Science.gov

Sample records for callosum fractional anisotropy

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

    PubMed

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

    2015-04-01

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

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

    PubMed Central

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

    2014-01-01

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

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

    PubMed Central

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

    2014-01-01

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

  4. Cosmic ray anisotropy in fractional differential models of anomalous diffusion

    SciTech Connect

    Uchaikin, V. V.

    2013-06-15

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

  5. Fractional anisotropy in individuals with schizophrenia and their nonpsychotic siblings

    PubMed Central

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

    2014-01-01

    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

  6. Fractional anisotropy of water diffusion in cerebral white matter across the lifespan

    PubMed Central

    Kochunov, P.; Williamson, D.E.; Lancaster, J.; Fox, P.; Cornell, J; Blangero, J.; Glahn, DC

    2010-01-01

    Determining the time of peak of cerebral maturation is vital for our understanding of when cerebral maturation ceases and the cerebral degeneration in healthy aging begins. We carefully mapped changes in fractional anisotropy (FA) of water diffusion for eleven major cerebral white matter tracts in a large group (831) of healthy human subjects aged 1190. FA is a neuroimaging index of micro-structural white matter integrity, sensitive to age-related changes in cerebral myelin levels, measured using diffusion tensor imaging. The average FA values of cerebral white matter (WM) reached peak at the age 326 years. FA measurements for all but one major cortical white matter tract (cortico-spinal) reached peaks between 23 and 39 years of age. The maturation rates, prior to age-of-peak were significantly correlated (r=0.74; p=.01) with the rates of decline, past age-of-peak. Regional analysis of corpus callosum (CC) showed that thinly-myelinated, densely packed fibers in the genu, that connect pre-frontal areas, maturated later and showed higher decline in aging than the more thickly myelinated motor and sensory areas in the body and splenium of CC. Our findings can be summarized as: associative, cerebral WM tracts that reach their peak FA values later in life also show progressively higher age-related decline than earlier maturing motor and sensory tracts. These findings carry multiple and diverse implications for both theoretical studies of the neurobiology of maturation and aging and for the clinical studies of neuropsychiatric disorders. PMID:20122755

  7. Tractography of the Spider Monkey (Ateles geoffroyi) Corpus Callosum Using Diffusion Tensor Magnetic Resonance Imaging

    PubMed Central

    Platas-Neri, Diana; Hidalgo-Tobón, Silvia; da Celis Alonso, Benito; de León, Fernando Chico-Ponce; Muñoz-Delgado, Jairo; Phillips, Kimberley A.

    2015-01-01

    The objective of this research was to describe the organization, connectivity and microstructure of the corpus callosum of the spider monkey (Ateles geoffroyi). Non-invasive magnetic resonance imaging and diffusion-tensor imaging were obtained from three subjects using a 3T Philips scanner. We hypothesized that the arrangement of fibers in spider monkeys would be similar to that observed in other non-human primates. A repeated measure (n = 3) of fractional anisotropy values was obtained of each subject and for each callosal subdivision. Measurements of the diffusion properties of corpus callosum fibers exhibited a similar pattern to those reported in the literature for humans and chimpanzees. No statistical difference was reached when comparing this parameter between the different CC regions (p = 0.066). The highest fractional anisotropy values corresponded to regions projecting from the corpus callosum to the posterior cortical association areas, premotor and supplementary motor cortices. The lowest fractional anisotropy corresponded to projections to motor and sensory cortical areas. Analyses indicated that approximately 57% of the fibers projects to the frontal cortex and 43% to the post-central cortex. While this study had a small sample size, the results provided important information concerning the organization of the corpus callosum in spider monkeys. PMID:25693078

  8. Tractography of the spider monkey (Ateles geoffroyi) corpus callosum using diffusion tensor magnetic resonance imaging.

    PubMed

    Platas-Neri, Diana; Hidalgo-Tobn, Silvia; de Celis Alonso, Benito; da Celis Alonso, Benito; de Len, Fernando Chico-Ponce; Muoz-Delgado, Jairo; Phillips, Kimberley A

    2015-01-01

    The objective of this research was to describe the organization, connectivity and microstructure of the corpus callosum of the spider monkey (Ateles geoffroyi). Non-invasive magnetic resonance imaging and diffusion-tensor imaging were obtained from three subjects using a 3T Philips scanner. We hypothesized that the arrangement of fibers in spider monkeys would be similar to that observed in other non-human primates. A repeated measure (n = 3) of fractional anisotropy values was obtained of each subject and for each callosal subdivision. Measurements of the diffusion properties of corpus callosum fibers exhibited a similar pattern to those reported in the literature for humans and chimpanzees. No statistical difference was reached when comparing this parameter between the different CC regions (p = 0.066). The highest fractional anisotropy values corresponded to regions projecting from the corpus callosum to the posterior cortical association areas, premotor and supplementary motor cortices. The lowest fractional anisotropy corresponded to projections to motor and sensory cortical areas. Analyses indicated that approximately 57% of the fibers projects to the frontal cortex and 43% to the post-central cortex. While this study had a small sample size, the results provided important information concerning the organization of the corpus callosum in spider monkeys. PMID:25693078

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

    PubMed

    Lawrenz, Marco; Brassen, Stefanie; Finsterbusch, Jrgen

    2015-04-01

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

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

    SciTech Connect

    Aukema, Eline J.; Oudhuis, Nienke; Vos, Frans M.; Reneman, Liesbeth; Last, Bob F.; Grootenhuis, Martha A.

    2009-07-01

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

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

    PubMed Central

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

    2013-01-01

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

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

    PubMed Central

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

    2012-01-01

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

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

    PubMed Central

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

    2013-01-01

    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

  14. Bilingual Corpus Callosum Variability

    ERIC Educational Resources Information Center

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

    2004-01-01

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

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

    PubMed Central

    Giordano, Chiara; Kleiven, Svein

    2014-01-01

    Brain tissue modelling has been an active area of research for years. Brain matter does not follow the constitutive relations for common materials and loads applied to the brain turn into stresses and strains depending on tissue local morphology. In this work, a hyperviscoelastic fibre-reinforced anisotropic law is used for computational brain injury prediction. Thanks to a fibre-reinforcement dispersion parameter, this formulation accounts for anisotropic features and heterogeneities of the tissue owing to different axon alignment. The novelty of the work is the correlation of the material mechanical anisotropy with fractional anisotropy (FA) from diffusion tensor images. Finite-element (FE) models are used to investigate the influence of the fibre distribution for different loading conditions. In the case of tensilecompressive loads, the comparison between experiments and simulations highlights the validity of the proposed FAk 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

  16. Case Series: Fractional Anisotropy Profiles of the Cerebellar Peduncles in Adolescents Born Preterm With Ventricular Dilation.

    PubMed

    Travis, Katherine E; Leitner, Yael; Ben-Shachar, Michal; Yeom, Kristen W; Feldman, Heidi M

    2016-03-01

    This case series assesses white matter microstructure of the cerebellar peduncles in 4 adolescents born preterm with enlarged ventricles and reduced white matter volume in the cerebrum but no apparent injury to the cerebellum. Subjects (ages 12-17 years, gestational age 26-32 weeks, birth weight 825-2211 g) were compared to a normative sample of 19 full-term controls (9-17 years, mean gestational age 39 weeks, mean birth weight 3154 g). Tract profiles for each of the cerebellar peduncles were generated by calculating fractional anisotropy at 30 points along the central portion of each tract. One or more case subjects exhibited higher fractional anisotropy beyond the 90th percentile in the inferior, middle, and superior cerebellar peduncles. Findings demonstrate that differences in cerebellar white matter microstructure can be detected in the absence of macrostructural cerebellar abnormalities. PMID:26116381

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

    PubMed Central

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

    2014-01-01

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

  18. Regional Microstructural and Volumetric Magnetic Resonance Imaging (MRI) Abnormalities in the Corpus Callosum of Neonates With Congenital Heart Defect Undergoing Cardiac Surgery.

    PubMed

    Hagmann, Cornelia; Singer, Jitka; Latal, Beatrice; Knirsch, Walter; Makki, Malek

    2016-03-01

    The purpose of the study is to investigate the structural development of the corpus callosum in term neonates with congenital heart defect before and after surgery using diffusion tensor imaging and 3-dimensional T1-weighted magnetic resonance imaging (MRI). We compared parallel and radial diffusions, apparent diffusion coefficient (ADC), fractional anisotropy, and volume of 5 substructures of the corpus callosum: genu, rostral body, body, isthmus, and splenium. Compared to healthy controls, we found a significantly lower volume of the splenium and total corpus callosum and a higher radial diffusion and lower fractional anisotropy in the splenium of patients presurgery; a lower volume in all substructures in the postsurgery group; higher radial diffusion in the rostral body, body, and splenium; and a higher apparent diffusion coefficient in the splenium of postsurgery patients. Similar fractional anisotropy changes in congenital heart defect patients were reported in preterm infants. Our findings in apparent diffusion coefficient in the splenium of these patients (pre and postsurgery) are comparable to findings in preterm neonates with psychomotor delay. Delayed maturation of the isthmus was also reported in preterm infants. PMID:26129977

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

    PubMed Central

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

    2014-01-01

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

  20. Diffusion tensor imaging in the corpus callosum in children after moderate to severe traumatic brain injury.

    PubMed

    Wilde, Elisabeth A; Chu, Zili; Bigler, Erin D; Hunter, Jill V; Fearing, Michael A; Hanten, Gerri; Newsome, Mary R; Scheibel, Randall S; Li, Xiaoqi; Levin, Harvey S

    2006-10-01

    Diffusion tensor imaging (DTI) is a recent imaging technique that assesses the microstructure of the cerebral white matter (WM) based on anisotropic diffusion (i.e., water molecules move faster in parallel to nerve fibers than perpendicular to them). Fractional anisotropy (FA), which ranges from 0 to 1.0, increases with myelination of WM tracts and is sensitive to diffuse axonal injury (DAI) in adults with traumatic brain injury (TBI). However, previous DTI studies of pediatric TBI were case reports without detailed outcome measures. Using mean FA derived from DTI fiber tractography, we compared DTI findings of the corpus callosum for 16 children who were at least 1 year (mean 3.1 years) post-severe TBI and individually matched, uninjured children. Interexaminer and intraexaminer reliability in measuring FA was satisfactory. FA was significantly lower in the patients for the genu, body, and splenium of the corpus callosum. Higher FA was related to increased cognitive processing speed and faster interference resolution on an inhibition task. In the TBI patients, higher FA was related to better functional outcome as measured by the dichotomized Glasgow Outcome Scale (GOS). FA also increased as a function of the area of specific regions of the corpus callosum such as the genu and splenium, and FA in the splenium was reduced with greater volume of lesions in this region. DTI may be useful in identifying biomarkers related to DAI and outcome of TBI in children. PMID:17020479

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

    PubMed Central

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

    2014-01-01

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

  2. Reduced anterior corpus callosum white matter integrity is related to increased impulsivity and reduced discriminability in cocaine-dependent subjects: diffusion tensor imaging.

    PubMed

    Moeller, Frederick Gerard; Hasan, Khader M; Steinberg, Joel L; Kramer, Larry A; Dougherty, Donald M; Santos, Rafael M; Valdes, Ignacio; Swann, Alan C; Barratt, Ernest S; Narayana, Ponnada A

    2005-03-01

    Brain imaging studies find evidence of prefrontal cortical dysfunction in cocaine-dependent subjects. Similarly, cocaine-dependent subjects have problems with behaviors related to executive function and impulsivity. Since prefrontal cortical axonal tracts cross between hemispheres in the corpus callosum, it is possible that white matter integrity in the corpus callosum could also be diminished in cocaine-dependent subjects. The purpose of this study was to compare corpus callosum white matter integrity as measured by the fractional anisotropy (FA) on diffusion tensor imaging (DTI) between 18 cocaine-dependent subjects and 18 healthy controls. The Barratt Impulsiveness Scale (BIS-11) and a continuous performance test: the Immediate and Delayed Memory Task (IMT/DMT) were also collected. Results of the DTI showed significantly reduced FA in the genu and rostral body of the anterior corpus callosum in cocaine-dependent subjects compared to controls. Cocaine-dependent subjects also had significantly higher BIS-11 scores, greater impulsive (commission) errors, and reduced ability to discriminate target from catch stimuli (discriminability) on the IMT/DMT. Within cocaine dependent subjects there was a significant negative correlation between FA in the anterior corpus callosum and behavioral laboratory measured impulsivity, and there was a positive correlation between FA and discriminability. The finding that reduced integrity of anterior corpus callosum white matter in cocaine users is related to impaired impulse control and reduced ability to discriminate between target and catch stimuli is consistent with prior theories regarding frontal cortical involvement in impaired inhibitory control in cocaine-dependent subjects. PMID:15637640

  3. Fractional anisotropy of the fornix and hippocampal atrophy in Alzheimer's disease.

    PubMed

    Kantarci, Kejal

    2014-01-01

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

  4. Fractional anisotropy in white matter tracts of very-low-birth-weight infants

    PubMed Central

    Lequin, Maarten; van Pul, Carola; Buijs, Jan; Conneman, Nikk; van Goudoever, Johannes; Govaert, Paul

    2007-01-01

    Background Advances in neonatal intensive care have not yet reduced the high incidence of neurodevelopmental disability among very-low-birth-weight (VLBW) infants. As neurological deficits are related to white-matter injury, early detection is important. Diffusion tensor imaging (DTI) could be an excellent tool for assessment of white-matter injury. Objective To provide DTI fractional anisotropy (FA) reference values for white-matter tracts of VLBW infants for clinical use. Materials and methods We retrospectively analysed DTI images of 28 VLBW infants (26–32 weeks gestational age) without evidence of white-matter abnormalities on conventional MRI sequences, and normal developmental outcome (assessed at age 1–3 years). For DTI an echoplanar sequence with diffusion gradient (b = 1,000 s/mm2) applied in 25 non-collinear directions was used. We measured FA and apparent diffusion coefficient (ADC) of different white-matter tracts in the first 4 days of life. Results A statistically significant correlation was found between gestational age and FA of the posterior limb of the internal capsule in VLBW infants (r = 0.495, P<0.01). Conclusion Values of FA and ADC were measured in white-matter tracts of VLBW infants. FA of the pyramidal tracts measured in the first few days after birth is related to gestational age. PMID:17909782

  5. Diffusion tensor imaging and myelin composition analysis reveal abnormal myelination in corpus callosum of canine mucopolysaccharidosis I.

    PubMed

    Provenzale, James M; Nestrasil, Igor; Chen, Steven; Kan, Shih-Hsin; Le, Steven Q; Jens, Jacqueline K; Snella, Elizabeth M; Vondrak, Kristen N; Yee, Jennifer K; Vite, Charles H; Elashoff, David; Duan, Lewei; Wang, Raymond Y; Ellinwood, N Matthew; Guzman, Miguel A; Shapiro, Elsa G; Dickson, Patricia I

    2015-11-01

    Children with mucopolysaccharidosis I (MPS I) develop hyperintense white matter foci on T2-weighted brain magnetic resonance (MR) imaging that are associated clinically with cognitive impairment. We report here a diffusion tensor imaging (DTI) and tissue evaluation of white matter in a canine model of MPS I. We found that two DTI parameters, fractional anisotropy (a measure of white matter integrity) and radial diffusivity (which reflects degree of myelination) were abnormal in the corpus callosum of MPS I dogs compared to carrier controls. Tissue studies of the corpus callosum showed reduced expression of myelin-related genes and an abnormal composition of myelin in MPS I dogs. We treated MPS I dogs with recombinant alpha-L-iduronidase, which is the enzyme that is deficient in MPS I disease. The recombinant alpha-L-iduronidase was administered by intrathecal injection into the cisterna magna. Treated dogs showed partial correction of corpus callosum myelination. Our findings suggest that abnormal myelination occurs in the canine MPS I brain, that it may underlie clinically-relevant brain imaging findings in human MPS I patients, and that it may respond to treatment. PMID:26222335

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

    PubMed Central

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

    2013-01-01

    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

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

    PubMed

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

    2014-09-01

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

  8. Correlation of Apparent Diffusion Coefficient and Fractional Anisotropy Values in the Developing Infant Brain

    PubMed Central

    Provenzale, James M.; Isaacson, Jared; Chen, Steven; Stinnett, Sandra; Liu, Chunlei

    2013-01-01

    OBJECTIVE The purpose of our study was to correlate decrease in apparent diffusion coefficient (ADC) and increase in fractional anisotropy (FA) in various white matter (WM) regions using diffusion tenor imaging (DTI) within the first year of life. MATERIALS AND METHODS We performed DTI on 53 infants and measured FA and ADC within 10 WM regions important in brain development. For each region, we calculated the slope of ADC as a function of FA, the correlation coefficient (r) and correlation of determination (r2). We performed a group analysis of r values and r2 values for six WM regions primarily composed of crossing fibers and four regions primarily having parallel fibers. Upon finding that a strong correlation of FA with age existed, we adjusted for age and calculated partial correlation coefficients. RESULTS Slopes of FA versus ADC ranged from −1.00711 to −1.67592 (p < 0.05); r values ranged from −0.81 to −0.50 and r2 values from 0.25 to 0.66. The four greatest r2 values were within WM regions having large numbers of crossing fibers and the three lowest r2 values were in regions having predominantly parallel fibers. After adjusting for age, slopes ranged from −1.08095 to 0.09612 (p < 0.05 in five cases); partial correlation coefficients ranged from −0.49 to 0.03 and r2 values from 0.31 to 0.79. The highest partial correlation coefficients were then relatively equally distributed between the two types of WM regions. CONCLUSION In various regions, FA and ADC evolved with differing degrees of correlation. We found a strong influence of age on the relationship between FA and ADC. PMID:21098179

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

    PubMed Central

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

    2011-01-01

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

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

    PubMed Central

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

    2013-01-01

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

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

    PubMed Central

    2014-01-01

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

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

    PubMed Central

    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

    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

  13. Influence of the packing fraction and host matrix on the magnetoelastic anisotropy in Ni nanowire composite arrays

    NASA Astrophysics Data System (ADS)

    Piraux, Luc; Hamoir, Gal; Encinas, Armando; De La Torre Medina, Joaquin; Abreu Araujo, Flavio

    2013-09-01

    The influence of the packing fraction on thermally induced magnetoelastic effects has been studied in Ni nanowires embedded in polycarbonate, poly(vinylidene difluoride), and alumina nanoporous membranes of different porosities for temperatures between 77 K and 345 K. For nanowires embedded in polymer membranes, the contrasting shift in the ferromagnetic resonance frequency when the temperature is either above or below ambient temperature is consistent with the occurrence of uniaxial magnetoelastic anisotropy effects due to the large thermal expansion coefficient mismatch between the metal nanowires and the membrane. A model which considers the influence of the nanowires packing fraction and the membrane material on the magnetoelastic effects, arising from the matrix-assisted deformation process, is proposed. The model is able to successfully explain the experimentally observed effects for the Ni nanowire arrays embedded in the different porous membranes and their variation with the packing fraction. The possibility to modulate the magnetic anisotropy of such nanocomposites by an appropriate choice of membrane material, packing fraction, and sample temperature is of considerable importance to achieve magnetically tunable devices.

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

    PubMed Central

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

    2014-01-01

    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

  15. Conduct disorder in females is associated with reduced corpus callosum structural integrity independent of comorbid disorders and exposure to maltreatment.

    PubMed

    Lindner, P; Savic, I; Sitnikov, R; Budhiraja, M; Liu, Y; Jokinen, J; Tiihonen, J; Hodgins, S

    2016-01-01

    The behavioral phenotype and genotype of conduct disorder (CD) differ in males and females. Abnormalities of white matter integrity have been reported among males with CD and antisocial personality disorder (ASPD). Little is known about white matter integrity in females with CD. The present study aimed to determine whether abnormalities of white matter are present among young women who presented CD before the age of 15, and whether abnormalities are independent of the multiple comorbid disorders and experiences of maltreatment characterizing females with CD that may each in themselves be associated with alterations of the white matter. Three groups of women, aged on average 24 years, were scanned using diffusion tensor imaging and compared: 28 with prior CD, three of whom presented ASPD; a clinical comparison (CC) group of 15 women with no history of CD but with similar proportions who presented alcohol dependence, drug dependence, anxiety disorders, depression disorders and physical and sexual abuse as the CD group; and 24 healthy women. Whole-brain, tract-based spatial statistics were computed to investigate differences in fractional anisotropy, axial diffusivity and radial diffusivity. Compared with healthy women, women with prior CD showed widespread reductions in axial diffusivity primarily in frontotemporal regions. After statistically adjusting for comorbid disorders and maltreatment, group differences in the corpus callosum body and genu (including forceps minor) remained significant. Compared with the CC group, women with CD showed reduced fractional anisotropy in the body and genu of the corpus callosum. No differences were detected between the CD and healthy women in the uncinate fasciculus. PMID:26784968

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

    PubMed

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

    2013-01-16

    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

  17. Conditional Tat protein brain expression in the GT-tg bigenic mouse induces cerebral fractional anisotropy abnormalities

    PubMed Central

    Carey, Amanda N.; Liu, Xiaoxu; Mintzopoulos, Dionyssios; Paris, Jason J.; McLaughlin, Jay P.; Kaufman, Marc J.

    2015-01-01

    Cerebral white matter changes including tissue water diffusion abnormalities detected with diffusion tensor magnetic resonance imaging (DTI) are commonly found in humans with Human Immunodeficiency Virus (HIV) infection, as well as in animal models of the disorder. The severities of some of these abnormalities have been reported to correlate with measures of disease progression or severity, or with the degree of cognitive dysfunction. Accordingly, DTI may be a useful translational biomarker. HIV-Tat protein appears to be an important factor in the viral pathogenesis of HIV-associated neurotoxicity. We previously reported cerebral gray matter density reductions in the GT-tg bigenic mouse treated with doxycycline (Dox) to conditionally induce Tat protein expression. Presently, we administered intraperitoneal (i.p.) Dox (100 mg/kg/day) for 7 days to GT-tg mice to determine whether induction of conditional Tat expression led to the development of cerebral DTI abnormalities. Perfused and fixed brains from eight GT-tg mice administered Dox and eight control mice administered saline i.p. were extracted and underwent DTI scans on a 9.4 Tesla scanner. A whole brain analysis detected fractional anisotropy (FA) reductions in several areas including insular and endopiriform regions, as well as within the dorsal striatum. These findings suggest that exposure to Tat protein is sufficient to induce FA abnormalities, and further support the use of the GT-tg mouse to model some effects of HIV. PMID:25619988

  18. Individual differences in regional prefrontal gray matter morphometry and fractional anisotropy are associated with different constructs of executive function

    PubMed Central

    Smolker, H. R.; Reineberg, A. E.; Orr, J. M.; Banich, M. T.

    2015-01-01

    Although the relationship between structural differences within the prefrontal cortex (PFC) and executive function (EF) has been widely explored in cognitively impaired populations, little is known about this relationship in healthy young adults. Using optimized voxel-based morphometry (VBM), surface-based morphometry (SBM), and fractional anisotropy (FA) we determined the association between regional PFC grey matter (GM) morphometry and white matter tract diffusivity with performance on tasks that tap different aspects of EF as drawn from Miyake et al.’s three-factor model of EF. Reductions in both GM volume (VBM) and cortical folding (SBM) in the ventromedial PFC (vmPFC), ventrolateral PFC (vlPFC), and dorsolateral PFC (dlPFC) predicted better common EF, shifting-specific, and updating-specific performance, respectively. Despite capturing different components of GM morphometry, voxel- and surface-based findings were highly related, exhibiting regionally overlapping relationships with EF. Increased white matter FA in fiber tracts that connect the vmPFC and vlPFC with posterior regions of the brain also predicted better common EF and shifting-specific performance, respectively. These results suggest that the neural mechanisms supporting distinct aspects of EF may differentially rely on distinct regions of the PFC, and at least in healthy young adults, are influenced by regional morphometry of the PFC and the FA of major white matter tracts that connect the PFC with posterior cortical and subcortical regions. PMID:24562372

  19. Longitudinal assessment of fractional anisotropy alterations caused by simian immunodeficiency virus infection: a preliminary diffusion tensor imaging study.

    PubMed

    Tang, Zhenchao; Dong, Enqing; Liu, Jiaojiao; Liu, Zhenyu; Wei, Wenjuan; Wang, Bo; Li, Hongjun; Tian, Jie

    2016-04-01

    Previous diffusion tensor imaging (DTI) studies found that human immunodeficiency virus (HIV) infection led to white matter (WM) microstructure degeneration. Most of the DTI studies were cross-sectional and thus merely investigated only one specific point in the disease. In order to systematically study the WM impairments caused by HIV infection, more longitudinal studies are needed. However, longitudinal studies on HIV patients are very difficult to conduct. To address this question, we employed the simian immunodeficiency virus (SIV)-infected rhesus monkeys model to carry out a longitudinal DTI study. We aimed to longitudinally access the WM abnormalities of SIV-infected rhesus monkeys by studying the fractional anisotropy (FA) alterations with Tract Based Spatial Statistic (TBSS) analysis. Four rhesus monkeys inoculated intravenously with SIVmac239 were utilized in the study. DTI scans and peripheral blood CD4(+) and CD8(+) T cell counts were acquired prior to virus inoculation (as the baseline) and in the 12th and 24th week postvirus inoculation. Significant FA alterations were found in the two areas of the inferotemporal regions (iTE), respectively located in the ventral subregion of posterior iTE (iTEpv) and the dorsal subregion of iTE (iTEpd). The decreased FA values in iTEpd were found significantly negatively correlated with the elevated peripheral blood CD4(+)/CD8(+) ratios. It might suggest that WM in iTEpd was still impaired even though the immune dysfunction alleviated temporally. PMID:26438160

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

    PubMed Central

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

    2014-01-01

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

  1. Correlation Between Fractional Anisotropy and Motor Outcomes in One-Year-Old Infants with Periventricular Brain Injury

    PubMed Central

    Madhavan, Sangeetha; Campbell, Suzann K.; Campise-Luther, Rose; Gaebler-Spira, Deborah; Zawacki, Laura; Clark, April; Boynewicz, Kara; Kale, Dipti; Bulanda, Michelle; Yu, Jinsheng; Sui, Yi; Zhou, Xiaohong Joe

    2014-01-01

    Purpose To determine whether motor outcomes of an exercise intervention beginning at 2 months corrected age (CA) in children with periventricular brain injury (PBI) are correlated with fractional anisotropy (FA) measures derived from diffusion tensor imaging (DTI) at 12 months CA. Materials and Methods DTI was performed in eight infants with PBI who were randomly assigned to kicking and treadmill stepping exercise or a no-training condition. Development was assessed using the Alberta Infant Motor Scale (AIMS) and the Gross Motor Function Classification System (GMFCS). FA values were derived from regions of interest (ROI) in the middle third of the posterior limb of the internal capsule (PLIC) and the posterior thalamic radiation (PTR). Results Significant correlations were observed between motor development and FA measures. For PLIC, the correlation coefficients were 0.82 between FA and AIMS, and -0.92 between FA and GMFCS, while for PTR the corresponding correlation coefficients were 0.73 and -0.80, respectively. Conclusion Results of this study suggest that quantitative evaluation of white matter tracts using DTI at 12 months CA may be useful for assessment of brain plasticity in children. PMID:24136687

  2. Corpus Callosum Volume and Neurocognition in Autism

    ERIC Educational Resources Information Center

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

    2009-01-01

    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

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

    PubMed

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

    2015-05-01

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

  4. Corpus Callosum MR Image Classification

    NASA Astrophysics Data System (ADS)

    Elsayed, A.; Coenen, F.; Jiang, C.; Garca-Fiana, M.; Sluming, V.

    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.

  5. Structure, Integrity, and Function of the Hypoplastic Corpus Callosum in Spina Bifida Myelomeningocele

    PubMed Central

    Crawley, Jennifer T.; Hasan, Khader; Hannay, H. Julia; Dennis, Maureen; Jockell, Catherine

    2014-01-01

    Abstract Although there are many studies of people with complete or partial hypogenesis of the corpus callosum (CC), little is understood about the hypoplastic CC in which all structures are present but thinned. Spina bifida myelomeningocele (SBM) is a model organism for such studies because many have either a hypogenetic or hypoplastic CC. We used diffusion tensor tractography (DTT) to evaluate the hypoplastic CC in SBM and its relation to interhemispheric functions and intelligence quotient (IQ). Participants were individuals with SBM and an intact or hypoplastic CC (n=28), who were compared to a typically developing comparison group (n=32). Total and regional DTT volume and integrity measures (fractional anisotropy, axial diffusivity, and radial diffusivity) of the CC were related to measures of intelligence (IQ), bimanual motor functioning, and dichotic auditory performance. As predicted, DTT showed variations in volume and integrity that were maximized in the entire CC and the posterior CC. IQ correlated with entire CC volume, anterior and posterior regional CC volumes, and also with measures of integrity. Bimanual motor functioning correlated with the anterior and posterior volumes of the CC but not with any integrity measures. Axial diffusivity in the posterior CC was negatively correlated with right ear dichotic listening performance. The hypoplastic CC is not macrostructurally or microstructurally intact in SBM, even when it appears radiologically intact. Both volume and integrity of the posterior regions were related to reductions in IQ and to interhemispheric processing. These findings may transfer to other disorders characterized by a hypoplastic CC. PMID:25014561

  6. Watershed-based segmentation of the corpus callosum in diffusion MRI

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

    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.

  7. A comparative diffusion tensor imaging study of corpus callosum subregion integrity in bipolar disorder and schizophrenia.

