WorldWideScience

Sample records for weakly susceptible cortex

  1. Susceptibility of Primary Sensory Cortex to Spreading Depolarizations

    OpenAIRE

    Bogdanov, VB; Middleton, NA; Theriot, JJ; Parker, PD; Abdullah, OM; Ju, YS; Hartings, JA; Brennan, KC

    2016-01-01

    Spreading depolarizations (SDs) are recognized as actors in neurological disorders as diverse as migraine and traumatic brain injury (TBI). Migraine aura involves sensory percepts, suggesting that sensory cortices might be intrinsically susceptible to SDs. We used optical imaging, MRI, and field potential and potassium electrode recordings in mice and electrocorticographic recordings in humans to determine the susceptibility of different brain regions to SDs. Optical imaging experiments in mi...

  2. Susceptibility to social pressure following ventromedial prefrontal cortex damage.

    Science.gov (United States)

    Chen, Kuan-Hua; Rusch, Michelle L; Dawson, Jeffrey D; Rizzo, Matthew; Anderson, Steven W

    2015-11-01

    Social pressure influences human behavior including risk taking, but the psychological and neural underpinnings of this process are not well understood. We used the human lesion method to probe the role of ventromedial prefrontal cortex (vmPFC) in resisting adverse social pressure in the presence of risk. Thirty-seven participants (11 with vmPFC damage, 12 with brain damage outside the vmPFC and 14 without brain damage) were tested in driving simulator scenarios requiring left-turn decisions across oncoming traffic with varying time gaps between the oncoming vehicles. Social pressure was applied by a virtual driver who honked aggressively from behind. Participants with vmPFC damage were more likely to select smaller and potentially unsafe gaps under social pressure, while gap selection by the comparison groups did not change under social pressure. Participants with vmPFC damage also showed prolonged elevated skin conductance responses (SCR) under social pressure. Comparison groups showed similar initial elevated SCR, which then declined prior to making left-turn decisions. The findings suggest that the vmPFC plays an important role in resisting explicit and immediately present social pressure with potentially negative consequences. The vmPFC appears to contribute to the regulation of emotional responses and the modulation of decision making to optimize long-term outcomes.

  3. Magnetic susceptibility in the deep layers of the primary motor cortex in Amyotrophic Lateral Sclerosis

    Directory of Open Access Journals (Sweden)

    M. Costagli

    2016-01-01

    Full Text Available Amyotrophic Lateral Sclerosis (ALS is a progressive neurological disorder that entails degeneration of both upper and lower motor neurons. The primary motor cortex (M1 in patients with upper motor neuron (UMN impairment is pronouncedly hypointense in Magnetic Resonance (MR T2* contrast. In the present study, 3D gradient-recalled multi-echo sequences were used on a 7 Tesla MR system to acquire T2*-weighted images targeting M1 at high spatial resolution. MR raw data were used for Quantitative Susceptibility Mapping (QSM. Measures of magnetic susceptibility correlated with the expected concentration of non-heme iron in different regions of the cerebral cortex in healthy subjects. In ALS patients, significant increases in magnetic susceptibility co-localized with the T2* hypointensity observed in the middle and deep layers of M1. The magnetic susceptibility, hence iron concentration, of the deep cortical layers of patients' M1 subregions corresponding to Penfield's areas of the hand and foot in both hemispheres significantly correlated with the clinical scores of UMN impairment of the corresponding limbs. QSM therefore reflects the presence of iron deposits related to neuroinflammatory reaction and cortical microgliosis, and might prove useful in estimating M1 iron concentration, as a possible radiological sign of severe UMN burden in ALS patients.

  4. Magnetic susceptibility in the deep layers of the primary motor cortex in Amyotrophic Lateral Sclerosis.

    Science.gov (United States)

    Costagli, M; Donatelli, G; Biagi, L; Caldarazzo Ienco, E; Siciliano, G; Tosetti, M; Cosottini, M

    2016-01-01

    Amyotrophic Lateral Sclerosis (ALS) is a progressive neurological disorder that entails degeneration of both upper and lower motor neurons. The primary motor cortex (M1) in patients with upper motor neuron (UMN) impairment is pronouncedly hypointense in Magnetic Resonance (MR) T2* contrast. In the present study, 3D gradient-recalled multi-echo sequences were used on a 7 Tesla MR system to acquire T2*-weighted images targeting M1 at high spatial resolution. MR raw data were used for Quantitative Susceptibility Mapping (QSM). Measures of magnetic susceptibility correlated with the expected concentration of non-heme iron in different regions of the cerebral cortex in healthy subjects. In ALS patients, significant increases in magnetic susceptibility co-localized with the T2* hypointensity observed in the middle and deep layers of M1. The magnetic susceptibility, hence iron concentration, of the deep cortical layers of patients' M1 subregions corresponding to Penfield's areas of the hand and foot in both hemispheres significantly correlated with the clinical scores of UMN impairment of the corresponding limbs. QSM therefore reflects the presence of iron deposits related to neuroinflammatory reaction and cortical microgliosis, and might prove useful in estimating M1 iron concentration, as a possible radiological sign of severe UMN burden in ALS patients.

  5. The contribution of PSInSAR interferometry to landslide susceptibility assessment in weak rock-dominated areas

    Science.gov (United States)

    Oliveira, Sérgio C.; Zêzere, José L.; Catalão, João; Nico, Giovanni

    2015-04-01

    In the Grande da Pipa river basin (north of Lisbon, Portugal), 64% of the landslides inventoried occur on a particular weak rock lithological unit composed by clay and with sandstone intercalations, that is present in 58% of the study (Oliveira et al., 2014). Deep-seated slow moving rotational slides occur essentially on this lithological unit and are responsible for the major damages verified along roads and buildings in the study area. Within this context, landslide hazard assessment, is limited by two major constrains: (i) the slope instability signs may not be sufficiently clear and observable and consequently may not be correctly identifiable through traditional geomorphologic survey techniques and (ii) the non-timely recognition of precursor signs of instability both in landslides activated for the first time and in previously landslide-affected areas (landslide reactivation). To encompass these limitations, the Persistent Scatterer synthetic aperture radar interferometry technique is applied to a data set of 16 TerraSAR-X SAR images, from April of 2010 to March of 2011, available for a small test site of 12.5 square kilometers (Laje-Salema) located on south-central part of the study area. This work's specific objectives are the following: (i) to evaluate the capacity of the Persistent Scatterer displacement maps in assessing landslide susceptibility at the regional scale, and (ii) to assess the capacity of landslide susceptibility maps based on historical landslide inventories to predict the location of actual terrain displacement measured by the Persistent Scatterers technique. Landslide susceptibility was assessed for the test site using the Information Value bivariate statistical method and the susceptibility scores were exported to the Grande da Pipa river basin. The independent validation of the landslide susceptibility maps was made using the historical landslide inventory and the Persistent Scatterer displacement map. Results are compared by computing

  6. Depression of excitatory synapses onto parvalbumin interneurons in the medial prefrontal cortex in susceptibility to stress.

    Science.gov (United States)

    Perova, Zinaida; Delevich, Kristen; Li, Bo

    2015-02-18

    In response to extreme stress, individuals either show resilience or succumb to despair. The prefrontal cortex (PFC) is required for coping with stress, and PFC dysfunction has been implicated in stress-related mental disorders, including depression. Nevertheless, the mechanisms by which the PFC participates in stress responses remain unclear. Here, we investigate the role of parvalbumin (PV) interneurons in the medial PFC (mPFC) in shaping behavioral responses to stress induced by the learned helplessness procedure, in which animals are subjected to an unpredictable and inescapable stressor. PV interneurons in the mPFC were probed and manipulated in knock-in mice expressing the Cre recombinase under the endogenous parvalbumin promoter. Notably, we found that excitatory synaptic transmission onto these neurons was decreased in mice showing helplessness, a behavioral state that is thought to resemble features of human depression. Furthermore, selective suppression of PV interneurons in the mPFC using hM4Di, a DREADD (designer receptor exclusively activated by designer drug), promoted helplessness, indicating that activation of these neurons during stress promotes the establishment of resilient behavior. Our results reveal a cellular mechanism of mPFC dysfunction that may contribute to the emergence of maladaptive behavioral responses in the face of adverse life events.

  7. Early life exposure to chronic intermittent Hypoxia Primes Increased Susceptibility to Hypoxia-Induced Weakness in Rat Sternohyoid Muscle during adulthood.

    LENUS (Irish Health Repository)

    McDonald, Fiona B

    2016-03-01

    Intermittent hypoxia is a feature of apnea of prematurity (AOP), chronic lung disease, and sleep apnea. Despite the clinical relevance, the long-term effects of hypoxic exposure in early life on respiratory control are not well defined. We recently reported that exposure to chronic intermittent hypoxia (CIH) during postnatal development (pCIH) causes upper airway muscle weakness in both sexes, which persists for several weeks. We sought to examine if there are persistent sex-dependent effects of pCIH on respiratory muscle function into adulthood and\\/or increased susceptibility to re-exposure to CIH in adulthood in animals previously exposed to CIH during postnatal development. We hypothesized that pCIH would cause long-lasting muscle impairment and increased susceptibility to subsequent hypoxia. Within 24 h of delivery, pups and their respective dams were exposed to CIH: 90 s of hypoxia reaching 5% O2 at nadir; once every 5 min, 8 h per day for 3 weeks. Sham groups were exposed to normoxia in parallel. Three groups were studied: sham; pCIH; and pCIH combined with adult CIH (p+aCIH), where a subset of the pCIH-exposed pups were re-exposed to the same CIH paradigm beginning at 13 weeks. Following gas exposures, sternohyoid and diaphragm muscle isometric contractile and endurance properties were examined ex vivo. There was no apparent lasting effect of pCIH on respiratory muscle function in adults. However, in both males and females, re-exposure to CIH in adulthood in pCIH-exposed animals caused sternohyoid (but not diaphragm) weakness. Exposure to this paradigm of CIH in adulthood alone had no effect on muscle function. Persistent susceptibility in pCIH-exposed airway dilator muscle to subsequent hypoxic insult may have implications for the control of airway patency in adult humans exposed to intermittent hypoxic stress during early life.

  8. Early Life Exposure to Chronic Intermittent Hypoxia Primes Increased Susceptibility to Hypoxia-Induced Weakness in Rat Sternohyoid Muscle During Adulthood

    Directory of Open Access Journals (Sweden)

    Fiona B Mcdonald

    2016-03-01

    Full Text Available Intermittent hypoxia is a feature of apnea of prematurity, chronic lung disease and sleep apnea. Despite the clinical relevance, the long-term effects of hypoxic exposure in early life on respiratory control are not well defined. We recently reported that exposure to chronic intermittent hypoxia (CIH during postnatal development (pCIH causes upper airway muscle weakness in both sexes, which persists for several weeks. We sought to examine if there are persistent sex-dependent effects of pCIH on respiratory muscle function into adulthood and/or increased susceptibility to re-exposure to CIH in adulthood in animals previously exposed to CIH during postnatal development. We hypothesized that pCIH would cause long-lasting muscle impairment and increased susceptibility to subsequent hypoxia. Within 24 hours of delivery, pups and their respective dams were exposed to CIH: 90s of hypoxia reaching 5% O2 at nadir; once every 5 min, 8 hrs per day for 3 weeks. Sham groups were exposed to normoxia in parallel. Three groups were studied: sham; pCIH; and pCIH combined with adult CIH (p+aCIH, where a subset of the pCIH-exposed pups were re-exposed to the same CIH paradigm beginning at 13 weeks. Following gas exposures, sternohyoid and diaphragm muscle isometric contractile and endurance properties were examined ex vivo. There was no apparent lasting effect of pCIH on respiratory muscle function in adults. However, in both males and females, re-exposure to CIH in adulthood in pCIH-exposed animals caused sternohyoid (but not diaphragm weakness. Exposure to this paradigm of CIH in adulthood alone had no effect on muscle function. Persistent susceptibility in pCIH-exposed airway dilator muscle to subsequent hypoxic insult may have implications for the control of airway patency in adult humans exposed to intermittent hypoxic stress during early life.

  9. An Experimentally Based Description of the Ground-state Wavefunction for Two Weakly Coupled Electrons by Photoelectron Spectroscopy and Magnetic Susceptibility Measurements

    OpenAIRE

    Rankin, Richard; Seddon, Elaine A.; Teuben, Jan H.; Jonkman-Beuker, Anneke H.; Boer, Dirk K.G. de

    1981-01-01

    It is possible to extract values for the transfer energy, t, and the Coulomb interaction, U, in hydrogen-like systems from a combination of photoelectron and magnetic data, as both the form of the photoelectron spectrum and the exchange splitting are determined by these quantities. This procedure is used to evaluate the ground-state wavefunction for the two weakly coupled Ti 3d electrons in (C10H8)(C5H5)2Ti2Cl2.

  10. Weak Convergence and Weak Convergence

    Directory of Open Access Journals (Sweden)

    Narita Keiko

    2015-09-01

    Full Text Available In this article, we deal with weak convergence on sequences in real normed spaces, and weak* convergence on sequences in dual spaces of real normed spaces. In the first section, we proved some topological properties of dual spaces of real normed spaces. We used these theorems for proofs of Section 3. In Section 2, we defined weak convergence and weak* convergence, and proved some properties. By RNS_Real Mizar functor, real normed spaces as real number spaces already defined in the article [18], we regarded sequences of real numbers as sequences of RNS_Real. So we proved the last theorem in this section using the theorem (8 from [25]. In Section 3, we defined weak sequential compactness of real normed spaces. We showed some lemmas for the proof and proved the theorem of weak sequential compactness of reflexive real Banach spaces. We referred to [36], [23], [24] and [3] in the formalization.

  11. Short-latency afferent inhibition is a poor predictor of individual susceptibility to rTMS-induced plasticity in the motor cortex of young and older adults.

    Directory of Open Access Journals (Sweden)

    Marielle eYoung-Bernier

    2014-08-01

    Full Text Available Cortical plasticity, including long-term potentiation (LTP-like plasticity, can be assessed non-invasively with repetitive transcranial magnetic stimulation (rTMS protocols. In this study, we examined age differences in responses to intermittent theta burst stimulation (iTBS in a group of 20 young and 18 healthy older adults. Because the cholinergic system plays a role in the neural processes underlying learning and memory, including LTP, we also investigated whether short latency afferent inhibition (SAI, a neurophysiological marker of central cholinergic activity, would be associated with age-related differences in LTP-like plasticity induced by iTBS. Methods: SAI was first assessed by examining the modulation of motor evoked potentials (MEPs in response to median nerve conditioning 20 ms prior to TMS. Participants then underwent iTBS (3 pulses at 50 HZ every 200 ms for 2 s with 8 s between trains, repeated 20 times. MEP responses (120% RMT were assessed immediately after iTBS and 5, 10, and 20 min post-application. Results: Responses to iTBS were quite variable in both age groups, with only approximately 60% of the participants (n=13 young and 10 older adults showing the expected facilitation of MEP responses. There were no significant age group differences in MEP facilitation following iTBS. Although older adults exhibited reduced SAI, individual variations were not associated with susceptibility to express LTP-like induced plasticity after iTBS. Conclusion: Overall, these results are consistent with reports of high inter-individual variability in responses to iTBS. Although SAI was reduced in older adults, consistent with a deterioration of the cholinergic system with age, SAI levels were not associated with LTP-like plasticity as assessed with iTBS.

  12. Weak Force

    CERN Multimedia

    Without the weak force, the sun wouldn't shine. The weak force causes beta decay, a form of radioactivity that triggers nuclear fusion in the heart of the sun. The weak force is unlike other forces: it is characterised by disintegration. In beta decay, a down quark transforms into an up quark and an electron is emitted. Some materials are more radioactive than others because the delicate balance between the strong force and the weak force varies depending on the number of particles in the atomic nucleus. We live in the midst of a natural radioactive background that varies from region to region. For example, in Cornwall where there is a lot of granite, levels of background radiation are much higher than in the Geneva region. Text for the interactive: Move the Geiger counter to find out which samples are radioactive - you may be surprised. It is the weak force that is responsible for the Beta radioactivity here. The electrons emitted do not cross the plastic cover. Why do you think there is some detected radioa...

  13. Weak relativity

    CERN Document Server

    Selleri, Franco

    2015-01-01

    Weak Relativity is an equivalent theory to Special Relativity according to Reichenbach’s definition, where the parameter epsilon equals to 0. It formulates a Neo-Lorentzian approach by replacing the Lorentz transformations with a new set named “Inertial Transformations”, thus explaining the Sagnac effect, the twin paradox and the trip from the future to the past in an easy and elegant way. The cosmic microwave background is suggested as a possible privileged reference system. Most importantly, being a theory based on experimental proofs, rather than mutual consensus, it offers a physical description of reality independent of the human observation.

  14. Muscle Weakness

    Science.gov (United States)

    Al Kaissi, Ali; Ryabykh, Sergey; Ochirova, Polina; Kenis, Vladimir; Hofstätter, Jochen G.; Grill, Franz; Ganger, Rudolf; Kircher, Susanne Gerit

    2017-01-01

    Marked ligamentous hyperlaxity and muscle weakness/wasting associated with awkward gait are the main deficits confused with the diagnosis of myopathy. Seven children (6 boys and 1 girl with an average age of 8 years) were referred to our department because of diverse forms of skeletal abnormalities. No definitive diagnosis was made, and all underwent a series of sophisticated investigations in other institutes in favor of myopathy. We applied our methodology through the clinical and radiographic phenotypes followed by targeted genotypic confirmation. Three children (2 boys and 1 girl) were compatible with the diagnosis of progressive pseudorheumatoid chondrodysplasia. The genetic mutation was correlated with the WISP 3 gene actively expressed by articular chondrocytes and located on chromosome 6. Klinefelter syndrome was the diagnosis in 2 boys. Karyotyping confirmed 47,XXY (aneuploidy of Klinefelter syndrome). And 2 boys were finally diagnosed with Morquio syndrome (MPS type IV A) as both showed missense mutations in the N-acetylgalactosamine-sulfate sulfatase gene. Misdiagnosis can lead to the initiation of a long list of sophisticated investigations. PMID:28210640

  15. Input-dependent wave attenuation in a critically-balanced model of cortex.

    Directory of Open Access Journals (Sweden)

    Xiao-Hu Yan

    Full Text Available A number of studies have suggested that many properties of brain activity can be understood in terms of critical systems. However it is still not known how the long-range susceptibilities characteristic of criticality arise in the living brain from its local connectivity structures. Here we prove that a dynamically critically-poised model of cortex acquires an infinitely-long ranged susceptibility in the absence of input. When an input is presented, the susceptibility attenuates exponentially as a function of distance, with an increasing spatial attenuation constant (i.e., decreasing range the larger the input. This is in direct agreement with recent results that show that waves of local field potential activity evoked by single spikes in primary visual cortex of cat and macaque attenuate with a characteristic length that also increases with decreasing contrast of the visual stimulus. A susceptibility that changes spatial range with input strength can be thought to implement an input-dependent spatial integration: when the input is large, no additional evidence is needed in addition to the local input; when the input is weak, evidence needs to be integrated over a larger spatial domain to achieve a decision. Such input-strength-dependent strategies have been demonstrated in visual processing. Our results suggest that input-strength dependent spatial integration may be a natural feature of a critically-balanced cortical network.

  16. Weak Galois and Weak Cocleft Coextensions

    Institute of Scientific and Technical Information of China (English)

    J.N. Alonso (A)lvarez; J.M. Fernández Vilaboa; R. González Rodríguez; A.B. Rodríguez Raposo

    2007-01-01

    For a weak entwining structure (A, C,ψ) living in a braided monoidal category with equalizers and coequalizers, we formulate the notion of weak A-Galois coextension with normal basis and we show that these Galois coextensions are equivalent to the weak A-cocleft coextensions introduced by the authors.

  17. On Weak Regular *-semigroups

    Institute of Scientific and Technical Information of China (English)

    Yong Hua LI; Hai Bin KAN; Bing Jun YU

    2004-01-01

    In this paper, a special kind of partial algebras called projective partial groupoids is defined.It is proved that the inverse image of all projections of a fundamental weak regular *-semigroup under the homomorphism induced by the maximum idempotent-separating congruence of a weak regular *-semigroup has a projective partial groupoid structure. Moreover, a weak regular *-product which connects a fundamental weak regular *-semigroup with corresponding projective partial groupoid is defined and characterized. It is finally proved that every weak regular *-product is in fact a weak regular *-semigroup and any weak regular *-semigroup is constructed in this way.

  18. Cofinitely weak supplemented modules

    OpenAIRE

    Alizade, Rafail; Büyükaşık, Engin

    2003-01-01

    We prove that a module M is cofinitely weak supplemented or briefly cws (i.e., every submodule N of M with M/N finitely generated, has a weak supplement) if and only if every maximal submodule has a weak supplement. If M is a cws-module then every M-generated module is a cws-module. Every module is cws if and only if the ring is semilocal. We study also modules, whose finitely generated submodules have weak supplements.

  19. GENERALIZED WEAK FUNCTIONS

    Institute of Scientific and Technical Information of China (English)

    丁夏畦; 罗佩珠

    2004-01-01

    In this paper the authors introduce some new ideas on generalized numbers and generalized weak functions. They prove that the product of any two weak functions is a generalized weak function. So in particular they solve the problem of the multiplication of two generalized functions.

  20. On quark number susceptibilities at high temperatures

    CERN Document Server

    Bazavov, A; Hegde, P; Karsch, F; Miao, C; Mukherjee, Swagato; Petreczky, P; Schmidt, C; Velytsky, A

    2013-01-01

    We calculated second and fourth order quark number susceptibilities for 2+1 flavor QCD in the high temperature region using two improved staggered fermion formulations. The calculations are performed at several lattice spacing and we show that in the continuum limit the two formulations give consistent results. We compare our continuum extrapolated results on quark number susceptibilities with recent weak coupling calculations, and find that these cannot simultaneously explain the lattice results for second and fourth order quark number susceptibilities.

  1. On Weakly Semicommutative Rings*

    Institute of Scientific and Technical Information of China (English)

    CHEN WEI-XING; CUI SHU-YING

    2011-01-01

    A ring R is said to be weakly scmicommutative if for any a, b ∈ R,ab = 0 implies aRb C_ Nil(R), where Nil(R) is the set of all nilpotcnt elements in R.In this note, we clarify the relationship between weakly semicommutative rings and NI-rings by proving that the notion of a weakly semicommutative ring is a proper generalization of NI-rings. We say that a ring R is weakly 2-primal if the set of nilpotent elements in R coincides with its Levitzki radical, and prove that if R is a weakly 2-primal ring which satisfies oα-condition for an endomorphism α of R (that is, ab = 0 (←→) aα(b) = 0 where a, b ∈ R) then the skew polynomial ring R[π; αα]is a weakly 2-primal ring, and that if R is a ring and I is an ideal of R such that I and R/I are both weakly semicommutative then R is weakly semicommutative.Those extend the main results of Liang et al. 2007 (Taiwanese J. Math., 11(5)(2007),1359-1368) considerably. Moreover, several new results about weakly semicommutative rings and NI-rings are included.

  2. Idiopathic isolated orbicularis weakness

    Science.gov (United States)

    MacVie, O P; Majid, M A; Husssin, H M; Ung, T; Manners, R M; Ormerod, I; Pawade, J; Harrad, R A

    2012-01-01

    Purpose Orbicularis weakness is commonly associated with seventh nerve palsy or neuromuscular and myopathic conditions such as myotonic dystrophy and myasethenia gravis. We report four cases of idiopathic isolated orbicularis weakness. Methods All four cases were female and the presenting symptoms of ocular irritation and epiphora had been present for over 7 years in three patients. All patients had lagophthalmos and three had ectropion. Three patients underwent full investigations which excluded known causes of orbicularis weakness. Two patients underwent oribularis oculi muscle biopsy and histological confirmation of orbicularis atrophy. Results All patients underwent surgery to specifically address the orbicularis weakness with satisfactory outcomes and alleviation of symptoms in all cases. Isolated orbicularis weakness may be a relatively common entity that is frequently overlooked. Conclusion Early recognition of this condition may lead to better management and prevent patients undergoing unnecessary surgical procedures. PMID:22322997

  3. Mescaline-induced changes of brain-cortex ribosomes. Effect of mescaline on the stability of brain-cortex ribosomes.

    Science.gov (United States)

    Datta, R K; Ghosh, J J

    1970-05-01

    1. During the action of mescaline sulphate on goat brain-cortex slices the ribosomal particles become susceptible to breakdown, releasing protein, RNA, acidsoluble nucleotides and ninhydrin-positive materials, resulting in loss of ribosomal enzyme activities. 2. Ribosomes of the mescaline-treated cortex slices undergo rapid degradation in the presence of trypsin and ribonuclease. 3. Mescaline does not alter the chemical and nucleotide compositions or the u.v.-absorption characteristics of ribosomal particles, however.

  4. Deep prepiriform cortex kindling and amygdala interactions.

    Science.gov (United States)

    Zhao, D Y; Moshé, S L

    1987-03-01

    The deep prepiriform cortex (DPC) has been recently suggested to be a crucial epileptogenic site in the rat brain. We investigated the susceptibility of the DPC to the development of electrical kindling as compared to that of the superficial prepiriform cortex (SPC) and amygdala as well as the transfer interactions between the two prepiriform sites and amygdala. Adult rats with electrodes implanted in the right prepiriform cortex (DPC or SPC) and left amygdala were divided into a DPC-amygdala and SPC-amygdala group while a third group consisted of rats with electrodes implanted in the ipsilateral DPC and amygdala. Within each group the rats were initially kindled from one site selected randomly and then rekindled from the other site. Both DPC and SPC were as sensitive to the development of kindling as the amygdala. The behavioral seizures elicited with DPC or SPC primary kindling were identical to those induced by amygdala kindling. Initial DPC kindling facilitated the development of kindling from either ipsilateral or contralateral amygdala with the ipsilateral transfer being significantly more potent than the contralateral. SPC kindling also facilitated the development of contralateral amygdala kindling but was less effective than DPC kindling. On the other hand, amygdala kindling did not facilitate contralateral SPC or DPC kindling although it transferred to the ipsilateral DPC. These results indicate that the prepiriform cortex can be readily kindled but not faster than the amygdala and that there are unequal kindling transfer interactions between prepiriform cortex and amygdala.

  5. Addiction and the adrenal cortex

    Science.gov (United States)

    Vinson, Gavin P; Brennan, Caroline H

    2013-01-01

    Substantial evidence shows that the hypophyseal–pituitary–adrenal (HPA) axis and corticosteroids are involved in the process of addiction to a variety of agents, and the adrenal cortex has a key role. In general, plasma concentrations of cortisol (or corticosterone in rats or mice) increase on drug withdrawal in a manner that suggests correlation with the behavioural and symptomatic sequelae both in man and in experimental animals. Corticosteroid levels fall back to normal values in resumption of drug intake. The possible interactions between brain corticotrophin releasing hormone (CRH) and proopiomelanocortin (POMC) products and the systemic HPA, and additionally with the local CRH–POMC system in the adrenal gland itself, are complex. Nevertheless, the evidence increasingly suggests that all may be interlinked and that CRH in the brain and brain POMC products interact with the blood-borne HPA directly or indirectly. Corticosteroids themselves are known to affect mood profoundly and may themselves be addictive. Additionally, there is a heightened susceptibility for addicted subjects to relapse in conditions that are associated with change in HPA activity, such as in stress, or at different times of the day. Recent studies give compelling evidence that a significant part of the array of addictive symptoms is directly attributable to the secretory activity of the adrenal cortex and the actions of corticosteroids. Additionally, sex differences in addiction may also be attributable to adrenocortical function: in humans, males may be protected through higher secretion of DHEA (and DHEAS), and in rats, females may be more susceptible because of higher corticosterone secretion. PMID:23825159

  6. Weak decays. [Lectures, phenomenology

    Energy Technology Data Exchange (ETDEWEB)

    Wojcicki, S.

    1978-11-01

    Lectures are given on weak decays from a phenomenological point of view, emphasizing new results and ideas and the relation of recent results to the new standard theoretical model. The general framework within which the weak decay is viewed and relevant fundamental questions, weak decays of noncharmed hadrons, decays of muons and the tau, and the decays of charmed particles are covered. Limitation is made to the discussion of those topics that either have received recent experimental attention or are relevant to the new physics. (JFP) 178 references

  7. Weakly asymptotically hyperbolic manifolds

    CERN Document Server

    Allen, Paul T; Lee, John M; Allen, Iva Stavrov

    2015-01-01

    We introduce a class of "weakly asymptotically hyperbolic" geometries whose sectional curvatures tend to $-1$ and are $C^0$, but are not necessarily $C^1$, conformally compact. We subsequently investigate the rate at which curvature invariants decay at infinity, identifying a conformally invariant tensor which serves as an obstruction to "higher order decay" of the Riemann curvature operator. Finally, we establish Fredholm results for geometric elliptic operators, extending the work of Rafe Mazzeo and John M. Lee to this setting. As an application, we show that any weakly asymptotically hyperbolic metric is conformally related to a weakly asymptotically hyperbolic metric of constant negative curvature.

  8. Strange Weak Values

    CERN Document Server

    Hosoya, Akio

    2010-01-01

    We develop a formal theory of the weak values with emphasis on the consistency conditions and a probabilistic interpretation in the counter-factual processes. We present the condition for the choice of the post-selected state to give a negative weak value of a given projection operator and strange values of an observable in general. The general framework is applied to Hardy's paradox and the spin $1/2$ system to explicitly address the issues of counter-factuality and strange weak values. The counter-factual arguments which characterize the paradox specifies the pre-selected state and a complete set of the post-selected states clarifies how the strange weak values emerge.

  9. Coherence for weak units

    CERN Document Server

    Joyal, André

    2009-01-01

    We define weak units in a semi-monoidal 2-category $\\CC$ as cancellable pseudo-idempotents: they are pairs $(I,\\alpha)$ where $I$ is an object such that tensoring with $I$ from either side constitutes a biequivalence of $\\CC$, and $\\alpha: I \\tensor I \\to I$ is an equivalence in $\\CC$. We show that this notion of weak unit has coherence built in: Theorem A: $\\alpha$ has a canonical associator 2-cell, which automatically satisfies the pentagon equation. Theorem B: every morphism of weak units is automatically compatible with those associators. Theorem C: the 2-category of weak units is contractible if non-empty. Finally we show (Theorem E) that the notion of weak unit is equivalent to the notion obtained from the definition of tricategory: $\\alpha$ alone induces the whole family of left and right maps (indexed by the objects), as well as the whole family of Kelly 2-cells (one for each pair of objects), satisfying the relevant coherence axioms.

  10. Neuropsychology of prefrontal cortex

    OpenAIRE

    2008-01-01

    The history of clinical frontal lobe study is long and rich which provides valuable insights into neuropsychologic determinants of functions of prefrontal cortex (PFC). PFC is often classified as multimodal association cortex as extremely processed information from various sensory modalities is integrated here in a precise fashion to form the physiologic constructs of memory, perception, and diverse cognitive processes. Human neuropsychologic studies also support the notion of different funct...

  11. WEAK CONVERGENCE OF SOME SERIES

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    This paper continues the study of [1] on weak functions.The weak convergence theory is investigated in complex analysis,Fourier transform and Mellin transform.A Mobius inverse formula of weak functions is obtained.

  12. On Weak Markov's Principle

    DEFF Research Database (Denmark)

    Kohlenbach, Ulrich Wilhelm

    2002-01-01

    We show that the so-called weak Markov's principle (WMP) which states that every pseudo-positive real number is positive is underivable in E-HA + AC. Since allows one to formalize (atl eastl arge parts of) Bishop's constructive mathematics, this makes it unlikely that WMP can be proved within the...

  13. On closed weak supplemented modules

    Institute of Scientific and Technical Information of China (English)

    ZENG Qing-yi; SHI Mei-hua

    2006-01-01

    A module M is called closed weak supplemented if for any closed submodule N of M, there is a submodule K of M such that M=K+N and K(c)N<<M. Any direct summand of closed weak supplemented module is also closed weak supplemented.Any nonsingular image of closed weak supplemented module is closed weak supplemented. Nonsingular V-rings in which all nonsingular modules are closed weak supplemented are characterized in Section 4.

  14. Electoral Susceptibility

    CERN Document Server

    Levine, G C; Cerise, J E

    2012-01-01

    In the United States electoral system, a candidate is elected indirectly by winning a majority of electoral votes cast by individual states, the election usually being decided by the votes cast by a small number of "swing states" where the two candidates historically have roughly equal probabilities of winning. The effective value of a swing state in deciding the election is determined not only by the number of its electoral votes but by the frequency of its appearance in the set of winning partitions of the electoral college. Since the electoral vote values of swing states are not identical, the presence or absence of a state in a winning partition is generally correlated with the frequency of appearance of other states and, hence, their effective values. We quantify the effective value of states by an {\\sl electoral susceptibility}, $\\chi_j$, the variation of the winning probability with the "cost" of changing the probability of winning state $j$. We study $\\chi_j$ for realistic data accumulated for the 201...

  15. Weak Polarized Electron Scattering

    CERN Document Server

    Erler, Jens; Mantry, Sonny; Souder, Paul A

    2014-01-01

    Scattering polarized electrons provides an important probe of the weak interactions. Precisely measuring the parity-violating left-right cross section asymmetry is the goal of a number of experiments recently completed or in progress. The experiments are challenging, since A_{LR} is small, typically between 10^(-4) and 10^(-8). By carefully choosing appropriate targets and kinematics, various pieces of the weak Lagrangian can be isolated, providing a search for physics beyond the Standard Model. For other choices, unique features of the strong interaction are studied, including the radius of the neutron density in heavy nuclei, charge symmetry violation, and higher twist terms. This article reviews the theory behind the experiments, as well as the general techniques used in the experimental program.

  16. Composite weak bosons

    Energy Technology Data Exchange (ETDEWEB)

    Suzuki, M.

    1988-04-01

    Dynamical mechanism of composite W and Z is studied in a 1/N field theory model with four-fermion interactions in which global weak SU(2) symmetry is broken explicitly by electromagnetic interaction. Issues involved in such a model are discussed in detail. Deviation from gauge coupling due to compositeness and higher order loop corrections are examined to show that this class of models are consistent not only theoretically but also experimentally.

  17. The Weak Haagerup Property II

    DEFF Research Database (Denmark)

    Haagerup, Uffe; Knudby, Søren

    2015-01-01

    The weak Haagerup property for locally compact groups and the weak Haagerup constant were recently introduced by the second author [27]. The weak Haagerup property is weaker than both weak amenability introduced by Cowling and the first author [9] and the Haagerup property introduced by Connes [6......] and Choda [5]. In this paper, it is shown that a connected simple Lie group G has the weak Haagerup property if and only if the real rank of G is zero or one. Hence for connected simple Lie groups the weak Haagerup property coincides with weak amenability. Moreover, it turns out that for connected simple...... Lie groups the weak Haagerup constant coincides with the weak amenability constant, although this is not true for locally compact groups in general. It is also shown that the semidirect product R2 × SL(2,R) does not have the weak Haagerup property....

  18. Weak martingale Hardy spaces and weak atomic decompositions

    Institute of Scientific and Technical Information of China (English)

    HOU; Youliang; REN; Yanbo

    2006-01-01

    In this paper we define some weak martingale Hardy spaces and three kinds of weak atoms. They are the counterparts of martingale Hardy spaces and atoms in the classical martingale Hp-theory. And then three atomic decomposition theorems for martingales in weak martingale Hardy spaces are proved. With the help of the weak atomic decompositions of martingale, a sufficient condition for a sublinear operator defined on the weak martingale Hardy spaces to be bounded is given. Using the sufficient condition, we obtain a series of martingale inequalities with respect to the weak Lp-norm, the inequalities of weak (p ,p)-type and some continuous imbedding relationships between various weak martingale Hardy spaces. These inequalities are the weak versions of the basic inequalities in the classical martingale Hp-theory.

  19. Inversion assuming weak scattering

    DEFF Research Database (Denmark)

    Xenaki, Angeliki; Gerstoft, Peter; Mosegaard, Klaus

    2013-01-01

    The study of weak scattering from inhomogeneous media or interface roughness has long been of interest in sonar applications. In an acoustic backscattering model of a stationary field of volume inhomogeneities, a stochastic description of the field is more useful than a deterministic description...... due to the complex nature of the field. A method based on linear inversion is employed to infer information about the statistical properties of the scattering field from the obtained cross-spectral matrix. A synthetic example based on an active high-frequency sonar demonstrates that the proposed...

  20. The Weak Neutral Current

    CERN Document Server

    Erler, Jens

    2013-01-01

    This is a review of electroweak precision physics with particular emphasis on low-energy precision measurements in the neutral current sector of the electroweak theory and includes future experimental prospects and the theoretical challenges one faces to interpret these observables. Within the minimal Standard Model they serve as determinations of the weak mixing angle which are competitive with and complementary to those obtained near the Z-resonance. In the context of new physics beyond the Standard Model these measurements are crucial to discriminate between models and to reduce the allowed parameter space within a given model. We illustrate this for the minimal supersymmetric Standard Model with or without R-parity.

  1. Measurement of weak radioactivity

    CERN Document Server

    Theodorsson , P

    1996-01-01

    This book is intended for scientists engaged in the measurement of weak alpha, beta, and gamma active samples; in health physics, environmental control, nuclear geophysics, tracer work, radiocarbon dating etc. It describes the underlying principles of radiation measurement and the detectors used. It also covers the sources of background, analyzes their effect on the detector and discusses economic ways to reduce the background. The most important types of low-level counting systems and the measurement of some of the more important radioisotopes are described here. In cases where more than one type can be used, the selection of the most suitable system is shown.

  2. Weakly broken galileon symmetry

    Energy Technology Data Exchange (ETDEWEB)

    Pirtskhalava, David [Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa (Italy); Santoni, Luca; Trincherini, Enrico [Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa (Italy); INFN, Sezione di Pisa, Piazza dei Cavalieri 7, 56126 Pisa (Italy); Vernizzi, Filippo [Institut de Physique Théorique, Université Paris Saclay, CEA, CNRS, Gif-sur-Yvette cédex, F-91191 (France)

    2015-09-01

    Effective theories of a scalar ϕ invariant under the internal galileon symmetryϕ→ϕ+b{sub μ}x{sup μ} have been extensively studied due to their special theoretical and phenomenological properties. In this paper, we introduce the notion of weakly broken galileon invariance, which characterizes the unique class of couplings of such theories to gravity that maximally retain their defining symmetry. The curved-space remnant of the galileon’s quantum properties allows to construct (quasi) de Sitter backgrounds largely insensitive to loop corrections. We exploit this fact to build novel cosmological models with interesting phenomenology, relevant for both inflation and late-time acceleration of the universe.

  3. Faciolingual Hemiparesis with Mild Limb Weakness of Cortical Origin.

    Science.gov (United States)

    Ruisanchez-Nieva, Aintzine; Bocos-Portillo, Jone; Vazquez-Picon, Rakel; Tamayo, David Anguizola; Pardina-Vilella, Lara; Gomez-Beldarrain, Marian; Garcia-Monco, Juan Carlos

    2016-09-01

    The clinical combination of unilateral facial and hypoglossal palsy with upper limb weakness is known as the capsular genu syndrome and responds most often to an ischemic infarct in the internal capsule. We here describe a patient with this peculiar combination, in whom the responsible lesion was located in the contralateral prefrontal cortex, involving the corresponding areas of the Penfield's homunculus. Contralateral cortical frontal lesions should be considered in patients with facial and hypoglossal palsy with upper limb weakness. Copyright © 2016 National Stroke Association. Published by Elsevier Inc. All rights reserved.

  4. Weak Decay of Hypernuclei

    CERN Document Server

    Alberico, W M

    2004-01-01

    The focus of these Lectures is on the weak decay modes of hypernuclei, with special attention to Lambda-hypernuclei. The subject involves many fields of modern theoretical and experimental physics, from nuclear structure to the fundamental constituents of matter and their interactions. The various weak decay modes of Lambda-hypernuclei are described: the mesonic mode and the non-mesonic ones. The latter are the dominant decay channels of medium--heavy hypernuclei, where, on the contrary, the mesonic decay is disfavoured by Pauli blocking effect on the outgoing nucleon. In particular, one can distinguish between one-body and two-body induced decays. Theoretical models employed to evaluate the (partial and total) decay widths of hypernuclei are illustrated, and their results compared with existing experimental data. Open problems and recent achievements are extensively discussed, in particular the determination of the ratio Gamma_n/Gamma_p, possible tests of the Delta I=1/2 rule in non-mesonic decays and the pu...

  5. ICU-Acquired Weakness.

    Science.gov (United States)

    Jolley, Sarah E; Bunnell, Aaron E; Hough, Catherine L

    2016-11-01

    Survivorship after critical illness is an increasingly important health-care concern as ICU use continues to increase while ICU mortality is decreasing. Survivors of critical illness experience marked disability and impairments in physical and cognitive function that persist for years after their initial ICU stay. Newfound impairment is associated with increased health-care costs and use, reductions in health-related quality of life, and prolonged unemployment. Weakness, critical illness neuropathy and/or myopathy, and muscle atrophy are common in patients who are critically ill, with up to 80% of patients admitted to the ICU developing some form of neuromuscular dysfunction. ICU-acquired weakness (ICUAW) is associated with longer durations of mechanical ventilation and hospitalization, along with greater functional impairment for survivors. Although there is increasing recognition of ICUAW as a clinical entity, significant knowledge gaps exist concerning identifying patients at high risk for its development and understanding its role in long-term outcomes after critical illness. This review addresses the epidemiologic and pathophysiologic aspects of ICUAW; highlights the diagnostic challenges associated with its diagnosis in patients who are critically ill; and proposes, to our knowledge, a novel strategy for identifying ICUAW. Copyright © 2016 American College of Chest Physicians. Published by Elsevier Inc. All rights reserved.

  6. [Neuroanatomy of Frontal Association Cortex].

    Science.gov (United States)

    Takada, Masahiko

    2016-11-01

    The frontal association cortex is composed of the prefrontal cortex and the motor-related areas except the primary motor cortex (i.e., the so-called higher motor areas), and is well-developed in primates, including humans. The prefrontal cortex receives and integrates large bits of diverse information from the parietal, temporal, and occipital association cortical areas (termed the posterior association cortex), and paralimbic association cortical areas. This information is then transmitted to the primary motor cortex via multiple motor-related areas. Given these facts, it is likely that the prefrontal cortex exerts executive functions for behavioral control. The functional input pathways from the posterior and paralimbic association cortical areas to the prefrontal cortex are classified primarily into six groups. Cognitive signals derived from the prefrontal cortex are conveyed to the rostral motor-related areas to transform them into motor signals, which finally enter the primary motor cortex via the caudal motor-related areas. Furthermore, it has been shown that, similar to the primary motor cortex, areas of the frontal association cortex form individual networks (known as "loop circuits") with the basal ganglia and cerebellum via the thalamus, and hence are extensively involved in the expression and control of behavioral actions.

  7. Effects of Weak Ties on Epidemic Predictability in Community Networks

    CERN Document Server

    Shu, Panpan; Gong, Kai; Liu, Ying

    2012-01-01

    Weak ties play a significant role in the structures and the dynamics of community networks. Based on the susceptible-infected model in contact process, we study numerically how weak ties influence the predictability of epidemic dynamics. We first investigate the effects of different kinds of weak ties on the variabilities of both the arrival time and the prevalence of disease, and find that the bridgeness with small degree can enhance the predictability of epidemic spreading. Once weak ties are settled, compared with the variability of arrival time, the variability of prevalence displays a diametrically opposed changing trend with both the distance of the initial seed to the bridgeness and the degree of the initial seed. More specifically, the further distance and the larger degree of the initial seed can induce the better predictability of arrival time and the worse predictability of prevalence. Moreover, we discuss the effects of weak tie number on the epidemic variability. As community strength becomes ver...

  8. Weak Quantum Ergodicity

    CERN Document Server

    Kaplan, L

    1998-01-01

    We examine the consequences of classical ergodicity for the localization properties of individual quantum eigenstates in the classical limit. We note that the well known Schnirelman result is a weaker form of quantum ergodicity than the one implied by random matrix theory. This suggests the possibility of systems with non-gaussian random eigenstates which are nonetheless ergodic in the sense of Schnirelman and lead to ergodic transport in the classical limit. These we call "weakly quantum ergodic.'' Indeed for a class of "slow ergodic" classical systems, it is found that each eigenstate becomes localized to an ever decreasing fraction of the available state space, in the semiclassical limit. Nevertheless, each eigenstate in this limit covers phase space evenly on any classical scale, and long-time transport properties betwen individual quantum states remain ergodic due to the diffractive effects which dominate quantum phase space exploration.

  9. Regulating prefrontal cortex activation

    DEFF Research Database (Denmark)

    Aznar, Susana; Klein, Anders Bue

    2013-01-01

    of emotion-based actions, such as addiction and other impulse-related behaviors. In this review, we give an overview of the 5-HT2A receptor distribution (neuronal, intracellular, and anatomical) along with its functional and physiological effect on PFC activation, and how that relates to more recent findings......The prefrontal cortex (PFC) is involved in mediating important higher-order cognitive processes such as decision making, prompting thereby our actions. At the same time, PFC activation is strongly influenced by emotional reactions through its functional interaction with the amygdala...... is highly expressed in the prefrontal cortex areas, playing an important role in modulating cortical activity and neural oscillations (brain waves). This makes it an interesting potential pharmacological target for the treatment of neuropsychiatric modes characterized by lack of inhibitory control...

  10. Isolated shoulder weakness as a result of a cortical infarction in the precentral gyrus.

    Science.gov (United States)

    Entezami, Pouya; Hopper, John A

    2015-01-01

    Since its discovery, our understanding of the primary motor cortex has continued to evolve. The presentations of rare, isolated, motor palsies of small muscle groups have heavily contributed to the characterization of the somatotopic representation of the human body on the cortex. We present a case of localized, left shoulder small muscle group weakness secondary to ischemic cerebral infarction in the primary motor cortex. The patient experienced full recovery over several days. Strokes causing isolated shoulder weakness are rare due to the relatively small area dedicated to shoulder motor function in the precentral gyrus. However, our patient presented with a larger area of infarction than in previously reported cases, demonstrating the large individual variability that may exist within the motor cortex somatotopic map.

  11. Isolated shoulder weakness as a result of a cortical infarction in the precentral gyrus

    Directory of Open Access Journals (Sweden)

    Pouya Entezami

    2015-04-01

    Full Text Available Since its discovery, our understanding of the primary motor cortex has continued to evolve. The presentations of rare, isolated, motor palsies of small muscle groups have heavily contributed to the characterization of the somatotopic representation of the human body on the cortex. We present a case of localized, left shoulder small muscle group weakness secondary to ischemic cerebral infarction in the primary motor cortex. The patient experienced full recovery over several days. Strokes causing isolated shoulder weakness are rare due to the relatively small area dedicated to shoulder motor function in the precentral gyrus. However, our patient presented with a larger area of infarction than in previously reported cases, demonstrating the large individual variability that may exist within the motor cortex somatotopic map.

  12. Weak Cat-Operads

    CERN Document Server

    Dosen, K

    2010-01-01

    An operad (this paper deals with non-symmetric operads) may be conceived as a partial algebra with a family of insertion operations, Gerstenhaber's circle-i products, which satisfy two kinds of associativity, one of them involving commutativity. A Cat-operad is an operad enriched over the category Cat of small categories, as a 2-category with small hom-categories is a category enriched over Cat. The notion of weak Cat-operad is to the notion of Cat-operad what the notion of bicategory is to the notion of 2-category. The equations of operads like associativity of insertions are replaced by isomorphisms in a category. The goal of this paper is to formulate conditions concerning these isomorphisms that ensure coherence, in the sense that all diagrams of canonical arrows commute. This is the sense in which the notions of monoidal category and bicategory are coherent. The coherence proof in the paper is much simplified by indexing the insertion operations in a context-independent way, and not in the usual manner. ...

  13. Mescaline-induced changes of brain-cortex ribosomes. Role of sperimidine in counteracting the destabilizing effect of mescaline of brain-cortex ribosomes.

    Science.gov (United States)

    Datta, R K; Antopol, W; Ghosh, J J

    1971-11-01

    1. The effect of spermidine on the mescaline-induced changes of brain-cortex ribosomes was studied by adding spermidine during the treatment of goat brain-cortex slices with mescaline. 2. Mescaline treatment of brain-cortex slices removed a portion of the endogenous spermidine from ribosomes and this removal was significantly prevented when spermidine was present during mescaline treatment. 3. Spermidine present during mescaline treatment of brain-cortex slices counteracted, to some extent, the destabilizing effect of mescaline on ribosomes with respect to heat denaturation. 4. Mescaline treatment of brain-cortex slices made ribosomes more susceptible to breakdown, releasing protein and RNA, and resulting in loss of ribosomal enzymic activities. However, spermidine present during mescaline treatment counteracted moderately the mescaline-induced ribosomal susceptibility to breakdown and ribosomal loss of enzymic activities. 5. Ribosomes of mescaline-treated cortex slices were rapidly degraded by ribonuclease and trypsin. However, if spermidine was present during mescaline treatment of brain-cortex slices the rates of degradation diminished.

  14. Epidemic extinction in a generalized susceptible-infected-susceptible model

    Science.gov (United States)

    Chen, Hanshuang; Huang, Feng; Zhang, Haifeng; Li, Guofeng

    2017-01-01

    We study the extinction of epidemics in a generalized susceptible-infected-susceptible model, where a susceptible individual becomes infected at the rate λ when contacting m infective individual(s) simultaneously, and an infected individual spontaneously recovers at the rate μ. By employing the Wentzel-Kramers-Brillouin approximation for the master equation, the problem is reduced to finding the zero-energy trajectories in an effective Hamiltonian system, and the mean extinction time depends exponentially on the associated action S and the size of the population N, ˜ \\exp ≤ft(NS\\right) . Because of qualitatively different bifurcation features for m  =  1 and m≥slant 2 , we derive independently the expressions of S as a function of the rescaled infection rate λ /μ . For the weak infection, S scales to the distance to the bifurcation with an exponent 2 for m  =  1 and 3/2 for m≥slant 2 . Finally, a rare-event simulation method is used to validate the theory.

  15. Weak Total Resolvability In Graphs

    Directory of Open Access Journals (Sweden)

    Casel Katrin

    2016-02-01

    Full Text Available A vertex v ∈ V (G is said to distinguish two vertices x, y ∈ V (G of a graph G if the distance from v to x is di erent from the distance from v to y. A set W ⊆ V (G is a total resolving set for a graph G if for every pair of vertices x, y ∈ V (G, there exists some vertex w ∈ W − {x, y} which distinguishes x and y, while W is a weak total resolving set if for every x ∈ V (G−W and y ∈ W, there exists some w ∈ W −{y} which distinguishes x and y. A weak total resolving set of minimum cardinality is called a weak total metric basis of G and its cardinality the weak total metric dimension of G. Our main contributions are the following ones: (a Graphs with small and large weak total metric bases are characterised. (b We explore the (tight relation to independent 2-domination. (c We introduce a new graph parameter, called weak total adjacency dimension and present results that are analogous to those presented for weak total dimension. (d For trees, we derive a characterisation of the weak total (adjacency metric dimension. Also, exact figures for our parameters are presented for (generalised fans and wheels. (e We show that for Cartesian product graphs, the weak total (adjacency metric dimension is usually pretty small. (f The weak total (adjacency dimension is studied for lexicographic products of graphs.

  16. The anterior cingulate cortex

    Directory of Open Access Journals (Sweden)

    Pavlović D.M.

    2009-01-01

    Full Text Available The anterior cingulate cortex (ACC has a role in attention, analysis of sensory information, error recognition, problem solving, detection of novelty, behavior, emotions, social relations, cognitive control, and regulation of visceral functions. This area is active whenever the individual feels some emotions, solves a problem, or analyzes the pros and cons of an action (if it is a right decision. Analogous areas are also found in higher mammals, especially whales, and they contain spindle neurons that enable complex social interactions. Disturbance of ACC activity is found in dementias, schizophrenia, depression, the obsessive-compulsive syndrome, and other neuropsychiatric diseases.

  17. Unified properties of a weakly interacting Fermi gas in a weak magnetic field

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    When the orbital motion and the spin motion of particles were considered simultaneously,the thermodynamic potential function of a weakly interacting Fermi gas in a weak magnetic field was derived using the thermodynamics method. Based on the derived expression,the analytical expressions of energy,heat capacity,chemical potential,susceptibility and stability conditions of the system were given,and the effects of the interparticle interactions as well as the magnetic field on the properties of the system were analyzed. It was shown that the magnetic field always causes energy and stability to decrease,while the chemical potential of the system to increase. The repulsive(attractive) interactions always increase(decrease) energy and stability,but decrease(increase) the chemical potential and paramagnetism. The repulsive(attractive) interactions decrease(increase) heat capacity of the system at high temperatures but increase(decrease) it at low temperatures.

  18. Sensing with the Motor Cortex

    OpenAIRE

    Hatsopoulos, Nicholas G.; Suminski, Aaron J.

    2011-01-01

    The primary motor cortex is a critical node in the network of brain regions responsible for voluntary motor behavior. It has been less appreciated, however, that the motor cortex exhibits sensory responses in a variety of modalities including vision and somatosensation. We review current work that emphasizes the heterogeneity in sensori-motor responses in the motor cortex and focus on its implications for cortical control of movement as well as for brain-machine interface development.

  19. Weak compactness of biharmonic maps

    Directory of Open Access Journals (Sweden)

    Shenzhou Zheng

    2012-10-01

    Full Text Available This article shows that if a sequence of weak solutions of a perturbed biharmonic map satisfies $Phi_ko 0$ in $(W^{2,2}^*$ and $u_kightharpoonup u$ weakly in $W^{2,2}$, then $u$ is a biharmonic map. In particular, we show that the space of biharmonic maps is sequentially compact under the weak-$W^{2,2}$ topology.

  20. Susceptibilities of Escherichia coli, Salmonella and Staphylococcus aureus isolated from animals to ofloxacin and commonly used antimicrobial agents

    National Research Council Canada - National Science Library

    Takahashi, I; Yoshida, T; Higashide, Y; Sakano, T

    1990-01-01

    .... Drugs to which these isolates responded with moderate to weak susceptibilities (MIC50 25 approximately greater than 800 micrograms/ml) were doxycycline (DOXY), streptomycin (SM), spectinomycin (SPCM...

  1. [Systemic lupus erythematosus and weakness].

    Science.gov (United States)

    Vinagre, Filipe; Santos, Maria José; da Silva, José Canas

    2006-01-01

    We report a case of a 13-year old young girl, with Juvenile Systemic Lupus Erythematosus and recent onset of muscle weakness. Investigations lead to the diagnosis of Myasthenia Gravis. The most important causes of muscle weakness in lupus patients are discussed.

  2. Word Recognition in Auditory Cortex

    Science.gov (United States)

    DeWitt, Iain D. J.

    2013-01-01

    Although spoken word recognition is more fundamental to human communication than text recognition, knowledge of word-processing in auditory cortex is comparatively impoverished. This dissertation synthesizes current models of auditory cortex, models of cortical pattern recognition, models of single-word reading, results in phonetics and results in…

  3. Entorhinal cortex and consolidated memory.

    Science.gov (United States)

    Takehara-Nishiuchi, Kaori

    2014-07-01

    The entorhinal cortex is thought to support rapid encoding of new associations by serving as an interface between the hippocampus and neocortical regions. Although the entorhinal-hippocampal interaction is undoubtedly essential for initial memory acquisition, the entorhinal cortex contributes to memory retrieval even after the hippocampus is no longer necessary. This suggests that during memory consolidation additional synaptic reinforcement may take place within the cortical network, which may change the connectivity of entorhinal cortex with cortical regions other than the hippocampus. Here, I outline behavioral and physiological findings which collectively suggest that memory consolidation involves the gradual strengthening of connection between the entorhinal cortex and the medial prefrontal/anterior cingulate cortex (mPFC/ACC), a region that may permanently store the learned association. This newly formed connection allows for close interaction between the entorhinal cortex and the mPFC/ACC, through which the mPFC/ACC gains access to neocortical regions that store the content of memory. Thus, the entorhinal cortex may serve as a gatekeeper of cortical memory network by selectively interacting either with the hippocampus or mPFC/ACC depending on the age of memory. This model provides a new framework for a modification of cortical memory network during systems consolidation, thereby adding a fresh dimension to future studies on its biological mechanism.

