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1

Reduced fractional anisotropy in the anterior corpus callosum is associated with reduced speech fluency in persistent developmental stuttering.  

PubMed

Developmental stuttering is a speech disorder that severely limits one's ability to communicate. White matter anomalies were reported in stuttering, but their functional significance is unclear. We analyzed the relation between white matter properties and speech fluency in adults who stutter (AWS). We used diffusion tensor imaging with tract-based spatial statistics, and examined group differences as well as correlations with behavioral fluency measures. We detected a region in the anterior corpus callosum with significantly lower fractional anisotropy in AWS relative to controls. Within the AWS group, reduced anisotropy in that region is associated with reduced fluency. A statistically significant interaction was found between group and age in two additional regions: the left Rolandic operculum and the left posterior corpus callosum. Our findings suggest that anterior callosal anomaly in stuttering may represent a maladaptive reduction in interhemispheric inhibition, possibly leading to a disadvantageous recruitment of right frontal cortex in speech production. PMID:25728013

Civier, Oren; Kronfeld-Duenias, Vered; Amir, Ofer; Ezrati-Vinacour, Ruth; Ben-Shachar, Michal

2015-04-01

2

Corpus callosum size and diffusion tensor anisotropy in adolescents and adults with schizophrenia.  

PubMed

The corpus callosum has been implicated as a region of dysfunctional connectivity in schizophrenia, but the association between age and callosal pathology is unclear. Magnetic resonance imaging (MRI) and diffusion-tensor imaging (DTI) were performed on adults (n=34) and adolescents (n=17) with schizophrenia and adult (n=33) and adolescent (n=15) age- and sex-matched healthy controls. The corpus callosum was manually traced on each participant?s MRI, and the DTI scan was co-registered to the MRI. The corpus callosum was divided into five anteroposterior segments. Area and anisotropy were calculated for each segment. Both patient groups demonstrated reduced callosal anisotropy; however, the adolescents exhibited reductions mostly in anterior regions while the reductions were more prominent in posterior regions of the adults. The adolescent patients showed greater decreases in absolute area as compared with the adult patients, particularly in the anterior segments. However, the adults showed greater reductions when area was considered relative to whole brain white matter volume. Our results suggest that the initial stages of the illness are characterized by deficiencies in frontal connections, and the chronic phase is characterized by deficits in the posterior corpus callosum; or, alternatively, adolescent-onset schizophrenia may represent a different or more severe form of the illness. PMID:25637358

Balevich, Emily C; Haznedar, M Mehmet; Wang, Eugene; Newmark, Randall E; Bloom, Rachel; Schneiderman, Jason S; Aronowitz, Jonathan; Tang, Cheuk Y; Chu, King-Wai; Byne, William; Buchsbaum, Monte S; Hazlett, Erin A

2015-03-30

3

Voxel-Based Analysis of Fractional Anisotropy in Post-Stroke Apathy  

PubMed Central

Objective To explore the structural basis of post-stroke apathy by using voxel-based analysis (VBA) of fractional anisotropy (FA) maps. Methods We enrolled 54 consecutive patients with ischemic stroke during convalescence, and divided them into apathy (n?=?31) and non-apathy (n?=?23) groups. We obtained magnetic resonance images of their brains, including T1, T2 and DTI sequences. Age, sex, education level, Hamilton Depression Scale (HAMD) scores, Mini-Mental State Examination (MMSE) scores, National Institutes of Health Stroke Scale (NIHSS) scores, and infarct locations for the two groups were compared. Finally, to investigate the structural basis of post-stroke apathy, VBA of FA maps was performed in which we included the variables that a univariate analysis determined had P-values less than 0.20 as covariates. Results HAMD (P?=?0.01) and MMSE (P<0.01) scores differed significantly between the apathy and non-apathy groups. After controlling for age, education level, HAMD scores, and MMSE scores, significant FA reduction was detected in four clusters with peak voxels at the genu of the corpus callosum (X?=??16, Y?=?30, Z?=?8), left anterior corona radiata (?22, 30, 10), splenium of the corpus callosum (?24, ?56, 18), and right inferior frontal gyrus white matter (52, 24, 18), after family-wise error correction for multiple comparisons. Conclusions Post-stroke apathy is related to depression and cognitive decline. Damage to the genu of the corpus callosum, left anterior corona radiata, splenium of the corpus callosum, and white matter in the right inferior frontal gyrus may lead to apathy after ischemic stroke. PMID:25555189

Yang, Song-ran; Shang, Xin-yuan; Tao, Jun; Liu, Jian-yang; Hua, Ping

2015-01-01

4

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

5

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

6

Fractional anisotropy helps predicts memory rehabilitation outcome after traumatic brain injury.  

PubMed

Traumatic brain injury (TBI) commonly results in residual memory difficulties. Such deficits are amenable to cognitive rehabilitation, but optimal selection of rehabilitation interventions remains a challenge. We hypothesized that diffusion tensor imaging (DTI) could be used to predict which individuals were likely to benefit from a specific memory rehabilitation intervention. Thirty-seven individuals with TBI, of all severities, first underwent DTI scanning, along with 18 matched controls. Participants with TBI then attended a 12-session memory intervention emphasizing internal memory strategies (I-MEMS). Primary outcome measures (HVLT, RBMT) were collected at the time of DTI scanning, and both immediately and one month post-therapy. In contrast to typical neuroimaging analysis, fractional anisotropy (FA) was used to predict long-term outcome scores, adjusting for typical predictors (injury severity, age, education, time since injury, pretest score). FA of the parahippocampal white matter was a significant negative predictor of HVLT, while the anterior corpus callosum, left anterior internal capsule, and right anterior corona radiata were negative predictors of RBMT outcome. The importance of these predictors rivaled those of pretest scores. Thus, FA measures may provide substantial predictive value for other cognitive interventions as well. The reason why higher FA was associated with less successful response to cognitive intervention remains unclear and will require further study. PMID:23093456

Strangman, Gary E; O'Neil-Pirozzi, Therese M; Supelana, Christina; Goldstein, Richard; Katz, Douglas I; Glenn, Mel B

2012-01-01

7

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

PubMed Central

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

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

2013-01-01

8

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

PubMed

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

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

2013-01-01

9

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

PubMed Central

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 shape was analyzed. Fractional anisotropy, mean, axial and radial diffusivity measures were obtained from within the corpus callosum, with additional probabilistic tractography analysis. Very preterm infants had significantly reduced callosal cross sectional area compared with term infants (p=0.004), particularly for the mid-body and posterior sub-regions. Very preterm callosi were more circular (p=0.01). Fractional anisotropy was lower (p=0.007) and mean (p=0.006) and radial (p=0.001) diffusivity values were higher in very preterm infants’ callosi, particularly at the anterior and posterior ends. The volume of tracts originating from the corpus callosum was reduced in very preterm infants (p=0.001), particularly for anterior mid-body (p=0.01) and isthmus tracts (p=0.04). This study characterizes callosal size, shape and diffusion in typically developing infants at term equivalent age, and reports macro- and micro-structural abnormalities as a result of prematurity. PMID:21168519

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

2011-01-01

10

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

SciTech Connect

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

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

2009-07-01

11

White matter fractional anisotropy is related to processing speed in metabolic syndrome patients: a case-control study  

PubMed Central

Background Metabolic Syndrome (MetSd) is a cluster of vascular risk factors that may influence cerebrovascular pathology during aging. Recently, microstructural white matter (WM) changes detected by diffusion tensor imaging (DTI) and processing speed deficits have been reported in MetSd patients. We aimed to test the relationship between WM alteration and cognitive impairment in these patients. Methods The sample comprised 38 subjects (19 patients aged between 50 and 80 years old, and 19 controls). All patients fulfilled National Cholesterol Education Program Adult Treatment Panel III (NCEP ATP-III) criteria for MetSd. Speed of information processing was measured by the Symbol Digit Modalities Test (SDMT) and reaction time (RT) on the Continuous Performance Test (CPT-II) and the Grooved Pegboard Test (GPT). DTI images were acquired in a 3 Tesla Siemens Trio scanner. Voxelwise statistical analysis of the fractional anisotropy (FA) data was performed using the Tract-Based Spatial Statistics part of the FMRIB Software Library. A correlation analysis was performed between processing speed variables and FA values. Results There was a larger proportion of slow subjects (percentile below 25th) in the patient group (Chi2 = 7.125 p = 0.008). FA values correlated positively with SDMT in anterior and posterior parts of the corpus callosum, and RT CPT-II correlated negatively with FA values in the anterior corpus callosum (p < 0.05 corrected) in the patient group. Conclusion We found significant correlations between WM alterations and cognitive impairment in MetSd patients, especially in the frontal lobe. These findings highlight the importance of MetSd prevention and control due to its association with structural and functional damage in the central nervous system. PMID:20663196

2010-01-01

12

Microscopic diffusion anisotropy in the human brain: Reproducibility, normal values, and comparison with the fractional anisotropy.  

PubMed

Human neuroimaging of tissue microstructure, such as axonal density and integrity, is key in clinical and neuroscience research. Most studies rely on diffusion tensor imaging (DTI) and the measures derived from it, most prominently fractional anisotropy (FA). However, FA also depends on fiber orientation distribution, a more macroscopic tissue property. Recently introduced measures of so-called microscopic diffusion anisotropy, diffusion anisotropy on a cellular or microscopic level, overcome this limitation because they are independent of the orientation distributions of axons and fibers. In this study, we evaluate the feasibility of two measures of microscopic diffusion anisotropy IMA and MA indices, for human neuroscience and clinical research. Both indices reflect the eccentricity of the cells but while IMA also depends on the cell size, MA is independent of the cell size and, like FA, scaled between 0 and 1. In whole-brain measurements of a group of 19 healthy volunteers, we measured average values and variability, evaluated their reproducibility, both within and between sessions, and compared MA to FA values in selected regions-of-interest (ROIs). The within- and between-session comparison did not show substantial differences but the reproducibility was much better for the MA than IMA (coefficient of variation between sessions 10.5% vs. 28.9%). The reproducibility was less for MA than FA overall, but comparable in the defined ROIs and the average group sizes required for between-group comparisons was similar (about 60 participants for a relative difference of 5%). Group-averaged values of MA index were generally larger and showed less variation across white-matter brain ROIs than FA (mean±standard deviation of seven ROIs 0.83±0.10 vs. 0.58±0.13). Even in some gray-matter ROIs, MA values comparable to those of white matter ROIs were observed. Furthermore, the within-group variation of the values in white matter ROIs was lower for the MA compared to the FA (mean standard deviation over volunteers 0.038 vs. 0.049) which could be due to significant variability in the distribution of fiber orientation contributing to FA. These results indicate that MA (i) should be preferred to IMA, (ii) has a reproducibility and group-size requirements comparable to those of FA; (iii) is less sensitive to the fiber orientation distribution than FA; and (iv) could be more sensitive to differences or changes of the tissue microstructure than FA. R1.1. PMID:25595503

Lawrenz, Marco; Brassen, Stefanie; Finsterbusch, Jürgen

2015-04-01

13

Gene Effects Mapped Using Fractional and Geodesic Anisotropy in Diffusion Tensor Images of 92  

E-print Network

, Fractional Anisotropy, Geodesic Anisotropy, Twins, quantitative genetics, path analysis. 1 Introduction influence brain structure. A structural MRI study of twins [2] found that genetic factors strongly influence Monozygotic and Dizygotic Twins Agatha D. Lee1 , Natasha Leporé1 , Marina Barysheva1 , Yiyu Chou1 , Caroline

Thompson, Paul

14

Maturation of Corpus Callosum Anterior Midbody Is Associated with Neonatal Motor Function in Eight Preterm-Born Infants  

PubMed Central

Background. The etiology of motor impairments in preterm infants is multifactorial and incompletely understood. Whether corpus callosum development is related to impaired motor function is unclear. Potential associations between motor-related measures and diffusion tensor imaging (DTI) of the corpus callosum in preterm infants were explored. Methods. Eight very preterm infants (gestational age of 28–32 weeks) underwent the Hammersmith neonatal neurological examination and DTI assessments at gestational age of 42 weeks. The total Hammersmith score and a motor-specific score (sum of Hammersmith motor subcategories) were calculated. Six corpus callosum regions of interest were defined on the mid-sagittal DTI slice—genu, rostral body, anterior midbody, posterior midbody, isthmus, and splenium. The fractional anisotropy (FA) and mean diffusivity (MD) of these regions were computed, and correlations between these and Hammersmith measures were sought. Results. Anterior midbody FA measures correlated positively with total Hammersmith (rho = 0.929, P = 0.001) and motor-specific scores (rho = 0.857, P = 0.007). Total Hammersmith scores also negatively correlated with anterior midbody MD measures (rho = ?0.714, P = 0.047). Discussion. These results suggest the integrity of corpus callosum axons, particularly anterior midbody axons, is important in mediating neurological functions. Greater callosal maturation was associated with greater motor function. Corpus callosum DTI may prove to be a valuable screening or prognostic marker. PMID:23509639

Mathew, Preethi; Pannek, Kerstin; D'Acunto, M. Giulia; Guzzetta, Andrea; Rose, Stephen E.; Colditz, Paul B.; Finnigan, Simon

2013-01-01

15

Corpus callosum morphology of  

E-print Network

Corpus callosum morphology of Williams syndrome: relation to genetics and behavior J Eric Schmitt development such as Williams syndrome (WS). Individuals with WS possess a remarkable array of neurobehavioral between genetics, neuroanatomy, and neurobehavior. Specifically, Williams syndrome (WS), a condition

16

Spatially fractional-order viscoelasticity, non-locality and a new kind of anisotropy  

E-print Network

Spatial non-locality of space-fractional viscoelastic equations of motion is studied. Relaxation effects are accounted for by replacing second-order time derivatives by lower-order fractional derivatives and their generalizations. It is shown that space-fractional equations of motion of an order strictly less than 2 allow for a new kind anisotropy, associated with angular dependence of non-local interactions between stress and strain at different material points. Constitutive equations of such viscoelastic media are determined. Explicit fundamental solutions of the Cauchy problem are constructed for some cases isotropic and anisotropic non-locality.

Andrzej Hanyga; Malgorzata Seredynska

2011-11-07

17

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

PubMed Central

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

Giordano, Chiara; Kleiven, Svein

2014-01-01

18

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

2014-01-01

19

Segmentation of the Canine Corpus Callosum using Diffusion Tensor Imaging Tractography  

PubMed Central

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

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

2014-01-01

20

Performance Asymmetries in Tool Use are Associated with Corpus Callosum Integrity in Chimpanzees (Pan troglodytes): A Diffusion Tensor Imaging Study  

PubMed Central

We examined the relationship of corpus callosum morphology and organization to hand preference and performance on a motor skill task in chimpanzees. Handedness was assessed using a complex tool use task that simulated termite fishing. Chimpanzees were initially allowed to perform the task wherein they could choose which hand to use (preference measure); then they were required to complete trials using each hand (performance measure). Two measures were used to assess the corpus callosum: midsagittal area obtained from in vivo magnetic resonance images and density of transcallosal connections as determined by fractional anisotropy values obtained from diffusion tensor imaging. We hypothesized that chimpanzees would perform better on their preferred hand compared to the non-preferred hand, and that strength of behavioral lateralization (rather the direction) on this task would be negatively correlated to regions of the corpus callosum involved in motor processing. Our results indicate that the preferred hand was the most adept hand. Performance asymmetries correlated with FA measures but not area measures of the CC. PMID:23398443

Phillips, Kimberley A.; Schaeffer, Jennifer; Barrett, Elizabeth; Hopkins, William D.

2014-01-01

21

Tractography of the Corpus Callosum in Huntington’s Disease  

PubMed Central

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

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

2013-01-01

22

Fractional Anisotropy of the Fornix and Hippocampal Atrophy in Alzheimer’s Disease  

PubMed Central

Decrease in the directionality of water diffusion measured with fractional anisotropy (FA) on diffusion tensor imaging has been linked to loss of myelin and axons in the white matter. Fornix FA is consistently decreased in patients with mild cognitive impairment (MCI) and Alzheimer’s disease (AD). Furthermore, decreased fornix FA is one of the earliest MRI abnormalities observed in cognitively normal individuals who are at an increased risk for AD, such as in pre-symptomatic carriers of familial AD mutations and in pre-clinical AD. Reductions of FA at these early stages, which predicted the decline in memory function. Fornix carries the efferent projections from the CA1 and CA3 pyramidal neurons of the hippocampus and subiculum, connecting these structures to the septal nuclei, anterior thalamic nucleus, mammillary bodies, and medial hypothalamus. Fornix also carries the afferent cholinergic and GABAergic projections from the medial septal nuclei and the adjacent diagonal band back to the medial temporal lobe, interconnecting the core limbic structures. Because fornix carries the axons projecting from the hippocampus, integrity of the fornix is in-part linked to the integrity of the hippocampus. In keeping with that, fornix FA is reduced in subjects with hippocampal atrophy, correlating with memory function. The literature on FA reductions in the fornix in the clinical spectrum of AD from pre-symptomatic carriers of familial AD mutations to pre-clinical AD, MCI, and dementia stages is reviewed. PMID:25431558

Kantarci, Kejal

2014-01-01

23

Higher diffusion in striatum and lower fractional anisotropy in white matter of methamphetamine users.  

PubMed

Methamphetamine (METH) users showed structural and chemical abnormalities on magnetic resonance (MRI) studies, particularly in the frontal and basal ganglia brain regions. Diffusion tensor imaging (DTI) may provide further insights regarding the microstructural changes in METH users. We investigated diffusion tensor measures in frontal white matter and basal ganglia of 30 adult METH users and 30 control subjects using a 3 T MR scanner. Compared with healthy control subjects, METH users showed lower fractional anisotropy (FA) in right frontal white matter, and higher apparent diffusion coefficient (ADC) in left caudate and bilateral putamen. Higher left putamen ADC was associated with earlier initiation of METH use, greater daily amounts, and a higher cumulative lifetime dose. Similarly, higher right putamen ADC was associated with greater daily amounts and a higher cumulative lifetime dose. The lower FA in the right frontal white matter suggests axonal injury in these METH users. The higher ADC in the basal ganglia suggests greater inflammation or less myelination in these brain regions of those with younger age of first METH use and greater METH usage. PMID:19782540

Alicata, Daniel; Chang, Linda; Cloak, Christine; Abe, Kylie; Ernst, Thomas

2009-10-30

24

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

25

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

26

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

PubMed Central

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

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

2011-01-01

27

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

PubMed Central

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

2014-01-01

28

Diffusion properties of NAA in human corpus callosum as studied with diffusion tensor spectroscopy.  

PubMed

In diffusion tensor imaging (DTI) the anisotropic movement of water is exploited to characterize microstructure. One confounding issue of DTI is the presence of intra- and extracellular components contributing to the measured diffusivity. This causes an ambiguity in determining the underlying cause of diffusion properties, particularly the fractional anisotropy (FA). In this study an intracellular constituent, N-acetyl aspartate (NAA), was used to probe intracellular diffusion, while water molecules were used to probe the combined intra- and extracellular diffusion. NAA and water diffusion measurements were made in anterior and medial corpus callosum (CC) regions, which are referred to as R1 and R2, respectively. FA(NAA) was found to be greater than FA(Water) in both CC regions, thus indicating a higher degree of anisotropy within the intracellular space in comparison to the combined intra- and extracellular spaces. A decreasing trend in the FA of NAA and water was observed between R1 and R2, while the radial diffusivity (RD) for both molecules increased. The increase in RD(NAA) is particularly significant, thus explaining the more significant decrease in FA(NAA) between the two regions. It is suggested that diffusion tensor spectroscopy of NAA can potentially be used to further characterize microscopic anatomic organization in white matter. PMID:17969098

Upadhyay, Jaymin; Hallock, Kevin; Erb, Kelley; Kim, Dae-Shik; Ronen, Itamar

2007-11-01

29

Microstructural White Matter Changes in the Corpus Callosum of Young People with Bipolar Disorder: A Diffusion Tensor Imaging Study  

PubMed Central

To date, most studies of white matter changes in Bipolar Disorder (BD) have been conducted in older subjects and with well-established disorders. Studies of young people who are closer to their illness onset may help to identify core neurobiological characteristics and separate these from consequences of repeated illness episodes or prolonged treatment. Diffusion tensor imaging (DTI) was used to examine white matter microstructural changes in 58 young patients with BD (mean age 23 years; range 16–30 years) and 40 controls. Whole brain voxelwise measures of fractional anisotropy (FA), parallel diffusivity (?//) and radial diffusivity (??) were calculated for all subjects. White matter microstructure differences (decreased FA corrected p<.05) were found between the patients with BD and controls in the genu, body and splenium of the corpus callosum as well as the superior and anterior corona radiata. In addition, significantly increased radial diffusivity (p<.01) was found in the BD group. Neuroimaging studies of young patients with BD may help to clarify neurodevelopmental aspects of the illness and for identifying biomarkers of disease onset and progression. Our findings provide evidence of microstructural white matter changes early in the course of illness within the corpus callosum and the nature of these changes suggest they are associated with abnormalities in the myelination of axons. PMID:23527101

Lagopoulos, Jim; Hermens, Daniel F.; Hatton, Sean N.; Tobias-Webb, Juliette; Griffiths, Kristi; Naismith, Sharon L.; Scott, Elizabeth M.; Hickie, Ian B.

2013-01-01

30

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

31

Fractions!  

NSDL National Science Digital Library

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

Miss Lerdahl

2011-02-01

32

Abnormal corpus callosum integrity in bipolar disorder: a diffusion tensor imaging study  

PubMed Central

Objective Abnormalities in the anterior interhemispheric connections provided by the corpus callosum (CC) have long been implicated in bipolar disorder (BD). In this study, we used complementary diffusion tensor imaging (DTI) methods to study the structural integrity of the CC and localization of potential abnormalities in BD. Methods Subjects included 33 participants with BD and 40 healthy comparison participants. Fractional anisotropy (FA) measures were compared between groups using region of interest (ROI) methods to investigate the anterior, middle and posterior CC and voxel-based methods to further localize abnormalities. Results In ROI-based analyses, FA was significantly decreased in the anterior and middle CC in the BD group (P<0.05). Voxel-based analyses similarly localized group differences to the genu, rostral body and anterior midbody of CC (P<0.05, corrected). Conclusion The findings demonstrate abnormalities in the structural integrity of the anterior CC in BD which may contribute to altered inter-hemispheric connectivity in this disorder. PMID:18620337

Wang, Fei; Kalmar, Jessica H.; Edmiston, Erin; Chepenik, Lara G.; Bhagwagar, Zubin; Spencer, Linda; Pittman, Brian; Jackowski, Marcel; Papademetris, Xenophon; Constable, R. Todd; Blumberg, Hilary P.

2008-01-01

33

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

PubMed Central

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

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

2015-01-01

34

Heritability of fractional anisotropy in human white matter: A comparison of Human Connectome Project and ENIGMA-DTI data.  

PubMed

The degree to which genetic factors influence brain connectivity is beginning to be understood. Large-scale efforts are underway to map the profile of genetic effects in various brain regions. The NIH-funded Human Connectome Project (HCP) is providing data valuable for analyzing the degree of genetic influence underlying brain connectivity revealed by state-of-the-art neuroimaging methods. We calculated the heritability of the fractional anisotropy (FA) measure derived from diffusion tensor imaging (DTI) reconstruction in 481 HCP subjects (194/287 M/F) consisting of 57/60 pairs of mono- and dizygotic twins, and 246 siblings. FA measurements were derived using (Enhancing NeuroImaging Genetics through Meta-Analysis) ENIGMA DTI protocols and heritability estimates were calculated using the SOLAR-Eclipse imaging genetic analysis package. We compared heritability estimates derived from HCP data to those publicly available through the ENIGMA-DTI consortium, which were pooled together from five-family based studies across the US, Europe, and Australia. FA measurements from the HCP cohort for eleven major white matter tracts were highly heritable (h(2)=0.53-0.90, p<10(-5)), and were significantly correlated with the joint-analytical estimates from the ENIGMA cohort on the tract and voxel-wise levels. The similarity in regional heritability suggests that the additive genetic contribution to white matter microstructure is consistent across populations and imaging acquisition parameters. It also suggests that the overarching genetic influence provides an opportunity to define a common genetic search space for future gene-discovery studies. Uniquely, the measurements of additive genetic contribution performed in this study can be repeated using online genetic analysis tools provided by the HCP ConnectomeDB web application. PMID:25747917

Kochunov, Peter; Jahanshad, Neda; Marcus, Daniel; Winkler, Anderson; Sprooten, Emma; Nichols, Thomas E; Wright, Susan N; Hong, L Elliot; Patel, Binish; Behrens, Timothy; Jbabdi, Saad; Andersson, Jesper; Lenglet, Christophe; Yacoub, Essa; Moeller, Steen; Auerbach, Eddie; Ugurbil, Kamil; Sotiropoulos, Stamatios N; Brouwer, Rachel M; Landman, Bennett; Lemaitre, Hervé; den Braber, Anouk; Zwiers, Marcel P; Ritchie, Stuart; van Hulzen, Kimm; Almasy, Laura; Curran, Joanne; deZubicaray, Greig I; Duggirala, Ravi; Fox, Peter; Martin, Nicholas G; McMahon, Katie L; Mitchell, Braxton; Olvera, Rene L; Peterson, Charles; Starr, John; Sussmann, Jessika; Wardlaw, Joanna; Wright, Margie; Boomsma, Dorret I; Kahn, Rene; de Geus, Eco J C; Williamson, Douglas E; Hariri, Ahmad; van 't Ent, Dennis; Bastin, Mark E; McIntosh, Andrew; Deary, Ian J; Hulshoff Pol, Hilleke E; Blangero, John; Thompson, Paul M; Glahn, David C; Van Essen, David C

2015-05-01

35

Fractions  

NSDL National Science Digital Library

Welcome to Fractions. This program uses three different Internet sites to learn fractions. On each site you will learn the basics of fractions and how to add, and multiply fractions. The three sites are Fractions, Mathsisfun.com and Who wants pizza?; a fun way to learn fractions. Even if you have never understood fractions before, you will understand them after visiting all three web sites. Two students will work together so that you can help eachother. Take turns using the keyboard so that each person gets a chance at the computer. . Let\\'s begin by going to the first site, \\"Fractions\\". Click on the line under \\"Beginning Fractions\\". Scroll down to the red border where it says \\"Fractions\\" and read the material about fractions. Click on \\"Start Fractions\\" and then click on the box that shows what fraction of the box is ...

Richard S. Melenson

2005-11-25

36

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

37

Corpus callosum: ovarian hormones and feminization.  

PubMed

The rat's corpus callosum is sexually dimorphic with the male's being larger. This difference appears to depend in part on the neonatal presence of testosterone in the male and ovarian hormones in the female. To further investigate the possibility that ovarian hormones participate in the differentiation of the rat's callosum, females received one of the following treatments on postnatal day 8, 12 or 16: (1) ovariectomy (Ovx); (2) 1 mg of testosterone propionate (TP); or (3) sham surgery. All animals were handled daily from birth until weaning. They were sacrificed at 110 days and a mid-sagittal section of the callosum was obtained. From this section measures of callosal area, perimeter, length, and 99 widths were derived. Widths were averaged into 7 factors as defined by prior factor analysis. Ovariectomy, whether on day 8, 12 or 16, enlarged callosal area and 3 of the callosal width factors. TP had no effect on any callosal variable when administered on day 8, 12 or 16. A comparison of control males and females replicated our prior findings of sexual dimorphism. We conclude that ovarian hormones act to feminize the female callosum, and that their removal results in defeminization. Furthermore, the fact that ovariectomy was effective as late as day 16, while TP treatment on day 8 or later had no effect, suggests that masculinization and feminization of this structure constitute separate processes with distinct sensitive periods. PMID:2029639

Fitch, R H; Cowell, P E; Schrott, L M; Denenberg, V H

1991-03-01

38

Hurtful Words: Exposure to Peer Verbal Aggression is Associated with Elevated Psychiatric Symptom Scores and Corpus Callosum Abnormalities  

PubMed Central

Objective Previous studies have shown that exposure to parental verbal abuse (VA) in childhood was associated with higher rates of adult psychopathology and alterations in brain structure. Here we examine the potential consequences of exposure to peer VA during childhood. Method A total of 848 young adults (ages 18 to 25 years) with no history of exposure to domestic violence, sexual abuse, or parental physical abuse rated their childhood exposure to parental and peer VA and completed a self-report packet that included the Kellner Symptom Questionnaire, the Limbic Symptom Checklist-33, and the Dissociative Experiences Scale. Diffusion tensor images were collected on a subset of 63 young adults with no history of abuse or exposure to parental VA selected for varying degrees of exposure to peer VA. Images were analyzed using tract based spatial statistics Results Analysis of covariance revealed ‘dose-dependent’ effects of peer VA on anxiety, depression, anger-hostility, dissociation, ‘limbic irritability’, and drug use. Peer and parental VA were essentially equivalent in effect size on these ratings. Path analysis indicated that peer VA during middle school years had the most significant effect on symptom scores. Degree of exposure to peer VA correlated with increased mean and radial diffusivity and decreased fractional anisotropy in corpus callosum and corona radiata. Conclusions These findings parallel previous reports of psychopathology associated with childhood exposure to parental VA, and support the hypothesis that exposure to peer VA is an aversive stimulus associated with increased symptom ratings and meaningful alterations in brain structure. PMID:20634370

Teicher, Martin H.; Samson, Jacqueline A.; Sheu, Yi-Shin; Polcari, Ann; McGreenery, Cynthia E.

