame and show that a similarly defined real null coframe is closely related to the GPS type coordinates recently introduced by Rovelli.

  9. A Nulling Coronagraph for TPF-C

    Science.gov (United States)

    Shao, Michael; Levine, Bruce Martin; Wallace, James Kent; Orton, Glenn S.; Schmidtlin, Edouard; Lane, Benjamin F.; Seager, Sara; Tolls, Volker; Lyon, Richard G.; Samuele, Rocco; Tenerelli, Domenick J.; Woodruff, Robert; Ge, Jian

    2006-01-01

    The nulling coronagraph is one of 5 instrument concepts selected by NASA for study for potential use in the TPF-C mission. This concept for extreme starlight suppression has two major components, a nulling interferometer to suppress the starlight to 10(sup -10) per airy spot within 2 (lamda)/D of the star, and a calibration interferometer to measure the residual scattered starlight. The ability to work at 2 (lamda)/D dramatically improves the science throughput of a space based coronagraph like TPF-C. The calibration interferometer is an equally important part of the starlight suppression system. It measures the measures the wavefront of the scattered starlight with very high SNR, to 0.05nm in less than 5 minutes on a 5mag star. In addition, the post coronagraph wavefront sensor will be used to measure the residual scattered light after the coronagraph and subtract it in post processing to 12x10(sup -11) to enable detection of an Earthlike planet with a SNR of 510.

  10. Quasilocal energy exchange and the null cone

    CERN Document Server

    Uzun, Nezihe

    2016-01-01

    Energy is at best defined quasilocally in general relativity. Quasilocal energy definitions depend on the conditions one imposes on the boundary Hamiltonian, i.e., how a finite region of spacetime is "isolated". Here, we propose a method to define and investigate systems in terms of their matter plus gravitational energy content. We adopt a generic construction, that involves embedding of an arbitrary dimensional worldsheet into an arbitrary dimensional spacetime, to a 2 + 2 picture. In our case, the closed 2-dimensional spacelike surface $\\mathbb{S}$, that is orthogonal to the 2-dimensional timelike worldsheet $\\mathbb{T}$ at every point, encloses the system in question. The integrability conditions of $\\mathbb{T}$ and $\\mathbb{S}$ correspond to three null tetrad gauge conditions once we transform our notation to the one of the null cone observables. We interpret the Raychaudhuri equation of $\\mathbb{T}$ as a work-energy relation for systems that are not in equilibrium with their surroundings. We achieve thi...

  11. On the null origin of the ambitwistor string

    CERN Document Server

    Casali, Eduardo

    2016-01-01

    In this paper we present the null string origin of the ambitwistor string. Classically, the null string is the tensionless limit of string theory, and so too is the Ambitwistor string. Both have as constraint algebra the Galilean Conformal Algebra in two dimensions. But something interesting happens in the quantum theory since there is an ambiguity in quantizing the null string. We show that, given a particular choice of quantization scheme and a particular gauge, the null string coincides with the ambitwistor string both classically and quantum mechanically. We also show that the same holds for the spinning versions of the null string and Ambitwistor string. With these results we clarify the relationship between the Ambitwistor string, the null string, the usual string and the Hohm-Siegel-Zwiebach theory.

  12. Null subjects and agreement marks in European and Brazilian Portuguese

    OpenAIRE

    Duarte, Maria Eugênia Lammoglia; Varejão, Filomena

    2013-01-01

    The purpose of this article is to discuss the relation between the presence of agreement marks and null subjects in contemporary European and Brazilian Portuguese based on very recent samples of speech collected in Lisbon and Rio de Janeiro. In order to bring additional evidence to support the analysis, we will briefly review the issues involving the Null Subject in Romance Languages and some diachronic and synchronic analyses which distinguish Brazilian and European Portuguese as far as null...

  13. Are Null Results Becoming an Endangered Species in Marketing?

    OpenAIRE

    Raymond Hubbard; JS Armstrong

    1992-01-01

    Editorial procedures in the social and biomedical sciences are said to promote studies that falsely reject the null hypothesis. This problem may also exist in major marketing journals. Of 692 papers using statistical significance tests sampled from the Journal of Marketing, Journal of Marketing Research, and Journal of Consumer Research between 1974 and 1989, only 7.8% failed to reject the null hypothesis. The percentage of null results declined by one-half from the 1970s to the 1980s. The...

  14. Averaged Null Energy Condition from Causality

    CERN Document Server

    Hartman, Thomas; Tajdini, Amirhossein

    2016-01-01

    Unitary, Lorentz-invariant quantum field theories in flat spacetime obey microcausality: commutators vanish at spacelike separation. For interacting theories in more than two dimensions, we show that this implies that the averaged null energy, $\\int du T_{uu}$, must be positive. This non-local operator appears in the operator product expansion of local operators in the lightcone limit, and therefore contributes to $n$-point functions. We derive a sum rule that isolates this contribution and is manifestly positive. The argument also applies to certain higher spin operators other than the stress tensor, generating an infinite family of new constraints of the form $\\int du X_{uuu\\cdots u} \\geq 0$. These lead to new inequalities for the coupling constants of spinning operators in conformal field theory, which include as special cases (but are generally stronger than) the existing constraints from the lightcone bootstrap, deep inelastic scattering, conformal collider methods, and relative entropy. We also comment ...

  15. Null fluid collapse in brane world models

    CERN Document Server

    Harko, Tiberiu

    2013-01-01

    The brane world description of our universe entails a large extra dimension and a fundamental scale of gravity that may be lower than the Planck scale by several orders of magnitude. An interesting consequence of this scenario occurs in the nature of spherically-symmetric vacuum solutions to the brane gravitational field equations, which often have properties quite distinct from the standard black hole solutions of general relativity. In this paper, the spherically-symmetric collapse on the brane world of four types of null fluid, governed by the barotropic, polytropic, strange quark "bag" model and Hagedorn equations of state, is investigated. In each case, we solve the approximate gravitational field equations, obtained in the high density limit, determine the equation which governs the formation of apparent horizons and investigate the conditions for the formation of naked singularities. Though, naively, one would expect the increased effective energy density on the brane to favor the formation of black ho...

  16. Wormholes minimally violating the null energy condition

    CERN Document Server

    Bouhmadi-Lopez, Mariam; Martin-Moruno, Prado

    2014-01-01

    We consider novel wormhole solutions supported by a matter content that minimally violates the null energy condition. More specifically, we consider an equation of state in which the sum of the energy density and radial pressure is proportional to a constant with a value smaller than that of the inverse area characterising the system, i.e., the area of the wormhole mouth. This approach is motivated by a recently proposed cosmological event, denoted "the little sibling of the big rip", where the Hubble rate and the scale factor blow up but the cosmic derivative of the Hubble rate does not [1]. By using the cut-and-paste approach, we match interior spherically symmetric wormhole solutions to an exterior Schwarzschild geometry, and analyze the stability of the thin-shell to linearized spherically symmetric perturbations around static solutions, by choosing suitable properties for the exotic material residing on the junction interface radius. Furthermore, we also consider an inhomogeneous generalisation of the eq...

  17. Blob dynamics in TORPEX poloidal null configurations

    CERN Document Server

    Shanahan, Brendan

    2016-01-01

    Three dimensional blob dynamics are simulated in X-point magnetic configurations in the TORPEX device via a non-field-aligned coordinate system, using an isothermal model which evolves density, vorticity, parallel velocity and parallel current density. By modifying the parallel gradient operator to include perpendicular perturbations from poloidal field coils, numerical singularities associated with field aligned coordinates are avoided. Blobs are found to propagate according to the sheath-connected scaling, and a validation with experiment is performed. It is determined that the null region can cause an acceleration of filaments due to increasing connection length, but this accleration is small relative to other effects, which we quantify. A comparison with a previously developed analytical model is performed and an agreement is found with minimal modification. Experimental measurements are reproduced, and the dominant acceleration mechanism is identified as that of a developing dipole in a moving background...

  18. Null radiation zone at the LHC

    CERN Document Server

    Hagiwara, Kaoru

    2012-01-01

    The null radiation zone theorem states that, when special kinematical conditions are satisfied, all the helicity amplitudes of a parton-level subprocess where a vector current is emitted vanish due to destructive interference among different diagrams. We study the manifestation of the theorem in $pp$ collisions at the $\\sqrt{s}=8$ TeV LHC. The theorem predicts that the cross section for $p p \\rightarrow j j \\gamma$ events is suppressed when the transverse momenta of the two jets are similar and when the rapidity difference between the photon and the cluster of the jets is nearly zero, because the $u u \\rightarrow u u \\gamma$ subprocess, which dominates in events with large $j j \\gamma$ invaraint mass, has strong destructive interference in this region. We confirm this prediction by the calculation with MadGraph 5, and show that the suppression on the $p p \\rightarrow j j \\gamma$ cross section is observable at the LHC.

  19. Exoplanet detection using a nulling interferometer.

    Science.gov (United States)

    Cagigal, M; Canales, V

    2001-07-01

    The detection of extra solar planets is a topic of growing interest, which stretches current technology and knowledge to their limits. Indirect measurement confirms the existence of a considerable number. However, direct imaging is the only way to obtain information about the nature of these planets and to detect Earth-like planets, which could support life. The main problem for direct imaging is that planets are associated with a much brighter source of light. Here, we propose the use of the nulling interferometer along with a photon counting technique called Dark Speckle. Using a simple model the behavior of the technique is predicted. The signal-to-noise ratio estimated confirms that it is a promising way to detect faint objects.

  20. MAGNETIC NULL POINTS IN KINETIC SIMULATIONS OF SPACE PLASMAS

    Energy Technology Data Exchange (ETDEWEB)

    Olshevsky, Vyacheslav; Innocenti, Maria Elena; Cazzola, Emanuele; Lapenta, Giovanni [Centre for Mathematical Plasma Astrophysics (CmPA), KU Leuven (Belgium); Deca, Jan [Laboratory for Atmospheric and Space Physics (LASP), University of Colorado Boulder, Boulder, CO (United States); Divin, Andrey [St. Petersburg State University, St. Petersburg (Russian Federation); Peng, Ivy Bo; Markidis, Stefano, E-mail: sya@mao.kiev.ua [High Performance Computing and Visualization (HPCViz), KTH Royal Institute of Technology, Stockholm (Sweden)

    2016-03-01

    We present a systematic attempt to study magnetic null points and the associated magnetic energy conversion in kinetic particle-in-cell simulations of various plasma configurations. We address three-dimensional simulations performed with the semi-implicit kinetic electromagnetic code iPic3D in different setups: variations of a Harris current sheet, dipolar and quadrupolar magnetospheres interacting with the solar wind, and a relaxing turbulent configuration with multiple null points. Spiral nulls are more likely created in space plasmas: in all our simulations except lunar magnetic anomaly (LMA) and quadrupolar mini-magnetosphere the number of spiral nulls prevails over the number of radial nulls by a factor of 3–9. We show that often magnetic nulls do not indicate the regions of intensive energy dissipation. Energy dissipation events caused by topological bifurcations at radial nulls are rather rare and short-lived. The so-called X-lines formed by the radial nulls in the Harris current sheet and LMA simulations are rather stable and do not exhibit any energy dissipation. Energy dissipation is more powerful in the vicinity of spiral nulls enclosed by magnetic flux ropes with strong currents at their axes (their cross sections resemble 2D magnetic islands). These null lines reminiscent of Z-pinches efficiently dissipate magnetic energy due to secondary instabilities such as the two-stream or kinking instability, accompanied by changes in magnetic topology. Current enhancements accompanied by spiral nulls may signal magnetic energy conversion sites in the observational data.

  1. Logarithmic corrections to gravitational entropy and the null energy condition

    Science.gov (United States)

    Parikh, Maulik; Svesko, Andrew

    2016-10-01

    Using a relation between the thermodynamics of local horizons and the null energy condition, we consider the effects of quantum corrections to the gravitational entropy. In particular, we find that the geometric form of the null energy condition is not affected by the inclusion of logarithmic corrections to the Bekenstein-Hawking entropy.

  2. Visual and Plastic Arts in Teaching Literacy: Null Curricula?

    Science.gov (United States)

    Wakeland, Robin Gay

    2010-01-01

    Visual and plastic arts in contemporary literacy instruction equal null curricula. Studies show that painting and sculpture facilitate teaching reading and writing (literacy), yet such pedagogy has not been formally adopted into USA curriculum. An example of null curriculum can be found in late 19th - early 20th century education the USA…

  3. Magnetic null points in kinetic simulations of space plasmas

    CERN Document Server

    Olshevsky, Vyacheslav; Divin, Andrey; Peng, Ivy Bo; Markidis, Stefano; Innocenti, Maria Elena; Cazzola, Emanuele; Lapenta, Giovanni

    2015-01-01

    We present a systematic attempt to study magnetic null points and the associated magnetic energy conversion in kinetic Particle-in-Cell simulations of various plasma configurations. We address three-dimensional simulations performed with the semi-implicit kinetic electromagnetic code iPic3D in different setups: variations of a Harris current sheet, dipolar and quadrupolar magnetospheres interacting with the solar wind; and a relaxing turbulent configuration with multiple null points. Spiral nulls are more likely created in space plasmas: in all our simulations except lunar magnetic anomaly and quadrupolar mini-magnetosphere the number of spiral nulls prevails over the number of radial nulls by a factor of 3-9. We show that often magnetic nulls do not indicate the regions of intensive energy dissipation. Energy dissipation events caused by topological bifurcations at radial nulls are rather rare and short-lived. The so-called X-lines formed by the radial nulls in the Harris current sheet and lunar magnetic ano...

  4. Sidelobe Suppression with Null Steering by Independent Weight Control

    Directory of Open Access Journals (Sweden)

    Zafar-Ullah Khan

    2015-01-01

    Full Text Available A uniform linear array of n antenna elements can steer up to n-1 nulls. In situations where less than n-1 nulls are required to be steered, the existing algorithms have no criterion to utilize the remaining weights for sidelobe suppression. This work combines sidelobe suppression capability with null steering by independent weight control. For this purpose, the array factor is transformed as the product of two polynomials. One of the polynomials is used for null steering by independent weight control, while the second one is for sidelobe suppression whose coefficients or weights are determined by using convex optimization. Finally, a new structure is proposed to incorporate the product of two polynomials such that sidelobe suppression weights are decoupled from those of null steering weights. Simulation results validate the effectiveness of the proposed scheme.

  5. Energy dissipation in magnetic null points at kinetic scales

    CERN Document Server

    Olshevsky, Vyacheslav; Eriksson, Elin; Markidis, Stefano; Lapenta, Giovanni

    2015-01-01

    We use kinetic particle-in-cell and magnetohydrodynamic simulations supported by an observational dataset to investigate magnetic reconnection in clusters of null points in space plasma. The magnetic configuration under investigation is driven by fast adiabatic flux rope compression that dissipates almost half of the initial magnetic field energy. In this phase powerful currents are excited producing secondary instabilities, and the system is brought into a state of `intermittent turbulence' within a few ion gyro-periods. Reconnection events are distributed all over the simulation domain and energy dissipation is rather volume-filling. Numerous spiral null points interconnected via their spines form null lines embedded into magnetic flux ropes; null point pairs demonstrate the signatures of torsional spine reconnection. However, energy dissipation mainly happens in the shear layers formed by adjacent flux ropes with oppositely directed currents. In these regions radial null pairs are spontaneously emerging an...

  6. The curious case of null warped space

    Science.gov (United States)

    Anninos, Dionysios; Compère, Geoffrey; de Buyl, Sophie; Detournay, Stéphane; Guica, Monica

    2010-11-01

    We initiate a comprehensive study of a set of solutions of topologically massive gravity known as null warped anti-de Sitter spacetimes. These are pp-wave extensions of three-dimensional anti-de Sitter space. We first perform a careful analysis of the linearized stability of black holes in these spacetimes. We find two qualitatively different types of solutions to the linearized equations of motion: the first set has an exponential time dependence, the second — a polynomial time dependence. The solutions polynomial in time induce severe pathologies and moreover survive at the non-linear level. In order to make sense of these geometries, it is thus crucial to impose appropriate boundary conditions. We argue that there exists a consistent set of boundary conditions that allows us to reject the above pathological modes from the physical spectrum. The asymptotic symmetry group associated to these boundary conditions consists of a centrally-extended Virasoro algebra. Using this central charge we can account for the entropy of the black holes via Cardy's formula. Finally, we note that the black hole spectrum is chiral and prove a Birkoff theorem showing that there are no other stationary axisymmetric black holes with the specified asymptotics. We extend most of the analysis to a larger family of pp-wave black holes which are related to Schrödinger spacetimes with critical exponent z.

  7. The Curious Case of Null Warped Space

    CERN Document Server

    Anninos, Dionysios; de Buyl, Sophie; Detournay, Stéphane; Guica, Monica

    2010-01-01

    We initiate a comprehensive study of a set of solutions of topologically massive gravity known as null warped anti-de Sitter spacetimes. These are pp-wave extensions of three-dimensional anti-de Sitter space. We first perform a careful analysis of the linearized stability of black holes in these spacetimes. We find two qualitatively different types of solutions to the linearized equations of motion: the first set has an exponential time dependence, the second - a polynomial time dependence. The solutions polynomial in time induce severe pathologies and moreover survive at the non-linear level. In order to make sense of these geometries, it is thus crucial to impose appropriate boundary conditions. We argue that there exists a consistent set of boundary conditions that allows us to reject the above pathological modes from the physical spectrum. The asymptotic symmetry group associated to these boundary conditions consists of a centrally-extended Virasoro algebra. Using this central charge we can account for th...

  8. Wormholes minimally violating the null energy condition

    Energy Technology Data Exchange (ETDEWEB)

    Bouhmadi-López, Mariam [Departamento de Física, Universidade da Beira Interior, 6200 Covilhã (Portugal); Lobo, Francisco S N; Martín-Moruno, Prado, E-mail: mariam.bouhmadi@ehu.es, E-mail: fslobo@fc.ul.pt, E-mail: pmmoruno@fc.ul.pt [Centro de Astronomia e Astrofísica da Universidade de Lisboa, Campo Grande, Edifício C8, 1749-016 Lisboa (Portugal)

    2014-11-01

    We consider novel wormhole solutions supported by a matter content that minimally violates the null energy condition. More specifically, we consider an equation of state in which the sum of the energy density and radial pressure is proportional to a constant with a value smaller than that of the inverse area characterising the system, i.e., the area of the wormhole mouth. This approach is motivated by a recently proposed cosmological event, denoted {sup t}he little sibling of the big rip{sup ,} where the Hubble rate and the scale factor blow up but the cosmic derivative of the Hubble rate does not [1]. By using the cut-and-paste approach, we match interior spherically symmetric wormhole solutions to an exterior Schwarzschild geometry, and analyse the stability of the thin-shell to linearized spherically symmetric perturbations around static solutions, by choosing suitable properties for the exotic material residing on the junction interface radius. Furthermore, we also consider an inhomogeneous generalization of the equation of state considered above and analyse the respective stability regions. In particular, we obtain a specific wormhole solution with an asymptotic behaviour corresponding to a global monopole.

  9. Null fluid collapse in brane world models

    Science.gov (United States)

    Harko, Tiberiu; Lake, Matthew J.

    2014-03-01

    The brane world description of our Universe entails a large extra dimension and a fundamental scale of gravity that may be lower than the Planck scale by several orders of magnitude. An interesting consequence of this scenario occurs in the nature of spherically symmetric vacuum solutions to the brane gravitational field equations, which often have properties quite distinct from the standard black hole solutions of general relativity. In this paper, the spherically symmetric collapse on the brane world of four types of null fluid, governed by the barotropic, polytropic, strange quark "bag" model and Hagedorn equations of state, is investigated. In each case, we solve the approximate gravitational field equations, obtained in the high-density limit, determine the equation which governs the formation of apparent horizons and investigate the conditions for the formation of naked singularities. Though, naively, one would expect the increased effective energy density on the brane to favor the formation of black holes over naked singularities, we find that, for the types of fluid considered, this is not the case. However, the black hole solutions differ substantially from their general-relativistic counterparts and brane world corrections often play a role analogous to charge in general relativity. As an astrophysical application of this work, the possibility that energy emission from a Hagedorn fluid collapsing to form a naked singularity may be a source of GRBs in the brane world is also considered.

  10. The Density of Coronal Null Points from Hinode and MDI

    CERN Document Server

    Longcope, Dana; DeForest, Craig

    2009-01-01

    Magnetic null points can be located numerically in a potential field extrapolation or their average density can be estimated from the Fourier spectrum of a magnetogram. We use both methods to compute the null point density from a quiet Sun magnetogram made with Hinode's NFI and from magnetograms from SOHO's MDI in both its high-resolution and low-resolution modes. All estimates of the super-chromospheric column density (z>1.5 Mm) agree with one another and with the previous measurements: 0.003 null points per square Mm of solar surface.

  11. Molecular basis for the CAT-2 null phenotype in maize

    International Nuclear Information System (INIS)

    Previous reports have described several maize lines whose developmental patterns of catalase gene expression vary from the typical maize line, W64A. Among these variants are the lines A16 and A338, both found to be null for the CAT-2 protein. Identification of a third CAT-2 null line, designated A340, is described. RNA blots and S1 nuclease protection analysis, using [32P]-labeled dCTP, indicate that all three CAT-2 null lines produce a similarly shortened Cat2 transcript. The molecular basis for this aberrant Cat2 transcript is discussed

  12. A Null Space Approach for Solving Nonlinear Complementarity Problems

    Institute of Scientific and Technical Information of China (English)

    Pu-yan Nie

    2006-01-01

    In this work, null space techniques are employed to tackle nonlinear complementarity problems(NCPs). NCP conditions are transform into a nonlinear programming problem, which is handled by null space algorithms. The NCP conditions are divided into two groups. Some equalities and inequalities in an NCP are treated as constraints. While other equalities and inequalities in an NCP are to be regarded as objective function.Two groups are all updated in every step. Null space approaches are extended to nonlinear complementarity problems. Two different solvers are employed for an NCP in an algorithm.

  13. The Importance of Phase in Nulling Interferometry and a Three Telescope Closure-Phase Nulling Interferometer Concept

    OpenAIRE

    Danchi, W. C.; Rajagopal, J.; Kuchner, M.; Richardson, J; Deming, D.

    2006-01-01

    We discuss the theory of the Bracewell nulling interferometer and explicitly demonstrate that the phase of the "white light" null fringe is the same as the phase of the bright output from an ordinary stellar interferometer. As a consequence a "closure phase" exists for a nulling interferometer with three or more telescopes. We calculate the phase offset as a function of baseline length for an Earth-like planet around the Sun at 10 pc, with a contrast ratio of $10^{-6}$ at 10 $\\mu$m. The magni...

  14. Waves and null congruences in a draining bathtub

    CERN Document Server

    Dempsey, David

    2016-01-01

    We study wave propagation in a draining bathtub: a fluid-mechanical black hole analogue in which perturbations are governed by a Klein-Gordon equation on an effective Lorentzian geometry. Like the Kerr spacetime, the draining bathtub geometry possesses an (effective) horizon, an ergosphere and null circular orbits. We propose that a `pulse' disturbance may be used to map out the light-cone of the effective geometry. First, we apply the eikonal approximation to elucidate the link between wavefronts, null geodesic congruences and the Raychaudhuri equation. Next, we solve the wave equation numerically in the time domain using the method of lines. Starting with Gaussian initial data, we demonstrate that a pulse will propagate along a null congruence and thus trace out the light-cone of the effective geometry. Our numerical results reveal features, such as wavefront intersections, frame-dragging, winding and interference effects, that are closely associated with the presence of null circular orbits and the ergosph...

  15. Worldtube conservation laws for the null-timelike evolution problem

    CERN Document Server

    Winicour, Jeffrey

    2011-01-01

    I treat the worldtube constraints which arise in the null-timelike initial-boundary value problem for the Bondi-Sachs formulation of Einstein's equations. Boundary data on a worldtube and initial data on an outgoing null hypersurface determine the exterior spacetime by integration along the outgoing null geodsics. The worldtube constraints are a set of conservation laws which impose conditions on the integration constants. I show how these constraints lead to a well-posed initial value problem governing the extrinsic curvature of the worldtube, whose components are related to the integration constants. Possible applications to gravitational waveform extraction and to the well-posedness of the null-timelike initial-boundary value problem are discussed.

  16. Another Nulling Hall-Effect Current-Measuring Circuit

    Science.gov (United States)

    Thibodeau, Phillip E.; Sullender, Craig C.

    1993-01-01

    Lightweight, low-power circuit provides noncontact measurement of alternating or direct current of many ampheres in main conductor. Advantages of circuit over other nulling Hall-effect current-measuring circuits is stability and accuracy increased by putting both analog-to-digital and digital-to-analog converters in nulling feedback loop. Converters and rest of circuit designed for operation at sampling rate of 100 kHz, but rate changed to alter time or frequency response of circuit.

  17. The geometry of D=11 null killing spinors

    Energy Technology Data Exchange (ETDEWEB)

    Gauntlett, Jerome P.; Gutowski, Jan B. E-mail: gutowski@maths.ox.ac.uk; Stathis Pakis

    2003-12-01

    We determine the necessary and sufficient conditions on the metric and the four-form for the most general bosonic supersymmetric configurations of D=11 supergravity which admit a null Killing spinor i.e. a Killing spinor which can be used to construct a null Killing vector. This class covers all supersymmetric time-dependent configurations and completes the classification of the most general supersymmetric configurations initiated in hep-th/0212008. (author)

  18. The Geometry of D=11 Null Killing Spinors

    CERN Document Server

    Gauntlett, J P; Pakis, S

    2003-01-01

    We determine the necessary and sufficient conditions on the metric and the four-form for the most general bosonic supersymmetric configurations of D=11 supergravity which admit a null Killing spinor i.e. a Killing spinor which can be used to construct a null Killing vector. This class covers all supersymmetric time-dependent configurations and completes the classification of the most general supersymmetric configurations initiated in hep-th/0212008.

  19. Using Multivalued Logic in Relational Database Containing Null Value

    Institute of Scientific and Technical Information of China (English)

    马宗民; YanLi

    1996-01-01

    In this paper,several kinds of multivalued logic for relational database and their developing process are presented on the basis of null value's semantics.A new 5 valued logic is led into relational database containing null value.The feasibility and necessity of using 5 valued logic are expounded.Comparative calculation and logical calculation under 5 valued logic are defined at the end of the paper.

  20. Overt and Null Subject Pronouns in Jordanian Arabic

    Directory of Open Access Journals (Sweden)

    Islam M. Al-Momani

    2015-08-01

    Full Text Available The paper aims at examining the role that morphology plays in allowing and/or motivating sentences in Jordanian Arabic (hereafter JA to be formed with or without subject pronouns. It also aims at giving a comprehensive and descriptive presentation of the distribution of overt and null subject pronouns in JA, and tries to determine to what extent there is optionality in its system.Keywords: null subject pronouns, overt subjects, pro-drop languages, verbal inflectional morphology

  1. 水通道蛋白7对蛋白激酶B的影响%The Effect of Aquaglyceroporin 7 on Protein Kinase B Signaling Pathway

    Institute of Scientific and Technical Information of China (English)

    潘伟; 沈飞霞; 谷雪梅; 叶菁; 顾雪疆; 倪连松; 李卫平

    2013-01-01

    该文旨在探讨水通道蛋白7(AQP7)在3T3-L1脂肪细胞不同分化阶段的表达以及其对胰岛素信号通路中蛋白激酶B(PKB)的影响.通过培养3T3-L1前体脂肪细胞,诱导分化为成熟的脂肪细胞,用荧光定量PCR,Western blot、酶学方法分析显示,随3T3-L1脂肪细胞分化过程,AQP7与PKB磷酸化水平同步上升,同时培养基中释放的甘油浓度伴随AQP7的表达平行增加.以TNF-α处理分化成熟的脂肪细胞构建胰岛素抵抗模型,AQP7与PKB磷酸化水平均下降,转染高表达AQP7基因的重组腺病毒载体(Ad-AQP7)之后,随着AQP7表达上调,胰岛素刺激下的PKB磷酸化水平提高,并且葡萄糖代谢能力增强.由此可见,AQP7水平随3T3-L1脂肪细胞分化过程逐渐上升,其高表达可能通过增加PKB磷酸化水平改善胰岛素敏感性,提示AQP7可能成为治疗肥胖的一个重要作用靶点.%Aquaglyceroporin 7 (AQP7) is a water transporting protein which also regulates the glycerol efflux in adipocytes. The study of AQP7 might shed new light on the prevention and control of obesity. In this study, we aimed to analyze expression profiles of AQP7 in the different differentiation phase of adipocytes and the relationship between AQP7 and PKB in the insulin pathway. 3T3-L1 preadipocyte cells were induced fully differentiated. Insulin resistance in differentiated adipocytes was induced by TNF-α. Adenovirus overexpression AQP7 (Ad-AQP7) was constructed and transfected to adipocytes. The expression levels of AQP7 and phosphorylated PKB (p-PKB) were measured. The glycerol release from adipocytes and the change of glucose concentration in the culture medium were also tested.The AQP7 levels were gradually up-regulated along with the differentiation phase of 3T3-L1 preadipocytes, which was consistent with the expression levels of p-PKB. Overexpression of AQP7 by transfecting Ad-AQP7 to insulin resistant adipocytes could improve insulin sensitivity and glucose utilization, in

  2. Visible Nulling Coronagraphy Testbed Development for Exoplanet Detection

    Science.gov (United States)

    Lyon, Richard G.; Clampin, Mark; Woodruff, Robert A.; Vasudevan, Gopal; Thompson, Patrick; Chen, Andrew; Petrone, Peter; Booth, Andrew; Madison, Timothy; Bolcar, Matthew; Noecker, M. Charley; Kendrick, Stephen; Melnick, Gary; Tolls, Volker

    2010-01-01

    Three of the recently completed NASA Astrophysics Strategic Mission Concept (ASMC) studies addressed the feasibility of using a Visible Nulling Coronagraph (VNC) as the prime instrument for exoplanet science. The VNC approach is one of the few approaches that works with filled, segmented and sparse or diluted aperture telescope systems and thus spans the space of potential ASMC exoplanet missions. NASA/Goddard Space Flight Center (GSFC) has a well-established effort to develop VNC technologies and has developed an incremental sequence of VNC testbeds to advance the this approach and the technologies associated with it. Herein we report on the continued development of the vacuum Visible Nulling Coronagraph testbed (VNT). The VNT is an ultra-stable vibration isolated testbed that operates under high bandwidth closed-loop control within a vacuum chamber. It will be used to achieve an incremental sequence of three visible light nulling milestones of sequentially higher contrasts of 10(exp 8) , 10(exp 9) and 10(exp 10) at an inner working angle of 2*lambda/D and ultimately culminate in spectrally broadband (>20%) high contrast imaging. Each of the milestones, one per year, is traceable to one or more of the ASMC studies. The VNT uses a modified Mach-Zehnder nulling interferometer, modified with a modified "W" configuration to accommodate a hex-packed MEMS based deformable mirror, a coherent fiber bundle and achromatic phase shifters. Discussed will be the optical configuration laboratory results, critical technologies and the null sensing and control approach.

  3. Long-term Observations of Three Nulling Pulsars

    CERN Document Server

    Young, N J; Stappers, B W; Lyne, A G; Kramer, M

    2015-01-01

    We present an analysis of approximately 200 hours of observations of the pulsars J1634$-$5107, J1717$-$4054 and J1853$+$0505, taken over the course of 14.7 yr. We show that all of these objects exhibit long term nulls and radio-emitting phases (i.e. minutes to many hours), as well as considerable nulling fractions (NFs) in the range $\\sim67\\,\\% - 90\\,\\%$. PSR J1717$-$4054 is also found to exhibit short timescale nulls ($1 - 40~P$) and burst phases ($\\lesssim 200~P$) during its radio-emitting phases. This behaviour acts to modulate the NF, and therefore the detection rate of the source, over timescales of minutes. Furthermore, PSR J1853$+$0505 is shown to exhibit a weak emission state, in addition to its strong and null states, after sufficient pulse integration. This further indicates that nulls may often only represent transitions to weaker emission states which are below the sensitivity thresholds of particular observing systems. In addition, we detected a peak-to-peak variation of $33\\pm1\\,\\%$ in the spin-...

  4. Three-dimensional magnetic reconnection through a moving magnetic null

    Directory of Open Access Journals (Sweden)

    V. S. Lukin

    2011-11-01

    Full Text Available A computational study of three-dimensional magnetic reconnection between two flux ropes through a moving reconnection site is presented. The configuration is considered in the context of two interacting spheromaks constrained by a perfectly conducting cylindrical boundary and oriented to form a single magnetic field null at its center. The initial magnetic field configuration is embedded into a uniform thermal plasma and is unstable to tilting. As the spheromaks tilt, their magnetic fields begin to reconnect at the null, subsequently displacing both the null and the reconnection site. The motion of the reconnection region and the magnetic null are shown to be correlated, with stronger correlation and faster reconnection observed in plasmas with lower thermal to magnetic pressure ratio. It is also shown that ion inertial effects allow for yet faster reconnection, but do not qualitatively change the dynamics of the process. Implications of the coupling between moving magnetic nulls and reconnection sites, as well as of possible mechanisms for fast reconnection through a moving reconnection region, are discussed. The simulations are conducted using both single-fluid and Hall MHD plasma models within the HiFi multi-fluid modeling framework.

  5. The causal topology of neutral 4-manifolds with null boundary

    CERN Document Server

    Georgiou, Nikos

    2016-01-01

    This paper considers aspects of 4-manifold topology from the point of view of a neutral metric, a point of view we call neutral causal topology. In particular, we construct and investigate neutral 4-manifolds with null boundary that arise from canonical 3- and 4-dimensional settings. A null hypersurface is foliated by its normal and, in the neutral case, inherits a pair of totally null planes at each point. This paper focuses on this structure in a number of classical settings The first construction is the conformal compactification of flat neutral 4-space into the 4-ball. The null foliation on the boundary in this case is the Hopf fibration on the 3-sphere and the totally null planes in the boundary are integrable. The metric on the 4-ball is a conformally flat, scalar-flat, positive Ricci curvature neutral metric. The second constructions are subsets of the 4-dimensional space of oriented geodesics in a 3-dimensional space-form, equipped with its canonical neutral metric. We consider all oriented geodesics ...

  6. Resistivity at the field null of the FRC plasma

    International Nuclear Information System (INIS)

    In the absence of the major destructive instabilities, the configuration time is ultimately determined by particle and flux containment. If the profiles are ''gentle,'' then the anomalous flux-loss rate depends essentially on the anomalous resistivity at the field null. Conventional electrostatic quasi-linear models of anomalous cross-field resistive diffusivity are based upon the use of rvec E x rvec B drift velocities, and hence break down at the magnetic field null. In this paper, an electromagnetic treatment valid at the field null is developed, based upon the presence of flute-parity perturbations. An expression for anomalous resistivity at the field null in the quasi-linear approximation is derived by averaging in the ignorable direction over the random phases of the perturbations. The expression is valid for arbitrary (non-local) radial shapes of the perturbing modes (for example, the eigenfunctions need not be centered at the field null), and for an arbitrary ratio of real frequency to growth rate. The effective resistivity due to flute perturbations of the MHD type will be considered. 1 ref

  7. Do Null Subjects (mis-)Trigger Pro-drop Grammars?

    Science.gov (United States)

    Frazier, Lyn

    2015-12-01

    Native speakers of English regularly hear sentences without overt subjects. Nevertheless, they maintain a [−pro] grammar that requires sentences to have an overt subject. It is proposed that listeners of English recognize that speakers reduce predictable material and thus attribute null subjects to this process, rather than changing their grammars to a [−pro] setting. Mack et al. (J Memory Lang 67(1):211-223, 2012) showed that sentences with noise covering the subject are analyzed as having null subjects more often with a first person pronoun and with a present tense--properties correlated with more predictable referents--compared to a third person pronoun and past tense. However, those results might in principle have been due to reporting null subjects for verbs that often occur with null subjects. An experiment is reported here in which comparable results are found for sentences containing nonsense verbs. Participants preferred a null subject more often for first person present tense sentences than for third person past tense sentences. The results are as expected if participants are responding to predictability, the likelihood of reduction, rather than to lexical statistics. The results are argued to be important in removing a class of mis-triggering examples from the language acquisition problem. PMID:25086703

  8. Pedestal and ELM characterisation of highly shaped single null and quasi double null plasmas in JET

    Energy Technology Data Exchange (ETDEWEB)

    Saibene, G.; Sartori, R.; Ingesson, L.C.; Loarte, A. [European Fusion Development Agreement Close Support Unit - Garching (Germany); Lomas, P.J.; Andrew, P.; Andrew, Y.; Guenther, K.; Korothov, A.; McDonald, D.; Meigs, A.G.; Parail, V.V.; Sharapov, S. [Euratom/Ukaea Association, Culham Science Centre, Abingdon, OX (United Kingdom); Becoulet, M.; Monier Garbet, P.; Rimini, F.G.; Thomas, P.R. [Association Euratom-CEA Cadarache, 13 - Saint-Paul-lez-Durance (France); Conway, G.D.; Stober, J. [Association Euratom-IPP, MPI fur Plasmophysik, Garching (Germany); Kempenaars, M. [Association Euratom-FOM, Rijnhuizen (Netherlands); Koslowski, H.R.; Perez, C.P. [Forschungszentrum Juelich GmbH, Inst. fuer Plasmaphysik, Euratom Association, Trilateral Euregio Cluster, Julich (Germany); Lonnroth, J.S.; Saarelma, S. [Association Euratom-Tekes, Helsinki Univ. of Techn., Hut (Finland); Nave, M.F. [Association Euratom/IST, Centro de Fusao Nuclear, Lisbon (Portugal); Ongena, J. [ECOLE ROYALE MILITAIRE (ERM-KMS), Lab. Plasma Physics, Bruxelles (Belgium)

    2003-07-01

    This paper presents the results of experiments carried out in JET to study the plasma pedestal and ELM (edge localized modes) behaviour of high density/high confinement ELMy H-modes, focusing on the exploration of the effects of the plasma boundary magnetic geometry (triangularity {delta}, as well as proximity to Double-Null (DN)) and of q{sub 95} on the pedestal parameters, edge stability and ELM losses. These experiments were aimed at the study of Type-I ELMs at high density and of the access to steady-state Type-II ELM regime for JET plasma conditions, comparing pedestal and ELM characteristics in high {delta} SN (single-null) and QDN (quasi double-null) plasmas, in similar experimental conditions. To date, complete Type-I ELM suppression has not been achieved in JET in steady state conditions, although at high shaping and density mixed phases of Type-I and Type-II ELMs are observed, both for SN and QDN plasmas. Long periods of Type II ELMs (up to 150 ms in QDN) are obtained at high n(pedestal), associated with an increase of magnetic and density fluctuations, compared to levels in pure Type-I ELMy H-modes. The location of these enhanced fluctuation region is likely to be near the pedestal top. Increasing q{sub 95} from {approx} 3 to {approx} 4.5 (by varying either Ip or Bt), does not facilitate the access to the Type-II ELM regime, in contrast to indications from other experiments. In general, at high q{sub 95}, the Type-I ELMs frequency is much higher than at q{sub 95} {approx} 3 (typical for JET ELMy H-modes), the plasma global confinement is reduced, the Type II activity weakens, with the Type I-III transition occurring at lower pedestal density than at lower q{sub 95}. The enhanced {approx} 20 kHz magnetic fluctuations with Type-II ELMs are identified with strong washboard modes, possible responsible for the increased inter-ELM transport. Power balance calculations do indeed show that the power carried by ELMs is reduced by more than a factor of two in the

  9. The appearance, motion, and disappearance of three-dimensional magnetic null points

    CERN Document Server

    Murphy, Nicholas A; Haynes, Andrew L

    2015-01-01

    While theoretical models and simulations of magnetic reconnection often assume symmetry such that the magnetic null point when present is co-located with a flow stagnation point, the introduction of asymmetry typically leads to non-ideal flows across the null point. To understand this behavior, we present exact expressions for the motion of three-dimensional linear null points. The most general expression shows that linear null points move in the direction along which the vector field and its time derivative are antiparallel. Null point motion in resistive magnetohydrodynamics results from advection by the bulk plasma flow and resistive diffusion of the magnetic field, which allows non-ideal flows across topological boundaries. Null point motion is described intrinsically by parameters evaluated locally; however, global dynamics help set the local conditions at the null point. During a bifurcation of a degenerate null point into a null-null pair or the reverse, the instantaneous velocity of separation or conv...

  10. Stabilising a nulling interferometer using optical path difference dithering

    CERN Document Server

    Gabor, Pavel; Brachet, Frank; Ollivier, Marc; Decaudin, Michel; Jacquinod, Sophie; Labèque, Alain; Léger, Alain

    2008-01-01

    Context. Nulling interferometry has been suggested as the underlying principle for the Darwin and TPF-I exoplanet research missions. Aims. There are constraints both on the mean value of the nulling ratio, and on its stability. Instrument instability noise is most detrimental to the stability of the nulling performance. Methods. We applied a modified version of the classical dithering technique to the optical path difference in the scientific beam. Results. Using only this method, we repeatedly stabilised the dark fringe for several hours. This method alone sufficed to remove the 1/ f component of the noise in our setup for periods of 10 minutes, typically. These results indicate that performance stability may be maintained throughout the long-duration data acquisitions typical of exoplanet spectroscopy. Conclusions. We suggest that further study of possible stabilisation strategies should be an integral part of Darwin/TPF-I research and development

  11. Null-steering techniques for application to large array antennas

    Science.gov (United States)

    Hockham, G. A.; Cho, C.; Parr, J. C.; Wolfson, R. I.

    A multimode waveguide can be employed to design an antenna which produces a beam for each propagating mode. A dual-beam waveguide slot array is particularly attractive. The antenna is compact, highly efficient, and has lower sidelobe-level performance than can be achieved with conventional monopulse techniques. Adaptive phase steering for jammer nulling is considered, taking into account a large phased array using a series feed system. The considered configuration was selected for computer simulation. A description is presented of a multiple beam antenna with independent steerable nulls. The multiple beam low-sidelobe antenna configuration has the ability to provide a radiation pattern with multiple and independently-located nulls, with minimal effect on the sidelobes of the unperturbed pattern.

  12. Thermodynamical interpretation of the geometrical variables associated with null surfaces

    CERN Document Server

    Chakraborty, Sumanta

    2015-01-01

    The emergent gravity paradigm interprets gravitational field equations as a describing the thermodynamic limit of the underlying statistical mechanics of microscopic degrees of freedom of the spacetime. The connection is established by attributing a heat density Ts to the null surfaces where T is the appropriate Davies-Unruh temperature and s is the entropy density. The field equations can be obtained from a thermodynamic variational principle which extremises the total heat density of all null surfaces. The explicit form of s determines the nature of the theory. We explore the consequences of this paradigm for an arbitrary null surface and highlight the thermodynamic significance of various geometrical quantities. In particular, we show that: (a) A conserved current, associated with the time development vector in a natural fashion, has direct thermodynamic interpretation in all Lanczos-Lovelock models of gravity. (b) One can generalize the notion of gravitational momentum, introduced in arXiv 1506.03814 to a...

  13. Phase closure nulling: results from the 2009 campaign

    Science.gov (United States)

    Duvert, Gilles; Malbet, Fabien; Chelli, Alain; Millan-Gabet, Rafael; Monnier, John D.; Schaefer, Gail H.

    2010-07-01

    We present here a new observational technique, Phase Closure Nulling (PCN), which has the potential to obtain very high contrast detection and spectroscopy of faint companions to bright stars. PCN consists in measuring closure phases of fully resolved objects with a baseline triplet where one of the baselines crosses a null of the object visibility function. For scenes dominated by the presence of a stellar disk, the correlated flux of the star around nulls is essentially canceled out, and in these regions the signature of fainter, unresolved, scene object(s) dominates the imaginary part of the visibility in particular the closure phase. We present here the basics of the PCN method, the initial proof-of-concept observation, the envisioned science cases and report about the first observing campaign made on VLTI/AMBER and CHARA/MIRC using this technique.

  14. Phase Closure Nulling: results from the 2009 campaign

    CERN Document Server

    Duvert, Gilles; Chelli, Alain; Millan-Gabet, Rafael; Monnier, John D; Schaefer, Gail H

    2010-01-01

    We present here a new observational technique, Phase Closure Nulling (PCN), which has the potential to obtain very high contrast detection and spectroscopy of faint companions to bright stars. PCN consists in measuring closure phases of fully resolved objects with a baseline triplet where one of the baselines crosses a null of the object visibility function. For scenes dominated by the presence of a stellar disk, the correlated flux of the star around nulls is essentially canceled out, and in these regions the signature of fainter, unresolved, scene object(s) dominates the imaginary part of the visibility in particular the closure phase. We present here the basics of the PCN method, the initial proof-of-concept observation, the envisioned science cases and report about the first observing campaign made on VLTI/AMBER and CHARA/MIRC using this technique.

  15. Null but not void: considerations for hypothesis testing.

    Science.gov (United States)

    Shaw, Pamela A; Proschan, Michael A

    2013-01-30

    Standard statistical theory teaches us that once the null and alternative hypotheses have been defined for a parameter, the choice of the statistical test is clear. Standard theory does not teach us how to choose the null or alternative hypothesis appropriate to the scientific question of interest. Neither does it tell us that in some cases, depending on which alternatives are realistic, we may want to define our null hypothesis differently. Problems in statistical practice are frequently not as pristinely summarized as the classic theory in our textbooks. In this article, we present examples in statistical hypothesis testing in which seemingly simple choices are in fact rich with nuance that, when given full consideration, make the choice of the right hypothesis test much less straightforward. Published 2012. This article is a US Government work and is in the public domain in the USA. PMID:22807023

  16. Neutral evolution: A null model for language dynamics

    CERN Document Server

    Blythe, R A

    2011-01-01

    We review the task of aligning simple models for language dynamics with relevant empirical data, motivated by the fact that this is rarely attempted in practice despite an abundance of abstract models. We propose that one way to meet this challenge is through the careful construction of null models. We argue in particular that rejection of a null model must have important consequences for theories about language dynamics if modelling is truly to be worthwhile. Our main claim is that the stochastic process of neutral evolution (also known as genetic drift or random copying) is a viable null model for language dynamics. We survey empirical evidence in favour and against neutral evolution as a mechanism behind historical language changes, highlighting the theoretical implications in each case.

  17. Optimization of myocardial nulling in pediatric cardiac MRI

    Energy Technology Data Exchange (ETDEWEB)

    Tham, Edythe B. [Stollery Children' s Hospital, University of Alberta, Department of Pediatrics, Division of Pediatric Cardiology, Edmonton, Alberta (Canada); Hung, Ryan W.; Crawley, Cinzia; Noga, Michelle L. [University of Alberta, Pediatric Radiology, Stollery Children' s Hospital, Edmonton (Canada); Myers, Kimberley A. [Alberta Children' s Hospital, Calgary (Canada)

    2012-04-15

    Current protocols to determine optimal nulling time in late enhancement imaging using adult techniques may not apply to children. To determine the optimal nulling time in anesthetised children, with the hypothesis that this occurs earlier than in adults. Sedated cardiac MRI was performed in 12 children (median age: 12 months, range: 1-60 months). After gadolinium administration, scout images at 2, 3, 4 and 10 min and phase sensitive inversion recovery (PSIR) images from 5 to 10 min were obtained. Signal-to-noise ratio (SNR) and inversion time (TI) were determined. Quality of nulling was assessed according to a grading score by three observers. Data was analysed using linear regression, Kruskal-Wallis and quadratic-weighted kappa statistics. One child with a cardiomyopathy had late enhancement. Good agreement in nulling occurred for scout images at 2 ({kappa} = 0.69) and 3 ({kappa} = 0.66) min and moderate agreement at 4 min ({kappa} = 0.57). Agreement of PSIR images was moderate at 7 min ({kappa} = 0.44) and poor-fair at other times. There were significant correlations between TI and scout time (r = 0.61, P < 0.0001), and SNR and kappa (r = 0.22, P = 0.017). Scout images at 2-4 min can be used to determine the TI with little variability. Image quality for PSIR images was highest at 7 min and SNR optimal at 7-9 min. TI increases with time and should be adjusted frequently during imaging. Thus, nulling times in children differ from nulling times in adults when using standard adult techniques. (orig.)

  18. Quantization in Spacetime from Null Paths in Higher Dimensions

    OpenAIRE

    Wesson, Paul S.

    2008-01-01

    Massive particles on timelike paths in spacetime can be viewed as moving on null paths in a higher-dimensional manifold. This and other consequences follow from the use of Campbell's theorem to embed 4D general relativity in non-compactified 5D Kaluza-Klein theory. We now show that it is possible in principle to obtain the standard rule for quantization in 4D from the canonical metric with null paths in 5D. Particle mass can be wavelike, as suggested originally by Dirac, and other 4D/5D conse...

  19. A Matrix Model for the Null-Brane

    OpenAIRE

    Robbins, Daniel; Sethi, Savdeep

    2005-01-01

    The null-brane background is a simple smooth 1/2 BPS solution of string theory. By tuning a parameter, this background develops a big crunch/big bang type singularity. We construct the DLCQ description of this space-time in terms of a Yang-Mills theory on a time-dependent space-time. Our dual Matrix description provides a non-perturbative framework in which the fate of both (null) time, and the string S-matrix can be studied.

  20. Circumpulsar Asteroids: Inferences from Nulling Statistics and High Energy Correlations

    Science.gov (United States)

    Shannon, Ryan; Cordes, J. M.

    2006-12-01

    We have proposed that some classes of radio pulsar variability are associated with the entry of neutral asteroidal material into the pulsar magnetosphere. The region surrounding neutron stars is polluted with supernova fall-back material, which collapses and condenses into an asteroid-bearing disk that is stable for millions of years. Over time, collisional and radiative processes cause the asteroids to migrate inward until they are heated to the point of ionization. For older and cooler pulsars, asteroids ionize within the large magnetospheres and inject a sufficient amount of charged particles to alter the electrodynamics of the gap regions and modulate emission processes. This extrinsic model unifies many observed phenomena of variability that occur on time scales that are disparate with the much shorter time scales associated with pulsars and their magnetospheres. One such type of variability is nulling, in which certain pulsars exhibit episodes of quiescence that for some objects may be as short as a few pulse periods, but, for others, is longer than days. Here, in the context of this model, we examine the nulling phenomenon. We analyze the relationship between in-falling material and the statistics of nulling. In addition, as motivation for further high energy observations, we consider the relationship between the nulling and other magnetospheric processes.

  1. Quantization in Spacetime from Null Paths in Higher Dimensions

    CERN Document Server

    Wesson, Paul S

    2008-01-01

    Massive particles in spacetime can be viewed as moving on null paths in a higher-dimensional manifold. Using a novel gauge, we show that geometric structure in 5D can lead to the standard rule for quantization in 4D. Particle mass can be wavelike, as suggested originally by Dirac, and other 5D/4D consequences are outlined.

  2. Testing the null hypothesis: the forgotten legacy of Karl Popper?

    Science.gov (United States)

    Wilkinson, Mick

    2013-01-01

    Testing of the null hypothesis is a fundamental aspect of the scientific method and has its basis in the falsification theory of Karl Popper. Null hypothesis testing makes use of deductive reasoning to ensure that the truth of conclusions is irrefutable. In contrast, attempting to demonstrate the new facts on the basis of testing the experimental or research hypothesis makes use of inductive reasoning and is prone to the problem of the Uniformity of Nature assumption described by David Hume in the eighteenth century. Despite this issue and the well documented solution provided by Popper's falsification theory, the majority of publications are still written such that they suggest the research hypothesis is being tested. This is contrary to accepted scientific convention and possibly highlights a poor understanding of the application of conventional significance-based data analysis approaches. Our work should remain driven by conjecture and attempted falsification such that it is always the null hypothesis that is tested. The write up of our studies should make it clear that we are indeed testing the null hypothesis and conforming to the established and accepted philosophical conventions of the scientific method.

  3. Progress in broadband infrared nulling technology for TPF

    Science.gov (United States)

    Wallace, J. Kent; Brown, Ken; Bartos, Randall; Gappinger, Robert; Loya, Frank; Macdonald, Dan; Moser, Steve; Negron, John

    2005-01-01

    TPF-I has set for itself a host of challenging technical milestones along its path to demonstrating the feasibility of infrared nulling for planet detection Progress in each of these areas of technical development will be reviewed as well as progress in meeting the overarching technical milestones.

  4. Design of a polarization nulling interferometer for exoplanet detection

    NARCIS (Netherlands)

    Spronck, J.; Vosteen, L.L.A.; Pereira, S.F.; Braat, J.J.M.

    2007-01-01

    We present the design of a new testbed experiment to demonstrate nulling interferometry using polarization properties. This three-beam set-up is perfectly symmetric with respect to the number of reflections and transmissions and should therefore allow a high rejection ratio in a wide spectral band.

  5. Nulling interferometry for exoplanet detection using polarization properties

    NARCIS (Netherlands)

    Spronck, J.; Pereira, S.F.; Braat, J.J.M.

    2006-01-01

    We present a new type of nulling interferometer that makes use of polarization properties to have on-axis destructive interference. The proposed design, which only involves commercial components and no achromatic device, is also suitable for internal modulation. This type of interferometer should en

  6. Dispersion in nulling interferometry for exoplanet detection: experimental validation

    NARCIS (Netherlands)

    Spronck, J.F.P.; Los, J.W.N.; Pereira, S.F.

    2009-01-01

    It is well known that dispersion affects the performance of a wide-band nulling interferometer, since it induces wavelength-dependent phase differences between the arms of the interferometer. This property is used to create achromatic phase shift by combining several dielectric plates. In this paper

  7. Compensation and optimization of dispersion in nulling interferometry

    NARCIS (Netherlands)

    Spronck, J.F.P.; Los, J.W.N.; Pereira, S.F.

    2008-01-01

    The optical properties of materials are wavelength-dependent. This property, called dispersion, affects the performance of a wide-band nulling interferometer by inducing wavelength-dependent phase differences between the arms of the interferometer. In this paper, we analyze the influence of dispersi

  8. The appearance, motion, and disappearance of three-dimensional magnetic null points

    Energy Technology Data Exchange (ETDEWEB)

    Murphy, Nicholas A., E-mail: namurphy@cfa.harvard.edu [Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138 (United States); Parnell, Clare E.; Haynes, Andrew L. [School of Mathematics and Statistics, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS (United Kingdom)

    2015-10-15

    While theoretical models and simulations of magnetic reconnection often assume symmetry such that the magnetic null point when present is co-located with a flow stagnation point, the introduction of asymmetry typically leads to non-ideal flows across the null point. To understand this behavior, we present exact expressions for the motion of three-dimensional linear null points. The most general expression shows that linear null points move in the direction along which the magnetic field and its time derivative are antiparallel. Null point motion in resistive magnetohydrodynamics results from advection by the bulk plasma flow and resistive diffusion of the magnetic field, which allows non-ideal flows across topological boundaries. Null point motion is described intrinsically by parameters evaluated locally; however, global dynamics help set the local conditions at the null point. During a bifurcation of a degenerate null point into a null-null pair or the reverse, the instantaneous velocity of separation or convergence of the null-null pair will typically be infinite along the null space of the Jacobian matrix of the magnetic field, but with finite components in the directions orthogonal to the null space. Not all bifurcating null-null pairs are connected by a separator. Furthermore, except under special circumstances, there will not exist a straight line separator connecting a bifurcating null-null pair. The motion of separators cannot be described using solely local parameters because the identification of a particular field line as a separator may change as a result of non-ideal behavior elsewhere along the field line.

  9. Proof of a Null Penrose Conjecture using a new Quasi-local Mass

    CERN Document Server

    Roesch, Henri

    2016-01-01

    We define an explicit quasi-local mass functional which is non-decreasing along all foliations (satisfying a convexity assumption) of null cones. We use this new functional to prove the null Penrose conjecture under fairly generic conditions.