  4. Cerebral cortex modulation of pain

    Institute of Scientific and Technical Information of China (English)

    Yu-feng XIE; Fu-quan HUO; Jing-shi TANG

    2009-01-01

    Pain is a complex experience encompassing sensory-discriminative, affective-motivational and cognitiv e-emotional com-ponents mediated by different mechanisms. Contrary to the traditional view that the cerebral cortex is not involved in pain perception, an extensive cortical network associated with pain processing has been revealed using multiple methods over the past decades. This network consistently includes, at least, the anterior cingulate cortex, the agranular insular cortex, the primary (SⅠ) and secondary somatosensory (SⅡ) cortices, the ventrolateral orbital cortex and the motor cortex. These corti-cal structures constitute the medial and lateral pain systems, the nucleus submedius-ventrolateral orbital cortex-periaque-ductal gray system and motor cortex system, respectively. Multiple neurotransmitters, including opioid, glutamate, GABA and dopamine, are involved in the modulation of pain by these cortical structures. In addition, glial cells may also be in-volved in cortical modulation of pain and serve as one target for pain management research. This review discusses recent studies of pain modulation by these cerebral cortical structures in animals and human.

  5. AC susceptibilities of grain-textured superconductors

    Science.gov (United States)

    Sakamoto, N.; Fukuda, Y.; Koga, M.; Akune, T.; Khan, H. R.; Lüders, K.

    2008-09-01

    In-phase χ n‧ and out-phase χ n″ components of nth harmonics of AC susceptibility with measuring parameters of a DC magnetic field Bdc, an amplitude Ba and a frequency f of the superimposed AC magnetic fields give substantial information of the superconducting properties. In low- Tc metallic superconductors, χ1‧ shows smooth transition and χ1″ does single peak. High- Tc oxide superconductors with anisotropic and grain-textured structures show deformed complex characteristics. Double peaks in χ1″ and shoulders in χ1‧ appear in AC susceptibility of Hg-1223 superconductors. Instead of simple Bean model, a grained model, where the superconducting grains are immersed in weak superconducting matrix, are proposed. The susceptibilities numerically analyzed using the model show varied and deformed curves and are successfully compared with the measured results.

  6. Precision Metrology Using Weak Measurements

    Science.gov (United States)

    Zhang, Lijian; Datta, Animesh; Walmsley, Ian A.

    2015-05-01

    Weak values and measurements have been proposed as a means to achieve dramatic enhancements in metrology based on the greatly increased range of possible measurement outcomes. Unfortunately, the very large values of measurement outcomes occur with highly suppressed probabilities. This raises three vital questions in weak-measurement-based metrology. Namely, (Q1) Does postselection enhance the measurement precision? (Q2) Does weak measurement offer better precision than strong measurement? (Q3) Is it possible to beat the standard quantum limit or to achieve the Heisenberg limit with weak measurement using only classical resources? We analyze these questions for two prototypical, and generic, measurement protocols and show that while the answers to the first two questions are negative for both protocols, the answer to the last is affirmative for measurements with phase-space interactions, and negative for configuration space interactions. Our results, particularly the ability of weak measurements to perform at par with strong measurements in some cases, are instructive for the design of weak-measurement-based protocols for quantum metrology.

  7. Precision metrology using weak measurements.

    Science.gov (United States)

    Zhang, Lijian; Datta, Animesh; Walmsley, Ian A

    2015-05-29

    Weak values and measurements have been proposed as a means to achieve dramatic enhancements in metrology based on the greatly increased range of possible measurement outcomes. Unfortunately, the very large values of measurement outcomes occur with highly suppressed probabilities. This raises three vital questions in weak-measurement-based metrology. Namely, (Q1) Does postselection enhance the measurement precision? (Q2) Does weak measurement offer better precision than strong measurement? (Q3) Is it possible to beat the standard quantum limit or to achieve the Heisenberg limit with weak measurement using only classical resources? We analyze these questions for two prototypical, and generic, measurement protocols and show that while the answers to the first two questions are negative for both protocols, the answer to the last is affirmative for measurements with phase-space interactions, and negative for configuration space interactions. Our results, particularly the ability of weak measurements to perform at par with strong measurements in some cases, are instructive for the design of weak-measurement-based protocols for quantum metrology.

  8. Acute muscular weakness in children

    Directory of Open Access Journals (Sweden)

    Ricardo Pablo Javier Erazo Torricelli

    Full Text Available ABSTRACT Acute muscle weakness in children is a pediatric emergency. During the diagnostic approach, it is crucial to obtain a detailed case history, including: onset of weakness, history of associated febrile states, ingestion of toxic substances/toxins, immunizations, and family history. Neurological examination must be meticulous as well. In this review, we describe the most common diseases related to acute muscle weakness, grouped into the site of origin (from the upper motor neuron to the motor unit. Early detection of hyperCKemia may lead to a myositis diagnosis, and hypokalemia points to the diagnosis of periodic paralysis. Ophthalmoparesis, ptosis and bulbar signs are suggestive of myasthenia gravis or botulism. Distal weakness and hyporeflexia are clinical features of Guillain-Barré syndrome, the most frequent cause of acute muscle weakness. If all studies are normal, a psychogenic cause should be considered. Finding the etiology of acute muscle weakness is essential to execute treatment in a timely manner, improving the prognosis of affected children.

  9. Chemosensory Learning in the Cortex

    Directory of Open Access Journals (Sweden)

    Edmund eRolls

    2011-09-01

    Full Text Available Taste is a primary reinforcer. Olfactory-taste and visual-taste association learning takes place in the primate including human orbitofrontal cortex to build representations of flavour. Rapid reversal of this learning can occur using a rule-based learning system that can be reset when an expected taste or flavour reward is not obtained, that is by negative reward prediction error, to which a population of neurons in the orbitofrontal cortex responds. The representation in the orbitofrontal cortex but not the primary taste or olfactory cortex is of the reward value of the visual / olfactory / taste / input as shown by devaluation experiments in which food is fed to satiety, and by correlations with the activations with subjective pleasantness ratings in humans. Sensory-specific satiety for taste, olfactory, visual, and oral somatosensory inputs produced by feeding a particular food to satiety are implemented it is proposed by medium-term synaptic adaptation in the orbitofrontal cortex. Cognitive factors, including word-level descriptions, modulate the representation of the reward value of food in the orbitofrontal cortex, and this effect is learned it is proposed by associative modification of top-down synapses onto neurons activated by bottom-up taste and olfactory inputs when both are active in the orbitofrontal cortex. A similar associative synaptic learning process is proposed to be part of the mechanism for the top-down attentional control to the reward value vs the sensory properties such as intensity of taste and olfactory inputs in the orbitofrontal cortex, as part of a biased activation theory of selective attention.

  10. Weakness

    Science.gov (United States)

    ... stroke After injury to a nerve During a flare-up of multiple sclerosis (MS) You may feel ... Duchenne) Myotonic dystrophy POISONING Botulism Poisoning ( insecticides , nerve gas) Shellfish poisoning OTHER Not enough healthy red blood ...

  11. Neuroanatomic Differences Associated With Stress Susceptibility and Resilience.

    Science.gov (United States)

    Anacker, Christoph; Scholz, Jan; O'Donnell, Kieran J; Allemang-Grand, Rylan; Diorio, Josie; Bagot, Rosemary C; Nestler, Eric J; Hen, René; Lerch, Jason P; Meaney, Michael J

    2016-05-15

    We examined the neurobiological mechanisms underlying stress susceptibility using structural magnetic resonance imaging and diffusion tensor imaging to determine neuroanatomic differences between stress-susceptible and resilient mice. We also examined synchronized anatomic differences between brain regions to gain insight into the plasticity of neural networks underlying stress susceptibility. C57BL/6 mice underwent 10 days of social defeat stress and were subsequently tested for social avoidance. For magnetic resonance imaging, brains of stressed (susceptible, n = 11; resilient, n = 8) and control (n = 12) mice were imaged ex vivo at 56 µm resolution using a T2-weighted sequence. We tested for behavior-structure correlations by regressing social avoidance z-scores against local brain volume. For diffusion tensor imaging, brains were scanned with a diffusion-weighted fast spin echo sequence at 78 μm isotropic voxels. Structural covariance was assessed by correlating local volume between brain regions. Social avoidance correlated negatively with local volume of the cingulate cortex, nucleus accumbens, thalamus, raphe nuclei, and bed nucleus of the stria terminals. Social avoidance correlated positively with volume of the ventral tegmental area (VTA), habenula, periaqueductal gray, cerebellum, hypothalamus, and hippocampal CA3. Fractional anisotropy was increased in the hypothalamus and hippocampal CA3. We observed synchronized anatomic differences between the VTA and cingulate cortex, hippocampus and VTA, hippocampus and cingulate cortex, and hippocampus and hypothalamus. These correlations revealed different structural covariance between brain regions in susceptible and resilient mice. Stress-integrative brain regions shape the neural architecture underlying individual differences in susceptibility and resilience to chronic stress. Copyright © 2016. Published by Elsevier Inc.

  12. Peripheral facial weakness (Bell's palsy).

    Science.gov (United States)

    Basić-Kes, Vanja; Dobrota, Vesna Dermanović; Cesarik, Marijan; Matovina, Lucija Zadro; Madzar, Zrinko; Zavoreo, Iris; Demarin, Vida

    2013-06-01

    Peripheral facial weakness is a facial nerve damage that results in muscle weakness on one side of the face. It may be idiopathic (Bell's palsy) or may have a detectable cause. Almost 80% of peripheral facial weakness cases are primary and the rest of them are secondary. The most frequent causes of secondary peripheral facial weakness are systemic viral infections, trauma, surgery, diabetes, local infections, tumor, immune disorders, drugs, degenerative diseases of the central nervous system, etc. The diagnosis relies upon the presence of typical signs and symptoms, blood chemistry tests, cerebrospinal fluid investigations, nerve conduction studies and neuroimaging methods (cerebral MRI, x-ray of the skull and mastoid). Treatment of secondary peripheral facial weakness is based on therapy for the underlying disorder, unlike the treatment of Bell's palsy that is controversial due to the lack of large, randomized, controlled, prospective studies. There are some indications that steroids or antiviral agents are beneficial but there are also studies that show no beneficial effect. Additional treatments include eye protection, physiotherapy, acupuncture, botulinum toxin, or surgery. Bell's palsy has a benign prognosis with complete recovery in about 80% of patients, 15% experience some mode of permanent nerve damage and severe consequences remain in 5% of patients.

  13. Warping the Weak Gravity Conjecture

    Directory of Open Access Journals (Sweden)

    Karta Kooner

    2016-08-01

    Full Text Available The Weak Gravity Conjecture, if valid, rules out simple models of Natural Inflation by restricting their axion decay constant to be sub-Planckian. We revisit stringy attempts to realise Natural Inflation, with a single open string axionic inflaton from a probe D-brane in a warped throat. We show that warped geometries can allow the requisite super-Planckian axion decay constant to be achieved, within the supergravity approximation and consistently with the Weak Gravity Conjecture. Preliminary estimates of the brane backreaction suggest that the probe approximation may be under control. However, there is a tension between large axion decay constant and high string scale, where the requisite high string scale is difficult to achieve in all attempts to realise large field inflation using perturbative string theory. We comment on the Generalized Weak Gravity Conjecture in the light of our results.

  14. The developing cortex.

    Science.gov (United States)

    Ben-Ari, Yehezkel

    2013-01-01

    Cortical maturation is associated with a series of developmental programs encompassing neuronal and network-driven patterns. Thus, voltage-gated and synapse-driven ionic currents are very different in immature and adult neurons with slower kinetics in the former than in the latter. These features are neuron and developmental stage dependent. GABA, which is the main inhibitory neurotransmitter in adult brain, depolarizes and excites immature neurons and its actions are thought to exert a trophic role in developmental processes. Networks follow a parallel sequence with voltage-gated calcium currents followed by calcium plateaux and synapse-driven patterns in vitro. In vivo, early activity exhibits discontinuous temporal organization with alternating bursts. Early cortical patterns are driven by sensory input from the periphery providing a basis for activity-dependent modulation of the cortical networks formation. These features and notably the excitatory GABA underlie the high susceptibility of immature neurons to seizures. Alterations of these sequences play a central role in developmental malformations, notably migration disorders and associated neurological sequelae.

  15. Interpolation for weak Orlicz spaces with condition

    Institute of Scientific and Technical Information of China (English)

    JIAO Yong; PENG LiHua; LIU PeiDe

    2008-01-01

    An interpolation theorem for weak Orlicz spaces generalized by N-functions satisfying M△ condition is given.It is proved to be true for weak Orlicz martingale spaces by weak atomic decomposition of weak Hardy martingale spaces.And applying the interpolation theorem,we obtain some embedding relationships among weak Orlicz martingale spaces.

  16. Electromagnetism in nonleptonic weak interactions

    Energy Technology Data Exchange (ETDEWEB)

    Ecker, G. E-mail: ecker@doppler.thp.univie.ac.at; Isidori, G.; Mueller, G.; Neufeld, H.; Pich, A

    2000-12-18

    We construct a low-energy effective field theory that permits the complete treatment of isospin-breaking effects in nonleptonic weak interactions to next-to-leading order. To this end, we enlarge the chiral Lagrangian describing strong and {delta}S=1 weak interactions by including electromagnetic terms with the photon as additional dynamical degree of freedom. The complete and minimal list of local terms at next-to-leading order is given. We perform the one-loop renormalization at the level of the generating functional and specialize to K{yields}{pi}{pi} decays.

  17. Cosmology and the weak interaction

    Energy Technology Data Exchange (ETDEWEB)

    Schramm, D.N. (Fermi National Accelerator Lab., Batavia, IL (USA)):(Chicago Univ., IL (USA))

    1989-12-01

    The weak interaction plays a critical role in modern Big Bang cosmology. This review will emphasize two of its most publicized cosmological connections: Big Bang nucleosynthesis and Dark Matter. The first of these is connected to the cosmological prediction of Neutrino Flavours, N{sub {nu}} {approximately} 3 which is now being confirmed at SLC and LEP. The second is interrelated to the whole problem of galaxy and structure formation in the universe. This review will demonstrate the role of the weak interaction both for dark matter candidates and for the problem of generating seeds to form structure. 87 refs., 3 figs., 5 tabs.

  18. Weak disorder in Fibonacci sequences

    Energy Technology Data Exchange (ETDEWEB)

    Ben-Naim, E [Theoretical Division and Center for Nonlinear Studies, Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Krapivsky, P L [Department of Physics and Center for Molecular Cybernetics, Boston University, Boston, MA 02215 (United States)

    2006-05-19

    We study how weak disorder affects the growth of the Fibonacci series. We introduce a family of stochastic sequences that grow by the normal Fibonacci recursion with probability 1 - {epsilon}, but follow a different recursion rule with a small probability {epsilon}. We focus on the weak disorder limit and obtain the Lyapunov exponent that characterizes the typical growth of the sequence elements, using perturbation theory. The limiting distribution for the ratio of consecutive sequence elements is obtained as well. A number of variations to the basic Fibonacci recursion including shift, doubling and copying are considered. (letter to the editor)

  19. The cohomology group of weak entwining structure

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In this paper, we reveal that a weak entwining structure admits a rich cohomology theory. As an application we compute the cohomology of a weak entwining structure associated to a weak coalgebra-Galois extension.

  20. Second threshold in weak interactions

    NARCIS (Netherlands)

    Veltman, M.J.G.

    1977-01-01

    The point of view that weak interactions must have a second threshold below 300 – 600 GeV is developed. Above this threshold new physics must come in. This new physics may be the Higgs system, or some other nonperturbative system possibly having some similarities to the Higgs system. The limit of la

  1. Beam splitting on weak illumination.

    Science.gov (United States)

    Snyder, A W; Buryak, A V; Mitchell, D J

    1998-01-01

    We demonstrate, in both two and three dimensions, how a self-guided beam in a non-Kerr medium is split into two beams on weak illumination. We also provide an elegant physical explanation that predicts the universal character of the observed phenomenon. Possible applications of our findings to guiding light with light are also discussed.

  2. Weak measurements and supraluminal communication

    CERN Document Server

    Belinsky, A V

    2016-01-01

    There is suggested a version of the experiment with a correlated pair of particles in the entangled state. The experiment demonstrates that, in the case of weak and/or non-demolition measurements of one of the particles, it is possible to transmit information with a speed not limited by velocity of light.

  3. On Weak-BCC-Algebras

    Science.gov (United States)

    Thomys, Janus; Zhang, Xiaohong

    2013-01-01

    We describe weak-BCC-algebras (also called BZ-algebras) in which the condition (x∗y)∗z = (x∗z)∗y is satisfied only in the case when elements x, y belong to the same branch. We also characterize ideals, nilradicals, and nilpotent elements of such algebras. PMID:24311983

  4. Eldercare at Home: Bone Weakness

    Science.gov (United States)

    ... socialize. This can make exercising fun. If you don't exercise, your bones and muscles will become weak and your chances of falling will increase. Let’s exercise together. I will pick you up and we will go to the mall and walk for a little ...

  5. Submanifolds Weakly Associated with Graphs

    Indian Academy of Sciences (India)

    A Carriazo; L M Fernández; A Rodríguez-Hidalgo

    2009-06-01

    We establish an interesting link between differential geometry and graph theory by defining submanifolds weakly associated with graphs. We prove that, in a local sense, every submanifold satisfies such an association, and other general results. Finally, we study submanifolds associated with graphs either in low dimensions or belonging to some special families.

  6. MR susceptibility imaging

    Science.gov (United States)

    Duyn, Jeff

    2013-04-01

    This work reviews recent developments in the use of magnetic susceptibility contrast for human MRI, with a focus on the study of brain anatomy. The increase in susceptibility contrast with modern high field scanners has led to novel applications and insights into the sources and mechanism contributing to this contrast in brain tissues. Dedicated experiments have demonstrated that in most of healthy brain, iron and myelin dominate tissue susceptibility variations, although their relative contribution varies substantially. Local variations in these compounds can affect both amplitude and frequency of the MRI signal. In white matter, the myelin sheath introduces an anisotropic susceptibility that has distinct effects on the water compartments inside the axons, between the myelin sheath, and the axonal space, and renders their signals dependent on the angle between the axon and the magnetic field. This offers opportunities to derive tissue properties specific to these cellular compartments.

  7. On the weak project construction cost management

    Institute of Scientific and Technical Information of China (English)

    高守刚; 姜婧; 李玲

    2013-01-01

    the weak cost management is the most talked about topics in the weak industry, but also the basis of the weak construction business management and focus. With the increasingly fierce market competition, weak construction enterprises, the competition among enterprises wil gradual y transition from product quality competition to price competition. To strengthen the management of the weak construction enterprises cost, cut public spending ef iciency, improve market competitiveness, wil be the main way most weak construction corporate earnings and long-term business strategy. Based on the to weak project construction cost management based on analysis of the type of project construction costs, and further proposed the weak project construction cost management measures.

  8. Visual Cortex Plasticity Following Peripheral Damage To The Visual System: fMRI Evidence.

    Science.gov (United States)

    Lemos, João; Pereira, Daniela; Castelo-Branco, Miguel

    2016-10-01

    Over the last two decades, functional magnetic resonance imaging (fMRI) has become a powerful research method to investigate cortical visual plasticity. Abnormal fMRI response patterns have been occasionally detected in the visually deprived cortex of patients with bilateral retinal diseases. Controversy remains whether these observations indicate structural reorganization of the visual cortex or unmasking of previously silent cortico-cortical connections. In optic nerve diseases, there is weak evidence showing that early visual cortex seems to lack reorganization, while higher-order visual areas undergo plastic changes which may contribute to optimise visual function. There is however accumulating imaging evidence demonstrating trans-synaptic degeneration of the visual cortex in patients with disease of the anterior visual pathways. This may preclude the use of restorative treatments in these patients. Here, we review and update the body of fMRI evidence on visual cortical plasticity.

  9. Spatiotemporal integration of tactile information in human somatosensory cortex

    Directory of Open Access Journals (Sweden)

    Zumer Johanna M

    2007-03-01

    Full Text Available Abstract Background Our goal was to examine the spatiotemporal integration of tactile information in the hand representation of human primary somatosensory cortex (anterior parietal somatosensory areas 3b and 1, secondary somatosensory cortex (S2, and the parietal ventral area (PV, using high-resolution whole-head magnetoencephalography (MEG. To examine representational overlap and adaptation in bilateral somatosensory cortices, we used an oddball paradigm to characterize the representation of the index finger (D2; deviant stimulus as a function of the location of the standard stimulus in both right- and left-handed subjects. Results We found that responses to deviant stimuli presented in the context of standard stimuli with an interstimulus interval (ISI of 0.33s were significantly and bilaterally attenuated compared to deviant stimulation alone in S2/PV, but not in anterior parietal cortex. This attenuation was dependent upon the distance between the deviant and standard stimuli: greater attenuation was found when the standard was immediately adjacent to the deviant (D3 and D2 respectively, with attenuation decreasing for non-adjacent fingers (D4 and opposite D2. We also found that cutaneous mechanical stimulation consistently elicited not only a strong early contralateral cortical response but also a weak ipsilateral response in anterior parietal cortex. This ipsilateral response appeared an average of 10.7 ± 6.1 ms later than the early contralateral response. In addition, no hemispheric differences either in response amplitude, response latencies or oddball responses were found, independent of handedness. Conclusion Our findings are consistent with the large receptive fields and long neuronal recovery cycles that have been described in S2/PV, and suggest that this expression of spatiotemporal integration underlies the complex functions associated with this region. The early ipsilateral response suggests that anterior parietal fields also

  10. Osseointegration in periodontitis susceptible individuals.

    Science.gov (United States)

    Cecchinato, Denis; Bressan, Eriberto A; Toia, Marco; Araújo, Mauricio G; Liljenberg, Birgitta; Lindhe, Jan

    2012-01-01

    The aim of the present study was to examine tissue integration of implants placed (i) in subjects who had lost teeth because of advanced periodontal disease or for other reasons, (ii) in the posterior maxilla exhibiting varying amounts of mineralized bone. Thirty-six subjects were enrolled; 19 had lost teeth because of advanced periodontitis (group P) while the remaining 17 subjects had suffered tooth loss from other reasons (group NP). As part of site preparation for implant placement, a 3 mm trephine drill was used to remove one or more 2 mm wide and 5-6 mm long block of hard tissue [biopsy site; Lindhe et al. (2011). Clinical of Oral Implants Research, DOI: 10.1111/j.1600-0501.2011.02205.x]. Lateral to the biopsy site a twist drill (diameter 2 mm) was used to prepare the hard tissue in the posterior maxilla for the placement of a screw-shaped, self-tapping micro-implant (implant site). The implants used were 5 mm long, had a diameter of 2.2 mm. After 3 months of healing, the micro-implants with surrounding hard tissue cores were retrieved using a trephine drill. The tissue was processed for ground sectioning. The blocks were cut parallel to the long axis of the implant and reduced to a thickness of about 20 μm and stained in toluidine blue. The percentage of (i) implant surface that was in contact with mineralized bone as well as (ii) the amount of bone present within the threads of the micro-implants (percentage bone area) was determined. Healing including hard tissue formation around implants placed in the posterior maxilla was similar in periodontitis susceptible and non-susceptible subjects. Thus, the degree of bone-to-implant contact (about 59%) as well as the amount of mineralized bone within threads of the micro-implant (about 45-50%) was similar in the two groups of subjects. Pearson's coefficient disclosed that there was a weak negative correlation (-0.49; P < 0.05) between volume of fibrous tissue (biopsy sites) and the length of bone to implant

  11. The Weak Scale from BBN

    CERN Document Server

    Hall, Lawrence J; Ruderman, Joshua T

    2014-01-01

    The measured values of the weak scale, $v$, and the first generation masses, $m_{u,d,e}$, are simultaneously explained in the multiverse, with all these parameters scanning independently. At the same time, several remarkable coincidences are understood. Small variations in these parameters away from their measured values lead to the instability of hydrogen, the instability of heavy nuclei, and either a hydrogen or a helium dominated universe from Big Bang Nucleosynthesis. In the 4d parameter space of $(m_u,m_d,m_e,v)$, catastrophic boundaries are reached by separately increasing each parameter above its measured value by a factor of $(1.4,1.3,2.5,\\sim5)$, respectively. The fine-tuning problem of the weak scale in the Standard Model is solved: as $v$ is increased beyond the observed value, it is impossible to maintain a significant cosmological hydrogen abundance for any values of $m_{u,d,e}$ that yield both hydrogen and heavy nuclei stability. For very large values of $v$ a new regime is entered where weak in...

  12. Cubic ideal ferromagnets at low temperature and weak magnetic field

    Science.gov (United States)

    Hofmann, Christoph P.

    2017-04-01

    The low-temperature series for the free energy density, pressure, magnetization and susceptibility of cubic ideal ferromagnets in weak external magnetic fields are discussed within the effective Lagrangian framework up to three loops. The structure of the simple, body-centered, and face-centered cubic lattice is taken into account explicitly. The expansion involves integer and half-integer powers of the temperature. The corresponding coefficients depend on the magnetic field and on low-energy effective constants that can be expressed in terms of microscopic quantities. Our formulas may also serve as efficiency or consistency check for other techniques like Green's function methods, where spurious terms in the low-temperature expansion have appeared. We explore the sign and magnitude of the spin-wave interaction in the pressure, magnetization and susceptibility, and emphasize that our effective field theory approach is fully systematic and rigorous.

  13. Weak intermolecular interactions in gas-phase NMR

    CERN Document Server

    Garbacz, Piotr; Jackowski, Karol; Moszynski, Robert; Jaszunski, Michal

    2011-01-01

    Gas-phase NMR spectra demonstrating the effect of weak intermolecular forces on the NMR shielding constants of the interacting species are reported. We analyse the interaction of the molecular hydrogen isotopomers with He, Ne, and Ar, and the interaction in the He-CO_2 dimer. The same effects are studied for all these systems in the ab initio calculations. The comparison of the experimental and computed shielding constants is shown to depend strongly on the treatment of the bulk susceptibility effects, which determine in practice the pressure dependence of the experimental values. Best agreement of the results is obtained when the bulk susceptibility correction in rare gas solvents is evaluated from the analysis of the He-rare gas interactions, and when the shielding of deuterium in D_2-rare gas systems is considered.

  14. A 3 T event-related functional magnetic resonance imaging (fMRI) study of primary and secondary gustatory cortex localization using natural tastants

    Energy Technology Data Exchange (ETDEWEB)

    Smits, Marion [Erasmus MC, University Medical Center Rotterdam, Department of Radiology, P.O. Box 2040, CA Rotterdam (Netherlands); K.U.Leuven, Department of Radiology, University Hospitals, Leuven (Belgium); Peeters, Ronald R.; Hecke, Paul van; Sunaert, Stefan [K.U.Leuven, Department of Radiology, University Hospitals, Leuven (Belgium)

    2007-01-15

    It is known that taste is centrally represented in the insula, frontal and parietal operculum, as well as in the orbitofrontal cortex (secondary gustatory cortex). In functional MRI (fMRI) experiments activation in the insula has been confirmed, but activation in the orbitofrontal cortex is only infrequently found, especially at higher field strengths (3 T). Due to large susceptibility artefacts, the orbitofrontal cortex is a difficult region to examine with fMRI. Our aim was to localize taste in the human cortex at 3 T, specifically in the orbitofrontal cortex as well as in the primary gustatory cortex. Event-related fMRI was performed at 3 T in seven healthy volunteers. Taste stimuli consisted of lemon juice and chocolate. To visualize activation in the orbitofrontal cortex a dedicated 3D SENSE EPI fMRI sequence was used, in addition to a 2D SENSE EPI fMRI sequence for imaging the entire brain. Data were analyzed using a perception-based model. The dedicated 3D SENSE EPI sequence successfully reduced susceptibility artefacts in the orbitofrontal area. Significant taste-related activation was found in the orbitofrontal and insular cortices. fMRI of the orbitofrontal cortex is feasible at 3 T, using a dedicated sequence. Our results corroborate findings from previous studies. (orig.)

  15. Monkey brain cortex imaging by photoacoustic tomography

    OpenAIRE

    Yang, Xinmai; Wang, Lihong V.

    2008-01-01

    Photoacoustic tomography (PAT) is applied to image the brain cortex of a monkey through the intact scalp and skull ex vivo. The reconstructed PAT image shows the major blood vessels on the monkey brain cortex. For comparison, the brain cortex is imaged without the scalp, and then imaged again without the scalp and skull. Ultrasound attenuation through the skull is also measured at various incidence angles. This study demonstrates that PAT of the brain cortex is capable of surviving the ultras...

  16. The Functions of the Orbitofrontal Cortex

    Science.gov (United States)

    Rolls, Edmund T.

    2004-01-01

    The orbitofrontal cortex contains the secondary taste cortex, in which the reward value of taste is represented. It also contains the secondary and tertiary olfactory cortical areas, in which information about the identity and also about the reward value of odours is represented. The orbitofrontal cortex also receives information about the sight…

  17. Evolutionary specializations of human association cortex

    NARCIS (Netherlands)

    Mars, R.B.; Passingham, R.E.; Neubert, F.X.; Verhagen, L.; Sallet, J.

    2017-01-01

    Is the human brain a big ape brain? We argue that the human association cortex is larger than would be expected for an equivalent ape brain, suggesting human association cortex is a unique adaptation. The internal organization of the human association cortex shows modifications of the ape plan in

  18. Inhibition in the Human Auditory Cortex.

    Directory of Open Access Journals (Sweden)

    Koji Inui

    Full Text Available Despite their indispensable roles in sensory processing, little is known about inhibitory interneurons in humans. Inhibitory postsynaptic potentials cannot be recorded non-invasively, at least in a pure form, in humans. We herein sought to clarify whether prepulse inhibition (PPI in the auditory cortex reflected inhibition via interneurons using magnetoencephalography. An abrupt increase in sound pressure by 10 dB in a continuous sound was used to evoke the test response, and PPI was observed by inserting a weak (5 dB increase for 1 ms prepulse. The time course of the inhibition evaluated by prepulses presented at 10-800 ms before the test stimulus showed at least two temporally distinct inhibitions peaking at approximately 20-60 and 600 ms that presumably reflected IPSPs by fast spiking, parvalbumin-positive cells and somatostatin-positive, Martinotti cells, respectively. In another experiment, we confirmed that the degree of the inhibition depended on the strength of the prepulse, but not on the amplitude of the prepulse-evoked cortical response, indicating that the prepulse-evoked excitatory response and prepulse-evoked inhibition reflected activation in two different pathways. Although many diseases such as schizophrenia may involve deficits in the inhibitory system, we do not have appropriate methods to evaluate them; therefore, the easy and non-invasive method described herein may be clinically useful.

  19. Strengths, weaknesses, opportunities and threats

    DEFF Research Database (Denmark)

    Bull, J. W.; Jobstvogt, N.; Böhnke-Henrichs, A.;

    2016-01-01

    environmental awareness. Threats include resistance to change, and difficulty with interdisciplinary collaboration. Consideration of SWOT themes suggested five strategic areas for developing and implementing ES.The ES concept could improve decision-making related to natural resource use, and interpretation...... facilitate interdisciplinary research, ensuring decision-making that supports sustainable development........ Such an assessment could form the basis for improving ES thinking, further embedding it into environmental decisions and management.The Young Ecosystem Services Specialists (YESS) completed a Strengths-Weaknesses-Opportunities-Threats (SWOT) analysis of ES through YESS member surveys. Strengths include the approach...

  20. Weak Precedence Story Parsing Grammar

    Institute of Scientific and Technical Information of China (English)

    张松懋

    1995-01-01

    Story understanding is one of the important branches of natural language understanding research in AI techniques.The story understanding approach based on Story Parsing Grammar (SPG) involves that SPG is used to represent different abstracting processes of stories with different levels in story understanding and that the story understanding process is converted to the recognition process of stories using the syntactic parser of SPG.This kind of story understanding is called story parsing.In this paper,firstly a subclass of SPG,called Weak Precedence SPG(WPSPG),is defined.Afterwards the syntactic parsing algorithm of WPSPG is studied.An example of story parsing is also given.

  1. Weakly distributive domains(Ⅱ)

    Institute of Scientific and Technical Information of China (English)

    JIANG Ying; ZHANG Guo-Qiang

    2007-01-01

    In our previous work(Inform.and Comput.,2005,202:87-103),we have shown that for any ω-algebraic meet-cpo D,if all higher-order stable function spaces built from D are ω-algebraic,then D is finitary.This accomplishes the first of a possible,two-step process in solving the problem raised(LNCS,1991,530:16-33;Domainsand lambda-calculi,Cambridge Univ.Press,1998)whetherthe category of stable bifinite domains of Amadio-Droste-G(o)bel(LNCS,1991,530:16-33;Theor.Comput.Sci.,1993,111:89-101)is the largest cartesian closed full subcategory within the category of ω-algebraic meet-cpos with stable functions.This paper presents the results of the second step,which is to show that for any ω-algebraic meet-cpo D satisfying axioms M and I to be contained in a cartesian closed full sub-category using ω-algebraic meet-cpos with stable functions,it must not violate M I∞.We introduce a new class of domains called weakly distributive domains and show that for these domains to be in a cartesian closed category using ω-algebraic meet-cpos,property M I must not be violated.Further,we demonstrate that principally distributive domains(those for which each principle ideal is distributive)form a proper subclass of weakly distributive domains,and Birkhoff's M3 and N5(Introduction to Lattices and order,Cambridge Univ.Press,2002)are weakly distributive(but non-distributive).Then,we establish characterization results for weakly distributive domains.We also introduce the notion of meet-generators in constructing stable functions and show that if an ω-algebraic meet-cpo D contains an infinite number of meet-generators,then[D→D]fails I.However,the original problem of Amadio and Curien remains open.

  2. Weakly circadian cells improve resynchrony.

    Directory of Open Access Journals (Sweden)

    Alexis B Webb

    Full Text Available The mammalian suprachiasmatic nuclei (SCN contain thousands of neurons capable of generating near 24-h rhythms. When isolated from their network, SCN neurons exhibit a range of oscillatory phenotypes: sustained or damping oscillations, or arrhythmic patterns. The implications of this variability are unknown. Experimentally, we found that cells within SCN explants recover from pharmacologically-induced desynchrony by re-establishing rhythmicity and synchrony in waves, independent of their intrinsic circadian period We therefore hypothesized that a cell's location within the network may also critically determine its resynchronization. To test this, we employed a deterministic, mechanistic model of circadian oscillators where we could independently control cell-intrinsic and network-connectivity parameters. We found that small changes in key parameters produced the full range of oscillatory phenotypes seen in biological cells, including similar distributions of period, amplitude and ability to cycle. The model also predicted that weaker oscillators could adjust their phase more readily than stronger oscillators. Using these model cells we explored potential biological consequences of their number and placement within the network. We found that the population synchronized to a higher degree when weak oscillators were at highly connected nodes within the network. A mathematically independent phase-amplitude model reproduced these findings. Thus, small differences in cell-intrinsic parameters contribute to large changes in the oscillatory ability of a cell, but the location of weak oscillators within the network also critically shapes the degree of synchronization for the population.

  3. Optimal Weak Lensing Skewness Measurements

    CERN Document Server

    Zhang, T J; Zhang, P; Dubinski, J; Zhang, Tong-Jie; Pen, Ue-Li; Zhang, Pengjie; Dubinski, John

    2003-01-01

    Weak lensing measurements are entering a precision era to statistically map the distribution of matter in the universe. The most common measurement has been of the variance of the projected surface density of matter, which corresponds to the induced correlation in alignments of background galaxies. This measurement of the fluctuations is insensitive to the total mass content, like using waves on the ocean to measure its depths. But when the depth is shallow as happens near a beach, waves become skewed. Similarly, a measurement of skewness in the projected matter distribution directly measures the total matter content of the universe. While skewness has already been convincingly detected, its constraint on cosmology is still weak. We address optimal analyses for the CFHT Legacy Survey in the presence of noise. We show that a compensated Gaussian filter with a width of 2.5 arc minutes optimizes the cosmological constraint, yielding $\\Delta \\Omega_m/\\Omega_m\\sim 10%$. This is significantly better than other filt...

  4. The weak scale from BBN

    Science.gov (United States)

    Hall, Lawrence J.; Pinner, David; Ruderman, Joshua T.

    2014-12-01

    The measured values of the weak scale, v, and the first generation masses, m u, d, e , are simultaneously explained in the multiverse, with all these parameters scanning independently. At the same time, several remarkable coincidences are understood. Small variations in these parameters away from their measured values lead to the instability of hydrogen, the instability of heavy nuclei, and either a hydrogen or a helium dominated universe from Big Bang Nucleosynthesis. In the 4d parameter space of ( m u , m d , m e , v), catastrophic boundaries are reached by separately increasing each parameter above its measured value by a factor of (1.4, 1.3, 2.5, ˜ 5), respectively. The fine-tuning problem of the weak scale in the Standard Model is solved: as v is increased beyond the observed value, it is impossible to maintain a significant cosmological hydrogen abundance for any values of m u, d, e that yield both hydrogen and heavy nuclei stability.

  5. Weak Quasielastic Production of Hyperons

    CERN Document Server

    Athar, M Sajjad; Alam, M Rafi; Chauhan, S; Singh, S K

    2016-01-01

    We present the results for antineutrino induced quasielastic hyperon production from nucleon and nuclear targets \\cite{Alam:2014bya,Singh:2006xp}. The inputs are the nucleon-hyperon(N--Y) transition form factors determined from the analysis of neutrino-nucleon scattering and semileptonic decays of neutron and hyperons using SU(3) symmetry. The calculations for the nuclear targets are done in local density approximation. The nuclear medium effects(NME) like Fermi motion, Pauli blocking and final state interaction(FSI) effects due to hyperon-nucleon scattering have been taken into account. The hyperons giving rise to pions through weak decays also contribute to the weak pion production in addition to the $\\Delta$ excitation mechanism which dominates in the energy region of $<$ 0.7 GeV. We also present the results of longitudinal and perpendicular components of polarization of final hyperon \\cite{Akbar:2016awk}. These measurements in the future accelerator experiments with antineutrinos may give some informat...

  6. Weak lensing and cosmological investigation

    CERN Document Server

    Acquaviva, V

    2005-01-01

    In the last few years the scientific community has been dealing with the challenging issue of identifying the dark energy component. We regard weak gravitational lensing as a brand new, and extremely important, tool for cosmological investigation in this field. In fact, the features imprinted on the cosmic microwave background radiation by the lensing from the intervening distribution of matter represent a pretty unbiased estimator, and can thus be used for putting constraints on different dark energy models. This is true in particular for the magnetic-type B-modes of CMB polarization, whose unlensed spectrum at large multipoles (l approximately=1000) is very small even in presence of an amount of gravitational waves as large as currently allowed by the experiments: therefore, on these scales the lensing phenomenon is the only responsible for the observed power, and this signal turns out to be a faithful tracer of the dark energy dynamics. We first recall the formal apparatus of the weak lensing in extended t...

  7. Political corruption and weak state

    Directory of Open Access Journals (Sweden)

    Stojiljković Zoran

    2013-01-01

    Full Text Available The author starts from the hypothesis that it is essential for the countries of the region to critically assess the synergy established between systemic, political corruption and a selectively weak, “devious” nature of the state. Moreover, the key dilemma is whether the expanded practice of political rent seeking supports the conclusion that the root of all corruption is in the very existence of the state - particularly in excessive, selective and deforming state interventions and benefits that create a fertile ground for corruption? The author argues that the destructive combination of weak government and rampant political corruption is based on scattered state intervention, while also rule the parties cartel in the executive branch subordinate to parliament, the judiciary and the police. Corrupt exchange takes place with the absence of strong institutional framework and the precise rules of the political and electoral games, control of public finances and effective political and anti-monopoly legislation and practice included. Exit from the current situation can be seen in the realization of effective anti­corruption strategy that integrates preventive and repressive measures and activities and lead to the establishment of principles of good governance. [Projekat Ministarstva nauke Republike Srbije, br. 179076: Politički identitet Srbije u regionalnom i globalnom kontekstu

  8. Time—periodic weak solutions

    Directory of Open Access Journals (Sweden)

    Eliana Henriques de Brito

    1990-01-01

    Full Text Available In continuing from previous papers, where we studied the existence and uniqueness of the global solution and its asymptotic behavior as time t goes to infinity, we now search for a time-periodic weak solution u(t for the equation whose weak formulation in a Hilbert space H isddt(u′,v+δ(u′,v+αb(u,v+βa(u,v+(G(u,v=(h,vwhere: ′=d/dt; (′ is the inner product in H; b(u,v, a(u,v are given forms on subspaces U⊂W, respectively, of H; δ>0, α≥0, β≥0 are constants and α+β>0; G is the Gateaux derivative of a convex functional J:V⊂H→[0,∞ for V=U, when α>0 and V=W when α=0, hence β>0; v is a test function in V; h is a given function of t with values in H.

  9. Genetic susceptibility of periodontitis

    NARCIS (Netherlands)

    Laine, M.L.; Crielaard, W.; Loos, B.G.

    2012-01-01

    In this systematic review, we explore and summarize the peer-reviewed literature on putative genetic risk factors for susceptibility to aggressive and chronic periodontitis. A comprehensive literature search on the PubMed database was performed using the keywords ‘periodontitis’ or ‘periodontal dise

  10. Casimir torque in weak coupling

    CERN Document Server

    Milton, Kimball A; Long, William

    2013-01-01

    In this paper, dedicated to Johan H{\\o}ye on the occasion of his 70th birthday, we examine manifestations of Casimir torque in the weak-coupling approximation, which allows exact calculations so that comparison with the universally applicable, but generally uncontrolled, proximity force approximation may be made. In particular, we examine Casimir energies between planar objects characterized by $\\delta$-function potentials, and consider the torque that arises when angles between the objects are changed. The results agree very well with the proximity force approximation when the separation distance between the objects is small compared with their sizes. In the opposite limit, where the size of one object is comparable to the separation distance, the shape dependence starts becoming irrelevant. These calculations are illustrative of what to expect for the torques between, for example, conducting planar objects, which eventually should be amenable to both improved theoretical calculation and experimental verific...

  11. New Weak Keys in RSA

    Institute of Scientific and Technical Information of China (English)

    WANG Baocang; LIU Shuanggen; HU Yupu

    2006-01-01

    The security of the RSA system with the prime pairs of some special form is investigated. A new special-purpose algorithm for factoring RSA numbers is proposed. The basic idea of the method is to factor RSA numbers by factoring a well-chosen quadratic polynomial with integral coefficients. When viewed as a general-purpose algorithm, the new algorithm has a high computational complexity. It is shown that the RSA number n=pq can be easily factored if p and q have the special form of p=as+b, q=cs+d, where a, b, c, d are relatively small numbers. Such prime pairs (p, q) are the weak keys of RSA, so when we generate RSA modulus, we should avoid using such prime pairs (p, q).

  12. Genetic Susceptibility to Atherosclerosis

    Directory of Open Access Journals (Sweden)

    Sanja Kovacic

    2012-01-01

    Full Text Available Atherosclerosis is a complex multifocal arterial disease involving interactions of multiple genetic and environmental factors. Advances in techniques of molecular genetics have revealed that genetic ground significantly influences susceptibility to atherosclerotic vascular diseases. Besides further investigations of monogenetic diseases, candidate genes, genetic polymorphisms, and susceptibility loci associated with atherosclerotic diseases have been identified in recent years, and their number is rapidly increasing. This paper discusses main genetic investigations fields associated with human atherosclerotic vascular diseases. The paper concludes with a discussion of the directions and implications of future genetic research in arteriosclerosis with an emphasis on prospective prediction from an early age of individuals who are predisposed to develop premature atherosclerosis as well as to facilitate the discovery of novel drug targets.

  13. On fuzzy weakly-closed sets

    OpenAIRE

    Mahanta, J.; P. K. Das

    2012-01-01

    A new class of fuzzy closed sets, namely fuzzy weakly closed set in a fuzzy topological space is introduced and it is established that this class of fuzzy closed sets lies between fuzzy closed sets and fuzzy generalized closed sets. Alongwith the study of fundamental results of such closed sets, we define and characterize fuzzy weakly compact space and fuzzy weakly closed space.

  14. Twisting theory for weak Hopf algebras

    Institute of Scientific and Technical Information of China (English)

    CHEN Ju-zhen; ZHANG Yan; WANG Shuan-hong

    2008-01-01

    The main aim of this paper is to study the twisting theory of weak Hopf algebras and give an equivalence between the (braided) monoidal categories of weak Hopf bimodules over the original and the twisted weak Hopf algebra to generalize the result from Oeckl (2000).

  15. Reconstruction of weak quasi-Hopf algebras

    CERN Document Server

    Häring, Reto Andreas

    1995-01-01

    All rational semisimple braided tensor categories are representation categories of weak quasi Hopf algebras. To proof this result we construct for any given category of this kind a weak quasi tensor functor to the category of finite dimensional vector spaces. This allows to reconstruct a weak quasi Hopf algebra with the given category as its representation category.

  16. AC susceptibilities of grain-textured superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Sakamoto, N. [Department of Electrical Engineering, Kyushu Sangyo University, 2-3-1 Matsukadai, 813-8503 Fukuoka (Japan)], E-mail: saka@te.kyusan-u.ac.jp; Fukuda, Y.; Koga, M.; Akune, T. [Department of Electrical Engineering, Kyushu Sangyo University, 2-3-1 Matsukadai, 813-8503 Fukuoka (Japan); Khan, H.R. [Institut von Ionenstrahl und Vakuum Technologie, 73728 Esslingen (Germany); Lueders, K. [Freie Universitaet Berlin, Arnimallee, Fac.Physik, D-14195 Berlin (Germany)

    2008-09-15

    In-phase {chi}{sub n}' and out-phase {chi}{sub n}'' components of nth harmonics of AC susceptibility with measuring parameters of a DC magnetic field B{sub dc}, an amplitude B{sub a} and a frequency f of the superimposed AC magnetic fields give substantial information of the superconducting properties. In low-T{sub c} metallic superconductors, {chi}{sub 1}' shows smooth transition and {chi}{sub 1}'' does single peak. High-T{sub c} oxide superconductors with anisotropic and grain-textured structures show deformed complex characteristics. Double peaks in {chi}{sub 1}'' and shoulders in {chi}{sub 1}' appear in AC susceptibility of Hg-1223 superconductors. Instead of simple Bean model, a grained model, where the superconducting grains are immersed in weak superconducting matrix, are proposed. The susceptibilities numerically analyzed using the model show varied and deformed curves and are successfully compared with the measured results.

  17. Application of ultra-weak photon emission measurements in agriculture.

    Science.gov (United States)

    Kato, Kimihiko; Iyozumi, Hiroyuki; Kageyama, Chizuko; Inagaki, Hidehiro; Yamaguchi, Akira; Nukui, Hideki

    2014-10-05

    Here we report our two applications of ultra-weak photon emission (UPE) measurements in agriculture. One is to find new types of agrochemicals that potentiate plants' defense, so-called "plant activator". We first analyzed the relation between plant defense and Elicitor-Responsive Photon Emission (ERPE) using a combination of rice cells and a chitin elicitor. Pharmacological analyses clarified that ERPE was generated as a part of the chitin elicitor-responsive defense in close relation with the generation of reactive oxygen species (ROS). Then we successfully detected the activity of plant activators as the potentiation of ERPE, and developed a new screening system for plant activators based on this principle. Another UPE application is to distinguish herbicide-resistant weeds from susceptible ones by measuring UPE in weeds. In our study, it was revealed that the weed biotypes resistant to sulfonylurea (SU) herbicides, one of the major herbicide groups, showed stronger UPE than susceptible ones after an SU herbicide treatment. By further analysis with a pharmacological and RNAi study, we found that the detoxifying enzyme P450s contributed to the UPE increase in SU herbicide resistant weeds. It is considered that weeds resistant to herbicides other than SU might also be able to be distinguished from susceptible ones by UPE measurement, as long as the herbicides are subject to detoxification by P450s.

  18. Weakly Distributive Modules. Applications to Supplement Submodules

    Indian Academy of Sciences (India)

    Engin Büyükaşik; Yilmaz M Demirci

    2010-11-01

    In this paper, we define and study weakly distributive modules as a proper generalization of distributive modules. We prove that, weakly distributive supplemented modules are amply supplemented. In a weakly distributive supplemented module every submodule has a unique coclosure. This generalizes a result of Ganesan and Vanaja. We prove that -projective duo modules, in particular commutative rings, are weakly distributive. Using this result we obtain that in a commutative ring supplements are unique. This generalizes a result of Camillo and Lima. We also prove that any weakly distributive $\\oplus$-supplemented module is quasi-discrete.

  19. Weakly relativistic dispersion of Bernstein waves

    Science.gov (United States)

    Robinson, P. A.

    1988-01-01

    Weakly relativistic effects on the dispersion of Bernstein waves are investigated for waves propagating nearly perpendicular to a uniform magnetic field in a Maxwellian plasma. Attention is focused on those large-wave-vector branches that are either weakly damped or join continuously onto weakly damped branches since these are the modes of most interest in applications. The transition between dispersion at perpendicular and oblique propagation is examined and major weakly relativistic effects can dominate even in low-temperature plasmas. A number of simple analytic criteria are obtained which delimit the ranges of harmonic number and propagation angle within which various types of weakly damped Bernstein modes can exist.

  20. Weakly relativistic dispersion of Bernstein waves

    Science.gov (United States)

    Robinson, P. A.

    1988-01-01

    Weakly relativistic effects on the dispersion of Bernstein waves are investigated for waves propagating nearly perpendicular to a uniform magnetic field in a Maxwellian plasma. Attention is focused on those large-wave-vector branches that are either weakly damped or join continuously onto weakly damped branches since these are the modes of most interest in applications. The transition between dispersion at perpendicular and oblique propagation is examined and major weakly relativistic effects can dominate even in low-temperature plasmas. A number of simple analytic criteria are obtained which delimit the ranges of harmonic number and propagation angle within which various types of weakly damped Bernstein modes can exist.

  1. Extracellular matrix plasticity and GABAergic inhibition of prefrontal cortex pyramidal cells facilitates relapse to heroin seeking

    OpenAIRE

    2010-01-01

    Abstract Successful treatment of drug addiction is hampered by high relapse rates during periods of abstinence. Neuroadaptation in the medial prefrontal cortex (mPFC) is thought to play a crucial role in vulnerability to relapse to drug seeking, but the molecular and cellular mechanisms remain largely unknown. To identify protein changes that contribute to relapse susceptibility, we investigated synaptic membrane fractions from the mPFC of rats that underwent 21 days of forced abst...

  2. Cocaine-induced Modification of Synaptic Plasticity in Rat Medial Prefrontal Cortex

    OpenAIRE

    Lu, Hui

    2009-01-01

    Medial prefrontal cortex (mPFC) is involved in relapse after withdrawal for cocaine exposure, but changes in synaptic function and plasticity in the mPFC during the period of withdrawal remain largely unknown. After the termination of repeated cocaine treatments in rats, I observed a gradual enhancement in the susceptibility of excitatory synapses on layer V mPFC pyramidal neurons to activity-induced long-term potentiation (LTP). This enhanced synaptic plasticity could be attributed to a grad...

  3. Increased BOLD sensitivity in the orbitofrontal cortex using slice-dependent echo times at 3 T.

    Science.gov (United States)

    Domsch, Sebastian; Linke, Julia; Heiler, Patrick M; Kroll, Alexander; Flor, Herta; Wessa, Michèle; Schad, Lothar R

    2013-02-01

    Functional magnetic resonance imaging (fMRI) exploits the blood oxygenation level dependent (BOLD) effect to detect neuronal activation related to various experimental paradigms. Some of these, such as reversal learning, involve the orbitofrontal cortex and its interaction with other brain regions like the amygdala, striatum or dorsolateral prefrontal cortex. These paradigms are commonly investigated with event-related methods and gradient echo-planar imaging (EPI) with short echo time of 27 ms. However, susceptibility-induced signal losses and image distortions in the orbitofrontal cortex are still a problem for this optimized sequence as this brain region consists of several slices with different optimal echo times. An EPI sequence with slice-dependent echo times is suitable to maximize BOLD sensitivity in all slices and might thus improve signal detection in the orbitofrontal cortex. To test this hypothesis, we first optimized echo times via BOLD sensitivity simulation. Second, we measured 12 healthy volunteers using a standard EPI sequence with an echo time of 27 ms and a modified EPI sequence with echo times ranging from 22 ms to 47 ms. In the orbitofrontal cortex, the number of activated voxels increased from 87 ± 44 to 549 ± 83 and the maximal t-value increased from 4.4 ± 0.3 to 5.4 ± 0.3 when the modified EPI was used. We conclude that an EPI with slice-dependent echo times may be a valuable tool to mitigate susceptibility artifacts in event-related whole-brain fMRI studies with a focus on the orbitofrontal cortex.

  4. A Universe without Weak Interactions

    Energy Technology Data Exchange (ETDEWEB)

    Harnik, Roni; Kribs, Graham D.; Perez, Gilad

    2006-04-07

    A universe without weak interactions is constructed that undergoes big-bang nucleosynthesis, matter domination, structure formation, and star formation. The stars in this universe are able to burn for billions of years, synthesize elements up to iron, and undergo supernova explosions, dispersing heavy elements into the interstellar medium. These definitive claims are supported by a detailed analysis where this hypothetical ''Weakless Universe'' is matched to our Universe by simultaneously adjusting Standard Model and cosmological parameters. For instance, chemistry and nuclear physics are essentially unchanged. The apparent habitability of the Weakless Universe suggests that the anthropic principle does not determine the scale of electroweak breaking, or even require that it be smaller than the Planck scale, so long as technically natural parameters may be suitably adjusted. Whether the multi-parameter adjustment is realized or probable is dependent on the ultraviolet completion, such as the string landscape. Considering a similar analysis for the cosmological constant, however, we argue that no adjustments of other parameters are able to allow the cosmological constant to raise up even remotely close to the Planck scale while obtaining macroscopic structure. The fine-tuning problems associated with the electroweak breaking scale and the cosmological constant therefore appear to be qualitatively different from the perspective of obtaining a habitable universe.

  5. A universe without weak interactions

    Science.gov (United States)

    Harnik, Roni; Kribs, Graham D.; Perez, Gilad

    2006-08-01

    A universe without weak interactions is constructed that undergoes big-bang nucleosynthesis, matter domination, structure formation, and star formation. The stars in this universe are able to burn for billions of years, synthesize elements up to iron, and undergo supernova explosions, dispersing heavy elements into the interstellar medium. These definitive claims are supported by a detailed analysis where this hypothetical “weakless universe” is matched to our Universe by simultaneously adjusting standard model and cosmological parameters. For instance, chemistry and nuclear physics are essentially unchanged. The apparent habitability of the weakless universe suggests that the anthropic principle does not determine the scale of electroweak breaking, or even require that it be smaller than the Planck scale, so long as technically natural parameters may be suitably adjusted. Whether the multiparameter adjustment is realized or probable is dependent on the ultraviolet completion, such as the string landscape. Considering a similar analysis for the cosmological constant, however, we argue that no adjustments of other parameters are able to allow the cosmological constant to raise up even remotely close to the Planck scale while obtaining macroscopic structure. The fine-tuning problems associated with the electroweak breaking scale and the cosmological constant therefore appear to be qualitatively different from the perspective of obtaining a habitable universe.