2011-01-01

39

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

40

Infarction of the Corpus Callosum: A Retrospective Clinical Investigation  

PubMed Central

Objectives The aim of this study was to investigate patients with ischemic infarctions in the territory of the corpus callosum to advance our understanding of this rare stroke subtype by providing comprehensive descriptive and epidemiological data. Methods From January 1, 2010 to June 30, 2014, all cases of acute ischemic stroke diagnosed by clinical manifestation and diffusion weighted imaging in Dalian Municipal Central Hospital were investigated. The patients presenting with corpus callosum infarctions were selected and further allocated into genu and/or body and splenium infarction groups. Proportion, lesion patterns, clinical features, risk factors and etiology of corpus callosum infarction were analyzed. Results Out of 1,629 cases, 59 patients (3.6%) with corpus callosum infarctions were identified by diffusion weighted imaging, including 7 patients who had ischemic lesions restricted to the corpus callosum territory. Thirty six patients had lesions in the splenium (61.0%). Corpus callosum infarction patients suffered from a broad spectrum of symptoms including weakness and/or numbness of the limbs, clumsy speech, and vertigo, which could not be explained by lesions in corpus callosum. A classical callosal disconnection syndrome was found in 2 out of all patients with corpus callosum infarctions. Statistical differences in the risk factor and infarct pattern between the genu and/or body group and splenium group were revealed. Conclusion Corpus callosum infarction and the callosal disconnection syndrome were generally rare. The most susceptible location of ischemic corpus callosum lesion was the splenium. Splenium infarctions were often associated with bilateral cerebral hemisphere involvement (46.2%). The genu and/or body infarctions were associated with atherosclerosis. The most common cause of corpus callosum infarction probably was embolism. PMID:25785450

Bai, Yu-meng; Qin, Hua-min; Wu, Xiao-mei; Zhang, Xiao; Jolkkonen, Jukka; Boltze, Johannes; Wang, Su-ping

2015-01-01

41

Corpus Callosum Morphology in Twin Pairs Discordant for Bipolar Disorder  

E-print Network

Corpus Callosum Morphology in Twin Pairs Discordant for Bipolar Disorder Submission No: 3973 callosal volume reduction in patients with bipolar disorder, but it is not yet known whether these deficits callosum (CC) thickness and curvature in a population-based sample of twin pairs discordant for bipolar

Thompson, Paul

42

Agenesis and lipoma of corpus callosum. Case report.  

PubMed

The agenesis and lipoma of the corpus callosum is a very rare association. We report the case of a 18-years old woman with rare epileptic seizures since the age of 6 years, normal neurological examination, as well as normal electroencephalogram. The brain computed tomography scanning and the magnetic resonance showed the lipoma and the agenesis of the corpus callosum. PMID:8585829

Silva, D F; Lima, M M; Oliveira, C O; Oliveira, W N; Anghinah, R; Lima, J G

1995-09-01

43

Fractions  

NSDL National Science Digital Library

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

K. Cowley

2011-05-09

44

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

45

P5A-5 Dependence of Both Slow and Fast Wave Mode Properties on Bone Volume Fraction and Structural Anisotropy in Human Trabecular Bone: A 3D Simulation Study  

Microsoft Academic Search

Quantitative ultrasonic techniques are clinically used to estimate bone mechanical properties. Two longitudinal wave modes may be observed in vitro in trabecular bone, but the observation of the two waves depends on bone volume fraction (BV\\/TV), structural anisotropy and on the direction of propagation relatively to the direction of main trabecular alignment (MTA). Both wave modes are predicted by the

Guillaume Haïat; Frédéric Padilla; Pascal Laugier

2007-01-01

46

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

PubMed Central

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.

2014-01-01

47

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

48

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

49

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

50

Shape modeling of the corpus callosum.  

PubMed

A novel approach for shape modeling of the corpus callosum (cc) is introduced where the contours of the cc are extracted by image/volume segmentation, and a Bezier curve is used to connect the vertices of the sampled contours, generating a parametric polynomial representation. These polynomials are shown to maintain the characteristics of the original cc, thus are suitable for classification of populations. The Bernstein polynomials are used in fitting the Bezier curves. The coefficients of the Bernstein polynomials are shown to capture the geometric features of the cc, and are able to describe deformations. We use these coefficients, in conjunction with the Fourier Descriptors and other features, to discriminate between autistic and normal brains. The approach is tested on T1-weighted MRI scans of 16 normal and 22 autistic subjects and shows its ability to provide perfect classification, suggesting that the approach is worth investigating on a larger population with the hope of providing early identification and intervention of autism using neuroimaging. PMID:21095752

Farag, Ahmed; Elhabian, Shireen; Abdelrahman, Mostafa; Graham, James; Farag, Aly; Chen, Dongqing; Casanova, Manuel F

2010-01-01

51

Morphometric changes of the corpus callosum in congenital blindness.  

PubMed

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

52

Automated measurement of the human corpus callosum using MRI  

PubMed Central

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

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

2012-01-01

53

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

54

Ovarian hormones can organize the rat corpus callosum in adulthood.  

PubMed

The rat corpus callosum (CC) is larger in males than females, and is responsive to hormone manipulations during development. Previous data suggest that CC sensitivity to testosterone ends by postnatal day 8 (P8). In contrast, responsivity to ovarian hormones extends as late as P25. The current series of experiments investigates whether ovarian hormone effects on the callosum are permanent and whether CC sensitivity to ovarian hormones extends beyond P25. We found that P70 ovariectomy (Ovx) did not affect callosal size, suggesting that ovarian hormone exposure sometime prior to P70 is sufficient to feminize the CC, and that once the callosum is feminized, the effects can not be reversed. We also found that P25 ovariectomy enlarged, or defeminized, adult female CC, whereas ovary transfer starting on P55 or P70 counteracted this enlarging effect, resulting in feminized adult CC. Thus, although a previously feminized callosum is not affected by P70 ovarian hormone removal, a not-yet feminized callosum can still be feminized after P70. These findings indicate that there is flexibility in the developmental window within which the female brain is responsive to the active feminization process initiated by ovarian hormones. PMID:10876029

Bimonte, H A; Mack, C M; Stavnezer, A J; Denenberg, V H

2000-06-30

55

Corpus Callosum Volume in Railroad Workers With Chronic Exposure to Solvents  

E-print Network

Corpus Callosum Volume in Railroad Workers With Chronic Exposure to Solvents Marc W. Haut, Ph railroad workers and 31 matched controls. Results: There was a decrease in the genu of the corpus callosum

56

The visual map in the corpus callosum of the cat.  

PubMed

The corpus callosum conveys all the fibers that connect areas 17 and 18 in the 2 cerebral hemispheres of the cat. The purpose of the present study was to ascertain the organization of the visual field map described by these fibers in the corpus callosum. This was achieved by injecting anterograde and retrograde pathway tracers at known locations in the callosally connected zones of areas 17 and 18. The positions of the injection sites were varied systematically to include all visual field elevations represented along the marginal and posterolateral gyri. Overall, the results show (1) that callosal fibers projecting between the 2 marginal gyri, where the lower visual fields are represented, pass through the body of the corpus callosum; (2) that fibers connecting the junction of the marginal and posterolateral gyri in the 2 hemispheres, where central fields are represented, pass through the dorsal splenium of the corpus callosum; and (3) that fibers passing between the ventral portions of the 2 posterolateral gyri, where upper fields are represented, pass through posterior and ventral splenium. In addition, the density of visual fibers in the splenium is greater than in the body of the corpus callosum. Within the overall pattern, a finer arrangement exists, and it was possible, by comparison with the cortical visual field maps, to describe a map of visual field elevations in the corpus callosum. In this map, the representations of the different visual field elevations are not a simple reflection of the map in the cortex. The map of the lower fields contained in the body is spread out, whereas the map of the central and upper fields in the splenium is highly compressed. The high degree with which observations can be reproduced in different cats indicates that the map is stereotyped from one animal to another. PMID:1822731

Payne, B R; Siwek, D F

1991-01-01

57

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

58

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

59

Disrupted developmental organization of the structural connectome in fetuses with corpus callosum agenesis.  

PubMed

Agenesis of the corpus callosum is a model disease for disrupted connectivity of the human brain, in which the pathological formation of interhemispheric fibers results in subtle to severe cognitive deficits. Postnatal studies suggest that the characteristic abnormal pathways in this pathology are compensatory structures that emerge via neural plasticity. We challenge this hypothesis and assume a globally different network organization of the structural interconnections already in the fetal acallosal brain. Twenty fetuses with isolated corpus callosum agenesis with or without associated malformations were enrolled and fiber connectivity among 90 brain regions was assessed using in utero diffusion tensor imaging and streamline tractography. Macroscopic scale connectomes were compared to 20 gestational age-matched normally developing fetuses with multiple granularity of network analysis. Gradually increasing connectivity strength and tract diffusion anisotropy during gestation were dominant in antero-posteriorly running paramedian and antero-laterally running aberrant pathways, and in short-range connections in the temporoparietal regions. In fetuses with associated abnormalities, more diffuse reduction of cortico-cortical and cortico-subcortical connectivity was observed than in cases with isolated callosal agenesis. The global organization of anatomical networks consisted of less segregated nodes in acallosal brains, and hubs of dense connectivity, such as the thalamus and cingulate cortex, showed reduced network centrality. Acallosal fetal brains show a globally altered connectivity network structure compared to normals. Besides the previously described Probst and sigmoid bundles, we revealed a prenatally differently organized macroconnectome, dominated by increased connectivity. These findings provide evidence that abnormal pathways are already present during at early stages of fetal brain development in the majority of cerebral white matter. PMID:25725467

Jakab, András; Kasprian, Gregor; Schwartz, Ernst; Gruber, Gerlinde Maria; Mitter, Christian; Prayer, Daniela; Schöpf, Veronika; Langs, Georg

2015-05-01

60

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

PubMed Central

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

Liang, Fanrong; Huang, Wenhua

2015-01-01

61

Autism traits in individuals with agenesis of the corpus callosum  

PubMed Central

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

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

62

Statistical shape analysis of the corpus callosum in Schizophrenia  

PubMed Central

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

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

2013-01-01

63

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

E-print Network

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

Paris-Sud XI, Université de

64

Alcohol consumption and premotor corpus callosum in older adults  

PubMed Central

Heavy alcohol consumption is toxic to the brain, especially to the frontal white matter (WM), but whether lesser amounts of alcohol negatively impact the brain WM is unclear. In this study, we examined the relationship between self-reported alcohol consumption and regional WM and grey matter (GM) volume in fifty-six men and thirtyseven women (70 +- 7 years) cognitively intact participants of the Baltimore Longitudinal Study of Aging (BLSA) with no history of alcohol abuse. We used regional analysis of volumes examined in normalized space (RAVENS) maps methodology for WM and GM segmentation and normalization followed by voxel based morphometry statistical parametric mapping (in SPM8) to examine the cross-sectional association between alcohol consumption and WM (and, separately, GM) volume controlling for age, sex, smoking, blood pressure and dietary thiamine intake. WM VBM revealed that in men, but not in women, higher alcohol consumption was associated with lower volume in premotor frontal corpus callosum. This finding suggests that even moderate amounts of alcohol may be detrimental to corpus callosum and white matter integrity. PMID:22401959

Kapogiannis, Dimitrios; Kisser, Jason; Davatzikos, Christos; Ferrucci, Luigi; Metter, Jeffrey; Resnick, Susan

2012-01-01

65

Corpus callosum morphology in capuchin monkeys is influenced by sex and handedness.  

PubMed

Sex differences have been reported in both overall corpus callosum area and its regional subdivisions in humans. Some have suggested this reflects a unique adaptation in humans, as similar sex differences in corpus callosum morphology have not been reported in any other species of primate examined to date. Furthermore, an association between various measurements of corpus callosum morphology and handedness has been found in humans and chimpanzees. In the current study, we report measurements of corpus callosum cross-sectional area from midsagittal MR images collected in vivo from 14 adult capuchin monkeys, 9 of which were also characterized for hand preference on a coordinated bimanual task. Adult females were found to have a significantly larger corpus callosum: brain volume ratio, rostral body, posterior midbody, isthmus, and splenium than adult males. Left-handed individuals had a larger relative overall corpus callosum area than did right-handed individuals. Additionally, a significant sex and handedness interaction was found for anterior midbody, with right-handed males having a significantly smaller area than right-handed females. These results suggest that sex and handedness influences on corpus callosum morphology are not restricted to Homo sapiens. PMID:17726522

Phillips, Kimberley A; Sherwood, Chet C; Lilak, Alayna L

2007-01-01

66

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

67

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

PubMed Central

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

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

2013-01-01

68

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

E-print Network

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

Hamarneh, Ghassan

69

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

PubMed Central

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

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

2013-01-01

70

Volume Fractions of Texture Components  

E-print Network

1 Volume Fractions of Texture Components A. D. Rollett 27-750 Texture, Microstructure & Anisotropy intensities in a discrete OD from counts of grains, points or volumes. · Define volume fraction to calculate volume fractions given a discrete orientation distribution. · Describe the calculation

Rollett, Anthony D.

71

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

SciTech Connect

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

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

2007-11-01

72

Ovarian estrogen acts to feminize the female rat's corpus callosum.  

PubMed

The rat corpus callosum (CC) is sexually dimorphic, with the male CC being larger. Ovariectomy (Ovx) on day 12 has been shown to eliminate this sex difference, with callosal values of Ovx females approaching those of male controls. This suggested that postnatal ovarian estrogen affects the size of the female CC. In the present experiment, one group of female rats received Ovx on day 12, and a second group received Ovx followed by chronic implantation of a silastic tube containing beta-estradiol on day 25. Unmanipulated males and sham females served as controls. Examination of the CC at 110 days confirmed our prior findings that males have larger callosa than females and that the Ovx group had increased CC's compared to sham controls. Our new finding was that estrogen treatment was capable of reversing the effects of Ovx. Ovx+estrogen-treated females had decreased CC size as compared to Ovx alone. Indeed, they also had smaller CC values than control females. These findings indicate that ovarian estrogen plays a role in determining CC morphology and that estrogen in the female acts to inhibit overall callosal growth as measured by changes in gross callosal size. PMID:8431995

Mack, C M; Fitch, R H; Cowell, P E; Schrott, L M; Denenberg, V H

1993-01-15

73

Detecting corpus callosum abnormalities in autism based on anatomical landmarks  

PubMed Central

Autism is a severe developmental disorder whose neurological basis is largely unknown. Autism is a subtype of autism that displays more homogeneous features within group. The aim of this study was to identify the shape differences of the corpus callosum between patients with autism and the controls. Anatomical landmarks were collected from mid-sagittal MRI of 25 patients and 18 controls. Euclidean distance matrix analysis and thin-plate spline were used to analyze the landmark forms. Point-by-point shape comparison was performed both globally and locally. A new local shape comparison scheme was proposed which compared each part of the shape in its local coordinate system. Point correspondence was established among individual shapes based on the inherent landmark correspondence. No significant difference was found in the landmark form between patients and controls, but the distance between interior genu and posterior most was found significantly shorter in patients. Thin-plate spline analysis showed significant group difference between the landmark configurations in terms of the deformation from the overall mean configuration. Significant global shape differences were found in the anterior lower body and posterior bottom, and local shape difference existed in the anterior bottom. This study can serve as both clinical reference and a detailed procedure guideline for similar studies in the future. PMID:20620032

He, Qing; Duan, Ye; Karsch, Kevin; Miles, Judith

2010-01-01

74

Social cognition in individuals with agenesis of the corpus callosum.  

PubMed

Past research has revealed that individuals with agenesis of the corpus callosum (ACC) have deficits in interhemispheric transfer, complex novel problem-solving, and the comprehension of paralinguistic aspects of language. Case studies and family reports also suggest problems in social cognition. The performance of 11 individuals with complete ACC and with normal intelligence was compared to that of 13 IQ- and age-matched controls on three measures of social cognition. Individuals with ACC were indistinguishable from controls on the Happe Theory of Mind Stories and the Adult Faux Pas Test, but performed significantly worse on various portions of the Thames Awareness of Social Inference Test (TASIT) involving interpretations of videotaped social vignettes. Further analysis of the TASIT indicated that individuals with ACC showed deficiency in the recognition of emotion, weakness in understanding paradoxical sarcasm, and particular difficulty interpreting textual versus visual social cues. These results suggest that the tendency for deficient social cognition in individuals with ACC stems from a combination of difficulty integrating information from multiple sources, using paralinguistic cues for emotion, and understanding nonliteral speech. Together, these deficits would contribute to a less robust theory of mind. PMID:20162492

Symington, Scott H; Paul, Lynn K; Symington, Melissa F; Ono, Makoto; Brown, Warren S

2010-01-01

75

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

PubMed Central

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

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

2013-01-01

76

The detection of a cosmic-ray electron-positron anisotropy is a sufficient (but not necessary) condition to discard a Dark Matter origin for the anomalous positron fraction  

E-print Network

I demonstrate that if an anisotropy in the arrival direction of high-energy cosmic-ray electrons and positrons is observed, then dark matter annihilation is ruled out as an explanation to the positron excess. For an observable anisotropy to originate from dark matter annihilation, the high-energy electrons and positrons must be produced in a nearby clump. I consider the annihilation pathway producing the smallest flux of gamma rays versus electrons and positrons, and the combination of clump distance and luminosity that minimizes the gamma-ray flux. I show that if an anisotropy from such a clump were detected, then the clump would be clearly detectable as an anomalous, bright gamma-ray source with the Fermi Large Area Telescope. I also point out that the non-detection of an anisotropy is perfectly compatible with an astrophysical origin for the excess positrons that has nothing to do with dark matter.

Profumo, Stefano

2014-01-01

77

PEDF is a novel oligodendrogenic morphogen acting on the adult SVZ and corpus callosum  

PubMed Central

Pigment epithelium-derived factor (PEDF) is a serpin protein with well-established neuroprotective and anti-angiogenic properties. Recent studies have also shown that PEDF enhances renewal of adult subventricular zone (SVZ) neural precursors. In neurosphere cultures prepared from the SVZ of adult mice, we found that addition of recombinant PEDF to the medium enhanced expressions of oligodendroglial lineage markers (NG2 and PDGFr?) and transcription factors (Olig1, Olig2 and Sox10). Similarly, continuous PEDF administration into the lateral ventricles of adult glial fibrillary acidic protein:green fluorescent protein (GFAP:GFP) transgenic mice increased the proportions of GFAP:GFP+ and GFAP:GFP- SVZ neural precursors co-expressing oligodendroglial lineage markers and transcription factors. Notably, PEDF infusion also resulted in an induction of doublecortin (DCX) and Sox10 double-positive cells in the adult SVZ. Immunoreactive PEDF receptor (PEDFr) was detectable in multiple cell types in both adult SVZ and corpus callosum. Furthermore, PEDF intracerebral infusion enhanced survival and maturation of newly born oligodendroglial progenitor cells (OPCs) in the normal corpus callosum, and accelerated oligodendroglial regeneration in lysolecithin-induced corpus callosum demyelinative lesions. Western blot analysis showed a robust upregulation of endogenous PEDF in the corpus callosum upon lysolecithin-induced demyelination. Our results document previously unrecognized oligodendrotrophic effects of recombinant PEDF on the adult SVZ and corpus callosum, demonstrate induction of endogenous CNS PEDF production following demyelination, and make PEDF a strong candidate for pharmacological intervention in demyelinative diseases. PMID:22933798

Sohn, Jiho; Selvaraj, Vimal; Wakayama, Kouji; Orosco, Lori; Lee, Eunyoung; Crawford, Susan E.; Guo, Fuzheng; Lang, Jordan; Horiuchi, Makoto; Zarbalis, Konstantinos; Itoh, Takayuki; Deng, Wenbin; Pleasure, David

2012-01-01

78

PEDF is a novel oligodendrogenic morphogen acting on the adult SVZ and corpus callosum.  

PubMed

Pigment epithelium-derived factor (PEDF) is a serine protease inhibitor (serpin) protein with well established neuroprotective and anti-angiogenic properties. Recent studies have also shown that PEDF enhances renewal of adult subventricular zone (SVZ) neural precursors. In neurosphere cultures prepared from the SVZ of adult mice, we found that addition of recombinant PEDF to the medium enhanced expressions of oligodendroglial lineage markers (NG2 and PDGFr?) and transcription factors (Olig1, Olig2, and Sox10). Similarly, continuous PEDF administration into the lateral ventricles of adult glial fibrillary acidic protein:green fluorescent protein (GFAP:GFP) transgenic mice increased the proportions of GFAP:GFP+ and GFAP:GFP- SVZ neural precursors coexpressing oligodendroglial lineage markers and transcription factors. Notably, PEDF infusion also resulted in an induction of doublecortin- and Sox10 double-positive cells in the adult SVZ. Immunoreactive PEDF receptor was detectable in multiple cell types in both adult SVZ and corpus callosum. Furthermore, PEDF intracerebral infusion enhanced survival and maturation of newly born oligodendroglial progenitor cells in the normal corpus callosum, and accelerated oligodendroglial regeneration in lysolecithin-induced corpus callosum demyelinative lesions. Western blot analysis showed a robust upregulation of endogenous PEDF in the corpus callosum upon lysolecithin-induced demyelination. Our results document previously unrecognized oligodendrotrophic effects of recombinant PEDF on the adult SVZ and corpus callosum, demonstrate induction of endogenous CNS PEDF production following demyelination, and make PEDF a strong candidate for pharmacological intervention in demyelinative diseases. PMID:22933798

Sohn, Jiho; Selvaraj, Vimal; Wakayama, Kouji; Orosco, Lori; Lee, Eunyoung; Crawford, Susan E; Guo, Fuzheng; Lang, Jordan; Horiuchi, Makoto; Zarbalis, Konstantinos; Itoh, Takayuki; Deng, Wenbin; Pleasure, David

2012-08-29

79

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

80

Fatigue and progression of corpus callosum atrophy in multiple sclerosis.  

PubMed

Fatigue is one of the most disabling symptoms in multiple sclerosis (MS) patients. There is no or only weak correlation between conventional magnetic resonance imaging (MRI) parameters and level of fatigue. The aim of this study was to investigate the relationship between progression of corpus callosum (CC) atrophy and fatigue in MS patients. This was a cohort study in 70 patients with relapsing form of MS (RRMS) and serial MRIs over a mean follow-up of 4.8 years [67% female, mean age 42 ± 11 years, mean disease duration 9.7 ± 7.6 years, mean Expanded Disability Status Scale (EDSS) 2.8 ± 1.6]. Fatigue was assessed by the Fatigue Severity Scale (FSS). CC size was measured with the CC index (CCI). In total, 40% of the patients suffered from fatigue (mean FSS score 5.3 ± 1.1) and 60% patients had no fatigue (mean FSS score of 2.1 ± 1). Patients with fatigue had higher EDSS scores (p = 0.01) and CC atrophy was more pronounced in patients with fatigue (-21.8 vs. -12.1%, p = 0.005). FSS correlated with CCI change over time (r = -0.33; p = 0.009) and EDSS (p = 0.008; r = 0.361). The association between annualized CCI change and FSS was independent from EDSS, disease duration, gender and age in a multivariate linear regression analysis (p < 0.001). Progression of CC atrophy may play a role in the evolution of MS-related fatigue. PMID:21594686

Yaldizli, Özgür; Glassl, Stephanie; Sturm, Dietrich; Papadopoulou, Athina; Gass, Achim; Tettenborn, Barbara; Putzki, Norman

2011-12-01

81

Quantitative analysis of the corpus callosum in children with cerebral palsy and developmental delay: correlation with cerebral white matter volume  

Microsoft Academic Search

Background: The direct quantitative correlation between thickness of the corpus callosum and volume of cerebral white matter in children with cerebral palsy and developmental delay has not been demonstrated. Objective: This study was conducted to quantitatively correlate the thickness of the corpus callosum with the volume of cerebral white matter in children with cerebral palsy and developmental delay. Material and

Ashok Panigrahy; Patrick D. Barnes; Robert L. Robertson; Lynn A. Sleeper; James W. Sayre

2005-01-01

82

Shape analysis of the corpus callosum in Alzheimer’s disease and frontotemporal lobar degeneration subtypes  

PubMed Central

Morphology of the corpus callosum is a useful biomarker of neuronal loss, as different patterns of cortical atrophy help to distinguish between dementias such as Alzheimer’s disease (AD) and frontotemporal lobar degeneration (FTLD). We used a sophisticated morphometric analysis of the corpus callosum in FTLD subtypes including frontotemporal dementia (FTD) semantic dementia (SD), and progressive non-fluent aphasia (PNFA), and compared them to AD patients and 27 matched controls. FTLD patient subgroups diverged in their callosal morphology profiles, with: FTD patients showing marked widespread differences, PNFA patients with differences largely in the anterior half of the callosum, and SD patients differences in a small segment of the genu. AD patients showed differences in predominantly posterior callosal regions. This study is consistent with our previous findings showing significant cortical and subcortical regional atrophy across FTLD subtypes, and suggests that callosal atrophy patterns differentiate AD from FTLD, and FTLD subtypes. PMID:24531157

Walterfang, Mark; Luders, Eileen; Looi, Jeffrey C.L.; Rajagopalan, Priya; Velakoulis, Dennis; Thompson, Paul M.; Lindberg, Olof; Östberg, Per; Nordin, Love E.; Svensson, Leif; Wahlund, Lars-Olof

2014-01-01

83

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.

2010-07-02

84

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

85

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

ERIC Educational Resources Information Center

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

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

2012-01-01

86

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

E-print Network

Distinct regional atrophy in the corpus callosum of patients with temporal lobe epilepsy Bernd that epilepsy is associated with a decreased thickness in posterior callosal regions. Patients with an early as on cortical structures and development (Hermann et al., 2003b; Bernasconi et al., 2004; Elger et al., 2004

Thompson, Paul

87

The indusium griseum and the longitudinal striae of the corpus callosum.  

PubMed

In the eighteenth century, Lancisi described the indusium griseum (IG) and the longitudinal striae (LS) of the corpus callosum. The IG is a thin neuronal lamina above the corpus callosum, covered on each side of the midline by the medial and lateral LS. The medial LS (nerves of Lancisi) and lateral LS are two pairs of myelinated fiber bands found in the gray matter of the IG on the dorsal aspect of the corpus callosum. Embryologically, the IG and LS are dorsal remnants of the archicortex of the hippocampus and fornix and thus they are considered components of the limbic system. Recent studies using immunohistochemistry reported that acetylcholine, dopamine, noradrenaline, 5-hydroxytryptamine and GABA neurons innervate the IG. Newer imaging techniques, such as high field MRI and diffusion tensor imaging, provide new tools for studying these structures, whose true function remains still unclear. The present paper reviews the history of the discovery of the IG and LS of the corpus callosum, with a holistic overview on these interesting structures from the anatomical, embryological, neurochemical, radiological and clinical perspective. PMID:25091482

Di Ieva, Antonio; Fathalla, Hussein; Cusimano, Michael D; Tschabitscher, Manfred

2015-01-01

88

Regional MRI measurements of the corpus callosum: a methodological and developmental study  

Microsoft Academic Search

A technique for quantifying the midsagittal size and shape of the corpus callosum (CC) from magnetic resonance brain scans is presented. The technique utilizes the distances to the ventral and dorsal boundaries of small sectors of the CC from a reference point to compute the size and shape parameters of the CC and its subdivisions. Intrarater and interrater interclass correlation

Jagath C. Rajapakse; Jay N. Giedd; Judith M. Rumsey; A. Catherine Vaituzis; Susan D. Hamburger; Judith L. Rapoport

1996-01-01

89

Psychosis in Apert's syndrome with partial agenesis of the corpus callosum.  

