Sample records for callosum fractional anisotropy

  1. Fractional Anisotropy in Corpus Callosum Is Associated with Facilitation of Motor Representation during Ipsilateral Hand Movements

    PubMed Central

    Chiou, Shin-Yi; Wang, Ray-Yau; Roberts, R. Edward; Wu, Yu-Te; Lu, Chia-Feng; Liao, Kwong-Kum; Yang, Yea-Ru

    2014-01-01

    Background Coactivation of primary motor cortex ipsilateral to a unilateral movement (M1ipsilateral) has been observed, and the magnitude of activation is influenced by the contracting muscles. It has been suggested that the microstructural integrity of the callosal motor fibers (CMFs) connecting M1 regions may reflect the observed response. However, the association between the structural connectivity of CMFs and functional changes in M1ipsilateral remains unclear. The purpose of this study was to investigate the relationship between functional changes within M1ipsilateral during unilateral arm or leg movements and the microstructure of the CMFs connecting both homotopic representations (arm or leg). Methods Transcranial magnetic stimulation was used to assess changes in motor evoked potentials (MEP) in an arm muscle during unilateral movements compared to rest in fifteen healthy adults. Functional magnetic resonance imaging was then used to identify regions of M1 associated with either arm or leg movements. Diffusion-weighted imaging data was acquired to generate CMFs for arm and leg areas using the areas of activation from the functional imaging as seed masks. Individual values of regional fractional anisotropy (FA) of arm and leg CMFs was then calculated by examining the overlap between CMFs and a standard atlas of corpus callosum. Results The change in the MEP was significantly larger in the arm movement compared to the leg movement. Additionally, regression analysis revealed that FA in the arm CMFs was positively correlated with the change in MEP during arm movement, whereas a negative correlation was observed during the leg movement. However, there was no significant relationship between FA in the leg CMF and the change in MEP during the movements. Conclusions These findings suggest that individual differences in interhemispheric structural connectivity may be used to explain a homologous muscle-dominant effect within M1ipsilateral hand representation during unilateral movement with topographical specificity. PMID:25118828

  2. Differential fractional anisotropy abnormalities in adolescents with ADHD or schizophrenia

    PubMed Central

    Davenport, Nicholas D.; Karatekin, Canan; White, Tonya; Lim, Kelvin O.

    2010-01-01

    Schizophrenia and ADHD are associated with similar deficits in working memory, attention, and inhibition. Both disorders also involve abnormalities of white matter integrity, possibly reflecting neural communication disruptions. There are likely some regional white matter abnormalities that underlie the common cognitive impairment, though also some regional abnormalities unique to each disorder. We used diffusion tensor imaging (DTI) to compare white matter integrity, as indicated by fractional anisotropy (FA), in adolescents with schizophrenia (n=15) or ADHD (n=14) and healthy controls (n=26). Schizophrenia patients had uniquely low FA, relative to the other two groups, in bilateral cerebral peduncles, anterior and posterior corpus callosum, right anterior corona radiata, and right superior longitudinal fasciculus. ADHD patients had uniquely high FA in left inferior and right superior frontal regions. Both clinical groups had lower FA than controls in left posterior fornix. The two disorders generally demonstrated distinct patterns of abnormal connectivity suggesting that common cognitive and behavioral deficits derive from distinct sources, though the posterior fornix may be involved in both disorders. Schizophrenia was associated with abnormally low FA in widespread circuitry indicative of general connectivity disruptions, whereas ADHD was associated with abnormally high FA in frontal networks that may indicate impaired branching of fibers. PMID:20153608

  3. STATISTICAL TESTS OF ANISOTROPY FOR FRACTIONAL BROWNIAN TEXTURES.

    E-print Network

    Biermé, Hermine

    STATISTICAL TESTS OF ANISOTROPY FOR FRACTIONAL BROWNIAN TEXTURES. APPLICATION TO FULL-FIELD DIGITAL methodology for the analysis of texture anisotropy. The methodology is based on the stochastic modeling of textures by anisotropic fractional Brownian fields. It includes original statistical tests that permit

  4. Acute nicotine administration effects on fractional anisotropy of cerebral white matter and associated attention performance

    PubMed Central

    Kochunov, Peter; Du, Xiaoming; Moran, Lauren V.; Sampath, Hemalatha; Wijtenburg, S. Andrea; Yang, Yihong; Rowland, Laura M.; Stein, Elliot A.; Hong, L. Elliot

    2013-01-01

    Introduction: Nicotinic acetylcholine receptors are present in the cerebral white matter (WM). We hypothesized that WM response to nicotine can be detected by diffusion tensor imaging (DTI); and that such responses may be associated with nicotine-led cognitive enhancement in sustained attention. Methods: A randomized, nicotine-placebo patch, crossover, double-blind clinical trial in two non-overlapping cohorts of smokers was used to test the hypothesis. The discovery cohort consisted of 39 subjects (N = 20/19 controls/schizophrenic patients, age = 36.8 ± 10.1 years) and the replication cohorts consisted of 38 healthy smokers (31.7 ± 10.5 years). WM integrity was measured by fractional anisotropy (FA) values for the whole brain and nine preselected WM tracts using tract-based-spatial-statistics. Results: Nicotine significantly enhanced FA values for the genu of corpus callosum compared with placebo (?FAgenu) (p = 0.01) in smokers with low recent smoking exposure as measured by low average cotinine level. This finding was replicated in the second cohort (p = 0.02). ?FAgenu values explained 22% of variance in performance of a sustained attention task during the nicotine session (p = 0.006). However, this effect was limited to schizophrenia patients (r = 0.62 and 0.09; p = 0.003 and 0.7 for patients and controls, respectively). Conclusion: Acute pharmacological influence of nicotine patch on WM integrity appeared present, but was dependent on nicotine intake from recent smoking. Change in the WM integrity in the genu of corpus callosum was associated with a significant proportion of variability of nicotine-led changes in sustained attention/working memory of the smokers. Further studies will be necessary to understand biophysical underpinning of the nicotine-related changes in FA. PMID:24065920

  5. Attenuated Fractional Wave Equations With Anisotropy.

    PubMed

    Meerschaert, Mark M; McGough, Robert J

    2014-10-01

    This paper develops new fractional calculus models for wave propagation. These models permit a different attenuation index in each coordinate to fully capture the anisotropic nature of wave propagation in complex media. Analytical expressions that describe power law attenuation and anomalous dispersion in each direction are derived for these fractional calculus models. PMID:25278739

  6. The effect of injury timing on white matter changes in the corpus callosum following unilateral brain injury?

    PubMed Central

    Hawe, Rachel L.; Sukal-Moulton, Theresa; Dewald, Julius P.A.

    2013-01-01

    Motor impairments following unilateral brain injuries may be related to changes in the corpus callosum. The purpose of this study was to determine if the corpus callosum is impacted differently in pediatric versus adult hemiplegia. Diffusion tensor imaging was completed on 41 participants (11 pediatric hemiplegia, 10 adult hemiplegia, 10 pediatric control and 10 adult control). Fractional anisotropy values and cross-sectional areas for five regions of the corpus callosum were compared between subject groups. Additionally, the amount of involuntary activity in the paretic elbow was quantified during non-paretic elbow flexion tasks for a subset of pediatric hemiplegia participants. Fractional anisotropy values were reduced in pediatric hemiplegia compared to pediatric control subjects in callosal regions corresponding to premotor and supplementary motor areas, primary sensory cortex, and parietal, temporal, and occipital cortices. Differences in fractional anisotropy between adult stroke and adult controls were only found in the region corresponding to parietal, temporal, and occipital cortices. Cross-sectional area was affected in all regions of the corpus callosum in pediatric hemiplegia, but only in the primary sensory region in adult hemiplegia. Additionally, changes in the cross-sectional areas were correlated with involuntary mirror movements in the pediatric hemiplegia group. In conclusion, the corpus callosum is affected to a greater extent in pediatric compared to adult hemiplegia, which may explain why unsuppressed mirror movements and difficulty with bimanual coordination are greater problems in this population. PMID:24179855

  7. Reduced Interhemispheric Connectivity in Schizophrenia- Tractography Based Segmentation of the Corpus Callosum

    PubMed Central

    Kubicki, M.; Styner, M.; Bouix, S.; Gerig, G.; Markant, D.; Smith, K.; Kikinis, R.; McCarley, R.W.; Shenton, M.E.

    2008-01-01

    Background A reduction in interhemispheric connectivity is thought to contribute to the etiology of schizophrenia. Diffusion Tensor Imaging (DTI) measures the diffusion of water and can be used to describe the integrity of the corpus callosum white matter tracts, thereby providing information concerning possible interhemispheric connectivity abnormalities. Previous DTI studies in schizophrenia are inconsistent in reporting decreased Fractional Anisotropy (FA), a measure of anisotropic diffusion, within different portions of the corpus callosum. Moreover, none of these studies has investigated corpus callosum systematically, using anatomical subdivisions. Methods DTI and structural MRI scans were obtained from 32 chronic schizophrenic subjects and 42 controls. Corpus callosum cross sectional area and its probabilistic subdivisions were determined automatically from structural MRI scans using a model based deformable contour segmentation. These subdivisions employ a previously generated probabilistic subdivision atlas, based on fiber tractography and anatomical lobe subdivision. The structural scan was then co-registered with the DTI scan and the anatomical corpus callosum subdivisions were propagated to the associated FA map. Results Results revealed decreased FA within parts of the corpus interconnecting frontal regions in schizophrenia compared with controls, but no significant changes for callosal fibers interconnecting parietal and temporo-occipital brain regions. In addition, integrity of the anterior corpus was statistically significantly correlated with negative as well as positive symptoms, while posterior measures correlated with positive symptoms only. Conclusions This study provides quantitative evidence for a reduction of interhemispheric brain connectivity in schizophrenia, involving corpus callosum, and further points to frontal connections as possibly disrupted in schizophrenia. PMID:18829262

  8. Permeability–diffusivity modeling vs. fractional anisotropy on white matter integrity assessment and application in schizophrenia?

    PubMed Central

    Kochunov, P.; Chiappelli, J.; Hong, L.E.

    2013-01-01

    Introduction Diffusion tensor imaging (DTI) assumes a single pool of anisotropically diffusing water to calculate fractional anisotropy (FA) and is commonly used to ascertain white matter (WM) deficits in schizophrenia. At higher b-values, diffusion-signal decay becomes bi-exponential, suggesting the presence of two, unrestricted and restricted, water pools. Theoretical work suggests that semi-permeable cellular membrane rather than the presence of two physical compartments is the cause. The permeability–diffusivity (PD) parameters measured from bi-exponential modeling may offer advantages, over traditional DTI-FA, in identifying WM deficits in schizophrenia. Methods Imaging was performed in N = 26/26 patients/controls (age = 20–61 years, average age = 40.5 ± 12.6). Imaging consisted of fifteen b-shells: b = 250–3800 s/mm2 with 30 directions/shell, covering seven slices of mid-sagittal corpus callosum (CC) at 1.7 × 1.7 × 4.6 mm. 64-direction DTI was also collected. Permeability–diffusivity-index (PDI), the ratio of restricted to unrestricted apparent diffusion coefficients, and the fraction of unrestricted compartment (Mu) were calculated for CC and cingulate gray matter (GM). FA values for CC were calculated using tract-based-spatial-statistics. Results Patients had significantly reduced PDI in CC (p ? 10? 4) and cingulate GM (p = 0.002), while differences in CC FA were modest (p ? .03). There was no group-related difference in Mu. Additional theoretical-modeling analysis suggested that reduced PDI in patients may be caused by reduced cross-membrane water molecule exchanges. Conclusion PDI measurements for cerebral WM and GM yielded more robust patient–control differences than DTI-FA. Theoretical work offers an explanation that patient–control PDI differences should implicate abnormal active membrane permeability. This would implicate abnormal activities in ion-channels that use water as substrate for ion exchange, in cerebral tissues of schizophrenia patients. PMID:24179845

  9. White Matter Fractional Anisotropy Correlates With Speed of Processing and Motor Speed in Young Childhood Cancer Survivors

    SciTech Connect

    Aukema, Eline J. [Pediatric Psychosocial Department, Emma Children's Hospital/Academic Medical Center, Amsterdam (Netherlands)], E-mail: e.j.aukema@amc.uva.nl; Caan, Matthan W.A. [Department of Radiology, Academic Medical Center, University of Amsterdam, Amsterdam (Netherlands); Delft University of Technology, Delft (Netherlands); Oudhuis, Nienke [Pediatric Psychosocial Department, Emma Children's Hospital/Academic Medical Center, Amsterdam (Netherlands); Majoie, Charles [Department of Radiology, Academic Medical Center, University of Amsterdam, Amsterdam (Netherlands); Vos, Frans M. [Department of Radiology, Academic Medical Center, University of Amsterdam, Amsterdam (Netherlands); Delft University of Technology, Delft (Netherlands); Reneman, Liesbeth [Department of Radiology, Academic Medical Center, University of Amsterdam, Amsterdam (Netherlands); Last, Bob F. [Pediatric Psychosocial Department, Emma Children's Hospital/Academic Medical Center, Amsterdam (Netherlands); Department of Developmental Psychology, Free University of Amsterdam, Amsterdam (Netherlands); Grootenhuis, Martha A. [Pediatric Psychosocial Department, Emma Children's Hospital/Academic Medical Center, Amsterdam (Netherlands); Schouten-van Meeteren, Antoinette Y.N. [Department of Pediatric Oncology, Emma Children's Hospital/Academic Medical Center, Amsterdam (Netherlands)

    2009-07-01

    Purpose: To determine whether childhood medulloblastoma and acute lymphoblastic leukemia (ALL) survivors have decreased white matter fractional anisotropy (WMFA) and whether WMFA is related to the speed of processing and motor speed. Methods and Materials: For this study, 17 patients (6 medulloblastoma, 5 ALL treated with high-dose methotrexate (MTX) (4 x 5 g/m{sup 2}) and 6 with low-dose MTX (3 x 2 g/m{sup 2})) and 17 age-matched controls participated. On a 3.0-T magnetic resonance imaging (MRI) scanner, diffusion tensor imaging (DTI) was performed, and WMFA values were calculated, including specific regions of interest (ROIs), and correlated with the speed of processing and motor speed. Results: Mean WMFA in the patient group, mean age 14 years (range 8.9 - 16.9), was decreased compared with the control group (p = 0.01), as well as WMFA in the right inferior fronto-occipital fasciliculus (IFO) (p = 0.03) and in the genu of the corpus callosum (gCC) (p = 0.01). Based on neurocognitive results, significant positive correlations were present between processing speed and WMFA in the splenium (sCC) (r = 0.53, p = 0.03) and the body of the corpus callosum (bCC) (r = 0.52, p = 0.03), whereas the right IFO WMFA was related to motor speed (r = 0.49, p < 0.05). Conclusions: White matter tracts, using a 3.0-T MRI scanner, show impairment in childhood cancer survivors, medulloblastoma survivors, and also those treated with high doses of MTX. In particular, white matter tracts in the sCC, bCC and right IFO are positively correlated with speed of processing and motor speed.

  10. Interleukin-6, age, and corpus callosum integrity.

    PubMed

    Bettcher, Brianne M; Watson, Christa L; Walsh, Christine M; Lobach, Iryna V; Neuhaus, John; Miller, Joshua W; Green, Ralph; Patel, Nihar; Dutt, Shubir; Busovaca, Edgar; Rosen, Howard J; Yaffe, Kristine; Miller, Bruce L; Kramer, Joel H

    2014-01-01

    The contribution of inflammation to deleterious aging outcomes is increasingly recognized; however, little is known about the complex relationship between interleukin-6 (IL-6) and brain structure, or how this association might change with increasing age. We examined the association between IL-6, white matter integrity, and cognition in 151 community dwelling older adults, and tested whether age moderated these associations. Blood levels of IL-6 and vascular risk (e.g., homocysteine), as well as health history information, were collected. Processing speed assessments were administered to assess cognitive functioning, and we employed tract-based spatial statistics to examine whole brain white matter and regions of interest. Given the association between inflammation, vascular risk, and corpus callosum (CC) integrity, fractional anisotropy (FA) of the genu, body, and splenium represented our primary dependent variables. Whole brain analysis revealed an inverse association between IL-6 and CC fractional anisotropy. Subsequent ROI linear regression and ridge regression analyses indicated that the magnitude of this effect increased with age; thus, older individuals with higher IL-6 levels displayed lower white matter integrity. Finally, higher IL-6 levels were related to worse processing speed; this association was moderated by age, and was not fully accounted for by CC volume. This study highlights that at older ages, the association between higher IL-6 levels and lower white matter integrity is more pronounced; furthermore, it underscores the important, albeit burgeoning role of inflammatory processes in cognitive aging trajectories. PMID:25188448

  11. Interleukin-6, Age, and Corpus Callosum Integrity

    PubMed Central

    Bettcher, Brianne M.; Watson, Christa L.; Walsh, Christine M.; Lobach, Iryna V.; Neuhaus, John; Miller, Joshua W.; Green, Ralph; Patel, Nihar; Dutt, Shubir; Busovaca, Edgar; Rosen, Howard J.; Yaffe, Kristine; Miller, Bruce L.; Kramer, Joel H.

    2014-01-01

    The contribution of inflammation to deleterious aging outcomes is increasingly recognized; however, little is known about the complex relationship between interleukin-6 (IL-6) and brain structure, or how this association might change with increasing age. We examined the association between IL-6, white matter integrity, and cognition in 151 community dwelling older adults, and tested whether age moderated these associations. Blood levels of IL-6 and vascular risk (e.g., homocysteine), as well as health history information, were collected. Processing speed assessments were administered to assess cognitive functioning, and we employed tract-based spatial statistics to examine whole brain white matter and regions of interest. Given the association between inflammation, vascular risk, and corpus callosum (CC) integrity, fractional anisotropy (FA) of the genu, body, and splenium represented our primary dependent variables. Whole brain analysis revealed an inverse association between IL-6 and CC fractional anisotropy. Subsequent ROI linear regression and ridge regression analyses indicated that the magnitude of this effect increased with age; thus, older individuals with higher IL-6 levels displayed lower white matter integrity. Finally, higher IL-6 levels were related to worse processing speed; this association was moderated by age, and was not fully accounted for by CC volume. This study highlights that at older ages, the association between higher IL-6 levels and lower white matter integrity is more pronounced; furthermore, it underscores the important, albeit burgeoning role of inflammatory processes in cognitive aging trajectories. PMID:25188448

  12. Simultaneous changes in gray matter volume and white matter fractional anisotropy in Alzheimer's disease revealed by multimodal CCA and joint ICA.

    PubMed

    Ouyang, X; Chen, K; Yao, L; Hu, B; Wu, X; Ye, Q; Guo, X

    2015-08-20

    The prominent morphometric alterations of Alzheimer's disease (AD) occur both in gray matter and in white matter. Multimodal fusion can examine joint information by combining multiple neuroimaging datasets to identify the covariant morphometric alterations in AD in greater detail. In the current study, we conducted a multimodal canonical correlation analysis and joint independent component analysis to identify the covariance patterns of the gray and white matter by fusing structural magnetic resonance imaging and diffusion tensor imaging data of 39 AD patients (23 males and 16 females, mean age: 74.91±8.13years) and 41 normal controls (NCs) (20 males and 21 females, mean age: 73.97±6.34years) derived from the Alzheimer's Disease Neuroimaging Initiative database. The results revealed 25 joint independent components (ICs), of which three joint ICs exhibited strong links between the gray matter volume and the white matter fractional anisotropy (FA) and significant differences between the AD and NC group. The joint IC maps revealed that the simultaneous changes in the gray matter and FA values primarily involved the following areas: (1) the temporal lobe/hippocampus-cingulum, (2) the frontal/cingulate gyrus-corpus callosum, and (3) the temporal/occipital/parietal lobe-corpus callosum/corona radiata. Our findings suggest that gray matter atrophy is associated with reduced white matter fiber integrity in AD and possibly expand the understanding of the neuropathological mechanisms in AD. PMID:26116521

  13. Organising white matter in a brain without corpus callosum fibres.

    PubMed

    Bénézit, Audrey; Hertz-Pannier, Lucie; Dehaene-Lambertz, Ghislaine; Monzalvo, Karla; Germanaud, David; Duclap, Delphine; Guevara, Pamela; Mangin, Jean-François; Poupon, Cyril; Moutard, Marie-Laure; Dubois, Jessica

    2015-02-01

    Isolated corpus callosum dysgenesis (CCD) is a congenital malformation which occurs during early development of the brain. In this study, we aimed to identify and describe its consequences beyond the lack of callosal fibres, on the morphology, microstructure and asymmetries of the main white matter bundles with diffusion imaging and fibre tractography. Seven children aged between 9 and 13 years old and seven age- and gender-matched control children were studied. First, we focused on bundles within the mesial region of the cerebral hemispheres: the corpus callosum, Probst bundles and cingulum which were selected using a conventional region-based approach. We demonstrated that the Probst bundles have a wider connectivity than the previously described rostrocaudal direction, and a microstructure rather distinct from the cingulum but relatively close to callosal remnant fibres. A sigmoid bundle was found in two partial ageneses. Second, the corticospinal tract, thalamic radiations and association bundles were extracted automatically via an atlas of adult white matter bundles to overcome bias resulting from a priori knowledge of the bundles' anatomical morphology and trajectory. Despite the lack of callosal fibres and the colpocephaly observed in CCD, all major white matter bundles were identified with a relatively normal morphology, and preserved microstructure (i.e. fractional anisotropy, mean diffusivity) and asymmetries. Consequently the bundles' organisation seems well conserved in brains with CCD. These results await further investigations with functional imaging before apprehending the cognition variability in children with isolated dysgenesis. PMID:25282054

  14. Relationship between white matter fractional anisotropy and other indices of cerebral health in normal aging: tract-based spatial statistics study of aging.

    PubMed

    Kochunov, P; Thompson, P M; Lancaster, J L; Bartzokis, G; Smith, S; Coyle, T; Royall, D R; Laird, A; Fox, P T

    2007-04-01

    White matter (WM) fractional anisotropy (FA) is thought to be related to WM integrity and decline in FA is often used as an index of decreasing WM health. However, the relationship of FA to other structural indices of cerebral health has not been well studied. We hypothesized that the decline in WM health will be associated with changes in several other indices of cerebral health. In this manuscript we studied the correlation between whole-brain/hemispheric/corpus callosum FA and gray matter (GM) thickness, sulcal span, and the volume of T2-hyperintense WM in a group of 31 healthy aging individuals (12 males/19 females) aged 57-82 years old. Individual subjects' FA measures were calculated from diffusion tracing imaging (DTI) data using tract-based spatial statistics--an approach specifically designed and validated for voxel-wise multi-subject FA analysis. Age-controlled correlation analysis showed that whole-brain average FA values were significantly and positively correlated with the subject's average GM thickness and negatively correlated with hyperintense WM volume. Intra-hemispheric correlations between FA and other measures of cerebral health had generally greater effect sizes than inter-hemispheric correction, with correlation between left FA and left GM thickness being the most significant (r=0.6, p<0.01). Regional analysis of FA values showed that late-myelinating fiber tracts of the genu of corpus callosum had higher association with other cerebral health indices. These data are consistent with the hypothesis that late-myelinating regions of the brain bear the brunt of age-related degenerative changes. PMID:17292629

  15. Age-Associated Alterations in Corpus Callosum White Matter Integrity in Bipolar Disorder Assessed Using Probabilistic Tractography

    PubMed Central

    Toteja, Nitin; Cokol, Perihan Guvenek; Ikuta, Toshikazu; Kafantaris, Vivian; Peters, Bart D.; Burdick, Katherine E.; John, Majnu; Malhotra, Anil K.; Szeszko, Philip R.

    2014-01-01

    Objectives Atypical age-associated changes in white matter integrity may play a role in the neurobiology of bipolar disorder, but no studies have examined the major white matter tracts using nonlinear statistical modeling across a wide age range in this disorder. The goal of this study was to identify possible deviations in the typical pattern of age-associated changes in white matter integrity in patients with bipolar disorder across the age range of 9 to 62 years. Methods Diffusion tensor imaging was performed in 57 (20M/37F) patients with a diagnosis of bipolar disorder and 57 (20M/37F) age- and sex-matched healthy volunteers. Mean diffusivity and fractional anisotropy were computed for the genu and splenium of the corpus callosum, two projection tracts, and five association tracts using probabilistic tractography. Results Overall, patients had lower fractional anisotropy and higher mean diffusivity compared to healthy volunteers across all tracts (while controlling for the effects of age and age2). In addition, there were greater age-associated increases in mean diffusivity in patients compared to healthy volunteers within the genu and splenium of the corpus callosum beginning in the second and third decades of life. Conclusions Our findings provide evidence for alterations in the typical pattern of white matter development in patients with bipolar disorder compared to healthy volunteers. Changes in white matter development within the corpus callosum may lead to altered inter-hemispheric communication that is considered integral to the neurobiology of the disorder. PMID:25532972

  16. Fiber Demixing with the Tensor Distribution Function avoids errors in Fractional Anisotropy maps

    E-print Network

    Thompson, Paul

    Fiber Demixing with the Tensor Distribution Function avoids errors in Fractional Anisotropy maps Psychiatry Associates, USA Introduction: DTI has been used to study white matter microstructure and fiber tensor model cannot resolve more complicated fiber configurations, e.g., tract crossings that occur

  17. Segmentation of the Canine Corpus Callosum using Diffusion Tensor Imaging Tractography

    PubMed Central

    Pierce, T.T.; Calabrese, E.; White, L.E.; Chen, S.D.; Platt, S.R.; Provenzale, J.M.

    2014-01-01

    Background We set out to determine functional white matter (WM) connections passing through the canine corpus callosum useful for subsequent studies of canine brains that serve as models for human WM pathway disease. Based on prior studies, we anticipated that the anterior corpus callosum would send projections to the anterior cerebral cortex while progressively posterior segments would send projections to more posterior cortex. Methods A post mortem canine brain was imaged using a 7T MRI producing 100 micron isotropic resolution DTI analyzed by tractography. Using ROIs within cortical locations, which were confirmed by a Nissl stain that identified distinct cortical architecture, we successfully identified 6 important WM pathways. We also compared fractional anisotropy (FA), apparent diffusion coefficient (ADC), radial diffusivity (RD), and axial diffusivity (AD) in tracts passing through the genu and splenium. Results Callosal fibers were organized based upon cortical destination, i.e. fibers from the genu project to the frontal cortex. Histologic results identified the motor cortex based on cytoarchitectonic criteria that allowed placement of ROIs to discriminate between frontal and parietal lobes. We also identified cytoarchitecture typical of the orbital frontal, anterior frontal, and occipital regions and placed ROIs accordingly. FA, ADC, RD and AD values were all higher in posterior corpus callosum fiber tracts. Conclusions Using 6 cortical ROIs, we identified 6 major white matter tracts that reflect major functional divisions of the cerebral hemispheres and we derived quantitative values that can be used for study of canine models of human WM pathological states. PMID:24370161

  18. New non-linear color look-up table for visualization of brain fractional anisotropy based on normative measurements - principals and first clinical use.

    PubMed

    Keller, Ji?í; Rulseh, Aaron M; Komárek, Arnošt; Latnerová, Iva; Rusina, Robert; Brožová, Hana; Vymazal, Josef

    2013-01-01

    Fractional anisotropy (FA) is the most commonly used quantitative measure of diffusion in the brain. Changes in FA have been reported in many neurological disorders, but the implementation of diffusion tensor imaging (DTI) in daily clinical practice remains challenging. We propose a novel color look-up table (LUT) based on normative data as a tool for screening FA changes. FA was calculated for 76 healthy volunteers using 12 motion-probing gradient directions (MPG), a subset of 59 subjects was additionally scanned using 30 MPG. Population means and 95% prediction intervals for FA in the corpus callosum, frontal gray matter, thalamus and basal ganglia were used to create the LUT. Unique colors were assigned to inflection points with continuous ramps between them. Clinical use was demonstrated on 17 multiple system atrophy (MSA) patients compared to 13 patients with Parkinson disease (PD) and 17 healthy subjects. Four blinded radiologists classified subjects as MSA/non-MSA. Using only the LUT, high sensitivity (80%) and specificity (84%) were achieved in differentiating MSA subjects from PD subjects and controls. The LUTs generated from 12 and 30 MPG were comparable and accentuate FA abnormalities. PMID:23990954

  19. New Non-Linear Color Look-Up Table for Visualization of Brain Fractional Anisotropy Based on Normative Measurements – Principals and First Clinical Use

    PubMed Central

    Keller, Ji?í; Rulseh, Aaron M.; Komárek, Arnošt; Latnerová, Iva; Rusina, Robert; Brožová, Hana; Vymazal, Josef

    2013-01-01

    Fractional anisotropy (FA) is the most commonly used quantitative measure of diffusion in the brain. Changes in FA have been reported in many neurological disorders, but the implementation of diffusion tensor imaging (DTI) in daily clinical practice remains challenging. We propose a novel color look-up table (LUT) based on normative data as a tool for screening FA changes. FA was calculated for 76 healthy volunteers using 12 motion-probing gradient directions (MPG), a subset of 59 subjects was additionally scanned using 30 MPG. Population means and 95% prediction intervals for FA in the corpus callosum, frontal gray matter, thalamus and basal ganglia were used to create the LUT. Unique colors were assigned to inflection points with continuous ramps between them. Clinical use was demonstrated on 17 multiple system atrophy (MSA) patients compared to 13 patients with Parkinson disease (PD) and 17 healthy subjects. Four blinded radiologists classified subjects as MSA/non-MSA. Using only the LUT, high sensitivity (80%) and specificity (84%) were achieved in differentiating MSA subjects from PD subjects and controls. The LUTs generated from 12 and 30 MPG were comparable and accentuate FA abnormalities. PMID:23990954

  20. Connecting fractional anisotropy from medical images with mechanical anisotropy of a hyperviscoelastic fibre-reinforced constitutive model for brain tissue

    PubMed Central

    Giordano, Chiara; Kleiven, Svein

    2014-01-01

    Brain tissue modelling has been an active area of research for years. Brain matter does not follow the constitutive relations for common materials and loads applied to the brain turn into stresses and strains depending on tissue local morphology. In this work, a hyperviscoelastic fibre-reinforced anisotropic law is used for computational brain injury prediction. Thanks to a fibre-reinforcement dispersion parameter, this formulation accounts for anisotropic features and heterogeneities of the tissue owing to different axon alignment. The novelty of the work is the correlation of the material mechanical anisotropy with fractional anisotropy (FA) from diffusion tensor images. Finite-element (FE) models are used to investigate the influence of the fibre distribution for different loading conditions. In the case of tensile–compressive loads, the comparison between experiments and simulations highlights the validity of the proposed FA–k correlation. Axon alignment affects the deformation predicted by FE models and, when the strain in the axonal direction is large with respect to the maximum principal strain, decreased maximum deformations are detected. It is concluded that the introduction of fibre dispersion information into the constitutive law of brain tissue affects the biofidelity of the simulations. PMID:24258158

  1. Distinguishing Left or Right Temporal Lobe Epilepsy from Controls Using Fractional Anisotropy Asymmetry Analysis

    Microsoft Academic Search

    Hai Li; Zhong Xue; Mario F. Dulay; Amit Verma; Solomon Wong; Christof Karmonik; Robert G. Grossman; Stephen T. C. Wong

    2010-01-01

    \\u000a This paper presents an automatic fractional anisotropy (FA) asymmetry analysis and applies it to determine the FA asymmetry\\u000a (FAA) changes associated with the sides of seizure origin of patients with temporal lobe epilepsy (TLE) using diffusion tensor\\u000a imaging (DTI). All the control and patient images are first normalized onto the JHU-DTI-MNI atlas using a simultaneous deformable\\u000a DTI registration algorithm, and

  2. Vestibular Loss and Balance Training Cause Similar Changes in Human Cerebral White Matter Fractional Anisotropy

    PubMed Central

    Hummel, Nadine; Hüfner, Katharina; Stephan, Thomas; Linn, Jennifer; Kremmyda, Olympia; Brandt, Thomas; Flanagin, Virginia L.

    2014-01-01

    Patients with bilateral vestibular loss suffer from severe balance deficits during normal everyday movements. Ballet dancers, figure skaters, or slackliners, in contrast, are extraordinarily well trained in maintaining balance for the extreme balance situations that they are exposed to. Both training and disease can lead to changes in the diffusion properties of white matter that are related to skill level or disease progression respectively. In this study, we used diffusion tensor imaging (DTI) to compare white matter diffusivity between these two study groups and their age- and sex-matched controls. We found that vestibular patients and balance-trained subjects show a reduction of fractional anisotropy in similar white matter tracts, due to a relative increase in radial diffusivity (perpendicular to the main diffusion direction). Reduced fractional anisotropy was not only found in sensory and motor areas, but in a widespread network including long-range connections, limbic and association pathways. The reduced fractional anisotropy did not correlate with any cognitive, disease-related or skill-related factors. The similarity in FA between the two study groups, together with the absence of a relationship between skill or disease factors and white matter changes, suggests a common mechanism for these white matter differences. We propose that both study groups must exert increased effort to meet their respective usual balance requirements. Since balance training has been shown to effectively reduce the symptoms of vestibular failure, the changes in white matter shown here may represent a neuronal mechanism for rehabilitation. PMID:24776524

  3. Transient decrease in cerebral motor pathway fractional anisotropy after focal ischemic stroke in monkey.

    PubMed

    Chin, Yo; Sato, Yuki; Mase, Mitsuhito; Kato, Tomomasa; Herculano, Bruno; Sekino, Masaki; Ohsaki, Hiroyuki; Ageyama, Naohide; Ono, Fumiko; Terao, Keiji; Yoshikawa, Yasuhiro; Hisatsune, Tatsuhiro

    2010-04-01

    In this study, diffusion tensor MRI was used to examine the restoration of the cerebral white matter of macaque monkeys after unilateral cerebral multiple microinfarctions. Post-stroke, the monkeys showed deficits in several neurological functions, including motor functions, but most of the deficits resolved within 6 weeks. Very interestingly, the fractional anisotropy (a value determined by diffusion tensor MRI), of the monkeys' affected motor pathways dropped transiently, indicating a damage in the neural tracts. However, it returned to normal levels within 6 weeks after the stroke, concomitant with the gradual recovery of motor functions at subacute phase. PMID:20117152

  4. White matter fractional anisotropy is inversely related to anxious symptoms in older adults with atherosclerosis

    PubMed Central

    Bijanki, Kelly C. R.; Stillman, Ashley N.; Arndt, Stephan; Magnotta, Vincent A.; Fiedorowicz, Jess G.; Haynes, William G.; Matsui, Joy T.; Johnson, Hans J.; Moser, David J.

    2013-01-01

    Objective Clinical anxiety disorders are associated with white matter hyperintensities and diffusion abnormalities measured using diffusion tensor imaging (DTI). However, it is not known if this association extends into individuals with mild anxious symptoms without formal diagnosis, in those who are older, or in those who have atherosclerosis. The current study explored whether white matter integrity and/or organization significantly associates with anxious symptoms in older adults with and without atherosclerosis. Methods We recruited older adults (ages 55–90); 35 with clinically diagnosed atherosclerotic vascular disease (AVD) and 22 without AVD. Anxious symptoms were measured using the validated Symptom Checklist-90-Revised. Fractional anisotropy (FA), a proxy for white matter organization and health, was measured in the white matter globally, by lobe, and in several smaller regions of interest suggested by the literature. Partial correlations between anxious symptoms and FA were calculated, controlling for significant covariates. Results Participants with and without AVD did not differ in severity of anxious symptom endorsement. There was a unique inverse relationship between white matter health and anxious symptoms in the AVD participants, but not in healthy comparisons. Significant relationships were observed in the superior longitudinal fasciculus (r=?.476, df=32, p=.004), as well as the cingulum bundle, the frontal lobes, and the parietal lobes. Conclusions Anxiety symptoms uniquely correlated with low fractional anisotropy in older adults with atherosclerosis. These findings may have implications for future research on the topic of anxiety in aging and vascular disease and warrant replication. PMID:23348834

  5. Tractography of the Corpus Callosum in Huntington’s Disease

    PubMed Central

    Phillips, Owen; Sanchez-Castaneda, Cristina; Elifani, Francesca; Maglione, Vittorio; Di Pardo, Alba; Caltagirone, Carlo; Squitieri, Ferdinando; Sabatini, Umberto; Di Paola, Margherita

    2013-01-01

    White matter abnormalities have been shown in presymptomatic and symptomatic Huntington’s disease (HD) subjects using Magnetic Resonance Imaging (MRI) and Diffusion Tensor Imaging (DTI) methods. The largest white matter tract, the corpus callosum (CC), has been shown to be particularly vulnerable; however, little work has been done to investigate the regional specificity of tract abnormalities in the CC. Thus, this study examined the major callosal tracts by applying DTI-based tractography. Using TrackVis, a previously defined region of interest tractography method parcellating CC into seven major tracts based on target region was applied to 30 direction DTI data collected from 100 subjects: presymptomatic HD (Pre-HD) subjects (n?=?25), HD patients (n?=?25) and healthy control subjects (n?=?50). Tractography results showed decreased fractional anisotropy (FA) and increased radial diffusivity (RD) across broad regions of the CC in Pre-HD subjects. Similar though more severe deficits were seen in HD patients. In Pre-HD and HD, callosal FA and RD were correlated with Disease Burden/CAG repeat length as well as motor (UHDRSI) and cognitive (URDRS2) assessments. These results add evidence that CC pathways are compromised prior to disease onset with possible demyelination occurring early in the disease and suggest that CAG repeat length is a contributing factor to connectivity deficits. Furthermore, disruption of these callosal pathways potentially contributes to the disturbances of motor and cognitive processing that characterize HD. PMID:24019913

  6. Not lesser but Greater fractional anisotropy in adolescents with alcohol use disorders?

    PubMed Central

    Cardenas, Valerie A.; Greenstein, David; Fouche, Jean-Paul; Ferrett, Helen; Cuzen, Natalie; Stein, Dan J.; Fein, George

    2013-01-01

    Objective The objective of this study is to examine white matter microstructure using diffusion tensor imaging (DTI) in a sample of adolescents with alcohol use disorders (AUD) and no psychiatric or substance co-morbidity. Methods Fifty adolescents with AUD and fifty non-alcohol abusing controls matched on gender and age were studied with DTI, neurocognitive testing, and a clinical assessment that included measures of alcohol use and childhood trauma. Maps of fractional anisotropy (FA) and mean diffusivity (MD) were computed, registered to a common template, and voxel-wise statistical analysis used to assess group differences. Associations between regions of altered WM microstructure and clinical or neurocognitive measures were also assessed. Results Compared with controls, adolescent drinkers without co-morbid substance abuse or externalizing disorder, showed 1) no regions of significantly lower FA, 2) increased FA in WM tracts of the limbic system; 3) no MD differences; and 4) within the region of higher FA in AUD, there were no associations between FA and alcohol use, cognition, or trauma. Discussion The most important observation of this study is our failure to observe significantly smaller FA in this relatively large alcohol abuse/dependent adolescent sample. Greater FA in the limbic regions observed in this study may index a risk for adolescent AUD instead of a consequence of drinking. Drinking behavior may be reinforced in those with higher FA and perhaps greater myelination in these brain regions involved in reward and reinforcement. PMID:24179831

  7. Reduced Fractional Anisotropy in the Visual Limbic Pathway of Young Adults Witnessing Domestic Violence in Childhood

    PubMed Central

    Choi, Jeewook; Jeong, Bumseok; Polcari, Ann; Rohan, Michael L.; Teicher, Martin H.

    2011-01-01

    Witnessing domestic violence (WDV) is a traumatic childhood experience associated with increased risk for depression, posttraumatic stress disorder and reduced IQ scores. Specific affects of WDV on brain development have not been assessed. We sought to ascertain whether WDV was associated with abnormalities in white matter (WM) tract integrity using diffusion tensor imaging (DTI). Twenty subjects who witnessed domestic violence (16F/ 4M, mean age 22.4±2.48 yrs) but were not physically or sexually abused were compared to 27 healthy controls (19F/ 8M, 21.9±1.97 yrs) without exposure to trauma or Axis I and II disorders. DTI images were acquired with a 3T Siemens Trio scanner. Group differences in fractional anisotropy (FA), covaried by age, gender, parental education, perceived financial sufficiency, IQ and degree of exposure to parental verbal aggression were assessed using tract-based spatial statistics (TBSS), which projects FA values onto an alignment-invariant fiber tract representation. FA values in the inferior longitudinal fasciculus of left lateral occipital lobe were significantly lower (p<0.05 corrected for multiple comparison) in the WDV group. FA values correlated inversely with ratings of depression, anxiety, somatization, ‘limbic irritability’ and neuropsychological measures of processing speed. Measures of radial but not axial diffusivity were affected suggesting alterations in myelination. Degree of FA reduction was associated with duration of witnessing interparental verbal aggression and with exposure between ages 7 – 13 years. The inferior longitudinal fasciculus connects occipital and temporal cortex and is the main component of the visual–limbic pathway that subserves emotional, learning and memory functions that are modality specific to vision. This finding is consistent with the hypothesis that exposure to childhood maltreatment is associated with alterations in fiber pathways that convey the adverse experience to frontal, temporal or limbic regions. PMID:21985907

  8. Fractional anisotropy asymmetry and the side of seizure origin for partial onset-temporal lobe epilepsy.

    PubMed

    Li, Hai; Xue, Zhong; Dulay, Mario F; Verma, Amit; Karmonik, Christof; Grossman, Robert G; Wong, Stephen T

    2014-09-01

    This paper presents a fractional anisotropy asymmetry (FAA) method to detect the asymmetry of white matter (WM) integrity and its correlation with the side of seizure origin for partial onset temporal lobe epilepsy (TLE) using diffusion tensor image (DTI). In this study, FAA analysis is applied to 30 patients of partial TLE (15 left, 15 right) and 14 matched normal controls. Specifically, after registering all the images with the JHU-DTI-MNI template the average FA value of each FA skeleton section is calculated using the tract-based spatial statistics (TBSS) method. Then, FAA is calculated to quantify the WM diffusivity asymmetry of the corresponding region-pairs between the left and right hemispheres. Using FAA the regional asymmetry contributing significantly to the group differences of controls and left/right TLE, as well as the left and right TLE, is identified. As a comparison, the ROI-based average FA values for WM and corresponding FAAs are also calculated. TBSS-based analysis reflects the average of local maximal FA values along the white matter skeleton sections, and ROI-based analysis shows the average of WM FA values within each anatomical region. The FAA statistical results indicated that the FA values of anatomical region-pairs are asymmetric in the ipsilateral hemisphere with seizure origin against the contralateral hemisphere. Particularly, FAA values within the temporal lobe (superior, middle, and inferior temporal WM) are significantly different between the left and right TLE patients, consistently found from both analysis methods. The study suggests that FAA values can be potentially used to identify the seizures of origin of TLE and to help understand the relationship between fiber tracts with the side of seizure origin of TLE. PMID:25037096

  9. Genetic Analysis of Cortical Thickness and Fractional Anisotropy of Water Diffusion in the Brain

    PubMed Central

    Kochunov, Peter; Glahn, David C.; Nichols, Thomas E.; Winkler, Anderson M.; Hong, Elliot L.; Holcomb, Henry H.; Stein, Jason L.; Thompson, Paul M.; Curran, Joanne E.; Carless, Melanie A.; Olvera, Rene L.; Johnson, Matthew P.; Cole, Shelley A.; Kochunov, Valeria; Kent, Jack; Blangero, John

    2011-01-01

    Objectives: The thickness of the brain’s cortical gray matter (GM) and the fractional anisotropy (FA) of the cerebral white matter (WM) each follow an inverted U-shape trajectory with age. The two measures are positively correlated and may be modulated by common biological mechanisms. We employed four types of genetic analyses to localize individual genes acting pleiotropically upon these phenotypes. Methods: Whole-brain and regional GM thickness and FA values were measured from high-resolution anatomical and diffusion tensor MR images collected from 712, Mexican American participants (438 females, age?=?47.9?±?13.2?years) recruited from 73 (9.7?±?9.3 individuals/family) large families. The significance of the correlation between two traits was estimated using a bivariate genetic correlation analysis. Localization of chromosomal regions that jointly influenced both traits was performed using whole-genome quantitative trait loci (QTL) analysis. Gene localization was performed using SNP genotyping on Illumina 1M chip and correlation with leukocyte-based gene-expression analyses. The gene-expressions were measured using the Illumina BeadChip. These data were available for 371 subjects. Results: Significant genetic correlation was observed among GM thickness and FA values. Significant logarithm of odds (LOD???3.0) QTLs were localized within chromosome 15q22–23. More detailed localization reported no significant association (p?

  10. Intercentre reproducibility of cardiac apparent diffusion coefficient and fractional anisotropy in healthy volunteers

    PubMed Central

    2014-01-01

    Background Diffusion tensor cardiac magnetic resonance (DT-CMR) enables probing of the microarchitecture of the myocardium, but the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) reported in healthy volunteers have been inconsistent. The aim of this study was to validate a stimulated-echo diffusion sequence using phantoms, and to assess the intercentre reproducibility of in-vivo diffusion measures using the sequence. Methods and results A stimulated-echo, cardiac-gated DT-CMR sequence with a reduced-field-of-view, single-shot EPI readout was used at two centres with 3 T MRI scanners. Four alkane phantoms with known diffusivities were scanned at a single centre using a stimulated echo sequence and a spin-echo Stejskal-Tanner diffusion sequence. The median (maximum, minimum) difference between the DT-CMR sequence and Stejskal-Tanner sequence was 0.01 (0.04, 0.0006) × 10-3 mm2/s (2%), and between the DT-CMR sequence and literature diffusivities was 0.02 (0.05, 0.006) × 10-3 mm2/s (4%). The same ten healthy volunteers were scanned using the DT-CMR sequence at the two centres less than seven days apart. Average ADC and FA were calculated in a single mid-ventricular, short axis slice. Intercentre differences were tested for statistical significance at the p??0.05), and only the diastolic ADC showed a statistically significant, but numerically small, difference of 0.07 × 10-3 mm2/s (p?=?0.047). The intercentre, intrasubject coefficients of variance were: systolic ADC 7%, FA 6%; diastolic ADC 7%, FA 3%. Conclusions This is the first study to demonstrate the accuracy of a stimulated-echo DT-CMR sequence in phantoms, and demonstrates the feasibility of obtaining reproducible ADC and FA in healthy volunteers at separate centres with well-matched sequences and processing. PMID:24886285

  11. Cystic periventricular leukomalacia of the corpus callosum

    Microsoft Academic Search

    Brian D. Coley; Mark J. Hogan

    1997-01-01

    Periventricular leukomalacia (PVL) is a common finding during neurosonography of preterm infants. Secondary thinning of the\\u000a corpus callosum is seen following PVL, typically from loss of hemispheric white matter tracts. We report a case of direct\\u000a involvement of the corpus callosum with PVL, its pathogenesis, and its potential as a cause of corpus callosal thinning.

  12. Bone volume fraction and fabric anisotropy are better determinants of trabecular bone stiffness than other morphological variables.

    PubMed

    Maquer, Ghislain; Musy, Sarah N; Wandel, Jasmin; Gross, Thomas; Zysset, Philippe K

    2015-06-01

    As our population ages, more individuals suffer from osteoporosis. This disease leads to impaired trabecular architecture and increased fracture risk. It is essential to understand how morphological and mechanical properties of the cancellous bone are related. Morphology-elasticity relationships based on bone volume fraction (BV/TV) and fabric anisotropy explain up to 98% of the variation in elastic properties. Yet, other morphological variables such as individual trabeculae segmentation (ITS) and trabecular bone score (TBS) could improve the stiffness predictions. A total of 743 micro-computed tomography (?CT) reconstructions of cubic trabecular bone samples extracted from femur, radius, vertebrae, and iliac crest were analyzed. Their morphology was assessed via 25 variables and their stiffness tensor (CFE) was computed from six independent load cases using micro finite element (?FE) analyses. Variance inflation factors were calculated to evaluate collinearity between morphological variables and decide upon their inclusion in morphology-elasticity relationships. The statistically admissible morphological variables were included in a multiple linear regression model of the dependent variable CFE. The contribution of each independent variable was evaluated (ANOVA). Our results show that BV/TV is the best determinant of CFE(r(2) adj ?=?0.889), especially in combination with fabric anisotropy (r(2) adj ?=?0.968). Including the other independent predictors hardly affected the amount of variance explained by the model (r(2) adj ?=?0.975). Across all anatomical sites, BV/TV explained 87% of the variance of the bone elastic properties. Fabric anisotropy further described 10% of the bone stiffness, but the improvement in variance explanation by adding other independent factors was marginal (<1%). These findings confirm that BV/TV and fabric anisotropy are the best determinants of trabecular bone stiffness and show, against common belief, that other morphological variables do not bring any further contribution. These overall conclusions remain to be confirmed for specific bone diseases and postelastic properties. © 2015 American Society for Bone and Mineral Research. PMID:25529534

  13. Functional Diffusion Tensor Imaging: Measuring Task-Related Fractional Anisotropy Changes in the Human Brain along White Matter Tracts

    PubMed Central

    Mandl, René C. W.; Schnack, Hugo G.; Zwiers, Marcel P.; van der Schaaf, Arjen; Kahn, René S.; Hulshoff Pol, Hilleke E.

    2008-01-01

    Background Functional neural networks in the human brain can be studied from correlations between activated gray matter regions measured with fMRI. However, while providing important information on gray matter activation, no information is gathered on the co-activity along white matter tracts in neural networks. Methodology/Principal Findings We report on a functional diffusion tensor imaging (fDTI) method that measures task-related changes in fractional anisotropy (FA) along white matter tracts. We hypothesize that these fractional anisotropy changes relate to morphological changes of glial cells induced by axonal activity although the exact physiological underpinnings of the measured FA changes remain to be elucidated. As expected, these changes are very small as compared to the physiological noise and a reliable detection of the signal change would require a large number of measurements. However, a substantial increase in signal-to-noise ratio was achieved by pooling the signal over the complete fiber tract. Adopting such a tract-based statistics enabled us to measure the signal within a practically feasible time period. Activation in the sensory thalamocortical tract and optic radiation in eight healthy human subjects was found during tactile and visual stimulation, respectively. Conclusions/Significance The results of our experiments indicate that these FA changes may serve as a functional contrast mechanism for white matter. This noninvasive fDTI method may provide a new approach to study functional neural networks in the human brain. PMID:18982065

  14. Application of Principal Component Analysis to Distinguish Patients with Schizophrenia from Healthy Controls Based on Fractional Anisotropy Measurements

    PubMed Central

    Caprihan, A.; Pearlson, G.D.; Calhoun, V.D.

    2008-01-01

    Principal component analysis (PCA) is often used to reduce the dimension of data before applying more sophisticated data analysis methods such as non-linear classification algorithms or independent component analysis. This practice is based on selecting components corresponding to the largest eigenvalues. If the ultimate goal is separation of data in two groups, then these set of components need not have the most discriminatory power. We measured the distance between two such populations using Mahalanobis distance and chose the eigenvectors to maximize it, a modified PCA method, which we call the discriminant PCA (DPCA). DPCA was applied to diffusion tensor based fractional anisotropy images to distinguish age-matched schizophrenia subjects from healthy controls. The performance of the proposed method was evaluated by the one-leave-out method. We show that for this fractional anisotropy data-set, the classification error with 60 components was close to the minimum error and that the Mahalanobis distance was twice as large with DPCA, than with PCA. Finally, by masking the discriminant function with the white matter tracts of the John Hopkins University atlas, we identified left superior longitudinal fasciculus as the tract which gave the least classification error. In addition, with six optimally chosen tracts the classification error was zero. PMID:18571937

  15. Skyrmion fractionalization and merons in chiral magnets with easy-plane anisotropy

    NASA Astrophysics Data System (ADS)

    Lin, Shi-Zeng; Saxena, Avadh; Batista, Cristian D.

    2015-06-01

    We study the equilibrium phase diagram of ultrathin chiral magnets with easy-plane anisotropy A . The vast triangular skyrmion lattice phase that is stabilized by an external magnetic field evolves continuously as a function of increasing A into a regime in which nearest-neighbor skyrmions start overlapping with each other. This overlap leads to a continuous reduction of the skyrmion number from its quantized value Q =1 and to the emergence of antivortices at the center of the triangles formed by nearest-neighbor skyrmions. The antivortices also carry a small "skyrmion number" QA?1 that grows as a function of increasing A . The system undergoes a first order phase transition into a square vortex-antivortex lattice at a critical value of A . Finally, a canted ferromagnetic state becomes stable through another first order transition for a large enough anisotropy A . Interestingly enough, this first order transition is accompanied by metastable meron solutions.

  16. Abnormality of the Corpus Callosum in Coalmine Gas Explosion-Related Posttraumatic Stress Disorder

    PubMed Central

    Lang, Xu; Zhuo, Chuanjun; Qin, Wen; Zhang, Quan

    2015-01-01

    Abnormal corpus callosum (CC) has been reported in childhood trauma-related posttraumatic stress disorder (PTSD); however, the nature of white matter (WM) integrity alterations in the CC of young adult-onset PTSD patients is unknown. In this study, 14 victims of a coal mine gas explosion with PTSD and 23 matched coal miners without experiencing the coal mine explosion were enrolled. The differences in fractional anisotropy (FA) within 7 sub-regions of the CC were compared between the two groups. Compared to the controls, PTSD coal miners exhibited significantly reduced FA values in the anterior sub-regions of the CC (P < 0.05, Bonferroni-corrected), which mainly interconnect the bilateral frontal cortices. Our findings indicated that the anterior part of the CC was more severely impaired than the posterior part in young adult-onset PTSD, which suggested the patterns of CC impairment may depend on the developmental stage of the structure when the PTSD occurs. PMID:25799310

  17. Reduced white matter connectivity in the corpus callosum of children with Tourette syndrome

    PubMed Central

    Plessen, Kerstin J.; Grüner, Renate; Lundervold, Arvid; Hirsch, Jochen G.; Xu, Dongrong; Bansal, Ravi; Hammar, Åsa; Lundervold, Astri J.; Wentzel-Larsen, Tore; Lie, Stein Atle; Gass, Achim; Peterson, Bradley S.; Hugdahl, Kenneth

    2008-01-01

    Background Brain imaging studies have revealed anatomical anomalies in the brains of individuals with Tourette syndrome (TS). Prefrontal regions have been found to be larger and the corpus callosum (CC) area smaller in children and young adults with TS compared with healthy control subjects, and these anatomical features have been understood to reflect neural plasticity that helps to attenuate the severity of tics. Method CC white matter connectivity, as measured by the Fractional Anisotropy (FA) index from diffusion tensor images, was assessed in 20 clinically well-defined boys with Tourette syndrome and 20 age- and gender-matched controls. Results The hypothesis that children with TS would show reduced measures of connectivity in CC fibers was confirmed for all subregions of the CC. There was no significant interaction of TS and region. Reductions in FA in CC regions may reflect either fewer interhemispheric fibers or reduced axonal myelination. FA values did not correlate significantly with the severity of tic symptoms. Group differences in measures of connectivity did not seem to be attributable to the presence of comorbid ADHD or OCD, to medication exposure, or group differences in IQ. Conclusion Our findings of a reduced interhemispheral white matter connectivity add to the understanding of neural connectivity and plasticity in the brains of children who have TS. PMID:17073980

  18. Corpus callosum alterations in very preterm infants: perinatal correlates and 2 year neurodevelopmental outcomes.

    PubMed

    Thompson, Deanne K; Inder, Terrie E; Faggian, Nathan; Warfield, Simon K; Anderson, Peter J; Doyle, Lex W; Egan, Gary F

    2012-02-15

    The aim of this study was to relate altered corpus callosum (CC) integrity in 106 very preterm (VPT) infants (<30 weeks' gestational age or <1250 g birth weight) at term equivalent to perinatal predictors and neurodevelopmental outcomes at two years. T1 and diffusion magnetic resonance images were obtained. The CC was traced, and divided into six sub-regions for cross-sectional area and shape analyses. Fractional anisotropy, mean, axial and radial diffusivity were sampled within the CC, and probabilistic tractography was performed. Perinatal predictors were explored. The Bayley Scales of Infant Development (BSID-II) was administered at two years. Intraventricular hemorrhage was associated with a smaller genu and altered diffusion values within the anterior and posterior CC of VPT infants. White matter injury was associated with widespread alterations to callosal diffusion values, especially posteriorly, and radial diffusivity was particularly elevated, indicating altered myelination. Reduced CC tract volume related to lower gestational age, particularly posteriorly. Reduced posterior callosal skew was associated with postnatal corticosteroid exposure. This more circular CC was associated with delayed cognitive development. Higher diffusivity, particularly in splenium tracts, was associated with impaired motor development. This study elucidates perinatal predictors and adverse neurodevelopmental outcomes associated with altered callosal integrity in VPT infants. PMID:22154956

  19. Response inhibition deficits in children with Fetal Alcohol Spectrum Disorder: Relationship between diffusion tensor imaging of the corpus callosum and eye movement control

    PubMed Central

    Paolozza, Angelina; Treit, Sarah; Beaulieu, Christian; Reynolds, James N.

    2014-01-01

    Response inhibition is the ability to suppress irrelevant impulses to enable goal-directed behavior. The underlying neural mechanisms of inhibition deficits are not clearly understood, but may be related to white matter connectivity, which can be assessed using diffusion tensor imaging (DTI). The goal of this study was to investigate the relationship between response inhibition during the performance of saccadic eye movement tasks and DTI measures of the corpus callosum in children with or without Fetal Alcohol Spectrum Disorder (FASD). Participants included 43 children with an FASD diagnosis (12.3 ± 3.1 years old) and 35 typically developing children (12.5 ± 3.0 years old) both aged 7–18, assessed at three sites across Canada. Response inhibition was measured by direction errors in an antisaccade task and timing errors in a delayed memory-guided saccade task. Manual deterministic tractography was used to delineate six regions of the corpus callosum and calculate fractional anisotropy (FA), mean diffusivity (MD), parallel diffusivity, and perpendicular diffusivity. Group differences in saccade measures were assessed using t-tests, followed by partial correlations between eye movement inhibition scores and corpus callosum FA and MD, controlling for age. Children with FASD made more saccade direction errors and more timing errors, which indicates a deficit in response inhibition. The only group difference in DTI metrics was significantly higher MD of the splenium in FASD compared to controls. Notably, direction errors in the antisaccade task were correlated negatively to FA and positively to MD of the splenium in the control, but not the FASD group, which suggests that alterations in connectivity between the two hemispheres of the brain may contribute to inhibition deficits in children with FASD. PMID:24967159

  20. More is not always better: increased fractional anisotropy of superior longitudinal fasciculus associated with poor visuospatial abilities in Williams syndrome.

    PubMed

    Hoeft, Fumiko; Barnea-Goraly, Naama; Haas, Brian W; Golarai, Golijeh; Ng, Derek; Mills, Debra; Korenberg, Julie; Bellugi, Ursula; Galaburda, Albert; Reiss, Allan L

    2007-10-31

    We used diffusion tensor imaging to examine white matter integrity in the dorsal and ventral streams among individuals with Williams syndrome (WS) compared with two control groups (typically developing and developmentally delayed) and using three separate analysis methods (whole brain, region of interest, and fiber tractography). All analysis methods consistently showed that fractional anisotropy (FA; a measure of microstructural integrity) was higher in the right superior longitudinal fasciculus (SLF) in WS compared with both control groups. There was a significant association with deficits in visuospatial construction and higher FA in WS individuals. Comparable increases in FA across analytic methods were not observed in the left SLF or the bilateral inferior longitudinal fasciculus in WS subjects. Together, these findings suggest a specific role of right SLF abnormality in visuospatial construction deficits in WS. PMID:17978036

  1. Fractions

    NSDL National Science Digital Library

    AAA Math

    2007-12-12

    This site has explanatory lessons, interactive practice, and challenges all dealing with fractions. Includes information, practice, and games on basic fractions, adding fractions, subtracting fractions, multiplying fractions, dividing fractions, reducing fractions, comparing fractions, converting fractions, relating fractions to decimals and decimals to fractions, and divisibility rules to help simplify fractions. Problems are randomly selected and students receive immediate feedback with the correct response. The bottom of each lesson page contains timed exercises.