  6. Weak homology of elliptical galaxies

    CERN Document Server

    Bertin, G; Principe, M D

    2002-01-01

    We start by studying a small set of objects characterized by photometric profiles that have been pointed out to deviate significantly from the standard R^{1/4} law. For these objects we confirm that a generic R^{1/n} law, with n a free parameter, can provide superior fits (the best-fit value of n can be lower than 2.5 or higher than 10), better than those that can be obtained by a pure R^{1/4} law, by an R^{1/4}+exponential model, and by other dynamically justified self--consistent models. Therefore, strictly speaking, elliptical galaxies should not be considered homologous dynamical systems. Still, a case for "weak homology", useful for the interpretation of the Fundamental Plane of elliptical galaxies, could be made if the best-fit parameter n, as often reported, correlates with galaxy luminosity L, provided the underlying dynamical structure also follows a systematic trend with luminosity. We demonstrate that this statement may be true even in the presence of significant scatter in the correlation n(L). Pr...

  7. Testing the weak equivalence principle

    Science.gov (United States)

    Nobili, Anna M.; Comandi, Gian Luca; Pegna, Raffaello; Bramanti, Donato; Doravari, Suresh; Maccarone, Francesco; Lucchesi, David M.

    2010-01-01

    The discovery of Dark Energy and the fact that only about 5% of the mass of the universe can be explained on the basis of the current laws of physics have led to a serious impasse. Based on past history, physics might indeed be on the verge of major discoveries; but the challenge is enormous. The way to tackle it is twofold. On one side, scientists try to perform large scale direct observations and measurements - mostly from space. On the other, they multiply their efforts to put to the most stringent tests ever the physical theories underlying the current view of the physical world, from the very small to the very large. On the extremely small scale very exciting results are expected from one of the most impressive experiments in the history of mankind: the Large Hadron Collider. On the very large scale, the universe is dominated by gravity and the present impasse undoubtedly calls for more powerful tests of General Relativity - the best theory of gravity to date. Experiments testing the Weak Equivalence Principle, on which General Relativity ultimately lies, have the strongest probing power of them all; a breakthrough in sensitivity is possible with the “Galileo Galilei” (GG) satellite experiment to fly in low Earth orbit.

  8. Triterpenoid saponins from Cortex Albiziae

    OpenAIRE

    Zou, Kun; Zhao, Yuying

    2004-01-01

    Cortex Albiziae, the dried stem bark of a leguminous plant, Albizia julibrissin Durazz, was specified in Chinese Pharmacopoeia (1995 edit.) as a traditional Chinese medicine to be used.to relieve melancholia and uneasiness of body and mind, to invigorate the circulation of blood and subside a swelling. In a course of our quality assessment of traditional Chinese medicines, the n-BuOH soluble part of 95% EtOH extracts from the stem barks of Albizia julibrissin was subjected to a series of sol...

  9. The Geometry And Significance Of Weak Energy

    CERN Document Server

    Parks, A D

    2000-01-01

    Summary: The theory of weak values for quantum mechanical observables has come to serve as a useful basis for contemporary discussions concerning such varied topics as the tunnelling-time controversy and quantum stochastic processes. An intrinsic complex-valued weak energy has recently been observed experimentally and reported in the literature. In this paper it is shown that: (a) the real and imaginary valued parts of this weak energy have geometric interpretations related to a phase acquired from parallel transport in Hilbert space and the variational dynamics occurring in the associated projective Hilbert space, respectively; (b) the weak energy defines functions which translate correlation amplitudes and probabilities in time; (c) correlation probabilities can be controlled by manipulating the weak energy and there exists a condition of weak stationarity that guarantees their time invariance; and (d) a time-weak energy uncertainty relation of the usual form prevails when a suitable set of dynamical constr...

  10. Monkey brain cortex imaging by photoacoustic tomography.

    Science.gov (United States)

    Yang, Xinmai; Wang, Lihong V

    2008-01-01

    Photoacoustic tomography (PAT) is applied to image the brain cortex of a monkey through the intact scalp and skull ex vivo. The reconstructed PAT image shows the major blood vessels on the monkey brain cortex. For comparison, the brain cortex is imaged without the scalp, and then imaged again without the scalp and skull. Ultrasound attenuation through the skull is also measured at various incidence angles. This study demonstrates that PAT of the brain cortex is capable of surviving the ultrasound signal attenuation and distortion caused by a relatively thick skull.

  11. Prefrontal cortex glutamate and extraversion.

    Science.gov (United States)

    Grimm, Simone; Schubert, Florian; Jaedke, Maren; Gallinat, Jürgen; Bajbouj, Malek

    2012-10-01

    Extraversion is considered one of the core traits of personality. Low extraversion has been associated with increased vulnerability to affective and anxiety disorders. Brain imaging studies have linked extraversion, approach behaviour and the production of positive emotional states to the dorsolateral prefrontal cortex (DLPFC) and glutamatergic neurotransmission. However, the relationship between extraversion and glutamate in the DLPFC has not been investigated so far. In order to address this issue, absolute glutamate concentrations in the DLPFC and the visual cortex as a control region were measured by 3-Tesla proton magnetic resonance spectroscopy (1H-MRS) in 29 subjects with high and low extraversion. We found increased glutamate levels in the DLPFC of introverts as compared with extraverts. The increased glutamate concentration was specific for the DLPFC and negatively associated with state anxiety. Although preliminary, results indicate altered top-down control of DLPFC due to reduced glutamate concentration as a function of extraversion. Glutamate measurement with 1H-MRS may facilitate the understanding of biological underpinnings of personality traits and psychiatric diseases associated with dysfunctions in approach behaviour and the production of positive emotional states.

  12. Weak* convergence of operator means

    Energy Technology Data Exchange (ETDEWEB)

    Romanov, Alexandr V [Moscow State Institute of Electronics and Mathematics (Technical University), Moscow (Russian Federation)

    2011-12-31

    For a linear operator U with ||U'n||{<=}const on a Banach space X we discuss conditions for the convergence of ergodic operator nets T{sub {alpha}} corresponding to the adjoint operator U* of U in the W*O-topology of the space EndX*. The accumulation points of all possible nets of this kind form a compact convex set L in EndX*, which is the kernel of the operator, where {Gamma}{sub 0}={l_brace}U{sub n}*, n{>=}0{r_brace}. It is proved that all ergodic nets T{sub {alpha}} weakly* converge if and only if the kernel L consists of a single element. In the case of X=C({Omega}) and the shift operator U generated by a continuous transformation {phi} of a metrizable compactum {Omega} we trace the relationships among the ergodic properties of U, the structure of the operator semigroups L, G and {Gamma}={Gamma}-bar{sub 0}, and the dynamical characteristics of the semi-cascade ({phi},{Omega}). In particular, if cardL=1, then a) for any {omega} element of {Omega} the closure of the trajectory {l_brace}{phi}{sup n}{omega}, n{>=}0{r_brace} contains precisely one minimal set m, and b) the restriction ({phi},m) is strictly ergodic. Condition a) implies the W*O-convergence of any ergodic sequence of operators T{sub n} element of EndX* under the additional assumption that the kernel of the enveloping semigroup E({phi},{Omega}) contains elements obtained from the 'basis' family of transformations {l_brace}{phi}{sup n}, n{>=}0{r_brace} of the compact set {Omega} by using some transfinite sequence of sequential passages to the limit.

  13. Magnetic irreversibility in granular superconductors: ac susceptibility study

    Energy Technology Data Exchange (ETDEWEB)

    Perez, F.; Obradors, X.; Fontcuberta, J. (ICMAB, CSIC, Bellaterra, Barcelona (Spain)); Vallet, M.; Gonzalez-Calbet, J. (Lab. Magnetismo Aplicado, RENFE-U.C. Madrid, Las Matas (Spain))

    1991-12-01

    Ac susceptibility measurements of a ceramic weak-coupled superconductor in very low ac fields (2mG, 111Hz) are reported. We present evidence for the observation of the magnetic irreversibility following a ZFC-FC thermal cycling by means of ac susceptibilty measurements. It is shown that this technique also reflect local magnetic field effects in granular superconductors, as previously suggested in microwave surface resistance and I-V characteristics. (orig.).

  14. Weakly and Strongly Regular Near-rings

    Institute of Scientific and Technical Information of China (English)

    N.Argac; N.J.Groenewald

    2005-01-01

    In this paper, we prove some basic properties of left weakly regular near-rings.We give an affirmative answer to the question whether a left weakly regular near-ring with left unity and satisfying the IFP is also right weakly regular. In the last section, we use among others left 0-prime and left completely prime ideals to characterize strongly regular near-rings.

  15. WEAK CONVERGENCE OF HENSTOCK INTEGRABLE SEQUENCES

    Institute of Scientific and Technical Information of China (English)

    LuisaDiPiazza

    1994-01-01

    Some relationships between pointwise and weak convergence of a sequence of Henstock integrable functions are studied, In particular it is provided an example of a sequence of Henstock integrable functions whose pointwise limit is different from the weak one. By introducing an asymptotic version of the Henstock equiintegrability notion it is given a necessary and sufficient condition in order that a pointwisely convergent sequence of Henstock integrable functions is weakly convergent to its pointwise limit.

  16. Transversality theorems for the weak topology

    OpenAIRE

    2011-01-01

    In his 1979 paper Trotman proves, using the techniques of the Thom transversality theorem, that under some conditions on the dimensions of the manifolds under consideration, openness of the set of maps transverse to a stratification in the strong (Whitney) topology implies that the stratification is $(a)$-regular. Here we first discuss the Thom transversality theorem for the weak topology and then give a similiar kind of result for the weak topology, under very weak hypotheses. Recently sever...

  17. Spin effects in the weak interaction

    Energy Technology Data Exchange (ETDEWEB)

    Freedman, S.J. (Argonne National Lab., IL (USA) Chicago Univ., IL (USA). Dept. of Physics Chicago Univ., IL (USA). Enrico Fermi Inst.)

    1990-01-01

    Modern experiments investigating the beta decay of the neutron and light nuclei are still providing important constraints on the theory of the weak interaction. Beta decay experiments are yielding more precise values for allowed and induced weak coupling constants and putting constraints on possible extensions to the standard electroweak model. Here we emphasize the implications of recent experiments to pin down the strengths of the weak vector and axial vector couplings of the nucleon.

  18. On Weakly P.P. Rings

    Institute of Scientific and Technical Information of China (English)

    Xiang Yue-ming; Ouyang Lun-qun; Wang Shu-gui

    2015-01-01

    We introduce, in this paper, the right weakly p.p. rings as the generaliza-tion of right p.p. rings. It is shown that many properties of the right p.p. rings can be extended onto the right weakly p.p. rings. Relative examples are constructed. As applications, we also characterize the regular rings and the semisimple rings in terms of the right weakly p.p. rings.

  19. Weak measurements with a qubit meter

    DEFF Research Database (Denmark)

    Wu, Shengjun; Mølmer, Klaus

    2009-01-01

    We derive schemes to measure the so-called weak values of quantum system observables by coupling of the system to a qubit meter system. We highlight, in particular, the meaning of the imaginary part of the weak values, and show how it can be measured directly on equal footing with the real part...... of the weak value. We present compact expressions for the weak value of single qubit observables and of product observables on qubit pairs. Experimental studies of the results are suggested with cold trapped ions....

  20. Mapping Prefrontal Cortex Functions in Human Infancy

    Science.gov (United States)

    Grossmann, Tobias

    2013-01-01

    It has long been thought that the prefrontal cortex, as the seat of most higher brain functions, is functionally silent during most of infancy. This review highlights recent work concerned with the precise mapping (localization) of brain activation in human infants, providing evidence that prefrontal cortex exhibits functional activation much…

  1. Network susceptibilities: Theory and applications

    Science.gov (United States)

    Manik, Debsankha; Rohden, Martin; Ronellenfitsch, Henrik; Zhang, Xiaozhu; Hallerberg, Sarah; Witthaut, Dirk; Timme, Marc

    2017-01-01

    We introduce the concept of network susceptibilities quantifying the response of the collective dynamics of a network to small parameter changes. We distinguish two types of susceptibilities: vertex susceptibilities and edge susceptibilities, measuring the responses due to changes in the properties of units and their interactions, respectively. We derive explicit forms of network susceptibilities for oscillator networks close to steady states and offer example applications for Kuramoto-type phase-oscillator models, power grid models, and generic flow models. Focusing on the role of the network topology implies that these ideas can be easily generalized to other types of networks, in particular those characterizing flow, transport, or spreading phenomena. The concept of network susceptibilities is broadly applicable and may straightforwardly be transferred to all settings where networks responses of the collective dynamics to topological changes are essential.

  2. Topological Susceptibility from Slabs

    CERN Document Server

    Bietenholz, Wolfgang; Gerber, Urs

    2015-01-01

    In quantum field theories with topological sectors, a non-perturbative quantity of interest is the topological susceptibility chi_t. In principle it seems straightforward to measure chi_t by means of Monte Carlo simulations. However, for local update algorithms and fine lattice spacings, this tends to be difficult, since the Monte Carlo history rarely changes the topological sector. Here we test a method to measure chi_t even if data from only one sector are available. It is based on the topological charges in sub-volumes, which we denote as slabs. Assuming a Gaussian distribution of these charges, this method enables the evaluation of chi_t, as we demonstrate with numerical results for non-linear sigma-models.

  3. Susceptibility to anchoring effects

    Directory of Open Access Journals (Sweden)

    Todd McElroy

    2007-02-01

    Full Text Available Previous research on anchoring has shown this heuristic to be a very robust psychological phenomenon ubiquitous across many domains of human judgment and decision-making. Despite the prevalence of anchoring effects, researchers have only recently begun to investigate the underlying factors responsible for how and in what ways a person is susceptible to them. This paper examines how one such factor, the Big-Five personality trait of openness-to-experience, influences the effect of previously presented anchors on participants' judgments. Our findings indicate that participants high in openness-to-experience were significantly more influenced by anchoring cues relative to participants low in this trait. These findings were consistent across two different types of anchoring tasks providing convergent evidence for our hypothesis.

  4. Quark number density and susceptibility calculation under one-loop correction in the mean-field potential

    Indian Academy of Sciences (India)

    S SOMORENDRO SINGH; G SAXENA

    2017-06-01

    We calculate quark number density and susceptibility under one-loop correction in the mean-field potential. The calculation shows continuous increase in the number density and susceptibility up to the temperature $T = 0.4 \\rm{GeV}$. Then the values of number density and susceptibility approach the very weakly result with higher values of temperature. The result indicates that the calculated values fit well with increase in temperature to match the lattice QCD simulations of the same quantities.

  5. A BOLD signature of eyeblinks in the visual cortex.

    Science.gov (United States)

    Hupé, Jean-Michel; Bordier, Cécile; Dojat, Michel

    2012-05-15

    We are usually unaware of the brief but large illumination changes caused by blinks, presumably because of blink suppression mechanisms. In fMRI however, increase of the BOLD signal was reported in the visual cortex, e.g. during blocks of voluntary blinks (Bristow, Frith and Rees, 2005) or after spontaneous blinks recorded during the prolonged fixation of a static stimulus (Tse, Baumgartner and Greenlee, 2010). We tested whether such activation, possibly related to illumination changes, was also present during standard fMRI retinotopic and visual experiments and was large enough to contaminate the BOLD signal we are interested in. We monitored in a 3T scanner the eyeblinks of 14 subjects who observed three different types of visual stimuli, including periodic rotating wedges and contracting/expanding rings, event-related Mondrians and graphemes, while fixating. We performed event-related analyses on the set of detected spontaneous blinks. We observed large and widespread BOLD responses related to blinks in the visual cortex of every subject and whatever the visual stimulus. The magnitude of the modulation was comparable to visual stimulation. However, blink-related activations lay mostly in the anterior parts of retinotopic visual areas, coding the periphery of the visual field well beyond the extent of our stimuli. Blinks therefore represent an important source of BOLD variations in the visual cortex and a troublesome source of noise since any correlation, even weak, between the distribution of blinks and a tested protocol could trigger artifactual activities. However, the typical signature of blinks along the anterior calcarine and the parieto-occipital sulcus allows identifying, even in the absence of eyetracking, fMRI protocols possibly contaminated by a heterogeneous distribution of blinks.

  6. Weak interaction: past answers, present questions

    Energy Technology Data Exchange (ETDEWEB)

    Ne' eman, Y.

    1977-02-01

    A historical sketch of the weak interaction is presented. From beta ray to pion decay, the V-A theory of Marshak and Sudarshan, CVC principle of equivalence, universality as an algebraic condition, PCAC, renormalized weak Hamiltonian in the rehabilitation of field theory, and some current issues are considered in this review. 47 references. (JFP)

  7. On modeling weak sinks in MODPATH

    Science.gov (United States)

    Abrams, Daniel B.; Haitjema, Henk; Kauffman, Leon J.

    2012-01-01

    Regional groundwater flow systems often contain both strong sinks and weak sinks. A strong sink extracts water from the entire aquifer depth, while a weak sink lets some water pass underneath or over the actual sink. The numerical groundwater flow model MODFLOW may allow a sink cell to act as a strong or weak sink, hence extracting all water that enters the cell or allowing some of that water to pass. A physical strong sink can be modeled by either a strong sink cell or a weak sink cell, with the latter generally occurring in low resolution models. Likewise, a physical weak sink may also be represented by either type of sink cell. The representation of weak sinks in the particle tracing code MODPATH is more equivocal than in MODFLOW. With the appropriate parameterization of MODPATH, particle traces and their associated travel times to weak sink streams can be modeled with adequate accuracy, even in single layer models. Weak sink well cells, on the other hand, require special measures as proposed in the literature to generate correct particle traces and individual travel times and hence capture zones. We found that the transit time distributions for well water generally do not require special measures provided aquifer properties are locally homogeneous and the well draws water from the entire aquifer depth, an important observation for determining the response of a well to non-point contaminant inputs.

  8. Spin Seebeck effect in a weak ferromagnet

    Science.gov (United States)

    Arboleda, Juan David; Arnache Olmos, Oscar; Aguirre, Myriam Haydee; Ramos, Rafael; Anadon, Alberto; Ibarra, Manuel Ricardo

    2016-06-01

    We report the observation of room temperature spin Seebeck effect (SSE) in a weak ferromagnetic normal spinel Zinc Ferrite (ZFO). Despite the weak ferromagnetic behavior, the measurements of the SSE in ZFO show a thermoelectric voltage response comparable with the reported values for other ferromagnetic materials. Our results suggest that SSE might possibly originate from the surface magnetization of the ZFO.

  9. CP Violation, Neutral Currents, and Weak Equivalence

    Science.gov (United States)

    Fitch, V. L.

    1972-03-23

    Within the past few months two excellent summaries of the state of our knowledge of the weak interactions have been presented. Correspondingly, we will not attempt a comprehensive review but instead concentrate this discussion on the status of CP violation, the question of the neutral currents, and the weak equivalence principle.

  10. Towards a classification of weak hand holds

    NARCIS (Netherlands)

    Kimmelman, V.; Sáfár, A.; Crasborn, O.

    2016-01-01

    The two symmetrical manual articulators (the hands) in signed languages are a striking modalityspecific phonetic property. The weak hand can maintain the end position of an articulation while the other articulator continues to produce additional signs. This weak hand spreading (hold) has been

  11. Revisiting Weak Simulation for Substochastic Markov Chains

    DEFF Research Database (Denmark)

    Jansen, David N.; Song, Lei; Zhang, Lijun

    2013-01-01

    The spectrum of branching-time relations for probabilistic systems has been investigated thoroughly by Baier, Hermanns, Katoen and Wolf (2003, 2005), including weak simulation for systems involving substochastic distributions. Weak simulation was proven to be sound w.r.t. the liveness fragment...

  12. S-parameters for weakly excited slots

    DEFF Research Database (Denmark)

    Albertsen, Niels Christian

    1999-01-01

    A simple approach to account for parasitic effects in weakly excited slots cut in the broad wall of a rectangular waveguide is proposed......A simple approach to account for parasitic effects in weakly excited slots cut in the broad wall of a rectangular waveguide is proposed...

  13. Weakly exact categories and the snake lemma

    CERN Document Server

    Jafari, Amir

    2009-01-01

    We generalize the notion of an exact category and introduce weakly exact categories. A proof of the snake lemma in this general setting is given. Some applications are given to illustrate how one can do homological algebra in a weakly exact category.

  14. Strong Connections and Invertible Weak Entwining Structures

    Institute of Scientific and Technical Information of China (English)

    J.N.ALONSO (A)LVAREZ; J.M.FERN(A)NDEZ VILABOA; R.GONZ(A)LEZ RODR(I)GUEZ

    2012-01-01

    In this paper we obtain a criterion under which the bijectivity of the canonical morphism of a weak Galois extension associated to a weak invertible entwining structure is equivalent to the existence of a strong connection form.Also we obtain an explicit formula for a strong connection under equivariant projective conditions or under coseparability conditions.

  15. Weakly tight functions and their decomposition

    Directory of Open Access Journals (Sweden)

    Mona Khare

    2005-01-01

    Full Text Available The present paper deals with the study of a weakly tight function and its relation to tight functions. We obtain a Jordan-decomposition-type theorem for a locally bounded weakly tight real-valued function defined on a sublattice of IX, followed by the notion of a total variation.

  16. Cohomology of Weakly Reducible Maximal Triangular Algebras

    Institute of Scientific and Technical Information of China (English)

    董浙; 鲁世杰

    2000-01-01

    In this paper, we introduce the concept of weakly reducible maximal triangular algebras φwhich form a large class of maximal triangular algebras. Let B be a weakly closed algebra containing 5φ, we prove that the cohomology spaces Hn(φ, B) (n≥1) are trivial.

  17. Fixed points of occasionally weakly biased mappings

    Directory of Open Access Journals (Sweden)

    Y. Mahendra Singh, M. R. Singh

    2012-09-01

    Full Text Available Common fixed point results due to Pant et al. [Pant et al., Weak reciprocal continuity and fixed point theorems, Ann Univ Ferrara, 57(1, 181-190 (2011] are extended to a class of non commuting operators called occasionally weakly biased pair[ N. Hussain, M. A. Khamsi A. Latif, Commonfixed points for JH-operators and occasionally weakly biased pairs under relaxed conditions, Nonlinear Analysis, 74, 2133-2140 (2011]. We also provideillustrative examples to justify the improvements. Abstract. Common fixed point results due to Pant et al. [Pant et al., Weakreciprocal continuity and fixed point theorems, Ann Univ Ferrara, 57(1, 181-190 (2011] are extended to a class of non commuting operators called occasionally weakly biased pair[ N. Hussain, M. A. Khamsi A. Latif, Common fixed points for JH-operators and occasionally weakly biased pairs under relaxed conditions, Nonlinear Analysis, 74, 2133-2140 (2011]. We also provide illustrative examples to justify the improvements.

  18. Self-Dual Weak Hopf Algebras

    Institute of Scientific and Technical Information of China (English)

    Munir AHMED; Fang LI

    2008-01-01

    In this paper, we define the notion of self-dual graded weak Hopf algebra and self-dual semilattice graded weak Hopf algebra. We give characterization of finite-dimensional such algebras when they are in structually simple forms in the sense of E. L. Green and E. N. Morcos. We also give the definition of self-dual weak Hopf quiver and apply these types of quivers to classify the finite-dimensional self-dual semilattice graded weak Hopf algebras. Finally, we prove partially the conjecture given by N. Andruskiewitsch and H.-J. Schneider in the case of finite-dimensional pointed semilattice graded weak Hopf algebra H when grH is self-dual.

  19. Atomic homodyne detection of weak atomic transitions.

    Science.gov (United States)

    Gunawardena, Mevan; Elliott, D S

    2007-01-26

    We have developed a two-color, two-pathway coherent control technique to detect and measure weak optical transitions in atoms by coherently beating the transition amplitude for the weak transition with that of a much stronger transition. We demonstrate the technique in atomic cesium, exciting the 6s(2)S(1/2) --> 8s(2)S(1/2) transition via a strong two-photon transition and a weak controllable Stark-induced transition. We discuss the enhancement in the signal-to-noise ratio for this measurement technique over that of direct detection of the weak transition rate, and project future refinements that may further improve its sensitivity and application to the measurement of other weak atomic interactions.

  20. Weak chemical weathering during the Little Ice Age recorded by lake sediments

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Low magnetic susceptibility, low Sr content and hence high Rb/Sr ratio in the lake sediment sequence indicate a weak chemical weathering process under arid and cold climate of the Little Ice Age in a single closed lake watershed. According to different geochemical behavior between rubidium and strontium in earth surface processes, variation of Rb/Sr ratios in the lake sediment sequence can be used as an effective geochemical proxy with definite climatic significance of chemical weathering in watershed. Unlike chemical weathering process in tropic zone and modern temperate-humid climate, concordant changes in both Sr content and magnetic susceptibility with d18O values of Dunde ice core suggest that the weak chemical weathering was controlled by air temperature during the Little Ice Age maximum. After the Little Ice Age, chemical weathering intensity was controlled also gradually by precipitation with increasing in temperature.

  1. Relative entropies, suitable weak solutions, and weak strong uniqueness for the compressible Navier-Stokes system

    CERN Document Server

    Feireisl, Eduard; Novotny, Antonin

    2011-01-01

    We introduce the notion of relative entropy for the weak solutions of the compressible Navier-Stokes system. We show that any finite energy weak solution satisfies a relative entropy inequality for any pair of sufficiently smooth test functions. As a corollary we establish weak-strong uniqueness principle for the compressible Navier-Stokes system.

  2. A Construction of Weakly Inverse Semigroups

    Institute of Scientific and Technical Information of China (English)

    Bing Jun YU; Yan LI

    2009-01-01

    Let S° be an inverse semigroup with semilattice biordered set E° of idempotents and E a weakly inverse biordered set with a subsemilattice Ep = { e ∈ E |(V) f ∈ E, S(f , e)(C) w(e) } isomorphic to E° by θ:Ep→E°. In this paper, it is proved that if(V)f, g∈E, f ←→ ,g(→) f°θ (ζ)s° g°θand there exists a mapping φ from Ep into the symmetric weakly inverse semigroup (ζξ)(E ∪S°) satisfying six appropriate conditions, then a weakly inverse semigroup ∑ can be constructed in (ζξ)(S°), called the weakly inverse hull of a weakly inverse system (S°, E, θ, φ) with I(∑) ≌ S°, E(∑) (≌) E. Conversely,every weakly inverse semigroup can be constructed in this way. Furthermore, a sufficient and necessary condition for two weakly inverse hulls to be isomorphic is also given.

  3. Ultra-small phase estimation via weak measurement with postselection: A comparison of joint weak measurement and weak value amplification

    CERN Document Server

    Fang, Chen; Yu, Yang; Li, Qin-Zheng; Zeng, Guihua

    2015-01-01

    We derive a general theory for the joint weak measurement with arbitrary postselection and employ it in the time-delay measurement. Especially, we study two special cases, i.e., the balanced and unbalanced postselection regimes, and present an experiment to verify the theoretical results. The experimental results show that under similar conditions, the signal-to-noise ratio of using joint weak measurement scheme remains higher than 12 dB when the measured time-delay is smaller the ultimate precision limit of the weak-value amplification scheme. Moreover, the joint weak measurement scheme is robust to the misalignment errors and the wavelength-dependency of optical components, which indicates its advantage of improving the measurement precision with convenient laboratory equipments.

  4. Preparatory attention in visual cortex.

    Science.gov (United States)

    Battistoni, Elisa; Stein, Timo; Peelen, Marius V

    2017-05-01

    Top-down attention is the mechanism that allows us to selectively process goal-relevant aspects of a scene while ignoring irrelevant aspects. A large body of research has characterized the effects of attention on neural activity evoked by a visual stimulus. However, attention also includes a preparatory phase before stimulus onset in which the attended dimension is internally represented. Here, we review neurophysiological, functional magnetic resonance imaging, magnetoencephalography, electroencephalography, and transcranial magnetic stimulation (TMS) studies investigating the neural basis of preparatory attention, both when attention is directed to a location in space and when it is directed to nonspatial stimulus attributes (content-based attention) ranging from low-level features to object categories. Results show that both spatial and content-based attention lead to increased baseline activity in neural populations that selectively code for the attended attribute. TMS studies provide evidence that this preparatory activity is causally related to subsequent attentional selection and behavioral performance. Attention thus acts by preactivating selective neurons in the visual cortex before stimulus onset. This appears to be a general mechanism that can operate on multiple levels of representation. We discuss the functional relevance of this mechanism, its limitations, and its relation to working memory, imagery, and expectation. We conclude by outlining open questions and future directions. © 2017 New York Academy of Sciences.

  5. Entorhinal cortex stimulation modulates amygdala and piriform cortex responses to olfactory bulb inputs in the rat.

    Science.gov (United States)

    Mouly, A-M; Di Scala, G

    2006-01-01

    The rodent olfactory bulb sends direct projections to the piriform cortex and to two structures intimately implicated in memory processes, the entorhinal cortex and the amygdala. The piriform cortex has monosynaptic projections with the amygdala and the piriform cortex and is therefore in a position to modulate olfactory input either directly in the piriform cortex, or via the amygdala. In order to investigate this hypothesis, field potential signals induced in anesthetized rats by electrical stimulation of the olfactory bulb or the entorhinal cortex were recorded simultaneously in the piriform cortex (anterior part and posterior part) and the amygdala (basolateral nucleus and cortical nucleus). Single-site paired-pulse stimulation was used to assess the time courses of short-term inhibition and facilitation in each recording site in response to electrical stimulation of the olfactory bulb and entorhinal cortex. Paired-pulse stimulation of the olfactory bulb induced homosynaptic inhibition for short interpulse interpulse intervals (20-30 ms) in all the recording sites, with a significantly lower degree of inhibition in the anterior piriform cortex than in the other structures. At longer intervals (40-80 ms), paired-pulse facilitation was observed in all the structures. Paired-pulse stimulation of the entorhinal cortex mainly resulted in inhibition for the shortest interval duration (20 ms) in anterior piriform cortex, posterior piriform cortex and amygdala basolateral but not cortical nucleus. Double-site paired-pulse stimulation was then applied to determine if stimulation of the entorhinal cortex can modulate responses to olfactory bulb stimulation. For short interpulse intervals (20 ms) heterosynaptic inhibition was observed in anterior piriform cortex, posterior piriform cortex and amygdala basolateral but not cortical nucleus. The level of inhibition was greater in the basolateral nucleus than in the other structures. Taken together these data suggest that the

  6. Thermodynamics of gravity favours Weak Censorship Conjecture

    CERN Document Server

    Acquaviva, Giovanni; Hamid, Aymen I M; Maharaj, Sunil D

    2015-01-01

    We use the formulation of thermodynamics of gravity as proposed by Clifton, Ellis and Tavakol on the gravitational collapse of dustlike matter, that violates the strong or weak cosmic censorship conjecture depending on the initial data. We transparently demonstrate that the gravitational entropy prefers the scenario where the stronger version is violated but the weak censorship conjecture is satisfied. This is a novel result, showing the weak cosmic censorship and hence the future asymptotically simple structure of spacetime, is being validated by the nature of gravity, without imposing any extra constraint on the form of matter.

  7. Weak, strong, and uniform quantum simulations

    Science.gov (United States)

    Wang, Dong-Sheng

    2015-01-01

    In this work, we introduce different types of quantum simulations according to different operator topologies on a Hilbert space, namely, uniform, strong, and weak quantum simulations. We show that they have the same computational power that the efficiently solvable problems are in bounded-error quantum polynomial time. For the weak simulation, we formalize a general weak quantum simulation problem and construct an algorithm which is valid for all instances. Also, we analyze the computational power of quantum simulations by proving the query lower bound for simulating a general quantum process.

  8. Structural features of sequential weak measurements

    Science.gov (United States)

    Diósi, Lajos

    2016-07-01

    We discuss the abstract structure of sequential weak measurement (WM) of general observables. In all orders, the sequential WM correlations without postselection yield the corresponding correlations of the Wigner function, offering direct quantum tomography through the moments of the canonical variables. Correlations in spin-1/2 sequential weak measurements coincide with those in strong measurements, they are constrained kinematically, and they are equivalent with single measurements. In sequential WMs with postselection, an anomaly occurs, different from the weak value anomaly of single WMs. In particular, the spread of polarization σ ̂ as measured in double WMs of σ ̂ will diverge for certain orthogonal pre- and postselected states.

  9. Weak Gauge Boson Radiation in Parton Showers

    CERN Document Server

    Christiansen, Jesper Roy

    2014-01-01

    The emission of W and Z gauge boson is included in a traditional QCD + QED shower. The unitarity of the shower algorithm links the real radiation of the weak gauge bosons to the negative weak virtual corrections. The shower evolution process leads to a competition between QCD, QED and weak radiation, and allows for W and Z boson production inside jets. Various effects on LHC physics are studied, both at low and high transverse momenta, and effects at higher-energy hadron colliders are outlined.

  10. Weak network efficiency in young children with Autism Spectrum Disorder: Evidence from a functional near-infrared spectroscopy study.

    Science.gov (United States)

    Li, Yanwei; Yu, Dongchuan

    2016-10-01

    Functional near infrared spectroscopy (fNIRS) is particularly suited for the young population and ecological measurement. However, thus far, not enough effort has been given to the clinical diagnosis of young children with Autism Spectrum Disorder (ASD) by using fNIRS. The current study provided some insights into the quantitative analysis of functional networks in young children (ages 4.8-8.0years old) with and without ASD and, in particular, investigated the network efficiency and lobe-level connectivity of their functional networks while watching a cartoon. The main results included that: (i) Weak network efficiency was observed in young children with ASD, even for a wide range of threshold for the binarization of functional networks; (ii) A maximum classification accuracy rate of 83.3% was obtained for all participants by using the k-means clustering method with network efficiencies as the feature parameters; and (iii) Weak lobe-level inter-region connections were uncovered in the right prefrontal cortex, including its linkages with the left prefrontal cortex and the bilateral temporal cortex. Such results indicate that the right prefrontal cortex might make a major contribution to the psychopathology of young children with ASD at the functional network architecture level, and at the functional lobe-connectivity level, respectively.

  11. Tonotopic organization of human auditory association cortex.

    Science.gov (United States)

    Cansino, S; Williamson, S J; Karron, D

    1994-11-07

    Neuromagnetic studies of responses in human auditory association cortex for tone burst stimuli provide evidence for a tonotopic organization. The magnetic source image for the 100 ms component evoked by the onset of a tone is qualitatively similar to that of primary cortex, with responses lying deeper beneath the scalp for progressively higher tone frequencies. However, the tonotopic sequence of association cortex in three subjects is found largely within the superior temporal sulcus, although in the right hemisphere of one subject some sources may be closer to the inferior temporal sulcus. The locus of responses for individual subjects suggests a progression across the cortical surface that is approximately proportional to the logarithm of the tone frequency, as observed previously for primary cortex, with the span of 10 mm for each decade in frequency being comparable for the two areas.

  12. Where does TMS Stimulate the Motor Cortex?

    DEFF Research Database (Denmark)

    Bungert, Andreas; Antunes, André; Espenhahn, Svenja;

    2016-01-01

    Much of our knowledge on the physiological mechanisms of transcranial magnetic stimulation (TMS) stems from studies which targeted the human motor cortex. However, it is still unclear which part of the motor cortex is predominantly affected by TMS. Considering that the motor cortex consists...... of functionally and histologically distinct subareas, this also renders the hypotheses on the physiological TMS effects uncertain. We use the finite element method (FEM) and magnetic resonance image-based individual head models to get realistic estimates of the electric field induced by TMS. The field changes...... in different subparts of the motor cortex are compared with electrophysiological threshold changes of 2 hand muscles when systematically varying the coil orientation in measurements. We demonstrate that TMS stimulates the region around the gyral crown and that the maximal electric field strength in this region...

  13. Weak layer fracture: facets and depth hoar

    Directory of Open Access Journals (Sweden)

    I. Reiweger

    2013-05-01

    Full Text Available Understanding the fracture behavior of weak snow layers is essential for modeling and predicting dry-snow slab avalanches. We therefore performed laboratory experiments with snow samples containing a weak layer consisting of either faceted crystals or depth hoar. During these experiments the samples were loaded with different loading rates and at various tilt angles until fracture. The strength of the samples decreased with increasing loading rate and increasing tilt angle. Additionally, we took pictures of the side of the samples with a high-speed video camera and calculated the displacement using a particle image velocimetry (PIV algorithm. The fracture process within the weak layer could thus be studied in detail. We found a fracture in shear immediately followed by a collapse of the weak layer.

  14. Weak Markov Processes as Linear Systems

    CERN Document Server

    Gohm, Rolf

    2012-01-01

    A noncommutative Fornasini-Marchesini system (a multi-variable version of a linear system) can be realized within a weak Markov process (a model for quantum evolution). For a discrete time parameter this is worked out systematically as a theory of representations of structure maps of a system by a weak process. We introduce subprocesses and quotient processes which can be described naturally by a suitable category of weak processes. A corresponding notion of cascade for processes induces a represented cascade of systems. We study the control theoretic notion of observability which turns out to be particularly interesting in connection with a cascade structure. As an application we gain new insights into stationary Markov chains where observability for the system is closely related to asymptotic completeness in the scattering theory of the chain. This motivates a general definition of asymptotic completeness in the category of weak processes.

  15. Weak Lensing Simulations for the SKA

    CERN Document Server

    Patel, Prina; Makhathini, Sphesihle; Abdalla, Filipe; Bacon, David; Brown, Michael L; Heywood, Ian; Jarvis, Matt; Smirnov, Oleg

    2015-01-01

    Weak gravitational lensing measurements are traditionally made at optical wavelengths where many highly resolved galaxy images are readily available. However, the Square Kilometre Array (SKA) holds great promise for this type of measurement at radio wavelengths owing to its greatly increased sensitivity and resolution over typical radio surveys. The key to successful weak lensing experiments is in measuring the shapes of detected sources to high accuracy. In this document we describe a simulation pipeline designed to simulate radio images of the quality required for weak lensing, and will be typical of SKA observations. We provide as input, images with realistic galaxy shapes which are then simulated to produce images as they would have been observed with a given radio interferometer. We exploit this pipeline to investigate various stages of a weak lensing experiment in order to better understand the effects that may impact shape measurement. We first show how the proposed SKA1-Mid array configurations perfor...

  16. Vibration diagnostics of weak base embankments

    Institute of Scientific and Technical Information of China (English)

    Evgenij Ashpiz; Vladimir Kapustin; Svetlana Klepikova; Maxim Shirobokov

    2013-01-01

    In this paper the theoretical background was analyzed for vibration diagnostics method and experience in its application for weak base embankments. General schemes of survey and recommendations on hardware systems and further prospective development are outlined.

  17. Weak entropy inequalities and entropic convergence

    Institute of Scientific and Technical Information of China (English)

    GAO FuQing; LI LiNa

    2008-01-01

    A criterion for algebraic convergence of the entropy is presented and an algebraic convergence result for the entropy of an exclusion process is improved.A weak entropy inequality is considered and its relationship to entropic convergence is discussed.

  18. Weak entropy inequalities and entropic convergence

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    A criterion for algebraic convergence of the entropy is presented and an algebraic convergence result for the entropy of an exclusion process is improved. A weak entropy inequality is considered and its relationship to entropic convergence is discussed.

  19. The Sloan Nearby Cluster Weak Lensing Survey

    CERN Document Server

    Kubo, Jeffrey M; Hardin, Frances Mei; Kubik, Donna; Lawhorn, Kelsey; Lin, Huan; Nicklaus, Liana; Nelson, Dylan; Reis, Ribamar R R; Seo, Hee-Jong; Soares-Santos, Marcelle; Stebbins, Albert; Yunker, Tony

    2009-01-01

    We describe and present initial results of a weak lensing survey of nearby ($\\rm{z}\\lesssim0.1$) galaxy clusters in the Sloan Digital Sky Survey (SDSS). In this first study, galaxy clusters are selected from the SDSS spectroscopic galaxy cluster catalogs of \\citet{miller05} and \\citet{berlind06}. We report a total of seven individual low redshift cluster weak lensing measurements which include: A2048, A1767, A2244, A1066, A2199, and two clusters specifically identified with the C4 algorithm. Our program of weak lensing of nearby galaxy clusters in the SDSS will eventually reach $\\sim 200$ clusters, making it the largest weak lensing survey of individual galaxy clusters to date.

  20. Food related processes in the insular cortex

    Directory of Open Access Journals (Sweden)

    Sabine eFrank

    2013-08-01

    Full Text Available The insular cortex is a multimodal brain region with regional cytoarchitectonic differences indicating various functional specializations. As a multisensory neural node, the insular cortex integrates perception, emotion, interoceptive awareness, cognition, and gustation. Regarding the latter, predominantly the anterior part of the insular cortex is regarded as the primary taste cortex.In this review, we will specifically focus on the involvement of the insula in food processing and on multimodal integration of food-related items. Influencing factors of insular activation elicited by various foods range from calorie-content to the internal physiologic state, body mass index or eating behavior. Sensory perception of food-related stimuli including seeing, smelling, and tasting elicits increased activation in the anterior and mid-dorsal part of the insular cortex. Apart from the pure sensory gustatory processing, there is also a strong association with the rewarding/hedonic aspects of food items, which is reflected in higher insular activity and stronger connections to other reward-related areas. Interestingly, the processing of food items has been found to elicit different insular activation in lean compared to obese subjects and in patients suffering from an eating disorder (anorexia nervosa, bulimia nervosa. The knowledge of functional differences in the insular cortex opens up the opportunity for possible noninvasive treatment approaches for obesity and eating disorders. To target brain functions directly, real-time functional magnetic resonance imaging neurofeedback offers a state-of-the-art tool to learn to control the anterior insular cortex activity voluntarily. First evidence indicates that obese adults have an enhanced ability to regulate the anterior insular cortex.

  1. Motor Cortex Stimulation in Parkinson's Disease

    OpenAIRE

    Marisa De Rose; Giusy Guzzi; Domenico Bosco; Mary Romano; Serena Marianna Lavano; Massimiliano Plastino; Giorgio Volpentesta; Rosa Marotta; Angelo Lavano

    2012-01-01

    Motor Cortex Stimulation (MCS) is less efficacious than Deep Brain Stimulation (DBS) in Parkinson's disease. However, it might be proposed to patients excluded from DBS or unresponsive to DBS. Ten patients with advanced PD underwent unilateral MCS contralaterally to the worst clinical side. A plate electrode was positioned over the motor cortex in the epidural space through single burr hole after identification of the area with neuronavigation and neurophysiological tests. Clinical assessment...

  2. Electromagnetic and Weak transitions in light nuclei

    Energy Technology Data Exchange (ETDEWEB)

    M. Viviani; L.E. Marcucci; A. Kievsky; S. Rosati; R. Schiavilla

    2002-09-01

    Recent advances in the study of the p -- d radiative and mu -- {sup 3}He weak capture processes by our group are presented and discussed. The trinucleon bound and scattering states have been obtained from variational calculations by expanding the corresponding wave functions in terms of correlated hyper-spherical harmonic functions. The electromagnetic and weak transition currents include one- and two-body operators. The accuracy achieved in these calculations allows for interesting comparisons with experimental data.

  3. Model reduction of strong-weak neurons

    OpenAIRE

    Steven James Cox; Bosen eDu; Danny eSorensen

    2014-01-01

    We consider neurons with large dendritic trees that are weakly excitable in the sense that back propagating action potentials are severly attenuated as they travel from the small, strongly excitable, spike initiation zone. In previous work we have shown that the computational size of weakly excitable cell models may be reduced by two or more orders of magnitude, and that the size of strongly excitable models may be reduced by at least one order of magnitude, without sacrificing the spatio–tem...

  4. Agile Software Methodologies: Strength and Weakness

    OpenAIRE

    Dr. Adel Hamdan Mohammad; Dr. Tariq Alwada’n; Dr. Jafar "M.Ali" Ababneh

    2013-01-01

    Agile methodologies are great software development methodologies. No doubt that these methodologies have widespread reputation. The core of agile methodologies is people. Customer and each team member in agiledevelopment teams are the key success or failure factor in agile process. In this paper authors demonstrate strength and weakness points in agile methodologies. Also authors demonstrate how strength and weakness factors can affect the overall results of agile development process.

  5. Weak measurement and the traversal time problem

    OpenAIRE

    Iannaccone, G.

    1996-01-01

    The theory of weak measurement, proposed by Aharonov and coworkers, has been applied by Steinberg to the long-discussed traversal time problem. The uncertainty and ambiguity that characterize this concept from the perspective of von Neumann measurement theory apparently vanish, and joint probabilities and conditional averages become meaningful concepts. We express the Larmor clock and some other well-known methods in the weak measurement formalism. We also propose a method to determine higher...

  6. Drift waves in a weakly ionized plasma

    DEFF Research Database (Denmark)

    Popovic, M.; Melchior, H.

    1968-01-01

    A dispersion relation for low frequency drift waves in a weakly ionized plasma has been derived, and through numerical calculations the effect of collisions between the charged and the neutral particles is estimated.......A dispersion relation for low frequency drift waves in a weakly ionized plasma has been derived, and through numerical calculations the effect of collisions between the charged and the neutral particles is estimated....

  7. [Investigation on chemical constituents of processed products of Eucommiae Cortex].

    Science.gov (United States)

    Tao, Yi; Sheng, Chen; Li, Wei-dong; Cai, Bao-chang; Lu, Tu-lin

    2014-11-01

    According to the 2010 Chinese pharmacopeia, salt processed and charcoal processed Eucommiae Cortex were pre- pared. HPLC-DAD analysis of the content of the bark and leaf of Eucommiae Cortex showed that the bark of Eucommiae Cortex mainly contained lignans such as pinoresinol glucose and iridoid including genipin, geniposide, geniposidic acid, while the leaf of Eucommiae Cortex consisted of flavonoids such as quercetin and phenolic compound such as chlorogenic acid. The content of pinoresinol diglucoside in the bark of Eucommiae Cortex was about 18 times more than that in the leaf of Eucommiae Cortex. The content of pinoresinol diglucoside in salted and charcoal processed Eucommiae Cortex decreased approximately by 30% and 85%, respectively. The content of genipin, geniposide and geniposidic acid in the bark of Eucommiae Cortex was about 3 times, 23 times, 28 times more than that in the leaf of Eucommiae Cortex. The content of genipin, geniposide and geniposidic acid in salted Eucommiae Cortex were reduced by 25%, 40% and 40%, respectively. The content of genipin, geniposide and geniposidic acid in charcoal processed Eucommiae Cortex were reduced by 98%, 70%, 70%, respectively. The content of caffeic acid in bark of Eucommiae Cortex was about 3 times more than that in the leaf of Eucommiae Cortex. The content of caffeic acid was decreased by about 50% in the salted Eucommiae Cortex. While the content of caffeic acid in charcoal processed Eucommiae Cortex was decreased approximately 75%; the content of chlorogenic acid in bark of Eucommiae Cortex was about 1/6 of that in the leaf of Eucommiae Cortex. The content of chlorogenic acid in salted and charcoal processed Eucommiae Cortex decreased by 40% and 75%, respectively; the content of quercetin in bark of Eucommiae Cortex was only 1/40 of that in the leaf of Eucommiae Cortex. The content of quercetin in salted and charcoal processed Eucommiae Cortex were reduced by 60% and 50%, respectively.

  8. The adrenal cortex and life.

    Science.gov (United States)

    Vinson, Gavin P

    2009-03-05

    The template for our understanding of the physiological role of the adrenal cortex was set by Hans Selye, who demonstrated its key involvement in the response to stress, of whatever origin, and who also introduced the terms glucocorticoid and mineralocorticoid. Despite this, from the late 1940s on there was certainly general awareness of the multiple actions of glucocorticoids, including effects on the thymus and immune system, cardiovascular system, water balance, and the CNS. For these reasons, and perhaps because in the early studies of the actions of individual steroids there was less clear-cut difference between them, there was some initial resistance to the use of these terms. Today they are universal and unchallenged. It can be argued that, with respect to the glucocorticoids, this term colours our perception of their physiological importance, and may be misleading. By taking evidence from disease states, emphasis is placed on extreme conditions that do not necessarily reveal normal physiology. In particular, evidence for the role of glucocorticoid regulation of gluconeogenesis and blood glucose in the normal subject or animal is inconclusive. Similarly, while highly plausible theories explaining glucocorticoid actions on inflammation or the immune system as part of normal physiology have been presented, direct evidence to support them is hard to find. Under extreme conditions of chronic stress, the cumulative actions of glucocorticoids on insulin resistance or immunocompromise may indeed seem to be actually damaging. Two well-documented and long recognized situations create huge variation in glucocorticoid secretion. These are the circadian rhythm, and the acute response to mild stress, such as handling, in the rat. Neither of these can be adequately explained by the need for glucocorticoid action, as we currently understand it, particularly on carbohydrate metabolism or on the immune system. Perhaps we should re-examine other targets at the physiological

  9. [Antimicrobial susceptibility in Chile 2012].

    Science.gov (United States)

    Cifuentes-D, Marcela; Silva, Francisco; García, Patricia; Bello, Helia; Briceño, Isabel; Calvo-A, Mario; Labarca, Jaime

    2014-04-01

    Bacteria antimicrobial resistance is an uncontrolled public health problem that progressively increases its magnitude and complexity. The Grupo Colaborativo de Resistencia, formed by a join of experts that represent 39 Chilean health institutions has been concerned with bacteria antimicrobial susceptibility in our country since 2008. In this document we present in vitro bacterial susceptibility accumulated during year 2012 belonging to 28 national health institutions that represent about 36% of hospital discharges in Chile. We consider of major importance to report periodically bacteria susceptibility so to keep the medical community updated to achieve target the empirical antimicrobial therapies and the control measures and prevention of the dissemination of multiresistant strains.

  10. The Role of Human Parietal Cortex in Attention Networks

    Science.gov (United States)

    Han, Shihui; Jiang, Yi; Gu, Hua; Rao, Hengyi; Mao, Lihua; Cui, Yong; Zhai, Renyou

    2004-01-01

    The parietal cortex has been proposed as part of the neural network for guiding spatial attention. However, it is unclear to what degree the parietal cortex contributes to the attentional modulations of activities of the visual cortex and the engagement of the frontal cortex in the attention network. We recorded behavioural performance and…

  11. Neuregulin 1/ErbB4 enhances synchronized oscillations of prefrontal cortex neurons via inhibitory synapses.

    Science.gov (United States)

    Hou, X-J; Ni, K-M; Yang, J-M; Li, X-M

    2014-03-07

    Both neuregulin 1 (NRG1) and its receptor ErbB4 are susceptibility genes for schizophrenia. Reduced synchronization of evoked oscillations in several cortical regions, especially in the prefrontal cortex, is associated with the core symptoms of schizophrenia. Recent studies have reported that NRG1 may affect the hippocampal oscillations. However, the role of NRG1/ErbB4 signaling in the synchronization of neurons in the prefrontal cortex is unclear. Here, we found that NRG1 enhanced the synchrony of pyramidal neurons via presynaptic interneurons. Meanwhile, NRG1 also increased the synchrony between pairs of fast-spiking interneurons and pairs of fast-spiking and non-fast-spiking interneurons in the prefrontal cortex, and this effect was mediated by ErbB4 receptors. Moreover, the NRG1-enhanced synchrony of interneurons was through their mutually-inhibitory synapses but not electrical coupling. Furthermore, kainate-induced gamma oscillations in vivo were enhanced by NRG1 and did not change in Dlx5/6-ErbB4(-/-) mice in which the ErbB4 receptors were specifically knocked out in interneurons of the frontal brain. Overall, our findings suggested that NRG1/ErbB4 signaling plays an important role in the synchronized oscillations of the whole network in the prefrontal cortex that are impaired in schizophrenia.

  12. Serological Characterization and Antimicrobial Susceptibility ...

    African Journals Online (AJOL)

    300L Coordinator

    identified and antibiotic susceptibility test was performed using standard procedures. The total .... serotypes and their antimicrobial resistivity patterns from patients ..... the best of our knowledge). ... Testing of Bacterial Pathogens of Public.

  13. Enhancing QKD security with weak measurements

    Science.gov (United States)

    Farinholt, Jacob M.; Troupe, James E.

    2016-10-01

    Publisher's Note: This paper, originally published on 10/24/2016, was replaced with a corrected/revised version on 11/8/2016. If you downloaded the original PDF but are unable to access the revision, please contact SPIE Digital Library Customer Service for assistance. In the late 1980s, Aharonov and colleagues developed the notion of a weak measurement of a quantum observable that does not appreciably disturb the system.1, 2 The measurement results are conditioned on both the pre-selected and post-selected state of the quantum system. While any one measurement reveals very little information, by making the same measurement on a large ensemble of identically prepared pre- and post-selected (PPS) states and averaging the results, one may obtain what is known as the weak value of the observable with respect to that PPS ensemble. Recently, weak measurements have been proposed as a method of assessing the security of QKD in the well-known BB84 protocol.3 This weak value augmented QKD protocol (WV-QKD) works by additionally requiring the receiver, Bob, to make a weak measurement of a particular observable prior to his strong measurement. For the subset of measurement results in which Alice and Bob's measurement bases do not agree, the weak measurement results can be used to detect any attempt by an eavesdropper, Eve, to correlate her measurement results with Bob's. Furthermore, the well-known detector blinding attacks, which are known to perfectly correlate Eve's results with Bob's without being caught by conventional BB84 implementations, actually make the eavesdropper more visible in the new WV-QKD protocol. In this paper, we will introduce the WV-QKD protocol and discuss its generalization to the 6-state single qubit protocol. We will discuss the types of weak measurements that are optimal for this protocol, and compare the predicted performance of the 6- and 4-state WV-QKD protocols.

  14. SIMULATION OF SUBGRADE EMBANKMENT ON WEAK BASE

    Directory of Open Access Journals (Sweden)

    V. D. Petrenko

    2015-08-01

    Full Text Available Purpose. This article provides: the question of the sustainability of the subgrade on a weak base is considered in the paper. It is proposed to use the method of jet grouting. Investigation of the possibility of a weak base has an effect on the overall deformation of the subgrade; the identification and optimization of the parameters of subgrade based on studies using numerical simulation. Methodology. The theoretical studies of the stress-strain state of the base and subgrade embankment by modeling in the software package LIRA have been conducted to achieve this goal. Findings. After making the necessary calculations perform building fields of a subsidence, borders cramped thickness, bed’s coefficients of Pasternak and Winkler. The diagrams construction of vertical stress performs at any point of load application. Also, using the software system may perform peer review subsidence, rolls railroad tracks in natural and consolidated basis. Originality. For weak soils is the most appropriate nonlinear model of the base with the existing areas of both elastic and limit equilibrium, mixed problem of the theory of elasticity and plasticity. Practical value. By increasing the load on the weak base as a result of the second track construction, adds embankment or increasing axial load when changing the rolling stock process of sedimentation and consolidation may continue again. Therefore, one of the feasible and promising options for the design and reconstruction of embankments on weak bases is to strengthen the bases with the help of jet grouting. With the expansion of the railway infrastructure, increasing speed and weight of the rolling stock is necessary to ensure the stability of the subgrade on weak bases. LIRA software package allows you to perform all the necessary calculations for the selection of a proper way of strengthening weak bases.

  15. Genetic diversity and disease susceptibility.

    OpenAIRE

    Bodmer, W F

    1997-01-01

    The range of genetic diversity within human populations is enormous. Genetic susceptibility to common chronic disease is a significant part of this genetic diversity, which also includes a variety of rare clear-cut inherited diseases. Modern DNA-based genomic analysis can now routinely lead to the identification of genes involved in disease susceptibility, provides the basis for genetic counselling in affected families, and more widely for a genetically targeted approach to disease prevention...