PubMed Central

A 19-year-old male with Apert's syndrome developed psychotic symptoms that responded to haloperidol. He was also found to have partial agenesis of the corpus callosum and enlarged lateral ventricles on a head CT scan. The implications of these findings in the context of psychotic symptoms are discussed. There are no previous reports of psychosis in patients with Apert's syndrome. PMID:7647085

Gupta, S; Popli, A

1995-01-01

90

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

91

Factors Shaping the Corpus Callosum MICHAEL P. STRYKER AND ANTONELLA ANTONINI  

E-print Network

in the TZ occupying contralateral eye ocular domi- nance columns, whereas those in immediately adjacent- verted by the lens of the eye and split into two halves, represented in the two hemispheres, such as orienta- tion and ocular dominance columns, it was not surprising that investigations of the callosum

Stryker, Michael

92

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

ERIC Educational Resources Information Center

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

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

2011-01-01

93

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

E-print Network

of the Corpus Callosum. The resulting segments are then processed further using a graph mining technique% in the case of the given application. 1 Introduction The application of established data mining techniques as some form of feature vector, to allow the application of a desired data mining technique. In this paper

Coenen, Frans

94

A magnetization transfer imaging study of corpus callosum myelination in young children with autism  

PubMed Central

Background Several lines of evidence suggest that autism may be associated with abnormalities in white matter development. However, inconsistencies remain in the literature regarding the nature and extent of these abnormalities, partly due to the limited types of measurements that have been used. Here, we used Magnetization Transfer Imaging (MTI) to provide insight into the myelination of the corpus callosum in children with autism. Methods MTI scans were obtained in 101 children with autism and 35 typically developing children who did not significantly differ with regard to gender or age. The midsagittal area of the corpus callosum was manually traced and the magnetization transfer ratio (MTR) was calculated for each voxel within the corpus callosum. Mean MTR and height and location of the MTR histogram peak were analyzed. Results Mean MTR and MTR histogram peak height and location were significantly higher in children with autism than typically developing children, suggesting abnormal myelination of the corpus callosum in autism. Conclusions The differences in callosal myelination suggested by these results may reflect an alteration in the normally well-regulated process of myelination of the brain, with broad implications for neuropathology, diagnosis, and treatment of autism. PMID:22386453

Gozzi, Marta; Nielson, Dylan M.; Lenroot, Rhoshel K.; Ostuni, John L.; Luckenbaugh, David A.; Thurm, Audrey E.; Giedd, Jay N.; Swedo, Susan E.

2012-01-01

95

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

96

Partial agenesis of the corpus callosum in spina bifida meningomyelocele and potential compensatory mechanisms  

Microsoft Academic Search

After a review of Arthur Benton's conceptual and methodological contributions to the understanding of normal and pathological development, we discuss agenesis of the corpus callosum (CC), criteria for potential neuroanatomical compensatory mechanisms in CC agenesis, and the results of an examination of magnetic resonance imaging (MRI) data of the CC in 193 children with spina bifida meningomyelocele (SBM). There were

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

2009-01-01

97

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

98

Agenesis of the corpus callosum and cerebral anomalies in inborn errors of metabolism.  

PubMed

Dysgenesis of the corpus callosum has been recognized as a marker for aberrant development of the central nervous system. It has been suggested that developmental defects of the corpus callosum may be more frequently encountered in patients with inborn errors of metabolism. The objectives of the present study were to determine the prevalence of developmental defects of the corpus callosum in patients attending a genetics-metabolic disorders clinic, to describe the spectrum of abnormalities in brain development in patients with confirmed inborn errors of metabolism and abnormalities of the corpus callosum as ascertained by neuroimaging and/or postmortem studies. Nineteen patients (10 males, 9 females) with confirmed metabolic diagnoses were identified by systematic search of the genetics clinic database. All 19 (100%) expressed variable degrees of hypoplasia, complete or partial agenesis (ACC). Abnormalities of head size were noted in 17/19 (89.5%). The majority 12/17 (70.5%) were associated with microcephaly, while macrocrania was noted in 5/17 (29.5%). Associated central nervous system (CNS) anomalies included abnormalities in ventricular morphology in 18/19 (94.7%), ventriculomegaly in 11/19 (63.1%), increased extraxial cerebrospinal fluid space in 11/19 (57.9%), changes in the gray matter (neuronal migration defects, porencephaly) in 9/19 (47.3%), white matter changes in 12/19 (63.1%) and abnormalities of the posterior fossa and hindbrain in 12/19 (63.1%). In patients with inborn errors of metabolism, dysgenesis of the corpus callosum serves as a marker for other developmental defects within the nervous system. We discuss here potential mechanisms by which metabolic defects affect diverse biochemical pathways, altering key neurobiological processes (e.g. defective cell membrane formation, cellular bioenergetics and cell-to-cell signaling), that eventually lead to structural abnormalities in the developing nervous system. PMID:17988254

Prasad, Asuri N; Bunzeluk, Kelly; Prasad, Chitra; Chodirker, Bernard N; Magnus, Kenneth G; Greenberg, Cheryl R

2007-12-01

99

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.

Ng Wei Chong

2012-11-24

100

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!! ...

Ms. Terch

2010-03-11

101

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

102

Developmental changes in the corpus callosum from infancy to early adulthood: a structural magnetic resonance imaging study.  

PubMed

Previous research has reported on the development trajectory of the corpus callosum morphology. However, there have been only a few studies that have included data on infants. The goal of the present study was to examine the morphology of the corpus callosum in healthy participants of both sexes, from infancy to early adulthood. We sought to characterize normal development of the corpus callosum and possible sex differences in development. We performed a morphometric magnetic resonance imaging (MRI) study of 114 healthy individuals, aged 1 month to 25 years old, measuring the size of the corpus callosum. The corpus callosum was segmented into seven subareas of the rostrum, genu, rostral body, anterior midbody, posterior midbody, isthmus and splenium. Locally weighted regression analysis (LOESS) indicated significant non-linear age-related changes regardless of sex, particularly during the first few years of life. After this increase, curve slopes gradually became flat during adolescence and adulthood in both sexes. Age of local maximum for each subarea of the corpus callosum differed across the sexes. Ratios of total corpus callosum and genu, posterior midbody, as well as splenium to the whole brain were significantly higher in females compared with males. The present results demonstrate that the developmental trajectory of the corpus callosum during early life in healthy individuals is non-linear and dynamic. This pattern resembles that found for the cerebral cortex, further suggesting that this period plays a very important role in neural and functional development. In addition, developmental trajectories and changes in growth do show some sex differences. PMID:25790124

Tanaka-Arakawa, Megumi M; Matsui, Mie; Tanaka, Chiaki; Uematsu, Akiko; Uda, Satoshi; Miura, Kayoko; Sakai, Tomoko; Noguchi, Kyo

2015-01-01

103

Developmental Changes in the Corpus Callosum from Infancy to Early Adulthood: A Structural Magnetic Resonance Imaging Study  

PubMed Central

Previous research has reported on the development trajectory of the corpus callosum morphology. However, there have been only a few studies that have included data on infants. The goal of the present study was to examine the morphology of the corpus callosum in healthy participants of both sexes, from infancy to early adulthood. We sought to characterize normal development of the corpus callosum and possible sex differences in development. We performed a morphometric magnetic resonance imaging (MRI) study of 114 healthy individuals, aged 1 month to 25 years old, measuring the size of the corpus callosum. The corpus callosum was segmented into seven subareas of the rostrum, genu, rostral body, anterior midbody, posterior midbody, isthmus and splenium. Locally weighted regression analysis (LOESS) indicated significant non-linear age-related changes regardless of sex, particularly during the first few years of life. After this increase, curve slopes gradually became flat during adolescence and adulthood in both sexes. Age of local maximum for each subarea of the corpus callosum differed across the sexes. Ratios of total corpus callosum and genu, posterior midbody, as well as splenium to the whole brain were significantly higher in females compared with males. The present results demonstrate that the developmental trajectory of the corpus callosum during early life in healthy individuals is non-linear and dynamic. This pattern resembles that found for the cerebral cortex, further suggesting that this period plays a very important role in neural and functional development. In addition, developmental trajectories and changes in growth do show some sex differences. PMID:25790124

Tanaka-Arakawa, Megumi M.; Matsui, Mie; Tanaka, Chiaki; Uematsu, Akiko; Uda, Satoshi; Miura, Kayoko; Sakai, Tomoko; Noguchi, Kyo

2015-01-01

104

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

105

Plastic Anisotropy: Relaxed Constraints,  

E-print Network

Objective Properties Vectorz. Taylor- factor Sngl.-slip RC model 1 Plastic Anisotropy Objective · The objective of this lecture is to complete the description of plastic anisotropy analysis of plastic deformation and texture development.! · Reid: Deformation Geometry for Materials

Rollett, Anthony D.

106

CORPUS CALLOSUM AND EXPERIMENTAL STROKE: STUDIES IN CALLOSOTOMIZED RATS AND ACALLOSAL MICE  

PubMed Central

Background and Purpose Interhemispheric inhibition via the corpus callosum has been proposed as an exacerbating factor in outcome from stroke. Methods We measured infarct volume and behavioral outcome following middle cerebral artery occlusion in callosotomized rats and acallosal mice. Results Neither callosotomy in rats nor callosal agenesis in mice improved infarct volume or behavioral outcome after middle cerebral artery occlusion. Conclusions These findings argue against a role for transcallosal projections in exacerbating focal cerebral ischemia. PMID:21737800

Jin, Kunlin; Xie, Lin; Sun, Fen; Mao, XiaoOu; Greenberg, David A.

2011-01-01

107

Agenesis of the corpus callosum and congenital lymphedema: A novel recognizable syndrome?  

PubMed

We present double first cousins, a girl and a boy, with the uncommon association of agenesis of the corpus callosum and congenital lymphedema. Other features shared by both include oligohydramnios, similar facial dysmorphism, sacral dimple, developmental delay, and sociable personality. While some of these findings overlap with FG syndrome and Hennekam syndrome, the findings in our patients are sufficiently different to exclude these diagnoses. We propose that this is a new syndrome with presumed autosomal recessive inheritance. PMID:20583147

O'Driscoll, Mary C; Jenny, Kim; Saitta, Sulagna; Dobyns, William B; Gripp, Karen W

2010-07-01

108

Mobility decline in the elderly relates to lesion accrual in the splenium of the corpus callosum  

Microsoft Academic Search

In a previous cross-sectional study on baseline data, we demonstrated that the volume of brain white matter hyperintensities\\u000a (WMH) in the splenium of corpus callosum (SCC) predicted the current mobility function of older persons. The primary aim of\\u000a this follow-up study was to determine the relation of WMH volume change in SCC (SCC-?WMH) with change in mobility measures.\\u000a A secondary

Nicola Moscufo; Leslie Wolfson; Dominik Meier; Maria Liguori; Peter G. Hildenbrand; Dorothy Wakefield; Julia A. Schmidt; Godfrey D. Pearlson; Charles R. G. Guttmann

109

Lipoma of corpus callosum associated with dysraphic lesions and trisomy 13  

SciTech Connect

We report on a further case of corpus callosal lipoma and frontal cranial defects. Most cases in the literature of corpus callosal lipoma in association with {open_quotes}dysraphic{close_quotes} lesions have been frontal in location. Malformation of the corpus callosum is said to be associated with 50% of these lipomas. Trisomy 13 was confirmed by the 13q14 cosmid probe on paraffin-embedded liver tissue. 19 refs., 5 figs.

Wainwright, H.; Bowen, R.; Radcliffe, M. [Univ. of Cape Town Medical School (South Africa)

1995-05-22

110

Posterior polymorphous corneal dystrophy 3 is associated with agenesis and hypoplasia of the corpus callosum.  

PubMed

Posterior polymorphous corneal dystrophy (PPCD) is a dominantly inherited disorder of the corneal endothelium that has been associated with mutations in the zinc-finger E-box binding homeobox 1 gene (ZEB1) gene in approximately one-third of affected families. While the corneal dystrophies have traditionally been considered isolated disorders of the corneal endothelium, we have recently identified two cases of maldevelopment of the corpus callosum in unrelated individuals with PPCD. The proband of the first family was diagnosed shortly after birth with agenesis of the corpus callosum and several other developmental abnormalities. Karyotype, FISH and whole genome copy number variant analyses were normal. She was subsequently diagnosed with PPCD, prompting screening of the ZEB1 gene, which identified a novel deletion (c.449delG; p.(Gly150Alafs*36)) present in the heterozygous state that was not identified in either unaffected parent. The proband of the second family was diagnosed several months after birth with thinning of the corpus callosum and PPCD. Whole genome copy number variant analysis revealed a 1.79 Mb duplication of 17q12 in the proband and her father and brother, neither of whom had PPCD. ZEB1 sequencing identified a novel deletion (c.1913-1914delCA; p.(Ser638Cysfs*5)) present in the heterozygous state, which was also identified in the proband's affected mother. Thus, we report the first two cases of the association of PPCD with a developmental abnormality of the brain, in this case maldevelopment of the corpus callosum. PMID:24780443

Jang, Michelle S; Roldan, Ashley N; Frausto, Ricardo F; Aldave, Anthony J

2014-07-01

111

Detecting functional magnetic resonance imaging activation in white matter: Interhemispheric transfer across the corpus callosum  

PubMed Central

Background It is generally believed that activation in functional magnetic resonance imaging (fMRI) is restricted to gray matter. Despite this, a number of studies have reported white matter activation, particularly when the corpus callosum is targeted using interhemispheric transfer tasks. These findings suggest that fMRI signals may not be neatly confined to gray matter tissue. In the current experiment, 4 T fMRI was employed to evaluate whether it is possible to detect white matter activation. We used an interhemispheric transfer task modelled after neurological studies of callosal disconnection. It was hypothesized that white matter activation could be detected using fMRI. Results Both group and individual data were considered. At liberal statistical thresholds (p < 0.005, uncorrected), group level activation was detected in the isthmus of the corpus callosum. This region connects the superior parietal cortices, which have been implicated previously in interhemispheric transfer. At the individual level, five of the 24 subjects (21%) had activation clusters that were located primarily within the corpus callosum. Consistent with the group results, the clusters of all five subjects were located in posterior callosal regions. The signal time courses for these clusters were comparable to those observed for task related gray matter activation. Conclusion The findings support the idea that, despite the inherent challenges, fMRI activation can be detected in the corpus callosum at the individual level. Future work is needed to determine whether the detection of this activation can be improved by utilizing higher spatial resolution, optimizing acquisition parameters, and analyzing the data with tissue specific models of the hemodynamic response. The ability to detect white matter fMRI activation expands the scope of basic and clinical brain mapping research, and provides a new approach for understanding brain connectivity. PMID:18789154

Mazerolle, Erin L; D'Arcy, Ryan CN; Beyea, Steven D

2008-01-01

112

Postnatal Lesion Evidence Against a Primary Role for the Corpus Callosum in Mouse Sociability  

PubMed Central

BTBR T+tf/J (BTBR) is an inbred strain of mice that displays prominent social deficits and repetitive behaviors analogous to the defining symptoms of autism, along with a complete congenital agenesis of corpus callosum. BTBR is genetically distant from the widely used C57BL/6J (B6) strain, which exhibits high levels of sociability, low repetitive behaviors, and an intact corpus callosum. Emerging evidence implicates compromised inter-hemispherical connectivity in some cases of autism. We investigated the hypothesis that the disconnection of corpus callosum (CC) fiber tracts contribute to behavioral traits in mice that are relevant to the behavioral symptoms of autism. Surgical lesion of the CC in B6 mice at postnatal day 7 had no effect on juvenile play and adult social approach, and did not elevate repetitive self-grooming. No correlations were detected between rostral-caudal extent of the CC lesion and behavioral scores. In addition, LP/J, the strain that is genetically closest to BTBR but has an intact CC, displayed juvenile play deficits and repetitive self-grooming similar to those seen in BTBR. These corroborative results offer evidence against the hypothesis that the corpus callosum disconnection is a primary cause of low sociability and high repetitive behaviors in inbred mice. Our findings indicate that genes mediating other aspects of neurodevelopment, including those whose mutations underlie more subtle disruptions in white matter pathways and connectivity, are more likely to contribute to the aberrant behavioral phenotypes in the BTBR mouse model of autism. PMID:19419429

Yang, Mu; Clarke, Andrew M.; Crawley, Jacqueline N.

2009-01-01

113

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

PubMed Central

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

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

2014-01-01

114

Functional topography of the corpus callosum investigated by DTI and fMRI  

PubMed Central

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

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

2014-01-01

115

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. PMID:25479858

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

2014-01-01

116

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 ...

Ms. Cate

2008-04-12

117

White Matter Loss in the Splenium of the Corpus callosum in a Case of Posterior Cortical Atrophy: A Diffusion Tensor Imaging Study  

Microsoft Academic Search

There have been several functional imaging studies using PET and SPECT to investigate posterior cortical atrophy (PCA). These studies have suggested dysfunction of corticocortical connections which is consistent with the occipitoparietal stream. However, there are no reports suggesting disturbance of the white matter that interconnects the temporal, parietal and occipital cortices. We measured fractional anisotropy (FA) in the genu and

Tomokatsu Yoshida; Kensuke Shiga; Kenji Yoshikawa; Kei Yamada; Masanori Nakagawa

2004-01-01

118

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

119

Fraction Fun  

NSDL National Science Digital Library

In this lesson you will learn about equivalent fractions, how to add fractions, and factoring Learn how to create equivalent fractions Equivalent Fractions In this game you will practice using smaller pieces or fractions to fill the larger circle Equivalent Fractions Practice adding fractions with unlike denominators. Adding Fractions Identify the Least Common Multiple and Greatest Common Factor LCM and GCF Plug in a number and find the Least Common Multiple or Greatest Common ...

Miss Evans

2007-10-03

120

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

121

Seismic Anisotropy Workshop  

NASA Astrophysics Data System (ADS)

P wave anisotropy, the direction dependence of P wave velocities, is widely recognized to exist in the crust and upper mantle. The anisotropic effects of layered media, of aligned crystals in ductile rock, and of aligned cracks in brittle rock have been observed or have been speculated to yield information on earth structure and geomechanical processes. Crustal and upper mantle P wave seismic anisotropy were the principal subject in 1982 at the First International Workshop on Seismic Anisotropy (IIWSA), at Suzdal, U.S.S.R. The workshop proceedings, with a comprehensive overview of seismic anisotropy, appeared in the January 1984 issue of the Geophysical Journal of the Royal Astronomical Society (GJRAS, vol. 76).

Leary, Peter

122

[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

123

Improper Fractions  

NSDL National Science Digital Library

Let's review improper fractions by playing some fun games! Ice Cream Fractions Shop! Improper Fractions Jeopardy! For this game, type in your name and select "one player game". Click on different number amounts to try many different improper fraction problems! Improper Fractions Jeopardy! Type in your name to begin the ice cream shop game. Convert the improper fractions given to proper fractions then deliver the proper amount of ice ...

Ms. Kellersberger

2011-12-12

124

Fraction Track  

NSDL National Science Digital Library

This interactive applet provides a visual model to help students compare fractions and understand equivalent fractions. The applet displays eight fraction tracks (unit number lines) divided into fractional increments from halves to twelfths. The user turns over cards displaying fractions and moves sliders on the tracks a distance equal to or less than the target fractions. The goal is to move all the sliders to the end of each fraction track in the least number of moves.

2009-01-01

125

Fraction Frenzy  

NSDL National Science Digital Library

Playing Fraction Frenzy will help you to learn about equivalent fractions. During the game, a group of fractions will be displayed on the screen. You will then match the equivalent fractions until all fractions have been matched. The game is over if you allow time to run out.

2010-01-01

126

Fraction Quiz  

NSDL National Science Digital Library

Test your fraction skills by answering questions. This quiz asks you to simplify fractions, convert fractions to decimals and percentages, and answer algebra questions involving fractions. Choose difficulty level, question types, and time. Fraction Quiz is one of the Interactivate assessment quizzes.

127

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

128

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

E-print Network

Depression in elderly persons subject to childhood maltreatment is not modulated by corpus callosum School of Psychology and Psychiatry, Melbourne, Australia g Centre for Mental Health Research, Australian.03.035 #12;Key Words: corpus callosum, hippocampus, depression, magnetic resonance imaging, child abuse

Boyer, Edmond

129

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.

Illuminations National Council of Teachers of Mathematics

2009-05-12

130

Fraction Pointer  

NSDL National Science Digital Library

Graphically determine the value of 2 given fractions represented as points on a number line then graphically find a fraction whose value is in between the value of the 2 given fractions and determine its value.

The Shodor Education Foundation, Inc.

2007-12-12

131

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.

132

Dandy-Walker syndrome and corpus callosum agenesis in 5p deletion.  

PubMed

5p deletion syndrome commonly known as cri du chat is well described in affected neonates with catlike cry and hypotonia. Karyotyping will usually show a deletion of the short arm of one chromosome 5 with variable breakpoints. Only a few cases have been reported prenatally, and the fetal form of the syndrome has not been clearly individualised. We report a new case of 5p deletion syndrome diagnosed prenatally in association with Dandy-Walker syndrome and agenesis of the corpus callosum. Other brain anomalies have been reported previously, but this unusual association suggests the use of a specific probe in the investigation of these malformations. PMID:15849798

Vialard, F; Robyr, R; Hillion, Y; Molina Gomes, D; Selva, J; Ville, Y

2005-04-01

133

Corpus callosum functioning in patients with normal pressure hydrocephalus before and after surgery  

Microsoft Academic Search

Objectives  Our aim was to evaluate corpus callosum functioning in a group of patients with normal pressure hydrocephalus (NPH) before\\u000a and after shunting.\\u000a \\u000a \\u000a \\u000a Methods  Left ear–extinction under a dichotic listening task was evaluated in twenty–three patients with NPH, 30 patients with Alzheimer's\\u000a disease and 30 aged controls.\\u000a \\u000a \\u000a \\u000a Results  Patients with NPH had higher levels of left ear extinction than the control and Alzheimer's

Maria Mataró; Maria Antonia Poca; M. Matarín; J. Sahuquillo; N. Sebastián; C. Junqué

2006-01-01

134

Severe psychiatric disturbance and abnormalities of the corpus callosum: review and case series.  

PubMed Central

The association between developmental defects of the corpus callosum and major psychiatric disturbance is discussed with a review of published cases. Seven new cases are presented, of which four had clear psychotic symptoms, two receiving a diagnosis of schizophrenia. Of the remainder, one had a developmental disorder affecting social interaction and speech which could be classed as Asperger's syndrome, one had a personality disorder with depressive and conversion symptoms, and the last was an adolescent boy with severe behavioural problems. The difficulties in determining the precise relevance of the callosal anomalies to these clinical manifestations are discussed especially since the prevalence of such anomalies in the population is uncertain. Images PMID:8429328

David, A S; Wacharasindhu, A; Lishman, W A

1993-01-01

135

International Workshop on Anisotropy  

NASA Astrophysics Data System (ADS)

The first International Workshop on Seismic Anisotropy was held in Suzdal, USSR, from the 11th to the 19th of May 1982. The meeting was sponsored by IASPEI, UNESCO, and the Academy of Sciences, USSR, and was organized largely by E. M. Chesnokov and V. A. Magnitsky. Forty-five scientists from Czechoslovakia (2), FRG (1), GDR (1), Japan (1), India (1), UK (4), USA (3), and USSR (32) discussed the theory, observation, and causes o f seismic anisotropy.The most important conclusion from a wide variety of observations was that seismic anisotropy can be demonstrated as a very common, if not ubiquitous, property of much of the crust and upper mantle of the earth and may be important in a wide range of investigations. The anisotropy may be caused by a number of phenomena, including oriented crystals (mechanisms reviewed by Christensen, USA, and Babuska, Czechoslovakia); lithological alignments, as in oil shales; fine layering (reviewed by Liakhovitsky, USSR); and the direct effects o f stress (Nikitin and Chesnokov, USSR); but the commonest cause of anisotropy in the upper crust is probably aligned cracks (Crampin, UK).

Crampin, S.

136

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

137

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

138

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

139

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

140

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

141

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.

J.C. Banfill

2007-12-12

142

Fraction Four  

NSDL National Science Digital Library

Students play a generalized version of connect four, gaining the chance to place a piece after simplifying fractions, converting fractions to decimals and percentages, and answering algebra questions involving fractions. Choose difficulty level, question types, and time. Fraction Four is one of the Interactivate assessment games.

143

Visual Fractions  

NSDL National Science Digital Library

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

144

Cosmic Microwave Background Anisotropies  

Microsoft Academic Search

Cosmic microwave background (CMB) temperature anisotropies have and will continue to revolutionize our understanding of cosmology. The recent discovery of the previously predicted acoustic peaks in the power spectrum has established a working cosmological model: a critical density universe consisting of mainly dark matter and dark energy, which formed its structure through gravitational instability from quantum fluctuations during an inflationary

Wayne Hu; Scott Dodelson

2002-01-01

145

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

146

Acoustical anisotropy of Cotton Valley shale  

SciTech Connect

The dynamic elastic stiffnesses of transversely isotropic Cotton Valley silty shale were computed from ultrasonic-frequency compressionaland shear-wave velocity measurements. The measurements were made in three oriented right cylinders of fully water-saturated shale. Confining pressure was varied to 1100 bars for a constant pore pressure of 50 bars. All velocities and corresponding elastic stiffnesses increased with differential pressure in a manner that suggested continuous closure of pores and cracks and increasing alignment of platy clay particles with pressure. In addition, elastic anisotropy was found to increase with stress level, evidently approaching the intrinsic anisotropy of the zero-porosity, statistically weighted, aggregated volume fraction of the dominant clay mineral. Expressions for the elastic stiffnesses were derived for the boundary-value problem of plane strain, the conditions for which are approximated by wave-propagation measurements using an ultrasonic-frequency, pulse-transmission technique.

Fosaya, C.A.

1982-09-01

147

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

148

Neurotransmitter receptors and voltage-dependent Ca2+ channels encoded by mRNA from the adult corpus callosum.  

PubMed Central

The presence of mRNAs encoding neurotransmitter receptors and voltage-gated channels in the adult human and bovine corpus callosum was investigated using Xenopus oocytes. Oocytes injected with mRNA extracted from the corpus callosum expressed functional receptors to glutamate, acetylcholine, and serotonin, and also voltage-operated Ca2+ channels, all with similar properties in the two species studied. Acetylcholine and serotonin elicited oscillatory Cl- currents due to activation of the inositol phosphate-Ca2+ receptor-channel coupling system. Glutamate and its analogs N-methyl-D-aspartate (NMDA), kainate, quisqualate, and alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) induced smooth currents. The non-NMDA responses showed a strong inward rectification at positive potentials and were potently blocked by 6,7-dinitroquinoxaline-2,3-dione, as observed for the AMPA/kainate glutamate receptors GLUR1 and GLUR3. Furthermore, in situ hybridization experiments showed that GLUR1 and GLUR3 mRNAs are present in corpus callosum cells that were labeled with antiserum to glial fibrillary acid protein and that, in primary cell cultures, had the morphology of type 2 astrocytes. These results indicate that glial cells in the adult corpus callosum possess mRNA encoding functional neurotransmitter receptors and Ca2+ channels. These molecules may provide a mechanism for glial-neuronal interactions. Images Fig. 1 Fig. 5 Fig. 6 Fig. 7 PMID:7682696

Matute, C; Miledi, R

1993-01-01

149

Corpus Callosum Morphology in Children and Adolescents With Attention Deficit Hyperactivity Disorder: A Meta-Analytic Review  

Microsoft Academic Search

Several studies have examined corpus callosum (CC) morphology in children and adolescents with attention deficit hyperactivity disorder (ADHD). A meta-analysis of atypical brain morphology in children and adolescents with ADHD by Valera, Faraone, Murray, and Seidman (2006) reported a reduction in the splenium of the CC in this group compared with healthy controls. This meta-analysis undertook a more detailed examination

A. D. Hutchinson; J. L. Mathias; M. T. Banich

2008-01-01

150

The subventricular zone continues to generate corpus callosum and rostral migratory stream astroglia in normal adult mice.  

