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1

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

2

Fractional anisotropy in individuals with schizophrenia and their nonpsychotic siblings.  

PubMed

Fractional anisotropy (FA) was examined in a priori selected fiber tracts in individuals with schizophrenia (n=25) and their non-psychotic siblings (n=29) versus controls (n=35). FA was reduced in a portion of the fornix in individuals with schizophrenia (although this did not survive correction for the number of tracts investigated). FA in the siblings did not differ from that in controls in any of the investigated tracts. PMID:25453989

Harms, Michael P; Akhter, Kazi D; Csernansky, John G; Mori, Susumu; Barch, Deanna M

2015-01-30

3

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

4

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

5

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

6

Evidence for fractional anisotropy and mean diffusivity white matter abnormalities in the internal capsule and cingulum in patients with obsessive–compulsive disorder  

PubMed Central

Background There is evidence to suggest that obsessive–compulsive disorder (OCD) is associated with structural abnormalities in cortico–striato–thalamic circuits, yet the extent of white matter abnormalities is not well established. In this study, we used diffusion tensor imaging (DTI) to examine white matter integrity in specific regions of interest (ROIs) in patients with OCD. Methods Patients with OCD and sex-, age- and IQ-matched healthy controls underwent DTI. The primary objective was to explore whether patients with OCD had white matter abnormalities in the anterior limb of the internal capsule (ALIC), the uncinate fasciculus, the genu of the corpus callosum and the cingulum. The secondary objective was to evaluate the relation between fractional anisotropy and mean diffusivity in these ROIs and other clinical variables (including age at onset of OCD, OCD severity and levels of depressive and anxiety symptomatology) in patients with OCD. Results There were 15 patients and 17 controls enrolled in our study. Compared with healthy controls, patients with OCD showed increased fractional anisotropy in bilateral regions of the ALIC adjacent to the body of the caudate, as well as decreased fractional anisotropy in the right anterior limb near the head of the caudate. Patients also had decreased mean diffusivity in the body of the right cingulum and the left anterior cingulum compared with controls. Correlational analyses revealed significant associations of fractional anisotropy and mean diffusivity in select circuits with OCD, depression and anxiety severity scores. Limitations Inclusion of patients with OCD receiving pharmacotherapy may have been a limitation. In addition, the patients were heterogeneous in terms of their obsessive–compulsive symptom profiles; we did not distinguish between different obsessive–compulsive symptom dimensions. Conclusion The study results provide further evidence for OCD-related white matter abnormalities in the ALIC and cingulum, consistent with a corticostriatal model of OCD. PMID:22297066

Lochner, Christine; Fouché, Jean-Paul; du Plessis, Stefan; Spottiswoode, Bruce; Seedat, Soraya; (Psych), MMed; Fineberg, Naomi; Chamberlain, Samuel R.; Stein, Dan J.

2012-01-01

7

Abnormal White Matter Integrity in the Corpus Callosum among Smokers: Tract-Based Spatial Statistics  

PubMed Central

In the present study, we aimed to investigate the difference in white matter between smokers and nonsmokers. In addition, we examined relationships between white matter integrity and nicotine dependence parameters in smoking subjects. Nineteen male smokers were enrolled in this study. Eighteen age-matched non-smokers with no current or past psychiatric history were included as controls. Diffusion tensor imaging scans were performed, and the analysis was conducted using a tract-based special statistics approach. Compared with nonsmokers, smokers exhibited a significant decrease in fractional anisotropy (FA) throughout the whole corpus callosum. There were no significant differences in radial diffusivity or axial diffusivity between the two groups. There was a significant negative correlation between FA in the whole corpus callosum and the amount of tobacco use (cigarettes/day; R?=?? 0.580, p?=?0.023). These results suggest that the corpus callosum may be one of the key areas influenced by chronic smoking. PMID:24516568

Umene-Nakano, Wakako; Yoshimura, Reiji; Kakeda, Shingo; Watanabe, Keita; Hayashi, Kenji; Nishimura, Joji; Takahashi, Hidehiko; Moriya, Junji; Ide, Satoru; Ueda, Issei; Hori, Hikaru; Ikenouchi-Sugita, Atsuko; Katsuki, Asuka; Atake, Kiyokazu; Abe, Osamu; Korogi, Yukunori; Nakamura, Jun

2014-01-01

8

Cingulate and Temporal Lobe Fractional Anisotropy in Schizotypal Personality Disorder  

PubMed Central

Background Consistent with the clinical picture of milder symptomatology in schizotypal personality disorder (SPD) than schizophrenia, morphological studies indicate SPD abnormalities in temporal lobe regions but to a much lesser extent in prefrontal regions implicated in schizophrenia. Lower fractional anisotropy (FA), a measure of white-matter integrity within prefrontal, temporal, and cingulate regions has been reported in schizophrenia but has been little studied in SPD. Aims To examine temporal and prefrontal FA in 30 neuroleptic-naïve SPD patients and 35 matched healthy controls. We hypothesized that compared with healthy controls (HCs), SPD patients would exhibit lower FA in temporal and anterior cingulum regions but relative sparing in prefrontal regions. Method We acquired diffusion tensor imaging (DTI) in all participants and examined FA in the white matter underlying Brodmann areas (BAs) in dorsolateral prefrontal (BA44,45,46), temporal (BA22,21,20), and cingulum (BA25,24,31,23,29) regions using multivariate-ANOVAs. Results Compared with healthy controls, the SPD group had significantly lower FA in left temporal but not prefrontal regions. In the cingulum, FA was lower in the SPD group in posterior regions (BA31 and 23), higher in anterior (BA25) regions and lower overall in the right but not left cingulum. Among the SPD group, lower FA in the cingulum was associated with more severe negative symptoms (e.g., odd speech). Conclusions Similar to schizophrenia, our results indicate cingulum-temporal lobe FA abnormalities in SPD and suggest that cingulum abnormalities are associated with negative symptoms. PMID:21223999

Hazlett, Erin A.; Goldstein, Kim E.; Tajima-Pozo, Kazuhiro; Speidel, Elizabeth R.; Zelmanova, Yuliya; Entis, Jonathan J.; Silverman, Jeremy M.; New, Antonia S.; Koenigsberg, Harold W.; Haznedar, M. Mehmet; Byne, William; Siever, Larry J.

2012-01-01

9

Quantitative Cortical Mapping of Fractional Anisotropy in Developing Rat Brains  

PubMed Central

Cortical development is associated with a series of events that involve axon and dendrite growth and synaptic formation. Although these developmental processes have been investigated in detail with histology, three-dimensional and quantitative imaging methods for rodent brains may be useful for genetic and pharmacological studies in which cortical developmental abnormalities are suspected. It has been shown that diffusion tensor imaging (DTI) can delineate the columnar organization of the fetal and early neonatal cortex based on a high degree of diffusion anisotropy along the columnar structures. This anisotropy is known to decrease during brain development. In this study, we applied DTI to developing rat brains at five developmental stages, postnatal days 0, 3, 7, 11 and 19, and used diffusion anisotropy as an index to characterize the structural change. Statistical analysis reveals four distinctive cortical areas that demonstrate a characteristic time course of anisotropy loss. This method may provide a means to delineate specific cortical areas and a quantitative method to detect abnormalities in cortical development in rodent pathological models. PMID:18256263

Huang, Hao; Yamamoto, Akria; Hossain, Mir Ahamed; Younes, Laurent; Mori, Susumu

2010-01-01

10

Interleukin-6, Age, and Corpus Callosum Integrity  

PubMed Central

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

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

2014-01-01

11

White Matter Integrity Measured by Fractional Anisotropy Correlates Poorly with Actual Individual Fiber Anisotropy  

E-print Network

angular and radial resolutions, such as the high angular resolution diffusion imaging (HARDI) or diffusion), a very widely used measure of fiber integrity based on diffusion tensor imaging (DTI), is a problematic each voxel, each fiber's anisotropy, and partial volume effects from neighboring gray matter. High

Thompson, Paul

12

Segmented corpus callosum diffusivity correlates with the Expanded Disability Status Scale score in the early stages of relapsing-remitting multiple sclerosis  

PubMed Central

OBJECTIVE: The aim of this study was to characterize the microscopic damage to the corpus callosum in relapsing-remitting multiple sclerosis (RRMS) with diffusion tensor imaging and to investigate the correlation of this damage with disability. The diffusion tensor imaging parameters of fractional anisotropy and mean diffusivity provide information about the integrity of cell membranes, offering two more specific indices, namely the axial and radial diffusivities, which are useful for discriminating axon loss from demyelination. METHOD: Brain magnetic resonance imaging exams of 30 relapsing-remitting multiple sclerosis patients and 30 age- and sex-matched healthy controls were acquired in a 3T scanner. The axial diffusivities, radial diffusivities, fractional anisotropy, and mean diffusivity of five segments of the corpus callosum, correlated to the Expanded Disability Status Scale score, were obtained. RESULTS: All corpus callosum segments showed increased radial diffusivities and mean diffusivity, as well as decreased fractional anisotropy, in the relapsing-remitting multiple sclerosis group. The axial diffusivity was increased in the posterior midbody and splenium. The Expanded Disability Status Scale scores correlated more strongly with axial diffusivities and mean diffusivity, with an isolated correlation with radial diffusivities in the posterior midbody of the corpus callosum. There was no significant correlation with lesion loads. CONCLUSION: Neurological dysfunction in relapsing-remitting multiple sclerosis can be influenced by commissural disconnection, and the diffusion indices of diffusion tensor imaging are potential biomarkers of disability that can be assessed during follow-up. PMID:24037007

de Medeiros Rimkus, Carolina; de Faria Junqueira, Thiago; Callegaro, Dagoberto; Otaduy, Maria Concepción García; da Costa Leite, Claudia

2013-01-01

13

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

E-print Network

. High angular resolution diffusion imaging (HARDI) addresses this problem by applying more than 6Fiber Demixing with the Tensor Distribution Function avoids errors in Fractional Anisotropy maps of Neuro Imaging, Dept. of Neurology, UCLA School of Medicine, Los Angeles, CA, USA 2 Department

Thompson, Paul

14

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

15

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

PubMed

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

2014-02-01

16

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

PubMed Central

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

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

2013-01-01

17

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

18

Organising white matter in a brain without corpus callosum fibres.  

PubMed

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

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

2014-09-11

19

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

NASA Astrophysics Data System (ADS)

A class of non-local viscoelastic equations of motion including equations of fractional order with respect to the spatial variables is studied. It is shown that space-fractional equations of motion of an order strictly less than 2 allow for a new kind of anisotropy, associated with azimuthal dependence of non-local interactions between stress and strain at different material points. Constitutive equations of such viscoelastic media are determined. Relaxation effects are additionally accounted for by replacing second-order time derivatives by lower-order fractional derivatives. Explicit fundamental solutions of the Cauchy problem for scalar equations with isotropic and anisotropic non-locality are constructed. For some particular choices of the parameters, numerical solutions are constructed.

Hanyga, A.; Seredy?ska, M.

2012-05-01

20

Apparent Diffusion Coefficient, Fractional Anisotropy and T2 Relaxation Time Measurement  

Microsoft Academic Search

Background:  Quantification of apparent diffusion coefficient (ADC), fractional anisotropy (FA), and T2 relaxation time are increasingly\\u000a important for neuroradiologic applications. A transfer of the values established for 1.5-T to 3-T MRI must be supported by\\u000a a dedicated comparison with special emphasis on possible differences in the spatial distribution.\\u000a \\u000a \\u000a \\u000a Material and Methods:  In the present study, brain scans were carried out in 16

Xiao-Qi Ding; Jürgen Finsterbusch; Oliver Wittkugel; Christian Saager; Einar Goebell; Thies Fitting; Ulrich Grzyska; Hermann Zeumer; Jens Fiehler

2007-01-01

21

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

22

The relationship between early life stress and microstructural integrity of the corpus callosum in a non-clinical population  

PubMed Central

Background Previous studies have examined the impact of early life stress (ELS) on the gross morphometry of brain regions, including the corpus callosum. However, studies have not examined the relationship between ELS and the microstructural integrity of the brain. Methods In the present study we evaluated this relationship in healthy non-clinical participants using diffusion tensor imaging (DTI) and self-reported history of ELS. Results Regression analyses revealed significant reductions in fractional anisotropy (FA) within the genu of the corpus callosum among those exposed to the greatest number of early life stressors, suggesting reduced microstructural integrity associated with increased ELS. These effects were most pronounced in the genu of the corpus callosum compared to the body and splenium, and were evident for females rather than males despite no differences in total ELS exposure between the sexes. In addition, a further comparison of those participants who were exposed to no ELS vs. three or more ELS events revealed lower FA in the genu of the corpus callosum among the ELS-exposed group, with trends of FA reduction in the body and the whole corpus callosum. By contrast, there were no relationships between ELS and volumetric analysis of the CC regions. The two group did not differ significantly on measures of current depression, stress or anxiety. Conclusion Our results reveal that greater exposure to ELS is associated with microstructural alterations in the white matter in the absence of significant volumetric changes. Importantly, our results indicate that exposure to ELS is associated with abnormalities on DTI despite the absence of clinically significant psychiatric symptoms. Future studies are needed to determine whether specific types of ELS are more likely to impact brain structure and function. PMID:18728817

Paul, Robert; Henry, Lorrie; Grieve, Stuart M; Guilmette, Thomas J; Niaura, Raymond; Bryant, Richard; Bruce, Steven; Williams, Leanne M; Richard, Clark C; Cohen, Ronald A; Gordon, Evian

2008-01-01

23

Case Series: Fractional Anisotropy Along the Trajectory of Selected White Matter Tracts in Adolescents Born Preterm With Ventricular Dilation  

PubMed Central

This case series assesses white matter microstructure in 3 adolescents born preterm with nonshunted ventricular dilation secondary to intraventricular hemorrhage. Subjects (ages 12–17 years, gestational age 26–29 weeks, birth weight 825–1624 g) were compared to 3 full-term controls (13–17 years, 39–40 weeks, 3147–3345 g) and 3 adolescents born preterm without ventricular dilatation (10–13 years, 26–29 weeks, 630–1673 g). Tractography using a 2 region of interest method reconstructed the following white matter tracts: superior longitudinal/arcuate fasciculus, inferior longitudinal fasciculus, inferior fronto-occipital fasciculus, uncinate fasciculus, and corticospinal tract. Subjects showed increased fractional anisotropy and changes in the pattern of fractional anisotropy along the trajectory of tracts adjacent to the lateral ventricles. Tensor shape at areas of increased fractional anisotropy demonstrated increased linear anisotropy at the expense of planar and spherical anisotropy. These findings suggest increased axonal packing density and straightening of fibers secondary to ventricular enlargement. PMID:22859695

Myall, Nathaniel J.; Yeom, Kristen W.; Yeatman, Jason D.; Gaman-Bean, Shayna; Feldman, Heidi M.

2014-01-01

24

Beyond fractional anisotropy: extraction of bundle-specific structural metrics from crossing fiber models.  

PubMed

Diffusion MRI (dMRI) measurements are used for inferring the microstructural properties of white matter and to reconstruct fiber pathways. Very often voxels contain complex fiber configurations comprising multiple bundles, rendering the simple diffusion tensor model unsuitable. Multi-compartment models deliver a convenient parameterization of the underlying complex fiber architecture, but pose challenges for fitting and model selection. Spherical deconvolution, in contrast, very economically produces a fiber orientation density function (fODF) without any explicit model assumptions. Since, however, the fODF is represented by spherical harmonics, a direct interpretation of the model parameters is impossible. Based on the fact that the fODF can often be interpreted as superposition of multiple peaks, each associated to one relatively coherent fiber population (bundle), we offer a solution that seeks to combine the advantages of both approaches: first the fiber configuration is modeled as fODF represented by spherical harmonics and then each of the peaks is parameterized separately in order to characterize the underlying bundle. In this work, the fODF peaks are approximated by Bingham distributions, capturing first and second-order statistics of the fiber orientations, from which we derive metrics for the parametric quantification of fiber bundles. We propose meaningful relationships between these measures and the underlying microstructural properties. We focus on metrics derived directly from properties of the Bingham distribution, such as peak length, peak direction, peak spread, integral over the peak, as well as a metric derived from the comparison of the largest peaks, which probes the complexity of the underlying microstructure. We compare these metrics to the conventionally used fractional anisotropy (FA) and show how they may help to increase the specificity of the characterization of microstructural properties. While metrics relying on the first moments of the Bingham distributions provide relatively robust results, second-order metrics representing the peak spread are only meaningful, if the SNR is very high and no fiber crossings are present in the voxel. PMID:24936681

Riffert, Till W; Schreiber, Jan; Anwander, Alfred; Knösche, Thomas R

2014-10-15

25

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

PubMed Central

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

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

2013-01-01

26

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

PubMed Central

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

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

2014-01-01

27

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

28

Reduced fractional anisotropy in the visual limbic pathway of young adults witnessing domestic violence in childhood.  

PubMed

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 years) but were not physically or sexually abused were compared to 27 healthy controls (19F/8M, 21.9 ± 1.97 years) 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 and 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

2012-01-16

29

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

30

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

PubMed Central

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

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

2009-01-01

31

Connectivity and the corpus callosum in autism spectrum conditions  

Microsoft Academic Search

Neural models of autism spectrum disorders (ASDs) have moved, in recent years, from a lesion model to a focus on abnormal connectivity. In this chapter, we review this work and summarize findings from our recent research comparing autism and agenesis of the corpus callosum (AgCC). We discuss our findings in the context of the “fractionable triad” account and highlight three

Rhonda Booth; Gregory L. Wallace; Francesca Happé

2011-01-01

32

COMPARISON OF FRACTIONAL AND GEODESIC ANISOTROPY IN DIFFUSION TENSOR IMAGES OF 90 MONOZYGOTIC AND DIZYGOTIC TWINS  

E-print Network

. FA is generally reduced in diseases that affect fiber integrity (e.g., Alzheimer's disease), and may connectivity and composition in the healthy and diseased brain. Simple scalar measures, derived from be used to map disease effects on white matter. A related scalar measure, the Geodesic Anisotropy (GA) [3

Thompson, Paul

33

Bimanual motor deficits in older adults predicted by diffusion tensor imaging metrics of corpus callosum subregions.  

PubMed

Age-related changes in the microstructural organization of the corpus callosum (CC) may explain declines in bimanual motor performance associated with normal aging. We used diffusion tensor imaging in young (n = 33) and older (n = 33) adults to investigate the microstructural organization of seven specific CC subregions (prefrontal, premotor, primary motor, primary sensory, parietal, temporal and occipital). A set of bimanual tasks was used to assess various aspects of bimanual motor functioning: the Purdue Pegboard test, simultaneous and alternating finger tapping, a choice reaction time test and a complex visuomotor tracking task. The older adults showed age-related deficits on all measures of bimanual motor performance. Correlation analyses within the older group showed that white matter fractional anisotropy of the CC occipital region was associated with bimanual fine manipulation skills (Purdue Pegboard test), whereas better performance on the other bimanual tasks was related to higher fractional anisotropy in the more anterior premotor, primary motor and primary sensory CC subregions. Such associations were less prominent in the younger group. Our findings suggest that structural alterations of subregional callosal fibers may account for bimanual motor declines in normal aging. PMID:24158531

Serbruyns, L; Gooijers, J; Caeyenberghs, K; Meesen, R L; Cuypers, K; Sisti, H M; Leemans, A; Swinnen, Stephan P

2015-01-01

34

Instrument specific use-dependent plasticity shapes the anatomical properties of the corpus callosum: a comparison between musicians and non-musicians  

PubMed Central

Long-term musical expertise has been shown to be associated with a number of functional and structural brain changes, making it an attractive model for investigating use-dependent plasticity in humans. Physiological interhemispheric inhibition (IHI) as examined by transcranial magnetic stimulation has been shown to be correlated with anatomical properties of the corpus callosum as indexed by fractional anisotropy (FA). However, whether or not IHI or the relationship between IHI and FA in the corpus callosum can be modified by different musical training regimes remains largely unknown. We investigated this question in musicians with different requirements for bimanual finger movements (piano and string players) and non-expert controls. IHI values were generally higher in musicians, but differed significantly from non-musicians only in string players. IHI was correlated with FA in the posterior midbody of the corpus callosum across all participants. Interestingly, subsequent analyses revealed that this relationship may indeed be modulated by different musical training regimes. Crucially, while string players had greater IHI than non-musicians and showed a positive structure-function relationship, the amount of IHI in pianists was comparable to that of non-musicians and there was no significant structure-function relationship. Our findings indicate instrument specific use-dependent plasticity in both functional (IHI) and structural (FA) connectivity of motor related brain regions in musicians. PMID:25076879

Vollmann, Henning; Ragert, Patrick; Conde, Virginia; Villringer, Arno; Classen, Joseph; Witte, Otto W.; Steele, Christopher J.

2014-01-01

35

Oculomotor-corpus callosum dysplasia.  

PubMed Central

An infant with congenital bilateral ophthalmoplegia with levator and pupillary sparing is presented. The eyes are fixed in a divergent position with no apparent motility. The baby is otherwise clinically normal and is developing in a normal fashion except for delayed growth pattern. Visual attention is present and he fixates with either eye. Computed tomography demonstrates an associated dysplasia of the corpus callosum and an abnormal ventricular system. Neuroendocrine studies performed at one year of age demonstrate subnormal levels of growth hormone. It is postulated that this represents an embryodysgenesis involving the developing mesencephalic tegmentum (oculomotor nuclei) and the diencephalic lamina reuniens (corpus callosum). It is the first reported case of congenital ophthalmoplegia with corpus callosum dysplasia. The "embryodysgenic" relationship with other forebrain-ocular anomalies has been alluded to and remains speculative. Images FIGURE 1 FIGURE 2 A FIGURE 2 B PMID:7182958

Acers, T E; Blackwell, C

1982-01-01

36

Genetics of Microstructure of the Corpus Callosum in Older Adults  

PubMed Central

The current study sought to examine the relative influence of genetic and environmental factors on corpus callosum (CC) microstructure in a community sample of older adult twins. Analyses were undertaken in 284 healthy older twins (66% female; 79 MZ and 63 DZ pairs) from the Older Australian Twins Study. The average age of the sample was 69.82 (SD?=?4.76) years. Brain imaging scans were collected and DTI measures were estimated for the whole CC as well as its five subregions. Parcellation of the CC was performed using Analyze. In addition, white matter lesion (WMLs) burden was estimated. Heritability and genetic correlation analyses were undertaken using the SOLAR software package. Age, sex, scanner, handedness and blood pressure were considered as covariates. Heritability (h2) analysis for the DTI metrics of whole CC, indicated significant h2 for fractional anisotropy (FA) (h2?=?0.56; p?=?2.89×10?10), mean diffusivity (MD) (h2?=?0.52; p?=?0.30×10?6), radial diffusivity (RD) (h2?=?0.49; p?=?0.2×10?6) and axial diffusivity (AD) (h2?=?0.37; p?=?8.15×10?5). We also performed bivariate genetic correlation analyses between (i) whole CC DTI measures and (ii) whole CC DTI measures with total brain WML burden. Across the DTI measures for the whole CC, MD and RD shared 84% of the common genetic variance, followed by MD- AD (77%), FA - RD (52%), RD - AD (37%) and FA – MD (11%). For total WMLs, significant genetic correlations indicated that there was 19% shared common genetic variance with whole CC MD, followed by CC RD (17%), CC AD (16%) and CC FA (5%). Our findings suggest that the CC microstructure is under moderate genetic control. There was also evidence of shared genetic factors between the CC DTI measures. In contrast, there was less shared genetic variance between WMLs and the CC DTI metrics, suggesting fewer common genetic variants. PMID:25514436

Kanchibhotla, Sri C.; Mather, Karen A.; Thalamuthu, Anbupalam; Zhuang, Lin; Schofield, Peter R.; Kwok, John B. J.; Ames, David; Wright, Margaret J.; Trollor, Julian N.; Wen, Wei; Sachdev, Perminder S.

2014-01-01

37

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

38

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 ...

Lerdahl, Miss

2011-02-01

39

Corpus Callosum Volume and Neurocognition in Autism  

ERIC Educational Resources Information Center

The corpus callosum has recently been considered as an index of interhemispheric connectivity. This study applied a novel volumetric method to examine the size of the corpus callosum in 32 individuals with autism and 34 age-, gender- and IQ-matched controls and to investigate the relationship between this structure and cognitive measures linked to…

Keary, Christopher J.; Minshew, Nancy J.; Bansal, Rahul; Goradia, Dhruman; Fedorov, Serguei; Keshavan, Matcheri S.; Hardan, Antonio Y.

2009-01-01

40

Diffusion Tensor MRI of the Corpus Callosum in Amyotrophic Lateral Sclerosis  

PubMed Central

Purpose To determine if decline in corpus callosum (CC) white matter integrity in patients with amyotrophic lateral sclerosis (ALS) is localized to motor-related areas. Materials and Methods Twenty-one ALS patients and 21 controls participated. Diffusion tensor images (DTI) were acquired using 3 Tesla (T) MRI. Tract-based spatial statistics were used to examine whole-brain white matter damage. A segmentation schema was used to define CC volumes-of-interest (VOI). Fractional anisotropy (FA) and radial- and axial-diffusivity (RD, AD) were extracted from VOIs and compared between groups. DTI measurements in motor-related Area III were tested for correlation with symptoms and disease duration. Results Extracted FA values from CC VOIs were reduced in ALS patients (P?0.0001), particularly in Areas II and III (P?0.01). Reduced FA in Area III correlated with disease symptomology (P?0.05) and duration (P?0.02). Between-group whole-brain comparisons (P?0.05, corrected) showed reduced FA and increased RD throughout white matter regions including the CC, corona radiata, and internal capsule. AD was increased in the left corona radiata and internal and external capsules. Conclusion FA in motor-related regions of the CC is more affected than other CC areas in ALS patients. Microstructural pathology of transcallosal fiber tracts may represent a future component of an imaging biomarker for ALS. PMID:23843179

Chapman, Molly C.; Jelsone-Swain, Laura; Johnson, Timothy D.; Gruis, Kirsten L.; Welsh, Robert C.

2013-01-01

41

Frontal Corpus Callosum Alterations in Progressive Supranuclear Palsy but Not in Parkinson's Disease.  

PubMed

Background: Frontal lobe involvement is considered a clinical and magnetic resonance imaging (MRI) feature in later stages of progressive supranuclear palsy (PSP). Objective: Diffusion tensor imaging (DTI) was used to investigate the integrity of frontal pathways in PSP and Parkinson's disease (PD) patients. Methods: DTI and 3-D MRI were performed in 15 PSP patients (parkinsonism subtype: n = 8; Richardson subtype: n = 7), 15 PD patients, and 18 matched controls. DTI analysis was performed in order to identify differences along frontal white matter structures including the corpus callosum (CC) and was complemented by atlas-based volumetry and planimetry. Results: Significantly reduced regional fractional anisotropy was observed for PSP patients versus controls and PSP versus PD patients, respectively, in frontal areas including the area II of the CC and bilaterally in the callosal radiation. The DTI findings correlated with frontal lobe volumes. These differences were not observed between PD patients and controls. Conclusion: DTI identified a PSP-associated microstructural alteration pattern in the frontal lobes and in the CC area II including the corresponding bilateral callosal radiation tracts that could not be identified in both control samples, supporting the prominent PSP-associated frontal involvement as a potential neuroimaging marker. © 2014 S. Karger AG, Basel. PMID:25377379

Rosskopf, Johannes; Müller, Hans-Peter; Huppertz, Hans-Jürgen; Ludolph, Albert C; Pinkhardt, Elmar H; Kassubek, Jan

2014-11-01

42

Watershed-based segmentation of the corpus callosum in diffusion MRI  

NASA Astrophysics Data System (ADS)

The corpus callosum (CC) is one of the most important white matter structures of the brain, interconnecting the two cerebral hemispheres, and is related to several neurodegenerative diseases. Since segmentation is usually the first step for studies in this structure, and manual volumetric segmentation is a very time-consuming task, it is important to have a robust automatic method for CC segmentation. We propose here an approach for fully automatic 3D segmentation of the CC in the magnetic resonance diffusion tensor images. The method uses the watershed transform and is performed on the fractional anisotropy (FA) map weighted by the projection of the principal eigenvector in the left-right direction. The section of the CC in the midsagittal slice is used as seed for the volumetric segmentation. Experiments with real diffusion MRI data showed that the proposed method is able to quickly segment the CC without any user intervention, with great results when compared to manual segmentation. Since it is simple, fast and does not require parameter settings, the proposed method is well suited for clinical applications.