  16. Perirhinal cortex and temporal lobe epilepsy

    Directory of Open Access Journals (Sweden)

    Giuseppe eBiagini

    2013-08-01

    Full Text Available The perirhinal cortex – which is interconnected with several limbic structures and is intimately involved in learning and memory - plays major roles in pathological processes such as the kindling phenomenon of epileptogenesis and the spread of limbic seizures. Both features may be relevant to the pathophysiology of mesial temporal lobe epilepsy that represents the most refractory adult form of epilepsy with up to 30% of patients not achieving adequate seizure control. Compared to other limbic structures such as the hippocampus or the entorhinal cortex, the perirhinal area remains understudied and, in particular, detailed information on its dysfunctional characteristics remains scarce; this lack of information may be due to the fact that the perirhinal cortex is not grossly damaged in mesial temporal lobe epilepsy and in models mimicking this epileptic disorder. However, we have recently identified in pilocarpine-treated epileptic rats the presence of selective losses of interneuron subtypes along with increased synaptic excitability. In this review we: (i highlight the fundamental electrophysiological properties of perirhinal cortex neurons; (ii briefly stress the mechanisms underlying epileptiform synchronization in perirhinal cortex networks following epileptogenic pharmacological manipulations; and (iii focus on the changes in neuronal excitability and cytoarchitecture of the perirhinal cortex occurring in the pilocarpine model of mesial temporal lobe epilepsy. Overall, these data indicate that perirhinal cortex networks are hyperexcitable in an animal model of temporal lobe epilepsy, and that this condition is associated with a selective cellular damage that is characterized by an age-dependent sensitivity of interneurons to precipitating injuries, such as status epilepticus.

  17. Age-Related Deterioration of Perineuronal Nets in the Primary Auditory Cortex of Mice

    Directory of Open Access Journals (Sweden)

    Dustin H Brewton

    2016-11-01

    Full Text Available Age-related changes in inhibitory neurotransmission in sensory cortex may underlie deficits in sensory function. Perineuronal nets (PNNs are extracellular matrix components that ensheath some inhibitory neurons, particularly parvalbumin positive (PV+ interneurons. PNNs may protect PV+ cells from oxidative stress and help establish their rapid spiking properties. Although PNN expression has been well characterized during development, possible changes in aging sensory cortex have not been investigated. Here we tested the hypothesis that PNN+, PV+ and PV/PNN co-localized cell densities decline with age in the primary auditory cortex (A1. This hypothesis was tested using immunohistochemistry in two strains of mice (C57BL/6 and CBA/CaJ with different susceptibility to age-related hearing loss and at three different age ranges (1-3, 6-8 and 14-24 months old. We report that PNN+ and PV/PNN co-localized cell densities decline significantly with age in A1 in both mouse strains. In the PNN+ cells that remain in the old group, the intensity of PNN staining is reduced in the C57 strain, but not the CBA strain. PV+ cell density also declines only in the C57, but not the CBA, mouse suggesting a potential exacerbation of age-effects by hearing loss in the PV/PNN system. Taken together, these data suggest that PNN deterioration may be a key component of altered inhibition in the aging sensory cortex, that may lead to altered synaptic function, susceptibility to oxidative stress and processing deficits.

  18. Experimental noiseless linear amplification using weak measurements

    Science.gov (United States)

    Ho, Joseph; Boston, Allen; Palsson, Matthew; Pryde, Geoff

    2016-09-01

    The viability of quantum communication schemes rely on sending quantum states of light over long distances. However, transmission loss can degrade the signal strength, adding noise. Heralded noiseless amplification of a quantum signal can provide a solution by enabling longer direct transmission distances and by enabling entanglement distillation. The central idea of heralded noiseless amplification—a conditional modification of the probability distribution over photon number of an optical quantum state—is suggestive of a parallel with weak measurement: in a weak measurement, learning partial information about an observable leads to a conditional back-action of a commensurate size. Here we experimentally investigate the application of weak, or variable-strength, measurements to the task of heralded amplification, by using a quantum logic gate to weakly couple a small single-optical-mode quantum state (the signal) to an ancilla photon (the meter). The weak measurement is carried out by choosing the measurement basis of the meter photon and, by conditioning on the meter outcomes, the signal is amplified. We characterise the gain of the amplifier as a function of the measurement strength, and use interferometric methods to show that the operation preserves the coherence of the signal.

  19. Weak crystallization theory of metallic alloys

    Science.gov (United States)

    Martin, Ivar; Gopalakrishnan, Sarang; Demler, Eugene A.

    2016-06-01

    Crystallization is one of the most familiar, but hardest to analyze, phase transitions. The principal reason is that crystallization typically occurs via a strongly first-order phase transition, and thus rigorous treatment would require comparing energies of an infinite number of possible crystalline states with the energy of liquid. A great simplification occurs when crystallization transition happens to be weakly first order. In this case, weak crystallization theory, based on unbiased Ginzburg-Landau expansion, can be applied. Even beyond its strict range of validity, it has been a useful qualitative tool for understanding crystallization. In its standard form, however, weak crystallization theory cannot explain the existence of a majority of observed crystalline and quasicrystalline states. Here we extend the weak crystallization theory to the case of metallic alloys. We identify a singular effect of itinerant electrons on the form of weak crystallization free energy. It is geometric in nature, generating strong dependence of free energy on the angles between ordering wave vectors of ionic density. That leads to stabilization of fcc, rhombohedral, and icosahedral quasicrystalline (iQC) phases, which are absent in the generic theory with only local interactions. As an application, we find the condition for stability of iQC that is consistent with the Hume-Rothery rules known empirically for the majority of stable iQC; namely, the length of the primary Bragg-peak wave vector is approximately equal to the diameter of the Fermi sphere.

  20. Weak KAM theory for a weakly coupled system of Hamilton–Jacobi equations

    KAUST Repository

    Figalli, Alessio

    2016-06-23

    Here, we extend the weak KAM and Aubry–Mather theories to optimal switching problems. We consider three issues: the analysis of the calculus of variations problem, the study of a generalized weak KAM theorem for solutions of weakly coupled systems of Hamilton–Jacobi equations, and the long-time behavior of time-dependent systems. We prove the existence and regularity of action minimizers, obtain necessary conditions for minimality, extend Fathi’s weak KAM theorem, and describe the asymptotic limit of the generalized Lax–Oleinik semigroup. © 2016, Springer-Verlag Berlin Heidelberg.

  1. Antimicrobial susceptibility and susceptibility testing of Mycoplasma hominis: a review.

    Science.gov (United States)

    Bygdeman, S M; Mårdh, P A

    1983-01-01

    The determination of the minimal growth-inhibiting concentration (MIC), the minimal metabolism-inhibiting concentration (MMC), and the minimal mycoplasmacidal concentration (MCC) of various antimicrobial compounds for Mycoplasma hominis is influenced by the pH of the test media, the inoculum size, and the incubation time, although each of these factors generally do not affect the minimal concentration more than fourfold. M. hominis is resistant to beta-lactam antibiotics, vancomycin, sulfonamides, trimethoprim, and polymyxin B. There are great differences in the susceptibility of M. hominis to various macrolide antibiotics. Thus the organism is resistant to erythromycin and oleandomycin, moderately resistant to tylosin and spiramycin, susceptible to josamycin as well as to another macrolide drug, labelled M-4365G. M. hominis is also highly susceptible to the macrolide-like compound rosaramicin and to the tetracyclines (although resistant strains occur). It is susceptible to lincomycin and clindamycin, and moderately susceptible to chloramphenicol and rifampicin. The aminoglycosides have limited activity against M. hominis.

  2. Optical response of a quantum dot-metal nanoparticle hybrid interacting with a weak probe field.

    Science.gov (United States)

    Kosionis, Spyridon G; Terzis, Andreas F; Sadeghi, Seyed M; Paspalakis, Emmanuel

    2013-01-30

    We study optical effects in a hybrid system composed of a semiconductor quantum dot and a spherical metal nanoparticle that interacts with a weak probe electromagnetic field. We use modified nonlinear density matrix equations for the description of the optical properties of the system and obtain a closed-form expression for the linear susceptibilities of the quantum dot, the metal nanoparticle, and the total system. We then investigate the dependence of the susceptibility on the interparticle distance as well as on the material parameters of the hybrid system. We find that the susceptibility of the quantum dot exhibits optical transparency for specific frequencies. In addition, we show that there is a range of frequencies of the applied field for which the susceptibility of the semiconductor quantum dot leads to gain. This suggests that in such a hybrid system quantum coherence can reverse the course of energy transfer, allowing flow of energy from the metallic nanoparticle to the quantum dot. We also explore the susceptibility of the metal nanoparticle and show that it is strongly influenced by the presence of the quantum dot.

  3. Weak layer fracture: facets and depth hoar

    Directory of Open Access Journals (Sweden)

    I. Reiweger

    2013-09-01

    Full Text Available Understanding failure initiation within weak snow layers is essential for modeling and predicting dry-snow slab avalanches. We therefore performed laboratory experiments with snow samples containing a weak layer consisting of either faceted crystals or depth hoar. During these experiments the samples were loaded with different loading rates and at various tilt angles until fracture. The strength of the samples decreased with increasing loading rate and increasing tilt angle. Additionally, we took pictures of the side of four samples with a high-speed video camera and calculated the displacement using a particle image velocimetry (PIV algorithm. The fracture process within the weak layer could thus be observed in detail. Catastrophic failure started due to a shear fracture just above the interface between the depth hoar layer and the underlying crust.

  4. Weakly isolated horizon information loss paradox

    CERN Document Server

    Chen, Ge-Rui

    2014-01-01

    In this paper we investigate the information loss paradox of weakly isolated horizon(WIH) based on the Parikh and Wilczek's tunneling spectrum. We find that there are correlations among Hawking radiations from weakly isolated horizon, the information can be carried out in terms of correlations between sequential emissions, and the radiation is an entropy conservation process. We generalize Refs.[11-13]' results to a more general spacetime. Through revisiting the calculation of tunneling of weakly isolated horizon, we find that Ref.[12]'s requirement that radiating particles have the same angular momenta of unit mass as that of black hole is not needed, and the energy and angular momenta of emitting particles are very arbitrary, which should be restricted only by keeping the cosmic censorship of black hole.

  5. Revealed Quantum Information in Weak Interaction Processes

    CERN Document Server

    Hiesmayr, B C

    2014-01-01

    We analyze the achievable limits of the quantum information processing of the weak interaction revealed by hyperons with spin. We find that the weak decay process corresponds to an interferometric device with a fixed visibility and fixed phase difference for each hyperon. Nature chooses rather low visibilities expressing a preference to parity conserving or violating processes (except for the decay $\\Sigma^+\\longrightarrow p \\pi^0$). The decay process can be considered as an open quantum channel that carries the information of the hyperon spin to the angular distribution of the momentum of the daughter particles. We find a simple geometrical information theoretic interpretation of this process: two quantization axes are chosen spontaneously with probabilities $\\frac{1\\pm\\alpha}{2}$ where $\\alpha$ is proportional to the visibility times the real part of the phase shift. Differently stated the weak interaction process corresponds to spin measurements with an imperfect Stern-Gerlach apparatus. Equipped with this...

  6. Respiratory muscle weakness in peripheral neuropathies.

    Science.gov (United States)

    Burakgazi, Ahmet Z; Höke, Ahmet

    2010-12-01

    Common peripheral neuropathies do not usually cause diaphragmatic weakness and subsequent respiratory compromise. However, respiratory involvement is relatively common in Guillain-Barré syndrome (GBS). Experience in GBS has led to a standardized approach to manage respiratory problems in peripheral neuropathies. Diaphragmatic weakness is not common in chronic inflammatory demyelinating polyneuropathy and extremely rare in multifocal motor neuropathy. The linkage has been described between certain subtypes of Charcot-Marie-Tooth (CMT) disease such as CMT2C and CMT4B1 and diaphragmatic weakness. A correlation usually has not been found between electrophysiologic findings and clinical respiratory signs or spirometric abnormalities in peripheral neuropathies except in amplitudes of evoked phrenic nerve responses. Careful and frequent assessment of respiratory function by a qualified team of healthcare professionals and physicians is essential. Criteria established for mechanical ventilation in GBS cases may be applied to other peripheral neuropathies with respiratory compromise as necessary.

  7. Evidence for a Lattice Weak Gravity Conjecture

    CERN Document Server

    Heidenreich, Ben; Rudelius, Tom

    2016-01-01

    The Weak Gravity Conjecture postulates the existence of superextremal charged particles, i.e. those with mass smaller than or equal to their charge in Planck units. We present further evidence for our recent observation that in known examples a much stronger statement is true: an infinite tower of superextremal particles of different charges exists. We show that effective Kaluza-Klein field theories and perturbative string vacua respect the Sublattice Weak Gravity Conjecture, namely that a finite index sublattice of the full charge lattice exists with a superextremal particle at each site. In perturbative string theory we show that this follows from modular invariance. However, we present counterexamples to the stronger possibility that a superextremal state exists at every lattice site, including an example in which the lightest charged state is subextremal. The Sublattice Weak Gravity Conjecture has many implications both for abstract theories of quantum gravity and for real-world physics. For instance, it ...

  8. Weak lensing in the Dark Energy Survey

    Science.gov (United States)

    Troxel, Michael

    2016-03-01

    I will present the current status of weak lensing results from the Dark Energy Survey (DES). DES will survey 5000 square degrees in five photometric bands (grizY), and has already provided a competitive weak lensing catalog from Science Verification data covering just 3% of the final survey footprint. I will summarize the status of shear catalog production using observations from the first year of the survey and discuss recent weak lensing science results from DES. Finally, I will report on the outlook for future cosmological analyses in DES including the two-point cosmic shear correlation function and discuss challenges that DES and future surveys will face in achieving a control of systematics that allows us to take full advantage of the available statistical power of our shear catalogs.

  9. The strong side of weak topological insulators

    Science.gov (United States)

    Kraus, Yaacov; Ringel, Zohar; Stern, Ady

    2012-02-01

    Three-dimensional topological insulators are classified into ``strong'' (STI) and ``weak'' (WTI) according to the nature of their surface states. While the surface states of the STI are topologically protected, in the WTI they are believed to be very fragile to disorder. In this work we show that the WTI surface states are actually protected from any random perturbation which does not break time-reversal symmetry, and does not close the bulk energy gap. Consequently, the conductivity of metallic surfaces in the clean system will remain finite even in the presence of strong disorder of this type. In the weak disorder limit the surfaces are perfect metals, and strong surface disorder only acts to push them inwards. We find that WTI's differ from STI's primarily in their anisotropy, and that the anisotropy is not a sign of their weakness but rather of their richness.

  10. No-Hair Theorem for Weak Pulsar

    CERN Document Server

    Gruzinov, Andrei

    2015-01-01

    It is proposed that there exists a class of pulsars, called weak pulsars, for which the large-scale magnetosphere, and hence the gamma-ray emission, are independent of the detailed pattern of plasma production. The weak pulsar magnetosphere and its gamma-ray emission are uniquely determined by just three parameters: spin, dipole, and the spin-dipole angle. We calculate this supposedly unique pulsar magnetosphere in the axisymmetric case. The magnetosphere is found to be very close to (although interestingly not fully identical with) the magnetosphere we have previously calculated, explaining the phenomenological success of the old calculation. We offer only a highly tentative proof of this "Pulsar No-Hair Theorem". Our analytics, while convincing in its non-triviality, is incomplete, and counts only as a plausibility argument. Our numerics, while complete, is dubious. The plasma flow in the weak pulsar magnetosphere turns out to be even more intricate than what we have previously proposed: some particles, aft...

  11. Phase slips in superconducting weak links

    Energy Technology Data Exchange (ETDEWEB)

    Kimmel, Gregory; Glatz, Andreas; Aranson, Igor S.

    2017-01-01

    Superconducting vortices and phase slips are primary mechanisms of dissipation in superconducting, superfluid, and cold-atom systems. While the dynamics of vortices is fairly well described, phase slips occurring in quasi-one- dimensional superconducting wires still elude understanding. The main reason is that phase slips are strongly nonlinear time-dependent phenomena that cannot be cast in terms of small perturbations of the superconducting state. Here we study phase slips occurring in superconducting weak links. Thanks to partial suppression of superconductivity in weak links, we employ a weakly nonlinear approximation for dynamic phase slips. This approximation is not valid for homogeneous superconducting wires and slabs. Using the numerical solution of the time-dependent Ginzburg-Landau equation and bifurcation analysis of stationary solutions, we show that the onset of phase slips occurs via an infinite period bifurcation, which is manifested in a specific voltage-current dependence. Our analytical results are in good agreement with simulations.

  12. Motor cortex neuroplasticity following brachial plexus transfer

    Directory of Open Access Journals (Sweden)

    Stefan eDimou

    2013-08-01

    Full Text Available In the past decade, research has demonstrated that cortical plasticity, once thought only to exist in the early stages of life, does indeed continue on into adulthood. Brain plasticity is now acknowledged as a core principle of brain function and describes the ability of the central nervous system to adapt and modify its structural organization and function as an adaptive response to functional demand. In this clinical case study we describe how we used neuroimaging techniques to observe the functional topographical expansion of a patch of cortex along the sensorimotor cortex of a 27 year-old woman following brachial plexus transfer surgery to re-innervate her left arm. We found bilateral activations present in the thalamus, caudate, insula as well as across the sensorimotor cortex during an elbow flex motor task. In contrast we found less activity in the sensorimotor cortex for a finger tap motor task in addition to activations lateralised to the left inferior frontal gyrus and thalamus and bilaterally for the insula. From a pain perspective the patient who had experienced extensive phantom limb pain before surgery found these sensations were markedly reduced following transfer of the right brachial plexus to the intact left arm. Within the context of this clinical case the results suggest that functional improvements in limb mobility are associated with increased activation in the sensorimotor cortex as well as reduced phantom limb pain.

  13. [Prefrontal cortex in memory and attention processes].

    Science.gov (United States)

    Allegri, R F; Harris, P

    The role of the prefrontal cortex still remains poorly understood. Only after 1970, the functions of the frontal lobes have been conceptualized from different points of view (behaviorism, cognitivism). Recently,different parallel circuits connecting discrete cortical and subcortical regions of the frontal lobes have been described. Three of these circuits are the most relevant to understanding of behavior: the dorsolateral prefrontal circuit, that mediates executive behavior; the orbitofrontal prefrontal circuit, mediating social behavior, and the medial frontal circuit, involved in motivation. Damage to the frontal cortex impairs planning, problem solving, reasoning, concept formation, temporal ordering of stimuli, estimation, attention, memory search, maintaining information in working memory, associative learning,certain forms of skilled motor activities, image generation and manipulation of the spatial properties of a stimulus, metacognitive thinking, and social cognition. Several theories have been proposed to explain the functions of the prefrontal cortex. Currently,the most influential cognitive models are: the Norman and Shallice supervisory attentional system, involved in non-routine selection; the Baddeley working memory model with the central executive as a supervisory controlling system, in which impairment leads to a 'dysexecutive syndrome'; and the Grafman's model of managerial knowledge units, stored as macrostructured information in the frontal cortex. The prefrontal cortex is essential for attentional control, manipulation of stored knowledge and modulation of complex actions, cognition, emotion and behavior.

  14. Interpolation for weak Orlicz spaces with M_Δ condition

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    An interpolation theorem for weak Orlicz spaces generalized by N-functions satisfying MΔ condition is given. It is proved to be true for weak Orlicz martingale spaces by weak atomic decomposition of weak Hardy martingale spaces. And applying the interpolation theorem, we obtain some embedding relationships among weak Orlicz martingale spaces.

  15. Complex magnetic susceptibility setup for spectroscopy in the extremely low-frequency range

    NARCIS (Netherlands)

    Kuipers, B.W.M.; Bakelaar, I.A.; Klokkenburg, M.; Erne, B.H.

    2008-01-01

    A sensitive balanced differential transformer was built to measure complex initial parallel magnetic susceptibility spectra in the 0.01–1000 Hz range. The alternating magnetic field can be chosen sufficiently weak that the magnetic structure of the samples is only slightly perturbed and the low freq

  16. Weak Acid Ionization Constants and the Determination of Weak Acid-Weak Base Reaction Equilibrium Constants in the General Chemistry Laboratory

    Science.gov (United States)

    Nyasulu, Frazier; McMills, Lauren; Barlag, Rebecca

    2013-01-01

    A laboratory to determine the equilibrium constants of weak acid negative weak base reactions is described. The equilibrium constants of component reactions when multiplied together equal the numerical value of the equilibrium constant of the summative reaction. The component reactions are weak acid ionization reactions, weak base hydrolysis…

  17. Weak Acid Ionization Constants and the Determination of Weak Acid-Weak Base Reaction Equilibrium Constants in the General Chemistry Laboratory

    Science.gov (United States)

    Nyasulu, Frazier; McMills, Lauren; Barlag, Rebecca

    2013-01-01

    A laboratory to determine the equilibrium constants of weak acid negative weak base reactions is described. The equilibrium constants of component reactions when multiplied together equal the numerical value of the equilibrium constant of the summative reaction. The component reactions are weak acid ionization reactions, weak base hydrolysis…

  18. Representation of nonspatial and spatial information in the lateral entorhinal cortex

    Directory of Open Access Journals (Sweden)

    Sachin S Deshmukh

    2011-10-01

    Full Text Available Some theories of memory propose that the hippocampus integrates the individual items and events of experience within a contextual or spatial framework. The hippocampus receives cortical input from two major pathways: the medial entorhinal cortex (MEC and the lateral entorhinal cortex (LEC. During exploration in an open field, the firing fields of MEC grid cells form a periodically repeating, triangular array. In contrast, LEC neurons show little spatial selectivity, and it has been proposed that the LEC may provide nonspatial input to the hippocampus. Here, we recorded MEC and LEC neurons while rats explored an open field that contained discrete objects. LEC cells fired selectively at locations relative to the objects, whereas MEC cells were weakly influenced by the objects. These results provide the first direct demonstration of a double dissociation between LEC and MEC inputs to the hippocampus under conditions of exploration typically used to study hippocampal place cells.

  19. Dixon's extended bodies and weak gravitational waves

    CERN Document Server

    Bini, Donato; Geralico, Andrea; Ortolan, Antonello

    2009-01-01

    General relativity considers Dixon's theory as the standard theory to deal with the motion of extended bodies in a given gravitational background. We discuss here the features of the "reaction" of an extended body to the passage of a weak gravitational wave. We find that the body acquires a dipolar moment induced by its quadrupole structure. Furthermore, we derive the "world function" for the weak field limit of a gravitational wave background and use it to estimate the deviation between geodesics and the world lines of structured bodies. Measuring such deviations, due to the existence of cumulative effects, should be favorite with respect to measuring the amplitude of the gravitational wave itself.

  20. Landau Weak Crystallization Theory and its Applications

    Science.gov (United States)

    Kats, E. I.

    Aim of this lecture is to explain main features and ingredients of weak first order phase transitions between liquid-like (uniform in space) and solid-like (non-uniform with characteristic wave vector q0) states. We illustrate how this theory (traditionally termed as Landau weak crystallization theory) works. We consider two examples describing universal temperature dependence of shear viscosity in liquids, and so-called main phase transition in membranes. Our results are in a good qualitative agreement with experimental data, offering a deeper understanding of this kind of phase transitions. We discuss also why and where predicted universal effects can be masked.

  1. Simple understanding of quantum weak values

    Science.gov (United States)

    Qin, Lupei; Feng, Wei; Li, Xin-Qi

    2016-02-01

    In this work we revisit the important and controversial concept of quantum weak values, aiming to provide a simplified understanding to its associated physics and the origin of anomaly. Taking the Stern-Gerlach setup as a working system, we base our analysis on an exact treatment in terms of quantum Bayesian approach. We also make particular connection with a very recent work, where the anomaly of the weak values was claimed from the pure statistics in association with “disturbance” and “post-selection”, rather than the unique quantum nature. Our analysis resolves the related controversies through a clear and quantitative way.

  2. Critical level statistics for weakly disordered graphene.

    Science.gov (United States)

    Amanatidis, E; Kleftogiannis, I; Katsanos, D E; Evangelou, S N

    2014-04-16

    In two dimensions chaotic level statistics with the Wigner spacing distribution P(S) is expected for massless fermions in the Dirac region. The obtained P(S) for weakly disordered finite graphene samples with zigzag edges turns out, however, to be neither chaotic (Wigner) nor localized (Poisson). It is similar to the intermediate statistics at the critical point of the Anderson metal-insulator transition. The quantum transport of finite graphene for weak disorder, with critical level statistics can occur via edge states as in topological insulators, and for strong disorder, graphene behaves as an ordinary Anderson insulator with Poisson statistics.

  3. A Weakly Homomorphic Encryption with LDN

    Directory of Open Access Journals (Sweden)

    Chao Feng

    2014-06-01

    Full Text Available As an effective solution to protect the privacy of the data, homomorphic encryption has become a hot research topic. Existing homomorphic schemes are not truly practical due to their huge key size. In this paper, we present a simple weakly homomorphic encryption scheme using only elementary modular arithmetic over the integers rather than working with ideal lattices. Compared with DGHV’s construction, the proposed scheme has shorter public key and ciphertext size. The main appeal of our approach is the conceptual simplicity. We reduce the security of weakly homomorphic scheme to “learning divisor with noise (LDN”

  4. Charged current weak electroproduction of $\\Delta$ resonance

    CERN Document Server

    Alvarez-Ruso, L; Vacas, M J V

    1998-01-01

    We study the weak production of $\\Delta$ (i.e. $e^{-} + p \\to \\Delta^{0}+ energy range corresponding to the Mainz and TJNAF electron accelerators. The differential cross sections $\\sigma(\\theta)$ are found to be of the order of $ 10^{-39}$ cm$^2$/sr, over a range of angles which increases with energy. The possibility of observing these reactions with the high luminosities available at these accelerators, and studying the weak N-$\\Delta$ transition form factors through these reactions is discussed. The production cross section of N$^*(1440)$ in the kinematic region of $\\Delta$ production is also estimated and found to be small.

  5. Students’ Weakness Detective in Traditional Class

    Directory of Open Access Journals (Sweden)

    Fatimah Altuhaifa

    2016-10-01

    Full Text Available In Artificial Intelligent in Education in learning contexts and domains, the traditional classroom is tough to find students’ weakness during lecture due to the student’s number and because the instruction is busy with explaining the lesson. According to that, choosing teaching style that can improve student talent or skills to performs better in their classes or professional life would not be an easy task. This system is going to detect the average of students’ weakness and find either a solution for this or instruction a style that can increase students’ ability and skills by filtering the collection data, understanding the problem. After that, it provides a teaching style.

  6. Compressive wavefront sensing with weak values.

    Science.gov (United States)

    Howland, Gregory A; Lum, Daniel J; Howell, John C

    2014-08-11

    We demonstrate a wavefront sensor that unites weak measurement and the compressive-sensing, single-pixel camera. Using a high-resolution spatial light modulator (SLM) as a variable waveplate, we weakly couple an optical field's transverse-position and polarization degrees of freedom. By placing random, binary patterns on the SLM, polarization serves as a meter for directly measuring random projections of the wavefront's real and imaginary components. Compressive-sensing optimization techniques can then recover the wavefront. We acquire high quality, 256 × 256 pixel images of the wavefront from only 10,000 projections. Photon-counting detectors give sub-picowatt sensitivity.

  7. From Suitable Weak Solutions to Entropy Viscosity

    KAUST Repository

    Guermond, Jean-Luc

    2010-12-16

    This paper focuses on the notion of suitable weak solutions for the three-dimensional incompressible Navier-Stokes equations and discusses the relevance of this notion to Computational Fluid Dynamics. The purpose of the paper is twofold (i) to recall basic mathematical properties of the three-dimensional incompressible Navier-Stokes equations and to show how they might relate to LES (ii) to introduce an entropy viscosity technique based on the notion of suitable weak solution and to illustrate numerically this concept. © 2010 Springer Science+Business Media, LLC.

  8. Weak interactions at high energies. [Lectures, review

    Energy Technology Data Exchange (ETDEWEB)

    Ellis, J.

    1978-08-01

    Review lectures are presented on the phenomenological implications of the modern spontaneously broken gauge theories of the weak and electromagnetic interactions, and some observations are made about which high energy experiments probe what aspects of gauge theories. Basic quantum chromodynamics phenomenology is covered including momentum dependent effective quark distributions, the transverse momentum cutoff, search for gluons as sources of hadron jets, the status and prospects for the spectroscopy of fundamental fermions and how fermions may be used to probe aspects of the weak and electromagnetic gauge theory, studies of intermediate vector bosons, and miscellaneous possibilities suggested by gauge theories from the Higgs bosons to speculations about proton decay. 187 references. (JFP)

  9. Measuring the dark side (with weak lensing)

    CERN Document Server

    Amendola, Luca; Sapone, Domenico

    2007-01-01

    We introduce a convenient parametrization of dark energy models that is general enough to include several modified gravity models and generalized forms of dark energy. In particular we take into account the linear perturbation growth factor, the anisotropic stress and the modified Poisson equation. We discuss the sensitivity of large scale weak lensing surveys like the proposed DUNE satellite to these parameters. We find that a large-scale weak-lensing tomographic survey is able to easily distinguish the Dvali-Gabadadze-Porrati model from LCDM and to determine the perturbation growth index to an absolute error of 0.02-0.03.

  10. Weak Lie symmetry and extended Lie algebra

    Energy Technology Data Exchange (ETDEWEB)

    Goenner, Hubert [Institute for Theoretical Physics, Friedrich-Hund-Platz 1, University of Goettingen, D-37077 Gottingen (Germany)

    2013-04-15

    The concept of weak Lie motion (weak Lie symmetry) is introduced. Applications given exhibit a reduction of the usual symmetry, e.g., in the case of the rotation group. In this context, a particular generalization of Lie algebras is found ('extended Lie algebras') which turns out to be an involutive distribution or a simple example for a tangent Lie algebroid. Riemannian and Lorentz metrics can be introduced on such an algebroid through an extended Cartan-Killing form. Transformation groups from non-relativistic mechanics and quantum mechanics lead to such tangent Lie algebroids and to Lorentz geometries constructed on them (1-dimensional gravitational fields).

  11. A Continuation Method for Weakly Kannan Maps

    Directory of Open Access Journals (Sweden)

    Ariza-Ruiz David

    2010-01-01

    Full Text Available The first continuation method for contractive maps in the setting of a metric space was given by Granas. Later, Frigon extended Granas theorem to the class of weakly contractive maps, and recently Agarwal and O'Regan have given the corresponding result for a certain type of quasicontractions which includes maps of Kannan type. In this note we introduce the concept of weakly Kannan maps and give a fixed point theorem, and then a continuation method, for this class of maps.

  12. Rare regions of the susceptible-infected-susceptible model on Barabási-Albert networks.

    Science.gov (United States)

    Ódor, Géza

    2013-04-01

    I extend a previous work to susceptible-infected-susceptible (SIS) models on weighted Barabási-Albert scale-free networks. Numerical evidence is provided that phases with slow, power-law dynamics emerge as the consequence of quenched disorder and tree topologies studied previously with the contact process. I compare simulation results with spectral analysis of the networks and show that the quenched mean-field (QMF) approximation provides a reliable, relatively fast method to explore activity clustering. This suggests that QMF can be used for describing rare-region effects due to network inhomogeneities. Finite-size study of the QMF shows the expected disappearance of the epidemic threshold λ(c) in the thermodynamic limit and an inverse participation ratio ~0.25, meaning localization in case of disassortative weight scheme. Contrarily, for the multiplicative weights and the unweighted trees, this value vanishes in the thermodynamic limit, suggesting only weak rare-region effects in agreement with the dynamical simulations. Strong corrections to the mean-field behavior in case of disassortative weights explains the concave shape of the order parameter ρ(λ) at the transition point. Application of this method to other models may reveal interesting rare-region effects, Griffiths phases as the consequence of quenched topological heterogeneities.

  13. Mismatch Receptive Fields in Mouse Visual Cortex.

    Science.gov (United States)

    Zmarz, Pawel; Keller, Georg B

    2016-11-23

    In primary visual cortex, a subset of neurons responds when a particular stimulus is encountered in a certain location in visual space. This activity can be modeled using a visual receptive field. In addition to visually driven activity, there are neurons in visual cortex that integrate visual and motor-related input to signal a mismatch between actual and predicted visual flow. Here we show that these mismatch neurons have receptive fields and signal a local mismatch between actual and predicted visual flow in restricted regions of visual space. These mismatch receptive fields are aligned to the retinotopic map of visual cortex and are similar in size to visual receptive fields. Thus, neurons with mismatch receptive fields signal local deviations of actual visual flow from visual flow predicted based on self-motion and could therefore underlie the detection of objects moving relative to the visual flow caused by self-motion. VIDEO ABSTRACT.

  14. Detecting Cortex Fragments During Bacterial Spore Germination.

    Science.gov (United States)

    Francis, Michael B; Sorg, Joseph A

    2016-06-25

    The process of endospore germination in Clostridium difficile, and other Clostridia, increasingly is being found to differ from the model spore-forming bacterium, Bacillus subtilis. Germination is triggered by small molecule germinants and occurs without the need for macromolecular synthesis. Though differences exist between the mechanisms of spore germination in species of Bacillus and Clostridium, a common requirement is the hydrolysis of the peptidoglycan-like cortex which allows the spore core to swell and rehydrate. After rehydration, metabolism can begin and this, eventually, leads to outgrowth of a vegetative cell. The detection of hydrolyzed cortex fragments during spore germination can be difficult and the modifications to the previously described assays can be confusing or difficult to reproduce. Thus, based on our recent report using this assay, we detail a step-by-step protocol for the colorimetric detection of cortex fragments during bacterial spore germination.

  15. The Age of Human Cerebral Cortex Neurons

    Energy Technology Data Exchange (ETDEWEB)

    Bhardwaj, R D; Curtis, M A; Spalding, K L; Buchholz, B A; Fink, D; Bjork-Eriksson, T; Nordborg, C; Gage, F H; Druid, H; Eriksson, P S; Frisen, J

    2006-04-06

    The traditional static view of the adult mammalian brain has been challenged by the realization of continuous generation of neurons from stem cells. Based mainly on studies in experimental animals, adult neurogenesis may contribute to recovery after brain insults and decreased neurogenesis has been implicated in the pathogenesis of neurological and psychiatric diseases in man. The extent of neurogenesis in the adult human brain has, however, been difficult to establish. We have taken advantage of the integration of {sup 14}C, generated by nuclear bomb tests during the Cold War, in DNA to establish the age of neurons in the major areas of the human cerebral cortex. Together with the analysis of the cortex from patients who received BrdU, which integrates in the DNA of dividing cells, our results demonstrate that whereas non-neuronal cells turn over, neurons in the human cerebral cortex are not generated postnatally at detectable levels, but are as old as the individual.

  16. Susceptibility Genes in Thyroid Autoimmunity

    Directory of Open Access Journals (Sweden)

    Yoshiyuki Ban

    2005-01-01

    Full Text Available The autoimmune thyroid diseases (AITD are complex diseases which are caused by an interaction between susceptibility genes and environmental triggers. Genetic susceptibility in combination with external factors (e.g. dietary iodine is believed to initiate the autoimmune response to thyroid antigens. Abundant epidemiological data, including family and twin studies, point to a strong genetic influence on the development of AITD. Various techniques have been employed to identify the genes contributing to the etiology of AITD, including candidate gene analysis and whole genome screening. These studies have enabled the identification of several loci (genetic regions that are linked with AITD, and in some of these loci, putative AITD susceptibility genes have been identified. Some of these genes/loci are unique to Graves' disease (GD and Hashimoto's thyroiditis (HT and some are common to both the diseases, indicating that there is a shared genetic susceptibility to GD and HT. The putative GD and HT susceptibility genes include both immune modifying genes (e.g. HLA, CTLA-4 and thyroid specific genes (e.g. TSHR, Tg. Most likely, these loci interact and their interactions may influence disease phenotype and severity.

  17. Analysis of the susceptibility of condensed oxygen under high pressures and in strong magnetic fields

    Science.gov (United States)

    Kilit Doğan, E.; Yurtseven, H.

    2017-03-01

    The temperature dependence of the magnetic susceptibility is analyzed at some constant pressures by a power-law formula using the experimental data from the literature for the α - β and β - γ transitions in oxygen. A weak discontinuous (nearly continuous) transition occurring from the α to the β phase, becomes more discontinuous (weakly first order) for the β - γ transition as observed experimentally, which can be explained in terms of the critical exponents deduced from our analysis. The magnetic field dependence of the differential susceptibility is also analyzed in this study for the α -O2 at 4.2 K by a power-law formula using the experimental data. λ-type of observed behaviour of the differential susceptibility is discussed in terms of our analysis for the α -O2 .

  18. A weak balance: the contribution of muscle weakness to postural instability and falls.

    NARCIS (Netherlands)

    Horlings, C.G.; Engelen, B.G.M. van; Allum, J.H.; Bloem, B.R.

    2008-01-01

    Muscle strength is a potentially important factor contributing to postural control. In this article, we consider the influence of muscle weakness on postural instability and falling. We searched the literature for research evaluating muscle weakness as a risk factor for falls in community-dwelling e

  19. What Weak Measurements and Weak Values Really Mean: Reply to Kastner

    Science.gov (United States)

    Cohen, Eliahu

    2017-06-01

    Despite their important applications in metrology and in spite of numerous experimental demonstrations, weak measurements are still confusing for part of the community. This sometimes leads to unjustified criticism. Recent papers have experimentally clarified the meaning and practical significance of weak measurements, yet in Kastner (Found Phys 47:697-707, 2017), Kastner seems to take us many years backwards in the the debate, casting doubt on the very term "weak value" and the meaning of weak measurements. Kastner appears to ignore both the basics and frontiers of weak measurements and misinterprets the weak measurement process and its outcomes. In addition, she accuses the authors of Aharonov et al. (Ann Phys 355:258-268, 2015) in statements completely opposite to the ones they have actually made. There are many points of disagreement between Kastner and us, but in this short reply I will leave aside the ontology (which is indeed interpretational and far more complex than that described by Kastner) and focus mainly on the injustice in her criticism. I shall add some general comments regarding the broader theory of weak measurements and the two-state-vector formalism, as well as supporting experimental results. Finally, I will point out some recent promising results, which can be proven by (strong) projective measurements, without the need of employing weak measurements.

  20. Weak monotonicity inequality and partial regularity for harmonic maps

    Institute of Scientific and Technical Information of China (English)

    沈尧天; 严树森

    1999-01-01

    The notion of locally weak monotonicity inequality for weakly harmonic maps is introduced and various results on this class of maps are obtained. For example, the locally weak monotonicity inequality is nearly equivalent to the ε-regularity.

  1. Toward unraveling reading-related modulations of tDCS-induced neuroplasticity in the human visual cortex.

    OpenAIRE

    Antal, Andrea; Ambrus, Géza Gergely; Chaieb, Leila

    2014-01-01

    Stimulation using weak electrical direct currents has shown to be capable of inducing polarity-dependent diminutions or elevations in motor and visual cortical excitability. The aim of the present study was to test if reading during transcranial direct current stimulation (tDCS) is able to modify stimulation-induced plasticity in the visual cortex. Phosphene thresholds (PTs) in 12 healthy subjects were recorded before and after 10 min of anodal, cathodal, and sham tDCS in combination with rea...

  2. The Anterior Cingulate Cortex and Pain Processing

    Directory of Open Access Journals (Sweden)

    Perry Neil Fuchs

    2014-05-01

    Full Text Available The neural network that contributes to the suffering which accompanies persistent pain states involves a number of brain regions. Of primary interest is the contribution of the cingulate cortex in processing the affective component of pain. The purpose of this review is to summarize recent data obtained using novel behavioral paradigms in animals based on measuring escape and/or avoidance of a noxious stimulus. These paradigms have successfully been used to study the nature of the neuroanatomical and neurochemical contributions of the anterior cingulate cortex to higher order pain processing in rodents.

  3. Coding of movements in the motor cortex.

    Science.gov (United States)

    Georgopoulos, Apostolos P; Carpenter, Adam F

    2015-08-01

    The issue of coding of movement in the motor cortex has recently acquired special significance due to its fundamental importance in neuroprosthetic applications. The challenge of controlling a prosthetic arm by processed motor cortical activity has opened a new era of research in applied medicine but has also provided an 'acid test' for hypotheses regarding coding of movement in the motor cortex. The successful decoding of movement information from the activity of motor cortical cells using their directional tuning and population coding has propelled successful neuroprosthetic applications and, at the same time, asserted the utility of those early discoveries, dating back to the early 1980s.

  4. Postictal inhibition of the somatosensory cortex

    DEFF Research Database (Denmark)

    Beniczky, Sándor; Jovanovic, Marina; Atkins, Mary Doreen

    2011-01-01

    Transient suppression of the motor cortex and of the speech areas cause well-described postictal phenomena following seizures involving the respective cortical areas. Pain is a rare symptom in epileptic seizures. We present a patient with painful tonic seizures in the left leg. The amplitude...... of the cortical component of the somatosensory evoked potential following stimulation of the left tibial nerve was reduced immediately after the seizure. Our findings suggest that the excitability of the sensory cortex is transiently reduced following a seizure involving the somatosensory area....

  5. Hard-Thermal-Loop QCD thermodynamics and quark number susceptibility

    Directory of Open Access Journals (Sweden)

    Mogliacci Sylvain

    2014-04-01

    Full Text Available The weak-coupling expansion of the QCD pressure is known up to the order g6 log g. However, at experimentally relevant temperatures, the corresponding series is poorly convergent. In this proceedings, we discuss at which extent the gauge-invariant resummation scheme, Hard-Thermal-Loop perturbation theory (HTLpt, improves the apparent convergence. We first present HTLpt results for QCD thermodynamic functions up to three-loop order at vanishing chemical potential. Then, we report a preliminary HTLpt result of one-loop quark number susceptibility, probing the finite density equation of state. Our results are consistent with lattice data down to 2 − 3Tc, reinforcing the weakly-coupled quasiparticle picture in the intermediate coupling regime.

  6. Higgs Boson Production and Weak Boson Structure

    OpenAIRE

    1995-01-01

    The influence of the QCD structure of the weak bosons on the Higgs boson production in $e$-$p$ scattering is studied. The energy and Higgs boson mass dependence of the cross-section, following from the new contributions, is calculated.

  7. Fermi and the Theory of Weak Interactions

    CERN Document Server

    Rajasekaran, G

    2014-01-01

    The history of weak interactions starting with Fermi's creation of the beta decay theory and culminating in its modern avatar in the form of the electroweak gauge theory is described. Discoveries of parity violation, matter-antimatter asymmetry, W and Z bosons and neutrino mass are highlighted.

  8. Studying dark matter haloes with weak lensing

    NARCIS (Netherlands)

    Velander, Malin Barbro Margareta

    2012-01-01

    Our Universe is comprised not only of normal matter but also of unknown components: dark matter and dark energy. This Thesis recounts studies of dark matter haloes, using a technique known as weak gravitational lensing, in order to learn more about the nature of these dark components. The haloes

  9. Modeling, Measuring, and Compensating Color Weak Vision.

    Science.gov (United States)

    Oshima, Satoshi; Mochizuki, Rika; Lenz, Reiner; Chao, Jinhui

    2016-06-01

    We use methods from Riemann geometry to investigate transformations between the color spaces of color-normal and color-weak observers. The two main applications are the simulation of the perception of a color weak observer for a color-normal observer, and the compensation of color images in a way that a color-weak observer has approximately the same perception as a color-normal observer. The metrics in the color spaces of interest are characterized with the help of ellipsoids defined by the just-noticeable-differences between the colors which are measured with the help of color-matching experiments. The constructed mappings are the isometries of Riemann spaces that preserve the perceived color differences for both observers. Among the two approaches to build such an isometry, we introduce normal coordinates in Riemann spaces as a tool to construct a global color-weak compensation map. Compared with the previously used methods, this method is free from approximation errors due to local linearizations, and it avoids the problem of shifting locations of the origin of the local coordinate system. We analyze the variations of the Riemann metrics for different observers obtained from new color-matching experiments and describe three variations of the basic method. The performance of the methods is evaluated with the help of semantic differential tests.

  10. Modelling, Measuring and Compensating Color Weak Vision.

    Science.gov (United States)

    Oshima, Satoshi; Mochizuki, Rika; Lenz, Reiner; Chao, Jinhui

    2016-03-08

    We use methods from Riemann geometry to investigate transformations between the color spaces of color-normal and color weak observers. The two main applications are the simulation of the perception of a color weak observer for a color normal observer and the compensation of color images in a way that a color weak observer has approximately the same perception as a color normal observer. The metrics in the color spaces of interest are characterized with the help of ellipsoids defined by the just-noticable-differences between color which are measured with the help of color-matching experiments. The constructed mappings are isometries of Riemann spaces that preserve the perceived color-differences for both observers. Among the two approaches to build such an isometry, we introduce normal coordinates in Riemann spaces as a tool to construct a global color-weak compensation map. Compared to previously used methods this method is free from approximation errors due to local linearizations and it avoids the problem of shifting locations of the origin of the local coordinate system. We analyse the variations of the Riemann metrics for different observers obtained from new color matching experiments and describe three variations of the basic method. The performance of the methods is evaluated with the help of semantic differential (SD) tests.

  11. TRANSPORTATION INEQUALITIES FOR WEAKLY DEPENDENT SEQUENCES

    Institute of Scientific and Technical Information of China (English)

    Ma Yutao

    2011-01-01

    In[3],they gave necessary and sufficient condition for T1C and then as applications T1C for weakly dependent sequences was established.In this note,based on Gozlan-Léonard characterization for W1H-inequalities,we extends this result to W1Hinequalities.

  12. On Uniform Weak König's Lemma

    DEFF Research Database (Denmark)

    Kohlenbach, Ulrich

    2002-01-01

    is of interest in the context of explicit mathematics as developed by S. Feferman. The elimination process in Kohlenbach [10] actually can be used to eliminate even this uniform weak Konig's lemma provided that PRA only has a quantifier-free rule of extensionality QF-ER instead of the full axioms (E...

  13. Weak organic acid stress in Bacillus subtilis

    NARCIS (Netherlands)

    ter Beek, A.S.

    2009-01-01

    Weak organic acids are commonly used food preservatives that protect food products from bacterial contamination. A variety of spore-forming bacterial species pose a serious problem to the food industry by causing extensive food spoilage or even food poisoning. Understanding the mechanisms of

  14. Quantum trajectories based on the weak value

    Science.gov (United States)

    Mori, Takuya; Tsutsui, Izumi

    2015-04-01

    The notion of the trajectory of an individual particle is strictly inhibited in quantum mechanics because of the uncertainty principle. Nonetheless, the weak value, which has been proposed as a novel and measurable quantity definable to any quantum observable, can offer a possible description of trajectory on account of its statistical nature. In this paper, we explore the physical significance provided by this "weak trajectory" by considering various situations where interference takes place simultaneously with the observation of particles, that is, in prototypical quantum situations for which no classical treatment is available. These include the double slit experiment and Lloyd's mirror, where in the former case it is argued that the real part of the weak trajectory describes an average over the possible classical trajectories involved in the process, and that the imaginary part is related to the variation of interference. It is shown that this average interpretation of the weak trajectory holds universally under the complex probability defined from the given transition process. These features remain essentially unaltered in the case of Lloyd's mirror where interference occurs with a single slit.

  15. Axion monodromy and the weak gravity conjecture

    Energy Technology Data Exchange (ETDEWEB)

    Hebecker, Arthur; Rompineve, Fabrizio [Heidelberg Univ. (Germany). Inst. for Theoretical Physics; Westphal, Alexander [DESY Hamburg (Germany). Theory Group

    2015-12-15

    Axions with broken discrete shift symmetry (axion monodromy) have recently played a central role both in the discussion of inflation and the 'relaxion' approach to the hierarchy problem. We suggest a very minimalist way to constrain such models by the weak gravity conjecture for domain walls: While the electric side of the conjecture is always satisfied if the cosine-oscillations of the axion potential are sufficiently small, the magnetic side imposes a cutoff, Λ{sup 3}∝mfM{sub pl}, independent of the height of these 'wiggles'. We compare our approach with the recent related proposal by Ibanez, Montero, Uranga and Valenzuela. We also discuss the non-trivial question which version, if any, of the weak gravity conjecture for domain walls should hold. In particular, we show that string compactifications with branes of different dimensions wrapped on different cycles lead to a 'geometric weak gravity conjecture' relating volumes of cycles, norms of corresponding forms and the volume of the compact space. Imposing this 'geometric conjecture', e.g. on the basis of the more widely accepted weak gravity conjecture for particles, provides at least some support for the (electric and magnetic) conjecture for domain walls.

  16. Weakly nonlinear density-velocity relation

    CERN Document Server

    Chodorowski, M J; Chodorowski, Michal J; Lokas, Ewa L

    1996-01-01

    We rigorously derive weakly nonlinear relation between cosmic density and velocity fields up to third order in perturbation theory. The density field is described by the mass density contrast, \\de. The velocity field is described by the variable \\te proportional to the velocity divergence, \\te = - f(\\Omega)^{-1} H_0^{-1} \

  17. Studying dark matter haloes with weak lensing

    NARCIS (Netherlands)

    Velander, Malin Barbro Margareta

    2012-01-01

    Our Universe is comprised not only of normal matter but also of unknown components: dark matter and dark energy. This Thesis recounts studies of dark matter haloes, using a technique known as weak gravitational lensing, in order to learn more about the nature of these dark components. The haloes ana

  18. TAUBERIAN THEOREMS FOR WEAK ALMOST CONVERGENT FUNCTIONS

    Institute of Scientific and Technical Information of China (English)

    Meng-Kuang Kuo

    2011-01-01

    The almost convergent function which was introduced by Raimi [6] and dis- cussed by Ho [4], Das and Nanda [2, 3], is the continuous analogue of almost convergent sequences (see [5]). In this paper, we establish the Tauberian conditions and the Cauchy criteria for weak almost convergent functions on R2+.

  19. Collisional properties of weakly bound heteronuclear dimers

    NARCIS (Netherlands)

    Marcelis, B.; Kokkelmans, S.J.J.M.F.; Shlyapnikov, G.V.; Petrov, D.S.

    2008-01-01

    We consider collisional properties of weakly bound heteronuclear molecules (dimers) formed in a two-species mixture of atoms with a large mass difference. We focus on dimers containing light fermionic atoms as they manifest collisional stability due to an effective dimer-dimer repulsion originating

  20. Common Fixed Points for Weakly Compatible Maps

    Indian Academy of Sciences (India)

    Renu Chugh; Sanjay Kumar

    2001-05-01

    The purpose of this paper is to prove a common fixed point theorem, from the class of compatible continuous maps to a larger class of maps having weakly compatible maps without appeal to continuity, which generalized the results of Jungck [3], Fisher [1], Kang and Kim [8], Jachymski [2], and Rhoades [9].

  1. Spurious Shear in Weak Lensing with LSST

    CERN Document Server

    Chang, C; Jernigan, J G; Peterson, J R; AlSayyad, Y; Ahmad, Z; Bankert, J; Bard, D; Connolly, A; Gibson, R R; Gilmore, K; Grace, E; Hannel, M; Hodge, M A; Jee, M J; Jones, L; Krughoff, S; Lorenz, S; Marshall, P J; Marshall, S; Meert, A; Nagarajan, S; Peng, E; Rasmussen, A P; Shmakova, M; Sylvestre, N; Todd, N; Young, M

    2012-01-01

    The Large Synoptic Survey Telescope (LSST) is one of the most powerful ground-based weak lensing survey telescopes in the upcoming decade. The complete 10-year survey will image $\\sim$ 20,000 square degrees of sky in six filter bands every few nights, bringing the final survey depth to $r\\sim27.5$, with over 4 billion well measured galaxies. To take full advantage of this unprecedented statistical power, the systematic errors associated with weak lensing measurements need to be controlled to a level similar to the statistical errors. This work is the first attempt to quantitatively estimate the absolute level and statistical properties of the systematic errors on weak lensing shear measurements due to the most important physical effects in the LSST system via high fidelity ray-tracing simulations. We identify and isolate the different sources of \\textit{additive} systematic errors on shear measurements for LSST and predict their impact on the final cosmic shear measurements using conventional weak lensing ana...

  2. Weak organic acid stress in Bacillus subtilis

    NARCIS (Netherlands)

    ter Beek, A.S.

    2009-01-01

    Weak organic acids are commonly used food preservatives that protect food products from bacterial contamination. A variety of spore-forming bacterial species pose a serious problem to the food industry by causing extensive food spoilage or even food poisoning. Understanding the mechanisms of bacteri

  3. Engineering molecular crystals with abnormally weak cohesion.

    Science.gov (United States)

    Maly, Kenneth E; Gagnon, Eric; Wuest, James D

    2011-05-14

    Adding astutely placed methyl groups to hexaphenylbenzene increases molecular weight but simultaneously weakens key C-H···π interactions, thereby leading to decreased enthalpies of sublimation and showing that materials with abnormally weak cohesion can be made by identifying and then obstructing interactions that help control association.

  4. Efficient bootstrap with weakly dependent processes

    NARCIS (Netherlands)

    Bravo, Francesco; Crudu, Federico

    2012-01-01

    The efficient bootstrap methodology is developed for overidentified moment conditions models with weakly dependent observation. The resulting bootstrap procedure is shown to be asymptotically valid and can be used to approximate the distributions of t-statistics, the J-statistic for overidentifying

  5. Modeling, Measuring, and Compensating Color Weak Vision

    Science.gov (United States)

    Oshima, Satoshi; Mochizuki, Rika; Lenz, Reiner; Chao, Jinhui

    2016-06-01

    We use methods from Riemann geometry to investigate transformations between the color spaces of color-normal and color weak observers. The two main applications are the simulation of the perception of a color weak observer for a color normal observer and the compensation of color images in a way that a color weak observer has approximately the same perception as a color normal observer. The metrics in the color spaces of interest are characterized with the help of ellipsoids defined by the just-noticable-differences between color which are measured with the help of color-matching experiments. The constructed mappings are isometries of Riemann spaces that preserve the perceived color-differences for both observers. Among the two approaches to build such an isometry, we introduce normal coordinates in Riemann spaces as a tool to construct a global color-weak compensation map. Compared to previously used methods this method is free from approximation errors due to local linearizations and it avoids the problem of shifting locations of the origin of the local coordinate system. We analyse the variations of the Riemann metrics for different observers obtained from new color matching experiments and describe three variations of the basic method. The performance of the methods is evaluated with the help of semantic differential (SD) tests.

  6. Strong suppression of weak localization in graphene

    NARCIS (Netherlands)

    Morozov, S.V.; Novoselov, K.S.; Katsnelson, M.I.; Schedin, F.; Ponomarenko, L.A.; Jiang, D.; Geim, A.K.

    2006-01-01

    Low-field magnetoresistance is ubiquitous in low-dimensional metallic systems with high resistivity and well understood as arising due to quantum interference on self-intersecting diffusive trajectories. We have found that in graphene this weak-localization magnetoresistance is strongly suppressed a

  7. The Strengths and Weaknesses of Universal Grammar

    Institute of Scientific and Technical Information of China (English)

    华芳

    2013-01-01

      Chomsky’s universal grammar (UG) has always had a following among certain linguists. This article discusses the strengths and weaknesses of UG in the L2 setting according to its proponents and opponents. The author also evaluates it using Ka⁃plan’s five-point tool and Long’s eight-point measuring stick.

  8. Quantum Signature Scheme with Weak Arbitrator

    Science.gov (United States)

    Luo, Ming-Xing; Chen, Xiu-Bo; Yun, Deng; Yang, Yi-Xian

    2012-07-01

    In this paper, we propose one quantum signature scheme with a weak arbitrator to sign classical messages. This scheme can preserve the merits in the original arbitrated scheme with some entanglement resources, and provide a higher efficiency in transmission and reduction the complexity of implementation. The arbitrator is costless and only involved in the disagreement case.

