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1

Multimodal white matter imaging to investigate reduced fractional anisotropy and its age-related decline in schizophrenia.  

PubMed

We hypothesized that reduced fractional anisotropy (FA) of water diffusion and its elevated aging-related decline in schizophrenia patients may be caused by elevated hyperintensive white matter (HWM) lesions, by reduced permeability-diffusivity index (PDI), or both. We tested this hypothesis in 40/30 control/patient participants. FA values for the corpus callosum were calculated from high angular resolution diffusion tensor imaging (DTI). Whole-brain volume of HWM lesions was quantified by 3D-T2w-fluid-attenuated inversion recovery (FLAIR) imaging. PDI for corpus callosum was ascertained using multi b-value diffusion imaging (15 b-shells with 30 directions per shell). Patients had significantly lower corpus callosum FA values, and there was a significant age-by-diagnosis interaction. Patients also had significantly reduced PDI but no difference in HWM volume. PDI and HWM volume were significant predictors of FA and captured the diagnosis-related variance. Separately, PDI robustly explained FA variance in schizophrenia patients, but not in controls. Conversely, HWM volume made equally significant contributions to variability in FA in both groups. The diagnosis-by-age effect of FA was explained by a PDI-by-diagnosis interaction. Post hoc testing showed a similar trend for PDI of gray mater. Our study demonstrated that reduced FA and its accelerated decline with age in schizophrenia were explained by pathophysiology indexed by PDI, rather than HWM volume. PMID:24909602

Kochunov, Peter; Chiappelli, Joshua; Wright, Susan N; Rowland, Laura M; Patel, Beenish; Wijtenburg, S Andrea; Nugent, Katie; McMahon, Robert P; Carpenter, William T; Muellerklein, Florian; Sampath, Hemalatha; Hong, L Elliot

2014-08-30

2

Cosmic ray anisotropy in fractional differential models of anomalous diffusion  

SciTech Connect

The problem of galactic cosmic ray anisotropy is considered in two versions of the fractional differential model for anomalous diffusion. The simplest problem of cosmic ray propagation from a point instantaneous source in an unbounded medium is used as an example to show that the transition from the standard diffusion model to the Lagutin-Uchaikin fractional differential model (with characteristic exponent {alpha} = 3/5 and a finite velocity of free particle motion), which gives rise to a knee in the energy spectrum at 10{sup 6} GeV, increases the anisotropy coefficient only by 20%, while the anisotropy coefficient in the Lagutin-Tyumentsev model (with exponents {alpha} = 0.3 and {beta} = 0.8, a long stay of particles in traps, and an infinite velocity of their jumps) is close to one. This is because the parameters of the Lagutin-Tyumentsev model have been chosen improperly.

Uchaikin, V. V., E-mail: vuchaikin@gmail.com [Ulyanovsk State University (Russian Federation)

2013-06-15

3

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

PubMed Central

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

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

4

STATISTICAL TESTS OF ANISOTROPY FOR FRACTIONAL BROWNIAN TEXTURES.  

E-print Network

characterization of bone architecture and the evaluation of osteoporotic fracture risk [7]. However, it is well-established that the anisotropy of the bone is an important predictor of fracture risk [15, 36]. Hence fractal analysis

Biermé, Hermine

5

Increased Regional Fractional Anisotropy in Highly Screened Attention-Deficit Hyperactivity Disorder (ADHD)  

PubMed Central

Diffusion tensor imaging data were collected at 3.0 Tesla from 16 children with attention-deficit hyperactivity disorder (ADHD) and 16 typically developing controls, ages 9 to 14 years. Fractional anisotropy images were calculated and normalized by linear transformation. Voxel-wise and atlas-based region-of-interest analyses were performed. Using voxel-wise analysis, fractional anisotropy was found to be significantly increased in the attention-deficit hyperactivity disorder group in the right superior frontal gyrus and posterior thalamic radiation, and left dorsal posterior cingulate gyrus, lingual gyrus, and parahippocampal gyrus. No regions showed significantly decreased fractional anisotropy in attention-deficit hyperactivity disorder. Region-of-interest analysis revealed increased fractional anisotropy in the left sagittal stratum, that is, white matter that connects the temporal lobe to distant cortical regions. Only fractional anisotropy in the left sagittal stratum was significantly associated with attention-deficit hyperactivity disorder symptom severity. Several recent studies have reported pathological increases in fractional anisotropy in other conditions, highlighting the relevance of diffusion tensor imaging in identifying atypical white matter structure associated with neurodevelopmental processes. PMID:21628699

Peterson, Daniel J.; Ryan, Matthew; Rimrodt, Sheryl L.; Cutting, Laurie E.; Denckla, Martha B.; Kaufmann, Walter E.; Mahone, E. Mark

2012-01-01

6

Interleukin-6, Age, and Corpus Callosum Integrity  

PubMed Central

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

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

7

Mean diffusivity and fractional anisotropy as indicators of disease and genetic liability to schizophrenia  

Microsoft Academic Search

The goals of this study were to first determine whether the fractional anisotropy (FA) and mean diffusivity (MD) of major white matter pathways associate with schizophrenia, and secondly to characterize the extent to which differences in these metrics might reflect a genetic predisposition to schizophrenia. Differences in FA and MD were identified using a comprehensive atlas-based tract mapping approach using

Kristi A. Clark; Keith H. Nuechterlein; Robert F. Asarnow; Liberty S. Hamilton; Owen R. Phillips; Nathan S. Hageman; Roger P. Woods; Jeffry R. Alger; Arthur W. Toga; Katherine L. Narr

2011-01-01

8

Diffusion Tensor Measures of the Corpus Callosum in Adolescents With Adolescent Onset Alcohol Use Disorders  

PubMed Central

Background In adults, myelination injury is associated with alcoholism. Maturation of the corpus callosum is prominent during adolescence. We hypothesized that subjects with adolescent-onset alcohol use disorders (AUD; defined as Diagnostic and Statistical Manual of Mental Disorders-IV alcohol dependence or abuse) would have myelination mircostructural differences compared to controls. Methods Adolescent subjects (25 males, 7 females) with an AUD (16.9 ± 1.2 years), who were recruited from substance abuse treatment programs and had co-morbid mental disorders, and 28 sociodemographically similar healthy controls (17 males, 11 females; 15.9 ± 1.1 years) underwent a 3.0 T MRI diffusion tensor imaging scan. Results Measures of rostral body fractional anisotropy (FA) were higher in the AUD group than in the control group. Compared to controls, mean diffusivity (MD) was lower, while FA was higher, in the AUD group in the isthmus region. Anterior corpus callosum mircostructural development differed in adolescents with AUD, as age was positively (not negatively) associated with rostrum MD and age was negatively (not positively) associated with rostrum FA. There were sex by group interactions in that control females had higher posterior midbody FA when com pared to female adolescents with AUD. Conclusions Lower MD and higher FA values in the AUD group suggest pre-morbid vulnerability for accelerated prefrontal and temporo-parietal myelin maturation that may enhance the risk for adolescent AUD. Significant (and opposite to developmentally expected) correlations were seen between anterior corpus callosum MD and FA measures and age in the AUD group, suggesting neurotoxic effects of alcohol on adolescent corpus callosum microstructure. As seen in adults, female adolescents with AUD may be especially vulnerable to corpus callosum mircostructural injury. Further diffusion tensor imaging studies of corpus callosum maturation in children at familial risk for alcoholism, and in those with AUD, need to be done to elucidate these mechanisms. PMID:18241319

De Bellis, Michael D.; Van Voorhees, Elizabeth; Hooper, Stephen R.; Gibler, Nicole; Nelson, Lauren; Hege, Steve G.; Payne, Martha E.; MacFall, James

2013-01-01

9

Vestibular loss and balance training cause similar changes in human cerebral white matter fractional anisotropy.  

PubMed

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

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

2014-01-01

10

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

PubMed Central

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

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

2014-01-01

11

Bilingual Corpus Callosum Variability  

ERIC Educational Resources Information Center

Magnetic resonance imaging was used to produce midsagittal images of the corpus callosum of 19 right-handed adult male and female subjects. The preliminary findings of this study indicate that significant adaptation in the anterior midbody of the corpus callosum has occurred to accommodate multiple language capacity in bilingual individuals…

Coggins, Porter E., III.; Kennedy, Teresa J.; Armstrong, Terry A.

2004-01-01

12

A NOVEL APPROACH TO CONSTRAIN THE ESCAPE FRACTION AND DUST CONTENT AT HIGH REDSHIFT USING THE COSMIC INFRARED BACKGROUND FRACTIONAL ANISOTROPY  

SciTech Connect

The Cosmic Infrared Background (CIB) provides an opportunity to constrain many properties of the high-redshift (z > 6) stellar population as a whole. This background, specifically from 1 to 200 {mu}m, should contain information about the era of reionization and the stars that are responsible for these ionizing photons. In this paper, we look at the fractional anisotropy ({delta}I/I) of this high-redshift population, where {delta}I is the ratio of the magnitude of the fluctuations and I is the mean intensity. We show that this can be used to constrain the escape fraction of the population as a whole, because the magnitude of the fluctuations of the CIB depends on the escape fraction, while the mean intensity does not. This results in lower values of the escape fraction producing higher values of the fractional anisotropy. This difference is predicted to be larger at longer wavelength bands (above 10 {mu}m), albeit it is also much harder to observe in that range. We show that the fractional anisotropy can also be used to separate a dusty from a dust-free population. Finally, we discuss the constraints provided by current observations on the CIB fractional anisotropy.

Fernandez, Elizabeth R.; Dole, Herve [Institut d'Astrophysique Spatiale, Universite Paris-Sud 11 and CNRS, F-91405 Orsay (France)] [Institut d'Astrophysique Spatiale, Universite Paris-Sud 11 and CNRS, F-91405 Orsay (France); Iliev, Ilian T., E-mail: Elizabeth.Fernandez@ias.u-psud.fr [Astronomy Centre, Department of Physics and Astronomy, Pevensey II Building, University of Sussex, Falmer, Brighton BN1 9QH (United Kingdom)

2013-02-10

13

Acquisition parameters for diffusion tensor imaging to emphasize fractional anisotropy: phantom study.  

PubMed

Diffusion tensor imaging (DTI) is a magnetic resonance (MR) imaging technique that has attracted attention in recent years for applications such as nerve fiber tracking, neurography, and tumor detection. In DTI measurements, 2 motion-probing gradient (MPG) pulses are applied to evaluate water diffusion. In DTI for nerve fiber tracking, acquisition parameters, such as strength, duration, and separation of MPGs, influence the MR signal. In this study, we set acquisition parameters in DTI to emphasize fractional anisotropy to clarify the direction of nerve fibers. We performed Monte Carlo simulations of restricted diffusion in a cylinder model and phantom measurements with capillary plates to examine the relationship between the acquisition parameters in DTI and the size of restricted structures, particularly their diameter and length, which we will refer to as "compartment size." We confirmed that normalized signal intensities in DTI measurements depend on diffusion time, which, in turn, depends on the separation and duration of the MPG, and they decrease with increase in compartment size. Furthermore, our simulation and phantom results suggest that use of a longer diffusion time effectively emphasizes fractional anisotropy to clarify the direction of nerve fibers. PMID:21720114

Oida, Takenori; Nagahara, Shizue; Kobayashi, Tetsuo

2011-01-01

14

Microstructural Corpus Callosum Anomalies in Children With Prenatal Alcohol Exposure: An Extension of Previous Diffusion Tensor Imaging Findings  

PubMed Central

Background Several studies have now shown corpus callosum abnormalities using diffusion tensor imaging (DTI) in children with fetal alcohol spectrum disorders (FASD) in comparison with nonexposed controls. The data suggest that posterior regions of the callosum may be disproportionately affected. The current study builds on previous efforts, including our own work, and moves beyond midline corpus callosum to probe major inter-hemispheric white matter pathways with an improved DTI tractographic method. This study also expands on our prior work by evaluating a larger sample and by incorporating children with a broader range of clinical effects including full-criteria fetal alcohol syndrome (FAS). Methods Participants included 33 children with FASD (8 FAS, 23 partial FAS, 2 static encephalopathy) and 19 nonexposed controls between the ages of 10 and 17 years. Participants underwent DTI scans and intelligence testing. Groups (FASD vs. controls) were compared on fractional anisotropy (FA) and mean diffusivity (MD) in 6 white matter tracts projected through the corpus callosum. Exploratory analyses were also conducted examining the relationships between DTI measures in the corpus callosum and measures of intellectual functioning and facial dysmorphology. Results In comparison with the control group, the FASD group had significantly lower FA in 3 posterior tracts of the corpus callosum: the posterior mid-body, the isthmus, and the splenium. A trend-level finding also suggested lower FA in the genu. Measures of white matter integrity and cognition were correlated and suggest some regional specificity, in that only posterior regions of the corpus callosum were associated with visual-perceptual skills. Correlations between measures of facial dysmorphology and posterior regions of the corpus callosum were nonsignificant. Conclusions Consistent with previous DTI studies, these results suggest that microstructural posterior corpus callosum abnormalities are present in children with prenatal alcohol exposure and cognitive impairment. These abnormalities are clinically relevant because they are associated with cognitive deficits and appear to provide evidence of abnormalities associated with prenatal alcohol exposure independent of dysmorphic features. As such, they may yield important diagnostic and prognostic information not provided by the traditional facial characteristics. PMID:19645729

Wozniak, Jeffrey R.; Muetzel, Ryan L.; Mueller, Bryon A.; McGee, Christie L.; Freerks, Melesa A.; Ward, Erin E.; Nelson, Miranda L.; Chang, Pi-Nian; Lim, Kelvin O.

2010-01-01

15

Relationship between fractional anisotropy of cerebral white matter and metabolite concentrations measured using 1H magnetic resonance spectroscopy in healthy adults  

PubMed Central

Fractional anisotropy (FA) of water diffusion in cerebral white matter (WM), derived from diffusion tensor imaging (DTI), is a sensitive index of microscopic WM integrity. Physiological and metabolic factors that explain intersubject variability in FA values were evaluated in two cohorts of healthy adults of different age spans (N=65, range: 28–50 years; and N=25, age=66.6±6.2, range:57–80 years). Single voxel magnetic resonance spectroscopy (MRS) was used to measure N-acetylaspartate (NAA), total choline-containing compounds, and total creatine, bilaterally in an associative WM tract: anterior corona radiata (ACR). FA values were calculated for the underlying, proximal and two distal WM regions. Two-stage regression analysis was used to calculate the proportion of variability in FA values explained by spectroscopy measurements, at the first stage, and subject’s age, at the second stage. WM NAA concentration explained 23% and 66% of intersubject variability (p<0.001) in the FA of the underlying WM in the younger and older cohorts, respectively. WM NAA concentration also explained a significant proportion of variability in FA of the genu of corpus callosum (CC), a proximal WM tract where some of the fibers contained within the spectroscopic voxel decussate spectroscopic voxel decussate. NAA concentrations also explained a significant proportion of variability in the FA values in the splenium of CC, a distal WM tract that also carries associative fibers, in both cohorts. These results suggest that MRS measurements explained a significant proportion of variability in FA values in both proximal and distal WM tracts that carry similar fiber-types. PMID:23073233

Wijtenburg, S.A.; McGuire, S.A.; Rowland, L.M.; Sherman, P.M.; Lancaster, J.L.; Tate, D.F.; Hardies, L.J.; Patel, B.; Glahn, D.C.; Hong, L.E.; Fox, P.T.; Kochunov, P.

2012-01-01

16

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

PubMed Central

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

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

2013-01-01

17

Associations between fractional anisotropy and problematic alcohol use in juvenile justice-involved adolescents  

PubMed Central

Background Studies have shown associations between heavy alcohol use and white matter alterations in adolescence. Youth involved with the juvenile justice system engage in high levels of risk behavior generally and alcohol use in particular as compared to their non-justice-involved peers. Objectives This study explored white matter integrity among justice-involved adolescents. Analyses examined fractional anisotropy (FA) and mean diffusivity (MD) between adolescents with low and high levels of problematic alcohol use as assessed by the Alcohol Use Disorders Identification Test (AUDIT). Methods Participants (N = 125; 80% male; 14–18 years) completed measures assessing psychological status and substance use followed by diffusion tensor imaging (DTI). DTI data for low (n = 51) and high AUDIT (n = 74) adolescents were subjected to cluster-based group comparisons on skeletonized FA and MD data. Results Whole-brain analyses revealed significantly lower FA in clusters in the right and left posterior corona radiata (PCR) and right superior longitudinal fasciculus (SLF) in the high AUDIT group, as well as one cluster in the right anterior corona radiata that showed higher FA in the high AUDIT group. No differences in MD were identified. Exploratory analyses correlated cluster FA with measures of additional risk factors. FA in the right SLF and left PCR was negatively associated with impulsivity. Conclusion Justice-involved adolescents with alcohol use problems generally showed poorer FA than their low problematic alcohol use peers. Future research should aim to better understand the nature of the relationship between white matter development and alcohol use specifically as well as risk behavior more generally. PMID:24200206

Thayer, Rachel E.; Callahan, Tiffany J.; Weiland, Barbara J.; Hutchison, Kent E.; Bryan, Angela D.

2014-01-01

18

Reduced Right Frontal Fractional Anisotropy Correlated with Early Elevated Plasma LDL Levels in Obese Young Adults  

PubMed Central

Objective To investigate the underlying physiological mechanisms of the structural differences in gray matter (GM) and white matter (WM) associated with obesity in young Chinese adults. Materials and Methods A total of 49 right-handed obese or overweight (n?=?22, mean age 31.72±8.04 years) and normal weight (n?=?27, mean age 29.04±7.32 years) Han Chinese individuals were recruited. All participants underwent voxel-based morphometry analysis of T1-weighted MRI and tract-based spatial statistics analysis of diffusion tensor imaging. Partial correlation analysis was performed between the physiological data obtained and the abnormal structural alterations. Results In the OO group, GM atrophy occurred in the left prefrontal cortex, bilateral cingulate gyrus, and the right temporal lobe, while enlargement was observed in the bilateral putamen. WM atrophy was observed predominantly in the regions that regulate food intake, such as the bilateral basal ganglia, the right amygdala, and the left insula. The OO group exhibited lower fractional anisotropy (FA) in bilateral frontal corticospinal tracts and the right brainstem. Significant negative correlations were observed between FA values of those three clusters and BMI, and waist circumference, while the volume of bilateral putamen positively correlated with both BMI and waist circumference. High plasma LDL levels were correlated with low FA values in the right frontal corticospinal tract. Interestingly, the negative correlation was limited to male participants. Conclusions Obesity-related alterations of GM and WM volumes were observed predominantly in food reward circuit, which may motivate abnormal dietary intake. Further, early elevated plasma LDL might contribute to low right frontal FA values of male adults, which requires further demonstration by larger-scale and longitudinal studies. PMID:25279729

Lou, Baohui; Chen, Min; Luo, Xiaojie; Dai, Yongming

2014-01-01

19

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

PubMed Central

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

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

2011-01-01

20

Enlarged Thalamic Volumes and Increased Fractional Anisotropy in the Thalamic Radiations in Veterans with Suicide Behaviors  

PubMed Central

Post-mortem studies have suggested a link between the thalamus, psychiatric disorders, and suicide. We evaluated the thalamus and anterior thalamic radiations (ATR) in a group of Veterans with and without a history of suicidal behavior (SB) to determine if thalamic abnormalities were associated with an increased risk of SB. Forty Veterans with mild traumatic brain injury (TBI) and no SB (TBI-SB), 19 Veterans with mild TBI and a history of SB (TB?+?SB), and 15 healthy controls (HC) underwent magnetic resonance imaging scanning including a structural and diffusion tensor imaging scan. SBs were evaluated utilizing the Columbia Suicide Rating Scale and impulsivity was measured using the Barratt Impulsiveness Scale (BIS). Differences in thalamic volumes and ATR fractional anisotropy (FA) were examined between (1) TBI?+?SB versus HC and (2) TBI?+?SB versus combined HC and TBI-SB and (3) between TBI?+?SB and TBI-SB. Left and right thalamic volumes were significantly increased in those with TBI?+?SB compared to the HC, TBI-SB, and the combined group. Veterans with TBI?+?SB had increased FA bilaterally compared to the HC, HC and TBI-SB group, and the TBI-SB only group. Significant positive associations were found for bilateral ATR and BIS in the TBI?+?SB group. Our findings of thalamic enlargement and increased FA in individuals with TBI?+?SB suggest that this region may be a biomarker for suicide risk. Our findings are consistent with previous evidence indicating that suicide may be associated with behavioral disinhibition and frontal-thalamic-limbic dysfunction and suggest a neurobiologic mechanism that may increase vulnerability to suicide. PMID:23964245

Lopez-Larson, Melissa; King, Jace B.; McGlade, Erin; Bueler, Elliott; Stoeckel, Amanda; Epstein, Daniel J.; Yurgelun-Todd, Deborah

2013-01-01

21

Corpus Callosum Abnormalities and their Association with Psychotic Symptoms in Patients with Schizophrenia  

PubMed Central

Background Whilst the neuroanatomical underpinnings of the functional brain disconnectivity observed in patients with schizophrenia remain elusive, white matter fiber bundles of the brain are a likely candidate given that they represent the infrastructure for long-distance neural communication. Methods This study investigated for diffusion abnormalities in 19 patients with chronic schizophrenia (SZ), relative to 19 matched controls, across tractography-defined segments of the Corpus Callosum. Diffusion-weighted images were acquired with 51 non-collinear gradients on a 3T scanner (1.7mm isotropic voxels). The Corpus Callosum was extracted by means of whole-brain tractography and automated fiber-clustering, and was parcellated into six segments on the basis of fiber trajectories. The diffusion indices of Fractional Anisotropy (FA) and Mode were calculated for each segment. Results Relative to the healthy controls, the SZ patients exhibited Mode increases in the Parietal fibers, suggesting a relative absence of crossing fibers. SZ patients also exhibited FA reductions in the Frontal fibers, which were underpinned by increased in Radial Diffusivity, consistent with myelin abnormalities. Significant correlations were observed between patients' degree of Reality Distortion and their FA and Radial Diffusivity, such that the most severely psychotic patients were the least abnormal in terms of their Frontal fiber diffusivity. Conclusions The SZ patients exhibited a variety of diffusion abnormalities in the Corpus Callosum, which were related to the severity of their psychotic symptoms. To the extent that diffusion abnormalities influence axonal transmission velocities, these results provide support for those theories that emphasize neural timing abnormalities in the etiology of schizophrenia. PMID:20494336

Whitford, Thomas J.; Kubicki, Marek; Schneiderman, Jason S.; O'Donnell, Lauren J.; King, Rebecca; Alvarado, Jorge L.; Khan, Usman; Markant, Douglas; Nestor, Paul G.; Niznikiewicz, Margaret; McCarley, Robert W.; Westin, Carl-Fredrik; Shenton, Martha E.

2010-01-01

22

MRI of the Corpus Callosum in Multiple Sclerosis: Association with Disability  

PubMed Central

Background Inflammatory demyelination and axon damage in the corpus callosum are prominent features of multiple sclerosis (MS) and may partially account for impaired performance on complex tasks. Objective To characterize quantitative callosal MRI abnormalities and their association with disability. Methods In 69 participants with MS and 29 healthy volunteers, lesional and extralesional callosal MRI indices were estimated via diffusion tensor tractography. Expanded disability status scale (EDSS) and MS functional composite (MSFC) scores were recorded in 53 of the participants with MS. Results All tested callosal MRI indices were diffusely abnormal in MS. EDSS score was correlated only with age (r=0.51). Scores on the overall MSFC and its paced serial auditory addition test (PASAT) and 9-hole peg test components were correlated with callosal fractional anisotropy (r=0.27, 0.35, 0.31, respectively) and perpendicular diffusivity (r=?0.29, ?0.30, and ?0.31) but not with overall callosal volume or callosal lesion volume; the PASAT score was more weakly correlated with callosal magnetization-transfer ratio (r=0.21). Anterior callosal abnormalities were associated with impaired PASAT performance and posterior abnormalities with slow performance on the 9-hole peg test. Conclusion Abnormalities in the corpus callosum can be assessed with quantitative MRI and are associated with cognitive and complex upper-extremity dysfunction in MS. PMID:20142309

Ozturk, A.; Smith, S. A.; Gordon-Lipkin, E. M.; Harrison, D. M.; Shiee, N.; Pham, D. L.; Caffo, B. S.; Calabresi, P. A.; Reich, D. S.

2009-01-01

23

Fiber Geometry in the Corpus Callosum in Schizophrenia: Evidence for Transcallosal Misconnection  

PubMed Central

Background Structural abnormalities in the callosal fibers connecting the heteromodal association areas of the prefrontal and temporoparietal cortices bilaterally have been suggested to play a role in the etiology of schizophrenia. Aims To investigate for geometric abnormalities in these callosal fibers in schizophrenia patients using a novel Diffusion-Tensor Imaging (DTI) metric of fiber geometry named Shape-Normalized Dispersion (SHD). Methods DTIs (3T, 51 gradient directions, 1.7 mm isotropic voxels) were acquired from 26 schizophrenia patients and 23 matched healthy controls. The prefrontal and temporoparietal fibers of the corpus callosum were extracted by means of whole-brain tractography, and their mean SHD calculated. Results The schizophrenia patients exhibited subnormal levels of SHD in the prefrontal callosal fibers when controlling for between-group differences in Fractional Anisotropy. Reduced SHD could reflect either irregularly turbulent or inhomogeneously distributed fiber trajectories in the corpus callosum. Conclusions The results suggest that the transcallosal misconnectivity believed to be associated with schizophrenia could arise from abnormalities in fiber geometry. These abnormalities in fiber geometry could potentially be underpinned by irregularities in the normative processes of neurodevelopment. PMID:21831601

Whitford, Thomas J.; Savadjiev, Peter; Kubicki, Marek; O'Donnell, Lauren J.; Terry, Douglas P.; Bouix, Sylvain; Westin, Carl-Fredrik; Schneiderman, Jason S.; Bobrow, Laurel; Rausch, Andrew C.; Niznikiewicz, Margaret; Nestor, Paul G.; Pantelis, Christos; Wood, Stephen J.; McCarley, Robert W.; Shenton, Martha E.

2011-01-01

24

Use of fractional anisotropy for determination of the cut-off value in 11C-methionine positron emission tomography for glioma  

Microsoft Academic Search

Multimodal imaging is one of the necessary steps in the treatment of malignant brain tumors, and use of magnetic resonance imaging (MRI) and positron emission tomography (PET) are the current gold standard technique for the morphological and biological assessment of malignant brain tumors. In addition, fractional anisotropy (FA) obtained from diffusion tensor imaging (DTI) and 11C-methionine PET are useful to

Manabu Kinoshita; Naoya Hashimoto; Tetsu Goto; Takufumi Yanagisawa; Yoshiko Okita; Naoki Kagawa; Haruhiko Kishima; Hisashi Tanaka; Norihiko Fujita; Eku Shimosegawa; Jun Hatazawa; Toshiki Yoshimine

2009-01-01

25

Biaxial normal strength behavior in the axial-transverse plane for human trabecular bone--effects of bone volume fraction, microarchitecture, and anisotropy.  

PubMed

The biaxial failure behavior of the human trabecular bone, which has potential relevance both for fall and gait loading conditions, is not well understood, particularly for low-density bone, which can display considerable mechanical anisotropy. Addressing this issue, we investigated the biaxial normal strength behavior and the underlying failure mechanisms for human trabecular bone displaying a wide range of bone volume fraction (0.06-0.34) and elastic anisotropy. Micro-computed tomography (CT)-based nonlinear finite element analysis was used to simulate biaxial failure in 15 specimens (5 mm cubes), spanning the complete biaxial normal stress failure space in the axial-transverse plane. The specimens, treated as approximately transversely isotropic, were loaded in the principal material orientation. We found that the biaxial stress yield surface was well characterized by the superposition of two ellipses--one each for yield failure in the longitudinal and transverse loading directions--and the size, shape, and orientation of which depended on bone volume fraction and elastic anisotropy. However, when normalized by the uniaxial tensile and compressive strengths in the longitudinal and transverse directions, all of which depended on bone volume fraction, microarchitecture, and mechanical anisotropy, the resulting normalized biaxial strength behavior was well described by a single pair of (longitudinal and transverse) ellipses, with little interspecimen variation. Taken together, these results indicate that the role of bone volume fraction, microarchitecture, and mechanical anisotropy is mostly accounted for in determining the uniaxial strength behavior and the effect of these parameters on the axial-transverse biaxial normal strength behavior per se is minor. PMID:24121715

Sanyal, Arnav; Keaveny, Tony M

2013-12-01

26

Early musical training and white-matter plasticity in the corpus callosum: evidence for a sensitive period.  

PubMed

Training during a sensitive period in development may have greater effects on brain structure and behavior than training later in life. Musicians are an excellent model for investigating sensitive periods because training starts early and can be quantified. Previous studies suggested that early training might be related to greater amounts of white matter in the corpus callosum, but did not control for length of training or identify behavioral correlates of structural change. The current study compared white-matter organization using diffusion tensor imaging in early- and late-trained musicians matched for years of training and experience. We found that early-trained musicians had greater connectivity in the posterior midbody/isthmus of the corpus callosum and that fractional anisotropy in this region was related to age of onset of training and sensorimotor synchronization performance. We propose that training before the age of 7 years results in changes in white-matter connectivity that may serve as a scaffold upon which ongoing experience can build. PMID:23325263

Steele, Christopher J; Bailey, Jennifer A; Zatorre, Robert J; Penhune, Virginia B

2013-01-16

27

Thalamic fractional anisotropy predicts accrual of cerebral white matter damage in older subjects with small-vessel disease.  

PubMed

White matter hyperintensities (WMHs) and lacunes are magnetic resonance imaging hallmarks of cerebral small-vessel disease, which increase the risk of stroke, cognitive, and mobility impairment. Although most studies of cerebral small-vessel disease have focused on white matter abnormalities, the gray matter (GM) is also affected, as evidenced by frequently observed lacunes in subcortical GM. Diffusion tensor imaging (DTI) is sensitive to subtle neurodegenerative changes in deep GM structures. We explored the relationship between baseline DTI characteristics of the thalamus, caudate, and putamen, and the volume and subsequent accrual of WMHs over a 4-year period in 56 community-dwelling older (?75 years) individuals. Baseline thalamic fractional anisotropy (FA) was an independent predictor of WMH accrual. WMH accrual also correlated with baseline lacune count and baseline WMH volume, the latter showing the strongest predictive power, explaining 27.3% of the variance. The addition of baseline thalamic FA in multivariate modeling increased this value by 70%, which explains 46.5% of the variance in WMH accrual rate. Thalamic FA might serve as a novel predictor of cerebral small-vessel disease progression in clinical settings and trials. Furthermore, our findings point to the possibility of a causal relationship between thalamic damage and the accrual of WMHs. PMID:24824915

Cavallari, Michele; Moscufo, Nicola; Meier, Dominik; Skudlarski, Pawel; Pearlson, Godfrey D; White, William B; Wolfson, Leslie; Guttmann, Charles R G

2014-08-01

28

Diffusion tensor imaging (DTI) and colored fractional anisotropy (FA) mapping of the subthalamic nucleus (STN) and the globus pallidus interna (GPi)  

Microsoft Academic Search

Introduction  The subthalamic nucleus (STN) and the globus pallidus internus (GPi) are the most common surgical targets for the treatment\\u000a of Parkinson’s disease. We studied directionally colored fractional anisotropy (FA) and diffusion tensor imaging (DTI) sequences\\u000a to better target these anatomical regions.\\u000a \\u000a \\u000a \\u000a \\u000a Methods  Four patients undergoing stereotactic surgery for movement disorders were studied. Stereotactic targets and fiber tractography\\u000a were determined on MRIs

Mark Sedrak; Alessandra Gorgulho; Ausaf Bari; Eric Behnke; Andrew Frew; Inga Gevorkyan; Nader Pouratian; Antonio DeSalles

2010-01-01

29

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

PubMed

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

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

2014-01-01

30

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

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

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

2014-01-01

31

Fractions  

NSDL National Science Digital Library

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.

Blundred, A.

2012-01-01

32

Fractions  

NSDL National Science Digital Library

This interactive Flash applet can be used to compare and explore equivalence among fractions, decimals and percentages. It allows a child or teacher to represent fractions on one or more fraction strips, and to color individual parts. Each displayed strip can be labelled as a fraction, a decimal (to three decimal places) or a percentage; the ratio of yellow to green parts of each strip can also be displayed. It lends itself well to use with an interactive white board. A pdf guide to this collection of teaching applets is cataloged separately.

2006-01-01

33

Corpus Callosum Area in Children and Adults with Autism  

ERIC Educational Resources Information Center

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…

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

34

Fractional anisotropy changes in Alzheimer's disease depend on the underlying fiber tract architecture: a multiparametric DTI study using joint independent component analysis.  

PubMed

Diffusion tensor imaging (DTI) allows the simultaneous measurement of several diffusion indices that provide complementary information on the substrate of white matter alterations in neurodegenerative diseases. These indices include fractional anisotropy (FA) as measure of fiber tract integrity, and the mode of anisotropy (Mode) reflecting differences in the shape of the diffusion tensor. We used a multivariate approach based on joint independent component analysis of FA and Mode in a large sample of 138 subjects with Alzheimer's disease (AD) dementia, 37 subjects with cerebrospinal fluid biomarker positive mild cognitive impairment (MCI-AD), and 153 healthy elderly controls from the European DTI Study on Dementia to comprehensively study alterations of microstructural white matter integrity in AD dementia and predementia AD. We found a parallel decrease of FA and Mode in intracortically projecting fiber tracts, and a parallel increase of FA and Mode in the corticospinal tract in AD patients compared to controls. Subjects with MCI-AD showed a similar, but spatially more restricted pattern of diffusion changes. Our findings suggest an early axonal degeneration in intracortical projecting fiber tracts in dementia and predementia stages of AD. An increase of Mode, parallel to an increase of FA, in the corticospinal tract suggests a more linear shape of diffusion due to loss of crossing fibers along relatively preserved cortico-petal and cortico-fugal fiber tracts in AD. Supporting this interpretation, we found three populations of fiber tracts, namely cortico-petal and cortico-fugal, commissural, and intrahemispherically projecting fiber tracts, in the peak area of parallel FA and Mode increase. PMID:24577476

Teipel, Stefan J; Grothe, Michel J; Filippi, Massimo; Fellgiebel, Andreas; Dyrba, Martin; Frisoni, Giovanni B; Meindl, Thomas; Bokde, Arun L W; Hampel, Harald; Klöppel, Stefan; Hauenstein, Karlheinz

2014-01-01

35

Interhemispheric hypoconnectivity in schizophrenia: fiber integrity and volume differences of the corpus callosum in patients and unaffected relatives.  

PubMed

Changes in hemispheric asymmetry and inter-hemispheric connectivity have been reported in schizophrenia. However, the genetic contribution to these alterations is still unclear. In the current study, we applied an automatic segmentation method to structural MRI and diffusion tensor imaging (DTI) data and examined volume and fiber integrity of the corpus callosum (CC), the main interhemispheric fiber tract, in 16 chronic schizophrenia (SZ) patients, matched first degree relatives and controls. SZ patients and relatives had smaller CC volumes than controls, particularly in the posterior genu, isthmus and splenium. Fractional anisotropy (FA), an indicator of fiber integrity, was reduced in patients and relatives in the whole CC, the inferior genu, the superior genu and the isthmus. Correspondingly, the mean diffusivity (MD) values of the whole CC and the isthmus were higher in patients and their unaffected relatives, indicating decreased compactness and increased intercellular space. Relatives had intermediate values in the volumetric and fiber integrity measurements between patients and controls. Lower CC volume and fiber integrity in SZ patients were associated with more severe auditory hallucinations. These results support the connectivity hypothesis of SZ (Friston, 1998) and particularly highlight the altered interhemispheric connectivity, which appears to be a genetic feature of SZ risk. PMID:21964509

Knöchel, Christian; Oertel-Knöchel, Viola; Schönmeyer, Ralf; Rotarska-Jagiela, Anna; van de Ven, Vincent; Prvulovic, David; Haenschel, Corinna; Uhlhaas, Peter; Pantel, Johannes; Hampel, Harald; Linden, David E J

2012-01-16

36

Diffusion Tensor Tractography Analysis of the Corpus Callosum Fibers in Amyotrophic Lateral Sclerosis  

PubMed Central

Background and Purpose Involvement of the corpus callosum (CC) is reported to be a consistent feature of amyotrophic lateral sclerosis (ALS). We examined the CC pathology using diffusion tensor tractography analysis to identify precisely which fiber bundles are involved in ALS. Methods Diffusion tensor imaging was performed in 14 sporadic ALS patients and 16 age-matched healthy controls. Whole brain tractography was performed using the multiple-region of interest (ROI) approach, and CC fiber bundles were extracted in two ways based on functional and structural relevance: (i) cortical ROI selection based on Brodmann areas (BAs), and (ii) the sulcal-gyral pattern of cortical gray matter using FreeSurfer software, respectively. Results The mean fractional anisotropy (FA) values of the CC fibers interconnecting the primary motor (BA4), supplementary motor (BA6), and dorsolateral prefrontal cortex (BA9/46) were significantly lower in ALS patients than in controls, whereas those of the primary sensory cortex (BA1, BA2, BA3), Broca's area (BA44/45), and the orbitofrontal cortex (BA11/47) did not differ significantly between the two groups. The FreeSurfer ROI approach revealed a very similar pattern of abnormalities. In addition, a significant correlation was found between the mean FA value of the CC fibers interconnecting the primary motor area and disease severity, as assessed using the revised Amyotrophic Lateral Sclerosis Functional Rating Scale, and the clinical extent of upper motor neuron signs. Conclusions Our findings suggest that there is some degree of selectivity or a gradient in the CC pathology in ALS. The CC fibers interconnecting the primary motor and dorsolateral prefrontal cortices may be preferentially involved in ALS. PMID:25045379

Kim, Jee-Eun; Oh, Jungsu S.; Sung, Jung-Joon; Lee, Kwang-Woo

2014-01-01

37

A Preliminary Investigation of Corpus Callosum and Anterior Commissure Aberrations in Aggressive Youth with Bipolar Disorders  

PubMed Central

Abstract Objective Although behavioral deficits in bipolar disorder (BPD) are well described, the specific brain white matter (WM) disruptions have not been completely characterized, and neural mechanisms underlying dysfunction in BPD are not well established, particularly for youth with BPD and aggression. This preliminary study utilized diffusion tensor imaging (DTI) to investigate commissural tracts (corpus callosum [CC] and anterior commissure [AC]) in youth with BPD, because disruption of interhemispheric communication may contribute to the emotional deficits that are characteristic of the illness. Method DTI was used to investigate WM in 10 youth (7–17 years of age) with BPD and 10 typically developing age-matched controls. Tract-based spatial statistics voxel-wise analysis was used to compare fractional anisotropy (FA) of the two groups. We specifically focused on five subdivisions of the midsagittal CC as well as on the decussation of AC, which connects the temporal lobes. Exploratory correlations between FA values and life history of aggression scores were calculated for the BPD group. Results Youth with BPD had significantly lower FA values in the callosal genu and AC. FA values in the AC were negatively correlated with a life history of aggression in the BPD group. Conclusions These results contribute to a growing literature implicating a role for the genu of the CC in BPD and are the first to report WM variations in the AC of children with BPD. Taken together with the correlational data for aggression and the role of the AC in emotional processing, our data provide preliminary evidence for a possible association between the structural integrity of the WM of the AC and aggression in pediatric BPD. PMID:22375854

Tamm, Leanne; Walley, Annie; Simmons, Alex; Rollins, Nancy; Chia, Jonathan; Soares, Jair C.; Emslie, Graham J.; Fan, Xin; Huang, Hao

2012-01-01

38

Diffusion Tensor Anisotropy in Adolescents and Adults  

Microsoft Academic Search

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

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

39

Sirenomelia with agenesis of corpus callosum.  