PubMed

Astrocytes are the most abundant cells in the CNS, and have many essential functions, including maintenance of blood-brain barrier integrity, and CNS water, ion, and glutamate homeostasis. Mammalian astrogliogenesis has generally been considered to be completed soon after birth, and to be reactivated in later life only under pathological circumstances. Here, by using genetic fate-mapping, we demonstrate that new corpus callosum astrocytes are continuously generated from nestin(+) subventricular zone (SVZ) neural progenitor cells (NPCs) in normal adult mice. These nestin fate-mapped corpus callosum astrocytes are uniformly postmitotic, express glutamate receptors, and form aquaporin-4(+) perivascular endfeet. The entry of new astrocytes from the SVZ into the corpus callosum appears to be balanced by astroglial apoptosis, because overall numbers of corpus callosum astrocytes remain constant during normal adulthood. Nestin fate-mapped astrocytes also flow anteriorly from the SVZ in association with the rostral migratory stream, but do not penetrate into the deeper layers of the olfactory bulb. Production of new astrocytes from nestin(+) NPCs is absent in the normal adult cortex, striatum, and spinal cord. Our study is the first to demonstrate ongoing SVZ astrogliogenesis in the normal adult mammalian forebrain. PMID:25740506

Sohn, Jiho; Orosco, Lori; Guo, Fuzheng; Chung, Seung-Hyuk; Bannerman, Peter; Mills Ko, Emily; Zarbalis, Kostas; Deng, Wenbin; Pleasure, David

2015-03-01

151

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

E-print Network

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

Smith, Desmond J.

152

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; Pärtan, Gerald; Klaushofer, Klaus; Ganger, Rudolf; Grill, Franz

2014-01-01

153

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

Microsoft Academic Search

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

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

2007-01-01

154

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

155

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).

Illuminations National Council of Teachers of Mathematics

2009-07-23

156

Fractional Clothesline  

NSDL National Science Digital Library

This lesson fosters a student's conceptual fraction sense with proper fractions, improper fractions, and mixed numbers by placing thirty fraction cards in order between given whole numbers on a number line clothesline. Users will visually identify that all proper fractions are grouped between zero and one, and that improper fractions or mixed numbers are all grouped above one. Users also play an estimation game with groups using the same principle. Instructional plan, questions for the students, assessment options, extensions, and teacher reflections are given.

Corey Heitschmidt

2008-01-01

157

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

158

Fractions Jigsaw  

NSDL National Science Digital Library

This problem provides students an opportunity to find equivalent fractions and carry out some simple additions and subtractions of fractions in a context that may challenge and motivate students. Users need to download, print, and cut-out the fraction jigsaw. Then, they must arrange the square pieces right-side up so that the edges that touch contain equivalent fractions. The Teachers' Notes page offers rationale, suggestions for implementation, discussion questions, and ideas for extension and support.

159

Equivalent Fractions!  

NSDL National Science Digital Library

How good at determining equivalent fractions are you? Test your skills with these various fraction games to find out! You have recently been learning about fractions and their equivalency. Try this game to test your knowledge of Equivalent Fractions!! Be sure to notice the "hints" under some of the questions to help you get the correct answer. Good Luck! Continue to master your skills by playing the Dirt Bike Proportions! game. How quickly you ...

Ms. Pearce

2011-11-06

160

Comparing Fractions  

NSDL National Science Digital Library

This lesson is designed to give students practice in comparing fractions, determining whether one is greater or less than the other. The lesson provides links to discussions and activities related to fractions and fraction conversion as well as suggested ways to integrate them into the lesson.

2010-01-01

161

Comparing Fractions  

NSDL National Science Digital Library

After reviewing two algorithms for comparing fractions (equivalent fractions with common denominators; cross multiplication), this interactive quiz gives students practice with 20 examples. Students choose the math symbol that will make each fraction pair a true equation or inequality. If incorrect, the correct answer is shown.

2010-01-01

162

Algebraic Fractions  

NSDL National Science Digital Library

Do you need help understanding how to use fractions when the numerators and denominators contain algebraic expressions? This simulation will help you to see that an algebraic fraction is the same as an ordinary fraction but with letters on the top or on the bottom. Test your knowledge out by taking a short quiz at the end.

2006-01-01

163

Equivalent Fractions  

NSDL National Science Digital Library

This interactive Java applet presents an array of common fractions sometimes referred to as a wall. Fractions less than one with denominators from 2 through 16 are placed to scale horizontally. The learner then moves a mouse to highlight equivalent sets of fractions vertically. Links to related topics are included.

2012-01-01

164

Macroscopic model with anisotropy based on micro-macro informations  

E-print Network

volume (packing) fraction and stress, while the microstructure is not accessible and thus neglected. Here, volumetric and deviatoric stresses and strains are cross-coupled via a single anisotropy modulus, which is proportional to the product of deviatoric fabric and bulk modulus (i.e. the isotropic fabric). Interestingly

Luding, Stefan

165

A two-year longitudinal MRI study of the corpus callosum in autism.  

PubMed

A growing body of literature has identified size reductions of the corpus callosum (CC) in autism. However, to our knowledge, no published studies have reported on the growth of CC volumes in youth with autism. Volumes of the total CC and its sub-divisions were obtained from 23 male children with autism and 23 age- and gender-matched controls at baseline and 2-year follow-up. Persistent reductions in total CC volume were observed in participants with autism relative to controls. Only the rostral body subdivision showed a normalization of size over time. Persistent reductions are consistent with the diagnostic stability and life-long impairment observed in many individuals with autism. Multi-modal imaging studies are needed to identify specific fiber tracks contributing to CC reductions. PMID:22350341

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

2012-11-01

166

Quantitative morphology of the corpus callosum in obsessive-compulsive disorder.  

PubMed

Neuroimaging studies have implicated the corpus callosum (CC) in the pathophysiology of obsessive-compulsive disorder (OCD). Putative dysfunctions in prefrontal cortical regions suggest anomalies in anterior segments of the CC. However, recent studies have also implicated the middle and posterior CC. The present study soughts to examine the CC using parcellation scheme informed by diffusion tensor imaging. Anatomic brain magnetic resonance scans were obtained from 21 OCD subjects (mean age=26.9 ± 9.93) and 42 healthy age- and sex-matched controls (mean age=26.6 ± 9.46) between the ages of 14 and 49. Area and volume measures of five subregions of the CC were obtained via manual tracings. A multivariate analysis of variance (after correcting for multiple comparisons) identified smaller area and volume in the mid-anterior region of the CC in OCD patients relative to controls. These findings implicate medio-frontal regions of the cortex in the pathophysiology of OCD. PMID:23453697

Lopez, Katherine C; Lalonde, Francois; Mattai, Anand; Wade, Benjamin; Clasen, Liv; Rapoport, Judith; Giedd, Jay N

2013-04-30

167

Correlation between Corpus Callosum Sub-Segmental Area and Cognitive Processes in School-Age Children  

PubMed Central

We assessed the relationship between structural characteristics (area) and microstructure (apparent diffusion coefficient; ADC) of the corpus callosum (CC) in 57 healthy children aged 7.0 to 9.1 years, with diverse cognitive and academic abilities as well as executive functions evaluated with a neuropsychological battery for children. The CC was manually delineated and sub-segmented into six regions, and their ADC and area were measured. There were no significant differences between genders in the callosal region area or in ADC. The CC area and ADC, mainly of anterior regions, correlated with different cognitive abilities for each gender. Our results suggest that the relationship between cognitive abilities and CC characteristics is different between girls and boys and between the anterior and posterior regions of the CC. Furthermore, these findings strenghten the idea that regardless of the different interhemispheric connectivity schemes per gender, the results of cognitive tasks are very similar for girls and boys throughout childhood. PMID:25170897

Moreno, Martha Beatriz; Concha, Luis; González-Santos, Leopoldo; Ortiz, Juan Jose; Barrios, Fernando Alejandro

2014-01-01

168

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

PubMed Central

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

Dunham, Leslie; Cantalupo, Claudio; Taglialatela, Jared

2007-01-01

169

Anisotropy and superconductivity  

E-print Network

The mean field method is applied for analysis of valence electrons in metals. It is shown that at low temperatures electrons have two wave-vector distribution patterns. Isotropic distribution refers to the first pattern. Anisotropic distribution refers to another pattern, particularly to specific wave-vector values occurred nearby the Fermi sphere. It is shown that it is the anisotropy that makes the metal obtain its specific superconductor features.

Boris Bondarev

2013-02-12

170

The Fractionator  

NSDL National Science Digital Library

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

Jeff LeMieux

2007-12-12

171

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.

Lisa Fazio

2012-01-01

172

Fraction Splat  

NSDL National Science Digital Library

Looking for a fun way to learn about fractions? Playing this fraction game will help you to learn all about them. To play the game, you simply click on the target type of fraction while avoiding the others. The game includes three rounds and each round has a different target. The targets include: mixed numbers, fractions that are greater than or equal to one, and fractions that are less than one-half. Your goal is to complete each round in the shortest amount of time possible.

2010-01-01

173

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

174

Fraction Finder  

NSDL National Science Digital Library

In this activity, students highlight portions of two squares or circles so that the highlighted portions or the area are equal to two given fractions. Then the student must highlight another square or circle that is between the two given fractions. This activity allows students to practice comparing fractions with different denominators. 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

175

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.

2010-07-02

176

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

177

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

178

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

179

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

180

CMB spectrum: dipole anisotropy Dipole anisotropy in COBE data can  

E-print Network

CMB spectrum: dipole anisotropy Dipole anisotropy in COBE data can be explained as a Doppler effect ±- CMBLG vv rr #12;CMB spectrum: removing the galaxy WMAP: 23 to 90 GHz image of the CMB after dipole subtraction. The galaxy emission is dominated by dust #12;CMB spectrum: removing the galaxy Cosmic Background

Aretxaga, Itziar

181

Fraction Beach  

NSDL National Science Digital Library

In this interactive Flash game, students are challenged to identify a fraction from a picture of a group of objects or from a geometric diagram, or they are asked to create a diagram or picture given a common fraction. Motivation is provided by earning buckets of sand to built a sand castle.

2007-01-01

182

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?"

A. Blundred

2012-01-01

183

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.

2011-05-24

184

Gross Anatomy of the Corpus Callosum in Alzheimer’s Disease: Regions of Degeneration and Their Neuropsychological Correlates  

Microsoft Academic Search

Background\\/Aims: Differences in the gross shape of the corpus callosum (CC) and its subregional areas were investigated on brain MRI of patients with probable Alzheimer’s disease (AD) and age- and gender-matched healthy normal control subjects. The AD patients differed from the normal control subjects in terms of a more convex shape and a reduced area of the CC. Methods: As

F. Tomaiuolo; M. Scapin; M. Di Paola; P. Le Nezet; L. Fadda; M. Musicco; C. Caltagirone; D. L. Collins

2007-01-01

185

Demyelination and axonal degeneration in corpus callosum assessed by analysis of transcallosally mediated inhibition in multiple sclerosis  

Microsoft Academic Search

Objective: Following focal transcranial magnetic cortex stimulation (fTMS), inhibition of voluntary EMG activity in the ipsilateral first dorsal interosseus (FDI) muscle was studied, in order to assess the functional integrity of the corpus callosum in patients with multiple sclerosis (MS).Methods and results: Thirty-four patients suffering from definite MS and 12 healthy, age-matched normal subjects were examined. In mid-sagittal slices, 29

J Höppner; E Kunesch; J Buchmann; A Hess; A Gro?mann; R Benecke

1999-01-01

186

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

PubMed Central

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

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

2014-01-01

187

White matter fractional anisotropy predicts balance performance in older adults  

Microsoft Academic Search

Aging is characterized by brain structural changes that may compromise motor functions. In the context of postural control, white matter integrity is crucial for the efficient transfer of visual, proprioceptive and vestibular feedback in the brain. To determine the role of age-related white matter decline as a function of the sensory feedback necessary to correct posture, we acquired diffusion weighted

Annouchka Van Impe; James P. Coxon; Daniel J. Goble; Mihail Doumas; Stephan P. Swinnen

188

[Comparative studies of cerebral blood flow measurements and measurements of the size of the corpus callosum in patients with schizophrenia].  

PubMed

In this study healthy subjects and schizophrenic patients of the so-called Type I and Type II subgroups were examined in each case with a morphological method to determine the size of the corpus callosum and with a method to measure a physiological functional parameter, namely, the regional cerebral blood flow (rCBF). MR and dynamic single photon emission CT were used (in our case as differential method). The study reveals for the first time classified into subgroups of the disease, scientifically measured differences both in the size of the corpus callosum and in the distribution pattern of the blood flow. Whereas the patients of type I had an enlarged corpus callosum and increased blood flow during the task with which they were confronted, these organs were mainly smaller in size with type II patients without an increase in the global blood flow during the relevant task. The statistical data--averaged over patient groups--show these differences clearly, but due to biological scatter it has so far not been possible to arrive at a diagnosis in individual cases. PMID:3264776

Petsch, R; Günther, W; Moser, E; Heller, H

1988-12-01

189

Electromagnetic electron temperature anisotropy instabilities  

NASA Technical Reports Server (NTRS)

This paper considers electromagnetic Vlasov instabilities driven by electron temperature anisotropies in a homogeneous, nonrelativistic magnetized plasma. Numerical solutions of the full linear dispersion equation for bi-Maxwellian distribution functions and instabilities propagating parallel to the magnetic field are presented. Parametric dependences of the maximum growth rates of the electron fire hose and whistler anisotropy instabilities are given.

Gary, S. P.; Madland, C. D.

1985-01-01

190

Electromagnetic electron temperature anisotropy instabilities  

NASA Astrophysics Data System (ADS)

This paper considers electromagnetic Vlasov instabilities driven by electron temperature anisotropies in a homogeneous, nonrelativistic magnetized plasma. Numerical solutions of the full linear dispersion equation for bi-Maxwellian distribution functions and instabilities propagating parallel to the magnetic field are presented. Parametric dependences of the maximum growth rates of the electron fire hose and whistler anisotropy instabilities are given.

Gary, S. P.; Madland, C. D.

1985-08-01

191

Thermal conductivity anisotropy of rocks  

NASA Astrophysics Data System (ADS)

The interior heat of the lithosphere of the Earth is mainly transferred by conduction that depends on thermal conductivity of rocks. Many sedimentary and metamorphic rocks have thermal conductivity anisotropy, i.e. heat is preferentially transferred in the direction parallel to the bedding and foliation of these rocks. Deming (JGR, 1994) proposed an empirical relationship between K(perp) and anisotropy (K(par)/K(perp)) using 89 measurements on rock samples from literatures. In Deming's model, thermal conductivity is almost isotropic for K(perp) > 4 W/mK, but anisotropy is exponentially increasing with decreasing K(perp), with final anisotropy of ~2.5 at K(perp) < 1.0 W/mK. However, Davis et al. (JGR, 2007) argued that there is little evidence for Deming's suggestion that thermal conductivity anisotropy of all rocks increases systematically to about 2.5 for rocks with low thermal conductivity. Davis et al. insisted that Deming's increase in anisotropy for 1 < K(perp) < 4 W/mK with decreasing K(perp) could be due to the fractures filled with air or water, which causes thermal conductivity anisotropy. To test Deming's suggestion and Davis et al.'s argument on thermal conductivity anisotropy, we measured thermal conductivity parallel (K(par)) and perpendicular (K(perp)) to bedding or foliation and performed analytical & numerical modeling. Our measurements on 53 rock samples show the anisotropy range from 0.79 to 1.36 for 1.84 < K(prep) < 4.06 W/mK. Analytical models show that anisotropy can increase or stay the same at the range of 1 < K(perp) < 4 W/mK. Numerical modeling for gneiss shows that anisotropy ranges 1.21 to 1.36 for 2.5 < K(perp) < 4.8 W/mK. Another numerical modeling with interbedded coal layers in high thermal conductivity rocks (3.5 W/mK) shows anisotropy of 1.87 when K(perp) is 1.7 W/mK. Finally, numerical modeling with fractures indicates that the fractures does not seem to affect thermal conductivity anisotropy significantly. In conclusion, our preliminary results imply that thermal conductivity anisotropy can increase or stay at low value in the range of 1.0 < K(perp) < 4.0 W/mK. Both cases are shown to be possible through lab measurements and analytical & numerical modeling.

Lee, Youngmin; Keehm, Youngseuk; Shin, Sang Ho

2013-04-01

192

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

193

Magnetic anisotropy of asbestos fibers  

NASA Astrophysics Data System (ADS)

The anisotropy of magnetic susceptibility of single asbestos fibers is measured. The alignment of both chrysotile and crocidolite fibers in magnetic fields is found to be due to the anisotropy. The average measured anisotropy of volume susceptibility is 0.40×10-6 for chrysotile and 83×10-6 for crocidolite. Fiber shape effects are estimated to contribute, on average, about 10% and 6%, respectively, to the total anisotropy of the two types of fiber. There is no evidence of significant permanent magnetic moments. The magnitude of the observed alignment makes the effect potentially useful in real-time detection of airborne asbestos fibers. The experimental technique developed in the study can be used for measuring the anisotropy of small particles of well-defined shape. High sensitivity of the technique permits the measurement of torques lower than 10-21 Nm on particles down to picogram mass.

Ulanowski, Z.; Kaye, P. H.

1999-04-01

194

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. ...

Ms. Jackson

2007-10-25

195

Fraction Strip  

NSDL National Science Digital Library

This interactive Flash applet displays eight fraction strips (bars, ribbons) of unit length. Denominators range from halves to twelfths. Segments of each bar can be dragged and dropped for close comparisons.

2012-01-01

196

Wilkinson Microwave Anisotropy Probe  

NSDL National Science Digital Library

NASA's Wilkinson Microwave Anisotropy Probe mission attempts to reveal conditions as they existed in the early universe by measuring the properties of the cosmic microwave background radiation over the full sky. Visitors can learn more about the particulars of the mission, explore the subjects of cosmology and the "Big Bang Theory" on the Universe link, view images of the probe and its launch in June 2001, and study the first detailed full-sky map of the oldest light in the universe. Although it may not seem it at first, this site contains a lot of material to browse, including an attempt in the FAQ section to answer whether or not there is there a conflict between science and religion.

1969-12-31

197

Adding Fractions  

NSDL National Science Digital Library

This tutorial helps students understand the basic concept of adding fractions. Each problem is illustrated with pizza slices and the steps for finding the least common denominator are clear. There is also a video in which students can watch a problem being solved on paper. There are also links to further information about finding the common denominator using two methods (either by multiplying the denominators or finding the least common denominator) and adding mixed fractions.

2010-08-09

198

Fraction Facts  

NSDL National Science Digital Library

This lesson is designed to develop students' abilities to add, subtract, multiply, and divide fractions. This lesson provides links to discussions, activities, and an online game related to performing operations with fractions as well as suggested ways to integrate them into the lesson. The lesson provides links to follow-up lessons designed for use in succession with the current one. Note, student reading level is not indicated because the lesson does not include student reading material.

2011-05-24

199

Fantastic Fractions  

NSDL National Science Digital Library

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

2012-10-22

200

Identification of genomic loci contributing to agenesis of the corpus callosum.  

PubMed

Agenesis of the corpus callosum (ACC) is a common brain malformation of variable clinical expression that is seen in many syndromes of various etiologies. Although ACC is predominantly genetic, few genes have as yet been identified. We have constructed and analyzed a comprehensive map of ACC loci across the human genome using data generated from 374 patients with ACC and structural chromosome rearrangements, most having heterozygous loss or gain of genomic sequence and a few carrying apparently balanced rearrangements hypothesized to disrupt key functional genes. This cohort includes more than 100 previously unpublished patients. The subjects were ascertained from several large research databases as well as the published literature over the last 35 years. We identified 12 genomic loci that are consistently associated with ACC, and at least 30 other recurrent loci that may also contain genes that cause or contribute to ACC. Our data also support the hypothesis that many ACC loci confer susceptibility to other brain malformations as well as ACC, such as cerebellar hypoplasia, microcephaly, and polymicrogyria. The database presented here provides a valuable resource for diagnosis and management of individuals with ACC and individuals with chromosome rearrangements in whom ACC should be suspected, and of course for identifying ACC causal and contributory genes. Well-defined diagnostic criteria, improved scanning techniques, and increased recognition of associated abnormalities will further facilitate gene mapping and allow definition of distinct syndromes within this heterogeneous group of patients. PMID:20683985

O'Driscoll, Mary C; Black, Graeme C M; Clayton-Smith, Jill; Sherr, Elliott H; Dobyns, William B

2010-09-01

201

Mapping Corpus Callosum Morphology in Twin Pairs Discordant for Bipolar Disorder  

PubMed Central

Callosal volume reduction has been observed in patients with bipolar disorder, but whether these deficits reflect genetic vulnerability to the illness remains unresolved. Here, we used computational methods to map corpus callosum abnormalities in a population-based sample of twin pairs discordant for bipolar disorder. Twenty-one probands with bipolar I disorder (mean age 44.4 ± 7.5 years; 48% female), 19 of their non-bipolar co-twins, and 34 demographically matched control twin individuals underwent magnetic resonance imaging. Three-dimensional callosal surface models were created to visualize its morphologic variability and to localize group differences. Neurocognitive correlates of callosal area differences were additionally investigated in a subsample of study participants. Bipolar (BPI) probands, but not their co-twins, showed significant callosal thinning and area reduction, most pronounced in the genu and splenium, relative to healthy twins. Altered callosal curvature was additionally observed in BPI probands. In bipolar probands and co-twins, genu and splenium midsagittal areas were significantly correlated with verbal processing speed and response inhibition. These findings suggest that aberrant connections between cortical regions—possibly reflecting decreased myelination of white matter tracts—may be involved in bipolar pathophysiology. However, findings of callosal thinning appear to be disease related, rather than reflecting genetic vulnerability to bipolar illness. PMID:21383237

van Erp, Theo G. M.; Dutton, Rebecca A.; Boyle, Christina; Madsen, Sarah; Luders, Eileen; Kieseppa, Tuula; Tuulio-Henriksson, Annamari; Huttunen, Matti; Partonen, Timo; Kaprio, Jaakko; Lönnqvist, Jouko; Thompson, Paul M.; Cannon, Tyrone D.

2011-01-01

202

Partial agenesis of the corpus callosum, hippocampal atrophy, and stable intellectual disability associated with Roifman syndrome.  

PubMed

In 2006, we reported the cognitive and behavioral phenotype of the seventh case of Roifman syndrome (OMIM 300258). Aged 11 years 6 months, the patient displayed significant intellectual disability with proportionate impairments in attentional-executive, memory, and visuo-spatial abilities despite appearing socially "able." This discrepancy may be explained by good social-emotional skills masking his intellectual disability, by decline in cognitive abilities over time, or by unusual neuroradiological abnormalities not previously examined in Roifman syndrome. Here, we present results from a structural MRI scan, neurocognitive evaluations repeated 2 and 5 years post-baseline and assessments of face and emotional processing. The MRI revealed partial agenesis of the corpus callosum, bilateral hypoplastic hippocampi but bilaterally intact amygdala. No evidence was found for decline in the patient's neurocognitive profile. Emotional processing data indicated an age-appropriate pattern of reactivity to emotional stimuli and preserved facial identity recognition abilities, but impairments in recognition of negative facial expressions. The results confirmed a stable pattern of intellectual disability, and indicated that Roifman syndrome may be associated with major structural neuro-anatomical abnormalities. We suggest that the relative strengths in emotion and face processing are consistent with the patient's apparently able social behavior, and with intact amygdalar function. PMID:21910238

Fairchild, Helen R; Fairchild, Graeme; Tierney, Kevin M; McCartney, Deborah L; Cross, Justin J; de Vries, Petrus J

2011-10-01

203

Second trimester prenatal alcohol exposure alters development of rat corpus callosum.  

PubMed

Prenatal alcohol exposure produces many developmental defects of the central nervous system (CNS), such as in the corpus callosum (CC). This study was designed to observe the effect of prenatal alcohol exposure during the second trimester equivalent on the development of dendritic arbors of CC projection neurons (CCpn) in rat visual cortex. In addition, the effect of second trimester equivalent prenatal alcohol exposure on brain weight was determined. Pregnant dams received 1.2-6.0 g/kg ethanol (EtOH) during gestational day (G) 11-20. Controls consisted of normal and nutritionally matched pairfed (PF) dams. Pups were sacrificed on the day of birth, G26, G29 and G33. DiI crystals were placed in the midsagittal CC bundle to retrogradely label CCpn. Images of visual cortex were obtained from tissue slices using a confocal laser scanning microscope. The number and length of apical and basilar dendrite branches were determined. The results show that prenatal alcohol exposure restricted to the second trimester equivalent alters the development of the CCpn dendritic arbor and the brain weight in a blood alcohol concentration (BAC)-dependent manner. The alteration in the EtOH CCpn is manifested as an increase in the number and length of CCpn apical and basilar dendrite branches, while brain weight is reduced compared with Controls. PMID:12460654

Qiang, Mei; Wang, Ming Wei; Elberger, Andrea J

2002-01-01

204

Gli3 controls corpus callosum formation by positioning midline guideposts during telencephalic patterning.  

PubMed

The corpus callosum (CC) represents the major forebrain commissure connecting the 2 cerebral hemispheres. Midline crossing of callosal axons is controlled by several glial and neuronal guideposts specifically located along the callosal path, but it remains unknown how these cells acquire their position. Here, we show that the Gli3 hypomorphic mouse mutant Polydactyly Nagoya (Pdn) displays agenesis of the CC and mislocation of the glial and neuronal guidepost cells. Using transplantation experiments, we demonstrate that agenesis of the CC is primarily caused by midline defects. These defects originate during telencephalic patterning and involve an up-regulation of Slit2 expression and altered Fgf and Wnt/?-catenin signaling. Mutations in sprouty1/2 which mimic the changes in these signaling pathways cause a disorganization of midline guideposts and CC agenesis. Moreover, a partial recovery of midline abnormalities in Pdn/Pdn;Slit2(-/-) embryos mutants confirms the functional importance of correct Slit2 expression levels for callosal development. Hence, Gli3 controlled restriction of Fgf and Wnt/?-catenin signaling and of Slit2 expression is crucial for positioning midline guideposts and callosal development. PMID:23042737

Magnani, Dario; Hasenpusch-Theil, Kerstin; Benadiba, Carine; Yu, Tian; Basson, M Albert; Price, David J; Lebrand, Cécile; Theil, Thomas

2014-01-01

205

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

206

Attenuation of corpus callosum axon myelination and remyelination in the absence of circulating sex hormones.  

PubMed

Sex differences in the structure and organization of the corpus callosum (CC) can be attributed to genetic, hormonal or environmental effects, or a combination of these factors. To address the role of gonadal hormones on axon myelination, functional axon conduction and immunohistochemistry analysis of the CC in intact, gonadectomized and hormone-replaced gonadectomized animals were used. These groups were subjected to cuprizone diet-induced demyelination followed by remyelination. The myelinated component of callosal compound action potential was significantly decreased in ovariectomized and castrated animals under normal myelinating condition. Compared to gonadally intact cohorts, both gonadectomized groups displayed more severe demyelination and inhibited remyelination. Castration in males was more deleterious than ovariectomy in females. Callosal conduction in estradiol-supplemented ovariectomized females was significantly increased during normal myelination, less attenuated during demyelination, and increased beyond placebo-treated ovariectomized or intact female levels during remyelination. In castrated males, the non-aromatizing steroid dihydrotestosterone was less efficient than testosterone and estradiol in restoring normal myelination/axon conduction and remyelination to levels of intact males. Furthermore, in both sexes, estradiol supplementation in gonadectomized groups increased the number of oligodendrocytes. These studies suggest an essential role of estradiol to promote efficient CC myelination and axon conduction in both sexes. PMID:23311751

Patel, Rhusheet; Moore, Spencer; Crawford, Daniel K; Hannsun, Gemmy; Sasidhar, Manda V; Tan, Kevin; Molaie, Donna; Tiwari-Woodruff, Seema K

2013-07-01

207

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

PubMed

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

?çer, Semra

2013-10-01

208

Detection of corpus callosum malformations in pediatric population using the discriminative direction in multiple kernel learning.  

PubMed

In this paper we propose a Multiple Kernel Learning (MKL) classifier to detect malformations of the Corpus Callosum (CC) and apply it in a pediatric population. Furthermore, we extend the concept of discriminative direction to the linear MKL methods, implementing it in a single subject analysis framework. The CC is characterized using different measures derived from Magnetic Resonance Imaging (MRI) data and the MKL approach is used to efficiently combine them. The discriminative direction analysis highlights those features that lead the classification for each given subject. In the case of a CC with malformation this means highlighting the abnormal characteristics of the CC that guide the diagnosis. Experiments show that the method correctly identifies the malformative aspects of the CC. Moreover, it is able to identify dishomogeneus, localized or widespread abnormalities among the different features. The proposed method is therefore suitable for supporting neuroradiologists in the decision-making process, providing them not only with a suggested diagnosis, but also with a description of the pathology. PMID:25485392

Peruzzo, Denis; Arrigoni, Filippo; Triulzi, Fabio; Parazzini, Cecilia; Castellani, Umberto

2014-01-01

209

Introducing Fractions Slideshow- Flowering Fractions  

NSDL National Science Digital Library

This online resource is a story of a girl and her father planting flowers that your children and you interact with. Help them fill in the fractions as they practice dividing the garden up for their flowers!