  9. Efficient bootstrap with weakly dependent processes

    NARCIS (Netherlands)

    Bravo, Francesco; Crudu, Federico

    2012-01-01

    The efficient bootstrap methodology is developed for overidentified moment conditions models with weakly dependent observation. The resulting bootstrap procedure is shown to be asymptotically valid and can be used to approximate the distributions of t-statistics, the J-statistic for overidentifying

  10. [A strong man with a weak shoulder].

    Science.gov (United States)

    Henket, Marjolijn; Lycklama á Nijeholt, Geert J; van der Zwaal, Peer

    2013-01-01

    A 47-year-old former olympic athlete had pain and weakness of his left shoulder. There was no prior trauma. He had full range-of-motion and a scapular dyskinesia. There was atrophy of the trapezius and sternocleidomastoideus muscles. He was diagnosed with 'idiopathic neuritis of the accessorius nerve'.

  11. Quantum mechanical calculations on weakly interacting complexes

    NARCIS (Netherlands)

    Heijmen, T.G.A.

    1998-01-01

    Symmetry-adapted perturbation theory (SAPT) has been applied to compute the intermolecular potential energy surfaces and the interaction-induced electrical properties of weakly interacting complexes. Asymptotic (large R) expressions have been derived for the contributions to the collision-induced pr

  12. On properties of (weakly) small groups

    CERN Document Server

    Milliet, Cédric

    2011-01-01

    A group is small if it has countably many complete $n$-types over the empty set for each natural number n. More generally, a group $G$ is weakly small if it has countably many complete 1-types over every finite subset of G. We show here that in a weakly small group, subgroups which are definable with parameters lying in a finitely generated algebraic closure satisfy the descending chain conditions for their traces in any finitely generated algebraic closure. An infinite weakly small group has an infinite abelian subgroup, which may not be definable. A small nilpotent group is the central product of a definable divisible group with a definable one of bounded exponent. In a group with simple theory, any set of pairwise commuting elements is contained in a definable finite-by-abelian subgroup. First corollary : a weakly small group with simple theory has an infinite definable finite-by-abelian subgoup. Secondly, in a group with simple theory, a normal solvable group A of derived length n is contained in an A-def...

  13. Annihilators on weakly standard BCC-algebras

    OpenAIRE

    R. Halaš; L. Plojhar

    2005-01-01

    In a recent paper the authors presented a new construction of BCC-algebras derived from posets with the top element 1. Resulting BCC-algebras, called weakly standard, are those for which every 4-element subset containing 1 is a subalgebra. In this paper we continue our investigations focusing on the properties of their lattices of congruence kernels.

  14. Legitimacy Building under Weak Institutional Settings

    DEFF Research Database (Denmark)

    Wejs, Anja; Harvold, Kjell; Larsen, Sanne Vammen;

    2014-01-01

    Local strategies for adaptation to climate change in Denmark and Norway are discussed. In both countries, the national impetus for local adaptation is weak; it is largely left to local actors to take the initiative. The dynamics of the different approaches to climate-change adaptation at the loca...

  15. WEAKLY ALGEBRAIC REFLEXIVITY AND STRONGLY ALGEBRAIC REFLEXIVITY

    Institute of Scientific and Technical Information of China (English)

    TaoChangli; LuShijie; ChenPeixin

    2002-01-01

    Algebraic reflexivity introduced by Hadwin is related to linear interpolation. In this paper, the concepts of weakly algebraic reflexivity and strongly algebraic reflexivity which are also related to linear interpolation are introduced. Some properties of them are obtained and some relations between them revealed.

  16. Weak chaos in the asymmetric heavy top

    CERN Document Server

    Barrientos, M; Ranada, A F

    1995-01-01

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

  17. Solitons and Weakly Nonlinear Waves in Plasmas

    DEFF Research Database (Denmark)

    Pécseli, Hans

    1985-01-01

    Theoretical descriptions of solitons and weakly nonlinear waves propagating in plasma media are reviewed, with particular attention to the Korteweg-de Vries (KDV) equation and the Nonlinear Schrödinger equation (NLS). The modifications of these basic equations due to the effects of resonant...

  18. Many-body chaos at weak coupling

    Science.gov (United States)

    Stanford, Douglas

    2016-10-01

    The strength of chaos in large N quantum systems can be quantified using λ L , the rate of growth of certain out-of-time-order four point functions. We calculate λ L to leading order in a weakly coupled matrix Φ4 theory by numerically diagonalizing a ladder kernel. The computation reduces to an essentially classical problem.

  19. 关于Weakly Almost Clean环

    Institute of Scientific and Technical Information of China (English)

    孟文静; 陈焕艮

    2015-01-01

    This paper defines weakly almost clean rings .A commutative ring R is a weakly almost clean ring if every element x∈ R can be written in the form x= r+ e or x= r-e where r∈ reg(R) and e∈ Id(R) .Firstly , for a nonempty collection {Ri}of rings Ri ,the product R = ∏ i∈ IRi is weakly almost clean if and only if there exists m∈ I such that Rm is weakly almost clean and Rn is almost clean for all n≠ m .Further ,let R be a ring and M be an R‐module ,the trivial extension R(M) of R and M is weakly almost clean if and only if each x∈ R can be written in the form x= r+ e or x= r-e where r∈ R-(Z(R)∪ Z(M)) and e∈ Id(R) .These extend the corre‐sponding results on almost clean rings .%定义了weakly almost clean环。交换环R叫做weakly almost clean环,如果对于任意一个元素 x ∈ R可以写成 x = r+ e或x = r-e的形式,其中r∈ reg(R)且e∈ Id(R)。首先,对于环Ri的非空集合{Ri},证明了直和R=∏ i∈ IRi为weakly almost clean当且仅当存在 m ∈ I使Rm为weakly almost clean且对所有的n≠ m ,Rn为almost clean 。然后,设R是一个环且 M为一个R‐模,得到了R和M的平凡扩张R(M)为weakly almost clean当且仅当每个 x∈ R可以写成x= r+e或x= r-e的形式,其中 r∈ R-(Z(R)∪ Z(M))且e∈ Id(R)。进而推广了almost clean环的相应结果。

  20. Down but not out in posterior cingulate cortex: Deactivation yet functional coupling with prefrontal cortex during demanding semantic cognition.

    Science.gov (United States)

    Krieger-Redwood, Katya; Jefferies, Elizabeth; Karapanagiotidis, Theodoros; Seymour, Robert; Nunes, Adonany; Ang, Jit Wei Aaron; Majernikova, Vierra; Mollo, Giovanna; Smallwood, Jonathan

    2016-11-01

    The posterior cingulate cortex (pCC) often deactivates during complex tasks, and at rest is often only weakly correlated with regions that play a general role in the control of cognition. These observations led to the hypothesis that pCC contributes to automatic aspects of memory retrieval and cognition. Recent work, however, has suggested that the pCC may support both automatic and controlled forms of memory processing and may do so by changing its communication with regions that are important in the control of cognition across multiple domains. The current study examined these alternative views by characterising the functional coupling of the pCC in easy semantic decisions (based on strong global associations) and in harder semantic tasks (matching words on the basis of specific non-dominant features). Increasingly difficult semantic decisions led to the expected pattern of deactivation in the pCC; however, psychophysiological interaction analysis revealed that, under these conditions, the pCC exhibited greater connectivity with dorsolateral prefrontal cortex (PFC), relative to both easier semantic decisions and to a period of rest. In a second experiment using different participants, we found that functional coupling at rest between the pCC and the same region of dorsolateral PFC was stronger for participants who were more efficient at semantic tasks when assessed in a subsequent laboratory session. Thus, although overall levels of activity in the pCC are reduced during external tasks, this region may show greater coupling with executive control regions when information is retrieved from memory in a goal-directed manner. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

  1. Susceptibility to Frost-Bite

    Directory of Open Access Journals (Sweden)

    Bal Krishna

    1966-11-01

    Full Text Available The body protects its susceptible parts e.g. hands and feet from cold injury by allowing a surge of blood to flow through them on exposure to severe cold. This occurs through alternate vasodilatation and vasoconstriction known as Lewis Hunting Reaction. This phenomenon is influenced by several factors, which indirectly may also affect individual susceptibility to cold injury. The role of nutrition, adequate insulation of the body and positive heat balance in relation to the protective mechanism have been reviewed and discussed. Available literature on various factors has been surveyed and discussed in the light of recent advances in the physiology of cold exposure. Certain tests based on the present knowledge, to be developed and standardised for screening susceptible individuals to frost-bite have been suggested.

  2. Spontaneous pattern formation and pinning in the visual cortex

    Science.gov (United States)

    Baker, Tanya I.

    Bifurcation theory and perturbation theory can be combined with a knowledge of the underlying circuitry of the visual cortex to produce an elegant story explaining the phenomenon of visual hallucinations. A key insight is the application of an important set of ideas concerning spontaneous pattern formation introduced by Turing in 1952. The basic mechanism is a diffusion driven linear instability favoring a particular wavelength that determines the size of the ensuing stripe or spot periodicity of the emerging spatial pattern. Competition between short range excitation and longer range inhibition in the connectivity profile of cortical neurons provides the difference in diffusion length scales necessary for the Turing mechanism to occur and has been proven by Ermentrout and Cowan to be sufficient to explain the generation of a subset of reported geometric hallucinations. Incorporating further details of the cortical circuitry, namely that neurons are also weakly connected to other neurons sharing a particular stimulus orientation or spatial frequency preference at even longer ranges and the resulting shift-twist symmetry of the neuronal connectivity, improves the story. We expand this approach in order to be able to include the tuned responses of cortical neurons to additional visual stimulus features such as motion, color and disparity. We apply a study of nonlinear dynamics similar to the analysis of wave propagation in a crystalline lattice to demonstrate how a spatial pattern formed through the Turing instability can be pinned to the geometric layout of various feature preferences. The perturbation analysis is analogous to solving the Schrodinger equation in a weak periodic potential. Competition between the local isotropic connections which produce patterns of activity via the Turing mechanism and the weaker patchy lateral connections that depend on a neuron's particular set of feature preferences create long wavelength affects analogous to commensurate

  3. Olfactory consciousness and gamma oscillation couplings across the olfactory bulb, olfactory cortex, and orbitofrontal cortex.

    Science.gov (United States)

    Mori, Kensaku; Manabe, Hiroyuki; Narikiyo, Kimiya; Onisawa, Naomi

    2013-01-01

    The orbitofrontal cortex receives multi-modality sensory inputs, including olfactory input, and is thought to be involved in conscious perception of the olfactory image of objects. Generation of olfactory consciousness may require neuronal circuit mechanisms for the "binding" of distributed neuronal activities, with each constituent neuron representing a specific component of an olfactory percept. The shortest neuronal pathway for odor signals to reach the orbitofrontal cortex is olfactory sensory neuron-olfactory bulb-olfactory cortex-orbitofrontal cortex, but other pathways exist, including transthalamic pathways. Here, we review studies on the structural organization and functional properties of the shortest pathway, and propose a model of neuronal circuit mechanisms underlying the temporal bindings of distributed neuronal activities in the olfactory cortex. We describe a hypothesis that suggests functional roles of gamma oscillations in the bindings. This hypothesis proposes that two types of projection neurons in the olfactory bulb, tufted cells and mitral cells, play distinct functional roles in bindings at neuronal circuits in the olfactory cortex: tufted cells provide specificity-projecting circuits which send odor information with early-onset fast gamma synchronization, while mitral cells give rise to dispersedly-projecting feed-forward binding circuits which transmit the response synchronization timing with later-onset slow gamma synchronization. This hypothesis also suggests a sequence of bindings in the olfactory cortex: a small-scale binding by the early-phase fast gamma synchrony of tufted cell inputs followed by a larger-scale binding due to the later-onset slow gamma synchrony of mitral cell inputs. We discuss that behavioral state, including wakefulness and sleep, regulates gamma oscillation couplings across the olfactory bulb, olfactory cortex, and orbitofrontal cortex.

  4. Olfactory consciousness and gamma oscillation couplings across the olfactory bulb, olfactory cortex and orbitofrontal cortex

    Directory of Open Access Journals (Sweden)

    Kensaku eMori

    2013-10-01

    Full Text Available The orbitofrontal cortex receives multi-modality sensory inputs, including olfactory input, and is thought to be involved in conscious perception of the olfactory image of objects. Generation of olfactory consciousness requires neuronal circuit mechanisms for the ‘binding’ of distributed neuronal activities, with each constituent neuron representing a specific component of an olfactory percept. The shortest neuronal pathway for odor signals to reach the orbitofrontal cortex is olfactory sensory neuron – olfactory bulb – olfactory cortex – orbitofrontal cortex, but other pathways exist, including transthalamic pathways. Here, we review studies on the structural organization and functional properties of the shortest pathway, and propose a model of neuronal circuit mechanisms underlying the temporal bindings of distributed neuronal activities in the olfactory cortex. We describe a hypothesis that suggests functional roles of gamma oscillations in the bindings. This hypothesis proposes that two types of projection neurons in the olfactory bulb, tufted cells and mitral cells, play distinct functional roles in bindings at neuronal circuits in the olfactory cortex: tufted cells provide specificity-projecting circuits which send odor information with early-onset fast gamma synchronization, while mitral cells give rise to dispersedly-projecting feed-forward binding circuits which transmit the response synchronization timing with later-onset slow gamma synchronization. This hypothesis also suggests a sequence of bindings in the olfactory cortex: a small-scale binding by the early-phase fast gamma synchrony of tufted cell inputs followed by a larger-scale binding due to the later-onset slow gamma synchrony of mitral cell inputs. We discuss that behavioral state, including wakefulness and sleep, regulates gamma oscillation couplings across the olfactory bulb, olfactory cortex, and orbitofrontal cortex.

  5. Inherited susceptibility and radiation exposure

    Energy Technology Data Exchange (ETDEWEB)

    Little, J.B. [Harvard School of Public Health, Boston, MA (United States)

    1997-03-01

    There is continuing concern that some people in the general population may have genetic makeups that place them at particularly high risk for radiation-induced cancer. The existence of such a susceptible subpopulation would have obvious implications for the estimation of risks of radiation exposure. Although it has been long known that familial aggregations of cancer do sometimes occur, recent evidence suggests that a general genetic predisposition to cancer does not exist; most cancers occur sporadically. On the other hand, nearly 10% of the known Mendelian genetic disorders are associated with cancer. A number of these involve a familial predisposition to cancer, and some are characterized by an enhanced susceptibility to the induction of cancer by various physical and chemical carcinogens, including ionizing radiation. Such increased susceptibility will depend on several factors including the frequency of the susceptibility gene in the population and its penetrance, the strength of the predisposition, and the degree to which the cancer incidence in susceptible individuals may be increased by the carcinogen. It is now known that these cancer-predisposing genes may be responsible not only for rare familial cancer syndromes, but also for a proportion of the common cancers. Although the currently known disorders can account for only a small fraction of all cancers, they serve as models for genetic predisposition to carcinogen-induced cancer in the general population. In the present report, the author describes current knowledge of those specific disorders that are associated with an enhanced predisposition to radiation-induced cancer, and discusses how this knowledge may bear on the susceptibility to radiation-induced cancer in the general population and estimates of the risk of radiation exposure.

  6. Heck's disease: diagnosis and susceptibility.

    Science.gov (United States)

    Bennett, Lindsey K; Hinshaw, Molly

    2009-01-01

    Focal epithelial hyperplasia, or Heck's disease, is an uncommon proliferation of oral mucosa that presents primarily in Native Central and South American populations. It presents as asymptomatic papules or nodules on the oral mucosa, gingiva, tongue, and lips. In the majority of cases, human papilloma virus 13 or 32 is detected. Factors that determine disease susceptibility are unclear, but genetics, and having the human lymphocytic antigen-DR4 (DRB1*0404) allele in particular, are thought to play a major role in disease vulnerability. We report another case of focal epithelial hyperplasia, hypothesize on disease susceptibility, and review the current understanding of this uncommon disorder.

  7. Underconnectivity between voice-selective cortex and reward circuitry in children with autism.

    Science.gov (United States)

    Abrams, Daniel A; Lynch, Charles J; Cheng, Katherine M; Phillips, Jennifer; Supekar, Kaustubh; Ryali, Srikanth; Uddin, Lucina Q; Menon, Vinod

    2013-07-16

    Individuals with autism spectrum disorders (ASDs) often show insensitivity to the human voice, a deficit that is thought to play a key role in communication deficits in this population. The social motivation theory of ASD predicts that impaired function of reward and emotional systems impedes children with ASD from actively engaging with speech. Here we explore this theory by investigating distributed brain systems underlying human voice perception in children with ASD. Using resting-state functional MRI data acquired from 20 children with ASD and 19 age- and intelligence quotient-matched typically developing children, we examined intrinsic functional connectivity of voice-selective bilateral posterior superior temporal sulcus (pSTS). Children with ASD showed a striking pattern of underconnectivity between left-hemisphere pSTS and distributed nodes of the dopaminergic reward pathway, including bilateral ventral tegmental areas and nucleus accumbens, left-hemisphere insula, orbitofrontal cortex, and ventromedial prefrontal cortex. Children with ASD also showed underconnectivity between right-hemisphere pSTS, a region known for processing speech prosody, and the orbitofrontal cortex and amygdala, brain regions critical for emotion-related associative learning. The degree of underconnectivity between voice-selective cortex and reward pathways predicted symptom severity for communication deficits in children with ASD. Our results suggest that weak connectivity of voice-selective cortex and brain structures involved in reward and emotion may impair the ability of children with ASD to experience speech as a pleasurable stimulus, thereby impacting language and social skill development in this population. Our study provides support for the social motivation theory of ASD.

  8. A dendritic mechanism for decoding traveling waves: principles and applications to motor cortex.

    Directory of Open Access Journals (Sweden)

    Stewart Heitmann

    2013-10-01

    Full Text Available Traveling waves of neuronal oscillations have been observed in many cortical regions, including the motor and sensory cortex. Such waves are often modulated in a task-dependent fashion although their precise functional role remains a matter of debate. Here we conjecture that the cortex can utilize the direction and wavelength of traveling waves to encode information. We present a novel neural mechanism by which such information may be decoded by the spatial arrangement of receptors within the dendritic receptor field. In particular, we show how the density distributions of excitatory and inhibitory receptors can combine to act as a spatial filter of wave patterns. The proposed dendritic mechanism ensures that the neuron selectively responds to specific wave patterns, thus constituting a neural basis of pattern decoding. We validate this proposal in the descending motor system, where we model the large receptor fields of the pyramidal tract neurons - the principle outputs of the motor cortex - decoding motor commands encoded in the direction of traveling wave patterns in motor cortex. We use an existing model of field oscillations in motor cortex to investigate how the topology of the pyramidal cell receptor field acts to tune the cells responses to specific oscillatory wave patterns, even when those patterns are highly degraded. The model replicates key findings of the descending motor system during simple motor tasks, including variable interspike intervals and weak corticospinal coherence. By additionally showing how the nature of the wave patterns can be controlled by modulating the topology of local intra-cortical connections, we hence propose a novel integrated neuronal model of encoding and decoding motor commands.

  9. The Malaysian Public Procurement's Prevalent System and its Weaknesses

    Directory of Open Access Journals (Sweden)

    Rohana Othman

    2010-01-01

    Full Text Available Problem statement: This study examined the public procurement system as prevalent in the Malaysian government system of administration. Various aspects of public procurement are outlined including types and the processes that entail public procurement. This study also highlighted the weaknesses in the manual public procurement processes that are opened to potential abuse and mismanagement resulting in corruption. This study places the Malaysian Government public procurement system under the spotlight zeroing on allegations of abuse, tampering and corrupt practices. The study concluded that the large amount of funds allocated to public procurement coupled with excessive human intervention opportunities opened avenues that increase the risk of system abuse, profiteering and corruption. Case studies on the abuse and corruption of the public procurement system highlight the need for the Malaysian Government to eliminate the loopholes in the system, arrest the rot and implement a transparent, efficient and accountable public procurement system. Approach: Documents from the Ministry of Finance on public procurement including, among others, the Procurement Guideline Book, The Financial Procedures Act 1957, the Treasury Instructions (TI and the Treasury Circular Letter (TCL were scrutinized in studying the Malaysian Government public procurement system, its various attributes, types and processes that reflect a diversified approach to public procurement. Three case studies were cited to illustrate the susceptibility of the system to abuse and corruption. Results: Despite claims of openness and transparency of the public procurement system, it was found the current system is replete with the risk of abuse, unethical manipulations and corrupt practices. This research is limited to the analysis of data and processes related to the Malaysian Government public procurement system. The sensitivity of the subject may inhibit the collection of empirical data via

  10. Insular cortex and neuropsychiatric disorders: a review of recent literature.

    Science.gov (United States)

    Nagai, M; Kishi, K; Kato, S

    2007-09-01

    The insular cortex is located in the centre of the cerebral hemisphere, having connections with the primary and secondary somatosensory areas, anterior cingulate cortex, amygdaloid body, prefrontal cortex, superior temporal gyrus, temporal pole, orbitofrontal cortex, frontal and parietal opercula, primary and association auditory cortices, visual association cortex, olfactory bulb, hippocampus, entorhinal cortex, and motor cortex. Accordingly, dense connections exist among insular cortex neurons. The insular cortex is involved in the processing of visceral sensory, visceral motor, vestibular, attention, pain, emotion, verbal, motor information, inputs related to music and eating, in addition to gustatory, olfactory, visual, auditory, and tactile data. In this article, the literature on the relationship between the insular cortex and neuropsychiatric disorders was summarized following a computer search of the Pub-Med database. Recent neuroimaging data, including voxel based morphometry, PET and fMRI, revealed that the insular cortex was involved in various neuropsychiatric diseases such as mood disorders, panic disorders, PTSD, obsessive-compulsive disorders, eating disorders, and schizophrenia. Investigations of functions and connections of the insular cortex suggest that sensory information including gustatory, olfactory, visual, auditory, and tactile inputs converge on the insular cortex, and that these multimodal sensory information may be integrated there.

  11. Comment on "Nature of the Epidemic Threshold for the Susceptible-Infected-Susceptible Dynamics in Networks" [arXiv:1305.4819

    CERN Document Server

    Lee, Hyun Keun; Noh, Jae Dong

    2013-01-01

    Recently, Bogu\\~{n}\\'{a} {\\it et. al.} [Phys. Rev. Lett. {\\bf 111}, 068701 (2013), arXiv:1305.4819] claimed that the epidemic threshold of the susceptible-infected-susceptible (SIS) model is zero on random scale-free (SF) networks with the small-world (SW) property. They drew the conclusion by taking into account a long-range reinfection mechanism. In this Comment, we will show that such an effect is too weak to guarantee an endemic phase with a {\\em finite} fraction of infected nodes. Consequently, the epidemic threshold can be finite in random SF networks.

  12. The weak measurement process and the weak value of spin for metastable helium 23S1

    Science.gov (United States)

    Monachello, Vincenzo; Barker, Peter; Flack, Robert; Hiley, Basil

    2016-05-01

    An experiment is being designed and constructed in order to measure the weak value of spin for an atomic system. The principle of the ``weak measurement'' process was first proposed by Aharonov, Albert and Vaidman, and describes a scenario in which a system is weakly coupled to a pointer between well-defined pre- and post-selected states. This experiment will utilise a pulsed supersonic beam of spin-1 metastable Helium (He*) atoms in the 23S1 state. The spin of the pre-selected He* atoms will be weakly coupled to its centre-of-mass. During its flight, the atomic beam will be prepared in a desired quantum state and travel through two inhomogeneous magnets (weak and strong) which both comprise the ``weak measurement'' process. The deviation of the post-selected ms = + 1 state as measured using a micro-channel plate, phosphor screen and CCD camera setup will allow for the determination of the weak value of spin. This poster will report on the methods used and the experimental realisation.

  13. Microglia in the Cerebral Cortex in Autism

    Science.gov (United States)

    Tetreault, Nicole A.; Hakeem, Atiya Y.; Jiang, Sue; Williams, Brian A.; Allman, Elizabeth; Wold, Barbara J.; Allman, John M.

    2012-01-01

    We immunocytochemically identified microglia in fronto-insular (FI) and visual cortex (VC) in autopsy brains of well-phenotyped subjects with autism and matched controls, and stereologically quantified the microglial densities. Densities were determined blind to phenotype using an optical fractionator probe. In FI, individuals with autism had…

  14. Structure of Orbitofrontal Cortex Predicts Social Influence

    DEFF Research Database (Denmark)

    Campbell-Meiklejohn, Daniel; Kanai, Ryota; Bahrami, Bahador

    2012-01-01

    to guide choices and behaviour. These values can often be updated by the expressed preferences of other people as much as by independent experience. In this correspondence, we report a linear relationship between grey matter volume (GM) in a region of lateral orbitofrontal cortex (lOFCGM) and the tendency...

  15. Primary Auditory Cortex Regulates Threat Memory Specificity

    Science.gov (United States)

    Wigestrand, Mattis B.; Schiff, Hillary C.; Fyhn, Marianne; LeDoux, Joseph E.; Sears, Robert M.

    2017-01-01

    Distinguishing threatening from nonthreatening stimuli is essential for survival and stimulus generalization is a hallmark of anxiety disorders. While auditory threat learning produces long-lasting plasticity in primary auditory cortex (Au1), it is not clear whether such Au1 plasticity regulates memory specificity or generalization. We used…

  16. The Piriform Cortex and Human Focal Epilepsy

    Directory of Open Access Journals (Sweden)

    David eVaughan

    2014-12-01

    Full Text Available It is surprising that the piriform cortex, when compared to the hippocampus, has been given relatively little significance in human epilepsy. Like the hippocampus, it has a phylogenetically preserved three-layered cortex that is vulnerable to excitotoxic injury, has broad connections to both limbic and cortical areas, and is highly epileptogenic - being critical to the kindling process. The well-known phenomenon of early olfactory auras in temporal lobe epilepsy highlights its clinical relevance in humans. Perhaps because it is anatomically indistinct and difficult to approach surgically, as it clasps the middle cerebral artery, it has, until now, been understandably neglected. In this review we emphasize how its unique anatomical and functional properties, as primary olfactory cortex, predispose it to involvement in focal epilepsy. From recent convergent findings in human neuroimaging, clinical epileptology and experimental animal models, we make the case that the piriform cortex is likely to play a facilitating and amplifying role in human focal epileptogenesis, and may influence progression to epileptic intractability.

  17. The piriform cortex and human focal epilepsy.

    Science.gov (United States)

    Vaughan, David N; Jackson, Graeme D

    2014-01-01

    It is surprising that the piriform cortex, when compared to the hippocampus, has been given relatively little significance in human epilepsy. Like the hippocampus, it has a phylogenetically preserved three-layered cortex that is vulnerable to excitotoxic injury, has broad connections to both limbic and cortical areas, and is highly epileptogenic - being critical to the kindling process. The well-known phenomenon of early olfactory auras in temporal lobe epilepsy highlights its clinical relevance in human beings. Perhaps because it is anatomically indistinct and difficult to approach surgically, as it clasps the middle cerebral artery, it has, until now, been understandably neglected. In this review, we emphasize how its unique anatomical and functional properties, as primary olfactory cortex, predispose it to involvement in focal epilepsy. From recent convergent findings in human neuroimaging, clinical epileptology, and experimental animal models, we make the case that the piriform cortex is likely to play a facilitating and amplifying role in human focal epileptogenesis, and may influence progression to epileptic intractability.

  18. Contour extracting networks in early extrastriate cortex

    NARCIS (Netherlands)

    Dumoulin, Serge O.; Hess, Robert F.; May, Keith A.; Harvey, Ben M.; Rokers, Bas; Barendregt, Martijn

    2014-01-01

    Neurons in the visual cortex process a local region of visual space, but in order to adequately analyze natural images, neurons need to interact. The notion of an ''association field'' proposes that neurons interact to extract extended contours. Here, we identify the site and properties of contour

  19. Mapping tonotopy in human auditory cortex

    NARCIS (Netherlands)

    van Dijk, Pim; Langers, Dave R M; Moore, BCJ; Patterson, RD; Winter, IM; Carlyon, RP; Gockel, HE

    2013-01-01

    Tonotopy is arguably the most prominent organizational principle in the auditory pathway. Nevertheless, the layout of tonotopic maps in humans is still debated. We present neuroimaging data that robustly identify multiple tonotopic maps in the bilateral auditory cortex. In contrast with some earlier

  20. The Harmonic Organization of Auditory Cortex

    Directory of Open Access Journals (Sweden)

    Xiaoqin eWang

    2013-12-01

    Full Text Available A fundamental structure of sounds encountered in the natural environment is the harmonicity. Harmonicity is an essential component of music found in all cultures. It is also a unique feature of vocal communication sounds such as human speech and animal vocalizations. Harmonics in sounds are produced by a variety of acoustic generators and reflectors in the natural environment, including vocal apparatuses of humans and animal species as well as music instruments of many types. We live in an acoustic world full of harmonicity. Given the widespread existence of the harmonicity in many aspects of the hearing environment, it is natural to expect that it be reflected in the evolution and development of the auditory systems of both humans and animals, in particular the auditory cortex. Recent neuroimaging and neurophysiology experiments have identified regions of non-primary auditory cortex in humans and non-human primates that have selective responses to harmonic pitches. Accumulating evidence has also shown that neurons in many regions of the auditory cortex exhibit characteristic responses to harmonically related frequencies beyond the range of pitch. Together, these findings suggest that a fundamental organizational principle of auditory cortex is based on the harmonicity. Such an organization likely plays an important role in music processing by the brain. It may also form the basis of the preference for particular classes of music and voice sounds.

  1. Primary Auditory Cortex Regulates Threat Memory Specificity

    Science.gov (United States)

    Wigestrand, Mattis B.; Schiff, Hillary C.; Fyhn, Marianne; LeDoux, Joseph E.; Sears, Robert M.

    2017-01-01

    Distinguishing threatening from nonthreatening stimuli is essential for survival and stimulus generalization is a hallmark of anxiety disorders. While auditory threat learning produces long-lasting plasticity in primary auditory cortex (Au1), it is not clear whether such Au1 plasticity regulates memory specificity or generalization. We used…

  2. Hierarchical error representation in medial prefrontal cortex.

    Science.gov (United States)

    Zarr, Noah; Brown, Joshua W

    2016-01-01

    The medial prefrontal cortex (mPFC) is reliably activated by both performance and prediction errors. Error signals have typically been treated as a scalar, and it is unknown to what extent multiple error signals may co-exist within mPFC. Previous studies have shown that lateral frontal cortex (LFC) is arranged in a hierarchy of abstraction, such that more abstract concepts and rules are represented in more anterior cortical regions. Given the close interaction between lateral and medial prefrontal cortex, we explored the hypothesis that mPFC would be organized along a similar rostro-caudal gradient of abstraction, such that more abstract prediction errors are represented further anterior and more concrete errors further posterior. We show that multiple prediction error signals can be found in mPFC, and furthermore, these are arranged in a rostro-caudal gradient of abstraction which parallels that found in LFC. We used a task that requires a three-level hierarchy of rules to be followed, in which the rules changed without warning at each level of the hierarchy. Task feedback indicated which level of the rule hierarchy changed and led to corresponding prediction error signals in mPFC. Moreover, each identified region of mPFC was preferentially functionally connected to correspondingly anterior regions of LFC. These results suggest the presence of a parallel structure between lateral and medial prefrontal cortex, with the medial regions monitoring and evaluating performance based on rules maintained in the corresponding lateral regions.

  3. Contour extracting networks in early extrastriate cortex

    NARCIS (Netherlands)

    Dumoulin, Serge O.; Hess, Robert F.; May, Keith A.; Harvey, Ben M.; Rokers, Bas; Barendregt, Martijn

    2014-01-01

    Neurons in the visual cortex process a local region of visual space, but in order to adequately analyze natural images, neurons need to interact. The notion of an ''association field'' proposes that neurons interact to extract extended contours. Here, we identify the site and properties of contour i

  4. Social closeness and feedback modulate susceptibility to the framing effect.

    Science.gov (United States)

    Sip, Kamila E; Smith, David V; Porcelli, Anthony J; Kar, Kohitij; Delgado, Mauricio R

    2015-01-01

    Although we often seek social feedback (SFB) from others to help us make decisions, little is known about how SFB affects decisions under risk, particularly from a close peer. We conducted two experiments using an established framing task to probe how decision-making is modulated by SFB valence (positive, negative) and the level of closeness with feedback provider (friend, confederate). Participants faced mathematically equivalent decisions framed as either an opportunity to keep (gain frame) or lose (loss frame) part of an initial endowment. Periodically, participants were provided with positive (e.g., "Nice!") or negative (e.g., "Lame!") feedback about their choices. Such feedback was provided by either a confederate (Experiment 1) or a gender-matched close friend (Experiment 2). As expected, the framing effect was observed in both experiments. Critically, an individual's susceptibility to the framing effect was modulated by the valence of the SFB, but only when the feedback provider was a close friend. This effect was reflected in the activation patterns of ventromedial prefrontal cortex and posterior cingulate cortex, regions involved in complex decision-making. Taken together, these results highlight social closeness as an important factor in understanding the impact of SFB on neural mechanisms of decision-making.

  5. Cortex Matures Faster in Youths With Highest IQ

    Science.gov (United States)

    ... Current Issue Past Issues Research News From NIH Cortex Matures Faster in Youths With Highest IQ Past ... scans showed that their brains' outer mantle, or cortex, thickens more rapidly during childhood, reaching its peak ...

  6. Prion protein and scrapie susceptibility

    NARCIS (Netherlands)

    Smits, M.A.; Bossers, A.; Schreuder, B.E.C.

    1997-01-01

    This article presents briefly current views on the role of prion protein (PrP) in Transmissible Spongiform Encephalopathies or prion diseases and the effect of PrP polymoryhisms on the susceptibility to these diseases, with special emphasis on sheep scrapie. The PrP genotype of sheep apears to be a

  7. Topological susceptibility from overlap fermion

    Institute of Scientific and Technical Information of China (English)

    应和平; 张剑波

    2003-01-01

    We numerically calculate the topological charge of the gauge configurations on a finite lattice by the fermionic method with overlap fermions. By using the lattice index theorem, we identify the index of the massless overlap fermion operator to the topological charge of the background gauge configuration. The resulting topological susceptibility X is in good agreement with the anticipation made by Witten and Veneziano.

  8. [Raman spectra of monkey cerebral cortex tissue].

    Science.gov (United States)

    Zhu, Ji-chun; Guo, Jian-yu; Cai, Wei-ying; Wang, Zu-geng; Sun, Zhen-rong

    2010-01-01

    Monkey cerebral cortex, an important part in the brain to control action and thought activities, is mainly composed of grey matter and nerve cell. In the present paper, the in situ Raman spectra of the cerebral cortex of the birth, teenage and aged monkeys were achieved for the first time. The results show that the Raman spectra for the different age monkey cerebral cortex exhibit most obvious changes in the regions of 1000-1400 and 2800-3000 cm(-1). With monkey growing up, the relative intensities of the Raman bands at 1313 and 2885 cm(-1) mainly assigned to CH2 chain vibrational mode of lipid become stronger and stronger whereas the relative intensities of the Raman bands at 1338 and 2932 cm(-1) mainly assigned to CH3 chain vibrational mode of protein become weaker and weaker. In addition, the two new Raman bands at 1296 and 2850 cm(-1) are only observed in the aged monkey cerebral cortex, therefore, the two bands can be considered as a character or "marker" to differentiate the caducity degree with monkey growth In order to further explore the changes, the relative intensity ratios of the Raman band at 1313 cm(-1) to that at 1338 cm(-1) and the Raman band at 2885 cm(-1) to that at 2 932 cm(-1), I1313/I1338 and I2885/I2932, which are the lipid-to-protein ratios, are introduced to denote the degree of the lipid content. The results show that the relative intensity ratios increase significantly with monkey growth, namely, the lipid content in the cerebral cortex increases greatly with monkey growth. So, the authors can deduce that the overmuch lipid is an important cause to induce the caducity. Therefore, the results will be a powerful assistance and valuable parameter to study the order of life growth and diagnose diseases.

  9. The Q_weak Experimental Apparatus

    CERN Document Server

    Allison, T; Androic, D; Armstrong, D S; Asaturyan, A; Averett, T D; Averill, R; Balewski, J; Beaufait, J; Beminiwattha, R S; Benesch, J; Benmokhtar, F; Bessuille, J; Birchall, J; Bonnell, E; Bowman, J; Brindza, P; Brown, D B; Carlini, R D; Cates, G D; Cavness, B; Clark, G; Cornejo, J C; Dusa, S Covrig; Dalton, M M; Davis, C A; Dean, D C; Deconinck, W; Diefenbach, J; Dow, K; Dowd, J F; Dunne, J A; Dutta, D; Duvall, W S; Echols, J R; Elaasar, M; Falk, W R; Finelli, K D; Finn, J M; Gaskell, D; Gericke, M T W; Grames, J; Gray, V M; Grimm, K; Guo, F; Hansknecht, J; Harrison, D J; Henderson, E; Hoskins, J R; Ihloff, E; Johnston, K; Jones, D; Jones, M; Jones, R; Kargiantoulakis, M; Kelsey, J; Khan, N; King, P M; Korkmaz, E; Kowalski, S; Kubera, A; Leacock, J; Leckey, J P; Lee, A R; Lee, J H; Lee, L; Liang, Y; MacEwan, S; Mack, D; Magee, J A; Mahurin, R; Mammei, J; Martin, J W; McCreary, A; McDonald, M H; McHugh, M J; Medeiros, P; Meekins, D; Mei, J; Michaels, R; Micherdzinska, A; Mkrtchyan, A; Mkrtchyan, H; Morgan, N; Musson, J; Mesick, K E; Narayan, A; Ndukum, L Z; Nelyubin, V; Nuruzzaman,; van Oers, W T H; Opper, A K; Page, S A; Pan, J; Paschke, K D; Phillips, S K; Pitt, M L; Poelker, M; Rajotte, J F; Ramsay, W D; Roberts, W R; Roche, J; Rose, P W; Sawatzky, B; Seva, T; Shabestari, M H; Silwal, R; Simicevic, N; Smith, G R; Sobczynski, S; Solvignon, P; Spayde, D T; Stokes, B; Storey, D W; Subedi, A; Subedi, R; Suleiman, R; Tadevosyan, V; Tobias, W A; Tvaskis, V; Urban, E; Waidyawansa, B; Wang, P; Wells, S P; Wood, S A; Yang, S; Zhamkochyan, S; Zielinski, R B

    2014-01-01

    The Jefferson Lab Q_weak experiment determined the weak charge of the proton by measuring the parity-violating elastic scattering asymmetry of longitudinally polarized electrons from an unpolarized liquid hydrogen target at small momentum transfer. A custom apparatus was designed for this experiment to meet the technical challenges presented by the smallest and most precise ${\\vec{e}}$p asymmetry ever measured. Technical milestones were achieved at Jefferson Lab in target power, beam current, beam helicity reversal rate, polarimetry, detected rates, and control of helicity-correlated beam properties. The experiment employed 180 microA of 89% longitudinally polarized electrons whose helicity was reversed 960 times per second. The electrons were accelerated to 1.16 GeV and directed to a beamline with extensive instrumentation to measure helicity-correlated beam properties that can induce false asymmetries. Moller and Compton polarimetry were used to measure the electron beam polarization to better than 1%. The ...

  10. Universal portfolios generated by weakly stationary processes

    Science.gov (United States)

    Tan, Choon Peng; Pang, Sook Theng

    2014-12-01

    Recently, a universal portfolio generated by a set of independent Brownian motions where a finite number of past stock prices are weighted by the moments of the multivariate normal distribution is introduced and studied. The multivariate normal moments as polynomials in time consequently lead to a constant rebalanced portfolio depending on the drift coefficients of the Brownian motions. For a weakly stationary process, a different type of universal portfolio is proposed where the weights on the stock prices depend only on the time differences of the stock prices. An empirical study is conducted on the returns achieved by the universal portfolios generated by the Ornstein-Uhlenbeck process on selected stock-price data sets. Promising results are demonstrated for increasing the wealth of the investor by using the weakly-stationary-process-generated universal portfolios.

  11. Weak cosmic censorship: as strong as ever.

    Science.gov (United States)

    Hod, Shahar

    2008-03-28

    Spacetime singularities that arise in gravitational collapse are always hidden inside of black holes. This is the essence of the weak cosmic censorship conjecture. The hypothesis, put forward by Penrose 40 years ago, is still one of the most important open questions in general relativity. In this Letter, we reanalyze extreme situations which have been considered as counterexamples to the weak cosmic censorship conjecture. In particular, we consider the absorption of scalar particles with large angular momentum by a black hole. Ignoring back reaction effects may lead one to conclude that the incident wave may overspin the black hole, thereby exposing its inner singularity to distant observers. However, we show that when back reaction effects are properly taken into account, the stability of the black-hole event horizon is irrefutable. We therefore conclude that cosmic censorship is actually respected in this type of gedanken experiments.

  12. A dynamical weak scale from inflation

    Science.gov (United States)

    You, Tevong

    2017-09-01

    Dynamical scanning of the Higgs mass by an axion-like particle during inflation may provide a cosmological component to explaining part of the hierarchy problem. We propose a novel interplay of this cosmological relaxation mechanism with inflation, whereby the backreaction of the Higgs vacuum expectation value near the weak scale causes inflation to end. As Hubble drops, the relaxion's dissipative friction increases relative to Hubble and slows it down enough to be trapped by the barriers of its periodic potential. Such a scenario raises the natural cut-off of the theory up to ~ 1010 GeV, while maintaining a minimal relaxion sector without having to introduce additional scanning scalars or new physics coincidentally close to the weak scale.

  13. The regularization of Old English weak verbs

    Directory of Open Access Journals (Sweden)

    Marta Tío Sáenz

    2015-07-01

    Full Text Available This article deals with the regularization of non-standard spellings of the verbal forms extracted from a corpus. It addresses the question of what the limits of regularization are when lemmatizing Old English weak verbs. The purpose of such regularization, also known as normalization, is to carry out lexicological analysis or lexicographical work. The analysis concentrates on weak verbs from the second class and draws on the lexical database of Old English Nerthus, which has incorporated the texts of the Dictionary of Old English Corpus. As regards the question of the limits of normalization, the solution adopted are, in the first place, that when it is necessary to regularize, normalization is restricted to correspondences based on dialectal and diachronic variation and, secondly, that normalization has to be unidirectional.

  14. Towards weakly constrained double field theory

    Directory of Open Access Journals (Sweden)

    Kanghoon Lee

    2016-08-01

    Full Text Available We show that it is possible to construct a well-defined effective field theory incorporating string winding modes without using strong constraint in double field theory. We show that X-ray (Radon transform on a torus is well-suited for describing weakly constrained double fields, and any weakly constrained fields are represented as a sum of strongly constrained fields. Using inverse X-ray transform we define a novel binary operation which is compatible with the level matching constraint. Based on this formalism, we construct a consistent gauge transform and gauge invariant action without using strong constraint. We then discuss the relation of our result to the closed string field theory. Our construction suggests that there exists an effective field theory description for massless sector of closed string field theory on a torus in an associative truncation.

  15. Weak Convergence Theorems for Nonself Mappings

    Institute of Scientific and Technical Information of China (English)

    Liu Yong-quan; Guo Wei-ping; Ji You-qing

    2015-01-01

    Let E be a real uniformly convex and smooth Banach space, and K be a nonempty closed convex subset of E with P as a sunny nonexpansive retrac-tion. Let T1, T2 : K → E be two weakly inward nonself asymptotically nonexpan-sive mappings with respect to P with a sequence {k(i)n } ⊂ [1,∞) (i = 1, 2), and F := F (T1)∩F (T2) = ∅. An iterative sequence for approximation common fixed points of the two nonself asymptotically nonexpansive mappings is discussed. If E has also a Fr´echet differentiable norm or its dual E∗ has Kadec-Klee property, then weak convergence theorems are obtained.

  16. Model Reduction of Strong-Weak Neurons

    Directory of Open Access Journals (Sweden)

    Steven James Cox

    2014-12-01

    Full Text Available We consider neurons with large dendritic trees that are weakly excitable in the sense that back propagating action potentials are severly attenuated as they travelfrom the small, strongly excitable, spike initiation zone. In previous workwe have shown that the computational size of weakly excitable cell modelsmay be reduced by two or more orders of magnitude, and that the size of stronglyexcitable models may be reduced by at least one order of magnitude,without sacrificing thespatio-temporal nature of its inputs (in the sense we reproduce the cell's precise mapping of inputs to outputs. We combine the best of these twostrategies via a predictor--corrector decomposition scheme andachieve a drastically reduced highly accurate model of a caricature of the neuron responsible for collision detection in the locust.

  17. Model reduction of strong-weak neurons.

    Science.gov (United States)

    Du, Bosen; Sorensen, Danny; Cox, Steven J

    2014-01-01

    We consider neurons with large dendritic trees that are weakly excitable in the sense that back propagating action potentials are severly attenuated as they travel from the small, strongly excitable, spike initiation zone. In previous work we have shown that the computational size of weakly excitable cell models may be reduced by two or more orders of magnitude, and that the size of strongly excitable models may be reduced by at least one order of magnitude, without sacrificing the spatio-temporal nature of its inputs (in the sense we reproduce the cell's precise mapping of inputs to outputs). We combine the best of these two strategies via a predictor-corrector decomposition scheme and achieve a drastically reduced highly accurate model of a caricature of the neuron responsible for collision detection in the locust.

  18. Weak lensing tomography with orthogonal polynomials

    CERN Document Server

    Schaefer, Bjoern Malte

    2011-01-01

    The topic of this article is weak cosmic shear tomography where the line of sight-weighting is carried out with a set of specifically constructed orthogonal polynomials, dubbed TaRDiS (Tomography with orthogonAl Radial Distance polynomIal Systems). We investigate the properties of these polynomials and employ weak convergence spectra, which have been obtained by weighting with these polynomials, for the estimation of cosmological parameters. We quantify their power in constraining parameters in a Fisher-matrix technique and demonstrate how each polynomial projects out statistically independent information, and how the combination of multiple polynomials lifts degeneracies. The assumption of a reference cosmology is needed for the construction of the polynomials, and as a last point we investigate how errors in the construction with a wrong cosmological model propagate to misestimates in cosmological parameters. TaRDiS performs on a similar level as traditional tomographic methods and some key features of tomo...

  19. Weak lensing tomography with orthogonal polynomials

    Science.gov (United States)

    Schäfer, Björn Malte; Heisenberg, Lavinia

    2012-07-01

    The topic of this paper is weak cosmic shear tomography where the line-of-sight weighting is carried out with a set of specifically constructed orthogonal polynomials, dubbed Tomography with Orthogonal Radial Distance Polynomial Systems (TaRDiS). We investigate the properties of these polynomials and employ weak convergence spectra, which have been obtained by weighting with these polynomials, for the estimation of cosmological parameters. We quantify their power in constraining parameters in a Fisher matrix technique and demonstrate how each polynomial projects out statistically independent information, and how the combination of multiple polynomials lifts degeneracies. The assumption of a reference cosmology is needed for the construction of the polynomials, and as a last point we investigate how errors in the construction with a wrong cosmological model propagate to misestimates in cosmological parameters. TaRDiS performs on a similar level as traditional tomographic methods and some key features of tomography are made easier to understand.

  20. Atmospheric dispersion effects in weak lensing measurements

    CERN Document Server

    Plazas, Andrés A

    2012-01-01

    The wavelength dependence of atmospheric refraction causes elongation of finite-bandwidth images along the elevation vector, which produces spurious signals in weak gravitational lensing shear measurements unless this atmospheric dispersion is calibrated and removed to high precision. Because astrometric solutions and point spread function (PSF) characteristics are typically calibrated from stellar images, differences between the reference stars' spectra and the galaxies' spectra will leave residual errors in both the astrometric positions ($\\Delta{\\bar{R}}$) and in the second moment (width) of the wavelength-averaged PSF ($\\Delta{v}$) for galaxies. We estimate the level of $\\Delta{V}$ that will induce spurious weak lensing signals in PSF-corrected galaxy shapes that exceed the statistical errors of the {\\em Dark Energy Survey (DES)} and the {\\em Large Synoptic Survey Telescope (LSST)} cosmic-shear experiments. We also estimate the $\\Delta{\\bar{R}}$ signals that will produce unacceptable spurious distortions ...

  1. Towards weakly constrained double field theory

    Science.gov (United States)

    Lee, Kanghoon

    2016-08-01

    We show that it is possible to construct a well-defined effective field theory incorporating string winding modes without using strong constraint in double field theory. We show that X-ray (Radon) transform on a torus is well-suited for describing weakly constrained double fields, and any weakly constrained fields are represented as a sum of strongly constrained fields. Using inverse X-ray transform we define a novel binary operation which is compatible with the level matching constraint. Based on this formalism, we construct a consistent gauge transform and gauge invariant action without using strong constraint. We then discuss the relation of our result to the closed string field theory. Our construction suggests that there exists an effective field theory description for massless sector of closed string field theory on a torus in an associative truncation.

  2. Shock Wave Dynamics in Weakly Ionized Plasmas

    Science.gov (United States)

    Johnson, Joseph A., III

    1999-01-01

    An investigation of the dynamics of shock waves in weakly ionized argon plasmas has been performed using a pressure ruptured shock tube. The velocity of the shock is observed to increase when the shock traverses the plasma. The observed increases cannot be accounted for by thermal effects alone. Possible mechanisms that could explain the anomalous behavior include a vibrational/translational relaxation in the nonequilibrium plasma, electron diffusion across the shock front resulting from high electron mobility, and the propagation of ion-acoustic waves generated at the shock front. Using a turbulence model based on reduced kinetic theory, analysis of the observed results suggest a role for turbulence in anomalous shock dynamics in weakly ionized media and plasma-induced hypersonic drag reduction.

  3. Asymptotic theory of weakly dependent random processes

    CERN Document Server

    Rio, Emmanuel

    2017-01-01

    Presenting tools to aid understanding of asymptotic theory and weakly dependent processes, this book is devoted to inequalities and limit theorems for sequences of random variables that are strongly mixing in the sense of Rosenblatt, or absolutely regular. The first chapter introduces covariance inequalities under strong mixing or absolute regularity. These covariance inequalities are applied in Chapters 2, 3 and 4 to moment inequalities, rates of convergence in the strong law, and central limit theorems. Chapter 5 concerns coupling. In Chapter 6 new deviation inequalities and new moment inequalities for partial sums via the coupling lemmas of Chapter 5 are derived and applied to the bounded law of the iterated logarithm. Chapters 7 and 8 deal with the theory of empirical processes under weak dependence. Lastly, Chapter 9 describes links between ergodicity, return times and rates of mixing in the case of irreducible Markov chains. Each chapter ends with a set of exercises. The book is an updated and extended ...

  4. Strong side of weak topological insulators

    Science.gov (United States)

    Ringel, Zohar; Kraus, Yaacov E.; Stern, Ady

    2012-07-01

    Three-dimensional topological insulators are classified into “strong” (STI) and “weak” (WTI) according to the nature of their surface states. While the surface states of the STI are topologically protected from localization, this does not hold for the WTI. In this work, we show that the surface states of the WTI are actually protected from any random perturbation that does not break time-reversal symmetry, and does not close the bulk energy gap. Consequently, the conductivity of metallic surfaces in the clean system remains finite even in the presence of strong disorder of this type. In the weak disorder limit, the surfaces are found to be perfect metals, and strong surface disorder only acts to push the metallic surfaces inwards. We find that the WTI differs from the STI primarily in its anisotropy, and that the anisotropy is not a sign of its weakness but rather of its richness.

  5. The Weak Gravity Conjecture in three dimensions

    Energy Technology Data Exchange (ETDEWEB)

    Montero, Miguel [Departamento de Física Teórica, Facultad de Ciencias,Universidad Autónoma de Madrid,Calle Francisco Tomás y Valiente 7, 28049 Madrid (Spain); Instituto de Física Teórica IFT-UAM/CSIC, Campus de Cantoblanco,C/ Nicolás Cabrera 13-15, 28049 Madrid (Spain); Shiu, Gary; Soler, Pablo [Department of Physics, University of Wisconsin-Madison,1150 University Ave, Madison, WI 53706 (United States); Department of Physics & Institute for Advanced Study,Hong Kong University of Science and Technology,Lo Ka Chung Building, Lee Shau Kee Campus, Clear Water Bay (Hong Kong)

    2016-10-28

    We study weakly coupled U(1) theories in AdS{sub 3}, their associated charged BTZ solutions, and their charged spectra. We find that modular invariance of the holographic dual two-dimensional CFT and compactness of the gauge group together imply the existence of charged operators with conformal dimension significantly below the black hole threshold. We regard this as a form of the Weak Gravity Conjecture (WGC) in three dimensions. We also explore the constraints posed by modular invariance on a particular discrete ℤ{sub N} symmetry which arises in our discussion. In this case, modular invariance does not guarantee the existence of light ℤ{sub N}-charged states. We also highlight the differences between our discussion and the usual heuristic arguments for the WGC based on black hole remnants.

  6. Security Weaknesses in Arbitrated Quantum Signature Protocols

    Science.gov (United States)

    Liu, Feng; Zhang, Kejia; Cao, Tianqing

    2014-01-01

    Arbitrated quantum signature (AQS) is a cryptographic scenario in which the sender (signer), Alice, generates the signature of a message and then a receiver (verifier), Bob, can verify the signature with the help of a trusted arbitrator, Trent. In this paper, we point out there exist some security weaknesses in two AQS protocols. Our analysis shows Alice can successfully disavow any of her signatures by a simple attack in the first protocol. Furthermore, we study the security weaknesses of the second protocol from the aspects of forgery and disavowal. Some potential improvements of this kind of protocols are given. We also design a new method to authenticate a signature or a message, which makes AQS protocols immune to Alice's disavowal attack and Bob's forgery attack effectively.

  7. The Weak Gravity Conjecture in three dimensions

    CERN Document Server

    Montero, Miguel; Soler, Pablo

    2016-01-01

    We study weakly coupled $U(1)$ theories in $AdS_3$, their associated charged BTZ solutions, and their charged spectra. We find that modular invariance of the holographic dual two-dimensional CFT and compactness of the gauge group together imply the existence of charged operators with conformal dimension significantly below the black hole threshold. We regard this as a form of the Weak Gravity Conjecture (WGC) in three dimensions. We also explore the constraints posed by modular invariance on a particular discrete $\\mathbb{Z}_N$ symmetry which arises in our discussion. In this case, modular invariance does not guarantee the existence of light $\\mathbb{Z}_N$-charged states. We also highlight the differences between our discussion and the usual heuristic arguments for the WGC based on black hole remnants.

  8. Testing Lorentz invariance in weak decays

    Energy Technology Data Exchange (ETDEWEB)

    Sytema, Auke; Dijck, Elwin; Hoekstra, Steven; Jungmann, Klaus; Mueller, Stefan; Noordmans, Jacob; Onderwater, Gerco; Pijpker, Coen; Timmermans, Rob; Vos, Keri; Willmann, Lorenz; Wilschut, Hans [Van Swinderen Institute, University of Groningen (Netherlands)

    2015-07-01

    Lorentz invariance is the invariance of physical laws under orientations and boosts. It is a key assumption in Special Relativity and the Standard Model of Particle Physics. Several theories unifying General Relativity and Quantum Mechanics allow breaking of Lorentz invariance. At the Van Swinderen Institute in Groningen a theoretical and experimental research program was started to study Lorentz invariance violation (LIV) in weak interactions. The theoretical work allowed a systematic approach to LIV in weak decays. Limits could be set on parameters that quantify LIV. A novel beta decay experiment was designed which tests rotational invariance with respect to the orientation of nuclear spin. In particular, using the isotope {sup 20}Na, the decay rate dependence on the nuclear polarization direction was measured. Searching for sidereal variations, systematic errors can be suppressed. The result of the experiment is presented.