Freitas, Pedro; Rittner, Leticia; Appenzeller, Simone; Lapa, Aline; Lotufo, Roberto

2012-02-01

43

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

PubMed Central

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

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

2014-01-01

44

Fractions!  

NSDL National Science Digital Library

On this page you will practice adding, subtracting, multiplying, and dividing fractions. 1. Practice identifying equivalent fractions. Finding equivalent fractions 2. Add and subtract fractions. The first levels have like denominators, but then the levels get harder with unlike denominators. Make sure you use some scratch paper. Get to the highest level you can! Fraction Race (adding and subtracting, like and unlike denominators) 3. Practice adding fractions with mixed numbers. Math splat -adding fractions using mixed numbers 4. Finally, get with a partner ...

Hbinggeli

2010-08-24

45

Glioma infiltration of the corpus callosum: early signs detected by DTI.  

PubMed

The most frequent primary brain tumors, anaplastic astrocytomas (AA) and glioblastomas (GBM): tend to invasion of the surrounding brain. Histopathological studies found malignant cells in macroscopically unsuspicious brain parenchyma remote from the primary tumor, even affecting the contralateral hemisphere. In early stages, diffuse interneural infiltration with changes of the apparent diffusion coefficient (ADC) and fractional anisotropy (FA) is suspected. The purpose of this study was to investigate the value of DTI as a possible instrument of depicting evidence of tumor invasion into the corpus callosum (CC). Preoperatively, 31 patients with high-grade brain tumors (8 AA and 23 GBM) were examined by MRI at 3 T, applying a high-resolution diffusion tensor imaging (DTI) sequence. ADC- and FA-values were analyzed in the tumor-associated area of the CC as identified by fiber tracking, and were compared to matched healthy controls. In (MR-)morphologically normal appearing CC the ADC values were elevated in the tumor patients (n = 22; 0.978 × 10(-3) mm²/s) compared to matched controls (0.917 × 10(-3) mm²/s, p < 0.05), and the corresponding relative FA was reduced (rFA: 88 %, p < 0.01). The effect was pronounced in case of affection of the CC visible on MRI (n = 9; 0.978 × 10(-3) mm²/s, p < 0.05; rFA: 72 %, p < 0.01). Changes in diffusivity and anisotropy in the CC can be interpreted as an indicator of tumor spread into the contralateral hemisphere not visible on conventional MRI. PMID:23344787

Kallenberg, K; Goldmann, T; Menke, J; Strik, H; Bock, H C; Stockhammer, F; Buhk, J H; Frahm, J; Dechent, P; Knauth, M

2013-04-01

46

Corpus Callosum MR Image Classification  

NASA Astrophysics Data System (ADS)

An approach to classifying Magnetic Resonance (MR) image data is described. The specific application is the classification of MRI scan data according to the nature of the corpus callosum, however the approach has more general applicability. A variation of the “spectral segmentation with multi-scale graph decomposition” mechanism is introduced. The result of the segmentation is stored in a quad-tree data structure to which a weighted variation (also developed by the authors) of the gSpan algorithm is applied to identify frequent sub-trees. As a result the images are expressed as a set frequent sub-trees. There may be a great many of these and thus a decision tree based feature reduction technique is applied before classification takes place. The results show that the proposed approach performs both efficiently and effectively, obtaining a classification accuracy of over 95% in the case of the given application.

Elsayed, A.; Coenen, F.; Jiang, C.; García-Fiñana, M.; Sluming, V.

47

Fraction  

NSDL National Science Digital Library

These games are mostly for you to review. Start by practicing your fractions...in this game you will need to match the fraction to a picture Equivalent Fraction Click here in order to test your skills. You will get 4 different answers, it will be your job to save the bugs. Equivalent Fraction Click here to practice adding and subtraction using different denominators. Race ...

Castro, Ms.

2007-10-03

48

Fractions.  

ERIC Educational Resources Information Center

An extensive investigation of pupil understanding of fractions at the secondary education level showed the majority tended to avoid using fractions, could not generalize about them, and probably did not see them as an extension of the set of whole numbers. (MP)

Hart, K.

1981-01-01

49

[Case report of corpus callosum lipoma diagnosed with computer tomography].  

PubMed

The case of corpus callosum lipoma that was accidentally discovered during the routine brain examination by computed tomography had been described. The CT features of corpus callosum lipoma were described as well as differential-diagnostic differences with epidermoid cyst agenesia of corpus callosum and cyst of the pellucid septum (cavum vergae). PMID:9720452

Markovi?, N; Ciri?, S; Stanojevi?, B; Vujnovi?, M

1998-01-01

50

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

51

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

PubMed Central

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

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

2014-01-01

52

Diffusion Tensor Anisotropy in Adolescents and Adults  

Microsoft Academic Search

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

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

2007-01-01

53

Quantitative assessment of corpus callosum morphology in periventricular nodular heterotopia.  

PubMed

We investigated systematic differences in corpus callosum morphology in periventricular nodular heterotopia (PVNH). Differences in corpus callosum mid-sagittal area and subregional area changes were measured using an automated software-based method. Heterotopic gray matter deposits were automatically labeled and compared with corpus callosum changes. The spatial pattern of corpus callosum changes were interpreted in the context of the characteristic anterior-posterior development of the corpus callosum in healthy individuals. Individuals with periventricular nodular heterotopia were imaged at the Melbourne Brain Center or as part of the multi-site Epilepsy Phenome Genome project. Whole brain T1 weighted MRI was acquired in cases (n=48) and controls (n=663). The corpus callosum was segmented on the mid-sagittal plane using the software "yuki". Heterotopic gray matter and intracranial brain volume was measured using Freesurfer. Differences in corpus callosum area and subregional areas were assessed, as well as the relationship between corpus callosum area and heterotopic GM volume. The anterior-posterior distribution of corpus callosum changes and heterotopic GM nodules were quantified using a novel metric and compared with each other. Corpus callosum area was reduced by 14% in PVNH (p=1.59×10(-9)). The magnitude of the effect was least in the genu (7% reduction) and greatest in the isthmus and splenium (26% reduction). Individuals with higher heterotopic GM volume had a smaller corpus callosum. Heterotopic GM volume was highest in posterior brain regions, however there was no linear relationship between the anterior-posterior position of corpus callosum changes and PVNH nodules. Reduced corpus callosum area is strongly associated with PVNH, and is probably associated with abnormal brain development in this neurological disorder. The primarily posterior corpus callosum changes may inform our understanding of the etiology of PVNH. Our results suggest that interhemispheric pathways are affected in PVNH. PMID:25524841

Pardoe, Heath R; Mandelstam, Simone A; Hiess, Rebecca Kucharsky; Kuzniecky, Ruben I; Jackson, Graeme D

2015-01-01

54

Evaluation of some GRIN fiber parameters and the associated fraction mode loss due to mechanically induced optical anisotropy.  

PubMed

Some of the optical parameters of the bent multimode graded-index (GRIN) optical fiber in terms of indices of refraction, where the bending stresses broke the radial symmetry, are evaluated by use of multiple-beam Fizeau fringes. The variation of the index difference between the cladding index and core index in both the compression and tensile fiber regions is measured. The accuracy of measuring the index is +/- 1 x 10(-4). The spatial resolution of the method is 1.39 microm. Evaluation of the acceptance angle, the numerical aperture, and the V number profiles of the bent fiber from the interference pattern at both sides of the bent fiber are presented. The fraction of the mode number lost has been evaluated. The method was used to study the influence of compression on diminishing the index difference that leads to a dissipation of energy and a considerable mode loss. It is obvious from the experimental data that the change of the index difference due to bending strongly affects the fraction of propagating mode number, especially at the small radii of curvature. Ignoring the variation of the index difference we evaluating the number of propagated modes number leads to an insufficient determination of the mode loss. It subsequently leads to an incorrect determination of the mode dispersion and the interface loss in bent GRIN fibers. The study confirms that the deviation of the guide axis from straightness with the radius of curvature of less than 1 cm could lead to a significant fraction mode loss. PMID:14503694

El-Diasty, Fouad

2003-09-10

55

Potential role of fractional anisotropy derived from diffusion tensor imaging in differentiating high-grade gliomas from low-grade gliomas: a meta-analysis  

PubMed Central

Background and purpose: It is crucial to accurately differentiate high-grade gliomas (HGGs) from low-grade gliomas (LGGs) preoperatively, as treatment strategies vary. So we performed a meta-analysis to assess the sensitivity and specificity of fractional anisotropy (FA) value derived from diffusion tensor imaging (DTI) in differentiating HGGs from LGGs. Materials and methods: Between January 2005 and June 2014, relevant articles were searched from the Embase and Medline databases for analysis. Statistical analyses were performed using Meta-Disc 1.4. Results: A total of 221 patients included in the FA analysis: 127 with HGGs and 94 LGGs. The pooled sensitivity, specificity and diagnostic odds ratio (DOR) for differentiating HGGs from LGGs were 93% (95% CI 0.87-0.97), 85% (95% CI 0.76-0.92), and 55.41 (95% CI 16.77-183.07), respectively. And computation of heterogeneity metrics revealed an acceptable level of the between-study heterogeneity of DOR (I2=30.9%). Conclusions: The results of our meta-analysis present that the FA derived from DTI act as a useful diagnostic marker could be used in distinguishing the HGGs from LGGs in the preoperative and the clinical application values are to be confirmed by further larger case-control studies. PMID:25419413

Liang, Ruofei; Wang, Xiang; Li, Mao; Yang, Yuan; Luo, Jiewen; Mao, Qing; Liu, Yanhui

2014-01-01

56

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

PubMed Central

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

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

2010-01-01

57

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

58

Secondary corpus callosum abnormalities associated with antiepileptic drugs in temporal lobe epilepsy. A diffusion tensor imaging study.  

PubMed

Epilepsy is more than a grey-matter disorder affecting large white matter connections of the brain with seizure generation and propagation. The mechanism for such changes remains unclear. The purpose of this study was to investigate the microstructural changes in the corpus callosum in temporal lobe epilepsy (TLE) patients and whether these abnormalities are related to antiepileptic drug (AED) therapy. Ten TLE patients receiving AED therapy, ten TLE patients with no therapy and ten controls were included in the study. The regions of interest in the corpus callosum were outlined to each Witelson region (WR). Fractional anisotrophy (FA), apparent diffusion coefficient (ADC), three main diffusivity values (?1, ?2, ?3) and tractography were acquired from each WR. DTI indices of these tracts and each WR were compared between the three subject groups and correlates examined with clinical variables that included duration of epilepsy, gender, AED type and AED therapy exposure. In TLE subjects with receiving AED therapy significantly (p<0.05) decreased FA and increased ADC values of corpus callosum were obtained when compared to the other groups. There was no significant relationship between AED type and DTI indices. Analysis of eigen values in the splenium of corpus callosum (WR7) showed ?1 values were significantly decreased in relation to AED medication duration (p<0.05). FA values of rostrum and corpus showed a reduction with duration of epilepsy. TLE is associated with abnormal integrity of corpus callosum white matter tracts. AED therapy may cause additional damage on secondary degeneration and medication time effects especially on the splenium of corpus callosum. PMID:24059625

Günbey, H P; Ercan, K; F?nd?ko?lu, A S; Bilir, E; Karaoglanoglu, M; Komurcu, F; Alhan, A

2011-05-15

59

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

60

Educational Implications for Agenesis of the Corpus Callosum.  

ERIC Educational Resources Information Center

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

Ritter, Shirley A.

61

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

62

The relationship between regional microstructural abnormalities of the corpus callosum and physical and cognitive disability in relapsing–remitting multiple sclerosis  

PubMed Central

Significant corpus callosum (CC) involvement has been found in relapsing–remitting multiple sclerosis (RRMS), even if conventional magnetic resonance imaging measures have shown poor correlation with clinical disability measures. In this work, we tested the potential of multimodal imaging of the entire CC to explain physical and cognitive disability in 47 patients with RRMS. Values of thickness, fractional anisotropy (FA) and mean diffusivity (MD) were extracted from 50 regions of interest (ROIs) sampled along the bundle. The relationships between clinical, neuropsychological and imaging variables were assessed by using Spearman's correlation. Multiple linear regression analysis was employed in order to identify the relative importance of imaging metrics in modeling different clinical variables. Regional fiber composition of the CC differentially explained the response variables (Expanded Disability Status Scale [EDSS], cognitive impairment). Increases in EDSS were explained by reductions in CC thickness and MD. Cognitive impairment was mainly explained by FA reductions in the genu and splenium. Regional CC imaging properties differentially explained disability within RRMS patients revealing strong, distinct patterns of correlation with clinical and cognitive status of patients affected by this specific clinical phenotype. PMID:25610764

Caligiuri, Maria Eugenia; Barone, Stefania; Cherubini, Andrea; Augimeri, Antonio; Chiriaco, Carmelina; Trotta, Maria; Granata, Alfredo; Filippelli, Enrica; Perrotta, Paolo; Valentino, Paola; Quattrone, Aldo

2014-01-01

63

The relationship between regional microstructural abnormalities of the corpus callosum and physical and cognitive disability in relapsing-remitting multiple sclerosis.  

PubMed

Significant corpus callosum (CC) involvement has been found in relapsing-remitting multiple sclerosis (RRMS), even if conventional magnetic resonance imaging measures have shown poor correlation with clinical disability measures. In this work, we tested the potential of multimodal imaging of the entire CC to explain physical and cognitive disability in 47 patients with RRMS. Values of thickness, fractional anisotropy (FA) and mean diffusivity (MD) were extracted from 50 regions of interest (ROIs) sampled along the bundle. The relationships between clinical, neuropsychological and imaging variables were assessed by using Spearman's correlation. Multiple linear regression analysis was employed in order to identify the relative importance of imaging metrics in modeling different clinical variables. Regional fiber composition of the CC differentially explained the response variables (Expanded Disability Status Scale [EDSS], cognitive impairment). Increases in EDSS were explained by reductions in CC thickness and MD. Cognitive impairment was mainly explained by FA reductions in the genu and splenium. Regional CC imaging properties differentially explained disability within RRMS patients revealing strong, distinct patterns of correlation with clinical and cognitive status of patients affected by this specific clinical phenotype. PMID:25610764

Caligiuri, Maria Eugenia; Barone, Stefania; Cherubini, Andrea; Augimeri, Antonio; Chiriaco, Carmelina; Trotta, Maria; Granata, Alfredo; Filippelli, Enrica; Perrotta, Paolo; Valentino, Paola; Quattrone, Aldo

2015-01-01

64

Decrease in glucose metabolism in frontal cortex associated with deterioration of microstructure of corpus callosum measured by diffusion tensor imaging in healthy elderly.  

PubMed

The neural functions of signaling are carried out by the interconnection of neurons via neuronal fibers. Diffusion tensor imaging has recently become an established technique that enables the in vivo visualization of white matter (WM) fibers. Studies of normal aging have suggested the disruption of WM fiber microstructures with anterior-posterior gradient. Because neuronal activity is tightly coupled with glucose metabolism, neuronal death or a decrease in synaptic activity with aging may cause a decrease in glucose metabolism in the brain. We examined whether the disruption of callosal fiber microstructures in the healthy elderly is accompanied by changes in regional glucose metabolism (rMGlu) in the brain. Fifteen healthy volunteers in their seventies participated. Fractional anisotropies (FAs) of the genu and splenium of the corpus callosum (CC) were measured for each subject, and their correlations with rMGlu were analyzed using SPM2 software. We found a statistically significant positive correlation of rMGlu in the bilateral frontal cortices with the FA of the genu of the CC, whereas there was no correlation of the FA of the splenium of the CC and rMGlu. By voxel-based morphometry, we found no decrease in gray matter concentration associated with FA. The results indicate that neuronal activity in the frontal cortices may decrease with the disruption of the microstructures of the CC without corresponding gray matter atrophy. PMID:17450581

Inoue, Kentaro; Ito, Hiroshi; Uchida, Shinya; Taki, Yasuyuki; Kinomura, Shigeo; Tsuji, Ichiro; Sato, Shigeru; Horie, Kaoru; Kawashima, Ryuta; Ito, Masatoshi; Fukuda, Hiroshi

2008-04-01

65

Corpus Callosum Microstructural Changes Correlate with Cognitive Dysfunction in Early Stages of Relapsing-Remitting Multiple Sclerosis: Axial and Radial Diffusivities Approach  

PubMed Central

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

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

2011-01-01

66

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

PubMed

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

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

2011-01-01

67

Corpus callosum damage predicts disability progression and cognitive dysfunction in primary-progressive MS after five years.  

PubMed

We aim to identify specific areas of white matter (WM) and grey matter (GM), which predict disability progression and cognitive dysfunction after five years in patients with primary-progressive multiple sclerosis (PPMS). Thirty-two patients with early PPMS were assessed at baseline and after five years on the Expanded Disability Status Scale (EDSS), and EDSS step-changes were calculated. At year five, a subgroup of 25 patients and 31 healthy controls underwent a neuropsychological assessment. Baseline imaging consisted of dual-echo (proton density and T2-weighted), T1-weighted volumetric, and diffusion tensor imaging. Fractional anisotropy (FA) maps were created, and fed into tract-based spatial statistics. To compensate for the potential bias introduced by WM lesions, the T1 volumes underwent a lesion-filling procedure before entering a voxel-based morphometry protocol. To investigate whether FA and GM volume predicted EDSS step-changes over five years and neuropsychological tests scores at five years, voxelwise linear regression analyses were performed. Lower FA in the splenium of the corpus callosum (CC) predicted a greater progression of disability over the follow-up. Lower FA along the entire CC predicted worse verbal memory, attention and speed of information processing, and executive function at five years. GM baseline volume did not predict any clinical variable. Our findings highlight the importance of damage to the interhemispheric callosal pathways in determining physical and cognitive disability in PPMS. Disruption of these pathways, which interconnect motor and cognitive networks between the two hemispheres, may result in a disconnection syndrome that contributes to long-term physical and cognitive disability. PMID:22328451

Bodini, Benedetta; Cercignani, Mara; Khaleeli, Zhaleh; Miller, David H; Ron, Maria; Penny, Sophie; Thompson, Alan J; Ciccarelli, Olga

2013-05-01

68

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

PubMed Central

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

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

2013-01-01

69

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

PubMed Central

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

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

2010-01-01

70

Metabolic levels in the corpus callosum and their structural and behavioral correlates after moderate to severe pediatric TBI.  

PubMed

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

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

2010-03-01

71

[Agenesis of corpus callosum - a review].  

PubMed

The subject herein discussed is malformations about which information abounds. This is due to constant improvements in approaches to obtaining such information through images generated by modern imaging technology. As the examination of structures at hand progresses, so does the possibility for precise imaging diagnostics. Agenesis of the corpus callosum is one those subtle and difficult to detect malformations which are currently becoming subjects of research. Agenesis of the corpus callosum is a brain anomaly with incidence of occurrence from 0.05 to 0.7%. It could be either observed in 49% of cases unaccompanied by other conditions or accompanied by other anomaly syndromes. This cerebral malformation is usually diagnosed post partum in children suffering from epilepsy or behaviour or cognitive disorders. In consideration of the necessity of early fetal abnormality detection and the conduct of the obstetrician in a social aspect, the above-mentioned is a prerequisite which makes discussions necessary. Constant up-dating and discussions allow periodic revision and optimizations of prenatal diagnostics. PMID:20734653

Christova, R

2010-01-01

72

Cavernous Angioma of the Corpus Callosum Presenting with Acute Psychosis  

PubMed Central

Psychiatric symptoms may occasionally be related to anatomic alterations of brain structures. Particularly, corpus callosum lesions seem to play a role in the change of patients' behavior. We present a case of a sudden psychotic attack presumably due to a hemorrhagic cavernous angioma of the corpus callosum, which was surgically removed with complete resolution of symptoms. Although a developmental defect like agenesis or lipoma is present in the majority of these cases, a growing lesion of the corpus callosum can rarely be the primary cause. Since it is potentially possible to cure these patients, clinicians should be aware of this association. PMID:24825949

Pavesi, Giacomo; Causin, Francesco; Feletti, Alberto

2014-01-01

73

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

74

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

75

The corpus callosum, interhemisphere interactions, and the function of the right hemisphere of the brain  

Microsoft Academic Search

A complex clinical-neuropsychological study was performed by the Luriya method before and after surgery in 36 patients with arteriovenous malformations (AVM) of the corpus callosum. The symptoms of local lesions to the various parts of the corpus callosum are described. Symptoms of partial lesioning of the corpus callosum were found to be modality-specific, though only relatively. The symptoms of dyscopia

S. B. Buklina

2005-01-01

76

Agenesis of Corpus Callosum and Frontotemporal Dementia: A Casual Finding?  

PubMed

Agenesis of corpus callosum (AgCC) is a congenital malformation characterized by total or partial absence of corpus callosum with a good neuropsychological profile. Frontotemporal dementia (FTD) is the third most common cause of cortical dementia, and it is characterized by alterations in personality and social relationship, often associated with deficits in attention, abstraction, planning, and problem solving. Herein, we report a case of a 73-year-old woman presenting with FTD associated with primary AgCC. The possible "causal or casual" relationship between these 2 different conditions should be investigated in large prospective studies. PMID:25194000

Calabrò, Rocco Salvatore; Spadaro, Letteria; Marra, Angela; Balletta, Tina; Cammaroto, Simona; Bramanti, Placido

2014-09-01

77

Primary human chorionic gonadotropin secreting germinoma of the corpus callosum  

PubMed Central

Background: Primary intracranial germinomas are a rare subset of intracranial tumors derived from mis-incorporated germ cells within the folding neural plate during embryogenesis. Though known to arise from midline structures in the central nervous system (CNS), occurrence within the corpus callosum is exceedingly rare. Case Description: We present a rare case of secreting primary intracranial germinoma with extensive intraventricular metastasis presenting as a multi-cystic butterfly lesion in the genu of the corpus callosum in a young boy. Conclusion: Intracranial germ cell tumors must be considered for any multi-cystic lesion arising from midline structures in the CNS in the preadult population. PMID:24233184

Chuan Aaron, Foo Song; Dawn, Chong Q. Q.; Kenneth, Chang T. E.; Hoe, Ng Wai; Yen, Soh Shui; Chee Kian, Tham

2013-01-01

78

On Automating and Standardising Corpus Callosum Analysis in Brain MRI  

E-print Network

Estimation The human brain consists on a coarse level of the cerebrum, the cerebellum and the brainstem. Most prominent is the cerebrum which is divided into hemispheres connected by a nervous fibre bundle; the corpus callosum. The surface partitioning this approximate bilateral symmetry of the cerebrum is typically denoted

79

Prenatal diagnosis of colpocephaly with absent corpus callosum.  

PubMed

Colpocephaly is a rare abnormality of the brain, described as persistence of primitive foetal configuration of lateral ventricles. It has been found in association with several abnormalities of the brain. Herein we report a case of colpocephaly with absent corpus callosum, confirmed antenatally with foetal MRI following diagnostic suspicion based on absent septum pellucidum at prenatal sonography. PMID:25468365

Ansary, Althaf; Manjunatha, Cm; Ibhanesebhor, Samuel

2014-12-01

80

Corpus Callosum Differences Associated with Persistent Stuttering in Adults  

ERIC Educational Resources Information Center

Recent studies have implicated anatomical differences in speech-relevant brain regions of adults who stutter (AWS) compared to normally fluent adults (NFA). The present study focused on the region of the corpus callosum (CC) which is involved in interhemispheric processing between the left and right cerebral hemispheres. Two-dimensional…

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

2011-01-01

81

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

82

A factor analysis of the rat's corpus callosum  

Microsoft Academic Search

Previous work from our laboratory (Berrebi et al., Brain Research, 438 (1988) 216-224) demonstrated region-specific sexual dimorphisms in the size of the rat's corpus callosum, which are modifiable by extra stimulation in early life. These differences are assumed to reflect regional corticocortical fibers of passage which are altered differentially by gender and our experimental manipulations. In this paper, we report

Victor H. Denenberg; Albert S. Berrebi; Roslyn H. Fitch

1989-01-01

83

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

84

Corpus callosum atrophy and neuropsychological outcome following carbon monoxide poisoning  

Microsoft Academic Search

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

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

2002-01-01

85

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

ERIC Educational Resources Information Center

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

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

2008-01-01

86

Prenatal PCB exposure, the corpus callosum, and response inhibition.  

PubMed Central

The present study reports the association between prenatal exposure to polychlorinated biphenyls (PCBs), the corpus callosum, and response inhibition in children who are 4.5 years old. Children (n = 189) enrolled in the Oswego study were tested using a continuous performance test. We measured (square millimeters) the splenium of the corpus callosum, a pathway implicated in the regulation of response inhibition, using magnetic resonance imaging. Results indicated a dose-dependent association between cord blood PCBs and errors of commission. Splenium size but not other brain areas predicted errors of commission (r(2) = 0.20), with smaller size associated with more errors of commission. There was an interaction between splenium size and PCB exposure. The smaller the splenium, the larger the association between PCBs and errors of commission. If the association between PCBs and response inhibition is indeed causal, then children with suboptimal development of the splenium are particularly vulnerable to these effects. These data await replication. PMID:14527849

Stewart, Paul; Fitzgerald, Susan; Reihman, Jacqueline; Gump, Brooks; Lonky, Edward; Darvill, Thomas; Pagano, Jim; Hauser, Peter

2003-01-01

87

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

88

Corpus callosum thickness in children: an MR pattern-recognition approach on the midsagittal image.  

PubMed

Thickening of the corpus callosum is an important feature of development, whereas thinning of the corpus callosum can be the result of a number of diseases that affect development or cause destruction of the corpus callosum. Corpus callosum thickness reflects the volume of the hemispheres and responds to changes through direct effects or through Wallerian degeneration. It is therefore not only important to evaluate the morphology of the corpus callosum for congenital anomalies but also to evaluate the thickness of specific components or the whole corpus callosum in association with other findings. The goal of this pictorial review is raise awareness that the thickness of the corpus callosum can be a useful feature of pathology in pediatric central nervous system disease and must be considered in the context of the stage of development of a child. Thinning of the corpus callosum can be primary or secondary, and generalized or focal. Primary thinning is caused by abnormal or failed myelination related to the hypomyelinating leukoencephalopathies, metabolic disorders affecting white matter, and microcephaly. Secondary thinning of the corpus callosum can be caused by diffuse injury such as hypoxic-ischemic encephalopathy, human immunodeficiency virus (HIV) encephalopathy, hydrocephalus, dysmyelinating conditions and demyelinating conditions. Focal disturbance of formation or focal injury also causes localized thinning, e.g., callosal dysgenesis, metabolic disorders with localized effects, hypoglycemia, white matter injury of prematurity, HIV-related atrophy, infarction and vasculitis, trauma and toxins. The corpus callosum might be too thick because of a primary disorder in which the corpus callosum finding is essential to diagnosis; abnormal thickening can also be secondary to inflammation, infection and trauma. PMID:25173405

Andronikou, Savvas; Pillay, Tanyia; Gabuza, Lungile; Mahomed, Nasreen; Naidoo, Jaishree; Hlabangana, Linda Tebogo; du Plessis, Vicci; Prabhu, Sanjay P

2015-02-01

89

Histological correlation of diffusional kurtosis and white matter modeling metrics in cuprizone-induced corpus callosum demyelination.  