PubMed

Sirenomelia is a very rare anomaly presented with fusion of the lower limbs. Genitourinary, neural tube, and vertebral anomalies are found in most cases. We report a case of sirenomelia with agenesis of corpus callosum, which has not been reported previously. PMID:16859065

Shirani, Shapour; Rekabi, Vahab; Kamalian, Naser

2006-07-01

40

Fractional anisotropy (FA) changes after several weeks of daily left high frequency rTMS of the prefrontal cortex to treat major depression  

PubMed Central

Objectives As part of a sham controlled treatment trial using daily left rTMS, brain changes associated with four to six weeks of treatment were examined using diffusion tensor imaging (DTI) in order to non-invasively evaluate prefrontal white matter microstructure. A decrease in fractional anisotropy (FA) values of the left prefrontal white matter could indicate damage to the region. Methods DTI was performed prior to and after 4–6 weeks of daily rTMS treatments. Mean FA levels associated with active rTMS and sham rTMS for the right and left prefrontal white matter (LPF-WM) were assessed. Results Adequate images were acquired for eight participants (active n=4, sham n=4) before and after rTMS. A mean increase was found for the LPF-WM. The mixed model revealed a trend toward a significant Treatment Group × Region interaction effect (p=0.11). Further, simple Region effects (left prefrontal WM vs. right prefrontal WM) were at a trend toward significance for difference after treatment within the active rTMS group (p=.07), but not within the sham rTMS group (p=.88). Conclusions RTMS resulted in no evidence of damage to WM on the side of stimulation. DTI may offer a unique modality to increase our understanding of mechanisms of action for rTMS. PMID:20559144

Kozel, F. Andrew; Johnson, Kevin A.; Nahas, Ziad; Nakonezny, Paul A.; Morgan, Paul S.; Anderson, Berry; Kose, Samet; Li, Xingbao; Lim, Kelvin O.; Trivedi, Madhukar; George, Mark S.

2010-01-01

41

Effects of SNR on the Accuracy and Reproducibility of DTI-derived Fractional Anisotropy, Mean Diffusivity, and Principal Eigenvector Measurements at 1.5T  

PubMed Central

Purpose To develop an experimental protocol to calculate the precision and accuracy of fractional anisotropy (FA), mean diffusivity (MD), and the orientation of the principal eigenvector (PEV) as a function of the signal to noise ratio (SNR) in vivo. Materials and Methods A healthy male volunteer was scanned in three separate scanning sessions, yielding a total of 45 DTI scans. To provide FA, MD, and PEV as a function of SNR, sequential scans from a scan session were grouped into non-intersecting sets. Analysis of the accuracy and precision of the DTI-derived contrasts was done in both a voxel-wise and ROI-based manner. Results An upward bias of FA and no significant bias in MD were present as SNR decreased, confirming results from simulation-based studies. Notably, while the precision of the PEV became worse at low SNR, no bias in the PEV orientation was observed. Overall, an accurate and precise quantification of FA values in GM requires substantially more SNR than the quantification of WM FA values Conclusion This study provides guidance for FA, MD, and PEV quantification and a means to investigate the minimal detectable differences within and across scan sessions as a function of SNR. PMID:17729339

Farrell, Jonathan A.D.; Landman, Bennett A.; Jones, Craig K.; Smith, Seth A.; Prince, Jerry L.; van Zijl, Peter C.M.; Mori, Susumu

2010-01-01

42

Alteration of Fractional Anisotropy and Mean Diffusivity in Glaucoma: Novel Results of a Meta-Analysis of Diffusion Tensor Imaging Studies  

PubMed Central

Objectives We hypothesized that a meta-analysis of existing studies may help to reveal significant changes on diffusion tensor imaging (DTI) in patients with glaucoma. Therefore, a meta-analysis was utilized to investigate the possibility that DTI can detect white matter damage in patients with glaucoma. Methods The study design and report adhered to the PRISMA Statement guidelines. DTI studies that compared glaucoma patients and controls were surveyed using PubMed, Web of Science and EMBASE (January 2008 to September 2013). Stata was used to analyze the decrease in fractional anisotropy (FA) and increase in mean diffusivity (MD) in the optic nerve and optic radiation in patients with glaucoma. Results Eleven DTI studies were identified through a comprehensive literature search, and 10 independent DTI studies of glaucoma patients were eligible for the meta-analysis. A random effects model revealed a significant FA reduction in the optic nerve and optic radiation, as well as a significant MD increase in the tracts. A heterogeneity analysis suggested that FA may be related to glaucoma severity. Conclusions Our findings revealed that the optic nerve and optic radiation were vulnerable regions in patients with glaucoma and that FA may be correlated with glaucoma severity and age. Furthermore, this study suggests that magnetic resonance imaging in patients with glaucoma may help to provide objective evidence to aid in the diagnosis and management of glaucoma. PMID:24828063

Li, Ke; Lu, Cuixin; Huang, Yufei; Yuan, Li; Zeng, Dong; Wu, Kan

2014-01-01

43

Use of fractional anisotropy for determination of the cut-off value in 11C-methionine positron emission tomography for glioma.  

PubMed

Multimodal imaging is one of the necessary steps in the treatment of malignant brain tumors, and use of magnetic resonance imaging (MRI) and positron emission tomography (PET) are the current gold standard technique for the morphological and biological assessment of malignant brain tumors. In addition, fractional anisotropy (FA) obtained from diffusion tensor imaging (DTI) and 11C-methionine PET are useful to determine the tumor border at the tumor and white matter interface. Although there is no question of their value, a universally accepted cut-off value to discriminate normal and abnormal tissue has not been established. In this study we attempted to calculate and determine the cut-off values in FA and 11C-methionine PET that will allow delineation of the tumor border at the tumor and white matter interface by combining these two modalities. We were able to determine individual cut-off values for 11 patients, and then found an average cut-off value in the T/N ratio of 11C-methionine PET of 1.27 and in FA of 0.26, values similar to those previously confirmed by histological study. Moreover, reconstructing images delineating the tumor border was possible combining these two imaging modalities. We propose that the combined analysis of DTI and 11C-methionine PET has the potential to improve tumor border imaging in glioma patients, providing important information for establishing neurosurgical strategies. PMID:19111621

Kinoshita, Manabu; Hashimoto, Naoya; Goto, Tetsu; Yanagisawa, Takufumi; Okita, Yoshiko; Kagawa, Naoki; Kishima, Haruhiko; Tanaka, Hisashi; Fujita, Norihiko; Shimosegawa, Eku; Hatazawa, Jun; Yoshimine, Toshiki

2009-04-01

44

Predicting Inter-Hemispheric Transfer Time from the Diffusion Properties of the Corpus Callosum in Healthy Individuals and Schizophrenia Patients: A Combined ERP and DTI Study  

PubMed Central

Background Several theories of schizophrenia have emphasized the role of aberrant neural timing in the etiology of the disease, possibly as a consequence of conduction delays caused by structural damage to the white-matter fasciculi. Consistent with this theory, increased inter-hemispheric transmission times (IHTTs) to unilaterally-presented visual stimuli have been reported in patients with schizophrenia. The present study investigated whether or not these IHTT abnormalities could be underpinned by structural damage to the visual fibers of the corpus callosum. Methods 30 schizophrenia patients and 22 matched controls underwent Event Related Potential (ERP) recording, and a subset of 19 patients and 16 controls also underwent 3T Diffusion-Tensor Imaging (DTI). Unilateral visual stimuli (squares, 2 × 2 degrees) were presented 6 degrees lateral to either side of a central fixation point. IHTTs (ipsilateral minus contralateral latencies) were calculated for the P1 and N1 components at occipital-temporal sites in current source density-transformed ERPs. The visual fibers of the corpus callosum were extracted with streamline tractography and the diffusion metrics of Fractional Anisotropy (FA) and Mode calculated. Results While both subject groups exhibited highly significant IHTTs across a range of posterior electrode pairs, and significantly shorter IHTTs from left-to-right hemisphere than vice versa, no significant groupwise differences in IHTT were observed. However, participants’ IHTTs were linearly related to their FA and Mode, with longer IHTTs being associated with lower FA and more prolate diffusion ellipsoids. Conclusions These results suggest that IHTTs are estimable from DTI measures of white matter integrity. In light of the range of diffusion abnormalities that have been reported in patients with schizophrenia, particularly in frontal fasciculi, these results support the conjecture that schizophrenia is ultimately underpinned by abnormalities in neural timing. PMID:20977941

Whitford, Thomas J.; Kubicki, Marek; Ghorashi, Shahab; Schneiderman, Jason S.; Hawley, Kathryn J.; McCarley, Robert W.; Shenton, Martha E.; Spencer, Kevin M.

2010-01-01

45

Multi-site study of additive genetic effects on fractional anisotropy of cerebral white matter: Comparing meta and megaanalytical approaches for data pooling.  

PubMed

Combining datasets across independent studies can boost statistical power by increasing the numbers of observations and can achieve more accurate estimates of effect sizes. This is especially important for genetic studies where a large number of observations are required to obtain sufficient power to detect and replicate genetic effects. There is a need to develop and evaluate methods for joint-analytical analyses of rich datasets collected in imaging genetics studies. The ENIGMA-DTI consortium is developing and evaluating approaches for obtaining pooled estimates of heritability through meta-and mega-genetic analytical approaches, to estimate the general additive genetic contributions to the intersubject variance in fractional anisotropy (FA) measured from diffusion tensor imaging (DTI). We used the ENIGMA-DTI data harmonization protocol for uniform processing of DTI data from multiple sites. We evaluated this protocol in five family-based cohorts providing data from a total of 2248 children and adults (ages: 9-85) collected with various imaging protocols. We used the imaging genetics analysis tool, SOLAR-Eclipse, to combine twin and family data from Dutch, Australian and Mexican-American cohorts into one large "mega-family". We showed that heritability estimates may vary from one cohort to another. We used two meta-analytical (the sample-size and standard-error weighted) approaches and a mega-genetic analysis to calculate heritability estimates across-population. We performed leave-one-out analysis of the joint estimates of heritability, removing a different cohort each time to understand the estimate variability. Overall, meta- and mega-genetic analyses of heritability produced robust estimates of heritability. PMID:24657781

Kochunov, Peter; Jahanshad, Neda; Sprooten, Emma; Nichols, Thomas E; Mandl, René C; Almasy, Laura; Booth, Tom; Brouwer, Rachel M; Curran, Joanne E; de Zubicaray, Greig I; Dimitrova, Rali; Duggirala, Ravi; Fox, Peter T; Elliot Hong, L; Landman, Bennett A; Lemaitre, Hervé; Lopez, Lorna M; Martin, Nicholas G; McMahon, Katie L; Mitchell, Braxton D; Olvera, Rene L; Peterson, Charles P; Starr, John M; Sussmann, Jessika E; Toga, Arthur W; Wardlaw, Joanna M; Wright, Margaret J; Wright, Susan N; Bastin, Mark E; McIntosh, Andrew M; Boomsma, Dorret I; Kahn, René S; den Braber, Anouk; de Geus, Eco J C; Deary, Ian J; Hulshoff Pol, Hilleke E; Williamson, Douglas E; Blangero, John; van 't Ent, Dennis; Thompson, Paul M; Glahn, David C

2014-07-15

46

Brain-behavior relationships in young traumatic brain injury patients: fractional anisotropy measures are highly correlated with dynamic visuomotor tracking performance.  

PubMed

Traumatic brain injury (TBI) patients have a high incidence of eye-hand coordination deficits. Diffuse axonal injury is common in TBI and is presumed to contribute to persistent motor problems. Using Diffusion Tensor Imaging (DTI), this study sought to identify changes in (sensori)motor white matter (WM) pathways/regions in a TBI group during the chronic recovery stage. A secondary objective was to examine the relationship between WM integrity and upper-limb visuomotor tracking performance. A young TBI (n=17) and control (n=14) group performed a dynamic tracking task, characterized by increasing information processing speed and predictive movement control. DTI scans were administered along with standard anatomical scans. The TBI group was found to perform inferior to the control group on the tracking task. Decreased fractional anisotropy was found in the TBI group in dedicated pathways involved in transmission of afferent and efferent information, i.e., corticospinal tract, posterior thalamic radiation, and optic radiation, due to increased diffusivity parallel and perpendicular to axonal fibre direction. This decrease in WM integrity was associated with inferior visuomotor tracking performance. Moreover, discriminant function analysis demonstrated that the model, based on the combined application of DTI and behavioral measures, was the most effective in distinguishing between TBI patients and controls. This study shows that specific eye-hand coordination deficits in a young TBI group are related to microstructural abnormalities in task-specific cerebral WM structures. Measures of white matter integrity are potentially important biomarkers for TBI that may support prognosis of motor deficits. PMID:20117121

Caeyenberghs, K; Leemans, A; Geurts, M; Taymans, T; Vander Linden, C; Smits-Engelsman, B C M; Sunaert, S; Swinnen, S P

2010-04-01

47

Left hemisphere fractional anisotropy increase in noise-induced tinnitus: a diffusion tensor imaging (DTI) study of white matter tracts in the brain.  

PubMed

Diffusion tensor imaging (DTI) is a contemporary neuroimaging modality used to study connectivity patterns and microstructure of white matter tracts in the brain. The use of DTI in the study of tinnitus is a relatively unexplored methodology with no studies focusing specifically on tinnitus induced by noise exposure. In this investigation, participants were two groups of adults matched for etiology, age, and degree of peripheral hearing loss, but differed by the presence or absence (+/-) of tinnitus. It is assumed that matching individuals on the basis of peripheral hearing loss, allows for differentiating changes in white matter microstructure due to hearing loss from changes due to the effects of chronic tinnitus. Alterations in white matter tracts, using the fractional anisotropy (FA) metric, which measures directional diffusion of water, were quantified using tract-based spatial statistics (TBSS) with additional details provided by in vivo probabilistic tractography. Our results indicate that 10 voxel clusters differentiated the two groups, including 9 with higher FA in the group with tinnitus. A decrease in FA was found for a single cluster in the group with tinnitus. However, seven of the 9 clusters with higher FA were in left hemisphere thalamic, frontal, and parietal white matter. These foci were localized to the anterior thalamic radiations and the inferior and superior longitudinal fasciculi. The two right-sided clusters with increased FA were located in the inferior fronto-occipital fasciculus and superior longitudinal fasciculus. The only decrease in FA for the tinnitus-positive group was found in the superior longitudinal fasciculus of the left parietal lobe. PMID:24212050

Benson, Randall R; Gattu, Ramtilak; Cacace, Anthony T

2014-03-01

48

The corpus callosum: white matter or terra incognita  

PubMed Central

The corpus callosum is the largest white matter structure in the brain, consisting of 200–250 million contralateral axonal projections and the major commissural pathway connecting the hemispheres of the human brain. The pathology of the corpus callosum includes a wide variety of entities that arise from different causes such as congenital, inflammatory, tumoural, degenerative, infectious, metabolic, traumatic, vascular and toxic agents. The corpus callosum, or a specific part of it, can be affected selectively. Numerous pathologies of the corpus callosum are encountered during CT and MRI. The aim of this study is to facilitate a better understanding and thus treatment of the pathological entities of the corpus callosum by categorising them according to their causes and their manifestations in MR and CT imaging. Familiarity with its anatomy and pathology is important to the radiologist in order to recognise its disease at an early stage and help the clinician establish the optimal therapeutic approach. PMID:21172964

Fitsiori, A; Nguyen, D; Karentzos, A; Delavelle, J; Vargas, M I

2011-01-01

49

Corpus callosum microstructural changes correlate with cognitive dysfunction in early stages of relapsing-remitting multiple sclerosis: axial and radial diffusivities approach.  

PubMed

The corpus callosum is the largest fiber bundle in the central nervous system and it takes part in several cognitive pathways. It can be affected by multiple sclerosis (MS) early in the disease. DTI is capable of infering the microstructural organization of the white matter. The vectorial analysis of the DTI offers the more specific indices of axial diffusivity (AD) and radial diffusivity (RD), which have shown to be useful to discriminate myelin damage from axon loss, respectively. This study presents DTI results (mean diffusivity (MD), fractional anisotropy (FA), RD, and AD) of 23 relapsing-remitting MS patients and its correlation with cognitive performance. There were 47.8% of cognitive impaired patients (MS CI). We found signs of demyelination, reflected by increased RD, and incipient axon loss, reflected by AD increase, which was slightly higher in the MS CI. The cognitive changes correlated with the DTI parameters, suggesting that loss of complexity in CC connections can impair neural conduction. Thus, cognitive impairment can be related to callosal disconnection, and DTI can be a promising tool to evaluate those changes. PMID:22096634

Rimkus, Carolina de Medeiros; Junqueira, Thiago de Faria; Lyra, Katarina Paz; Jackowski, Marcel P; Machado, Melissa A R; Miotto, Eliane C; Callegaro, Dagoberto; Otaduy, Maria Concepción García; Leite, Claudia da Costa

2011-01-01

50

Working Memory and Corpus Callosum Microstructural Integrity after Pediatric Traumatic Brain Injury: A Diffusion Tensor Tractography Study  

PubMed Central

Abstract Deficits in working memory (WM) are a common consequence of pediatric traumatic brain injury (TBI) and are believed to contribute to difficulties in a range of cognitive and academic domains. Reduced integrity of the corpus callosum (CC) after TBI may disrupt the connectivity between bilateral frontoparietal neural networks underlying WM. In the present investigation, diffusion tensor imaging (DTI) tractography of eight callosal subregions (CC1–CC8) was examined in relation to measures of verbal and visuospatial WM in 74 children sustaining TBI and 49 typically developing comparison children. Relative to the comparison group, children with TBI demonstrated poorer visuospatial WM, but comparable verbal WM. Microstructure of the CC was significantly compromised in brain-injured children, with lower fractional anisotropy (FA) and higher axial and radial diffusivity metrics in all callosal subregions. In both groups of children, lower FA and/or higher radial diffusivity in callosal subregions connecting anterior and posterior parietal cortical regions predicted poorer verbal WM, whereas higher radial diffusivity in callosal subregions connecting anterior and posterior parietal, as well as temporal, cortical regions predicted poorer visuospatial WM. DTI metrics, especially radial diffusivity, in predictive callosal subregions accounted for significant variance in WM over and above remaining callosal subregions. Reduced microstructural integrity of the CC, particularly in subregions connecting parietal and temporal cortices, may act as a neuropathological mechanism contributing to long-term WM deficits. The future clinical use of neuroanatomical biomarkers may allow for the early identification of children at highest risk for WM deficits and earlier provision of interventions for these children. PMID:23627735

Treble, Amery; Hasan, Khader M.; Iftikhar, Amal; Stuebing, Karla K.; Kramer, Larry A.; Cox, Charles S.; Swank, Paul R.

2013-01-01

51

Metabolic Levels in the Corpus Callosum and Their Structural and Behavioral Correlates after Moderate to Severe Pediatric TBI  

PubMed Central

Abstract Diffuse axonal injury (DAI) secondary to traumatic brain injury (TBI) contributes to long-term functional morbidity. The corpus callosum (CC) is particularly vulnerable to this type of injury. Magnetic resonance spectroscopy (MRS) was used to characterize the metabolic status of two CC regions of interest (ROIs) (anterior and posterior), and their structural (diffusion tensor imaging; DTI) and neurobehavioral (neurocognitive functioning, bimanual coordination, and interhemispheric transfer time [IHTT]) correlates. Two groups of moderate/severe TBI patients (ages 12–18 years) were studied: post-acute (5 months post-injury; n?=?10), and chronic (14.7 months post-injury; n?=?8), in addition to 10 age-matched healthy controls. Creatine (energy metabolism) did not differ between groups across both ROIs and time points. In the TBI group, choline (membrane degeneration/inflammation) was elevated for both ROIs at the post-acute but not chronic period. N-acetyl aspartate (NAA) (neuronal/axonal integrity) was reduced initially for both ROIs, with partial normalization at the chronic time point. Posterior, not anterior, NAA was positively correlated with DTI fractional anisotropy (FA) (r?=?0.88), and most domains of neurocognition (r range 0.22–0.65), and negatively correlated with IHTT (r?=??0.89). Inverse corerlations were noted between creatine and posterior FA (r?=??0.76), neurocognition (r range ?0.22 to ?0.71), and IHTT (r?=?0.76). Multimodal studies at distinct time points in specific brain structures are necessary to delineate the course of the degenerative and reparative processes following TBI, which allows for preliminary hypotheses about the nature and course of the neural mechanisms of subsequent functional morbidity. This will help guide the future development of targeted therapeutic agents. PMID:19925210

Marion, Sarah DeBoard; Copeland, Sarah; Alger, Jeffry R.; O'Neill, Joseph; Cazalis, Fabienne; Mink, Richard; Giza, Christopher C.; Vu, Jennifer A.; Hilleary, Suzanne M.; Kernan, Claudia L.; Newman, Nina; Asarnow, Robert F.

2010-01-01

52

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

PubMed

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

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

2012-01-01

53

Corpus callosum size in schizophrenia – a magnetic resonance imaging analysis  

Microsoft Academic Search

Previous MRI studies have shown differences in corpus callosum size between schizophrenic patients and controls. The corpus\\u000a callosum (CC), as the main interhemispheric fiber tract, plays an important role in interhemispheric integration and communication.\\u000a Though MRI studies suggest smaller CC in schizophrenia, there are still conflicting findings. Using in vivo magnetic resonance\\u000a imaging, it was investigated whether the midsagittal area

E. M. Meisenzahl; T. Frodl; J. Greiner; G. Leinsinger; K.-P. Maag; D. Heiss; K. Hahn; U. Hegerl; H.-J. Möller

1999-01-01

54

Morphometric Changes of the Corpus Callosum in Congenital Blindness  

PubMed Central

We examined the effects of visual deprivation at birth on the development of the corpus callosum in a large group of congenitally blind individuals. We acquired high-resolution T1-weighted MRI scans in 28 congenitally blind and 28 normal sighted subjects matched for age and gender. There was no overall group effect of visual deprivation on the total surface area of the corpus callosum. However, subdividing the corpus callosum into five subdivisions revealed significant regional changes in its three most posterior parts. Compared to the sighted controls, congenitally blind individuals showed a 12% reduction in the splenium, and a 20% increase in the isthmus and the posterior part of the body. A shape analysis further revealed that the bending angle of the corpus callosum was more convex in congenitally blind compared to the sighted control subjects. The observed morphometric changes in the corpus callosum are in line with the well-described cross-modal functional and structural neuroplastic changes in congenital blindness. PMID:25255324

Tomaiuolo, Francesco; Campana, Serena; Collins, D. Louis; Fonov, Vladimir S.; Ricciardi, Emiliano; Sartori, Giuseppe; Pietrini, Pietro; Kupers, Ron; Ptito, Maurice

2014-01-01

55

In vivo measurement of axon diameter distribution in the corpus callosum of rat brain  

PubMed Central

Here, we present the first in vivo non-invasive measurement of the axon diameter distribution in the rat corpus callosum. Previously, this measurement was only possible using invasive histological methods. The axon diameter, along with other physical properties, such as the intra-axonal resistance, membrane resistance and capacitance etc. helps determine many important functional properties of nerves, such as their conduction velocity. In this work, we provide a novel magnetic resonance imaging method called AxCaliber, which can resolve the distinct signatures of trapped water molecules diffusing within axons as well as water molecules diffusing freely within the extra-axonal space. Using a series of diffusion weighted magnetic resonance imaging brain scans, we can reliably infer both the distribution of axon diameters and the volume fraction of these axons within each white matter voxel. We were able to verify the known microstructural variation along the corpus callosum of the rat from the anterior (genu) to posterior (splenium) regions. AxCaliber yields a narrow distribution centered ?1 ?m in the genu and splenium and much broader distributions centered ?3 ?m in the body of the corpus callosum. The axon diameter distribution found by AxCaliber is generally broader than those usually obtained by histology. One factor contributing to this difference is the significant tissue shrinkage that results from histological preparation. To that end, AxCaliber might provide a better estimate of the in vivo morphology of white matter. Being a magnetic resonance imaging based methodology, AxCaliber has the potential to be used in human scanners for morphological studies of white matter in normal and abnormal development, and white matter related diseases. PMID:19403788

Barazany, Daniel; Basser, Peter J.

2009-01-01

56

Characterization of the corpus callosum in very preterm and full-term infants utilizing MRI  

Microsoft Academic Search

The corpus callosum is the largest white matter tract, important for interhemispheric communication. The aim of this study was to investigate and compare corpus callosum size, shape and diffusion characteristics in 106 very preterm infants and 22 full-term infants. Structural and diffusion magnetic resonance images were obtained at term equivalent. The corpus callosum was segmented, cross-sectional areas were calculated, and

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

2011-01-01

57

Longitudinal Changes in the Corpus Callosum following Pediatric Traumatic Brain Injury  

PubMed Central

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 such as volume and microstructural changes develop over time following pediatric TBI, and their relation to a measure of processing speed is the focus of this longitudinal investigation. As such, DTI and volumetric changes in the CC in participants with TBI and a comparison group at approximately 3 and 18 months after injury as well as their relation to processing speed were determined. Methods Forty-eight children and adolescents aged 7–17 years who sustained either complicated mild or moderate-to-severe TBI (n = 23) or orthopedic injury (OI; n = 25) were studied. The participants underwent brain MRI and were administered the Eriksen flanker task at both time points. Results At 3 months after injury, there were significant group differences in DTI metrics in the total CC and its subregions (genu/anterior, body/central and splenium/posterior), with the TBI group demonstrating significantly lower fractional anisotropy (FA) and a higher apparent diffusion coefficient (ADC) in comparison to the OI group. These group differences were also present at 18 months after injury in all CC subregions, with lower FA and a higher ADC in the TBI group. In terms of longitudinal changes in DTI, despite the group difference in mean FA, both groups generally demonstrated a modest increase in FA over time though this increase was only significant in the splenium/posterior subregion. Interestingly, the TBI group also generally demonstrated ADC increases from 3 to 18 months though the OI group demonstrated ADC decreases over time. Volumetrically, the group differences at 3 months were marginal for the midanterior and body/central subregions and total CC. However, by 18 months, the TBI group demonstrated a significantly decreased volume in all subregions except the splenium/posterior area relative to the OI group. Unlike the OI group, which showed a significant volume increase in subregions of the CC over time, the TBI group demonstrated a significant and consistent volume decrease. Performance on a measure of processing speed did not differentiate the groups at either visit, and only the OI group showed significantly improved performance over time. Processing speed was related to FA in the splenium/posterior and total CC only in the TBI group on both occasions, with a stronger relation at 18 months. Conclusion In response to TBI, macrostructural volume loss in the CC occurred over time; yet, at the microstructural level, DTI demonstrated both indicators of continued maturation and development even in the damaged CC, as well as evidence of potential degenerative change. Unlike volumetrics, which likely reflects the degree of overall neuronal loss and axonal damage, DTI may reflect some aspects of postinjury maturation and adaptation in white matter following TBI. Multimodality imaging studies may be important to further understand the long-term consequences of pediatric TBI. PMID:20948181

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

2011-01-01

58

Diffusion tensor imaging of normal white matter maturation from late childhood to young adulthood: voxel-wise evaluation of mean diffusivity, fractional anisotropy, radial and axial diffusivities, and correlation with reading development.  

PubMed

Using diffusion tensor MR imaging (DTI) and advanced voxel-wise analysis tools, we study diffusivity and anisotropy changes of white matter from late childhood to young adulthood, and correlate quantitative diffusion indices with Chinese and English reading performance scores. Seventy-five normal healthy school going ethnic Chinese students and young adults of three age groups were recruited (group 1, n=24, mean+/-SD=7.4+/-0.3 years; group 2, n=27, mean+/-SD=10.3+/-0.5 years; group 3, n=24, mean+/-SD=22.8+/-2.3 years). DTI was performed with 3 mm isotropic resolution to cover the entire brain. Voxel-wise analysis was performed using Tract-Based Spatial Statistics (TBSS) to localize regions of white matter showing significant changes of fractional anisotropy (FA), mean diffusivity (MD), and axial and radial diffusivities between groups. We found increased FA and decreased MD with increasing age in regions of cerebellar white matter, right temporal white matter, and a large portion of the superior frontal and parietal white matter driven by both the reduction of radial diffusivity and axial diffusivity with the former to a greater extent. Changes were continual from late childhood to young adulthood. Findings were confirmed by region-of-interest analysis in specific white matter tracts. After controlling for the effect of age, significant correlation was found between diffusion indices of the anterior limb of the left internal capsule and Chinese reading score (p=0.05), and of the corona radiata and English reading score (p=0.026 and p=0.029 for left and right, respectively). These DTI indices likely reflect the multiple biological processes that occur during brain development which provide the neural substrate for ongoing functional connectivity including for reading development. PMID:18395471

Qiu, Deqiang; Tan, Li-Hai; Zhou, Ke; Khong, Pek-Lan

2008-06-01

59

Commissurotomy of the Corpus Callosum and the Remedial Reader.  

ERIC Educational Resources Information Center

Testimony presented at a congressional hearing on illiteracy (March 1986) indicated that good readers use their myelinated corpus callosum fibers (which connect the left and right hemispheres of the brain) at millisecond speeds to coordinate the two brain hemispheres. Students taught using the whole-word recognition method (also called the…

Albert, Elaine

60

Perspectives on Dichotic Listening and the Corpus Callosum  

ERIC Educational Resources Information Center

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,…

Musiek, Frank E.; Weihing, Jeffrey

2011-01-01

61

Corpus callosum atrophy and neuropsychological outcome following carbon monoxide poisoning  

Microsoft Academic Search

This study assessed the effects of carbon monoxide (CO) poisoning on the corpus callosum (CC). Sixty-two CO-poisoned patients had MRI scans and a battery of neuropsychological tests within 24 h (day of exposure) of CO poisoning and at 6 months post CO exposure. Serial quantitative magnetic resonance imaging (QMRI) analysis of the CC was carried out, with the day of

Scott S Porter; Ramona O Hopkins; Lindell K Weaver; Erin D Bigler; Duane D Blatter

2002-01-01

62

Corpus Callosum Anatomy in Chronically Treated and Stimulant Naive ADHD  

ERIC Educational Resources Information Center

Objective: To determine the effect of chronic stimulant treatment on corpus callosum (CC) size in children with ADHD using volumetric and area measurements. Previously published research indicated possible medication effects on specific areas of the CC. Method: Measurements of the CC from anatomical MRIs were obtained from children aged 9-16 in…

Schnoebelen, Sarah; Semrud-Clikeman, Margaret; Pliszka, Steven R.

2010-01-01

63

Autism Traits in Individuals with Agenesis of the Corpus Callosum  

ERIC Educational Resources Information Center

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 =…

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

64

The corpus callosum: a commissural road to anger and aggression.  

PubMed

According to the frontal cortical asymmetry model of motivational direction, anger and aggression are associated with approach motivation and a dominant left frontal hemisphere. Functional interhemispheric connectivity has been proposed as a possible mechanism that could explain the frontal cortical asymmetry of anger and aggression. Reciprocal interactions between the cerebral hemispheres are primarily established by the corpus callosum which is the largest white matter bundle of the human brain. Experimental brain research has now provided evidence for callosal involvement in approach-motivation. In line with the frontal cortical asymmetry model of motivational direction, differences in the direction of interhemispheric signal transfer are proposed to contribute to anger and aggression. It is concluded that the human corpus callosum provides a possible neuroanatomical correlate for frontal cortical asymmetries and that interhemispheric signal transfer plays a role in the emergence of approach-related motivation and behaviour. PMID:23911937

Schutter, Dennis J L G; Harmon-Jones, Eddie

2013-12-01

65

Thickness profile generation for the corpus callosum using Laplace's equation.  

PubMed

The corpus callosum facilitates communication between the cerebral hemispheres. Morphological abnormalities of the corpus callosum have been identified in numerous psychiatric and neurological disorders. To quantitatively analyze the thickness profile of the corpus callosum, we adapted an automatic thickness measurement method, which was originally used on magnetic resonance (MR) images of the cerebral cortex (Hutton et al. [2008]: NeuroImage 40:1701-10; Jones et al. [2002]: Hum Brain Mapp 11:12-32; Schmitt and Böhme [2002]: NeuroImage 16:1103-9; Yezzi and Prince [2003]: IEEE Trans Med Imaging 22:1332-9), to MR images of the corpus callosum. The thickness model was derived by computing a solution to Laplace's equation evaluated on callosal voxels. The streamlines from this solution form non-overlapping, cross-sectional contours the lengths of which are modeled as the callosal thickness. Apart from the semi-automated segmentation and endpoint selection procedures, the method is fully automated, robust, and reproducible. We compared the Laplace method with the orthogonal projection technique previously published (Walterfang et al. [2009a]: Psych Res Neuroimaging 173:77-82; Walterfang et al. [2008a]: Br J Psychiatry 192:429-34; Walterfang et al. [2008b]: Schizophr Res 103:1-10) on a cohort of 296 subjects, composed of 86 patients with chronic schizophrenia (CSZ), 110 individuals with first-episode psychosis, 100 individuals at ultra-high risk for psychosis (UHR; 27 of whom later developed psychosis, UHR-P, and 73 who did not, UHR-NP), and 55 control subjects (CTL). We report similar patterns of statistically significant differences in regional callosal thickness with respect to the comparisons CSZ vs. CTL, UHR vs. CTL, UHR-P vs. UHR-NP, and UHR vs. CTL. PMID:21305661

Adamson, Christopher L; Wood, Amanda G; Chen, Jian; Barton, Sarah; Reutens, David C; Pantelis, Christos; Velakoulis, Dennis; Walterfang, Mark

2011-12-01

66

The development of the corpus callosum in semilobar and lobar holoprosencephaly  

Microsoft Academic Search

Objective  The objective of this study was to determine whether and how a true corpus callosum develops in milder cases of holoprosencephaly.\\u000a \\u000a \\u000a \\u000a Materials and methods  The MR scans of seven patients with holoprosencephaly and a callosum-like structure were reviewed. The anatomy of the callosum-like\\u000a structure and the pericallosal anatomy were evaluated.\\u000a \\u000a \\u000a \\u000a Results  Six of the seven cases had a posterior corpus callosum. The

David Rubinstein; Ana G. Cajade-Law; Vicky Youngman; Joseph M. Hise; Mark Baganz

1996-01-01

67

Automated Diagnosis of Autism Using Fourier Series Expansion of Corpus Callosum Boundary  

E-print Network

' & $ % Automated Diagnosis of Autism Using Fourier Series Expansion of Corpus Callosum Boundary diagnostic tool for detecting autism based on MRI measurements. Since the two previous structural imaging

Chung, Moo K.

68

Corpus Callosum and Prefrontal Functions in Adolescents with History of Very Preterm Birth  

ERIC Educational Resources Information Center

Very preterm (VPT) birth can account for thinning of the corpus callosum and poorer cognitive performance. Research findings about preterm and VPT adolescents usually describe a small posterior corpus callosum, although our research group has also found reductions of the anterior part, specifically the genu. The aim of the present study was to…

Narberhaus, Ana; Segarra, Dolors; Caldu, Xavier; Gimenez, Monica; Pueyo, Roser; Botet, Francesc; Junque, Carme

2008-01-01

69

A Multi-Scale Spectral Image Segmentation Method for Corpus Callosum Classification in MR Images  

E-print Network

A Multi-Scale Spectral Image Segmentation Method for Corpus Callosum Classification in MR Images visible structure contained within MR images whose function is to connect the left hemisphere of the brain callosum is of particular interest to the medical profession in the context of neurological diseases

Coenen, Frans

70

Suicidal behavior is associated with reduced corpus callosum area. Cyprien Fabienne*1,2,3  

E-print Network

1 Suicidal behavior is associated with reduced corpus callosum area. Cyprien Fabienne*1 45 79 Email: sylvaine.artero@inserm.fr Key Words: corpus callosum, suicidal behavior, magnetic. As such deficits are also found in suicidal behavior, we investigated specifically the association between CC

Paris-Sud XI, Université de

71

A study of the reproducibility and etiology of diffusion anisotropy differences in developmental stuttering: a potential role for impaired myelination  

PubMed Central

Several diffusion tensor imaging (DTI) studies have reported fractional anisotropy (FA) reductions within the left perisylvian white matter (WM) of persistent developmental stutterers (PSs). However, these studies have not reached the same conclusions in regard to the presence, spatial distribution (focal/ diffuse), and directionality (elevated/reduced) of FA differences outside of the left perisylvian region. In addition, supplemental DTI measures (axial and radial diffusivities, diffusion trace) have yet to be utilized to examine the potential etiology of these FA reductions. Therefore, the present study sought to reexamine earlier findings through a sex- and age-controlled replication analysis and then to extend these findings with the aforementioned non-FA measures. The replication analysis showed that robust FA reductions in PSs were largely focal, left hemispheric, and within late-myelinating associative and commissural fibers (division III of the left superior longitudinal fasciculus, callosal body, forceps minor of the corpus callosum). Additional DTI measures revealed that these FA reductions were attributable to an increase in diffusion perpendicular to the affected fiber tracts (elevated radial diffusivity). These findings suggest a hypothesis that will be testable in future studies: that myelogenesis may be abnormal in PSs within left-hemispheric fiber tracts that begin a prolonged course of myelination in the first postnatal year. PMID:20471482

Cykowski, M.D.; Fox, P.T.; Ingham, R.J.; Ingham, J.C.; Robin, D.A.

2011-01-01

72

Corpus Callosum Differences associated with Persistent Stuttering in Adults  

PubMed Central

Recent studies have implicated anatomical differences in speech-relevant brain regions of adults who stutter (AWS) compared to normally fluent adults (NFA). The present study focused on the region of the corpus callosum (CC) which is involved in interhemispheric processing between the left and right cerebral hemispheres. Two-dimensional segmentation of area and voxel based morphometry were used to evaluate the corpus callosum. Results revealed that the rostrum and anterior midbody of the CC was larger in AWS than NFA. In addition, the overall callosa area was larger in AWS than NFA. The group comparison of white matter volume showed a cluster of increased white matter volume predominantly encompassing the rostrum across the midline portion in AWS. These results potentially reflect anatomical changes associated with differences in the hemispheric distribution of language processes that has been reported previously in AWS. Educational objectives After reading this article, the reader will be able to: (1) summarize research findings on functional and anatomical differences between AWS and NFA; (2) summarize research findings on anatomical anomalies observed in AWS; (3) discuss the possible relationships between functional and anatomical aberrations in AWS; and (4) discuss how the findings of the present study may support results of previous behavioral investigations (e.g. dichotic listening) in AWS. PMID:21513943

Choo, Ai Leen; Kraft, Shelly Jo; Olivero, William; Ambrose, Nicoline G.; Sharma, Harish; Chang, Soo-Eun; Loucks, Torrey

2011-01-01

73

Demyelination increases radial diffusivity in corpus callosum of mouse brain.  