  9. Image Segmentation Using Weak Shape Priors

    CERN Document Server

    Xu, Robert Sheng; Salama, Magdy

    2010-01-01

    The problem of image segmentation is known to become particularly challenging in the case of partial occlusion of the object(s) of interest, background clutter, and the presence of strong noise. To overcome this problem, the present paper introduces a novel approach segmentation through the use of "weak" shape priors. Specifically, in the proposed method, an segmenting active contour is constrained to converge to a configuration at which its geometric parameters attain their empirical probability densities closely matching the corresponding model densities that are learned based on training samples. It is shown through numerical experiments that the proposed shape modeling can be regarded as "weak" in the sense that it minimally influences the segmentation, which is allowed to be dominated by data-related forces. On the other hand, the priors provide sufficient constraints to regularize the convergence of segmentation, while requiring substantially smaller training sets to yield less biased results as compare...

  10. Towards Weakly Constrained Double Field Theory

    CERN Document Server

    Lee, Kanghoon

    2015-01-01

    We show that it is possible to construct a well-defined effective field theory incorporating string winding modes without using strong constraint in double field theory. We show that X-ray (Radon) transform on a torus is well-suited for describing weakly constrained double fields, and any weakly constrained fields are represented as a sum of strongly constrained fields. Using inverse X- ray transform we define a novel binary operation which is compatible with the level matching constraint. Based on this formalism, we construct a consistent gauge transform and gauge invariant action without using strong constraint. We then discuss the relation of our result to the closed string field theory. Our construction suggests that there exists an effective field theory description for massless sector of closed string field theory on a torus in an associative truncation.

  11. Olfactory consciousness and gamma oscillation couplings across the olfactory bulb, olfactory cortex, and orbitofrontal cortex

    OpenAIRE

    Kensaku eMori; Hiroyuki eManabe; Kimiya eNarikiyo; Naomi eOnisawa

    2013-01-01

    The orbitofrontal cortex receives multi-modality sensory inputs, including olfactory input, and is thought to be involved in conscious perception of the olfactory image of objects. Generation of olfactory consciousness requires neuronal circuit mechanisms for the ‘binding’ of distributed neuronal activities, with each constituent neuron representing a specific component of an olfactory percept. The shortest neuronal pathway for odor signals to reach the orbitofrontal cortex is olfactory senso...

  12. Premotor cortex modulates somatosensory cortex during voluntary movements without proprioceptive feedback

    DEFF Research Database (Denmark)

    Christensen, Mark Schram; Lundbye-Jensen, Jesper; Geertsen, Svend Sparre;

    2007-01-01

    Movement perception relies on sensory feedback, but the involvement of efference copies remains unclear. We investigated movements without proprioceptive feedback using ischemic nerve block during fMRI in healthy humans, and found preserved activation of the primary somatosensory cortex. This act......Movement perception relies on sensory feedback, but the involvement of efference copies remains unclear. We investigated movements without proprioceptive feedback using ischemic nerve block during fMRI in healthy humans, and found preserved activation of the primary somatosensory cortex...

  13. Projection from the perirhinal cortex to the frontal motor cortex in the rat.

    Science.gov (United States)

    Kyuhou, Shin ichi; Gemba, Hisae

    2002-03-01

    Stimulation of the anterior perirhinal cortex (PERa) induced marked surface-negative and depth-positive field potentials in the rat frontal motor cortex (MC) including the rostral and caudal forelimb areas. Injection of biotinylated dextran into the PERa densely labeled axon terminals in the superficial layers of the MC, where vigorous unit responses were evoked after PERa stimulation, indicated that the perirhinal-frontal projection preferentially activates the superficial layer neurons of the MC.

  14. Mixed methods for elastodynamics with weak symmetry

    OpenAIRE

    Arnold, Douglas N.; Lee, Jeonghun J.

    2013-01-01

    We analyze the application to elastodynamic problems of mixed finite element methods for elasticity with weak symmetry. Our approach leads to a semidiscrete method which consists of a system of ordinary differential equations without algebraic constraints. Our error analysis, which is based on a new elliptic projection operator, applies to several mixed finite element spaces developed for elastostatics. The error estimates we obtain are robust for nearly incompressible materials.

  15. Nonuniversality of weak synchronization in chaotic systems

    OpenAIRE

    Vieira, M. de Sousa; Lichtenberg, A.J.

    1997-01-01

    We show that the separate properties of weak synchronization (WS) and strong synchronization (SS), reported recently by Pyragas [K. Pyragas, Phys. Rev. E, 54, R4508 (1996)], in unidirectionally coupled chaotic systems, are not generally distinct properties of such systems. In particular, we find analytically for the tent map and numerically for some parameters of the circle map that the transition to WS and SS coincide.

  16. Acute neuromuscular weakness associated with dengue infection

    OpenAIRE

    Harmanjit Singh Hira; Amandeep Kaur; Anuj Shukla

    2012-01-01

    Background: Dengue infections may present with neurological complications. Whether these are due to neuromuscular disease or electrolyte imbalance is unclear. Materials and Methods: Eighty-eight patients of dengue fever required hospitalization during epidemic in year 2010. Twelve of them presented with acute neuromuscular weakness. We enrolled them for study. Diagnosis of dengue infection based on clinical profile of patients, positive serum IgM ELISA, NS1 antigen, and sero-typing. Complete ...

  17. Acute neuromuscular weakness associated with dengue infection

    Directory of Open Access Journals (Sweden)

    Harmanjit Singh Hira

    2012-01-01

    Full Text Available Background: Dengue infections may present with neurological complications. Whether these are due to neuromuscular disease or electrolyte imbalance is unclear. Materials and Methods: Eighty-eight patients of dengue fever required hospitalization during epidemic in year 2010. Twelve of them presented with acute neuromuscular weakness. We enrolled them for study. Diagnosis of dengue infection based on clinical profile of patients, positive serum IgM ELISA, NS1 antigen, and sero-typing. Complete hemogram, kidney and liver functions, serum electrolytes, and creatine phosphokinase (CPK were tested. In addition, two patients underwent nerve conduction velocity (NCV test and electromyography. Results: Twelve patients were included in the present study. Their age was between 18 and 34 years. Fever, myalgia, and motor weakness of limbs were most common presenting symptoms. Motor weakness developed on 2 nd to 4 th day of illness in 11 of 12 patients. In one patient, it developed on 10 th day of illness. Ten of 12 showed hypokalemia. One was of Guillain-Barré syndrome and other suffered from myositis; they underwent NCV and electromyography. Serum CPK and SGOT raised in 8 out of 12 patients. CPK of patient of myositis was 5098 IU. All of 12 patients had thrombocytopenia. WBC was in normal range. Dengue virus was isolated in three patients, and it was of serotype 1. CSF was normal in all. Within 24 hours, those with hypokalemia recovered by potassium correction. Conclusions: It was concluded that the dengue virus infection led to acute neuromuscular weakness because of hypokalemia, myositis, and Guillain-Barré syndrome. It was suggested to look for presence of hypokalemia in such patients.

  18. Precision frequency measurements with interferometric weak values

    CERN Document Server

    Starling, David J; Jordan, Andrew N; Howell, John C; 10.1103/PhysRevA.82.063822

    2011-01-01

    We demonstrate an experiment which utilizes a Sagnac interferometer to measure a change in optical frequency of 129 kHz per root Hz with only 2 mW of continuous wave, single mode input power. We describe the measurement of a weak value and show how even higher frequency sensitivities may be obtained over a bandwidth of several nanometers. This technique has many possible applications, such as precision relative frequency measurements and laser locking without the use of atomic lines.

  19. Synchronization of cardiorhythm by weak external forcing

    Directory of Open Access Journals (Sweden)

    V. S. Anishchenko

    2000-01-01

    Full Text Available We study the possibility to synchronize cardiorhythm of a human by periodic and aperiodic sequences of light and sound pulses. Aperiodic forcing is defined by variation of RR intervals of another subject. Phase locking between cardiorhythm and weak external forcing is detected on finite time intervals. We observe the 1:1 synchronization for periodic forcing and n:m synchronization for aperiodic one.

  20. On weak solutions of random differential inclusions

    Directory of Open Access Journals (Sweden)

    Mariusz Michta

    1995-01-01

    where G is a given set-valued mapping value in the space Kn of all nonempty, compact and convex subsets of the space ℝn, and μ is some probability measure on the Borel σ-algebra in ℝn. Under certain restrictions imposed on F and μ, we obtain weak solutions of problem (I, where the initial condition requires that the solution of (I has a given distribution at time t=0.

  1. On weakly D-differentiable operators

    DEFF Research Database (Denmark)

    Christensen, Erik

    2016-01-01

    Let DD be a self-adjoint operator on a Hilbert space HH and aa a bounded operator on HH. We say that aa is weakly DD-differentiable, if for any pair of vectors ξ,ηξ,η from HH the function 〈eitDae−itDξ,η〉〈eitDae−itDξ,η〉 is differentiable. We give an elementary example of a bounded operator aa, suc...

  2. [Weak signal detection in every heart cycle].

    Science.gov (United States)

    Yuan, J; Xu, X; Gao, D; Shi, G

    2001-12-01

    In this article, a new approach is introduced to lowering the myo-electronic noise in weak ECG signals. We use artificial neural network to make the noise be white, and then we adopt an adaptive filter of which the reference signal is achieved by extracting from other ECG cycle. The outcome is the reduction of both white noise and non-white noise in ECG signal. Satisfactory results have been achieved by using this method in the experiment of late potential detection.

  3. Orbitofrontal cortex, decision-making and drug addiction

    OpenAIRE

    Schoenbaum, Geoffrey; Roesch, Matthew R.; Stalnaker, Thomas A

    2006-01-01

    The orbitofrontal cortex, as a part of prefrontal cortex, is implicated in executive function. However, within this broad region, the orbitofrontal cortex is distinguished by its unique pattern of connections with crucial subcortical associative learning nodes, such as basolateral amygdala and nucleus accumbens. By virtue of these connections, the orbitofrontal cortex is uniquely positioned to use associative information to project into the future, and to use the value of perceived or expecte...

  4. The Weak Expectation Property and Riesz Interpolation

    CERN Document Server

    Kavruk, Ali S

    2012-01-01

    We show that Lance's weak expectation property is connected to tight Riesz interpolations in lattice theory. More precisely we first prove that if A \\subset B(H) is a unital C*-subalgebra, where B(H) is the bounded linear operators on a Hilbert space H, then A has (2,2) tight Riesz interpolation property in B(H) (defined below). An extension of this requires an additional assumption on A: A has (2,3) tight Riesz interpolation property in B(H) at every matricial level if and only if A has the weak expectation property. Let $J = span{(1,1,-1,-1,-1)}$ in $C^5$ . We show that a unital C*-algebra A has the weak expectation property if and only if $A \\otimesmin (C^5/J) = A \\otimesmax (C^5/J)$ (here \\otimesmin and \\otimesmax are the minimal and the maximal operator system tensor products, respectively, and $C^5/J$ is the operator system quotient of $C^5$ by $J$). We express the Kirchberg conjecture (KC) in terms of a four dimensional operator system problem. We prove that KC has an affirmative answer if and only if ...

  5. Heating Cooling Flows with Weak Shock Waves

    CERN Document Server

    Mathews, W G; Brighenti, F

    2006-01-01

    The discovery of extended, approximately spherical weak shock waves in the hot intercluster gas in Perseus and Virgo has precipitated the notion that these waves may be the primary heating process that explains why so little gas cools to low temperatures. This type of heating has received additional support from recent gasdynamical models. We show here that outward propagating, dissipating waves deposit most of their energy near the center of the cluster atmosphere. Consequently, if the gas is heated by (intermittent) weak shocks for several Gyrs, the gas within 30-50 kpc is heated to temperatures that far exceed observed values. This heating can be avoided if dissipating shocks are sufficiently infrequent or weak so as not to be the primary source of global heating. Local PV and viscous heating associated with newly formed X-ray cavities are likely to be small, which is consistent with the low gas temperatures generally observed near the centers of groups and clusters where the cavities are located.

  6. Evidence for a sublattice weak gravity conjecture

    Science.gov (United States)

    Heidenreich, Ben; Reece, Matthew; Rudelius, Tom

    2017-08-01

    The Weak Gravity Conjecture postulates the existence of superextremal charged particles, i.e. those with mass smaller than or equal to their charge in Planck units. We present further evidence for our recent observation that in known examples a much stronger statement is true: an infinite tower of superextremal particles of different charges exists. We show that effective Kaluza-Klein field theories and perturbative string vacua respect the Sublattice Weak Gravity Conjecture, namely that a finite index sublattice of the full charge lattice exists with a superextremal particle at each site. In perturbative string theory we show that this follows from modular invariance. However, we present counterexamples to the stronger possibility that a superextremal particle exists at every lattice site, including an example in which the lightest charged particle is subextremal. The Sublattice Weak Gravity Conjecture has many implications both for abstract theories of quantum gravity and for real-world physics. For instance, it implies that if a gauge group with very small coupling e exists, then the fundamental gravitational cutoff energy of the theory is no higher than ˜ e 1/3 M Pl.

  7. Topic Level Disambiguation for Weak Queries

    Directory of Open Access Journals (Sweden)

    Zhang, Hui

    2013-09-01

    Full Text Available Despite limited success, today's information retrieval (IR systems are not intelligent or reliable. IR systems return poor search results when users formulate their information needs into incomplete or ambiguous queries (i.e., weak queries. Therefore, one of the main challenges in modern IR research is to provide consistent results across all queries by improving the performance on weak queries. However, existing IR approaches such as query expansion are not overly effective because they make little effort to analyze and exploit the meanings of the queries. Furthermore, word sense disambiguation approaches, which rely on textual context, are ineffective against weak queries that are typically short. Motivated by the demand for a robust IR system that can consistently provide highly accurate results, the proposed study implemented a novel topic detection that leveraged both the language model and structural knowledge of Wikipedia and systematically evaluated the effect of query disambiguation and topic-based retrieval approaches on TREC collections. The results not only confirm the effectiveness of the proposed topic detection and topic-based retrieval approaches but also demonstrate that query disambiguation does not improve IR as expected.

  8. Francium Spectroscopy for Weak Interaction Studies

    Science.gov (United States)

    Orozco, Luis

    2014-05-01

    Francium, a radioactive element, is the heaviest alkali. Its atomic and nuclear structure makes it an ideal laboratory to study the weak interaction. Laser trapping and cooling in-line with the superconducting LINAC accelerator at Stony Brook opened the precision study of its atomic structure. I will present our proposal and progress towards weak interaction measurements at TRIUMF, the National Canadian Accelerator in Vancouver. These include the commissioning run of the Francium Trapping Facility, hyperfine anomaly measurements on a chain of Fr isotopes, the nuclear anapole moment through parity non-conserving transitions in the ground state hyperfine manifold. These measurements should shed light on the nucleon-nucleon weak interaction. This work is done by the FrPNC collaboration: S. Aubin College of William and Mary, J. A. Behr TRIUMF, R. Collister U. Manitoba, E. Gomez UASLP, G. Gwinner U. Manitoba, M. R. Pearson TRIUMF, L. A. Orozco UMD, M. Tandecki TRIUMF, J. Zhang UMD Supported by NSF and DOE from the USA; TRIUMF, NRC and NSERC from Canada; and CONACYT from Mexico

  9. Cholecystokinin from the entorhinal cortex enables neural plasticity in the auditory cortex.

    Science.gov (United States)

    Li, Xiao; Yu, Kai; Zhang, Zicong; Sun, Wenjian; Yang, Zhou; Feng, Jingyu; Chen, Xi; Liu, Chun-Hua; Wang, Haitao; Guo, Yi Ping; He, Jufang

    2014-03-01

    Patients with damage to the medial temporal lobe show deficits in forming new declarative memories but can still recall older memories, suggesting that the medial temporal lobe is necessary for encoding memories in the neocortex. Here, we found that cortical projection neurons in the perirhinal and entorhinal cortices were mostly immunopositive for cholecystokinin (CCK). Local infusion of CCK in the auditory cortex of anesthetized rats induced plastic changes that enabled cortical neurons to potentiate their responses or to start responding to an auditory stimulus that was paired with a tone that robustly triggered action potentials. CCK infusion also enabled auditory neurons to start responding to a light stimulus that was paired with a noise burst. In vivo intracellular recordings in the auditory cortex showed that synaptic strength was potentiated after two pairings of presynaptic and postsynaptic activity in the presence of CCK. Infusion of a CCKB antagonist in the auditory cortex prevented the formation of a visuo-auditory association in awake rats. Finally, activation of the entorhinal cortex potentiated neuronal responses in the auditory cortex, which was suppressed by infusion of a CCKB antagonist. Together, these findings suggest that the medial temporal lobe influences neocortical plasticity via CCK-positive cortical projection neurons in the entorhinal cortex.

  10. The role of the ventromedial prefrontal cortex in purchase intent among older adults

    Directory of Open Access Journals (Sweden)

    Bryan P Koestner

    2016-08-01

    Full Text Available Older adults are frequently the targets of scams and deception, with millions of individuals being affected each year in the United States alone. Previous research has shown that the ventromedial prefrontal cortex may play a role in vulnerability to fraud. The current study examined brain activation patterns in relation to susceptibility to scams and fraud using functional magnetic resonance imaging. Twenty-eight healthy, community-dwelling older adults were subdivided into groups of impaired and unimpaired decision makers as determined by their performance on the Iowa Gambling Task. While in the scanner, the participants viewed advertisements that were created directly from cases deemed deceptive by the Federal Trade Commission. We then obtained behavioral measures involving comprehension of claims and purchase intentions of the product in each advertisement. Contrasts show brain activity in the ventromedial prefrontal cortex was less correlated with purchase intention in impaired versus unimpaired older adult decision makers. Our results have important implications for both future research and recognizing the possible causes of fraud susceptibility among older adults.

  11. Sensitive Dependence of Mental Function on Prefrontal Cortex

    OpenAIRE

    Alen J Salerian

    2015-01-01

    This study offers evidence to suggest that both normalcy and psychiatric illness are sensitively dependent upon prefrontal cortex function. In general, the emergence of psychiatric symptoms coincide with diminished influence of prefrontal cortex function. The mediating influence of prefrontal cortex may be independent of molecular and regional brain dysfunctions contributory to psychiatric illness.

  12. The prefrontal cortex and variants of sequential behaviour: indications of functional differentiation between subdivisions of the rat's prefrontal cortex

    DEFF Research Database (Denmark)

    Mogensen, Jesper; Holm, Søren

    1994-01-01

    Neurobiologi, præfrontal cortex, sekventiel adfærd, rotte, adfærdsprogrammering, informationsbearbejdning......Neurobiologi, præfrontal cortex, sekventiel adfærd, rotte, adfærdsprogrammering, informationsbearbejdning...

  13. Policy-based benchmarking of weak heaps and their relatives

    DEFF Research Database (Denmark)

    Bruun, Asger; Edelkamp, Stefan; Katajainen, Jyrki

    2010-01-01

    In this paper we describe an experimental study where we evaluated the practical efficiency of three worst-case efficient priority queues: 1) a weak heap that is a binary tree fulfilling half-heap ordering, 2) a weak queue that is a forest of perfect weak heaps, and 3) a runrelaxed weak queue...

  14. Nuclear Dependence in Weak Structure Functions and the Determination of Weak Mixing Angle

    CERN Document Server

    Athar, M Sajjad; Simo, I Ruiz; Vacas, M J Vicente

    2013-01-01

    We have studied nuclear medium effects in the weak structure functions $F^A_2(x)$ and $F^A_3(x)$ and in the extraction of weak mixing angle using Paschos Wolfenstein(PW) relation. We have modified the PW relation for nonisoscalar nuclear target. We have incorporated the medium effects like Pauli blocking, Fermi motion, nuclear binding energy, nucleon correlations, pion $\\&$ rho cloud contributions, and shadowing and antishadowing effects.

  15. Projections from Orbitofrontal Cortex to Anterior Piriform Cortex in the Rat Suggest a Role in Olfactory Information Processing

    OpenAIRE

    ILLIG, KURT R.

    2005-01-01

    The orbitofrontal cortex (OFC) has been characterized as a higher-order, multimodal sensory cortex. Evidence from electrophysiological and behavioral studies in the rat has suggested that OFC plays a role in modulating olfactory guided behavior, and a significant projection to OFC arises from piriform cortex, the traditional primary olfactory cortex. To discern how OFC interacts with primary olfactory structures, the anterograde tracer Phaseolus vulgaris leucoagglutinin was injected into orbi...

  16. Riemann Geometric Color-Weak Compensationfor Individual Observers

    OpenAIRE

    Kojima, Takanori; Mochizuki, Rika; Lenz, Reiner; Chao, Jinhui

    2014-01-01

    We extend a method for color weak compensation based on the criterion of preservation of subjective color differences between color normal and color weak observers presented in [2]. We introduce a new algorithm for color weak compensation using local affine maps between color spaces of color normal and color weak observers. We show howto estimate the local affine map and how to determine correspondences between the origins of local coordinates in color spaces of color normal and color weak ob...

  17. Perfectly conducting channel on the dark surface of weak topological insulators

    Science.gov (United States)

    Yoshimura, Yukinori; Matsumoto, Akihiko; Takane, Yositake; Imura, Ken-Ichiro

    2013-07-01

    A weak topological insulator (WTI) bears, generally, an even number of Dirac cones on its surface; they are susceptible to doubling, while on the surface of a certain orientation it shows no Dirac cone. On this “dark” surface of a WTI, we predict that a single pair of isolated one-dimensional perfectly conducting channels emerges and forms either a closed loop or a segment of a line. The former is associated typically with a single-atomic-layer-thick island formed on the dark surface, while the latter is shown to be the consequence of a pair of crystal (screw) dislocations terminating on the dark surface.

  18. Biofilm susceptibility to metal toxicity.

    Science.gov (United States)

    Harrison, Joe J; Ceri, Howard; Stremick, Carol A; Turner, Raymond J

    2004-12-01

    This study compared bacterial biofilm and planktonic cell susceptibility to metal toxicity by evaluating the minimum inhibitory concentration (MIC), the planktonic minimum bactericidal concentration (MBC), and minimum biofilm eradication concentration (MBEC) using the MBEC device. In total, 17 metal cations and oxyanions, chosen to represent groups VIB to VIA of the periodic table, were each tested on biofilm and planktonic cultures of Escherichia coli JM109, Staphylococcus aureus ATCC 29213, and Pseudomonas aeruginosa ATCC 27853. In contrast to control antibiotic assays, where biofilm cultures were 2 to 64 times less susceptible to killing than logarithmically growing planktonic bacteria, metal compounds killed planktonic and biofilm cultures at the same concentration in the vast majority of combinations. Our data indicate that, under the conditions reported, growth in a biofilm does not provide resistance to bacteria against killing by metal cations or oxyanions.

  19. Topological susceptibility from the overlap

    CERN Document Server

    Del Debbio, L; Debbio, Luigi Del; Pica, Claudio

    2004-01-01

    The chiral symmetry at finite lattice spacing of Ginsparg-Wilson fermionic actions constrains the renormalization of the lattice operators; in particular, the topological susceptibility does not require any renormalization, when using a fermionic estimator to define the topological charge. Therefore, the overlap formalism appears as an appealing candidate to study the continuum limit of the topological susceptibility while keeping the systematic errors under theoretical control. We present results for the SU(3) pure gauge theory using the index of the overlap Dirac operator to study the topology of the gauge configurations. The topological charge is obtained from the zero modes of the overlap and using a new algorithm for the spectral flow analysis. A detailed comparison with cooling techniques is presented. Particular care is taken in assessing the systematic errors. Relatively high statistics (500 to 1000 independent configurations) yield an extrapolated continuum limit with errors that are comparable with ...

  20. Topological susceptibility from the overlap

    DEFF Research Database (Denmark)

    Del Debbio, Luigi; Pica, Claudio

    2003-01-01

    The chiral symmetry at finite lattice spacing of Ginsparg-Wilson fermionic actions constrains the renormalization of the lattice operators; in particular, the topological susceptibility does not require any renormalization, when using a fermionic estimator to define the topological charge....... Therefore, the overlap formalism appears as an appealing candidate to study the continuum limit of the topological susceptibility while keeping the systematic errors under theoretical control. We present results for the SU(3) pure gauge theory using the index of the overlap Dirac operator to study...... the topology of the gauge configurations. The topological charge is obtained from the zero modes of the overlap and using a new algorithm for the spectral flow analysis. A detailed comparison with cooling techniques is presented. Particular care is taken in assessing the systematic errors. Relatively high...

  1. Structure of a single whisker representation in layer 2 of mouse somatosensory cortex.

    Science.gov (United States)

    Clancy, Kelly B; Schnepel, Philipp; Rao, Antara T; Feldman, Daniel E

    2015-03-04

    Layer (L)2 is a major output of primary sensory cortex that exhibits very sparse spiking, but the structure of sensory representation in L2 is not well understood. We combined two-photon calcium imaging with deflection of many whiskers to map whisker receptive fields, characterize sparse coding, and quantitatively define the point representation in L2 of mouse somatosensory cortex. Neurons within a column-sized imaging field showed surprisingly heterogeneous, salt-and-pepper tuning to many different whiskers. Single whisker deflection elicited low-probability spikes in highly distributed, shifting neural ensembles spanning multiple cortical columns. Whisker-evoked response probability correlated strongly with spontaneous firing rate, but weakly with tuning properties, indicating a spectrum of inherent responsiveness across pyramidal cells. L2 neurons projecting to motor and secondary somatosensory cortex differed in whisker tuning and responsiveness, and carried different amounts of information about columnar whisker deflection. From these data, we derive a quantitative, fine-scale picture of the distributed point representation in L2. Copyright © 2015 the authors 0270-6474/15/353946-13$15.00/0.

  2. Formation and disruption of tonotopy in a large-scale model of the auditory cortex.

    Science.gov (United States)

    Tomková, Markéta; Tomek, Jakub; Novák, Ondřej; Zelenka, Ondřej; Syka, Josef; Brom, Cyril

    2015-10-01

    There is ample experimental evidence describing changes of tonotopic organisation in the auditory cortex due to environmental factors. In order to uncover the underlying mechanisms, we designed a large-scale computational model of the auditory cortex. The model has up to 100 000 Izhikevich's spiking neurons of 17 different types, almost 21 million synapses, which are evolved according to Spike-Timing-Dependent Plasticity (STDP) and have an architecture akin to existing observations. Validation of the model revealed alternating synchronised/desynchronised states and different modes of oscillatory activity. We provide insight into these phenomena via analysing the activity of neuronal subtypes and testing different causal interventions into the simulation. Our model is able to produce experimental predictions on a cell type basis. To study the influence of environmental factors on the tonotopy, different types of auditory stimulations during the evolution of the network were modelled and compared. We found that strong white noise resulted in completely disrupted tonotopy, which is consistent with in vivo experimental observations. Stimulation with pure tones or spontaneous activity led to a similar degree of tonotopy as in the initial state of the network. Interestingly, weak white noise led to a substantial increase in tonotopy. As the STDP was the only mechanism of plasticity in our model, our results suggest that STDP is a sufficient condition for the emergence and disruption of tonotopy under various types of stimuli. The presented large-scale model of the auditory cortex and the core simulator, SUSNOIMAC, have been made publicly available.

  3. Direct evidence for local oscillatory current sources and intracortical phase gradients in turtle visual cortex.

    Science.gov (United States)

    Prechtl, J C; Bullock, T H; Kleinfeld, D

    2000-01-18

    Visual stimuli induce oscillations in the membrane potential of neurons in cortices of several species. In turtle, these oscillations take the form of linear and circular traveling waves. Such waves may be a consequence of a pacemaker that emits periodic pulses of excitation that propagate across a network of excitable neuronal tissue or may result from continuous and possibly reconfigurable phase shifts along a network with multiple weakly coupled neuronal oscillators. As a means to resolve the origin of wave propagation in turtle visual cortex, we performed simultaneous measurements of the local field potential at a series of depths throughout this cortex. Measurements along a single radial penetration revealed the presence of broadband current sources, with a center frequency near 20 Hz (gamma band), that were activated by visual stimulation. The spectral coherence between sources at two well-separated loci along a rostral-caudal axis revealed the presence of systematic timing differences between localized cortical oscillators. These multiple oscillating current sources and their timing differences in a tangential plane are interpreted as the neuronal activity that underlies the wave motion revealed in previous imaging studies. The present data provide direct evidence for the inference from imaging of bidirectional wave motion that the stimulus-induced electrical waves in turtle visual cortex correspond to phase shifts in a network of coupled neuronal oscillators.

  4. Antimycotics susceptibility testing of dermatophytes

    Directory of Open Access Journals (Sweden)

    Arsić-Arsenijević Valentina

    2010-01-01

    Full Text Available Dermatophytes are moulds that produce infections of the skin, hair and nails of humans and animals. The most common forms among these infections are onychomycosis and tinea pedis affecting 20% of world population. These infections are usually chronic. The treatment of dermatophytoses tends to be prolonged partly because available treatments are not very effective. Antifungal drug consumption and public health expenditure are high worldwide, as well as in Serbia. For adequate therapy, it is necessary to prove infection by isolation of dermatophytes and to test the antifungal susceptibility of isolates. Susceptibility testing is important for the resistance monitoring, epidemiological research and to compare in vitro activities of new antifungal agents. The diffusion and dilution methods of susceptibility tests are used, and technical issues of importance for the proper performance and interpretation of test results are published in the document E.DEF 9.1 (EUCAST and M38-A2 (CLSI. The aim of our paper is to promptly inform the public about technical achievements in this area, as well as the new organization of laboratory for medical mycology in our country. The formation of laboratory networks coordinated by the National Reference Laboratory for the cause of mycosis need to enable interlaboratory studies and further standardization of methods for antifungal susceptibility testing of dermatophytes, reproducibility of tests and clinical correlation monitoring (MIK values and clinical outcome of dermatophytosis. The importance of the new organization is expected efficient improvement in the dermatophytosis therapy at home, better quality of patient's life and the reduction of the cost of treatment.

  5. Social distance evaluation in human parietal cortex.

    Science.gov (United States)

    Yamakawa, Yoshinori; Kanai, Ryota; Matsumura, Michikazu; Naito, Eiichi

    2009-01-01

    Across cultures, social relationships are often thought of, described, and acted out in terms of physical space (e.g. "close friends" "high lord"). Does this cognitive mapping of social concepts arise from shared brain resources for processing social and physical relationships? Using fMRI, we found that the tasks of evaluating social compatibility and of evaluating physical distances engage a common brain substrate in the parietal cortex. The present study shows the possibility of an analytic brain mechanism to process and represent complex networks of social relationships. Given parietal cortex's known role in constructing egocentric maps of physical space, our present findings may help to explain the linguistic, psychological and behavioural links between social and physical space.

  6. Determining physical properties of the cell cortex

    CERN Document Server

    Saha, A; Behrndt, M; Heisenberg, C -P; Jülicher, F; Grill, S W

    2015-01-01

    Actin and myosin assemble into a thin layer of a highly dynamic network underneath the membrane of eukaryotic cells. This network generates the forces that drive cell and tissue-scale morphogenetic processes. The effective material properties of this active network determine large-scale deformations and other morphogenetic events. For example,the characteristic time of stress relaxation (the Maxwell time)in the actomyosin sets the time scale of large-scale deformation of the cortex. Similarly, the characteristic length of stress propagation (the hydrodynamic length) sets the length scale of slow deformations, and a large hydrodynamic length is a prerequisite for long-ranged cortical flows. Here we introduce a method to determine physical parameters of the actomyosin cortical layer (in vivo). For this we investigate the relaxation dynamics of the cortex in response to laser ablation in the one-cell-stage {\\it C. elegans} embryo and in the gastrulating zebrafish embryo. These responses can be interpreted using ...

  7. Apraxia, pantomime and the parietal cortex

    Directory of Open Access Journals (Sweden)

    E. Niessen

    2014-01-01

    In contrast to previous suggestions, current analyses show that both lesion and functional studies support the notion of a left-hemispheric fronto-(temporal-parietal network underlying pantomiming object use. Furthermore, our review demonstrates that the left parietal cortex plays a key role in pantomime-related processes. More specifically, stringently controlled fMRI-studies suggest that in addition to storing motor schemas, left parietal cortex is also involved in activating these motor schemas in the context of pantomiming object use. In addition to inherent differences between structural and functional imaging studies and consistent with the dedifferentiation hypothesis, the age difference between young healthy subjects (typically included in functional imaging studies and elderly neurological patients (typically included in structural lesion studies may well contribute to the finding of a more distributed representation of pantomiming within the motor-dominant left hemisphere in the elderly.

  8. Monkey cortex through fMRI glasses.

    Science.gov (United States)

    Vanduffel, Wim; Zhu, Qi; Orban, Guy A

    2014-08-06

    In 1998 several groups reported the feasibility of fMRI experiments in monkeys, with the goal to bridge the gap between invasive nonhuman primate studies and human functional imaging. These studies yielded critical insights in the neuronal underpinnings of the BOLD signal. Furthermore, the technology has been successful in guiding electrophysiological recordings and identifying focal perturbation targets. Finally, invaluable information was obtained concerning human brain evolution. We here provide a comprehensive overview of awake monkey fMRI studies mainly confined to the visual system. We review the latest insights about the topographic organization of monkey visual cortex and discuss the spatial relationships between retinotopy and category- and feature-selective clusters. We briefly discuss the functional layout of parietal and frontal cortex and continue with a summary of some fascinating functional and effective connectivity studies. Finally, we review recent comparative fMRI experiments and speculate about the future of nonhuman primate imaging.

  9. Effects of aging on motor cortex excitability.

    Science.gov (United States)

    Oliviero, A; Profice, P; Tonali, P A; Pilato, F; Saturno, E; Dileone, M; Ranieri, F; Di Lazzaro, V

    2006-05-01

    To determine whether aging is associated with changes in excitability of the cerebral cortex, we evaluated the excitability of the motor cortex with transcranial magnetic stimulation (TMS). We compared TMS related measures obtained in a group of young people with those of a group of old people. Motor evoked potential (MEP) amplitude was significantly smaller in older than in younger controls (1.3+/-0.8 mV versus 2.7+/-1.1 mV; p<0.0071). Mean cortical silent period (CSP) duration was shorter in older than in younger controls (87+/-29 ms versus 147+/-39 ms; p<0.0071). SP duration/MEP amplitude ratios were similar in both groups. Our results are consistent with an impaired efficiency of some intracortical circuits in old age.

  10. Spurious Shear in Weak Lensing with LSST

    Energy Technology Data Exchange (ETDEWEB)

    Chang, C.; Kahn, S.M.; Jernigan, J.G.; Peterson, J.R.; AlSayyad, Y.; Ahmad, Z.; Bankert, J.; Bard, D.; Connolly, A.; Gibson, R.R.; Gilmore, K.; Grace, E.; Hannel, M.; Hodge, M.A.; Jee, M.J.; Jones, L.; Krughoff, S.; Lorenz, S.; Marshall, P.J.; Marshall, S.; Meert, A.

    2012-09-19

    The complete 10-year survey from the Large Synoptic Survey Telescope (LSST) will image {approx} 20,000 square degrees of sky in six filter bands every few nights, bringing the final survey depth to r {approx} 27.5, with over 4 billion well measured galaxies. To take full advantage of this unprecedented statistical power, the systematic errors associated with weak lensing measurements need to be controlled to a level similar to the statistical errors. This work is the first attempt to quantitatively estimate the absolute level and statistical properties of the systematic errors on weak lensing shear measurements due to the most important physical effects in the LSST system via high fidelity ray-tracing simulations. We identify and isolate the different sources of algorithm-independent, additive systematic errors on shear measurements for LSST and predict their impact on the final cosmic shear measurements using conventional weak lensing analysis techniques. We find that the main source of the errors comes from an inability to adequately characterise the atmospheric point spread function (PSF) due to its high frequency spatial variation on angular scales smaller than {approx} 10{prime} in the single short exposures, which propagates into a spurious shear correlation function at the 10{sup -4}-10{sup -3} level on these scales. With the large multi-epoch dataset that will be acquired by LSST, the stochastic errors average out, bringing the final spurious shear correlation function to a level very close to the statistical errors. Our results imply that the cosmological constraints from LSST will not be severely limited by these algorithm-independent, additive systematic effects.

  11. The magnetosphere under weak solar wind forcing

    Directory of Open Access Journals (Sweden)

    C. J. Farrugia

    2007-02-01

    Full Text Available The Earth's magnetosphere was very strongly disturbed during the passage of the strong shock and the following interacting ejecta on 21–25 October 2001. These disturbances included two intense storms (Dst*≈−250 and −180 nT, respectively. The cessation of this activity at the start of 24 October ushered in a peculiar state of the magnetosphere which lasted for about 28 h and which we discuss in this paper. The interplanetary field was dominated by the sunward component [B=(4.29±0.77, −0.30±0.71, 0.49±0.45 nT]. We analyze global indicators of geomagnetic disturbances, polar cap precipitation, ground magnetometer records, and ionospheric convection as obtained from SuperDARN radars. The state of the magnetosphere is characterized by the following features: (i generally weak and patchy (in time low-latitude dayside reconnection or reconnection poleward of the cusps; (ii absence of substorms; (iii a monotonic recovery from the previous storm activity (Dst corrected for magnetopause currents decreasing from ~−65 to ~−35 nT, giving an unforced decreased of ~1.1 nT/h; (iv the probable absence of viscous-type interaction originating from the Kelvin-Helmholtz (KH instability; (v a cross-polar cap potential of just 20–30 kV; (vi a persistent, polar cap region containing (vii very weak, and sometimes absent, electron precipitation and no systematic inter-hemisphere asymmetry. Whereas we therefore infer the presence of a moderate amount of open flux, the convection is generally weak and patchy, which we ascribe to the lack of solar wind driver. This magnetospheric state approaches that predicted by Cowley and Lockwood (1992 but has never yet been observed.

  12. A New Approach for Calculating Vacuum Susceptibility

    Institute of Scientific and Technical Information of China (English)

    宗红石; 平加伦; 顾建中

    2004-01-01

    Based on the Dyson-Schwinger approach, we propose a new method for calculating vacuum susceptibilities. As an example, the vector vacuum susceptibility is calculated. A comparison with the results of the previous approaches is presented.

  13. Enumeration, Isolation and Antibiotic Susceptibility Profile of ...

    African Journals Online (AJOL)

    Antibiotic susceptibility testing of the isolates indicated that S. aureus species had the highest susceptibility of 14(93.3%) .... which sterile forceps were used to carefully remove the disc from its ..... micro-organisms found in public telephones.

  14. Antibiotic susceptibility of Atopobium vaginae

    Directory of Open Access Journals (Sweden)

    Verschraegen Gerda

    2006-03-01

    Full Text Available Abstract Background Previous studies have indicated that a recently described anaerobic bacterium, Atopobium vaginae is associated with bacterial vaginosis (BV. Thus far the four isolates of this fastidious micro-organism were found to be highly resistant to metronidazole and susceptible for clindamycin, two antibiotics preferred for the treatment of BV. Methods Nine strains of Atopobium vaginae, four strains of Gardnerella vaginalis, two strains of Lactobacillus iners and one strain each of Bifidobacterium breve, B. longum, L. crispatus, L. gasseri and L. jensenii were tested against 15 antimicrobial agents using the Etest. Results All nine strains of A. vaginae were highly resistant to nalidixic acid and colistin while being inhibited by low concentrations of clindamycin (range: G. vaginalis strains were also susceptible for clindamycin ( 256 μg/ml but susceptible to clindamycin (0.023 – 0.125 μg/ml. Conclusion Clindamycin has higher activity against G. vaginalis and A. vaginae than metronidazole, but not all A. vaginae isolates are metronidazole resistant, as seemed to be a straightforward conclusion from previous studies on a more limited number of strains.

  15. Planetary migration in weakly magnetized turbulent discs

    Science.gov (United States)

    Baruteau, C.; Fromang, S.; Nelson, R. P.; Masset, F.

    2011-12-01

    In laminar viscous disc models, the migration of protoplanets embedded in their nascent protoplanetary discs may be directed inwards or outwards, depending on the relative magnitude of the Lindblad and corotation torques. The long-term evolution of the corotation torque is intimately related to diffusion processes inside the planet's horseshoe region. This communication examines the properties of the corotation torque in discs where magnetohydrodynamic (MHD) turbulence develops as a result of the magnetorotational instability (MRI), considering a weak initial toroidal magnetic field. We show that the differential Lindblad torque takes very similar values in MHD turbulent and laminar viscous discs, and there exists an unsaturated corotation torque in MHD turbulent discs.

  16. Weak interactions and photoinitiated unimolecular decomposition

    Science.gov (United States)

    Mikhaylichenko, K.; Wittig, C.

    1998-04-01

    Numerical studies have been carried out to examine the applicability of the density of states measured just below dissociation threshold to transition state rate theory. The model system consists of two weakly interacting manifolds of levels, one of which is optically accessible. Both manifolds are coupled to dissociative continua. These studies demonstrate that immediately above reaction threshold, coupling to continua is relatively slow on the time scale of inter-manifold coupling, and it is the mixed manifolds which decay. At higher energies, couplings to continua exceed inter-manifold couplings, and it is the photoexcited bright states which undergo unimolecular decomposition.

  17. Weakly disordered two-dimensional Frenkel excitons

    Science.gov (United States)

    Boukahil, A.; Zettili, Nouredine

    2004-03-01

    We report the results of studies of the optical properties of weakly disordered two- dimensional Frenkel excitons in the Coherent Potential Approximation (CPA). An approximate complex Green's function for a square lattice with nearest neighbor interactions is used in the self-consistent equation to determine the coherent potential. It is shown that the Density of States is very much affected by the logarithmic singularities in the Green's function. Our CPA results are in excellent agreement with previous investigations by Schreiber and Toyozawa using the Monte Carlo simulation.

  18. Neutrino propagation in a weakly magnetized medium

    Indian Academy of Sciences (India)

    Sushan Konar; Subinoy Das

    2004-06-01

    Neutrino—photon processes, forbidden in vacuum, can take place in the presence of a thermal medium and/or an external electro-magnetic field, mediated by the corresponding charged leptons (real or virtual). Such interactions affect the propagation of neutrinos through a magnetized plasma. We investigate the neutrino—photon absorptive processes, at the one-loop level, for massless neutrinos in a weakly magnetized plasma. We find that there is no correction to the absorptive part of the axial-vector—vector amplitude due to the presence of a magnetic field, to the linear order in the field strength.

  19. Are the Weak Measurements Really Measurements?

    Directory of Open Access Journals (Sweden)

    Dmitri Sokolovski

    2013-05-01

    Full Text Available Weak measurements can be seen as an attempt at answering the Which way? question without destroying interference between the pathways involved. Unusual mean values obtained in such measurements represent the response of a quantum system to this forbidden question, in which the true composition of virtual pathways is hidden from the observer. Such values indicate a failure of a measurement where the uncertainty principle says it must fail, rather than provide an additional insight into physical reality.Quanta 2013; 2: 50–57.

  20. Weak $\\eta$ production off the nucleon

    CERN Document Server

    Alam, M Rafi; Athar, M Sajjad; Vacas, M J Vicente

    2013-01-01

    The weak $\\eta$-meson production off the nucleon induced by (anti)neutrinos is studied at low and intermediate energies, the range of interest for several ongoing and future neutrino experiments. We consider Born diagrams and the excitation of $N^\\ast (1535)S_{11}$ and $N^\\ast(1650)S_{11}$ resonances. The vector part of the N-$S_{11}$ transition form factors has been obtained from the MAID helicity amplitudes while the poorly known axial part is constrained with the help of the partial conservation of the axial current (PCAC) and assuming the pion-pole dominance of the pseudoscalar form factor.

  1. Weak η production off the nucleon

    Energy Technology Data Exchange (ETDEWEB)

    Alam, M. Rafi; Athar, M. Sajjad [Department of Physics, Aligarh Muslim University, Aligarh-202 002 (India); Alvarez-Ruso, L.; Vacas, M. J. Vicente [Departamento de Física Teórica and Instituto de Física Corpuscular, Centro Mixto Universidad de Valencia-CSIC, E-46071 Valencia (Spain)

    2015-05-15

    The weak η-meson production off the nucleon induced by (anti)neutrinos is studied at low and intermediate energies, the range of interest for several ongoing and future neutrino experiments. We consider Born diagrams and the excitation of N{sup *} (1535)S{sub 11} and N{sup *} (1650)S{sub 11} resonances. The vector part of the N-S{sub 11} transition form factors has been obtained from the MAID helicity amplitudes while the poorly known axial part is constrained with the help of the partial conservation of the axial current (PCAC) and assuming the pion-pole dominance of the pseudoscalar form factor.

  2. LensTools: Weak Lensing computing tools

    Science.gov (United States)

    Petri, A.

    2016-02-01

    LensTools implements a wide range of routines frequently used in Weak Gravitational Lensing, including tools for image analysis, statistical processing and numerical theory predictions. The package offers many useful features, including complete flexibility and easy customization of input/output formats; efficient measurements of power spectrum, PDF, Minkowski functionals and peak counts of convergence maps; survey masks; artificial noise generation engines; easy to compute parameter statistical inferences; ray tracing simulations; and many others. It requires standard numpy and scipy, and depending on tools used, may require Astropy (ascl:1304.002), emcee (ascl:1303.002), matplotlib, and mpi4py.

  3. Weak Quasi-elastic Production of Hyperons

    CERN Document Server

    Singh, S K

    2006-01-01

    The quasielastic weak production of $\\Lambda$ and $\\Sigma$ hyperons from nucleons and nuclei induced by antineutrinos is studied in the energy region of some ongoing neutrino oscillation experiments in the intermediate energy region. The hyperon nucleon transition form factors determined from neutrino nucleon scattering and an analysis of high precision data on semileptonic decays of neutron and hyperons using SU(3) symmetry have been used. The nuclear effects due to Fermi motion and final state interaction effects due to hyperon nucleon scattering have also been studied. The numerical results for differential and total cross sections have been presented.

  4. Plasma ion stratification by weak planar shocks

    Science.gov (United States)

    Simakov, Andrei N.; Keenan, Brett D.; Taitano, William T.; Chacón, Luis

    2017-09-01

    We derive fluid equations for describing steady-state planar shocks of a moderate strength ( 0 shock Mach number) propagating through an unmagnetized quasineutral collisional plasma comprising two separate ion species. In addition to the standard fluid shock quantities, such as the total mass density, mass-flow velocity, and electron and average ion temperatures, the equations describe shock stratification in terms of variations in the relative concentrations and temperatures of the two ion species along the shock propagation direction. We have solved these equations analytically for weak shocks ( 0 shocks, and they have been used to verify kinetic simulations of shocks in multi-ion plasmas.

  5. Precision frequency measurements with interferometric weak values

    Science.gov (United States)

    Starling, David J.; Dixon, P. Ben; Jordan, Andrew N.; Howell, John C.

    2010-12-01

    We demonstrate an experiment which utilizes a Sagnac interferometer to measure a change in optical frequency of 129 ± 7 kHz/Hz with only 2 mW of continuous-wave, single-mode input power. We describe the measurement of a weak value and show how even higher-frequency sensitivities may be obtained over a bandwidth of several nanometers. This technique has many possible applications, such as precision relative frequency measurements and laser locking without the use of atomic lines.

  6. Weakly bound systems, continuum effects, and reactions

    CERN Document Server

    Jaganathen, Y; Ploszajczak, M

    2012-01-01

    Structure of weakly bound/unbound nuclei close to particle drip lines is different from that around the valley of beta stability. A comprehensive description of these systems goes beyond standard Shell Model and demands an open quantum system description of the nuclear many-body system. We approach this problem using the Gamow Shell Model which provides a fully microscopic description of bound and unbound nuclear states, nuclear decays, and reactions. We present in this paper the first application of the GSM for a description of the elastic and inelastic scattering of protons on 6He.

  7. Weak 'Antigravity' Fields in General Relativity

    CERN Document Server

    Felber, F S

    2005-01-01

    Within the weak-field approximation of general relativity, new exact solutions are derived for the gravitational field of a mass moving with arbitrary velocity and acceleration. Owing to an inertial-pushing effect, a mass having a constant velocity greater than 3^-1/2 times the speed of light gravitationally repels other masses at rest within a narrow cone. At high Lorentz factors (gamma >> 1), the force of repulsion in the forward direction is about -8(gamma^5) times the Newtonian force, offering opportunities for laboratory tests of gravity at extreme velocities.

  8. Resonance phenomena for asymmetric weakly nonlinear oscillator

    Institute of Scientific and Technical Information of China (English)

    钱定边

    2002-01-01

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

  9. Improved Quantum Signature Scheme with Weak Arbitrator

    Science.gov (United States)

    Su, Qi; Li, Wen-Min

    2013-09-01

    In this paper, we find a man-in-the-middle attack on the quantum signature scheme with a weak arbitrator (Luo et al., Int. J. Theor. Phys., 51:2135, 2012). In that scheme, the authors proposed a quantum signature based on quantum one way function which contains both verifying the signer phase and verifying the signed message phase. However, after our analysis we will show that Eve can adopt different strategies in respective phases to forge the signature without being detected. Then we present an improved scheme to increase the security.

  10. Strong holism, weak holism, and health.

    Science.gov (United States)

    Täljedal, Inge-Bert

    2004-01-01

    The health theories of Nordenfelt and Boorse are compared. Critical attention is focused on Nordenfelt's description of his theory as one of holistic welfare, contrasting with Boorse's analytical and statistical approach. Neither theory is found to give an entirely satisfactory account of 'health' in scientific medicine or common usage. Because Nordenfelt attenuates the ontological significance of organs and organ parts and simplifies the role of statistics, his theory is regarded as weakly holistic. Boorse underrates the importance of non-statistical evaluation. A mediating position, termed 'strong holism' is suggested as a way of integrating normative and statistical elements in a more adequate health concept.

  11. Dynamical Model of Weak Pion Production Reactions

    CERN Document Server

    Sato, T; Lee, T S H

    2003-01-01

    The dynamical model of pion electroproduction has been extended to investigate the weak pion production reactions. The predicted cross sections of neutrino-induced pion production reactions are in good agreement with the existing data. We show that the renormalized(dressed) axial N-$\\Delta$ form factor contains large dynamical pion cloud effects and this renormalization effects are crucial in getting agreement with the data. We conclude that the N-$\\Delta$ transitions predicted by the constituent quark model are consistent with the existing neutrino induced pion production data in the $\\Delta$ region.

  12. Infrared spectroscopy of weakly bound molecular ions

    Energy Technology Data Exchange (ETDEWEB)

    Yeh, Lisa I-Ching

    1988-11-01

    The infrared spectra of a series of hydrated hydronium cluster ions and of protonated ethane ion are presented. A tandem mass spectrometer is ideally suited to obtaining the spectra of such weakly bound molecular ions. Traditional absorption spectroscopy is not feasible in these situations, so the techniques described in this thesis make use of some consequence of photon absorption with higher sensitivity than simply attenuation of laser power. That consequence is dissociation. By first mass selecting the parent ion under study and then mass selecting the fragment ion formed from dissociation, the near unit detection efficiency of ion counting methods has been used to full advantage.

  13. Parametric Amplification For Detecting Weak Optical Signals

    Science.gov (United States)

    Hemmati, Hamid; Chen, Chien; Chakravarthi, Prakash

    1996-01-01

    Optical-communication receivers of proposed type implement high-sensitivity scheme of optical parametric amplification followed by direct detection for reception of extremely weak signals. Incorporates both optical parametric amplification and direct detection into optimized design enhancing effective signal-to-noise ratios during reception in photon-starved (photon-counting) regime. Eliminates need for complexity of heterodyne detection scheme and partly overcomes limitations imposed on older direct-detection schemes by noise generated in receivers and by limits on quantum efficiencies of photodetectors.

  14. Orbitofrontal Cortex, Associative Learning, and Expectancies

    Science.gov (United States)

    Schoenbaum, Geoffrey; Roesch, Matthew

    2009-01-01

    Orbitofrontal cortex is characterized by its unique pattern of connections with subcortical areas, such as basolateral amygdala. Here we distinguish between the critical role of these areas in associative learning and the pivotal contribution of OFC to the manipulation of this information to control behavior. This contribution reflects the ability of OFC to signal the desirability of expected outcomes, which requires the integration of associative information with information concerning internal states and goals in representational memory. PMID:16129393

  15. Cone inputs to murine striate cortex

    Directory of Open Access Journals (Sweden)

    Gouras Peter

    2008-11-01

    Full Text Available Abstract Background We have recorded responses from single neurons in murine visual cortex to determine the effectiveness of the input from the two murine cone photoreceptor mechanisms and whether there is any unique selectivity for cone inputs at this higher region of the visual system that would support the possibility of colour vision in mice. Each eye was stimulated by diffuse light, either 370 (strong stimulus for the ultra-violet (UV cone opsin or 505 nm (exclusively stimulating the middle wavelength sensitive (M cone opsin, obtained from light emitting diodes (LEDs in the presence of a strong adapting light that suppressed the responses of rods. Results Single cells responded to these diffuse stimuli in all areas of striate cortex. Two types of responsive cells were encountered. One type (135/323 – 42% had little to no spontaneous activity and responded at either the on and/or the off phase of the light stimulus with a few impulses often of relatively large amplitude. A second type (166/323 – 51% had spontaneous activity and responded tonically to light stimuli with impulses often of small amplitude. Most of the cells responded similarly to both spectral stimuli. A few (18/323 – 6% responded strongly or exclusively to one or the other spectral stimulus and rarely in a spectrally opponent manner. Conclusion Most cells in murine striate cortex receive excitatory inputs from both UV- and M-cones. A small fraction shows either strong selectivity for one or the other cone mechanism and occasionally cone opponent responses. Cells that could underlie chromatic contrast detection are present but extremely rare in murine striate cortex.

  16. Working Memory in the Prefrontal Cortex

    Directory of Open Access Journals (Sweden)

    Shintaro Funahashi

    2017-04-01

    Full Text Available The prefrontal cortex participates in a variety of higher cognitive functions. The concept of working memory is now widely used to understand prefrontal functions. Neurophysiological studies have revealed that stimulus-selective delay-period activity is a neural correlate of the mechanism for temporarily maintaining information in working memory processes. The central executive, which is the master component of Baddeley’s working memory model and is thought to be a function of the prefrontal cortex, controls the performance of other components by allocating a limited capacity of memory resource to each component based on its demand. Recent neurophysiological studies have attempted to reveal how prefrontal neurons achieve the functions of the central executive. For example, the neural mechanisms of memory control have been examined using the interference effect in a dual-task paradigm. It has been shown that this interference effect is caused by the competitive and overloaded recruitment of overlapping neural populations in the prefrontal cortex by two concurrent tasks and that the information-processing capacity of a single neuron is limited to a fixed level, can be flexibly allocated or reallocated between two concurrent tasks based on their needs, and enhances behavioral performance when its allocation to one task is increased. Further, a metamemory task requiring spatial information has been used to understand the neural mechanism for monitoring its own operations, and it has been shown that monitoring the quality of spatial information represented by prefrontal activity is an important factor in the subject's choice and that the strength of spatially selective delay-period activity reflects confidence in decision-making. Although further studies are needed to elucidate how the prefrontal cortex controls memory resource and supervises other systems, some important mechanisms related to the central executive have been identified.