    PubMed

    Li, Jian; Kale Edmiston, Elliot; Chen, Kaiyuan; Tang, Yanqing; Ouyang, Xuan; Jiang, Yifeng; Fan, Guoguang; Ren, Ling; Liu, Jie; Zhou, Yifang; Jiang, Wenyan; Liu, Zhening; Xu, Ke; Wang, Fei

    2014-01-30

    Structural magnetic resonance imaging (MRI) studies have provided evidence for corpus callosum (CC) white matter abnormalities in bipolar disorder (BD) and schizophrenia (SZ). These findings include alterations in shape, volume, white matter intensity and structural integrity compared to healthy control populations. Although CC alterations are implicated in both SZ and BD, no study of which we are aware has investigated callosal subregion differences between these two patient populations. We used diffusion tensor imaging (DTI) to assess CC integrity in patients with BD (n=16), SZ (n=19) and healthy controls (HC) (n=24). Fractional anisotropy (FA) of CC subregions was measured using region of interest (ROI) analysis and compared in the three groups. Significant group differences of FA values were revealed in five CC subregions, including the anterior genu, middle genu, posterior genu, posterior body and anterior splenium. FA values of the same subregions were significantly reduced in patients with SZ compared with HC. FA values were also significantly reduced in patients with BD compared to the HC group in the same subregions, excepting the middle genu. No significant difference was found between patient groups in any region. Most of the alterations in CC subregions were present in both the BD and SZ groups. These results imply an overlap in potential pathology, possibly relating to risk factors common to both disorders. The one region that differed between patient groups, the middle genu area, may serve as an illness marker and is perhaps involved in the different cognitive impairments observed in BD and SZ. PMID:24300086

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed Central

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

    2015-01-01

    Background Cardiac diffusion tensor imaging (cDTI) by cardiovascular magnetic resonance has the potential to assess microstructural changes through measures of fractional anisotropy (FA) and mean diffusivity (MD). However, normal variation in regional and transmural FA and MD is not well described. Methods Twenty normal subjects were scanned using an optimised cDTI sequence at 3T in systole. FA and MD were quantified in 3 transmural layers and 4 regional myocardial walls. Results FA was higher in the mesocardium (0.46 0.04) than the endocardium (0.40 0.04, p?0.001) and epicardium (0.39 0.04, p?0.001). On regional analysis, the FA in the septum was greater than the lateral wall (0.44 0.03 vs 0.40 0.05 p = 0.04). There was a transmural gradient in MD increasing towards the endocardium (epicardium 0.87 0.07 vs endocardium 0.91 0.0810-3 mm2/s, p = 0.04). With the lateral wall (0.87 0.0810-3 mm2/s) as the reference, the MD was higher in the anterior wall (0.92 0.0810-3 mm2/s, p = 0.016) and septum (0.92 0.0710-3 mm2/s, p = 0.028). Transmurally the signal to noise ratio (SNR) was greatest in the mesocardium (14.5 2.5 vs endocardium 13.1 2.2, p<0.001; vs epicardium 12.0 2.4, p<0.001) and regionally in the septum (16.0 3.4 vs lateral wall 11.5 1.5, p<0.001). Transmural analysis suggested a relative reduction in the rate of change in helical angle (HA) within the mesocardium. Conclusions In vivo FA and MD measurements in normal human heart are heterogeneous, varying significantly transmurally and regionally. Contributors to this heterogeneity are many, complex and interactive, but include SNR, variations in cardiac microstructure, partial volume effects and strain. These data indicate that the potential clinical use of FA and MD would require measurement standardisation by myocardial region and layer, unless pathological changes substantially exceed the normal variation identified. PMID:26177211

  10. Puberty in the Corpus Callosum

    PubMed Central

    Chavarria, Mary C.; Snchez, Francisco J.; Chou, Yi-Yu; Thompson, Paul M.; Luders, Eileen

    2014-01-01

    Adolescence is an important period for brain development. White matter growth is influenced by sex hormones such as testosterone, and the corpus callosumthe largest white matter structure in the human brainmay change structurally during the hormone-laden period of adolescence. Little is known about pubertys relationship to structural brain development, even though pubertal stage may better predict cognitive and behavioral maturity than chronological age. We therefore aimed to establish the presence and direction of pubertal effects on callosal anatomy. For this purpose, we applied advanced surface-based mesh-modeling to map correlations between callosal thickness and pubertal stage in a large and well-matched sample of 124 children and adolescents (62 female and 62 male) aged 518 years from a normative database. When linking callosal anatomy to pubertal status, only positive correlations reached statistical significance, indicating that callosal growth advances with puberty. In tests of differences in callosal anatomy at different stages of puberty, callosal growth was concentrated in different locations depending on the pubertal stage. Changing levels of circulating sex hormones during different phases of puberty likely contributed to the observed effects, and further research is clearly needed. Direct quantification of sex hormone levels and regional fiber connectivityideally using fiber tractographywill reveal whether hormones are the main drivers of callosal change during puberty. These callosal findings may lead to hypotheses regarding cortical changes during puberty, which may promote or result from changes in interhemispheric connectivity. PMID:24468104

  11. Altered White Matter Microstructure in the Corpus Callosum in Huntington’s Disease: implications for cortical “disconnection”

    PubMed Central

    Diana Rosas, H; Lee, Stephanie Y; Bender, Alexander; Zaleta, Alexandra K; Vange, Mark; Yu, Peng; Fischl, Bruce; Pappu, Vasanth; Cha, Jang-Ho; Salat, David H; Hersch, Steven M.

    2011-01-01

    The corpus callosum (CC) is the major conduit for information transfer between the cerebral hemispheres and plays an integral role in relaying sensory, motor and cognitive information between homologous cortical regions. The majority of fibers that make up the CC arise from large pyramidal neurons in layers III and V, which project contra-laterally. These neurons degenerate in Huntington’s disease (HD) in a topographically and temporally selective way. Since any focus of cortical degeneration could be expected to secondarily de-afferent homologous regions of cortex, we hypothesized that regionally selective cortical degeneration would be reflected in regionally selective degeneration of the CC. We used conventional T1-weighted, diffusion tensor imaging (DTI), and a modified corpus callosum segmentation scheme to examine the CC in healthy controls, huntingtin gene-carriers and symptomatic HD subjects. We measured mid-sagittal callosal cross-sectional thickness and several DTI parameters, including fractional anisotropy (FA), which reflects the degree of white matter organization, radial diffusivity, a suggested index of myelin integrity, and axial diffusivity, a suggested index of axonal damage of the CC. We found a topologically selective pattern of alterations in these measures in pre-manifest subjects that were more extensive in early symptomatic HD subjects and that correlated with performance on distinct cognitive measures, suggesting an important role of for disrupted inter-hemispheric transfer in the clinical symptoms of HD. Our findings provide evidence for early degeneration of commissural pyramidal neurons in the neocortex, loss of cortico-cortical connectivity, and functional compromise of associative cortical processing. PMID:19850138

  12. Facial emotion recognition in agenesis of the corpus callosum

    PubMed Central

    2014-01-01

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

  13. Corpus Callosum Area in Children and Adults with Autism

    ERIC Educational Resources Information Center

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

    2013-01-01

    Despite repeated findings of abnormal corpus callosum structure in autism, the developmental trajectories of corpus callosum growth in the disorder have not yet been reported. In this study, we examined corpus callosum size from a developmental perspective across a 30-year age range in a large cross-sectional sample of individuals with autism

  14. Corpus Callosum Area in Children and Adults with Autism

    ERIC Educational Resources Information Center

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

    2013-01-01

    Despite repeated findings of abnormal corpus callosum structure in autism, the developmental trajectories of corpus callosum growth in the disorder have not yet been reported. In this study, we examined corpus callosum size from a developmental perspective across a 30-year age range in a large cross-sectional sample of individuals with autism…

  15. A DTI study on the corpus callosum of treatment-naïve boys with 'pure' Tourette syndrome.

    PubMed

    Wolff, Nicole; Luehr, Ina; Sender, Jennifer; Ehrlich, Stefan; Schmidt-Samoa, Carsten; Dechent, Peter; Roessner, Veit

    2016-01-30

    Disturbances in the corpus callosum (CC) indicating altered interhemispheric connectivity have been associated with Tourette syndrome (TS). The objective of the present study was to refine knowledge about interhemispheric connectivity in TS by analyzing four different diffusion tensor imaging (DTI) parameters in a very homogeneous group of treatment-naïve boys with pure TS in comparison to male healthy controls (HC). Fractional anisotropy (FA), radial diffusivity (RD), axial diffusivity (AD) and mean diffusivity (MD) of five CC-segments were assessed from DTI of 26 treatment-naïve boys with pure TS and 24 HC. We observed no group differences in both FA and RD. However, we found a significant effect for AD and a trend for MD, being both reduced in boys with TS in comparison to HC. Moreover, a negative correlation between AD and the Yale Global Tic Severity Scale total score was observed. Reduced AD of the CC in treatment-naïve boys with pure TS in comparison to HC may indicate that significant alterations in white matter microstructure of the CC contribute to tic symptomatology per se and seem not to be related to confounders such as consequences of long-term medication, tic performance or tic suppression. PMID:26747579

  16. Age at First Exposure to Football Is Associated with Altered Corpus Callosum White Matter Microstructure in Former Professional Football Players.

    PubMed

    Stamm, Julie M; Koerte, Inga K; Muehlmann, Marc; Pasternak, Ofer; Bourlas, Alexandra P; Baugh, Christine M; Giwerc, Michelle Y; Zhu, Anni; Coleman, Michael J; Bouix, Sylvain; Fritts, Nathan G; Martin, Brett M; Chaisson, Christine; McClean, Michael D; Lin, Alexander P; Cantu, Robert C; Tripodis, Yorghos; Stern, Robert A; Shenton, Martha E

    2015-11-15

    Youth football players may incur hundreds of repetitive head impacts (RHI) in one season. Our recent research suggests that exposure to RHI during a critical neurodevelopmental period prior to age 12 may lead to greater later-life mood, behavioral, and cognitive impairments. Here, we examine the relationship between age of first exposure (AFE) to RHI through tackle football and later-life corpus callosum (CC) microstructure using magnetic resonance diffusion tensor imaging (DTI). Forty retired National Football League (NFL) players, ages 40-65, were matched by age and divided into two groups based on their AFE to tackle football: before age 12 or at age 12 or older. Participants underwent DTI on a 3 Tesla Siemens (TIM-Verio) magnet. The whole CC and five subregions were defined and seeded using deterministic tractography. Dependent measures were fractional anisotropy (FA), trace, axial diffusivity, and radial diffusivity. Results showed that former NFL players in the AFE <12 group had significantly lower FA in anterior three CC regions and higher radial diffusivity in the most anterior CC region than those in the AFE ≥12 group. This is the first study to find a relationship between AFE to RHI and later-life CC microstructure. These results suggest that incurring RHI during critical periods of CC development may disrupt neurodevelopmental processes, including myelination, resulting in altered CC microstructure. PMID:26200068

  17. Mild Cognitive Impairment is Associated With White Matter Integrity Changes in Late-Myelinating Regions Within the Corpus Callosum.

    PubMed

    Stricker, Nikki H; Salat, David H; Kuhn, Taylor P; Foley, Jessica M; Price, Jenessa S; Westlye, Lars T; Esterman, Michael S; McGlinchey, Regina E; Milberg, William P; Leritz, Elizabeth C

    2016-02-01

    Degenerative brain changes in Alzheimer's disease may occur in reverse order of normal brain development based on the retrogenesis model. This study tested whether evidence of reverse myelination was observed in mild cognitive impairment (MCI) using a data-driven analytic approach based on life span developmental data. Whole-brain high-resolution diffusion tensor imaging scans were obtained for 31 patients with MCI and 79 demographically matched healthy older adults. Comparisons across corpus callosum (CC) regions of interest (ROIs) showed decreased fractional anisotropy (FA) in the body but not in the genu or splenium; early-, middle-, and late-myelinating ROIs restricted to the CC revealed decreased FA in late- but not early- or middle-myelinating ROIs. Voxelwise group differences revealed areas of lower FA in MCI, but whole-brain differences were equally distributed across early-, middle-, and late-myelinating regions. Overall, results within the CC support the retrogenesis model, although caution is needed when generalizing these results beyond the CC. PMID:25904759

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

    PubMed

    Epstein, Katherine A; Kumra, Sanjiv

    2015-04-30

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

  19. Infarction of the Corpus Callosum: A Retrospective Clinical Investigation

    PubMed Central

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

    2015-01-01

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

  20. Multi-channel registration of fractional anisotropy and T1-weighted images in the presence of atrophy: application to multiple sclerosis

    PubMed Central

    Roura, Eloy; Schneider, Torben; Modat, Marc; Daga, Pankaj; Muhlert, Nils; Chard, Declan; Ourselin, Sebastien; Lladó, Xavier; Wheeler-Kingshott, Claudia Gandini

    2015-01-01

    Summary Co-registration of structural T1-weighted (T1w) scans and diffusion tensor imaging (DTI)-derived fractional anisotropy (FA) maps to a common space is of particular interest in neuroimaging, as T1w scans can be used for brain segmentation while DTI can provide microstructural tissue information. While the effect of lesions on registration has been tackled and solutions are available, the issue of atrophy is still open to discussion. Multi-channel (MC) registration algorithms have the advantage of maintaining anatomical correspondence between different contrast images after registration to any target space. In this work, we test the performance of an MC registration approach applied to T1w and FA data using simulated brain atrophy images. Experimental results are compared with a standard single-channel registration approach. Both qualitative and quantitative evaluations are presented, showing that the MC approach provides better alignment with the target while maintaining better T1w and FA co-alignment. PMID:26727703

  1. Evolution of Apparent Diffusion Coefficient and Fractional Anisotropy in the Cerebrum of Asphyxiated Newborns Treated with Hypothermia over the First Month of Life.

    PubMed

    Kwan, Saskia; Boudes, Elodie; Benseler, Anouk; Gilbert, Guillaume; Saint-Martin, Christine; Shevell, Michael; Wintermark, Pia

    2015-01-01

    The objective of this study was to assess the evolution of diffusion-weighted imaging (DWI) and diffusion-tensor imaging (DTI) over the first month of life in asphyxiated newborns treated with hypothermia and to compare it with that of healthy newborns. Asphyxiated newborns treated with hypothermia were enrolled prospectively; and the presence and extent of brain injury were scored on each MRI. Apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values were measured in the basal ganglia, in the white matter and in the cortical grey matter. Sixty-one asphyxiated newborns treated with hypothermia had a total of 126 ADC and FA maps. Asphyxiated newborns developing brain injury eventually had significantly decreased ADC values on days 2-3 of life and decreased FA values around day 10 and 1 month of life compared with those not developing brain injury. Despite hypothermia treatment, asphyxiated newborns may develop brain injury that still can be detected with advanced neuroimaging techniques such as DWI and DTI as early as days 2-3 of life. A study of ADC and FA values over time may aid in the understanding of how brain injury develops in these newborns despite hypothermia treatment. PMID:26229690

  2. Adding insult to injury: childhood and adolescent risk factors for psychosis predict lower fractional anisotropy in the superior longitudinal fasciculus in healthy adults

    PubMed Central

    DeRosse, Pamela; Ikuta, Toshikazu; Peters, Bart D.; Karlsgodt, Katherine H.; Szeszko, Philip R.; Malhotra, Anil K.

    2014-01-01

    Although epidemiological studies provide strong support for demographic and environmental risk factors in psychotic disorders, few data examine how these risk factors relate to the putative aberrant neurodevelopment associated with illness. The present study examined how the accumulation of risk factors including low IQ, low parental socioeconomic status, history of adolescent cannabis use and childhood trauma, and high levels of subclinical psychotic-like experiences contributed to aberrant neurodevelopmental outcomes in 112 otherwise healthy adults recruited from the community. Participants were studied with diffusion tensor imaging, and voxel-wise statistical analysis of fractional anisotropy (FA) using tract-based spatial statistics was used to examine the relation between cumulative risk (CR) for psychosis and white matter (WM) integrity across the whole brain. Analyses revealed that higher CR was significantly associated with lower FA in a cluster in the left superior longitudinal fasciculus. These results suggest that risk factors previously associated with psychotic disorders are associated with WM integrity even in otherwise healthy adults and may provide insight into how previously identified risk factors contribute to the structural brain abnormalities associated with psychotic illness. Prospective longitudinal studies examining the effect of risk factors on the developmental trajectory of brain WM are warranted. PMID:25277095

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

    PubMed Central

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

    2010-01-01

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

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

    PubMed Central

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

    2015-01-01

    Motivated by the frontal- and white matter (WM) retrogenesis hypotheses and the assumptions that fronto-striatal circuits are especially vulnerable in normal aging, the goal of the present study was to identify fiber bundles connecting subcortical nuclei and frontal areas and obtain site-specific information about age related fractional anisotropy (FA) changes. Multimodal magnetic resonance image acquisitions [3D T1-weighted and diffusion weighted imaging (DWI)] were obtained from healthy older adults (N = 76, range 49–80 years at inclusion) at two time points, 3 years apart. A subset of the participants (N = 24) was included at a third time-point. In addition to the frontal-subcortical fibers, the anterior callosal fiber (ACF) and the corticospinal tract (CST) was investigated by its mean FA together with tract parameterization analysis. Our results demonstrated fronto-striatal structural connectivity decline (reduced FA) in normal aging with substantial inter-individual differences. The tract parameterization analysis showed that the along tract FA profiles were characterized by piece-wise differential changes along their extension rather than being uniformly affected. To the best of our knowledge, this is the first longitudinal study detecting age-related changes in frontal-subcortical WM connections in normal aging. PMID:26029102

  5. Educational Implications for Agenesis of the Corpus Callosum.

    ERIC Educational Resources Information Center

    Ritter, Shirley A.

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

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

    ERIC Educational Resources Information Center

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

    2006-01-01

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

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

    ERIC Educational Resources Information Center

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

    2006-01-01

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

  8. The corpus callosum: white matter or terra incognita

    PubMed Central

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

    2011-01-01

    The corpus callosum is the largest white matter structure in the brain, consisting of 200250 million contralateral axonal projections and the major commissural pathway connecting the hemispheres of the human brain. The pathology of the corpus callosum includes a wide variety of entities that arise from different causes such as congenital, inflammatory, tumoural, degenerative, infectious, metabolic, traumatic, vascular and toxic agents. The corpus callosum, or a specific part of it, can be affected selectively. Numerous pathologies of the corpus callosum are encountered during CT and MRI. The aim of this study is to facilitate a better understanding and thus treatment of the pathological entities of the corpus callosum by categorising them according to their causes and their manifestations in MR and CT imaging. Familiarity with its anatomy and pathology is important to the radiologist in order to recognise its disease at an early stage and help the clinician establish the optimal therapeutic approach. PMID:21172964

  9. Corpus callosum involvement and postoperative outcomes of patients with gliomas.

    PubMed

    Chen, Ko-Ting; Wu, Tai-Wei Erich; Chuang, Chi-Cheng; Hsu, Yung-Hsin; Hsu, Peng-Wei; Huang, Yin-Cheng; Lin, Tzu-Kang; Chang, Chen-Nen; Lee, Shih-Tseng; Wu, Chieh-Tsai; Tseng, Chen-Kan; Wang, Chun-Chieh; Pai, Ping-Ching; Wei, Kuo-Chen; Chen, Pin-Yuan

    2015-09-01

    Corpus callosum involvement is associated with poorer survival in high grade glioma (HGG), but the prognostic value in low grade glioma (LGG) is unclear. To determine the prognostic impact of corpus callosum involvement on progression free survival (PFS) and overall survival (OS) in HGG and LGG, the records of 233 glioma patients treated from 2008 to 2011 were retrospectively reviewed. Preoperative magnetic resonance (MR) images were used to identify corpus callosum involvement. Age, sex, preoperative Karnofsky performance scale, postoperative Eastern Cooperative Oncology Group (ECOG) score and extent of resection (EOR) were evaluated with respect to PFS and OS. The incidence of corpus callosum involvement was similar among HGG (14%) and LGG (14.5%). Univariate analysis revealed that PFS and OS were significantly shorter in both WHO grade II and grade IV glioma with corpus callosum involvement (both, p<0.05). Multivariate analysis showed that grade II glioma with corpus callosum involvement have shorter PFS (p=0.03), while EOR, instead of corpus callosum involvement (p=0.16), was an independent factor associated with PFS in grade IV glioma (p<0.05). Corpus callosum involvement was no longer significantly associated with OS after adjusting age, gender, EOR, preoperative and postoperative performance status (p=0.16, 0.17 and 0.56 in grade II, III and IV gliomas, respectively). Corpus callosum involvement happened in both LGG and HGG, and is associated with lower EOR and higher postoperative ECOG score both in LGG and HGG. Corpus callosum involvement tends to be an independent prognostic factor for PFS in LGG, but not for OS in LGG or in HGG. PMID:26033546

  10. Multi-site study of additive genetic effects on fractional anisotropy of cerebral white matter: comparing meta and mega analytical approaches for data pooling

    PubMed Central

    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.; Hong, L. Elliot; Landman, Bennett A.; Lemaitre, Hervé; Lopez, Lorna; 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 JC; Deary, Ian J.; Hulshoff Pol, Hilleke E.; Williamson, Douglas E.; Blangero, John; van ’t Ent, Dennis; Thompson, Paul M.; Glahn, David C.

    2014-01-01

    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

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

    PubMed

    Kochunov, Peter; Jahanshad, Neda; Sprooten, Emma; Nichols, Thomas E; Mandl, Ren C; Almasy, Laura; Booth, Tom; Brouwer, Rachel M; Curran, Joanne E; de Zubicaray, Greig I; Dimitrova, Rali; Duggirala, Ravi; Fox, Peter T; Hong, L Elliot; Landman, Bennett A; Lemaitre, Herv; 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, Ren 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

    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

  12. Utility of fractional anisotropy imaging analyzed by statistical parametric mapping for detecting minute brain lesions in chronic-stage patients who had mild or moderate traumatic brain injury.

    PubMed

    Asano, Yoshitaka; Shinoda, Jun; Okumura, Ayumi; Aki, Tatsuki; Takenaka, Shunsuke; Miwa, Kazuhiro; Yamada, Mikito; Ito, Takeshi; Yokoyama, Kazutoshi

    2012-01-01

    Diffusion tensor imaging (DTI) has recently evolved as valuable technique to investigate diffuse axonal injury (DAI). This study examined whether fractional anisotropy (FA) images analyzed by statistical parametric mapping (FA-SPM images) are superior to T(2)*-weighted gradient recalled echo (T2*GRE) images or fluid-attenuated inversion recovery (FLAIR) images for detecting minute lesions in traumatic brain injury (TBI) patients. DTI was performed in 25 patients with cognitive impairments in the chronic stage after mild or moderate TBI. The FA maps obtained from the DTI were individually compared with those from age-matched healthy control subjects using voxel-based analysis and FA-SPM images (p < 0.001). Abnormal low-intensity areas on T2*GRE images (T2* lesions) were found in 10 patients (40.0%), abnormal high-intensity areas on FLAIR images in 4 patients (16.0%), and areas with significantly decreased FA on FA-SPM image in 16 patients (64.0%). Nine of 10 patients with T2* lesions had FA-SPM lesions. FA-SPM lesions topographically included most T2* lesions in the white matter and the deep brain structures, but did not include T2* lesions in the cortex/near-cortex or lesions containing substantial hemosiderin regardless of location. All 4 patients with abnormal areas on FLAIR images had FA-SPM lesions. FA-SPM imaging is useful for detecting minute lesions because of DAI in the white matter and the deep brain structures, which may not be visualized on T2*GRE or FLAIR images, and may allow the detection of minute brain lesions in patients with post-traumatic cognitive impairment. PMID:22278025

  13. Automatic recognition of corpus callosum from sagittal brain MR images

    NASA Astrophysics Data System (ADS)

    Lee, Chulhee; Unser, Michael A.; Ketter, Terence A.

    1995-08-01

    We propose a new method to find the corpus callosum from sagittal brain MR images automatically. First, we calculate the statistical characteristics of the corpus callosum and obtain shape information. The recognition algorithm consists of two stages: extracting regions satisfying the statistical characteristics (gray level distribtuions) of the corpus callosum, and finding a region matching the shape information. An innovative feature of the algorithm is that we adaptively relax the statistical requirement until we find a region matching the shape information. In order to match the shape information, we propose a new directed window region growing algorithm instead of using conventional contour matching. Experiments show promising results.

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

    PubMed

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

    2013-05-01

    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

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

    PubMed

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

    2012-01-01

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

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

    PubMed Central

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

    2014-01-01

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

  17. Relationship between Stereoscopic Vision, Visual Perception, and Microstructure Changes of Corpus Callosum and Occipital White Matter in the 4-Year-Old Very Low Birth Weight Children

    PubMed Central

    Kwinta, Przemko; Herman-Sucharska, Izabela; Le?niak, Anna; Klimek, Ma?gorzata; Karcz, Paulina; Durlak, Wojciech; Nitecka, Magdalena; Dutkowska, Gra?yna; Kubatko-Zieli?ska, Anna; Romanowska-Dixon, Bo?ena; Pietrzyk, Jacek Jzef

    2015-01-01

    Aim. To assess the relationship between stereoscopic vision, visual perception, and microstructure of the corpus callosum (CC) and occipital white matter, 61 children born with a mean birth weight of 1024?g (SD 270?g) were subjected to detailed ophthalmologic evaluation, Developmental Test of Visual Perception (DTVP-3), and diffusion tensor imaging (DTI) at the age of 4. Results. Abnormal stereoscopic vision was detected in 16 children. Children with abnormal stereoscopic vision had smaller CC (CC length: 53 6?mm versus 61 4?mm; p < 0.01; estimated CC area: 314 106?mm2 versus 446 79?mm2; p < 0.01) and lower fractional anisotropy (FA) values in CC (FA value of rostrum/genu: 0.7 0.09 versus 0.79 0.07; p < 0.01; FA value of CC body: 0.74 0.13 versus 0.82 0.09; p = 0.03). We found a significant correlation between DTVP-3 scores, CC size, and FA values in rostrum and body. This correlation was unrelated to retinopathy of prematurity. Conclusions. Visual perceptive dysfunction in ex-preterm children without major sequelae of prematurity depends on more subtle changes in the brain microstructure, including CC. Role of interhemispheric connections in visual perception might be more complex than previously anticipated. PMID:26451381

  18. Depressive symptoms related to low fractional anisotropy of white matter underlying the right ventral anterior cingulate in older adults with atherosclerotic vascular disease

    PubMed Central

    Bijanki, Kelly R.; Matsui, Joy T.; Mayberg, Helen S.; Magnotta, Vincent A.; Arndt, Stephan; Johnson, Hans J.; Nopoulos, Peg; Paradiso, Sergio; McCormick, Laurie M.; Fiedorowicz, Jess G.; Epping, Eric A.; Moser, David J.

    2015-01-01

    We sought to characterize the relationship between integrity of the white matter underlying the ventral anterior cingulate (vAC) and depressive symptoms in older adults with atherosclerotic vascular disease (AVD), a condition associated with preferential degeneration of the white matter. The vAC was defined as including white matter underlying ventral Brodmann Area 24 and Brodmann Area 25, corresponding with the “subcallosal” and “subgenual” cingulate respectively. This region of interest was chosen based on the preponderance of evidence that the white matter in the region plays a critical role in the manifestation of depressive symptoms. Participants had current unequivocal diagnoses of AVD and were between 55 and 90 years-old. Fractional anisotropy (FA) was used as an index of white matter integrity and organization. Whole-brain mean diffusivity (MD) was used as an index of global white matter lesion burden. Depressive symptoms were measured using the Symptom Checklist-90-Revised (SCL-90-R) Depression Scale. Depressive symptoms were significantly related to low FA in the right vAC (r = -0.356, df = 30, p = 0.045) but not the left vAC (r = 0.024, df = 30, p = 0.896) after controlling for total brain MD (a statistical control for global white matter lesion burden). Further, depressive symptoms were significantly related to low FA in the right vAC (r = -0.361, df = 31, p = 0.039), but not the left vAC (r = 0.259, df = 31, p = 0.145) when controlled for the contralateral vAC FA. The correlation coefficients for this follow-up analysis were found to be significantly different between left and right vAC (Z = 2.310, p = 0.021). Poor white matter health in the vAC may be a biological mechanism for depressive symptoms in older adults with vascular disease. Further studies may corroborate that the right vAC plays a unique role in depressive symptom manifestation in cases where the white matter is preferentially affected, as is the case in AVD. This could lead to future targeting of the region for somatic antidepressant treatment, as well as the development of a precise approach for patients with white matter damage, which could produce significant improvement in quality of life, medical morbidity, and mortality. PMID:26236221

  19. Evaluation of normal appearing spinal cord by diffusion tensor imaging, fiber tracking, fractional anisotropy, and apparent diffusion coefficient measurement in 13 dogs

    PubMed Central

    2013-01-01

    Background Functional magnetic resonance (fMR) imaging offers plenty of new opportunities in the diagnosis of central nervous system diseases. Diffusion tensor imaging (DTI) is a technique sensitive to the random motion of water providing information about tissue architecture. We applied DTI to normal appearing spinal cords of 13 dogs of different breeds and body weights in a 3.0 T magnetic resonance (MR) scanner. The aim was to study fiber tracking (FT) patterns by tractography and the variations of the fractional anisotropy (FA) and the apparent diffusion coefficient (ADC) observed in the spinal cords of dogs with different sizes and at different locations (cervical and thoracolumbar). For that reason we added a DTI sequence to the standard clinical MR protocol. The values of FA and ADC were calculated by means of three regions of interest defined on the cervical or the thoracolumbar spinal cord (ROI 1, 2, and 3). Results The shape of the spinal cord fiber tracts was well illustrated following tractography and the exiting nerve roots could be differentiated from the spinal cord fiber tracts. Routine MR scanning times were extended for 8 to 12min, depending on the size of the field of view (FOV), the slice thickness, and the size of the interslice gaps. In small breed dogs (?25kg body weight) the traceable fiber length was about 5 vertebral bodies which took 10 to 12min scanning time. FA and ADC values showed mean values of 0.447 (FA), and 0.560??10-3mm2/s (ADC), respectively without any differences detected with regard to different dog sizes and spinal cord 45 segments examined. Conclusion FT is suitable for the graphical depiction of the canine spinal cord and the exiting nerve roots. The FA and ADC values offer an objective measure for evaluation of the spinal cord fiber integrity in dogs. PMID:23618404

  20. Corpus Callosum Area in Children and Adults with Autism

    PubMed Central

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

    2012-01-01

    Despite repeated findings of abnormal corpus callosum structure in autism, the developmental trajectories of corpus callosum growth in the disorder have not yet been reported. In this study, we examined corpus callosum size from a developmental perspective across a 30-year age range in a large cross-sectional sample of individuals with autism compared to a typically developing sample. Midsagittal corpus callosum area and the 7 Witelson subregions were examined in 68 males with autism (mean age 14.1 years; range 336 years) and 47 males with typical development (mean age 15.3 years; range 429 years). Controlling for total brain volume, increased variability in total corpus callosum area was found in autism. In autism, increased midsagittal areas were associated with reduced severity of autism behaviors, higher intelligence, and faster speed of processing (p=0.003, p=0.011, p=0.013, respectively). A trend toward group differences in isthmus development was found (p=0.029, uncorrected). These results suggest that individuals with autism benefit functionally from increased corpus callosum area. Our cross-sectional examination also shows potential maturational abnormalities in autism, a finding that should be examined further with longitudinal datasets. PMID:23130086

  1. Shape modeling of the corpus callosum.

    PubMed

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

    2010-01-01

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

  2. Prosody meets syntax: the role of the corpus callosum.

    PubMed

    Sammler, Daniela; Kotz, Sonja A; Eckstein, Korinna; Ott, Derek V M; Friederici, Angela D

    2010-09-01

    Contemporary neural models of auditory language comprehension proposed that the two hemispheres are differently specialized in the processing of segmental and suprasegmental features of language. While segmental processing of syntactic and lexical semantic information is predominantly assigned to the left hemisphere, the right hemisphere is thought to have a primacy for the processing of suprasegmental prosodic information such as accentuation and boundary marking. A dynamic interplay between the hemispheres is assumed to allow for the timely coordination of both information types. The present event-related potential study investigated whether the anterior and/or posterior portion of the corpus callosum provide the crucial brain basis for the online interaction of syntactic and prosodic information. Patients with lesions in the anterior two-thirds of the corpus callosum connecting orbital and frontal structures, or the posterior third of the corpus callosum connecting temporal, parietal and occipital areas, as well as matched healthy controls, were tested in a paradigm that crossed syntactic and prosodic manipulations. An anterior negativity elicited by a mismatch between syntactically predicted phrase structure and prosodic intonation was analysed as a marker for syntax-prosody interaction. Healthy controls and patients with lesions in the anterior corpus callosum showed this anterior negativity demonstrating an intact interplay between syntax and prosody. No such effect was found in patients with lesions in the posterior corpus callosum, although they exhibited intact, prosody-independent syntactic processing comparable with healthy controls and patients with lesions in the anterior corpus callosum. These data support the interplay between the speech processing streams in the left and right hemispheres via the posterior portion of the corpus callosum, building the brain basis for the coordination and integration of local syntactic and prosodic features during auditory speech comprehension. PMID:20802205