PubMed

Myelin damage, as seen in multiple sclerosis (MS) and other demyelinating diseases, impairs axonal conduction and can also be associated with axonal degeneration. Accurate assessments of these conditions may be highly beneficial in evaluating and selecting therapeutic strategies for patient management. Recently, an analytical approach examining diffusion tensor imaging (DTI) derived parameters has been proposed to assess the extent of axonal damage, demyelination, or both. The current study uses the well-characterized cuprizone model of experimental demyelination and remyelination of corpus callosum in mouse brain to evaluate the ability of DTI parameters to detect the progression of myelin degeneration and regeneration. Our results demonstrate that the extent of increased radial diffusivity reflects the severity of demyelination in corpus callosum of mouse brain affected by cuprizone treatment. Subsequently, radial diffusivity decreases with the progression of remyelination. Furthermore, radial diffusivity changes were specific to the time course of changes in myelin integrity as distinct from axonal injury, which was detected by betaAPP immunostaining and shown to be most extensive prior to demyelination. Radial diffusivity offers a specific assessment of demyelination and remyelination, as distinct from acute axonal damage. PMID:15862213

Song, Sheng-Kwei; Yoshino, Jun; Le, Tuan Q; Lin, Shiow-Jiuan; Sun, Shu-Wei; Cross, Anne H; Armstrong, Regina C

2005-05-15

74

Verbal learning and memory in agenesis of the corpus callosum.  

PubMed

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

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

2014-07-01

75

An MRI review of acquired corpus callosum lesions.  

PubMed

Lesions of the corpus callosum (CC) are seen in a multitude of disorders including vascular diseases, metabolic disorders, tumours, demyelinating diseases, trauma and infections. In some diseases, CC involvement is typical and sometimes isolated, while in other diseases CC lesions are seen only occasionally in the presence of other typical extra-callosal abnormalities. In this review, we will mainly discuss the MRI characteristics of acquired lesions involving the CC. Identification of the origin of the CC lesion depends on the exact localisation of the lesion(s) inside the CC, presence of other lesions seen outside the CC, signal changes on different MRI sequences, evolution over time of the radiological abnormalities, history and clinical state of the patient, and other radiological and non-radiological examinations. PMID:24563521

Renard, Dimitri; Castelnovo, Giovanni; Campello, Chantal; Bouly, Stephane; Le Floch, Anne; Thouvenot, Eric; Waconge, Anne; Taieb, Guillaume

2014-09-01

76

Interhemispheric Osteolipoma with Agenesis of the Corpus Callosum  

PubMed Central

Osteolipoma is an ossified lipoma with distinct components of fat and bone. We present a case of interhemispheric osteolipoma associated with total agenesis of the corpus callosum. A 20-year-old man complained of severe headache, nausea and vomiting. Brain computed tomography showed a low-density mass in an interhemispheric fissure, with high T1 and T2 magnetic resonance signals compatible with fat. The mass measured 4.9 × 2.9 cm in size and showed peripheral calcifications. There was another small piece of same signal mass within the lateral ventricular choroid plexus. The interhemispheric lesion was removed by an interhemispheric approach. Osteolipoma is rare in interhemispheric region, however, it should be a differential diagnosis of lesions with fat intensity mass and calcifications. PMID:20224717

Park, Yong-Sook; Park, Un-Sub

2010-01-01

77

SELECTIVELY DIMINISHED CORPUS CALLOSUM FIBERS IN CONGENITAL CENTRAL HYPOVENTILATION SYNDROME  

PubMed Central

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

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

2011-01-01

78

Dividing Fractions by Fractions  

NSDL National Science Digital Library

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.

Banfill, J. C.

2007-12-12

79

Agenesis of the Corpus Callosum in a Newborn with Turner Mosaicism  

PubMed Central

The agenesis of the corpus callosum results from a failure in the development of the largest fiber bundle that connects cerebral hemispheres. Patient’s outcome is influenced by etiology and associated central nervous system malformations. We describe a child with Turner syndrome (TS) mosaicism, with particular phenotype features and a complete agenesis of the corpus callosum. To our knowledge, this is the second case report of TS mosaicism associated with complete agenesis of the corpus callosum. Anatomical brain magnetic resonance imaging and diffusion tensor imaging were useful to confirm the complete absence of the corpus callosum, evaluate associated central nervous system malformations, visualize abnormal white matter tracts (Probst bundles) and assess the remaining commissures. PMID:24987509

Pereira, Ester; Polo, Monica Rebollo; Lopez, Jordi Muchart; Quijano, Thais Agut; Garcia-Alix, Alfredo; Fons, Carmen

2014-01-01

80

Brain anatomy of autism spectrum disorders I. Focus on corpus callosum.  

PubMed

This brief review aims to examine the structural magnetic resonance imaging (sMRI) studies on corpus callosum in autism spectrum disorders (ASD) and discuss the clinical and demographic factors involved in the interpretation of results. PMID:23531487

Bellani, M; Calderoni, S; Muratori, F; Brambilla, P

2013-09-01

81

MRI evaluation of pathologies affecting the corpus callosum: A pictorial essay  

PubMed Central

The corpus callosum is a midline cerebral structure and has a unique embryological development pattern. In this article, we describe the pathophysiology and present imaging findings of various typical/atypical conditions affecting the corpus callosum. Since many of these pathologies have characteristic appearances on magnetic resonance imaging (MRI) and their therapeutic approaches are poles apart, ranging from medical to surgical, the neuroradiologist should be well aware of them. PMID:24604936

Kazi, Aamish Z; Joshi, Priscilla C; Kelkar, Abhimanyu B; Mahajan, Mangal S; Ghawate, Amit S

2013-01-01

82

Determination of indices of the corpus callosum associated with normal aging in Japanese individuals.  

PubMed

Indices of the corpus callosum with normal aging and their sex differences were elucidated using quantitative MRI. We studied 94 Japanese men (mean+/-SD 57.3+/-20.8 years, range 6-90 years) and 111 Japanese women (mean+/-SD 61.2+/-17.6 years, range 9-86 years) who had no intracranial lesions on MRI and no history of neurological illness. The widths of the rostrum, body and splenium, the anterior to posterior length, and the maximum height in the midsagittal image were selected for measurement. The Evans index, which is the relative ratio of lateral ventricle expansion, and the maximum width of the third ventricle in the axial image were also estimated for comparison. The widths of rostrum, body and splenium of the corpus callosum became thinner with age. Conversely, the anterior to posterior length and the maximum height of the corpus callosum increased with age. The ratio of the width of the body to the length of the corpus callosum and the ratio of the width of the body to the height of the corpus callosum are best correlated with age. No sex differences in regional size of corpus callosum, including these two ratios, were observed in any raw measures, although ventricular indices were larger in men than women. Evaluation of the ratio of the width of the body to its length and the ratio of the width of the body to its height may enable accurate estimation of normal or pathological changes of the corpus callosum. Aging and pathological atrophy of corpus callosum can be evaluated without any adjustment for gender. PMID:12879325

Takeda, S; Hirashima, Y; Ikeda, H; Yamamoto, H; Sugino, M; Endo, S

2003-08-01

83

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

PubMed Central

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. TAI was produced in the rostral body of the corpus callosum by impact onto the skull at bregma. During the first week post-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 post-injury but labeling was increased between 2 to 7 days post-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 following TAI that may affect axon vulnerability vs. recovery following brain injury. PMID:24226267

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

2014-01-01

84

Oligodendrocyte lineage and subventricular zone response to traumatic axonal injury in the corpus callosum.  

PubMed

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/CreER(T):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

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

2013-12-01

85

MODELING URBAN THERMAL ANISOTROPY  

Microsoft Academic Search

Thermal remote sensing of urban areas is affected by directional variations (anisotropy) of the upwelling thermal radiation. The anisotropy arises due to the three-dimensionally rough urban surface that creates microscale patterns of surface temperature variability associated with surface position, orientation and composition, coupled with a biased view of this rough surface by the remote sensor. The large magnitudes of observed

J. A. Voogt; E. S. Krayenhoff

86

The combination of thermal dysregulation and agenesis of corpus callosum: Shapiro's or/and reverse Shapiro's syndrome  

PubMed Central

Shapiro syndrome is an extremely rare condition consisting the clinical triad of recurrent hypothermia, hyperhydrosis and agenesis of the corpus callosum. On the other hand, reverse Shapiro's sydrome is characterized periodic hyperthermia and agenesis of the corpus callosum. Here, we describe a 3.5-year-old girl with complete agenesis of corpus callosum presenting with recurrent fever and vomiting. She also had hypothermia attacks with accompanying diaphoresis. To the best of our knowledge, there is no described case with episodes of hyperthermia, hypothermia, and vomiting associated with agenesis of the corpus callosum. Recurrent vomiting may be a newly defined symptom associated with these syndromes. PMID:24339619

Topcu, Yasemin; Bayram, Erhan; Karaoglu, Pakize; Yis, Uluc; Kurul, Semra Hiz

2013-01-01

87

Automatic corpus callosum segmentation for standardized MR brain scanning  

NASA Astrophysics Data System (ADS)

Magnetic Resonance (MR) brain scanning is often planned manually with the goal of aligning the imaging plane with key anatomic landmarks. The planning is time-consuming and subject to inter- and intra- operator variability. An automatic and standardized planning of brain scans is highly useful for clinical applications, and for maximum utility should work on patients of all ages. In this study, we propose a method for fully automatic planning that utilizes the landmarks from two orthogonal images to define the geometry of the third scanning plane. The corpus callosum (CC) is segmented in sagittal images by an active shape model (ASM), and the result is further improved by weighting the boundary movement with confidence scores and incorporating region based refinement. Based on the extracted contour of the CC, several important landmarks are located and then combined with landmarks from the coronal or transverse plane to define the geometry of the third plane. Our automatic method is tested on 54 MR images from 24 patients and 3 healthy volunteers, with ages ranging from 4 months to 70 years old. The average accuracy with respect to two manually labeled points on the CC is 3.54 mm and 4.19 mm, and differed by an average of 2.48 degrees from the orientation of the line connecting them, demonstrating that our method is sufficiently accurate for clinical use.

Xu, Qing; Chen, Hong; Zhang, Li; Novak, Carol L.

2007-03-01

88

The structure of the corpus callosum in obsessive compulsive disorder.  

PubMed

Abnormal brain connectivity has recently been reported in obsessive compulsive disorder (OCD). However, structural differences in the corpus callosum (CC), the primary structure connecting the two hemispheres, have not been extensively studied. In this case-control study, we recruited 30 patients with OCD and 30 healthy control subjects carefully matched for age, sex and handedness. Combining surface-based mesh-modeling and voxel-based morphometry (VBM), we compared callosal thickness and white matter (WM) density in patients and controls. We investigated associations between callosal structure and cortical gray matter (GM) density, and we related CC measures to neuropsychological performance in OCD. OCD patients showed small anterior and posterior callosal regions compared to healthy control subjects. In the OCD group, anterior callosal thickness was positively correlated with GM density of the right mid-dorso-lateral prefrontal (BA 9/46) area, while posterior callosal thickness was positively correlated with GM density in the left supramarginal gyrus (BA 40). Moreover, posterior callosal WM density was positively correlated with verbal memory, visuo-spatial memory, verbal fluency, and visuo-spatial reasoning performances. Callosal attributes were related to GM density in cortical areas innervated by the CC, and were also related to performance in cognitive domains impaired in the disorder. The CC may therefore be integrally involved in OCD. PMID:23078960

Di Paola, M; Luders, E; Rubino, I A; Siracusano, A; Manfredi, G; Girardi, P; Martinotti, G; Thompson, P M; Chou, Y-Y; Toga, A W; Caltagirone, C; Spalletta, G

2013-10-01

89

Fraction Basics  

NSDL National Science Digital Library

This iOS app contains 12 computer animated videos on understanding fractions, improper fractions & mixed fractions, equivalent fractions, adding fractions, adding fractions examples, subtracting fractions, multiplying fractions. Each video presents important vocabulary and concepts, there is a table of contents, and an option to skip to later lessons.

Chong, Ng W.

2012-11-24

90

Fun Fractions  

NSDL National Science Digital Library

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!! ...

Terch, Ms.

2010-03-11

91

Comprehension of humor in primary agenesis of the corpus callosum.  

PubMed

Individuals with agenesis of the corpus callosum (ACC) can, in some cases, perform normally on standardized intelligence tests. Nevertheless, recent studies suggest that individuals with ACC and normal IQ scores have deficits in domains of fluid and social intelligence. Anecdotal reports from families suggest diminished appreciation of the subtleties of social interactions, and deficits in the comprehension of jokes and stories. In this research, both the cartoon and narrative joke subtests of a humor test (developed by Brownell et al. [Brownell, H., Michel, D., Powelson, J., & Gardner, H. (1983). Surprise but not coherence: sensitivity to verbal humor in right-hemisphere patients. Brain and language, 18(1), 20-27] and Bihrle et al. [Bihrle, A. M., Brownell, H. H., Powelson, J. A., & Gardner, H. (1986). Comprehension of humorous and non-humorous materials by left and right brain-damaged patients. Brain and Cognition, 5(4), 399-411]) were given to 16 adults with complete ACC (all with IQs>80) and 31 controls of similar age and IQ. Individuals with ACC performed worse than controls on the narrative joke subtest (p<.025) when VIQ was controlled. However, on the cartoon subtest the two groups were not significantly different. Covarying age, forms of IQ, narrative memory, set-switching, and literal language comprehension did not substantially alter the group difference. However, covarying comprehension of nonliteral language and proverbs eliminated the difference, suggesting a common origin for the comprehension of jokes, nonliteral language, and proverbs, most likely related to capacity for understanding second-order meanings. PMID:15716161

Brown, Warren S; Paul, Lynn K; Symington, Melissa; Dietrich, Rosalind

2005-01-01

92

Magnetic anisotropy of chloritoid  

NASA Astrophysics Data System (ADS)

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.

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

2013-08-01

93

Dipole shear anisotropy logging  

SciTech Connect

Sonic-scale shear anisotropy of formations are obtained from dipole-shear measurements acquired by orthogonal source and receiver pairs. These measurements resemble miniature 4-component shear VSP surveys inside the borehole. Data from two orthogonal sources and an array of orthogonal receivers are processed providing three main logs; the fast and slow shear slownesses, and the fast shear polarization angle. Potential applications include: shale anisotropy for better seismic models, maximum stress and fracture/microcrack strike direction for horizontal well drilling and fracture height and azimuth determination in hydraulic fracturing.

Esmersoy, C.; Kane, M. [Schlumberger-Doll Research, Ridgefield, CT (United States); Koster, K.; Williams, M. [Amoco Production, Denver, CO (United States); Boyd, A. [GeoQuest, Aurora, CO (United States)

1994-12-31

94

The gene responsible for a severe form of peripheral neuropathy and agenesis of the corpus callosum maps to chromosome 15q  

SciTech Connect

Peripheral neuropathy with or without agenesis of the corpus callosum (ACCPN) is a devastating neurodegenerative disorder that is transmitted as an autosomal recessive trait. Genealogical studies in a large number of affected French Canadian individuals suggest that ACCPN results from a single founder mutation. A genomewide search using 120 microsatellite DNA markers in 14 French Canadian families allowed the mapping of the ACCPN gene to a 5-cM region on chromosome 15q13-q15 that is flanked by markers D15S1040 and D15S118. A maximum two-point LOD score of 11.1 was obtained with the marker D15S971 at a recombination fraction of 0. Haplotype analysis and linkage disequilibrium support a founder effect. These findings are the first step in the identification of the gene responsible for ACCPN, which may shed some light on the numerous conditions associated with progressive peripheral neuropathy or agenesis of the corpus callosum. 28 refs., 2 figs., 3 tabs.

Casaubon, L.K.; Melanson, M.; Marineau, C. [McGill Univ., Quebec (Canada)]|[Montreal General Hospital Research Institute (Canada)] [and others

1996-01-01

95

Fantastic Fractions  

NSDL National Science Digital Library

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 ...

Cate, Ms.

2008-04-12

96

Fraction Finder  

NSDL National Science Digital Library

Determine the value of two given fractions represented as points on a number line. Then find a fraction whose value is between the two given fractions and determine its value. Fraction Finder is one of the Interactivate assessment explorers.

97

What does anisotropy measure? Insights from increased and decreased anisotropy in selective fiber tracts in schizophrenia  

PubMed Central

Schizophrenia is a common, severe, and chronically disabling mental illness of unknown cause. Recent MRI studies have focused attention on white matter abnormalities in schizophrenia using diffusion tensor imaging (DTI). Indices commonly derived from DTI include (1) mean diffusivity, independent of direction, (2) fractional anisotropy (FA) or relative anisotropy (RA), (3) axial diffusivity, and (4) radial diffusivity. In cerebral white matter, contributions to these indices come from fiber arrangements, degree of myelination, and axonal integrity. Relatively pure deficits in myelin result in a modest increase in radial diffusivity, without affecting axial diffusivity and with preservation of anisotropy. Although schizophrenia is not characterized by gross abnormalities of white matter, it does involve a profound dysregulation of myelin-associated gene expression, reductions in oligodendrocyte numbers, and marked abnormalities in the ultrastructure of myelin sheaths. Since each oligodendrocyte myelinates as many as 40 axon segments, changes in the number of oligodendrocytes (OLG), and/or in the integrity of myelin sheaths, and/or axoglial contacts can have a profound impact on signal propagation and the integrity of neuronal circuits. Whereas a number of studies have revealed inconsistent decreases in anisotropy in schizophrenia, we and others have found increased FA in key subcortical tracts associated with the circuits underlying symptom generation in schizophrenia. We review data revealing increased anisotropy in dopaminergic tracts in the mesencephalon of schizophrenics and their unaffected relatives, and discuss the possible biological underpinnings and physiological significance of this finding. PMID:23483798

Alba-Ferrara, L. M.; de Erausquin, Gabriel A.

2012-01-01

98

Introduction Magnetic Anisotropy of  

E-print Network

not completely understood interesting for dilute magnetic semiconductors (DMSs) transparent ferromagnetsIntroduction Results Magnetic Anisotropy of Transition Metal Monoxides Andreas Schrön Institut für Introduction Why are Transition Metal Oxides so interesting? Theoretical Approach ­ Density Functional Theory

Rossak, Wilhelm R.

99

CMB ANISOTROPIES: AN OVERVIEW  

E-print Network

A brief outline of the current status of CMB anisotropies and what they might mean, heavily biased towards the perspective of Berkeley theorists. Based on a talk presented at the 17th Texas Symposium on Relativistic Astrophysics held in Munich, December 1994.

Douglas Scott

1995-02-02

100

Psychological Correlates of Handedness and Corpus Callosum Asymmetry in Autism: The Left Hemisphere Dysfunction Theory Revisited  

ERIC Educational Resources Information Center

Rightward cerebral lateralization has been suggested to be involved in the neuropathology of autism spectrum conditions. We investigated functional and neuroanatomical asymmetry, in terms of handedness and corpus callosum measurements in male adolescents with autism, their unaffected siblings and controls, and their associations with executive…

Floris, Dorothea L.; Chura, Lindsay R.; Holt, Rosemary J.; Suckling, John; Bullmore, Edward T.; Baron-Cohen, Simon; Spencer, Michael D.

2013-01-01

101

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

ERIC Educational Resources Information Center

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…

Hynd, George W.; And Others

1991-01-01

102

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

ERIC Educational Resources Information Center

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…

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

103

ORIGINAL PAPER Corpus Callosum Anatomy in Right-Handed Homosexual and  

E-print Network

ORIGINAL PAPER Corpus Callosum Anatomy in Right-Handed Homosexual and Heterosexual Men Sandra F The results of several studies have shown that homosexual men have an increased prevalence of non that isthmal area would be greater in homosexual men, even among right handers. Twelve homosexual and ten

Stanchev, Peter

104

Congenital and Acquired Abnormalities of the Corpus Callosum: A Pictorial Essay  

PubMed Central

The purpose of this review is to illustrate the wide spectrum of lesions in the corpus callosum, both congenital and acquired: developmental abnormalities, phakomatoses, neurometabolic disorders, demyelinating diseases, infection and inflammation, vascular lesions, neoplasms, traumatic and iatrogenic injury, and others. Cases include fetuses, children, and adults with rich iconography from the authors' own archive. PMID:24027754

Krupa, Katarzyna; Bekiesinska-Figatowska, Monika

2013-01-01

105

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

PubMed Central

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

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

2014-01-01

106

Corpus Callosum Analysis using MDL-based Sequential Models of Shape and Appearance  

E-print Network

as a fully automated clinical tool for analysis and segmentation. Keywords: registration, atlases, deformable This paper describes a method for automatically analysing and segmenting the corpus callosum from magnetic remain applicable to other domain problems. The well-known multi-resolution AAM optimisation is extended

107

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

PubMed

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

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

2005-08-01

108

Neuropeptide Y immunoreactive axons in the corpus callosum of the cat during postnatal development  

Microsoft Academic Search

Many immunocytochemical studies have identified different types of neurotransmitters localized in the corpus callosum (CC) axons in the adult mammal. Few studies have looked at the development of different neurochemically identified CC systems. Previous studies on the development of cat CC axons have indicated that a large number of transitory CC axons project to the cortex during early postnatal development.

Song-Lin Ding; Andrea J. Elberger

1994-01-01

109

Corpus callosum size in adults with high-functioning autism and the relevance of gender  

Microsoft Academic Search

The goal of the study was to investigate the size of the corpus callosum (CC) and its subsegments in relation to total brain volume (TBV) as an empirical indicator of impaired connectivity in autism with special respect to gender. In MRI data sets of 29 adults with high-functioning autism (HFA) and 29 age-, gender- and IQ-matched control subjects, the TBV

Ralf Tepest; Esther Jacobi; Astrid Gawronski; Barbara Krug; Walter Möller-Hartmann; Fritz G. Lehnhardt; Kai Vogeley

2010-01-01

110

Automatic corpus callosum segmentation using a deformable active Fourier contour model  

E-print Network

neuroimaging studies of neuro-developmental pathol- ogy such as autism. It plays an integral role in relaying component shape space. Using MNI space aligned T1w MRI data, the CC segmentation is initialized on the mid to a large longitudinal pediatric study of brain development in autism. Keywords: corpus callosum

Utah, University of

111

Corpus callosum size is linked to dichotic deafness and hemisphericity, not sex or handedness  

Microsoft Academic Search

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 predominance in mathematics, as well as for aggressive behavior. Ultimately,

Bruce E. Morton; Stein E. Rafto

2006-01-01

112

The Brain Connection: The Corpus Callosum is Larger in Left-Handers.  

ERIC Educational Resources Information Center

Discusses the neurobiological basis for functional specialization of the cerebral hemispheres, indicating that the size of the corpus callosum is correlated with the neurophysiological measure of hand preference. In postmortem examinations of 42 subjects there were no sex differences, but mixed-handers had significantly larger total areas of the…

Witelson, Sandra F.

1985-01-01

113

Interocular transfer in guinea pigs following section of the corpus callosum  

Microsoft Academic Search

Measured interocular transfer of an active-avoidance habit, based on discriminations of shape discriminanda or of slant discriminanda, in 27 ocularly pigmented male American Brown guinea pigs, after section of the corpus callosum or a sham operation. Mastery of discriminations was not retarded by the section, but interocular transfer, while nearly perfect in sham-operated Ss, was significantly inferior in callosally sectioned

Daniel M. Levinson

1972-01-01

114

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

ERIC Educational Resources Information Center

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…

Morton, Bruce E.; Rafto, Stein E.

2006-01-01

115

Magnetic anisotropy of chloritoid  

NASA Astrophysics Data System (ADS)

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.

Haerinck, Tom; Debacker, Timothy; Sintubin, Manuel

2013-04-01

116

Local Anisotropy in Globally Isotropic Granular Packings  

NASA Astrophysics Data System (ADS)

We report on two-dimensional computer simulations of frictionless granular packings at various area fractions ? above the jamming point ?c. We measure the anisotropy in coarse-grained stress ?s and shear modulus ?m as functions of coarse-graining scale, R. ?s can be collapsed onto a master curve after rescaling R by a characteristic length scale ? and ?s by an anisotropy magnitude A. Both A and ? accelerate as ???c from above, consistent with a divergence at ?c. ?m shows no characteristic length scale and has a nontrivial power-law form, ?m˜R-0.62, over almost the entire range of R at all ?. These results suggest that the force chains present in the spatial structure of the quenched stress may be governed by different physics than the anomalous elastic response near jamming.

Karimi, K.; Maloney, C. E.

2011-12-01

117

Equivalent Fractions  

NSDL National Science Digital Library

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 ...

Ogle, Miss

2012-04-05

118

Fraction Match  

NSDL National Science Digital Library

In this online game students must match the fraction to a model of the fraction (rectangular, triangular, or circular). For each fraction several representations match and each one must be chosen before a new fraction appears. Each round of the game is timed for 1-minute and score is tracked to see how many fraction matches can be made in that time frame.

Games, Mari

2013-01-01

119

ORIGINAL RESEARCH Diffusion Tensor Microscopy Indicates the Cytoarchitectural Basis for Diffusion Anisotropy in the Human Hippocampus  

Microsoft Academic Search

BACKGROUND AND PURPOSE: Observing changes to water diffusivity and fractional anisotropy (FA) for particular hippocampal regions may improve the sensitivity and specificity of diffusion tensor MR imaging for hippocampal pathologies like Alzheimer disease and mesial temporal sclerosis. As a first step toward this goal, this study characterized the cytoarchitectural features underlying diffusion anisotropy in human hippocampus autopsy specimens at 60-m

T. M. Shepherd; E. Ozarslan; A. T. Yachnis; M. A. King; S. J. Blackband

120

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

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

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

2010-01-01

121

Fraction Track  

NSDL National Science Digital Library

"This applet allows students to individually practice working with relationships among fractions and ways of combining fractions. For a two person version of this applet see the Fraction Track E-Example." from NCTM Illuminations.

Mathematics, Illuminations N.

2009-05-12

122

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.

123

Association of type I neurons positive for NADPH-diaphorase with blood vessels in the adult monkey corpus callosum  

E-print Network

Sagittal sections through the corpus callosum of adult macaque monkeys (n = 7) reveal a subpopulation of neurons positive for NADPH-diaphorase (NADPHd). These are sparsely distributed, with 2–12 neurons scored over the ...

Rockland, Kathleen

124

Corpus Callosum Size Is Highly Heritable in Humans, and May Reflect Distinct Genetic Influences on Ventral and Rostral Regions  

PubMed Central

Anatomical differences in the corpus callosum have been found in various psychiatric disorders, but data on the genetic contributions to these differences have been limited. The current study used morphometric MRI data to assess the heritability of corpus callosum size and the genetic correlations among anatomical sub-regions of the corpus callosum among individuals with and without mood disorders. The corpus callosum (CC) was manually segmented at the mid-sagittal plane in 42 women (healthy, n?=?14; major depressive disorder, n?=?15; bipolar disorder, n?=?13) and their 86 child or adolescent offspring. Four anatomical sub-regions (CC-genu, CC2, CC3 and CC-splenium) and total CC were measured and analyzed. Heritability and genetic correlations were estimated using a variance components method, with adjustment for age, sex, diagnosis, and diagnosis x age, where appropriate. Significant heritability was found for several CC sub-regions (P<0.01), with estimated values ranging from 48% (splenium) to 67% (total CC). There were strong and significant genetic correlations among most sub regions. Correlations between the genu and mid-body, between the genu and total corpus callosum, and between anterior and mid body were all >90%, but no significant genetic correlations were detected between ventral and rostral regions in this sample. Genetic factors play an important role in corpus callosum size among individuals. Distinct genetic factors seem to be involved in caudal and rostral regions, consistent with the divergent functional specialization of these brain areas. PMID:24968245

Woldehawariat, Girma; Martinez, Pedro E.; Hauser, Peter; Hoover, David M.; Drevets, Wayne W. C.; McMahon, Francis J.

2014-01-01

125

Equivalent Fractions  

NSDL National Science Digital Library

"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)

Alabama Learning Exchange (alex)

2009-03-23

126

Fraction Feud  

NSDL National Science Digital Library

In this interactive game from NCTM's Calculation Nation, players try to create fractions that are either larger or smaller than their opponents' fractions. Each player begins with twelve cards and can only use them once in each round of play. Players can play against another player or against the computer. A fraction bar chart is available to help students compare fractions.

2013-01-01

127

Multiplying Fractions  

NSDL National Science Digital Library

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.

Banfill, J. C.

2007-12-12

128

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

PubMed

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

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

2012-04-01

129

Shape analysis of corpus callosum in phenylketonuria using a new 3D correspondence algorithm  

NASA Astrophysics Data System (ADS)

Statistical shape analysis of brain structures has gained increasing interest from neuroimaging community because it can precisely locate shape differences between healthy and pathological structures. The most difficult and crucial problem is establishing shape correspondence among individual 3D shapes. This paper proposes a new algorithm for 3D shape correspondence. A set of landmarks are sampled on a template shape, and initial correspondence is established between the template and the target shape based on the similarity of locations and normal directions. The landmarks on the target are then refined by iterative thin plate spline. The algorithm is simple and fast, and no spherical mapping is needed. We apply our method to the statistical shape analysis of the corpus callosum (CC) in phenylketonuria (PKU), and significant local shape differences between the patients and the controls are found in the most anterior and posterior aspects of the corpus callosum.

He, Qing; Christ, Shawn E.; Karsch, Kevin; Peck, Dawn; Duan, Ye

2010-03-01

130

Agenesis of the corpus callosum with mosaicism 46,XY/47,XY, extra ring chromosome.  

PubMed Central

A case of agenesis of the corpus callosum with a chromosomal abnormality is reported. The patient was a male infant, born to phenotypically normal, non-consanguineous parents. He had an abnormal phenotype, mental retardation, and chromosome mosaicism 46,XY/47,XY,+r. Chromosomal analysis of both parents showed a normal karotype. The origin of the small ring chromosome could not be determined and it is difficult to relate the phenotype of the infant to the cytogenetic findings. Images PMID:7365765

Zamboni, G; Bernardi, F; Danesino, C; del Majno, U M; Beghini, G; Dalla Bernardina, B

1980-01-01

131

Corpus Callosum Anatomy in Right-Handed Homosexual and Heterosexual Men  

Microsoft Academic Search

The results of several studies have shown that homosexual men have an increased prevalence of non-right-handedness and atypical\\u000a patterns of hemispheric functional asymmetry. Non-right-handedness in men has been associated with increased size of the corpus\\u000a callosum (CC), particularly of the isthmus, which is the posterior region of the callosal body connecting parietotemporal\\u000a cortical regions. We hypothesized that isthmal area would

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

2008-01-01

132

Monozygotic twins with trisomy 21 and partial agenesis of the corpus callosum.  

PubMed

Trisomy 21 is the most common viable trisomy. Although it is invariably associated with mild to severe developmental delay and intellectual disability, no gross central nervous system malformation has been consistently identified in individuals with trisomy 21. We present the case of a monozygotic twin pregnancy in which both fetuses were identified as having trisomy 21 and partial agenesis of the corpus callosum. We discuss this rare association in the context of an emerging understanding of the neurobiology of trisomy 21. PMID:23498567

Jacob, Francois D; Dobson, Lori J; Estroff, Judy A; Khwaja, Omar S

2013-04-01

133

Ribbon Fractions  

NSDL National Science Digital Library

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.

2009-01-01

134

Evaporation Anisotropy of Forsterite  

NASA Astrophysics Data System (ADS)

Evaporation anisotropy of a synthetic single crystal of forsterite was investigated by high temperature vacuum experiments. The (001), (010), and (001) surfaces show microstructures characteristic for each surface. Obtained overall linear evaporation rates for the (001), (010), and (001) surfaces are ~17, ~7, and ~22 mm/hour, and the intrinsic evaporation rates, obtained by the change in surface microstructures, are ~10, ~4.5, and ~35 mm/hour, respectively. The difference between the intrinsic evaporation rates and overall rates can be regarded as contribution of dislocation, which is notable for the (100) and (010) surfaces and insignificant for the (001) surface. This is consistent with observed surface microstructures.

Ozawa, K.; Nagahara, H.; Morioka, M.

1996-03-01

135

Antenatal diagnosis and outcome of agenesis of corpus callosum: A retrospective review of 33 cases  

PubMed Central

Objective To present antenatal sonographic findings and postnatal outcome of a population of foetuses diagnosed with agenesis of corpus callosum. Material and Methods The database of our ultrasound laboratory was retrospectively searched for cases of agenesis of the corpus callosum suspected at antenatal sonography between 2002 and 2012. The following variables were assessed: maternal age, gestational age at diagnosis, gender, any additional cerebral and extra-cerebral malformations, results of karyotype analysis and pregnancy and foetal/neonatal outcomes. Results During the study period, 33 foetuses with agenesis of the corpus callosum were identified antenatally, with a male preponderance. The mean maternal age was 28.48 years. In all cases, pre/postnatal MRI and/or necropsy were performed in order to confirm the diagnosis. Among those, there were additional brain findings in 23 (69.7%) and additional extra-cerebral anomalies in 3 (9.1%) foetuses. Karyotype analysis was performed in 21 of 33 (63.6%) cases. As for pregnancy outcome, the pregnancy was terminated in 14 (42.4%) of the remaining 19 foetuses; eighteen (54.5%) were delivered near term and one (3.1%) who was delivered prematurely died during the neonatal period. Conclusion The diagnosis of congenital brain malformation is a challenging issue, since additional findings have a considerable effect on prognosis; detailed examination with genetic counselling should be performed. PMID:24790511

Ozyuncu, Ozgur; Yaz?c?oglu, Asl?han; Turgal, Mert

2014-01-01

136

Organizational effects of fetal testosterone on human corpus callosum size and asymmetry.  

PubMed

Previous theory and research in animals has identified the critical role that fetal testosterone (FT) plays in organizing sexually dimorphic brain development. However, to date there are no studies in humans directly testing the organizational effects of FT on structural brain development. In the current study we investigated the effects of FT on corpus callosum size and asymmetry. High-resolution structural magnetic resonance images (MRI) of the brain were obtained on 28 8-11-year-old boys whose exposure to FT had been previously measured in utero via amniocentesis conducted during the second trimester. Although there was no relationship between FT and midsaggital corpus callosum size, increasing FT was significantly related to increasing rightward asymmetry (e.g., Right>Left) of a posterior subsection of the callosum, the isthmus, that projects mainly to parietal and superior temporal areas. This potential organizational effect of FT on rightward callosal asymmetry may be working through enhancing the neuroprotective effects of FT and result in an asymmetric distribution of callosal axons. We suggest that this possible organizational effect of FT on callosal asymmetry may also play a role in shaping sexual dimorphism in functional and structural brain development, cognition, and behavior. PMID:19833443

Chura, Lindsay R; Lombardo, Michael V; Ashwin, Emma; Auyeung, Bonnie; Chakrabarti, Bhismadev; Bullmore, Edward T; Baron-Cohen, Simon

2010-01-01

137

Pediatric neurofunctional intervention in agenesis of the corpus callosum: a case report?  

PubMed Central

Objective: To describe a clinical report pre- and post-neurofunctional intervention in a case of agenesis of the corpus callosum. Case description: Preterm infant with corpus callosum agenesis and hypoplasia of the cerebellum vermis and lateral ventricles, who, at the age of two years, started the proposed intervention. Functional performance tests were used such as the neurofunctional evaluation, the Gross Motor Function Measure and the Gross Motor Function Classification System. In the initial evaluation, absence of equilibrium reactions, postural transfers, deficits in manual and trunk control were observed. The intervention was conducted with a focus on function, prioritizing postural control and guidance of the family to continue care in the home environment. After the intervention, there was an improvement of body reactions, postural control and movement acquisition of hands and limbs. The intervention also showed improvement in functional performance. Comments: Postural control and transfers of positions were benefited by the neurofunction intervention in this case of agenesis of the corpus callosum. The approach based on function with activities that involve muscle strengthening and balance reactions training, influenced the acquisition of a more selective motor behavior.

Pacheco, Sheila Cristina da Silva; Queiroz, Ana Paula Adriano; Niza, Nathália Tiepo; da Costa, Letícia Miranda Resende; Ries, Lilian Gerdi Kittel

2014-01-01

138

Fraction Game  

NSDL National Science Digital Library

This interactive game provides an opportunity for students to think about how fractions are related to a unit whole, compare fractional parts of a whole, and find equivalent fractions. Players move markers a total distance that is less than or equal to the random target fraction, along their choice of seven parallel number line tracks, which are divided into different fractional parts. The goal is to move each of the seven markers to the right side of the game board using as few fraction target cards as possible. Instructions and exploration questions are included.

2011-01-01

139

Fractional Clothesline  

NSDL National Science Digital Library

A string will be stretched across the classroom and various points will be marked for 0, 1, 2, 3, and 4. This classroom number line will be used to show that all proper fractions are grouped between 0 and 1, and that improper fractions or mixed numbers are all grouped above 1. Students clip index cards with various proper fractions, improper fractions, and mixed numbers on the clothesline to visually see groupings. Students then play an estimation game with groups using the same principle. Encouraging students to look at fractions in various ways will help foster their conceptual fraction sense (from NCTM's Illuminations).

Mathematics, Illuminations N.