PubMed

The cuprizone mouse model is well established for studying the processes of both demyelination and remyelination in the corpus callosum, and it has been utilized together with diffusion tensor imaging (DTI) to investigate myelin and axonal pathology. Although some underlying morphological mechanisms contributing to the changes in diffusion tensor (DT) metrics have been identified, the understanding of specific associations between histology and diffusion measures remains limited. Diffusional kurtosis imaging (DKI) is an extension of DTI that provides metrics of diffusional non-Gaussianity, for which an associated white matter modeling (WMM) method has been developed. The main goal of the present study was to quantitatively assess the relationships between diffusion measures and histological measures in the mouse model of cuprizone-induced corpus callosum demyelination. The diffusional kurtosis (DK) and WMM metrics were found to provide additional information that enhances the sensitivity to detect the morphological heterogeneity in the chronic phase of the disease process in the rostral segment of the corpus callosum. Specifically, in the rostral segment, axonal water fraction (d?=?2.6; p?

Falangola, Maria F; Guilfoyle, David N; Tabesh, Ali; Hui, Edward S; Nie, Xingju; Jensen, Jens H; Gerum, Scott V; Hu, Caixia; LaFrancois, John; Collins, Heather R; Helpern, Joseph A

2014-08-01

90

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

91

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

ERIC Educational Resources Information Center

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

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

2008-01-01

92

A quantitative MRI study of the corpus callosum in children and adolescents  

Microsoft Academic Search

Total midsagittal area and seven subdivisions of the corpus callosum were measured on magnetic resonance images of 114 healthy boys and girls, aged 4 to 18. Striking variability of size was noted for all measures. Total midsagittal corpus callosum area increased in a robust and linear fashion from ages 4 to 18 (slope = 13.1 mm2\\/year, P = 0.0001 and

Jay N. Giedd; Judith M. Rumsey; F. Xavier Castellanos; Jagath C. Rajapakse; Debra Kaysen; A. Catherine Vaituzis; Yolanda C. Vauss; Susan D. Hamburger; Judith L. Rapoport

1996-01-01

93

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

94

Perspectives on dichotic listening and the corpus callosum.  

PubMed

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, age related, and genetic factors are also discussed. Finally, some attention is given to recent trends in audiology research to develop improved diagnostic and rehabilitation tools for individuals with dichotic deficits potentially related to callosal dysfunction. PMID:21531063

Musiek, Frank E; Weihing, Jeffrey

2011-07-01

95

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.

96

Ultrasound measurement of the corpus callosum and neural development of premature infants  

PubMed Central

Length and thickness of 152 corpus callosa were measured in neonates within 24 hours of birth. Using ultrasonic diagnostic equipment with a neonatal brain-specific probe, corpus callosum length and thickness of the genu, body, and splenium were measured on the standard mid-sagittal plane, and the anteroposterior diameter of the genu was measured in the coronal plane. Results showed that corpus callosum length as well as thickness of the genu and splenium increased with tional age and birth weight, while other measures did not. These three factors on the standard mid-sagittal plane are therefore likely to be suitable for real-time evaluation of corpus callosum velopment in premature infants using cranial ultrasound. Further analysis revealed that thickness of the body and splenium and the anteroposterior diameter of the genu were greater in male infants than in female infants, suggesting that there are sex differences in corpus callosum size during the neonatal period. A second set of measurements were taken from 40 premature infants whose gestational age was 34 weeks or less. Corpus callosum measurements were corrected to a gestational age of 40 weeks, and infants were grouped for analysis depending on the outcome of a neonatal behavioral neurological assessment. Compared with infants with a normal neurological assessment, corpus callosum length and genu and splenium thicknesses were less in those with abnormalities, indicating that corpus callosum growth in premature infants is associated with neurobehavioral development during the early extrauterine stage. PMID:25206553

Liu, Fang; Cao, Shikao; Liu, Jiaoran; Du, Zhifang; Guo, Zhimei; Ren, Changjun

2013-01-01

97

An MRI review of acquired corpus callosum lesions.  

PubMed

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

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

2014-09-01

98

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

99

Clinical features of acute corpus callosum infarction patients  

PubMed Central

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

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

2014-01-01

100

Hypoplasia of the corpus callosum in Niemann-Pick type C disease  

Microsoft Academic Search

In two unrelated patients with Niemann-Pick type C disease MRI showed symmetrical cerebral and cerebellar atrophy and hypoplasia of the corpus callosum. T2-weighted images in one showed high signal areas in the posterior white matter.

S. Palmeri; C. Battisti; A. Federico; G. C. Guazzi

1994-01-01

101

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

102

AUTOMATIC CLUSTER ANALYSIS OF CORPUS CALLOSUM SUBDIVISIONS IN SCHIZOPHRENIA: A DIFFUSION TENSOR IMAGING STUDY  

E-print Network

an important role in relaying sensory, cognitive, and motor information throughout the brain. While MRI studies for the Corpus Callosum. Figure 6 DTI ACQUSITION: · 3 Tesla GE system (General Electric Medical Systems

103

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

104

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

PubMed Central

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

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

2013-01-01

105

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

106

Automatic corpus callosum segmentation for standardized MR brain scanning  

NASA Astrophysics Data System (ADS)

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

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

2007-03-01

107

Agenesis of the corpus callosum: a clinical approach to diagnosis.  

PubMed

This review article aims to guide the clinician in establishing a diagnosis in patients with agenesis of the corpus callosum (ACC), presenting antenatally or postnatally. ACC may be isolated, or occur in association with other neuroanatomical lesions and/or congenital anomalies, and has many different genetic causes. Neuropsychological outcome varies considerably from normal to profound intellectual disability depending on the etiology. Approximately 25% of individuals with antenatally diagnosed apparently isolated ACC have intellectual disability. Subtle neurological, social, and learning deficits may still occur in those with normal intelligence and longitudinal neurocognitive follow-up is recommended for all children with ACC. The finding of ACC should prompt detailed clinical assessment in order to determine and manage the underlying condition. It is recognized that genetic factors contribute to ACC in the vast majority of cases. Less commonly ACC can result from antenatal infections, vascular or toxic insults, and it is increasingly recognized that ACC, particularly isolated ACC, may be due to an interaction of a number of "modifier" genetic and environmental factors. There are a large number of genetic conditions in which ACC may be a feature. We suggest a diagnostic algorithm to help guide the clinician towards diagnosis, to provide outcome advice and to aid in genetic counseling. PMID:24866859

Palmer, Elizabeth Emma; Mowat, David

2014-06-01

108

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

109

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

110

[Comparative MRI morphometric study of the corpus callosum at term and preterm infants].  

PubMed

A comparative morphometric analysis of MRI brain tomograms of term ant preterm born children was conducted. Common morphometric indexes and a novel quantitative parameter, a coefficient of corpus callosum (kCC), developed with regard to prenatal cortex ontogenesis pattern were applied to the study in order to get objective structural characteristics of the brain. All these quantitative indexes display anatomical features of the preterm brain. Reduced values of corpus callosum coefficient at preterm born children are known to associate with altered proportion between its rostral and caudal segments. A threshold coefficient value was established to differentiate preterm brain from the term one and it has proven its statistical significance. PMID:25272766

Tkachenko, L A; Toronova, N O; Krasnoshchekova, E I; Aleksandrov, T A; Zykin, P A; Ialfimov, A N

2014-01-01

111

Fraction Action  

NSDL National Science Digital Library

Have fun playing these games and learning more about Fractions. Start off with your very own personal Fractions Tutor. Next, practice your fractions...in this game you will need to match the fraction to a picture of an Equivalent Fraction. Try Visualizing Fractions, which will help you see what fractions look like. Design your own flag, following the hints given in ...

Ms. Chase

2009-03-07

112

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

ERIC Educational Resources Information Center

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

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

2007-01-01

113

A 23-Year Review of Communication Development in an Individual with Agenesis of the Corpus Callosum.  

ERIC Educational Resources Information Center

Twenty-three years of observation and testing of the communication skills of a male with agenesis of the corpus callosum and normal IQ revealed initial weakness in language. Difficulties with fluent speech persisted into young adulthood. With intensive intervention, communication and academic skills developed and the participant completed high…

Stickles, Judith L.; Schilmoeller, Gary L.; Schilmoeller, Kathryn J.

2002-01-01

114

Agenesis of the Corpus Callosum: Assessment and Remediation of School-Related Problems.  

ERIC Educational Resources Information Center

The paper examines three cases of children born with brain damage (absence of corpus callosum). Common problems (attentional, cognitive, visuo-motor, and motor deficits) are noted, and the impact of secondary emotional involvement is considered. Intervention approaches with two of the children are described as inconsistent and inadequate, while…

Puente, Antonio, E.

115

Corpus callosum: effects of neonatal hormones on sexual dimorphism in the rat  

Microsoft Academic Search

The rat's corpus callosum is sexually dimorphic, with the male's being larger. In addition, giving rats extra stimulaUon m infancy via handhng increases callosal area in males, but not in females. To determine if this dimorphism is testosterone-dependent, male pups were castrated on Day 1 of life while females received an injection of testosterone proplonate (TP) on Day 4. Control

Roslyn H. Fitch; Albert S. Berrebi; Patricia E. Cowell; Lisa M. Schrott; Victor H. Denenberg

1990-01-01

116

Sex differences in the distribution of axon types within the genu of the rat corpus callosum  

Microsoft Academic Search

Neuroanatomical sex differences have been documented in the rat neocortex, including dimorphism of its predominant commissure, the corpus callosum (CC). In particular, CC sex differences have been reported in the ultrastructure of the posterior callosal region, the splenium. Since the CC is a heterogeneous fiber tract with its axons arising from distinct cortical areas and passing through restricted regions along

Christine M. Mack; Gary W. Boehm; Albert S. Berrebi; Victor H. Denenberg

1995-01-01

117

The Role of the Corpus Callosum in the Coupling of Bimanual Isometric Force Pulses  

E-print Network

The Role of the Corpus Callosum in the Coupling of Bimanual Isometric Force Pulses J of bimanual isometric force pulses. J Neurophysiol 90: 2409­2418, 2003; 10.1152/jn.00250.2003. Two split- ual force production task. The participants produced isometric responses with their index fingers

Ivry, Rich

118

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

119

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

120

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

121

Neuroaxonal ion dyshomeostasis of the normal-appearing corpus callosum in experimental autoimmune encephalomyelitis  

Microsoft Academic Search

Atrophy of the corpus callosum (CC) is a well-documented observation in clinically definite multiple sclerosis (MS) patients. One recent hypothesis for the neurodegeneration that occurs in MS is that ion dyshomeostasis leads to neuroaxonal damage. To examine whether ion dyshomeostasis occurs in the CC during MS onset, experimental autoimmune encephalomyelitis (EAE) was utilized as an animal MS model to induce

Chiao-Chi V. Chen; Anil Zechariah; Yi-Hua Hsu; Hsiao-Wen Chen; Li-Chuan Yang; Chen Chang

2008-01-01

122

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

PubMed Central

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

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

2011-01-01

123

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

E-print Network

of connectivity did not seem to be attributable to the presence of comorbid ADHD or OCD, to medication exposureReduced white matter connectivity in the corpus callosum of children with Tourette syndrome Kerstin, Norway; 2 Department of Biological and Medical Psychology, University of Bergen, Norway; 3 Department

124

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

125

Corpus callosum atrophy is associated with gait disorders in patients with leukoaraiosis  

Microsoft Academic Search

Cognitive impairment and gait disturbances are the most frequent clinical findings in patients with leukoaraiosis (LA). Corpus callosum (CC) atrophy has been associated with dementia in patients with LA, as well as with gait disturbances in patients with normal pressure hydrocephalus. We investigated, in patients with LA, the possible association between gait impairment and CC atrophy, taking into account cognitive

M. Moretti; G. Carlucci; A. Di Carlo; C. Fonda; M. Prieto; S. Mugnai; L. Bracco; C. Piccini; G. Pracucci; D. Inzitari

2005-01-01

126

Corpus callosum and visual cortex of mice with deletion of the NMDA-NR1 receptor  

Microsoft Academic Search

Offspring of transgenic mice with deletion of the NMDA-NR1 (NR1) receptor received prenatal alcohol exposure during most of gestation. Before and after birth, offspring were sacrificed in order to examine the morphological consequences of the prenatal exposure. Previously, we reported that the dendritic arborization of corpus callosum projection neurons (CCpn) in visual cortex was abnormal in rats given prenatal alcohol

Jinbo Deng; Andrea J Elberger

2003-01-01

127

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

ERIC Educational Resources Information Center

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

Morton, Bruce E.; Rafto, Stein E.

2006-01-01

128

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

129

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

PubMed Central

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

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

1990-01-01

130

Anterior genu corpus callosum and impulsivity in suicidal patients with bipolar disorder  

Microsoft Academic Search

Suicidality is a life-threatening symptom in patients with bipolar disorder (BD). Impulsivity and mood instability are associated with suicidality in mood disorders. Evidence suggests that gray and white matter abnormalities are linked with impulsivity in mood disorders, but little is known about the association between corpus callosum (CC) and impulsivity in BD. We examined the relationship between CC areas, impulsivity

Koji Matsuo; Niels Nielsen; Mark A. Nicoletti; John P. Hatch; E. Serap Monkul; Yoshifumi Watanabe; Giovana B. Zunta-Soares; Fabiano G. Nery; Jair C. Soares

2010-01-01

131

Fantastic Fractions  

NSDL National Science Digital Library

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

Cate, Ms.

2008-04-12

132

Fraction Quiz  

NSDL National Science Digital Library

Test your fraction skills by answering questions on this site. This quiz asks you to simplify fractions, convert fractions to decimals and percentages, and answer algebra questions involving fractions. You can even choose difficulty level, question types, and time limit.

2010-01-01

133

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 ...

Evans, Miss

2007-10-03

134

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

135

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

136

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

137

Fantastic Fractions  

NSDL National Science Digital Library

Fractions are fabulous! Fractions are new for us, so let's start out slow and then pick up some speed! First, Create Your Own Flag by coloring in half the flag with the colors! Next, have some more Fun with Fractions by picking out which picture shows the fraction! Finally, let's have some Fraction Pie - count the pieces of pie to figure out how much ...

Ms. Stabler

2011-03-29

138

Shape anisotropy and Voids  

E-print Network

Numerical simulations on a 2-dimensional model system showed that voids are induced primarily due to shape anisotropy in binary mixtures of interacting disks. The results of such a simple model account for the key features seen in a variety of flux experiments using liposomes and biological membranes.

Gauri R. Pradhan; Sagar A. Pandit; Anil D. Gangal; V. Sitaramam

2000-02-10

139

CMB ANISOTROPIES: AN OVERVIEW  

E-print Network

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

Douglas Scott

1995-02-02

140

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

PubMed Central

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

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

2014-01-01

141

Azimuthal Anisotropy and the QGP  

SciTech Connect

Study of azimuthal anisotropy have played very important role at RHIC(Relativistic Heavy Ion Collider) Physics. The large azimuthal anisotropy is the proof of very early thermalization of the system which cannot be obtained without introducing interactions at the partonic level. Quark number scaling of the azimuthal anisotropy suggests a new particle production mechanism characteristic in dense matter.

Miake, Yasuo [Institute of Physics, University of Tsukuba, Tsukuba, 305-8571 (Japan)

2006-11-02

142

Fraction Track  

NSDL National Science Digital Library

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

Mathematics, Illuminations N.

2009-05-12

143

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

144

Age at developmental cortical injury differentially Alters corpus callosum volume in the rat  

PubMed Central

Background Freezing lesions to developing rat cortex induced between postnatal day (P) one and three (P1 – 3) lead to malformations similar to human microgyria, and further correspond to reductions in brain weight and cortical volume. In contrast, comparable lesions on P5 do not produce microgyric malformations, nor the changes in brain weight seen with microgyria. However, injury occurring at all three ages does lead to rapid auditory processing deficits as measured in the juvenile period. Interestingly, these deficits persist into adulthood only in the P1 lesion case [1]. Given prior evidence that early focal cortical lesions induce abnormalities in cortical morphology and connectivity [1-4], we hypothesized that the differential behavioral effects of focal cortical lesions on P1, P3 or P5 may be associated with underlying neuroanatomical changes that are sensitive to timing of injury. Clinical studies indicate that humans with perinatal brain injury often show regional reductions in corpus callosum size and abnormal symmetry, which frequently correspond to learning impairments [5-7]. Therefore, in the current study the brains of P1, 3 or 5 lesion rats, previously evaluated for brain weight, and cortical volume changes and auditory processing impairments (P21-90), were further analyzed for changes in corpus callosum volume. Results Results showed a significant main effect of Treatment on corpus callosum volume [F (1,57) = 10.2, P < .01], with lesion subjects showing significantly smaller callosal volumes as compared to shams. An Age at Treatment × Treatment interaction [F(2,57) = 3.2, P < .05], indicated that corpus callosum size decreased as the age of injury decreased from P5 to P1. Simple effects analysis showed significant differences between P1 and P3 [F(1,28) = 8.7, P < .01], and P1 and P5 [F(1,28) = 15.1, P < .001], subjects. Rats with P1 injury resulting in microgyria had the greatest reduction in corpus callosum volume (22% reduction), followed by the P3 group (11% reduction), which showed a significant reduction in corpus callosum volume compared to shams [F(1,31) = 5.9, P < .05]. Finally, the P5 lesion group did not significantly differ from the sham subjects in callosal volume. Conclusion Decrements in corpus callosum volume in the P1 and 3 lesion groups are consistent with the reductions in brain weight and cortical volume previously reported for microgyric rats [1,8]. Current results suggest that disruption to the cortical plate during early postnatal development may lead to more widely dispersed neurovolumetric anomalies and subsequent behavioral impairments [1], compared with injury that occurs later in development. Further, these results suggest that in a human clinical setting decreased corpus callosum volume may represent an additional marker for long-term behavioral outcome. PMID:17997836

Threlkeld, Steven W; Rosen, Glenn D; Fitch, R Holly

2007-01-01

145

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

146

Interactive Color Embedding-based Corpus Callosum Segmentation and Fiber Clustering in DTI  

Microsoft Academic Search

We propose an inter-discipl inary project to develop a new interactive tool for color embedding-based corpus callosum segmentation. By integrating color-coding of tractography paths, our tool will allow user to interactively adjust the clustering and segmentation based on their observation of the fiber tracks. The tool will be developed and evaluated in close collaboration with neuropsychologists studying abnormal changes in

Wenjin Zhou; Peter G. Sibley; David F. Tate; Song Zhang

147

Rare combination of gelastic epilepsy, agenesis of the corpus callosum, and hamartoma.  

PubMed

Gelastic seizures are rare and are associated with different conditions, but mainly with hypothalamic hamartoma. We report on a boy who presented with mental retardation, aggressive behavior, and generalized tonic-clonic and gelastic seizures. Cranial imaging studies revealed a very rare combination of hypothalamic hamartoma and agenesis of the corpus callosum, which was only reported once previously. His seizure activities demonstrated a modest response to anticonvulsants. PMID:21907892

Chen, Chia-Chun; Lin, Yu-Ting; Chang, Wen-Cheng; Hsieh, Li-Chun; Liang, Jao-Shwann

2011-10-01

148

Genomic microarray analysis identifies candidate loci in patients with corpus callosum anomalies.  

PubMed

Absence of the corpus callosum is often associated with cognitive deficits, autism, and epilepsy. Using a genomic microarray, the authors analyzed DNA from 25 patients with radiographically confirmed callosal anomalies and identified three patients with de novo copy number changes in chromosome regions 2q37, 6qter, and 8p. Chromosomal deletions and duplications may be a relatively common cause of cerebral malformations. PMID:16275846

Sherr, E H; Owen, R; Albertson, D G; Pinkel, D; Cotter, P D; Slavotinek, A M; Hetts, S W; Jeremy, R J; Schilmoeller, G; Schilmoeller, K; Wakahiro, M; Barkovich, A J

2005-11-01

149

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

PubMed

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

2014-12-28

150

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

151

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

PubMed Central

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

Özyüncü, Özgür; Yaz?c?o?lu, Asl?han; Tur?al, Mert

2014-01-01

152

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.

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

2014-01-01

153

Quarkonium dissociation by anisotropy  

NASA Astrophysics Data System (ADS)

We compute the screening length for quarkonium mesons moving through an anisotropic, strongly coupled mathcal{N} = 4 super Yang-Mills plasma by means of its gravity dual. We present the results for arbitrary velocities and orientations of the mesons, as well as for arbitrary values of the anisotropy. The anisotropic screening length can be larger or smaller than the isotropic one, and this depends on whether the comparison is made at equal temperatures or at equal entropy densities. For generic motion we find that: (i) mesons dissociate above a certain critical value of the anisotropy, even at zero temperature; (ii) there is a limiting velocity for mesons in the plasma, even at zero temperature; (iii) in the ultra-relativistic limit the screening length scales as (1 - v 2)? with ? = 1 /2, in contrast with the isotropic result ? = 1 /4.

Chernicoff, Mariano; Fernández, Daniel; Mateos, David; Trancanelli, Diego

2013-01-01

154

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

155

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

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

Fractional Clothesline  

NSDL National Science Digital Library

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

Mathematics, Illuminations N.

2009-07-23

158

Separating intrinsic and apparent anisotropy  

NASA Astrophysics Data System (ADS)

Seismic anisotropy plays a key role in studies of the Earth's rheology and deformation because of its relation to flow-induced lattice-preferred orientation (LPO) of intrinsically anisotropic minerals. In addition to LPO, small-scale heterogeneity produces apparent anisotropy that need not be related to deformation in the same way as intrinsic anisotropy. Quantitative interpretations of observed anisotropy therefore require the separation of its intrinsic and apparent components. We analyse the possibility to separate intrinsic and apparent anisotropy in media with hexagonal symmetry - typically used in surface wave tomography and SKS splitting studies. Our analysis is on the level of the wave equation, which makes it general and independent of specific data types or tomographic techniques. We find that observed anisotropy can be explained by isotropic heterogeneity when elastic parameters take specific combinations of values. In practice, the uncertainties of inferred anisotropy are large enough to ensure that such a combination is always within the error bars. It follows that commonly observed anisotropy can always be explained completely by a purely isotropic laminated medium unless all anisotropic parameters are known with unrealistic accuracy. Most importantly, minute changes in the poorly constrained P wave anisotropy and the parameter ? can switch between the possible or impossible existence of an isotropic equivalent. Important implications of our study include: (1) Intrinsic anisotropy over tomographically resolved length scales is never strictly required when reasonable error bars for anisotropic parameters are taken into account. (2) Currently available seismic observables provide weak constraints on the relative contributions of intrinsic and apparent anisotropy. (3) Therefore, seismic observables alone are not sufficient to constrain the magnitude of mantle flow. (4) Quantitative interpretations of anisotropy in terms of mantle flow require combined seismic/geodynamic inversions, as well as the incorporation of additional data such as topography, gravity and scattered waves.

Fichtner, Andreas; Kennett, Brian L. N.; Trampert, Jeannot

2013-06-01

159

Anisotropy in a Nonsingular Bounce  

E-print Network

Following recent claims relative to the question of large anisotropy production in regular bouncing scenarios, we study the evolution of such anisotropies in a model where an Ekpyrotic phase of contraction is followed by domination of a Galileon-type Lagrangian which generates a non-singular bounce. We show that the anisotropies decrease during the phase of Ekpyrotic contraction (as expected) and that they can be constrained to remain small during the non-singular bounce phase (a non-trivial result). Specifically, we derive the e-folding number of the phase of Ekpyrotic contraction which leads to a present-day anisotropy in agreement with current observational bounds.

Cai, Yi-Fu; Peter, Patrick

2013-01-01

160

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

161

Fractions Intro  

NSDL National Science Digital Library

This downloadable Java applet allows students to experiment with fractions by building and displaying fractions in the "Intro" tab. Students may explore the "Build a Fraction", "Equality Lab", and "Matching Game" tabs for more directed simulations. The website includes a teacher's guide (PDF) for suggested user tips.

Simulations, Phet I.

2013-01-01

162

Relationship among petrofabric, magnetic anisotropy and seismic anisotropy in dunite  

NASA Astrophysics Data System (ADS)

Physical anisotropies in rocks arise from the preferred alignment of the rock's constituents, which include mineral grains, organic matter or pore space. Different physical properties will be affected to a greater or lesser extent by these various factors. The anisotropy of magnetic susceptibility (AMS) is dependent on mineral orientation, particularly of minerals with high susceptibility and strong intrinsic anisotropy. Seismic anisotropy will also be controlled predominantly by mineral texture for rocks deformed at high pressure, where pore space or cracks are closed. During high-temperature ductile flow of the upper mantle, peridotite will develop a permanent deformation texture, which will be responsible for its physical anisotropies. Olivine develops characteristic crystal-preferred orientations (CPO) under different thermal-mechanical conditions. In this study we examine the relationship among mineral texture, magnetic anisotropy and seismic anisotropy of dunites from the Western Gneiss Region, Norway. Because dunite consists of > 90% olivine, the intrinsic magnetic anisotropy of single crystals of olivine is also investigated. AMS was measured with a high-field torsion magnetometer at room temperature and 77 K, in order to separate the paramagnetic sub-fabric from the total anisotropy. Our results indicate that olivine has a prolate anisotropy, in which the minimum, intermediate, and maximum axes of susceptibility correspond to the [010], [100] and [001] axes of olivine, respectively; this is partially contrary to an earlier investigation by Belley et al. (2009, EPSL, 284, 516-526). The degree of anisotropy increases by a factor of 7.1 - 8.2 at 77 K, and the shape becomes more triaxial. The CPO of olivine was measured using electron backscatter diffraction technique or X-ray texture goniometry. Although olivine grains in the samples develop two fabric types, namely [100](010) or [001](010), there is the same very good agreement between the orientation of the principal axes of the AMS ellipsoid and the texture ellipsoid of olivine. The minimum axes of the AMS ellipsoid are coaxial with the [010] axes in all samples, and maximum axes are coaxial with [001] in all but two samples; for these the intermediate axes are along the [100] direction of olivine. In addition, the degree of AMS increases with increasing texture strength. Seismic velocities and anisotropy are determined from the orientation distribution function and elastic constants of olivine, using the method described by Mainprice (1990, Comput. Geosci., 16, 385-393). A significant linear correlation is found between the degree of P- and S-wave anisotropies and AMS degree. Our results indicate that AMS can be used to infer the petrofabric and seismic anisotropy of olivine-rich rocks.

Hirt, A. M.; Wang, Q.; Biedermann, A. R.

2012-04-01

163

Seismic anisotropy of shales  

NASA Astrophysics Data System (ADS)

The seismic properties and preferred clay material orientation of a suite of shales are investigated using laboratory velocity measurements as a function of confining pressure, X ray diffraction techniques, and electron microprobe backscatter (BSE) imaging. The velocity measurements indicate that these shales are transversely isotropic with the main symmetry axis perpendicular to bedding. Anisotropy, at elevated pressures caused mainly by preferred orientation of clays (illite) parallel to bedding, ranges from 20% (V(sub p)) and 19% (V(sub s)) for a sample of New Albany Shale to 30% (V(sub p)) and 35% (V(sub s)) for a sample of Chattanooga Shale. The degree of clay mineral alignment in the shales is constrained by 'orientation indices' produced using simple X ray diffraction techniques. A strong positive correlation is found between the degree of preferred orientation, as expressed in the orientation indices, and seismic anisotropy. BSE images of the shale fabrics confirm in a qualitative manner the results of the X ray study. To investigate wave propagation in the shales, elastic constants of each sample are calculated and used to produce phase and group (wave) velocity surfaces, which describe variation in velocity as a function of angle to the bedding normal. The calculated velocity surfaces, constrained by independent velocity measurements, display a lack of shear wave splitting at 'near-normal incidence' in even the most anisotropic shales. For the highly anisotropic Chattanooga shales, group velocity surfaces differ significantly from correspondiong phase velocity surfaces.

Johnston, Joel E.; Christensen, Nikolas I.