  3. Morphometric Changes of the Corpus Callosum in Congenital Blindness

    PubMed Central

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

    2014-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    PubMed

    Barazany, Daniel; Basser, Peter J; Assaf, Yaniv

    2009-05-01

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

  6. Quantitative analysis of mouse corpus callosum from electron microscopy images.

    PubMed

    West, Kathryn L; Kelm, Nathaniel D; Carson, Robert P; Does, Mark D

    2015-12-01

    This article provides morphometric analysis of 72 electron microscopy images from control (n=4) and hypomyelinated (n=2) mouse corpus callosum. Measures of axon diameter and g-ratio were tabulated across all brains from two regions of the corpus callosum and a non-linear relationship between axon diameter and g-ratio was observed. These data are related to the accompanying research article comparing multiple methods of measuring g-ratio entitled 'A revised model for estimating g-ratio from MRI' (West et al., NeuroImage, 2015). PMID:26504893

  7. Primary human chorionic gonadotropin secreting germinoma of the corpus callosum

    PubMed Central

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

    2013-01-01

    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

  8. Quantitative analysis of the myelin g-ratio from electron microscopy images of the macaque corpus callosum

    PubMed Central

    Stikov, Nikola; Campbell, Jennifer S.W.; Stroh, Thomas; Lavele, Mariette; Frey, Stephen; Novek, Jennifer; Nuara, Stephen; Ho, Ming-Kai; Bedell, Barry J.; Dougherty, Robert F.; Leppert, Ilana R.; Boudreau, Mathieu; Narayanan, Sridar; Duval, Tanguy; Cohen-Adad, Julien; Picard, Paul-Alexandre; Gasecka, Alicja; Ct, Daniel; Pike, G. Bruce

    2015-01-01

    We provide a detailed morphometric analysis of eight transmission electron micrographs (TEMs) obtained from the corpus callosum of one cynomolgus macaque. The raw TEM images are included in the article, along with the distributions of the axon caliber and the myelin g-ratio in each image. The distributions are analyzed to determine the relationship between axon caliber and g-ratio, and compared against the aggregate metrics (myelin volume fraction, fiber volume fraction, and the aggregate g-ratio), as defined in the accompanying research article entitled In vivo histology of the myelin g-ratio with magnetic resonance imaging (Stikov et al., NeuroImage, 2015). PMID:26217818

  9. Corpus callosum in sexually dimorphic and nondimorphic primates.

    PubMed

    Holloway, R L; Heilbroner, P

    1992-03-01

    The midsagittal area and other morphological measures were taken on the corpus callosum of four different species of primate: Macaca mulatta, M. fascicularis, Callithrix jacchus, and Saguinus oedipus. The first two species are strongly dimorphic, whereas the New World forms show little dimorphism with regard to overall body size, canines, and brain weight. Neither total corpus callosal area (TOTALCC), or other parts of the corpus callosum (CC) showed any significant sexual dimorphism in any of the primate species sampled. Only in M. mulatta did a sexual dimorphism appear to be significant. In males of this species, the dorsoventral width of the splenium was larger than in females. In addition, the anterior commissure (ANTCOMM) evinced no sexual dimorphism in the different species. Brain weight was significantly dimorphic in only M. mulatta, and when ratio data were used to correct for brain weight, no significant differences were found in the corpus callosum. This is in contrast to Homo sapiens, where the relative size of the CC has been reported to be larger in females, and particularly so in the posterior, or splenial portion of the CC. Correlation coefficients were calculated for the various variables within each species. In general, most of the callosal measures are significantly inter-correlated, although the exact pattern varies for each species. Thus, unlike Homo sapiens, or pongids such as Gorilla and Pan, neither New nor Old World monkeys show any striking evidence for sexual dimorphism in the corpus callosum. PMID:1562061

  10. Autism Traits in Individuals with Agenesis of the Corpus Callosum

    ERIC Educational Resources Information Center

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

    2013-01-01

    Autism spectrum disorders (ASD) have numerous etiologies, including structural brain malformations such as agenesis of the corpus callosum (AgCC). We sought to directly measure the occurrence of autism traits in a cohort of individuals with AgCC and to investigate the neural underpinnings of this association. We screened a large AgCC cohort (n =

  11. Commissurotomy of the Corpus Callosum and the Remedial Reader.

    ERIC Educational Resources Information Center

    Albert, Elaine

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

  12. Corpus Callosum Anatomy in Chronically Treated and Stimulant Naive ADHD

    ERIC Educational Resources Information Center

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

    2010-01-01

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

  13. Perspectives on Dichotic Listening and the Corpus Callosum

    ERIC Educational Resources Information Center

    Musiek, Frank E.; Weihing, Jeffrey

    2011-01-01

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

  14. Parenting, corpus callosum, and executive function in preschool children.

    PubMed

    Kok, Rianne; Lucassen, Nicole; Bakermans-Kranenburg, Marian J; van IJzendoorn, Marinus H; Ghassabian, Akhgar; Roza, Sabine J; Govaert, Paul; Jaddoe, Vincent W; Hofman, Albert; Verhulst, Frank C; Tiemeier, Henning

    2014-01-01

    In this longitudinal population-based study (N?=?544), we investigated whether early parenting and corpus callosum length predict child executive function abilities at 4 years of age. The length of the corpus callosum in infancy was measured using postnatal cranial ultrasounds at 6 weeks of age. At 3 years, two aspects of parenting were observed: maternal sensitivity during a teaching task and maternal discipline style during a discipline task. Parents rated executive function problems at 4 years of age in five domains of inhibition, shifting, emotional control, working memory, and planning/organizing, using the Behavior Rating Inventory of Executive Function-Preschool Version. Maternal sensitivity predicted less executive function problems at preschool age. A significant interaction was found between corpus callosum length in infancy and maternal use of positive discipline to determine child inhibition problems: The association between a relatively shorter corpus callosum in infancy and child inhibition problems was reduced in children who experienced more positive discipline. Our results point to the buffering potential of positive parenting for children with biological vulnerability. PMID:24028215

  15. Corpus Callosum Differences Associated with Persistent Stuttering in Adults

    ERIC Educational Resources Information Center

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

    2011-01-01

    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

  16. Quantitative assessment of diffusional kurtosis anisotropy.

    PubMed

    Glenn, G Russell; Helpern, Joseph A; Tabesh, Ali; Jensen, Jens H

    2015-04-01

    Diffusional kurtosis imaging (DKI) measures the diffusion and kurtosis tensors to quantify restricted, non-Gaussian diffusion that occurs in biological tissue. By estimating the kurtosis tensor, DKI accounts for higher order diffusion dynamics, when compared with diffusion tensor imaging (DTI), and consequently can describe more complex diffusion profiles. Here, we compare several measures of diffusional anisotropy which incorporate information from the kurtosis tensor, including kurtosis fractional anisotropy (KFA) and generalized fractional anisotropy (GFA), with the diffusion tensor-derived fractional anisotropy (FA). KFA and GFA demonstrate a net enhancement relative to FA when multiple white matter fiber bundle orientations are present in both simulated and human data. In addition, KFA shows net enhancement in deep brain structures, such as the thalamus and the lenticular nucleus, where FA indicates low anisotropy. Thus, KFA and GFA provide additional information relative to FA with regard to diffusional anisotropy, and may be particularly advantageous for the assessment of diffusion in complex tissue environments. PMID:25728763

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

    PubMed Central

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

    2011-01-01

    Background Atrophy of the corpus callosum (CC) is a documented consequence of moderate-to-severe traumatic brain injury (TBI), which has been expressed as volume loss using quantitative magnetic resonance imaging (MRI). Other advanced imaging modalities such as diffusion tensor imaging (DTI) have also detected white matter microstructural alteration following TBI in the CC. The manner and degree to which macrostructural changes such as volume and microstructural changes develop over time following pediatric TBI, and their relation to a measure of processing speed is the focus of this longitudinal investigation. As such, DTI and volumetric changes in the CC in participants with TBI and a comparison group at approximately 3 and 18 months after injury as well as their relation to processing speed were determined. Methods Forty-eight children and adolescents aged 717 years who sustained either complicated mild or moderate-to-severe TBI (n = 23) or orthopedic injury (OI; n = 25) were studied. The participants underwent brain MRI and were administered the Eriksen flanker task at both time points. Results At 3 months after injury, there were significant group differences in DTI metrics in the total CC and its subregions (genu/anterior, body/central and splenium/posterior), with the TBI group demonstrating significantly lower fractional anisotropy (FA) and a higher apparent diffusion coefficient (ADC) in comparison to the OI group. These group differences were also present at 18 months after injury in all CC subregions, with lower FA and a higher ADC in the TBI group. In terms of longitudinal changes in DTI, despite the group difference in mean FA, both groups generally demonstrated a modest increase in FA over time though this increase was only significant in the splenium/posterior subregion. Interestingly, the TBI group also generally demonstrated ADC increases from 3 to 18 months though the OI group demonstrated ADC decreases over time. Volumetrically, the group differences at 3 months were marginal for the midanterior and body/central subregions and total CC. However, by 18 months, the TBI group demonstrated a significantly decreased volume in all subregions except the splenium/posterior area relative to the OI group. Unlike the OI group, which showed a significant volume increase in subregions of the CC over time, the TBI group demonstrated a significant and consistent volume decrease. Performance on a measure of processing speed did not differentiate the groups at either visit, and only the OI group showed significantly improved performance over time. Processing speed was related to FA in the splenium/posterior and total CC only in the TBI group on both occasions, with a stronger relation at 18 months. Conclusion In response to TBI, macrostructural volume loss in the CC occurred over time; yet, at the microstructural level, DTI demonstrated both indicators of continued maturation and development even in the damaged CC, as well as evidence of potential degenerative change. Unlike volumetrics, which likely reflects the degree of overall neuronal loss and axonal damage, DTI may reflect some aspects of postinjury maturation and adaptation in white matter following TBI. Multimodality imaging studies may be important to further understand the long-term consequences of pediatric TBI. PMID:20948181

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

    PubMed Central

    Liang, Fanrong; Huang, Wenhua

    2015-01-01

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

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

    PubMed Central

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

    2014-01-01

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

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

    PubMed

    Paul, Lynn K; Corsello, Christina; Kennedy, Daniel P; Adolphs, Ralph

    2014-06-01

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

  1. Freezing of gait associated with a corpus callosum lesion.

    PubMed

    Dale, Marian L; Mancini, Martina; Curtze, Carolin; Horak, Fay B; Fling, Brett W

    2016-01-01

    Freezing of gait (FoG) is a debilitating feature of Parkinson's disease and other parkinsonian disorders. This case demonstrates a variant of freezing of gait in a non-parkinsonian patient with a lesion of the anterior corpus callosum. The freezing improved with increased upper extremity sensory input, suggesting that compensatory circuits for use of somatosensory inputs from the arms to postural and locomotor centers were intact. PMID:26835154

  2. Agenesis of the corpus callosum and the establishment of handedness.

    PubMed

    Sacco, Silvia; Moutard, Marie-Laure; Fagard, Jacqueline

    2006-09-01

    The goal of this study was to check whether an isolated agenesis of the corpus callosum, detected in utero with ultrasound recording, would impair the early development of unimanual and bimanual handedness. Twelve infants with isolated agenesis of the corpus callosum, either total (TACC) or partial (PACC) were tested for handedness at the end of their first year, and were compared to infants with typical development (TD), matched for age and sex. A majority of infants showed right-handedness at the unimanual grasping tasks, with no significant difference between the TD and ACC groups. When the object was presented to the left, the TACC infants were more likely to grasp the object with their right hand (with or without the left hand) than both the TD and the PACC infants who used mostly the ipsilateral left hand. The only significant difference between TD and ACC infants concerned bimanual coordination, as less ACC infants (especially TACC) succeeded at the bimanual task, compared with TD infants. In addition, the strategy of the former tended to be less right-handed than that of the latter. Our results confirm the role of the CC in bimanual coordination, indicating that the early emergence of bimanual coordination and, if confirmed, bimanual handedness, are likely to be delayed in the absence of corpus callosum, especially if agenesis is total. They do not support the idea that the CC is necessary for the early onset of handedness. PMID:16886185

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

    ERIC Educational Resources Information Center

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

    2008-01-01

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

  4. Difference between smokers and non-smokers in the corpus callosum volume.

    PubMed

    Choi, Mi-Hyun; Lee, Su-Jeong; Yang, Jae-Woong; Kim, Ji-Hye; Choi, Jin-Seung; Park, Jang-Yeon; Jun, Jae-Hoon; Tack, Gye-Rae; Lee, Beob-Yi; Kim, Hyun-Jun; Chung, Soon-Cheol

    2010-11-12

    The purpose of this study was to analyze the effects of smoking on corpus callosum volume. In addition, the relationships between smoking duration, smoking frequency, and corpus callosum volume were analyzed. Magnetic resonance brain images were acquired for 58 normal Korean men (30 smokers (age 32.8214.12 years) and 28 non-smokers (age 35.4913.11 years)). The corpus callosum volume was measured using Brain Voyager 2000S/W and was normalized by intracranical volume, which was calculated using cerebral sizes. The corpus callosum volume for smokers was significantly smaller than that for non-smokers. Also, there was a negative correlation between corpus callosum volume and smoking duration. The change of white matter volume (e.g., corpus callosum) might be a primary factor for characterizing the effects of smoking. PMID:20804817

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

    PubMed

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

    2015-02-01

    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

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

    ERIC Educational Resources Information Center

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

    2008-01-01

    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

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

    PubMed

    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

    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?

  8. Automated segmentation of the corpus callosum in midsagittal brain magnetic resonance images

    NASA Astrophysics Data System (ADS)

    Lee, Chulhee; Huh, Shin; Ketter, Terence A.; Unser, Michael A.

    2000-04-01

    We propose a new algorithm to find the corpus callosum automatically from midsagittal brain MR (magnetic resonance) images using the statistical characteristics and shape information of the corpus callosum. We first extract regions satisfying the statistical characteristics (gray level distributions) of the corpus callosum that have relatively high intensity values. Then we try to find a region matching the shape information of the corpus callosum. In order to match the shape information, we propose a new directed window region growing algorithm instead of using conventional contour matching. An innovative feature of the algorithm is that we adaptively relax the statistical requirement until we find a region matching the shape information. After the initial segmentation, a directed border path pruning algorithm is proposed in order to remove some undesired artifacts, especially on the top of the corpus callosum. The proposed algorithm was applied to over 120 images and provided promising results.

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

    PubMed Central

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

    2015-01-01

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

  10. A computerized approach for morphological analysis of the corpus callosum

    SciTech Connect

    Davatzikos, C.; Vaillant, M.; Letovsky, S.; Bryan, R.N.; Prince, J.L.; Resnick, S.M.

    1996-01-01

    A new technique for analyzing the morphology of the corpus callosum is presented, and it is applied to a group of elderly subjects. The proposed approach normalizes subject data into the Talairach space using an elastic deformation transformation. The properties of this transformation are used as a quantitative description of the callosal shape with respect to the Talairach atlas, which is treated as a standard. In particular, a deformation function measures the enlargement/shrinkage associated with this elastic deformation. Intersubject comparisons are made by comparing deformation functions. This technique was applied to eight male and eight female subjects. Based on the average deformation functions of each group, the posterior region of the female corpus callosum was found to be larger than its corresponding region in the males. The average callosal shape of each group was also found, demonstrating visually the callosal shape differences between the two groups in this sample. The proposed methodology utilizes the full resolution of the data, rather than relying on global descriptions such as area measurements. The application of this methodology to an elderly group indicated sex-related differences in the callosal shape and size. 29 refs., 16 figs.

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

    SciTech Connect

    Qiu Deqiang; Kwong, Dora; Chan, Godfrey; Leung, Lucullus; Khong, P.-L.

    2007-11-01

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

  12. Axon position within the corpus callosum determines contralateral cortical projection.

    PubMed

    Zhou, Jing; Wen, Yunqing; She, Liang; Sui, Ya-Nan; Liu, Lu; Richards, Linda J; Poo, Mu-Ming

    2013-07-16

    How developing axons in the corpus callosum (CC) achieve their homotopic projection to the contralateral cortex remains unclear. We found that axonal position within the CC plays a critical role in this projection. Labeling of nearby callosal axons in mice showed that callosal axons were segregated in an orderly fashion, with those from more medial cerebral cortex located more dorsally and subsequently projecting to more medial contralateral cortical regions. The normal axonal order within the CC was grossly disturbed when semaphorin3A/neuropilin-1 signaling was disrupted. However, the order in which axons were positioned within the CC still determined their contralateral projection, causing a severe disruption of the homotopic contralateral projection that persisted at postnatal day 30, when the normal developmental refinement of contralateral projections is completed in wild-type (WT) mice. Thus, the orderly positioning of axons within the CC is a primary determinant of how homotopic interhemispheric projections form in the contralateral cortex. PMID:23812756

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

    PubMed Central

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

    2013-01-01

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

  14. Segmentation of corpus callosum using diffusion tensor imaging: validation in patients with glioblastoma

    PubMed Central

    2012-01-01

    Background This paper presents a three-dimensional (3D) method for segmenting corpus callosum in normal subjects and brain cancer patients with glioblastoma. Methods Nineteen patients with histologically confirmed treatment nave glioblastoma and eleven normal control subjects underwent DTI on a 3T scanner. Based on the information inherent in diffusion tensors, a similarity measure was proposed and used in the proposed algorithm. In this algorithm, diffusion pattern of corpus callosum was used as prior information. Subsequently, corpus callosum was automatically divided into Witelson subdivisions. We simulated the potential rotation of corpus callosum under tumor pressure and studied the reproducibility of the proposed segmentation method in such cases. Results Dice coefficients, estimated to compare automatic and manual segmentation results for Witelson subdivisions, ranged from 94% to 98% for control subjects and from 81% to 95% for tumor patients, illustrating closeness of automatic and manual segmentations. Studying the effect of corpus callosum rotation by different Euler angles showed that although segmentation results were more sensitive to azimuth and elevation than skew, rotations caused by brain tumors do not have major effects on the segmentation results. Conclusions The proposed method and similarity measure segment corpus callosum by propagating a hyper-surface inside the structure (resulting in high sensitivity), without penetrating into neighboring fiber bundles (resulting in high specificity). PMID:22591335

  15. Counseling in fetal medicine: agenesis of the corpus callosum.

    PubMed

    Santo, S; D'Antonio, F; Homfray, T; Rich, P; Pilu, G; Bhide, A; Thilaganathan, B; Papageorghiou, A T

    2012-11-01

    In this Review, we aim to provide up-to-date and evidence-based answers to common questions regarding the diagnosis and prognosis of prenatally detected agenesis of the corpus callosum (ACC). A systematic literature search was performed to identify all reports of ACC and reference lists of articles were identified. ACC involves partial or complete absence of the main commissural pathway that connects the two cerebral hemispheres, and can be isolated (with no other abnormalities) or complex (coexisting with other abnormalities). It is a rare finding and the prevalence is difficult to estimate because of selection bias in reported series. The corpus callosum (CC) can be assessed on ultrasound by direct visualization, but indirect features, such as ventriculomegaly, absence of the cavum septi pellucidi or widening of interhemispheric fissure, are often the reason for detection in a screening population. Careful imaging in a center with a high level of expertise is required to make a full assessment and to exclude coexisting abnormalities, which occur in about 46% of fetuses. When available, magnetic resonance imaging appears to be an important adjunct as it allows direct visualization. It can reduce false-positive rates on ultrasound and can confirm ACC, it can assess whether this is complete or partial and it can help in detecting coexisting brain abnormalities not seen on ultrasound. The overall rate of chromosomal abnormality in fetuses with ACC is 18%, but this high rate includes both isolated and complex ACC; more recent studies suggest that chromosomal abnormalities are rare in isolated cases. Nevertheless, postnatal follow-up studies suggest that about 15% of cases thought to be isolated prenatally were found to have associated abnormalities after birth. Neurodevelopmental outcome in isolated ACC was recently reported in a systematic review and suggested normal outcome in about 65-75% of cases. Findings need to be considered in light of the several limitations of existing studies, in terms of study design, selection bias, varying definitions and imaging protocols, ascertainment bias and lack of control groups. These uncertainties mean that antenatal counseling is difficult and further large prospective studies are needed. PMID:23024003

  16. Automatic corpus callosum segmentation for standardized MR brain scanning

    NASA Astrophysics Data System (ADS)

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

    2007-03-01

    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.

  17. Genetic Contributions to the Midsagittal Area of the Corpus Callosum

    PubMed Central

    Phillips, Kimberley A.; Rogers, Jeffrey; Barrett, Elizabeth A.; Glahn, David C; Kochunov, Peter

    2012-01-01

    The degree to which genes and environment determine variations in brain structure and function is fundamentally important to understanding normal and disease-related patterns of neural organization and activity. We studied genetic contributions to the midsagittal area of the corpus callosum (CC) in pedigreed baboons (68 males/112 females) to replicate findings of high genetic contribution to area of the CC, reported in humans, and to determine if the heritability of the CC midsaggital area in adults was modulated by fetal development rate. Measurements of callosal area were obtained from high-resolution MRI scans. Heritability was estimated from pedigree based maximum likelihood estimation of genetic and non-genetic variance components as implemented in SOLAR. Our analyses revealed significant heritability for the total area of the CC and all of its subdivisions, with h2 = 0.46 for the total CC and h2 = .54, .37, .62, .56, and 0.29 for genu, anterior midbody, medial midbody, posterior midbody and splenium, respectively. Genetic correlation analysis demonstrated that the individual subdivisions shared between 41% and 98% of genetic variability. Combined with previous research reporting high heritability of other brain structures in baboons, these results reveal a consistent pattern of high heritability for brain morphometric measures in baboons. PMID:22856367

  18. Structural changes of the corpus callosum in tinnitus

    PubMed Central

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

    2012-01-01

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

  19. Decomposition of brain diffusion imaging data uncovers latent schizophrenias with distinct patterns of white matter anisotropy.

    PubMed

    Arnedo, Javier; Mamah, Daniel; Baranger, David A; Harms, Michael P; Barch, Deanna M; Svrakic, Dragan M; de Erausquin, Gabriel A; Cloninger, C Robert; Zwir, Igor

    2015-10-15

    Fractional anisotropy (FA) analysis of diffusion tensor-images (DTI) has yielded inconsistent abnormalities in schizophrenia (SZ). Inconsistencies may arise from averaging heterogeneous groups of patients. Here we investigate whether SZ is a heterogeneous group of disorders distinguished by distinct patterns of FA reductions. We developed a Generalized Factorization Method (GFM) to identify biclusters (i.e., subsets of subjects associated with a subset of particular characteristics, such as low FA in specific regions). GFM appropriately assembles a collection of unsupervised techniques with Non-negative Matrix Factorization to generate biclusters, rather than averaging across all subjects and all their characteristics. DTI tract-based spatial statistics images, which output is the locally maximal FA projected onto the group white matter skeleton, were analyzed in 47 SZ and 36 healthy subjects, identifying 8 biclusters. The mean FA of the voxels of each bicluster was significantly different from those of other SZ subjects or 36 healthy controls. The eight biclusters were organized into four more general patterns of low FA in specific regions: 1) genu of corpus callosum (GCC), 2) fornix (FX)+external capsule (EC), 3) splenium of CC (SCC)+retrolenticular limb (RLIC)+posterior limb (PLIC) of the internal capsule, and 4) anterior limb of the internal capsule. These patterns were significantly associated with particular clinical features: Pattern 1 (GCC) with bizarre behavior, pattern 2 (FX+EC) with prominent delusions, and pattern 3 (SCC+RLIC+PLIC) with negative symptoms including disorganized speech. The uncovered patterns suggest that SZ is a heterogeneous group of disorders that can be distinguished by different patterns of FA reductions associated with distinct clinical features. PMID:26151103

  20. Corpus Callosum Area and Brain Volume in Autism Spectrum Disorder: Quantitative Analysis of Structural MRI from the ABIDE Database

    ERIC Educational Resources Information Center

    Kucharsky Hiess, R.; Alter, R.; Sojoudi, S.; Ardekani, B. A.; Kuzniecky, R.; Pardoe, H. R.

    2015-01-01

    Reduced corpus callosum area and increased brain volume are two commonly reported findings in autism spectrum disorder (ASD). We investigated these two correlates in ASD and healthy controls using T1-weighted MRI scans from the Autism Brain Imaging Data Exchange (ABIDE). Automated methods were used to segment the corpus callosum and intracranial

  1. Corpus Callosum Area and Brain Volume in Autism Spectrum Disorder: Quantitative Analysis of Structural MRI from the ABIDE Database

    ERIC Educational Resources Information Center

    Kucharsky Hiess, R.; Alter, R.; Sojoudi, S.; Ardekani, B. A.; Kuzniecky, R.; Pardoe, H. R.

    2015-01-01

    Reduced corpus callosum area and increased brain volume are two commonly reported findings in autism spectrum disorder (ASD). We investigated these two correlates in ASD and healthy controls using T1-weighted MRI scans from the Autism Brain Imaging Data Exchange (ABIDE). Automated methods were used to segment the corpus callosum and intracranial…

  2. Velocity anisotropy in tidally limited star clusters

    NASA Astrophysics Data System (ADS)

    Tiongco, Maria A.; Vesperini, Enrico; Varri, Anna Lisa

    2016-02-01

    We explore the long-term evolution of the anisotropy in the velocity space of star clusters starting with different structural and kinematical properties. We show that the evolution of the radial anisotropy strength and its radial variation within a cluster contain distinct imprints of the cluster initial structural properties, dynamical history, and of the external tidal field of its host galaxy. Initially isotropic and compact clusters with small initial values of the ratio of the half-mass to Jacobi radius, rh/rJ, develop a strong radial anisotropy during their long-term dynamical evolution. Many clusters, if formed with small values of rh/rJ, should now be characterized by a significant radial anisotropy increasing with the distance from the cluster centre, reaching its maximum at a distance between 0.2 rJ and 0.4 rJ, and then becoming more isotropic or mildly tangentially anisotropic in the outermost regions. A similar radial variation of the anisotropy can also result from an early violent relaxation phase. In both cases, as a cluster continues its evolution and loses mass, the anisotropy eventually starts to decrease and the system evolves towards an isotropic velocity distribution. However, in order to completely erase the strong anisotropy developed by these compact systems during their evolution, they must be in the advanced stages of their evolution and lose a large fraction of their initial mass. Clusters that are initially isotropic and characterized by larger initial values of rh/rJ, on the other hand, never develop a significant radial anisotropy.

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

    ERIC Educational Resources Information Center

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

    2007-01-01

    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

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

    ERIC Educational Resources Information Center

    Witelson, Sandra F.

    1985-01-01

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

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

    ERIC Educational Resources Information Center

    Puente, Antonio, E.

    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

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

    ERIC Educational Resources Information Center

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

    2002-01-01

    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

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

    ERIC Educational Resources Information Center

    Hynd, George W.; And Others

    1991-01-01

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

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

    ERIC Educational Resources Information Center

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

    2011-01-01

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

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

    ERIC Educational Resources Information Center

    Morton, Bruce E.; Rafto, Stein E.

    2006-01-01

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

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

    ERIC Educational Resources Information Center

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

    2013-01-01

    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

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

    ERIC Educational Resources Information Center

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

    2011-01-01

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

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

    ERIC Educational Resources Information Center

    Morton, Bruce E.; Rafto, Stein E.

    2006-01-01

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

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

    ERIC Educational Resources Information Center

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

    2012-01-01

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

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

    ERIC Educational Resources Information Center

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

    2013-01-01

    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…

  15. Somatosensory receptive fields of fibres in the rostral corpus callosum of the cat.

    PubMed

    Guillemot, J P; Lepore, F; Prevost, L; Richer, L; Guilbert, M

    1988-02-16

    The corpus callosum is the principal neocortical commissure which transmits lateralized information between the hemispheres. The aim of the present experiment was to study the receptive field (RF) properties of somatosensory callosal fibres in the cat. The callosum was approached under direct visual control and axonic responses were recorded under N2O anaesthesia using tungsten microelectrodes or, mostly, glass micropipettes. RFs representing all the sensory submodalities tested (light touch, medium and deep pressure, joint movement and light pinches) were found to be present in the axons which travelled through the callosum. Rapidly adapting units were more common than slowly adapting ones. The axial and para-axial portions of the body accounted for about three-fifths of all RFs, followed by the head (about one-fifth), with the rest responding to stimulation of the extremities. The medial borders of most of the unilateral RFs situated on the trunk and, to a lesser degree, the head, extended to the mid-line. The results are interpreted in terms of the roles of the corpus callosum in mid-line fusion and interhemispheric transfer. PMID:3359233

  16. Quantitative Analysis of the Shape of the Corpus Callosum in Autistic Individuals

    PubMed Central

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

    2012-01-01

    Multiple studies suggest that the corpus callosum in patients with autism is reduced in size. This study attempts to elucidate the nature of this morphometric abnormality by analyzing the shape of this structure in 17 high-functioning patients with autism and an equal number of comparison participants matched for age, sex, IQ, and handedness. The corpus callosum was segmented from T1 weighted images acquired with a Siemens 1.5 T scanner. Transformed coordinates of the curvilinear axis were aggregated into a parametric map and compared across series to derive regions of statistical significance. Our results indicate that in subjects with autism reduction in size of the corpus callosum occurs over all of its subdivisions (genu, body, splenium) with a small area of overgrowth at its caudal pole. Since the commisural fibers that traverse the different anatomical compartments of the corpus callosum originate in disparate brain regions our results suggest the presence of widely distributed cortical abnormalities in people with autism. PMID:21363871

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

    ERIC Educational Resources Information Center

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

    2006-01-01

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

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

    PubMed Central

    Krupa, Katarzyna; Bekiesinska-Figatowska, Monika

    2013-01-01

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

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

    SciTech Connect

    Casaubon, L.K.; Melanson, M.; Marineau, C. |

    1996-01-01

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

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

    PubMed Central

    Casaubon, L. K.; Melanson, M.; Lopes-Cendes, I.; Marineau, C.; Andermann, E.; Andermann, F.; Weissenbach, J.; Prvost, C.; Bouchard, J. P.; Mathieu, J.; Rouleau, G. A.