  2. Fractions!

    NSDL National Science Digital Library

    Miss Lerdahl

    2011-02-01

    Practice all of the activities to help you learn fractions! Go through all five levels of Fractions Review Activities Practice Naming Fractions Do you remember how to do Fraction Sets? Play these games when you have finished the top three activities: Cross the River Pizza Party Fractions Rescue Island Adding Subtracting Fractions SPLAT Mrs. Anderson's Fraction Games Action Fraction Soccer Shootout Fraction Multiplication Soccer Shootout Fraction Division Dirt Bike Fractions Comparisons ...

  3. Facial emotion recognition in agenesis of the corpus callosum

    PubMed Central

    2014-01-01

    Background Impaired social functioning is a common symptom of individuals with developmental disruptions in callosal connectivity. Among these developmental conditions, agenesis of the corpus callosum provides the most extreme and clearly identifiable example of callosal disconnection. To date, deficits in nonliteral language comprehension, humor, theory of mind, and social reasoning have been documented in agenesis of the corpus callosum. Here, we examined a basic social ability as yet not investigated in this population: recognition of facial emotion and its association with social gaze. Methods Nine individuals with callosal agenesis and nine matched controls completed four tasks involving emotional faces: emotion recognition from upright and inverted faces, gender recognition, and passive viewing. Eye-tracking data were collected concurrently on all four tasks and analyzed according to designated facial regions of interest. Results Individuals with callosal agenesis exhibited impairments in recognizing emotions from upright faces, in particular lower accuracy for fear and anger, and these impairments were directly associated with diminished attention to the eye region. The callosal agenesis group exhibited greater consistency in emotion recognition across conditions (upright vs. inverted), with poorest performance for fear identification in both conditions. The callosal agenesis group also had atypical facial scanning (lower fractional dwell time in the eye region) during gender naming and passive viewing of faces, but they did not differ from controls on gender naming performance. The pattern of results did not differ when taking into account full-scale intelligence quotient or presence of autism spectrum symptoms. Conclusions Agenesis of the corpus callosum results in a pattern of atypical facial scanning characterized by diminished attention to the eyes. This pattern suggests that reduced callosal connectivity may contribute to the development and maintenance of emotion processing deficits involving reduced attention to others' eyes. PMID:25705318

  4. Fractional anisotropy and mean diffusivity measurements on normal human brain: comparison between low- and high-resolution diffusion tensor imaging sequences

    Microsoft Academic Search

    Nickolas Papanikolaou; Spyros Karampekios; Efrosyni Papadaki; Menelaos Malamas; Thomas Maris; Nicholas Gourtsoyiannis

    2006-01-01

    Non-invasive in vivo visualization of white matter fiber tracts is currently feasible by means of diffusion tensor imaging (DTI) techniques. DTI-derived metrics, like fractional anisotropy (FA) and mean diffusivity (MD), have the potential to improve tissue characterization. Technical optimization of diffusion tensor sequences, including signal-to-noise ratio and spatial resolution, was performed for 20 normal subjects. High- and low-resolution DTI sequences

  5. Body Mass Index Correlates Negatively With White Matter Integrity in The Fornix And Corpus Callosum: A Diffusion Tensor Imaging Study

    PubMed Central

    Xu, Jiansong; Li, Yang; Lin, Haiqun; Sinha, Rajita; Potenza, Marc N.

    2011-01-01

    Overweight or obese body habitus is associated with cognitive deficits, impaired brain function, gray matter atrophy, and white matter (WM) hyperintensities. However, few diffusion tensor imaging (DTI) studies have assessed WM integrity in relation to overweight or obese status. This study assessed relationships between body mass index (BMI) and values of DTI parameters among 51 normal-weight (lean), overweight and obese participants who were otherwise healthy. BMI correlated negatively with fractional anisotropy (FA) and axial eigenvalues (?1) in the body of corpus callosum (CC), positively with mean diffusivity and radial eigenvalues (??) in the fornix and splenium of CC, and positively with ?1 in the right corona radiata (CR) and superior longitudinal fasciculus (SLF). These data indicate that BMI correlates negatively with WM integrity in the fornix and CC. Furthermore, the different patterns of BMI-related differences in DTI parameters at the fornix, body and splenium of the CC, and the right CR and SLF suggest that different biological processes may underlie BMI-related impairments of WM integrity in different brain regions. PMID:22139809

  6. In vivo and ex vivo Diffusion Tensor Imaging of Cuprizone Induced Demyelination in the Mouse Corpus Callosum

    PubMed Central

    Zhang, Jiangyang; Jones, Melina V.; McMahon, Michael T.; Mori, Susumu; Calabresi, Peter A.

    2011-01-01

    Diffusion tensor imaging (DTI) has been widely used in studying rodent models of white matter diseases. In this study, we examined the differences between in vivo and ex vivo fractional anisotropy (FA) and diffusivity measurements in the mouse cuprizone model. In the control mouse corpus callosum (CC), ex vivo diffusivities were significantly lower than in vivo measurements, but ex vivo FA values were not significantly different from in vivo FA values. With cuprizone induced demyelination and accompanying pathology in the CC, changes in in vivo and ex vivo FA and diffusivity measurements were not always in agreement. Our results suggest that ex vivo ?? was a more reliable indicator of white matter demyelination than in vivo ?? and in vivo ?? was a more reliable indicator of axonal injury than ex vivo ?? in this model. When comparing in vivo and ex vivo DTI results of axon and myelin pathology in the rodent models, potential changes in tissue microstructures associated with perfusion fixation should be considered. PMID:21656567

  7. Heterogeneity of Fractional Anisotropy and Mean Diffusivity Measurements by In Vivo Diffusion Tensor Imaging in Normal Human Hearts

    PubMed Central

    Ferreira, Pedro F.; Nielles-Vallespin, Sonia; Ismail, Tevfik; Kilner, Philip J.; Gatehouse, Peter D.; de Silva, Ranil; Prasad, Sanjay K.; Giannakidis, Archontis; Firmin, David N.; Pennell, Dudley J.

    2015-01-01

    Background Cardiac diffusion tensor imaging (cDTI) by cardiovascular magnetic resonance has the potential to assess microstructural changes through measures of fractional anisotropy (FA) and mean diffusivity (MD). However, normal variation in regional and transmural FA and MD is not well described. Methods Twenty normal subjects were scanned using an optimised cDTI sequence at 3T in systole. FA and MD were quantified in 3 transmural layers and 4 regional myocardial walls. Results FA was higher in the mesocardium (0.46 ±0.04) than the endocardium (0.40 ±0.04, p?0.001) and epicardium (0.39 ±0.04, p?0.001). On regional analysis, the FA in the septum was greater than the lateral wall (0.44 ±0.03 vs 0.40 ±0.05 p = 0.04). There was a transmural gradient in MD increasing towards the endocardium (epicardium 0.87 ±0.07 vs endocardium 0.91 ±0.08×10-3 mm2/s, p = 0.04). With the lateral wall (0.87 ± 0.08×10-3 mm2/s) as the reference, the MD was higher in the anterior wall (0.92 ±0.08×10-3 mm2/s, p = 0.016) and septum (0.92 ±0.07×10-3 mm2/s, p = 0.028). Transmurally the signal to noise ratio (SNR) was greatest in the mesocardium (14.5 ±2.5 vs endocardium 13.1 ±2.2, p<0.001; vs epicardium 12.0 ± 2.4, p<0.001) and regionally in the septum (16.0 ±3.4 vs lateral wall 11.5 ± 1.5, p<0.001). Transmural analysis suggested a relative reduction in the rate of change in helical angle (HA) within the mesocardium. Conclusions In vivo FA and MD measurements in normal human heart are heterogeneous, varying significantly transmurally and regionally. Contributors to this heterogeneity are many, complex and interactive, but include SNR, variations in cardiac microstructure, partial volume effects and strain. These data indicate that the potential clinical use of FA and MD would require measurement standardisation by myocardial region and layer, unless pathological changes substantially exceed the normal variation identified. PMID:26177211

  8. Fractions

    NSDL National Science Digital Library

    A. Blundred

    2012-01-01

    In this collection of 13 interactive Flash applets learners can check their understanding of various fraction concepts, including comparison to 1/2, location on the number line, equivalent fractions, and simplest form. Activities for the learners include sorting, labeling, constructing diagrams, and converting improper fractions. Displays are suitable for classroom demonstrations.

  9. Educational Implications for Agenesis of the Corpus Callosum.

    ERIC Educational Resources Information Center

    Ritter, Shirley A.

    This case study evaluates the case of a 20-year-old young Australian adult born with agenesis of the corpus callosum, the area of the brain uniting the hemispheres. Deficits commonly associated with agenesis of the corpus callosum are mental retardation, motor involvement, seizure activity, and lateral transfer difficulties. The report: (1)…

  10. Corpus Callosum Morphometrics in Young Children with Autism Spectrum Disorder

    ERIC Educational Resources Information Center

    Boger-Megiddo, Inbal; Shaw, Dennis W. W.; Friedman, Seth D.; Sparks, Bobbi F.; Artru, Alan A.; Giedd, Jay N.; Dawson, Geraldine; Dager, Stephen R.

    2006-01-01

    This study assessed digital corpus callosum cross sectional areas in 3-4 year olds with autism spectrum disorder (ASD) compared to typically developing (TD) and developmentally delayed (DD) children. Though not different in absolute size compared to TD, ASD callosums were disproportionately small adjusted for increased ASD cerebral volume. ASD…

  11. Analysis of vegetation index NDVI anisotropy to improve the accuracy of the GOES-R green vegetation fraction product

    Microsoft Academic Search

    Yuhong Tian; Peter Romanov; Yunyue Yu; Hui Xu; Dan Tarpley

    2010-01-01

    Green Vegetation Fraction (GVF) is the fraction of area within the instrument footprint occupied by green vegetation. Information on GVF is needed to estimate the surface energy balance in numerical weather prediction (NWP) and climate models. For the Geostationary Operational Environmental Satellite-R Series (GOES-R) Advanced Baseline Imager (ABI) algorithm development, a normalized difference vegetation index (NDVI) based linear mixture algorithm

  12. Diffusion Tensor Anisotropy in Adolescents and Adults

    Microsoft Academic Search

    Jason S. Schneiderman; Monte S. Buchsbaum; M. Mehmet. Haznedar; Erin A. Hazlett; Adam M. Brickman; Lina Shihabuddin; Jesse G. Brand; Yuliya Torosjan; Randall E. Newmark; Cheuk Tang; Jonathan Aronowitz; Reshmi Paul-Odouard; William Byne; Patrick R. Hof

    2007-01-01

    We acquired diffusion tensor images on 33 normal adults aged 22–64 and 15 adolescents aged 14–21. We assessed relative anisotropy in stereotaxically located regions of interest in the internal capsule, corpus callosum, anterior thalamic radiations, frontal anterior fasciculus, fronto-occipital fasciculus, temporal lobe white matter, cingulum bundle, frontal inferior longitudinal fasciculus, frontal superior longitudinal fasciculus, and optic radiations. All of these

  13. Maximum Principal Strain and Strain Rate Associated with Concussion Diagnosis Correlates with Changes in Corpus Callosum White Matter Indices

    PubMed Central

    MCALLISTER, THOMAS W.; FORD, JAMES C.; JI, SONGBAI; BECKWITH, JONATHAN G.; FLASHMAN, LAURA A.; PAULSEN, KEITH; GREENWALD, RICHARD M.

    2014-01-01

    On-field monitoring of head impacts, combined with finite element (FE) biomechanical simulation, allow for predictions of regional strain associated with a diagnosed concussion. However, attempts to correlate these predictions with in vivo measures of brain injury have not been published. This article reports an approach to and preliminary results from the correlation of subject-specific FE model-predicted regions of high strain associated with diagnosed concussion and diffusion tensor imaging to assess changes in white matter integrity in the corpus callosum (CC). Ten football and ice hockey players who wore instrumented helmets to record head impacts sustained during play completed high field magnetic resonance imaging preseason and within 10 days of a diagnosed concussion. The Dartmouth Subject-Specific FE Head model was used to generate regional predictions of strain and strain rate following each impact associated with concussion. Maps of change in fractional anisotropy (FA) and median diffusivity (MD) were generated for the CC of each athlete to correlate strain with change in FA and MD. Mean and maximum strain rate correlated with change in FA (Spearman ? = 0.77, p = 0.01; 0.70, p = 0.031), and there was a similar trend for mean and maximum strain (0.56, p = 0.10; 0.6, p = 0.07), as well as for maximum strain with change in MD (?0.63, p = 0.07). Change in MD correlated with injury-to-imaging interval (? = ?0.80, p = 0.006) but change in FA did not (? = 0.18, p = 0.62). These results provide preliminary confirmation that model-predicted strain and strain rate in the CC correlate with changes in indices of white matter integrity. PMID:21994062

  14. Maximum principal strain and strain rate associated with concussion diagnosis correlates with changes in corpus callosum white matter indices.

    PubMed

    McAllister, Thomas W; Ford, James C; Ji, Songbai; Beckwith, Jonathan G; Flashman, Laura A; Paulsen, Keith; Greenwald, Richard M

    2012-01-01

    On-field monitoring of head impacts, combined with finite element (FE) biomechanical simulation, allow for predictions of regional strain associated with a diagnosed concussion. However, attempts to correlate these predictions with in vivo measures of brain injury have not been published. This article reports an approach to and preliminary results from the correlation of subject-specific FE model-predicted regions of high strain associated with diagnosed concussion and diffusion tensor imaging to assess changes in white matter integrity in the corpus callosum (CC). Ten football and ice hockey players who wore instrumented helmets to record head impacts sustained during play completed high field magnetic resonance imaging preseason and within 10 days of a diagnosed concussion. The Dartmouth Subject-Specific FE Head model was used to generate regional predictions of strain and strain rate following each impact associated with concussion. Maps of change in fractional anisotropy (FA) and median diffusivity (MD) were generated for the CC of each athlete to correlate strain with change in FA and MD. Mean and maximum strain rate correlated with change in FA (Spearman ? = 0.77, p = 0.01; 0.70, p = 0.031), and there was a similar trend for mean and maximum strain (0.56, p = 0.10; 0.6, p = 0.07), as well as for maximum strain with change in MD (-0.63, p = 0.07). Change in MD correlated with injury-to-imaging interval (? = -0.80, p = 0.006) but change in FA did not (? = 0.18, p = 0.62). These results provide preliminary confirmation that model-predicted strain and strain rate in the CC correlate with changes in indices of white matter integrity. PMID:21994062

  15. White matter fractional anisotropy over two time points in early onset schizophrenia and adolescent cannabis use disorder: A naturalistic diffusion tensor imaging study.

    PubMed

    Epstein, Katherine A; Kumra, Sanjiv

    2015-04-30

    Recurrent exposure to cannabis in adolescence increases the risk for later development of psychosis, but there are sparse data regarding the impact of cannabis use on brain structure during adolescence. This pilot study investigated the effect of cannabis use disorder (CUD) upon white matter fractional anisotropy (WM FA) values in non-psychotic treatment-seeking adolescents relative to adolescents with early onset schizophrenia-spectrum disorders (EOSS) and to healthy control (HC) participants. Diffusion tensor imaging (DTI) and tractography methods were used to examine fractional anisotropy (FA) of the cingulum bundle, superior longitudinal fasciculus (SLF), corticospinal tract (CST), inferior longitudinal fasciculus (ILF), inferior fronto-occipital fasciculus (IFOF) and uncinate fasciculus in adolescents with EOSS (n=34), CUD (n=19) and HC (n=29). Participants received DTI and substance use assessments at baseline and at 18-month follow-up. Using multivariate analysis of variance, a significant main effect of diagnostic group was observed. Post-hoc testing revealed that adolescents with CUD showed an altered change in FA values in the left ILF and in the left IFOF (trend level) compared with HC adolescents. Greater consumption of cannabis during the inter-scan interval predicted a greater decrease in left ILF FA in CUD. These preliminary longitudinal data suggest that heavy cannabis use during adolescence, or some factor associated with cannabis use, is associated with an altered change in WM FA values in a fiber bundle that has been implicated in the pathophysiology of EOSS (i.e., the left ILF). Additional studies are needed to clarify the clinical significance of these findings. PMID:25779033

  16. Corpus callosum agenesis and rehabilitative treatment

    PubMed Central

    2010-01-01

    Corpus callosum agenesis is a relatively common brain malformation. It can be isolated or included in a complex alteration of brain (or sometimes even whole body) morphology. It has been associated with a number of neuropsychiatric disorders, from subtle neuropsychological deficits to Pervasive Developmental Disorders. Etiology and pathogenetic mechanisms have been better understood in recent years, due to the availability of more adequate animal models and the relevant progresses in developmental neurosciences. These recent findings are reviewed (through a MedLine search including papers published in the last 5 years and most relevant previously published papers) in view of the potential impact on children's global functioning and on the possible rehabilitative treatment, with an emphasis on the possibility to exploit brain plasticity and on the use of the ICF-CY framework. PMID:20849621

  17. Corpus Callosum Shape Analysis with Application to Dyslexia

    PubMed Central

    Casanova, Manuel F.; El-Baz, Ayman; Elnakib, Ahmed; Giedd, Jay; Rumsey, Judith M.; Williams, Emily L.; Switala, Andrew E.

    2012-01-01

    Morphometric studies of the corpus callosum suggest its involvement in a number of psychiatric conditions. In the present study we introduce a novel pattern recognition technique that offers a point-by-point shape descriptor of the corpus callosum. The method uses arc lengths of electric field lines in order to avoid discontinuities caused by folding anatomical contours. We tested this technique by comparing the shape of the corpus callosum in a series of dyslexic men (n = 16) and age-matched controls (n = 14). The results indicate a generalized increase in size of the corpus callosum in dyslexia with a concomitant diminution at its rostral and caudal poles. The reported shape analysis and 2D-reconstruction provide information of anatomical importance that would otherwise passed unnoticed when analyzing size information alone. PMID:22545196

  18. Fractions

    NSDL National Science Digital Library

    K. Cowley

    2011-05-09

    This is an accessible, easy-to-read book introducing fractions. It can be downloaded in PowerPoint, Impress, and Flash formats. For struggling or non-readers the book can be read aloud in a variety of voices. All of the books on the Tar Heel Reader site can be used with the Intellikeys keyboard with a custom overlay, a touch screen, and/or 1-3 switches. The text and background colors can be modified for students with visual impairments.

  19. Corpus Callosum Area in Children and Adults with Autism.

    PubMed

    Prigge, Molly B D; Lange, Nicholas; Bigler, Erin D; Merkley, Tricia L; Neeley, E Shannon; Abildskov, Tracy J; Froehlich, Alyson L; Nielsen, Jared A; Cooperrider, Jason R; Cariello, Annahir N; Ravichandran, Caitlin; Alexander, Andrew L; Lainhart, Janet E

    2013-01-01

    Despite repeated findings of abnormal corpus callosum structure in autism, the developmental trajectories of corpus callosum growth in the disorder have not yet been reported. In this study, we examined corpus callosum size from a developmental perspective across a 30-year age range in a large cross-sectional sample of individuals with autism compared to a typically developing sample. Midsagittal corpus callosum area and the 7 Witelson subregions were examined in 68 males with autism (mean age 14.1 years; range 3-36 years) and 47 males with typical development (mean age 15.3 years; range 4-29 years). Controlling for total brain volume, increased variability in total corpus callosum area was found in autism. In autism, increased midsagittal areas were associated with reduced severity of autism behaviors, higher intelligence, and faster speed of processing (p=0.003, p=0.011, p=0.013, respectively). A trend toward group differences in isthmus development was found (p=0.029, uncorrected). These results suggest that individuals with autism benefit functionally from increased corpus callosum area. Our cross-sectional examination also shows potential maturational abnormalities in autism, a finding that should be examined further with longitudinal datasets. PMID:23130086

  20. Corpus Callosum Area in Children and Adults with Autism

    PubMed Central

    Prigge, Molly B. D.; Lange, Nicholas; Bigler, Erin D.; Merkley, Tricia L.; Neeley, E. Shannon; Abildskov, Tracy J.; Froehlich, Alyson L.; Nielsen, Jared A.; Cooperrider, Jason R.; Cariello, Annahir N.; Ravichandran, Caitlin; Alexander, Andrew L.; Lainhart, Janet E.

    2012-01-01

    Despite repeated findings of abnormal corpus callosum structure in autism, the developmental trajectories of corpus callosum growth in the disorder have not yet been reported. In this study, we examined corpus callosum size from a developmental perspective across a 30-year age range in a large cross-sectional sample of individuals with autism compared to a typically developing sample. Midsagittal corpus callosum area and the 7 Witelson subregions were examined in 68 males with autism (mean age 14.1 years; range 3–36 years) and 47 males with typical development (mean age 15.3 years; range 4–29 years). Controlling for total brain volume, increased variability in total corpus callosum area was found in autism. In autism, increased midsagittal areas were associated with reduced severity of autism behaviors, higher intelligence, and faster speed of processing (p=0.003, p=0.011, p=0.013, respectively). A trend toward group differences in isthmus development was found (p=0.029, uncorrected). These results suggest that individuals with autism benefit functionally from increased corpus callosum area. Our cross-sectional examination also shows potential maturational abnormalities in autism, a finding that should be examined further with longitudinal datasets. PMID:23130086

  1. Automated measurement of the human corpus callosum using MRI

    PubMed Central

    Herron, Timothy J.; Kang, Xiaojian; Woods, David L.

    2012-01-01

    The corpus callosum includes the majority of fibers that connect the two cortical hemispheres. Studies of cross-sectional callosal morphometry and area have revealed developmental, gender, and hemispheric differences in healthy populations and callosal deficits associated with neurodegenerative disease and brain injury. However, accurate quantification of the callosum using magnetic resonance imaging is complicated by intersubject variability in callosal size, shape, and location and often requires manual outlining of the callosum in order to achieve adequate performance. Here we describe an objective, fully automated protocol that utilizes voxel-based images to quantify the area and thickness both of the entire callosum and of different callosal compartments. We verify the method's accuracy, reliability, robustness, and multisite consistency and make comparisons with manual measurements using public brain-image databases. An analysis of age-related changes in the callosum showed increases in length and reductions in thickness and area with age. A comparison of older subjects with and without mild dementia revealed that reductions in anterior callosal area independently predicted poorer cognitive performance after factoring out Mini-Mental Status Examination scores and normalized whole brain volume. Open-source software implementing the algorithm is available at www.nitrc.org/projects/c8c8. PMID:22988433

  2. Fractional anisotropy shows differential reduction in frontal-subcortical fiber bundles—A longitudinal MRI study of 76 middle-aged and older adults

    PubMed Central

    Vik, Alexandra; Hodneland, Erlend; Haász, Judit; Ystad, Martin; Lundervold, Astri J.; Lundervold, Arvid

    2015-01-01

    Motivated by the frontal- and white matter (WM) retrogenesis hypotheses and the assumptions that fronto-striatal circuits are especially vulnerable in normal aging, the goal of the present study was to identify fiber bundles connecting subcortical nuclei and frontal areas and obtain site-specific information about age related fractional anisotropy (FA) changes. Multimodal magnetic resonance image acquisitions [3D T1-weighted and diffusion weighted imaging (DWI)] were obtained from healthy older adults (N = 76, range 49–80 years at inclusion) at two time points, 3 years apart. A subset of the participants (N = 24) was included at a third time-point. In addition to the frontal-subcortical fibers, the anterior callosal fiber (ACF) and the corticospinal tract (CST) was investigated by its mean FA together with tract parameterization analysis. Our results demonstrated fronto-striatal structural connectivity decline (reduced FA) in normal aging with substantial inter-individual differences. The tract parameterization analysis showed that the along tract FA profiles were characterized by piece-wise differential changes along their extension rather than being uniformly affected. To the best of our knowledge, this is the first longitudinal study detecting age-related changes in frontal-subcortical WM connections in normal aging.

  3. Outcome in Prenatally Diagnosed Fetal Agenesis of the Corpus callosum

    Microsoft Academic Search

    P. W. A. Goodyear; C. M. Bannister; S. Russell; S. Rimmer

    2001-01-01

    This study of the outcome and prognostic factors in prenatally diagnosed agenesis of the corpus callosum (ACC) was undertaken to see if there are any differences between subgroups, what relationship they have to neurodevelopmental outcome and whether this information aids the counselling of parents of fetuses with the condition. The outcome of 14 prenatally diagnosed fetuses with ACC and 61

  4. Perspectives on Dichotic Listening and the Corpus Callosum

    ERIC Educational Resources Information Center

    Musiek, Frank E.; Weihing, Jeffrey

    2011-01-01

    The present review summarizes historic and recent research which has investigated the role of the corpus callosum in dichotic processing within the context of audiology. Examination of performance by certain clinical groups, including split brain patients, multiple sclerosis cases, and other types of neurological lesions is included. Maturational,…

  5. The Microstructural Status of the Corpus Callosum Is Associated with the Degree of Motor Function and Neurological Deficit in Stroke Patients

    PubMed Central

    Liang, Fanrong; Huang, Wenhua

    2015-01-01

    Human neuroimaging studies and animal models have suggested that white matter damage from ischemic stroke leads to the functional and structural reorganization of perilesional and remote brain regions. However, the quantitative relationship between the transcallosal tract integrity and clinical motor performance score after stroke remains unexplored. The current study employed a tract-based spatial statistics (TBSS) analysis on diffusion tensor imaging (DTI) to investigate the relationship between white matter diffusivity changes and the clinical scores in stroke patients. Probabilistic fiber tracking was also used to identify structural connectivity patterns in the patients. Thirteen ischemic stroke patients and fifteen healthy control subjects participated in this study. TBSS analyses showed that the corpus callosum (CC) and bilateral corticospinal tracts (CST) in the stroke patients exhibited significantly decreased fractional anisotropy and increased axial and radial diffusivity compared with those of the controls. Correlation analyses revealed that the motor and neurological deficit scores in the stroke patients were associated with the value of diffusivity indices in the CC. Compared with the healthy control group, probabilistic fiber tracking analyses revealed that significant changes in the inter-hemispheric fiber connections between the left and right motor cortex in the stroke patients were primarily located in the genu and body of the CC, left anterior thalamic radiation and inferior fronto-occipital fasciculus, bilateral CST, anterior/superior corona radiate, cingulum and superior longitudinal fasciculus, strongly suggesting that ischemic induces inter-hemispheric network disturbances and disrupts the white matter fibers connecting motor regions. In conclusion, the results of the present study show that DTI-derived measures in the CC can be used to predict the severity of motor skill and neurological deficit in stroke patients. Changes in structural connectivity pattern tracking between the left and right motor areas, particularly in the body of the CC, might reflect functional reorganization and behavioral deficit. PMID:25875333

  6. Identical, but not the same: intra-site and inter-site reproducibility of fractional anisotropy measures on two 3.0T scanners.

    PubMed

    Vollmar, Christian; O'Muircheartaigh, Jonathan; Barker, Gareth J; Symms, Mark R; Thompson, Pamela; Kumari, Veena; Duncan, John S; Richardson, Mark P; Koepp, Matthias J

    2010-07-15

    Diffusion Tensor Imaging (DTI) is being increasingly used to assess white matter integrity and it is therefore paramount to address the test-retest reliability of DTI measures. In this study we assessed inter- and intra-site reproducibility of two nominally identical 3T scanners at different sites in nine healthy controls using a DTI protocol representative of typical current "best practice" including cardiac gating, a multichannel head coil, parallel imaging and optimized diffusion gradient parameters. We calculated coefficients of variation (CV) and intraclass correlation coefficients (ICC) of fractional anisotropy (FA) measures for the whole brain, for three regions of interest (ROI) and for three tracts derived from these ROI by probabilistic tracking. We assessed the impact of affine, nonlinear and template based methods for spatially aligning FA maps on the reproducibility. The intra-site CV for FA ranged from 0.8% to 3.0% with ICC from 0.90 to 0.99, while the inter-site CV ranged from 1.0% to 4.1% with ICC of 0.82 to 0.99. Nonlinear image coregistration improved reproducibility compared to affine coregistration. Normalization to template space reduced the between-subject variation, resulting in lower ICC values and indicating a possibly reduced sensitivity. CV from probabilistic tractography were about 50% higher than for the corresponding seed ROI. Reproducibility maps of the whole scan volume showed a low variation of less than 5% in the major white matter tracts but higher variations of 10-15% in gray matter regions. One of the two scanners showed better intra-site reproducibility, while the intra-site CV for both scanners was significantly better than inter-site CV. However, when using nonlinear coregistration of FA maps, the average inter-site CV was below 2%. There was a consistent inter-site bias, FA values on site 2 were 1.0-1.5% lower than on site 1. Correction for this bias with a global scaling factor reduced the inter-site CV to the range of intra-site CV. Our results are encouraging for multi-centre DTI studies in larger populations, but also illustrate the importance of the image processing pipeline for reproducibility. PMID:20338248

  7. Agenesis of the corpus callosum and autism: a comprehensive comparison

    PubMed Central

    Corsello, Christina; Kennedy, Daniel P.; Adolphs, Ralph

    2014-01-01

    The corpus callosum, with its ?200 million axons, remains enigmatic in its contribution to cognition and behaviour. Agenesis of the corpus callosum is a congenital condition in which the corpus callosum fails to develop; such individuals exhibit localized deficits in non-literal language comprehension, humour, theory of mind and social reasoning. These findings together with parent reports suggest that behavioural and cognitive impairments in subjects with callosal agenesis may overlap with the profile of autism spectrum disorders, particularly with respect to impairments in social interaction and communication. To provide a comprehensive test of this hypothesis, we directly compared a group of 26 adults with callosal agenesis to a group of 28 adults with a diagnosis of autism spectrum disorder but no neurological abnormality. All participants had full-scale intelligence quotient scores >78 and groups were matched on age, handedness, and gender ratio. Using the Autism Diagnostic Observation Schedule together with current clinical presentation to assess autistic symptomatology, we found that 8/26 (about a third) of agenesis subjects presented with autism. However, more formal diagnosis additionally involving recollective parent-report measures regarding childhood behaviour showed that only 3/22 met complete formal criteria for an autism spectrum disorder (parent reports were unavailable for four subjects). We found no relationship between intelligence quotient and autism symptomatology in callosal agenesis, nor evidence that the presence of any residual corpus callosum differentiated those who exhibited current autism spectrum symptoms from those who did not. Relative to the autism spectrum comparison group, parent ratings of childhood behaviour indicated children with agenesis were less likely to meet diagnostic criteria for autism, even for those who met autism spectrum criteria as adults, and even though there was no group difference in parent report of current behaviours. The findings suggest two broad conclusions. First, they support the hypothesis that congenital disruption of the corpus callosum constitutes a major risk factor for developing autism. Second, they quantify specific features that distinguish autistic behaviour associated with callosal agenesis from autism more generally. Taken together, these two findings also leverage specific questions for future investigation: what are the distal causes (genetic and environmental) determining both callosal agenesis and its autistic features, and what are the proximal mechanisms by which absence of the callosum might generate autistic symptomatology? PMID:24771497

  8. Autism traits in individuals with agenesis of the corpus callosum

    PubMed Central

    Lau, Yolanda C.; Hinkley, Leighton B. N.; Bukshpun, Polina; Strominger, Zoe A.; Wakahiro, Mari L. J.; Baron-Cohen, Simon; Allison, Carrie; Auyeung, Bonnie; Jeremy, Rita J.; Nagarajan, Srikantan S.; Sherr, Elliott H.; Marco, Elysa J.

    2013-01-01

    Autism spectrum disorders (ASD) have numerous etiologies, including structural brain malformations such as agenesis of the corpus callosum (AgCC). We sought to directly measure the occurrence of autism traits in a cohort of individuals with AgCC and to investigate the neural underpinnings of this association. We screened a large AgCC cohort (n = 106) with the Autism Spectrum Quotient (AQ) and found that 45% of children, 35% of adolescents, and 18% of adults exceeded the predetermined autism-screening cut-off. Interestingly, performance on the AQ’s imagination domain was inversely correlated with magnetoencephalography measures of resting-state functional connectivity in the right superior temporal gyrus. Individuals with AgCC should be screened for ASD and disorders of the corpus callosum should be considered in autism diagnostic evaluations as well. PMID:23054201

  9. Statistical shape analysis of the corpus callosum in Schizophrenia

    PubMed Central

    Joshi, Shantanu H.; Narr, Katherine L.; Philips, Owen R.; Nuechterlein, Keith H.; Asarnow, Robert F.; Toga, Arthur W.; Woods, Roger P.

    2013-01-01

    We present a statistical shape-analysis framework for characterizing and comparing morphological variation of the corpus callosum. The midsagittal boundary of the corpus callosum is represented by a closed curve and analyzed using an invariant shape representation. The shape space of callosal curves is endowed with a Riemannian metric. Shape distances are given by the length of shortest paths (geodesics) that are invariant to shape-confounding transformations. The statistical framework enables computation of shape averages and covariances on the shape space in an intrinsic manner (unique to the shape space). The statistical framework makes use of the tangent principal component approach to achieve dimension reduction on the space of corpus callosum shapes. The advantages of this approach are – it is fully automatic, invariant, and avoids the use of landmarks to define shapes. We applied our method to determine the effects of sex, age, schizophrenia and schizophrenia-related genetic liability on callosal shape in a large sample of patients and controls and their first-degree relatives (N=218). Results showed significant age, sex, and schizophrenia effects on both global and local callosal shape structure. PMID:23000788

  10. Microstructural Integrity of the Corpus Callosum Linked with Neuropsychological Performance in Adolescents

    ERIC Educational Resources Information Center

    Fryer, Susanna L.; Frank, Lawrence R.; Spadoni, Andrea D.; Theilmann, Rebecca J.; Nagel, Bonnie J.; Schweinsburg, Alecia D.; Tapert, Susan F.

    2008-01-01

    Background: Diffusion tensor imaging (DTI) has revealed microstructural aspects of adolescent brain development, the cognitive correlates of which remain relatively uncharacterized. Methods: DTI was used to assess white matter microstructure in 18 typically developing adolescents (ages 16-18). Fractional anisotropy (FA) and mean diffusion (MD)…

  11. The Size of the Corpus Callosum in Males and Females: Implications of a Lack of Allometry

    Microsoft Academic Search

    Michael Peters

    1988-01-01

    There is much disagreement in the literature about whether or not certain parts of the corpus callosum show a sexual dimorphism. Amidst this debate, a rather surprising area of agreement is neglected: Even though there are dramatic overall sex differences in brain size (brain size being quite directly related to body surface), the corpus callosum of males and females shows

  12. Distinct regional atrophy in the corpus callosum of patients with temporal lobe epilepsy

    E-print Network

    Thompson, Paul

    Distinct regional atrophy in the corpus callosum of patients with temporal lobe epilepsy Bernd epilepsy on the thickness of the corpus callosum (CC) in a large sample of well-characterized patients (n are differentially affected depending on the affected hemisphere and age of epilepsy onset. Overall, we observed

  13. 1 | P a g e Corpus Callosum deformation analysis in Multiple Sclerosis

    E-print Network

    Paris-Sud XI, Université de

    1 | P a g e Corpus Callosum deformation analysis in Multiple Sclerosis *F. Derraz, **A. Pinti, *B to Multiple Sclerosis (MS) lesion. We propose an approach for 3D segmentation of the volume of interest based the criterion established in this paper. Key words : Segmentation, multiple sclerosis, corpus callosum, medical

  14. Solar wind turbulence: anisotropy, anisotropy, anisotropy!

    NASA Astrophysics Data System (ADS)

    Wicks, R.; Forman, M. A.; Summerlin, E. J.; Roberts, D. A.; Salem, C. S.

    2014-12-01

    Turbulence heats the solar wind as it expands away from the Sun, but where and how does heating of ions and electrons occur? In order to understand this we must first look at the fluctuations making up the cascade, the properties and anisotropies of which will determine whether ions or electrons are heated and whether field-parallel or -perpendicular heating will occur, all of which amounts to a lot of different anisotropies! With this in mind, we present a review of recent advances in the observation of plasma turbulence in the solar wind and comparison with simulations; which features of solar wind turbulence are well reproduced and which need to be captured better? The first anisotropy is that of the fluctuations making up the turbulent cascade itself, fluctuations are known to be highly transverse, meaning that the perpendicular magnetic field components are dominant over the field-parallel component. The second anisotropy is that of the scaling of amplitude towards smaller scales with steeper spectra parallel to the local magnetic field direction. Observations of the anisotropy of the full power spectral tensor will be discussed, in particular with reference to Alfvenic and pseudo-Alfvenic fluctuations (effectively two different polarizations of Alfven waves), the next step beyond the traditional "slab + 2D" approach to incompressible MHD turbulence. The third anisotropy is that of the ion and electron distributions. Both sets of charged particles frequently show non-Maxwellian distributions with higher temperatures found either perpendicular to or parallel to the magnetic field direction. Proton distributions often show beams and the heavier alpha particles are often hotter than the protons. Localized structures such as current sheets and magnetic discontinuities are shown to be sites of intense and anisotropic heating. Small scale fluctuations filling the space between such discontinuities may also dissipate energy into ions and electrons, either through electric fields intrinsic to the modes generated by the turbulence or through resonant or stochastic processes. Observations show that kinetic Alfven waves are the dominant mode.

  15. Verbal learning and memory in agenesis of the corpus callosum.

    PubMed

    Erickson, Roger L; Paul, Lynn K; Brown, Warren S

    2014-07-01

    The role of interhemispheric interactions in the encoding, retention, and retrieval of verbal memory can be clarified by assessing individuals with complete or partial agenesis of the corpus callosum (AgCC), but who have normal intelligence. This study assessed verbal learning and memory in AgCC using the California Verbal Learning Test-Second Edition (CVLT-II). Twenty-six individuals with AgCC were compared to 24 matched controls on CVLT-II measures, as well as Donders? four CVLT-II factors (i.e., Attention Span, Learning Efficiency, Delayed Memory, and Inaccurate Memory). Individuals with AgCC performed significantly below healthy controls on the Delayed Memory factor, confirmed by significant deficits in short and long delayed free recall and cued recall. They also performed less well in original learning. Deficient performance by individuals with AgCC during learning trials, as well as deficits in all forms of delayed memory, suggest that the corpus callosum facilitates interhemispheric elaboration and encoding of verbal information. PMID:24933663

  16. Dichotic listening in patients with partial section of the corpus callosum.

    PubMed

    Sugishita, M; Otomo, K; Yamazaki, K; Shimizu, H; Yoshioka, M; Shinohara, A

    1995-04-01

    Patients with a complete section of the corpus callosum have been observed to exhibit strong left-ear suppression when different speech stimuli are presented to both ears simultaneously (so-called dichotic listening). Data concerning the locus of corpus callosum damage that causes strong left-ear suppression remains scanty. In the present investigation, a consonant-vowel syllable dichotic listening test was given to five right-handed patients with partial sections of the corpus callosum, which were located using MRI and accurately defined measurement procedures. The following two measurement methods were used: (i) the genu-splenium (G-S) method, in which a lesion was localized in the anteroposterior dimension relative to the total length of the corpus callosum, defined as the distance between the most anterior point of the genu to the most posterior point of the splenium; and (ii) the rostrum-splenium (R-S) method, which takes into account the curvature of the corpus callosum, and in which a lesion was localized relative to the total length of the corpus callosum, defined as the length of the curved line from the tip of the rostrum to the end of the splenium. Results were compared with scores from 50 normal control subjects. Strong left-ear suppression was observed in two patients, who had surgical sections of the posterior 15.5-18.5% of the corpus callosum as measured with the G-S method, or the posterior 20-24% of the corpus callosum as measured with the R-S method. The suppression phenomenon persisted for more than 10 years post-surgery. On the other hand, the remaining three patients, who had lesions anterior to the posterior 17-28% of the corpus callosum as measured with the G-S method or 20-33% as measured with the R-S method exhibited no left-ear extinction. Despite the common assumption that damage to the posterior part of the trunk of the corpus callosum causes strong left-ear suppression, the results from the G-S method indicated that damage to the splenium defined as the posterior one-fifth of the segment between the anterior-most and posterior-most points of the corpus callosum, cause strong left-ear suppression. By the R-S method, results showed that damage to the splenium (the posterior one-fifth of the curvature of the corpus callosum) and possibly the part extending to the most posterior part of the trunk (the posterior one-quarter of the curvature) causes strong left-ear suppression. PMID:7735883

  17. Corpus callosum and inferior forebrain white matter microstructure are related to functional outcome from raised intracranial pressure in child traumatic brain injury.

    PubMed

    Tasker, Robert C; Westland, Amber Gunn; White, Deborah K; Williams, Guy B

    2010-01-01

    In severe paediatric traumatic brain injury (TBI), a common focus of treatment is raised intracranial pressure (ICP). We have previously reported frontal cerebral vulnerability with executive deficits from raised ICP in paediatric TBI. Now, using diffusion tensor imaging (DTI) in a different population, we have examined fractional anisotropy (FA), and mean, axial and radial diffusivity (MD, AD, RD) in 4 regions of the corpus callosum (CC) and in both inferior frontal regions. Our aim was to examine during the chronic phase of TBI whether the CC cross-sectional area correlated with regional DTI metrics of white matter microstructure, with global outcome ratings of function (Functional Independence Measure and Multiattribute Health Status Classification) and with performance in the Rey-Osterrieth Complex Figure (ROCF) test. We examined 33 paediatric TBI cases who were followed, on average, 4.9 years after severe injury. All cases had received mechanical ventilation during their acute treatment and, a priori, they were assigned to a non-ICP or a raised ICP group. Twenty-two participants had mainly right-sided injury at the time of acute ictus. The findings confirm that severe TBI in childhood, complicated by intracranial hypertension, results in CC vulnerability. In the chronic phase of recovery, it is reduced in the cross-sectional area, it is more compact and thinned, and the anterior region is disproportionately small. Late after raised ICP, we have also found that individuals exhibit regional microstructural abnormality with combined reduced FA and increased MD, AD and RD. Smaller size and such microstructural changes in the anterior CC were associated with similar right-sided (rather than left-sided) frontal microstructural changes in the ICP group. Taken together, this evidence points to an interaction between raised ICP-related brain tissue perturbation and focal frontal extracallosal injury, leading to anterior CC regional vulnerability, most likely wallerian degeneration. At long-term follow-up, this lack of white matter integrity in the anterior CC is correlated with functional outcome, particularly in aspects of social interaction and the copy component of the ROCF test, which suggests that the CC-to-forebrain function warrants further study in chronic TBI. PMID:20829579

  18. SELECTIVELY DIMINISHED CORPUS CALLOSUM FIBERS IN CONGENITAL CENTRAL HYPOVENTILATION SYNDROME

    PubMed Central

    Kumar, Rajesh; Macey, Paul M.; Woo, Mary A.; Harper, Ronald M.

    2011-01-01

    Congenital central hypoventilation syndrome (CCHS), a condition associated with mutations in the PHOX2B gene, is characterized by loss of breathing drive during sleep, insensitivity to CO2 and O2, and multiple somatomotor, autonomic, neuropsychological, and ophthalmologic deficits, including impaired intrinsic and extrinsic eye muscle control. Brain structural studies show injury in peri-callosal regions and the corpus callosum (CC), which has the potential to affect functions disturbed in the syndrome; however, the extent of CC injury in CCHS is unclear. Diffusion tensor imaging (DTI)-based fiber tractography procedures display fiber directional information and allow quantification of fiber integrity. We performed DTI in 13 CCHS children (age, 18.2±4.7 years; 8 male) and 31 control (17.4±4.9 years; 18 male) subjects using a 3.0-Tesla magnetic resonance imaging scanner; CC fibers were assessed globally and regionally with tractography procedures, and fiber counts and densities compared between groups using analysis-of-covariance (covariates; age and sex). Global CC evaluation showed reduced fiber counts and densities in CCHS over control subjects (CCHS vs controls; fiber-counts, 4490±854 vs 5232±777, p<0.001; fiber-density, 10.0±1.5 vs 10.8±0.9 fibers/mm2, p<0.020), and regional examination revealed that these changes are localized to callosal axons projecting to prefrontal (217±47 vs 248±32, p<0.005), premotor (201±51 vs 241±47, p<0.012), parietal (179±64 vs 238±54, p<0.002), and occipital regions (363±46 vs 431±82, p<0.004). Corpus callosum fibers in CCHS are compromised in motor, cognitive, speech, and ophthalmologic regulatory areas. The mechanisms of fiber injury are unclear, but may result from hypoxia or perfusion deficits accompanying the syndrome, or from consequences of PHOX2B action. PMID:21256194

  19. Clinical features of acute corpus callosum infarction patients

    PubMed Central

    Yang, Li-Li; Huang, Yi-Ning; Cui, Zhi-Tang

    2014-01-01

    The clinical manifestation of acute corpus callosum (CC) infarction is lack of specificity and complex, so it is easily missed diagnosis and misdiagnosis in the early stage. The present study aims to describe the clinical features of the acute CC infarction. In this study, 25 patients with corpus callosum infarction confirmed by the brain MRI/DWI and the risk factors were summarized. Patients were classified into genu infarction (3 cases), body infarction (4cases), body and genu infarction (4 cases), body and splenium infarction (1 case), splenium infarction (13 cases) according to lesion location. Clinical manifestation and prognosis were analyzed among groups. The results indicated that CC infarction in patients with high-risk group accounted for 72%, moderate-risk group accounted for 20%, low-risk group (8%). The main risk factors are carotid intimal thickening or plaque formation, hypertension, hyperlipidemia, cerebral artery stenosis, and so on. The CC infarction often merged with other parts infarction, and splenium infarction had the highest incidence, the clinical symptoms in the body infarction which can appear typical signs and symptoms, but in other parts infarction which always merged many nerve defect symptoms. The body infarction prognosis is poor; the rest parts of infarction are more favorable prognosis. In conclusion, CC infarction has the highest incidence in the stroke of high-risk group; neck color Doppler and TCD examination can be found as early as possible to explore the pathogenic factors. Prognosis is usually much better by treatment according to the location and risk factors. PMID:25197390

  20. Measurement of the corpus callosum using magnetic resonance imaging: analyses of methods and techniques.

    PubMed

    Dorion, A A; Capron, C; Duyme, M

    2001-06-01

    Since the first postmortem report of sex-related differences in the size of the human corpus callosum, a number of studies on sex differences have been published, but results conflicted. The aim of this review was not to assess the possible existence and magnitude of sex variations in the size of the corpus callosum but to analyze methodological differences in several studies using Magnetic Resonance Imaging to investigate the sexual dimorphism in the size of the corpus callosum. Methodological problems arise at several steps of the method: sampling, imagery techniques, and measurements. Moreover, the means of callosal areas obtained by the nine reported studies are significantly different. The hypothesis that methodoiogical differences could explain these differences is supported by statistical results. A common method for investigating sex-related differences in callosal morphology appears necessary to resolve the question of a real sexual dimorphism of the corpus callosum and its subregions. PMID:11565916

  1. Automatic corpus callosum segmentation using a deformable active Fourier contour model

    E-print Network

    Utah, University of

    Automatic corpus callosum segmentation using a deformable active Fourier contour model Clement sensory, motor and cognitive information from homologous regions in both hemispheres. We have developed approach employs constrained elastic deformation of flexible Fourier contour model, and is an extension

  2. Whole-Exome Sequencing Identifies Mutated C12orf57 in Recessive Corpus Callosum Hypoplasia

    PubMed Central

    Akizu, Naiara; Shembesh, Nuri M.; Ben-Omran, Tawfeg; Bastaki, Laila; Al-Tawari, Asma; Zaki, Maha S.; Koul, Roshan; Spencer, Emily; Rosti, Rasim Ozgur; Scott, Eric; Nickerson, Elizabeth; Gabriel, Stacey; da Gente, Gilberto; Li, Jiang; Deardorff, Matthew A.; Conlin, Laura K.; Horton, Margaret A.; Zackai, Elaine H.; Sherr, Elliott H.; Gleeson, Joseph G.

    2013-01-01

    The corpus callosum is the principal cerebral commissure connecting the right and left hemispheres. The development of the corpus callosum is under tight genetic control, as demonstrated by abnormalities in its development in more than 1,000 genetic syndromes. We recruited more than 25 families in which members affected with corpus callosum hypoplasia (CCH) lacked syndromic features and had consanguineous parents, suggesting recessive causes. Exome sequence analysis identified C12orf57 mutations at the initiator methionine codon in four different families. C12orf57 is ubiquitously expressed and encodes a poorly annotated 126 amino acid protein of unknown function. This protein is without significant paralogs but has been tightly conserved across evolution. Our data suggest that this conserved gene is required for development of the human corpus callosum. PMID:23453666

  3. Longitudinal, Regional and Deformation-Specific Corpus Callosum Shape Analysis for Multiple Sclerosis

    E-print Network

    Hamarneh, Ghassan

    brain scans of a group of multiple sclerosis patients undergoing a longitudinal (serial) study transmit neural impulses between the hemispheres. Multiple Sclerosis is an inflammatory and degenerativeLongitudinal, Regional and Deformation-Specific Corpus Callosum Shape Analysis for Multiple

  4. Oligodendrocyte Lineage and Subventricular Zone Response to Traumatic Axonal Injury in the Corpus Callosum

    PubMed Central

    Sullivan, Genevieve M.; Mierzwa, Amanda J.; Kijpaisalratana, Naruchorn; Tang, *Haiying; Wang, Yong; Song, Sheng-Kwei; Selwyn, Reed

    2013-01-01

    Abstract Traumatic brain injury frequently causes traumatic axonal injury (TAI) in white matter tracts. Experimental TAI in the corpus callosum of adult mice was used to examine the effects on oligodendrocyte lineage cells and myelin in conjunction with neuroimaging. The injury targeted the corpus callosum over the subventricular zone, a source of neural stem/progenitor cells. Traumatic axonal injury was produced in the rostral body of the corpus callosum by impact onto the skull at the bregma. During the first week after injury, magnetic resonance diffusion tensor imaging showed that axial diffusivity decreased in the corpus callosum and that corresponding regions exhibited significant axon damage accompanied by hypertrophic microglia and reactive astrocytes. Oligodendrocyte progenitor proliferation increased in the subventricular zone and corpus callosum. Oligodendrocytes in the corpus callosum shifted toward upregulation of myelin gene transcription. Plp/CreERT:R26IAP reporter mice showed normal reporter labeling of myelin sheaths 0 to 2 days after injury but labeling was increased between 2 and 7 days after injury. Electron microscopy revealed axon degeneration, demyelination, and redundant myelin figures. These findings expand the cell types and responses to white matter injuries that inform diffusion tensor imaging evaluation and identify pivotal white matter changes after TAI that may affect axon vulnerability vs. recovery after brain injury. PMID:24226267

  5. Magnetic resonance findings of the corpus callosum in canine and feline lysosomal storage diseases.

    PubMed

    Hasegawa, Daisuke; Tamura, Shinji; Nakamoto, Yuya; Matsuki, Naoaki; Takahashi, Kimimasa; Fujita, Michio; Uchida, Kazuyuki; Yamato, Osamu

    2013-01-01

    Several reports have described magnetic resonance (MR) findings in canine and feline lysosomal storage diseases such as gangliosidoses and neuronal ceroid lipofuscinosis. Although most of those studies described the signal intensities of white matter in the cerebrum, findings of the corpus callosum were not described in detail. A retrospective study was conducted on MR findings of the corpus callosum as well as the rostral commissure and the fornix in 18 cases of canine and feline lysosomal storage diseases. This included 6 Shiba Inu dogs and 2 domestic shorthair cats with GM1 gangliosidosis; 2 domestic shorthair cats, 2 familial toy poodles, and a golden retriever with GM2 gangliosidosis; and 2 border collies and 3 chihuahuas with neuronal ceroid lipofuscinoses, to determine whether changes of the corpus callosum is an imaging indicator of those diseases. The corpus callosum and the rostral commissure were difficult to recognize in all cases of juvenile-onset gangliosidoses (GM1 gangliosidosis in Shiba Inu dogs and domestic shorthair cats and GM2 gangliosidosis in domestic shorthair cats) and GM2 gangliosidosis in toy poodles with late juvenile-onset. In contrast, the corpus callosum and the rostral commissure were confirmed in cases of GM2 gangliosidosis in a golden retriever and canine neuronal ceroid lipofuscinoses with late juvenile- to early adult-onset, but were extremely thin. Abnormal findings of the corpus callosum on midline sagittal images may be a useful imaging indicator for suspecting lysosomal storage diseases, especially hypoplasia (underdevelopment) of the corpus callosum in juvenile-onset gangliosidoses. PMID:24386203

  6. Magnetic Resonance Findings of the Corpus Callosum in Canine and Feline Lysosomal Storage Diseases

    PubMed Central

    Hasegawa, Daisuke; Tamura, Shinji; Nakamoto, Yuya; Matsuki, Naoaki; Takahashi, Kimimasa; Fujita, Michio; Uchida, Kazuyuki; Yamato, Osamu

    2013-01-01

    Several reports have described magnetic resonance (MR) findings in canine and feline lysosomal storage diseases such as gangliosidoses and neuronal ceroid lipofuscinosis. Although most of those studies described the signal intensities of white matter in the cerebrum, findings of the corpus callosum were not described in detail. A retrospective study was conducted on MR findings of the corpus callosum as well as the rostral commissure and the fornix in 18 cases of canine and feline lysosomal storage diseases. This included 6 Shiba Inu dogs and 2 domestic shorthair cats with GM1 gangliosidosis; 2 domestic shorthair cats, 2 familial toy poodles, and a golden retriever with GM2 gangliosidosis; and 2 border collies and 3 chihuahuas with neuronal ceroid lipofuscinoses, to determine whether changes of the corpus callosum is an imaging indicator of those diseases. The corpus callosum and the rostral commissure were difficult to recognize in all cases of juvenile-onset gangliosidoses (GM1 gangliosidosis in Shiba Inu dogs and domestic shorthair cats and GM2 gangliosidosis in domestic shorthair cats) and GM2 gangliosidosis in toy poodles with late juvenile-onset. In contrast, the corpus callosum and the rostral commissure were confirmed in cases of GM2 gangliosidosis in a golden retriever and canine neuronal ceroid lipofuscinoses with late juvenile- to early adult-onset, but were extremely thin. Abnormal findings of the corpus callosum on midline sagittal images may be a useful imaging indicator for suspecting lysosomal storage diseases, especially hypoplasia (underdevelopment) of the corpus callosum in juvenile-onset gangliosidoses. PMID:24386203

  7. Bimanual motor coordination in agenesis of the corpus callosum.

    PubMed

    Mueller, Kendra L Oakes; Marion, Sarah DeBoard; Paul, Lynn K; Brown, Warren S

    2009-10-01

    The nature and extent of deficiencies in bimanual motor coordination in individuals with agenesis of the corpus callosum (ACC) was studied using the computerized Bimanual Coordination Test (cBCT). Compared with previous bimanual tasks, the cBCT is more specifically reliant on interhemispheric interactions of lateralized motor control, allows more precise measurement, and permits examination of performance over a wider range of bimanual challenges. The cBCT performance of 13 high-functioning individuals with complete ACC was compared to 21 age- and IQ-matched controls. The groups did not differ in unimanual response speed. On trials involving angled paths that require bimanual coordination, the ACC group performed significantly slower and less accurately across all angles. The largest group differences in speed occurred on trials where the hands must respond symmetrically, while mirror-image (vs. parallel) responding produced the greatest deficits in accuracy. These data confirm previous findings of deficits in bimanual coordination in callosal absence, but using significantly improved measurement technology. Deficits in bimanual coordination in ACC are present across different demands for interhand interactions in the speed and direction of movement. PMID:19824766

  8. Preliminary evidence that prenatal alcohol damage may be visible in averaged ultrasound images of the neonatal human corpus callosum

    Microsoft Academic Search

    Fred L. Bookstein; Paul D. Connor; Kristi D. Covell; Helen M. Barr; Christine A. Gleason; Raymond W. Sze; Jenny A. McBroom; Ann P. Streissguth

    2005-01-01

    Brain damage consequent to prenatal alcohol exposure can be detected by measurements of the corpus callosum in the midline magnetic resonance (MR) brain image in adolescents and adults. The present article extends this finding into the neonatal period, when the power of detection to ameliorate the quality of the child's future life is greatest. The midline corpus callosum of the

  9. Structural changes of the corpus callosum in tinnitus

    PubMed Central

    Diesch, Eugen; Schummer, Verena; Kramer, Martin; Rupp, Andre

    2012-01-01

    Objectives: In tinnitus, several brain regions seem to be structurally altered, including the medial partition of Heschl's gyrus (mHG), the site of the primary auditory cortex. The mHG is smaller in tinnitus patients than in healthy controls. The corpus callosum (CC) is the main interhemispheric commissure of the brain connecting the auditory areas of the left and the right hemisphere. Here, we investigate whether tinnitus status is associated with CC volume. Methods: The midsagittal cross-sectional area of the CC was examined in tinnitus patients and healthy controls in which an examination of the mHG had been carried out earlier. The CC was extracted and segmented into subregions which were defined according to the most common CC morphometry schemes introduced by Witelson (1989) and Hofer and Frahm (2006). Results: For both CC segmentation schemes, the CC posterior midbody was smaller in male patients than in male healthy controls and the isthmus, the anterior midbody, and the genou were larger in female patients than in female controls. With CC size normalized relative to mHG volume, the normalized CC splenium was larger in male patients than male controls and the normalized CC splenium, the isthmus and the genou were larger in female patients than female controls. Normalized CC segment size expresses callosal interconnectivity relative to auditory cortex volume. Conclusion: It may be argued that the predominant function of the CC is excitatory. The stronger callosal interconnectivity in tinnitus patients, compared to healthy controls, may facilitate the emergence and maintenance of a positive feedback loop between tinnitus generators located in the two hemispheres. PMID:22470322

  10. Acute infarct of the corpus callosum: appearance on diffusion-weighted MR imaging and MR spectroscopy.

    PubMed

    Riedy, Gerard; Melhem, Elias R

    2003-08-01

    Few reports of corpus callosum infarction are published in the radiologic literature. We present a case of an atypical infarction of the corpus callosum and adjacent gyri involving both anterior cerebral artery territories. Standard magnetic resonance (MR) imaging was performed including diffusion weighted imaging. In addition, perfusion-weighted imaging and MR spectroscopy were employed to further characterize the patient's corpus callosal lesion. On MR imaging and spectroscopic examination, the lesion demonstrated T2 hyper-intensity, restricted diffusion, and the metabolite lactate. While the MR imaging appearance of this bilateral infarction has some characteristics that mimic tumor, employment of the full range of MR techniques can obviate the need for biopsy in acute infarcts of the corpus callosum. PMID:12884339

  11. Diffusion Tensor Magnetic Resonance Imaging Finding of Discrepant Fractional Anisotropy Between the Frontal and Parietal Lobes After Whole-Brain Irradiation in Childhood Medulloblastoma Survivors: Reflection of Regional White Matter Radiosensitivity?