  10. Analysis of nulling phase functions suitable to image plane coronagraphy

    CERN Document Server

    Henault, Francois; Verinaud, Christophe

    2016-01-01

    Coronagraphy is a very efficient technique for identifying and characterizing extra-solar planets orbiting in the habitable zone of their parent star, especially when used in a space environment. An important family of coronagraphs is based on phase plates located at an intermediate image plane of the optical system, that spread the starlight outside the "Lyot" exit pupil plane of the instrument. In this communication we present a set of candidate phase functions generating a central null at the Lyot plane, and study how it propagates to the image plane of the coronagraph. These functions include linear azimuthal phase ramps (the well-known optical vortex), azimuthally cosine-modulated phase profiles, and circular phase gratings. Numerical simulations of the expected null depth, inner working angle, sensitivity to pointing errors, effect of central obscuration located at the pupil or image planes, and effective throughput including image mask and Lyot stop transmissions are presented and discussed. The prelim...

  11. Conserved quantities at spatial and null infinity: The Penrose potential

    International Nuclear Information System (INIS)

    We define a superpotential for energy-momentum and rotation momentum which is built out of the conformal tensor and a bivector. This superpotential is identified with that used by Penrose in his definition of quasilocal energy. It is applied to the definition of energy-momentum and rotation momentum at spatial and at null infinities. At spatial infinity the results are in agreement with those of Ashtekar and Hansen. At null infinity the results are unsatisfactory; they are tied to a specific Bondi frame. Thus, they are not in agreement with the results of Tamburino and Winicour, Geroch and Winicour, nor with those of Dray and Streubel. Some reasons for this failure are discussed

  12. Holographic proof of the quantum null energy condition

    Science.gov (United States)

    Koeller, Jason; Leichenauer, Stefan

    2016-07-01

    We use holography to prove the quantum null energy condition (QNEC) at leading order in large N for CFTs and relevant deformations of CFTs in Minkowski space which have Einstein gravity duals. Given any codimension-two surface Σ which is locally stationary under a null deformation in the direction k at the point p , the QNEC is a lower bound on the energy-momentum tensor at p in terms of the second variation of the entropy to one side of Σ : ⟨Tk k⟩≥S''/2 π √{h } . In a CFT, conformal transformations of this inequality give results which apply when Σ is not locally stationary. The QNEC was proven previously for free theories, and taken together with our result this provides strong evidence that the QNEC is a true statement about quantum field theory in general.

  13. Averaged null energy condition in Loop Quantum Cosmology

    CERN Document Server

    Li, Li-Fang

    2008-01-01

    Wormhole and time machine are very interesting objects in general relativity. However, they need exotic matters which are impossible in classical level to support them. But if we introduce the quantum effects of gravity into the stress-energy tensor, these peculiar objects can be constructed self-consistently. Fortunately, loop quantum cosmology (LQC) has the potential to serve as a bridge connecting the classical theory and quantum gravity. Therefore it provides a simple way for the study of quantum effect in the semiclassical case. As is well known, loop quantum cosmology is very successful to deal with the behavior of early universe. In the early stage, if taken the quantum effect into consideration, inflation is natural because of the violation of every kind of local energy conditions. Similar to the inflationary universe, the violation of the averaged null energy condition is the necessary condition for the traversable wormholes. In this paper, we investigate the averaged null energy condition in LQC in ...

  14. Null Cones and Einstein's Equations in Minkowski Spacetime

    CERN Document Server

    Pitts, J B

    2004-01-01

    If Einstein's equations are to describe a field theory of gravity in Minkowski spacetime, then causality requires that the effective curved metric must respect the flat background metric's null cone. The kinematical problem is solved using a generalized eigenvector formalism based on the Segr\\'{e} classification of symmetric rank 2 tensors with respect to a Lorentzian metric. Securing the correct relationship between the two null cones dynamically plausibly is achieved using the naive gauge freedom. New variables tied to the generalized eigenvector formalism reduce the configuration space to the causality-respecting part. In this smaller space, gauge transformations do not form a group, but only a groupoid. The flat metric removes the difficulty of defining equal-time commutation relations in quantum gravity and guarantees global hyperbolicity.

  15. Magnetic Reconnection at a Three-dimensional Solar Null Point

    DEFF Research Database (Denmark)

    Frederiksen, Jacob Trier; Baumann, Gisela; Galsgaard, Klaus;

    2012-01-01

    Using a specific solar null point reconnection case studied by Masson et al (2009; ApJ 700, 559) we investigate the dependence of the reconnection rate on boundary driving speed, numerical resolution, type of resistivity (constant or numerical), and assumed stratification (constant density or solar......-like). The MHD simulations start out from a potential magnetic field containing a null-point, obtained from a SOHO magnetogram extrapolation approximately 8 hours before a C-class flare was observed. The magnetic field is stressed with a boundary motion pattern similar to the horizontal motions observed by SOHO...... during the period preceding the flare. The general behavior is nearly independent of driving speed and numerical resolution, and is also very similar in stratified and unstratified models, provided only that the boundary motions are slow enough....

  16. Null warped AdS in higher spin gravity

    CERN Document Server

    Breunhoelder, Veronika; Grumiller, Daniel; Prohazka, Stefan

    2015-01-01

    We equip three-dimensional spin-3 gravity in the principal embedding with a new set of boundary conditions that we call "asymptotically null warped AdS". We find a chiral copy of the Polyakov-Bershadsky algebra as asymptotic symmetry algebra, reminiscent of the situation in topologically massive gravity with strict null warped AdS boundary conditions. We prove the invertibility of the map between zuvielbein and metric variables and construct a global gauge transformation to half of AdS spin-3 gravity in the diagonal embedding. This explains why the theory is chiral and why the Polyakov-Bershadsky algebra arises. We then introduce chemical potentials, derive the entropy, free energy, and the holographic response functions, and conclude with a discussion.

  17. The Tolman VII solution, trapped null orbits and w - modes

    CERN Document Server

    Neary, N J; Lake, K; Neary, Nicholas; Ishak, Mustapha; Lake, Kayll

    2001-01-01

    The Tolman VII solution is an exact static spherically symmetric perfect fluid solution of Einstein's equations that exhibits a surprisingly good approximation to a neutron star. We show that this solution exhibits trapped null orbits in a causal region even for a tenuity (total radius to mass ratio) $> 3$. In this region the dynamical part of the potential for axial w - modes dominates over the centrifugal part.

  18. Lie groups of conformal motions acting on null orbits

    CERN Document Server

    Sintes, A M; Carot, J

    1997-01-01

    Space-times admitting a 3-dimensional Lie group of conformal motions $C_3$ acting on null orbits are studied. Coordinate expressions for the metric and the conformal Killing vectors (CKV) are provided (irrespectively of the matter content) and then all possible perfect fluid solutions are found, although none of these verify the weak and dominant energy conditions over the whole space-time manifold.

  19. A null model for testing thermodynamic optimization in ecological systems

    OpenAIRE

    Doyle, Santiago R.; Carusela, Florencia; Guala, Sebastián; Momo, Fernando

    2011-01-01

    Several authors have hypothesized that ecological systems are subject to thermodynamic optimization, which, if proven correct, could represent a long sought general principle of organization in ecology. Although there have been recent advances, this still remains as an unresolved topic, and ecologists lack a general method to test thermodynamic optimization hypotheses in specific systems. Here we present a general, novel approach that allows generating a null model for testing thermodynamic o...

  20. Nulling Hall-Effect Current-Measuring Circuit

    Science.gov (United States)

    Sullender, Craig C.; Vazquez, Juan M.; Berru, Robert I.

    1993-01-01

    Circuit measures electrical current via combination of Hall-effect-sensing and magnetic-field-nulling techniques. Known current generated by feedback circuit adjusted until it causes cancellation or near cancellation of magnetic field produced in toroidal ferrite core by current measured. Remaining magnetic field measured by Hall-effect sensor. Circuit puts out analog signal and digital signal proportional to current measured. Accuracy of measurement does not depend on linearity of sensing components.

  1. Do electromagnetic waves always propagate along null geodesics?

    CERN Document Server

    Asenjo, Felipe A

    2016-01-01

    We find exact solutions to Maxwell equations written in terms of four-vector potentials in non--rotating, as well as in G\\"odel and Kerr spacetimes. Exact electromagnetic waves solutions are written on given gravitational field backgrounds where they evolve. We find that in non--rotating spherical symmetric spacetimes, electromagnetic plane waves travel along null geodesics. However, electromagnetic plane waves on G\\"odel and Kerr spacetimes do not exhibit that behavior.

  2. Nulling interferometry for exoplanet detection using polarization properties

    OpenAIRE

    Spronck, J.; Pereira, S.F.; Braat, J.J.M.

    2006-01-01

    We present a new type of nulling interferometer that makes use of polarization properties to have on-axis destructive interference. The proposed design, which only involves commercial components and no achromatic device, is also suitable for internal modulation. This type of interferometer should enable a high rejection ratio in a theoretically unlimited spectral band. We implemented that concept on a two-beam white-light interferometer and we present here the first experimental results

  3. Self-attraction and natural curvature in null DNA.

    Science.gov (United States)

    Manning, G S

    1989-08-01

    Forces of self-attraction inherent in DNA are unmasked when its ionic charge is neutralized. On the global level, self-attraction operates between segments to condense null (charge-neutralized) DNA into a segment-rich particle. Locally, self-attraction tends to contract an individual segment along its axis. If certain conditions are satisfied, the compressed segment buckles outward from the original line of the axis. Its most stable shape is then curved, or, as an extreme case, even completely folded. Buckling conditions are derived and shown to be met by DNA, thus explaining the high degree of ordered curvature and folding in the observed morphologies of condensed null DNA. The central concept employed is the buckling persistence length. It is evaluated for null DNA (40-50 bp) and agrees with experimental data (less than 60 bp). It helps in understanding the observed cooperative unit in the condensation/decondensation equilibrium (about 60 bp) and the observed size of digestion fragments unstable in the condensed phase (about 80 bp). The root-mean-square thermal compression/extension fluctuation in DNA is estimated at about 0.1 A/bp. PMID:2684222

  4. Non-null annular subaperture stitching interferometry for aspheric test

    Science.gov (United States)

    Zhang, Lei; Liu, Dong; Shi, Tu; Yang, Yongying; Chong, Shiyao; Miao, Liang; Huang, Wei; Shen, Yibing; Bai, Jian

    2015-10-01

    A non-null annular subaperture stitching interferometry (NASSI), combining the subaperture stitching idea and non-null test method, is proposed for steep aspheric testing. Compared with standard annular subaperture stitching interferometry (ASSI), a partial null lens (PNL) is employed as an alternative to the transmission sphere, to generate different aspherical wavefronts as the references. The coverage subaperture number would thus be reduced greatly for the better performance of aspherical wavefronts in matching the local slope of aspheric surfaces. Instead of various mathematical stitching algorithms, a simultaneous reverse optimizing reconstruction (SROR) method based on system modeling and ray tracing is proposed for full aperture figure error reconstruction. All the subaperture measurements are simulated simultaneously with a multi-configuration model in a ray-tracing program, including the interferometric system modeling and subaperture misalignments modeling. With the multi-configuration model, full aperture figure error would be extracted in form of Zernike polynomials from subapertures wavefront data by the SROR method. This method concurrently accomplishes subaperture retrace error and misalignment correction, requiring neither complex mathematical algorithms nor subaperture overlaps. A numerical simulation exhibits the comparison of the performance of the NASSI and standard ASSI, which demonstrates the high accuracy of the NASSI in testing steep aspheric. Experimental results of NASSI are shown to be in good agreement with that of Zygo® VerifireTM Asphere interferometer.

  5. Retarded Fields of Null Particles and the Memory Effect

    CERN Document Server

    Tolish, Alexander

    2014-01-01

    We consider the retarded solution to the scalar, electromagnetic, and linearized gravitational field equations in Minkowski spacetime, with source given by a particle moving on a null geodesic. In the scalar case and in the Lorenz gauge in the electromagnetic and gravitational cases, the retarded integral over the infinite past of the source does not converge as a distribution, so we cut off the null source suitably at a finite time $t_0$ and then consider two different limits: (i) the limit as the observation point goes to null infinity at fixed $t_0$, from which the ``$1/r$'' part of the fields can be extracted and (ii) the limit $t_0 \\to - \\infty$ at fixed ``observation point.'' The limit (i) gives rise to a ``velocity kick'' on distant test particles in the scalar and electromagnetic cases, and it gives rise to a ``memory effect'' (i.e., a permanent change in relative separation of two test particles) in the linearized gravitational case, in agreement with previous analyses. Although the second limit does...

  6. Zero emission city. Preliminary study; Null-Emissions-Stadt. Sondierungsstudie

    Energy Technology Data Exchange (ETDEWEB)

    Diefenbach, N.; Enseling, A.; Werner, P.; Flade, A.; Greiff, R.; Hennings, D.; Muehlich, E.; Wullkopf, U.; Sturm, P.; Kieslich, W.; Born, R.; Grossklos, M.; Hatteh, R.; Mueller, K.; Ratschow, A.; Valouch-Fornoff, C.

    2002-10-01

    The idea of a 'zero emission city' is investigated by the Institut Wohnen und Umwelt on behalf of the Federal Minister of Education and Research. After describing the current situation and defining the key parameters of a 'zero emission city', settlement structures, power supply, production processes and transportation are analyzed and linked with the communal action level to obtain a framework for research, activities and actions. The study ends with recommendations for a research programme 'zero emission city'. (orig.) [German] Die von den Staedten der Industrielaender ausgehenden Emissionen stellen im Hinblick auf die globalen Belastungen wie z.B. Treibhauseffekt, Ozonabbau und Versauerung das Hauptproblem dar. Aus diesem Grunde bietet es sich an, den Gedanken der 'Null-Emissions-Stadt', der Vision einer moeglichst emissionsfreien Stadt, aufzugreifen und auf seine Tragfaehigkeit fuer innovative Handlungsmodelle forschungsstrategisch zu ueberpruefen. Das Bundesministerium fuer Bildung und Forschung hat das Institut Wohnen und Umwelt beauftragt, in einer Sondierungsstudie dieser Fragestellung nachzugehen. Nach der Festlegung der Ausgangsbedingungen und Eckpunkte der Vision 'Null-Emissions-Stadt' und der Analyse der vier Handlungsfelder Siedlungsstrukturen, Energieversorgung, Produktionsprozesse (Kreislaufwirtschaft) und Verkehr werden diese aufgegriffen und mit der kommunalen Handlungsebene verknuepft und zu einem Forschungs-, Handlungs- und moeglichen Aktionsrahmen zusammengefuegt. Die Studie schliesst mit Hinweisen fuer die Gestaltung eines Forschungsprogramms 'Null-Emissions-Stadt'. (orig.)

  7. Variational principle for gravity with null and non-null boundaries: a unified boundary counter-term

    Energy Technology Data Exchange (ETDEWEB)

    Parattu, Krishnamohan; Chakraborty, Sumanta; Padmanabhan, T. [IUCAA, Post Bag 4, Pune (India)

    2016-03-15

    It is common knowledge that the Einstein-Hilbert action does not furnish a well-posed variational principle. The usual solution to this problem is to add an extra boundary term to the action, called a counter-term, so that the variational principle becomes well-posed. When the boundary is spacelike or timelike, the Gibbons-Hawking-York counter-term is the most widely used. For null boundaries, we had proposed a counter-term in a previous paper. In this paper, we extend the previous analysis and propose a counter-term that can be used to eliminate variations of the ''off-the-surface'' derivatives of the metric on any boundary, regardless of its spacelike, timelike or null nature. (orig.)

  8. Variational Principle for Gravity with Null and Non-null boundaries: A Unified Boundary Counter-term

    CERN Document Server

    Parattu, Krishnamohan; Padmanabhan, T

    2016-01-01

    It is common knowledge that the Einstein-Hilbert action does not furnish a well-posed variational principle. The usual solution to this problem is to add an extra boundary term to the action, called a counter-term, so that the variational principle becomes well-posed. When the boundary is spacelike or timelike, the Gibbons-Hawking-York counter-term is the most widely used. For null boundaries, we had proposed a counter-term in a previous paper. In this paper, we extend the previous analysis and propose a counter-term that can be used to eliminate variations of the "off-the-surface" derivatives of the metric on any boundary, regardless of its spacelike, timelike or null nature.

  9. Null controllable region of delta operator systems subject to actuator saturation

    Science.gov (United States)

    Yang, Hongjiu; Yan, Ce; Xia, Yuanqing; Zhang, Jinhui

    2016-07-01

    In this paper, we give exact description of null controllable regions for delta operator systems subject to actuator saturation. The null controllable region is in terms of a set of extremal trajectories of anti-stable subsystems. For the delta operator system with real eigenvalues or complex eigenvalues, the description is simplified to an explicit formula which is used to characterise the boundary of a null controllable region. The relations of null controllable regions are shown separately for continuous-time systems, discrete-time systems and delta operator systems. Two numerical examples are given to illustrate the effectiveness of the proposed techniques on null controllable regions.

  10. DBI Genesis: An Improved Violation of the Null Energy Condition

    CERN Document Server

    Hinterbichler, Kurt; Khoury, Justin; Miller, Godfrey E J

    2013-01-01

    We show that the DBI conformal galileons, derived from the world-volume theory of a 3-brane moving in an AdS bulk, admit a background, stable under quantum corrections, which violates the Null Energy Condition (NEC). The perturbations around this background are stable and propagate subluminally. Unlike other known examples of NEC violation, such as ghost condensation and conformal galileons, this theory also admits a stable, Poincare-invariant vacuum, with a Lorentz-invariant S-matrix satisfying standard analyticity conditions. Like conformal galileons, perturbations around deformations of the Poincare invariant vacuum propagate superluminally.

  11. Why is the null HBT result at RHIC so interesting?

    CERN Document Server

    Gyulassy, M

    2003-01-01

    Pion interferometry (HBT of A+A) data have posed a thorn in the theoretical interpretation of AA collisions at RHIC (sq root s = 130 AGeV). How can R sub o sub u sub t approx R sub s sub i sub d sub e approx R sub l sub o sub n sub g and remain so between AGS and RHIC? Where is the QGP Stall? Can elephants hide along the x sub 0 sup + dimension? We rummage old hydrodynamic scenarios and uncover some previously ignored NULL solutions. (author)

  12. Null controllability in a fluid-solid structure model

    Science.gov (United States)

    Raymond, J.-P.; Vanninathan, M.

    We consider a system coupling the Stokes equations in a two-dimensional domain with a structure equation which is a system of ordinary differential equations corresponding to a finite dimensional approximation of equations modeling deformations of an elastic body or vibrations of a rigid body. For that system we establish a null controllability result for localized distributed controls acting only in the fluid equations and there is no control in the solid part. This controllability result follows from a Carleman inequality that we prove for the adjoint system.

  13. Conformal symmetry wormholes and the null energy condition

    CERN Document Server

    Kuhfittig, Peter K F

    2016-01-01

    In this paper we seek a relationship between the assumption of conformal symmetry and the exotic matter needed to hold a wormhole open. By starting with a Morris-Thorne wormhole having a constant energy density, it is shown that the conformal factor provides the extra degree of freedom sufficient to account for the exotic matter. The same holds for Morris-Thorne wormholes in a noncommutative-geometry setting. Applied to thin shells, there would exist a radius that results in a wormhole with positive surface density and negative surface pressure and which violates the null energy condition on the thin shell.

  14. A Visualization of Null Geodesics for the Bonnor Massive Dipole

    CERN Document Server

    Oliva-Mercado, Guillermo Andree; Cordero-García, Iván; Frutos-Alfaro, Francisco

    2015-01-01

    In this work we simulate null geodesics for the Bonnor massive dipole metric by implementing a symbolic-numerical algorithm in Sage and Python. This program is also capable of visualizing in 3D, in principle, the geodesics for any given metric. Geodesics are launched from a common point, collectively forming a cone of light beams, simulating a solid-angle section of a point source in front of a massive object with a magnetic field. Parallel light beams also were considered, and their bending due to the curvature of the space-time was simulated.

  15. Does horizon entropy satisfy a Quantum Null Energy Conjecture?

    CERN Document Server

    Fu, Zicao

    2016-01-01

    A modern version of the idea that the area of event horizons gives $4G$ times an entropy is the Hubeny-Rangamani Causal Holographic Information (CHI) proposal for holographic field theories. Given a region $R$ of a holographic QFTs, CHI computes $A/4G$ on a certain cut of an event horizon in the gravitational dual. The result is naturally interpreted as a coarse-grained entropy. CHI is known to be finitely greater than the fine-grained Hubeny-Rangamani-Takayanagi (HRT) entropy when $\\partial R$ lies on a Killing horizon of the QFT spacetime, and in this context satisfies other non-trivial properties expected of an entropy. Here we present evidence that it also satisfies the quantum null energy condition (QNEC), which bounds the second derivative of the entropy of a quantum field theory on one side of a non-expanding null surface by the flux of stress-energy across the surface. In particular, we show CHI to satisfy the QNEC in 1+1 holographic CFTs when evaluated in states dual to conical defects in AdS$_3$. Th...

  16. Particle Acceleration at Reconnecting 3D Null Points

    Science.gov (United States)

    Stanier, A.; Browning, P.; Gordovskyy, M.; Dalla, S.

    2012-12-01

    Hard X-ray observations from the RHESSI spacecraft indicate that a significant fraction of solar flare energy release is in non-thermal energetic particles. A plausible acceleration mechanism for these are the strong electric fields associated with reconnection, a process that can be particularly efficient when particles become unmagnetised near to null points. This mechanism has been well studied in 2D, at X-points within reconnecting current sheets; however, 3D reconnection models show significant qualitative differences and it is not known whether these new models are efficient for particle acceleration. We place test particles in analytic model fields (eg. Craig and Fabling 1996) and numerical solutions to the the resistive magnetohydrodynamic (MHD) equations near reconnecting 3D nulls. We compare the behaviour of these test particles with previous results for test particle acceleration in ideal MHD models (Dalla and Browning 2005). We find that the fan model is very efficient due to an increasing "guide field" that stabilises particles against ejection from the current sheet. However, the spine model, which was the most promising in the ideal case, gives weak acceleration as the reconnection electric field is localised to a narrow cylinder about the spine axis.

  17. Holographic Description of Negative Null Energy in Squeezed Vacuum States

    CERN Document Server

    Lee, Da-Shin

    2016-01-01

    Using the AdS/CFT duality, we study the expectation value of stress tensor in squeezed vacuum states of $2+1$-dimensional quantum critical theories with a general dynamical scaling $z$. The holographic dual theory is the theory of gravity in 3+1-dimensional Lifshitz backgrounds. We then adopt a consistent approach to obtain the boundary stress tensor from bulk construction, which satisfies the trace Ward identity associated with Lifshitz scaling symmetry. The scheme for holographic dual of squeezed vacuum states is found to be the gravity theory in the geometry perturbed by gravitational wave. For small squeezing parameters, the expectation value of stress tensor in squeezed vacuum states is obtained for both strongly coupled quantum critical fields and free relativistic fields. We find that, in both cases with $z=1$, the stress tensor satisfies the averaged null energy condition and is consistent with the quantum interest conjecture. In particular, the negative lower bound on null-contracted stress tensor, w...

  18. Error analysis and system optimization of non-null aspheric testing system

    Science.gov (United States)

    Luo, Yongjie; Yang, Yongying; Liu, Dong; Tian, Chao; Zhuo, Yongmo

    2010-10-01

    A non-null aspheric testing system, which employs partial null lens (PNL for short) and reverse iterative optimization reconstruction (ROR for short) technique, is proposed in this paper. Based on system modeling in ray tracing software, the parameter of each optical element is optimized and this makes system modeling more precise. Systematic error of non-null aspheric testing system is analyzed and can be categorized into two types, the error due to surface parameters of PNL in the system modeling and the rest from non-null interferometer by the approach of error storage subtraction. Experimental results show that, after systematic error is removed from testing result of non-null aspheric testing system, the aspheric surface is precisely reconstructed by ROR technique and the consideration of systematic error greatly increase the test accuracy of non-null aspheric testing system.

  19. Quantification of adsorbed human serum albumin : a comparison between radioimmunoassay and simple null ellipsometry

    OpenAIRE

    Benesch, Johan; Askendal, A.; Tengvall, P.

    2000-01-01

    Radioimmunoassay (RIA) and null ellipsometry are two common methods to quantify adsorbed proteins. However, the accuracy of null ellipsometry with a constant protein refractive index (n 1.465, k 0) at l 632.8 nm has this far not been explored. The present study compared the methods, and the degree of agreement between the simplified single wavelength null ellipsometry and RIA to quantify adsorbed proteins was explored on different surfaces. The quantification methods agreed well w...

  20. Null quadrature domains and a free boundary problem for the Laplacian

    CERN Document Server

    Karp, Lavi

    2010-01-01

    Null quadrature domains are unbounded domains in $\\R^n$ ($n \\geq 2$) with external gravitational force zero in some generalized sense. In this paper we prove a quadratic growth estimate of the Schwarz potential of a null quadrature domain and conclude by a theorem of Caffarelli, Karp and Shahgolian that any null quadrature domain is the complement of a convex set with analytic boundary. Using this result we prove that a null quadrature domain with a non-zero upper Lebesgue density at infinity is half-space.

  1. Does anomalous violation of null energy condition invalidate holographic c-theorem?

    International Nuclear Information System (INIS)

    Null energy condition plays a crucial role in holographic renormalization group flow, leading to the holographic c-theorem. Unfortunately, the null energy condition is quantum mechanically violated. Even the averaged version can be violated. We discuss how the anomalous violation of the null energy condition affects the holographic renormalization group flow in (1+3)-dimensional bulk gravity. We show that despite the violation of the null energy condition, a suitably modified holographic c-function with a peculiar log correction is still monotonically decreasing in so far as we add the counterterm that removes a ghost mode of gravity

  2. Principles: when there should be no difference--how to fail to reject the null hypothesis.

    Science.gov (United States)

    Lew, Michael J

    2006-05-01

    It is common to perform experiments in which a 'success' is claimed when the null hypothesis is discarded. However, there is a category of experiment that has become important in which a success is when the null hypothesis is not rejected. Failing to discard the null hypothesis is different from proving it to be valid, a distinction that is particularly important in experiments in which any inadequacy of experimental design or implementation enhances the likelihood of a success. The appropriate analysis of such experiments tests for evidence of the validity of the null hypothesis rather than simply failing to find evidence against it. PMID:16595154

  3. Alignment of optical system components using an ADM beam through a null assembly

    Science.gov (United States)

    Hayden, Joseph E. (Inventor); Olczak, Eugene G. (Inventor)

    2010-01-01

    A system for testing an optical surface includes a rangefinder configured to emit a light beam and a null assembly located between the rangefinder and the optical surface. The null assembly is configured to receive and to reflect the emitted light beam toward the optical surface. The light beam reflected from the null assembly is further reflected back from the optical surface toward the null assembly as a return light beam. The rangefinder is configured to measure a distance to the optical surface using the return light beam.

  4. Review of OCA activities on nulling testbench PERSEE

    Science.gov (United States)

    Hénault, François; Girard, Paul; Marcotto, Aurélie; Mauclert, Nicolas; Bailet, Christophe; Clausse, Jean-Michel; Mourard, Denis; Rabbia, Yves; Roussel, Alain; Barillot, Marc; Cassaing, Frédéric; Le Duigou, Jean-Michel

    2010-07-01

    We present a review of our activities on PERSEE (Pégase Experiment for Research and Stabilization of Extreme Extinction) at Observatoire de la Côte d'Azur (OCA). PERSEE is a laboratory testbench aiming at achieving a stabilized nulling ratio better than 10-4 in the astronomical bands K and M, in presence of flight-representative spacecraft perturbations. The bench has been jointly developed by a Consortium of six French institutes and companies, among which OCA was responsible for the star simulator and of the opto-mechanical studies, procurement and manufacturing of the optical train. In this communication are presented the alignment and image quality requirements and the optomechanical design of the illumination module and main optical train, including a periscope Achromatic Phase Shifter (APS), tip-tilt mirrors used to introduce and then compensate for dynamic disturbances, delay lines, beam compressors and fiber injection optics. Preliminary test results of the star simulator are also provided.

  5. An Operator Product Expansion for Polygonal null Wilson Loops

    CERN Document Server

    Alday, Luis F; Maldacena, Juan; Sever, Amit; Vieira, Pedro

    2010-01-01

    We consider polygonal Wilson loops with null edges in conformal gauge theories. We derive an OPE-like expansion when several successive lines of the polygon are becoming aligned. The limit corresponds to a collinear, or multicollinear, limit and we explain the systematics of all the subleading corrections, going beyond the leading terms that were previously considered. These subleading corrections are governed by excitations of high spin operators, or excitations of a flux tube that goes between two Wilson lines. The discussion is valid for any conformal gauge theory, for any coupling and in any dimension. For N=4 super Yang Mills we check this expansion at strong coupling and at two loops at weak coupling . We also make predictions for the remainder function at higher loops. In the process, we also derived a new version for the TBA integral equations that determine the strong coupling answer and present the area as the associated Yang-Yang functional.

  6. A new interferometer architecture combining nulling with phase closure measurements

    CERN Document Server

    Lacour, S; Monnier, J D; Kotani, T; Gauchet, L; Labeye, P

    2013-01-01

    Imaging the direct light signal from a faint exoplanet against the overwhelming glare of its host star presents one of the fundamental challenges to modern astronomical instrumentation. Achieving sufficient signal-to-noise for detection by direct imaging is limited by three basic physical processes: aberration of the wavefronts (both instrumental and atmospheric), photon noise, and detector noise. In this paper, we advance a novel optical setup which synthesizes the advantages of two different techniques: nulling interferometry to mitigate photon noise, and closure phase to combat optical aberrations. Our design, which employs technology from integrated optics and photonics, is intended to combine the advantageous aspects of both a coronagraph and a non-redundant interferometer. We show that such an instrument would allow readout noise limited detection of exoplanets, even in the presence of residual co-phasing errors. As a result, this concept would be ideal for space interferometry and for ground based obse...

  7. Imaging and Nulling with the Space Interferometry Mission

    CERN Document Server

    Böker, T

    1999-01-01

    We present numerical simulations for a possible synthesis imaging mode of the Space Interferometer Mission (SIM). We summarize the general techniques that SIM offers to perform imaging of high surface brightness sources, and discuss their strengths and weaknesses. We describe an interactive software package that is used to provide realistic, photometrically correct estimates of SIM performance for various classes of astronomical objects. In particular, we simulate the cases of gaseous disks around black holes in the nuclei of galaxies, and zodiacal dust disks around young stellar objects. Regarding the first, we show that a Keplerian velocity gradient of the line-emitting gaseous disk -- and thus the mass of the putative black hole -- can be determined with SIM to unprecedented accuracy in about 5 hours of integration time for objects with H_alpha surface brigthness comparable to the prototype M 87. Detections and observations of exo-zodiacal dust disks depend critically on the disk properties and the nulling...

  8. Linearized gravitational waves near space-like and null infinity

    CERN Document Server

    Beyer, Florian; Frauendiener, Jörg; Whale, Ben

    2013-01-01

    Linear perturbations on Minkowski space are used to probe numerically the remote region of an asymptotically flat space-time close to spatial infinity. The study is undertaken within the framework of Friedrich's conformal field equations and the corresponding conformal representation of spatial infinity as a cylinder. The system under consideration is the (linear) zero-rest-mass equation for a spin-2 field. The spherical symmetry of the underlying background is used to decompose the field into separate non-interacting multipoles. It is demonstrated that it is possible to reach null-infinity from initial data on an asymptotically Euclidean hyper-surface and that the physically important radiation field can be extracted accurately on $\\scri^+$.

  9. From Satisfying to Violating the Null Energy Condition

    CERN Document Server

    Elder, Benjamin; Khoury, Justin

    2013-01-01

    We construct a theory which admits a time-dependent solution smoothly interpolating between a null energy condition (NEC)-satisfying phase at early times and a NEC-violating phase at late times. We first review earlier attempts to violate the NEC and an argument of Rubakov, presented in 1305.2614, which forbids the existence of such interpolating solutions in a single-field dilation-invariant theory. We then construct a theory which, in addition to possessing a Poincar\\'e-invariant vacuum, does admit such a solution. For a wide range of parameters, perturbations around this solution are at all times stable, comfortably subluminal and weakly-coupled. The theory requires us to explicitly break dilation-invariance, so it is unlikely that the theory is fully stable under quantum corrections, but we argue that the existence of a healthy interpolating solution is quantum-mechanically robust.

  10. Causal Space-Times on a Null Lattice

    CERN Document Server

    Schaden, Martin

    2015-01-01

    I investigate a model of quantum gravity based on the first order Hilbert Palatini action with cosmological constant, discretized on a causal null-lattice with SL(2,C) structure group. The description is coordinate invariant and foliates in a causal and physically transparent manner. Lattice variables and observables are constructed. Conditions for a lattice configuration to describe a triangulated causal manifold are derived and encoded by a topological lattice theory. An equivariant BRST-construction is used to partially localize the SL(2,C) structure group of this model to the compact SU(2) of local spatial rotations. The latter in turn is completely localized using the spinors of this formulation. The integration measure of this completely localized model is derived from the SL(2,C)-invariant integration measure and is expressed in terms of SL(2,C)-invariant variables. An invariant regularization of the lattice integration measure that suppresses configurations with small local four-volumes is proposed. N...

  11. Radiation Hardened NULL Convention Logic Asynchronous Circuit Design

    Directory of Open Access Journals (Sweden)

    Liang Zhou

    2015-10-01

    Full Text Available This paper proposes a radiation hardened NULL Convention Logic (NCL architecture that can recover from a single event latchup (SEL or single event upset (SEU fault without deadlock or any data loss. The proposed architecture is analytically proved to be SEL resistant, and by extension, proved to be SEU resistant. The SEL/SEU resistant version of a 3-stage full-word pipelined NCL 4 × 4 unsigned multiplier was implemented using the IBM cmrf8sf 130 nm 1.2 V process at the transistor level and simulated exhaustively with SEL fault injection to validate the proposed architectures. Compared with the original version, the SEL/SEU resilient version has 1.31× speed overhead, 2.74× area overhead, and 2.79× energy per operation overhead.

  12. Power spectrum nulls due to nonstandard inflationary evolution

    Science.gov (United States)

    Goswami, Gaurav; Souradeep, Tarun

    2011-01-01

    The simplest models of inflation based on slow roll produce nearly scale invariant primordial power spectra (PPS). But there are also numerous models that predict radically broken scale invariant PPS. In particular, markedly cuspy dips in the PPS correspond to nulls where the perturbation amplitude, hence PPS, goes through a zero at a specific wave number. Near this wave number, the true quantum nature of the generation mechanism of the primordial fluctuations may be revealed. Naively these features may appear to arise from fine-tuned initial conditions. However, we show that this behavior arises under fairly generic set of conditions involving super-Hubble scale evolution of perturbation modes during inflation. We illustrate this with the well-studied examples of punctuated inflation and the Starobinsky-break model.

  13. Power spectrum nulls due to non-standard inflationary evolution

    CERN Document Server

    Goswami, Gaurav

    2010-01-01

    The simplest models of inflation based on slow roll produce nearly scale invariant primordial power spectra (PPS). But there are also numerous models that predict radically broken scale invariant PPS. In particular, markedly cuspy dips in the PPS correspond to nulls where the perturbation amplitude, hence PPS, goes through a zero at a specific wavenumber. Near this wavenumber, the true quantum nature of the generation mechanism of the primordial fluctuations may be revealed. Naively these features may appear to arise from fine tuned initial conditions. However, we show that this behavior arises under fairly generic set of conditions involving super-Hubble scale evolution of perturbation modes during inflation. We illustrate this with the well-studied examples of punctuated inflation and the Starobinsky-break model.

  14. Null-stream pointing with pulsar timing arrays

    CERN Document Server

    Hazboun, Jeffrey S

    2016-01-01

    Locating sources on the sky is one of the largest challenges in gravitational wave astronomy, owing to the omni-directional nature of gravitational wave detection techniques, and the often intrinsically weak signals being observed. Ground-based detectors can address the pointing problem by observing with a network of detectors, effectively triangulating signal locations by observing the arrival times across the network. Space-based detectors will observe long-lived sources that persist while the detector moves relative to their location on the sky, using Doppler shifts of the signal to locate the sky position. While these methods improve the pointing capability of a detector or network, the angular resolution is still coarse compared to the standards one expects from electromagnetic astronomy. Another technique that can be used for sky localization is null-stream pointing. In the case where multiple independent data streams exist, a single astrophysical source of gravitational waves will appear in each of the...

  15. Dinucleotide controlled null models for comparative RNA gene prediction

    Directory of Open Access Journals (Sweden)

    Gesell Tanja

    2008-05-01

    Full Text Available Abstract Background Comparative prediction of RNA structures can be used to identify functional noncoding RNAs in genomic screens. It was shown recently by Babak et al. [BMC Bioinformatics. 8:33] that RNA gene prediction programs can be biased by the genomic dinucleotide content, in particular those programs using a thermodynamic folding model including stacking energies. As a consequence, there is need for dinucleotide-preserving control strategies to assess the significance of such predictions. While there have been randomization algorithms for single sequences for many years, the problem has remained challenging for multiple alignments and there is currently no algorithm available. Results We present a program called SISSIz that simulates multiple alignments of a given average dinucleotide content. Meeting additional requirements of an accurate null model, the randomized alignments are on average of the same sequence diversity and preserve local conservation and gap patterns. We make use of a phylogenetic substitution model that includes overlapping dependencies and site-specific rates. Using fast heuristics and a distance based approach, a tree is estimated under this model which is used to guide the simulations. The new algorithm is tested on vertebrate genomic alignments and the effect on RNA structure predictions is studied. In addition, we directly combined the new null model with the RNAalifold consensus folding algorithm giving a new variant of a thermodynamic structure based RNA gene finding program that is not biased by the dinucleotide content. Conclusion SISSIz implements an efficient algorithm to randomize multiple alignments preserving dinucleotide content. It can be used to get more accurate estimates of false positive rates of existing programs, to produce negative controls for the training of machine learning based programs, or as standalone RNA gene finding program. Other applications in comparative genomics that require

  16. Cadmium modulates adipocyte functions in metallothionein-null mice

    International Nuclear Information System (INIS)

    Our previous study has demonstrated that exposure to cadmium (Cd), a toxic heavy metal, causes a reduction of adipocyte size and the modulation of adipokine expression. To further investigate the significance of the Cd action, we studied the effect of Cd on the white adipose tissue (WAT) of metallothionein null (MT−/−) mice, which cannot form atoxic Cd–MT complexes and are used for evaluating Cd as free ions, and wild type (MT+/+) mice. Cd administration more significantly reduced the adipocyte size of MT−/− mice than that of MT+/+ mice. Cd exposure also induced macrophage recruitment to WAT with an increase in the expression level of Ccl2 (MCP-1) in the MT−/− mice. The in vitro exposure of Cd to adipocytes induce triglyceride release into culture medium, decrease in the expression levels of genes involved in fatty acid synthesis and lipid hydrolysis at 24 h, and at 48 h increase in phosphorylation of the lipid-droplet-associated protein perilipin, which facilitates the degradation of stored lipids in adipocytes. Therefore, the reduction in adipocyte size by Cd may arise from an imbalance between lipid synthesis and lipolysis. In addition, the expression levels of leptin, adiponectin and resistin decreased in adipocytes. Taken together, exposure to Cd may induce unusually small adipocytes and modulate the expression of adipokines differently from the case of physiologically small adipocytes, and may accelerate the risk of developing insulin resistance and type 2 diabetes. - Highlights: • Cd causes a marked reduction in adipocyte size in MT-null mice. • Cd enhances macrophage migration into adipose tissue and disrupt adipokine secretion. • MT gene alleviates Cd-induced adipocyte dysfunctions. • Cd enhances the degradation of stored lipids in adipocytes, mediated by perilipin. • Cd induces unusually small adipocytes and the abnormal expression of adipokines

  17. Cadmium modulates adipocyte functions in metallothionein-null mice

    Energy Technology Data Exchange (ETDEWEB)

    Kawakami, Takashige; Nishiyama, Kaori; Kadota, Yoshito; Sato, Masao; Inoue, Masahisa; Suzuki, Shinya, E-mail: suzukis@ph.bunri-u.ac.jp

    2013-11-01

    Our previous study has demonstrated that exposure to cadmium (Cd), a toxic heavy metal, causes a reduction of adipocyte size and the modulation of adipokine expression. To further investigate the significance of the Cd action, we studied the effect of Cd on the white adipose tissue (WAT) of metallothionein null (MT{sup −/−}) mice, which cannot form atoxic Cd–MT complexes and are used for evaluating Cd as free ions, and wild type (MT{sup +/+}) mice. Cd administration more significantly reduced the adipocyte size of MT{sup −/−} mice than that of MT{sup +/+} mice. Cd exposure also induced macrophage recruitment to WAT with an increase in the expression level of Ccl2 (MCP-1) in the MT{sup −/−} mice. The in vitro exposure of Cd to adipocytes induce triglyceride release into culture medium, decrease in the expression levels of genes involved in fatty acid synthesis and lipid hydrolysis at 24 h, and at 48 h increase in phosphorylation of the lipid-droplet-associated protein perilipin, which facilitates the degradation of stored lipids in adipocytes. Therefore, the reduction in adipocyte size by Cd may arise from an imbalance between lipid synthesis and lipolysis. In addition, the expression levels of leptin, adiponectin and resistin decreased in adipocytes. Taken together, exposure to Cd may induce unusually small adipocytes and modulate the expression of adipokines differently from the case of physiologically small adipocytes, and may accelerate the risk of developing insulin resistance and type 2 diabetes. - Highlights: • Cd causes a marked reduction in adipocyte size in MT-null mice. • Cd enhances macrophage migration into adipose tissue and disrupt adipokine secretion. • MT gene alleviates Cd-induced adipocyte dysfunctions. • Cd enhances the degradation of stored lipids in adipocytes, mediated by perilipin. • Cd induces unusually small adipocytes and the abnormal expression of adipokines.

  18. null Faults, null Images

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Through the study of faults and their effects, much can be learned about the size and recurrence intervals of earthquakes. Faults also teach us about crustal...

  19. Agreement and Null Subjects in German L2 Development: New Evidence from Reaction-Time Experiments.

    Science.gov (United States)

    Clahsen, Harald; Hong, Upyong

    1995-01-01

    Reports on reaction time experiments investigating subject-verb agreement and null subjects in 33 Korean learners of German and a control group of 20 German native speakers. Results found that the two phenomena do not covary in the Korean learners, indicating that properties of agreement and null subjects are acquired separately from one another.…

  20. Null controllability of the viscous Camassa–Holm equation with moving control

    Indian Academy of Sciences (India)

    Peng Gao

    2016-02-01

    In this paper, we study the null controllability of the viscous Camassa–Holm equation on the one-dimensional torus. By using a moving distributed control, we obtain that the system is null controllable for a given data with certain regularity.

  1. The role of amplitude, phase, polarization and their interconnection in nulling interferometry

    NARCIS (Netherlands)

    Spronck, J.F.P.

    2008-01-01

    Nulling interferometry is a promising technique to directly detect Earth-like exoplanets. Unfortunately, it is extremely challenging to build a nulling interferometer and to meet the requirements needed for Earth-like planet detection. In this, thesis, we analyze the role of amplitude, phase and pol

  2. Chromatism compensation in wide-band nulling interferometry for exoplanet detection

    NARCIS (Netherlands)

    Spronck, J.; Pereira, S.F.; Braat, J.J.M.

    2006-01-01

    We introduce the concept of chromatism compensation in nulling interferometry that enables a high rejection ratio in a wide spectral band. Therefore the achromaticity condition considered in most nulling interferometers can be relaxed. We show that this chromatism compensation cannot be applied to a

  3. The effect of the longitudinal polarization component in multi-axial nulling interferometry for exoplanet detection

    NARCIS (Netherlands)

    Spronck, J.F.P.; Pereira, S.F.

    2009-01-01

    We show a fundamental limitation of multi-axial beam combiners in nulling interferometry. The longitudinal electric field induced by the focusing optics can drastically limit the performance of such a nulling interferometer. We further analyze the filtering capabilities of a single-mode optical fibe

  4. Spacetime characterizations of $\\Lambda$-vacuum metrics with a null Killing 2-form

    CERN Document Server

    Mars, Marc

    2016-01-01

    An exhaustive list of four-dimensional $\\Lambda$-vacuum spacetimes admitting a Killing vector whose self-dual Killing two-form ${\\cal F}$ is null is obtained assuming that the self-dual Weyl tensor is proportional to the tensor product of ${\\cal F}$ by itself. Our analysis complements previous results concerning the case with non-null ${\\cal F}$. We analyze both cases with $\\Lambda$ vanishing or not. In the latter case we prove that $\\Lambda< 0$ must hold necessarily, and we find a characterization of the Einstein spacetimes conformal to pp-waves. In the former case we obtain spacetime characterizations of vacuum plane waves and of the stationary vacuum Brinkmann spacetimes. At the light of the full set of results, old and new, we reformulate the case with non-null ${\\cal F}$ and $\\Lambda= 0$. We finally present a table collecting the results for both null, and non-null, ${\\cal F}$.

  5. Abnormal Mammary Development in 129:STAT1-Null Mice is Stroma-Dependent.

    Directory of Open Access Journals (Sweden)

    Jane Q Chen

    Full Text Available Female 129:Stat1-null mice (129S6/SvEvTac-Stat1(tm1Rds homozygous uniquely develop estrogen-receptor (ER-positive mammary tumors. Herein we report that the mammary glands (MG of these mice have altered growth and development with abnormal terminal end buds alongside defective branching morphogenesis and ductal elongation. We also find that the 129:Stat1-null mammary fat pad (MFP fails to sustain the growth of 129S6/SvEv wild-type and Stat1-null epithelium. These abnormalities are partially reversed by elevated serum progesterone and prolactin whereas transplantation of wild-type bone marrow into 129:Stat1-null mice does not reverse the MG developmental defects. Medium conditioned by 129:Stat1-null epithelium-cleared MFP does not stimulate epithelial proliferation, whereas it is stimulated by medium conditioned by epithelium-cleared MFP from either wild-type or 129:Stat1-null females having elevated progesterone and prolactin. Microarrays and multiplexed cytokine assays reveal that the MG of 129:Stat1-null mice has lower levels of growth factors that have been implicated in normal MG growth and development. Transplanted 129:Stat1-null tumors and their isolated cells also grow slower in 129:Stat1-null MG compared to wild-type recipient MG. These studies demonstrate that growth of normal and neoplastic 129:Stat1-null epithelium is dependent on the hormonal milieu and on factors from the mammary stroma such as cytokines. While the individual or combined effects of these factors remains to be resolved, our data supports the role of STAT1 in maintaining a tumor-suppressive MG microenvironment.

  6. Why Are Flare Ribbons Associated with the Spines of Magnetic Null Points Generically Elongated?

    Science.gov (United States)

    Pontin, David; Galsgaard, Klaus; Démoulin, Pascal

    2016-08-01

    Coronal magnetic null points exist in abundance, as demonstrated by extrapolations of the coronal field, and have been inferred to be important for a broad range of energetic events. These null points and their associated separatrix and spine field lines represent discontinuities of the field line mapping, making them preferential locations for reconnection. This field line mapping also exhibits strong gradients adjacent to the separatrix (fan) and spine field lines, which can be analysed using the "squashing factor", Q. In this article we analyse in detail the distribution of Q in the presence of magnetic nulls. While Q is formally infinite on both the spine and fan of the null, the decay of Q away from these structures is shown in general to depend strongly on the null-point structure. For the generic case of a non-radially-symmetric null, Q decays most slowly away from the spine or fan in the direction in which |{B}| increases most slowly. In particular, this demonstrates that the extended elliptical high-Q halo around the spine footpoints observed by Masson et al. ( Astrophys. J. 700, 559, 2009) is a generic feature. This extension of the Q halos around the spine or fan footpoints is important for diagnosing the regions of the photosphere that are magnetically connected to any current layer that forms at the null. In light of this, we discuss how our results can be used to interpret the geometry of observed flare ribbons in circular ribbon flares, in which typically a coronal null is implicated. We conclude that both the physics in the vicinity of the null and how this is related to the extension of Q away from the spine or fan can be used in tandem to understand observational signatures of reconnection at coronal null points.

  7. Why Are Flare Ribbons Associated with the Spines of Magnetic Null Points Generically Elongated?

    Science.gov (United States)

    Pontin, David; Galsgaard, Klaus; Démoulin, Pascal

    2016-06-01

    Coronal magnetic null points exist in abundance, as demonstrated by extrapolations of the coronal field, and have been inferred to be important for a broad range of energetic events. These null points and their associated separatrix and spine field lines represent discontinuities of the field line mapping, making them preferential locations for reconnection. This field line mapping also exhibits strong gradients adjacent to the separatrix (fan) and spine field lines, which can be analysed using the "squashing factor", Q. In this article we analyse in detail the distribution of Q in the presence of magnetic nulls. While Q is formally infinite on both the spine and fan of the null, the decay of Q away from these structures is shown in general to depend strongly on the null-point structure. For the generic case of a non-radially-symmetric null, Q decays most slowly away from the spine or fan in the direction in which |{B}| increases most slowly. In particular, this demonstrates that the extended elliptical high- Q halo around the spine footpoints observed by Masson et al. (Astrophys. J. 700, 559, 2009) is a generic feature. This extension of the Q halos around the spine or fan footpoints is important for diagnosing the regions of the photosphere that are magnetically connected to any current layer that forms at the null. In light of this, we discuss how our results can be used to interpret the geometry of observed flare ribbons in circular ribbon flares, in which typically a coronal null is implicated. We conclude that both the physics in the vicinity of the null and how this is related to the extension of Q away from the spine or fan can be used in tandem to understand observational signatures of reconnection at coronal null points.

  8. Strong subadditivity, null energy condition and charged black holes

    International Nuclear Information System (INIS)

    Using the Hubeny-Rangamani-Takayanagi (HRT) conjectured formula for entanglement entropy in the context of the AdS/CFT correspondence with time-dependent backgrounds, we investigate the relation between the bulk null energy condition (NEC) of the stress-energy tensor with the strong sub-additivity (SSA) property of entanglement entropy in the boundary theory. In a background that interpolates between an AdS to an AdS-Reissner-Nordstrom-type geometry, we find that generically there always exists a critical surface beyond which the violation of NEC would naively occur. However, the extremal area surfaces that determine the entanglement entropy for the boundary theory, can penetrate into this forbidden region only for certain choices for the mass and the charge functions in the background. This penetration is then perceived as the violation of SSA in the boundary theory. We also find that this happens only when the critical surface lies above the apparent horizon, but not otherwise. We conjecture that SSA, which is thus non-trivially related to NEC, also characterizes the entire time-evolution process along which the dual field theory may thermalize

  9. Invariance Techniques And High-Resolution Null Steering

    Science.gov (United States)

    Roy, R.; Kailath, T.

    1988-02-01

    Over the past several decades, a significant amount of research has been performed in the area of high-resolution signal parameter estimation. It is a problem of significance in many signal processing applications including direction-of-arrival estimation in which the locations of multiple sources whose radiation is received by an array of sensors are sought. Much of the research has focussed on approaches based on the formation of optimal weight or copy vectors, procedures derived from the conventional practice of beamforming. This class of approached to parameter estimation problems has come to be known as high-resolution spectral analysis/beamforming since the introduction of the maximum entropy (MEM) method by Burg in 1967, and the maximum-likelihood (ML) method by Capon in 1969. These techniques provide increased resolution and accuracy over their predecessors (including conventional beamforming, but suffer from model mismatch. MUSIC and ESPRIT are recently developed geometric techniques that exploit the underlying model and thereby achieve significant improvements in performance. In this paper, these techniques are summarized. From basic physical principles, it is shown that ESPRIT is actually a multidimensional null steering algorithm, an interpretation with significant intuitive appeal. Finally, optimal signal copy vectors that naturally arise from the algorithm are presented, and their properties as beamforming vectors for this class of problems are discussed.

  10. Strong Subadditivity, Null Energy Condition and Charged Black Holes

    CERN Document Server

    Caceres, Elena; Pedraza, Juan F; Tangarife, Walter

    2014-01-01

    Using the Hubeny-Rangamani-Takayanagi (HRT) conjectured formula for entanglement entropy in the context of the AdS/CFT correspondence with time-dependent backgrounds, we investigate the relation between the bulk null energy condition (NEC) of the stress-energy tensor with the strong sub-additivity (SSA) property of entanglement entropy in the boundary theory. In a background that interpolates between an AdS to an AdS-Reissner-Nordstrom-type geometry, we find that generically there always exists a critical surface beyond which the violation of NEC would naively occur. However, the extremal area surfaces that determine the entanglement entropy for the boundary theory, can penetrate into this forbidden region only for certain choices for the mass and the charge functions in the background. This penetration is then perceived as the violation of SSA in the boundary theory. We also find that this happens only when the critical surface lies above the apparent horizon, but not otherwise. We conjecture that SSA, which...

  11. Impairment in motor learning of somatostatin null mutant mice.

    Science.gov (United States)

    Zeyda, T; Diehl, N; Paylor, R; Brennan, M B; Hochgeschwender, U

    2001-07-01

    Somatostatin was first identified as a hypothalamic factor which inhibits the release of growth hormone from the anterior pituitary (somatotropin release inhibitory factor, SRIF). Both SRIF and its receptors were subsequently found widely distributed within and outside the nervous system, in the adult as well as in the developing organism. Reflecting this wide distribution, somatostatin has been implicated regulating a diverse array of biological processes. These include body growth, homeostasis, sensory perception, autonomous functions, rate of intestinal absorption, behavior, including cognition and memory, and developmental processes. We produced null mutant mice lacking somatostatin through targeted mutagenesis. The mutant mice are healthy, fertile, and superficially indistinguishable from their heterozygous and wildtype littermates. A 'first round' phenotype screen revealed that mice lacking somatostatin have elevated plasma growth hormone levels, despite normal body size, and have elevated basal plasma corticosterone levels. In order to uncover subtle and unexpected differences, we carried out a systematic behavioral phenotype screen which identified a significant impairment in motor learning revealed when increased demands were made on motor coordination. Motor coordination and motor learning require an intact cerebellum. While somatostatin is virtually absent from the adult cerebellum, the ligand and its receptor(s) are transiently expressed at high levels in the developing cerebellum. This result suggests the functional significance of transient expression of SRIF and its receptors in the development of the cerebellum. PMID:11430867

  12. Aspects of QCD Current Algebra on a Null Plane

    CERN Document Server

    Beane, Silas R

    2015-01-01

    Consequences of QCD current algebra formulated on a light-like hyperplane are derived for the forward scattering of vector and axial-vector currents on an arbitrary hadronic target. It is shown that current algebra gives rise to a special class of sum rules that are direct consequences of the independent chiral symmetry that exists at every point on the two-dimensional transverse plane orthogonal to the lightlike direction. These sum rules are obtained by exploiting the closed, infinite-dimensional algebra satisfied by the transverse moments of null-plane axial-vector and vector charge distributions. In the special case of a nucleon target, this procedure leads to the Adler-Weisberger, Gerasimov-Drell-Hearn, Cabbibo-Radicatti and Fubini-Furlan-Rossetti sum rules. Matching to the dispersion-theoretic language which is usually invoked in deriving these sum rules, the moment sum rules are shown to be equivalent to algebraic constraints on forward S-matrix elements in the Regge limit.

  13. Aspects of QCD current algebra on a null plane

    Science.gov (United States)

    Beane, S. R.; Hobbs, T. J.