2009-07-23

140

Agenesis and Dysgenesis of the Corpus Callosum: Clinical, Genetic and Neuroimaging Findings in a Series of 41 Patients  

PubMed Central

Agenesis of the corpus callosum (ACC) is among the most frequent human brain malformations with an incidence of 0.5–70 in 10,000. It is a heterogeneous condition, for which several different genetic causes are known, for example, ACC as part of monogenic syndromes or complex chromosomal rearrangements. We systematically evaluated the data of 172 patients with documented corpus callosum abnormalities in the records, and 23 patients with chromosomal rearrangements known to be associated with corpus callosum changes. All available neuroimaging data, including CT and MRI, were re-evaluated following a standardized protocol. Whenever feasible chromosome and subtelomere analyses as well as molecular genetic testing were performed in patients with disorders of the corpus callosum in order to identify a genetic diagnosis. Our results showed that 41 patients with complete absence (agenesis of the corpus callosum—ACC) or partial absence (dysgenesis of the corpus callosum—DCC) were identified. Out of these 28 had ACC, 13 had DCC. In 11 of the 28 patients with ACC, the following diagnoses could be established: Mowat–Wilson syndrome (n = 2), Walker–Warburg syndrome (n = 1), oro-facial-digital syndrome type 1 (n = 1), and chromosomal rearrangements (n = 7), including a patient with an apparently balanced reciprocal translocation, which led to the disruption and a predicted loss of function in the FOXG1B gene. The cause of the ACC in 17 patients remained unclear. In 2 of the 13 patients with DCC, unbalanced chromosomal rearrangements could be detected (n = 2), while the cause of DCC in 11 patients remained unclear. In our series of cases a variety of genetic causes of disorders of the corpus callosum were identified with cytogenetic anomalies representing the most common underlying etiology. PMID:18792984

Schell-Apacik, Chayim Can; Wagner, Kristina; Bihler, Moritz; Ertl-Wagner, Birgit; Heinrich, Uwe; Klopocki, Eva; Kalscheuer, Vera M.; Muenke, Maximilian; von Voss, Hubertus

2009-01-01

141

Equivalent Fractions  

NSDL National Science Digital Library

In this interactive activity a user identifies two pairs of equivalent fractions for a given random fraction or one of the player's own and the user creates their representations by dividing and shading either a square or circular region. The fractions are shown as locations on the number line and their equivalency is demonstrated when they are at the same point. The user has the ability to construct a table of equivalent fractions. Instructions and exploration questions are given.

2011-01-01

142

Anisotropy of Weakly Vibrated Granular Flows  

E-print Network

We experimentally probe the anisotropy of the fabric of weakly vibrated, flowing granular media. Depending on the driving parameters --- flow rate and vibration strength --- this anisotropy varies significantly. We show how the anisotropy collapses when plotted as function of the driving stresses, uncovering a direct link between stresses and anisotropy. Moreover, our data suggests that for small anisotropies, the shear stresses vanish. Anisotropy of the fabric of granular media thus plays a crucial role in determining the rheology of granular flows.

Geert Wortel; Martin van Hecke

2014-10-16

143

Fractions Intro  

NSDL National Science Digital Library

Explore fractions while you help yourself to 1/3 of a chocolate cake and wash it down with 1/2 a glass of orange juice! Create your own fractions using fun interactive objects. Match shapes and numbers to earn stars in the fractions games. Challenge yourself on any level you like. Try to collect lots of stars!

Simulations, Phet I.; Paul, Ariel; Reid, Sam; Perkins, Kathy; Loeblein, Trish; Dubson, Mike

2012-08-17

144

Footprints of Statistical Anisotropies  

E-print Network

We propose and develop a formalism to describe and constrain statistically anisotropic primordial perturbations. Starting from a decomposition of the primordial power spectrum in spherical harmonics, we find how the temperature fluctuations observed in the CMB sky are directly related to the coefficients in this harmonic expansion. Although the angular power spectrum does not discriminate between statistically isotropic and anisotropic perturbations, it is possible to define analogous quadratic estimators that are direct measures of statistical anisotropy. As a simple illustration of our formalism we test for the existence of a preferred direction in the primordial perturbations using full-sky CMB maps. We do not find significant evidence supporting the existence of a dipole component in the primordial spectrum.

C. Armendariz-Picon

2005-09-29

145

Magnetic anisotropy and domain structure in gadolinium.  

E-print Network

??The magnetocrystalline anisotropy constants of high quality single crystals of gadolinium have been measured using torque magnetometry. The redetermination of the anisotropy constants was necessary… (more)

Smith, Ronald Leslie

1978-01-01

146

Registering Fiber Tracts with Fractional Anisotropy for Functional Sites Localization  

E-print Network

is used to compute a rigid plus scale transformation matrix (translation, rotation and scaling registration methods: a classical method using a FA image match metric and a new method using fiber tracts (FT) from an individual and a template FA map. By reduc- ing the candidate individual to a geometric

147

Teaching Fractions  

NSDL National Science Digital Library

This research guide provides suggestions for specialists and teachers looking to improve fraction instruction in their classrooms or schools. The guide starts with ideas for introducing fraction concepts in kindergarten and early elementary school and continues with activities and teaching strategies designed to help older students understand fraction magnitudes and computational procedures involving fractions. It then examines ways of helping students use fractions to solve rate, ratio, and proportion problems. Each recommendation includes a brief summary of supporting research and descriptions of classroom activities that can be used to implement the recommendation.

Fazio, Lisa; Siegler, Robert

2012-01-01

148

[A case of spastic paraparesis with mental deterioration and markedly thin corpus callosum--callosal dysfunction demonstrated by magnetic stimulation].  

PubMed

We have studied function of the corpus callosum in a patient with spastic paraparesis with mental deterioration and markedly thin corpus callosum using magnetic stimulation methods. In a 21-year-old woman with slowly progressive gait disturbance, neurological examination showed mental deterioration, euphoria, spastic paraparesis, bilateral Babinski's sign, and hyperesthesia caudal to the eighth thoracic level. No abnormalities were observed in electroencephalograms. Magnetic resonance imaging (MRI) studies of the brain showed cerebral cortical atrophy, markedly thin corpus callosum, and dilated cavum septum pellucidum and cavum Vergae, but spinal cord MRIs showed no abnormalities. The lysosomal enzyme activities, whose reduction was known to cause leukodystrophy, were all normal. Very long chain fatty acid was not increased in her blood, which is against adrenoleukodystrophy. She had no anti-HTLV-1 virus antibody. Based on these clinical features and the results of biochemical analyses, we diagnosed this patient as having spastic paraplegia associated with hypoplasia of the corpus callosum (Nojima and Iwabuchi). We performed three studies on the central motor pathways in this patient. The latencies of responses recorded from upper or lower limb muscles were all within the normal range, despite that the thresholds were slightly increased. This suggests that axonal degeneration occurs in the central motor pathways, which is consistent with the autopsy findings of a patient with hereditary spastic paraplegia associated with hypoplasia of the corpus callosum. Connection between the bilateral motor cortices was investigated by magnetic stimulation of both motor cortices. The suppression of the motor cortex evoked by stimulation of the contralateral motor cortex through the corpus callosum was absent in this patient. Intracortical inhibition within the motor cortex was demonstrated to be normal by a paired-magnetic stimulation technique. Based on the results of these results of these two experiments, we conclude that the function of the corpus callosum was disturbed in the present patient. This report first shows the functional abnormality of the extremely thin corpus callosum in a patient with hereditary spastic paraplegia associated with hypoplasia of the corpus callosum. PMID:9805987

Katayama, T; Sakamoto, N; Kuroda, K; Yahara, O; Ugawa, Y

1998-05-01

149

Permeability anisotropy and resistivity anisotropy of mechanically compressed mudrocks  

E-print Network

Permeability anisotropy (the ratio of the horizontal to vertical permeability) is an important parameter used in sedimentary basin models and geotechnical design to model fluid flow, locate hydrocarbon reserves and estimate ...

Adams, Amy Lynn

2014-01-01

150

Non-Bunch-Davies Anisotropy  

E-print Network

We introduce a generic mechanism that can extend the effects of relic anisotropies at the beginning of inflation to relatively much shorter scales in density perturbations. This is induced by non-Bunch-Davies states of the quantum fluctuations, and can show up in the non-oscillatory components of the density perturbations. This mechanism works for general forms of anisotropies, and, to illustrate it, we use an example of relic vector field. The detailed scale-dependence of these anisotropies can be used to probe the initial quantum state of our universe.

Xingang Chen; Yi Wang

2013-06-03

151

Automatic corpus callosum segmentation using a deformable active Fourier contour model  

NASA Astrophysics Data System (ADS)

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.

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

2012-03-01

152

Beginning Fractions  

NSDL National Science Digital Library

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.

Banfill, J. C.

2007-12-12

153

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

PubMed

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

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

2014-04-01

154

Corpus callosum hematoma secondary to cerebral venous malformation presenting as alien hand syndrome.  

PubMed

A 26-year-old right-handed female presented with alien hand syndrome (AHS) secondary to corpus callosum (CC) hematoma. The patient had abnormal feelings in the left upper limb and exhibited intermanual conflict. Imaging studies demonstrated acute hemorrhage in the genu and body of the CC secondary to cerebral venous malformation. Callosal hemorrhage is usually caused by head trauma or a ruptured arteriovenous that extends beyond the CC. We report what may be the first case of AHS caused by callosal hemorrhage due to venous malformation. PMID:22784383

Huang, Ying; Jia, Jianping

2013-08-01

155

Agenesis of the corpus callosum: symptoms consistent with developmental disability in two siblings.  

PubMed

Agenesis of the corpus callosum (AgCC) is a congenital disorder that disrupts the development of neurological structures connecting the right and left hemispheres of the brain. In addition to neurological symptoms, many individuals with AgCC demonstrate marked deficits in social, communication, and adaptive skills. This paper presents two case studies of congenital AgCC in siblings with socioemotional and behavioral symptoms consistent with developmental disability, but with notably different symptom presentations and clinical needs. Conclusions from these cases suggest that unique symptom profiles of individuals with AgCC warrant careful consideration for referral to appropriate academic and habilitative services. PMID:24417213

Cavalari, Rachel N S; Donovick, Peter J

2015-02-01

156

Equivalent Fractions  

NSDL National Science Digital Library

In this NCTM Android app a user identifies equivalent fractions for a given random fraction or one of the player's own. The user creates their representations by dividing and shading either a square or circular region. The fractions are shown as locations on the number line and their equivalency is demonstrated when they are at the same point. The user has the ability to construct a table of equivalent fractions. This app is related to an Illuminations activity and an iOS app that are cataloged separately.

2012-07-31

157

Equivalent Fractions  

NSDL National Science Digital Library

In this NCTM iOS app a user identifies equivalent fractions for a given random fraction or one of the player's own. The user creates their representations by dividing and shading either a square or circular region. The fractions are shown as locations on the number line and their equivalency is demonstrated when they are at the same point. The user has the ability to construct a table of equivalent fractions. This app is related to an Illuminations activity and an Android app that are cataloged separately.

2012-08-10

158

Fraction Monkeys  

NSDL National Science Digital Library

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.

2012-01-01

159

Dark energy and CMB anisotropy  

E-print Network

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 ...

Lam, Yukyam, 1982-

2004-01-01

160

Wind anisotropies and GRB progenitors  

E-print Network

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.

Georges Meynet; Andre Maeder

2007-01-17

161

The elastic anisotropy of marble  

E-print Network

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...

Gebhard, Susan Nash

2012-06-07

162

Mowat-Wilson syndrome in a fetus with antenatal diagnosis of short corpus callosum: advocacy for standard autopsy.  

PubMed

Mowat-Wilson syndrome (MWS) is a genetic disease caused by heterozygous mutations or deletions of the ZEB2 gene rarely diagnosed prenatally and with little fetal description reported. It is mainly characterized by moderate-to-severe intellectual disability, epilepsy, facial dysmorphism and various malformations including Hirschsprung disease and corpus callosum anomalies. Here we report a fetal case of MWS well described, suspected at standard autopsy. The association of a corpus callosum hypoplasia with a histological Hirschsprung disease and a typical facial gestalt allowed the guiding of genetic testing. Classical fetopathological examination still keeps indications in cases of syndromic association in the era of virtual autopsy. PMID:23523603

Spaggiari, Emmanuel; Baumann, Clarisse; Alison, Marianne; Oury, Jean-François; Belarbi, Nadia; Dupont, Céline; Guimiot, Fabien; Delezoide, Anne-Lise

2013-06-01

163

Understanding Fractions  

NSDL National Science Digital Library

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.

Pennant, Jennie; Woodham, Liz

2013-01-01

164

What fraction?  

NSDL National Science Digital Library

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?"

Blundred, A.

2012-01-01

165

Fraction Tutorial  

NSDL National Science Digital Library

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.

Webb, B. J.

2000-01-01

166

Fraction Conversion  

NSDL National Science Digital Library

This lesson is designed to develop students' abilities to convert between fractions and decimals. This lesson provides links to discussions and activities related to fraction conversion as well as suggested ways to integrate them into the lesson. Finally, the lesson provides links to follow-up lessons designed for use in succession with the current one.

2010-01-01

167

Corpus callosum analysis using MDL-based sequential models of shape and appearance  

NASA Astrophysics Data System (ADS)

This paper describes a method for automatically analysing and segmenting the corpus callosum from magnetic resonance images of the brain based on the widely used Active Appearance Models (AAMs) by Cootes et al. Extensions of the original method, which are designed to improve this specific case are proposed, but all remain applicable to other domain problems. The well-known multi-resolution AAM optimisation is extended to include sequential relaxations on texture resolution, model coverage and model parameter constraints. Fully unsupervised analysis is obtained by exploiting model parameter convergence limits and a maximum likelihood estimate of shape and pose. Further, the important problem of modelling object neighbourhood is addressed. Finally, we describe how correspondence across images is achieved by selecting the minimum description length (MDL) landmarks from a set of training boundaries using the recently proposed method of Davies et al. This MDL-approach ensures a unique parameterisation of corpus callosum contour variation, which is crucial for neurological studies that compare reference areas such as rostrum, splenium, et cetera. We present quantitative and qualitative results that show that the method produces accurate, robust and rapid segmentations in a cross sectional study of 17 subjects, establishing its feasibility as a fully automated clinical tool for analysis and segmentation.

Stegmann, Mikkel B.; Davies, Rhodri H.; Ryberg, Charlotte

2004-05-01

168

Ontophyletics of the nervous system: development of the corpus callosum and evolution of axon tracts.  

PubMed Central

The evolution of nervous systems has included significant changes in the axon tracts of the central nervous system. These evolutionary changes required changes in axonal growth in embryos. During development, many axons reach their targets by following guidance cues that are organized as pathways in the embryonic substrate, and the overall pattern of the major axon tracts in the adult can be traced back to the fundamental pattern of such substrate pathways. Embryological and comparative anatomical studies suggest that most axon tracts, such as the anterior commissure, have evolved by the modified use of preexisting substrate pathways. On the other hand, recent developmental studies suggest that a few entirely new substrate pathways have arisen during evolution; these apparently provided opportunities for the formation of completely new axon tracts. The corpus callosum, which is found only in placental mammals, may be such a truly new axon tract. We propose that the evolution of the corpus callosum is founded on the emergence of a new preaxonal substrate pathway, the "glial sling," which bridges the two halves of the embryonic forebrain only in placental mammals. Images PMID:6577462

Katz, M J; Lasek, R J; Silver, J

1983-01-01

169

Structural and Functional Reorganization of the Corpus Callosum between the Age of 6 and 8 Years  

PubMed Central

The establishment of an efficient exchange of information between the cerebral hemispheres is of crucial importance in the developing functionally lateralized brain. The corpus callosum, the major connection between the cerebral hemispheres, grows constantly throughout childhood and adolescence. However, behavioral studies suggest the existence of a critical time period for callosal functional development starting around the age of 6 years. In the present longitudinal study, examining a cohort of 20 children at the age of 6 and 8 years, we assessed the relationship between structural and functional callosal development during this time period. The structural development was quantified by calculating the increase in callosal thickness using a shape-based computational analysis of the mid-sagittal corpus callosum as obtained with magnetic resonance imaging. The functional development was assessed with a speech discrimination task based on the dichotic presentation of consonant–vowel syllables. The statistical analysis revealed that children whose callosal isthmus increased in thickness over the course of 2 years showed a decrease in interhemispheric information transfer. However, children exhibiting a decrease in isthmus thickness revealed an increase in information transfer. These results might indicate a refinement process of the callosal connections to optimize the neuronal communication between the developing cerebral hemispheres. PMID:20847151

Luders, Eileen; Specht, Karsten; Ofte, Sonja H.; Toga, Arthur W.; Thompson, Paul M.; Helland, Turid; Hugdahl, Kenneth

2011-01-01

170

fMRI and corpus callosum relationships in monozygotic twins discordant for handedness.  

PubMed

To further investigate brain structure and function in 26 handedness discordant monozygotic twin pairs (MzHd), MRI and behavioural assessments were carried out. These showed significant correlation between language-specific functional laterality in inferior and middle frontal gyri, and anterior corpus callosum. Previous studies of handedness discordant monozygotic twins failed to resolve the issue concerning handedness and hemispheric laterality for language due to methodological disparities. The results would be relevant to genetic theories as well as to brain structure:function explanations. MzHd twins underwent MRI and fMRI scanning as well as behavioural assessment of motor performance and cognition. There were significant differences on MRI and fMRI laterality measures, as well as a significant correlation between anterior callosal widths and functional laterality. LH twins showed higher frequencies of atypical functional laterality. There was no significant within-twin pair correlation on fMRI verbal laterality, nor did results show within-twin pair differences on verbal fluency or IQ. Implications for the field of laterality research pertain to frontal hemispheric equipotentiality for verbal processes in healthy individuals. In particular, there can be an apparent lack of cognitive 'cost' to atypical laterality. An fMRI verbal laterality index correlated significantly with corpus callosum widths near Broca's area. PMID:22527119

Gurd, J M; Cowell, P E; Lux, S; Rezai, R; Cherkas, L; Ebers, G C

2013-03-01

171

Unmyelinated Axons Show Selective Rostrocaudal Pathology in the Corpus Callosum Following Traumatic Brain Injury  

PubMed Central

Axonal injury is consistently observed following traumatic brain injury (TBI). Prior research has extensively characterized the post-TBI response in myelinated axons. Despite evidence that unmyelinated axons comprise a numerical majority of cerebral axons, pathological changes in unmyelinated axons following TBI have not been systematically studied. To identify morphological correlates of functional impairment of unmyelinated fibers following TBI, we assessed ultrastructural changes in corpus callosum axons. Adult rats received moderate fluid percussion TBI, which produced diffuse injury with no contusion. Cross-sectional areas of 13,797 unmyelinated, and 3,278 intact myelinated axons were stereologically measured at survival intervals from 3 hours to 15 days post-injury. The mean caliber of unmyelinated axons was significantly reduced at 3 to 7 days, and recovered by 15 days, but the time course of this shrinkage varied among the genu, mid-callosum and splenium. Relatively large unmyelinated axons appeared to be particularly vulnerable. Injury-induced decreases in unmyelinated fiber density were also observed but they were more variable than caliber reductions. By contrast, no significant morphometric changes were observed in myelinated axons. The finding of a preferential vulnerability in unmyelinated axons has implications for current concepts of axonal responses following TBI and for development of specifically targeted therapies. PMID:22318124

Reeves, Thomas M.; Smith, Terry L.; Williamson, Judy C.; Phillips, Linda L.

2012-01-01

172

Genetic, Morphometric, and Behavioral Factors Linked to the Midsagittal Area of the Corpus Callosum  

PubMed Central

The corpus callosum is the main commissure connecting left and right cerebral hemispheres, and varies widely in size. Differences in the midsagittal area of the corpus callosum (MSACC) have been associated with a number of cognitive and behavioral phenotypes, including obsessive-compulsive disorders, psychopathy, suicidal tendencies, bipolar disorder, schizophrenia, autism, and attention deficit hyperactivity disorder. Although there is evidence to suggest that MSACC is heritable in normal human populations, there is surprisingly little evidence concerning the genetic modulation of this variation. Mice provide a potentially ideal tool to dissect the genetic modulation of MSACC. Here, we use a large genetic reference panel – the BXD recombinant inbred line – to dissect the natural variation of the MSACC. We estimated the MSACC in over 300 individuals from nearly 80 strains. We found a 4-fold difference in MSACC between individual mice, and a 2.5-fold difference among strains. MSACC is a highly heritable trait (h2?=?0.60), and we mapped a suggestive QTL to the distal portion of Chr 14. Using sequence data and neocortical expression databases, we were able to identify eight positional and plausible biological candidate genes within this interval. Finally, we found that MSACC correlated with behavioral traits associated with anxiety and attention. PMID:22666227

Newbury, Alex J.; Rosen, Glenn D.

2012-01-01

173

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

NASA Astrophysics Data System (ADS)

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.

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

2009-02-01

174

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

PubMed Central

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

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

175

Limits on the gravity wave contribution to microwave anisotropies  

E-print Network

We present limits on the fraction of large angle microwave anisotropies which could come from tensor perturbations. We use the COBE results as well as smaller scale CMB observations, measurements of galaxy correlations, abundances of galaxy clusters, and Lyman alpha absorption cloud statistics. Our aim is to provide conservative limits on the tensor-to-scalar ratio for standard inflationary models. For power-law inflation, for example, we find T/S1.

J. P. Zibin; Douglas Scott; Martin White

1999-01-05

176

Adding Fractions  

NSDL National Science Digital Library

In this web-based tutorial, students learn procedures for adding fractions with like and unlike denominators. The tutorial includes visual representations of the problems using pizzas, animations of the algorithm, and links to related lessons, worksheets, and practice problems.

Website, Math I.

2011-09-23

177

Fraction Fanatic  

NSDL National Science Digital Library

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. ...

Jackson, Ms.

2007-10-25

178

Comparing Fractions  

NSDL National Science Digital Library

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.

2011-01-01

179

Fraction Pieces  

NSDL National Science Digital Library

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.

2005-01-01

180

Gender differences in brain volume and size of corpus callosum and amygdala of rhesus monkey measured from MRI images  

Microsoft Academic Search

While it has been established that the weight of the female rhesus monkey brain is less than that of the male, the sexual dimorphism of specific brain structures has not been well-documented. To further understand potential sex differences, we measured the whole brain volume and the size of the corpus callosum (mid-sagittal) and amygdala (largest coronal section) in MRI images

Michael S. Franklin; Gary W. Kraemer; Steven E. Shelton; Eva Baker; Ned H. Kalin; Hideo Uno

2000-01-01

181

Comparison of the pattern of atrophy of the corpus callosum in frontotemporal dementia, progressive supranuclear palsy, and Alzheimer's disease  

Microsoft Academic Search

OBJECTIVESThe loss of the neurons in layer 3, one of the groups of cortical neurons most vulnerable in various degenerative brain diseases, results in axonal degeneration leading to atrophy of the corpus callosum. Previous studies showed callosal atrophy in three degenerative dementias: frontotemporal dementia (FTD), progressive supranuclear palsy (PSP), and Alzheimer's disease (AD). However, it is unclear whether a characteristic

Hiroshi Yamauchi; Hidenao Fukuyama; Yasuhiro Nagahama; Yukinori Katsumi; Takuya Hayashi; Chisako Oyanagi; Junji Konishi; Hideo Shio

2000-01-01

182

Agenesis of the Corpus Callosum and Skeletal Deformities in Two Unrelated Patients: Analysis via MRI and Radiography.  

PubMed

Purpose. Mental retardation, mild to severe epilepsy and cerebral palsy often of hemiplegic type are common accompaniments in patients with agenesis/hypoplasia of the corpus callosum. Skeletal deformities of bilateral radiohumeral synostosis, brachydactyly, bilateral elbow dislocation, talipes equinovarus, and juxtacalcaneal accessory bones have been encountered in two unrelated children with agenesis of the corpus callosum. Methods. We report on two unrelated children who presented with the full clinical criteria of agenesis of the corpus callosum. Strikingly, both presented with variable upper and lower limb deformities. The clinical features, radiographic and MRI findings in our current patients, have been compared with previously reported cases identified through a PubMed literature review. Results. Bilateral radiohumeral synostosis associated with pyruvate dehydrogenase deficiency has been encountered in one patient. The other patient manifested bilateral elbow dislocation, coxa valga, talipes equinovarus, and bilateral juxtacalcaneal accessory bones. Conclusion. The constellation of malformation complexes in our current patients have the hitherto not been reported and expanding the spectrum of skeletal deformities in connection with agenesis of the corpus callosum. PMID:24592343

Al Kaissi, Ali; Kurz, Herbert; Bock, Wolfgang; Pärtan, Gerald; Klaushofer, Klaus; Ganger, Rudolf; Grill, Franz

2014-01-01

183

Clinical Features: Hereditary Motor and Sensory Neuropathy with Agenesis of the Corpus Callosum (HMSN/ACC) [OMIM #218000  

E-print Network

1/13 Clinical Features: Hereditary Motor and Sensory Neuropathy with Agenesis of the Corpus sensorimotor neuropathy resulting in hypotonia, areflexia and amyotrophy, variable degrees of dysgenesis Neuropathy with Agenesis of the Corpus Callosum #12;1/13 Prenatal testing for a known mutation Sample

Ober, Carole

184

Median cleft face syndrome in association with hydrocephalus, agenesis of the corpus callosum, holoprosencephaly and choanal atresia  

Microsoft Academic Search

A premature female infant had the characteristic features of the median cleft face syndrome in association with holoprosencephaly, agenesis of the corpus callosum, hydrocephalus and choanal atresia. Whereas the nervous system is rarely affected in patients with the median cleft face syndrome, severe mental retardation has been reported in three previously published cases and is suggested in our own patient.

T. Bömelburg; W. Lenz; T. Eusterbrock

1987-01-01

185

Agenesis of the Corpus Callosum and Skeletal Deformities in Two Unrelated Patients: Analysis via MRI and Radiography  

PubMed Central

Purpose. Mental retardation, mild to severe epilepsy and cerebral palsy often of hemiplegic type are common accompaniments in patients with agenesis/hypoplasia of the corpus callosum. Skeletal deformities of bilateral radiohumeral synostosis, brachydactyly, bilateral elbow dislocation, talipes equinovarus, and juxtacalcaneal accessory bones have been encountered in two unrelated children with agenesis of the corpus callosum. Methods. We report on two unrelated children who presented with the full clinical criteria of agenesis of the corpus callosum. Strikingly, both presented with variable upper and lower limb deformities. The clinical features, radiographic and MRI findings in our current patients, have been compared with previously reported cases identified through a PubMed literature review. Results. Bilateral radiohumeral synostosis associated with pyruvate dehydrogenase deficiency has been encountered in one patient. The other patient manifested bilateral elbow dislocation, coxa valga, talipes equinovarus, and bilateral juxtacalcaneal accessory bones. Conclusion. The constellation of malformation complexes in our current patients have the hitherto not been reported and expanding the spectrum of skeletal deformities in connection with agenesis of the corpus callosum. PMID:24592343

Bock, Wolfgang; Partan, Gerald; Klaushofer, Klaus; Ganger, Rudolf; Grill, Franz

2014-01-01

186

Heliospheric Influence on the Anisotropy of TeV Cosmic Rays  

NASA Astrophysics Data System (ADS)

This paper provides a theory of using Liouville's theorem to map the anisotropy of TeV cosmic rays seen at Earth using the particle distribution function in the local interstellar medium (LISM). The ultimate source of cosmic ray anisotropy is the energy, pitch angle, and spatial dependence of the cosmic ray distribution function in the LISM. Because young nearby cosmic ray sources can make a special contribution to the cosmic ray anisotropy, the anisotropy depends on the source age, distance and magnetic connection, and particle diffusion of these cosmic rays, all of which make the anisotropy sensitive to the particle energy. When mapped through the magnetic and electric field of a magnetohydrodynamic model heliosphere, the large-scale dipolar and bidirectional interstellar anisotropy patterns become distorted if they are seen from Earth, resulting in many small structures in the observations. Best fits to cosmic ray anisotropy measurements have allowed us to estimate the particle density gradient and pitch angle anisotropies in the LISM. It is found that the heliotail, hydrogen deflection plane, and the plane perpendicular to the LISM magnetic field play a special role in distorting cosmic ray anisotropy. These features can lead to an accurate determination of the LISM magnetic field direction and polarity. The effects of solar cycle variation, the Sun's coronal magnetic field, and turbulence in the LISM and heliospheric magnetic fields are minor but clearly visible at a level roughly equal to a fraction of the overall anisotropy amplitude. The heliospheric influence becomes stronger at lower energies. Below 1 TeV, the anisotropy is dominated by small-scale patterns produced by disturbances in the heliosphere.

Zhang, Ming; Zuo, Pingbing; Pogorelov, Nikolai

2014-07-01

187

Anisotropy of conductivity in carbon fiber-reinforced plastics with continuous fibers  

NASA Astrophysics Data System (ADS)

Carbon fiber-reinforced plastics (CFRP), as high strength advanced materials are often used as media for embedding sensors and actuators. Due to the properties of components and processing conditions they are electrically anisotropic, with coefficient of anisotropy sometimes exceeding several thousands. This may prevent elimination of static electricity and cause erosion of material due to micro discharges at contacts with fastenings and embedded sensors and actuators, causing their malfunction. For this reason, the investigation of electrical properties of CFRP may provide the solution to this problem. Distribution of electric current field in CFRP and related with it possible errors in measurements of longitudinal conductivity and anisotropy are analyzed. CFRP have been prepared from PAN or cellulose fibers with different heat treatment temperatures and conductivity anisotropy was measured as a function of filler volume fraction and processing conditions. With increasing loading coefficient of anisotropy (alpha) decreases. Lower values of (alpha) were observed when curing agents containing ionic complexes of metals were used. Modifications of fiber surface with hydrophobic agents results in increased anisotropy. Composites prepared with carbon fabrics are isotropic in the fabric plane. Coefficient of anisotropy decreases with increasing molding pressure and depends on the type of weaving of fabric. In hybrid composites with alternating layers of carbon fabric and complex fiber fabric anisotropy is higher due to partial decomposition of conducting layer on top of complex fibers. A method for reducing anisotropy by introducing conducting `jumpers', shorting individual fibers or layers of fabric is proposed. The change of anisotropy in the process of fabrication of carbon-carbon composite by passing electric current through fibers has been investigated. In conclusion, alternative uses of CFRP with reduced anisotropy for contact elements of electric current through fibers has been investigated. In conclusion, alternative uses of CFRP with reduced anisotropy for contact elements of electric machines and geological prospecting as imitations of rocks are discussed.

Ponomarenko, Anatoliy T.; Shevchenko, Vitaliy G.; Letyagin, Sergey V.; Klason, Carl

1995-05-01

188

Crustal Anisotropy in Eastern Tibet  

NASA Astrophysics Data System (ADS)

A growing list and wide variety of evidence suggests that the Tibetan middle and lower crust is warm and presumably ductile. This list includes extensive Cenozoic volcanism, low electrical resistivity, satellite magnetic anomalies consistent with a raised Curie isotherm, and the lack of mid- to lower-crustal earthquakes. Seismological observations include strong P-to-S conversion bright-spots on active source wide-angle reflection data, strong crustal attenuation, pervasive crustal low velocity zones (LVZs) inferred from receiver functions or surface wave dispersion that are strongest near the periphery of the Plateau, and strong radial anisotropy, characteristic of significant shear strains, in the middle crust. Yet, surface strain rates and finite strains, as measured by GPS and SKS splitting fast axis orientations, respectively, appear to imply a vertical coherence of deformation from the uppermost crust into the upper mantle. Thus, questions about the mechanism of deformation of the Tibetan crust remain, including: (1) To what extent is deformation of the middle crust localized in a channel (channel flow) and hence different from that above and perhaps below it? (2) Or, conversely, to what extent is deformation of the entire lithosphere vertically coherent? Observations of crustal anisotropy can help to answer these questions, but although such observations are widespread, for the most part they remain either localized or so poorly resolved that exploiting such observations to answer these questions remains difficult. We summarize recently constructed models of radial and azimuthal anisotropy in the middle and lower crust beneath eastern Tibet. The models result from Bayesian Monte Carlo inversion of surface wave dispersion derived from ambient noise cross-correlations for Rayleigh and Love waves using Chinese Earthquake Array and PASSCAL data in and surrounding Tibet. (1) Significant middle-to-lower crustal radial anisotropy characterizes the crust beneath most of E. Tibet, but vanishes toward the S. China block in the east and north of the Kunlun fault in the north. Radial anisotropy is confined to the middle to perhaps lower crust with an upper boundary at about 20 km depth and a less well resolved lower boundary, but, on average, radial anisotropy is found between 40%-80% of the Moho depth. (2) In the upper crust, azimuthal anisotropy is strong (~4%) and fast axis orientations are roughly parallel to strikes of major strike-slip faults. Azimuthal anisotropy is weak in the middle crust (<2%) where radial anisotropy is strongest and increases in the lower crust. The azimuthal anisotropy in the lower crust and uppermost mantle is coherent with upper crustal anisotropy across some but not all of E. Tibet. On a preliminary basis, the seismological evidence is consistent with channel flow in the middle crust but with vertically coherent deformation across only part of E. Tibet. The marked radial anisotropy in the middle crust may result from layers of partial melt, which would not affect shear on vertical planes.

Ritzwoller, M. H.; Xie, J.; Shen, W.; Molnar, P. H.; Yang, Y.; Zhou, L.; Zheng, Y.

2012-12-01

189

Balanced interhemispheric cortical activity is required for correct targeting of the corpus callosum.  

PubMed

Bilateral integration of sensory and associative brain processing is achieved by precise connections between homologous regions in the two hemispheres via the corpus callosum. These connections form postnatally, and unilateral deprivation of sensory or spontaneous cortical activity during a critical period severely disrupts callosal wiring. However, little is known about how this early activity affects precise circuit formation. Here, using in utero electroporation of reporter genes, optogenetic constructs, and direct disruption of activity in callosal neurons combined with whisker ablations, we show that balanced interhemispheric activity, and not simply intact cortical activity in either hemisphere, is required for functional callosal targeting. Moreover, bilateral ablation of whiskers in symmetric or asymmetric configurations shows that spatially symmetric interhemispheric activity is required for appropriate callosal targeting. Our findings reveal a principle governing axon targeting, where spatially balanced activity between regions is required to establish their appropriate connectivity. PMID:24945772

Suárez, Rodrigo; Fenlon, Laura R; Marek, Roger; Avitan, Lilach; Sah, Pankaj; Goodhill, Geoffrey J; Richards, Linda J

2014-06-18

190

Callosal disconnection syndrome after corpus callosum infarct: a diffusion tensor tractography study.  

PubMed

We report a patient who presented with callosal disconnection syndrome (CDS) and fiber disconnection on diffusion tensor tractography (DTT) after an infarct of the corpus callosum (CC). A 72-year-old woman presented with manifestations of CDS, including frontal alien hand syndrome (AHS), left agraphia, right hemiparesis, right somatosensory deficit, left neglect, and impaired visual recognition. DTT was performed for the evaluation of CC fibers, followed by comparison with DTT findings of normal subjects. DTT of the normal subject revealed bilateral extension of CC fibers to the frontal, parietal, and occipitotemporal cortices. By contrast, CC fibers of the patient revealed extensive disruption, with the exception of CC fibers passing through the anterior genu and the posterior splenium. The extensive disruption of CC fibers appears to explain the patient's various CDS symptoms. In brief, DTT could be useful for detection of CC lesions in patients with CDS. PMID:23246180

Jang, Sung Ho; Lee, Jun; Yeo, Sang Seok; Chang, Min Cheol

2013-10-01

191

Transient lesion in the splenium of the corpus callosum in acute uncomplicated falciparum malaria.  

PubMed

Patients with acute uncomplicated Plasmodium falciparum malaria have no evident neurologic disorder, vital organ dysfunction, or other severe manifestations of infection. Nonetheless, parasitized erythrocytes cytoadhere to the endothelium throughout their microvasculature, especially within the brain. We aimed to determine if 3 Tesla magnetic resonance imaging studies could detect evidence of cerebral abnormalities in these patients. Within 24 hours of admission, initial magnetic resonance imaging examinations found a lesion with restricted water diffusion in the mid-portion of the splenium of the corpus callosum of 4 (40%) of 10 male patients. The four patients who had a splenial lesion initially had evidence of more severe hemolysis and thrombocytopenia than the six patients who had no apparent abnormality. Repeat studies four weeks later found no residua of the lesions and resolution of the hematologic differences. These observations provide evidence for acute cerebral injury in the absence of severe or cerebral malaria. PMID:24615139

Laothamatas, Jiraporn; Sammet, Christina L; Golay, Xavier; Van Cauteren, Marc; Lekprasert, Varinee; Tangpukdee, Noppadon; Krudsood, Srivicha; Leowattana, Wattana; Wilairatana, Polrat; Swaminathan, Srirama V; DeLaPaz, Robert L; Brown, Truman R; Looareesuwan, Sornchai; Brittenham, Gary M

2014-06-01

192

Intact bilateral resting-state networks in the absence of the corpus callosum  

PubMed Central

Temporal correlations between different brain regions in the resting-state BOLD signal are thought to reflect intrinsic functional brain connectivity (Biswal et al., 1995; Greicius et al., 2003; Fox et al., 2007). The functional networks identified are typically bilaterally distributed across the cerebral hemispheres, show similarity to known white matter connections (Greicius et al., 2009), and are seen even in anesthetized monkeys (Vincent et al., 2007). Yet it remains unclear how they arise. Here we tested two distinct possibilities: (1) functional networks arise largely from structural connectivity constraints, and generally require direct interactions between functionally coupled regions mediated by white-matter tracts; (2) functional networks emerge flexibly with the development of normal cognition and behavior and can be realized in multiple structural architectures. We conducted resting-state fMRI in eight adult humans with complete agenesis of the corpus callosum (AgCC) and normal intelligence, and compared their data to those from eight healthy matched controls. We carried out three main analyses: anatomical region-of-interest based correlations to test homotopic functional connectivity, independent component analysis (ICA) to reveal functional networks with a data-driven approach, and ICA-based inter-hemispheric correlation analysis. Both groups showed equivalently strong homotopic BOLD correlation. Surprisingly, almost all of the group-level ICs identified in AgCC were observed in controls and were predominantly bilaterally symmetric. The results argue that a normal complement of resting-state networks and intact functional coupling between the hemispheres can emerge in the absence of the corpus callosum, favoring the second over the first possibility above. PMID:22016549

Tyszka, J. Michael; Kennedy, Daniel P.; Adolphs, Ralph; Paul, Lynn K.

2011-01-01

193

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

PubMed Central

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

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

2010-01-01

194

The Role of Corpus Callosum Development in Functional Connectivity and Cognitive Processing  

PubMed Central

The corpus callosum is hypothesized to play a fundamental role in integrating information and mediating complex behaviors. Here, we demonstrate that lack of normal callosal development can lead to deficits in functional connectivity that are related to impairments in specific cognitive domains. We examined resting-state functional connectivity in individuals with agenesis of the corpus callosum (AgCC) and matched controls using magnetoencephalographic imaging (MEG-I) of coherence in the alpha (8–12 Hz), beta (12–30 Hz) and gamma (30–55 Hz) bands. Global connectivity (GC) was defined as synchronization between a region and the rest of the brain. In AgCC individuals, alpha band GC was significantly reduced in the dorsolateral pre-frontal (DLPFC), posterior parietal (PPC) and parieto-occipital cortices (PO). No significant differences in GC were seen in either the beta or gamma bands. We also explored the hypothesis that, in AgCC, this regional reduction in functional connectivity is explained primarily by a specific reduction in interhemispheric connectivity. However, our data suggest that reduced connectivity in these regions is driven by faulty coupling in both inter- and intrahemispheric connectivity. We also assessed whether the degree of connectivity correlated with behavioral performance, focusing on cognitive measures known to be impaired in AgCC individuals. Neuropsychological measures of verbal processing speed were significantly correlated with resting-state functional connectivity of the left medial and superior temporal lobe in AgCC participants. Connectivity of DLPFC correlated strongly with performance on the Tower of London in the AgCC cohort. These findings indicate that the abnormal callosal development produces salient but selective (alpha band only) resting-state functional connectivity disruptions that correlate with cognitive impairment. Understanding the relationship between impoverished functional connectivity and cognition is a key step in identifying the neural mechanisms of language and executive dysfunction in common neurodevelopmental and psychiatric disorders where disruptions of callosal development are consistently identified. PMID:22870191

Findlay, Anne M.; Honma, Susanne; Jeremy, Rita J.; Strominger, Zoe; Bukshpun, Polina; Wakahiro, Mari; Brown, Warren S.; Paul, Lynn K.; Barkovich, A. James; Mukherjee, Pratik; Nagarajan, Srikantan S.; Sherr, Elliott H.