    SciTech Connect

    Qiu Deqiang [Department of Diagnostic Radiology, Queen Mary Hospital, University of Hong Kong, Hong Kong (China); Kwong, Dora [Department of Clinical Oncology, Queen Mary Hospital, University of Hong Kong, Hong Kong (China); Chan, Godfrey [Department of Pediatric and Adolescent Medicine, Queen Mary Hospital, University of Hong Kong, Hong Kong (China); Leung, Lucullus [Department of Oncology, Princess Margaret Hospital, Hong Kong (China); Khong, P.-L. [Department of Diagnostic Radiology, Queen Mary Hospital, University of Hong Kong, Hong Kong (China)], E-mail: plkhong@hkucc.hku.hk

    2007-11-01

    Purpose: To test the hypothesis that fractional anisotropy (FA) is more severely reduced in white matter of the frontal lobe compared with the parietal lobe after receiving the same whole-brain irradiation dose in a cohort of childhood medulloblastoma survivors. Methods and Materials: Twenty-two medulloblastoma survivors (15 male, mean [{+-} SD] age = 12.1 {+-} 4.6 years) and the same number of control subjects (15 male, aged 12.0 {+-} 4.2 years) were recruited for diffusion tensor magnetic resonance imaging scans. Using an automated tissue classification method and the Talairach Daemon atlas, FA values of frontal and parietal lobes receiving the same radiation dose, and the ratio between them were quantified and denoted as FFA, PFA, and FA{sub f/p}, respectively. The Mann-Whitney U test was used to test for significant differences of FFA, PFA, and FA{sub f/p} between medulloblastoma survivors and control subjects. Results: Frontal lobe and parietal lobe white matter FA were found to be significantly less in medulloblastoma survivors compared with control subjects (frontal p = 0.001, parietal p = 0.026). Moreover, these differences were found to be discrepant, with the frontal lobe having a significantly larger difference in FA compared with the parietal lobe. The FA{sub f/p} of control and medulloblastoma survivors was 1.110 and 1.082, respectively (p = 0.029). Conclusion: Discrepant FA changes after the same irradiation dose suggest radiosensitivity of the frontal lobe white matter compared with the parietal lobe. Special efforts to address the potentially vulnerable frontal lobe after treatment with whole-brain radiation may be needed so as to balance disease control and treatment-related morbidity.

  12. Shape Analysis of Corpus Callosum in Autism Subtype using Planar Conformal Mapping

    E-print Network

    Yin, Xiaotian "Tim"

    cannot be reflected in volume measurements. Shape morphology of the CC in autism has been studied in [1Shape Analysis of Corpus Callosum in Autism Subtype using Planar Conformal Mapping Qing He*1 , Ye Brook, New York, USA 11794 3 Thompson Center for Autism, University of Missouri-Columbia, Columbia, MO

  13. Longitudinal Changes in the Corpus Callosum following Pediatric Traumatic Brain Injury

    Microsoft Academic Search

    Trevor C. Wu; Elisabeth A. Wilde; Erin D. Bigler; Xiaoqi Li; Tricia L. Merkley; Ragini Yallampalli; Stephen R. McCauley; Kathleen P. Schnelle; Ana C. Vasquez; Zili Chu; Gerri Hanten; Jill V. Hunter; Harvey S. Levin

    2010-01-01

    Background: Atrophy of the corpus callosum (CC) is a documented consequence of moderate-to-severe traumatic brain injury (TBI), which has been expressed as volume loss using quantitative magnetic resonance imaging (MRI). Other advanced imaging modalities such as diffusion tensor imaging (DTI) have also detected white matter microstructural alteration following TBI in the CC. The manner and degree to which macrostructural changes

  14. Reduced White Matter Connectivity in the Corpus Callosum of Children with Tourette Syndrome

    ERIC Educational Resources Information Center

    Plessen, Kerstin J.; Gruner, Renate; Lundervold, Arvid; Hirsch, Jochen G.; Xu, Dongrong; Bansal, Ravi; Hammar, Asa; Lundervold, Astri J.; Wentzel-Larsen, Tore; Lie, Stein Atle; Gass, Achim; Peterson, Bradley S.; Hugdahl, Kenneth

    2006-01-01

    Background: Brain imaging studies have revealed anatomical anomalies in the brains of individuals with Tourette syndrome (TS). Prefrontal regions have been found to be larger and the corpus callosum (CC) area smaller in children and young adults with TS compared with healthy control subjects, and these anatomical features have been understood to…

  15. Concussion causes transient dysfunction in cortical inhibitory networks but not the corpus callosum

    Microsoft Academic Search

    G. D. Hammond-Tooke; J. Goei; L. J. du Plessis; E. A. Franz

    2010-01-01

    The corpus callosum (CC) is thought to be especially vulnerable in traumatic brain injury. Bimanual cost (a slowing of reaction time with bimanual compared to unimanual responses) is a sensitive indicator of CC function. To determine whether CC dysfunction is a significant feature of mild traumatic brain injury, unimanual and bimanual reaction times were studied in 10 recently concussed patients

  16. Hallermann-Streiff syndrome associated with complete agenesis of the corpus callosum.

    PubMed

    Sigirci, Ahmet; Alkan, Alpay; Bicak, Ugur; Yakinci, Cengiz

    2005-08-01

    Hallermann-Streiff syndrome is a rare clinical entity with unknown etiology characterized by a birdlike face, microphthalmia, a beaked nose, hypotrichosis, and proportional small stature. We present a 4-year-old boy in whom magnetic resonance imaging showed complete agenesis of the corpus callosum, which has not been presented in the literature. PMID:16225817

  17. Sex differences in corpus callosum size: relationship to age and intracranial size

    Microsoft Academic Search

    Edith V. Sullivan; Margaret J. Rosenbloom; John E. Desmond; Adolf Pfefferbaum

    2001-01-01

    This quantitative MRI study reports measurement of corpus callosum area taken from midsagittal brain images in 51 healthy men and 41 healthy women, spanning the adult age range (22 to 71 years). Men had larger brains and corpora callosa than women, but callosal size did not correlate with age in either sex. Intracranial (i.c.) volume (ICV) and midsagittal i.c. area

  18. MRI Findings of Coexistence of Ectopic Neurohypophysis, Corpus Callosum Dysgenesis, and Periventricular Neuronal Heterotopia

    PubMed Central

    Arslan, Harun; Sayl?k, Metin; Akdeniz, Hüseyin

    2014-01-01

    Ectopic neurohypophysis is a pituitary gland abnormality, which can accompany growth hormone deficiency associated with dwarfism. Here we present magnetic resonance imaging (MRI) findings of a rare case of ectopic neurohypophysis, corpus callosum dysgenesis, and periventricular neuronal heterotopia coexisting, with a review of the literature. PMID:24987569

  19. Corpus Callosum Morphology in Attention Deficit-Hyperactivity Disorder: Morphometric Analysis of MRI.

    ERIC Educational Resources Information Center

    Hynd, George W.; And Others

    1991-01-01

    Morphometric analysis of magnetic resonance imaging scans revealed that, compared to nondisabled controls, the seven children with attention deficit hyperactivity disorder had a smaller corpus callosum. Results suggest that subtle differences may exist in the brains of these children and that deviations in normal corticogenesis may underlie the…

  20. Demyelination and remyelination in anatomically distinct regions of the corpus callosum following cuprizone intoxication

    PubMed Central

    Steelman, Andrew J.; Thompson, Jeffrey P.; Li, Jianrong

    2011-01-01

    Multiple sclerosis is a chronic demyelinating disease of the central nervous system. Spontaneous remyelination during early disease stages is thought to preserve and partially restore function. However, this process ceases in later stages despite the presence of pre-oligodendrocytes. Cuprizone-induced demyelination is a useful model with which to study the remyelination process. Previous studies have demonstrated heterogeneities in demyelination in individual animals. Here we investigated regional differences in demyelination and remyelination within the corpus callosum. C57BL/6 mice were fed 0.2% cuprizone for 5 weeks to induce demyelination. Remyelination was examined 2–5 weeks after cuprizone withdrawal. Immunohistochemistry and electron microscopy were used to quantify regional differences in demyelination, gliosis, and remyelination. We found that, while demyelination was limited in the rostral region of corpus callosum, nearly complete demyelination occurred in the caudal callosum, beginning at approximately ?0.5 mm from bregma. Astrogliosis and microgliosis were correlated with demyelination and differed between the rostral and caudal callosal structures. Remyelination upon cessation of cuprizone ensued at different rates with splenium remyelinating faster than dorsal hippocampal commissure. Our data show anatomical differences of cuprizone-induced demyelination and remyelination in the corpus callosum and the importance of examining specific callosal regions in myelin repair studies using this model. PMID:22015947

  1. Morphometry of the corpus callosum in monozygotic twins discordant for schizophrenia: a magnetic resonance imaging study.

    PubMed Central

    Casanova, M F; Sanders, R D; Goldberg, T E; Bigelow, L B; Christison, G; Torrey, E F; Weinberger, D R

    1990-01-01

    The corpus callosum (CC) has been the focus of several morphometric studies of patients with schizophrenia, but the results of these studies have been contradictory. In an attempt to improve the reliability of morphometric measurements of the corpus callosum, a computerised image analysis system was used to measure the shape, area, thickness and length of the CC on magnetic resonance imaging (MRI) in 12 pairs of monozygotic twins discordant for schizophrenia (SC). No differences in CC area (anterior, middle, posterior thirds and total), length or vertical thickness of the CC body (at three levels) were demonstrated by t test comparisons of the affected SC and unaffected twins. Statistical analysis of a Fourier expansion series suggested differences in shape between normal and SC cotwins in the second harmonic of the anterior and middle segments and effects of gender on posterior CC shape. These results fail to replicate previous findings of altered length, thickness and area in the schizophrenic CC, but implicate disease-related shape differences in the anterior and middle segment of the corpus callosum and gender-related differences in splenium shape. The disease-related shape distortion suggest ventriculomegaly rather than an intrinsic abnormality of the corpus callosum. Images PMID:2351971

  2. Effects of prenatal irradiation on the development of cerebral cortex and corpus callosum of the mouse

    Microsoft Academic Search

    Sergio L. Schmidt; Roberto Lent

    1987-01-01

    Defects of the cerebral cortex and corpus callosum of mice subjected prenatally to gamma irradiation were evaluated as a function of dose and of embryonic age at irradiation. Pregnant mice were exposed to a gamma source at 16, 17, and 19 days of gestation (E16, E17, and E19, respectively), with total doses of 2 Gy and 3 Gy, in order

  3. Quantitative Analysis of the Shape of the Corpus Callosum in Patients with Autism and Comparison Individuals

    ERIC Educational Resources Information Center

    Casanova, Manuel F.; El-Baz, Ayman; Elnakib, Ahmed; Switala, Andrew E.; Williams, Emily L.; Williams, Diane L.; Minshew, Nancy J.; Conturo, Thomas E.

    2011-01-01

    Multiple studies suggest that the corpus callosum in patients with autism is reduced in size. This study attempts to elucidate the nature of this morphometric abnormality by analyzing the shape of this structure in 17 high-functioning patients with autism and an equal number of comparison participants matched for age, sex, IQ, and handedness. The…

  4. A Two-Year Longitudinal MRI Study of the Corpus Callosum in Autism

    ERIC Educational Resources Information Center

    Frazier, Thomas W.; Keshavan, Matcheri S.; Minshew, Nancy J.; Hardan, Antonio Y.

    2012-01-01

    A growing body of literature has identified size reductions of the corpus callosum (CC) in autism. However, to our knowledge, no published studies have reported on the growth of CC volumes in youth with autism. Volumes of the total CC and its sub-divisions were obtained from 23 male children with autism and 23 age- and gender-matched controls at…

  5. Corpus Callosum Size is Linked to Dichotic Deafness and Hemisphericity, Not Sex or Handedness

    ERIC Educational Resources Information Center

    Morton, Bruce E.; Rafto, Stein E.

    2006-01-01

    Individuals differ in the number of corpus callosum (CC) nerve fibers interconnecting their cerebral hemispheres by about threefold. Early reports suggested that males had smaller CCs than females. This was often interpreted to support the concept that the male brain is more "lateralized" or "specialized," thus accounting for presumed male…

  6. Dividing Fractions by Fractions

    NSDL National Science Digital Library

    J.C. Banfill

    2007-12-12

    This site gives a description of how to divide fractions and gives a sample problem in which the denominator fraction is inverted, the numerators and denominators are multiplied, and the resulting fraction is simplified. It also includes the same problem solved by 'canceling' the fractions to simplify, and completing the process. There is also a game for students to practice their new skill of dividing and simplifying fractions.

  7. Boomerang sign: Clinical significance of transient lesion in splenium of corpus callosum

    PubMed Central

    Malhotra, Hardeep Singh; Garg, Ravindra Kumar; Vidhate, Mukund R.; Sharma, Pawan Kumar

    2012-01-01

    Transient signal abnormality in the splenium of corpus callosum on magnetic resonance imaging (MRI) is occasionally encountered in clinical practice. It has been reported in various clinical conditions apart from patients with epilepsy. We describe 4 patients with different etiologies presenting with signal changes in the splenium of corpus callosum. They were diagnosed as having progressive myoclonic epilepsy (case 1), localization-related epilepsy (case 2), hemicrania continua (case 3), and postinfectious parkinsonism (case 4). While three patients had complete involvement of the splenium on diffusion-weighted image (“boomerang sign”), the patient having hemicrania continua showed semilunar involvement (“mini-boomerang”) on T2-weighted and FLAIR image. All the cases had noncontiguous involvement of the splenium. We herein, discuss these cases with transient splenial involvement and stress that such patients do not need aggressive diagnostic and therapeutic interventions. An attempt has been made to review the literature regarding the pathophysiology, etiology, and outcome of such lesions. PMID:22566735

  8. Boomerang sign: Clinical significance of transient lesion in splenium of corpus callosum.

    PubMed

    Malhotra, Hardeep Singh; Garg, Ravindra Kumar; Vidhate, Mukund R; Sharma, Pawan Kumar

    2012-04-01

    Transient signal abnormality in the splenium of corpus callosum on magnetic resonance imaging (MRI) is occasionally encountered in clinical practice. It has been reported in various clinical conditions apart from patients with epilepsy. We describe 4 patients with different etiologies presenting with signal changes in the splenium of corpus callosum. They were diagnosed as having progressive myoclonic epilepsy (case 1), localization-related epilepsy (case 2), hemicrania continua (case 3), and postinfectious parkinsonism (case 4). While three patients had complete involvement of the splenium on diffusion-weighted image ("boomerang sign"), the patient having hemicrania continua showed semilunar involvement ("mini-boomerang") on T2-weighted and FLAIR image. All the cases had noncontiguous involvement of the splenium. We herein, discuss these cases with transient splenial involvement and stress that such patients do not need aggressive diagnostic and therapeutic interventions. An attempt has been made to review the literature regarding the pathophysiology, etiology, and outcome of such lesions. PMID:22566735

  9. Developmental Trajectories of the Corpus Callosum in Attention-Deficit/Hyperactivity Disorder

    PubMed Central

    Gilliam, Mary; Stockman, Michael; Malek, Meaghan; Sharp, Wendy; Greenstein, Deanna; Lalonde, Francois; Clasen, Liv; Giedd, Jay; Rapoport, Judith; Shaw, Philip

    2010-01-01

    Background It was recently found that the development of typical patterns of prefrontal, but not posterior, cortical asymmetry is disrupted in right handed youth with attention-deficit/hyperactivity disorder (ADHD). Using longitudinal data, we tested the hypothesis that there would be a congruent disruption in the growth of the anterior corpus callosum, which contains white matter tracts connecting prefrontal cortical regions. Methods Areas of five subregions of the corpus callosum were quantified using a semiautomated method from 828 neuroanatomic magnetic resonance scans acquired from 236 children and adolescents with ADHD (429 scans) and 230 typically developing youth (399 scans), the majority of whom had repeated neuroimaging. Growth rates of each diagnostic group were defined using mixed-model linear regression. Results Right handed participants with ADHD showed a significantly higher rate of growth in the anterior-most region of the corpus callosum (estimated annual increase in area of 0.97%, SEM 0.12%) than their typically developing peers (annual increase in area of 0.32% SEM 0.13%; t=3.64, p=0.0003). No significant diagnostic differences in growth rates were found in any other regions in right handed participants, and no significant diagnostic differences were found in non-right handed participants. Conclusions As hypothesized, we found anomalous growth trajectories in the anterior corpus callosum in ADHD. This disrupted anterior callosal growth may reflect, or even drive, the previously reported disruption in the development of prefrontal cortex asymmetry. The finding documents the dynamic, age-dependent nature of callosal and congruent prefrontal cortical abnormalities characterizing ADHD. PMID:21247556

  10. Relationship between discrimination tasks of the cantab and the corpus callosum morphology in Alzheimer's disease.

    PubMed

    Dorion, A A; Duyme, M; Zanca, M; Dubois, B; Beau, J

    2001-06-01

    The relationship between performances on a simple discrimination task of the Attentional Set Shifting of the Cambridge Neuropsychological Test Auto mated Battery (CANTAB) and morphometry of the corpus callosum is examined in patients with Alzheimer's disease. Analysis showed patients with probable Alzheimer's disease are heterogeneous for the relationship between performances in the attentional test of the CANTAB and the anterior callosal atrophies. Interest in these results for clinical diagnosis of this mental disease is discussed. PMID:11565930

  11. Social communication in young children with traumatic brain injury: Relations with corpus callosum morphometry

    Microsoft Academic Search

    Linda Ewing-Cobbs; Mary R. Prasad; Paul Swank; Larry Kramer; Donna Mendez; Amery Treble; Christa Payne; Jocelyne Bachevalier

    The purpose of the present investigation was to characterize the relations of specific social communication behaviors, including joint attention, gestures, and verbalization, with surface area of midsagittal corpus callosum (CC) subregions in children who sustained traumatic brain injury (TBI) before 7 years of age. Participants sustained mild (n=10) or moderate–severe (n=26) noninflicted TBI. The mean age at injury was 33.6

  12. Altered corpus callosum morphology associated with autism over the first 2 years of life.

    PubMed

    Wolff, Jason J; Gerig, Guido; Lewis, John D; Soda, Takahiro; Styner, Martin A; Vachet, Clement; Botteron, Kelly N; Elison, Jed T; Dager, Stephen R; Estes, Annette M; Hazlett, Heather C; Schultz, Robert T; Zwaigenbaum, Lonnie; Piven, Joseph

    2015-07-01

    Numerous brain imaging studies indicate that the corpus callosum is smaller in older children and adults with autism spectrum disorder. However, there are no published studies examining the morphological development of this connective pathway in infants at-risk for the disorder. Magnetic resonance imaging data were collected from 270 infants at high familial risk for autism spectrum disorder and 108 low-risk controls at 6, 12 and 24 months of age, with 83% of infants contributing two or more data points. Fifty-seven children met criteria for ASD based on clinical-best estimate diagnosis at age 2 years. Corpora callosa were measured for area, length and thickness by automated segmentation. We found significantly increased corpus callosum area and thickness in children with autism spectrum disorder starting at 6 months of age. These differences were particularly robust in the anterior corpus callosum at the 6 and 12 month time points. Regression analysis indicated that radial diffusivity in this region, measured by diffusion tensor imaging, inversely predicted thickness. Measures of area and thickness in the first year of life were correlated with repetitive behaviours at age 2 years. In contrast to work from older children and adults, our findings suggest that the corpus callosum may be larger in infants who go on to develop autism spectrum disorder. This result was apparent with or without adjustment for total brain volume. Although we did not see a significant interaction between group and age, cross-sectional data indicated that area and thickness differences diminish by age 2 years. Regression data incorporating diffusion tensor imaging suggest that microstructural properties of callosal white matter, which includes myelination and axon composition, may explain group differences in morphology. PMID:25937563

  13. A novel locus on proximal chromosome 18 associated with agenesis of the corpus callosum in mice.

    PubMed

    Mizuno, Seiya; Mizobuchi, Atsushi; Iseki, Hiroyoshi; Iijima, Saori; Matsuda, Yoichi; Kunita, Satoshi; Sugiyama, Fumihiro; Yagami, Ken-ichi

    2010-12-01

    Agenesis of the corpus callosum (ACC) is a congenital abnormality of the brain structure. We have produced transgenic mice expressing both reverse tetracycline-controlled transactivator (rtTA) and transcriptional silencer (tTS) ubiquitously. Although the transgene products do not affect development of the mouse brain, one of the founder lines, TAS, showed ACC, suggesting transgenic disruption of endogenous gene(s). To identify the causative gene and its role in ACC, we performed pathological investigations of the brain and chromosomal mapping of foreign genes in TAS mice. Sixty-two percent of the heterozygous TAS mice showed ACC accompanied with formation of Probst bundles, as seen in human. Complete penetrance of ACC was observed in homozygous TAS mice. Furthermore, homozygous TAS fetuses revealed that ACC is a congenital anomaly. Moreover, axons of the corpus callosum were not repelled by the midline glial structures in TAS mice. These findings suggested that the causative gene for ACC is involved in critical steps in corpus callosum development. Multiple FISH analyses were performed to determine the site of transgene insertion. On 1-color FISH analyses, rtTA and tTS were detected on the A/B region of chromosome 18, suggesting cointegration of the transgenes. On 2-color FISH analyses, tTS signal was observed in a region from 9.3 to 16.9 Mb on chromosome 18. The TAS mice may serve as a useful model to identify a novel gene regulating corpus callosum development and to gain a new insight into molecular genetics of ACC. PMID:20967545

  14. Social and Behavioral Problems of Children with Agenesis of the Corpus Callosum

    Microsoft Academic Search

    Denise H. Badaruddin; Glena L. Andrews; Sven Bölte; Kathryn J. Schilmoeller; Gary Schilmoeller; Lynn K. Paul; Warren S. Brown

    2007-01-01

    Archival data from a survey of parent observations was used to determine the prevalence of social and behavioral problems\\u000a in children with agenesis of the corpus callosum (ACC). Parent observations were surveyed using the Child Behavior Checklist\\u000a (CBCL) for 61 children with ACC who were selected from the archive based on criteria of motor development suggesting a relatively\\u000a high general

  15. Clinical, genetic and imaging findings identify new causes for corpus callosum development syndromes

    PubMed Central

    Edwards, Timothy J.; Sherr, Elliott H.; Barkovich, A. James

    2014-01-01

    The corpus callosum is the largest fibre tract in the brain, connecting the two cerebral hemispheres, and thereby facilitating the integration of motor and sensory information from the two sides of the body as well as influencing higher cognition associated with executive function, social interaction and language. Agenesis of the corpus callosum is a common brain malformation that can occur either in isolation or in association with congenital syndromes. Understanding the causes of this condition will help improve our knowledge of the critical brain developmental mechanisms required for wiring the brain and provide potential avenues for therapies for callosal agenesis or related neurodevelopmental disorders. Improved genetic studies combined with mouse models and neuroimaging have rapidly expanded the diverse collection of copy number variations and single gene mutations associated with callosal agenesis. At the same time, advances in our understanding of the developmental mechanisms involved in corpus callosum formation have provided insights into the possible causes of these disorders. This review provides the first comprehensive classification of the clinical and genetic features of syndromes associated with callosal agenesis, and provides a genetic and developmental framework for the interpretation of future research that will guide the next advances in the field. PMID:24477430

  16. Agenesis of the corpus callosum associated with spinal open neural tube defect

    PubMed Central

    Elgamal, Essam A.; Elwatidy, Sherif M.; Alhabib, Amro F.; Jamjoom, Zain B.; Murshid, Waleed R.; Hassan, Hamdy H.; Salih, Mustafa A.

    2014-01-01

    Objective: To ascertain the incidence and clinical implications of agenesis of the corpus callosum (ACC) in spinal open neural tube defects (SONTD). Methods: All cases of SONTD registered at the Spina Bifida Clinic in King Khalid University Hospital, Riyadh, Saudi Arabia between 1995 and 2010 were retrospectively reviewed, and mid-sagittal MRI of the corpus callosum (CC) area was analyzed in each case. Neurodevelopmental outcome was classified as poor in children with seizures, severe neurodevelopmental impairment, or death. Results: Thirty-eight patients (45.8%) with ACC were identified among 83 cases with SONTD. Patients’ age ranged between one and 16 years. Total ACC was found in 10 patients, partial ACC in 25, and in 3 patients, the CC was hypoplastic. Active hydrocephalus was an associated finding in 9 out of 10 patients with total ACC, 22 out of 25 with partial ACC, and in all patients with hypoplasia of the CC. Thirteen patients (34.2%) had normal intellectual function, whereas 24 patients presented with learning disability, epilepsy, or poor intellectual function; and one patient died of respiratory failure. Conclusion: Agenesis of the corpus callosum is found in a significant portion of patients with SONTD. When associated with hydrocephalus, its presence affects neuro-developmental outcome. PMID:25551114

  17. Functional topography of the corpus callosum investigated by DTI and fMRI

    PubMed Central

    Fabri, Mara; Pierpaoli, Chiara; Barbaresi, Paolo; Polonara, Gabriele

    2014-01-01

    This short review examines the most recent functional studies of the topographic organization of the human corpus callosum, the main interhemispheric commissure. After a brief description of its anatomy, development, microstructure, and function, it examines and discusses the latest findings obtained using diffusion tensor imaging (DTI) and tractography (DTT) and functional magnetic resonance imaging (fMRI), three recently developed imaging techniques that have significantly expanded and refined our knowledge of the commissure. While DTI and DTT have been providing insights into its microstructure, integrity and level of myelination, fMRI has been the key technique in documenting the activation of white matter fibers, particularly in the corpus callosum. By combining DTT and fMRI it has been possible to describe the trajectory of the callosal fibers interconnecting the primary olfactory, gustatory, motor, somatic sensory, auditory and visual cortices at sites where the activation elicited by peripheral stimulation was detected by fMRI. These studies have demonstrated the presence of callosal fiber tracts that cross the commissure at the level of the genu, body, and splenium, at sites showing fMRI activation. Altogether such findings lend further support to the notion that the corpus callosum displays a functional topographic organization that can be explored with fMRI. PMID:25550994

  18. Atrophy of the corpus callosum associated with a decrease in cortical benzodiazepine receptor in large cerebral arterial occlusive diseases

    PubMed Central

    Yamauchi, H; Fukuyama, H; Dong, Y; Nabatame, H; Nagahama, Y; Nishizawa, S; Konishi, J; Shio, H

    2000-01-01

    OBJECTIVES—It remains controversial whether selective neuronal ischaemic change develops in patients with occlusion of the large cerebral arteries. Previous studies have shown atrophy of the corpus callosum with reduced cortical oxygen metabolism in large cerebral arterial occlusive diseases, which might be indirect evidence of loss of the neurons in cortical layer 3. Recent studies of patients with ischaemic cerebrovascular diseases have demonstrated reduced central benzodiazepine receptor (BZR) binding in the normal appearing cortical areas, which might be more direct evidence of changes of the neurons. Although pathophysiology of the decreased BZR is unclear, a decrease in the cortical BZR binding with neuronal loss would cause atrophy of the corpus callosum. The purpose of this study was to determine whether atrophy of the corpus callosum is associated with a decrease in cortical BZR binding in large cerebral arterial occlusive diseases.?METHODS—Seven patients with occlusive diseases of the middle cerebral or internal carotid artery and only minor subcortical infarctions were studied. Single photon emission tomographic images of 123I labelled iomazenil (IMZ) obtained 180 minutes after injection were analysed for BZR binding. The midsagittal corpus callosum area/skull area ratio (on T1 weighted magnetic resonance images) was compared with the cerebral IMZ uptake/cerebellar IMZ uptake ratio.?RESULTS—Compared with 23 age and sex matched control subjects, the patients had significantly decreased callosal area/skull area ratio. The degree of corpus callosum atrophy was significantly and strongly (?=0.99, p<0.02) correlated with that of the decreases in the mean cerebral cortical IMZ uptake ratio.?CONCLUSION—Corpus callosum atrophy may occur in association with a decrease in cortical BZR binding in large cerebral arterial occlusive diseases. Corpus callosum atrophy with decreased cortical BZR binding might reflect cortical neuronal damage in large cerebral arterial occlusive diseases.?? PMID:10675213

  19. Fun Fractions

    NSDL National Science Digital Library

    Ms. Terch

    2010-03-11

    Fractions mean that we are breaking up one thing into smaller things! See how you can do! Let's see How Fractions Work!! Let's make a flag using Flag Fractions. Let's try some more fractions with Fraction Blocks!! ...

  20. Corpus Callosum and Inferior Forebrain White Matter Microstructure Are Related to Functional Outcome from Raised Intracranial Pressure in Child Traumatic Brain Injury

    Microsoft Academic Search

    Robert C. Tasker; Amber Gunn Westland; Deborah K. White; Guy B. Williams

    2010-01-01

    In severe paediatric traumatic brain injury (TBI), a common focus of treatment is raised intracranial pressure (ICP). We have previously reported frontal cerebral vulnerability with executive deficits from raised ICP in paediatric TBI. Now, using diffusion tensor imaging (DTI) in a different population, we have examined fractional anisotropy (FA), and mean, axial and radial diffusivity (MD, AD, RD) in 4

  1. Automatic corpus callosum segmentation using a deformable active Fourier contour model.

    PubMed

    Vachet, Clement; Yvernault, Benjamin; Bhatt, Kshamta; Smith, Rachel G; Gerig, Guido; Hazlett, Heather Cody; Styner, Martin

    2012-03-23

    The corpus callosum (CC) is a structure of interest in many neuroimaging studies of neuro-developmental pathology such as autism. It plays an integral role in relaying sensory, motor and cognitive information from homologous regions in both hemispheres. We have developed a framework that allows automatic segmentation of the corpus callosum and its lobar subdivisions. Our approach employs constrained elastic deformation of flexible Fourier contour model, and is an extension of Szekely's 2D Fourier descriptor based Active Shape Model. The shape and appearance model, derived from a large mixed population of 150+ subjects, is described with complex Fourier descriptors in a principal component shape space. Using MNI space aligned T1w MRI data, the CC segmentation is initialized on the mid-sagittal plane using the tissue segmentation. A multi-step optimization strategy, with two constrained steps and a final unconstrained step, is then applied. If needed, interactive segmentation can be performed via contour repulsion points. Lobar connectivity based parcellation of the corpus callosum can finally be computed via the use of a probabilistic CC subdivision model. Our analysis framework has been integrated in an open-source, end-to-end application called CCSeg both with a command line and Qt-based graphical user interface (available on NITRC). A study has been performed to quantify the reliability of the semi-automatic segmentation on a small pediatric dataset. Using 5 subjects randomly segmented 3 times by two experts, the intra-class correlation coefficient showed a superb reliability (0.99). CCSeg is currently applied to a large longitudinal pediatric study of brain development in autism. PMID:24353382

  2. Automatic corpus callosum segmentation using a deformable active Fourier contour model

    NASA Astrophysics Data System (ADS)

    Vachet, Clement; Yvernault, Benjamin; Bhatt, Kshamta; Smith, Rachel G.; Gerig, Guido; Cody Hazlett, Heather; Styner, Martin

    2012-03-01

    The corpus callosum (CC) is a structure of interest in many neuroimaging studies of neuro-developmental pathology such as autism. It plays an integral role in relaying sensory, motor and cognitive information from homologous regions in both hemispheres. We have developed a framework that allows automatic segmentation of the corpus callosum and its lobar subdivisions. Our approach employs constrained elastic deformation of flexible Fourier contour model, and is an extension of Szekely's 2D Fourier descriptor based Active Shape Model. The shape and appearance model, derived from a large mixed population of 150+ subjects, is described with complex Fourier descriptors in a principal component shape space. Using MNI space aligned T1w MRI data, the CC segmentation is initialized on the mid-sagittal plane using the tissue segmentation. A multi-step optimization strategy, with two constrained steps and a final unconstrained step, is then applied. If needed, interactive segmentation can be performed via contour repulsion points. Lobar connectivity based parcellation of the corpus callosum can finally be computed via the use of a probabilistic CC subdivision model. Our analysis framework has been integrated in an open-source, end-to-end application called CCSeg both with a command line and Qt-based graphical user interface (available on NITRC). A study has been performed to quantify the reliability of the semi-automatic segmentation on a small pediatric dataset. Using 5 subjects randomly segmented 3 times by two experts, the intra-class correlation coefficient showed a superb reliability (0.99). CCSeg is currently applied to a large longitudinal pediatric study of brain development in autism.

  3. Cortical dysplasias, and corpus callosum and posterior fossa abnormalities: correlation of clinical findings with magnetic resonance imaging (MRI) characteristics.

    PubMed

    Caksen, Hüseyin; K?z?ly?ld?z, Baran Serdar; Avcu, Serhat

    2014-04-01

    This study examined clinical findings and magnetic resonance imaging (MRI) characteristics in 114 patients with cortical dysplasia and corpus callosum and posterior fossa abnormalities to determine the clinical findings with the extent of the lesions on MRI. The age of patients was between 1 day and 15 years. Group 1 included 74 patients with corpus callosum abnormalities and/or cortical dysplasias and group 2 included 40 patients with posterior fossa abnormalities, which were isolated and/or associated with cortical dysplasia and/or corpus callosum abnormalities. Although associated congenital abnormality apart from central nervous system abnormalities, syndrome, or systemic disorder were more common in group 2 than group 1 patients (P < .05), we did not find a difference between the groups for psychomotor retardation and epilepsy (P > .05). PMID:23589375

  4. Fantastic Fractions

    NSDL National Science Digital Library

    Ms. Cate

    2008-04-12

    Play these games to practice your knowledge of fractions! Have fun! Travel to Ancient Egypt with the Fraction Cats to practice adding fractions. Follow this link toAdd like fractions using circles Practice your estimation and Find Grampy ...

  5. Early-life stress, corpus callosum development, hippocampal volumetrics, and anxious behavior in male nonhuman primates.

    PubMed

    Jackowski, Andrea; Perera, Tarique D; Abdallah, Chadi G; Garrido, Griselda; Tang, Cheuk Y; Martinez, Jose; Mathew, Sanjay J; Gorman, Jack M; Rosenblum, Leonard A; Smith, Eric L P; Dwork, Andrew J; Shungu, Dikoma C; Kaffman, Arie; Gelernter, Joel; Coplan, Jeremy D; Kaufman, Joan

    2011-04-30

    Male bonnet monkeys (Macaca radiata) were subjected to the variable foraging demand (VFD) early stress paradigm as infants, MRI scans were completed an average of 4 years later, and behavioral assessments of anxiety and ex-vivo corpus callosum (CC) measurements were made when animals were fully matured. VFD rearing was associated with smaller CC size, CC measurements were found to correlate with fearful behavior in adulthood, and ex-vivo CC assessments showed high consistency with earlier MRI measures. Region of interest (ROI) hippocampus and whole brain voxel-based morphometry assessments were also completed and VFD rearing was associated with reduced hippocampus and inferior and middle temporal gyri volumes. The animals were also characterized according to serotonin transporter genotype (5-HTTLPR), and the effect of genotype on imaging parameters was explored. The current findings highlight the importance of future research to better understand the effects of stress on brain development in multiple regions, including the corpus callosum, hippocampus, and other regions involved in emotion processing. Nonhuman primates provide a powerful model to unravel the mechanisms by which early stress and genetic makeup interact to produce long-term changes in brain development, stress reactivity, and risk for psychiatric disorders. PMID:21377844

  6. Early-life stress, corpus callosum development, hippocampal volumetrics, and anxious behavior in male nonhuman primates

    PubMed Central

    Jackowski, Andrea; Perera, Tarique D.; Abdallah, Chadi G.; Garrido, Griselda; Tang, Cheuk Y.; Martinez, Jose; Mathew, Sanjay J.; Gorman, Jack M.; Rosenblum, Leonard A.; Smith, Eric L.P.; Dwork, Andrew J.; Shungu, Dikoma C.; Kaffman, Arie; Gelernter, Joel; Coplan, Jeremy D.; Kaufman, Joan

    2014-01-01

    Male bonnet monkeys (Macaca radiata) were subjected to the Variable Foraging Demand (VFD) early stress paradigm as infants, MRI scans were completed an average of four years later, and behavioral assessments of anxiety and ex-vivo corpus callosum (CC) measurements were made when animals were fully matured. VFD rearing was associated with smaller CC size, CC measurements were found to correlate with fearful behavior in adulthood, and ex-vivo CC assessments showed high consistency with earlier MRI measures. Region of Interest (ROI) hippocampus and whole brain voxel- based morphometry assessments were also completed and VFD rearing was associated with reduced hippocampus and inferior and middle temporal gyri volumes. Animals were also characterized according to serotonin transporter genotype (5-HTTLPR), and the effect of genotype on imaging parameters was explored. The current findings highlight the importance of future research to better understand the effects of stress on brain development in multiple regions, including the corpus callosum, hippocampus, and other regions involved in emotion processing. Nonhuman primates provide a powerful model to unravel the mechanisms by which early stress and genetic makeup interact to produce long-term changes in brain development, stress reactivity, and risk for psychiatric disorders. PMID:21377844

  7. Transient lesion in the splenium of the corpus callosum due to rotavirus infection.

    PubMed

    Mazur-Melewska, Katarzyna; Jonczyk-Potoczna, Katarzyna; Szpura, Krystyna; Biega?ski, Grzegorz; Mania, Anna; Kemnitz, Pawe?; S?u?ewski, Wojciech; Figlerowicz, Magdalena

    2015-06-01

    Transient signal changes in magnetic resonance imaging (MRI) of the splenium of the corpus callosum (SCC) can result from many different reasons, including encephalitis and encephalopathy caused by infection, seizures, metabolic disorders and asphyxia. We report a case of a 6-year-old Polish girl with rotavirus infection demonstrating a reversible SCC lesion on diffusion-weighted MRI images. She presented six episodes of generalized tonic seizures with mild acute gastroenteritis. Stool test for rotavirus antigen was positive. At the time of admission imaging showed the hyperintense region in T2-weighted and fluid-attenuated inversion-recovery MRI, a well-defined lesion in the splenium of the corpus callosum with restricted diffusion in diffusion-weighted MRI and no enhancement in post contrast T1-weighted imaging. Her first EEG showed slow brain activity in the posterior occipitotemporal portion, consisting mainly of theta waves with a frequency of 4.5-5.5 Hz and amplitude of 40 uV. The lesion had completely disappeared on follow-up MRI 10 days later. The patient recovered fully without any sequelae. PMID:25686898

  8. Peritrigonal and temporo-occipital heterotopia with corpus callosum and cerebellar dysgenesis

    PubMed Central

    Pisano, Tiziana; Barkovich, A. James; Leventer, Richard J.; Squier, Waney; Scheffer, Ingrid E.; Parrini, Elena; Blaser, Susan; Marini, Carla; Robertson, Stephen; Tortorella, Gaetano; Rosenow, Felix; Thomas, Pierre; McGillivray, George; Andermann, Eva; Andermann, Frederick; Berkovic, Samuel F.; Dobyns, William B.

    2012-01-01

    Objective: To describe a homogeneous subtype of periventricular nodular heterotopia (PNH) as part of a newly defined malformation complex. Methods: Observational study including review of brain MRI and clinical findings of a cohort of 50 patients with PNH in the temporo-occipital horns and trigones, mutation analysis of the FLNA gene, and anatomopathologic study of a fetal brain. Results: There were 28 females and 22 males. All were sporadic with the exception of an affected mother and son. Epilepsy occurred in 62%, cerebellar signs in 56%, cognitive impairment in 56%, and autism in 12%. Seventy percent were referred within the 3rd year of life. Imaging revealed a normal cerebral cortex in 76% and abnormal cortical folding in 24%. In all patients the hippocampi were under-rotated and in 10% they merged with the heterotopia. Cerebellar dysgenesis was observed in 84% and a hypoplastic corpus callosum in 60%. There was no gender bias or uneven gender distribution of clinical and anatomic severity. No mutations of FLNA occurred in 33 individuals examined. Heterotopia in the fetal brain revealed cytoarchitectonic characteristics similar to those associated with FLNA mutations; cortical pathology was not typical of polymicrogyria. Cerebellar involvement was more severe and the hippocampi appeared simple and under-rotated. Conclusions: This series delineates a malformation complex in which PNH in the trigones and occipito-temporal horns is associated with hippocampal, corpus callosum, and cerebellar dysgenesis. This subtype of PNH is distinct from classic PNH caused by FLNA mutations. PMID:22914838

  9. Shape analysis of corpus callosum in autism subtype using planar conformal mapping

    NASA Astrophysics Data System (ADS)

    He, Qing; Duan, Ye; Yin, Xiaotian; Gu, Xianfeng; Karsch, Kevin; Miles, Judith

    2009-02-01

    A number of studies have documented that autism has a neurobiological basis, but the anatomical extent of these neurobiological abnormalities is largely unknown. In this study, we aimed at analyzing highly localized shape abnormalities of the corpus callosum in a homogeneous group of autism children. Thirty patients with essential autism and twenty-four controls participated in this study. 2D contours of the corpus callosum were extracted from MR images by a semiautomatic segmentation method, and the 3D model was constructed by stacking the contours. The resulting 3D model had two openings at the ends, thus a new conformal parameterization for high genus surfaces was applied in our shape analysis work, which mapped each surface onto a planar domain. Surface matching among different individual meshes was achieved by re-triangulating each mesh according to a template surface. Statistical shape analysis was used to compare the 3D shapes point by point between patients with autism and their controls. The results revealed significant abnormalities in the anterior most and anterior body in essential autism group.

  10. Fractions 1

    NSDL National Science Digital Library

    Mrs. Taylor

    2010-09-28

    This lesson is a review of fractions. dsd video 1. Start at the district web page 2. Go to My DSD 3. Click on OnDemand 4. In the custom search box, type "fractions" 5. Watch the "Fun with Fractions, Math all Around us" video. Visual Fractions Follow this link to explore fractions. Click on "Identify Fractions". Work on identifying fractions with lines until you have done at ...

  11. Fraction Review

    NSDL National Science Digital Library

    Mrs. Benson

    2010-01-26

    Review fraction concepts by playing games on any 3 of the following websites. When you're done write down the names of the games you played on a piece of paper and hand it in to the math box. Equivalent fractions Find fractional parts of a set Cross the River by matching fractions to pictures Fraction Practice (choose equivalent fractions please) matching fractions to pictures ...

  12. Configurational Anisotropy in Nanomagnets

    Microsoft Academic Search

    R. P. Cowburn; A. O. Adeyeye; M. E. Welland

    1998-01-01

    A novel magneto-optical method has been used to probe the internal magnetic energy surface in 150×150×15 nm3 square Ni80Fe14Mo5 (``supermalloy'') nanomagnets which were fabricated by electron beam lithography. A strong fourfold symmetric anisotropy field of strength 365+\\/-20 Oe is found, which confirms a recent prediction of the appearance of a configurational anisotropy due to the small deviations of the magnetization

  13. Configurational Anisotropy in Nanomagnets

    NASA Astrophysics Data System (ADS)

    Cowburn, R. P.; Adeyeye, A. O.; Welland, M. E.

    1998-12-01

    A novel magneto-optical method has been used to probe the internal magnetic energy surface in 150×150×15 nm3 square Ni80Fe14Mo5 (``supermalloy'') nanomagnets which were fabricated by electron beam lithography. A strong fourfold symmetric anisotropy field of strength 365+/-20 Oe is found, which confirms a recent prediction of the appearance of a configurational anisotropy due to the small deviations of the magnetization from the uniform state.

  14. Many Infants Prenatally Exposed to High Levels of Alcohol Show One Particular Anomaly of the Corpus Callosum

    Microsoft Academic Search

    Fred L. Bookstein; Paul D. Connor; Janet E. Huggins; Helen M. Barr; Kristi D. Pimentel; Ann P. Streissguth

    2007-01-01

    Introduction: Effects of prenatal alcohol exposure on the brain are seen at every age. The earlier they can be quantified, the better the prognosis for the affected child. Here we show measurable alcohol effects at birth on a structure currently used for nosology only much later in life. Methods: Midline shape of the corpus callosum was imaged in infants via

  15. Functional Analysis of Genes Implicated in Down Syndrome: 2. Laterality and Corpus Callosum Size in Mice Transpolygenic

    E-print Network

    Smith, Desmond J.

    Functional Analysis of Genes Implicated in Down Syndrome: 2. Laterality and Corpus Callosum Size in Mice Transpolygenic for Down Syndrome Chromosomal Region )1 (DCR-1) Pierre L. Roubertoux,1,3,7 Zoe in Down syndrome (DS). We investigated common genetic correlates of these components of the syndrome

  16. Equivalent Fractions

    NSDL National Science Digital Library

    Miss Ogle

    2012-04-05

    What is an equivalent fraction? Students, I want you to create song about fractions. Here is a fraction song video to help you get and idea. Remember your song should be at least five sentences long. Math Song- Equivalent Fractions Students, I want you to click on the website below and the play the fraction game. Let's see how many ...

  17. Fraction Finder

    NSDL National Science Digital Library

    2010-01-01

    In this activity, you will graphically determine the value of two given fractions represented as points on a number line. You will then graphically find a fraction whose value is between the two given fractions and determine its value.

  18. Fraction Sorter

    NSDL National Science Digital Library

    Visualize fractions by coloring in the appropriate portions of either a circle or a square, then order those fractions from least to greatest. Fraction Sorter is one of the Interactivate assessment explorers.

  19. Aging and the myelinated fibers in prefrontal cortex and corpus callosum of the monkey.

    PubMed

    Peters, Alan; Sethares, Claire

    2002-01-14

    In the rhesus monkey, the myelin sheaths of nerve fibers in area 46 of prefrontal cortex and in splenium of the corpus callosum show age-related alterations in their structure. The alterations are of four basic types. Most common is splitting of the dense line of myelin sheaths to accommodate electron dense cytoplasm derived from the oligodendroglia. Less common are splits of the intraperiod line to form balloons or blisters that appear to contain fluid, the occurrence of sheaths with redundant myelin, and thick sheaths that are almost completely split so that one set of compact lamellae is surrounded by another set. But despite these alterations in the sheaths, few nerve fibers show axonal degeneration. To quantify the frequency of the age-related alterations in myelin, transversely sectioned nerve fibers from the splenium of the corpus callosum and from the vertical bundles of nerve fibers within area 46 were examined in electron photomicrographs. The material was taken from 19 monkeys, ranging between 5 and 35 years of age. It was found that the frequency of alterations in myelin sheaths from both locations correlates significantly with age. In area 46, the age-related alterations also significantly correlate (P < 0.001) with an overall assessment of impairment in cognition, i.e., the cognitive impairment index, displayed by individual monkeys. The correlation is also significant when only the old monkeys are considered as a group. A similar result was obtained previously in our examination of the effects of age on the myelin sheaths of nerve fibers in primary visual cortex (Peters et al. [2000] J Comp Neurol. 419:364-376). However, in the corpus callosum the myelin alterations correlate significantly with only one component of the cognitive impairment index, namely the delayed nonmatching to sample task with a 2-minute delay. It is proposed that age-related myelin alterations are ubiquitous and that the correlations between their frequency and impairments in cognition occur because the conduction velocity along the affected nerve fibers is reduced, so that the normal timing sequences within neuronal circuits break down. PMID:11774342

  20. Fantastic Fractions

    NSDL National Science Digital Library

    Ms. Covey

    2010-04-14

    Here you will practice will equivalent fractions and making wholes out of different fraction pieces. First take the clients order and figure out how to make a whole pizza for the customer. Making a whole pizza! Next match up all the equivalent fractions on your virtual board. Matching equivalent fractions Last shoot the correct equivalent fraction in space to earn points. Shoot the equivalent fraction in SPACE! ...

  1. Magnetic anisotropy of chloritoid

    NASA Astrophysics Data System (ADS)

    Haerinck, Tom; Debacker, Timothy N.; Sintubin, Manuel

    2013-08-01

    The magnetocrystalline anisotropy of monoclinic chloritoid, a relatively common mineral in aluminum-rich, metapelitic rocks, has been determined for the first time by measuring the high-field anisotropy of magnetic susceptibility (HF-AMS), using two independent approaches, i.e., (a) directional magnetic hysteresis measurements and (b) torque magnetometry, on a collection of single crystals collected from different tectonometamorphic settings worldwide. Magnetic remanence experiments show that all specimens contain ferromagnetic (s.l.) impurities, being mainly magnetite. The determined HF-AMS ellipsoids have a highly oblate shape with the minimum susceptibility direction subparallel to the crystallographic c-axis of chloritoid. In the basal plane of chloritoid, though the HF-AMS can be considered isotropic. The degree of anisotropy is found to be 1.47, which is significantly higher than the anisotropy of most paramagnetic silicates and even well above the frequently used upper limit (i.e., 1.35) for the paramagnetic contribution to the AMS of siliciclastic rocks. The obtained values for the paramagnetic Curie temperature parallel (??) and perpendicular (??) to the basal plane indicate that this pronounced magnetocrystalline anisotropy is related to strong antiferromagnetic exchange interactions in the direction of the crystallographic c-axis (?? < 0) and rather weak ferromagnetic exchange interactions within the basal plane (?? > 0). As a consequence, chloritoid-bearing metapelites with a pronounced mineral alignment can have a high degree of anisotropy without the need of invoking a significant contribution of strongly anisotropic, ferromagnetic (s.l.) minerals. The newly discovered magnetocrystalline anisotropy of chloritoid thus calls for a revised approach of magnetic fabric interpretations in chloritoid-bearing rocks.

  2. Neonatal transection of the corpus callosum affects paw preference lateralization of adult Swiss mice.

    PubMed

    Manhães, Alex C; Krahe, Thomas E; Caparelli-Dáquer, Egas; Ribeiro-Carvalho, Anderson; Schmidt, Sergio L; Filgueiras, Cláudio C

    2003-09-11

    In the present work, the hypothesis that the ontogenetic development of the corpus callosum (CC) affects the establishment of behavioral lateralization was tested by studying paw preference performance in adult Swiss mice that were subjected to mid-sagittal transection of the CC on the first postnatal day. Magnitude and direction of laterality were evaluated independently. No significant differences between groups were found for the magnitude of paw preference. On the other hand, the transected group presented a significant populational bias favoring the left paw that was not present in the control groups. These results lend support to the hypothesis that the development of the CC plays a role in the establishment of the normal pattern of behavioral lateralization. PMID:12902020

  3. The Association between Handedness, Brain Asymmetries, and Corpus Callosum Size in Chimpanzees (Pan troglodytes)

    PubMed Central

    Dunham, Leslie; Cantalupo, Claudio; Taglialatela, Jared

    2007-01-01

    It has been suggested from studies in human subjects that sex, handedness, and brain asymmetries influence variation in corpus callosum (CC) size and these differences reflect the degree of connectivity between homotopic regions of the left and right cerebral hemispheres. Here we report that handedness is associated with variation in the size of the CC in chimpanzees. We further report that variation in brain asymmetries in a cortical region homologous to Broca's area is associated with the size of the CC but differs for right- and left-handed individuals. Collectively, the results suggest that individual differences in functional and neuroanatomical asymmetries are associated with CC variation not just in humans but also in chimpanzees and therefore may reflect a common neural basis for laterality in these 2 species. PMID:17012376

  4. Relationship between attentional performance and corpus callosum morphometry in patients with Alzheimer's disease.

    PubMed

    Dorion, Agnès A; Sarazin, Marie; Hasboun, Dominique; Hahn-Barma, Valerie; Dubois, Bruno; Zouaoui, Adberrezak; Marsault, Claude; Duyme, Michel

    2002-01-01

    There has been considerable interest in cognitive deficits associated with Alzheimer's disease (AD) and relationships between these impairments and specific cortical atrophies. Two previous studies [Neuropsychologia 28 (1990) 1197; Dementia 3 (1992) 350] have found that AD patients exhibit significant impairments in the attentional ID/ED set-shifting tasks of the CANTAB battery which involved attentional shifting abilities. But, at present, no study has examined the neural bases of these abilities in AD patients. In the present study, the relationship between performances on this attentional test and morphometry of the anterior and posterior corpus callosum is examined in AD patients in the mild to moderate stages of the disease (n=30, mean age=74.1+/-4.9 years, mean MMSE score=23.9+/-2.6). A control group is constituted (n=20, mean age=73.15+/-5.5 years) for comparison of cerebral measurements. The stepwise multiple regression analysis indicates that the relative contribution for the total callosal and the anterior CC areas of the simple discrimination subtest is significantly positive whereas for the posterior callosal areas the relative contribution of the more complex subtest is significantly positive. AD patients from the subgroup "low", who failed to do the nine subtests of the attentional set-shifting tasks, exhibit smaller callosal areas than control subjects. There is no significant difference for all callosal measurements between AD patients from the subgroup "high", who completely succeeded the test, and control subjects. Our findings suggest that the anterior corpus callosum would be related to attentional shifting abilities in AD patients. Moreover, these patients with probable AD seem heterogeneous for performances in the attentional test of the CANTAB and for callosal atrophies. PMID:11900746

  5. When more is less: associations between corpus callosum size and handedness lateralization

    PubMed Central

    Luders, Eileen; Cherbuin, Nicolas; Thompson, Paul M.; Gutman, Boris; Anstey, Kaarin J.; Sachdev, Perminder; Toga, Arthur W.

    2010-01-01

    Although not consistently replicated, a substantial number of studies suggest that left-handers have larger callosal regions than right-handers. We challenge this notion and propose that callosal size is not linked to left-handedness or right-handedness per se but to the degree of handedness lateralization. To test this hypothesis, we investigated the thickness of the corpus callosum in a large data set (n=361). We analyzed the correlations between callosal thickness and the degree of handedness lateralization in 324 right-handers and 37 left-handers at 100 equidistant points across the corpus callosum. We revealed significant negative correlations within the anterior and posterior midbody suggesting that larger callosal dimensions in these regions are associated with a weaker handedness lateralization. Significant positive correlations were completely absent. In addition, we compared callosal thickness between moderately lateralized left-handers (n=37) and three equally sized groups (n=37) of right-handers (strongly, moderately, and weakly lateralized). The outcomes of these group analyses confirmed the negative association between callosal size and handedness lateralization, although callosal differences between right- and left-handers did not reach statistical significance. This suggests that callosal differences are rather small, if examined as a dichotomy between two handedness groups. Future studies will expand this line of research by increasing the number of left-handers to boost statistical power, and by combining macro- and micro-structural, as well as functional and behavioral measurements to identify the biological mechanisms linking callosal morphology and handedness lateralization. PMID:20394828

  6. Multiplying Fractions

    NSDL National Science Digital Library

    J.C. Banfill

    2007-12-12

    This site gives a description of how to multiply fractions and gives a sample problem in which the numerators and denominators are multiplied and the resulting fraction is simplified. It also includes the same problem solved by 'canceling' the fractions to simplify, and completing the process. There is also a game for students to practice their new skill of multiplying and simplifying fractions.

  7. Equivalent Fractions

    NSDL National Science Digital Library

    Alabama Learning Exchange (alex)

    2009-03-23

    "This lesson helps students discover how to obtain equal fractions by using both fraction strips and playing a fraction matching game. Students will learn that to obtain equal fractions they may multiply the numerator and denominator by the same number." (from ALEX - Alabama Learning Exchange)

  8. Visual Fractions

    NSDL National Science Digital Library

    Visual Fractions is "a tutorial that offers instruction and practice in identifying, renaming, and operating on fractions" and was created by Richard E. Rand. The website reviews examples of fractions, which are modeled with number lines or circles. Throughout the website are instructions to follow, encouraging students to try a few activities on their own. For a more light-hearted approach, Rand has a game that involves using fractions to help Grammy find Grampy and to make treats for Grampy. The software programs used to create the line and circle fractions, Fraction Modeler and Fraction Maker, are available for purchase and described on this website.

  9. Ribbon Fractions

    NSDL National Science Digital Library

    2009-01-01

    This interactive applet helps develop the concept of fractions as equal parts of a whole unit. Students estimate common unit fractions of a "ribbon" length and duplicate them to check accuracy. Then they extend this technique to explore the relationship of unit fractions with non-unit fractions and mixed numbers, to find the whole from a given fractional portion, and finally to use shorter ribbon pieces to measure longer ones. The Control Room allows teachers to customize several parameters.

  10. Killing vectors and anisotropy

    E-print Network

    J. P. Krisch; E. N. Glass

    2009-08-03

    We consider an action that can generate fluids with three unequal stresses for metrics with a spacelike Killing vector. The parameters in the action are directly related to the stress anisotropies. The field equations following from the action are applied to an anisotropic cosmological expansion and an extension of the Gott-Hiscock cosmic string.

  11. Killing vectors and anisotropy

    SciTech Connect

    Krisch, J. P.; Glass, E. N. [Department of Physics, University of Michigan, Ann Arbor, Michigan 48109 (United States)

    2009-08-15

    We consider an action that can generate fluids with three unequal stresses for metrics with a spacelike Killing vector. The parameters in the action are directly related to the stress anisotropies. The field equations following from the action are applied to an anisotropic cosmological expansion and an extension of the Gott-Hiscock cosmic string.

  12. MAGNETOCRYSTALLINE ANISOTROPY OF GADOLINIUM

    Microsoft Academic Search

    C. D. Graham; C. D. Jr

    1962-01-01

    Torque measurements on single crystals of Gd (hexagonal structure) are ; made at 10 to 350 deg K and at magnetic fields up to 20 kOe, and Fourier analysis ; of the measured torque curves is used to determine the anisotropy constants. ; (T.F.H.);

  13. Magnetic anisotropy of chloritoid

    NASA Astrophysics Data System (ADS)

    Haerinck, Tom; Debacker, Timothy; Sintubin, Manuel

    2013-04-01

    The anisotropy of magnetic susceptibility (AMS) is commonly used as a petrofabric tool. Whereas qualitative relationships between AMS and the petrofabric are well established, quantitative correlations are often ambiguous. For a quantitative interpretation of the paramagnetic component of a rock's AMS, the mineral source(s) of the paramagnetic fabric and their intrinsic contribution(s) should be understood. This requires knowledge about the intrinsic AMS of the rock-forming, paramagnetic minerals. For this study, the magnetocrystalline anisotropy of monoclinic chloritoid, a relatively common mineral in aluminium-rich, metapelitic rocks, has been determined for the first time by measuring the high-field anisotropy of magnetic susceptibility (HF-AMS) on a collection of single crystals, collected from different tectonometamorphic settings worldwide. Magnetic remanence experiments, i.e. (a) alternating-field (AF) demagnetization of a 1 T isothermal remanent magnetization (IRM) and a 200 mT anhysteretic remanent magnetization (ARM) and (b) low-temperature cycling of a room temperature saturation isothermal remanent magnetization (RT-SIRM), show that all specimens contain ferromagnetic (s.l.) impurities, being mainly magnetite. The determined HF-AMS ellipsoids have a highly oblate shape with the minimum susceptibility direction subparallel to the crystallographic c-axis of chloritoid. In the basal plane of chloritoid, however, the HF-AMS can be considered isotropic. The paramagnetic Curie temperature (?), which has been determined parallel and perpendicular to the basal plane, indicates a weak antiferromagnetic interaction in the direction of the crystallographic c-axis and a ferromagnetic interaction within the basal plane. The degree of anisotropy is found to be 1.48, which is significantly higher than the anisotropy of most paramagnetic silicates, i.e. the Fe-bearing phyllosilicates and the mafic silicates pyroxene, orthopyroxene, amphibole and olive, and even well above the frequently used upper limit (i.e. 1.35) for the paramagnetic contribution to AMS in siliciclastic rocks. As a consequence, chloritoid-bearing metapelites with a pronounced mineral alignment can have a higher degree of anisotropy than expected, without a significant contribution of strongly anisotropic, ferromagnetic (s.l.) minerals. The newly discovered magnetocrystalline anisotropy of chloritoid thus calls for a revised approach of magnetic fabric interpretations in chloritoid-bearing rocks.

  14. Hereditary spastic paraplegia with mental impairment and thin corpus callosum in Tunisia: SPG11, SPG15 and further genetic heterogeneity.