    1996-01-01

    Peripheral neuropathy with or without agenesis of the corpus callosum (ACCPN) is a devastating neurodegenerative disorder that is transmitted as an autosomal recessive trait. Genealogical studies in a large number of affected French Canadian individuals suggest that ACCPN results from a single founder mutation. A genomewide search using 120 microsatellite DNA markers in 14 French Canadian families allowed the mapping of the ACCPN gene to a 5-cM region on chromosome 15q13-q15 that is flanked by markers D15S1040 and D15S118. A maximum two-point LOD score of 11.1 was obtained with the marker D15S971 at a recombination fraction of 0. Haplotype analysis and linkage disequilibrium support a founder effect. These findings are the first step in the identification of the gene responsible for ACCPN, which may shed some light on the numerous conditions associated with the progressive peripheral neuropathy or agenesis of the corpus callosum. PMID:8554065

  1. Cognitive impairments associated with corpus callosum infarction: a ten cases study

    PubMed Central

    Huang, Xiaoqin; Du, Xiangnan; Song, Haiqing; Zhang, Qian; Jia, Jianping; Xiao, Tianyi; Wu, Jian

    2015-01-01

    The aim of this study was to determine whether the cognitive impairment is associated with corpus callosum infarctions. Ten corpus callosum infarction patients were enrolled in this study. Their emotions, cognitive and language abilities, memory, comprehensive perception were assessed using the Chinese version of following measures: Mini Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA), World Health Organization-University of California-Los Angeles Auditory Verbal Learning Test (WHO-UCLA AVLT), Wechsler Adult Intelligence Scale (WAIS) Digit Span subtest and so on. The same measurements were performed on healthy control participants as contrast for analysis. Infarction most frequently occurred in the body and/or splenium of the corpus callosum. The scores of the most cognitive tests in the corpus callosum infarction patients were significantly worse than those of the control participants (P<0.05). Except for the naming ability, the patients showed significantly poorer performance at the overall level of MMSE than the controls did (P<0.05). Consistently, the results of MoCA suggested a significant reduction in visuospatial abilities of execution, orientation, attention, calculation, delayed memory, language, and repetition capabilities in the patients with respect to the control (P<0.05). In addition, the scores in the case group were significantly worse than those in the control group in the auditory word learning test, digital span and Rey complex figure test (P<0.05). Corpus callosum infarction can cause cognitive dysfunction, which poses obstacles to memory in the acute phase, accompanied by different degrees of decline in visuospatial abilities, attention and calculating abilities. PMID:26885171

  2. Hippocampal commissure defects in crosses of four inbred mouse strains with absentcorpus callosum

    PubMed Central

    Bohlen, M. O.; Bailoo, Jeremy D.; Jordan, R. L.; Wahlsten, D.

    2012-01-01

    It is known that four common inbred mouse strains show defects of the forebrain commissures. The BALB/cJ strain has a low frequency of abnormally small corpus callosum, while the 129 strains have many animals with deficient corpus callosum. The I/LnJ and BTBR T+ tf/J strains never have a corpus callosum, while half of I/LnJ and almost all BTBR show severely reduced size of the hippocampal commissure. Certain of the F1 hybrid crosses among these strains are known to be less severely abnormal than the inbred parents, suggesting the parent strains have different genetic causes of commissure defects. In this study, all hybrid crosses among the four strains were investigated. The BTBR x I/Ln hybrid expressed almost no defects of the hippocampal commissure, unlike its inbred parent strains. Numerous 3-way crosses among the four strains yielded many mice with no corpus callosum and severely reduced hippocampal commissure, which shows that the phenotypic defect can result from several different combinations of genetic alleles. The F2 and F3 hybrid crosses of BTBR and I/LnJ had almost 100% absence of the corpus callosum but about 50% frequency of deficient hippocampal commissure. The 4-way hybrid cross among all four abnormal strains involved highly fertile parents and yielded a very wide phenotypic range of defects from almost no hippocampal commissure to totally normal forebrain commissures. The F2 and F3 crosses as well as the 4-way cross provide excellent material for studies of genetic linkage and behavioral consequences of commissure defects. PMID:22537318

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

    PubMed Central

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

    2015-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-03-01

    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.

  5. Early suppressive antiretroviral therapy in HIV infection is associated with measurable changes in the corpus callosum.

    PubMed

    Kelly, Sean G; Taiwo, Babafemi O; Wu, Ying; Bhatia, Ramona; Kettering, Casey S; Gao, Yi; Li, Suyang; Hutten, Ryan; Ragin, Ann B

    2014-10-01

    The purpose of this study was to examine the impact of early suppressive antiretroviral therapy (ART) on brain structure and neurocognitive outcomes. We conducted an observational study of subjects within 1 year of HIV infection. Ten ART-nave and 10 ART-suppressed individuals were matched for age and infection duration and age-matched to 10 HIV-seronegative controls. Quantitative brain imaging and neurocognitive data were analyzed. Subjects on suppressive ART had diminished corpus callosum structural integrity on macromolecular and microstructural imaging, higher cerebrospinal fluid percent, higher depression scores, and lower functional performance. Early suppressive ART may alter the trajectory of neurological progression of HIV infection, particularly in the corpus callosum. PMID:24965253

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

    PubMed

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

    2012-04-01

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

  7. A Context-Sensitive Active Contour for 2D Corpus Callosum Segmentation

    PubMed Central

    He, Qing; Duan, Ye; Miles, Judith; Takahashi, Nicole

    2007-01-01

    We propose a new context-sensitive active contour for 2D corpus callosum segmentation. After a seed contour consisting of interconnected parts is being initialized by the user, each part will start to deform according to its own motion law derived from high-level prior knowledge, and is constantly aware of its own orientation and destination during the deformation process. Experimental results demonstrate the accuracy and robustness of our algorithm. PMID:18320009

  8. Lipoma of corpus callosum associated with dysraphic lesions and trisomy 13

    SciTech Connect

    Wainwright, H.; Bowen, R.; Radcliffe, M.

    1995-05-22

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

  9. A de novo mutation in PRICKLE1 in fetal agenesis of the corpus callosum and polymicrogyria

    PubMed Central

    Bassuk, Alexander G.; Sherr, Elliott H.

    2016-01-01

    Homozygous recessive mutations in the PRICKLE1 gene were originally reported in three consanguineous families with myoclonic epilepsy. Subsequently, several studies have identified neurological abnormalities in animal models with both heterozygous and homozygous mutations in PRICKLE1 orthologues, including epilepsy in flies and in mice with heterozygous PRICKLE1 mutations. We describe a fetus with a novel de novo mutation in PRICKLE1 associated with agenesis of the corpus callosum. PMID:26727662

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

    PubMed Central

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

    2014-01-01

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

  11. MIR137HG risk variant rs1625579 genotype is related to corpus callosum volume in schizophrenia.

    PubMed

    Patel, Veena S; Kelly, Sinead; Wright, Carrie; Gupta, Cota Navin; Arias-Vasquez, Alejandro; Perrone-Bizzozero, Nora; Ehrlich, Stefan; Wang, Lei; Bustillo, Juan R; Morris, Derek; Corvin, Aiden; Cannon, Dara M; McDonald, Colm; Donohoe, Gary; Calhoun, Vince D; Turner, Jessica A

    2015-08-18

    Genome-wide association studies implicate the MIR137HG risk variant rs1625579 (MIR137HGrv) within the host gene for microRNA-137 as a potential regulator of schizophrenia susceptibility. We examined the influence of MIR137HGrv genotype on 17 subcortical and callosal volumes in a large sample of individuals with schizophrenia and healthy controls (n=841). Although the volumes were overall reduced relative to healthy controls, for individuals with schizophrenia the homozygous MIR137HGrv risk genotype was associated with attenuated reduction of mid-posterior corpus callosum volume (p=0.001), along with trend-level effects in the adjacent central and posterior corpus callosum. These findings are unique in the literature and remain robust after analysis in ethnically homogenous and single-scanner subsets of the larger sample. Thus, our study suggests that the mechanisms whereby MIR137HGrv works to increase schizophrenia risk are not those that generate the corpus callosum volume reductions commonly found in the disorder. PMID:26123324

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

    PubMed Central

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

    2014-01-01

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

  13. Growth of the Human Corpus Callosum: Modular and Laminar Morphogenetic Zones

    PubMed Central

    Jovanov-Milošević, Nataša; Čuljat, Marko; Kostović, Ivica

    2009-01-01

    The purpose of this focused review is to present and discuss recent data on the changing organization of cerebral midline structures that support the growth and development of the largest commissure in humans, the corpus callosum. We will put an emphasis on the callosal growth during the period between 20 and 45 postconceptual weeks (PCW) and focus on the advantages of a correlated histological/magnetic resonance imaging (MRI) approach. The midline structures that mediate development of the corpus callosum in rodents, also mediate its early growth in humans. However, later phases of callosal growth in humans show additional medial transient structures: grooves made up of callosal septa and the subcallosal zone. These modular (septa) and laminar (subcallosal zone) structures enable the growth of axons along the ventral callosal tier after 18 PCW, during the rapid increase in size of the callosal midsagittal cross-section area. Glial fibrillary acidic protein positive cells, neurons, guidance molecule semaphorin3A in cells and extracellular matrix (ECM), and chondroitin sulfate proteoglycan in the ECM have been identified along the ventral callosal tier in the protruding septa and subcallosal zone. Postmortem MRI at 3 T can demonstrate transient structures based on higher water content in ECM, and give us the possibility to follow the growth of the corpus callosum in vivo, due to the characteristic MR signal. Knowledge about structural properties of midline morphogenetic structures may facilitate analysis of the development of interhemispheric connections in the normal and abnormal fetal human brain. PMID:19562029

  14. Processing Speed Delays Contribute to Executive Function Deficits in Individuals with Agenesis of the Corpus Callosum

    PubMed Central

    Marco, Elysa J.; Harrell, Kathryn M.; Brown, Warren S.; Hill, Susanna S.; Jeremy, Rita J.; Kramer, Joel H.; Sherr, Elliott H.; Paul, Lynn K.

    2013-01-01

    Corpus callosum malformation and dysfunction are increasingly recognized causes of cognitive and behavioral disability. Individuals with agenesis of the corpus callosum (AgCC) offer unique insights regarding the cognitive skills that depend specifically upon callosal connectivity. We examined the impact of AgCC on cognitive inhibition, flexibility, and processing speed using the Color-Word Interference Test (CWIT) and Trail Making Test (TMT) from the Delis-Kaplan Executive Function System. We compared 36 individuals with AgCC and IQs within the normal range to 56 matched controls. The AgCC cohort was impaired on timed measures of inhibition and flexibility; however, group differences on CWIT Inhibition, CWIT Inhibition/Switching and TMT Number-Letter Switching appear to be largely explained by slow performance in basic operations such as color naming and letter sequencing. On CWIT Inhibition/Switching, the AgCC group was found to commit significantly more errors which suggests that slow performance is not secondary to a cautious strategy. Therefore, while individuals with agenesis of the corpus callosum show real deficits on tasks of executive function, this impairment appears to be primarily a consequence of slow cognitive processing. Additional studies are needed to investigate the impact of AgCC on other aspects of higher order cortical function. PMID:22390821

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

    PubMed Central

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

    2014-01-01

    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

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

    PubMed Central

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

    2014-01-01

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

  17. Anisotropy across Superplume Boundaries

    NASA Astrophysics Data System (ADS)

    Cottaar, S.; Romanowicz, B. A.

    2011-12-01

    Sdiff data sets are presented for paths that run parallel to the African and the Pacific superplume boundaries. Objective clustering of waveforms illustrates sharp changes across these boundaries. The African plume shows a sharp offset in travel times in the SHdiff phase, while a more gradual offset towards slower arrivals is seen in the case of the Pacific superplume. Additionally, Pdiff phases display no offset around the African plume and a weak one around the Pacific plume. Here we focus mainly on another striking feature observed in both cases: outside of the superplume the Sdiff particle motion is strongly elliptical, but becomes linear within the superplume (first noticed by To et al. 2005 in the African superplume case). For the African plume we argue that these observations of delayed SV at large distances (~120 degrees) are indicative of the occurrence of azimuthal anisotropy. The SV arrivals have similar polarity as SH, opposite from what their radiation pattern predicts. Azimuthal anisotropy causes SH energy to be converted to SV (Maupin, 1994), explaining the travel time, polarity and amplitude. Forward modeling through different isotropic and anisotropic models supports this statement, although there are trade-offs between direction and magnitude of azimuthal anisotropy. The strong elliptical particle motions are also observed outside the Pacific plume, but at shorter distances (95-105 degrees). Elliptical motions can occur in the absence of anisotropy when strong velocity deviations or layering occurs close to the CMB, which, based on velocity profiles with depth in global tomographic models would be more likely within the superplume rather than on the fast side. The elliptical particle motions here can be modelled with a simple transverse isotropic model with VSH>VSV, but azimuthal anisotropy cannot be ruled out. The complexities within the Pacific superplume, including strong amplitude drop and existence of a post-cursor, are likely caused by an ultra low velocity zone (Cottaar and Romanowicz, this meeting) and make it difficult to constrain anisotropy within the Pacific superplume. Notably, however, in both cases, elliptical particle motions become more linear, and thus anisotropy decreases, from the fast side towards the slow side across superplume boundaries. Possibly this is caused by a rotation in the deformational regime, causing rotation of the pre-existing anisotropic fast directions. Forward modeling of deformation using tracers in mantle convection models, considering different mineral physics scenarios (Wenk et al., 2011) suggest that the boundaries in anisotropy from downwellings to upwellings can be sharp, and could possibly contribute to explaining the sharp boundary in VSH, in addition to effects of lateral variations in temperature and composition. Moreover the model for post-perovskite with (001)-slip predicts anti-correlation between S and P wave anisotropy. Variation in VPH due to anisotropy would then be anti-correlated with the variation caused by temperature, and this could explain the lack of correlation in the variations of VSH and VPH across the superplume boundary. Our modeling shows that care must be taken when computing R=dlnVs/dlnVp in the presence of anisotropy.

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

    PubMed Central

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

    2012-01-01

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

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

    PubMed Central

    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

    Agenesis of the corpus callosum (ACC) is among the most frequent human brain malformations with an incidence of 0.570 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 callosumACC) or partial absence (dysgenesis of the corpus callosumDCC) 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: MowatWilson syndrome (n = 2), WalkerWarburg 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

  20. A solution to the cosmic ray anisotropy problem

    NASA Astrophysics Data System (ADS)

    Mertsch, P.; Funk, S.

    2015-10-01

    Observations of the cosmic ray (CR) anisotropy are widely advertised as a means of finding nearby sources. This idea has recently gained currency after the discovery of a rise in the positron fraction and is the goal of current experimental efforts, e.g., with AMS-02 on the International Space Station. Yet, even the anisotropy observed for hadronic CRs is not understood, in the sense that isotropic diffusion models overpredict the dipole anisotropy in the TeV-PeV range by almost two orders of magnitude. Here, we consider two additional effects normally not considered in isotropic diffusion models: anisotropic diffusion due to the presence of a background magnetic field and intermittency effects of the turbulent magnetic fields. We numerically explore these effect by tracking test-particles through individual realisations of the turbulent field. We conclude that a large misalignment between the CR gradient and the background field can explain the observed low level of anisotropy.

  1. Anisotropy in OLEDs

    NASA Astrophysics Data System (ADS)

    Callens, M. K.; Yokoyama, D.; Neyts, K.

    2015-09-01

    Small-molecule OLEDs, deposited by thermal evaporation, allow for precise control over layer thicknesses. This enables optimisation of the optical behaviour of the stack which ultimately determines the outcoupling efficiency. In terms of optical outcoupling there are limits to the efficiency by which the generated electromagnetic radiation can be extracted from the stack. These limitations are linked to the refractive indices of the individual layers. Values for maximum outcoupling efficiency are sometimes calculated under the implicit assumptions that the OLED stack is planar, that all layers are isotropic with a certain refractive index and that the emitters are not preferentially oriented. In reality it is known that these assumptions are not always valid, be it intentional or unintentional. In our work we transcend these limiting assumptions and look at different forms of anisotropy in OLEDs. Anisotropy in OLEDs comes in three distinct flavours; 1. Geometrical anisotropy, as for example in gratings, lenses or other internal or external scattering centres, 2. Anisotropic emitters, where the orientation significantly influences the direction in which radiation is emitted and 3. Anisotropic optical materials, where their anisotropic nature breaks the customary assumption of isotropic OLED materials. We investigate the effect of these anisotropic features on the outcoupling efficiency and ultimately, on the external quantum efficiency (EQE).

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

    SciTech Connect

    Schmidt, S.L.; Lent, R.

    1987-10-08

    Defects of the cerebral cortex and corpus callosum of mice subjected prenatally to gamma irradiation were evaluated as a function of dose and of embryonic age at irradiation. Pregnant mice were exposed to a gamma source at 16, 17, and 19 days of gestation (E16, E17, and E19, respectively), with total doses of 2 Gy and 3 Gy, in order to produce brain defects on their progeny. At 60 postnatal days, the brains of the offspring were analyzed qualitatively and quantitatively and compared with those of nonirradiated animals. Mice irradiated at E16 were all acallosal. Those that were exposed to 2 Gy displayed an aberrant longitudinal bundle typical of other acallosals, but this was not the case in those irradiated with 3 Gy. The corpus callosum of animals irradiated at E17 with 3 Gy was pronouncedly hypotrophic, but milder effects were observed in the other groups. Quantitative analysis confirmed a dependence of callosal midsagittal area upon dose and age at irradiation, and, in addition, indicated an interaction between these variables. The neocortex of irradiated animals was hypotrophic: layers II-III were much more affected than layer V, and this was more affected than layer VI. Quantitative analysis indicated that this effect also depended on dose and age at irradiation and that it was due to a loss of cortical neurons. Furthermore, a positive correlation was found between the number of neurons within layers II-III, and V and the midsagittal area of the corpus callosum. Ectopic neurons were found in the white matter and in layer I of animals irradiated at E16 and E17, indicating that fetal exposure to ionizing radiation interfered with the migration of cortical neuroblasts.

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

    NASA Astrophysics Data System (ADS)

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

    2012-03-01

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

  4. Recessively inherited spastic paraplegia associated with ataxia, congenital cataracts, thin corpus callosum and axonal neuropathy.

    PubMed

    Yamashita, I; Sasaki, H; Yabe, I; Kikuchi, S; Chin, S; Fukazawa, T; Okumura, H; Tashiro, K

    2000-07-01

    We investigated a consanguineous Japanese family with a complicated form of familial spastic paraplegia (FSP). Three siblings were affected, probably by autosomal recessive inheritance. All showed ataxia, subnormal mentality, congenital cataracts, and slight cerebellar atrophy on CT scans. Spastic paraplegia was predominant in 2 siblings, while ataxia was more marked in the other. Slight but definite atrophy of the corpus callosum and axonal neuropathy were demonstrated in 1 sibling who underwent detailed investigation. Review of similar cases reported in the literature indicates that this recessively inherited disorder probably represents a homogeneous group within the heterogeneous cluster of complicated FSP. PMID:10893066

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

    PubMed Central

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

    1993-01-01

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

  6. Associated Anisotropy Decays of Ethidium Bromide Interacting with DNA

    PubMed Central

    Chib, Rahul; Raut, Sangram; Sabnis, Sarika; Singhal, Preeti; Gryczynski, Zygmunt; Gryczynski, Ignacy

    2015-01-01

    Ethidium Bromide (EB) is a commonly used dye in a deoxyribonucleic acid (DNA) study. Upon an intercalation, this dye significantly increases its brightness and fluorescence lifetime. In this report we have studied the time-resolved fluorescence properties of EB existing simultaneously in free and DNA-bound forms in the solution. Fluorescence intensity decays were fitted globally to a double exponential model with lifetimes corresponding to free (1.6ns) and bound (22ns) forms, and molar fractions were determined for all used solutions. Anisotropy decays displayed characteristic time dependence with an initial rapid decline followed by recovery and slow decay. The short-lived fraction associated with free EB molecules decreases faster than long-lived fraction associated with EB bound to DNA. Consequently, contribution from fast rotation leads to initial rapid decay in anisotropy. On the other hand bound fraction, due to slow rotation helps recover anisotropy in time. This effect of associated anisotropy decays in systems such as EB free/EB-DNA is clearly visible in a wide range of concentrations, and should be taken into account in polarization assays and biomolecule dynamics studies. PMID:26640693

  7. Evaporation Anisotropy of Forsterite

    NASA Astrophysics Data System (ADS)

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

    1996-03-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2004-05-01

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

  9. Communicative deficits in agenesis of the corpus callosum: nonliteral language and affective prosody.

    PubMed

    Paul, Lynn K; Van Lancker-Sidtis, Diana; Schieffer, Beatrix; Dietrich, Rosalind; Brown, Warren S

    2003-05-01

    While some individuals with agenesis of the corpus callosum can perform normally on standardized intelligence tests, clinical observations suggest that they nevertheless have deficits in the domains of fluid and social intelligence. Particularly important for social competence is adequate understanding and use of paralinguistic information. This study examined the impact of callosal absence on the processing of pragmatic and paralinguistic information. Young adult males with agenesis of the corpus callosum (ACC) were evaluated in the areas of nonliteral language comprehension, proverb recognition and interpretation, and perception of affective prosody. Ten ACC individuals with normal Wechsler IQ were compared to 14 sex, age, and IQ matched normal controls. The Formulaic and Novel Language Comprehension Test (FANL-C), Gorham Proverbs Test, and LA Prosody Test were administered. ACC subjects exhibited significant impairment on the nonliteral items of the FANL-C, but no significant difference from controls in comprehension of literal items. ACC subjects also exhibited significant deficits in both self-generated interpretation and recognition of proverb meaning, and in recognition of affective prosody. These results demonstrate that normally intelligent individuals with ACC are impaired in the understanding of nonliteral language and emotional-prosodic cues that are important in social communication. In all three tests, the performance of individuals with ACC was similar to patients with right hemisphere brain damage. Thus, persons with ACC appear to lack interhemispheric integration of critical aspects of language processed by the right hemisphere. PMID:12735947

  10. Propagation of Epileptiform Events across the Corpus Callosum in a Cingulate Cortical Slice Preparation

    PubMed Central

    Quach-Wong, Bonnie; Sonnenfeld, Julian; Aaron, Gloster

    2012-01-01

    We report on a novel mouse in vitro brain slice preparation that contains intact callosal axons connecting anterior cingulate cortices (ACC). Callosal connections are demonstrated by the ability to regularly record epileptiform events between hemispheres (bilateral events). That the correlation of these events depends on the callosum is demonstrated by the bisection of the callosum in vitro. Epileptiform events are evoked with four different methods: (1) bath application of bicuculline (a GABA-A antagonist); (2) bicuculline+MK801 (an NMDA receptor antagonist), (3) a zero magnesium extracellular solution (0Mg); (4) focal application of bicuculline to a single cortical hemisphere. Significant increases in the number of epileptiform events, as well as increases in the ratio of bilateral events to unilateral events, are observed during bath applications of bicuculline, but not during applications of bicuculline+MK-801. Long ictal-like events (defined as events >20 seconds) are only observed in 0Mg. Whole cell patch clamp recordings of single neurons reveal strong feedforward inhibition during focal epileptiform events in the contralateral hemisphere. Within the ACC, we find differences between the rostral areas of ACC vs. caudal ACC in terms of connectivity between hemispheres, with the caudal regions demonstrating shorter interhemispheric latencies. The morphologies of many patch clamped neurons show callosally-spanning axons, again demonstrating intact callosal circuits in this in vitro preparation. PMID:22363643

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

    PubMed

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

    2013-03-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2009-02-01

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

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

    PubMed

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

    2015-06-01

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

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

    ERIC Educational Resources Information Center

    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

    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…

  15. Maturation of the corpus callosum of the rat: II. Influence of thyroid hormones on the number and maturation of axons.

    PubMed

    Gravel, C; Sasseville, R; Hawkes, R

    1990-01-01

    Quantitative electron microscopy has been used to study the number of callosal axons in the corpus callosum of normal and hypothyroid rats during postnatal development. At birth, the normal corpus callosum contains 4.4 x 10(6) axons. This number increases to 11.4 x 10(6) by 5 days of age (P5) and then, in contrast to cats and primates, remains constant until at least P60, the oldest age examined. The number of axons in the corpus callosum of hypothyroid animals is not significantly different from the values observed in normal rats at all ages studied, although the callosal axons of hypothyroid rats remain structurally immature. As extensive elimination of callosal axons has been shown to occur in normal rats past P5, we conclude that new callosal processes grow through the corpus callosum past this age that compensate numerically for the loss. Moreover, as the number of callosally projecting neurons seems to be higher in hypothyroid rats than in normal controls, it seems that the constant axon number derives from more parent neurons, and thus that there are more axon collaterals per callosal neuron in a normal animal than in a hypothyroid one. Taken together, these data indicate that although hypothyroidism does not alter the total number of callosally projecting axons, it interferes with the normal processes that define or sculpt the projection fields, thereby leading to a numerically normal projection with abnormal topography. PMID:2298928

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

    ERIC Educational Resources Information Center

    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

    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

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

    PubMed

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

    2015-03-01

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

  18. Magnetic anisotropy of asbestos fibers

    NASA Astrophysics Data System (ADS)

    Ulanowski, Z.; Kaye, P. H.

    1999-04-01

    The anisotropy of magnetic susceptibility of single asbestos fibers is measured. The alignment of both chrysotile and crocidolite fibers in magnetic fields is found to be due to the anisotropy. The average measured anisotropy of volume susceptibility is 0.4010-6 for chrysotile and 8310-6 for crocidolite. Fiber shape effects are estimated to contribute, on average, about 10% and 6%, respectively, to the total anisotropy of the two types of fiber. There is no evidence of significant permanent magnetic moments. The magnitude of the observed alignment makes the effect potentially useful in real-time detection of airborne asbestos fibers. The experimental technique developed in the study can be used for measuring the anisotropy of small particles of well-defined shape. High sensitivity of the technique permits the measurement of torques lower than 10-21 Nm on particles down to picogram mass.

  19. [Case of suspected multiple sclerosis with transcallosal lesions involving the upper surface of the corpus callosum].

    PubMed

    Shirafuji, Toshihiko; Oya, Yasushi; Nakamura, Harumasa; Ogata, Katsuhisa; Ogawa, Masafumi; Kawai, Mitsuru

    2008-05-01

    A 26-year-old woman noticed gradually progressive, right lower leg weakness over a 1.5-month period. Neurological examination revealed right hemiparesis with slightly increased deep tendon reflexes, Babinski's sign on the right side, loss of position sense in the right leg, and slight loss of superficial sensation in the right toes. MR FLAIR images showed a high intensity area measuring 5 x 2 x 3 cm in the left frontal lobe, extending to the outer surface of the body of the corpus callosum and the adjacent right cingulate gyrus. Gadolinium enhancement was seen along the cortex and the outer surface of the body of the corpus callosum. CSF findings showed no pleocytosis, a protein content of 32 mg/dl, a sugar level of 85 mg/dl, and an IgG index of 0.46. The biopsy specimen obtained from the superior frontal gyrus showed perivascular cuffing of T-lymphocytes and some B-lymphocytes, as well as multiple small foci of demyelination. Starting on the second day of admission, the patient was treated with methylprednisolone pulse therapy (1,000 mg/day for 3 days); she was then switched to oral prednisolone (20 mg/day). Thereafter, the patient had two clinical relapses: one was due to a lesion in the dorsal part of the medulla oblongata associated with a disturbance of deep sensation in both hands, and the other was due to a lesion involving the right internal capsule, the globus pallidus, and the caudate nucleus associated with left facial nerve palsy. Visual evoked potentials suggested a demyelinating lesion in the right optic nerve. We suspected a diagnosis of multiple sclerosis based on the presence of more than two clinical episodes of neurological deficits with identifiable lesions on MRI. Multiple sclerosis should be considered in the differential diagnosis of lesions located in the outer part of the corpus callosum and transcallosal bilateral hemispheres on MRI, even though inner callosal lesions are common in multiple sclerosis. PMID:18540378

  20. Spintronic magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Misiorny, Maciej; Hell, Michael; Wegewijs, Maarten R.

    2013-12-01

    Superparamagnetism of magnetic adatoms and molecules--preferential alignment of their spins along an easy axis--is a useful effect for nanoscale applications as it prevents undesired spin reversal. The underlying magnetic anisotropy barrier--a quadrupolar energy splitting--originates from spin-orbit interaction and can nowadays be probed by electronic transport measurements. Here we predict that in a much broader class of systems, quantum dots with spins larger than 1/2, superparamagnetism can arise without spin-orbit interaction: by attaching them to ferromagnets, a quadrupolar spintronic exchange field is generated locally. It is observable by means of conductance measurements and leads to enhanced spin filtering even in a state with zero average spin. Analogously to the spintronic dipolar exchange field, giving rise to a local spin torque, the effect is susceptible to electric control and increases with tunnel coupling as well as with spin polarization.