1995-04-01

164

Microstructural Damage of the Posterior Corpus Callosum Contributes to the Clinical Severity of Neglect  

PubMed Central

One theory to account for neglect symptoms in patients with right focal damage invokes a release of inhibition of the right parietal cortex over the left parieto-frontal circuits, by disconnection mechanism. This theory is supported by transcranial magnetic stimulation studies showing the existence of asymmetric inhibitory interactions between the left and right posterior parietal cortex, with a right hemispheric advantage. These inhibitory mechanisms are mediated by direct transcallosal projections located in the posterior portions of the corpus callosum. The current study, using diffusion imaging and tract-based spatial statistics (TBSS), aims at assessing, in a data-driven fashion, the contribution of structural disconnection between hemispheres in determining the presence and severity of neglect. Eleven patients with right acute stroke and 11 healthy matched controls underwent MRI at 3T, including diffusion imaging, and T1-weighted volumes. TBSS was modified to account for the presence of the lesion and used to assess the presence and extension of changes in diffusion indices of microscopic white matter integrity in the left hemisphere of patients compared to controls, and to investigate, by correlation analysis, whether this damage might account for the presence and severity of patients' neglect, as assessed by the Behavioural Inattention Test (BIT). None of the patients had any macroscopic abnormality in the left hemisphere; however, 3 cases were discarded due to image artefacts in the MRI data. Conversely, TBSS analysis revealed widespread changes in diffusion indices in most of their left hemisphere tracts, with a predominant involvement of the corpus callosum and its projections on the parietal white matter. A region of association between patients' scores at BIT and brain FA values was found in the posterior part of the corpus callosum. This study strongly supports the hypothesis of a major role of structural disconnection between the right and left parietal cortex in determining ‘neglect’. PMID:23110177

Bozzali, Marco; Mastropasqua, Chiara; Cercignani, Mara; Giulietti, Giovanni; Bonnì, Sonia; Caltagirone, Carlo; Koch, Giacomo

2012-01-01

165

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

166

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

167

S100B is downregulated in the nuclear proteome of schizophrenia corpus callosum.  

PubMed

Here we report the downregulation of S100B in the nuclear proteome of the corpus callosum from nine schizophrenia patients compared to seven mentally healthy controls. Our data have been obtained primarily by mass spectrometry and later confirmed by Western blot. This is an intriguing finding coming from a brain region which is essentially composed by white matter, considering the potential role of S100B in the control of oligodendrocyte maturation. This data reinforce the importance of oligodendrocytes in schizophrenia, shedding more light to its pathobiology. PMID:24504531

Steiner, Johann; Schmitt, Andrea; Schroeter, Matthias L; Bogerts, Bernhard; Falkai, Peter; Turck, Christoph W; Martins-de-Souza, Daniel

2014-06-01

168

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

169

Quantifying reflectance anisotropy of photosynthetically active radiation in grasslands  

SciTech Connect

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

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

1992-11-30

170

Myelination of the corpus callosum in male and female rats following complex environment housing during adulthood  

PubMed Central

Myelination is an important process in brain development, and delays or abnormalities in this process have been associated with a number of conditions including autism, developmental delay, attention deficit disorder, and schizophrenia. Myelination can be sensitive to developmental experience; however, although the adult brain remains highly plastic, it is unknown whether myelination continues to be sensitive to experience during adulthood. Male and female rats were socially housed until four months of age, at which time they were moved into either a complex or “enriched” environment (EC) or an isolated condition (IC). Although the area of the splenium (posterior 20% of the callosum, which contains axons from visual cortical neurons) increased by about 10% following two months of EC housing, the area occupied by myelinated axons was not influenced by adult housing condition. Instead, it was the area occupied by glial cell processes and unmyelinated axons which significantly increased following EC housing. Neither the size nor the myelin content of the genu (anterior 15% of the callosum) was sensitive to manipulations of adult housing condition, but males had more area occupied by myelinated axons in both callosal regions. Finally, the inability of two months of complex environment housing during adulthood to impact the number of myelinated axons in the splenium was confirmed in a subset of animals using quantitative electron microscopy. We conclude that the sensitivity of myelination to experience is reduced in adulthood relative to development in both sexes. PMID:19596280

Markham, Julie A.; Herting, Megan M.; Luszpak, Agatha E.; Juraska, Janice M.; Greenough, William T.

2009-01-01

171

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

172

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

PubMed

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

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

2011-04-30

173

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

174

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

175

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

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

Anisotropy-Compensated Magnetic Nanostructures  

NASA Astrophysics Data System (ADS)

Nanostructuring can be used to tailor the magnetic anisotropy K1 as function of temperature, which is important in permanent magnetism and magnetic recording. Anisotropy is an atomic quantity, but the ferromagnetic exchange ensures an anisotropy averaging over a few nanometers, in contrast to the absence of nanoscale Curie-temperature averaging [1]. An intriguing and largely overlooked feature is the possibility of temperature- dependent anisotropy zeros, which yields a potential write-field reduction in magnetic recording. On an atomic scale, this effect is well-known but limited to a relatively narrow range of rare- earth transition-metal intermetallics. Nanostructuring greatly extends the range of materials. Explicitly considered structures are thin films, where the determination of the anisotropy zero (s) yields algebraic equations whose roots depend on the thicknesses, Curie temperatures, and zero-temperature anisotropies of the involved phases. On a somewhat larger length scale (> 5 to 10 nm), there is no longer a well-defined anisotropy, but the corresponding micromagnetic corrections are easily incorporated into the theory. - [1] R. Skomski, ``Simple Models of Magnetism,'' University Press, Oxford 2008.

Skomski, Ralph; George, Tom A.; Sellmyer, D. J.

2008-03-01

178

Lattice preferred orientation and seismic anisotropy in sedimentary rocks  

NASA Astrophysics Data System (ADS)

Although it is well known that sedimentary rocks can be seismically anisotropic, there have been few detailed investigations of the underlying cause of such anisotropy. Here, we investigate anisotropy due to the preferred orientation of minerals, or lattice preferred orientation (LPO), in a suite of sedimentary rocks. Seismic properties are predicted by averaging single-crystal elastic constants of minerals according to their crystal orientation and modal volume fraction in the rock aggregate. Both Electron Backscattered Diffraction (EBSD) and X-ray Texture Goniometry (XTG) are tested as quantitative techniques for measuring the LPO of sedimentary rocks. Although EBSD has promise for future LPO measurements in polymineralic sedimentary rocks, problems currently remain in measuring low-symmetry phases (e.g. feldspars) and very small clay or mica particles. However, the LPO of very fine-grained phyllosilicates can be measured using XTG and the LPO of low-symmetry minerals can be measured using manual EBSD pattern analysis. Here, we use such a hybrid approach to estimate LPO in a suite of sedimentary samples. The seismic properties calculated from LPO data show anisotropy values for P-waves ranging from 1.5 per cent in sandstones, to over 3.5 per cent in a siltstone, to 12 per cent in a shale. The effect of thin multilayering on long-wavelength propagation in a siltstone is predicted by applying Backus-type averaging. The layering does not enhance the anisotropy because of the small differences in density and in elasticity between the two layer types. The LPO of phyllosilicates and to a lesser extent dolomite and siderite seem to contribute significantly to the seismic anisotropy of phyllosilicate-rich rocks (siltstones and shales). The weak LPO of quartz in sandstones causes a few per cent anisotropy. Cumulatively, our results suggest that field observations of seismic anisotropy have the potential to be used as an indicator of rock lithology.

Valcke, S. L. A.; Casey, M.; Lloyd, G. E.; Kendall, J.-M.; Fisher, Q. J.

2006-08-01

179

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

180

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

181

What fraction?  

NSDL National Science Digital Library

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

Blundred, A.

2012-01-01

182

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

183

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

Microsoft Academic Search

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

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

2000-01-01

184

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.

185

Corpus Callosum Size, Reaction Time Speed and Variability in Mild Cognitive Disorders and in a Normative Sample  

ERIC Educational Resources Information Center

Intra-individual variability in reaction time increases with age and with neurological disorders, but the neural correlates of this increased variability remain uncertain. We hypothesized that both faster mean reaction time (RT) and less intra-individual RT variability would be associated with larger corpus callosum (CC) size in older adults, and…

Anstey, Kaarin J.; Mack, Holly A.; Christensen, Helen; Li, Shu-Chen; Reglade-Meslin, Chantal; Maller, Jerome; Kumar, Rajeev; Dear, Keith; Easteal, Simon; Sachdev, Perminder

2007-01-01

186

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

187

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

188

Temperature dependent magnetization in Co-base nanowire arrays: Role of crystalline anisotropy  

NASA Astrophysics Data System (ADS)

Co, Co(1-x)Pdx, and Co(1-y)Niy nanowire arrays have been prepared by electrochemical template-assisted growth. Hcp, fcc or both phases are detected in Co nanowires depending on their length (300 nm to 40 ?m) and on the content of Pd (0 ? x ? 0.4) and Ni (0 ? y ? 0.8). Their magnetic behavior has been studied under longitudinal and perpendicular applied fields. The effective magnetic anisotropy is mostly determined by the balance between the shape and the crystalline terms, the latter depending on the fractional volume of hcp phase with strong perpendicular anisotropy and fcc phase with weaker longitudinal anisotropy. The temperature dependence of remanence and coercivity and the eventual observation of compensation temperature is interpreted as due to the different temperature dependence of shape and hcp crystalline anisotropy. Optimum longitudinal magnetic anisotropy is achieved in low Pd-content CoPd nanowires and in short Co nanowires.

Vivas, L. G.; Vázquez, M.; Vega, V.; García, J.; Rosa, W. O.; del Real, R. P.; Prida, V. M.

2012-04-01

189

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

190

Fraction Models  

NSDL National Science Digital Library

This interactive activity allows users the ability to explore different representations for fractions and how they are equivalent to mixed numbers, decimals, and percentages. Users adjust the numerator (up to 100) and the denominator (1 to 25) in order to see a visual representation of the fraction. The visual representation can be seen as a length, area, region, or set model. Users also have the ability to keep track of the equivalent forms of fractions in a table. Instructions and exploration questions are given.

2011-01-01

191

Limits on the gravity wave contribution to microwave anisotropies  

E-print Network

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

J. P. Zibin; Douglas Scott; Martin White

1999-01-05

192

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

193

Adding Fractions  

NSDL National Science Digital Library

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

Website, Math I.

2011-09-23

194

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.

Lessonplans, Utah

2012-10-22

195

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

196

Reversible splenial lesion on the corpus callosum in nonfulminant hepatitis A presenting as encephalopathy  

PubMed Central

Reversible focal lesions on the splenium of the corpus callosum (SCC) have been reported in patients with mild encephalitis/encephalopathy caused by various infectious agents, such as influenza, mumps, adenovirus, Varicella zoster, Escherichia coli, Legionella pneumophila, and Staphylococcus aureus. We report a case of a reversible SCC lesion causing reversible encephalopathy in nonfulminant hepatitis A. A 30-year-old healthy male with dysarthria and fever was admitted to our hospital. After admission his mental status became confused, and so we performed electroencephalography (EEG) and magnetic resonance imaging (MRI) of the brain, which revealed an intensified signal on diffusion-weighted imaging (DWI) at the SCC. His mental status improved 5 days after admission, and the SCC lesion had completely disappeared 15 days after admission. PMID:25548747

Ko, Soon Young; Kim, Byung Kook; Kim, Dong Wook; Kim, Jeong Han; Choe, Won Hyeok; Seo, Hee Yeon

2014-01-01

197

Properties of angiotensin II receptors in glial cells from the adult corpus callosum.  

PubMed Central

The existence and the properties of angiotensin II receptors in the adult bovine and human corpus callosum (CC) were investigated by using Xenopus oocytes and primary glial cell cultures. In oocytes injected with CC mRNA, angiotensin II elicited oscillatory Cl- currents due to activation of the inositol phosphate/Ca(2+)-receptor-channel coupling system. The receptors expressed in oocytes and in CC cultures were pharmacologically similar to the AT1 receptor type as assayed by binding. Northern blot analysis and in situ hybridization studies in sections from CC and in glial cultures revealed that the receptors were molecularly related to the AT1 receptor and that they were present in astrocytes. In these cells, activation of the receptors with angiotensin II increased de novo DNA synthesis, promoted the release of aldosterone, and induced c-Fos expression. These findings indicate that CC astrocytes possess functional AT1 receptors that participate in various physiological processes. Images PMID:8170986

Matute, C; Pulakat, L; Río, C; Valcárcel, C; Miledi, R

1994-01-01

198

Reversible splenial lesion on the corpus callosum in nonfulminant hepatitis A presenting as encephalopathy.  

PubMed

Reversible focal lesions on the splenium of the corpus callosum (SCC) have been reported in patients with mild encephalitis/encephalopathy caused by various infectious agents, such as influenza, mumps, adenovirus, Varicella zoster, Escherichia coli, Legionella pneumophila, and Staphylococcus aureus. We report a case of a reversible SCC lesion causing reversible encephalopathy in nonfulminant hepatitis A. A 30-year-old healthy male with dysarthria and fever was admitted to our hospital. After admission his mental status became confused, and so we performed electroencephalography (EEG) and magnetic resonance imaging (MRI) of the brain, which revealed an intensified signal on diffusion-weighted imaging (DWI) at the SCC. His mental status improved 5 days after admission, and the SCC lesion had completely disappeared 15 days after admission. PMID:25548747

Ko, Soon Young; Kim, Byung Kook; Kim, Dong Wook; Kim, Jeong Han; Choe, Won Hyeok; Seo, Hee Yeon; Kwon, So Young

2014-12-01

199

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

200

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

201

Fraction War  

NSDL National Science Digital Library

This lesson is meant to be utilized as a means to enhance previous instruction of fractions that are greater than, or less than one. It is best utilized to build fluency, as this is meant to be a fast paced game to make learning interactive and engaging.

2013-01-24

202

Dividing Fractions  

NSDL National Science Digital Library

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

2012-10-17

203

Fraction Penguin  

NSDL National Science Digital Library

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

Sciences, California A.

2008-01-01

204

Congenital pulmonary airway malformation (CPAM) [congenital cystic adenomatoid malformation] associated with tracheoesophageal fistula and agensesis of the corpus callosum.  

PubMed

Congenital pulmonary airway malformations (CPAM) are a family of hamartomatous disorders due to the uncontrolled overgrowth of the terminal bronchioles. Congenital pulmonary airway malformations can co-exist with cardiovascular and/or urogenital malformations, but their association with thoracopulmonary malformations is extremely rare. We report the first case of CPAM type I, co-existing with tracheo-esophageal fistula and corpus callosum agenesis. PMID:22414029

Pizzi, Marco; Fassan, Matteo; Ludwig, Kathrin; Cassina, Matteo; Gervasi, Maria Teresa; Salmaso, Roberto

2012-06-01

205

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

PubMed

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

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

2012-09-01

206

Magnetic anisotropy data of CBrN  

NASA Astrophysics Data System (ADS)

This document is part of Subvolume C `Diamagnetic Susceptibility and Magnetic Anisotropy of Organic Compounds' of Volume 27 `Diamagnetic Susceptibility and Anisotropy' of Landolt-Börnstein - Group II Molecules and Radicals.

Kumar, M.; Gupta, R.

207

Larger corpus callosum size with better motor performance in prematurely born children.  

PubMed

The objective of this study is to determine the relation between the size of the corpus callosum (CC) and motor performance in a population-based cohort of preterm children. Preterm born children (n = 221) with a gestational age less than or equal to 32 weeks and/or a birth weight below 1500 g were eligible for this study. At the age of 7 or 8 years, frontal, middle, posterior, and total areas (mm2) of the corpus callosum were measured on true midsagittal MRI. Due to anxiety of 10 children and motion artifacts in 7 other children, 204 MRIs could be assessed in the preterm group (mean GA 29.4 weeks, sd 2.0,mean BW 1200 g, sd 323). The preterm group consisted of 15 children with cerebral palsy (CP) and 189 children without CP. Motor function was established by using the Movement Assessment Battery for Children, and the Developmental Test of Visual Motor Integration was obtained. The same examinations were performed in 21 term born children. The mean total cross-sectional CC area was significantly smaller in preterm born infants compared with their term born controls (338 mm2 versus 422 mm2, P < 0.0001). The preterm children with CP had significantly smaller mean CC areas compared with the preterms who did not develop CP (P < 0.0001-P < 0.002). However, the preterms born without CP also had significantly smaller body, posterior, and total CC areas compared with term born controls (P < 0.0001-P < 0.002). Only the difference in frontal area measurements dilrc) -3.3 mm2/score point (95% CI -4.5, -2.1). The association existed in all parts of the CC but increased in the direction of the posterior part: frontal: lrc -0.8 mm2/score point (-1.2, -0.4), middle: lrc -1.1 mm2/score point (-1.7, -0.5) and posterior: lrc -1.4 mm2/score point (-1.8, -0.9). An association between CC area and its subareas and the standard scores of the VMI was also found. A larger CC was strongly related t o better scores onthe VMI test total area CC: lrc 0.05 score/mm2 (95% CI 0.03, 0.07), frontal: lrc 0.12 score/mm2 (0.05,0.19), middle: lrc 0.10 score/mm2 (0.05, 0.15) and posterior: lrc 0.12 score/mm2 (0.06, 0.18). After adjustment for gestational age, birth weight, and total cerebral area, these associations were still significant. There is a strong association between the size of the corpus callosum (total midsagittal cross area as well as frontal, middle, and posterior area) and motor function in preterm children, investigated at school age. A poorer score on the Movement ABC was related to a smaller CC. A larger CC was strongly associated with better VMI standard scores. PMID:15565788

Rademaker, K J; Lam, J N G P; Van Haastert, I C; Uiterwaal, C S P M; Lieftink, A F; Groenendaal, F; Grobbee, D E; de Vries, L S

2004-08-01

208

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

209

Fraction four  

NSDL National Science Digital Library

In this two-player online game, students combine math skills and strategies to practice simplifying, converting, and multiplying decimals, percentages, and fractions. For each correct answer, the player places a colored ball on a 10-by-10 grid. The first person to place four balls of his or her color together in a row or diagonally wins. Students can choose different difficulty levels, response time limits, and types of questions. Problems range from simple calculations for reducing fractions to solving proportions. From the online game page, What, How, and Why buttons open sections that explain the activity's purpose, function, and where the mathematics fits into the curriculum. Supporting information includes links to related lessons and student discussion questions, which help determine what strategies the winning student used to arrive at the correct answers. Copyright 2005 Eisenhower National Clearinghouse

Foundation, Shodor E.

2004-01-01

210

Fraction Tracks  

NSDL National Science Digital Library

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

Boston, Wgbh

1996-01-01

211

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

212

Segmentation of DT-MRI Anisotropy Isosurfaces  

Microsoft Academic Search

While isosurfaces of anisotropy measures for data from diffusion tensor magnetic resonance imaging (DT-MRI) are known to depict major anatomical structures, the anisotropy metric reduces the rich tensor data to a simple scalar eld. In this work, we suggest that the part of the data which has been ignored by the metric can be used to segment anisotropy isosurfaces into

Thomas Schultz; Holger Theisel; Hans-peter Seidel

2007-01-01

213

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

214

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

PubMed

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

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

2014-11-01

215

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

PubMed Central

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 26 CC regional patterns. Although complete agenesis did not occur, partial agenesis was observed in 102 children and within 15 CC regional patterns. Only 4.1% had a normal CC. Quantitative assessment of the area of the CC in 26 NC children and 68 children with SBM revealed that all subgroups with CC anomalies had smaller areas than did a subgroup with a normal CC. Areas were especially small in rostral/splenial agenesis and splenial agenesis but larger with rostral agenesis. Subgroups with normal/hypoplastic regions or complete hypoplasia also had CC areas that were smaller than normal but larger than the areas for the splenial agenesis groups. The relative rarity of anterior commissure enlargement (3.1%) and longitudinal bundles of Probst (0.1%) suggest that these particular fiber tract anomalies are unlikely candidates for structural compensatory mechanisms. The hippocampal commissure, enlarged in 13%, may be a more promising candidate. Overall, however, the functionality of anomalous fiber tracts and commissures in SBM is yet to be determined. PMID:19052950

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

2009-01-01

216

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

PubMed Central

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

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

2014-01-01

217

Improved corpus callosum area measurements by analysis of adjoining parasagittal slices  

PubMed Central

The corpus callosum (CC) is a bundle of approximately 180 million axons connecting homologous areas of the left and right cerebral cortex. Because CC projections are topographically organized, regional CC morphological abnormalities may reflect regional cortical developmental abnormalities. We assess the variance characteristics of three CC area measurement techniques by comparing a single midsagittal slice versus three slices (midsagittal plus one parasagittal on each side) and five slices (midsagittal plus two parasagittal on each side). CC images were partitioned into five subregions using the Hofer–Frahm scheme under the three methods and variance was examined via two complementary data sets. In the first, to control for intersubject variability, 12 scans were acquired from a single subject over the course of 3 h. In the second, we used scans from 56 healthy male volunteers between the ages of 10 and 27 years (mean=17.47, S.D.=3.42). Increasing the number of slices from one to three to five diminished the coefficient of variation (CV) within subregions and increased the power to detect differences between groups. A power analysis was conducted for the sample under each method to determine the sample size necessary to discern a given percent change (delta) ranging from 1 to 20% iteratively. PMID:23149042

Wade, Benjamin Seavey Cutler; Stockman, Michael; McLaughlin, Michael Joseph; Raznahan, Armin; Lalonde, Francois; Giedd, Jay Norman

2014-01-01

218

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

PubMed

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

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

2015-01-01

219

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

PubMed Central

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

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

2013-01-01

220

Functional Topography of Human Corpus Callosum: An fMRI Mapping Study  

PubMed Central

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

Fabri, Mara; Polonara, Gabriele

2013-01-01

221

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

222

Galaxy clusters and microwave background anisotropy  

E-print Network

Previous estimates of the microwave background anisotropies produced by freely falling spherical clusters are discussed. These estimates are based on the Swiss-Cheese and Tolman-Bondi models. It is proved that these models give only upper limits to the anisotropies produced by the observed galaxy clusters. By using spherically symmetric codes including pressureless matter and a hot baryonic gas, new upper limits are obtained. The contributions of the hot gas and the pressureless component to the total anisotropy are compared. The effects produced by the pressure are proved to be negligible; hence, estimations of the cluster anisotropies based on N-body simulations are hereafter justified. After the phenomenon of violent relaxation, any realistic rich cluster can only produce small anisotropies with amplitudes of order $10^{-7}$. During the rapid process of violent relaxation, the anisotropies produced by nonlinear clusters are expected to range in the interval $(10^{-6},10^{-5})$. The angular scales of these anisotropies are discussed.

V. Quilis; J. M. Ibanez; D. Saez

1995-07-08

223

Azimuthal anisotropy of direct photons  

SciTech Connect

The electromagnetic bremsstrahlung produced by a quark interacting with nucleons or nuclei is azimuthally asymmetric. In the light-cone dipole approach this effect is related to the orientation dependent dipole cross section. Such a radiation anisotropy is expected to contribute to the azimuthal asymmetry of direct photons in pA and AA collisions, as well as in deep-inelastic scattering and in the production of dileptons.

Kopeliovich, B. Z. [Departamento de Fisica y Centro de Estudios Subatomicos, Universidad Tecnica Federico Santa Maria, Casilla 110-V, Valparaiso (Chile); Joint Institute for Nuclear Research, Dubna (Russian Federation); Pirner, H. J. [Institute for Theoretical Physics, University of Heidelberg, Philosophenweg 19, D-69120 Heidelberg (Germany); Rezaeian, A. H.; Schmidt, Ivan [Departamento de Fisica y Centro de Estudios Subatomicos, Universidad Tecnica Federico Santa Maria, Casilla 110-V, Valparaiso (Chile)

2008-02-01

224

The elastic anisotropy of marble  

E-print Network

, for his many suggestions and for the use of his petrofabric laboratory. I am grateful to Neville Carter for his advice and to Nik Christensen for supplying the samples for this study. I am indebted to Michele Scarmardo for typing this thesis. A special... al. , 1969). This important observation has led others (e. g. Hess, 1964; Ave Lallement and Carter, 1970; Christensen and Salisbury, 1979) to suggest that the anisotropy is a result of preferred orienta- tion of the highly anisotropic mineral...

Gebhard, Susan Nash

1982-01-01

225

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

226

Genetics of White Matter Asymmetry Mapped using Diffusion Tensor Anisotropy Measures in 100 Twins  

Microsoft Academic Search

Introduction: Structural and functional brain asymmetry are of great interest in neuroscience, shedding light on the functional specialization of the two hemispheres. With the advent of diffusion tensor imaging (DTI), white matter connectivity can be visualized and fiber asymmetries can be investigated using measures sensitive to myelination, such as fractional and geodesic anisotropy (FA, GA). Here we examined hemispheric asymmetries

N. Jahanshad; A. D. Lee; N. Lepore; C. Brun; M. Barysheva; Y. Chou; A. W. Toga; K. L. McMahon; G. I. de Zubicaray; M. J. Wright; P. M. Thompson

2009-01-01

227

[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

228

Fractional Electromagnetic Equations Using Fractional Forms  

NASA Astrophysics Data System (ADS)

The generalized physics laws involving fractional derivatives give new models and conceptions that can be used in complex systems having memory effects. Using the fractional differential forms, the classical electromagnetic equations involving the fractional derivatives have been worked out. The fractional conservation law for the electric charge and the wave equations were derived by using this method. In addition, the fractional vector and scalar potentials and the fractional Poynting theorem have been derived.

Baleanu, Dumitru; Golmankhaneh, Ali Khalili; Golmankhaneh, Alireza Khalili; Baleanu, Mihaela Cristina

2009-08-01

229

In vivo imaging of region and cell type specific neocortical neurodegeneration in Alzheimer's disease. Perspectives of MRI derived corpus callosum measurement for mapping disease progression and effects of therapy. Evidence from studies with MRI, EEG and PET.  

PubMed

Neuropathological studies in Alzheimer's disease (AD) indicate specific loss of layer III and V large pyramidal neurons in association cortex. These neurons give rise to long cortico-cortical connections, projecting through the corpus callosum, in an anterior-posterior topology. Based on these findings we hypothesized that regional corpus callosum atrophy may be a potential in vivo marker for neocortical neuronal loss in AD. To evaluate this hypothesis, we developed a method to measure cross-sectional area of the corpus callosum and of five corpus callosum subregions on midsagittal magnetic resonance imaging scans (MRI). In a subsequent series of six experimental studies using MRI, (18)FDG-PET and EEG, we investigated the relation of white matter hyperintensities (WMH) to corpus callosum size and correlated regional pattern of corpus callosum atrophy with regional cortical metabolic decline as well as intracortical coherencies. Mean total corpus callosum area was reduced significantly in AD patients compared to healthy age-matched controls, with the greatest changes in the rostrum and the splenium and relative sparing of the truncus. The regional pattern of corpus callosum atrophy was independent of WMH load and correlated significantly with pattern of regional metabolic decline measured with (18)FDG-PET, the degree of cognitive impairment and regional decline of bilateral intracortical-coherency in EEG in AD patients. We further found that hippocampus atrophy, as a marker of early allocortical degeneration, was more pronounced than total corpus callosum atrophy in mild stages of AD. Regional corpus callosum atrophy in mild disease, however, suggested early neocortical degeneration in AD. In a longitudinal study, AD patients showed significantly greater rates of corpus callosum atrophy than controls. Rates of atrophy correlated with progression of clinical dementia severity in AD. Our results indicate that regional corpus callosum atrophy in AD patients represents the loss of callosal efferent neurons in corresponding regions of the neocortex. As these neurons are a subset of cortico-cortical projecting neurons, region-specific corpus callosum atrophy may serve as a marker of progressive neocortical disconnection in AD. In combination with measurement of hippocampal atrophy, assessment of corpus callosum atrophy over time in individual patients is useful to evaluate effects on brain structure of currently developed drugs, thought to slow or modify AD progression. PMID:12111472

Hampel, H; Teipel, S J; Alexander, G E; Pogarell, O; Rapoport, S I; Möller, H-J

2002-05-01

230

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

231

Abnormalities of the Corpus Callosum in Non-Psychotic high-risk offspring of schizophrenia patients  

PubMed Central

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

Francis, A.; Bhojraj, TS; Prasad, K; Kulkarni, S; Montrose, D; Eack, S; Keshavan, MS

2010-01-01

232

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

233

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

PubMed Central

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

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

2013-01-01

234

The corpus callosum modulates spindle-burst activity within homotopic regions of somatosensory cortex in newborn rats.  