    E-print Network

    Paris-Sud XI, Université de

    Hereditary spastic paraplegia with mental impairment and thin corpus callosum in Tunisia: SPG11 of Neurology, Habib Bourguiba University Hospital, Sfax, Tunisia (A.Bo., I.F., N.E., M.I.M, C.M.), the Faculté de Médecine de Sfax, Tunisia (A.Bo., I.F., N.E., M.I.M, C.M.), the INSERM, U679, Paris, France (A

  15. Effects of Severing the Corpus Callosum on Electrical and BOLD Functional Connectivity and Spontaneous Dynamic Activity in the Rat Brain

    PubMed Central

    Magnuson, Matthew E.; Thompson, Garth J.; Pan, Wen-Ju

    2014-01-01

    Abstract Functional networks, defined by synchronous spontaneous blood oxygenation level-dependent (BOLD) oscillations between spatially distinct brain regions, appear to be essential to brain function and have been implicated in disease states, cognitive capacity, and sensing and motor processes. While the topographical extent and behavioral function of these networks has been extensively investigated, the neural functions that create and maintain these synchronizations remain mysterious. In this work callosotomized rodents are examined, providing a unique platform for evaluating the influence of structural connectivity via the corpus callosum on bilateral resting state functional connectivity. Two experimental groups were assessed, a full callosotomy group, in which the corpus callosum was completely sectioned, and a sham callosotomy group, in which the gray matter was sectioned but the corpus callosum remained intact. Results indicated a significant reduction in interhemispheric connectivity in the full callosotomy group as compared with the sham group in primary somatosensory cortex and caudate-putamen regions. Similarly, electrophysiology revealed significantly reduced bilateral correlation in band limited power. Bilateral gamma Band-limited power connectivity was most strongly affected by the full callosotomy procedure. This work represents a robust finding indicating the corpus callosum's influence on maintaining integrity in bilateral functional networks; further, functional magnetic resonance imaging (fMRI) and electrophysiological connectivity share a similar decrease in connectivity as a result of the callosotomy, suggesting that fMRI-measured functional connectivity reflects underlying changes in large-scale coordinated electrical activity. Finally, spatiotemporal dynamic patterns were evaluated in both groups; the full callosotomy rodents displayed a striking loss of bilaterally synchronous propagating waves of cortical activity. PMID:24117343

  16. Macroscopic model with anisotropy based on micro-macro informations

    E-print Network

    Luding, Stefan

    and deviatoric fabric (anisotropy) for an independent undrained cyclic shear test, including the response characterize the elastic response of granular materials in terms of macro- scopic state-variables, namely volume (packing) fraction and stress, while the microstructure is not accessible and thus neglected. Here

  17. Rod Fractions

    NSDL National Science Digital Library

    This problem allows students an opportunity to think about fraction comparisons and equivalencies in a different way using interactive rods. Students are given two different fraction rods of unknown lengths and the goal is to find out what fraction the shorter rod is of the longer rod. A Teacher's Notes page, hints, solution, and printable pages are provided.

  18. Fraction Action

    NSDL National Science Digital Library

    Miss Broadhead

    2008-03-26

    Get into action and play with fractions! Practice your fractions with this website first: Learn Yo Fractions. Read the directions! The \\"Start\\" is at the top of the page. Now, same rules, but you have to find Grampy. Find him here: Find Grampy! Want another challenge? Now the scientist Melvin needs help with his mixed-up potions! ...

  19. Elastic Anisotropy of Basalt

    NASA Astrophysics Data System (ADS)

    Becker, K.; Shapiro, S.; Stanchits, S.; Dresen, G.; Kaselow, A.; Vinciguerra, S.

    2005-12-01

    Elastic properties of rocks are sensitive to changes of the in-situ stress and damage state. In particular, seismic velocities are strongly affected by stress-induced formation and deformation of cracks or shear-enhanced pore collapse. The effect of stress on seismic velocities as a result of pore space deformation in isotropic rock at isostatic compression may be expressed by the equation: A+K*P-B*exp (-D*P) (1), where P=Pc-Pp is the effective pressure, the pure difference between confining pressure and pore pressure. The parameter A, K, B and D describe material constants determined using experimental data. The physical meaning of the parameters is given by Shapiro (2003, in Geophysics Vol.68(Nr.2)). Parameter D is related to the stress sensitivity of the rock. A similar relation was derived by Shapiro and Kaselow (2005, in Geophysics in press) for weak anisotropic rocks under arbitrary load. They describe the stress dependent anisotropy in terms of Thomson's (1986, in Geophysics, Vol. 51(Nr.10)) anisotropy parameters ? and ? as a function of stress in the case of an initially isotropic rock: ? ? E2-E3, ? ? E3-E2 (2) with Ei=exp (D*Pi). The exponential terms Ei are controlled by the effective stress components Pi. To test this relation, we have conducted a series of triaxial compression tests on dry samples of initially isotropic Etnean Basalt in a servo-controlled MTS loading frame equipped with a pressure cell. Confining pressure was 60, 40 and 20 MPa. Samples were 5 cm in diameter and 10 cm in length. Elastic anisotropy was induced by axial compression of the samples through opening and growth of microcracks predominantly oriented parallel to the sample axis. Ultrasonic P- and S- wave velocities were monitored parallel and normal to the sample axis by an array of 20 piezoceramic transducers glued to the surface. Preamplified full waveform signals were stored in two 12 channel transient recorders. According to equation 2 the anisotropy parameters are linear functions of the stress exponents. In order to verify the linear dependence of ? and ? from the stress exponents, these exponents and the anisotropy parameters based on the measured velocities have been computed. Parameter D was found from fitting equation 1 to the experimental data. Our experimental results are in an excellent agreement with a linear relation between the exponential terms and the seismic anisotropy parameters as theoretically predicted by equation 2.

  20. The Fractionator

    NSDL National Science Digital Library

    Jeff LeMieux

    2007-12-12

    Created by math teacher Jeff LeMieux, the Fractionator offers hands-on tools to help students develop an understanding of fractions. The online tools model two fractions to be added (or subtracted) based on unit squares and then creates equivalent fraction models, allowing students to solve the problem. Two of the online demonstrations show a unique problem each time a new problem is requested, while a third tool allows students themselves to enter the two fractions. Also provided are links to printable materials, such as overhead transparencies and student worksheets.

  1. Magnetocrystalline anisotropy of magnetite.

    PubMed

    ?ezní?ek, R; Chlan, V; Št?pánková, H; Novák, P; Maryško, M

    2012-02-01

    The spin reorientation temperature T(SR) of stoichiometric Fe(3)O(4), as well as of magnetite with a small number of vacancies and magnetite containing a low concentration of Ti, Zn, Al and Ga was measured on single-crystal samples using the ac susceptibility. In the same experiment the temperature T(V) of the Verwey transition was also found. The results show that a correlation between T(SR) and T(V) exists. The electronic structure of the compounds studied was determined using the density-functional-based GGA + U method. For stoichiometric magnetite the first and second cubic anisotropy constants were calculated, while for magnetite with defects the distribution of electron density using the 'atoms in molecules' approach was determined. Based on a combination of experimental results with the electronic structure calculations an explanation of the temperature dependence of the magnetocrystalline anisotropy of magnetite is suggested. PMID:22227433

  2. Splenium of Corpus Callosum: Patterns of Interhemispheric Interaction in Children and Adults

    PubMed Central

    Knyazeva, Maria G.

    2013-01-01

    The splenium of the corpus callosum connects the posterior cortices with fibers varying in size from thin late-myelinating axons in the anterior part, predominantly connecting parietal and temporal areas, to thick early-myelinating fibers in the posterior part, linking primary and secondary visual areas. In the adult human brain, the function of the splenium in a given area is defined by the specialization of the area and implemented via excitation and/or suppression of the contralateral homotopic and heterotopic areas at the same or different level of visual hierarchy. These mechanisms are facilitated by interhemispheric synchronization of oscillatory activity, also supported by the splenium. In postnatal ontogenesis, structural MRI reveals a protracted formation of the splenium during the first two decades of human life. In doing so, the slow myelination of the splenium correlates with the formation of interhemispheric excitatory influences in the extrastriate areas and the EEG synchronization, while the gradual increase of inhibitory effects in the striate cortex is linked to the local inhibitory circuitry. Reshaping interactions between interhemispherically distributed networks under various perceptual contexts allows sparsification of responses to superfluous information from the visual environment, leading to a reduction of metabolic and structural redundancy in a child's brain. PMID:23577273

  3. Corpus callosum anatomy in right-handed homosexual and heterosexual men.

    PubMed

    Witelson, Sandra F; Kigar, Debra L; Scamvougeras, Anton; Kideckel, David M; Buck, Brian; Stanchev, Peter L; Bronskill, Michael; Black, Sandra

    2008-12-01

    The results of several studies have shown that homosexual men have an increased prevalence of non-right-handedness and atypical patterns of hemispheric functional asymmetry. Non-right-handedness in men has been associated with increased size of the corpus callosum (CC), particularly of the isthmus, which is the posterior region of the callosal body connecting parietotemporal cortical regions. We hypothesized that isthmal area would be greater in homosexual men, even among right handers. Twelve homosexual and ten heterosexual healthy young men, all consistently right-handed, underwent a research-designed magnetic resonance imaging scan. We found that the isthmal area was larger in the homosexual group, adding to the body of findings of structural brain differences between homosexual and heterosexual men. This result suggests that right-handed homosexual men have less marked functional asymmetry compared to right-handed heterosexual men. The results also indicate that callosal anatomy and laterality for motoric functions are dissociated in homosexual men. A logistic regression analysis to predict sexual orientation category correctly classified 21 of the 22 men (96% correct classification) based on area of the callosal isthmus, a left-hand performance measure, water level test score, and a measure of abstraction ability. Our findings indicate that neuroanatomical structure and cognition are associated with sexual orientation in men and support the hypothesis of a neurobiological basis in the origin of sexual orientation. PMID:17975723

  4. Hemispheric asymmetry and corpus callosum morphometry: a magnetic resonance imaging study.

    PubMed

    Dorion, A A; Chantôme, M; Hasboun, D; Zouaoui, A; Marsault, C; Capron, C; Duyme, M

    2000-01-01

    Previous post-mortem studies (Aboitiz, F., Scheibel, A.B., Fisher, R.S., Zaidel, E., 1992. Brain Res. 598, 154-161 and Aboitiz, F., Scheibel, A.B., Zaidel, E., 1992. Brain 115, 1521-1541) have shown an inverse association between asymmetry in perisylvian areas and the size of a specific segment, the isthmus, of the corpus callosum (CC) in males. The purpose of this work was to study in vivo the association between hemispheric asymmetry and the total size of the CC in 35 right-handed subjects (16 males, 19 females; mean age 24.9 +/- 3.9). An MRI scan was performed for each subject. The area of the right (RH) and left (LH) hemispheres were measured from images in the sagittal plane and the area of the CC from images in the mid-sagittal plane. The index of hemispheric asymmetry was absolute value((LH - RH)/[(LH + RH)/2]). There was a negative correlation between the absolute value of hemispheric asymmetry and the size of the CC in males (r = -0.55, P = 0.03) but not in females (r = -0.20, P = 0.42). These findings, like those of Aboitiz et al. (Aboitiz, F., Scheibel, A.B., Zaidel, E., 1992. Brain 115, 1521-1541), suggest a sex-dependent decrease in interhemispheric connectivity with increasing hemispheric asymmetry. PMID:10678527

  5. Neuropilin 1-Sema Signaling Regulates Crossing of Cingulate Pioneering Axons during Development of the Corpus Callosum

    PubMed Central

    Piper, Michael; Plachez, Céline; Zalucki, Oressia; Fothergill, Thomas; Goudreau, Guy; Erzurumlu, Reha; Gu, Chenghua

    2009-01-01

    Pioneer axons from the cingulate cortex initiate corpus callosum (CC) development, yet nothing is known about the molecules that regulate their guidance. We demonstrate that neuropilin 1 (Npn1) plays an integral role in the development of the CC. Npn1 is localized to axons of cingulate neurons as they cross the midline, and multiple class 3 semaphorins (Semas) are expressed around the developing CC, implicating these guidance molecules in the regulation of Npn1-expressing axons emanating from the cingulate cortex. Furthermore, axons from the cingulate cortex display guidance errors in Npn1Sema- mice, a knockin mouse line in which Npn1 is unable to bind Semas. Analysis of mice deficient in the transcription factor Emx2 demonstrated that the cingulate cortex of these mice was significantly reduced in comparison to wild-type controls at E17 and that the CC was absent in rostral sections. Expression of Npn1 was absent in rostral sections of Emx2 mutants, suggesting that Npn1-expressing cingulate pioneers are required for CC formation. These data highlight a central role for Npn1 in the development of projections from the cingulate cortex and further illustrate the importance of these pioneer axons in the formation of the CC. PMID:19357391

  6. Structural and functional brain rewiring clarifies preserved interhemispheric transfer in humans born without the corpus callosum

    PubMed Central

    Tovar-Moll, Fernanda; Monteiro, Myriam; Andrade, Juliana; Bramati, Ivanei E.; Vianna-Barbosa, Rodrigo; Marins, Theo; Rodrigues, Erika; Dantas, Natalia; Behrens, Timothy E. J.; de Oliveira-Souza, Ricardo; Moll, Jorge; Lent, Roberto

    2014-01-01

    Why do humans born without the corpus callosum, the major interhemispheric commissure, lack the disconnection syndrome classically described in callosotomized patients? This paradox was discovered by Nobel laureate Roger Sperry in 1968, and has remained unsolved since then. To tackle the hypothesis that alternative neural pathways could explain this puzzle, we investigated patients with callosal dysgenesis using structural and functional neuroimaging, as well as neuropsychological assessments. We identified two anomalous white-matter tracts by deterministic and probabilistic tractography, and provide supporting resting-state functional neuroimaging and neuropsychological evidence for their functional role in preserved interhemispheric transfer of complex tactile information, such as object recognition. These compensatory pathways connect the homotopic posterior parietal cortical areas (Brodmann areas 39 and surroundings) via the posterior and anterior commissures. We propose that anomalous brain circuitry of callosal dysgenesis is determined by long-distance plasticity, a set of hardware changes occurring in the developing brain after pathological interference. So far unknown, these pathological changes somehow divert growing axons away from the dorsal midline, creating alternative tracts through the ventral forebrain and the dorsal midbrain midline, with partial compensatory effects to the interhemispheric transfer of cortical function. PMID:24821757

  7. Automatic segmentation of corpus callosum using Gaussian mixture modeling and Fuzzy C means methods.

    PubMed

    ?çer, Semra

    2013-10-01

    This paper presents a comparative study of the success and performance of the Gaussian mixture modeling and Fuzzy C means methods to determine the volume and cross-sectionals areas of the corpus callosum (CC) using simulated and real MR brain images. The Gaussian mixture model (GMM) utilizes weighted sum of Gaussian distributions by applying statistical decision procedures to define image classes. In the Fuzzy C means (FCM), the image classes are represented by certain membership function according to fuzziness information expressing the distance from the cluster centers. In this study, automatic segmentation for midsagittal section of the CC was achieved from simulated and real brain images. The volume of CC was obtained using sagittal sections areas. To compare the success of the methods, segmentation accuracy, Jaccard similarity and time consuming for segmentation were calculated. The results show that the GMM method resulted by a small margin in more accurate segmentation (midsagittal section segmentation accuracy 98.3% and 97.01% for GMM and FCM); however the FCM method resulted in faster segmentation than GMM. With this study, an accurate and automatic segmentation system that allows opportunity for quantitative comparison to doctors in the planning of treatment and the diagnosis of diseases affecting the size of the CC was developed. This study can be adapted to perform segmentation on other regions of the brain, thus, it can be operated as practical use in the clinic. PMID:23871683

  8. [Dysconnection syndrome in a boy with tumorous lesion of corpus callosum].

    PubMed

    Jovi?, N; Vranjesevi?, D; Naguli?, M

    1995-01-01

    We report on a 12-years-old boy with glioma of the septum pellucidum which invaded and infiltrated the adjacent structures including neocortical commissures. Neuropsychological evaluation revealed the loss of interhemispheric integration and hemisphere dysconnection syndrome. Our patient demonstrated left-sided ideo-motor apraxia to verbal commands and left-sided agrafia, being unable to copy, write to dictation and formulate his own sentences with the left hand. He partly failed in attempts to name or describe objects out of sight in the left hand and showing an unilateral tactile anomia. The patient performed the block-design-test better with the left hand than the right hand, and demonstrated a right-sided constructive apraxia. He had extinction of his left ear on dichotic listening, despite a normal audiogram in both ears. Because of progressive defects of visual function, a tachistoscoping testing was not performed. There was no evidence of the alien hand syndrome, reported earlier. The general dysconnection syndrome caused by lesion of the corpus callosum, was associated with cognitive dysfunctions. Attention, memory and speech disorders were attributed to the progressive extra-callosal cerebral neoplastic lesion. The neurosurgical treatment was performed by transcallosal anterior approach. On neuropsychological retesting, 4 months later symptoms of hemisphere dysconnection were stabilized. PMID:17974475

  9. Dehydration-Induced Anorexia Reduces Astrocyte Density in the Rat Corpus Callosum

    PubMed Central

    Reyes-Haro, Daniel; Labrada-Moncada, Francisco Emmanuel; Miledi, Ricardo; Martínez-Torres, Ataúlfo

    2015-01-01

    Anorexia nervosa is an eating disorder associated with severe weight loss as a consequence of voluntary food intake avoidance. Animal models such as dehydration-induced anorexia (DIA) mimic core features of the disorder, including voluntary reduction in food intake, which compromises the supply of energy to the brain. Glial cells, the major population of nerve cells in the central nervous system, play a crucial role in supplying energy to the neurons. The corpus callosum (CC) is the largest white matter tract in mammals, and more than 99% of the cell somata correspond to glial cells in rodents. Whether glial cell density is altered in anorexia is unknown. Thus, the aim of this study was to estimate glial cell density in the three main regions of the CC (genu, body, and splenium) in a murine model of DIA. The astrocyte density was significantly reduced (~34%) for the DIA group in the body of the CC, whereas in the genu and the splenium no significant changes were observed. DIA and forced food restriction (FFR) also reduced the ratio of astrocytes to glial cells by 57.5% and 22%, respectively, in the body of CC. Thus, we conclude that DIA reduces astrocyte density only in the body of the rat CC.

  10. Beginning Fractions

    NSDL National Science Digital Library

    J.C. Banfill

    2007-12-12

    For the learner just being introduced to fractions, this site is an excellent resource. It contain a very basic explanation of what a fraction is and a game for students to practice naming the fraction presented. The game can also be manipulated to have a time limit, to award time for each correct answer, and to time how fast students can get 20 more answers right than wrong.

  11. Fraction Monkeys

    NSDL National Science Digital Library

    2012-01-01

    This interactive Flash applet gives students practice in ordering fractions and matching equivalent fractions. Each round displays a 0-1 number line with increments of a specific denominator labeled. Monkeys holding fraction cards appear one at a time; users hang them on rings on the number line to match the labeled fractions, or their equivalents. Denominators increase through each successive round and range from 1/4s to 1/16s. Versions for iPad and iPhone are available in the iTunes AppStore.

  12. Ion Temperature Anisotropy across Reconnection Exhaust Jets

    NASA Astrophysics Data System (ADS)

    Hietala, H.; Drake, J. F.; Phan, T. D.; Eastwood, J. P.; McFadden, J. P.

    2014-12-01

    Magnetic reconnection redistributes energy by releasing magnetic energy into plasma kinetic energy - high speed bulk flows, heating, and particle acceleration. In the magnetotail, most of the released energy appears to go into ion heating. However, previous observations and simulations show that this heating is anisotropic with the plasma temperature parallel to the magnetic field generally increasing more than the perpendicular temperature. Simulations and theory indicate that this temperature anisotropy can balance part of the magnetic tension force that accelerates the jet, and may even exceed it leading to firehose instability.Here we report the results of a new study of ion temperature anisotropy in reconnection exhausts generated by anti-parallel reconnection. We have examined ARTEMIS dual-spacecraft observations of long-duration magnetotail exhausts at lunar distances in conjunction with Particle-In-Cell simulations. In particular, we have studied spatial variations in the ion temperature anisotropy across the outflows far away (>100 ion inertial lengths) from the X-line. A consistent pattern is found in both the spacecraft data and the simulations: whilst the total temperature profile across the exhaust is flat, near the exhaust boundaries the parallel temperature dominates. A consequence of this is that firehose threshold is greatly exceeded in a significant fraction of the exhaust. In contrast, the perpendicular temperature dominates at the neutral plane (|BX| < 0.1 B0), indicating that, despite the turbulence and the large distance to the X-line, particles undergo Speiser-like motion (rather than isotropization by scattering). We also analyse the characteristics of the particle distributions leading to these anisotropies at different distances from the mid-plane.

  13. Microwave anisotropies from the Galactic halo

    E-print Network

    Mark Walker; Michiko Ohishi; Masaki Mori

    2003-02-11

    Models in which a large fraction of the Galactic dark matter takes the form of cold gas clouds imply that there is thermal microwave emission from the Galactic dark halo. Such models can therefore be directly constrained by data on the microwave sky, and in particular the very sensitive observations of microwave anisotropies which are now being made. To this end we have computed the anisotropy power-spectrum expected for a Galactic dark halo made of cold, dense gas clouds, including the effects of clustering with a CDM-like mass spectrum of mini-halo substructure. The power-spectrum displays two peaks: one, at l~50, is the Poisson noise for the mini-halos, and the second, much larger and at much higher l, is the Poisson noise of the individual clouds. Because it appears on small (milli-arcsecond) angular scales, where the instrumental sensitivity is inevitably very poor, the latter signal is not directly detectable. By contrast, clusters of cold gas clouds may contribute significantly to the observed anisotropies if their emission has a grey-body spectrum. In this case the peak fluctuation, at l~50, amounts to 4/|sin b| micro-K in the Rayleigh-Jeans limit, and is the dominant Galactic foreground between 40 and 80 GHz. It will be possible to constrain this foreground component using low-latitude data from the MAP satellite, providing that its spectrum conforms to a grey-body. If the spectrum is ``dusty'' there will be relatively little power at frequencies below the thermal peak, and in this case the predicted anisotropies are shown to be negligible.

  14. Optical Anisotropy of Semiconductor Nanowires

    Microsoft Academic Search

    Jaime Gómez Rivas; Otto L. Muskens; Magnus T. Borgström; Silke L. Diedenhofen; Erik P. A. M. Bakkers

    Semiconductor nanowires are novel nanostructures full of promise for optical applications. Nanowires have subwavelength diameters\\u000a and large aspect ratios, which combined with the high permittivity of semiconductors lead to a strong optical anisotropy.\\u000a We review in this chapter this optical anisotropy, focusing on the polarization anisotropy of the photoluminescence of individual\\u000a nanowires and the propagation of light through birefringent ensembles

  15. Fraction Tutorial

    NSDL National Science Digital Library

    B. J. Webb

    2000-01-01

    This site provides an introduction to fractions, including the concept of equivalency, and shows how to reduce, decompose, multiply, divide, add, and subtract them. Illustrations cover all these concepts, beginning with the idea of fractions as parts of a whole, continuing through equivalency, addition and subtraction with like denominators, and finishing with multiplication of mixed numbers. Practice exercises are offered at all levels.

  16. Understanding Fractions

    NSDL National Science Digital Library

    Jennie Pennant

    2013-01-01

    In this article Pennant and Woodham discuss the importance of rich tasks in the teaching of fractions. In order to prepare for new more rigorous standards, the authors have compiled a list of rich tasks and a description of others that aim to improve how children think about fractions.

  17. What fraction?

    NSDL National Science Digital Library

    A. Blundred

    2012-01-01

    This collection of 22 Flash applets, intended for use with a projector or interactive whiteboard (IWB), gives the educator the ability to display and alter questions about fractions of a group. The teacher chooses from among a variety of graphics and a fixed or varying denominator (group size) and clicks to alter the numerator (subset size). The question is "What fraction?"

  18. Comparison of trabecular bone anisotropies based on fractal dimensions and mean intercept length determined by principal axes of inertia

    Microsoft Academic Search

    Won-Jin Yi; Min-Suk Heo; Sam-Sun Lee; Soon-Chul Choi; Kyung-Hoe Huh

    2007-01-01

    The mechanical quality of trabecular bone depends on both its stiffness and its strength characteristics, which can be predicted\\u000a indirectly by the combination of bone volume fraction and architectural anisotropy. To analyze the directional anisotropy\\u000a of the trabecular bone, we applied the fractal geometry technique to plain radiographs. The anisotropy of the bone was quantified\\u000a from an ellipse, based on

  19. Corpus Callosum Measurements Correlate with Developmental Delay in Smith-Lemli-Opitz Syndrome

    PubMed Central

    Lee, Ryan W.Y.; Yoshida, Shoko; Jung, Eun Sol; Mori, Susumu; Baker, Eva H.; Porter, Forbes D.

    2013-01-01

    Background Smith-Lemli-Opitz syndrome (SLOS) is a multiple malformation, neurodevelopmental disorder of cholesterol metabolism caused by mutations in 7-dehydrocholesterol reductase (DHCR7). Corpus callosum (CC) malformations and developmental delay are common manifestations of this disorder, but the relationship between the two has not been evaluated. We tested the hypothesis that shorter callosal length and smaller area correlates with higher serum 7-dehydrocholesterol (7DHC) and increased severity of neurodevelopmental delay in a large cohort of SLOS patients. Methods Thirty-six individuals with SLOS (18M/18F) between 0.20 and 12.5 years (mean = 3.9, SD = 3.6) and 36 typically developing controls (18M/18F) between 0.12 and 12.8 years (mean = 4.0, SD = 3.6) were each imaged one time on a 1.5T MR scanner. One mid-sagittal image per study was selected for manual measurement of CC cross-sectional area and length. Gross motor, fine motor, and language developmental quotients, anatomical severity score, and serum sterol levels were assessed with imaging measurements. Results Shorter CC length and smaller area correlated with lower developmental quotient in gross motor and language domains. Furthermore, length and area negatively correlated with a serum 7DHC, 8DHC, sterol ratio, and anatomical severity score, and positively correlated with total cholesterol. The degree of developmental delay ranged from mild to severe, involving all domains. Conclusions For individuals with SLOS, smaller callosal area and length are associated with higher serum 7DHC, anatomic severity, and motor and language delay. These findings suggest the relationship between callosal development, biochemistry, and neurodevelopment may lead to finding predictors of outcome in SLOS. PMID:23859856

  20. Age and sex effects on corpus callosum morphology across the lifespan.

    PubMed

    Prendergast, Daniel M; Ardekani, Babak; Ikuta, Toshikazu; John, Majnu; Peters, Bart; DeRosse, Pamela; Wellington, Robin; Malhotra, Anil K; Szeszko, Philip R

    2015-07-01

    The corpus callosum (CC) is the largest interhemispheric white matter tract in the human brain, and is characterized by pronounced differences in morphology among individuals. There are limited data, however, regarding typical development, sex differences, and the neuropsychological correlates of individual differences within CC subregions. Magnetic resonance (MR) imaging exams were collected in a large cohort (N?=?305) of healthy individuals (ages 8-68). We used a highly reliable program to automatically identify the midsagittal plane and obtain CC subregion measures according to approaches described by Witelson [1989]: Brain 112:799-835 and Hampel et al. [1998]: Arch Neurol 55:193-198 and a measure of whole CC shape (i.e., circularity). CC measurement parameters, including area, perimeter, length, circularity, and CC subregion area values were generally characterized by inverted U-shaped curves across the observed age range. Peak values for CC subregions were observed between ages 32 and 45, and descriptive linear correlations were consistent with sharper area changes in development. We also observed differing age-associated changes across the lifespan between males and females in the CC subregion corresponding to the genu (Witelson's subregion 2), as well as CC circularity. Mediation analysis using path modeling indicated that genu area mediated the relationship between age and processing speed for females, and the relationship between age and visual learning and executive functioning for males. Taken together, our findings implicate sex differences in CC morphology across the lifespan that are localized to the genu, which appear to mediate neuropsychological functions. Hum Brain Mapp 36:2691-2702, 2015. © 2015 Wiley Periodicals, Inc. PMID:25833103

  1. Abnormalities of the corpus callosum in non-psychotic high-risk offspring of schizophrenia patients.

    PubMed

    Francis, Alan N; Bhojraj, Tejas S; Prasad, Konasale M; Kulkarni, Shreedhar; Montrose, Debra M; Eack, Shaun M; Keshavan, Matcheri S

    2011-01-30

    Alterations in the structure of the corpus callosum (CC) have been observed in schizophrenia. Offspring of schizophrenia parents have 10-15 times higher risk for developing schizophrenia. We examined CC volume in offspring at genetic high-risk (HR) subjects. Since the sub-regions of the CC are topographically mapped to cortical brain regions, we hypothesized that HR subjects may show a decrement in total volume and differential volume decreases in sub-regions of the CC. The offspring of schizophrenia parents (HR; n=70; 36 males) and healthy volunteers with no family or personal history of psychotic disorders (healthy controls (HC); n=73; 37 males) matched for age, gender and education were selected for the study. Magnetic resonance images were collected using a GE 1.5 T scanner and processed using FreeSurfer image analysis software. The CC was divided into five neuroanatomically based partitions. The volume of total CC and the five sub-regions were measured blind to clinical information. With covariation for intracranial volume, HR subjects had significantly reduced total CC, more prominently observed in the anterior splenium. An age-related increase in CC volume was found in the anterior and posterior splenium of healthy controls but not in HR subjects. The volume reduction was greater in male than female HR subjects. The volume reduction in the CC may reflect a reduction in axonal fibers crossing the hemispheres and/or myelination between the left and right temporo-parietal cortices. The absence of an age-related volume increase suggests an abnormal developmental trajectory that may underlie susceptibility to schizophrenia. PMID:21145214

  2. N-Methyl-D-Aspartate Receptor-Mediated Axonal Injury in Adult Rat Corpus Callosum

    PubMed Central

    Zhang, Jingdong; Liu, Jianuo; Fox, Howard S.; Xiong, Huangui

    2013-01-01

    Damage to white matter such as corpus callosum (CC) is a pathological characteristic in many brain disorders. Glutamate (Glut) excitotoxicity through AMPA receptors on oligodendrocyte (OL) was previously considered as a mechanism for white matter damage. Recent studies have shown that N-methyl-D-aspartate receptors (NMDARs) are expressed on myelin sheath of neonatal rat OL processes and that activation of these receptors mediated demyelization. Whether NMDARs are expressed in the adult CC and are involved in excitotoxic axonal injury remains to be determined. In this study, we demonstrate the presence of NMDARs in the adult rat CC and their distributions in myelinated nerve fibers and OL somata by means of immunocytochemical staining and Western blot. Incubation of the CC slices with Glut or NMDA induced axonal injury as revealed by analyzing amplitude of CC fiber compound action potentials (CAPs) and input–output response. Both Glut and NMDA decreased the CAP amplitude and input–output responses, suggesting an involvement of NMDARs in Glut- and NMDA-induced axonal injury. The involvement of NMDAR in Glut-induced axonal injury was further assayed by detection of ?-amyloid precursor protein (?-APP) in the CC axonal fibers. Treatment of the CC slices with Glut resulted in ?-APP accumulation in the CC fibers as detected by Western blot, reflecting an impairment of axonal transport function. This injurious effect of Glut on CC axonal transport was significantly blocked by MK801. Taken together, these results show that NMDARs are expressed in the adult CC and are involved in excitotoxic activity in adult CC slices in vitro. PMID:23161705

  3. Corpus Callosum Atrophy Rate in Mild Cognitive Impairment and Prodromal Alzheimer’s Disease

    PubMed Central

    Elahi, Sahar; Bachman, Alvin H.; Lee, Sang Han; Sidtis, John J.; Ardekani, Babak A.

    2015-01-01

    Background Corpus callosum (CC) size and shape have been previously studied in Alzheimer’s disease (AD) with the majority of studies having been cross-sectional. Due to the large variance in normal CC morphology, cross-sectional studies are limited in statistical power. Determining individual rates of change requires longitudinal data. Physiological changes are particularly relevant in mild cognitive impairment (MCI), in which CC morphology has not been previously studied longitudinally. Objective To study temporal rates of change in CC morphology in MCI patients over a one-year period, and to determine whether these rates differ between MCI subjects who converted to AD (MCI-C) and those who did not (MCI-NC) over an average (±SD) observation period of 5.4 (±1.6) years. Methods We used a novel multi-atlas based algorithm to segment the mid-sagittal cross-sectional area of the CC in longitudinal MRI scans. Rates of change of CC circularity, total area, and five sub-areas were compared between 57 MCI-NC and 81 MCI-C subjects. Results The CC became less circular (?0.89% per year in MCI-NC, ?1.85% per year in MCI-C) with time, with faster decline in MCI-C (p=0.0002). In females, atrophy rates were higher in MCI-C relative to MCI-NC in total CC area (p=0.0006), genu/rostrum (p=0.005), and splenium (0.002). In males, these rates did not differ between groups. Conclusion A greater than normal decline in CC circularity was shown to be an indicator of prodromal AD in MCI subjects. This measure is potentially useful as an imaging biomarker of disease and a therapeutic target in clinical trials. PMID:25633676

  4. Effects of sex chromosome dosage on corpus callosum morphology in supernumerary sex chromosome aneuploidies

    PubMed Central

    2014-01-01

    Background Supernumerary sex chromosome aneuploidies (sSCA) are characterized by the presence of one or more additional sex chromosomes in an individual’s karyotype; they affect around 1 in 400 individuals. Although there is high variability, each sSCA subtype has a characteristic set of cognitive and physical phenotypes. Here, we investigated the differences in the morphometry of the human corpus callosum (CC) between sex-matched controls 46,XY (N =99), 46,XX (N =93), and six unique sSCA karyotypes: 47,XYY (N =29), 47,XXY (N =58), 48,XXYY (N =20), 47,XXX (N =30), 48,XXXY (N =5), and 49,XXXXY (N =6). Methods We investigated CC morphometry using local and global area, local curvature of the CC boundary, and between-landmark distance analysis (BLDA). We hypothesized that CC morphometry would vary differentially along a proposed spectrum of Y:X chromosome ratio with supernumerary Y karyotypes having the largest CC areas and supernumerary X karyotypes having significantly smaller CC areas. To investigate this, we defined an sSCA spectrum based on a descending Y:X karyotype ratio: 47,XYY, 46,XY, 48,XXYY, 47,XXY, 48,XXXY, 49,XXXXY, 46,XX, 47,XXX. We similarly explored the effects of both X and Y chromosome numbers within sex. Results of shape-based metrics were analyzed using permutation tests consisting of 5,000 iterations. Results Several subregional areas, local curvature, and BLDs differed between groups. Moderate associations were found between area and curvature in relation to the spectrum and X and Y chromosome counts. BLD was strongly associated with X chromosome count in both male and female groups. Conclusions Our results suggest that X- and Y-linked genes have differential effects on CC morphometry. To our knowledge, this is the first study to compare CC morphometry across these extremely rare groups. PMID:25780557

  5. Fractionalized gapless quantum vortex liquids

    NASA Astrophysics Data System (ADS)

    Wang, Chong; Senthil, T.

    2015-05-01

    The standard theoretical approach to gapless spin liquid phases of two-dimensional frustrated quantum antiferromagnets invokes the concept of fermionic slave particles into which the spin fractionalizes. As an alternate we explore different kinds of gapless spin liquid phases in frustrated quantum magnets with X Y anisotropy where the vortex of the spin fractionalizes into gapless itinerant fermions. The resulting gapless fractionalized vortex liquid phases are studied within a slave particle framework that is dual to the usual one. We demonstrate the stability of some such phases and describe their properties. We give an explicit construction in an X Y -spin-1 system on triangular lattice, and interpret it as a critical phase in the vicinity of spin-nematic states.

  6. Quantifying reflectance anisotropy of photosynthetically active radiation in grasslands

    SciTech Connect

    Middleton, E.M. (NASA Goddard Space Flight Center, Greenbelt, MD (United States))

    1992-11-30

    This work is part of the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE), an international land-surface-atmosphere experiment aimed at improving the way climate models represent energy, water, heat, and carbon exchanges, and improving the utilization of satellite based remote sensing to monitor such parameters. This paper reports on a study to quantify the reflectance anisotropy of the photosynthetically active radiation (PAR) for grasslands. PAR falls in the wavelength range 0.4 to 0.7[mu]m. The study looks at the variation of PAR with illumination and vegetative canopy conditions. It uses bidirectional reflectance distribution function data, and measures of anisotropy derived from reflectance factor and reflectance fraction data to aid in the analysis. The data used for this analysis came from an intense effort mounted to measure diurnal changes in the anisotropy of surface reflectance from prairie grassland as a function of the vegetative canopy.

  7. Magnetic nanoparticles and magnetocrystalline anisotropy

    Microsoft Academic Search

    S. A. Majetich; J. H. Scott; E. M. Kirkpatrick; K. Chowdary; K. Gallagher; M. E. McHenry

    1997-01-01

    The size dependent properties of monodomain ferromagnets are described. Following an introduction to the technical magnetics parameters used to describe bulk ferromagnets, the size dependence of these parameters is described. Bulk ferromagnetic materials are generally described as either hard or soft, depending on the value of their magnetocrystalline anisotropy. The role of anisotropy in monodomain ferromagnets is investigated through examination

  8. Material Behavior: Texture and Anisotropy

    E-print Network

    Hielscher, Ralf

    Material Behavior: Texture and Anisotropy Ralf Hielscher David Mainprice Helmut Schaeben; Material Behavior: Texture and Anisotropy Abstract This contribution is an attempt to present a self-contained and comprehensive sur- vey of the mathematics and physics of material behavior of rocks in terms of texture

  9. Fraction Fanatic

    NSDL National Science Digital Library

    Ms. Jackson

    2007-10-25

    We are going to practice our fraction skills with addition, subtraction, and equivalents. Let\\'s save the bugs with Math Splat. Check your skill with Equivalents. Get it straight with Lines and Circles. ...

  10. Comparing Fractions

    NSDL National Science Digital Library

    2011-01-01

    Teachers can use this interactive tool to help students build a conceptual understanding of fractions by comparing and ordering numeric representations, or comparing fractions using symbols (>, < or =). This page includes a video demonstration of the tool and sample lessons from the Conceptua curriculum. Free registration is required to use the tool. A paid subscription is necessary to access full curriculum and allow full student use.

  11. Fraction Pieces

    NSDL National Science Digital Library

    2005-01-01

    Students use this Java applet to explore pieces representing fractional portions of a circle or square. This virtual manipulative can be used to explore patterns and symmetry with young children, or to develop fluency in fraction operations and equivalency in older students. Instructions for using the applet and teaching ideas for parents/teachers are available through the links at the top of the page.

  12. Fantastic Fractions

    NSDL National Science Digital Library

    2012-10-22

    In this math lesson, learners compare pattern blocks to visually understand halves, thirds, and sixths. First, learners look at all the different ways they can make a hexagon using other pattern block pieces. After the investigation, they represent their solutions using pictures and fractional notation. Then, learners play a game to increase their understanding of equivalence and fractions. The game can be played on its own--with or without the preceding lesson.

  13. Macroscopic model with anisotropy based on micro-macro informations

    E-print Network

    Nishant Kumar; Stefan Luding; Vanessa Magnanimo

    2015-06-15

    Physical experiments can characterize the elastic response of granular materials in terms of macroscopic state-variables, namely volume (packing) fraction and stress, while the microstructure is not accessible and thus neglected. Here, by means of numerical simulations, we analyze dense, frictionless, granular assemblies with the final goal to relate the elastic moduli to the fabric state, i.e., to micro-structural averaged contact network features as contact number density and anisotropy. The particle samples are first isotropically compressed and later quasi-statically sheared under constant volume (undrained conditions). From various static, relaxed configurations at different shear strains, now infinitesimal strain steps are applied to "measure" the effective elastic response; we quantify the strain needed so that plasticity in the sample develops as soon as contact and structure rearrangements happen. Because of the anisotropy induced by shear, volumetric and deviatoric stresses and strains are cross-coupled via a single anisotropy modulus, which is proportional to the product of deviatoric fabric and bulk modulus (i.e. the isotropic fabric). Interestingly, the shear modulus of the material depends also on the actual stress state, along with the contact configuration anisotropy. Finally, a constitutive model based on incremental evolution equations for stress and fabric is introduced. By using the previously measured dependence of the stiffness tensor (elastic moduli) on the microstructure, the theory is able to predict with good agreement the evolution of pressure, shear stress and deviatoric fabric (anisotropy) for an independent undrained cyclic shear test, including the response to reversal of strain.

  14. Intracranial Hemorrhage in the Corpus Callosum Presenting as Callosal Disconnection Syndrome: FDG-PET and Tractography: A Case Report

    PubMed Central

    Kim, In Hwan; Lee, Soyoung; Lee, Chang-Young

    2014-01-01

    We report the findings of 18F-fluorodeoxyglocese positron emission tomography (FDG-PET) and diffusion tensor tractography (DTT) in a right-handed patient presenting with callosal disconnection syndrome, including alien hand syndrome, after an anterior communicating artery aneurysmal rupture. The 49-year-old patient had right hemiparesis and unintended movement of the right hand during action of the left hand. A brain magnetic resonance imaging revealed lesions in the upper part of the genu and body in the corpus callosum as well as hemorrhage in the inter-hemispheric fissure. We observed extensive disruption of corpus callosum fibers in the upper genu and trunk by DTT for the evaluation of inter-hemispheric connection. FDG-PET revealed severe hypometabolism in the left cerebral hemisphere, including basal ganglia and thalamus, and hypermetabolism in the right cerebral hemisphere. Based on findings of FDG-PET and DTT, the callosal disconnection syndrome presented in the patient could be the result of loss of transcallosal inhibition in the contralateral hemisphere. PMID:25566491

  15. A COMPARATIVE STUDY OF CORPUS CALLOSUM SIZE AND SIGNAL INTENSITY IN CAPUCHIN MONKEYS (CEBUS apella) AND CHIMPANZEES (PAN troglodytes)

    PubMed Central

    PHILLIPS, K. A.; KAPFENBERGER, N.; HOPKINS, W. D.

    2009-01-01

    The evolution of corpus callosum (CC) was integral to the development of higher cognitive processes and hemispheric specialization. An examination of CC morphology and organization across different primate species will further our understanding of the evolution of these specified functions. Using magnetic resonance imaging (MRI) as a non-invasive technique to measure CC size and to approximate the degree of myelination in the corpus callosum, we report differences in CC morphology and organization in capuchin monkeys and chimpanzees, two divergent primate species that have independently evolved several behavioral and anatomical characteristics. Species differences in CC morphology were detected, with chimpanzees having a larger overall CC compared to capuchin monkeys. Additionally, chimpanzees had the genu as the largest subdivision; in capuchin monkeys, the genu and splenium were the largest subdivisions. Sex differences in signal intensity were detected; capuchin monkey males had higher signal intensity values whereas chimpanzee females had higher signal intensity values. Thus, while capuchin monkeys and chimpanzees show some similarity in patterns of CC morphology, these species differ significantly in the regional organization of the CC. PMID:19356692

  16. Metabolic alterations in corpus callosum may compromise brain functional connectivity in MTBI patients: an 1H-MRS study

    PubMed Central

    Johnson, Brian; Zhang, Kai; Gay, Michael; Neuberger, Thomas; Horovitz, Silvina; Hallett, Mark; Sebastianelli, Wayne; Slobounov, Semyon

    2011-01-01

    After clinical resolution of signs and symptoms of mild traumatic brain injury (MTBI) it is still not clear if there are residual abnormalities of structural or functional brain networks. We have previously documented disrupted interhemispheric functional connectivity in “asymptomatic” concussed individuals during the sub-acute phase of injury. Testing of 15 normal volunteers (NV) and 15 subacute MTBI subjects was performed within 24 hours of clinical symptoms resolution and medical clearance for the first stage of aerobic activity. In this MRS study we report (a) both in the genu and splenium of the corpus callosum NAA/Cho and NAA/Cr ratios were significantly (p<0.05) lower in MTBI subjects shortly after the injury compared to NVs, and (b) the metabolic ratio NAA/Cho in the splenium significantly correlated with the magnitude of inter-hippocampal functional connectivity in normal volunteers, but not in MTBI. This novel finding supports our hypothesis that the functional disruption of interhemispheric brain networks in MTBI subjects results from compromised metabolic integrity of the corpus callosum and that this persists despite apparent clinical return to baseline. PMID:22108503

  17. Anisotropy and AVO from walkaways

    SciTech Connect

    Leaney, W.S. [Schlumberger Interpretation Development, Jakarta (Indonesia)

    1994-12-31

    A multi-offset VSP or ``walkaway`` is a wide aperture borehole seismic experiment ideal for studying angle-dependent wave propagation. In this paper, two aspects of elastic wave propagation are studied with walkaways: anisotropy (transverse isotropy) and AVO (amplitude variation with offset). Anisotropy is measured from walkaway data using extracted vertical and horizontal phase slownesses. Results are shown for a Java Sea walkaway data set and tabulated for walkaways from different locations. The anisotropy measurements are classified using Schoenberg`s parameters of ellipticity and anellipticity. Shale anisotropy is found to be significant and variable. Anisotropic AVO is studied on Ostrander`s shale-sand model and through the computation of anisotropic ray-trace synthetics. The ratio of ellipticity to anellipticity is found to be a good measure of shale anisotropy in the context of AVO. Depending on the ``flavor`` of shale anisotropy, AVO can be significantly reduced or exaggerated. The AVO response of a reservoir sequence can also be measured (as opposed to modeled) with a properly designed walkaway. The results of processing a walkaway for AVO are shown. Such a seismic experiment is arguably the best way to determine the AVO response of a reservoir or reservoir sequence. Together, these two new applications of walkaways -- to measure anisotropy and AVO -- can be used to: (1) Establish the viability of using AVO to map a reservoir. (2) Reduce the risk involved with the added cost of AVO studies. (3) Improve the reliability of AVO interpretations.

  18. The theory of CMB anisotropies

    E-print Network

    Ruth Durrer

    2001-09-27

    This is a review of the theory of CMB anisotropies, an updated version of a course given at the troisieme cycle de la Suisse Romande. An introduction to gauge invariant cosmological perturbation theory is given and the theory CMB anisotropies is develiped in this context. Simple analytical approximations for the acoustic peak positions for adiabatic and isocurvature perturbations are derived. Silk damping is discussed by an analytic approximation. A short description of the present status of observations and parameter estimation followed by a critical discussion terminate the review. The full system of differential equations for CMB anisotropies and polarization needed in a numerical treatment is also developed and given in an appendix.

  19. Fraction King

    NSDL National Science Digital Library

    2011-05-24

    This lesson is designed to develop students' abilities to find fractions of whole numbers by dividing the number into portions then selecting the proper number of portions. This lesson provides links to an applet, discussions, and hands-on activities related to fractions as well as suggested ways to integrate them into the lesson. The lesson provides links to follow-up lessons designed for use in succession with the current one. Note, reading level is not indicated because the lesson does not include student reading material.

  20. Matching Fractions

    NSDL National Science Digital Library

    NRICH team

    2012-01-01

    In this interactive game similar to Concentration(TM) students match fractions (1/2, 1/3, 3/4, and 5/9) to images that represent those fractions. This game can be played in pairs with the printed out cards or as a whole class on the interactive white board (IWB). This resource includes teacher notes with suggestions for introducing the game, discussion questions, support suggestions, a set of cards to be printed (PDF), a blank set of cards to make your own (PDF), and a full screen version of the game.

  1. Anisotropy in collective precessional dynamics in arrays of Ni80Fe20 nanoelements

    E-print Network

    Otani, Yoshichika

    FeB/MgO/CoFeB magnetic tunnel junction nanopillars J. Appl. Phys. 111, 07C520 (2012) Effect of packing fractionAnisotropy in collective precessional dynamics in arrays of Ni80Fe20 nanoelements B. Rana, D. Kumar://jap.aip.org/about/rights_and_permissions #12;Anisotropy in collective precessional dynamics in arrays of Ni80Fe20 nanoelements B. Rana,1 D

  2. Magnetocrystalline anisotropy of rare earth intermetallics

    Microsoft Academic Search

    A. S. Ermolenko

    1976-01-01

    The peculiarities of the magnetocrystalline anisotropy of the rare earth intermetallics are discussed briefly. Only the part of the magnetic anisotropy energy related to the rare earth ion system is analyzed. This anisotropy in most cases can be satisfactorily described in terms of a single-ion model. Theory and experiment relating to magnetocrystalline anisotropy of RCo5compounds are reviewed as an example

  3. Abnormal Corpus Callosum Connectivity, Socio-Communicative Deficits, and Motor Deficits in Children with Autism Spectrum Disorder: A Diffusion Tensor Imaging Study

    ERIC Educational Resources Information Center

    Hanaie, Ryuzo; Mohri, Ikuko; Kagitani-Shimono, Kuriko; Tachibana, Masaya; Matsuzaki, Junko; Watanabe, Yoshiyuki; Fujita, Norihiko; Taniike, Masako

    2014-01-01

    In addition to social and communicative deficits, many studies have reported motor deficits in autism spectrum disorder (ASD). This study investigated the macro and microstructural properties of the corpus callosum (CC) of 18 children with ASD and 12 typically developing controls using diffusion tensor imaging tractography. We aimed to explore…

  4. Depression in elderly persons subject to childhood maltreatment is not modulated by corpus callosum and hippocampal changes Karen Ritchie*a,b,c

    E-print Network

    Boyer, Edmond

    .03.035 #12;Key Words: corpus callosum, hippocampus, depression, magnetic resonance imaging, child abuse manuscript, published in "Journal of Affective Disorders 2012;141(2-3):294-9" DOI : 10.1016/j.jad.2012 multiple aspects of abuse. Adjusted gender-stratified analyses found no significant reduction in corpus

  5. Dividing Fractions

    NSDL National Science Digital Library

    2012-10-17

    In this lesson students will explore the different methods available for dividing fractions through a student based investigation. The teacher will facilitate the discussion but the students will discover the different methods on their own or with a partner as they work through the different steps.

  6. Vectorkids- Fractions

    NSDL National Science Digital Library

    2010-01-01

    In this interactive activity users are given pies. Part of the pie is shaded yellow and the total number of pieces is given. The user has to identify the fraction by entering the part divided by the whole. Once the user completes ten problems the score is given.

  7. Dark energy and CMB anisotropy

    E-print Network

    Lam, Yukyam, 1982-

    2004-01-01

    According to the WMAP and earlier COBE observations, the Cosmic Microwave Background (CMB) anisotropy power on large angular scales appears to be significantly lower than predicted by the standard model of cosmology. We ...

  8. The Physics of CMBR Anisotropies

    E-print Network

    Kandaswamy Subramanian

    2004-11-02

    The observed structures in the universe are thought to have arisen from gravitational instability acting on small fluctuations generated in the early universe. These spatial fluctuations are imprinted on the CMBR as angular anisotropies. The physics which connects initial fluctuations in the early universe to the observed anisotropies is fairly well understood, since for most part it involves linear perturbation theory. This makes CMBR anisotropies one of the cleanest probes of the initial fluctuations, various cosmological parameters governing their evolution and also the geometry of the universe. We review here in a fairly pedagogical manner the physics of the CMBR anisotropies and explain the role they play in probing cosmological parameters, especially in the light of the latest observations from the WMAP satellite.

  9. Wind anisotropies and GRB progenitors

    E-print Network

    Georges Meynet; Andre Maeder

    2007-01-17

    We study the effect of wind anisotropies on the stellar evolution leading to collapsars. Rotating models of a 60 M$_\\odot$ star with $\\Omega/\\Omega_{\\rm crit}=0.75$ on the ZAMS, accounting for shellular rotation and a magnetic field, with and without wind anisotropies, are computed at $Z$=0.002 until the end of the core He-burning phase. Only the models accounting for the effects of the wind anisotropies retain enough angular momentum in their core to produce a Gamma Ray Burst (GRB). The chemical composition is such that a type Ic supernova event occurs. Wind anisotropies appear to be a key physical ingredient in the scenario leading to long GRBs.

  10. Traumatic axonal injury: the prognostic value of lesion load in corpus callosum, brain stem, and thalamus in different magnetic resonance imaging sequences.

    PubMed

    Moen, Kent G; Brezova, Veronika; Skandsen, Toril; Håberg, Asta K; Folvik, Mari; Vik, Anne

    2014-09-01

    The aim of this study was to explore the prognostic value of visible traumatic axonal injury (TAI) loads in different MRI sequences from the early phase after adjusting for established prognostic factors. Likewise, we sought to explore the prognostic role of early apparent diffusion coefficient (ADC) values in normal-appearing corpus callosum. In this prospective study, 128 patients (mean age, 33.9 years; range, 11-69) with moderate (n?=?64) and severe traumatic brain injury (TBI) were examined with MRI at a median of 8 days (range, 0-28) postinjury. TAI lesions in fluid-attenuated inversion recovery (FLAIR), diffusion-weighted imaging (DWI), and T2*-weighted gradient echo (T2*GRE) sequences were counted and FLAIR lesion volumes estimated. In patients and 47 healthy controls, mean ADC values were computed in 10 regions of interests in the normal-appearing corpus callosum. Outcome measure was the Glasgow Outcome Scale-Extended (GOS-E) at 12 months. In patients with severe TBI, number of DWI lesions and volume of FLAIR lesions in the corpus callosum, brain stem, and thalamus predicted outcome in analyses with adjustment for age, Glasgow Coma Scale score, and pupillary dilation (odds ratio, 1.3-6.9; p?=?<0.001-0.017). The addition of Rotterdam CT score and DWI lesions in the corpus callosum yielded the highest R2 (0.24), compared to all other MRI variables, including brain stem lesions. For patients with moderate TBI only the number of cortical contusions (p?=?0.089) and Rotterdam CT score (p?=?0.065) tended to predict outcome. Numbers of T2*GRE lesions did not affect outcome. Mean ADC values in the normal-appearing corpus callosum did not differ from controls. In conclusion, the loads of visible TAI lesions in the corpus callosum, brain stem, and thalamus in DWI and FLAIR were independent prognostic factors in patients with severe TBI. DWI lesions in the corpus callosum were the most important predictive MRI variable. Interestingly, number of cortical contusions in MRI and CT findings seemed more important for patients with moderate TBI. PMID:24773587

  11. The elastic anisotropy of marble 

    E-print Network

    Gebhard, Susan Nash

    1982-01-01

    THE ELASTIC ANISOTROPY OF MARBLE A Thesis by SUSAN NASH GEBHARD Submitted to the Graduate College of Texas AIIM University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE December 1982 Major Subject...: Geophysics THE ELASTIC ANISOTROPY OF MARBLE A Thesis by SUSAN NASH GEBHARO Approved as to style and content by: Richard L. Carlson (Chairman of Committee) riedman (Member) Neville L. Carter (Member) Neville L. Carter (Head of Department...

  12. Anisotropy in solid inflation

    SciTech Connect

    Bartolo, Nicola; Matarrese, Sabino; Ricciardone, Angelo [Dipartimento di Fisica e Astronomia ''G. Galilei'', Università degli Studi di Padova, I-35131 Padova (Italy); Peloso, Marco, E-mail: nicola.bartolo@pd.infn.it, E-mail: sabino.matarrese@pd.infn.it, E-mail: peloso@physics.umn.edu, E-mail: angelo.ricciardone@pd.infn.it [INFN, Sezione di Padova, I-35131 Padova (Italy)

    2013-08-01

    In the model of solid / elastic inflation, inflation is driven by a source that has the field theoretical description of a solid. To allow for prolonged slow roll inflation, the solid needs to be extremely insensitive to the spatial expansion. We point out that, because of this property, the solid is also rather inefficient in erasing anisotropic deformations of the geometry. This allows for a prolonged inflationary anisotropic solution, providing the first example with standard gravity and scalar fields only which evades the conditions of the so called cosmic no-hair conjecture. We compute the curvature perturbations on the anisotropic solution, and the corresponding phenomenological bound on the anisotropy. Finally, we discuss the analogy between this model and the f(?)F{sup 2} model, which also allows for anisotropic inflation thanks to a suitable coupling between the inflaton ? and a vector field. We remark that the bispectrum of the curvature perturbations in solid inflation is enhanced in the squeezed limit and presents a nontrivial angular dependence, as had previously been found for the f(?)F{sup 2} model.

  13. Fraction Reduction through Continued Fractions

    ERIC Educational Resources Information Center

    Carley, Holly

    2011-01-01

    This article presents a method of reducing fractions without factoring. The ideas presented may be useful as a project for motivated students in an undergraduate number theory course. The discussion is related to the Euclidean Algorithm and its variations may lead to projects or early examples involving efficiency of an algorithm.

  14. Fraction Tracks

    NSDL National Science Digital Library

    WGBH Boston

    1996-01-01

    This 17:29 minute video from the classic Annenberg Learner series illustrates the practice standard of communication about mathematics among a teacher and her students as they learn and play the "fraction tracks" game. The video also shows how activities like this allow students to use communication as a tool to deepen their understanding of mathematics. Three analysis questions are given at the end of the video to promote dialogue among teachers of mathematics.

  15. Fractional Triangles

    NSDL National Science Digital Library

    NRICH team

    2012-01-01

    This open-ended problem requires students to use the pattern of triangles on the given figure to divide the square into halves, thirds, sixths, and ninths. The problem asks students to find the part of the whole that is squares or triangles and then determine how these shapes represent each fraction of the whole. Included with this problem are teacher notes with suggestions for introducing the problem, discussion questions, support suggestions, and a printable version of the square.

  16. Mapping average axon diameters in porcine spinal cord white matter and rat corpus callosum using d-PFG MRI

    PubMed Central

    Komlosh, M.E.; Özarslan, E.; Lizak, M. J.; Horkayne-Szakaly, I.; Freidlin, R. Z.; Horkay, F.; Basser, P. J.

    2013-01-01

    Knowledge of microstructural features of nerve fascicles, such as axon diameter, is crucial for understanding normal function in the central and peripheral nervous systems as well as assessing changes due to pathologies. In this study double-pulsed field gradient (d-PFG) filtered MRI was used to map the average axon diameter (AAD) in porcine spinal cord, which was then compared to AADs measured with optical microscopy of the same specimen, as a way to further validate this MRI method. A novel 3D acquisition scheme was then used to obtain AADs in each voxel of a coronal slice of rat brain corpus callosum. AAD measurements were also acquired using optical microscopy performed on histological sections and validated using a novel MRI glass capillary array phantom. PMID:23583426

  17. Auditory interhemispheric transfer in relation to patterns of partial agenesis and hypoplasia of the corpus callosum in spina bifida meningomyelocele

    PubMed Central

    Hannay, H. Julia; Walker, Amy; Dennis, Maureen; Kramer, Larry; Blaser, Susan; Fletcher, Jack M.

    2009-01-01

    Spina bifida meningomyelocele with hydrocephalus (SBM) is commonly associated with anomalies of the corpus callosum (CC). We describe MRI patterns of regional CC agenesis and relate CC anomalies to functional laterality based on a dichotic listening test in 90 children with SBM and 27 typically developing controls. Many children with SBM (n = 40) showed regional CC anomalies in the form of agenesis of the rostrum and0or splenium, and a smaller number (n = 20) showed hypoplasia (thinning) of all CC regions (rostrum, genu, body, and splenium). The expected right ear advantage (REA) was exhibited by normal controls and children with SBM having a normal or hypoplastic splenium. It was not shown by children with SBM who were left handed, missing a splenium, or had a higher level spinal cord lesion. Perhaps the right hemisphere of these children is more involved in processing some aspects of linguistic stimuli. PMID:18764972

  18. Taurine attenuates hippocampal and corpus callosum damage, and enhances neurological recovery after closed head injury in rats.

    PubMed

    Gu, Y; Zhao, Y; Qian, K; Sun, M

    2015-04-16

    The protective effects of taurine against closed head injury (CHI) have been reported. This study was designed to investigate whether taurine reduced white matter damage and hippocampal neuronal death through suppressing calpain activation after CHI in rats. Taurine (50 mg/kg) was administered intravenously 30 min and 4 h again after CHI. It was found that taurine lessened the corpus callosum damage, attenuated the neuronal cell death in hippocampal CA1 and CA3 subfields and improved the neurological functions 7 days after CHI. Moreover, it suppressed the over-activation of calpain, enhanced the levels of calpastatin, and reduced the degradation of neurofilament heavy protein, myelin basic protein and ?II-spectrin in traumatic tissue 24 h after CHI. These data confirm the protective effects of taurine against gray and white matter damage due to CHI, and suggest that down-regulating calpain activation could be one of the protective mechanisms of taurine against CHI. PMID:25290011

  19. Resting-State Networks and the Functional Connectome of the Human Brain in Agenesis of the Corpus Callosum

    PubMed Central

    Owen, Julia P.; Li, Yi-Ou; Yang, Fanpei G.; Shetty, Charvi; Bukshpun, Polina; Vora, Shivani; Wakahiro, Mari; Hinkley, Leighton B.N.; Nagarajan, Srikantan S.; Sherr, Elliott H.