    2016-09-01

    Consequences of QCD current algebra formulated on a light-like hyperplane are derived for the forward scattering of vector and axial-vector currents on an arbitrary hadronic target. It is shown that current algebra gives rise to a special class of sum rules that are direct consequences of the independent chiral symmetry that exists at every point on the two-dimensional transverse plane orthogonal to the lightlike direction. These sum rules are obtained by exploiting the closed, infinite-dimensional algebra satisfied by the transverse moments of null-plane axial-vector and vector charge distributions. In the special case of a nucleon target, this procedure leads to the Adler-Weisberger, Gerasimov-Drell-Hearn, Cabibbo-Radicati and Fubini-Furlan-Rossetti sum rules. Matching to the dispersion-theoretic language which is usually invoked in deriving these sum rules, the moment sum rules are shown to be equivalent to algebraic constraints on forward S-matrix elements in the Regge limit.

  14. Strong subadditivity, null energy condition and charged black holes

    Energy Technology Data Exchange (ETDEWEB)

    Caceres, Elena [Facultad de Ciencias, Universidad de Colima,Bernal Diaz del Castillo 340, Colima (Mexico); Theory Group, Department of Physics, The University of Texas,Austin, TX 78712 (United States); Kundu, Arnab [Theory Group, Department of Physics, The University of Texas,Austin, TX 78712 (United States); Pedraza, Juan F.; Tangarife, Walter [Theory Group, Department of Physics, The University of Texas,Austin, TX 78712 (United States); Texas Cosmology Center, The University of Texas,Austin, TX 78712 (United States)

    2014-01-16

    Using the Hubeny-Rangamani-Takayanagi (HRT) conjectured formula for entanglement entropy in the context of the AdS/CFT correspondence with time-dependent backgrounds, we investigate the relation between the bulk null energy condition (NEC) of the stress-energy tensor with the strong sub-additivity (SSA) property of entanglement entropy in the boundary theory. In a background that interpolates between an AdS to an AdS-Reissner-Nordstrom-type geometry, we find that generically there always exists a critical surface beyond which the violation of NEC would naively occur. However, the extremal area surfaces that determine the entanglement entropy for the boundary theory, can penetrate into this forbidden region only for certain choices for the mass and the charge functions in the background. This penetration is then perceived as the violation of SSA in the boundary theory. We also find that this happens only when the critical surface lies above the apparent horizon, but not otherwise. We conjecture that SSA, which is thus non-trivially related to NEC, also characterizes the entire time-evolution process along which the dual field theory may thermalize.

  15. Investigation of nulling and subpulse drifting properties of PSR J1727-2739

    Science.gov (United States)

    Wen, Z. G.; Wang, N.; Yuan, J. P.; Yan, W. M.; Manchester, R. N.; Yuen, R.; Gajjar, V.

    2016-08-01

    Aims: We intend to study of the nulling and subpulse drifting in PSR J1727-2739 in detail to investigate its radiation properties. Methods: The observations were carried out on 20 March, 2004 using the Parkes 64-m radio telescope with a central frequency of 1518 MHz. A total of 5568 single pulses were analysed. Results: This pulsar shows well-defined nulls with lengths lasting from 6 to 281 pulses and separated by burst phases ranging from 2 to 133 pulses. We estimate a nulling fraction of around 68%. No emission in the average pulse profile integrated over all null pulses is detected with significance above 3σ. Most transitions from nulls to bursts are within a few pulses, whereas the transitions from bursts to nulls exhibit two patterns of decay; these transitions either decrease gradually or rapidly. In the burst phase, we find that there are two distinct subpulse drift modes with vertical spacing between the drift bands of 9.7 ± 1.6 and 5.2 ± 0.9 pulse periods, while sometimes there is a third mode with no subpulse drifting. Some mode transitions occur within a single burst, while others are separated by nulls. Different modes have different average pulse profiles. Possible physical mechanisms are discussed.

  16. Progesterone facilitates chromosome instability (aneuploidy) in p53 null normal mammary epithelial cells

    Science.gov (United States)

    Goepfert, T. M.; McCarthy, M.; Kittrell, F. S.; Stephens, C.; Ullrich, R. L.; Brinkley, B. R.; Medina, D.

    2000-01-01

    Mammary epithelial cells from p53 null mice have been shown recently to exhibit an increased risk for tumor development. Hormonal stimulation markedly increased tumor development in p53 null mammary cells. Here we demonstrate that mammary tumors arising in p53 null mammary cells are highly aneuploid, with greater than 70% of the tumor cells containing altered chromosome number and a mean chromosome number of 56. Normal mammary cells of p53 null genotype and aged less than 14 wk do not exhibit aneuploidy in primary cell culture. Significantly, the hormone progesterone, but not estrogen, increases the incidence of aneuploidy in morphologically normal p53 null mammary epithelial cells. Such cells exhibited 40% aneuploidy and a mean chromosome number of 54. The increase in aneuploidy measured in p53 null tumor cells or hormonally stimulated normal p53 null cells was not accompanied by centrosome amplification. These results suggest that normal levels of progesterone can facilitate chromosomal instability in the absence of the tumor suppressor gene, p53. The results support the emerging hypothesis based both on human epidemiological and animal model studies that progesterone markedly enhances mammary tumorigenesis.

  17. Resistance to acetaminophen-induced hepatotoxicity in glutathione S-transferase Mu 1-null mice.

    Science.gov (United States)

    Arakawa, Shingo; Maejima, Takanori; Fujimoto, Kazunori; Yamaguchi, Takashi; Yagi, Masae; Sugiura, Tomomi; Atsumi, Ryo; Yamazoe, Yasushi

    2012-01-01

    We investigated the role of glutathione S-transferases Mu 1 (GSTM1) in acetaminophen (APAP)-induced hepatotoxicity using Gstm1-null mice. A single oral administration of APAP resulted in a marked increase in plasma alanine aminotransferase accompanied by hepatocyte necrosis 24 hr after administration in wild-type mice, but its magnitude was unexpectedly attenuated in Gstm1-null mice. Therefore, it is suggested that Gstm1-null mice are resistant to APAP-induced hepatotoxicity. To examine the mechanism of this resistance in Gstm1-null mice, we measured phosphorylation of c-jun N-terminal kinase (JNK), which mediates the signal of APAP-induced hepatocyte necrosis, by Western blot analysis 2 and 6 hr after APAP administration. A marked increase in phosphorylated JNK was observed in wild-type mice, but the increase was markedly suppressed in Gstm1-null mice. Therefore, it is suggested that suppressed phosphorylation of JNK may be a main mechanism of the resistance to APAP-induced hepatotoxicity in Gstm1-null mice, although other possibilities of the mechanism cannot be eliminated. Additionally, phosphorylation of glycogen synthase kinase-3β and mitogen-activated protein kinase kinase 4, which are upstream kinases of JNK in APAP-induced hepatotoxicity, were also suppressed in Gstm1-null mice. A decrease in liver total glutathione 2 hr after APAP administration, which is an indicator for exposure to N-acetyl-p-benzoquinoneimine, the reactive metabolite of APAP, were similar in wild-type and Gstm1-null mice. In conclusion, Gstm1-null mice are considered to be resistant to APAP-induced hepatotoxicity perhaps by the suppression of JNK phosphorylation. This study indicates the novel role of GSTM1 as a factor mediating the cellular signal for APAP-induced hepatotoxicity.

  18. Mechanical Forces Exacerbate Periodontal Defects in Bsp-null Mice.

    Science.gov (United States)

    Soenjaya, Y; Foster, B L; Nociti, F H; Ao, M; Holdsworth, D W; Hunter, G K; Somerman, M J; Goldberg, H A

    2015-09-01

    Bone sialoprotein (BSP) is an acidic phosphoprotein with collagen-binding, cell attachment, and hydroxyapatite-nucleating properties. BSP expression in mineralized tissues is upregulated at onset of mineralization. Bsp-null (Bsp(-/-)) mice exhibit reductions in bone mineral density, bone turnover, osteoclast activation, and impaired bone healing. Furthermore, Bsp(-/-) mice have marked periodontal tissue breakdown, with a lack of acellular cementum leading to periodontal ligament detachment, extensive alveolar bone and tooth root resorption, and incisor malocclusion. We hypothesized that altered mechanical stress from mastication contributes to periodontal destruction observed in Bsp(-/-) mice. This hypothesis was tested by comparing Bsp(-/-) and wild-type mice fed with standard hard pellet diet or soft powder diet. Dentoalveolar tissues were analyzed using histology and micro-computed tomography. By 8 wk of age, Bsp(-/-) mice exhibited molar and incisor malocclusion regardless of diet. Bsp(-/-) mice with hard pellet diet exhibited high incidence (30%) of severe incisor malocclusion, 10% lower body weight, 3% reduced femur length, and 30% elevated serum alkaline phosphatase activity compared to wild type. Soft powder diet reduced severe incisor malocclusion incidence to 3% in Bsp(-/-) mice, supporting the hypothesis that occlusal loading contributed to the malocclusion phenotype. Furthermore, Bsp(-/-) mice in the soft powder diet group featured normal body weight, long bone length, and serum alkaline phosphatase activity, suggesting that tooth dysfunction and malnutrition contribute to growth and skeletal defects reported in Bsp(-/-) mice. Bsp(-/-) incisors also erupt at a slower rate, which likely leads to the observed thickened dentin and enhanced mineralization of dentin and enamel toward the apical end. We propose that the decrease in eruption rate is due to a lack of acellular cementum and associated defective periodontal attachment. These data demonstrate the

  19. Serological analysis of cell surface antigens of null cell acute lymphocytic leukemia by mouse monoclonal antibodies.

    OpenAIRE

    Ueda, R; Tanimoto, M; Takahashi, T.; Ogata, S; Nishida, K; Namikawa, R.; Nishizuka, Y; Ota, K.

    1982-01-01

    Nine antigens systems were defined. Two were related to HLA-A,B,C and to Ia-like antigens; the others could be grouped into three categories. (i) NL-22, NL-1: NL-22 antibody reacted with leukemia cells from 12 to 16 cases of null cell acute lymphocytic leukemia (null-ALL) but not with any other type of leukemia tested or with lymphoid cells of various origins. Among cultured cell lines tested, one (NALM-6) of three null-ALL cell lines was positive, the others were negative. Absorption analysi...

  20. Direction finding of GPS receiver interference based on the nulling weights

    Science.gov (United States)

    Wang, Jing; Amin, Moeness

    2007-04-01

    Most military applications of GPS require performing both jammer nulling and localization. While nulling can be achieved using adaptive gradient techniques applied to the input sampled data, high resolution direction of arrival estimation can precede using subspace and eigenstructure methods applied to the estimate of the covariance matrix. In this paper, we extract the jammer direction of arrival (DOA) information directly from the adaptive weights, in which case we assume interference nulling precedes interference localization. This high resolution DOA estimation approach based on available beamforming weight values leads to simplified receiver structure and allows a choice of IF or baseband processing as well as flexibility for analog, digital or mixed mode implementations.

  1. The Determining Method about the Conflict between the Null Constraints and the Set of Functional Dependencies

    Institute of Scientific and Technical Information of China (English)

    刘惟一

    1989-01-01

    In this paper the conflict between the null constraints and the set of functional dependencies is defined.Some rules for determining the conflicts and a method for processing the conflicts are obtained.

  2. Current Singularities at Quasi-Separatrix Layers and Three-Dimensional Magnetic Nulls

    CERN Document Server

    Craig, I J D

    2014-01-01

    The open problem of how singular current structures form in line-tied, three-dimensional magnetic fields is addressed. A Lagrangian magneto-frictional relaxation method is employed to model the field evolution towards the final near-singular state. Our starting point is an exact force-free solution of the governing magnetohydrodynamic (MHD) equations which is sufficiently general to allow for topological features like magnetic nulls to be inside or outside the computational domain, depending on a simple set of parameters. Quasi-separatrix layers (QSLs) are present in these structures and together with the magnetic nulls, they significantly influence the accumulation of current. It is shown that perturbations affecting the lateral boundaries of the configuration lead not only to collapse around the magnetic null, but also to significant QSL currents. Our results show that once a magnetic null is present, the developing currents are always attracted to that specific location and show a much stronger scaling wit...

  3. Vectorial analysis of polarization issues in multi-axial nulling interferometers for exoplanet detection

    NARCIS (Netherlands)

    Spronck, J.; Pereira, S.F.; Braat, J.J.M.

    2007-01-01

    We show the theoretical limitations of a multi-axial nulling interferometer with respect to longitudinal polarization. We furthermore analyze the filtering capabilities of a single-mode fiber in this case.

  4. Null test of the cosmic curvature using $H(z)$ and supernovae data

    CERN Document Server

    Cai, Rong-Gen; Yang, Tao

    2015-01-01

    We introduce a model-independent approach to the null test of the cosmic curvature which is geometrically related to the Hubble parameter $H(z)$ and luminosity distance $d_L(z)$. Combining the independent observations of $H(z)$ and $d_L(z)$, we use the model-independent smoothing technique, Gaussian processes, to reconstruct them and determine the cosmic curvature $\\Omega_K^{(0)}$ in the null test relation. The null test is totally geometrical and without assuming any cosmological model. We show that the cosmic curvature $\\Omega_K^{(0)}=0$ is consistent with current observational data sets, falling within the $1\\sigma$ limit. To demonstrate the effect on the precision of the null test, we produce a series of simulated data of the models with different $\\Omega_K^{(0)}$. Future observations in better quality can provide a greater improvement to constrain or refute the flat universe with $\\Omega_K^{(0)}=0$.

  5. Entropy of a generic null surface from its associated Virasoro algebra

    CERN Document Server

    Chakraborty, Sumanta; Padmanabhan, T

    2016-01-01

    Null surfaces act as one-way membranes, blocking information from those observers who do not cross them (e.g., in the black hole and the Rindler spacetimes) and these observers associate an entropy (and temperature) with the null surface. The black hole entropy can be computed from the central charge of an appropriately defined, local, Virasoro algebra on the horizon. We show that one can extend these ideas to a general class of null surfaces, all of which possess a Virasoro algebra and a central charge, leading to an entropy density (i.e., per unit area) which is just $(1/4)$. All the previously known results of associating entropy with horizons arise as special cases of this very general property of null surfaces demonstrated here. The implications are discussed.

  6. Null Controllability for Some Systems of Two Backward Stochastic Heat Equations with One Control Force

    Institute of Scientific and Technical Information of China (English)

    Hongheng LI; Qi L(U)

    2012-01-01

    The authors establish the null controllability for some systems coupled by two backward stochastic heat equations.The desired controllability result is obtained by means of proving a suitable observability estimate for the dual system of the controlled system.

  7. Dynamics-independent null experiment for testing time-reversal invariance

    Science.gov (United States)

    Arash, Firooz; Moravcsik, Michael J.; Goldstein, Gary R.

    1985-06-01

    It is shown that it is impossible to construct, in any reaction in atomic, nuclear, or particle physics, a null experiment that would unambiguously test the validity of time-reversal invariance independently of dynamical assumptions.

  8. Dynamics-independent null experiment for testing time-reversal invariance

    International Nuclear Information System (INIS)

    It is shown that it is impossible to construct, in any reaction in atomic, nuclear, or particle physics, a null experiment that would unambiguously test the validity of time-reversal invariance independently of dynamical assumptions

  9. Vlasov Fluid stability of a 2-D plasma with a linear magnetic field null

    International Nuclear Information System (INIS)

    Vlasov Fluid stability of a 2-dimensional plasma near an O type magnetic null is investigated. Specifically, an elongated Z-pinch is considered, and applied to Field Reversed Configurations at Los Alamos National Laboratory by making a cylindrical approximation of the compact torus. The orbits near an elliptical O type null are found to be very complicated; the orbits are large and some are stochastic. The kinetic corrections to magnetohydrodynamics (MHD) are investigated by evaluating the expectation values of the growth rates of a Vlasov Fluid dispersion functional by using a set of trial functions based on ideal MHD. The dispersion functional involves fluid parts and orbit dependent parts. The latter involves phase integral of two time correlations. The phase integral is replaced by the time integral both for the regular and for the stochastic orbits. Two trial functions are used; one has a large displacement near the null and the other away from the null

  10. Structures of magnetic null points in reconnection diffusion region: Cluster observations

    Institute of Scientific and Technical Information of China (English)

    HU YunHui; R.NAKAMURA; W.BAUMJOHANN; H.R'EME; C.M.CARR; DENG XiaoHua; ZHOU Meng; TANG RongXin; ZHAO Hui; FU Song; SU ZhiWen; WANG JingFang; YUAN ZhiGang

    2008-01-01

    Magnetic reconnection is a very important and fundamental plasma process in transferring energy from magnetic field into plasma. Previous theory, numerical simulations and observations mostly concen-trate on 2-dimensional (2D) model; however, magnetic reconnection is a 3-dimensional (3D) nonlinear process in nature. The properties of reconnection in 3D and its associated singular structure have not been resolved completely. Here we investigate the structures and characteristics of null points inside the reconnection diffusion region by introducing the discretized Poincaré index through Gauss integral and using magnetic field data with high resolution from the four satellites of Cluster mission. We esti-mate the velocity and trajectory of null points by calculating its position in different times, and compare and discuss the observations with different reconnection models with null points based on character-istics of electric current around null points.

  11. Kahel korral järjest null häält / Maarius Suviste

    Index Scriptorium Estoniae

    Suviste, Maarius, 1966-

    2005-01-01

    Kohalike omavalitsuste volikogude valimistel ei saanud ühtegi häält 233 kandidaati. Oma kandideerimise põhjusi selgitavad juba teist korda valimistel null häält saanud Viljandi tisler Kaljo Jürman, Põlvamaa mahetalunik Liisi Kutkina ja Ida-Virumaa pensionär Vaike Zaitseva. Lisatud statistilised andmed null häält saanud kandidaatide kohta maakondade ja erakondade kaupa

  12. Increased Fibronectin Deposition in Embryonic Hearts of Retinol-Binding Protein–Null Mice

    OpenAIRE

    Wendler, Christopher C.; Schmoldt, Angela; Flentke, George R.; Case, Lauren C.; Quadro, Loredana; Blaner, William S.; Lough, John; Susan M. Smith

    2003-01-01

    Precise regulation of retinoid levels is critical for normal heart development. Retinol-binding protein (RBP), an extracellular retinol transporter, is strongly secreted by cardiogenic endoderm. This study addresses whether RBP gene ablation affects heart development. Despite exhibiting an >85% decrease in serum retinol, adult RBP-null mice are viable, breed, and have normal vision when maintained on a vitamin A-sufficient diet. Comparison of RBP-null with wild-type (WT) hearts from embryos a...

  13. Power Analysis and Experimental Study of the Fiber Null Coupler with an Acousto-optic Device

    Institute of Scientific and Technical Information of China (English)

    WU Lei; ZHENG Yuan; QI Jiang; PU Hongtu; CHEN Shuqiang

    2002-01-01

    A single-mode fiber acousto-optic (AO) switch based on a null coupler at wavelength of 1.55 μm is reported.According to the coupled mode theory,power distribution of the null coupler with the acoustic-wave is formulated for general case.Excess loss of 0.1 dB and the schematic graph of throughput and coupled power are obtained experimentally.

  14. Human Cancer Growth and Therapy In NOD/SCID/IL2Rγnull (NSG) Mice

    OpenAIRE

    Shultz, Leonard D.; Goodwin, Neal; Ishikawa, Fumihiko; Hosur, Vishnu; Lyons, Bonnie L.; Greiner, Dale L.

    2014-01-01

    Since the discovery of the “nude” mouse over 40 years ago, investigators have attempted to model human tumor growth in immunodeficient mice. The field has advanced significantly over the ensuing years due to improvements in the murine recipient of human tumors. These improvements include the discovery of the scid mutation and development of targeted mutations in the recombination activating genes 1 and 2 (Rag1null, Rag2null) that severely cripple the adaptive immune response of the murine hos...

  15. Increased Oxidative Stress Impairs Adipose Tissue Function in Sphingomyelin Synthase 1 Null Mice

    OpenAIRE

    Masato Yano; Tadashi Yamamoto; Naotaka Nishimura; Tomomi Gotoh; Ken Watanabe; Kazutaka Ikeda; Yohei Garan; Ryo Taguchi; Koichi Node; Toshiro Okazaki; Yuichi Oike

    2013-01-01

    Sphingomyelin synthase 1 (SMS1) catalyzes the conversion of ceramide to sphingomyelin. Here, we found that SMS1 null mice showed lipodystrophic phenotype. Mutant mice showed up-regulation of plasma triglyceride concentrations accompanied by reduction of white adipose tissue (WAT) as they aged. Lipoprotein lipase (LPL) activity was severely reduced in mutant mice. In vivo analysis indicated that fatty acid uptake in WAT but not in liver decreased in SMS1 null compared to wild-type mice. In vit...

  16. Leucine supplementation via drinking water reduces atherosclerotic lesions in apoE null mice

    OpenAIRE

    Zhao, Yang; Dai, Xiao-Yan; Zhou, Zhou; Zhao, Ge-xin; Wang, Xian; Xu, Ming-Jiang

    2015-01-01

    Aim: Recent evidence suggests that the essential amino acid leucine may be involved in systemic cholesterol metabolism. In this study, we investigated the effects of leucine supplementation on the development of atherosclerosis in apoE null mice. Methods: ApoE null mice were fed with chow supplemented with leucine (1.5% w/v) in drinking water for 8 week. Aortic atherosclerotic lesions were examined using Oil Red O staining. Plasma lipoprotein-cholesterol levels were measured with fast protein...

  17. pyNSMC: A Python Module for Null-Space Monte Carlo Uncertainty Analysis

    Science.gov (United States)

    White, J.; Brakefield, L. K.

    2015-12-01

    The null-space monte carlo technique is a non-linear uncertainty analyses technique that is well-suited to high-dimensional inverse problems. While the technique is powerful, the existing workflow for completing null-space monte carlo is cumbersome, requiring the use of multiple commandline utilities, several sets of intermediate files and even a text editor. pyNSMC is an open-source python module that automates the workflow of null-space monte carlo uncertainty analyses. The module is fully compatible with the PEST and PEST++ software suites and leverages existing functionality of pyEMU, a python framework for linear-based uncertainty analyses. pyNSMC greatly simplifies the existing workflow for null-space monte carlo by taking advantage of object oriented design facilities in python. The core of pyNSMC is the ensemble class, which draws and stores realized random vectors and also provides functionality for exporting and visualizing results. By relieving users of the tedium associated with file handling and command line utility execution, pyNSMC instead focuses the user on the important steps and assumptions of null-space monte carlo analysis. Furthermore, pyNSMC facilitates learning through flow charts and results visualization, which are available at many points in the algorithm. The ease-of-use of the pyNSMC workflow is compared to the existing workflow for null-space monte carlo for a synthetic groundwater model with hundreds of estimable parameters.

  18. [Development of a new type soybean germplasm with null lipoxygenase isozymes].

    Science.gov (United States)

    Han, Fen-Xia; Ding, An-Lin; Sun, Jun-Ming; Li, Gui-Ying

    2005-02-01

    Soybean protein is a kind of high-quality protein composed of balanced amino acids. It contains all kinds of amino acids, especially eight amino acids necessary for human, but also contains some components that are not good for human and affect food quality, such as Lipoxygenase (Lox) and Trypsin inhibitor (Ti). Nutritional value and processing quality of soybean can be improved by means of development of new variety with null Lox and Ti. In this paper, a new type soybean germplasm with null lipoxygenase isozymes was developed by Institute of Crop Sciences, Chinese Academy of Agricultural Sciences through years of biochemical marker assistant selection for null lipoxygenase by means of isoelectric focusing-polyacrylamid gel electrophoresis (IEF-PAGE) in the hybrid progenies of "96P17" (Female parent, a null lipoxygenase 2.3 line) and "93704" (Male parent, a null lipoxygenase 1.3 line). It is the first new soybean germplasm with null Lox1.2.3 genes in our country, which will contribute to soybean breeding for high quality, soybean production and utilization. In this paper, the development process of new type soybean germplasm is described. PMID:15759868

  19. Why are flare ribbons associated with the spines of magnetic null points generically elongated?

    CERN Document Server

    Pontin, D I; Demoulin, P

    2016-01-01

    Coronal magnetic null points exist in abundance as demonstrated by extrapolations of the coronal field, and have been inferred to be important for a broad range of energetic events. These null points and their associated separatrix and spine field lines represent discontinuities of the field line mapping, making them preferential locations for reconnection. This field line mapping also exhibits strong gradients adjacent to the separatrix (fan) and spine field lines, that can be analysed using the `squashing factor', $Q$. In this paper we make a detailed analysis of the distribution of $Q$ in the presence of magnetic nulls. While $Q$ is formally infinite on both the spine and fan of the null, the decay of $Q$ away from these structures is shown in general to depend strongly on the null-point structure. For the generic case of a non-radially-symmetric null, $Q$ decays most slowly away from the spine/fan in the direction in which $|{\\bf B}|$ increases most slowly. In particular, this demonstrates that the extend...

  20. Observation of Magnetic reconnection at a 3D null point associated with a solar eruption

    CERN Document Server

    Sun, J Q; Yang, K; Cheng, X; Ding, M D

    2016-01-01

    Magnetic null has long been recognized as a special structure serving as a preferential site for magnetic reconnection (MR). However, the direct observational study of MR at null-points is largely lacking. Here, we show the observations of MR around a magnetic null associated with an eruption that resulted in an M1.7 flare and a coronal mass ejection. The GOES X- ray profile of the flare exhibited two peaks at 02:23 UT and 02:40 UT on 2012 November 8, respectively. Based on the imaging observations, we find that the first and also primary X- ray peak was originated from MR in the current sheet underneath the erupting magnetic flux rope (MFR). On the other hand, the second and also weaker X-ray peak was caused by MR around a null-point located above the pre-eruption MFR. The interaction of the null-point and the erupting MFR can be described as a two-step process. During the first step, the erupting and fast expanding MFR passed through the null-point, resulting in a significant displacement of the magnetic fi...

  1. Investigation of nulling and subpulse drifting properties of PSR J1727$-$2739

    CERN Document Server

    Wen, Z G; Yuan, J P; Yan, W M; Manchester, R N; Yuen, R; Gajjar, V

    2016-01-01

    Aims. To make a detailed study of the nulling and subpulse drifting in PSR J1727$-$2739 for investigation of its radiation properties. Methods. The observations were carried out on 20 March, 2004 using the Parkes 64-m radio telescope, with a central frequency of 1518 MHz. A total of 5568 single pulses were analysed. Results. This pulsar shows well defined nulls with lengths lasting from 6 to 281 pulses and separated by burst phases ranging from 2 to 133 pulses. We estimate a nulling fraction of around 68\\%. No emission in the average pulse profile integrated over all null pulses is detected with significance above $3\\sigma$. Most transitions from nulls to bursts are within a few pulses, whereas the transitions from bursts to nulls exhibit two patterns of decay: decrease gradually or rapidly. In the burst phase, we find that there are two distinct subpulse drift modes with vertical spacing between the drift bands of $9.7 \\pm 1.6$ and $5.2 \\pm 0.9$ pulse periods, while sometimes there is a third mode with no su...

  2. Abnormal Activation of BMP Signaling Causes Myopathy in Fbn2 Null Mice.

    Science.gov (United States)

    Sengle, Gerhard; Carlberg, Valerie; Tufa, Sara F; Charbonneau, Noe L; Smaldone, Silvia; Carlson, Eric J; Ramirez, Francesco; Keene, Douglas R; Sakai, Lynn Y

    2015-06-01

    Fibrillins are large extracellular macromolecules that polymerize to form the backbone structure of connective tissue microfibrils. Mutations in the gene for fibrillin-1 cause the Marfan syndrome, while mutations in the gene for fibrillin-2 cause Congenital Contractural Arachnodactyly. Both are autosomal dominant disorders, and both disorders affect musculoskeletal tissues. Here we show that Fbn2 null mice (on a 129/Sv background) are born with reduced muscle mass, abnormal muscle histology, and signs of activated BMP signaling in skeletal muscle. A delay in Myosin Heavy Chain 8, a perinatal myosin, was found in Fbn2 null forelimb muscle tissue, consistent with the notion that muscle defects underlie forelimb contractures in these mice. In addition, white fat accumulated in the forelimbs during the early postnatal period. Adult Fbn2 null mice are already known to demonstrate persistent muscle weakness. Here we measured elevated creatine kinase levels in adult Fbn2 null mice, indicating ongoing cycles of muscle injury. On a C57Bl/6 background, Fbn2 null mice showed severe defects in musculature, leading to neonatal death from respiratory failure. These new findings demonstrate that loss of fibrillin-2 results in phenotypes similar to those found in congenital muscular dystrophies and that FBN2 should be considered as a candidate gene for recessive congenital muscular dystrophy. Both in vivo and in vitro evidence associated muscle abnormalities and accumulation of white fat in Fbn2 null mice with abnormally activated BMP signaling. Genetic rescue of reduced muscle mass and accumulation of white fat in Fbn2 null mice was accomplished by deleting a single allele of Bmp7. In contrast to other reports that activated BMP signaling leads to muscle hypertrophy, our findings demonstrate the exquisite sensitivity of BMP signaling to the fibrillin-2 extracellular environment during early postnatal muscle development. New evidence presented here suggests that fibrillin-2 can

  3. Abnormal Activation of BMP Signaling Causes Myopathy in Fbn2 Null Mice.

    Directory of Open Access Journals (Sweden)

    Gerhard Sengle

    2015-06-01

    Full Text Available Fibrillins are large extracellular macromolecules that polymerize to form the backbone structure of connective tissue microfibrils. Mutations in the gene for fibrillin-1 cause the Marfan syndrome, while mutations in the gene for fibrillin-2 cause Congenital Contractural Arachnodactyly. Both are autosomal dominant disorders, and both disorders affect musculoskeletal tissues. Here we show that Fbn2 null mice (on a 129/Sv background are born with reduced muscle mass, abnormal muscle histology, and signs of activated BMP signaling in skeletal muscle. A delay in Myosin Heavy Chain 8, a perinatal myosin, was found in Fbn2 null forelimb muscle tissue, consistent with the notion that muscle defects underlie forelimb contractures in these mice. In addition, white fat accumulated in the forelimbs during the early postnatal period. Adult Fbn2 null mice are already known to demonstrate persistent muscle weakness. Here we measured elevated creatine kinase levels in adult Fbn2 null mice, indicating ongoing cycles of muscle injury. On a C57Bl/6 background, Fbn2 null mice showed severe defects in musculature, leading to neonatal death from respiratory failure. These new findings demonstrate that loss of fibrillin-2 results in phenotypes similar to those found in congenital muscular dystrophies and that FBN2 should be considered as a candidate gene for recessive congenital muscular dystrophy. Both in vivo and in vitro evidence associated muscle abnormalities and accumulation of white fat in Fbn2 null mice with abnormally activated BMP signaling. Genetic rescue of reduced muscle mass and accumulation of white fat in Fbn2 null mice was accomplished by deleting a single allele of Bmp7. In contrast to other reports that activated BMP signaling leads to muscle hypertrophy, our findings demonstrate the exquisite sensitivity of BMP signaling to the fibrillin-2 extracellular environment during early postnatal muscle development. New evidence presented here suggests that

  4. Üheksa nulli : null null null null null null null... / Anthony de Kowalsky

    Index Scriptorium Estoniae

    Kowalsky, Anthony de

    2008-01-01

    Lühiarvustus 18.- 20. 07. Põlvamaal Intsikurmu laululaval etendunud vabaõhulavastusele "Üheksa nulliga Eesti". Stsenaariumi on kirjutanud Kadri Pettai, Aapo Ilves, Olavi Ruitlane ja Veiko Märka. Lavastanud Reeda Toots

  5. Susceptibility to hepatocellular carcinoma associated with null genotypes of GSTM1 and GSTT1

    Institute of Scientific and Technical Information of China (English)

    Jian Chao Bian; Fu Min Shen; Li Shen; Tian Ru Wang; Xiao Hong Wang; Gong Chao Chen; Jin Bing Wang

    2000-01-01

    ALM In order to study the association between the null genotypes of GSTM1 and GSTT1 and the genetic susceptibility to hepatocellular carcinoma (HCC). METHODS The genotypes of GSTM1 and GSTT1 of 63 cases of HCC and 88 controls were detected with the multiple PCR technique. RESULTS The frequency of GSTM1 null genotype was 57.1% among the cases, and 42.0% among the controls, the difference being statistically significant (x2 = 3.35, P = 0.067),but X2 value approaching the significance level.The odds ratio was 1.84 (95% Cl=0.91 - 3.37).The frequency of GSTT1 non-null genotype was 87.3% among the cases and 62.5% among the controls, the difference being statistically significant (X2=11.42, P=0.0007274). The odds ratio was 4.13 (95% Cl = 1.64 - 10.70).According to the cross analysis, the GSTT1 nonnull genotype was more closely associated with HCC than GSTM1 null genotype, and these two factors play an approximate addlitive interaction in the occurrence of HCC. CONCLUSION The persons with GSTM1 nullgenotype and GSTT1 non-null genotype have the increased risk to HCC.

  6. A Null Space Control of Two Wheels Driven Mobile Manipulator Using Passivity Theory

    Science.gov (United States)

    Shibata, Tsuyoshi; Murakami, Toshiyuki

    This paper describes a control strategy of null space motion of a two wheels driven mobile manipulator. Recently, robot is utilized in various industrial fields and it is preferable for the robot manipulator to have multiple degrees of freedom motion. Several studies of kinematics for null space motion have been proposed. However stability analysis of null space motion is not enough. Furthermore, these approaches apply to stable systems, but they do not apply unstable systems. Then, in this research, base of manipulator equips with two wheels driven mobile robot. This robot is called two wheels driven mobile manipulator, which becomes unstable system. In the proposed approach, a control design of null space uses passivity based stabilizing. A proposed controller is decided so that closed-loop system of robot dynamics satisfies passivity. This is passivity based control. Then, control strategy is that stabilizing of the robot system applies to work space observer based approach and null space control while keeping end-effector position. The validity of the proposed approach is verified by simulations and experiments of two wheels driven mobile manipulator.

  7. 3D Alfven wave behaviour around proper and improper magnetic null points

    CERN Document Server

    Thurgood, J O

    2013-01-01

    Context: MHD waves and magnetic null points are both prevalent in many astrophysical plasmas, including the solar atmosphere. Interaction between waves and null points has been implicated as a possible mechanism for localised heating events. Aims: Here we investigate the transient behaviour of the Alfven wave about fully 3D proper and improper 3D magnetic null points. Previously, the behaviour of fast magnetoacoustic waves at null points in 3D, cold MHD was considered by Thurgood & McLaughlin (Astronomy & Astrophysics, 2012, 545, A9). Methods: We introduce an Alfven wave into the vicinity of both proper and improper null points by numerically solving the ideal, $\\beta=0$ MHD equations using the LARE3D code. A magnetic fieldline and flux-based coordinate system permits the isolation of resulting wave-modes and the analysis of their interaction. Results: We find that the Alfven wave propagates throughout the region and accumulates near the fan-plane, causing current build up. For different values of nul...

  8. The Three Discrete Nulling Timescales of PSR J1717-4054

    CERN Document Server

    Kerr, Matthew; Shannon, Ryan; Kiczynski, Mitchell; Hollow, Robert; Johnston, Simon

    2014-01-01

    PSR J1717-4054 is one of the small class of pulsars which null on intermediate (~hour) timescales. Such pulsars represent an important link between classical nullers, whose emission vanishes for a few rotations, and the intermittent pulsars which null for months and years. Using the Parkes radio telescope and the Australia Telescope Compact Array, we have studied the emission from PSR J1717-4054 over intervals from single pulses to years. We have identified and characterised nulling at three discrete timescales: the pulsar emits during "active states" separated by nulls lasting many thousands of rotations, while active states themselves are interrupted by nulls with a bimodal distribution of durations; one to two rotations, or tens of rotations. We detect no subpulse structure or flux density variations during active states, and we place stringent limits (<0.1% of the mean active flux density) on pulsed emission during inactive states. Finally, our high-quality data have also allowed us to measure for the ...

  9. Null reconstruction of orthogonal circular polarization hologram with large recording angle.

    Science.gov (United States)

    Wu, An'an; Kang, Guoguo; Zang, Jinliang; Liu, Ying; Tan, Xiaodi; Shimura, Tsutomu; Kuroda, Kazuo

    2015-04-01

    We report on the null reconstruction of polarization volume hologram recorded by orthogonal circularly polarized waves with a large cross angle. Based on the recently developed tensor theory for polarization holography, the disappearance of the reconstruction was analytically verified, where a nice agreement was found between the experimental and theoretical results. When the polarization and intensity hologram attain a balance, not only the null reconstruction but also the faithful reconstruction can be realized by the illumination of the orthogonal reference wave and original reference wave. As a consequence of the hologram recorded without paraxial approximation, the null reconstruction may lead to important applications, such as a potential enhancement in optical storage capacity for volume holograms.

  10. Investigation of the extraordinary null reconstruction phenomenon in polarization volume hologram.

    Science.gov (United States)

    Wang, J; Kang, G; Wu, A; Liu, Y; Zang, J; Li, P; Tan, X; Shimura, T; Kuroda, K

    2016-01-25

    Polarization holography is the superposition of differently polarized beams. Due to its ability to record the polarization states, some extraordinary optical phenomena were found in the polarization holography. For example, the recently reported null-reconstruction phenomenon in polarization volume hologram is odd for the conventional holography which only records the amplitude and phase. In this paper, we perform a thorough investigation of the null reconstruction of polarization hologram recorded by orthogonal circularly polarized waves. To explore the mechanism behind this phenomenon, an interferometry was built to measure the phase difference between the same polarized components within the reconstructed wave. The phase difference of π was secured in our experiment, indicating a destructive interfering effect, which nicely explains the extraordinary null reconstruction observed in the polarization hologram.

  11. Phase Retrieval with One or Two Diffraction Patterns by Alternating Projections of the Null Vector

    CERN Document Server

    Chen, Pengwen; Liu, Gi-Ren

    2015-01-01

    Two versions of alternating projection (AP), the parallel alternating projection (PAP) and the serial alternating projection (SAP), are proposed to solve phase retrieval with at most two coded diffraction patterns. The proofs of geometric convergence are given with sharp bounds on the rates of convergence in terms of a spectral gap condition. To compensate for the local nature of convergence, the null vector method is proposed for initialization and proved to produce asymptotically accurate initialization for the Gaussian case. Extensive numerical experiments are performed to show that the null vector method produces more accurate initialization than the spectral vector method and that PAP/SAP converge faster to more accurate solutions than other iterative schemes for non-convex optimization such as the Wirtinger flow. Moreover, SAP converges still faster than PAP. In practice AP and the null vector method together produce globally convergent iterates to the true object.

  12. TPF Planet Detection Testbed: demonstrating deep, stable nulling and planet detection

    Science.gov (United States)

    Martin, Stefan

    2005-01-01

    The design of a testbed being built at the Jet Propulsion Laboratory is described. Simulatiung a dual chopped Bracewell interferometer, the testbed comprises a four beam star and planet source and nulling beam combiner. Since achieving a stable null is of great concern the testbed has many control systems designed to achieve stability of alignment and optical path difference over long periods of time. Comparisons between the testbed and the flight system are drawn and key performance parameters are discussed. The interaction between designs for phaseplate systems that achromatically invert the electric field of one of each pair of the incoming beams to achieve the null and the choice of fringe tracking schemes is also discussed.

  13. Nulling interferometry: performance comparison between Antarctica and other ground-based sites

    CERN Document Server

    Absil, O; Barillot, M; Swain, M R

    2007-01-01

    Detecting the presence of circumstellar dust around nearby solar-type main sequence stars is an important pre-requisite for the design of future life-finding space missions such as ESA's Darwin or NASA's Terrestrial Planet Finder (TPF). The high Antarctic plateau may provide appropriate conditions to perform such a survey from the ground. We investigate the performance of a nulling interferometer optimised for the detection of exozodiacal discs at Dome C, on the high Antarctic plateau, and compare it to the expected performance of similar instruments at temperate sites. Based on the currently available measurements of the turbulence characteristics at Dome C, we adapt the GENIEsim software (Absil et al. 2006, A&A 448) to simulate the performance of a nulling interferometer on the high Antarctic plateau. To feed a realistic instrumental configuration into the simulator, we propose a conceptual design for ALADDIN, the Antarctic L-band Astrophysics Discovery Demonstrator for Interferometric Nulling. We assum...

  14. Quasi-local mass at the null infinity of the Vaidya spacetime

    CERN Document Server

    Chen, Po-Ning; Yau, Shing-Tung

    2016-01-01

    There are two important statements regarding the Trautman-Bondi mass [1,8,5] at null infinity: one is the positivity [7,6], and the other is the Bondi mass loss formula [1], which are both global in nature. The positivity of the quasi-local mass can potentially lead to a local description at null infinity. This is confirmed for the Vaidya spacetime in this note. We study the Wang-Yau quasi-local mass on surfaces of fixed size at the null infinity of the Vaidya spacetime. The optimal embedding equation is solved explicitly and the quasi-local mass is evaluated in terms of the mass aspect function of the Vaidya spacetime.

  15. High performance testbed for four-beam infrared interferometric nulling and exoplanet detection.

    Science.gov (United States)

    Martin, Stefan; Booth, Andrew; Liewer, Kurt; Raouf, Nasrat; Loya, Frank; Tang, Hong

    2012-06-10

    Technology development for a space-based infrared nulling interferometer capable of earthlike exoplanet detection and characterization started in earnest in the last 10 years. At the Jet Propulsion Laboratory, the planet detection testbed was developed to demonstrate the principal components of the beam combiner train for a high performance four-beam nulling interferometer. Early in the development of the testbed, the importance of "instability noise" for nulling interferometer sensitivity was recognized, and the four-beam testbed would produce this noise, allowing investigation of methods for mitigating this noise source. The testbed contains the required features of a four-beam combiner for a space interferometer and performs at a level matching that needed for the space mission. This paper describes in detail the design, functions, and controls of the testbed.

  16. Null subjects: a problem for parameter-setting models of language acquisition.

    Science.gov (United States)

    Valian, V

    1990-05-01

    Some languages, like English, require overt surface subjects, while others, like Italian and Spanish, allow "null" subjects. How does the young child determine whether or not her language allows null subjects? Modern parameter-setting theory has proposed a solution, in which the child begins acquisition with the null subject parameter set for either the English-like value or the Italian-like value. Incoming data, or the absence thereof, force a resetting of the parameter if the original value was incorrect. This paper argues that the single-value solution cannot work, no matter which value is chosen as the initial one, because of inherent limitations in the child's parser, and because of the presence of misleading input. An alternative dual-value solution is proposed, in which the child begins acquisition with both values available, and uses theory-confirmation procedures to decide which value is best supported by the available data.

  17. Shear Nulling after PSF Gaussianisation: moment-based weak lensing measurements with subpercent noise bias

    CERN Document Server

    Herbonnet, Ricardo; Kuijken, Konrad

    2016-01-01

    Current optical imaging surveys for cosmology are covering large areas of sky. To exploit the statistical power of these surveys for weak lensing measurements requires shape measurement methods with subpercent systematic errors. We introduce a new weak lensing shear measurement algorithm, Shear Nulling after PSF Gaussianisation (SNAPG), designed to avoid the noise biases that affect most other methods. SNAPG operates on images that have been convolved with a kernel that renders the Point Spread Function (PSF) a circular Gaussian, and uses weighted second moments of the sources. The response of such second moments to a shear of the pre-seeing galaxy image can be predicted analytically, allowing us to construct a shear nulling scheme that finds the shear parameters for which the observed galaxies are consistent with an unsheared, isotropically oriented population of sources. The inverse of this nulling shear is then an estimate of the gravitational lensing shear. We identify the uncertainty of the estimated cen...

  18. Forge-Hardened TiZr Null-Matrix Alloy for Neutron Scattering under Extreme Conditions

    Directory of Open Access Journals (Sweden)

    Takuo Okuchi

    2015-12-01

    Full Text Available For neutron scattering research that is performed under extreme conditions, such as high static pressures, high-strength metals that are transparent to the neutron beam are required. The diffraction of the neutron beam by the metal, which follows Bragg’s law, can be completely removed by alloying two metallic elements that have coherent scattering lengths with opposite signs. An alloy of Ti and Zr, which is known as a TiZr null-matrix alloy, is an ideal combination for such purposes. In this study, we increased the hardness of a TiZr null-matrix alloy via extensive mechanical deformation at high temperatures. We successfully used the resulting product in a high-pressure cell designed for high-static-pressure neutron scattering. This hardened TiZr null-matrix alloy may play a complementary role to normal TiZr alloy in future neutron scattering research under extreme conditions.

  19. A New Method of Identifying 3D Null Points in Solar Vector Magnetic Fields

    Institute of Scientific and Technical Information of China (English)

    Hui Zhao; Jing-Xiu Wang; Jun Zhang; Chi-Jie Xiao

    2005-01-01

    Employing the Poincaré index of isolated null-points in a vector field,we worked out a mathematical method of searching for 3D null-points in coronal magnetic fields. After introducing the relevant differential topology, we test the method by using the analytical model of Brown & Priest. The location of nullpoint identified by our method coincides precisely with the analytical solution.Finally we apply the method to the 3D coronal magnetic fields reconstructed from an observed MDI magnetogram of a super-active region (NOAA 10488). We find that the 3D null-point seems to be a key element in the magnetic topology associated with flare occurrence.

  20. Observation of the lower hybrid waves near the three-dimensional null pair

    Institute of Scientific and Technical Information of China (English)

    ZHOU Meng; DENG XiaoHua; FU Song; TANG RongXin; HU YunHui; LI ShiYou; A. VAIVADS; M. ANDRE; LIN Xi; LIN MingHui; ZHOU XiaoMin

    2009-01-01

    Magnetic reconnection is a fundamental process in plasma, which is thought to play important roles both in laboratory and natural plasmas through affecting magnetic topology, heating and accelerating particles. During an event on Oct. 1st, 2001, the Cluster tetrahedron circled around the magnetic re-connection region several times, and Xiao et al. First identified the null pair and found that the spectrum of the null-point oscillation shows the maximum power near the lower-hybrid frequency. In this paper we report the observation of electromagnetic and electrostatic wave enhancements near lower hybrid frequency associated with the reconnection process near the null pair. The lower hybrid waves (LHWs) with quasi-perpendicular propagation were identified and also confirmed by the power law of the spectrum of electric and magnetic fields.

  1. Observation of the lower hybrid waves near the three-dimensional null pair

    Institute of Scientific and Technical Information of China (English)

    A.; VAIVADS; M.; ANDRE

    2009-01-01

    Magnetic reconnection is a fundamental process in plasma,which is thought to play important roles both in laboratory and natural plasmas through affecting magnetic topology,heating and accelerating particles. During an event on Oct. 1st,2001,the Cluster tetrahedron circled around the magnetic reconnection region several times,and Xiao et al. first identified the null pair and found that the spectrum of the null-point oscillation shows the maximum power near the lower-hybrid frequency. In this paper we report the observation of electromagnetic and electrostatic wave enhancements near lower hybrid frequency associated with the reconnection process near the null pair. The lower hybrid waves(LHWs) with quasi-perpendicular propagation were identified and also confirmed by the power law of the spectrum of electric and magnetic fields.

  2. Energetics of kinetic reconnection in a three-dimensional null points cluster

    CERN Document Server

    Olshevsky, Vyacheslav; Markidis, Stefano

    2015-01-01

    We performed three-dimensional Particle-in-Cell simulations of magnetic reconnection with multiple magnetic null points. Magnetic field energy conversion into kinetic energy was about five times higher than in traditional Harris sheet configuration. More than 85% of initial magnetic field energy was transferred to particle energy during 25 reversed ion cyclofrequencies. Magnetic reconnection in the cluster of null points evolved in three phases. During the first phase, ion beams were excited, that then gave part of their energy back to magnetic field in the second phase. In the third phase, magnetic reconnection occurs in many small patches around the current channels formed along the stripes of low magnetic field. Magnetic reconnection in null points presents essentially three-dimensional features, with no two dimensional symmetries or current sheets.

  3. On geometry of congruences of null strings in 4-dimensional complex and real pseudo-Riemannian spaces

    CERN Document Server

    Chudecki, Adam

    2016-01-01

    4-dimensional spaces equipped with 2-dimensional (complex holomorphic or real smooth) completely integrable distributions are considered. The integral manifolds of such distributions are totally null and totally geodesics 2-dimensional surfaces which are called the null strings. Properties of congruences (foliations) of such 2-surfaces are studied. Relation between properties of congruences of null strings and Petrov-Penrose type of SD Weyl spinor and algebraic types of traceless Ricci tensor is analyzed.

  4. Integration of Frequency Domain Wideband Antenna Nulling and Wavenumber Domain Image Formation for Multi-Channel SAR

    OpenAIRE

    Bucciarelli, M.; D. Pastina; Cristallini, D.; M. Sedehi; Lombardo, P.

    2016-01-01

    A Multichannel Synthetic Aperture Radar (M-SAR) exploiting an antenna nulling based Electronic Counter-Counter Measures (ECCM) technique shall be able to cancel the effects of noise-like interferences over the collected SAR data. Since SAR systems often work with wide bandwidths to provide high resolution images, ECCM technique must account for the presence of wideband interference signal. In this paper we consider a wideband antenna nulling technique based on space-frequency adaptive nulling...

  5. Formation of Nulls in Vector Beam Patterns of Monopulse Arrays of Rectangular Waveguides by Correcting Currents in Some Array Elements

    Science.gov (United States)

    Manuilov, B. D.; Bashly, P. N.; Klimukhin, D. V.

    2003-12-01

    In this paper, we consider a method for null synthesis in the vector sum and difference beam patterns of a monopulse array of rectangular waveguides. The synthesis of nulls is reached due to variation of complex currents in some elements. The proposed method eliminates shifts of the primary maximum and the nulls of the sum and difference beam patterns, respectively, of a monopulse array. Numerical studies confirming the efficiency of the proposed method are described.

  6. Analysis of null sets (zero cat ch) made by the Mexican tuna pur se seine fleet (20002013)

    OpenAIRE

    Michel J Dreyfus-León; Adán Mejía-Trejo; Juan Carlos Villaseñor-Derbez

    2015-01-01

    The world tuna fishing fleet is dominated by purse seine boats . Purse seine sets are sometimes unsuccessful in capturing fish ; these unsuccessful attempts are known as null sets. Null sets h ave been widely documented and the numbers indicate that they h appen in large proportions. In Mexico, the tuna fishery represents the second most important fishery by volume and value. The frequency of oc currence of null sets during the period 20002013 wa s analyzed to identify the r egions, perio...

  7. Balance recovery control for biped robot based on reaction null space method

    Institute of Scientific and Technical Information of China (English)

    Baoping WANG; Renxi HU; Jinming ZHANG; Chuangfeng HUAI

    2009-01-01

    A biped walking robot should be able to keep balance even in the presence of disturbing forces.This paper presents a step strategy concept of biped walking robot that is stabilized by using reaction null space method.The called "step strategy" can be modeled by means of the reaction null space method that introduced earlier to tackle dynamic interaction problems of free-floating robots,or moving base robots in general.6-DOF biped robot model simulations are used to confirm the validity.

  8. Causality and entropic arguments pointing to a null Big Bag hypersurface

    Energy Technology Data Exchange (ETDEWEB)

    Minguzzi, E, E-mail: ettore.minguzzi@unifi.it [Dipartimento di Matematica Applicata, Universita degli Studi di Firenze, Via S. Marta 3, I-50139 Firenze (Italy)

    2011-09-22

    I propose a causality argument in order to solve the homogeneity (horizon) problem and the entropy problem of cosmology. The solution is based on the replacement of the spacelike Big Bang boundary with a null boundary behind which stays a chronology violating region. This solution requires a tilting of the light cones near the null boundary and thus it is based more on the behavior of the light cones and hence on causality than on the behavior of the scale factor (expansion). The connection of this picture with Augustine of Hippo famous philosophical discussion on time and creation is mentioned.

  9. From GLC to double-null coordinates and illustration with static black holes

    CERN Document Server

    Nugier, Fabien

    2016-01-01

    We present a system of coordinates deriving directly from the so-called Geodesic Light-Cone (GLC) coordinates and made of two null scalars intersecting on a 2-dimensional sphere parameterized by two constant angles along geodesics. These coordinates are shown to be equivalent to the well-known double-null coordinates. As GLC, they present interesting properties for cosmology and astrophysics. We discuss this latter topic for static black holes, showing simple descriptions for the metric or particles and photons trajectories. We also briefly comment on the time of flight of ultra-relativistic particles.

  10. Propagation of errors from a null balance terahertz reflectometer to a sample's relative water content

    OpenAIRE

    Hadjiloucas, Sillas; Walker, Gillian Claire; Bowen, John Wesley; Zafiropoulos, Apostolos

    2009-01-01

    The THz water content index of a sample is defined and advantages in using such metric in estimating a sample's relative water content are discussed. The errors from reflectance measurements performed at two different THz frequencies using a quasi-optical null-balance reflectometer are propagated to the errors in estimating the sample water content index.

  11. Cell therapy of congenital corneal diseases with umbilical mesenchymal stem cells: lumican null mice.

    Directory of Open Access Journals (Sweden)

    Hongshan Liu

    Full Text Available BACKGROUND: Keratoplasty is the most effective treatment for corneal blindness, but suboptimal medical conditions and lack of qualified medical personnel and donated cornea often prevent the performance of corneal transplantation in developing countries. Our study aims to develop alternative treatment regimens for congenital corneal diseases of genetic mutation. METHODOLOGY/PRINCIPAL FINDINGS: Human mesenchymal stem cells isolated from neonatal umbilical cords were transplanted to treat thin and cloudy corneas of lumican null mice. Transplantation of umbilical mesenchymal stem cells significantly improved corneal transparency and increased stromal thickness of lumican null mice, but human umbilical hematopoietic stem cells failed to do the same. Further studies revealed that collagen lamellae were re-organized in corneal stroma of lumican null mice after mesenchymal stem cell transplantation. Transplanted umbilical mesenchymal stem cells survived in the mouse corneal stroma for more than 3 months with little or no graft rejection. In addition, these cells assumed a keratocyte phenotype, e.g., dendritic morphology, quiescence, expression of keratocyte unique keratan sulfated keratocan and lumican, and CD34. Moreover, umbilical mesenchymal stem cell transplantation improved host keratocyte functions, which was verified by enhanced expression of keratocan and aldehyde dehydrogenase class 3A1 in lumican null mice. CONCLUSIONS/SIGNIFICANCE: Umbilical mesenchymal stem cell transplantation is a promising treatment for congenital corneal diseases involving keratocyte dysfunction. Unlike donated corneas, umbilical mesenchymal stem cells are easily isolated, expanded, stored, and can be quickly recovered from liquid nitrogen when a patient is in urgent need.

  12. Interaction between filaggrin null mutations and tobacco smoking in relation to asthma

    DEFF Research Database (Denmark)

    Husemoen, Lise Lotte N; Thuesen, Betina Heinsbæk; Hersoug, Lars-Georg;

    2012-01-01

    between FLG deficiency and environmental exposures play a role in asthma development. OBJECTIVE: We sought to investigate possible interactions between FLG null mutations and tobacco smoking in relation to asthma. METHODS: A total of 3471 adults from a general population sample participated in a health...

  13. Magnetohydrodynamics dynamical relaxation of coronal magnetic fields. IV. 3D tilted nulls

    CERN Document Server

    Fuentes-Fernandez, Jorge

    2013-01-01

    In this paper we study current accumulations in 3D "tilted" nulls formed by a folding of the spine and fan. A non-zero component of current parallel to the fan is required such that the null's fan plane and spine are not perpendicular. Our aims are to provide valid magnetohydrostatic equilibria and to describe the current accumulations in various cases involving finite plasma pressure.To create our equilibrium current structures we use a full, non-resistive, magnetohydrodynamic (MHD) code so that no reconnection is allowed. A series of experiments are performed in which a perturbed 3D tilted null relaxes towards an equilibrium via real, viscous damping forces. Changes to the initial plasma pressure and to magnetic parameters are investigated systematically.An initially tilted fan is associated with a non-zero Lorentz force that drives the fan and spine to collapse towards each other, in a similar manner to the collapse of a 2D X-point. In the final equilibrium state for an initially radial null with only the ...