PubMed

The corpus callosum, a major interhemispheric fiber tract, mediates communication between homotopic regions within the primary somatosensory cortex (S1). Recently, in 1- to 6-day-old rats, brief bursts of oscillatory activity - called spindle-bursts (SBs) - were described in cortical somatosensory areas following sensory feedback from sleep-related myoclonic twitches or specific peripheral stimulation. To determine whether interhemispheric communication via the corpus callosum modulates the expression of SBs during this early period of development, we investigated the spontaneous expression of SBs in unanesthetized 1- to 6-day-old rats as well as SBs evoked by plantar surface stimulation of the forepaw. We hypothesized that surgically disrupting transcallosal communication (i.e. with callosotomy) or unilateral pharmacological manipulation of S1 activity (e.g. by blocking muscarinic receptors) would alter S1 activity in one or both hemispheres. First, callosotomy doubled the rate of spontaneous, twitch-related SBs in left and right S1s by reducing the interval between successive SBs. Second, unilateral infusion into the left S1 of the muscarinic receptor antagonist, scopolamine, inhibited SBs in response to right forepaw stimulation; importantly, SBs were now disinhibited in the right S1 to right forepaw stimulation, thus 'unmasking' an ipsilateral representation. Subsequent callosotomy reinstated contralateral SB responses in the left S1. Finally, tactile and proprioceptive stimulation produced dissociable neurophysiological S1 responses; specifically, SBs were produced in response to proprioceptive, but not tactile, stimulation. We conclude that the corpus callosum modulates functionally inhibitory interactions between homotopic regions in left and right S1s during the early developmental period when organized neurophysiological activity is first detected in the neocortex. PMID:18973571

Marcano-Reik, Amy Jo; Blumberg, Mark S

2008-10-01

235

A Diagnostic Conundrum: Ectopic Nasal Ossification, Submucosal Alveolar Cleft, Absent Posterior Atlantal Arch, and Corpus Callosum Lipoma.  

PubMed

A 19-year-old woman was referred for nasal breathing and aesthetic concerns regarding her nose. A computed tomography scan revealed a massive osseous shield anterior to the piriform aperture. Furthermore, there was a submucosal median alveolar cleft, and the posterior arch of C1 was missing. The magnetic resonance imaging brain scan revealed a curvilinear lipoma of corpus callosum. The ectopic nasal bone was removed by open rhinoplast,y and nasal function and aesthetics were restored. The described features defy conventional clinical diagnosis and severity classifications and present a diagnostic conundrum somewhere between a mild form of frontonasal dysplasia, oculoauriculofrontonasal syndrome, and Pai syndrome. PMID:25291089

Borumandi, Farzad; Chadha, Ambika; Dediol, Emil; Ugleši?, Vedran

2014-10-01

236

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

237

Thermal expansion and elastic anisotropies of SiC as related to polytype structure  

NASA Technical Reports Server (NTRS)

The concept of the fraction of hexagonal stacking is used to describe the anisotropic thermal expansion coefficients of polytypes of SiC. The single crystal elastic anisotropy for the SiC polytype structures and the temperature dependencies of the anisotropies are examined. The anisotropic thermoelastic stress index for the 3C and 6H SiC polytypes are illustrated graphically. It is shown that this index is useful for predicting the most desirable crystal growth orientations for SiC whisker incorporation into composite matrices.

Li, Z.; Bradt, R. C.

1989-01-01

238

Dimethyl sulfoxide cataract: a model for optical anisotropy fluctuations  

NASA Astrophysics Data System (ADS)

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

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

1996-07-01

239

Azimuthal anisotropy measurements by STAR  

NASA Astrophysics Data System (ADS)

The recent study of centrality and transverse momentum (pT) dependence of inclusive charged hardron elliptic anisotropy (v2) at midrapidity (|?|<1.0) in Au+Au collision at ?{sNN}=7.7,11.5,19.6,27, and 39 GeV in STAR Beam Energy Scan program is presented. We show that the observed increase of inclusive v2 is mainly due to the average pT increase with energy. In Au+Au 200 GeV collisions, the triangular anisotropy (v3) measurements highly depend on measurement methods; v3 is strongly dependent on ??. The difference between two- and four-particle cumulants v2{2} and v2{4} for Au+Au and Cu+Cu collision at ?{sNN}=62.4 and 200 GeV is used to explore flow fluctuations. Furthermore, by exploiting the symmetry of average flow in pseudorapidity ? about midrapidity, the ??-dependent and independent components are separated using v2{2} and v2{4}.

Yi, Li

2014-06-01

240

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

PubMed Central

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

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

2012-01-01

241

Intermanual interactions during initiation and production of rhythmic and discrete movements in individuals lacking a corpus callosum.  

PubMed

Three individuals lacking a corpus callosum, two due to callosotomy and one agenesis, and three age-matched healthy controls were tested on a bimanual task in which a discrete or rhythmic arm movement was initiated following a visual signal while the other arm produced continuous, rhythmic movements. The control participants initiated the secondary, rhythmic movement in phase with the ongoing rhythmic base movement and the two limbs were coupled in an inphase mode across the duration of the trial. In contrast, the acallosal individuals failed to show phase entrainment at the initiation of the secondary, rhythmic movements. Moreover, the callosotomy patients exhibited weak coupling between the rhythmically moving limbs while the individual with callosal agenesis consistently synchronized in an antiphase mode. The control participants exhibited increased perturbation of the ongoing base movement when initiating a discrete movement; for the acallosal participants, the base movement was similarly perturbed in both secondary movement conditions. These results are consistent with the hypothesis that intermanual interactions observed during bimanual movements arise from various levels of control, and that these are distinct for discrete and rhythmic movements. Temporal coupling during rhythmic movements arises in large part from transcallosal interactions between the two hemispheres. The imposition of a secondary movement may transiently disrupt an ongoing rhythmic movement even in the absence of the corpus callosum. This may reflect subcortical interactions associated with response initiation, or, due to dual task demands, a transient shift in attentional resources. PMID:16917769

Sternad, Dagmar; Wei, Kunlin; Diedrichsen, Jörn; Ivry, Richard B

2007-02-01

242

Corpus Callosum Shape and Size Changes in Early Alzheimer's Disease: A Longitudinal MRI Study Using the OASIS Brain Database  

PubMed Central

Background Alzheimer's disease (AD) has been shown to be associated with shrinkage of the corpus callosum mid-sagittal cross-sectional area (CCA). Objective To study temporal rates of corpus callosum atrophy not previously reported for early AD. Methods We used longitudinal MRI scans to study the rates of change of CCA and circularity (CIR), a measure of its shape, in normal controls (NC, n = 75), patients with very mild AD (AD-VM, n = 51), and mild AD (AD-M, n = 21). Results There were significant reduction rates in CCA and CIR in all three groups. While CCA reduction rates were not statistically different between groups, the CIR declined faster in AD-VM (p < 0.03) and AD-M (p < 0.0001) relative to NC, and in AD-M relative to AD-VM (p < 0.0004). Conclusion CIR declines at an accelerated rate with AD severity. Its rate of change is more closely associated with AD progression than CCA or any of its sub-regions. CIR may be a useful group biomarker for objective assessment of treatments that aim to slow AD progression. PMID:24121963

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

2015-01-01

243

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

244

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

245

Anisotropy factor of saturated and unsaturated soils  

Microsoft Academic Search

Variations in the degree of anisotropy in soil hydraulic conductivity with changes in water saturation (Se) may adversely impact predictability of flow and transport processes. The conceptual “layered cake” model was extended to consider effects of bulk density variations within a particular soil type. The anisotropy factor as function of matric potential A(?) exhibits different behavior for different soil textures.

S. Assouline; D. Or

2006-01-01

246

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

247

Polymer shape anisotropy and the depletion interaction.  

PubMed

We calculate the second and third virial coefficients of the effective sphere-sphere interaction due to polymer-induced depletion forces. By utilizing the anisotropy of a typical polymer conformation, we can consider polymers that are roughly the same size as the spheres. We argue that recent experiments are laboratory evidence for polymer shape anisotropy. PMID:11969544

Triantafillou, M; Kamien, R D

1999-05-01

248

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

249

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

250

The Effect of Playbased Music Therapy on the Motor and Communication Skills with a Child with Partial Agenesis of the Corpus Callosum  

Microsoft Academic Search

The purpose of this case study was to examine the effect of playbased music therapy on the motor and communication skills with a child with partial agenesis of the corpus callosum. The subject participated in 30 minute playbased music therapy sessions three times a week for three months. Data were collected using the Developmental Assessment of Young Children as a

Jessica P. Albright

2011-01-01

251

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

252

Separating intrinsic and apparent seismic anisotropy  

NASA Astrophysics Data System (ADS)

Seismic anisotropy plays a key role in studies of the Earth's rheology and deformation because of its relation to flow-induced lattice-preferred orientation (LPO) of intrinsically anisotropic minerals. In addition to LPO, small-scale heterogeneity produces apparent anisotropy that need not be related to deformation in the same way as intrinsic anisotropy. Quantitative interpretations of observed anisotropy therefore require the separation of its intrinsic and apparent components. We analyse the possibility of separating intrinsic and apparent anisotropy in media with hexagonal symmetry - typically used in surface wave tomography and SKS splitting studies. Our analysis is on the level of the wave equation, which makes it general and independent of specific data types. We find that commonly observed anisotropy can always be explained by a purely isotropic laminated medium unless all anisotropic parameters are known with unrealistic accuracy. Most importantly, minute changes in the poorly constrained P wave anisotropy and the parameter eta can switch between the existence or not of a laminated isotropic equivalent. Important implications of our study are: (1) Intrinsic anisotropy over tomographically resolved length scales is never strictly required when reasonable error bars for anisotropic parameters are taken into account. (2) Currently available seismic observables do not provide adequate constraints on the relative contributions of intrinsic and apparent anisotropy. (3) Therefore, seismic observables alone do not provide compelling constraints on the magnitude of mantle flow. (4) Quantitative interpretations of anisotropy in terms of mantle flow require a combined seismic/geodynamic inversion that properly accounts for the formation of both LPO and small-scale heterogeneity.

Trampert, Jeannot; Fichtner, Andreas; Kennett, Brian

2013-04-01

253

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

254

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

255

Fraction Feud: Comparing and Ordering Fractions  

NSDL National Science Digital Library

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

Rising, Jennifer

2011-01-01

256

A Longitudinal Magnetic Resonance Imaging Study of the Apparent Diffusion Coefficient Values in Corpus Callosum during the First Year after Traumatic Brain Injury  

PubMed Central

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

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

2014-01-01

257

Fractional Modified Special Relativity  

E-print Network

Fractional calculus represents a natural tool for describing relativistic phenomena in pseudo-Euclidean space-time. In this study, Fractional modified special relativity is presented. We obtain fractional generalized relation for the time dilation.

Hosein Nasrolahpour

2011-03-31

258

Local Control of Single Atom Magnetocrystalline Anisotropy  

NASA Astrophysics Data System (ADS)

Individual Fe atoms on a Cu2N/Cu(100) surface exhibit strong magnetic anisotropy due to the crystal field. We show that we can controllably enhance or reduce this anisotropy by adjusting the relative position of a second nearby Fe atom, with atomic precision, in a low-temperature scanning tunneling microscope. Local inelastic electron tunneling spectroscopy, combined with a qualitative first-principles model, reveal that the change in uniaxial anisotropy is driven by local strain due to the presence of the second Fe atom.

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

2013-09-01

259

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

260

Non-Bunch-Davies statistical anisotropies  

NASA Astrophysics Data System (ADS)

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

Chen, Xingang; Wang, Yi

2014-07-01

261

Cortical depth dependence of the diffusion anisotropy in the human cortical gray matter in vivo.  

PubMed

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

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

2014-01-01

262

Modeling Multiplication with Fractions  

NSDL National Science Digital Library

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

Joseph Ratasky

2012-08-18

263

Blindness, dancing extremities, and corpus callosum and brain stem involvement: an unusual presentation of fulminant subacute sclerosing panencephalitis.  

PubMed

A 4-year-old girl presented with acute visual loss followed 2 weeks later with loss of speech and audition, fulminant neuroregression, and choreo-athetoid movements of extremities. Fundus showed bilateral chorioretinitis. Electroencephalography showed periodic complexes. Measles antibody titers were elevated in both serum and cerebrospinal fluid, consistent with subacute sclerosing panencephalitis. Neuroimaging showed discontiguous involvement of splenium of the corpus callosum and ventral pons with sparing of cortical white matter. Our case highlights the atypical clinical and radiologic presentations of subacute sclerosing panencephalitis. Pediatricians need to be aware that necrotizing chorioretinitis in a child and/or atypical brain stem changes could be the heralding feature of this condition in endemic countries. PMID:24700664

Singhi, Pratibha; Saini, Arushi Gahlot; Sankhyan, Naveen; Gupta, Pankaj; Vyas, Sameer

2015-01-01

264

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

2014-10-01

265

Acute encephalopathy with a lesion of the splenium of the corpus callosum--a report of two cases.  

PubMed

We report two cases of encephalopathy following a short febrile illness. Case one was a five year old child whose magnetic resonance imaging (MRI) of the brain showed a reversible discrete lesion in the splenium of the corpus callosum (SCC) and a ten year old boy who had extensive hyperintensity of the SCC. As these children have presented while there was an outbreak of influenza in our locality and since the second child tested positive for H1N1 antigen on PCR test, we feel that as previous authors have pointed out, these cases are cases of possible influenza encephalopathy. This awareness needs to be disseminated as this specific MRI finding should prompt one to test for H1N1 antigen and offer specific antiviral agent. Case one showed signs that support the existence of a splenial syndrome. PMID:21723059

Iype, Mary; Ahamed, Shahanaz; Thomas, Bejoy; Kailas, Lalitha

2012-04-01

266

Atrophy analysis of corpus callosum in Alzheimer brain MR images using anisotropic diffusion filtering and level sets.  

PubMed

In this work, an attempt has been made to analyze the atrophy of Corpus Callosum (CC) in Alzheimer brain magnetic resonance images using anisotropic diffusion filtering and modified distance regularized level set method. Anisotropic diffusion filtering is used as preprocessing to obtain the edge map. The modified distance regularized level set method is employed to segment CC using this edge map. Geometric features are extracted from the segmented CC and are analyzed. Results show that anisotropic diffusion filtering is able to extract the edge map with high contrast and continuous boundaries. Modified distance regularized level set method could perform the segmentation of CC in both normal and Alzheimer images. The extracted geometric features such as minor axis, Euler number and solidity are able to demarcate the Alzheimer subjects from the control normals. As atrophy of CC is closely associated with the pathology, this study seems to be clinically useful. PMID:25570361

Anandh, K R; Sujatha, C M; Ramakrishnan, S

2014-08-01

267

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

268

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

269

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

PubMed Central

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

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

2013-01-01

270

Anisotropy in a non-singular bounce  

NASA Astrophysics Data System (ADS)

Following recent claims relative to the question of large anisotropy production in regular bouncing scenarios, we study the evolution of such anisotropies in a model where an ekpyrotic phase of contraction is followed by domination of a Galileon-type Lagrangian which generates a non-singular bounce. We show that the anisotropies decrease during the phase of ekpyrotic contraction (as expected) and that they can be constrained to remain small during the non-singular bounce phase (a non-trivial result). Specifically, we derive the e-folding number of the phase of ekpyrotic contraction which leads to a present-day anisotropy in agreement with current observational bounds. Communicated by P Singh

Cai, Yi-Fu; Brandenberger, Robert; Peter, Patrick

2013-04-01

271

CONSTRAINTS ON SUBDUCTION GEODYNAMICS FROM SEISMIC ANISOTROPY  

E-print Network

planet's interior. Subducting slabs represent the main driving mechanism for plate motion and also represent prime sites for natural hazards such as earthquakes, volcanoes, and tsunamis seismic anisotropy. (In contrast, inferences on mantle dynamics from other observations can be somewhat

272

Separating intrinsic and apparent seismic anisotropy (Invited)  

NASA Astrophysics Data System (ADS)

Seismic anisotropy plays a key role in studies of the Earth's rheology and deformation because of its relation to flow-induced lattice-preferred orientation (LPO) of intrinsically anisotropic minerals. In addition to LPO, small-scale heterogeneity produces apparent anisotropy that need not be related to deformation in the same way as intrinsic anisotropy. Quantitative interpretations of observed anisotropy therefore require the separation of its intrinsic and apparent components. We analyse the possibility of separating intrinsic and apparent anisotropy in media with hexagonal symmetry - typically used in surface wave tomography and SKS splitting studies. Our analysis is on the level of the wave equation, which makes it general and independent of specific data types. We find that commonly observed anisotropy can always be explained by a purely isotropic laminated medium unless all anisotropic parameters are known with unrealistic accuracy. Most importantly, minute changes in the poorly constrained P wave anisotropy and the parameter eta can switch between the existence or not of a laminated isotropic equivalent. Important implications of our study are: (1) Intrinsic anisotropy over tomographically resolved length scales is never strictly required when reasonable error bars for anisotropic parameters are taken into account. (2) Currently available seismic observables do not provide adequate constraints on the relative contributions of intrinsic and apparent anisotropy. (3) Therefore, seismic observables alone do not provide compelling constraints on the magnitude of mantle flow. (4) Quantitative interpretations of anisotropy in terms of mantle flow require a combined seismic/geodynamic inversion that properly accounts for the formation of both LPO and small-scale heterogeneity. Equivalence diagrams used to investigate the possibility to explain observed seismic anisotropy in terms of purely isotropic models. Earth models with elastic parameters falling into the black regions are unstable and do not exist. Anisotropic Earth models falling into the grey regions are not equivalent to a complex purely isotropic medium. For Earth models falling into the coloured regions, purely isotropic equivalents do exist. Note that the patterns of the equivalence diagrams change completely in response to only minor changes of the poorly constrained elastic parameter eta.

Fichtner, A.; Kennett, B. L.; Trampert, J.

2013-12-01

273

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

274

Magnetic Anisotropy of a Single Cobalt Nanocluster  

Microsoft Academic Search

Using a new micro-SQUID setup, we investigate magnetic anisotropy in a single 1000-atom cobalt cluster. This system opens new fields in the characterization and understanding of the origin of magnetic anisotropy in such nanoparticles. For this purpose, we report three-dimensional switching field measurements performed on a 3 nm cobalt cluster embedded in a niobium matrix. We are able to separate

M. Jamet; W. Wernsdorfer; C. Thirion; D. Mailly; V. Dupuis; P. Mélinon; A. Pérez

2001-01-01

275

Po Anisotropy in Old Pacific Lithosphere  

NASA Astrophysics Data System (ADS)

Po is the high frequency, scattered P phase guided within the oceanic lithosphere, sometimes known as Pn. During the PLATE experiment (Pacific Lithosphere Anisotropy and Thickness Experiment), in which two subarrays of ocean bottom seismometers were deployed on old seafloor (~150-160 Ma) in the northwestern Pacific south of the Shatsky Rise, we recorded 5 to 6 Po phases per day generated by earthquakes in western Pacific subduction zones. Each subarray was deployed on an arm of a magnetic bight, where the magnetic anomalies form a 90° bend that was created at a ridge-ridge-ridge triple junction. Spreading rates on both limbs were fast, about 70 mm/yr halfrate. Our goal is to decipher the pattern of anisotropy as a function of depth in the oceanic lithosphere and asthenosphere, taking advantage of the right angle bend in seafloor spreading direction to more clearly reveal the transition between fossil anisotropy in the lithosphere and dynamically maintained anisotropy in the asthenosphere. Po and So anisotropy as a function of frequency will provide some of the needed constraints on lithospheric anisotropy. Using more than 600 Po phases from earthquakes listed in PDE catalogs during the one year deployment, we find that the velocity on each limb as measured by the onsets of the phases in the 10 to 15 Hz band varies from 8.6 km/s in the fast direction perpendicular to the magnetic anomalies to about 7.9 km/s parallel to the anomalies. This large anisotropy is consistent with seismic refraction measurements and the idea that anisotropy in the shallow lithosphere is strongest at fast spreading rates.

Forsyth, D. W.; Weeraratne, D. S.; Rau, C. J.; Rowe, Z.

2011-12-01

276

Multiply Fractions Jeopardy  

NSDL National Science Digital Library

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

2006-01-01

277

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

278

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

279

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

280

Cosmic microwave background anisotropies in the timescape cosmology  

E-print Network

We analyze the spectrum of cosmic microwave background (CMB) anisotropies in the timescape cosmology: a potentially viable alternative to homogeneous isotropic cosmologies without dark energy. We exploit the fact that the timescape cosmology is extremely close to the standard cosmology at early epochs to adapt existing numerical codes to produce CMB anisotropy spectra, and to match these as closely as possible to the timescape expansion history. A variety of matching methods are studied and compared. We perform Markov Chain Monte Carlo analyses on the parameter space, and fit CMB multipoles $50 \\le \\ell \\le 2500$ to the Planck satellite data. Parameter fits include a dressed Hubble constant, $H_0 = 61.0$ km/s/Mpc ($\\pm$ 1.3% stat) ($\\pm$ 8% sys), and a present void volume fraction $f_{v0} = 0.627$ ($\\pm$ 2.3% stat) ($\\pm$ 13% sys). We find best fit likelihoods which are comparable to that of the best fit Lambda CDM cosmology in the same multipole range. In contrast to earlier results, the parameter constraint...

Nazer, M Ahsan

2014-01-01

281

Fantastic Fraction Falcons  

NSDL National Science Digital Library

Explore the fun skills of manipulating fractions Add like fractions Add Fractions With Lines or Add Fractions With Circles will give instruction and practice in addition of fractions. Each addend in this program has like denominators. Follow the directions on the link and have fun. Keep track of your score and report to me. Adding like denominators with lines Follow the directions on the circle ...

Hawkes, Kae

2004-09-16

282

Interactive Fraction Number Lines  

NSDL National Science Digital Library

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

Green, Michael

2012-05-25

283

Super Heavy Dark Matter and UHECR Anisotropy at Low Energy  

E-print Network

Super Heavy quasi-stable particles are naturally produced in the early universe and could represent a substantial fraction of the Dark Matter: the so-called Super Heavy Dark Matter (SHDM). The decay of SHDM represents also a possible source of Ultra High Energy Cosmic Rays (UHECR), with a reliably calculated spectrum of the particles produced in the decay $(\\propto E^{-1.9})$. The SHDM model for the production of UHECR can explain quantitatively only the excess of UHE events observed by AGASA. In the case of an observed spectrum not showing the AGASA excess the SHDM model can provide only a {\\it subdominant} contribution to the UHECR flux. We discuss here the basic features of SHDM for the production of a {\\it subdominant} UHECR flux, we refer our study to the possible signatures of the model at the Auger observatory discussing in particular the expected chemical composition and anisotropy.

Aloisio, R

2008-01-01

284

Simultaneous measurements of fluorescence lifetimes, anisotropy, and FRAP recovery curves  

NASA Astrophysics Data System (ADS)

We present fluorescence lifetime imaging (FLIM) and fluorescence anisotropy imaging along with translational diffusion measurements of living cells labelled with green fluorescent protein (GFP) recorded in a single experiment. The experimental set-up allows for time and polarization-resolved fluorescence images to be measured in every frame of a fluorescence recovery after photobleaching (FRAP) series. We have validated the method using rhodamine 123 in homogeneous solution prior to measurements of living A431 cells labelled with cdc42-GFP, for which the FRAP recovery exhibits an immobile fraction and the rotational mobility of the protein is hindered while the fluorescence lifetime fairly homogeneous across the cell. By eliminating the need for sequential measurements to extract fluorescence lifetimes and molecular diffusion coefficients we remove artefacts arising from changes in sample morphology and excessive photobleaching during sequential experiments.

Levitt, James A.; Chung, Pei-Hua; Alibhai, Dominic R.; Suhling, Klaus

2011-02-01

285

How to separate intrinsic and artificial anisotropy  

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

286

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

287

CRASH syndrome: clinical spectrum of corpus callosum hypoplasia, retardation, adducted thumbs, spastic paraparesis and hydrocephalus due to mutations in one single gene, L1.  

PubMed

L1 is a neuronal cell adhesion molecule with important functions in the development of the nervous system. The gene encoding L1 is located near the telomere of the long arm of the X chromosome in Xq28. We review here the evidence that several X-linked mental retardation syndromes including X-linked hydrocephalus (HSAS), MASA syndrome, X-linked complicated spastic paraparesis (SP1) and X-linked corpus callosum agenesis (ACC) are all due to mutations in the L1 gene. The inter- and intrafamilial variability in families with an L1 mutation is very wide, and patients with HSAS, MASA, SP1 and ACC can be present within the same family. Therefore, we propose here to refer to this clinical syndrome with the acronym CRASH, for Corpus callosum hypoplasia, Retardation, Adducted thumbs, Spastic paraplegia and Hydrocephalus. PMID:8556302

Fransen, E; Lemmon, V; Van Camp, G; Vits, L; Coucke, P; Willems, P J

1995-01-01

288

Magnetic anisotropy in the trenton limestone: Results of a new technique, anisotropy of anhysteretic susceptibility  

Microsoft Academic Search

A new method for determining magnetic anisotropy using anhysteric remanence susceptibility is described. The magnetic fabric of a collection of Trenton Limestone specimens has been determined using this method, as well as by conventional anisotropy of magnetic susceptibility. The results demonstrate the usefulness of the new method for finding the magnetic fabric of rock units such as the Trenton in

Chad McCabe; Michael Jackson; Brooks B. Ellwood

1985-01-01

289

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

290

Spastic paraplegia with thin corpus callosum: description of 20 new families, refinement of the SPG11 locus, candidate gene analysis and evidence of genetic heterogeneity  

Microsoft Academic Search

We studied 20 Mediterranean families (40 patients) with autosomal recessive hereditary spastic paraplegia and thin corpus callosum (ARHSP-TCC, MIM 604360) to characterize their clinical and genetic features. In six families (17 patients) of Algerian Italian, Moroccan, and Portuguese ancestry, we found data consistent with linkage to the SPG11 locus on chromosome 15q13–15, whereas, in four families (nine patients of Italian,

Giovanni Stevanin; Giorgia Montagna; Hamid Azzedine; Enza Maria Valente; Alexandra Durr; Valentina Scarano; Naima Bouslam; Denise Cassandrini; Paola S. Denora; Chiara Criscuolo; Soraya Belarbi; Antonio Orlacchio; Philippe Jonveaux; Gabriella Silvestri; Anne Marie Ouvrad Hernandez; Giuseppe De Michele; Meriem Tazir; Caterina Mariotti; Knut Brockmann; Alessandro Malandrini; Marjo S. van der Knapp; Marcella Neri; Hassan Tonekaboni; Mariarosa A. B. Melone; Alessandra Tessa; M. Teresa Dotti; Michela Tosetti; Flavia Pauri; Antonio Federico; Carlo Casali; Vitor T. Cruz; José L. Loureiro; Federico Zara; Sylvie Forlani; Enrico Bertini; Paula Coutinho; Alessandro Filla; Alexis Brice; Filippo M. Santorelli

2006-01-01

291

FRACTIONAL INTEGRATION TOOLBOX  

PubMed Central

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

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

2014-01-01

292

FRACTIONAL INTEGRATION TOOLBOX.  

PubMed

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

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

2013-09-01

293

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

294

Peripersonal spatial attention in children with spina bifida: associations between horizontal and vertical line bisection and congenital malformations of the corpus callosum, midbrain, and posterior cortex.  

