Primary postural instability: a cause of recurrent sudden falls in the elderly.

Science.gov (United States)

Djaldetti, R; Lorberboym, M; Melamed, E

2006-12-01

Elderly patients with recurrent falls are frequently diagnosed with an extrapyramidal syndrome. This study aims to characterise a distinct group of patients with recurrent falls and postural instability as a hallmark of the clinical examination. The study took place in the Movement Disorders Unit, Rabin Medical Center, Petah Tiqva, Israel among 26 patients with recurrent falls who had no clinical evidence of a neurodegenerative disease. Medical records, neurological examination and brain imaging studies were assessed. Falls in these patients were sudden, unprovoked, with no vertigo or loss of consciousness. All had postural instability with minimal or no abnormality on the neurological examination. Brain imaging showed diffuse ischaemic changes in 65%. [(123)I]-FPCIT SPECT with the dopamine transporter ligand, performed in five patients, was normal in all. Recurrent falls might be caused by a neurological syndrome that primarily affects balance control. The importance of identifying this disorder is its distinction from other parkinsonian syndromes causing falls.

Analysis of fluid structural instability in water

International Nuclear Information System (INIS)

Piccirillo, N.

1997-02-01

Recent flow testing of stainless steel hardware in a high pressure/high temperature water environment produced an apparent fluid-structural instability. The source of instability was investigated by studying textbook theory and by performing NASTRAN finite element analyses. The modal analyses identified the mode that was being excited, but the flutter instability analysis showed that the design is stable if minimal structural damping is present. Therefore, it was suspected that the test hardware was the root cause of the instability. Further testing confirmed this suspicion

Genomic instability and radiation effects

International Nuclear Information System (INIS)

Christian Streffer

2007-01-01

Complete text of publication follows. Cancer, genetic mutations and developmental abnormalities are apparently associated with an increased genomic instability. Such phenomena have been frequently shown in human cancer cells in vitro and in situ. It is also well-known that individuals with a genetic predisposition for cancer proneness, such as ataxia telangiectesia, Fanconi anaemia etc. demonstrate a general high genomic instability e.g. in peripheral lymphocytes before a cancer has developed. Analogous data have been found in mice which develop a specific congenital malformation which has a genetic background. Under these aspects it is of high interest that ionising radiation can increase the genomic instability of mammalian cells after exposures in vitro an in vivo. This phenomenon is expressed 20 to 40 cell cycles after the exposure e.g. by de novo chromosomal aberrations. Such effects have been observed with high and low LET radiation, high LET radiation is more efficient. With low LET radiation a good dose response is observed in the dose range 0.2 to 2.0 Gy, Recently it has been reported that senescence and genomic instability was induced in human fibroblasts after 1 mGy carbon ions (1 in 18 cells are hit), apparently bystander effects also occurred under these conditions. The instability has been shown with DNA damage, chromosomal aberrations, gene mutation and cell death. It is also transferred to the next generation of mice with respect to gene mutations, chromosomal aberrations and congenital malformations. Several mechanisms have been discussed. The involvement of telomeres has gained interest. Genomic instability seems to be induced by a general lesion to the whole genome. The transmission of one chromosome from an irradiated cell to an non-irradiated cell leads to genomic instability in the untreated cells. Genomic instability increases mutation rates in the affected cells in general. As radiation late effects (cancer, gene mutations and congenital

Ion temperature gradient instability

International Nuclear Information System (INIS)

1989-01-01

Anomalous ion thermal conductivity remains an open physics issue for the present generation of high temperature Tokamaks. It is generally believed to be due to Ion Temperature Gradient Instability (η i mode). However, it has been difficult, if not impossible to identify this instability and study the anomalous transport due to it, directly. Therefore the production and identification of the mode is pursued in the simpler and experimentally convenient configuration of the Columbia Linear Machine (CLM). CLM is a steady state machine which already has all the appropriate parameters, except η i . This parameter is being increased to the appropriate value of the order of 1 by 'feathering' a tungsten screen located between the plasma source and the experimental cell to flatten the density profile and appropriate redesign of heating antennas to steepen the ion temperature profile. Once the instability is produced and identified, a thorough study of the characteristics of the mode can be done via a wide range of variation of all the critical parameters: η i , parallel wavelength, etc

The Rayleigh-Taylor instability in the spherical pinch

International Nuclear Information System (INIS)

Chen, H.B.; Hilko, B.; Panarella, E.

1994-01-01

The spherical pinch (SP) concept is an outgrowth of the inertial confinement model (ICF). Unlike the ICF where instabilities, especially the Rayleigh-Taylor instability, have been studied extensively, the instability study of the spherical pinch has just begun. The Raleigh-Taylor instability is investigated for the first time in the SP in the present work. By using the simple condition for the Rayleigh-Taylor instability ∇p · ∇p < O (density and pressure gradients have opposite direction), we have qualitatively identified the regions for development of instabilities in the SP. It is found that the explosion phase (central discharge) is stable and instabilities take place in the imploding phase. However, the growth rate for the instability is not in exponential form, and the appearance of the Rayleigh-Taylor instability does not prevent the main shock wave from converging to the center of the sphere

Colon and rectal cancer survival by tumor location and microsatellite instability: the Colon Cancer Family Registry.

Science.gov (United States)

Phipps, Amanda I; Lindor, Noralane M; Jenkins, Mark A; Baron, John A; Win, Aung Ko; Gallinger, Steven; Gryfe, Robert; Newcomb, Polly A

2013-08-01

Cancers in the proximal colon, distal colon, and rectum are frequently studied together; however, there are biological differences in cancers across these sites, particularly in the prevalence of microsatellite instability. We assessed the differences in survival by colon or rectal cancer site, considering the contribution of microsatellite instability to such differences. This is a population-based prospective cohort study for cancer survival. This study was conducted within the Colon Cancer Family Registry, an international consortium. Participants were identified from population-based cancer registries in the United States, Canada, and Australia. Information on tumor site, microsatellite instability, and survival after diagnosis was available for 3284 men and women diagnosed with incident invasive colon or rectal cancer between 1997 and 2002, with ages at diagnosis ranging from 18 to 74. Cox regression was used to calculate hazard ratios for the association between all-cause mortality and tumor location, overall and by microsatellite instability status. Distal colon (HR, 0.59; 95% CI, 0.49-0.71) and rectal cancers (HR, 0.68; 95% CI, 0.57-0.81) were associated with lower mortality than proximal colon cancer overall. Compared specifically with patients with proximal colon cancer exhibiting no/low microsatellite instability, patients with distal colon and rectal cancers experienced lower mortality, regardless of microsatellite instability status; patients with proximal colon cancer exhibiting high microsatellite instability had the lowest mortality. Study limitations include the absence of stage at diagnosis and cause-of-death information for all but a subset of study participants. Some patient groups defined jointly by tumor site and microsatellite instability status are subject to small numbers. Proximal colon cancer survival differs from survival for distal colon and rectal cancer in a manner apparently dependent on microsatellite instability status. These

Anticipating Terrorist Safe Havens from Instability Induced Conflict

Science.gov (United States)

Shearer, Robert; Marvin, Brett

This chapter presents recent methods developed at the Center for Army Analysis to classify patterns of nation-state instability that lead to conflict. The ungoverned areas endemic to failed nation-states provide terrorist organizations with safe havens from which to plan and execute terrorist attacks. Identification of those states at risk for instability induced conflict should help to facilitate effective counter terrorism policy planning efforts. Nation-states that experience instability induced conflict are similar in that they share common instability factors that make them susceptible to experiencing conflict. We utilize standard pattern classification algorithms to identify these patterns. First, we identify features (political, military, economic and social) that capture the instability of a nation-state. Second, we forecast the future levels of these features for each nation-state. Third, we classify each future state’s conflict potential based upon the conflict level of those states in the past most similar to the future state.

Dynamics and instabilities in nuclear fragmentation

International Nuclear Information System (INIS)

Colonna, M.; Guarnera, A.; Di Toro, M.; Latora, V.; Smerzi, A.; Catania Univ.

1993-01-01

A general procedure to identify instability regions which lead to multifragmentation events is presented. The method covers all possible sources of dynamical instabilities. Informations on the instability point, like the time when the nuclear system enters the critical region, the most unstable modes and the time constant of the exponential growing of the relative variances, are deduced without any numerical bias. Important memory effects in the fragmentation pattern are revealed. Some hints towards a fully dynamical picture of fragmentation processes are finally suggested. (author) 7 refs., 3 figs

Clinical forms of shoulder instability in pediatric patients

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Yaroslav N. Proshchenko

2016-12-01

Full Text Available Background. The recurrence rate of adolescent chronic shoulder instability is approximately 56%–68%. However, this pathology is often missed in childhood and adolescence. Aim. To identify the clinical forms of shoulder joint instability in pediatric patients. Materials and methods. The authors present the data from 57 pediatric patients aged 3−17 years with a total of 61 unstable shoulder joints. All patients were divided into groups according to the form of instability. Traumatic chronic shoulder instability was identified in 40 patients (Bankart and Hill–Sachs injuries. Of these, non-traumatic shoulder instability was diagnose in 17, including five with recurrent dislocation, and spontaneous shoulder dislocation due to dysplasia of glenoid and labrum was diagnosed in 12. Of the 57 patients in the study cohort, 53 underwent surgery. Postoperatively, two patients developed recurrent shoulder dislocation (Andreev–Boichev technique due type III shoulder dysplasia in the first patient and multidirectional injury in the second. Conclusions. Shoulder joint instability should be considered as the traumatic or non-traumatic form. Treatment decisions should be based on anatomical characteristics that predispose to recurrent dislocation.

Midflexion instability in primary total knee replacement: a review

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Ramappa Manjunath

2015-01-01

Full Text Available Introduction: Midflexion instability in primary total knee replacement (TKR is an evolving concept. Successful treatment of instability requires an understanding of the different types of instability. Methods: A literature review was performed to identify information pertinent to midflexion instability in primary total knee replacement, utilising PRISMA guidelines. Databases searched included Embase, Medline, All of the Cochrane Library, PubMed and cross references. Results: Three factors, i.e., elevated joint line, multiradii femoral component and medial collateral ligament (MCL laxity, were identified to influence midflexion instability. Literature suggested mediolateral instability at 30–60° of flexion as diagnostic of midflexion instability. Literature search also revealed paucity in clinical studies analysing midflexion instability. Most of the evidence was obtained from cadaveric studies for elevated joint line and MCL laxity. Clinical studies on multiradii femoral component were limited by their small study size and early followup period. Conclusion: Elevated joint line, multiradii femoral component and MCL laxity have been suggested to cause midflexion laxity in primary TKR. Due to limitations in available evidence, this review was unable to raise the strength of overall evidence. Future well-designed clinical studies are essential to make definitive conclusions. This review serves as a baseline for future researchers and creates awareness for routine assessment of midflexion instability in primary total knee replacement.

Further characterization of field strains of rotavirus from Nigeria VP4 genotype P6 most frequently identified among symptomatically infected children.

Science.gov (United States)

Adah, M I; Rohwedder, A; Olaleye, O D; Durojaiye, O A; Werchau, H

1997-10-01

Polymerase chain reaction was utilized to characterize the VP4 types of 39 Rotavirus field isolates from symptomatically infected children in Nigeria. Genotype P6 was identified most frequently, occurring in 41.03 per cent of the typed specimens. Genotype P8 was identified as the next most prevalent (33.3% per cent). Genotype p6 was widespread (68.75 per cent) among infected neonates in Southern Nigeria, but mix infection was more prevalent (70 per cent) among Northern Nigerian children. Four distinct strains were identified with four different P genotypes. Overall strain G1P8 predominated (22.22 per cent) followed by G3P6 (17.8 per cent). Strain G1P8 was most prevalent (70 per cent) among infants aged 3.1-9 months, but strain G3P6 was most frequently identified among neonates occurance of mix infection genotype demonstrates the potential for reassortment events among different rotavirus genogroups in Nigeria. The epidemiological implications of these findings for rotavirus vaccine development and application in the country were discussed.

Causes of genome instability

DEFF Research Database (Denmark)

Langie, Sabine A S; Koppen, Gudrun; Desaulniers, Daniel

2015-01-01

function, chromosome segregation, telomere length). The purpose of this review is to describe the crucial aspects of genome instability, to outline the ways in which environmental chemicals can affect this cancer hallmark and to identify candidate chemicals for further study. The overall aim is to make......Genome instability is a prerequisite for the development of cancer. It occurs when genome maintenance systems fail to safeguard the genome's integrity, whether as a consequence of inherited defects or induced via exposure to environmental agents (chemicals, biological agents and radiation). Thus...

Mutations in the newly identified RAX regulatory sequence are not a frequent cause of micro/anophthalmia.

Science.gov (United States)

Chassaing, Nicolas; Vigouroux, Adeline; Calvas, Patrick

2009-06-01

Microphthalmia and anophthalmia are at the severe end of the spectrum of abnormalities in ocular development. A few genes (SOX2, OTX2, RAX, and CHX10) have been implicated in isolated micro/anophthalmia, but causative mutations of these genes explain less than a quarter of these developmental defects. A specifically conserved SOX2/OTX2-mediated RAX expression regulatory sequence has recently been identified. We postulated that mutations in this sequence could lead to micro/anophthalmia, and thus we performed molecular screening of this regulatory element in patients suffering from micro/anophthalmia. Fifty-one patients suffering from nonsyndromic microphthalmia (n = 40) or anophthalmia (n = 11) were included in this study after negative molecular screening for SOX2, OTX2, RAX, and CHX10 mutations. Mutation screening of the RAX regulatory sequence was performed by direct sequencing for these patients. No mutations were identified in the highly conserved RAX regulatory sequence in any of the 51 patients. Mutations in the newly identified RAX regulatory sequence do not represent a frequent cause of nonsyndromic micro/anophthalmia.

Demonstration of various rotor instabilities (exhibit of Bently Rotor Dynamics Research Corporation Laborator rigs at symposium on instability in rotaing machinery)

Science.gov (United States)

Muszynska, A.

1985-01-01

The operation of rotor rigs used to demonstrate various instability phenomena occurring in rotating machines is described. The instability phenomena demonstrated included oil whirl/whip antiswirl, rub, loose rotating parts, water-lubricated bearing instabilities, and cracked shaft. The rotor rigs were also used to show corrective measures for preventing instabilities. Vibrational response data from the rigs were taken with modern, computerized instrumentation. The rotor nonsynchronous perturbation rig demonstrated modal identification techniques for rotor/bearing systems. Computer-aided data acquisition and presentation, using the dynamic stiffness method, makes it possible to identify rotor and bearing parameters for low modes. The shaft mode demonstrator presented the amplified modal shape line of the shaft excited by inertia forces of unbalance (synchronous perturbation). The first three bending modes of the shaft can be demonstrated. The user-friendly software, Orbits, presented a simulation of rotor precessional motion that is characteristic of various instability phenomena. The data presentation demonstration used data measured on a turbine driven compressor train as an example of how computer aided data acquisition and presentation assists in identifying rotating machine malfunctions.

Alternative Splicing of CHEK2 and Codeletion with NF2 Promote Chromosomal Instability in Meningioma

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Hong Wei Yang

2012-01-01

Full Text Available Mutations of the NF2 gene on chromosome 22q are thought to initiate tumorigenesis in nearly 50% of meningiomas, and 22q deletion is the earliest and most frequent large-scale chromosomal abnormality observed in these tumors. In aggressive meningiomas, 22q deletions are generally accompanied by the presence of large-scale segmental abnormalities involving other chromosomes, but the reasons for this association are unknown. We find that large-scale chromosomal alterations accumulate during meningioma progression primarily in tumors harboring 22q deletions, suggesting 22q-associated chromosomal instability. Here we show frequent codeletion of the DNA repair and tumor suppressor gene, CHEK2, in combination with NF2 on chromosome 22q in a majority of aggressive meningiomas. In addition, tumor-specific splicing of CHEK2 in meningioma leads to decreased functional Chk2 protein expression. We show that enforced Chk2 knockdown in meningioma cells decreases DNA repair. Furthermore, Chk2 depletion increases centrosome amplification, thereby promoting chromosomal instability. Taken together, these data indicate that alternative splicing and frequent codeletion of CHEK2 and NF2 contribute to the genomic instability and associated development of aggressive biologic behavior in meningiomas.

Causation of cancer by ionizing radiation and genomic instability

International Nuclear Information System (INIS)

Streffer, Christian

2013-01-01

The causation of cancer by ionizing radiation has been shown in many epidemiological (with exposed humans) as well as experimental studies with mammals especially mice but also rats, dogs and monkeys. Risk values have been determined in medium radiation dose ranges (∼100 to 2,000 mSv). However, in the low dose range (<100 mSv) the situation is unclear and unsolved up to now. A better knowledge of the mechanisms for the development of cancer in humans over decades after low to medium radiation exposures is necessary for the understanding of the open questions. An increase of chromosomal aberrations and other genetic changes have been frequently observed directly after radiation exposures in many cell systems including human cells. However, in 1989 it was found that an increase of genomic instability occurred after irradiation of mouse zygotes in the fibroblasts of the neonates developing from the irradiated zygotes. That means genomic instability developed many cell generations later in cells which never had been exposed to various qualities of ionizing radiations in vivo and any treatment and secondary cancers developed in photon irradiated M.Hodgkin patients preferentially in those patients who showed a comparatively high genomic instability in their lymphocytes. Since several decades it has been experienced that certain cancer patients show an extremely high radio-sensitivity. This clinical observation has been confirmed by experimental investigations with cells of such patients. It has been proven that this increased radio-sensitivity is due to genetic mutations. A number of syndromes could be defined on such a genetic basis like ataxia telangiectasia, bloom's syndrome, fanconi anemia, retinoblasoma and others. In all these syndromes mutations occur in genes which are to regulation of the cell cycle or DNA repair (preferentially repair of DSBs). These patients with an increased radio-sensitivity frequently develop cancer - very often lymphoma - and they also

Mood instability and impulsivity as trait predictors of suicidal thoughts.

Science.gov (United States)

Peters, Evyn M; Balbuena, Lloyd; Marwaha, Steven; Baetz, Marilyn; Bowen, Rudy

2016-12-01

Impulsivity, the tendency to act quickly without adequate planning or concern for consequences, is a commonly cited risk factor for suicidal thoughts and behaviour. There are many definitions of impulsivity and how it relates to suicidality is not well understood. Mood instability, which describes frequent fluctuations of mood over time, is a concept related to impulsivity that may help explain this relationship. The purpose of this study was to determine whether impulsivity could predict suicidal thoughts after controlling for mood instability. This study utilized longitudinal data from the 2000 Adult Psychiatric Morbidity Survey (N = 2,406). There was a time interval of 18 months between the two waves of the study. Trait impulsivity and mood instability were measured with the Structured Clinical Interview for DSM-IV Axis II Personality Disorders. Logistic regression analyses were used to evaluate baseline impulsivity and mood instability as predictors of future suicidal thoughts. Impulsivity significantly predicted the presence of suicidal thoughts, but this effect became non-significant with mood instability included in the same model. Impulsivity may be a redundant concept when predicting future suicidal thoughts if mood instability is considered. The significance is that research and therapy focusing on mood instability along with impulsivity may be useful in treating the suicidal patient. Mood instability and impulsivity both predict future suicidal thoughts. Impulsivity does not predict suicidal thoughts after controlling for mood instability. Assessing and treating mood instability could be important aspects of suicide prevention and risk management. © 2015 The British Psychological Society.

Effect of viscosity and surface tension on the growth of Rayleigh-Taylor instability and Richtmyer-Meshkov instability under nonlinear domain

International Nuclear Information System (INIS)

Rahul Banerjee; Khan, M.; Mandal, L.K.; Roy, S.; Gupta, M.R.

2010-01-01

Complete text of publication follows. The Rayleigh-Taylor (R-T) instability and Richtmyer-Meshkov (R-M) instability are well known problems in the formation of some astrophysical structures such as the supernova remnants in the Eagle and Crab nebula. A core collapse supernova is driven by an externally powerful shock, and strong shocks are the breeding ground of hydrodynamic instability such as Rayleigh-Taylor instability or Richtmyer-Meshkov instability. These instabilities are also important issues in the design of targets for inertial confinement fusion (ICF). In an ICF target, a high density fluid is frequently accelerated by the pressure of a low density fluid and after ablation the density quickly decays. So, small ripples at such an interface will grow. Under potential flow model, the perturbed interface between heavier fluid and lighter fluid form bubble and spike like structures. The bubbles are in the form of columns of lighter fluid interleaved by falling spike of heavy fluid. In this paper, we like to presented the effect of viscosity and surface tension on Rayleigh-Taylor instability and Richtmyer-Meshkov instability under the non-linear Layzer's approach and described the displacement curvature, growth and velocity of the tip of the bubble as well as spike. It is seen that, in absence of surface tension the lowering of the asymptotic velocity of the tip of the bubble which is formed when the lighter fluid penetrates into the denser fluid and thus encounters the viscous drag due to the denser fluid, which depends only on the denser fluid's viscosity coefficient. On the other hand the asymptotic velocity of the tip of the spike formed as the denser fluid penetrates into the lighter fluid is reduced by an amount which depends only on the viscosity coefficient of the lighter fluid and the spike is resisted by the viscous drag due to the lighter fluid. However, in presence of surface tension the asymptotic velocity of the tip of the bubble (spike) and

Detecting instability in animal social networks: genetic fragmentation is associated with social instability in rhesus macaques.

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Brianne A Beisner

2011-01-01

Full Text Available The persistence of biological systems requires evolved mechanisms which promote stability. Cohesive primate social groups are one example of stable biological systems, which persist in spite of regular conflict. We suggest that genetic relatedness and its associated kinship structure are a potential source of stability in primate social groups as kinship structure is an important organizing principle in many animal societies. We investigated the effect of average genetic relatedness per matrilineal family on the stability of matrilineal grooming and agonistic interactions in 48 matrilines from seven captive groups of rhesus macaques. Matrilines with low average genetic relatedness show increased family-level instability such as: more sub-grouping in their matrilineal groom network, more frequent fighting with kin, and higher rates of wounding. Family-level instability in multiple matrilines within a group is further associated with group-level instability such as increased wounding. Stability appears to arise from the presence of clear matrilineal structure in the rhesus macaque group hierarchy, which is derived from cohesion among kin in their affiliative and agonistic interactions with each other. We conclude that genetic relatedness and kinship structure are an important source of group stability in animal societies, particularly when dominance and/or affilative interactions are typically governed by kinship.

Role of oxidative DNA damage in genome instability and cancer

International Nuclear Information System (INIS)

Bignami, M.; Kunkel, T.

2009-01-01

Inactivation of mismatch repair (MMR) is associated with a dramatic genomic instability that is observed experimentally as a mutator phenotype and micro satellite instability (MSI). It has been implicit that the massive genetic instability in MMR defective cells simply reflects the accumulation of spontaneous DNA polymerase errors during DNA replication. We recently identified oxidation damage, a common threat to DNA integrity to which purines are very susceptible, as an important cofactor in this genetic instability

Arthroscopic Findings in Anterior Shoulder Instability

OpenAIRE

Hantes, Michael; Raoulis, Vasilios

2017-01-01

Background: In the last years, basic research and arthroscopic surgery, have improved our understanding of shoulder anatomy and pathology. It is a fact that arthroscopic treatment of shoulder instability has evolved considerably over the past decades. The aim of this paper is to present the variety of pathologies that should be identified and treated during shoulder arthroscopy when dealing with anterior shoulder instability cases. Methods: A review of the current literature regarding arthros...

Breast tumor copy number aberration phenotypes and genomic instability

International Nuclear Information System (INIS)

Fridlyand, Jane; Jain, Ajay N; McLennan, Jane; Ziegler, John; Chin, Koei; Devries, Sandy; Feiler, Heidi; Gray, Joe W; Waldman, Frederic; Pinkel, Daniel; Albertson, Donna G; Snijders, Antoine M; Ylstra, Bauke; Li, Hua; Olshen, Adam; Segraves, Richard; Dairkee, Shanaz; Tokuyasu, Taku; Ljung, Britt Marie

2006-01-01

Genomic DNA copy number aberrations are frequent in solid tumors, although the underlying causes of chromosomal instability in tumors remain obscure. Genes likely to have genomic instability phenotypes when mutated (e.g. those involved in mitosis, replication, repair, and telomeres) are rarely mutated in chromosomally unstable sporadic tumors, even though such mutations are associated with some heritable cancer prone syndromes. We applied array comparative genomic hybridization (CGH) to the analysis of breast tumors. The variation in the levels of genomic instability amongst tumors prompted us to investigate whether alterations in processes/genes involved in maintenance and/or manipulation of the genome were associated with particular types of genomic instability. We discriminated three breast tumor subtypes based on genomic DNA copy number alterations. The subtypes varied with respect to level of genomic instability. We find that shorter telomeres and altered telomere related gene expression are associated with amplification, implicating telomere attrition as a promoter of this type of aberration in breast cancer. On the other hand, the numbers of chromosomal alterations, particularly low level changes, are associated with altered expression of genes in other functional classes (mitosis, cell cycle, DNA replication and repair). Further, although loss of function instability phenotypes have been demonstrated for many of the genes in model systems, we observed enhanced expression of most genes in tumors, indicating that over expression, rather than deficiency underlies instability. Many of the genes associated with higher frequency of copy number aberrations are direct targets of E2F, supporting the hypothesis that deregulation of the Rb pathway is a major contributor to chromosomal instability in breast tumors. These observations are consistent with failure to find mutations in sporadic tumors in genes that have roles in maintenance or manipulation of the genome

Overexpression screens identify conserved dosage chromosome instability genes in yeast and human cancer

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Duffy, Supipi; Fam, Hok Khim; Wang, Yi Kan; Styles, Erin B.; Kim, Jung-Hyun; Ang, J. Sidney; Singh, Tejomayee; Larionov, Vladimir; Shah, Sohrab P.; Andrews, Brenda; Boerkoel, Cornelius F.; Hieter, Philip

2016-01-01

Somatic copy number amplification and gene overexpression are common features of many cancers. To determine the role of gene overexpression on chromosome instability (CIN), we performed genome-wide screens in the budding yeast for yeast genes that cause CIN when overexpressed, a phenotype we refer to as dosage CIN (dCIN), and identified 245 dCIN genes. This catalog of genes reveals human orthologs known to be recurrently overexpressed and/or amplified in tumors. We show that two genes, TDP1, a tyrosyl-DNA-phosphdiesterase, and TAF12, an RNA polymerase II TATA-box binding factor, cause CIN when overexpressed in human cells. Rhabdomyosarcoma lines with elevated human Tdp1 levels also exhibit CIN that can be partially rescued by siRNA-mediated knockdown of TDP1. Overexpression of dCIN genes represents a genetic vulnerability that could be leveraged for selective killing of cancer cells through targeting of an unlinked synthetic dosage lethal (SDL) partner. Using SDL screens in yeast, we identified a set of genes that when deleted specifically kill cells with high levels of Tdp1. One gene was the histone deacetylase RPD3, for which there are known inhibitors. Both HT1080 cells overexpressing hTDP1 and rhabdomyosarcoma cells with elevated levels of hTdp1 were more sensitive to histone deacetylase inhibitors valproic acid (VPA) and trichostatin A (TSA), recapitulating the SDL interaction in human cells and suggesting VPA and TSA as potential therapeutic agents for tumors with elevated levels of hTdp1. The catalog of dCIN genes presented here provides a candidate list to identify genes that cause CIN when overexpressed in cancer, which can then be leveraged through SDL to selectively target tumors. PMID:27551064

Anisotropic gravitational instability

International Nuclear Information System (INIS)

Polyachenko, V.L.; Fridman, A.M.

1988-01-01

Exact solutions of stability problems are obtained for two anisotropic gravitational systems of different geometries - a layer of finite thickness at rest and a rotating cylinder of finite radius. It is shown that the anisotropic gravitational instability which develops in both cases is of Jeans type. However, in contrast to the classical aperiodic Jeans instability, this instability is oscillatory. The physics of the anisotropic gravitational instability is investigated. It is shown that in a gravitating layer this instability is due, in particular, to excitation of previously unknown interchange-Jeans modes. In the cylinder, the oscillatory Jeans instability is associated with excitation of a rotational branch, this also being responsible for the beam gravitational instability. This is the reason why this instability and the anisotropic gravitational instability have so much in common

Chromosomal instability determines taxane response

DEFF Research Database (Denmark)

Swanton, C.; Nicke, B.; Schuett, M.

2009-01-01

chromosomal instability (CIN). Silencing 22/50 of these genes, many of which are involved in DNA repair, caused cancer cell death, suggesting that these genes are involved in the survival of aneuploid cells. Overexpression of these "CIN-survival'' genes is associated with poor outcome in estrogen receptor......-positive breast cancer and occurs frequently in basal-like and Her2-positive cases. In diploid cells, but not in chromosomally unstable cells, paclitaxel causes repression of CIN-survival genes, followed by cell death. In the OV01 ovarian cancer clinical trial, a high level of CIN was associated with taxane...

Whole exome analysis identifies frequent CNGA1 mutations in Japanese population with autosomal recessive retinitis pigmentosa.

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Satoshi Katagiri

Full Text Available OBJECTIVE: The purpose of this study was to investigate frequent disease-causing gene mutations in autosomal recessive retinitis pigmentosa (arRP in the Japanese population. METHODS: In total, 99 Japanese patients with non-syndromic and unrelated arRP or sporadic RP (spRP were recruited in this study and ophthalmic examinations were conducted for the diagnosis of RP. Among these patients, whole exome sequencing analysis of 30 RP patients and direct sequencing screening of all CNGA1 exons of the other 69 RP patients were performed. RESULTS: Whole exome sequencing of 30 arRP/spRP patients identified disease-causing gene mutations of CNGA1 (four patients, EYS (three patients and SAG (one patient in eight patients and potential disease-causing gene variants of USH2A (two patients, EYS (one patient, TULP1 (one patient and C2orf71 (one patient in five patients. Screening of an additional 69 arRP/spRP patients for the CNGA1 gene mutation revealed one patient with a homozygous mutation. CONCLUSIONS: This is the first identification of CNGA1 mutations in arRP Japanese patients. The frequency of CNGA1 gene mutation was 5.1% (5/99 patients. CNGA1 mutations are one of the most frequent arRP-causing mutations in Japanese patients.

Kinematics of Nonlinearly Interacting MHD Instabilities in a Plasma

International Nuclear Information System (INIS)

Hansen, Alexander K.

2000-01-01

Plasmas play host to a wide variety of instabilities. For example, tearing instabilities use finite plasma resistivity to exploit the free energy provided by plasma currents parallel to the magnetic field to alter the magnetic topology of the plasma through a process known as reconnection. These instabilities frequently make themselves known in magnetic confinement experiments such as tokamaks and reversed field pinches (RFPs). In RFP plasmas, in fact, several tearing instabilities (modes) are simultaneously active, and are of large amplitude. Theory predicts that in addition to interacting linearly with magnetic perturbations from outside the plasma, such as field errors or as resistive wall, the modes in the RFP can interact nonlinearly with each other through a three-wave interaction. In the current work investigations of both the linear (external) and nonlinear contributions to the kinematics of the tearing modes in the Madison Symmetric Torus (MST) RFP are reported Theory predicts that tearing modes will respond only to magnetic perturbations that are spatially resonant with them, and was supported by experimental work done on tokamak devices. The results in this work verified that the theory is still applicable to the RFP, in spite of its more complicated magnetic mode structure, involving perturbations of a single poloidal mode number

Multiple sclerosis and employment: Associations of psychological factors and work instability.

Science.gov (United States)

Wicks, Charlotte Rose; Ward, Karl; Stroud, Amanda; Tennant, Alan; Ford, Helen L

2016-10-12

People with multiple sclerosis often stop working earlier than expected. Psychological factors may have an impact on job retention. Investigation may inform interventions to help people stay in work. To investigate the associations between psychological factors and work instability in people with multiple sclerosis. A multi-method, 2-phased study. Focus groups were held to identify key themes. Questionnaire packs using validated scales of the key themes were completed at baseline and at 8-month follow-up. Four key psychological themes emerged. Out of 208 study subjects 57.2% reported medium/high risk of job loss, with marginal changes at 8 months. Some psychological variables fluctuated significantly, e.g. depression fell from 24.6% to 14.5%. Work instability and anxiety and depression were strongly correlated (χ2 p work instability, and baseline depression levels also predicted later work instability (Hosmer-Lemeshow test 0.899; Nagelkerke R Square 0.579). Psychological factors fluctuated over the 8-month follow-up period. Some psychological variables, including anxiety and depression, were significantly associated with, and predictive of, work instability. Longitudinal analysis should further identify how these psychological attributes impact on work instability and potential job loss in the longer term.

Detrusor instability in children with recurrent urinary tract infection and/or enuresis. II

DEFF Research Database (Denmark)

Qvist, N; Nielsen, K K; Kristensen, E S

1986-01-01

Of 41 children, aged 5-15 years, referred consecutively because of recurrent urinary tract infections (UTIs) and/or enuresis, 18 (44%) showed detrusor instability (DI) in at least 2 of 6 CO2 cystometries. One child was excluded from the study because of lack of follow-up. Four children with less...... pronounced DI (instability during less than or equal to 50% of the cystometries performed) and frequent UTIs were given antibiotics prophylactically for 3 months. In the remaining 13 children, DI was found during more than half the cystometries performed, and 11 of these children, who also had urge...... incontinence, were treated with emepronium bromide, 400-600 mg daily (10-12 mg/kg) for 3 months. In 7 of the patients this treatment was supplemented by antibiotics prophylactically because of frequent UTIs. Two children with special problems received other types of treatment. All children were free from...

Buneman instability and Pierce instability in a collisionless bounded plasma

International Nuclear Information System (INIS)

Iizuka, Satoru; Saeki, Koichi; Sato, Noriyoshi; Hatta, Yoshisuke

1983-01-01

A systematic experiment is performed on the Buneman instability and the Pierce instability in a bounded plasma consisting of beam electrons and stationary ions. Current fluctuations are confirmed to be induced by the Buneman instability. On the other hand, the Pierce instability gives rise to a current limitation. The phenomena are well explained by Mikhailovskii's theory taking account of ion motion in a bounded plasma. (author)

Circuit effects on pierce instabilities, and double-layer formation

International Nuclear Information System (INIS)

Raadu, M.A.; Silevitch, M.B.

1982-11-01

The role of the Pierce instability in the formation of double layers is considered and compared with that of the Buneman instability. Pierce instabilities have been identified in a double-layer experiment, where they lead to ion trapping. Here the effects of external circuit elements are considered. In the case of immobile ions the onset criteria are unaffected, but in the unstable range the growth rate is reduced by the external impedance. Required experimental values of the circuit elements are estimated. The possible relevance to computer simulations is noted. (Authors)

Instabilities in inhomogeneous plasma

International Nuclear Information System (INIS)

Mikhailovsky, A.B.

1983-01-01

The plasma inhomogeneity across the magnetic field causes a wide class of instabilities which are called instabilities of an inhomogeneous plasma or gradient instabilities. The instabilities that can be studied in the approximation of a magnetic field with parallel straight field lines are treated first, followed by a discussion of the influence of shear on these instabilities. The instabilities of a weakly inhomogeneous plasma with the Maxwellian velocity distribution of particles caused by the density and temperature gradients are often called drift instabilities, and the corresponding types of perturbations are the drift waves. An elementary theory of drift instabilities is presented, based on the simplest equations of motion of particles in the field of low-frequency and long-wavelength perturbations. Following that is a more complete theory of inhomogeneous collisionless plasma instabilities which uses the permittivity tensor and, in the case of electrostatic perturbations, the scalar of permittivity. The results are used to study the instabilities of a strongly inhomogeneous plasma. The instabilities of a plasma in crossed fields are discussed and the electromagnetic instabilities of plasma with finite and high pressure are described. (Auth.)

Kinetic instabilities in relativistic plasmas: the Harris instability revisited

International Nuclear Information System (INIS)

Tautz, R.C.

2008-01-01

Plasma instabilities that generate aperiodic fluctuations are of outstanding importance in the astrophysical context. Two prominent examples are the electromagnetic Weibel instability and the electrostatic Harris instability, which operate in initially non-magnetized and magnetized plasmas, respectively. In this talk, the original formulation of the Harris instability will be reviewed and generalizations will be presented such as the inclusion of (1) relativistic effects, (2) ion effects, and (3) mode coupling. It will be shown that, with these modifications, a powerful method has been developed for the determination of both the existence and the growth rate of low-frequency instabilities. Applications can be found in astrophysical jets, where the rest frame can be used and so no parallel motion is present. At the end of the talk, how the particle composition of gamma-ray burst jets can be predicted using the Harris technique. (author)

Carpal instability

International Nuclear Information System (INIS)

Schmitt, R.; Froehner, S.; Coblenz, G.; Christopoulos, G.

2006-01-01

This review addresses the pathoanatomical basics as well as the clinical and radiological presentation of instability patterns of the wrist. Carpal instability mostly follows an injury; however, other diseases, like CPPD arthropathy, can be associated. Instability occurs either if the carpus is unable to sustain physiologic loads (''dyskinetics'') or suffers from abnormal motion of its bones during movement (''dyskinematics''). In the classification of carpal instability, dissociative subcategories (located within proximal carpal row) are differentiated from non-dissociative subcategories (present between the carpal rows) and combined patterns. It is essential to note that the unstable wrist initially does not cause relevant signs in standard radiograms, therefore being ''occult'' for the radiologic assessment. This paper emphasizes the high utility of kinematographic studies, contrast-enhanced magnetic resonance imaging (MRI) and MR arthrography for detecting these predynamic and dynamic instability stages. Later in the natural history of carpal instability, static malalignment of the wrist and osteoarthritis will develop, both being associated with significant morbidity and disability. To prevent individual and socio-economic implications, the handsurgeon or orthopedist, as well as the radiologist, is challenged for early and precise diagnosis. (orig.)

Identifying the underlying causes of biological instability in a full-scale drinking water supply system.

Science.gov (United States)

Nescerecka, Alina; Juhna, Talis; Hammes, Frederik

2018-05-15

Changes in bacterial concentration and composition in drinking water during distribution are often attributed to biological (in)stability. Here we assessed temporal biological stability in a full-scale distribution network (DN) supplied with different types of source water: treated and chlorinated surface water and chlorinated groundwater produced at three water treatment plants (WTP). Monitoring was performed weekly during 12 months in two locations in the DN. Flow cytometric total and intact cell concentration (ICC) measurements showed considerable seasonal fluctuations, which were different for two locations. ICC varied between 0.1-3.75 × 10 5  cells mL -1 and 0.69-4.37 × 10 5  cells mL -1 at two locations respectively, with ICC increases attributed to temperature-dependent bacterial growth during distribution. Chlorinated water from the different WTP was further analysed with a modified growth potential method, identifying primary and secondary growth limiting compounds. It was observed that bacterial growth in the surface water sample after chlorination was primarily inhibited by phosphorus limitation and secondly by organic carbon limitation, while carbon was limiting in the chlorinated groundwater samples. However, the ratio of available nutrients changed during distribution, and together with disinfection residual decay, this resulted in higher bacterial growth potential detected in the DN than at the WTP. In this study, bacterial growth was found to be higher (i) at higher water temperatures, (ii) in samples with lower chlorine residuals and (iii) in samples with less nutrient (carbon, phosphorus, nitrogen, iron) limitation, while this was significantly different between the samples of different origin. Thus drinking water microbiological quality and biological stability could change during different seasons, and the extent of these changes depends on water temperature, the water source and treatment. Furthermore, differences in primary

Instability timescale for the inclination instability in the solar system

Science.gov (United States)

Zderic, Alexander; Madigan, Ann-Marie; Fleisig, Jacob

2018-04-01

The gravitational influence of small bodies is often neglected in the study of solar system dynamics. However, this is not always an appropriate assumption. For example, mutual secular torques between low mass particles on eccentric orbits can result in a self-gravity instability (`inclination instability'; Madigan & McCourt 2016). During the instability, inclinations increase exponentially, eccentricities decrease (detachment), and orbits cluster in argument of perihelion. In the solar system, the orbits of the most distant objects show all three of these characteristics (high inclination: Volk & Malhotra (2017), detachment: Delsanti & Jewitt (2006), and argument of perihelion clustering: Trujillo & Sheppard (2014)). The inclination instability is a natural explanation for these phenomena.Unfortunately, full N-body simulations of the solar system are unfeasible (N ≈ O(1012)), and the behavior of the instability depends on N, prohibiting the direct application of lower N simulations. Here we present the instability timescale's functional dependence on N, allowing us to extrapolate our simulation results to that appropriate for the solar system. We show that ~5 MEarth of small icy bodies in the Sedna region is sufficient for the inclination instability to occur in the outer solar system.

The appearance of scapulohumeral instability on computerized tomography

International Nuclear Information System (INIS)

Schedel, H.; Knollmann, F.D.; Granrath, M.; Suedkamp, N.; Siekmann, R.; Felix, R.

1995-01-01

In order to analyze the computed-tomographical appearance of scapulohumeral instability 18 patients showing clinical signs of the disease were examined using a double-contrast technique and the findings thus obtained evaluated in a retrograde procedure. The overall results fell into two categories, one being that of elderly patients with degenerative soft tissue lesions, while the other one comprised youngish individuals more frequently tending to bone defects. The pathophysiological differences between those groups point to the need of different therapeutic approaches. (orig.) [de

Thermal instabilities in the edge region of reversed-field pinches

International Nuclear Information System (INIS)

Goedert, J.; Mondt, J.P.

1984-04-01

Thermal stability of the edge region of reversed-field pinch configurations is analyzed within the context of a two-fluid model. Two major sources of instability are identified in combination with a parallel electric field: either an electron temperature gradient and/or a density gradient that leads to rapid growth (of several to many ohmic heating rates) over a region of several millimeters around the mode-rational surfaces in the edge region. The basic signature of both instabilities is electrostatic. In the case of the density gradient mode, the signature relies on the effects of electron compressibility, whereas the temperature gradient mode can be identified as the current-convective instability by taking the limit of zero diamagnetic drift, density gradient, thermal force, drift heat flux, and electron compressibility

Emergency Department Frequent Users for Acute Alcohol Intoxication.

Science.gov (United States)

Klein, Lauren R; Martel, Marc L; Driver, Brian E; Reing, Mackenzie; Cole, Jon B

2018-03-01

A subset of frequent users of emergency services are those who use the emergency department (ED) for acute alcohol intoxication. This population and their ED encounters have not been previously described. This was a retrospective, observational, cohort study of patients presenting to the ED for acute alcohol intoxication between 2012 and 2016. We collected all data from the electronic medical record. Frequent users for alcohol intoxication were defined as those with greater than 20 visits for acute intoxication without additional medical chief complaints in the previous 12 months. We used descriptive statistics to evaluate characteristics of frequent users for alcohol intoxication, as well as their ED encounters. We identified 32,121 patient encounters. Of those, 325 patients were defined as frequent users for alcohol intoxication, comprising 11,370 of the encounters during the study period. The median maximum number of encounters per person for alcohol intoxication in a one-year period was 47 encounters (range 20 to 169). Frequent users were older (47 years vs. 39 years), and more commonly male (86% vs. 71%). Frequent users for alcohol intoxication had higher rates of medical and psychiatric comorbidities including liver disease, chronic kidney disease, ischemic vascular disease, dementia, chronic obstructive pulmonary disease, history of traumatic brain injury, schizophrenia, and bipolar disorder. In this study, we identified a group of ED frequent users who use the ED for acute alcohol intoxication. This population had higher rates of medical and psychiatric comorbidities compared to non-frequent users.

On the identification of instabilities with neural networks on JET

International Nuclear Information System (INIS)

Murari, A.; Arena, P.; Buscarino, A.; Fortuna, L.; Iachello, M.

2013-01-01

JET plasmas are affected by various instabilities, which can be particularly dangerous in high performance discharges. An identification method, based on the use of advanced neural networks, called Recurrent Neural Networks (RNNs), has been applied to ELMs. The potential of the recurrent networks to identify the dynamics of the instabilities has been first tested using synthetic data. The networks have then been applied to JET experimental signals. An appropriate selection of the networks topology allows identifying quite well the time evolution of the edge temperature and of the magnetic fields, considered the best indicators of the ELMs. A quite limited number of periodic oscillations are used to train the networks, which then manage to follow quite well the dynamics of the instabilities, in a recurrent configuration on one of the inputs. The time evolution of the aforementioned signals, also during intervals not used in the training and never seen by the networks, are properly reproduced. A careful analysis of the various terms in the RNNs has the potential to give clear indications about the nature of these instabilities and their dynamical behaviour

Localized multi-scale energy and vorticity analysis. II. Finite-amplitude instability theory and validation

Science.gov (United States)

San Liang, X.; Robinson, Allan R.

2007-12-01

A novel localized finite-amplitude hydrodynamic stability analysis is established in a unified treatment for the study of real oceanic and atmospheric processes, which are in general highly nonlinear, and intermittent in space and time. We first re-state the classical definition using the multi-scale energy and vorticity analysis (MS-EVA) developed in Liang and Robinson [Liang, X.S., Robinson, A.R., 2005. Localized multiscale energy and vorticity analysis. I. Fundamentals. Dyn. Atmos. Oceans 38, 195-230], and then manipulate certain global operators to achieve the temporal and spatial localization. The key of the spatial localization is transfer-transport separation, which is made precise with the concept of perfect transfer, while relaxation of marginalization leads to the localization of time. In doing so the information of transfer lost in the averages is retrieved and an easy-to-use instability metric is obtained. The resulting metric is field-like (Eulerian), conceptually generalizing the classical formalism, a bulk notion over the whole system. In this framework, an instability has a structure, which is of particular use for open flow processes. We check the structure of baroclinic instability with the benchmark Eady model solution, and the Iceland-Faeroe Frontal (IFF) intrusion, a highly localized and nonlinear process occurring frequently in the region between Iceland and Faeroe Islands. A clear isolated baroclinic instability is identified around the intrusion, which is further found to be characterized by the transition from a spatially growing mode to a temporally growing mode. We also check the consistency of the MS-EVA dynamics with the barotropic Kuo model. An observation is that a local perturbation burst does not necessarily imply an instability: the perturbation energy could be transported from other processes occurring elsewhere. We find that our analysis yields a Kuo theorem-consistent mean-eddy interaction, which is not seen in a conventional

A perfect storm: examining the synergistic effects of negative and positive emotional instability on promoting weight loss activities in anorexia nervosa

Science.gov (United States)

Selby, Edward A.; Cornelius, Talea; Fehling, Kara B.; Kranzler, Amy; Panza, Emily A.; Lavender, Jason M.; Wonderlich, Stephen A.; Crosby, Ross D.; Engel, Scott G.; Mitchell, James E.; Crow, Scott J.; Peterson, Carol B.; Grange, Daniel Le

2015-01-01

Growing evidence indicates that both positive and negative emotion potentially influence the development and maintenance of anorexia nervosa, through both positive and negative reinforcement of weight loss activities. Such reactive emotional experience may be characterized by frequent and intense fluctuations in emotion, a construct known as “emotional instability.” The purpose of this study was to investigate the association between positive emotional instability and weight loss activities in anorexia nervosa, and to investigate the synergistic effects of positive and negative emotional instability on promoting weight loss activities. Using ecological momentary assessment methods, 118 participants with anorexia nervosa reported their emotional experiences and behaviors at least six times daily over 2 weeks using a portable digital device. Using generalized linear modeling, results indicated that high levels of both positive and negative emotional instability, and the interaction between the two, were associated with more frequent weight-loss activities, beyond anorexia subtype and mean levels of emotional intensity. These findings indicate that when women with anorexia exhibit both high levels of both positive and negative emotional instability they are more prone to a variety of weight loss activities. The importance of addressing the role of both positive and negative emotion in anorexia treatment is discussed. PMID:26379588

Housing Instability Is as Strong a Predictor of Poor Health Outcomes as Level of Danger in an Abusive Relationship: Findings from the SHARE Study

Science.gov (United States)

Rollins, Chiquita; Glass, Nancy E.; Perrin, Nancy A.; Billhardt, Kris A.; Clough, Amber; Barnes, Jamie; Hanson, Ginger C.; Bloom, Tina L.

2012-01-01

Advocates, clinicians, policy makers, and survivors frequently cite intimate partner violence (IPV) as an immediate cause of or precursor to housing problems. Research has indicated an association between homelessness and IPV, yet few studies examine IPV and housing instability. Housing instability differs from homelessness, in that someone…

Subatmospheric boiling study of the operation of a horizontal thermosyphon reboiler loop: Instability

International Nuclear Information System (INIS)

Agunlejika, Ezekiel O.; Langston, Paul A.; Azzopardi, Barry J.; Hewakandamby, Buddhika N.

2016-01-01

Graphical abstract: The highlight of the characteristics of the geysering instability from analysed WMS data. Pictorial view of geysering instability, heat flux 9 kW/m"2 (P_S = 1.14 bar(a)), Static head = 1.265 m, valve setting = 1.0, process side pressure = 0.5 bar(a). - Highlights: • Characteristics of geysering instability in a horizontal thermosyphon reboiler loop is highlighted using Wire Mesh Sensor. • Interconnection between geysering instability and accompanying churn flow is identified. • Effects of stability parameters and pressure drop feedbacks on the loop at low heat fluxes are described. - Abstract: Distillation and chemical processing under vacuum is of immense interest to petroleum and chemical industries due to lower energy costs and improved safety. To tap into these benefits, energy efficient reboilers with lower maintenance costs are required. Here, a horizontal thermosyphon reboiler is investigated at subatmospheric pressures and low heat fluxes. This paper presents detailed experimental data obtained using Wire Mesh Sensor in a gas-liquid flow with heat transfer as well as temperatures, pressures and recirculation rates around the loop. Flow regimes which have been previously identified in other systems were detected. The nature of the instability which underpins the mechanisms involved and conditions aiding instability are reported. Churn flow pattern is persistently detected during instability. The nature of the instability and existence of oscillatory churn flow are interconnected.

The Internal Causes of Political Instability in the Republic of Turkey

Directory of Open Access Journals (Sweden)

Sergey Borisovich Druzhilovsky

2016-01-01

Full Text Available The article examines the causes of the permanent political instability in the Turkish Republic, which leads to frequent change of governments, degradation of political parties and changing of policies. On the example of the activities of different cabinets it is showen that the basis of their instability is the frequent creation of coalition governments consisting of parties that stand on different ideological positions. Inter-party antagonism, in its turn, is a consequence of the split of the Turkish society along civilizational, ethnic and religious grounds, which determines the different political orientation of the various layers of the Turkish society. At the same time the article shows the examples of the undoubted efficiency of one-party governments, however they never get support from the opposition parties, and eventually also fail to effectively and consistently implement their proposed policies. The author also deals with a policy of the ruling today in Turkey, the Islamist Party of Justice and Development, which after several years of successful political and economic reforms to date entered the period of deep crisis and is increasingly losing its authority and influence both in Turkey and in neighboring countries.

Emergency Department Frequent Users for Acute Alcohol Intoxication

Directory of Open Access Journals (Sweden)

Marc L. Martel

2018-02-01

Full Text Available Introduction: A subset of frequent users of emergency services are those who use the emergency department (ED for acute alcohol intoxication. This population and their ED encounters have not been previously described. Methods: This was a retrospective, observational, cohort study of patients presenting to the ED for acute alcohol intoxication between 2012 and 2016. We collected all data from the electronic medical record. Frequent users for alcohol intoxication were defined as those with greater than 20 visits for acute intoxication without additional medical chief complaints in the previous 12 months. We used descriptive statistics to evaluate characteristics of frequent users for alcohol intoxication, as well as their ED encounters. Results: We identified 32,121 patient encounters. Of those, 325 patients were defined as frequent users for alcohol intoxication, comprising 11,370 of the encounters during the study period. The median maximum number of encounters per person for alcohol intoxication in a one-year period was 47 encounters (range 20 to 169. Frequent users were older (47 years vs. 39 years, and more commonly male (86% vs. 71%. Frequent users for alcohol intoxication had higher rates of medical and psychiatric comorbidities including liver disease, chronic kidney disease, ischemic vascular disease, dementia, chronic obstructive pulmonary disease, history of traumatic brain injury, schizophrenia, and bipolar disorder. Conclusion: In this study, we identified a group of ED frequent users who use the ED for acute alcohol intoxication. This population had higher rates of medical and psychiatric comorbidities compared to non-frequent users.

Frequently cited journals in forensic psychology.

Science.gov (United States)

Black, Steve

2012-02-01

Works cited in six forensic psychology journals published 2008-2010 were counted to identify the most frequently cited journals. The sample of works cited (N = 21,776) was not a definitive ranked list of important journals in forensic psychology, but was large enough to indicate high-impact journals. The list of frequently cited publications included more general psychiatry and psychology journals than titles specific to forensic psychology. The implications of the proportion of general versus specific titles for collections supporting research in forensic psychology were discussed.

Hydrodynamic instabilities in inertial fusion

International Nuclear Information System (INIS)

Hoffman, N.M.

1994-01-01

This report discusses topics on hydrodynamics instabilities in inertial confinement: linear analysis of Rayleigh-Taylor instability; ablation-surface instability; bubble rise in late-stage Rayleigh-Taylor instability; and saturation and multimode interactions in intermediate-stage Rayleigh-Taylor instability

Failure of operative treatment for glenohumeral instability: etiology and management.

Science.gov (United States)

Shah, Apurva S; Karadsheh, Mark S; Sekiya, Jon K

2011-05-01

Failure of primary shoulder stabilization procedures is often related to uncorrected anatomic pathology. Orthopaedic surgeons must recognize excessive capsular laxity or large glenohumeral bone defects preoperatively to avoid recurrence of instability. When history, physical examination, and radiographic evaluation are used in conjunction, patients at risk for failure can be identified. The instability severity index score permits precise identification of patients at risk. When treating patients in whom prior surgical intervention has failed, the success of revision procedures correlates to the surgeon's ability to identify the essential pathology and use lesion-specific treatment strategies. Revision procedures remain technically demanding. Keen preoperative and intraoperative judgment is required to avoid additional recurrence of instability after revision procedures, particularly because results deteriorate with each successive operation. Glenoid or humeral defects with greater than 25% bone loss compromise stability provided through the mechanism of concavity compression. These defects must be specifically addressed to avoid recurrence of instability. We prefer anatomic reconstruction techniques combined with capsulolabral repair and, if bone defects are present, anatomic reconstruction with osteochondral allograft. Copyright © 2011 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.

Frequent flyer business travelers: major exposure hazards.

Science.gov (United States)

Tompkins, Olga S; Randolph, Susan A; Ostendorf, Judith S

2005-02-01

Bagshaw (2004) notes "the modern commercial aircraft cabin is maintained with adequate environmental control for the comfort of most healthy individuals" (p. 417). Occupational health nurses frequently deal with a population that may include unhealthy individuals or those with pre-existing conditions. It is critical for occupational health nurses to stay current with major hazards faced by frequent flyer business travelers to assist in identifying and preventing adverse health effects associated with these exposures.

The role of arthroscopy in chronic elbow instability.

Science.gov (United States)

Goodwin, David; Dynin, Maria; Macdonnell, J Ryan; Kessler, Michael W

2013-12-01

Elbow arthroscopy has had an emerging role in the management of many disorders of the elbow. In patients with chronic elbow instability, several arthroscopic techniques have been described in the diagnosis and management of posterolateral rotatory instability and valgus instability. We performed a systematic review investigating the role of arthroscopy in posterolateral rotatory instability and valgus instability in the elbow using the PubMed and CINAHL (Cumulative Index to Nursing and Allied Health Literature) databases, and the Cochrane Database of Systematic Reviews, consisting of articles from peer-reviewed journals published in the English language after January 1, 1991. Search criteria initially identified 249 articles. Twenty-five articles met criteria for inclusion. This included 17 review articles, 4 cadaveric studies, 3 retrospective studies, and 1 prospective study. Two of the retrospective studies compared arthroscopic and open techniques. Articles included in this systematic review concluded that arthroscopy is an accurate adjunct to physical examination and imaging in the diagnosis of chronic elbow instability and affords an exceptional view of the joint with the ability to address intra-articular pathologic conditions. Arthroscopic surgical techniques have shown equivalent clinical outcomes in a comparison of arthroscopic and open techniques. Elbow arthroscopy is a valuable tool in the diagnosis and management of chronic elbow instability. Patients treated arthroscopically benefit from additional diagnostic techniques, improved visualization of the elbow joint, the ability to address coexisting intra-articular pathologic conditions, and minimal soft tissue injury with no clinical consequences in outcomes. With such significant advantages, the use of elbow arthroscopy is likely to expand in the management of chronic elbow instability. Level IV, systematic review. Copyright © 2013 Arthroscopy Association of North America. Published by Elsevier Inc

Theory and models of material erosion and lifetime during plasma instabilities in a tokamak environment

International Nuclear Information System (INIS)

Hassanein, A.; Konkashbaev, I.

1999-01-01

Surface and structural damage to plasma-facing components (PFCs) due to the frequent loss of plasma confinement remains a serious problem for the tokamak reactor concept. The deposited plasma energy causes significant surface erosion, possible structural failure, and frequent plasma contamination. Surface damage consists of vaporization, spallation, and liquid splatter of metallic materials. Structural damage includes large temperature increases in structural materials and at the interfaces between surface coatings and structural members. To evaluate the lifetimes of plasma-facing materials and nearby components and to predict the various forms of damage that they experience, comprehensive models (contained in the HEIGHTS computer simulation package) are developed, integrated self-consistently, and enhanced. Splashing mechanisms such as bubble boiling and various liquid magnetohydrodynamic instabilities and brittle destruction mechanisms of nonmelting materials are being examined. The design requirements and implications of plasma-facing and nearby components are discussed, along with recommendations to mitigate and reduce the effects of plasma instabilities on reactor components

Assessment of instability of the long head of the biceps tendon by MRI

International Nuclear Information System (INIS)

Spritzer, C.E.; Collins, A.J.; Cooperman, A.; Speer, K.P.

2001-01-01

Objective. To determine whether MRI can identify instability of the long head of the biceps tendon (LBT) in the rotator interval.Design and patients. A retrospective review was carried out of 19 patients, all arthroscopically examined, nine of whom had surgically confirmed instability of the LBT.Results. A LBT perched on the lesser tuberosity correctly indicated all nine cases of instability with one false positive. In six of seven cases where the LBT was oval in shape, no instability of the biceps tendon existed, whereas LBT instability was present in eight of 12 patients with a flat long head of the biceps tendon. In seven of eight acutely angled intertubercular sulci there was no instability of the LBT while eight of 11 obtusely angled sulci were associated with LBT instability. By consensus impression, instability of the LBT could be determined with 67% sensitivity, 90% specificity, 86% positive predictive value, and 75% negative predictive value.Conclusions. A flat LBT perched on the lesser tuberosity with an obtusely angled intertubercular sulcus suggests the diagnosis of instability of the LBT in the correct clinical setting. (orig.)

Classification of instability after reverse shoulder arthroplasty guides surgical management and outcomes.