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

    PubMed

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

    2014-12-01

    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

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

    PubMed Central

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

    2015-01-01

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

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

    PubMed Central

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

    2014-01-01

    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

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

    PubMed Central

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

    2012-01-01

    The corpus callosum is hypothesized to play a fundamental role in integrating information and mediating complex behaviors. Here, we demonstrate that lack of normal callosal development can lead to deficits in functional connectivity that are related to impairments in specific cognitive domains. We examined resting-state functional connectivity in individuals with agenesis of the corpus callosum (AgCC) and matched controls using magnetoencephalographic imaging (MEG-I) of coherence in the alpha (812 Hz), beta (1230 Hz) and gamma (3055 Hz) bands. Global connectivity (GC) was defined as synchronization between a region and the rest of the brain. In AgCC individuals, alpha band GC was significantly reduced in the dorsolateral pre-frontal (DLPFC), posterior parietal (PPC) and parieto-occipital cortices (PO). No significant differences in GC were seen in either the beta or gamma bands. We also explored the hypothesis that, in AgCC, this regional reduction in functional connectivity is explained primarily by a specific reduction in interhemispheric connectivity. However, our data suggest that reduced connectivity in these regions is driven by faulty coupling in both inter- and intrahemispheric connectivity. We also assessed whether the degree of connectivity correlated with behavioral performance, focusing on cognitive measures known to be impaired in AgCC individuals. Neuropsychological measures of verbal processing speed were significantly correlated with resting-state functional connectivity of the left medial and superior temporal lobe in AgCC participants. Connectivity of DLPFC correlated strongly with performance on the Tower of London in the AgCC cohort. These findings indicate that the abnormal callosal development produces salient but selective (alpha band only) resting-state functional connectivity disruptions that correlate with cognitive impairment. Understanding the relationship between impoverished functional connectivity and cognition is a key step in identifying the neural mechanisms of language and executive dysfunction in common neurodevelopmental and psychiatric disorders where disruptions of callosal development are consistently identified. PMID:22870191

  5. PEG-PDLLA Micelle Treatment Improves Axonal Function of the Corpus Callosum following Traumatic Brain Injury

    PubMed Central

    Ping, Xingjie; Jiang, Kewen; Lee, Seung-Young; Cheng, Ji-Xing

    2014-01-01

    Abstract The initial pathological changes of diffuse axonal injury following traumatic brain injury (TBI) include membrane disruption and loss of ionic homeostasis, which further lead to dysfunction of axonal conduction and axon disconnection. Resealing the axolemma is therefore a potential therapeutic strategy for the early treatment of TBI. Monomethoxy poly (ethylene glycol)-poly (D, Llactic acid) di-block copolymer micelles (mPEG-PDLLA) have been shown to restore depressed compound action potentials (CAPs) of spinal axons and promote functional recovery after spinal cord injury. Here, we evaluate the effect of the micelles on repairing the injured cortical axons following TBI. Adult mice subjected to controlled cortical impact (CCI) were treated with intravenous injection of the micelles at 0?h or 4?h after injury. Evoked CAPs were recorded from the corpus callosum of coronal cortical slices at 2 days after injury. The CCI caused significant decreases in the amplitudes of two CAP peaks that were respectively generated by the faster myelinated axons and slower unmyelinated axons. Micelle treatment at both 0?h and 4?h after CCI resulted in significant increases in both CAP peak amplitudes. Injection of fluorescent dye-labeled micelles revealed high fluorescent staining in cortical gray and white matters underneath the impact site. Labeling membrane-perforated neurons by injecting a membrane impermeable dye Texas Red-labeled dextran into lateral ventricles at 2?h post-CCI revealed that immediate micelle injection after CCI did not reduce the number of dye-stained cortical neurons and dentate granule cells of the hippocampus, indicating its ineffectiveness in repairing plasma membrane of neuronal somata. We conclude that intravenous administration of mPEG-PDLLA micelles immediately or at 4?h after TBI allows brain penetration via the compromised blood brainbarrier, and thereby improves the function of both myelinated and unmyelinated axons of the corpus callosum. PMID:24579802

  6. Linking strain anisotropy and plasticity in copper metallization

    SciTech Connect

    Murray, Conal E. Jordan-Sweet, Jean; Priyadarshini, Deepika; Nguyen, Son

    2015-05-04

    The elastic anisotropy of copper leads to significant variation in the x-ray elastic constants (XEC), which link diffraction-based strain measurements to stress. An accurate depiction of the mechanical response in copper thin films requires a determination of an appropriate grain interaction model that lies between Voigt and Reuss limits. It is shown that the associated XEC weighting fraction, x*, between these limits provides a metric by which strain anisotropy can be quantified. Experimental values of x*, as determined by a linear regression scheme of diffraction data collected from multiple reflections, reveal the degree of strain anisotropy and its dependence on plastic deformation induced during in-situ and ex-situ thermal treatments.

  7. Quantifying reflectance anisotropy of photosynthetically active radiation in grasslands

    SciTech Connect

    Middleton, E.M. )

    1992-11-30

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

  8. Stress anisotropy and velocity anisotropy in low porosity shale

    NASA Astrophysics Data System (ADS)

    Kuila, U.; Dewhurst, D. N.; Siggins, A. F.; Raven, M. D.

    2011-04-01

    Shales are known for often marked intrinsic anisotropy of many of their properties, including strength, permeability and velocity for example. In addition, it is well known that anisotropic stress fields can also have a significant impact on anisotropy of velocity, even in an isotropic medium. This paper sets out to investigate the ultrasonic velocity response of well-characterised low porosity shales from the Officer Basin in Western Australia to both isotropic and anisotropic stress fields and to evaluate the velocity response to the changing stress field. During consolidated undrained multi-stage triaxial tests on core plugs cut normal to bedding, V pv increases monotonically with increasing effective stress and V s1 behaves similarly although with some scatter. V ph and V sh remain constant initially but then decrease within each stage of the multi-stage test, although velocity from stage to stage at any given differential stress increases. This has the impact of decreasing both P-wave (?) and S-wave anisotropy (?) through application of differential stress within each loading stage. However, increasing the magnitude of an isotropic stress field has little effect on the velocity anisotropies. The intrinsic anisotropy of the shale remains reasonably high at the highest confining pressures. The results indicate the magnitude and orientation of the stress anisotropy with respect to the shale microfabric has a significant impact on the velocity response to changing stress fields.

  9. Anisotropy in solid inflation

    SciTech Connect

    Bartolo, Nicola; Matarrese, Sabino; Ricciardone, Angelo; Peloso, Marco E-mail: sabino.matarrese@pd.infn.it E-mail: angelo.ricciardone@pd.infn.it

    2013-08-01

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

  10. Magnetic anisotropies of quantum dots

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

    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).

  11. Laboratory seismic anisotropy in mylonites

    NASA Astrophysics Data System (ADS)

    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

    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.

  12. Extraction of the plane of minimal cross-sectional area of the corpus callosum using template-driven segmentation.

    PubMed

    Changizi, Neda; Hamarneh, Ghassan; Ishaq, Omer; Ward, Aaron; Tam, Roger

    2010-01-01

    Changes in corpus callosum (CC) size are typically quantified in clinical studies by measuring the CC cross-sectional area on a midsagittal plane. We propose an alternative measurement plane based on the role of the CC as a bottleneck structure in determining the rate of interhemispheric neural transmission. We designate this plane as the Minimum Corpus Callosum Area Plane (MCCAP), which captures the cross section of the CC that best represents an upper bound on interhemispheric transmission. Our MCCAP extraction method uses a nested optimization framework, segmenting the CC as it appears on each candidate plane, using registration-based segmentation. We demonstrate the robust convergence and high accuracy of our method for magnetic resonance images and present preliminary clinical results showing higher sensitivity to disease-induced atrophy. PMID:20879378

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

    NASA Astrophysics Data System (ADS)

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

    2012-04-01

    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.

  14. Fractionalized gapless quantum vortex liquids

    NASA Astrophysics Data System (ADS)

    Wang, Chong; Senthil, T.

    2015-05-01

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

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

    PubMed Central

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

    2014-01-01

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

  16. [Transient high-intensity T2 signal in the splenium of the corpus callosum in a non-epileptic patient].

    PubMed

    Nifle, C; Couratier, M; Jallade, C; Sarfati, Y; Mignon, F; Pico, F

    2007-06-01

    Transient splenial lesions of the corpus callosum have been mainly reported in epileptic patients. We report the case of a non-epileptic woman with bipolar affective disorder treated by oxcarbazepine which was withdrawn because of a mild hyponatremia (128 mmol/l). A confusional state followed withdrawal and the electroencephalogram was free of spike or sharp waves. Brain MRI showed a single splenial lesion of the corpus callosum revealed by a high intensity T2 signal on FLAIR and diffusion sequences. Because of a major depressive episode, twelve sessions of electroconvulsive therapy were performed and yielded clinical improvement. A second brain MRI performed 5 weeks later was normal. The relevances of this cases are the non-epileptic status of the patient, the drug incriminated (oxcarbazepine), and the normalisation of brain MRI despite electroconvulsive therapy. Different mechanisms of this brain MRI abnormality are discussed including the sudden withdraw of oxcarbazepine. Prognosis of transient splenial lesions of the corpus callosum is good. Clinicians should search for recent metabolic disorders and therapeutic modifications. PMID:17607208

  17. Size dependence and field-induced magnetic anisotropy of granular nanophases. Application to microwave isolation

    NASA Astrophysics Data System (ADS)

    Mallgol, Stphane; Brosseau, Christian; Qufflec, Patrick; Konn, Anne-Marie

    2004-05-01

    The induced anisotropy of magnetized nanocomposite samples is investigated through the experimental determination of a non-zero off-diagonal effective permeability tensor term ?. The samples are constituted of ferrimagnetic (?-Fe 2O 3) or ferromagnetic (Ni) grains uniformly dispersed in a matrix composed of ZnO particles. We characterize the volume fraction and grain size dependences of ?. Then, we show that the induced anisotropy of the nanophases can be exploited to realize a microwave resonance isolator.

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

    PubMed Central

    Reyes-Haro, Daniel; Labrada-Moncada, Francisco Emmanuel; Miledi, Ricardo; Martnez-Torres, Atalfo

    2015-01-01

    Anorexia nervosa is an eating disorder associated with severe weight loss as a consequence of voluntary food intake avoidance. Animal models such as dehydration-induced anorexia (DIA) mimic core features of the disorder, including voluntary reduction in food intake, which compromises the supply of energy to the brain. Glial cells, the major population of nerve cells in the central nervous system, play a crucial role in supplying energy to the neurons. The corpus callosum (CC) is the largest white matter tract in mammals, and more than 99% of the cell somata correspond to glial cells in rodents. Whether glial cell density is altered in anorexia is unknown. Thus, the aim of this study was to estimate glial cell density in the three main regions of the CC (genu, body, and splenium) in a murine model of DIA. The astrocyte density was significantly reduced (~34%) for the DIA group in the body of the CC, whereas in the genu and the splenium no significant changes were observed. DIA and forced food restriction (FFR) also reduced the ratio of astrocytes to glial cells by 57.5% and 22%, respectively, in the body of CC. Thus, we conclude that DIA reduces astrocyte density only in the body of the rat CC. PMID:26090235

  19. Automated segmentation of the canine corpus callosum for the measurement of diffusion tensor imaging.

    PubMed

    Peterson, David E; Chen, Steven D; Calabrese, Evan; White, Leonard E; Provenzale, James M

    2016-02-01

    The goal of this study was to apply image registration-based automated segmentation methods to measure diffusion tensor imaging (DTI) metrics within the canine brain. Specifically, we hypothesized that this method could measure DTI metrics within the canine brain with greater reproducibility than with hand-drawn region of interest (ROI) methods.We performed high-resolution post-mortem DTI imaging on two canine brains on a 7?T MR scanner. We designated the two brains as brain 1 and brain 2. We measured DTI metrics within the corpus callosum of brain 1 using a hand-drawn ROI method and an automated segmentation method in which ROIs from brain 2 were transformed into the space of brain 1. We repeated both methods in order to measure their reliability.Mean differences between the two sets of hand-drawn ROIs ranged from 4% to 10%. Mean differences between the hand-drawn ROIs and the automated ROIs were less than 3%. The mean differences between the first and second automated ROIs were all less than 0.25%.Our findings indicate that the image registration-based automated segmentation method was clearly the more reproducible method. These results provide the groundwork for using image registration-based automated segmentation methods to measure DTI metrics within the canine brain. Such methods will facilitate the study of white matter pathology in canine models of neurologic disease. PMID:26577603

  20. Inter-hemispheric functional connectivity changes with corpus callosum morphology in multiple sclerosis.

    PubMed

    Zito, G; Luders, E; Tomasevic, L; Lupoi, D; Toga, A W; Thompson, P M; Rossini, P M; Filippi, M M; Tecchio, F

    2014-04-25

    Multiple sclerosis (MS) affects myelin sheaths within the central nervous system, concurring to cause brain atrophy and neurodegeneration as well as gradual functional disconnections. To explore early signs of altered connectivity in MS from a structural and functional perspective, the morphology of corpus callosum (CC) was correlated with a dynamic inter-hemispheric connectivity index. Twenty mildly disabled patients affected by a relapsing-remitting (RR) form of MS (EDSS?3.5) and 15 healthy subjects underwent structural MRI to measure CC thickness over 100 sections and electroencephalography to assess a spectral coherence index between primary regions devoted to hand control, at rest and during an isometric handgrip. In patients, an overall CC atrophy was associated with increased lesion load. A less efficacious inter-hemispheric coherence (IHCoh) during movement was associated with CC atrophy in sections interconnecting homologous primary motor areas (anterior mid-body). In healthy controls, less efficacious IHCoh at rest was associated with a thinner CC splenium. Our data suggest that in mildly disabled RR-MS patients a covert impairment may be detected in the correlation between the structural (CC thickness) and functional (IHCoh) measures of homologous networks, whereas these two counterparts do not yet differ individually from controls. PMID:24486438

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

    PubMed

    Martn-Loeches, Manuel; Bruner, Emiliano; de la Cutara, Jos Manuel; Colom, Roberto

    2013-05-01

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

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

    PubMed Central

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

    2009-01-01

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

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

    PubMed

    İçer, Semra

    2013-10-01

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

  4. Light microscopic identification of immature glial cells in semithin sections of the developing mouse corpus callosum.

    PubMed Central

    Sturrock, R R

    1976-01-01

    Four distinct types of glial cell were recognized in the corpus callosum of young postnatal mice: the early glioblast; the small glioblast; the large glioblast; and the young astrocyte. As well as these, mature microglia could be recognized from birth. In semithin, toluidine blue stained sections early glioblasts had large, fair to moderately stained nuclei, and a thin rim of pale cytoplasm; small glioblasts had small, dark nuclei and a rim of darkly stained cytoplasm; large glioblasts had moderately unevenly stained nuclei and a thin rim of moderately stained cytoplasm; and young astrocytes had fairly small nuclei, moderately stained cytoplasm, and one or more processes, which could usually be seen extending for 5 mum or more from the perikaryon. Differential glial counts using the criteria described above, in conjunction with electron microscopic analysis, suggested that early glioblasts gave rise to small glioblasts and large glioblasts; that small glioblasts gave rise directly to astrocytes, large glioblasts, oligodendrocytes and possibly microglia; that large glioblasts formed oligodendrocytes only, and might be immature light oligodendrocytes; and that part of the microglial population might arise from vascular pericytes. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 9 Fig. 10 Fig. 11 Fig. 12 Fig. 13 Fig. 14 PMID:795801

  5. Orodental manifestations in cases with partial agenesis of corpus callosum-rare phenomena

    PubMed Central

    Bhambal, Annette M.; Bhambal, Ajay; Nair, Preeti; Bhambal, Sheela S.

    2015-01-01

    This article focuses on the associated signs and symptoms of patients with partial agenesis of the corpus callosum. The orodental manifestations of such cases have been given special weightage which will prove to be of great help to oral physician when encountered with such cases. Case details Two siblings, aged 14 and 16 years, reported with a chief complaint of severe crowding of teeth with mouth breathing habit. They were low birth-weight babies and had been born to non-consanguinous parents. The distinguishing features of these children were craniofacial abnormalities, delayed developmental milestones, mild mental retardation and abnormal gait. The nosological features and the clinical manifestations of this syndrome and the plausible autosomal recessive inheritance of this rare syndrome have been elicited. The diagnosis was based on characteristic phenotype, in particular striking craniofacial and skeletal abnormalities and neuroimaging. Conclusion It is a challenge for healthcare professionals to help these youths to maximize their potential as human beings and help them achieve a meaningful adulthood. On the other hand, diagnosing such cases can be a challenge to dentistry. A systematic protocol, if adhered, can lead to a more appropriate diagnosis. Managing such cases in a clinical setup involves a multispeciality and interdisciplinary approach. PMID:26258024

  6. Association between linear measurements of corpus callosum and gait in the elderly

    PubMed Central

    Brodoefel, Harald; Ramachandran, Ramesh; Pantol, Gustavo; Bergethon, Peter; Qiu, Wei Qiao; Scott, Tammy; Rojas, Rafael; Horger, Marius; Rosenberg, Irwin; Bhadelia, Rafeeque A.

    2015-01-01

    Purpose Segmentation and diffusion-tensor-imaging of the corpus callosum (CC) have been linked to gait impairment. However, such measurements are impracticable in clinical routine. The purpose of this study was to evaluate the association between simple linear measurements of CC thickness with gait. Methods Two hundred and seventy-two community-dwelling subjects underwent neurological assessment and brain MRI. Mid-sagittal reformats of T1-weighted images were used to determine CC thickness. The association of measurements with clinical evaluation of gait was assessed by multivariate regression, controlling for numerous clinical and imaging confounders. Differences in CC thickness were, moreover, compared between subgroups with no, moderate or severe impairment of gait. Results In univariate analyses, thickness of the genu and body of CC but not the splenium were associated with postural stability (P<0.01). Multivariate regression revealed thickness of CC genu as the only imaging variable independently associated with gait (P=0.01). Genu thickness was significantly different between subjects with high and low (P=0.0003) or high and moderate (P=0.001) risk of fall. Conclusion Atrophy of the CC genu is an imaging marker of gait impairment in the elderly suggesting higher risk of fall. Simple linear measurements of CC can help in MRI evaluation of patients with gait impairment. PMID:23512195

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

    PubMed

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

    2014-05-27

    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

  8. Transcriptome analysis of amoeboid and ramified microglia isolated from the corpus callosum of rat brain

    PubMed Central

    2012-01-01

    Background Microglia, the resident immune cells of the central nervous system (CNS), have two distinct phenotypes in the developing brain: amoeboid form, known to be amoeboid microglial cells (AMC) and ramified form, known to be ramified microglial cells (RMC). The AMC are characterized by being proliferative, phagocytic and migratory whereas the RMC are quiescent and exhibit a slow turnover rate. The AMC transform into RMC with advancing age, and this transformation is indicative of the gradual shift in the microglial functions. Both AMC and RMC respond to CNS inflammation, and they become hypertrophic when activated by trauma, infection or neurodegenerative stimuli. The molecular mechanisms and functional significance of morphological transformation of microglia during normal development and in disease conditions is not clear. It is hypothesized that AMC and RMC are functionally regulated by a specific set of genes encoding various signaling molecules and transcription factors. Results To address this, we carried out cDNA microarray analysis using lectin-labeled AMC and RMC isolated from frozen tissue sections of the corpus callosum of 5-day and 4-week old rat brain respectively, by laser capture microdissection. The global gene expression profiles of both microglial phenotypes were compared and the differentially expressed genes in AMC and RMC were clustered based on their functional annotations. This genome wide comparative analysis identified genes that are specific to AMC and RMC. Conclusions The novel and specific molecules identified from the trancriptome explains the quiescent state functioning of microglia in its two distinct morphological states. PMID:22697290

  9. Functional Topography of Human Corpus Callosum: An fMRI Mapping Study

    PubMed Central

    Fabri, Mara; Polonara, Gabriele

    2013-01-01

    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

  10. The corpus callosum in primates: processing speed of axons and the evolution of hemispheric asymmetry.

    PubMed

    Phillips, Kimberley A; Stimpson, Cheryl D; Smaers, Jeroen B; Raghanti, Mary Ann; Jacobs, Bob; Popratiloff, Anastas; Hof, Patrick R; Sherwood, Chet C

    2015-11-01

    Interhemispheric communication may be constrained as brain size increases because of transmission delays in action potentials over the length of axons. Although one might expect larger brains to have progressively thicker axons to compensate, spatial packing is a limiting factor. Axon size distributions within the primate corpus callosum (CC) may provide insights into how these demands affect conduction velocity. We used electron microscopy to explore phylogenetic variation in myelinated axon density and diameter of the CC from 14 different anthropoid primate species, including humans. The majority of axons were less than 1 m in diameter across all species, indicating that conduction velocity for most interhemispheric communication is relatively constant regardless of brain size. The largest axons within the upper 95th percentile scaled with a progressively higher exponent than the median axons towards the posterior region of the CC. While brain mass among the primates in our analysis varied by 97-fold, estimates of the fastest cross-brain conduction times, as conveyed by axons at the 95th percentile, varied within a relatively narrow range between 3 and 9 ms across species, whereas cross-brain conduction times for the median axon diameters differed more substantially between 11 and 38 ms. Nonetheless, for both size classes of axons, an increase in diameter does not entirely compensate for the delay in interhemispheric transmission time that accompanies larger brain size. Such biophysical constraints on the processing speed of axons conveyed by the CC may play an important role in the evolution of hemispheric asymmetry. PMID:26511047

  11. Inter-hemispheric Functional Connectivity Changes with Corpus Callosum Morphology in Multiple Sclerosis

    PubMed Central

    Zito, Giancarlo; Luders, Eileen; Tomasevic, Leo; Lupoi, Domenico; Toga, Arthur W.; Thompson, Paul M.; Rossini, Paolo M.; Filippi, Maria M.; Tecchio, Franca

    2014-01-01

    Multiple sclerosis (MS) affects myelin sheaths within the central nervous system, concurring to cause brain atrophy and neurodegeneration as well as gradual functional disconnections. To explore early signs of altered connectivity in MS from a structural and functional perspective, the morphology of corpus callosum (CC) was correlated with a dynamic inter-hemispheric connectivity index. Twenty mildly disabled patients affected by a relapsing-remitting (RR) form of MS (EDSS ? 3.5) and 15 healthy subjects underwent structural MRI to measure CC thickness over 100 sections and electroencephalography to assess a spectral coherence index between primary regions devoted to hand control, at rest and during an isometric handgrip. In patients, an overall CC atrophy was associated with increased lesion load. A less efficacious inter-hemispheric coherence during movement was associated with CC atrophy in sections interconnecting homologous primary motor areas (anterior mid-body). In healthy controls, less efficacious inter-hemispheric coherence at rest was associated with a thinner CC splenium. Our data suggest that in mildly disabled RR-MS patients a covert impairment may be detected in the correlation between the structural (CC thickness) and functional (inter-hemispheric coherence) measures of homologous networks, whereas these two counterparts do not yet differ individually from controls. PMID:24486438

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

    PubMed Central

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

    2014-01-01

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

  13. Crustal Anisotropy in Eastern Tibet

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  14. Heliospheric influence on the anisotropy of TeV cosmic rays

    SciTech Connect

    Zhang, Ming; Zuo, Pingbing; Pogorelov, Nikolai

    2014-07-20

    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.

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

    NASA Astrophysics Data System (ADS)

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

    1995-05-01

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

  16. Magnetic anisotropy data of CH2NCl

    NASA Astrophysics Data System (ADS)

    Kumar, M.; Gupta, R.

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

  17. Anisotropy of machine building materials

    NASA Technical Reports Server (NTRS)

    Ashkenazi, Y. K.

    1981-01-01

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

  18. Fraction Reduction through Continued Fractions

    ERIC Educational Resources Information Center

    Carley, Holly

    2011-01-01

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

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

    PubMed Central

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

    2013-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

    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.

  1. Longitudinal, regional and deformation-specific corpus callosum shape analysis for multiple sclerosis.

    PubMed

    Ishaq, Omer; Hamarneh, Ghassan; Tam, Roger; Traboulsee, Anthony

    2007-01-01

    The corpus callosum (CC) is an anatomical structure which connects the two brain hemispheres. Neurological diseases can cause atrophy of the CC resulting in a change in its size and shape. The measurement and analysis of this change is one of the goals of clinical research. We perform statistical analysis of the shape of the CC extracted from MR brain scans of a group of multiple sclerosis patients undergoing a longitudinal (serial) study. In contrast to the classical boundary-based, global shape variability measures, e.g. principal component analysis (PCA) of CC boundary vertices, we perform a deformation-specific PCA for analyzing the global and regional shape of the CC. This deformation-specific PCA is based on a medial-based shape representation. The adopted shape representation describes shape variability in terms of intuitive deformations (e.g. bending, stretching and thickness). We present qualitative and quantitative results for 412 MR images of the CC. We show that our method is successful in identifying and quantifying the effect of each type of deformation on the shape variability of the CC. In addition to analyzing the spatial shape variability in the CC, we explore shape changes as the disease progresses. Our method allows the exploration of the shape variability quantitatively (e.g. the amount of variance explained by a particular principal mode of shape variation) as well as in a qualitative visual manner (e.g. by visualizing, say, the 2nd principal mode of shape variation due to bending at the 4th sub-region of the CC) which is useful for developing an intuitive understanding of the effects of MS on the CC shape. PMID:18002404

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

    PubMed Central

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

    2010-01-01

    Alterations in the structure of the corpus callosum (CC) have been observed in schizophrenia. Offspring of schizophrenia parents have 1015 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

  3. Characterization of NO-producing neurons in the rat corpus callosum

    PubMed Central

    Barbaresi, Paolo; Fabri, Mara; Mensà, Emanuela

    2014-01-01

    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-μm 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

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

    PubMed Central

    2014-01-01

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

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

    PubMed Central

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

    2013-01-01

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

  6. Precipitate-induced plastic anisotropy: Explicit solutions of the plastic anisotropy due to plate-shaped precipitates

    SciTech Connect

    Lyttle, M.T.; Wert, J.A.

    1999-05-01

    In some aluminum alloys, the observed plastic anisotropy cannot be explained solely by the measured Taylor factor variation. Qualitatively, it has been suggested that this difference results from a secondary effect due to plate-shaped precipitates. Models addressing the effect of plastically-deforming and elastically-deforming precipitates have been previously proposed. In the present article, explicit solutions of the anisotropic strengthening increment are presented for the case of plate-shaped precipitates. These solutions allow a quantitative consideration of the effect of precipitates on different habit planes and of the effect due to stress aging. Generally, in fcc materials, precipitates on {l_brace}100{r_brace} habit planes are predicted to minimize the anisotropy due to texture; precipitates on {l_brace}111{r_brace} habit planes are predicted to accentuate the anisotropy due to texture; and precipitates on other habit planes are predicted to produce a minor effect resulting from an averaging over a greater number of crystallographically equivalent habit planes. Stress aging to alter the relative orientation distribution of a single precipitate type is predicted to produce only slight changes in the plastic anisotropy. Larger effects on the yield variation will be observed when stress aging alters the relative volume fractions of two precipitate types on different habit planes.

  7. Fractional damped oscillators and fractional forced oscillators

    NASA Astrophysics Data System (ADS)

    Chung, Won Sang; Jung, Min

    2014-01-01

    In this paper, we use fractional calculus to discuss fractional mechanics, where the time derivative is replaced with the fractional derivative of order ?. We deal with the motion of a body in a resisting medium where the retarding force is assumed to be proportional to the fractional velocity that is obtained by applying the fractional derivative to the position. The fractional oscillator problem, the fractional oscillator problem with resistance and the fractional forced oscillator problem are also studied

  8. Anisotropy Studies in Central Greece

    NASA Astrophysics Data System (ADS)

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

    2007-12-01

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

  9. Rare association of thin corpus callosum with infantile tremor syndrome in a 5.5-month-old infant

    PubMed Central

    Sharma, Chandra Madhur; Sharma, Deepti; Kumar, Romal; Ranjan, Rahul

    2015-01-01

    Infantile tremor syndrome (ITS) is a clinical disorder characterized by coarse tremors, anemia and regression of motor and mental milestones, presenting in malnourished children aged between 5 months and 3 years. Few reports of neuroimaging abnormalities in children with ITS are present. The most common finding of neuroimaging in ITS is cerebral atrophy with ex-vacuo enlargement of ventricles and subarachnoid space, some recent reports also showed pontine myelinolysis and cerebral hyperintensities. We did not find any report of thin corpus callosum associated with ITS in the literature. PMID:26557175

  10. Ion temperature anisotropy across a magnetotail reconnection jet

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

    A significant fraction of the energy released by magnetotail reconnection appears to go into ion heating, but this heating is generally anisotropic. We examine ARTEMIS dual-spacecraft observations of a long-duration magnetotail exhaust generated by antiparallel reconnection in conjunction with particle-in-cell simulations, showing spatial variations in the anisotropy across the outflow far (>100di) downstream of the X line. A consistent pattern is found in both the spacecraft data and the simulations: While the total temperature across the exhaust is rather constant, near the boundaries Ti,|| dominates. The plasma is well above the firehose threshold within patchy spatial regions at |BX|?[0.1,0.5]B0, suggesting that the drive for the instability is strong and the instability is too weak to relax the anisotropy. At the midplane (|BX|?0.1B0), Ti,?>Ti,|| and ions undergo Speiser-like motion despite the large distance from the X line.

  11. Anisotropy, inhomogeneity, and conservation laws

    NASA Astrophysics Data System (ADS)

    Olszewski, E. A.

    1983-10-01

    We consider two versions of Minkowski space, each of which is connected in a nontrivial way. In the first version, which corresponds physically to a static universe with one spatial dimension finite, we introduce a variation of the twin paradox in which neither twin undergoes any acceleration. The resolution of the paradox is shown to derive from the (global) anisotropy of this version of space-time. Furthermore, the (global) anisotropy is shown to imply the existence of a set of preferred inertial frames and the possibility of nonconservation of angular momentum in the absence of any torque. In the second version, which corresponds physically to a universe with one spatial dimension finite but expanding in time, we show that the (global) inhomogeneity of this version of space-time can cause nonconservation of energy and momentum in the absence of any force.

  12. Magnetic anisotropy in single clusters

    NASA Astrophysics Data System (ADS)

    Jamet, Matthieu; Wernsdorfer, Wolfgang; Thirion, Christophe; Dupuis, Vronique; Mlinon, Patrice; Prez, Alain; Mailly, Dominique

    2004-01-01

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

  13. [Cosmic Microwave Background (CMB) Anisotropies

    NASA Technical Reports Server (NTRS)

    Silk, Joseph

    1998-01-01

    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.

  14. A T1 and DTI fused 3D Corpus Callosum analysis in pre- vs. post-season contact sports players

    PubMed Central

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

    2015-01-01

    Sports related traumatic brain injury (TBI) is a worldwide public health issue, and damage to the corpus callosum (CC) has been considered as an important indicator of TBI. However, contact sports players suffer repeated hits to the head during the course of a season even in the absence of diagnosed concussion, and less is known about their effect on callosal anatomy. In addition, T1-weighted and diffusion tensor brain magnetic resonance images (DTI) have been analyzed separately, but a joint analysis of both types of data may increase statistical power and give a more complete understanding of anatomical correlates of subclinical concussions in these athletes. Here, for the first time, we fuse T1 surface-based morphometry and a new DTI analysis on 3D surface representations of the CCs into a single statistical analysis on these subjects. Our new combined method successfully increases detection power in detecting differences between pre- vs. post-season contact sports players. Alterations are found in the ventral genu, isthmus, and splenium of CC. Our findings may inform future health assessments in contact sports players. The new method here is also the first truly multimodal diffusion and T1-weighted analysis of the CC in TBI, and may be useful to detect anatomical changes in the corpus callosum in other multimodal datasets. PMID:26412925

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

    NASA Astrophysics Data System (ADS)

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

    2015-01-01

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

  16. DNA damage and oxidative injury are associated with hypomyelination in the corpus callosum of newborn Nbn(CNS-del) mice.