2012-01-01

195

Agenesis of the Corpus Callosum in California 1983-2003: A Population-Based Study  

PubMed Central

The objective of this study was to characterize the prevalence, demographic risk factors, and malformations associated with agenesis and hypoplasia of the corpus callosum diagnosed in infancy. Using a large population-based registry of birth defects, we ascertained 630 cases of agenesis (ACC) and hypoplasia (HCC) of the corpus callosum diagnosed in the first year of life among 3.4 million live births from 1983?2003. Infants with destructive lesions or specific complex central nervous system malformations (neural tube defects, lissencephaly, and holoprosencephaly) were excluded. Multivariable Poisson regression analysis was used to examine demographic risk factors. The combined prevalence of ACC and HCC was 1.8 per 10,000 live births. Fifty-two percent of cases were male. Infants with ACC had an almost four-fold higher prevalence among infants born prematurely when compared with children born ? 37 weeks gestation (RR 3.7, 95% CI 2.5?5.3). After adjusting for paternal age, advanced maternal age ?40 years was associated with ACC in infants with a chromosomal disorder (ACC RR 5.9; 95% CI 1.8?19.3, HCC RR 3.5; 95% CI 0.9?14.1). Paternal age was not significantly associated with ACC after adjusting for maternal age. Callosal anomalies were often seen in the context of a chromosomal abnormality (17.3%) and with accompanying somatic (musculoskeletal 33.5% and cardiac 27.6%) and central nervous system malformations (49.5%). Callosal anomalies form a clinically significant and relatively frequent group of malformations of the central nervous system that are associated with increased risk of premature birth, are more common with advanced maternal age and are frequently part of a complex, multisystem disorder. PMID:18642362

Glass, Hannah C.; Shaw, Gary M.; Ma, Chen; Sherr, Elliott H.

2008-01-01

196

Current profiles of astrocytes from the corpus callosum of newborn and 28-day-old rats.  

PubMed

In astrocytes, ion currents are predominantly carried by K(+) ions, and their potassium channel expression changes during development. Here, we studied ion current generated by voltage-ramp protocols in cultured astrocytes from the corpus callosum of newborn (P0) and 28-day-old (P28) rats. Inward currents measured at -140 mV and chord conductances measured from -140 to -75 mV, were smaller in P0-astrocytes than in P28-astrocytes, and in P28-astrocytes were affected by 100 ?M Ba(2+), indicating the presence of an inward rectifier K(+) (Kir) current. On the other hand, P0-astrocytes showed higher outward current measured at 80 mV and a higher chord conductance, between 0 and 80 mV, than P28-astrocytes. The outward current was more potently reduced by 2mM Ba(2+) in P0-astrocytes than in P28-astrocytes, and slightly reduced at both ages using low concentrations of Ba(2+). Moreover, outward current was partially blocked by iberiotoxin in P0-astrocytes, indicating the presence of big-conductance Ca(2+)-activated K(+) (BK) channels. In addition, 4-aminopyridine inhibited the outward current in P0- and P28-astrocytes. In summary, P0-astrocytes exhibited the BK current, a major density of delayed rectifier K(+) (K(DR)) current, and a low density of the Kir current, whereas P28-astrocytes presented a major density of Kir current, a low density of the K(DR) current, and the absence of BK current. These results could contribute to a better understanding of the role of K(+) currents in the corpus callosum. PMID:20851740

Montiel-Herrera, Marcelino; García-Colunga, Jesús

2010-11-26

197

Anisotropy of machine building materials  

NASA Technical Reports Server (NTRS)

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.

Ashkenazi, Y. K.

1981-01-01

198

Dividing Fractions  

NSDL National Science Digital Library

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.

2012-10-17

199

Fraction Penguin  

NSDL National Science Digital Library

In this craft activity, learners will recognize, name, and compare the fractions 1/2, 1/4, and 1/8 by constructing a penguin out of portions of paper circles. This detailed lesson plan includes key vocabulary words, background information for educators, extension ideas, and resources.

Sciences, California A.

2008-01-01

200

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

Microsoft Academic Search

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

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

2010-01-01

201

The microwave background anisotropies: Observations  

PubMed Central

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 ?K 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° 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

Wilkinson, David

1998-01-01

202

Can we understand rocks without anisotropy?  

NASA Astrophysics Data System (ADS)

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

Dabrowski, Marcin

2014-05-01

203

Fraction Reduction through Continued Fractions  

ERIC Educational Resources Information Center

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.

Carley, Holly

2011-01-01

204

Fraction Tracks  

NSDL National Science Digital Library

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.

Boston, Wgbh

1996-01-01

205

Anisotropy Studies in Central Greece  

NASA Astrophysics Data System (ADS)

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.

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

2007-12-01

206

Magnetic anisotropy in nanostructured gadolinium  

NASA Astrophysics Data System (ADS)

This experimental work evaluates the magnetic response of 25-nm-thick Gd thin film and 1400 × 70 × 50 nm3 Gd nanobar structures. Neither the thin film nor the nanobars exhibited single domain behavior at temperatures down to 53 K. The Gd thin film exhibited a magnetocrystalline anisotropy induced spin-reorientation due to a hexagonal close-packed (002) texture, something different from that previously reported on epitaxial Gd thin film. The discrepancy is due to grain boundary induced spin-disorder in the nanosacle. The Gd nanobars had a saturation magnetization 75% smaller than the thin film or bulk and is attributed to oxidation as well as the crystallinity changes from hexagonal close-packed to face-centered cubic caused by stress induced stacking faults. These experimental results for both thin film and nanobar show that the crystallinity has a substantial impact to the magnetic anisotropy of Gd nanostructures as well as the formation of single domain structures.

Hsu, Chin-Jui; Prikhodko, Sergey V.; Wang, Chiu-Yen; Chen, Lih-Juann; Carman, Gregory P.

2012-03-01

207

The Ciliogenic Transcription Factor RFX3 Regulates Early Midline Distribution of Guidepost Neurons Required for Corpus Callosum Development  

Microsoft Academic Search

The corpus callosum (CC) is the major commissure that bridges the cerebral hemispheres. Agenesis of the CC is associated with human ciliopathies, but the origin of this default is unclear. Regulatory Factor X3 (RFX3) is a transcription factor involved in the control of ciliogenesis, and Rfx3–deficient mice show several hallmarks of ciliopathies including left–right asymmetry defects and hydrocephalus. Here we

Carine Benadiba; Dario Magnani; Mathieu Niquille; Laurette Morlé; Delphine Valloton; Homaira Nawabi; Aouatef Ait-Lounis; Belkacem Otsmane; Walter Reith; Thomas Theil; Jean-Pierre Hornung; Cécile Lebrand; Bénédicte Durand

2012-01-01

208

Effects of severing the corpus callosum on electrical and BOLD functional connectivity and spontaneous dynamic activity in the rat brain.  

PubMed

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

Magnuson, Matthew E; Thompson, Garth J; Pan, Wen-Ju; Keilholz, Shella D

2014-02-01

209

Semiquantitative analysis of corpus callosum injury using magnetic resonance imaging indicates clinical severity in patients with diffuse axonal injury  

PubMed Central

Objective: To evaluate the hypothesis that the extent of corpus callosum injury indicates the depth of shearing lesions in the central brain structure and therefore relates to the clinical severity of diffuse axonal injury. Methods: A simple and objective procedure for semiquantitative analysis of magnetic resonance images (MRI)—the maximum signal intensity ratio (MSIR)—was employed prospectively in 21 patients with diffuse axonal injury but without apparent injury to the ventral pons. All were diagnosed using serial combination MRI scans of fluid attenuated inversion recovery (FLAIR) and T2* weighted gradient echo imaging during the initial two weeks after the injury. The signal intensity ratio between the two regions of interest—the corpus callosum and the normal appearing ventral pons—was calculated serially in mid-sagittal and parasagittal FLAIR image sections in each patient. The MSIR during the study period was determined as a semiquantitative index of corpus callosum injury in each patient. The correlations between MSIR and the duration of unconsciousness, Glasgow outcome scale at six months, and the presence of apparent midbrain injury were investigated. Results: The mean (SD) MSIR value was 1.12 (0.18) at 7.4 (3.1) days after the injury (n = 21). MSIR correlated strongly with the duration of unconsciousness (n = 19, R2 = 0.74, p < 0.0001), and was higher in patients with both an unfavourable GOS outcome (p = 0.020) and apparent midbrain injury (p < 0.001). Conclusions: MSIR, which is a simple and objective procedure for semiquantitative analysis of corpus callosum damage in diffuse axonal injury, correlated with clinical severity. A high MSIR value may indicate the presence of concomitant midbrain injury. PMID:12185160

Takaoka, M; Tabuse, H; Kumura, E; Nakajima, S; Tsuzuki, T; Nakamura, K; Okada, A; Sugimoto, H

2002-01-01

210

[Cosmic Microwave Background (CMB) Anisotropies  

NASA Technical Reports Server (NTRS)

One of the main areas of research is the theory of cosmic microwave background (CMB) anisotropies and analysis of CMB data. Using the four year COBE data we were able to improve existing constraints on global shear and vorticity. We found that, in the flat case (which allows for greatest anisotropy), (omega/H)0 less than 10(exp -7), where omega is the vorticity and H is the Hubble constant. This is two orders of magnitude lower than the tightest, previous constraint. We have defined a new set of statistics which quantify the amount of non-Gaussianity in small field cosmic microwave background maps. By looking at the distribution of power around rings in Fourier space, and at the correlations between adjacent rings, one can identify non-Gaussian features which are masked by large scale Gaussian fluctuations. This may be particularly useful for identifying unresolved localized sources and line-like discontinuities. Levin and collaborators devised a method to determine the global geometry of the universe through observations of patterns in the hot and cold spots of the CMB. We have derived properties of the peaks (maxima) of the CMB anisotropies expected in flat and open CDM models. We represent results for angular resolutions ranging from 5 arcmin to 20 arcmin (antenna FWHM), scales that are relevant for the MAP and COBRA/SAMBA space missions and the ground-based interferometer. Results related to galaxy formation and evolution are also discussed.

Silk, Joseph

1998-01-01

211

Corpus callosum abnormalities, intellectual disability, speech impairment, and autism in patients with haploinsufficiency of ARID1B.  

PubMed

Corpus callosum abnormalities, intellectual disability, speech impairment, and autism in patients with haploinsufficiency of ARID1B. Corpus callosum abnormalities are common brain malformations with a wide clinical spectrum ranging from severe intellectual disability to normal cognitive function. The etiology is expected to be genetic in as much as 30-50% of the cases, but the underlying genetic cause remains unknown in the majority of cases. By next-generation mate-pair sequencing we mapped the chromosomal breakpoints of a patient with a de novo balanced translocation, t(1;6)(p31;q25), agenesis of corpus callosum (CC), intellectual disability, severe speech impairment, and autism. The chromosome 6 breakpoint truncated ARID1B which was also truncated in a recently published translocation patient with a similar phenotype. Quantitative polymerase chain reaction (Q-PCR) data showed that a primer set proximal to the translocation showed increased expression of ARID1B, whereas primer sets spanning or distal to the translocation showed decreased expression in the patient relative to a non-related control set. Phenotype-genotype comparison of the translocation patient to seven unpublished patients with various sized deletions encompassing ARID1B confirms that haploinsufficiency of ARID1B is associated with CC abnormalities, intellectual disability, severe speech impairment, and autism. Our findings emphasize that ARID1B is important in human brain development and function in general, and in the development of CC and in speech development in particular. PMID:21801163

Halgren, C; Kjaergaard, S; Bak, M; Hansen, C; El-Schich, Z; Anderson, C M; Henriksen, K F; Hjalgrim, H; Kirchhoff, M; Bijlsma, E K; Nielsen, M; den Hollander, N S; Ruivenkamp, C A L; Isidor, B; Le Caignec, C; Zannolli, R; Mucciolo, M; Renieri, A; Mari, F; Anderlid, B-M; Andrieux, J; Dieux, A; Tommerup, N; Bache, I

2012-09-01

212

Parameter inversion for seismic anisotropy  

NASA Astrophysics Data System (ADS)

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.

Kumar, Chandan

213

Fractions are Fun  

NSDL National Science Digital Library

Teaching 1st Graders that Learning about Fractions can be fun Learning Fractions using Pattern blocks. using pattern blocks Learning Fraction using number line. Grump fractions More fun with Fractions. interactive math ...

Black, Mrs.

2005-04-06

214

The tumor suppressor Nf2 regulates corpus callosum development by inhibiting the transcriptional coactivator Yap.  

PubMed

The corpus callosum connects cerebral hemispheres and is the largest axon tract in the mammalian brain. Callosal malformations are among the most common congenital brain anomalies and are associated with a wide range of neuropsychological deficits. Crossing of the midline by callosal axons relies on a proper midline environment that harbors guidepost cells emitting guidance cues to instruct callosal axon navigation. Little is known about what controls the formation of the midline environment. We find that two components of the Hippo pathway, the tumor suppressor Nf2 (Merlin) and the transcriptional coactivator Yap (Yap1), regulate guidepost development and expression of the guidance cue Slit2 in mouse. During normal brain development, Nf2 suppresses Yap activity in neural progenitor cells to promote guidepost cell differentiation and prevent ectopic Slit2 expression. Loss of Nf2 causes malformation of midline guideposts and Slit2 upregulation, resulting in callosal agenesis. Slit2 heterozygosity and Yap deletion both restore callosal formation in Nf2 mutants. Furthermore, selectively elevating Yap activity in midline neural progenitors is sufficient to disrupt guidepost formation, upregulate Slit2 and prevent midline crossing. The Hippo pathway is known for its role in controlling organ growth and tumorigenesis. Our study identifies a novel role of this pathway in axon guidance. Moreover, by linking axon pathfinding and neural progenitor behaviors, our results provide an example of the intricate coordination between growth and wiring during brain development. PMID:25336744

Lavado, Alfonso; Ware, Michelle; Paré, Joshua; Cao, Xinwei

2014-11-01

215

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

PubMed Central

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

Knyazeva, Maria G.

2013-01-01

216

Biallelic SZT2 mutations cause infantile encephalopathy with epilepsy and dysmorphic corpus callosum.  

PubMed

Epileptic encephalopathies are genetically heterogeneous severe disorders in which epileptic activity contributes to neurological deterioration. We studied two unrelated children presenting with a distinctive early-onset epileptic encephalopathy characterized by refractory epilepsy and absent developmental milestones, as well as thick and short corpus callosum and persistent cavum septum pellucidum on brain MRI. Using whole-exome sequencing, we identified biallelic mutations in seizure threshold 2 (SZT2) in both affected children. The causative mutations include a homozygous nonsense mutation and a nonsense mutation together with an exonic splice-site mutation in a compound-heterozygous state. The latter mutation leads to exon skipping and premature termination of translation, as shown by RT-PCR in blood RNA of the affected boy. Thus, all three mutations are predicted to result in nonsense-mediated mRNA decay and/or premature protein truncation and thereby loss of SZT2 function. Although the molecular role of the peroxisomal protein SZT2 in neuronal excitability and brain development remains to be defined, Szt2 has been shown to influence seizure threshold and epileptogenesis in mice, consistent with our findings in humans. We conclude that mutations in SZT2 cause a severe type of autosomal-recessive infantile encephalopathy with intractable seizures and distinct neuroradiological anomalies. PMID:23932106

Basel-Vanagaite, Lina; Hershkovitz, Tova; Heyman, Eli; Raspall-Chaure, Miquel; Kakar, Naseebullah; Smirin-Yosef, Pola; Vila-Pueyo, Marta; Kornreich, Liora; Thiele, Holger; Bode, Harald; Lagovsky, Irina; Dahary, Dvir; Haviv, Ami; Hubshman, Monika Weisz; Pasmanik-Chor, Metsada; Nürnberg, Peter; Gothelf, Doron; Kubisch, Christian; Shohat, Mordechai; Macaya, Alfons; Borck, Guntram

2013-09-01

217

Biallelic SZT2 Mutations Cause Infantile Encephalopathy with Epilepsy and Dysmorphic Corpus Callosum  

PubMed Central

Epileptic encephalopathies are genetically heterogeneous severe disorders in which epileptic activity contributes to neurological deterioration. We studied two unrelated children presenting with a distinctive early-onset epileptic encephalopathy characterized by refractory epilepsy and absent developmental milestones, as well as thick and short corpus callosum and persistent cavum septum pellucidum on brain MRI. Using whole-exome sequencing, we identified biallelic mutations in seizure threshold 2 (SZT2) in both affected children. The causative mutations include a homozygous nonsense mutation and a nonsense mutation together with an exonic splice-site mutation in a compound-heterozygous state. The latter mutation leads to exon skipping and premature termination of translation, as shown by RT-PCR in blood RNA of the affected boy. Thus, all three mutations are predicted to result in nonsense-mediated mRNA decay and/or premature protein truncation and thereby loss of SZT2 function. Although the molecular role of the peroxisomal protein SZT2 in neuronal excitability and brain development remains to be defined, Szt2 has been shown to influence seizure threshold and epileptogenesis in mice, consistent with our findings in humans. We conclude that mutations in SZT2 cause a severe type of autosomal-recessive infantile encephalopathy with intractable seizures and distinct neuroradiological anomalies. PMID:23932106

Basel-Vanagaite, Lina; Hershkovitz, Tova; Heyman, Eli; Raspall-Chaure, Miquel; Kakar, Naseebullah; Smirin-Yosef, Pola; Vila-Pueyo, Marta; Kornreich, Liora; Thiele, Holger; Bode, Harald; Lagovsky, Irina; Dahary, Dvir; Haviv, Ami; Hubshman, Monika Weisz; Pasmanik-Chor, Metsada; Nurnberg, Peter; Gothelf, Doron; Kubisch, Christian; Shohat, Mordechai; Macaya, Alfons; Borck, Guntram

2013-01-01

218

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

PubMed

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

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

2014-05-27

219

Correlation between corpus callosum shape and cognitive performance in healthy young adults.  

PubMed

Corpus callosum (CC) might be related to cognitive performance because of its role in interhemispheric communication. Previous research has focused mainly on volumetric analyses of the CC, yielding contradictory results to some extent. Shape is an approach that integrates and extends the data obtained with the volumetric methodology. Here, we analyze the relationships between midsagittal CC shape variation and several cognitive measures. 2D coordinates from 102 MRI-scanned young adult human CCs were superimposed through a Procrustes approach. The residual variation was regressed onto 21 cognitive measures completed by the participants. Most of these measures (including general intelligence, working memory, executive functioning, and mental speed) were unrelated to midsagittal CC morphology. However, attentional control did show consistent and significant correlations with CC shape variation. Slower responses in attentional control were systematically associated with more curved and thinner CC, with consequent rotation of the splenium and the genu. Although the magnitude of the correlations suggests a small relationship of midsagittal CC geometry and attention, the results provide interesting clues regarding the links between brain anatomical configuration and human cognitive function. PMID:22581173

Martín-Loeches, Manuel; Bruner, Emiliano; de la Cuétara, José Manuel; Colom, Roberto

2013-05-01

220

Progesterone and nestorone promote myelin regeneration in chronic demyelinating lesions of corpus callosum and cerebral cortex.  

PubMed

Multiple Sclerosis affects mainly women and consists in intermittent or chronic damages to the myelin sheaths, focal inflammation, and axonal degeneration. Current therapies are limited to immunomodulators and antiinflammatory drugs, but there is no efficient treatment for stimulating the endogenous capacity of myelin repair. Progesterone and synthetic progestins have been shown in animal models of demyelination to attenuate myelin loss, reduce clinical symptoms severity, modulate inflammatory responses and partially reverse the age-dependent decline in remyelination. Moreover, progesterone has been demonstrated to promote myelin formation in organotypic cultures of cerebellar slices. In the present study, we show that progesterone and the synthetic 19-nor-progesterone derivative Nestorone® promote the repair of severe chronic demyelinating lesions induced by feeding cuprizone to female mice for up to 12 weeks. Progesterone and Nestorone increase the density of NG2(+) oligodendrocyte progenitor cells and CA II(+) mature oligodendrocytes and enhance the formation of myelin basic protein (MBP)- and proteolipid protein (PLP)-immunoreactive myelin. However, while demyelination in response to cuprizone was less marked in corpus callosum than in cerebral cortex, remyelination appeared earlier in the former. The remyelinating effect of progesterone was progesterone receptor (PR)-dependent, as it was absent in PR-knockout mice. Progesterone and Nestorone also decreased (but did not suppress) neuroinflammatory responses, specifically astrocyte and microglial cell activation. Therefore, some progestogens are promising therapeutic candidates for promoting the regeneration of myelin. GLIA 2015;63:104-117. PMID:25092805

El-Etr, Martine; Rame, Marion; Boucher, Celine; Ghoumari, Abdel M; Kumar, Narender; Liere, Philippe; Pianos, Antoine; Schumacher, Michael; Sitruk-Ware, Regine

2015-01-01

221

Corpus callosum size in adults with high-functioning autism and the relevance of gender.  

PubMed

The goal of the study was to investigate the size of the corpus callosum (CC) and its subsegments in relation to total brain volume (TBV) as an empirical indicator of impaired connectivity in autism with special respect to gender. In MRI data sets of 29 adults with high-functioning autism (HFA) and 29 age-, gender- and IQ-matched control subjects, the TBV was measured and the CC was analyzed as a whole and in subsegments employing two different manual segmentation procedures. With respect to diagnosis, there were no significant differences in the dependent variables (CC, CC subsegments, and TBV). With respect to gender, only TBV was significantly increased in males compared with females, resulting in a significantly decreased CC/TBV ratio in males. This finding, however, was independent from gender and can be fully attributed to brain size. Our findings do not support the following hypotheses: (1) a hypothesis of impaired CC in HFA adults as a subgroup of patients with autism spectrum disorders, and (2) the sexual dimorphism hypothesis of the CC. PMID:20542669

Tepest, Ralf; Jacobi, Esther; Gawronski, Astrid; Krug, Barbara; Möller-Hartmann, Walter; Lehnhardt, Fritz G; Vogeley, Kai

2010-07-30

222

Noninvasive detection of cuprizone induced axonal damage and demyelination in the mouse corpus callosum.  

PubMed

Previously, we tested the prediction that axonal damage results in decreased axial diffusivity (lambda(parallel)) while demyelination leads to increased radial diffusivity (lambda(perpendicular)). Cuprizone treatment of C57BL/6 mice was a highly reproducible model of CNS white matter demyelination and remyelination affecting the corpus callosum (CC). In the present study, six C57BL/6 male mice were fed 0.2% cuprizone for 12 weeks followed by 12 weeks of recovery on normal chow. The control mice were fed normal chow and imaged in parallel. Biweekly in vivo DTI examinations showed transient decrease of lambda(parallel) in CC at 2-6 weeks of cuprizone treatment. Immunostaining for nonphosphorylated neurofilaments demonstrated corresponding axonal damage at 4 weeks of treatment. Significant demyelination was evident from loss of Luxol fast blue staining at 6-12 weeks of cuprizone ingestion and was paralleled by increased lambda(perpendicular) values, followed by partial normalization during the remyelination phase. The sensitivity of lambda(perpendicular) to detect demyelination may be modulated in the presence of axonal damage during the early stage of demyelination at 4 weeks of cuprizone treatment. Our results suggest that lambda(parallel) and lambda(perpendicular) may be useful in vivo surrogate markers of axonal and myelin damage in mouse CNS white matter. PMID:16408263

Sun, Shu-Wei; Liang, Hsiao-Fang; Trinkaus, Kathryn; Cross, Anne H; Armstrong, Regina C; Song, Sheng-Kwei

2006-02-01

223

Functional Topography of Human Corpus Callosum: An fMRI Mapping Study  

PubMed Central

The concept of a topographical map of the corpus callosum (CC) has emerged from human lesion studies and from electrophysiological and anatomical tracing investigations in other mammals. Over the last few years a rising number of researchers have been reporting functional magnetic resonance imaging (fMRI) activation in white matter, particularly the CC. In this study the scope for describing CC topography with fMRI was explored by evoking activation through simple sensory stimulation and motor tasks. We reviewed our published and unpublished fMRI and diffusion tensor imaging data on the cortical representation of tactile, gustatory, auditory, and visual sensitivity and of motor activation, obtained in 36 normal volunteers and in 6 patients with partial callosotomy. Activation foci were consistently detected in discrete CC regions: anterior (taste stimuli), central (motor tasks), central and posterior (tactile stimuli), and splenium (auditory and visual stimuli). Reconstruction of callosal fibers connecting activated primary gustatory, motor, somatosensory, auditory, and visual cortices by diffusion tensor tracking showed bundles crossing, respectively, through the genu, anterior and posterior body, and splenium, at sites harboring fMRI foci. These data confirm that the CC commissure has a topographical organization and demonstrate that its functional topography can be explored with fMRI. PMID:23476810

Fabri, Mara; Polonara, Gabriele

2013-01-01

224

Fractional Derivative as Fractional Power of Derivative  

E-print Network

Definitions of fractional derivatives as fractional powers of derivative operators are suggested. The Taylor series and Fourier series are used to define fractional power of self-adjoint derivative operator. The Fourier integrals and Weyl quantization procedure are applied to derive the definition of fractional derivative operator. Fractional generalization of concept of stability is considered.

Vasily E. Tarasov

2007-11-16

225

FRACTIONAL CURL OPERATOR AND FRACTIONAL WAVEGUIDES  

Microsoft Academic Search

Abstract—Fractional curl operator has been utilized to study the fractional waveguide. The fractional waveguide may,be regarded as intermediate step between the two given waveguides. The two given waveguides are related through the principle of duality. Behavior of field lines in fractional waveguides are studied withrespect to fractional parameter ?.

Akhtar Hussain; Saima Ishfaq; Qaisar A. Naqvi

2006-01-01

226

Characteristics of diffusion-tensor imaging for healthy adult rhesus monkey brains  

PubMed Central

Diffusion-tensor imaging can be used to observe the microstructure of brain tissue. Fractional sotropy reflects the integrity of white matter fibers. Fractional anisotropy of a young adult brain is low in gray matter, high in white matter, and highest in the splenium of the corpus callosum. Thus, we selected the anterior and posterior limbs of the internal capsule, head of the caudate nucleus, semioval center, thalamus, and corpus callosum (splenium and genu) as regions of interest when using diffusion-tensor imaging to observe fractional anisotropy of major white matter fiber tracts and the deep gray matter of healthy rhesus monkeys aged 4–8 years. Results showed no laterality ferences in fractional anisotropy values. Fractional anisotropy values were low in the head of date nucleus and thalamus in gray matter. Fractional anisotropy values were highest in the splenium of corpus callosum in the white matter, followed by genu of the corpus callosum and the posterior limb of the internal capsule. Fractional anisotropy values were lowest in the semioval center and posterior limb of internal capsule. These results suggest that fractional anisotropy values in major white matter fibers and the deep gray matter of 4–8-year-old rhesus monkeys are similar to those of healthy young people.

Zhao, Xinxiang; Pu, Jun; Fan, Yaodong; Niu, Xiaoqun; Yu, Danping; Zhang, Yanglin

2013-01-01

227

Fractions and Decimals  

NSDL National Science Digital Library

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 A basic visual representation of fractions. Visual Fractions Learning how to add and subtract Decimals A list of games about ...

Brinton, Miss

2007-10-08

228

A de novo 163 kb interstitial 1q44 microdeletion in a boy with thin corpus callosum, psychomotor delay and seizures.  

PubMed

The 1q44 deletion syndrome has shown to be a recognizable phenotype with developmental delay, short stature and corpus callosum abnormalities as relatively consistent features. However, the disorder is still clinically heterogeneous and a genotype-phenotype correlation has been challenging to establish. In particular, a delineation of a critical region for the corpus callosum development has turned out to be difficult, and many candidate genes have been proposed. We present here a patient boy with a clinical picture of the 1q44 deletion syndrome, including a thin corpus callosum, and a small de novo 1q44 deletion. The deletion spans a maximum of 163 kb, a region which only contains the two genes FAM36A and HNRNPU. This finding supports the previously suggested hypothesis that the HNRNPU is an essential gene to the development of corpus callosum. However, as patients with deletions outside this interval also have been reported to have corpus callosum abnormalities, other mechanisms are probably also involved. We also identified two conserved non-coding regions in the deleted region of the patient, and speculate that also other elements interfere with the complex interplay and spatiotemporal gene expression during embryonic development. PMID:22975012

Selmer, Kaja K; Bryne, Einar; Rødningen, Olaug K; Fannemel, Madeleine

2012-12-01

229

Characterization of NO-producing neurons in the rat corpus callosum  

PubMed Central

Introduction The aim of this study was to determine the presence and distribution of nitric oxide (NO)-producing neurons in the rat corpus callosum (cc). Material and methods To investigate this aspect of cc organization we used nicotinamide adenine dinucleotide phosphate diaphorase (NADPH-d) histochemistry and neuronal NO synthase (nNOS) immunocytochemistry. Results Intense NADPH-d-positive (NADPH-d+) neurons were found along the rostrocaudal extension of the cc (sagittal sections). They were more numerous in the lateral cc and gradually decreased in the more medial regions, where they were very few or absent. The Golgi-like appearance of NADPH-d+ intracallosal neurons allowed dividing them into five morphological types: (1) bipolar; (2) fusiform; (3) round; (4) polygonal; and (5) pyramidal. The number of NADPH-d+ neurons (both hemispheres) was counted in two brains using 50-?m thick sections. In the first brain, counts involved 145 sections and neurons were 2959; in the second, 2227 neurons were counted in 130 sections. The distribution and morphology of nNOS-immunopositive (nNOSIP) neurons was identical to that of NADPH-d+neurons. Some of these neurons were observed in the cc ependymal region, where they might be in contact with cerebrospinal fluid (CSF), monitoring its composition, pH, and osmolality changes, or playing a role in regulating the synthesis and release of several peptides. The somatic, dendritic, and axonal processes of many NADPH-d+/nNOSIP neurons were closely associated with intracallosal blood vessels. Conclusions Such close relationship raises the possibility that these neurons are a major source of NO during neural activity. As NO is a potent vasodilator, these findings strongly suggest that NO-positive neurons transduce neuronal signals into vascular responses in selected cc regions, thus giving rise to hemodynamic changes detectable by neuroimaging. PMID:24944862

Barbaresi, Paolo; Fabri, Mara; Mensa, Emanuela

2014-01-01

230

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

PubMed Central

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

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

2013-01-01

231

N-methyl-D-aspartate receptor-mediated axonal injury in adult rat corpus callosum.  

PubMed

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

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

2013-02-01

232

Age-related differences in corpus callosum area of capuchin monkeys.  

PubMed

Capuchin monkeys (Cebus apella) are New World primates with relatively large brains for their body size. The developmental trajectories of several brain regions-including cortical white matter, frontal lobe white matter, and basal ganglia nuclei-are similar to humans. Additionally, capuchins have independently evolved several behavioral and anatomical characteristics in common with humans and chimpanzees-including complex manipulative abilities, use of tools, and the use of precision grips-making them interesting species for studies of comparative brain morphology and organization. Here, we report the first investigation into the development of the corpus callosum (CC) and its regional subdivisions in capuchins. CC development was quantified using high-resolution structural magnetic resonance imaging (MRI) images from 39 socially reared subjects (male n=22; female n=18) ranging in age from 4 days (infancy) to 20 years (middle adulthood). The total area of the CC and the subdivisions of the genu, rostral midbody, medial midbody, caudal midbody, and splenium were traced from the midsagittal section. Total CC area displayed significant differences across this time span and was best explained by quadratic growth. Sustained linear growth was observed in the subdivisions of the genu, rostral midbody, and splenium; sustained quadratic growth was seen in the subdivision of the medial midbody. Differences in growth were not detected in the subdivision of the caudal midbody. Females had a larger raw area of the total CC and of the medial midbody and caudal midbody throughout the lifespan. Our results indicate that capuchins show continued white matter development beyond adolescence in regions related to cognitive and motor development. PMID:22173013

Phillips, K A; Sherwood, C C

2012-01-27

233

Large-scale anisotropy at centimeter wavelengths  

Microsoft Academic Search

Intrinsic effects in the case of large-scale anisotropy measurements could possibly provide much information about the early universe. Techniques for experimental investigations at centimeter wavelengths are discussed, taking into account the basic problem to measure the difference in the radiation temperature form two directions in the sky with an accuracy of better than 0.0001 K. The largest anisotropy in the

D. T. Wilkinson

1983-01-01

234

Diamagnetic Anisotropy of the Peptide Group  

Microsoft Academic Search

A simple theory of the diamagnetic anisotropy of noncyclic planar groups of atoms with resonance structures (mobile electrons) leads to the value -5.36 × 10-6 cm-g-sec electromagnetic units for the molar diamagnetic anisotropy of the peptide group.

Linus Pauling

1979-01-01

235

Low-Altitude Plasma Line Anisotropy  

Microsoft Academic Search

Plasma line observations obtained from incoherent radar backscatter have been used as a ground-based method for deriving information about the size and anisotropy of the ionospheric photoelectron fluxes. In the past, data interpretation has been confined to altitudes above the F. peak. Measurements below the F. peak consistently show an anisotropy in the ratio of the downshifted to upshifted amplitudes

Elaine S. Oran; Peter J. Palmadesso; Suman Ganguly

1978-01-01

236

Acoustic axes in triclinic anisotropy Vclav Vavrycuka  

E-print Network

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

Cerveny, Vlastislav

237

Anisotropy in high-resolution diffusion-weighted MRI and anomalous diffusion  

NASA Astrophysics Data System (ADS)

It is shown below that complex diffusion anisotropy observed in diffusion-weighted MRI can be fully accounted for by allowing for non-locality of the spatial operator in the diffusion equation. The anisotropy is represented by a distribution over directions on a sphere. It allows recognition of fiber tracts crossing at arbitrary angles. A simple generalization of the Stejskal-Tanner equation for the determination of the ODF is presented. Furthermore, an explicit solution of the Bloch-Torrey equation for an anisotropic time-fractional diffusion equation is obtained in terms of a generalized Mittag-Leffler type function.

Hanyga, A.; Seredy?ska, M.

2012-07-01

238

High Anisotropy Magnetic Recording Media  

NASA Astrophysics Data System (ADS)

Areal densities in magnetic recording have exhibited Moore's Law like increases in the last ten years. This is partially due to improvements in the media microstructure where reduced grain sizes, tighter grain size distribution, and chemical isolation between grains to break exchange provided increased signal-to-noise from decreased transition noise. With the recent shift from longitudinal to perpendicular recording, areal densities have again continued to increase with demonstrations of over 250 Gbits/in^2. However, areal density is limited by thermal stability considerations where the ratio of stored magnetic energy KuV (anisotropy energy times the magnetic switching volume) to the thermal energy kT must be ˜ 50-70. The projected limit for traditional CoPtCr(X) granular media is on the order of 500 Gbits/in^2. Further increases in the areal density will require greater reduction in the grain size (switching volume), which necessitates finding media with higher anisotropy to maintain thermal stability. Possible candidate materials systems include FePt and SmCo5, which have bulk Ku values 50 to 100 times greater than CoPtCr(X) media materials. High Ku allows for thermally stable grains sizes down to ˜ 2.5 nm, which would permit areal densities in the Tbit/in^2 regime. Accompanying this increase in Ku is an increase in the media switching field (H0), which is proportional to the ratio Ku/Ms where Ms is the saturation magnetization. Therefore, while providing thermal stability, these high Ku materials would potentially require writing fields greater than 50 kOe which far exceed those of available recording head materials. One possible solution is heat-assisted magnetic recording (HAMR) where a laser locally heats the media in order to reduce the coercivity so that available head fields are sufficient. Numerous challenges exist for HAMR including high cooling rates so that the heating process does not render adjacent bits thermally unstable. This paper will review recent progress in this area and concentrate on the challenges for the production of high anisotropy media for Tbit/in^2 areal densities, such as maintaining grain sizes of 2 to 4 nm with the correct crystallographic texture and sufficient grain isolation to break exchange.

Wittig, James

2007-03-01

239

Match My Fraction  

NSDL National Science Digital Library

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.

Network, Utah E.

2012-04-30

240

Fractional Schrödinger equation  

Microsoft Academic Search

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

Nick Laskin

2002-01-01

241

X-Ray Diffraction Study on the Strain Anisotropy and Dislocation Structure of Deformed Lath Martensite  

NASA Astrophysics Data System (ADS)

18Ni (300) maraging steel possessing lath martensite structure was deformed by four passes of equal-channel angular pressing (ECAP) at ambient temperature. Line profile analysis (LPA) of X-ray diffraction (XRD) patterns identified strong strain anisotropy and remarkable increases in the relative fraction of screw dislocations after ECAP. The strain anisotropy was reasonably accounted for by the anisotropy of elastic constants. Domination of screw dislocations in the deformed structure was attributed to the preferred annihilation of edge dislocations in the early stages of deformation along with the difficulties for annihilation of screw dislocations by cross slipping. Cobalt addition was mainly assumed to make cross slipping difficult by reducing stacking-fault energy and favoring short-range ordering.

Hossein Nedjad, S.; Hosseini Nasab, F.; Movaghar Garabagh, M. R.; Damadi, S. R.; Nili Ahmadabadi, M.

2011-08-01

242

Primordial Anisotropies in Gauged Hybrid Inflation  

E-print Network

We study primordial anisotropies generated in the model of gauged hybrid inflation in which the complex waterfall field is charged under a $U(1)$ gauge field. Primordial anisotropies are generated either actively during inflation or from inhomogeneities modulating the surface of end of inflation during waterfall transition. We present a consistent $\\delta N$ mechanism to calculate the anisotropic power spectrum and bispectrum. We show that the primordial anisotropies generated at the surface of end of inflation do not depend on the number of e-folds and therefore do not produce dangerously large anisotropies associated with the IR modes. Furthermore, one can find the parameter space that the anisotropies generated from the surface of end of inflation cancel the anisotropies generated during inflation, therefore relaxing the constrains on model parameters imposed from IR anisotropies. We also show that the gauge field fluctuations induce a red-tilted power spectrum so the averaged power spectrum from the gauge field can change the total power spectrum from blue to red. Therefore, hybrid inflation, once gauged under a $U(1)$ field, can be consistent with the cosmological observations.