Beacon Learning Center

2011-10-24

210

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

211

Fraction King  

NSDL National Science Digital Library

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

2011-05-24

212

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

213

Magnetic nanoparticles with combined anisotropy  

NASA Astrophysics Data System (ADS)

We study the influence of the distribution of the particles' aspect ratio on the magnetostatic properties of an assembly of nanoparticles with cubic magnetocrystalline anisotropy, such as iron, nickel, iron oxides, and ferrites. Because of the large values of the dimensionless ratio Ms2/|Kc| for these particles, the shape anisotropy energy makes considerable contribution to the total nanoparticle energy even for relatively small shape distortions, with equivalent ellipsoids having aspect ratios ? ? 1.1. As a result, the magnetostatic properties of a randomly oriented assembly of particles with combined anisotropy at ? ? 1.1 are similar to those for an assembly of particles with purely uniaxial magnetic anisotropy. This conclusion is shown to be valid not only for the assembly hysteresis loops but also for the magnetic relaxation characteristics, at least in the high damping limit.

Usov, N. A.; Barandiarán, J. M.

2012-09-01

214

Magnetic anisotropies of quantum dots  

NASA Astrophysics Data System (ADS)

Magnetic anisotropies in quantum dots (QDs) doped by magnetic ions are discussed in terms of two frameworks: anisotropic g-factors and magnetocrystalline anisotropy energy [1]. Two examples, related to zinc-blende p-doped materials, are given of how these frameworks are utilized: four-level Hamiltonian of a flat QD and a cuboid infinite-well QD containing a single hole. The latter model, despite being an idealization of a real QD, displays a rich phenomenology of anisotropies. We quantify the anisotropy constants for ZnSe and CdTe QDs, confirming that the Ising-like effective Hamiltonians apply to magnetic QDs [2]. Compared to bulk systems, confinement tuning offers a new way to control easy axes in magnetic QDs. [1] K. Vyborny et al., preprint (2011). [2] C. Le Gall et al., Phys. Rev. Lett. 107, 057401 (2011).

Vyborny, Karel; Han, J. E.; Oszwaldowski, Rafal; Zutic, Igor; Petukhov, A. G.

2012-02-01

215

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

216

Anisotropy in solid inflation  

SciTech Connect

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

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

2013-08-01

217

Magnetocrystalline Anisotropy in Permalloy Revisited  

Microsoft Academic Search

Permalloy with a body-centered-cubic structure has been grown on GaAs(001) by molecular beam epitaxy. Its magnetism, Curie temperature, and magnetic anisotropy are determined experimentally and compared to those of conventional face-centered-cubic Permalloy. Unexpectedly the vanishing magnetic cubic anisotropy in Permalloy is found to be independent of its atomic structure but depends only upon the stoichiometry of Fe and Ni in

L. F. Yin; D. H. Wei; N. Lei; L. H. Zhou; C. S. Tian; G. S. Dong; X. F. Jin; L. P. Guo; Q. J. Jia; R. Q. Wu

2006-01-01

218

Effect of registration on corpus callosum population differences found with DBM analysis  

NASA Astrophysics Data System (ADS)

Deformation Based Morphometry (DBM) is a relatively new method used for characterizing anatomical differences among populations. DBM is based on the analysis of the deformation fields generated by non-rigid registration algorithms, which warp the individual volumes to one standard coordinate system. Although several studies have compared non-rigid registration algorithms for segmentation tasks, few studies have compared the effect of the registration algorithm on population differences that may be uncovered through DBM. In this study, we compared DBM results obtained with five well established non-rigid registration algorithms on the corpus callosum (CC) in thirteen subjects with Williams Syndrome (WS) and thirteen Normal Control (NC) subjects. The five non-rigid registration algorithms include: (1) The Adaptive Basis Algorithm (ABA); (2) Image Registration Toolkit (IRTK); (3) FSL Nonlinear Image Registration Tool (FSL); (4) Automatic Registration Tools (ART); and (5) the normalization algorithm available in SPM8. For each algorithm, the 3D deformation fields from all subjects to the atlas were obtained and used to calculate the Jacobian determinant (JAC) at each voxel in the mid-sagittal slice of the CC. The mean JAC maps for each group were compared quantitatively across different nonrigid registration algorithms. An ANOVA test performed on the means of the JAC over the Genu and the Splenium ROIs shows the JAC differences between nonrigid registration algorithms are statistically significant over the Genu for both groups and over the Splenium for the NC group. These results suggest that it is important to consider the effect of registration when using DBM to compute morphological differences in populations.

Han, Zhaoying; Thornton-Wells, Tricia A.; Gore, John C.; Dawant, Benoit M.

2011-03-01

219

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

PubMed Central

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

2014-01-01

220

Corpus callosum abnormalities in medication-naïve adult patients with obsessive compulsive disorder.  

PubMed

Emerging evidence demonstrates widespread abnormalities involving white matter (WM) tracts connecting different cortical regions in obsessive-compulsive disorder (OCD). The corpus callosum (CC), the largest inter-hemispheric tract connecting the association cortices, has been shown to be affected in OCD. This study examines CC abnormalities in a large sample of medication-naïve OCD patients in comparison to matched healthy controls (HCs). We examined the mid-sagittal area of the CC in medication-naïve OCD patients (n=49) in comparison with age-, sex-, and handedness-matched HCs (n=38). Witelson?s method was used to measure the sub-regions of the CC - namely, the genu, body, isthmus and splenium - with good inter-rater reliability. The area of the body of the CC and total CC area were significantly larger in OCD patients than in HCs after controlling for age, sex and intracranial area. The Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) compulsion score had a significant negative correlation with the areas of the isthmus and splenium of the CC in addition to the total CC area. The region-specific differences in the body of the CC and the region-specific association of severity score with posterior regions of the CC might be indicative of the involvement of additional areas like the dorsolateral prefrontal cortex, posterior parietal areas, occipital and association cortices in OCD that extend beyond the conventional orbito-fronto-striatal circuitry that is often posited to be involved in OCD. PMID:25686521

Jose, Dania; Narayanaswamy, Janardhanan C; Agarwal, Sri Mahavir; Kalmady, Sunil V; Venkatasubramanian, Ganesan; Reddy, Y C Janardhan

2015-03-30

221

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

222

Relevance of corpus callosum splenium versus middle cerebellar peduncle hyperintensity for FXTAS diagnosis in clinical practice.  

PubMed

Fragile X-associated tremor ataxia syndrome (FXTAS) is caused by FMR1 premutation. The features include ataxia, action tremor and middle cerebellar peduncle (MCP) hyperintensity, the latter being the only major radiological criterion in the diagnosis of definite FXTAS until very recently. The importance of corpus callosum splenium (CCS) hyperintensity was recently reported and this sign is now considered as an additional major radiological diagnostic criterion in the diagnosis of FXTAS. However, little is known about its relevance for the diagnosis of FXTAS in clinical practice. We report a practical justification of the relevance of CCS hyperintensity in parallel with MCP hyperintensity for the diagnosis of FXTAS. Clinical and radiological study of 22 FMR1 premutation carriers with neurological signs that may be encountered in FXTAS compared to series of patients with essential tremor, multiple system atrophy of cerebellar type, Parkinson's disease, Alzheimer's disease and stroke. Among the 22 patients with FMR1 premutation [17 men, 5 women; mean age, 63 ± 7.5 (46-84)], 14 were diagnosed with definite FXTAS with the initial criteria. Considering CCS hyperintensity as a new major radiological criterion permitted the diagnosis of definite FXTAS in 3 additional patients. Overall CCS proved as frequent as MCP hyperintensity (64 versus 64 %), while 23 % of patients had CCS but not MCP hyperintensity, 14 % of patients had CCS hyperintensity but neither MCP, nor brainstem hyperintensity. In contrast with CCS hyperintensity, MCP hyperintensity proved less frequent in women than in men. CCS and MCP hyperintensity were more frequent in FXTAS than in the other neurodegenerative disorders. The combination of CCS and MCP hyperintensity was specific of FXTAS. We confirmed the relevance of CCS hyperintensity in FXTAS and we clarified its interest compared to MCP hyperintensity. Our results support the inclusion of CCS hyperintensity in the diagnostic criteria as a new major radiological criterion. PMID:25451852

Renaud, Mathilde; Perriard, Julien; Coudray, Sarah; Sévin-Allouet, Mathieu; Marcel, Christophe; Meissner, Wassilios G; Chanson, Jean-Baptiste; Collongues, Nicolas; Philippi, Nathalie; Gebus, Odile; Quenardelle, Véronique; Castrioto, Anna; Krack, Paul; N'Guyen, Karine; Lefebvre, François; Echaniz-Laguna, Andoni; Azulay, Jean-Philippe; Meyer, Nicolas; Labauge, Pierre; Tranchant, Christine; Anheim, Mathieu

2015-02-01

223

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; Mensà, Emanuela

2014-01-01

224

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.

2012-06-26

225

Laboratory seismic anisotropy in mylonites  

NASA Astrophysics Data System (ADS)

Tectonic strain is often accommodated along narrow zones in the Earth's crust and upper mantle, and these high-strain zones represent an important mechanical and rheological component in geodynamics. In outcrop we observe the intense deformation along and across these structures. But at depth, in the mid and lower crust, and in the mantle, we are dependent on geophysical methods for analysis of structures, such as seismic reflection and refraction surveys. A natural progression has therefore been to understand the remote geophysical signal in terms of laboratory ultrasonic pulse transmission measurements on rock cores, collected in the field or from borehole drill core. Here we first present a brief review that consider key studies in the area of laboratory seismic measurements in strongly anisotropic rocks, ranging from calcite mylonites to metapelites. In the second part we focus attention on ongoing research projects targetting laboratory seismic anisotropy in mylonitized rocks, and associated challenges. Measurements of compressional (P) and shear (S) waves were made at high confining pressure (up to 5 kbar). Mineral texture analysis was performed with electron backscatter diffraction (EBSD) and neutron texture diffraction to determine crystallographic preferred orientation (CPO). So-called "rock-recipe" models are used to calculate seismic anisotropy, which consider the elastic properties of minerals that constitutes the rock, and their respective CPO. However, the outcome of such models do not always simply correspond to the measured seismic anisotropy. Differences are attributed to several factors, such as grain boundaries, mineral microstructures including shape-preferred orientation (SPO), micro-cracks and pores, and grain-scale stress-strain conditions. We highlight the combination of these factors in case studies on calcite and peridotite mylonites. In calcite mylonites, sampled in the Morcles nappe shear zone, the measured seismic anisotropy generally match the calculated seismic anisotropy. However, anisotropy may be reinforced by the contribution of grain-boundary effects and calcite SPO, as is indicated by microCT imaging and SEM analysis. This is evident in one case where the measured P wave anisotropy exceeded the calculated anisotropy by more than 5%, and by ~4 % higher shear-wave splitting. An even greater discrepancy can be found when comparing measured and calculated seismic anisotropy in mylonitized peridotites from shear zones in the Lanzo (Italy) and Ronda (Spain) massifs. This is in part related to serpentinization of olivine, which remains a challenge for laboratory measurements of peridotites. Highest values of calculated anisotropy, for both the calcite and peridotite mylonites, are found in near monomineralic specimens (i.e., 8 - 10% P wave anisotropy). In comparison, polymineralic specimens have calculated P wave anisotropy ranging between <2 - 5%. In contrast, the laboratory measured seismic anisotropy do not display a simple relationship as a function of mono- versus polymineralic composition. Seismic properties and anisotropy are discussed in light of conditions and mechanisms of deformation, and the possible role and influence of second-phase minerals. Laboratory measurements offers a venue for exploring the relationship between deformation and seismic anisotropy. Such investigation may, in combination with high-resolution geophysical methods and increasingly sophisticated numerical models, yield further insight on remote active deformation in the mid and lower crust, and in the upper mantle.

Almqvist, B. S. G.; Herwegh, M.; Hirt, A. M.; Ebert, A.; Linckens, J.; Precigout, J.; Leiss, B.; Walter, J. M.; Burg, J.-P.

2012-04-01

226

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

227

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

228

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.

WGBH Boston

1996-01-01

229

Fraction Bars  

NSDL National Science Digital Library

This virtual manipulative is a Java applet that allows students to explore concepts in whole number operations and fractions, just as they would with a physical manipulative such as Cuisinaire Rods. The user can add bars of length 1 to 10 to the workspace, change their color, and move, duplicate, or remove them. 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

230

Polymicrogyria, Large Corpus Callosum and Psychomotor Retardation in Four-Year-Old Girl: Potential Association Based on MR Findings. A Case Report and Literature Review.  

PubMed

SUMMARY - We describe a child from consanguineous parents presenting mega corpus callosum (MegaCC), polymicrogyria, psychomotor retardation with swallowing difficulties and language impairment perhaps linked to the syndrome of megalencephaly-polymicrogyria-mega corpus callosum (MEG-PMG-MegaCC). Reviewing the literature, we speculate that MegaCC, psychomotor retardation and anomalies in cortical migration are the three pathognomonic features. The presence of additional possibly associated anomalies such as megalencephaly, indicates that the spectrum of linked malformations with this rare syndrome is broad and yet to be defined. PMID:25260206

Budai, Caterina; Moscato, Giulia; Patruno, Francesco; Leonardi, Marco; Maffei, Monica

2014-10-01

231

Asthenospheric Anisotropy Beneath North America  

NASA Astrophysics Data System (ADS)

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

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

2005-12-01

232

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

PubMed

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

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

2014-12-01

233

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

PubMed Central

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

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

2009-01-01

234

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

PubMed Central

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

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

2014-01-01

235

A T1 and DTI fused 3D corpus callosum analysis in pre- vs. post-season contact sports players  

NASA Astrophysics Data System (ADS)

Sports related traumatic brain injury (TBI) is a worldwide public health issue, and damage to the corpus callosum (CC) has been considered as an important indicator of TBI. However, contact sports players suffer repeated hits to the head during the course of a season even in the absence of diagnosed concussion, and less is known about their effect on callosal anatomy. In addition, T1-weighted and diffusion tensor brain magnetic resonance images (DTI) have been analyzed separately, but a joint analysis of both types of data may increase statistical power and give a more complete understanding of anatomical correlates of subclinical concussions in these athletes. Here, for the first time, we fuse T1 surface-based morphometry and a new DTI analysis on 3D surface representations of the CCs into a single statistical analysis on these subjects. Our new combined method successfully increases detection power in detecting differences between pre- vs. post-season contact sports players. Alterations are found in the ventral genu, isthmus, and splenium of CC. Our findings may inform future health assessments in contact sports players. The new method here is also the first truly multimodal diffusion and T1-weighted analysis of the CC, and may be useful to detect anatomical changes in the corpus callosum in other multimodal datasets.

Lao, Yi; Law, Meng; Shi, Jie; Gajawelli, Niharika; Haas, Lauren; Wang, Yalin; Leporé, Natasha

2015-01-01

236

A comparative study of corpus callosum size and signal intensity in capuchin monkeys (Cebus apella) and chimpanzees (Pan troglodytes).  

PubMed

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

Phillips, K A; Kapfenberger, N; Hopkins, W D

2009-03-31

237

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

238

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. PMID:25206616

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

2013-01-01

239

Cell fractionation.  

PubMed

Proteins within a cell are localized into specific cellular compartments, allowing compartmentalization of distinct tasks. If we consider lipid bilayers as compartments, then gram-negative bacteria such as Pseudomonas aeruginosa can target proteins to five distinct locations: the cytoplasm, the inner membrane, the periplasm, the outer membrane, and the extracellular environment. In this chapter, we describe how the different compartments can be selectively isolated by a combination of centrifugation and disruption techniques. Fractionation of the cells into subcellular compartments enables protein enrichment and is essential to accurately determine the localization of specific proteins, which is the first step towards understanding the function of a protein in the cell. PMID:24818905

Ize, Bérengère; Viarre, Véronique; Voulhoux, Romé

2014-01-01

240

Concepts in CMB Anisotropy Formation  

E-print Network

These lecture notes form a primer on the theory of cosmic microwave background (CMB) anisotropy formation. With emphasis on conceptual aspects rather than technical issues, we examine the physical foundations of anisotropy evolution in relativistic kinetic and perturbation theory as well as the manifestation of these principles in primary and secondary anisotropies. We discuss gauge choice and gauge invariance and their use in understanding the CMB. Acoustic, gravitational redshift and ionization effects have robust signatures in the CMB spectrum and may allow determination of classical cosmological parameters as well as reveal general distinctions between models for structure formation. We develop the tight and weak coupling approximations as analytic tools to help understand these effects and the robustness of their signatures.

Wayne Hu

1995-11-27

241

Ferroelectric control of magnetic anisotropy.  

PubMed

We demonstrate unambiguous evidence of the electric field control of magnetic anisotropy in a wedge-shaped Co film of varying thickness. A copolymer ferroelectric of 70% vinylidene fluoride with 30% trifluoroethylene, P(VDF-TrFE) overlays the Co wedge, providing a large switchable electric field. As the ferroelectric polarization is switched from up to down, the magnetic anisotropy of the Co films changes by as much as 50%. At the lowest Co thickness the magnetic anisotropy switches from out-of-plane to in-plane as the ferroelectric polarization changes from up to down, enabling us to rotate the magnetization through a large angle at constant magnetic field merely by switching the ferroelectric polarization. The large mismatch in the stiffness coefficients between the polymer ferroelectric and metallic ferromagnet excludes typical magnetoelectric strain coupling; rather, the magnetic changes arise from the large electric field at the ferroelectric/ferromagnet interface. PMID:21823660

Mardana, A; Ducharme, Stephen; Adenwalla, S

2011-09-14

242

Equivalent Fractions Pointer  

NSDL National Science Digital Library

Visually represent two unique fractions that are equivalent to a given fraction. The fractional value is shown on a number line as you color in the fraction. Equivalent Fraction Pointer is one of the Interactivate assessment explorers.

243

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

244

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

245

Focal Lesion in the Splenium of the Corpus Callosum on FLAIR MR Images: A Common Finding with Aging and after Brain Radiation Therapy  

Microsoft Academic Search

BACKGROUND AND PURPOSE: Focal high signal intensity in the splenium of the corpus callosum on fluid-attenuated inversion-recovery (FLAIR) images is generally considered an abnormal MR finding. We identified high signal intensity in the splenium on FLAIR images in patients of advanced age with otherwise normal images and in patients who had received brain radiation therapy. We undertook an investigation to

Joseph S. Pekala; Alexander C. Mamourian; Heather A. Wishart; William F. Hickey; James D. Raque

246

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

247

The Physics of Microwave Background Anisotropies  

E-print Network

Cosmic microwave background anisotropies provide a vast amount of information on both structure formation in the universe and the background dynamics and geometry. The full physical content and detailed structure of anisotropies can be understood in a simple and intuitive fashion through a systematic investigation of the individual mechanisms for anisotropy formation, based on elementary gravitational and fluid dynamics.

Wayne Hu; Naoshi Sugiyama; Joseph Silk

1995-04-18

248

Anisotropy of the cosmic microwave background radiation  

Microsoft Academic Search

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

J. Silk

1981-01-01

249

Anisotropy and particle-size effects in nanostructured plasmonic metamaterials.  

PubMed

We study the optical properties of metamaterials formed by layers of metallic nanoparticles. The effective optical constants of these materials are retrieved from the calculated angle-dependent Fresnel reflection coefficients for s and p incident-light polarization. We investigate the degree of anisotropy in the effective permittivity as a function of inter-layer spacing, particle size, filling fraction of the metal, and particle shape. For layers of spherical particles periodically arranged in a hexagonal lattice, the anisotropy disappears for the three inter-layer spacings corresponding to simple cubic (sc), bcc, and fcc volume symmetry. For non-spherical particles, an isotropic response can be still obtained with other values of the inter-layer spacing. Finally, we provide a quantitative answer to the question of how many layers are needed to form an effectively homogeneous metamaterial slab. Surprisingly, only one layer can be enough, except in the spectral range close to the particle plasmon resonances. PMID:19997446

Romero, Isabel; de Abajo, F Javier García

2009-11-23

250

Exploring the relative contribution of mineralogy and CPO to the seismic velocity anisotropy of evaporites  

NASA Astrophysics Data System (ADS)

We present the influence of mineralogy and microstructure on the seismic velocity anisotropy of evaporites. Bulk elastic properties and seismic velocities are calculated for a suite of 20 natural evaporite samples, which consist mainly of halite, anhydrite, and gypsum. They exhibit strong fabrics as a result of tectonic and diagenetic processes. Sample mineralogy and crystallographic preferred orientation (CPO) were obtained with the electron backscatter diffraction (EBSD) technique and the data used for seismic velocity calculations. Bulk seismic properties for polymineralic evaporites were evaluated with a rock recipe approach. Ultrasonic velocity measurements were also taken on cube shaped samples to assess the contribution of grain-scale shape preferred orientation (SPO) to the total seismic anisotropy. The sample results suggest that CPO is responsible for a significant fraction of the bulk seismic properties, in agreement with observations from previous studies. Results from the rock recipe indicate that increasing modal proportion of anhydrite grains can lead to a greater seismic anisotropy of a halite-dominated rock. Conversely, it can lead to a smaller seismic anisotropy degree of a gypsum-dominated rock until an estimated threshold proportion after which anisotropy increases again. The difference between the predicted anisotropy due to CPO and the anisotropy measured with ultrasonic velocities is attributed to the SPO and grain boundary effects in these evaporites.

Vargas-Meleza, Liliana; Healy, David; Alsop, G. Ian; Timms, Nicholas E.

2015-01-01

251

The microwave background anisotropies: observations.  

PubMed

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

Wilkinson, D

1998-01-01

252

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

253

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 ...

Miss Brinton

2007-10-08

254

Increases in size and myelination of the rat corpus callosum during adulthood are maintained into old age  

PubMed Central

Although there are indications of growth in the size and myelination of the rat corpus callosum during adulthood, it is not known how long this growth continues. In addition, the potential for age-related changes in these measures to affect the sex differences seen in adulthood has not been examined. Here the size of callosal subregions and area occupied by myelin were examined in the genu and splenium of male and female rats in adulthood, middle-age, and old age. Our findings revealed increases both in size and in the area composed of myelin between adulthood and middle-age that were maintained into old age, with no indications of age-related loss in either the genu or splenium of the rat. PMID:17300760

Yates, M.A.; Juraska, J.M.

2007-01-01

255

Microcephaly-thin corpus callosum syndrome maps to 8q23.2-q24.12.  

PubMed

Postnatal microcephaly is defined as normal head circumference at birth, which progressively declines to more than 2 standard deviations below the average for the patient's age and sex. We describe four patients from three consanguineous families of Arab Bedouin origin who presented with autosomal recessive inheritance of progressive microcephaly, spasticity, thin corpus callosum, pyramidal signs, and intellectual disability. Homozygosity mapping (Human Mapping NspI 250K arrays, Affymetrix, Santa Clara, CA) placed the disease locus at 8q23.2-q24.12. The candidate region includes 22 known or predicted genes, including RAD21, which is related to the cohesion complex EIF3H, which is involved in translation initiation, and TAF2, which may be involved in intellectual disability. Identification of the causative gene in our reported family will shed light on the pathogenesis of this severe condition. PMID:22633631

Halevy, Ayelet; Basel-Vanagaite, Lina; Shuper, Avinoam; Helman, Shlomit; Har-Zahav, Adi; Birk, Efrat; Maya, Idit; Kornreich, Liora; Inbar, Dov; Nürnberg, Gudrun; Nürnberg, Peter; Steinberg, Tamar; Straussberg, Rachel

2012-06-01

256

Human amniotic epithelial cells express specific markers of nerve cells and migrate along the nerve fibers in the corpus callosum?  

PubMed Central

Human amniotic epithelial cells were isolated from a piece of fresh amnion. Using immunocytochemical methods, we investigated the expression of neuronal phenotypes (microtubule-associated protein-2, glial fibrillary acidic protein and nestin) in human amniotic epithelial cells. The conditioned medium of human amniotic epithelial cells promoted the growth and proliferation of rat glial cells cultured in vitro, and this effect was dose-dependent. Human amniotic epithelial cells were further transplanted into the corpus striatum of healthy adult rats and the grafted cells could integrate with the host and migrate 1–2 mm along the nerve fibers in corpus callosum. Our experimental findings indicate that human amniotic epithelial cells may be a new kind of seed cells for use in neurograft.

Wu, Zhiyuan; Hui, Guozhen; Lu, Yi; Liu, Tianjin; Huang, Qin; Guo, Lihe

2012-01-01

257

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

PubMed

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

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

2015-04-16

258

Frameshift mutation of the zinc finger homeo box 1 B gene in syndromic corpus callosum agenesis (Mowat-Wilson syndrome).  

PubMed

We report a girl who had Hirschsprung disease in association with distinct facial appearance, microcephaly, agenesis of the corpus callosum and mental retardation (Mowat-Wilson syndrome). Mutation analysis of the zinc finger homeo box 1 B (ZFHX1 B) gene revealed a de novo 7 bp deletion (TGGCCCC) at nucleotide 1773 (1773 delTGGCCCC) resulting in a frameshift and leading to a termination codon at amino acid residue 604 (604 X) in exon 8 C. The zinc finger homeo box 1 B (Smad interacting protein-1) is a transcription corepressor of Smad target genes with functions in the patterning of neural crest derived cells, CNS, and midline structures. Mutations in ZFHX1 B can lead to neurological disorders in addition to dysmorphic features, megacolon, and other malformations. PMID:14681759

Sztriha, L; Espinosa-Parrilla, Y; Gururaj, A; Amiel, J; Lyonnet, S; Gerami, S; Johansen, J G

2003-12-01

259

Trisomy 8 syndrome owing to isodicentric 8p chromosomes: regional assignment of a presumptive gene involved in corpus callosum development.  

PubMed Central

Two patients with trisomy 8 syndrome owing to an isodicentric 8p;8p chromosome are described. Case 1 had a 46,XX/46,XX,-8,+idic(8)(p23) karyotype while case 2, a male, had the same abnormal karyotype without evidence of mosaicism. In situ hybridisation, performed in case 1, showed that the isochromosome was asymmetrical. Agenesis of the corpus callosum (ACC), which is a feature of trisomy 8 syndrome, was found in both patients. Although ACC is associated with aneuploidies for different chromosomes, a review of published reports indicates that, when associated with chromosome 8, this defect is the result of duplication of a gene located within 8p21-pter. Molecular analysis in one of our patients led us to exclude the distal 23 Mb of 8p from this ACC region. Images PMID:8014974

Digilio, M C; Giannotti, A; Floridia, G; Uccellatore, F; Mingarelli, R; Danesino, C; Dallapiccola, B; Zuffardi, O

1994-01-01

260

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

261

Single Fraction Finder  

NSDL National Science Digital Library

Determine the value of a given fraction represented as a point on a number line. Then find a fraction whose value is a given fraction. Fraction Pointer is one of the Interactivate assessment explorers.

262

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.

Utah Education Network

2012-04-30

263

Magnetic anisotropy in single clusters  

NASA Astrophysics Data System (ADS)

The magnetic measurements on single cobalt and iron nanoclusters containing almost 1000 atoms are presented. Particles are directly buried within the superconducting film of a micro-SQUID (superconducting quantum interference device) which leads to the required sensitivity. The angular dependence of the switching field in three dimensions turns out to be in good agreement with a uniform rotation of cluster magnetization. The Stoner and Wohlfarth model yields therefore an estimation of magnetic anisotropy in a single cluster. In particular, uniaxial, biaxial, and cubic contributions can be separated. Results are interpreted on the basis of a simple atomic model in which clusters are assimilated to “giant spins.” We present an extension of the Néel model to clusters in order to estimate surface anisotropy. In the case of cobalt, this last contribution dominates and numerical simulations allow us to get the morphology of the investigated clusters.

Jamet, Matthieu; Wernsdorfer, Wolfgang; Thirion, Christophe; Dupuis, Véronique; Mélinon, Patrice; Pérez, Alain; Mailly, Dominique

2004-01-01

264

Magnetic Anisotropy of Igneous Rocks  

Microsoft Academic Search

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

F. D. Stacey

1960-01-01

265

Large Scale Coherent Dipole Anisotropy?  

NASA Astrophysics Data System (ADS)

We reanalyzed and compared the QDOT and 1.2 Jy IRAS dipoles using exactly the same procedure and we find strong indications from both samples for (a) significant contributions from large depths ~170 h^{-1}Mpc and (b) a large -scale coherence anisotropy.These indications are provided by the fact that the differential dipoles of large equal volume shells are well aligned with the CMB dipole.

Basilakos, S.; Plionis, M.