  14. Experimental progress in deep and broadband infrared nulling for TPF-I

    Science.gov (United States)

    Wallace, J. Kent; Bartos, Randall; Gappinger, Robert; Loya, Frank; Moser, Steve; Negron, John

    2005-01-01

    Our activities are focused upon the experimental demonstration of deep nulling in the mid-IR over a wide bandpass. Specifically, our near-term goal is demonstrating a contrast of 10^-6 at 10 um with a 25% spectral bandwidth.

  15. Path Length Control in a Nulling Coronagraph with a MEMS Deformable Mirror and a Calibration Interferometer

    Science.gov (United States)

    Rao, Shanti R.; Wallacea, J. Kent; Samuele, Rocco; Chakrabarti, Supriya; Cook, Timothy; Hicks, Brian; Jung, Paul; Lane, Benjamin; Levine, B. Martin; Mendillo, Chris; Schmidtlin, Edouard; Shao, Mike; Stewart, Jason B.

    2008-01-01

    We report progress on a nulling coronagraph intended for direct imaging of extrasolar planets. White light is suppressed in an interferometer, and phase errors are measured by a second interferometer. A 1020-pixel MEMS deformable mirror in the first interferometer adjusts the path length across the pupil. A feedback control system reduces deflections of the deformable mirror to order of 1 nm rms.

  16. Topology optimization of piezo modal transducers with null-polarity phases

    DEFF Research Database (Denmark)

    Donoso, A.; Sigmund, O.

    2016-01-01

    Piezo modal transducers in 2d can be designed theoretically by tailoring polarity of the surface electrodes. However, it is also necessary to include null-polarity phases of known width separating areas of opposite polarity in the manufacturing process in order to avoid short-circuiting. Otherwise...

  17. The Acquisition of Null and Overt Pronominals in Japanese by English Speakers.

    Science.gov (United States)

    Kanno, Kazue

    1997-01-01

    Examines the role of Universal Grammar in the second-language acquisition of Japanese by English speakers. The study focuses on the acquisition of the principle that prevents overt pronouns from having quantified noun phrases as antecedents in languages (such as Japanese) that have null pronouns. (16 references) (Author/CK)

  18. Determination of the true null electrode spacing of an extrapolation chamber for X-ray dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Figueiredo, M.T.T.; Bastos, F.M.; Silva, T.A. da, E-mail: mttf@cdtn.br, E-mail: fmb@cdtn.br, E-mail: silvata@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil). Pos-Graduacao em Ciencia e Tecnologia da Radiacao, Minerais e Materiais

    2015-07-01

    An accurate determination of the actual null distance is critical for the establishment of primary measurement method for absorbed dose in tissue, since the concept of the true null electrode spacing is used to define the sensitive volume of an extrapolation chamber. In this paper, a critical analysis of two methodologies for determining the true null electrode spacing of an extrapolation chamber was done. Firstly, the ionization current as a function of electrode spacing was measured in ISO 4037 low energy X-ray beams. In the second procedure, a LC Bridge was used to measure the capacitance between the electrodes of a 23392 Böhm model PTW ionization chamber and a reliable relationship between capacitance and relative distance was established. Results showed that the true null spacing values varied from 0.0015 to 0.38 mm. Since capacitance meters with high resolution are not always available in calibration laboratories, the second method showed values with large uncertainties. The first method proved to be highly sensitive to the quality of the X-ray beams used. (author)

  19. Stable deep nulling in polychromatic unpolarized light with multiaxial beam combination.

    Science.gov (United States)

    Buisset, Christophe; Rejeaunier, Xavier; Rabbia, Yves; Barillot, Marc

    2007-11-10

    In the context of the space-based nulling mission ESA-Darwin, Thales Alenia Space has developed a nulling breadboard for the European Space Agency (ESA): the multiaperture imaging interferometer (MAII) to demonstrate deep and stable nulling and to investigate various subsystems of the ESA-Darwin interferometer. Recently, we have extended our investigations to the multiaxial beam combination. This combination scheme presents many advantages: simplicity, compactness, and a high coupling efficiency for a three-beam combination. The near-infrared (lambda approximately 1.55 microm) MAII breadboard has been upgraded to the multiaxial beam combination. Polarization and stability issues have been thoroughly investigated. We report on the recent results we have obtained with the multiaxial configuration of MAII in unpolarized light with a relative spectral bandwidth of 5%: nulling ratios of mean value N=1.7 x 10(-5), stable over 1 h with a standard deviation sigma( N )=5.7 x 10(-7). These results indicate that the multiaxial beam combination has the potential to meet Darwin requirements. PMID:17994130

  20. Electric Current Filamentation at a Non-potential Magnetic Null-point Due to Pressure Perturbation

    Science.gov (United States)

    Jelínek, P.; Karlický, M.; Murawski, K.

    2015-10-01

    An increase of electric current densities due to filamentation is an important process in any flare. We show that the pressure perturbation, followed by an entropy wave, triggers such a filamentation in the non-potential magnetic null-point. In the two-dimensional (2D), non-potential magnetic null-point, we generate the entropy wave by a negative or positive pressure pulse that is launched initially. Then, we study its evolution under the influence of the gravity field. We solve the full set of 2D time dependent, ideal magnetohydrodynamic equations numerically, making use of the FLASH code. The negative pulse leads to an entropy wave with a plasma density greater than in the ambient atmosphere and thus this wave falls down in the solar atmosphere, attracted by the gravity force. In the case of the positive pressure pulse, the plasma becomes evacuated and the entropy wave propagates upward. However, in both cases, owing to the Rayleigh-Taylor instability, the electric current in a non-potential magnetic null-point is rapidly filamented and at some locations the electric current density is strongly enhanced in comparison to its initial value. Using numerical simulations, we find that entropy waves initiated either by positive or negative pulses result in an increase of electric current densities close to the magnetic null-point and thus the energy accumulated here can be released as nanoflares or even flares.

  1. ELECTRIC CURRENT FILAMENTATION AT A NON-POTENTIAL MAGNETIC NULL-POINT DUE TO PRESSURE PERTURBATION

    Energy Technology Data Exchange (ETDEWEB)

    Jelínek, P. [University of South Bohemia, Faculty of Science, Institute of Physics and Biophysics, Branišovská 10, CZ-37005 České Budějovice (Czech Republic); Karlický, M. [Academy of Sciences of the Czech Republic, v. v. i., Astronomical Institute, Fričova 258, CZ-25165 Ondřejov (Czech Republic); Murawski, K., E-mail: pjelinek@prf.jcu.cz [Maria Curie-Skłodowska University, Institute of Physics, Group of Astrophysics, Radziszewskiego 10, PL-20031 Lublin (Poland)

    2015-10-20

    An increase of electric current densities due to filamentation is an important process in any flare. We show that the pressure perturbation, followed by an entropy wave, triggers such a filamentation in the non-potential magnetic null-point. In the two-dimensional (2D), non-potential magnetic null-point, we generate the entropy wave by a negative or positive pressure pulse that is launched initially. Then, we study its evolution under the influence of the gravity field. We solve the full set of 2D time dependent, ideal magnetohydrodynamic equations numerically, making use of the FLASH code. The negative pulse leads to an entropy wave with a plasma density greater than in the ambient atmosphere and thus this wave falls down in the solar atmosphere, attracted by the gravity force. In the case of the positive pressure pulse, the plasma becomes evacuated and the entropy wave propagates upward. However, in both cases, owing to the Rayleigh–Taylor instability, the electric current in a non-potential magnetic null-point is rapidly filamented and at some locations the electric current density is strongly enhanced in comparison to its initial value. Using numerical simulations, we find that entropy waves initiated either by positive or negative pulses result in an increase of electric current densities close to the magnetic null-point and thus the energy accumulated here can be released as nanoflares or even flares.

  2. The frequency of GSTT1 null genotype in Turkish population and lung cancer risk

    Directory of Open Access Journals (Sweden)

    Demir A

    2005-01-01

    Full Text Available BACKGROUND : Previous studies have suggested that Glutathione S -transferase (GST genotypes may play a role in determining susceptibility to lung cancer, though the data are often conflicting. In different ethnic groups variations in null allele frequency has been observed. AIMS: We aimed to evaluate whether genetic polymorphisms of Glutathione S -transferase theta (GSTT1 influence individual susceptibility to lung cancer in Turkish population. We tried to clarify the frequencies of GSTM1 gene polymorphisms in a Turkish population. METHODS: DNA samples, extracted from the whole blood were amplified using polymerase chain reaction (PCR method in all of the 68 cases, composed of 31 previously diagnosed lung cancer and 37 healthy controls. RESULTS: The prevalence of GSTT1 null genotype in the lung cancer patients was 29%, compared to 11% in control group. GSTT1 null genotype was found to be higher in cancer group compared to the control group, although it was not statistically significant (OR = 3.37, 95% CI = 0.92-12.32, P = 0.06. There was also no significant relation in GSTT1 genotypes among histopathology types of lung cancers. The frequency of GSTT1 was found to be 25.4% ( n = 952 when the studies of Turkish population were reviewed. CONCLUSION: It can be concluded that carrying the GSTT1 null genotype may be accepted as a weak risk factor for the susceptibility to lung cancer.

  3. Nonlinear Alfv\\'en wave dynamics at a 2D magnetic null point: ponderomotive force

    CERN Document Server

    Thurgood, J O

    2013-01-01

    Context : In the linear, {\\beta}=0 MHD regime, the transient properties of MHD waves in the vicinity of 2D null points are well known. The waves are decoupled and accumulate at predictable parts of the magnetic topology: fast waves accumulate at the null point; whereas Alfv\\'en waves cannot cross the separatricies. However, in nonlinear MHD mode conversion can occur at regions of inhomogeneous Alfv\\'en speed, suggesting that the decoupled nature of waves may not extend to the nonlinear regime. Aims: We investigate the behaviour of low-amplitude Alfv\\'en waves about a 2D magnetic null point in nonlinear, {\\beta}= 0 MHD. Methods: We numerically simulate the introduction of low-amplitude Alfv\\'en waves into the vicinity of a magnetic null point using the nonlinear LARE2D code. Results: Unlike in the linear regime, we find that the Alfv\\'en wave sustains cospatial daughter disturbances, manifest in the transverse and longitudinal fluid velocity, owing to the action of nonlinear magnetic pressure gradients (viz. t...

  4. Determination of the true null electrode spacing of an extrapolation chamber for X-ray dosimetry

    International Nuclear Information System (INIS)

    An accurate determination of the actual null distance is critical for the establishment of primary measurement method for absorbed dose in tissue, since the concept of the true null electrode spacing is used to define the sensitive volume of an extrapolation chamber. In this paper, a critical analysis of two methodologies for determining the true null electrode spacing of an extrapolation chamber was done. Firstly, the ionization current as a function of electrode spacing was measured in ISO 4037 low energy X-ray beams. In the second procedure, a LC Bridge was used to measure the capacitance between the electrodes of a 23392 Böhm model PTW ionization chamber and a reliable relationship between capacitance and relative distance was established. Results showed that the true null spacing values varied from 0.0015 to 0.38 mm. Since capacitance meters with high resolution are not always available in calibration laboratories, the second method showed values with large uncertainties. The first method proved to be highly sensitive to the quality of the X-ray beams used. (author)

  5. Active optics null test system based on a liquid crystal programmable spatial light modulator.

    Science.gov (United States)

    Ares, Miguel; Royo, Santiago; Sergievskaya, Irina; Riu, Jordi

    2010-11-10

    We present an active null test system adapted to test lenses and wavefronts with complex shapes and strong local deformations. This system provides greater flexibility than conventional static null tests that match only a precisely positioned, individual wavefront. The system is based on a cylindrical Shack-Hartmann wavefront sensor, a commercial liquid crystal programmable phase modulator (PPM), which acts as the active null corrector, enabling the compensation of large strokes with high fidelity in a single iteration, and a spatial filter to remove unmodulated light when steep phase changes are compensated. We have evaluated the PPM's phase response at 635 nm and checked its performance by measuring its capability to generate different amounts of defocus aberration, finding root mean squared errors below λ/18 for spherical wavefronts with peak-to-valley heights of up to 78.7λ, which stands as the limit from which diffractive artifacts created by the PPM have been found to be critical under no spatial filtering. Results of a null test for a complex lens (an ophthalmic customized progressive addition lens) are presented and discussed. PMID:21068848

  6. Reduced infarct size in neuroglobin-null mice after experimental stroke in vivo

    Directory of Open Access Journals (Sweden)

    Raida Zindy

    2012-08-01

    Full Text Available Abstract Background Neuroglobin is considered to be a novel important pharmacological target in combating stroke and neurodegenerative disorders, although the mechanism by which this protection is accomplished remains an enigma. We hypothesized that if neuroglobin is directly involved in neuroprotection, then permanent cerebral ischemia would lead to larger infarct volumes in neuroglobin-null mice than in wild-type mice. Methods Using neuroglobin-null mice, we estimated the infarct volume 24 hours after permanent middle cerebral artery occlusion using Cavalieri’s Principle, and compared the infarct volume in neuroglobin-null and wild-type mice. Neuroglobin antibody staining was used to examine neuroglobin expression in the infarct area of wild-type mice. Results Infarct volumes 24 hours after permanent middle cerebral artery occlusion were significantly smaller in neuroglobin-null mice than in wild-types (p  Conclusions Neuroglobin-deficiency resulted in reduced tissue infarction, suggesting that, at least at endogenous expression levels, neuroglobin in itself is non-protective against ischemic injury.

  7. Development of IR single mode optical fibers for DARWIN-nulling interferometry

    NARCIS (Netherlands)

    Chakkalakkal Abdulla, S.M.; Cheng, L.K.; Bosch, B. van den; Dijkhuizen, N.; Nieuwland, R.A.; Gielesen, W.L.M.; Lucas, J.; Boussard-Plédel, C.; Conseil, C.; Bureau, B.; Carmo, J.P. do

    2014-01-01

    The DARWIN mission aims to detect weak infra-red emission lines from distant orbiting earth-like planets using nulling interferometry. This requires filtering of wavefront errors using single mode waveguides operating at a wavelength range of 6.5-20 μm. This article describes the optical design of t

  8. Active optics null test system based on a liquid crystal programmable spatial light modulator

    Energy Technology Data Exchange (ETDEWEB)

    Ares, Miguel; Royo, Santiago; Sergievskaya, Irina; Riu, Jordi

    2010-11-10

    We present an active null test system adapted to test lenses and wavefronts with complex shapes and strong local deformations. This system provides greater flexibility than conventional static null tests that match only a precisely positioned, individual wavefront. The system is based on a cylindrical Shack-Hartmann wavefront sensor, a commercial liquid crystal programmable phase modulator (PPM), which acts as the active null corrector, enabling the compensation of large strokes with high fidelity in a single iteration, and a spatial filter to remove unmodulated light when steep phase changes are compensated. We have evaluated the PPM's phase response at 635 nm and checked its performance by measuring its capability to generate different amounts of defocus aberration, finding root mean squared errors below {lambda}/18 for spherical wavefronts with peak-to-valley heights of up to 78.7{lambda}, which stands as the limit from which diffractive artifacts created by the PPM have been found to be critical under no spatial filtering. Results of a null test for a complex lens (an ophthalmic customized progressive addition lens) are presented and discussed.

  9. Global Null Controllability of the 1-Dimensional Nonlinear Slow Diffusion Equation

    Institute of Scientific and Technical Information of China (English)

    Jean-Michel CORON; Jesús Ildefonso D(I)AZ; Abdelmalek DRICI; Tommaso MINGAZZINI

    2013-01-01

    The authors prove the global null controllability for the 1-dimensional nonlinear slow diffusion equation by using both a boundary and an internal control.They assume that the internal control is only time dependent.The proof relies on the return method in combination with some local controllability results for nondegenerate equations and rescaling techniques.

  10. Dmp1 Null Mice Develop a Unique Osteoarthritis-like Phenotype

    Science.gov (United States)

    Zhang, Qi; Lin, Shuxian; Liu, Ying; Yuan, Baozhi; Harris, Steph E; Feng, Jian Q.

    2016-01-01

    Patients with hypophosphatemia rickets (including DMP1 mutations) develop severe osteoarthritis (OA), although the mechanism is largely unknown. In this study, we first identified the expression of DMP1 in hypertrophic chondrocytes using immunohistochemistry (IHC) and X-gal analysis of Dmp1-knockout-lacZ-knockin heterozygous mice. Next, we characterized the OA-like phenotype in Dmp1 null mice from 7-week-old to one-year-old using multiple techniques, including X-ray, micro-CT, H&E staining, Goldner staining, scanning electronic microscopy, IHC assays, etc. We found a classical OA-like phenotype in Dmp1 null mice such as articular cartilage degradation, osteophyte formation, and subchondral osteosclerosis. These Dmp1 null mice also developed unique pathological changes, including a biphasic change in their articular cartilage from the initial expansion of hypertrophic chondrocytes at the age of 1-month to a quick diminished articular cartilage layer at the age of 3-months. Further, these null mice displayed severe enlarged knees and poorly formed bone with an expanded osteoid area. To address whether DMP1 plays a direct role in the articular cartilage, we deleted Dmp1 specifically in hypertrophic chondrocytes by crossing the Dmp1-loxP mice with Col X Cre mice. Interestingly, these conditional knockout mice didn't display notable defects in either the articular cartilage or the growth plate. Because of the hypophosphatemia remained in the entire life span of the Dmp1 null mice, we also investigated whether a high phosphate diet would improve the OA-like phenotype. A 8-week treatment of a high phosphate diet significantly rescued the OA-like defect in Dmp1 null mice, supporting the critical role of phosphate homeostasis in maintaining the healthy joint morphology and function. Taken together, this study demonstrates a unique OA-like phenotype in Dmp1 null mice, but a lack of the direct impact of DMP1 on chondrogenesis. Instead, the regulation of phosphate homeostasis

  11. Population estimators or progeny tests: what is the best method to assess null allele frequencies at SSR loci?

    NARCIS (Netherlands)

    Oddou-Muratorio, S.; Vendramin, G.G.; Buiteveld, J.; Fady, B.

    2009-01-01

    Nuclear SSRs are notorious for having relatively high frequencies of null alleles, i.e. alleles that fail to amplify and are thus recessive and undetected in heterozygotes. In this paper, we compare two kinds of approaches for estimating null allele frequencies at seven nuclear microsatellite marker

  12. Isolation of two independent allyl alcohol resistant Adh-1 null mutants following selection of pollen and seeds.

    NARCIS (Netherlands)

    Wisman, E.; Ramanna, M.S.; Zabel, P.

    1993-01-01

    The Adh-1 null mutant (B15-1-8) isolated previously was used to establish conditions that allow the selection of ADH-deficient pollen grains and seeds of tomato. New Adh-1 null mutants were then selected among the progenies derived from crosses between the genetically unstable tomato lines Yvms, Sul

  13. Effects of Lipoxygenase Null Genes of Soybean in Controlling Beany-flavor of Soymilk and Soyflour

    Institute of Scientific and Technical Information of China (English)

    MA Hao; GUAN Chun-yun; HE Xiao-ling; ZHANG Guo-zheng; DIN An-lin

    2002-01-01

    The flavor of the soymilk and soyflour obtained from the lipoxygenase mutant isolines was concentrated by simultaneous distillation and extraction (SDE), and its constituents were identified by gas chromatography (GC) and gas chromatography-mass spectrometry. Results showed that the same 24 flavor constituents were isolated in both soymilk and soyflour, and most of them were aldehydes and alcohols. Lox2 was most responsible for the production of the volatile and beany-flavor components, and Lox1 less responsible.Lox3 was least responsible and can reduce the yield of hexanal. Either Lx1 or Lx2 could significantly reduce the volatile and beany-flavor, and Lx3 could significantly increase the yield of hexanal. Primary and secondary interactions existed among the null mutant genes, and the major effects and interactions could be affected by processing conditions. The isoline with triple lipoxygenase null genes yielded the least volatile and beany-flavor components, and the isoline without the lipoxygenase gene Lx3 produced the greatest amount of the volatile and beany-flavor components. The amounts of volatile and beany-flavor components produced by the other isolines were between that of the isoline with triple lipoxygenase null genes and the isoline without lipoxygenase gene Lx3. According to the correlation analysis, the hexanal amount could be used as an index in evaluating the importance of lipoxygenase isozymes in the yield of beany-flavor compounds, and the effects of the different types of lipoxygenase null mutants in controlling beany-flavor compounds. The cultivars with triple lipoxygenase null genes will be a quality raw material for soyfood processing.

  14. Inhibition of urethane-induced genotoxicity and cell proliferation in CYP2E1-null mice

    Energy Technology Data Exchange (ETDEWEB)

    Hoffler, Undi [Department of Pharmacology, Meharry Medical College, Nashville, TN (United States); Laboratory of Pharmacology and Chemistry, National Institute of Environmental Health Sciences, National Institute of Health, Research Triangle Park, NC 27709 (United States); Dixon, Darlene [Laboratory of Experimental Pathology, National Institute of Environmental Health Sciences, National Institute of Health, Research Triangle Park, NC 27709 (United States); Peddada, Shyamal [Biostatics Branch, National Institute of Environmental Health Sciences, National Institute of Health, Research Triangle Park, NC 27709 (United States); Ghanayem, Burhan I. [Department of Pharmacology, Meharry Medical College, Nashville, TN (United States) and Laboratory of Pharmacology and Chemistry, National Institute of Environmental Health Sciences, National Institute of Health, Research Triangle Park, NC 27709 (United States)]. E-mail: ghanayem@niehs.nih.gov

    2005-05-02

    Urethane is a multi-site animal carcinogen and was classified as 'reasonably anticipated to be a human carcinogen.' Urethane is a fermentation by-product and found at appreciable levels in alcoholic beverages and foods such as bread and cheese. Recent work in this laboratory demonstrated for the first time that CYP2E1 is the principal enzyme responsible for urethane metabolism. The current studies were undertaken to assess the relationships between CYP2E1-mediated metabolism and urethane-induced genotoxicity and cell proliferation as determined by induction of micronucleated erythrocytes (MN) and expression of Ki-67, respectively, using CYP2E1-null and wild-type mice. Urethane was administered at 0 (vehicle), 1, 10, or 100 mg/kg/day (p.o.), 5 days/week for 6 weeks. A significant dose-dependent increase in MN was observed in wild-type mice; however, a slight increase was measured in the MN-polychromatic erythrocytes in CYP2E1-null mice treated with 100 mg/kg. A significant increase in the expression of Ki-67 was detected in the livers and the lungs (terminal bronchioles, alveoli, and bronchi) of wild-type mice administered 100 mg urethane/kg in comparison to controls. In contrast, CYP2E1-null mice administered this dose exhibited negligible alterations in Ki-67 expression in the livers and lungs compared to controls. Interestingly, while Ki-67 expression in the forestomach decreased in wild-type mice, it increased in CYP2E1-null mice. Subsequent comparative metabolism studies demonstrated that total urethane-derived radioactivity in the plasma, liver, and lung was significantly higher in CYP2E1-null versus wild-type mice and un-metabolized urethane constituted greater than 83% of the radioactivity in CYP2E1-null mice. Un-metabolized urethane was not detectable in the plasma, liver, and lung of wild-type mice. In conclusion, these data demonstrated that CYP2E1-mediated metabolism of urethane, presumably via epoxide formation, is necessary for the induction

  15. Nonminimal curvature-matter coupled wormholes with matter satisfying the null energy condition

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, Nadiezhda Montelongo; Lobo, Francisco S N, E-mail: nadiezhda@cosmo.fis.fc.ul.pt, E-mail: flobo@cii.fc.ul.pt [Centro de Astronomia e Astrofisica da Universidade de Lisboa, Campo Grande, Edificio C8 1749-016 Lisboa (Portugal)

    2011-04-21

    Recently, the exact solutions of wormhole geometries supported by a nonminimal curvature-matter coupling were found, where the nonminimal coupling minimizes the violation of the null energy condition of normal matter at the throat. In this brief report, we present a solution where normal matter satisfies the energy conditions at the throat and it is the higher order curvature derivatives of the nonminimal coupling that are responsible for the null energy condition violation, and consequently for supporting the respective wormhole geometries. For simplicity, we consider a linear R nonmiminal curvature-matter coupling and an explicit monotonically increasing function for the energy density. Thus, the solution found is not asymptotically flat, but may in principle be matched to an exterior vacuum solution.

  16. Optical codeword demodulation with error rates below standard quantum limit using a conditional nulling receiver

    CERN Document Server

    Chen, Jian; Dutton, Zachary; Lazarus, Richard; Guha, Saikat

    2011-01-01

    The quantum states of two laser pulses---coherent states---are never mutually orthogonal, making perfect discrimination impossible. Even so, coherent states can achieve the ultimate quantum limit for capacity of a classical channel, the Holevo capacity. Attaining this requires the receiver to make joint-detection measurements on long codeword blocks, optical implementations of which remain unknown. We report the first experimental demonstration of a joint-detection receiver, demodulating quaternary pulse-position-modulation (PPM) codewords at a word error rate of up to 40% (2.2 dB) below that attained with direct-detection, the largest error-rate improvement over the standard quantum limit reported to date. This is accomplished with a conditional nulling receiver, which uses optimized-amplitude coherent pulse nulling, single photon detection and quantum feedforward. We further show how this translates into coding complexity improvements for practical PPM systems, such as in deep-space communication. We antici...

  17. Common-path lateral-shearing nulling interferometry with a Savart plate for exoplanet detection.

    Science.gov (United States)

    Murakami, Naoshi; Baba, Naoshi

    2010-09-15

    We propose a common-path lateral-shearing nulling interferometer for direct detection of exoplanets. A Savart plate is placed between crossed polarizers to produce a lateral shear and realize fully achromatic and highly stable nulling interference for starlight. We construct a double-shearing interferometer using two Savart plates for implementing orthogonal x and y shears. A laboratory demonstration is carried out using a broadband light source with a bandwidth of Δλ/λ(0)=0.33 (Δλ=0.2 μm and λ(0)=0.6 μm). As a result, achieved extinction levels are 4 × 10(-4) at peak and 4 × 10(-7) at 10λ(0)/D(L) (D(L) is the diameter of a Lyot stop).

  18. Internalizing Null Extraterrestrial "Signals": An Astrobiological App for a Technological Society

    CERN Document Server

    Chaisson, Eric J

    2014-01-01

    One of the beneficial outcomes of searching for life in the Universe is that it grants greater awareness of our own problems here on Earth. Lack of contact with alien beings to date might actually comprise a null "signal" pointing humankind toward a viable future. Astrobiology has surprising practical applications to human society; within the larger cosmological context of cosmic evolution, astrobiology clarifies the energetic essence of complex systems throughout the Universe, including technological intelligence that is intimately dependent on energy and likely will be for as long as it endures. The "message" contained within the "signal" with which today's society needs to cope is reasonably this: Only solar energy can power our civilization going forward without soiling the environment with increased heat yet robustly driving the economy with increased per capita energy usage. The null "signals" from extraterrestrials also offer a rational solution to the Fermi paradox as a principle of cosmic selection l...

  19. JK null alleles identified from Japanese individuals with Jk(a−b−) phenotype.

    Science.gov (United States)

    Onodera, T; Sasaki, K; Tsuneyama, H; Isa, K; Ogasawara, K; Satake, M; Tadokoro, K; Uchikawa, M

    2014-05-01

    The Kidd blood group system consists of three common phenotypes: Jk(a+b−), Jk(a−b+) and Jk(a+b+), and one rare phenotype, Jk(a−b−). Jka/Jkb polymorphism is associated with c.838G>A (p.Asp280Asn) in exon 9 of the JK (SLC14A1) gene, and the corresponding alleles are named JK*01 and JK*02. The rare phenotype Jk(a−b−) was first found in a Filipina of Spanish and Chinese ancestry, and to date, several JK null alleles responsible for the Jk(a−b−) phenotype have been reported. We report seven novel JK null alleles, 4 with a JK*01 background and 3 with a JK*02 background, identified from Jk(a−b−) Japanese. PMID:24877238

  20. Gowdy-symmetric cosmological models with Cauchy horizons ruled by non-closed null generators

    Science.gov (United States)

    Hennig, Jörg

    2016-08-01

    Smooth Gowdy-symmetric generalized Taub-NUT solutions are a class of inhomogeneous cosmological models with spatial three-sphere topology. They have a past Cauchy horizon with closed null-generators, and they have been shown to develop a second, regular Cauchy horizon in the future, unless in special, well-defined singular cases. Here we generalize these models to allow for past Cauchy horizons ruled by non-closed null generators. In particular, we show local and global existence of such a class of solutions with two functional degrees of freedom. This removes a periodicity condition for the asymptotic data at the past Cauchy horizon that was required before. Moreover, we derive a three-parametric family of exact solutions within that class and study its properties.

  1. Double Force Compensation Method to Enhance the Performance of a Null Balance Force Sensor

    Science.gov (United States)

    Choi, In-Mook; Choi, Dong-June; Kim, Soo Hyun

    2002-06-01

    Microforce measurement is becoming more essential as precision industries such as biomedicine, precision chemistry, semiconductor manufacturing, and so forth develop. A null balance method has been introduced in order to improve on force measurement performances involving a loadcell. The null-balance type force sensor is analyzed and designed for the improvement of measurement performances. The measurement range and the resolution are dependent on the force generation capacity and the various error sources. These characteristics are estimated and verified according to the mechanical sensitivity and the force compensation sensitivity. Two different coil systems are designed and tested experimentally. Double force compensation is proposed in order to obtain a large range and high resolution. The measurement range of the large coil system and the resolution of the small one are fully realized by the double compensation method. After manufacturing, a range over 300 gf and resolution under ± 0.1 mgf were obtained by the double compensation method.

  2. Null hypothesis significance tests. A mix-up of two different theories

    DEFF Research Database (Denmark)

    Schneider, Jesper Wiborg

    2015-01-01

    Null hypothesis statistical significance tests (NHST) are widely used in quantitative research in the empirical sciences including scientometrics. Nevertheless, since their introduction nearly a century ago significance tests have been controversial. Many researchers are not aware of the numerous...... criticisms raised against NHST. As practiced, NHST has been characterized as a ‘null ritual’ that is overused and too often misapplied and misinterpreted. NHST is in fact a patchwork of two fundamentally different classical statistical testing models, often blended with some wishful quasi...... the theoretical origins of NHST, which is mostly absent from standard statistical textbooks, and we discuss some of the most prevalent problems relating to the practice of NHST and trace these problems back to the mix-up of the two different theoretical origins. Finally, we illustrate some of the...

  3. Quasinormal modes of nonlinear electromagnetic black holes from unstable null geodesics

    CERN Document Server

    Breton, N

    2016-01-01

    The expressions for the quasinormal modes (QNMs) of black holes with nonlinear electrodynamics, calculated in the eikonal approximation, are presented. In the eikonal limit QNMs of black holes are determined by the parameters of the circular null geodesics. The unstable circular null orbits are derived from the effective metric that is the one obeyed by light rays under the influence of a nonlinear electromagnetic field. As an illustration we calculate the QNMs of four nonlinear electromagnetic black holes, two singular and two regular, namely from Euler-Heisenberg and Born-Infeld theories, for singular, and the magnetic Bardeen black hole and the one derived by Bronnikov for regular ones. Comparison is shown with the QNMs of the linear electromagnetic counterpart, their Reissner-Nordstr\\"{o}m black hole.

  4. Simple Fourier optics formalism for high angular resolution systems and nulling interferometry

    CERN Document Server

    Henault, Francois

    2009-01-01

    In this paper are reviewed various designs of advanced, multi-aperture optical systems dedicated to high angular resolution imaging or to the detection of exo-planets by nulling interferometry. A simple Fourier optics formalism is presented, allowing to derive their imaging and nulling basic relationships as convolution or cross correlation products suitable for fast and accurate computation. The most promising designs seem to be the free-flying, axially recombined interferometers showing an unsurpassed imaging capacity, and a conceptual "super-resolving telescope" utilizing a mosaicing observation procedure. The entire study is only valid in the frame of first-order geometrical optics and scalar diffraction theory. Furthermore, it is assumed that all entrance sub-apertures are optically conjugated with their associated exit pupils, a particularity inducing an instrumental behaviour comparable with those of diffraction gratings.

  5. Semi-analytical approach for the Vaidya metric in double-null coordinates

    CERN Document Server

    Girotto, F; Girotto, Fernando; Saa, Alberto

    2004-01-01

    We reexamine here a problem considered in detail before by Waugh and Lake: the solutions of spherically symmetric Einstein's equations with a radial flow of unpolarized radiation (the Vaidya metric) in double-null coordinates. This problem is known to be not analytically solvable, the only known explicit solutions correspond to the constant mass case (Schwarzschild solution in Kruskal-Szekeres form) and the linear and exponential mass functions originally discovered by Waugh and Lake. We present here a semi-analytical approach that can be used to discuss some qualitative and quantitative aspects of the Vaidya metric in double-null coordinates for generic mass functions. We present also a new analytical solution corresponding to $(1/v)$-mass function.

  6. Asymptotic Properties of Parabolic Systems for Null-Recurrent Switching Diffusions

    Institute of Scientific and Technical Information of China (English)

    R.Z.Khasminskii; C.Zhu; G.Yin

    2007-01-01

    This work is concerned with the asymptotic behavior of systems of parabolic equations arising from null-recurrent switching diffusions,which are diffusion processes modulated by continuous-time Markov chains.A sufficient condition for null recurrence is presented.Moreover,convergence rate of the solutions of systems of homogeneous parabolic equations under suitable conditions is established.Then a case study on verifying one of the conditions proposed is provided with the use of a two-state Markov chain.To verify the condition,boundary value problems(BVPs)for parabolic systems are treated,which are not the usual two-point BVP type.An extra condition in the interior is needed resulting in jump discontinuity of the derivative of the corresponding solution.

  7. Local existence in retarded time under a weak decay on complete null cones

    CERN Document Server

    Li, Junbin

    2015-01-01

    In the previous paper \\cite{L-Z}, for a characteristic problem with not necessarily small initial data given on a complete null cone decaying like that in the work \\cite{Ch-K} of the stability of Minkowski spacetime by Christodoulou and Klainerman, we proved the local existence in retarded time, which means the solution to the vacuum Einstein equations exists in a uniform future neighborhood, while the global existence in retarded time is the weak cosmic censorship conjecture. In this paper, we prove that the local existence in retarded time still holds when the data is assumed to decay slower, like that in Bieri's work \\cite{Bie} on the extension to the stability of Minkowski spacetime. Such decay guarantees the existence of the limit of the Hawking mass on the initial null cone, when approaching to infinity, in an optimal way.

  8. Numerical Simulations of Solar Spicule Jets at a Magnetic Null-Point

    Science.gov (United States)

    Smirnova, V.; Konkol, P. M.; Solov'ev, A. A.; Murawski, K.

    2016-09-01

    Two-dimensional numerical simulations of jet-like structures in the solar atmosphere are performed. These structures result from a pressure pulse that is launched at the null point of a potential magnetic arcade. The plasma jet exhibits a double structure with two components: (a) dense, cool, and short vertical stream and (b) a less dense, hot and tall part of the jet. The upper part of the hot and tall jet may represent a direct response of the system to the pressure pulse launched at the null point, and the second, slower cool and dense part of the jet is formed later through the stretching up of the stream as a result of plasma evacuation from the top of the magnetic arcade. Numerical results show that jet-like structures mimic some properties of both type I and type II spicules, according to the classification provided by De Pontieu et al. (Publ. Astron. Soc. Japan 59, S655, 2007).

  9. Towards a stable and absolute atmospheric carbon dioxide instrument using spectroscopic null method

    Directory of Open Access Journals (Sweden)

    B. Xiang

    2013-07-01

    Full Text Available We present a novel spectral method to measure atmospheric carbon dioxide (CO2 with high precision and stability without resorting to calibration tanks during long-term operation. This spectral null method improves precision by reducing spectral proportional noise associated with laser emission instabilities. We employ sealed quartz cells with known CO2 column densities to serve as the permanent internal references in the null method, which improve the instrument's stability and accuracy. A prototype instrument – ABsolute Carbon dioxide (ABC is developed using this new approach. The instrument has a one-second precision of 0.02 ppm, which averages down to 0.007 ppm within one minute. Long-term stability of within 0.1 ppm is achieved without any calibrations for over a one-month period. These results have the potential for eliminating the need for calibration cylinders for high accuracy field measurements of carbon dioxide.

  10. Null Dust Solution in Ho\\v{r}ava-Lifshitz Gravity

    CERN Document Server

    Goldoni, O; Chan, R; Satheeshkumar, V H; da Rocha, J F Villas

    2016-01-01

    Non-stationary null dust in a spherically symmetric spacetime is studied in the context of a general-covariant Ho\\v{r}ava-Lifshitz gravity. The non-minimal coupling to matter is considered in the post-Newtonian approximation (PPN) in the infrared limit. The aim of this paper is to see if a general relativistic spacetime of a shearing null dust-like fluid can be a solution of Ho\\v{r}ava-Lifshitz theory in the infrared limit. We have shown that this solution admits the process of gravitational collapse leaving a singularity at the end. These solutions have, qualitatively, the same temporal behavior as the dust collapse in Einstein theory. We have also found other possible solutions, representing an expansion behavior that is not found in General Relativity (GR). This solution might represent a repulsive phantom energy in GR.

  11. DAMA confronts null searches in the effective theory of dark matter-nucleon interactions

    CERN Document Server

    Catena, Riccardo; Wild, Sebastian

    2016-01-01

    We examine the dark matter interpretation of the modulation signal reported by the DAMA experiment from the perspective of effective field theories displaying Galilean invariance. We consider the most general effective coupling leading to the elastic scattering of a dark matter particle with a nucleon, and we analyze the compatibility of the DAMA signal with the null results from other direct detection experiments, as well as with the non-observation of a high energy neutrino flux in the direction of the Sun from dark matter annihilation. Assuming the standard halo model, we find a strong tension between the dark matter interpretation of the DAMA modulation signal and the null result experiments. We also list possible ways-out to this conclusion.

  12. Space filling in the World Trade Web: measures and null models

    CERN Document Server

    Ruzzenenti, Franco; Garlaschelli, Diego; Basosi, Riccardo

    2012-01-01

    It is here proposed global and local, bynary and weighted measures of space filling, to detect the degree of stretching of a network within its embedding space. Measures are normalized indexes that vary from zero - a maximally shrunk network, to one -a maximally expanded network. We evaluated the indexes according to three different null models an propose an unbiased measure of network filling, suitable for confrontation of different (cross sectional) embedded networks or historical trends of the same network. We further develop a local measure of filling and thereby of vertex assortativity. Finally, we showed that in the WTW metric distances seem to have determined the links' allocation more than the present null models tend to have predicted and that this burden upon links has been changing in time. However, surprisingly, our analysis seems to indicate that during globalization the WTW expanded merely because of topology and contrary to expectations it actually shrunk.

  13. DAMA confronts null searches in the effective theory of dark matter-nucleon interactions

    OpenAIRE

    Catena, Riccardo; Ibarra, Alejandro; Wild, Sebastian

    2016-01-01

    We examine the dark matter interpretation of the modulation signal reported by the DAMA experiment from the perspective of effective field theories displaying Galilean invariance. We consider the most general effective coupling leading to the elastic scattering of a dark matter particle with spin 0 or 1/2 off a nucleon, and we analyze the compatibility of the DAMA signal with the null results from other direct detection experiments, as well as with the non-observation of a high energy neutrin...

  14. Cassegrainian/Gregorian-type null correctors for surface measurements of radio telescope reflectors.

    Science.gov (United States)

    Greve, A

    1997-08-01

    The (sub)millimeter wavelength radio observatory of the next generation will probably be an interferometer array of some 50 telescopes with parabolic reflectors 10-15 m in diameter. At this scale of mass production it is convenient to have at hand for workshop assembly a reflector surface measurement technique that is precise and easy to operate. We discuss the possibility of reflector measurements based on 10.6-microm CO2 laser interferometry using Cassegrainian/Gregorian-type null correctors.

  15. HIGH SPECTRAL RESOLUTION MEASUREMENT OF THE SUNYAEV–ZEL'DOVICH EFFECT NULL WITH Z-Spec

    International Nuclear Information System (INIS)

    The Sunyaev-Zel'dovich (SZ) effect spectrum crosses through a null where ΔTCMB = 0 near ν0 = 217 GHz. In a cluster of galaxies, ν0 can be shifted from the canonical thermal SZ effect value by corrections to the SZ effect scattering due to the properties of the inter-cluster medium. We have measured the SZ effect in the hot galaxy cluster RX J 1347.5 – 1145 with Z-Spec, an R ∼ 300 grating spectrometer sensitive between 185 and 305 GHz. These data comprise a high spectral resolution measurement around the null of the SZ effect and clearly exhibit the transition from negative to positive ΔTCMB over the Z-Spec band. The SZ null position is measured to be ν0 = 225.8 ± 2.5(stat.) ± 1.2(sys.) GHz, which differs from the canonical null frequency by 3.0σ and is evidence for modifications to the canonical thermal SZ effect shape. Assuming the measured shift in ν0 is due only to relativistic corrections to the SZ spectrum, we place the limit kTe = 17.1 ± 5.3 keV from the zero-point measurement alone. By simulating the response of the instrument to the sky, we are able to generate likelihood functions in {y0, Te, vpec} space. For vpec = 0 km s–1, we measure the best-fitting SZ model to be y0 = 4.6+0.6–0.9 × 10–4, Te,0 = 15.2+12–7.4 keV. When vpec is allowed to vary, a most probable value of vpec = + 450 ± 810 km s–1 is found.

  16. Fonction constante et d\\'eriv\\'ee nulle : un r\\'esultat si trivial..

    CERN Document Server

    Delcroix, Antoine

    2008-01-01

    We study various proofs of the caracterization of constant functions, more precisely of the theorem: a derivable function, defined on a real interval, is constant if, and only if, its derivative is null. Our aim is to study the relationships of these proofs with the mathematical curriculum of secondary schools and the begining of undergraduate studies in France, from various point of views (epistemological, historical, didactical).

  17. Likelihood of Null Effects of Large NHLBI Clinical Trials Has Increased over Time.

    Directory of Open Access Journals (Sweden)

    Robert M Kaplan

    Full Text Available We explore whether the number of null results in large National Heart Lung, and Blood Institute (NHLBI funded trials has increased over time.We identified all large NHLBI supported RCTs between 1970 and 2012 evaluating drugs or dietary supplements for the treatment or prevention of cardiovascular disease. Trials were included if direct costs >$500,000/year, participants were adult humans, and the primary outcome was cardiovascular risk, disease or death. The 55 trials meeting these criteria were coded for whether they were published prior to or after the year 2000, whether they registered in clinicaltrials.gov prior to publication, used active or placebo comparator, and whether or not the trial had industry co-sponsorship. We tabulated whether the study reported a positive, negative, or null result on the primary outcome variable and for total mortality.17 of 30 studies (57% published prior to 2000 showed a significant benefit of intervention on the primary outcome in comparison to only 2 among the 25 (8% trials published after 2000 (χ2=12.2,df= 1, p=0.0005. There has been no change in the proportion of trials that compared treatment to placebo versus active comparator. Industry co-sponsorship was unrelated to the probability of reporting a significant benefit. Pre-registration in clinical trials.gov was strongly associated with the trend toward null findings.The number NHLBI trials reporting positive results declined after the year 2000. Prospective declaration of outcomes in RCTs, and the adoption of transparent reporting standards, as required by clinicaltrials.gov, may have contributed to the trend toward null findings.

  18. EXACT NULL CONTROLLABILITY OF NON-AUTONOMOUS FUNCTIONAL EVOLUTION SYSTEMS WITH NONLOCAL CONDITIONS

    Institute of Scientific and Technical Information of China (English)

    Xianlong FU; Yu ZHANG

    2013-01-01

    In this article,by using theory of linear evolution system and Schauder fixed point theorem,we establish a sufficient result of exact null controllability for a non-autonomous functional evolution system with nonlocal conditions.In particular,the compactness condition or Lipschitz condition for the function g in the nonlocal conditions appearing in various literatures is not required here.An example is also provided to show an application of the obtained result.

  19. Reversing hypomyelination in BACE1-null mice with Akt-DD overexpression

    OpenAIRE

    Hu, Xiangyou; Schlanger, Rita; He, Wanxia; Macklin, Wendy B.; Yan, Riqiang

    2013-01-01

    β-Site amyloid precursor protein convertase enzyme 1 (BACE1), a type I transmembrane aspartyl protease required to cleave amyloid precursor protein for releasing a toxic amyloid peptide, also cleaves type I and type III neuregulin-1 (Nrg-1). BACE1 deficiency in mice causes hypomyelination during development and impairs remyelination if injured. In BACE1-null mice, the abolished cleavage of neuregulin-1 by BACE1 is speculated to cause reduced myelin sheath thickness in both the central nervous...

  20. SPARC-null mice exhibit increased adiposity without significant differences in overall body weight

    OpenAIRE

    Bradshaw, A. D.; Graves, D C; Motamed, K.; Sage, E H

    2003-01-01

    Secreted protein acidic and rich in cysteine/osteonectin/BM-40 (SPARC) is a matrix-associated protein that elicits changes in cell shape, inhibits cell-cycle progression, and influences the synthesis of extracellular matrix (ECM). The absence of SPARC in mice gives rise to aberrations in the structure and composition of the ECM that result in generation of cataracts, development of severe osteopenia, and accelerated closure of dermal wounds. In this report we show that SPARC-null mice have gr...

  1. Null Trajectories and Bending of Light in Charged Black Holes with Quintessence

    Science.gov (United States)

    Fernando, Sharmanthie; Meadows, Scott; Reis, Kevon

    2015-10-01

    We have studied null geodesics of the charged black hole surrounded by quintessence. Quintessence is a candidate for dark energy and is represented by a scalar field. Here, we have done a detailed study of the photon trajectories. The exact solutions for the trajectories are obtained in terms of the Jacobi-elliptic integrals for all possible energy and angular momentum of the photons. We have also studied the bending angle using the Rindler and Ishak method.

  2. Null trajectories and bending of light in charged black holes with quintessence

    CERN Document Server

    Fernando, Sharmanthie; Reis, Kevon

    2014-01-01

    We have studied null geodesics of the charged black hole surrounded by quintessence. Quintessence is a candidate for dark energy and is represented by a scalar field. Here, we have done a detailed study of the photon trajectories. The exact solutions for the trajectories are obtained in terms of the Jacobi-elliptic integrals for all possible energy and angular momentum of the photons. We have also studied the bending angle using the Rindler and Ishak method.

  3. Comparative proteomics of skeletal muscle mitochondria from myostatin-null mice

    OpenAIRE

    Puddick, Jonathan; Martinus, Ryan D

    2011-01-01

    Myostatin, a secreted protein, is a negative regulator of skeletal muscle growth. Down-regulating its expression increases skeletal muscle mass that is accompanied by a marked change in the fibre composition from one reliant on mitochondrial oxidative metabolism to glycolysis. A comparative proteomic investigation of this altered metabolism was carried out on mitochondria from the gastrocnemius muscle of myostatin-null mice compared with wild-type. Most of the proteins identified showed no si...

  4. Perfect fluid space-times admitting a 3-dimensional conformal group acting on null orbits

    CERN Document Server

    Sintes, A M

    1997-01-01

    Space-times admitting a 3-dimensional Lie group of conformal motions $C_3$ acting on null orbits are studied. Coordinate expressions for the metric and the conformal Killing vectors (CKV) are then provided (irrespectively of the matter content) and all possible perfect fluid solutions are found, although none of them verifies the weak and dominant energy conditions over the whole space-time manifold.

  5. Spin-2 fields on Minkowski space near space-like and null infinity

    OpenAIRE

    Friedrich, H

    2002-01-01

    We show that the spin-2 equations on Minkowski space in the gauge of the `regular finite initial value problem at space-like infinity' imply estimates which, together with the transport equations on the cylinder at space-like infinity, allow us to obtain for a certain class of initial data information on the behaviour of the solution near space-like and null infinity of any desired precision.

  6. Floral colour diversity in plant communities, bee colour space and a null model

    OpenAIRE

    Gumbert, A; Kunze, J.; Chittka, L.

    1999-01-01

    Evolutionary biologists have long hypothesized that the diversity of flower colours we see is in part a strategy to promote memorization by pollinators, pollinator constancy, and therefore, a directed and efficient pollen transfer between plants. However, this hypothesis has never been tested against a biologically realistic null model, nor were colours assessed in the way pollinators see them. Our intent here is to fill these gaps. Throughout one year, we sampled floral species compositions ...

  7. Null Geodesic Congruences, Asymptotically-Flat Spacetimes and Their Physical Interpretation

    Directory of Open Access Journals (Sweden)

    Timothy M. Adamo

    2012-01-01

    Full Text Available A priori, there is nothing very special about shear-free or asymptotically shear-free null geodesic congruences. Surprisingly, however, they turn out to possess a large number of fascinating geometric properties and to be closely related, in the context of general relativity, to a variety of physically significant effects. It is the purpose of this paper to try to fully develop these issues. This work starts with a detailed exposition of the theory of shear-free and asymptotically shear-free null geodesic congruences, i.e., congruences with shear that vanishes at future conformal null infinity. A major portion of the exposition lies in the analysis of the space of regular shear-free and asymptotically shear-free null geodesic congruences. This analysis leads to the space of complex analytic curves in an auxiliary four-complex dimensional space, H-space. They in turn play a dominant role in the applications. The applications center around the problem of extracting interior physical properties of an asymptotically-flat spacetime directly from the asymptotic gravitational (and Maxwell field itself, in analogy with the determination of total charge by an integral over the Maxwell field at infinity or the identification of the interior mass (and its loss by (Bondi's integrals of the Weyl tensor, also at infinity. More specifically, we will see that the asymptotically shear-free congruences lead us to an asymptotic definition of the center-of-mass and its equations of motion. This includes a kinematic meaning, in terms of the center-of-mass motion, for the Bondi three-momentum. In addition, we obtain insights into intrinsic spin and, in general, angular momentum, including an angular-momentum--conservation law with well-defined flux terms. When a Maxwell field is present, the asymptotically shear-free congruences allow us to determine/define at infinity a center-of-charge world line and intrinsic magnetic dipole moment.

  8. The null hypothesis significance test in health sciences research (1995-2006): statistical analysis and interpretation

    OpenAIRE

    Fernández-Somoano Ana; Suárez-Gil Patricio; Silva-Ayçaguer Luis

    2010-01-01

    Abstract Background The null hypothesis significance test (NHST) is the most frequently used statistical method, although its inferential validity has been widely criticized since its introduction. In 1988, the International Committee of Medical Journal Editors (ICMJE) warned against sole reliance on NHST to substantiate study conclusions and suggested supplementary use of confidence intervals (CI). Our objective was to evaluate the extent and quality in the use of NHST and CI, both in Englis...

  9. Null geodesics in the Alcubierre warp drive spacetime: the view from the bridge

    OpenAIRE

    Clark, Chad; Hiscock, William A.; Larson, Shane L.

    1999-01-01

    The null geodesic equations in the Alcubierre warp drive spacetime are numerically integrated to determine the angular deflection and redshift of photons which propagate through the distortion of the ``warp drive'' bubble to reach an observer at the origin of the warp effect. We find that for a starship with an effective warp speed exceeding the speed of light, stars in the forward hemisphere will appear closer to the direction of motion than they would to an observer at rest. This aberration...

  10. Establishment and characterization of immortalized Gli-null mouse embryonic fibroblast cell lines

    Directory of Open Access Journals (Sweden)

    Gipp Jerry J

    2008-09-01

    Full Text Available Abstract Background Hedgehog (Hh signaling is a conserved morphogenetic pathway which plays critical roles in embryonic development, with emerging evidence also supporting a role in healing and repair processes and tumorigenesis. The Gli family of transcription factors (Gli1, 2 and 3 mediate the Hedgehog morphogenetic signal by regulating the expression of downstream target genes. We previously characterized the individual and cooperative roles of the Gli proteins in Hh target gene regulation using a battery of primary embryonic fibroblasts from Gli null mice. Results Here, we describe the establishment of spontaneously immortalized mouse embryonic fibroblast (iMEF cell lines lacking single and multiple Gli genes. These non-clonal cell lines recapitulate the unique ligand mediated transcriptional response of primary MEFs. While loss of Gli1 had no effect on target gene induction, Gli2 null cells demonstrated reduced target gene induction while Gli3 null cells exhibited elevated basal and ligand-induced expression. Target gene response in Gli1-/-2-/- iMEFs was severely reduced while Gli2-/-3-/- iMEFs were incapable of ligand-induced transcriptional response. However, we found that both Gli1-/-2-/- and Gli2-/-3-/- iMEFs exhibited robust leukotriene synthesis-dependent migration responses to Hh ligand, demonstrating that this response is not transcriptionally-dependent. Conclusion This study provides fundamental characterizations of the transcriptional and non-transcriptional Hh responsiveness of a battery of Gli-null iMEFs. Moving forward, these cell lines should prove a valuable tool set to study the unique functional regulation of the Gli proteins in a Hh-responsive cell-type.

  11. Premature aggregation of type IV collagen and early lethality in lysyl hydroxylase 3 null mice

    OpenAIRE

    Rautavuoma, Kati; Takaluoma, Kati; Sormunen, Raija; Myllyharju, Johanna; Kivirikko, Kari I.; Soininen, Raija

    2004-01-01

    Collagens carry hydroxylysine residues that act as attachment sites for carbohydrate units and are important for the stability of crosslinks but have been regarded as nonessential for vertebrate survival. We generated mice with targeted inactivation of the gene for one of the three lysyl hydroxylase isoenzymes, LH3. The null embryos developed seemingly normally until embryonic day 8.5, but development was then retarded, with death around embryonic day 9.5. Electron microscopy (EM) revealed fr...

  12. Null Geodesic Congruences, Asymptotically-Flat Spacetimes and Their Physical Interpretation

    Directory of Open Access Journals (Sweden)

    Timothy M. Adamo

    2009-09-01

    Full Text Available A priori, there is nothing very special about shear-free or asymptotically shear-free null geodesic congruences. Surprisingly, however, they turn out to possess a large number of fascinating geometric properties and to be closely related, in the context of general relativity, to a variety of physically significant effects. It is the purpose of this paper to try to fully develop these issues. This work starts with a detailed exposition of the theory of shear-free and asymptotically shear-free null geodesic congruences, i.e., congruences with shear that vanishes at future conformal null infinity. A major portion of the exposition lies in the analysis of the space of regular shear-free and asymptotically shear-free null geodesic congruences. This analysis leads to the space of complex analytic curves in complex Minkowski space. They in turn play a dominant role in the applications. The applications center around the problem of extracting interior physical properties of an asymptotically-flat spacetime directly from the asymptotic gravitational (and Maxwell field itself, in analogy with the determination of total charge by an integral over the Maxwell field at infinity or the identification of the interior mass (and its loss by (Bondi’s integrals of the Weyl tensor, also at infinity. More specifically, we will see that the asymptotically shear-free congruences lead us to an asymptotic definition of the center-of-mass and its equations of motion. This includes a kinematic meaning, in terms of the center-of-mass motion, for the Bondi three-momentum. In addition, we obtain insights into intrinsic spin and, in general, angular momentum, including an angular-momentum–conservation law with well-defined flux terms. When a Maxwell field is present, the asymptotically shear-free congruences allow us to determine/define at infinity a center-of-charge world line and intrinsic magnetic dipole moment.