Ali Akbar Abolhasani; Razieh Emami; Hassan Firouzjahi

2013-11-03

243

Weak Elastic Anisotropy in a Cracked Rock  

NASA Astrophysics Data System (ADS)

Crack and textural fabrics have significant control over the development of mechanical anisotropy in a rock. Bedding in sedimentary rocks, cleavage in slates, preferred orientation of anisotropic minerals and anisotropic distribution of microcracks can all contribute to elastic anisotropy. Using Kachanov's (1992, 1993) formulation we analyzed the effects of an axisymmetric system of microcracks on seismic anisotropy. The elastic behavior of such a cracked rock is transversely isotropic, and its seismic properties can be characterized by the three Thomsen parameters. In this study we calculated the parameters ?, ? and ? under dry and saturated conditions. We derived analytic expressions for the model proposed by Sayers & Kachanov (1995), which assumes that the contribution from the fourth rank crack density tensor is negligible. This model predicts that the elliptic anisotropy condition ?=? is obeyed in a dry rock. Guided by microstructural observations we adopted a two-parameter axisymmetric distribution to characterize the crack density, which predicts that ? and ? in a fluid saturated rock are related to ? in a nonlinear manner. All three Thomsen parameters are sensitively dependent on the crack density difference. While our model shows basic agreement with some of the laboratory data on seismic anisotropy in saturated shale, there are discrepancies which suggest that the petrofabric associated with preferred orientation of clay minerals and elastic anisotropy of the rock matrix may have considerable influence which should not be neglected in model. Preliminary comparison with borehole log data suggests rock physics tests which may be useful for interpreting the shear wave anisotropy observations.

Zhu, W.; Wong, T.

2006-12-01

244

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

E-print Network

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.

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

2013-12-31

245

Orthogonal Invariant Sets of the Diffusion Tensor and the Development of a Curvilinear Set Suitable for Low-Anisotropy Tissues  

PubMed Central

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

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

2013-01-01

246

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

PubMed

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

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

2013-01-01

247

Fun with Fractions  

NSDL National Science Digital Library

In this five lesson unit with overview from Illuminations, student activities explore relationships among fractions through work with the length model. Students construct fraction strips and use fraction bars throughout the unit to make sense of basic fraction concepts, to compare fractions and order fractions and to work with equivalency in fractions. Specific learning objectives, a material list, an instructional plan, questions for the students, assessment options, extensions, and teacher reflections are given for each lesson.

Hargrove, Tracy Y.

2008-01-01

248

Math / Fractions and Decimals  

NSDL National Science Digital Library

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 ...

Petersen, Mr. L.

2008-10-01

249

Rostrocaudal analysis of corpus callosum demyelination and axon damage across disease stages refines diffusion tensor imaging correlations with pathological features.  

PubMed

Noninvasive assessment of the progression of axon damage is important for evaluating disease progression and developing neuroprotective interventions in multiple sclerosis patients. We examined the cellular responses correlated with diffusion tensor imaging-derived axial (lambda(parallel)) and radial (lambda(perpendicular)) diffusivity values throughout acute (4 weeks) and chronic (12 weeks) stages of demyelination and after 6 weeks of recovery using the cuprizone demyelination of the corpus callosum model in C57BL/6 and Thy1-YFP-16 mice. The rostrocaudal progression of pathological alterations in the corpus callosum enabled spatially and temporally defined correlations of pathological features with diffusion tensor imaging measurements. During acute demyelination, microglial/macrophage activation was most extensive and axons exhibited swellings, neurofilament dephosphorylation, and reduced diameters. Axial diffusivity values decreased in the acute phase but did not correlate with axonal atrophy during chronic demyelination. In contrast, radial diffusivity increased with the progression of demyelination but did not correlate with myelin loss or astrogliosis. Unlike other animal models with progressive neurodegeneration and axon loss, the acute axon damage did not progress to discontinuity or loss of axons even after a period of chronic demyelination. Correlations of reversible axon pathology, demyelination, microglia/macrophage activation, and astrogliosis with regional axial and radial diffusivity measurements will facilitate the clinical application of diffusion tensor imaging in multiple sclerosis patients. PMID:20535036

Xie, Mingqiang; Tobin, Jennifer E; Budde, Matthew D; Chen, Chin-I; Trinkaus, Kathryn; Cross, Anne H; McDaniel, Dennis P; Song, Sheng-Kwei; Armstrong, Regina C

2010-07-01

250

Reversible splenial lesion in the corpus callosum following rapid withdrawal of carbamazepine after neurosurgical decompression for trigeminal neuralgia.  

PubMed

Reversible splenial lesions (RSL) of the corpus callosum have been described in various clinical conditions, and some are attributed to the action of antiepileptic drugs (AED). Abrupt withdrawal of an AED in preparation for surgical treatment can result in RSL of the corpus callosum in patients with trigeminal neuralgia who do not have epilepsy. We report two patients who developed RSL following surgical treatment of trigeminal neuralgia. Since our two patients did not have epilepsy, it is strongly suggested that the AED, rather than convulsive status epilepticus, could be a contributing factor in RSL. The pathogenesis of AED-associated RSL is not clear. Similar RSL can appear under various circumstances, implying that factors other than AED can influence a common end-point mechanism that results in RSL. Nevertheless, delirium after surgery may be a cue for inquiring about RSL. This condition is transient and represents a clinicoradiological syndrome with an excellent prognosis. We should consider this phenomenon in the perioperative period after surgery for trigeminal neuralgia to avoid invasive diagnostic and therapeutic procedures. PMID:22349431

Mori, Harushi; Maeda, Masayuki; Takanashi, Jun-ichi; Kunimatsu, Akira; Matsushima, Nobuyoshi; Suzuki, Hidenori; Saito, Nobuhito; Ohtomo, Kuni

2012-08-01

251

A Computational Model of Visual Anisotropy  

PubMed Central

Visual anisotropy has been demonstrated in multiple tasks where performance differs between vertical, horizontal, and oblique orientations of the stimuli. We explain some principles of visual anisotropy by anisotropic smoothing, which is based on a variation on Koenderink's approach in [1]. We tested the theory by presenting Gaussian elongated luminance profiles and measuring the perceived orientations by means of an adjustment task. Our framework is based on the smoothing of the image with elliptical Gaussian kernels and it correctly predicted an illusory orientation bias towards the vertical axis. We discuss the scope of the theory in the context of other anisotropies in perception. PMID:21738607

Ons, Bart; Verstraelen, Leopold; Wagemans, Johan

2011-01-01

252

Non-Bunch-Davies statistical anisotropies  

NASA Astrophysics Data System (ADS)

We introduce a generic mechanism that can extend the effects of relic anisotropies at the beginning of inflation to relatively much shorter scales in density perturbations. This is induced by non-Bunch-Davies states of the quantum fluctuations, and can show up in the non-oscillatory components of the density perturbations. This mechanism works for general forms of anisotropies, and, to illustrate it, we use an example of relic vector field. The detailed scale-dependence of these anisotropies can be used to probe the initial quantum state of our universe.

Chen, Xingang; Wang, Yi

2014-07-01

253

Fractional Vector Calculus and Fractional Special Function  

Microsoft Academic Search

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.

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

2010-01-01

254

Fractional Vector Calculus and Fractional Special Function  

E-print Network

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.

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

2010-01-17

255

Fraction Feud: Comparing and Ordering Fractions  

NSDL National Science Digital Library

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).

Rising, Jennifer

2011-01-01

256

Clipart ETC Fractions  

NSDL National Science Digital Library

Illustrations that can be used for teaching and demonstrating fractions. Fractional representations are modeled in wedges of circles ("pieces of pie") and parts of polygons. There are also clipart images of numerical fractions, both proper and improper, from halves to twelfths. Fraction charts and fraction strips found in this collection can be used as manipulatives and are ready to print for classroom use.

Clearinghouse, Clipart E.

2010-06-29

257

Cortical Depth Dependence of the Diffusion Anisotropy in the Human Cortical Gray Matter In Vivo  

PubMed Central

Diffusion tensor imaging (DTI) is typically used to study white matter fiber pathways, but may also be valuable to assess the microstructure of cortical gray matter. Although cortical diffusion anisotropy has previously been observed in vivo, its cortical depth dependence has mostly been examined in high-resolution ex vivo studies. This study thus aims to investigate the cortical depth dependence of the diffusion anisotropy in the human cortex in vivo on a clinical 3 T scanner. Specifically, a novel multishot constant-density spiral DTI technique with inherent correction of motion-induced phase errors was used to achieve a high spatial resolution (0.625×0.625×3 mm) and high spatial fidelity with no scan time penalty. The results show: (i) a diffusion anisotropy in the cortical gray matter, with a primarily radial diffusion orientation, as observed in previous ex vivo and in vivo studies, and (ii) a cortical depth dependence of the fractional anisotropy, with consistently higher values in the middle cortical lamina than in the deep and superficial cortical laminae, as observed in previous ex vivo studies. These results, which are consistent across subjects, demonstrate the feasibility of this technique for investigating the cortical depth dependence of the diffusion anisotropy in the human cortex in vivo. PMID:24608869

Truong, Trong-Kha; Guidon, Arnaud; Song, Allen W.

2014-01-01

258

Elastic anisotropy of Earth's inner core.  

PubMed

Earth's solid-iron inner core is elastically anisotropic. Sound waves propagate faster along Earth's spin axis than in the equatorial plane. This anisotropy has previously been explained by a preferred orientation of the iron alloy hexagonal crystals. However, hexagonal iron becomes increasingly isotropic on increasing temperature at pressures of the inner core and is therefore unlikely to cause the anisotropy. An alternative explanation, supported by diamond anvil cell experiments, is that iron adopts a body-centered cubic form in the inner core. We show, by molecular dynamics simulations, that the body-centered cubic iron phase is extremely anisotropic to sound waves despite its high symmetry. Direct simulations of seismic wave propagation reveal an anisotropy of 12%, a value adequate to explain the anisotropy of the inner core. PMID:18258912

Belonoshko, Anatoly B; Skorodumova, Natalia V; Rosengren, Anders; Johansson, Börje

2008-02-01

259

Anisotropy and Corotation of Galactic Cosmic Rays  

E-print Network

The intensity of Galactic cosmic rays is nearly isotropic because of the influence of magnetic fields in the Milky Way. Here, we present two-dimensional high-precision anisotropy measurement for energies from a few to several hundred teraelectronvolts (TeV), using the large data sample of the Tibet Air Shower Arrays. Besides revealing finer details of the known anisotropies, a new component of Galactic cosmic ray anisotropy in sidereal time is uncovered around the Cygnus region direction. For cosmic-ray energies up to a few hundred TeV, all components of anisotropies fade away, showing a corotation of Galactic cosmic rays with the local Galactic magnetic environment. These results have broad implications for a comprehensive understanding of cosmic rays, supernovae, magnetic fields, and heliospheric and Galactic dynamic environments.

Tibet AS-gamma Collaboration; M. Amenomori

2006-10-23

260

Cellulose and the Control of Growth Anisotropy  

SciTech Connect

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.

Tobias I. Baskin

2004-04-01

261

Anisotropy and Corotation of Galactic Cosmic Rays  

E-print Network

The intensity of Galactic cosmic rays is nearly isotropic because of the influence of magnetic fields in the Milky Way. Here, we present two-dimensional high-precision anisotropy measurement for energies from a few to several hundred teraelectronvolts (TeV), using the large data sample of the Tibet Air Shower Arrays. Besides revealing finer details of the known anisotropies, a new component of Galactic cosmic ray anisotropy in sidereal time is uncovered around the Cygnus region direction. For cosmic-ray energies up to a few hundred TeV, all components of anisotropies fade away, showing a corotation of Galactic cosmic rays with the local Galactic magnetic environment. These results have broad implications for a comprehensive understanding of cosmic rays, supernovae, magnetic fields, and heliospheric and Galactic dynamic environments.

Amenomori, M; Bi, X J; Chen, D; Cui, S W; Danzengluobu; Ding, L K; Ding, X H; Feng Cun Feng; Zhaoyang Feng; Feng, Z Y; Gao, X Y; Geng, Q X; Guo, H W; He, H H; He, M; Hibino, K; Hotta, N; Haibing, H; Hu, H B; Huang, J; Huang, Q; Jia, H Y; Kajino, F; Kasahara, K; Katayose, Y; Kato, C; Kawata, K; Labaciren; Le, G M; Li, A F; Li, J Y; Lou, Y Q; Lü, H; Lu, S L; Meng, X R; Mizutani, K; Mu, J; Munakata, K; Nagai, A; Nanjo, H; Nishizawa, M; Ohnishi, M; Ohta, I; Onuma, H; Ouchi, T; Ozawa, S; Ren, J R; Saitô, T; Saito, T Y; Sakata, M; Sako, T K; Sasaki, T; Shibata, M; Shiomi, A; Shirai, T; Sugimoto, H; Takita, M; Tan, Y H; Tateyama, N; Torii, S; Tsuchiya, H; Udo, S; Wang, B; Wang, H; Wang, X; Wang, Y G; Wu, H R; Xue Liang; Yamamoto, Y; Yan, C T; Yang, X C; Yasue, S; Ye, Z H; Yu, G C; Yuan, A F; Yuda, T; Zhang, H M; Zhang, J L; Zhang, N J; Zhang, X Y; Zhang, Y; Zhaxisangzhu; Zhou, X X

2006-01-01

262

Scattering anisotropy-weighted mesoscopic imaging  

PubMed Central

Abstract. We report that when tissue images are formed via a small solid angle in the backward direction (i.e., back-directional gating), the image intensity is dominantly determined by tissue scattering anisotropy. Thus, this configuration allows for scattering anisotropy-weighted imaging that can provide an intrinsic contrast by capturing tissue structures and organizations. To demonstrate the immediate feasibility, we apply scattering anisotropy-weighted imaging to tissue blocks including basal-cell carcinomas as a pilot study. The main feature of our imaging approach is the high sensitivity to tumor locations and the simplicity for large-area visualization. We further envision that scattering anisotropy-weighted imaging could potentially be used to visualize tissue microenvironments in a mesoscopic (between microscopic and macroscopic) imaging setting. PMID:23085898

Xu, Zhengbin; Somani, Ally-Khan; Kim, Young L.

2012-01-01

263

Anisotropy studies around the galactic center  

Microsoft Academic Search

We present the first results for anisotropy searches around the galactic\\u000acenter at EeV energies using data from the Pierre Auger Observatory. Our\\u000aanalysis, based on a substantially larger data set, do not support previous\\u000aclaim of anisotropy found in this region by the AGASA and Sugar experiment.\\u000aFurthermore we place un upper limit on a possible point like source

Antoine Letessier-Selvon

2007-01-01

264

Seismic anisotropy beneath the Chinese mainland  

Microsoft Academic Search

We investigated the upper mantle anisotropy beneath China by applying teleseismic shear wave splitting measurements at 119\\u000a seismic stations from CDSN and GSN\\/IRIS networks in China. The splitting observations are characterized by apparent diversity\\u000a of anisotropy pattern in adjacent tectonic domains, including the Tianshan orogenic belt, Tibetan plateau, the Yangtze craton,\\u000a the North China craton and northeastern region. In western

Yuanyuan V. Fu; Yongshun John Chen; Aibing Li

2010-01-01

265

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).  

PubMed

The association between atypical laterality and mental retardation has been reported several times, particularly in Down syndrome (DS). We investigated common genetic correlates of these components of the syndrome, examining direction (number of right paw entries in the Collins test) and degree (absolute difference between the number of right paw entries and the number of left paw entries) in mice that had incorporated extra-contiguous HSA21 fragments covering DCR-1 (Down Chromosomal Region-1). As corpus callosum size is substantially reduced in DS, and as the structure has been suspected of playing a role in atypical laterality, we also measured the corpus callosum in these mice. Extra copies of two regions (F7 and E6) have been associated with an atypical degree of laterality (strongly reduced degree). Extra copies of E8, G6 and E6 are also linked to the reduced size of the corpus callosum, indicating that the abnormal number of fibers linking the two hemispheres is not associated with atypical laterality in DS. Together, these results indicate that some of the genes involved in atypical laterality and in the reduced size of the corpus callosum in DS are present on DCR-1. An extra copy of F7 and, to a lesser extent, an extra copy of E6, are also associated with cognitive impairment. These results support the hypothesis of common genetic correlates in atypical laterality and mental retardation in DS. PMID:15864448

Roubertoux, Pierre L; Bichler, Zoë; Pinoteau, Walter; Seregaza, Zohra; Fortes, Sylvia; Jamon, Marc; Smith, Desmond J; Rubin, Edward; Migliore-Samour, Danièle; Carlier, Michèle

2005-05-01

266

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

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…

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

2014-01-01

267

Bounded Fraction Finder  

NSDL National Science Digital Library

The same as "Bounded Fraction Pointer" but there is no arrow to help the user determine the value of a fraction between the two endpoints. Bounded Fraction Finder is one of the Interactivate assessment explorers.

268

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

E-print Network

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...

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

2014-01-01

269

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

PubMed

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

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

2014-09-01

270

How to change or remove the anisotropy of spin glasses, with some other reflections on the anisotropy problem  

E-print Network

- tional experiments find a unique anisotropy constant for a given spin glass at a given temperature (afterL-345 How to change or remove the anisotropy of spin glasses, with some other reflections'anisotropie. Abstract. 2014 We develop some ideas on the freezing of the macroscopic anisotropy energy of spin glasses

Boyer, Edmond

271

Modeling Multiplication with Fractions  

NSDL National Science Digital Library

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.

Ratasky, Joseph

2012-08-18

272

Cosmic microwave background anisotropies in the timescape cosmology  

E-print Network

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 constraint...

Nazer, M Ahsan

2014-01-01

273

A longitudinal magnetic resonance imaging study of the apparent diffusion coefficient values in corpus callosum during the first year after traumatic brain injury.  

PubMed

The objective of this study was to explore the evolution of apparent diffusion coefficient (ADC) values in magnetic resonance imaging (MRI) in normal-appearing tissue of the corpus callosum during the 1st year after traumatic brain injury (TBI), and relate findings to outcome. Fifty-seven patients (mean age 34 [range 11-63] years) with moderate to severe TBI were examined with diffusion weighted MRI at three time points (median 7 days, 3 and 12 months), and a sex- and age-matched control group of 47 healthy individuals, were examined once. The corpus callosum was subdivided and the mean ADC values computed blinded in 10 regions of interests without any visible lesions in the ADC map. Outcome measures were Glasgow Outcome Scale Extended (GOSE) and neuropsychological domain scores at 12 months. We found a gradual increase of the mean ADC values during the 12 month follow-up, most evident in the posterior truncus (r=0.19, p<0.001). Compared with the healthy control group, we found higher mean ADC values in posterior truncus both at 3 months (p=0.021) and 12 months (p=0.003) post-injury. Patients with fluid-attenuated inversion recovery (FLAIR) lesions in the corpus callosum in the early MRI, and patients with disability (GOSE score ?6) showed evidence of increased mean ADC values in the genu and posterior truncus at 12 months. Mean ADC values in posterior parts of the corpus callosum at 3 months predicted the sensory-motor function domain score (p=0.010-0.028). During the 1st year after moderate and severe TBI, we demonstrated a slowly evolving disruption of the microstructure in normal appearing corpus callosum in the ADC map, most evident in the posterior truncus. The mean ADC values were associated with both outcome and ability to perform speeded, complex sensory-motor action. PMID:23837731

Moen, Kent Gøran; Håberg, Asta Kristine; Skandsen, Toril; Finnanger, Torun Gangaune; Vik, Anne

2014-01-01

274

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

PubMed Central

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

2014-01-01

275

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

NASA Astrophysics Data System (ADS)

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.

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

2010-06-01

276

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

SciTech Connect

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.

Choi, Shi-Hoon; Kim, Dae-Wan; Yang, Hoe-Seok [Department of Materials Science and Metallurgical Engineering, Sunchon National University, Sunchon 540-742 (Korea, Republic of); Han, Seong-Ho [Automotive Steel Products Research Group, POSCO Technical Research Laboratories, Gwangyang 545-090 (Korea, Republic of); Yoon, Jeong Whan [Alcoa Technical Center, Materials Science Division, 100 Technical Drive, Alcoa Center, PA 15069-0001 (United States)

2010-06-15

277

Fractional vector calculus and fractional Maxwell's equations  

SciTech Connect

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.

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

278

Fractional Vector Calculus and Fractional Maxwell's Equations  

E-print Network

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.

Vasily E. Tarasov

2009-07-14

279

RAPID COMMUNICATION: Stress-induced optical anisotropy in polycrystalline copper studied by reflection anisotropy spectroscopy  

Microsoft Academic Search

The optical properties of polycrystalline copper subjected to tensile stress are monitored in situ and in real time using reflection anisotropy spectroscopy (RAS). It is shown that RAS allows investigation of the plastic regime. Here, in contrast to the Hooke's law regime, the stress-induced RAS lineshape is found to be dependent on the applied stress. The optical anisotropy in the

R. J. Cole; S. Kheradmand; D. D. Higgins; F. Madani; B. F. Macdonald; V. Koutsos; J. R. Blackford

2003-01-01

280

Hyperlexia and ambient echolalia in a case of cerebral infarction of the left anterior cingulate cortex and corpus callosum.  

PubMed

We report the case of a 69-year-old woman with cerebral infarction in the left anterior cingulate cortex and corpus callosum. She showed hyperlexia, which was a distinctive reading phenomenon, as well as ambient echolalia. Clinical features also included complex disorders such as visual groping, compulsive manipulation of tools, and callosal disconnection syndrome. She read words written on the cover of a book and repeated words emanating from unrelated conversations around her or from hospital announcements. The combination of these two features due to a focal lesion has never been reported previously. The supplementary motor area may control the execution of established subroutines according to external and internal inputs. Hyperlexia as well as the compulsive manipulation of tools could be interpreted as faulty inhibition of preexisting essentially intact motor subroutines by damage to the anterior cingulate cortex reciprocally interconnected with the supplementary motor area. PMID:19585352

Suzuki, Tadashi; Itoh, Shouichi; Hayashi, Mototaka; Kouno, Masako; Takeda, Katsuhiko

2009-10-01

281

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

PubMed Central

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

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

2009-01-01

282

Lesson 36: Algebraic Fractions  

NSDL National Science Digital Library

The lesson begins with the definition of an algebraic fraction and then a quick review of the fundamental principle of fractions. Exercises in reducing fractions follow before a brief procedure for reducing algebraic fractions is provided. Opposites of binomials are reviewed before rational functions are defined and a motion application problem is discussed.

2011-01-01

283

Multiplication of Fractions  

NSDL National Science Digital Library

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.

Manipulatives, National L.

2009-07-29

284

Initialized Fractional Calculus  

NASA Technical Reports Server (NTRS)

This paper demonstrates the need for a nonconstant initialization for the fractional calculus and establishes a basic definition set for the initialized fractional differintegral. This definition set allows the formalization of an initialized fractional calculus. Two basis calculi are considered; the Riemann-Liouville and the Grunwald fractional calculi. Two forms of initialization, terminal and side are developed.

Lorenzo, Carl F.; Hartley, Tom T.

2000-01-01

285

Fractional quantum mechanics  

Microsoft Academic Search

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

Nikolai Laskin

2000-01-01

286

Introduction to Proper Fractions  

NSDL National Science Digital Library

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).

2011-01-01

287

Fractional Poisson process  

NASA Astrophysics Data System (ADS)

A fractional non-Markov Poisson stochastic process has been developed based on fractional generalization of the Kolmogorov-Feller equation. We have found the probability of n arrivals by time t for fractional stream of events. The fractional Poisson process captures long-memory effect which results in non-exponential waiting time distribution empirically observed in complex systems. In comparison with the standard Poisson process the developed model includes additional parameter ?. At ?=1 the fractional Poisson becomes the standard Poisson and we reproduce the well known results related to the standard Poisson process. As an application of developed fractional stochastic model we have introduced and elaborated fractional compound Poisson process.

Laskin, Nick

2003-12-01

288

Preferred orientation and elastic anisotropy in shales.  

SciTech Connect

Anisotropy in shales is becoming an important issue in exploration and reservoir geophysics. In this study, the crystallographic preferred orientation of clay platelets that contributes to elastic anisotropy was determined quantitatively by hard monochromatic X-ray synchrotron diffraction in two different shales from drillholes off the coast of Nigeria. To analyze complicated diffraction images with five different phases (illite/smectite, kaolinite, quartz, siderite, feldspar) and many overlapping peaks, we applied a methodology based on the crystallographic Rietveld method. The goal was to describe the intrinsic physical properties of the sample (phase composition, crystallographic preferred orientation, crystal structure, and microstructure) and compute macroscopic elastic properties by averaging single crystal properties over the orientation distribution for each phase. Our results show that elastic anisotropy resulting from crystallographic preferred orientation of the clay particles can be determined quantitatively. This provides a possible way to compare measured seismic anisotropy and texture-derived anisotropy and to estimate the contribution of the low-aspect ratio pores aligned with bedding.

Lonardelli, I.; Wenk, H.-R.; Ren, Y.; Univ. of California at Berkeley

2007-03-01

289

Interactive Fraction Number Lines  

NSDL National Science Digital Library

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.

Green, Michael

2012-05-25

290

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

SciTech Connect

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%.

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

2009-06-30

291

Effects of anisotropy on gravitational infall in galaxy clusters using an exact general relativistic model  

E-print Network

We study the effects and implications of anisotropies at the scale of galaxy clusters by building an exact general relativistic model of a cluster using the inhomogeneous and anisotropic Szekeres metric. The model is built from a modified Navarro-Frenk-White (NFW) density profile. We compare this to a corresponding spherically symmetric structure in the Lemaitre-Tolman (LT) model and quantify the impact of introducing varying levels of anisotropy. We examine two physical measures of gravitational infall -- the growth rate of density and the velocity of the source dust in the model. We introduce a generalization of the LT dust velocity profile for the Szekeres metric and demonstrate its consistency with the growth rate of density. We find that the growth rate of density in one substructure increases by 0.5%, 1.5%, and 3.75% for 5%, 10%, and 15% levels of introduced anisotropy, which is measured as the fractional displaced mass relative to the spherically symmetric case. The infall velocity of the dust is found to increase by 2.5, 10, and 20 km/s (0.5%, 2%, and 4.5%), respectively, for the same three levels of anisotropy. This response to the anisotropy in a structure is found to be strongly nonlinear with respect to the strength of anisotropy. These relative velocities correspond to an equivalent increase in the total mass of the spherically symmetric structure of 1%, 3.8%, and 8.4%, indicating that not accounting for the presence of anisotropic mass distributions in cluster models can strongly bias the determination of physical properties like the total mass.

M. A. Troxel; Austin Peel; Mustapha Ishak

2013-11-22

292

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

PubMed

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

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

2013-10-18

293

Using diffusion tensor imaging and fiber tracking to characterize diffuse perinatal white matter injury: a case report.  

PubMed

Prematurity is associated with white matter injury. Diffusion tensor imaging, a new magnetic resonance imaging technique, identifies white matter fiber tracts and quantifies structural properties. We used diffusion tensor imaging fiber tracking to compare white matter characteristics in a 12-year-old born prematurely and full-term control. We divided fibers passing through the corpus callosum into 7 segments based on cortical projection zones and analyzed them for fractional anisotropy, axial diffusivity, and radial diffusivity. We also compared corticospinal and somatosensory tracts in the participant and control. The participant had decreased fractional anisotropy in every callosal segment, particularly in superior and posterior parietal projections. Fractional anisotropy of the corticospinal and somatosensory tracts was not lower in the participant than control. Fiber tracking allowed precise localization and visualization of white matter injuries of the corpus callosum associated with prematurity. Quantitative measures suggested myelin deficiencies across the corpus callosum, particularly in parietal projections. PMID:19435729

Yeatman, Jason D; Ben-Shachar, Michal; Bammer, Roland; Feldman, Heidi M

2009-07-01

294

A universal density slope - velocity anisotropy relation  

E-print Network

One can solve the Jeans equation analytically for equilibrated dark matter structures, once given two pieces of input from numerical simulations. These inputs are 1) a connection between phase-space density and radius, and 2) a connection between velocity anisotropy and density slope, the \\alpha-\\beta relation. The first (phase-space density v.s. radius) has been analysed through several different simulations, however the second (\\alpha-\\beta relation) has not been quantified yet. We perform a large set of numerical experiments in order to quantify the slope and zero-point of the \\alpha-\\beta relation. When combined with the assumption of phase-space being a power-law in radius this allows us to conclude that equilibrated dark matter structures indeed have zero central velocity anisotropy, central density slope of \\alpha_0 = -0.8, and outer anisotropy of approximately \\beta_\\infinity = 0.5.

Steen H. Hansen; Ben Moore; Joachim Stadel

2005-09-27

295

Large Friction Anisotropy of a Polydiacetylene Monolayer  

SciTech Connect

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.

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

1999-05-11

296

Measuring anisotropies in the cosmic neutrino background  

NASA Astrophysics Data System (ADS)

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.

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

2014-10-01

297

Narrow-angle cosmic-ray anisotropies  

NASA Technical Reports Server (NTRS)

An alternate interpretation is presented for the diurnal cosmic ray anisotropy measurements made with underground muons in London. From the widely accepted models of cosmic ray diffusion in the Galaxy, a diurnal anisotropy (24 h wave) would be expected. But from a model predicting the occurrence of an excess within some small region of the celestial sphere, it is suggested that the direction of this excess would depend on the orientation (in space and time) of the source relative to galactic magnetic field lines which connect the source with the solar system.

Barrowes, S.

1975-01-01

298

Overview of Secondary Anisotropies of the CMB  

E-print Network

While the major contribution to the Cosmic Microwave Background (CMB) anisotropies are the sought-after primordial fluctuations produced at the surface of last scattering, other effects produce secondary fluctuations at lower redshifts. These secondary fluctuations must be carefully accounted for, in order to isolate primordial fluctuations. In addition, they are interesting in their own right, since they provide a wealth of information on the geometry and local properties of the universe. Here, I survey the different sources of secondary anisotropies and extragalactic foregrounds of the CMB. I show their relative importance on the multipole-frequency plane. I discuss in particular their impact in the future CMB missions MAP and Planck Surveyor.

A. Refregier

1999-04-19

299

Anisotropy effects on 3D waveform inversion  

NASA Astrophysics Data System (ADS)

In the recent years 3D waveform inversion has become achievable procedure for seismic data processing. A number of datasets has been inverted and presented (Warner el al 2008, Ben Hadj at all, Sirgue et all 2010) using isotropic 3D waveform inversion. However the question arises will the results be affected by isotropic assumption. Full-wavefield inversion techniques seek to match field data, wiggle-for-wiggle, to synthetic data generated by a high-resolution model of the sub-surface. In this endeavour, correctly matching the travel times of the principal arrivals is a necessary minimal requirement. In many, perhaps most, long-offset and wide-azimuth datasets, it is necessary to introduce some form of p-wave velocity anisotropy to match the travel times successfully. If this anisotropy is not also incorporated into the wavefield inversion, then results from the inversion will necessarily be compromised. We have incorporated anisotropy into our 3D wavefield tomography codes, characterised as spatially varying transverse isotropy with a tilted axis of symmetry - TTI anisotropy. This enhancement approximately doubles both the run time and the memory requirements of the code. We show that neglect of anisotropy can lead to significant artefacts in the recovered velocity models. We will present inversion results of inverting anisotropic 3D dataset by assuming isotropic earth and compare them with anisotropic inversion result. As a test case Marmousi model extended to 3D with no velocity variation in third direction and with added spatially varying anisotropy is used. Acquisition geometry is assumed as OBC with sources and receivers everywhere at the surface. We attempted inversion using both 2D and full 3D acquisition for this dataset. Results show that if no anisotropy is taken into account although image looks plausible most features are miss positioned in depth and space, even for relatively low anisotropy, which leads to incorrect result. This may lead to misinterpretation of results. However if correct physics is used results agree with correct model. Our algorithm is relatively affordable and runs on standard pc clusters in acceptable time. Refferences: H. Ben Hadj Ali, S. Operto and J. Virieux. Velocity model building by 3D frequency-domain full-waveform inversion of wide-aperture seismic data, Geophysics (Special issue: Velocity Model Building), 73(6), P. VE101-VE117 (2008). L. Sirgue, O.I. Barkved, J. Dellinger, J. Etgen, U. Albertin, J.H. Kommedal, Full waveform inversion: the next leap forward in imaging at Valhall, First Brake April 2010 - Issue 4 - Volume 28 M. Warner, I. Stekl, A. Umpleby, Efficient and Effective 3D Wavefield Tomography, 70th EAGE Conference & Exhibition (2008)

Stekl, I.; Warner, M.; Umpleby, A.

2010-12-01

300

Bounded Fraction Pointer  

NSDL National Science Digital Library

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.

2010-01-01

301

Identifying Equivalent Fractions  

NSDL National Science Digital Library

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.

Banfill, J. C.

2007-12-12

302

Mapping Magnetic Susceptibility Anisotropies of White Matter in vivo in the Human Brain at 7 Tesla  

PubMed Central

High-resolution magnetic resonance phase- or frequency- shift images acquired at high field show contrast related to magnetic susceptibility differences between tissues. Such contrast varies with the orientation of the organ in the field, but the development of quantitative susceptibility mapping (QSM) has made it possible to reproducibly image the intrinsic tissue susceptibility contrast. However, recent studies indicate that magnetic susceptibility is anisotropic in brain white matter and, as such, needs to be described by a symmetric second-rank tensor (?¯¯). To fully determine the elements of this tensor, it would be necessary to acquire frequency data at six or more orientations. Assuming cylindrical symmetry of the susceptibility tensor in myelinated white matter fibers, we propose a simplified method to reconstruct the susceptibility tensor in terms of a mean magnetic susceptibility, MMS = (?? + 2??)/3 and a magnetic susceptibility anisotropy, MSA = ?? ? ??, where ?? and ?? are susceptibility parallel and perpendicular to the white matter fiber direction, respectively. Computer simulations show that with a practical head rotation angle of around 20°–30°, four head orientations suffice to reproducibly reconstruct the tensor with good accuracy. We tested this approach on whole brain 1×1×1 mm3 frequency data acquired from five healthy subjects at 7 T. The frequency information from phase images collected at four head orientations was combined with the fiber direction information extracted from diffusion tensor imaging (DTI) to map the white matter susceptibility tensor. The MMS and MSA were quantified for regions in several large white matter fiber structures, including the corona radiata, posterior thalamic radiation and corpus callosum. MMS ranged from ?0.037 to ?0.053 ppm (referenced to CSF being about zero). MSA values could be quantified without the need for a reference and ranged between 0.004 and 0.029 ppm, in line with the expectation that the susceptibility perpendicular to the fiber is more diamagnetic than the one parallel to it. PMID:22561358

Li, Xu; Vikram, Deepti S; Lim, Issel Anne L; Jones, Craig K; Farrell, Jonathan A.D.; van Zijl, Peter C. M.

2012-01-01

303

Elastic and viscous anisotropy in Earth's mantle : observations and implications  

E-print Network

In this thesis I address the topic of anisotropy - the directional dependence of physical properties of rocks - from two complementary angles: I use seismic anisotropy to detect deformation in the mantle, and I demonstrate ...

Lev, Einat

2009-01-01

304

Fraction Model III  

NSDL National Science Digital Library

An interactive tool to represent a fraction circle, rectangle, or set model with numerators and denominators ranging from 1 to 100. The decimal and percent equivalents of the created fraction are also displayed.

Mathematics, Illuminations N.

2009-03-11

305

Garden Variety Fractions  

NSDL National Science Digital Library

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.

Green, Michael

2012-07-23

306

Fractions and Decimals  

NSDL National Science Digital Library

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 ...

Perry, Miss

2007-11-29

307

The Fraction String  

NSDL National Science Digital Library

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.

Green, Michael

2012-06-26

308

Fractional Dynamical Systems  

E-print Network

In this paper the author presents the results of the preliminary investigation of fractional dynamical systems based on the results of numerical simulations of fractional maps. Fractional maps are equivalent to fractional differential equations describing systems experiencing periodic kicks. Their properties depend on the value of two parameters: the non-linearity parameter, which arises from the corresponding regular dynamical systems; and the memory parameter which is the order of the fractional derivative in the corresponding non-linear fractional differential equations. The examples of the fractional Standard and Logistic maps demonstrate that phase space of non-linear fractional dynamical systems may contain periodic sinks, attracting slow diverging trajectories, attracting accelerator mode trajectories, chaotic attractors, and cascade of bifurcations type trajectories whose properties are different from properties of attractors in regular dynamical systems. The author argues that discovered properties should be evident in the natural (biological, psychological, physical, etc.) and engineering systems with power-law memory.

Mark Edelman

2013-12-30

309

Area Models: Multiplying Fractions  

NSDL National Science Digital Library

In this lesson students will investigate relationship between area models and the concept of multiplying fractions. Students will use area model to develop understanding of the concept of multiplying fractions as well as to find the product of two common fraction. The teacher will use the free application GeoGebra (see download link under Suggested Technology) to provide students with a visual representation of how area models can be used at the time of multiplying fractions.

2012-11-05

310

Equivalent Fractions Finder  

NSDL National Science Digital Library

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.

2007-12-12

311

Fractional Poisson process  

Microsoft Academic Search

A fractional non-Markov Poisson stochastic process has been developed based on fractional generalization of the Kolmogorov–Feller equation. We have found the probability of n arrivals by time t for fractional stream of events. The fractional Poisson process captures long-memory effect which results in non-exponential waiting time distribution empirically observed in complex systems. In comparison with the standard Poisson process the

Nick Laskin

2003-01-01

312

Numerical likelihood analysis of cosmic ray anisotropies  

SciTech Connect

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.

Carlos Hojvat et al.

2003-07-02

313

Knitted Patterns as a Model for Anisotropy  

ERIC Educational Resources Information Center

Anisotropy is a difficult concept, although it is often met in everyday life. This paper describes a simple model--knitted patterns--having anisotropic elastic properties. The elastic constant is measured for the force applied in different directions with respect to the knitting direction. It is also shown that the deformation of the knitted…

Cepic, Mojca

2012-01-01

314

MATERIALS SCIENCE & ENGINEERING Texture, Microstructure & Anisotropy  

E-print Network

MATERIALS SCIENCE & ENGINEERING 27-750 Texture, Microstructure & Anisotropy formerly known hours lecture per week (12 units in the CMU system). Class Schedule. This is a 12 unit class for graduates Spring, 2014, and meets twice a week for a total of 4 hours, 10:00-noon, Monday and Wednesday

Rollett, Anthony D.

315

Magnetic anisotropy of strained epitaxial manganite films  

NASA Astrophysics Data System (ADS)

The in-plane magnetic anisotropy of epitaxial La0.7Sr0.3MnO3 (LSMO) films is studied at room temperature by the following three independent techniques: magnetooptical Kerr effect, ferromagnetic resonance at a frequency of 9.61 GHz, and recording of absorption spectra of electromagnetic radiation at a frequency of 290.6 MHz. The films are deposited onto NdGaO3 (NGO) substrates in which the (110)NGO plane is tilted at an angle of 0-25.7° to the substrate plane. The uniaxial magnetic anisotropy induced by the strain of the film is found to increase with the tilt angle of the (110)NGO plane. A model is proposed to describe the change in the magnetic anisotropy energy with the tilt angle. A sharp increase in the radio-frequency absorption in a narrow angular range of a dc magnetic field near a hard magnetization axis is detected The anisotropy parameters of the LSMO films grown on (110)NGO, (001)SrTiO3, and (001)[(LaAlO3)0.3 + (Sr2AlTaO6)0.7] substrates are compared.