266

Mechanical Anisotropy of Ankyrin Repeats  

PubMed Central

Red blood cells are frequently deformed and their cytoskeletal proteins such as spectrin and ankyrin-R are repeatedly subjected to mechanical forces. While the mechanics of spectrin was thoroughly investigated in vitro and in vivo, little is known about the mechanical behavior of ankyrin-R. In this study, we combine coarse-grained steered molecular dynamics simulations and atomic force spectroscopy to examine the mechanical response of ankyrin repeats (ARs) in a model synthetic AR protein NI6C, and in the D34 fragment of native ankyrin-R when these proteins are subjected to various stretching geometry conditions. Our steered molecular dynamics results, supported by AFM measurements, reveal an unusual mechanical anisotropy of ARs: their mechanical stability is greater when their unfolding is forced to propagate from the N-terminus toward the C-terminus (repeats unfold at ?60 pN), as compared to the unfolding in the opposite direction (unfolding force ? 30 pN). This anisotropy is also reflected in the complex refolding behavior of ARs. The origin of this unfolding and refolding anisotropy is in the various numbers of native contacts that are broken and formed at the interfaces between neighboring repeats depending on the unfolding/refolding propagation directions. Finally, we discuss how these complex mechanical properties of ARs in D34 may affect its behavior in vivo. PMID:22404934

Lee, Whasil; Zeng, Xiancheng; Rotolo, Kristina; Yang, Ming; Schofield, Christopher J.; Bennett, Vann; Yang, Weitao; Marszalek, Piotr E.

2012-01-01

267

[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

268

Cosmic Microwave Background Anisotropies: Beyond Standard Parameters  

E-print Network

In the first part of this work, I review the theoretical framework of cosmological perturbation theory necessary to understand the generation and evolution of cosmic microwave background (CMB) anisotropies. Using analytical and numerical techniques, in the second part I describe the impact on the CMB power spectra of the standard cosmological parameters (such as the matter-energy budget of the Universe, its curvature, the amplitude and spectral properties of the primordial fluctuations, etc.). I introduce the most general type of initial conditions for the primordial perturbations, deriving a new analytical approximation for the neutrino isocurvature modes. In the third part, I discuss the issue of extracting constraints on the parameters of interest from the recent, high-quality CMB measurements, presenting the relevant statistical tools and focusing on the Fisher matrix analysis as a technique to produce reliable forecasts for the performance of future observations. I then apply those tools to the study of several possible extensions of the (currently) standard Lambda CDM model: the presence of extra relativistic particles, possible time variations of the fine structure constant, and the value of the primordial Helium mass fraction. I also use the CMB as a tool to study the very early Universe, via its dependence on the type of initial conditions: I relax the assumption of purely adiabatic initial conditions and discuss the observational consequences and constraints on the presence of general isocurvature modes.

Roberto Trotta

2004-10-05

269

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.

Tracy Y. Hargrove

2008-01-01

270

Magnetic Anisotropy in the Radula of Chiton  

NASA Astrophysics Data System (ADS)

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

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

2000-07-01

271

Theoretical Overview of Cosmic Microwave Background Anisotropy  

E-print Network

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

E. L. Wright

2003-05-29

272

Escape from Fraction Manor: Reasoning with Fractions  

NSDL National Science Digital Library

In this interactive game, students collect cards as they journey through the maze of a house (Fraction Manor), avoiding monsters. With each level they complete, they are presented with a math puzzle: given a series of digits, arrange them into fractions in a given order. Some fractions may already be given. Puzzles increase in difficulty with each level.

2010-01-01

273

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).

Jennifer Rising

2011-01-01

274

The elastic anisotropy of marble  

E-print Network

) December 1982 ABSTRACT The Elastic Anisotropy of Marble. (December 1982) Susan Nash Gebhard, B. S. , St. Lawrence University; M. S. , Texas A8M Univeristy Chairman of Adv1sory Committee: Dr. Richard Carlson The effect of mechan1cal twinning... of the host and twinned portions of the crystals. The effect of the twins was determined by treating them as separate populat1ons with single crystal st1ffness coeff1c1ents identical to those of the host gra1ns. The aggregate elast1c constants were...

Gebhard, Susan Nash

1982-01-01

275

Equivalent Fractions Finder  

NSDL National Science Digital Library

Visually represent two unique fractions that are equivalent to a given fraction. The fractional value is shown on a number line after you check to see if your fraction is correct. Equivalent Fraction Finder is one of the Interactivate assessment explorers.

276

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.

Clipart ETC Educational Technology Clearinghouse

2010-06-29

277

Fraction Machine Tool  

NSDL National Science Digital Library

This interactive application requires students to create equivalent fractions given one fraction and either the numerator or denominator of the second fraction. Once students create their solution they compare and are shown a visual representation of their fractions. The teacher may create fractions or use the random generator.

2013-01-01

278

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

279

Random fractional Fourier transform.  

PubMed

We propose a novel random fractional Fourier transform by randomizing the transform kernel function of the conventional fractional Fourier transform. The random fractional Fourier transform inherits the excellent mathematical properties from the fractional Fourier transform and can be easily implemented in optics. As a primary application the random fractional Fourier transform can be directly used in optical image encryption and decryption. The double phase encoding image encryption schemes can thus be modeled with cascaded random fractional Fourier transformers. PMID:17671545

Liu, Zhengjun; Liu, Shutian

2007-08-01

280

Equivalent Fraction Activities  

NSDL National Science Digital Library

This web page contains four Flash applets that help students develop fraction concepts. In the three demonstrations, users can adjust the numerators and denominators of two fractions to compare them or to create two equivalent fractions, represented visually by either fraction bars or circles or by both. A game applet challenges the student to create a fraction equivalent to a given fraction and provides a check. The applets lend themselves well to classroom discussions with interactive white boards.

Mark Weddell

2003-01-01

281

Velocity anisotropy in shales: A petrophysical study  

Microsoft Academic Search

Using ultrasonic velocity and anisotropy measurements on a variety of shales with different clay and kerogen content, clay mineralogy, and porosity at a wide range of effective pressure, the authors find that elastic anisotropy of shales increases substantially with compaction. The effect is attributed to both porosity reduction and smectite-to-illite transformation with diagenesis. A means of kerogen content mapping using

Lev Vernik; X. Liu

1997-01-01

282

Uniaxial Anisotropy in Iron-Cobalt Ferrites  

Microsoft Academic Search

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

Shuichi Iida; Hisashi Sekizawa; Yoshimichi Aiyama

1958-01-01

283

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

284

Reservoir anisotropy determination with multiple probe pressures  

Microsoft Academic Search

Wireline formation testers are commonly used to produce a profile of pressure vs. depth through a reservoir by performing a series of point pressure tests during one descent in the well. A new test tool that can conduct a number of controlled pressure-interference tests between multiple probes produces a profile of permeability anisotropy vs. depth. Anisotropy, the vertical\\/horizontal permeability ratio,

E. L. Head; F. E. Bettis

1993-01-01

285

MATERIALS SCIENCE & ENGINEERING Texture, Microstructure & Anisotropy  

E-print Network

boundary distributions, along with the anisotropy associated with elastic and plastic properties; (2 microscopy. (5) The effect of texture on elastic and plastic anisotropy in polycrystals; the uniform stress of 3D information using stereology. Emphasis is placed on the use and understanding of quantitative

Rollett, Anthony D.

286

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; Björkhem, Ingemar; Sivan, Sara; Birk, Ohad S

2011-01-01

287

Corpus callosum agenesis, severe mental retardation, epilepsy, and dyskinetic quadriparesis due to a novel mutation in the homeodomain of ARX.  

PubMed

We report on a patient with agenesis of the corpus callosum (ACC), severe mental retardation, infantile spasms and subsequent intractable epilepsy, spastic/dyskinetic quadriparesis, severe limb contractures, and scoliosis. This complex, newly described phenotype, is due to a novel non-conservative missense mutation in the ARX homeodomain (c.1072A>T; p.R358W), inherited from the unaffected mother. Differently from previously reported non-conservative mutations falling within the same domain, p.R358W did not cause XLAG. It is therefore possible that differences in clinical manifestations between our patient and those with XLAG, are related to the different position of the amino acid substitution in the homeodomain, or to the different chemical properties introduced by the substitution itself. To test the hypothesis that the patient's mother was asymptomatic because of non-random X chromosome inactivation (XCI), we performed DNA methylation studies of the human androgen receptor gene, demonstrating skewing of the XCI ratio (85:15). The complex phenotype described here combines different traits that had previously been linked to various ARX mutations, including conservative missense mutations in the homeodomain and expansion in the first ARX polyalanine tract and contributes to the expanding pleiotropy associated with ARX mutations. PMID:21416597

Conti, Valerio; Marini, Carla; Gana, Simone; Sudi, Jyotsna; Dobyns, William B; Guerrini, Renzo

2011-04-01

288

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

289

[Nevoid basal cell carcinoma syndrome with corpus callosum agenesis, PTCH1 mutation and absence of basal cell carcinoma].  

PubMed

Nevoid Basal Cell Carcinoma Syndrome (NBCCS) or Gorlin-Goltz syndrome is a rare autosomal dominant disorder, mainly due to PTCH1 gene mutations, that comprises a broad spectrum of clinical manifestations. The presence of multiple basal cell carcinomas (BCCs) is a cardinal sign in NBCCS, therefore cases in which BCCs are absent entails a delay in the diagnosis.We present a 14 years old boy with a clinical diagnosis of NBCCS by the presence of odontogenic cysts, hypertelorism, macrocephaly, and corpus callosum agenesia, but with absence of skin lesions. His 43 years old mother has NBCCS diagnosis and no history of BCCs. For a deeper study, PTCH1 mutation screening from peripheral blood samples were performed by both bidirectional sequencing and multiplex ligation dependent probe amplification (MLPA) techniques. The proband and his mother carry 25 pb duplication in exon 10 (c.1375dupl25bp) that causes a reading frameshift with a premature stop codon. Bioinformatics analysis predicted that this mutation results in a truncated protein shorter than normal. Our results suggest that complete clinical and genealogical studies accompanied by genetic analysis are essential in the early detection of the NBCCS cases such the one presented here. PMID:25188659

Mazzuoccolo, Luis D; Martínez, María Florencia; Muchnik, Carolina; Azurmendi, Pablo J; Stengel, Fernando

2014-01-01

290

The influence of magnetic aftereffects on the magnetic anisotropy  

NASA Astrophysics Data System (ADS)

There were investigated the time dependences of the magnetic anisotropy characteristics of artificial depositions received in the geomagnetic field. The content of magnetite in the nonmagnetic matrix of kaolin did not exceed 1%. The Co content in the grains of magnetite Fe3 O4 was 0.0018%. The viscous magnetization was created in the depositions with grain sizes of Fe3O4 in micrometers (0 ÷ 8), (9 ÷ 16), (17 ÷ 32), (33 ÷ 64), (65 ÷ 100), (101 ÷ 150). The X-ray method of direct pole figures indicates that the intensity of the ordering of the ferromagnetic grains in the depositions depends strongly on the grain size in the above-mentioned ranges, getting reduced from 1.9 to 1.1. Compared with the characteristics received immediately after drying the samples and after holding them for two years in the earth's magnetic field in the direction of In, one could observe increase in all the characteristics of the magnetic anisotropy. The magnitude Hd of the magnetic field having the periodicity change of Hd 2? to ? increases. This indicates the stabilization of the new domain structure. The increase in the uniaxial anisotropy constant (K) is associated with the emergence of the large induced anisotropy due to the diffusion of Co ions. It was found out that the constant K decreases markedly with increasing particle size in the range from 8 mm to 40 microns. Based on the results of the X-ray analysis by using the method direct pole figures, it may be explained by the creation of the axial texture in the depositions with grains having the size less than 40 microns. The intensity of more than 40 microns decreases insignificantly - from 1.3 to 1.1. After creating the viscous magnetization in two years, the constant K has increased by 1.5 - 2 times. The influence of the magnetic after-effects on K in strong magnetic fields denotes the diffusion nature of the viscous magnetization. The losses of the rotational magnetic hysteresis (W) also rise in the presence of the structural defects and internal stresses. The value of the maximum loss (Wm) increases the more the smaller the grain size Fe3O4.The greatest influence of magnetic viscosity is exercised on the depositions having d < 40 microns. It is shown that there is a correlation between the dependence of the temporal variation of Wm and the dependence of the coefficients of the magnetic viscosity on the ferromagnetic grain size. The magnitude of the magnetic field (HW), corresponding to the maximum losses and characterizing the beginning of the transition of the spins from the connection with the crystal lattice to the connection with the external magnetic field, does not change. So, the magnetic field HW can be considered as an indicator of the composition of the ferromagnetic fraction. Depending on the composition of the ferromagnetic, value HW has a wide range of values. For the depositions, containing magnetite grains, the value of HW makes up 1.8 kOe, and for the grains of hematite it is 9 kOe. Thus, the contribution to the effective anisotropy of rocks containing large particles of the ferromagnetic fraction, can not be explained by the energy of crystallographic anisotropy. Diffusion magnetic anisotropy is a widely spread phenomenon in the rocks.

Mashukov, A.; Mashukova, A.

2012-04-01

291

Global Tomography of Seismic Anisotropy and Interpretations  

NASA Astrophysics Data System (ADS)

Seismic anisotropy, in spite of its inherent complexity is becoming an important ingredient for explaining various kinds of seismic data. Global tomographic models have been improved over years not only by an increase in the number of data but more importantly by using more general parameterizations, now including general anisotropy (both radial and azimuthal anisotropies). Different physical processes (lattice preferred orientation of crystals, cracks or fluid inclusions, fine layering...) related to strain field and/or stress field, give rise to observable seismic anisotropy (S-wave splitting, surface wave radial and azimuthal anisotropies), which makes its interpretation sometimes difficult and non-unique. Surface waves are well suited for imaging large scale (>1000km) lateral heterogeneities of velocity and anisotropy in the mantle by using fundamental and higher modes, since they provide an almost uniform lateral and azimuthal coverages, particularly below oceanic areas. The interpretation of anisotropy makes it possible to relate surface geology and plate tectonics to underlying mantle convection processes, and to map at depth the origin of geological objects such as continents, mountain ranges, slabs, ridges and plumes. Since different processes creating anisotropy are in play in different layers, a complex stratification of mantle anisotropy is observed and can be unraveled by simultaneously taking account of effects of anisotropy on body waves and surface waves. We present results of simultaneous inversion of Rayleigh and Love wave overtone data obtained by Beucler et al. (2006) and Visser et al. (2008) down to 1500km depth. New determinations of seismic anisotropy in the upper mantle and the transition zones are obtained from these higher mode phase velocity measurements. We show that seismic anisotropy is small below most of the transition zones except below subduction zones, all around the Pacific Ocean and beneath eastern Eurasia, reflecting complex past slab interactions. Since the presence of anisotropy is due to intense deformation of minerals, it is related to the existence of boundary layers in convective systems. Therefore,the transition zone seems to be a secondary boundary layer within the mantle. In conclusion, The imaging of seismic anisotropy renews our vision of mantle convection processes covering a wide range of applications for structural geologists and geophysicists.

Montagner, Jean-Paul

2013-04-01

292

On radial anisotropy limits in stellar systems  

NASA Astrophysics Data System (ADS)

Following earlier authors we re-examine the upper limits on the radial velocity anisotropy of general stellar systems; these constraints coming generically from phase-space density positivity, stability, and separability. Galaxy models almost always satisfy an inequality ? < ?/2, i.e. the radial anisotropy is locally no greater than half of the logarithmic density slope. Some complex separable models are the only known cases which disobey this inequality and do so by having an exceptionally large anisotropy at the centre. Here we present new families of non-separable but simple models which have ? > ?/2. Such large, superthreshold anisotropy always occurs in a finite region in between an isotropic core and an isotropic outer boundary. Our models are always self-consistent and hence maintain the positivity of the phase-space density. Nevertheless, regions with superthreshold anisotropy are potentially subject to secular instability and may thus be observed in a short-lived phase of galaxies.

Barber, Jeremy A.; Zhao, Hongsheng

2014-08-01

293

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

294

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

295

Indication for Primordial Anisotropies in the Neutrino Background from the Wilkinson Microwave Anisotropy Probe and the Sloan Digital Sky Survey  

NASA Astrophysics Data System (ADS)

We demonstrate that combining cosmic microwave background anisotropy measurements from the 1st year Wilkinson Microwave Anisotropy Probe observations with clustering data from the Sloan galaxy redshift survey yields an indication for primordial anisotropies in the cosmological neutrino background.

Trotta, Roberto; Melchiorri, Alessandro

2005-06-01

296

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

297

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

298

Ratcheting fluid with geometric anisotropy  

NASA Astrophysics Data System (ADS)

We investigate a mechanism that effectively transports fluids using vibrational motion imposed onto fluid boundary with anisotropy. In our experiment, two asymmetric, sawtooth-like structures are placed facing each other and form a corrugated fluid channel. This channel is then forced to open and close periodically. Under reciprocal motion, fluid fills in the gap during the expansion phase of the channel and is then forced out during contraction. Since the fluid experiences different impedances when flowing in different directions, the stagnation point that separates flows of two directions changes within each driving period. As a result, fluid is transported unidirectionally. This ratcheting effect of fluid is demonstrated through our measurements and its working principle discussed in some detail.

Thiria, Benjamin; Zhang, Jun

2015-02-01

299

Texture induced microwave background anisotropies  

SciTech Connect

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

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

1994-03-01

300

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.

National Library of Virtual Manipulatives

2009-07-29

301

Single Fraction Pointer  

NSDL National Science Digital Library

Determine the value of a given fraction represented as a point on a number line. Then find a fraction whose value is the given fraction using an arrow on the number line as a guide. Single Fraction Pointer is one of the Interactivate assessment explorers.

302

Bounded Fraction Pointer  

NSDL National Science Digital Library

Determine the value of two fractions you have chosen (which are represented as points on a number line). Then find a fraction whose value is between your two fractions (using an arrow on the number line as a guide) and determine its value. Bounded Fraction Pointer is one of the Interactivate assessment explorers.

303

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

304

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

305

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

306

Product of Simple Fractions  

NSDL National Science Digital Library

This Java applet displays the multiplication of two fractions as an overlaying of rectangular areas. The left rectangle illustrates the left fraction as a horizontal fraction bar; the right rectangle shows the right fraction as a vertical fraction bar; and the middle rectangle represents their overlay. To change the numerator or denominator of the multiplicands, click a digit slightly off-center (left to decrease, right to increase).

Interactive Math Miscellany and Puzzles, Alexander Bogomolny

2011-01-01

307

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.

Michael Green

2012-05-25

308

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

PubMed

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

Zolmajd-Haghighi, Zahra; Hanley, Quentin S

2014-04-01

309

A two-phase composite in simple shear: Effective mechanical anisotropy development and localization potential  

NASA Astrophysics Data System (ADS)

We present a combined shape and mechanical anisotropy evolution model for a two-phase inclusion-bearing rock subject to large deformation. A single elliptical inclusion embedded in a homogeneous but anisotropic matrix is used to represent a simplified shape evolution enforced on all inclusions. The mechanical anisotropy develops due to the alignment of elongated inclusions. The effective anisotropy is quantified using the differential effective medium (DEM) approach. The model can be run for any deformation path and an arbitrary viscosity ratio between the inclusion and host phase. We focus on the case of simple shear and weak inclusions. The shape evolution of the representative inclusion is largely insensitive to the anisotropy development and to parameter variations in the studied range. An initial hardening stage is observed up to a shear strain of ? = 1 irrespective of the inclusion fraction. The hardening is followed by a softening stage related to the developing anisotropy and its progressive rotation toward the shear direction. The traction needed to maintain a constant shear rate exhibits a fivefold drop at ? = 5 in the limiting case of an inviscid inclusion. Numerical simulations show that our analytical model provides a good approximation to the actual evolution of a two-phase inclusion-host composite. However, the inclusions develop complex sigmoidal shapes resulting in the formation of an S-C fabric. We attribute the observed drop in the effective normal viscosity to this structural development. We study the localization potential in a rock column bearing varying fraction of inclusions. In the inviscid inclusion case, a strain jump from ? = 3 to ? = 100 is observed for a change of the inclusion fraction from 20% to 33%.

Dabrowski, M.; Schmid, D. W.; Podladchikov, Y. Y.

2012-08-01

310

Pizza Fractions: Beginning With Simple Fractions  

NSDL National Science Digital Library

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

2013-01-15

311

Characterization of Optical Anisotropy of Chain Molecules.  

NASA Astrophysics Data System (ADS)

Molecular optical polarizability and its anisotropy in polymers and their model compounds are important properties which can be used in optical recording and storage media, optical mass memories, displays, fibers, films and rigid -rod molecular composite technology. There is a need for carefully calibrated equipment to measure the optical polarizability anisotropy and for appropriate data analysis. The objectives of this research are to study the structure-optical property relationship for polymers and their model compounds, and to identify and interpret the occurrence of the order-disorder transition in diblock copolymers. Another major focus of this experimental study is to support the simulation work on the prediction of molecular polarizability and optical anisotropy currently in progress in our laboratory. An improved depolarized Rayleigh scattering (DRS) photometer was built combining both high sensitivity and exceptional stability. High accuracy measurement of the DRS intensity is used to determine dependable measures of the optical anisotropy of solvents, melts and polymer compounds in solution. Structure-optical property relationships have been developed for polymers. Temperature dependence studies of the DRS intensity for benzene, hexafluorobenzene and carbon tetrachloride were carried out. Monotonic change in the intensity values was observed for the molecular liquids. Optical studies with bisphenol A polycarbonate and its model compounds gave quantitative information on the dependence of optical anisotropy on substitution, molecular weight and polydispersity index. Photometric studies with substituted benzene compounds showed an increase in optical anisotropy due to electronic polarization with substitution. Studies using fused benzene compounds showed that the optical anisotropy increased with increased number of fused rings. Studies with model compounds of lyotropic liquid crystalline polymers allowed prediction of trends of optical anisotropy in such polymers on a comparative basis. DRS photometry studies were also carried out to investigate the order-disorder transition (ODT) in copolymers. The ODT in polystyrene-polyisoprene diblock copolymer has been identified by a sharp change in the DRS intensity with temperature change and interpreted in terms of molecular optical anisotropy.

Sen, Sumit

312

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

NASA Astrophysics Data System (ADS)

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

Yoon, Sunghyun

2015-01-01

313

CMB Anisotropies: Their Discovery and Utilization  

E-print Network

This article is a written and modified version of a talk presented at the conference `A Century of Cosmology' held at San Servolo, Venice, Italy, in August 2007. The talk focuses on some of the cosmology history leading to the discovery and exploitation of Cosmic Microwave Background (CMB) Radiation anisotropies. We have made tremendous advances first in the development of the techniques to observe these anisotropies and in observing and interpreting them to extract their contained cosmological information. CMB anisotropies are now a cornerstone in our understanding of the cosmos and our future progress in the field. This is an outcome that Dennis Sciama hoped for and encouraged.

George F. Smoot

2008-01-16

314

Mechanical anisotropy of the Yucca Mountain tuffs  

SciTech Connect

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

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

1991-12-31

315

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

PubMed

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

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

2015-01-01

316

Postnatal cellular contributions of the hippocampus subventricular zone to the dentate gyrus, corpus callosum, fimbria, and cerebral cortex.  

PubMed

The rodent dentate gyrus (DG) is formed in the embryo when progenitor cells migrate from the dentate neuroepithelium to establish a germinal zone in the hilus and a secondary germinal matrix, near the fimbria, called the hippocampal subventricular zone (HSVZ). The developmental plasticity of progenitors within the HSVZ is not well understood. To delineate the migratory routes and fates of progenitors within this zone, we injected a replication-incompetent retrovirus, encoding the enhanced green fluorescent protein (EGFP), into the HSVZ of postnatal day 5 (P5) mice. Between P6 and P45, retrovirally-infected EGFP(+) of progenitors migrated into the DG, established a reservoir of progenitor cells, and differentiated into neurons and glia. By P6-7, EGFP(+) cells were observed migrating into the DG. Subsets of these EGFP(+) cells expressed Sox2 and Musashi-1, characteristic of neural stem cells. By P10, EGFP(+) cells assumed positions within the DG and expressed immature neuronal markers. By P20, many EGFP(+) cells expressed the homeobox prospero-like protein Prox1, an early and specific granule cell marker in the CNS, and extended mossy fiber projections into the CA3. A subset of non-neuronal EGFP(+) cells in the dentate gyrus acquired the morphology of astrocytes. Another subset included EGFP(+)/RIP(+) oligodendrocytes that migrated into the fimbria, corpus callosum, and cerebral cortex. Retroviral injections on P15 labeled very few cells, suggesting depletion of HSVZ progenitors by this age. These findings suggest that the early postnatal HSVZ progenitors are multipotent and migratory, and contribute to both dentate gyrus neurogenesis as well as forebrain gliogenesis. PMID:16786555

Navarro-Quiroga, Ivan; Hernandez-Valdes, Mariana; Lin, Stanley L; Naegele, Janice R

2006-08-10

317

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

318

Regional areas and widths of the midsagittal corpus callosum among HIV-infected patients on stable antiretroviral therapies  

PubMed Central

Recent reports suggest that a growing number of human immunodeficiency virus (HIV)-infected persons show signs of persistent cognitive impairment even in the context of combination antiretroviral therapies (cART). The basis for this finding remains poorly understood as there are only a limited number of studies examining the relationship between CNS injury, measures of disease severity, and cognitive function in the setting of stable disease. This study examined the effects of HIV infection on cerebral white matter using quantitative morphometry of the midsagittal corpus callosum (CC) in 216 chronically infected participants from the multisite HIV Neuroimaging Consortium study currently receiving cART and 139 controls. All participants underwent MRI assessment, and HIV-infected subjects also underwent measures of cognitive function and disease severity. The midsagittal slice of the CC was quantified using two semi-automated procedures. Group comparisons were accomplished using ANOVA, and the relationship between CC morphometry and clinical covariates (current CD4, nadir CD4, plasma and CSF HIV RNA, duration of HIV infection, age, and ADC stage) was assessed using linear regression models. HIV-infected patients showed significant reductions in both the area and linear widths for several regions of the CC. Significant relationships were found with ADC stage and nadir CD4 cell count, but no other clinical variables. Despite effective treatment, significant and possibly irreversible structural loss of the white matter persists in the setting of chronic HIV disease. A history of advanced immune suppression is a strong predictor of this complication and suggests that antiretroviral intervention at earlier stages of infection may be warranted. PMID:21556960

Sampat, Mehul; Harezlak, Jaroslaw; Fiecas, Mark; Hogan, Joseph; Dewey, Jeffrey; McCaffrey, Daniel; Branson, Daniel; Russell, Troy; Conley, Jared; Taylor, Michael; Schifitto, Giavoni; Zhong, J.; Daar, Eric S.; Alger, Jeffrey; Brown, Mark; Singer, Elyse; Campbell, T.; McMahon, D.; Tso, Y.; Matesan, Janetta; Letendre, Scott; Paulose, S.; Gaugh, Michelle; Tripoli, C.; Yiannoutsos, Constantine; Bigler, Erin D.; Cohen, Ronald A.; Guttmann, Charles R. G.

2014-01-01

319

Playing Fraction Tracks  

NSDL National Science Digital Library

This interactive game, similar to "Fraction Game" (catalogued separately) allows two students an opportunity to think about how fractions are related to a unit whole, compare fractional parts of a whole, and find equivalent fractions. Two players move markers a total distance (forwards and backwards directions) that equals the random target fraction box, 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 before your opponent does. Instructions and discussion questions are given.

2011-01-01

320

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.

J.C. Banfill

2007-12-12

321

Finite Difference Modeling of Attenuation and Anisotropy  

E-print Network

A nite difference scheme which includes the effects of attenuation and anisotropy is tested for seismic reflection and borehole acoustic models. The validity of the scheme is established using a 3D homogenous isotropic ...

Krasovec, Mary L.

2003-01-01

322

Seismic body-wave anisotropy beneath continents   

E-print Network

A search for the effects of anisotropy on seismic body-waves predicted by theory is described. Preliminary studies were based on long-period data from the WWSSN, HGLP and SRO networks. These showed that data from the ...

Singh, Jasbinder

1983-01-01

323

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

324

SOLARMAX/Electron Pitch Angle Anisotropy Distributions  

NASA Technical Reports Server (NTRS)

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

McKenzie, David L.; Anderson, Phillip C.