PubMed

Horizontal and vertical line bisection was studied in 129 children and adolescents between 8 and 19 years of age, one group (n=32) of typically developing controls and one group (n=97) with spina bifida (SBM), a neurodevelopmental disorder associated with dysmorphology of the corpus callosum, posterior cortex, and midbrain. For each participant, structural brain MRIs were analyzed qualitatively to identify beaking of the midbrain tectum and corpus callosum agenesis and hypoplasia and quantitatively by segmentation and volumetric analyses of regional cortical white and gray matter. Each group showed the line length effect, whereby greater estimation errors are made with longer lines. The group with SBM differed from controls in terms of both accuracy and variability of line bisection. Children with SBM showed pseudoneglect, attending more than controls to left hemispace. The extent of rightward bisection bias was unrelated to right posterior brain volumes, although an intact corpus callosum during development moderated and normalized the exaggerated leftward line bisection bias. More children with SBM than controls attended to inferior hemispace. A normal midbrain and greater posterior cortex volume during development moderated and normalized the downward bias. Children with SBM showed more intra-subject variability than controls. Line bisection in children with SBM reflects three deficits: an exaggerated attentional bias to left hemispace, an abnormal attentional bias to inferior hemispace; and a larger zone of subjective uncertainty in bisection judgments. PMID:15893777

Dennis, Maureen; Edelstein, Kim; Frederick, Jon; Copeland, Kim; Francis, David; Blaser, Susan E; Kramer, Larry A; Drake, James M; Brandt, Michael; Hetherington, Ross; Fletcher, Jack M

2005-01-01

295

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

296

ANISOTROPY FACTORS FOR A 252Cf SOURCE  

SciTech Connect

A new 252Cf source has been procured for use at the Dosimetry Applications and Research (DOSAR) facility at the Oak Ridge National Laboratory (ORNL). This source was encapsulated by the Californium Facility at ORNL, however, the encapsulation differs from previous designs designated as SR-Cf-100. The new encapsulation, designated SR-Cf-3000, has a similar cylindrical radius to the previous generation, but is 1.6 cm longer. Since the encapsulation geometries differ the amount of internal scattering of neutrons will also differ leading to changes in anisotropy factors between the two designs. Additionally, the different encapsulations will affect the absorbed dose and dose equivalent delivered per neutron emitted by the source since both the quantity and energy distribution of the emitted neutrons will vary with irradiation angle. This work presents the fluence anisotropy factors for the SR-Cf-3000 series encapsulation as well as absorbed dose and dose equivalent values calculated for various angles of irradiation. The fluence anisotropy factors vary from a maximum of 1.037 to a minimum of 0.641 for irradiation angles perpendicular and parallel to the source axis, respectively. Anisotropy in absorbed dose varied from a maximum of 1.033 to a minimum of 0.676 while anisotropy of dose equivalent varied from 1.035 to 0.657.

Veinot, K. G. [Y-12 National Security Complex; Bogard, James S [ORNL

2009-01-01

297

Higher order fractional derivatives  

E-print Network

Based on the Liouville-Weyl definition of the fractional derivative, a new direct fractional generalization of higher order derivatives is presented. It is shown, that the Riesz and Feller derivatives are special cases of this approach.

Richard Herrmann

2009-06-12

298

Garden Variety Fractions  

NSDL National Science Digital Library

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

Michael Green

2012-07-23

299

The Fraction String  

NSDL National Science Digital Library

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

Green, Michael

2012-06-26

300

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.

Rand, Richard E.

2011-01-01

301

Correlation Functions of CMB Anisotropy and Polarization  

E-print Network

We give a full analysis of the auto- and cross-correlations between the Stokes parameters of the cosmic microwave background. In particular, we derive the windowing function for an antenna with Gaussian response in polarization experiment, and construct correlation function estimators corrected for instrumental noise. They are applied to calculate the signal to noise ratios for future anisotropy and polarization measurements. While the small-angular-scale anisotropy-polarization correlation would be likely detected by the MAP satellite, the detection of electric and magnetic polarization would require higher experimental sensitivity. For large-angular-scale measurements such as the being planned SPOrt/ISS, the expected signal to noise ratio for polarization is greater than one only for reionized models with high reionization redshifts, and the ratio is less for anisotropy-polarization correlation. Correlation and covariance matrices for likelihood analyses of ground-based and satellite data are also given.

Kin-Wang Ng; Guo-Chin Liu

1998-02-25

302

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

303

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

304

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

305

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.

Uhe, Shanna

2012-07-31

306

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.

Adults, Skillwise: E.

2012-08-03

307

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.

Lessonplans, Utah

2012-10-22

308

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

309

DIY Fraction Pack.  

ERIC Educational Resources Information Center

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

Graham, Alan; Graham, Louise

2003-01-01

310

Precision measurement of positron fraction by AMS-02  

NASA Astrophysics Data System (ADS)

A precision measurement by AMS-02 of the positron fraction in primary cosmic rays is presented. The very accurate data show that the positron fraction is steadily increasing from 10 to 250GeV,but the slope decreases by an order of magnitude from 20 to 250GeV. A systematic searching for positron anisotropy shows the data is consistent with the hypothesis of isotropy. The measurement of separate fluxes show smooth behavior of both electron and positron fluxes. Positron shows different spectral index than electron, and a change of spectral index is clearly seen at ~ 30GeV.

Xu, Weiwei

2014-06-01

311

Anisotropy effects on 3D waveform inversion  

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

312

Anisotropy in Gravity and Holography  

NASA Astrophysics Data System (ADS)

In this thesis, we examine the dynamical structure of Ho?ava-Lifshitz gravity, and investigate its relationship with holography for anisotropic systems. Ho?ava-Lifshitz gravity refers to a broad class of gravitational models that incorporate anisotropy at a fundamental level. The idea behind Ho?ava-Lifshitz gravity is to utilize ideas from the theory of dynamical critical phenomena into gravity to produce a theory of dynamical spacetime that is power-counting renormalizable, and is thus a candidate renormalizable quantum field theory of gravity. One of the most distinctive features of Ho?ava-Lifshitz gravity is that its group of symmetries consists not of the diffeomorphisms of spacetime, but instead of the group of diffeomorphisms that preserve a given foliation by spatial slices. As a result of having a smaller group of symmetries, HL gravity naturally has one more propagating degree of freedom than general relativity. The extra mode presents two possible difficulties with the theory, one relating to consistency, and the second to its viability as a phenomenological model. (1) It may destabilize the theory. (2) Phenomenologically, there are severe constraints on the existence of an extra propagating graviton polarization, as well as strong experimental constraints on the value of a parameter appearing in the dispersion relation of the extra mode. In the first part of this dissertation we show that the extra mode can be eliminated by introducing a new local symmetry which steps in and takes the place of general covariance in the anisotropic context. While the identification of the appropriate symmetry is quite subtle in the full non-linear theory, once the dust settles, the resulting theory has a spectrum which matches that of general relativity in the infrared. This goes a good way toward answering the question of how close Ho?ava-Lifshitz gravity can come to reproducing general relativity in the infrared regime. In the second part of the thesis we pursue the relationship between Ho?ava-Lifshitz gravity and holographic duals for anisotropic systems. A holographic correspondence is one that posits an equivalence between a theory of gravity on a given spacetime background and a field theory living on the "boundary" of that spacetime, which resides at infinite spatial separation from the interior. It is a non-trivial problem how to define this boundary, but in the case of relativistic boundary field theories, there is a well-known definition due to Penrose of the boundary which produces the geometric structure required to make sense of the correspondence. However, the proposed dual geometries to anisotropic quantum field theories have a Penrose boundary that is incompatible with the assumed correspondence. We generalize Penrose's approach, using concepts from Ho?ava-Lifshitz gravity, to spacetimes with anisotropic boundary conditions, thereby arriving at the concept of anisotropic conformal infinity that is compatible with the holographic correspondence in these spacetimes. We then apply this work to understanding the structure of holography for anisotropic systems in more detail. In particular, we examine the structure of divergences of a certain theory of gravity on Lifshitz space. We find, using our construction of anisotropic conformal infinity, that the appropriate geometric structure of the boundary is that of a foliated spacetime with an anisotropic metric complex. We then perform holographic renormalization in these spacetimes, yielding a computation of the divergent part of the effective action, and find that it exhibits precisely the structure of a Ho?ava-Lifshitz action. Moreover, we find that, for dynamical exponent z = 2, the logarithmic divergence gives rise to a conformal anomaly in 2+1 dimensions, whose general form is precisely that of conformal Ho?ava-Lifshitz gravity with detailed balance.

Melby-Thompson, Charles Milton

313

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

314

Amygdala, hippocampal and corpus callosum size following severe early institutional deprivation: the English and Romanian Adoptees study pilot.  

PubMed

The adoption into the UK of children who have been reared in severely deprived conditions provides an opportunity to study possible association between very early negative experiences and subsequent brain development. This cross-sectional study was a pilot for a planned larger study quantifying the effects of early deprivation on later brain structure. We used magnetic resonance imaging (MRI) to measure the sizes of three key brain regions hypothesized to be sensitive to early adverse experiences. Our sample was a group of adoptee adolescents (N = 14) who had experienced severe early institutional deprivation in Romania and a group of non-institutionalised controls (N = 11). The total grey and white matter volumes were significantly smaller in the institutionalised group compared with a group of non-deprived, non-adopted UK controls. After correcting for difference in brain volume, the institutionalised group had greater amygdala volumes, especially on the right, but no differences were observed in hippocampal volume or corpus callosum mid-sagittal area. The left amygdala volume was also related to the time spent in institutions, with those experiencing longer periods of deprivation having a smaller left amygdala volume. These pilot findings highlight the need for future studies to confirm the sensitivity of the amygdala to early deprivation. PMID:19457047

Mehta, Mitul A; Golembo, Nicole I; Nosarti, Chiara; Colvert, Emma; Mota, Ashley; Williams, Steven C R; Rutter, Michael; Sonuga-Barke, Edmund J S

2009-08-01

315

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

PubMed

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

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

2014-02-01

316

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

317

Temperature Anisotropies in a Universe with Global Defects  

E-print Network

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

David Coulson

1994-07-15

318

Role of anisotropy in noncontacting thermoelectric materials characterization  

E-print Network

Role of anisotropy in noncontacting thermoelectric materials characterization Adnan H. Nayfeh by the intrinsic thermoelectric anisotropy and inhomogeneity of the material to be inspected. This article presents for non- destructive evaluation NDE and materials characterization. Most existing thermoelectric NDE

Nagy, Peter B.

319

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

320

Anisotropy Creases Delineate White Matter Structure in Diffusion Tensor MRI  

Microsoft Academic Search

Current methods for extracting models of white matter architecture from diffusion tensor MRI are generally based on fiber\\u000a tractography. For some purposes a compelling alternative may be found in analyzing the first and second derivatives of diffusion\\u000a anisotropy. Anisotropy creases are ridges and valleys of locally extremal anisotropy, where the gradient of anisotropy is orthogonal to one or more eigenvectors

Gordon L. Kindlmann; Xavier Tricoche; Carl-fredrik Westin

2006-01-01

321

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

322

Temperture anisotropy effect on the tearing mode  

Microsoft Academic Search

Previous study of the Plasma temperature anisotropy in the current sheet have shown that alphaj > 1 (alphaj = Tj,perp\\/Tj,para , j = ion or electron) significantly enhances the growth rate of tearing instability (TI), and the maximum growth wave length shift for shorter by the linear theory [Chen & Palmadesso, Phys. Fluds 1984; Ambrosiano, Geophys. Res. 1986]. Recent result

K. Haijima; K. Tanaka; M. Fujimoto; I. Shinohara

2006-01-01

323

Grain Boundary Properties: Texture, Microstructure & Anisotropy  

E-print Network

- creep strength in high service temperature alloys - weld cracking (under investigation (embrittlement, formation of second phases) #12;7 Grain Boundary Diffusion · Especially for high symmetry boundaries, there is a very strong anisotropy of diffusion coefficients as a function of boundary type

Rollett, Anthony D.

324

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

325

Ill. -FUNDAMENTAL PROPERTIES, EXCHANGE, AND ANISOTROPIES.  

E-print Network

Ill. - FUNDAMENTAL PROPERTIES, EXCHANGE, AND ANISOTROPIES. MAGNETIC PROPERTIES OF SOFT G or carbon, usually exhibit low coercive forces and high permeabilities characteristic of soft magnetic Jersey 07974, U. S. A. R&um(t. - Dcs rubans ferromagnbtiques amorphes de composition generale (Co

Paris-Sud XI, Université de

326

Rain anisotropy prediction - Theory and experiment  

Microsoft Academic Search

Measurements of electromagnetic wave attenuation due to intense rain at frequencies above 10 GHz are used to estimate the rain anisotropy and aid in predicting depolarization. The estimate requires assumptions about rain parameters such as raindrop size distribution, water temperature, and the distribution of ellipsoidal drop orientation. A theoretical analysis supported by experimental data is made to assess these factors

Carlo Capsoni; Dario Maggiori; Emilio Matricciani; Aldo Paraboni

1981-01-01

327

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

328

Magnetic anisotropy of strained epitaxial manganite films  

SciTech Connect

The in-plane magnetic anisotropy of epitaxial La{sub 0.7}Sr{sub 0.3}MnO{sub 3} (LSMO) films is studied at room temperature by the following three independent techniques: magnetooptical Kerr effect, ferromagnetic resonance at a frequency of 9.61 GHz, and recording of absorption spectra of electromagnetic radiation at a frequency of 290.6 MHz. The films are deposited onto NdGaO{sub 3} (NGO) substrates in which the (110)NGO plane is tilted at an angle of 0-25.7 Degree-Sign to the substrate plane. The uniaxial magnetic anisotropy induced by the strain of the film is found to increase with the tilt angle of the (110)NGO plane. A model is proposed to describe the change in the magnetic anisotropy energy with the tilt angle. A sharp increase in the radio-frequency absorption in a narrow angular range of a dc magnetic field near a hard magnetization axis is detected The anisotropy parameters of the LSMO films grown on (110)NGO, (001)SrTiO{sub 3}, and (001)[(LaAlO{sub 3}){sub 0.3} + (Sr{sub 2}AlTaO{sub 6}){sub 0.7}] substrates are compared.

Demidov, V. V., E-mail: demidov@cplire.ru; Borisenko, I. V.; Klimov, A. A.; Ovsyannikov, G. A.; Petrzhik, A. M.; Nikitov, S. A. [Russian Academy of Sciences, Institute of Radio-Engineering and Electronics (Russian Federation)

2011-05-15

329

Variance Anisotropy of Solar Wind fluctuations  

NASA Astrophysics Data System (ADS)

Solar wind observations at MHD scales indicate that the energy associated with velocity and magnetic field fluctuations transverse to the mean magnetic field is typically much larger than that associated with parallel fluctuations [eg, 1]. This is often referred to as variance anisotropy. Various explanations for it have been suggested, including that the fluctuations are predominantly shear Alfven waves [1] and that turbulent dynamics leads to such states [eg, 2]. Here we investigate the origin and strength of such variance anisotropies, using spectral method simulations of the compressible (polytropic) 3D MHD equations. We report on results from runs with initial conditions that are either (i) broadband turbulence or (ii) fluctuations polarized in the same sense as shear Alfven waves. The dependence of the variance anisotropy on the plasma beta and Mach number is examined [3], along with the timescale for any variance anisotropy to develop. Implications for solar wind fluctuations will be discussed. References: [1] Belcher, J. W. and Davis Jr., L. (1971), J. Geophys. Res., 76, 3534. [2] Matthaeus, W. H., Ghosh, S., Oughton, S. and Roberts, D. A. (1996), J. Geophys. Res., 101, 7619. [3] Smith, C. W., B. J. Vasquez and K. Hamilton (2006), J. Geophys. Res., 111, A09111.

Oughton, S.; Matthaeus, W. H.; Wan, M.; Osman, K.

2013-12-01

330

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

E-print Network

The Pierre Auger Collaboration has reported evidence for anisotropy in the distribution of arrival directions of the cosmic rays with energies $E>E_{th}=5.5\\times 10^{19}$ 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 $E>E_{th}$ 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 $E_{th}/Z$ (for illustrative values of $Z=6,\\ 13,\\ 26$). If the anisotropies above $E_{th}$ 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; Ahn, E J; Albuquerque, I F M; Allard, D; Allekotte, I; Allen, J; Allison, P; Castillo, J Alvarez; Alvarez-Muñiz, J; Ambrosio, M; Aminaei, A; Anchordoqui, L; Andringa, S; Anti?i?, T; Anzalone, A; Aramo, C; Arganda, E; Arqueros, F; Asorey, H; Assis, P; Aublin, J; Ave, M; Avenier, M; Avila, G; Bäcker, T; Balzer, M; Barber, K B; Barbosa, A F; Bardenet, R; Barroso, S L C; Baughman, B; Bäuml, J; Beatty, J J; Becker, B R; Becker, K H; Bellétoile, A; Bellido, J A; BenZvi, S; Berat, C; Bertou, X; Biermann, P L; Billoir, P; Blanco, F; Blanco, M; Bleve, C; Blümer, H; Bohá?ová, M; Boncioli, D; Bonifazi, C; Bonino, R; Borodai, N; Brack, J; Brogueira, P; Brown, W C; Bruijn, R; Buchholz, P; Bueno, A; Burton, R E; Caballero-Mora, K S; Caramete, L; Caruso, R; Castellina, A; Catalano, O; Cataldi, G; Cazon, L; Cester, R; Chauvin, J; Cheng, S H; Chiavassa, A; Chinellato, J A; Chou, A; Chudoba, J; Clay, R W; Coluccia, M R; Conceição, R; Contreras, F; Cook, H; Cooper, M J; Coppens, J; Cordier, A; Cotti, U; Coutu, S; Covault, C E; Creusot, A; Criss, A; Cronin, J; Curutiu, A; Dagoret-Campagne, S; Dallier, R; Dasso, S; Daumiller, K; Dawson, B R; de Almeida, R M; De Domenico, M; De Donato, C; de Jong, S J; De La Vega, G; Junior, W J M de Mello; Neto, J R T de Mello; De Mitri, I; de Souza, V; de Vries, K D; Decerprit, G; del Peral, L; Deligny, O; Dembinski, H; Dhital, N; Di Giulio, C; Diaz, J C; Castro, M L Díaz; Diep, P N; Dobrigkeit, C; Docters, W; D'Olivo, J C; Dong, P N; Dorofeev, A; Anjos, J C dos; Dova, M T; D'Urso, D; Dutan, I; Ebr, J; Engel, R; Erdmann, M; Escobar, C O; Etchegoyen, A; Luis, P Facal San; Tapia, I Fajardo; Falcke, H; Farrar, G; Fauth, A C; Fazzini, N; Ferguson, A P; Ferrero, A; Fick, B; Filevich, A; Filip?i?, A; Fliescher, S; Fracchiolla, C E; Fraenkel, E D; Fröhlich, U; Fuchs, B; Gaior, R; Gamarra, R F; Gambetta, S; García, B; Gámez, D García; Garcia-Pinto, D; Gascon, A; Gemmeke, H; Gesterling, K; Ghia, P L; Giaccari, U; Giller, M; Glass, H; Gold, M S; Golup, G; Albarracin, F Gomez; Berisso, M Gómez; Gonçalves, P; Gonzalez, D; Gonzalez, J G; Gookin, B; Góra, D; Gorgi, A; Gouffon, P; Gozzini, S R; Grashorn, E; Grebe, S; Griffith, N; Grigat, M; Grillo, A F; Guardincerri, Y; Guarino, F; Guedes, G P; Guzman, A; Hague, J D; Hansen, P; Harari, D; Harmsma, S; Harton, J L; Haungs, A; Hebbeker, T; Heck, D; Herve, A E; Hojvat, C; Hollon, N; Holmes, V C; Homola, P; Hörandel, J R; Horneffer, A; Hrabovský, M; Huege, T; Insolia, A; Ionita, F; Italiano, A; Jarne, C; Jiraskova, S; Kadija, K; Kampert, K H; Karhan, P; Kasper, P; Kégl, B; Keilhauer, B; Keivani, A; Kelley, J L; Kemp, E; Kieckhafer, R M; Klages, H O; Kleifges, M; Kleinfeller, J; Knapp, J; Koang, D -H; Kotera, K; Krohm, N; Krömer, O; Kruppke-Hansen, D; Kuehn, F; Kuempel, D; Kulbartz, J K; Kunka, N; La Rosa, G; Lachaud, C; Lautridou, P; Leão, M S A B; Lebrun, D; Lebrun, P; de Oliveira, M A Leigui; Lemiere, A; Letessier-Selvon, A; Lhenry-Yvon, I; López, K Link R; Agüera, A Lopez; Louedec, K; Bahilo, J Lozano; Lucero, A; Ludwig, M; Lyberis, H; Maccarone, M C; Macolino, C; Maldera, S; Mandat, D; Mantsch, P; Mariazzi, A G; Marin, J; Marin, V; Maris, I C; Falcon, H R Marquez; Marsella, G; Martello, D; Martin, L; Martinez, H; Bravo, O Martínez; Mathes, H J; Matthews, J; Matthews, J A J; Matthiae, G; Maurizio, D; Mazur, P O; Medina-Tanco, G; Melissas, M; Melo, D; Menichetti, E; Menshikov, A; Mertsch, P; Meurer, C; Mi?anovi?, S; Micheletti, M I; Miller, W; Miramonti, L; Mollerach, S; Monasor, M; Ragaigne, D Monnier; Montanet, F; Morales, B; Morello, C; Moreno, E; Moreno, J C; Morris, C; Mostafá, M; Moura, C A; Mueller, S; Muller, M A; Müller, G; Münchmeyer, M; Mussa, R; Navarra, G; Navarro, J L; Navas, S; Necesal, P; Nellen, L; Nelles, A; Nhung, P T; Niemietz, L; Nierstenhoefer, N; Nitz, D; Nosek, D; Nožka, L; Nyklicek, M; Oehlschläger, J; Olinto, A; Oliva, P; Olmos-Gilbaja, V M; Ortiz, M; Pacheco, N; Selmi-Dei, D Pakk; Palatka, M; Pallotta, J; Palmieri, N; Parente, G; Parizot, E; Parra, A; Parsons, R D; Pastor, S; Paul, T; Pech, M; P?kala, J; Pelayo, R; Pepe, I M; Perrone, L; Pesce, R; Petermann, E; Petrera, S; Petrinca, P; Petrolini, A; Petrov, Y; Petrovic, J; Pfendner, C; Phan, N; Piegaia, R; Pierog, T; Pieroni, P; Pimenta, M; Pirronello, V; Platino, M; Ponce, V H; Pontz, M; Privitera, P; Prouza, M; Quel, E J; Querchfeld, S; Rautenberg, J; Ravel, O; Ravignani, D; Revenu, B; Ridky, J; Riggi, S; Risse, M; Ristori, P; Rivera, H; Rizi, V; Roberts, J; Robledo, C; de Carvalho, W Rodrigues; Rodriguez, G; Martino, J Rodriguez; Rojo, J Rodriguez; Rodriguez-Cabo, I; Rodríguez-Frías, M D; Ros, G; Rosado, J; Rossler, T; Roth, M; Rouillé-d'Orfeuil, B; Roulet, E; Rovero, A C; Rühle, C; Salamida, F; Salazar, H; Salina, G; Sánchez, F; Santander, M; Santo, C E; Santos, E

2011-01-01

331

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

332

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

333

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

334

Longitudinal complex magnetic susceptibility and relaxation times of superparamagnetic particles with triaxial anisotropy  

NASA Astrophysics Data System (ADS)

The longitudinal relaxation time and spectrum of the complex magnetic susceptibility of single domain ferromagnetic particles with triaxial (orthorhombic) anisotropy are calculated by averaging the Gilbert-Langevin equation for the magnetization of an individual particle and by reducing the problem to that of solving a system of linear differential-recurrence relations for the appropriate equilibrium correlation functions. The solution of this system is obtained in terms of matrix continued fractions. It is shown that in contrast to the linear magnetic response of particles with uniaxial anisotropy, there is an inherent geometric dependence of the complex susceptibility and the relaxation time on the damping parameter arising from coupling of longitudinal and transverse relaxation modes. Simple analytic equations, which allow one to understand the qualitative behavior of the system and to accurately predict the spectrum of the longitudinal complex susceptibility in wide ranges of the barrier height and dissipation parameters, are proposed.

Kalmykov, Yuri P.; Ouari, Bachir

2005-03-01

335

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,

336

FRACTIONAL PEARSON DIFFUSIONS  

PubMed Central

Pearson diffusions are governed by diffusion equations with polynomial coefficients. Fractional Pearson diffusions are governed by the corresponding time-fractional diffusion equation. They are useful for modeling sub-diffusive phenomena, caused by particle sticking and trapping. This paper provides explicit strong solutions for fractional Pearson diffusions, using spectral methods. It also presents stochastic solutions, using a non-Markovian inverse stable time change. PMID:23626377

Leonenko, Nikolai N.; Meerschaert, Mark M.

2013-01-01

337

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

338

Anisotropy engineering in Co nanodiscs fabricated using prepatterned silicon pillars  

NASA Astrophysics Data System (ADS)

Magnetic nanodiscs are fabricated by depositing cobalt onto 10-30 nm diameter silicon nanopillars, which were prepatterned using gold colloids as etch masks. The magnetic anisotropy energy of individual nanodiscs is studied by measuring the angular dependence of switching fields using the micro-SQUID technique. The Stoner-Wohlfarth model, describing the magnetization reversal by unifom rotation, is used to analyse the data. The switching astroids of pure Co exhibit a cubic magnetocrystalline anisotropy indicating that the Co crystallites are fcc. After controlled oxidation of the nanoparticles, the anisotropy is dominated by a defect-induced uniaxial anisotropy, which means that the anisotropy can be used as a quality gauge.

Thirion, C.; Wernsdorfer, W.; Kläui, M.; Vaz, C. A. F.; Lewis, P.; Ahmed, H.; Bland, J. A. C.; Mailly, D.

2006-04-01

339

Gettin' Fancy with Fractions  

NSDL National Science Digital Library

In this lesson, students engage in problem solving, a fraction sort activity and play the game "Fraction War" to practice and demonstrate understanding of using benchmark fractions when comparing fractions with different numerators and denominators.

Lejeune, Jacqueline

2012-07-19

340

SPG11 mutations cause Kjellin syndrome, a hereditary spastic paraplegia with thin corpus callosum and central retinal degeneration.  

PubMed

Autosomal recessive hereditary spastic paraplegia (ARHSP) with thin corpus callosum (TCC) is genetically heterogenous and approximately 35% of patients carry mutations in either of the SPG11 or SPG15 genes. Disease onset is during the first three decades of life with spastic paraplegia and mental impairment. Peripheral neuropathy and amyotrophy may occur. Kjellin syndrome is characterized by central retinal degeneration in addition to ARHSP-TCC and the disease is associated with mutations in the SPG15 gene. We identified five patients in four unrelated kindreds with spastic paraplegia and mental impairment. Magnetic resonance imaging revealed TCC, atrophy elsewhere in the brain and increased T2 signal intensity in the periventricular white matter. Probands from the four kindreds were screened for mutations in the SPG11 gene. All patients were found homozygous or compound heterozygous for truncating SPG11 mutations of which four are reported for the first time. Ophthalmological investigations revealed that the four index cases have central retinal degeneration consistent with Kjellin syndrome. PET examinations with N-[11C-methyl]-L-deuterodeprenyl (DED) and fluor-18 2-fluorodeoxyglucose (FDG) were performed in two patients with Kjellin syndrome. We observed a reduced glucose uptake in the thalami, anterior cingulum, and sensorimotor cortex indicating neuronal loss, and an increased DED binding in the thalami and pons which suggests astrogliosis. From our results we extend the SPG11 associated phenotype to comprise also Kjellin syndrome, previously found to be associated with mutations in the SPG15 gene. We anticipate that degeneration of the central retina is a common and previously unrecognized feature in SPG11 related disease. PMID:19194956

Orlén, Hanna; Melberg, Atle; Raininko, Raili; Kumlien, Eva; Entesarian, Miriam; Söderberg, Per; Påhlman, Magnus; Darin, Niklas; Kyllerman, Mårten; Holmberg, Eva; Engler, Henry; Eriksson, Urban; Dahl, Niklas

2009-10-01

341

Corpus callosum shape changes in early Alzheimer’s disease: an MRI study using the OASIS brain database  

PubMed Central

The corpus callosum (CC) is the largest fiber bundle connecting the left and right cerebral hemispheres. It has been a region examined extensively for indications of various pathologies, including Alzheimer’s disease (AD). Almost all previous studies of the CC in AD have been concerned with its size, particularly its mid-sagittal cross-sectional area (CCA). In this study, we show that the CC shape, characterized by its circularity (CIR), may be affected more profoundly than its size in early AD. MRI scans (n = 196) were obtained from the publicly available Open Access Series of Imaging Studies database. The CC cross-sectional region on the mid-sagittal section of the brain was automatically segmented using a novel algorithm. The CCA and CIR were compared in 98 normal controls (NC) subjects, 70 patients with very mild AD (AD-VM), and 28 patients with mild AD (AD-M). Statistical analysis of covariance controlling for age and intracranial capacity showed that both the CIR and the CCA were significantly reduced in the AD-VM group relative to the NC group (CIR: p = 0.004; CCA: p = 0.005). However, only the CIR was significantly different between the AD-M and AD-VM groups (p = 0.006) being smaller in the former. The CCA was not significantly different between the AD-M and AD-VM groups. The results suggest that CC shape may be a more sensitive marker than its size for monitoring the progression of AD. In order to facilitate independent analyses, the CC segmentations and the CCA and CIR data used in this study have been made publicly available (http://www.nitrc.org/projects/art). PMID:23322167

Bachman, Alvin H.; Figarsky, Khadija; Sidtis, John J.