Demidov, V. V.; Borisenko, I. V.; Klimov, A. A.; Ovsyannikov, G. A.; Petrzhik, A. M.; Nikitov, S. A.

2011-05-01

316

The Standard Cosmological Model and CMB Anisotropies  

E-print Network

This is a course on cosmic microwave background (CMB) anisotropies in the standard cosmological model, designed for beginning graduate students and advanced undergraduates. ``Standard cosmological model'' in this context means a Universe dominated by some form of cold dark matter (CDM) with adiabatic perturbations generated at some initial epoch, e.g., Inflation, and left to evolve under gravity alone (which distinguishes it from defect models). The course is primarily theoretical and concerned with the physics of CMB anisotropies in this context and their relation to structure formation. Brief presentations of the uniform Big Bang model and of the observed large--scale structure of the Universe are given. The bulk of the course then focuses on the evolution of small perturbations to the uniform model and on the generation of temperature anisotropies in the CMB. The theoretical development is performed in the (pseudo--)Newtonian gauge because it aids intuitive understanding by providing a quick reference to classical (Newtonian) concepts. The fundamental goal of the course is not to arrive at a highly exact nor exhaustive calculation of the anisotropies, but rather to a good understanding of the basic physics that goes into such calculations.

James G. Bartlett

1999-03-17

317

Anisotropy of Wood in the Microwave Region  

ERIC Educational Resources Information Center

Wood is transparent for microwaves and due to its anisotropic structure has anisotropic dielectric properties. A laboratory experiment that allows for the qualitative demonstration and quantitative measurements of linear dichroism and birefringence in the microwave region is presented. As the proposed experiments are based on the anisotropy (of…

Ziherl, Sasa; Bajc, Jurij; Urankar, Bernarda; Cepic, Mojca

2010-01-01

318

Laser-induced anisotropy near a focus  

Microsoft Academic Search

Optically isotropic materials may become anisotropic when illuminated by a strong laser beam. The induced anisotropy is proportional to the beam intensity, and it produces a depolarization of the laser beam. If the material is placed near the beam focus, usually the induced depolarization is strong due to the high beam intensity. We observed that in terbium gallium garnet, however,

X. Chen; H. Berger

1999-01-01

319

Knitted patterns as a model for anisotropy  

Microsoft Academic Search

Anisotropy is a difficult concept, although it is often met in everyday life. This paper describes a simple model—knitted patterns—having anisotropic elastic properties. The elastic constant is measured for the force applied in different directions with respect to the knitting direction. It is also shown that the deformation of the knitted pattern does not always have the same direction as

Mojca ?epi?

2012-01-01

320

Anisotropy of magnetic susceptibility of some metamorphic minerals  

Microsoft Academic Search

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

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

1987-01-01

321

Fractions Decimals & Percentages  

NSDL National Science Digital Library

This web page contains three Flash applets that help students explore relationships among fractions, decimals and percents. Users adjust the values represented visually by bars to compare or find equivalents of fractions to percents, fractions to decimals, or percents to decimals. The applets lend themselves well to classroom discussions with interactive white boards.

Weddell, Mark

2003-01-01

322

Comparing Fractions with Pizza  

NSDL National Science Digital Library

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.

Uhe, Shanna

2012-07-31

323

Comparing and Ordering Fractions  

NSDL National Science Digital Library

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.

2007-12-12

324

Time fractional Schrödinger equation  

Microsoft Academic Search

The Schrödinger equation is considered with the first order time derivative changed to a Caputo fractional derivative, the time fractional Schrödinger equation. The resulting Hamiltonian is found to be non-Hermitian and nonlocal in time. The resulting wave functions are thus not invariant under time reversal. The time fractional Schrödinger equation is solved for a free particle and for a potential

Mark Naber

2004-01-01

325

HOMOGENEOUS FRACTIONAL EMBEDDINGS PIERRE INIZAN  

E-print Network

HOMOGENEOUS FRACTIONAL EMBEDDINGS PIERRE INIZAN Abstract. Fractional equations appear from the classical one and may induce problems of temporal homogeneity in fractional objects it to construct two equivalent fractional embeddings which retain homogeneity. The notion of fractional constant

Paris-Sud XI, Université de

326

Significant seismic anisotropy beneath the southern Lhasa Terrane, Tibetan Plateau  

E-print Network

Significant seismic anisotropy beneath the southern Lhasa Terrane, Tibetan Plateau Stephen S. Gao Terrane of the Tibetan Plateau reveal significant azimuthal anisotropy with a splitting time of up to 1), Significant seismic anisotropy beneath the southern Lhasa Terrane, Tibetan Plateau, Geochem. Geophys. Geosyst

Gao, Stephen Shangxing

327

Probability of radial anisotropy in the deep mantle  

Microsoft Academic Search

It is well established that the Earth's uppermost mantle is anisotropic, but observations of anisotropy in the deeper mantle have been more ambiguous. Radial anisotropy, the discrepancy between Love and Rayleigh waves, was included in the top 220 km of PREM, but there is no consensus whether anisotropy is present below that depth. Fundamental mode surface waves, for commonly used periods

K. Visser; J. Trampert; S. Lebedev; B. L. N. Kennett

2008-01-01

328

Anisotropy in MHD turbulence due to a mean magnetic field  

Microsoft Academic Search

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

John V. Shebalin; W. H. Matthaeus; David Montgomery

1983-01-01

329

Seismic Anisotropy Beneath California: Constraints from Rayleigh Wave Tomography  

Microsoft Academic Search

Lateral variations in the azimuthal anisotropy of fundamental mode Rayleigh wave propagation are well-resolved in the 18 to 143 s period range using teleseismic sources and the Transportable Array of the USArray experiment. The variations in azimuthal anisotropy with period provide constraints on the vertical distribution of anisotropy within the lithosphere and asthenosphere that are not resolved from shear wave

J. Seavey; D. W. Forsyth; C. J. Rau

2010-01-01

330

Anisotropy in MHD turbulence due to a mean magnetic field  

NASA Technical Reports Server (NTRS)

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.

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

1982-01-01

331

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

NASA Astrophysics Data System (ADS)

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.

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

332

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

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 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.

Abreu, P [Lisbon, IST; Aglietta, M [IFSI, Turin; Ahn, E J [Fermilab; Albuquerque, I F.M. [Sao Paulo U.; Allard, D [APC, Paris; Allekotte, I [Centro Atomico Bariloche; Allen, J [New York U.; Allison, P [Ohio State U.; Alvarez Castillo, J [Mexico U., ICN; Alvarez-Muniz, J [Santiago de Compostela U.; Ambrosio, M [Napoli Seconda U.; INFN, Naples; Nijmegen U., IMAPP

2011-06-17

333

The influence of structural/shape anisotropy in 2-D photonic crystals  

NASA Astrophysics Data System (ADS)

Using the finite-difference time-domain method, photonic bandgaps and defect modes in two-dimensional photonic crystals based on “triangular cylinders” are simulated. Compared with the circular cross-section rods, there is a structural/shape anisotropy in triangular cross-section based cylinders. When all cylinders are rotated for different angles along clockwise or counter-clockwise, a small shift at the high band-edge is observed even if the filling fraction did not change. When defect is introduced in photonic crystals, the defect modes can be adjusted by rotation of cylinders which are in the neighborhood of the defect. All results show that the structural/shape anisotropy of cylinders can be used to adjust the photonic bandgap and defect modes.

Feng, Zhifang; Zhang, Dandan; Zhan, Ketao; Shao, Xiaohong; Raja, M. Yasin Akhtar

2013-08-01

334

Using nanoscale and mesoscale anisotropy to engineer the optical response of three-dimensional plasmonic metamaterials.  

PubMed

The a priori ability to design electromagnetic wave propagation is crucial for the development of novel metamaterials. Incorporating plasmonic building blocks is of particular interest due to their ability to confine visible light. Here we explore the use of anisotropy in nanoscale and mesoscale plasmonic array architectures to produce noble metal-based metamaterials with unusual optical properties. We find that the combination of nanoscale and mesoscale anisotropy leads to rich opportunities for metamaterials throughout the visible and near-infrared. The low volume fraction (<5%) plasmonic metamaterials explored herein exhibit birefringence, a skin depth approaching that of pure metals for selected wavelengths, and directionally confined waves similar to those found in optical fibres. These data provide design principles with which the electromagnetic behaviour of plasmonic metamaterials can be tailored using high aspect ratio nanostructures that are accessible via a variety of synthesis and assembly methods. PMID:24934374

Ross, Michael B; Blaber, Martin G; Schatz, George C

2014-01-01

335

Using nanoscale and mesoscale anisotropy to engineer the optical response of three-dimensional plasmonic metamaterials  

NASA Astrophysics Data System (ADS)

The a priori ability to design electromagnetic wave propagation is crucial for the development of novel metamaterials. Incorporating plasmonic building blocks is of particular interest due to their ability to confine visible light. Here we explore the use of anisotropy in nanoscale and mesoscale plasmonic array architectures to produce noble metal-based metamaterials with unusual optical properties. We find that the combination of nanoscale and mesoscale anisotropy leads to rich opportunities for metamaterials throughout the visible and near-infrared. The low volume fraction (<5%) plasmonic metamaterials explored herein exhibit birefringence, a skin depth approaching that of pure metals for selected wavelengths, and directionally confined waves similar to those found in optical fibres. These data provide design principles with which the electromagnetic behaviour of plasmonic metamaterials can be tailored using high aspect ratio nanostructures that are accessible via a variety of synthesis and assembly methods.

Ross, Michael B.; Blaber, Martin G.; Schatz, George C.

2014-06-01

336

Complex-anisotropy-induced pattern formation in bistable media.  

PubMed

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

He, Zhi Zhu; Liu, Jing

2009-02-01

337

Application of fractal and grey level co-occurrence matrix analysis in evaluation of brain corpus callosum and cingulum architecture.  

PubMed

This aim of this study was to assess the discriminatory value of fractal and grey level co-occurrence matrix (GLCM) analysis methods in standard microscopy analysis of two histologically similar brain white mass regions that have different nerve fiber orientation. A total of 160 digital micrographs of thionine-stained rat brain white mass were acquired using a Pro-MicroScan DEM-200 instrument. Eighty micrographs from the anterior corpus callosum and eighty from the anterior cingulum areas of the brain were analyzed. The micrographs were evaluated using the National Institutes of Health ImageJ software and its plugins. For each micrograph, seven parameters were calculated: angular second moment, inverse difference moment, GLCM contrast, GLCM correlation, GLCM variance, fractal dimension, and lacunarity. Using the Receiver operating characteristic analysis, the highest discriminatory value was determined for inverse difference moment (IDM) (area under the receiver operating characteristic (ROC) curve equaled 0.925, and for the criterion IDM?0.610 the sensitivity and specificity were 82.5 and 87.5%, respectively). Most of the other parameters also showed good sensitivity and specificity. The results indicate that GLCM and fractal analysis methods, when applied together in brain histology analysis, are highly capable of discriminating white mass structures that have different axonal orientation. PMID:24967845

Pantic, Igor; Dacic, Sanja; Brkic, Predrag; Lavrnja, Irena; Pantic, Senka; Jovanovic, Tomislav; Pekovic, Sanja

2014-10-01

338

Cross-sectional analysis of the association between age and corpus callosum size in chimpanzees (Pan troglodytes).  

PubMed

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 posterior midbody and anterior midbody displayed nonlinear 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 nonlinear 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

Hopkins, William D; Phillips, Kimberley A

2010-03-01

339

Reduced corpus-callosum volume in posttraumatic stress disorder highlights the importance of interhemispheric connectivity for associative memory.  

PubMed

Memory deficits are a common complaint of patients with posttraumatic stress disorder (PTSD). Despite vivid trauma-related memory, previous studies report memory impairment for nontrauma-related stimuli when compared to controls, specifically in associative memory (Guez et al., 2011). Healthy individuals show hemispheric memory asymmetry with left-prefrontal lateralization of encoding and right-prefrontal lateralization of episodic retrieval, suggesting a role for interhemispheric communication in memory-related tasks (Gazzaniga, ; Ringo, Doty, Demeter, & Simard, ). Because brain magnetic resonance imaging (bMRI) studies in PTSD patients report volume changes in various regions, including white matter and corpus callosum (CC), we aimed to test the relationship between memory deficits and CC volume in PTSD patients. We probed for specific alterations in associative memory in PTSD and measured the volume of subportions within the CC employing bMRI. Our main finding was a reduction in CC white-matter volume in PTSD patients, as compared to controls, t(35) = -2.7, p = .010, that was correlated with lower associative performance (r = .76, p = .003). We propose that CC volume reduction is a substrate for the associative memory deficits found in PTSD. PMID:24473965

Saar-Ashkenazy, Rotem; Cohen, Jonathan E; Guez, Jonathan; Gasho, Chris; Shelef, Ilan; Friedman, Alon; Shalev, Hadar

2014-02-01

340

The desmosterolosis phenotype: spasticity, microcephaly and micrognathia with agenesis of corpus callosum and loss of white matter  

PubMed Central

Desmosterolosis is a rare autosomal recessive disorder of elevated levels of the cholesterol precursor desmosterol in plasma, tissue and cultured cells. With only two sporadic cases described to date with two very different phenotypes, the clinical entity arising from mutations in 24-dehydrocholesterol reductase (DHCR24) has yet to be defined. We now describe consanguineous Bedouin kindred with four surviving affected individuals, all presenting with severe failure to thrive, psychomotor retardation, microcephaly, micrognathia and spasticity with variable degree of hand contractures. Convulsions near birth, nystagmus and strabismus were found in most. Brain MRI demonstrated significant reduction in white matter and near agenesis of corpus callosum in all. Genome-wide linkage analysis and fine mapping defined a 6.75?cM disease-associated locus in chromosome 1 (maximum multipoint LOD score of six), and sequencing of candidate genes within this locus identified in the affected individuals a homozygous missense mutation in DHCR24 leading to dramatically augmented plasma desmosterol levels. We thus establish a clear consistent phenotype of desmosterolosis (MIM 602398). PMID:21559050

Zolotushko, Jenny; Flusser, Hagit; Markus, Barak; Shelef, Ilan; Langer, Yshaia; Heverin, Maura; Bjorkhem, Ingemar; Sivan, Sara; Birk, Ohad S

2011-01-01

341

West syndrome, microcephaly, grey matter heterotopia and hypoplasia of corpus callosum due to a novel ARFGEF2 mutation.  

PubMed

West syndrome (WS) is an epileptic encephalopathy of childhood, defined by the presence of clustered spasms usually occurring before the age of 1 year, hypsarrhythmia on EEG that is notoriously difficult to define, and developmental arrest or regression. The incidence of WS is 1:3200 live births with an aetiology-dependent prognosis. Up to 80% of children with symptomatic WS suffer from mental retardation, and approximately 50% develop Lennox-Gastaut syndrome. Using homozygosity mapping followed by exome sequencing, we identified a ADP-ribosylation factor (ARF) guanine nucleotide-exchange factor two (brefeldin A-inhibited) (ARFGEF2) mutation in five related infants with WS. ARFGEF2 is involved in the activation of ARFs by accelerating replacement of bound guanosine diphosphate (GDP) with Guanosine triphosphate (GTP), and is involved in Golgi transport. A mutation in ARFGEF2 has been previously described only once, causing microcephaly and periventricular heterotopia. Here, we describe a novel ARFGEF2 mutation in five related patients presenting with WS, microcephaly, periventricular heterotopia and thin corpus callosum. PMID:23812912

Banne, Ehud; Atawneh, Osama; Henneke, Marco; Brockmann, Knut; Gärtner, Jutta; Elpeleg, Orly; Edvardson, Simon

2013-11-01

342

East-West and Radial Anisotropy in Cosmic Ray Modulation  

NASA Astrophysics Data System (ADS)

The cosmic ray (CR) data observed with the Deep River neutron monitoring station has been harmonically analyzed for the period 1964--95 to obtain the diurnal and semi-diurnal components of cosmic ray intensity on geomagnetically 60 quiet days. The annual diurnal anisotropy vectors have been resolved into two components: one along the 12-Hr direction, the radial anisotropy component; and the other along 18-Hr direction, east-west anisotropy component. It is observed that when the polarity of solar poloidal magnetic field (SPMF) in northern hemisphere (NH) is positive, the radial anisotropy component increases; whereas, the east-west anisotropy component decreases. This results in shifting the diurnal anisotropy vector towards earlier hours during the positive polarity epoch. During the negative polarity epoch, the east-west anisotropy component attains its maximum and the radial anisotropy component attains its minimum, which results in shifting the anisotropy vector gradually towards later hours. For semi-diurnal anisotropy, it is found that the magnitude of the 3-Hr component is larger than the 6-Hr component during the positive polarity epoch; which results in shifting the anisotropy vector towards earlier hours, but the same does not hold good for the negative polarity epoch i.e., the magnitude of 6-Hr component is not always found to be greater than the 3-Hr component.

Agarwal Mishra, Rekha; Mishra, Rajesh K.

2005-05-01

343

In Plane Resistivity Anisotropy in iron Chalcogenides  

NASA Astrophysics Data System (ADS)

FeTe suffers a bicolinear antiferromagnetic ordering, with a (12 0) ordering wave-vector, in contrast to the (12 12) ordering wave-vector found in underdoped ``122'' and ``1111'' iron pnictides. At the optimal doping the static (12 0) order disappears and a spin resonance at the (12 12) wave-vector emerges. Here we report measurements of the in-plane resistivity anisotropy of single crystals of Fe1+?Te1-xSex for underdoped and optimally doped compositions. The underdoped compounds were partially detwinned by applying uni-axial strain along the (12 0), revealing a larger resistivity along the antiferromagnetic ordering direction. However, for optimal doping uni-axial strain induces the largest resistivity anisotropy along the (12 12) direction, similar to the ``122'' family of compounds. This behaviour suggests that in addition to the presence of spin resonance, a divergent nematic susceptibility might be a key feature associated with optimal doping in iron based superconductors.

Chu, Jiun-Haw; Kucharczyk, Chris; Fisher, Ian

2012-02-01

344

Friction Anisotropy with Respect to Topographic Orientation  

PubMed Central

Friction characteristics with respect to surface topographic orientation were investigated using surfaces of different materials and fabricated with grooves of different scales. Scratching friction tests were conducted using a nano-indentation-scratching system with the tip motion parallel or perpendicular to the groove orientation. Similar friction anisotropy trends were observed for all the surfaces studied, which are (1) under a light load and for surfaces with narrow grooves, the tip motion parallel to the grooves offers higher friction coefficients than does that perpendicular to them, (2) otherwise, equal or lower friction coefficients are found under this motion. The influences of groove size relative to the diameter of the mating tip (as a representative asperity), surface contact stiffness, contact area, and the characteristic stiction length are discussed. The appearance of this friction anisotropy is independent of material; however, the boundary and the point of trend transition depend on material properties. PMID:23248751

Yu, Chengjiao; Wang, Q. Jane

2012-01-01

345

Anisotropies in the Cosmic Microwave Background: Theory  

E-print Network

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 ouline 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 specturm 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.

Scott Dodelson

1997-02-14

346

Tailored magnetic anisotropy in an amorphous trilayer  

SciTech Connect

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.

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

347

Anisotropy in twinned terfenol-D crystals  

NASA Astrophysics Data System (ADS)

The highly magnetostrictive cubic compound Terfenol-D (Tb0.3Dy0.7Fe2) solidifies via a (211) dendritic growth front when growth by a free-standing zone technique. The resulting material is usually composed of dendritic plates often containing crystallographic twins, the predominant plate and twin plane being the (1-11) orthogonal to the (-2-11) growth plane. Results of room temperature magnetic torque analysis from (011) disk specimens, having differing twin densities, are presented which yield both the magnetic anisotropy constants, K(sub 1) = -1.6 x 10(exp 5) J/cu m and K(sub 2) = -0.16 x 10(exp 5) J/cu m, and the relative parent/twin volume. Magnetic susceptibility data both parallel and transverse to the applied field are presented which, in conjunction with the anisotropy results, emphasize the importance of twin density on magnetoelastic response for typical application geometries.

Lord, D. G.; Harvey, D.

1994-11-01

348

Local anisotropy of fluids using Minkowski tensors  

NASA Astrophysics Data System (ADS)

Statistics of the free volume available to individual particles have previously been studied for simple and complex fluids, granular matter, amorphous solids, and structural glasses. Minkowski tensors provide a set of shape measures that are based on strong mathematical theorems and easily computed for polygonal and polyhedral bodies such as free volume cells (Voronoi cells). They characterize the local structure beyond the two-point correlation function and are suitable to define indices 0 <= ??a, b <= 1 of local anisotropy. Here, we analyze the statistics of Minkowski tensors for configurations of simple liquid models, including the ideal gas (Poisson point process), the hard disks and hard spheres ensemble, and the Lennard-Jones fluid. We show that Minkowski tensors provide a robust characterization of local anisotropy, which ranges from ??a, b?0.3 for vapor phases to \\beta_\

Kapfer, S. C.; Mickel, W.; Schaller, F. M.; Spanner, M.; Goll, C.; Nogawa, T.; Ito, N.; Mecke, K.; Schröder-Turk, G. E.

2010-11-01

349

Fractional vector calculus and fractional Maxwell's equations  

Microsoft Academic Search

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

Vasily E. Tarasov

2008-01-01

350

Multiplying a Fraction by a Fraction  

NSDL National Science Digital Library

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.

Admin, Admin

2012-04-16

351

Fractions--Equivalent  

NSDL National Science Digital Library

Students use this virtual manipulative to visualize and name equivalent fractions. The applet presents a shape divided into equal parts, with some parts shaded. Students change the number of divisions of the shape to visualize equivalent fractions, name the fractions, and check their answers. Instructions for using the applet and teaching ideas for parents/teachers are available through the links at the top of the page.

2000-01-01

352

Fabulous Fraction Fun  

NSDL National Science Digital Library

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 ...

Alman, Mrs.

2008-03-26

353

Fractional Electromagnetic Waves  

E-print Network

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.

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

2011-08-31

354

Pn anisotropy in Mesozoic western Pacific lithosphere  

NASA Astrophysics Data System (ADS)

is the high-frequency, scattered P phase guided for great distances within the old oceanic lithosphere. Two arrays of ocean bottom seismometers were deployed on old (150-160 Ma) seafloor in the northwestern Pacific south of Shatsky Rise for the Pacific Lithosphere Anisotropy and Thickness Experiment. We use Pn phases from 403 earthquakes during the 1 year of deployment to measure apparent velocities across the arrays. Each array was deployed on a separate limb of a magnetic bight, formed near a fast-spreading, ridge-ridge-ridge triple junction. Using high-frequency waves (5-10 Hz), we look at variations of Pn velocities as a function of azimuth. In the western array, we find Pn anisotropy with velocities ranging from ~8.7 km/s in the back azimuth (?) direction of 310° to ~7.7 km/s at ~350°. In the eastern array, the velocity ranges from ~8.5 km/s in back azimuth direction of ~210° to ~7.7 km/s at 260° and ~310°. We observe rapid velocity changes with azimuth in the both arrays requiring sinusoidal variations of roughly equal amplitude as a function of both 2? and 4?, which is not expected for the orthorhombic symmetry of olivine or orthopyroxene. The fastest directions on the two limbs are roughly orthogonal to each other suggesting the dominance of fossil anisotropy, but the fast directions of the 2? components are skewed counterclockwise from the spreading directions. We speculate that the rapid azimuthal variations may be caused by vertical stratification with changing anisotropy with depth in the oceanic lithosphere.

Shintaku, Natsumi; Forsyth, Donald W.; Hajewski, Christina J.; Weeraratne, Dayanthie S.

2014-04-01

355

Fractional order differentiation by integration: an application to fractional  

E-print Network

the output of a fractional linear system defined through a linear fractional differential equation (FDE. Keywords: Differential equations; Differentiators; Parameter estimation. 1. INTRODUCTION Fractional], signal process- ing [4], and finance [5], etc. Unlike classical differential equations, fractional

Boyer, Edmond

356

The velocity anisotropy - density slope relation  

E-print Network

One can solve the Jeans equation analytically for equilibrated dark matter structures, once given two pieces of input from numerical simulations. These inputs are 1) a connection between phase-space density and radius, and 2) a connection between velocity anisotropy and density slope, the \\alpha-\\beta relation. The first (phase-space density v.s. radius) has already been analysed through several different simulations, however the second (\\alpha-\\beta relation) has not been quantified yet. We perform a large set of numerical experiments in order to quantify the slope and zero-point of the \\alpha-\\beta relation. We find strong indication that the relation is indeed an attractor. When combined with the assumption of phase-space being a power-law in radius, this allows us to conclude that equilibrated dark matter structures indeed have zero central velocity anisotropy \\beta_0 = 0, central density slope of \\alpha_0 = -0.8, and outer anisotropy of \\beta_\\infty = 0.5.

Steen H. Hansen; Joachim Stadel

2005-10-21

357

Anisotropy in the Interactions of Ultracold Dysprosium  

NASA Astrophysics Data System (ADS)

The ground 4f^106s^2 configuration of atomic dysprosium has an unfilled 4f^10 shell lying beneath a closed 6s^2 shell. This so-called ``submerged-shell'' atom has a large orbital (L = 6) and total (J = 8) electron angular momenta and, consequently, an extremely large magnetic moment of 10?B. Only recently the first laser cooling and trapping experiment of dysprosium atoms has been reported [1]. The experiment suggested that the anisotropy from the submerged shell and magnetic moment plays a significant role in the interactions of dysprosium atoms. Here, we explore the anisotropies from the electrostatic dispersion and magnetic dipole-dipole interactions. We use a relativistic configuration interaction valence-bond method to obtain short-range chemical potentials. Dispersion coefficients have been calculated using known atomic data. Comparison of the strengths of dispersion and magnetic dipole interactions shows that the anisotropy in the dispersion dominates for atomic separations less than 50 bohr and can lead to a rapid reorientation of the Dy angular momenta.[4pt] [1] M. Lu, S. Ho Youn, and B. Lev, Phys. Rev. Lett. 104, 063001 (2010).

Kotochigova, Svetlana; Petrov, Alexander

2011-06-01

358

Influence of ferroelectric polarization on magnetic anisotropy  

NASA Astrophysics Data System (ADS)

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)

Mardana, A.; Ducharme, S.; Adenwalla, S.

2010-03-01

359

Anisotropy of permeability in faulted porous sandstones  

NASA Astrophysics Data System (ADS)

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.

Farrell, N. J. C.; Healy, D.; Taylor, C. W.

2014-06-01

360

Cosmic ray anisotropies near the heliopause  

NASA Astrophysics Data System (ADS)

Context. The Voyager 1 spacecraft became the first man-made probe to cross the heliopause into the local interstellar medium and measure the galactic environment, including charged particle intensities, in situ. Aims: We qualitatively explain the observed anisotropies of galactic and anomalous cosmic rays in the interstellar medium. Methods: A pitch-angle-dependent numerical model was constructed and applied to the study of both heliospheric (anomalous cosmic rays and termination shock particles) and galactic cosmic rays near the heliopause region. Results: In accordance with the observations, the model is able to reproduce the observed anisotropic nature of both particle populations. In the interstellar medium, the heliospheric particle distribution shows a peak at pitch angles near 90°, while for galactic particles, their distribution shows a deficiency at these pitch-angle values. Conclusions: The observed anisotropies are related to the pitch-angle dependence of the perpendicular diffusion coefficient, and if this dependence is chosen appropriately, the anisotropies observed by Voyager 1 can be explained naturally.

Strauss, R. D.; Fichtner, H.

2014-12-01

361

Anisotropy of ice Ih: Developement of fabric and effects of anisotropy on deformation  

NASA Astrophysics Data System (ADS)

The anisotropy arising from preferred crystal orientation of ice I h is examined. To understand plastic anisotropy of polycrystalline materials it is necessary to examine the behavior at the single crystal level. Ice crystals have extremely strong plastic anisotropy that strongly influences the bulk behavior. There are several ways to relate single crystal deformation to the bulk behavior. Two approaches are used here. The first one is to assume a homogeneous stress throughout the bulk, which allows us to derive analytical relations between stress and strain rate. The anisotropy affects the strain rate-stress relationship significantly. For example strongly anisotropic ice, with a vertically symmetric fabric, can deform transversely to the applied stress in pure shear, be nearly undeformable in vertical compression, and shear easily in simple shear. The second approach takes the interaction between neighboring crystals into account, and recrystallization processes are also considered. Comparison of fabric evolution using the model and fabric from the GRIP ice core indicates that nearest neighbor interaction is necessary to explain observations. Quantification of the interaction is complicated by recrystallization processes. A consistent method of characterizing measured fabric is needed to verify models of fabric development. Here the elastic anisotropy of ice plays a central role, and relations between fabric and elastic wave velocities are used to characterize fabric. As always, several other methods are possible, but comparison indicates that sonic measurements give an accurate estimate for deformation effects from vertically symmetric fabric especially in simple shear. The deformation of the borehole at Dye 3, Greenland, has been measured with borehole inclinometry. Sonic velocity measurements done in the borehole allow us to model the deformation using an anisotropic flow law. Anisotropy alone cannot explain all the deformation. The additional processes responsible for the extra deformation are still unknown. The anisotropy effects the deformation of polycrystalline ice, and therefore the flow of ice sheets. Criteria for folding is modified by the anisotropy. Anisotropy of polycrystalline ice must be taken into account when modeling the flow of ice sheets and interpreting ice core records.

Thorsteinsson, Throstur

362

Diels-Alder reaction of mesophase pitch insoluble fractions with maleic anhydride  

Microsoft Academic Search

Pyridine insoluble fractions in the mesophase pitches derived from a decant oil (PMP-PI) and naphthalene (NMP-PI) were found to be rendered almost completely soluble in pyridine by the Diels-Alder reaction with maleic anhydride, maintaining their optical anisotropy and molecular association. Their solubility in pyridine reached up to 95 wt % by the reaction at 175–200 °C. Solubilized fractions were analysed

H. Toshima; T. Hino; K. Murakami; I. Mochida

1994-01-01

363

Seismic Anisotropy Beneath the Sumatra Subduction Zone  

NASA Astrophysics Data System (ADS)

The Sumatra subduction zone is located on the eastern side of the Sunda Arc between the Sunda Strait and the Andaman Islands, where the Indo-Australian plate is subducting beneath the Eurasian plate. An important tool in understanding the style and geometry of deformation within a subduction zone is the measurement of seismic anisotropy, through observations of shear wave splitting, which provides information about the mantle flow. In Sumatra two temporary seismic networks were deployed within the Mentawai and Northern region, between December 2007 and October 2008 and April 2008 and February 2009, respectively. Here we use new splitting measurements from SKS and local S phases from these networks, to characterize the type and amount of anisotropy within the region. High quality SKS splitting results obtained from 16 stations show a coherent fast direction of NNW (350°) to SSE (170°) with delay times of 1.0 to 3.0s. The observations do not conform to the standard classification of trench parallel and trench perpendicular, instead they are trench oblique, approximately parallel to the direction of motion of the subducting Indo-Australian plate. The magnitude and direction of splitting suggests that the anisotropy is due too entrained flow in the asthenosphere beneath the subducting lithosphere. Local S wave splitting measurements were obtained from 85 rays, generated by earthquakes at focal depths of 15 km-200 km and recorded across 39 stations. The polarization of the fast shear wave is trench parallel along the islands and can be contributed to shape preferred orientation of cracks in the top of the subducting slab and overriding crust. In the forearc a rotation in fast direction to trench perpendicular is observed, with a clear positive correlation between the distance the ray has traveled in the mantle and delay time, suggesting anisotropy originates from entrained flow within the mantle wedge. In the Sumatra fault region and the back arc, events originating at the plate interface show both trench perpendicular and trench parallel fast directions with delay times of up to 0.4 s, while shallow events on the Sumatra fault indicate a clear fault parallel direction with delay times of 0.1 s to 0.18 s. This pattern of shear wave splitting suggests layers of different anisotropy, one deeper layer due to entrained flow within the Sumatran mantle wedge causing trench perpendicular direction, and the second shallower one within the overriding crust due to shape preferred orientation possibly caused by the Sumatran Fault.

Collings, R.; Rietbrock, A.; Nippress, S.; Lange, D.; Tilmann, F. J.; Natawidjaja, D.; Suwargadi, B.

2011-12-01

364

(Carbon isotope fractionation inplants)  

SciTech Connect

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.

O'Leary, M.H.

1990-01-01

365

Fraction Model III  

NSDL National Science Digital Library

This tool allows the individual or the classroom to explore several representations of fractions. After selecting numerator and denominator, any number from 1 to 100, learners see the fraction itself, a visual model, as well as decimal and percent equivalents. They can choose the model to be a circle, a rectangle, or a set model.

Illuminations, Nctm

2000-01-01

366

Holographic fractional topological insulators  

SciTech Connect

We give a holographic realization of the recently proposed low-energy effective action describing a fractional topological insulator. In particular we verify that the surface of this hypothetical material supports a fractional quantum Hall current corresponding to half that of a Laughlin state.

Hoyos, Carlos; Jensen, Kristan; Karch, Andreas [Department of Physics, University of Washington, Seattle, Washington 98195-1560 (United States)

2010-10-15

367

Fresh Baked Fractions  

NSDL National Science Digital Library

In this interactive game students practice their knowledge of equivalent fractions. Students are given four fractions and are asked to select the one that isn't equivalent to the other three. There are four levels of difficulty, each with ten examples. Players are shown the correct answer for each missed item.

2011-01-01

368

Can Kindergartners Do Fractions?  

ERIC Educational Resources Information Center

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…

Cwikla, Julie

2014-01-01

369

Paper Folding Fractions  

ERIC Educational Resources Information Center

In this article, the author presents a paper folding activity that can be used for teaching fractions. This activity can be used to describe areas of folded polygons in terms of a standard unit of measure. A paper folding fractions worksheet and its corresponding solutions are also presented in this article. (Contains 2 figures.)

Pagni, David

2007-01-01

370

Mariana's fractions (grade 3)  

NSDL National Science Digital Library

This is a sample PARCC assessment task based on CCSS grade 3 fraction standards. In this interactive five-part task students reason about fractions used to represent part of a whole or a location on a number line. Included are the alignments to the CCSS, a scoring rubric, and background on the task itself.

2013-01-01

371

Cooking with Fractions  

NSDL National Science Digital Library

In this lesson, students will examine real-world recipes and determine if the fractions are less than one or greater than one. Fractions and ingredients are recorded on a chart within the groups. Games are mixed in to make learning interactive and engaging.

2012-09-25

372

Sweet Work with Fractions  

NSDL National Science Digital Library

This lesson activity from NCTM's Mathematics Teaching in the Middle School presents a fraction activity in which comparing fractions is explored through the use of sharing chocolate bars. In the lesson students present their reasoning, keep a table, and discover patterns. The PDF lesson/article contains many variations for challenge and extension.

Vinogradova, Natalya; Blaine, Larry

2013-04-01

373

An Appetite for Fractions  

ERIC Educational Resources Information Center

This article describes how using candy bars as models gives sixth-grade students a taste for learning to represent fractions whose denominators are factors of twelve. Using paper models of the candy bars, students explored and compared fractions. They noticed fewer different representations for one-third than for one-half. The authors conclude…

Wilkerson, Trena L.; Bryan, Tommy; Curry, Jane

2012-01-01

374

Anisotropy of transcallosal motor fibers indicates functional impairment in children with periventricular leukomalacia  

PubMed Central

Aim In children with bilateral spastic cerebral palsy (CP), periventricular leukomalacia (PVL) is commonly identified on magnetic resonance imaging. We characterized this white matter condition by examining callosal microstructure, interhemispheric inhibitory competence (IIC), and mirror movements. Method We examined 7 children (age range 11y 9mo–17y 9mo, median age 15y 10mo, 4 females) with bilateral spastic CP/PVL (Gross Motor Function Classification System level I or II, Manual Ability Classification System level I) and 12 age-matched controls (age range 11y 7mo–17y 1mo, median age 15y 6mo, 7 females). Fractional anisotropy of the transcallosal motor fibers (TCMF) and the corticospinal tract (CST) of both sides were calculated. The parameters of IIC (transcranial magnetic stimulation) and mirror movements were measured using standardized clinical examination and a computer-based hand motor test. Results Fractional anisotropy was lower in children with bilateral spastic CP/PVL regarding the TCMF, but not the left or right CST. Resting motor threshold was elevated in children with bilateral spastic CP/PVL whereas measures of IIC tended to be lower. Mirror movements were markedly elevated in bilateral spastic CP/PVL. Interpretation This study provides new information on different aspects of motor function in children with bilateral spastic CP/PVL. Decreased fractional anisotropy of TCMF is consistent with impairment of hand motor function in children with bilateral spastic CP/PVL. The previously overlooked microstructure of the TCMF may serve as a potential indicator for hand motor function in patients with bilateral spastic CP/PVL. PMID:21121906

KOERTE, INGA; PELAVIN, PAULA; KIRMESS, BERIT; FUCHS, TERESA; BERWECK, STEFFEN; LAUBENDER, RUEDIGER PAUL; BORGGRAEFE, INGO; SCHROEDER, SEBASTIAN; DANEK, ADRIAN; RUMMENY, CLAUDIA; REISER, MAXIMILIAN; KUBICKI, MAREK; SHENTON, MARTHA E; ERTL-WAGNER, BIRGIT; HEINEN, FLORIAN

2010-01-01

375

Fractional diffusion and fractional heat equation  

Microsoft Academic Search

This paper introduces a fractional heat equation, where the diffusion\\u000aoperator is the composition of the Bessel and Riesz potentials. Sharp bounds\\u000aare obtained for the variance of the spatial and temporal increments of the\\u000asolution. These bounds establish the degree of singularity of the sample\\u000apaths of the solution. In the case of unbounded spatial domain, a solution\\u000ais

J. M. Angulo; M. D. Ruiz-Medina; V. V. Anh; W. Grecksch

2000-01-01

376

Fractions--a Booster Activity  

NSDL National Science Digital Library

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.

Bcc/netmedia

2007-01-01

377

Thermal expansion and thermal expansion anisotropy of SiC polytypes  

NASA Technical Reports Server (NTRS)

The principal axial coefficients of thermal expansion for the (3C), (4H), and (6H) polytypes of SiC are considered to identify the structural role of the stacking layer sequence as it affects the thermal expansion. A general equation based on the fractions of cubic and hexagonal layer stacking is developed that expresses the principal axial thermal expansion coefficients of all of the SiC polytypes. It is then applied to address the thermal expansion anisotropy of the noncubic SiC structures.

Li, Z.; Bradt, R. C.

1987-01-01

378

Novel de novo SPOCK1 mutation in a proband with developmental delay, microcephaly and agenesis of corpus callosum.  