Science.gov (United States)

Abdelfattah, Adham; Otto, Randall J; Simon, Peter; Christmas, Kaitlyn N; Tanner, Gregory; LaMartina, Joey; Levy, Jonathan C; Cuff, Derek J; Mighell, Mark A; Frankle, Mark A

2018-04-01

Revision of unstable reverse shoulder arthroplasty (RSA) remains a significant challenge. The purpose of this study was to determine the reliability of a new treatment-guiding classification for instability after RSA, to describe the clinical outcomes of patients stabilized operatively, and to identify those with higher risk of recurrence. All patients undergoing revision for instability after RSA were identified at our institution. Demographic, clinical, radiographic, and intraoperative data were collected. A classification was developed using all identified causes of instability after RSA and allocating them to 1 of 3 defined treatment-guiding categories. Eight surgeons reviewed all data and applied the classification scheme to each case. Interobserver and intraobserver reliability was used to evaluate the classification scheme. Preoperative clinical outcomes were compared with final follow-up in stabilized shoulders. Forty-three revision cases in 34 patients met the inclusion for study. Five patients remained unstable after revision. Persistent instability most commonly occurred in persistent deltoid dysfunction and postoperative acromial fractures but also in 1 case of soft tissue impingement. Twenty-one patients remained stable at minimum 2 years of follow-up and had significant improvement of clinical outcome scores and range of motion. Reliability of the classification scheme showed substantial and almost perfect interobserver and intraobserver agreement among all the participants (κ = 0.699 and κ = 0.851, respectively). Instability after RSA can be successfully treated with revision surgery using the reliable treatment-guiding classification scheme presented herein. However, more understanding is needed for patients with greater risk of recurrent instability after revision surgery. Copyright © 2017 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.

Electromagnetic radiation from beam-plasma instabilities

International Nuclear Information System (INIS)

Stenzel, R.L.; Whelan, D.A.

1982-01-01

This chapter investigates the mechanism by which unstable electrostatic waves of an electron-beam plasma system are converted into observed electromagnetic waves. Electromagnetic radiation arises from both natural beam-plasma systems (e.g., type III solar bursts and kilometric radiation), and from man-made electron beams injected from rockets and spacecraft. A pulsed magnetized discharge plasma is produced with a 1 m diam. oxide-coated cathode and the discussed experiment is performed in the quiescent afterglow. The primary beam-plasma instability involves the excitation of electrostatic plasma waves. Electromagnetic radiation from the beam-plasma system is observed with microwave antennas outside the plasma (all probes removed) or with coax-fed dipoles which can be inserted radially and axially into the plasma. The physical process of mode coupling by which electromagnetic radiation is generated in an electrostatic beam-plasma instability is identified. The results are relevant to beam injection experiments from rockets or satellites into space plasmas. The limited penetration of the beam current into the plasma due to instabilities is demonstrated

Importance of Resolving the Spectral Support of Beam-plasma Instabilities in Simulations

Energy Technology Data Exchange (ETDEWEB)

Shalaby, Mohamad; Broderick, Avery E. [Department of Physics and Astronomy, University of Waterloo, 200 University Avenue West, Waterloo, ON, N2L 3G1 (Canada); Chang, Philip [Department of Physics, University of Wisconsin-Milwaukee, 1900 E. Kenwood Boulevard, Milwaukee, WI 53211 (United States); Pfrommer, Christoph [Heidelberg Institute for Theoretical Studies, Schloss-Wolfsbrunnenweg 35, D-69118 Heidelberg (Germany); Lamberts, Astrid [Theoretical Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Puchwein, Ewald, E-mail: mshalaby@live.ca [Institute of Astronomy and Kavli Institute for Cosmology, University of Cambridge, Madingley Road, Cambridge, CB3 0HA (United Kingdom)

2017-10-20

Many astrophysical plasmas are prone to beam-plasma instabilities. For relativistic and dilute beams, the spectral support of the beam-plasma instabilities is narrow, i.e., the linearly unstable modes that grow with rates comparable to the maximum growth rate occupy a narrow range of wavenumbers. This places stringent requirements on the box-sizes when simulating the evolution of the instabilities. We identify the implied lower limits on the box size imposed by the longitudinal beam plasma instability, i.e., typically the most stringent condition required to correctly capture the linear evolution of the instabilities in multidimensional simulations. We find that sizes many orders of magnitude larger than the resonant wavelength are typically required. Using one-dimensional particle-in-cell simulations, we show that the failure to sufficiently resolve the spectral support of the longitudinal instability yields slower growth and lower levels of saturation, potentially leading to erroneous physical conclusion.

Importance of Resolving the Spectral Support of Beam-plasma Instabilities in Simulations

International Nuclear Information System (INIS)

Shalaby, Mohamad; Broderick, Avery E.; Chang, Philip; Pfrommer, Christoph; Lamberts, Astrid; Puchwein, Ewald

2017-01-01

Many astrophysical plasmas are prone to beam-plasma instabilities. For relativistic and dilute beams, the spectral support of the beam-plasma instabilities is narrow, i.e., the linearly unstable modes that grow with rates comparable to the maximum growth rate occupy a narrow range of wavenumbers. This places stringent requirements on the box-sizes when simulating the evolution of the instabilities. We identify the implied lower limits on the box size imposed by the longitudinal beam plasma instability, i.e., typically the most stringent condition required to correctly capture the linear evolution of the instabilities in multidimensional simulations. We find that sizes many orders of magnitude larger than the resonant wavelength are typically required. Using one-dimensional particle-in-cell simulations, we show that the failure to sufficiently resolve the spectral support of the longitudinal instability yields slower growth and lower levels of saturation, potentially leading to erroneous physical conclusion.

Genomic instability following irradiation

International Nuclear Information System (INIS)

Hacker-Klom, U.B.; Goehde, W.

2001-01-01

Ionising irradiation may induce genomic instability. The broad spectrum of stress reactions in eukaryontic cells to irradiation complicates the discovery of cellular targets and pathways inducing genomic instability. Irradiation may initiate genomic instability by deletion of genes controlling stability, by induction of genes stimulating instability and/or by activating endogeneous cellular viruses. Alternatively or additionally it is discussed that the initiation of genomic instability may be a consequence of radiation or other agents independently of DNA damage implying non nuclear targets, e.g. signal cascades. As a further mechanism possibly involved our own results may suggest radiation-induced changes in chromatin structure. Once initiated the process of genomic instability probably is perpetuated by endogeneous processes necessary for proliferation. Genomic instability may be a cause or a consequence of the neoplastic phenotype. As a conclusion from the data available up to now a new interpretation of low level radiation effects for radiation protection and in radiotherapy appears useful. The detection of the molecular mechanisms of genomic instability will be important in this context and may contribute to a better understanding of phenomenons occurring at low doses <10 cSv which are not well understood up to now. (orig.)

Enumerating all maximal frequent subtrees in collections of phylogenetic trees.

Science.gov (United States)

Deepak, Akshay; Fernández-Baca, David

2014-01-01

A common problem in phylogenetic analysis is to identify frequent patterns in a collection of phylogenetic trees. The goal is, roughly, to find a subset of the species (taxa) on which all or some significant subset of the trees agree. One popular method to do so is through maximum agreement subtrees (MASTs). MASTs are also used, among other things, as a metric for comparing phylogenetic trees, computing congruence indices and to identify horizontal gene transfer events. We give algorithms and experimental results for two approaches to identify common patterns in a collection of phylogenetic trees, one based on agreement subtrees, called maximal agreement subtrees, the other on frequent subtrees, called maximal frequent subtrees. These approaches can return subtrees on larger sets of taxa than MASTs, and can reveal new common phylogenetic relationships not present in either MASTs or the majority rule tree (a popular consensus method). Our current implementation is available on the web at https://code.google.com/p/mfst-miner/. Our computational results confirm that maximal agreement subtrees and all maximal frequent subtrees can reveal a more complete phylogenetic picture of the common patterns in collections of phylogenetic trees than maximum agreement subtrees; they are also often more resolved than the majority rule tree. Further, our experiments show that enumerating maximal frequent subtrees is considerably more practical than enumerating ordinary (not necessarily maximal) frequent subtrees.

Non-contrast MR imaging of the glenohumeral joint. Part II. Glenohumeral instability and labrum tears

International Nuclear Information System (INIS)

Rafii, Mahvash

2004-01-01

MR imaging of the shoulder without contrast is frequently used for evaluation of glenohumeral instability in spite of the popularity of MR arthrography. With proper imaging technique, familiarity with normal anatomy and variants as well as knowledge of the expected pathologic findings high diagnostic accuracy may be achieved. (orig.)

Non-contrast MR imaging of the glenohumeral joint. Part II. Glenohumeral instability and labrum tears

Energy Technology Data Exchange (ETDEWEB)

Rafii, Mahvash [NYU School of Medicine, NYU Medical Center, Department of Radiology, New York (United States)

2004-11-01

MR imaging of the shoulder without contrast is frequently used for evaluation of glenohumeral instability in spite of the popularity of MR arthrography. With proper imaging technique, familiarity with normal anatomy and variants as well as knowledge of the expected pathologic findings high diagnostic accuracy may be achieved. (orig.)

The role of MHD instabilities in the improved H-mode scenario

International Nuclear Information System (INIS)

Flaws, Asher

2009-01-01

Recently a regime of tokamak operation has been discovered, dubbed the improved H-mode scenario, which simultaneously achieves increased energy confinement and stability with respect to standard H-mode discharges. It has been suggested that magnetohydrodynamic (MHD) instabilities play some role in establishing this regime. In this thesis MHD instabilities were identified, characterised, and catalogued into a database of improved H-mode discharges in order to statistically examine their behaviour. The onset conditions of MHD instabilities were compared to existing models based on previous H-mode studies. Slight differences were found, most notably a reduced β N onset threshold for the frequently interrupted regime for neoclassical tearing modes (NTM). This reduced threshold is due to the relatively low magnetic shear of the improved H-mode regime. This study also provided a first-time estimate for the seed island size of spontaneous onset NTMs, a phenomenon characteristic of the improved H-mode scenario. Energy confinement investigations found that, although the NTM impact on confinement follows the same model applicable to other operating regimes, the improved H-mode regime acts to mitigate the impact of NTMs by limiting the saturated island sizes for NTMs with toroidal mode number n ≥ 2. Surprisingly, although a significant loss in energy confinement is observed during the sawtooth envelope, it has been found that discharges containing fishbones and low frequency sawteeth achieve higher energy confinement than those without. This suggests that fishbone and sawtooth reconnection may indeed play a role in establishing the high confinement regime. It was found that the time evolution of the central magnetic shear consistently locks in the presence of sawtooth and fishbone reconnection. Presumably this is due to the periodic redistribution of the central plasma current, an effect which is believed to help establish and maintain the characteristic current profile

The role of MHD instabilities in the improved H-mode scenario

Energy Technology Data Exchange (ETDEWEB)

Flaws, Asher

2009-02-16

Recently a regime of tokamak operation has been discovered, dubbed the improved H-mode scenario, which simultaneously achieves increased energy confinement and stability with respect to standard H-mode discharges. It has been suggested that magnetohydrodynamic (MHD) instabilities play some role in establishing this regime. In this thesis MHD instabilities were identified, characterised, and catalogued into a database of improved H-mode discharges in order to statistically examine their behaviour. The onset conditions of MHD instabilities were compared to existing models based on previous H-mode studies. Slight differences were found, most notably a reduced {beta}{sub N} onset threshold for the frequently interrupted regime for neoclassical tearing modes (NTM). This reduced threshold is due to the relatively low magnetic shear of the improved H-mode regime. This study also provided a first-time estimate for the seed island size of spontaneous onset NTMs, a phenomenon characteristic of the improved H-mode scenario. Energy confinement investigations found that, although the NTM impact on confinement follows the same model applicable to other operating regimes, the improved H-mode regime acts to mitigate the impact of NTMs by limiting the saturated island sizes for NTMs with toroidal mode number n {>=} 2. Surprisingly, although a significant loss in energy confinement is observed during the sawtooth envelope, it has been found that discharges containing fishbones and low frequency sawteeth achieve higher energy confinement than those without. This suggests that fishbone and sawtooth reconnection may indeed play a role in establishing the high confinement regime. It was found that the time evolution of the central magnetic shear consistently locks in the presence of sawtooth and fishbone reconnection. Presumably this is due to the periodic redistribution of the central plasma current, an effect which is believed to help establish and maintain the characteristic current

Triclade: influence of a sinuous secondary instability on the Richtmyer-Meshkov instabilities

International Nuclear Information System (INIS)

Boulet, M.; Griffond, J.

2004-01-01

Occurrence of a secondary instability developing after the Richtmyer-Meshkov (primary) instability is emphasized thanks to numerical simulations with the TRICLADE code. We are mainly considering 2D perturbations describes by trigonometric function cosine or [cosine]. However, the 3D case is also tackled. The sinuous secondary instability is characterized by the loss of the symmetries in the direction normal to the interface at its crests. It reduces the late time growing rate of the 'mushrooms' formed by the Richtmyer-Meshkov instability. Related simplified problems, like symmetrical Riemann problems or the Mallier-Maslowe array of counter-rotating vortices, allow us to perform 2D linear stability analysis. Thus, we show that the sinuous secondary instability is not a numerical artifact and that is comes from the continuous incompressible velocity field in the interface region. This instability implies temporal limitations for the validity of single mode simulations; therefore multimode simulations are necessary to study the ]ate-time behaviour of interfaces bitted by shocks. (authors)

Spondylolysis and spondylolisthesis: prevalence of different forms of instability and clinical implications.

Science.gov (United States)

Niggemann, Pascal; Kuchta, Johannes; Beyer, Hans-Konrad; Grosskurth, D; Schulze, Thorsten; Delank, Karl-Stefan

2011-10-15

Imaging study with an evaluation of incidences and clinical correlation. To evaluate the incidence of 3 different types of instabilities in patients with spondylolysis or isthmic spondylolisthesis. Clinical findings are correlated with imaging findings, and the imaging findings are analyzed with regard to their clinical implications. Spondylolysis and isthmic spondylolisthesis are common disorders. An unstable slip is the most well-known form of instability, but other forms also exist. However, the incidence of these instabilities and their clinical implications are yet unclear. A total of 140 patients with 141 levels of spondylolysis identified by MRI (magnetic resonance imaging) were included in this study. Using positional MRI, the instability of the slip, an increased angular movement, and movement in the spondylolytic cleft were assessed. On the basis of clinical findings, the patients were classified as presenting with either radicular or nonradicular symptoms. The incidence of the instabilities was recorded and correlated with the incidence of radicular symptoms. Fifteen patients had an unstable slip (anterior instability); 35, an increased angular movement (angular instability); and 34 patients, a movement in the spondylolytic cleft (posterior instability). All forms of instability could be found together. No instability at all was found in 76 patients. Radicular symptoms were found significantly more often in patients with one or more of the described instabilities compared with patients without instability. All 3 described forms of instability are common in spondylolysis or isthmic spondylolisthesis and associated with radicular pain. This finding stresses the value of positional MRI in the evaluation of patients with spondylolysis and isthmic spondylolisthesis, especially if radicular symptoms are present.

On MHD waves, fire-hose and mirror instabilities in anisotropic plasmas

Directory of Open Access Journals (Sweden)

L.-N. Hau

2007-09-01

Full Text Available Temperature or pressure anisotropies are characteristic of space plasmas, standard magnetohydrodynamic (MHD model for describing large-scale plasma phenomena however usually assumes isotropic pressure. In this paper we examine the characteristics of MHD waves, fire-hose and mirror instabilities in anisotropic homogeneous magnetized plasmas. The model equations are a set of gyrotropic MHD equations closed by the generalized Chew-Goldberger-Low (CGL laws with two polytropic exponents representing various thermodynamic conditions. Both ions and electrons are allowed to have separate plasma beta, pressure anisotropy and energy equations. The properties of linear MHD waves and instability criteria are examined and numerical examples for the nonlinear evolutions of slow waves, fire-hose and mirror instabilities are shown. One significant result is that slow waves may develop not only mirror instability but also a new type of compressible fire-hose instability. Their corresponding nonlinear structures thus may exhibit anticorrelated density and magnetic field perturbations, a property used for identifying slow and mirror mode structures in the space plasma environment. The conditions for nonlinear saturation of both fire-hose and mirror instabilities are examined.

Metamorphosis of helical magnetorotational instability in the presence of axial electric current.

Science.gov (United States)

Priede, Jānis

2015-03-01

This paper presents numerical linear stability analysis of a cylindrical Taylor-Couette flow of liquid metal carrying axial electric current in a generally helical external magnetic field. Axially symmetric disturbances are considered in the inductionless approximation corresponding to zero magnetic Prandtl number. Axial symmetry allows us to reveal an entirely new electromagnetic instability. First, we show that the electric current passing through the liquid can extend the range of helical magnetorotational instability (HMRI) indefinitely by transforming it into a purely electromagnetic instability. Two different electromagnetic instability mechanisms are identified. The first is an internal pinch-type instability, which is due to the interaction of the electric current with its own magnetic field. Axisymmetric mode of this instability requires a free-space component of the azimuthal magnetic field. When the azimuthal component of the magnetic field is purely rotational and the axial component is nonzero, a new kind of electromagnetic instability emerges. The latter, driven by the interaction of electric current with a weak collinear magnetic field in a quiescent fluid, gives rise to a steady meridional circulation coupled with azimuthal rotation.

Harmonic Instability Source Identification in Large Wind Farms

DEFF Research Database (Denmark)

Ebrahimzadeh, Esmaeil; Blaabjerg, Frede; Wang, Xiongfei

2017-01-01

A large-scale power electronics based power system like a wind farm introduces the passive and active impedances. The interactions between the active and passive impedances can lead to harmonic-frequency oscillations above the fundamental frequency, which can be called harmonic instability....... This paper presents an approach to identify which wind turbine and which bus has more contribution to the harmonic instability problems. In the approach, a wind farm is modeled as a Multi-Input Multi-Output (MIMO) dynamic system. The poles of the MIMO transfer matrix are used to predict the system...... instability and the eigenvalues sensitivity analysis in respect to the elements of the MIMO matrix locates the most influencing buses of the wind farm. Time-domain simulations in PSCAD software environment for a 400-MW wind farm validate that the presented approach is an effective tool to determine the main...

The temporal interplay of self-esteem instability and affective instability in borderline personality disorder patients' everyday lives.

Science.gov (United States)

Santangelo, Philip S; Reinhard, Iris; Koudela-Hamila, Susanne; Bohus, Martin; Holtmann, Jana; Eid, Michael; Ebner-Priemer, Ulrich W

2017-11-01

Borderline personality disorder (BPD) is defined by a pervasive pattern of instability. Although there is ample empirical evidence that unstable self-esteem is associated with a myriad of BPD-like symptoms, self-esteem instability and its temporal dynamics have received little empirical attention in patients with BPD. Even worse, the temporal interplay of affective instability and self-esteem instability has been neglected completely, although it has been hypothesized recently that the lack of specificity of affective instability in association with BPD might be explained by the highly intertwined temporal relationship between affective and self-esteem instability. To investigate self-esteem instability, its temporal interplay with affective instability, and its association with psychopathology, 60 patients with BPD and 60 healthy controls (HCs) completed electronic diaries for 4 consecutive days during their everyday lives. Participants reported their current self-esteem, valence, and tense arousal levels 12 times a day in approximately one-hr intervals. We used multiple state-of-the-art statistical techniques and graphical approaches to reveal patterns of instability, clarify group differences, and examine the temporal interplay of self-esteem instability and affective instability. As hypothesized, instability in both self-esteem and affect was clearly elevated in the patients with BPD. In addition, self-esteem instability and affective instability were highly correlated. Both types of instability were related to general psychopathology. Because self-esteem instability could not fully explain affective instability and vice versa and neither affective instability nor self-esteem instability was able to explain psychopathology completely, our findings suggest that these types of instability represent unique facets of BPD. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Operative shoulder instability injury management in Australian Football League players: A case series.

Science.gov (United States)

Bonacci, Jason; Manson, Brent; Bowe, Steven J; Gill, Stephen; Seward, Hugh; Hoy, Greg; Page, Richard

2017-11-27

The purpose of this study was to review the surgical management procedures of shoulder instability injuries in Australian Football League (AFL) players, and determine outcomes regarding return to sport and injury recurrence. Retrospective cohort study. Elite AFL players with shoulder instability resulting in surgery were assessed in a retrospective cohort design (72 players/77 shoulders). Type of initial injury, surgical management, return to sport and injury recurrence were obtained. The mean follow-up period post-surgery was 2.9 years. Return to sport outcomes were compared between arthroscopic and open surgery using a Kaplan-Meier survival analysis. Logistic regression modelling was used to determine associations between injury recurrence, type of injury, participant age and method of surgery. Shoulder instability injuries occurred most frequently during tackling (40%). Arthroscopic surgery was preferred for primary shoulder instability. Nine (16%) recurrences occurred in those who underwent arthroscopic surgery compared to two (9%) following open surgery. Return to the elite level was slightly but significantly (2 weeks, p=0.049) longer for open compared to arthroscopic surgery. Recurrence was 5 times more likely if the primary injury was a dislocation and more likely in players who were younger at the time of surgery. Tackling was the predominant mechanism for shoulder instability injuries in AFL players and arthroscopic surgery was more commonly performed for primary injuries. Sustaining a dislocation as the primary injury and younger age increased the likelihood of recurrent instability. Careful consideration should be given to the operative management of these individuals. Copyright © 2017. Published by Elsevier Ltd.

A Study of Current Driven Electrostatic Instability on the Auroral Zone

Directory of Open Access Journals (Sweden)

S. Y. Kim

1986-12-01

Full Text Available According to recent satellite observations, strong ion transverse acceleration to the magnetic field(ion conics has been known. The ion conics may be a result of electrostatic waves frequently observed on the auroral zone. Both linear and nonlinear theory of electrostatic instability driven by an electron current based on 1-dimenstional particle simulation experiment have been considered. From the results of simulation strong ion transverse acceleration has been shown.

Tearing instabilities in turbulence

International Nuclear Information System (INIS)

Ishizawa, A.; Nakajima, N.

2009-01-01

Full text: Effects of micro-turbulence on tearing instabilities are investigated by numerically solving a reduced set of two-fluid equations. Micro-turbulence excites both large-scale and small-scale Fourier modes through energy transfer due to nonlinear mode coupling. The energy transfer to large scale mode does not directly excite tearing instability but it gives an initiation of tearing instability. When tearing instability starts to grow, the excited small scale mode plays an important role. The mixing of magnetic flux by micro-turbulence is the dominant factor of non-ideal MHD effect at the resonant surface and it gives rise to magnetic reconnection which causes tearing instability. Tearing instabilities were investigated against static equilibrium or flowing equilibrium so far. On the other hand, the recent progress of computer power allows us to investigate interactions between turbulence and coherent modes such as tearing instabilities in magnetically confined plasmas by means of direct numerical simulations. In order to investigate effects of turbulence on tearing instabilities we consider a situation that tearing mode is destabilized in a quasi-equilibrium including micro-turbulence. We choose an initial equilibrium that is unstable against kinetic ballooning modes and tearing instabilities. Tearing instabilities are current driven modes and thus they are unstable for large scale Fourier modes. On the other hand kinetic ballooning modes are unstable for poloidal Fourier modes that are characterized by ion Larmor radius. The energy of kinetic ballooning modes spreads over wave number space through nonlinear Fourier mode coupling. We present that micro-turbulence affects tearing instabilities in two different ways by three-dimensional numerical simulation of a reduced set of two-fluid equations. One is caused by energy transfer to large scale modes, the other is caused by energy transfer to small scale modes. The former is the excitation of initial

Review of two-phase instabilities

Energy Technology Data Exchange (ETDEWEB)

Kang, Han Ok; Seo, Han Ok; Kang, Hyung Suk; Cho, Bong Hyun; Lee, Doo Jeong

1997-06-01

KAERI is carrying out a development of the design for a new type of integral reactors. The once-through helical steam generator is important design features. The study on designs and operating conditions which prevent flow instability should precede the introduction of one-through steam generator. Experiments are currently scheduled to understand two-phase instability, evaluate the effect of each design parameter on the critical point, and determine proper inlet throttling for the prevention of instability. This report covers general two-phase instability with review of existing studies on this topics. The general classification of two phase flow instability and the characteristics of each type of instability are first described. Special attention is paid to BWR core flow instability and once-through steam generator instability. The reactivity feedback and the effect of system parameters are treated mainly for BWR. With relation to once-through steam generators, the characteristics of convective heating and dryout point oscillation are first investigated and then the existing experimental studies are summarized. Finally chapter summarized the proposed correlations for instability boundary conditions. (author). 231 refs., 5 tabs., 47 figs

Joint instability and osteoarthritis.

Science.gov (United States)

Blalock, Darryl; Miller, Andrew; Tilley, Michael; Wang, Jinxi

2015-01-01

Joint instability creates a clinical and economic burden in the health care system. Injuries and disorders that directly damage the joint structure or lead to joint instability are highly associated with osteoarthritis (OA). Thus, understanding the physiology of joint stability and the mechanisms of joint instability-induced OA is of clinical significance. The first section of this review discusses the structure and function of major joint tissues, including periarticular muscles, which play a significant role in joint stability. Because the knee, ankle, and shoulder joints demonstrate a high incidence of ligament injury and joint instability, the second section summarizes the mechanisms of ligament injury-associated joint instability of these joints. The final section highlights the recent advances in the understanding of the mechanical and biological mechanisms of joint instability-induced OA. These advances may lead to new opportunities for clinical intervention in the prevention and early treatment of OA.

MHD instabilities in astrophysical plasmas: very different from MHD instabilities in tokamaks!

Science.gov (United States)

Goedbloed, J. P.

2018-01-01

The extensive studies of MHD instabilities in thermonuclear magnetic confinement experiments, in particular of the tokamak as the most promising candidate for a future energy producing machine, have led to an ‘intuitive’ description based on the energy principle that is very misleading for most astrophysical plasmas. The ‘intuitive’ picture almost directly singles out the dominant stabilizing field line bending energy of the Alfvén waves and, consequently, concentrates on expansion schemes that minimize that contribution. This happens when the wave vector {{k}}0 of the perturbations, on average, is perpendicular to the magnetic field {B}. Hence, all macroscopic instabilities of tokamaks (kinks, interchanges, ballooning modes, ELMs, neoclassical tearing modes, etc) are characterized by satisfying the condition {{k}}0 \\perp {B}, or nearly so. In contrast, some of the major macroscopic instabilities of astrophysical plasmas (the Parker instability and the magneto-rotational instability) occur when precisely the opposite condition is satisfied: {{k}}0 \\parallel {B}. How do those instabilities escape from the dominance of the stabilizing Alfvén wave? The answer to that question involves, foremost, the recognition that MHD spectral theory of waves and instabilities of laboratory plasmas could be developed to such great depth since those plasmas are assumed to be in static equilibrium. This assumption is invalid for astrophysical plasmas where rotational and gravitational accelerations produce equilibria that are at best stationary, and the associated spectral theory is widely, and incorrectly, believed to be non-self adjoint. These complications are addressed, and cured, in the theory of the Spectral Web, recently developed by the author. Using this method, an extensive survey of instabilities of astrophysical plasmas demonstrates how the Alfvén wave is pushed into insignificance under these conditions to give rise to a host of instabilities that do not

Enumerating all maximal frequent subtrees in collections of phylogenetic trees

Science.gov (United States)

2014-01-01

Background A common problem in phylogenetic analysis is to identify frequent patterns in a collection of phylogenetic trees. The goal is, roughly, to find a subset of the species (taxa) on which all or some significant subset of the trees agree. One popular method to do so is through maximum agreement subtrees (MASTs). MASTs are also used, among other things, as a metric for comparing phylogenetic trees, computing congruence indices and to identify horizontal gene transfer events. Results We give algorithms and experimental results for two approaches to identify common patterns in a collection of phylogenetic trees, one based on agreement subtrees, called maximal agreement subtrees, the other on frequent subtrees, called maximal frequent subtrees. These approaches can return subtrees on larger sets of taxa than MASTs, and can reveal new common phylogenetic relationships not present in either MASTs or the majority rule tree (a popular consensus method). Our current implementation is available on the web at https://code.google.com/p/mfst-miner/. Conclusions Our computational results confirm that maximal agreement subtrees and all maximal frequent subtrees can reveal a more complete phylogenetic picture of the common patterns in collections of phylogenetic trees than maximum agreement subtrees; they are also often more resolved than the majority rule tree. Further, our experiments show that enumerating maximal frequent subtrees is considerably more practical than enumerating ordinary (not necessarily maximal) frequent subtrees. PMID:25061474

Sausage instability in a proton-beam transport through wall-confined plasma channel

International Nuclear Information System (INIS)

Yamada, Tetsuo; Masugata, Katsumi; Matsui, Masao; Yatsui, Kiyoshi

1983-01-01

An instability observed previously in a 800-keV of proton-beam transport through a wall-confined, z-discharged plasma channel (1-m long) has been identified as a sausage type from measurements made using an image converter campera. Clear evidence of the sausage instability has been obtained from the streak and framing photographs. When the instability grows with time, the wavelength tends to increase. The pinch velocity of the channel has also been measured in a parameter space, which gives reasonable agreement with the existing theory. (author)

A Minimal Model to Explore the Influence of Distant Modes on Mode-Coupling Instabilities

Science.gov (United States)

Kruse, Sebastian; Hoffmann, Norbert

2010-09-01

The phenomenon of mode-coupling instability is one of the most frequently explored mechanisms to explain self-excited oscillation in sliding systems with friction. A mode coupling instability is usually due to the coupling of two modes. However, further modes can have an important influence on the coupling of two modes. This work extends a well-known minimal model to describe mode-coupling instabilities in order to explore the influence of a distant mode on the classical mode-coupling pattern. This work suggests a new minimal model. The model is explored and it is shown that a third mode can have significant influence on the classical mode-coupling instabilities where two modes are coupling. Different phenomena are analysed and it is pointed out that distant modes can only be ignored in very special cases and that the onset friction-induced oscillations can even be very sensitive to minimal variation of a distant mode. Due to the chosen academic minimal-model and the abandonment of a complex Finite-Element model the insight stays rather phenomenological but a better understanding of the mode-coupling mechnanism can be gained.

Gene methylation profiles of normal mucosa, and benign and malignant colorectal tumors identify early onset markers

Directory of Open Access Journals (Sweden)

Vatn Morten

2008-12-01

Full Text Available Abstract Background Multiple epigenetic and genetic changes have been reported in colorectal tumors, but few of these have clinical impact. This study aims to pinpoint epigenetic markers that can discriminate between non-malignant and malignant tissue from the large bowel, i.e. markers with diagnostic potential. The methylation status of eleven genes (ADAMTS1, CDKN2A, CRABP1, HOXA9, MAL, MGMT, MLH1, NR3C1, PTEN, RUNX3, and SCGB3A1 was determined in 154 tissue samples including normal mucosa, adenomas, and carcinomas of the colorectum. The gene-specific and widespread methylation status among the carcinomas was related to patient gender and age, and microsatellite instability status. Possible CIMP tumors were identified by comparing the methylation profile with microsatellite instability (MSI, BRAF-, KRAS-, and TP53 mutation status. Results The mean number of methylated genes per sample was 0.4 in normal colon mucosa from tumor-free individuals, 1.2 in mucosa from cancerous bowels, 2.2 in adenomas, and 3.9 in carcinomas. Widespread methylation was found in both adenomas and carcinomas. The promoters of ADAMTS1, MAL, and MGMT were frequently methylated in benign samples as well as in malignant tumors, independent of microsatellite instability. In contrast, normal mucosa samples taken from bowels without tumor were rarely methylated for the same genes. Hypermethylated CRABP1, MLH1, NR3C1, RUNX3, and SCGB3A1 were shown to be identifiers of carcinomas with microsatellite instability. In agreement with the CIMP concept, MSI and mutated BRAF were associated with samples harboring hypermethylation of several target genes. Conclusion Methylated ADAMTS1, MGMT, and MAL are suitable as markers for early tumor detection.

Joint Instability and Osteoarthritis

Directory of Open Access Journals (Sweden)

Darryl Blalock

2015-01-01

Full Text Available Joint instability creates a clinical and economic burden in the health care system. Injuries and disorders that directly damage the joint structure or lead to joint instability are highly associated with osteoarthritis (OA. Thus, understanding the physiology of joint stability and the mechanisms of joint instability-induced OA is of clinical significance. The first section of this review discusses the structure and function of major joint tissues, including periarticular muscles, which play a significant role in joint stability. Because the knee, ankle, and shoulder joints demonstrate a high incidence of ligament injury and joint instability, the second section summarizes the mechanisms of ligament injury-associated joint instability of these joints. The final section highlights the recent advances in the understanding of the mechanical and biological mechanisms of joint instability-induced OA. These advances may lead to new opportunities for clinical intervention in the prevention and early treatment of OA.

System Detects Vibrational Instabilities

Science.gov (United States)

Bozeman, Richard J., Jr.

1990-01-01

Sustained vibrations at two critical frequencies trigger diagnostic response or shutdown. Vibration-analyzing electronic system detects instabilities of combustion in rocket engine. Controls pulse-mode firing of engine and identifies vibrations above threshold amplitude at 5.9 and/or 12kHz. Adapted to other detection and/or control schemes involving simultaneous real-time detection of signals above or below preset amplitudes at two or more specified frequencies. Potential applications include rotating machinery and encoders and decoders in security systems.

Tertiary instability of zonal flows within the Wigner-Moyal formulation of drift turbulence

Science.gov (United States)

Zhu, Hongxuan; Ruiz, D. E.; Dodin, I. Y.

2017-10-01

The stability of zonal flows (ZFs) is analyzed within the generalized-Hasegawa-Mima model. The necessary and sufficient condition for a ZF instability, which is also known as the tertiary instability, is identified. The qualitative physics behind the tertiary instability is explained using the recently developed Wigner-Moyal formulation and the corresponding wave kinetic equation (WKE) in the geometrical-optics (GO) limit. By analyzing the drifton phase space trajectories, we find that the corrections proposed in Ref. to the WKE are critical for capturing the spatial scales characteristic for the tertiary instability. That said, we also find that this instability itself cannot be adequately described within a GO formulation in principle. Using the Wigner-Moyal equations, which capture diffraction, we analytically derive the tertiary-instability growth rate and compare it with numerical simulations. The research was sponsored by the U.S. Department of Energy.

Early Life Psychosocial Stressors and Housing Instability among Young Sexual Minority Men: the P18 Cohort Study.

Science.gov (United States)

Krause, Kristen D; Kapadia, Farzana; Ompad, Danielle C; D'Avanzo, Paul A; Duncan, Dustin T; Halkitis, Perry N

2016-06-01

Homelessness and housing instability is a significant public health problem among young sexual minority men. While there is a growing body of literature on correlates of homelessness among sexual minority men, there is a lack of literature parsing the different facets of housing instability. The present study examines factors associated with both living and sleeping in unstable housing among n = 600 sexual minority men (ages 18-19). Multivariate models were constructed to examine the extent to which sociodemographic, interpersonal, and behavioral factors as well as adverse childhood experiences explain housing instability. Overall, 13 % of participants reported sleeping in unstable housing and 18 % had lived in unstable housing at some point in the 6 months preceding the assessment. The odds of currently sleeping in unstable housing were greater among those who experienced more frequent lack of basic needs (food, proper hygiene, clothing) during their childhoods. More frequent experiences of childhood physical abuse and a history of arrest were associated with currently living in unstable housing. Current enrollment in school was a protective factor with both living and sleeping in unstable housing. These findings indicate that being unstably housed can be rooted in early life experiences and suggest a point of intervention that may prevent unstable housing among sexual minority men.

Nonideal magnetohydrodynamic instabilities and toroidal magnetic confinement

International Nuclear Information System (INIS)

Furth, H.P.

1985-05-01

The marked divergence of experimentally observed plasma instability phenomena from the predictions of ideal magnetohydrodynamics led in the early 1960s to the formulations of finite-resistivity stability theory. Beginning in the 1970s, advanced plasma diagnostics have served to establish a detailed correspondence between the predictions of the finite-resistivity theory and experimental plasma behavior - particularly in the case of the resistive kink mode and the tokamak plasma. Nonlinear resistive-kink phenomena have been found to govern the transport of magnetic flux and plasma energy in the reversed-field pinch. The other predicted finite-resistivity instability modes have been more difficult to identify directly and their implications for toroidal magnetic confinement are still unresolved

Relativistic gravitational instabilities

International Nuclear Information System (INIS)

Schutz, B.F.

1987-01-01

The purpose of these lectures is to review and explain what is known about the stability of relativistic stars and black holes, with particular emphases on two instabilities which are due entirely to relativistic effects. The first of these is the post-Newtonian pulsational instability discovered independently by Chandrasekhar (1964) and Fowler (1964). This effectively ruled out the then-popular supermassive star model for quasars, and it sets a limit to the central density of white dwarfs. The second instability was also discovered by Chandrasekhar (1970): the gravitational wave induced instability. This sets an upper bound on the rotation rate of neutron stars, which is near that of the millisecond pulsar PSR 1937+214, and which is beginning to constrain the equation of state of neutron matter. 111 references, 5 figures

GSK-3 inhibitors induce chromosome instability

Directory of Open Access Journals (Sweden)

Staples Oliver D

2007-08-01

Full Text Available Abstract Background Several mechanisms operate during mitosis to ensure accurate chromosome segregation. However, during tumour evolution these mechanisms go awry resulting in chromosome instability. While several lines of evidence suggest that mutations in adenomatous polyposis coli (APC may promote chromosome instability, at least in colon cancer, the underlying mechanisms remain unclear. Here, we turn our attention to GSK-3 – a protein kinase, which in concert with APC, targets β-catenin for proteolysis – and ask whether GSK-3 is required for accurate chromosome segregation. Results To probe the role of GSK-3 in mitosis, we inhibited GSK-3 kinase activity in cells using a panel of small molecule inhibitors, including SB-415286, AR-A014418, 1-Azakenpaullone and CHIR99021. Analysis of synchronised HeLa cells shows that GSK-3 inhibitors do not prevent G1/S progression or cell division. They do, however, significantly delay mitotic exit, largely because inhibitor-treated cells have difficulty aligning all their chromosomes. Although bipolar spindles form and the majority of chromosomes biorient, one or more chromosomes often remain mono-oriented near the spindle poles. Despite a prolonged mitotic delay, anaphase frequently initiates without the last chromosome aligning, resulting in chromosome non-disjunction. To rule out the possibility of "off-target" effects, we also used RNA interference to selectively repress GSK-3β. Cells deficient for GSK-3β exhibit a similar chromosome alignment defect, with chromosomes clustered near the spindle poles. GSK-3β repression also results in cells accumulating micronuclei, a hallmark of chromosome missegregation. Conclusion Thus, not only do our observations indicate a role for GSK-3 in accurate chromosome segregation, but they also raise the possibility that, if used as therapeutic agents, GSK-3 inhibitors may induce unwanted side effects by inducing chromosome instability.

A reactive decision-making approach to reduce instability in a Master Production Schedule

OpenAIRE

Herrera , Carlos; Belmokhtar Berraf , Sana; Thomas , André; Parada , Victor

2016-01-01

International audience; One of the primary factors that impact the master production scheduling performance is demand fluctuation, which leads to frequently updated decisions, thereby causing instability. Consequently, global cost deteriorates, and productivity decreases. A reactive approach based on parametric mixed-integer programming is proposed that aims to provide a set of plans such that a compromise between production cost and production stability is ensured. Several stability measures...

Nuclear-Coupled Flow Instabilities and Their Effects on Dryout

Energy Technology Data Exchange (ETDEWEB)

M. Ishii; X. Sunn; S. Kuran

2004-09-27

Nuclear-coupled flow/power oscillations in boiling water reactors (BWRs) are investigated experimentally and analytically. A detailed literature survey is performed to identify and classify instabilities in two-phase flow systems. The classification and the identification of the leading physical mechanisms of the two-phase flow instabilities are important to propose appropriate analytical models and scaling criteria for simulation. For the purpose of scaling and the analysis of the nonlinear aspects of the coupled flow/power oscillations, an extensive analytical modeling strategy is developed and used to derive both frequency and time domain analysis tools.

Majority of Solar Wind Intervals Support Ion-Driven Instabilities

Science.gov (United States)

Klein, K. G.; Alterman, B. L.; Stevens, M. L.; Vech, D.; Kasper, J. C.

2018-05-01

We perform a statistical assessment of solar wind stability at 1 AU against ion sources of free energy using Nyquist's instability criterion. In contrast to typically employed threshold models which consider a single free-energy source, this method includes the effects of proton and He2 + temperature anisotropy with respect to the background magnetic field as well as relative drifts between the proton core, proton beam, and He2 + components on stability. Of 309 randomly selected spectra from the Wind spacecraft, 53.7% are unstable when the ion components are modeled as drifting bi-Maxwellians; only 4.5% of the spectra are unstable to long-wavelength instabilities. A majority of the instabilities occur for spectra where a proton beam is resolved. Nearly all observed instabilities have growth rates γ slower than instrumental and ion-kinetic-scale timescales. Unstable spectra are associated with relatively large He2 + drift speeds and/or a departure of the core proton temperature from isotropy; other parametric dependencies of unstable spectra are also identified.

Sudden onset odontoid fracture caused by cervical instability in hypotonic cerebral palsy.

Science.gov (United States)

Shiohama, Tadashi; Fujii, Katsunori; Kitazawa, Katsuhiko; Takahashi, Akiko; Maemoto, Tatsuo; Honda, Akihito

2013-11-01

Fractures of the upper cervical spine rarely occur but carry a high rate of mortality and neurological disabilities in children. Although odontoid fractures are commonly caused by high-impact injuries, cerebral palsy children with cervical instability have a risk of developing spinal fractures even from mild trauma. We herein present the first case of an odontoid fracture in a 4-year-old boy with cerebral palsy. He exhibited prominent cervical instability due to hypotonic cerebral palsy from infancy. He suddenly developed acute respiratory failure, which subsequently required mechanical ventilation. Neuroimaging clearly revealed a type-III odontoid fracture accompanied by anterior displacement with compression of the cervical spinal cord. Bone mineral density was prominently decreased probably due to his long-term bedridden status and poor nutritional condition. We subsequently performed posterior internal fixation surgically using an onlay bone graft, resulting in a dramatic improvement in his respiratory failure. To our knowledge, this is the first report of an odontoid fracture caused by cervical instability in hypotonic cerebral palsy. Since cervical instability and decreased bone mineral density are frequently associated with cerebral palsy, odontoid fractures should be cautiously examined in cases of sudden onset respiratory failure and aggravated weakness, especially in hypotonic cerebral palsy patients. Copyright © 2012 The Japanese Society of Child Neurology. Published by Elsevier B.V. All rights reserved.

Predictors of Frequent Emergency Room Visits among a Homeless Population.

Science.gov (United States)

Thakarar, Kinna; Morgan, Jake R; Gaeta, Jessie M; Hohl, Carole; Drainoni, Mari-Lynn

2015-01-01

Homelessness, HIV, and substance use are interwoven problems. Furthermore, homeless individuals are frequent users of emergency services. The main purpose of this study was to identify risk factors for frequent emergency room (ER) visits and to examine the effects of housing status and HIV serostatus on ER utilization. The second purpose was to identify risk factors for frequent ER visits in patients with a history of illicit drug use. A retrospective analysis was performed on 412 patients enrolled in a Boston-based health care for the homeless program (HCH). This study population was selected as a 2:1 HIV seronegative versus HIV seropositive match based on age, sex, and housing status. A subgroup analysis was performed on 287 patients with history of illicit drug use. Chart data were analyzed to compare demographics, health characteristics, and health service utilization. Results were stratified by housing status. Logistic models using generalized estimating equations were used to predict frequent ER visits. In homeless patients, hepatitis C was the only predictor of frequent ER visits (OR 4.49, phomeless patients. HIV seropositivity did not predict frequent ER visits, likely because HIV seropositive HCH patients are engaged in care. In patients with history of illicit drug use, hepatitis C and mental health disorders predicted frequent ER visits. Supportive housing for patients with mental health disorders and hepatitis C may help prevent unnecessary ER visits in this population.

Non-random distribution of instability-associated chromosomal rearrangement breakpoints in human lymphoblastoid cells

International Nuclear Information System (INIS)

Moore, Stephen R.; Papworth, David; Grosovsky, Andrew J.

2006-01-01

Genomic instability is observed in tumors and in a large fraction of the progeny surviving irradiation. One of the best-characterized phenotypic manifestations of genomic instability is delayed chromosome aberrations. Our working hypothesis for the current study was that if genomic instability is in part attributable to cis mechanisms, we should observe a non-random distribution of chromosomes or sites involved in instability-associated rearrangements, regardless of radiation quality, dose, or trans factor expression. We report here the karyotypic examination of 296 instability-associated chromosomal rearrangement breaksites (IACRB) from 118 unstable TK6 human B lymphoblast, and isogenic derivative, clones. When we tested whether IACRB were distributed across the chromosomes based on target size, a significant non-random distribution was evident (p < 0.00001), and three IACRB hotspots (chromosomes 11, 12, and 22) and one IACRB coldspot (chromosome 2) were identified. Statistical analysis at the chromosomal band-level identified four IACRB hotspots accounting for 20% of all instability-associated breaks, two of which account for over 14% of all IACRB. Further, analysis of independent clones provided evidence within 14 individual clones of IACRB clustering at the chromosomal band level, suggesting a predisposition for further breaks after an initial break at some chromosomal bands. All of these events, independently, or when taken together, were highly unlikely to have occurred by chance (p < 0.000001). These IACRB band-level cluster hotspots were observed independent of radiation quality, dose, or cellular p53 status. The non-random distribution of instability-associated chromosomal rearrangements described here significantly differs from the distribution that was observed in a first-division post-irradiation metaphase analysis (p = 0.0004). Taken together, these results suggest that genomic instability may be in part driven by chromosomal cis mechanisms

Flow instability and critical heat flux in a ribbed annulus

International Nuclear Information System (INIS)

Yang, B.W.; Dougherty, T.; Fighetti, C.; Kokolis, S.; Reddy, G.D.; McAssey, E.V. Jr.; Coutts, A.

1993-01-01

An experimental program has been conducted to determine the onset of flow instability point in a heated annulus which is divided into four sub channels by non-conducting ribs. The onset of flow instability is identified by the minimum point in the pressure drop-velocity curve. Comparison with a ribless annulus show that the presence of ribs increases the minimum point velocity. In addition, data are presented which show that under certain conditions premature CHF can be induced by the ribs

Electron/electron acoustic instability

International Nuclear Information System (INIS)

Gary, S.P.

1987-01-01

The electron acoustic wave becomes a normal mode of an unmagnetized collisionless plasma in the presence of two electron components with similar densities, but strongly disparate temperatures. The characteristic frequency of this mode is the plasma frequency of the cooler electron component. If these two electron components have a relative drift speed several times the thermal speed of the cooler component, the electron/electron acoustic instability may arise. This paper describes the parametric dependences of the threshold drift speed and maximum growth rate of this instability, and compares these with the same properties of the electron/ion acoustic instability. Under the condition of zero current, the electron/ion acoustic instability typically has the lower threshold drift speed, so that observation of the electron/electron acoustic instability is a strong indication of the presence of an electrical current in the plasma

Macroeconomic instability: its causes and consequences for the economy of Ukraine

Directory of Open Access Journals (Sweden)

Natalia SKOROBOGATOVA

2016-06-01

Full Text Available The article deals with the concepts of appearance and elimination of macroeconomic instability, and the Keynesian approach for overcoming issues in Ukraine’s macroeconomic instability. Based on the Ukraine Statistics Service and World Bank data, Ukraine's economy tendencies have been defined: the country has not reached the pre-crisis economic level. The article identifies the reasons of negative balance payments and budget deficit: a decrease in production value, negative trade balance, growth of foreign creditor’s debt, currency instability, an increase in budget spending. The dynamics of income and expenditure within Ukraine budget has been analyzed, and also the destructiveness of existing approaches for the main financial documents has been grounded. Considering Ukraine’s economic and political situation, the main causes of macroeconomic instability are systematized. Government-implemented approaches for overcoming the macroeconomic instability have been suggested. The article introduces an approach for minimizing the negative effects on businesses, based on the timely identification of macroeconomic risks in terms of internal and external management. The possible negative impacts in case the timely decisions are not implemented have been assessed.

Modulational instability and discrete breathers in a nonlinear helicoidal lattice model

Science.gov (United States)

Ding, Jinmin; Wu, Tianle; Chang, Xia; Tang, Bing

2018-06-01

We investigate the problem on the discrete modulation instability of plane waves and discrete breather modes in a nonlinear helicoidal lattice model, which is described by a discrete nonlinear Schrödinger equation with the first-, second-, and third-neighbor coupling. By means of the linear stability analysis, we present an analytical expression of the instability growth rate and identify the regions of modulational instability of plane waves. It is shown that the introduction of the third-neighbor coupling will affect the shape of the areas of modulational instability significantly. Based on the results obtained by the modulational instability analysis, we predict the existence conditions for the stationary breather modes. Otherwise, by making use of the semidiscrete multiple-scale method, we obtain analytical solutions of discrete breather modes and analyze their properties for different types of nonlinearities. Our results show that the discrete breathers obtained are stable for a long time only when the system exhibits the repulsive nonlinearity. In addition, it is found that the existence of the stable bright discrete breather closely relates to the presence of the third-neighbor coupling.

Electron-acoustic Instability Simulated By Modified Zakharov Equations

Science.gov (United States)

Jásenský, V.; Fiala, V.; Vána, O.; Trávnícek, P.; Hellinger, P.

We present non-linear equations describing processes in plasma when electron - acoustic waves are excited. These waves are present for instance in the vicinity of Earth's bow shock and in the polar ionosphere. Frequently they are excited by an elec- tron beam in a plasma with two electron populations, a cold and hot one. We derive modified Zakharov equations from kinetic theory for such a case together with numer- ical method for solving of this type of equations. Bispectral analysis is used to show which non-linear wave processes are of importance in course of the instability. Finally, we compare these results with similar simulations using Vlasov approach.

Instabilities in strongly coupled plasmas

CERN Document Server

Kalman, G J

2003-01-01

The conventional Vlasov treatment of beam-plasma instabilities is inappropriate when the plasma is strongly coupled. In the strongly coupled liquid state, the strong correlations between the dust grains fundamentally affect the conditions for instability. In the crystalline state, the inherent anisotropy couples the longitudinal and transverse polarizations, and results in unstable excitations in both polarizations. We summarize analyses of resonant and non-resonant, as well as resistive instabilities. We consider both ion-dust streaming and dust beam-plasma instabilities. Strong coupling, in general, leads to an enhancement of the growth rates. In the crystalline phase, a resonant transverse instability can be excited.

Primary versus revision arthroscopic reconstruction with remplissage for shoulder instability with moderate bone loss.

Science.gov (United States)

McCabe, Michael P; Weinberg, Douglas; Field, Larry D; O'Brien, Michael J; Hobgood, E Rhett; Savoie, Felix H

2014-04-01

This study aims to evaluate our outcomes of arthroscopic remplissage in this setting. A retrospective review was performed to identify patients who underwent arthroscopic remplissage of an engaging Hill-Sachs lesion along with anterior capsulolabral reconstruction for anterior glenohumeral instability with moderate glenohumeral bone loss at our institution. Thirty-five patients, with a minimum of 2 years' follow-up, were identified. We assessed the American Shoulder and Elbow Surgeons score, incidence of recurrent instability, and postoperative Rowe instability score. Follow-up was available for 30 patients (31 shoulders). The mean age was 24.6 years, with a mean follow-up period of 41 months. Prior instability surgery had failed in 11 patients, and they underwent capsulolabral reconstruction and remplissage ("revision surgery"). The failure rate in revision cases (36%) was significantly higher than the failure rate in primary surgery cases (0%) (P = .01). Failure resulted from trauma in all 4 patients, and none required further surgery. The mean American Shoulder and Elbow Surgeons score for all patients improved from 50 preoperatively to 91 postoperatively (P instability patients with moderate bone loss and engaging humeral Hill-Sachs lesions yields acceptable outcomes for primary instability surgery. However, a significantly higher failure rate occurred when arthroscopic reconstruction with remplissage was performed in the revision setting. Level IV, therapeutic case series. Copyright © 2014 Arthroscopy Association of North America. All rights reserved.

Predictors of Frequent Emergency Room Visits among a Homeless Population.

Directory of Open Access Journals (Sweden)

Kinna Thakarar

Full Text Available Homelessness, HIV, and substance use are interwoven problems. Furthermore, homeless individuals are frequent users of emergency services. The main purpose of this study was to identify risk factors for frequent emergency room (ER visits and to examine the effects of housing status and HIV serostatus on ER utilization. The second purpose was to identify risk factors for frequent ER visits in patients with a history of illicit drug use.A retrospective analysis was performed on 412 patients enrolled in a Boston-based health care for the homeless program (HCH. This study population was selected as a 2:1 HIV seronegative versus HIV seropositive match based on age, sex, and housing status. A subgroup analysis was performed on 287 patients with history of illicit drug use. Chart data were analyzed to compare demographics, health characteristics, and health service utilization. Results were stratified by housing status. Logistic models using generalized estimating equations were used to predict frequent ER visits.In homeless patients, hepatitis C was the only predictor of frequent ER visits (OR 4.49, p<0.01. HIV seropositivity was not predictive of frequent ER visits. In patients with history of illicit drug use, mental health (OR 2.53, 95% CI 1.07-5.95 and hepatitis C (OR 2.85, 95% CI 1.37-5.93 were predictors of frequent ER use. HIV seropositivity did not predict ER use (OR 0.45, 95% CI 0.21 - 0.97.In a HCH population, hepatitis C predicted frequent ER visits in homeless patients. HIV seropositivity did not predict frequent ER visits, likely because HIV seropositive HCH patients are engaged in care. In patients with history of illicit drug use, hepatitis C and mental health disorders predicted frequent ER visits. Supportive housing for patients with mental health disorders and hepatitis C may help prevent unnecessary ER visits in this population.

Genomic instability and radiation

Energy Technology Data Exchange (ETDEWEB)

Little, John B [Harvard School of Public Health, Boston, MA 02115 (United States)

2003-06-01

Genomic instability is a hallmark of cancer cells, and is thought to be involved in the process of carcinogenesis. Indeed, a number of rare genetic disorders associated with a predisposition to cancer are characterised by genomic instability occurring in somatic cells. Of particular interest is the observation that transmissible instability can be induced in somatic cells from normal individuals by exposure to ionising radiation, leading to a persistent enhancement in the rate at which mutations and chromosomal aberrations arise in the progeny of the irradiated cells after many generations of replication. If such induced instability is involved in radiation carcinogenesis, it would imply that the initial carcinogenic event may not be a rare mutation occurring in a specific gene or set of genes. Rather, radiation may induce a process of instability in many cells in a population, enhancing the rate at which the multiple gene mutations necessary for the development of cancer may arise in a given cell lineage. Furthermore, radiation could act at any stage in the development of cancer by facilitating the accumulation of the remaining genetic events required to produce a fully malignant tumour. The experimental evidence for such induced instability is reviewed. (review)

Genomic instability and radiation

International Nuclear Information System (INIS)

Little, John B

2003-01-01

Genomic instability is a hallmark of cancer cells, and is thought to be involved in the process of carcinogenesis. Indeed, a number of rare genetic disorders associated with a predisposition to cancer are characterised by genomic instability occurring in somatic cells. Of particular interest is the observation that transmissible instability can be induced in somatic cells from normal individuals by exposure to ionising radiation, leading to a persistent enhancement in the rate at which mutations and chromosomal aberrations arise in the progeny of the irradiated cells after many generations of replication. If such induced instability is involved in radiation carcinogenesis, it would imply that the initial carcinogenic event may not be a rare mutation occurring in a specific gene or set of genes. Rather, radiation may induce a process of instability in many cells in a population, enhancing the rate at which the multiple gene mutations necessary for the development of cancer may arise in a given cell lineage. Furthermore, radiation could act at any stage in the development of cancer by facilitating the accumulation of the remaining genetic events required to produce a fully malignant tumour. The experimental evidence for such induced instability is reviewed. (review)

Strain-induced shear instability in Liverpool Bay

Science.gov (United States)

Wihsgott, Juliane; Palmer, Matthew R.

2013-04-01

Liverpool Bay is a shallow subsection of the eastern Irish Sea with large tides (10 m), which drive strong tidal currents (1 ms-1). The Bay is heavily influenced by large freshwater inputs from several Welsh and English rivers that maintain a strong and persistent horizontal density gradient. This gradient interacts with the sheared tidal currents to strain freshwater over denser pelagic water on a semi-diurnal frequency. This Strain-Induced-Periodic-Stratification (SIPS) has important implications on vertical and horizontal mixing. The subtle interaction between stratification and turbulence in this complex environment is shown to be of critical importance to freshwater transport, and subsequently the fate of associated biogeochemical and pollutant pathways. Recent work identified an asymmetry of current ellipses due to SIPS that increases shear instability in the halocline with the potential to enhance diapycnal mixing. Here, we use data from a short, high intensity process study which reveals this mid-water mechanism maintains prolonged periods of sub-critical gradient Richardson number (Ri ≤ ¼) that suggests shear instability is likely. A time series of measurements from a microstructure profiler identifies the associated increase in turbulence is short lived and 'patchy' but sufficient to promote diapycnal mixing. The significance of this mixing process is further investigated by comparing our findings with long-term observations from the Liverpool Bay Coastal Observatory. We identify that the conditions for shear instability during SIPS are regularly met and suggest that this process contributes to the current underestimates of near coastal mixing observed in regional models. To assist our understanding of the observed processes and to test the current capability of turbulence 'closure schemes' we employ a one-dimensional numerical model to investigate the physical mechanisms driving diapycnal mixing in Liverpool Bay.

Frequent hospital admissions in Singapore: clinical risk factors and impact of socioeconomic status.

Science.gov (United States)

Low, Lian Leng; Tay, Wei Yi; Ng, Matthew Joo Ming; Tan, Shu Yun; Liu, Nan; Lee, Kheng Hock

2018-01-01

Frequent admitters to hospitals are high-cost patients who strain finite healthcare resources. However, the exact risk factors for frequent admissions, which can be used to guide risk stratification and design effective interventions locally, remain unknown. Our study aimed to identify the clinical and sociodemographic risk factors associated with frequent hospital admissions in Singapore. An observational study was conducted using retrospective 2014 data from the administrative database at Singapore General Hospital, Singapore. Variables were identified a priori and included patient demographics, comorbidities, prior healthcare utilisation, and clinical and laboratory variables during the index admission. Multivariate logistic regression analysis was used to identify independent risk factors for frequent admissions. A total of 16,306 unique patients were analysed and 1,640 (10.1%) patients were classified as frequent admitters. On multivariate logistic regression, 16 variables were independently associated with frequent hospital admissions, including age, cerebrovascular disease, history of malignancy, haemoglobin, serum creatinine, serum albumin, and number of specialist outpatient clinic visits, emergency department visits, admissions preceding index admission and medications dispensed at discharge. Patients staying in public rental housing had a 30% higher risk of being a frequent admitter after adjusting for demographics and clinical conditions. Our study, the first in our knowledge to examine the clinical risk factors for frequent admissions in Singapore, validated the use of public rental housing as a sensitive indicator of area-level socioeconomic status in Singapore. These risk factors can be used to identify high-risk patients in the hospital so that they can receive interventions that reduce readmission risk. Copyright: © Singapore Medical Association

Modes of storage ring coherent instabilities

Energy Technology Data Exchange (ETDEWEB)

Wang, J.M.