2013-01-01

342

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

343

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

344

Negative associations between corpus callosum midsagittal area and IQ in a representative sample of healthy children and adolescents.  

PubMed

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

345

Heparan Sulfotransferases Hs6st1 and Hs2st Keep Erk in Check for Mouse Corpus Callosum Development  

PubMed Central

The corpus callosum (CC) connects the left and right cerebral hemispheres in mammals and its development requires intercellular communication at the telencephalic midline mediated by signaling proteins. Heparan sulfate (HS) is a sulfated polysaccharide that decorates cell surface and extracellular matrix proteins and regulates the biological activity of numerous signaling proteins via sugar–protein interactions. HS is subject to regulated enzymatic sulfation and desulfation and an attractive, although not proven, hypothesis is that the biological activity of HS is regulated by a sugar sulfate code. Mutant mouse embryos lacking the heparan sulfotransferases Hs2st or Hs6st1 have severe CC phenotypes and form Probst bundles of noncrossing axons flanking large tangles of midline glial processes. Here, we identify a precocious accumulation of Sox9-expressing glial cells in the indusium griseum region and a corresponding depletion at the glial wedge associated with the formation of Probst bundles along the rostrocaudal axis in both mutants. Molecularly, we found a surprising hyperactivation of Erk signaling in Hs2st?/? (2-fold) and Hs6st1?/? (6-fold) embryonic telencephalon that was most striking at the midline, where Erk signaling is lowest in wild-types, and a 2-fold increase in Fgf8 protein levels in Hs6st1?/? embryos that could underpin Erk hyperactivation and excessive glial movement to the indusium griseum. The tightly linked Hs6st1?/? CC glial and axonal phenotypes can be rescued by genetic or pharmacological suppression of Fgf8/Erk axis components. Overall, our data fit a model in which Hs2st and Hs6st1 normally generate conditions conducive to CC development by generating an HS-containing environment that keeps Erk signaling in check. PMID:24501377

Clegg, James M.; Conway, Christopher D.; Howe, Kathy M.; Price, David J.; Mason, John O.; Turnbull, Jeremy E.; Basson, M. Albert

2014-01-01

346

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 ...

Marsh, Mrs.

2006-10-27

347

Paper Folding Fractions  

ERIC Educational Resources Information Center

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

Pagni, David

2007-01-01

348

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

349

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

350

(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

351

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

352

Fraction Flags Halves  

NSDL National Science Digital Library

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

Mark Cogan

2002-01-01

353

Fraction Flags Thirds  

NSDL National Science Digital Library

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

Mark Cogan

2002-01-01

354

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

355

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

356

Fraction Counting Book  

NSDL National Science Digital Library

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

2012-12-17

357

Holographic fractional topological insulators  

SciTech Connect

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

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

2010-10-15

358

Exome sequencing identifies compound heterozygous mutations in C12orf57 in two siblings with severe intellectual disability, hypoplasia of the corpus callosum, chorioretinal coloboma, and intractable seizures.  

PubMed

In patients with genetically heterogeneous disorders such as intellectual disability or epilepsy, exome sequencing is a powerful tool to elucidate the underlying genetic cause. Homozygous and compound heterozygous mutations in C12orf57 have recently been described to cause an autosomal recessive syndromic form of intellectual disability, including agenesis/hypoplasia of the corpus callosum, optic coloboma, and intractable seizures. Here, we report on two siblings from nonconsanguineous parents harboring two compound heterozygous loss-of-function mutations in C12orf57 identified by exome sequencing, including a novel nonsense mutation, and review the patients described in the literature. PMID:24798461

Platzer, Konrad; Hüning, Irina; Obieglo, Carolin; Schwarzmayr, Thomas; Gabriel, Rainer; Strom, Tim M; Gillessen-Kaesbach, Gabriele; Kaiser, Frank J

2014-08-01

359

Anisotropy of magnetic susceptibility and magnetic properties of obsidians: volcanic implications  

NASA Astrophysics Data System (ADS)

The anisotropy of magnetic susceptibility (AMS), hysteresis and thermomagnetic curves of two sets of obsidians with contrasting bulk compositions are reported in this work. The cooling and deformation history of one of those obsidians is perfectly known, as these specimens were produced in the laboratory using material from a basaltic lava flow. The other samples are occurrences of a more silicic composition and for which the AMS has been documented to have a close relationship with the distribution of microlites. The results of our measurements indicate that although the deformation and cooling histories of the lava might influence the exact composition of the ferromagnetic fraction, the relationship between the AMS and the deformation history does not seem to be altered. Furthermore, the results of this work indicate that the AMS can be associated to a population of ferromagnetic minerals of a submicroscopic size, despite of which it can be very well defined and yield large degrees of anisotropy. It is suggested that the AMS associated to such population of small grains might indeed be the origin of the AMS of other igneous rocks that have an optically observable fraction of mineral grains, although until present it had been overlooked in most instances. Use of tests designed to identify the contribution of a superparamagnetic fraction (SP) in the magnetic properties of a rock can help us to identify the presence of such a SP-related AMS in other cases.

Cañón-Tapia, E.; Cárdenas, K.

2012-04-01

360

Statistical anisotropy in the inflationary universe  

SciTech Connect

During cosmological inflation, quasiclassical perturbations are permanently generated on super-Hubble spatial scales, their power spectrum being determined by the fundamental principles of quantum field theory. By the end of inflation, they serve as primeval seeds for structure formation in the universe. At early stages of inflation, such perturbations break homogeneity and isotropy of the inflationary background. In the present paper, we perturbatively take into account this quasiclassical background inhomogeneity of the inflationary universe while considering the evolution of small-scale (sub-Hubble) quantum modes. As a result, the power spectrum of primordial perturbations develops statistical anisotropy, which can subsequently manifest itself in the large-scale structure and cosmic microwave background. The statistically anisotropic contribution to the primordial power spectrum is predicted to have almost scale-invariant form dominated by a quadrupole. Theoretical expectation of the magnitude of this anisotropy depends on the assumptions about the physics in the trans-Planckian region of wave numbers.

Shtanov, Yuri [Bogolyubov Institute for Theoretical Physics, Kiev 03680 (Ukraine); Pyatkovska, Hanna [Department of Physics, Taras Shevchenko National University of Kiev (Ukraine)

2009-07-15

361

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

362

Induced electronic anisotropy in bismuth thin films  

NASA Astrophysics Data System (ADS)

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.; Yao, Mengliang; Katmis, Ferhat; Li, Mingda; Tang, Shuang; Moodera, Jagadeesh S.; Opeil, Cyril; Dresselhaus, Mildred S.

2014-08-01

363

Two-photon fluorescence anisotropy imaging  

NASA Astrophysics Data System (ADS)

We have developed a novel method for imaging the fluorescence intensity and anisotropy by two-photon fluorescence microscopy and tested its capability in biological application. This method is applied to model sample including FITC and FITC-CD44 antibody solution and also FITC-CD44 stained cells. The fluorescence anisotropy (FA) of FITC-CD44ab solution is higher than the FITC solution with the same concentration. The fluorescence in cell sample has even higher FA than in solution because the rotation diffusion is restrained in membrane. The method is employed to study the effect of berberine a kind of Chinese medicine, on tumor metastasis. The results indicated that tumor cell membrane fluidity is decreasing with increasing the concentration of berberine in culture medium.

Li, Wei; Wang, Yi; Shao, Hanrong; He, Yonghong; Ma, Hui

2006-09-01

364

Finite-temperature anisotropy of magnetic alloys  

NASA Astrophysics Data System (ADS)

The temperature dependence of the magnetic anisotropy of ferromagnetic materials is analyzed. Simple ferromagnets, such as Fe and Co, obey the m=n(n+1)/2 power laws predicted by the Callen and Callen [Phys. Rev. 129, 578 (1963)] theory, but in alloys, the applicability of the theory is an exception rather than the rule. Many alloys, such as the rare-earth transition-metal intermetallics and L10 magnets, violate a basic assumption of the theory, namely, that the single-ion anisotropy and the spontaneous magnetization have the same origin. This is the reason for significant deviations from the Callen and Callen behavior, such as the m=2 law we obtained for L10 alloys.

Skomski, R.; Mryasov, O. N.; Zhou, J.; Sellmyer, D. J.

2006-04-01

365

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

366

Complex Visibilities of Cosmic Microwave Background Anisotropies  

E-print Network

We study the complex visibilities of the cosmic microwave background anisotropies that are observables in interferometric observations of the cosmic microwave background, using the multipole expansion methods commonly adopted in analyzing single-dish experiments. This allows us to recover the properties of the visibilities that is obscured in the flat-sky approximation. Discussions of the window function, multipole resolution, instrumental noise, pixelization, and polarization are given.

Kin-Wang Ng

2000-09-18

367

A fluid metamaterial with tunable anisotropy  

Microsoft Academic Search

We demonstrate a fluid metamaterial consisting of gold nanorods coated with an organic molecular corona, whose anisotropy can be controlled by applied mechanical shear force. ©2011 Optical Society of America OCIS codes: (160.3918) Metamaterials; (160.3900) Metals; (350.4238); Nanophotonics and photonic crystals Metamaterials with hyperbolic dispersion, in which different elements of the electric permittivity tensor have different signs, have been proposed

M. Mayy; G. Zhu; J. K. Kitur; N. Noginova; C. E. Bonner; R. R. Bhattacharjee; E. P. Giannelis; M. A. Noginov

2011-01-01

368

Pn anisotropy in Mesozoic western Pacific lithosphere  

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

369

Global azimuthal anisotropy from Rayleigh waves and  

E-print Network

anisotropy 2 #12;Finite strain rules O(h5 ) Runge-Kutta for tracer advection, tc = 43 Ma advect until -500 0 500 1000 1500 x [km]A1 B1 0 100 200 300 z[km] -1500 -1000 -500 0 500 1000 1500 x [km]A2 B2 0 100 200 300 z[km] -1500 -1000 -500 0 500 1000 1500 x [km]A3 B3 plate motion related flow only 2 #12;Trench

Becker, Thorsten W.

370

Fractional topological superconductor with fractionalized Majorana fermions  

NASA Astrophysics Data System (ADS)

In this paper, we introduce a two-dimensional fractional topological superconductor (FTSC) as a strongly correlated topological state which can be achieved by inducing superconductivity into an Abelian fractional quantum Hall state, through the proximity effect. When the proximity coupling is weak, the FTSC has the same topological order as its parent state and is thus Abelian. However, upon increasing the proximity coupling, the bulk gap of such an Abelian FTSC closes and reopens, resulting in a new topological order: a non-Abelian FTSC. Using several arguments we will conjecture that the conformal field theory (CFT) that describes the edge state of the non-Abelian FTSC is U(1)/Z2 orbifold theory and use this to write down the ground-state wave function. Further, we predict FTSC based on the Laughlin state at ?=1/m filling to host fractionalized Majorana zero modes bound to superconducting vortices. These zero modes are non-Abelian quasiparticles, which is evident in their quantum dimension of dm=2m. Using the multi-quasi-particle wave function based on the edge CFT, we derive the projective braid matrix for the zero modes. Finally, the connection between the non-Abelian FTSCs and the Z2m rotor model with a similar topological order is illustrated.

Vaezi, Abolhassan

2013-01-01

371

Fractional topological superconductors with fractionalized Majorana fermions  

NASA Astrophysics Data System (ADS)

In Ref[1], I introduced a two dimensional fractional topological superconductor (FTSC) as a strongly correlated topological state which can be achieved by inducing superconductivity into an Abelian fractional quantum Hall (FQH) state, through the proximity effect. When the proximity coupling is weak, the FTSC has the same topological order as its parent state, and thus Abelian. However, upon increasing the proximity coupling, the bulk gap of such an Abelian FTSC closes and reopens resulting in a new topological order: a non-Abelian FTSC. I show that the conformal field theory (CFT) that describes the edge state of non-Abelian FTSC is U(1)/Z2 orbifold theory and use this to write down the ground-state wave-function. Further, I predict FTSC based on Laughlin state at ?=1/m filling to host vortices with fractionalized Majorana zero modes. These zero modes are non-Abelian quasi-particles which is evident in their quantum dimension of dm=?2m. Using the multi-quasi-particle wave-function based on the edge CFT, I derive the braid matrix for the zero modes. Finally, the potential applications of the non-Abelian FTSCs in the topological quantum computation will be illustrated. [1] A. Vaezi, ArXiv:1204.6245 (2012)

Vaezi, Abolhassan

2013-03-01

372

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

373

Anisotropy done right: a geometric algebra approach  

NASA Astrophysics Data System (ADS)

For simple electric (magnetic) anisotropy a single function - one that maps a given direction of space to a specific value of permittivity (permeability) - is able to describe the electromagnetic behavior of the medium. Accordingly, the well-known classification of non-magnetic anisotropic crystals, as either uniaxial or biaxial, depends only on the characteristics of the permittivity function. However, when studying metamaterials, we frequently deal with general anisotropy characterized by two linear constitutive operators: the permittivity and permeability functions. Using the mathematical language of Clifford (geometric) algebra, we show - for general (reciprocal) anisotropy - that the direct interpretation of those two constitutive operators cannot provide an accurate description of the medium anymore. Namely, a new operator - one that depends on both those two constitutive operators - is needed, thereby leading to a new classification scheme. Therefore, although the uniaxial/biaxial characterization is still possible, the corresponding physical meaning is completely restated. Furthermore, a new concept - the pseudo-isotropic medium - emerges as a natural consequence of the new classification scheme.

Matos, S. A.; Paiva, C. R.; Barbosa, A. M.

2010-03-01

374

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

375

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

376

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

377

Engineering Functional Anisotropy in Fibrocartilage Neotissues  

PubMed Central

The knee meniscus, intervertebral disc, and temporomandibular joint (TMJ) disc all possess complex geometric shapes and anisotropic matrix organization. While these characteristics are imperative for proper tissue function, they are seldom recapitulated following injury or disease. Thus, this study’s objective was to engineer fibrocartilages that capture both gross and molecular structural features of native tissues. Self-assembled TMJ discs were selected as the model system, as the disc exhibits a unique biconcave shape and functional anisotropy. To drive anisotropy, 50:50 co-cultures of meniscus cells and articular chondrocytes were grown in biconcave, TMJ-shaped molds and treated with two exogenous stimuli: biomechanical (BM) stimulation via passive axial compression and bioactive agent (BA) stimulation via chondroitinase-ABC and transforming growth factor-?1. BM+BA synergistically increased Col/WW, Young’s modulus, and ultimate tensile strength 5.8-fold, 14.7-fold, and 13.8-fold that of controls, respectively; it also promoted collagen fibril alignment akin to native tissue. Finite element analysis found BM stimulation to create direction-dependent strains within the neotissue, suggesting shape plays an essential role toward driving in vitro anisotropic neotissue development. Methods used in this study offer insight on the ability to achieve physiologic anisotropy in biomaterials through the strategic application of spatial, biomechanical, and biochemical cues. PMID:24075479

MacBarb, R.F.; Chen, A.L.; Hu, J.C.; Athanasiou, K.A.

2013-01-01

378

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

379

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

PubMed Central

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

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

2010-01-01

380

Fractional calculus in bioengineering.  

PubMed

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

Magin, Richard L

2004-01-01

381

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

382

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

383

Fractional order differentiation by integration: an application to fractional  

E-print Network

Fractional order differentiation by integration: an application to fractional linear systems D the output of a fractional linear system defined through a linear fractional differential equation (FDE of the fractional derivative of an unknown signal, which is defined by an integral formula obtained by calculating

Boyer, Edmond

384

Ratio and Fractions.  

ERIC Educational Resources Information Center

Findings on ratio and on fractions from a research project on strategies and errors in secondary mathematics are discussed, with typical errors described. Pupils seemed to learn rules without understanding. (MNS)

Hart, K.

1983-01-01

385

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

386

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

PubMed Central

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

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

2014-01-01

387

Diffusion tensor mode in imaging of intracranial epidermoid cysts: one step ahead of fractional anisotropy  

Microsoft Academic Search

Introduction  The signal characteristics of an epidermoid on T2-weighted imaging have been attributed to the presence of increased water\\u000a content within the tumor. In this study, we explore the utility of diffusion tensor imaging (DTI) and diffusion tensor metrics\\u000a (DTM) in knowing the microstructural anatomy of epidermoid cysts.\\u000a \\u000a \\u000a \\u000a Materials and methods  DTI was performed in ten patients with epidermoid cysts. Directionally averaged

Milan Jolapara; Chandrasekharan Kesavadas; V. V. Radhakrishnan; Jitender Saini; Satya Narayan Patro; Arun Kumar Gupta; Tirur Raman Kapilamoorthy; Narendra Bodhey

2009-01-01

388

Estimating with Benchmark Fractions  

NSDL National Science Digital Library

Teachers can use this interactive tool to help students develop fraction sense. After a teacher places a fraction, decimal, or expression on the screen, students determine which given benchmark number it is closest to. An adjustable number line supports conceptual understanding. This page includes a video demonstration of the tool and sample lessons from the Conceptua curriculum. Free registration is required to use the tool. A paid subscription is necessary to access full curriculum and allow full student use.

2011-01-01

389

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

390

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

391

Magnetic phases in the S =1 Shastry-Sutherland model with uniaxial anisotropy  

NASA Astrophysics Data System (ADS)

We explore the field-induced magnetic phases of an S =1 XXZ model with single-ion anisotropy and large Ising-like anisotropy on a Shastry-Sutherland lattice over a wide range of Hamiltonian parameters and applied magnetic field. The multitude of ground-state phases are characterized in detail in terms of their thermodynamic properties, and the underlying classical (Ising limit) spin arrangements for the plateau phases are identified by calculating the static structure factors. The enlarged local Hilbert space of the S =1 spins results in several ground state phases that are not realized for S =1/2 spins. These include the quantum paramagnetic state that is ubiquitous to S =1 spins with single-ion anisotropy, two different spin supersolid phases (with distinct longitudinal ordering), and a magnetization plateau that arises as a direct descendant of the 1/3 plateau due to quantum fluctuations that are not possible for S =1/2 spins. We predict the same mechanism will lead to plateaus at smaller fractions of 1/3 for higher spins. The full momentum dependence of the longitudinal and transverse components of the static structure factor is calculated in the spin supersolid phase to demonstrate the simultaneous existence of diagonal and off-diagonal long-range order as well as the different longitudinal orderings.

Su, Lei; Wierschem, Keola; Sengupta, Pinaki

2014-06-01

392

Fractional laser skin resurfacing.  

PubMed

Laser skin resurfacing (LSR) has evolved over the past 2 decades from traditional ablative to fractional nonablative and fractional ablative resurfacing. Traditional ablative LSR was highly effective in reducing rhytides, photoaging, and acne scarring but was associated with significant side effects and complications. In contrast, nonablative LSR was very safe but failed to deliver consistent clinical improvement. Fractional LSR has achieved the middle ground; it combined the efficacy of traditional LSR with the safety of nonablative modalities. The first fractional laser was a nonablative erbium-doped yttrium aluminum garnet (Er:YAG) laser that produced microscopic columns of thermal injury in the epidermis and upper dermis. Heralding an entirely new concept of laser energy delivery, it delivered the laser beam in microarrays. It resulted in microscopic columns of treated tissue and intervening areas of untreated skin, which yielded rapid reepithelialization. Fractional delivery was quickly applied to ablative wavelengths such as carbon dioxide, Er:YAG, and yttrium scandium gallium garnet (2,790 nm), providing more significant clinical outcomes. Adjustable laser parameters, including power, pitch, dwell time, and spot density, allowed for precise determination of percent surface area, affected penetration depth, and clinical recovery time and efficacy. Fractional LSR has been a significant advance to the laser field, striking the balance between safety and efficacy. PMID:23135075

Alexiades-Armenakas, Macrene R; Dover, Jeffrey S; Arndt, Kenneth A

2012-11-01

393

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

394

Frozen and active seismic anisotropy beneath southern Africa  

NASA Astrophysics Data System (ADS)

P receiver functions from 23 stations of the SASE experiment in southern Africa are inverted simultaneously with SKS waveforms for azimuthal anisotropy in the upper mantle. Our analysis resolves the long-standing issue of depth dependence and origins of anisotropy beneath southern Africa. In the uppermost mantle we observe anisotropy with a nearly E-W fast direction, parallel to the trend of the Limpopo belt. This anisotropy may be frozen since the Archean. At a depth of 160 km the fast direction of anisotropy changes to 40° and becomes close to the recent plate motion direction. This transition is nearly coincident in depth with activation of dominant glide systems in olivine and with a pronounced change in other properties of the upper mantle. Another large change in the fast direction of anisotropy corresponds to the previously found low-S-velocity layer atop the 410-km discontinuity.

Vinnik, L.; Kiselev, S.; Weber, M.; Oreshin, S.; Makeyeva, L.

2012-04-01

395

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

396

Anisotropies in the gravitational-wave stochastic background  

SciTech Connect

We consider anisotropies in the stochastic background of gravitational-waves (SBGW) arising from random fluctuations in the number of gravitational-wave sources. We first develop the general formalism which can be applied to different cosmological or astrophysical scenarios. We then apply this formalism to calculate the anisotropies of SBGW associated with the fluctuations in the number of cosmic string loops, considering both cosmic string cusps and kinks. We calculate the anisotropies as a function of angle and frequency.

Ölmez, S.; Mandic, V. [School of Physics and Astronomy, University of Minnesota, Minneapolis, MN 55455 (United States); Siemens, X., E-mail: olmez@physics.umn.edu, E-mail: mandic@physics.umn.edu, E-mail: siemens@gravity.phys.uwm.edu [Center for Gravitation and Cosmology, University of Wisconsin-Milwaukee, Milwaukee, WI 53201 (United States)

2012-07-01

397

Large-scale anisotropies of the extragalactic infrared background  

SciTech Connect

A general formalism for computing the harmonic expansion of the anisotropy for an arbitrary diffuse background originating from unresolved sources is developed. The anisotropy is assumed to arise from small-amplitude, large-scale inhomogeneities in the cosmic matter density, and the formalism is applied to the large-scale anisotropy of the infrared background to calculate the harmonic amplitudes up to l = 5 for the case of a spherical inhomogeneity on the flat-space Friedmann cosmology. 41 references.

Fabbri, R.; Andreani, P.; Melchiorri, F.; Nisini, B.

1987-04-01

398

Mirror and ion cyclotron anisotropy instabilities in the magnetosheath  

NASA Technical Reports Server (NTRS)

The kinetic properties of the ion cyclotron anisotropy and the mirror instabilities are investigated using one-dimensional hybrid simulations. It is found that, for moderate values of the ion beta and the proton temperature anisotropy, the two instabilities produce similar levels of turbulence. For high values of beta or temperature anisotropy, the ion cyclotron instability produces higher fluctuation levels of turbulence than does the mirror instability.

Mckean, M. E.; Winske, D.; Gary, S. P.

1992-01-01

399

Polarization-shaped laser pulses for improved fluorescence anisotropy contrast  

NASA Astrophysics Data System (ADS)

We present a method to change the fluorescence contrast between two dyes with high fluorescence anisotropy in the same solution under different polarization directions by using polarization-shaped pulses. First a theoretical relationship between contrast, anisotropy and polarization is derived for this case. Then the wavelength dependent polarization anisotropy and the change of contrast by phase-shaping for a solution of Rhodamine B and Stilbene 3 in glycerol is shown. Finally, the application of the polarization-shaped pulses is demonstrated.

Achazi, Georg; Hermes, Nils; Patas, Alexander; Tolksdorf, Daniel; Lindinger, Albrecht

2013-08-01

400

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

PubMed

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

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

2013-01-01

401

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

PubMed Central

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

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

2012-01-01

402

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

403

Upper mantle anisotropy structure beneath eastern Tibet  

NASA Astrophysics Data System (ADS)

Continental collision between the Indian and the Eurasian plates resulted in uplift of the Tibetan plateau and the thickening of the crust. A lot of work has been done on the crust structures beneath Tibet, and several tectonic models are proposed to explain the mechanism of the uplift and thickening. But due to the absence of the upper mantle structures, those models are still under debate. Fine upper mantle velocity and anisotropy structures can help us understand the dynamic process of the Tibetan plateau. Previous studies used shear wave splitting and surface wave analysis to study anisotropy structures beneath the Tibetan plateau. But those two methods provide a poor vertical resolution in upper mantle. Waveform modeling of upper mantle triplication phases can provide a good vertical resolution, but present methods for calculating synthetic seismograms cannot process anisotropic media. We develop a method based on the generalized reflection and transmission method (GRTM) to calculate synthetic seismograms for wave propagating in stratified VTI media, so we can waveform model upper mantle triplications propagating in anisotropic media. Recently, the increasing number of permanent and temporary seismic stations near Tibet provides us a good opportunity to study fine upper mantle structures beneath the Tibetan plateau. In this study, we waveform model the tangential and radial seismic triplication data recorded in Chinese digital seismic stations at a epicentral distance of 10-30 degree for several events occurring in middle Tibet to constrain fine upper mantle velocity and anisotropy structures beneath eastern Tibet. We also use mineral physics modeling method to explore thermal and compositional models that would explain the inferred seismic structures.

Wang, Y.; Wang, W.; Wen, L.; Chen, X.

2013-12-01

404

Detecting Mantle Anisotropy with Marine CSEM Sounding  

NASA Astrophysics Data System (ADS)

We can detect transverse electrical anisotropy in the oceanic crust and upper mantle using circular transmitter tows around a pair of highly sensitive controlled-source electromagnetic (CSEM) receivers. Our long-wire electromagnetic (LEM) receivers, equipped with 100-200 m antennas, improve signal to noise by about an order of magnitude over standard EM receivers using 8-10 m antennas. LEMs work well in deep water where voltage noise from electrodes and amplifiers dominates, and electric field noise from magnetotelluric signals and water motion is low. When combined with SUESI, our marine EM transmitter, which emits 300 amps across a 250 m antenna, noise floors of 10-17~V/Am2 may be obtained at 2-4 Hz over 40-minute stacks. Towing a transmitter in a 30 km circle around an orthogonal pair of LEMs samples propagation though the crust and upper mantle in all horizontal directions. This purely azimuthal geometry generates linearly polarized data for an isotropic earth, but in the presence of anisotropy the minor axis of the polarization ellipse develops a characteristic clover-leaf pattern when plotted against source-receiver direction, and the major axis becomes elongated. We have conducted such experiments on 40 Ma lithosphere offshore California (the APPLE experiment), and 24 Ma lithosphere as it subducts into the Nicaraguan trench (part of the SERPENT expedition). Both regions produce remarkably similar results, with increased conductivity in the fossil ridge-parallel directions, which we interpret to be caused by serpentinized mantle-penetrating faults. This pattern of anisotropy is modified in the outer rise of the trench, as the lithosphere bends and shallower (crustal) fractures develop.