PubMed

Whole exome sequencing made it possible to identify novel de novo mutations in genes that might be linked to human syndromes (genotype first analysis). We describe a female patient with a novel de novo SPOCK1 variant, which has not been previously been associated with a human phenotype. Her features include intellectual disability with dyspraxia, dysarthria, partial agenesis of corpus callosum, prenatal-onset microcephaly and atrial septal defect with aberrant subclavian artery. Previous genetic, cytogenomic and metabolic studies were unrevealing. At age 13 years, exome sequencing on the patient and her parents revealed a de novo novel missense mutation in SPOCK1 (coding for Testican-1) on chromosome 5q31: c.239A>T (p.D80V). This mutation affects a highly evolutionarily conserved area of the gene, replacing a polar aspartic acid with hydrophobic nonpolar valine, and changing the chemical properties of the protein product, likely representing a pathogenic variant. Previous microdeletions of 5q31 including SPOCK1 have suggested genes on 5q31 as candidates for intellectual disability. No mutations or variants in other genes potentially linked to her phenotype were identified. Testicans are proteoglycans belonging to the BM-40/SPARC/osteonectin family of extracellular calcium-binding proteins. Testican-1 is encoded by the SPOCK1 gene, and mouse models have been shown it to be strongly expressed in the brain and to be involved in neurogenesis. We hypothesize that because this gene function is critical for neurogenesis, mutations could potentially lead to a phenotype with developmental delay and microcephaly. PMID:24583203

Dhamija, Radhika; Graham, John M; Smaoui, Nizar; Thorland, Erik; Kirmani, Salman

2014-03-01

379

Negative Associations between Corpus Callosum Midsagittal Area and IQ in a Representative Sample of Healthy Children and Adolescents  

PubMed Central

Documented associations between corpus callosum size and cognitive ability have heretofore been inconsistent potentially owing to differences in sample characteristics, differing methodologies in measuring CC size, or the use of absolute versus relative measures. We investigated the relationship between CC size and intelligence quotient (IQ) in the NIH MRI Study of Normal Brain Development sample, a large cohort of healthy children and adolescents (aged six to 18, n?=?198) recruited to be representative of the US population. CC midsagittal area was measured using an automated system that partitioned the CC into 25 subregions. IQ was measured using the Wechsler Abbreviated Scale of Intelligence (WASI). After correcting for total brain volume and age, a significant negative correlation was found between total CC midsagittal area and IQ (r?=??0.147; p?=?0.040). Post hoc analyses revealed a significant negative correlation in children (age<12) (r?=??0.279; p?=?0.004) but not in adolescents (age?12) (r?=??0.005; p?=?0.962). Partitioning the subjects by gender revealed a negative correlation in males (r?=??0.231; p?=?0.034) but not in females (r?=?0.083; p?=?0.389). Results suggest that the association between CC and intelligence is mostly driven by male children. In children, a significant gender difference was observed for FSIQ and PIQ, and in males, a significant age-group difference was observed for FSIQ and PIQ. These findings suggest that the correlation between CC midsagittal area and IQ may be related to age and gender. PMID:21625542

Ganjavi, Hooman; Lewis, John D.; Bellec, Pierre; MacDonald, Penny A.; Waber, Deborah P.; Evans, Alan C.; Karama, Sherif

2011-01-01

380

Tempered fractional Brownian motion  

NASA Astrophysics Data System (ADS)

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.

Sabzikar, Farzad

381

Comparing Fractions with Lines  

NSDL National Science Digital Library

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.

Rand, Richard E.

2007-12-12

382

Fraction Comparison Sped up  

NSDL National Science Digital Library

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."

Interactive Math Miscellany And Puzzles, Alexander B.

2011-01-01

383

Intermetallic compounds containing lanthanides (studies of magnetic anisotropy)  

Microsoft Academic Search

The powerful permanent magnetism of certain rare earth intermetallics (e.g., SmCo5) is a consequence of the strong magnetic anisotropy in these materials. Both sublattices contribute to magnetic anisotropy. Usually the contribution of the rare earth predominates over that of its chemical partner, a d-transition element in systems of practical interest. The rare earth anisotropy has been treated by quantum mechanics

W. E. Wallace

1977-01-01

384

Magnetic anisotropy in geometrically frustrated kagome staircase lattices  

Microsoft Academic Search

This paper reviews experimental results concerning magnetic anisotropy in geometrically frustrated kagome staircase lattices. Following problems are discussed: high-temperature susceptibility measurements of kagome single crystals; inelastic neutron scattering measurements on Co3V2O8 single crystals; EPR of Co2+ ions in kagome staircase Mg3V2O8 single crystals. The single-ion anisotropy Hamiltonian is used to analyze experimental results. It is suggested that the magnetic anisotropy

R. Szymczak; P. Aleshkevych; C. P. Adams; S. N. Barilo; A. J. Berlinsky; J. P. Clancy; V. Domuchowski; J. Fink-Finowicki; B. D. Gaulin; M. Ramazanoglu; S. V. Shiryaev; Z. Yamani; H. Szymczak

2009-01-01

385

CMB statistical anisotropy from noncommutative gravitational waves  

NASA Astrophysics Data System (ADS)

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.

Shiraishi, Maresuke; Mota, David F.; Ricciardone, Angelo; Arroja, Frederico

2014-07-01

386

Diffusion Anisotropy in Collagen Gels and Tumors: The Effect of Fiber Network Orientation  

PubMed Central

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

Stylianopoulos, Triantafyllos; Diop-Frimpong, Benjamin; Munn, Lance L.; Jain, Rakesh K.

2010-01-01

387

Magnetic Edge Anisotropy in Graphenelike Honeycomb Crystals  

NASA Astrophysics Data System (ADS)

The independent predictions of edge ferromagnetism and the quantum spin Hall phase in graphene have inspired the quest of other two-dimensional honeycomb systems, such as silicene, germanene, stanene, iridates, and organometallic lattices, as well as artificial superlattices, all of them with electronic properties analogous to those of graphene, but a larger spin-orbit coupling. Here, we study the interplay of ferromagnetic order and spin-orbit interactions at the zigzag edges of these graphenelike systems. We find an in-plane magnetic anisotropy that opens a gap in the otherwise conducting edge channels that should result in large changes of electronic properties upon rotation of the magnetization.

Lado, J. L.; Fernández-Rossier, J.

2014-07-01

388

Seismic anisotropy above a subducting plate  

SciTech Connect

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.

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

389

Universal anisotropy in force networks under shear  

NASA Astrophysics Data System (ADS)

Scaling properties of patterns formed by large contact forces are studied as a function of the applied shear stress, in two-dimensional static packings generated from the force network ensemble. An anisotropic finite-size-scaling analysis shows that the applied shear does not affect the universal scaling properties of these patterns, but simply induces different length scales in the principal directions of the macroscopic stress tensor. The ratio of these length scales quantifies the anisotropy of the force networks, and is found not to depend on the details of the underlying contact network, in contrast with other properties such as the yield stress.

Ostojic, Srdjan; Vlugt, Thijs J. H.; Nienhuis, Bernard

2007-03-01

390

Knitted patterns as a model for anisotropy  

NASA Astrophysics Data System (ADS)

Anisotropy is a difficult concept, although it is often met in everyday life. This paper describes a simple model—knitted patterns—having anisotropic elastic properties. The elastic constant is measured for the force applied in different directions with respect to the knitting direction. It is also shown that the deformation of the knitted pattern does not always have the same direction as the applied force, a behaviour that is also typical for anisotropic systems. The dependence of the elastic coefficient on the direction of applied force has the same form as the refraction coefficient of an extraordinary ray in a uniaxial anisotropic crystal.

?epi?, Mojca

2012-07-01

391

Anisotropy modeling of polarization dependent terahertz metamaterials  

NASA Astrophysics Data System (ADS)

In this study, we propose a novel anisotropy modeling of the polarization dependent meta-atoms at terahertz frequencies. The proposed anisotropic metamaterials are composed of metallic microstructures combined with various numbers of Hshaped meta-atoms. We confirm that the proposed metamaterials successfully realize the unique properties that can modulate the resonance frequency for the specific polarization of an incident wave, while can keep one identical resonance frequency for its orthogonal polarization direction, simultaneously. Moreover, regardless of the number of Hshaped meta-atoms, their bandwidth can be kept identical by coupling effects between adjacent meta-atoms and their excited electric dipole moments.

Jung, Hyunseung; Lee, Hojin

2014-09-01

392

Microscopic origin of the reduced magnetocrystalline anisotropy with increasing oxide content in Co80Pt20?:?oxide thin films  

NASA Astrophysics Data System (ADS)

Angle-dependent x-ray magnetic circular dichroism at the Co L2.3 edges has been utilized to systematically study Co80Pt20?:?WO3 perpendicular magnetic recording thin films, in which the magnetocrystalline anisotropy significantly drops as the oxide volume fraction increases. The microscopic origin of this phenomenon in the studied films can be mainly attributed to an increase in orbital moment normal to the grain-oxide interface, with increasing oxide volume fraction, which arises from a more pronounced effect of symmetry breaking at the grain-oxide interface in smaller grains.

Zhang, Wen; Morton, Simon A.; Wong, P. K. Johnny; Lu, Bin; Xu, Yongbing; de Jong, Michel P.; van der Wiel, Wilfred G.; van der Laan, Gerrit

2013-10-01

393

Middle-energy electron anisotropies in the auroral region  

NASA Astrophysics Data System (ADS)

. Field-aligned anisotropic electron distribution functions of T_perp$ -> type are observed on auroral field lines at both low and high altitudes. We show that typically the anisotropy is limited to a certain range of energies, often below 1keV, although sometimes extending to slightly higher energies as well. Almost always there is simultaneously an isotropic electron distribution at higher energies. Often the anisotropies are up/down symmetrical, although cases with net upward or downward electron flow also occur. For a statistical analysis of the anisotropies we divide the energy range into low (below 100eV), middle (100eV-1keV) and high (above 1keV) energies and develop a measure of anisotropy expressed in density units. The statistical magnetic local time and invariant latitude distribution of the middle-energy anisotropies obeys that of the average auroral oval, whereas the distributions of the low and high energy anisotropies are more irregular. This suggests that it is specifically the middle-energy anisotropies that have something to do with auroral processes. The anisotropy magnitude decreases monotonically with altitude, as one would expect, because electrons have high mobility along the magnetic field and thus, the anisotropy properties spread rapidly to different altitudes.

Janhunen, P.; Olsson, A.; Laakso, H.; Vaivads, A.

2004-01-01

394

Molecular anisotropy effects in carbon K-edge scattering: Depolarized diffuse scattering and optical anisotropy  

NASA Astrophysics Data System (ADS)

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.

Stone, Kevin H.; Kortright, Jeffrey B.

2014-09-01

395

Fractional Derivative Cosmology  

E-print Network

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.

Mark D. Roberts

2009-09-07

396

Kindergarten: Number & Operations: Fractions  

NSDL National Science Digital Library

This supplemental lessons and activities guide (PDF) includes three fraction lesson plans designed to teach kindergartners how to understand and represent one-half. Each lesson includes the necessary blackline masters, guide questions, and extension ideas.

2013-01-01

397

Fractional Vector Calculus  

Microsoft Academic Search

\\u000a The calculus of derivatives and integrals of non-integer order go back to Leibniz, Liouville, Grünwald, Letnikov and Riemann.\\u000a The fractional calculus has a long history from 1695, when the derivative of order ? = 0.5 was described by Leibniz (Oldham and Spanier, 1974; Samko et al., 1993; Ross, 1975). The history of fractional vector\\u000a calculus (FVC) is not so long.

Vasily E. Tarasov

398

Thinking Blocks Fractions  

NSDL National Science Digital Library

This iOS app gives students an opportunity to visually model and calculate six different types of fraction applications, all in the context of solving word problems. Types of problems include finding a fraction of a number, using a known part to find the whole or another part, and problems using the four operations. Teachers can track a student's progress throughout the problem sets. An online version of this application is cataloged separately as a related resource.

King, Colleen

2013-07-19

399

Comparing Fractions and Decimals  

NSDL National Science Digital Library

This lesson provides practice in converting common fractions (tenths, fifths and halves) to decimal equivalents and expressing decimals (tenths) as equivalent fractions in reduced form. It includes instructions and a link to an interactive Java applet. Students get feedback for each of the 18 examples in a round. A downloadable student worksheet with warm-up and follow-up exercises is included in Word and pdf formats.

2011-01-01

400

Estimating with Benchmark Fractions  

NSDL National Science Digital Library

Teachers can use this interactive tool to help students develop fraction sense. After a teacher places a fraction, decimal, or expression on the screen, students determine which given benchmark number it is closest to. An adjustable number line supports conceptual understanding. 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.

2011-01-01

401

Fraction Conversion II  

NSDL National Science Digital Library

This lesson is designed to develop students' abilities to convert between fractions, decimals, and percents. This lesson provides links to discussions, activities, and an online game related to fraction conversion 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.

2010-01-01

402

Investigating preferential flow processes in soils using anisotropy in electrical resistivity  

NASA Astrophysics Data System (ADS)

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.

Al-Hazaimay, S.; Huisman, J. A.; Zimmermann, E.; Kemna, A.; Vereecken, H.

2012-12-01

403

Analytic spectra of CMB anisotropies and polarization generated by scalar perturbations in synchronous gauge  

NASA Astrophysics Data System (ADS)

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.

Cai, Z.; Zhang, Y.

2012-05-01

404

Texture and anisotropy analysis of a laminated lower crust: a neutron diffraction study of felsic granulites  

NASA Astrophysics Data System (ADS)

Quantitative fabric analyses of high-P and high-T tectonites were done with HIPPO, a Time-Of-Flight (TOF) neutron diffractometer at Los Alamos National Lab. Samples were collected in the Sobrado unit (NW Spain), a tectonic stack of highly deformed slices of metabasites, paragneisses and ultramafic rocks. Metamorphism ranges from granulites on top, to eclogites at the bottom of the unit. The ensemble represents and excellent example of laminated lower crust. The alternation of mechanically contrasted lithologies and/or the development of crystal preferred orientation might result into anisotropy. We explore the contribution of crystallographic preferred orientation or texture to the seismic anisotropy of the lower crust. Since strain partitioning occurred between mechanically strong and weak lithologies, a higher crystal preferred orientation is expected along the weak levels: the metasediments. TOF neutron diffraction experiments were conducted in HIPPO (LANSCE) with high-P and high-T mylonitic felsic paragneisses. Quantitative texture analysis of neutron data was accomplished by using the Rietveld method, with E-WIMW algorithm, implemented in the program package MAUD (Material Analysis Using Diffraction; Lutterotti, 1999). The orientation distribution function (ODF) for each mineral was calculated in MAUD and then processed in BEARTEX (Wenk et al. 1998). Selected pole figures were plotted for major components, quartz, plagioclase and biotite (first setting in monoclinic crystals). Texture patterns are compatible with non-coaxial progressive deformation and discussed accordingly in terms of dislocation activity. Besides, seismic waves velocities were computed from the texture data in BEARTEX. Calculated velocities and anisotropy were based on ODF, volume fraction of each mineral and their single-crystal elastic constant. Kinematic and mechanical implications are discussed in terms of the regional geology. The correlation of texture, mineral composition and seismic anisotropy in the model is also presented.

Benitez Perez, J.; Gomez Barreiro, J.; Martinez-Catalan, J. R.; Castiñeiras Garcia, P.; Vogel, S. C.; Wenk, H.; Alvarez Valero, A.

2013-12-01

405

THE NEAR-INFRARED BACKGROUND INTENSITY AND ANISOTROPIES DURING THE EPOCH OF REIONIZATION  

SciTech Connect

A fraction of the extragalactic near-infrared (near-IR) background light involves redshifted photons from the ultraviolet (UV) emission from galaxies present during reionization at redshifts above 6. The absolute intensity and the anisotropies of the near-IR background provide an observational probe of the first-light galaxies and their spatial distribution. We estimate the extragalactic background light intensity during reionization by accounting for the stellar and nebular emission from first-light galaxies. We require the UV photon density from these galaxies to generate a reionization history that is consistent with the optical depth to electron scattering from cosmic microwave background measurements. We also require the bright-end luminosity function (LF) of galaxies in our models to reproduce the measured Lyman-dropout LFs at redshifts of 6-8. The absolute intensity is about 0.1-0.4 nW m{sup -2} sr{sup -1} at the peak of its spectrum at {approx}1.1 {mu}m. We also discuss the anisotropy power spectrum of the near-IR background using a halo model to describe the galaxy distribution. We compare our predictions for the anisotropy power spectrum to existing measurements from deep near-IR imaging data from Spitzer/IRAC, Hubble/NICMOS, and AKARI. The predicted rms fluctuations at tens of arcminute angular scales are roughly an order of magnitude smaller than the existing measurements. While strong arguments have been made that the measured fluctuations do not have an origin involving faint low-redshift galaxies, we find that measurements in the literature are also incompatible with galaxies present during the era of reionization. The measured near-IR background anisotropies remain unexplained with an unknown origin.

Cooray, Asantha; Gong Yan; Smidt, Joseph [Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Santos, Mario G. [CENTRA, Instituto Superior Tecnico, Technical University of Lisbon, Lisboa 1049-001 (Portugal)

2012-09-01

406

Heterogeneity and Anisotropy of Earth's Inner Core  

NASA Astrophysics Data System (ADS)

Seismic observations provide strong evidence that Earth's inner core is anisotropic, with larger velocity in the polar than in the equatorial direction. The top 60-80 km of the inner core is isotropic; evidence for an innermost inner core is less compelling. The anisotropy is most likely due to alignment of hcp (hexagonal close-packed) iron crystals, aligned either during solidification or by deformation afterward. The existence of hemispherical variations used to be controversial, but there is now strong evidence from both seismic body wave and normal mode observations, showing stronger anisotropy, less attenuation, and a lower isotropic velocity in the western hemisphere. Two mechanisms have been proposed to explain the hemispherical pattern: either (a) inner core translation, wherein one hemisphere is melting and the other is solidifying, or (b) thermochemical convection in the outer core, leading to different solidification conditions at the inner core boundary. Neither is (yet) able to explain all seismically observed features, and a combination of different mechanisms is probably required.

Deuss, Arwen

2014-05-01

407

Results from the Wilkinson Microwave Anisotropy Probe  

NASA Astrophysics Data System (ADS)

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 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 (? CDM) 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, the flatness of the 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.

Komatsu, Eiichiro; Bennett, Charles L.; Barnes, C.; Bean, R.; Bennett, C. L.; Doré, O.; Dunkley, J.; Gold, B.; Greason, M. R.; Halpern, M.; Hill, R. S.; Hinshaw, G.; Jarosik, N.; Kogut, A.; Komatsu, E.; Larson, D.; Limon, M.; Meyer, S. S.; Nolta, M. R.; Odegard, N.; Page, L.; Peiris, H. V.; Smith, K. M.; Spergel, D. N.; Tucker, G. S.; Verde, L.; Weiland, J. L.; Wollack, E.; Wright, E. L.

2014-06-01

408

Calculation of Chemical Shift Anisotropy in Proteins  

PubMed Central

Individual peptide groups in proteins must exhibit some variation in the chemical shift anisotropy (CSA) of their constituent atoms, but not much is known about the extent or origins of this dispersion. Direct spectroscopic measurement of CSA remains technically challenging, and theoretical methods can help to overcome these limitations by estimating shielding tensors for arbitrary structures. Here we use an automated fragmentation quantum mechanics/molecular mechanics (AF-QM/MM) approach to compute 15N, 13C? and 1H chemical shift tensors for human ubiquitin and the GB1 and GB3 fragments of staphylococcal protein G. The average and range of variation of the anisotropies is in good agreement with experimental estimates from solid-state NMR, and the variation among residues is somewhat smaller than that estimated from solution-state measurements. Hydrogen-bond effects account for much of the variation, both between helix and sheet regions, and within elements of secondary structure, but other effects (including variations in torsion angles) may play a role as well. PMID:21866436

Tang, Sishi; Case, David A.

2011-01-01

409

Scattering polarization due to light source anisotropy  

E-print Network

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 distorted scattering envelopes leads to more complex polarimetric behavior such that the source characteristics should be carefully considered when interpreting polarimetric data.

R Ignace; M Al-Malki; J Simmons; J C Brown; D Clarke; J Carson

2008-12-15

410

Anisotropy of the Indian continental lithospheric mantle  

NASA Astrophysics Data System (ADS)

Due to the paucity of seismological data available in the public domain, the structure of the Indian lithosphere is still little known. We investigate the lithospheric structure and potential mechanical coupling between the crust and upper mantle along the Himalayan arc and underneath peninsular India using seismic anisotropy. Shear wave splitting measurements are performed on core-refracted phases. For each event recorded at a given seismological station we measured the orientation of the polarization plane of the fast S wave (phi), assumed to be a proxy for the orientation of the a axis of olivine, and the delay (dt) between the arrival time of the fast and slow S waves. We present a very comprehensive data set recorded at 86 seismological stations, deployed from the Himalayas to the southern tip of the Indian peninsula, in a joint effort by the National Geophysical Research Institute, Hyderabad, India, the University of Cambridge and the Indian Institute of Astrophysics. The unprecedented data set we present sheds light on the mechanisms involved in the India-Eurasia continental collision in a region along the Himalayan arc, south of the Indus-Tsangpo suture zone. At the scale of the Indian plate, the majority of the stations show a NNE-SSW orientation of phi over hundreds of kilometres, from Sri Lanka to the northern part of the Dharwar craton. This direction closely parallels the trend of the Indian plate motion, with respect to a fixed Eurasian plate, as defined through the NUVEL1A plate model. Along the Himalayan arc, from Ladakh in the northwest, to Bhutan and the Shillong plateau in the east, the orientation of phi rotates to become ~EW, perpendicular to the plate motion as defined through NUVEL1A. Unlike previous studies, we do find strong evidence for seismic anisotropy south of the Indus Tsangpo suture zone. A large number of null results have been computed, with consistent orientation of the two fast polarization directions (phi) across the subcontinent. We demonstrate the potential value of the too often neglected null measurements in the interpretation of seismic anisotropy. From these results, we infer the dominance, beneath the Indian lithosphere, of the asthenospheric flow in aligning minerals in the sheared lithosphere-asthenosphere boundary layer, masking any compression induced anisotropy expected to be normal to this direction. Closer to the collision front in northern India, the anisotropy may in part, be due to the foliation planes of the Himalayan fold and thrust belt aligning the a axis of olivine perpendicular to the compression axis, but more likely to the turning of the relative asthenospheric flow along the strike caused by the downthrusting Indian lithosphere acting as a barrier. The continent-wide consistency of results strengthens the understanding that the Indian lithosphere has distinct anisotropic signatures, contrary to the hitherto assumed isotropy and allows one to interpret the results in a coherent framework of Indo-Eurasian convergence.

Heintz, Maggy; Kumar, V. Pavan; Gaur, Vinod K.; Priestley, Keith; Rai, Shyam S.; Prakasam, K. Surya

2009-12-01

411

Low-temperature magnetic anisotropy in micas and chlorite  

NASA Astrophysics Data System (ADS)

Phyllosilicates, such as micas and chlorite, are common rock-forming minerals and often show preferred orientation in deformed rocks. In combination with single-crystal anisotropy, this leads to anisotropy of physical properties in the rock, such as magnetic susceptibility. In order to effectively use the magnetic anisotropy to understand a rock fabric, it is necessary to identify the minerals responsible for the magnetic anisotropy. Techniques have been developed to separate contributions of the ferrimagnetic, antiferromagnetic, paramagnetic, and diamagnetic susceptibilities to the anisotropy of magnetic susceptibility. Because diamagnetic and paramagnetic susceptibility are both linearly dependent on field, separation of the anisotropic contributions requires understanding how the degree of anisotropy of the paramagnetic susceptibility changes as a function of temperature. Note that diamagnetic susceptibility is not dependent on temperature. The increase in paramagnetic anisotropy at low temperature is used to separate the paramagnetic and diamagnetic subfabrics, and can be expressed by the p77 factor. In this study, we determined p77, which is the change in the degree of anisotropy (?k) between room temperature (298 K) and liquid nitrogen temperature (77 K), for a series of micas and chlorite. The paramagnetic susceptibility ellipsoid is highly oblate with the minimum principal susceptibility normal to the silicate layers at both 77 K and RT. The degree of anisotropy ?k increases by a factor of approximately 6.3-8.7 for individual samples of muscovite, phlogopite and chlorite on cooling from RT to 77 K and between 11.2 and 12.4 for biotite. A decrease in temperature enhances the paramagnetic anisotropy in a mineral. Biotite exhibits a relatively stronger enhancement due to the onset of magnetic ordering below ~ 100 K. This can have important implications for interpreting low temperature anisotropy in mudstones, mica schists and gneisses.

Biedermann, Andrea R.; Bender Koch, Christian; Lorenz, Wolfram E. A.; Hirt, Ann M.

2014-08-01

412

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

SciTech Connect

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.

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

2013-07-20

413

Fun with Fractions: Making and Investigating Fraction Strips  

NSDL National Science Digital Library

In this first of 5 lessons, "Students make and use a set of fraction strips to represent the length model, discover fraction relationships, and work with equivalent fractions." (from Illuminations from NCTM).

Math, Illuminations N.

2009-03-17

414

Goal Sketches in Fraction Learning  

ERIC Educational Resources Information Center

To examine how conceptual knowledge about fraction magnitudes changes as students' learning progresses, 5th and 7th-grade students were asked to solve fraction magnitude problems that entailed finding a fraction between two given fractions and then to evaluate solutions for similar problems that were modeled for them. When the given fractions

Sophian, Catherine; Madrid, Samara

2003-01-01

415

Grade One: Number & Operations: Fractions  

NSDL National Science Digital Library

This fraction supplement includes three activities in which students name and represent commonly used fractions, such as 1/2, 1/3, and 1/4. Through these activities students explore unit fractions and non-unit fractions of a whole as well as fractions of a set. Each activity includes instructions, guide questions, and extension suggestions.

2013-01-01

416

Self-referential and social cognition in a case of autism and agenesis of the corpus callosum  

PubMed Central

Background While models of autism spectrum conditions (ASC) are emerging at the genetic level of analysis, clear models at higher levels of analysis, such as neuroanatomy, are lacking. Here we examine agenesis of the corpus callosum (AgCC) as a model at the level of neuroanatomy that may be relevant for understanding self-referential and social-cognitive difficulties in ASC. Methods We examined performance on a wide array of tests in self-referential and social-cognitive domains in a patient with both AgCC and a diagnosis of ASC. Tests included a depth-of-processing memory paradigm with self-referential and social-cognitive manipulations, self-report measures of self-consciousness, alexithymia, and empathy, as well as performance measures of first-person pronoun usage and mentalizing ability. The performance of the AgCC patient was compared to a group of individuals with ASC but without AgCC and with neurotypical controls. These comparison groups come from a prior study where group differences were apparent across many measures. We used bootstrapping to assess whether the AgCC patient exhibited scores that were within or outside the 95% bias-corrected and accelerated bootstrap confidence intervals observed in both comparison groups. Results Within the depth-of-processing memory paradigm, the AgCC patient showed decreased memory sensitivity that was more extreme than both comparison groups across all conditions. The patient’s most pronounced difficulty on this task emerged in the social-cognitive domain related to information-processing about other people. The patient was similar to the ASC group in benefiting less from self-referential processing compared to the control group. Across a variety of other self-referential (i.e. alexithymia, private self-consciousness) and social-cognitive measures (i.e. self-reported imaginative and perspective-taking subscales of empathy, mentalizing), the AgCC patient also showed more extreme scores than those observed for both of the comparison groups. However, the AgCC patient scored within the range observed in the comparison groups on measures of first-person pronoun usage and self-reported affective empathy subscales. Conclusions We conclude that AgCC co-occurring with a diagnosis of ASC may be a relevant model at the level of neuroanatomy for understanding mechanisms involved in self-referential and high-level social-cognitive difficulties in ASC. PMID:23171505

2012-01-01

417

Local anisotropy and power spectra in magnetohydrodynamic turbulence  

NASA Astrophysics Data System (ADS)

Correlation and spectral anisotropy play important roles in solar wind and astrophysical plasmas, having significant impact on descriptions of the turbulence cascade, particle scattering, the nature of kinetic dissipation, and the transport of turbulence. Anisotropy emerges dynamically in MHD, producing stronger gradients across the large-scale mean magnetic field than along it, and occurring both globally and locally. Recently, properties of correlation anisotropy have been investigated through numerical simulations, showing the effect is intensified for more localized estimates of the mean magnetic field. The mathematical formulation of this property shows that local anisotropy mixes second-order with higher order correlations [1]. 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 study establishes that anisotropy of the local structure function is not a measure of anisotropy of the energy spectrum, but is rather related to higher order statistics. [1] Matthaeus et al, Astrophys. J., 750, 103 (2012)

Matthaeus, W. H.; Servidio, S.; Dmitruk, P.; Carbone, V.; Oughton, S.; Wan, M.; Osman, K. T.

2012-12-01

418

CMB anisotropy induced by tachyonic perturbations of dark energy  

Microsoft Academic Search

We consider the effects of possible tachyonic perturbations of dark energy on the CMB anisotropy. Such perturbations emerge, in particular, in models with phantom dark energy violating Lorentz invariance. Therefore, we discuss tachyonic perturbations with a Lorentz-violating dispersion relation. We show that the corresponding contribution to the CMB anisotropy can have an appreciable amplitude, while the angular spectrum has a

M. V. Libanov; V. A. Rubakov; O. S. Sazhina; M. V. Sazhin

2009-01-01

419

Peculiarities of acoustooptic interaction in media with strong acoustic anisotropy  

E-print Network

devices operation [1,2]. Media acoustic anisotropy also influences on the structure of acoustic beam [2Peculiarities of acoustooptic interaction in media with strong acoustic anisotropy S. N beam diffraction in the anisotropic media was obtained. This expression gives a possibility

Paris-Sud XI, Université de

420

Perpendicular magnetic recording with a composite anisotropy film  

Microsoft Academic Search

For a recently proposed perpendicular recording system, a composite anisotropy medium has been developed to improve the recording sensitivity of the perpendicular recording head. The medium is composed of a Fe-Ni soft magnetic film and a Co-Cr perpendicular anisotropy film, which are successively deposited on a base by an r. f. sputtering. By using the new double layer medium, an

S. Iwasaki; Y. Nakamura; K. Ouchi

1979-01-01

421

Cosmic Background Anisotropies in Cold Dark Matter Cosmology  

Microsoft Academic Search

Cosmic microwave background (CMB) anisotropies and density fluctuations are calculated for flat cold dark matter (CDM) models with a wide range of parameters, viz., Omega0, h, and OmegaB, for standard recombination and for various epochs of reionization. Tables of the power spectrum of CMB anisotropies in the form of C1 values as a function of l are presented. Although the

Naoshi Sugiyama

1995-01-01

422

SUBMITTED TO GRL 1 Thermal Anisotropies in the Solar Wind  

E-print Network

SUBMITTED TO GRL 1 E Thermal Anisotropies in the Solar Wind: vidence of Heating by Interstellar cyclotron instabilit s generated by newly created pickup ions and heats the thermal solar wind protons TO GRL 2 T Introduction he thermal anisotropy of the solar wind is the ratio between the temperatures p

Richardson, John

423

Magnetic anisotropy in Terfenol-D thin films (abstract)  

NASA Astrophysics Data System (ADS)

Thin-film Terfenol-D has attracted considerable attention for applications as microactuators and sensors. Depending on applications, the magnetic anisotropy plays a key role in physical property control. In this paper, the magnetic anisotropy of sputter-deposited Terfenol-D thin films on single-crystal Si substrates was studied by both dynamic torque and magnetization measurements. The evolution of magnetic anisotropy in the course of annealing treatment was followed by both types of experiments. It was found that there is a strong growth-induced anisotropy in the as-grown amorphous films, which is attributed to Fe-rare-earth bond orientation anisotropy. In samples treated at high temperatures, this growth-induced anistropy is overshadowed by the elastic anisotropy resulting from the substantial stresses in the films of giant magnetostrictive material. Domain patterns of different kinds of anisotropy were also monitored using a magnetic force microscope. The consequences of the growth-induced and elastomagnetic anisotropies to possible applications to microactuation are discussed.

Su, Q.; Teter, J. P.; Wen, Y.; Cullen, J. R.; Wuttig, M.

1997-04-01

424

Magnetic anisotropy of CuMn spin glasses  

NASA Astrophysics Data System (ADS)

Hysteresis and ac-susceptibility measurements of various remanent states of CuMn have been performed to further elucidate the problem of magnetic anisotropy energy below Tf. Our experimental data are well described by a phenomenological model based on the existence of two different spin systems. We conclude that the anisotropy energy of CuMn is a field-dependent quantity.

Felten, G.; Schwink, Ch.

1986-02-01

425

Anisotropy tensor of the potential model of steady creep  

NASA Astrophysics Data System (ADS)

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.

Annin, B. D.; Ostrosablin, N. I.

2014-01-01

426

OBSERVATIONAL SCAN-INDUCED ARTIFICIAL COSMIC MICROWAVE BACKGROUND ANISOTROPY  

SciTech Connect

Reliably detecting the cosmic microwave background (CMB) anisotropy is of great importance in understanding the birth and evolution of the universe. One of the difficulties in CMB experiments is the domination of measured CMB anisotropy maps by the Doppler dipole moment from the motion of the antenna relative to the CMB. For each measured temperature, the expected dipole component has to be calculated separately and then subtracted from the data. A small error in dipole direction, antenna pointing direction, sidelobe pickup contamination, and/or timing synchronism can introduce a significant deviation in the dipole-cleaned CMB temperature. After a full-sky observational scan, the accumulated deviations will be structured with a pattern closely correlated with the observation pattern with artificial anisotropies, including artificial quadrupole, octupole, etc., on large scales in the final CMB map. Such scan-induced anisotropies on large scales can be predicted by the true dipole moment and observational scan scheme. Indeed, the expected scan-induced quadrupole pattern of the Wilkinson Microwave Anisotropy Probe (WMAP) mission is perfectly in agreement with the published WMAP quadrupole. With the scan strategy of the Planck mission, we predict that scan-induced anisotropies will also produce an artificially aligned quadrupole. The scan-induced anisotropy is a common problem for all sweep missions and, like the foreground emissions, has to be removed from observed maps. Without doing so, CMB maps from COBE, WMAP, and Planck are not reliable for studying the CMB anisotropy.

Liu Hao; Li Tipei, E-mail: liuhao@ihep.ac.cn, E-mail: litp@tsinghua.edu.cn [Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing (China)

2011-05-10

427

Giant Magnetic Anisotropy of Single Cobalt Atoms and  

E-print Network

Giant Magnetic Anisotropy of Single Cobalt Atoms and Nanoparticles P. Gambardella,1,2 * S. Rusponi. Dederichs,5 K. Kern,1,2 C. Carbone,3,5 H. Brune1 The isotropic magnetic moment of a free atom is shown to develop giant magnetic anisotropy energy due to symmetry reduction at an atomically ordered surface

Brune, Harald

428

Anisotropy Creases Delineate White Matter Structure in Diffusion Tensor MRI  

E-print Network

Anisotropy Creases Delineate White Matter Structure in Diffusion Tensor MRI Gordon Kindlmann1, University of Utah, USA Abstract. Current methods for extracting models of white matter architecture from for extracting a skeleton of white matter pathways, in that ridges of anisotropy coincide with interiors of fiber

Utah, University of

429

Piezoelectric properties of domain engineered barium titanate single crystals with different volume fractions of domain walls  

PubMed Central

A piezoelectric domain wall model has been developed to analyze the effective piezoelectric properties of domain engineered BaTiO3 (BT) single crystals with different volume fractions of 90° domain walls. The model takes into account the nonuniform deformation in the domain wall region, which can create additional anisotropy to enhanced functional properties of multidomain single crystals. Our theoretical results indicate that a larger volume fraction of domain walls will produce larger effective piezoelectric coefficients. In addition, with the increase in domain wall volume fraction, [011]c poled BT single crystals will have a much larger piezoelectric property enhancement than [111]c poled BT single crystals. PMID:19865498

Xiang, Yang; Zhang, Rui; Cao, Wenwu

2009-01-01

430

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

PubMed

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

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

2013-01-01

431

Reading performance correlates with white-matter properties in preterm and term children  

PubMed Central

Aim We used diffusion tensor imaging to investigate the association between white-matter integrity and reading ability in a cohort of 28 children. Nineteen preterm children (14 males, five females; mean age 11y 11mo [SD 1y 10mo], mean gestational age 30.5wks (SD 3.2), mean birthweight was 1455g [SD 625]); and nine term children (five males, four females; mean age 12y 8mo [SD 2y 5mo], mean gestational age 39.6 weeks (SD 1.2), and mean birthweight 3877g [SD 473]). Method We tested whether fractional anisotropy in a left hemisphere temporoparietal region and in the corpus callosum correlates with birthweight and scores on the following three subtests of the Woodcock-Johnson III Tests of Achievement: word identification, word attack, and passage comprehension. Results Preterm children had lower reading scores than a comparison group for all reading subtests (p<0.05). We found significant correlations between birthweight and fractional anisotropy in the whole corpus callosum (p=0.001), and between fractional anisotropy and reading skill in the genu (p=0.001) and body (p=0.001) of the corpus callosum. The correlation between reading skill and fractional anisotropy in a left temporoparietal region previously associated with reading disability was not significant (p=0.095). Interpretation We conclude that perinatal white-matter injury of the central corpus callosum may have long-term developmental implications for reading performance. PMID:19747208

Andrews, James S; Ben-Shachar, Michal; Yeatman, Jason D; Flom, Lynda L; Luna, Beatriz; Feldman, Heidi M

2010-01-01

432

Shear Wave Velocity (Vs) Anisotropy of Kaolinite and Fly Ash Kaolinite Mixtures Modified with Controlled Organics.  

National Technical Information Service (NTIS)

Anisotropy is an inherent property of soils. The anisotropy could either be induced by applied stress or inherent from particle eccentricity and preferential deposition. Other than stress and deposition, the anisotropy was also found resulted from the phy...

B. Bate, X. Kang

2014-01-01

433

Anisotropy of the electrical conductivity and mechanical properties of extruded aluminum alloys  

Microsoft Academic Search

1.Recrystallized extruded rods and strips of aluminum alloys with a fibrous structure and texture show anisotropy of the electrical conductivity.2.A correlation was found between the anisotropy of the electrical conductivity and the anisotropy of the ultimate strength.

N. M. Naumov; P. G. Miklyaev; I. I. Novikov

1972-01-01

434

Subduction zone anisotropy beneath Corvallis, Oregon: A serpentinite skid mark of trench-parallel  

E-print Network

Subduction zone anisotropy beneath Corvallis, Oregon: A serpentinite skid mark of trench: Rheology--crust and lithosphere; KEYWORDS: anisotropy, Cascadia, subduction Citation: Park, J., H. Yuan, and V. Levin (2004), Subduction zone anisotropy beneath Corvallis, Oregon: A serpentinite skid mark