    2013-01-01

    Abstract The corpus callosum is the largest white matter fiber bundle connecting the two cerebral hemispheres. In this work, we investigate the effect of callosal dysgenesis on functional magnetic resonance imaging (fMRI) resting-state networks and the functional connectome. Since alternate commissural routes between the cerebral hemispheres exist, we hypothesize that bilateral cortical networks can still be maintained in partial or even complete agenesis of the corpus callosum (AgCC). However, since these commissural routes are frequently indirect, requiring polysynaptic pathways, we hypothesize that quantitative measurements of interhemispheric functional connectivity in bilateral networks will be reduced in AgCC compared with matched controls, especially in the most highly interconnected cortical regions that are the hubs of the connectome. Seventeen resting-state networks were extracted from fMRI of 11 subjects with partial or complete AgCC and 11 matched controls. The results show that the qualitative organization of resting-state networks is very similar between controls and AgCC. However, interhemispheric functional connectivity of precuneus, posterior cingulate cortex, and insular-opercular regions was significantly reduced in AgCC. The preserved network organization was confirmed with a connectomic analysis of the resting-state fMRI data, showing five functional modules that are largely consistent across the control and AgCC groups. Hence, the reduction or even complete absence of callosal connectivity does not affect the qualitative organization of bilateral resting-state networks or the modular organization of the functional connectome, although quantitatively reduced functional connectivity can be demonstrated by measurements within bilateral cortical hubs, supporting the hypothesis that indirect polysynaptic pathways are utilized to preserve interhemispheric temporal synchrony. PMID:24063289

  20. Sgk1 regulates desmoglein 1 expression levels in oligodendrocytes in the mouse corpus callosum after chronic stress exposure.

    PubMed

    Miyata, Shingo; Yoshikawa, Keiko; Taniguchi, Manabu; Ishikawa, Toshiko; Tanaka, Takashi; Shimizu, Shoko; Tohyama, Masaya

    2015-08-14

    Major depression, one of the most prevalent mental illnesses, is thought to be a multifactorial disease related to both genetic and environmental factors. However, the genes responsible for and the pathogenesis of major depression at the molecular level remain unclear. Recently, we reported that stressed mice with elevated plasma corticosterone levels show upregulation and activation of serum glucocorticoid-regulated kinase (Sgk1) in oligodendrocytes. Active Sgk1 causes phosphorylation of N-myc downstream-regulated gene 1 (Ndrg1), and phospho-Ndrg1 increases the expression of N-cadherin, ?-catenin, and ?-catenin in oligodendrocytes. This activation of the Sgk1 cascade results in morphological changes in the oligodendrocytes of nerve fiber bundles, such as those present in the corpus callosum. However, little is known about the molecular functions of the traditional and/or desmosomal cadherin superfamily in oligodendrocytes. Therefore, in this study, we aimed to elucidate the functions of the desmosomal cadherin superfamily in oligodendrocytes. Desmoglein (Dsg) 1, Dsg2, and desmocollin 1 (Dsc1) were found to be expressed in the corpus callosum of mouse brain, and the expression of a subtype of Dsg1, Dsg1c, was upregulated in oligodendrocytes after chronic stress exposure. Furthermore, Dsg1 proteins were localized around the plasma membrane regions of oligodendrocytes. A study in primary oligodendrocyte cultures also revealed that chronic upregulation of Sgk1 by dexamethasone administration is involved in upregulation of Dsg1c mRNA. These results may indicate that chronic stress induced Sgk1 activation in oligodendrocytes, which increases Dsg1 expression near the plasma membrane. Thus, Dsg1 upregulation may be implicated in the molecular mechanisms underlying the morphological changes in oligodendrocytes in response to chronic stress exposure. PMID:26043694

  1. Asthenospheric Anisotropy Beneath North America

    NASA Astrophysics Data System (ADS)

    Fischer, K. M.; McCarthy, C. M.; Zaranek, S. E.; Rychert, C. A.; Li, A.

    2005-12-01

    We are studying how anisotropy varies from the lithosphere to the asthenosphere using teleseismic body and surface waves in eastern and central North America, and we are investigating the relationship of observed asthenospheric anisotropy to numerical models of asthenospheric flow. Surface wave inversions and migration of teleseismic scattered waves define a decrease in lithospheric thickness from more than 200 km in Proterozoic regions to less than 100 km at the eastern continental margin. Shear-wave splitting in SKS phases indicates significant anisotropy beneath the region, but alone these data cannot constrain the depth at which the anisotropy occurs. In an area of the northeastern United States and southeastern Canada that is relatively densely sampled by permanent broadband stations and past temporary broadband arrays, inversion of Rayleigh waves reveals very little azimuthal anisotropy at lithospheric depths; when the Rayleigh waves are integrated with observations of roughly 1 s of SKS splitting, significant asthenospheric anisotropy is required. Further insight on the asthenosphere in this area comes from inversions of Ps phases which reveal a very rapid drop in shear velocity across the lithosphere-asthenosphere boundary (3-11% over less than 11 km). This velocity gradient is too sharp to be explained by purely thermal models, but is consistent with an asthenosphere that contains a few per cent partial melt or that is enriched in volatiles relative to the lithosphere. Evidence for azimuthal anisotropy in the asthenosphere has also been obtained across a broader region of the eastern and central United States. Love and Rayleigh wave inversions along portions of the Florida to Edmonton (FLED) IRIS/PASSCAL array show that Love wave velocities are fast relative to Rayleigh wavespeeds, similar to the findings of Gaherty (2004) using data from the Missouri to Massachusetts (MOMA) IRIS/PASSCAL array. Given that these linear arrays are orthogonal with respect to each other, and that SKS splitting fast directions in the region are fairly consistent and parallel to the MOMA array, the surface waves are most simply explained by radial anisotropy (a fast horizontal plane and a slow vertical axis) in the upper 200 km of the mantle, again requiring azimuthal anisotropy in the sub-lithospheric mantle to produce the SKS splitting. These results suggest that deformation fabrics in the lithosphere and asthenosphere are fundamentally different. The orientations of observed SKS fast directions are in general consistent with the direction of asthenospheric flow around the base of the lithosphere predicted by models in which flow is dominated by plate motion.

  2. Microwave Background Anisotropies from Scaling Seed Perturbations

    E-print Network

    Durrer, Ruth

    Microwave Background Anisotropies from Scaling Seed Perturbations Ruth Durrer and Mairi, Switzerland Abstract We study microwave background anisotropies induced by scaling seed pertur- bations. Thus, compensation, which is mainly the consequence of physically sensible initial conditions, is very

  3. Effect of Fluid on Seismic Anisotropy

    Microsoft Academic Search

    K. Bandyopadhyay; T. Mukerji; G. Mavko

    2007-01-01

    We present the effect of fluid on the anisotropic Thomsen's parameters for rocks with transversely isotropic and orthorhombic symmetry. We use the anisotropic form of Gassmann's equation for fluid substitution and consider the following origins of anisotropy in the rock: (a) anisotropy due to aligned fractures, (b) thin layers of isotropic sands with different elastic properties, (c) thin layer anisotropy

  4. Anisotropy of the cosmic microwave background radiation

    Microsoft Academic Search

    J. Silk

    1981-01-01

    Theoretical predictions of the angular anisotropy in the cosmic microwave background radiation on both small and large angular scales are presented, and the effect of massive neutrinos on both the background radiation anisotropy and on the galaxy correlation function over very large scales is reviewed. Current observations show that the quadrupole anisotropy provides the greatest constraint on theory, and the

  5. CMB Anisotropies by Collapsing Textures

    E-print Network

    Kepa Sousa; Jon Urrestilla

    2013-02-22

    CMB photons passing through a collapsing texture knot receive an energy shift, creating characteristic cold and hot spots on the sky. We calculate the anisotropy pattern produced by collapsing texture knots of arbitrary shape. The texture dynamics are solved numerically on a Minkowski background.

  6. Anisotropy of machine building materials

    NASA Technical Reports Server (NTRS)

    Ashkenazi, Y. K.

    1981-01-01

    The results of experimental studies of the anisotropy of elastic and strength characteristics of various structural materials, including pressure worked metals and alloys, laminated fiberglass plastics, and laminated wood plastics, are correlated and classified. Strength criteria under simple and complex stresses are considered as applied to anisotropic materials. Practical application to determining the strength of machine parts and structural materials is discussed.

  7. The Magnetocrystalline Anisotropy of Gadolinium

    Microsoft Academic Search

    W. D. Corner; W. C. Roe; K. N. R. Taylor

    1962-01-01

    Measurements of the magnetocrystalline anisotropy constants have been made on a single crystal of gadolinium using a torque magnetometer. The apparatus used is briefly described and the application of corrections for lack of saturation and for a paramagnetic component are explained. Measurements have been made between 37.5 °K and 315 °K and it is found that three constants are required

  8. anisotropy of Earth's inner core

    Microsoft Academic Search

    Xiaodong Song; Don V. Helmberger

    1993-01-01

    In an effort to confirm inner core anisotropy, we conducted a systematic search for PKP ray paths with various angles from the Earth's spin axis. In particular, we studied paths nearly parallel to the spin axis (polar paths) and those nearly parallel to the equatorial plane (equatorial paths). Data for earthquakes and explosions were collected from Worldwide Standardized Seismograph Network

  9. Lateral interface anisotropy in nanomagnets

    NASA Astrophysics Data System (ADS)

    Cowburn, R. P.; Koltsov, D. K.; Adeyeye, A. O.; Welland, M. E.

    2000-05-01

    The results are presented of a study into the magnetic properties of deep submicron elliptical nanomagnets. Small arrays of 2:1 aspect ratio ellipses of major axis size 500-100 nm and of thickness 5-10 nm have been fabricated out of supermalloy. A high sensitivity magneto-optical method has then been used to measure the hysteresis loops of each array. From these measurements the effective shape anisotropy in the elongated elements can be accurately determined. The measured shape anisotropy is found to be significantly smaller (approximately 50%) than that which would be expected from standard magnetostatic calculations. It is shown experimentally and theoretically that lateral interface (i.e., edge) roughness of only a few nanometers, which is present in any real nanomagnet, leads to the appearance of a powerful anisotropy of magnetostatic origin which competes strongly with the in-plane shape anisotropy, thus accounting for the anomalously low experimental values. The significance of this for data stability in magnetic random access memory is discussed.

  10. Can we understand rocks without anisotropy?

    NASA Astrophysics Data System (ADS)

    Dabrowski, Marcin

    2014-05-01

    An effectively isotropic heterogeneous medium subject to deformation should develop compositional layering parallel to stretching direction. A layered anisotropic rock subject to layer-parallel extension may undergo mechanical instability leading to internal boudinage development. The question that arises is as to whether the formation of layering could be hampered by boudinage formation before the compositional layering is well developed. With regard to the issue, the three critical questions are: (1) How does the rock fabric evolution depend on the mechanical properties of rock constituents and the initial microstructure? (2) How does the mechanical (viscous) anisotropy relate to the shape anisotropy of a composite rock? (3) How does the internal boudinage development manifest in a rock consisting of elongated elements rather than well-developed layers? I will numerically investigate the development of shape preferred orientation and mechanical anisotropy in a composite two-phase rock undergoing stretching. A two-dimensional inclusion-host type of composite, in which an interconnected host embeds non-overlapping inclusions, is considered. Different inclusion fractions, shapes and size distributions are studied. The initial spatial distribution of the inclusions is intended to be random, statistically homogeneous (no clustering) and isotropic. In a series of complementary simulation runs, periodic inclusion arrays are analyzed. Both the inclusion and host materials are considered as viscous fluids and the intrinsic viscosities of the inclusion and the host phases are isotropic. A coherent inclusion-host interface is assumed and interfacial processes such as surface tension or diffusional mass transfer are neglected. The deformation is studied in the Stokes limit and under no gravity. A self-developed FEM code (www.milamin.org, Dabrowski et al., 2008) is used to find the velocity vectors at the inclusion interfaces. Unstructured triangular computational meshes fitting all the internal inclusion boundaries are used in the simulations. To achieve the necessary resolution of the complex geometry of evolving inclusion-host interfaces, a large number of computational points is required. References: Dabrowski, M., M. Krotkiewski, and D. W. Schmid MILAMIN: MATLAB-based finite element method solver for large problems, Geochem. Geophys. Geosyst., 9, Q04030, 2008

  11. Age-related changes in the corpus callosum in early-onset bipolar disorder assessed using volumetric and cross-sectional measurements

    Microsoft Academic Search

    Melissa Lopez-Larson; Janis L. Breeze; David N. Kennedy; Steven M. Hodge; Lena Tang; Constance Moore; Anthony J. Giuliano; Nikos Makris; Verne S. Caviness; Jean A. Frazier

    2010-01-01

    Corpus callosum (CC) area abnormalities have been reported in magnetic resonance imaging (MRI) studies of adults and youths\\u000a with bipolar disorder (BPD), suggesting interhemispheric communication may be abnormal in BPD and may be present early in\\u000a the course of illness and affect normal neuromaturation of this structure throughout the lifecycle. Neuroimaging scans from\\u000a 44 youths with DSM-IV BPD and 22

  12. The microwave background anisotropies: observations.

    PubMed

    Wilkinson, D

    1998-01-01

    Most cosmologists now believe that we live in an evolving universe that has been expanding and cooling since its origin about 15 billion years ago. Strong evidence for this standard cosmological model comes from studies of the cosmic microwave background radiation (CMBR), the remnant heat from the initial fireball. The CMBR spectrum is blackbody, as predicted from the hot Big Bang model before the discovery of the remnant radiation in 1964. In 1992 the cosmic background explorer (COBE) satellite finally detected the anisotropy of the radiation-fingerprints left by tiny temperature fluctuations in the initial bang. Careful design of the COBE satellite, and a bit of luck, allowed the 30 microK fluctuations in the CMBR temperature (2.73 K) to be pulled out of instrument noise and spurious foreground emissions. Further advances in detector technology and experiment design are allowing current CMBR experiments to search for predicted features in the anisotropy power spectrum at angular scales of 1 degrees and smaller. If they exist, these features were formed at an important epoch in the evolution of the universe--the decoupling of matter and radiation at a temperature of about 4,000 K and a time about 300,000 years after the bang. CMBR anisotropy measurements probe directly some detailed physics of the early universe. Also, parameters of the cosmological model can be measured because the anisotropy power spectrum depends on constituent densities and the horizon scale at a known cosmological epoch. As sophisticated experiments on the ground and on balloons pursue these measurements, two CMBR anisotropy satellite missions are being prepared for launch early in the next century. PMID:9419320

  13. "Multicystic dysplastic kidney (Potter type II syndrome) and agenesis of corpus callosum (ACC) in two consecutive pregnancies: a possible teratogenic effect of electromagnetic exposure in utero".

    PubMed

    Tonni, Gabriele; Azzoni, Daniela; Ventura, Alessandro; Ambrosetti, Fabrizio; De Felice, Claudio

    2008-01-01

    Agenesis of the corpus callosum is found in about 5 per 1,000 births and it is due to maldevelopment or, secondary, to destructive lesions. Multicystic dysplastic kidneys is a consequence of either developmental failure of the mesonephric blastema to form nephrons or to early urinary obstruction due to urethral or ureteric atresia and can be found in about 1 per 1,000 live births. A case of fetal multicystic dysplastic kidney disease (Potter type II syndrome) and complete agenesis of the corpus callosum demonstrated by the presence of Probst bundles associated with colpocephaly occurring in the same mother in her two consecutive pregnancies is reported. Data regarding possible teratogenetic effect due to electromagnetic exposure in utero have also been investigated and raised suspicionus as a potential risk factor. In cases of suspected second trimester ultrasound diagnosis of agenesis of corpus callosum (ACC), the following clinical management should be recommended: fetal karyotype; a second level scan with differentiation between underlying conditions such as hydrocephalus and holoprosencephaly; antenatal MRI to enhance the diagnostic accuracy of possible associated neuronal migration (when possible); and direct demonstration of the presence of the Probst bundles to neurohistology. PMID:19065324

  14. Perpendicular anisotropy in granular Co-Zr-O C. R. Sullivan

    E-print Network

    , and high in-plane anisotropy field Hk should have great advantages over other metal-alloy soft magnetic magnetization Ms, a high fraction of cobalt is desired. Ohnuma et al.2,3 have also reported that favorable soft of this material is permitted. However, permission to reprint or republish this material for advertising

  15. Match My Fraction

    NSDL National Science Digital Library

    Utah Education Network

    2012-04-30

    The students will use pattern blocks to demonstrate fractions and equivalent fractions. They begin by finding and modeling equivalent fractions with pattern blocks, then they are asked to match cards to show the equivalent fractions.

  16. Fractions Made Faster

    NSDL National Science Digital Library

    In this problem students use a visual representation of fractions to compare fractions. Students are given two fractions and using the fraction wall they must compare them and find the difference between them. A Teacher's Notes page, hints, solutions, and printable pages are provided. The goal of this problem is for students to compare the two fractions given by using the visual fraction wall or their knowledge of equivalent fractions and subtracting fractions.

  17. Fractional Schrödinger equation.

    PubMed

    Laskin, Nick

    2002-11-01

    Some properties of the fractional Schrödinger equation are studied. We prove the Hermiticity of the fractional Hamilton operator and establish the parity conservation law for fractional quantum mechanics. As physical applications of the fractional Schrödinger equation we find the energy spectra of a hydrogenlike atom (fractional "Bohr atom") and of a fractional oscillator in the semiclassical approximation. An equation for the fractional probability current density is developed and discussed. We also discuss the relationships between the fractional and standard Schrödinger equations. PMID:12513557

  18. Fractional Schrödinger equation

    Microsoft Academic Search

    Nick Laskin

    2002-01-01

    Some properties of the fractional Schrödinger equation are studied. We prove the Hermiticity of the fractional Hamilton operator and establish the parity conservation law for fractional quantum mechanics. As physical applications of the fractional Schrödinger equation we find the energy spectra of a hydrogenlike atom (fractional ``Bohr atom'') and of a fractional oscillator in the semiclassical approximation. An equation for

  19. Anisotropy Studies in Central Greece

    NASA Astrophysics Data System (ADS)

    Kaviris, G.; Papadimitriou, P.; Makropoulos, K.

    2007-12-01

    The Gulf of Corinth, located in Central Greece, is a tectonic graben characterized by high seismicity level. GPS measurements indicate extension of the Gulf in an approximately N-S direction, with a rate of 10 to 15 mm/year. The southern part of the Gulf is dominated by the presence of large active normal faults in an almost E-W direction, dipping north, resulting to the subsidence of the central part of the graben. Analysis of data recorded by the Cornet network, which is the permanent network of the University of Athens, revealed the existence of an anisotropic upper crust at the eastern part of the Gulf of Corinth. Anisotropy was also observed at the western part of Corinth Gulf, using data recorded by a temporary seismological network installed in the area. Furthermore, shear wave splitting analysis was performed in the region of Attica (to the NE of the Gulf) that hosts Athens, the capital of Greece, using aftershocks of the 1999 Athens earthquake (Mw=6.0) that caused 143 fatalities. The methods used for the determination of the splitting parameters are the polarization vector as a function of time (polarigram) and the hodogram. For each selected event the direction of polarization of the fast shear wave, the delay between the two split shear waves and the polarization of the source were measured. Concerning both parts of the Gulf of Corinth, the obtained mean values of anisotropy vary between N90° and N142°. In the region of Attica the mean values of the anisotropy direction of all stations vary between N95° and N100°, almost parallel to the azimuth of the Parnitha fault. The time delay between the split shear waves vary between 0.020s and 0.130s. The obtained anisotropy measurements are in agreement with the extensive dilatancy anisotropy (EDA) model, since the direction of anisotropy is independent from the event-station azimuth and perpendicular to the direction of extension. ACKNOWLEDGMENTS The present study was co-funded by the European Social Fund and National Resources - (EPEAEK II) PYTHAGORAS, contract No. 70/3/7306.

  20. Cross-Sectional Analysis of the Association Between Age and Corpus Callosum Size in Chimpanzees (Pan troglodytes)

    PubMed Central

    Hopkins, William D.; Phillips, Kimberley A

    2015-01-01

    The CC is the major white matter tract connecting the cerebral hemispheres and provides for interhemispheric integration of sensory, motor and higher-order cognitive information. The midsagittal area of the CC has been frequently used as a marker of brain development in humans. We report the first investigation into the development of the corpus callosum and its regional subdivisions in chimpanzees (Pan troglodytes). Magnetic resonance images were collected from 104 chimpanzees (female n = 63, male n = 41) ranging in age from 6 years (pre-pubescent period) to 54 years (old age). Sustained linear growth was observed in the area of the CC subdivision of the genu; areas of the the posterior midbody and anterior midbody displayed non-linear growth during development. After adjusting for total brain size, we observed linear growth trajectories of the total CC and CC subdivisions of the genu, posterior midbody, isthmus and splenium, and non-linear growth trajectories of the rostral body and anterior midbody. These developmental patterns are similar to the development of the CC in humans. As the growth curves of the CC mirrors growth seen in the percentage of white matter in humans, our results suggest chimpanzees show continued white matter development in regions related to cognitive development. PMID:20091760

  1. Single-shot T1 mapping of the corpus callosum: a rapid characterization of fiber bundle anatomy

    PubMed Central

    Hofer, Sabine; Wang, Xiaoqing; Roeloffs, Volkert; Frahm, Jens

    2015-01-01

    Using diffusion-tensor magnetic resonance imaging and fiber tractography the topographic organization of the human corpus callosum (CC) has been described to comprise five segments with fibers projecting into prefrontal (I), premotor and supplementary motor (II), primary motor (III), and primary sensory areas (IV), as well as into parietal, temporal, and occipital cortical areas (V). In order to more rapidly characterize the underlying anatomy of these segments, this study used a novel single-shot T1 mapping method to quantitatively determine T1 relaxation times in the human CC. A region-of-interest analysis revealed a tendency for the lowest T1 relaxation times in the genu and the highest T1 relaxation times in the somatomotor region of the CC. This observation separates regions dominated by myelinated fibers with large diameters (somatomotor area) from densely packed smaller axonal bundles (genu) with less myelin. The results indicate that characteristic T1 relaxation times in callosal profiles provide an additional means to monitor differences in fiber anatomy, fiber density, and gray matter in respective neocortical areas. In conclusion, rapid T1 mapping allows for a characterization of the axonal architecture in an individual CC in less than 10 s. The approach emerges as a valuable means for studying neocortical brain anatomy with possible implications for the diagnosis of neurodegenerative processes. PMID:26029059

  2. AGE CHANGES IN MYELINATED NERVE FIBERS OF THE CINGULATE BUNDLE AND CORPUS CALLOSUM IN THE RHESUS MONKEY

    PubMed Central

    Bowley, Michael P.; Cabral, Howard; Rosene, Douglas L.; Peters, Alan

    2010-01-01

    Aging is accompanied by deficits in cognitive function, which may be related to the vulnerability of myelinated nerve fibers to the normal process of aging. Loss of nerve fibers, together with age-related alterations in myelin sheath structure, may result in the inefficient and poorly coordinated conduction of neuronal signals. Until now, the ultrastructural analysis of cerebral white matter fiber tracts associated with frontal lobe areas critical in cognitive processing has been limited. In this study we have analyzed the morphology and area number density of myelinated nerve fibers in the cingulate bundle and genu of the corpus callosum in behaviorally assessed young, middle aged, and old rhesus monkeys (Macaca mulatta). In both structures, normal aging results in a 20% decrease in the number of myelinated nerve fibers per unit area, while remaining nerve fibers exhibit an increasing frequency of degenerative changes in their myelin sheaths throughout middle and old age. Concomitantly, myelination continues in older monkeys, suggesting ongoing, albeit inadequate, reparative processes. Despite similar patterns of degeneration in both fiber tracts, only the age-related changes in the cingulate bundle correlate with declining cognitive function, underscoring its role as a critical corticocortical pathway linking the medial prefrontal, cingulate, and parahippocampal cortices in processes of working memory, recognition memory, and other higher cognitive faculties. These results further demonstrate the important role myelinated nerve fiber degeneration plays in the pathogenesis of age-related cognitive decline. PMID:20533359

  3. Lipoma in the Corpus Callosum Presenting with Epileptic Seizures Associated with Expanding Perifocal Edema: A Case Report and Literature Review

    PubMed Central

    Fuga, Michiyasu; Yamamoto, Yohei; Hasegawa, Yuzuru; Murayama, Yuichi; Takahashi-Fujigasaki, Junko

    2015-01-01

    This report describes a rare case of a patient with lipoma presenting with epileptic seizures associated with expanding perifocal edema. The patient was a 48-year-old man who presented with loss of consciousness and convulsions. Magnetic resonance imaging (MRI) revealed a calcified mass in the corpus callosum with perifocal edema causing mass effect. An interhemispheric approach was used to biopsy the mass lesion. Histological examination revealed typical adipose cells, along with hamartomatous components. These components contained neurofilament and S-100-positive structures showing marked calcification. Fibrous cells immunoreactive for ?-smooth muscle actin and epithelial membrane antigen proliferated with focal granulomatous inflammatory changes. MIB-1 index was approximately 5% in immature cells observed in granulomatous areas. We thus suspected a coexisting neoplastic component. The residual lesion persisted in a dormant state for 2 years following biopsy. Surgical resection of a lipoma is extremely difficult and potentially dangerous. However, in the present case, the lesion was accompanied by atypical, expanding, and perifocal edema. Surgical treatment was inevitable for the purpose of histological confirmation, considering differential diagnoses such as dermoid, epidermoid, and glioma. In the end, anticonvulsant therapy proved effective for controlling epileptic seizures.

  4. Magnetic Anisotropy of Igneous Rocks

    Microsoft Academic Search

    F. D. Stacey

    1960-01-01

    A torque-meter method of measuring the magnetic anisotropy of rocks has been used in a study of a 1050-foot bore core from a Tasmanian dolerite sill. Each cylindrical specimen was suspended in a uniform field of 10.6 kilo-oersteds perpendicular to its axis, and the torque T exerted on it was measured at 10 ø intervals of the angle # between

  5. Effect of Fluid on Seismic Anisotropy

    NASA Astrophysics Data System (ADS)

    Bandyopadhyay, K.; Mukerji, T.; Mavko, G.

    2007-12-01

    We present the effect of fluid on the anisotropic Thomsen's parameters for rocks with transversely isotropic and orthorhombic symmetry. We use the anisotropic form of Gassmann's equation for fluid substitution and consider the following origins of anisotropy in the rock: (a) anisotropy due to aligned fractures, (b) thin layers of isotropic sands with different elastic properties, (c) thin layer anisotropy with alternate layering of anisotropic sand, and (d) stress induced anisotropy. Our modeling results show that fractured rocks exhibit significant changes in anisotropy due to fluid substitution. The predicted change in such situations can reach even five times the initial anisotropy. The magnitude of change in anisotropy arising from nonhydrostatic stress or layering of different facies is less significant. We find that, it is the initial anisotropy of the medium that controls the fluid effect on anisotropy. Higher initial anisotropy causes larger change in anisotropic parameters due to fluid substitution. We present an approximate fluid substitution equation for vertical velocity in anisotropic medium. We express the changes in vertical P-wave velocity due to fluid substitution by isotropic fluid substitution plus a correction term proportional to the Thomsen's parameter 'delta'. This simplification reduces the number of parameters required for fluid substitution in anisotropic rocks. It also helps us to explain the over- or under-prediction of isotropic Gassmann's prediction in anisotropic rock in terms of the magnitude and sign of 'delta'.

  6. Math / Fractions and Decimals

    NSDL National Science Digital Library

    Mr. Larry Petersen

    2008-10-01

    Compute problems involving multiplication and division of whole numbers and addition and subtraction of simple fractions and decimals. Learning how to add and subtract Fractions Here is a fun game on adding fractions with like Denominators. Click on \\"Adding Fractions With Like Denominators\\" Fraction Addition A Basic explanation of adding Fractions. (Especially for teachers) Adding Fractions Learning how to add and subtract Decimals Practice on adding Decimals Decimals Blog post link Let me know what you think ...

  7. Towards metamaterials with giant dielectric anisotropy via homogenization: An analytical study

    NASA Astrophysics Data System (ADS)

    Mackay, Tom G.

    2015-01-01

    A random mixture of two isotropic dielectric materials, one composed of oriented spheroidal particles of relative permittivity ?a and the other composed of oriented spheroidal particles of relative permittivity ?b, was considered in the long wavelength regime. The permittivity dyadic of the resulting homogenized composite material (HCM) was estimated using the Bruggeman homogenization formalism. The HCM was an orthorhombic biaxial material if the symmetry axes of the two populations of spheroids were mutually perpendicular and a uniaxial material if these two axes were mutually aligned. The degree of anisotropy of the HCM, as gauged by the ratio of the eigenvalues of the HCM's permittivity dyadic, increased as the shape of the constituent particles became more eccentric. The greatest degrees of HCM anisotropy were achieved for the limiting cases wherein the constituent particles were shaped as needles or discs. In these instances explicit formulas for the HCM anisotropy were derived from the dyadic Bruggeman equation. Using these formulas it was found that the degrees of HCM anisotropy are proportional to ?{?b } or ?b, at fixed values of volume fraction and ?a, for ?b > ?a. Thus, in principle, metamaterials can be conceptualized via homogenization with extremely large degrees of anisotropy, by controlling the geometries and orientations of remarkably simple constituent particles. In practice, the degree of anisotropy would be limited by the available value of ?b (and/or ?a).

  8. Parameter inversion for seismic anisotropy

    NASA Astrophysics Data System (ADS)

    Kumar, Chandan

    An important objective of reflection seismology is to transform a seismic dataset into a reflectivity image of the subsurface. Reflectivity imaging involves removal of propagation effects by creating an inverse propagation operator using an estimated macro velocity model. The accuracy of a reflectivity image depends on the accuracy of the velocity model used. Hence, the estimation of a good velocity model is crucial. Flat sedimentary layers, though laterally homogeneous over small-scale, often exhibit a simple kind of anisotropy called vertical transverse isotropy (VTI). Negligence of anisotropy in migration may result in significant deviation of an imaged reflector from its true position. Our ability to estimate anisotropic parameters using limited aperture, limited bandwidth seismic data is restricted. Several recent developments in data acquisition including more intense acquisition (e.g., 3-D), broader bandwidths, and new survey methodologies (e.g., Ocean Bottom Seismics and vertical cables) have improved our ability in dealing with anisotropy. In light of these recent developments the objective of my research is three-fold---(i) finding better algorithms for anisotropy estimation that makes use of enhanced data acquisition, more powerful computers and graphical interfaces, (ii) understanding and re-evaluating our limitations/capabilities of anisotropy estimation in light of the new algorithms, and (iii) using the results of analysis as an aid to constrain anisotropy estimates. The Common Focus Point (CFP) technology defines a recent method of prestack migration velocity analysis which has several advantages over other popular methods. One remarkable advantage is that the imaging error is given directly in time allowing easier model updates through inversion. The CFP technique has been used in recent past for estimating isotropic heterogeneous velocity model for geologically complex subsurface. For my research, I extend this method to anisotropic parameter inversion by suitably implementing the space-time domain version of CFP method for picking the traveltime error resulting from the incorrect guess model. I successfully implement this approach to estimate anisotropy of the shale thrust-sheets in the Canadian Foothills model. This model has targets of interest below transversely isotropic shale thrust-sheets and estimating anisotropic parameters is important for proper depth imaging of target zone. The synthetic P-mode data used for the analysis has been generated using a finite difference algorithm. In order to quantitatively assess the advantages or limitations of CFP domain velocity analysis in estimating the anisotropic parameters, I have performed sensitivity analysis under different experimental settings like different observation apertures, layer thicknesses, tilt in symmetry axis, picking error and the use of mode converted data. The results quantitatively establish the advantage of joint inversion of P-P and P-Sv over the conventional inversion of solely P-P data in constraining the depth and anisotropic parameters. Also the constraint on parameter estimation improves with increase in angle of tilt of symmetry axis with respect to the reflector. The CFP domain analysis also has advantages in dealing with mode converted P-Sv data as separate focusing at the receiver side and source side allows it to deal with one wave type at a time. In complex media, this helps avoid the cumbersome calculation of common conversion point (CCP) location. The CFP analysis has been applied for estimating anisotropic parameters as well as layer thickness by joint inversion of P-P and P-Sv synthetic data for the geology encountered in Blackfoot field.

  9. Fractional Vector Calculus and Fractional Special Function

    E-print Network

    Ming-Fan Li; Ji-Rong Ren; Tao Zhu

    2010-01-17

    Fractional vector calculus is discussed in the spherical coordinate framework. A variation of the Legendre equation and fractional Bessel equation are solved by series expansion and numerically. Finally, we generalize the hypergeometric functions.

  10. Fractions are Fun!

    NSDL National Science Digital Library

    Mrs.Carter

    2005-10-25

    Fractions are an important part of our lives. This project will help you become more familiar with fractions Go to this website and do the first three exercisesComplex Fraction -- from MathWorld Explore these two websites! Reduced Fraction -- from MathWorld Fractions ...

  11. Fraction Number Line

    NSDL National Science Digital Library

    2010-01-01

    Using this interactive fraction number line, students can identify and locate equivalent fractions as well as compare fractions. They can move the mouse to the left or right and "mark" fractions on the number line. A section called "Which is Larger?" provides examples of fraction pairs to compare.

  12. Fraction Feud: Comparing and Ordering Fractions

    NSDL National Science Digital Library

    Jennifer Rising

    2011-01-01

    In this lesson plan students use fraction bars to explore and compare the sizes of fractions. The lesson includes an activity sheet, answer key, guiding questions and prompts, assessment options and extensions, and a link to Fraction Feud, an interactive game (cataloged separately and listed as a related resource).

  13. Magnetic Anisotropy in the Radula of Chiton

    NASA Astrophysics Data System (ADS)

    Zhao, Jian-Gao; Qian, Xia; Liu, Wei; Liu, Chuan-Lin; Zhan, Wen-Shan

    2000-07-01

    Radular teeth of chitons were studied by using magnetic torque-meter and transmission electron microscopy (TEM). The magnetic torque curves give clear evidence of presence of strong uni-axial magnetic anisotropy. The easy axis is along the length direction of tongue-like radula. The TEM pattern shows that long chip-like magnetite nano-scaled particles packed in the radular teeth with both uni-axial shape anisotropy and magneto-crystalline anisotropy.

  14. Magnetocrystalline Anisotropy of Magnetite at Low Temperature

    Microsoft Academic Search

    Wilfred Palmer

    1963-01-01

    The magnetocrystalline anisotropy of magnetite has been measured by the torque method between 4.2 and 110°K. The anisotropy energy of the orthorhombic phase which exists below 114.5°K is represented by the formula Ea=Kaalphaa2+Kbalphab2+Kaaalphaa4+Kabalphaa2alphab2+Kbbalphab4, where alphaa and alphab are the direction cosines of the magnetization with respect to the hard and intermediate axes, respectively. The five anisotropy coefficients were determined from

  15. Effects of diagenetic processes on seismic velocity anisotropy in near-surface sandstone and carbonate rocks

    NASA Astrophysics Data System (ADS)

    Koesoemadinata, Adam P.; McMechan, George A.

    2004-10-01

    The effects of diagenetic processes on velocity anisotropy in Ferron sandstone and Ellenburger carbonate core samples are investigated using petrophysical/petrological and P-wave velocity ( Vp) data at room pressure and ambient (air dry) saturation. The Vp data are measured in both vertical ( Vpv) and horizontal ( Vph) directions (parallel and perpendicular to the axes of the cores, respectively), using a 125-kHz sonic probe. The petrophysical/petrological properties for the Ferron sandstone are bulk porosity, fluid permeability and volume fractions of quartz, clay, feldspar and calcite; for the Ellenburger carbonate, they are bulk porosity, vertical permeability, horizontal permeability, maximum permeability, grain density and bulk density. In the Ferron sandstone samples, the Vph values are higher (˜8.5%) than the Vpv values, which is attributed to laminated bedding or alignment of grain orientation. Correlations between Vp anisotropy and minerals that represent diagenetic processes are clearly demonstrated in the Ferron sandstone. Anisotropy decreases with decreasing feldspar, increasing calcite and increasing clay. This correlation suggests that calcite cementation and pore-filling kaolinite reduce velocity anisotropy of the Ferron sandstone by reduction of the net grain alignment or preferred pore orientations. The heterogeneity of the Ellenburger carbonate caused by multiple karsting and burials does not provide observable correlations between the velocity anisotropy and petrophysical/petrographic properties. In the Ellenburger carbonate, Vpv values are mostly higher (˜7.9%) than the Vph values and are likely to be related to near-vertically aligned regional fractures. The orientation and amount of velocity anisotropy and of permeability is scale dependent when fractures are present. Seismic anisotropy is closely related to subsurface lithology, rock fabric and texture, and to its diagenetic history. Consequently, analysis of seismic anisotropy provides an important tool for reservoir characterization and environmental and engineering applications.

  16. Theoretical Overview of Cosmic Microwave Background Anisotropy

    E-print Network

    E. L. Wright

    2003-05-29

    The theoretical basis for the prediction of anisotropies in the cosmic microwave background is very well developed. Very low amplitude density and temperature perturbations produce small gravitational effects, leading to an anisotropy that is a combination of temperature fluctuations at the surface of last scattering and gravitational redshifts both at last scattering and along the path to the observer. All of the primary anisotropy can be handled by linear perturbation theory, which allows a very accurate calculation of the predicted anisotropy from different models of the Universe.

  17. Dimethyl sulfoxide cataract: a model for optical anisotropy fluctuations

    NASA Astrophysics Data System (ADS)

    Bettelheim, Frederick A.; Churchill, A. C.; Robison, W. G.; Zigler, J. S.

    1996-07-01

    Rat lenses incubated in dimethyl sulfoxide (DMSO)-water binary mixtures of different compositions became turbid. A slight haziness developed up to 0.062 mole fraction f DMSO; at higher concentrations dense turbidity developed. Microscopic examination of the incubated rat lenses showed damage restricted to the epithelium and outer cortex at low DMSO concentrations; maximum damage occurred, in terms of fiber cell swelling, extracellular fluid formation and disintegration of epithelium, at 0.25 mole ratio of DMSO. Scanning electron microscopic observation showed that at high DMSO concentrations, especially at 0.25 mole fraction, the contents of the fiber cells were greatly damaged. Apparently a large part of the crystallins had coalesced around the cytoskeletal bodies. Polarized light-scattering intensity measurements and their analyses indicated that when dense opacities developed at high DMSO concentrations, the major contribution to the turbidity came for the optical anisotropy fluctuations. The change in the organization of the components within the fiber cells disturbs the balance between intrinsic birefringence and form birefringence necessary for transparency. Thus, the DMSO-caused opacification can be described as a good model for the involvement of optical anisotropy fluctuations in cataractogenesis.

  18. Quiz: Those Frustrating Fractions

    NSDL National Science Digital Library

    Denise

    2007-10-16

    This blog page proposes five questions about fraction operations that cause students difficulty. Procedures for calculating with fractions can seem inconsistent and counterintuitive; understanding them requires a conceptual understanding of the meaning of fractions and operations.

  19. Sub-regional volumes changes of the corpus callosum in the drug naive patients with late-onset depression.

    PubMed

    Hahn, Changtae; Lim, Hyun-Kook; Won, Wang Youn; Joo, Soo-Hyun; Ahn, Kook Jin; Jung, Won-Sang; Lee, Chang Uk

    2015-01-01

    Although sub-regional analysis methods of the corpus callosum (CC) have been developed, there has been no in vivo magnetic resonance imaging (MRI) study on a sub-regional volume analysis of the CC of late-onset depression (LOD). The aim of this study was to investigate the CC volume differences between LOD subjects and healthy elderly controls using a sub-regional analysis technique. Forty subjects with LOD and thirty nine group-matched healthy control subjects underwent 3T MRI scanning, and sub-regional volumes of the CC were measured and compared between the groups. The volumes of total (F=5.8, p=0.001), the anterior (F=5.2, p=0.001) and the posterior CC (F=5.1, p=0.001) were significantly reduced in the LOD group as compared to the control group. We measured cognitive functions in several different domains (language functions, verbal learning, visuospatial functions, delayed recall, memory consolidation, recognition memory, and executive functions) through the Korean version of the Consortium to Establish a Registry for Alzheimer's Disease. The anterior CC volume in the LOD group showed significant positive correlation with the Verbal Fluency scores. The posterior CC volume in the LOD group was positively correlated significantly with the Word List Memory, the Word List Recall and the Constructional Praxis scores. This study is the first to elaborate the sub-regional volume differences of the CC between controls and LOD patients. These structural changes in the CC might be at the core of the underlying neurobiological mechanisms in LOD. PMID:25134843

  20. Modeling Multiplication with Fractions

    NSDL National Science Digital Library

    Joseph Ratasky

    2012-08-18

    Students will relate multiplication strategies with fractions through problem solving situations. This lesson connects prior understanding of multiplication and equal groups to multiplication of fractions.

  1. Orthogonal invariant sets of the diffusion tensor and the development of a curvilinear set suitable for low-anisotropy tissues.

    PubMed

    Damion, Robin A; Radjenovic, Aleksandra; Ingham, Eileen; Jin, Zhongmin; Ries, Michael E

    2013-01-01

    We develop a curvilinear invariant set of the diffusion tensor which may be applied to Diffusion Tensor Imaging measurements on tissues and porous media. This new set is an alternative to the more common invariants such as fractional anisotropy and the diffusion mode. The alternative invariant set possesses a different structure to the other known invariant sets; the second and third members of the curvilinear set measure the degree of orthotropy and oblateness/prolateness, respectively. The proposed advantage of these invariants is that they may work well in situations of low diffusion anisotropy and isotropy, as is often observed in tissues such as cartilage. We also explore the other orthogonal invariant sets in terms of their geometry in relation to eigenvalue space; a cylindrical set, a spherical set (including fractional anisotropy and the mode), and a log-Euclidean set. These three sets have a common structure. The first invariant measures the magnitude of the diffusion, the second and third invariants capture aspects of the anisotropy; the magnitude of the anisotropy and the shape of the diffusion ellipsoid (the manner in which the anisotropy is realised). We also show a simple method to prove the orthogonality of the invariants within a set. PMID:24244366

  2. Perpendicular anisotropy in Co-Cr films

    NASA Astrophysics Data System (ADS)

    Ishizuka, M.; Komoda, T.; Tsuchimoto, S.; Yoshikawa, M.; Ishio, S.; Takahashi, M.

    1983-03-01

    The temperature dependence of saturation magnetization and perpendicular magnetic anisotropy for 16 and 18% Cr-Co sputtered films was studied. The following were found: (i) the Curie temperatures of films are higher than those of bulk alloys; (ii) the perpendicular anisotropy constant increases after being heated to 400°C; and (iii) it changes from positive to negative at about 640°C.

  3. Cabo, January 2009 Secondary CMB Anisotropy

    E-print Network

    Hu, Wayne

    1 (2006) Secondary Anisotropy:Aghanim, Majumdar, Silk Rep. Prog. Phys. 71 066902 (2008) Reionization, Majumdar, Silk Rep. Prog. Phys. 71 066902 (2008) · Reionization: Zaldarriaga et al, CMBpol White Paper) · Lensing: Lewis & Challinor Phys Rep. 429 1 (2006) · Secondary Anisotropy: Aghanim, Majumdar, Silk Rep

  4. Uniaxial Anisotropy in Iron-Cobalt Ferrites

    Microsoft Academic Search

    Shuichi Iida; Hisashi Sekizawa; Yoshimichi Aiyama

    1958-01-01

    The uniaxial anisotropy induced by the magnetic annealing in both single and poly-crystals of iron-cobalt ferrites has been studied experimentally. It is shown that the magnitudes of the uniaxial anisotropy depend essentially on the degree of oxidation of the specimens and become almost zero after deoxidizing heat treatments. Contrary to the conclusion by Bozorth et al., the dependence of the

  5. TILTED SAMPLE ACOUSTIC MICROSCOPY FOR ANISOTROPY MEASUREMENT

    E-print Network

    Khuri-Yakub, Butrus T. "Pierre"

    acoustic microscope with the spherical lens insonifies the samples with circularly symmetric fieldsTILTED SAMPLE ACOUSTIC MICROSCOPY FOR ANISOTROPY MEASUREMENT F. L. Degertekin, B.V. Honein and B a method in which the sample is simply tilted to improve anisotropy sensitivity of the acoustic microscope

  6. Acoustic axes in triclinic anisotropy Vclav Vavrycuka

    E-print Network

    Cerveny, Vlastislav

    Acoustic axes in triclinic anisotropy Václav Vavrycuka Geophysical Institute, Academy of Sciences May 2005 Calculation of acoustic axes in triclinic elastic anisotropy is considerably more complicated. In this way we obtain 16 isolated acoustic axes, which can run in real or complex directions. The real

  7. Mantle Anisotropy Beneath China: Measurements and Implications

    Microsoft Academic Search

    Y. Gao; J. Wu; K. H. Liu; S. S. Gao; Y. Shi

    2006-01-01

    Seismic anisotropy in the mantle beneath mainland China was studied using data from the China Digital Seismograph Network (CDSN) by Zheng & Gao (1994), and later by using data from more stations and different seismograph networks. The present study utilizes data from the recently-completed China National Seismograph Network (CNSN) from 2001 to 2005 to further improve the coverage of anisotropy

  8. Linear Decrease in the Magnetocrystalline Anisotropy

    Microsoft Academic Search

    C. Abraham; A. Aharoni

    1960-01-01

    In a previous paper, an attempt was made to reduce the theoretical coercive force by assuming that the magnetocrystalline anisotropy constant vanished in a certain region. A modification of this assumption was made in the present work, namely, the magnetocrystalline anisotropy was taken as zero in a part of the \\

  9. Magnetocrystalline anisotropy of ferro- and ferrimagnetics

    Microsoft Academic Search

    M. Darby; E. Isaac

    1974-01-01

    The phenomenology and atomic origins of magnetocrystalline anisotropy are reviewed, and the experimental data are summarized for the spinel ferrites, garnets, metals of the 3d and 4f transition series, and some selected rare earth compounds. Only intrinsic magnetocrystalline anisotropy is covered, and attention is principally confined to single-crystal results. Antiferromagnetic materials have been omitted.

  10. AVO and anisotropy from logs and walkaways

    SciTech Connect

    Leaney, S.W.; Borland, W.E. (Schlumberger Geophysics Nusantara, Jakarta (Indonesia))

    1994-07-01

    AVO (amplitude versus offset) is the seismic technique used for mapping lithology, and modeling is an important step for successful AVO interpretations. Shear velocity measurements are essential, since AVO attempts to exploit the elastic (as opposed to acoustic) nature of seismic wave propagation. A property of seismic wave propagation not often considered is anisotropy. This is probably because the magnitude of the anisotropy has been difficult to measure, and its effect on AVO is not widely known. New technology is helping to improve AVO modeling. Dipole source shear logging tools can now measure very slow shear velocities, increasing the range of applicability of AVO, and new borehole seismic techniques can measure anisotropy. When integrated, these new measurements provide more detailed information about the elastic moduli that govern wave propagation, and bring the possibility for greater reliability in AVO interpretation. Two examples of ray-trace AVO synthetics are shown to illustrate typical AVO responses and the importance of shear velocity information. An overview of anisotropy is given and a new technique to estimate anisotropy from walkaway surveys (multi-offset VSPs) is described. The log and walkaway measurements are then integrated to study the impact of anisotropy on AVO. First, the effect of anisotropy on Ostrander's shale-sand model is investigated, and second, isotropic and anisotropic ray-trace synthetics are compared. The effect of anisotropy on AVO is found to be significant and may be lead to misinterpretations of AVO anomalies.

  11. Fractional vector calculus and fractional Maxwell's equations

    SciTech Connect

    Tarasov, Vasily E. [Skobeltsyn Institute of Nuclear Physics, Moscow State University, Leninskie gory, Moscow 119991 (Russian Federation)], E-mail: tarasov@theory.sinp.msu.ru

    2008-11-15

    The theory of derivatives and integrals of non-integer order goes back to Leibniz, Liouville, Grunwald, Letnikov and Riemann. The history of fractional vector calculus (FVC) has only 10 years. The main approaches to formulate a FVC, which are used in the physics during the past few years, will be briefly described in this paper. We solve some problems of consistent formulations of FVC by using a fractional generalization of the Fundamental Theorem of Calculus. We define the differential and integral vector operations. The fractional Green's, Stokes' and Gauss's theorems are formulated. The proofs of these theorems are realized for simplest regions. A fractional generalization of exterior differential calculus of differential forms is discussed. Fractional nonlocal Maxwell's equations and the corresponding fractional wave equations are considered.

  12. Optical and diamagnetic anisotropy of graphene oxide

    NASA Astrophysics Data System (ADS)

    Exarhos, A. L.; Vora, P. M.; Lou, Z.; Johnson, A. T.; Kikkawa, J. M.

    2009-03-01

    We have recently shown that graphene oxide (GO) emits a broad photoluminescence (PL) band in both solid and aqueous preparations. The origin of this PL is not yet well understood, but for absorptive and emissive optical processes originating in the two dimensional GO plane, one expects an in-plane polarization. Studies of optical anisotropy can therefore help to clarify the origin of the PL. Here we use a method of optical nanomagnetometry (Torrens, et al, JACS 129, p. 252 (2007)) to extract these quantities, also determining the magnetic anisotropy. We find that when aqueous preparations of GO are placed in a magnetic field, diamagnetically induced alignment leads to marked linear polarization anisotropy of absorbance and photoluminescence. By taking six optical measurements at each magnetic field, we are able to extract the intrinsic polarization anisotropies of optical absorption and emission of GO flakes and to quantify the orbital diamagnetic anisotropy. We discuss how these quantities give insight into electronic delocalization in these systems.

  13. Introduction to Proper Fractions

    NSDL National Science Digital Library

    2011-01-01

    In this lesson students learn the meaning of fractions as parts of a whole and parts of a set. They learn key vocabulary and how to compare and order fractions. The lesson links to an interactive game, Fraction Fun (catalogued separately), which gives practice in naming fractions, and to downloadable follow-up exercises (Word and pdf).

  14. Multiply Fractions Jeopardy

    NSDL National Science Digital Library

    2006-01-01

    This interactive game for one or two players is presented Jeopardy-style with five categories: Multiply a Whole Number by a Fraction, Multiply a Fraction by a Fraction, Problem Solving, Estimate Products, and More Multiplying Fractions. Participants gain or lose points as they get answers right or wrong, and correct answers are displayed with a solution is submitted.

  15. Unfolding Fraction Multiplication

    ERIC Educational Resources Information Center

    Wyberg, Terry; Whitney, Stephanie R.; Cramer, Kathleen A.; Monson, Debra S.; Leavitt, Seth

    2011-01-01

    Students often have difficulty understanding fractions, in general, and understanding how to multiply fractions, in particular. To move past this potential problem area, students need to develop a deeper understanding of multiplication and connect the ideas to fractions. In this article, the authors share their insights into teaching fraction…

  16. Fractional quantum mechanics

    Microsoft Academic Search

    Nikolai Laskin

    2000-01-01

    A path integral approach to quantum physics has been developed. Fractional path integrals over the paths of the Lévy flights are defined. It is shown that if the fractality of the Brownian trajectories leads to standard quantum and statistical mechanics, then the fractality of the Lévy paths leads to fractional quantum mechanics and fractional statistical mechanics. The fractional quantum and

  17. Multiplication of Fractions

    NSDL National Science Digital Library

    National Library of Virtual Manipulatives

    2009-07-29

    Use this virtual manipulative to graphically demonstrate, explore, and practice multiplying fractions. The grid shows two fractions multiplied together by showing one fraction in red on the left and another in blue on the bottom of a grid. The area of the overlapping region shown in purple is the product (result of multiplying) the fractions.

  18. Fractions Are Fun!!

    NSDL National Science Digital Library

    Ms. McMickell

    2005-10-25

    This project will help you be more familiar with fractions. Go to this website and do the first three exercises. Complex Fraction -- from MathWorld Choos one of these activites: Reduced Fraction -- from MathWorld Here are some activites fun activities. Choose one. Fractions ...

  19. Cup-Drawing Behavior of High-Strength Steel Sheets Containing Different Volume Fractions of Martensite

    NASA Astrophysics Data System (ADS)

    Choi, Shi-Hoon; Kim, Dae-Wan; Yang, Hoe-Seok; Han, Seong-Ho; Yoon, Jeong Whan

    2010-06-01

    Planar anisotropy and cup-drawing behavior were investigated for high-strength steel sheets containing different volume fractions of martensite. Macrotexture analysis using XRD was conducted to capture the effect of crystallographic orientation on the planar anisotropy of high-strength steel sheets. A phenomenological yield function, Yld96, which accounts for the anisotropy of yield stress and r-values, was implemented into ABAQUS using the user subroutine UMAT. Cup drawing of high-strength steel sheets was simulated using the FEM code. The profiles of earing and thickness strain were compared with the experimentally measured results.

  20. Tempered fractional calculus

    NASA Astrophysics Data System (ADS)

    Sabzikar, Farzad; Meerschaert, Mark M.; Chen, Jinghua

    2015-07-01

    Fractional derivatives and integrals are convolutions with a power law. Multiplying by an exponential factor leads to tempered fractional derivatives and integrals. Tempered fractional diffusion equations, where the usual second derivative in space is replaced by a tempered fractional derivative, govern the limits of random walk models with an exponentially tempered power law jump distribution. The limiting tempered stable probability densities exhibit semi-heavy tails, which are commonly observed in finance. Tempered power law waiting times lead to tempered fractional time derivatives, which have proven useful in geophysics. The tempered fractional derivative or integral of a Brownian motion, called a tempered fractional Brownian motion, can exhibit semi-long range dependence. The increments of this process, called tempered fractional Gaussian noise, provide a useful new stochastic model for wind speed data. A tempered fractional difference forms the basis for numerical methods to solve tempered fractional diffusion equations, and it also provides a useful new correlation model in time series.

  1. Interactive Fraction Number Lines

    NSDL National Science Digital Library

    Michael Green

    2012-05-25

    In this lesson students make models of fractions, including a human number line. Using a number line, students develop conceptual understanding of fractions. Students use the number line to represent and compare fractions less than one. The activities are engaging and include full participation/engagement of all students. The fractions are limited to positive fractions less than one with a denominator of 2 or 4 including 0 and 1 whole.

  2. When one plus one does not equal two: fluorescence anisotropy in aggregates and multiply labeled proteins.

    PubMed

    Zolmajd-Haghighi, Zahra; Hanley, Quentin S

    2014-04-01

    The behavior of fluorescence anisotropy and polarization in systems with multiple dyes is well known. Homo-FRET and its consequent energy migration cause the fluorescence anisotropy to decrease as the number of like fluorophores within energy transfer distance increases. This behavior is well understood when all subunits within a cluster are saturated with fluorophores. However, incomplete labeling as might occur from a mixture of endogenous and labeled monomer units, incomplete saturation of binding sites, or photobleaching produces stochastic mixtures. Models in widespread and longstanding use that describe these mixtures apply an assumption of equal fluorescence efficiency for all sites first stated by Weber and Daniel in 1966. The assumption states that fluorophores have the same brightness when free in solution as they do in close proximity to each other in a cluster. The assumption simplifies descriptions of anisotropy trends as the fractional labeling of the cluster changes. However, fluorophores in close proximity often exhibit nonadditivity due to such things as self-quenching behavior or exciplex formation. Therefore, the anisotropy of stochastic mixtures of fluorophore clusters of a particular size will depend on the behavior of those fluorophores in clusters. We present analytical expressions for fractionally labeled clusters exhibiting a range of behaviors, and experimental results from two systems: an assembled tetrameric cluster of fluorescent proteins and stochastically labeled bovine serum albumin containing up to 24 fluorophores. The experimental results indicate that clustered species do not follow the assumption of equal fluorescence efficiency in the systems studied with clustered fluorophores showing reduced fluorescence intensity. Application of the assumption of equal fluorescence efficiency will underpredict anisotropy and consequently underestimate cluster size in these two cases. The theoretical results indicate that careful selection of the fractional labeling in strongly quenched systems will enhance opportunities to determine cluster sizes, making accessible larger clusters than are currently considered possible. PMID:24703307

  3. N-Methyl-D-aspartate receptor antagonists memantine and MK-801 attenuate the cerebral infarct accelerated by intracorpus callosum injection of lipopolysaccharides.

    PubMed

    Cho, Geum-Sil; Lee, Jae-Chul; Ju, Chung; Kim, Chunsook; Kim, Won-Ki

    2013-03-22

    Inflammatory responses have been shown to modulate the pattern and degree of ischemic injury. Previously, we demonstrated that intracorpus callosum microinjection of lipopolysaccharide (LPS, a well-known endotoxin) markedly induced inflammatory responses confined to ipsilateral hemisphere and aggravated cerebral ischemic injury. Here we report that LPS injection increases the degree of N-methyl-d-aspartate (NMDA) receptor-mediated excitotoxicity, one of major causes of cerebral ischemic injury. Intracorpus callosum microinjection of LPS 1 day prior to ischemic insults augmented intraneuronal Ca(2+) rise in rat brains subjected to transient occlusion of middle cerebral artery. Intraperitoneal administration of memantine, a NMDA receptor antagonist, reduced the LPS-enhanced calcium response as well as ischemic tissue damage. Western blot and immunohistochemistry data showed that the level of IL-1? was enhanced in LPS-injected rat brains, particularly in isolectin-B4 immunoreactive cells. Intraventricular microinjection of recombinant rat IL-1? aggravated cerebral ischemic injury, which was significantly reduced by memantine. Intraventricular injection of anti-IL-1? antibody significantly reduced the cerebral infarction aggravated by LPS preinjection. The results indicate that IL-1? released from isolectin-B4 immunoreactive cells enhanced excitotoxicity, consequently aggravating ischemic brain injury. PMID:23376060

  4. A study of rotationally invariant and symmetric indices of diffusion anisotropy.

    PubMed

    Papadakis, N G; Xing, D; Houston, G C; Smith, J M; Smith, M I; James, M F; Parsons, A A; Huang, C L; Hall, L D; Carpenter, T A

    1999-07-01

    This study investigated the properties of a class of rotationally invariant and symmetric (relative to the principal diffusivities) indices of the anisotropy of water self-diffusion, namely fractional anisotropy (FA), relative anisotropy (RA), and volume ratio (VR), with particular emphasis to their measurement in brain tissues. A simplified theoretical analysis predicted significant differences in the sensitivities of the anisotropy indices (AI) over the distribution of the principal diffusivities. Computer simulations were used to investigate the effects on AI image quality of three magnetic resonance (MR) diffusion tensor imaging (DTI) acquisition schemes, one being novel: the schemes were simulated on cerebral model fibres varying in shape and spatial orientation. The theoretical predictions and the results of the simulations were corroborated by experimentally determined spatial maps of the AI in a normal feline brain in vivo. We found that FA mapped diffusion anisotropy with the greatest detail and SNR whereas VR provided the strongest contrast between low- and high-anisotropy areas at the expense of increased noise contamination and decreased resolution in anisotropic regions. RA proved intermediate in quality. By sampling the space of the effective diffusion ellipsoid more densely and uniformly and requiring the same total imaging time as the published schemes, the novel DTI scheme achieved greater rotational invariance than the published schemes, with improved noise characteristics, resulting in improved image quality of the AI examined. Our findings suggest that significant improvements in diffusion anisotropy mapping are possible and provide criteria for the selection of the most appropriate AI for a particular application. PMID:10402595

  5. Texture induced microwave background anisotropies

    SciTech Connect

    Borrill, Julian; Copeland, Edmund J.; Liddle, Andrew R.; Stebbins, Albert; Veeraraghavan, Shoba

    1994-03-01

    We use numerical simulations to calculate the cosmic microwave background anisotropy induced by the evolution of a global texture field, with special emphasis on individual textures. Both spherically symmetric and general configurations are analyzed, and in the latter case we consider field configurations which exhibit unwinding events and also ones which do not. We compare the results given by evolving the field numerically under both the expanded core (XCORE) and non-linear sigma model (NLSM) approximations with the analytic predictions of the NLSM exact solution for a spherically symmetric self-similar (SSSS) unwinding. We find that the random unwinding configuration spots' typical peak height is 60-75\\% and angular size typically only 10% of those of the SSSS unwinding, and that random configurations without an unwinding event nonetheless may generate indistinguishable hot and cold spots. A brief comparison is made with other work.