  13. Internalizing Null Extraterrestrial "Signals": An Astrobiological App for a Technological Society

    OpenAIRE

    Chaisson, Eric J.

    2014-01-01

    One of the beneficial outcomes of searching for life in the Universe is that it grants greater awareness of our own problems here on Earth. Lack of contact with alien beings to date might actually comprise a null "signal" pointing humankind toward a viable future. Astrobiology has surprising practical applications to human society; within the larger cosmological context of cosmic evolution, astrobiology clarifies the energetic essence of complex systems throughout the Universe, including tech...

  14. Snail1 controls epithelial–mesenchymal lineage commitment in focal adhesion kinase–null embryonic cells

    OpenAIRE

    Li, Xiao-Yan; Zhou, Xiaoming; Rowe, R. Grant; Hu, Yuexian; Schlaepfer, David D.; Ilić, Dusko; Dressler, Gregory; Park, Ann; Guan, Jun-Lin; Weiss, Stephen J.

    2011-01-01

    Mouse embryonic cells isolated from focal adhesion kinase (FAK)–null animals at embryonic day 7.5 display multiple defects in focal adhesion remodeling, microtubule dynamics, mechanotransduction, proliferation, directional motility, and invasion. To date, the ability of FAK to modulate cell function has been ascribed largely to its control of posttranscriptional signaling cascades in this embryonic cell population. In this paper, we demonstrate that FAK unexpectedly exerts control over an epi...

  15. The Well-posedness of the Null-Timelike Boundary Problem for Quasilinear Waves

    OpenAIRE

    Kreiss, H.; Winicour, J.

    2010-01-01

    The null-timelike initial-boundary value problem for a hyperbolic system of equations consists of the evolution of data given on an initial characteristic surface and on a timelike worldtube to produce a solution in the exterior of the worldtube. We establish the well-posedness of this problem for the evolution of a quasilinear scalar wave by means of energy estimates. The treatment is given in characteristic coordinates and thus provides a guide for developing stable finite difference algori...

  16. Anaphoric Preferences of Null and Overt Subjects in Italian and Spanish: a Cross-linguistic Comparison

    OpenAIRE

    Filiaci, Francesca

    2011-01-01

    This thesis focuses on the cross-linguistic differences between Italian and Spanish regarding the pragmatic restrictions on the resolution of null and overt subject pronouns (NS and OSP). It also tries to identify possible links between such cross-linguistic differences and morpho-syntactic differences at the level of the verbal morphology of the two languages. Spanish and Italian are typologically related and morpho-syntactically similar and have been assumed to instantiate the same setti...

  17. Phylogeny can make the mid-domain effect an inappropriate null model

    OpenAIRE

    Jonathan Davies, T; Grenyer, Richard; Gittleman, John L.

    2005-01-01

    The mid-domain effect (MDE), a bias in species richness towards the midpoint of a given geographical dimension, has been used as a null model in macro-ecological studies. Departures from a MDE are often thought of as interesting. The MDE is a product of the interaction between geometric boundaries and range locations, with species being forced to occupy more central positions in proportion to their range size. We criticize this mechanism for assuming species' locations to be wholly independen...

  18. Violation of the averaged null energy condition in semiclassical black-hole evaporation

    CERN Document Server

    Levi, Adam

    2016-01-01

    We report here on a new method for calculating the renormalized stress-energy tensor (RSET) in black-hole (BH) spacetimes, which should be applicable to dynamical BHs as well. We used this method to calculate the RSET of a massless, minimally coupled scalar field in Schwarzschild and Reissner-Nordstrom backgrounds, for several quantum states. We present here the results for the RSET in the Schwarzschild case in Unruh state (the state describing BH evaporation). The RSET is type I at weak field, and becomes type IV at $r\\lesssim2.78M$. Then we use the RSET results to explore violation of the weak and null Energy conditions. We find that both conditions are violated all the way from $r\\simeq4.9M$ to the horizon. We also find that the averaged weak energy condition is violated by a class of (unstable) circular timelike geodesics. Most remarkably, the circular null geodesic at $r=3M$ is found to violate the averaged null energy condition (ANEC). To the best of our knowledge this is the first demonstration of ANEC...

  19. [Development of new soybean germplasm with null lipoxygenase and Kunitz trypsin inhibitor genes].

    Science.gov (United States)

    Han, Fen-Xia; Ding, An-Lin; Sun, Jun-Ming; Li, Gui-Ying

    2005-04-01

    Soybean is one of the most important sources of plant protein for human. Soybean protein is a kind of high-quality protein composed of balanced amino acids, which contains all kinds of amino acids, especially 8 amino acids necessary for human. But it also contains some components that are not good for human and affect food quality, such as lipoxygenase (Lox) and trypsin inhibitor (Ti). Those are important anti-nutritious factors. Nutritional value and processing quality of soybean can be improved by means of development of new variety with null Lox and Ti. In this paper, new soybean germplasms that pyramided multiple genes of high quality, null lipoxygenase and trypsin inhibitor genes (Ix1, Ix2, Ix3 and ti) were developed by means of cross and biochemical marker-assisted selection of progenies for null lipoxygenase and trypsin inhibitor genes using known Lox and Ti markers (protein markers). Female parents were soybean varieties Ludou 4, Zhongpin 661, Yudou 8,91D15, wei8640 popularized in Huanghuaihai Plain. Male parents were varieties introduced from US, trypsin-inhibitor (Ti)-deficient varieties P. I. L83-4387 and near isogenic lines of varieties Century for lipoxygenase (Lox)-deficient genes, Century-2 (Ix2), Century-2.3 (Ix2Ix3) and Century-1.3 (Ix1 Ix3). These new germplasms will promote soybean breeding for improved quality production,and utilization. PMID:16011034

  20. Entropy on a null surface for interacting quantum field theories and the Bousso bound

    CERN Document Server

    Bousso, Raphael; Fisher, Zachary; Maldacena, Juan

    2014-01-01

    We study the vacuum-subtracted von Neumann entropy of a segment on a null plane. We argue that for interacting quantum field theories in more than two dimensions, this entropy has a simple expression in terms of the expectation value of the null components of the stress tensor on the null interval. More explicitly $\\Delta S = 2\\pi \\int d^{d-2}y \\int_0^1 dx^+\\, g(x^+)\\, \\langle T_{++}\\rangle$, where $g(x^+)$ is a theory-dependent function. This function is constrained by general properties of quantum relative entropy. These constraints are enough to extend our recent free field proof of the quantum Bousso bound to the interacting case. This unusual expression for the entropy as the expectation value of an operator implies that the entropy is equal to the modular Hamiltonian, $\\Delta S = \\langle \\Delta K \\rangle $, where $K$ is the operator in the right hand side. We explain how this equality is compatible with a non-zero value for $\\Delta S$. Finally, we also compute explicitly the function $g(x^+)$ for theori...

  1. Multi-transmitter multi-receiver null coupled systems forinductive detection and characterization of metallic objects

    Energy Technology Data Exchange (ETDEWEB)

    Smith, J. Torquil; Morrison, H. Frank; Doolittle, Lawrence R.; Tseng, Hung-Wen

    2005-10-17

    Equivalent dipole polarizabilities are a succinct way tosummarize the inductive response of an isolated conductive body atdistances greater than the scale of the body. Their estimation requiresmeasurement of secondary magnetic fields due to currents induced in thebody by time varying magnetic fields in at least three linearlyindependent (e.g., orthogonal) directions. Secondary fields due to anobject are typically orders of magnitude smaller than the primaryinducing fields near the primary field sources (transmitters). Receivercoils may be oriented orthogonal to primary fields from one or twotransmitters, nulling their response to those fields, but simultaneouslynulling to fields of additional transmitters is problematic. Iftransmitter coils are constructed symmetrically with respect to inversionin a point, their magnetic fields are symmetric with respect to thatpoint. If receiver coils are operated in pairs symmetric with respect toinversion in the same point, then their differenced output is insensitiveto the primary fields of any symmetrically constructed transmitters,allowing nulling to three (or more) transmitters. With a sufficientnumber of receivers pairs, object equivalent dipole polarizabilities canbe estimated in situ from measurements at a single instrument sitting,eliminating effects of inaccurate instrument location on polarizabilityestimates. The method is illustrated with data from a multi-transmittermulti-receiver system with primary field nulling through differencedreceiver pairs, interpreted in terms of principal equivalent dipolepolarizabilities as a function of time.

  2. Internal structure of an optical null Ronchi grating test for a plano-parabolic lens.

    Science.gov (United States)

    Ortega-Vidals, Paula; Juárez-Reyes, Salvador Alejandro; Silva-Ortigoza, Gilberto; Cabrera-Rosas, Omar de J

    2016-01-01

    In this work we use geometrical optics and the caustic touching theorem, introduced by Berry, to describe the internal structure of the null Ronchi grating for a plano-parabolic lens illuminated by a point light source placed on the optical axis. The aim of this work is to explain the role of the caustic region in the process of morphology change between image and object in computing the null Ronchi grating. To this end, we obtain the analytic expression of the null Ronchi grating, and after that we deeply study the change in morphology between a single straight fringe image at the Ronchigram and the multiple curve rulings that can generate it (one open and one closed). We analyze exactly how multiple rulings generate the same straight image fringe, or how an entire ruling collapses into a single point image. For this analysis, we take different observation planes at different positions with respect to the caustic region. Finally, we characterize this topological change as one of two possible kinds depending on the relative position between the observation plane and the caustic region.

  3. Gravitational Field equations near an Arbitrary Null Surface expressed as a Thermodynamic Identity

    CERN Document Server

    Chakraborty, Sumanta; Padmanabhan, T

    2015-01-01

    Previous work has demonstrated that the gravitational field equations in all Lanczos-Lovelock models imply a thermodynamic identity TdS=dE+PdV (where the variations are interpreted as changes due to virtual displacement along the affine parameter) in the near-horizon limit in static spacetimes. Here we generalize this result to any arbitrary null surface in an arbitrary spacetime and show that certain components of the Einstein's equations can be expressed in the form of the above thermodynamic identity. We also obtain an explicit expression for the thermodynamic energy associated with the null surface. Under appropriate limits, our expressions reduce to those previously derived in the literature. The components of the field equations used in obtaining the current result are orthogonal to the components used previously to obtain another related result, viz. that some components of the field equations reduce to a Navier-Stokes equation on any null surface, in any spacetime. We also describe the structure of Ei...

  4. Designing null phase screens to test a fast plano-convex aspheric lens

    Science.gov (United States)

    DelOlmo-Márquez, Jesús; Castán-Ricaño, Diana; Avendaño-Alejo, Maximino; Díaz-Uribe, Rufino

    2015-08-01

    We have obtained a formula to represent the wavefront produced by a plano-convex aspheric lens with symmetry of revolution considering a plane wavefront propagating parallel to the optical axis and impinging on the refracting surface, it is called a zero-distance phase front, being it the first wavefront to be out of the optical system. Using a concept of differential geometry called parallel curves it is possible to obtain an analytic formula to represent the wavefront propagated at arbitrary distances through the optical axis. In order to evaluate qualitatively a plano-convex aspheric lens, we have modified slightly an interferometer Tywman-Green as follow: In the reference beam we use a plane mirror and the beam of test we have used a spatial light modulator (SLM) to compensate the phase produced by the lens under test. It will be called a null phase interferometer. The main idea is to recombine both wavefronts in order to get a null interferogram, otherwise we will associate the patterns of the interferogram to deformations of the lens under test. The null phase screens are formed with concentric circumferences assuming different gray levels printed on SLM.

  5. Granule stores from cellubrevin/VAMP-3 null mouse platelets exhibit normal stimulus-induced release.

    Science.gov (United States)

    Schraw, Todd D; Rutledge, Tara W; Crawford, Garland L; Bernstein, Audrey M; Kalen, Amanda L; Pessin, Jeffery E; Whiteheart, Sidney W

    2003-09-01

    It is widely accepted that the platelet release reaction is mediated by heterotrimeric complexes of integral membrane proteins known as SNAREs (SNAP receptors). In an effort to define the precise molecular machinery required for platelet exocytosis, we have analyzed platelets from cellubrevin/VAMP-3 knockout mice. Cellubrevin/VAMP-3 has been proposed to be a critical v-SNARE for human platelet exocytosis; however, data reported here suggest that it is not required for platelet function. Upon stimulation with increasing concentrations of thrombin, collagen, or with thrombin for increasing time there were no differences in secretion of [3H]-5HT (dense core granules), platelet factor IV (alpha granules), or hexosaminidase (lysosomes) between null and wild-type platelets. There were no gross differences in bleeding times nor in agonist-induced aggregation measured in platelet-rich plasma or with washed platelets. Western blotting of wild-type, heterozygous, and null platelets confirmed the lack of cellubrevin/VAMP-3 in nulls and showed that most elements of the secretion machinery are expressed at similar levels. While the secretory machinery in mice was similar to humans, mice did express apparently higher levels of synaptobrevin/VAMP-2. These data show that the v-SNARE, cellubrevin/VAMP-3 is not a requirement for the platelet release reaction in mice.

  6. Null Models of Economic Networks: The Case of the World Trade Web

    CERN Document Server

    Fagiolo, Giorgio; Garlaschelli, Diego

    2014-01-01

    In all empirical-network studies, the observed properties of economic networks are informative only if compared with a well-defined null model that can quantitatively predict the behavior of such properties in constrained graphs. However, predictions of the available null-model methods can be derived analytically only under assumptions (e.g., sparseness of the network) that are unrealistic for most economic networks like the World Trade Web (WTW). In this paper we study the evolution of the WTW using a recently-proposed family of null network models. The method allows to analytically obtain the expected value of any network statistic across the ensemble of networks that preserve on average some local properties, and are otherwise fully random. We compare expected and observed properties of the WTW in the period 1950-2000, when either the expected number of trade partners or total country trade is kept fixed and equal to observed quantities. We show that, in the binary WTW, node-degree sequences are sufficient...

  7. Reduced inflammation accompanies diminished myelin damage and repair in the NG2 null mouse spinal cord

    Directory of Open Access Journals (Sweden)

    Kucharova Karolina

    2011-11-01

    Full Text Available Abstract Background Multiple sclerosis (MS is a demyelinating disease in which blood-derived immune cells and activated microglia damage myelin in the central nervous system. While oligodendrocyte progenitor cells (OPCs are essential for generating oligodendrocytes for myelin repair, other cell types also participate in the damage and repair processes. The NG2 proteoglycan is expressed by OPCs, pericytes, and macrophages/microglia. In this report we investigate the effects of NG2 on these cell types during spinal cord demyelination/remyelination. Methods Demyelinated lesions were created by microinjecting 1% lysolecithin into the lumbar spinal cord. Following demyelination, NG2 expression patterns in wild type mice were studied via immunostaining. Immunolabeling was also used in wild type and NG2 null mice to compare the extent of myelin damage, the kinetics of myelin repair, and the respective responses of OPCs, pericytes, and macrophages/microglia. Cell proliferation was quantified by studies of BrdU incorporation, and cytokine expression levels were evaluated using qRT-PCR. Results The initial volume of spinal cord demyelination in wild type mice is twice as large as in NG2 null mice. However, over the ensuing 5 weeks there is a 6-fold improvement in myelination in wild type mice, versus only a 2-fold improvement in NG2 null mice. NG2 ablation also results in reduced numbers of each of the three affected cell types. BrdU incorporation studies reveal that reduced cell proliferation is an important factor underlying NG2-dependent decreases in each of the three key cell populations. In addition, NG2 ablation reduces macrophage/microglial cell migration and shifts cytokine expression from a pro-inflammatory to anti-inflammatory phenotype. Conclusions Loss of NG2 expression leads to decreased proliferation of OPCs, pericytes, and macrophages/microglia, reducing the abundance of all three cell types in demyelinated spinal cord lesions. As a result

  8. null Erosional Landforms, null Images

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The hydrologic system, which includes all possible paths of motion of Earth's near-surface fluids including air and water, is largely responsible for the variety of...

  9. null Seismic Creep, null Images

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Seismic creep is the constant or periodic movement on a fault as contrasted with the sudden rupture associated with an earthquake. It is a usually slow deformation...

  10. GSTT1 Null Genotype Significantly Increases the Susceptibility to Urinary System Cancer: Evidences from 63,876 Subjects

    Science.gov (United States)

    Wang, Ying; He, Jing; Ma, Tian-Jiao; Lei, Wei; Li, Feng; Shen, Han; Shen, Zhen-Ya

    2016-01-01

    GSTT1 gene plays an important role in detoxification and clearance of reactive oxygen species(ROS). A null variant in this gene has been demonstrated to confer cancer susceptibility. Although many studies have demonstrated the association between GSTT1 null polymorphism and urinary system cancer susceptibility, several publications reported opposite conclusions. For better understanding the effects of this polymorphism on the risk of urinary system cancer, a updated meta-analysis was performed with a total of 26,666 cases and 37,210 controls extracted from 117 studies, by following the latest meta-analysis guidelines (PRISMA). The results suggested that the GSTT1 null genotype was significantly associated with an increased risk of urinary system cancer (OR=1.13, 95%CI=1.05-1.22). Furthermore, stratified analyses by the type of cancer, ethnicity, source of control and quality score presented a significantly increased risk associated with GSTT1 null genotype in bladder and prostate cancer subgroup, Caucasians and Indians subgroup, population-based(PB) subgroup, medium quality and low quality subgroup. Overall, our meta-analysis suggested that GSTT1 null genotype is a potential cancer susceptibility variant. Well-designed and large-cohort studies are needed to confirm the association between GSTT1 null genotype and urinary system cancer risk.

  11. Concentration of electrostatic solitary waves around magnetic nulls within magnetic reconnection diffusion region: single-event-based statistics

    Science.gov (United States)

    Li, Shiyou; Zhang, Shifeng; Cai, Hong; Yu, Sufang

    2014-12-01

    It is important to study the `concentrated' electrostatic solitary waves/structures (ESWs) associated with the magnetic reconnection. In the literature published as regards this topic, very few studies have reported the observation of such a large number of ESWs in a single magnetic reconnection event. In this work, we report our observation of a large number of ESWs around the magnetic null-pairs within the magnetic reconnection ion diffusion region of Earth's magnetosphere on 10 September 2001. With more than 9,600 cases of ESWs observed around magnetic null-pairs and more than 97,600 cases observed during the ion diffusion region crossing time span, the observation of such a large number of ESWs in the diffusion region has not been reported often in published works. We further perform single-event-based statistical analysis of the characteristics of the ESWs around magnetic null-pairs. Based on the statistical result, we speculate that the two-stream instability originating from the magnetic null and traveling outward along the plasma sheet boundary layer (PSBL) is the candidate mechanism of the large number of observed ESWs. Our observation and analysis in this work suggests that even with the presence of a complex magnetic structure around a magnetic null-pair in the three-dimensional regime, concentrated ESWs can be observed. This single-reconnection-event-based statistical result of ESWs around the magnetic null-pairs can aid in understanding the microdynamics associated with three-dimensional (3D) magnetic reconnection.

  12. Three-Year Global Survey of Coronal Null Points from Potential-Field-Source-Surface (PFSS) Modeling and Solar Dynamics Observatory (SDO) Observations

    Science.gov (United States)

    Freed, M. S.; Longcope, D. W.; McKenzie, D. E.

    2015-02-01

    This article compiles and examines a comprehensive coronal magnetic-null-point survey created by potential-field-source-surface (PFSS) modeling and Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) observations. The locations of 582 potential magnetic null points in the corona were predicted from the PFSS model between Carrington Rotations (CR) 2098 (June 2010) and 2139 (July 2013). These locations were manually inspected, using contrast-enhanced SDO/AIA images in 171 Å at the East and West solar limb, for structures associated with nulls. A Kolmogorov-Smirnov (K-S) test showed a statistically significant difference between observed and predicted latitudinal distributions of null points. This finding is explored further to show that the observability of null points could be affected by the Sun's asymmetric hemisphere activity. Additional K-S tests show no effect on observability related to eigenvalues associated with the fan and spine structure surrounding null points or to the orientation of the spine. We find that approximately 31 % of nulls obtained from the PFSS model were observed in SDO/AIA images at one of the solar limbs. An observed null on the East solar limb had a 51.6 % chance of being observed on the West solar limb. Predicted null points going back to CR 1893 (March 1995) were also used for comparing radial and latitudinal distributions of nulls to previous work and to test for correlation of solar activity to the number of predicted nulls.

  13. Fast beating null strip during the reflection of pulsed Gaussian beams incident at the Rayleigh angle.

    Science.gov (United States)

    Declercq, Nico F

    2006-12-22

    It is well known that harmonic bounded Gaussian beams undergo a transformation into two bounded beams upon reflection on a solid immersed in a liquid. The effect is known as the Schoch effect and can be found at the Rayleigh angle for thick plates and at the different Lamb angles for thin plates. Here, a study is made on the effect of pulsed Gaussian beams reflected on solids. It is found experimentally that the Rayleigh wave phenomenon still generates two reflected bounded beams, whereas Lamb wave phenomena do not generate this effect. This fact may be explained intuitively by realizing that the Rayleigh phenomenon is a coincidental phenomenon that is generated in situ, whereas the Lamb wave phenomenon is a non-coincidental phenomenon that is generated only after incident sound is influenced by both sides of a thin plate. Another explanation is the fact that Rayleigh waves are not dispersive, whereas stimulation and propagation of Lamb waves is frequency dependent. A pulse contains many frequencies and therefore only a fraction of the incident pulse is transformed into a Lamb wave. In this paper, numerical simulations are performed that show that actually the Schoch effect does occur neither for Rayleigh waves, nor for Lamb waves. As a matter of fact, a pulse, incident at the Rayleigh angle, generates two reflected lobes with a null zone of a different kind. The null zone is beating several times during the passage of each pulse. This results in a 'null zone' having a lower mean intensity than any of the two lobes, still less outspoken than for the case of harmonic incident bounded beams. This effect does only occur for Rayleigh wave generation and is much less outspoken for Lamb wave generation. PMID:16815510

  14. A critical discussion of null hypothesis significance testing and statistical power analysis within psychological research

    DEFF Research Database (Denmark)

    Jones, Allan; Sommerlund, Bo

    2007-01-01

    The uses of null hypothesis significance testing (NHST) and statistical power analysis within psychological research are critically discussed. The article looks at the problems of relying solely on NHST when dealing with small and large sample sizes. The use of power-analysis in estimating...... the potential error introduced by small and large samples is advocated. Power analysis is not recommended as a replacement to NHST but as an additional source of information about the phenomena under investigation. Moreover, the importance of conceptual analysis in relation to statistical analysis of hypothesis...

  15. Wilson loop remainder function for null polygons in the limit of self-crossing

    CERN Document Server

    Dorn, Harald

    2011-01-01

    The remainder function of Wilson loops for null polygons becomes divergent if two vertices approach each other. We apply RG techniques to the limiting configuration of a contour with self-intersection. As a result for the two loop remainder we find a quadratic divergence in the logarithm of the distance between the two approaching vertices. The divergence is multiplied by a factor, which is given by a pure number plus the product of two logarithms of cross-ratios characterising the conformal geometry of the self-crossing.

  16. Testing the null hypothesis of the nonexistence of a preseizure state

    International Nuclear Information System (INIS)

    A rapidly growing number of studies deals with the prediction of epileptic seizures. For this purpose, various techniques derived from linear and nonlinear time series analysis have been applied to the electroencephalogram of epilepsy patients. In none of these works, however, the performance of the seizure prediction statistics is tested against a null hypothesis, an otherwise ubiquitous concept in science. In consequence, the evaluation of the reported performance values is problematic. Here, we propose the technique of seizure time surrogates based on a Monte Carlo simulation to remedy this deficit

  17. Impaired Thermogenesis and a Molecular Signature for Brown Adipose Tissue in Id2 Null Mice

    OpenAIRE

    Peng Zhou; Maricela Robles-Murguia; Deepa Mathew; Duffield, Giles E.

    2016-01-01

    Inhibitor of DNA binding 2 (ID2) is a helix-loop-helix transcriptional repressor rhythmically expressed in many adult tissues. Our previous studies have demonstrated that Id2 null mice have sex-specific elevated glucose uptake in brown adipose tissue (BAT). Here we further explored the role of Id2 in the regulation of core body temperature over the circadian cycle and the impact of Id2 deficiency on genes involved in insulin signaling and adipogenesis in BAT. We discovered a reduced core body...

  18. The spacetime outside a source of gravitational radiation: The axially symmetric null fluid

    CERN Document Server

    Herrera, L; Ospino, J

    2016-01-01

    We carry out a study of the exterior of an axially and reflection symmetric source of gravitational radiation. The exterior of such a source is filled with a null fluid produced by the dissipative processes inherent to the emission of gravitational radiation, thereby representing a generalization of the Vaidya metric for axially and reflection symmetric spacetimes. The role of the vorticity, and its relationship with the presence of gravitational radiation is put in evidence. The spherically symmetric case (Vaidya) is, asymptotically, recovered within the context of the $1+3$ formalism.

  19. Phase Closure Nulling: A "Lyot Mask" on correlated flux of stars

    Science.gov (United States)

    Duvert, G.; Chelli, A.; Malbet F.; Kern, P.

    2010-10-01

    "Phase closure nulling" (PCN in short) is a technique which consists of observing fully resolved stars around the spatial frequency regions where the interferometric visibility amplitude is close to zero. Chelli et al. (2009) have shown that the phase closure in these regions is dominated by the signature of close and faint companions (if present), as if a "Lyot mask" was blocking the correlated flux of the star. This contribution will present the theory of PCN and results obtained on recent AMBER/VLTI and CHARA/MIRC observations, showing the high detection dynamics achieved by this observational technique.

  20. Cassegrainian/Gregorian-type null correctors for surface measurements of radio telescope reflectors.

    Science.gov (United States)

    Greve, A

    1997-08-01

    The (sub)millimeter wavelength radio observatory of the next generation will probably be an interferometer array of some 50 telescopes with parabolic reflectors 10-15 m in diameter. At this scale of mass production it is convenient to have at hand for workshop assembly a reflector surface measurement technique that is precise and easy to operate. We discuss the possibility of reflector measurements based on 10.6-microm CO2 laser interferometry using Cassegrainian/Gregorian-type null correctors. PMID:18259343

  1. Comments on correlation functions of large spin operators and null polygonal Wilson loops

    International Nuclear Information System (INIS)

    We discuss the relation between correlation functions of twist-two large spin operators and expectation values of Wilson loops along light-like trajectories. After presenting some heuristic field theoretical arguments suggesting this relation, we compute the divergent part of the correlator in the limit of large 't Hooft coupling and large spins, using a semi-classical world-sheet which asymptotically looks like a GKP rotating string. We show this diverges as expected from the expectation value of a null Wilson loop, namely, as (lnμ−2)2, μ being a cut-off of the theory.

  2. Estimation of Neutral Density in Edge Plasma with Double Null Configuration in EAST%Estimation of Neutral Density in Edge Plasma with Double Null Configuration in EAST

    Institute of Scientific and Technical Information of China (English)

    张凌; 常加峰; 张炜; 李颖颖; 钱金平; 徐国盛; 丁斯晔; 高伟; 吴振伟; 陈颖杰; 黄娟; 刘晓菊; 臧庆

    2011-01-01

    In this work, population coefficients of hydrogen's n = 3 excited state from the hydrogen collisional-radiative (CR) model, from the data file of DEGAS 2, are used to calculate the photon emissivity coefficients (PECs) of hydrogen Balmer-α (n = 3 →n = 2) (Hα). The results are compared with the PECs from Atomic Data and Analysis Structure (ADAS) database, and a good agreement is found. A magnetic surface-averaged neutral density profile of typical double-null (DN) plasma in EAST is obtained by using FRANTIC, the 1.5-D fluid transport code. It is found that the sum of integral Dα and Hα emission intensity calculated via the neutral density agrees with the measured results obtained by using the absolutely calibrated multi-channel poloidal photodiode array systems viewing the lower divertor at the last closed flux surface (LCFS). It is revealed that the typical magnetic surface-averaged neutral density at LCFS is about 3.5×10^16 m^-3 .

  3. Null Models and Modularity Based Community Detection in Multi-Layer Networks

    CERN Document Server

    Paul, Subhadeep

    2016-01-01

    Multi-layer networks are networks on a set of entities (nodes) with multiple types of relations (edges) among them where each type of relation/interaction is represented as a network layer. As with single layer networks, community detection is an important task in multi-layer networks. A large group of popular community detection methods in networks are based on optimizing a quality function known as the modularity score, which is a measure of presence of modules or communities in networks. Hence a first step in community detection is defining a suitable modularity score that is appropriate for the network in question. Here we introduce several multi-layer network modularity measures under different null models of the network, motivated by empirical observations in networks from a diverse field of applications. In particular we define the multi-layer configuration model, the multi-layer expected degree model and their various modifications as null models for multi-layer networks to derive different modulariti...

  4. GPS Jamming: Strengthening Anti Jam GPS System with Adaptive Phase Only Nulling Using Cuckoo Search

    Directory of Open Access Journals (Sweden)

    V. Thyagarajan

    2014-08-01

    Full Text Available Global Positioning System (GPS signals are spread spectrum, modulated with very low average power caused by background noise. Signal received is mostly 165 dB down than thermal noise level. Such signals are easily jammed either through intentional noise sources (jammer or unintentionally from broadcasting stations harmonics or other out of band sources. This study proposes to reveal how a nulling antenna with adaptive spatial filtering technique can efficiently mitigate intentional and non-intentional interference. A beam forming antenna array is an antennas set whose outputs are weighted by complex values and combined form array output. The complex valued weights effect is to steer the array pattern’s main lobes to desired directions which may be unknown and hence antenna weights are adjusted adaptively till some array performance measure is improved, revealing proper lobe or null placement. This study proposes a Cuckoo Search (CS algorithm based new optimization method for multiple interference cancellation design that increases gain to desired signal and improves jamming rejection performance.

  5. Nulling Data Reduction and On-sky Performance of the Large Binocular Telescope Interferometer

    Science.gov (United States)

    Defrère, D.; Hinz, P. M.; Mennesson, B.; Hoffmann, W. F.; Millan-Gabet, R.; Skemer, A. J.; Bailey, V.; Danchi, W. C.; Downey, E. C.; Durney, O.; Grenz, P.; Hill, J. M.; McMahon, T. J.; Montoya, M.; Spalding, E.; Vaz, A.; Absil, O.; Arbo, P.; Bailey, H.; Brusa, G.; Bryden, G.; Esposito, S.; Gaspar, A.; Haniff, C. A.; Kennedy, G. M.; Leisenring, J. M.; Marion, L.; Nowak, M.; Pinna, E.; Powell, K.; Puglisi, A.; Rieke, G.; Roberge, A.; Serabyn, E.; Sosa, R.; Stapeldfeldt, K.; Su, K.; Weinberger, A. J.; Wyatt, M. C.

    2016-06-01

    The Large Binocular Telescope Interferometer (LBTI) is a versatile instrument designed for high angular resolution and high-contrast infrared imaging (1.5–13 μm). In this paper, we focus on the mid-infrared (8–13 μm) nulling mode and present its theory of operation, data reduction, and on-sky performance as of the end of the commissioning phase in 2015 March. With an interferometric baseline of 14.4 m, the LBTI nuller is specifically tuned to resolve the habitable zone of nearby main-sequence stars, where warm exozodiacal dust emission peaks. Measuring the exozodi luminosity function of nearby main-sequence stars is a key milestone to prepare for future exo-Earth direct imaging instruments. Thanks to recent progress in wavefront control and phase stabilization, as well as in data reduction techniques, the LBTI demonstrated in 2015 February a calibrated null accuracy of 0.05% over a 3 hr long observing sequence on the bright nearby A3V star β Leo. This is equivalent to an exozodiacal disk density of 15–30 zodi for a Sun-like star located at 10 pc, depending on the adopted disk model. This result sets a new record for high-contrast mid-infrared interferometric imaging and opens a new window on the study of planetary systems.

  6. Cdk2-Null Mice Are Resistant to ErbB-2-Induced Mammary Tumorigenesis

    Directory of Open Access Journals (Sweden)

    Dipankar Ray

    2011-05-01

    Full Text Available The concept of targeting G1 cyclin-dependent kinases (CDKs in breast cancer treatments is supported by the fact that the genetic ablation of Cdk4 had minimal impacts on normal cell proliferation in majority of cell types, resulting in near-normal mouse development, whereas such loss of Cdk4 completely abrogated ErbB-2/neu-induced mammary tumorigenesis in mice. In most human breast cancer tissues, another G1-regulatory CDK, CDK2, is also hyperactivated by various mechanisms and is believed to be an important therapeutic target. In this report, we provide genetic evidence that CDK2 is essential for proliferation and oncogenesis of murine mammary epithelial cells. We observed that 87% of Cdk2-null mice were protected from ErbB-2-induced mammary tumorigenesis. Mouse embryonic fibroblasts isolated from Cdk2-null mouse showed resistance to various oncogene-induced transformation. Previously, we have reported that hemizygous loss of Cdc25A, the major activator of CDK2, can also protect mice from ErbB-2-induced mammary tumorigenesis [Cancer Res (2007 67(14: 6605–11]. Thus, we propose that CDC25A-CDK2 pathway is critical for the oncogenic action of ErbB-2 in mammary epithelial cells, in a manner similar to Cyclin D1/CDK4 pathway.

  7. Thrombospondin 2-null mice display an altered brain foreign body response to polyvinyl alcohol sponge implants

    Energy Technology Data Exchange (ETDEWEB)

    Tian Weiming; Kyriakides, Themis R, E-mail: themis.kyriakides@yale.ed [Vascular Biology and Therapeutics Program, Departments of Pathology and Biomedical Engineering, Yale University, New Haven, CT 06519 (United States)

    2009-02-15

    Thrombospondin (TSP)-2 is a matricellular protein that participates in the processes of tissue repair and the foreign body response. In addition, TSP2 has been shown to influence synaptogenesis and recovery of the brain following stroke. In the present study we investigated the response following the implantation of polyvinyl alcohol (PVA) sponges in the brain. PVA sponges were implanted into the brain cortex of wild type and TSP2-null mice for a period of 4 and 8 weeks and the response was analyzed by histochemistry and quantitative immunohistochemistry. TSP2 expression was detected in the interstices of the sponge and co-localized with the extracellular matrix and astrocytes. PVA sponge invasion in TSP2-null mice was characterized by dense deposition of extracellular matrix and increased invasion of reactive astrocytes and macrophages/microglia. Furthermore, the angiogenic response was elevated and the detection of mouse serum albumin (MSA) in the brain cortex indicated excessive vessel leakage, suggesting that TSP2 plays a role in the repair/maintenance of the blood brain barrier. Finally, immunostaining demonstrated an increase in the levels of matrix metalloproteinase (MMP)-2 and MMP-9. Taken together, our observations support a role for TSP2 as critical determinant of the brain response to biomaterials.

  8. Telescopes in Near Space: Balloon Exoplanet Nulling Interferometer (BigBENI)

    Science.gov (United States)

    Lyon, Richard G.; Clampin, Mark; Petrone, Peter; Mallik, Udayan; Mauk, Robin

    2012-01-01

    A significant and often overlooked path to advancing both science and technology for direct imaging and spectroscopic characterization of exosolar planets is to fly "near space" missions, i.e. balloon borne exosolar missions. A near space balloon mission with two or more telescopes, coherently combined, is capable of achieving a subset of the mission science goals of a single large space telescope at a small fraction of the cost. Additionally such an approach advances technologies toward flight readiness for space flight. Herein we discuss the feasibility of flying two 1.2 meter telescopes, with a baseline separation of 3.6 meters, operating in visible light, on a composite boom structure coupled to a modified visible nulling coronagraph operating to achieve an inner working angle of 60 milli-arcseconds. We discuss the potential science return, atmospheric residuals at 135,000 feet, pointing control and visible nulling and evaluate the state-or-art of these technologies with regards to balloon missions.

  9. Optimized scheduling technique of null subcarriers for peak power control in 3GPP LTE downlink.

    Science.gov (United States)

    Cho, Soobum; Park, Sang Kyu

    2014-01-01

    Orthogonal frequency division multiple access (OFDMA) is a key multiple access technique for the long term evolution (LTE) downlink. However, high peak-to-average power ratio (PAPR) can cause the degradation of power efficiency. The well-known PAPR reduction technique, dummy sequence insertion (DSI), can be a realistic solution because of its structural simplicity. However, the large usage of subcarriers for the dummy sequences may decrease the transmitted data rate in the DSI scheme. In this paper, a novel DSI scheme is applied to the LTE system. Firstly, we obtain the null subcarriers in single-input single-output (SISO) and multiple-input multiple-output (MIMO) systems, respectively; then, optimized dummy sequences are inserted into the obtained null subcarrier. Simulation results show that Walsh-Hadamard transform (WHT) sequence is the best for the dummy sequence and the ratio of 16 to 20 for the WHT and randomly generated sequences has the maximum PAPR reduction performance. The number of near optimal iteration is derived to prevent exhausted iterations. It is also shown that there is no bit error rate (BER) degradation with the proposed technique in LTE downlink system.

  10. FAILURE CORRECTION OF LINEAR ARRAY ANTENNA WITH MULTIPLE NULL PLACEMENT USING CUCKOO SEARCH ALGORITHM

    Directory of Open Access Journals (Sweden)

    R. Muralidaran

    2014-03-01

    Full Text Available The influence of evolutionary algorithms enhanced its scope of getting its existence in almost every complex optimization problems. In this paper, cuckoo search algorithm, an algorithm based on the brood parasite behavior along with Levy weights has been proposed for the radiation pattern correction of a linear array of isotropic antennas with uniform spacing when failed with more than one antenna element. Even though deterioration produced by the failure of antenna elements results in various undesirable effects, consideration in this paper is given to the correction of side lobe level and null placement at two places. Various articles in the past have already shown that the idea to correct the radiation pattern is to alter the amplitude weights of the remaining unfailed elements, instead of replacing the faulty elements. This approach is made use of modifying the current excitations of unfailed elements using cuckoo search algorithm such that the resulting radiation pattern is similar to the unfailed original pattern in terms of side lobe level and null placement at two places. Examples shown in this paper demonstrate the effectiveness of this algorithm in achieving the desired objectives.

  11. On the Apparent Nulls and Extreme Variability of PSR J1107-5907

    CERN Document Server

    Young, N J; Stappers, B W; Lyne, A G; Kramer, M

    2014-01-01

    We present an analysis of the emission behaviour of PSR J1107-5907, a source known to exhibit separate modes of emission, using observations obtained over approximately 10 yr. We find that the object exhibits two distinct modes of emission; a strong mode with a broad profile and a weak mode with a narrow profile. During the strong mode of emission, the pulsar typically radiates very energetic emission over sequences of ~200-6000 pulses (~60 s-24 min), with apparent nulls over time-scales of up to a few pulses at a time. Emission during the weak mode is observed outside of these strong-mode sequences and manifests as occasional bursts of up to a few clearly detectable pulses at a time, as well as low-level underlying emission which is only detected through profile integration. This implies that the previously described null mode may in fact be representative of the bottom-end of the pulse intensity distribution for the source. This is supported by the dramatic pulse-to-pulse intensity modulation and rarity of ...

  12. Accuracy analysis of the Null-Screen method for the evaluation of flat heliostats

    Science.gov (United States)

    Cebrian-Xochihuila, P.; Huerta-Carranza, O.; Díaz-Uribe, R.

    2016-04-01

    In this work we develop an algorithm to determinate the accuracy of the Null-Screen Method, used for the testing of flat heliostats used as solar concentrators in a central tower configuration. We simulate the image obtained on a CCD camera when an orderly distribution of points are displayed on a Null-Screen perpendicular to the heliostat under test. The deformations present in the heliostat are represented as a cosine function of the position with different periods and amplitudes. As a resolution criterion, a deformation on the mirror can be detected when the differences in position between the spots on the image plane for the deformed surface as compared with those obtained for an ideally flat heliostat are equal to one pixel. For 6.4μm pixel size and 18mm focal length, the minimum deformation we can measure in the heliostat, correspond to amplitude equal a 122μm for a period equal to 1m; this is equivalent to 0.8mrad in slope. This result depends on the particular configuration used during the test and the size of the heliostat.

  13. Seizure phenotypes, periodicity, and sleep-wake pattern of seizures in Kcna-1 null mice.

    Science.gov (United States)

    Wright, Samantha; Wallace, Eli; Hwang, Youngdeok; Maganti, Rama

    2016-02-01

    This study was undertaken to describe seizure phenotypes, natural progression, sleep-wake patterns, as well as periodicity of seizures in Kcna-1 null mutant mice. These mice were implanted with epidural electroencephalography (EEG) and electromyography (EMG) electrodes, and simultaneous video-EEG recordings were obtained while animals were individually housed under either diurnal (LD) condition or constant darkness (DD) over ten days of recording. The video-EEG data were analyzed to identify electrographic and behavioral phenotypes and natural progression and to examine the periodicity of seizures. Sleep-wake patterns were analyzed to understand the distribution and onset of seizures across the sleep-wake cycle. Four electrographically and behaviorally distinct seizure types were observed. Regardless of lighting condition that animals were housed in, Kcna-1 null mice initially expressed only a few of the most severe seizure types that progressively increased in frequency and decreased in seizure severity. In addition, a circadian periodicity was noted, with seizures peaking in the first 12h of the Zeitgeber time (ZT) cycle, regardless of lighting conditions. Interestingly, seizure onset differed between lighting conditions where more seizures arose out of sleep in LD conditions, whereas under DD conditions, the majority occurred out of the wakeful state. We suggest that this model be used to understand the circadian pattern of seizures as well as the pathophysiological implications of sleep and circadian disturbances in limbic epilepsies. PMID:26724401

  14. Identifying the null subject: evidence from event-related brain potentials.

    Science.gov (United States)

    Demestre, J; Meltzer, S; García-Albea, J E; Vigil, A

    1999-05-01

    Event-related brain potentials (ERPs) were recorded during spoken language comprehension to study the on-line effects of gender agreement violations in controlled infinitival complements. Spanish sentences were constructed in which the complement clause contained a predicate adjective marked for syntactic gender. By manipulating the gender of the antecedent (i.e., the controller) of the implicit subject while holding constant the gender of the adjective, pairs of grammatical and ungrammatical sentences were created. The detection of such a gender agreement violation would indicate that the parser had established the coreference relation between the null subject and its antecedent. The results showed a complex biphasic ERP (i.e., an early negativity with prominence at anterior and central sites, followed by a centroparietal positivity) in the violating condition as compared to the non-violating conditions. The brain reacts to NP-adjective gender agreement violations within a few hundred milliseconds of their occurrence. The data imply that the parser has properly coindexed the null subject of an infinitive clause with its antecedent. PMID:10344021

  15. Achieving Data Privacy through Secrecy Views and Null-Based Virtual Updates

    CERN Document Server

    Bertossi, Leopoldo

    2011-01-01

    There may be sensitive information in a relational database, and we might want to keep it hidden from a user or group thereof. In this work, sensitive data is characterized as the contents of a set of secrecy views. For a user without permission to access that sensitive data, the database instance he queries is updated to make the contents of the views empty or contain only tuples with null values. In particular, if this user poses a query about any of these views, no meaningful information is returned. Since the database is not expected to be physically changed to produce this result, the updates are only virtual. And also minimal in a precise way. These minimal updates are reflected in the secrecy view contents, and also in the fact that query answers, while being privacy preserving, are also maximally informative. Virtual updates are based on the use of null values as used in the SQL standard. We provide the semantics of secrecy views and the virtual updates. The different ways in which the underlying data...

  16. Biological and genetic properties of the p53 null preneoplastic mammary epithelium

    Science.gov (United States)

    Medina, Daniel; Kittrell, Frances S.; Shepard, Anne; Stephens, L. Clifton; Jiang, Cheng; Lu, Junxuan; Allred, D. Craig; McCarthy, Maureen; Ullrich, Robert L.

    2002-01-01

    The absence of the tumor suppressor gene p53 confers an increased tumorigenic risk for mammary epithelial cells. In this report, we describe the biological and genetic properties of the p53 null preneoplastic mouse mammary epithelium in a p53 wild-type environment. Mammary epithelium from p53 null mice was transplanted serially into the cleared mammary fat pads of p53 wild-type BALB/c female to develop stable outgrowth lines. The outgrowth lines were transplanted for 10 generations. The outgrowths were ductal in morphology and progressed through ductal hyperplasia and ductal carcinoma in situ before invasive cancer. The preneoplastic outgrowth lines were immortal and exhibited activated telomerase activity. They are estrogen and progesterone receptor-positive, and aneuploid, and had various levels of tumorigenic potential. The biological and genetic properties of these lines are distinct from those found in most hyperplastic alveolar outgrowth lines, the form of mammary preneoplasia occurring in most traditional models of murine mammary tumorigenesis. These results indicate that the preneoplastic cell populations found in this genetically engineered model are similar in biological properties to a subset of precurser lesions found in human breast cancer and provide a unique model to identify secondary events critical for tumorigenicity and invasiveness.

  17. Nulling Data Reduction and On-Sky Performance of the Large Binocular Telescope Interferometer

    CERN Document Server

    Defrère, D; Mennesson, B; Hoffmann, W F; Millan-Gabet, R; Skemer, A J; Bailey, V; Danchi, W C; Downey, E C; Durney, O; Grenz, P; Hill, J M; McMahon, T J; Montoya, M; Spalding, E; Vaz, A; Absil, O; Arbo, P; Bailey, H; Brusa, G; Bryden, G; Esposito, S; Gaspar, A; Haniff, C A; Kennedy, G M; Leisenring, J M; Marion, L; Nowak, M; Pinna, E; Powell, K; Puglisi, A; Rieke, G; Roberge, A; Serabyn, E; Sosa, R; Stapeldfeldt, K; Su, K; Weinberger, A J; Wyatt, M C

    2016-01-01

    The Large Binocular Telescope Interferometer (LBTI) is a versatile instrument designed for high-angular resolution and high-contrast infrared imaging (1.5-13 microns). In this paper, we focus on the mid-infrared (8-13 microns) nulling mode and present its theory of operation, data reduction, and on-sky performance as of the end of the commissioning phase in March 2015. With an interferometric baseline of 14.4 meters, the LBTI nuller is specifically tuned to resolve the habitable zone of nearby main-sequence stars, where warm exozodiacal dust emission peaks. Measuring the exozodi luminosity function of nearby main-sequence stars is a key milestone to prepare for future exoEarth direct imaging instruments. Thanks to recent progress in wavefront control and phase stabilization, as well as in data reduction techniques, the LBTI demonstrated in February 2015 a calibrated null accuracy of 0.05% over a three-hour long observing sequence on the bright nearby A3V star beta Leo. This is equivalent to an exozodiacal dis...

  18. Modular Hamiltonians for Deformed Half-Spaces and the Averaged Null Energy Condition

    CERN Document Server

    Faulkner, Thomas; Parrikar, Onkar; Wang, Huajia

    2016-01-01

    We study modular Hamiltonians corresponding to the vacuum state for deformed half-spaces in relativistic quantum field theories on $\\mathbb{R}^{1,d-1}$. We show that in addition to the usual boost generator, there is a contribution to the modular Hamiltonian at first order in the shape deformation, proportional to the integral of the null components of the stress tensor along the Rindler horizon. We use this fact along with monotonicity of relative entropy to prove the averaged null energy condition in Minkowski space-time. This subsequently gives a new proof of the Hofman-Maldacena bounds on the parameters appearing in CFT three-point functions. Our main technical advance involves adapting newly developed perturbative methods for calculating entanglement entropy to the problem at hand. These methods were recently used to prove certain results on the shape dependence of entanglement in CFTs and here we generalize these results to excited states and real time dynamics. We also discuss the AdS/CFT counterpart o...

  19. P63 null mutation protects mouse oocytes from radio-induced apoptosis

    Energy Technology Data Exchange (ETDEWEB)

    Livera, G.; Petre-Lazar, B.; Guerquin, M.J.; Trautmann, E.; Coffigny, H.; Habert, R. [CEA, DSV/DRR/SEGG/LDRG, Unit Gametogenesis et Genotoxic, F-92265 Fontenay Aux Roses (France); Univ Paris 07 Denis Diderot, UFR Biol, UMR S 566, F-92265 Fontenay Aux Roses (France); INSERM, U566, F-92265 Fontenay Aux Roses (France)

    2008-07-01

    Female fertility in mammals is determined by the pool of primordial follicles and low doses of radiation induce a major loss of primordial follicles in the ovary. We investigated the expression of p53 and its homologues, p63 and p73, in the normal and irradiated neonatal ovary. p63 was the only member of the p53 family detected in oocyte nucleus. No p63 transcripts or protein were detected in the early foetal ovary. p63 production began in late pachytene-stage oocytes and peaked in diplotene oocytes in mice and humans. The production of p63 was correlated with meiotic DNA double-strand break repair. Only trans-activation (TA) isoforms were present in the ovary, with TAp63 alpha by far the most abundant in terms of mRNA and protein levels. Complete p63 null mutation did not affect normal ovary development. Irradiation rapidly triggered p63 phosphorylation. p63 null mutation prevented the cleavage of caspases-9 and -3 and the follicle loss induced by ionizing radiation. Thus, our results evidence that irradiation-induced depletion of the primordial follicle pool results from the activation of p63 in quiescent oocytes. (authors)

  20. Neto2-null mice have impaired GABAergic inhibition and are susceptible to seizures

    Directory of Open Access Journals (Sweden)

    Vivek eMahadevan

    2015-09-01

    Full Text Available Neto2 is a transmembrane protein that interacts with the neuron-specific K+-Cl- cotransporter (KCC2 in the CNS. Efficient KCC2 transport is essential for setting the neuronal Cl- gradient, which is required for fast GABAergic inhibition. Neto2 is required to maintain the normal abundance of KCC2 in neurons, and increases KCC2 function by binding to the active oligomeric form of this cotransporter. In the present study we characterized GABAergic inhibition and KCC2-mediated neuronal chloride homeostasis in pyramidal neurons from adult hippocampal slices. Using gramicidin perforated patch clamp recordings we found that the reversal potential for GABA (EGABA was significantly depolarized. We also observed that surface levels of KCC2 and phosphorylation of KCC2 serine 940 (Ser940 were reduced in Neto2-/- neurons compared to wild-type controls. To examine GABAergic inhibition we recorded spontaneous inhibitory postsynaptic currents (sIPSCs and found that Neto2-/- neurons had significant reductions in both their amplitude and frequency. Based on the critical role of Neto2 in regulating GABAergic inhibition we rationalized that Neto2-null mice would be prone to seizure activity. We found that Neto2-null mice demonstrated a decrease in the latency to pentylenetetrazole (PTZ-induced seizures and an increase in seizure severity.

  1. Towards a stable and absolute atmospheric carbon dioxide instrument using spectroscopic null method

    Directory of Open Access Journals (Sweden)

    B. Xiang

    2013-02-01

    Full Text Available We present a novel spectral method to measure atmospheric carbon dioxide (CO2 with high precision and stability without resorting to calibration tanks during long-term operation. This spectral null method improves precision by reducing spectral proportional noise associated with laser emission instabilities. We employ sealed quartz cells with known CO2 column densities to serve as the permanent internal references in the null method, which improve the instrument's stability and accuracy. A prototype instrument – ABsolute Carbon dioxide (ABC is developed using this new approach. The instrument has one-second precision of 0.02 ppm, which averages down to 0.007 ppm within one minute. Long-term stability of within 0.1 ppm is achieved without any calibrations for over a one-month period. These results have the potential for eliminating the need for calibration cylinders for high accuracy field measurements of carbon dioxide.

  2. Improving the quantitative testing of fast aspherics surfaces with null screen using Dijkstra algorithm

    Science.gov (United States)

    Moreno Oliva, Víctor Iván; Castañeda Mendoza, Álvaro; Campos García, Manuel; Díaz Uribe, Rufino

    2011-09-01

    The null screen is a geometric method that allows the testing of fast aspherical surfaces, this method measured the local slope at the surface and by numerical integration the shape of the surface is measured. The usual technique for the numerical evaluation of the surface is the trapezoidal rule, is well-known fact that the truncation error increases with the second power of the spacing between spots of the integration path. Those paths are constructed following spots reflected on the surface and starting in an initial select spot. To reduce the numerical errors in this work we propose the use of the Dijkstra algorithm.1 This algorithm can find the shortest path from one spot (or vertex) to another spot in a weighted connex graph. Using a modification of the algorithm it is possible to find the minimal path from one select spot to all others ones. This automates and simplifies the integration process in the test with null screens. In this work is shown the efficient proposed evaluating a previously surface with a traditional process.

  3. Null Aether Theory: $pp$-Wave and AdS Wave Solutions

    CERN Document Server

    Gurses, Metin

    2016-01-01

    General quantum gravity arguments predict that Lorentz symmetry might not hold exactly in nature. This has motivated much interest in Lorentz breaking gravity theories recently. Among such models are vector-tensor theories with preferred direction established at every point of spacetime by a fixed-norm vector field. The dynamical vector field defined in this way is referred to as the aether. In this work, we study plane wave metrics in such a theory. For this purpose, we assume that the aether field is a null vector field satisfying certain conditions--we refer to the theory constructed in this way as Null Aether Theory (NAT). Assuming the Kerr-Schild form for such metrics we show that the theory admits exact plane wave solutions in any dimension $D\\geq3$. The field equations are reduced to two, in general coupled, differential equations when the background metric assumes the maximally symmetric form. Specifically, when the background metric is flat, i.e. for the $pp$-wave spacetimes, these equations decouple...

  4. A robust statistical method to detect null alleles in microsatellite and SNP datasets in both panmictic and inbred populations.

    Science.gov (United States)

    Girard, Philippe

    2011-01-01

    Null alleles are common technical artifacts in genetic-based analysis. Powerful methods enabling their detection in either panmictic or inbred populations have been proposed. However, none of these methods appears unbiased in both types of mating systems, necessitating a priori knowledge of the inbreeding level of the population under study. To counter this problem, I propose to use the software FDist2 to detect the atypical fixation indices that characterize markers with null alleles. The rational behind this approach and the parameter settings are explained. The power of the method for various sample sizes, degrees of inbreeding and null allele frequencies is evaluated using simulated microsatellite and SNP datasets and then compared to two other null allele detection methods. The results clearly show the robustness of the method proposed here as well as its greater accuracy in both panmictic and inbred populations for both types of marker. By allowing a proper detection of null alleles for a wide range of mating systems and markers, this new method is particularly appealing for numerous genetic studies using co-dominant loci. PMID:21381434

  5. Integration of Frequency Domain Wideband Antenna Nulling and Wavenumber Domain Image Formation for Multi-Channel SAR

    Directory of Open Access Journals (Sweden)

    M. Bucciarelli

    2016-01-01

    Full Text Available A Multichannel Synthetic Aperture Radar (M-SAR exploiting an antenna nulling based Electronic Counter-Counter Measures (ECCM technique shall be able to cancel the effects of noise-like interferences over the collected SAR data. Since SAR systems often work with wide bandwidths to provide high resolution images, ECCM technique must account for the presence of wideband interference signal. In this paper we consider a wideband antenna nulling technique based on space-frequency adaptive nulling and we propose an integration of the WB antenna nulling scheme within the focusing algorithm for M-SAR systems, thus allowing a fusion between ECCM and usual SAR processing steps. The computational cost of the integrated algorithm is compared with the cost of more traditional sequence of the wideband extension of the Side-Lobe Canceller and the focusing operation, to show the computational feasibility of the proposed integrated algorithm. The possibility to perform suboptimally the space-frequency adaptive nulling is also considered.