1986-12-01

Longitudinal impedance in a beam and various modes of longitudinal coherent instabilities are discussed. The coasting beam coherent instability, microwave instability, and single-bunch longitudinal coherent instabilities are considered. The Vlasov equation is formulated, and a method of solving it is developed. The synchrotron modes are treated, which take the possible bunch shape distortion fully into consideration. A method of treating the synchrotron mode coupling in the case of a small bunch is discussed which takes advantage of the fact that only a few of the synchrotron modes can contribute in such a case. The effect of many bunches on the coherent motion of the beam and the longitudinal symmetric coupled bunch modes are discussed. The transverse impedance is then introduced, and the transverse coasting beam instability is discussed. Various bunched beam instabilities are discussed, including both single bunch instabilities and coupled bunch instabilities. The Vlasov equation for transverse as well as longitudinal motion of particles is introduced as well as a method of solving it within a linear approximation. Head-tail modes and short bunch instabilities and strong coupling instabilities in the long bunch case are covered. (LEW)

Modes of storage ring coherent instabilities

International Nuclear Information System (INIS)

Wang, J.M.

1986-12-01

Longitudinal impedance in a beam and various modes of longitudinal coherent instabilities are discussed. The coasting beam coherent instability, microwave instability, and single-bunch longitudinal coherent instabilities are considered. The Vlasov equation is formulated, and a method of solving it is developed. The synchrotron modes are treated, which take the possible bunch shape distortion fully into consideration. A method of treating the synchrotron mode coupling in the case of a small bunch is discussed which takes advantage of the fact that only a few of the synchrotron modes can contribute in such a case. The effect of many bunches on the coherent motion of the beam and the longitudinal symmetric coupled bunch modes are discussed. The transverse impedance is then introduced, and the transverse coasting beam instability is discussed. Various bunched beam instabilities are discussed, including both single bunch instabilities and coupled bunch instabilities. The Vlasov equation for transverse as well as longitudinal motion of particles is introduced as well as a method of solving it within a linear approximation. Head-tail modes and short bunch instabilities and strong coupling instabilities in the long bunch case are covered

Development of potential map for landslides by comparing instability indices of various time periods

Science.gov (United States)

Chiang, Jie-Lun; Tian, Yu-Qing; Chen, Yie-Ruey; Tsai, Kuang-Jung

2017-04-01

In recent years, extreme rainfall events occur frequently and induced serious landslides and debris flow disasters in Taiwan. The instability indices will differ when using landslide maps of different time periods. We analyzed the landslide records during the period year, 2008 2012, the landslide area contributed 0.42% 2.94% of the total watershed area, the 2.94% was caused by the typhoon Morakot in August, 2009, which brought massive rainfall in which the cumulative maximum rainfall was up to 2900 mm. We analyzed the instability factors including elevation, slope, aspect, soil, and geology. And comparing the instability indices by using individual landslide map of 2008 2012, the landslide maps of the union of the five years, and interaction of the five years. The landslide area from union of the five years contributed 3.71%,the landslide area from interaction of the five years contributed 0.14%. In this study, Kriging was used to establish the susceptibility map in selected watershed. From interaction of the five years, we found the instability index above 4.3 can correspond to those landslide records. The potential landslide area of the selected watershed, where collapses occur more likely, belongs to high level and medium-high level; the area is 13.43% and 3.04% respectively.

Thermal shrinkage for shoulder instability.

Science.gov (United States)

Toth, Alison P; Warren, Russell F; Petrigliano, Frank A; Doward, David A; Cordasco, Frank A; Altchek, David W; O'Brien, Stephen J

2011-07-01

Thermal capsular shrinkage was popular for the treatment of shoulder instability, despite a paucity of outcomes data in the literature defining the indications for this procedure or supporting its long-term efficacy. The purpose of this study was to perform a clinical evaluation of radiofrequency thermal capsular shrinkage for the treatment of shoulder instability, with a minimum 2-year follow-up. From 1999 to 2001, 101 consecutive patients with mild to moderate shoulder instability underwent shoulder stabilization surgery with thermal capsular shrinkage using a monopolar radiofrequency device. Follow-up included a subjective outcome questionnaire, discussion of pain, instability, and activity level. Mean follow-up was 3.3 years (range 2.0-4.7 years). The thermal capsular shrinkage procedure failed due to instability and/or pain in 31% of shoulders at a mean time of 39 months. In patients with unidirectional anterior instability and those with concomitant labral repair, the procedure proved effective. Patients with multidirectional instability had moderate success. In contrast, four of five patients with isolated posterior instability failed. Thermal capsular shrinkage has been advocated for the treatment of shoulder instability, particularly mild to moderate capsular laxity. The ease of the procedure makes it attractive. However, our retrospective review revealed an overall failure rate of 31% in 80 patients with 2-year minimum follow-up. This mid- to long-term cohort study adds to the literature lacking support for thermal capsulorrhaphy in general, particularly posterior instability. The online version of this article (doi:10.1007/s11420-010-9187-7) contains supplementary material, which is available to authorized users.

Instabilities in the 'on' phase of the plasma focus

International Nuclear Information System (INIS)

Kaeppeler, H.J.

1990-07-01

In the operation of large plasma focus devices, e.g. POSEIDON, there appear saturation phenomena in the neutron production when the charging energy of the condensor bank approaches its nominal value. This saturation is attributed to the action of impurities. It is assumed that there appear instabilities which are in part caused by impurities. In order to be able to answer this question, the linear dispersion relation was derived from a three-fluid theory (electrons, ions and neutrals) with the aid of the computer algebra (CA) code MACSYMA. The inversion of the 17x17 matrix (it is assumed that v a =v i and T a =T i ) and solution of the determinant was carried out on a CONVEX C 120 computer using the CA code MAPLE. The calculation of the zeros was done with a modified CPZERO program from the SLATEC library. There appear four instabilities in the rundown phase of the plasma focus, two of them gradient driven. The first two are unstable electrostatic waves with very high phase velocities, thus they do not contribute to anomalous dissipation. The third is identified as a gradient driven space charge instability which may possibly lead to current chopping. The electron acoustic wave instability, here gradient driven, is the fourth. It was found in a previous study of MPD thruster instabilities. (orig.)

R-loops: targets for nuclease cleavage and repeat instability.

Science.gov (United States)

Freudenreich, Catherine H

2018-01-11

R-loops form when transcribed RNA remains bound to its DNA template to form a stable RNA:DNA hybrid. Stable R-loops form when the RNA is purine-rich, and are further stabilized by DNA secondary structures on the non-template strand. Interestingly, many expandable and disease-causing repeat sequences form stable R-loops, and R-loops can contribute to repeat instability. Repeat expansions are responsible for multiple neurodegenerative diseases, including Huntington's disease, myotonic dystrophy, and several types of ataxias. Recently, it was found that R-loops at an expanded CAG/CTG repeat tract cause DNA breaks as well as repeat instability (Su and Freudenreich, Proc Natl Acad Sci USA 114, E8392-E8401, 2017). Two factors were identified as causing R-loop-dependent breaks at CAG/CTG tracts: deamination of cytosines and the MutLγ (Mlh1-Mlh3) endonuclease, defining two new mechanisms for how R-loops can generate DNA breaks (Su and Freudenreich, Proc Natl Acad Sci USA 114, E8392-E8401, 2017). Following R-loop-dependent nicking, base excision repair resulted in repeat instability. These results have implications for human repeat expansion diseases and provide a paradigm for how RNA:DNA hybrids can cause genome instability at structure-forming DNA sequences. This perspective summarizes mechanisms of R-loop-induced fragility at G-rich repeats and new links between DNA breaks and repeat instability.

Bone fragment union and remodeling after arthroscopic bony bankart repair for traumatic anterior shoulder instability with a glenoid defect: influence on postoperative recurrence of instability.

Science.gov (United States)

Nakagawa, Shigeto; Ozaki, Ritsuro; Take, Yasuhiro; Mae, Tatsuo; Hayashida, Kenji

2015-06-01

Although good clinical outcomes have been reported after arthroscopic bony Bankart repair, the extent of bone union is still unclear. To investigate bone union after arthroscopic bony Bankart repair and its influence on postoperative recurrence of instability. Cohort study; Level of evidence, 3. Among 113 consecutive shoulders that underwent arthroscopic bony Bankart repair, postoperative evaluation of bone union by computed tomography (CT) was performed at various times in 81 shoulders. Bone union was investigated during 3 periods: 3 to 6 months postoperatively (first period), 7 to 12 months postoperatively (second period), and 13 months or more postoperatively (third period). The influence of the size of the preoperative glenoid defect and the size of the bone fragment on bone union was investigated, as well as the influence of bone union on postoperative recurrence of instability. In shoulders with bone union, bone fragment remodeling and changes in the glenoid defect size were also investigated. The bone union rate was 30.5% in the first period, 55.3% in the second period, and 84.6% in the third period. Among 53 shoulders with CT evaluation in the second period or later and follow-up for a minimum of 1 year, there was complete union in 33 shoulders (62.3%), partial union in 3 (5.7%), nonunion in 8 (15.1%), and no fragment on CT in 9 (17.0%). The complete union rate was 50% for 22 shoulders with small bone fragments (fragments (5%-10%), and 86.7% for 15 shoulders with large fragments (>10%). The recurrence rate for postoperative instability was only 6.1% for shoulders with complete union, while it was 50% for shoulders with partial union, nonunion, no fragment, and no fragment on CT. The recurrence rate was significantly higher (36.4%) in shoulders with small fragments, but it was significantly lower in shoulders with bone union. In shoulders with bone union, the bone fragment frequently became larger over time, while the size of the glenoid defect decreased

Shoulder instability in professional football players.

Science.gov (United States)

Leclere, Lance E; Asnis, Peter D; Griffith, Matthew H; Granito, David; Berkson, Eric M; Gill, Thomas J

2013-09-01

Shoulder instability is a common problem in American football players entering the National Football League (NFL). Treatment options include nonoperative and surgical stabilization. This study evaluated how the method of treatment of pre-NFL shoulder instability affects the rate of recurrence and the time elapsed until recurrence in players on 1 NFL team. Retrospective cohort. Medical records from 1980 to 2008 for 1 NFL team were reviewed. There were 328 players included in the study who started their career on the team and remained on the team for at least 2 years (mean, 3.9 years; range, 2-14 years). The history of instability prior to entering the NFL and the method of treatment were collected. Data on the occurrence of instability while in the NFL were recorded to determine the rate and timing of recurrence. Thirty-one players (9.5%) had a history of instability prior to entering the NFL. Of the 297 players with no history of instability, 39 (13.1%) had a primary event at a mean of 18.4 ± 22.2 months (range, 0-102 months) after joining the team. In the group of players with prior instability treated with surgical stabilization, there was no statistical difference in the rate of recurrence (10.5%) or the timing to the instability episode (mean, 26 months) compared with players with no history of instability. Twelve players had shoulder instability treated nonoperatively prior to the NFL. Five of these players (41.7%) had recurrent instability at a mean of 4.4 ± 7.0 months (range, 0-16 months). The patients treated nonoperatively had a significantly higher rate of recurrence (P = 0.02) and an earlier time of recurrence (P = 0.04). The rate of contralateral instability was 25.8%, occurring at a mean of 8.6 months. Recurrent shoulder instability is more common in NFL players with a history of nonoperative treatment. Surgical stabilization appears to restore the rate and timing of instability to that of players with no prior history of instability.

Plasma physics and instabilities

International Nuclear Information System (INIS)

Lashmore-Davies, C.N.

1981-01-01

These lectures procide an introduction to the theory of plasmas and their instabilities. Starting from the Bogoliubov, Born, Green, Kirkwood, and Yvon (BBGKY) hierarchy of kinetic equations, the additional concept of self-consistent fields leads to the fundamental Vlasov equation and hence to the warm two-fluid model and the one-fluid MHD, or cold, model. The properties of small-amplitude waves in magnetized (and unmagnetized) plasmas, and the instabilities to which they give rise, are described in some detail, and a complete chapter is devoted to Landau damping. The linear theory of plasma instabilities is illustrated by the current-driven electrostatic kind, with descriptions of the Penrose criterion and the energy principle of ideal MHD. There is a brief account of the application of feedback control. The non-linear theory is represented by three examples: quasi-linear velocity-space instabilities, three-wave instabilities, and the stability of an arbitrarily largeamplitude wave in a plasma. (orig.)

New diagnostics and cures for coupled-bunch instabilities

International Nuclear Information System (INIS)

Prabhakar, S.

2000-01-01

Electromagnetic interaction between a charged particle beam and its surroundings causes collective instabilities, which must be controlled if the new light sources and colliders are to meet their design goals. Control requires a combination of passive damping and fast active feedback on an unprecedented technological scale. Efficient instability diagnosis techniques are also needed for machines with large numbers of bunches. This thesis describes new methods of measuring and analyzing coupled-bunch instabilities in circular accelerators, and demonstrates the existence of a new cure. A new technique is demonstrated for simultaneous measurement of growth rates, damping rates and coherent tune shifts of all unstable coupled-bunch eigenmodes from a single 10-25-ms transient snapshot of beam motion. The technique has been used to locate and quantify beam impedance resonances at PEP-II, ALS and SPEAR. This method is faster than existing spectral scan methods by at least an order of magnitude, and has the added advantage of revealing coupled-bunch dynamics in the linear small-signal regime. A method is also presented for estimating beam impedance from multi-bunch fill shape and synchronous phase measurements. Phase space tracking of multi-bunch instabilities is introduced as a ''complete instability diagnostic.'' Digitized multi-bunch data is analyzed offline, to estimate the phase space trajectories of bunches and modes. Availability of phase space trajectories is shown to open up a variety of possibilities, including measurement of reactive impedance, and diagnosis of the fast beam-ion instability. Knowledge gained from longitudinal measurements (all made using a digital longitudinal feedback system) has been used to optimize cavity temperatures, tuner positions and feedback parameters, and also to identify sources of beam noise at the three machines. A matrix-based method is presented for analyzing the beneficial effect of bunch-to-bunch tune variation on instability

Understanding Transient Forcing with Plasma Instability Model, Ionospheric Propagation Model and GNSS Observations

Science.gov (United States)

Deshpande, K.; Zettergren, M. D.; Datta-Barua, S.

2017-12-01

Fluctuations in the Global Navigation Satellite Systems (GNSS) signals observed as amplitude and phase scintillations are produced by plasma density structures in the ionosphere. Phase scintillation events in particular occur due to structures at Fresnel scales, typically about 250 meters at ionospheric heights and GNSS frequency. Likely processes contributing to small-scale density structuring in auroral and polar regions include ionospheric gradient-drift instability (GDI) and Kelvin-Helmholtz instability (KHI), which result, generally, from magnetosphere-ionosphere interactions (e.g. reconnection) associated with cusp and auroral zone regions. Scintillation signals, ostensibly from either GDI or KHI, are frequently observed in the high latitude ionosphere and are potentially useful diagnostics of how energy from the transient forcing in the cusp or polar cap region cascades, via instabilities, to small scales. However, extracting quantitative details of instabilities leading to scintillation using GNSS data drastically benefits from both a model of the irregularities and a model of GNSS signal propagation through irregular media. This work uses a physics-based model of the generation of plasma density irregularities (GEMINI - Geospace Environment Model of Ion-Neutral Interactions) coupled to an ionospheric radio wave propagation model (SIGMA - Satellite-beacon Ionospheric-scintillation Global Model of the upper Atmosphere) to explore the cascade of density structures from medium to small (sub-kilometer) scales. Specifically, GEMINI-SIGMA is used to simulate expected scintillation from different instabilities during various stages of evolution to determine features of the scintillation that may be useful to studying ionospheric density structures. Furthermore we relate the instabilities producing GNSS scintillations to the transient space and time-dependent magnetospheric phenomena and further predict characteristics of scintillation in different geophysical

Gravitational Instabilities in Circumstellar Disks

Science.gov (United States)

Kratter, Kaitlin; Lodato, Giuseppe

2016-09-01

Star and planet formation are the complex outcomes of gravitational collapse and angular momentum transport mediated by protostellar and protoplanetary disks. In this review, we focus on the role of gravitational instability in this process. We begin with a brief overview of the observational evidence for massive disks that might be subject to gravitational instability and then highlight the diverse ways in which the instability manifests itself in protostellar and protoplanetary disks: the generation of spiral arms, small-scale turbulence-like density fluctuations, and fragmentation of the disk itself. We present the analytic theory that describes the linear growth phase of the instability supplemented with a survey of numerical simulations that aim to capture the nonlinear evolution. We emphasize the role of thermodynamics and large-scale infall in controlling the outcome of the instability. Despite apparent controversies in the literature, we show a remarkable level of agreement between analytic predictions and numerical results. In the next part of our review, we focus on the astrophysical consequences of the instability. We show that the disks most likely to be gravitationally unstable are young and relatively massive compared with their host star, Md/M*≥0.1. They will develop quasi-stable spiral arms that process infall from the background cloud. Although instability is less likely at later times, once infall becomes less important, the manifestations of the instability are more varied. In this regime, the disk thermodynamics, often regulated by stellar irradiation, dictates the development and evolution of the instability. In some cases the instability may lead to fragmentation into bound companions. These companions are more likely to be brown dwarfs or stars than planetary mass objects. Finally, we highlight open questions related to the development of a turbulent cascade in thin disks and the role of mode-mode coupling in setting the maximum angular

Effects of three-body interactions in the parametric and modulational instabilities of Bose–Einstein condensates

International Nuclear Information System (INIS)

Wamba, Etienne; Mohamadou, Alidou; Ekogo, Thierry B.; Atangana, Jacque; Kofane, Timoleon C.

2011-01-01

The parametric modulational instability for a discrete nonlinear Schrödinger equation with a cubic–quintic nonlinearity is analyzed. This model describes the dynamics of BECs, with both two- and three-body interatomic interactions trapped in an optical lattice. We identify and discuss the salient features of the three-body interaction in the parametric modulational instability. It is shown that the three-body interaction term can both, shift as well as narrow the window of parametric instability, and also change the behavior of a modulationally stable and parametrically unstable BEC with attractive two-body interaction. We explore this instability through the multiple-scale analysis and identify it numerically. The effect of the three body losses have also been investigated. -- Highlights: ► The parametric MI for the 1D GPE with a cubic–quintic nonlinearity is analyzed. ► The two- and three-body recombination and time-dependent scattering length is considered. ► We generate bright matter waves soliton through MI.

Instability characteristics of fluidelastic instability of tube rows in crossflow

International Nuclear Information System (INIS)

Chen, S.S.; Jendrzejczyk, J.A.

1986-04-01

An experimental study is reported to investigate the jump phenomenon in critical flow velocities for tube rows with different pitch-to-diameter ratios and the excited and intrinsic instabilities for a tube row with a pitch-to-diameter ratio of 1.75. The experimental data provide additional insights into the instability phenomena of tube arrays in crossflow. 9 refs., 10 figs

Helical instability in film blowing process: Analogy to buckling instability

Science.gov (United States)

Lee, Joo Sung; Kwon, Ilyoung; Jung, Hyun Wook; Hyun, Jae Chun

2017-12-01

The film blowing process is one of the most important polymer processing operations, widely used for producing bi-axially oriented film products in a single-step process. Among the instabilities observed in this film blowing process, i.e., draw resonance and helical motion occurring on the inflated film bubble, the helical instability is a unique phenomenon portraying the snake-like undulation motion of the bubble, having the period on the order of few seconds. This helical instability in the film blowing process is commonly found at the process conditions of a high blow-up ratio with too low a freezeline position and/or too high extrusion temperature. In this study, employing an analogy to the buckling instability for falling viscous threads, the compressive force caused by the pressure difference between inside and outside of the film bubble is introduced into the simulation model along with the scaling law derived from the force balance between viscous force and centripetal force of the film bubble. The simulation using this model reveals a close agreement with the experimental results of the film blowing process of polyethylene polymers such as low density polyethylene and linear low density polyethylene.

Functional Instability of the Ankle Joint: Etiopathogenesis

Directory of Open Access Journals (Sweden)

Aydan ÖRSÇELİK

2016-09-01

Full Text Available Ankle sprain is one of the most common sports injuries. Chronic ankle instability is a common complication of ankle sprains. Two causes of chronic ankle instability are mechanical instability and functional instability. It is important to understand functional instability etiopathogenesis of the ankle joint in order to guide diagnosis and treatment. This article aims to understand the etiopathogenesis of functional ankle instability.

Chromosomal instability induced by ionizing radiation

International Nuclear Information System (INIS)

Morgan, W.F.; Marder, B.A.; Day, J.P.

1995-01-01

There is accumulating evidence indicating genomic instability can manifest multiple generations after cellular exposure to DNA damaging agents. For instance, some cells surviving exposure to ionizing radiations show delayed reproductive cell death, delayed mutation and / or delayed chromosomal instability. Such instability, especially chromosome destabilization has been implicated in mutation, gene amplification, cellular transformation, and cell killing. To investigate chromosomal instability following DNA damage, we have used fluorescence in situ hybridization to detect chromosomal rearrangements in a human/hamster somatic hybrid cell line following exposure to ionizing radiation. Delayed chromosomal instability was detected when multiple populations of uniquely arranged metaphases were observed in clonal isolates raised from single cells. The relationship between delayed chromosomal destabilization and other endpoints of genomic instability, namely; delayed mutation and gene amplification will be discussed, as will the potential cytogenetic and molecular mechanisms contributing to delayed chromosomal instability

Management of failed instability surgery: how to get it right the next time.

Science.gov (United States)

Boone, Julienne L; Arciero, Robert A

2010-07-01

Traumatic anterior shoulder dislocations are the most frequent type of joint dislocation and affect approximately 1.7% of the general population. The literature supports the consideration of primary stabilization in high-risk patients because of reported recurrences as high as 80% to 90% with nonoperative treatment regimens. Successful stabilization of anterior glenohumeral instability relies on not only good surgical techniques but also careful patient selection. Failure rates after open and arthroscopic stabilization have been reported to range from 2% to 8% and 4% to 13%, respectively. Recurrent shoulder instability leads to increased morbidity to the patient, increased pain, decreased activity level, prolonged time away from work and sports, and a general decrease in quality of life. This article reviews the potential pitfalls in anterior shoulder stabilization and discusses appropriate methods of addressing them in revision surgery. Copyright 2010 Elsevier Inc. All rights reserved.

Sister chromatid cohesion defects are associated with chromosome instability in Hodgkin lymphoma cells

International Nuclear Information System (INIS)

Sajesh, Babu V; Lichtensztejn, Zelda; McManus, Kirk J

2013-01-01

Chromosome instability manifests as an abnormal chromosome complement and is a pathogenic event in cancer. Although a correlation between abnormal chromosome numbers and cancer exist, the underlying mechanisms that cause chromosome instability are poorly understood. Recent data suggests that aberrant sister chromatid cohesion causes chromosome instability and thus contributes to the development of cancer. Cohesion normally functions by tethering nascently synthesized chromatids together to prevent premature segregation and thus chromosome instability. Although the prevalence of aberrant cohesion has been reported for some solid tumors, its prevalence within liquid tumors is unknown. Consequently, the current study was undertaken to evaluate aberrant cohesion within Hodgkin lymphoma, a lymphoid malignancy that frequently exhibits chromosome instability. Using established cytogenetic techniques, the prevalence of chromosome instability and aberrant cohesion was examined within mitotic spreads generated from five commonly employed Hodgkin lymphoma cell lines (L-1236, KM-H2, L-428, L-540 and HDLM-2) and a lymphocyte control. Indirect immunofluorescence and Western blot analyses were performed to evaluate the localization and expression of six critical proteins involved in the regulation of sister chromatid cohesion. We first confirmed that all five Hodgkin lymphoma cell lines exhibited chromosome instability relative to the lymphocyte control. We then determined that each Hodgkin lymphoma cell line exhibited cohesion defects that were subsequently classified into mild, moderate or severe categories. Surprisingly, ~50% of the mitotic spreads generated from L-540 and HDLM-2 harbored cohesion defects. To gain mechanistic insight into the underlying cause of the aberrant cohesion we examined the localization and expression of six critical proteins involved in cohesion. Although all proteins produced the expected nuclear localization pattern, striking differences in RAD21

Dynamical instabilities in a simple minority game with discounting

International Nuclear Information System (INIS)

Challet, D; De Martino, A; Marsili, M

2008-01-01

We explore the effect of discounting and experimentation in a simple model of interacting adaptive agents. Agents belong to either of two types and each has to decide whether to participate in a game or not, the game being profitable when there is an excess of players of the other type. We find the emergence of large fluctuations as a result of the onset of a dynamical instability which may arise discontinuously (increasing the discount factor) or continuously (decreasing the experimentation rate). The phase diagram is characterized in detail and noise amplification close to a bifurcation point is identified as the physical mechanism behind the instability. (letter)

Nonlinear evolution of MHD instabilities

International Nuclear Information System (INIS)

Bateman, G.; Hicks, H.R.; Wooten, J.W.; Dory, R.A.

1975-01-01

A 3-D nonlinear MHD computer code was used to study the time evolution of internal instabilities. Velocity vortex cells are observed to persist into the nonlinear evolution. Pressure and density profiles convect around these cells for a weak localized instability, or convect into the wall for a strong instability. (U.S.)

Dynamical Instability and Soliton Concept

International Nuclear Information System (INIS)

Kartavenko, V.G.

1994-01-01

The problem of dynamical instability and clustering (stable fragments formation) in a breakup of excited nuclear systems are considered from the points of view of the soliton concept. It is noted that the volume (spinodal) instability can be associated with nonlinear terms, and the surface (Rayleigh-Taylor type) instability, with the dispersion terms in the evolution equations. The spinodal instability and the Rayleigh-Taylor instability may compensate each other and lead to stable quasi-soliton type objects. The simple analytical model is presented to illustrate this physical picture. The time evolution of an initially compressed cold nuclear system is analysed in the framework of the inverse mean-field method. It is demonstrated that the nonlinearity and dispersion terms of the evolution equations can lead to clusterization in the final channel. 8 p

Initiation of genome instability and preneoplastic processes through loss of Fhit expression.

Directory of Open Access Journals (Sweden)

Joshua C Saldivar

Full Text Available Genomic instability drives tumorigenesis, but how it is initiated in sporadic neoplasias is unknown. In early preneoplasias, alterations at chromosome fragile sites arise due to DNA replication stress. A frequent, perhaps earliest, genetic alteration in preneoplasias is deletion within the fragile FRA3B/FHIT locus, leading to loss of Fhit protein expression. Because common chromosome fragile sites are exquisitely sensitive to replication stress, it has been proposed that their clonal alterations in cancer cells are due to stress sensitivity rather than to a selective advantage imparted by loss of expression of fragile gene products. Here, we show in normal, transformed, and cancer-derived cell lines that Fhit-depletion causes replication stress-induced DNA double-strand breaks. Using DNA combing, we observed a defect in replication fork progression in Fhit-deficient cells that stemmed primarily from fork stalling and collapse. The likely mechanism for the role of Fhit in replication fork progression is through regulation of Thymidine kinase 1 expression and thymidine triphosphate pool levels; notably, restoration of nucleotide balance rescued DNA replication defects and suppressed DNA breakage in Fhit-deficient cells. Depletion of Fhit did not activate the DNA damage response nor cause cell cycle arrest, allowing continued cell proliferation and ongoing chromosomal instability. This finding was in accord with in vivo studies, as Fhit knockout mouse tissue showed no evidence of cell cycle arrest or senescence yet exhibited numerous somatic DNA copy number aberrations at replication stress-sensitive loci. Furthermore, cells established from Fhit knockout tissue showed rapid immortalization and selection of DNA deletions and amplifications, including amplification of the Mdm2 gene, suggesting that Fhit loss-induced genome instability facilitates transformation. We propose that loss of Fhit expression in precancerous lesions is the first step in the

The Role of Chromosomal Instability and Epigenetics in Colorectal Cancers Lacking β-Catenin/TCF Regulated Transcription

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Wael M. Abdel-Rahman

2016-01-01

Full Text Available All colorectal cancer cell lines except RKO displayed active β-catenin/TCF regulated transcription. This feature of RKO was noted in familial colon cancers; hence our aim was to dissect its carcinogenic mechanism. MFISH and CGH revealed distinct instability of chromosome structure in RKO. Gene expression microarray of RKO versus 7 colon cancer lines (with active Wnt signaling and 3 normal specimens revealed 611 differentially expressed genes. The majority of the tested gene loci were susceptible to LOH in primary tumors with various β-catenin localizations as a surrogate marker for β-catenin activation. The immunohistochemistry of selected genes (IFI16, RGS4, MCTP1, DGKI, OBCAM/OPCML, and GLIPR1 confirmed that they were differentially expressed in clinical specimens. Since epigenetic mechanisms can contribute to expression changes, selected target genes were evaluated for promoter methylation in patient specimens from sporadic and hereditary colorectal cancers. CMTM3, DGKI, and OPCML were frequently hypermethylated in both groups, whereas KLK10, EPCAM, and DLC1 displayed subgroup specificity. The overall fraction of hypermethylated genes was higher in tumors with membranous β-catenin. We identified novel genes in colorectal carcinogenesis that might be useful in personalized tumor profiling. Tumors with inactive Wnt signaling are a heterogeneous group displaying interaction of chromosomal instability, Wnt signaling, and epigenetics.

Electromagnetic Weible Instability in Intense Charged Particle Beams with Large Energy Anisotropy

International Nuclear Information System (INIS)

Startsev, Edward A.; Davidson, Ronald C.

2003-01-01

In plasmas with strongly anisotropic distribution functions, collective instabilities may develop if there is sufficient coupling between the transverse and longitudinal degrees of freedom. Our previous numerical and theoretical studies of intense charged particle beams with large temperature anisotropy [E. A. Startsev, R. C. Davidson and H. Qin, PRSTAB, 6, 084401 (2003); Phys. Plasmas 9, 3138 (2002)] demonstrated that a fast, electrostatic, Harris-like instability develops, and saturates nonlinearly, for sufficiently large temperature anisotropy (T perpendi c ular b /T parallelb >> 1). The total distribution function after saturation, however, is still far from equipartitioned. In this paper the linearized Vlasov-Maxwell equations are used to investigate detailed properties of the transverse electromagnetic Weibel-type instability for a long charge bunch propagating through a cylindrical pipe of radius r w . The kinetic stability analysis is carried out for azimuthally symmetric perturbations about a two-temperature thermal equilibrium distribution in the smooth-focusing approximation. The most unstable modes are identified, and their eigenfrequencies, radial mode structure and instability thresholds are determined. The stability analysis shows that, although there is free energy available to drive the electromagnetic Weibel instability, the finite transverse geometry of the charged particle beam introduces a large threshold value for the temperature anisotropy ((T perpendi c ularb /T parallelb ) Weibel >> (T perpendi c ularb /T parallelb ) Harris ) below which the instability is absent. Hence, unlike the case of an electrically neutral plasma, the Weibel instability is not expected to play as significant a role in the process of energy isotropization of intense unneutralized charged particle beams as the electrostatic Harris-type instability

Recurrent instability after revision anterior shoulder stabilization surgery.

Science.gov (United States)

Friedman, Lisa Genevra Mandeville; Griesser, Michael J; Miniaci, Anthony A; Jones, Morgan H

2014-03-01

The purpose of this study was to perform a systematic review of the literature to compare outcomes of revision anterior stabilization surgeries based on technique. This study also sought to compare the impact of bone defects on outcomes. A systematic review of the electronic databases PubMed, Cochrane Central Register of Controlled Trials, and Scopus was performed in July 2012 and March 2013. Of 345 articles identified in the search, 17 studies with Level I to IV Evidence satisfied the inclusion criteria and were analyzed according to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines. Recurrent instability was defined as redislocation, resubluxation, or a positive apprehensive test after revision surgery. Procedures were categorized as arthroscopic Bankart repair, open Bankart repair, Bristow-Latarjet procedure, and other open procedures. In total, 388 shoulders were studied. Male patients comprised 74.1% of patients, 66.7% of cases involved the dominant shoulder, the mean age was 28.2 years, and the mean follow-up period was 44.2 months. The surgical procedures classified as "other open procedures" had the highest rate of recurrent instability (42.7%), followed by arthroscopic Bankart repair (14.7%), the Bristow-Latarjet procedure (14.3%), and open Bankart repair (5.5%). Inconsistent reporting of bone defects precluded drawing significant conclusions. A number of different procedures are used to address recurrent instability after a primary operation for anterior shoulder instability has failed. There is significant variability in the rate of recurrent instability after revision anterior shoulder stabilization surgery. Level IV, systematic review of Level I to IV studies. Copyright © 2014 Arthroscopy Association of North America. Published by Elsevier Inc. All rights reserved.

Fluid aspects of electron streaming instability in electron-ion plasmas

International Nuclear Information System (INIS)

Jao, C.-S.; Hau, L.-N.

2014-01-01

Electrons streaming in a background electron and ion plasma may lead to the formation of electrostatic solitary wave (ESW) and hole structure which have been observed in various space plasma environments. Past studies on the formation of ESW are mostly based on the particle simulations due to the necessity of incorporating particle's trapping effects. In this study, the fluid aspects and thermodynamics of streaming instabilities in electron-ion plasmas including bi-streaming and bump-on-tail instabilities are addressed based on the comparison between fluid theory and the results from particle-in-cell simulations. The energy closure adopted in the fluid model is the polytropic law of d(pρ −γ )/dt=0 with γ being a free parameter. Two unstable modes are identified for the bump-on-tail instability and the growth rates as well as the dispersion relation of the streaming instabilities derived from the linear theory are found to be in good agreement with the particle simulations for both bi-streaming and bump-on-tail instabilities. At the nonlinear saturation, 70% of the electrons are trapped inside the potential well for the drift velocity being 20 times of the thermal velocity and the pρ −γ value is significantly increased. Effects of ion to electron mass ratio on the linear fluid theory and nonlinear simulations are also examined

Beam instability Workshop - plenary sessions

International Nuclear Information System (INIS)

2001-01-01

The purpose of this workshop was to provide a review of the mechanisms of limiting beam instabilities, their cures, including feedback, and beam measurement for synchrotron radiation light sources. 12 plenary sessions took place whose titles are: 1) challenging brilliance and lifetime issues with increasing currents; 2) limiting instabilities in multibunch; 3) experience from high currents in B factories; 4) longitudinal dynamics in high intensity/bunch; 5) Transverse instabilities for high intensity/bunch; 6) working group introduction from ESRF experience; 7) impedance modelling: simulations, minimization; 8) report on the broadband impedance measurements and modelling workshop; 9) feedback systems for synchrotron light sources; 10) beam instabilities diagnostics; 11) harmonic cavities: the pros and cons; and 12) experimental study of fast beam-ion instabilities at PLS. This document gathers the 12 articles that were presented during these sessions

Beam instability Workshop - plenary sessions

Energy Technology Data Exchange (ETDEWEB)

NONE

2001-07-01

The purpose of this workshop was to provide a review of the mechanisms of limiting beam instabilities, their cures, including feedback, and beam measurement for synchrotron radiation light sources. 12 plenary sessions took place whose titles are: 1) challenging brilliance and lifetime issues with increasing currents; 2) limiting instabilities in multibunch; 3) experience from high currents in B factories; 4) longitudinal dynamics in high intensity/bunch; 5) Transverse instabilities for high intensity/bunch; 6) working group introduction from ESRF experience; 7) impedance modelling: simulations, minimization; 8) report on the broadband impedance measurements and modelling workshop; 9) feedback systems for synchrotron light sources; 10) beam instabilities diagnostics; 11) harmonic cavities: the pros and cons; and 12) experimental study of fast beam-ion instabilities at PLS. This document gathers the 12 articles that were presented during these sessions.

Instability and dynamics of volatile thin films

Science.gov (United States)

Ji, Hangjie; Witelski, Thomas P.

2018-02-01

Volatile viscous fluids on partially wetting solid substrates can exhibit interesting interfacial instabilities and pattern formation. We study the dynamics of vapor condensation and fluid evaporation governed by a one-sided model in a low-Reynolds-number lubrication approximation incorporating surface tension, intermolecular effects, and evaporative fluxes. Parameter ranges for evaporation-dominated and condensation-dominated regimes and a critical case are identified. Interfacial instabilities driven by the competition between the disjoining pressure and evaporative effects are studied via linear stability analysis. Transient pattern formation in nearly flat evolving films in the critical case is investigated. In the weak evaporation limit unstable modes of finite-amplitude nonuniform steady states lead to rich droplet dynamics, including flattening, symmetry breaking, and droplet merging. Numerical simulations show that long-time behaviors leading to evaporation or condensation are sensitive to transitions between filmwise and dropwise dynamics.

Character of decay instability

International Nuclear Information System (INIS)

Polovin, R.V.; Demutskii, V.P.

1981-01-01

If the initial wave is unstable in the upper half plane Im ω>0 and there are no branch points of the quasiwave number, or if waves traveling in the same direction coalesce at a branch point, the instability is convective. On the other hand, if a branch point k(ω) does exist in the upper half-plane Im ω>0, and not all the waves that merge at this point travel in the same direction, the instability is absolute. A Green's function that describes the evolution of the perturbations of the initial wave in space and in time is constructed. The growth rates of the decay instability of the harmonics are determined. The produced waves are richer in harmonics than the initial waves. It is shown that the decay instability of an Alfven wave is absolute

Transmission of chromosomal and instability via a chromosome irradiated with ionizing radiation

International Nuclear Information System (INIS)

Kodama, Seiji; Tanabe, Masateru; Shiraishi, Kazunori; Oshimura, Mitsuo

2010-01-01

We examined the stability of the transferred chromosome in 5 and 12 microcell hybrids including unirradiated human chromosomes 6 and 8, respectively, and 6 and 19 microcell hybrids including 4 Gy-irradiated human chromosomes 6 and 8, respectively. The transferred chromosome was structurally stable in most microcell hybrids transferred with the unirradiated chromosomes 6 and 8. In contrast, the 4 Gy-irradiated human chromosomes were unstable in 3 out of 6 hybrids (50%) with chromosome 6 and 3 out of 19 hybrids (16%) with chromosome 8, showing multiple aberrations in high frequencies (35∼98%). To know the cause of delayed chromosomal instability, intrachromosomal rearrangements of the human chromosome is investigated by subtelomere FISH in 17 microcell hybrids transferred with chromosomes 6 and 8. We found frequent intrachromosomal in 7 microcell hybrids (41%). However, no clear correlation was observed between the intrachromosomal rearrangements and the induction of delayed chromosomal instability by ionizing radiation

MULTIDETECTOR COMPUTED TOMOGRAPHY FOR IDENTIFICATION OF INSTABILITY OF AORTIC ANEURYSM WALL

Directory of Open Access Journals (Sweden)

M. V. Vishnyakova Jr.

2015-01-01

Full Text Available Background: Aortic aneurysm is characterized by high incidence, polymorphic clinical features and sudden onset of severe complications.Aim: To develop a standard multidetector computed tomography (MDCT protocol for aortic aneurysm examination and image analysis for detection the signs of aortic wall instability.Materials and methods: The data of 279 patients with aortic aneurysm who underwent MDCT examination during 2009–2014 was analyzed to identify aortic wall instability signs.Results: Complicated course of aortic aneurysm was observed in 100 cases (36%. The most common sign of aortic wall instability was aortic dissection. According to our results, a new definition of aortic aneurysm complications was elaborated. It included signs of aortic wall instability with incomplete and/or complete disruption of aortic wall layers. A scheme of the most common patterns of aortic wall abnormalities was proposed, allowing a radiologist to reach high accuracy in characterizing this pathology.Conclusion: A dedicated MDCT protocol for aortic aneurysm detection and image analysis can increase quality of radiologic assessment of aneurysm wall allowing to approach to the level of histological accuracy.

History of shoulder instability surgery.

Science.gov (United States)

Randelli, Pietro; Cucchi, Davide; Butt, Usman

2016-02-01

The surgical management of shoulder instability is an expanding and increasingly complex area of study within orthopaedics. This article describes the history and evolution of shoulder instability surgery, examining the development of its key principles, the currently accepted concepts and available surgical interventions. A comprehensive review of the available literature was performed using PubMed. The reference lists of reviewed articles were also scrutinised to ensure relevant information was included. The various types of shoulder instability including anterior, posterior and multidirectional instability are discussed, focussing on the history of surgical management of these topics, the current concepts and the results of available surgical interventions. The last century has seen important advancements in the understanding and treatment of shoulder instability. The transition from open to arthroscopic surgery has allowed the discovery of previously unrecognised pathologic entities and facilitated techniques to treat these. Nevertheless, open surgery still produces comparable results in the treatment of many instability-related conditions and is often required in complex or revision cases, particularly in the presence of bone loss. More high-quality research is required to better understand and characterise this spectrum of conditions so that successful evidence-based management algorithms can be developed. IV.

Ionospheric modification and parametric instabilities

International Nuclear Information System (INIS)

Fejer, J.A.

1979-01-01

Thresholds and linear growth rates for stimulated Brillouin and Raman scattering and for the parametric decay instability are derived by using arguments of energy transfer. For this purpose an expression for the ponderomotive force is derived. Conditions under which the partial pressure force due to differential dissipation exceeds the ponderomotive force are also discussed. Stimulated Brillouin and Raman scattering are weakly excited by existing incoherent backscatter radars. The parametric decay instability is strongly excited in ionospheric heating experiments. Saturation theories of the parametric decay instability are therefore described. After a brief discussion of the purely growing instability the effect of using several pumps is discussed as well as the effects of inhomogenicity. Turning to detailed theories of ionospheric heating, artificial spread F is discussed in terms of a purely growing instability where the nonlinearity is due to dissipation. Field-aligned short-scale striations are explained in terms of dissipation of the parametrically excited Langmuir waves (plasma oscillations): they might be further amplified by an explosive instability (except the magnetic equator). Broadband absorption is probably responsible for the 'overshoot' effect: the initially observed level of parametrically excited Langmuir waves is much higher than the steady state level

Instabilities in mimetic matter perturbations

Energy Technology Data Exchange (ETDEWEB)

Firouzjahi, Hassan; Gorji, Mohammad Ali [School of Astronomy, Institute for Research in Fundamental Sciences (IPM), P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of); Mansoori, Seyed Ali Hosseini, E-mail: firouz@ipm.ir, E-mail: gorji@ipm.ir, E-mail: shosseini@shahroodut.ac.ir, E-mail: shossein@ipm.ir [Physics Department, Shahrood University of Technology, P.O. Box 3619995161 Shahrood (Iran, Islamic Republic of)

2017-07-01

We study cosmological perturbations in mimetic matter scenario with a general higher derivative function. We calculate the quadratic action and show that both the kinetic term and the gradient term have the wrong sings. We perform the analysis in both comoving and Newtonian gauges and confirm that the Hamiltonians and the associated instabilities are consistent with each other in both gauges. The existence of instabilities is independent of the specific form of higher derivative function which generates gradients for mimetic field perturbations. It is verified that the ghost instability in mimetic perturbations is not associated with the higher derivative instabilities such as the Ostrogradsky ghost.

The simultaneous onset and interaction of Taylor and Dean instabilities in a Couette geometry

International Nuclear Information System (INIS)

Hills, C P; Bassom, A P

2005-01-01

The fluid flow between a pair of coaxial circular cylinders generated by the uniform rotation of the inner cylinder and an azimuthal pressure gradient is susceptible to both Taylor and Dean type instabilities. The flow can be characterised by two parameters: a measure of the relative magnitude of the rotation and pressure effects and a non-dimensional Taylor number. Neutral curves associated with each instability can be constructed but it has been suggested that these curves do not cross but rather posses 'kinks'. Our work is based in the small gap, large wavenumber limit and considers the simultaneous onset of Taylor and Dean instabilities. The two linear instabilities interact at exponentially small orders and a consistent, matched asymptotic solution is found across the whole annular domain, identifying five regions of interest: two boundary adjustment regions and three internal critical points. We construct necessary conditions for the concurrent onset of the linear Taylor and Dean instabilities and show that neutral curve crossing is possible

Spondylolisthesis and Posterior Instability

International Nuclear Information System (INIS)

Niggemann, P.; Beyer, H.K.; Frey, H.; Grosskurth, D.; Simons, P.; Kuchta, J.

2009-01-01

We present the case of a patient with a spondylolisthesis of L5 on S1 due to spondylolysis at the level L5/S1. The vertebral slip was fixed and no anterior instability was found. Using functional magnetic resonance imaging (MRI) in an upright MRI scanner, posterior instability at the level of the spondylolytic defect of L5 was demonstrated. A structure, probably the hypertrophic ligament flava, arising from the spondylolytic defect was displaced toward the L5 nerve root, and a bilateral contact of the displaced structure with the L5 nerve root was shown in extension of the spine. To our knowledge, this is the first case described of posterior instability in patients with spondylolisthesis. The clinical implications of posterior instability are unknown; however, it is thought that this disorder is common and that it can only be diagnosed using upright MRI

Spondylolisthesis and Posterior Instability

Energy Technology Data Exchange (ETDEWEB)

Niggemann, P.; Beyer, H.K.; Frey, H.; Grosskurth, D. (Privatpraxis fuer Upright MRT, Koeln (Germany)); Simons, P.; Kuchta, J. (Media Park Klinik, Koeln (Germany))

2009-04-15

We present the case of a patient with a spondylolisthesis of L5 on S1 due to spondylolysis at the level L5/S1. The vertebral slip was fixed and no anterior instability was found. Using functional magnetic resonance imaging (MRI) in an upright MRI scanner, posterior instability at the level of the spondylolytic defect of L5 was demonstrated. A structure, probably the hypertrophic ligament flava, arising from the spondylolytic defect was displaced toward the L5 nerve root, and a bilateral contact of the displaced structure with the L5 nerve root was shown in extension of the spine. To our knowledge, this is the first case described of posterior instability in patients with spondylolisthesis. The clinical implications of posterior instability are unknown; however, it is thought that this disorder is common and that it can only be diagnosed using upright MRI.

Feedback stabilization of plasma instabilities

International Nuclear Information System (INIS)

Cap, F.F.

1977-01-01

This paper reviews the theoretical and experimental aspects of feedback stabilization. After giving an outline of a general theoretical model for electrostatic instabilities the author provides a theoretical analysis of the suppression of various types of instability. Experiments which have been carried out on the feedback stabilization of various types of plasma instability are reported. An extensive list of references is given. (B.R.H.)

Localized instabilities and spinodal decomposition in driven systems in the presence of elasticity

Science.gov (United States)

Meca, Esteban; Münch, Andreas; Wagner, Barbara

2018-01-01

We study numerically and analytically the instabilities associated with phase separation in a solid layer on which an external material flux is imposed. The first instability is localized within a boundary layer at the exposed free surface by a process akin to spinodal decomposition. In the limiting static case, when there is no material flux, the coherent spinodal decomposition is recovered. In the present problem, stability analysis of the time-dependent and nonuniform base states as well as numerical simulations of the full governing equations are used to establish the dependence of the wavelength and onset of the instability on parameter settings and its transient nature as the patterns eventually coarsen into a flat moving front. The second instability is related to the Mullins-Sekerka instability in the presence of elasticity and arises at the moving front between the two phases when the flux is reversed. Stability analyses of the full model and the corresponding sharp-interface model are carried out and compared. Our results demonstrate how interface and bulk instabilities can be analyzed within the same framework which allows us to identify and distinguish each of them clearly. The relevance for a detailed understanding of both instabilities and their interconnections in a realistic setting is demonstrated for a system of equations modeling the lithiation and delithiation processes within the context of lithium ion batteries.

Defining spinal instability and methods of classification to optimise care for patients with malignant spinal cord compression: A systematic review

International Nuclear Information System (INIS)

Sheehan, C.

2016-01-01

The incidence of Malignant Spinal Cord Compression (MSCC) is thought to be increasing in the UK due to an aging population and improving cancer survivorship. The impact of such a diagnosis requires emergency treatment. In 2008 the National Institute of Clinical Excellence produced guidelines on the management of MSCC which includes a recommendation to assess spinal instability. However, a lack of guidelines to assess spinal instability in oncology patients is widely acknowledged. This can result in variations in the management of care for such patients. A spinal instability assessment can influence optimum patient care (bed rest or encouraged mobilisation) and inform the best definitive treatment modality (surgery or radiotherapy) for an individual patient. The aim of this systematic review is to attempt to identify a consensus definition of spinal instability and methods by which it can be classified. - Highlights: • A lack of guidance on metastatic spinal instability results in variations of care. • Definitions and assessments for spinal instability are explored in this review. • A Spinal Instability Neoplastic Scoring (SINS) system has been identified. • SINS could potentially be adopted to optimise and standardise patient care.

Multifragmentation: Surface instabilities or statistical decay

International Nuclear Information System (INIS)

Moretto, L.G.; Tso, K.; Delis, D.; Colonna, N.; Wozniak, G.J.

1992-11-01

Boltzmann-Nordheim-Vlasov calculations show multifragmentation that seems to originate from surface instabilities. These instabilities are traced to a sheet instability caused by the proximity interaction. Experimental data, on the other hand, suggest that multifragmentation may be dominated by phase space

Neutron star pulsations and instabilities

International Nuclear Information System (INIS)

Lindblom, L.

2001-01-01

Gravitational radiation (GR) drives an instability in certain modes of rotating stars. This instability is strong enough in the case of the r-modes to cause their amplitudes to grow on a timescale of tens of seconds in rapidly rotating neutron stars. GR emitted by these modes removes angular momentum from the star at a rate which would spin it down to a relatively small angular velocity within about one year, if the dimensionless amplitude of the mode grows to order unity. A pedagogical level discussion is given here on the mechanism of GR instability in rotating stars, on the relevant properties of the r-modes, and on our present understanding of the dissipation mechanisms that tend to suppress this instability in neutron stars. The astrophysical implications of this GR driven instability are discussed for young neutron stars, and for older systems such as low mass x-ray binaries. Recent work on the non-linear evolution of the r-modes is also presented. (author)

Multifragmentation: surface instabilities or statistical decay?

International Nuclear Information System (INIS)

Moretto, L.G.; Tso, K.; Delis, D.; Colonna, N.; Wozniak, G.J.

1993-01-01

Boltzmann-Nordheim-Vlasov calculations show multifragmentation that seems to originate from surface instabilities. These instabilities are traced to a sheet instability caused by the proximity interaction. Experimental data, on the other hand, suggest that multifragmentation may be dominated by phase space. (author)

Dynamic ultrasound of peroneal tendon instability.

Science.gov (United States)

Pesquer, Lionel; Guillo, Stéphane; Poussange, Nicolas; Pele, Eric; Meyer, Philippe; Dallaudière, Benjamin

2016-07-01

Ankle snapping may be caused by peroneal tendon instability. Anterior instability occurs after traumatic superior peroneal retinaculum injury, whereas peroneal tendon intrasheath subluxation is atraumatic. Whereas subluxation is mainly dynamic, ultrasound allows for the diagnosis and classification of peroneal instability because it allows for real-time exploration. The purpose of this review is to describe the anatomic and physiologic bases for peroneal instability and to heighten the role of dynamic ultrasound in the diagnosis of snapping.

Collective instabilities of self-gravitating systems, 2

International Nuclear Information System (INIS)

Nakamura, Takashi; Takahara, Fumio; Ikeuchi, Satoru

1975-01-01

The instability modes of rotating self-gravitating systems are investigated on the assumption of infinitely long cylinder. The systems under consideration are a collisionless stellar system with anisotropic velocity dispersion and a gaseous system with anisotropic pressure. In the collisionless stellar system, the Jeans instability mode and the Harris instability mode exist. The dispersion relation is solved numerically and the following results are obtained: the Harris instability occurs even in the region where Wu did not treat, and although its growth rate amounts to the order of angular velocity of the system for sufficient anisotropy, the Harris instability always accompanies the Jeans instability and the latter is always greater than the former in growth rate. In the gaseous system exist the Jeans instability mode and a certain overstable mode, which are different from the Harris instability mode. It is shown that the overstable mode occurs due to coupling of modes. In relation to these results, some problems in galactic structure are discussed. (auth.)

Electron beam instabilities in gyrotron beam tunnels

International Nuclear Information System (INIS)

Pedrozzi, M.; Alberti, S.; Hogge, J.P.; Tran, M.Q.; Tran, T.M.

1997-10-01

Electron beam instabilities occurring in a gyrotron electron beam can induce an energy spread which might significantly deteriorate the gyrotron efficiency. Three types of instabilities are considered to explain the important discrepancy found between the theoretical and experimental efficiency in the case of quasi-optical gyrotrons (QOG): the electron cyclotron maser instability, the Bernstein instability and the Langmuir instability. The low magnetic field gradient in drift tubes of QOG makes that the electron cyclotron maser instability can develop in the drift tube at very low electron beam currents. Experimental measurements show that with a proper choice of absorbing structures in the beam tunnel, this instability can be suppressed. At high beam currents, the electrostatic Bernstein instability can induce a significant energy spread at the entrance of the interaction region. The induced energy spread scales approximately linearly with the electron beam density and for QOG one observes that the beam density is significantly higher than the beam density of an equivalent cylindrical cavity gyrotron. (author) figs., tabs., refs

Mode-locking via dissipative Faraday instability.

Science.gov (United States)

Tarasov, Nikita; Perego, Auro M; Churkin, Dmitry V; Staliunas, Kestutis; Turitsyn, Sergei K

2016-08-09

Emergence of coherent structures and patterns at the nonlinear stage of modulation instability of a uniform state is an inherent feature of many biological, physical and engineering systems. There are several well-studied classical modulation instabilities, such as Benjamin-Feir, Turing and Faraday instability, which play a critical role in the self-organization of energy and matter in non-equilibrium physical, chemical and biological systems. Here we experimentally demonstrate the dissipative Faraday instability induced by spatially periodic zig-zag modulation of a dissipative parameter of the system-spectrally dependent losses-achieving generation of temporal patterns and high-harmonic mode-locking in a fibre laser. We demonstrate features of this instability that distinguish it from both the Benjamin-Feir and the purely dispersive Faraday instability. Our results open the possibilities for new designs of mode-locked lasers and can be extended to other fields of physics and engineering.

Frequent methodological errors in clinical research.

Science.gov (United States)

Silva Aycaguer, L C

2018-03-07

Several errors that are frequently present in clinical research are listed, discussed and illustrated. A distinction is made between what can be considered an "error" arising from ignorance or neglect, from what stems from a lack of integrity of researchers, although it is recognized and documented that it is not easy to establish when we are in a case and when in another. The work does not intend to make an exhaustive inventory of such problems, but focuses on those that, while frequent, are usually less evident or less marked in the various lists that have been published with this type of problems. It has been a decision to develop in detail the examples that illustrate the problems identified, instead of making a list of errors accompanied by an epidermal description of their characteristics. Copyright © 2018 Elsevier España, S.L.U. y SEMICYUC. All rights reserved.

Centrifugally Driven Rayleigh-Taylor Instability

Science.gov (United States)

Scase, Matthew; Hill, Richard

2017-11-01

The instability that develops at the interface between two fluids of differing density due to the rapid rotation of the system may be considered as a limit of high-rotation rate Rayleigh-Taylor instability. Previously the authors have considered the effect of rotation on a gravitationally dominated Rayleigh-Taylor instability and have shown that some growth modes of instability may be suppressed completely by the stabilizing effect of rotation (Phys. Rev. Fluids 2:024801, Sci. Rep. 5:11706). Here we consider the case of very high rotation rates and a negligible gravitational field. The initial condition is of a dense inner cylinder of fluid surrounded by a lighter layer of fluid. As the system is rotated about the generating axis of the cylinder, the dense inner fluid moves away from the axis and the familiar bubbles and spikes of Rayleigh-Taylor instability develop at the interface. The system may be thought of as a ``fluid-fluid centrifuge''. By developing a model based on an Orr-Sommerfeld equation, we consider the effects of viscosity, surface tension and interface diffusion on the growth rate and modes of instability. We show that under particular circumstances some modes may be stabilized. School of Mathematical Sciences.

Stimulated ion Compton scattering instability of whistlers in plasmas

International Nuclear Information System (INIS)

Shukla, P. K.; Shukla, Nitin; Stenflo, L.

2006-01-01

The nonlinear interactions between magnetic field-aligned broadband whistler wave packets (hereafter referred to as whistlerons) and ion quasimodes in magnetized plasmas are considered. By treating the whistlerons as quasiparticles, their nonlinear propagation in a slowly varying medium supported by ion quasimode density perturbations is studied. A nonlinear dispersion relation within the framework of the wave-kinetic (for the whistlerons) and Vlasov (for the ion quasimodes) descriptions is derived. The dispersion relation admits a kinetic modulational instability. The growth rate of the latter is presented. The present result can improve our understanding of the nonlinear propagation of incoherent whistlers, which have been frequently observed in the Earth's magnetosphere as well as in laboratory plasmas

Thermal Shrinkage for Shoulder Instability

OpenAIRE

Toth, Alison P.; Warren, Russell F.; Petrigliano, Frank A.; Doward, David A.; Cordasco, Frank A.; Altchek, David W.; O’Brien, Stephen J.

2010-01-01

Thermal capsular shrinkage was popular for the treatment of shoulder instability, despite a paucity of outcomes data in the literature defining the indications for this procedure or supporting its long-term efficacy. The purpose of this study was to perform a clinical evaluation of radiofrequency thermal capsular shrinkage for the treatment of shoulder instability, with a minimum 2-year follow-up. From 1999 to 2001, 101 consecutive patients with mild to moderate shoulder instability underwent...

Assessment of postural instability in patients with Parkinson's disease.

Science.gov (United States)

Błaszczyk, J W; Orawiec, R; Duda-Kłodowska, D; Opala, G

2007-10-01

Postural instability is one of the most disabling features of idiopathic Parkinson's disease (PD). In this study, we focused on postural instability as the main factor predisposing parkinsonians to falls. For this purpose, changes in sway characteristics during quiet stance due to visual feedback exclusion were studied. We searched for postural sway measures that could be potential discriminators for an increased fall risk. A group of 110 subjects: 55 parkinsonians (Hoehn and Yahr: 1-3), and 55 age-matched healthy volunteers participated in the experiment. Their spontaneous sway characteristics while standing quiet with eyes open and eyes closed were analyzed. We found that an increased mediolateral sway and sway area while standing with eyes closed are characteristic of parkinsonian postural instability and may serve to quantify well a tendency to fall. These sway indices significantly correlated with disease severity rated both by the Hoehn and Yahr scale as well as by the Motor Section of the UPDRS. A forward shift of a mean COP position in parkinsonians which reflects their flexed posture was also significantly greater to compare with the elderly subjects and exhibited a high sensitivity to visual conditions. Both groups of postural sway abnormalities identified here may be used as accessible and reliable measures which allow for quantitative assessment of postural instability in Parkinson's disease.

Identifying Characteristics of Airline Frequent-Fliers in Australia: Implications for Market Segmentation, Target Marketing, and Product Differentiation

Science.gov (United States)

1998-01-01

Airlines can cultivate new business, enjoy repeat patronage through progressively attractive awards given directly to frequent fliers, deter emerging airlines from entering established markets, and compile the demographic profiles and travel characte...

Pearling Instabilities of a Viscoelastic Thread

Science.gov (United States)

Deblais, A.; Velikov, K. P.; Bonn, D.