Constable, S.; Key, K. W.; Behrens, J. P.; MacGregor, L.; Evans, R. L.

2010-12-01

405

CMB statistical anisotropy from noncommutative gravitational waves  

NASA Astrophysics Data System (ADS)

Primordial statistical anisotropy is a key indicator to investigate early Universe models and has been probed by the cosmic microwave background (CMB) anisotropies. In this paper, we examine tensor-mode CMB fluctuations generated from anisotropic gravitational waves, parametrised by Ph(k) = Ph(0)(k) [ 1 + ?LM fL(k) gLM YLM (hat k)], where Ph(0)(k) is the usual scale-invariant power spectrum. Such anisotropic tensor fluctuations may arise from an inflationary model with noncommutativity of fields. It is verified that in this model, an isotropic component and a quadrupole asymmetry with f0(k) = f2(k) propto k-2 are created and hence highly red-tilted off-diagonal components arise in the CMB power spectra, namely l2 = l1 ± 2 in TT, TE, EE and BB, and l2 = l1 ± 1 in TB and EB. We find that B-mode polarisation is more sensitive to such signals than temperature and E-mode polarisation due to the smallness of large-scale cosmic variance and we can potentially measure g00 = 30 and g2M = 58 at 68% CL in a cosmic-variance-limited experiment. Such a level of signal may be measured in a PRISM like experiment, while the instrumental noise contaminates it in the Planck experiment. These results imply that it is impossible to measure the noncommutative parameter if it is small enough for the perturbative treatment to be valid. Our formalism and methodology for dealing with the CMB tensor statistical anisotropy are general and straightforwardly applicable to other early Universe models.

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

2014-07-01

406

Transport of spin anisotropy without spin currents  

NASA Astrophysics Data System (ADS)

We revisit the transport of spin-degrees of freedom across an electrically and thermally biased tunnel junction between two ferromagnets with noncollinear magnetizations. Besides the well-known charge current and spin current we show that a nonzero spin-quadrupole current flows between the ferromagnets. This tensor-valued current describes the nonequilibrium transport of spin anisotropy relating to both local and nonlocal multiparticle spin correlations of the circuit. This quadratic spin anisotropy, quantified in terms of the spin-quadrupole moment, is fundamentally a two-electron quantity. In spin valves with an embedded quantum dot such currents have been shown to result in a quadrupole accumulation that affects the measurable quantum dot spin and charge dynamics. The spin-valve model studied here allows fundamental questions about spin-quadrupole storage and transport to be worked out in detail, while ignoring the detection by a quantum dot. The physical understanding of this particular device is of importance for more complex devices where spin-quadrupole transport can be detected. We demonstrate that, as far as storage and transport are concerned, the spin anisotropy is only partly determined by the spin polarization. In fact, for a thermally biased spin valve the charge current and spin current may vanish, while a pure exchange spin-quadrupole current remains, which appears as a fundamental consequence of Pauli's principle. We extend the real-time diagrammatic approach to efficiently calculate the average of multiparticle spin observables, in particular the spin-quadrupole current. Although the paper addresses only leading-order and spin-conserving tunneling, we formulate the technique for arbitrary order in an arbitrary, spin-dependent tunnel coupling in a way that lends itself to extension to quantum-dot spin-valve structures.

Hell, Michael; Das, Sourin; Wegewijs, Maarten R.

2013-09-01

407

Depth-dependent crustal anisotropy at Midwestern Honshu, Japan  

NASA Astrophysics Data System (ADS)

Aligned cracks, possibly induced by tectonic stress, produce anisotropy in the Earth's crust. Permeability and state of stress at several depths in the crust can be estimated from the state of crack distribution. We present clear evidence that crustal anisotropy changes with depth at the Inagawa earthquake swarm area, mid-western Honshu, Japan. The observed fast shear-wave directions are parallel to the maximum horizontal compressional axes obtained from a hydro-fracturing test at a depth of 0.80 km and focal mechanism solution at depths 4-8 km in the same area. These observations provide us the evidence that the crustal anisotropy in this region is controlled by the tectonic stress. We estimated the degree of anisotropy, that is, the ratio of the difference between fast and slow S-wave velocities, as a function of depth using the layer-stripping method. The obtained value is 2% or less at most depths but anisotropy of 11% is observed at depths 6-8 km. This high-anisotropy layer has a local gradient in seismicity rates. We infer that vertical fluid flow from the high-anisotropy layer would be trapped in the low-anisotropy layer above, pore pressure would increase, and it could generate earthquakes. This correspondence suggests that the degree of anisotropy in the upper crust changes with depth and has some relation to seismicity.

Nakamura, Mamoru; Ando, Masataka; Kusunose, Kinichiro; Sato, Takashi

408

Knitted patterns as a model for anisotropy  

NASA Astrophysics Data System (ADS)

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

?epi?, Mojca

2012-07-01

409

Concave nanomagnets with widely tunable anisotropy  

DOEpatents

A nanomagnet having widely tunable anisotropy is disclosed. The disclosed nanomagnet is a magnetic particle with a convex shape having a first magnetically easy axis. The convex shape is modified to include at least one concavity to urge a second magnetically easy axis to form substantially offset from the first magnetically easy axis. In at least one embodiment, the convex shape is also modified to include at least one concavity to urge a second magnetically easy axis to form with a magnetic strength substantially different from the first magnetically easy axis.

Lambson, Brian; Gu, Zheng; Carlton, David; Bokor, Jeffrey

2014-07-01

410

Asymmetric beams and CMB statistical anisotropy  

SciTech Connect

Beam asymmetries result in statistically anisotropic cosmic microwave background (CMB) maps. Typically, they are studied for their effects on the CMB power spectrum, however they more closely mimic anisotropic effects such as gravitational lensing and primordial power asymmetry. We discuss tools for studying the effects of beam asymmetry on general quadratic estimators of anisotropy, analytically for full-sky observations as well as in the analysis of realistic data. We demonstrate this methodology in application to a recently detected 9{sigma} quadrupolar modulation effect in the WMAP data, showing that beams provide a complete and sufficient explanation for the anomaly.

Hanson, Duncan [Institute of Astronomy and Kavli Institute for Cosmology Cambridge, University of Cambridge, Madingley Road, Cambridge CB3 OHA (United Kingdom); Lewis, Antony [Institute of Astronomy and Kavli Institute for Cosmology Cambridge, University of Cambridge, Madingley Road, Cambridge CB3 OHA (United Kingdom); Department of Physics and Astronomy, Pevensey II Building, University of Sussex, Falmer, Brighton BN1 9QH (United Kingdom); Challinor, Anthony [Institute of Astronomy and Kavli Institute for Cosmology Cambridge, University of Cambridge, Madingley Road, Cambridge CB3 OHA (United Kingdom); DAMTP, Centre for Mathematical Sciences, University of Cambridge, Wilberforce Road, Cambridge CB3 OWA (United Kingdom)

2010-05-15

411

Critical Current Anisotropy in High Temperature Superconductors  

E-print Network

wires subject to a self field. 2.2.4. The Flux Line Each flux line that nucleates in a Type II superconductor is surrounded by a circulating current which screens the rest of the superconductor. It is these circulating currents that give rise... Current Anisotropy in High Temperature Superconductors John Durrell 12 As the lattice structure is known the nearest neighbour lattice spacing, a0, may be calculated. The flux vortex number density is simply nv=B/?0. Each vortex line accounts for 1/nv...

Durrell, John H

412

Seismic anisotropy above a subducting plate  

SciTech Connect

Shear-wave splitting observed in northeastern Colombia has provided evidence of seismic anisotropy in a shear zone immediately above a subducting plate. In an upper mantle composed mainly of olivine (57%) and orthopyroxene (17%), the splitting can be interpreted by wave propagation in an anisotropic medium of orthorhombic symmetry that results from alignment of these intrinsically anisotropic minerals. The mechanism of alignment is most likely the shearing associated with the subduction, aided by fluids migrating from the subducting plate when the plate exceeds 100 km in depth.

Shih, X.R.; Meyer, R.P. (Univ. of Wisconsin, Madison (United States)); Schneider, J.F. (Electric Power Research Inst., Palo Alto, CA (United States))

1991-08-01

413

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

SciTech Connect

Some polymer properties, such as conductivity, are very sensitive to short- and intermediate-range orientational and positional ordering of anisotropic molecular functional groups, and yet means to characterize orientational order in disordered systems are very limited. We demonstrate that resonant scattering at the carbon K-edge is uniquely sensitive to short-range orientation correlations in polymers through depolarized scattering at high momentum transfers, using atactic polystyrene as a well-characterized test system. Depolarized scattering is found to coexist with unpolarized fluorescence, and to exhibit pronounced anisotropy. We also quantify the spatially averaged optical anisotropy from low-angle reflectivity measurements, finding anisotropy consistent with prior visible, x-ray absorption, and theoretical studies. The average anisotropy is much smaller than that in the depolarized scattering and the two have different character. Both measurements exhibit clear spectral signatures from the phenyl rings and the polyethylene-like backbone. Discussion focuses on analysis considerations and prospects for using this depolarized scattering for studies of disorder in soft condensed matter.

Stone, Kevin H.

2014-07-14

414

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

415

The Anisotropy of Magnetic Susceptibility of Igneous Rocks: Lessons From Obsidians and Pyroclastic Deposits  

NASA Astrophysics Data System (ADS)

The anisotropy of magnetic susceptibility (AMS) of igneous rocks differs from that of other lithologies in several aspects that are related to their characteristics of emplacement history. Nevertheless, within the group of igneous rocks there are also differences on emplacement mechanisms that can lead to specific and distinctive AMS signatures. In this work, a review of the most important emplacement regimes is made, paying special attention to the extreme conditions represented by obsidians and pyroclastic deposits. These two extreme emplacement regimes are controlled mainly by the viscosity of the fluid phase, but the differences in AMS signatures also includes other differences in the nature of the ferromagnetic grains that are present in the rocks during emplacement. For example, the results of this work indicate that the AMS can be associated to a population of ferromagnetic minerals of a submicroscopic size, despite of which it can be very well defined and yield large degrees of anisotropy. It is suggested that the AMS associated to such population of small grains might indeed be the origin of the AMS of other igneous rocks that have an optically observable fraction of mineral grains, although until present it had been overlooked in most instances. As it had been suggested before, use of tests designed to identify the contribution of a superparamagnetic fraction (SP) in the magnetic properties of a rock can help us to identify the presence of such a SP-related AMS in other cases.

Canon-Tapia, E.

2013-05-01

416

Limits on isocurvature perturbations from non-Gaussianity in WMAP temperature anisotropy  

NASA Astrophysics Data System (ADS)

We study the effect of primordial isocurvature perturbations on non-Gaussian properties of cosmic microwave background (CMB) temperature anisotropies. We consider generic forms of the non-linearity of isocurvature perturbations which can be applied to a wide range of theoretical models. We derive analytical expressions for the bispectrum and the Minkowski Functionals for CMB temperature fluctuations to describe the non-Gaussianity from isocurvature perturbations. We find that the isocurvature non-Gaussianity in the quadratic isocurvature model, where the isocurvature perturbation S is written as a quadratic function of the Gaussian variable ?,S = ?2 - , can give the same signal-to-noise ratio as fNL = 30 even if we impose the current observational limit on the fraction of isocurvature perturbations contained in the primordial power spectrum ?. We give constraints on isocurvature non-Gaussianity from Minkowski Functionals using the Wilkinson Microwave Anisotropy Probe (WMAP) 5-year data. We do not find a significant signal of isocurvature non-Gaussianity. For the quadratic isocurvature model, we obtain a stringent upper limit on the isocurvature fraction ? < 0.070 (95 per cent CL) for a scale-invariant spectrum which is comparable to the limit obtained from the power spectrum.

Hikage, Chiaki; Koyama, Kazuya; Matsubara, Takahiko; Takahashi, Tomo; Yamaguchi, Masahide

2009-10-01

417

Elasticity and Anisotropy of Common Crustal Minerals  

NASA Astrophysics Data System (ADS)

Full interpretation of crustal seismology in terms of composition and fabric is difficult in the absence of high quality elasticity data for the constituent minerals. Over the last forty years, a limited data set based on 1-bar ultrasonic determinations has served as the principal foundation for such discussions. We have now measured single crystal elastic properties of several dominant crustal minerals in both feldspar and amphibole mineral series. We use impulsively stimulated light scattering to determine body wave or surface wave velocities as a function of propagation direction on crystals having dimensions of tens to hundreds of microns. Full tensor elastic constants for these low symmetry (monoclinic and triclinic) crystals were obtained by inverting the velocity data. We observe greater velocity anisotropy and find constants that are 10 to 25% larger than previously reported constants. Some of the constants that appear biased low in the older data set are associated with strains in common cleavage directions; this underscores the need for a full re-examination of crustal scale elasticity modeled from properties of constituent minerals. In particular, the new data suggest that minerals less abundant than feldspars and amphiboles have a significant role in obtaining an adequate fit to crustal velocity profiles and that large-scale elastic anisotropy of the crust must be addressed in the next generation of crustal velocity models.

Teel, A.; Brown, J. M.; Abramson, E.; West-Foyle, H.; Angel, R.; Johnson, E.

2006-12-01

418

Cosmic microwave anisotropies from BPS semilocal strings  

SciTech Connect

We present the first ever calculation of cosmic microwave background (CMB) anisotropy power spectra from semilocal cosmic strings, obtained via simulations of a classical field theory. Semilocal strings are a type of non-topological defect arising in some models of inflation motivated by fundamental physics, and are thought to relax the constraints on the symmetry breaking scale as compared to models with (topological) cosmic strings. We derive constraints on the model parameters, including the string tension parameter {mu}, from fits to cosmological data, and find that in this regard Bogomol'nyi-Prasad-Sommerfield (BPS) semilocal strings resemble global textures more than topological strings. The observed microwave anisotropy at l=10 is reproduced if G{mu} = 5.3 Multiplication-Sign 10{sup -6} (G is Newton's constant). However as with other defects the spectral shape does not match observations, and in models with inflationary perturbations plus semilocal strings the 95% confidence level upper bound is G{mu}<2.0 Multiplication-Sign 10{sup -6} when CMB, Hubble key project and big bang nucleosynthesis data are used (cf G{mu}<0.9 Multiplication-Sign 10{sup -6} for cosmic strings). We additionally carry out a Bayesian model comparison of several models with and without defects, showing that models with defects are neither conclusively favoured nor disfavoured at present.

Urrestilla, Jon; Bevis, Neil; Hindmarsh, Mark; Kunz, Martin; Liddle, Andrew R, E-mail: j.urrestilla@sussex.ac.uk, E-mail: n.bevis@imperial.ac.uk, E-mail: m.b.hindmarsh@sussex.ac.uk, E-mail: martin.kunz@physics.unige.ch, E-mail: a.liddle@sussex.ac.uk [Department of Physics and Astronomy, University of Sussex, Brighton BN1 9QH (United Kingdom)

2008-07-15

419

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 pr...

Hu, W

1994-01-01

420

Anisotropy beneath a highly extended continental rift  

NASA Astrophysics Data System (ADS)

have employed shear wave splitting techniques to image anisotropy beneath the D'Entrecasteaux Islands, in southeastern Papua New Guinea. Our results provide a detailed picture of the extending continent that lies immediately ahead of a propagating mid-ocean ridge tip; we image the transition from continental to oceanic extension. A dense shear wave splitting data set from a 2010 to 2011 passive-source seismic deployment is analyzed using single and multichannel methods. Splitting delay times of 1-1.5 s are observed and fast axes of anisotropy trending N-S, parallel to rifting direction, predominate the results. This trend is linked to lattice-preferred orientation of olivine, primarily in the shallow convecting mantle, driven by up to 200 km of N-S continental extension ahead of the westward-propagating Woodlark Rift. This pattern differs from several other continental rifts that evince rift-strike-parallel fast axes and is evident despite the complex recent tectonic history. We contend that across most of this rift, the unusually high rate and magnitude of extension has been sufficient to produce a regime change to a mid-ocean-ridge-like mantle fabric. Stations in the south of our array show more complex splitting that might be related to melt or to complex inherited structure at the edge of the extended region.

Eilon, Zachary; Abers, Geoffrey A.; Jin, Ge; Gaherty, James B.

2014-03-01

421

The Background Emission Anisotropy Scanning Telescope (BEAST)  

NASA Astrophysics Data System (ADS)

Since 1988 the UCSB Cosmology Group has performed a number of measurements of the degree scale structure in the Cosmic Background Radiation. These include 3 South Pole expeditions in 1989, 91 and 94. and 8 balloon flights using SIS, HEMTs and bolometer based detectors. We will present a summary of these measurements focusing onthe recent results. In addition, we will describe the recent flight of HACME, a balloon- borne experiment to map CMB anisotropies with 0.75 degree angular resolution over several hundred square degrees. This experiment is a prototype for our next generation CMB experiment, the Background Emission Anisotropy Scanning Telescope (BEAST). BEAST will feature a 2 m diameter carbon fiber composite primary mirror for high angular resolution and a sensitive array of ultra-low noise HEMT amplifiers at 30, 40, and 90 GHz. BEAST is designed for an Antarctic long duration balloon flight allowing an observing time of order two weeks. This experiment will provide an unprecedented combination of sensitivty and angular resolution across a significant region of sky.

Seiffert, M.

1996-12-01

422

Anisotropy in the Interaction of Ultracold Dysprosium  

E-print Network

The nature of the interaction between ultracold atoms with a large orbital and spin angular momentum has attracted considerable attention. It was suggested that such interactions can lead to the realization of exotic states of highly correlated matter. Here, we report on a theoretical study of the competing anisotropic dispersion, magnetic dipole-dipole, and electric quadrupole-quadrupole forces between two dysprosium atoms. Each dysprosium atom has an orbital angular momentum L=6 and magnetic moment $\\mu=10\\mu_B$. We show that the dispersion coefficients of the ground state adiabatic potentials lie between 1865 a.u. and 1890 a.u., creating a non-negligible anisotropy with a spread of 25 a.u. and that the electric quadrupole-quadrupole interaction is weak compared to the other interactions. We also find that for interatomic separations $R< 50\\,a_0$ both the anisotropic dispersion and magnetic dipole-dipole potential are larger than the atomic Zeeman splittings for external magnetic fields of order 10 G to 100 G. At these separations spin exchange can occur. We finish by describing two scattering models for inelastic spin exchange. A universal scattering theory is used to model loss due to the anisotropy in the dispersion and a distorted-wave-Born theory is used to model losses from the magnetic dipole-dipole interaction for the $^{164}$Dy isotope. These models find loss rates that are the same order of magnitude as the experimental value.

Svetlana Kotochigova; Alexander Petrov

2011-04-28

423

Reflectance anisotropy spectroscopy of magnetite (110) surfaces  

NASA Astrophysics Data System (ADS)

Reflectance anisotropy spectroscopy (RAS) has been used to measure the optical anisotropies of bulk and thin-film Fe3O4(110) surfaces. The spectra indicate that small shifts in energy of the optical transitions, associated with anisotropic strain or electric field gradients caused by the (110) surface termination or a native oxide layer, are responsible for the strong signal observed. The RAS response was then measured as a function of temperature. A distinct change in the RAS line-shape amplitude was observed in the spectral range from 0.8 to 1.6 eV for temperatures below the Verwey transition of the crystal. Finally, thin-film magnetite was grown by molecular beam epitaxy on MgO(110) substrates. Changes in the RAS spectra were found for different film thickness, suggesting that RAS can be used to monitor the growth of magnetite (110) films in situ. The thickness dependence of the RAS is discussed in terms of various models for the origin of the RAS signal.

Fleischer, K.; Verre, R.; Mauit, O.; Sofin, R. G. S.; Farrell, L.; Byrne, C.; Smith, C. M.; McGilp, J. F.; Shvets, I. V.

2014-05-01

424

Low-temperature magnetic anisotropy in micas and chlorite  

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

425

FRACTIONAL CRYSTALLIZATION FEED ENVELOPE  

SciTech Connect

Laboratory work was completed on a set of evaporation tests designed to establish a feed envelope for the fractional crystallization process. The feed envelope defines chemical concentration limits within which the process can be operated successfully. All 38 runs in the half-factorial design matrix were completed successfully, based on the qualitative definition of success. There is no feed composition likely to be derived from saltcake dissolution that would cause the fractional crystallization process to not meet acceptable performance requirements. However, some compositions clearly would provide more successful operation than other compositions.

HERTING DL

2008-03-19

426

Lagrangian Mechanics of Fractional Order, Hamilton-Jacobi Fractional PDE  

E-print Network

Lagrangian Mechanics of Fractional Order, Hamilton-Jacobi Fractional PDE and Taylor's Series of the reader, one gives a brief background on the Taylor's series of fractional order )()()( xfDhEhxf x geometry of fractional order are outlined. In this framework, the use of complex-valued variables

Nottale, Laurent

427

Fractional Variational Iteration Method for Fractional Nonlinear Differential Equations  

E-print Network

Recently, fractional differential equations have been investigated via the famous variational iteration method. However, all the previous works avoid the term of fractional derivative and handle them as a restricted variation. In order to overcome such shortcomings, a fractional variational iteration method is proposed. The Lagrange multipliers can be identified explicitly based on fractional variational theory.

Guo-cheng Wu

2010-07-12

428

Experiments to Separate the Effect of Texture on Anisotropy of Pipeline Steel  

E-print Network

Experiments to Separate the Effect of Texture on Anisotropy of Pipeline Steel M. S. Jooa , D the anisotropy of Charpy test energy. Keywords: pipeline steel, anisotropy, crystallographic texture, memory

Cambridge, University of

429

Anisotropy of ultrasonic propagation and scattering properties in fresh rat skeletal muscle in vitro  

E-print Network

Anisotropy of ultrasonic propagation and scattering properties in fresh rat skeletal muscle frequency dependent information in the 4­14 MHz range. The attenuation coefficient in each muscle anisotropy. Anisotropy in ultrasonic parameters characterizing biological tissue has been reported

Illinois at Urbana-Champaign, University of

430

Fractions with Borrowing  

NSDL National Science Digital Library

In this 14-minute video Beverly Gonzalez demonstrates teaching her students how to use decomposition to subtract fractions and mixed numbers. Throughout the video Gonzalez details her teaching strategies starting with an application, including high student motivation, and constant reflection and growth. This resource includes a transcript of the video (pdf).

2013-01-01

431

Fractions and Chemistry  

NSDL National Science Digital Library

In this problem set, learners will practice fractions by working with the ratios of various molecules or atoms in different compounds to answer a series of questions. Answer key is provided. This is part of Earth Math: A Brief Mathematical Guide to Earth Science and Climate Change.

2012-08-03

432

Rayleigh fractionation visualization  

NSDL National Science Digital Library

Students answer several questions about Rayleigh fractionation and the oxygen isotope composition of ice cores which require them to manipulate the values and equations in a MS Excel spreadsheet. This helps them to see how the oxygen isotope composition of ice cores changes with temperature in the high latitudes. Future iterations of the exercise should include a visualization of the Clausius-Clapeyron equation.

Farmer, E. C.

433

Decimals, Fractions, and Percentages  

NSDL National Science Digital Library

This webpage develops students' understanding of how fractions, decimals, and percents are related. An interactive applet displays visual and numerical representations of all three forms. As users change one form, they see the equivalents in the other two forms. The page provides procedures for converting between forms and 12 questions to check for understanding.

2011-01-01

434

An Inexpensive Fraction Collector.  

ERIC Educational Resources Information Center

Describes the construction of a low-cost (about $70.00) alternative to the commercial fraction collector. Outlines the separate parts of the collector and provides a schematic of electronic circuitry of the instrument. Lists special items required for the development of this project. (TW)

Fisher, Tom Lyons; McGinnis, James S.

1986-01-01

435

Sweet Work with Fractions  

ERIC Educational Resources Information Center

Almost everyone loves chocolate. However, the same cannot be said about fractions, which are loved by markedly fewer. Middle school students tend to view them with wary respect, but little affection. The authors attempt to sweeten the subject by describing a type of game involving division of chocolate bars. The activity they describe provides a…

Vinogradova, Natalya; Blaine, Larry

2013-01-01

436

Field-Flow Fractionation.  

ERIC Educational Resources Information Center

Describes a technique for separating samples that range over 15 orders of magnitude in molecular weight. Discusses theory, apparatus, and sample preparation techniques. Lists several types of field-flow fractionation (FFF) and their uses: sedimentation FFF, thermal FFF, flow FFF, electrical FFF, and steric FFF. (ML)

Caldwell, Karin D.

1988-01-01

437

Fraction collector for electrophoresis  

NASA Technical Reports Server (NTRS)

Rotating-tube electrophoresis apparatus employs rotating jet of eluting buffer to reduce effects of convection during separation. Designed for separation of microorganisms and biological species, system combines gravity/gradient compensating of lumen with buffer flush at fraction outlet to increase separation efficiency.

Bier, M.

1977-01-01

438

Multiplying Fractions (Area Model)  

NSDL National Science Digital Library

In this teaching idea, students will learn how to use the area model to find the product when two fractions are multiplied. NOTE: Click the Download link on the right side of the screen to display the lesson without ads and to view the graphic example of the model.

Page, Audrey P.

2012-04-22

439

Determination of the optical anisotropy of magnetic garnet films.  

PubMed

We show that the application of isotropic coupling prisms instead of birefringent prisms permits the precise determination of the optical anisotropy of magnetic garnet films; these measurements are essential for phase matching and conversion of optical modes. Using this technique, the anisotropy of a (211)-oriented film was measured with silicon prisms. PMID:19741925

Hemme, H; Dötsch, H; Middelberg, J; Kappelt, R; Tolksdorf, W

1987-11-01

440

Perpendicular magnetic recording with a composite anisotropy film  

Microsoft Academic Search

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

S. Iwasaki; Y. Nakamura; K. Ouchi

1979-01-01

441

Cosmic Background Anisotropies in Cold Dark Matter Cosmology  

Microsoft Academic Search

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

Naoshi Sugiyama

1995-01-01

442

Evolution of Tidally Truncated Globular Clusters with Anisotropy  

E-print Network

The evolution of tidally truncated globular clusters is investigated by integrating two-dimensional Fokker-Planck equation that allows the development of velocity anisotropy. We start from the isotropic Plummer model with tidal cut off and followed the evolution through the corecollapse. The heating by three-binary is included to obtain the evolution past the corecollapse. The anisotropy in velocity dispersion develops during the precollapse evolution. However, the anisotropy becomes highly depressed during the post-collapse evolution because of rapid loss of radial orbits. Maximum radial anisotropy appears just after the beginning of the expansion, and degree of anisotropy decreases slowly as the total mass of the cluster decreases. Thus it may be possible to determine the evolutionary status of a cluster if the velocity anisotropy can be measured in the sense that the postcollapse clusters always have very little degree of anisotropy. The structure of the post-collapse cluster can be well fitted to King models because the degree of anisotropy is rather small.

K. Takahashi; H. M. Lee; S. Inagaki

1997-05-03

443

Giant Magnetic Anisotropy of Single Cobalt Atoms and  

E-print Network

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

Brune, Harald

444

Significant seismic anisotropy beneath the southern Lhasa Terrane, Tibetan Plateau  

Microsoft Academic Search

Shear wave splitting measurements using teleseismic PKS, SKKS, and SKS phases recorded by station LSA on the southern part of the Lhasa Terrane of the Tibetan Plateau reveal significant azimuthal anisotropy with a splitting time of up to 1.5 s, a conclusion that is contradictory to previous studies which suggested isotropy or weak anisotropy. In addition, systematic variations of the

Stephen S. Gao; Kelly H. Liu

2009-01-01

445

OBSERVATIONAL SCAN-INDUCED ARTIFICIAL COSMIC MICROWAVE BACKGROUND ANISOTROPY  

SciTech Connect

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

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

2011-05-10