  17. Processing of sound location in human cortex.

    Science.gov (United States)

    Lewald, Jörg; Riederer, Klaus A J; Lentz, Tobias; Meister, Ingo G

    2008-03-01

    This functional magnetic resonance imaging study was focused on the neural substrates underlying human auditory space perception. In order to present natural-like sound locations to the subjects, acoustic stimuli convolved with individual head-related transfer functions were used. Activation foci, as revealed by analyses of contrasts and interactions between sound locations, formed a complex network, including anterior and posterior regions of temporal lobe, posterior parietal cortex, dorsolateral prefrontal cortex and inferior frontal cortex. The distinct topography of this network was the result of different patterns of activation and deactivation, depending on sound location, in the respective voxels. These patterns suggested different levels of complexity in processing of auditory spatial information, starting with simple left/right discrimination in the regions surrounding the primary auditory cortex, while the integration of information on hemispace and eccentricity of sound may take place at later stages. Activations were identified as being located in regions assigned to both the dorsal and ventral auditory cortical streams, that are assumed to be preferably concerned with analysis of spatial and non-spatial sound features, respectively. The finding of activations also in the ventral stream could, on the one hand, reflect the well-known functional duality of auditory spectral analysis, that is, the concurrent extraction of information based on location (due to the spectrotemporal distortions caused by head and pinnae) and spectral characteristics of a sound source. On the other hand, this result may suggest the existence of shared neural networks, performing analyses of auditory 'higher-order' cues for both localization and identification of sound sources.

  18. The role of prefrontal cortex in psychopathy

    OpenAIRE

    Koenigs, Michael

    2012-01-01

    Psychopathy is a personality disorder characterized by remorseless and impulsive antisocial behavior. Given the significant societal costs of the recidivistic criminal activity associated with the disorder, there is a pressing need for more effective treatment strategies, and hence, a better understanding of the psychobiological mechanisms underlying the disorder. The prefrontal cortex (PFC) is likely to play an important role in psychopathy. In particular, the ventromedial and anterior cingu...

  19. ITI-signals and prelimbic cortex facilitate avoidance acquisition and reduce avoidance latencies, respectively, in male WKY rats

    Directory of Open Access Journals (Sweden)

    Kevin D Beck

    2014-11-01

    Full Text Available As a model of anxiety disorder vulnerability, male Wistar-Kyoto (WKY rats acquire lever-press avoidance behavior more readily than outbred Sprague Dawley rats, and their acquisition is enhanced by the presence of a discrete signal presented during the inter-trial intervals (ITIs, suggesting it is perceived as a safety signal. A series of experiments were conducted to determine if this is the case. Additional experiments investigated if the avoidance facilitation relies upon processing through medial prefrontal cortex (mPFC. The results suggest that the ITI-signal facilitates acquisition during the early stages of the avoidance acquisition process, when the rats are initially acquiring escape behavior and then transitioning to avoidance behavior. Post-avoidance introduction of the visual ITI-signal into other associative learning tasks failed to confirm that the visual stimulus had acquired the properties of a conditioned inhibitor. Shortening the signal from the entirety of the 3 min ITI to only the first 5 s of the 3 min ITI slowed acquisition during the first 4 sessions, suggesting the flashing light is not functioning as a feedback signal. The prelimbic (PL cortex showed greater activation during the period of training when the transition from escape responding to avoidance responding occurs. Only combined PL+infralimbic cortex lesions modestly slowed avoidance acquisition, but PL cortex lesions slowed avoidance response latencies. Thus, the flashing light ITI-signal is not likely perceived as a safety signal nor is it serving as a feedback signal. The functional role of the PL cortex appears to be to increase the drive towards responding to the threat of the warning signal. Hence, avoidance susceptibility displayed by male WKY rats may be driven, in part, both by external stimuli (ITI signal as well as by enhanced threat recognition to the warning signal via the PL cortex.

  20. Specialized elements of orbitofrontal cortex in primates.

    Science.gov (United States)

    Barbas, Helen

    2007-12-01

    The orbitofrontal cortex is associated with encoding the significance of stimuli within an emotional context, and its connections can be understood in this light. This large cortical region is architectonically heterogeneous, but its connections and functions can be summarized by a broad grouping of areas by cortical type into posterior and anterior sectors. The posterior (limbic) orbitofrontal region is composed of agranular and dysgranular-type cortices and has unique connections with primary olfactory areas and rich connections with high-order sensory association cortices. Posterior orbitofrontal areas are further distinguished by dense and distinct patterns of connections with the amygdala and memory-related anterior temporal lobe structures that may convey signals about emotional import and their memory. The special sets of connections suggest that the posterior orbitofrontal cortex is the primary region for the perception of emotions. In contrast to orbitofrontal areas, posterior medial prefrontal areas in the anterior cingulate are not multi-modal, but have strong connections with auditory association cortices, brain stem vocalization, and autonomic structures, in pathways that may mediate emotional communication and autonomic activation in emotional arousal. Posterior orbitofrontal areas communicate with anterior orbitofrontal areas and, through feedback projections, with lateral prefrontal and other cortices, suggesting a sequence of information processing for emotions. Pathology in orbitofrontal cortex may remove feedback input to sensory cortices, dissociating emotional context from sensory content and impairing the ability to interpret events.

  1. Emotion, decision making and the orbitofrontal cortex.

    Science.gov (United States)

    Bechara, A; Damasio, H; Damasio, A R

    2000-03-01

    The somatic marker hypothesis provides a systems-level neuroanatomical and cognitive framework for decision making and the influence on it by emotion. The key idea of this hypothesis is that decision making is a process that is influenced by marker signals that arise in bioregulatory processes, including those that express themselves in emotions and feelings. This influence can occur at multiple levels of operation, some of which occur consciously and some of which occur non-consciously. Here we review studies that confirm various predictions from the hypothesis. The orbitofrontal cortex represents one critical structure in a neural system subserving decision making. Decision making is not mediated by the orbitofrontal cortex alone, but arises from large-scale systems that include other cortical and subcortical components. Such structures include the amygdala, the somatosensory/insular cortices and the peripheral nervous system. Here we focus only on the role of the orbitofrontal cortex in decision making and emotional processing, and the relationship between emotion, decision making and other cognitive functions of the frontal lobe, namely working memory.

  2. Binocular form deprivation influences the visual cortex

    Institute of Scientific and Technical Information of China (English)

    Mingming Liu; Chuanhuang Weng; Hanping Xie; Wei Qin

    2012-01-01

    1a-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors are considered to play a crucial role in synaptic plasticity in the developing visual cortex. In this study, we established a rat model of binocular form deprivation by suturing the rat binocular eyelids before eye-opening at postnatal day 14. During development, the decay time of excitatory postsynaptic currents mediated by 1a-amino-3- hydroxy-5-methyl-4-isoxazolepropionic acid receptors of normal rats became longer after eyeopening; however, the decay time did not change significantly in binocular form deprivation rats. The peak value in the normal group became gradually larger with age, but there was no significant change in the binocular form deprivation group. These findings indicate that binocular form deprivation influences the properties of excitatory postsynaptic currents mediated by β-amino-3- hydroxy-5-methyl-4-isoxazolepropionic acid receptors in the rat visual cortex around the end of the critical period, indicating that form stimulation is associated with the experience-dependent modification of neuronal synapses in the visual cortex.

  3. Rhythmic spontaneous activity in the piriform cortex.

    Science.gov (United States)

    Sanchez-Vives, Maria V; Descalzo, V F; Reig, R; Figueroa, N A; Compte, A; Gallego, R

    2008-05-01

    Slow spontaneous rhythmic activity is generated and propagates in neocortical slices when bathed in an artificial cerebrospinal fluid with ionic concentrations similar to the ones in vivo. This activity is extraordinarily similar to the activation of the cortex in physiological conditions (e.g., slow-wave sleep), thus representing a unique in vitro model to understand how cortical networks maintain and control ongoing activity. Here we have characterized the activity generated in the olfactory or piriform cortex and endopiriform nucleus (piriform network). Because these structures are prone to generate epileptic discharges, it seems critical to understand how they generate and regulate their physiological rhythmic activity. The piriform network gave rise to rhythmic spontaneous activity consisting of a succession of up and down states at an average frequency of 1.8 Hz, qualitatively similar to the corresponding neocortical activity. This activity originated in the deep layers of the piriform network, which displayed higher excitability and denser connectivity. A remarkable difference with neocortical activity was the speed of horizontal propagation (114 mm/s), one order of magnitude faster in the piriform network. Properties of the piriform cortex subserving fast horizontal propagation may underlie the higher vulnerability of this area to epileptic seizures.

  4. Human prefrontal cortex: evolution, development, and pathology.

    Science.gov (United States)

    Teffer, Kate; Semendeferi, Katerina

    2012-01-01

    The prefrontal cortex is critical to many cognitive abilities that are considered particularly human, and forms a large part of a neural system crucial for normal socio-emotional and executive functioning in humans and other primates. In this chapter, we survey the literature regarding prefrontal development and pathology in humans as well as comparative studies of the region in humans and closely related primate species. The prefrontal cortex matures later in development than more caudal regions, and some of its neuronal subpopulations exhibit more complex dendritic arborizations. Comparative work suggests that the human prefrontal cortex differs from that of closely related primate species less in relative size than it does in organization. Specific reorganizational events in neural circuitry may have taken place either as a consequence of adjusting to increases in size or as adaptive responses to specific selection pressures. Living in complex environments has been recognized as a considerable factor in the evolution of primate cognition. Normal frontal lobe development and function are also compromised in several neurological and psychiatric disorders. A phylogenetically recent reorganization of frontal cortical circuitry may have been critical to the emergence of human-specific executive and social-emotional functions, and developmental pathology in these same systems underlies many psychiatric and neurological disorders, including autism and schizophrenia.

  5. An integrator circuit in cerebellar cortex.

    Science.gov (United States)

    Maex, Reinoud; Steuber, Volker

    2013-09-01

    The brain builds dynamic models of the body and the outside world to predict the consequences of actions and stimuli. A well-known example is the oculomotor integrator, which anticipates the position-dependent elasticity forces acting on the eye ball by mathematically integrating over time oculomotor velocity commands. Many models of neural integration have been proposed, based on feedback excitation, lateral inhibition or intrinsic neuronal nonlinearities. We report here that a computational model of the cerebellar cortex, a structure thought to implement dynamic models, reveals a hitherto unrecognized integrator circuit. In this model, comprising Purkinje cells, molecular layer interneurons and parallel fibres, Purkinje cells were able to generate responses lasting more than 10 s, to which both neuronal and network mechanisms contributed. Activation of the somatic fast sodium current by subthreshold voltage fluctuations was able to maintain pulse-evoked graded persistent activity, whereas lateral inhibition among Purkinje cells via recurrent axon collaterals further prolonged the responses to step and sine wave stimulation. The responses of Purkinje cells decayed with a time-constant whose value depended on their baseline spike rate, with integration vanishing at low ( 30 per s). The model predicts that the apparently fast circuit of the cerebellar cortex may control the timing of slow processes without having to rely on sensory feedback. Thus, the cerebellar cortex may contain an adaptive temporal integrator, with the sensitivity of integration to the baseline spike rate offering a potential mechanism of plasticity of the response time-constant.

  6. Egocentric and allocentric representations in auditory cortex.

    Science.gov (United States)

    Town, Stephen M; Brimijoin, W Owen; Bizley, Jennifer K

    2017-06-01

    A key function of the brain is to provide a stable representation of an object's location in the world. In hearing, sound azimuth and elevation are encoded by neurons throughout the auditory system, and auditory cortex is necessary for sound localization. However, the coordinate frame in which neurons represent sound space remains undefined: classical spatial receptive fields in head-fixed subjects can be explained either by sensitivity to sound source location relative to the head (egocentric) or relative to the world (allocentric encoding). This coordinate frame ambiguity can be resolved by studying freely moving subjects; here we recorded spatial receptive fields in the auditory cortex of freely moving ferrets. We found that most spatially tuned neurons represented sound source location relative to the head across changes in head position and direction. In addition, we also recorded a small number of neurons in which sound location was represented in a world-centered coordinate frame. We used measurements of spatial tuning across changes in head position and direction to explore the influence of sound source distance and speed of head movement on auditory cortical activity and spatial tuning. Modulation depth of spatial tuning increased with distance for egocentric but not allocentric units, whereas, for both populations, modulation was stronger at faster movement speeds. Our findings suggest that early auditory cortex primarily represents sound source location relative to ourselves but that a minority of cells can represent sound location in the world independent of our own position.

  7. Hierarchical Bayesian inference in the visual cortex

    Science.gov (United States)

    Lee, Tai Sing; Mumford, David

    2003-07-01

    Traditional views of visual processing suggest that early visual neurons in areas V1 and V2 are static spatiotemporal filters that extract local features from a visual scene. The extracted information is then channeled through a feedforward chain of modules in successively higher visual areas for further analysis. Recent electrophysiological recordings from early visual neurons in awake behaving monkeys reveal that there are many levels of complexity in the information processing of the early visual cortex, as seen in the long-latency responses of its neurons. These new findings suggest that activity in the early visual cortex is tightly coupled and highly interactive with the rest of the visual system. They lead us to propose a new theoretical setting based on the mathematical framework of hierarchical Bayesian inference for reasoning about the visual system. In this framework, the recurrent feedforward/feedback loops in the cortex serve to integrate top-down contextual priors and bottom-up observations so as to implement concurrent probabilistic inference along the visual hierarchy. We suggest that the algorithms of particle filtering and Bayesian-belief propagation might model these interactive cortical computations. We review some recent neurophysiological evidences that support the plausibility of these ideas. 2003 Optical Society of America

  8. Does intrinsic motivation enhance motor cortex excitability?

    Science.gov (United States)

    Radel, Rémi; Pjevac, Dusan; Davranche, Karen; d'Arripe-Longueville, Fabienne; Colson, Serge S; Lapole, Thomas; Gruet, Mathieu

    2016-11-01

    Intrinsic motivation (IM) is often viewed as a spontaneous tendency for action. Recent behavioral and neuroimaging evidence indicate that IM, in comparison to extrinsic motivation (EM), solicits the motor system. Accordingly, we tested whether IM leads to greater excitability of the motor cortex than EM. To test this hypothesis, we used two different tasks to induce the motivational orientation using either words representing each motivational orientation or pictures previously linked to each motivational orientation through associative learning. Single-pulse transcranial magnetic stimulation over the motor cortex was applied when viewing the stimuli. Electromyographic activity was recorded on the contracted first dorsal interosseous muscle. Two indexes of corticospinal excitability (the amplitude of motor-evoked potential and the length of cortical silent period) were obtained through unbiased automatic detection and analyzed using a mixed model that provided both statistical power and a high level of control over all important individual, task, and stimuli characteristics. Across the two tasks and the two indices of corticospinal excitability, the exposure to IM-related stimuli did not lead to a greater corticospinal excitability than EM-related stimuli or than stimuli with no motivational valence (ps > .20). While these results tend to dismiss the advantage of IM at activating the motor cortex, we suggest alternative hypotheses to explain this lack of effect, which deserves further research. © 2016 Society for Psychophysiological Research.

  9. Human Choice Strategy Varies with Anatomical Projections from Ventromedial Prefrontal Cortex to Medial Striatum.

    Science.gov (United States)

    Piray, Payam; Toni, Ivan; Cools, Roshan

    2016-03-09

    Two distinct systems, goal-directed and habitual, support decision making. It has recently been hypothesized that this distinction may arise from two computational mechanisms, model-based and model-free reinforcement learning, neuronally implemented in frontostriatal circuits involved in learning and behavioral control. Here, we test whether the relative strength of anatomical connectivity within frontostriatal circuits accounts for variation in human individuals' reliance on model-based and model-free control. This hypothesis was tested by combining diffusion tensor imaging with a multistep decision task known to distinguish model-based and model-free control in humans. We found large interindividual differences in the degree of model-based control, and those differences are predicted by the structural integrity of white-matter tracts from the ventromedial prefrontal cortex to the medial striatum. Furthermore, an analysis based on masking out of bottom-up tracts suggests that this effect is driven by top-down influences from ventromedial prefrontal cortex to medial striatum. Our findings indicate that individuals with stronger afferences from the ventromedial prefrontal cortex to the medial striatum are more likely to rely on a model-based strategy to control their instrumental actions. These findings suggest a mechanism for instrumental action control through which medial striatum determines, at least partly, the relative contribution of model-based and model-free systems during decision-making according to top-down model-based information from the ventromedial prefrontal cortex. These findings have important implications for understanding the neural circuitry that might be susceptible to pathological computational processes in impulsive/compulsive psychiatric disorders.

  10. A comparison of weak-turbulence and PIC simulations of weak electron-beam plasma interaction

    CERN Document Server

    Ratcliffe, Heather; Rozenan, Mohammed B Che; Nakariakov, Valery

    2014-01-01

    Quasilinear theory has long been used to treat the problem of a weak electron beam interacting with plasma and generating Langmuir waves. Its extension to weak-turbulence theory treats resonant interactions of these Langmuir waves with other plasma wave modes, in particular ion-sound waves. These are strongly damped in plasma of equal ion and electron temperatures, as sometimes seen in, for example, the solar corona and wind. Weak turbulence theory is derived in the weak damping limit, with a term describing ion-sound wave damping then added. In this paper we use the EPOCH particle-in-cell code to numerically test weak turbulence theory for a range of electron-ion temperature ratios. We find that in the cold ion limit the results agree well, but increasing ion temperature the three-wave resonance becomes broadened in proportion to the ion-sound wave damping rate. This may be important in, for example, the theory of solar radio bursts, where the spectrum of Langmuir waves is critical. Additionally we establish...

  11. Cortex-M0处理器初探%Cortex-M0 Processor:An Initial Survey

    Institute of Scientific and Technical Information of China (English)

    范云龙; 方安平; 李宁

    2010-01-01

    介绍Cortex-M0处理器的特点;详细分析Cortex-M0处理器的编程模型、存储模型、异常处理和功耗管理,并将Cortex-M0与Cortex-M3和基于8/16位架构的处理器作了对比分析;最后简要介绍Cortex-M0处理器的相关开发工具.

  12. Associative Encoding in Anterior Piriform Cortex versus Orbitofrontal Cortex during Odor Discrimination and Reversal Learning

    Science.gov (United States)

    Roesch, Matthew R.; Stalnaker, Thomas A.; Schoenbaum, Geoffrey

    2008-01-01

    Recent proposals have conceptualized piriform cortex as an association cortex, capable of integrating incoming olfactory information with descending input from higher order associative regions such as orbitofrontal cortex (OFC). If true, encoding in piriform cortex should reflect associative features prominent in these areas during associative learning involving olfactory cues. To test this hypothesis, we recorded from neurons in OFC and anatomically related parts of the anterior piriform cortex (APC) in rats, learning and reversing novel odor discriminations. Findings in OFC were similar to what we have reported previously, with nearly all the cue-selective neurons exhibiting substantial plasticity during learning and reversal. Also, many of the cue-selective neurons were originally responsive in anticipation of the outcomes early in learning, thereby providing a single-unit representation of the cue-outcome associations. Some of these features were also evident in firing activity in APC, including some plasticity across learning and reversal. However, APC neurons failed to reverse cue selectivity when the associated outcome was changed, and the cue-selective population did not include neurons that were active prior to outcome delivery. Thus, although representations in APC are substantially more associative than expected in a purely sensory region, they do appear to be somewhat more constrained by the sensory features of the odor cues than representations in downstream areas of OFC. PMID:16699083

  13. Weak Completeness of Coalgebraic Dynamic Logics

    Directory of Open Access Journals (Sweden)

    Helle Hvid Hansen

    2015-09-01

    Full Text Available We present a coalgebraic generalisation of Fischer and Ladner's Propositional Dynamic Logic (PDL and Parikh's Game Logic (GL. In earlier work, we proved a generic strong completeness result for coalgebraic dynamic logics without iteration. The coalgebraic semantics of such programs is given by a monad T, and modalities are interpreted via a predicate lifting λ whose transpose is a monad morphism from T to the neighbourhood monad. In this paper, we show that if the monad T carries a complete semilattice structure, then we can define an iteration construct, and suitable notions of diamond-likeness and box-likeness of predicate-liftings which allows for the definition of an axiomatisation parametric in T, λ and a chosen set of pointwise program operations. As our main result, we show that if the pointwise operations are "negation-free" and Kleisli composition left-distributes over the induced join on Kleisli arrows, then this axiomatisation is weakly complete with respect to the class of standard models. As special instances, we recover the weak completeness of PDL and of dual-free Game Logic. As a modest new result we obtain completeness for dual-free GL extended with intersection (demonic choice of games.

  14. Baryons, Neutrinos, Feedback and Weak Gravitational Lensing

    CERN Document Server

    Harnois-Déraps, Joachim; Viola, Massimo; Heymans, Catherine

    2014-01-01

    (Abridged) The effect of baryonic feedback on the dark matter mass distribution is generally considered to be a nuisance to weak gravitational lensing. Measurements of cosmological parameters are affected as feedback alters the cosmic shear signal on angular scales smaller than a few arcminutes. Recent progress on the numerical modelling of baryon physics has shown that this effect could be so large that, rather than being a nuisance, the effect can be constrained with current weak lensing surveys, hence providing an alternative astrophysical insight on one of the most challenging questions of galaxy formation. In order to perform our analysis, we construct an analytic fitting formula that describes the effect of the baryons on the mass power spectrum. This fitting formula is based on three scenarios of the OWL hydrodynamical simulations. It is specifically calibrated for $z<1.5$, where it models the simulations to an accuracy that is better than $2\\%$ for scales $k<10 h\\mbox{Mpc}^{-1}$ and better than ...

  15. Conformational transitions of a weak polyampholyte

    KAUST Repository

    Narayanan Nair, Arun Kumar

    2014-10-07

    Using grand canonical Monte Carlo simulations of a flexible polyelectrolyte where the charges are in contact with a reservoir of constant chemical potential given by the solution pH, we study the behavior of weak polyelectrolytes in poor and good solvent conditions for polymer backbone. We address the titration behavior and conformational properties of a flexible diblock polyampholyte chain formed of two oppositely charged weak polyelectrolyte blocks, each containing equal number of identical monomers. The change of solution pH induces charge asymmetry in a diblock polyampholyte. For diblock polyampholyte chains in poor solvents, we demonstrate that a discontinuous transition between extended (tadpole) and collapsed (globular) conformational states is attainable by varying the solution pH. The double-minima structure in the probability distribution of the free energy provides direct evidence for the first-order like nature of this transition. At the isoelectric point electrostatically driven coil-globule transition of diblock polyampholytes in good solvents is found to consist of different regimes identified with increasing electrostatic interaction strength. At pH values above or below the isoelectric point diblock chains are found to have polyelectrolyte-like behavior due to repulsion between uncompensated charges along the chain.

  16. Weak Scale From the Maximum Entropy Principle

    CERN Document Server

    Hamada, Yuta; Kawana, Kiyoharu

    2015-01-01

    The theory of multiverse and wormholes suggests that the parameters of the Standard Model are fixed in such a way that the radiation of the $S^{3}$ universe at the final stage $S_{rad}$ becomes maximum, which we call the maximum entropy principle. Although it is difficult to confirm this principle generally, for a few parameters of the Standard Model, we can check whether $S_{rad}$ actually becomes maximum at the observed values. In this paper, we regard $S_{rad}$ at the final stage as a function of the weak scale ( the Higgs expectation value ) $v_{h}$, and show that it becomes maximum around $v_{h}={\\cal{O}}(300\\text{GeV})$ when the dimensionless couplings in the Standard Model, that is, the Higgs self coupling, the gauge couplings, and the Yukawa couplings are fixed. Roughly speaking, we find that the weak scale is given by \\begin{equation} v_{h}\\sim\\frac{T_{BBN}^{2}}{M_{pl}y_{e}^{5}},\

  17. Weak scale from the maximum entropy principle

    Science.gov (United States)

    Hamada, Yuta; Kawai, Hikaru; Kawana, Kiyoharu

    2015-03-01

    The theory of the multiverse and wormholes suggests that the parameters of the Standard Model (SM) are fixed in such a way that the radiation of the S3 universe at the final stage S_rad becomes maximum, which we call the maximum entropy principle. Although it is difficult to confirm this principle generally, for a few parameters of the SM, we can check whether S_rad actually becomes maximum at the observed values. In this paper, we regard S_rad at the final stage as a function of the weak scale (the Higgs expectation value) vh, and show that it becomes maximum around vh = {{O}} (300 GeV) when the dimensionless couplings in the SM, i.e., the Higgs self-coupling, the gauge couplings, and the Yukawa couplings are fixed. Roughly speaking, we find that the weak scale is given by vh ˜ T_{BBN}2 / (M_{pl}ye5), where ye is the Yukawa coupling of electron, T_BBN is the temperature at which the Big Bang nucleosynthesis starts, and M_pl is the Planck mass.

  18. Quantum counterfactual communication without a weak trace

    Science.gov (United States)

    Arvidsson-Shukur, D. R. M.; Barnes, C. H. W.

    2016-12-01

    The classical theories of communication rely on the assumption that there has to be a flow of particles from Bob to Alice in order for him to send a message to her. We develop a quantum protocol that allows Alice to perceive Bob's message "counterfactually"; that is, without Alice receiving any particles that have interacted with Bob. By utilizing a setup built on results from interaction-free measurements, we outline a communication protocol whereby the information travels in the opposite direction of the emitted particles. In comparison to previous attempts on such protocols, this one is such that a weak measurement at the message source would not leave a weak trace that could be detected by Alice's receiver. While some interaction-free schemes require a large number of carefully aligned beam splitters, our protocol is realizable with two or more beam splitters. We demonstrate this protocol by numerically solving the time-dependent Schrödinger equation for a Hamiltonian that implements this quantum counterfactual phenomenon.

  19. Weak gravity conjecture and effective field theory

    Science.gov (United States)

    Saraswat, Prashant

    2017-01-01

    The weak gravity conjecture (WGC) is a proposed constraint on theories with gauge fields and gravity, requiring the existence of light charged particles and/or imposing an upper bound on the field theory cutoff Λ . If taken as a consistency requirement for effective field theories (EFTs), it rules out possibilities for model building including some models of inflation. I demonstrate simple models which satisfy all forms of the WGC, but which through Higgsing of the original gauge fields produce low-energy EFTs with gauge forces that badly violate the WGC. These models illustrate specific loopholes in arguments that motivate the WGC from a bottom-up perspective; for example the arguments based on magnetic monopoles are evaded when the magnetic confinement that occurs in a Higgs phase is accounted for. This indicates that the WGC should not be taken as a veto on EFTs, even if it turns out to be a robust property of UV quantum gravity theories. However, if the latter is true, then parametric violation of the WGC at low energy comes at the cost of nonminimal field content in the UV. I propose that only a very weak constraint is applicable to EFTs, Λ ≲(log 1/g )-1 /2Mpl , where g is the gauge coupling, motivated by entropy bounds. Remarkably, EFTs produced by Higgsing a theory that satisfies the WGC can saturate but not violate this bound.

  20. Do weak global stresses synchronize earthquakes?

    Science.gov (United States)

    Bendick, R.; Bilham, R.

    2017-08-01

    Insofar as slip in an earthquake is related to the strain accumulated near a fault since a previous earthquake, and this process repeats many times, the earthquake cycle approximates an autonomous oscillator. Its asymmetric slow accumulation of strain and rapid release is quite unlike the harmonic motion of a pendulum and need not be time predictable, but still resembles a class of repeating systems known as integrate-and-fire oscillators, whose behavior has been shown to demonstrate a remarkable ability to synchronize to either external or self-organized forcing. Given sufficient time and even very weak physical coupling, the phases of sets of such oscillators, with similar though not necessarily identical period, approach each other. Topological and time series analyses presented here demonstrate that earthquakes worldwide show evidence of such synchronization. Though numerous studies demonstrate that the composite temporal distribution of major earthquakes in the instrumental record is indistinguishable from random, the additional consideration of event renewal interval serves to identify earthquake groupings suggestive of synchronization that are absent in synthetic catalogs. We envisage the weak forces responsible for clustering originate from lithospheric strain induced by seismicity itself, by finite strains over teleseismic distances, or by other sources of lithospheric loading such as Earth's variable rotation. For example, quasi-periodic maxima in rotational deceleration are accompanied by increased global seismicity at multidecadal intervals.

  1. The weak gravity conjecture and scalar fields

    Science.gov (United States)

    Palti, Eran

    2017-08-01

    We propose a generalisation of the Weak Gravity Conjecture in the presence of scalar fields. The proposal is guided by properties of extremal black holes in N=2 supergravity, but can be understood more generally in terms of forbidding towers of stable gravitationally bound states. It amounts to the statement that there must exist a particle on which the gauge force acts more strongly than gravity and the scalar forces combined. We also propose that the scalar force itself should act on this particle stronger than gravity. This implies that generically the mass of this particle decreases exponentially as a function of the scalar field expectation value for super-Planckian variations, which is behaviour predicted by the Refined Swampland Conjecture. In the context of N=2 supergravity the Weak Gravity Conjecture bound can be tied to bounds on scalar field distances in field space. Guided by this, we present a general proof that for any linear combination of moduli in any Calabi-Yau compactification of string theory the proper field distance grows at best logarithmically with the moduli values for super-Planckian distances.

  2. Droplet breakup dynamics of weakly viscoelastic fluids

    Science.gov (United States)

    Marshall, Kristin; Walker, Travis

    2016-11-01

    The addition of macromolecules to solvent, even in dilute quantities, can alter a fluid's response in an extensional flow. For low-viscosity fluids, the presence of elasticity may not be apparent when measured using a standard rotational rheometer, yet it may still alter the response of a fluid when undergoing an extensional deformation, especially at small length scales where elastic effects are enhanced. Applications such as microfluidics necessitate investigating the dynamics of fluids with elastic properties that are not pronounced at large length scales. In the present work, a microfluidic cross-slot configuration is used to study the effects of elasticity on droplet breakup. Droplet breakup and the subsequent iterated-stretching - where beads form along a filament connecting two primary droplets - were observed for a variety of material and flow conditions. We present a relationship on the modes of bead formation and how and when these modes will form based on key parameters such as the properties of the outer continuous-phase fluid. The results are vital not only for simulating the droplet breakup of weakly viscoelastic fluids but also for understanding how the droplet breakup event can be used for characterizing the extensional properties of weakly-viscoelastic fluids.

  3. Probing hysteretic elasticity in weakly nonlinear materials

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Paul A [Los Alamos National Laboratory; Haupert, Sylvain [UPMC UNIV PARIS; Renaud, Guillaume [UPMC UNIV PARIS; Riviere, Jacques [UPMC UNIV PARIS; Talmant, Maryline [UPMC UNIV PARIS; Laugier, Pascal [UPMC UNIV PARIS

    2010-12-07

    Our work is aimed at assessing the elastic and dissipative hysteretic nonlinear parameters' repeatability (precision) using several classes of materials with weak, intermediate and high nonlinear properties. In this contribution, we describe an optimized Nonlinear Resonant Ultrasound Spectroscopy (NRUS) measuring and data processing protocol applied to small samples. The protocol is used to eliminate the effects of environmental condition changes that take place during an experiment, and that may mask the intrinsic elastic nonlinearity. As an example, in our experiments, we identified external temperature fluctuation as a primary source of material resonance frequency and elastic modulus variation. A variation of 0.1 C produced a frequency variation of 0.01 %, which is similar to the expected nonlinear frequency shift for weakly nonlinear materials. In order to eliminate environmental effects, the variation in f{sub 0} (the elastically linear resonance frequency proportional to modulus) is fit with the appropriate function, and that function is used to correct the NRUS calculation of nonlinear parameters. With our correction procedure, we measured relative resonant frequency shifts of 10{sup -5} , which are below 10{sup -4}, often considered the limit to NRUS sensitivity under common experimental conditions. Our results show that the procedure is an alternative to the stringent control of temperature often applied. Applying the approach, we report nonlinear parameters for several materials, some with very small nonclassical nonlinearity. The approach has broad application to NRUS and other Nonlinear Elastic Wave Spectroscopy approaches.

  4. Shear calibration biases in weak lensing surveys

    CERN Document Server

    Hirata, C M; Hirata, Christopher M.; Seljak, Uros

    2003-01-01

    We investigate biases induced by the conversion between the observed image shape to shear distortion in current weak lensing analysis methods. Such overall calibration biases cannot be detected by the standard tests such as E/B decomposition or calibration with stars. We find that the non-Gaussianity of point spread function has a significant effect and can lead to up to 15 per cent error on the linear amplitude of fluctuations sigma_8 depending on the method of analysis. This could explain some of the discrepancies seen in recent amplitude determinations from weak lensing. Using an elliptical Laguerre expansion method we develop a re-Gaussianization method which reduces the error to calibration error of order 1 per cent even for poorly resolved galaxies. We also discuss a new type of shear selection bias which results in up to roughly 8 percent underestimation of the signal. It is expected to scale with redshift, inducing errors in the growth factor extraction if not properly corrected for. Understanding and...

  5. Cannula-aided penetration: a simple method to insert structurally weak electrodes into brain through the dura mater.

    Science.gov (United States)

    Matsuzaka, Yoshiya; Sakamoto, Kazuhiro; Tanaka, Tetsu; Furusawa, Yoshihito; Mushiake, Hajime

    2009-09-01

    We developed a simple and inexpensive method to insert structurally weak electrodes into the brain through the thickened dura mater in chronic animal experiments. It uses a commonly available intravenous (IV) needle and a cannula to secure a small puncture in the dura mater, through which an electrode is advanced into the underlying cerebral cortex. In addition to its simplicity and cost-effectiveness, this method provides greater degree of freedom regarding the shape and the placement of electrodes compared to the conventional guide tube systems.

  6. [Effect of rabies virus infection on the expression of parvalbumin, calbindin and calretinin in mouse cerebral cortex].

    Science.gov (United States)

    Torres-Fernández, Orlando; Yepes, Gloria E; Gómez, Javier E; Pimienta, Hernán J

    2004-03-01

    Some clinical features of rabies and experimental evidence from cell culture and laboratory animals suggest impairment of gabaergic neurotransmission. Several types of gabaergic neurons occur in the cerebral cortex. They can be identified by three neuronal markers: the calcium binding proteins (CaBPs) parvalbumin (PV), calbindin (CB) and calretinin (CR). Rabies virus spreads throughout the cerebral cortex; however, rabies cytopathic effects on gabaergic neurons are unknown. The expression of calcium-binding proteins (CaBPs) parvalbumin (PV), calbindin (CB) and calretinin (CR) was studied in the frontal cortex of mice. The effect of gabaergic neurons was evaluated immunohistochemically. The distribution patterns of CaBPs in normal mice and in mice infected with 'fixed' or 'street' rabies virus were compared. PV was found in multipolar neurons located in all cortical layers except layer I, and in pericellular clusters of terminal knobs surrounding the soma of pyramidal neurons. CB-immunoreactivity was distributed in two cortical bands. One was composed of round neurons enclosed by a heavily labeled neuropil; this band corresponds to supragranular layers II and III. The other was a weakly stained band of neuropil which contained scattered multipolar CB-ir neurons; this corresponds to infragranular layers V and VI. The CR-ir neurons were bipolar fusiform cells located in all layers of cortex, but concentrated in layers II and III. A feature common to samples infected with both types of viruses was a more intense immunoreactivity to PV in contrast to normal samples. The infection with 'street' virus did not cause additional changes in the expression of CaBPs. However, the infection with 'fixed' virus produced a remarkable reduction of CB-immunoreactivity demonstrated by the loss of CB-ir neurons and low neuropil stain in the frontal cortex. In addition, the size of CR-ir neurons in the cingulate cortex was decreased.

  7. The reactivation of somatosensory cortex and behavioral recovery after sensory loss in mature primates

    Directory of Open Access Journals (Sweden)

    Hui-Xin eQi

    2014-05-01

    Full Text Available In our experiments, we removed a major source of activation of somatosensory cortex in mature monkeys by unilaterally sectioning the sensory afferents in the dorsal columns of the spinal cord at a high cervical level. At this level, the ascending branches of tactile afferents from the hand are cut, while other branches of these afferents remain intact to terminate on neurons in the dorsal horn of the spinal cord. Immediately after such a lesion, the monkeys seem relatively unimpaired in locomotion and often use the forelimb, but further inspection reveals that they prefer to use the unaffected hand in reaching for food. In addition, systematic testing indicates that they make more errors in retrieving pieces of food, and start using visual inspection of the rotated hand to confirm the success of the grasping of the food. Such difficulties are not surprising as a complete dorsal column lesion totally deactivates the contralateral hand representation in primary somatosensory cortex (area 3b. However, hand use rapidly improves over the first post-lesion weeks, and much of the hand representational territory in contralateral area 3b is reactivated by inputs from the hand in roughly a normal somatotopic pattern. Quantitative measures of single neuron response properties reveal that reactivated neurons respond to tactile stimulation on the hand with high firing rates and only slightly longer latencies. We conclude that preserved dorsal column afferents after nearly complete lesions contribute to the reactivation of cortex and the recovery of the behavior, but second-order sensory pathways in the spinal cord may also play an important role. Our microelectrode recordings indicate that these preserved first-order, and second-order pathways are initially weak and largely ineffective in activating cortex, but they are potentiated during the recovery process. Therapies that would promote this potentiation could usefully enhance recovery after spinal cord

  8. Temporal binding of sound emerges out of anatomical structure and synaptic dynamics of auditory cortex

    Directory of Open Access Journals (Sweden)

    Patrick eMay

    2013-11-01

    Full Text Available The ability to represent and recognize naturally occuring sounds such as speech depends not only on spectral analysis carried out by the subcortical auditory system but also on the ability of the cortex to bind spectral information over time. In primates, these temporal binding processes are mirrored as selective responsiveness of neurons to species-specific vocalizations. Here, we used computational modelling of auditory cortex to investigate how selectivity to spectrally and temporally complex stimuli is achieved. A set of 208 microcolumns were arranged in a serial core-belt-parabelt structure documented in both humans and animals. Stimulus material comprised multiple consonant-vowel pseudowords. Selectivity to the spectral structure of the sounds was commonly found in all regions of the model (N = 122 columns out of 208, and this selectivity was only weakly affected by manipulating the structure and dynamics of the model. In contrast, temporal binding was rarer (N = 39, found mostly in the belt and parabelt regions. Thus the serial core-belt-parabelt structure of auditory cortex is necessary for temporal binding. Further, adaptation due to synaptic depression - rendering the cortical network malleable by stimulus history - was crucial for the emergence of neurons sensitive to the temporal structure of the stimuli. Both spectral selectivity and temporal binding required that a sufficient proportion of the columns interacted in an inhibitory manner. The model and its structural modifications had a small-world structure (i.e., columns formed clusters and were within short node-to-node distances from each other. However, simulations showed that a small-world structure is not a necessary condition for spectral selectivity and temporal binding to emerge. In summary, this study suggests that temporal binding arises out of the (1 serial structure typical to the auditory cortex, (2 synaptic adaptation, and (3 inhibitory interactions between

  9. Equal pain – Unequal fear response: Enhanced susceptibility of tooth pain to fear conditioning

    Directory of Open Access Journals (Sweden)

    Michael Lukas Meier

    2014-07-01

    Full Text Available Experimental fear conditioning in humans is widely used as a model to investigate the neural basis of fear learning and to unravel the pathogenesis of anxiety disorders. It has been observed that fear conditioning depends on stimulus salience and subject vulnerability to fear. It is further known that the prevalence of dental-related fear and phobia is exceedingly high in the population. Dental phobia is unique as no other body part is associated with a specific phobia. Therefore, we hypothesized that painful dental stimuli exhibit an enhanced susceptibility to fear conditioning when comparing to equal perceived stimuli applied to other body sites. Differential susceptibility to pain-related fear was investigated by analyzing responses to an unconditioned stimulus (UCS applied to the right maxillary canine (UCS-c versus the right tibia (UCS-t. For fear conditioning, UCS-c and USC-t consisted of painful electric stimuli, carefully matched at both application sites for equal intensity and quality perception. UCSs were paired to simple geometrical forms which served as conditioned stimuli (CS+. Unpaired CS+ were presented for eliciting and analyzing conditioned fear responses. Outcome parameter were 1 skin conductance changes and 2 time-dependent brain activity (BOLD responses in fear-related brain regions such as the amygdala, anterior cingulate cortex, insula, thalamus, orbitofrontal cortex and medial prefrontal cortex.A preferential susceptibility of dental pain to fear conditioning was observed, reflected by heightened skin conductance responses and enhanced time-dependent brain activity (BOLD responses in the fear network. For the first time, this study demonstrates fear-related neurobiological mechanisms that point towards a superior conditionability of tooth pain. Beside traumatic dental experiences our results offer novel evidence that might explain the high prevalence of dental-related fears in the population.

  10. Equal pain-Unequal fear response: enhanced susceptibility of tooth pain to fear conditioning.

    Science.gov (United States)

    Meier, Michael L; de Matos, Nuno M P; Brügger, Mike; Ettlin, Dominik A; Lukic, Nenad; Cheetham, Marcus; Jäncke, Lutz; Lutz, Kai

    2014-01-01

    Experimental fear conditioning in humans is widely used as a model to investigate the neural basis of fear learning and to unravel the pathogenesis of anxiety disorders. It has been observed that fear conditioning depends on stimulus salience and subject vulnerability to fear. It is further known that the prevalence of dental-related fear and phobia is exceedingly high in the population. Dental phobia is unique as no other body part is associated with a specific phobia. Therefore, we hypothesized that painful dental stimuli exhibit an enhanced susceptibility to fear conditioning when comparing to equal perceived stimuli applied to other body sites. Differential susceptibility to pain-related fear was investigated by analyzing responses to an unconditioned stimulus (UCS) applied to the right maxillary canine (UCS-c) vs. the right tibia (UCS-t). For fear conditioning, UCS-c and USC-t consisted of painful electric stimuli, carefully matched at both application sites for equal intensity and quality perception. UCSs were paired to simple geometrical forms which served as conditioned stimuli (CS+). Unpaired CS+ were presented for eliciting and analyzing conditioned fear responses. Outcome parameter were (1) skin conductance changes and (2) time-dependent brain activity (BOLD responses) in fear-related brain regions such as the amygdala, anterior cingulate cortex, insula, thalamus, orbitofrontal cortex, and medial prefrontal cortex. A preferential susceptibility of dental pain to fear conditioning was observed, reflected by heightened skin conductance responses and enhanced time-dependent brain activity (BOLD responses) in the fear network. For the first time, this study demonstrates fear-related neurobiological mechanisms that point toward a superior conditionability of tooth pain. Beside traumatic dental experiences our results offer novel evidence that might explain the high prevalence of dental-related fears in the population.

  11. 关于Weakly J-Clean环%On Weakly J-Clean Rings

    Institute of Scientific and Technical Information of China (English)

    沈洪地; 陈焕艮

    2015-01-01

    A ring R is called a weakly J‐clean ring if every element a∈ R can be written in the form of a=e+ j or a= -e+ j where e is an idempotent and j belongs to the Jacobson radical .The paper explores various properties of weakly J‐clean rings ,proves that a ring R is weakly J‐clean if and only if R is clean and R/J(R) is weakly Boolean ,if and only if R/6R is weakly J‐clean and idempotents can lift J(R) .A ring R is uniquely weakly nil clean if and only if R is abelian;J(R) is nil and R is weakly J‐clean .Each weakly J‐clean ring R is right(left) quasi‐duo ring .Furthermore ,the paper proves that the following are equivalent :R is J‐clean;there is an integer n≥1 such that Tn (R) is J‐clean ;there is an integer n≥2 such that Tn (R) is weakly J‐clean;there is an integer n≥2 such that × n R is w eakly J‐clean .%一个环 R叫做w eakly J‐clean环,如果R中的每一个元素都可以写成a= e+ j或a=-e+ j的形式,其中e是幂等元,j属于Jacobson根。文章探究了weakly J‐clean环的各种性质,证明了 R是weakly J‐clean环当且仅当 R是clean环并且 R/J(R)是弱布尔环,当且仅当R/6 R是w eakly J‐clean环且幂等元关于 J(R)可以提升。一个环R是唯一w eakly nil clean环当且仅当 R是阿贝尔环;J(R)是幂零的并且 R是w eakly J‐clean环。每个w eakly J‐clean环 R是右(左)quasi‐duo环。并进一步证明以下几点是等价的:R是 J‐clean环;存在一个大于等于1的整数 n ,使得 Tn (R)是 J‐clean环;存在一个大于等于2的整数 n ,使得 Tn (R)是w eakly J‐clean环;存在一个大于等于2的整数 n ,使得× n R 是w eakly J‐clean环。

  12. Neural structures underlying set-shifting: roles of medial prefrontal cortex and anterior cingulate cortex.

    Science.gov (United States)

    Bissonette, Gregory B; Powell, Elizabeth M; Roesch, Matthew R

    2013-08-01

    Impaired attentional set-shifting and inflexible decision-making are problems frequently observed during normal aging and in several psychiatric disorders. To understand the neuropathophysiology of underlying inflexible behavior, animal models of attentional set-shifting have been developed to mimic tasks such as the Wisconsin Card Sorting Task (WCST), which tap into a number of cognitive functions including stimulus-response encoding, working memory, attention, error detection, and conflict resolution. Here, we review many of these tasks in several different species and speculate on how prefrontal cortex and anterior cingulate cortex might contribute to normal performance during set-shifting. Copyright © 2013 Elsevier B.V. All rights reserved.

  13. Mechanisms of inherited cancer susceptibility

    Institute of Scientific and Technical Information of China (English)

    Shirley HODGSON

    2008-01-01

    A small proportion of many cancers are due to inherited mutations in genes, which result in a high risk to the individual of developing specific cancers. There are several classes of genes that may be involved: tumour suppressor genes, oncogenes, genes encoding proteins involved in DNA repair and cell cycle control, and genes involved in stimulating the angiogenic pathway. Alterations in susceptibility to cancer may also be due to variations in genes involved in carcinogen metabolism. This review discusses examples of some of these genes and the associated clinical conditions caused by the inheritance of mutations in such genes.

  14. Genetic susceptibility to environmental toxicants

    DEFF Research Database (Denmark)

    2001-01-01

    combined with well conducted clinical trials and epidemiological studies will greatly improve our chances of devising strategies for the reduction of harm. This symposium can, at least in part, make a contribution to our current understanding of genetic susceptibility to environmental toxicants...... to take toxicological data and both interpret and extrapolate it in a manner as to cause exaggerated concern. The challenge to the toxicologist is to explain what data means and in a way that inspires the confidence in those who have to apply data to the assessment of hazard and risk management. It seems...

  15. Polygenic susceptibility to testicular cancer

    DEFF Research Database (Denmark)

    Litchfield, Kevin; Mitchell, Jonathan S; Shipley, Janet

    2015-01-01

    BACKGROUND: The increasing incidence of testicular germ cell tumour (TGCT) combined with its strong heritable basis suggests that stratified screening for the early detection of TGCT may be clinically useful. We modelled the efficiency of such a personalised screening approach, based on genetic...... known TGCT susceptibility variants. The diagnostic performance of testicular biopsy and non-invasive semen analysis was also assessed, within a simulated combined screening programme. RESULTS: The area under the curve for the TGCT PRS model was 0.72 with individuals in the top 1% of the PRS having...

  16. Casimir apparatuses in a weak gravitational field

    DEFF Research Database (Denmark)

    Bimonte, Giuseppe; Calloni, Enrico; Esposito, Giampiero

    2009-01-01

    We review and assess a part of the recent work on Casimir apparatuses in the weak gravitational field of the Earth. For a free, real massless scalar field subject to Dirichlet or Neumann boundary conditions on the parallel plates, the resulting regularized and renormalized energy-momentum tensor...... is covariantly conserved, while the trace anomaly vanishes if the massless field is conformally coupled to gravity. Conformal coupling also ensures a finite Casimir energy and finite values of the pressure upon parallel plates. These results have been extended to an electromagnetic field subject to perfect...... conductor (hence idealized) boundary conditions on parallel plates, by various authors. The regularized and renormalized energy-momentum tensor has beene valuated up to second order in the gravity acceleration. In both the scalar and the electromagnetic case, studied to first order in the gravity...

  17. Entanglement in Weakly Coupled Lattice Gauge Theories

    CERN Document Server

    Radicevic, Djordje

    2015-01-01

    We present a direct lattice gauge theory computation that, without using dualities, demonstrates that the entanglement entropy of Yang-Mills theories with arbitrary gauge group $G$ contains a generic logarithmic term at sufficiently weak coupling $e$. In two spatial dimensions, for a region of linear size $r$, this term equals $\\frac{1}{2} \\dim(G) \\log\\left(e^2 r\\right)$ and it dominates the universal part of the entanglement entropy. Such logarithmic terms arise from the entanglement of the softest mode in the entangling region with the environment. For Maxwell theory in two spatial dimensions, our results agree with those obtained by dualizing to a compact scalar with spontaneous symmetry breaking.

  18. Weakly Asymmetric Bridges and the KPZ Equation

    Science.gov (United States)

    Labbé, Cyril

    2017-08-01

    We consider the corner growth dynamics on discrete bridges from (0, 0) to (2 N, 0), or equivalently, the weakly asymmetric simple exclusion process with N particles on 2 N sites. We take an asymmetry of order N -α with α ∈ (0, 1) and provide a complete description of the asymptotic behaviour of this model. In particular, we show that the hydrodynamic limit of the density of particles is given by the inviscid Burgers equation with zero-flux boundary condition. When the interface starts from the flat initial profile, we show that KPZ fluctuations occur whenever α ∈ (0, 1/3]. In the particular regime α = 1/3, these KPZ fluctuations suddenly vanish at a deterministic time.

  19. Anisotropic turbulence in weakly stratified rotating magnetoconvection

    CERN Document Server

    Giesecke, A

    2010-01-01

    Numerical simulations of the 3D MHD-equations that describe rotating magnetoconvection in a Cartesian box have been performed using the code NIRVANA. The characteristics of averaged quantities like the turbulence intensity and the turbulent heat flux that are caused by the combined action of the small-scale fluctuations are computed. The correlation length of the turbulence significantly depends on the strength and orientation of the magnetic field and the anisotropic behavior of the turbulence intensity induced by Coriolis and Lorentz force is considerably more pronounced for faster rotation. The development of isotropic behavior on the small scales -- as it is observed in pure rotating convection -- vanishes even for a weak magnetic field which results in a turbulent flow that is dominated by the vertical component. In the presence of a horizontal magnetic field the vertical turbulent heat flux slightly increases with increasing field strength, so that cooling of the rotating system is facilitated. Horizont...

  20. Geometry of weak lensing of CMB polarization

    CERN Document Server

    Challinor, A D; Challinor, Anthony; Chon, Gayoung

    2002-01-01

    Hu has presented a harmonic-space method for calculating the effects of weak gravitational lensing on the cosmic microwave background (CMB) over the full sky. Computing the lensed power spectra to first order in the deflection power requires one to formulate the lensing displacement beyond the tangent-space approximation. We point out that for CMB polarization this displacement must undergo geometric corrections on the spherical sky to maintain statistical isotropy of the lensed fields. Although not discussed by Hu, these geometric effects are implicit in his analysis. However, there they are hidden by an overly-compact notation that is both unconventional and rather confusing. Here we aim to ameliorate this deficiency by providing a rigorous derivation of the lensed spherical power spectra.

  1. Weak Hamiltonian, CP Violation and Rare Decays

    CERN Document Server

    Buras, Andrzej J

    1998-01-01

    These lectures describe in detail the effective Hamiltonians for weak decays of mesons constructed by means of the operator product expansion and the renormalization group method. We calculate Wilson coeffcients of local operators, discuss mixing of operators under renormalization, the anomalous dimensions of operators and anomalous dimension matrices. We elaborate on the renormalzation scheme and renormalization scale dependences and their cancellations in physical amplitudes. In particular we discuss the issue of gamma-5 in D-dimensions and the role of evanescent operators in the calculation of two-loop anomalous dimensions. We present an explicit calculation of the 6 times 6 one-loop anomalous dimension matrix involving current-current and QCD-penguin operators and we give some hints how to properly calculate two-loop anomalous dimensions of these operators. In the phenonomenological part of these lectures we discuss in detail: CKM matrix, the unitarity triangle and its determination, two-body non-leptonic...

  2. Cluster mass reconstruction from weak gravitational lensing

    CERN Document Server

    Wilson, G; Frenk, C S; Wilson, Gillian; Cole, Shaun; Frenk, Carlos S

    1996-01-01

    Kaiser & Squires have proposed a technique for mapping the dark matter in galaxy clusters using the coherent weak distortion of background galaxy images caused by gravitational lensing. We investigate the effectiveness of this technique under controlled conditions by creating simulated CCD frames containing galaxies lensed by a model cluster, measuring the resulting galaxy shapes, and comparing the reconstructed mass distribution with the original. Typically, the reconstructed surface density is diminished in magnitude when compared to the original. The main cause of this reduced signal is the blurring of galaxy images by atmospheric seeing, but the overall factor by which the reconstructed surface density is reduced depends also on the signal-to-noise ratio in the CCD frame and on both the sizes of galaxy images and the magnitude limit of the sample that is analysed. We propose a method for estimating a multiplicative compensation factor. We test our technique using a lensing cluster drawn from a cosmolo...

  3. Weak Kaon Production off the Nucleon

    CERN Document Server

    Alam, M Rafi; Athar, M Sajjad; Vacas, M J Vicente

    2010-01-01

    The weak kaon production off the nucleon induced by neutrinos is studied at the low and intermediate energies of interest for some ongoing and future neutrino oscillation experiments. This process is also potentially important for the analysis of proton decay experiments. We develop a microscopical model based on the SU(3) chiral Lagrangians. The basic parameters of the model are fpi, the pion decay constant, Cabibbo's angle, the proton and neutron magnetic moments and the axial vector coupling constants for the baryons octet, D and F, that are obtained from the analysis of the semileptonic decays of neutron and hyperons. The studied mechanisms are the main source of kaon production for neutrino energies up to 1.2 to 1.5 GeV for the various channels and the cross sections are large enough to be amenable to be measured by experiments such as Minerva and T2K.

  4. Can weak lensing surveys confirm BICEP2 ?

    CERN Document Server

    Chisari, Nora Elisa; Schmidt, Fabian

    2014-01-01

    The detection of B-modes in the Cosmic Microwave Background (CMB) polarization by the BICEP2 experiment, if interpreted as evidence for a primordial gravitational wave background, has enormous ramifications for cosmology and physics. It is crucial to test this hypothesis with independent measurements. A gravitational wave background leads to B-modes in galaxy shape correlations (shear) both through lensing and tidal alignment effects. Since the systematics and foregrounds of galaxy shapes and CMB polarization are entirely different, a detection of a cross-correlation between the two observables would provide conclusive proof for the existence of a primordial gravitational wave background. We find that upcoming weak lensing surveys will be able to detect the cross-correlation between B-modes of the CMB and galaxy shapes. However, this detection is not sufficient to confirm or falsify the hypothesis of a primordial origin for CMB B-mode polarization.

  5. Spherical Accretion in Nearby Weakly Active Galaxies

    CERN Document Server

    Moscibrodzka, M A

    2005-01-01

    We consider the sample of weakly active galaxies situated in 'Local Universe' collected in the paper of Pellegrini (2005) with inferred accretion efficiencies from $10^{-2}$ to $10^{-7}$. We apply a model of spherically symmetrical Bondi accretion for given parameters ($M_{BH}$,$T_{\\infty}$,$\\rho_{\\infty}$,) taken from observation. We calculate spectra emitted by the gas accreting onto its central objects using Monte Carlo method including synchrotron and bremsstrahlung photons as seed photons. We compare our results with observed nuclear X-ray luminosities $L_{X,nuc}$ (0.3-10 keV) of the sample. Model is also tested for different external medium parameters ($\\rho_{\\infty}$ and $T_{\\infty}$) and different free parameters of the model. Our model is able to explain most of the observed nuclear luminosities $L_X$ under an assumption that half of the compresion energy is transfered directly to the electrons.