2002-01-01

325

Magnetic anisotropy due to the Casimir effect  

SciTech Connect

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

Metalidis, G.; Bruno, P. [Institut fuer Theoretische Festkoerperphysik, Karlsruhe Institut fuer Technologie (KIT), D-76131 Karlsruhe (Germany); European Synchrotron Radiation Facility, Boite Postale 220, F-38043 Grenoble Cedex (France)

2010-02-15

326

On discrete symmetries and relic radiation anisotropy  

E-print Network

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

M. V. Altaisky; N. E. Kaputkina

2014-06-17

327

Pressure anisotropy in Jupiter's magnetodisc  

NASA Astrophysics Data System (ADS)

The magnetosphere-ionosphere coupling current system at Jupiter has been studied by a number of authors over the last decade. Until recently, however, the various modelling studies treated the magnetic field as an empirically-based input derived from Voyager observations. This limitation was removed by Nichols (2011), who employed a self-consistent field model calculated using force-balance between the outward plasma pressure gradients plus the centrifugal force of the rotating iogenic plasma, and the inward JxB force arising from the azimuthal current sheet. However, the above study, which incorporated the magnetic field model of Caudal (1983), employed isotropic plasma pressure, whereas it is known that anisotropic plasma pressure plays a key role in the stress balance at Jupiter (e.g. Paranicas et al., 1991). In this paper we generalise the computation to include anisotropic pressure, and compute the magnetic field by summing over elliptical integrals. We then calculate the magnetosphere-ionosphere coupling currents assuming an equatorial parallel-to-perpendicular pressure ratio of 1.14, the value determined by Paranicas et al. (1991), and we also consider the effect on the system of solar wind-induced compression events. We find that the anisotropy current dominates the current sheet in the middle magnetosphere between 20-40RJ, and that Jupiter's magnetosphere is susceptible to the firehose instability.

Nichols, J. D.; Achilleos, N.; Cowley, S. W. H.

2013-09-01

328

Microwave Background Anisotropies from Alfven waves  

E-print Network

We investigate microwave background anisotropies in the presence of primordial magnetic fields. We show that a homogeneous field with fixed direction can amplify vector perturbations. We calculate the correlations of $\\delta T/T$ explicitly and show that a large scale coherent field induces correlations between $a_{\\ell-1,m}$ and $a_{\\ell+1,m}$. We discuss constraints on amplitude and spectrum of a primordial magnetic field imposed by observations of CMB anisotropies.

Ruth Durrer; Tina Kahniashvili; Andrew Yates

1998-07-09

329

Cosmic microwave background anisotropies in the timescape cosmology  

NASA Astrophysics Data System (ADS)

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 ???2500 to the Planck satellite data. Parameter fits include a dressed Hubble constant, H0=61.0 km sec-1 Mpc-1 (±1.3 % stat) (±8 % sys), and a present void volume fraction fv 0=0.627 (±2.3 % stat) (±13 % sys). We find best fit likelihoods which are comparable to that of the best fit ? CDM cosmology in the same multipole range. In contrast to earlier results, the parameter constraints afforded by this analysis no longer admit the possibility of a solution to the primordial lithium abundance anomaly. This issue is related to a strong constraint between the ratio of baryonic to nonbaryonic dark matter and the ratio of heights of the second and third acoustic peaks, which cannot be changed as long as the standard cosmology is assumed up to the surface of last scattering. These conclusions may change if backreaction terms are also included in the radiation-dominated primordial plasma.

Nazer, M. Ahsan; Wiltshire, David L.

2015-03-01

330

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.

Michael Green

2012-06-26

331

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.

Illuminations National Council of Teachers of Mathematics

2009-03-11

332

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 ...

Miss Perry

2007-11-29

333

Constraints on Subduction Geodynamics from Seismic Anisotropy  

NASA Astrophysics Data System (ADS)

Much progress has been made over the past several decades in delineating the structure of subducting slabs, but several key aspects of their dynamics remain poorly constrained. Major unsolved problems in subduction geodynamics include those related to mantle wedge viscosity and rheology, slab hydration and dehydration, mechanical coupling between slabs and the ambient mantle, the geometry of mantle flow above and beneath slabs, and the interactions between slabs and deep discontinuities such as the core-mantle boundary. Observations of seismic anisotropy can provide relatively direct constraints on mantle dynamics because of the link between deformation and the resulting anisotropy: when mantle rocks are deformed, a preferred orientation of individual mineral crystals or materials such as partial melt often develops, resulting in the directional dependence of seismic wave speeds. Measurements of seismic anisotropy thus represent a powerful tool for probing mantle dynamics in subduction systems. Here I review the observational constraints on seismic anisotropy in subduction zones and discuss how seismic data can place constraints on wedge, slab, and sub-slab anisotropy. I also discuss constraints from mineral physics investigations and geodynamical modeling studies and how they inform our interpretation of observations. I evaluate different models in light of constraints from seismology, geodynamics, and mineral physics. Finally, I discuss some of the major unsolved problems related to the dynamics of subduction systems and how ongoing and future work on the characterization and interpretation of seismic anisotropy can lead to progress, particularly in frontier areas such as understanding slab dynamics in the deep mantle.

Long, Maureen D.

2013-01-01

334

ANISOTROPY DETERMINATIONS IN EXCHANGE SPRING MAGNETS.  

SciTech Connect

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

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

2002-08-18

335

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

336

Visual Fractions: Home Page  

NSDL National Science Digital Library

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

Richard E. Rand

2011-01-01

337

Fractionation of palm oil  

Microsoft Academic Search

Because of its fatty acid composition, which includes 50% saturated and 50% unsaturated fatty acids, palm oil can readily\\u000a be fractionated, i.e. partially crystallized and separated into a high melting fraction or stearin and a low melting fraction\\u000a or olein.\\u000a \\u000a Three main commercial processes for fractionating palm oil are in use: the fast dry process, the slow dry process and

E. Deffense

1985-01-01

338

Fractional Abstract Cauchy Problems  

Microsoft Academic Search

This paper is concerned with fractional abstract Cauchy problems with order $${\\\\alpha\\\\in(1,2)}$$. The notion of fractional solution operator is introduced, its some properties are obtained. A generation theorem for exponentially\\u000a bounded fractional solution operators is given. It is proved that the homogeneous fractional Cauchy problem (FACP\\u000a 0) is well-posed if and only if its coefficient operator A generates an ?-order

Li Kexue; Peng Jigen

2011-01-01

339

Building Fractions Game  

NSDL National Science Digital Library

In this math lesson, learners investigate fractions by playing a game. To play, learners roll two dice and create a fraction, using the larger number rolled as the denominator and the smaller number as the numerator. Learners then build that fractional amount on the game mat with pattern block pieces. The winner is the player who builds the greatest number of hexagons.

2012-10-22

340

Fraction Model II  

NSDL National Science Digital Library

With this tool, students can explore different representations for fractions. They can create a fraction, selecting any numerator or denominator up to 20, and see a model of the fraction as well as its percent and decimal equivalents. For the model, they can choose either a circle, a rectangle, or a set model.

NCTM Illuminations

2000-01-01

341

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.

Shanna Uhe

2012-07-31

342

Comparing Fractions with Brownies  

NSDL National Science Digital Library

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

Shanna Uhe

2012-07-31

343

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

344

Fraction Compare: Beach Balls  

NSDL National Science Digital Library

In this online game students must identify which fractions fit the inequality shown. Fractions range from proper to improper fractions and from positive to negative values. Each round of the game is 30 seconds long and keeps track of student's score.

2013-01-01

345

Comparing Fractions and %  

NSDL National Science Digital Library

In this interactive simulation students are asked to compare fractions and percents using one of four visual representation options. Students can choose either the fraction or percent first and then see how many ways they can represent the equivalent in the alternate format. If an incorrect answer is given it will be visually evident and the computer will prompt is the fraction is improper.

2012-01-01

346

Fractions Dolphin Racing Game  

NSDL National Science Digital Library

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

Skillwise: English and Maths for Adults

2012-08-03

347

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.

Mark Weddell

2003-01-01

348

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 PMID:25232291

2014-01-01

349

Anisotropy of Silicate-Hosted Magnetite Inclusions  

NASA Astrophysics Data System (ADS)

Anisotropy of magnetic properties is a hallmark of silicate crystals with oriented iron-oxide inclusions. Strongly magnetic magnetite-bearing silicates (10-1 A m-1) are common components of gabbros and layered intrusions, contributing to local and regional magnetic anomalies. Additionally, these iron-oxide silicates hold the promise of being exceptional paleomagnetic recorders owing to their features of: physical/chemical isolation from altering fluids, chemical equilibrium with their silicate host, and long relaxation times (enhanced coercivity). However, anisotropy of remanence must be understood before these advantageous features can be utilized. Measurements of single crystals of clinopyroxene and plagioclase (10-4 g) show anisotropy in direction and intensity that directly reflect the crystallography of the silicate host. The host controls both the crystallographic orientation of the magnetite (magnetocrystalline anisotropy) and the elongation direction of the magnetite inclusion (shape anisotropy). We have found another source of anisotropy that involves an internal exsolution of ulvöspinel within titanomagnetite inclusions. This also reflects a host control as this second exsolution occurs along the magnetite \\{100\\}. This fixed wall shape anisotropy creates an array of interacting single domain magnetite parallelepipeds, parallel to \\{100\\}. Each of these anisotropies contributes to enhanced coercivity of remanence, which significantly exceeds the IRM saturation magnetization for magnetite (300 mT). The anisotropy of IRM (aIRM@ 1.1 T) of magnetite-bearing clinopyroxene and plagioclase shows clustering of directions, reflecting the mixture of variables that include: inclusion elongation direction and abundance, orientation of magnetite easy axes relative to the applied field, inclusion aspect ratio and diameter, and pre-existing magnetic domain structure. For pyroxene (monoclinic) with two arrays of needle-shaped magnetite inclusions, the aIRM is strongly planar, showing two sets of antipodal direction clusters. The total intensity is uniform over ˜60% of the remanence plane. The component of magnetization perpendicular to the applied IRM (transverse remanence) exceeds the parallel remanence in some crystallographic directions. For plagioclase (triclinic) with three to five arrays of needle-shaped magnetite inclusions (see Feinberg, et al. this conference), the aIRM is subspherical with numerous minor clusters of directions. Transverse remanence is less important than parallel remanence in plagioclase. Thus, the greater number of inclusion arrays in plagioclase decreases the severity of the IRM anisotropy relative to the two arrays in pyroxene.

Scott, G. R.; Feinberg, J. M.; Renne, P. R.

2004-12-01

350

Fruit Shoot Fraction Addition  

NSDL National Science Digital Library

In this interactive game users are given fractions to add and they need to identify the fraction sum by picking the correct answer that rotates around the screen. There are three levels of difficulty (adding two fractions with like denominators, adding three fractions with like denominators, or adding two fractions with unlike denominators) and for each level you can decide whether you want to do relaxed mode (ten problems, untimed) or timed mode (answer quickly and it increases your score). The goal is to get as many correct as possible.

2011-01-01

351

Coolmath.com: Fractions  

NSDL National Science Digital Library

For many elementary and middle school students, fractions are one of the most difficult topics to learn. The Fractions Web site on Coolmath.com offers seventeen lessons explaining everything from basic definitions to multiplying and dividing fractions. Color illustrations let students visualize exactly what fractions are and how they are used. For each lesson there is a thorough description, followed by numerous examples and practice problems with their solutions. This site does an excellent job of showing just how easy fractions can be and will hopefully relieve some student frustration.

352

Introducing anisotropic Minkowski functionals and quantitative anisotropy measures for local structure analysis in biomedical imaging  

NASA Astrophysics Data System (ADS)

The ability of Minkowski Functionals to characterize local structure in different biological tissue types has been demonstrated in a variety of medical image processing tasks. We introduce anisotropic Minkowski Functionals (AMFs) as a novel variant that captures the inherent anisotropy of the underlying gray-level structures. To quantify the anisotropy characterized by our approach, we further introduce a method to compute a quantitative measure motivated by a technique utilized in MR diffusion tensor imaging, namely fractional anisotropy. We showcase the applicability of our method in the research context of characterizing the local structure properties of trabecular bone micro-architecture in the proximal femur as visualized on multi-detector CT. To this end, AMFs were computed locally for each pixel of ROIs extracted from the head, neck and trochanter regions. Fractional anisotropy was then used to quantify the local anisotropy of the trabecular structures found in these ROIs and to compare its distribution in different anatomical regions. Our results suggest a significantly greater concentration of anisotropic trabecular structures in the head and neck regions when compared to the trochanter region (p < 10-4). We also evaluated the ability of such AMFs to predict bone strength in the femoral head of proximal femur specimens obtained from 50 donors. Our results suggest that such AMFs, when used in conjunction with multi-regression models, can outperform more conventional features such as BMD in predicting failure load. We conclude that such anisotropic Minkowski Functionals can capture valuable information regarding directional attributes of local structure, which may be useful in a wide scope of biomedical imaging applications.

Wismüller, Axel; De, Titas; Lochmüller, Eva; Eckstein, Felix; Nagarajan, Mahesh B.

2013-03-01

353

Anisotropies in the cosmic neutrino background after Wilkinson Microwave Anisotropy Probe five-year data  

SciTech Connect

We search for the presence of cosmological neutrino background (CNB) anisotropies in recent Wilkinson Microwave Anisotropy Probe (WMAP) five-year data using their signature imprinted on modifications to the cosmic microwave background (CMB) anisotropy power spectrum. By parameterizing the neutrino background anisotropies with the speed viscosity parameter c{sub vis}, we find that the WMAP five-year data alone provide only a weak indication for CNB anisotropies with c{sub vis}{sup 2}>0.06 at the 95% confidence level. When we combine CMB anisotropy data with measurements of galaxy clustering, the SN-Ia Hubble diagram, and other cosmological information, the detection increases to c{sub vis}{sup 2}>0.16 at the same 95% confidence level. Future data from Planck, combined with a weak lensing survey such as the one expected with DUNE from space, will be able to measure the CNB anisotropy parameter at about 10% accuracy. We discuss the degeneracy between neutrino background anisotropies and other cosmological parameters such as the number of effective neutrinos species and the dark energy equation of state.

De Bernardis, Francesco; Pagano, Luca; Melchiorri, Alessandro [Physics Department and Sezione INFN, University of Rome 'La Sapienza', Piazzale Aldo Moro 2, 00185 Rome (Italy)] [Physics Department and Sezione INFN, University of Rome 'La Sapienza', Piazzale Aldo Moro 2, 00185 Rome (Italy); Serra, Paolo; Cooray, Asantha, E-mail: francesco.debernardis@roma1.infn.it, E-mail: luca.pagano@roma1.infn.it, E-mail: pserra@uci.edu, E-mail: alessandro.melchiorri@roma1.infn.it, E-mail: acooray@uci.edu [Department of Physics and Astronomy, University of California Irvine, Irvine, CA 92697-4575 (United States)] [Department of Physics and Astronomy, University of California Irvine, Irvine, CA 92697-4575 (United States)

2008-06-15

354

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

355

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

356

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

357

The expected anisotropy in solid inflation  

NASA Astrophysics Data System (ADS)

Solid inflation is an effective field theory of inflation in which isotropy and homogeneity are accomplished via a specific combination of anisotropic sources (three scalar fields that individually break isotropy). This results in specific observational signatures that are not found in standard models of inflation: a non-trivial angular dependence for the squeezed bispectrum, and a possibly long period of anisotropic inflation (to drive inflation, the ``solid'' must be very insensitive to any deformation, and thus background anisotropies are very slowly erased). In this paper we compute the expected level of statistical anisotropy in the power spectrum of the curvature perturbations of this model. To do so, we account for the classical background values of the three scalar fields that are generated on large (superhorizon) scales during inflation via a random walk sum, as the perturbation modes leave the horizon. Such an anisotropy is unavoidably generated, even starting from perfectly isotropic classical initial conditions. The expected level of anisotropy is related to the duration of inflation and to the amplitude of the squeezed bispectrum. If this amplitude is close to its current observational limit (so that one of the most interesting predictions of the model can be observed in the near future), we find that a level of statistical anisotropy F2 gives frozen and scale invariant vector perturbations on superhorizon scales.

Bartolo, Nicola; Peloso, Marco; Ricciardone, Angelo; Unal, Caner

2014-11-01

358

Decimals, Fractions & Percentages  

NSDL National Science Digital Library

Students learn about and practice converting between fractions, decimals and percentages. Using a LEGO® MINDSTORMS® NXT robot and a touch sensor, each group inputs a fraction of its choosing. Team members convert this same fraction into a decimal, and then a percentage via hand calculations, and double check their work using the NXT robot. Then they observe the robot moving forward and record that distance. Students learn that the distance moved is a fraction of the full distance, based on the fraction that they input, so if they input ½, the robot moves half of the original distance. From this, students work backwards to compute the full distance. Groups then compete in a game in which they are challenged to move the robot as close as possible to a target distance by inputting a fraction into the NXT bot.

AMPS GK-12 Program,

359

Bounded Fraction Finder  

NSDL National Science Digital Library

In this activity, students highlight segments of a square or circle equal to two different fractions then use those areas to visualize the difference between the two fractions. This activity allows students to explore the relationship between the value of fractions and areas within a square or circle. 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

360

Pie Chart with Fractions  

NSDL National Science Digital Library

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

S. M. Blinder

2012-01-01

361

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 ...

Mrs. Alman

2008-03-26

362

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

363

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

364

Fractional Diffusion Equations  

Microsoft Academic Search

\\u000a The Riemann-Liouville fractional integrals and derivatives. There exist many definitions of fractional derivatives and integrals,\\u000a which are meaningful for different classes of functions, inspired by various applications etc. See [202] for a general survey\\u000a and a detailed exposition of many aspects of the fractional calculus. Here we touch only a few of them necessary for the sequel.\\u000a For the proofs

Samuil D. Eidelman; Anatoly N. Kochubei; Stepan D. Ivasyshen

365

Anisotropy of Spin Relaxation in Metals  

NASA Astrophysics Data System (ADS)

The concept of anisotropy of spin relaxation in nonmagnetic metals with respect to the spin direction of the injected electrons relative to the crystal orientation is introduced. The effect is related to an anisotropy of the Elliott-Yafet parameter, arising from a modulation of the decomposition of the spin-orbit Hamiltonian into spin-conserving and spin-flip terms as the spin quantization axis is varied. This anisotropy, reaching gigantic values for uniaxial transition metals (e.g., 830% for hcp Hf) as density-functional calculations show, is related to extended “spin-flip hot areas” on the Fermi surface created by the proximity of extended sheets of the surface, or “spin-flip hot loops” at the Brillouin zone boundary, and has no theoretical upper limit. Possible ways of measuring the effect as well as consequences in application are briefly outlined.

Zimmermann, Bernd; Mavropoulos, Phivos; Heers, Swantje; Long, Nguyen H.; Blügel, Stefan; Mokrousov, Yuriy

2012-12-01

366

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

367

COSMIC-RAY TRANSPORT AND ANISOTROPIES  

SciTech Connect

We show that the large-scale cosmic-ray anisotropy at {approx}10 TeV can be explained by a modified Compton-Getting effect in the magnetized flow field of old supernova remnants. Cosmic rays arrive isotropically to the flow field and are then carried along with the flow to produce a large-scale anisotropy in the arrival direction. This approach suggests an optimum energy scale for detecting the anisotropy. Two key assumptions are that propagation is based on turbulence following a Kolmogorov law and that cosmic-ray interactions are dominated by transport via cosmic-ray-excited magnetic irregularities through the stellar wind of an exploding star and its shock shell. A prediction is that the amplitude is smaller at lower energies due to incomplete sampling of the velocity field and also smaller at larger energies due to smearing.

Biermann, Peter L. [MPI for Radioastronomy, Auf dem Huegel 69, D-53121 Bonn (Germany); Becker Tjus, Julia; Mandelartz, Matthias [Ruhr-Universitaet Bochum, Fakultaet fuer Physik and Astronomie, Theoretische Physik I, D-44780 Bochum (Germany); Seo, Eun-Suk [Department of Physics, University of Maryland, College Park, MD 20742 (United States)

2013-05-10

368

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

369

Anisotropy of the cosmic microwave background radiation  

NASA Technical Reports Server (NTRS)

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

Silk, J.

1981-01-01

370

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

371

The Ellipsoidal Area Ratio (EAR): An Alternative Anisotropy Index for Diffusion Tensor Imaging  

PubMed Central

In the processing and analysis of Diffusion Tensor Imaging (DTI) data, certain predefined morphological features of diffusion tensors are often represented as simplified scalar indices, termed Diffusion Anisotropy Indices (DAIs). When comparing tensor morphologies across differing voxels of an image, or across corresponding voxels in different images, DAIs are mathematically and statistically more tractable than are the full tensors, which are probabilistic ellipsoids consisting of 3 orthogonal vectors that each has a direction and an associated scalar magnitude. We have developed a new DAI, the “Ellipsoidal Area Ratio” (EAR), to represent the degree of anisotropy in the morphological features of a diffusion tensor. The EAR is a normalized geometrical measure of surface curvature in the 3D diffusion ellipsoid. Monte Carlo simulations and applications to the study of in vivo human data demonstrate that, at low noise levels, EAR provides a similar contrast-to-noise ratio (CNR) but a higher signal-to-noise ratio (SNR) than does fractional anisotropy (FA), which is currently the most popular anisotropy index in active use. Moreover, at the high noise levels encountered most commonly in real-world DTI datasets, EAR compared with FA is consistently much more robust to perturbations from noise and it provides a higher CNR, features useful for the analysis of DTI data that are inherently noise-sensitive. PMID:18835122

Xu, Dongrong; Cui, Jiali; Bansal, Ravi; Hao, Xuejun; Liu, Jun; Peterson, Bradley S.

2012-01-01

372

Continued Fractions Cor Kraaikamp  

E-print Network

continued fractions . . . . . . . . . . . . . . . 26 2 Planetaria 35 2.1 Huygens's Planetarium . . . . . . . . . . . . . . . . . . . . . . 36 2.2 Eisinga's Planetarium . . . . . . . . . . . . . . . . . . . . . . 36 2.3 Mathematical Issues

Bosma, Wieb

373

Hydraulic Conductivity Anisotropy of Heterogeneous Unsaturated Soils  

NASA Astrophysics Data System (ADS)

The effects of saturation degree (or capillary pressure) on hydraulic conductivity anisotropy in unsaturated soils have not been fully understood. This study developed an approach based on a conceptualization of combining the neural network based pedo-transfer function (PTF) results with the thin layer concept to explore the capillary pressure-dependent anisotropy in relation to soil texture and soil bulk density. The main objective is to examine how anisotropy characteristics are related to the relationships between hydraulic parameters and the basic soil attributes such as texture and bulk density. The hydraulic parameters are correlated with the texture and bulk density based on the pedo-transfer function (PTF) results. It is demonstrated that non-monotonic behavior of the unsaturated soil anisotropy in relation to the capillary pressure is only observed when the saturated hydraulic conductivity and the shape parameter are both related to the mean particle diameter. When only one hydraulic parameter is related to the grain diameter or when both are not related to the same attribute simultaneously, the unsaturated soil anisotropy increases monotonically with the increasing capillary pressure head. Therefore, it is suggested that this behavior is mainly due to the coupled dependence of the layer saturated hydraulic conductivities and the shape factors on the texture and bulk density. The correlation between the soil grain diameter and bulk density decreases the anisotropy effects of the unsaturated layered soils. The study illustrates that the inter-relationships of soil texture, bulk density, and hydraulic properties may cause vastly different characteristics of anisotropic unsaturated soils.

Sun, Dongmin; Zhu, Jianting

2010-05-01

374

The Damping Tail of CMB Anisotropies  

E-print Network

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

Wayne Hu; Martin White

1996-09-10

375

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

376

Anisotropy Effects on Microseismic Event Location  

NASA Astrophysics Data System (ADS)

Seismic anisotropy in sedimentary environments is significant—microseismic waveforms often show strong shear-wave splitting, with differences reaching 40% between horizontally and vertically-polarized shear-wave velocities. Failure to account for this anisotropy is shown to result in large microseismic event location errors. A method is presented here for determining the five elastic parameters of a homogeneous, vertical transverse-isotropic (VTI) model from calibration shot data. The method can also use data from mining-induced seismic events, which are then simultaneously located. This simple model provides a good fit to arrival times from coal-environment data, and results in dramatic shifts in interpreted event locations.

King, Andrew; Talebi, Shahriar

2007-12-01

377

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.

Natalya Vinogradova

378

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

379

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

380

(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

381

Everyday Mathematics Equivalent Fractions  

NSDL National Science Digital Library

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

2011-02-03

382

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.

NCTM Illuminations

2000-01-01

383

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

384

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

385

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

386

Fractions and Decimals  

ERIC Educational Resources Information Center

Investigating the relationship between fractions and their equivalent decimal representations helps clarify to students that both representations stand for a single (rational) number on the number line. Since students are taught to perform computations with fractions and also to compute with decimals, performing these computations side-by-side…

Pagni, David

2004-01-01

387

Change Fractions into Decimals  

NSDL National Science Digital Library

This five-minute video presents two algorithms for converting a fraction into decimal form. After a brief discussion of decimal place value, the first method, changing a fraction to an equivalent number of tenths or hundredths, is shown. Next, the division of numerator by the denominator is demonstrated.

2011-01-01

388

The Future of Fractions  

ERIC Educational Resources Information Center

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

Usiskin, Zalman P.

2007-01-01

389

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

390

CMB anisotropies caused by gravitational waves: A parameter study  

E-print Network

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

Durrer, Ruth

391

Identify fractions in multiple ways  

NSDL National Science Digital Library

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

Mrs. Marsh

2006-10-27

392

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

393

Fractional Dissipative Standard Map  

E-print Network

Using kicked differential equations of motion with derivatives of noninteger orders, we obtain generalizations of the dissipative standard map. The main property of these generalized maps, which are called fractional maps, is long-term memory.The memory effect in the fractional maps means that their present state of evolution depends on all past states with special forms of weights. Already a small deviation of the order of derivative from the integer value corresponding to the regular dissipative standard map (small memory effects) leads to the qualitatively new behavior of the corresponding attractors. The fractional dissipative standard maps are used to demonstrate a new type of fractional attractors in the wide range of the fractional orders of derivatives.

Vasily E. Tarasov; Mark Edelman

2011-07-27

394

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

DOE PAGESBeta

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

395

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

396

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

397

Differences in white matter architecture between musicians and non-musicians: a diffusion tensor imaging study  

Microsoft Academic Search

Previous studies found structural brain differences between musicians and non-musicians. In order to determine possible differences in white matter architecture, diffusion tensor imaging was performed on five adult subjects with musical training since early childhood, and seven adult controls. The musicians displayed significantly greater fractional anisotropy (FA) in the genu of the corpus callosum, while significantly less FA was found

Vincent J. Schmithorst; Marko Wilke

2002-01-01

398

Single crystal articles having reduced anisotropy  

SciTech Connect

This paper describes a method of modifying the nickel base superalloy composition Ni-5Co-10Cr-4W-5Al-1.5Ti-12Ta such that single crystal castings made therefrom have reduced anisotropy. It comprises: adding an effective amount of hafnium to the alloy composition.

Shah, D.M.; Duhl, D.N.

1990-04-10

399

Relative sensitivity of formability to anisotropy  

SciTech Connect

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

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

1997-01-01

400

Cosmic microwave anisotropies from BPS semilocal strings  

Microsoft Academic Search

We present the first ever calculation of cosmic microwave background (CMB) anisotropy power spectra from semilocal cosmic strings, obtained via simulations of a classical field theory. Semilocal strings are a type of non-topological defect arising in some models of inflation motivated by fundamental physics, and are thought to relax the constraints on the symmetry breaking scale as compared to models

Jon Urrestilla; Neil Bevis; Mark Hindmarsh; Martin Kunz; Andrew R. Liddle

2008-01-01

401

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

402

Toward Understanding CMB Anisotropies and Their Implications  

E-print Network

Working toward a model independent understanding of cosmic microwave background (CMB) anisotropies and their significance, we undertake a comprehensive and self-contained study of scalar perturbation theory. Initial conditions, evolution, thermal history, matter content, background dynamics, and geometry all play a role in determining the anisotropy. By employing {\\it analytic} techniques to illuminate the numerical results, we are able to separate and identify each contribution. We thus bring out the nature of the {\\it total} Sachs-Wolfe effect, acoustic oscillations, diffusion damping, Doppler shifts, and reionization, as well as their particular manifestation in a critical, curvature, or cosmological constant dominated universe. By studying the full angular {\\it and} spatial content of the resultant anisotropies, we isolate the signature of these effects from the dependence on initial conditions. Whereas structure in the Sachs-Wolfe anisotropy depends strongly on the underlying power spectra, the acoustic oscillations provide features which are nearly model independent. This may allow for future determination of the matter content of the universe as well as the adiabatic and/or isocurvature nature of the initial fluctuations.