  6. Dynamic topology and flux rope evolution during non-linear tearing of 3D null point current sheets

    Energy Technology Data Exchange (ETDEWEB)

    Wyper, P. F., E-mail: peterw@maths.dundee.ac.uk; Pontin, D. I., E-mail: dpontin@maths.dundee.ac.uk [Division of Mathematics, University of Dundee, Dundee (United Kingdom)

    2014-10-15

    In this work, the dynamic magnetic field within a tearing-unstable three-dimensional current sheet about a magnetic null point is described in detail. We focus on the evolution of the magnetic null points and flux ropes that are formed during the tearing process. Generally, we find that both magnetic structures are created prolifically within the layer and are non-trivially related. We examine how nulls are created and annihilated during bifurcation processes, and describe how they evolve within the current layer. The type of null bifurcation first observed is associated with the formation of pairs of flux ropes within the current layer. We also find that new nulls form within these flux ropes, both following internal reconnection and as adjacent flux ropes interact. The flux ropes exhibit a complex evolution, driven by a combination of ideal kinking and their interaction with the outflow jets from the main layer. The finite size of the unstable layer also allows us to consider the wider effects of flux rope generation. We find that the unstable current layer acts as a source of torsional magnetohydrodynamic waves and dynamic braiding of magnetic fields. The implications of these results to several areas of heliophysics are discussed.

  7. Three-Year Global Survey of Coronal Null Points from Potential-Field-Source-Surface (PFSS) Modeling and Solar Dynamics Observatory (SDO) Observations

    CERN Document Server

    Freed, Michael; McKenize, David

    2014-01-01

    This article compiles and examines a comprehensive coronal magnetic-null-point survey created by potential-field-source-surface (PFSS) modeling and Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) observations. The locations of 582 potential magnetic null points in the corona were predicted from the PFSS model between Carrington Rotations (CR) 2098 (June 2010) and 2139 (July 2013). These locations were manually inspected, using contrast-enhanced SDO/AIA images in 171 angstroms at the east and west solar limb, for structures associated with nulls. A Kolmogorov--Smirnov (K--S) test showed a statistically significant difference between observed and predicted latitudinal distributions of null points. This finding is explored further to show that the observability of null points could be affected by the Sun's asymmetric hemisphere activity. Additional K--S tests show no effect on observability related to eigenvalues associated with the fan and spine structure surrounding null points or to the orie...

  8. Human PTCHD3 nulls: rare copy number and sequence variants suggest a non-essential gene

    Directory of Open Access Journals (Sweden)

    Lionel Anath C

    2011-03-01

    Full Text Available Abstract Background Copy number variations (CNVs can contribute to variable degrees of fitness and/or disease predisposition. Recent studies show that at least 1% of any given genome is copy number variable when compared to the human reference sequence assembly. Homozygous deletions (or CNV nulls that are found in the normal population are of particular interest because they may serve to define non-essential genes in human biology. Results In a genomic screen investigating CNV in Autism Spectrum Disorders (ASDs we detected a heterozygous deletion on chromosome 10p12.1, spanning the Patched-domain containing 3 (PTCHD3 gene, at a frequency of ~1.4% (6/427. This finding seemed interesting, given recent discoveries on the role of another Patched-domain containing gene (PTCHD1 in ASD. Screening of another 177 ASD probands yielded two additional heterozygous deletions bringing the frequency to 1.3% (8/604. The deletion was found at a frequency of ~0.73% (27/3,695 in combined control population from North America and Northern Europe predominately of European ancestry. Screening of the human genome diversity panel (HGDP-CEPH covering worldwide populations yielded deletions in 7/1,043 unrelated individuals and those detected were confined to individuals of European/Mediterranean/Middle Eastern ancestry. Breakpoint mapping yielded an identical 102,624 bp deletion in all cases and controls tested, suggesting a common ancestral event. Interestingly, this CNV occurs at a break of synteny between humans and mouse. Considering all data, however, no significant association of these rare PTCHD3 deletions with ASD was observed. Notwithstanding, our RNA expression studies detected PTCHD3 in several tissues, and a novel shorter isoform for PTCHD3 was characterized. Expression in transfected COS-7 cells showed PTCHD3 isoforms colocalize with calnexin in the endoplasmic reticulum. The presence of a patched (Ptc domain suggested a role for PTCHD3 in various biological

  9. Sensory-motor deficits and neurofilament disorganization in gigaxonin-null mice

    Directory of Open Access Journals (Sweden)

    Boizot Alexia

    2011-04-01

    Full Text Available Abstract Background Giant Axonal Neuropathy (GAN is a fatal neurodegenerative disorder with early onset characterized by a severe deterioration of the peripheral and central nervous system, involving both the motor and the sensory tracts and leading to ataxia, speech defect and intellectual disabilities. The broad deterioration of the nervous system is accompanied by a generalized disorganization of the intermediate filaments, including neurofilaments in neurons, but the implication of this defect in disease onset or progression remains unknown. The identification of gigaxonin, the substrate adaptor of an E3 ubiquitin ligase, as the defective protein in GAN allows us to now investigate the crucial role of the gigaxonin-E3 ligase in sustaining neuronal and intermediate filament integrity. To study the mechanisms controlled by gigaxonin in these processes and to provide a relevant model to test the therapeutic approaches under development for GAN, we generated a Gigaxonin-null mouse by gene targeting. Results We investigated for the first time in Gigaxonin-null mice the deterioration of the motor and sensory functions over time as well as the spatial disorganization of neurofilaments. We showed that gigaxonin depletion in mice induces mild but persistent motor deficits starting at 60 weeks of age in the 129/SvJ-genetic background, while sensory deficits were demonstrated in C57BL/6 animals. In our hands, another gigaxonin-null mouse did not display the early and severe motor deficits reported previously. No apparent neurodegeneration was observed in our knock-out mice, but dysregulation of neurofilaments in proximal and distal axons was massive. Indeed, neurofilaments were not only more abundant but they also showed the abnormal increase in diameter and misorientation that are characteristics of the human pathology. Conclusions Together, our results show that gigaxonin depletion in mice induces mild motor and sensory deficits but recapitulates the

  10. Chemical changes in DMP1-null murine bone & silica based pecvd coatings for titanium implant osseoapplications

    Science.gov (United States)

    Maginot, Megen

    In order to improve clinical outcomes in bone-implant systems, a thorough understanding of both local bone chemistry and implant surface chemistry is necessary. This study consists, therefore, of two main parts: one focused on determining the nature of the changes in bone chemistry in a DMP1-null transgenic disease model and the other on the development of amorphous silica-based coatings for potential use as titanium bone implant coatings. For the study of bone mineral in the DMP1 transgenic model, which is known to have low serum phosphate levels, transgenic DMP1-null and wild type mice were fed a high phosphate diet, sacrificed, and had their long bone harvested. This bone was characterized using SEM, FTIR, microCT and XANES and compared to DMP1-null and wild type control groups to assess the therapeutic effect of high Pi levels on the phenotype and the role of DMP1 in mineralization in vivo. Findings suggest that though the high phosphate diet results in restoring serum phosphate levels, it does not completely rescue the bone mineral phenotype at an ultrastructural level and implicates DMP1 in phosphate nucleation. Since plasma enhanced chemical vapor deposition (PECVD) silica like coatings have not previously been fabricated for use in oessoapplications, the second part of this study initially focused on the characterization of novel SiOx chemistries fabricated via a chemical vapor deposition process that were designed specifically to act as bioactive coatings with a loose, hydrogenated structure. These coatings were then investigated for their potential initial stage response to bone tissue through immersion in a simulated body fluid and through the culture of MC3T3 cells on the coating surfaces. Coating surfaces were characterized by SEM, FTIR, contact angle measurements, and XANES. Coating dissolution and ionic release were also investigated by ICP-OES. Findings suggest that some SiOx chemistries may form a bioactive coating while more highly substituted

  11. GSTM1 null genotype in COPD and lung cancer: evidence of a modifier or confounding effect?

    Directory of Open Access Journals (Sweden)

    Young RP

    2011-09-01

    Full Text Available Robert P Young1,2, Raewyn J Hopkins1, Bryan A Hay1, Gregory D Gamble11Schools of Biological Science and Health Sciences, University of Auckland, 2Department of Medicine, Auckland City Hospital, Auckland, New ZealandBackground: Studies over the past two decades have reported associations between GSTM1 (glutathione S-transferase mu 1 null genotype and chronic obstructive pulmonary disease (COPD or lung cancer. However, a modifier or confounding effect from COPD mediating the GSTM1 association with lung cancer has not been previously explored.Aim and methods: This variant was examined in a case-control study of current or former smokers with COPD (n = 669, lung cancer (n = 454, or normal lung function (n = 488. Sex, age, and smoking history were comparable between groups.Results: The GSTM1 null genotype was found to be more frequent in smokers with COPD alone (odds ratio [OR] 1.30, 95% confidence interval [CI] 1.02–1.66, P = 0.031 and lung cancer (OR 1.26, 95% CI 0.96–1.65, P = 0.083 than in matched smokers with normal lung function (62%, 61%, and 56%, respectively. However, when smokers with lung cancer were subgrouped according to the presence of COPD, then the association with all COPD subjects (OR 1.34, 95% CI 1.07–1.70, P = 0.010 and with COPD and lung cancer (OR 1.50, 95% CI 1.06–2.12, P = 0.018 continued to be significant while that with lung cancer only was reduced (OR 1.11, 95% CI 0.78–1.56, P = 0.55. These associations were independent of age, sex, height, lung function, and smoking history.Conclusion: Findings suggest that COPD is an important subphenotype of lung cancer and may underlie previously reported associations with the GSTM1 null genotype.Keywords: lung cancer, chronic obstructive pulmonary disease, GSTM1, association study, polymorphism, copy number variant

  12. Frequency of glutathione-S-transferase null-M1 and null-T1 genotypes among the Turabah population in Saudi Arabia.

    Science.gov (United States)

    Mansour, A A; Saleh, O M; Askar, T; Salim, A M; Mergani, A

    2015-12-14

    Glutathione-S-transferases (GST) are key phase II detoxifying enzymes that play critical roles in protection against products of oxidative stress and against electrophiles. Glutathione S-transferase mu (GST-M1) and theta (GST-T1) are isoforms of glutathione transferase enzymes that participate in the metabolism of a wide range of chemicals. Deletion variants that are associated with a lack of enzyme function exist at both these loci. The frequencies of homozygous GSTM1 and GSTT1 deletion carriers are very high in most of the populations studied to date. The aim of this study was to investigate the frequencies of GSTM1 and GSTT1 genotypes among the Turabah population in Saudi Arabia in comparison with the data published for some other Arabic populations. The subjects consisted of 164 unrelated healthy individuals from the Turabah population. GST genotyping was performed by multiplex polymerase chain reaction-based methods. The GSTM1 deletion homozygosity was 56.1% and GSTT1 deletion homozygosity was 20.7%, while the GSTM1 and GSTT1 double-deletion homozygosity was 11.0%. Comparison with published data from Bahraini, Lebanese, and Tunisian populations demonstrated no significant difference for GSTM1 between these populations. The GSTT1 null-allele frequency was significantly lower than those for the Lebanese and Tunisian populations (P = 0.001) but similar to that for the Bahraini population (P = 0.099). Characterization of GST genetic polymorphisms in the Saudi population may aid in genetic studies on the association of GSTM1 and GSTT1 polymorphisms with disease risks and the pharmacogenetics of chemotherapy.

  13. Generalized Robertson-Walker Space-Time Admitting Evolving Null Horizons Related to a Black Hole Event Horizon

    Science.gov (United States)

    2016-01-01

    A new technique is used to study a family of time-dependent null horizons, called “Evolving Null Horizons” (ENHs), of generalized Robertson-Walker (GRW) space-time (M¯,g¯) such that the metric g¯ satisfies a kinematic condition. This work is different from our early papers on the same issue where we used (1 + n)-splitting space-time but only some special subcases of GRW space-time have this formalism. Also, in contrast to previous work, we have proved that each member of ENHs is totally umbilical in (M¯,g¯). Finally, we show that there exists an ENH which is always a null horizon evolving into a black hole event horizon and suggest some open problems. PMID:27722202

  14. c-myc null cells misregulate cad and gadd45 but not other proposed c-Myc targets

    Science.gov (United States)

    Bush, Andrew; Mateyak, Maria; Dugan, Kerri; Obaya, Alvaro; Adachi, Susumu; Sedivy, John; Cole, Michael

    1998-01-01

    We report here that the expression of virtually all proposed c-Myc target genes is unchanged in cells containing a homozygous null deletion of c-myc. Two noteworthy exceptions are the gene cad, which has reduced log phase expression and serum induction in c-myc null cells, and the growth arrest gene gadd45, which is derepressed by c-myc knockout. Thus, cad and gadd45 are the only proposed targets of c-Myc that may contribute to the dramatic slow growth phenotype of c-myc null cells. Our results demonstrate that a loss-of-function approach is critical for the evaluation of potential c-Myc target genes. PMID:9869632

  15. Hormone-sensitive lipase null mice exhibit signs of impaired insulin sensitivity whereas insulin secretion is intact

    DEFF Research Database (Denmark)

    Mulder, Hindrik; Sörhede-Winzell, Maria; Contreras, Juan Antonio;

    2003-01-01

    Lipid metabolism plays an important role in glucose homeostasis under normal and pathological conditions. In adipocytes, skeletal muscle, and pancreatic beta-cells, lipids are mobilized from acylglycerides by the hormone-sensitive lipase (HSL). Here, the consequences of a targeted disruption...... of the HSL gene for glucose homeostasis were examined. HSL null mice were slightly hyperglycemic in the fasted, but not fed state, which was accompanied by moderate hyperinsulinemia. During glucose challenges, however, disposal of the sugar was not affected in HSL null mice, presumably because of release...... of increased amounts of insulin. Impaired insulin sensitivity was further indicated by retarded glucose disposal during an insulin tolerance test. A euglycemic hyperinsulinemic clamp revealed that hepatic glucose production was insufficiently blocked by insulin in HSL null mice. In vitro, insulin...

  16. In situ evidence for the structure of the magnetic null in a 3D reconnection event in the Earth's magnetotail

    CERN Document Server

    Xiao, C J; Pu, Z Y; Zhao, H; Wang, J X; Ma, Z W; Fu, S Y; Kivelson, M G; Liu, Z X; Zong, Q G; Glassmeier, K H; Balogh, A; Korth, A; Reme, H; Escoubet, C P

    2006-01-01

    Magnetic reconnection is one of the most important processes in astrophysical, space and laboratory plasmas. Identifying the structure around the point at which the magnetic field lines break and subsequently reform, known as the magnetic null point, is crucial to improving our understanding reconnection. But owing to the inherently three-dimensional nature of this process, magnetic nulls are only detectable through measurements obtained simultaneously from at least four points in space. Using data collected by the four spacecraft of the Cluster constellation as they traversed a diffusion region in the Earth's magnetotail on 15 September, 2001, we report here the first in situ evidence for the structure of an isolated magnetic null. The results indicate that it has a positive-spiral structure whose spatial extent is of the same order as the local ion inertial length scale, suggesting that the Hall effect could play an important role in 3D reconnection dynamics.

  17. GST M1-T1 null allele frequency patterns in geographically assorted human populations: a phylogenetic approach.

    Directory of Open Access Journals (Sweden)

    Senthilkumar Pitchalu Kasthurinaidu

    Full Text Available Genetic diversity in drug metabolism and disposition is mainly considered as the outcome of the inter-individual genetic variation in polymorphism of drug-xenobiotic metabolizing enzyme (XME. Among the XMEs, glutathione-S-transferases (GST gene loci are an important candidate for the investigation of diversity in allele frequency, as the deletion mutations in GST M1 and T1 genotypes are associated with various cancers and genetic disorders of all major Population Affiliations (PAs. Therefore, the present population based phylogenetic study was focused to uncover the frequency distribution pattern in GST M1 and T1 null genotypes among 45 Geographically Assorted Human Populations (GAHPs. The frequency distribution pattern for GST M1 and T1 null alleles have been detected in this study using the data derived from literatures representing 44 populations affiliated to Africa, Asia, Europe, South America and the genome of PA from Gujarat, a region in western India. Allele frequency counting for Gujarat PA and scattered plot analysis for geographical distribution among the PAs were performed in SPSS-21. The GST M1 and GST T1 null allele frequencies patterns of the PAs were computed in Seqboot, Gendist program of Phylip software package (3.69 versions and Unweighted Pair Group method with Arithmetic Mean in Mega-6 software. Allele frequencies from South African Xhosa tribe, East African Zimbabwe, East African Ethiopia, North African Egypt, Caucasian, South Asian Afghanistan and South Indian Andhra Pradesh have been identified as the probable seven patterns among the 45 GAHPs investigated in this study for GST M1-T1 null genotypes. The patternized null allele frequencies demonstrated in this study for the first time addresses the missing link in GST M1-T1 null allele frequencies among GAHPs.

  18. Deficient and Null Variants of SERPINA1 Are Proteotoxic in a Caenorhabditis elegans Model of α1-Antitrypsin Deficiency.

    Directory of Open Access Journals (Sweden)

    Erin E Cummings

    Full Text Available α1-antitrypsin deficiency (ATD predisposes patients to both loss-of-function (emphysema and gain-of-function (liver cirrhosis phenotypes depending on the type of mutation. Although the Z mutation (ATZ is the most prevalent cause of ATD, >120 mutant alleles have been identified. In general, these mutations are classified as deficient (<20% normal plasma levels or null (<1% normal levels alleles. The deficient alleles, like ATZ, misfold in the ER where they accumulate as toxic monomers, oligomers and aggregates. Thus, deficient alleles may predispose to both gain- and loss-of-function phenotypes. Null variants, if translated, typically yield truncated proteins that are efficiently degraded after being transiently retained in the ER. Clinically, null alleles are only associated with the loss-of-function phenotype. We recently developed a C. elegans model of ATD in order to further elucidate the mechanisms of proteotoxicity (gain-of-function phenotype induced by the aggregation-prone deficient allele, ATZ. The goal of this study was to use this C. elegans model to determine whether different types of deficient and null alleles, which differentially affect polymerization and secretion rates, correlated to any extent with proteotoxicity. Animals expressing the deficient alleles, Mmalton, Siiyama and S (ATS, showed overall toxicity comparable to that observed in patients. Interestingly, Siiyama expressing animals had smaller intracellular inclusions than ATZ yet appeared to have a greater negative effect on animal fitness. Surprisingly, the null mutants, although efficiently degraded, showed a relatively mild gain-of-function proteotoxic phenotype. However, since null variant proteins are degraded differently and do not appear to accumulate, their mechanism of proteotoxicity is likely to be different to that of polymerizing, deficient mutants. Taken together, these studies showed that C. elegans is an inexpensive tool to assess the proteotoxicity of

  19. Design of Hartmann type null screens for testing a plano-convex aspheric lens with a CCD sensor inside the caustic.

    Science.gov (United States)

    Castillo-Santiago, Gabriel; Castán-Ricaño, Diana; Avendaño-Alejo, Maximino; Castañeda, Luis; Díaz-Uribe, Rufino

    2016-08-22

    A new method to design Hartmann type null screens to test either qualitatively or quantitatively fast plano-convex aspherical lenses is presented. We design both radial and square null screens that produce arrays of circular spots uniformly distributed at predefined planes, considering that the CCD sensor is solely placed inside the caustic region. The designs of these null screens are based on knowledge of the caustic by refraction and on exact ray tracing. The null screens also serve to improve the alignment in optical systems. PMID:27557218

  20. CFD analysis of flow forces and energy loss characteristics in a flapper–nozzle pilot valve with different null clearances

    International Nuclear Information System (INIS)

    Highlights: • Multi-directional vortexes are found in the annulus of flapper–nozzle pilot stage. • CFD results show better agreement to momentum conversation based flow force model. • Conner vortex forces increase with increment of inlet pressure and null clearance. • Smaller flappers are favorable to reduce impact of flow reattachment. • Energy loss increases with increasing of inlet pressure and null clearance. - Abstract: A well understanding on the flow forces and energy loss characteristics in a flapper–nozzle pilot valve is necessarily important in the performance improvement of a two-stage electrohydraulic servo-valve. This paper presents the CFD analysis of flow forces and energy loss characteristics in a flapper–nozzle pilot valve with different null clearances. Five different flapper–nozzle structures with three different null clearances of 0.1 mm, 0.05 mm and 0.033 mm are considered in this analysis. For every flapper–nozzle structure, the systematic CFD simulations of flow forces and energy loss characteristics are performed for seven different flow conditions varying nozzle inlet pressures from 1 MPa to 7 MPa. Experimental measurements are also conducted for energy loss characteristics and then compared with simulated results. Meanwhile, the CFD flow force results are verified with the results of exiting simplified flow force models and vice versa. From each nozzle side, the main flow force acting on the flapper is accompanied by four tiny lateral forces resulted from the impact of radial jet reattachment on the flapper curved surface. For each of given null clearances, the main flow force and lateral forces linearly increase with the increment of nozzle inlet pressure. For the same null clearance, applying larger flapper can give 1.5–13.6% larger lateral force in drag direction and 1.5–10.2% larger lateral force in lift direction compared to deploying smaller flapper. Compared to the main flow force, the magnitudes of the

  1. Csf2 Null Mutation Alters Placental Gene Expression and Trophoblast Glycogen Cell and Giant Cell Abundance in Mice1

    OpenAIRE

    Sferruzzi-Perri, Amanda N.; Macpherson, Anne M.; Roberts, Claire T.; Robertson, Sarah A.

    2009-01-01

    Genetic deficiency in granulocyte-macrophage colony-stimulating factor (CSF2, GM-CSF) results in altered placental structure in mice. To investigate the mechanism of action of CSF2 in placental morphogenesis, the placental gene expression and cell composition were examined in Csf2 null mutant and wild-type mice. Microarray and quantitative RT-PCR analyses on Embryonic Day (E) 13 placentae revealed that the Csf2 null mutation caused altered expression of 17 genes not previously known to be ass...

  2. Null Geodesics and Strong Field Gravitational Lensing of Black Hole with Global Monopole

    Directory of Open Access Journals (Sweden)

    M. Sharif

    2015-01-01

    Full Text Available We study two interesting features of a black hole with an ordinary as well as phantom global monopole. Firstly, we investigate null geodesics which imply unstable orbital motion of particles for both cases. Secondly, we evaluate deflection angle in strong field regime. We then find Einstein rings, magnifications, and observables of the relativistic images for supermassive black hole at the center of galaxy NGC4486B. We also examine time delays for different galaxies and present our results numerically. It is found that the deflection angle for ordinary/phantom global monopole is greater/smaller than that of Schwarzschild black hole. In strong field limit, the remaining properties of these black holes are quite different from the Schwarzschild black hole.

  3. Predictive uncertainty analysis of a saltwater intrusion model using null-space Monte Carlo

    DEFF Research Database (Denmark)

    Herckenrath, Daan; Langevin, Christian D.; Doherty, John

    2011-01-01

    . Random noise was added to the observations to approximate realistic field conditions. The NSMC method was used to calculate 1000 calibration-constrained parameter fields. If the dimensionality of the solution space was set appropriately, the estimated uncertainty range from the NSMC analysis encompassed...... the truth. Several variants of the method were implemented to investigate their effect on the efficiency of the NSMC method. Reducing the dimensionality of the null-space for the processing of the random parameter sets did not result in any significant gains in efficiency and compromised the ability...... variability did not make a noticeable difference to the uncertainty of the prediction. With this higher level of heterogeneity, however, the computational burden of generating calibration-constrained parameter fields approximately doubled. Predictive uncertainty variance computed through the NSMC method...

  4. A Nulling Wide Field Imager for Exoplanets Detection and General Astrophysics

    CERN Document Server

    Guyon, O; Guyon, Olivier; Roddier, Francois

    2002-01-01

    We present a solution to obtain a high-resolution image of a wide field with the central source removed by destructive interference. The wide-field image is created by aperture synthesis with a rotating sparse array of telescopes in space. Nulling of the central source is achieved using a phase-mask coronagraph. The full (u,v) plane coverage delivered by the 60m, six 3-meter telescope array is particularly well-suited for the detection and characterization of exoplanets in the infrared (DARWIN and Terrestrial Planet Finder (TPF) missions) as well as for other generic science observations. Detection (S/N=10) of an Earth-like planet is achieved in less than 10 hours with a 1 micron bandwidth at 10 micron.

  5. Nulling interferometry: performance comparison between space and ground-based sites for exozodiacal disc detection

    CERN Document Server

    Defrère, D; Foresto, V Coudé du; Danchi, W C; Hartog, R den

    2008-01-01

    Characterising the circumstellar dust around nearby main sequence stars is a necessary step in understanding the planetary formation process and is crucial for future life-finding space missions such as ESA's Darwin or NASA's Terrestrial Planet Finder (TPF). Besides paving the technological way to Darwin/TPF, the space-based infrared interferometers Pegase and FKSI (Fourier-Kelvin Stellar Interferometer) will be valuable scientific precursors in that respect. In this paper, we investigate the performance of Pegase and FKSI for exozodiacal disc detection and compare the results with ground-based nulling interferometers. Besides their main scientific goal (characterising hot giant extrasolar planets), Pegase and FKSI are very efficient in assessing within a few minutes the level of circumstellar dust in the habitable zone around nearby main sequence stars. They are capable of detecting exozodiacal discs respectively 5 and 1 time as dense as the solar zodiacal cloud and they outperform any ground-based instrumen...

  6. Mild Lesch-Nyhan Disease in a Boy with a Null Mutation inHPRT1

    DEFF Research Database (Denmark)

    Bayat, Allan; Christensen, Mette; Wibrand, Flemming;

    2015-01-01

    Hypoxanthine-guanine phosphoribosyltransferase (HPRT) deficiency results in a continuous spectrum of clinical phenotypes though all include overproduction of uric acid with hyperuricaemia, urate nephrolithiasis and gout. HPRT1 mutations that result in very low or no HPRT enzyme activities...... are generally associated with the classic Lesch-Nyhan disease (LND) phenotype with intellectual disability, motor handicap and self-injurious behaviour. Mutations that permit a higher residual HPRT activity are seen in some patients with the milder LND variant phenotypes with varying degrees of cognitive, motor......-injurious behaviour. KEY CLINICAL MESSAGE: HPRT1 mutations that result in very low or no hypoxanthine-guanine phosphoribosyltransferase enzyme activities are generally associated with the classic Lesch-Nyhan disease. This report presents one of the rare cases with a null mutation in the HPRT1 gene that associates...

  7. A HIGH RESOLUTION WIDE SWATH SAR METHOD BASED ON INTRA-PULSE NULL STEERING AND MIMO

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    High Resolution Wide Swath(HRWS)Synthetic Aperture Radar(SAR)often Sufiers from low Signal-to-Noise Ratio(SNR)due to small transmitting antenna,especially in phased array antenna systems.Digital Beam Forming(DBF)based on Single Input and Multiple Output(SIMO)achieves receiving array gain at the cost of increasing data rate.This letter proposes a new HRWS SAR method, which employs intra-pulse null steering to get receiving gain in elevation and decrease the data rate,and Multiple Input and Multiple Output(MIMO)using Space-Time Block Coding(STBC)in azimuth to get transmitting gain and receiving array gain simultaneously.The feasibility is verified by deduction and simulations.

  8. Impaired Thermogenesis and a Molecular Signature for Brown Adipose Tissue in Id2 Null Mice

    Directory of Open Access Journals (Sweden)

    Peng Zhou

    2016-01-01

    Full Text Available Inhibitor of DNA binding 2 (ID2 is a helix-loop-helix transcriptional repressor rhythmically expressed in many adult tissues. Our previous studies have demonstrated that Id2 null mice have sex-specific elevated glucose uptake in brown adipose tissue (BAT. Here we further explored the role of Id2 in the regulation of core body temperature over the circadian cycle and the impact of Id2 deficiency on genes involved in insulin signaling and adipogenesis in BAT. We discovered a reduced core body temperature in Id2−/− mice. Moreover, in Id2−/− BAT, 30 genes including Irs1, PPARs, and PGC-1s were identified as differentially expressed in a sex-specific pattern. These data provide valuable insights into the impact of Id2 deficiency on energy homeostasis of mice in a sex-specific manner.

  9. Impaired Thermogenesis and a Molecular Signature for Brown Adipose Tissue in Id2 Null Mice.

    Science.gov (United States)

    Zhou, Peng; Robles-Murguia, Maricela; Mathew, Deepa; Duffield, Giles E

    2016-01-01

    Inhibitor of DNA binding 2 (ID2) is a helix-loop-helix transcriptional repressor rhythmically expressed in many adult tissues. Our previous studies have demonstrated that Id2 null mice have sex-specific elevated glucose uptake in brown adipose tissue (BAT). Here we further explored the role of Id2 in the regulation of core body temperature over the circadian cycle and the impact of Id2 deficiency on genes involved in insulin signaling and adipogenesis in BAT. We discovered a reduced core body temperature in Id2-/- mice. Moreover, in Id2-/- BAT, 30 genes including Irs1, PPARs, and PGC-1s were identified as differentially expressed in a sex-specific pattern. These data provide valuable insights into the impact of Id2 deficiency on energy homeostasis of mice in a sex-specific manner. PMID:27144179

  10. Characterization of (asymptotically) Kerr-de Sitter-like spacetimes at null infinity

    CERN Document Server

    Mars, Marc; Senovilla, José M M; Simon, Walter

    2016-01-01

    We investigate solutions $(\\mathcal{M}, g)$ to Einstein's vacuum field equations with positive cosmological constant $\\Lambda$ which admit a smooth past null infinity $\\mathcal{J}^-$ \\`a la Penrose and a Killing vector field whose associated Mars-Simon tensor (MST) vanishes. The main purpose of this work is to provide a characterization of these spacetimes in terms of their Cauchy data on $\\mathcal{J}^-$. Along the way, we also study spacetimes for which the MST does not vanish. In that case there is an ambiguity in its definition which is captured by a scalar function $Q$. We analyze properties of the MST for different choices of $Q$. In doing so, we are led to a definition of "asymptotically Kerr-de Sitter-like spacetimes", which we also characterize in terms of their asymptotic data on $\\mathcal{J}^-$.

  11. Characterization of (asymptotically) Kerr–de Sitter-like spacetimes at null infinity

    Science.gov (United States)

    Mars, Marc; Paetz, Tim-Torben; Senovilla, José M. M.; Simon, Walter

    2016-08-01

    We investigate solutions ({M},g) to Einstein's vacuum field equations with positive cosmological constant Λ which admit a smooth past null infinity {{I}}- à la Penrose and a Killing vector field whose associated Mars–Simon tensor (MST) vanishes. The main purpose of this work is to provide a characterization of these spacetimes in terms of their Cauchy data on {{I}}-. Along the way, we also study spacetimes for which the MST does not vanish. In that case there is an ambiguity in its definition which is captured by a scalar function Q. We analyze properties of the MST for different choices of Q. In doing so, we are led to a definition of ‘asymptotically Kerr–de Sitter-like spacetimes’, which we also characterize in terms of their asymptotic data on {{I}}-. Preprint UWThPh-2016-5.

  12. Causality of spacetimes admitting a parallel null vector and weak KAM theory

    CERN Document Server

    Minguzzi, E

    2012-01-01

    The causal spacetimes admitting a covariantly constant null vector provide a connection between relativistic and non-relativistic physics. We explore this relationship in several directions. We start proving a formula which relates the Lorentzian distance in the full spacetime with the least action of a mechanical system living in a quotient classical space time. The timelike eikonal equation satisfied by the Lorentzian distance is proved to be equivalent to the Hamilton-Jacobi equation for the least action. We also prove that the Legendre transform on the classical base corresponds to the musical isomorphism on the light cone, and the Young-Fenchel inequality is nothing but a well known geometric inequality in Lorentzian geometry. A strategy to simplify the dynamics passing to a reference frame moving with the E.-L. flow is explained. It is then proved that the causality properties can be conveniently expressed in terms of the least action. In particular, strong causality coincides with stable causality and ...

  13. Are effect sizes and confidence levels problems for or solutions to the null hypothesis test?

    Science.gov (United States)

    Riopelle, A J

    2000-04-01

    Some have proposed that the null hypothesis significance test, as usually conducted using the t test of the difference between means, is an impediment to progress in psychology. To improve its prospects, using Neyman-Pearson confidence intervals and Cohen's standardized effect sizes, d, is recommended. The purpose of these approaches is to enable us to understand what can appropriately be said about the distances between the means and their reliability. Others have written extensively that these recommended strategies are highly interrelated and use identical information. This essay was written to remind us that the t test, based on the sample--not the true--standard deviation, does not apply solely to distance between means. The t test pertains to a much more ambiguous specification: the difference between samples, including sampling variations of the standard deviation. PMID:10843262

  14. Nutritional intervention restores muscle but not kidney phenotypes in adult calcineurin aα null mice

    DEFF Research Database (Denmark)

    Madsen, Kirsten; Reddy, Ramesh N; Price, S Russ;

    2013-01-01

    to thrive and early lethality of most null pups. Work in our laboratory led to the rescue of CnAα-/- mice by supplemental feeding to compensate for a defect in salivary enzyme secretion. The data revealed that, without intervention, knockout mice suffer from severe caloric restriction. Since nutritional...... and function persist in adult CnAα-/- mice including a significant decrease in glomerular filtration rate and an increase in blood urea nitrogen levels. These data indicate that impaired renal development we previously reported was not due to caloric restriction but rather a specific role for CnAα in renal......Aα likely alters insulin response due to a reduction in insulin receptor substrate-2 (IRS2) expression and signaling in muscle. This study illustrates the importance of re-examining the phenotypes of CnAα-/- mice and the advances that are now possible with the use of adult, rescued knockout animals....

  15. Reaction Null Space of a multibody system with applications in robotics

    Directory of Open Access Journals (Sweden)

    D. N. Nenchev

    2013-02-01

    Full Text Available This paper provides an overview of implementation examples based on the Reaction Null Space formalism, developed initially to tackle the problem of satellite-base disturbance of a free-floating space robot, when the robot arm is activated. The method has been applied throughout the years to other unfixed-base systems, e.g. flexible-base and macro/mini robot systems, as well as to the balance control problem of humanoid robots. The paper also includes most recent results about complete dynamical decoupling of the end-link of a fixed-base robot, wherein the end-link is regarded as the unfixed-base. This interpretation is shown to be useful with regard to motion/force control scenarios. Respective implementation results are provided.

  16. Almost Linear Systems - A null-model for genetic regulatory networks

    International Nuclear Information System (INIS)

    Intracellular signalling in general or genetic regulation and enzyme kinetics in specific are processes known to be of highly non linear nature. Yet, the idea of parsimony guides evolution of theory along the way of the simplest available models in sufficient agreement with experimental observations. Almost Linear Systems, - i.e. systems that follow a linear dynamic for the concentration of agents under the constraint that agent concentrations must be non-negative -, can be understood as a null-model of observed genetic regulation processes like for instance - the recruitment of various agents into functional protein complexes. In this way Almost Linear Systems provide a starting-point for a systematic identification of crucial non-linear agent interactions that defy linearization or can be used to predict the dynamics of agents missing in considered assays. (author)

  17. Lightlike sets with applications to the rigidity of null geodesic incompleteness

    CERN Document Server

    Silva, I P Costa e

    2014-01-01

    An important, if relatively less well known aspect of the singularity theorems in Lorentzian Geometry is to understand how their conclusions fare upon weakening or suppression of one or more of their hypotheses. Then, theorems with modified concusions may arise, showing that those conclusions will fail only in special cases, at least some of which may be described. These are the so-called rigidity theorems, and have many important examples in the especialized literature. In this paper, we prove rigidity results for generalized plane waves and certain globally hyperbolic spacetimes in the presence of maximal compact surfaces. Motivated by some general properties appearing in these proofs, we develop the theory of lightlike sets, entities similar to achronal sets, but more appropriate to deal with low-regularity null submanifolds.

  18. Slow-Mode MHD Wave Penetration into a Coronal Null Point due to the Mode Transmission

    Science.gov (United States)

    Afanasyev, Andrey N.; Uralov, Arkadiy M.

    2016-05-01

    Recent observations of magnetohydrodynamic oscillations and waves in solar active regions revealed their close link to quasi-periodic pulsations in flaring light curves. The nature of that link has not yet been understood in detail. In our analytical modelling we investigate propagation of slow magnetoacoustic waves in a solar active region, taking into account wave refraction and transmission of the slow magnetoacoustic mode into the fast one. The wave propagation is analysed in the geometrical acoustics approximation. Special attention is paid to the penetration of waves in the vicinity of a magnetic null point. The modelling has shown that the interaction of slow magnetoacoustic waves with the magnetic reconnection site is possible due to the mode transmission at the equipartition level where the sound speed is equal to the Alfvén speed. The efficiency of the transmission is also calculated.

  19. Weak and Strong Convergence of Algorithms for the Split Common Null Point Problem

    CERN Document Server

    Byrne, Charles; Gibali, Aviv; Reich, Simeon

    2011-01-01

    We introduce and study the Split Common Null Point Problem (SCNPP) for set-valued maximal monotone mappings in Hilbert space. This problem generalizes our Split Variational Inequality Problem (SVIP) [Y. Censor, A. Gibali and S. Reich, Algorithms for the split variational inequality problem, Numerical Algorithms, accepted for publication, DOI 10.1007/s11075-011-9490-5]. The SCNPP with only two set-valued mappings entails finding a zero of a maximal monotone mapping in one space, the image of which under a given bounded linear transformation is a zero of another maximal monotone mapping. We present three iterative algorithms that solve such problems in Hilbert space, and establish weak convergence for one and strong convergence for the other two.

  20. Development of a two-dimensional skin friction balance nulling circuit using multivariable control theory

    Science.gov (United States)

    Tripp, John S.; Patek, Stephen D.

    1988-01-01

    Measurement of planar skin friction forces in aerodynamic testing currently requires installation of two perpendicularly mounted, single-axis balances; consequently, force components must be sensed at two distinct locations. A two-axis instrument developed at the Langley Research Center to overcome this disadvantage allows measurement of a two-dimensional force at one location. This paper describes a feedback-controlled nulling circuit developed for the NASA two-axis balance which, without external compensation, is inherently unstable because of its low friction mechanical design. Linear multivariable control theory is applied to an experimentally validated mathematical model of the balance to synthesize a state-variable feedback control law. Pole placement techniques and computer simulation studies are employed to select eigenvalues which provide ideal transient response with decoupled sensing dynamics.

  1. Precise Wavefront Correction with an Unbalanced Nulling Interferometer for Exo-Planet Imaging Coronagraphs

    CERN Document Server

    Nishikawa, J; Murakami, N; Kotani, T

    2008-01-01

    Very high dynamical range coronagraphs targeting direct exo-planet detection (10^9 - 10^10 contrast) at small angular separation (few lambda/D units) usually require an input wavefront quality on the order of ten thousandths of wavelength RMS. We propose a novel method based on a pre-optics setup that behaves partly as a low-efficiency coronagraph, and partly as a high-sensitivity wavefront aberration compensator (phase and amplitude). The combination of the two effects results in a highly accurate corrected wavefront. First, an (intensity-) unbalanced nulling interferometer (UNI) performs a rejection of part of the wavefront electric field. Then the recombined output wavefront has its input aberrations magnified. Because of the unbalanced recombination scheme, aberrations can be free of phase singular points (zeros) and can therefore be compensated by a downstream phase and amplitude correction (PAC) adaptive optics system, using two deformable mirrors. In the image plane, the central star's peak intensity a...

  2. Two special classes of space-times admitting a non-null valence two Killing spinor

    CERN Document Server

    Bergh, Norbert Van den

    2009-01-01

    Non-conformally flat space-times admitting a non-null Killing spinor of valence two are investigated in the Geroch-Held-Penrose formalism. Contrary to popular belief these space-times are not all explicitly known. It is shown that the standard construction hinges on the tacit assumption that certain integrability conditions hold, implying two algebraic relations, KS1 and KS2, for the spin coefficients and the components of the Ricci spinor. An exhaustive list of (conformal classes of) space-times, in which either KS1 or KS2 are violated, is presented. The resulting space-times are each other's Sachs transforms, in general admit no Killing vectors and are characterized by a single arbitrary function.

  3. Reactivation of autophagy by spermidine ameliorates the myopathic defects of collagen VI-null mice.

    Science.gov (United States)

    Chrisam, Martina; Pirozzi, Marinella; Castagnaro, Silvia; Blaauw, Bert; Polishchuck, Roman; Cecconi, Francesco; Grumati, Paolo; Bonaldo, Paolo

    2015-01-01

    Autophagy is a self-degradative process responsible for the clearance of damaged or unnecessary cellular components. We have previously found that persistence of dysfunctional organelles due to autophagy failure is a key event in the pathogenesis of COL6/collagen VI-related myopathies, and have demonstrated that reactivation of a proper autophagic flux rescues the muscle defects of Col6a1-null (col6a1(-/-)) mice. Here we show that treatment with spermidine, a naturally occurring nontoxic autophagy inducer, is beneficial for col6a1(-/-) mice. Systemic administration of spermidine in col6a1(-/-) mice reactivated autophagy in a dose-dependent manner, leading to a concurrent amelioration of the histological and ultrastructural muscle defects. The beneficial effects of spermidine, together with its being easy to administer and the lack of overt side effects, open the field for the design of novel nutraceutical strategies for the treatment of muscle diseases characterized by autophagy impairment.

  4. Non-contact time-resolved diffuse reflectance imaging at null source-detector separation.

    Science.gov (United States)

    Mazurenka, M; Jelzow, A; Wabnitz, H; Contini, D; Spinelli, L; Pifferi, A; Cubeddu, R; Mora, A Dalla; Tosi, A; Zappa, F; Macdonald, R

    2012-01-01

    We report results of the proof-of-principle tests of a novel non-contact tissue imaging system. The system utilizes a quasi-null source-detector separation approach for time-domain near-infrared spectroscopy, taking advantage of an innovative state-of-the-art fast-gated single photon counting detector. Measurements on phantoms demonstrate the feasibility of the non-contact approach for the detection of optically absorbing perturbations buried up to a few centimeters beneath the surface of a tissue-like turbid medium. The measured depth sensitivity and spatial resolution of the new system are close to the values predicted by Monte Carlo simulations for the inhomogeneous medium and an ideal fast-gated detector, thus proving the feasibility of the non-contact approach for high density diffuse reflectance measurements on tissue. Potential applications of the system are also discussed. PMID:22274351

  5. Theoretical size distribution of fossil taxa: analysis of a null model

    Directory of Open Access Journals (Sweden)

    Hughes Barry D

    2007-03-01

    Full Text Available Abstract Background This article deals with the theoretical size distribution (of number of sub-taxa of a fossil taxon arising from a simple null model of macroevolution. Model New species arise through speciations occurring independently and at random at a fixed probability rate, while extinctions either occur independently and at random (background extinctions or cataclysmically. In addition new genera are assumed to arise through speciations of a very radical nature, again assumed to occur independently and at random at a fixed probability rate. Conclusion The size distributions of the pioneering genus (following a cataclysm and of derived genera are determined. Also the distribution of the number of genera is considered along with a comparison of the probability of a monospecific genus with that of a monogeneric family.

  6. Phase Mixing of Alfvén Waves Near a 2D Magnetic Null Point

    Indian Academy of Sciences (India)

    J. A. McLaughlin

    2013-09-01

    The propagation of linear Alfvén wave pulses in an inhomogeneous plasma near a 2D coronal null point is investigated. When a uniform plasma density is considered, it is seen that an initially planar Alfvén wavefront remains planar, despite the varying equilibrium Alfvén speed, and that all the wave collects at the separatrices. Thus, in the non-ideal case, these Alfvénic disturbances preferentially dissipate their energy at these locations. For a non-uniform equilibrium density, it is found that the Alfvén wavefront is significantly distorted away from the initially planar geometry, inviting the possibility of dissipation due to phase mixing. Despite this however, we conclude that for the Alfvén wave, current density accumulation and preferential heating still primarily occur at the separatrices, even when an extremely non-uniform density profile is considered.

  7. Behavioral Disturbances in Estrogen-Related Receptor alpha-Null Mice

    Directory of Open Access Journals (Sweden)

    Huxing Cui

    2015-04-01

    Full Text Available Eating disorders, such as anorexia nervosa and bulimia nervosa, are common and severe mental illnesses of unknown etiology. Recently, we identified a rare missense mutation in the transcription factor estrogen-related receptor alpha (ESRRA that is associated with the development of eating disorders. However, little is known about ESRRA function in the brain. Here, we report that Esrra is expressed in the mouse brain and demonstrate that Esrra levels are regulated by energy reserves. Esrra-null female mice display a reduced operant response to a high-fat diet, compulsivity/behavioral rigidity, and social deficits. Selective Esrra knockdown in the prefrontal and orbitofrontal cortices of adult female mice recapitulates reduced operant response and increased compulsivity, respectively. These results indicate that Esrra deficiency in the mouse brain impairs behavioral responses in multiple functional domains.

  8. Behavioral disturbances in estrogen-related receptor alpha-null mice.

    Science.gov (United States)

    Cui, Huxing; Lu, Yuan; Khan, Michael Z; Anderson, Rachel M; McDaniel, Latisha; Wilson, Hannah E; Yin, Terry C; Radley, Jason J; Pieper, Andrew A; Lutter, Michael

    2015-04-21

    Eating disorders, such as anorexia nervosa and bulimia nervosa, are common and severe mental illnesses of unknown etiology. Recently, we identified a rare missense mutation in the transcription factor estrogen-related receptor alpha (ESRRA) that is associated with the development of eating disorders. However, little is known about ESRRA function in the brain. Here, we report that Esrra is expressed in the mouse brain and demonstrate that Esrra levels are regulated by energy reserves. Esrra-null female mice display a reduced operant response to a high-fat diet, compulsivity/behavioral rigidity, and social deficits. Selective Esrra knockdown in the prefrontal and orbitofrontal cortices of adult female mice recapitulates reduced operant response and increased compulsivity, respectively. These results indicate that Esrra deficiency in the mouse brain impairs behavioral responses in multiple functional domains.

  9. Preamble and pilot symbol design for channel estimation in OFDM systems with null subcarriers

    Directory of Open Access Journals (Sweden)

    Ohno Shuichi

    2011-01-01

    Full Text Available Abstract In this article, design of preamble for channel estimation and pilot symbols for pilot-assisted channel estimation in orthogonal frequency division multiplexing system with null subcarriers is studied. Both the preambles and pilot symbols are designed to minimize the l 2 or the l ∞ norm of the channel estimate mean-squared errors (MSE in frequency-selective environments. We use convex optimization technique to find optimal power distribution to the preamble by casting the MSE minimization problem into a semidefinite programming problem. Then, using the designed optimal preamble as an initial value, we iteratively select the placement and optimally distribute power to the selected pilot symbols. Design examples consistent with IEEE 802.11a as well as IEEE 802.16e are provided to illustrate the superior performance of our proposed method over the equi-spaced equi-powered pilot symbols and the partially equi-spaced pilot symbols.

  10. Null Geodesics and Strong Field Gravitational Lensing of Black Hole with Global Monopole

    International Nuclear Information System (INIS)

    We study two interesting features of a black hole with an ordinary as well as phantom global monopole. Firstly, we investigate null geodesics which imply unstable orbital motion of particles for both cases. Secondly, we evaluate deflection angle in strong field regime. We then find Einstein rings, magnifications, and observables of the relativistic images for supermassive black hole at the center of galaxy NGC4486B. We also examine time delays for different galaxies and present our results numerically. It is found that the deflection angle for ordinary/phantom global monopole is greater/smaller than that of Schwarzschild black hole. In strong field limit, the remaining properties of these black holes are quite different from the Schwarzschild black hole

  11. Nonlinear Wave Equations With Null Condition On Extremal Reissner-Nordstr\\"om Spacetimes I: Spherical Symmetry

    CERN Document Server

    Angelopoulos, Yannis

    2014-01-01

    We study spherically symmetric solutions of semilinear wave equations in the case where the nonlinearity satisfies the null condition on extremal Reissner--Nordstrom black hole spacetimes. We show that solutions which arise from sufficiently small compactly supported smooth data prescribed on a Cauchy hypersfurace \\widetilde{{\\Sigma}}_0 crossing the future event horizon \\mathcal{H}^{+} are globally well-posed in the domain of outer communications up to and including \\mathcal{H}^{+}. Our method allows us to close all bootstrap estimates under very weak decay results (compatible with those known for the linear case). Moreover we establish a certain number of non-decay and blow-up results along the horizon \\mathcal{H}^{+} which generalize known instability results for the linear case. Our results apply to spherically symmetric wave maps for a wide class of target spaces.

  12. Differential expression of pancreatic protein andchemosensing receptor mRNAs in NKCC1-null intestine

    Institute of Scientific and Technical Information of China (English)

    2016-01-01

    AIM To investigate the intestinal functions of the NKCC1Na+-K+-2Cl cotransporter (SLC12a2 gene), differentialmRNA expression changes in NKCC1-null intestine wereanalyzed.METHODS: Microarray analysis of mRNA from intestinesof adult wild-type mice and gene-targeted NKCC1-null mice (n = 6 of each genotype) was performed toidentify patterns of differential gene expression changes.Differential expression patterns were further examinedby Gene Ontology analysis using the online Gorillaprogram, and expression changes of selected genes wereverified using northern blot analysis and quantitativereal time-polymerase chain reaction. Histological stainingand immunofluorescence were performed to identify celltypes in which upregulated pancreatic digestive enzymeswere expressed.RESULTS: Genes typically associated with pancreaticfunction were upregulated. These included lipase,amylase, elastase, and serine proteases indicative ofpancreatic exocrine function, as well as insulin andregenerating islet genes, representative of endocrinefunction. Northern blot analysis and immunohistochemistryshowed that differential expression of exocrinepancreas mRNAs was specific to the duodenum andlocalized to a subset of goblet cells. In addition, a majorpattern of changes involving differential expression ofolfactory receptors that function in chemical sensing, aswell as other chemosensing G-protein coupled receptors,was observed. These changes in chemosensory receptorexpression may be related to the failure of intestinalfunction and dependency on parenteral nutritionobserved in humans with SLC12a2 mutations.CONCLUSION: The results suggest that loss of NKCC1affects not only secretion, but also goblet cell functionand chemosensing of intestinal contents via G-proteincoupled chemosensory receptors.

  13. Altered lipid and salt taste responsivity in ghrelin and GOAT null mice.

    Directory of Open Access Journals (Sweden)

    Huan Cai

    Full Text Available Taste perception plays an important role in regulating food preference, eating behavior and energy homeostasis. Taste perception is modulated by a variety of factors, including gastric hormones such as ghrelin. Ghrelin can regulate growth hormone release, food intake, adiposity, and energy metabolism. Octanoylation of ghrelin by ghrelin O-acyltransferase (GOAT is a specific post-translational modification which is essential for many biological activities of ghrelin. Ghrelin and GOAT are both widely expressed in many organs including the gustatory system. In the current study, overall metabolic profiles were assessed in wild-type (WT, ghrelin knockout (ghrelin(-/-, and GOAT knockout (GOAT(-/- mice. Ghrelin(-/- mice exhibited decreased food intake, increased plasma triglycerides and increased ketone bodies compared to WT mice while demonstrating WT-like body weight, fat composition and glucose control. In contrast GOAT(-/- mice exhibited reduced body weight, adiposity, resting glucose and insulin levels compared to WT mice. Brief access taste behavioral tests were performed to determine taste responsivity in WT, ghrelin(-/- and GOAT(-/- mice. Ghrelin and GOAT null mice possessed reduced lipid taste responsivity. Furthermore, we found that salty taste responsivity was attenuated in ghrelin(-/- mice, yet potentiated in GOAT(-/- mice compared to WT mice. Expression of the potential lipid taste regulators Cd36 and Gpr120 were reduced in the taste buds of ghrelin and GOAT null mice, while the salt-sensitive ENaC subunit was increased in GOAT(-/- mice compared with WT mice. The altered expression of Cd36, Gpr120 and ENaC may be responsible for the altered lipid and salt taste perception in ghrelin(-/- and GOAT(-/- mice. The data presented in the current study potentially implicates ghrelin signaling activity in the modulation of both lipid and salt taste modalities.

  14. How to interpret a discovery or null result of the 0ν2β decay

    Energy Technology Data Exchange (ETDEWEB)

    Xing, Zhi-zhong; Zhou, Ye-Ling [Chinese Academy of Sciences, Institute of High Energy Physics, Beijing (China); Peking University, Center for High Energy Physics, Beijing (China); Zhao, Zhen-hua [Chinese Academy of Sciences, Institute of High Energy Physics, Beijing (China)

    2015-09-15

    The Majorana nature of massive neutrinos will be crucially probed in the next-generation experiments of the neutrinoless double-beta (0ν2β) decay. The effective mass term of this process, left angle m right angle {sub ee}, may be contaminated by new physics. So how to interpret a discovery or null result of the 0ν2β decay in the foreseeable future is highly nontrivial. In this paper we introduce a novel three-dimensional description of vertical stroke left angle m right angle {sub ee} vertical stroke, which allows us to see its sensitivity to the lightest neutrino mass and two Majorana phases in a transparent way. We take a look at to what extent the free parameters of vertical stroke left angle m right angle {sub ee} vertical stroke can be well constrained provided a signal of the 0ν2β decay is observed someday. To fully explore lepton number violation, all the six effective Majorana mass terms left angle m right angle {sub αβ} (for α, β = e, μ, τ) are calculated and their lower bounds are illustrated with the two-dimensional contour figures. The effect of possible new physics on the 0ν2β decay is also discussed in a model-independent way. We find that the result of vertical stroke left angle m right angle {sub ee} vertical stroke in the normal (or inverted) neutrino mass ordering case modified by the new physics effect may somewhat mimic that in the inverted (or normal) mass ordering case in the standard three-flavor scheme. Hence a proper interpretation of a discovery or null result of the 0ν2β decay may demand extra information from some other measurements. (orig.)

  15. Multi-Threshold NULL Convention Logic (MTNCL: An Ultra-Low Power Asynchronous Circuit Design Methodology

    Directory of Open Access Journals (Sweden)

    Liang Zhou

    2015-05-01

    Full Text Available This paper develops an ultra-low power asynchronous circuit design methodology, called Multi-Threshold NULL Convention Logic (MTNCL, also known as Sleep Convention Logic (SCL, which combines Multi-Threshold CMOS (MTCMOS with NULL Convention Logic (NCL, to yield significant power reduction without any of the drawbacks of applying MTCMOS to synchronous circuits. In contrast to other power reduction techniques that usually result in large area overhead, MTNCL circuits are actually smaller than their original NCL versions. MTNCL utilizes high-Vt transistors to gate power and ground of a low-Vt logic block to provide for both fast switching and very low leakage power when idle. To demonstrate the advantages of MTNCL, a number of 32-bit IEEE single-precision floating-point co-processors were designed for comparison using the 1.2 V IBM 8RF-LM 130 nm CMOS process: original NCL, MTNCL with just combinational logic (C/L slept, Bit-Wise MTNCL (BWMTNCL, MTNCL with C/L and completion logic slept, MTNCL with C/L, completion logic, and registers slept, MTNCL with Safe Sleep architecture, and synchronous MTCMOS. These designs are compared in terms of throughput, area, dynamic energy, and idle power, showing the tradeoffs between the various MTNCL architectures, and that the best MTNCL design is much better than the original NCL design in all aspects, and much better than the synchronous MTCMOS design in terms of area, energy per operation, and idle power, although the synchronous design can operate faster.