    PubMed

    Liu, B; Chen, X; Wang, Z Q; Tong, W M

    2014-02-01

    Nijmegen breakage syndrome (NBS), caused by mutation of the Nbn gene, is a recessive genetic disorder characterized by immunodeficiency, elevated sensitivity to ionizing radiation, chromosomal instability, microcephaly, and high predisposition to malignancies. To explore the underlying molecular mechanisms of NBS microcephaly, Frappart et al. previously inactivated Nbn gene in the central nervous system (CNS) of mice by the nestin-Cre targeting gene system and generated Nbn(CNS-del) mice. Here we first report that Nbn gene inactivation induces the defective proliferation and enhanced apoptosis of the oligodendrocyte precursor cells (OPCs), contributing to the severe hypomyelination of the nerve fibers of the corpus callosum. Under conditions of DNA damage and oxidative stress, the distinct regulatory roles of ATM-Chk2 signaling and AKT/mTOR signaling are responsible for the defective proliferation and enhanced apoptosis of the Nbn-deficient OPCs. In addition, specific HDAC isoforms may play distinctive roles in regulating the myelination of the Nbn-deficient OPCs. However, brain-derived neurotrophic factor and nerve growth factor stimulation attenuates the oxidative stress and thereby increases the proliferation of the Nbn-deficient OPCs, which is accompanied by upregulation of the AKT/mTOR/P70S6K signaling pathway. Taken together, these findings demonstrate that DNA damage and oxidative stress resulting from Nbn gene inactivation are associated with hypomyelination of the nerve fibers of corpus callosum. PMID:24272991

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

    PubMed Central

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

    2014-01-01

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

  18. Search for a positron anisotropy with PAMELA experiment

    NASA Astrophysics Data System (ADS)

    Panico, B.; Adriani, O.; Barbarino, G. C.; Bazilevskaya, G. A.; Bellotti, R.; Boezio, M.; Bogomolov, E. A.; Bongi, M.; Bonvicini, V.; Bottai, S.; Bruno, A.; Cafagna, F.; Campana, D.; Carlson, P.; Casolino, M.; Castellini, G.; De Donato, C.; De Santis, C.; De Simone, N.; Di Felice, V.; Formato, V.; Galper, A. M.; Giaccari, U.; Karelin, A. V.; Koldashov, S. V.; Koldobskiy, S.; Krutkov, S. Y.; Kvashnin, A. N.; Leonov, A.; Malakhov, V.; Marcelli, L.; Martucci, M.; Mayorov, A. G.; Menn, W.; Merg, M.; Mikhailov, V. V.; Mocchiutti, E.; Monaco, A.; Mori, N.; Munini, R.; Osteria, G.; Palma, F.; Pearce, M.; Picozza, P.; Ricci, M.; Ricciarini, S. B.; Sarkar, R.; Scotti, V.; Simon, M.; Sparvoli, R.; Spillantini, P.; Stozhkov, Y. I.; Vacchi, A.; Vannuccini, E.; Vasilyev, G. I.; Voronov, S. A.; Yurkin, Y. T.; Zampa, G.; Zampa, N.

    2015-09-01

    The PAMELA experiment has been collecting data since 2006; its results indicate a rise in the positron fraction with respect to the sum of electrons and positrons in the cosmic-ray (CR) spectrum above 10 GeV. This excess can be due to additional sources, as SNRs or pulsars, which can lead to an anisotropy in the local CR positron, detectable from current experiments. We report on the analysis on spatial distributions of positron events collected by PAMELA, taking into account also the geomagnetic field effects. No significant deviation from the isotropy has been observed.

  19. Cosmic Ray Anisotropy with KASCADE

    NASA Astrophysics Data System (ADS)

    Maier, G.; Antoni, T.; Apel, W. D.; Badea, F.; Bekk, K.; Bercuci, A.; Blmer, H.; Bozdog, H.; Brancus, I. M.; Bttner, C.; Chilingarian, A.; Daumiller, K.; Doll, P.; Engel, R.; Engler, J.; Feler, F.; Gils, H. J.; Glasstetter, R.; Haungs, A.; Heck, D.; Hrandel, J. R.; Iwan, A.; Kampert, K. H.; Klages, H. O.; Mathes, H. J.; Mayer, H. J.; Milke, J.; Mller, M.; Obenland, R.; Oehlschlger, J.; Ostapchenko, S.; Petcu, M.; Rebel, H.; Risse, M.; Schatz, G.; Schieler, H.; Scholz, J.; Thouw, T.; Ulrich, H.; van Buren, J.; Vardanyan, A.; Weindl, A.; Wochele, J.; Zabierowski, J.

    2003-07-01

    The anisotropy of cosmic rays with energies in the region of the knee in the energy spectrum is investigated in three different persp ectives based on the arrival directions of about 150 Mio. extensive air showers measured by KASCADE. The different analyses are a harmonic analysis of the right ascension distribution and a point source search of showers above 0.5 PeV as well as an auto correlation analysis of showers above 100 PeV. All three analyses agree inside the statistical limits with an isotropic distribution of the arrival directions of cosmic rays.

  20. Magnetic Anisotropy in the Radula of Chiton

    NASA Astrophysics Data System (ADS)

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

    2000-07-01

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

  1. Saturation-dependent anisotropy in the Hanford subsurface hydraulic conductivity

    NASA Astrophysics Data System (ADS)

    Blank, L.; Skinner, T.; Hunt, A.

    2006-12-01

    In previous work anisotropy in a fracture network was shown to provide a possible explanation for the observed scale-effect in the hydraulic conductivity of a carbonate aquifer. Use was made of a coordinate transformation and reference made to the transverse and longitudinal electrical conductivities of thin (disordered) solid films. An analogous approach is now developed to describe the inferred anisotropy of the hydraulic conductivity as a function of saturation in the Hanford subsurface. Here different soil types play the role of fractures of different apertures, while the spatial anisotropy is generated by soils of higher silt and clay fractions. A quasi- equilibrium condition (equal matric potentials) is implemented at matric potentials believed characteristic of the Hanford subsurface (several hundred centimeters) and theoretical results for the hydraulic conductivity (modified by known values at saturation) are used to develop the distribution of K values at the appropriate potential. The results are hoped to be relevant to the dispersion of a Tc plume. Work was supported by DOE grant DE-FG02-05ER64067 and -06ER64196 and NSF grant EAR 0609884

  2. Nonlinear CMB temperature anisotropy from gravitational perturbations

    SciTech Connect

    Gao Xian

    2010-11-15

    Nonlinear CMB temperature anisotropies up to the third order on large scales are calculated. On large scales and in the Sachs-Wolfe limit, we give the explicit expression for the observed temperature anisotropy in terms of the primordial curvature perturbation up to the third order. We derived the final bispectrum and trispectrum of anisotropies and the corresponding nonlinear parameters, in which the contributions to the observed non-Gaussianity from primordial perturbations and from the nonlinear mapping from primordial curvature perturbation to the temperature anisotropy are transparently separated.

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

    ERIC Educational Resources Information Center

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

    2014-01-01

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

  4. Fractional vector calculus for fractional advection dispersion

    NASA Astrophysics Data System (ADS)

    Meerschaert, Mark M.; Mortensen, Jeff; Wheatcraft, Stephen W.

    2006-07-01

    We develop the basic tools of fractional vector calculus including a fractional derivative version of the gradient, divergence, and curl, and a fractional divergence theorem and Stokes theorem. These basic tools are then applied to provide a physical explanation for the fractional advection-dispersion equation for flow in heterogeneous porous media.

  5. 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

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

    2014-01-01

    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 1163] 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=0.0100.028). 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

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

    PubMed Central

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

    2013-01-01

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

  7. Exome sequencing identifies recessive CDK5RAP2 variants in patients with isolated agenesis of corpus callosum.

    PubMed

    Jouan, Loubna; Ouled Amar Bencheikh, Bouchra; Daoud, Hussein; Dionne-Laporte, Alexandre; Dobrzeniecka, Sylvia; Spiegelman, Dan; Rochefort, Daniel; Hince, Pascale; Szuto, Anna; Lassonde, Maryse; Barbelanne, Marine; Tsang, William Y; Dion, Patrick A; Théoret, Hugo; Rouleau, Guy A

    2016-04-01

    Agenesis of the corpus callosum (ACC) is a common brain malformation which can be observed either as an isolated condition or as part of numerous congenital syndromes. Therefore, cognitive and neurological involvements in patients with ACC are variable, from mild linguistic and behavioral impairments to more severe neurological deficits. To date, the underlying genetic causes of isolated ACC remains elusive and causative genes have yet to be identified. We performed exome sequencing on three acallosal siblings from the same non-consanguineous family and identified compound heterozygous variants, p.[Gly94Arg];[Asn1232Ser], in the protein encoded by the CDK5RAP2 gene, also known as MCPH3, a gene previously reported to cause autosomal recessive primary microcephaly. Our findings suggest a novel role for this gene in the pathogenesis of isolated ACC. PMID:26197979

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

    PubMed Central

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

    2012-01-01

    Human amniotic epithelial cells were isolated from a piece of fresh amnion. Using immunocytochemical methods, we investigated the expression of neuronal phenotypes (microtubule-associated protein-2, glial fibrillary acidic protein and nestin) in human amniotic epithelial cells. The conditioned medium of human amniotic epithelial cells promoted the growth and proliferation of rat glial cells cultured in vitro, and this effect was dose-dependent. Human amniotic epithelial cells were further transplanted into the corpus striatum of healthy adult rats and the grafted cells could integrate with the host and migrate 12 mm along the nerve fibers in corpus callosum. Our experimental findings indicate that human amniotic epithelial cells may be a new kind of seed cells for use in neurograft. PMID:25806057

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

    PubMed Central

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

    1994-01-01

    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

  10. QL-07TREATMENT OF FATIGUE IN A PATIENT WITH CORPUS-CALLOSUM GLIOMA AND ATYPICAL SLEEP DISORDER

    PubMed Central

    Butts, Alissa; Johnson, Derek; Brown, Paul; Cerhan, Jane

    2014-01-01

    We present the case of a 53 year-old married gentleman with above-average IQ who has a high-grade glioma of the corpus callosum, severe fatigue, cognitive concerns, and an atypical sleep disorder. He has had severe daytime somnolence and poor concentration since childhood, with normal nighttime sleep. Since his teens, he has had two hours of alertness in the morning, followed by disabling sleepiness for the rest of the day. Epworth sleepiness scores have been extremely high (20 to 24). Diagnoses of ADHD, narcolepsy, and idiopathic hypersomnia had been applied, but he has not met full diagnostic criteria. From 2007 to 2012, escalating doses of stimulant medication were utilized, with the best response ("can attempt some household tasks" and "approaching a normal life" per his wife) on 400 mg modafinil, and 456 mg methylphenidate (seven times the recommended maximum). This allowed him to stay awake for some normal activities such as attending his child's baseball game. In June of 2012, the modafanil and methylphenidate were discontinued by his doctor because the sleep disorder could not be confirmed with polysomnograph and multiple sleep latency testing. The somnolence returned, and the patient became distraught and expressed suicidal ideation. He saw a psychotherapist who referred him to Neurology where the corpus callosum glioma was identified incidentally (biopsy confirmed grade III astrocytoma). Pre-treatment neuropsychological evaluation revealed impairment on digit-symbol coding (z= -2.0) and was otherwise normal. The tumor was treated with radiation and temozolamide, and is currently radiographically stable. Fatigue is an ongoing problem (Epworth = 17, he rates fatigue at 8/10). He takes 80 mg Adderall. He would like to resume the previous regimen and high dose of Ritalin. We explore practical and ethical considerations in the treatment of fatigue with special consideration for quality of life in the context of high-grade glioma.

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

    PubMed

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

    2015-08-14

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

  12. Seismic anisotropy beneath stable continental interiors

    NASA Astrophysics Data System (ADS)

    Fouch, Matthew J.; Rondenay, Stphane

    2006-10-01

    A robust knowledge of seismic anisotropy beneath the continents is essential to our understanding of plate tectonic theory, as anisotropy provides a unique constraint on the character of past and present deformation in the lithosphere and sublithospheric mantle. This review paper summarizes the range of techniques currently available to image seismic anisotropy with passive source seismic data, and addresses current issues surrounding the observation and interpretation of continental seismic anisotropy. To this end, we present case studies for four regions where seismic anisotropy has been extensively investigated in recent years: eastern North America, the Canadian Shield, Australia, and southern Africa. Based on this full suite of results, we infer that stable continental regions generally contain seismic anisotropy that is clearly located within both the lithosphere and the sublithospheric mantle, usually to depths of at least 200 km and perhaps more. An implication of these results is that tectonic plates are, at most, only partially coupled to the underlying mantle. The results from these case studies also demonstrate that while remarkable progress in seismic anisotropy imaging has been achieved in recent years, it is clear that much more work will be required to adequately understand the origin of continental seismic anisotropy. We suggest that a more robust characterization of anisotropic parameters can only be achieved by integrating complementary seismic datasets and by incorporating constraints from key related datasets from mineral physics, magnetotellurics, gravity, and geodesy.

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

    NASA Astrophysics Data System (ADS)

    Koesoemadinata, Adam P.; McMechan, George A.

    2004-10-01

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

  14. Global Tomography of Seismic Anisotropy and Interpretations

    NASA Astrophysics Data System (ADS)

    Montagner, Jean-Paul

    2013-04-01

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

  15. Seismic anisotropy observed in upper oceanic crust

    SciTech Connect

    Stephen, R.A.

    1981-08-01

    Seismic anisotropy in the upper 150Om. of oceanic basement has been observed by polarization analysis of three-component bore-hole seismometer records. The most convincing evidence for the anisotropy is shear wave splitting for explosive sources at four azimuths. Compressional wave particle motion deviations suggestive of anisotropy are also observed but they may be caused by lateral inhomogeneities. The anisotropy was not resolved by travel-time analysis. The observed velocities and particle motions in the horizontal plane can be modelled to within a standard deviation by assuming a perfectly elastic, homogeneous, anisotropic layer 2 with hexagonal symmetry and a horizontal symmetry axis. The most probable cause of the anisotropy is preferred crack orientation.

  16. Ratcheting fluid with geometric anisotropy

    NASA Astrophysics Data System (ADS)

    Thiria, Benjamin; Zhang, Jun

    2015-02-01

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

  17. Ratcheting Fluid using Geometric Anisotropy

    NASA Astrophysics Data System (ADS)

    Thiria, Benjamin; Zhang, Jun

    2010-11-01

    We discuss a new type of pump that can effectively transport fluids using vibrational motion imposed onto shapes with anisotropy. In our experiment, two asymmetric, sawtooth-like structures are placed facing each other and form a fluid channel. This channel is then forced to open and close periodically. Under symmetric, reciprocal motion, fluid fills in the gap during the expansion phase of the channel and is then forced out during contraction. Since the fluid experiences different impedence when it takes different directions in the gap, the stagnation point that separates flows of two directions changes within one driving period. As a result, fluid is transported or pumped from one end of the gap to the other. This ratcheting effect of fluid is demonstrated through our measurements and its working principle is discussed in some detail. We also discuss the potential applications of this vibratory fluid pump.

  18. Anisotropy in Pulsar Interstellar Scattering

    NASA Astrophysics Data System (ADS)

    Rickett, Barney

    2006-12-01

    Pulsar observers have to contend with several effects of propagation through the ionized interstellar medium. I review those effects and how they can be used to study the interstellar plasma. Pulsars are normally observed under conditions of strong scintillation and show both diffractive and refractive effects. I emphasize the diffractive scintillation as exhibited in the dynamic spectrum and in its converse -- pulse broadening. From Parkes observations of the pulse broadening of PSR J1644-45, I estimate the inner scale in an interstellar region of strong plasma turbulence to be about 100 km. I discuss the representation of dynamic spectra in terms of their ``secondary spectra'' and show how the arcs, that are often revealed, are related to both angular broadening and pulse broadening. Anisotropy in the scattering both changes the scattered pulse shape but also enhances the visibility of the arcs.

  19. Texture induced microwave background anisotropies

    SciTech Connect

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

    1994-03-01

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

  20. The influence of magnetic aftereffects on the magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Mashukov, A.; Mashukova, A.

    2012-04-01

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

  1. Azimuthal anisotropy of the Pacific region

    NASA Astrophysics Data System (ADS)

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

    2006-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-08-01

    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.

  3. Anisotropy in a fractal model of conductivity

    NASA Astrophysics Data System (ADS)

    Kneevi?, Milan

    1992-04-01

    Using an exact set of recursion relations we study the anisotropy of dc electrical conductivity on Dhar's modified rectangular lattice of index p. It is found that in the limit of large values of p the asymptotic ratio of parallel to vertical macroscopic conductivity approaches the value 2p {2}/{3}. The opposite limit of low anisotropy, p ? 1, is studied by means of infinitesimal recursion relations. We discuss the influence of anisotropy on critical behavior of the model and make a comparison with some other lattice models.

  4. Apparent resistivity of azimuthal anisotropy layered media

    NASA Astrophysics Data System (ADS)

    Ruan, Ai-Guo; Mao, Tong-En; Li, Qing-He; Ge, Shuang-Cheng

    2002-09-01

    The electric field, equations of boundary conditions and calculation formula of apparent resistivity are derived for azimuthal anisotropy layered media with DC method based on anisotropic Ohms law. Taking Schlumberger symmetric system as an example and using recurrence formula of nuclear function, the paper theoretically simulates a model of four layers with the same anisotropy coefficient for each layer. The deep sounding curves of resistivity and the pattern of contours are obtained for the model. The results shows the theoretical formula of this paper is correct, the deep sounding curves not only exhibit the difference of resistivity among layers but also indicate the anisotropy characteristics of layers.

  5. Mechanical anisotropy of the Yucca Mountain tuffs

    SciTech Connect

    Price, R.H.; Boyd, P.J.; Martin, R.J.; Haupt, R.W.; Noel, J.S.

    1991-12-31

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

  6. Macroscopic anisotropy in AA5019A sheets

    SciTech Connect

    Choi, S.H.; Brem, J.C.; Barlat, F.; Oh, K.H.

    2000-05-11

    The macroscopic anisotropy for typical texture components in aluminum alloys and AA5019A sheet samples (H48 and O temper conditions) were investigated. In order to simultaneously consider the effects of morphological texture and crystallographic texture on macroscopic anisotropy, predictions of plastic properties were carried out using a full-constraints Taylor model and a visco-plastic self-consistent (VPSC) polycrystal model. The yield stress and r-value (width-to-thickness plastic strain ratio in uniaxial tension) anisotropy predicted using the VPSC model were in good agreement with experimental data.

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

    PubMed Central

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

    2013-01-01

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

  8. Anisotropy of X-Ray Bursts from Neutron Stars with Concave Accretion Disks

    NASA Astrophysics Data System (ADS)

    He, C.-C.; Keek, L.

    2016-03-01

    Emission from neutron stars and accretion disks in low-mass X-ray binaries is anisotropic. The non-spherical shape of the disk as well as blocking of the neutron star by the disk make the observed flux dependent on the inclination angle of the disk with respect to the line of sight. This is of importance for the interpretation of thermonuclear X-ray bursts from neutron stars. Because part of the X-ray burst is reflected off the disk, the observed burst flux depends on the anisotropies for both direct emission from the neutron star and reflection off the disk. This influences measurements of source distance, mass accretion rate, and constraints on the neutron star’s equation of state. Previous predictions of the anisotropy factors assumed a geometrically flat disk. Detailed observations of two so-called superbursts allowed for the direct and the reflected burst fluxes to each be measured separately. The reflection fraction was much higher than what the anisotropies of a flat disk can account for. We create numerical models to calculate the anisotropy factors for different disk shapes, including concave disks. We present the anisotropy factors of the direct and reflected burst fluxes separately, as well as the anisotropy of the persistent flux. Reflection fractions substantially larger than unity are produced in the case where the inner accretion disk increases steeply in height, such that part of the star is blocked from view. Such a geometry could possibly be induced by the X-ray burst if X-ray heating causes the inner disk to puff up.

  9. Pressure anisotropy in Jupiter's magnetodisc

    NASA Astrophysics Data System (ADS)

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

    2013-09-01

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

  10. Cosmic Defects and CMB Anisotropy

    NASA Astrophysics Data System (ADS)

    Pogosian, Levon

    Recent measurements of the cosmic microwave background (CMB) anisotropies by BOOMERANG and MAXIMA collaborations have tightened the observational constraints on theories of structure formation. They disagree with the predictions of conventional topological defect models. Considering the fact that topological defects are predicted by the majority of realistic particle physics models, the exact nature of the constraints imposed by the recent data on the population and the properties of the defects must be fully understood. We show that the predictions of current cosmic string models can be brought into a closer agreement with the observations by choosing a closed universe with ? = 1.3 and by including the effects of the small-scale structure and radiation products of the strings. These alone, however, are not sufficient for obtaining a good fit to the measured shape of the angular power spectrum. To fit the data cosmic strings would either have to be correlated on large (perhaps superhorizon) scales or would have to possess a higher degree of coherence, i.e. be more ``time-correlated''.

  11. Matrix fractional systems

    NASA Astrophysics Data System (ADS)

    Tenreiro Machado, J. A.

    2015-08-01

    This paper addresses the matrix representation of dynamical systems in the perspective of fractional calculus. Fractional elements and fractional systems are interpreted under the light of the classical Cole-Cole, Davidson-Cole, and Havriliak-Negami heuristic models. Numerical simulations for an electrical circuit enlighten the results for matrix based models and high fractional orders. The conclusions clarify the distinction between fractional elements and fractional systems.

  12. Atomic scale evolution of magnetic anisotropies

    NASA Astrophysics Data System (ADS)

    Bland, J. A. C.; Hope, S.; Tselepi, M.; Choi, B.

    1998-03-01

    The results of in situ studies of the evolution of the magnetic anisotropy of Co(100) and Co(110) epitaxial films are discussed. It is shown that uniaxial magnetic anisotropies are the generic signature of symmetry breaking atomic and nm scale structures, e.g. steps, clusters, islands revealed by scanning tunnelling microscopy (STM) studies, and are strongly affected by nonmagnetic overlayers. However, the thickness dependent behaviour is surprisingly complex, with strong changes in anisotropy behaviour occurring with submonolayer depositions of nonmagnetic overlayers. These effects cannot be understood within the usual framework of the Nel model but are discussed in terms of several contributing mechanisms, e.g. strain, dipolar interactions and edge and surface anisotropies.

  13. Magnetic anisotropy due to the Casimir effect

    SciTech Connect

    Metalidis, G.; Bruno, P.

    2010-02-15

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

  14. SOLARMAX/Electron Pitch Angle Anisotropy Distributions

    NASA Technical Reports Server (NTRS)

    McKenzie, David L.; Anderson, Phillip C.

    2002-01-01

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

  15. Cellulose and the Control of Growth Anisotropy

    SciTech Connect

    Tobias I. Baskin

    2004-04-01

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

  16. Imprint of a 2 Million Year Old Source on the Cosmic-Ray Anisotropy

    NASA Astrophysics Data System (ADS)

    Savchenko, V.; Kachelrie, M.; Semikoz, D. V.

    2015-08-01

    We study numerically the anisotropy of the cosmic-ray (CR) flux emitted by a single source calculating the trajectories of individual CRs. We show that the contribution of a single source to the observed anisotropy is determined solely by the fraction the source contributes to the total CR intensity, its age, and its distance and does not depend on the CR energy at late times. Therefore, the observation of a constant dipole anisotropy indicates that a single source dominates the CR flux in the corresponding energy range. A natural explanation for the plateau between 2-20 TeV observed in the CR anisotropy is thus the presence of a single, nearby source. For the source age of 2 Myr, as suggested by the explanation of the antiproton and positron data from PAMELA and AMS-02 through a local source, we determine the source distance as 200 pc. Combined with the contribution of the global CR sea calculated in the escape model, we can explain qualitatively the data for the dipole anisotropy. Our results suggest that the assumption of a smooth CR source distribution should be abandoned between ?200 GeV and 1 PeV.

  17. Grain size dependence of coercivity in magnetic metal-insulator nanogranular films with uniaxial magnetic anisotropy

    NASA Astrophysics Data System (ADS)

    Yao, Dongsheng; Ge, Shihui; Zhou, Xueyun; Zuo, Huaping

    2010-04-01

    Excellent soft magnetic properties and appropriate uniaxial magnetic anisotropy field have been achieved in a wide metal volume fraction (x) range for as-deposited (Fe65Co35)x(SiO2)1-x granular films fabricated by magnetron sputtering. With decreasing x from 0.86 to 0.53, the coercive force of easy axis Hce decreases clearly and shows the minimum value (Hce=0.85 Oe) at x =0.53. More importantly, not only nanoscale grain-size D contributing to small coercivity is proved, but also a D3 dependence of Hce is observed in the range of 0.53anisotropy model of Suzuki and Herzer, the grain-size D dependence of coercivity Hce in our metal-insulator granular film system was analyzed. Analyze results indicate that strong coherent uniaxial anisotropy which dominates over the random anisotropy ?K1? of magnetic grains obtained by the random anisotropy model can be responsible for the D3 dependence of the coercivity Hce. In addition, in the range of 0.42

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

    PubMed

    Zolmajd-Haghighi, Zahra; Hanley, Quentin S

    2014-04-01

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

  19. ANISOTROPY DETERMINATIONS IN EXCHANGE SPRING MAGNETS.

    SciTech Connect

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

    2002-08-18

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

  20. Fractional vector calculus and fractional Maxwell's equations

    SciTech Connect

    Tarasov, Vasily E.

    2008-11-15

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

  1. Magnetic anisotropy in pyroxene single crystals

    NASA Astrophysics Data System (ADS)

    Biedermann, Andrea Regina; Hirt, Ann Marie; Pettke, Thomas; Bender Koch, Christian

    2014-05-01

    Anisotropy of magnetic susceptibility (AMS) is often used as a proxy for the mineral fabric in a rock. This requires understanding the intrinsic magnetic anisotropy of the minerals that define the rock fabric. With their prismatic habit, pyroxenes describe the texture in mafic and ultramafic rocks. Magnetic anisotropy in pyroxene crystals often arises from both paramagnetic and ferromagnetic components that can be separated from high-field magnetic data. The paramagnetic component is related to the silicate lattice, whereas the ferromagnetic part arises from the magnetic properties of ferromagnetic inclusions that were further characterized by isothermal remanent magnetization measurements. These inclusions often have needle-like habit and are located on the well-defined cleavage planes within the pyroxenes. We characterize low-field and high-field AMS in pyroxene single crystals of diverse orthopyroxene and clinopyroxene minerals. In addition to the magnetic measurements, we analyzed their chemical composition and Fe2+/Fe3+ distribution. The anisotropy arising from inclusions in some augite crystals displays consistent principal susceptibility directions, whereas no preferred orientation is found in other crystals. The principal susceptibilities of the paramagnetic component can be related to the crystal lattice, with the intermediate susceptibility parallel to the b-axis, and minimum and maximum in the a-c-plane for diopside, augite and spodumene. The degree of anisotropy increases with iron concentration. Aegirine shows a different behavior; not only is its maximum susceptibility parallel to the c-axis, but the anisotropy degree is also lower in relation to its iron concentration. This possibly relates to a predominance of Fe3+ in aegirine, whereas Fe2+ is dominant in the other minerals. In orthopyroxene, the maximum susceptibility is parallel to the c-axis and the minimum is parallel to b. The degree of anisotropy increases linearly with iron concentration. The difference in principal directions between clino- and orthopyroxene reflects their different crystal structure; in clinopyroxene, iron mainly occupies M1 sites, whereas it prefers the distorted M2 sites in orthopyroxene. The difference in anisotropy degree between aegirine and the other clinopyroxenes suggests that Fe2+ causes a stronger anisotropy than Fe3+. Thus, the magnetic anisotropy in pyroxenes is mainly dominated by the concentration, oxidation state and site occupancy of iron. The results from this study are important when interpreting magnetic fabrics in ultramafic rocks that contain both olivine and pyroxenes.

  2. Cosmic microwave background anisotropies in the timescape cosmology

    NASA Astrophysics Data System (ADS)

    Nazer, M. Ahsan; Wiltshire, David L.

    2015-03-01

    We analyze the spectrum of cosmic microwave background (CMB) anisotropies in the timescape cosmology: a potentially viable alternative to homogeneous isotropic cosmologies without dark energy. We exploit the fact that the timescape cosmology is extremely close to the standard cosmology at early epochs to adapt existing numerical codes to produce CMB anisotropy spectra, and to match these as closely as possible to the timescape expansion history. A variety of matching methods are studied and compared. We perform Markov chain Monte Carlo analyses on the parameter space, and fit CMB multipoles 50 ???2500 to the Planck satellite data. Parameter fits include a dressed Hubble constant, H0=61.0 km sec-1 Mpc-1 (1.3 % stat) (8 % sys), and a present void volume fraction fv 0=0.627 (2.3 % stat) (13 % sys). We find best fit likelihoods which are comparable to that of the best fit ? CDM cosmology in the same multipole range. In contrast to earlier results, the parameter constraints afforded by this analysis no longer admit the possibility of a solution to the primordial lithium abundance anomaly. This issue is related to a strong constraint between the ratio of baryonic to nonbaryonic dark matter and the ratio of heights of the second and third acoustic peaks, which cannot be changed as long as the standard cosmology is assumed up to the surface of last scattering. These conclusions may change if backreaction terms are also included in the radiation-dominated primordial plasma.

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

    PubMed Central

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

    2015-01-01

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

  4. Restricted diffusion in the splenium of the corpus callosum in organophosphate induced delayed neuropathy: case report and review of literatures

    PubMed Central

    Wang, Jie; Shao, Yankun; Shi, Kai; Yang, Hong; Li, Miao

    2015-01-01

    We described a 35 year-old female who developed organophosphate induced delayed neuropathy (OPIDN) with an unusal clinical manifestation and neuroradiological presentation. Case report: A 35-year-old woman came into contact with organophosphate pesticide by remissly inhalation. She got transient unconsciousness lasting for nearly 2 hours and developed transient hematuria and hyperhidrotic subsequently. She received atropine as treatment and got a satisfying recovery and was hospital discharged without any symptoms. But 20 days later the patient displayed symptoms including headache, vertigo, mental and memory decline, and was hospitalized again. Clinical manifestations, laboratorial findings, images data will be presented. The brain magnetic resonance imaging (MRI) showed an unusal neuroradiological presentation characterized by restricted diffusion in the splenium of the corpus callosum. The patient recovered satisfactorily after administration of corticosteroids and immunogloblin. Conclusion: OPIDN may develop in some susceptible individuals even by inhalation and sometimes with central nervous system involvement. Treatment with corticosteroids and intravenous immunogloblins was found to achieve good results. PMID:26550404

  5. SLC1A4 mutations cause a novel disorder of intellectual disability, progressive microcephaly, spasticity and thin corpus callosum.