2018-05-01

Pearling instabilities of slender viscoelastic threads have received much attention, but remain incompletely understood. We study the instabilities in polymer solutions subject to uniaxial elongational flow. Two distinctly different instabilites are observed: beads on a string and blistering. The beads-on-a-string structure arises from a capillary instability whereas the blistering instability has a different origin: it is due to a coupling between stress and polymer concentration. By varying the temperature to change the solution properties we elucidate the interplay between flow and phase separation.

Effects of mass transfer on a resonance instability in the laminar ...

Indian Academy of Sciences (India)

pressible boundary layer flow due to a rotating-disk is investigated in this paper based on the linear stability theory. The possible .... Reynolds number limit to the inviscid modes strongly suggests that the resonance instability identified here ...

Identifying Instability Pockets

Science.gov (United States)

2014-12-04

Shalini Signh, Domestic Tourism in Asia: A Diversity and Divergence (London: Earthscan), 183. 30...125 Solomon. 126 Globalpolicy.Org, “Water In Conflict,” (2014), accessed June 30, 2014, http://www.globalpolicy.org/the- dark -side-of-natural-resources...Globalpolicy.Org. “Water In Conflict,” (2014). Accessed June 30, 2014. http://www.globalpolicy.org/the- dark -side-of-natural-resources-st/water-in-conflict.html

Political Instability and Economic Growth

OpenAIRE

Alberto Alesina; Sule Ozler; Nouriel Roubini; Phillip Swagel

1992-01-01

This paper investigates the relationship between political instability and per capita GDP growth in a sample of 113 countries for the period 1950-1982. We define ?political instability? as the propensity of a government collapse, and we estimate a model in which political instability and economic growth are jointly determined. The main result of this paper is that in countries and time periods with a high propensity of government collapse, growth is significantly lower than otherwise. This ef...

Defining frequent use of an urban emergency department

Science.gov (United States)

Locker, Thomas E; Baston, Simon; Mason, Suzanne M; Nicholl, Jon

2007-01-01

Objective This study aimed to develop a definition of frequent use of an emergency department (ED) by comparing differences in the observed frequency distribution with that of a theoretical frequency distribution. Methods A retrospective analysis of attendance of ED and minor injury unit attendances in one city over 1 year was conducted. From these data, the expected frequency distribution was determined based upon a Poisson distribution. Results During the period studied, 75 141 people attended on 98 908 occasions. The theoretical frequency distribution showed that there were 2764 (3.7%) “frequent users” presenting repeatedly due to non‐random events. These patients made 12 316 (12.4%) attendances. Frequent users were older than chance users (mean age 49.7 vs 44.5 years). A greater proportion arrived by ambulance (55.3% vs 27.5%), presented with psychiatric problems (5.8% vs 1.1%) or alcohol intoxication (1.3% vs 0.5%), and were admitted to hospital (37.4% vs 19.6%). Conclusion We have identified that there is a group of patients who present repeatedly due to non‐random events, confirming the existence of “frequent users”. Their characteristics are clearly different to other patients in the ED. We propose that “frequent users” be defined as any patient who makes more than four attendances per year. PMID:17513534

Kinetic theory of tearing instabilities

International Nuclear Information System (INIS)

Drake, J.F.; Lee, Y.C.

1977-01-01

The transition of the tearing instability from the collisional to the collisionless regime is investigated kinetically using a Fokker--Planck collision operator to represent electron-ion collisions. As a function of the collisionality of the plasma, the tearing instability falls into three regions, which are referred to as collisionless, semi-collisional, and collisional. The width Δ of the singular layer around kxB 0 =0 is limited by electron thermal motion along B 0 in the collisional and semi-collisional regimes and is typically smaller than rho/sub i/, the ion Larmor radius. Previously accepted theories, which are based on the assumption Δvery-much-greater-thanrho/sub i/, are found to be valid only in the collisional regime. The effects of density and temperature gradients on the instabilities are also studied. The tearing instability is only driven by the temperature gradient in the collisional and semi-collisional regimes. Numerical calculations indicate that the semi-collisional tearing instability is particularly relevant to present day high temperature tokamak discharges

Pick-Up Ion Instabilities at Planetary Magnetospheres

Science.gov (United States)

Strangeway, Robert J.; Sharber, James (Technical Monitor)

2001-01-01

This effort involved the analysis of low frequency waves as observed by the Galileo spacecraft near the Galilean moon, Io. Io is a significant source of material, especially SO2, and various products of dissociation, and further these atoms and molecules are readily ionized. The initial velocity of the ions is essentially that of the neutral species, i.e., the Keplerian velocity. The plasma, on the other hand is co-rotating, and there is a differential flow of the order 57 km/s between the plasma and the neutral particles. Thus pick-up ion instabilities are Rely to occur within the Jovian magnetosphere. Indeed, magnetometer observations from the Galileo spacecraft clearly show ion cyclotron waves that have been identified with a large variety of plasma species, such as O+, S++ (which has the same gyro-frequency as O+), S+, and SO2+. Typically, however, the dominant frequency is near the SO2+ gyro-frequency. The research effort was originally planned to be a team effort between Robert J. Strangeway as the Principal Investigator, and Debbie Huddleston, who was an Assistant Research Geophysicist at UCLA. Unfortunately, Dr. Huddleston took a position within Industry. The effort was therefore descoped, and Dr. Strangeway instead pursued a collaboration with Dr. Xochitl Blanco-Cano, of the Instituto de Geofisica, Universidad Nacional Autonoma de Mexico. This has proved to be a productive collaboration, with several papers and publications arising out of the effort. The magnetic field oscillations near lo generally fall into two types: ion cyclotron waves, with frequencies near an ion gyro-frequency, and lower frequency mirror-mode waves. The ion cyclotron waves are mainly transverse, and frequently propagate along the ambient magnetic field. The mirror-mode waves are compressional waves, and they have essentially zero frequency in the plasma rest frame. One of the purposes of our investigation is to understand what controls the types of wave modes that occur, since both

Instability in nuclear dynamics: loss of collectivity and multifragmentation

International Nuclear Information System (INIS)

Colonna, M.; Di Toro, M.; Guarnera, A.; Latora, V.; Smerzi, A.

1995-01-01

Two limiting cases of nuclear dynamics are analysed: the disappearing of giant collective motions in hot nuclei and the nuclear disassembly in violent heavy ion collisions. For collective vibration build on excited states we get a dramatic increase of the widths of hot Giant Dipole Resonances (GDR). As a consequence of the competition with particle evaporation we get a sharp quenching of giant photon emission. Pre-equilibrium effects on the GDR formation are also accounted for. At high temperature and low density the collective motions can become unstable leading to multifragmentation events in heavy ion collisions. We present a general procedure to identify instability regions and to get informations on the instability point. Some hints towards fully dynamical picture of multi-fragmentation processes are finally suggested. (author)

End Point of Black Ring Instabilities and the Weak Cosmic Censorship Conjecture.

Science.gov (United States)

Figueras, Pau; Kunesch, Markus; Tunyasuvunakool, Saran

2016-02-19

We produce the first concrete evidence that violation of the weak cosmic censorship conjecture can occur in asymptotically flat spaces of five dimensions by numerically evolving perturbed black rings. For certain thin rings, we identify a new, elastic-type instability dominating the evolution, causing the system to settle to a spherical black hole. However, for sufficiently thin rings the Gregory-Laflamme mode is dominant, and the instability unfolds similarly to that of black strings, where the horizon develops a structure of bulges connected by necks which become ever thinner over time.

Radiation-induced genomic instability driven by de novo chromosomal rearrangement hot spots

International Nuclear Information System (INIS)

Grosovsky, A.J.; Allen, R.N.; Moore, S.R.

2003-01-01

Genomic instability has become generally recognized as a critical contributor to tumor progression by generating the necessary number of genetic alterations required for expression of a clinically significant malignancy. Our study of chromosomal instability investigates the hypothesis that chromosomal rearrangements can generate novel breakage-prone sites, resulting in instability acting predominantly in cis. Here we present an analysis of the karyotypic distribution of instability associated chromosomal rearrangements in TK6 and derivative human lymphoblasts. Karyotypic analysis performed on a total of 455 independent clones included 183 rearrangements distributed among 100 separate unstable clones. The results demonstrate that the breakpoints of chromosomal rearrangements in unstable clones are non-randomly distributed throughout the genome. This pattern is statistically significant, and incompatible with expectations for random breakage associated with loss or alteration of a trans-acting factor. Furthermore, specific chromosomal breakage hot spots associated with instability have been identified; these occur in several independent unstable clones and are often repeatedly broken and rejoined during the outgrowth of an individual clone. In complimentary studies, genomic instability was generated without any exposure to a DNA-damaging agent, but rather by transfection with alpha heterochromatin DNA. In a prospective analysis, human-hamster hybrid AL cells containing a single human chromosome 11 were transfected with heterochromatic alpha DNA repeats and clones were analyzed by chromosome 11 painting. Transfection with alpha DNA was associated with karyotypic heterogeneity in 40% of clones examined; control transfections with plasmid alone did not lead to karyotypic heterogeneity

Instabilities in thin tunnel junctions

International Nuclear Information System (INIS)

Konkin, M.K.; Adler, J.G.

1978-01-01

Tunnel junctions prepared for inelastic electron tunneling spectroscopy are often plagued by instabilities in the 0-500-meV range. This paper relates the bias at which the instability occurs to the barrier thickness

Damage-induced tensile instability

International Nuclear Information System (INIS)

Hult, J.

1975-01-01

The paper presents a unified description of ductile and brittle rupture phenomena in structural components under tensile loading with particular emphasis on creep rupture. Two structural elements are analyzed in detail: 1) the uniform tensile bar subject to a Heaviside history of tensile force and superimposed such loadings, i.e. staircase histories, and 2) the thinwalled spherical pressure vessel subject to a Heaviside history of internal pressure. For both these structures the conditions for instantaneous as well as delayed rupture are analysed. It is shown that a state of mechanical instability will be reached at a certain load or after a certain time. The cases of purely ductile rupture and purely brittle fracture are identified as two limiting cases of this general instability phenomenon. The Kachanov-Rabotnov damage law implies that a structural component will fail in tension only when it has reached a state of complete damage, i.e. zero load carrying capacity. The extended law predicts failure at an earlier stage of the deterioration process and is therefore more compatible with experimental observation. Further experimental support is offered by predictions for staircase loading histories, both step-up and step-down type. The presented damage theory here predicts strain histories which are in closer agreement with test data than predictions based on other phenomenological theories

Summary of longitudinal instabilities workshop

Energy Technology Data Exchange (ETDEWEB)

Chasman, R.

1976-01-01

A five-day ISABELLE workshop on longitudinal instabilities was held at Brookhaven, August 9-13, 1976. About a dozen outside accelerator experts, both from Europe and the U.S.A., joined the local staff for discussions of longitudinal instabilities in ISABELLE. An agenda of talks was scheduled for the first day of the workshop. Later during the week, a presentation was given on the subject ''A more rigorous treatment of Landau damping in longitudinal beam instabilities''. A few progress meetings were held in which disagreements regarding calculations of coupling impedances were clarified. A summary session was held on the last day. Heavy emphasis was put on single bunched beam instabilities in the microwave region extending above the cut-off frequency of the ISABELLE vacuum chamber.

Instability of ties in compression

DEFF Research Database (Denmark)

Buch-Hansen, Thomas Cornelius

2013-01-01

Masonry cavity walls are loaded by wind pressure and vertical load from upper floors. These loads results in bending moments and compression forces in the ties connecting the outer and the inner wall in a cavity wall. Large cavity walls are furthermore loaded by differential movements from...... the temperature gradient between the outer and the inner wall, which results in critical increase of the bending moments in the ties. Since the ties are loaded by combined compression and moment forces, the loadbearing capacity is derived from instability equilibrium equations. Most of them are iterative, since...... exact instability solutions are complex to derive, not to mention the extra complexity introducing dimensional instability from the temperature gradients. Using an inverse variable substitution and comparing an exact theory with an analytical instability solution a method to design tie...

Fringe instability in constrained soft elastic layers.

Science.gov (United States)

Lin, Shaoting; Cohen, Tal; Zhang, Teng; Yuk, Hyunwoo; Abeyaratne, Rohan; Zhao, Xuanhe

2016-11-04

Soft elastic layers with top and bottom surfaces adhered to rigid bodies are abundant in biological organisms and engineering applications. As the rigid bodies are pulled apart, the stressed layer can exhibit various modes of mechanical instabilities. In cases where the layer's thickness is much smaller than its length and width, the dominant modes that have been studied are the cavitation, interfacial and fingering instabilities. Here we report a new mode of instability which emerges if the thickness of the constrained elastic layer is comparable to or smaller than its width. In this case, the middle portion along the layer's thickness elongates nearly uniformly while the constrained fringe portions of the layer deform nonuniformly. When the applied stretch reaches a critical value, the exposed free surfaces of the fringe portions begin to undulate periodically without debonding from the rigid bodies, giving the fringe instability. We use experiments, theory and numerical simulations to quantitatively explain the fringe instability and derive scaling laws for its critical stress, critical strain and wavelength. We show that in a force controlled setting the elastic fingering instability is associated with a snap-through buckling that does not exist for the fringe instability. The discovery of the fringe instability will not only advance the understanding of mechanical instabilities in soft materials but also have implications for biological and engineered adhesives and joints.

Modeling and analysis of hydrodynamic instabilities in two-phase flow using two-fluid model

International Nuclear Information System (INIS)

Zhou, J.; Podowski, M.Z.

2001-01-01

Because of the practical importance of two-phase flow instabilities, especially in boiling water nuclear reactor technology, substantial efforts have been made to date to understand the physical phenomena governing such instabilities and to develop computational tools to model the dynamics of marginally-stable/unstable boiling systems. The purpose of this paper is to present an integrated methodology for the analysis of flow-induced instabilities in boiling channels and systems. The major novel aspects of the proposed approach are: (a) it is based on the combined frequency-domain and time-domain methods, the former used to quantify stability margins and to determine the onset of instability conditions, the latter to study the nonlinear system response outside the stability boundaries identified using the nearly-exact results of the frequency-domain analysis; (b) the two-fluid model of two-phase flow has been used for the first time to analytically derive the boiling channel transfer functions for the parallel-channel and channel-to-channel instability modes. In this way, the major characteristics of a boiling system, including the onset-of-instability conditions, can be readily evaluated by using the qualitative frequency-domain approach, whereas the explicit time-domain integration is performed, if necessary, only for the operating conditions that have already been identified as unstable. Both methods use the same physical two-fluid model that, in one case, is linearized and used to derive a rigorous analytical solution in the complex domain, and, in the other case, is solved numerically using an algorithm developed especially for this purpose. The results using both methods have been compared against each other and extensively tested. The testing and validation of the new model included comparisons of the predicted steady-state distributions of major parameters and of the transient channel response against experimental data

Topographic-driven instabilities in terrestrial bodies

Science.gov (United States)

Vantieghem, S.; Cebron, D.; Herreman, W.; Lacaze, L.

2013-12-01

Models of internal planetary fluid layers (core flows, subsurface oceans) commonly assume that these fluid envelopes have a spherical shape. This approximation however entails a serious restriction from the fluid dynamics point of view. Indeed, in the presence of mechanical forcings (precession, libration, nutation or tides) due to gravitational interaction with orbiting partners, boundary topography (e.g. of the core-mantle boundary) may excite flow instabilities and space-filling turbulence. These phenomena may affect heat transport and dissipation at the main order. Here, we focus on instabilities driven by longitudinal libration. Using a suite of theoretical tools and numerical simulations, we are able to discern a parameter range for which instability may be excited. We thereby consider deformations of different azimuthal order. This study gives the first numerical evidence of the tripolar instability. Furthermore, we explore the non-linear regime and investigate the amplitude as well as the dissipation of the saturated instability. Indeed, these two quantities control the torques on the solid layers and the thermal transport. Furthermore, based on this results, we address the issue of magnetic field generation associated with these flows (by induction or by dynamo process). This instability mechanism applies to both synchronized as non-synchronized bodies. As such, our results show that a tripolar instability might be present in various terrestrial bodies (Early Moon, Gallilean moons, asteroids, etc.), where it could participate in dynamo action. Simulation of a libration-driven tripolar instability in a deformed spherical fluid layer: snapshot of the velocity magnitude, where a complex 3D flow pattern is established.

Comprehensive experimental and numerical analysis of instability phenomena in pump turbines

International Nuclear Information System (INIS)

Gentner, Ch; Sallaberger, M; Widmer, Ch; Bobach, B-J; Jaberg, H; Schiffer, J; Senn, F; Guggenberger, M

2014-01-01

The changes in the electricity market have led to changed requirements for the operation of pump turbines. Utilities need to change fast and frequently between pumping and generating modes and increasingly want to operate at off-design conditions for extended periods. Operation of the units in instable areas of the machine characteristic is not acceptable and may lead to self-excited vibration of the hydraulic system. In turbine operation of pump turbines unstable behaviour can occur at low load off-design operation close to runaway conditions (S-shape of the turbine characteristic). This type of instability may impede the synchronization of the machine in turbine mode and thus increase start-up and switch over times. A pronounced S-shaped instability can also lead to significant drop of discharge in the event of load rejection. Low pressure on the suction side and in the tail-race tunnel could cause dangerous separation of the water column. Understanding the flow features that lead to the instable behaviour of pump turbines is a prerequisite to the design of machines that can fulfil the growing requirements relating to operational flexibility. Flow simulation in these instability zones is demanding due to the complex and highly unsteady flow patterns. Only unsteady simulation methods are able to reproduce the governing physical effects in these operating regions. ANDRITZ HYDRO has been investigating the stability behaviour of pump turbines in turbine operation in cooperation with several universities using simulation and measurements. In order to validate the results of flow simulation of unstable operating points, the Graz University of Technology (Austria) performed detailed experimental investigations. Within the scope of a long term research project, the operating characteristics of several pump turbine runners have been measured and flow patterns in the pump turbine at speed no load and runaway have been examined by 2D Laser particle image velocimetry (PIV

Two or more impingement and/or instability deformities are often present in patients with hip pain.

Science.gov (United States)

Tibor, Lisa M; Liebert, Gunnar; Sutter, Reto; Impellizzeri, Franco M; Leunig, Michael

2013-12-01

Damage to the hip can occur due to impingement or instability caused by anatomic factors such as femoral and acetabular version, neck-shaft angle, alpha angle, and lateral center-edge angle (CEA). The associations between these anatomic factors and how often they occur in a painful hip are unclear but if unaddressed might explain failed hip preservation surgery. We determined (1) the influence of sex on the expression of impingement-related or instability-related factors, (2) the associations among these factors, and (3) how often both impingement and/or instability factors occur in the same hip. We retrospectively reviewed a cohort of 170 hips (145 patients) undergoing MR arthrography of the hip for any reason. We excluded 58 hips with high-grade dysplasia, Perthes' sequelae, previous surgery, or incomplete radiographic information, leaving 112 hips (96 patients). We measured femoral version and alpha angles on MR arthrograms. Acetabular anteversion, lateral CEA, and neck-shaft angle were measured on pelvic radiographs. We observed a correlation between sex and alpha angle. Weak or no correlations were observed between the other five parameters. In 66% of hips, two or more (of five) impingement parameters, and in 51% of hips, two or more (of five) instability parameters were found. Patients with hip pain frequently have several anatomic factors potentially contributing to chondrolabral damage. To address pathologic hip loading due to impingement and/or instability, all of the anatomic influences should be known. As we found no associations between anatomic factors, we recommend an individualized assessment of each painful hip.

Relativistic centrifugal instability

Science.gov (United States)

Gourgouliatos, Konstantinos N.; Komissarov, Serguei S.

2018-03-01

Near the central engine, many astrophysical jets are expected to rotate about their axis. Further out they are expected to go through the processes of reconfinement and recollimation. In both these cases, the flow streams along a concave surface and hence, it is subject to the centrifugal force. It is well known that such flows may experience the centrifugal instability (CFI), to which there are many laboratory examples. The recent computer simulations of relativistic jets from active galactic nuclei undergoing the process of reconfinement show that in such jets CFI may dominate over the Kelvin-Helmholtz instability associated with velocity shear (Gourgouliatos & Komissarov). In this letter, we generalize the Rayleigh criterion for CFI in rotating fluids to relativistic flows using a heuristic analysis. We also present the results of computer simulations which support our analytic criterion for the case of an interface separating two uniformly rotating cylindrical flows. We discuss the difference between CFI and the Rayleigh-Taylor instability in flows with curved streamlines.

Electromagnetic theory of the radiative Pierce instability

International Nuclear Information System (INIS)

Klochkov, D.N.; Rukhadze, A.A.

1997-01-01

A study is made of the radiative Pierce instability of a relativistic electron beam propagating in a waveguide in the presence of an infinitely strong magnetic field. The perturbation theory is used to find the growth rates and conditions of instability over a broad range of the beam current. It is shown that, under the Pierce boundary conditions, the instability is Raman in nature, and there is no current threshold for the instability. This allows the instability saturation level to be accurately determined from the condition for the violation of the Cherenkov resonance and the radiation efficiency to be estimated

Radiation-induced instability of human genome

International Nuclear Information System (INIS)

Ryabchenko, N.N.; Demina, Eh.A.

2014-01-01

A brief review is dedicated to the phenomenon of radiation-induced genomic instability where the increased level of genomic changes in the offspring of irradiated cells is characteristic. Particular attention is paid to the problems of genomic instability induced by the low-dose radiation, role of the bystander effect in formation of radiation-induced instability, and its relationship with individual radiosensitivity. We believe that in accordance with the paradigm of modern radiobiology the increased human individual radiosensitivity can be formed due to the genome instability onset and is a significant risk factor for radiation-induced cancer

Radiation-induced chromosomal instability

International Nuclear Information System (INIS)

Ritter, S.

1999-01-01

Recent studies on radiation-induced chromosomal instability in the progeny of exposed mammalian cells were briefly described as well as other related studies. For the analysis of chromosomal damage in clones, cells were seeded directly after exposure in cell well-dish to form single cell clones and post-irradiation chromosome aberrations were scored. Both exposure to isoeffective doses of X-ray or 270 MeV/u C-ions (13 keV/μm) increased the number of clones with abnormal karyotype and the increase was similar for X-ray and for C-ions. Meanwhile, in the progeny of cells for mass cultures, there was no indication of a delayed expression of chromosomal damage up to 40 population doublings after the exposure. A high number of aberrant cells were only observed directly after exposure to 10.7 MeV/u O-ions, i.e. in the first cycle cells and decreased with subsequent cell divisions. The reason for these differences in the radiation-induced chromosomal instability between clonal isolates and mass culture has not been clarified. Recent studies indicated that genomic instability occurs at a high frequency in the progeny of cells irradiated with both sparsely and densely ionizing radiation. Such genomic instability is thought likely to increase the risk of carcinogenesis, but more data are required for a well understanding of the health risks resulting from radiation-induced delayed instability. (M.N.)

MR imaging in sports-related glenohumeral instability

International Nuclear Information System (INIS)

Woertler, Klaus; Waldt, Simone

2006-01-01

Sports-related shoulder pain and injuries represent a common problem. In this context, glenohumeral instability is currently believed to play a central role either as a recognized or as an unrecognized condition. Shoulder instabilities can roughly be divided into traumatic, atraumatic, and microtraumatic glenohumeral instabilities. In athletes, atraumatic and microtraumatic instabilities can lead to secondary impingement syndromes and chronic damage to intraarticular structures. Magnetic resonance (MR) arthrography is superior to conventional MR imaging in the diagnosis of labro-ligamentous injuries, intrinsic impingement, and SLAP (superior labral anteroposterior) lesions, and thus represents the most informative imaging modality in the overall assessment of glenohumeral instability. This article reviews the imaging criteria for the detection and classification of instability-related injuries in athletes with special emphasis on the influence of MR findings on therapeutic decisions. (orig.)

Taylor instability in rhyolite lava flows

Science.gov (United States)

Baum, B. A.; Krantz, W. B.; Fink, J. H.; Dickinson, R. E.

1989-01-01

A refined Taylor instability model is developed to describe the surface morphology of rhyolite lava flows. The effect of the downslope flow of the lava on the structures resulting from the Taylor instability mechanism is considered. Squire's (1933) transformation is developed for this flow in order to extend the results to three-dimensional modes. This permits assessing why ridges thought to arise from the Taylor instability mechanism are preferentially oriented transverse to the direction of lava flow. Measured diapir and ridge spacings for the Little and Big Glass Mountain rhyolite flows in northern California are used in conjunction with the model in order to explore the implications of the Taylor instability for flow emplacement. The model suggests additional lava flow features that can be measured in order to test whether the Taylor instability mechanism has influenced the flows surface morphology.

Formal Solutions for Polarized Radiative Transfer. III. Stiffness and Instability

Science.gov (United States)

Janett, Gioele; Paganini, Alberto

2018-04-01

Efficient numerical approximation of the polarized radiative transfer equation is challenging because this system of ordinary differential equations exhibits stiff behavior, which potentially results in numerical instability. This negatively impacts the accuracy of formal solvers, and small step-sizes are often necessary to retrieve physical solutions. This work presents stability analyses of formal solvers for the radiative transfer equation of polarized light, identifies instability issues, and suggests practical remedies. In particular, the assumptions and the limitations of the stability analysis of Runge–Kutta methods play a crucial role. On this basis, a suitable and pragmatic formal solver is outlined and tested. An insightful comparison to the scalar radiative transfer equation is also presented.

Tracking Code for Microwave Instability

International Nuclear Information System (INIS)

Heifets, S.; SLAC

2006-01-01

To study microwave instability the tracking code is developed. For bench marking, results are compared with Oide-Yokoya results [1] for broad-band Q = 1 impedance. Results hint to two possible mechanisms determining the threshold of instability

Outcomes and complications following graft reconstruction for anterior sternoclavicular joint instability.

Science.gov (United States)

Willinger, Lukas; Schanda, Jakob; Herbst, Elmar; Imhoff, Andreas B; Martetschläger, Frank

2016-12-01

Publications describing tendon graft reconstruction for anterior sternoclavicular joint (SCJ) instability are rare and usually refer to small patient numbers. The aim of this study was to systematically review the literature regarding outcomes and complications following tendon graft reconstruction techniques for anterior SCJ instability. An online database was systematically searched to identify studies on graft reconstruction for anterior SCJ instability. Reported outcome scores were graded as excellent, good, fair and poor to summarize the study results. All reported complications were recorded. Five articles with a total of 80 patients met the inclusion criteria. Reported outcomes were excellent in 10 %, good in 89 % and fair in 1 %. Recurrent instability was found in 10 % of the patients, and 5 % underwent revision surgery due to persistent impairment of shoulder function related to SCJ instability or osteoarthritis. Surgical stabilization techniques for the SCJ using autologous tendon grafts have shown to be safe and reliable and make better patients' pain situation and shoulder function. However, a certain amount of impairment might persist, which needs to be discussed with patients. Severe complications were rare and revision rates were as low as 5 %. Therefore, graft reconstruction techniques should be considered for patients with chronic anterior SCJ instability after a course of failed conservative treatment. This study is valuable for clinicians in daily clinical practice when dealing with this difficult-to-treat pathology and can help surgeons to better predict the clinical outcomes and complications following SCJ graft reconstruction. It should, however, not lead to underestimation of the potential risks of the procedure. Systematic review, Level IV.

Corona-induced electrohydrodynamic instabilities in low conducting liquids

Energy Technology Data Exchange (ETDEWEB)

Vega, F.; Perez, A.T. [Depto. Electronica y Electromagnetismo, Facultad de Fisica, Universidad de Sevilla, Avda. Reina Mercedes, s/n. 41012, Sevilla (Spain)

2003-06-01

The rose-window electrohydrodynamic (EHD) instability has been observed when a perpendicular field with an additional unipolar ion injection is applied onto a low conducting liquid surface. This instability has a characteristic pattern with cells five to 10 times greater than those observed in volume instabilities caused by unipolar injection. We have used corona discharge from a metallic point to perform some measurements of the rose-window instability in low conducting liquids. The results are compared to the linear theoretical criterion for an ohmic liquid. They confirmed that the minimum voltage for this instability is much lower than that for the interfacial instability in high conducting liquids. This was predicted theoretically in the dependence of the critical voltage as a function of the non-dimensional conductivity. It is shown that in a non-ohmic liquid the rose window appears as a secondary instability after the volume instability. (orig.)

Instability and star evolution

International Nuclear Information System (INIS)

Mirzoyan, L.V.

1981-01-01

The observational data are discussed which testify that the phenomena of dynamical instability of stars and stellar systems are definite manifestations of their evolution. The study of these phenomena has shown that the instability is a regular phase of stellar evolution. It has resulted in the recognition of the most important regularities of the process of star formation concerning its nature. This became possible due to the discovery in 1947 of stellar associations in our Galaxy. The results of the study of the dynamical instability of stellar associations contradict the predictions of classical hypothesis of stellar condensation. These data supplied a basis for a new hypothesis on the formation of stars and nebulae by the decay of superdense protostars [ru

Secondary instabilities of hypersonic stationary crossflow waves

Science.gov (United States)

Edelman, Joshua B.

A sharp, circular 7° half-angle cone was tested in the Boeing/AFOSR Mach-6 Quiet Tunnel at 6° angle of attack. Using a variety of roughness configurations, measurements were made using temperature-sensitive paint (TSP) and fast pressure sensors. High-frequency secondary instabilities of the stationary crossflow waves were detected near the aft end of the cone, from 110° to 163° from the windward ray. At least two frequency bands of the secondary instabilities were measured. The secondary instabilities have high coherence between upstream and downstream sensor pairs. In addition, the amplitudes of the instabilities increase with the addition of roughness elements near the nose of the cone. Two of the measured instabilities were captured over a range of axial Reynolds numbers of about 1 - 2 million, with amplitudes ranging from low to turbulent breakdown. For these instabilities, the wave speed and amplitude growth can be calculated. The wave speeds were all near the edge velocity. Measured growth before breakdown for the two instabilities are between e3 and e4 from background noise levels. The initial linear growth rates for the instabilities are near 50 /m. Simultaneous measurement of two frequency bands of the secondary instabilities was made during a single run. It was found that each mode was spatially confined within a small azimuthal region, and that the regions of peak amplitude for one mode correspond to regions of minimal amplitude for the other.

Distinguishing the relevant features of frequent suicide attempters.

Science.gov (United States)

Lopez-Castroman, Jorge; Perez-Rodriguez, Maria de las Mercedes; Jaussent, Isabelle; Alegria, Analucia A; Artes-Rodriguez, Antonio; Freed, Peter; Guillaume, Sébastien; Jollant, Fabrice; Leiva-Murillo, Jose Miguel; Malafosse, Alain; Oquendo, Maria A; de Prado-Cumplido, Mario; Saiz-Ruiz, Jeronimo; Baca-Garcia, Enrique; Courtet, Philippe

2011-05-01

In spite of the high prevalence of suicide behaviours and the magnitude of the resultant burden, little is known about why individuals reattempt. We aim to investigate the relationships between clinical risk factors and the repetition of suicidal attempts. 1349 suicide attempters were consecutively recruited in the Emergency Room (ER) of two academic hospitals in France and Spain. Patients were extensively assessed and demographic and clinical data obtained. Data mining was used to determine the minimal number of variables that blinded the rest in relation to the number of suicide attempts. Using this set, a probabilistic graph ranking relationships with the target variable was constructed. The most common diagnoses among suicide attempters were affective disorders, followed by anxiety disorders. Risk of frequent suicide attempt was highest among middle-aged subjects, and diminished progressively with advancing age of onset at first attempt. Anxiety disorders significantly increased the risk of presenting frequent suicide attempts. Pathway analysis also indicated that frequent suicide attempts were linked to greater odds for alcohol and substance abuse disorders and more intensive treatment. Novel statistical methods found several clinical features that were associated with a history of frequent suicide attempts. The identified pathways may promote new hypothesis-driven studies of suicide attempts and preventive strategies. Copyright © 2010 Elsevier Ltd. All rights reserved.

MR imaging findings and MR criteria for instability in osteochondritis dissecans of the elbow in children

International Nuclear Information System (INIS)

Jans, Lennart B.O.; Ditchfield, Michael; Anna, Gomez; Jaremko, Jacob L.; Verstraete, Koenraad L.

2012-01-01

Purpose: Osteochondritis dissecans (OCD) of the elbow is an uncommon cause of elbow pain in adolescents and occurs at different locations in the elbow joint. Early diagnosis and treatment may prevent surgery. The aim of the study is to describe the MR imaging features of OCD at initial imaging, and to correlate these findings with surgical findings of stability and instability with arthroscopic findings as the reference standard. Methods: Patients were identified through a keyword search of the radiology information system from 2000 to 2009. Twenty-five patients (26 elbows) with OCD of the elbow were identified (age 10.4–18 years, mean age 14 years). MR studies were retrospectively reviewed by two radiologists in consensus to define MR imaging findings and to determine the presence of previously described MR imaging criteria for OCD instability (i.e., high T2 signal rim, surrounding cysts, high T2 signal fracture line, fluid-filled osteochondral defect). Sensitivity of the individual and combined criteria was calculated. Results: OCD occurred in the capitellum in 24 patients (92%), in the trochlea in 2 patients (8%) and radial head in 1 patient (4%). Loose bodies were identified in 11 (42%) patients. Eighteen patients demonstrated MRI findings in keeping with unstable lesions. In all 11 patients who had surgery the surgical findings of instability correlated with the MRI findings. When combined, the MR criteria were 100% sensitive for instability of OCD lesions of the elbow. Conclusion: The vast majority of OCD of the elbow occurs in the capitellum. When used together, the MR criteria for instability were 100% sensitive for evaluation OCD lesions of the elbow.

Aeroelastic instability problems for wind turbines

DEFF Research Database (Denmark)

Hansen, Morten Hartvig

2007-01-01

This paper deals with the aeroelostic instabilities that have occurred and may still occur for modem commercial wind turbines: stall-induced vibrations for stall-turbines, and classical flutter for pitch-regulated turbines. A review of previous works is combined with derivations of analytical...... stiffness and chordwise position of the center of gravity along the blades are the main parameters for flutter. These instability characteristics are exemplified by aeroelastic stability analyses of different wind turbines. The review of each aeroelastic instability ends with a list of current research...... issues that represent unsolved aeroelostic instability problems for wind turbines. Copyright (c) 2007 John Wiley & Sons, Ltd....

Predicting the transition from frequent cannabis use to cannabis dependence: a three-year prospective study.

NARCIS (Netherlands)

van der Pol, P.; Liebregts, N.; de Graaf, R.; Korf, D.J.; van den Brink, W.; van Laar, M.

2013-01-01

Background Frequent cannabis users are at high risk of dependence, still most (near) daily users are not dependent. It is unknown why some frequent users develop dependence, whereas others do not. This study aims to identify predictors of first-incidence DSM-IV cannabis dependence in frequent

Clinical and radiological instability following standard fenestration discectomy

Directory of Open Access Journals (Sweden)

Mascarenhas Amrithlal

2009-01-01

Full Text Available Background: Post-surgical lumbar instability is an established complication but there is limited evidence in the literature regarding the incidence of lumbar instability following fenestration and discectomy. We analyzed our results following fenestration discectomy with a special focus on instability. Materials and Methods: Eighty-three patients between the age of 17 and 52 years who had undergone fenestration discectomy for a single-level lumbar intervertebral disc prolapse were followed-up for a period of 1-5 years. The criteria for instability included "instability catch,", "painful catch," and "apprehension." The working capacity of the patient and the outcome score of the surgery were assessed by means of the Oswestry disability score and the Prolo economic and functional outcome score. Flexion-extension lateral radiographs were taken and analyzed for abnormal tilt and translation. Results: Of the 83 patients included, 70 were men and 13 were women, with an average age of 37.35 years (17-52 years at 5 years follow-up. Clinical instability was seen in 10 (12.04% patients. Radiological instability was noted in 29 (34.9% patients. Only six (60% of the 10 patients who demonstrated clinical instability had radiological evidence of instability. Twenty (68.96% patients with radiological instability were asymptomatic. Three (10.34% patients with only radiological instability had unsatisfactory outcome. The Oswestry scoring showed an average score of 19.8%. Mild disability was noted in 59 (71.08% patients and moderate disability was seen in 24 (28.91% patients. None of the patients had severe disability. These outcomes were compared with the outcomes in other studies in the literature for microdiscectomy and the results were found to be comparable. Conclusion: The favorable outcome of this study is in good agreement with other studies on microdiscectomy. Clinical instability in 12.04% of the patients is in agreement with other studies. Radiological

Numerical MHD study for plasmoid instability in uniform resistivity

Science.gov (United States)

Shimizu, Tohru; Kondoh, Koji; Zenitani, Seiji

2017-11-01

The plasmoid instability (PI) caused in uniform resistivity is numerically studied with a MHD numerical code of HLLD scheme. It is shown that the PI observed in numerical studies may often include numerical (non-physical) tearing instability caused by the numerical dissipations. By increasing the numerical resolutions, the numerical tearing instability gradually disappears and the physical tearing instability remains. Hence, the convergence of the numerical results is observed. Note that the reconnection rate observed in the numerical tearing instability can be higher than that of the physical tearing instability. On the other hand, regardless of the numerical and physical tearing instabilities, the tearing instability can be classified into symmetric and asymmetric tearing instability. The symmetric tearing instability tends to occur when the thinning of current sheet is stopped by the physical or numerical dissipations, often resulting in the drastic changes in plasmoid chain's structure and its activity. In this paper, by eliminating the numerical tearing instability, we could not specify the critical Lundquist number Sc beyond which PI is fully developed. It suggests that Sc does not exist, at least around S = 105.

[Microsatellite instability and human papilloma virus genotypes in preneoplastic and neoplastic uterine cervix lesions].

Science.gov (United States)

Roa S, Juan Carlos; Martínez S, Ricardo; Montenegro, Sonia; Roa E, Iván; Capurro V, Italo; Ibacache S, Gilda; Melo A, Angélica

2007-01-01

The association between some specific human papilloma virus (HPV) types and cervix cancer is well known. However, the genetic conditions that favor the development of cervical cancer are less well known. To determine the presence of satellite instability (MSI) in preneoplastic and neoplastic lesions of the cervix and correlate these findings with HPV genotypes. Biopsy samples of cervical lesions were studied. Sixteen had low grade lesions, 22 had high grade lesions and 28 had an epidermoid cancer. Viral types were identified with polymerase chain reaction, dot-blot hybridization and restriction fragment length polymorphism. MSI was determined using a panel of eight highly informative microsatellites. Microsatellite instability in at least one locus was observed in 91, 56 and 69% of low grade lesions, high grade lesions and epidermoid carcinomas, respectively. MSI-High grade, MSI-Low grade instability and microsatellite stability were observed in 5, 60 and 46% of samples, respectively. Two of three samples with high grade instability had HPV 52 genotype. Other viral subtypes had frequencies that ranged from 78% to 100%, with the exception of HPV16 that was present in only 53% of samples with low grade instability. Two thirds of biopsy samples from cervical lesions had MSI, mechanism that can be involved in the first stages of cervical carcinogenesis. The low frequency of high grade instability, its association with HPV52 and the low frequency of HPV16 in samples with low grade instability, suggest different coadjutant mechanisms in cervical carcinogenesis.

Segmental lumbar spine instability at flexion-extension radiography can be predicted by conventional radiography

Energy Technology Data Exchange (ETDEWEB)

Pitkaenen, M.T.; Manninen, H.I.; Lindgren, K.-A.J.; Sihvonen, T.A.; Airaksinen, O.; Soimakallio, S

2002-07-01

AIM: To identify plain radiographic findings that predict segmental lumbar spine instability as shown by functional flexion-extension radiography. MATERIALS AND METHODS: Plain radiographs and flexion-extension radiographs of 215 patients with clinically suspected lumbar spine instability were analysed. Instability was classified into anterior or posterior sliding instability. The registered plain radiographic findings were traction spur, spondylarthrosis, arthrosis of facet joints, disc degeneration, retrolisthesis, degenerative spondylolisthesis, spondylolytic spondylolisthesis and vacuum phenomena. Factors reaching statistical significance in univariate analyses (P < 0.05) were included in stepwise multiple logistic regression analysis. RESULTS: Degenerative spondylolisthesis (P = 0.004 at L3-4 level and P = 0.017 at L4-5 level in univariate analysis and odds ratio 16.92 at L4-5 level in multiple logistic regression analyses) and spondylolytic spondylolisthesis (P = 0.003 at L5-S1 level in univariate analyses) were the strongest independent determinants of anterior sliding instability. Retrolisthesis (odds ratio 10.97), traction spur (odds ratio 4.45) and spondylarthrosis (odds ratio 3.20) at L3-4 level were statistically significant determinants of posterior sliding instability in multivariate analysis. CONCLUSION: Sliding instability is strongly associated with various plain radiographic findings. In mechanical back pain, functional flexion-extension radiographs should be limited to situations when symptoms are not explained by findings of plain radiographs and/or when they are likely to alter therapy. Pitkaenen, M.T. et al. (2002)

Segmental lumbar spine instability at flexion-extension radiography can be predicted by conventional radiography

International Nuclear Information System (INIS)

Pitkaenen, M.T.; Manninen, H.I.; Lindgren, K.-A.J.; Sihvonen, T.A.; Airaksinen, O.; Soimakallio, S.

2002-01-01

AIM: To identify plain radiographic findings that predict segmental lumbar spine instability as shown by functional flexion-extension radiography. MATERIALS AND METHODS: Plain radiographs and flexion-extension radiographs of 215 patients with clinically suspected lumbar spine instability were analysed. Instability was classified into anterior or posterior sliding instability. The registered plain radiographic findings were traction spur, spondylarthrosis, arthrosis of facet joints, disc degeneration, retrolisthesis, degenerative spondylolisthesis, spondylolytic spondylolisthesis and vacuum phenomena. Factors reaching statistical significance in univariate analyses (P < 0.05) were included in stepwise multiple logistic regression analysis. RESULTS: Degenerative spondylolisthesis (P = 0.004 at L3-4 level and P = 0.017 at L4-5 level in univariate analysis and odds ratio 16.92 at L4-5 level in multiple logistic regression analyses) and spondylolytic spondylolisthesis (P = 0.003 at L5-S1 level in univariate analyses) were the strongest independent determinants of anterior sliding instability. Retrolisthesis (odds ratio 10.97), traction spur (odds ratio 4.45) and spondylarthrosis (odds ratio 3.20) at L3-4 level were statistically significant determinants of posterior sliding instability in multivariate analysis. CONCLUSION: Sliding instability is strongly associated with various plain radiographic findings. In mechanical back pain, functional flexion-extension radiographs should be limited to situations when symptoms are not explained by findings of plain radiographs and/or when they are likely to alter therapy. Pitkaenen, M.T. et al. (2002)

Numerical study of jets secondary instabilities

International Nuclear Information System (INIS)

Brancher, Pierre

1996-01-01

The work presented in this dissertation is a contribution to the study of the transition to turbulence in open shear flows. Results from direct numerical simulations are interpreted within the framework of hydrodynamic stability theory. The first chapter is an introduction to the primary and secondary instabilities observed in jets and mixing layers. The numerical method used in the present study is detailed in the second chapter. The dynamics of homogeneous circular jets subjected to stream wise and azimuthal perturbations are investigated in the third chapter. A complete scenario describing the evolution of the jet is proposed with emphasis on the dynamics of vorticity within the flow. In the fourth chapter a parametric study reveals a three-dimensional secondary instability mainly controlled in the linear regime by the Strouhal number of the primary instability. In the nonlinear regime the dynamics of the azimuthal harmonies are described by means of model equations and are linked to the formation of stream wise vortices in the braid. The fifth chapter is dedicated to the convective or absolute nature of the secondary instabilities in plane shear layers. It is shown that there are flow configurations for which the two-dimensional secondary instability (pairing) is absolute even though the primary instability (Kelvin-Helmholtz) is convective. Some preliminary results concerning the three-dimensional secondary instabilities arc presented at the end of this chapter. The last chapter summarizes the main results and examines possible extensions of this work. (author) [fr

Edge instabilities of topological superconductors

Energy Technology Data Exchange (ETDEWEB)

Hofmann, Johannes S. [Institut fuer Theoretische Physik und Astrophysik, Universitaet Wuerzburg (Germany); Max-Planck-Institut fuer Festkoerperforschung, Stuttgart (Germany); Assaad, Fakher F. [Institut fuer Theoretische Physik und Astrophysik, Universitaet Wuerzburg (Germany); Schnyder, Andreas P. [Max-Planck-Institut fuer Festkoerperforschung, Stuttgart (Germany)

2016-07-01

Nodal topological superconductors display zero-energy Majorana flat bands at generic edges. The flatness of these edge bands, which is protected by time-reversal and translation symmetry, gives rise to an extensive ground state degeneracy and a diverging density of states. Therefore, even arbitrarily weak interactions lead to an instability of the flat-band edge states towards time-reversal and translation-symmetry broken phases, which lift the ground-state degeneracy. Here, we employ Monte Carlo simulations combined with mean-field considerations to examine the instabilities of the flat-band edge states of d{sub xy}-wave superconductors. We find that attractive interactions induce a complex s-wave pairing instability together with a density wave instability. Repulsive interactions, on the other hand, lead to ferromagnetism mixed with spin-triplet pairing at the edge. We discuss the implications of our findings for experiments on cuprate high-temperature superconductors.

WELLBORE INSTABILITY: CAUSES AND CONSEQUENCES

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Borivoje Pašić

2007-12-01

Full Text Available Wellbore instability is one of the main problems that engineers meet during drilling. The causes of wellbore instability are often classified into either mechanical (for example, failure of the rock around the hole because of high stresses, low rock strength, or inappropriate drilling practice or chemical effects which arise from damaging interaction between the rock, generally shale, and the drilling fluid. Often, field instances of instability are a result of a combination of both chemical and mechanical. This problem might cause serious complication in well and in some case can lead to expensive operational problems. The increasing demand for wellbore stability analyses during the planning stage of a field arise from economic considerations and the increasing use of deviated, extended reach and horizontal wells. This paper presents causes, indicators and diagnosing of wellbore instability as well as the wellbore stresses model.

Nonlinear behavior of the radiative condensation instability

International Nuclear Information System (INIS)

McCarthy, D.; Drake, J.F.

1991-01-01

An investigation of the nonlinear behavior of the radiative condensation instability is presented in a simple one-dimensional magnetized plasma. It is shown that the radiative condensation is typically a nonlinear instability---the growth of the instability is stronger once the disturbance reaches finite amplitude. Moreover, classical parallel thermal conduction is insufficient by itself to saturate the instability. Radiative collapse continues until the temperature in the high density condensation falls sufficiently to reduce the radiation rate

About the magneto-acoustic instabilities in mirrors

International Nuclear Information System (INIS)

Zvonkov, A.V.; Timofeev, A.V.

1984-01-01

It is shown that the characteristic of a plasma in mirrors anisotropy of io on distribution function versus velocities may results in the drive of magneto-acoustic instabilities. This instability, in contast to the well known Alyven oscillation instability, is driven on ion cyclotron frequency harmonics The instability in question has been possibly observed during the experiments a at the tmx device, where the oscillations have been excited both at the ion cycl tron frequency and harmonics

A general approach to optomechanical parametric instabilities

International Nuclear Information System (INIS)

Evans, M.; Barsotti, L.; Fritschel, P.

2010-01-01

We present a simple feedback description of parametric instabilities which can be applied to a variety of optical systems. Parametric instabilities are of particular interest to the field of gravitational-wave interferometry where high mechanical quality factors and a large amount of stored optical power have the potential for instability. In our use of Advanced LIGO as an example application, we find that parametric instabilities, if left unaddressed, present a potential threat to the stability of high-power operation.

Predicting the transition from frequent cannabis use to cannabis dependence: a three-year prospective study

NARCIS (Netherlands)

van der Pol, Peggy; Liebregts, Nienke; de Graaf, Ron; Korf, Dirk J.; van den Brink, Wim; van Laar, Margriet

2013-01-01

Frequent cannabis users are at high risk of dependence, still most (near) daily users are not dependent. It is unknown why some frequent users develop dependence, whereas others do not. This study aims to identify predictors of first-incidence DSM-IV cannabis dependence in frequent cannabis users. A

Nonlinear instabilities induced by the F coil power amplifier at FTU: Modeling and control

International Nuclear Information System (INIS)

Zaccarian, L.; Boncagni, L.; Cascone, D.; Centioli, C.; Cerino, S.; Gravanti, F.; Iannone, F.; Mecocci, F.; Pangione, L.; Podda, S.; Vitale, V.; Vitelli, R.

2009-01-01

In this paper we focus on the instabilities caused by the nonlinear behavior of the F coil current amplifier at FTU. This behavior induces closed-loop instability of the horizontal position stabilizing loop whenever the requested current is below the circulating current level. In the paper we first illustrate a modeling phase where nonlinear dynamics are derived and identified to reproduce the open-loop responses measured by the F coil current amplifier. The derived model is shown to successfully reproduce the experimental behavior by direct comparison with experimental data. Based on this dynamic model, we then reproduce the closed-loop scenario of the experiment and show that the proposed nonlinear model successfully reproduces the nonlinear instabilities experienced in the experimental sessions. Given the simulation setup, we next propose a nonlinear control solution to this instability problem. The proposed solution is shown to recover stability in closed-loop simulations. Experimental tests are scheduled for the next experimental campaign after the FTU restart.

Experimental investigation on flow instability of forced circulation in a vertical mini-rectangular channel

International Nuclear Information System (INIS)

Yu Zhiting; Tan Sichao; Yuan Hongsheng; Zhuang Nailiang; Chen Hanying

2015-01-01

An experimental study was conducted to investigate the flow instability in a vertical mini-rectangular channel with distilled water as the working fluid. The rotational speed of the primary pump is gradually reduced to lower the inlet flow rate until the flow becomes unstable, while maintaining all other thermal parameters unchanged. Three types of instability, characterized by large amplitude oscillation, small amplitude oscillation and flow excursion, were identified from the experimental data. A stability map for the vertical mini-rectangular channel under forced circulation was established based on the Subcooling number and Phase Change number. The oscillation periods were correlated with the fluid transit time and the boiling delay time. A flow pattern map for vertical upward flow in a mini-rectangular channel was applied to confirm the flow patterns during the oscillation. The mechanisms of the three types of instability were obtained by considering several types of flow instabilities and comparing them with the oscillations observed in this work. (author)

Promiscuous 2-aminothiazoles (PrATs): a frequent hitting scaffold.

Science.gov (United States)

Devine, Shane M; Mulcair, Mark D; Debono, Cael O; Leung, Eleanor W W; Nissink, J Willem M; Lim, San Sui; Chandrashekaran, Indu R; Vazirani, Mansha; Mohanty, Biswaranjan; Simpson, Jamie S; Baell, Jonathan B; Scammells, Peter J; Norton, Raymond S; Scanlon, Martin J

2015-02-12

We have identified a class of molecules, known as 2-aminothiazoles (2-ATs), as frequent-hitting fragments in biophysical binding assays. This was exemplified by 4-phenylthiazol-2-amine being identified as a hit in 14/14 screens against a diverse range of protein targets, suggesting that this scaffold is a poor starting point for fragment-based drug discovery. This prompted us to analyze this scaffold in the context of an academic fragment library used for fragment-based drug discovery (FBDD) and two larger compound libraries used for high-throughput screening (HTS). This analysis revealed that such "promiscuous 2-aminothiazoles" (PrATs) behaved as frequent hitters under both FBDD and HTS settings, although the problem was more pronounced in the fragment-based studies. As 2-ATs are present in known drugs, they cannot necessarily be deemed undesirable, but the combination of their promiscuity and difficulties associated with optimizing them into a lead compound makes them, in our opinion, poor scaffolds for fragment libraries.

Tidal instability in exoplanetary systems evolution

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Le Gal P.

2011-02-01

Full Text Available A new element is proposed to play a role in the evolution of extrasolar planetary systems: the tidal (or elliptical instability. It comes from a parametric resonance and takes place in any rotating fluid whose streamlines are (even slightly elliptically deformed. Based on theoretical, experimental and numerical works, we estimate the growth rate of the instability for hot-jupiter systems, when the rotation period of the star is known. We present the physical process, its application to stars, and preliminary results obtained on a few dozen systems, summarized in the form of a stability diagram. Most of the systems are trapped in the so-called "forbidden zone", where the instability cannot grow. In some systems, the tidal instability is able to grow, at short timescales compared to the system evolution. Implications are discussed in the framework of misaligned transiting systems, as the rotational axis of the star would be unstable in systems where this elliptical instability grows.

Self-reported knee joint instability is related to passive mechanical stiffness in medial knee osteoarthritis.

Science.gov (United States)

Creaby, Mark W; Wrigley, Tim V; Lim, Boon-Whatt; Hinman, Rana S; Bryant, Adam L; Bennell, Kim L

2013-11-20

Self-reported knee joint instability compromises function in individuals with medial knee osteoarthritis and may be related to impaired joint mechanics. The purpose of this study was to evaluate the relationship between self-reported instability and the passive varus-valgus mechanical behaviour of the medial osteoarthritis knee. Passive varus-valgus angular laxity and stiffness were assessed using a modified isokinetic dynamometer in 73 participants with medial tibiofemoral osteoarthritis. All participants self-reported the absence or presence of knee instability symptoms and the degree to which instability affected daily activity on a 6-point likert scale. Forward linear regression modelling identified a significant inverse relationship between passive mid-range knee stiffness and symptoms of knee instability (r = 0.27; P 0.05). Conceivably, a stiffer passive system may contribute toward greater joint stability during functional activities. Importantly however, net joint stiffness is influenced by both active and passive stiffness, and thus the active neuromuscular system may compensate for reduced passive stiffness in order to maintain joint stability. Future work is merited to examine the role of active stiffness in symptomatic joint stability.

Saturation of equatorial inertial instability

NARCIS (Netherlands)

Kloosterziel, R.C.; Orlandi, P.; Carnevale, G.F.

2015-01-01

Inertial instability in parallel shear flows and circular vortices in a uniformly rotating system ( $f$f-plane) redistributes absolute linear momentum or absolute angular momentum in such a way as to neutralize the instability. In previous studies we showed that, in the absence of other

Generalized laser filamentation instability coupled to cooling instability

International Nuclear Information System (INIS)

Liang, E.P.; Wong, J.; Garrison, J.

1984-01-01

We consider the propagation of laser light in an initially slightly nonuniform plasma. The classical dispersion relation for the laser filamentation growth rate (see e.g., B. Langdon, in the 1980 Lawrence Livermore National Laboratory Laser Program Annual Report, pp. 3-56, UCRL-50021-80, 1981) can be generalized to include other acoustical effects. For example, we find that the inclusion of potential imbalances in the heating and cooling rates of the ambient medium due to density and temperature perturbations can cause the laser filamentation mode to bifurcate into a cooling instability mode at long acoustic wavelengths. We also attempt to study semi-analytically the nonlinear evolution of this and related instabilities. These results have wide applications to a variety of chemical gas lasers and phenomena related to laser-target interactions (e.g., jet-like behavior)

Faraday instability on patterned surfaces

Science.gov (United States)

Feng, Jie; Rubinstein, Gregory; Jacobi, Ian; Stone, Howard

2013-11-01

We show how micro-scale surface patterning can be used to control the onset of the Faraday instability in thin liquid films. It is well known that when a liquid film on a planar substrate is subject to sufficient vibrational accelerations, the free surface destabilizes, exhibiting a family of non-linear standing waves. This instability remains a canonical problem in the study of spontaneous pattern formation, but also has practical uses. For example, the surface waves induced by the Faraday instability have been studied as a means of enhanced damping for mechanical vibrations (Genevaux et al. 2009). Also the streaming within the unstable layer has been used as a method for distributing heterogeneous cell cultures on growth medium (Takagi et al. 2002). In each of these applications, the roughness of the substrate significantly affects the unstable flow field. We consider the effect of patterned substrates on the onset and behavior of the Faraday instability over a range of pattern geometries and feature heights where the liquid layer is thicker than the pattern height. Also, we describe a physical model for the influence of patterned roughness on the destabilization of a liquid layer in order to improve the design of practical systems which exploit the Faraday instability.

Defocusing of an ion beam propagating in background plasma due to two-stream instability

Energy Technology Data Exchange (ETDEWEB)

Tokluoglu, Erinc; Kaganovich, Igor D. [Princeton Plasma Physics Laboratory, Princeton, New Jersey 08543 (United States)

2015-04-15

The current and charge neutralization of charged particle beams by background plasma enable ballistic beam propagation and have a wide range of applications in inertial fusion and high energy density physics. However, the beam-plasma interaction can result in the development of collective instabilities that may have deleterious effects on ballistic propagation of an ion beam. In the case of fast, light-ion beams, non-linear fields created by instabilities can lead to significant defocusing of the beam. We study an ion beam pulse propagating in a background plasma, which is subjected to two-stream instability between the beam ions and plasma electrons, using PIC code LSP. The defocusing effects of the instability on the beam can be much more pronounced in small radius beams. We show through simulations that a beamlet produced from an ion beam passed through an aperture can be used as a diagnostic tool to identify the presence of the two-stream instability and quantify its defocusing effects. The effect can be observed on the Neutralized Drift Compression Experiment-II facility by measuring the spot size of the extracted beamlet propagating through several meters of plasma.

Coupled-bunch instabilities in the APS ring

International Nuclear Information System (INIS)

Emery, L.

1991-01-01

A study of coupled bunch instabilities for the APS storage ring is presented. The instabilities are driven by the higher-order modes of the fifteen 352-MHz single-cell RF cavities. These modes are modeled using the 2-D cavity program URMEL. The program ZAP is then used to estimate the growth time of the instabilities for an equally-spaced bunch pattern. The cavity modes most responsible for the instabilities will be singles out for damping. 7 refs., 5 tabs

Kelvin-Helmholtz instability in solar spicules

Directory of Open Access Journals (Sweden)

H Ebadi

2016-12-01

Full Text Available Magneto hydrodynamic waves, propagating along spicules, may become unstable and the expected instability is of Kelvin-Helmholtz type. Such instability can trigger the onset of wave turbulence leading to an effective plasma heating and particle acceleration. In present study, two-dimensional magneto hydrodynamic simulations performed on a Cartesian grid is presented in spicules with different densities, moving at various speeds depending on their environment. Simulations being applied in this study show the onset of Kelvin-Helmholtz type instability and transition to turbulent flow in spicules. Development of Kelvin-Helmholtz instability leads to momentum and energy transport, dissipation, and mixing of fluids. When magnetic fields are involved, field amplification is also possible to take place

Model of oscillatory instability in vertically-homogeneous atmosphere

Directory of Open Access Journals (Sweden)

P. B. Rutkevich

2009-02-01

Full Text Available Existence and repeatability of tornadoes could be straightforwardly explained if there existed instability, responsible for their formation. However, it is well known that convection is the only instability in initially stable air, and the usual convective instability is not applicable for these phenomena. In the present paper we describe an instability in the atmosphere, which can be responsible for intense vortices. This instability appears in a fluid with Coriolis force and dissipation and has oscillatory behaviour, where the amplitude growth is accompanied by oscillations with frequency comparable to the growth rate of the instability. In the paper, both analytical analysis of the linear phase of the instability and nonlinear simulation of the developed stage of the air motion are addressed. This work was supported by the RFBR grant no. 09-05-00374-a.