  16. Nucleus-targeted Dmp1 transgene fails to rescue dental defects in Dmp1 null mice

    Institute of Scientific and Technical Information of China (English)

    Shu-Xian Lin; Qi Zhang; Hua Zhang; Kevin Yan; Leanne Ward; Yong-Bo Lu; Jian-Quan Feng

    2014-01-01

    Dentin matrix protein 1 (DMP1) is essential to odontogenesis. Its mutations in human subjects lead to dental problems such as dental deformities, hypomineralization and periodontal impairment. Primarily, DMP1 is considered as an extracellular matrix protein that promotes hydroxyapatite formation and activates intracellular signaling pathway via interacting with avb3 integrin. Recent in vitro studies suggested that DMP1 might also act as a transcription factor. In this study, we examined whether full-length DMP1 could function as a transcription factor in the nucleus and regulate odontogenesis in vivo. We first demonstrated that a patient with the DMP1 M1V mutation, which presumably causes a loss of the secretory DMP1 but does not affect the nuclear translocation of DMP1, shows a typical rachitic tooth defect. Furthermore, we generated transgenic mice expressing NLSDMP1, in which the endoplasmic reticulum (ER) entry signal sequence of DMP1 was replaced by a nuclear localization signal (NLS) sequence, under the control of a 3.6 kb rat type I collagen promoter plus a 1.6 kb intron 1. We then crossbred the NLSDMP1 transgenic mice with Dmp1 null mice to express the NLSDMP1 in Dmp1-deficient genetic background. Although immunohistochemistry demonstrated that NLSDMP1 was localized in the nuclei of the preodontoblasts and odontoblasts, the histological, morphological and biochemical analyses showed that it failed to rescue the dental and periodontal defects as well as the delayed tooth eruption in Dmp1 null mice. These data suggest that the full-length DMP1 plays no apparent role in the nucleus during odontogenesis.

  17. Detection of Fatigue Cracks at Rivets with Self-Nulling Probe

    Science.gov (United States)

    Wincheski, Buzz; Fulton, Jim; Nath, Shridhar; Namkung, Min

    1994-01-01

    A new eddy current probe developed at NASA Langley Research Center has been used to detect small cracks at rivets in aircraft lap splices [1]. The device has earlier been used to detect isolated fatigue cracks with a minimum detectable flaw size of roughly 1/2 to 1/3 the diameter of the probe [2]. The present work shows that the detectable flaw size for cracks originating at rivets can be greatly improved upon from that of isolated flaws. The use of a rotating probe method combined with spatial filtering has been used to detect 0.18 cm EDM notches, as measured from the rivet shank, with a 1.27 cm diameter probe and to detect flaws buried under the rivet head, down to a length of 0.076 cm, using a 0.32 cm diameter probe. The Self-Nulling Electromagnetic Flaw Detector induces a high density eddy current ring in the sample under test. A ferromagnetic flux focusing lens is incorporated such that in the absence of any inhomogeneities in the material under test only a minimal magnetic field will reach the interior of the probe. A magnetometer (pickup coil) located in the center of the probe therefore registers a null voltage in the absence of material defects. When a fatigue crack or other discontinuity is present in the test article the path of the eddy currents in the material is changed. The magnetic field associated with these eddy currents then enter into the interior of the probe, producing a large output voltage across the pickup coil leads. Further

  18. Differential expression of pancreatic protein and chemosensing receptor mRNAs in NKCC1-null intestine

    Science.gov (United States)

    Bradford, Emily M; Vairamani, Kanimozhi; Shull, Gary E

    2016-01-01

    AIM: To investigate the intestinal functions of the NKCC1 Na+-K+-2Cl cotransporter (SLC12a2 gene), differential mRNA expression changes in NKCC1-null intestine were analyzed. METHODS: Microarray analysis of mRNA from intestines of adult wild-type mice and gene-targeted NKCC1-null mice (n = 6 of each genotype) was performed to identify patterns of differential gene expression changes. Differential expression patterns were further examined by Gene Ontology analysis using the online Gorilla program, and expression changes of selected genes were verified using northern blot analysis and quantitative real time-polymerase chain reaction. Histological staining and immunofluorescence were performed to identify cell types in which upregulated pancreatic digestive enzymes were expressed. RESULTS: Genes typically associated with pancreatic function were upregulated. These included lipase, amylase, elastase, and serine proteases indicative of pancreatic exocrine function, as well as insulin and regenerating islet genes, representative of endocrine function. Northern blot analysis and immunohistochemistry showed that differential expression of exocrine pancreas mRNAs was specific to the duodenum and localized to a subset of goblet cells. In addition, a major pattern of changes involving differential expression of olfactory receptors that function in chemical sensing, as well as other chemosensing G-protein coupled receptors, was observed. These changes in chemosensory receptor expression may be related to the failure of intestinal function and dependency on parenteral nutrition observed in humans with SLC12a2 mutations. CONCLUSION: The results suggest that loss of NKCC1 affects not only secretion, but also goblet cell function and chemosensing of intestinal contents via G-protein coupled chemosensory receptors. PMID:26909237

  19. The glutathione-S-transferase Mu 1 null genotype modulates ozone-induced airway inflammation in humans*

    Science.gov (United States)

    Background: The Glutathione-S-Transferase Mu 1 null genotype has been reported to be a risk factor for acute respiratory disease associated with increases in ambient air ozone. Ozone is known to cause an immediate decrease in lung function and increased airway inflammation. Howev...

  20. A possible association between a dysfunctional skin barrier (filaggrin null-mutation status) and diabetes: a cross-sectional study

    DEFF Research Database (Denmark)

    Thyssen, Jacob P; Linneberg, Allan; Carlsen, Berit C;

    2011-01-01

    Background Filaggrin proteins are located in the skin and prevent epidermal water loss and impede the entry of micro-organisms, allergens and chemicals. Filaggrin null mutations are strongly associated with ichthyosis vulgaris and atopic dermatitis. Objective The authors aimed to investigate...

  1. Relativistic Bound States in 2+1 and 1+1 Dimensions in the Null-Plane

    CERN Document Server

    Pacheco-Bicudo-Cabral de Melo, J; Tomio, L; Frederico, T; Tomio, Lauro

    1998-01-01

    The Relativistic formulation of the three-boson model interacting via a zero-range two-body force in the null-plane is given in 2+1 and 1+1 space-time dimension. The bound state energy is calculed as function of the two-body boson binding energy.

  2. First-light LBT nulling interferometric observations: warm exozodiacal dust resolved within a few AU of eta Corvi

    CERN Document Server

    Defrère, D; Skemer, A J; Kennedy, G M; Bailey, V P; Hoffmann, W F; Mennesson, B; Millan-Gabet, R; Danchi, W C; Absil, O; Arbo, P; Beichman, C; Brusa, G; Bryden, G; Downey, E C; Durney, O; Esposito, S; Gaspar, A; Grenz, P; Haniff, C; Hill, J M; Lebreton, J; Leisenring, J M; Males, J R; Marion, L; McMahon, T J; Montoya, M; Morzinski, K M; Pinna, E; Puglisi, A; Rieke, G; Roberge, A; Serabyn, E; Sosa, R; Stapeldfeldt, K; Su, K; Vaitheeswaran, V; Vaz, A; Weinberger, A J; Wyatt, M C

    2015-01-01

    We report on the first nulling interferometric observations with the Large Binocular Telescope Interferometer (LBTI), resolving the N' band (9.81 - 12.41 um) emission around the nearby main-sequence star eta Crv (F2V, 1-2 Gyr). The measured source null depth amounts to 4.40% +/- 0.35% over a field-of-view of 140 mas in radius (~2.6\\,AU at the distance of eta Corvi) and shows no significant variation over 35{\\deg} of sky rotation. This relatively low null is unexpected given the total disk to star flux ratio measured by Spitzer/IRS (~23% across the N' band), suggesting that a significant fraction of the dust lies within the central nulled response of the LBTI (79 mas or 1.4 AU). Modeling of the warm disk shows that it cannot resemble a scaled version of the Solar zodiacal cloud, unless it is almost perpendicular to the outer disk imaged by Herschel. It is more likely that the inner and outer disks are coplanar and the warm dust is located at a distance of 0.5-1.0 AU, significantly closer than previously predic...

  3. Echo-to-reverberation enhancement based on decomposition of time reversal operator with forward and backward reverberation nulling constrains

    Institute of Scientific and Technical Information of China (English)

    GUO Guoqiang; YANG Yixin; SUN Chao

    2009-01-01

    Abstract Combined the decomposition of time reversal operator and the time reversal reverberation nulling, a new time reversal processing approach for echo-to-reverberation ratio enhancement is proposed. In this method, a 2-dimensional signal subspace for the range of the target and two bottom focusing weight vectors for the ranges near the target are obtained by the decomposition of time reversal operator. From the signal subspace and focusing weight vectors, a constrained optimal excitation weight vector of source receiver array can be deduced to null the acoustic energy on the corresponding bottom and maximize the energy at the target. This method remedies the shortages of conventional time reversal processing, time reversal reverberation nulling and time reversal selective focusing method. It focuses sound energy at the target and nulls the energy at the bottom near the target range simultaneously, therefore enhancing the echo-to-reverberation ratio without probe source and prior-knowledge of the relative scattering intensity of target and bottom. Numerical simulations in typical shallow water environments showed the effectiveness of the proposed method and its improved performance for echo-reverberation enhancement than conventional time reversal processing.

  4. GSTT1 null genotype contributes to lung cancer risk in asian populations: a meta-analysis of 23 studies.

    Directory of Open Access Journals (Sweden)

    Xin Yang

    Full Text Available BACKGROUND: Genetic variation in glutathione S-transferases (GSTs may contribute to lung cancer risk. Many studies have investigated the correlation between the Glutathione S-transferase T1 (GSTT1 null genotype and lung cancer risk in Asian population but yielded inconclusive results. METHODOLOGY/PRINCIPAL FINDINGS: We performed a meta-analysis of 23 studies including 4065 cases and 5390 controls. We assessed the strength of the association of GSTT1 with lung cancer risk and performed sub-group analyses by source of controls, smoking status, histological types, and sample size. A statistically significant correlation between GSTT1 null genotype and lung cancer in Asian population was observed (OR = 1.28, 95% CI = 1.10, 1.49; Pheterogeneity<0.001 and I(2 = 62.0%. Sub-group analysis revealed there was a statistically increased lung cancer risk in ever-smokers who carried the GSTT1 null genotype (OR = 1.94, 95% CI = 1.27, 2.96; P heterogeneity = 0.02 and I(2 = 58.1%. It was also indicated that GSTT1 null genotype could increase lung cancer risk among population-based studies (OR = 1.25, 95% CI = 1.04, 1.50; Pheterogeneity = 0.003 and I(2 = 56.8%. The positive association was also found in studies of sample size (≤500 participants (OR = 1.34, 95% CI = 1.10, 1.62; Pheterogeneity<0.001 and I(2 = 65.4%. CONCLUSIONS: These meta-analysis results suggest that GSTT1 null genotype is associated with a significantly increased risk of lung cancer in Asian population.

  5. Comprehensive Analysis of the 16p11.2 Deletion and Null Cntnap2 Mouse Models of Autism Spectrum Disorder.

    Directory of Open Access Journals (Sweden)

    Daniela Brunner

    Full Text Available Autism spectrum disorder comprises several neurodevelopmental conditions presenting symptoms in social communication and restricted, repetitive behaviors. A major roadblock for drug development for autism is the lack of robust behavioral signatures predictive of clinical efficacy. To address this issue, we further characterized, in a uniform and rigorous way, mouse models of autism that are of interest because of their construct validity and wide availability to the scientific community. We implemented a broad behavioral battery that included but was not restricted to core autism domains, with the goal of identifying robust, reliable phenotypes amenable for further testing. Here we describe comprehensive findings from two known mouse models of autism, obtained at different developmental stages, using a systematic behavioral test battery combining standard tests as well as novel, quantitative, computer-vision based systems. The first mouse model recapitulates a deletion in human chromosome 16p11.2, found in 1% of individuals with autism. The second mouse model harbors homozygous null mutations in Cntnap2, associated with autism and Pitt-Hopkins-like syndrome. Consistent with previous results, 16p11.2 heterozygous null mice, also known as Del(7Slx1b-Sept14Aam weighed less than wild type littermates displayed hyperactivity and no social deficits. Cntnap2 homozygous null mice were also hyperactive, froze less during testing, showed a mild gait phenotype and deficits in the three-chamber social preference test, although less robust than previously published. In the open field test with exposure to urine of an estrous female, however, the Cntnap2 null mice showed reduced vocalizations. In addition, Cntnap2 null mice performed slightly better in a cognitive procedural learning test. Although finding and replicating robust behavioral phenotypes in animal models is a challenging task, such functional readouts remain important in the development of

  6. Comprehensive Analysis of the 16p11.2 Deletion and Null Cntnap2 Mouse Models of Autism Spectrum Disorder.

    Science.gov (United States)

    Brunner, Daniela; Kabitzke, Patricia; He, Dansha; Cox, Kimberly; Thiede, Lucinda; Hanania, Taleen; Sabath, Emily; Alexandrov, Vadim; Saxe, Michael; Peles, Elior; Mills, Alea; Spooren, Will; Ghosh, Anirvan; Feliciano, Pamela; Benedetti, Marta; Luo Clayton, Alice; Biemans, Barbara

    2015-01-01

    Autism spectrum disorder comprises several neurodevelopmental conditions presenting symptoms in social communication and restricted, repetitive behaviors. A major roadblock for drug development for autism is the lack of robust behavioral signatures predictive of clinical efficacy. To address this issue, we further characterized, in a uniform and rigorous way, mouse models of autism that are of interest because of their construct validity and wide availability to the scientific community. We implemented a broad behavioral battery that included but was not restricted to core autism domains, with the goal of identifying robust, reliable phenotypes amenable for further testing. Here we describe comprehensive findings from two known mouse models of autism, obtained at different developmental stages, using a systematic behavioral test battery combining standard tests as well as novel, quantitative, computer-vision based systems. The first mouse model recapitulates a deletion in human chromosome 16p11.2, found in 1% of individuals with autism. The second mouse model harbors homozygous null mutations in Cntnap2, associated with autism and Pitt-Hopkins-like syndrome. Consistent with previous results, 16p11.2 heterozygous null mice, also known as Del(7Slx1b-Sept1)4Aam weighed less than wild type littermates displayed hyperactivity and no social deficits. Cntnap2 homozygous null mice were also hyperactive, froze less during testing, showed a mild gait phenotype and deficits in the three-chamber social preference test, although less robust than previously published. In the open field test with exposure to urine of an estrous female, however, the Cntnap2 null mice showed reduced vocalizations. In addition, Cntnap2 null mice performed slightly better in a cognitive procedural learning test. Although finding and replicating robust behavioral phenotypes in animal models is a challenging task, such functional readouts remain important in the development of therapeutics and we

  7. Self-Nulling Lock-in Detection Electronics for Capacitance Probe Electrometer

    Science.gov (United States)

    Blaes, Brent R.; Schaefer, Rembrandt T.

    2012-01-01

    A multi-channel electrometer voltmeter that employs self-nulling lock-in detection electronics in conjunction with a mechanical resonator with noncontact voltage sensing electrodes has been developed for space-based measurement of an Internal Electrostatic Discharge Monitor (IESDM). The IESDM is new sensor technology targeted for integration into a Space Environmental Monitor (SEM) subsystem used for the characterization and monitoring of deep dielectric charging on spacecraft. Use of an AC-coupled lock-in amplifier with closed-loop sense-signal nulling via generation of an active guard-driving feedback voltage provides the resolution, accuracy, linearity and stability needed for long-term space-based measurement of the IESDM. This implementation relies on adjusting the feedback voltage to drive the sense current received from the resonator s variable-capacitance-probe voltage transducer to approximately zero, as limited by the signal-to-noise performance of the loop electronics. The magnitude of the sense current is proportional to the difference between the input voltage being measured and the feedback voltage, which matches the input voltage when the sense current is zero. High signal-to-noise-ratio (SNR) is achieved by synchronous detection of the sense signal using the correlated reference signal derived from the oscillator circuit that drives the mechanical resonator. The magnitude of the feedback voltage, while the loop is in a settled state with essentially zero sense current, is an accurate estimate of the input voltage being measured. This technique has many beneficial attributes including immunity to drift, high linearity, high SNR from synchronous detection of a single-frequency carrier selected to avoid potentially noisy 1/f low-frequency spectrum of the signal-chain electronics, and high accuracy provided through the benefits of a driven shield encasing the capacitance- probe transducer and guarded input triaxial lead-in. Measurements obtained from a

  8. Optical Surface Transformation: Changing the optical surface by homogeneous optic-null medium at will

    Science.gov (United States)

    Sun, Fei; He, Sailing

    2015-10-01

    A new theory on designing electromagnetic/optical devices is proposed, namely, an optical surface transformation (OST). One arbitrary surface can establish the corresponding relationship with another surface entirely optically with an optic-null medium (ONM), (i.e. the electromagnetic wave propagates from one surface to its equivalent surface without any phase delay). Many novel optical devices can be designed by an OST with the help of an ONM. Compared with traditional devices designed by Transformation Optics, our optical surface-reshaping devices have two main advantages. Firstly, the design process is very simple (i.e. we do not need to consider any mathematics on how to make a coordinate transformation, and what we need to do is simply to design the shapes of the input and the output surfaces of the devices). Secondly, we only need one homogeneous anisotropic medium to realize all devices designed by this method. Our method will explore a new way to design novel optical devices without considering any coordinate transformations.

  9. Calcium Homeostasis and Muscle Energy Metabolism Are Modified in HspB1-Null Mice

    Directory of Open Access Journals (Sweden)

    Brigitte Picard

    2016-05-01

    Full Text Available Hsp27—encoded by HspB1—is a member of the small heat shock proteins (sHsp, 12–43 kDa (kilodalton family. This protein is constitutively present in a wide variety of tissues and in many cell lines. The abundance of Hsp27 is highest in skeletal muscle, indicating a crucial role for muscle physiology. The protein identified as a beef tenderness biomarker was found at a crucial hub in a functional network involved in beef tenderness. The aim of this study was to analyze the proteins impacted by the targeted invalidation of HspB1 in the Tibialis anterior muscle of the mouse. Comparative proteomics using two-dimensional gel electrophoresis revealed 22 spots that were differentially abundant between HspB1-null mice and their controls that could be identified by mass spectrometry. Eighteen spots were more abundant in the muscle of the mutant mice, and four were less abundant. The proteins impacted by the absence of Hsp27 belonged mainly to calcium homeostasis (Srl and Calsq1, contraction (TnnT3, energy metabolism (Tpi1, Mdh1, PdhB, Ckm, Pygm, ApoA1 and the Hsp proteins family (HspA9. These data suggest a crucial role for these proteins in meat tenderization. The information gained by this study could also be helpful to predict the side effects of Hsp27 depletion in muscle development and pathologies linked to small Hsps.

  10. Dancing with the dead: Eph receptors and their kinase-null partners.

    Science.gov (United States)

    Truitt, Luke; Freywald, Andrew

    2011-04-01

    Eph receptor tyrosine kinases and their ligands, ephrins, are membrane proteins coordinating a wide range of biological functions both in developing embryos and in adult multicellular organisms. Numerous studies have implicated Eph receptors in the induction of opposing responses, including cell adhesion or repulsion, support or inhibition of cell proliferation and cell migration, and progression or suppression of multiple malignancies. Similar to other receptor tyrosine kinases, Eph receptors rely on their ability to catalyze tyrosine phosphorylation for signal transduction. Interestingly, however, Eph receptors also actively utilize three kinase-deficient receptor tyrosine kinases, EphB6, EphA10, and Ryk, in their signaling network. The accumulating evidence suggests that the unusual flexibility of the Eph family, allowing it to initiate antagonistic responses, might be partially explained by the influence of the kinase-dead participants and that the exact outcome of an Eph-mediated action is likely to be defined by the balance between the signaling of catalytically potent and catalytically null receptors. We discuss in this minireview the emerging functions of the kinase-dead EphB6, EphA10, and Ryk receptors both in normal biological responses and in malignancy, and analyze currently available information related to the molecular mechanisms of their action in the context of the Eph family. PMID:21455264

  11. Was Lates Late? A Null Model for the Nile Perch Boom in Lake Victoria

    Science.gov (United States)

    Downing, Andrea S.; Galic, Nika; Goudswaard, Kees P. C.; van Nes, Egbert H.; Scheffer, Marten; Witte, Frans; Mooij, Wolf M.

    2013-01-01

    Nile perch (Lates niloticus) suddenly invaded Lake Victoria between 1979 and 1987, 25 years after its introduction in the Ugandan side of the lake. Nile perch then replaced the native fish diversity and irreversibly altered the ecosystem and its role to lakeshore societies: it is now a prised export product that supports millions of livelihoods. The delay in the Nile perch boom led to a hunt for triggers of the sudden boom and generated several hypotheses regarding its growth at low abundances – all hypotheses having important implications for the management of Nile perch stocks. We use logistic growth as a parsimonious null model to predict when the Nile perch invasion should have been expected, given its growth rate, initial stock size and introduction year. We find the first exponential growth phase can explain the timing of the perch boom at the scale of Lake Victoria, suggesting that complex mechanisms are not necessary to explain the Nile perch invasion or its timing. However, the boom started in Kenya before Uganda, indicating perhaps that Allee effects act at smaller scales than that of the whole Lake. The Nile perch invasion of other lakes indicates that habitat differences may also have an effect on invasion success. Our results suggest there is probably no single management strategy applicable to the whole lake that would lead to both efficient and sustainable exploitation of its resources. PMID:24204684

  12. The Covariant Entropy Bound, Brane Cosmology, and the Null Energy Condition

    CERN Document Server

    McInnes, B

    2002-01-01

    In discussions of Bousso's Covariant Entropy Bound, the Null Energy Condition is always assumed, as a sufficient *but not necessary* condition which helps to ensure that the entropy on any lightsheet shall necessarily be finite. The spectacular failure of the Strong Energy Condition in cosmology has, however, led many astrophysicists and cosmologists to consider models which violate all of the energy conditions, and indeed the current data do not completely rule out such models. The NEC also has a questionable status in brane cosmology: it is probably necessary to violate the NEC in the bulk in order to obtain a "self-tuning" theory of the cosmological constant. In order to investigate these proposals, we modify the Karch-Randall model by introducing NEC-violating matter into $AdS_5$ in such a way that the brane cosmological constant relaxes to zero. The entropy on lightsheets remains finite. However, we still find that the spacetime is fundamentally incompatible with the Covariant Entropy Bound machinery, in...

  13. TEMPEST simulations of the plasma transport in a single-null tokamak geometry

    Science.gov (United States)

    Xu, X. Q.; Bodi, K.; Cohen, R. H.; Krasheninnikov, S.; Rognlien, T. D.

    2010-06-01

    We present edge kinetic ion transport simulations of tokamak plasmas in magnetic divertor geometry using the fully nonlinear (full-f) continuum code TEMPEST. Besides neoclassical transport, a term for divergence of anomalous kinetic radial flux is added to mock up the effect of turbulent transport. To study the relative roles of neoclassical and anomalous transport, TEMPEST simulations were carried out for plasma transport and flow dynamics in a single-null tokamak geometry, including the pedestal region that extends across the separatrix into the scrape-off layer and private flux region. A series of TEMPEST simulations were conducted to investigate the transition of midplane pedestal heat flux and flow from the neoclassical to the turbulent limit and the transition of divertor heat flux and flow from the kinetic to the fluid regime via an anomalous transport scan and a density scan. The TEMPEST simulation results demonstrate that turbulent transport (as modelled by large diffusion) plays a similar role to collisional decorrelation of particle orbits and that the large turbulent transport (large diffusion) leads to an apparent Maxwellianization of the particle distribution. We also show the transition of parallel heat flux and flow at the entrance to the divertor plates from the fluid to the kinetic regime. For an absorbing divertor plate boundary condition, a non-half-Maxwellian is found due to the balance between upstream radial anomalous transport and energetic ion endloss.

  14. TEMPEST simulations of the neoclassical transport in a single-null tokamak geometry

    Science.gov (United States)

    Xu, X. Q.; Cohen, R. H.; Rognlien, T. D.

    2009-05-01

    TEMPEST simulations were carried out for plasma transport and flow dynamics in a single-null tokamak geometry. The core radial boundary ion distribution is a fixed Maxwellian FM with N0=N(ψ0) and Ti0=Ti(ψ0)=300eV, and exterior radial boundary ion distribution is Neumann boundary condition with Fi(,,μ)/ψ|ψw=0 during a simulation. Given boundary conditions and initial profiles, the interior plasmas in the simulations should evolve into a neoclassical steady state. A volume source term in the private flux region is included, representing the ionization in the private flux region to achieve the neoclassical steady state. A series of TEMPEST simulations are conducted to investigate the scaling characteristics of the neoclassical transport and flow as a function of ν*i via a density scan. Here ν*i is the effective collision frequency, defined by ν*i=&-3/2circ;νii√2qR0/vTi, νii is the ion-ion collision, and vTi the ion thermal velocity. Simulation results show significant poloidal variation of density and ion temperature profiles due to the endloss machanism at the divertor plates. Each region (Edge, the SOL and private flux) achieves the dynamical steady state at its own time scale due to the different physical processes. The impact of self-consistent electric field on transport and flow will be presented.

  15. Joint dysfunction and functional decline in middle age myostatin null mice.

    Science.gov (United States)

    Guo, Wen; Miller, Andrew D; Pencina, Karol; Wong, Siu; Lee, Amanda; Yee, Michael; Toraldo, Gianluca; Jasuja, Ravi; Bhasin, Shalender

    2016-02-01

    Since its discovery as a potent inhibitor for muscle development, myostatin has been actively pursued as a drug target for age- and disease-related muscle loss. However, potential adverse effects of long-term myostatin deficiency have not been thoroughly investigated. We report herein that male myostatin null mice (mstn(-/-)), in spite of their greater muscle mass compared to wild-type (wt) mice, displayed more significant functional decline from young (3-6months) to middle age (12-15months) than age-matched wt mice, measured as gripping strength and treadmill endurance. Mstn(-/-) mice displayed markedly restricted ankle mobility and degenerative changes of the ankle joints, including disorganization of bone, tendon and peri-articular connective tissue, as well as synovial thickening with inflammatory cell infiltration. Messenger RNA expression of several pro-osteogenic genes was higher in the Achilles tendon-bone insertion in mstn(-/-) mice than wt mice, even at the neonatal age. At middle age, higher plasma concentrations of growth factors characteristic of excessive bone remodeling were found in mstn(-/-) mice than wt controls. These data collectively indicate that myostatin may play an important role in maintaining ankle and wrist joint health, possibly through negative regulation of the pro-osteogenic WNT/BMP pathway. PMID:26549246

  16. Null geodesics in the Alcubierre warp drive spacetime the view from the bridge

    CERN Document Server

    Clark, C; Larson, S L; Clark, Chad; Hiscock, William A.; Larson, Shane L.

    1999-01-01

    The null geodesic equations in the Alcubierre warp drive spacetime are numerically integrated to determine the angular deflection and redshift of photons which propagate through the distortion of the ``warp drive'' bubble to reach an observer at the origin of the warp effect. We find that for a starship with an effective warp speed exceeding the speed of light, stars in the forward hemisphere will appear closer to the direction of motion than they would to an observer at rest. This aberration is qualitatively similar to that caused by special relativity. Behind the starship, a conical region forms from within which no signal can reach the starship, an effective ``horizon''. Conversely, there is also an horizon-like structure in a conical region in front of the starship, into which the starship cannot send a signal. These causal structures are somewhat analogous to the Mach cones associated with supersonic fluid flow. The existence of these structures suggests that the divergence of quantum vacuum energy when ...

  17. The Primordial Inflation Explorer (PIXIE): A Nulling Polarimeter for Cosmic Microwave Background Observations

    Science.gov (United States)

    Kogut, Alan J.; Fixsen, D. J.; Chuss, D. T.; Dotson, J.; Dwek, E.; Halpern, M.; Hinshaw, G. F.; Meyer, S. M.; Moseley, S. H.; Seiffert, M. D.; Spergel, D. N.; Wollack, E. J.

    2011-01-01

    The Primordial Inflation Explorer (PIXIE) is a concept for an Explorer-class mission to measure the gravity-wave signature of primordial inflation through its distinctive imprint on the linear polarization of the cosmic microwave background. The instrument consists of a polarizing Michelson interferometer configured as a nulling polarimeter to measure the difference spectrum between orthogonal linear polarizations from two co-aligned beams. Either input can view the sky or a temperature-controlled absolute reference blackbody calibrator. Rhe proposed instrument can map the absolute intensity and linear polarization (Stokes I, Q, and U parameters) over the full sky in 400 spectral channels spanning 2.5 decades in frequency from 30 GHz to 6 THz (1 cm to 50 micron wavelength). Multi-moded optics provide background-limited sensitivity using only 4 detectors, while the highly symmetric design and multiple signal modulations provide robust rejection of potential systematic errors. The principal science goal is the detection and characterization of linear polarization from an inflationary epoch in the early universe, with tensor-to-scalar ratio r cosmology to the nature of the first stars to physical conditions within the interstellar medium of the Galaxy.

  18. Estimation of Neutral Density in Edge Plasma with Double Null Configuration in EAST

    Science.gov (United States)

    Zhang, Ling; Xu, Guosheng; Ding, Siye; Gao, Wei; Wu, Zhenwei; Chen, Yingjie; Huang, Juan; Liu, Xiaoju; Zang, Qing; Chang, Jiafeng; Zhang, Wei; Li, Yingying; Qian, Jinping

    2011-08-01

    In this work, population coefficients of hydrogen's n = 3 excited state from the hydrogen collisional-radiative (CR) model, from the data file of DEGAS 2, are used to calculate the photon emissivity coefficients (PECs) of hydrogen Balmer-α (n = 3 → n = 2) (Hα). The results are compared with the PECs from Atomic Data and Analysis Structure (ADAS) database, and a good agreement is found. A magnetic surface-averaged neutral density profile of typical double-null (DN) plasma in EAST is obtained by using FRANTIC, the 1.5-D fluid transport code. It is found that the sum of integral Dα and Hα emission intensity calculated via the neutral density agrees with the measured results obtained by using the absolutely calibrated multi-channel poloidal photodiode array systems viewing the lower divertor at the last closed flux surface (LCFS). It is revealed that the typical magnetic surface-averaged neutral density at LCFS is about 3.5 × 1016 m-3.

  19. Estimation of Neutral Density in Edge Plasma with Double Null Configuration in EAST

    International Nuclear Information System (INIS)

    In this work, population coefficients of hydrogen's n = 3 excited state from the hydrogen collisional-radiative (CR) model, from the data file of DEGAS 2, are used to calculate the photon emissivity coefficients (PECs) of hydrogen Balmer-α (n = 3 → n = 2) (Hα). The results are compared with the PECs from Atomic Data and Analysis Structure (ADAS) database, and a good agreement is found. A magnetic surface-averaged neutral density profile of typical double-null (DN) plasma in EAST is obtained by using FRANTIC, the 1.5-D fluid transport code. It is found that the sum of integral Dα and Hα emission intensity calculated via the neutral density agrees with the measured results obtained by using the absolutely calibrated multi-channel poloidal photodiode array systems viewing the lower divertor at the last closed flux surface (LCFS). It is revealed that the typical magnetic surface-averaged neutral density at LCFS is about 3.5 x 1016 m-3. (magnetically confined plasma)

  20. Naphthoquinone Derivative PPE8 Induces Endoplasmic Reticulum Stress in p53 Null H1299 Cells

    Directory of Open Access Journals (Sweden)

    Jin-Cherng Lien

    2015-01-01

    Full Text Available Endoplasmic reticulum (ER plays a key role in synthesizing secretory proteins and sensing signal function in eukaryotic cells. Responding to calcium disturbance, oxidation state change, or pharmacological agents, ER transmembrane protein, inositol-regulating enzyme 1 (IRE1, senses the stress and triggers downstream signals. Glucose-regulated protein 78 (GRP78 dissociates from IRE1 to assist protein folding and guard against cell death. In prolonged ER stress, IRE1 recruits and activates apoptosis signal-regulating kinase 1 (ASK1 as well as downstream JNK for cell death. Naphthoquinones are widespread natural phenolic compounds. Vitamin K3, a derivative of naphthoquinone, inhibits variant tumor cell growth via oxygen uptake and oxygen stress. We synthesized a novel naphthoquinone derivative PPE8 and evaluated capacity to induce ER stress in p53 null H1299 and p53 wild-type A549 cells. In H1299 cells, PPE8 induced ER enlargement, GRP78 expression, and transient IER1 activation. Activated IRE1 recruited ASK1 for downstream JNK phosphorylation. IRE1 knockdown by siRNA attenuated PPE8-induced JNK phosphorylation and cytotoxicity. Prolonged JNK phosphorylation may be involved in PPE8-induced cytotoxicity. Such results did not arise in A549 cells, but p53 knockdown by siRNA restored PPE8-induced GRP78 expression and JNK phosphorylation. We offer a novel compound to induce ER stress and cytotoxicity in p53-deficient cancer cells, presenting an opportunity for treatment.

  1. Lack of major genome instability in tumors of p53 null rats.

    Directory of Open Access Journals (Sweden)

    Roel Hermsen

    Full Text Available Tumorigenesis is often associated with loss of tumor suppressor genes (such as TP53, genomic instability and telomere lengthening. Previously, we generated and characterized a rat p53 knockout model in which the homozygous rats predominantly develop hemangiosarcomas whereas the heterozygous rats mainly develop osteosarcomas. Using genome-wide analyses, we find that the tumors that arise in the heterozygous and homozygous Tp53C273X mutant animals are also different in their genomic instability profiles. While p53 was fully inactivated in both heterozygous and homozygous knockout rats, tumors from homozygous animals show very limited aneuploidy and low degrees of somatic copy number variation as compared to the tumors from heterozygous animals. In addition, complex structural rearrangements such as chromothripsis and breakage-fusion-bridge cycles were never found in tumors from homozygous animals, while these were readily detectable in tumors from heterozygous animals. Finally, we measured telomere length and telomere lengthening pathway activity and found that tumors of homozygous animals have longer telomeres but do not show clear telomerase or alternative lengthening of telomeres (ALT activity differences as compared to the tumors from heterozygous animals. Taken together, our results demonstrate that host p53 status in this rat p53 knockout model has a large effect on both tumor type and genomic instability characteristics, where full loss of functional p53 is not the main driver of large-scale structural variations. Our results also suggest that chromothripsis primarily occurs under p53 heterozygous rather than p53 null conditions.

  2. Particle transport studies for single-null divertor discharges in DIII-D

    International Nuclear Information System (INIS)

    In this paper an investigation of the particle confinement for beam-heated single-null discharges in the open divertor configuration of Doublet III-D (DIII-D) [E. J. Doyle et al., Phys. Fluids B 3, 2300 (1991)] is described. Results are based on a Monte Carlo neutral transport model with a relatively simple plasma model that utilizes experimental data on density, temperature, and heat flux profiles in the edge plasma. For a typical discharge, it is found that the particle confinement time in the quiescent H-mode phase is only about a factor of 2 larger than during the L-mode phase, an increase comparable to the energy confinement time increase. For both H-mode and L-mode phases the particle confinement time is about a factor of 4 larger than the energy confinement time. It is also found that the core plasma fueling rate is higher in the H mode due to the increased transparency of a thinner scrape-off layer. The longer particle confinement time and the increased fueling rate both contribute to the observed density rise during the quiescent period following the L--H transition. Flux surface-averaged transport modeling of the time evolution for the core plasma density profile during H mode suggests that a strong inward particle pinch is necessary near the separatrix

  3. Evidence of Aortopathy in Mice with Haploinsufficiency of Notch1 in Nos3-Null Background

    Directory of Open Access Journals (Sweden)

    Sara N. Koenig

    2015-03-01

    Full Text Available Thoracic aortic aneurysms (TAA are a significant cause of morbidity and mortality in humans. While the exact etiology is unknown, genetic factors play an important role. Mutations in NOTCH1 have been linked to bicuspid aortic valve (BAV and aortopathy in humans. The aim of this study was to determine if haploinsufficiency of Notch1 contributes to aortopathy using Notch1+/−; Nos3−/− mice. Echocardiographic analysis of Notch1+/−; Nos3−/− mice reveals effacement of the sinotubular junction and a trend toward dilation of the aortic sinus. Furthermore, examination of the proximal aorta of Notch1+/−; Nos3−/− mice reveals elastic fiber degradation, a trend toward increased matrix metalloproteinase 2 expression, and increased smooth muscle cell apoptosis, features characteristic of aneurysmal disease. Although at a lower penetrance, we also found features consistent with aortopathic changes in Notch1 heterozygote mice and in Nos3-null mice. Our findings implicate a novel role for Notch1 in aortopathy of the proximal aorta.

  4. Enhanced activity of the CREB co-activator Crtc1 in LKB1 null lung cancer.

    Science.gov (United States)

    Komiya, T; Coxon, A; Park, Y; Chen, W-D; Zajac-Kaye, M; Meltzer, P; Karpova, T; Kaye, F J

    2010-03-18

    Activation of Crtc1 (also known as Mect1/Torc1) by a t(11;19) chromosomal rearrangement underlies the etiology of malignant salivary gland tumors. As LKB1 is a target for mutational inactivation in lung cancer and was recently shown to regulate hepatic Crtc2/CREB transcriptional activity in mice, we now present evidence suggesting disruption of an LKB1/Crtc pathway in cancer. Although Crtc1 is preferentially expressed in adult brain tissues, we observed elevated levels of steady-state Crtc1 in thoracic tumors. In addition, we show that somatic loss of LKB1 is associated with underphosphorylation of endogenous Crtc1, enhanced Crtc1 nuclear localization and enhanced expression of the Crtc prototypic target gene, NR4A2/Nurr1. Inhibition of NR4A2 was associated with growth suppression of LKB1 null tumors, but showed little effect on LKB1-wildtype cells. These data strengthen the role of dysregulated Crtc as a bona fide cancer gene, present a new element to the complex LKB1 tumorigenic axis, and suggest that Crtc genes may be aberrantly activated in a wider range of common adult malignancies.

  5. Juvenile manifestation of ultrasound communication deficits in the neuroligin-4 null mutant mouse model of autism.

    Science.gov (United States)

    Ju, Anes; Hammerschmidt, Kurt; Tantra, Martesa; Krueger, Dilja; Brose, Nils; Ehrenreich, Hannelore

    2014-08-15

    Neuroligin-4 (Nlgn4) is a member of the neuroligin family of postsynaptic cell adhesion molecules. Loss-of-function mutations of NLGN4 are among the most frequent, known genetic causes of heritable autism. Adult Nlgn4 null mutant (Nlgn4(-/-)) mice are a construct valid model of human autism, with both genders displaying a remarkable autistic phenotype, including deficits in social interaction and communication as well as restricted and repetitive behaviors. In contrast to adults, autism-related abnormalities in neonatal and juvenile Nlgn4(-/-) mice have not been reported yet. The present study has been designed to systematically investigate in male and female Nlgn4(-/-) pups versus wildtype littermates (WT, Nlgn4(+/+)) developmental milestones and stimulus-induced ultrasound vocalization (USV). Neonatal development, followed daily from postnatal days (PND) 4 to 21, including physical development, neurological reflexes and neuromotor coordination, did not yield any differences between Nlgn4(-/-) and their WT littermates. USV in pups (PND8-9) in response to brief separation from their mothers revealed remarkable gender effects, and a genotype influence in females regarding latency to first call. In juveniles (PND22-23), USV monitoring upon exposure to an anesthetized female intruder mouse uncovered a clear genotype effect with reduced USV in Nlgn4(-/-) mice, and again a more prominent phenotype in females. Together, these data support an early manifestation of communication deficits in Nlgn4(-/-) mice that appear more pronounced in immature females with their overall stronger USV as compared to males. PMID:24855039

  6. Forelimb contractures and abnormal tendon collagen fibrillogenesis in fibulin-4 null mice.

    Science.gov (United States)

    Markova, Dessislava Z; Pan, Te-Cheng; Zhang, Rui-Zhu; Zhang, Guiyun; Sasaki, Takako; Arita, Machiko; Birk, David E; Chu, Mon-Li

    2016-06-01

    Fibulin-4 is an extracellular matrix glycoprotein essential for elastic fiber formation. Mice deficient in fibulin-4 die perinatally because of severe pulmonary and vascular defects associated with the lack of intact elastic fibers. Patients with fibulin-4 mutations demonstrate similar defects, and a significant number die shortly after birth or in early childhood from cardiopulmonary failure. The patients also demonstrate skeletal and other systemic connective tissue abnormalities, including joint laxity and flexion contractures of the wrist. A fibulin-4 null mouse strain was generated and used to analyze the roles of fibulin-4 in tendon fibrillogenesis. This mouse model displayed bilateral forelimb contractures, in addition to pulmonary and cardiovascular defects. The forelimb and hindlimb tendons exhibited disruption in collagen fibrillogenesis in the absence of fibulin-4 as analyzed by transmission electron microscopy. Fewer fibrils were assembled, and fibrils were disorganized compared with wild-type controls. The organization of developing tenocytes and compartmentalization of the extracellular space was also disrupted. Fibulin-4 was co-localized with fibrillin-1 and fibrillin-2 in limb tendons by using immunofluorescence microscopy. Thus, fibulin-4 seems to play a role in regulating tendon collagen fibrillogenesis, in addition to its essential function in elastogenesis. PMID:26711913

  7. The Primordial Inflation Explorer (PIXIE): a nulling polarimeter for cosmic microwave background observations

    International Nuclear Information System (INIS)

    The Primordial Inflation Explorer (PIXIE) is a concept for an Explorer-class mission to measure the gravity-wave signature of primordial inflation through its distinctive imprint on the linear polarization of the cosmic microwave background. The instrument consists of a polarizing Michelson interferometer configured as a nulling polarimeter to measure the difference spectrum between orthogonal linear polarizations from two co-aligned beams. Either input can view the sky or a temperature-controlled absolute reference blackbody calibrator. Rhe proposed instrument can map the absolute intensity and linear polarization (Stokes I, Q, and U parameters) over the full sky in 400 spectral channels spanning 2.5 decades in frequency from 30 GHz to 6 THz (1 cm to 50 μm wavelength). Multi-moded optics provide background-limited sensitivity using only 4 detectors, while the highly symmetric design and multiple signal modulations provide robust rejection of potential systematic errors. The principal science goal is the detection and characterization of linear polarization from an inflationary epoch in the early universe, with tensor-to-scalar ratio r −3 at 5 standard deviations. The rich PIXIE data set can also constrain physical processes ranging from Big Bang cosmology to the nature of the first stars to physical conditions within the interstellar medium of the Galaxy

  8. Reproducible Analysis and Blindness in a Null Test of Newton's Gravitational Inverse Square Law At Sub-millimeter Scales

    Science.gov (United States)

    Hagedorn, Charles; Venkateswara, Krishna; Gundlach, Jens

    2016-03-01

    Proper execution of an experiment is independent of its result. Physicists who test fundamental physical law face the reality that signals for new physics receive more attention and scrutiny than null results. Yet, null results may have greater impact upon the direction of both experiment and theory. Blind experiments and result-blind review are bulwarks against systematic human bias for both experimenters and referees. I'll describe the method that made possible an irreversible public unblinding of our torsion-balance parallel-plate test of gravity at submillimeter scales in 2015. One publicly-available computer procedure generated from blind raw data the analysis, the final result, and the complete documenting thesis. The experiment included an optical ``foil monitor'' to constrain a systematic effect intrinsic to all short-range parallel-plate gravity experiments. I'll describe the experiment, successes, lessons learned, and result. Supported by NSF (PHY-1305726) and DOE support for CENPA.

  9. No actual measurement ... was required: Maxwell and Cavendish's null method for the inverse square law of electrostatics

    CERN Document Server

    Falconer, Isobel

    2016-01-01

    In 1877 James Clerk Maxwell and his student Donald McAlister refined Henry Cavendish's 1773 null experiment demonstrating the absence of electric charge inside a charged conductor. Such absence of charge was a mathematical prediction of the inverse square law, and both Cavendish and Maxwell took the experiment as verifying the law. However, Maxwell had previously expressed absolute conviction in the law, based on results of Faraday's. So what was the value to Maxwell of replicating Cavendish's experiment? This paper examines the mathematical and instrumental contexts of Maxwell's experiment. It situates the experiment in an assessment of the status of the inverse square law in the 1870s based on textbooks, Maxwell's drive to develop both an electrical programme and a "doctrine of method", and an investigation of the understanding of null methods in the 1870s. It demonstrates that he had previously shifted the evidential context of Faraday's work to suit his aims. It concludes that the experiment served both a...

  10. Performance Analysis of Anti-Interference Wireless Packet Networks for LEO Micro-Satellite with Adaptive Nulling Antenna Array

    Institute of Scientific and Technical Information of China (English)

    LIU Hai-tao; HAN Fang-jing; WAN Jian-wei

    2006-01-01

    Information integrity is key to successful operations in intricacy environments in the future, especially when strong interferences exist. This paper presents the design of a novel wireless packet network receiver system for Low Earth Orbit (LEO) micro-satellites with adaptive nulling antenna arrays. It uses three types of interference suppression in cascade: namely spread spectrum, adaptive array nulling, and transform domain filtering. This paper proposes a pilot channel-aided method in order to make full advantage of this arrangement, and analyzes its throughput and delay performance using the Markov chain model. Our results show that this method can achieve excellent delay and throughput performance: When the number of array antenna is 8, its throughput increase relative to the standard Slot-ALOHA protocol is 125 %.

  11. Co-channel Interference Cancellation for Space-Time Coded OFDM Systems Using Adaptive Beamforming and Null Deepening

    CERN Document Server

    Suleesathira, Raungrong

    2010-01-01

    Combined with space-time coding, the orthogonal frequency division multiplexing (OFDM) system explores space diversity. It is a potential scheme to offer spectral efficiency and robust high data rate transmissions over frequency-selective fading channel. However, space-time coding impairs the system ability to suppress interferences as the signals transmitted from two transmit antennas are superposed and interfered at the receiver antennas. In this paper, we developed an adaptive beamforming based on least mean squared error algorithm and null deepening to combat co-channel interference (CCI) for the space-time coded OFDM (STC-OFDM) system. To illustrate the performance of the presented approach, it is compared to the null steering beamformer which requires a prior knowledge of directions of arrival (DOAs). The structure of space-time decoders are preserved although there is the use of beamformers before decoding. By incorporating the proposed beamformer as a CCI canceller in the STC-OFDM systems, the perform...

  12. Enhanced Food Anticipatory Activity Associated with Enhanced Activation of Extrahypothalamic Neural Pathways in Serotonin2C Receptor Null Mutant Mice

    OpenAIRE

    Mistlberger, Ralph; Hsu, Jennifer; Yu, Lisa; Bowman, Melody; Tecott, Laurence; Sullivan, Elinor

    2010-01-01

    The ability to entrain circadian rhythms to food availability is important for survival. Food-entrained circadian rhythms are characterized by increased locomotor activity in anticipation of food availability (food anticipatory activity). However, the molecular components and neural circuitry underlying the regulation of food anticipatory activity remain unclear. Here we show that serotonin2C receptor (5-HT2CR) null mutant mice subjected to a daytime restricted feeding schedule exhibit enhanc...

  13. The Influence of Matrix Size on Statistical Properties of Co-Occurrence and Limiting Similarity Null Models.

    Science.gov (United States)

    Lavender, Thomas Michael; Schamp, Brandon S; Lamb, Eric G

    2016-01-01

    Null models exploring species co-occurrence and trait-based limiting similarity are increasingly used to explore the influence of competition on community assembly; however, assessments of common models have not thoroughly explored the influence of variation in matrix size on error rates, in spite of the fact that studies have explored community matrices that vary considerably in size. To determine how smaller matrices, which are of greatest concern, perform statistically, we generated biologically realistic presence-absence matrices ranging in size from 3-50 species and sites, as well as associated trait matrices. We examined co-occurrence tests using the C-Score statistic and independent swap algorithm. For trait-based limiting similarity null models, we used the mean nearest neighbour trait distance (NN) and the standard deviation of nearest neighbour distances (SDNN) as test statistics, and considered two common randomization algorithms: abundance independent trait shuffling (AITS), and abundance weighted trait shuffling (AWTS). Matrices as small as three × three resulted in acceptable type I error rates (p ) was associated with increased type I error rates, particularly for matrices with fewer than eight species. Type I error rates increased for limiting similarity tests using the AWTS randomization scheme when community matrices contained more than 35 sites; a similar randomization used in null models of phylogenetic dispersion has previously been viewed as robust. Notwithstanding other potential deficiencies related to the use of small matrices to represent communities, the application of both classes of null model should be restricted to matrices with 10 or more species to avoid the possibility of type II errors. Additionally, researchers should restrict the use of the AWTS randomization to matrices with fewer than 35 sites to avoid type I errors when testing for trait-based limiting similarity. The AITS randomization scheme performed better in terms of

  14. FIRST-LIGHT LBT NULLING INTERFEROMETRIC OBSERVATIONS: WARM EXOZODIACAL DUST RESOLVED WITHIN A FEW AU OF η Crv

    Energy Technology Data Exchange (ETDEWEB)

    Defrère, D.; Hinz, P. M.; Skemer, A. J.; Bailey, V. P.; Hoffmann, W. F.; Arbo, P.; Brusa, G.; Downey, E. C.; Durney, O.; Gaspar, A.; Grenz, P. [Steward Observatory, Department of Astronomy, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Kennedy, G. M. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Mennesson, B.; Bryden, G. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109-8099 (United States); Millan-Gabet, R.; Beichman, C. [NASA Exoplanet Science Institute, California Institute of Technology, 770 South Wilson Avenue, Pasadena, CA 91125 (United States); Danchi, W. C. [NASA Goddard Space Flight Center, Exoplanets and Stellar Astrophysics Laboratory, Code 667, Greenbelt, MD 20771 (United States); Absil, O. [Département d' Astrophysique, Géophysique et Océanographie, Université de Liège, 17 Allée du Six Août, B-4000 Sart Tilman (Belgium); Esposito, S. [INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze (Italy); Haniff, C., E-mail: ddefrere@email.arizona.edu [Cavendish Laboratory, University of Cambridge, JJ Thomson Avenue, Cambridge CB3 0HE (United Kingdom); and others

    2015-01-20

    We report on the first nulling interferometric observations with the Large Binocular Telescope Interferometer (LBTI), resolving the N' band (9.81-12.41 μm) emission around the nearby main-sequence star η Crv (F2V, 1-2 Gyr). The measured source null depth amounts to 4.40% ± 0.35% over a field-of-view of 140 mas in radius (∼2.6 AU for the distance of η Crv) and shows no significant variation over 35° of sky rotation. This relatively low null is unexpected given the total disk to star flux ratio measured by the Spitzer Infrared Spectrograph (IRS; ∼23% across the N' band), suggesting that a significant fraction of the dust lies within the central nulled response of the LBTI (79 mas or 1.4 AU). Modeling of the warm disk shows that it cannot resemble a scaled version of the solar zodiacal cloud unless it is almost perpendicular to the outer disk imaged by Herschel. It is more likely that the inner and outer disks are coplanar and the warm dust is located at a distance of 0.5-1.0 AU, significantly closer than previously predicted by models of the IRS spectrum (∼3 AU). The predicted disk sizes can be reconciled if the warm disk is not centrosymmetric, or if the dust particles are dominated by very small grains. Both possibilities hint that a recent collision has produced much of the dust. Finally, we discuss the implications for the presence of dust for the distance where the insolation is the same as Earth's (2.3 AU)

  15. Enhanced Aortic Macrophage Lipid Accumulation and Inflammatory Response in LDL Receptor Null Mice Fed an Atherogenic Diet

    OpenAIRE

    Wang, Shu; Wu, Dayong; Matthan, Nirupa R.; Lamon-Fava, Stefania; Lecker, Jaime L; Lichtenstein, Alice H

    2010-01-01

    The effect of an atherogenic diet on inflammatory response and elicited peritoneal macrophage (Mφ) cholesterol accumulation in relation to aortic lesion formation was assessed in LDL receptor null (LDLr−/−) mice. Mice were fed an atherogenic or control diet for 32 weeks. The atherogenic relative to control diet resulted in significantly higher plasma monocyte chemoattractant protein-1 (MCP-1), tumor necrosis factor alpha (TNFα) and interleukin-6 (IL-6) concentrations, more aortic wall Mφ depo...

  16. Modal Filtering for Nulling Interferometry-First Single-Mode Conductive Waveguides in the Mid-Infrared

    OpenAIRE

    Labadie, L.; Labeye, P.; Kern, P.; Schanen, I.; Arezki, B.; Broquin, J. -E.

    2005-01-01

    This paper presents the work achieved for the manufacturing and characterization of first single-mode waveguides to be used as modal filters for nulling interferometry in the mid-infrared range [4-20 um]. As very high dynamic range is mandatory for detection of Earth-like planets, modal filtering is one of the most stringent instrumental aspects. The hollow metallic waveguides (HMW) presented here are manufactured using micro-machining techniques. Single-mode behavior has been investigated in...

  17. On the behaviour of non-radial null geodesics in self-similar Tolman-Bondi collapse

    CERN Document Server

    Ortiz, Néstor; Zannias, Thomas

    2015-01-01

    Motivated by recent work on the structure of the singularity in inhomogeneous Tolman-Bondi collapse models, we investigate the behaviour of null geodesics in the particular case where the collapse is self-similar. The presence of the homothetic Killing vector field implies that the geodesic equation can be described by an integrable Hamiltonian system, and exploiting this fact we provide a full qualitative picture for its phase flow.

  18. Enhanced Food Anticipatory Activity Associated with Enhanced Activation of Extrahypothalamic Neural Pathways in Serotonin2C Receptor Null Mutant Mice

    OpenAIRE

    Hsu, Jennifer L.; Lisa Yu; Elinor Sullivan; Melodi Bowman; Mistlberger, Ralph E.; Tecott, Laurence H.

    2010-01-01

    The ability to entrain circadian rhythms to food availability is important for survival. Food-entrained circadian rhythms are characterized by increased locomotor activity in anticipation of food availability (food anticipatory activity). However, the molecular components and neural circuitry underlying the regulation of food anticipatory activity remain unclear. Here we show that serotonin(2C) receptor (5-HT2CR) null mutant mice subjected to a daytime restricted feeding schedule exhibit enha...

  19. Fibrillin levels in a severely affected Marfan syndrome patient with a null allele

    Energy Technology Data Exchange (ETDEWEB)

    Boxer, M.; Withers, A.P.; Al-Ghaban, Z. [Univ. of Wales, Cardiff (United Kingdom)]|[Ninewells Hospital and Medical School, Dundee (United Kingdom)] [and others

    1994-09-01

    Marfan syndrome is an autosomal dominantly inherited connective tissue disorder characterized by defects in the cardiovascular, skeletal and ocular systems. A patient was first examined in 1992 having survived an acute sortic dissection with subsequent composite repair and insertion of a prosthetic aortic valve. Clinical examination revealed arachnodactyly, narrow, high arched palate with dental crowding, an arm span exceeding her height by 10.5 cm, joint laxity and bilateral lens subluxation. Analysis of the family showed affected members in three generations and the fibrillin gene, FBN1, was shown to segregate with the disease when using polymorphic markers including an RsaI polymorphism in the 3{prime}-untranslated region of the gene. Analysis of patient mRNA for this RsaI polymorphism by RT-PCR (reverse transcriptase-PCR) amplification and restriction enzyme digestion of the PCR products showed that the copy of the gene segregating with the disease was not transcribed. No low level expression of this allele was observed despite RT-PCR amplification incorporating radioactively labelled dCTP, thus revealing a null allele phenotype. Western blotting analysis of fibrillin secreted by the patient`s dermal fibroblasts using fibrillin-specific antibodies showed only normal sized fibrillin protein. However, immunohistochemical studies of the patient`s tissue and fibroblasts showed markedly lowered levels in staining of microfibrillar structures compared with age-matched controls. This low level of expression of the protein affected in Marfan syndrome in a patient with such severe clinical manifestations is surprising since current understanding would suggest that this molecular phenotype should lead to a mild clinical disorder.