    PubMed

    Heimer, G; Marek-Yagel, D; Eyal, E; Barel, O; Oz Levi, D; Hoffmann, C; Ruzzo, E K; Ganelin-Cohen, E; Lancet, D; Pras, E; Rechavi, G; Nissenkorn, A; Anikster, Y; Goldstein, D B; Ben Zeev, B

    2015-10-01

    Two unrelated patients, presenting with significant global developmental delay, severe progressive microcephaly, seizures, spasticity and thin corpus callosum (CC) underwent trio whole-exome sequencing. No candidate variant was found in any known genes related to the phenotype. However, crossing the data of the patients illustrated that they both manifested pathogenic variants in the SLC1A4 gene which codes the ASCT1 transporter of serine and other neutral amino acids. The Ashkenazi patient is homozygous for a deleterious missense c.766G>A, p.(E256K) mutation whereas the Ashkenazi-Iraqi patient is compound heterozygous for this mutation and a nonsense c.945delTT, p.(Leu315Hisfs*42) mutation. Structural prediction demonstrates truncation of significant portion of the protein by the nonsense mutation and speculates functional disruption by the missense mutation. Both mutations are extremely rare in general population databases, however, the missense mutation was found in heterozygous mode in 1:100 Jewish Ashkenazi controls suggesting a higher carrier rate among Ashkenazi Jews. We conclude that SLC1A4 is the disease causing gene of a novel neurologic disorder manifesting with significant intellectual disability, severe postnatal microcephaly, spasticity and thin CC. The role of SLC1A4 in the serine transport from astrocytes to neurons suggests a possible pathomechanism for this disease and implies a potential therapeutic approach. PMID:26138499

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

    PubMed Central

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

    2015-01-01

    This report describes a rare case of a patient with lipoma presenting with epileptic seizures associated with expanding perifocal edema. The patient was a 48-year-old man who presented with loss of consciousness and convulsions. Magnetic resonance imaging (MRI) revealed a calcified mass in the corpus callosum with perifocal edema causing mass effect. An interhemispheric approach was used to biopsy the mass lesion. Histological examination revealed typical adipose cells, along with hamartomatous components. These components contained neurofilament and S-100-positive structures showing marked calcification. Fibrous cells immunoreactive for ?-smooth muscle actin and epithelial membrane antigen proliferated with focal granulomatous inflammatory changes. MIB-1 index was approximately 5% in immature cells observed in granulomatous areas. We thus suspected a coexisting neoplastic component. The residual lesion persisted in a dormant state for 2 years following biopsy. Surgical resection of a lipoma is extremely difficult and potentially dangerous. However, in the present case, the lesion was accompanied by atypical, expanding, and perifocal edema. Surgical treatment was inevitable for the purpose of histological confirmation, considering differential diagnoses such as dermoid, epidermoid, and glioma. In the end, anticonvulsant therapy proved effective for controlling epileptic seizures. PMID:26078892

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

    PubMed

    Mazzuoccolo, Luis D; Martnez, Mara Florencia; Muchnik, Carolina; Azurmendi, Pablo J; Stengel, Fernando

    2014-01-01

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

  8. Corpus Callosum Segment Circumference Is Associated With Response Control in Children With Attention-Deficit Hyperactivity Disorder (ADHD)

    PubMed Central

    McNally, Melanie A.; Crocetti, Deana; Mahone, E. Mark; Denckla, Martha B.; Suskauer, Stacy J.; Mostofsky, Stewart H.

    2010-01-01

    Response control is impaired in attention-deficit hyperactivity disorder (ADHD). Given the corpus callosum's role in response control, we compared callosal morphology in 64 children with ADHD and 64 typically developing children, aged 7 to 13 years, and investigated the relationships between callosal morphology and response control. Area and circumference of 5 callosal segments (genu, rostral body, midbody, isthmus, and splenium) were normalized for cerebral volume and examined for correlation with mean reaction time, intrasubject variability, and/or commission error rate from a go/no-go task. There were no between-group differences in segment areas or circumferences. Reaction time correlated with midbody circumference for boys with ADHD and isthmus circumference for girls with ADHD. For the entire cohort, rostral body circumference correlated with intra-subject variability. Impaired response control in ADHD is associated with anomalies in frontal interhemispheric connections. Future studies examining callosal shape will illuminate the anatomic basis of correlations between callosal segment circumference and response control. PMID:20139403

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

    PubMed Central

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

    2010-01-01

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

  10. A nonsense variant in HERC1 is associated with intellectual disability, megalencephaly, thick corpus callosum and cerebellar atrophy.

    PubMed

    Nguyen, Lam Son; Schneider, Taiane; Rio, Marlne; Moutton, Sbastien; Siquier-Pernet, Karine; Verny, Florine; Boddaert, Nathalie; Desguerre, Isabelle; Munich, Arnold; Rosa, Jos Luis; Cormier-Daire, Valrie; Colleaux, Laurence

    2016-03-01

    Megalencephaly is a congenital condition characterized by severe overdeveloped brain size. This phenotype is often caused by mutations affecting the RTK/PI3K/mTOR (receptor tyrosine kinase-phosphatidylinositol-3-kinase-AKT) signaling and its downstream pathway of mammalian target of rapamycin (mTOR). Here, using a whole-exome sequencing in a Moroccan consanguineous family, we show that a novel autosomal-recessive neurological condition characterized by megalencephaly, thick corpus callosum and severe intellectual disability is caused by a homozygous nonsense variant in the HERC1 gene. Assessment of the primary skin fibroblast from the proband revealed complete absence of the HERC1 protein. HERC1 is an ubiquitin ligase that interacts with tuberous sclerosis complex 2, an upstream negative regulator of the mTOR pathway. Our data further emphasize the role of the mTOR pathway in the regulation of brain development and the power of next-generation sequencing technique in elucidating the genetic etiology of autosomal-recessive disorders and suggest that HERC1 defect might be a novel cause of autosomal-recessive syndromic megalencephaly. PMID:26153217

  11. Unfolding Fraction Multiplication

    ERIC Educational Resources Information Center

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

    2011-01-01

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

  12. Initialized Fractional Calculus

    NASA Technical Reports Server (NTRS)

    Lorenzo, Carl F.; Hartley, Tom T.

    2000-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Matczak, Micha?; Szyma?ski, Bogdan; Ku?wik, Piotr; Urbaniak, Maciej; Stobiecki, Feliks; Kurant, Zbigniew; Maziewski, Andrzej; Lengemann, Daniel; Ehresmann, Arno

    2014-08-01

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

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

    PubMed Central

    2014-01-01

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

  15. Tempered fractional calculus

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2010-06-01

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

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

    SciTech Connect

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

    2010-06-15

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

  18. Galaxy cluster baryon fractions revisited

    SciTech Connect

    Gonzalez, Anthony H.; Sivanandam, Suresh; Zabludoff, Ann I.; Zaritsky, Dennis

    2013-11-20

    We measure the baryons contained in both the stellar and hot-gas components for 12 galaxy clusters and groups at z ? 0.1 with M = 1-5 10{sup 14} M {sub ?}. This paper improves upon our previous work through the addition of XMM-Newton X-ray data, enabling measurements of the total mass and masses of each major baryonic componentintracluster medium, intracluster stars, and stars in galaxiesfor each system. We recover a mean relation for the stellar mass versus halo mass, M{sub ?}?M{sub 500}{sup ?0.520.04}, that is 1? shallower than in our previous result. We confirm that the partitioning of baryons between the stellar and hot-gas components is a strong function of M {sub 500}; the fractions of total mass in stars and X-ray gas within a sphere of radius r {sub 500} scale as f{sub ?}?M{sub 500}{sup ?0.450.04} and f{sub gas}?M{sub 500}{sup 0.260.03}, respectively. We also confirm that the combination of the brightest cluster galaxy and intracluster stars is an increasingly important contributor to the stellar baryon budget in lower halo masses. Studies that fail to fully account for intracluster stars typically underestimate the normalization of the stellar baryon fraction versus M {sub 500} relation by ?25%. Our derived stellar baryon fractions are also higher, and the trend with halo mass weaker, than those derived from recent halo occupation distribution and abundance matching analyses. One difference from our previous work is the weak, but statistically significant, dependence here of the total baryon fraction upon halo mass: f{sub bary}?M{sub 500}{sup 0.160.04}. For M {sub 500} ? 2 10{sup 14}, the total baryon fractions within r {sub 500} are on average 18% below the universal value from the seven year Wilkinson Microwave Anisotropy Probe (WMAP) analysis, or 7% below for the cosmological parameters from the Planck analysis. In the latter case, the difference between the universal value and cluster baryon fractions is less than the systematic uncertainties associated with the M {sub 500} determinations. The total baryon fractions exhibit significant scatter, particularly at M {sub 500} < 2 10{sup 14} M {sub ?} where they range from 60%-90%, or 65%-100%, of the universal value for WMAP7 and Planck, respectively. The ratio of the stellar-to-gas mass within r {sub 500} (M {sub *}/M {sub gas}), a measure of integrated star-formation efficiency, strongly decreases with increasing M {sub 500}. This relation is tight, with an implied intrinsic scatter of 12%. The fact that this relation remains tight at low mass implies that the larger scatter in the total baryon fractions at these masses arises from either true scatter in the total baryon content or observational scatter in M {sub 500} rather than late-time physical processes such as redistribution of gas to beyond r {sub 500}. If the scatter in the baryon content at low mass is physical, then our results imply that in this mass range, the integrated star-formation efficiency rather than the baryon fraction that is constant at fixed halo mass.

  19. Turbulence anisotropy and the SO3 description.

    PubMed

    Staicu, Adrian; Vorselaars, Bart; van de Water, Willem

    2003-10-01

    We study strongly turbulent windtunnel flows with controlled anisotropy. Using a recent formalism based on angular momentum and the irreducible representations of the SO(3) rotation group, we attempt to extract this anisotropy from the angular dependence of second-order structure functions. Our instrumentation allows a measurement of both the separation and the angle dependence of the structure function. In axisymmetric turbulence which has a weak anisotropy, this more extended information produces ambiguous results. In more strongly anisotropic shear turbulence, the SO(3) description enables one to find the anisotropy scaling exponent. The key quality of the SO(3) description is that structure functions are a mixture of algebraic functions of the scale with exponents ordered such that the contribution of anisotropies diminishes at small scales. However, we find that in third-order structure functions of homogeneous shear turbulence the anisotropic contribution is always large and of the same order of magnitude as the isotropic part. Our results concern the minimum instrumentation needed to determine the parameters of the SO(3) description, and raise several questions about its ability to describe the angle dependence of high-order structure functions. PMID:14683040

  20. Turbulence anisotropy and the SO(3) description

    NASA Astrophysics Data System (ADS)

    Staicu, Adrian; Vorselaars, Bart; van de Water, Willem

    2003-10-01

    We study strongly turbulent windtunnel flows with controlled anisotropy. Using a recent formalism based on angular momentum and the irreducible representations of the SO(3) rotation group, we attempt to extract this anisotropy from the angular dependence of second-order structure functions. Our instrumentation allows a measurement of both the separation and the angle dependence of the structure function. In axisymmetric turbulence which has a weak anisotropy, this more extended information produces ambiguous results. In more strongly anisotropic shear turbulence, the SO(3) description enables one to find the anisotropy scaling exponent. The key quality of the SO(3) description is that structure functions are a mixture of algebraic functions of the scale with exponents ordered such that the contribution of anisotropies diminishes at small scales. However, we find that in third-order structure functions of homogeneous shear turbulence the anisotropic contribution is always large and of the same order of magnitude as the isotropic part. Our results concern the minimum instrumentation needed to determine the parameters of the SO(3) description, and raise several questions about its ability to describe the angle dependence of high-order structure functions.

  1. The expected anisotropy in solid inflation

    SciTech Connect

    Bartolo, Nicola; Ricciardone, Angelo; Peloso, Marco; Unal, Caner E-mail: peloso@physics.umn.edu E-mail: unal@physics.umn.edu

    2014-11-01

    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 F{sup 2} gives frozen and scale invariant vector perturbations on superhorizon scales.

  2. Preferred orientation and elastic anisotropy in shales.

    SciTech Connect

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

    2007-03-01

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

  3. Anisotropy in solar wind plasma turbulence.

    PubMed

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

    2015-05-13

    A review of spectral anisotropy and variance anisotropy for solar wind fluctuations is given, with the discussion covering inertial range and dissipation range scales. For the inertial range, theory, simulations and observations are more or less in accord, in that fluctuation energy is found to be primarily in modes with quasi-perpendicular wavevectors (relative to a suitably defined mean magnetic field), and also that most of the fluctuation energy is in the vector components transverse to the mean field. Energy transfer in the parallel direction and the energy levels in the parallel components are both relatively weak. In the dissipation range, observations indicate that variance anisotropy tends to decrease towards isotropic levels as the electron gyroradius is approached; spectral anisotropy results are mixed. Evidence for and against wave interpretations and turbulence interpretations of these features will be discussed. We also present new simulation results concerning evolution of variance anisotropy for different classes of initial conditions, each with typical background solar wind parameters. PMID:25848082

  4. The expected anisotropy in solid inflation

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

    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.

  5. Ion anisotropies in the outer Jovian magnetosphere

    SciTech Connect

    Carbary, J.F.; Krimigis, S.M.; Keath, E.P.; Gloeckler, G.; Axford, W.I.; Armstrong, T.P.

    1981-09-30

    We present results from the Voyager 1 and 2 low-energy charged particle measurement of ion anisotropies in the outer Jovian magnetosphere (R> or approx. =20 R/sub J/). Theses anisotropies represent the first observed from an instrument rotating in the spin plane of Jupiter. For the several ion species ivestigated the first-order anisotropies are all strongly in the corotational sense throughout most of the Jovian magnestophere and out to the magnetopause on the dayside. There is some evidence for a small component of outward flow in the corotating region. Beyond approx.130--150 R/sub J/ along the Voyager outbound trajectories the anisotropies indicate a magnetospheric wind flowing outward from Jupiter. The change corotational to tailward flow on the nightside occurs well inside the magnetopause. The anisotropy amplitudes increase linearly with radial distance and, in the disc regions, decrease with distance from the magnetodisc mid-plane. In one case examined in detail using separtely identified H, He, and O/S ions the convection speed at 58 R/sub J/ is found to agree with the corotation speed (..cap omega..R) to within approx.3%. A linear Compton-Getting analysis reveals that the convective speeds in the dayside magnetosphere are in agreement with rigid corotation whenever the plasma flow direction is approximately in the corotation sense, while at other times the convection speeds are substantially less than corotation.

  6. FRACTIONAL INTEGRATION TOOLBOX

    PubMed Central

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

    2014-01-01

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

  7. FRACTIONAL INTEGRATION TOOLBOX.

    PubMed

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

    2013-09-01

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

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

    NASA Astrophysics Data System (ADS)

    Wismller, Axel; De, Titas; Lochmller, Eva; Eckstein, Felix; Nagarajan, Mahesh B.

    2013-03-01

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

  9. Detection of target proteins by fluorescence anisotropy.

    PubMed

    Wang, Lin; Clifford, Brendan; Graybeal, Lacey; Tolley, Luke; McCarroll, Matthew E

    2013-09-01

    Understanding molecular interactions is critical to understanding most biological mechanisms of cells and organisms. In the case of small molecule-protein interactions, many molecules have significant biological activity through interactions with unknown target proteins and by unknown modes of action. Identifying these target proteins is of significant importance and ongoing work in our laboratories is developing a technique termed Dynamic Isoelectric Anisotropy Binding Ligand Assay (DIABLA) to meet this need. Work presented in this manuscript aims to characterize the fundamental parameters affecting the use of fluorescence anisotropy to detect target proteins for a given ligand. Emphasis is placed on evaluating the use of fluorescence anisotropy as a detection mechanism, including optimization factors that affect the protein detection limit. Effects of ligand concentration, pH, and nonspecific binding are also examined. PMID:23576004

  10. Anisotropy in nonprimordial cosmic background radiation

    SciTech Connect

    Hogan, C.J.

    1982-05-15

    In the standard cosmological model, large-scale anisotropy in microwave background temperature is generally attributed to primordial fluctuations. However, anisotropy may also be produced by radiation emitted inhomogeneously at relatively recent epochs (z< or approx. =200) and thermalized by grains or molecules. This hypothesis predicts a white noise angular distribution of deltaT/T on large scales, with amplitude determined by the inhomogeneity of the sources of radiation, and a smooth distribution below an angle theta/sub 1/roughly-equal3/sup 0/--15/sup 0/ where scattering becomes important. The angular scale of the smoothing may increase with frequency if dust or molecular opacity dominates over Thomson scattering. Nonstandard big bangs or theories of galaxy formation which have smooth initial conditions may be tested by current observations of anisotropy at roughly-equal6/sup 0/ and roughly-equal90/sup 0/.

  11. The electromagnetic ion cyclotron beam anisotropy instability

    NASA Technical Reports Server (NTRS)

    Peter Gary, S.; Schriver, David

    1987-01-01

    Electromagnetic instabilities driven by an anisotropic, relatively cool ion beam are studied for the case in which both the beam and the instabilities propagate parallel or antiparallel to a uniform magnetic field. At modest beam-core relative drift speeds, sufficiently large perpendicular-to-parallel beam temperature ratios and sufficiently large plasma beta, the mode of fastest growth rate is the ion cyclotron beam anisotropy instability. Because the right-hand polarized waves observed upstream of slow shocks in the earth's magnetotail can lead to the appropriate beam anisotropy, the ion cyclotron instability may be present and account for the left-hand polarized magnetic waves observed there. Also, because of its relatively low phase speed, the ion cyclotron beam anisotropy instability may provide the scattering necessary for ion Fermi acceleration at slow shocks of sufficiently high plasma beta.

  12. Large Friction Anisotropy of a Polydiacetylene Monolayer

    SciTech Connect

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

    1999-05-11

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

  13. Psychophysics and the anisotropy of time.

    PubMed

    Riemer, Martin

    2015-12-15

    In psychophysics, experimental control over the presented stimuli is an important prerequisite. Due to the anisotropy of time, this prerequisite is not given in psychophysical experiments on time perception. Many important factors (e.g., the direction of perceived time flow) cannot be manipulated in timing experiments. The anisotropy of time is a peculiarity, which distinguishes the time dimension from other perceptual qualities. Here I summarize the anisotropy-related differences between the perception of time and the perception of other qualities. It is discussed to what extent these differences might affect results and interpretations in psychophysical experiments. In conclusion, I argue for a 'view from nowhen' on the psychophysical study of time perception. PMID:26121957

  14. Large directional optical anisotropy in multiferroic ferroborate

    NASA Astrophysics Data System (ADS)

    Kuzmenko, A. M.; Dziom, V.; Shuvaev, A.; Pimenov, Anna; Schiebl, M.; Mukhin, A. A.; Ivanov, V. Yu.; Gudim, I. A.; Bezmaternykh, L. N.; Pimenov, A.

    2015-11-01

    One of the most fascinating and counterintuitive recent effects in multiferroics is directional anisotropy, the asymmetry of light propagation with respect to the direction of propagation. In such case the absorption in a material can be different for opposite directions. Besides absorption, different velocities of light for different directions of propagation may be also expected, which is termed directional birefringence. In this work, we demonstrate large directional anisotropy in multiferroic samarium ferroborate. The effect is observed for linear polarization of light in the range of millimeter wavelengths, and it survives down to low frequencies. The dispersion and absorption close to the electromagnon resonance can be controlled by external magnetic field and are fully suppressed in one direction. By changing the geometry of the external field, samarium ferroborate shows giant optical activity, which makes this material a universal tool for optical control: with a magnetic field as an external parameter it allows switching between two functionalities: polarization rotation and directional anisotropy.

  15. Measuring anisotropies in the cosmic neutrino background

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    Neutrino capture on tritium has emerged as a promising method for detecting the cosmic neutrino background (C ν 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 ν 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 ν 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.

  16. COSMIC-RAY TRANSPORT AND ANISOTROPIES

    SciTech Connect

    Biermann, Peter L.; Becker Tjus, Julia; Mandelartz, Matthias; Seo, Eun-Suk

    2013-05-10

    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.

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

    SciTech Connect

    Wenk, H.-R.; Voltolini, M.; Mazurek, M.; Van Loon, L.R.; Vinsot, A.

    2009-06-30

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

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

    SciTech Connect

    Troxel, M.A.; Peel, Austin; Ishak, Mustapha E-mail: austin.peel@utdallas.edu

    2013-12-01

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

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

    PubMed

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

    2013-10-18

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

  20. Hydraulic Conductivity Anisotropy of Heterogeneous Unsaturated Soils

    NASA Astrophysics Data System (ADS)

    Sun, Dongmin; Zhu, Jianting

    2010-05-01

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

  1. Heterogeneity and anisotropy in the lithospheric mantle

    NASA Astrophysics Data System (ADS)

    Tommasi, Andréa; Vauchez, Alain

    2015-10-01

    The lithospheric mantle is intrinsically heterogeneous and anisotropic. These two properties govern the repartition of deformation, controlling intraplate strain localization and development of new plate boundaries. Geophysical and geological observations provide clues on the types, ranges, and characteristic length scales of heterogeneity and anisotropy in the lithospheric mantle. Seismic tomography points to variations in geothermal gradient and hence in rheological behavior at scales of hundreds of km. Seismic anisotropy data substantiate anisotropic physical properties consistent at scales of tens to hundreds of km. Receiver functions imply lateral and vertical heterogeneity at scales < 10 km, which might record gradients in composition or anisotropy. Observations on naturally deformed peridotites establish that compositional heterogeneity and Crystal Preferred Orientations (CPOs) are ubiquitous from the mm to the km scales. These data allow discussing the processes that produce/destroy heterogeneity and anisotropy and constraining the time scales over which they are active. This analysis highlights: (i) the role of deformation and reactive percolation of melts and fluids in producing compositional and structural heterogeneity and the feedbacks between these processes, (ii) the weak mechanical effect of mineralogical variations, and (iii) the low volumes of fine-grained microstructures and difficulty to preserve them. In contrast, olivine CPO and the resulting anisotropy of mechanical and thermal properties are only modified by deformation. Based on this analysis, we propose that strain localization at the plate scale is, at first order, controlled by large-scale variations in thermal structure and in CPO-induced anisotropy. In cold parts of the lithospheric mantle, grain size reduction may contribute to strain localization, but the low volume of fine-grained domains limits this effect.

  2. Energetic ion anisotropies in the geomagnetic tail. I - A statistical survey. II - Magnetic field and substorm characteristics

    NASA Technical Reports Server (NTRS)

    Kettmann, Georg; Fritz, Theodore A.; Hones, Edward W., Jr.; Daly, Patrick W.

    1993-01-01

    A comprehensive data set from the ISEE 2 spacecraft is used here to perform a statistical study of events in the earth's central magnetotail that are characterized by high anisotropies of energetic ions. In about 75 percent of the cases the anisotropy vector deviates no more than 45 deg from the tidal axis. High-anisotropy samples within 45 deg of the tidal axis are dominated by the earthward fraction. High ion anisotropies are observed continuously for longer than 1 min only in a few cases. The probability of observing high ion anisotropies is significantly enhanced beyond about 16 R(E) downtail distance within a few earth radii of the neutral sheet and on the duskside of the magnetotail. The analysis is extended with respect to the local magnetic field and to the relationship between energetic ion anisotropies and substorm phases. It is found that the events can be well organized in terms of substorm expansion phase and substorm recovery. These relations and the magnetic field characteristics during the events support the notion that the near-earth source of tailward streaming ions is identical with a substorm neutral line.

  3. Temperature anisotropy and beam type whistler instabilities

    NASA Technical Reports Server (NTRS)

    Hashimoto, K.; Matsumoto, H.

    1976-01-01

    Whistler instabilities have been investigated for two different types; i.e., a temperature-anisotropy type instability and a beam-type instability. A comparison between the two types of whistler instabilities is made within the framework of linear theory. A transition from one type to the other is also discussed, which is an extension of the work on electrostatic beam and Landau instabilities performed by O'Neil and Malmberg (1968) for electromagnetic whistler instabilities. It is clarified that the essential source of the whistler instability is not beam kinetic energy but a temperature anisotropy, even for the beam-type whistler instability.

  4. Anisotropy of the Topopah Spring Member Tuff

    SciTech Connect

    Martin, R.J. III; Boyd, P.J.; Haupt, R.W.; Price, R.H.

    1992-07-01

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

  5. Anisotropy of dilepton emission from nuclear collisions

    SciTech Connect

    Bratkovskaya, E.L.; Teryaev, O.V.; Toneev, V.D. |

    1994-11-07

    Attention is paid to studying the angular characteristics of e{sup +}e{sup {minus}} pairs created in collisions with nuclear targets at intermediate and relativistic energies. Arising due to general spin and angular momentum constraints, the dilepton anisotropy seems to be quite sensitive to the contribution of different sources and may be used for disentangling these sources (or models) as well as an additional signature of a possible chiral symmetry restoration and phase transition of hadrons into the quark-gluon plasma. An anisotropy estimate for some dilepton sources is given and its relevance to the problems mentioned is discussed.

  6. Ion anisotropy instabilities in the magnetosheath

    NASA Technical Reports Server (NTRS)

    Gary, S. P.; Fuselier, Stephen A.; Anderson, Brian J.

    1993-01-01

    Recent observations in Earth's magnetosheath have delineated several different kinds of magnetic fluctuation spectra below the proton cyclotron frequency. This paper provides a theoretical interpretation for some of these observations describing solutions of the linear Vlasov dispersion equation for fully electromagnetic instabilities for particle distributions which model those observed in the magnetosheath. This model yields three growing modes: the proton cyclotron anisotropy the helium cyclotron anisotropy, and the mirror instabilities. The results show very good agreement with the observations of mirror-like and proton-cyclotron-like events. This agreement with observations implies that the transition between cyclotron and mirror fluctuation dominance is consistent with linear theory.

  7. Weak Elastic Anisotropy in Global Seismology

    NASA Astrophysics Data System (ADS)

    Thomsen, L.; Anderson, D. L.

    2014-12-01

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

  8. Effects of anisotropy on dynamic tensile behavior

    SciTech Connect

    Schifert, S.K.; Davidson, R.F.; Maudlin, P.J.

    1991-01-01

    A stability analysis for an anisotropic stretching rod is presented. We consider the particular case of a rapidly stretching titanium jet using a continuum code to examine anisotropic plastic response in the finite-neck regime. It was found that the classical analysis (yield strength is inversely proportional to stability) is insufficient; anisotropic jets can be more or less stable than their maximum or minimum yield strengths, depending on initial perturbations and the orientation of the anisotropy. One particular anisotropy -- with the weak direction along the jet axis -- appears to be generally stabilizing. 10 refs., 6 figs.

  9. Direct expressions for magnetic anisotropy constants

    NASA Astrophysics Data System (ADS)

    Miura, Daisuke; Sasaki, Ryo; Sakuma, Akimasa

    2015-11-01

    Direct expressions for the magnetic anisotropy constants are given at a finite temperature from a microscopic viewpoint. The present derivation assumes that the Hamiltonian is a linear function with respect to the magnetization direction. We discuss in detail the first-order anisotropy constant K1 and show that our present results reproduce previous results. We applied our method to Nd2Fe14B compounds and confirmed that the present method can reproduce the temperature dependence of the magnetocrystalline anisotoropy constants K1, K2, and K3 well.

  10. Radiologic Determination of Corpus Callosum Injury in Patients with Mild Traumatic Brain Injury and Associated Clinical Characteristics

    PubMed Central

    Kim, Dong Shin; Yang, Jin Seo; Cho, Yong Jun; Kang, Suk Hyung

    2015-01-01

    Objective To investigate the incidence of corpus callosum injury (CCI) in patients with mild traumatic brain injury (TBI) using brain MRI. We also performed a review of the clinical characteristics associated with this injury. Methods A total of 356 patients in the study were diagnosed with TBI, with 94 patients classified as having mild TBI. We included patients with mild TBI for further evaluation if they had normal findings via brain computed tomography (CT) scans and also underwent brain MRI in the acute phase following trauma. As assessed by brain MRI, CCI was defined as a high-signal lesion in T2 sagittal images and a corresponding low-signal lesion as determined by axial gradient echo (GRE) imaging. Based on these criteria, we divided patients into two groups for further analysis : Group I (TBI patients with CCI) and Group II (TBI patients without CCI). Results A total of 56 patients were enrolled in this study (including 16 patients in Group I and 40 patients in Group II). Analysis of clinical symptoms revealed a significant difference in headache severity between groups. Over 50% of patients in Group I experienced prolonged neurological symptoms including dizziness and gait disturbance and were more common in Group I than Group II (dizziness : 37 and 12% in Groups I and II, respectively; gait disturbance : 12 and 0% in Groups I and II, respectively). Conclusion The incidence of CCI in patients with mild TBI was approximately 29%. We suggest that brain MRI is a useful method to reveal the cause of persistent symptoms and predict clinical prognosis. PMID:26361529

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

    PubMed Central

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

    2011-01-01

    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

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

    PubMed Central

    Benadiba, Carine; Magnani, Dario; Niquille, Mathieu; Morl, Laurette; Valloton, Delphine; Nawabi, Homaira; Ait-Lounis, Aouatef; Otsmane, Belkacem; Reith, Walter; Theil, Thomas; Hornung, Jean-Pierre

    2012-01-01

    The corpus callosum (CC) is the major commissure that bridges the cerebral hemispheres. Agenesis of the CC is associated with human ciliopathies, but the origin of this default is unclear. Regulatory Factor X3 (RFX3) is a transcription factor involved in the control of ciliogenesis, and Rfx3deficient mice show several hallmarks of ciliopathies including leftright asymmetry defects and hydrocephalus. Here we show that Rfx3deficient mice suffer from CC agenesis associated with a marked disorganisation of guidepost neurons required for axon pathfinding across the midline. Using transplantation assays, we demonstrate that abnormalities of the mutant midline region are primarily responsible for the CC malformation. Conditional genetic inactivation shows that RFX3 is not required in guidepost cells for proper CC formation, but is required before E12.5 for proper patterning of the cortical septal boundary and hence accurate distribution of guidepost neurons at later stages. We observe focused but consistent ectopic expression of Fibroblast growth factor 8 (Fgf8) at the rostro commissural plate associated with a reduced ratio of GLIoma-associated oncogene family zinc finger 3 (GLI3) repressor to activator forms. We demonstrate on brain explant cultures that ectopic FGF8 reproduces the guidepost neuronal defects observed in Rfx3 mutants. This study unravels a crucial role of RFX3 during early brain development by indirectly regulating GLI3 activity, which leads to FGF8 upregulation and ultimately to disturbed distribution of guidepost neurons required for CC morphogenesis. Hence, the RFX3 mutant mouse model brings novel understandings of the mechanisms that underlie CC agenesis in ciliopathies. PMID:22479201

  13. Corpus callosum area in patients with bipolar disorder with and without psychotic features: an international multicentre study

    PubMed Central

    Sarrazin, Samuel; d’Albis, Marc-Antoine; McDonald, Colm; Linke, Julia; Wessa, Michèle; Phillips, Mary; Delavest, Marine; Emsell, Louise; Versace, Amelia; Almeida, Jorge; Mangin, Jean-François; Poupon, Cyril; Le Dudal, Katia; Daban, Claire; Hamdani, Nora; Leboyer, Marion; Houenou, Josselin

    2015-01-01

    Background Previous studies have reported MRI abnormalities of the corpus callosum (CC) in patients with bipolar disorder (BD), although only a few studies have directly compared callosal areas in psychotic versus nonpsychotic patients with this disorder. We sought to compare regional callosal areas in a large international multicentre sample of patients with BD and healthy controls. Methods We analyzed anatomic T1 MRI data of patients with BD-I and healthy controls recruited from 4 sites (France, Germany, Ireland and the United States). We obtained the mid-sagittal areas of 7 CC subregions using an automatic CC delineation. Differences in regional callosal areas between patients and controls were compared using linear mixed models (adjusting for age, sex, handedness, brain volume, history of alcohol abuse/dependence, lithium or antipsychotic medication status, symptomatic status and site) and multiple comparisons correction. We also compared regional areas of the CC between patients with BD with and without a history of psychotic features. Results We included 172 patients and 146 controls in our study. Patients with BD had smaller adjusted mid-sagittal CC areas than controls along the posterior body, the isthmus and the splenium of the CC. Patients with a positive history of psychotic features had greater adjusted area of the rostral CC region than those without a history of psychotic features. Limitations We found small to medium effect sizes, and there was no calibration technique among the sites. Conclusion Our results suggest that BD with psychosis is associated with a different pattern of interhemispheric connectivity than BD without psychosis and could be considered a relevant neuroimaging subtype of BD. PMID:26151452

  14. The role of primary cilia in corpus callosum formation is mediated by production of the Gli3 repressor.

    PubMed

    Laclef, Christine; Anselme, Isabelle; Besse, Laurianne; Catala, Martin; Palmyre, Aurlien; Baas, Dominique; Paschaki, Marie; Pedraza, Maria; Mtin, Christine; Durand, Bndicte; Schneider-Maunoury, Sylvie

    2015-09-01

    Agenesis of the corpus callosum (AgCC) is a frequent brain disorder found in over 80 human congenital syndromes including ciliopathies. Here, we report a severe AgCC in Ftm/Rpgrip1l knockout mouse, which provides a valuable model for Meckel-Grber syndrome. Rpgrip1l encodes a protein of the ciliary transition zone, which is essential for ciliogenesis in several cell types in mouse including neuroepithelial cells in the developing forebrain. We show that AgCC in Rpgrip1l(-/-) mouse is associated with a disturbed location of guidepost cells in the dorsomedial telencephalon. This mislocalization results from early patterning defects and abnormal cortico-septal boundary (CSB) formation in the medial telencephalon. We demonstrate that all these defects primarily result from altered GLI3 processing. Indeed, AgCC, together with patterning defects and mispositioning of guidepost cells, is rescued by overexpressing in Rpgrip1l(-/-) embryos, the short repressor form of the GLI3 transcription factor (GLI3R), provided by the Gli3(?699) allele. Furthermore, Gli3(?699) also rescues AgCC in Rfx3(-/-) embryos deficient for the ciliogenic RFX3 transcription factor that regulates the expression of several ciliary genes. These data demonstrate that GLI3 processing is a major outcome of primary cilia function in dorsal telencephalon morphogenesis. Rescuing CC formation in two independent ciliary mutants by GLI3(?699) highlights the crucial role of primary cilia in maintaining the proper level of GLI3R required for morphogenesis of the CC. PMID:26071364

  15. Segmentation and Analysis of Corpus Callosum in Alzheimer MR Images using Total Variation Based Diffusion Filter and Level Set Method.