Measurements of beam-ion confinement during tangential beam-driven instabilities in PBX [Princeton Beta Experiment

International Nuclear Information System (INIS)

Heidbrink, W.W.; Kaita, R.; Takahashi, H.; Gammel, G.; Hammett, G.W.; Kaye, S.

1987-01-01

During tangential injection of neutral beams into low density tokamak plasmas with β > 1% in the Princeton Beta Experiment (PBX), instabilities are observed that degrade the confinement of beam ions. Neutron, charge-exchange, and diamagnetic loop measurements are examined in order to identify the mechanism or mechanisms responsible for the beam-ion transport. The data suggest a resonant interaction between the instabilities and the parallel energetic beam ions. Evidence for some nonresonant transport also exists

Delayed chromosomal instability induced by DNA damage

International Nuclear Information System (INIS)

Morgan, W.F.; Marder, B.A.; Day, J.P.

1994-01-01

Cellular exposure to DNA damaging agents rapidly results in a dose dependent increase in chromosomal breakage and gross structural chromosomal rearrangements. Over recent years, evidence has been accumulating indicating genomic instability can manifest multiple generations after cellular exposure to physical and chemical DNA damaging agents. Genomic instability manifests in the progeny of surviving cells, and has been implicated in mutation, gene application, cellular transformation, and cell killing. To investigate chromosome instability following DNA damage, we have used fluorescence in situ hybridization to detect chromosomal rearrangements in a human/hamster somatic hybrid cell line following exposure to ionizing radiation. Delayed chromosomal instability was detected when multiple populations of uniquely arranged metaphases were observed in clonal isolates raised from single cells surviving X-irradiation many generations after exposure. At higher radiation doses, chromosomal instability was observed in a relatively high frequency of surviving clones and, in general, those clones showed delayed chromosome instability also showed reduced survival as measured by colony forming ability

Ban the Book Report: Promoting Frequent and Enthusiastic Reading

Science.gov (United States)

Foster, Graham

2012-01-01

Teachers recognize that frequent independent reading increases student knowledge on a wide range of topics, enhances vocabulary, and improves comprehension. "Ban the Book Report" inspires teachers to go beyond narrow and analytical book reports by exploring the potential of book talks, alternate book covers, identifying features of informational…

Streaming gravity mode instability

International Nuclear Information System (INIS)

Wang Shui.

1989-05-01

In this paper, we study the stability of a current sheet with a sheared flow in a gravitational field which is perpendicular to the magnetic field and plasma flow. This mixing mode caused by a combined role of the sheared flow and gravity is named the streaming gravity mode instability. The conditions of this mode instability are discussed for an ideal four-layer model in the incompressible limit. (author). 5 refs

Somatic frameshift mutations in the Bloom syndrome BLM gene are frequent in sporadic gastric carcinomas with microsatellite mutator phenotype

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Matei Irina

2001-08-01

Full Text Available Abstract Background Genomic instability has been reported at microsatellite tracts in few coding sequences. We have shown that the Bloom syndrome BLM gene may be a target of microsatelliteinstability (MSI in a short poly-adenine repeat located in its coding region. To further characterize the involvement of BLM in tumorigenesis, we have investigated mutations in nine genes containing coding microsatellites in microsatellite mutator phenotype (MMP positive and negative gastric carcinomas (GCs. Methods We analyzed 50 gastric carcinomas (GCs for mutations in the BLM poly(A tract aswell as in the coding microsatellites of the TGFβ1-RII, IGFIIR, hMSH3, hMSH6, BAX, WRN, RECQL and CBL genes. Results BLM mutations were found in 27% of MMP+ GCs (4/15 cases but not in any of the MMP negative GCs (0/35 cases. The frequency of mutations in the other eight coding regions microsatellite was the following: TGFβ1-RII (60 %, BAX (27%, hMSH6 (20%,hMSH3 (13%, CBL (13%, IGFIIR (7%, RECQL (0% and WRN (0%. Mutations in BLM appear to be more frequently associated with frameshifts in BAX and in hMSH6and/or hMSH3. Tumors with BLM alterations present a higher frequency of unstable mono- and trinucleotide repeats located in coding regions as compared with mutator phenotype tumors without BLM frameshifts. Conclusions BLM frameshifts are frequent alterations in GCs specifically associated with MMP+tumors. We suggest that BLM loss of function by MSI may increase the genetic instability of a pre-existent unstable genotype in gastric tumors.

Somatic frameshift mutations in the Bloom syndrome BLM gene are frequent in sporadic gastric carcinomas with microsatellite mutator phenotype

Science.gov (United States)

Calin, George; Ranzani, Guglielmina N; Amadori, Dino; Herlea, Vlad; Matei, Irina; Barbanti-Brodano, Giuseppe; Negrini, Massimo

2001-01-01

Background Genomic instability has been reported at microsatellite tracts in few coding sequences. We have shown that the Bloom syndrome BLM gene may be a target of microsatelliteinstability (MSI) in a short poly-adenine repeat located in its coding region. To further characterize the involvement of BLM in tumorigenesis, we have investigated mutations in nine genes containing coding microsatellites in microsatellite mutator phenotype (MMP) positive and negative gastric carcinomas (GCs). Methods We analyzed 50 gastric carcinomas (GCs) for mutations in the BLM poly(A) tract aswell as in the coding microsatellites of the TGFβ1-RII, IGFIIR, hMSH3, hMSH6, BAX, WRN, RECQL and CBL genes. Results BLM mutations were found in 27% of MMP+ GCs (4/15 cases) but not in any of the MMP negative GCs (0/35 cases). The frequency of mutations in the other eight coding regions microsatellite was the following: TGFβ1-RII (60 %), BAX (27%), hMSH6 (20%),hMSH3 (13%), CBL (13%), IGFIIR (7%), RECQL (0%) and WRN (0%). Mutations in BLM appear to be more frequently associated with frameshifts in BAX and in hMSH6and/or hMSH3. Tumors with BLM alterations present a higher frequency of unstable mono- and trinucleotide repeats located in coding regions as compared with mutator phenotype tumors without BLM frameshifts. Conclusions BLM frameshifts are frequent alterations in GCs specifically associated with MMP+tumors. We suggest that BLM loss of function by MSI may increase the genetic instability of a pre-existent unstable genotype in gastric tumors. PMID:11532193

Disruptive instabilities in the TBR-1

International Nuclear Information System (INIS)

Vannucci, A.

1987-01-01

The disruptive instabilities in the TBR-1 tokamak of the Plasma Physics Laboratory of the Institute of Physics-USP were investigated by using surface-barrier detectors and Mirnov magnetic coils, measuring soft X-ray emited by the plasma and poloidal magnetic fluctuations, respectively. Minor and major disruptions, as well sawteeth oscillations, were identified at the TBR-1 discharges, and their main characteristics were studied. Comparing the measured period of the internal disruptions (sawteeth) with the ones expected from scaling laws, good agreements is reached. The measured sawteeth crashes agree with the values expected from the Kadomtsev's model. External helical fields (CHR), corresponding to m/n=2/1 helicity were produced in order to inhibit or criate disruptive instabilities. A strong weakening of the mhd activity, present in the TBR-1 discharges, was clearly detected. The soft X-ray detection system, projected and constructed for this work, was used to obtain the electron temperatures of regions close to the center of the plasma column (T(r=0) ∼ 205 eV and T(r ± 3,8) ∼ 85 eV), using the absorbing foils method. Using the Spitzer formula, Z sub (eff) values were also obtained. (author) [pt

Midcarpal instability: a diagnostic role for dynamic ultrasound?

Science.gov (United States)

Toms, A; Chojnowski, A; Cahir, J

2009-06-01

The aim of this study was to describe the technique of dynamic ultrasound (US) examination of the triquetral clunk, and to illustrate the range of findings in four patients with midcarpal instability (MCI). Four patients were identified (3 men, 1 woman). The case notes, plain radiographs, MRI and dynamic US for each patient were reviewed. Digital video files recording the dynamic US of the triquetral clunks were analysed for the following features of abnormal triquetral mobility: direction and speed of triquetral snap, amount of anteroposterior translocation, and flexion or extension during the snap. Five different triquetral clunks were recorded in 4 patients. In four out of five cases the clunk occurred during ulnar translocation of the wrist, and in one during radial translocation. Anteroposterior translocation was anterior (3.4 - 4.7 mm) in three of the clunks and posterior (1 - 10 mm) in two. The degree of flexion or extension varied between 1 and 16 degrees . The snapping phase of the clunk lasted between 0.17 and 0.25 seconds. Dynamic US can be used to confirm the diagnosis of midcarpal instability by identifying a triquetral catch-up clunk. Quantification of carpal mobility with US may lead to further insights into the mechanics of MCI.

Electrothermal instability growth in magnetically driven pulsed power liners

International Nuclear Information System (INIS)

Peterson, Kyle J.; Sinars, Daniel B.; Yu, Edmund P.; Herrmann, Mark C.; Cuneo, Michael E.; Slutz, Stephen A.; Smith, Ian C.; Atherton, Briggs W.; Knudson, Marcus D.; Nakhleh, Charles

2012-01-01

This paper explores the role of electro-thermal instabilities on the dynamics of magnetically accelerated implosion systems. Electro-thermal instabilities result from non-uniform heating due to temperature dependence in the conductivity of a material. Comparatively little is known about these types of instabilities compared to the well known Magneto-Rayleigh-Taylor (MRT) instability. We present simulations that show electrothermal instabilities form immediately after the surface material of a conductor melts and can act as a significant seed to subsequent MRT instability growth. We also present the results of several experiments performed on Sandia National Laboratories Z accelerator to investigate signatures of electrothermal instability growth on well characterized initially solid aluminum and copper rods driven with a 20 MA, 100 ns risetime current pulse. These experiments show excellent agreement with electrothermal instability simulations and exhibit larger instability growth than can be explained by MRT theory alone.

Imaging findings in posterior instability of the shoulder

International Nuclear Information System (INIS)

Harish, Srinivasan; Rebello, Ryan; O'Neill, John; Nagar, Arpit; Moro, Jaydeep; Pugh, David

2008-01-01

Posterior shoulder instability refers to the symptoms and signs resulting from excessive posterior translation of the humerus. Magnetic resonance (MR) imaging is the radiological modality of choice in the diagnostic assessment of posterior instability. Computed tomography (CT) is useful in the evaluation of osseous abnormalities associated with posterior instability. A detailed description of the posterior osseous and labroligamentous abnormalities has evolved recently, and many variant lesions of the posteroinferior labrum and/or capsular structures have been described. As the recommended surgical management of lesions associated with posterior instability is a lesion-specific approach, awareness of the specific lesions that have been described in association with posterior instability helps in pre-surgical planning. The purpose of this article is to review the classification of, and injury mechanisms leading to, posterior shoulder instability and to describe imaging findings associated with posterior instability, with emphasis on MR imaging. (orig.)

Imaging findings in posterior instability of the shoulder

Energy Technology Data Exchange (ETDEWEB)

Harish, Srinivasan; Rebello, Ryan; O' Neill, John [St. Joseph' s Healthcare, Department of Diagnostic Imaging, Hamilton, ON (Canada); McMaster University, Faculty of Health Sciences, Hamilton (Canada); Nagar, Arpit [St. Joseph' s Healthcare, Department of Diagnostic Imaging, Hamilton, ON (Canada); Moro, Jaydeep [St. Joseph' s Healthcare, Department of Orthopedic Surgery, Hamilton, ON (Canada); McMaster University, Faculty of Health Sciences, Hamilton (Canada); Pugh, David [Brantford General Hospital, Department of Orthopedic Surgery, Brantford, ON (Canada)

2008-08-15

Posterior shoulder instability refers to the symptoms and signs resulting from excessive posterior translation of the humerus. Magnetic resonance (MR) imaging is the radiological modality of choice in the diagnostic assessment of posterior instability. Computed tomography (CT) is useful in the evaluation of osseous abnormalities associated with posterior instability. A detailed description of the posterior osseous and labroligamentous abnormalities has evolved recently, and many variant lesions of the posteroinferior labrum and/or capsular structures have been described. As the recommended surgical management of lesions associated with posterior instability is a lesion-specific approach, awareness of the specific lesions that have been described in association with posterior instability helps in pre-surgical planning. The purpose of this article is to review the classification of, and injury mechanisms leading to, posterior shoulder instability and to describe imaging findings associated with posterior instability, with emphasis on MR imaging. (orig.)

Cultural diversity, economic development and societal instability

Science.gov (United States)

Nettle, D.; Grace, J.B.; Choisy, M.; Cornell, H.V.; Guegan, J.-F.; Hochberg, M.E.

2007-01-01

Background. Social scientists have suggested that cultural diversity in a nation leads to societal instability. However, societal instability may be affected not only by within-nation on ?? diversity, but also diversity between a nation and its neighbours or ?? diversity. It is also necessary to distinguish different domains of diversity, namely linguistic, ethnic and religious, and to distinguish between the direct effects of diversity on societal instability, and effects that are mediated by economic conditions. Methodology/Principal Findings. We assembled a large cross-national dataset with information on ?? and ?? cultural diversity, economic conditions, and indices of societal instability. Structural equation modeling was used to evaluate the direct and indirect effects of cultural diversity on economics and societal stability. Results show that different type and domains of diversity have interacting effects. As previously documented, linguistic ?? diversity has a negative effect on economic performance, and we show that it is largely through this economic mechanism that it affects societal instability. For ?? diversity, the higher the linguistic diversity among nations in a region, the less stable the nation. But, religious ?? diversity has the opposite effect, reducing instability, particularly in the presence of high linguistic diversity. Conclusions. Within-nation linguistic diversity is associated with reduced economic performance, which, in turn, increases societal instability. Nations which differ linguistically from their neighbors are also less stable. However, religious diversity between, neighboring nations has the opposite effect, decreasing societal instability.

Cultural diversity, economic development and societal instability.

Science.gov (United States)

Nettle, Daniel; Grace, James B; Choisy, Marc; Cornell, Howard V; Guégan, Jean-François; Hochberg, Michael E

2007-09-26

Social scientists have suggested that cultural diversity in a nation leads to societal instability. However, societal instability may be affected not only by within-nation or alpha diversity, but also diversity between a nation and its neighbours or beta diversity. It is also necessary to distinguish different domains of diversity, namely linguistic, ethnic and religious, and to distinguish between the direct effects of diversity on societal instability, and effects that are mediated by economic conditions. We assembled a large cross-national dataset with information on alpha and beta cultural diversity, economic conditions, and indices of societal instability. Structural equation modeling was used to evaluate the direct and indirect effects of cultural diversity on economics and societal stability. Results show that different types and domains of diversity have interacting effects. As previously documented, linguistic alpha diversity has a negative effect on economic performance, and we show that it is largely through this economic mechanism that it affects societal instability. For beta diversity, the higher the linguistic diversity among nations in a region, the less stable the nation. But, religious beta diversity has the opposite effect, reducing instability, particularly in the presence of high linguistic diversity. Within-nation linguistic diversity is associated with reduced economic performance, which, in turn, increases societal instability. Nations which differ linguistically from their neighbors are also less stable. However, religious diversity between neighboring nations has the opposite effect, decreasing societal instability.

Fingerprints of dynamical instabilities

International Nuclear Information System (INIS)

Chomaz, Ph.; Colonna, M.; Guarnera, A.

1993-01-01

It is explained why any reduced descriptions, such as mean field approximation, are stochastic in nature. It is shown that the introduction of this stochastic dynamics leads to a predictive theory in a statistical sens whatever the individual trajectories are characterized by the occurrence of bifurcations, instabilities or phase transitions. Concerning nuclear matter, the spinodal instability is discussed. In such a critical situation, the possibility to replace the stochastic part of the collision integral in the Boltzmann-Langevin model by the numerical noise associated with the finite number of test particles in ordinary BUU treatment is studied. It is shown that the fingerprints of these instabilities are kept during the evolution because of the relatively long recombination time compared with the typical time scales imposed by the Coulomb repulsion and the possible collective expansion. (author) 5 refs., 12 figs

Electromagnetic theory of the radiative Pierce instability

International Nuclear Information System (INIS)

Klochkov, D.N.; Rukhadze, A.A.

1997-01-01

The radiative Pierce instability of a relativistic electron beam in a waveguide stabilized by an infinite strong magnetic field is considered. the increment and conditions for instability development in a wide interval of the beam currents are determined on the basis of the perturbation theory. It is shown that the instability has always the Raman character and is threshold less in current for the Pierce boundary conditions. It permits sufficiently strictly to define the instability saturation level from breaking the resonance condition and to estimate the radiation efficiency

D branes in background fluxes and Nielsen-Olesen instabilities

International Nuclear Information System (INIS)

Russo, Jorge G.

2016-01-01

In quantum field theory, charged particles with spin ≥1 may become tachyonic in the present of magnetic fluxes above some critical field, signaling an instability of the vacuum. The phenomenon is generic, in particular, similar instabilities are known to exist in open and closed string theory, where a spinning string state can become tachyonic above a critical field. In compactifications involving RR fluxes F_p_+_2, the quantum states which could become tachyonic by the same Nielsen-Olesen mechanism are Dp branes. By constructing an appropriate background with RR magnetic flux that takes into account back-reaction, we identify the possible tachyonic Dp brane states and compute the formula for the energy spectrum in a sector. More generally, we argue that in any background RR magnetic flux, there are high spin Dp quantum states which become very light at critical fields.

D branes in background fluxes and Nielsen-Olesen instabilities

Energy Technology Data Exchange (ETDEWEB)

Russo, Jorge G. [Institució Catalana de Recerca i Estudis Avançats (ICREA),Pg. Lluis Companys, 23, 08010 Barcelona (Spain); Department de Fisica Cuantica i Astrofisica and Institut de Ciències del Cosmos,Universitat de Barcelona, Martí Franquès, 1, 08028 Barcelona (Spain)

2016-06-06

In quantum field theory, charged particles with spin ≥1 may become tachyonic in the present of magnetic fluxes above some critical field, signaling an instability of the vacuum. The phenomenon is generic, in particular, similar instabilities are known to exist in open and closed string theory, where a spinning string state can become tachyonic above a critical field. In compactifications involving RR fluxes F{sub p+2}, the quantum states which could become tachyonic by the same Nielsen-Olesen mechanism are Dp branes. By constructing an appropriate background with RR magnetic flux that takes into account back-reaction, we identify the possible tachyonic Dp brane states and compute the formula for the energy spectrum in a sector. More generally, we argue that in any background RR magnetic flux, there are high spin Dp quantum states which become very light at critical fields.

Size effects on cavitation instabilities

DEFF Research Database (Denmark)

Niordson, Christian Frithiof; Tvergaard, Viggo

2006-01-01

growth is here analyzed for such cases. A finite strain generalization of a higher order strain gradient plasticity theory is applied for a power-law hardening material, and the numerical analyses are carried out for an axisymmetric unit cell containing a spherical void. In the range of high stress...... triaxiality, where cavitation instabilities are predicted by conventional plasticity theory, such instabilities are also found for the nonlocal theory, but the effects of gradient hardening delay the onset of the instability. Furthermore, in some cases the cavitation stress reaches a maximum and then decays...... as the void grows to a size well above the characteristic material length....

Upper Extremity Injured Workers Stratified by Current Work Status: An Examination of Health Characteristics, Work Limitations and Work Instability

Directory of Open Access Journals (Sweden)

D Pichora

2010-06-01

Full Text Available Background: Upper extremity injured workers are an under-studied population. A descriptive comparison of workers with shoulder, elbow and hand injuries reporting to a Canadian Workplace Safety and Insurance Board (WSIB clinic was undertaken. Objective: To determine if differences existed between injury groups stratified by current work status. Methods: All WSIB claimants reporting to our upper extremity clinic between 2003 and 2008 were approached to participate in this descriptive study. 314 working and 146 non-working WSIB claimants completed the Disabilities of the Arm, Shoulder and Hand questionnaire (DASH; Short Form health survey (SF36; Worker’s Limitations Questionnaire and the Work Instability Scale. Various parametric and non-parametric analyses were used to assess significant differences between groups on demographic, work and health related variables. Results: Hand, followed by the shoulder and elbow were the most common site of injury. Most non-workers listed their current injury as the reason for being off work, and attempted to return to work once since their injury occurrence. Non-workers and a subset of workers at high risk for work loss showed significantly worse mental functioning. Workers identified physical demands as the most frequent injury-related on the job limitation. 60% of current workers were listed as low risk for work loss on the Work Instability Scale. Conclusions: Poorer mental functioning, being female and sustaining a shoulder injury were risk factors for work instability. Our cohort of injured non-workers were unable to return to work due to their current injury, reinforcing the need to advocate for modified duties, shorter hours and a work environment where stress and injury recurrence is reduced. Future studies examining pre-injury depression as a risk factor for prolonged work absences are warranted.

Compensation of longitudinal coupled-bunch instability in the advanced photon source storage ring

International Nuclear Information System (INIS)

Harkay, K.C.; Nassiri, A.; Song, J.J.; Kang, Y.W.; Kustom, R.L.

1997-01-01

A longitudinal couple-bunch (CB) instability was encountered in the 7-GeV storage ring. This instability was found to depend on the bunch fill pattern as well as on the beam intensity. The beam spectrum exhibited a coupled-bunch signature, which could be reproduced by an analytical model. The oscillations were also observed on a horizontal photon monitor. The beam fluctuations exhibited two periodicities, which were found to be correlated with the rf cavity temperatures. This correlation is consistent with the measured temperature dependence of the higher-order mode (HOM) frequencies. The HOM impedance drives the beam when brought into resonance with the CB mode by the temperature variation. Increasing the inlet cavity water temperature suppressed the instability. The experimental results are compared to an analytical model which characterizes the fill-pattern dependence. Studies to identify the offending HOMs are also presented

Investigation of global Alfven instabilities in TFTR

International Nuclear Information System (INIS)

Wong, K.L.; Paul, S.F.; Fredrickson, E.D.; Nazikian, R.; Park, H.K.; Bell, M.; Bretz, N.L.; Budny, R.; Cheng, C.Z.; Cohen, S.; Hammett, G.W.; Jobes, F.C.; Johnson, L.; Meade, D.M.; Medley, S.S.; Mueller, D.; Nagayama, Y.; Owens, D.K.; Synakowski, E.J.; Roberts, D.R.; Sabbagh, S.

1992-01-01

Toroidal Alfven Eigenmodes (TAE) were excited by the energetic neutral beam ions tangentially injected into TFTR plasmas at low magnetic field such that the injection velocities were comparable to the Alfven speed. The modes were identified by measurements from Mirnov coils and beam emission spectroscopy (BES). TAE modes appear in bursts whose repetition rate increases with beam power. The neutron emission rate exhibits sawtooth-like behavior and the crashes always coincide with TAE bursts. This indicates ejection of fast ions from the plasma until these modes are stabilized. The dynamics of growth and stabilization was investigated at various plasma current and magnetic field. The results indicate that the instability can effectively clamp the number of energetic ions in the plasma. The observed instability threshold is discussed in the light of recent theories. In addition to these TAE modes, intermittent oscillations at three times the fundamental TAE frequency were observed by Mirnov coils, but no corresponding signal was found in BES. It appears that these high frequency oscillations do not have direct effect on the plasma neutron source strength

Treatment of the subject of tearing instability

International Nuclear Information System (INIS)

Paris, P.C.

1977-07-01

A simple approach is taken to the mechanics of potential instability associated with the steady tearing portion of J-Integral R-curves. The analysis is developed from simple examples of structural component (or test specimen) configurations with cracks, examining their instability possibilities individually, in order to draw more general conclusions about elastic-plastic cracking instability as contrasted to linear-elastic behavior. Finally, an attempt is made to model a more local cleavage-like instability for material in the fracture process zone just ahead of a crack tip. Results are then presented of a testing program which clearly demonstrates the appropriateness of the tearing instability analysis and which illustrates its broad potential for future application, as well as presenting guidelines for its further development. The material selected for analysis was Ni-Cr-Mo-V rotor steel

Understanding Etna flank instability through numerical models

Science.gov (United States)

Apuani, Tiziana; Corazzato, Claudia; Merri, Andrea; Tibaldi, Alessandro

2013-02-01

As many active volcanoes, Mount Etna shows clear evidence of flank instability, and different mechanisms were suggested to explain this flank dynamics, based on the recorded deformation pattern and character. Shallow and deep deformations, mainly associated with both eruptive and seismic events, are concentrated along recognised fracture and fault systems, mobilising the eastern and south-eastern flank of the volcano. Several interacting causes were postulated to control the phenomenon, including gravity force, magma ascent along the feeding system, and a very complex local and/or regional tectonic activity. Nevertheless, the complexity of such dynamics is still an open subject of research and being the volcano flanks heavily urbanised, the comprehension of the gravitative dynamics is a major issue for public safety and civil protection. The present research explores the effects of the main geological features (in particular the role of the subetnean clays, interposed between the Apennine-Maghrebian flysch and the volcanic products) and the role of weakness zones, identified by fracture and fault systems, on the slope instability process. The effects of magma intrusions are also investigated. The problem is addressed by integrating field data, laboratory tests and numerical modelling. A bi- and tri-dimensional stress-strain analysis was performed by a finite difference numerical code (FLAC and FLAC3D), mainly aimed at evaluating the relationship among geological features, volcano-tectonic structures and magmatic activity in controlling the deformation processes. The analyses are well supported by dedicated structural-mechanical field surveys, which allowed to estimate the rock mass strength and deformability parameters. To take into account the uncertainties which inevitably occur in a so complicated model, many efforts were done in performing a sensitivity analysis along a WNW-ESE section crossing the volcano summit and the Valle del Bove depression. This was

Surface instabilities in shock loaded granular media

Science.gov (United States)

Kandan, K.; Khaderi, S. N.; Wadley, H. N. G.; Deshpande, V. S.

2017-12-01

The initiation and growth of instabilities in granular materials loaded by air shock waves are investigated via shock-tube experiments and numerical calculations. Three types of granular media, dry sand, water-saturated sand and a granular solid comprising PTFE spheres were experimentally investigated by air shock loading slugs of these materials in a transparent shock tube. Under all shock pressures considered here, the free-standing dry sand slugs remained stable while the shock loaded surface of the water-saturated sand slug became unstable resulting in mixing of the shocked air and the granular material. By contrast, the PTFE slugs were stable at low pressures but displayed instabilities similar to the water-saturated sand slugs at higher shock pressures. The distal surfaces of the slugs remained stable under all conditions considered here. Eulerian fluid/solid interaction calculations, with the granular material modelled as a Drucker-Prager solid, reproduced the onset of the instabilities as seen in the experiments to a high level of accuracy. These calculations showed that the shock pressures to initiate instabilities increased with increasing material friction and decreasing yield strain. Moreover, the high Atwood number for this problem implied that fluid/solid interaction effects were small, and the initiation of the instability is adequately captured by directly applying a pressure on the slug surface. Lagrangian calculations with the directly applied pressures demonstrated that the instability was caused by spatial pressure gradients created by initial surface perturbations. Surface instabilities are also shown to exist in shock loaded rear-supported granular slugs: these experiments and calculations are used to infer the velocity that free-standing slugs need to acquire to initiate instabilities on their front surfaces. The results presented here, while in an idealised one-dimensional setting, provide physical understanding of the conditions required to

Casimir effect and thermodynamics of horizon instabilities

International Nuclear Information System (INIS)

Hartnoll, Sean A.

2004-01-01

We propose a dual thermodynamic description of a classical instability of generalized black hole spacetimes. From a thermodynamic perspective, the instability is due to negative compressibility in regions where the Casimir pressure is large. The argument indicates how the correspondence between thermodynamic and classical instability for horizons may be extended to cases without translational invariance

Prevalence of knee instability in relation to sports activity

DEFF Research Database (Denmark)

Hahn, Thomas; Foldspang, Anders; Hansen, Thorsten Ingemann

2001-01-01

to be positively associated with female gender and different features of occupational work. In conclusion, knee instability is a commonly reported phenomenon among active athletes. It was found to be independent of the type and the amount of sports activity but highly dependent on female gender, type and amount......The objective was to estimate the prevalence of knee instability among active athletes and to investigate potential associations to type, amount and duration of sports participation. Based on a questionnaire, 339 athletes provided information about different features of occupation, sports activity...... and knee instability. The 12-month period prevalence of knee instability and constant or recurrent knee instability, and absence from sport and absence from work due to knee instability, was 22%, 14%, 5% and 1%, respectively. Knee instability as such, and constant or recurrent knee instability were found...

Conservation laws in baroclinic inertial-symmetric instabilities

Science.gov (United States)

Grisouard, Nicolas; Fox, Morgan B.; Nijjer, Japinder

2017-04-01

Submesoscale oceanic density fronts are structures in geostrophic and hydrostatic balance, but are more prone to instabilities than mesoscale flows. As a consequence, they are believed to play a large role in air-sea exchanges, near-surface turbulence and dissipation of kinetic energy of geostrophically and hydrostatically balanced flows. We will present two-dimensional (x, z) Boussinesq numerical experiments of submesoscale baroclinic fronts on the f-plane. Instabilities of the mixed inertial and symmetric types (the actual name varies across the literature) develop, with the absence of along-front variations prohibiting geostrophic baroclinic instabilities. Two new salient facts emerge. First, contrary to pure inertial and/or pure symmetric instability, the potential energy budget is affected, the mixed instability extracting significant available potential energy from the front and dissipating it locally. Second, in the submesoscale regime, the growth rate of this mixed instability is sufficiently large that significant radiation of near-inertial internal waves occurs. Although energetically small compared to e.g. local dissipation within the front, this process might be a significant source of near-inertial energy in the ocean.

Two-phase flow instability and propagation of disturbances

International Nuclear Information System (INIS)

Yadigaroglu, G.

1984-01-01

Various mechanisms of static and dynamic macroinstabilities, appearing in two-phase flows, have been considered. Types of instabilities, conditioned by the form of hydraulic characteristics of the channel and density waves are analyzed in detail. Problems of instabilities in nuclear reactor circuits, in particular problems of instabilities, conditioned by water and steam mixing and vapour condensation, and problems of steam generator operation instability are discussed

Simulations relevant to the beam instability in the foreshock

Science.gov (United States)

Cairns, I. H.; Nishikawa, K.-I.

1989-01-01

The results presently obtained from two-dimensional simulations of the reactive instability for Maxwellian beams and cutoff distributions are noted to be consistent with recent suggestions that electrons backstreaming into earth's foreshock have steep-sided cutoff distributions, which are initially unstable to the reactive instability, and that the back-reaction to the wave growth causes the instability to pass into its kinetic phase. It is demonstrated that the reactive instability is a bunching instability, and that the reactive instability saturates and passes over into the kinetic phase by particle trapping.

Off-equatorial current-driven instabilities ahead of approaching dipolarization fronts

Science.gov (United States)

Zhang, Xu; Angelopoulos, V.; Pritchett, P. L.; Liu, Jiang

2017-05-01

Recent kinetic simulations have revealed that electromagnetic instabilities near the ion gyrofrequency and slightly away from the equatorial plane can be driven by a current parallel to the magnetic field prior to the arrival of dipolarization fronts. Such instabilities are important because of their potential contribution to global electromagnetic energy conversion near dipolarization fronts. Of the several instabilities that may be consistent with such waves, the most notable are the current-driven electromagnetic ion cyclotron instability and the current-driven kink-like instability. To confirm the existence and characteristics of these instabilities, we used observations by two Time History of Events and Macroscale Interactions during Substorms satellites, one near the neutral sheet observing dipolarization fronts and the other at the boundary layer observing precursor waves and currents. We found that such instabilities with monochromatic signatures are rare, but one of the few cases was selected for further study. Two different instabilities, one at about 0.3 Hz and the other at a much lower frequency, 0.02 Hz, were seen in the data from the off-equatorial spacecraft. A parallel current attributed to an electron beam coexisted with the waves. Our instability analysis attributes the higher-frequency instability to a current-driven ion cyclotron instability and the lower frequency instability to a kink-like instability. The current-driven kink-like instability we observed is consistent with the instabilities observed in the simulation. We suggest that the currents needed to excite these low-frequency instabilities are so intense that the associated electron beams are easily thermalized and hence difficult to observe.

High-resolution MR imaging of glenohumeral instability lesions

International Nuclear Information System (INIS)

Rafii, M.; Firooznia, H.; Sherman, O.; Minkoff, J.; Sherman, M.; Golimbu, C.

1991-01-01

This paper determines the accuracy of conventual MR imaging in the diagnosis of glenohumeral instabilities and evaluates various pathologic aspects of these lesions. Records were reviewed in 80 consecutive patients with known or suspected instability who underwent MR imaging. The routine shoulder protocol included a proton density- or T2-weighted sequence. Surgical correlation was available in 31 cases. Diagnosis of glenohumeral instability was based on the presence of a combination of findings of appropriately located tear, osseous abnormality of glenoid margin, capsular abnormalities and Hill-Sachs deformity. In 28 surgically correlated patients with glenohumeral instability an accurate diagnosis was made in all but 1 case of posterior instability. A false diagnosis of instability was suggested in 3 cases by signal abnormality of the labrum and/or a prominent capsule

Population genetic structure of a centipede species with high levels of developmental instability.

Directory of Open Access Journals (Sweden)

Giuseppe Fusco

Full Text Available European populations of the geophilomorph centipede Haplophilus subterraneus show a high proportion of individuals with morphological anomalies, suggesting high levels of developmental instability. The broad geographic distribution of this phenomenon seems to exclude local environmental causes, but the source of instability is still to be identified. The goal of the present study was to collect quantitative data on the occurrence of phenodeviants in different populations, along with data on the patterns of genetic variation within and between populations, in order to investigate possible association between developmental instability and genetic features. In a sample of 11 populations of H. subterraneus, distributed in western and central Europe, we looked for phenodeviants, in particular with respect to trunk morphology, and studied genetic variation through the genotyping of microsatellite loci. Overall, no support was found to the idea that developmental instability in H. subterraneus is related to a specific patterns of genetic variation, including inbreeding estimates. We identified a major genetic partition that subdivides French populations from the others, and a low divergence among northwestern areas, which are possibly related to the post-glacial recolonization from southern refugia and/or to recent anthropogenic soil displacements. A weak correlation between individual number of leg bearing segments and the occurrence of trunk anomalies seems to support a trade-off between these two developmental traits. These results, complemented by preliminary data on developmental stability in two related species, suggest that the phenomenon has not a simple taxonomic distribution, while it exhibits an apparent localization in central and eastern Europe.

The Growth Effects of Institutional Instability

DEFF Research Database (Denmark)

Berggren, Niclas; Bergh, Andreas; Bjørnskov, Christian

 Both institutional quality and institutional stability have been argued to stimulate economic growth. But to improve institutional quality, a country must endure a period of institutional change, which implies at least a little and possibly a lot of institutional instability. We investigate...... the growth effects of institutional quality and instability, using the political risk index from the ICRG in a cross-country study of 132 countries, measuring instability as the coefficient of variation. Using the aggregate index, we find evidence that institutional quality is positively linked to growth....... While institutional instability is negatively related to growth in the baseline case, there are indications that the effect can be positive in rich countries, suggesting that institutional reform is not necessarily costly even during a transition period. Sensitivity analysis, e.g., decomposing...

Designing services for frequent attenders to the emergency department: a characterisation of this population to inform service design.

Science.gov (United States)

Jacob, Rebecca; Wong, Mai Luen; Hayhurst, Catherine; Watson, Peter; Morrison, Cecily

2016-08-01

Frequent attendance to the emergency department (ED) is a growing public health concern. Designing services for frequent attenders poses challenges, given the heterogeneous nature of this group. This was a two-part observational study identifying frequent attenders from ED records. The first stage studied trends and developed personas with emphasis on differentiating moderate frequent attenders (attending between 5 and 20 times per year) and extreme frequent attenders (attending more than 20 times). Stage 2 included a case note review of 100 consecutive frequent attenders. Results showed an increase in frequent attendance from 2.59% to 4.12% over 8 years. Moderate frequent attenders accounted for 97%. Of the 100 frequent attenders studied, 45% had medically unexplained symptoms (MUS), associated with younger age (p0.05). In conclusion, the ED is a useful hub for identifying frequent attenders with MUS, particularly among moderate frequent attenders; service design for this group should consider a 'whole-systems approach' with integration between primary and secondary care, including specialist liaison psychiatry services where appropriate. © 2016 Royal College of Physicians.

Telomere dysfunction and chromosome instability

Energy Technology Data Exchange (ETDEWEB)

Murnane, John P., E-mail: jmurnane@radonc.ucsf.edu [Department of Radiation Oncology, University of California San Francisco, 2340 Sutter Street, San Francisco, CA 94143-1331 (United States)

2012-02-01

The ends of chromosomes are composed of a short repeat sequence and associated proteins that together form a cap, called a telomere, that keeps the ends from appearing as double-strand breaks (DSBs) and prevents chromosome fusion. The loss of telomeric repeat sequences or deficiencies in telomeric proteins can result in chromosome fusion and lead to chromosome instability. The similarity between chromosome rearrangements resulting from telomere loss and those found in cancer cells implicates telomere loss as an important mechanism for the chromosome instability contributing to human cancer. Telomere loss in cancer cells can occur through gradual shortening due to insufficient telomerase, the protein that maintains telomeres. However, cancer cells often have a high rate of spontaneous telomere loss despite the expression of telomerase, which has been proposed to result from a combination of oncogene-mediated replication stress and a deficiency in DSB repair in telomeric regions. Chromosome fusion in mammalian cells primarily involves nonhomologous end joining (NHEJ), which is the major form of DSB repair. Chromosome fusion initiates chromosome instability involving breakage-fusion-bridge (B/F/B) cycles, in which dicentric chromosomes form bridges and break as the cell attempts to divide, repeating the process in subsequent cell cycles. Fusion between sister chromatids results in large inverted repeats on the end of the chromosome, which amplify further following additional B/F/B cycles. B/F/B cycles continue until the chromosome acquires a new telomere, most often by translocation of the end of another chromosome. The instability is not confined to a chromosome that loses its telomere, because the instability is transferred to the chromosome donating a translocation. Moreover, the amplified regions are unstable and form extrachromosomal DNA that can reintegrate at new locations. Knowledge concerning the factors promoting telomere loss and its consequences is

Diffusive instabilities in hyperbolic reaction-diffusion equations

Science.gov (United States)

Zemskov, Evgeny P.; Horsthemke, Werner

2016-03-01

We investigate two-variable reaction-diffusion systems of the hyperbolic type. A linear stability analysis is performed, and the conditions for diffusion-driven instabilities are derived. Two basic types of eigenvalues, real and complex, are described. Dispersion curves for both types of eigenvalues are plotted and their behavior is analyzed. The real case is related to the Turing instability, and the complex one corresponds to the wave instability. We emphasize the interesting feature that the wave instability in the hyperbolic equations occurs in two-variable systems, whereas in the parabolic case one needs three reaction-diffusion equations.

Systems and methods for controlling flame instability

KAUST Repository

Cha, Min Suk

2016-07-21

A system (62) for controlling flame instability comprising: a nozzle (66) coupled to a fuel supply line (70), an insulation housing (74) coupled to the nozzle, a combustor (78) coupled to the nozzle via the insulation housing, where the combustor is grounded (80), a pressure sensor (82) coupled to the combustor and configured to detect pressure in the combustor, and an instability controlling assembly coupled to the pressure sensor and to an alternating current power supply (86), where, the instability controlling assembly can control flame instability of a flame in the system based on pressure detected by the pressure sensor.

Effects of visual feedback balance training on the balance and ankle instability in adult men with functional ankle instability.

Science.gov (United States)

Nam, Seung-Min; Kim, Kyoung; Lee, Do Youn

2018-01-01

[Purpose] This study examined the effects of visual feedback balance training on the balance and ankle instability in adult men with functional ankle instability. [Subjects and Methods] Twenty eight adults with functional ankle instability, divided randomly into an experimental group, which performed visual feedback balance training for 20 minutes and ankle joint exercises for 10 minutes, and a control group, which performed ankle joint exercise for 30 minutes. Exercises were completed three times a week for 8 weeks. Bio rescue was used for balance ability. It measured limit of stability at one minute. For ankle instability was measured using Cumberland ankle instability tool (CAIT). This measure was performed before and after the experiments in each group. [Results] The experimental group had significant increase in the Limit of Stability and CAIT score. The control group had significant increase in CAIT score. While the Limit of Stability increased without significance. [Conclusion] In conclusion, visual feedback balance training can be recommended as a treatment method for patients with functional ankle instability.

Faraday instability in deformable domains

International Nuclear Information System (INIS)

Pucci, G.

2013-01-01

Hydrodynamical instabilities are usually studied either in bounded regions or free to grow in space. In this article we review the experimental results of an intermediate situation, in which an instability develops in deformable domains. The Faraday instability, which consists in the formation of surface waves on a liquid experiencing a vertical forcing, is triggered in floating liquid lenses playing the role of deformable domains. Faraday waves deform the lenses from the initial circular shape and the mutual adaptation of instability patterns with the lens boundary is observed. Two archetypes of behaviour have been found. In the first archetype a stable elongated shape is reached, the wave vector being parallel to the direction of elongation. In the second archetype the waves exceed the response of the lens border and no equilibrium shape is reached. The lens stretches and eventually breaks into fragments that have a complex dynamics. The difference between the two archetypes is explained by the competition between the radiation pressure the waves exert on the lens border and its response due to surface tension.

Lending sociodynamics and economic instability

Science.gov (United States)

Hawkins, Raymond J.

2011-11-01

We show how the dynamics of economic instability and financial crises articulated by Keynes in the General Theory and developed by Minsky as the Financial Instability Hypothesis can be formalized using Weidlich’s sociodynamics of opinion formation. The model addresses both the lending sentiment of a lender in isolation as well as the impact on that lending sentiment of the behavior of other lenders. The risk associated with lending is incorporated through a stochastic treatment of loan dynamics that treats prepayment and default as competing risks. With this model we are able to generate endogenously the rapid changes in lending opinion that attend slow changes in lending profitability and find these dynamics to be consistent with the rise and collapse of the non-Agency mortgage-backed securities market in 2007/2008. As the parameters of this model correspond to well-known phenomena in cognitive and social psychology, we can both explain why economic instability has proved robust to advances in risk measurement and suggest how policy for reducing economic instability might be formulated in an experimentally sound manner.

Risk Factors for the Postoperative Recurrence of Instability After Arthroscopic Bankart Repair in Athletes.

Science.gov (United States)

Nakagawa, Shigeto; Mae, Tatsuo; Sato, Seira; Okimura, Shinichiro; Kuroda, Miki

2017-09-01

Several risk factors for the postoperative recurrence of instability after arthroscopic Bankart repair have been reported, but there have been few detailed investigations of the specific risk factors in relation to the type of sport. This study investigated the postoperative recurrence of instability after arthroscopic Bankart repair without additional reinforcement procedures in competitive athletes, including athletes with a large glenoid defect. The purpose of this study was to investigate risk factors related to the postoperative recurrence of instability in athletes. Case-control study; Level of evidence, 3. A total of 115 athletes (123 shoulders) were classified into 5 groups according to type of sport: rugby (41 shoulders), American football (32 shoulders), other collision sports (18 shoulders), contact sports (15 shoulders), and overhead sports (17 shoulders). First, the recurrence rate in each sporting category was investigated, with 113 shoulders followed up for a minimum of 2 years. Then, factors related to postoperative recurrence were investigated in relation to the type of sport. Postoperative recurrence of instability was noted in 23 of 113 shoulders (20.4%). The recurrence rate was 33.3% in rugby, 17.2% in American football, 11.1% in other collision sports, 14.3% in contact sports, and 12.5% in overhead sports. The most frequent cause of recurrence was tackling, and recurrence occurred with tackling in 12 of 16 athletes playing rugby or American football. Reoperation was completed in 11 shoulders. By univariate analysis, significant risk factors for postoperative recurrence of instability included playing rugby, age between 10 and 19 years at surgery, preoperative glenoid defect, small bone fragment of bony Bankart lesion, and capsular tear. However, by multivariate analysis, the most significant factor was not the type of sport but younger age at operation and a preoperative glenoid defect with small or no bone fragment. Compared with the other

The large density electron beam-plasma Buneman instability

International Nuclear Information System (INIS)

Mantei, T.D.; Doveil, F.; Gresillon, D.

1976-01-01

The threshold conditions and growth rate of the Buneman (electron beam-stationary ion) instability are calculated with kinetic theory, including a stationary electronic population. A criteria on the wave energy sign is used to separate the Buneman hydrodynamic instability from the ion-acoustic kinetic instability. The stationary electron population raises the instability threshold and, for large beam velocities yields a maximum growth rate oblique to the beam. (author)

Resistive hose instability in the Bennet beam

International Nuclear Information System (INIS)

Nadezhdin, E.R.; Sorokin, G.A.

1983-01-01

Development of resistive hose instability of a relativistic electron beam with the Bennet current density distribution in a homogeneous unlimited plasma in the range of a high, 4πσ 0 a/c >> 1, and a low, 4πσ 0 a/c 0 =conductivity, c=light velocity, a = equilibrium beam radius) has been cansidered. Spatial and temporal increments of the instability development are calculated. In both cases the instability is of a convective nature. At 4πσ 0 a/c >> 1 the instability is shifted to the region of low frequencies as compared with the previously considered case of the Bennet profile of the plasma conductivity, σ(r)=σ 0 /(1+r 2 /a 2 ) 2 . It is shown that in an unlimited plasma a considerable decrease in the spatial and especially temporal increment of the instability development takes place

Role of microsatellite instability in colon cancer

Directory of Open Access Journals (Sweden)

M. Yu. Fedyanin

2012-01-01

Full Text Available Coloncancer is among leading causes of cancer morbidity and mortality both inRussiaand worldwide. Development of molecular biology lead to decoding of carcinogenesis and tumor progression mechanisms. These processes require accumulation of genetic and epigenetic alterations in a tumor cell.Coloncancer carcinogenesis is characterized by mutations cumulation in genes controlling growth and differentiation of epithelial cells, which leads to their genetic instability. Microsatellite instability is a type of genetic instability characterized by deterioration of mismatch DNA repair. This leads to faster accumulation of mutations in DNA. Loss of mismatch repair mechanism can easily be diagnosed by length of DNA microsatellites. These alterations are termed microsatellite instability. They can be found both in hereditary and sporadic colon cancers. This review covers the questions of microsatellite instability, its prognostic and predictive value in colon cancer.

[Patellar instability : diagnosis and treatment].

Science.gov (United States)

Ngo, Trieu Hoai Nam; Martin, Robin

2017-12-13

The aim of this paper is to present recent advances in surgical management of patellar instability. Several anatomical factors were reported to promote instability. We propose to classify them in two groups. Extra articular factors are valgus and torsion deformity. Articular factors include trochlea and patella dysplasia, tibial tubercle lateralization and medial patellofemoral ligament (MPFL) insufficiency. Acute patellar dislocations are treated conservatively, with exception for osteochondral and MPFL avulsion fractures that require acute reinsertion. Surgery is considered for recurrent instability. As we aim for a correction of all contributing elements, we prefer a two stages approach. Extra articular factors are treated first by osteotomy, followed by articular factors after 4-6 months. This allows separate rehabilitation protocols.

In-plane fluidelastic instability analysis for large steam generators

International Nuclear Information System (INIS)

Mureithi, Njuki; Olala, Stephen; Hadji, Abdallah

2015-01-01

Fluidelastic instability remains the most important vibration excitation mechanism in nuclear steam generators (SGs). Design guidelines, aimed at eliminating the possibility of fluidelastic instability, have been developed over the past 40 years. The design guidelines, based on the Connors equation, depend on a large database on cross-flow fluidelastic instability i.e. instability in the direction transverse to the flow. Past experience had shown that for an axi-symmetrically flexible tube, instability generally occurred in the transverse direction, at least at first. Although often not explicitly stated, there has been an implicit assumption that the in-plane direction was either stable, or would only suffer instability at velocities significantly higher than the transverse direction. This explains why SGs are fitted with anti-vibrations bars (AVBs) to mitigate transverse (out-of-plane) vibrations with no equivalent consideration for potential in-plane instability. This 'oversight' recently came to a head when SG at the San-Onofre NPP suffered in-plane fluidelastic instability. The present paper addresses the question of in-plane fluidelastic instability in large SGs. A historical review is presented to explain why this potential problem was left unresolved (or ignored) over the past 40+ years, and why engineers got away with it - at least until recently. Following the review, some recent work on in-plane fluidelastic instability modeling, using the quasi-steady model is presented. It is shown that in-plane fluidelastic instability can be fully modelled using this approach. The model results are used to propose some changes to existing design guidelines to cover the case of in-plane fluidelastic instability. (author)

Modeling and Identification of Harmonic Instability Problems In Wind Farms

DEFF Research Database (Denmark)

Ebrahimzadeh, Esmaeil; Blaabjerg, Frede; Wang, Xiongfei

2016-01-01

In power electronics based power systems like wind farms, the interactions between the inner control systems of the power converters and the passive components may lead to high frequency oscillations, which can be called harmonic instability. In this paper, a simple methodology is presented...... to identify harmonic instability problems in wind farms, where many wind turbines, cables, transformers, capacitor banks, shunt reactors, etc, typically are located. This methodology introduces the wind farm as a Multi-Input Multi-Outpur (MIMO) control system, where the linearized models of fast inner control....../EMTDC software environment for a 400-MW wind farm. The proposed analytical analysis method and time-domain simulation results show that both dynamics of the power electronic converter and the parameters of the passive component can effect on the wind farm stability....

Observation of Parametric Instability in Advanced LIGO.

Science.gov (United States)

Evans, Matthew; Gras, Slawek; Fritschel, Peter; Miller, John; Barsotti, Lisa; Martynov, Denis; Brooks, Aidan; Coyne, Dennis; Abbott, Rich; Adhikari, Rana X; Arai, Koji; Bork, Rolf; Kells, Bill; Rollins, Jameson; Smith-Lefebvre, Nicolas; Vajente, Gabriele; Yamamoto, Hiroaki; Adams, Carl; Aston, Stuart; Betzweiser, Joseph; Frolov, Valera; Mullavey, Adam; Pele, Arnaud; Romie, Janeen; Thomas, Michael; Thorne, Keith; Dwyer, Sheila; Izumi, Kiwamu; Kawabe, Keita; Sigg, Daniel; Derosa, Ryan; Effler, Anamaria; Kokeyama, Keiko; Ballmer, Stefan; Massinger, Thomas J; Staley, Alexa; Heinze, Matthew; Mueller, Chris; Grote, Hartmut; Ward, Robert; King, Eleanor; Blair, David; Ju, Li; Zhao, Chunnong

2015-04-24

Parametric instabilities have long been studied as a potentially limiting effect in high-power interferometric gravitational wave detectors. Until now, however, these instabilities have never been observed in a kilometer-scale interferometer. In this Letter, we describe the first observation of parametric instability in a gravitational wave detector, and the means by which it has been removed as a barrier to progress.

Frameshift mutational target gene analysis identifies similarities and differences in constitutional mismatch repair-deficiency and Lynch syndrome.

Science.gov (United States)

Maletzki, Claudia; Huehns, Maja; Bauer, Ingrid; Ripperger, Tim; Mork, Maureen M; Vilar, Eduardo; Klöcking, Sabine; Zettl, Heike; Prall, Friedrich; Linnebacher, Michael

2017-07-01

Mismatch-repair deficient (MMR-D) malignancies include Lynch Syndrome (LS), which is secondary to germline mutations in one of the MMR genes, and the rare childhood-form of constitutional mismatch repair-deficiency (CMMR-D); caused by bi-allelic MMR gene mutations. A hallmark of LS-associated cancers is microsatellite instability (MSI), characterized by coding frameshift mutations (cFSM) in target genes. By contrast, tumors arising in CMMR-D patients are thought to display a somatic mutation pattern differing from LS. This study has the main goal to identify cFSM in MSI target genes relevant in CMMR-D and to compare the spectrum of common somatic mutations, including alterations in DNA polymerases POLE and D1 between LS and CMMR-D. CMMR-D-associated tumors harbored more somatic mutations compared to LS cases, especially in the TP53 gene and in POLE and POLD1, where novel mutations were additionally identified. Strikingly, MSI in classical mononucleotide markers BAT40 and CAT25 was frequent in CMMR-D cases. MSI-target gene analysis revealed mutations in CMMR-D-associated tumors, some of them known to be frequently hit in LS, such as RNaseT2, HT001, and TGFβR2. Our results imply a general role for these cFSM as potential new drivers of MMR-D tumorigenesis. © 2017 Wiley Periodicals, Inc.

Frequent Users of Hospital Emergency Departments in Korea Characterized by Claims Data from the National Health Insurance: A Cross Sectional Study

Science.gov (United States)

Woo, Jung Hoon; Grinspan, Zachary; Shapiro, Jason; Rhee, Sang Youl

2016-01-01

The Korean National Health Insurance, which provides universal coverage for the entire Korean population, is now facing financial instability. Frequent emergency department (ED) users may represent a medically vulnerable population who could benefit from interventions that both improve care and lower costs. To understand the nature of frequent ED users in Korea, we analyzed claims data from a population-based national representative sample. We performed both bivariate and multivariable analyses to investigate the association between patient characteristics and frequent ED use (4+ ED visits in a year) using claims data of a 1% random sample of the Korean population, collected in 2009. Among 156,246 total ED users, 4,835 (3.1%) were frequent ED users. These patients accounted for 14% of 209,326 total ED visits and 17.2% of $76,253,784 total medical expenses generated from all ED visits in the 1% data sample. Frequent ED users tended to be older, male, and of lower socio-economic status compared with occasional ED users (p users had longer stays in the hospital when admitted, higher probability of undergoing an operative procedure, and increased mortality. Among 8,425 primary diagnoses, alcohol-related complaints and schizophrenia showed the strongest positive correlation with the number of ED visits. Among the frequent ED users, mortality and annual outpatient department visits were significantly lower in the alcohol-related patient subgroup compared with other frequent ED users; furthermore, the rate was even lower than that for non-frequent ED users. Our findings suggest that expanding mental health and alcohol treatment programs may be a reasonable strategy to decrease the dependence of these patients on the ED. PMID:26809051

[Instability of the distal radioulnar joint: Treatment options for ulnar lesions of the triangular fibrocartilage complex].

Science.gov (United States)

Spies, C K; Prommersberger, K J; Langer, M; Müller, L P; Hahn, P; Unglaub, F

2015-08-01

Injuries of the triangular fibrocartilage complex (TFCC) may be fatal to the distal radioulnar joint (DRUJ). This structure is one of the crucial stabilizers and guarantees unrestricted pronosupination of the forearm. A systematic examination is mandatory to diagnose DRUJ instability reliably. A clinical examination in comparison to the contralateral side is obligatory. Plain radiographs are required to exclude osseous lesions or deformities. Computed tomography of both wrists in neutral, pronation and supination is necessary to verify DRUJ instability in ambiguous situations. Based on a systematic examination wrist and DRUJ arthroscopy identify lesions clearly. Injuries of the radioulnar ligaments which entail DRUJ instability, should be reconstructed preferably anatomically. Ulnar-sided TFCC lesions may often cause DRUJ instability. Osseous ligament avulsions are mostly treated osteosynthetically. Ligament tears may be refixated using anchor or transosseous sutures. Tendon transplants are necessary for an anatomical reconstruction in cases of irreparable ruptures.

Systematics of shoulder instability; Systematik der Schulterinstabilitaet

Energy Technology Data Exchange (ETDEWEB)

Kreitner, K.F.; Maehringer-Kunz, A. [Johannes-Gutenberg-Universitaet Mainz, Klinik und Poliklinik fuer Diagnostische und Interventionelle Radiologie, Mainz (Germany)

2015-03-01

Shoulder instability is defined as a symptomatic abnormal motion of the humeral head relative to the glenoid during active shoulder motion. Glenohumeral instabilities are classified according to the causative factors as the pathogenesis of instability plays an important role with respect to treatment options. Instabilities are classified into traumatic and atraumatic instabilities as part of a multidirectional instability syndrome and into microtraumatic instabilities. For diagnostics plain radiographs (''trauma series'') are performed to document shoulder dislocation and its successful repositioning. Direct magnetic resonance (MR) arthrography is the most important imaging modality for delineation of the different injury patterns of the labral-ligamentous complex and bony structures. Monocontrast computed tomography (CT) arthrography with the use of multidetector CT scanners represents an alternative imaging modality; however, MR imaging should be preferred in the work-up of shoulder instabilities due to the mostly younger age of patients. (orig.) [German] Unter einer Schulterinstabilitaet versteht man jede zu Beschwerden fuehrende Translation des Humeruskopfs in Relation zur Gelenkpfanne waehrend einer aktiven Bewegung der Schulter. Glenohumerale Instabilitaeten werden heute nach ihrer Aetiologie eingeteilt, da bei der Wahl der Therapie der Entstehungsmechanismus der Instabilitaet eine wichtige Rolle spielt. Danach unterscheidet man primaer traumatisch von atraumatisch entstandenen Instabilitaeten sowie Mikroinstabilitaeten. Bei der Diagnostik dienen konventionelle Roentgenuebersichtsaufnahmen nur noch zur Dokumentation einer Luxation und zur Beurteilung der Reposition. Die durch eine Instabilitaet hervorgerufenen Verletzungsfolgen am labroligamentaeren Komplex und den knoechernen Strukturen werden heute bevorzugt mit der direkten MR-Arthrographie dargestellt. Hierbei koennen unterschiedliche Verletzungsmuster dargestellt werden. Nach

Toward a definition of affective instability.

Science.gov (United States)

Renaud, Suzane M; Zacchia, Camillo

2012-01-01

Affective instability is a psychophysiological symptom observed in some psychopathologies. It is a complex construct that encompasses (1) primary emotions, or affects, and secondary emotions, with each category having its own characteristics, amplitude, and duration, (2) rapid shifting from neutral or valenced affect to intense affect, and (3) dysfunctional modulation of emotions. Affective instability is often confused with mood lability, as in bipolar disorders, as well as with other terms. To clarify the concept, we searched databases for the term affective instability and read related articles on the topic. In this article we situate the term within the current affective nomenclature and human emotional experience, explore its psychophysiological features, and place it within the context of psychopathology. We explain why the term can potentially be confused with mood pathology and then define affective instability as an inherited temperamental trait modulated by developmental experience.

3-D nonlinear evolution of MHD instabilities

International Nuclear Information System (INIS)

Bateman, G.; Hicks, H.R.; Wooten, J.W.

1977-03-01

The nonlinear evolution of ideal MHD internal instabilities is investigated in straight cylindrical geometry by means of a 3-D initial-value computer code. These instabilities are characterized by pairs of velocity vortex cells rolling off each other and helically twisted down the plasma column. The cells persist until the poloidal velocity saturates at a few tenths of the Alfven velocity. The nonlinear phase is characterized by convection around these essentially fixed vortex cells. For example, the initially centrally peaked temperature profile is convected out and around to form an annulus of high temperature surrounding a small region of lower temperature. Weak, centrally localized instabilities do not alter the edge of the plasma. Strong, large-scale instabilities, resulting from a stronger longitudinal equilibrium current, drive the plasma against the wall. After three examples of instability are analyzed in detail, the numerical methods and their verification are discussed

Gravitational waves from instabilities in relativistic stars

International Nuclear Information System (INIS)

Andersson, Nils

2003-01-01

This paper provides an overview of stellar instabilities as sources of gravitational waves. The aim is to put recent work on secular and dynamical instabilities in compact stars in context, and to summarize the current thinking about the detectability of gravitational waves from various scenarios. As a new generation of kilometre length interferometric detectors is now coming online this is a highly topical theme. The review is motivated by two key questions for future gravitational-wave astronomy: are the gravitational waves from various instabilities detectable? If so, what can these gravitational-wave signals teach us about neutron star physics? Even though we may not have clear answers to these questions, recent studies of the dynamical bar-mode instability and the secular r-mode instability have provided new insights into many of the difficult issues involved in modelling unstable stars as gravitational-wave sources. (topical review)

New instability strip for hot degenerates

International Nuclear Information System (INIS)

Starrfield, S.G.; Cox, A.N.; Hodson, S.W.