  6. Temperature dependence of magnetic anisotropy constant in CoFe2O4 nanoparticles examined by Mössbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Yoon, Sunghyun

    2015-04-01

    The temperature dependence of the effective magnetic anisotropy constant of CoFe2O4 nanoparticles is determined based on the measurements of SQUID magnetometry and Mössbauer spectroscopy. Under an intuitive assumption that the superparamagnetic fraction of the cumulative area in the particle size distribution at a temperature is equal to the doublet fraction in the Mössbauer spectra at that temperature, we are able to get a relation between r and T B, from which the temperature dependence of the effective magnetic anisotropy constant is determined. The resultant magnetic anisotropy constant increases markedly with decreasing temperature from 2.0 ×105 J/m 3 at 300 K to 8.3 ×106 J/m 3 at 125 K.

  7. Pizza Fractions: Beginning With Simple Fractions

    NSDL National Science Digital Library

    2013-01-15

    In this iOS app students are introduced visually to the concept of fractions by having them identify the simple fraction (denominators 1-12, excluding sevenths and elevenths) represented by pizza picture example. Each round of the game includes ten visual models; at the end of the round students receive a score for accuracy and speed.

  8. Azimuthal anisotropy of the Pacific region

    NASA Astrophysics Data System (ADS)

    Maggi, Alessia; Debayle, Eric; Priestley, Keith; Barruol, Guilhem

    2006-10-01

    Azimuthal anisotropy is the dependence of local seismic properties on the azimuth of propagation. We present the azimuthally anisotropic component of a 3D SV velocity model for the Pacific Ocean, derived from the waveform modeling of over 56,000 multi-mode Rayleigh waves followed by a simultaneous inversion for isotropic and azimuthally anisotropic vsv structure. The isotropic vsv model is discussed in a previous paper (A. Maggi, E. Debayle, K. Priestley, G. Barruol, Multi-mode surface waveform tomography of the Pacific Ocean: a close look at the lithospheric cooling signature, Geophys. J. Int. 166 (3) (2006). doi:10.1111/j.1365-246x.2006.03037.x). The azimuthal anisotropy we find is consistent with the lattice preferred orientation model (LPO): the hypothesis of anisotropy generation in the Earth's mantle by preferential alignment of anisotropic crystals in response to the shear strains induced by mantle flow. At lithospheric depths we find good agreement between fast azimuthal anisotropy orientations and ridge spreading directions recorded by sea-floor magnetic anomalies. At asthenospheric depths we find a strong correlation between fast azimuthal anisotropy orientations and the directions of current plate motions. We observe perturbations in the pattern of seismic anisotropy close to Pacific hot-spots that are consistent with the predictions of numerical models of LPO generation in plume-disturbed plate motion-driven mantle flow. These observations suggest that perturbations in the patterns of azimuthal anisotropy may provide indirect evidence for plume-like upwelling in the mantle.

  9. Identifying Equivalent Fractions

    NSDL National Science Digital Library

    J.C. Banfill

    2007-12-12

    This site helps students understand how to identify equivalent fractions by explaining what equivalent fractions are and how to compare two fractions to see if they are equivalent. There is also a list of fractions equivalent to 1/2, 1/3, 1/4, 1/5, and 2/5 so students can begin to see the pattern that emerges. Finally, the site presents an interactive game in which students can practice by naming the equivalent fraction to a given fraction.

  10. FRACTIONAL INTEGRATION TOOLBOX.

    PubMed

    Marinov, Toma M; Ramirez, Nelson; Santamaria, Fidel

    2013-09-01

    The problems formulated in the fractional calculus framework often require numerical fractional integration/differentiation of large data sets. Several existing fractional control toolboxes are capable of performing fractional calculus operations, however, none of them can efficiently perform numerical integration on multiple large data sequences. We developed a Fractional Integration Toolbox (FIT), which efficiently performs fractional numerical integration/differentiation of the Riemann-Liouville type on large data sequences. The toolbox allows parallelization and is designed to be deployed on both CPU and GPU platforms. PMID:24812536

  11. Bounded Fraction Pointer

    NSDL National Science Digital Library

    2010-01-01

    In this activity, students pick two fractions between zero and one and select portions of a square or circle so that the highlighted portion matches each of the two fractions. Then they must highlight portions of another square or circle to make a fraction that lies in between the two previous fractions. As they highlight portions of the third shape, a pointer indicates whether they are in between the two other fractions. This activity allows students to practice comparing fractions. This activity includes supplemental materials, including background information about the topics covered, a description of how to use the application, and exploration questions for use with the java applet.

  12. Local control of single atom magnetocrystalline anisotropy.

    PubMed

    Bryant, B; Spinelli, A; Wagenaar, J J T; Gerrits, M; Otte, A F

    2013-09-20

    Individual Fe atoms on a Cu(2)N/Cu(100) surface exhibit strong magnetic anisotropy due to the crystal field. We show that we can controllably enhance or reduce this anisotropy by adjusting the relative position of a second nearby Fe atom, with atomic precision, in a low-temperature scanning tunneling microscope. Local inelastic electron tunneling spectroscopy, combined with a qualitative first-principles model, reveal that the change in uniaxial anisotropy is driven by local strain due to the presence of the second Fe atom. PMID:24093296

  13. Mechanical anisotropy of the Yucca Mountain tuffs

    SciTech Connect

    Price, R.H. [Sandia National Labs., Albuquerque, NM (United States); Boyd, P.J.; Martin, R.J.; Haupt, R.W.; Noel, J.S. [New England Research Inc., White River Junction, VT (United States)

    1991-12-31

    Three series of measurements were performed on oriented cores of several Yucca Mountain tuffs to determine the importance of mechanical anisotropy in the intact rock. Outcrop and drillhole samples were tested for acoustic velocities, linear compressibilities, and strengths in different orientations. The present data sets are preliminary, but suggest the tuffs are transversely anisotropic for these mechanical properties. The planar fabric that produces the anisotropy is believed to be predominantly the result of the preferred orientation of shards and pumice fragments. The potential of significant anisotropy has direct relevance to the formulation of constitutive formulation and the analyses of an underground opening within the Yucca Mountain.

  14. Galactic foreground contributions to the 5-year Wilkinson Microwave Anisotropy Probe maps

    Microsoft Academic Search

    N. Macellari; E. Pierpaoli; C. Dickinson; J. E. Vaillancourt

    2011-01-01

    We compute the cross-correlation between intensity and polarization from the 5-year Wilkinson Microwave Anisotropy Probe (WMAP5) data in different sky regions with respect to template maps for synchrotron, dust and free-free emission. We derive the frequency dependence and polarization fraction for all three components in 48 different sky regions of HEALPIX (Nside= 2) pixelization. The anomalous emission associated with dust

  15. On the suspected timing error in Wilkinson microwave anisotropy probe map-making

    Microsoft Academic Search

    B. F. Roukema

    2010-01-01

    Context. It has recently been suggested that the compilation of the calibrated time-ordered-data (TOD) of the Wilkinson Microwave Anisotropy Probe (WMAP) observations of the cosmic microwave background (CMB) into full-year or multi-year maps may have been carried out with a small timing interpolation error. A large fraction of the previously estimated WMAP CMB quadrupole signal would be an artefact of

  16. Dependence of Co anisotropy constants on temperature, processing, and underlayer

    E-print Network

    Laughlin, David E.

    -8979 00 69908-5 The magnetocrystalline anisotropy is an important prop- erty of Co-alloy materials of the magnetocrystalline anisotropy. This article will focus on pure Co anisotropy constants as functionsDependence of Co anisotropy constants on temperature, processing, and underlayer Wei Yanga

  17. Fractions and Decimals

    NSDL National Science Digital Library

    Miss Perry

    2007-11-29

    Fractions and decimals are used in our everyday lives! We will learn why we need fractions and decimals by playing games and doing activities with candy bars and other fun things! By the end of the unit you will be such an expert that you will be able to do math problems involving fractions and decimals! Then our whole class will have a pizza party that you will plan using your knowledge to figure out how many pizzas we need and how to divide them into equal slices. Days 1 & 2 Get acquainted with fractions and decimals by exploring the following links: Naming Fractions Visual Fractions Choose ten fractions that you used from these activities and draw them on a paper which you will hand in to the teacher. Make sure you use fractions with different numerators and denominators. Use ...

  18. Fractional Quantum Mechanics

    NASA Astrophysics Data System (ADS)

    Laskin, Nikolai

    2000-06-01

    A new application of a fractal concept to quantum physics has been developed. The fractional path integrals over the paths of the Levy flights are defined. It is shown that if fractality of the Brownian trajectories leads to standard quantum mechanics, then the fractality of the Levy paths leads to fractional quantum mechanics. The fractional quantum mechanics has been developed via the new fractional path integrals approach. A fractional generalization of the Schrodinger equation has been discovered. The new relationship between the energy and the momentum of the non-relativistic fractional quantum-mechanical particle has been found, and the Levy wave packet has been introduced into quantum mechanics. We have derived a free particle quantum-mechanical propagator using Fox's H-function. A fractional generalization of the Heisenberg uncertainty relation has been established. We also discuss the relationships between fractional and the well-known Feynman path integrals approaches to quantum mechanics.

  19. The Fraction String

    NSDL National Science Digital Library

    Michael Green

    2012-06-26

    In this lesson students create a model of a number line using string and adding machine tape. Students discover how to partition the string into equal sections, and name the fractional pieces, including fractions greater than 1.

  20. Garden Variety Fractions

    NSDL National Science Digital Library

    Michael Green

    2012-07-23

    Students explore the multiplication of a fraction times a fraction through story problems about a garden using models on Geoboards and pictorial representations on grid paper. Students make a connection between their models and the numerical representation of the equation.

  1. Fractional Classical Mechanics

    E-print Network

    Nick Laskin

    2013-02-03

    Fractional classical mechanics has been introduced and developed as a classical counterpart of the fractional quantum mechanics. Lagrange, Hamilton and Hamilton-Jacobi frameworks have been implemented for the fractional classical mechanics. The Lagrangian of fractional classical mechanics has been introduced, and equation of motion has been obtained. Fractional oscillator model has been launched and solved in 1D case. A new equation for the period of oscillations of fractional classical oscillator has been found. The interplay between the energy dependency of the period of classical oscillations and the non-equidistant distribution of the energy levels for fractional quantum oscillator has been discussed. We discuss as well, the relationships between new equations of fractional classical mechanics and the well-known fundamental equations of classical mechanics.

  2. Decimals before Fractions

    ERIC Educational Resources Information Center

    Berryman, Jack

    1972-01-01

    A method of showing the meaning of decimal fraction without using fraction words or notation. One technique described in detail uses large squares, strips, and small squares; using the metric system and decimal coinage is also suggested. (DT)

  3. Measurements of the cosmic microwave background anisotropies with ARCHEOPS

    NASA Astrophysics Data System (ADS)

    Beno??t, A.; Archeops Collaboration

    2004-01-01

    ARCHEOPS is a balloon-borne instrument dedicated to measure cosmic microwave background (CMB) temperature anisotropies at high angular resolution (about 10 ') over a large fraction (30%) of the sky in the (sub)millimetre domain (from 143 to 545 GHz). Here, we describe the latest results from the instrument during the last flight that happened during the Arctic night from Kiruna (Sweden) to Russia in February 2002. Various sources of noise are discussed, including atmospheric noise, parasitic noise, photon noise, cosmic variance,... The white noise sensitivity for the eight best bolometers is below 200 ?K CMB s 1/2 per bolometer. Best estimates of the angular power spectrum of the CMB anisotropies are presented, giving for the first time a continuous link between COBE scales and the first acoustic peak. The consequences in terms of cosmological parameters are outlined that reinforce the flatness of the Universe. Other results include the first measurement of polarization and accurate maps of the galactic plane diffuse (sub)millimetre emission.

  4. Fractions--Naming

    NSDL National Science Digital Library

    2005-01-01

    This applet lets students practice naming fractions, by presenting various shapes divided into equal parts with some parts shaded. Students write the fraction in the boxes provided, and check. Equivalent fractions are recognized, but students are encouraged to name the fraction using the denominator indicated by the shape. Instructions for using the applet and teaching ideas for parents/teachers are available through the links at the top of the page.

  5. Experimenting With Fractions!

    NSDL National Science Digital Library

    Mr. Holmgren

    2005-10-25

    For this project we are going to look at fractions as parts of a whole. Fractions are parts of a whole. In the following links you will explore fractions! When you click on a link and arrive at an activity, read and follow the directions on the page. When you feel that you have mastered the fraction concept in one link close that window and ...

  6. Equivalent Fractions Finder

    NSDL National Science Digital Library

    2007-12-12

    This activity allows students to visually experiment with the relationship between the values of equivalent fractions and areas within a square or a circle. The activity provides the user with a fraction, its equivalent representation as a shaded portion of a square or circle, and a number line. Also displayed are two empty squares or circles. The user can add and color sections to the blank shapes to create a fraction equivalent to the computer generated fraction.

  7. Visual Fractions: Home Page

    NSDL National Science Digital Library

    Richard E. Rand

    2011-01-01

    This collection of lessons, interactive Flash exercises and teacher utilities supports the learning of fraction concepts using side-by-side symbolic and pictorial representations. The lessons cover identifying, comparing, renaming and operating with fractions using circle and number line models. The Fraction Maker feature allows a teacher to create visual models to illustrate those same topics with fractions chosen by the user. The site includes student games and worksheets as well as suggestions and resources for the teacher.

  8. SOLARMAX/Electron Pitch Angle Anisotropy Distributions

    NASA Technical Reports Server (NTRS)

    McKenzie, David L.; Anderson, Phillip C.

    2002-01-01

    This final research report summarizes the scientific work performed by The Aerospace Corporation on SOLARMAX/Electron Pitch Angle Anisotropy Distributions. The period of performance was from June 1, 2000 to December 31, 2001.

  9. On discrete symmetries and relic radiation anisotropy

    E-print Network

    M. V. Altaisky; N. E. Kaputkina

    2014-06-17

    It is argued that large scale angle correlations of the Cosmic Microwave Background Radiation (CMBR) temperature fluctuations measured by Wilkinson Microwave Anisotropy Probe (WMAP) mission may have a trace of discrete symmetries of quantum gravity

  10. Magnetocrystalline anisotropy in Ni3Fe

    Microsoft Academic Search

    S. Takahashi

    1980-01-01

    The dependence of the first magnetocrystalline anisotropy constant, K1, on the annealing temperature was studied in a Ni3Fe single crystal. It was shown that K1 is a simple function of the long range order parameter.

  11. Magnetic anisotropy due to the Casimir effect

    NASA Astrophysics Data System (ADS)

    Metalidis, G.; Bruno, P.

    2010-02-01

    We consider the Casimir interaction between a ferromagnetic and a nonmagnetic mirror and show how the Casimir effect gives rise to a magnetic anisotropy in the ferromagnetic layer. The anisotropy is out of plane if the nonmagnetic plate is optically isotropic. If the nonmagnetic plate shows a uniaxial optical anisotropy (with optical axis in the plate plane), we find an in-plane magnetic anisotropy. In both cases, the energetically most favorable magnetization orientation is given by the competition between polar, longitudinal, and transverse contributions to the magneto-optical Kerr effect and will therefore depend on the interplate distance. Numerical results will be presented for a magnetic plate made out of Fe and nonmagnetic plates of Au (optically isotropic), quartz, calcite, and barium titanate (all uniaxially birefringent).

  12. Permeability anisotropy of layering rock model

    NASA Astrophysics Data System (ADS)

    Irayani, Zaroh; Fauzi, Umar; Latief, Fourier Dzar Eljabbar

    2015-04-01

    Computer models of layering system were generated to analyze the effect of layering to the permeability anisotropy. Six layering models were created using non-spherical grain models. Each model consist of three layers with different thickness ratios. The permeability of the generated models were calculated using Lattice Boltzmann Method. Analysis of the flow properties shows that the permeability in the horizontal direction is greater than in the vertical direction. From the permeability anisotropy analysis, it is shown that in the horizontal direction, the models are generally considered as isotropic. This is confirmed by the anisotropy values, which are close to 1. The permeability anisotropy of the vertical direction to horizontal direction varies in the range of 0.32 - 0.45.

  13. Cellulose and the Control of Growth Anisotropy

    SciTech Connect

    Tobias I. Baskin

    2004-04-01

    The authors research aims to understand morphogenesis, focusing on growth anisotropy, a process that is crucial to make organs with specific and heritable shapes. For the award, the specific aims were to test hypotheses concerning how growth anisotropy is controlled by cell wall structure, particularly by the synthesis and alignment of cellulose microfibrils, the predominant mechanical element in the cell wall. This research has involved characterizing the basic physiology of anisotropic expansion, including measuring it at high resolution; and second, characterizing the relationship between growth anisotropy, and cellulose microfibrils. Important in this relationship and also to the control of anisotropic expansion are structures just inside the plasma membrane called cortical microtubules, and the research has also investigated their contribution to controlling anisotropy and microfibril alignment. In addition to primary experimental papers, I have also developed improved methods relating to these objectives as well as written relevant reviews. Major accomplishments in each area will now be described.

  14. Comparing Fractions with Pizza

    NSDL National Science Digital Library

    Shanna Uhe

    2012-07-31

    In this lesson, students will demonstrate their understanding of comparing fractions with the same denominator through engaging problem solving with real-world application to pizza using a model. Students will be actively engaged in a Fraction War game and Would You Rather Have statements to solidify their understanding of comparing fractions with the same denominator.

  15. Fractions Dolphin Racing Game

    NSDL National Science Digital Library

    Skillwise: English and Maths for Adults

    2012-08-03

    In this online interactive game, students are tasked with using a variety of strategies to quickly compare fractions. By choosing the largest fraction, the student's dolphin travels further faster. This game encourages students to interpret the meaning of fractions and rely on strategies that go beyond finding common denominators.

  16. Comparing and Ordering Fractions

    NSDL National Science Digital Library

    2007-12-12

    Use area models to compare and order fractions. Also see a visual representation of the least common denominator of two fractions. With the visual representation of the LCD, this Gizmo can be an introduction to adding and subtracting fractions with unlike denominators.

  17. Comparing Fractions with Brownies

    NSDL National Science Digital Library

    Shanna Uhe

    2012-07-31

    Students will demonstrate their understanding of comparing fractions with the same numerator through engaging problem solving using real-world application with brownies as a model. Students will be actively engaged in a fraction war game and "would you rather have" statements to solidify their understanding of comparing fractions with the same numerator.

  18. Fractional Topological Insulators

    Microsoft Academic Search

    Michael Levin; Ady Stern

    2009-01-01

    We analyze generalizations of two-dimensional topological insulators which can be realized in interacting, time reversal invariant electron systems. These states, which we call fractional topological insulators, contain excitations with fractional charge and statistics in addition to protected edge modes. In the case of sz conserving toy models, we show that a system is a fractional topological insulator if and only

  19. DIY Fraction Pack.

    ERIC Educational Resources Information Center

    Graham, Alan; Graham, Louise

    2003-01-01

    Describes a very successful attempt to teach fractions to year 5 pupils based on pupils making their own fraction pack. Children decided for themselves how to make the fractional slices used in the activity using colored cardboard sheets and templates of a paper circle consisting of 24 equal slices. (Author/NB)

  20. Fractions with Grandpa

    NSDL National Science Digital Library

    Miss Law

    2009-04-15

    Get into action and play with fractions! Practice your fractions with this website first: Learn Yo Fractions. Read the directions! The \\"Start\\" is at the top of the page. Now, same rules, but you have to find Grampy. Find him here: Find Grampy! Want another challenge? Now the scientist Melvin needs help with his mixed-up potions! ...

  1. Forced Abstinence from Cocaine Self-Administration is Associated with DNA Methylation Changes in Myelin Genes in the Corpus Callosum: a Preliminary Study

    PubMed Central

    Nielsen, David A.; Huang, Wen; Hamon, Sara C.; Maili, Lorena; Witkin, Brian M.; Fox, Robert G.; Cunningham, Kathryn A.; Moeller, F. Gerard

    2012-01-01

    Background: Human cocaine abuse is associated with alterations in white matter integrity revealed upon brain imaging, an observation that is recapitulated in an animal model of continuous cocaine exposure. The mechanism through which cocaine may affect white matter is unknown and the present study tested the hypothesis that cocaine self-administration results in changes in DNA methylation that could result in altered expression of several myelin genes that could contribute to the effects of cocaine on white matter integrity. Methods: In the present study, we examined the impact of forced abstinence from cocaine self-administration on chromatin associated changes in white matter. To this end, rats were trained to self-administer cocaine (0.75?mg/kg/0.1?mL infusion) for 14?days followed by forced abstinence for 1?day (n?=?6) or 30?days (n?=?6) before sacrifice. Drug-free, sham surgery controls (n?=?7) were paired with the experimental groups. Global DNA methylation and DNA methylation at specific CpG sites in the promoter regions ofmyelin basic protein (Mbp), proteolipid protein-1 (Plp1), and SRY-related HMG-box-10 (Sox10) genes were analyzed in DNA extracted from corpus callosum. Results: Significant differences in the overall methylation patterns of the Sox10 promoter region were observed in the corpus callosum of rats at 30?days of forced abstinence from cocaine self-administration relative to sham controls; the ?189, ?142, ?93, and ?62 CpG sites were significantly hypomethylated point-wise at this time point. After correction for multiple comparisons, no differences in global methylation or the methylation patterns of Mbp or Plp1 were found. Conclusion: Forced abstinence from cocaine self-administration was associated with differences in DNA methylation at specific CpG sites in the promoter region of the Sox10 gene in corpus callosum. These changes may be related to reductions in normal age related changes in DNA methylation and could be a factor in white matter alterations seen after withdrawal from repeated cocaine self-administration. Further research is warranted examining the effects of cocaine on DNA methylation in white matter. PMID:22712019

  2. Wind anisotropy and stellar evolution

    E-print Network

    Cyril Georgy; Georges Meynet; André Maeder

    2008-07-31

    Mass loss is a determinant factor which strongly affects the evolution and the fate of massive stars. At low metallicity, stars are supposed to rotate faster than at the solar one. This favors the existence of stars near the critical velocity. In this rotation regime, the deformation of the stellar surface becomes important, and wind anisotropy develops. Polar winds are expected to be dominant for fast rotating hot stars. These polar winds allow the star to lose large quantities of mass and still retain a high angular momentum, and they modifie the evolution of the surface velocity and the final angular momentum kept in the star's core. We show here how these winds affect the final stages of massive stars, according to our knowledge about Gamma Ray Bursts. Computation of theoretical Gamma Ray Bursts rate indicates that our models have too fast rotating cores, and that we need to include an additional effect to spin them down. Magnetic fields in stars act in this direction, and we show how they modify the evolution of massive star up to the final stages.

  3. Single-molecule anisotropy imaging

    PubMed Central

    Harms, GS; Sonnleitner, M; Schutz, GJ; Gruber, HJ; Schmidt, T

    1999-01-01

    A novel method, single-molecule anisotropy imaging, has been employed to simultaneously study lateral and rotational diffusion of fluorescence-labeled lipids on supported phospholipid membranes. In a fluid membrane composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine, in which the rotational diffusion time is on the order of the excited-state lifetime of the fluorophore rhodamine, a rotational diffusion constant, D(rot) = 7 x 10(7) rad(2)/s, was determined. The lateral diffusion constant, measured by direct analysis of single-molecule trajectories, was D(lat) = 3.5 x 10(-8) cm(2)/s. As predicted from the free-volume model for diffusion, the results exhibit a significantly enhanced mobility on the nanosecond time scale. For membranes of DPPC lipids in the L(beta) gel phase, the slow rotational mobility permitted the direct observation of the rotation of individual molecules characterized by D(rot) = 1.2 rad(2)/s. The latter data were evaluated by a mean square angular displacement analysis. The technique developed here should prove itself profitable for imaging of conformational motions of individual proteins on the time scale of milliseconds to seconds. PMID:10545384

  4. Reflectance anisotropy for porphyrin ostaester

    NASA Astrophysics Data System (ADS)

    Vázquez-Nava, Raúl; Castillo, César; Mendoza, Bernardo

    2004-03-01

    We present a theoretical study for the reflectance anosotropy of prophyrin layers deposited onto gold substrates by Langmuir-Schaefer technique. We have used a polarizable dipole model, in which the effect of the electric local field is incorporated, to obtain the reflectance anisotropy spectra as function of the number of porphyrin layers. We show that the spectra changes from a peak-like to derivative-like line shape as the tilting and twisting of the molecules is varied. More specifically, at low coverage the molecules tend to be inclined relative to the substrate, due to stronger interaction with it, but as the number of layers is increased the substrate influence decreases as it is screened by the underlying layers, and the molecules tend to straighten up[1]. Our results coincide qualitatively with those of the experiments[2]. [1] C. Castillo, R. A. Vázquez-Nava and Bernardo S. Mendoza, Phys. stat. sol. (c) DOI 10.1002/pssc.200303859. [2] C. Goletti, R. Paolesse, E. Dalcanale, T. Berzina, C. Di Natale, G. Bussetti, P. Chiaradia, A. Froiio, L. Cristofolini, M. Costa and A. DÁmico, Lamgmuir 18, 6881 (2002).

  5. ANISOTROPY DETERMINATIONS IN EXCHANGE SPRING MAGNETS.

    SciTech Connect

    LEWIS,L.H.; HARLAND,C.L.

    2002-08-18

    Ferromagnetic nanocomposites, or ''exchange spring'' magnets, possess a nanoscaled microstructure that allows intergrain magnetic exchange forces to couple the constituent grains and alter the system's effective magnetic anisotropies. While the effects of the anisotropy alterations are clearly seen in macroscopic magnetic measurement, it is extremely difficult to determine the detailed effects of the system's exchange coupling, such as the interphase exchange length, the inherent domain wall widths or the effective anisotropies of the system. Clarification of these materials parameters may be obtained from the ''micromagnetic'' phenomenological model, where the assumption of magnetic reversal initiating in the magnetically-soft regions of the exchange-spring maqet is explicitly included. This approach differs from that typically applied by other researchers and allows a quantitative estimate of the effective anisotropies of an exchange spring system. Hysteresis loops measured on well-characterized nanocomposite alloys based on the composition Nd{sub 2}Fe{sub 14}B + {alpha}-Fe at temperatures above the spin reorientation temperature were analyzed within the framework of the micromagnetic phenomenological model. Preliminary results indicate that the effective anisotropy constant in the material is intermediate to that of bulk {alpha}-Fe and bulk Nd{sub 2}Fe{sub 14}B and increases with decreasing temperature. These results strongly support the idea that magnetic reversal in nanocomposite systems initiates in the lower-anisotropy regions of the system, and that the soft-phase regions become exchange-hardened by virtue of their proximity to the magnetically-hard regions.

  6. Tailoring magnetic anisotropy gradients by ion bombardment for domain wall positioning in magnetic multilayers with perpendicular anisotropy

    PubMed Central

    2014-01-01

    Graded anisotropy magnetic materials possess a coercive field changing laterally with position. A simple fabrication procedure to produce such an anisotropy gradient in a polycrystalline Au/Co layer system without lateral thickness variation and with perpendicular magnetic anisotropy, prototypical for a large variety of thin film systems, is shown. The procedure uses light-ion bombardment without the use of a mask. Magnetization reversal in this polycrystalline layer system takes place by unidirectional movement of a single domain wall only in regions with larger anisotropies and anisotropy gradients. In this anisotropy/anisotropy gradient regime, the domain wall is oriented perpendicular to the coercive field gradient, and it can be positioned along the gradient by an appropriate magnetic field pulse. For smaller anisotropies/anisotropy gradients, the natural anisotropy fluctuations of the polycrystalline layer system induce magnetization reversal dominated by domain nucleation. PACS 75.30.Gw; 75.70.Cn; 75.60.Ch PMID:25232291

  7. Equivalent Fractions Pointer

    NSDL National Science Digital Library

    2010-01-01

    In this activity, students highlight portions of circles or squares that are equivalent to a given fraction. As the student highlights sections, a pointer on a number line between zero and one updates so they can see when they are close or equal to the given fraction. This activity allows students to explore equivalent fractions by making it necessary that each of the three fractions have a different denominator but have the fractions be equal. This activity includes supplemental materials, including background information about the topics covered, a description of how to use the application, and exploration questions for use with the java applet.

  8. Fractional quantum mechanics

    PubMed

    Laskin

    2000-09-01

    A path integral approach to quantum physics has been developed. Fractional path integrals over the paths of the Levy flights are defined. It is shown that if the fractality of the Brownian trajectories leads to standard quantum and statistical mechanics, then the fractality of the Levy paths leads to fractional quantum mechanics and fractional statistical mechanics. The fractional quantum and statistical mechanics have been developed via our fractional path integral approach. A fractional generalization of the Schrodinger equation has been found. A relationship between the energy and the momentum of the nonrelativistic quantum-mechanical particle has been established. The equation for the fractional plane wave function has been obtained. We have derived a free particle quantum-mechanical kernel using Fox's H function. A fractional generalization of the Heisenberg uncertainty relation has been established. Fractional statistical mechanics has been developed via the path integral approach. A fractional generalization of the motion equation for the density matrix has been found. The density matrix of a free particle has been expressed in terms of the Fox's H function. We also discuss the relationships between fractional and the well-known Feynman path integral approaches to quantum and statistical mechanics. PMID:11088808

  9. How to separate intrinsic and artificial anisotropy

    NASA Astrophysics Data System (ADS)

    Wang, N.; Montagner, J.-P.; Capdeville, Y.; Burgos, G.; Cupillard, P.

    2012-04-01

    The effect of anisotropy on seismic waves and on the inversion for 3D tomographic models of velocity and anisotropy is not negligible and is used for different applications in geodynamics for both regional and global scale (Montagner, TOG, 2007). The exact determination and interpretation of anisotropy (amplitude and orientation) are quite difficult because the observed or inverted anisotropy is usually a mixture of intrinsic and artificial anisotropies, which may partly hide the true properties of the medium. The artificial anisotropy is due to two reasons: first of all, to the inversion technique and second of all, to the the fact that seismic waves do not see the real details of medium but a filtered (and imperfect) version of the earth model. Backus (1962) constructs the effective elastic coefficients for layered medium to present what is "seen" by the wave field at long periods which is called the "long-wavelength equivalent" effect. The homogenization method developed by Capdeville et al., (2007, 2010) uses a two-scale homogenization expansion to construct a new more continuous model based on filtering technique which can adapt the scales of the model to the seismic wavelengths. Such homogenized model is quite effective to compute full waveform seismograms in heterogeneous anisotropic medium. In this paper, we propose a strategy in order to separate artificial and intrinsic anisotropy. For the inversion technique, we use a quasi-Newton method (Tarantola, 2005) together with the GMRES method based on the first-order perturbation theory. We try to find and interpret the real and artificial anisotropy by introducing different prior information on both data and the reference model. We investigate a 1D isotropic smooth model and an isotropic discontinuous PREM model, together with their homogenized models which are anisotropic VTI models (Capdeville et al., 2007), try to estimate the amplitude of artificial radial anisotropy associated with the inversion technique and the homogenization as the effect of filtering. Actual seismic data for the 3D problem is left to the future for demonstrating the separation of intrinsic and artificial anisotropy.

  10. Preferred Orientations and Anisotropy in Shales: Callovo-Oxfordian Shale (France) and Opalinus Clay (Switzerland)

    SciTech Connect

    Wenk, H.-R.; Voltolini, M.; Mazurek, M.; Van Loon, L.R.; Vinsot, A. (PSI); (UCB); (Bern); (LSMHM)

    2009-06-30

    Anisotropy in clay-rich sedimentary rocks is receiving increasing attention. Seismic anisotropy is essential in the prospecting for petroleum deposits. Anisotropy of diffusion has become relevant for environmental contaminants, including nuclear waste. In both cases, the orientation of component minerals is a critical ingredient and, largely because of small grain size and poor crystallinity, the orientation distribution of clay minerals has been difficult to quantify. A method is demonstrated that relies on hard synchrotron X-rays to obtain diffraction images of shales and applies the crystallographic Rietveld method to deconvolute the images and extract quantitative information about phase fractions and preferred orientation that can then be used to model macroscopic physical properties. The method is applied to shales from European studies which investigate the suitability of shales as potential nuclear waste repositories (Meuse/Haute-Marne Underground Research Laboratory near Bure, France, and Benken borehole and Mont Terri Rock Laboratory, Switzerland). A Callovo-Oxfordian shale from Meuse/Haute-Marne shows a relatively weak alignment of clay minerals and a random distribution for calcite. Opalinus shales from Benken and Mont Terri show strong alignment of illite-smectite, kaolinite, chlorite, and calcite. This intrinsic contribution to anisotropy is consistent with macroscopic physical properties where anisotropy is caused both by the orientation distribution of crystallites and high-aspect-ratio pores. Polycrystal elastic properties are obtained by averaging single crystal properties over the orientation distribution and polyphase properties by averaging over all phases. From elastic properties we obtain anisotropies for p waves ranging from 7 to 22%.

  11. Measurement of structural anisotropy in femoral trabecular bone using clinical-resolution CT images.

    PubMed

    Kersh, Mariana E; Zysset, Philippe K; Pahr, Dieter H; Wolfram, Uwe; Larsson, David; Pandy, Marcus G

    2013-10-18

    Discrepancies in finite-element model predictions of bone strength may be attributed to the simplified modeling of bone as an isotropic structure due to the resolution limitations of clinical-level Computed Tomography (CT) data. The aim of this study is to calculate the preferential orientations of bone (the principal directions) and the extent to which bone is deposited more in one direction compared to another (degree of anisotropy). Using 100 femoral trabecular samples, the principal directions and degree of anisotropy were calculated with a Gradient Structure Tensor (GST) and a Sobel Structure Tensor (SST) using clinical-level CT. The results were compared against those calculated with the gold standard Mean-Intercept-Length (MIL) fabric tensor using micro-CT. There was no significant difference between the GST and SST in the calculation of the main principal direction (median error=28°), and the error was inversely correlated to the degree of transverse isotropy (r=-0.34, p<0.01). The degree of anisotropy measured using the structure tensors was weakly correlated with the MIL-based measurements (r=0.2, p<0.001). Combining the principal directions with the degree of anisotropy resulted in a significant increase in the correlation of the tensor distributions (r=0.79, p<0.001). Both structure tensors were robust against simulated noise, kernel sizes, and bone volume fraction. We recommend the use of the GST because of its computational efficiency and ease of implementation. This methodology has the promise to predict the structural anisotropy of bone in areas with a high degree of anisotropy, and may improve the in vivo characterization of bone. PMID:24007613

  12. A voxelized model of direct infusion into the corpus callosum and hippocampus of the rat brain: model development and parameter analysis

    PubMed Central

    Kim, Jung Hwan; Mareci, Thomas H.; Sarntinoranont, Malisa

    2010-01-01

    Recent experimental studies have shown convective-enhanced delivery (CED) to be useful for transporting macromolecular therapeutic agents over large tissue volumes in the central nervous system (CNS). There are limited tools currently available for predicting tissue distributions in the brain. We have developed a voxelized modeling methodology in which CNS tissues are modeled as porous media, and transport properties and anatomical boundaries are determined semi-automatically on a voxel-by-voxel basis using diffusion tensor imaging (DTI). By using this methodology, 3D extracellular transport models of the rat brain were developed. Macromolecular tracer distributions following CED in two different infusion sites (corpus callosum and hippocampus) were predicted. Sensitivity of models to changes in infusion parameters, transport properties, and modeling parameters was determined. Predicted tracer distributions were most sensitive to changes in segmentation threshold, DTI resolution, tissue porosity, and infusion site. This DTI-based voxelized modeling methodology provides a potentially rapid means of estimating CED transport. PMID:20033788

  13. High-Resolution Magnetic Resonance Microscopy and Diffusion Tensor Imaging to Assess Brain Structural Abnormalities in the Murine Mucopolysaccharidosis VII Model

    PubMed Central

    Poptani, Harish; Kumar, Manoj; Nasrallah, Ilya M; Kim, Sungheon; Ittyerah, Ranjit; Pickup, Stephen; Li, Joel; Parente, Michael K; Wolfe, John H.

    2014-01-01

    High-resolution microscopic magnetic resonance imaging (?MRI) and diffusion tensor imaging (DTI) were performed to characterize brain structural abnormalities in a mouse model of mucopolysaccharidosis type VII (MPS VII). ?MRI demonstrated a decrease in the volume of anterior commissure and corpus callosum and a slight increase in the volume of the hippocampus in MPS VII vs. wild-type mice. DTI indices were analyzed in gray and white matter. In vivo and ex vivo DTI demonstrated significantly reduced fractional anisotropy in the anterior commissure, corpus callosum, external capsule and hippocampus in MPS VII vs. control brains. Significantly increased mean diffusivity was also found in the anterior commissure and corpus callosum from ex-vivo DTI. Significantly reduced linear anisotropy was observed from the hippocampus from in-vivo DTI, whereas significantly decreased planar anisotropy and spherical anisotropy were observed in the external capsule from only ex-vivo DTI. There were corresponding morphological differences in the brains of MPS VII mice by hematoxylin and eosin staining. Luxol fast blue staining demonstrated less intense staining of the corpus callosum and external capsule; myelin abnormalities in the corpus callosum were also demonstrated quantitatively in toluidine blue-stained sections and confirmed by electron microscopy. These results demonstrate the potential for ?MRI and DTI for quantitative assessment of brain pathology in murine models of brain diseases. PMID:24335527

  14. Yokukansan normalizes glucocorticoid receptor protein expression in oligodendrocytes of the corpus callosum by regulating microRNA-124a expression after stress exposure.

    PubMed

    Shimizu, Shoko; Tanaka, Takashi; Tohyama, Masaya; Miyata, Shingo

    2015-05-01

    Stressful events are known to down-regulate expression levels of glucocorticoid receptors (GRs) in the brain. Recently, we reported that stressed mice with elevated plasma levels of corticosterone exhibit morphological changes in the oligodendrocytes of nerve fiber bundles, such as those in the corpus callosum. However, little is known about the molecular mechanism of GR expression regulation in oligodendrocytes after stress exposure. A previous report has suggested that GR protein levels might be regulated by microRNA (miR)-18 and/or -124a in the brain. In this study, we aimed to elucidate the GR regulation mechanism in oligodendrocytes and evaluate the effects of yokukansan (YKS), a Kampo medicine, on GR protein regulation. Acute exposure to stress increased plasma corticosterone levels, decreased GR protein expression, and increased miR-124a expression in the corpus callosum of adult male mice, though the GR mRNA and miR-18 expression levels were not significant changes. YKS normalized the stress-induced changes in the plasma corticosterone, GR protein, and miR124a expression levels. An oligodendrocyte primary culture study also showed that YKS down-regulated miR-124a, but not miR-18, expression levels in dexamethasone-treated cells. These results suggest that the down-regulation of miR124a expression might be involved in the normalization of stress-induced decreases in GR protein in oligodendrocytes by YKS. This effect may imply the molecular mechanisms underlying the ameliorative effects of YKS on psychological symptoms and stress-related behaviors. PMID:25857947

  15. CMB anisotropy power spectrum statistics

    E-print Network

    Benjamin D. Wandelt; Eric Hivon; Krzysztof M. Gorski

    1998-10-19

    Much attention has been given to the problem of estimating cosmological parameters from the $C_l$ measured by future experiments. Many of the approaches which are being used either invoke poorly controlled approximations or are computationally expensive. We derive exact results as well as fast and highly accurate approximations for mapping a theoretical model onto the observed power spectrum coefficients and computing their statistical properties. These results obtain from an analytic framework which applies for any azimuthally symmetric sky coverage regardless of the fraction of the sky observed by the experiment.

  16. Fabulous Fraction Fun

    NSDL National Science Digital Library

    Mrs. Alman

    2008-03-26

    Let\\'s practice with parts of a whole and parts of a group fractions! Hello! Today, we are going to have fun with fractions! Play the game in each section below and make sure you read those directions before you begin! PARTS OF A WHOLE First, we are going to review our skills with parts of a whole fractions! Once you enter the site, click ...

  17. Fractional Electromagnetic Waves

    E-print Network

    J. F. Gómez; J. J. Rosales; J. J. Bernal; V. I. Tkach; M. Guía

    2011-08-31

    In the present work we consider the electromagnetic wave equation in terms of the fractional derivative of the Caputo type. The order of the derivative being considered is 0 <\\gamma<1. A new parameter \\sigma, is introduced which characterizes the existence of the fractional components in the system. We analyze the fractional derivative with respect to time and space, for \\gamma = 1 and \\gamma = 1/2 cases.

  18. Pie Chart with Fractions

    NSDL National Science Digital Library

    S. M. Blinder

    2012-01-01

    This interactive Wolfram Demonstration helps students visualize and understand the relationship between fractions and decimals. Users manipulate controls to adjust the size of the decimal portion of a pie eaten, in increments of hundredths. The result is represented visually on the diagram of a pie as well as in fraction and decimal forms. The remainder of the pie is also displayed as a fraction and its decimal equivalent. Wolfram CDF Player, a free download, is required to view this resource.

  19. Continued Fractions: An Introduction

    NSDL National Science Digital Library

    Van Tuyl, Adam

    A brief introduction to the field of continued fractions, including some basic theory about the subject; the history of continued fractions, tracing some of the major developments in the field in the past 2500 years; some interactive applications that demonstrate the uses of continued fractions and let you calculate them; and the resources used in creating this site, including a bibliography and links to other sites on the Web.

  20. Multiplying a Fraction by a Fraction

    NSDL National Science Digital Library

    admin admin

    2012-04-16

    In this lesson, students will solve problems related to training for a marathon to apply and make sense of multiplying fractions. The student will complete a function table to help illustrate patterns in the numerator/denominator relationships. This lesson utilizes the linear model as a concrete representation and moves towards the standard algorithm (a/b) x (c/d) = ac/bd.

  1. Ejection Fraction Heart Failure Measurement

    MedlinePLUS

    ... HF with preserved ejection fraction. Preserved ejection fraction (HFpEF) – also referred to as diastolic heart failure. The ... fraction reading and still have heart failure (called HFpEF or heart failure with preserved ejection fraction). If ...

  2. Statistics of the CMB polarised anisotropies

    E-print Network

    Ferte, A

    2015-01-01

    This PhD thesis (defended in 2014) is focused on the estimation of the CMB polarised anisotropies power spectra on a masked sky and on forecasts of constraints set on the primordial universe physics thanks to these anisotropies. After an introduction on the light polarisation, the standard model of cosmology and the CMB properties, I show the results obtained on the use and efficiency of pseudospectrum methods to correct for the so-called E-to-B leakage. Afterwards, I present the forecasts obtained on the detection of the tensor-to-scalar ratio r and on the detection of chiral gravity, using the pure pseudospectrum method. The study of forecasts of a primordial magnetic field detection using the CMB polarised anisotropies is finally briefly tackled.

  3. Measuring anisotropies in the cosmic neutrino background

    NASA Astrophysics Data System (ADS)

    Lisanti, Mariangela; Safdi, Benjamin R.; Tully, Christopher G.

    2014-10-01

    Neutrino capture on tritium has emerged as a promising method for detecting the cosmic neutrino background (C ? B ). We show that relic neutrinos are captured most readily when their spin vectors are antialigned with the polarization axis of the tritium nuclei and when they approach along the direction of polarization. As a result, C ? B observatories may measure anisotropies in the cosmic neutrino velocity and spin distributions by polarizing the tritium targets. A small dipole anisotropy in the C ? B is expected due to the peculiar velocity of the lab frame with respect to the cosmic frame and due to late-time gravitational effects. The PTOLEMY experiment, a tritium observatory currently under construction, should observe a nearly isotropic background. This would serve as a strong test of the cosmological origin of a potential signal. The polarized-target measurements may also constrain nonstandard neutrino interactions that would induce larger anisotropies and help discriminate between Majorana versus Dirac neutrinos.

  4. Anisotropy of the cosmic microwave background radiation

    NASA Technical Reports Server (NTRS)

    Silk, J.

    1981-01-01

    Theoretical predictions of the angular anisotropy in the cosmic microwave background radiation on both small and large angular scales are presented, and the effect of massive neutrinos on both the background radiation anisotropy and on the galaxy correlation function over very large scales is reviewed. Current observations show that the quadrupole anisotropy provides the greatest constraint on theory, and the values for the gravitational potential fluctuations indicate that small amplitude but sufficiently large-scale density fluctuations, both at the present epoch and on the surface of last scattering, can produce significant large angular scale variations in the radiation temperature. Most importantly, it is proposed that the quadrupole moment is most simply and elegantly interpreted in terms of the density fluctuations on very large scales whose presence is inferred from the requirement that an initial fluctuation spectrum is required in order for structure to develop.

  5. Large Friction Anisotropy of a Polydiacetylene Monolayer

    SciTech Connect

    Burns, A.R.; Carpick, R.W.; Sasaki, D.Y.

    1999-05-11

    Friction force microscopy measurements of a polydiacetylene monolayer film reveal a 300% friction anisotropy that is correlated with the film structure. The film consists of a monolayer of the red form of N-(2-ethanol)- 10,12 pentacosadiynamide, prepared on a Langmuir trough and deposited on a mica substrate. As confirmed by atomic force microscopy and fluorescence microscopy, the monolayer consists of domains of linearly oriented conjugated backbones with pendant hydrocarbon side chains above and below the backbones. Maximum friction occurs when the sliding direction is perpendicular to the backbone. We propose that the backbones impose anisotropic packing of the hydrocarbon side chains which leads to the observed friction anisotropy. Friction anisotropy is therefore a sensitive, optically-independent indicator of polymer backbone direction and monolayer structural properties.

  6. On ductile fracture initiation toughness: Effects of void volume fraction, void shape and void distribution

    Microsoft Academic Search

    Xiaosheng Gao; Tianhong Wang; Jinkook Kim

    2005-01-01

    This paper studies the effects of the initial relative void spacing, void pattern, void shape and void volume fraction on ductile fracture toughness using three-dimensional, small scale yielding models, where voids are assumed to pre-exist in the material and are explicitly modeled using refined finite elements. Results of this study can be used to explain the observed fracture toughness anisotropy

  7. Fractions--a Booster Activity

    NSDL National Science Digital Library

    BCC/Netmedia

    2007-01-01

    This set of interactive activities for students introduces early fractions concepts. Students name the parts needed to divide a pizza, fill in a fraction wall with fraction bars, name a shaded fraction, arrange fractions on a number line, and subtract fractions from a whole using different denominators. The main page links to support materials for teachers: practice problems and exposition material.

  8. Identify fractions in multiple ways

    NSDL National Science Digital Library

    Mrs. Marsh

    2006-10-27

    Practice identifying fractions 1. Compare fractions and find different fractions using the same denominators. 2. Identify fractions on a number line and see if you can do it. 3. Help find grampy and identify the fraction to find him. 4. Comparing fractions with pie charts ...

  9. Probing Cosmic topology using CMB anisotropy

    E-print Network

    Tarun Souradeep; Dmitry Pogosyan; J. Richard Bond

    1998-04-04

    The measurements of CMB anisotropy have opened up a window for probing the global topology of the universe on length scales comparable to and beyond the Hubble radius. We have developed a new method for calculating the CMB anisotropy in models with nontrivial topology and apply it to open universe models with compact spatial topology. We conduct a Bayesian probability analysis for a selection of models which confronts the theoretical pixel-pixel temperature correlation function with the COBE-DMR data. Our results demonstrate that strong constraints on compactness arise: if the universe is small compared to the `horizon' size, correlations appear in the maps that are irreconcilable with the observations.

  10. Enhancements of Microwave Anisotropy Measurement Technique

    SciTech Connect

    Predak, S.; Busse, G. [Institute of Polymer Technology, Department of Non-Destructive Testing (IKT-ZFP), University of Stuttgart, Pfaffenwaldring 32, 70569 Stuttgart (Germany)

    2007-03-21

    Polarized microwaves are used for fiber orientation measurements in composites. The sample is placed in an open resonator system. Resonator length or frequency can be tuned while the intensity of the reflected microwave signal is recorded. For every direction of polarization versus fiber orientation, the resonator length (frequency) is correspondingly readjusted in a feedback circuitry. Direction and degree of anisotropy are determined from the direction dependence. The influence of sample position on the result can be used to improve the determination of the degree of anisotropy.

  11. The Damping Tail of CMB Anisotropies

    E-print Network

    Wayne Hu; Martin White

    1996-09-10

    By decomposing the damping tail of CMB anisotropies into a series of transfer functions representing individual physical effects, we provide ingredients that will aid in the reconstruction of the cosmological model from small-scale CMB anisotropy data. We accurately calibrate the model-independent effects of diffusion and reionization damping which provide potentially the most robust information on the background cosmology. Removing these effects, we uncover model-dependent processes such as the acoustic peak modulation and gravitational enhancement that can help distinguish between alternate models of structure formation and provide windows into the evolution of fluctuations at various stages in their growth.

  12. Microwave background anisotropy induced by gravitational waves

    NASA Technical Reports Server (NTRS)

    Linder, Eric V.

    1988-01-01

    A cosmological background of gravitational waves induces redshift perturbations in light transversing it. Calculations of this Sachs-Wolfe effect on the microwave background are presented in an Omega = 1 Friedmann universe as a function of angular scale and gravitational wave spectrum. Blurriness of the last-scattering surface can cause nonnegligible dilution of the anisotropy for wavelengths less than about 100 Mpc. The limit implied for the energy density of the gravitational waves is given. A difficulty in associating a linear scale with an angular anisotropy, due to the clumpiness of the universe, is also pointed out.

  13. The anisotropy of aluminum and aluminum alloys

    NASA Astrophysics Data System (ADS)

    Hosford, William F.

    2006-05-01

    The anisotropy of textured aluminum is approximated by a yield criterion with an exponent of eight. The use of this criterion in metal-forming analyses has improved the understanding of the formability of aluminum and other metals. The effect of anisotropy on the limiting drawing ratio in cupping is less than that expected from the quadratic Hill yield criterion and the effect of texture on forming limit diagrams is negligible. A method of predicting the effect of strain-path changes on forming limit curves of aluminum alloy sheets has proven to agree with experiments.

  14. Weak Elastic Anisotropy in Global Seismology

    NASA Astrophysics Data System (ADS)

    Thomsen, L.; Anderson, D. L.

    2014-12-01

    Most of the major features of the Earth's interior were discovered using the concepts of isotropic seismology; however, subtle features require more realistic concepts. Although the importance of anisotropy has been known for over 50 years, only in the last decade has the increasing quality and quantity of data forced the wide recognition that anisotropyis crucial for accurate descriptions of upper mantle structure. The persistence of the "plume hypothesis", in spite of abundant evidence to the contrary, is partly based on the neglect of anisotropy, sparse and biased ray coverage, and the misuse of Occam's razor. Whereas isotropic inversion of teleseismic near-vertical travel-time datasets suggests the presence of deep vertical zones of low velocity (interpreted as mantle plumes), anisotropic inversion of data having a range of polarizations and directions of approach suggests instead shallow zones of relatively high anisotropy. This raises the possibility that current understanding of manyof the subtle features of Earth structure could be erroneous, caused by over-simplified analysis. The simplest plausible anisotropic model is that of polar anisotropy ("VTI" [sic!]), with a radial symmetry axis. The essential idea which makes anisotropic seismology feasible is the recognition that, in the Earth, the anisotropy is almost invariably weak, and the anisotropic equations (linearized in appropriately chosen small parameters) are quite simple (see below). These equations show that, to first order, the anisotropic variation of velocity is not governed by the individual Cab , but rather by the combinations of parameters given above. Hence, inversions should seek these combinations, rather than the individual moduli. The Rayleigh velocity VR is a simple function of VS0 and the P- and SV- anisotropies. The Love velocity VL is a complicated function of VS0 and the SH anisotropy ?. The simplest plausible model of azimuthal anisotropy is orthorhombic (not ("HTI" [sic!]), which may be analyzed as a simple generalization of the foregoing. Along the two principle azimuths, the velocities are exactly those of two (different) polar anisotropic media, which may be simplified as above. At other azimuths, a 9th (?-like) parameter is required. The VR-VL discrepancy is best described in these terms.

  15. Anisotropy of the Topopah Spring Member Tuff

    SciTech Connect

    Martin, R.J. III; Boyd, P.J.; Haupt, R.W. [New England Research, Inc., White River Junction, VT (United States); Price, R.H. [Sandia National Labs., Albuquerque, NM (United States)

    1992-07-01

    Mechanical properties of the tuffaceous rocks within Yucca Mountain are needed for near and far-field modeling of the potential nuclear waste repository. If the mechanical properties are significantly anisotropic (i.e., direction-dependent), a more complex model is required. Relevant data from tuffs tested in earlier studies indicate that elastic and strength properties are anisotropic. This scoping study confirms the elastic anisotropy and concludes some tuffs are transversely isotropic. An approach for sampling and testing the rock to determine the magnitude of the anisotropy is proposed.

  16. The Future of Fractions

    ERIC Educational Resources Information Center

    Usiskin, Zalman P.

    2007-01-01

    In the 1970s, the movement to the metric system (which has still not completely occurred in the United States) and the advent of hand-held calculators led some to speculate that decimal representation of numbers would render fractions obsolete. This provocative proposition stimulated Zalman Usiskin to write "The Future of Fractions" in 1979. He…

  17. Fractions and Everyday Mathematics

    Microsoft Academic Search

    J. Jay Slosky

    Fractions are a basic building block in the foundation of mathematics. Students need a good understanding of the concept of fractions, in order to be comfortable performing operations with them as they move on to higher math. I have taught middle school for three years and I am currently in my ninth year teaching high school. I have observed my

  18. Can Kindergartners Do Fractions?

    ERIC Educational Resources Information Center

    Cwikla, Julie

    2014-01-01

    Mathematics professor Julie Cwikla decided that she needed to investigate young children's understandings and see what precurricular partitioning notions young minds bring to the fraction table. Cwikla realized that only a handful of studies have examined how preschool-age and early elementary school-age students solve fraction problems…

  19. Mars Fraction Hunt

    NSDL National Science Digital Library

    Paul T. Williams

    2011-01-01

    This lesson gives students practice in applying fraction concepts, interpreting positional words, and paying attention to details. In order to decode a message, students construct new words by using fractional parts of other words as specified in the clues. A correct analysis of the clues leads to a candy bar reward. The activity could be adapted to accommodate individual classes and situations.

  20. Fraction Counting Book

    NSDL National Science Digital Library

    2012-12-17

    Students will make a book of fractions in which they choose a denominator and count up to a whole and greater than a whole. They will represent the fractions as pictures, in number form, word form, and on a number line.

  1. Everyday Mathematics Equivalent Fractions

    NSDL National Science Digital Library

    2011-02-03

    This iOS app ($) provides students with practice and reinforcement of fraction concepts in a solitaire context. Users try to clear a board by matching cards displaying equivalent visual and numeric representations of fractions, while getting feedback and scoring points for accuracy. A tutorial with voice explains how to play.

  2. Fraction Flags Halves

    NSDL National Science Digital Library

    Mark Cogan

    2002-01-01

    In this interactive activity students practice with fraction halves and quarters while painting a flag. There are four different options for coloring the flag (using halves, using four one-quarters, using three-quarters and one-quarter, and using a half and two one-quarters). The goal is to paint a creative flag using the correct colors and fractions given.

  3. Fraction Flags Thirds

    NSDL National Science Digital Library

    Mark Cogan

    2002-01-01

    In this interactive activity the user can practice learning about fraction thirds while painting a creative flag. There are two different coloring options for the flag (using three one-thirds or using two-thirds and one third). The goal is to paint a creative flag using the correct colors and fractions given.

  4. (Carbon isotope fractionation inplants)

    SciTech Connect

    O'Leary, M.H.

    1990-01-01

    The objectives of this research are: To develop a theoretical and experimental framework for understanding isotope fractionations in plants; and to develop methods for using this isotope fractionation for understanding the dynamics of CO{sub 2} fixation in plants. Progress is described.

  5. Anisotropy and chemical composition of ultra-high energy cosmic rays using arrival directions measured by the Pierre Auger Observatory

    NASA Astrophysics Data System (ADS)

    Pierre Auger Collaboration; Abreu, P.; Aglietta, M.; Ahn, E. J.; Albuquerque, I. F. M.; Allard, D.; Allekotte, I.; Allen, J.; Allison, P.; Alvarez Castillo, J.; Alvarez-Muñiz, J.; Ambrosio, M.; Aminaei, A.; Anchordoqui, L.; Andringa, S.; Anti?i?, T.; Anzalone, A.; Aramo, C.; Arganda, E.; Arqueros, F.; Asorey, H.; Assis, P.; Aublin, J.; Ave, M.; Avenier, M.; Avila, G.; Bäcker, T.; Balzer, M.; Barber, K. B.; Barbosa, A. F.; Bardenet, R.; Barroso, S. L. C.; Baughman, B.; Bäuml, J.; Beatty, J. J.; Becker, B. R.; Becker, K. H.; Bellétoile, A.; Bellido, J. A.; BenZvi, S.; Berat, C.; Bertou, X.; Biermann, P. L.; Billoir, P.; Blanco, F.; Blanco, M.; Bleve, C.; Blümer, H.; Bohá?ová, M.; Boncioli, D.; Bonifazi, C.; Bonino, R.; Borodai, N.; Brack, J.; Brogueira, P.; Brown, W. C.; Bruijn, R.; Buchholz, P.; Bueno, A.; Burton, R. E.; Caballero-Mora, K. S.; Caramete, L.; Caruso, R.; Castellina, A.; Catalano, O.; Cataldi, G.; Cazon, L.; Cester, R.; Chauvin, J.; Cheng, S. H.; Chiavassa, A.; Chinellato, J. A.; Chou, A.; Chudoba, J.; Clay, R. W.; Coluccia, M. R.; Conceição, R.; Contreras, F.; Cook, H.; Cooper, M. J.; Coppens, J.; Cordier, A.; Cotti, U.; Coutu, S.; Covault, C. E.; Creusot, A.; Criss, A.; Cronin, J.; Curutiu, A.; Dagoret-Campagne, S.; Dallier, R.; Dasso, S.; Daumiller, K.; Dawson, B. R.; de Almeida, R. M.; De Domenico, M.; De Donato, C.; de Jong, S. J.; De La Vega, G.; de Mello Junior, W. J. M.; de Mello Neto, J. R. T.; De Mitri, I.; de Souza, V.; de Vries, K. D.; Decerprit, G.; del Peral, L.; Deligny, O.; Dembinski, H.; Dhital, N.; Di Giulio, C.; Diaz, J. C.; Díaz Castro, M. L.; Diep, P. N.; Dobrigkeit, C.; Docters, W.; D'Olivo, J. C.; Dong, P. N.; Dorofeev, A.; dos Anjos, J. C.; Dova, M. T.; D'Urso, D.; Dutan, I.; Ebr, J.; Engel, R.; Erdmann, M.; Escobar, C. O.; Etchegoyen, A.; Facal San Luis, P.; Fajardo Tapia, I.; Falcke, H.; Farrar, G.; Fauth, A. C.; Fazzini, N.; Ferguson, A. P.; Ferrero, A.; Fick, B.; Filevich, A.; Filip?i?, A.; Fliescher, S.; Fracchiolla, C. E.; Fraenkel, E. D.; Fröhlich, U.; Fuchs, B.; Gaior, R.; Gamarra, R. F.; Gambetta, S.; García, B.; García Gámez, D.; Garcia-Pinto, D.; Gascon, A.; Gemmeke, H.; Gesterling, K.; Ghia, P. L.; Giaccari, U.; Giller, M.; Glass, H.; Gold, M. S.; Golup, G.; Gomez Albarracin, F.; Gómez Berisso, M.; Gonçalves, P.; Gonzalez, D.; Gonzalez, J. G.; Gookin, B.; Góra, D.; Gorgi, A.; Gouffon, P.; Gozzini, S. R.; Grashorn, E.; Grebe, S.; Griffith, N.; Grigat, M.; Grillo, A. F.; Guardincerri, Y.; Guarino, F.; Guedes, G. P.; Guzman, A.; Hague, J. D.; Hansen, P.; Harari, D.; Harmsma, S.; Harton, J. L.; Haungs, A.; Hebbeker, T.; Heck, D.; Herve, A. E.; Hojvat, C.; Hollon, N.; Holmes, V. C.; Homola, P.; Hörandel, J. R.; Horneffer, A.; Hrabovský, M.; Huege, T.; Insolia, A.; Ionita, F.; Italiano, A.; Jarne, C.; Jiraskova, S.; Kadija, K.; Kampert, K. H.; Karhan, P.; Kasper, P.; Kégl, B.; Keilhauer, B.; Keivani, A.; Kelley, J. L.; Kemp, E.; Kieckhafer, R. M.; Klages, H. O.; Kleifges, M.; Kleinfeller, J.; Knapp, J.; Koang, D.-H.; Kotera, K.; Krohm, N.; Krömer, O.; Kruppke-Hansen, D.; Kuehn, F.; Kuempel, D.; Kulbartz, J. K.; Kunka, N.; La Rosa, G.; Lachaud, C.; Lautridou, P.; Leão, M. S. A. B.; Lebrun, D.; Lebrun, P.; Leigui de Oliveira, M. A.; Lemiere, A.; Letessier-Selvon, A.; Lhenry-Yvon, I.; Link, K.; López, R.; Lopez Aüera, A.; Louedec, K.; Lozano Bahilo, J.; Lucero, A.; Ludwig, M.; Lyberis, H.; Maccarone, M. C.; Macolino, C.; Maldera, S.; Mandat, D.; Mantsch, P.; Mariazzi, A. G.; Marin, J.; Marin, V.; Maris, I. C.; Marquez Falcon, H. R.; Marsella, G.; Martello, D.; Martin, L.; Martinez, H.; Martínez Bravo, O.; Mathes, H. J.; Matthews, J.; Matthews, J. A. J.; Matthiae, G.; Maurizio, D.; Mazur, P. O.; Medina-Tanco, G.; Melissas, M.; Melo, D.; Menichetti, E.; Menshikov, A.; Mertsch, P.; Meurer, C.; Mi?anovi?, S.; Micheletti, M. I.; Miller, W.; Miramonti, L.; Mollerach, S.; Monasor, M.; Monnier Ragaigne, D.; Montanet, F.; Morales, B.; Morello, C.; Moreno, E.; Moreno, J. C.; Morris, C.; Mostafá, M.; Moura, C. A.; Mueller, S.; Muller, M. A.; Müller, G.; Münchmeyer, M.; Mussa, R.; Navarra, G.; Navarro, J. L.; Navas, S.; Necesal, P.; Nellen, L.; Nelles, A.; Nhung, P. T.; Niemietz, L.; Nierstenhoefer, N.; Nitz, D.; Nosek, D.; Nožka, L.; Nyklicek, M.; Oehlschläger, J.; Olinto, A.; Oliva, P.; Olmos-Gilbaja, V. M.; Ortiz, M.; Pacheco, N.; Pakk Selmi-Dei, D.; Palatka, M.; Pallotta, J.; Palmieri, N.; Parente, G.; Parizot, E.; Parra, A.; Parsons, R. D.; Pastor, S.; Paul, T.; Pech, M.; P?kala, J.; Pelayo, R.; Pepe, I. M.; Perrone, L.; Pesce, R.; Petermann, E.; Petrera, S.; Petrinca, P.; Petrolini, A.; Petrov, Y.; Petrovic, J.; Pfendner, C.; Phan, N.; Piegaia, R.; Pierog, T.; Pieroni, P.; Pimenta, M.; Pirronello, V.