Wayne Hu; Naoshi Sugiyama

1994-11-01

403

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

404

Variable Azimuthal Anisotropy in Earth's Lowermost Mantle  

E-print Network

in the Dµ layer. The Dµ layer is located at the base of Earth_s silicate lower mantle, where it meets the liquid iron outer core. The Dµ layer plays a critical role in Earth_s dynamical evolution because it actsVariable Azimuthal Anisotropy in Earth's Lowermost Mantle Edward J. Garnero,1 * Vale´rie Maupin,2

Garnero, Ed

405

Anisotropies in Ultrahigh Energy Cosmic Rays  

E-print Network

The present status of anisotropy studies for the highest energy cosmic rays is presented including the first full sky survey. Directions and prospects for the future are also discussed in light of new statistical methods and the last quantities of data expected in the near future from the Pierre Auger Observatory.

John Swain

2004-01-30

406

Anisotropy universe in doubly warped product scheme  

E-print Network

We study the GMGHS spacetimes to analyze the evolution of the anisotropy universe, which can be treated as a doubly warped products manifold possessing warping functions (or scale factor) having the Kantowski-Sachs solution which represents homogeneous but anisotropically expanding(contracting) cosmology. We investigate the curvature associated with three phases in the evolution of the universe.

Jaedong Choi

2014-08-10

407

Local Anisotropy In Globally Isotropic Granular Packings  

E-print Network

Local Anisotropy In Globally Isotropic Granular Packings Kamran Karimi Craig E Maloney #12;Granular Moduli 17 C( 1 , 2 , 3 ) K C12 C13 C21 1 C23 C31 C32 2 : Bulk Modulus 1, 2: Shear Moduli max min C ( 1,C

Gruner, Daniel S.

408

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

409

Micro-Computed Tomography Derived Anisotropy Detects Tumor Provoked Deviations in Bone in an Orthotopic Osteosarcoma Murine Model  

PubMed Central

Radiographic imaging plays a crucial role in the diagnosis of osteosarcoma. Currently, computed-tomography (CT) is used to measure tumor-induced osteolysis as a marker for tumor growth by monitoring the bone fractional volume. As most tumors primarily induce osteolysis, lower bone fractional volume has been found to correlate with tumor aggressiveness. However, osteosarcoma is an exception as it induces osteolysis and produces mineralized osteoid simultaneously. Given that competent bone is highly anisotropic (systematic variance in its architectural order renders its physical properties dependent on direction of load) and that tumor induced osteolysis and osteogenesis are structurally disorganized relative to competent bone, we hypothesized that ?CT-derived measures of anisotropy could be used to qualitatively and quantitatively detect osteosarcoma provoked deviations in bone, both osteolysis and osteogenesis, in vivo. We tested this hypothesis in a murine model of osteosarcoma cells orthotopically injected into the tibia. We demonstrate that, in addition to bone fractional volume, ?CT-derived measure of anisotropy is a complete and accurate method to monitor osteosarcoma-induced osteolysis. Additionally, we found that unlike bone fractional volume, anisotropy could also detect tumor-induced osteogenesis. These findings suggest that monitoring tumor-induced changes in the structural property isotropy of the invaded bone may represent a novel means of diagnosing primary and metastatic bone tumors. PMID:24892952

Ichikawa, Jiro; Nyman, Jeffry S.; Cates, Justin M. M.; Haro, Hirotaka; Schwartz, Herbert S.; Schoenecker, Jonathan G.

2014-01-01

410

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

411

Magnetoelastic Nature of the Dodecagonal Anisotropy in Holmium Metal  

Microsoft Academic Search

We have investigated the magnetoelastic nature of the dodecagonal anisotropy in the magnetic anisotropy energy (MAE) in the basal plane of the hcp crystalline structure in holmium single crystal. We have proved that the origin of the second harmonic of the hexagonal symmetry in MAE clearly lies on a sixth-order magnetoelastic coupling term. The appearance of a 12-fold anisotropy in

L. Benito; M. Ciria; A. Fraile; D. Fort; J. S. Abell; J. I. Arnaudas

2007-01-01

412

Anisotropy of Arrival Directions of Ultrahigh Energy Cosmic Rays  

E-print Network

Anisotropy of Arrival Directions of Ultrahigh Energy Cosmic Rays Chad Barrett Finley Submitted;ABSTRACT Anisotropy of Arrival Directions of Ultrahigh Energy Cosmic Rays Chad Barrett Finley This thesis investigates the origins of ultrahigh energy cosmic rays by searching for evidence of small-scale anisotropy

413

Cosmic Microwave Background Anisotropies Wayne Hu1,2,3  

E-print Network

1 Cosmic Microwave Background Anisotropies Wayne Hu1,2,3 and Scott Dodelson2,3 1 Center microwave background (CMB) temperature anisotropies have and will continue to revolutionize our . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 1 INTRODUCTION The field of cosmic microwave background (CMB) anisotropies has dramatically

Hu, Wayne

414

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

415

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

E-print Network

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

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

2014-01-01

416

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

PubMed Central

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

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

2012-01-01

417

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

418

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.

2010-07-14

419

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 Bogomolny

2011-01-01

420

Plagioclase preferred orientation and induced seismic anisotropy in mafic igneous rocks  

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

421

Indication for primordial anisotropies in the neutrino background from the Wilkinson microwave anisotropy probe and the Sloan digital sky survey.  

PubMed

We demonstrate that combining cosmic microwave background anisotropy measurements from the 1st year Wilkinson Microwave Anisotropy Probe observations with clustering data from the Sloan galaxy redshift survey yields an indication for primordial anisotropies in the cosmological neutrino background. PMID:16090604

Trotta, Roberto; Melchiorri, Alessandro

2005-07-01

422

Anisotropies of partial anhysteretic remanence and susceptibility in compacted black shales: Grainsize- and composition-dependent magnetic fabric  

NASA Astrophysics Data System (ADS)

We have quantified the magnetic fabric of the highly-compacted Heebner Shale (Pennsylvanian) of Kansas in terms of the anisotropies of partial anhysteretic remanent magnetization (pARM) and low-field susceptibility. Hysteresis loops exhibit almost purely paramagnetic behavior, and the ratio of high-field linear susceptibility to low-field susceptibility is very close to one; the susceptibility anisotropy therefore reflects the fabric of the paramagnetic matrix, while the remanent anisotropies are due to the preferred orientations of ferrimagnetic grains. Both the paramagnetic and ferrimagnetic fabrics are dominated by a horizontal foliation, with a weak northeasterly lineation, but the pARM anisotropies are generally much larger than the susceptibility anisotropy. The degree of foliation measured with pARM's decreases markedly with increasing coercivities, indicating stronger foliation in the coarser grainsize fraction. In contrast, the pARM mean lineations are grainsize-independent, suggesting a post-compactional origin, related to tectonic compression. The susceptibility lineation appears to have a slightly different azimuth, and may therefore be due to paleocurrents.

Jackson, Mike; Sprowl, Don; Ellwood, Brooks

423

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

424

Intracellular Cadmium Isotope Fractionation  

NASA Astrophysics Data System (ADS)

Recent stable isotope studies into the biological utilization of transition metals (e.g. Cu, Fe, Zn, Cd) suggest several stepwise cellular processes can fractionate isotopes in both culture and nature. However, the determination of fractionation factors is often unsatisfactory, as significant variability can exist - even between different organisms with the same cellular functions. Thus, it has not been possible to adequately understand the source and mechanisms of metal isotopic fractionation. In order to address this problem, we investigated the biological fractionation of Cd isotopes within genetically-modified bacteria (E. coli). There is currently only one known biological use or requirement of Cd, a Cd/Zn carbonic anhydrase (CdCA, from the marine diatom T. weissfloggii), which we introduce into the E. coli genome. We have also developed a cleaning procedure that allows for the treating of bacteria so as to study the isotopic composition of different cellular components. We find that whole cells always exhibit a preference for uptake of the lighter isotopes of Cd. Notably, whole cells appear to have a similar Cd isotopic composition regardless of the expression of CdCA within the E. coli. However, isotopic fractionation can occur within the genetically modified E. coli during Cd use, such that Cd bound in CdCA can display a distinct isotopic composition compared to the cell as a whole. Thus, the externally observed fractionation is independent of the internal uses of Cd, with the largest Cd isotope fractionation occurring during cross-membrane transport. A general implication of these experiments is that trace metal isotopic fractionation most likely reflects metal transport into biological cells (either actively or passively), rather than relating to expression of specific physiological function and genetic expression of different metalloenzymes.

Horner, T. J.; Lee, R. B.; Henderson, G. M.; Rickaby, R. E.

2011-12-01

425

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.

Colleen King

2013-07-19

426

Fraction Model I  

NSDL National Science Digital Library

Explore different representations for fractions. This applet allows students to create a fraction,then see it as a visual model, and as percent and decimal equivalents. They can choose the model to be a circle, a rectangle, or a set model. Intended for the young learner, this version restricts the numerator to values from 0 to 20, and the denominator to benchmark values of 1, 2, 4, 5, 8, 10 and 20.

NCTM Illuminations

2000-01-01

427

Thermodynamics in Fractional Calculus  

NASA Astrophysics Data System (ADS)

A generalization of thermodynamics in the formalism of fractional-order derivatives is given. Results of the traditional thermodynamics of Carnot, Clausius, and Helmholtz are obtained in the particular case where the exponent of a fractional-order derivative is equal to unity. A one-parametric "fractal" equation of state is obtained with account of the second virial coefficient. The application of the resulting equation of state in the case of the gas argon is considered.

Meilanov, R. P.; Magomedov, R. A.

2014-11-01

428

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.

2011-05-24

429

Fractional-Parabolic Systems  

Microsoft Academic Search

We develop a theory of the Cauchy problem for linear evolution systems of partial differential equations with the Caputo-Dzhrbashyan\\u000a fractional derivative in the time variable t. The class of systems considered in the paper is a fractional extension of the class of systems of the first order in t satisfying the uniform strong parabolicity condition. We construct and investigate the

Anatoly N. Kochubei

430

Magnetic anisotropy of epitaxial Cu/Ni/Cu nanolines  

NASA Astrophysics Data System (ADS)

Continuous nickel films grown pseudoepitaxially between copper layers have been shown to have strong perpendicular magnetic anisotropy due to large magnetoelastic and interface magnetocrystalline anisotropy energies. These Cu/Ni/Cu films with tNi=6.9 nm have been patterned into lines approximately 200 nm wide using interferometric lithography and ion milling. Torque magnetometer measurements show the anisotropy of the nanolines to be significantly different from that of the continuous films. The magnetoelastic anisotropy (favoring perpendicular magnetization) decreases in the patterned films due to strain relaxation at the line edges. Although the anisotropy change for this line width is most likely due to shape anisotropy, we anticipate observation of magnetoelastic anisotropy due to strain relief at the edges of the lines at narrower line widths in future work.

Lyons, E. S.; O'Handley, R. C.; Ross, C. A.

2004-06-01

431

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).

Illuminations National Council of Teachers of Math

2009-03-17

432

A discrete fractional random transform  

E-print Network

We propose a discrete fractional random transform based on a generalization of the discrete fractional Fourier transform with an intrinsic randomness. Such discrete fractional random transform inheres excellent mathematical properties of the fractional Fourier transform along with some fantastic features of its own. As a primary application, the discrete fractional random transform has been used for image encryption and decryption.

Zhengjun Liu; Haifa Zhao; Shutian Liu

2006-05-20

433

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

434

Fractional extreme value adaptive training method: fractional steepest descent approach.  

PubMed

The application of fractional calculus to signal processing and adaptive learning is an emerging area of research. A novel fractional adaptive learning approach that utilizes fractional calculus is presented in this paper. In particular, a fractional steepest descent approach is proposed. A fractional quadratic energy norm is studied, and the stability and convergence of our proposed method are analyzed in detail. The fractional steepest descent approach is implemented numerically and its stability is analyzed experimentally. PMID:25314711

Pu, Yi-Fei; Zhou, Ji-Liu; Zhang, Yi; Zhang, Ni; Huang, Guo; Siarry, Patrick

2015-04-01

435

soil organic matter fractionation  

NASA Astrophysics Data System (ADS)

Carbon is essential for plant growth, due to its effects on other soil properties like aggregation. Knowledge of dynamics of organic matter in different locations in the soil matrix can provide valuable information which affects carbon sequestration and soil the other soil properties. Extraction of soil organic matter (SOM) fractions has been a long standing approach to elucidating the roles of soil organic matter in soil processes. Several kind fractionation methods are used and all provide information on soil organic matter function. Physical fractionation capture the effects on SOM dynamics of the spatial arrangement of primary and secondary organomineral particles in soil while chemical fractionation can not consider the spatial arrangement but their organic fractions are suitable for advanced chemical characterization. Three method of physical separation of soil have been used, sieving, sedimentation and densitometry. The distribution of organic matter within physical fractions of the soil can be assessed by sieving. Sieving separates soil particles based strictly on size. The study area is located on north central Iran, between 35° 41'- 36° 01' N and 50° 42'- 51° 14' E. Mean annual precipitation about 243.8 mm and mean annual air temperature is about 14.95 °C. The soil moisture and temperature regime vary between aridic-thermic in lower altitudes to xeric-mesic in upper altitudes. More than 36 surface soil samples (0-20 cm) were collected according to land-use map units. After preliminary analyzing of samples 10 samples were selected for further analyses in five size fractions and three different time intervals in September, January and April 2008. Fractionation carried out by dry sieving in five classes, 1-2 mm, 0.5-1 mm, 270 ?m-0.5mm, 53-270 ?m and <53 ?m. Organic matter and C/N ratio were determined for all fractions at different time intervals. Chemical fractionation of organic matter also carried out according to Tan (2003), also Mineralogical studies were carried out to illustrate the relationship between clay mineral series and organic matter. According to the results the amount of organic carbon increases by decreasing size fractions and reaches to its maximum in <250? classes, also 2:1 and expanding clays which have the ability to maintain larger amounts of organic carbon were the dominant clay minerals. Chemical fractionation of soil organic matter to humic acid and fulvic acid shows that there is a better correlation between humic acid contents and soil organic matter (R2 = 0.86) than fulvic acid and organic matter (R2=0.5). The amount of humic and fulvic acids varies in different size fractions and reaches to its minimum in the E fraction in all three stages. The relationships between fulvic and humic acids with organic matter content, demonstrating that at the lower organic matter content, humification is slow, thus humic acid content is rather low than the fulvic acid content. By increasing the organic matter content biological activity increases and followed by humification process proceeds so that the humic acid content locates over the fulvic acid content.

Osat, Maryam; Heidari, Ahmad

2010-05-01

436

The Cosmic Microwave Background Anisotropy Experiments  

E-print Network

This paper reports a summary of the contents contents of six hours of lectures on the CMB anisotropy experiments given at the Strasbourg NATO school on the CMB and cosmology. (Its companion paper, astro-ph/9705101 reports the lectures on the CMB spectrum.) A context is set as a bridge from the theoretical CMB anisotropy lectures and the experimental situation. The COBE DMR results are reveiwed in detail and as pioneer for future space missions. Current and planned experiments are discussed in preference to reviewing already completed observations. The NASA MidEX mission MAP is discussed in some detail including figures. The ESA M3 mission Max Planck Surveyor is also reviewed in some detail though its final configuration is not yet fully settled. The recent history and current versions are presented. Tables and references for experiments are included.

George F. Smoot

1997-05-19

437

Cosmic microwave background anisotropies: Nonlinear dynamics  

E-print Network

We develop a new approach to local nonlinear effects in cosmic microwave background anisotropies, and discuss the qualitative features of these effects. New couplings of the baryonic velocity to radiation multipoles are found, arising from nonlinear Thomson scattering effects. We also find a new nonlinear shear effect on small angular scales. The full set of evolution and constraint equations is derived, including the nonlinear generalizations of the radiation multipole hierarchy, and of the dynamics of multi-fluids. These equations govern radiation anisotropies in any inhomogeneous spacetime, but their main application is to second-order effects in a universe that is close to the Friedmann models. Qualitative analysis is given here, and quantitative calculations are taken up in further papers.

Roy Maartens; Tim Gebbie; George Ellis

1999-02-18

438

Induced electronic anisotropy in bismuth thin films  

SciTech Connect

We use magneto-resistance measurements to investigate the effect of texturing in polycrystalline bismuth thin films. Electrical current in bismuth films with texturing such that all grains are oriented with the trigonal axis normal to the film plane is found to flow in an isotropic manner. By contrast, bismuth films with no texture such that not all grains have the same crystallographic orientation exhibit anisotropic current flow, giving rise to preferential current flow pathways in each grain depending on its orientation. Extraction of the mobility and the phase coherence length in both types of films indicates that carrier scattering is not responsible for the observed anisotropic conduction. Evidence from control experiments on antimony thin films suggests that the anisotropy is a result of bismuth's large electron effective mass anisotropy.

Liao, Albert D., E-mail: aliao@mit.edu [Research Laboratory of Electronics, MIT, Cambridge, Massachusetts 02139 (United States); Yao, Mengliang; Opeil, Cyril [Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467 (United States); Katmis, Ferhat; Moodera, Jagadeesh S. [Department of Physics, MIT, Cambridge, Massachusetts 02139 (United States); Li, Mingda [Department of Nuclear Science and Engineering, MIT, Cambridge, Massachusetts 02139 (United States); Tang, Shuang [Department of Materials Science and Engineering, MIT, Cambridge, Massachusetts 02139 (United States); Dresselhaus, Mildred S. [Research Laboratory of Electronics, MIT, Cambridge, Massachusetts 02139 (United States); Department of Physics, MIT, Cambridge, Massachusetts 02139 (United States)

2014-08-11

439

CMB Anisotropies in the Weak Coupling Limit  

E-print Network

We present a new, more powerful and accurate, analytic treatment of cosmic microwave background (CMB) anisotropies in the weakly coupled regime. Three applications are presented: gravitational redshifts in a time dependent potential, the Doppler effect in reionized scenarios, and the Vishniac effect. The Vishniac effect can dominate primary anisotropies at small angles even in late and minimally reionized models in flat dark-matter dominated universes with Harrison-Zel'dovich initial conditions. The techniques developed here refine previous calculations yielding a larger coherence angle for the Vishniac effect and moreover can be applied to non-trivial ionization histories. These analytic expressions may be used to modify results for the standard cold dark matter model to its cosmological constant and reionized extensions without detailed and time consuming recalculation.

Wayne Hu; Martin White

1995-07-14

440

Cosmic-ray streaming and anisotropies  

NASA Technical Reports Server (NTRS)

The paper is concerned with the differential current densities and anisotropies that exist in the interplanetary cosmic-ray gas, and in particular with a correct formulation and simple interpretation of the momentum equation that describes these on a local basis. Two examples of the use of this equation in the interpretation of previous data are given. It is demonstrated that in interplanetary space, the electric-field drifts and convective flow parallel to the magnetic field of cosmic-ray particles combine as a simple convective flow with the solar wind, and that there exist diffusive currents and transverse gradient drift currents. Thus direct reference to the interplanetary electric-field drifts is eliminated, and the study of steady-state and transient cosmic-ray anisotropies is both more systematic and simpler.

Forman, M. A.; Gleeson, L. J.

1975-01-01

441

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

442

Microstructure anisotropy in polyolefin flexible foams  

NASA Astrophysics Data System (ADS)

The use of polyolefin flexible foams with typical thicknesses between 1 and 3 mm produced by a physical foaming extrusion process is nowadays quite widespread in the packaging sector. Their high flexibility and closed-cell structure allows them to show good energy absorption properties under low loading conditions. Although the compressive response of these materials is well known, the inner microstructure developed during processing induce a high anisotropy that is responsible for their direction-dependent tensile and fracture behaviours. In this work, two different polyolefin-based foams, with densities ranging from 20 to 45 kg/m3, were studied. The induced microstructure anisotropy was characterized by micro-Raman. With this technique, the relative orientations of both crystalline and amorphous phases in the foam's base polymer could be determined and thus related to their mechanical properties measured in the different directions.

Antunes, M.; Arencón, D.; Realinho, V.; Velasco, J. I.

2009-09-01

443

Elastic anisotropy of bone and dentitional tissues.  

PubMed

The calculation of the scalar compressive and shear anisotropy factors developed for single crystal refractory compounds has been adapted to the anisotropic elastic stiffness coefficients determined by a number of ultrasonic measurements of bone based on transverse isotropic symmetry. Later, this work was extended to include the ultrasonic measurements of bone based on orthotropic symmetry. Recently, the five transverse isotropic elastic constants for both wet and dry human dentin were determined using resonant ultrasound spectroscopy. The five transverse isotropic elastic constants for wet bovine enamel and dentin had been calculated based on modeling of ultrasonic wave propagation measurements and related data in the literature. The scalar compressive and shear anisotropy factors have been calculated from both these sets of data and are compared with a representative set from those published previously for both human and bovine bone and both fluoro- and hydroxyl-apatites. PMID:16167108

Katz, J Lawrence; Kinney, John H; Spencer, Paulette; Wang, Yong; Fricke, Brian; Walker, Mary P; Friis, Elizabeth A

2005-09-01

444

Physics of the cosmic microwave background anisotropy  

E-print Network

Observations of the cosmic microwave background (CMB), especially of its frequency spectrum and its anisotropies, both in temperature and in polarization, have played a key role in the development of modern cosmology and our understanding of the very early universe. We review the underlying physics of the CMB and how the primordial temperature and polarization anisotropies were imprinted. Possibilities for distinguishing competing cosmological models are emphasized. The current status of CMB experiments and experimental techniques with an emphasis toward future observations, particularly in polarization, is reviewed. The physics of foreground emissions, especially of polarized dust, is discussed in detail, since this area is likely to become crucial for measurements of the B modes of the CMB polarization at ever greater sensitivity.

Bucher, Martin

2015-01-01

445

Physics of the cosmic microwave background anisotropy  

NASA Astrophysics Data System (ADS)

Observations of the cosmic microwave background (CMB), especially of its frequency spectrum and its anisotropies, both in temperature and in polarization, have played a key role in the development of modern cosmology and of our understanding of the very early universe. We review the underlying physics of the CMB and how the primordial temperature and polarization anisotropies were imprinted. Possibilities for distinguishing competing cosmological models are emphasized. The current status of CMB experiments and experimental techniques with an emphasis toward future observations, particularly in polarization, is reviewed. The physics of foreground emissions, especially of polarized dust, is discussed in detail, since this area is likely to become crucial for measurements of the B modes of the CMB polarization at ever greater sensitivity.

Bucher, Martin

2015-01-01

446

Pn anisotropy in Mesozoic western Pacific lithosphere  

NASA Astrophysics Data System (ADS)

Pn 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

447

Inner-Core Anisotropy and Rotation  

Microsoft Academic Search

his paper reviews recent research focused on the Earth's inner core. Large inner-core traveltime anomalies and the anomalous splitting of core-sensitive free oscillations strongly suggest that the inner core is anisotropic. Initial models involved a simple, constant or depth-dependent cylindrical anisotropy at a level less than a few percent. Recent observations suggest that its eastern hemisphere is largely isotropic, whereas

Jeroen Tromp

2001-01-01

448

Interferometric Observation of Cosmic Microwave Background Anisotropies  

Microsoft Academic Search

We present a formalism for analyzing interferometric observations of Cosmic\\u000aMicrowave Background (CMB) anisotropy and polarization data. The formalism is\\u000abased upon the ell-space expansion of the angular power spectrum favoured in\\u000arecent years. Explicit discussions of maximum likelihood analysis, power\\u000aspectrum reconstruction, parameter estimation, imaging and polarization are\\u000agiven. As an example, several calculations for the Degree Angular Scale

Martin White; John E. Carlstrom; Mark Dragovan; William L. Holzapfel

1997-01-01

449

The physics of microwave background anisotropies  

Microsoft Academic Search

The residual radiation from the Big Bang is observable as the cosmic microwave background-a near-uniform sea of photons with an average temperature of 2.7 K. Small variations in the temperature of the microwave background reflect the conditions that prevailed in the early Universe. Analysis of the physical mechanisms by which these anisotropies formed shows how they may be used to

Wayne Hu; Naoshi Sugiyama; Joseph Silk

1997-01-01

450

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

451

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

NASA Astrophysics Data System (ADS)

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

Linden, Tim; Profumo, Stefano

2013-07-01

452

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

453

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

454

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

455

Fluorescence Anisotropy Studies of Molecularly Imprinted Polymers  

SciTech Connect

A molecularly imprinted polymer (MIP) is a biomimetic material that can be used as a biochemical sensing element. We studied the steady-state and time-resolved fluorescence and fluorescence anisotropy of anthracene imprinted polyurethane. We compared MIPs with imprinted analytes present, MIPs with the imprinted analytes extracted, MIPs with rebound analytes, non-imprinted control polymers (non-MIPs), and non-MIPs bound with analytes to understand MIP’s binding behavior. MIPs and non-MIPs had similar steady-state fluorescence anisotropy in the range of 0.11–0.24. Anthracene rebound in MIPs and non-MIPs had a fluorescence lifetime _=0.64 ns and a rotational correlation time _F =1.2–1.5 ns, both of which were shorter than that of MIPs with imprinted analytes present (_=2.03 ns and _F =2.7 ns). The steady-state anisotropy of polymer solutions increased exponentially with polymerization time and might be used to characterize the polymerization extent in-situ.

Chen, Yin-Chu; Wang, Zheming; Yan, Mingdi; Prahl, Scott A.

2006-01-01

456

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

457

Microstructure and Elastic Anisotropy of Shales  

NASA Astrophysics Data System (ADS)

Shales compose large parts of sedimentary basins and form the seal and source rocks for many hydrocarbon reservoirs. An understanding of their properties is critically important for seismic imaging, particularly due to the high anisotropy that is caused by the alignment of clay minerals during compaction and diagenesis. In this study we quantify composition and crystal preferred orientation of component minerals of a range of shales, using high energy synchrotron X-rays. From diffraction images we can infer composition and texture (relying on the Rietveld method), and from tomography we can determine 3D microstructures, including porosity. Averaging single crystal properties over orientation distributions provides estimates of polycrystal elastic properties. A comparison of shallow shales from Montana, the North Sea and Nigeria with deep shales from the Middle East and Central Europe documents that anisotropy increases with increasing phyllosilicates content (mainly illite and kaolinite) and increasing burial. The crystallite preferred orientation strengths, measured as (001) pole figure maxima, range for illite from 2.3 to 9.8 multiples of random distribution (m.r.d.) and for kaolinite from 1.2 to 9.3 m.r.d. P-wave anisotropies, obtained by averaging over the orientation distributions of mineral phases have been calculated (Vp = (200*Vpmax-Vpmin)/(Vpmax+Vpmin) and range between 10% and 40%.

Kanitpanyacharoen, W.; Wenk, H.; Kets, F.; Mokso, R.

2009-12-01

458

The Nature versus Nurture of Anisotropies  

E-print Network

With the rapidly growing number of cosmic microwave background measurements on various scales, there is real hope that the number of acceptable models for structure formation will be limited to a very few in the near future. Yet any given model can always be saved by introducing and tuning extraneous free parameters. To better understand this question of ``nature versus nurture'' for temperature fluctuations, it is useful to know not only the general features of anisotropy predictions but also their causes. Extracting the physical content of our other works, we present here a {\\it simple} account of cosmic microwave background anisotropies on all scales. In particular, we show that analytic approximations can trace the structure of the so-called ``Doppler peaks,'' which arise due to the {\\it adiabatic} oscillations in the photon-baryon fluid. We also show how the finite thickness of the last scattering surface and the Silk damping mechanism can be described in a unified way by photon diffusion. In order to present a specific example, we focus on comparing the primordial isocurvature baryon (PIB) model with the standard cold dark matter model (CDM). In particular, we explain why PIB generically predicts larger {\\it non}-oscillatory anisotropies from the 1$^\\circ$ to 10$^\\circ$ scale which may already be in conflict with experiments.

Wayne Hu

1994-06-28

459

Equivalency Detectives: Fractions and Decimals!  

NSDL National Science Digital Library

This is a lesson intended to reinforce students' ability to find equivalent fractions and decimals. The lesson requires prior essential vocabulary knowledge, and a basic understanding of converting fractions to decimals and decimals to fractions (specifically tenths and hundredths).

Maribel Magdaleno

2012-07-17

460

Neurobiology of Disease More Is Not Always Better: Increased Fractional Anisotropy  

E-print Network

Longitudinal Fasciculus Associated with Poor Visuospatial Abilities in Williams Syndrome Fumiko Hoeft,1 Naama in the dorsal and ventral streams among individuals with Williams syndrome in visuospatial construction deficits in WS. Key words: Williams syndrome; visuospatial construction; superior

Bellugi, Ursula