1980-01-01

A new kind of variable star, designated as PG1159-035 is distinguished not only by the complete lack of hydrogen in its spectrum but also by an effective temperature that exceeds 8 x 10 4 K. The star does not fall near any of the known regions of instability in the HR diagram which suggests that the instability mechanism will not be helium and hydrogen ionization as in the Cepheid variables. The more unusual compositions are examined in order to discover the cause of the instability in PG1159-035

Tearing instability in cylindrical plasma configuration

International Nuclear Information System (INIS)

Zelenyj, L.M.

1979-01-01

The effect of the neutral-layer cylindrical geometry on the development of the tearing instability has been investigated in detail. The increments of the instability for all the regimes have been found. The influence of cylindrical effects becomes manifesting itself at small, as compared to the layer characteristic thickness, distances from the axis, and, finally, the electron regime of the instability development transforms into an ion one. The results obtained are of interest for studying the plasma stability in the devices of the ''Astron'' type and in magnetospheres of cosmic objects

Numerical investigations of Z-pinch plasma instabilities

International Nuclear Information System (INIS)

Duan Yaoyong; Guo Yonghui; Wang Wensheng; Qiu Aici

2004-01-01

A two-dimensional, radiation magneto-hydrodynamics model is applied to the simulation of Z-pinch plasma sausage instability. Different implosion mechanisms in the cases of the existence and the non-existence of instability are analyzed, and the effects of various initial density perturbation levels on the x-ray power and energy are investigated. Numerical results show that x-ray energy output is not susceptive to sausage instabilities in a certain extent but x-ray power versus time is evidently dependent on the instabilities. In addition, this paper also studies the effects of numerical treatment of extreme low density in Z-pinch simulations on numerical results

Gravitational instability in isotropic MHD plasma waves

Science.gov (United States)

Cherkos, Alemayehu Mengesha

2018-04-01

The effect of compressive viscosity, thermal conductivity and radiative heat-loss functions on the gravitational instability of infinitely extended homogeneous MHD plasma has been investigated. By taking in account these parameters we developed the six-order dispersion relation for magnetohydrodynamic (MHD) waves propagating in a homogeneous and isotropic plasma. The general dispersion relation has been developed from set of linearized basic equations and solved analytically to analyse the conditions of instability and instability of self-gravitating plasma embedded in a constant magnetic field. Our result shows that the presence of viscosity and thermal conductivity in a strong magnetic field substantially modifies the fundamental Jeans criterion of gravitational instability.

3D Relativistic Magnetohydrodynamic Simulations of Current-Driven Instability. 1; Instability of a Static Column

Science.gov (United States)

Mizuno, Yosuke; Lyubarsky, Yuri; ishikawa, Ken-Ichi; Hardee, Philip E.

2010-01-01

We have investigated the development of current-driven (CD) kink instability through three-dimensional relativistic MHD simulations. A static force-free equilibrium helical magnetic configuration is considered in order to study the influence of the initial configuration on the linear and nonlinear evolution of the instability. We found that the initial configuration is strongly distorted but not disrupted by the kink instability. The instability develops as predicted by linear theory. In the non-linear regime the kink amplitude continues to increase up to the terminal simulation time, albeit at different rates, for all but one simulation. The growth rate and nonlinear evolution of the CD kink instability depends moderately on the density profile and strongly on the magnetic pitch profile. The growth rate of the kink mode is reduced in the linear regime by an increase in the magnetic pitch with radius and the non-linear regime is reached at a later time than for constant helical pitch. On the other hand, the growth rate of the kink mode is increased in the linear regime by a decrease in the magnetic pitch with radius and reaches the non-linear regime sooner than the case with constant magnetic pitch. Kink amplitude growth in the non-linear regime for decreasing magnetic pitch leads to a slender helically twisted column wrapped by magnetic field. On the other hand, kink amplitude growth in the non-linear regime nearly ceases for increasing magnetic pitch.

THREE-DIMENSIONAL RELATIVISTIC MAGNETOHYDRODYNAMIC SIMULATIONS OF CURRENT-DRIVEN INSTABILITY. I. INSTABILITY OF A STATIC COLUMN

International Nuclear Information System (INIS)

Mizuno, Yosuke; Nishikawa, Ken-Ichi; Lyubarsky, Yuri; Hardee, Philip E.

2009-01-01

We have investigated the development of current-driven (CD) kink instability through three-dimensional relativistic magnetohydrodynamic simulations. A static force-free equilibrium helical magnetic configuration is considered in order to study the influence of the initial configuration on the linear and nonlinear evolution of the instability. We found that the initial configuration is strongly distorted but not disrupted by the kink instability. The instability develops as predicted by linear theory. In the nonlinear regime, the kink amplitude continues to increase up to the terminal simulation time, albeit at different rates, for all but one simulation. The growth rate and nonlinear evolution of the CD kink instability depend moderately on the density profile and strongly on the magnetic pitch profile. The growth rate of the kink mode is reduced in the linear regime by an increase in the magnetic pitch with radius and reaches the nonlinear regime at a later time than the case with constant helical pitch. On the other hand, the growth rate of the kink mode is increased in the linear regime by a decrease in the magnetic pitch with radius and reaches the nonlinear regime sooner than the case with constant magnetic pitch. Kink amplitude growth in the nonlinear regime for decreasing magnetic pitch leads to a slender helically twisted column wrapped by magnetic field. On the other hand, kink amplitude growth in the nonlinear regime nearly ceases for increasing magnetic pitch.

The rheumatoid cervical spine: Signs of instability on plain cervical radiographs

International Nuclear Information System (INIS)

Roche, Clare J.; Eyes, Brian E.; Whitehouse, Graham H.

2002-01-01

The cervical spine is a common focus of destruction from rheumatoid arthritis, second only to the metacarpophalangeal joints. Joint, bone and ligament damage in the cervical spine leads to subluxations which can cause cervical cord compression resulting in paralysis and even sudden death. Because many patients with significant subluxations are asymptomatic, the radiologist plays a key role in recognizing the clinically important clues to instability on plain radiographs of the cervical spine-often difficult in rheumatoid arthritis when the bony landmarks are osteoporotic or eroded. This review focuses on the signs of instability on plain radiographs of the cervical spine, using diagrams and clinical examples to illustrate methods of identifying significant subluxations in rheumatoid arthritis. Roche, C.J., Eyes, B.E. and Whitehouse, G.H. (2002)

On some properties of longitudinal and transverse coupled-bunch instabilities

International Nuclear Information System (INIS)

Kamiya, Yukihide.

1983-02-01

Some properties of longitudinal and transverse coupled-bunch instabilities have been investigated theoretically and computationally, mainly based on a rigid-bunch model. In this report, we will study Robinson's stability, sum rules of the instabilities and the cure of instabilities by producing the oscillation frequencies different from bunch to bunch, and also give the numerical examples for KEK-PF storage ring. KEYWORD: storage ring, accelerator, bunched beam, longitudinal instability, transverse instability, coupled-bunch instability. (author)

Frequent Users of Hospital Emergency Departments in Korea Characterized by Claims Data from the National Health Insurance: A Cross Sectional Study.

Directory of Open Access Journals (Sweden)

Jung Hoon Woo

Full Text Available The Korean National Health Insurance, which provides universal coverage for the entire Korean population, is now facing financial instability. Frequent emergency department (ED users may represent a medically vulnerable population who could benefit from interventions that both improve care and lower costs. To understand the nature of frequent ED users in Korea, we analyzed claims data from a population-based national representative sample. We performed both bivariate and multivariable analyses to investigate the association between patient characteristics and frequent ED use (4+ ED visits in a year using claims data of a 1% random sample of the Korean population, collected in 2009. Among 156,246 total ED users, 4,835 (3.1% were frequent ED users. These patients accounted for 14% of 209,326 total ED visits and 17.2% of $76,253,784 total medical expenses generated from all ED visits in the 1% data sample. Frequent ED users tended to be older, male, and of lower socio-economic status compared with occasional ED users (p < 0.001 for each. Moreover, frequent ED users had longer stays in the hospital when admitted, higher probability of undergoing an operative procedure, and increased mortality. Among 8,425 primary diagnoses, alcohol-related complaints and schizophrenia showed the strongest positive correlation with the number of ED visits. Among the frequent ED users, mortality and annual outpatient department visits were significantly lower in the alcohol-related patient subgroup compared with other frequent ED users; furthermore, the rate was even lower than that for non-frequent ED users. Our findings suggest that expanding mental health and alcohol treatment programs may be a reasonable strategy to decrease the dependence of these patients on the ED.

Kinetic theory of tearing instability

International Nuclear Information System (INIS)

Hazeltine, R.D.; Dobrott, D.; Wang, T.S.

1975-01-01

The guiding-center kinetic equation with Fokker-Planck collision term is used to study, in cylindrical geometry, a class of dissipative instabilities of which the classical tearing mode is an archetype. Variational solution of the kinetic equation obviates the use of an approximate Ohm's law or adiabatic assumption, as used in previous studies, and it provides a dispersive relation which is uniformly valid for any ratio of wave frequency to collision frequency. One result of using the rigorous collision operator is the prediction of a new instability. This instability, driven by the electron temperature gradient, is predicted to occur under the long mean-free path conditions of present tokamak experiments, and has significant features in common with the kink-like oscillations observed in such experiments

Assessment of demographic and pathoanatomic risk factors in recurrent patellofemoral instability.

Science.gov (United States)

Hiemstra, Laurie Anne; Kerslake, Sarah; Lafave, Mark

2017-12-01

The WARPS/STAID classification employs clinical assessment of presenting features and anatomic characteristics to identify two distinct subsets of patients within the patellofemoral instability population. The purpose of this study was to further define the specific demographics and the prevalence of risky pathoanatomies in patients classified as either WARPS or STAID presenting with recurrent patellofemoral instability. A secondary purpose was to further validate the WARPS/STAID classification with the Banff Patella Instability Instrument (BPII), the Marx activity scale and the Patellar Instability Severity Score (ISS). A convenience sample of 50 patients with recurrent patellofemoral instability, including 25 WARPS and 25 STAID subtype patients, were assessed. Clinical data were collected including assessment of demographic risk factors (sex, BMI, bilaterality of symptoms, affected limb side and age at first dislocation) and pathoanatomic risk factors (TT-TG distance, patella height, patellar tilt, grade of trochlear dysplasia, Beighton score and rotational abnormalities of the tibia or femur). Patients completed the BPII and the Marx activity scale. The ISS was calculated from the clinical assessment data. Patients were stratified into the WARPS or STAID subtypes for comparative analysis. An independent t test was used to compare demographics, the pathoanatomic risk factors and subjective measures between the groups. Convergent validity was tested with a Pearson r correlation coefficient between the WARPS/STAID and ISS scores. Demographic risk factors statistically associated with a WARPS subtype included female sex, age at first dislocation and bilaterality. Pathoanatomic risk factors statistically associated with a WARPS subtype included trochlear dysplasia, TT-TG distance, generalized ligamentous laxity, patellar tilt and rotational abnormalities. The independent t test revealed a significant difference between the ISS scores: WARPS subtype (M = 4.4, SD�

Crystalline heterogeneities and instabilities in thermally convecting magma chamber

Science.gov (United States)

Culha, C.; Suckale, J.; Qin, Z.

2016-12-01

A volcanic vent can supply different densities of crystals over an eruption time period. This has been seen in Hawai'i's Kilauea Iki 1959 eruption; however it is not common for all Kilauea or basaltic eruptions. We ask the question: Under what conditions can homogenous magma chamber cultivate crystalline heterogeneities? In some laboratory experiments and numerical simulations, a horizontal variation is observed. The region where crystals reside is identified as a retention zone: convection velocity balances settling velocity. Simulations and experiments that observe retention zones assume crystals do not alter the convection in the fluid. However, a comparison of experiments and simulations of convecting magma with crystals suggest that large crystal volume densities and crystal sizes alter fluid flow considerably. We introduce a computational method that fully resolves the crystalline phase. To simulate basaltic magma chambers in thermal convection, we built a numerical solver of the Navier-Stoke's equation, continuity equation, and energy equation. The modeled magma is assumed to be a viscous, incompressible fluid with a liquid and solid phase. Crystals are spherical, rigid bodies. We create Rayleigh-Taylor instability through a cool top layer and hot bottom layer and update magma density while keeping crystal temperature and size constant. Our method provides a detailed picture of magma chambers, which we compare to other models and experiments to identify when and how crystals alter magma chamber convection. Alterations include stratification, differential settling and instabilities. These characteristics are dependent on viscosity, convection vigor, crystal volume density and crystal characteristics. We reveal that a volumetric crystal density variation may occur over an eruption time period, if right conditions are met to form stratifications and instabilities in magma chambers. These conditions are realistic for Kilauea Iki's 1959 eruption.

On the instability of a modified cup-burner flame in the infrared spectral region

Directory of Open Access Journals (Sweden)

Petr Bitala

2016-03-01

Full Text Available This study describes the modification of a standardised cup-burner apparatus. The replacement of the original glass chimney is performed by shielding a nitrogen co-flow enabled measurement at a wavelength of 3.9 μm. This modification, together with a special arrangement of the measuring system (spectral filtering, data acquisition and post-processing, permitted the observation of various types of hydrodynamic instabilities, including transition states. The advantages of our arrangement are demonstrated with an ethylene non-premixed flame with high sooting tendency. Two known modes of hydrodynamic instability (varicose and sinuous that occur in buoyant flames were studied and described quantitatively. Based on the intensity of the infrared emissions, we identified and qualitatively described the modes of periodic hydrodynamic instability that are accompanied by flame tip opening, which has not been observed for this type of flame.

Pad-mode-induced instantaneous mode instability for simple models of brake systems

Science.gov (United States)

Oberst, S.; Lai, J. C. S.

2015-10-01

Automotive disc brake squeal is fugitive, transient and remains difficult to predict. In particular, instantaneous mode squeal observed experimentally does not seem to be associated with mode coupling and its mechanism is not clear. The effects of contact pressures, friction coefficients as well as material properties (pressure and temperature dependency and anisotropy) for brake squeal propensity have not been systematically explored. By analysing a finite element model of an isotropic pad sliding on a plate similar to that of a previously reported experimental study, pad modes have been identified and found to be stable using conventional complex eigenvalue analysis. However, by subjecting the model to contact pressure harmonic excitation for a range of pressures and friction coefficients, a forced response analysis reveals that the dissipated energy for pad modes is negative and becomes more negative with increasing contact pressures and friction coefficients, indicating the potential for instabilities. The frequency of the pad mode in the sliding direction is within the range of squeal frequencies observed experimentally. Nonlinear time series analysis of the vibration velocity also confirms the evolution of instabilities induced by pad modes as the friction coefficient increases. By extending this analysis to a more realistic but simple brake model in the form of a pad-on-disc system, in-plane pad-modes, which a complex eigenvalue analysis predicts to be stable, have also been identified by negative dissipated energy for both isotropic and anisotropic pad material properties. The influence of contact pressures on potential instabilities has been found to be more dominant than changes in material properties owing to changes in pressure or temperature. Results here suggest that instantaneous mode squeal is likely caused by in-plane pad-mode instabilities.

Coulomb Fission in Multiply-Charged Ammonia Clusters: Accurate Measurements of the Rayleigh Instability Limit from Fragmentation Patterns.

Science.gov (United States)

Harris, Christopher; Stace, Anthony J

2018-03-15

A series of experiments have been undertaken on the fragmentation of multiply charged ammonia clusters, (NH 3 ) n z+ , where z ≤ 8 and n ≤ 850, to establish Rayleigh instability limits, whereby clusters at certain critical sizes become unstable due to Coulomb repulsion between the resident charges. Experimental results on size-selected clusters are found to be in excellent agreement with theoretical predictions of Rayleigh instability limits at all values of the charge. Electrostatic theory has been used to help identify fragmentation patterns on the assumption that the clusters separate into two dielectric spheres, and the predicted Coulomb repulsion energies used to establish pathways and the sizes of cluster fragments. The results show that fragmentation is very asymmetric in terms of both the numbers of molecules involved and the amount of charge each fragment accommodates. For clusters carrying a charge ≤+4, the results show that fragmentation proceeds via the loss of small, singly charged clusters. When clusters carry a charge of +5 or more, the experimental observations suggest a marked switch in behavior. Although the laboratory measurements equate to fragmentation via the loss of a large dication cluster, electrostatic theory supports an interpretation that involves the sequential loss of two smaller, singly charged clusters possibly accompanied by the extensive evaporation of neutral molecules. It is suggested that this change in fragmentation pattern is driven by the channelling of Coulomb repulsion energy into intermolecular modes within these larger clusters. Overall, the results appear to support the ion evaporation model that is frequently used to interpret electrospray experiments.

Plasma instabilities in high electric fields

DEFF Research Database (Denmark)

Morawetz, K.; Jauho, Antti-Pekka

1994-01-01

expression is derived for the nonequilibrium dielectric function epsilon(K, omega). For certain values of momenta K and frequency omega, Imepsilon(K, omega) becomes negative, implying a plasma instability. This new instability exists only for strong electric fields, underlining its nonequilibrium origin....

A statistical model for instable thermodynamical systems

International Nuclear Information System (INIS)

Sommer, Jens-Uwe

2003-01-01

A generic model is presented for statistical systems which display thermodynamic features in contrast to our everyday experience, such as infinite and negative heat capacities. Such system are instable in terms of classical equilibrium thermodynamics. Using our statistical model, we are able to investigate states of instable systems which are undefined in the framework of equilibrium thermodynamics. We show that a region of negative heat capacity in the adiabatic environment, leads to a first order like phase transition when the system is coupled to a heat reservoir. This phase transition takes place without a phase coexistence. Nevertheless, all intermediate states are stable due to fluctuations. When two instable system are brought in thermal contact, the temperature of the composed system is lower than the minimum temperature of the individual systems. Generally, the equilibrium states of instable system cannot be simply decomposed into equilibrium states of the individual systems. The properties of instable system depend on the environment, ensemble equivalence is broken

Gravitational instability of thermally anisotropic plasma

International Nuclear Information System (INIS)

Singh, B.; Kalra, G.L.

1986-01-01

The equations of Chew, Goldberger, and Low (1956) modified to include the heat flux vector and self-gravitation are used to study the gravitational instability of unbounded plasma placed in a uniform static magnetic field. The linear stability analysis shows that some of the additional terms which arise as a result of higher moments are of the same order of magnitude as the terms in the original Chew, Goldberger, and Low theory. The influence of these terms on the gravitational instability has been specially examined. It is found that the gravitational instability sets in at a comparatively shorter wavelength and the growth rate is enhanced owing to the inclusion of these terms in the case where the propagation vector is along the magnetic field. The condition for instability is, however, unaltered when the direction of propagation is transverse to the direction of magnetic field. 19 references

Genetic instability in urinary bladder cancer: An evolving hallmark.

Science.gov (United States)

Wadhwa, N; Mathew, B B; Jatawa, S K; Tiwari, A

2013-01-01

Bladder cancer is a major health-care concern. A successful treatment of bladder cancer depends on its early diagnosis at the initial stage. Genetic instability is an essential early step toward the development of bladder cancer. This instability is found more often at the chromosomal level than at the nucleotide level. Microsatellite and chromosomal instability markers can be used as a prognostic marker for screening bladder cancer. Bladder cancer can be distinguished in two different categories according to genetic instability: Cancers with chromosomal level instability and cancers with nucleotide level instability. Deoxyribonucleic acid (DNA) mismatch repair (MMR) system and its correlation with other biologic pathway, both are essential to understand the basic mechanisms of cancer development. Microsatellite instability occurs due to defects in DNA MMR genes, including human mutL homolog 1 and human mutL homolog 2. Chromosomal alterations including deletions on chromosome 3, 8, 9, 11, 13, 17 have been detected in bladder cancer. In the current review, the most recent literature of genetic instability in urinary bladder cancer has been summarized.

Genetic instability in urinary bladder cancer: An evolving hallmark

Directory of Open Access Journals (Sweden)

N Wadhwa

2013-01-01

Full Text Available Bladder cancer is a major health-care concern. A successful treatment of bladder cancer depends on its early diagnosis at the initial stage. Genetic instability is an essential early step toward the development of bladder cancer. This instability is found more often at the chromosomal level than at the nucleotide level. Microsatellite and chromosomal instability markers can be used as a prognostic marker for screening bladder cancer. Bladder cancer can be distinguished in two different categories according to genetic instability: Cancers with chromosomal level instability and cancers with nucleotide level instability. Deoxyribonucleic acid (DNA mismatch repair (MMR system and its correlation with other biologic pathway, both are essential to understand the basic mechanisms of cancer development. Microsatellite instability occurs due to defects in DNA MMR genes, including human mutL homolog 1 and human mutL homolog 2. Chromosomal alterations including deletions on chromosome 3, 8, 9, 11, 13, 17 have been detected in bladder cancer. In the current review, the most recent literature of genetic instability in urinary bladder cancer has been summarized.

Curvature-Induced Instabilities of Shells

Science.gov (United States)

Pezzulla, Matteo; Stoop, Norbert; Steranka, Mark P.; Bade, Abdikhalaq J.; Holmes, Douglas P.

2018-01-01

Induced by proteins within the cell membrane or by differential growth, heating, or swelling, spontaneous curvatures can drastically affect the morphology of thin bodies and induce mechanical instabilities. Yet, the interaction of spontaneous curvature and geometric frustration in curved shells remains poorly understood. Via a combination of precision experiments on elastomeric spherical shells, simulations, and theory, we show how a spontaneous curvature induces a rotational symmetry-breaking buckling as well as a snapping instability reminiscent of the Venus fly trap closure mechanism. The instabilities, and their dependence on geometry, are rationalized by reducing the spontaneous curvature to an effective mechanical load. This formulation reveals a combined pressurelike term in the bulk and a torquelike term in the boundary, allowing scaling predictions for the instabilities that are in excellent agreement with experiments and simulations. Moreover, the effective pressure analogy suggests a curvature-induced subcritical buckling in closed shells. We determine the critical buckling curvature via a linear stability analysis that accounts for the combination of residual membrane and bending stresses. The prominent role of geometry in our findings suggests the applicability of the results over a wide range of scales.

Cavitation instabilities in hydraulic machines

International Nuclear Information System (INIS)

Tsujimoto, Y

2013-01-01

Cavitation instabilities in hydraulic machines, hydro turbines and turbopump inducers, are reviewed focusing on the cause of instabilities. One-dimensional model of hydro turbine system shows that the overload surge is caused by the diffuser effect of the draft tube. Experiments show that this effect also causes the surge mode oscillations at part load. One dimensional model of a cavitating turbopump inducer shows that the mass flow gain factor, representing the cavity volume increase caused by the incidence angle increase is the cause of cavitation surge and rotating cavitation. Two dimensional model of a cavitating turbopump inducer shows that various modes of cavitation instabilities start to occur when the cavity length becomes about 65% of the blade spacing. This is caused by the interaction of the local flow near the cavity trailing edge with the leading edge of the next blade. It was shown by a 3D CFD that this is true also for real cases with tip cavitation. In all cases, it was shown that cavitation instabilities are caused by the fundamental characteristics of cavities that the cavity volume increases with the decrease of ambient pressure or the increase of the incidence angle

Noise analysis of Forsmark 1 data to investigate BWR core local instability

International Nuclear Information System (INIS)

Oguma, R.

1998-04-01

BWR core local instability was experienced at Forsmark 1 (F1) during reactor operation in cycle 16. The event has been studied by applying noise analysis and stability calculations to get insight into the event as well as to identify the cause of local instability. The present report is concerned with noise analysis of data collected during start-up in cycle 17. The results of the current study indicates: The F1 core is quite stable in cycle 17. The max. decay ratio (DR) value of 0.37 was obtained from the stability evaluation of an APRM (average power range monitor) and LPRM (local power range monitor) signals measured at 66% (APRM) of reactor power and 4252 Kg/s (SA-HC) of core flow. Compared with the power profile in cycle 17 (as well as in reactor F2), the core in cycle 16 had an extreme power profile with high power and bottom-shifted axial peak in the core periphery esp. at the four quadrant corners. Such a profile decreases the stability margin in the region. It is a common observation that the DR obtained from APRM tends to be higher than that from LPRM if the global instability mechanism is dominant in the core, and vice versa. The comparison of global and local DR values should be an effective method for detecting local instability during the reactor operation. In order to detect the local instability it is important to evaluate the core stability with sufficient number of LPRMs so as to cover the whole core cross section together with APRMs

Bridge scour and stream instability countermeasures : experience, selection, and design guidance : third edition. Volume 1

Science.gov (United States)

2009-09-01

This document identifies and provides design guidelines for bridge scour and stream instability countermeasures that have been implemented by various State departments of transportation (DOTs) in the United States. Countermeasure experience, selectio...

Bridge scour and stream instability countermeasures : experience, selection, and design guidance : third edition. Volume 2

Science.gov (United States)

2009-09-01

This document identifies and provides design guidelines for bridge scour and stream instability countermeasures that have been implemented by various State departments of transportation (DOTs) in the United States. Countermeasure experience, selectio...

An exact linear dispersion relation for CRM instability

International Nuclear Information System (INIS)

Choyal, Y; Minami, K

2011-01-01

An exact self-consistent linear dispersion relation of a large orbit electron beam including two principles of cyclotron emission with oscillation frequencies above and below the relativistic electron frequency is derived and analyzed numerically for the first time in the literature. The two principles are cyclotron resonance maser (CRM) instability and Cherenkov instability in the azimuthal direction. Self-consistency in the formulation and inclusion of proper boundary conditions have removed the unphysical instability existing for infinitely large k z observed in conventional dispersion relations of CRM instability.

Instabilities and nonequilibrium structures

International Nuclear Information System (INIS)

Tirapegui, E.; Villarroel, D.

1987-01-01

Physical systems can be studied both near to and far from equilibrium where instabilities appear. The behaviour in these two regions is reviewed in this book, from both the theoretical and application points of view. The influence of noise in these situations is an essential feature which cannot be ignored. It is therefore discussed using phenomenological and theoretical approaches for the numerous problems which still remain in the field. This volume should appeal to mathematicians and physicists interested in the areas of instability, bifurcation theory, dynamical systems, pattern formation, nonequilibrium structures and statistical mechanics. (Auth.)

Epstein–Barr virus particles induce centrosome amplification and chromosomal instability

Science.gov (United States)

Shumilov, Anatoliy; Tsai, Ming-Han; Schlosser, Yvonne T.; Kratz, Anne-Sophie; Bernhardt, Katharina; Fink, Susanne; Mizani, Tuba; Lin, Xiaochen; Jauch, Anna; Mautner, Josef; Kopp-Schneider, Annette; Feederle, Regina; Hoffmann, Ingrid; Delecluse, Henri-Jacques

2017-01-01

Infections with Epstein–Barr virus (EBV) are associated with cancer development, and EBV lytic replication (the process that generates virus progeny) is a strong risk factor for some cancer types. Here we report that EBV infection of B-lymphocytes (in vitro and in a mouse model) leads to an increased rate of centrosome amplification, associated with chromosomal instability. This effect can be reproduced with virus-like particles devoid of EBV DNA, but not with defective virus-like particles that cannot infect host cells. Viral protein BNRF1 induces centrosome amplification, and BNRF1-deficient viruses largely lose this property. These findings identify a new mechanism by which EBV particles can induce chromosomal instability without establishing a chronic infection, thereby conferring a risk for development of tumours that do not necessarily carry the viral genome. PMID:28186092

Numerical methods on flow instabilities in steam generator

International Nuclear Information System (INIS)

Yoshikawa, Ryuji; Hamada, Hirotsugu; Ohshima, Hiroyuki; Yanagisawa, Hideki

2008-06-01

The phenomenon of two-phase flow instability is important for the design and operation of many industrial systems and equipment, such as steam generators. The designer's job is to predict the threshold of flow instability in order to design around it or compensate for it. So it is essential to understand the physical phenomena governing such instability and to develop computational tools to model the dynamics of boiling systems. In Japan Atomic Energy Agency, investigations on heat transfer characteristics of steam generator are being performed for the development of Sodium-cooled Fast Breeder Reactor. As one part of the research work, the evaluations of two-phase flow instability in the steam generator are being carried out experimentally and numerically. In this report, the numerical methods were studied for two-phase flow instability analysis in steam generator. For numerical simulation purpose, the special algorithm to calculate inlet flow rate iteratively with inlet pressure and outlet pressure as boundary conditions for the density-wave instability analysis was established. There was no need to solve property derivatives and large matrices, so the spurious numerical instabilities caused by discontinuous property derivatives at boiling boundaries were avoided. Large time-step was possible. The flow instability in single heat transfer tube was successfully simulated with homogeneous equilibrium model by using the present algorithm. Then the drift-flux model including the effects of subcooled boiling and two phase slip was adopted to improve the accuracy. The computer code was developed after selecting the correlations of drift velocity and distribution parameter. The capability of drift flux model together with the present algorithm for simulating density-wave instability in single tube was confirmed. (author)

Gross Instability After Hip Arthroscopy: An Analysis of Case Reports Evaluating Surgical and Patient Factors.

Science.gov (United States)

Yeung, Marco; Memon, Muzammil; Simunovic, Nicole; Belzile, Etienne; Philippon, Marc J; Ayeni, Olufemi R

2016-06-01

Gross hip instability is a rare complication after hip arthroscopy, and there is limited literature surrounding this topic. This systematic review investigates cases of gross hip instability after arthroscopy and discusses the risk factors associated with this complication. A systematic search was performed in duplicate for studies investigating gross hip instability after hip arthroscopy up to October 2015. Study parameters including sample size, mechanism and type of dislocation, surgical procedure details, patient characteristics, postoperative rehabilitation protocol, and level of evidence were analyzed. The systematic review identified 9 case reports investigating gross hip instability after hip arthroscopy (10 patients). Anterior dislocation occurred in 66.7% of patients, and most injuries occurred with a low-energy mechanism. Common surgical factors cited included unrepaired capsulotomy (77.8%) and iliopsoas release (33.3%), whereas patient factors included female gender (77.8%), acetabular dysplasia (22.2%), and general ligamentous laxity (11.1%). Postoperative restrictions and protocols were variable and inconsistently reported, and their relation to post-arthroscopy instability was difficult to ascertain. This systematic review discussed various patient, surgical, and postoperative risk factors of gross hip instability after arthroscopy. Patient characteristics such as female gender, hip dysplasia, and ligamentous laxity may be risk factors for post-arthroscopy dislocation. Similarly, surgical risk factors for iatrogenic hip instability may include unrepaired capsulotomies and iliopsoas debridement, although the role of capsular closure in iatrogenic instability is not clear. The influences of postoperative restrictions and protocols on dislocation are also unclear in the current literature. Surgeons should be cognizant of these risk factors when performing hip arthroscopy and be mindful that these factors appear to occur in combination. Level IV

Experimental study on low pressure flow instability

International Nuclear Information System (INIS)

Jiang Shengyao; Wu Xinxin; Wu Shaorong; Bo Jinhai; Zhang Youjie

1997-05-01

The experiment was performed on the test loop (HRTL-5), which simulates the geometry and system design of the 5 MW reactor. The flow behavior for a wide range of inlet subcooling, in which the flow undergoes from single phase to two phase, is described in a natural circulation system at low pressure (p = 0.1, 0.24 MPa). Several kinds of flow instability, e.g. subcooled boiling instability, subcooled boiling induced flashing instability, pure flashing instability as well as flashing coupled density wave instability and high frequency flow oscillation, are investigated. The mechanism of flashing and flashing concerned flow instability, which has never been studied well in this field, is especially interpreted. The experimental results show that, firstly, for a low pressure natural circulation system the two phase flow is unstable in most of inlet subcooling conditions, the two phase stable flow can only be reached at very low inlet subcooling; secondly, at high inlet subcooling the flow instability is dominated by subcooled boiling in the heated section, and at middle inlet subcooling is dominated by void flashing in the adiabatic long riser; thirdly, in two phase stable flow region the condition for boiling out of the core, namely, single phase flow in the heated section, two phase flow in the riser due to vapor flashing, can be realized. The experimental results are very important for the design and accident analysis of the vessel and swimming pool type natural circulation nuclear heating reactor. (7 refs., 10 figs., 1 tab.)

Deep Ion Torrent sequencing identifies soil fungal community shifts after frequent prescribed fires in a southeastern US forest ecosystem.

Science.gov (United States)

Brown, Shawn P; Callaham, Mac A; Oliver, Alena K; Jumpponen, Ari

2013-12-01

Prescribed burning is a common management tool to control fuel loads, ground vegetation, and facilitate desirable game species. We evaluated soil fungal community responses to long-term prescribed fire treatments in a loblolly pine forest on the Piedmont of Georgia and utilized deep Internal Transcribed Spacer Region 1 (ITS1) amplicon sequencing afforded by the recent Ion Torrent Personal Genome Machine (PGM). These deep sequence data (19,000 + reads per sample after subsampling) indicate that frequent fires (3-year fire interval) shift soil fungus communities, whereas infrequent fires (6-year fire interval) permit system resetting to a state similar to that without prescribed fire. Furthermore, in nonmetric multidimensional scaling analyses, primarily ectomycorrhizal taxa were correlated with axes associated with long fire intervals, whereas soil saprobes tended to be correlated with the frequent fire recurrence. We conclude that (1) multiplexed Ion Torrent PGM analyses allow deep cost effective sequencing of fungal communities but may suffer from short read lengths and inconsistent sequence quality adjacent to the sequencing adaptor; (2) frequent prescribed fires elicit a shift in soil fungal communities; and (3) such shifts do not occur when fire intervals are longer. Our results emphasize the general responsiveness of these forests to management, and the importance of fire return intervals in meeting management objectives. © 2013 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.

On viscoelastic instability in polymeric filaments

DEFF Research Database (Denmark)

Rasmussen, Henrik Koblitz; Hassager, Ole

1999-01-01

The 3D Lagrangian Integral Method is used to simulate the effects of surface tension on the viscoelastic end-plate instability, occuring in the rapid extension of some polymeric filaments between parallel plates. It is shovn that the surface tension delays the onset of the instability. Furthermore...

Ion-cyclotron instability in magnetic mirrors

International Nuclear Information System (INIS)

Pearlstein, L.D.

1987-01-01

This report reviews the role of ion-cyclotron frequency instability in magnetic mirrors. The modes discussed here are loss-cone or anisotropy driven. The discussion includes quasilinear theory, explosive instabilities of 3-wave interaction and non-linear Landau damping, and saturation due to non-linear orbits

Frequent Exertion and Frequent Standing at Work, by Industry and Occupation Group - United States, 2015.

Science.gov (United States)

Shockey, Taylor M; Luckhaupt, Sara E; Groenewold, Matthew R; Lu, Ming-Lun

2018-01-12

Repeated exposure to occupational ergonomic hazards, such as frequent exertion (repetitive bending or twisting) and frequent standing, can lead to injuries, most commonly musculoskeletal disorders (1). Work-related musculoskeletal disorders have been estimated to cost the United States approximately $2.6 billion in annual direct and indirect costs (2). A recent literature review provided evidence that prolonged standing at work also leads to adverse health outcomes, such as back pain, physical fatigue, and muscle pain (3). To determine which industry and occupation groups currently have the highest prevalence rates of frequent exertion at work and frequent standing at work, CDC analyzed data from the 2015 National Health Interview Survey (NHIS) Occupational Health Supplement (OHS) regarding currently employed adults in the United States. By industry, the highest prevalence of both frequent exertion and frequent standing at work was among those in the agriculture, forestry, fishing, and hunting industry group (70.9%); by occupation, the highest prevalence was among those in the construction and extraction occupation group (76.9%). Large differences among industry and occupation groups were found with regard to these ergonomic hazards, suggesting a need for targeted interventions designed to reduce workplace exposure.

Single-mode coherent synchrotron radiation instability

Directory of Open Access Journals (Sweden)

S. Heifets

2003-06-01

Full Text Available The microwave instability driven by the coherent synchrotron radiation (CSR has been previously studied [S. Heifets and G. V. Stupakov, Phys. Rev. ST Accel. Beams 5, 054402 (2002] neglecting effect of the shielding caused by the finite beam pipe aperture. In practice, the unstable mode can be close to the shielding threshold where the spectrum of the radiation in a toroidal beam pipe is discrete. In this paper, the CSR instability is studied in the case when it is driven by a single synchronous mode. A system of equations for the beam-wave interaction is derived and its similarity to the 1D free-electron laser theory is demonstrated. In the linear regime, the growth rate of the instability is obtained and a transition to the case of continuous spectrum is discussed. The nonlinear evolution of the single-mode instability, both with and without synchrotron damping and quantum diffusion, is also studied.

Relativistic Buneman instability in the laser breakout afterburner

International Nuclear Information System (INIS)

Albright, B. J.; Yin, L.; Bowers, Kevin J.; Hegelich, B. M.; Flippo, K. A.; Kwan, T. J. T.; Fernandez, J. C.

2007-01-01

A new laser-driven ion acceleration mechanism has been identified in particle-in-cell simulations of high-contrast-ratio ultraintense lasers with very thin (10 s of nm) solid targets [Yin et al., Laser and Particle Beams 24, 291 (2006); Yin et al., Phys. Plasmas 13, 072701 (2007)]. After a brief period of target normal sheath acceleration (TNSA), 'enhanced' TNSA follows. In this stage, the laser rapidly heats all the electrons in the target as the target thickness becomes comparable to the skin depth and enhanced acceleration of the ions results. Then, concomitant with the laser penetrating the target, a large accelerating longitudinal electric field is generated that co-moves with the ions. This last phase has been termed the laser 'breakout afterburner' (BOA). Earlier work suggested that the BOA was associated with the Buneman instability that efficiently converts energy from the drift of the electrons into the ions. In this Brief Communication, this conjecture is found to be consistent with particle-in-cell simulation data and the analytic dispersion relation for the relativistic Buneman instability

Transient many-body instability in driven Dirac materials

Science.gov (United States)

Pertsova, Anna; Triola, Christopher; Balatsky, Alexander

The defining feature of a Dirac material (DM) is the presence of nodes in the low-energy excitation spectrum leading to a strong energy dependence of the density of states (DOS). The vanishing of the DOS at the nodal point implies a very low effective coupling constant which leads to stability of the node against electron-electron interactions. Non-equilibrium or driven DM, in which the DOS and hence the effective coupling can be controlled by external drive, offer a new platform for investigating collective instabilities. In this work, we discuss the possibility of realizing transient collective states in driven DMs. Motivated by recent pump-probe experiments which demonstrate the existence of long-lived photo-excited states in DMs, we consider an example of a transient excitonic instability in an optically-pumped DM. We identify experimental signatures of the transient excitonic condensate and provide estimates of the critical temperatures and lifetimes of these states for few important examples of DMs, such as single-layer graphene and topological-insulator surfaces.

Contact Line Instability Caused by Air Rim Formation under Nonsplashing Droplets.

Science.gov (United States)

Pack, Min; Kaneelil, Paul; Kim, Hyoungsoo; Sun, Ying

2018-05-01

Drop impact is fundamental to various natural and industrial processes such as rain-induced soil erosion and spray-coating technologies. The recent discovery of the role of air entrainment between the droplet and the impacting surface has produced numerous works, uncovering the unique physics that correlates the air film dynamics with the drop impact outcomes. In this study, we focus on the post-failure air entrainment dynamics for We numbers well below the splash threshold under different ambient pressures and elucidate the interfacial instabilities formed by air entrainment at the wetting front of impacting droplets on perfectly smooth, viscous films of constant thickness. A high-speed total internal reflection microscopy technique accounting for the Fresnel reflection at the drop-air interface allows for in situ measurements of an entrained air rim at the wetting front. The presence of an air rim is found to be a prerequisite to the interfacial instability which is formed when the capillary pressure in the vicinity of the contact line can no longer balance the increasing gas pressure near the wetting front. A critical capillary number for the air rim formation is experimentally identified above which the wetting front becomes unstable where this critical capillary number inversely scales with the ambient pressure. The contact line instabilities at relatively low We numbers ( We ∼ O(10)) observed in this study provide insight into the conventional understanding of hydrodynamic instabilities under drop impact which usually require We ≫ 10.

On the shear instability in relativistic neutron stars

Science.gov (United States)

Corvino, Giovanni; Rezzolla, Luciano; Bernuzzi, Sebastiano; De Pietri, Roberto; Giacomazzo, Bruno

2010-06-01

We present new results on instabilities in rapidly and differentially rotating neutron stars. We model the stars in full general relativity and describe the stellar matter adopting a cold realistic equation of state based on the unified SLy prescription (Douchin and Haensel 2001 Astron. Astrophys. 380 151-67). We provide evidence that rapidly and differentially rotating stars that are below the expected threshold for the dynamical bar-mode instability, βc ≡ T/|W| ~= 0.25, do nevertheless develop a shear instability on a dynamical timescale and for a wide range of values of β. This class of instability, which has so far been found only for small values of β and with very small growth rates, is therefore more generic than previously found and potentially more effective in producing strong sources of gravitational waves. Overall, our findings support the phenomenological predictions made by Watts et al (2005 Astrophys. J. 618 L37) on the nature of the low-T/|W| instability as the manifestation of a shear instability in a region where the latter is possible only for small values of β. Furthermore, our results provide additional insight on shear instabilities and on the necessary conditions for their development.

On the shear instability in relativistic neutron stars

Energy Technology Data Exchange (ETDEWEB)

Corvino, Giovanni; Rezzolla, Luciano; Giacomazzo, Bruno [Max-Planck-Institut fuer Gravitationsphysik, Albert-Einstein-Institut, Golm (Germany); Bernuzzi, Sebastiano [Theoretical Physics Institute, University of Jena, 07743 Jena (Germany); De Pietri, Roberto, E-mail: Giovanni.Corvino@roma1.infn.i [Physics Department, Parma University and INFN, Parma (Italy)

2010-06-07

We present new results on instabilities in rapidly and differentially rotating neutron stars. We model the stars in full general relativity and describe the stellar matter adopting a cold realistic equation of state based on the unified SLy prescription (Douchin and Haensel 2001 Astron. Astrophys. 380 151-67). We provide evidence that rapidly and differentially rotating stars that are below the expected threshold for the dynamical bar-mode instability, {beta}{sub c} {identical_to} T/|W| {approx_equal} 0.25, do nevertheless develop a shear instability on a dynamical timescale and for a wide range of values of {beta}. This class of instability, which has so far been found only for small values of {beta} and with very small growth rates, is therefore more generic than previously found and potentially more effective in producing strong sources of gravitational waves. Overall, our findings support the phenomenological predictions made by Watts et al (2005 Astrophys. J. 618 L37) on the nature of the low-T/|W| instability as the manifestation of a shear instability in a region where the latter is possible only for small values of {beta}. Furthermore, our results provide additional insight on shear instabilities and on the necessary conditions for their development.

Cures for the shock instability: Development of a shock-stable Roe scheme

CERN Document Server

Kim, S S; Rho, O H; Kyu-Hong, S

2003-01-01

This paper deals with the development of an improved Roe scheme that is free from the shock instability and still preserves the accuracy and efficiency of the original Roe's Flux Difference Splitting (FDS). Roe's FDS is known to possess good accuracy but to suffer from the shock instability, such as the carbuncle phenomenon. As the first step towards a shock-stable scheme, Roe's FDS is compared with the HLLE scheme to identify the source of the shock instability. Through a linear perturbation analysis on the odd-even decoupling problem, damping characteristic is examined and Mach number-based functions f and g are introduced to balance damping and feeding rates, which leads to a shock-stable Roe scheme. In order to satisfy the conservation of total enthalpy, which is crucial in predicting surface heat transfer rate in high-speed steady flows, an analysis of dissipation mechanism in the energy equation is carried out to find out the error source and to make the proposed scheme preserve total enthalpy. By modif...

Direct observation of nonequilibrium electroosmotic instability

NARCIS (Netherlands)

Rubinstein, S.M.; Manukyan, G.; Staicu, A.D.; Rubinstein, I.; Zaltzman, B.; Lammertink, Rob G.H.; Mugele, Friedrich Gunther; Wessling, Matthias

2008-01-01

We present a visualization of the predicted instability in ionic conduction from a binary electrolyte into a charge selective solid. This instability develops when a voltage greater than critical is applied to a thin layer of copper sulfate flanked by a copper anode and a cation selective membrane.

Profound Autonomic Instability Complicated by Multiple Episodes of Cardiac Asystole and Refractory Bradycardia in a Patient with Anti-NMDA Encephalitis

Directory of Open Access Journals (Sweden)

Stephanie R. Mehr

2016-01-01

Full Text Available Anti-N-methyl-D-aspartate receptor encephalitis (anti-NMDARE is autoimmune encephalitis primarily affecting young adults and children. First described about a decade ago, it frequently manifests as a syndrome that includes progressive behavioral changes, psychosis, central hypoventilation, seizures, and autonomic instability. Although cardiac arrhythmias often accompany anti-NMDARE, the need for long-term electrophysiological support is rare. We describe the case of NMDARE whose ICU course was complicated by progressively worsening episodes of tachyarrhythmia-bradyarrhythmia and episodes of asystole from which she was successfully resuscitated. Her life-threatening episodes of autonomic instability were successfully controlled only after the placement of a permanent pacemaker during her ICU stay. She made a clinical recovery and was discharged to a skilled nursing facility after a protracted hospital course.

Prevalence of chronic ankle instability and associated symptoms in university dance majors: an exploratory study.

Science.gov (United States)

Simon, Janet; Hall, Emily; Docherty, Carrie

2014-01-01

Previous investigations have established that dancers suffer a large number of injuries to the lower leg, foot, and ankle, with a portion of these being significant time loss injuries or in some cases career ending. Lateral ankle sprain is a common injury in dancers and can often lead to recurrent instability and repetitive injuries. Research in other active populations has linked ankle sprains to the development of chronic ankle instability (CAI). Therefore, the purpose of this study was to identify the prevalence of CAI and related symptoms of ankle sprain in a student dance population. Individuals were included if they were currently a modern or ballet dance major at the investigators' university (exclusion criterion: a history of fracture or surgery in the lower extremities). A self-reported demographic questionnaire and the Identification of Functional Ankle Instability survey were used to identify the presence and characteristics of CAI. A total of 83 questionnaires were collected, and after exclusions, 77 participants remained: 43 modern dancers and 34 ballet dancers (10 males and 67 females, mean age 19.61 ± 2.53 years, mean dance experience 13.61 ± 3.16 years). Of all dancers surveyed, 41 (53.2%) had CAI, and of those 24 (58.5%) were modern dancers, and 17 (41.5%) were ballet dancers. When looking only at those dancers who had a previous lateral ankle sprain, 75.9% were identified as having CAI. Chronic Ankle Instability can create long-term problems for anyone but especially female dancers, who place extreme stress on their feet and ankles from being en pointe or demi-pointe. It is important to educate dancers, instructors, and medical staff of the importance of recognizing CAI and seeking medical care for ankle sprains and their residual symptoms.

Analyses of MHD instabilities

International Nuclear Information System (INIS)

Takeda, Tatsuoki

1985-01-01

In this article analyses of the MHD stabilities which govern the global behavior of a fusion plasma are described from the viewpoint of the numerical computation. First, we describe the high accuracy calculation of the MHD equilibrium and then the analysis of the linear MHD instability. The former is the basis of the stability analysis and the latter is closely related to the limiting beta value which is a very important theoretical issue of the tokamak research. To attain a stable tokamak plasma with good confinement property it is necessary to control or suppress disruptive instabilities. We, next, describe the nonlinear MHD instabilities which relate with the disruption phenomena. Lastly, we describe vectorization of the MHD codes. The above MHD codes for fusion plasma analyses are relatively simple though very time-consuming and parts of the codes which need a lot of CPU time concentrate on a small portion of the codes, moreover, the codes are usually used by the developers of the codes themselves, which make it comparatively easy to attain a high performance ratio on the vector processor. (author)

Frequent alteration of MLL3 frameshift mutations in microsatellite deficient colorectal cancer.

Directory of Open Access Journals (Sweden)

Yoshiyuki Watanabe

Full Text Available MLL3 is a histone 3-lysine 4 methyltransferase with tumor-suppressor properties that belongs to a family of chromatin regulator genes potentially altered in neoplasia. Mutations in MLL3 were found in a whole genome analysis of colorectal cancer but have not been confirmed by a separate study.We analyzed mutations of coding region and promoter methylation in MLL3 using 126 cases of colorectal cancer. We found two isoforms of MLL3 and DNA sequencing revealed frameshift and other mutations affecting both isoforms of MLL3 in colorectal cancer cells and 19 of 134 (14% primary colorectal samples analyzed. Moreover, frameshift mutations were more common in cases with microsatellite instability (31% both in CRC cell lines and primary tumors. The largest isoform of MLL3 is transcribed from a CpG island-associated promoter that has highly homology with a pseudo-gene on chromosome 22 (psiTPTE22. Using an assay which measured both loci simultaneously we found prominent age related methylation in normal colon (from 21% in individuals less than 25 years old to 56% in individuals older than 70, R = 0.88, p<0.001 and frequent hypermethylation (83% in both CRC cell lines and primary tumors. We next studied the two loci separately and found that age and cancer related methylation was solely a property of the pseudogene CpG island and that the MLL3 loci was unmethylated.We found that frameshift mutations of MLL3 in both CRC cells and primary tumor that were more common in cases with microsatellite instability. Moreover, we have shown CpG island-associated promoter of MLL3 gene has no DNA methylation in CRC cells but also primary tumor and normal colon, and this region has a highly homologous of pseudo gene (psiTPTE22 that was age relate DNA methylation.

SPIRAL INSTABILITY CAN DRIVE THERMONUCLEAR EXPLOSIONS IN BINARY WHITE DWARF MERGERS

International Nuclear Information System (INIS)

Kashyap, Rahul; Fisher, Robert; García-Berro, Enrique; Aznar-Siguán, Gabriela; Ji, Suoqing; Lorén-Aguilar, Pablo

2015-01-01

Thermonuclear, or Type Ia supernovae (SNe Ia), originate from the explosion of carbon–oxygen white dwarfs, and serve as standardizable cosmological candles. However, despite their importance, the nature of the progenitor systems that give rise to SNe Ia has not been hitherto elucidated. Observational evidence favors the double-degenerate channel in which merging white dwarf binaries lead to SNe Ia. Furthermore, significant discrepancies exist between observations and theory, and to date, there has been no self-consistent merger model that yields a SNe Ia. Here we show that a spiral mode instability in the accretion disk formed during a binary white dwarf merger leads to a detonation on a dynamical timescale. This mechanism sheds light on how white dwarf mergers may frequently yield SNe Ia

SPIRAL INSTABILITY CAN DRIVE THERMONUCLEAR EXPLOSIONS IN BINARY WHITE DWARF MERGERS

Energy Technology Data Exchange (ETDEWEB)

Kashyap, Rahul; Fisher, Robert [Department of Physics, University of Massachusetts Dartmouth, 285 Old Westport Road, North Dartmouth, MA 02740 (United States); García-Berro, Enrique; Aznar-Siguán, Gabriela [Departament de Física Aplicada, Universitat Politècnica de Catalunya, c/Esteve Terrades, 5, E-08860 Castelldefels (Spain); Ji, Suoqing [Department of Physics, Broida Hall, University of California Santa Barbara, Santa Barbara, CA 93106–9530 (United States); Lorén-Aguilar, Pablo [School of Physics, University of Exeter, Stocker Road, Exeter EX4 4QL (United Kingdom)

2015-02-10

Thermonuclear, or Type Ia supernovae (SNe Ia), originate from the explosion of carbon–oxygen white dwarfs, and serve as standardizable cosmological candles. However, despite their importance, the nature of the progenitor systems that give rise to SNe Ia has not been hitherto elucidated. Observational evidence favors the double-degenerate channel in which merging white dwarf binaries lead to SNe Ia. Furthermore, significant discrepancies exist between observations and theory, and to date, there has been no self-consistent merger model that yields a SNe Ia. Here we show that a spiral mode instability in the accretion disk formed during a binary white dwarf merger leads to a detonation on a dynamical timescale. This mechanism sheds light on how white dwarf mergers may frequently yield SNe Ia.

Trans-generational radiation-induced chromosomal instability in the female enhances the action of chemical mutagens

International Nuclear Information System (INIS)

Camats, Nuria; Garcia, Francisca; Parrilla, Juan Jose; Calaf, Joaquim; Martin, Miguel; Caldes, Montserrat Garcia

2008-01-01

Genomic instability can be produced by ionising radiation, so-called radiation-induced genomic instability, and chemical mutagens. Radiation-induced genomic instability occurs in both germinal and somatic cells and also in the offspring of irradiated individuals, and it is characterised by genetic changes including chromosomal rearrangements. The majority of studies of trans-generational, radiation-induced genomic instability have been described in the male germ line, whereas the authors who have chosen the female as a model are scarce. The aim of this work is to find out the radiation-induced effects in the foetal offspring of X-ray-treated female rats and, at the same time, the possible impact of this radiation-induced genomic instability on the action of a chemical mutagen. In order to achieve both goals, the quantity and quality of chromosomal damage were analysed. In order to detect trans-generational genomic instability, a total of 4806 metaphases from foetal tissues from the foetal offspring of X-irradiated female rats (5 Gy, acute dose) were analysed. The study's results showed that there is radiation-induced genomic instability: the number of aberrant metaphases and the breaks per total metaphases studied increased and were found to be statistically significant (p ≤ 0.05), with regard to the control group. In order to identify how this trans-generational, radiation-induced chromosomal instability could influence the chromosomal behaviour of the offspring of irradiated rat females in front of a chemical agent (aphidicolin), a total of 2481 metaphases were studied. The observed results showed that there is an enhancement of the action of the chemical agent: chromosomal breaks per aberrant metaphases show significant differences (p ≤ 0.05) in the X-ray- and aphidicolin-treated group as regards the aphidicolin-treated group. In conclusion, our findings indicate that there is trans-generational, radiation-induced chromosomal instability in the foetal cells

Trans-generational radiation-induced chromosomal instability in the female enhances the action of chemical mutagens

Energy Technology Data Exchange (ETDEWEB)

Camats, Nuria [Institut de Biotecnologia i Biomedicina (IBB), Universitat Autonoma de Barcelona, 08193 Barcelona (Spain); Departament de Biologia Cel.lular, Fisiologia i Immunologia, Universitat Autonoma de Barcelona, 08193 Barcelona (Spain); Garcia, Francisca [Institut de Biotecnologia i Biomedicina (IBB), Universitat Autonoma de Barcelona, 08193 Barcelona (Spain); Parrilla, Juan Jose [Servicio de Ginecologia y Obstetricia, Hospital Universitario Virgen de la Arrixaca, 30120 El Palmar, Murcia (Spain); Calaf, Joaquim [Servei de Ginecologia i Obstetricia, Hospital Universitari de la Santa Creu i Sant Pau, 08025 Barcelona (Spain); Martin, Miguel [Departament de Pediatria, d' Obstetricia i Ginecologia i de Medicina Preventiva, Universitat Autonoma de Barcelona, 08193 Barcelona (Spain); Caldes, Montserrat Garcia [Institut de Biotecnologia i Biomedicina (IBB), Universitat Autonoma de Barcelona, 08193 Barcelona (Spain); Departament de Biologia Cel.lular, Fisiologia i Immunologia, Universitat Autonoma de Barcelona, 08193 Barcelona (Spain)], E-mail: Montserrat.Garcia.Caldes@uab.es

2008-04-02

Genomic instability can be produced by ionising radiation, so-called radiation-induced genomic instability, and chemical mutagens. Radiation-induced genomic instability occurs in both germinal and somatic cells and also in the offspring of irradiated individuals, and it is characterised by genetic changes including chromosomal rearrangements. The majority of studies of trans-generational, radiation-induced genomic instability have been described in the male germ line, whereas the authors who have chosen the female as a model are scarce. The aim of this work is to find out the radiation-induced effects in the foetal offspring of X-ray-treated female rats and, at the same time, the possible impact of this radiation-induced genomic instability on the action of a chemical mutagen. In order to achieve both goals, the quantity and quality of chromosomal damage were analysed. In order to detect trans-generational genomic instability, a total of 4806 metaphases from foetal tissues from the foetal offspring of X-irradiated female rats (5 Gy, acute dose) were analysed. The study's results showed that there is radiation-induced genomic instability: the number of aberrant metaphases and the breaks per total metaphases studied increased and were found to be statistically significant (p {<=} 0.05), with regard to the control group. In order to identify how this trans-generational, radiation-induced chromosomal instability could influence the chromosomal behaviour of the offspring of irradiated rat females in front of a chemical agent (aphidicolin), a total of 2481 metaphases were studied. The observed results showed that there is an enhancement of the action of the chemical agent: chromosomal breaks per aberrant metaphases show significant differences (p {<=} 0.05) in the X-ray- and aphidicolin-treated group as regards the aphidicolin-treated group. In conclusion, our findings indicate that there is trans-generational, radiation-induced chromosomal instability in the foetal

An Instability in Stratified Taylor-Couette Flow

Science.gov (United States)

Swinney, Harry

2015-11-01

In the late 1950s Russell Donnelly began conducting experiments at the University of Chicago on flow between concentric rotating cylinders, and his experiments together with complementary theory by his collaborator S. Chandrasekhar did much to rekindle interest in the flow instability discovered and studied by G.I. Taylor (1923). The present study concerns an instability in a concentric cylinder system containing a fluid with an axial density gradient. In 2005 Dubrulle et al. suggested that a `stratorotational instability' (SRI) in this system could provide insight into instability and angular momentum transport in astrophysical accretion disks. In 2007 the stratorotational instability was observed in experiments by Le Bars and Le Gal. We have conducted an experiment on the SRI in a concentric cylinder system (radius ratio η = 0 . 876) with buoyancy frequency N / 2 π = 0.25, 0.50, or 0.75 Hz. For N = 0.75 Hz we observe the SRI onset to occur for Ωouter /Ωinner > η , contrary to the prediction of Shalybkov and Rüdiger. Research conducted with Bruce Rodenborn and Ruy Ibanez.

Instability of flat space at finite temperature

International Nuclear Information System (INIS)

Gross, D.J.; Perry, M.J.; Yaffe, L.G.

1982-01-01

The instabilities of quantum gravity are investigated using the path-integral formulation of Einstein's theory. A brief review is given of the classical gravitational instabilities, as well as the stability of flat space. The Euclidean path-integral representation of the partition function is employed to discuss the instability of flat space at finite temperature. Semiclassical, or saddle-point, approximations are utilized. We show how the Jeans instability arises as a tachyon in the graviton propagator when small perturbations about hot flat space are considered. The effect due to the Schwarzschild instanton is studied. The small fluctuations about this instanton are analyzed and a negative mode is discovered. This produces, in the semiclassical approximation, an imaginary part of the free energy. This is interpreted as being due to the metastability of hot flat space to nucleate black holes. These then evolve by evaporation or by accretion of thermal gravitons, leading to the instability of hot flat space. The nucleation rate of black holes is calculated as a function of temperature

Analysis of beam transverse instability in electron linac

International Nuclear Information System (INIS)

Mondrus, I.N.; Shenderovich, A.M.