  20. Chronic Toxoplasma gondii in Nurr1-null heterozygous mice exacerbates elevated open field activity.

    Directory of Open Access Journals (Sweden)

    Jeffrey B Eells

    Full Text Available Latent infection with Toxoplasma gondii is common in humans (approximately 30% of the global population and is a significant risk factor for schizophrenia. Since prevalence of T. gondii infection is far greater than prevalence of schizophrenia (0.5-1%, genetic risk factors are likely also necessary to contribute to schizophrenia. To test this concept in an animal model, Nurr1-null heterozygous (+/- mice and wild-type (+/+ mice were evaluate using an emergence test, activity in an open field and with a novel object, response to bobcat urine and prepulse inhibition of the acoustic startle response (PPI prior to and 6 weeks after infection with T. gondii. In the emergence test, T. gondii infection significantly decreased the amount of time spent in the cylinder. Toxoplasma gondii infection significantly elevated open field activity in both +/+ and +/- mice but this increase was significantly exacerbated in +/- mice. T. gondii infection reduced PPI in male +/- mice but this was not statistically significant. Aversion to bobcat urine was abolished by T. gondii infection in +/+ mice. In female +/- mice, aversion to bobcat urine remained after T. gondii infection while the male +/- mice showed no aversion to bobcat urine. Antibody titers of infected mice were a critical variable associated with changes in open field activity, such that an inverted U shaped relationship existed between antibody titers and the percent change in open field activity with a significant increase in activity at low and medium antibody titers but no effect at high antibody titers. These data demonstrate that the Nurr1 +/- genotype predisposes mice to T. gondii-induced alterations in behaviors that involve dopamine neurotransmission and are associated with symptoms of schizophrenia. We propose that these alterations in murine behavior were due to further exacerbation of the altered dopamine neurotransmission in Nurr1 +/- mice.

  1. Multiple Null Point Reconnections in a limb faint cool jet ejection event

    Science.gov (United States)

    Tavabi, E.; Koutchmy, S.

    2016-09-01

    Giant spicules and macro- spicules are an important extended rather cool structure between the solar surface and the corona, partly filling the space inside the chromosphere and surrounded by a transition thin region. Their formation and dynamical properties are still mysterious. In order to explain solar limb and disc periodic recurrences of these events, a simulation model assuming quasi- random positions of spicules above the solar limb was studied. We allow a set number of spicules with different physical properties (such as height, lifetime and tilt angle as shown by an individual spicule) randomly occurring. It is assumed that after reaching a maximum length, the spicules are less rapidly falling back to the solar surface. This kind of limb event was often reported in the literature (spike; giant spicule; Ha ejection event; spray etc) but no serious quantitative analysis could be done. Indeed from ground-based observations, it is impossible to deduce precised parameters because the earth atmospheric turbulent effects makes impossible to make small scale measurements. SOT space-borne observations we use are unique in providing well reproducible observations permitting very precise measurements. The study of X-ray jets is an important topic to understand the heating of the solar corona and the origin of the fast wind. The recently launched Hinode mission permitted to observe the cool proxies of these jets with an unprecedented high spatial resolution of 120 km on the Sun. We selected a high cadence sequence of SOT (Hinode) observations taken with both the HCaII and the Hα filter to look at the details of the dynamics revealed by a large jet event. Both wavelet and amplitude spectra analysis were used to analyze the observed kink wave and the time variations of intensities during the event. The results are discussed in the frame of different models implying reconnections with the inference of the dynamical phenomena occurring in the vicinity of several null

  2. Timelike and null equatorial geodesics in the Bonnor-Sackfield relativistic disk

    Directory of Open Access Journals (Sweden)

    Guillermo A. González

    2011-06-01

    Full Text Available A study of timelike and null equatorial geodesics in the BonnorSackfield relativistic thin disk is presented. The motion of test particles in the equatorial plane is analyzed, both for the newtonian thin disk model as for the corresponding relativistic disk. The nature of the possible orbits is studied by means of a qualitative analysis of the effective potential and by numerically solving the motion equation for radial and non-radial equatorial trajectories. The existence of stable, unstable and marginally stable circular orbits is analyzed, both for the newtonian and relativistic case. Examples of the numerical results, obtained with some simple values of the parameters, are presented. Resumen. En este trabajo se presenta un estudio de las geodésicas temporales y nulas en el disco delgado relativista y newtoniano de Bonnor-Sackfield. Se analiza el movimiento de las partículas de prueba en el plano ecuatorial, tanto para el modelo newtoniano del disco delgado como para el disco relativista correspondiente. La naturaleza de las órbitas posibles se estudia por medio de un análisis cualitativo del potencial efectivo, y numéricamente mediante la solución de la ecuación de movimiento de las trayectorias ecuatorial radial y no radial: Se analiza la existencia de órbitas estables, circulares inestables y estables marginalmente, tanto para el caso newtoniano, como el relativista. Se presentan ejemplos de los resultados numéricos obtenidos con algunos valores de los parámetros simples.

  3. Lens transcriptome profile during cataract development in Mip-null mice.

    Science.gov (United States)

    Bennett, Thomas M; Zhou, Yuefang; Shiels, Alan

    2016-09-16

    Major intrinsic protein or aquaporin-0 (MIP/AQP0) functions as a water channel and a cell-junction molecule in the vertebrate eye lens. Loss of MIP function in the lens leads to degraded optical quality and cataract formation by pathogenic mechanisms that are unclear. Here we have used microarray-hybridization analysis to detect lens transcriptome changes during cataract formation in mice that are functionally null for MIP (Mip-/-). In newborn Mip-/- lenses (P1) 11 genes were up-regulated and 18 were down-regulated (>2-fold, p=6-fold) in the Mip-/- lens at P1 included those coding for a mitochondrial translocase (Timmdc1), a matrix metallopeptidase (Mmp2), a Rho GTPase-interacting protein (Ubxn11) and a transcription factor (Twist2). Apart from Mip, the most down-regulated genes (>4-fold) in the Mip-/- lens at P1 included those coding for a proteasome sub-unit (Psmd8), a ribonuclease (Pop4), and a heat-shock protein (Hspb1). Lens fiber cell degeneration in the Mip-/- lens was associated with increased numbers of TUNEL-positive cell nuclei and dramatically elevated levels of calpain-mediated proteolysis of αII-spectrin. However red-ox status, measured by glutathione and free-radical levels, was similar to that of wild-type. These data suggest that while relatively few genes (∼1.5% of the transcriptome) were differentially regulated >2-fold in the Mip-/- lens, calpain hyper-activation acts as a terminal pathogenic event during lens fiber cell death and cataract formation. PMID:27524245

  4. Calsequestrin (CASQ1) rescues function and structure of calcium release units in skeletal muscles of CASQ1-null mice.

    Science.gov (United States)

    Tomasi, Mirta; Canato, Marta; Paolini, Cecilia; Dainese, Marco; Reggiani, Carlo; Volpe, Pompeo; Protasi, Feliciano; Nori, Alessandra

    2012-02-01

    Amplitude of Ca(2+) transients, ultrastructure of Ca(2+) release units, and molecular composition of sarcoplasmic reticulum (SR) are altered in fast-twitch skeletal muscles of calsequestrin-1 (CASQ1)-null mice. To determine whether such changes are directly caused by CASQ1 ablation or are instead the result of adaptive mechanisms, here we assessed ability of CASQ1 in rescuing the null phenotype. In vivo reintroduction of CASQ1 was carried out by cDNA electro transfer in flexor digitorum brevis muscle of the mouse. Exogenous CASQ1 was found to be correctly targeted to the junctional SR (jSR), as judged by immunofluorescence and confocal microscopy; terminal cisternae (TC) lumen was filled with electron dense material and its width was significantly increased, as judged by electron microscopy; peak amplitude of Ca(2+) transients was significantly increased compared with null muscle fibers transfected only with green fluorescent protein (control); and finally, transfected fibers were able to sustain cytosolic Ca(2+) concentration during prolonged tetanic stimulation. Only the expression of TC proteins, such as calsequestrin 2, sarcalumenin, and triadin, was not rescued as judged by Western blot. Thus our results support the view that CASQ1 plays a key role in both Ca(2+) homeostasis and TC structure. PMID:22049211

  5. Toll-like receptor 4 mutant and null mice retain morphine-induced tolerance, hyperalgesia, and physical dependence.

    Directory of Open Access Journals (Sweden)

    Theresa Alexandra Mattioli

    Full Text Available The innate immune system modulates opioid-induced effects within the central nervous system and one target that has received considerable attention is the toll-like receptor 4 (TLR4. Here, we examined the contribution of TLR4 in the development of morphine tolerance, hyperalgesia, and physical dependence in two inbred mouse strains: C3H/HeJ mice which have a dominant negative point mutation in the Tlr4 gene rendering the receptor non-functional, and B10ScNJ mice which are TLR4 null mutants. We found that neither acute antinociceptive response to a single dose of morphine, nor the development of analgesic tolerance to repeated morphine treatment, was affected by TLR4 genotype. Likewise, opioid induced hyperalgesia and opioid physical dependence (assessed by naloxone precipitated withdrawal were not altered in TLR4 mutant or null mice. We also examined the behavioural consequence of two stereoisomers of naloxone: (- naloxone, an opioid receptor antagonist, and (+ naloxone, a purported antagonist of TLR4. Both stereoisomers of naloxone suppressed opioid induced hyperalgesia in wild-type control, TLR4 mutant, and TLR4 null mice. Collectively, our data suggest that TLR4 is not required for opioid-induced analgesic tolerance, hyperalgesia, or physical dependence.

  6. Recovery and Biodistribution of Ex Vivo Expanded Human Erythroblasts Injected into NOD/SCID/IL2Rγnull mice

    Directory of Open Access Journals (Sweden)

    Barbara Ghinassi

    2011-01-01

    Full Text Available Ex vivo expanded erythroblasts (EBs may serve as advanced transfusion products provided that lodgment occurs in the macrophage-niche of the marrow permitting maturation. EBs expanded from adult and cord blood expressed the receptors (CXCR4, VLA-4, and P-selectin ligand 1 necessary for interaction with macrophages. However, 4-days following transfusion to intact NOD/SCID/IL2Rγnull mice, CD235apos EBs were observed inside CD235aneg splenic cells suggesting that they underwent phagocytosis. When splenectomized and intact NOD/SCID/IL2Rγnull mice were transfused using retrovirally labeled human EBs, human cells were visualized by bioluminescence imaging only in splenectomized animals. Four days after injection, human CD235apos cells were detected in marrow and liver of splenectomized mice but only in spleen of controls. Human CD235apos erythrocytes in blood remained low in all cases. These studies establish splenectomized NOD/SCID/IL2Rγnull mice as a suitable model for tracking and quantification of human EBs in vivo.

  7. In-situ observations of flux ropes formed in association with a pair of spiral nulls in magnetotail plasmas

    Science.gov (United States)

    Guo, Ruilong; Pu, Zuyin; Chen, Li-Jen; Fu, Suiyan; Xie, Lun; Wang, Xiaogang; Dunlop, Malcolm; Bogdanova, Yulia V.; Yao, Zhonghua; Xiao, Chijie; He, Jiansen; Fazakerley, Andrew N.

    2016-05-01

    Signatures of secondary islands are frequently observed in the magnetic reconnection regions of magnetotail plasmas. In this paper, magnetic structures with the secondary-island signatures observed by Cluster are reassembled by a fitting-reconstruction method. The results show three-dimensionally that a secondary island event can manifest the flux rope formed with an As-type null and a Bs-type null paired via their spines. We call this As-spine-Bs-like configuration the helically wrapped spine model. The reconstructed field lines wrap around the spine to form the flux rope, and an O-type topology is therefore seen on the plane perpendicular to the spine. Magnetized electrons are found to rotate on and cross the fan surface, suggesting that both the torsional-spine and the spine-fan reconnection take place in the configuration. Furthermore, detailed analysis implies that the spiral nulls and flux ropes were locally generated nearby the spacecraft in the reconnection outflow region, indicating that secondary reconnection may occur in the exhaust away from the primary reconnection site.

  8. An Innovative Approach to Balancing Chemical-Reaction Equations: A Simplified Matrix-Inversion Technique for Determining The Matrix Null Space

    CERN Document Server

    Thorne, Lawrence R

    2011-01-01

    I propose a novel approach to balancing equations that is applicable to all chemical-reaction equations; it is readily accessible to students via scientific calculators and basic computer spreadsheets that have a matrix-inversion application. The new approach utilizes the familiar matrix-inversion operation in an unfamiliar and innovative way; its purpose is not to identify undetermined coefficients as usual, but, instead, to compute a matrix null space (or matrix kernel). The null space then provides the coefficients that balance the equation. Indeed, the null space contains everything there is to know about balancing any chemical-reaction equation!

  9. Putative null distributions corresponding to tests of differential expression in the Golden Spike dataset are intensity dependent

    Directory of Open Access Journals (Sweden)

    Gaile Daniel P

    2007-04-01

    Full Text Available Abstract Background We provide a re-analysis of the Golden Spike dataset, a first generation "spike-in" control microarray dataset. The original analysis of the Golden Spike dataset was presented in a manuscript by Choe et al. and raised questions concerning the performance of several statistical methods for the control of the false discovery rate (across a set of tests for differential expression. These original findings are now in question as it has been reported that the p-values associated with the tests of differential expression for null probesets (i.e., probesets designed to be fold change 1 across the two arms of the experiment are not uniformly distributed. Two recent publications have speculated as to the reasons the null distributions are non-uniform. A publication by Dabney and Storey concludes that the non-uniform distributions of null p-values are the direct consequence of an experimental design which requires technical replicates to approximate biological replicates. Irizarry et al. identify four characteristics of the feature level data (three related to experimental design and one artifact. Irizarry et al. argue that the four observed characteristics imply that the assumptions common to most pre-processing algorithms are not satisfied and hence the expression measure methodologies considered by Choe et al. are likely to be flawed. Results We replicate and extend the analyses of Dabney and Storey and present our results in the context of a two stage analysis. We provide evidence that the Stage I pre-processing algorithms considered in Dabney and Storey fail to provide expression values that are adequately centered or scaled. Furthermore, we demonstrate that the distributions of the p-values, test statistics, and probabilities associated with the relative locations and variabilities of the Stage II expression values vary with signal intensity. We provide diagnostic plots and a simple logistic regression based test statistic to

  10. Sex-specific dysregulation of cysteine oxidation and the methionine and folate cycles in female cystathionine gamma-lyase null mice: a serendipitous model of the methylfolate trap.

    Science.gov (United States)

    Jiang, Hua; Hurt, K Joseph; Breen, Kelsey; Stabler, Sally P; Allen, Robert H; Orlicky, David J; Maclean, Kenneth N

    2015-01-01

    In addition to its role in the endogenous synthesis of cysteine, cystathionine gamma-lyase (CGL) is a major physiological source of the vasorelaxant hydrogen sulfide. Cgl null mice are potentially useful for studying the influence of this compound upon vascular tone and endothelial function. Here, we confirm a previous report that female Cgl null mice exhibit an approximate 45-fold increase in plasma total homocysteine compared to wild type controls. This level of homocysteine is approximately 3.5-fold higher than that observed in male Cgl null mice and is essentially equivalent to that observed in mouse models of cystathionine beta synthase deficient homocystinuria. Cgl null mice of both sexes exhibited decreased expression of methylenetetrahydrofolate reductase and cysteinesulfinate decarboxylase compared to WT controls. Female Cgl null mice exhibited a sex-specific induction of betaine homocysteine S-methyltransferase and methionine adenosyltransferase 1, alpha and a 70% decrease in methionine synthase expression accompanied by significantly decreased plasma methionine. Decreased plasma cysteine levels in female Cgl null mice were associated with sex-specific dysregulation of cysteine dioxygenase expression. Comparative histological assessment between cystathionine beta-synthase and Cgl null mice indicated that the therapeutic potential of cystathionine against liver injury merits possible further investigation. Collectively, our data demonstrates the importance of considering sex when investigating mouse models of inborn errors of metabolism and indicate that while female Cgl null mice are of questionable utility for studying the physiological role of hydrogen sulfide, they could serve as a useful model for studying the consequences of methionine synthase deficiency and the methylfolate trap.

  11. Triadin/Junctin Double Null Mouse Reveals a Differential Role for Triadin and Junctin in Anchoring CASQ to the jSR and Regulating Ca2+ Homeostasis

    OpenAIRE

    Simona Boncompagni; Monique Thomas; Jose R Lopez; Allen, Paul D.; Qunying Yuan; Kranias, Evangelia G.; Clara Franzini-Armstrong; Perez, Claudio F.

    2012-01-01

    Triadin (Tdn) and Junctin (Jct) are structurally related transmembrane proteins thought to be key mediators of structural and functional interactions between calsequestrin (CASQ) and ryanodine receptor (RyRs) at the junctional sarcoplasmic reticulum (jSR). However, the specific contribution of each protein to the jSR architecture and to excitation-contraction (e-c) coupling has not been fully established. Here, using mouse models lacking either Tdn (Tdn-null), Jct (Jct-null) or both (Tdn/Jct-...

  12. Inhibition of GSK3B bypass drug resistance of p53-null colon carcinomas by enabling necroptosis in response to chemotherapy

    DEFF Research Database (Denmark)

    Grassilli, Emanuela; Narloch, Robert; Federzoni, Elena;

    2013-01-01

    Evasion from chemotherapy-induced apoptosis due to p53 loss strongly contributes to drug resistance. Identification of specific targets for the treatment of drug-resistant p53-null tumors would therefore increase the effectiveness of cancer therapy.......Evasion from chemotherapy-induced apoptosis due to p53 loss strongly contributes to drug resistance. Identification of specific targets for the treatment of drug-resistant p53-null tumors would therefore increase the effectiveness of cancer therapy....

  13. Sex-specific dysregulation of cysteine oxidation and the methionine and folate cycles in female cystathionine gamma-lyase null mice: a serendipitous model of the methylfolate trap

    Directory of Open Access Journals (Sweden)

    Hua Jiang

    2015-09-01

    Full Text Available In addition to its role in the endogenous synthesis of cysteine, cystathionine gamma-lyase (CGL is a major physiological source of the vasorelaxant hydrogen sulfide. Cgl null mice are potentially useful for studying the influence of this compound upon vascular tone and endothelial function. Here, we confirm a previous report that female Cgl null mice exhibit an approximate 45-fold increase in plasma total homocysteine compared to wild type controls. This level of homocysteine is approximately 3.5-fold higher than that observed in male Cgl null mice and is essentially equivalent to that observed in mouse models of cystathionine beta synthase deficient homocystinuria. Cgl null mice of both sexes exhibited decreased expression of methylenetetrahydrofolate reductase and cysteinesulfinate decarboxylase compared to WT controls. Female Cgl null mice exhibited a sex-specific induction of betaine homocysteine S-methyltransferase and methionine adenosyltransferase 1, alpha and a 70% decrease in methionine synthase expression accompanied by significantly decreased plasma methionine. Decreased plasma cysteine levels in female Cgl null mice were associated with sex-specific dysregulation of cysteine dioxygenase expression. Comparative histological assessment between cystathionine beta-synthase and Cgl null mice indicated that the therapeutic potential of cystathionine against liver injury merits possible further investigation. Collectively, our data demonstrates the importance of considering sex when investigating mouse models of inborn errors of metabolism and indicate that while female Cgl null mice are of questionable utility for studying the physiological role of hydrogen sulfide, they could serve as a useful model for studying the consequences of methionine synthase deficiency and the methylfolate trap.

  14. Influence of dietary iodine deficiency on the thyroid gland in Slc26a4-null mutant mice

    Directory of Open Access Journals (Sweden)

    Iwata Tomoyuki

    2011-06-01

    Full Text Available Abstract Background Pendred syndrome (PDS is an autosomal recessive disorder characterized by sensorineural hearing impairment and variable degree of goitrous enlargement of the thyroid gland with a partial defect in iodine organification. The thyroid function phenotype can range from normal function to overt hypothyroidism. It is caused by loss-of-function mutations in the SLC26A4 (PDS gene. The severity of the goiter has been postulated to depend on the amount of dietary iodine intake. However, direct evidence has not been shown to support this hypothesis. Because Slc26a4-null mice have deafness but do not develop goiter, we fed the mutant mice a control diet or an iodine-deficient diet to evaluate whether iodine deficiency is a causative environmental factor for goiter development in PDS. Methods We evaluated the thyroid volume in histological sections with the use of three-dimensional reconstitution software, we measured serum levels of total tri-iodothyronine (TT3 and total thyroxine (TT4 levels, and we studied the thyroid gland morphology by transmission electron microscopy. Results TT4 levels became low but TT3 levels did not change significantly after eight weeks of an iodine-deficient diet compared to levels in the control diet animals. Even in Slc26a4-null mice fed an iodine-deficient diet, the volume of the thyroid gland did not increase although the size of each epithelial cell increased with a concomitant decrease of thyroid colloidal area. Conclusions An iodine-deficient diet did not induce goiter in Slc26a4-null mice, suggesting that other environmental, epigenetic or genetic factors are involved in goiter development in PDS.

  15. Metabolic and Phenotypic Differences between Mice Producing a Werner Syndrome Helicase Mutant Protein and Wrn Null Mice.

    Directory of Open Access Journals (Sweden)

    Lucie Aumailley

    Full Text Available Werner syndrome (WS is a premature aging disorder caused by mutations in a RecQ-family DNA helicase, WRN. Mice lacking part of the helicase domain of the WRN orthologue exhibit many phenotypic features of WS, including metabolic abnormalities and a shorter mean life span. In contrast, mice lacking the entire Wrn protein (i.e. Wrn null mice do not exhibit a premature aging phenotype. In this study, we used a targeted mass spectrometry-based metabolomic approach to identify serum metabolites that are differentially altered in young Wrn helicase mutant and Wrn null mice. An antibody-based quantification of 43 serum cytokines and markers of cardiovascular disease risk complemented this study. We found that Wrn helicase mutants exhibited elevated and decreased levels, respectively, of the anti-inflammatory cytokine IL-10 and the pro-inflammatory cytokine IL-18. Wrn helicase mutants also exhibited an increase in serum hydroxyproline and plasminogen activator inhibitor-1, markers of extracellular matrix remodeling of the vascular system and inflammation in aging. We also observed an abnormal increase in the ratio of very long chain to short chain lysophosphatidylcholines in the Wrn helicase mutants underlying a peroxisome perturbation in these mice. Remarkably, the Wrn mutant helicase protein was mislocalized to the endoplasmic reticulum and the peroxisomal fractions in liver tissues. Additional analyses with mouse embryonic fibroblasts indicated a severe defect of the autophagy flux in cells derived from Wrn helicase mutants compared to wild type and Wrn null animals. These results indicate that the deleterious effects of the helicase-deficient Wrn protein are mediated by the dysfunction of several cellular organelles.

  16. Study on the Quality of NILs of Wheat cv.Longfumai 3 Possessing HMWGS Null and 1 Subunits

    Institute of Scientific and Technical Information of China (English)

    ZHANG Li-li; ZHANG Yan-bin; SONG Qing-jie; ZHAO Hai-bin; YU Hai-yang; ZHANG Chun-li; XIN Wen-li; XIAO Zhi-min

    2008-01-01

    To determine the genetic differences between high molecular weigh glutenin subunits(HMW-GS)null and 1.HMW-GS1 was introduced into Longfumai 3(N,7+8,5+10)by 5 consecutive backcrosses with biochemical marker assisted selection.The near isogenic lines(NILs)of HMW-GS null and 1 were obtained and planted in the experimental field of Crop Breeding Institute of Heilongjiang Academy of Agricultural Science in 2004 and 2005.The field experiments were designed using the method of two-line contrast arrangement with four replicates.The result of two years experiment showed that the statistic differences of quality parameters between Longfumai 3 with subunit 1 and with null were not significant in flour protein content,dry gluten content,and water absorption.However the gluten index,' Zeleny sedimentation,the ratio of sedimentation/dry gluten,the development time,stability,and the breakdown time in the NIL with 1 subunit were increased by 5.8% (P<0.01),9.3% (P<0.01),8.6% (P=0.01),127.3% (P<0.01),79.2% (P<0.01),and 53.6% (P<0.01),and the ratio of wet gluten/dry gluten and the degree of softening were decreased by 1.7%(P=0.05)and 16.5% (P=0.13),respectively.The impact of the HMW-GS 1 on the gluten strength was highly positive in NILs containing HMW-GS 5 + 10,suggesting that HMW-GS 1 can be an indispensable subunit for breeding strong gluten wheat.

  17. Identification of the GST-T1 and GST-M1 Null Genotypes using High Resolution Melting Analysis

    OpenAIRE

    Drobná, Zuzana; Del Razo, Luz Maria; Garcia-Vargas, Gonzalo; Sánchez-Ramírez, Blanca; González-Horta, Carmen; Ballinas-Casarrubias, Lourdes; Loomis, Dana; Stýblo, Miroslav

    2011-01-01

    Glutathione S-transferases, including GST-T1 and GST-M1, are known to be involved in the phase II detoxification pathways for xenobiotics as well as in the metabolism of endogenous compounds. Polymorphisms in these genes have been linked to an increased susceptibility to carcinogenesis and associated with risk factors that predispose to certain inflammatory diseases. In addition, GST-T1 and GST-M1 null genotypes have been shown to be responsible for interindividual variations in metabolism of...

  18. Null controllability for a heat equation with a singular inverse-square potential involving the distance to the boundary function

    Science.gov (United States)

    Biccari, Umberto; Zuazua, Enrique

    2016-09-01

    This article is devoted to the analysis of control properties for a heat equation with a singular potential μ /δ2, defined on a bounded C2 domain Ω ⊂RN, where δ is the distance to the boundary function. More precisely, we show that for any μ ≤ 1 / 4 the system is exactly null controllable using a distributed control located in any open subset of Ω, while for μ > 1 / 4 there is no way of preventing the solutions of the equation from blowing-up. The result is obtained applying a new Carleman estimate.

  19. Singular value decomposition for photon-processing nuclear imaging systems and applications for reconstruction and computing null functions

    International Nuclear Information System (INIS)

    Recent advances in technology are enabling a new class of nuclear imaging systems consisting of detectors that use real-time maximum-likelihood (ML) methods to estimate the interaction position, deposited energy, and other attributes of each photon-interaction event and store these attributes in a list format. This class of systems, which we refer to as photon-processing (PP) nuclear imaging systems, can be described by a fundamentally different mathematical imaging operator that allows processing of the continuous-valued photon attributes on a per-photon basis. Unlike conventional photon-counting (PC) systems that bin the data into images, PP systems do not have any binning-related information loss. Mathematically, while PC systems have an infinite-dimensional null space due to dimensionality considerations, PP systems do not necessarily suffer from this issue. Therefore, PP systems have the potential to provide improved performance in comparison to PC systems. To study these advantages, we propose a framework to perform the singular-value decomposition (SVD) of the PP imaging operator. We use this framework to perform the SVD of operators that describe a general two-dimensional (2D) planar linear shift-invariant (LSIV) PP system and a hypothetical continuously rotating 2D single-photon emission computed tomography (SPECT) PP system. We then discuss two applications of the SVD framework. The first application is to decompose the object being imaged by the PP imaging system into measurement and null components. We compare these components to the measurement and null components obtained with PC systems. In the process, we also present a procedure to compute the null functions for a PC system. The second application is designing analytical reconstruction algorithms for PP systems. The proposed analytical approach exploits the fact that PP systems acquire data in a continuous domain to estimate a continuous object function. The approach is parallelizable and

  20. Expression of TP53 Isoforms p53β or p53γ Enhances Chemosensitivity in TP53null Cell Lines

    OpenAIRE

    Elisabeth Silden; Hjelle, Sigrun M; Line Wergeland; André Sulen; Vibeke Andresen; Jean-Christophe Bourdon; Micklem, David R; Emmet McCormack; Bjørn Tore Gjertsen

    2013-01-01

    The carboxy-terminal truncated p53 alternative spliced isoforms, p53β and p53γ, are expressed at disparate levels in cancer and are suggested to influence treatment response and therapy outcome. However, their functional role in cancer remains to be elucidated. We investigated their individual functionality in the p53(null) background of cell lines H1299 and SAOS-2 by stable retroviral transduction or transient transfection. Expression status of p53β and p53γ protein was found to correlate wi...

  1. lon Incompatibility Associated with Mutations Causing SOS Induction: Null uvrD Alleles Induce an SOS Response in Escherichia coli

    OpenAIRE

    SaiSree, L.; Reddy, Manjula; Gowrishankar, J

    2000-01-01

    The uvrD gene in Escherichia coli encodes a 720-amino-acid 3′-5′ DNA helicase which, although nonessential for viability, is required for methyl-directed mismatch repair and nucleotide excision repair and furthermore is believed to participate in recombination and DNA replication. We have shown in this study that null mutations in uvrD are incompatible with lon, the incompatibility being a consequence of the chronic induction of SOS in uvrD strains and the resultant accumulation of the cell s...

  2. Inheritance of 15 microsatellites in the Pacific oyster Crassostrea gigas: segregation and null allele identification for linkage analysis

    Institute of Scientific and Technical Information of China (English)

    LI Li; GUO Ximing; ZHANG Guofan

    2009-01-01

    Microsatellites were screened in a backcross family of the Pacific oyster, Crassostrea gigas. Fifteen microsatellite loci were distinguishable and polymorphic with 6 types of allele-combinations. Null alleles were detected in 46.7% of loci, accounting for 11.7% of the total alleles. Four loci did not segregate in Mendelian Ratios. Three linkage groups were identified among 7 of the 15 segregating loci. Fluorescence-based automated capillary electrophoresis (ABI 310 Genetic Analyzer) that used to detect the microsatellite loci, has been proved a fast, precise, and reliable method in microsatellite genotyping.

  3. Singular value decomposition for photon-processing nuclear imaging systems and applications for reconstruction and computing null functions

    Science.gov (United States)

    Jha, Abhinav K.; Barrett, Harrison H.; Frey, Eric C.; Clarkson, Eric; Caucci, Luca; Kupinski, Matthew A.

    2015-09-01

    Recent advances in technology are enabling a new class of nuclear imaging systems consisting of detectors that use real-time maximum-likelihood (ML) methods to estimate the interaction position, deposited energy, and other attributes of each photon-interaction event and store these attributes in a list format. This class of systems, which we refer to as photon-processing (PP) nuclear imaging systems, can be described by a fundamentally different mathematical imaging operator that allows processing of the continuous-valued photon attributes on a per-photon basis. Unlike conventional photon-counting (PC) systems that bin the data into images, PP systems do not have any binning-related information loss. Mathematically, while PC systems have an infinite-dimensional null space due to dimensionality considerations, PP systems do not necessarily suffer from this issue. Therefore, PP systems have the potential to provide improved performance in comparison to PC systems. To study these advantages, we propose a framework to perform the singular-value decomposition (SVD) of the PP imaging operator. We use this framework to perform the SVD of operators that describe a general two-dimensional (2D) planar linear shift-invariant (LSIV) PP system and a hypothetical continuously rotating 2D single-photon emission computed tomography (SPECT) PP system. We then discuss two applications of the SVD framework. The first application is to decompose the object being imaged by the PP imaging system into measurement and null components. We compare these components to the measurement and null components obtained with PC systems. In the process, we also present a procedure to compute the null functions for a PC system. The second application is designing analytical reconstruction algorithms for PP systems. The proposed analytical approach exploits the fact that PP systems acquire data in a continuous domain to estimate a continuous object function. The approach is parallelizable and

  4. Expression of TP53 Isoforms p53β or p53γ Enhances Chemosensitivity in TP53null Cell Lines

    OpenAIRE

    Silden, Elisabeth; Hjelle, Sigrun M; Wergeland, Line; Sulen, André; Andresen, Vibeke; Bourdon, Jean-Christophe; Micklem, David R.; McCormack, Emmet; Gjertsen, Bjørn Tore

    2013-01-01

    The carboxy-terminal truncated p53 alternative spliced isoforms, p53β and p53γ, are expressed at disparate levels in cancer and are suggested to influence treatment response and therapy outcome. However, their functional role in cancer remains to be elucidated. We investigated their individual functionality in the p53null background of cell lines H1299 and SAOS-2 by stable retroviral transduction or transient transfection. Expression status of p53β and p53γ protein was found to correlate with...

  5. Glutathione S-transferase M1 null genotype: lack of association with tumour characteristics and survival in advanced breast cancer

    International Nuclear Information System (INIS)

    Glutathione S-transferase (GST)M1, a member of the μ class GST gene family, has been shown to be polymorphic because of a partial gene deletion. This results in a failure to express the GSTM1 gene in 50-60% of individuals. Several studies have demonstrated a possible link with the GSTM1-null genotype and susceptibility to cancer. Furthermore, a GSTM1 isoenzyme has been positively associated with protective effect against mutagenic drugs, such as alkylating agents and anthracyclines. To determine whether GSTM1 polymorphisms are associated with tumour characteristics and survival in advanced breast cancer patients, and whether it may constitute a prognostic factor. We genotyped 92 patients receiving primary chemotherapy, which included cyclophosphamide, doxorubicine and 5-fluorouracil. The relationships between allelism at GSTM1 and clinicopathological parameters including age, menopausal status, tumour size, grade hormone receptors, involved nodes and p53 gene mutations were analysed. Of the patients with GSTM1-positive genotype, tissue samples obtained before and after treatment were available from 28 cases, allowing RNA extraction and GSTM1 expression by reverse transcription polymerase chain reaction. Relationships with clinical response to chemotherapy, and disease-free and overall survival were also evaluated. The data obtained was analysed using logistic regression to estimate the odds ratio and 95% confidence interval. Of 92 patients, 57.6% (n = 53) were classified as heritably GSTM1-deficient, and 42.4% (n = 39) were of the GSTM1-positive genotype. There were no statistically significant relationships between GSTM1-null genotype and the clinicopathological parameters analysed. No relationship was observed between GSTM1 RNA expression and objective clinical response to chemotherapy. Objective clinical response to chemotherapy was related only to clinical tumour size (P = 0.0177) and to the absence of intraductal carcinoma (P = 0.0013). GSTM1-null genotype

  6. [Development of a new soybean variety with null trypsin inhibitor and lipoxygenase 2.3 genes--zhonghuang 16 and its cultivation practices].

    Science.gov (United States)

    Han, Fen-Xia; Ding, An-Lin; Sun, Jun-Ming

    2002-12-01

    Soybean protein is a kind of high-quality protein composed of balanced amino acids, which contains all kinds of amino acid, especially 8 amino acids necessary for human, but also contains some components that are not good for human and affect food quality, such as Trypsin inhibitor and Lipoxygenase. Nutritional value and processing quality of soybean can be improved by means of development of new variety with null Lox and Ti. In this paper, a new soybean variety Zhonghuang 16 (originally name as Zhongzuo 96-952) was developed by Institute of Crop Breeding and Cultivation Chinese Academy of Agricultural Sciences through years of biochemical marker assistant selection for null trypsin inhibitor by Native-polyacrylamid gel electrophoresis (Native-PAGE) and null lipoxygenase by means of isoelectric focusing-polyacrylamid gel electrophoresis (IEF-PAGE) in the hybrid progenies of "ti15176" (Female parent)--a high-yielding, mosaic virus resistant and null trypsin inhibitor line and "Century-2.3" (Male parent)--a null lipoxygenase near isogene line of an elite American variety "Century". This variety was subjected to Beijing regional trial for summer-sowing soybean during 1999-2000, and to Beijing demonstration test in 2001. In 2002, it was passed the examination and approval by the Beijing Committee of Crop Variety Examination and Approval because of its outstanding characteristics such as high and stable yielding, good quality (high protein and fat content, high protein content and good protein quality-null Ti and Lox2.3), disease resistant and good general character. It is the first new soybean variety with null Ti and Lox2.3 genes in our country. In this paper, the development process and cultivation of Zhonghuang 16 were described. PMID:12693103

  7. Microglia contribute to circuit defects in Mecp2 null mice independent of microglia-specific loss of Mecp2 expression.

    Science.gov (United States)

    Schafer, Dorothy P; Heller, Christopher T; Gunner, Georgia; Heller, Molly; Gordon, Christopher; Hammond, Timothy; Wolf, Yochai; Jung, Steffen; Stevens, Beth

    2016-01-01

    Microglia, the resident CNS macrophages, have been implicated in the pathogenesis of Rett Syndrome (RTT), an X-linked neurodevelopmental disorder. However, the mechanism by which microglia contribute to the disorder is unclear and recent data suggest that microglia do not play a causative role. Here, we use the retinogeniculate system to determine if and how microglia contribute to pathogenesis in a RTT mouse model, the Mecp2 null mouse (Mecp2(tm1.1Bird/y)). We demonstrate that microglia contribute to pathogenesis by excessively engulfing, thereby eliminating, presynaptic inputs at end stages of disease (≥P56 Mecp2 null mice) concomitant with synapse loss. Furthermore, loss or gain of Mecp2 expression specifically in microglia (Cx3cr1(CreER);Mecp2(fl/y)or Cx3cr1(Cr)(eER); Mecp2(LSL/y)) had little effect on excessive engulfment, synapse loss, or phenotypic abnormalities. Taken together, our data suggest that microglia contribute to end stages of disease by dismantling neural circuits rendered vulnerable by loss of Mecp2 in other CNS cell types. PMID:27458802

  8. Statistical test of a null hypothesis: Taser shocks have not caused or contributed to subsequent in-custody deaths

    Science.gov (United States)

    Lundquist, Marjorie

    2009-03-01

    Since 1999 over 425 in-custody deaths have occurred in the USA after law enforcement officers (LEOs) used an M26 or X26 Taser, causing Amnesty International and the ACLU to call for a moratorium on Taser use until its physiological effects on people have been better studied. A person's Taser dose is defined as the total duration (in seconds) of all Taser shocks received by that person during a given incident. Utilizing the concept of Taser dose for these deaths, TASER International's claim of Taser safety can be treated as a null hypothesis and its validity scientifically tested. Such a test using chi-square as the test statistic is presented. It shows that the null hypothesis should be rejected; i.e., model M26 and X26 Tasers are capable of producing lethal effects non-electrically and so have played a causal or contributory role in a great many of the in-custody deaths following their use. This implies that the Taser is a lethal weapon, and that LEOs have not been adequately trained in its safe use!

  9. Seizure susceptibility of neuropeptide-Y null mutant mice in amygdala kindling and chemical-induced seizure models.

    Science.gov (United States)

    Shannon, Harlan E; Yang, Lijuan

    2004-01-01

    Neuropeptide Y (NPY) administered exogenously is anticonvulsant, and, NPY null mutant mice are more susceptible to kainate-induced seizures. In order to better understand the potential role of NPY in epileptogenesis, the present studies investigated the development of amygdala kindling, post-kindling seizure thresholds, and anticonvulsant effects of carbamazepine and levetiracetam in 129S6/SvEv NPY(+/+) and NPY(-/-) mice. In addition, susceptibility to pilocarpine- and kainate-induced seizures was compared in NPY(+/+) and (-/-) mice. The rate of amygdala kindling development did not differ in the NPY(-/-) and NPY(+/+) mice either when kindling stimuli were presented once daily for at least 20 days, or, 12 times daily for 2 days. However, during kindling development, the NPY(-/-) mice had higher seizure severity scores and longer afterdischarge durations than the NPY(+/+) mice. Post-kindling, the NPY(-/-) mice had markedly lower afterdischarge thresholds and longer afterdischarge durations than NPY (+/+) mice. Carbamazepine and levetiracetam increased the seizure thresholds of both NPY (-/-) and (+/+) mice. In addition, NPY (-/-) mice had lower thresholds for both kainate- and pilocarpine-induced seizures. The present results in amygdala kindling and chemical seizure models suggest that NPY may play a more prominent role in determining seizure thresholds and severity of seizures than in events leading to epileptogenesis. In addition, a lack of NPY does not appear to confer drug-resistance in that carbamazepine and levetiracetam were anticonvulsant in both wild type (WT) and NPY null mutant mice.

  10. Quality of synthetic hexaploid wheat containing null alleles at Glu-A1 and Glu-B1 loci

    Indian Academy of Sciences (India)

    Xinkun Hu; Shoufen Dai; Zhien Pu; Dengcai Liu; Zongjun Pu; Jiaqi Jiang; Yuming Wei; Bihua Wu; Xiujin Lan; Youliang Zheng; Zehong Yan

    2013-08-01

    Triticum turgidum ssp. dicoccon PI94668 and PI349045 were identified as containing null alleles at Glu-A1 and Glu-B1 loci in previous investigation. Sequencing of the respective HMW-GS genes Ax, Bx, Ay and By in both accessions indicated equal DNA lengths with gene silencing caused by 1 to 4 in-frame stop codon(s) in the open reading frames. Six synthetic hexaploid wheat lines were produced by crossing PI94668 or PI349045 with six Aegilops tauschii by spontaneous chromosome doubling of unreduced gametes. As expected, these amphiploids had three different HMW-GS: Dx 3.1t + Dy11*t, Dx2.1t +10t and Dx2t + Dy12t in Glu-D1 but double nulls in Glu-A1 and Glu-B1. Quality tests showed that most quality parameters in two T. turgidum ssp. dicoccon parents were very low due to the lack of HMW-GSs. However, incorporation of HMW-GS from Ae. tauschii in six synthetic hexaploid wheat lines significantly increased most quality related parameters. The potential values of these wheat lines in improving the quality of wheat are discussed.

  11. CHANGES IN PARTICLE PUMPING DUE TO VARIATION IN MAGNETIC BALANCE NEAR DOUBLE-NULL IN DIII-D

    International Nuclear Information System (INIS)

    OAK-B135 The authors report on a recent experiment examining how changes in the divertor magnetic balance affect the rate that particles can be pumped at the divertor targets. They find that both the edge density of the core plasma and divertor recycling play important roles in properly interpreting this pumping result. Previous studies on DIII-D have identified several important differences between double-null (DN) and single-null (SN) divertor operation. Small variations in the magnetic balance near-DN have large effects on both the power- and particle loadings at the divertor targets. These most likely result from an interplay between the plasma geometry and ion particle drifts, e.g., ''B x (del)B'' and ''E x B'' drifts. Other studies have shown that changes in magnetic balance affect the core plasma and where ELMs strike the vessel. In this paper, they examine how variations in the magnetic balance impact the rate at which particles are removed from the core plasma via pumping

  12. Renoprotective Effects of Vitex megapotamica (Spreng. Moldenke in C57BL/6 LDLr-Null Mice Undergoing High Fat Diet

    Directory of Open Access Journals (Sweden)

    Valdinei de Oliveira Araújo

    2015-01-01

    Full Text Available Although Vitex megapotamica (Spreng. Moldenke is used in Brazilian folk medicine as hypolipidemic drug no study has been conducted to evaluate the effects of this species in an experimental model of atherosclerosis. So, the aim of this study was to evaluate the possible renoprotective activity of methanolic extract obtained from Vitex megapotamica (MEVM using C57BL/6 LDLr-null mice submitted to high fat diet (HFD. MEVM was orally administered at doses of 30, 100, and 300 mg/kg, for three weeks, starting from the 2nd week of HFD. Systolic blood pressure (SBP and diuretic activity were measured weekly. At the end of experiments the serum lipids, atherogenic index serum (AIS, oxidative stress, and markers of renal function were determined. HFD induced a significant increase in the systolic blood pressure, dyslipidemia, increase in AIS, and lipid peroxidation accompanied by an important reduction in renal function. Treatment with MEVM was able to prevent increase in SBP, total cholesterol, triglycerides, AIS, urea, and creatinine levels in LDLr-null mice. These effects were accompanied by a significant reduction in oxidative stress and renal injury. The data reported here support the potential of Vitex megapotamica as candidate to be an herbal medicine used in cardiovascular or renal diseases.

  13. Berberine Induces Apoptosis in p53-Null Leukemia Cells by Down-Regulating XIAP at the Post-Transcriptional Level

    Directory of Open Access Journals (Sweden)

    Jian Liu

    2013-11-01

    Full Text Available Background: Berberine exerts anticancer activities both in vitro and in vivo through different mechanisms. However, the underlying molecular mechanisms of berberine induced p53-independent apoptosis remain unclear. Methods: The p53-null leukemia cell line EU-4 cells were exposed to berberine. Then the cell viability and apoptosis were determined. Western blot and PCR were employed to detect the expression of apoptosis related protein, XIAP and MDM2. Small interfering RNA (siRNA was applied to knock down endogenous expression of MDM2 and XIAP. Results: Berberine induced p53-independent, XIAP-mediated apoptotic cell death in p53-null leukemia cells. Treatment with berberine resulted in suppression of XIAP protein in a dose- and time- dependent manner. Berberine induced down-regulation of XIAP protein involving inhibition of MDM2 expression and a proteasome-dependent pathway. Moreover, inhibition of XIAP by berberine or siRNA increased the sensitivity of leukemia cells to doxorubicin-induced apoptosis. Conclusion: Our findings characterize the molecular mechanisms of berberine-induced caspase activation and subsequent apoptosis, and berberine may be a novel candidate inducer of apoptosis in leukemia cells, which normally lack p53 expression.

  14. Fibronectin induction abrogates the BRAF inhibitor response of BRAF V600E/PTEN-null melanoma cells.

    Science.gov (United States)

    Fedorenko, I V; Abel, E V; Koomen, J M; Fang, B; Wood, E R; Chen, Y A; Fisher, K J; Iyengar, S; Dahlman, K B; Wargo, J A; Flaherty, K T; Sosman, J A; Sondak, V K; Messina, J L; Gibney, G T; Smalley, K S M

    2016-03-10

    The mechanisms by which some melanoma cells adapt to Serine/threonine-protein kinase B-Raf (BRAF) inhibitor therapy are incompletely understood. In the present study, we used mass spectrometry-based phosphoproteomics to determine how BRAF inhibition remodeled the signaling network of melanoma cell lines that were BRAF mutant and PTEN null. Short-term BRAF inhibition was associated with marked changes in fibronectin-based adhesion signaling that were PTEN dependent. These effects were recapitulated through BRAF siRNA knockdown and following treatment with chemotherapeutic drugs. Increased fibronectin expression was also observed in mouse xenograft models as well as specimens from melanoma patients undergoing BRAF inhibitor treatment. Analysis of a melanoma tissue microarray showed loss of PTEN expression to predict for a lower overall survival, with a trend for even lower survival being seen when loss of fibronectin was included in the analysis. Mechanistically, the induction of fibronectin limited the responses of these PTEN-null melanoma cell lines to vemurafenib, with enhanced cytotoxicity observed following the knockdown of either fibronectin or its receptor α5β1 integrin. This in turn abrogated the cytotoxic response to BRAF inhibition via increased AKT signaling, which prevented the induction of cell death by maintaining the expression of the pro-survival protein Mcl-1. The protection conveyed by the induction of FN expression could be overcome through combined treatment with a BRAF and PI3K inhibitor. PMID:26073081

  15. Simple Algorithms to Calculate Asymptotic Null Distributions of Robust Tests in Case-Control Genetic Association Studies in R

    Directory of Open Access Journals (Sweden)

    Wing Kam Fung

    2010-02-01

    Full Text Available The case-control study is an important design for testing association between genetic markers and a disease. The Cochran-Armitage trend test (CATT is one of the most commonly used statistics for the analysis of case-control genetic association studies. The asymptotically optimal CATT can be used when the underlying genetic model (mode of inheritance is known. However, for most complex diseases, the underlying genetic models are unknown. Thus, tests robust to genetic model misspecification are preferable to the model-dependant CATT. Two robust tests, MAX3 and the genetic model selection (GMS, were recently proposed. Their asymptotic null distributions are often obtained by Monte-Carlo simulations, because they either have not been fully studied or involve multiple integrations. In this article, we study how components of each robust statistic are correlated, and find a linear dependence among the components. Using this new finding, we propose simple algorithms to calculate asymptotic null distributions for MAX3 and GMS, which greatly reduce the computing intensity. Furthermore, we have developed the R package Rassoc implementing the proposed algorithms to calculate the empirical and asymptotic p values for MAX3 and GMS as well as other commonly used tests in case-control association studies. For illustration, Rassoc is applied to the analysis of case-control data of 17 most significant SNPs reported in four genome-wide association studies.

  16. Astrogliosis is delayed in type 1 interleukin-1 receptor-null mice following a penetrating brain injury

    Directory of Open Access Journals (Sweden)

    Krady J Kyle

    2006-06-01

    Full Text Available Abstract The cytokines IL-1α and IL-1β are induced rapidly after insults to the CNS, and their subsequent signaling through the type 1 IL-1 receptor (IL-1R1 has been regarded as essential for a normal astroglial and microglial/macrophage response. To determine whether abrogating signaling through the IL-1R1 will alter the cardinal astrocytic responses to injury, we analyzed molecules characteristic of activated astrocytes in response to a penetrating stab wound in wild type mice and mice with a targeted deletion of IL-1R1. Here we show that after a stab wound injury, glial fibrillary acidic protein (GFAP induction on a per cell basis is delayed in the IL-1R1-null mice compared to wild type counterparts. However, the induction of chondroitin sulfate proteoglycans, tenascin, S-100B as well as glutamate transporter proteins, GLAST and GLT-1, and glutamine synthetase are independent of IL-1RI signaling. Cumulatively, our studies on gliosis in the IL-1R1-null mice indicate that abrogating IL-1R1 signaling delays some responses of astroglial activation; however, many of the important neuroprotective adaptations of astrocytes to brain trauma are preserved. These data recommend the continued development of therapeutics to abrogate IL-1R1 signaling to treat traumatic brain injuries. However, astroglial scar related proteins were induced irrespective of blocking IL-1R1 signaling and thus, other therapeutic strategies will be required to inhibit glial scarring.

  17. CHANGES IN PARTICLE PUMPING DUE TO VARIATION IN MAGNETIC BALANCE NEAR DOUBLE-NULL IN DIII-D

    Energy Technology Data Exchange (ETDEWEB)

    PETRIE,TW; WATKINS,JG; ALLEN,SL; BROOKS,NH; FENSTERMACHER,ME; FERRON,JR; GREENFIELD,CM; GROTH,M; HYATT, AW; LUCE,TC; MAHDVI,MA; SCHAFFER,MJ; WADE,MR; WEST,WP; THE DIII-D TEAM

    2003-07-01

    OAK-B135 The authors report on a recent experiment examining how changes in the divertor magnetic balance affect the rate that particles can be pumped at the divertor targets. They find that both the edge density of the core plasma and divertor recycling play important roles in properly interpreting this pumping result. Previous studies on DIII-D have identified several important differences between double-null (DN) and single-null (SN) divertor operation. Small variations in the magnetic balance near-DN have large effects on both the power- and particle loadings at the divertor targets. These most likely result from an interplay between the plasma geometry and ion particle drifts, e.g., ''B x {del}B'' and ''E x B'' drifts. Other studies have shown that changes in magnetic balance affect the core plasma and where ELMs strike the vessel. In this paper, they examine how variations in the magnetic balance impact the rate at which particles are removed from the core plasma via pumping.

  18. Kharon1 null mutants of Leishmania mexicana are avirulent in mice and exhibit a cytokinesis defect within macrophages.

    Directory of Open Access Journals (Sweden)

    Khoa D Tran

    Full Text Available In a variety of eukaryotes, flagella play important roles both in motility and as sensory organelles that monitor the extracellular environment. In the parasitic protozoan Leishmania mexicana, one glucose transporter isoform, LmxGT1, is targeted selectively to the flagellar membrane where it appears to play a role in glucose sensing. Trafficking of LmxGT1 to the flagellar membrane is dependent upon interaction with the KHARON1 protein that is located at the base of the flagellar axoneme. Remarkably, while Δkharon1 null mutants are viable as insect stage promastigotes, they are unable to survive as amastigotes inside host macrophages. Although Δkharon1 promastigotes enter macrophages and transform into amastigotes, these intracellular parasites are unable to execute cytokinesis and form multinucleate cells before dying. Notably, extracellular axenic amastigotes of Δkharon1 mutants replicate and divide normally, indicating a defect in the mutants that is only exhibited in the intra-macrophage environment. Although the flagella of Δkharon1 amastigotes adhere to the phagolysomal membrane of host macrophages, the morphology of the mutant flagella is often distorted. Additionally, these null mutants are completely avirulent following injection into BALB/c mice, underscoring the critical role of the KHARON1 protein for viability of intracellular amastigotes and disease in the animal model of leishmaniasis.

  19. Uncoordinated transcription and compromised muscle function in the lmna-null mouse model of Emery- Emery-Dreyfuss muscular dystrophy.

    Science.gov (United States)

    Gnocchi, Viola F; Scharner, Juergen; Huang, Zhe; Brady, Ken; Lee, Jaclyn S; White, Robert B; Morgan, Jennifer E; Sun, Yin-Biao; Ellis, Juliet A; Zammit, Peter S

    2011-02-22

    LMNA encodes both lamin A and C: major components of the nuclear lamina. Mutations in LMNA underlie a range of tissue-specific degenerative diseases, including those that affect skeletal muscle, such as autosomal-Emery-Dreifuss muscular dystrophy (A-EDMD) and limb girdle muscular dystrophy 1B. Here, we examine the morphology and transcriptional activity of myonuclei, the structure of the myotendinous junction and the muscle contraction dynamics in the lmna-null mouse model of A-EDMD. We found that there were fewer myonuclei in lmna-null mice, of which ∼50% had morphological abnormalities. Assaying transcriptional activity by examining acetylated histone H3 and PABPN1 levels indicated that there was a lack of coordinated transcription between myonuclei lacking lamin A/C. Myonuclei with abnormal morphology and transcriptional activity were distributed along the length of the myofibre, but accumulated at the myotendinous junction. Indeed, in addition to the presence of abnormal myonuclei, the structure of the myotendinous junction was perturbed, with disorganised sarcomeres and reduced interdigitation with the tendon, together with lipid and collagen deposition. Functionally, muscle contraction became severely affected within weeks of birth, with specific force generation dropping as low as ∼65% and ∼27% of control values in the extensor digitorum longus and soleus muscles respectively. These observations illustrate the importance of lamin A/C for correct myonuclear function, which likely acts synergistically with myotendinous junction disorganisation in the development of A-EDMD, and the consequential reduction in force generation and muscle wasting.

  20. Cardiomyocyte-Restricted Deletion of PPARβ/δ in PPARα-Null Mice Causes Impaired Mitochondrial Biogenesis and Defense, but No Further Depression of Myocardial Fatty Acid Oxidation

    Directory of Open Access Journals (Sweden)

    Jian Liu

    2011-01-01

    Full Text Available It is well documented that PPARα and PPARβ/δ share overlapping functions in regulating myocardial lipid metabolism. However, previous studies demonstrated that cardiomyocyte-restricted PPARβ/δ deficiency in mice leads to severe cardiac pathological development, whereas global PPARα knockout shows a benign cardiac phenotype. It is unknown whether a PPARα-null background would alter the pathological development in mice with cardiomyocyte-restricted PPARβ/δ deficiency. In the present study, a mouse model with long-term PPARβ/δ deficiency in PPARα-null background showed a comparably reduced cardiac expression of lipid metabolism to those of single PPAR-deficient mouse models. The PPARα-null background did not rescue or aggravate the cardiac pathological development linked to cardiomyocyte-restricted PPARβ/δ deficiency. Moreover, PPARα-null did not alter the phenotypic development in adult mice with the short-term deletion of PPARβ/δ in their hearts, which showed mitochondrial abnormalities, depressed cardiac performance, and cardiac hypertrophy with attenuated expression of key factors in mitochondrial biogenesis and defense. The present study demonstrates that cardiomyocyte-restricted deletion of PPARβ/δ in PPARα-null mice causes impaired mitochondrial biogenesis and defense, but no further depression of fatty acid oxidation. Therefore, PPARβ/δ is essential for maintaining mitochondrial biogenesis and defense in cardiomyocytes independent of PPARα.