    2011-06-01

    The Pierre Auger Collaboration has reported evidence for anisotropy in the distribution of arrival directions of the cosmic rays with energies E > Eth = 5.5 × 1019 eV. These show a correlation with the distribution of nearby extragalactic objects, including an apparent excess around the direction of Centaurus A. If the particles responsible for these excesses at E > Eth are heavy nuclei with charge Z, the proton component of the sources should lead to excesses in the same regions at energies E/Z. We here report the lack of anisotropies in these directions at energies above Eth/Z (for illustrative values of Z = 6,13,26). If the anisotropies above Eth are due to nuclei with charge Z, and under reasonable assumptions about the acceleration process, these observations imply stringent constraints on the allowed proton fraction at the lower energies.

  6. Anisotropy and chemical composition of ultra-high energy cosmic rays using arrival directions measured by the Pierre Auger Observatory

    DOE PAGESBeta

    Abreu, P; Aglietta, M; Ahn, E J; Albuquerque, I F.M.; Allard, D; Allekotte, I; Allen, J; Allison, P; Alvarez Castillo, J; Alvarez-Muniz, J; et al

    2011-06-17

    The Pierre Auger Collaboration has reported evidence for anisotropy in the distribution of arrival directions of the cosmic rays with energies E > Eth = 5.5 x 1019 eV. These show a correlation with the distribution of nearby extragalactic objects, including an apparent excess around the direction of Centaurus A. If the particles responsible for these excesses at E > Eth are heavy nuclei with charge Z, the proton component of the sources should lead to excesses in the same regions at energies E/Z. We here report the lack of anisotropies in these directions at energies above Eth/Z (for illustrativemore »values of Z = 6,13,26). If the anisotropies above Eth are due to nuclei with charge Z, and under reasonable assumptions about the acceleration process, these observations imply stringent constraints on the allowed proton fraction at the lower energies.« less

  7. Determination of Near-Surface Anisotropy From Surface Electromagnetic Data

    E-print Network

    Al-Dajani, AbdulFattah

    2001-01-01

    Ground penetrating radar (GPR) signatures, such as reflection moveout, are sensitive to the presence of azimuthal anisotropy. Azimuthal anisotropy can occur as an intrinsic property of the medium and/or due to the presence ...

  8. CMB anisotropies caused by gravitational waves: A parameter study

    E-print Network

    Durrer, Ruth

    ave. 2a, 380060 Tbilisi, Georgia Abstract Anisotropies in the cosmic microwave background radiation imprint as anisotropies on the cosmic microwave background. We also take into account thatmassless parameters of the model. Keywords: Cosmology: cosmic microwave background; Gravitational waves; Cosmology

  9. Temperature Anisotropies in a Universe with Global Defects

    E-print Network

    David Coulson

    1994-07-15

    We present a technique of calculating microwave anisotropies from global defects in a reionised universe. We concentrate on angular scales down to one degree where we expect the nongaussianity of the temperature anisotropy in these models to become apparent.

  10. Thin genu of the corpus callosum points to mutation in FOXG1 in a child with acquired microcephaly, trigonocephaly, and intellectual developmental disorder: a case report and review of literature.

    PubMed

    De Bruyn, Caroline; Vanderhasselt, Tim; Tanyalçin, Ibrahim; Keymolen, Kathelijn; Van Rompaey, Katrijn L; De Meirleir, Linda; Jansen, Anna C

    2014-05-01

    The FOXG1 syndrome is emerging as a relative new entity in paediatric neurology. We report a boy with acquired microcephaly, mental retardation and a thin genu of the corpus callosum. The combination of these findings led to mutation analysis of FOXG1. The patient was found to be heterozygous for a novel mutation in FOXG1, c.506dup (p.Lys170GInfsX285), which occurred de novo. This frameshift mutation disturbs the three functional domains of the FOXG1 gene. Hypo- or agenesis of the anterior corpus callosum in combination with acquired microcephaly and neurologic impairment can be an important clue for identifying patients with a mutation in FOXG1. PMID:24388699

  11. An experimental test of the viscous anisotropy hypothesis for partially molten rocks

    E-print Network

    Qi, Chao; Katz, Richard F; Takei, Yasuko

    2014-01-01

    Chemical differentiation of rocky planets occurs by melt segregation away from the region of melting. The mechanics of this process, however, are complex and incompletely understood. In partially molten rocks undergoing shear deformation, melt pockets between grains align coherently in the stress field; it has been hypothesized that this anisotropy in microstructure creates an anisotropy in the viscosity of the aggregate. With the inclusion of anisotropic viscosity, continuum, two-phase-flow models reproduce the emergence and angle of melt-enriched bands that form in laboratory experiments. In the same theoretical context, these models also predict sample-scale melt migration due to a gradient in shear stress. Under torsional deformation, melt is expected to segregate radially inward. Here we present new torsional deformation experiments on partially molten rocks that test this prediction. Microstructural analyses of the distribution of melt and solid reveal a radial gradient in melt fraction, with more melt ...

  12. In Vivo Imaging of the Actin Polymerization State with Two-Photon Fluorescence Anisotropy

    PubMed Central

    Vishwasrao, Harshad D.; Trifilieff, Pierre; Kandel, Eric R.

    2012-01-01

    Using two-photon fluorescence anisotropy imaging of actin-GFP, we have developed a method for imaging the actin polymerization state that is applicable to a broad range of experimental systems extending from fixed cells to live animals. The incorporation of expressed actin-GFP monomers into endogenous actin polymers enables energy migration FRET (emFRET, or homoFRET) between neighboring actin-GFPs. This energy migration reduces the normally high polarization of the GFP fluorescence. We derive a simple relationship between the actin-GFP fluorescence polarization anisotropy and the actin polymer fraction, thereby enabling a robust means of imaging the actin polymerization state with high spatiotemporal resolution and providing what to the best of our knowledge are the first direct images of the actin polymerization state in live, adult brain tissue and live, intact Drosophila larvae. PMID:22404943

  13. Anisotropy of magnetic susceptibility of some metamorphic minerals

    Microsoft Academic Search

    G. Borradaile; W. Keeler; C. Alford; P. Sarvas

    1987-01-01

    The anisotropy of susceptibility of metamorphic rocks can be due to paramagnetic rock-forming silicates such as amphiboles, chlorites and micas. It is not always necessary to invoke fabrics of separate grains of iron oxide to explain the anisotropy. Minimum estimates of lattice anisotropies of typical samples of silicates have maximum-to-minimum ratios of 1.1-1.7. Since the magnetic anisotropies of most metamorphic

  14. Tempered fractional Brownian motion

    NASA Astrophysics Data System (ADS)

    Sabzikar, Farzad

    Tempered fractional Brownian motion (TFBM) modifies the power law kernel in the moving average representation of a fractional Brownian motion (FBM), adding an exponential tempering. It also has a harmonizable representation. The increments of TFBM are stationary, and the autocovariance of the resulting tempered fractional Gaussian noise (TFGN) has semi-long range dependence, in which the autocorrelations decay like a power law over a moderate length scale, but eventually fall off more rapidly. TFBM can be represented as the linear combination of tempered fractional derivative (or tempered fractional integral) of the indicator functions. This representation and the classical Ito isometry provides to characterize the class of all deterministic functions for which the stochastic integral with respect to TFBM is well defined. Replacing the Gaussian random measure (Brownian motion) in the moving average or harmonizable representation of TFBM by a stable random measure, a linear tempered fractional stable motion (LTFSM), or a real harmonizable tempered fractional stable motion (HTFSM), respectively. Unlike the Gaussian case, LTFSM and HTFSM are two completely different processes. Existence, basic properties, sample path behavior, and dependence structure of both processes will be described.

  15. Cosmic microwave background anisotropies in the timescape cosmology

    E-print Network

    M. Ahsan Nazer; David L. Wiltshire

    2015-03-13

    We analyze the spectrum of cosmic microwave background (CMB) anisotropies in the timescape cosmology: a potentially viable alternative to homogeneous isotropic cosmologies without dark energy. We exploit the fact that the timescape cosmology is extremely close to the standard cosmology at early epochs to adapt existing numerical codes to produce CMB anisotropy spectra, and to match these as closely as possible to the timescape expansion history. A variety of matching methods are studied and compared. We perform Markov Chain Monte Carlo analyses on the parameter space, and fit CMB multipoles $50 \\le \\ell \\le 2500$ to the Planck satellite data. Parameter fits include a dressed Hubble constant, $H_0 = 61.0$ km/s/Mpc ($\\pm$ 1.3% stat) ($\\pm$ 8% sys), and a present void volume fraction $f_{v0} = 0.627$ ($\\pm$ 2.3% stat) ($\\pm$ 13% sys). We find best fit likelihoods which are comparable to that of the best fit Lambda CDM cosmology in the same multipole range. In contrast to earlier results, the parameter constraints afforded by this analysis no longer admit the possibility of a solution to the primordial lithium abundance anomaly. This issue is related to a strong constraint between the ratio of baryonic to nonbaryonic dark matter and the ratio of heights of the second and third acoustic peaks, which cannot be changed as long as the standard cosmology is assumed up to the surface of last scattering. These conclusions may change if backreaction terms are also included in the radiation-dominated primordial plasma.

  16. Anisotropy in MHD turbulence due to a mean magnetic field

    NASA Technical Reports Server (NTRS)

    Shebalin, J. V.; Matthaeus, W. H.; Montgomery, D.

    1982-01-01

    The development of anisotropy in an initially isotropic spectrum is studied numerically for two-dimensional magnetohydrodynamic turbulence. The anisotropy develops due to the combined effects of an externally imposed dc magnetic field and viscous and resistive dissipation at high wave numbers. The effect is most pronounced at high mechanical and magnetic Reynolds numbers. The anisotropy is greater at the higher wave numbers.

  17. Study of magnetocrystalline anisotropy of some magnetic nanoparticles

    Microsoft Academic Search

    Chandra Thapa

    2006-01-01

    Magnetic nanoparticles have applications to a variety devices ranging from high density magnetic data storage to targeted drug delivery. The suitability of specific magnetic nanoparticles for a particular application is mainly determined by their magnetic anisotropy energy. Magnetic nanoparticles with large magnetic anisotropy energy are particularly useful for high density data storage while the magnetic nanoparticles with small magnetic anisotropy

  18. Vertically graded anisotropy in Co\\/Pd multilayers

    Microsoft Academic Search

    B. J. Kirby; J. E. Davies; Kai Liu; S. M. Watson; G. T. Zimanyi; R. D. Shull; P. A. Kienzle; J. A. Borchers

    2010-01-01

    Depth grading of magnetic anisotropy in perpendicular magnetic media has been predicted to reduce the field required to write data without sacrificing thermal stability. To study this prediction, we have produced Co\\/Pd multilayers with depth-dependent Co layer thickness. Polarized neutron reflectometry shows that the thickness grading results in a corresponding magnetic anisotropy gradient. Magnetometry reveals that the anisotropy gradient promotes

  19. THE MAGNETOCRYSTALLINE ANISOTROPY OF GALLIUM AND ALUMINIUM SUBSTITUTED MAGNETITE

    E-print Network

    Paris-Sud XI, Université de

    409 THE MAGNETOCRYSTALLINE ANISOTROPY OF GALLIUM AND ALUMINIUM SUBSTITUTED MAGNETITE By R. F of the magnetocrystalline anisotropy in magnetite (Fe3O4) as this shows a rather anomalous variation with temperature constante d'anisotropie K1 ont été mesurées de 120 °K à 400 °K par la méthode de torsion, pour sept cristaux

  20. MATERIA ux MA GNETIQUES DOUX THE EFFECT OF MAGNETOCRYSTALLINE ANISOTROPY

    E-print Network

    Paris-Sud XI, Université de

    MATERIA ux MA GNETIQUES DOUX THE EFFECT OF MAGNETOCRYSTALLINE ANISOTROPY AND STRESS ON THE DOMAIN with tension. 1. Introduction. -The first anisotropy constant K, of a quaternary alloy 77 Ni-14 Fe-5 Cu-4 Mo wt of residual internal stresses which constitute an effective anisotropy 21 1,oi. Almost nothing is known

  1. Fractional calculus in bioengineering.

    PubMed

    Magin, Richard L

    2004-01-01

    Fractional calculus (integral and differential operations of noninteger order) is not often used to model biological systems. Although the basic mathematical ideas were developed long ago by the mathematicians Leibniz (1695), Liouville (1834), Riemann (1892), and others and brought to the attention of the engineering world by Oliver Heaviside in the 1890s, it was not until 1974 that the first book on the topic was published by Oldham and Spanier. Recent monographs and symposia proceedings have highlighted the application of fractional calculus in physics, continuum mechanics, signal processing, and electromagnetics, but with few examples of applications in bioengineering. This is surprising because the methods of fractional calculus, when defined as a Laplace or Fourier convolution product, are suitable for solving many problems in biomedical research. For example, early studies by Cole (1933) and Hodgkin (1946) of the electrical properties of nerve cell membranes and the propagation of electrical signals are well characterized by differential equations of fractional order. The solution involves a generalization of the exponential function to the Mittag-Leffler function, which provides a better fit to the observed cell membrane data. A parallel application of fractional derivatives to viscoelastic materials establishes, in a natural way, hereditary integrals and the power law (Nutting/Scott Blair) stress-strain relationship for modeling biomaterials. In this review, I will introduce the idea of fractional operations by following the original approach of Heaviside, demonstrate the basic operations of fractional calculus on well-behaved functions (step, ramp, pulse, sinusoid) of engineering interest, and give specific examples from electrochemistry, physics, bioengineering, and biophysics. The fractional derivative accurately describes natural phenomena that occur in such common engineering problems as heat transfer, electrode/electrolyte behavior, and sub-threshold nerve propagation. By expanding the range of mathematical operations to include fractional calculus, we can develop new and potentially useful functional relationships for modeling complex biological systems in a direct and rigorous manner. PMID:15248549

  2. The Microwave Anisotropy Probe Attitude Control System

    Microsoft Academic Search

    F. L. Markley; S. F. Andrews; J. R. O'Donnell; D. K. Ward; A. J. Ericsson

    2001-01-01

    The Microwave Anisotropy Probe mission is designed to produce a map of the cosmic microwave background radiation over the entire celestial sphere by executing a fast spin and a slow precession of its spin axis about the Sun line to obtain a highly interconnected set of measurements. The spacecraft attitude is sensed and controlled using two inertial reference units, two

  3. Tensor Anisotropies in an Open Universe

    E-print Network

    Wayne Hu; Martin White

    1997-07-16

    We calculate the anisotropies in the cosmic microwave background induced by long-wavelength primordial gravitational waves in a universe with negative spatial curvature, such as are produced in the ``open inflation'' scenario. The impact of these results on the COBE normalization of open models is discussed.

  4. Numerical likelihood analysis of cosmic ray anisotropies

    SciTech Connect

    Carlos Hojvat et al.

    2003-07-02

    A numerical likelihood approach to the determination of cosmic ray anisotropies is presented which offers many advantages over other approaches. It allows a wide range of statistically meaningful hypotheses to be compared even when full sky coverage is unavailable, can be readily extended in order to include measurement errors, and makes maximum unbiased use of all available information.

  5. Microwave anisotropy due to cosmic strings

    Microsoft Academic Search

    Nick Kaiser; Albert Stebbins

    1984-01-01

    It is shown that cosmic strings would generate anisotropy of the microwave background temperature with a very distinctive feature: the temperature would have steplike discontinuities on curves on the sky. The dynamics of cosmic strings is reviewed, and the distribution of strings in the Universe is briefly discussed, and the geometry of space-time near a string is described. The general

  6. Global anisotropy and the thickness of continents.

    PubMed

    Gung, Yuancheng; Panning, Mark; Romanowicz, Barbara

    2003-04-17

    For decades there has been a vigorous debate about the depth extent of continental roots. The analysis of heat-flow, mantle-xenolith and electrical-conductivity data all indicate that the coherent, conductive part of continental roots (the 'tectosphere') is at most 200-250 km thick. Some global seismic tomographic models agree with this estimate, but others suggest that a much thicker zone of high velocities lies beneath continental shields, reaching a depth of at least 400 km. Here we show that this disagreement can be reconciled by taking into account seismic anisotropy. We show that significant radial anisotropy, with horizontally polarized shear waves travelling faster than those that are vertically polarized, is present under most cratons in the depth range 250-400 km--similar to that found under ocean basins at shallower depths of 80-250 km. We propose that, in both cases, the anisotropy is related to shear in a low-viscosity asthenospheric channel, located at different depths under continents and oceans. The seismically defined 'tectosphere' is then at most 200-250 km thick under old continents. The 'Lehmann discontinuity', observed mostly under continents at about 200-250 km, and the 'Gutenberg discontinuity', observed under oceans at depths of about 60-80 km, may both be associated with the bottom of the lithosphere, marking a transition to flow-induced asthenospheric anisotropy. PMID:12700758

  7. Supplementary Information for `Spintronic magnetic anisotropy'

    E-print Network

    Loss, Daniel

    Heisenberg interaction. Molecules with even larger gaps abound in the chemistry of molecular magnets, where of anisotropy by analysing the trans- port properties of a high-spin quantum dot embedded between two. The high-spin quantum dot, described by Hdot = ^n + U ^n^n + K^s · ^Simp, (S-1) is a composite system

  8. Relative sensitivity of formability to anisotropy

    SciTech Connect

    Logan, R.W.; Maker, B.N.

    1997-01-01

    This work compares the relative importance of material anisotropy in sheet forming as compared to other material and process variables. The comparison is made quantitative by the use of normalized dependencies of depth to failure (forming limit is reached) on various measures of anisotropy, as well as strain and rate sensitivity, friction, and tooling. Comparisons are made for a variety of forming processes examined previously in the literature as well as two examples of complex stampings in this work. 7 The examples rover a range from nearly pure draw to nearly pure stretch situations, and show that for materials following a quadratic yield criterion, anisotropy is among the most sensitive parameters influencing formability. For materials following higher-exponent yield criteria, the dependency is milder but is still of the order of most other process parameters. However, depending on the particular forming operation, it is shown that in some cases anisotropy may be ignored, whereas in others its consideration is crucial to a good quality analysis.

  9. Tuning the Magnetic Anisotropy of Single Molecules.

    PubMed

    Heinrich, Benjamin W; Braun, Lukas; Pascual, Jose I; Franke, Katharina J

    2015-06-10

    The magnetism of single atoms and molecules is governed by the atomic scale environment. In general, the reduced symmetry of the surrounding splits the d states and aligns the magnetic moment along certain favorable directions. Here, we show that we can reversibly modify the magnetocrystalline anisotropy by manipulating the environment of single iron(II) porphyrin molecules adsorbed on Pb(111) with the tip of a scanning tunneling microscope. When we decrease the tip-molecule distance, we first observe a small increase followed by an exponential decrease of the axial anisotropy on the molecules. This is in contrast to the monotonous increase observed earlier for the same molecule with an additional axial Cl ligand ( Nat. Phys. 2013 , 9 , 765 ). We ascribe the changes in the anisotropy of both species to a deformation of the molecules in the presence of the attractive force of the tip, which leads to a change in the d level alignment. These experiments demonstrate the feasibility of a precise tuning of the magnetic anisotropy of an individual molecule by mechanical control. PMID:25942560

  10. Magnetocrystalline anisotropy in Ni3Fe alloys

    Microsoft Academic Search

    H. Hatafuku; S. Takahashi; T. Sasaki; H. Ichinohe

    1983-01-01

    The first magnetocrystalline anisotropy constant, K1, was measured in Ni-Fe alloys containing 67 to 80 wt% Ni. In the disordered state, the present study is in good agreement with Bozorth's result. A remarkable difference between the two was found in the ordered state. This is attributed to the state of order due to annealing conditions.

  11. Global azimuthal anisotropy from Rayleigh waves and

    E-print Network

    Becker, Thorsten W.

    'Connell (1981) method of solving Stokes' equation viscosity varies only with depth, linear spherical harmonics? Is LPO orientation with the finite strain ellipsoid a valid explanation? Is finite strain from global inversions resolve D2 anisotropy? Yes! Is LPO orientation with the finite strain ellipsoid a valid

  12. Plagioclase preferred orientation and induced seismic anisotropy in mafic igneous rocks

    NASA Astrophysics Data System (ADS)

    Ji, Shaocheng; Shao, Tongbin; Salisbury, Matthew H.; Sun, Shengsi; Michibayashi, Katsuyoshi; Zhao, Weihua; Long, Changxing; Liang, Fenghua; Satsukawa, Takako

    2014-11-01

    Fractional crystallization and crystal segregation controlled by settling or floating of minerals during the cooling of magma can lead to layered structures in mafic and ultramafic intrusions in continental and oceanic settings in the lower crust. Thus, the seismic properties and fabrics of layered intrusions must be calibrated to gain insight into the origin of seismic reflections and anisotropy in the deep crust. To this end, we have measured P and S wave velocities and anisotropy in 17 plagioclase-rich mafic igneous rocks such as anorthosite and gabbro at hydrostatic pressures up to 650 MPa. Anorthosites and gabbroic anorthosites containing >80 vol% plagioclase and gabbros consisting of nearly equal modal contents of plagioclase and pyroxene display distinctive seismic anisotropy patterns: Vp(Z)/Vp(Y) ? 1 and Vp(Z)/Vp(X) ? 1 for anorthosites while 0.8 < Vp(Z)/Vp(Y) ? 1 and 0.8 < Vp(Z)/Vp(X) ? 1 for gabbros. Amphibolites lie in the same domain as gabbros, but show a significantly stronger tendency of Vp(X) > Vp(Y) than the gabbros. Laminated anorthosites with Vp(X) ? Vp(Y) ? Vp(Z) display a strong crystal preferred orientation (CPO) of plagioclase whose (010) planes and [100] and [001] directions parallel to the foliation. For the gabbros and amphibolites characterized by Vp(X) ? Vp(Y) > Vp(Z) and Vp(X) > Vp(Y) > Vp(Z), respectively, pyroxene and amphibole play a dominant role over plagioclase in the formation of seismic anisotropy. The Poisson's ratio calculated using the average P and S wave velocities from the three principal propagation-polarization directions (X, Y, and Z) of a highly anisotropic anorthosite cannot represent the value of a true isotropic equivalent. The CPO-induced anisotropy enhances and decreases the foliation-normal incidence reflectivity at gabbro-peridotite and anorthosite-peridotite interfaces, respectively.

  13. Comparing Fractions with Lines

    NSDL National Science Digital Library

    Richard E. Rand

    2007-12-12

    In this activity, students learn to compare fractions to understand which is larger or smaller by drawing or visualizing the two fractions represented on a line, as presented in the instructions. Students then determine which is larger and enter the appropriate <, >, or = sign to complete the statement. Once they have selected the correct answer, the solution is revealed with the fractions represented with common denominators. Each solution can be more thoroughly explained by clicking the "Explain" button. The student's score and percentage correct is tallied, and a report of that score can be printed from this page.

  14. Single Fraction Pointer

    NSDL National Science Digital Library

    2010-01-01

    Similar to Single Fraction Finder, in this activity, students highlight portions of a circle or square in order for the highlighted portion of the area to match a given fraction. The only difference is that when each section is highlighted, a pointer indicates where on the number line you are, between zero and one. This activity allows students to explore areas of circles and squares as well as fractions between zero and one. This activity includes supplemental materials, including background information about the topics covered, a description of how to use the application, and exploration questions for use with the java applet.

  15. Fraction Comparison Sped up

    NSDL National Science Digital Library

    Interactive Math Miscellany and Puzzles, Alexander Bogomolny

    2011-01-01

    This article explains several strategies for comparing fractions. It includes a Java applet that displays three fractions in a row for practice with these strategies. Modify the numerator or denominator of the middle one by clicking just to the left (decrease) or right (increase) of its center line so that it forms a valid inequality: either equal to or greater than the fraction to its left, and either equal to or less than the one to its right. The applet includes buttons to "Use common denominator" and "simplify."

  16. Reproducibility and optimization of in? vivo human diffusion-weighted MRS of the corpus callosum at 3T and 7T.

    PubMed

    Wood, Emily T; Ercan, Ayse Ece; Branzoli, Francesca; Webb, Andrew; Sati, Pascal; Reich, Daniel S; Ronen, Itamar

    2015-08-01

    Diffusion-weighted MRS (DWS) of brain metabolites enables the study of cell-specific alterations in tissue microstructure by probing the diffusion of intracellular metabolites. In particular, the diffusion properties of neuronal N-acetylaspartate (NAA), typically co-measured with N-acetylaspartyl glutamate (NAAG) (NAA?+?NAAG?=?tNAA), have been shown to be sensitive to intraneuronal/axonal damage in pathologies such as stroke and multiple sclerosis. Lacking, so far, are empirical assessments of the reproducibility of DWS measures across time and subjects, as well as a systematic investigation of the optimal acquisition parameters for DWS experiments, both of which are sorely needed for clinical applications of the method. In this study, we acquired comprehensive single-volume DWS datasets of the human corpus callosum at 3T and 7T. We investigated the inter- and intra-subject variability of empirical and modeled diffusion properties of tNAA [Davg (tNAA) and Dmodel (tNAA), respectively]. Subsequently, we used a jackknife-like resampling approach to explore the variance of these properties in partial data subsets reflecting different total scan durations. The coefficients of variation (CV ) and repeatability coefficients (CR ) for Davg (tNAA) and Dmodel (tNAA) were calculated for both 3T and 7T, with overall lower variability in the 7T results. Although this work is limited to the estimation of the diffusion properties in the corpus callosum, we show that a careful choice of diffusion-weighting conditions at both field strengths allows the accurate measurement of tNAA diffusion properties in clinically relevant experimental time. Based on the resampling results, we suggest optimized acquisition schemes of 13-min duration at 3T and 10-min duration at 7T, whilst retaining low variability (CV ???8%) for the tNAA diffusion measures. Power calculations for the estimation of Dmodel (tNAA) and Davg (tNAA) based on the suggested schemes show that less than 21 subjects per group are sufficient for the detection of a 10% effect between two groups in case-control studies. Copyright © 2015 John Wiley & Sons, Ltd. PMID:26084563

  17. In vivo detection of microscopic anisotropy using quadruple pulsed-field gradient (qPFG) diffusion MRI on a clinical scanner

    PubMed Central

    Avram, Alexandru V.; Özarslan, Evren; Sarlls, Joelle E.; Basser, Peter J.

    2012-01-01

    We report our design and implementation of a quadruple pulsed-field gradient (qPFG) diffusion MRI pulse sequence on a whole-body clinical scanner and demonstrate its ability to non-invasively detect restriction-induced microscopic anisotropy in human brain tissue. The microstructural information measured using qPFG diffusion MRI in white matter complements that provided by diffusion tensor imaging (DTI) and exclusively characterizes diffusion of water trapped in microscopic compartments with unique measures of average cell geometry. We describe the effect of white matter fiber orientation on the expected MR signal and highlight the importance of incorporating such information in the axon diameter measurement using a suitable mathematical framework. Integration of qPFG diffusion-weighted images (DWI) with fiber orientations measured using high-resolution DTI allows the estimation of average axon diameters in the corpus callosum of healthy human volunteers. Maps of inter-hemispheric average axon diameters reveal an anterior-posterior variation in good topographical agreement with anatomical measurements reported in previous post-mortem studies. With further technical refinements and additional clinical validation, qPFG diffusion MRI could provide a quantitative whole-brain histological assessment of white and gray matter, enabling a wide range of neuroimaging applications for improved diagnosis of neurodegenerative pathologies, monitoring neurodevelopmental processes, and mapping brain connectivity. PMID:22939872

  18. Fractional Derivative Cosmology

    E-print Network

    Mark D. Roberts

    2009-09-07

    The degree by which a function can be differentiated need not be restricted to integer values. Usually most of the field equations of physics are taken to be second order, curiosity asks what happens if this is only approximately the case and the field equations are nearly second order. For Robertson-Walker cosmology there is a simple fractional modification of the Friedman and conservation equations. In general fractional gravitational equations similar to Einstein's are hard to define as this requires fractional derivative geometry. What fractional derivative geometry might entail is briefly looked at and it turns out that even asking very simple questions in two dimensions leads to ambiguous or intractable results. A two dimensional line element which depends on the Gamma-function is looked at.

  19. Single Fraction Finder

    NSDL National Science Digital Library

    2010-01-01

    In this activity, students select portions of a square or circle so that the highlighted portion of the shape matches a given fraction. This activity allows students to explore areas of circles and squares as well as fractions between zero and one. This activity includes supplemental materials, including background information about the topics covered, a description of how to use the application, and exploration questions for use with the java applet.

  20. Complex-anisotropy-induced pattern formation in bistable media.

    PubMed

    He, Zhi Zhu; Liu, Jing

    2009-02-01

    A construct of anisotropy in bistable media is adopted to characterize the effects of anisotropy on pattern formation by means of anisotropic line tension. A velocity curvature relation is further derived to account for the anisotropic wave propagations. Stability analysis of transverse perturbations indicates that a sufficiently strong complex anisotropy can induce dynamical instabilities and even lead to a breakup of the wave patterns. Numerical simulations show that complex anisotropy can induce rich spatiotemporal behaviors in bistable media. The results of analysis and simulations demonstrate that this method successfully incorporates complex anisotropy into the reaction diffusion model and has general significance. PMID:19391804

  1. Probing the Pulsar Origin of the Anomalous Positron Fraction with AMS-02 and Atmospheric Cherenkov Telescopes

    NASA Astrophysics Data System (ADS)

    Linden, Tim; Profumo, Stefano

    2013-07-01

    Recent observations by PAMELA, Fermi-LAT, and AMS-02 have conclusively indicated a rise in the cosmic-ray positron fraction above 10 GeV, a feature which is impossible to mimic under the paradigm of secondary positron production with self-consistent Galactic cosmic-ray propagation models. A leading explanation for the positron fraction rise is an additional source of electron-positron pairs, for example one or more mature, energetic, and relatively nearby pulsars. We point out that any one of two well-known nearby pulsars, Geminga and Monogem, can satisfactorily provide enough positrons to reproduce AMS-02 observations. A smoking-gun signature of this scenario is an anisotropy in the arrival direction of the cosmic-ray electrons and positrons, which may be detectable by existing, or future, telescopes. The predicted anisotropy level is, at present, consistent with limits from Fermi-LAT and AMS-02. We argue that the large collecting area of atmospheric Cherenkov telescopes (ACTs) makes them optimal tools for detecting such an anisotropy. Specifically, we show that much of the proton and ?-ray background which affects measurements of the cosmic-ray electron-positron spectrum with ACTs may be controlled in the search for anisotropies. We conclude that observations using archival ACT data could already constrain or substantiate the pulsar origin of the positron anomaly, while upcoming instruments (such as the Cherenkov Telescope Array) will provide strong constraints on the source of the rising positron fraction.

  2. PROBING THE PULSAR ORIGIN OF THE ANOMALOUS POSITRON FRACTION WITH AMS-02 AND ATMOSPHERIC CHERENKOV TELESCOPES

    SciTech Connect

    Linden, Tim; Profumo, Stefano [Department of Physics, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States)

    2013-07-20

    Recent observations by PAMELA, Fermi-LAT, and AMS-02 have conclusively indicated a rise in the cosmic-ray positron fraction above 10 GeV, a feature which is impossible to mimic under the paradigm of secondary positron production with self-consistent Galactic cosmic-ray propagation models. A leading explanation for the positron fraction rise is an additional source of electron-positron pairs, for example one or more mature, energetic, and relatively nearby pulsars. We point out that any one of two well-known nearby pulsars, Geminga and Monogem, can satisfactorily provide enough positrons to reproduce AMS-02 observations. A smoking-gun signature of this scenario is an anisotropy in the arrival direction of the cosmic-ray electrons and positrons, which may be detectable by existing, or future, telescopes. The predicted anisotropy level is, at present, consistent with limits from Fermi-LAT and AMS-02. We argue that the large collecting area of atmospheric Cherenkov telescopes (ACTs) makes them optimal tools for detecting such an anisotropy. Specifically, we show that much of the proton and {gamma}-ray background which affects measurements of the cosmic-ray electron-positron spectrum with ACTs may be controlled in the search for anisotropies. We conclude that observations using archival ACT data could already constrain or substantiate the pulsar origin of the positron anomaly, while upcoming instruments (such as the Cherenkov Telescope Array) will provide strong constraints on the source of the rising positron fraction.

  3. Transit defect of potassium-chloride Co-transporter 3 is a major pathogenic mechanism in hereditary motor and sensory neuropathy with agenesis of the corpus callosum.

    PubMed

    Salin-Cantegrel, Adèle; Rivière, Jean-Baptiste; Shekarabi, Masoud; Rasheed, Sarah; Dacal, Sandra; Laganière, Janet; Gaudet, Rébecca; Rochefort, Daniel; Lesca, Gaëtan; Gaspar, Claudia; Dion, Patrick A; Lapointe, Jean-Yves; Rouleau, Guy A

    2011-08-12

    Missense and protein-truncating mutations of the human potassium-chloride co-transporter 3 gene (KCC3) cause hereditary motor and sensory neuropathy with agenesis of the corpus callosum (HMSN/ACC), which is a severe neurodegenerative disease characterized by axonal dysfunction and neurodevelopmental defects. We previously reported that KCC3-truncating mutations disrupt brain-type creatine kinase-dependent activation of the co-transporter through the loss of its last 140 amino acids. Here, we report a novel and more distal HMSN/ACC-truncating mutation (3402C ? T; R1134X) that eliminates only the last 17 residues of the protein. This small truncation disrupts the interaction with brain-type creatine kinase in mammalian cells but also affects plasma membrane localization of the mutant transporter. Although it is not truncated, the previously reported HMSN/ACC-causing 619C ? T (R207C) missense mutation also leads to KCC3 loss of function in Xenopus oocyte flux assay. Immunodetection in Xenopus oocytes and in mammalian cultured cells revealed a decreased amount of R207C at the plasma membrane, with significant retention of the mutant proteins in the endoplasmic reticulum. In mammalian cells, curcumin partially corrected these mutant protein mislocalizations, with more protein reaching the plasma membrane. These findings suggest that mis-trafficking of mutant protein is an important pathophysiological feature of HMSN/ACC causative KCC3 mutations. PMID:21628467

  4. Brief Report: VAX1 mutation associated with microphthalmia, corpus callosum agenesis and orofacial clefting – the first description of a VAX1 phenotype in humans

    PubMed Central

    Slavotinek, Anne M.; Chao, Ryan; Vacik, Tomas; Yahyavi, Mani; Abouzeid, Hana; Bardakjian, Tanya; Schneider, Adele; Shaw, Gary; Sherr, Elliott H.; Lemke, Greg; Youssef, Mohammed; Schorderet, Daniel F.

    2011-01-01

    Vax1 and Vax2 have been implicated in eye development and the closure of the choroid fissure in mice and zebrafish. We sequenced the coding exons of VAX1 and VAX2 in 70 patients with anophthalmia/microphthalmia. In VAX1, we observed homozygosity for two successive nucleotide substitutions c.453G>A and c.454C>A, predicting p.Arg152Ser, in a proband of Egyptian origin with microphthalmia, small optic nerves, cleft lip/palate and corpus callosum agenesis. This mutation affects an invariant residue in the homeodomain of VAX1 and was absent from 96 Egyptian controls. It is likely that the mutation results in a loss of function, as the mutation results in a phenotype similar to the Vax1 homozygous null mouse. We did not identify any mutations in VAX2. This is the first description of a phenotype associated with a VAX1 mutation in humans and establishes VAX1 as a new causative gene for anophthalmia/microphthalmia. PMID:22095910

  5. Childhood maltreatment and corpus callosum volume in recently diagnosed patients with bipolar I disorder: data from the Systematic Treatment Optimization Program for Early Mania (STOP-EM).

    PubMed

    Bücker, J; Muralidharan, K; Torres, I J; Su, W; Kozicky, J; Silveira, L E; Bond, D J; Honer, W G; Kauer-Sant'anna, M; Lam, R W; Yatham, L N

    2014-01-01

    Childhood trauma (CT) has been associated with abnormalities in the corpus callosum (CC). Decreased CC volumes have been reported in children and adolescents with trauma as well as adults with CT compared to healthy controls. CC morphology is potentially susceptible to the effects of Bipolar Disorder (BD) itself. Therefore, we evaluated the relationship between CT and CC morphology in BD. We using magnetic resonance imaging in 53 adults with BD recently recovered from their first manic episode, with (n = 23) and without (n = 30) CT, defined using the Childhood Trauma Questionnaire (CTQ) and 16 healthy controls without trauma. ANCOVA was performed with age, gender and intracranial volume as covariates in order to evaluate group differences in CC volume. The total CC volume was found to be smaller in BD patients with trauma compared to BD patients without trauma (p < .05). The differences were more pronounced in the anterior region of the CC. There was a significant negative correlation between CTQ scores and total CC volume in BD patients with trauma (p = .01). We did not find significant differences in the CC volume of patients with/without trauma compared to the healthy subjects. Our sample consists of patients recovered from a first episode of mania and are early in the course of illness and reductions in CC volume may occur late in the course of BD. It might mean there may be two sources of CC volume reduction in these patients: the reduction due to trauma, and the further reduction due to the illness. PMID:24183241

  6. A new X-linked syndrome with agenesis of the corpus callosum, mental retardation, coloboma, micrognathia, and a mutation in the Alpha 4 gene at Xq13.

    PubMed

    Graham, John M; Wheeler, Patricia; Tackels-Horne, Darci; Lin, Angela E; Hall, Bryan D; May, Melanie; Short, Kieran M; Schwartz, Charles E; Cox, Timothy C

    2003-11-15

    We describe two brothers with a unique pattern of malformations that includes coloboma (iris, optic nerve), high forehead, severe retrognathia, mental retardation, and agenesis of the corpus callosum (ACC). Both boys have low-set cupped ears with sensorineural hearing loss, normal phallus, pectus excavatum, scoliosis, and short stature. One brother had choanal atresia and cardiac defects consisting of ventricular septal defect (VSD) and patent ductus arteriosus (PDA) which resolved spontaneously. Differential diagnosis between a number of clinical entities was considered, however, because ACC and the distinctive facial features were reminiscent of FG syndrome, DNA was analyzed for markers linked to the FGS1 locus at Xq13-q21. Notably, the brothers were concordant for markers spanning this presumed FG region, and in both we have identified adjacent alterations (-57delT and T-55A) in the Alpha 4 gene located within this interval. Alpha 4 is a regulatory subunit of the major cellular phosphatase, PP2A, that has recently been shown to interact with MID1, the product of the gene mutated in X-linked Opitz GBBB syndrome. The double nucleotide change identified in this family was not observed in 410 control chromosomes, suggesting that it may be a pathogenetic change. Altered expression of Alpha 4, through either a change in translational efficiency, mRNA stability or splicing, could explain the clinical phenotype in these boys and the phenotypic overlap with Opitz GBBB syndrome. PMID:14556245

  7. Calcium, potassium, iron, copper and zinc concentrations in the white and gray matter of the cerebellum and corpus callosum in brain of four genetic mouse strains

    NASA Astrophysics Data System (ADS)

    Sergeant, C.; Vesvres, M. H.; Devès, G.; Guillou, F.

    2005-04-01

    In the central nervous system, metallic cations are involved in oligodendrocyte maturation and myelinogenesis. Moreover, the metallic cations have been associated with pathogenesis, particularly multiple sclerosis and malignant gliomas. The brain is vulnerable to either a deficit or an excess of available trace elements. Relationship between trace metals and myelinogenesis is important in understanding a severe human pathology : the multiple sclerosis, which remains without efficient treatment. One approach to understand this disease has used mutant or transgenic mice presenting myelin deficiency or excess. But to date, the concentration of trace metals and mineral elements in white and gray matter areas in wild type brain is unknown. The aim of this study is to establish the reference concentrations of trace metals (iron, copper and zinc) and minerals (potassium and calcium) in the white and gray matter of the mouse cerebellum and corpus callosum. The brains of four different genetic mouse strains (C57Black6/SJL, C57Black6/D2, SJL and C3H) were analyzed. The freeze-dried samples were prepared to allow PIXE (Proton-induced X-ray emission) and RBS (Rutherford backscattering spectrometry) analyses with the nuclear microprobe in Bordeaux. The results obtained give the first reference values. Furthermore, one species out of the fours testes exhibited differences in calcium, iron and zinc concentrations in the white matter.

  8. Equivalency Detectives: Fractions and Decimals!

    NSDL National Science Digital Library

    Maribel Magdaleno

    2012-07-17

    This is a lesson intended to reinforce students' ability to find equivalent fractions and decimals. The lesson requires prior essential vocabulary knowledge, and a basic understanding of converting fractions to decimals and decimals to fractions (specifically tenths and hundredths).

  9. Principles of Fractional Quantum Mechanics

    E-print Network

    Nick Laskin

    2010-09-28

    A review of fundamentals and physical applications of fractional quantum mechanics has been presented. Fundamentals cover fractional Schr\\"odinger equation, quantum Riesz fractional derivative, path integral approach to fractional quantum mechanics, hermiticity of the Hamilton operator, parity conservation law and the current density. Applications of fractional quantum mechanics cover dynamics of a free particle, new representation for a free particle quantum mechanical kernel, infinite potential well, bound state in {\\delta}-potential well, linear potential, fractional Bohr atom and fractional oscillator. We also review fundamentals of the L\\'evy path integral approach to fractional statistical mechanics.

  10. CMB Anisotropies in the Weak Coupling Limit

    E-print Network

    Wayne Hu; Martin White

    1995-07-14

    We present a new, more powerful and accurate, analytic treatment of cosmic microwave background (CMB) anisotropies in the weakly coupled regime. Three applications are presented: gravitational redshifts in a time dependent potential, the Doppler effect in reionized scenarios, and the Vishniac effect. The Vishniac effect can dominate primary anisotropies at small angles even in late and minimally reionized models in flat dark-matter dominated universes with Harrison-Zel'dovich initial conditions. The techniques developed here refine previous calculations yielding a larger coherence angle for the Vishniac effect and moreover can be applied to non-trivial ionization histories. These analytic expressions may be used to modify results for the standard cold dark matter model to its cosmological constant and reionized extensions without detailed and time consuming recalculation.

  11. Anisotropies in the cosmic microwave background: Theory

    SciTech Connect

    Dodelson, S.

    1998-02-01

    Anisotropies in the Cosmic Microwave Background (CMB) contain a wealth of information about the past history of the universe and the present values of cosmological parameters. I online some of the theoretical advances of the last few years. In particular, I emphasize that for a wide class of cosmological models, theorists can accurately calculate the spectrum to better than a percent. The spectrum of anisotropies today is directly related to the pattern of inhomogeneities present at the time of recombination. This recognition leads to a powerful argument that will enable us to distinguish inflationary models from other models of structure formation. If the inflationary models turn out to be correct, the free parameters in these models will be determined to unprecedented accuracy by the upcoming satellite missions.

  12. Physics of the cosmic microwave background anisotropy

    NASA Astrophysics Data System (ADS)

    Bucher, Martin

    2015-01-01

    Observations of the cosmic microwave background (CMB), especially of its frequency spectrum and its anisotropies, both in temperature and in polarization, have played a key role in the development of modern cosmology and of our understanding of the very early universe. We review the underlying physics of the CMB and how the primordial temperature and polarization anisotropies were imprinted. Possibilities for distinguishing competing cosmological models are emphasized. The current status of CMB experiments and experimental techniques with an emphasis toward future observations, particularly in polarization, is reviewed. The physics of foreground emissions, especially of polarized dust, is discussed in detail, since this area is likely to become crucial for measurements of the B modes of the CMB polarization at ever greater sensitivity.

  13. Two-photon fluorescence anisotropy imaging

    NASA Astrophysics Data System (ADS)

    Li, Wei; Wang, Yi; Shao, Hanrong; He, Yonghong; Ma, Hui

    2006-09-01

    We have developed a novel method for imaging the fluorescence intensity and anisotropy by two-photon fluorescence microscopy and tested its capability in biological application. This method is applied to model sample including FITC and FITC-CD44 antibody solution and also FITC-CD44 stained cells. The fluorescence anisotropy (FA) of FITC-CD44ab solution is higher than the FITC solution with the same concentration. The fluorescence in cell sample has even higher FA than in solution because the rotation diffusion is restrained in membrane. The method is employed to study the effect of berberine a kind of Chinese medicine, on tumor metastasis. The results indicated that tumor cell membrane fluidity is decreasing with increasing the concentration of berberine in culture medium.

  14. Tailored magnetic anisotropy in an amorphous trilayer

    SciTech Connect

    Fu Yu [Department of Physics, Southeast University, 211189 Nanjing (China); Fakultaet fuer Physik and Center for Nanointegration Duisburg-Essen (CeNIDE), Universitaet Duisburg-Essen, 47048 Duisburg (Germany); Barsukov, I.; Spasova, M.; Lindner, J.; Meckenstock, R.; Farle, M. [Fakultaet fuer Physik and Center for Nanointegration Duisburg-Essen (CeNIDE), Universitaet Duisburg-Essen, 47048 Duisburg (Germany); Raanaei, H. [Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala (Sweden); Department of Physics, Persian Gulf University, Bushehr 75168 (Iran, Islamic Republic of); Hjoervarsson, B. [Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala (Sweden)

    2011-06-01

    An amorphous Co{sub 68}Fe{sub 24}Zr{sub 8}(3 nm)/Al{sub 70}Zr{sub 30}(3 nm)/Co{sub 68}Fe{sub 24}Zr{sub 8}(3 nm) trilayer system has been investigated using in-plane and out-of-plane angular dependent ferromagnetic resonance at different frequencies. The in-plane magnetic anisotropy is uniaxial, retaining its value of (2.9 {+-} 0.1) x 10{sup 3} J/m{sup 3} for each magnetic layer, whereas its direction was tailored independently in an arbitrary manner by applying an external magnetic field during the film deposition. The perpendicular anisotropy constant, supposed to reflect the interface quality, is nearly identical for both layers. Furthermore, the magnetic layers act independently upon each other due to the absence of interlayer coupling.

  15. Scattering polarization due to light source anisotropy

    E-print Network

    Ignace, R; Simmons, J; Brown, J C; Clarke, D; Carson, J

    2008-01-01

    We consider the polarization arising from scattering in an envelope illuminated by a central anisotropic source. Spherical harmonics are used to describe both the light source anisotropy and the envelope density distribution functions of the scattering particles. This framework demonstrates how the net resultant polarization arises from a superposition of three basic "shape" functions: the distribution of source illumination, the distribution of envelope scatterers, and the phase function for dipole scattering. Specific expressions for the Stokes parameters and scattered flux are derived for the case of an ellipsoidal light source inside an ellipsoidal envelope, with principal axes that are generally not aligned. Two illustrative examples are considered: (a) axisymmetric mass loss from a rapidly rotating star, such as may apply to some Luminous Blue Variables, and (b) a Roche-lobe filling star in a binary system with a circumstellar envelope. As a general conclusion, the combination of source anisotropy with ...

  16. Microwave Anisotropies from Texture Seeded Structure Formation

    E-print Network

    R. Durrer; A. Howard; Z. -H. Zhou

    1993-11-17

    The cosmic microwave anisotropies in a scenario of large scale structure formation with cold dark matter and texture are discussed and compared with recent observational results of the COBE satellite. A couple of important statistical parameters are determined. The fluctuations are slightly non gaussian. The quadrupole anisotropy is $1.5\\pm 1.2\\times 10^{-5}$ and the fluctuations on a angular scale of 10 degrees are $ (3.8\\pm 2.6)\\times 10^{-5}$. The COBE are within about one standard deviation of the typical texture + CDM model discussed in this paper. Furthermore, we calculate fluctuations on intermediate scales (about 2 degrees) with the result $\\De T/T(\\theta \\sim 2^o) = 3.9\\pm 0.8)\\times 10^{-5}$. Collapsing textures are modeled by spherically symmetric field configurations. This leads to uncertainties of about a factor of~2.

  17. Fission Fragment Orientation and ?-RAY Emission Anisotropy

    NASA Astrophysics Data System (ADS)

    Adrich, P.; Kopatch, Yu. N.; Lubkiewicz, E.; Wollersheim, H. J.; Mutterer, M.

    2003-10-01

    Angular correlations of prompt ?-rays in binary spontaneous fission of 252Cf were measured with a GSI super clover detector. The position-sensitive ?-ray spectrometer was combined with an efficient detection system for fission fragments. For the study of ?-ray angular correlations the intensities of individual ?-transitions were measured relative to the fission axis. Surprisingly, the measured ?-ray angular correlations for stretched E2 transitions show a large anisotropy, which can be described by a complete alignment of the initial fragment spins.

  18. Multidimensional fractional Schrödinger equation

    NASA Astrophysics Data System (ADS)

    Rodrigues, M. M.; Vieira, N.

    2012-11-01

    This work is intended to investigate the multi-dimensional space-time fractional Schrödinger equation of the form (CDt0+?u)(t,x) = i?/2m(C??u)(t,x), with ? the Planck's constant divided by 2?, m is the mass and u(t,x) is a wave function of the particle. Here (CDt0+?,C?? are operators of the Caputo fractional derivatives, where ? ?]0,1] and ? ?]1,2]. The wave function is obtained using Laplace and Fourier transforms methods and a symbolic operational form of solutions in terms of the Mittag-Leffler functions is exhibited. It is presented an expression for the wave function and for the quantum mechanical probability density. Using Banach fixed point theorem, the existence and uniqueness of solutions is studied for this kind of fractional differential equations.

  19. Engineering Functional Anisotropy in Fibrocartilage Neotissues

    PubMed Central

    MacBarb, R.F.; Chen, A.L.; Hu, J.C.; Athanasiou, K.A.

    2013-01-01

    The knee meniscus, intervertebral disc, and temporomandibular joint (TMJ) disc all possess complex geometric shapes and anisotropic matrix organization. While these characteristics are imperative for proper tissue function, they are seldom recapitulated following injury or disease. Thus, this study’s objective was to engineer fibrocartilages that capture both gross and molecular structural features of native tissues. Self-assembled TMJ discs were selected as the model system, as the disc exhibits a unique biconcave shape and functional anisotropy. To drive anisotropy, 50:50 co-cultures of meniscus cells and articular chondrocytes were grown in biconcave, TMJ-shaped molds and treated with two exogenous stimuli: biomechanical (BM) stimulation via passive axial compression and bioactive agent (BA) stimulation via chondroitinase-ABC and transforming growth factor-?1. BM+BA synergistically increased Col/WW, Young’s modulus, and ultimate tensile strength 5.8-fold, 14.7-fold, and 13.8-fold that of controls, respectively; it also promoted collagen fibril alignment akin to native tissue. Finite element analysis found BM stimulation to create direction-dependent strains within the neotissue, suggesting shape plays an essential role toward driving in vitro anisotropic neotissue development. Methods used in this study offer insight on the ability to achieve physiologic anisotropy in biomaterials through the strategic application of spatial, biomechanical, and biochemical cues. PMID:24075479

  20. Influence of ferroelectric polarization on magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Mardana, A.; Ducharme, S.; Adenwalla, S.

    2010-03-01

    Thin film heterostructures of transition metal ferromagnets (FM) and polymer ferroelectrics (FE) are investigated to look for changes in the magnetic anisotropy of the FM layer that occur on switching the FE polarization (with an ensuing change in the electric field direction).[1] Samples of [Glass/ Pd (50 nm)/Co wedge (0.9-2.6nm)/ferroelectric P(VDF-TrFE) (53 nm)/Al (30nm)] are deposited via sputtering or evaporation for the metallic layers and via Langmuir-Schaefer deposition for the polymer ferroelectric. [2] Magnetic and FE properties have been characterized using the Magneto-Optical Kerr Effect (MOKE) and the pyroelectric effect. Polar and longitudinal MOKE loops are measured across the Co wedge for both positive and negative FE polarization and the difference in the two MOKE loops is ascribed to the changes in the magnetic anisotropy of the FM layer. [3] These changes are most apparent in the region where the Co undergoes a transition from in-plane to out-of-plane anisotropy. This research is supported by the NSF MRSEC through Grant No. DMR- 0820521 1. Chun-Gang Duan et al, Appl. Phys. Lett. 92, 122905 (2008) 2. A. V. Bune, et al, Nature (London) 391, 874 (1998) 3. P. F. Carcia, J.Appl. Phys. 63, 5066 (1988)

  1. CMB Anisotropies: Total Angular Momentum Method

    E-print Network

    Wayne Hu; Martin White

    1997-07-16

    A total angular momentum representation simplifies the radiation transport problem for temperature and polarization anisotropy in the CMB. Scattering terms couple only the quadrupole moments of the distributions and each moment corresponds directly to the observable angular pattern on the sky. We develop and employ these techniques to study the general properties of anisotropy generation from scalar, vector and tensor perturbations to the metric and the matter, both in the cosmological fluids and from any seed perturbations (e.g. defects) that may be present. The simpler, more transparent form and derivation of the Boltzmann equations brings out the geometric and model-independent aspects of temperature and polarization anisotropy formation. Large angle scalar polarization provides a robust means to distinguish between isocurvature and adiabatic models for structure formation in principle. Vector modes have the unique property that the CMB polarization is dominated by magnetic type parity at small angles (a factor of 6 in power compared with 0 for the scalars and 8/13 for the tensors) and hence potentially distinguishable independent of the model for the seed. The tensor modes produce a different sign from the scalars and vectors for the temperature-polarization correlations at large angles. We explore conditions under which one perturbation type may dominate over the others including a detailed treatment of the photon-baryon fluid before recombination.

  2. Anisotropy of permeability in faulted porous sandstones

    NASA Astrophysics Data System (ADS)

    Farrell, N. J. C.; Healy, D.; Taylor, C. W.

    2014-06-01

    Studies of fault rock permeabilities advance the understanding of fluid migration patterns around faults and contribute to predictions of fault stability. In this study a new model is proposed combining brittle deformation structures formed during faulting, with fluid flow through pores. It assesses the impact of faulting on the permeability anisotropy of porous sandstone, hypothesising that the formation of fault related micro-scale deformation structures will alter the host rock porosity organisation and create new permeability pathways. Core plugs and thin sections were sampled around a normal fault and oriented with respect to the fault plane. Anisotropy of permeability was determined in three orientations to the fault plane at ambient and confining pressures. Results show that permeabilities measured parallel to fault dip were up to 10 times higher than along fault strike permeability. Analysis of corresponding thin sections shows elongate pores oriented at a low angle to the maximum principal palaeo-stress (?1) and parallel to fault dip, indicating that permeability anisotropy is produced by grain scale deformation mechanisms associated with faulting. Using a soil mechanics 'void cell model' this study shows how elongate pores could be produced in faulted porous sandstone by compaction and reorganisation of grains through shearing and cataclasis.

  3. The Nature versus Nurture of Anisotropies

    NASA Astrophysics Data System (ADS)

    Hu, Wayne

    1994-04-01

    With the rapidly growing number of cosmic microwave background measurements on various scales, there is real hope that the number of acceptable models for structure formation will be limited to a very few in the near future. Yet any given model can always be saved by introducing and tuning extraneous free parameters. To better understand this question of ``nature versus nurture'' for temperature fluctuations, it is useful to know not only the general features of anisotropy predictions but also their causes. Extracting the physical content of our other works, we present here a {\\it simple} account of cosmic microwave background anisotropies on all scales. In particular, we show that analytic approximations can trace the structure of the so-called ``Doppler peaks,'' which arise due to the {\\it adiabatic} oscillations in the photon-baryon fluid. We also show how the finite thickness of the last scattering surface and the Silk damping mechanism can be described in a unified way by photon diffusion. In order to present a specific example, we focus on comparing the primordial baryon (PIB) model with the standard cold dark matter model (CDM). In particular, we explain why PIB generically predicts larger {\\it non}-oscillatory anisotropies from 1$^\\circ$ to 10$^\\circ$ scale which may already be in conflict with experiments.

  4. The Nature Versus Nurture of Anisotropies

    NASA Astrophysics Data System (ADS)

    Hu, Wayne

    With the rapidly growing number of cosmic microwave background measurements on various scales, there is real hope that the number of acceptable models for structure formation will be limited to a very few in the near future. Yet any given model can always be saved by introducing and tuning extraneous free parameters. To better understand this question of ``nature versus nurture'' for temperature fluctuations, it is useful to know not only the general features of anisotropy predictions but also their causes. Extracting the physical content of our other works, we present here a {\\it simple} account of cosmic microwave background anisotropies on all scales. In particular, we show that analytic approximations can trace the structure of the so-called ``Doppler peaks,'' which arise due to the {\\it adiabatic} oscillations in the photon-baryon fluid. We also show how the finite thickness of the last scattering surface and the Silk damping mechanism can be described in a unified way by photon diffusion. In order to present a specific example, we focus on comparing the primordial isocurvature baryon (PIB) model with the standard cold dark matter model (CDM). In particular, we explain why PIB generically predicts larger {\\it non}-oscillatory anisotropies from the 1$^\\circ$ to 10$^\\circ$ scale which may already be in conflict with experiments.