1990-01-01

Dispersion equations describing transverse beam instability in a single resonator section and in an accelerator comprising a sequence of resonator sections are derived. It is shown that close to parametric resonance of any multiplicity a reduction of cumulative instability incoherent takes place between nonsymmetric defocusing wave frequency and the frequency of accelerator cluster transport. Under exact resonance the increment equals to zero and under misalignment due to resonance depending on its sign and disturbance frequency an instability of either fast or slow wave takes place. It is shown that this effect leads to beam instability suppression of sections with the opposite sign of misalignment due to resonance are located in turn. The results obtained show that application of a parametric resonance through reducing slight the single section absolute instability threshold current, allows one to effectively suppress cumulative instability. The requirement to the accuracy of tuning to a resonance of identical sections is substantially reduced under the alternation of sections with different sign misalignment due to resonance and can be easily realized in practice

Dynamics of polaritons in semiconductor microcavities near instability thresholds

International Nuclear Information System (INIS)

He, Peng-Bin

2012-01-01

A theoretical study is presented on the dynamics of polaritons in semiconductor microcavities near parametric instability thresholds. With upward or downward ramp of optical pump, different instability modes emerge in parameter space defined by damping and detuning. According to these modes, stationary short-wave, stationary periodic, oscillatory periodic, and oscillatory uniform parametric instabilities are distinguished. By multiple scale expansion, the dynamics near threshold can be described by a critical mode with a slowly varying amplitude for the last three instabilities. Furthermore, it is found that the evolutions of their amplitudes are governed by real or complex Ginzburg–Landau equations. -- Highlights: ► Phase diagrams for different instability in extended parameter space. ► Different instability modes near thresholds. ► Different envelop equations near thresholds obtained by multi-scale expansion.

Cinerama sickness and postural instability.

Science.gov (United States)

Bos, Jelte E; Ledegang, Wietse D; Lubeck, Astrid J A; Stins, John F

2013-01-01

Motion sickness symptoms and increased postural instability induced by motion pictures have been reported in a laboratory, but not in a real cinema. We, therefore, carried out an observational study recording sickness severity and postural instability in 19 subjects before, immediately and 45 min after watching a 1 h 3D aviation documentary in a cinema. Sickness was significantly larger right after the movie than before, and in a lesser extent still so after 45 min. The average standard deviation of the lateral centre of pressure excursions was significantly larger only right afterwards. When low-pass filtered at 0.1 Hz, lateral and for-aft excursions were both significantly larger right after the movie, while for-aft excursions then remained larger even after 45 min. Speculating on previous findings, we predict more sickness and postural instability in 3D than in 2D movies, also suggesting a possible, but yet unknown risk for work-related activities and vehicle operation. Watching motion pictures may be sickening and posturally destabilising, but effects in a cinema are unknown. We, therefore, carried out an observational study showing that sickness then is mainly an issue during the exposure while postural instability is an issue afterwards.

Investigation on thermo-acoustic instability dynamic characteristics of hydrocarbon fuel flowing in scramjet cooling channel based on wavelet entropy method

Science.gov (United States)

Zan, Hao; Li, Haowei; Jiang, Yuguang; Wu, Meng; Zhou, Weixing; Bao, Wen

2018-06-01

As part of our efforts to find ways and means to further improve the regenerative cooling technology in scramjet, the experiments of thermo-acoustic instability dynamic characteristics of hydrocarbon fuel flowing have been conducted in horizontal circular tubes at different conditions. The experimental results indicate that there is a developing process from thermo-acoustic stability to instability. In order to have a deep understanding on the developing process of thermo-acoustic instability, the method of Multi-scale Shannon Wavelet Entropy (MSWE) based on Wavelet Transform Correlation Filter (WTCF) and Multi-Scale Shannon Entropy (MSE) is adopted in this paper. The results demonstrate that the developing process of thermo-acoustic instability from noise and weak signals is well detected by MSWE method and the differences among the stability, the developing process and the instability can be identified. These properties render the method particularly powerful for warning thermo-acoustic instability of hydrocarbon fuel flowing in scramjet cooling channels. The mass flow rate and the inlet pressure will make an influence on the developing process of the thermo-acoustic instability. The investigation on thermo-acoustic instability dynamic characteristics at supercritical pressure based on wavelet entropy method offers guidance on the control of scramjet fuel supply, which can secure stable fuel flowing in regenerative cooling system.

Hydrodynamick instabilities on ICF capsules

International Nuclear Information System (INIS)

Haan, S.W.

1991-01-01

This article summarizes our current understanding of hydrodynamic instabilities as relevant to ICF. First we discuss classical, single mode Rayleigh-Taylor instability, and nonlinear effects in the evolution of a single mode. Then we discuss multimode systems, considering: (1) the onset of nonlinearity; (2) a second order mode coupling theory for weakly nonlinear effects, and (3) the fully nonlinear regime. Two stabilization mechanisms relevant to ICF are described next: gradient scale length and convective stabilization. Then we describe a model which is meant to estimate the weakly nonlinear evolution of multi-mode systems as relevant to ICF, given the short-wavelength stabilization. Finally, we discuss the relevant code simulation capability, and experiments. At this time we are quite optimistic about our ability to estimate instability growth on ICF capsules, but further experiments and simulations are needed to verify the modeling. 52 refs

Microsatellite instability, immunohistochemistry, and additional PMS2 staining in suspected hereditary nonpolyposis colorectal cancer

NARCIS (Netherlands)

de Jong, Andrea E.; van Puijenbroek, Marjo; Hendriks, Yvonne; Tops, Carli; Wijnen, Juul; Ausems, Margreet G. E. M.; Meijers-Heijboer, Hanne; Wagner, Anja; van Os, Theo A. M.; Bröcker-Vriends, Annette H. J. T.; Vasen, Hans F. A.; Morreau, Hans

2004-01-01

Immunohistochemistry (IHC) and microsatellite instability (MSI) analysis can be used to identify patients with a possible DNA mismatch repair defect [hereditary nonpolyposis colorectal carcinoma (HNPCC)]. The Bethesda criteria have been proposed to select families for determination of MSI. The aims

Coherent Instabilities of ILC Damping Ring

Energy Technology Data Exchange (ETDEWEB)

Heifets, S.; Stupakov, G.; Bane, K.; /SLAC

2006-09-27

The paper presents the first attempt to estimates the ILC damping ring impedance and compare thresholds of the classical instabilities for several designs initially proposed for the DR. The work was carried out in the spring of 2006. Since then the choice of the DR is narrowed. Nevertheless, the analysis described may be useful for the next iterations of the beam stability. Overall, the conventional instabilities will have little impact on the ring performance provided the careful design of the ring minimizes the impedance below acceptable level indicated above. The only exception is the transverse CB instability. The longitudinal CB is less demanding. However, even the transverse CB instability would have threshold current above nominal provided the aperture in the wigglers is increased from 8 mm to 16 mm. The microwave instability needs more studies. Nevertheless, we should remember that the ILC DR is different from existing high-current machines at least in two respects: absence of the beam-beam tune spread stabilizing beams in colliders, and unusual strict requirements for low emittance. That may cause new problems such as bunch emittance dilution due to high-frequency wakes (BPMs, grooves), etc. Even if such a possibility exists, it probably universal for all machines and ought be addressed in the design of vacuum components rather than have effect on the choice of the machine design.

Kinetic simulations of Rayleigh-Taylor instabilities

International Nuclear Information System (INIS)

Sagert, Irina; Bauer, Wolfgang; Colbry, Dirk; Howell, Jim; Staber, Alec; Strother, Terrance

2014-01-01

We report on an ongoing project to develop a large scale Direct Simulation Monte Carlo code. The code is primarily aimed towards applications in astrophysics such as simulations of core-collapse supernovae. It has been tested on shock wave phenomena in the continuum limit and for matter out of equilibrium. In the current work we focus on the study of fluid instabilities. Like shock waves these are routinely used as test-cases for hydrodynamic codes and are discussed to play an important role in the explosion mechanism of core-collapse supernovae. As a first test we study the evolution of a single-mode Rayleigh-Taylor instability at the interface of a light and a heavy fluid in the presence of a gravitational acceleration. To suppress small-wavelength instabilities caused by the irregularity in the separation layer we use a large particle mean free path. The latter leads to the development of a diffusion layer as particles propagate from one fluid into the other. For small amplitudes, when the instability is in the linear regime, we compare its position and shape to the analytic prediction. Despite the broadening of the fluid interface we see a good agreement with the analytic solution. At later times we observe the development of a mushroom like shape caused by secondary Kelvin-Helmholtz instabilities as seen in hydrodynamic simulations and consistent with experimental observations.

High-Speed Imaging of Dusty Plasma Instabilities

International Nuclear Information System (INIS)

Tawidian, H.; Mikikian, M.; Lecas, T.; Boufendi, L.; Coueedel, L.; Vallee, O.

2011-01-01

Dust particles in a plasma acquire negative charges by capturing electrons. If the dust particle density is high, a huge loss of free electrons can trigger unstable behaviors in the plasma. Several types of plasma behaviors are analyzed thanks to a high-speed camera like dust particle growth instabilities (DPGI) and a new phenomenon called plasma spheroids. These small plasma spheroids are about a few mm, have a slightly enhanced luminosity, and are observed in the vicinity of the electrodes. Different behaviors are identified for these spheroids like a rotational motion, or a chaotic regime (fast appearance and disappearance).

High-Speed Imaging of Dusty Plasma Instabilities

Science.gov (United States)

Tawidian, H.; Couëdel, L.; Mikikian, M.; Lecas, T.; Boufendi, L.; Vallée, O.

2011-11-01

Dust particles in a plasma acquire negative charges by capturing electrons. If the dust particle density is high, a huge loss of free electrons can trigger unstable behaviors in the plasma. Several types of plasma behaviors are analyzed thanks to a high-speed camera like dust particle growth instabilities (DPGI) and a new phenomenon called plasma spheroids. These small plasma spheroids are about a few mm, have a slightly enhanced luminosity, and are observed in the vicinity of the electrodes. Different behaviors are identified for these spheroids like a rotational motion, or a chaotic regime (fast appearance and disappearance).

Surface instabilities during straining of anisotropic materials

DEFF Research Database (Denmark)

Legarth, Brian Nyvang; Richelsen, Ann Bettina

2006-01-01

The development of instabilities in traction-free surfaces is investigated numerically using a unit cell model. Full finite strain analyses are conducted using isotropic as well as anisotropic yield criteria and both plane strain tension and compression are considered. In the load range of tensio...... of principal overall strain. For other orientations surface instabilities are seen when non-associated plastic flow is taken into account. Compared to tension, smaller compressive deformations are needed in order to initiate a surface instability....

How does political instability affect economic growth?

OpenAIRE

Aisen, Ari; Veiga, Francisco José

2011-01-01

The purpose of this paper is to empirically determine the effects of political instability on economic growth. Using the system-GMM estimator for linear dynamic panel data models on a sample covering up to 169 countries, and 5-year periods from 1960 to 2004, we find that higher degrees of political instability are associated with lower growth rates of GDP per capita. Regarding the channels of transmission, we find that political instability adversely affects growth by lowering the rates of pr...

Rayleigh-Taylor instability in inertial confinement fusion

International Nuclear Information System (INIS)

Gupta, N.K.

1987-01-01

This report summarises the main results of theoretical analysis on the problem of Rayleigh-Tylor instability in inertial confinement fusion (ICF). Work presented in this report essentially covers four basic problems. Firstly, an analytical formulation to analyse the effects of plasma density inhomogeneities on the growth of the instability in plane geometry is presented. As a result of this analysis it is concluded that, for minimizing the growth rate of the instability, it may be advantageous to use the driver laser beams of higher irradiance and an optimum wave length in an ICF experiment. Secondly, a new formulation for the analysis of the instability in curved (cylindrical and spherical) geometries is presented. A general eigenvalue equation for the growth rate of the instability which is applicable for both plane and curved geometries is derived. A comparative study is made between the plane, cylindrical and spherical geometries. Also analytical expressions for the growth rates are obtained in the cases of spherical and cylindrical shell targets and their variations with respect to the aspect ratios of the shells are discussed. Thirdly, a semi-analytical analysis of the instability where the growth rate is obtained by solving numerically a (2N-1)x(2N-1) determinantal equation is presented. The semi-analytical analysis developed is applicable for the study of the growth of the instability in the present day multi-structured spherical shell targets. Finally, a dynamic analysis of the growth of the instability for a representative spherical solid target driven by laser beams symmetrically from all the sides is carried out numerically using a computer code developed for this purpose. This study confirms analytical predictions. Further, it is observed that an approximate analytical analysis with time independent density profile gives conservative estimates for the growth rate. In passing, the computer code is also used to estimate the pellet gain for spin

[Neurobiological aspects of personality disorders and emotional instability].

Science.gov (United States)

Petrovic, Predrag

2016-12-06

Neurobiological aspects of personality disorders and emotional instability ADHD and mental disorders encompassing emotional instability such as emotionally unstable personality disorder and antisocial personality disorder can potentially be explained by a suboptimal regulation of information processing in the brain. ADHD involves suboptimal function of non-emotional attentional regulatory processes and emotional instability involves suboptimal emotional regulation. A network including prefrontal areas, anterior cingulate cortex, basal ganglia and specific neuromodulatory systems such as the dopamine system are dysfunctional in both ADHD and emotional instability. One might suggest that a dimensional view better describes these mental states than categorical diagnoses.

Waves and instabilities in plasmas

International Nuclear Information System (INIS)

Chen, L.

1987-01-01

The contents of this book are: Plasma as a Dielectric Medium; Nyquist Technique; Absolute and Convective Instabilities; Landau Damping and Phase Mixing; Particle Trapping and Breakdown of Linear Theory; Solution of Viasov Equation via Guilding-Center Transformation; Kinetic Theory of Magnetohydrodynamic Waves; Geometric Optics; Wave-Kinetic Equation; Cutoff and Resonance; Resonant Absorption; Mode Conversion; Gyrokinetic Equation; Drift Waves; Quasi-Linear Theory; Ponderomotive Force; Parametric Instabilities; Problem Sets for Homework, Midterm and Final Examinations

Control of transversal instabilities in reaction-diffusion systems

Science.gov (United States)

Totz, Sonja; Löber, Jakob; Totz, Jan Frederik; Engel, Harald

2018-05-01

In two-dimensional reaction-diffusion systems, local curvature perturbations on traveling waves are typically damped out and vanish. However, if the inhibitor diffuses much faster than the activator, transversal instabilities can arise, leading from flat to folded, spatio-temporally modulated waves and to spreading spiral turbulence. Here, we propose a scheme to induce or inhibit these instabilities via a spatio-temporal feedback loop. In a piecewise-linear version of the FitzHugh–Nagumo model, transversal instabilities and spiral turbulence in the uncontrolled system are shown to be suppressed in the presence of control, thereby stabilizing plane wave propagation. Conversely, in numerical simulations with the modified Oregonator model for the photosensitive Belousov–Zhabotinsky reaction, which does not exhibit transversal instabilities on its own, we demonstrate the feasibility of inducing transversal instabilities and study the emerging wave patterns in a well-controlled manner.

Rayleigh-Taylor/gravitational instability in dense magnetoplasmas

Energy Technology Data Exchange (ETDEWEB)

Ali, S., E-mail: shahid.ali@ncp.edu.p [National Centre for Physics, Quaid-i-Azam University Campus, Islamabad (Pakistan); IPFN, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal); Ahmed, Z. [COMSATS Institute of Information Technology, Department of Physics, Wah Campus (Pakistan); Mirza, Arshad M. [Theoretical Plasma Physics Group, Physics Department, Quaid-i-Azam University, Islamabad 45320 (Pakistan); Ahmad, I. [COMSATS Institute of Information Technology, Department of Physics, Islamabad Campus (Pakistan)

2009-08-10

The Rayleigh-Taylor instability is investigated in a nonuniform dense quantum magnetoplasma. For this purpose, a quantum hydrodynamical model is used for the electrons whereas the ions are assumed to be cold and classical. The dispersion relation for the Rayleigh-Taylor instability becomes modified with the quantum corrections associated with the Fermi pressure law and the quantum Bohm potential force. Numerically, it is found that the quantum speed and density gradient significantly modify the growth rate of RT instability. In a dense quantum magnetoplasma case, the linear growth rate of RT instability becomes significantly higher than its classical value and the modes are found to be highly localized. The present investigation should be useful in the studies of dense astrophysical magnetoplasmas as well as in laser-produced plasmas.

Genomic instability--an evolving hallmark of cancer.

Science.gov (United States)

Negrini, Simona; Gorgoulis, Vassilis G; Halazonetis, Thanos D

2010-03-01

Genomic instability is a characteristic of most cancers. In hereditary cancers, genomic instability results from mutations in DNA repair genes and drives cancer development, as predicted by the mutator hypothesis. In sporadic (non-hereditary) cancers the molecular basis of genomic instability remains unclear, but recent high-throughput sequencing studies suggest that mutations in DNA repair genes are infrequent before therapy, arguing against the mutator hypothesis for these cancers. Instead, the mutation patterns of the tumour suppressor TP53 (which encodes p53), ataxia telangiectasia mutated (ATM) and cyclin-dependent kinase inhibitor 2A (CDKN2A; which encodes p16INK4A and p14ARF) support the oncogene-induced DNA replication stress model, which attributes genomic instability and TP53 and ATM mutations to oncogene-induced DNA damage.

Rayleigh-Taylor/gravitational instability in dense magnetoplasmas

International Nuclear Information System (INIS)

Ali, S.; Ahmed, Z.; Mirza, Arshad M.; Ahmad, I.

2009-01-01

The Rayleigh-Taylor instability is investigated in a nonuniform dense quantum magnetoplasma. For this purpose, a quantum hydrodynamical model is used for the electrons whereas the ions are assumed to be cold and classical. The dispersion relation for the Rayleigh-Taylor instability becomes modified with the quantum corrections associated with the Fermi pressure law and the quantum Bohm potential force. Numerically, it is found that the quantum speed and density gradient significantly modify the growth rate of RT instability. In a dense quantum magnetoplasma case, the linear growth rate of RT instability becomes significantly higher than its classical value and the modes are found to be highly localized. The present investigation should be useful in the studies of dense astrophysical magnetoplasmas as well as in laser-produced plasmas.

Approaching Pomeranchuk instabilities from ordered phase: A crossing-symmetric equation method

International Nuclear Information System (INIS)

Reidy, Kelly; Quader, Khandker; Bedell, Kevin

2014-01-01

We explore features of a 3D Fermi liquid near generalized Pomeranchuk instabilities using a tractable crossing-symmetric equation method. We approach the instabilities from the ordered ferromagnetic phase. We find “quantum multi-criticality” as approach to the ferromagnetic instability drives instability in other channel(s). It is found that a charge nematic instability precedes and is driven by Pomeranchuk instabilities in both the ℓ=0 spin and density channels

Harmonic Instability Assessment Using State-Space Modeling and Participation Analysis in Inverter-Fed Power Systems

DEFF Research Database (Denmark)

Wang, Yanbo; Wang, Xiongfei; Blaabjerg, Frede

2017-01-01

parameters on the harmonic instability of the power system. Moreover, the harmonic-frequency oscillation modes are identified, where participation analysis is presented to evaluate the contributions of different states to these modes and to further reveal how the system gives rise to harmonic instability......This paper presents a harmonic instability analysis method using state-space modeling and participation analysis in the inverter-fed ac power systems. A full-order state-space model for the droop-controlled Distributed Generation (DG) inverter is built first, including the time delay of the digital...... control system, inner current and voltage control loops, and outer droop-based power control loop. Based on the DG inverter model, an overall state-space model of a two-inverter-fed system is established. The eigenvalue-based stability analysis is then presented to assess the influence of controller...

Simulation and quasilinear theory of proton firehose instability

Energy Technology Data Exchange (ETDEWEB)

Seough, Jungjoon [Korean Astronomy and Space Science Institute, Daejeon (Korea, Republic of); Faculty of Human Development, University of Toyama, 3190, Gofuku, Toyama City, Toyama, 930-8555 (Japan); Yoon, Peter H. [University of Maryland, College Park, Maryland 20742 (United States); School of Space Research, Kyung Hee University, Yongin, Gyeonggi 446-701 (Korea, Republic of); Hwang, Junga [Korean Astronomy and Space Science Institute, Daejeon (Korea, Republic of); Korea, University of Science and Technology, Daejeon (Korea, Republic of)

2015-01-15

The electromagnetic proton firehose instability is driven by excessive parallel temperature anisotropy, T{sub ∥} > T{sub ⊥} (or more precisely, parallel pressure anisotropy, P{sub ∥} > P{sub ⊥}) in high-beta plasmas. Together with kinetic instabilities driven by excessive perpendicular temperature anisotropy, namely, electromagnetic proton cyclotron and mirror instabilities, its role in providing the upper limit for the temperature anisotropy in the solar wind is well-known. A recent Letter [Seough et al., Phys. Rev. Lett. 110, 071103 (2013)] employed quasilinear kinetic theory for these instabilities to explain the observed temperature anisotropy upper bound in the solar wind. However, the validity of quasilinear approach has not been rigorously tested until recently. In a recent paper [Seough et al., Phys. Plasmas 21, 062118 (2014)], a comparative study is carried out for the first time in which quasilinear theory of proton cyclotron instability is tested against results obtained from the particle-in-cell simulation method, and it was demonstrated that the agreement was rather excellent. The present paper addresses the same issue involving the proton firehose instability. Unlike the proton cyclotron instability, however, it is found that the quasilinear approximation enjoys only a limited range of validity, especially for the wave dynamics and for the relatively high-beta regime. Possible causes and mechanisms responsible for the discrepancies are speculated and discussed.

Beam--plasma instabilities and the beam--plasma discharge

International Nuclear Information System (INIS)

Kellogg, P.J.; Boswell, R.W.

1986-01-01

Using a new electron gun, a number of measurements bearing on the generation of beam--plasma discharge (BPD) in WOMBAT (waves on magnetized beams and turbulence) [R. W. Boswell and P. J. Kellogg, Geophys. Res. Lett. 10, 565 (1983)] have been made. A beam--plasma discharge is an rf discharge in which the rf fields are provided by instabilities [W. D. Getty and L. D. Smullin, J. Appl. Phys. 34, 3421 (1963)]. The new gun has a narrower divergence angle than the old, and comparison of the BPD thresholds for the two guns verifies that the BPD ignition current is proportional to the cross-sectional area of the plasma. The high-frequency instabilities, precursors to the BPD, are identified with the two Trivelpiece--Gould modes [A. W. Trivelpiece and R. W. Gould, J. Appl. Phys. 30, 1784 (1959)]. Which frequency appears depends on the neutral pressure. The measured frequencies are not consistent with the simple interpretation of the lower frequency as a Cerenkov resonance with the low-Trivelpiece--Gould mode; it must be a cyclotron resonance. As is generally true in such beam--plasma interaction experiments, strong low-frequency waves appear at currents far below those necessary for BPD ignition. These low-frequency waves are shown to control the onset of the high-frequency precursors to the BPD. A mechanism for this control is suggested, which involves the conversion of a convective instability to an absolute one by trapping of the unstable waves in the density perturbations of the low-frequency waves. This process greatly reduces the current necessary for BPD ignition

Marangoni instability in a thin film heated from below: Effect of nonmonotonic dependence of surface tension on temperature

Science.gov (United States)

Sarma, Rajkumar; Mondal, Pranab Kumar

2018-04-01

We investigate Marangoni instability in a thin liquid film resting on a substrate of low thermal conductivity and separated from the surrounding gas phase by a deformable free surface. Considering a nonmonotonic variation of surface tension with temperature, here we analytically derive the neutral stability curve for the monotonic and oscillatory modes of instability (for both the long-wave and short-wave perturbations) under the framework of linear stability analysis. For the long-wave instability, we derive a set of amplitude equations using the scaling k ˜(Bi) 1 /2 , where k is the wave number and Bi is the Biot number. Through this investigation, we demonstrate that for such a fluid layer upon heating from below, both monotonic and oscillatory instability can appear for a certain range of the dimensionless parameters, viz., Biot number (Bi ) , Galileo number (Ga ) , and inverse capillary number (Σ ) . Moreover, we unveil, through this study, the influential role of the above-mentioned parameters on the stability of the system and identify the critical values of these parameters above which instability initiates in the liquid layer.

Analysis of multi-bunch instabilities at the Diamond storage ring

CERN Document Server

Bartolini, Riccardo; Rehm, Guenther; Smaluk, Victor

2017-01-01

We present the result of the analytical, numerical and experimental analysis of multi-bunch instabilities at the Diamond storage ring. This work compares the impedance estimates with CST with the analysis of the growth rates of the excited multi-bunch modes in different machine configurations. The contribution of a number of wakefield sources has been identified with very high precision thanks to high quality data provided by the existing TMBF diagnostics.

MHD instabilities leading to disruption in JT-60U reversed shear plasmas

International Nuclear Information System (INIS)

Takechi, M.; Fujita, T.; Ishii, Y.; Ozeki, T.; Suzuki, T.; Isayama, A.

2005-01-01

High performance reversed shear discharges with strong internal transport barrier (ITB) and flat pressure profile in the plasma core region disrupt frequently even with low beta. We analyzed MHD instabilities leading to low beta disruption with measuring fluctuations and current profile with MSE measurement. We mainly observed two type of disruptions. One is the disruption without precursor at q surf ∼integer. The other is the disruption with n=1 precursor of γ>10 ms. The poloidal mode number of the n=1 mode is equal to outermost integer of q. The n=1 mode exist from peripheral region to ITB layer or peripheral region and ITB and the phase is 180 degree different between them. To explain these characteristics of disruption, we introduce the simple model such as, disruption occurs when the both MHD instabilities at plasma surface and at safety factor being equal to surface mode are unstable. This simple model can explain almost all observed disruption by two process. One is the surface mode triggered disruption, which occurs when q surf change, corresponding q surface at ITB layer change discretely. The other is the internal mode triggered disruption, which occurs when corresponding q surface become unstable gradually. (author)

Coherent betatron instability in the Tevatron

International Nuclear Information System (INIS)

Bogacz, S.A.; Harrison, M.; Ng, K.Y.

1988-01-01

The coherent betatron instability was first observed during the recent 1987-88 Tevatron fixed target run. In this operating mode 1000 consecutive bunches are loaded into the machine at 150 GeV with a bunch spacing of 18.8 /times/ 10 -9 sec (53 MHz). The normalized transverse emittance is typically 15 π /times/ 10 -6 m rad in each plane with a longitudinal emittance of about 1.5 eV-sec. The beam is accelerated to 800 GeV in 13 sec. and then it is resonantly extracted during a 23 sec flat top. As the run progressed the bunch intensities were increased until at about 1.4 /times/ 10 10 ppb (protons per bunch) we experienced the onset of a coherent horizontal oscillation taking place in the later stages of the acceleration cycle (>600 GeV). This rapidly developing coherent instability results in a significant emittance growth, which limits machine performance and in a catastrophic scenario it even prevents extraction of the beam. In this paper we will present a simple analytic description of the observed instability. We will show that a combination of a resistive wall coupled bunch effect and a single bunch slow head-tail instability is consistent with the above observations. Finally, a systematic numerical analysis of our model (growth-time vs chromaticity plots) points to the existence of the ≥1 slow head-tail modes as a plausible mechanism for the observed coherent instability. This last claim, as mentioned before, does not have conclusive experimental evidence, although it is based on a very good agreement between the measured values of the instability growth-time and the ones calculated on the basis of our model. 4 refs., 3 figs

Mix and hydrodynamic instabilities on NIF

Science.gov (United States)

Smalyuk, V. A.; Robey, H. F.; Casey, D. T.; Clark, D. S.; Döppner, T.; Haan, S. W.; Hammel, B. A.; MacPhee, A. G.; Martinez, D.; Milovich, J. L.; Peterson, J. L.; Pickworth, L.; Pino, J. E.; Raman, K.; Tipton, R.; Weber, C. R.; Baker, K. L.; Bachmann, B.; Berzak Hopkins, L. F.; Bond, E.; Caggiano, J. A.; Callahan, D. A.; Celliers, P. M.; Cerjan, C.; Dixit, S. N.; Edwards, M. J.; Felker, S.; Field, J. E.; Fittinghoff, D. N.; Gharibyan, N.; Grim, G. P.; Hamza, A. V.; Hatarik, R.; Hohenberger, M.; Hsing, W. W.; Hurricane, O. A.; Jancaitis, K. S.; Jones, O. S.; Khan, S.; Kroll, J. J.; Lafortune, K. N.; Landen, O. L.; Ma, T.; MacGowan, B. J.; Masse, L.; Moore, A. S.; Nagel, S. R.; Nikroo, A.; Pak, A.; Patel, P. K.; Remington, B. A.; Sayre, D. B.; Spears, B. K.; Stadermann, M.; Tommasini, R.; Widmayer, C. C.; Yeamans, C. B.; Crippen, J.; Farrell, M.; Giraldez, E.; Rice, N.; Wilde, C. H.; Volegov, P. L.; Gatu Johnson, M.

2017-06-01

Several new platforms have been developed to experimentally measure hydrodynamic instabilities in all phases of indirect-drive, inertial confinement fusion implosions on National Ignition Facility. At the ablation front, instability growth of pre-imposed modulations was measured with a face-on, x-ray radiography platform in the linear regime using the Hydrodynamic Growth Radiography (HGR) platform. Modulation growth of "native roughness" modulations and engineering features (fill tubes and capsule support membranes) were measured in conditions relevant to layered DT implosions. A new experimental platform was developed to measure instability growth at the ablator-ice interface. In the deceleration phase of implosions, several experimental platforms were developed to measure both low-mode asymmetries and high-mode perturbations near peak compression with x-ray and nuclear techniques. In one innovative technique, the self-emission from the hot spot was enhanced with argon dopant to "self-backlight" the shell in-flight. To stabilize instability growth, new "adiabat-shaping" techniques were developed using the HGR platform and applied in layered DT implosions.

Dorsal surgical stabilisation using tension bands for treatment of traumatic atlanto-occipital instability in a cat.

Science.gov (United States)

Vedrine, B; Maurin, M P

2017-12-01

An atlanto-occipital instability secondary to a dog bite was diagnosed in a 4-year-old Persian cat. Dorsal stabilisation of the instability was made with two OrthoFiber prostheses (Securos), which were used as tension bands between the nuchal crests of the occipital bone and the spinous process of the axis. Total recovery was achieved 4 days after surgery. Normal alignment of the atlanto-occipital joint was observed on survey radiographs taken 6 weeks post-surgery. Although the right loop had failed, the alignment was still normal and no neurological after-effects could be identified. Dorsal divergent tension bands between the nuchal crests of the occipital bone and the spinous process of the axis can be used to stabilise traumatic atlanto-occipital instability. © 2017 Australian Veterinary Association.

Posterior glenoid rim deficiency in recurrent (atraumatic) posterior shoulder instability

International Nuclear Information System (INIS)

Weishaupt, D.; Zanetti, M.; Hodler, J.; Nyffeler, R.W.; Gerber, C.

2000-01-01

Objective. To assess the shape of the posterior glenoid rim in patients with recurrent (atraumatic) posterior instability.Design and patients. CT examinations of 15 shoulders with recurrent (atraumatic) posterior instability were reviewed in masked fashion with regard to abnormalities of the glenoid shape, specifically of its posterior rim. The glenoid version was also assessed. The findings were compared with the findings in 15 shoulders with recurrent anterior shoulder instability and 15 shoulders without instability. For all patients, surgical correlation was available.Results. Fourteen of the 15 (93%) shoulders with recurrent (atraumatic) posterior shoulder instability had a deficiency of the posteroinferior glenoid rim. In patients with recurrent anterior instability or stable shoulders such deficiencies were less common (60% and 73%, respectively). The craniocaudal length of the deficiencies was largest in patients with posterior instability. When a posteroinferior deficiency with a craniocaudal length of 12 mm or more was defined as abnormal, sensitivity and specificity for diagnosing recurrent (atraumatic) posterior instability were 86.7% and 83.3%, respectively. There was a statistically significant difference in glenoid version between shoulders with posterior instability and stable shoulders (P=0.01).Conclusion. Recurrent (atraumatic) posterior shoulder instability should be considered in patients with a bony deficiency of the posteroinferior glenoid rim with a craniocaudal length of more than 12 mm. (orig.)

Instability of a Vacuum Arc Centrifuge

International Nuclear Information System (INIS)

Hole, M.J.; Dallaqua, R.S.; Bosco, E. del; Simpson, S.W.

2003-01-01

Ever since conception of the Vacuum Arc Centrifuge (VAC) in 1980, periodic fluctuations in the ion saturation current and floating potential have been observed in Langmuir probe measurements in the rotation region of a VAC. Our theoretical and experimental research suggests that these fluctuations are in fact a pressure-gradient driven drift mode. In this work, we summarise the properties of a theoretical model describing the range of instabilities in the VAC plasma column, present theoretical predictions and compare with detailed experiments conducted on the PCEN centrifuge at the Brazilian National Space Research Institute (INPE). We conclude that the observed instability is a 'universal' instability, driven by the density-gradient, in a plasma with finite conductivity

Microsatellite instability in bladder cancer

DEFF Research Database (Denmark)

Gonzalez-Zulueta, M; Ruppert, J M; Tokino, K

1993-01-01

Somatic instability at microsatellite repeats was detected in 6 of 200 transitional cell carcinomas of the bladder. Instabilities were apparent as changes in (GT)n repeat lengths on human chromosome 9 for four tumors and as alterations in a (CAG)n repeat in the androgen receptor gene on the X...... or larger (> 2 base pairs) alterations in repeat length. All six tumors were low stage (Ta-T1), suggesting that these alterations can occur early in bladder tumorigenesis....

Surgical treatment of chest instability

International Nuclear Information System (INIS)

Kitka, M.; Masek, M.

2015-01-01

Fractures of the ribs is the most common thoracic injury after blunt trauma. Chest wall instability (flail chest) is a common occurrence in the presence of multiple ribs fracture. Unilateral or bilateral fractures more ribs anteriorly or posteriorly will produce enough instability that paradoxical respiratory motion results in hypoventilation of an unacceptable degree. Open approach and surgical stabilisation of the chest preserved pulmonary function, improved pain control, minimized posttraumatic deformities and shorter back to work time. (author)

Performance through Deformation and Instability

Science.gov (United States)

Bertoldi, Katia

2015-03-01

Materials capable of undergoing large deformations like elastomers and gels are ubiquitous in daily life and nature. An exciting field of engineering is emerging that uses these compliant materials to design active devices, such as actuators, adaptive optical systems and self-regulating fluidics. Compliant structures may significantly change their architecture in response to diverse stimuli. When excessive deformation is applied, they may eventually become unstable. Traditionally, mechanical instabilities have been viewed as an inconvenience, with research focusing on how to avoid them. Here, I will demonstrate that these instabilities can be exploited to design materials with novel, switchable functionalities. The abrupt changes introduced into the architecture of soft materials by instabilities will be used to change their shape in a sudden, but controlled manner. Possible and exciting applications include materials with unusual properties such negative Poisson's ratio, phononic crystals with tunable low-frequency acoustic band gaps and reversible encapsulation systems.

Anisotropy-Driven Instability in Intense Charged Particle Beams

CERN Document Server

Startsev, Edward; Qin, Hong

2005-01-01

In electrically neutral plasmas with strongly anisotropic distribution functions, free energy is available to drive different collective instabilities such as the electrostatic Harris instability and the transverse electromagnetic Weibel instability. Such anisotropies develop naturally in particle accelerators and may lead to a detoriation of beam quality. We have generalized the analysis of the classical Harris and Weibel instabilities to the case of a one-component intense charged particle beam with anisotropic temperature including the important effects of finite transverse geometry and beam space-charge. For a long costing beam, the delta-f particle-in-cell code BEST and the eighenmode code bEASt have been used to determine detailed 3D stability properties over a wide range of temperature anisotropy and beam intensity. A theoretical model is developed which describes the essential features of the linear stage of these instabilities. Both, the simulations and analytical theory, clearly show that moderately...

Parametric instabilities in advanced gravitational wave detectors

International Nuclear Information System (INIS)

Gras, S; Zhao, C; Blair, D G; Ju, L

2010-01-01

As the LIGO interferometric gravitational wave detectors have finished gathering a large observational data set, an intense effort is underway to upgrade these observatories to improve their sensitivity by a factor of ∼10. High circulating power in the arm cavities is required, which leads to the possibility of parametric instability due to three-mode opto-acoustic resonant interactions between the carrier, transverse optical modes and acoustic modes. Here, we present detailed numerical analysis of parametric instability in a configuration that is similar to Advanced LIGO. After examining parametric instability for a single three-mode interaction in detail, we examine instability for the best and worst cases, as determined by the resonance condition of transverse modes in the power and signal recycling cavities. We find that, in the best case, the dual recycling detector is substantially less susceptible to instability than a single cavity, but its susceptibility is dependent on the signal recycling cavity design, and on tuning for narrow band operation. In all cases considered, the interferometer will experience parametric instability at full power operation, but the gain varies from 3 to 1000, and the number of unstable modes varies between 7 and 30 per test mass. The analysis focuses on understanding the detector complexity in relation to opto-acoustic interactions, on providing insights that can enable predictions of the detector response to transient disturbances, and of variations in thermal compensation conditions.

Value of stress ultrasound for the diagnosis of chronic ankle instability compared to manual anterior drawer test, stress radiography, magnetic resonance imaging, and arthroscopy.

Science.gov (United States)

Cho, Jae Ho; Lee, Doo Hyung; Song, Hyung Keun; Bang, Joon Young; Lee, Kyung Tai; Park, Young Uk

2016-04-01

Clinicians frequently diagnose chronic ankle instability using the manual anterior drawer test and stress radiography. However, both examinations can yield incorrect results and do not reveal the extent of ankle instability. Stress ultrasound has been reported to be a new diagnostic tool for the diagnosis of chronic ankle instability. The purpose of this study was to assess the diagnostic value of stress ultrasound for chronic ankle instability compared to the manual anterior drawer test, stress radiography, magnetic resonance imaging (MRI), and arthroscopy. Twenty-eight consecutive patients who underwent ankle arthroscopy and subsequent modified Broström repair for treatment of chronic ankle instability were included. The arthroscopic findings were used as the reference standard. A standardized physical examination (manual anterior drawer test), stress radiography, MRI, and stress ultrasound were performed to assess the anterior talofibular ligament (ATFL) prior to operation. Ultrasound images were taken in the resting position and the maximal anterior drawer position. Grade 3 lateral instability was verified arthroscopically in all 28 cases with a clinical diagnosis (100%). Twenty-two cases showed grade III instability on the manual anterior drawer test (78.6%). Twenty-four cases displayed anterior translation exceeding 5 mm on stress radiography (86%), and talar tilt angle exceeded 15° in three cases (11 %). Nineteen cases displayed a partial chronic tear (change in thickness or signal intensity), and nine cases displayed complete tear on MRI (100%). Lax and wavy ATFL was evident on stress ultrasound in all cases (100 %). The mean value of the ATFL length was 2.8 ± 0.3 cm for the stressed condition and 2.1 ± 0.2 cm for the resting condition (p radiography. III.

Flow-Induced Instabilities in Pump-Turbines in China

Directory of Open Access Journals (Sweden)

Zhigang Zuo

2017-08-01

Full Text Available The stability of pump-turbines is of great importance to the operation of pumped storage power (PSP stations. Both hydraulic instabilities and operational instabilities have been reported in PSP stations in China. In order to provide a reference to the engineers and scientists working on pump-turbines, this paper summarizes the hydraulic instabilities and performance characteristics that promote the operational instabilities encountered in pump-turbine operations in China. Definitions, analytical methods, numerical and experimental studies, and main results are clarified. Precautions and countermeasures are also provided based on a literature review. The gaps between present studies and the need for engineering practice are pointed out.

Magnetohydrodynamic instability in annular linear induction pump

International Nuclear Information System (INIS)

Araseki, Hideo; Kirillov, Igor R.; Preslitsky, Gennady V.; Ogorodnikov, Anatoly P.

2006-01-01

In the previous work, the authors showed some detailed aspects of the magnetohydrodynamic instability arising in an annular linear induction pump: the instability is accompanied with a low frequency pressure pulsation in the range of 0-10 Hz when the magnetic Reynolds number is larger than unity; the low frequency pressure pulsation is produced by the sodium vortices that come from some azimuthal non-uniformity of the applied magnetic field or of the sodium inlet velocity. In the present work, an experiment and a numerical analysis are carried out to verify the pump winding phase shift that is expected as an effective way to suppress the instability. The experimental data shows that the phase shift suppresses the instability unless the slip value is so high, but brings about a decrease of the developed pressure. The numerical results indicate that the phase shift causes a local decrease of the electromagnetic force, which results in the suppression of the instability and the decrease of the developed pressure. In addition, it is exhibited that the intensity of the double-supply-frequency pressure pulsation is in nearly the same level in the case with and without the phase shift

Preventing Instability Phenomenon in Gas-lift Optimization

Directory of Open Access Journals (Sweden)

Mohammad Reza Mahdiani

2015-01-01

Full Text Available One of the problems that sometimes occur in gas allocation optimization is instability phenomenon. This phenomenon reduces the oil production and damages downhole and surface facilities. Different works have studied the stability and suggested some solutions to override it, but most of them (such as making the well intelligent are very expensive and thus they are not applicable to many cases. In this paper, as a new approach, the stability has been studied in gas allocation optimization problems. To prevent the instability, instability has been assumed as a constraint for the optimizer and then the optimizer has been run. For the optimization, first a genetic algorithm and then a hybrid of genetic algorithm and Newton-Quasi have been used, and their results are compared to ensure the good performance of the optimizer; afterwards, the effect of adding the instability constraint to the problem on production reduction have been discussed. The results show that the production loss with adding this constraint to the system is very small and this method does not need any additional and expensive facilities for preventing the instability. Therefore, the new method is applicable to different problems.

Instability of plastid DNA in the nuclear genome.

Directory of Open Access Journals (Sweden)

Anna E Sheppard

2009-01-01

Full Text Available Functional gene transfer from the plastid (chloroplast and mitochondrial genomes to the nucleus has been an important driving force in eukaryotic evolution. Non-functional DNA transfer is far more frequent, and the frequency of such transfers from the plastid to the nucleus has been determined experimentally in tobacco using transplastomic lines containing, in their plastid genome, a kanamycin resistance gene (neo readymade for nuclear expression. Contrary to expectations, non-Mendelian segregation of the kanamycin resistance phenotype is seen in progeny of some lines in which neo has been transferred to the nuclear genome. Here, we provide a detailed analysis of the instability of kanamycin resistance in nine of these lines, and we show that it is due to deletion of neo. Four lines showed instability with variation between progeny derived from different areas of the same plant, suggesting a loss of neo during somatic cell division. One line showed a consistent reduction in the proportion of kanamycin-resistant progeny, suggesting a loss of neo during meiosis, and the remaining four lines were relatively stable. To avoid genomic enlargement, the high frequency of plastid DNA integration into the nuclear genome necessitates a counterbalancing removal process. This is the first demonstration of such loss involving a high proportion of recent nuclear integrants. We propose that insertion, deletion, and rearrangement of plastid sequences in the nuclear genome are important evolutionary processes in the generation of novel nuclear genes. This work is also relevant in the context of transgenic plant research and crop production, because similar processes to those described here may be involved in the loss of plant transgenes.

Secondary Instability of Second Modes in Hypersonic Boundary Layers

Science.gov (United States)

Li, Fei; Choudhari, Meelan M.; Chang, Chau-Lyan; White, Jeffery A.

2012-01-01

Second mode disturbances dominate the primary instability stage of transition in a number of hypersonic flow configurations. The highest amplification rates of second mode disturbances are usually associated with 2D (or axisymmetric) perturbations and, therefore, a likely scenario for the onset of the three-dimensionality required for laminar-turbulent transition corresponds to the parametric amplification of 3D secondary instabilities in the presence of 2D, finite amplitude second mode disturbances. The secondary instability of second mode disturbances is studied for selected canonical flow configurations. The basic state for the secondary instability analysis is obtained by tracking the linear and nonlinear evolution of 2D, second mode disturbances using nonlinear parabolized stability equations. Unlike in previous studies, the selection of primary disturbances used for the secondary instability analysis was based on their potential relevance to transition in a low disturbance environment and the effects of nonlinearity on the evolution of primary disturbances was accounted for. Strongly nonlinear effects related to the self-interaction of second mode disturbances lead to an upstream shift in the upper branch neutral location. Secondary instability computations confirm the previously known dominance of subharmonic modes at relatively small primary amplitudes. However, for the Purdue Mach 6 compression cone configuration, it was shown that a strong fundamental secondary instability can exist for a range of initial amplitudes of the most amplified second mode disturbance, indicating that the exclusive focus on subharmonic modes in the previous applications of secondary instability theory to second mode primary instability may not have been fully justified.

Rayleigh-Taylor instability in an equal mass plasma

Energy Technology Data Exchange (ETDEWEB)

Adak, Ashish, E-mail: ashish-adak@yahoo.com [Department of Instrumentation Science, Jadavpur University, Kolkata 700 032 (India); Ghosh, Samiran, E-mail: sran-g@yahoo.com [Department of Applied Mathematics, University of Calcutta 92, Acharya Prafulla Chandra Road, Kolkata 700 009 (India); Chakrabarti, Nikhil, E-mail: nikhil.chakrabarti@saha.ac.in [Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata 700 064 (India)

2014-09-15

The Rayleigh-Taylor (RT) instability in an inhomogeneous pair-ion plasma has been analyzed. Considering two fluid model for two species of ions (positive and negative), we obtain the possibility of the existence of RT instability. The growth rate of the RT instability as usual depends on gravity and density gradient scale length. The results are discussed in context of pair-ion plasma experiments.

The Frequent Unusual Headache Syndromes: A Proposed Classification Based on Lifetime Prevalence.

Science.gov (United States)

Valença, Marcelo M; de Oliveira, Daniella A

2016-01-01

There is no agreement on a single cutoff point or prevalence for regarding a given disease as rare. The concept of what is a rare headache disorder is even less clear and the spectrum from a very frequent, frequent, occasional to rare headache syndrome is yet to be established. An attempt has been made to estimate the lifetime prevalence of each of the headache subtypes classified in the ICHD-II. Using the ICHD-II, 199 different headache subtypes were identified. The following classification was made according to the estimated lifetime prevalence of each headache disorder: very frequent (prevalence >10%); frequent (between 1 and 10%); occasional (between 0.07 and 1%); and unusual or rare (headache disorders, 7/199 (4%) as very frequent, 9/199 (5%) as frequent, and 29/199 (15%) as occasional forms of headache disorder. The unusual headache syndromes do not appear to be as infrequent in clinical practice as has been generally believed. About three-fourths of the classified headache disorders found in the ICHD-II can be considered as rare. This narrative review article may be regarded as an introduction to the concept of unusual headaches and a proposed classification of all headaches (at least those listed in the ICHD-II). © 2015 American Headache Society.

Instability induced by cross-diffusion in reaction-diffusion systems

DEFF Research Database (Denmark)

Tian, Canrong; Lin, Zhigui; Pedersen, Michael

2010-01-01

In this paper the instability of the uniform equilibrium of a general strongly coupled reaction–diffusion is discussed. In unbounded domain and bounded domain the sufficient conditions for the instability are obtained respectively. The conclusion is applied to the ecosystem, it is shown that cros...... can induce the instability of an equilibrium which is stable for the kinetic system and for the self-diffusion–reaction system.......In this paper the instability of the uniform equilibrium of a general strongly coupled reaction–diffusion is discussed. In unbounded domain and bounded domain the sufficient conditions for the instability are obtained respectively. The conclusion is applied to the ecosystem, it is shown that cross-diffusion...

Anomalous plasma transport due to electron temperature gradient instability

International Nuclear Information System (INIS)

Tokuda, Sinji; Ito, Hiroshi; Kamimura, Tetsuo.

1979-01-01

The collisionless drift wave instability driven by an electron temperature inhomogeneity (electron temperature gradient instability) and the enhanced transport processes associated with it are studied using a two-and-a-half dimensional particle simulation code. The simulation results show that quasilinear diffusion in phase space is an important mechanism for the saturation of the electron temperature gradient instability. Also, the instability yields particle fluxes toward the hot plasma regions. The heat conductivity of the electron temperature perpendicular to the magnetic field, T sub(e'), is not reduced by magnetic shear but remains high, whereas the heat conductivity of the parallel temperature, T sub(e''), is effectively reduced, and the instability stabilized. (author)

Frequent visitors at the psychiatric emergency room - A literature review.

Science.gov (United States)

Schmidt, Manuela

2018-03-01

Frequent visitors at the psychiatric emergency room (PER) constitute a small subgroup of patients, yet they are responsible for a disproportionate number of visits and thus claim considerable resources. Their needs are often left unmet and their repetitive visits reflect their dissatisfaction as well as that of PERs' staff. Motivated by these dilemmas, this study systematically reviews the literature about frequent visitors at PER and seeks to answer two questions: What characterizes frequent visitors at PER in the literature? and What characterizes PER in the literature? Based on 29 studies, this paper offers answers to the two questions based on a strength weakness opportunities and threats (SWOT) analysis. The results of the review and subsequent analysis of the literature revealed the multiplicity and complexity of frequent visitors' characteristics and how they appear to converge. Commonalities were more difficult to identify in PER characteristics. In some cases, this happened because the characteristics were poorly described or were context specific. As a result, it was not easy to compare the studies on PER. Based on SWOT and the findings of the analysis, the paper proposes new venues of research and suggests how the field of mental health might develop by taking into account its opportunities and threats.

Plasma instability of a vacuum arc centrifuge

International Nuclear Information System (INIS)

Hole, M.J.; Dallaqua, R.S.; Simpson, S.W.; Del Bosco, E.

2002-01-01

Ever since conception of the vacuum arc centrifuge in 1980, periodic fluctuations in the ion saturation current and floating potential have been observed in Langmuir probe measurements in the rotation region of a vacuum arc centrifuge. In this work we develop a linearized theoretical model to describe a range of instabilities in the vacuum arc centrifuge plasma column, and then test the validity of the description through comparison with experiment. We conclude that the observed instability is a 'universal' instability, driven by the density gradient, in a plasma with finite conductivity

Self-focusing instability of two-dimensional solitons and vortices

DEFF Research Database (Denmark)

Kuznetsov, E.A.; Juul Rasmussen, J.

1995-01-01

The instability of two-dimensional solitons and vortices is demonstrated in the framework of the three-dimensional nonlinear Schrodinger equation (NLSE). The instability can be regarded as the analog of the Kadomtsev-Petviashvili instability [B. B. Kadomtsev and V. I. Petviashvili, Sov. Phys. Dokl...

Causes of genome instability: the effect of low dose chemical exposures in modern society

Science.gov (United States)

Langie, Sabine A.S.; Koppen, Gudrun; Desaulniers, Daniel; Al-Mulla, Fahd; Al-Temaimi, Rabeah; Amedei, Amedeo; Azqueta, Amaya; Bisson, William H.; Brown, Dustin; Brunborg, Gunnar; Charles, Amelia K.; Chen, Tao; Colacci, Annamaria; Darroudi, Firouz; Forte, Stefano; Gonzalez, Laetitia; Hamid, Roslida A.; Knudsen, Lisbeth E.; Leyns, Luc; Lopez de Cerain Salsamendi, Adela; Memeo, Lorenzo; Mondello, Chiara; Mothersill, Carmel; Olsen, Ann-Karin; Pavanello, Sofia; Raju, Jayadev; Rojas, Emilio; Roy, Rabindra; Ryan, Elizabeth; Ostrosky-Wegman, Patricia; Salem, Hosni K.; Scovassi, Ivana; Singh, Neetu; Vaccari, Monica; Van Schooten, Frederik J.; Valverde, Mahara; Woodrick, Jordan; Zhang, Luoping; van Larebeke, Nik; Kirsch-Volders, Micheline; Collins, Andrew R.

2015-01-01

Genome instability is a prerequisite for the development of cancer. It occurs when genome maintenance systems fail to safeguard the genome’s integrity, whether as a consequence of inherited defects or induced via exposure to environmental agents (chemicals, biological agents and radiation). Thus, genome instability can be defined as an enhanced tendency for the genome to acquire mutations; ranging from changes to the nucleotide sequence to chromosomal gain, rearrangements or loss. This review raises the hypothesis that in addition to known human carcinogens, exposure to low dose of other chemicals present in our modern society could contribute to carcinogenesis by indirectly affecting genome stability. The selected chemicals with their mechanisms of action proposed to indirectly contribute to genome instability are: heavy metals (DNA repair, epigenetic modification, DNA damage signaling, telomere length), acrylamide (DNA repair, chromosome segregation), bisphenol A (epigenetic modification, DNA damage signaling, mitochondrial function, chromosome segregation), benomyl (chromosome segregation), quinones (epigenetic modification) and nano-sized particles (epigenetic pathways, mitochondrial function, chromosome segregation, telomere length). The purpose of this review is to describe the crucial aspects of genome instability, to outline the ways in which environmental chemicals can affect this cancer hallmark and to identify candidate chemicals for further study. The overall aim is to make scientists aware of the increasing need to unravel the underlying mechanisms via which chemicals at low doses can induce genome instability and thus promote carcinogenesis. PMID:26106144

Hydrodynamic instabilities in astrophysics and ICF

International Nuclear Information System (INIS)

Paul Drake, R.

2005-01-01

Inertial fusion systems and astrophysical systems both involve hydrodynamic effects, including sources of pressure, shock waves, rarefactions, and plasma flows. In the evolution of such systems, hydrodynamic instabilities naturally evolve. As a result, a fundamental understanding of hydrodynamic instabilities is necessary to understand their behavior. In addition, high-energy-density facilities designed for ICF purposes can be used to provide and experimental basis for understanding astrophysical processes. In this talk. I will discuss the instabilities that appear in astrophysics and ICF from the common perspective of the basic mechanisms at work. Examples will be taken from experiments aimed at ICF, from astrophysical systems, and from experiments using ICF systems to address issues in astrophysics. The high-energy-density research facilities of today can accelerate small but macroscopic amounts of material to velocities above 100 km/s, can heat such material to temperature above 100 eV, can produce pressures far above a million atmospheres (10''12 dybes/cm''2 or 0.1 TPascal), and can do experiments under these conditions that address basic physics issues. This enables on to devise experiments aimed directly at important process such as the Rayleigh Taylor instability at an ablating surface or at an embedded interface that is accelerating, the Richtmeyer Meshkov evolution of shocked interfaces, and the Kelvin-Helmholtz instability of shear flows. The talk will include examples of such phenomena from the laboratory and from astrophysics, and will discuss experiments to study them. (Author)

POD analysis of the instability mode of a low-speed streak in a laminar boundary layer

Science.gov (United States)

Deng, Si-Chao; Pan, Chong; Wang, Jin-Jun; Rinoshika, Akira

2017-12-01

The instability of one single low-speed streak in a zero-pressure-gradient laminar boundary layer is investigated experimentally via both hydrogen bubble visualization and planar particle image velocimetry (PIV) measurement. A single low-speed streak is generated and destabilized by the wake of an interference wire positioned normal to the wall and in the upstream. The downstream development of the streak includes secondary instability and self-reproduction process, which leads to the generation of two additional streaks appearing on either side of the primary one. A proper orthogonal decomposition (POD) analysis of PIV measured velocity field is used to identify the components of the streak instability in the POD mode space: for a sinuous/varicose type of POD mode, its basis functions present anti-symmetric/symmetric distributions about the streak centerline in the streamwise component, and the symmetry condition reverses in the spanwise component. It is further shown that sinuous mode dominates the turbulent kinematic energy (TKE) through the whole streak evolution process, the TKE content first increases along the streamwise direction to a saturation value and then decays slowly. In contrast, varicose mode exhibits a sustained growth of the TKE content, suggesting an increasing competition of varicose instability against sinuous instability.

The Influence of Mulligan Ankle Taping on Dynamic Balance in the Athletes with and without Chronic Ankle Instability

Directory of Open Access Journals (Sweden)

Tahereh Pourkhani

2014-04-01

Full Text Available Objective: The ankle joint is the most frequently injured anatomical site in athletes. Ankle instability is responsible for 25% of all time lost from sport. Clinical efficacy of the effect of taping in athletes with chronic ankle instability is unknown. So the purpose of this investigation is the study of the influence of Mulligan ankle taping on dynamic balance in the athletes with and without chronic ankle instability. Materials & Methods: 32 athletes participated in this investigation: 16 subjects with chronic ankle instability, 6 women and 10 men (age 23.5±0.3 years, height 175.4±10.3 cm, weight 73.6±14.5 kg, Foot Ankle Disability Index 74.5±8.62% and Foot Ankle Disability Index Sport 63.5±7.86% and 16 healthy subjects, 6 women and 10 men (age 22.81±7.1 years, height 173.6±12.26 cm, weight 66.4±11.4 kg, Foot Ankle Disability Index and Foot Ankle Disability Index Sport 100%. Dynamic balance was assessed with Star Excursion Balance Test in 3 reaching directions (medial, antero-medial and postero-medial before and after Mulligan ankle taping. Independent and paired t-test were used for statistical analysis. Results: Dynamic balance in healthy group significantly was better than injured group (P&le0.05. Application of taping caused significantly improvement in dynamic balance in both groups (reaching in media, antero-medial and postero-medial directions (P&le0.05 (except reaching in antero-medial direction in healthy group (P>0.05. Conclusion: So it seems that Mulligan ankle taping can improve dynamic balance in the athletes with and without chronic ankle instability.

Sternal instability measured with radiostereometric analysis. A study of method feasibility, accuracy and precision

DEFF Research Database (Denmark)

Vestergaard, Rikke Falsig; Søballe, Kjeld; Hasenkam, John Michael

2018-01-01

BACKGROUND: A small, but unstable, saw-gap may hinder bone-bridging and induce development of painful sternal dehiscence. We propose the use of Radiostereometric Analysis (RSA) for evaluation of sternal instability and present a method validation. METHODS: Four bone analogs (phantoms) were sterno...... modality feasible for clinical evaluation of sternal stability in research. TRIAL REGISTRATION: ClinicalTrials.gov Identifier: NCT02738437 , retrospectively registered.......BACKGROUND: A small, but unstable, saw-gap may hinder bone-bridging and induce development of painful sternal dehiscence. We propose the use of Radiostereometric Analysis (RSA) for evaluation of sternal instability and present a method validation. METHODS: Four bone analogs (phantoms) were...

Helicobacter pylori infection generates genetic instability in gastric cells

DEFF Research Database (Denmark)

Machado, Ana Manuel Dantas; Figueiredo, Céu; Seruca, Raquel

2010-01-01

The discovery that Helicobacter pylori is associated with gastric cancer has led to numerous studies that investigate the mechanisms by which H. pylori induces carcinogenesis. Gastric cancer shows genetic instability both in nuclear and mitochondrial DNA, besides impairment of important DNA repair...... of the host, such as oxidative damage, methylation, chromosomal instability, microsatellite instability, and mutations. Interestingly, H. pylori infection generates genetic instability in nuclear and mitochondrial DNA. Based on the reviewed literature we conclude that H. pylori infection promotes gastric...