  6. Casimir apparatuses in a weak gravitational field

    DEFF Research Database (Denmark)

    Bimonte, Giuseppe; Calloni, Enrico; Esposito, Giampiero;

    2009-01-01

    We review and assess a part of the recent work on Casimir apparatuses in the weak gravitational field of the Earth. For a free, real massless scalar field subject to Dirichlet or Neumann boundary conditions on the parallel plates, the resulting regularized and renormalized energy-momentum tensor...... is covariantly conserved, while the trace anomaly vanishes if the massless field is conformally coupled to gravity. Conformal coupling also ensures a finite Casimir energy and finite values of the pressure upon parallel plates. These results have been extended to an electromagnetic field subject to perfect...... conductor (hence idealized) boundary conditions on parallel plates, by various authors. The regularized and renormalized energy-momentum tensor has beene valuated up to second order in the gravity acceleration. In both the scalar and the electromagnetic case, studied to first order in the gravity...

  7. Weak Gravity Conjecture and Extremal Black Holes

    CERN Document Server

    Cottrell, William; Soler, Pablo

    2016-01-01

    Motivated by the desire to improve our understanding of the Weak Gravity Conjecture, we compute the one-loop correction of charged particles to the geometry and entropy of extremal black holes in 4d. Contrary to expectations, we find that loops of massive charged particles can radically alter the classical black hole geometry and that fermion loops provide evidence for the necessity of the `magnetic' WGC cutoff. The corrections are reduced when supersymmetry is present, and disappear in ${\\cal N}=4$ supergravity. We further provide some speculative arguments that in a theory with only sub-extremal particles, classical Reisner-Nordstrom black holes actually possess an infinite microcanonical entropy, though only a finite amount is visible to an external observer.

  8. Meson exchange and neutral weak currents

    Energy Technology Data Exchange (ETDEWEB)

    Beck, D.H. [Univ. of Illinois, Urbana, IL (United States)

    1994-04-01

    Measurements of parity-violating electron scattering asymmetries to determine weak neutral currents in nuclei will be effected by the presence of meson exchange currents. Present low momentum transfer calculations, based on a flavor independent framework, show these effects to be small. In general, however, as the momentum transfer increases to values typical of deep-inelastic scattering, fragmentation functions show a clear flavor dependence. It is suggested that a good experimental starting point for understanding the flavor dependence of meson production and exchange currents is the Q{sup 2} dependence of parity-violating asymmetry in inclusive single pion electroproduction. A CEBAF facility with doubled energy is necessary to approach momentum transfers where this process begins to scale.

  9. Weak lensing using only galaxy position angles

    CERN Document Server

    Whittaker, Lee; Battye, Richard

    2013-01-01

    We develop a method for performing a weak lensing analysis using only measurements of galaxy position angles. By analyzing the statistical properties of the galaxy orientations given a known intrinsic ellipticity distribution, we show that it is possible to obtain estimates of the shear by minimizing a $\\chi^2$ statistic. The method is demonstrated using simulations where the components of the intrinsic ellipticity are taken to be Gaussian distributed. Uncertainties on the position angle measurements introduce a bias into the shear estimates which can be reduced to negligible levels by introducing a correction term into the formalism. We generalize our approach by developing an algorithm to obtain direct shear estimators given any azimuthally symmetric intrinsic ellipticity distribution. We demonstrate this technique by applying it to simulations where the ellipticities are taken to follow a log-normal distribution. We compare the performance of the position angle only method with the standard method based on...

  10. A heroin addict with focal weakness.

    Science.gov (United States)

    Galassi, Giuliana; Ariatti, Alessandra; Gozzi, Manuela; Cavazza, Stefano

    2013-05-01

    A 24-year-old female with 5 year history of heroin abuse experienced painless stiffness of elbow joints and weakness of shoulder and upper limb muscles. She was injecting herself 4-6 times daily alternatively in the upper extremities, sparing the lower limbs. Electromyography (EMG) showed myopathic changes in clinically affected and unaffected muscles. Magnetic resonance imaging (MRI) revealed muscle fibrosis in directly injected muscles, whereas in subcutaneous fat and within muscles of anterior and posterior compartments of both thighs, not directly injected, there were signal changes supportive of oedema and inflammation. EMG and MRI were congruent in showing abnormalities in muscles not directly injected, suggesting long distant effects of heroin or adulterants with a mechanism either toxic or immunologically mediated.

  11. General gauge mediation at the weak scale

    Science.gov (United States)

    Knapen, Simon; Redigolo, Diego; Shih, David

    2016-03-01

    We completely characterize General Gauge Mediation (GGM) at the weak scale by solving all IR constraints over the full parameter space. This is made possible through a combination of numerical and analytical methods, based on a set of algebraic relations among the IR soft masses derived from the GGM boundary conditions in the UV. We show how tensions between just a few constraints determine the boundaries of the parameter space: electroweak symmetry breaking (EWSB), the Higgs mass, slepton tachyons, and left-handed stop/sbottom tachyons. While these constraints allow the left-handed squarks to be arbitrarily light, they place strong lower bounds on all of the right-handed squarks. Meanwhile, light EW superpartners are generic throughout much of the parameter space. This is especially the case at lower messenger scales, where a positive threshold correction to m h coming from light Higgsinos and winos is essential in order to satisfy the Higgs mass constraint.

  12. Kolmogorov Dissipation scales in Weakly Ionized Plasmas

    CERN Document Server

    Krishan, V

    2009-01-01

    In a weakly ionized plasma, the evolution of the magnetic field is described by a "generalized Ohm's law" that includes the Hall effect and the ambipolar diffusion terms. These terms introduce additional spatial and time scales which play a decisive role in the cascading and the dissipation mechanisms in magnetohydrodynamic turbulence. We determine the Kolmogorov dissipation scales for the viscous, the resistive and the ambipolar dissipation mechanisms. The plasma, depending on its properties and the energy injection rate, may preferentially select one of the these dissipation scales. thus determining the shortest spatial scale of the supposedly self-similar spectral distribution of the magnetic field. The results are illustrated taking the partially ionized part of the solar atmosphere as an example. Thus the shortest spatial scale of the supposedly self-similar spectral distribution of the solar magnetic field is determined by any of the four dissipation scales given by the viscosity, the Spizer resistivity...

  13. Precision cluster mass determination from weak lensing

    CERN Document Server

    Mandelbaum, Rachel; Baldauf, Tobias; Smith, Robert E

    2009-01-01

    Weak gravitational lensing has been used extensively in the past decade to constrain the masses of galaxy clusters, and is the most promising observational technique for providing the mass calibration necessary for precision cosmology with clusters. There are several challenges in estimating cluster masses, particularly (a) the sensitivity to astrophysical effects and observational systematics that modify the signal relative to the theoretical expectations, and (b) biases that can arise due to assumptions in the mass estimation method, such as the assumed radial profile of the cluster. All of these challenges are more problematic in the inner regions of the cluster, suggesting that their influence would ideally be suppressed for the purpose of mass estimation. However, at any given radius the differential surface density measured by lensing is sensitive to all mass within that radius, and the corrupted signal from the inner parts is spread out to all scales. We develop a new statistic that is ideal for estima...

  14. Heterodyne detection with a weak local oscillator.

    Science.gov (United States)

    Jiang, Leaf A; Luu, Jane X

    2008-04-01

    Heterodyne detection in the limit of weak (a few photons) local oscillator and signal power levels has been largely neglected in the past, as authors almost always assumed that the noise was dominated by the shot noise from a strong local oscillator. We present the theory for heterodyne detection of diffuse and specular targets at arbitrary power levels, including the case where the local oscillator power is only a few photons per coherent integration period. The theory was tested with experimental results, and was found to show good agreement. We show how to interpret the power spectral density of the heterodyne signal and how to determine the optimal number of signal and local oscillator photons per coherent integration.

  15. Destabilization of free convection by weak rotation

    CERN Document Server

    Gelfgat, Alexander

    2011-01-01

    This study offers an explanation of a recently observed effect of destabilization of free convective flows by weak rotation. After studying several models where flows are driven by a simultaneous action of convection and rotation, it is concluded that the destabilization is observed in the cases where centrifugal force acts against main convective circulation. At relatively low Prandtl numbers this counter action can split the main vortex into two counter rotating vortices, where the interaction leads to instability. At larger Prandtl numbers, the counter action of the centrifugal force steepens an unstable thermal stratification, which triggers Rayleigh-B\\'enard instability mechanism. Both cases can be enhanced by advection of azimuthal velocity disturbances towards the axis, where they grow and excite perturbations of the radial velocity. The effect was studied considering a combined convective/rotating flow in a cylinder with a rotating lid and a parabolic temperature profile at the sidewall. Next, explana...

  16. General Gauge Mediation at the Weak Scale

    CERN Document Server

    Knapen, Simon; Shih, David

    2015-01-01

    We completely characterize General Gauge Mediation (GGM) at the weak scale by solving all IR constraints over the full parameter space. This is made possible through a combination of numerical and analytical methods, based on a set of algebraic relations among the IR soft masses derived from the GGM boundary conditions in the UV. We show how tensions between just a few constraints determine the boundaries of the parameter space: electroweak symmetry breaking (EWSB), the Higgs mass, slepton tachyons, and left-handed stop/sbottom tachyons. While these constraints allow the left-handed squarks to be arbitrarily light, they place strong lower bounds on all of the right-handed squarks. Meanwhile, light EW superpartners are generic throughout much of the parameter space. This is especially the case at lower messenger scales, where a positive threshold correction to $m_h$ coming from light Higgsinos and winos is essential in order to satisfy the Higgs mass constraint.

  17. Magnified Weak Lensing Cross Correlation Tomography

    Energy Technology Data Exchange (ETDEWEB)

    Ulmer, Melville P., Clowe, Douglas I.

    2010-11-30

    This project carried out a weak lensing tomography (WLT) measurement around rich clusters of galaxies. This project used ground based photometric redshift data combined with HST archived cluster images that provide the WLT and cluster mass modeling. The technique has already produced interesting results (Guennou et al, 2010,Astronomy & Astrophysics Vol 523, page 21, and Clowe et al, 2011 to be submitted). Guennou et al have validated that the necessary accuracy can be achieved with photometric redshifts for our purposes. Clowe et al titled "The DAFT/FADA survey. II. Tomographic weak lensing signal from 10 high redshift clusters," have shown that for the **first time** via this purely geometrical technique, which does not assume a standard rod or candle, that a cosmological constant is **required** for flat cosmologies. The intent of this project is not to produce the best constraint on the value of the dark energy equation of state, w. Rather, this project is to carry out a sustained effort of weak lensing tomography that will naturally feed into the near term Dark Energy Survey (DES) and to provide invaluable mass calibration for that project. These results will greatly advance a key cosmological method which will be applied to the top-rated ground-based project in the Astro2020 decadal survey, LSST. Weak lensing tomography is one of the key science drivers behind LSST. CO-I Clowe is on the weak lensing LSST committee, and senior scientist on this project, at FNAL James Annis, plays a leading role in the DES. This project has built on successful proposals to obtain ground-based imaging for the cluster sample. By 1 Jan, it is anticipated the project will have accumulated complete 5-color photometry on 30 (or about 1/3) of the targeted cluster sample (public webpage for the survey is available at http://cencos.oamp.fr/DAFT/ and has a current summary of the observational status of various clusters). In all, the project has now been awarded the equivalent of over 60

  18. Magnified Weak Lensing Cross Correlation Tomography

    Energy Technology Data Exchange (ETDEWEB)

    Ulmer, Melville P., Clowe, Douglas I.

    2010-11-30

    This project carried out a weak lensing tomography (WLT) measurement around rich clusters of galaxies. This project used ground based photometric redshift data combined with HST archived cluster images that provide the WLT and cluster mass modeling. The technique has already produced interesting results (Guennou et al, 2010,Astronomy & Astrophysics Vol 523, page 21, and Clowe et al, 2011 to be submitted). Guennou et al have validated that the necessary accuracy can be achieved with photometric redshifts for our purposes. Clowe et al titled "The DAFT/FADA survey. II. Tomographic weak lensing signal from 10 high redshift clusters," have shown that for the **first time** via this purely geometrical technique, which does not assume a standard rod or candle, that a cosmological constant is **required** for flat cosmologies. The intent of this project is not to produce the best constraint on the value of the dark energy equation of state, w. Rather, this project is to carry out a sustained effort of weak lensing tomography that will naturally feed into the near term Dark Energy Survey (DES) and to provide invaluable mass calibration for that project. These results will greatly advance a key cosmological method which will be applied to the top-rated ground-based project in the Astro2020 decadal survey, LSST. Weak lensing tomography is one of the key science drivers behind LSST. CO-I Clowe is on the weak lensing LSST committee, and senior scientist on this project, at FNAL James Annis, plays a leading role in the DES. This project has built on successful proposals to obtain ground-based imaging for the cluster sample. By 1 Jan, it is anticipated the project will have accumulated complete 5-color photometry on 30 (or about 1/3) of the targeted cluster sample (public webpage for the survey is available at http://cencos.oamp.fr/DAFT/ and has a current summary of the observational status of various clusters). In all, the project has now been awarded the equivalent of over 60

  19. Weak measurement of the Goos-Hanchen shift

    OpenAIRE

    Jayaswal, G.; Mistura, G.; Merano, M.

    2013-01-01

    It is well known from quantum mechanics that weak measurements offer a means of amplifying and detecting very small phenomena. We present here the first experimental observation of the Goos-Hanchen shift via a weak measurement approach.

  20. Residuation Properties and Weakly Primary Elements in Lattice Modules

    Directory of Open Access Journals (Sweden)

    C. S. Manjarekar

    2014-01-01

    Full Text Available We obtain some elementary residuation properties in lattice modules and obtain a relation between a weakly primary element in a lattice module M and weakly prime element of a multiplicative lattice L.

  1. Weak measurement of the Goos-Hänchen shift.

    Science.gov (United States)

    Jayaswal, G; Mistura, G; Merano, M

    2013-04-15

    It is well known from quantum mechanics that weak measurements offer a means of amplifying and detecting very small phenomena. We present here the experimental observation of the Goos-Hänchen shift via a weak measurement approach.

  2. Weak values obtained from mass-energy equivalence

    Science.gov (United States)

    Zhang, Miao

    2017-01-01

    Quantum weak measurement, measuring some observable quantities within the selected subensemble of the entire quantum ensemble, can produce many interesting results such as the superluminal phenomena. An outcome of such a measurement is the weak value which has been applied to amplify some weak signals of quantum interactions in lots of previous references. Here, we apply the weak measurement to the system of relativistic cold atoms. According to mass-energy equivalence, the internal energy of an atom will contribute its rest mass and consequently the external momentum of center of mass. This implies a weak coupling between the internal and external degrees of freedom of atoms moving in the free space. After a duration of this coupling, a weak value can be obtained by post-selecting an internal state of atoms. We show that the weak value can change the momentum uncertainty of atoms and consequently help us to experimentally measure the weak effects arising from mass-energy equivalence.

  3. RHEOLOGY OF CONFINED POLYMER MELTS UNDER SHEAR-FLOW - WEAK ADSORPTION LIMIT : Weak Adsorption Limit

    NARCIS (Netherlands)

    Subbotin, A.V.; Semenov, A.N.; Hadziioannou, G; ten Brinke, G.

    1995-01-01

    The dynamics of a confined polymer melt between weakly adsorbing surfaces is considered theoretically. The finite chain extensibility is taken into account explicitly, and the tangential stress and the first and the second normal-stress differences are calculated as functions of shear rate gamma.

  4. Short-term environmental enrichment exposure induces proliferation and maturation of doublecortin-positive cells in the prefrontal cortex

    Institute of Scientific and Technical Information of China (English)

    Chunling Fan; Mengqi Zhang; Lei Shang; Ngobe Akume Cynthia; Zhi Li; Zhenyu Yang; Dan Chen; Jufang Huang; Kun Xiong

    2014-01-01

    Previous studies have demonstrated that doublecortin-positive immature neurons exist pre-dominantly in the superficial layer of the cerebral cortex of adult mammals such as guinea pigs, and these neurons exhibit very weak properties of self-proliferation during adulthood under physiological conditions. To verify whether environmental enrichment has an impact on the proliferation and maturation of these immature neurons in the prefrontal cortex of adult guinea pigs, healthy adult guinea pigs were subjected to short-term environmental enrichment. Animals were allowed to play with various cognitive and physical stimulating objects over a period of 2 weeks, twice per day, for 60 minutes each. Immunolfuorescence staining results indicated that the number of doublecortin-positive cells in layer II of the prefrontal cortex was signiifcantly increased after short-term environmental enrichment exposure. In addition, these doublecortin-positive cells co-expressed 5-bromo-2-deoxyuridine (a marker of cell prolifera-tion), c-Fos (a marker of cell viability) and NeuN (a marker of mature neurons). Experimental ifndings showed that short-term environmental enrichment can induce proliferation, activation and maturation of doublecortin-positive cells in layer II of the prefrontal cortex of adult guinea pigs.

  5. Weak Hopf Algebras Corresponding to Borcherds-Cartan Matrices

    Institute of Scientific and Technical Information of China (English)

    Li Xia YE; Zhi Xiang WU; Xue Feng MEI

    2007-01-01

    Let y be a generalized Kac-Moody algebra with an integral Borcherds-Cartan matrix. Inthis paper, we define a d-type weak quantum generalized Kac-Moody algebra wUdq(y), which is a weakHopf algebra. We also study the highest weight module over the weak quantum algebra wUdq(y) andWeak A-forms of wUdq(y).

  6. Orbitofrontal cortex function and structure in depression.

    Science.gov (United States)

    Drevets, Wayne C

    2007-12-01

    The orbitofrontal cortex (OFC) has been implicated in the pathophysiology of major depression by evidence obtained using neuroimaging, neuropathologic, and lesion analysis techniques. The abnormalities revealed by these techniques show a regional specificity, and suggest that some OFC regions which appear cytoarchitectonically distinct also are functionally distinct with respect to mood regulation. For example, the severity of depression correlates inversely with physiological activity in parts of the posterior lateral and medial OFC, consistent with evidence that dysfunction of the OFC associated with cerebrovascular lesions increases the vulnerability for developing the major depressive syndrome. The posterior lateral and medial OFC function may also be impaired in individuals who develop primary mood disorders, as these patients show grey-matter volumetric reductions, histopathologic abnormalities, and altered hemodynamic responses to emotionally valenced stimuli, probabilistic reversal learning, and reward processing. In contrast, physiological activity in the anteromedial OFC situated in the ventromedial frontal polar cortex increases during the depressed versus the remitted phases of major depressive disorder to an extent that is positively correlated with the severity of depression. Effective antidepressant treatment is associated with a reduction in activity in this region. Taken together these data are compatible with evidence from studies in experimental animals indicating that some orbitofrontal and medial prefrontal cortex regions function to inhibit, while others function to enhance, emotional expression. Alterations in the functional balance between these regions and the circuits they form with anatomically related areas of the temporal lobe, striatum, thalamus, and brain stem thus may underlie the pathophysiology of mood disorders, such as major depression.

  7. Inhibition by somatostatin interneurons in olfactory cortex

    Directory of Open Access Journals (Sweden)

    Adam M Large

    2016-08-01

    Full Text Available Inhibitory circuitry plays an integral cortical network activity. The development of transgenic mouse lines targeting unique interneuron classes has significantly advanced our understanding of the functional roles of specific inhibitory circuits in neocortical sensory processing. In contrast, considerably less is known about the circuitry and function of interneuron classes in piriform cortex, a paleocortex responsible for olfactory processing. In this study, we sought to utilize transgenic technology to investigate inhibition mediated by somatostatin (SST interneurons onto pyramidal cells, parvalbumin (PV interneurons and other interneuron classes. As a first step, we characterized the anatomical distributions and intrinsic properties of SST and PV interneurons in four transgenic lines (SST-cre, GIN, PV-cre and G42 that are commonly interbred to investigate inhibitory connectivity. Surprisingly, the distributions SST and PV cell subtypes targeted in the GIN and G42 lines were sparse in piriform cortex compared to neocortex. Moreover, two-thirds of interneurons recorded in the SST-cre line had electrophysiological properties similar to fast spiking (FS interneurons rather than regular (RS or low threshold spiking (LTS phenotypes. Nonetheless, like neocortex, we find that SST-cells broadly inhibit a number of unidentified interneuron classes including putatively identified PV cells and surprisingly, other SST cells. We also confirm that SST-cells inhibit pyramidal cell dendrites and thus, influence dendritic integration of afferent and recurrent inputs to the piriform cortex. Altogether, our findings suggest that somatostatin interneurons play an important role in regulating both excitation and the global inhibitory network during olfactory processing.

  8. Apraxia, pantomime and the parietal cortex.

    Science.gov (United States)

    Niessen, E; Fink, G R; Weiss, P H

    2014-01-01

    Apraxia, a disorder of higher motor cognition, is a frequent and outcome-relevant sequel of left hemispheric stroke. Deficient pantomiming of object use constitutes a key symptom of apraxia and is assessed when testing for apraxia. To date the neural basis of pantomime remains controversial. We here review the literature and perform a meta-analysis of the relevant structural and functional imaging (fMRI/PET) studies. Based on a systematic literature search, 10 structural and 12 functional imaging studies were selected. Structural lesion studies associated pantomiming deficits with left frontal, parietal and temporal lesions. In contrast, functional imaging studies associate pantomimes with left parietal activations, with or without concurrent frontal or temporal activations. Functional imaging studies that selectively activated parietal cortex adopted the most stringent controls. In contrast to previous suggestions, current analyses show that both lesion and functional studies support the notion of a left-hemispheric fronto-(temporal)-parietal network underlying pantomiming object use. Furthermore, our review demonstrates that the left parietal cortex plays a key role in pantomime-related processes. More specifically, stringently controlled fMRI-studies suggest that in addition to storing motor schemas, left parietal cortex is also involved in activating these motor schemas in the context of pantomiming object use. In addition to inherent differences between structural and functional imaging studies and consistent with the dedifferentiation hypothesis, the age difference between young healthy subjects (typically included in functional imaging studies) and elderly neurological patients (typically included in structural lesion studies) may well contribute to the finding of a more distributed representation of pantomiming within the motor-dominant left hemisphere in the elderly.

  9. Determining Physical Properties of the Cell Cortex

    Science.gov (United States)

    Saha, Arnab; Nishikawa, Masatoshi; Behrndt, Martin; Heisenberg, Carl-Philipp; Jülicher, Frank; Grill, Stephan W.

    2016-03-01

    Actin and myosin assemble into a thin layer of a highly dynamic network underneath the membrane of eukaryotic cells. This network generates the forces that drive cell and tissue-scale morphogenetic processes. The effective material properties of this active network determine large-scale deformations and other morphogenetic events. For example,the characteristic time of stress relaxation (the Maxwell time)in the actomyosin sets the time scale of large-scale deformation of the cortex. Similarly, the characteristic length of stress propagation (the hydrodynamic length) sets the length scale of slow deformations, and a large hydrodynamic length is a prerequisite for long-ranged cortical flows. Here we introduce a method to determine physical parameters of the actomyosin cortical layer (in vivo). For this we investigate the relaxation dynamics of the cortex in response to laser ablation in the one-cell-stage {\\it C. elegans} embryo and in the gastrulating zebrafish embryo. These responses can be interpreted using a coarse grained physical description of the cortex in terms of a two dimensional thin film of an active viscoelastic gel. To determine the Maxwell time, the hydrodynamic length and the ratio of active stress and per-area friction, we evaluated the response to laser ablation in two different ways: by quantifying flow and density fields as a function of space and time, and by determining the time evolution of the shape of the ablated region. Importantly, both methods provide best fit physical parameters that are in close agreement with each other and that are similar to previous estimates in the two systems. We provide an accurate and robust means for measuring physical parameters of the actomyosin cortical layer.It can be useful for investigations of actomyosin mechanics at the cellular-scale, but also for providing insights in the active mechanics processes that govern tissue-scale morphogenesis.

  10. Genetic Susceptibility to Rhodococcus equi.

    Science.gov (United States)

    McQueen, C M; Dindot, S V; Foster, M J; Cohen, N D

    2015-01-01

    Rhodococcus equi pneumonia is a major cause of morbidity and mortality in neonatal foals. Much effort has been made to identify preventative measures and new treatments for R. equi with limited success. With a growing focus in the medical community on understanding the genetic basis of disease susceptibility, investigators have begun to evaluate the interaction of the genetics of the foal with R. equi. This review describes past efforts to understand the genetic basis underlying R. equi susceptibility and tolerance. It also highlights the genetic technology available to study horses and describes the use of this technology in investigating R. equi. This review provides readers with a foundational understanding of candidate gene approaches, single nucleotide polymorphism-based, and copy number variant-based genome-wide association studies, and next generation sequencing (both DNA and RNA). Copyright © 2015 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.

  11. The influence of weak impacts on certain processes of nanotechnology

    Science.gov (United States)

    Tupik, V. A.; Margolin, V. I.; Potekhin, M. S.

    2017-07-01

    The article deals with the influence of weak and super weak impacts on certain technological processes in nanotechnology related to the synthesis of nanoscale films and coatings. We also touch upon the impacts of weak diffraction fields of complex shape on the formation of fractal films and coatings.

  12. On Weakly Singular Versions of Discrete Nonlinear Inequalities and Applications

    Directory of Open Access Journals (Sweden)

    Kelong Cheng

    2014-01-01

    Full Text Available Some new weakly singular versions of discrete nonlinear inequalities are established, which generalize some existing weakly singular inequalities and can be used in the analysis of nonlinear Volterra type difference equations with weakly singular kernels. A few applications to the upper bound and the uniqueness of solutions of nonlinear difference equations are also involved.

  13. Neutrino energy transport in weak decoupling and big bang nucleosynthesis

    CERN Document Server

    Grohs, E; Kishimoto, C T; Paris, M W; Vlasenko, A

    2015-01-01

    We calculate the evolution of the early universe through the epochs of weak decoupling, weak freeze-out and big bang nucleosynthesis (BBN) by simultaneously coupling a full strong, electromagnetic, and weak nuclear reaction network with a multi-energy group Boltzmann neutrino energy transport scheme. Such an approach allows a detailed accounting of the evolution of the $\

  14. Animal model of differential susceptibility to stress in development: implications for schizophrenia

    OpenAIRE

    Daskalakis, Nikolaos P.; E. Ronald de Kloet

    2012-01-01

    Rationale/statement of the problem : Common gene variants predisposing for altered dopamine (DA) neurotransmission are candidates for schizophrenia-susceptibility genes, although genome-wide studies so far showed a weak association of these variants with schizophrenia. It has actually become apparent that the expression of psychotic symptoms in schizophrenia is associated with the exposure of the genetically predisposed individuals to environmental risk factors during development such as earl...

  15. Diagonal and off-diagonal quark number susceptibilities at high temperatures

    CERN Document Server

    Ding, H -T; Ohno, H; Petreczky, P; Schadler, H -P

    2015-01-01

    We present continuum extrapolated lattice QCD results for up to fourth order diagonal and off-diagonal quark number susceptibilities in the high temperature region of 300-700 MeV. Lattice QCD calculations are performed using 2+1 flavors of highly improved staggered quarks with nearly physical quark masses and at four different lattice spacings. Comparisons of our results with recent weak coupling perturbative calculations yield reasonably good agreements for the entire temperature range.

  16. Aberrant functional connectivity differentiates retrosplenial cortex from posterior cingulate cortex in prodromal Alzheimer's disease.

    Science.gov (United States)

    Dillen, Kim N H; Jacobs, Heidi I L; Kukolja, Juraj; von Reutern, Boris; Richter, Nils; Onur, Özgür A; Dronse, Julian; Langen, Karl-Josef; Fink, Gereon R

    2016-08-01

    The posterior cingulate cortex (PCC) is a key hub of the default mode network, a resting-state network involved in episodic memory, showing functional connectivity (FC) changes in Alzheimer's disease (AD). However, PCC is a cytoarchitectonically heterogeneous region. Specifically, the retrosplenial cortex (RSC), often subsumed under the PCC, is an area functionally and microanatomically distinct from PCC. To investigate FC patterns of RSC and PCC separately, we used resting-state functional magnetic resonance imaging in healthy aging participants, patients with subjective cognitive impairment, and prodromal AD. Compared to the other 2 groups, we found higher FC from RSC to frontal cortex in subjective cognitive impairment but higher FC to occipital cortex in prodromal AD. Conversely, FC from PCC to the lingual gyrus was higher in prodromal AD. Furthermore, data indicate that RSC and PCC are characterized by differential FC patterns represented by hub-specific interactions with memory and attentions scores in prodromal AD compared to cognitively normal individuals, possibly reflecting compensatory mechanisms for RSC and neurodegenerative processes for PCC. Data thus confirm and extend previous studies suggesting that the RSC is functionally distinct from PCC.

  17. Fluctuation scaling in the visual cortex at threshold

    Science.gov (United States)

    Medina, José M.; Díaz, José A.

    2016-05-01

    Fluctuation scaling relates trial-to-trial variability to the average response by a power function in many physical processes. Here we address whether fluctuation scaling holds in sensory psychophysics and its functional role in visual processing. We report experimental evidence of fluctuation scaling in human color vision and form perception at threshold. Subjects detected thresholds in a psychophysical masking experiment that is considered a standard reference for studying suppression between neurons in the visual cortex. For all subjects, the analysis of threshold variability that results from the masking task indicates that fluctuation scaling is a global property that modulates detection thresholds with a scaling exponent that departs from 2, β =2.48 ±0.07 . We also examine a generalized version of fluctuation scaling between the sample kurtosis K and the sample skewness S of threshold distributions. We find that K and S are related and follow a unique quadratic form K =(1.19 ±0.04 ) S2+(2.68 ±0.06 ) that departs from the expected 4/3 power function regime. A random multiplicative process with weak additive noise is proposed based on a Langevin-type equation. The multiplicative process provides a unifying description of fluctuation scaling and the quadratic S -K relation and is related to on-off intermittency in sensory perception. Our findings provide an insight into how the human visual system interacts with the external environment. The theoretical methods open perspectives for investigating fluctuation scaling and intermittency effects in a wide variety of natural, economic, and cognitive phenomena.

  18. Fluctuation scaling in the visual cortex at threshold.

    Science.gov (United States)

    Medina, José M; Díaz, José A

    2016-05-01

    Fluctuation scaling relates trial-to-trial variability to the average response by a power function in many physical processes. Here we address whether fluctuation scaling holds in sensory psychophysics and its functional role in visual processing. We report experimental evidence of fluctuation scaling in human color vision and form perception at threshold. Subjects detected thresholds in a psychophysical masking experiment that is considered a standard reference for studying suppression between neurons in the visual cortex. For all subjects, the analysis of threshold variability that results from the masking task indicates that fluctuation scaling is a global property that modulates detection thresholds with a scaling exponent that departs from 2, β=2.48±0.07. We also examine a generalized version of fluctuation scaling between the sample kurtosis K and the sample skewness S of threshold distributions. We find that K and S are related and follow a unique quadratic form K=(1.19±0.04)S^{2}+(2.68±0.06) that departs from the expected 4/3 power function regime. A random multiplicative process with weak additive noise is proposed based on a Langevin-type equation. The multiplicative process provides a unifying description of fluctuation scaling and the quadratic S-K relation and is related to on-off intermittency in sensory perception. Our findings provide an insight into how the human visual system interacts with the external environment. The theoretical methods open perspectives for investigating fluctuation scaling and intermittency effects in a wide variety of natural, economic, and cognitive phenomena.

  19. Neurons and circuits for odor processing in the piriform cortex.

    Science.gov (United States)

    Bekkers, John M; Suzuki, Norimitsu

    2013-07-01

    Increased understanding of the early stages of olfaction has lead to a renewed interest in the higher brain regions responsible for forming unified 'odor images' from the chemical components detected by the nose. The piriform cortex, which is one of the first cortical destinations of olfactory information in mammals, is a primitive paleocortex that is critical for the synthetic perception of odors. Here we review recent work that examines the cellular neurophysiology of the piriform cortex. Exciting new findings have revealed how the neurons and circuits of the piriform cortex process odor information, demonstrating that, despite its superficial simplicity, the piriform cortex is a remarkably subtle and intricate neural circuit.

  20. Quantum-memory-assisted entropic uncertainty relations under weak measurements

    Science.gov (United States)

    Li, Lei; Wang, Qing-Wen; Shen, Shu-Qian; Li, Ming

    2017-08-01

    We investigate quantum-memory-assisted entropic uncertainty relations (EURs) based on weak measurements. It is shown that the lower bound of EUR revealed by weak measurements is always larger than that revealed by the corresponding projective measurements. A series of lower bounds of EUR under both weak measurements and projective measurements are presented. Interestingly, the quantum-memory-assisted EUR based on weak measurements is a monotonically decreasing function of the strength parameter. Furthermore, some information-theoretic inequalities associated with weak measurements are also derived.

  1. Spatial-domain interactions between ultra-weak optical beams

    CERN Document Server

    Khadka, Utsab; Xiao, Min

    2013-01-01

    We have observed the spatial interactions between two ultra-weak optical beams that are initially collinear and non-overlapping. The weak beams are steered towards each other by a spatially varying cross-Kerr refractive index waveguide written by a strong laser beam in a three-level atomic medium utilizing quantum coherence. After being brought together, the weak beams show controllable phase-dependent outcomes. This is the first observation of soliton-like interactions between weak beams and can be useful for all-optically tunable beam-combining, switching and gates for weak photonic signals.

  2. Finger somatotopy in human motor cortex.

    Science.gov (United States)

    Beisteiner, R; Windischberger, C; Lanzenberger, R; Edward, V; Cunnington, R; Erdler, M; Gartus, A; Streibl, B; Moser, E; Deecke, L

    2001-06-01

    Although qualitative reports about somatotopic representation of fingers in the human motor cortex exist, up to now no study could provide clear statistical evidence. The goal of the present study was to reinvestigate finger motor somatotopy by means of a thorough investigation of standardized movements of the index and little finger of the right hand. Using high resolution fMRI at 3 Tesla, blood oxygenation level-dependent (BOLD) responses in a group of 26 subjects were repeatedly measured to achieve reliable statistical results. The center of mass of all activated voxels within the primary motor cortex was calculated for each finger and each run. Results of all runs were averaged to yield an individual index and little finger representation for each subject. The mean center of mass localizations for all subjects were then submitted to a paired t test. Results show a highly significant though small scale somatotopy of fingerspecific activation patterns in the order indicated by Penfields motor homunculus. In addition, considerable overlap of finger specific BOLD responses was found. Comparing various methods of analysis, the mean center of mass distance for the two fingers was 2--3 mm with overlapping voxels included and 4--5 mm with overlapping voxels excluded. Our data may be best understood in the context of the work of Schieber (1999) who recently described overlapping somatotopic gradients in lesion studies with humans. Copyright 2001 Academic Press.

  3. Cognitive Control Signals in Posterior Cingulate Cortex

    Directory of Open Access Journals (Sweden)

    Benjamin eHayden

    2010-12-01

    Full Text Available Efficiently shifting between tasks is a central function of cognitive control. The role of the default network—a constellation of areas with high baseline activity that declines during task performance—in cognitive control remains poorly understood. We hypothesized that task switching demands cognitive control to shift the balance of processing towards the external world, and therefore predicted that switching between the two tasks would require suppression of activity of neurons within the CGp. To test this idea, we recorded the activity of single neurons in posterior cingulate cortex (CGp, a central node in the default network, in monkeys performing two interleaved tasks. As predicted, we found that basal levels of neuronal activity were reduced following a switch from one task to another and gradually returned to pre-switch baseline on subsequent trials. We failed to observe these effects in lateral intraparietal cortex (LIP, part of the dorsal fronto-parietal cortical attention network directly connected to CGp. These findings indicate that suppression of neuronal activity in CGp facilitates cognitive control, and suggest that activity in the default network reflects processes that directly compete with control processes elsewhere in the brain..

  4. Motor cortex stimulation in Parkinson's disease.

    Science.gov (United States)

    De Rose, Marisa; Guzzi, Giusy; Bosco, Domenico; Romano, Mary; Lavano, Serena Marianna; Plastino, Massimiliano; Volpentesta, Giorgio; Marotta, Rosa; Lavano, Angelo

    2012-01-01

    Motor Cortex Stimulation (MCS) is less efficacious than Deep Brain Stimulation (DBS) in Parkinson's disease. However, it might be proposed to patients excluded from DBS or unresponsive to DBS. Ten patients with advanced PD underwent unilateral MCS contralaterally to the worst clinical side. A plate electrode was positioned over the motor cortex in the epidural space through single burr hole after identification of the area with neuronavigation and neurophysiological tests. Clinical assessment was performed by total UPDRS, UPDRS III total, UPDRS III-items 27-31, UPDRS IV, and UPDRS II before implantation in off-medication and on-medication states and after surgery at 1, 3, 6, 12, 18, 24, and 36 months in on-medication/on-stimulation and off-medication/on-stimulation states. We assessed changes of quality of life, throughout the Parkinson's disease quality of life scale (PDQoL-39), and the dose of anti-Parkinson's disease medications, throughout the Ldopa equivalent daily dose (LEDD). During off-medication state, we observed moderate and transitory reduction of total UPDRS and UPDRS total scores and significant and long-lasting improvement in UPDRS III items 27-31 score for axial symptoms. There was marked reduction of UPDRS IV score and LEDD. PDQL-39 improvement was also significant. No important complications and adverse events occurred.

  5. Motor Cortex Stimulation in Parkinson's Disease

    Directory of Open Access Journals (Sweden)

    Marisa De Rose

    2012-01-01

    Full Text Available Motor Cortex Stimulation (MCS is less efficacious than Deep Brain Stimulation (DBS in Parkinson's disease. However, it might be proposed to patients excluded from DBS or unresponsive to DBS. Ten patients with advanced PD underwent unilateral MCS contralaterally to the worst clinical side. A plate electrode was positioned over the motor cortex in the epidural space through single burr hole after identification of the area with neuronavigation and neurophysiological tests. Clinical assessment was performed by total UPDRS, UPDRS III total, UPDRS III-items 27–31, UPDRS IV, and UPDRS II before implantation in off-medication and on-medication states and after surgery at 1, 3, 6, 12, 18, 24, and 36 months in on-medication/on-stimulation and off-medication/on-stimulation states. We assessed changes of quality of life, throughout the Parkinson's disease quality of life scale (PDQoL-39, and the dose of anti-Parkinson's disease medications, throughout the Ldopa equivalent daily dose (LEDD. During off-medication state, we observed moderate and transitory reduction of total UPDRS and UPDRS total scores and significant and long-lasting improvement in UPDRS III items 27–31 score for axial symptoms. There was marked reduction of UPDRS IV score and LEDD. PDQL-39 improvement was also significant. No important complications and adverse events occurred.

  6. Frequency specific modulation of human somatosensory cortex

    Directory of Open Access Journals (Sweden)

    Matteo eFeurra

    2011-02-01

    Full Text Available Oscillatory neuronal activities are commonly observed in response to sensory stimulation. However, their functional roles are still the subject of debate. One way to probe the roles of oscillatory neural activities is to deliver alternating current to the cortex at biologically relevant frequencies and examine whether such stimulation influences perception and cognition. In this study, we tested whether transcranial alternating current stimulation (tACS over the primary somatosensory cortex (SI could elicit tactile sensations in humans in a frequency dependent manner. We tested the effectiveness of tACS over SI at frequency bands ranging from 2 to 70 Hz. Our results show that stimulation in alpha (10-14 Hz and high gamma (52-70 Hz frequency range produces a tactile sensation in the contralateral hand. A weaker effect was also observed for beta (16-20 Hz stimulation. These findings highlight the frequency-dependency of effective tACS over SI with the effective frequencies corresponding to those observed in previous EEG/MEG studies of tactile perception. Our present study suggests that tACS could be used as a powerful online stimulation technique to reveal the causal roles of oscillatory brain activities.

  7. Magnetic susceptibility properties of polluted soils

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    An investigation of magnetic properties using magnetic susceptibility (X) and frequency-dependent susceptibility (Xfd) was conducted on representative modern pollutants, which include smelted slag dust, automobile exhaust dust and coal ash. Their magnetic susceptibility values are more than 500×10-8 m3/kg, and frequency-dependent susceptibility values less than 3%, indicating that ample ferrimagnetic and scanty superparamagnetic grains occurred in the studied pollutants. Similar to the artificially synthetic polluted soils, the industrially-polluted soils display a negative relationship between magnetic susceptibility and frequency-dependent susceptibility. However, the unpolluted soils, e.g. the Quaternary loess in the Chinese Loess Plateau, show a positive relationship between them. In this note, we propose a convenient and effective approach for identifying the polluted soils.

  8. The Origin of Weak Lensing Convergence Peaks

    CERN Document Server

    Liu, Jia

    2016-01-01

    Weak lensing convergence peaks are a promising tool to probe nonlinear structure evolution at late times, providing additional cosmological information beyond second-order statistics. Previous theoretical and observational studies have shown that the cosmological constraints on $\\Omega_m$ and $\\sigma_8$ are improved by a factor of up to ~ 2 when peak counts and second-order statistics are combined, compared to using the latter alone. We study the origin of lensing peaks using observational data from the 154 deg$^2$ Canada-France-Hawaii Telescope Lensing Survey. We found that while high peaks (with height $\\kappa$ >3.5 $\\sigma_\\kappa$, where $\\sigma_\\kappa$ is the r.m.s. of the convergence $\\kappa$) are typically due to one single massive halo of ~$10^{15}M_\\odot$, low peaks ($\\kappa$ ~ their virial radii), compared with ~0.25 virial radii for halos linked with high peaks, hinting that low peaks are more immune to baryonic processes whose impact is confined to the inner regions of the dark matter halos. Our fi...

  9. NUMERICAL STUDIES OF WEAKLY STOCHASTIC MAGNETIC RECONNECTION

    Directory of Open Access Journals (Sweden)

    G. Kowal

    2009-01-01

    Full Text Available We study the e ects of turbulence on magnetic reconnection using three-dimensional numerical simulations.This is the rst attempt to test the model of fast magnetic reconnection proposed by Lazarian & Vishniac (1999, which assumes the presence of weak, small-scale magnetic eld structure near the current sheet. This a ects the rate of reconnection by reducing the transverse scale for reconnection ows and by allowing many independent ux reconnection events to occur simultaneously. We performed a number of simulations to test the dependencies of the reconnection speed, de ned as the ratio of the in ow velocity to the Alfv n speed, on the turbulence power, the injection scale and resistivity. Our results show that turbulence signi cantly a ects the topology of magnetic eld near the di usion region and increases the thickness of the out ow region. We con rm the predictions of the Lazarian & Vishniac model. In particular, we report the growth of the reconnection speed proportional to V 2 l , where Vl is the amplitude of velocity at the injection scale. It depends on the injection scale linj as (linj=L2=3, where L is the size of the system, which is somewhat faster but still roughly consistent with the theoretical expectations. We also show that for 3D reconnection the Ohmic resistivity is important in the local reconnection events only, and the global reconnection rate in the presence of turbulence does not depend on it.

  10. Relaxion monodromy and the Weak Gravity Conjecture

    Science.gov (United States)

    Ibáñez, L. E.; Montero, M.; Uranga, A. M.; Valenzuela, I.

    2016-04-01

    The recently proposed relaxion models require extremely large trans-Planckian axion excursions as well as a potential explicitly violating the axion shift symmetry. The latter property is however inconsistent with the axion periodicity, which corresponds to a gauged discrete shift symmetry. A way to make things consistent is to use monodromy, i.e. both the axion and the potential parameters transform under the discrete shift symmetry. The structure is better described in terms of a 3-form field C μνρ coupling to the SM Higgs through its field strength F 4. The 4-form also couples linearly to the relaxion, in the Kaloper-Sorbo fashion. The extremely small relaxion-Higgs coupling arises in a see-saw fashion as g ≃ F 4 /f , with f being the axion decay constant. We discuss constraints on this type of constructions from membrane nucleation and the Weak Gravity Conjecture. The latter requires the existence of membranes, whose too fast nucleation could in principle drive the theory out of control, unless the cut-off scale is lowered. This allows to rule out the simplest models with the QCD axion as relaxion candidate on purely theoretical grounds. We also discuss possible avenues to embed this structure into string theory.

  11. Autoresonance versus localization in weakly coupled oscillators

    Science.gov (United States)

    Kovaleva, Agnessa; Manevitch, Leonid I.

    2016-04-01

    We study formation of autoresonance (AR) in a two-degree of freedom oscillator array including a nonlinear (Duffing) oscillator (the actuator) weakly coupled to a linear attachment. Two classes of systems are studied. In the first class of systems, a periodic force with constant (resonance) frequency is applied to a nonlinear oscillator (actuator) with slowly time-decreasing stiffness. In the systems of the second class a nonlinear time-invariant oscillator is subjected to an excitation with slowly increasing frequency. In both cases, the attached linear oscillator and linear coupling are time-invariant, and the system is initially engaged in resonance. This paper demonstrates that in the systems of the first type AR in the nonlinear actuator entails oscillations with growing amplitudes in the linear attachment while in the system of the second type energy transfer from the nonlinear actuator is insufficient to excite high-energy oscillations of the attachment. It is also shown that a slow change of stiffness may enhance the response of the actuator and make it sufficient to support oscillations with growing energy in the attachment even beyond the linear resonance. Explicit asymptotic approximations of the solutions are obtained. Close proximity of the derived approximations to exact (numerical) results is demonstrated.

  12. Compact Groups analysis using weak gravitational lensing

    Science.gov (United States)

    Chalela, Martín; Johana Gonzalez, Elizabeth; Garcia Lambas, Diego; Foëx, Gael

    2017-01-01

    We present a weak lensing analysis of a sample of SDSS Compact Groups (CGs). Using the measured radial density contrast profile, we derive the average masses under the assumption of spherical symmetry, obtaining a velocity dispersion for the Singular Isothermal Spherical model, σV = 270 ± 40 km s-1, and for the NFW model, R_{200}=0.53± 0.10 h_{70}^{-1}Mpc. We test three different definitions of CGs centres to identify which best traces the true dark matter halo centre, concluding that a luminosity weighted centre is the most suitable choice. We also study the lensing signal dependence on CGs physical radius, group surface brightness, and morphological mixing. We find that groups with more concentrated galaxy members show steeper mass profiles and larger velocity dispersions. We argue that both, a possible lower fraction of interloper and a true steeper profile, could be playing a role in this effect. Straightforward velocity dispersion estimates from member spectroscopy yields σV ≈ 230 km s-1 in agreement with our lensing results.

  13. Strong eukaryotic IRESs have weak secondary structure.

    Directory of Open Access Journals (Sweden)

    Xuhua Xia

    Full Text Available BACKGROUND: The objective of this work was to investigate the hypothesis that eukaryotic Internal Ribosome Entry Sites (IRES lack secondary structure and to examine the generality of the hypothesis. METHODOLOGY/PRINCIPAL FINDINGS: IRESs of the yeast and the fruit fly are located in the 5'UTR immediately upstream of the initiation codon. The minimum folding energy (MFE of 60 nt RNA segments immediately upstream of the initiation codons was calculated as a proxy of secondary structure stability. MFE of the reverse complements of these 60 nt segments was also calculated. The relationship between MFE and empirically determined IRES activity was investigated to test the hypothesis that strong IRES activity is associated with weak secondary structure. We show that IRES activity in the yeast and the fruit fly correlates strongly with the structural stability, with highest IRES activity found in RNA segments that exhibit the weakest secondary structure. CONCLUSIONS: We found that a subset of eukaryotic IRESs exhibits very low secondary structure in the 5'-UTR sequences immediately upstream of the initiation codon. The consistency in results between the yeast and the fruit fly suggests a possible shared mechanism of cap-independent translation initiation that relies on an unstructured RNA segment.

  14. Forensic bitemark identification: weak foundations, exaggerated claims

    Science.gov (United States)

    Saks, Michael J.; Albright, Thomas; Bohan, Thomas L.; Bierer, Barbara E.; Bowers, C. Michael; Bush, Mary A.; Bush, Peter J.; Casadevall, Arturo; Cole, Simon A.; Denton, M. Bonner; Diamond, Shari Seidman; Dioso-Villa, Rachel; Epstein, Jules; Faigman, David; Faigman, Lisa; Fienberg, Stephen E.; Garrett, Brandon L.; Giannelli, Paul C.; Greely, Henry T.; Imwinkelried, Edward; Jamieson, Allan; Kafadar, Karen; Kassirer, Jerome P.; Koehler, Jonathan ‘Jay’; Korn, David; Mnookin, Jennifer; Morrison, Alan B.; Murphy, Erin; Peerwani, Nizam; Peterson, Joseph L.; Risinger, D. Michael; Sensabaugh, George F.; Spiegelman, Clifford; Stern, Hal; Thompson, William C.; Wayman, James L.; Zabell, Sandy; Zumwalt, Ross E.

    2016-01-01

    Abstract Several forensic sciences, especially of the pattern-matching kind, are increasingly seen to lack the scientific foundation needed to justify continuing admission as trial evidence. Indeed, several have been abolished in the recent past. A likely next candidate for elimination is bitemark identification. A number of DNA exonerations have occurred in recent years for individuals convicted based on erroneous bitemark identifications. Intense scientific and legal scrutiny has resulted. An important National Academies review found little scientific support for the field. The Texas Forensic Science Commission recently recommended a moratorium on the admission of bitemark expert testimony. The California Supreme Court has a case before it that could start a national dismantling of forensic odontology. This article describes the (legal) basis for the rise of bitemark identification and the (scientific) basis for its impending fall. The article explains the general logic of forensic identification, the claims of bitemark identification, and reviews relevant empirical research on bitemark identification—highlighting both the lack of research and the lack of support provided by what research does exist. The rise and possible fall of bitemark identification evidence has broader implications—highlighting the weak scientific culture of forensic science and the law's difficulty in evaluating and responding to unreliable and unscientific evidence. PMID:28852538

  15. Blind quantum computing with weak coherent pulses.

    Science.gov (United States)

    Dunjko, Vedran; Kashefi, Elham; Leverrier, Anthony

    2012-05-18

    The universal blind quantum computation (UBQC) protocol [A. Broadbent, J. Fitzsimons, and E. Kashefi, in Proceedings of the 50th Annual IEEE Symposiumon Foundations of Computer Science (IEEE Computer Society, Los Alamitos, CA, USA, 2009), pp. 517-526.] allows a client to perform quantum computation on a remote server. In an ideal setting, perfect privacy is guaranteed if the client is capable of producing specific, randomly chosen single qubit states. While from a theoretical point of view, this may constitute the lowest possible quantum requirement, from a pragmatic point of view, generation of such states to be sent along long distances can never be achieved perfectly. We introduce the concept of ϵ blindness for UBQC, in analogy to the concept of ϵ security developed for other cryptographic protocols, allowing us to characterize the robustness and security properties of the protocol under possible imperfections. We also present a remote blind single qubit preparation protocol with weak coherent pulses for the client to prepare, in a delegated fashion, quantum states arbitrarily close to perfect random single qubit states. This allows us to efficiently achieve ϵ-blind UBQC for any ϵ>0, even if the channel between the client and the server is arbitrarily lossy.

  16. Energy localization in weakly dissipative resonant chains

    Science.gov (United States)

    Kovaleva, Agnessa

    2016-08-01

    Localization of energy in oscillator arrays has been of interest for a number of years, with special attention paid to the role of nonlinearity and discreteness in the formation of localized structures. This work examines a different type of energy localization arising due to the presence of dissipation in nonlinear resonance arrays. As a basic model, we consider a Klein-Gordon chain of finite length subjected to a harmonic excitation applied at an edge of the chain. It is shown that weak dissipation may be a key factor preventing the emergence of resonance in the entire chain, even if its nondissipative analog is entirely captured into resonance. The resulting process in the dissipative oscillator array represents large-amplitude resonant oscillations in a part of the chain adjacent to the actuator and small-amplitude oscillations in the distant part of the chain. The conditions of the emergence of resonance as well as the conditions of energy localization are derived. An agreement between the obtained analytical results and numerical simulations is demonstrated.

  17. Fast Reconnection of Weak Magnetic Fields

    Science.gov (United States)

    Zweibel, Ellen G.

    1998-01-01

    Fast magnetic reconnection refers to annihilation or topological rearrangement of magnetic fields on a timescale that is independent (or nearly independent) of the plasma resistivity. The resistivity of astrophysical plasmas is so low that reconnection is of little practical interest unless it is fast. Yet, the theory of fast magnetic reconnection is on uncertain ground, as models must avoid the tendency of magnetic fields to pile up at the reconnection layer, slowing down the flow. In this paper it is shown that these problems can be avoided to some extent if the flow is three dimensional. On the other hand, it is shown that in the limited but important case of incompressible stagnation point flows, every flow will amplify most magnetic fields. Although examples of fast magnetic reconnection abound, a weak, disordered magnetic field embedded in stagnation point flow will in general be amplified, and should eventually modify the flow. These results support recent arguments against the operation of turbulent resistivity in highly conducting fluids.

  18. Planckian axions and the Weak Gravity Conjecture

    Science.gov (United States)

    Bachlechner, Thomas C.; Long, Cody; McAllister, Liam

    2016-01-01

    Several recent works [1-3] have claimed that the Weak Gravity Conjecture (WGC) excludes super-Planckian displacements of axion fields, and hence large-field axion inflation, in the absence of monodromy. We argue that in theories with N ≫ 1 axions, super-Planckian axion diameters D are readily allowed by the WGC. We clarify the non-trivial relationship between the kinetic matrix K — unambiguously defined by its form in a Minkowski-reduced basis — and the diameter of the axion fundamental domain, emphasizing that in general the diameter is not solely determined by the eigenvalues f 1 2 ≤ ṡ ṡ ṡ ≤ f N 2 of K: the orientations of the eigenvectors with respect to the identifications imposed by instantons must be incorporated. In particular, even if one were to impose the condition f N M pl does not immediately imply the existence of unsuppressed higher harmonic contributions to the potential. Finally, we argue that in effective axion-gravity theories, the zero-form version of the WGC can be satisfied by gravitational instantons that make negligible contributions to the potential.

  19. Planckian Axions and the Weak Gravity Conjecture

    CERN Document Server

    Bachlechner, Thomas C; McAllister, Liam

    2015-01-01

    Several recent works have claimed that the Weak Gravity Conjecture (WGC) excludes super-Planckian displacements of axion fields, and hence large-field axion inflation, in the absence of monodromy. We argue that in theories with $N\\gg1$ axions, super-Planckian axion diameters $\\cal{D}$ are readily allowed by the WGC. We clarify the nontrivial relationship between the kinetic matrix $K$ --- unambiguously defined by its form in a Minkowski-reduced basis --- and the diameter of the axion fundamental domain, emphasizing that in general the diameter is not solely determined by the eigenvalues $f_1^2 \\le ... \\le f_N^2$ of $K$: the orientations of the eigenvectors with respect to the identifications imposed by instantons must be incorporated. In particular, even if one were to impose the condition $f_NM_{pl}$ does not immediately imply the existence of unsuppressed higher harmonic contributions to the potential. Finally, we argue that in effective axion-gravity theories, the zero-form version of the WGC can be satisf...

  20. Weak gauge principle and electric charge quantization

    CERN Document Server

    Minguzzi, E; Almorox, A L

    2006-01-01

    We review the argument that relates the quantization of electric charge to the topology of the spacetime manifold starting from the gauge principle. We formulate it in the language of Cech cohomology so that its generalization to cases that do not involve a monopole field becomes straightforward. We consider two different formulations of the gauge principle, the usual (strong) version and a weaker version in which the transition functions can differ from matter field to matter field. From both versions it follows that the charges are quantized if the electromagnetic field is not exact. The weak case is studied in detail. To each pair of particles there corresponds an interference class $k \\in H^{1}(M,U(1))$ that controls the different behavior of the particles under topological Aharonov-Bohm experiments. If this class is trivial the phenomenology reduces to that of the usual strong gauge principle case. It is shown that the theory may give rise to two natural quantization units that we identify with the quant...