  5. Multiplying Whole Numbers & Fractions

    NSDL National Science Digital Library

    2013-01-01

    In this 9-minute video, Amy Spies shows her 4th grade class working through a problem multiplying a fraction by a whole number. During the lesson Amy realized that the students were not pulling out the knowledge that she had intended. She then revised the lesson and gave them examples and non-examples and through discussion had them make the connection between repeated addition and multiplying a fraction by a whole number. Students also gained a deeper understanding of the meaning of the numerator and denominator in these repeated addition problems.

  6. FRACTIONAL CRYSTALLIZATION FEED ENVELOPE

    SciTech Connect

    HERTING DL

    2008-03-19

    Laboratory work was completed on a set of evaporation tests designed to establish a feed envelope for the fractional crystallization process. The feed envelope defines chemical concentration limits within which the process can be operated successfully. All 38 runs in the half-factorial design matrix were completed successfully, based on the qualitative definition of success. There is no feed composition likely to be derived from saltcake dissolution that would cause the fractional crystallization process to not meet acceptable performance requirements. However, some compositions clearly would provide more successful operation than other compositions.

  7. 5.NF Egyptian Fractions

    NSDL National Science Digital Library

    This is a task from the Illustrative Mathematics website that is one part of a complete illustration of the standard to which it is aligned. Each task has at least one solution and some commentary that addresses important asects of the task and its potential use. Here are the first few lines of the commentary for this task: Ancient Egyptians used unit fractions, such as $\\frac{1}{2}$ and $\\frac{1}{3}$, to represent all fractions. For example, they might write the number $\\...

  8. Fractional Variational Iteration Method for Fractional Nonlinear Differential Equations

    E-print Network

    Guo-cheng Wu

    2010-07-12

    Recently, fractional differential equations have been investigated via the famous variational iteration method. However, all the previous works avoid the term of fractional derivative and handle them as a restricted variation. In order to overcome such shortcomings, a fractional variational iteration method is proposed. The Lagrange multipliers can be identified explicitly based on fractional variational theory.

  9. Neurobiology of Disease More Is Not Always Better: Increased Fractional Anisotropy

    E-print Network

    Bellugi, Ursula

    - some 7q11.23 (Hillier et al., 2003), offers a unique opportunity to investigate interplays between gene, brain, and behavior. Cogni- tive hallmarks of WS include severe visuospatial deficits and rel- ative

  10. Diffusion Anisotropy in Collagen Gels and Tumors: The Effect of Fiber Network Orientation

    PubMed Central

    Stylianopoulos, Triantafyllos; Diop-Frimpong, Benjamin; Munn, Lance L.; Jain, Rakesh K.

    2010-01-01

    The interstitial matrix is comprised of cross-linked collagen fibers, generally arranged in nonisotropic orientations. Spatial alignment of matrix components within the tissue can affect diffusion patterns of drugs. In this study, we developed a methodology for the calculation of diffusion coefficients of macromolecules and nanoparticles in collagenous tissues. The tissues are modeled as three-dimensional, stochastic, fiber networks with varying degrees of alignment. We employed a random walk approach to simulate diffusion and a Stokesian dynamics method to account for hydrodynamic hindrance. We performed our analysis for four different structures ranging from nearly isotropic to perfectly aligned. We showed that the overall diffusion coefficient is not affected by the orientation of the network. However, structural anisotropy results in diffusion anisotropy, which becomes more significant with increase in the degree of alignment, the size of the diffusing particle, and the fiber volume fraction. To test our model predictions we performed diffusion measurements in reconstituted collagen gels and tumor xenografts. We measured fiber alignment and diffusion with second harmonic generation and multiphoton fluorescent recovery after photobleaching techniques, respectively. The results showed for the first time in tumors that the structure and orientation of collagen fibers in the extracellular space leads to diffusion anisotropy. PMID:21081058

  11. Sweet Work with Fractions

    ERIC Educational Resources Information Center

    Vinogradova, Natalya; Blaine, Larry

    2013-01-01

    Almost everyone loves chocolate. However, the same cannot be said about fractions, which are loved by markedly fewer. Middle school students tend to view them with wary respect, but little affection. The authors attempt to sweeten the subject by describing a type of game involving division of chocolate bars. The activity they describe provides a…

  12. Fractionation of Cellulose

    Microsoft Academic Search

    John Eckelt; Sergej Stryuk; Bernhard A. Wolf

    2003-01-01

    Cellulose samples with molecular weight distributions that are considerably narrower than those of the natural products can be obtained by at least three fundamentally different routes. (i) Synthesis of easily soluble derivatives, fractionation by means of well-established methods and subsequent regeneration, (ii) selective extraction of short chains from activated cellulose, using solvents of suitable marginal quality, and (iii) partition of

  13. Decimals, Fractions, and Percentages

    NSDL National Science Digital Library

    2011-01-01

    This webpage develops students' understanding of how fractions, decimals, and percents are related. An interactive applet displays visual and numerical representations of all three forms. As users change one form, they see the equivalents in the other two forms. The page provides procedures for converting between forms and 12 questions to check for understanding.

  14. Field-Flow Fractionation.

    ERIC Educational Resources Information Center

    Caldwell, Karin D.

    1988-01-01

    Describes a technique for separating samples that range over 15 orders of magnitude in molecular weight. Discusses theory, apparatus, and sample preparation techniques. Lists several types of field-flow fractionation (FFF) and their uses: sedimentation FFF, thermal FFF, flow FFF, electrical FFF, and steric FFF. (ML)

  15. Multiplying Fractions (Area Model)

    NSDL National Science Digital Library

    Audrey Pruitt - on Hotchalk Lesson Plans Page

    2012-04-22

    In this teaching idea, students will learn how to use the area model to find the product when two fractions are multiplied. NOTE: Click the Download link on the right side of the screen to display the lesson without ads and to view the graphic example of the model.

  16. Rayleigh fractionation visualization

    NSDL National Science Digital Library

    E. Christa Farmer

    Students answer several questions about Rayleigh fractionation and the oxygen isotope composition of ice cores which require them to manipulate the values and equations in a MS Excel spreadsheet. This helps them to see how the oxygen isotope composition of ice cores changes with temperature in the high latitudes. Future iterations of the exercise should include a visualization of the Clausius-Clapeyron equation.

  17. Retinal nerve fibre layer thickness correlates with brain white matter damage in multiple sclerosis: a combined optical coherence tomography and diffusion tensor imaging study.

    PubMed

    Scheel, Michael; Finke, Carsten; Oberwahrenbrock, Timm; Freing, Alina; Pech, Luisa-Maria; Schlichting, Jeremias; Sömmer, Carina; Wuerfel, Jens; Paul, Friedemann; Brandt, Alexander U

    2014-12-01

    We investigated the association of retinal nerve fibre layer thickness (RNFL) with white matter damage assessed by diffusion tensor imaging (DTI). Forty-four MS patients and 30 healthy subjects underwent optical coherence tomography. DTI was analysed with a voxel-based whole brain and region-based analysis of optic radiation, corpus callosum and further white matter. Correlations between RNFL, fractional anisotropy (FA) and other DTI-based parameters were assessed in patients and controls. RNFL correlated with optic radiation FA, but also with corpus callosum and remaining white matter FA. Our findings demonstrate that RNFL changes indicate white matter damage exceeding the visual pathway. PMID:24842962

  18. Representing Fractional Distributions in Chemistry

    ERIC Educational Resources Information Center

    Ault, Addison

    2008-01-01

    Many phenomena in chemistry involve fractional distributions. Sometimes it is a chemical substance that is fractionally distributed, other times it is a chemical process that is fractionally distributed. The purpose of this paper is to present a common approach to the representation of all fractional distributions. Using a common approach provides…

  19. Young Children's Notations for Fractions

    ERIC Educational Resources Information Center

    Brizuela, Barbara M.

    2006-01-01

    This paper focuses on the kinds of notations young children make for fractional numbers. The extant literature in the area of fractional numbers acknowledges children's difficulties in conceptualizing fractional numbers. Some of the research suggests possibly delaying an introduction to conventional notations for algorithms and fractions until…

  20. An Introduction to Continued Fractions.

    ERIC Educational Resources Information Center

    Moore, Charles G.

    Provided is an introduction to the properties of continued fractions for the intellectually curious high school student. Among the topics included are (1) Expansion of Rational Numbers into Simple Continued Fractions, (2) Convergents, (3) Continued Fractions and Linear Diophantine Equations of the Type am + bn = c, (4) Continued Fractions and…

  1. A large anisotropy in the sky distribution of 3CRR quasars and other radio galaxies

    NASA Astrophysics Data System (ADS)

    Singal, Ashok K.

    2015-06-01

    We report the presence of large anisotropies in the sky distributions of powerful extended quasars as well as some other sub-classes of radio galaxies in the 3CRR survey, the most reliable and most intensively studied complete sample of strong steep-spectrum radio sources. The anisotropies lie about a plane passing through the equinoxes and the north celestial pole. Out of a total of 48 quasars in the sample, 33 of them lie in one half of the observed sky and the remaining 15 in the other half. The probability that in a random distribution of 3CRR quasars in the sky, statistical fluctuations could give rise to an asymmetry in observed numbers up to this level is only ˜1 %. Also only about 1/4th of Fanaroff-Riley 1 (FR1) type of radio galaxies lie in the first half of the observed sky and the remainder in the second half. If we include all the observed asymmetries in the sky distributions of quasars and radio galaxies in the 3CRR sample, the probability of their occurrence by a chance combination reduces to ˜2×10-5. Two pertinent but disturbing questions that could be raised here are—firstly why should there be such large anisotropies present in the sky distribution of some of the strongest and most distant discrete sources, implying inhomogeneities in the universe at very large scales (covering a fraction of the universe)? Secondly why should such anisotropies lie about a great circle decided purely by the orientation of earth's rotation axis and/or the axis of its revolution around the sun? It seems yet more curious when we consider the other anisotropies, e.g., an alignment of the four normals to the quadrupole and octopole planes in the CMBR with the cosmological dipole and the equinoxes. Then there is the other recently reported large dipole anisotropy in the NVSS radio source distribution differing in magnitude from the CMBR dipole by a factor of four, and therefore not explained as due to the peculiar motion of the Solar system, yet aligned with the CMBR dipole which itself lies close to the line joining the equinoxes. Are these alignments a mere coincidence or do they imply that these axes have a preferential placement in the larger scheme of things, implying an apparent breakdown of the Copernican principle or its more generalization, cosmological principle, upon which the standard cosmological model is based upon?

  2. Investigating preferential flow processes in soils using anisotropy in electrical resistivity

    NASA Astrophysics Data System (ADS)

    Al-Hazaimay, S.; Huisman, J. A.; Zimmermann, E.; Kemna, A.; Vereecken, H.

    2012-12-01

    Macropores occupy a small volume fraction of the pore space in the vadose zone. Water and solutes can quickly bypass the vadose zone through these macropores in a process known as macropore preferential flow. In the last few decades, many efforts were made to improve understanding the macropore preferential flow processes because of their importance in transporting agrochemicals and contaminants to the groundwater. Unfortunately, very few measurement methods provide insights into these preferential flow processes. In this context, the objective of this study is to evaluate whether anisotropy in electrical resistivity can be used to identify the existence of flow in macropores and perhaps even to characterize the exchange between macropores and bulk soil. In a first step, infiltration into a soil column with an artificial macropore was simulated using the HYDRUS software package that solves the pseudo three-dimensional axisymmetric Richards equation. The simulated temporal development of the resistivity anisotropy was obtained by solving the Poisson equation in MATLAB after converting the simulated water content distributions to electrical resistivity distributions. At the beginning of the simulation, a small anisotropy ratio was simulated because of the presence of the empty ('deactivated') macropore in the moist matrix. As soon as the infiltration process started, macropore flow occurred and both the horizontal and vertical resistivity decreased strongly. However, the vertical and horizontal resistivity reacted differently because of the presence of the conductive ('activated') macropore, which led to anisotropy in the resistivity. As soon as infiltration into the macropore stopped, water re-distributed from the macropore to the matrix domain and contrasts in electrical resistivity decreased within the column. To verify the simulation results in the laboratory, we measured the temporal dynamics of the anisotropy in resistivity during water infiltration into a soil column of 9 cm diameter and 40 cm length with an artificial macropore of 2 cm diameter in the center of the column. The first experimental results confirmed that the anisotropy in electrical resistivity can indeed be used to identify and perhaps even quantify macropore flow.

  3. Analytic spectra of CMB anisotropies and polarization generated by scalar perturbations in synchronous gauge

    NASA Astrophysics Data System (ADS)

    Cai, Z.; Zhang, Y.

    2012-05-01

    The temperature anisotropies and polarization of the cosmic microwave background (CMB) radiation not only serve as indispensable cosmological probes, but also provide a unique channel to detect relic gravitational waves (RGW) at very long wavelengths. Analytical studies of the anisotropies and polarization improve our understanding of various cosmic processes and help to separate the contribution of RGW from that of density perturbations. We present a detailed analytical calculation of CMB temperature anisotropies ?k and polarization ?k generated by scalar metric perturbations in synchronous gauge, parallel to our previous work with RGW as a generating source. This is realized primarily by an analytic time integration of Boltzmann’s equation, yielding the closed forms of ?k and ?k. Approximations, such as the tight-coupling approximation for photons a priori to the recombination and the long-wavelength limit for scalar perturbations, are used. The residual gauge modes in scalar perturbations are analyzed and a proper joining condition of scalar perturbations at the radiation-matter equality is chosen, ensuring the continuity of energy perturbation. The resulting analytic expressions of the multipole moments of polarization aEl and of temperature anisotropies aTl are explicit functions of the scalar perturbations, recombination time, recombination width, photon-free streaming damping factor, baryon fraction, initial amplitude, primordial scalar spectral index and the running index. These results show that a longer recombination width yields higher amplitudes of polarization on large scales and more damping on small scales, and that a late recombination time shifts the peaks of C^{XX^{\\prime }}_l to larger angular scales. Calculations show that aEl is generated in the presence of the quadrupole ?2 of temperature anisotropies via scattering, both having similar structures and being smaller than the total aTl, which consists of the contributions from the monopole, dipole, quadrupole and Sachs-Wolfe terms as well. The origin of the two bumps in CEEl on large angular scales is found to be due to the time derivative of the monopole of temperature anisotropies. Furthermore, aEl together with aTl demonstrates explicitly that the peaks of CEEl and CTTl alternate in the l-space. These results substantially extend earlier analytic work. The analytic spectra C^{XX^{\\prime }}_l agree with the numerical ones and with those observed by WMAP on large scales (l ? 500), but deviate considerably from the numerical results on smaller scales, showing the limitations of our approximate analytic calculations. Several possible improvements are pointed out for further studies.

  4. Frozen and active seismic anisotropy beneath southern Africa

    NASA Astrophysics Data System (ADS)

    Vinnik, L.; Kiselev, S.; Weber, M.; Oreshin, S.; Makeyeva, L.

    2012-04-01

    P receiver functions from 23 stations of the SASE experiment in southern Africa are inverted simultaneously with SKS waveforms for azimuthal anisotropy in the upper mantle. Our analysis resolves the long-standing issue of depth dependence and origins of anisotropy beneath southern Africa. In the uppermost mantle we observe anisotropy with a nearly E-W fast direction, parallel to the trend of the Limpopo belt. This anisotropy may be frozen since the Archean. At a depth of 160 km the fast direction of anisotropy changes to 40° and becomes close to the recent plate motion direction. This transition is nearly coincident in depth with activation of dominant glide systems in olivine and with a pronounced change in other properties of the upper mantle. Another large change in the fast direction of anisotropy corresponds to the previously found low-S-velocity layer atop the 410-km discontinuity.

  5. Role of anisotropy configuration in exchange-biased systems

    NASA Astrophysics Data System (ADS)

    Jiménez, E.; Camarero, J.; Perna, P.; Mikuszeit, N.; Terán, F. J.; Sort, J.; Nogués, J.; García-Martín, J. M.; Hoffmann, A.; Dieny, B.; Miranda, R.

    2011-04-01

    We present a systematic study of the anisotropy configuration effects on the magnetic properties of exchange-biased ferromagnetic/antiferromagnetic (FM/AFM) Co/IrMn bilayers. The interfacial unidirectional anisotropy is set extrinsically via a field cooling procedure with the magnetic field misaligned by an angle ?FC with respect to the intrinsic FM uniaxial anisotropy. High resolution angular dependence in-plane resolved Kerr magnetometry measurements have been performed for three different anisotropy arrangements, including collinear ?FC=0° and two opposite noncollinear cases. The symmetry breaking of the induced noncollinear configurations results in a peculiar nonsymmetric magnetic behavior of the angular dependence of magnetization reversal, coercivity, and exchange bias. The experimental results are well reproduced without any fitting parameter by using a simple model including the induced anisotropy configuration. Our finding highlights the importance of the relative angle between anisotropies in order to properly account for the magnetic properties of exchange-biased FM/AFM systems.

  6. Quantifying surface coverage of colloidal silica by a cationic peptide using a combined centrifugation/time-resolved fluorescence anisotropy approach.

    PubMed

    Tleugabulova, Dina; Brennan, John D

    2006-02-14

    Recent experimental studies have shown that time-resolved fluorescence anisotropy (TRFA) is a promising methodology for in situ characterization of the surface modification of aqueous silica nanocolloids. Here we provide a more fundamental insight into the principle of this approach and discuss how the adsorption parameters for a cationic peptide, Lys-Trp-Lys (denoted using the standard shortform KWK), onto Ludox nanoparticles (NPs) are linked to the rotational dynamics of rhodamine 6G (R6G) dispersed in the KWK/Ludox mixture. First, the adsorption isotherm of KWK on hydrophilic controlled pore glass (CPG-3000) was obtained using the traditional centrifugation method, which provides the total molar amount of KWK per unit surface area of the silica. Assuming that both CPG and Ludox particles possess identical surface properties when suspended in the same aqueous buffer, both materials should also have identical adsorption properties. Thus, the adsorbed amount of KWK per unit area at a given total KWK concentration, as determined by the centrifugation method, can be plotted against the fractions of R6G anisotropy decay components at the same KWK concentration to relate the anisotropy components to the absolute surface coverage. Using this approach, it was determined that the concentration of KWK at which the CPG surface was saturated corresponded to the condition g = 0 in the R6G decay, where g is the fraction of the nondecaying anisotropy component. This condition means that there is no R6G bound to the fraction of Ludox NPs with a radius R > 2.5 nm at maximum KWK coverage, consistent with the adsorbed peptide forming a continuous layer on the Ludox surface. Hence, the g value obtained from TRFA analysis can be used to assess the absolute surface coverage of monolayer coatings on colloidal nanoparticles. PMID:16460117

  7. Number Sense w/Fractions

    NSDL National Science Digital Library

    Ms. Hume

    2012-11-02

    These games will help you practice your fractions! Check out all the different ways we use fractions every day! Fractions, Decimals, Percents Jeopardy style!! - It's fractions, decimals, percents Jeopardy style! You can play alone or in teams. See how well you know your fractions and the conversions into decimals and percents! Pizza Mania! - Help out the chef by building all the pizzas he asks for using toppings. He will give you the ...

  8. Anisotropies in the gravitational-wave stochastic background

    SciTech Connect

    Ölmez, S.; Mandic, V. [School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455 (United States); Siemens, X., E-mail: olmez@physics.umn.edu, E-mail: mandic@physics.umn.edu, E-mail: siemens@gravity.phys.uwm.edu [Center for Gravitation and Cosmology, University of Wisconsin-Milwaukee, Milwaukee, WI 53201 (United States)

    2012-07-01

    We consider anisotropies in the stochastic background of gravitational-waves (SBGW) arising from random fluctuations in the number of gravitational-wave sources. We first develop the general formalism which can be applied to different cosmological or astrophysical scenarios. We then apply this formalism to calculate the anisotropies of SBGW associated with the fluctuations in the number of cosmic string loops, considering both cosmic string cusps and kinks. We calculate the anisotropies as a function of angle and frequency.

  9. Recovery of axonal myelination sheath and axonal caliber in the mouse corpus callosum following damage induced by N,N-diethyldithiocarbamate.

    PubMed

    Utrera, Juana; Romero, Rafael; Verdaguer, Ester; Junyent, Fèlix; Auladell, Carme

    2011-12-01

    Disulfiram is an aldehyde dehydrogenase inhibitor used for the treatment of alcohol dependence and of cocaine addiction. It has been demonstrated that subchronic administration of disulfiram or N,N-diethyldithiocarbamate (DEDTC), the main derivative of disulfiram, to rats can produce central-peripheral distal axonopathy. However, few data regarding the axonal effects of these compounds in the central nervous system exist. Our previous studies have revealed DEDTC-induced axonal damage in the mouse brain during the course of postnatal development, together with alterations in axonal pathfinding and in the myelination process, with partial recovery during the post-treatment period. In order to gather new data about how this axonal damage and recovery occurs in the central nervous system, we performed an ultrastructural analysis of the axons located in the corpus callosum from mice treated with DEDTC during postnatal development. The axonal caliber throughout the axonal area, the maximum axonal diameter, the maximum fiber diameter, and the axonal circularity, at different postnatal stages [from postnatal day (P)9 to P30], were analyzed. In addition, parameters related to the myelinization process (number of myelinated axons, sheath thickness, and the ratio of myelinated axons to total axons) were evaluated. A reduction in the average value of axonal caliber during treatment and a delay in the axonal myelination process were detected. Whereas early recovery of individual axons occurred after treatment (P22), complete recovery of myelinated axons occurred at late postnatal stages (P42). Therefore, chronic treatment with dithiocarbamates requires periods of rest to encourage the recovery of myelinated axons. PMID:22132728

  10. Impact of Early and Late Visual Deprivation on the Structure of the Corpus Callosum: A Study Combining Thickness Profile with Surface Tensor-Based Morphometry.

    PubMed

    Shi, Jie; Collignon, Olivier; Xu, Liang; Wang, Gang; Kang, Yue; Leporé, Franco; Lao, Yi; Joshi, Anand A; Leporé, Natasha; Wang, Yalin

    2015-07-01

    Blindness represents a unique model to study how visual experience may shape the development of brain organization. Exploring how the structure of the corpus callosum (CC) reorganizes ensuing visual deprivation is of particular interest due to its important functional implication in vision (e.g., via the splenium of the CC). Moreover, comparing early versus late visually deprived individuals has the potential to unravel the existence of a sensitive period for reshaping the CC structure. Here, we develop a novel framework to capture a complete set of shape differences in the CC between congenitally blind (CB), late blind (LB) and sighted control (SC) groups. The CCs were manually segmented from T1-weighted brain MRI and modeled by 3D tetrahedral meshes. We statistically compared the combination of local area and thickness at each point between subject groups. Differences in area are found using surface tensor-based morphometry; thickness is estimated by tracing the streamlines in the volumetric harmonic field. Group differences were assessed on this combined measure using Hotelling's T (2) test. Interestingly, we observed that the total callosal volume did not differ between the groups. However, our fine-grained analysis reveals significant differences mostly localized around the splenium areas between both blind groups and the sighted group (general effects of blindness) and, importantly, specific dissimilarities between the LB and CB groups, illustrating the existence of a sensitive period for reorganization. The new multivariate statistics also gave better effect sizes for detecting morphometric differences, relative to other statistics. They may boost statistical power for CC morphometric analyses. PMID:25649876

  11. Magnetic Anisotropy of a Three-Dimensional Honeycomb Iridate

    NASA Astrophysics Data System (ADS)

    Modic, Kimberly; McDonald, Ross; Shekter, Arkady; Analytis, James; Ramshaw, Brad

    2015-03-01

    We present the magnetic anisotropy of a 3-dimensional honeycomb iridate, where the large spin-orbit coupling of iridium provides the possibility for exotic magnetic ground states. A complete angular dependence of magnetic torque provides evidence for highly spin-anisotropic exchange interactions at low temperature. An extension of these measurements to high magnetic fields shows that the magnetic anisotropy switches sign at 50 T and becomes five times larger than the anisotropy at low fields. The anisotropy continues to increase up to the largest applied fields suggesting the presence of new magnetically ordered states.

  12. The Anisotropy of Magnetic Susceptibility of Igneous Rocks: Lessons From Obsidians and Pyroclastic Deposits

    NASA Astrophysics Data System (ADS)

    Canon-Tapia, E.

    2013-05-01

    The anisotropy of magnetic susceptibility (AMS) of igneous rocks differs from that of other lithologies in several aspects that are related to their characteristics of emplacement history. Nevertheless, within the group of igneous rocks there are also differences on emplacement mechanisms that can lead to specific and distinctive AMS signatures. In this work, a review of the most important emplacement regimes is made, paying special attention to the extreme conditions represented by obsidians and pyroclastic deposits. These two extreme emplacement regimes are controlled mainly by the viscosity of the fluid phase, but the differences in AMS signatures also includes other differences in the nature of the ferromagnetic grains that are present in the rocks during emplacement. For example, the results of this work indicate that the AMS can be associated to a population of ferromagnetic minerals of a submicroscopic size, despite of which it can be very well defined and yield large degrees of anisotropy. It is suggested that the AMS associated to such population of small grains might indeed be the origin of the AMS of other igneous rocks that have an optically observable fraction of mineral grains, although until present it had been overlooked in most instances. As it had been suggested before, use of tests designed to identify the contribution of a superparamagnetic fraction (SP) in the magnetic properties of a rock can help us to identify the presence of such a SP-related AMS in other cases.

  13. CMB statistical anisotropy from noncommutative gravitational waves

    NASA Astrophysics Data System (ADS)

    Shiraishi, Maresuke; Mota, David F.; Ricciardone, Angelo; Arroja, Frederico

    2014-07-01

    Primordial statistical anisotropy is a key indicator to investigate early Universe models and has been probed by the cosmic microwave background (CMB) anisotropies. In this paper, we examine tensor-mode CMB fluctuations generated from anisotropic gravitational waves, parametrised by Ph(k) = Ph(0)(k) [ 1 + ?LM fL(k) gLM YLM (hat k)], where Ph(0)(k) is the usual scale-invariant power spectrum. Such anisotropic tensor fluctuations may arise from an inflationary model with noncommutativity of fields. It is verified that in this model, an isotropic component and a quadrupole asymmetry with f0(k) = f2(k) propto k-2 are created and hence highly red-tilted off-diagonal components arise in the CMB power spectra, namely l2 = l1 ± 2 in TT, TE, EE and BB, and l2 = l1 ± 1 in TB and EB. We find that B-mode polarisation is more sensitive to such signals than temperature and E-mode polarisation due to the smallness of large-scale cosmic variance and we can potentially measure g00 = 30 and g2M = 58 at 68% CL in a cosmic-variance-limited experiment. Such a level of signal may be measured in a PRISM like experiment, while the instrumental noise contaminates it in the Planck experiment. These results imply that it is impossible to measure the noncommutative parameter if it is small enough for the perturbative treatment to be valid. Our formalism and methodology for dealing with the CMB tensor statistical anisotropy are general and straightforwardly applicable to other early Universe models.

  14. Fraction Decimal Conversion

    NSDL National Science Digital Library

    2011-01-01

    These three interactive games give students practice equating commonly used fractions with their decimal equivalents. The student can choose among a flash card drill, a matching game, or a concentration-type game, and adjust the number of objects in the concentration game (the challenge level). Quia Web offers free shared activities with teacher-made content. Subscriptions allow members to create or alter the content of the games.

  15. New Dry Fractionation Methods

    NASA Technical Reports Server (NTRS)

    McKay, David S.; Cooper, Bonnie L.

    2010-01-01

    This slide presentation describes new fractionation methods that are used to create dust that is respirable for testing the effects of inhalation of lunar dust in preparation for future manned lunar exploration. Because lunar dust is a very limited commodity, a method that does not result in loss of the material had to be developed. The dust separation system that is described incorporates some traditional methods, while preventing the dust from being contaminated or changed in reactivity properties while also limiting losses.

  16. Fractions, ratios, and percents

    NSDL National Science Digital Library

    Carol R. Findell

    2007-12-12

    In this workshop session, elementary and middle school teachers work with an area model for multiplication and division with fractions and examine operations with decimals. They also explore percents and the relationships among various representations of percentages. Finally, they consider Fibonacci numbers and the place of the golden rectangle as an architectural element throughout history. These ideas are investigated through interactive applets, problem sets, and video. This is session 9 of Learning Math: Number and Operations, a free online course.

  17. Release Fraction Evaluation

    Microsoft Academic Search

    Judith A. Bamberger; John A. Glissmeyer

    2004-01-01

    This document presents results of experiments conducted to measure release fractions during certain tank retrieval processes. The tests were performed in a 1\\/4 scale model of a waste storage tank. The retrieval processes simulated were: (1) Discharging liquid or slurry from the mouth of a vertically oriented two-in. Schedule 40 pipe. The discharging material was in free-fall from the mouth

  18. The Microwave Anisotropy Probe (MAP) Mission

    NASA Technical Reports Server (NTRS)

    Markley, F. Landis; Andrews, Stephen F.; ODonnell, James R., Jr.; Ward, David K.; Bauer, Frank H. (Technical Monitor)

    2002-01-01

    The Microwave Anisotropy Probe mission is designed to produce a map of the cosmic microwave background radiation over the entire celestial sphere by executing a fast spin and a slow precession of its spin axis about the Sun line to obtain a highly interconnected set of measurements. The spacecraft attitude is sensed and controlled using an inertial reference unit, two star trackers, a digital sun sensor, twelve coarse sun sensors, three reaction wheel assemblies, and a propulsion system. This paper presents an overview of the design of the attitude control system to carry out this mission and presents some early flight experience.

  19. Programming magnetic anisotropy in polymeric microactuators.

    PubMed

    Kim, Jiyun; Chung, Su Eun; Choi, Sung-Eun; Lee, Howon; Kim, Junhoi; Kwon, Sunghoon

    2011-10-01

    Polymeric microcomponents are widely used in microelectromechanical systems (MEMS) and lab-on-a-chip devices, but they suffer from the lack of complex motion, effective addressability and precise shape control. To address these needs, we fabricated polymeric nanocomposite microactuators driven by programmable heterogeneous magnetic anisotropy. Spatially modulated photopatterning was applied in a shape-independent manner to microactuator components by successive confinement of self-assembled magnetic nanoparticles in a fixed polymer matrix. By freely programming the rotational axis of each component, we demonstrate that the polymeric microactuators can undergo predesigned, complex two- and three-dimensional motion. PMID:21822261

  20. Seismic anisotropy above a subducting plate

    SciTech Connect

    Shih, X.R.; Meyer, R.P. (Univ. of Wisconsin, Madison (United States)); Schneider, J.F. (Electric Power Research Inst., Palo Alto, CA (United States))

    1991-08-01

    Shear-wave splitting observed in northeastern Colombia has provided evidence of seismic anisotropy in a shear zone immediately above a subducting plate. In an upper mantle composed mainly of olivine (57%) and orthopyroxene (17%), the splitting can be interpreted by wave propagation in an anisotropic medium of orthorhombic symmetry that results from alignment of these intrinsically anisotropic minerals. The mechanism of alignment is most likely the shearing associated with the subduction, aided by fluids migrating from the subducting plate when the plate exceeds 100 km in depth.

  1. Molecular anisotropy effects in carbon K-edge scattering: Depolarized diffuse scattering and optical anisotropy

    NASA Astrophysics Data System (ADS)

    Stone, Kevin H.; Kortright, Jeffrey B.

    2014-09-01

    Some polymer properties, such as conductivity, are very sensitive to short- and intermediate-range orientational and positional ordering of anisotropic molecular functional groups, and yet means to characterize orientational order in disordered systems are very limited. We demonstrate that resonant scattering at the carbon K edge is uniquely sensitive to short-range orientation correlations in polymers through depolarized scattering at high momentum transfers, using atactic polystyrene as a well-characterized test system. Depolarized scattering is found to coexist with unpolarized fluorescence and to exhibit pronounced anisotropy. We also quantify the spatially averaged optical anisotropy from low-angle reflectivity measurements, finding anisotropy consistent with prior visible, x-ray absorption, and theoretical studies. The average anisotropy is much smaller than that in the depolarized scattering and the two have different character. Both measurements exhibit clear spectral signatures from the phenyl rings and the polyethylenelike backbone. Discussion focuses on analysis considerations and prospects for using this depolarized scattering for studies of disorder in soft condensed matter.

  2. Axial Magnetic Anisotropy from Two Systems Fe2B and Co2B with Planar Anisotropy

    NASA Astrophysics Data System (ADS)

    Taufour, Valentin; Lamichhane, Tej; Bud'Ko, Sergey L.; Jesche, Anton; Goldman, Alan I.; Dennis, Kevin W.; McCallum, R. William; Antropov, Vladimir; Canfield, Paul C.

    2015-03-01

    Growth of single crystals of (Fe1-xCox)2B (0 <= x <= 1) and detailed characterization of their magnetic properties will be presented. Despite the fact that both Fe2B and Co2B show a planar anisotropy at room temperature, we observe a uniaxial anisotropy at intermediate doping which makes (Fe,Co)2B a promising system for permanent magnet applications in a system without rare-earth element. Comparison with recent band structure calculations will be presented. The temperature dependence of the anisotropy measured on single crystals from 2 K to 1000 K shows some unusual variations with an increase of the magnetic anisotropy with increasing temperature at some specific substitution. This work is supported by the Critical Materials Institute, an Energy Innovation Hub funded by the US DOE and by the Office of Basic Energy Science, Division of Materials Science and Engineering. Ames Laboratory is operated for the US DOE by Iowa State University under Contract No. DE-AC02-07CH11358.

  3. Molecular anisotropy effects in carbon K-edge scattering: depolarized diffuse scattering and optical anisotropy

    SciTech Connect

    Stone, Kevin H.

    2014-07-14

    Some polymer properties, such as conductivity, are very sensitive to short- and intermediate-range orientational and positional ordering of anisotropic molecular functional groups, and yet means to characterize orientational order in disordered systems are very limited. We demonstrate that resonant scattering at the carbon K-edge is uniquely sensitive to short-range orientation correlations in polymers through depolarized scattering at high momentum transfers, using atactic polystyrene as a well-characterized test system. Depolarized scattering is found to coexist with unpolarized fluorescence, and to exhibit pronounced anisotropy. We also quantify the spatially averaged optical anisotropy from low-angle reflectivity measurements, finding anisotropy consistent with prior visible, x-ray absorption, and theoretical studies. The average anisotropy is much smaller than that in the depolarized scattering and the two have different character. Both measurements exhibit clear spectral signatures from the phenyl rings and the polyethylene-like backbone. Discussion focuses on analysis considerations and prospects for using this depolarized scattering for studies of disorder in soft condensed matter.

  4. Uncovering Fractional Monodromy

    NASA Astrophysics Data System (ADS)

    Efstathiou, K.; Broer, H. W.

    2013-12-01

    The uncovering of the role of monodromy in integrable Hamiltonian fibrations has been one of the major advances in the study of integrable Hamiltonian systems in the past few decades: on one hand monodromy turned out to be the most fundamental obstruction to the existence of global action-angle coordinates while, on the other hand, it provided the correct classical analogue for the interpretation of the structure of quantum joint spectra. Fractional monodromy is a generalization of the concept of monodromy: instead of restricting our attention to the toric part of the fibration we extend our scope to also consider singular fibres. In this paper we analyze fractional monodromy for n 1:(- n 2) resonant Hamiltonian systems with n 1, n 2 coprime natural numbers. We consider, in particular, systems that for n 1, n 2 > 1 contain one-parameter families of singular fibres which are ‘curled tori’. We simplify the geometry of the fibration by passing to an appropriate branched covering. In the branched covering the curled tori and their neighborhood become untwisted thus simplifying the geometry of the fibration: we essentially obtain the same type of generalized monodromy independently of n 1, n 2. Fractional monodromy is then recovered by pushing the results obtained in the branched covering back to the original system.

  5. CHAPITRE 2 : FRACTIONS CONTINUES 1. Fractions continues finies

    E-print Network

    Walter, Charles

    CHAPITRE 2 : FRACTIONS CONTINUES 1. Fractions continues finies Une fraction continue finie est une fraction itérée du genre 1 + 1 2 + 1 1 + 1 2 + 1 1 + 1 2 , -1 + 1 1 + 1 3 + 1 5 + 1 7 + 1 9 La forme générale est a0 + 1 a1 + 1 a2 + 1 ... aN-1 + 1 aN (1) Les ai sont les quotients partiels ou parfois tout

  6. Computing CMB Anisotropy in Compact Hyperbolic Spaces

    E-print Network

    J. Richard Bond; Dmitri Pogosyan; Tarun Souradeep

    1998-07-09

    The measurements of CMB anisotropy have opened up a window for probing the global topology of the universe on length scales comparable to and beyond the Hubble radius. For compact topologies, the two main effects on the CMB are: (1) the breaking of statistical isotropy in characteristic patterns determined by the photon geodesic structure of the manifold and (2) an infrared cutoff in the power spectrum of perturbations imposed by the finite spatial extent. We present a completely general scheme using the regularized method of images for calculating CMB anisotropy in models with nontrivial topology, and apply it to the computationally challenging compact hyperbolic topologies. This new technique eliminates the need for the difficult task of spatial eigenmode decomposition on these spaces. We estimate a Bayesian probability for a selection of models by confronting the theoretical pixel-pixel temperature correlation function with the COBE-DMR data. Our results demonstrate that strong constraints on compactness arise: if the universe is small compared to the `horizon' size, correlations appear in the maps that are irreconcilable with the observations. If the universe is of comparable size, the likelihood function is very dependent upon orientation of the manifold wrt the sky. While most orientations may be strongly ruled out, it sometimes happens that for a specific orientation the predicted correlation patterns are preferred over the conventional infinite models.

  7. Electro-mechanical anisotropy of phosphorene

    NASA Astrophysics Data System (ADS)

    Wang, Luqing; Kutana, Alex; Zou, Xiaolong; Yakobson, Boris I.

    2015-05-01

    The applied uniaxial stress can break the original symmetry of a material, providing an experimentally feasible way to alter material properties. Here, we explore the effects of uniaxial stress along an arbitrary direction on mechanical and electronic properties of phosphorene, showing the enhancement of inherent anisotropy. Basic physical quantities including Young's modulus, Poisson's ratio, band gap, and effective carrier masses under external stress are all computed from first principles using density functional theory, while the final results are presented in compact analytical forms.The applied uniaxial stress can break the original symmetry of a material, providing an experimentally feasible way to alter material properties. Here, we explore the effects of uniaxial stress along an arbitrary direction on mechanical and electronic properties of phosphorene, showing the enhancement of inherent anisotropy. Basic physical quantities including Young's modulus, Poisson's ratio, band gap, and effective carrier masses under external stress are all computed from first principles using density functional theory, while the final results are presented in compact analytical forms. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr00355e

  8. Results from the Wilkinson Microwave Anisotropy Probe

    NASA Technical Reports Server (NTRS)

    Komatsu, E.; Bennett, Charles L.; Komatsu, Eiichiro

    2015-01-01

    The Wilkinson Microwave Anisotropy Probe (WMAP) mapped the distribution of temperature and polarization over the entire sky in five microwave frequency bands. These full-sky maps were used to obtain measurements of temperature and polarization anisotropy of the cosmic microwave background with the unprecedented accuracy and precision. The analysis of two-point correlation functions of temperature and polarization data gives determinations of the fundamental cosmological parameters such as the age and composition of the universe, as well as the key parameters describing the physics of inflation, which is further constrained by three-point correlation functions. WMAP observations alone reduced the flat ? cold dark matter (Lambda Cold Dark Matter) cosmological model (six) parameter volume by a factor of > 68, 000 compared with pre-WMAP measurements. The WMAP observations (sometimes in combination with other astrophysical probes) convincingly show the existence of non-baryonic dark matter, the cosmic neutrino background, flatness of spatial geometry of the universe, a deviation from a scale-invariant spectrum of initial scalar fluctuations, and that the current universe is undergoing an accelerated expansion. The WMAP observations provide the strongest ever support for inflation; namely, the structures we see in the universe originate from quantum fluctuations generated during inflation.

  9. Cosmic microwave anisotropies from BPS semilocal strings

    SciTech Connect

    Urrestilla, Jon; Bevis, Neil; Hindmarsh, Mark; Kunz, Martin; Liddle, Andrew R, E-mail: j.urrestilla@sussex.ac.uk, E-mail: n.bevis@imperial.ac.uk, E-mail: m.b.hindmarsh@sussex.ac.uk, E-mail: martin.kunz@physics.unige.ch, E-mail: a.liddle@sussex.ac.uk [Department of Physics and Astronomy, University of Sussex, Brighton BN1 9QH (United Kingdom)

    2008-07-15

    We present the first ever calculation of cosmic microwave background (CMB) anisotropy power spectra from semilocal cosmic strings, obtained via simulations of a classical field theory. Semilocal strings are a type of non-topological defect arising in some models of inflation motivated by fundamental physics, and are thought to relax the constraints on the symmetry breaking scale as compared to models with (topological) cosmic strings. We derive constraints on the model parameters, including the string tension parameter {mu}, from fits to cosmological data, and find that in this regard Bogomol'nyi-Prasad-Sommerfield (BPS) semilocal strings resemble global textures more than topological strings. The observed microwave anisotropy at l=10 is reproduced if G{mu} = 5.3 Multiplication-Sign 10{sup -6} (G is Newton's constant). However as with other defects the spectral shape does not match observations, and in models with inflationary perturbations plus semilocal strings the 95% confidence level upper bound is G{mu}<2.0 Multiplication-Sign 10{sup -6} when CMB, Hubble key project and big bang nucleosynthesis data are used (cf G{mu}<0.9 Multiplication-Sign 10{sup -6} for cosmic strings). We additionally carry out a Bayesian model comparison of several models with and without defects, showing that models with defects are neither conclusively favoured nor disfavoured at present.

  10. An Australia telescope survey for CMB anisotropies

    E-print Network

    R. Subrahmanyan; M. J. Kesteven; R. D. Ekers; M. Sinclair; J. Silk

    2000-02-24

    We have surveyed six distinct `empty fields' using the Australia Telescope Compact Array in an ultra-compact configuration with the aim of imaging, with a high brightness sensitivity, any arcmin-scale brightness-temperature anisotropies in the background radio sky. The six well-separated regions were observed at a frequency of 8.7 GHz and the survey regions were limited by the ATCA primary beams which have a full width at half maximum of 6 arcmin at this frequency; all fields were observed with a resolution of 2 arcmin and an rms thermal noise of 24 microJy/beam. After subtracting foreground confusion detected in higher resolution images of the fields, residual fluctuations in Stokes I images are consistent with the expectations from thermal noise and weaker (unidentified) foreground sources; the Stokes Q and U images are consistent with expectations from thermal noise. Within the sensitivity of our observations, we have no reason to believe that there are any Sunyaev-Zeldovich holes in the microwave sky surveyed. Assuming Gaussian-form CMB anisotropy with a `flat' spectrum, we derive 95 per cent confidence upper limits of Q_flat < 10--11 microK in polarized intensity and Q_flat < 25 microK in total intensity. The ATCA filter function peaks at l=4700 and has half maximum values at l=3350 and 6050.

  11. Anisotropy beneath a highly extended continental rift

    NASA Astrophysics Data System (ADS)

    Eilon, Zachary; Abers, Geoffrey A.; Jin, Ge; Gaherty, James B.

    2014-03-01

    have employed shear wave splitting techniques to image anisotropy beneath the D'Entrecasteaux Islands, in southeastern Papua New Guinea. Our results provide a detailed picture of the extending continent that lies immediately ahead of a propagating mid-ocean ridge tip; we image the transition from continental to oceanic extension. A dense shear wave splitting data set from a 2010 to 2011 passive-source seismic deployment is analyzed using single and multichannel methods. Splitting delay times of 1-1.5 s are observed and fast axes of anisotropy trending N-S, parallel to rifting direction, predominate the results. This trend is linked to lattice-preferred orientation of olivine, primarily in the shallow convecting mantle, driven by up to 200 km of N-S continental extension ahead of the westward-propagating Woodlark Rift. This pattern differs from several other continental rifts that evince rift-strike-parallel fast axes and is evident despite the complex recent tectonic history. We contend that across most of this rift, the unusually high rate and magnitude of extension has been sufficient to produce a regime change to a mid-ocean-ridge-like mantle fabric. Stations in the south of our array show more complex splitting that might be related to melt or to complex inherited structure at the edge of the extended region.

  12. Reflectance anisotropy spectroscopy of magnetite (110) surfaces

    NASA Astrophysics Data System (ADS)

    Fleischer, K.; Verre, R.; Mauit, O.; Sofin, R. G. S.; Farrell, L.; Byrne, C.; Smith, C. M.; McGilp, J. F.; Shvets, I. V.

    2014-05-01

    Reflectance anisotropy spectroscopy (RAS) has been used to measure the optical anisotropies of bulk and thin-film Fe3O4(110) surfaces. The spectra indicate that small shifts in energy of the optical transitions, associated with anisotropic strain or electric field gradients caused by the (110) surface termination or a native oxide layer, are responsible for the strong signal observed. The RAS response was then measured as a function of temperature. A distinct change in the RAS line-shape amplitude was observed in the spectral range from 0.8 to 1.6 eV for temperatures below the Verwey transition of the crystal. Finally, thin-film magnetite was grown by molecular beam epitaxy on MgO(110) substrates. Changes in the RAS spectra were found for different film thickness, suggesting that RAS can be used to monitor the growth of magnetite (110) films in situ. The thickness dependence of the RAS is discussed in terms of various models for the origin of the RAS signal.

  13. Experiments to Separate the Effect of Texture on Anisotropy of Pipeline Steel

    E-print Network

    Cambridge, University of

    Experiments to Separate the Effect of Texture on Anisotropy of Pipeline Steel M. S. Jooa , D the anisotropy of Charpy test energy. Keywords: pipeline steel, anisotropy, crystallographic texture, memory

  14. Body Fractions: A Physical Approach to Fraction Learning

    ERIC Educational Resources Information Center

    Mills, Judith

    2011-01-01

    Many students experience great difficulty understanding the meaning of fractions. For many students who have spent their early mathematics lessons focusing on counting (whole) numbers, recognising that there are many numbers between those whole numbers called fractional numbers, is quite revolutionary. The foundation of understanding fractions is…

  15. Equivalent Fractions and Comparing Fractions: Are You My Equal?

    NSDL National Science Digital Library

    Anastasia Trueman

    2003-01-01

    In this four-day lesson students use several models to explore equivalent fractions and to compare proper fractions with denominators of values up to 12. It incorporates the book "The Hershey's Milk Chocolate Bar Fractions Book" by Jerry Pallotta. The 30-page pdf includes lists of materials, teacher instructions, printable activity sheets, assessments, and a game.

  16. Fun with Fractions: Investigating Equivalent Fractions with Relationship Rods

    NSDL National Science Digital Library

    Illuminations National Council of Teachers of Mathematics

    2009-03-23

    "Students investigate the length model by working with relationship rods to find equivalent fractions and identify fractions in lowest terms. Students develop skills in reasoning and problem solving as they explain how two fractions are equivalent (the same length)." (from NCTM Illuminations) Lesson 4 of a five lesson unit. This is a progression from Lesson 3.

  17. Domain wall motion in perpendicular anisotropy nanowires with edge roughness

    E-print Network

    Domain wall motion in perpendicular anisotropy nanowires with edge roughness Maximilian Albert1@soton.ac.uk Abstract. We study field-driven domain wall motion in nanowires with perpendicu- lar magnetic anisotropy observe the Walker breakdown both with and without roughness, with steady domain wall motion for ap- plied

  18. Coherent spin control by electrical manipulation of the magnetic anisotropy

    E-print Network

    Richard E George; James P Edwards; Arzhang Ardavan

    2012-10-22

    High-spin paramagnetic manganese defects in polar piezoelectric zinc oxide exhibit a simple almost axial anisotropy and phase coherence times of the order of a millisecond at low temperatures. The anisotropy energy is tunable using an externally applied electric field. This can be used to control electrically the phase of spin superpositions and to drive spin transitions with resonant microwave electric fields.

  19. Effective Biaxial Anisotropy in Double-Layered Thin Magnetic Films

    Microsoft Academic Search

    Nobuo Hayashi; Elichi Goto

    1966-01-01

    Quantitative experimental results have been obtained in support of a previously developed theory which represents the deformation of the critical curves of multilayered magnetic thin films in terms of effective multiaxial anisotropies. The effective biaxial anisotropy field has been experimentally observed to be proportional to the square of film thickness in the case of thinner films, as expected from the

  20. Anisotropy tensor of the potential model of steady creep

    NASA Astrophysics Data System (ADS)

    Annin, B. D.; Ostrosablin, N. I.

    2014-01-01

    The Kelvin approach describing the structure of the generalized Hooke's law is used to analyze the potential model of anisotropic creep of materials. The creep equations of incompressible transversely isotropic, orthotropic materials and those with cubic symmetry are considered. The eigen coefficients of anisotropy and eigen tensors for the anisotropy tensors of these materials are determined.

  1. LOCAL ANISOTROPY, HIGHER ORDER STATISTICS, AND TURBULENCE SPECTRA

    SciTech Connect

    Matthaeus, W. H.; Wan, M.; Osman, K. T. [Department of Physics and Astronomy, University of Delaware, DE (United States); Servidio, S.; Carbone, V. [Dipartimento di Fisica, Universita della Calabria, I-87036 Cosenza (Italy); Dmitruk, P. [Departamento de Fisica (FCEN-UBA and IFIBA-CONICET), Buenos Aires (Argentina); Oughton, S. [Department of Mathematics, University of Waikato, Hamilton 3240 (New Zealand)

    2012-05-10

    Correlation anisotropy emerges dynamically in magnetohydrodynamics (MHD), producing stronger gradients across the large-scale mean magnetic field than along it. This occurs both globally and locally, and has significant implications in space and astrophysical plasmas, including particle scattering and transport, and theories of turbulence. Properties of local correlation anisotropy are further documented here by showing through numerical experiments that the effect is intensified in more localized estimates of the mean field. The mathematical formulation of this property shows that local anisotropy mixes second-order with higher order correlations. Sensitivity of local statistical estimates to higher order correlations can be understood in connection with the stochastic coordinate system inherent in such formulations. We demonstrate this in specific cases, and illustrate the connection to higher order statistics by showing the sensitivity of local anisotropy to phase randomization, after which the global measure of anisotropy is recovered at all scales of averaging. This establishes that anisotropy of the local structure function is not a measure of anisotropy of the energy spectrum. Evidently, the local enhancement of correlation anisotropy is of substantial fundamental interest and must be understood in terms of higher order correlations, specifically fourth-order and above.

  2. ORIGINAL PAPER Shear Wave Splitting and Mantle Anisotropy

    E-print Network

    ORIGINAL PAPER Shear Wave Splitting and Mantle Anisotropy: Measurements, Interpretations, and New the Earth's mantle yield constraints on the strength and geometry of elastic anisotropy in various regions, including the upper mantle, the transition zone, and the D00 layer. In turn, information about

  3. ORIGINAL PAPER Upper mantle anisotropy of southeast Arabia passive margin

    E-print Network

    Demouchy, Sylvie

    ORIGINAL PAPER Upper mantle anisotropy of southeast Arabia passive margin [Gulf of Aden northern and upper mantle structure and rheology. In this study, we use shear-wave splitting analysis to map lateral variations of upper mantle anisotropy beneath the study area. In this study, we found splitting magnitudes

  4. Cosmic Microwave Background Radiation Anisotropy Induced by Cosmic Strings

    Microsoft Academic Search

    B. Allen; R. R. Caldwell; E. P. S. Shellard; A. Stebbins; S. Veeraraghavan

    1994-01-01

    We report on a current investigation of the anisotropy pattern induced by cosmic strings on the cosmic microwave background radiation (MBR). We have numerically evolved a network of cosmic strings from a redshift of $Z = 100$ to the present and calculated the anisotropies which they induce. Based on a limited number of realizations, we have compared the results of

  5. Cosmic Microwave Background Anisotropies Wayne Hu1,2,3

    E-print Network

    Hu, Wayne

    1 Cosmic Microwave Background Anisotropies Wayne Hu1,2,3 and Scott Dodelson2,3 1 Center 60637 KEYWORDS: background radiation, cosmology, theory, dark matter, early universe ABSTRACT: Cosmic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 1 INTRODUCTION The field of cosmic microwave background (CMB) anisotropies has dramatically

  6. Crustal Shear Wave Anisotropy in the Taiwan Orogen

    Microsoft Academic Search

    R. Rau; C. Yang

    2002-01-01

    Crustal shear wave anisotropy is analyzed in seismograms from local earthquakes (1.5 < M < 4.5) recorded at 75 permanent network stations in Taiwan during the period between 1991 and 2000. We investigate the origin of Taiwan crustal anisotropy by analyzing splitting in recorded shear waves, which can be characterized by a fast polarization direction and a time delay between

  7. Seismic Anisotropy and Mantle Flow Across the Mariana Subduction System

    Microsoft Academic Search

    S. H. Pozgay; D. A. Wiens; H. Shiobara; H. Sugioka

    2005-01-01

    We investigate seismic anisotropy across the Mariana subduction system with local and teleseismic shear wave splitting analysis. Data from 48 ocean bottom seismographs and 20 land stations deployed by the Mariana SUBFAC imaging experiment provides an unparalleled opportunity to study anisotropy and mantle flow in an island arc-backarc system. We employ both the minimum eigenvalue and cross-correlation methods to solve

  8. Stress-induced upper crustal anisotropy in southern California

    Microsoft Academic Search

    Zhaohui Yang; Anne Sheehan; Peter Shearer

    2011-01-01

    We use an automated method to analyze shear wave splitting from local earthquakes recorded by the Southern California Seismic Network between 2000 and 2005. The observed fast directions of upper crustal anisotropy generally are consistent with the direction of maximum horizontal compression ?Hmax, suggesting that one major mechanism of anisotropy in the top 20 km of crust under southern California

  9. Significant seismic anisotropy beneath the southern Lhasa Terrane, Tibetan Plateau

    Microsoft Academic Search

    Stephen S. Gao; Kelly H. Liu

    2009-01-01

    Shear wave splitting measurements using teleseismic PKS, SKKS, and SKS phases recorded by station LSA on the southern part of the Lhasa Terrane of the Tibetan Plateau reveal significant azimuthal anisotropy with a splitting time of up to 1.5 s, a conclusion that is contradictory to previous studies which suggested isotropy or weak anisotropy. In addition, systematic variations of the

  10. Passive monitoring of anisotropy change for the Parkfield 2004 earthquake

    Microsoft Academic Search

    S. Durand; J. Montagner; P. Roux; F. Brenguier; S. Saumet; P. Cupillard; G. Burgos

    2010-01-01

    Measuring significant and systematic temporal variations of physical parameters is a major goal of seismologists for monitoring seismogenic zones. Seismic anisotropy is induced by the crack distribution within the continental crust, and it is very sensitive to stress-field changes. To date, anisotropy has been investigated through shear-wave splitting (SWS) measurements of local earthquakes. To avoid the erratic occurrence and spatial

  11. Helium production and limits on the anisotropy of the universe

    Microsoft Academic Search

    D. W. Olson

    1978-01-01

    If most of the presently observed ⁴He was synthesized in a primordial big-bang stage of the universe, then an indirect method due to Barrow can be used to set upper limits on the global anisotropy of the universe. Numerical results from an improved version of this method are compared with the more direct limits on anisotropy from observations of the

  12. The Magnetocrystalline Anisotropy of Cobalt-Substituted Manganese Ferrite

    Microsoft Academic Search

    R F Pearson

    1959-01-01

    The first order anisotropy constant K1 has been measured by torque methods on substituted manganese ferrite crystals containing 1, 2, 4, 6, 8, 10 and 25 mol% cobalt ferrite from 160° to 300°K. The contribution to the anisotropy from the cobalt ions is found to vary linearly with cobalt concentration up to 25%. The extrapolated contributions of the cobalt ions

  13. Monitoring changes in stress using temporal variations in seismic anisotropy

    Microsoft Academic Search

    M. Kendall; A. Caley; R. Jones

    2001-01-01

    In the crust the orientation of principal horizontal stress--axes controls the preferred alignment of cracks, which, in turn, can produce long-wavelength seismic anisotropy. For many years it has been proposed that observations of seismic anisotropy can be therefore used to monitor changes in stress, but conclusive evidence of this has been somewhat elusive. Here we present observations of temporal variations

  14. Asthenospheric channeling of the Icelandic upwelling: Evidence from seismic anisotropy

    E-print Network

    Allen, Richard M.

    Asthenospheric channeling of the Icelandic upwelling: Evidence from seismic anisotropy Mei Xue*,1 Iceland. Seismic anisotropy provides information on mantle flow, and therefore has the potential to discriminate these two geometries. In this study, we combine the HOTSPOT and SIL datasets (39 stations

  15. The Role of Photon Statistics in Fluorescence Anisotropy Imaging

    Microsoft Academic Search

    Keith A. Lidke; Bernd Rieger; Diane S. Lidke; Thomas M. Jovin

    2005-01-01

    Anisotropy imaging can be used to image resonance energy transfer between pairs of identical fluorophores and, thus, constitutes a powerful tool for monitoring protein homo-asso- ciation in living single cells. The requirement for only a single fluorophore significantly simplifies biological preparation and interpretation. We use quantitative methods for the acquisition and image processing of anisotropy data that return the expected

  16. Duality for nonlinear fractional programs

    Microsoft Academic Search

    R. Jagannathan

    1973-01-01

    Summary This paper develops duality results for nonlinear fractional programming problems. This is accomplished by using some known results connecting the solutions of a nonlinear fractional program with those of a suitably defined parametric convex program.

  17. 3.NF Comparing Fractions

    NSDL National Science Digital Library

    2012-08-15

    This is a task from the Illustrative Mathematics website that is one part of a complete illustration of the standard to which it is aligned. Each task has at least one solution and some commentary that addresses important asects of the task and its potential use. Here are the first few lines of the commentary for this task: Compare the fractions below. Use the symbols $\\gt$, =, or $\\lt$ to record your comparisons. Draw a picture to illustrate your answer. $\\frac{2}{6}$ and...

  18. Number Theory and Fractions

    NSDL National Science Digital Library

    This is a set of two, one-page problems about the sizes of moons in the solar system. Learners will use fractions to compare the sizes and distances of Jupiter's moons. Options are presented so that students may learn about the Juno mission through a NASA press release or by viewing a NASA eClips video [6 min.] about the creation of graphic of the 88 largest objects in our solar system. This activity is part of the Space Math multi-media modules that integrate NASA press releases, NASA archival video, and mathematics problems targeted at specific math standards commonly encountered in middle school.

  19. Fractional channel multichannel analyzer

    DOEpatents

    Brackenbush, Larry W. (Richland, WA); Anderson, Gordon A. (Benton City, WA)

    1994-01-01

    A multichannel analyzer incorporating the features of the present invention obtains the effect of fractional channels thus greatly reducing the number of actual channels necessary to record complex line spectra. This is accomplished by using an analog-to-digital converter in the asynscronous mode, i.e., the gate pulse from the pulse height-to-pulse width converter is not synchronized with the signal from a clock oscillator. This saves power and reduces the number of components required on the board to achieve the effect of radically expanding the number of channels without changing the circuit board.

  20. 3.NF Ordering Fractions

    NSDL National Science Digital Library

    This is a task from the Illustrative Mathematics website that is one part of a complete illustration of the standard to which it is aligned. Each task has at least one solution and some commentary that addresses important asects of the task and its potential use. Here are the first few lines of the commentary for this task: Arrange the fractions in order from least to greatest. Explain your answer with a picture. $\\frac{1}{5}, \\frac{1}{7}, \\frac{1}{3} $ $\\frac{2}{5}, \\frac...