Radiation-induced transgenerational instability.

Science.gov (United States)

Dubrova, Yuri E

2003-10-13

To date, the analysis of mutation induction has provided an irrefutable evidence for an elevated germline mutation rate in the parents directly exposed to ionizing radiation and a number of chemical mutagens. However, the results of numerous publications suggest that radiation may also have an indirect effect on genome stability, which is transmitted through the germ line of irradiated parents to their offspring. This review describes the phenomenon of transgenerational instability and focuses on the data showing increased cancer incidence and elevated mutation rates in the germ line and somatic tissues of the offspring of irradiated parents. The possible mechanisms of transgenerational instability are also discussed.

RINGED ACCRETION DISKS: INSTABILITIES

Energy Technology Data Exchange (ETDEWEB)

Pugliese, D.; Stuchlík, Z., E-mail: d.pugliese.physics@gmail.com, E-mail: zdenek.stuchlik@physics.cz [Institute of Physics and Research Centre of Theoretical Physics and Astrophysics, Faculty of Philosophy and Science, Silesian University in Opava, Bezručovo náměstí 13, CZ-74601 Opava (Czech Republic)

2016-04-01

We analyze the possibility that several instability points may be formed, due to the Paczyński mechanism of violation of mechanical equilibrium, in the orbiting matter around a supermassive Kerr black hole. We consider a recently proposed model of a ringed accretion disk, made up by several tori (rings) that can be corotating or counter-rotating relative to the Kerr attractor due to the history of the accretion process. Each torus is governed by the general relativistic hydrodynamic Boyer condition of equilibrium configurations of rotating perfect fluids. We prove that the number of the instability points is generally limited and depends on the dimensionless spin of the rotating attractor.

Investigation of Parametric Instability of the Planetary Gear under Speed Fluctuations

Directory of Open Access Journals (Sweden)

Xinghui Qiu

2017-01-01

Full Text Available Planetary gear is widely used in engineering and usually has symmetrical structure. As the number of teeth in contact changes during rotation, the time-varying mesh stiffness parametrically excites the planetary gear and may cause severe vibrations and instabilities. Taking speed fluctuations into account, the time-varying mesh stiffness is frequency modulated, and therefore sideband instabilities may arise and original instabilities are significantly affected. Considering two different speed fluctuations, original and sideband instabilities are numerically and analytically investigated. A rotational lumped-parameter model of the planetary gear is developed, in which the time-varying mesh stiffness, input speed fluctuations, and damping are considered. Closed-form approximations of instability boundaries for primary and combination instabilities are obtained by perturbation analysis and verified by numerical analysis. The effects of speed fluctuations and damping on parametric instability are systematically examined. Because of the frequency modulation, whether a parametric instability occurs cannot be simply predicted by the planet meshing phase which is applicable to constant speed. Besides adjusting the planet meshing phase, speed fluctuation supplies a new thought to minimize certain instability by adjusting the amplitude or frequency of the speed fluctuation. Both original and sideband instabilities are shrunken by damping, and speed fluctuation further shrinks the original instability.

Beam Instabilities in Hadron Synchrotrons

CERN Document Server

Métral, E; Bartosik, H; Biancacci, N; Buffat, X; Esteban Muller, J F; Herr, W; Iadarola, G; Lasheen, A; Li, K; Oeftiger, A; Pieloni, T; Quartullo, D; Rumolo, G; Salvant, B; Schenk, M; Shaposhnikova, E; Tambasco, C; Timko, H; Zannini, C; Burov, A; Banfi, D; Barranco, J; Mounet, N; Boine-Frankenheim, O; Niedermayer, U; Kornilov, V; White, S

2016-01-01

Beam instabilities cover a wide range of effects in particle accelerators and they have been the subjects of intense research for several decades. As the machines performance was pushed new mechanisms were revealed and nowadays the challenge consists in studying the interplays between all these intricate phenomena, as it is very often not possible to treat the different effects separately. The aim of this paper is to review the main mechanisms, discussing in particular the recent developments of beam instability theories and simulations.

Aerodynamic instability: A case history

Science.gov (United States)

Eisenmann, R. C.

1985-01-01

The identification, diagnosis, and final correction of complex machinery malfunctions typically require the correlation of many parameters such as mechanical construction, process influence, maintenance history, and vibration response characteristics. The progression is reviewed of field testing, diagnosis, and final correction of a specific machinery instability problem. The case history presented addresses a unique low frequency instability problem on a high pressure barrel compressor. The malfunction was eventually diagnosed as a fluidic mechanism that manifested as an aerodynamic disturbance to the rotor assembly.

Instabilities of higher dimensional compactifications

International Nuclear Information System (INIS)

Accetta, F.S.

1987-02-01

Various schemes for cosmological compactification of higher dimensional theories are considered. Possible instabilities which drive the ground state with static internal space to de Sitter-like expansion of all dimensions are discussed. These instabilities are due to semiclassical barrier penetration and classical thermal fluctuations. For the case of the ten dimensional Chapline-Manton action, it is possible to avoid such difficulties by balancing one-loop Casimir corrections against monopole contributions from the field strength H/sub MNP/ and fermionic condensates. 10 refs

Relativistic fluid model of the resistive hose instability

International Nuclear Information System (INIS)

Siambis, J.G.

1992-01-01

A systematic analysis of the hose instability using the relativistic fluid formulation is reported. In its basic nature, the hose instability is a macroscopic, low-frequency instability, hence a fluid model should, in principle, give an accurate account of the hose instability. It has been found that for zeroth-order beam displacements, giving rise to rigid beam displacements, the fluid wave equation and resulting dispersion relation are identical to the spread-mass model and the energy-group model results. When first-order fluid displacements are included as well, giving rise to compressible, nonfrozen displacements in the axial direction and beam cross-section distortion in the radial direction, then there is obtained a wave equation similar, but not identical to the multicomponent model. The dispersion relation is solved for numerically. The hose instability growth rate is found to be similar to the multicomponent model result, over part of the beam frame, real hose frequency range

Light-induced ion-acoustic instability of rarefied plasma

International Nuclear Information System (INIS)

Krasnov, I.V.; Sizykh, D.V.

1987-01-01

A new method of ion-acoustic instability excitation under the effect of coherent light, resonance to ion quantum transitions on collisionless plasma, is suggested. The light-induced ion-acoustic instability (LIIAI) considered is based on the induced progressive nonequilibrium resonance particles in the field of travelling electromagnetic wave. Principal possibility to use LIIAI in high-resolution spectroscopy and in applied problems of plasma physics, related to its instability, is pointed out

Hydrodynamic instability of compressible fluid in porous medium

International Nuclear Information System (INIS)

Argal, Shraddha; Tiwari, Anita; Sharma, P K; Prajapati, R P

2014-01-01

The hydrodynamic Rayleigh -Taylor instability of two superposed compressible fluids in porous medium has been studied. The dispersion relation is derived for such a medium by using normal mode analysis. The RT instability is discussed for various simplified configuration. The effect of porosity and dynamic viscosity has been analyzed and it is observed that porosity and dynamic viscosity have stabilizing effect on the Rayleigh- Taylor instability of compressible fluids.

Tangential neutral-beam--driven instabilities in the Princeton beta experiment

International Nuclear Information System (INIS)

Heidbrink, W.W.; Bol, K.; Buchenauer, D.

1986-01-01

During tangential neutral-beam injection into the PBX tokamak, bursts of two types of instabilities are observed. One instability occurs in the frequency range 120--210 kHz and the other oscillates predominantly near the frequency of bulk plasma rotation (20--30 kHz). Both instabilities correlate with drops in neutron emission and bursts in charge-exchange neutral flux, indicating that beam ions are removed from the center of the plasma by the instabilities. The central losses are comparable to the losses induced by the fishbone instability during perpendicular injection

Theoretical analysis of mode instability in high-power fiber amplifiers

DEFF Research Database (Denmark)

Hansen, Kristian Rymann; Alkeskjold, Thomas Tanggaard; Broeng, Jes

2013-01-01

We present a simple theoretical model of transverse mode instability in high-power rare-earth doped fiber amplifiers. The model shows that efficient power transfer between the fundamental and higher-order modes of the fiber can be induced by a nonlinear interaction mediated through the thermo......-optic effect, leading to transverse mode instability. The temporal and spectral characteristics of the instability dynamics are investigated, and it is shown that the instability can be seeded by both quantum noise and signal intensity noise, while pure phase noise of the signal does not induce instability...

A trickle instability

Science.gov (United States)

Bossa, Benjamin

2005-11-01

We address the problem of the free fall of a long, horizontal and narrow liquid layer squeezed in a vertical open Hele-Shaw cell. The layer destabilizes as it falls down, evolving into a series of liquid blobs linked together by thin bridges, which ultimately break, leaving the initially connex fluid layer as a set a disjointed drops. The mechanism of this instability is the onset of a vertical pressure gradient due to the curvature difference of the moving contact line between the advancing interface and the rear interface. This instability, whose growth rate scales with a non-trivial power of the capillary number, amplifies indifferently a broad band of wavenumbers because of the flat shape of its dispersion relation in the thin layer limit. We will finally comment on the nature of the final fragmentation process and drop size distributions.

The pathological phenotype of colon cancer with microsatellite instability

DEFF Research Database (Denmark)

Andersen, Helene Schou; Bertelsen, Claus Anders; Henriksen, Rikke

2016-01-01

proteins: pMLH1, pMSH2, pMSH6 and pPMS2 for the determination of microsatellite instability. Microsatellite instability was defined as deficient expression of one or more of these proteins. RESULTS: Of the 833 patients, 177 had microsatellite instable tumours (21%). Using multivariable logistic regression...

The coalescence instability in solar flares

Science.gov (United States)

Tajima, T.; Brunel, F.; Sakai, J.-I.; Vlahos, L.; Kundu, M. R.

1985-01-01

The nonlinear coalescence instability of current carrying solar loops can explain many of the characteristics of the solar flares such as their impulsive nature, heating and high energy particle acceleration, amplitude oscillations of electromagnetic and emission as well as the characteristics of two-dimensional microwave images obtained during a flare. The plasma compressibility leads to the explosive phase of loop coalescence and its overshoot results in amplitude oscillations in temperatures by adiabatic compression and decompression. It is noted that the presence of strong electric fields and super-Alfvenic flows during the course of the instability play an important role in the production of nonthermal particles. A qualitative explanation on the physical processes taking place during the nonlinear stages of the instability is given.

Pierce instability and bifurcating equilibria

International Nuclear Information System (INIS)

Godfrey, B.B.

1981-01-01

The report investigates the connection between equilibrium bifurcations and occurrence of the Pierce instability. Electrons flowing from one ground plane to a second through an ion background possess a countable infinity of static equilibria, of which only one is uniform and force-free. Degeneracy of the uniform and simplest non-uniform equilibria at a certain ground plan separation marks the onset of the Pierce instability, based on a newly derived dispersion relation appropriate to all the equilibria. For large ground plane separations the uniform equilibrium is unstable and the non-uniform equilibrium is stable, the reverse of their stability properties at small separations. Onset of the Pierce instability at the first bifurcation of equilibria persists in more complicated geometries, providing a general criterion for marginal stability. It seems probable that bifurcation analysis can be a useful tool in the overall study of stable beam generation in diodes and transport in finite cavities

Role of parametric decay instabilities in generating ionospheric irregularities

International Nuclear Information System (INIS)

Kuo, S.P.; Cheo, B.R.; Lee, M.C.

1983-01-01

We show that purely growing instabilities driven by the saturation spectrum of parametric decay instabilities can produce a broad spectrum of ionospheric irregularities. The threshold field Vertical BarE/sub th/Vertical Bar of the instabilities decreases with the scale lengths lambda of the ionospheric irregularities as Vertical BarE/sub th/Vertical Barproportionallambda -2 in the small-scale range ( -2 with scale lengths larger than a few kilometers. The excitation of kilometer-scale irregularities is strictly restricted by the instabilities themselves and by the spatial inhomogeneity of the medium. These results are drawn from the analyses of four-wave interaction. Ion-neutral collisions impose no net effect on the instabilities when the excited ionospheric irregularities have a field-aligned nature

Interplay between parametric instabilities in fusion - relevant laser plasmas

International Nuclear Information System (INIS)

Huller, St.

2003-01-01

The control of parametric instabilities plays an important role in laser fusion. They are driven by the incident laser beams in the underdense plasma surrounding a fusion capsule and hinder the absorption process of incident laser light which is necessary to heat the fusion target. Due to its high intensity and power, the laser light modifies the plasma density dynamically, such that two or more parametric instabilities compete, in particular stimulated Brillouin scattering and the filamentation instability. The complicated interplay between these parametric instabilities is studied in detail by developing an adequate model accompanied by numerical simulations with multidimensional codes. The model is applied to generic and to smoothed laser beams, which are necessary to limit parametric instabilities, with parameters close to experimental conditions. (author)

Magnetic field dynamos and magnetically triggered flow instabilities

Science.gov (United States)

Stefani, F.; Albrecht, T.; Arlt, R.; Christen, M.; Gailitis, A.; Gellert, M.; Giesecke, A.; Goepfert, O.; Herault, J.; Kirillov, O. N.; Mamatsashvili, G.; Priede, J.; Rüdiger, G.; Seilmayer, M.; Tilgner, A.; Vogt, T.

2017-07-01

The project A2 of the LIMTECH Alliance aimed at a better understanding of those magnetohydrodynamic instabilities that are relevant for the generation and the action of cosmic magnetic fields. These comprise the hydromagnetic dynamo effect and various magnetically triggered flow instabilities, such as the magnetorotational instability and the Tayler instability. The project was intended to support the experimental capabilities to become available in the framework of the DREsden Sodium facility for DYNamo and thermohydraulic studies (DRESDYN). An associated starting grant was focused on the dimensioning of a liquid metal experiment on the newly found magnetic destabilization of rotating flows with positive shear. In this survey paper, the main results of these two projects are summarized.

Investigation of universal plasma instabilities. Final report

International Nuclear Information System (INIS)

Lashinsky, H.

1977-01-01

This project was undertaken in order to carry out a comprehensive experimental investigation of universal plasma instabilities under a variety of conditions and a wide range of experimental parameters to scale the results appropriately to make comparisons with plasmas of thermonuclear interest. Of particular importance are the roles played by collisions and resonance particles (Landau damping and excitation) and the various stages in the development of the instabilities i.e., the linear onset of the instability, the quasilinear stage, and the transition to turbulence. General nonlinear effects such as mode locking and mode competition, and the relation of these phenomena to plasma turbulence, are also of great interest and were studied experimentally. The ultimate aim was to measure certain plasma transport coefficients in the plasma under stable and turbulent conditions with the particular view of evaluating the effect of the universal plasma instabilities of plasma confinement in a magnetic field

Teaching Rayleigh–Plateau instabilities in the laboratory

International Nuclear Information System (INIS)

Fragkopoulos, A A; Ellis, P W; Fernandez-Nieves, A

2015-01-01

The breakup of a liquid jet into spherical droplets via the Rayleigh–Plateau instability is a common and fundamental part of fluid mechanics. However, teaching this instability in a laboratory setting is challenging, requiring sophisticated methods to generate and study the jet dynamics. Recently, toroidal droplets were shown to break into one or more spherical droplets in the thin-drop limit via the Rayleigh–Plateau instability. We propose a simple experimental setup to generate toroidal droplets that break up on the order of tens of seconds, allowing for easy video capture using a basic CCD camera. With this setup, it is possible to quantify the Rayleigh–Plateau instability in a pedagogical laboratory setting. In addition, the role of curvature on jet breakup can be explored using thick toroidal droplets. We envision this setup as a powerful teaching tool for one of the most fundamental fluid dynamics processes. (paper)

The Rayleigh-Taylor instability in inertial fusion, astrophysical plasma and flames

International Nuclear Information System (INIS)

Bychkov, V; Modestov, M; Akkerman, V; Eriksson, L-E

2007-01-01

Previous results are reviewed and new results are presented on the Rayleigh-Taylor instability in inertial confined fusion, flames and supernovae including gravitational and thermonuclear explosion mechanisms. The instability couples micro-scale plasma effects to large-scale hydrodynamic phenomena. In inertial fusion the instability reduces target compression. In supernovae the instability produces large-scale convection, which determines the fate of the star. The instability is often accompanied by mass flux through the unstable interface, which may have either a stabilizing or a destabilizing influence. Destabilization happens due to the Darrieus-Landau instability of a deflagration front. Still, it is unclear whether the instabilities lead to well-organized large-scale structures (bubbles) or to relatively isotropic turbulence (mixing layer)

Turning Off Frequently Overridden Drug Alerts: Limited Opportunities for Doing It Safely

NARCIS (Netherlands)

I.H. van der Sijs (Heleen); J.E.C.M. Aarts (Jos); T. van Gelder (Teun); M. Berg (Marc); A.G. Vulto (Arnold)

2008-01-01

textabstractObjectives: This study sought to identify opportunities to safely turn off frequently overridden drug-drug interaction alerts (DDIs) in computerized physician order entry (CPOE). Design: Quantitative retrospective analysis of drug safety alerts overridden during 1 month and qualitative

Magnetically-Driven Convergent Instability Growth platform on Z.

Energy Technology Data Exchange (ETDEWEB)

Knapp, Patrick [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Mattsson, Thomas [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Martin, Matthew [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Benage, John F. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Jenkins, James [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Albright, Brian James [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

2017-09-01

Hydrodynamic instability growth is a fundamentally limiting process in many applications. In High Energy Density Physics (HEDP) systems such as inertial confinement fusion implosions and stellar explosions, hydro instabilities can dominate the evolution of the object and largely determine the final state achievable. Of particular interest is the process by which instabilities cause perturbations at a density or material interface to grow nonlinearly, introducing vorticity and eventually causing the two species to mix across the interface. Although quantifying instabilities has been the subject of many investigations in planar geometry, few have been done in converging geometry. During FY17, the team executed six convergent geometry instability experiments. Based on earlier results, the platform was redesigned and improved with respect to load centering at installation making the installation reproducible and development of a new 7.2 keV, Co He-a backlighter system to better penetrate the liner. Together, the improvements yielded significantly improved experimental results. The results in FY17 demonstrate the viability of using experiments on Z to quantify instability growth in cylindrically convergent geometry. Going forward, we will continue the partnership with staff and management at LANL to analyze the past experiments, compare to hydrodynamics growth models, and design future experiments.

Electron surfing acceleration by the electron two-stream instability in a weak magnetic field

International Nuclear Information System (INIS)

Dieckmann, M E; Shukla, P K

2006-01-01

The thermalization of relativistically flowing colliding plasmas is not well understood. The transition layer, in which both plasmas interact and thermalize, is wide and highly structured and the instabilities in this layer may yield non-thermal particle distributions and shock-less energy dissipation. The objective in this work is to explore the ability of an electron two-stream instability for thermalizing a plasma beam that moves at the mildly relativistic speed 0.3c through weakly magnetized plasma and to identify the resulting particle distributions. It is demonstrated here with particle-in-cell simulations that the electron two-stream instability leads to waves that propagate within a wide angular range relative to the flow velocity. The waves are thus not planar, as required for efficient electron surfing acceleration (ESA). The short lifetime of the waves implies, however, only weak modifications of the ESA by the oblique modes, since the waves are sufficiently homogeneous. The ion (proton) beams are not modulated, which would be required to extract some of their energy. The instability can thus heat the electrons significantly, but it fails to accelerate them to relativistic energies and it cannot form a shock layer by thermalizing the protons, at least not for the system and the resolved timescales considered here

Electron surfing acceleration by the electron two-stream instability in a weak magnetic field

Energy Technology Data Exchange (ETDEWEB)

Dieckmann, M E; Shukla, P K [Institut fuer Theoretische Physik IV, Ruhr-Universitaet Bochum, D-44780 Bochum (Germany)

2006-10-15

The thermalization of relativistically flowing colliding plasmas is not well understood. The transition layer, in which both plasmas interact and thermalize, is wide and highly structured and the instabilities in this layer may yield non-thermal particle distributions and shock-less energy dissipation. The objective in this work is to explore the ability of an electron two-stream instability for thermalizing a plasma beam that moves at the mildly relativistic speed 0.3c through weakly magnetized plasma and to identify the resulting particle distributions. It is demonstrated here with particle-in-cell simulations that the electron two-stream instability leads to waves that propagate within a wide angular range relative to the flow velocity. The waves are thus not planar, as required for efficient electron surfing acceleration (ESA). The short lifetime of the waves implies, however, only weak modifications of the ESA by the oblique modes, since the waves are sufficiently homogeneous. The ion (proton) beams are not modulated, which would be required to extract some of their energy. The instability can thus heat the electrons significantly, but it fails to accelerate them to relativistic energies and it cannot form a shock layer by thermalizing the protons, at least not for the system and the resolved timescales considered here.

Low-frequency instabilities of electron-hole plasmas in crossed fields

International Nuclear Information System (INIS)

Schneider, W.; Kirchesch, P.

1978-01-01

Using local point-contact probes, we observed two types of low-frequency instabilities in n-InSb at 85 K if the samples were exposed to crossed fields. One is a local density instability with threshold frequencies of f = 1 ... 20 Mc, the other a more turbulent current instability. The threshold values of U 0 and B for the onset of these instabilities and the dependence of their amplitudes on the fields have been measured. If a rectangular semiconductor slab is placed in crossed fields, regions of high electric field strength at opposite edges of the contacts are caused by the distortion of the Hall field, giving rise to the generation of electron-hole plasmas by impact ionization. These plasmas are the sources of the observed instabilities. This is especially evident in the case of the local density instability, which originates at the anode high field corner. Several possible reasons for the development of the instabilities are discussed. (orig.) [de

Instabilities in dark coupled models and constraints from cosmological data

CERN Document Server

Honorez, L Lopez

2010-01-01

Coupled dark matter-dark energy systems can suffer from non-adiabatic instabilities at early times and large scales. In these proceedings, we consider two parameterizations of the dark sector interaction. In the first one the energy-momentum transfer 4-vector is parallel to the dark matter 4-velocity and in the second one to the dark energy 4-velocity. In these cases, coupled models which suffer from non-adiabatic instabilities can be identified as a function of a generic coupling Q and of the dark energy equation of state. In our analysis, we do not refer to any particular cosmic field. We confront then a viable class of models in which the interaction is directly proportional to the dark energy density and to the Hubble rate parameter to recent cosmological data. In that framework, we show that correlations between the dark coupling and several cosmological parameters allow for a larger neutrino mass than in uncoupled models.

The short circuit instability in protoplanetary disks

DEFF Research Database (Denmark)

Hubbard, A.; McNally, C.P.; Mac Low, M.M.

2013-01-01

We introduce a magneto-hydrodynamic instability which occurs, among other locations, in the inner, hot regions of protoplanetary disks, and which alters the way in which resistive dissipation of magnetic energy into heat proceeds. This instability can be likened to both an electrical short circui...

Secular instabilities of Keplerian stellar discs

Science.gov (United States)

Kaur, Karamveer; Kazandjian, Mher V.; Sridhar, S.; Touma, Jihad R.

2018-05-01

We present idealized models of a razor-thin, axisymmetric, Keplerian stellar disc around a massive black hole, and study non-axisymmetric secular instabilities in the absence of either counter-rotation or loss cones. These discs are prograde mono-energetic waterbags, whose phase-space distribution functions are constant for orbits within a range of eccentricities (e) and zero outside this range. The linear normal modes of waterbags are composed of sinusoidal disturbances of the edges of distribution function in phase space. Waterbags that include circular orbits (polarcaps) have one stable linear normal mode for each azimuthal wavenumber m. The m = 1 mode always has positive pattern speed and, for polarcaps consisting of orbits with e normal modes for each m, which can be stable or unstable. We derive analytical expressions for the instability condition, pattern speeds, growth rates, and normal mode structure. Narrow bands are unstable to modes with a wide range in m. Numerical simulations confirm linear theory and follow the non-linear evolution of instabilities. Long-time integration suggests that instabilities of different m grow, interact non-linearly, and relax collisionlessly to a coarse-grained equilibrium with a wide range of eccentricities.

A fast beam-ion instability

Energy Technology Data Exchange (ETDEWEB)

Stupakov, G V [Stanford Linear Accelerator Center, Menlo Park, CA (United States)

1996-08-01

The ionization of residual gas by an electron beam in an accelerator generates ions that can resonantly couple to the beam through a wave propagating in the beam-ion system. Results of the study of a beam-ion instability are presented for a multi-bunch train taking into account the decoherence of ion oscillations due to the ion frequency spread and spatial variation of the ion frequency. It is shown that the combination of both effects can substantially reduce the growth rate of the instability. (author)

Buneman instability in hot electron plasma (Te>>Ti)

International Nuclear Information System (INIS)

Khalil, S.M.; Sayed, Y.A.; Sayed, R.A.

1986-07-01

We shall investigate the linear excitation of electrostatic current Buneman instability in both unmagnetized and magnetized homogeneous plasma. The frequency, growth rate and conditions of excitation of such instability are obtained analytically. We consider that the current velocity u (due to relative streaming of ions and electrons) slightly exceeds the instability threshold velocity u cr and that the electron temperature is much higher than the ion temperature (T e >>T i ). (author)

On the instability increments of a stationary pinch

International Nuclear Information System (INIS)

Bud'ko, A.B.

1989-01-01

The stability of stationary pinch to helical modes is numerically studied. It is shown that in the case of a rather fast plasma pressure decrease to the pinch boundary, for example, for an isothermal diffusion pinch with Gauss density distribution instabilities with m=0 modes are the most quickly growing. Instability increments are calculated. A simple analytical expression of a maximum increment of growth of sausage instability for automodel Gauss profiles is obtained

Reflex muscle contraction in anterior shoulder instability.

Science.gov (United States)

Wallace, D A; Beard, D J; Gill, R H; Eng, B; Carr, A J

1997-01-01

Reduced proprioception may contribute to recurrent anterior shoulder instability. Twelve patients with unilateral shoulder instability were investigated for evidence of deficient proprioception with an activated pneumatic cylinder and surface electromyography electrodes; the contralateral normal shoulder was used as a control. The latency between onset of movement and the detection of muscle contraction was used as an index of proprioception. No significant difference in muscle contraction latency was detected between the stable and unstable shoulders, suggesting that there was no significant defect in muscular reflex activity. This study does not support the use proprioception-enhancing physiotherapy in the treatment of posttraumatic anterior shoulder instability.

Identifying balance impairments in people with Parkinson's disease using video and wearable sensors.

Science.gov (United States)

Stack, Emma; Agarwal, Veena; King, Rachel; Burnett, Malcolm; Tahavori, Fatemeh; Janko, Balazs; Harwin, William; Ashburn, Ann; Kunkel, Dorit

2018-05-01

Falls and near falls are common among people with Parkinson's (PwP). To date, most wearable sensor research focussed on fall detection, few studies explored if wearable sensors can detect instability. Can instability (caution or near-falls) be detected using wearable sensors in comparison to video analysis? Twenty-four people (aged 60-86) with and without Parkinson's were recruited from community groups. Movements (e.g. walking, turning, transfers and reaching) were observed in the gait laboratory and/or at home; recorded using clinical measures, video and five wearable sensors (attached on the waist, ankles and wrists). After defining 'caution' and 'instability', two researchers evaluated video data and a third the raw wearable sensor data; blinded to each other's evaluations. Agreement between video and sensor data was calculated on stability, timing, step count and strategy. Data was available for 117 performances: 82 (70%) appeared stable on video. Ratings agreed in 86/117 cases (74%). Highest agreement was noted for chair transfer, timed up and go test and 3 m walks. Video analysts noted caution (slow, contained movements, safety-enhancing postures and concentration) and/or instability (saving reactions, stopping after stumbling or veering) in 40/134 performances (30%): raw wearable sensor data identified 16/35 performances rated cautious or unstable (sensitivity 46%) and 70/82 rated stable (specificity 85%). There was a 54% chance that a performance identified from wearable sensors as cautious/unstable was so; rising to 80% for stable movements. Agreement between wearable sensor and video data suggested that wearable sensors can detect subtle instability and near-falls. Caution and instability were observed in nearly a third of performances, suggesting that simple, mildly challenging actions, with clearly defined start- and end-points, may be most amenable to monitoring during free-living at home. Using the genuine near-falls recorded, work continues to

Radiologic signs of detrusor instability in children

International Nuclear Information System (INIS)

Hidalgo Teran, D.G.; Podesta, M.; Mendel, R.

2004-01-01

Purpose: To revalue radiologic signs of detrusor instability in children. Material and Methods: Retrospective analysis of videourodynamic studies performed in 85 children consulting for urinary incontinence and/or infection. Patients were free from neuropathic diseases, alterations of the urinary tract, previous surgery or anticholinergic treatment. Images of the bladder coinciding to the peaks of unstable detrusor contractions in patients with unstable bladders, and those at the end of filling in stable bladders were analyzed. Results: Bladder outlets were open in 38 patients and close in 47. Detrusor instability was found in 97 % of those with an open bladder outlet and in 36 % when close. Bladder outlets were open in all cases with contractions stronger than 60 cm.water. All 'spinning-top' urethras were associated to contractions stronger than 70 cm.water. Most false negatives (close bladder outlet in unstable bladders) corresponded to contractions lower than 30 cm.water. Different shapes of the bladder were found irrespective of detrusor instability. Conclusions: 1) An open bladder outlet observed during bladder filling is a reliable sign of significant detrusor instability in children without neuropathy; 2) It is highly specific of instability; 3) Most false negatives coincide with low amplitude contractions; 4) 'Spinning-top' images indicate strong contractions. (author)

Antibody deficiency in patients with frequent exacerbations of Chronic Obstructive Pulmonary Disease (COPD).

Science.gov (United States)

McCullagh, Brian N; Comellas, Alejandro P; Ballas, Zuhair K; Newell, John D; Zimmerman, M Bridget; Azar, Antoine E

2017-01-01

Chronic Obstructive Pulmonary Disease is the third leading cause of death in the US, and is associated with periodic exacerbations, which account for the largest proportion of health care utilization, and lead to significant morbidity, mortality, and worsening lung function. A subset of patients with COPD have frequent exacerbations, occurring 2 or more times per year. Despite many interventions to reduce COPD exacerbations, there is a significant lack of knowledge in regards to their mechanisms and predisposing factors. We describe here an important observation that defines antibody deficiency as a potential risk factor for frequent COPD exacerbations. We report a case series of patients who have frequent COPD exacerbations, and who were found to have an underlying primary antibody deficiency syndrome. We also report on the outcome of COPD exacerbations following treatment in a subset with of these patients with antibody deficiency. We identified patients with COPD who had 2 or more moderate to severe exacerbations per year; immune evaluation including serum immunoglobulin levels and pneumococcal IgG titers was performed. Patients diagnosed with an antibody deficiency syndrome were treated with either immunoglobulin replacement therapy or prophylactic antibiotics, and their COPD exacerbations were monitored over time. A total of 42 patients were identified who had 2 or more moderate to severe COPD exacerbations per year. Twenty-nine patients had an underlying antibody deficiency syndrome: common variable immunodeficiency (8), specific antibody deficiency (20), and selective IgA deficiency (1). Twenty-two patients had a follow-up for at least 1 year after treatment of their antibody deficiency, which resulted in a significant reduction of COPD exacerbations, courses of oral corticosteroid use and cumulative annual dose of oral corticosteroid use, rescue antibiotic use, and hospitalizations for COPD exacerbations. This case series identifies antibody deficiency as a

Filamentation instability of a self-pinched hollow electron beam

International Nuclear Information System (INIS)

Uhm, H.S.; Hughes, T.P.

1986-01-01

Filamentation stability properties of a self-pinched hollow electron beam propagating through a collisional plasma channel are investigated within the framework of linearized Vlasov--Maxwell equations, assuming that the beam is thin and that the equilibrium and perturbed space-charge fields are neutralized by background plasma. It is further assumed that the perturbations are well tuned with kβ/sub b/c+lω/sub b/ and satisfy la 0 , where l and k are the azimuthal and axial wavenumbers, β/sub b/c and ω/sub b/ are the axial velocity and the rotational frequency of the beam, and 2a and R 0 are the thickness and mean radius of the beam. From the stability analysis, two distinctive unstable mechanisms are identified: the return-current driven instability and the resistively driven instability. It is also found that high-l-mode perturbations are easily stabilized by a spread in the canonical angular momentum. Making use of a linearized particle-in-cell code, numerical simulations are performed. The agreement between the analytical results and those of simulations is excellent

Nonlinear Development and Secondary Instability of Traveling Crossflow Vortices

Science.gov (United States)

Li, Fei; Choudhari, Meelan M.; Duan, Lian; Chang, Chau-Lyan

2014-01-01

Transition research under NASA's Aeronautical Sciences Project seeks to develop a validated set of variable fidelity prediction tools with known strengths and limitations, so as to enable "sufficiently" accurate transition prediction and practical transition control for future vehicle concepts. This paper builds upon prior effort targeting the laminar breakdown mechanisms associated with stationary crossflow instability over a swept-wing configuration relevant to subsonic aircraft with laminar flow technology. Specifically, transition via secondary instability of traveling crossflow modes is investigated as an alternate scenario for transition. Results show that, for the parameter range investigated herein, secondary instability of traveling crossflow modes becomes insignificant in relation to the secondary instability of the stationary modes when the relative initial amplitudes of the traveling crossflow instability are lower than those of the stationary modes by approximately two orders of magnitudes or more. Linear growth predictions based on the secondary instability theory are found to agree well with those based on PSE and DNS, with the most significant discrepancies being limited to spatial regions of relatively weak secondary growth, i.e., regions where the primary disturbance amplitudes are smaller in comparison to its peak amplitude. Nonlinear effects on secondary instability evolution is also investigated and found to be initially stabilizing, prior to breakdown.

Instability in dynamic fracture

Science.gov (United States)

Fineberg, J.; Marder, M.

1999-05-01

The fracture of brittle amorphous materials is an especially challenging problem, because the way a large object shatters is intimately tied to details of cohesion at microscopic scales. This subject has been plagued by conceptual puzzles, and to make matters worse, experiments seemed to contradict the most firmly established theories. In this review, we will show that the theory and experiments fit within a coherent picture where dynamic instabilities of a crack tip play a crucial role. To accomplish this task, we first summarize the central results of linear elastic dynamic fracture mechanics, an elegant and powerful description of crack motion from the continuum perspective. We point out that this theory is unable to make predictions without additional input, information that must come either from experiment, or from other types of theories. We then proceed to discuss some of the most important experimental observations, and the methods that were used to obtain the them. Once the flux of energy to a crack tip passes a critical value, the crack becomes unstable, and it propagates in increasingly complicated ways. As a result, the crack cannot travel as quickly as theory had supposed, fracture surfaces become rough, it begins to branch and radiate sound, and the energy cost for crack motion increases considerably. All these phenomena are perfectly consistent with the continuum theory, but are not described by it. Therefore, we close the review with an account of theoretical and numerical work that attempts to explain the instabilities. Currently, the experimental understanding of crack tip instabilities in brittle amorphous materials is fairly detailed. We also have a detailed theoretical understanding of crack tip instabilities in crystals, reproducing qualitatively many features of the experiments, while numerical work is beginning to make the missing connections between experiment and theory.

Trisomy 21 and facial developmental instability.

Science.gov (United States)

Starbuck, John M; Cole, Theodore M; Reeves, Roger H; Richtsmeier, Joan T

2013-05-01

The most common live-born human aneuploidy is trisomy 21, which causes Down syndrome (DS). Dosage imbalance of genes on chromosome 21 (Hsa21) affects complex gene-regulatory interactions and alters development to produce a wide range of phenotypes, including characteristic facial dysmorphology. Little is known about how trisomy 21 alters craniofacial morphogenesis to create this characteristic appearance. Proponents of the "amplified developmental instability" hypothesis argue that trisomy 21 causes a generalized genetic imbalance that disrupts evolutionarily conserved developmental pathways by decreasing developmental homeostasis and precision throughout development. Based on this model, we test the hypothesis that DS faces exhibit increased developmental instability relative to euploid individuals. Developmental instability was assessed by a statistical analysis of fluctuating asymmetry. We compared the magnitude and patterns of fluctuating asymmetry among siblings using three-dimensional coordinate locations of 20 anatomic landmarks collected from facial surface reconstructions in four age-matched samples ranging from 4 to 12 years: (1) DS individuals (n = 55); (2) biological siblings of DS individuals (n = 55); 3) and 4) two samples of typically developing individuals (n = 55 for each sample), who are euploid siblings and age-matched to the DS individuals and their euploid siblings (samples 1 and 2). Identification in the DS sample of facial prominences exhibiting increased fluctuating asymmetry during facial morphogenesis provides evidence for increased developmental instability in DS faces. We found the highest developmental instability in facial structures derived from the mandibular prominence and lowest in facial regions derived from the frontal prominence. Copyright © 2013 Wiley Periodicals, Inc.

Beam Instabilities in Circular Particle Accelerators

CERN Document Server

AUTHOR|(CDS)2067185

2017-01-01

The theory of impedance-induced bunched-beam coherent instabilities is reviewed following Laclare's formalism, adding the effect of an electronic damper in the transverse plane. Both single-bunch and coupled-bunch instabilities are discussed, both low-intensity and high-intensity regimes are analysed, both longitudinal and transverse planes are studied, and both short-bunch and long-bunch regimes are considered. Observables and mitigation measures are also examined.

MHD instability studies in ISX-B

International Nuclear Information System (INIS)

Pare, V.K.; Dunlap, J.L.; Navarro, A.P.; Burris, R.D.

1979-01-01

MHD instabilities in Ohmically and beam heated ISX-B plasmas have been studied using collimated x-ray and Mirnov loop diagnostics. The diagnostic systems will be described and the instability signals will be illustrated for a variety of discharges. The latter will include those observed in connection with low and high β operation, density clamping, pellet injection, and deliberate introduction of toroidal field ripple

APC/C Dysfunction Limits Excessive Cancer Chromosomal Instability.

Science.gov (United States)

Sansregret, Laurent; Patterson, James O; Dewhurst, Sally; López-García, Carlos; Koch, André; McGranahan, Nicholas; Chao, William Chong Hang; Barry, David J; Rowan, Andrew; Instrell, Rachael; Horswell, Stuart; Way, Michael; Howell, Michael; Singleton, Martin R; Medema, René H; Nurse, Paul; Petronczki, Mark; Swanton, Charles

2017-02-01

Intercellular heterogeneity, exacerbated by chromosomal instability (CIN), fosters tumor heterogeneity and drug resistance. However, extreme CIN correlates with improved cancer outcome, suggesting that karyotypic diversity required to adapt to selection pressures might be balanced in tumors against the risk of excessive instability. Here, we used a functional genomics screen, genome editing, and pharmacologic approaches to identify CIN-survival factors in diploid cells. We find partial anaphase-promoting complex/cyclosome (APC/C) dysfunction lengthens mitosis, suppresses pharmacologically induced chromosome segregation errors, and reduces naturally occurring lagging chromosomes in cancer cell lines or following tetraploidization. APC/C impairment caused adaptation to MPS1 inhibitors, revealing a likely resistance mechanism to therapies targeting the spindle assembly checkpoint. Finally, CRISPR-mediated introduction of cancer somatic mutations in the APC/C subunit cancer driver gene CDC27 reduces chromosome segregation errors, whereas reversal of an APC/C subunit nonsense mutation increases CIN. Subtle variations in mitotic duration, determined by APC/C activity, influence the extent of CIN, allowing cancer cells to dynamically optimize fitness during tumor evolution. We report a mechanism whereby cancers balance the evolutionary advantages associated with CIN against the fitness costs caused by excessive genome instability, providing insight into the consequence of CDC27 APC/C subunit driver mutations in cancer. Lengthening of mitosis through APC/C modulation may be a common mechanism of resistance to cancer therapeutics that increase chromosome segregation errors. Cancer Discov; 7(2); 218-33. ©2017 AACR.See related commentary by Burkard and Weaver, p. 134This article is highlighted in the In This Issue feature, p. 115. ©2017 American Association for Cancer Research.

Jeans instability of self-gravitating magnetized strongly coupled plasma

International Nuclear Information System (INIS)

Prajapati, R P; Sharma, P K; Sanghvi, R K; Chhajlani, R K

2012-01-01

We investigate the Jeans instability of self-gravitating magnetized strongly coupled plasma. The equations of the problem are formulated using the generalized hydrodynamic model and a general dispersion relation is obtained using the normal mode analysis. This dispersion relation is discussed for transverse and longitudinal mode of propagations. The modified condition of Jeans instability is obtained for magnetized strongly coupled plasma. We find that strong coupling of plasma particles modify the fundamental criterion of Jeans gravitational instability. In transverse mode it is found that Jeans instability criterion gets modified due to the presence of magnetic field, shear viscosity and fluid viscosity but in longitudinal mode it is unaffected due to the presence of magnetic field. From the curves we found that all these parameters have stabilizing influence on the growth rate of Jeans instability.

Linear waves and instabilities

International Nuclear Information System (INIS)

Bers, A.

1975-01-01

The electrodynamic equations for small-amplitude waves and their dispersion relation in a homogeneous plasma are outlined. For such waves, energy and momentum, and their flow and transformation, are described. Perturbation theory of waves is treated and applied to linear coupling of waves, and the resulting instabilities from such interactions between active and passive waves. Linear stability analysis in time and space is described where the time-asymptotic, time-space Green's function for an arbitrary dispersion relation is developed. The perturbation theory of waves is applied to nonlinear coupling, with particular emphasis on pump-driven interactions of waves. Details of the time--space evolution of instabilities due to coupling are given. (U.S.)

Imaging of patellofemoral instability

International Nuclear Information System (INIS)

Waldt, S.; Rummeny, E.J.

2012-01-01

Patellofemoral instability remains a diagnostic and therapeutic challenge due to its multifactorial genesis. The purpose of imaging is to systematically analyze predisposing factors, such as trochlear dysplasia, patella alta, tibial tuberosity-trochlear groove (TT-TG) distance, rotational deformities of the lower limb and patellar tilt. In order to evaluate anatomical abnormalities with a sufficient diagnostic accuracy, standardized measurement methods and implementation of various imaging modalities are necessary. Diagnosis of acute and often overlooked lateral patellar dislocation can be established with magnetic resonance imaging (MRI) because of its characteristic patterns of injury. Damage to the medial patellofemoral ligament (MPFL) has a significance just as high as the predisposing risk factors in relation to the cause of chronic instability. (orig.) [de

Richtmyer-Meshkov instability in elastic-plastic media

Science.gov (United States)

Piriz, Antonio R.; López Cela, Juan J.; Tahir, Naeem A.; Hoffmann, Dieter H. H.

2008-04-01

Hydrodynamic instabilities are of great importance in the LAPLAS (Laboratory of Planetary Sciences) experiment that is being designed for the study of high energy density states of matter in the framework of the FAIR projectDuring the implosion of the LAPLAS cylindrical target Richtmyer-Meshkov (RM) instability occurs when a shock is launched into a material pusher with elastic and plastic properties that determines the physics of the instability evolution. We have studied the evolution of the interface from which the shock is launched as a consequence of the RM instability. For this we have developed an analytical model and we have performed two-dimensional numerical simulations in order to validate the model. Model and simulations show the asymptotic stability state in which the interface oscillates elastically around a mean value higher than the initial perturbation amplitude. Such a mean value is determined by an initial plastic phase. Applications to the measurement of the yield strength of materials under extreme conditions are foreseen.

Control of Coherent Instabilities by Linear Coupling

CERN Document Server

Cappi, R; Möhl, D

2001-01-01

One of the main challenges in the design of high-energy colliders is the very high luminosity necessary to provide significant event rates. This imposes strong constraints to achieve and preserve beams of high brightness, i.e. intensity to emittance ratio, all along the injector chain. Amongst the phenomena that can blow up and even destroy the beam are transverse coherent instabilities. Two methods are widely used to damp these instabilities. The first one is Landau damping by non-linearities. The second consists in using an electronic feedback system. However, non-linearities are harmful to single-particle motion due to resonance phenomena, and powerful wideband feedback systems are expensive. It is shown in this paper that linear coupling is a further method that can be used to damp transverse coherent instabilities. The theory of collective motion is outlined, including the coupling of instability rise and damping rates, chromaticity and Landau damping. Experimental results obtained at the CERN PS are rep...

Genome organization, instabilities, stem cells, and cancer

Directory of Open Access Journals (Sweden)

Senthil Kumar Pazhanisamy

2009-01-01

Full Text Available It is now widely recognized that advances in exploring genome organization provide remarkable insights on the induction and progression of chromosome abnormalities. Much of what we know about how mutations evolve and consequently transform into genome instabilities has been characterized in the spatial organization context of chromatin. Nevertheless, many underlying concepts of impact of the chromatin organization on perpetuation of multiple mutations and on propagation of chromosomal aberrations remain to be investigated in detail. Genesis of genome instabilities from accumulation of multiple mutations that drive tumorigenesis is increasingly becoming a focal theme in cancer studies. This review focuses on structural alterations evolve to raise a variety of genome instabilities that are manifested at the nucleotide, gene or sub-chromosomal, and whole chromosome level of genome. Here we explore an underlying connection between genome instability and cancer in the light of genome architecture. This review is limited to studies directed towards spatial organizational aspects of origin and propagation of aberrations into genetically unstable tumors.

Simulations relevant to the beam instability in the foreshock

International Nuclear Information System (INIS)

Cairns, I.H.; Nishikawa, K.I.

1989-01-01

Electrons backstreaming into Earth's foreshock generate waves near the plasma frequency f p by the beam instability. Tow versions of the beam instability exist: the reactive version, in which narrow-band waves grow by bunching the electrons in space, and the kinetic version, in which broadband growth occurs by a maser mechanism. Recently, it has been suggested that (1) the backstreaming electrons have steep-sided cutoff distributions which are initially unstable to the reactive instability, (2) the back reaction to the wave growth causes the instability to pass into its kinetic phase, and (3) the kinetic instability saturates by quasi-linear relaxation. In this paper the authors present two-dimensional simulations of the reactive instability for Maxwellian beams and cutoff distributions. They demonstrate that the reactive instability is a bunching instability and that the reactive instability saturates and passes over into the kinetic phase by particle trapping.A reactive/kinetic transition is shown to most likely occur within 1 km and 50 km of the bow shock. They suggest that the frequency of the intense narrow-band waves decrease from above f p to perhaps 0.9f p (dependent on the beam density) with increasing penetration into the high beam speed region of the foreshock, before the wave frequency rises again as the waves become broadband deeper in the foreshock. Both the simulation results and numerical solutions of the dispersion equation indicate that for the observed beam parameters the center frequency of the waves near the foreshock boundary should be between 0.9f p and 0.98f p , rather than above f p as previously believed. The simulation results indicate that the effects of spatial inhomogeneity are vital for a quantitative understanding of the foreshock waves

Higher-order modulation instability in nonlinear fiber optics.

Science.gov (United States)

Erkintalo, Miro; Hammani, Kamal; Kibler, Bertrand; Finot, Christophe; Akhmediev, Nail; Dudley, John M; Genty, Goëry

2011-12-16

We report theoretical, numerical, and experimental studies of higher-order modulation instability in the focusing nonlinear Schrödinger equation. This higher-order instability arises from the nonlinear superposition of elementary instabilities, associated with initial single breather evolution followed by a regime of complex, yet deterministic, pulse splitting. We analytically describe the process using the Darboux transformation and compare with experiments in optical fiber. We show how a suitably low frequency modulation on a continuous wave field induces higher-order modulation instability splitting with the pulse characteristics at different phases of evolution related by a simple scaling relationship. We anticipate that similar processes are likely to be observed in many other systems including plasmas, Bose-Einstein condensates, and deep water waves. © 2011 American Physical Society

Canonical momenta and numerical instabilities in particle codes

International Nuclear Information System (INIS)

Godfrey, B.B.

1975-01-01

A set of warm plasma dispersion relations appropriate to a large class of electromagnetic plasma simulation codes is derived. The numerical Cherenkov instability is shown by analytic and numerical analysis of these dispersion relations to be the most significant nonphysical effect involving transverse electromagnetic waves. The instability arises due to a spurious phase shift between resonant particles and light waves, caused by a basic incompatibility between the Lagrangian treatment of particle positions and the Eulerian treatment of particle velocities characteristic of most PIC--CIC algorithms. It is demonstrated that, through the use of canonical momentum, this mismatch is alleviated sufficiently to completely eliminate the Cherenkov instability. Collateral effects on simulation accuracy and on other numerical instabilities appear to be minor

Inhomogeneity driven by Higgs instability in a gapless superconductor

International Nuclear Information System (INIS)

Giannakis, Ioannis; Hou Defu; Huang Mei; Ren Haicang

2007-01-01

The fluctuations of the Higgs and pseudo Nambu-Goldstone fields in the 2-flavor color superconductivity (2SC) phase with mismatched pairing are described in the nonlinear realization framework of the gauged Nambu-Jona-Lasinio model. In the gapless 2SC phase, not only Nambu-Goldstone currents can be spontaneously generated, but also the Higgs field exhibits instablity. The Nambu-Goldstone currents generation indicates the formation of the single plane wave Larkin-Ovchinnikov-Fulde-Ferrel state and breaks rotation symmetry, while the Higgs instability favors spatial inhomogeneity and breaks translation invariance. In this paper, we focus on the Higgs instability which has not drawn much attention yet. The Higgs instability cannot be removed without a long range force, thus it persists in the gapless superfluidity and induces phase separation. In the case of gapless 2-flavor color superconductivity state, the Higgs instability can only be partially removed by the electric Coulomb energy. However, it is not excluded that the Higgs instability might be completely removed in the charge neutral gapless color-flavor locked phase by the color Coulomb energy

Fluid Instabilities of Magnetar-Powered Supernovae

Science.gov (United States)

Chen, Ke-Jung

2017-05-01

Magnetar-powered supernova explosions are competitive models for explaining very luminous optical transits. Until recently, these explosion models were mainly calculated in 1D. Radiation emitted from the magnetar snowplows into the previous supernovae ejecta and causes a nonphysical dense shell (spike) found in previous 1D studies. This suggests that strong fluid instabilities may have developed within the magnetar-powered supernovae. Such fluid instabilities emerge at the region where luminous transits later occur, so they can affect the consequent observational signatures. We examine the magnetar-powered supernovae with 2D hydrodynamics simulations and find that the 1D dense shell transforms into the development of Rayleigh-Taylor and thin shell instabilities in 2D. The resulting mixing is able to fragment the entire shell and break the spherical symmetry of supernovae ejecta.

Two-stream instability in pulsar magnetospheres

International Nuclear Information System (INIS)

Usov, V.V.

1987-01-01

If the electron-positron plasma flow from the pulsar environment is stationary, the two-stream instability does not have enough time to develop in the pulsar magnetosphere. In that case the outflowing electron-positron plasma gathers into separate clouds. The clouds move along magnetic field lines and disperse as they go farther from the pulsar. At a distance of about 10 to the 8th cm from the pulsar surface, the high-energy particles of a given cloud catch up with the low-energy particles that belong to the cloud going ahead of it. In this region of a pulsar magnetosphere, the energy distribution of plasma particles is two-humped, and a two-stream instability may develop. The growth rate of the instability is quite sufficient for its development. 17 references

Papaloizou-Pringle instability suppression by the magnetorotational instability in relativistic accretion discs

Science.gov (United States)

Bugli, M.; Guilet, J.; Müller, E.; Del Zanna, L.; Bucciantini, N.; Montero, P. J.

2018-03-01

Geometrically thick tori with constant specific angular momentum have been widely used in the last decades to construct numerical models of accretion flows on to black holes. Such discs are prone to a global non-axisymmetric hydrodynamic instability, known as Papaloizou-Pringle instability (PPI), which can redistribute angular momentum and also lead to an emission of gravitational waves. It is, however, not clear yet how the development of the PPI is affected by the presence of a magnetic field and by the concurrent development of the magnetorotational instability (MRI). We present a numerical analysis using three-dimensional GRMHD simulations of the interplay between the PPI and the MRI considering, for the first time, an analytical magnetized equilibrium solution as initial condition. In the purely hydrodynamic case, the PPI selects as expected the large-scale m = 1 azimuthal mode as the fastest growing and non-linearly dominant mode. However, when the torus is threaded by a weak toroidal magnetic field, the development of the MRI leads to the suppression of large-scale modes and redistributes power across smaller scales. If the system starts with a significantly excited m = 1 mode, the PPI can be dominant in a transient phase, before being ultimately quenched by the MRI. Such dynamics may well be important in compact star mergers and tidal disruption events.

Predicting ICU hemodynamic instability using continuous multiparameter trends.

Science.gov (United States)

Cao, Hanqing; Eshelman, Larry; Chbat, Nicolas; Nielsen, Larry; Gross, Brian; Saeed, Mohammed

2008-01-01

Identifying hemodynamically unstable patients in a timely fashion in intensive care units (ICUs) is crucial because it can lead to earlier interventions and thus to potentially better patient outcomes. Current alert algorithms are typically limited to detecting dangerous conditions only after they have occurred and suffer from high false alert rates. Our objective was to predict hemodynamic instability at least two hours before a major clinical intervention (e.g., vasopressor administration), while maintaining a low false alert rate. From the MIMIC II database, containing ICU minute-by-minute heart rate (HR) and invasive arterial blood pressure (BP) monitoring trend data collected between 2001 and 2005, we identified 132 stable and 104 unstable patients that met our stability-instability criteria and had sufficient data points. We first derived additional physiological parameters of shock index, rate pressure product, heart rate variability, and two measures of trending based on HR and BP. Then we developed 220 statistical features and systematically selected a small set to use for classification. We applied multi-variable logistic regression modeling to do classification and implemented validation via bootstrapping. Area under receiver-operating curve (ROC) 0.83+/-0.03, sensitivity 0.75+/-0.06, and specificity 0.80+/-0.07; if the specificity is targeted at 0.90, then the sensitivity is 0.57+/-0.07. Based on our preliminary results, we conclude that the algorithms we developed using HR and BP trend data may provide a promising perspective toward reliable predictive alerts for hemodynamically unstable patients.

Self-Induced Faraday Instability Laser

Science.gov (United States)

Perego, A. M.; Smirnov, S. V.; Staliunas, K.; Churkin, D. V.; Wabnitz, S.

2018-05-01

We predict the onset of self-induced parametric or Faraday instabilities in a laser, spontaneously caused by the presence of pump depletion, which leads to a periodic gain landscape for light propagating in the cavity. As a result of the instability, continuous wave oscillation becomes unstable even in the normal dispersion regime of the cavity, and a periodic train of pulses with ultrahigh repetition rate is generated. Application to the case of Raman fiber lasers is described, in good quantitative agreement between our conceptual analysis and numerical modeling.

Application of autoregressive methods and Lyapunov coefficients for instability studies of nuclear reactors

International Nuclear Information System (INIS)

Aruquipa Coloma, Wilmer

2017-01-01

Nuclear reactors are susceptible to instability, causing oscillations in reactor power in specific working regions characterized by determined values of power and coolant mass flow. During reactor startup, there is a greater probability that these regions of instability will be present; another reason may be due to transient processes in some reactor parameters. The analysis of the temporal evolution of the power reveals a stable or unstable process after the disturbance in a light water reactor of type BWR (Boiling Water Reactor). In this work, the instability problem was approached in two ways. The first form is based on the ARMA (Autoregressive Moving Average models) model. This model was used to calculate the Decay Ratio (DR) and natural frequency (NF) of the oscillations, parameters that indicate if the one power signal is stable or not. In this sense, the DRARMA code was developed. In the second form, the problems of instability were analyzed using the classical concepts of non-linear systems, such as Lyapunov exponents, phase space and attractors. The Lyapunov exponents quantify the exponential divergence of the trajectories initially close to the phase space and estimate the amount of chaos in a system; the phase space and the attractors describe the dynamic behavior of the system. The main aim of the instability phenomena studies in nuclear reactors is to try to identify points or regions of operation that can lead to power oscillations conditions. The two approaches were applied to two sets of signals. The first set comes from signals of instability events of the commercial Forsmark reactors 1 and 2 and were used to validate the DRARMA code. The second set was obtained from the simulation of transient events of the Peach Bottom reactor; for the simulation, the PARCS and RELAP5 codes were used for the neutronic/thermal hydraulic coupling calculation. For all analyzes made in this work, the Matlab software was used due to its ease of programming and

Bulge Growth Through Disc Instabilities in High-Redshift Galaxies

Science.gov (United States)

Bournaud, Frédéric

The role of disc instabilities, such as bars and spiral arms, and the associated resonances, in growing bulges in the inner regions of disc galaxies have long been studied in the low-redshift nearby Universe. There it has long been probed observationally, in particular through peanut-shaped bulges (Chap. 14 10.1007/978-3-319-19378-6_14"). This secular growth of bulges in modern disc galaxies is driven by weak, non-axisymmetric instabilities: it mostly produces pseudobulges at slow rates and with long star-formation timescales. Disc instabilities at high redshift (z > 1) in moderate-mass to massive galaxies (1010 to a few 1011 M⊙ of stars) are very different from those found in modern spiral galaxies. High-redshift discs are globally unstable and fragment into giant clumps containing 108-9 M⊙ of gas and stars each, which results in highly irregular galaxy morphologies. The clumps and other features associated to the violent instability drive disc evolution and bulge growth through various mechanisms on short timescales. The giant clumps can migrate inward and coalesce into the bulge in a few 108 years. The instability in the very turbulent media drives intense gas inflows toward the bulge and nuclear region. Thick discs and supermassive black holes can grow concurrently as a result of the violent instability. This chapter reviews the properties of high-redshift disc instabilities, the evolution of giant clumps and other features associated to the instability, and the resulting growth of bulges and associated sub-galactic components.

Reducing work disability in Ankylosing Spondylitis – development of a work instability scale for AS

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Helliwell Philip

2009-06-01

Full Text Available Abstract Background The Work Instability Scale for Rheumatoid Arthritis (RA-WIS is established and is used by physicians to identify patients at risk of job loss for rapid intervention. The study objective was to explore the concept of Work Instability (a mismatch between an individual's abilities and job demands in Ankylosing Spondylitis (AS and develop a Work Instability Scale specific to this population. Methods New items generated from qualitative interviews were combined with items from the RA-WIS to form a draft AS-WIS. Rasch analysis was used to examine the scaling properties of the AS-WIS using data generated through a postal survey. The scale was validated against a gold standard of expert assessment, a test-retest survey examined reliability. Results Fifty-seven participants who were in work returned the postal survey. Of the original 55 items 38 were shown to fit the Rasch model (χ2 37.5; df 38; p 0.494 and free of bias for gender and disease duration. Following analysis for discrimination against the gold standard assessments 20 items remained with good fit to the model (χ2 24.8; df 20; p 0.21. Test-retest reliability was 0.94. Conclusion The AS-WIS is a self-administered scale which meets the stringent requirements of modern measurement. Used as a screening tool it can identify those experiencing a mismatch at work who are at risk of job retention problems and work disability. Work instability is emerging as an important indication for the use of biologics, thus the AS-WIS has the potential to become an important outcome measure.

Nucleation versus instability race in strained films