    PubMed

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

    2015-01-01

    Alzheimer?s Disease (AD) is a common form of dementia that affects gray and white matter structures of brain. Manifestation of AD leads to cognitive deficits such as memory impairment problems, ability to think and difficulties in performing day to day activities. Although the etiology of this disease is unclear, imaging biomarkers are highly useful in the early diagnosis of AD. Magnetic resonance imaging is an indispensible non-invasive imaging modality that reflects both the geometry and pathology of the brain. Corpus Callosum (CC) is the largest white matter structure as well as the main inter-hemispheric fiber connection that undergoes regional alterations due to AD. Therefore, segmentation and feature extraction are predominantly essential to characterize the CC atrophy. In this work, an attempt has been made to segment CC using edge based level set method. Prior to segmentation, the images are pre-processed using Total Variation (TV) based diffusion filtering to enhance the edge information. Shape based geometric features are extracted from the segmented CC images to analyze the CC atrophy. Results show that the edge based level set method is able to segment CC in both the normal and AD images. TV based diffusion filtering has performed uniform region specific smoothing thereby preserving the texture and small scale details of the image. Consequently, the edge map of CC in both the normal and AD are apparently sharp and distinct with continuous boundaries. This facilitates the final contour to correctly segment CC from the nearby structures. The extracted geometric features such as area, perimeter and minor axis are found to have the percentage difference of 5.97%, 22.22% and 9.52% respectively in the demarcation of AD subjects. As callosal atrophy is significant in the diagnosis of AD, this study seems to be clinically useful. PMID:25996739

  16. DIY Fraction Pack.

    ERIC Educational Resources Information Center

    Graham, Alan; Graham, Louise

    2003-01-01

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

  17. A Instrument and Technique for Measuring the Anisotropy in the Cosmic Microwave Background Radiation

    NASA Astrophysics Data System (ADS)

    Wilson, Grant W.

    1997-09-01

    There is a wealth of information contained in the spatial temperature distribution of the Cosmic Microwave Background Radiation (CMB) >From the pioneering discovery of anisotropy by the COBE satellite to the latest balloon payloads and ground based observations, measurements of the CMB have become the cornerstone of our current understanding of the Universe. Currently, the second generation of CMB experiments are coming on-line. With improved detectors and novel observing strategies, these experiments are destined to make the transition from 'discovering' the anisotropy in the CMB to making precision measurements of the spatial correlation function. Herein I describe the most recent of these second generation experiments: the Medium Scale Anisotropy Measurement (MSAM II). MSAM II is a balloon-based telescope with a bolometric receiver cooled by an Adiabatic Demagnetization Refrigerator to 100 mK. MSAM II samples the sky with a 20 prime FWHM beam swept with a triangle wave at 2.5 Hz and will make a precision measurement of the spatial correlation function from 1 = 100 to 1 = 500. In addition to a comprehensive discussion of the fabrication and development of the cryogenic and optical systems of MSAM II, I present a novel method of estimating cosmological parameters from anisotropy measurements using a maximum Likelihood technique which employs the full covariance matrix of observations. This method has been used on the combined three years of MSAM I datasets to constrain the mass fraction of baryons in the universe, ?B, as well as a number of other cosmological parameters.

  18. Magnetic anisotropy data of C3H2NCl

    NASA Astrophysics Data System (ADS)

    Kumar, M.; Gupta, R.

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

  19. Tuning the Magnetic Anisotropy of Single Molecules.

    PubMed

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

    2015-06-10

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

  20. Knitted Patterns as a Model for Anisotropy

    ERIC Educational Resources Information Center

    Cepic, Mojca

    2012-01-01

    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…

  1. Knitted Patterns as a Model for Anisotropy

    ERIC Educational Resources Information Center

    Cepic, Mojca

    2012-01-01

    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

  2. Anisotropy of Wood in the Microwave Region

    ERIC Educational Resources Information Center

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

    2010-01-01

    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

  3. Magnetic Anisotropy in UMn2Ge2

    NASA Astrophysics Data System (ADS)

    Berg, Morgann; de Lozanne, Alex; Baumbach, Ryan; Kim, Jeehoon; Bauer, Eric; Thompson, Joe; Ronning, Filip

    2015-03-01

    UMn2Ge2, a permanent magnet, is a ternary intermetallic compound with a tetragonal crystal structure of type ThCr2Si2 and with space group I4/mmm. Local U and Mn moments in UMn2Ge2 order on their respective sublattices at temperatures near 100 and 380 K, respectively. Previous x-ray diffraction, Kerr rotation angle, and SQUID magnetometry data support the commonly accepted notion that U moments order at low temperature and align Mn moments along the c-axis, introducing anisotropy. Previous results obtained using a multi-mode atomic force microscope in magnetic force microscopy (MFM) mode indeed confirmed that UMn2Ge2 displays uniaxial anisotropy with an easy axis coinciding with the c-axis of the material. However, the branching domains in UMn2Ge2 consistent with uniaxial anisotropy were observed all the way up to room temperature by MFM. This indicates that the effect of uranium moments on the magnetic microstructure of UMn2Ge2 is not limited to low temperatures near the ordering temperature of the uranium sublattice. We further investigate closure domains in the surface of UMn2Ge2 and report on characteristics and signatures of anisotropy revealed by the orientation and periodic structures of closure domains. Supported by NSF Grant DMR-0810119.

  4. Relative sensitivity of formability to anisotropy

    SciTech Connect

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

    1997-01-01

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

  5. Anisotropy of Wood in the Microwave Region

    ERIC Educational Resources Information Center

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

    2010-01-01

    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…

  6. Variance Anisotropy of Solar Wind fluctuations

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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.

  7. Exponential anisotropy of solar cosmic rays

    NASA Technical Reports Server (NTRS)

    Bieber, J. W.; Evenson, P. A.; Pomerantz, M. A.

    1985-01-01

    On 16 February 1984 a flare on the Sun's invisible disk produced a large, highly anisotropic solar particle event. A technique, in which interplanetary scattering parameters are determined purely from the form of the particle anisotropy, is applied to energetic particle data from neutron monitors and the ICE spacecraft.

  8. Global anisotropy and the thickness of continents.

    PubMed

    Gung, Yuancheng; Panning, Mark; Romanowicz, Barbara

    2003-04-17

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

  9. Numerical likelihood analysis of cosmic ray anisotropies

    SciTech Connect

    Carlos Hojvat et al.

    2003-07-02

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

  10. The microwave background anisotropies: Observations

    PubMed Central

    Wilkinson, David

    1998-01-01

    Most cosmologists now believe that we live in an evolving universe that has been expanding and cooling since its origin about 15 billion years ago. Strong evidence for this standard cosmological model comes from studies of the cosmic microwave background radiation (CMBR), the remnant heat from the initial fireball. The CMBR spectrum is blackbody, as predicted from the hot Big Bang model before the discovery of the remnant radiation in 1964. In 1992 the cosmic background explorer (COBE) satellite finally detected the anisotropy of the radiation—fingerprints left by tiny temperature fluctuations in the initial bang. Careful design of the COBE satellite, and a bit of luck, allowed the 30 μK 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

  11. Mantle Anisotropy Beneath China: Measurements and Implications

    NASA Astrophysics Data System (ADS)

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

    2006-12-01

    Seismic anisotropy in the mantle beneath mainland China was studied using data from the China Digital Seismograph Network (CDSN) by Zheng & Gao (1994), and later by using data from more stations and different seismograph networks. The present study utilizes data from the recently-completed China National Seismograph Network (CNSN) from 2001 to 2005 to further improve the coverage of anisotropy measurements, and to search for the existence of complex anisotropy beneath stations with sufficient azimuthal coverage of the events. China is an ideal locale for studying the formation of mantle anisotropy by various mechanisms, such as continental collision along the Himalayas, slab-subducting beneath its eastern region, and continental splitting in the vicinity of the Shanxi and other rifts. Using data recorded over the past five years by the 48 stations in CNSN, this study obtains seismic anisotropic parameters (fast polarization directions and time delays) of split shear-waves. In addition, we use hundreds of events recorded by stations in the Global Seismograph Network (GSN) to detect and analyze complex anisotropy. Our results can be well-explained by coherent deformation of the lithosphere in the past or current orogenic belt, or by asthenospheric flow induced by subducting oceanic slabs. The measurements suggest that the western limit of the approximately westward asthenospheric flow induced by the subducting Pacific slab is consistent with the western boundary of the recent sedimentary basins in eastern China, suggesting that there is a possible connection between the formation of the large sedimentary basins and the slab, which is deflected horizontally in the mantle transition zone, as revealed by recent seismic tomographic studies. This study is supported by NSFC.

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

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

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

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

    PubMed Central

    2012-01-01

    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

  14. FRACTIONAL PEARSON DIFFUSIONS

    PubMed Central

    Leonenko, Nikolai N.; Meerschaert, Mark M.

    2013-01-01

    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

  15. Exchange-coupled Sm-Co/Nd-Co nanomagnets: correlation between soft phase anisotropy and exchange field

    NASA Astrophysics Data System (ADS)

    Guo, Z. J.; Jiang, J. S.; Pearson, J. E.; Bader, S. D.; Liu, J. P.

    2002-09-01

    The effect of the magnetic anisotropy of the Nd-Co soft phase on its exchange field (Hex) is reported for epitaxial Sm-Co/Nd-Co bilayers. It is found that Hex gradually increases with anisotropy K of the soft phase. The experimental values of Hex as well as its variation with K are quantitatively interpreted using an analytical model based on the formation of a partial domain wall on the soft phase side of the interface. The results suggest that one can enhance Hex, and hence, the volume fraction of the soft phase for effective exchange spring coupling between the hard and soft phases, by tailoring the anisotropy of the soft phase.

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

    NASA Astrophysics Data System (ADS)

    Pierre Auger Collaboration; Abreu, P.; Aglietta, M.; Ahn, E. J.; Albuquerque, I. F. M.; Allard, D.; Allekotte, I.; Allen, J.; Allison, P.; Alvarez Castillo, J.; Alvarez-Muiz, 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.; Bcker, T.; Balzer, M.; Barber, K. B.; Barbosa, A. F.; Bardenet, R.; Barroso, S. L. C.; Baughman, B.; Buml, J.; Beatty, J. J.; Becker, B. R.; Becker, K. H.; Belltoile, A.; Bellido, J. A.; BenZvi, S.; Berat, C.; Bertou, X.; Biermann, P. L.; Billoir, P.; Blanco, F.; Blanco, M.; Bleve, C.; Blmer, H.; Boh?ov, 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.; Conceio, R.; Contreras, F.; Cook, H.; Cooper, M. J.; Coppens, J.; Cordier, A.; Cotti, U.; Coutu, S.; Covault, C. E.; Creusot, A.; Criss, A.; Cronin, J.; Curutiu, A.; Dagoret-Campagne, S.; Dallier, R.; Dasso, S.; Daumiller, K.; Dawson, B. R.; de Almeida, R. M.; De Domenico, M.; De Donato, C.; de Jong, S. J.; De La Vega, G.; de Mello Junior, W. J. M.; de Mello Neto, J. R. T.; De Mitri, I.; de Souza, V.; de Vries, K. D.; Decerprit, G.; del Peral, L.; Deligny, O.; Dembinski, H.; Dhital, N.; Di Giulio, C.; Diaz, J. C.; Daz Castro, M. L.; Diep, P. N.; Dobrigkeit, C.; Docters, W.; D'Olivo, J. C.; Dong, P. N.; Dorofeev, A.; dos Anjos, J. C.; Dova, M. T.; D'Urso, D.; Dutan, I.; Ebr, J.; Engel, R.; Erdmann, M.; Escobar, C. O.; Etchegoyen, A.; Facal San Luis, P.; Fajardo Tapia, I.; Falcke, H.; Farrar, G.; Fauth, A. C.; Fazzini, N.; Ferguson, A. P.; Ferrero, A.; Fick, B.; Filevich, A.; Filip?i?, A.; Fliescher, S.; Fracchiolla, C. E.; Fraenkel, E. D.; Frhlich, U.; Fuchs, B.; Gaior, R.; Gamarra, R. F.; Gambetta, S.; Garca, B.; Garca Gmez, D.; Garcia-Pinto, D.; Gascon, A.; Gemmeke, H.; Gesterling, K.; Ghia, P. L.; Giaccari, U.; Giller, M.; Glass, H.; Gold, M. S.; Golup, G.; Gomez Albarracin, F.; Gmez Berisso, M.; Gonalves, P.; Gonzalez, D.; Gonzalez, J. G.; Gookin, B.; Gra, 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.; Hrandel, J. R.; Horneffer, A.; Hrabovsk, M.; Huege, T.; Insolia, A.; Ionita, F.; Italiano, A.; Jarne, C.; Jiraskova, S.; Kadija, K.; Kampert, K. H.; Karhan, P.; Kasper, P.; Kgl, 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.; Krmer, O.; Kruppke-Hansen, D.; Kuehn, F.; Kuempel, D.; Kulbartz, J. K.; Kunka, N.; La Rosa, G.; Lachaud, C.; Lautridou, P.; Leo, M. S. A. B.; Lebrun, D.; Lebrun, P.; Leigui de Oliveira, M. A.; Lemiere, A.; Letessier-Selvon, A.; Lhenry-Yvon, I.; Link, K.; Lpez, R.; Lopez Aera, A.; Louedec, K.; Lozano Bahilo, J.; Lucero, A.; Ludwig, M.; Lyberis, H.; Maccarone, M. C.; Macolino, C.; Maldera, S.; Mandat, D.; Mantsch, P.; Mariazzi, A. G.; Marin, J.; Marin, V.; Maris, I. C.; Marquez Falcon, H. R.; Marsella, G.; Martello, D.; Martin, L.; Martinez, H.; Martnez Bravo, O.; Mathes, H. J.; Matthews, J.; Matthews, J. A. J.; Matthiae, G.; Maurizio, D.; Mazur, P. O.; Medina-Tanco, G.; Melissas, M.; Melo, D.; Menichetti, E.; Menshikov, A.; Mertsch, P.; Meurer, C.; Mi?anovi?, S.; Micheletti, M. I.; Miller, W.; Miramonti, L.; Mollerach, S.; Monasor, M.; Monnier Ragaigne, D.; Montanet, F.; Morales, B.; Morello, C.; Moreno, E.; Moreno, J. C.; Morris, C.; Mostaf, M.; Moura, C. A.; Mueller, S.; Muller, M. A.; Mller, G.; Mnchmeyer, 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.; Noka, L.; Nyklicek, M.; Oehlschlger, J.; Olinto, A.; Oliva, P.; Olmos-Gilbaja, V. M.; Ortiz, M.; Pacheco, N.; Pakk Selmi-Dei, D.; Palatka, M.; Pallotta, J.; Palmieri, N.; Parente, G.; Parizot, E.; Parra, A.; Parsons, R. D.; Pastor, S.; Paul, T.; Pech, M.; P?kala, J.; Pelayo, R.; Pepe, I. M.; Perrone, L.; Pesce, R.; Petermann, E.; Petrera, S.; Petrinca, P.; Petrolini, A.; Petrov, Y.; Petrovic, J.; Pfendner, C.; Phan, N.; Piegaia, R.; Pierog, T.; Pieroni, P.; Pimenta, M.; Pirronello, V.

    2011-06-01

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

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

    DOE PAGESBeta

    Abreu, P

    2011-06-17

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

  18. EphB1 and EphB2 intracellular domains regulate the formation of the corpus callosum and anterior commissure.

    PubMed

    Robichaux, Michael A; Chenaux, George; Ho, Hsin-Yi Henry; Soskis, Michael J; Greenberg, Michael E; Henkemeyer, Mark; Cowan, Christopher W

    2016-04-01

    The two cortical hemispheres of the mammalian forebrain are interconnected by major white matter tracts, including the corpus callosum (CC) and the posterior branch of the anterior commissure (ACp), that bridge the telencephalic midline. We show here that the intracellular signaling domains of the EphB1 and EphB2 receptors are critical for formation of both the ACp and CC. We observe partial and complete agenesis of the corpus callosum, as well as highly penetrant ACp misprojection phenotypes in truncated EphB1/2 mice that lack intracellular signaling domains. Consistent with the roles for these receptors in formation of the CC and ACp, we detect expression of these receptors in multiple brain regions associated with the formation of these forebrain structures. Taken together, our findings suggest that a combination of forward and reverse EphB1/2 receptor-mediated signaling contribute to ACp and CC axon guidance. © 2015 Wiley Periodicals, Inc. Develop Neurobiol 76: 405-420, 2016. PMID:26148571

  19. The K-Cl cotransporter KCC3 is mutant in a severe peripheral neuropathy associated with agenesis of the corpus callosum.

    PubMed

    Howard, Heidi C; Mount, David B; Rochefort, Daniel; Byun, Nellie; Dupr, Nicolas; Lu, Jianming; Fan, Xuemo; Song, Luyan; Rivire, Jean-Baptiste; Prvost, Claude; Horst, Jrgen; Simonati, Alessandro; Lemcke, Beate; Welch, Rick; England, Roger; Zhan, Frank Q; Mercado, Adriana; Siesser, William B; George, Alfred L; McDonald, Michael P; Bouchard, Jean-Pierre; Mathieu, Jean; Delpire, Eric; Rouleau, Guy A

    2002-11-01

    Peripheral neuropathy associated with agenesis of the corpus callosum (ACCPN) is a severe sensorimotor neuropathy associated with mental retardation, dysmorphic features and complete or partial agenesis of the corpus callosum. ACCPN is transmitted in an autosomal recessive fashion and is found at a high frequency in the province of Quebec, Canada. ACCPN has been previously mapped to chromosome 15q. The gene SLC12A6 (solute carrier family 12, member 6), which encodes the K+-Cl- transporter KCC3 and maps within the ACCPN candidate region, was screened for mutations in individuals with ACCPN. Four distinct protein-truncating mutations were found: two in the French Canadian population and two in non-French Canadian families. The functional consequence of the predominant French Canadian mutation (2436delG, Thr813fsX813) was examined by heterologous expression of wildtype and mutant KCC3 in Xenopus laevis oocytes; the truncated mutant is appropriately glycosylated and expressed at the cellular membrane, where it is non-functional. Mice generated with a targeted deletion of Slc12a6 have a locomotor deficit, peripheral neuropathy and a sensorimotor gating deficit, similar to the human disease. Our findings identify mutations in SLC12A6 as the genetic lesion underlying ACCPN and suggest a critical role for SLC12A6 in the development and maintenance of the nervous system. PMID:12368912

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

    PubMed

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

    2014-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

  3. Quantification of microscopic diffusion anisotropy disentangles effects of orientation dispersion from microstructure: applications in healthy volunteers and in brain tumors.

    PubMed

    Szczepankiewicz, Filip; Lasi?, Samo; van Westen, Danielle; Sundgren, Pia C; Englund, Elisabet; Westin, Carl-Fredrik; Sthlberg, Freddy; Ltt, Jimmy; Topgaard, Daniel; Nilsson, Markus

    2015-01-01

    The anisotropy of water diffusion in brain tissue is affected by both disease and development. This change can be detected using diffusion MRI and is often quantified by the fractional anisotropy (FA) derived from diffusion tensor imaging (DTI). Although FA is sensitive to anisotropic cell structures, such as axons, it is also sensitive to their orientation dispersion. This is a major limitation to the use of FA as a biomarker for "tissue integrity", especially in regions of complex microarchitecture. In this work, we seek to circumvent this limitation by disentangling the effects of microscopic diffusion anisotropy from the orientation dispersion. The microscopic fractional anisotropy (?FA) and the order parameter (OP) were calculated from the contrast between signal prepared with directional and isotropic diffusion encoding, where the latter was achieved by magic angle spinning of the q-vector (qMAS). These parameters were quantified in healthy volunteers and in two patients; one patient with meningioma and one with glioblastoma. Finally, we used simulations to elucidate the relation between FA and ?FA in various micro-architectures. Generally, ?FA was high in the white matter and low in the gray matter. In the white matter, the largest differences between ?FA and FA were found in crossing white matter and in interfaces between large white matter tracts, where ?FA was high while FA was low. Both tumor types exhibited a low FA, in contrast to the ?FA which was high in the meningioma and low in the glioblastoma, indicating that the meningioma contained disordered anisotropic structures, while the glioblastoma did not. This interpretation was confirmed by histological examination. We conclude that FA from DTI reflects both the amount of diffusion anisotropy and orientation dispersion. We suggest that the ?FA and OP may complement FA by independently quantifying the microscopic anisotropy and the level of orientation coherence. PMID:25284306

  4. Quantification of microscopic diffusion anisotropy disentangles effects of orientation dispersion from microstructure: applications in healthy volunteers and in brain tumors

    PubMed Central

    Szczepankiewicz, Filip; Lasič, Samo; van Westen, Danielle; Sundgren, Pia C.; Englund, Elisabet; Westin, Carl-Fredrik; Ståhlberg, Freddy; Lätt, Jimmy; Topgaard, Daniel; Nilsson, Markus

    2014-01-01

    The anisotropy of water diffusion in brain tissue is affected by both disease and development. This change can be detected using diffusion MRI and is often quantified by the fractional anisotropy (FA) derived from diffusion tensor imaging (DTI). Although FA is sensitive to anisotropic cell structures, such as axons, it is also sensitive to their orientation dispersion. This is a major limitation to the use of FA as a biomarker for “tissue integrity”, especially in regions of complex microarchitecture. In this work, we seek to circumvent this limitation by disentangling the effects of microscopic diffusion anisotropy from the orientation dispersion. The microscopic fractional anisotropy (μFA) and the order parameter (OP) were calculated from the contrast between signal prepared with directional and isotropic diffusion encoding, where the latter was achieved by magic angle spinning of the q-vector (qMAS). These parameters were quantified in healthy volunteers and in two patients; one patient with meningioma and one with glioblastoma. Finally, we used simulations to elucidate the relation between FA and μFA in various micro-architectures. Generally, μFA was high in the white matter and low in the gray matter. In the white matter, the largest differences between μFA and FA were found in crossing white matter and in interfaces between large white matter tracts, where μFA was high while FA was low. Both tumor types exhibited a low FA, in contrast to the μFA which was high in the meningioma and low in the glioblastoma, indicating that the meningioma contained disordered anisotropic structures, while the glioblastoma did not. This interpretation was confirmed by histological examination. We conclude that FA from DTI reflects both the amount of diffusion anisotropy and orientation dispersion. We suggest that the μFA and OP may complement FA by independently quantifying the microscopic anisotropy and the level of orientation coherence. PMID:25284306

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

    PubMed Central

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

    2014-01-01

    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

  6. Microstructure anisotropy in polyolefin flexible foams

    NASA Astrophysics Data System (ADS)

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

    2009-09-01

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

  7. Tailored magnetic anisotropy in an amorphous trilayer

    SciTech Connect

    Fu Yu; Barsukov, I.; Spasova, M.; Lindner, J.; Meckenstock, R.; Farle, M.; Raanaei, H.; Hjoervarsson, B.

    2011-06-01

    An amorphous Co{sub 68}Fe{sub 24}Zr{sub 8}(3 nm)/Al{sub 70}Zr{sub 30}(3 nm)/Co{sub 68}Fe{sub 24}Zr{sub 8}(3 nm) trilayer system has been investigated using in-plane and out-of-plane angular dependent ferromagnetic resonance at different frequencies. The in-plane magnetic anisotropy is uniaxial, retaining its value of (2.9 {+-} 0.1) x 10{sup 3} J/m{sup 3} for each magnetic layer, whereas its direction was tailored independently in an arbitrary manner by applying an external magnetic field during the film deposition. The perpendicular anisotropy constant, supposed to reflect the interface quality, is nearly identical for both layers. Furthermore, the magnetic layers act independently upon each other due to the absence of interlayer coupling.

  8. Microwave background anisotropies in quasiopen inflation

    NASA Astrophysics Data System (ADS)

    García-Bellido, Juan; Garriga, Jaume; Montes, Xavier

    1999-10-01

    Quasiopenness seems to be generic to multifield models of single-bubble open inflation. Instead of producing infinite open universes, these models actually produce an ensemble of very large but finite inflating islands. In this paper we study the possible constraints from CMB anisotropies on existing models of open inflation. The effect of supercurvature anisotropies combined with the quasiopenness of the inflating regions make some models incompatible with observations, and severely reduces the parameter space of others. Supernatural open inflation and the uncoupled two-field model seem to be ruled out due to these constraints for values of Ω0<~0.98. Others, such as the open hybrid inflation model with suitable parameters for the slow roll potential can be made compatible with observations.

  9. Tailored magnetic anisotropy in an amorphous trilayer

    NASA Astrophysics Data System (ADS)

    Fu, Yu; Barsukov, I.; Raanaei, H.; Spasova, M.; Lindner, J.; Meckenstock, R.; Farle, M.; Hjörvarsson, B.

    2011-06-01

    An amorphous Co68Fe24Zr8(3 nm)/Al70Zr30(3 nm)/Co68Fe24Zr8(3 nm) trilayer system has been investigated using in-plane and out-of-plane angular dependent ferromagnetic resonance at different frequencies. The in-plane magnetic anisotropy is uniaxial, retaining its value of (2.9 ± 0.1) × 103 J/m3 for each magnetic layer, whereas its direction was tailored independently in an arbitrary manner by applying an external magnetic field during the film deposition. The perpendicular anisotropy constant, supposed to reflect the interface quality, is nearly identical for both layers. Furthermore, the magnetic layers act independently upon each other due to the absence of interlayer coupling.

  10. Induced electronic anisotropy in bismuth thin films

    SciTech Connect

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

    2014-08-11

    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.

  11. Friction Anisotropy with Respect to Topographic Orientation

    PubMed Central

    Yu, Chengjiao; Wang, Q. Jane

    2012-01-01

    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

  12. Large Flexoelectric Anisotropy in Paraelectric Barium Titanate.

    PubMed

    Narvaez, Jackeline; Saremi, Sahar; Hong, Jiawang; Stengel, Massimiliano; Catalan, Gustau

    2015-07-17

    The bending-induced polarization of barium titanate single crystals has been measured with an aim to elucidate the origin of the large difference between theoretically predicted and experimentally measured flexoelectricity in this material. The results indicate that part of the difference is due to polar regions (short-range order) that exist above T(C) and up to T*?200-225?C. Above T*, however, the flexovoltage coefficient still shows an unexpectedly large anisotropy for a cubic material, with (001)-oriented crystals displaying 10 times more flexoelectricity than (111)-oriented crystals. Theoretical analysis shows that this anisotropy cannot be a bulk property, and we therefore interpret it as indirect evidence for the theoretically predicted but experimentally elusive contribution of surface piezoelectricity to macroscopic bending-induced polarization. PMID:26230825

  13. Cosmic-ray streaming and anisotropies

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

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

  14. Optical and neural anisotropy in peripheral vision

    PubMed Central

    Zheleznyak, Len; Barbot, Antoine; Ghosh, Atanu; Yoon, Geunyoung

    2016-01-01

    Optical blur in the peripheral retina is known to be highly anisotropic due to nonrotationally symmetric wavefront aberrations such as astigmatism and coma. At the neural level, the visual system exhibits anisotropies in orientation sensitivity across the visual field. In the fovea, the visual system shows higher sensitivity for cardinal over diagonal orientations, which is referred to as the oblique effect. However, in the peripheral retina, the neural visual system becomes more sensitive to radially-oriented signals, a phenomenon known as the meridional effect. Here, we examined the relative contributions of optics and neural processing to the meridional effect in 10 participants at 0°, 10°, and 20° in the temporal retina. Optical anisotropy was quantified by measuring the eye's habitual wavefront aberrations. Alternatively, neural anisotropy was evaluated by measuring contrast sensitivity (at 2 and 4 cyc/deg) while correcting the eye's aberrations with an adaptive optics vision simulator, thus bypassing any optical factors. As eccentricity increased, optical and neural anisotropy increased in magnitude. The average ratio of horizontal to vertical optical MTF (at 2 and 4 cyc/deg) at 0°, 10°, and 20° was 0.96 ± 0.14, 1.41 ± 0.54 and 2.15 ± 1.38, respectively. Similarly, the average ratio of horizontal to vertical contrast sensitivity with full optical correction at 0°, 10°, and 20° was 0.99 ± 0.15, 1.28 ± 0.28 and 1.75 ± 0.80, respectively. These results indicate that the neural system's orientation sensitivity coincides with habitual blur orientation. These findings support the neural origin of the meridional effect and raise important questions regarding the role of peripheral anisotropic optical quality in developing the meridional effect and emmetropization. PMID:26928220

  15. Optical and neural anisotropy in peripheral vision.

    PubMed

    Zheleznyak, Len; Barbot, Antoine; Ghosh, Atanu; Yoon, Geunyoung

    2016-03-01

    Optical blur in the peripheral retina is known to be highly anisotropic due to nonrotationally symmetric wavefront aberrations such as astigmatism and coma. At the neural level, the visual system exhibits anisotropies in orientation sensitivity across the visual field. In the fovea, the visual system shows higher sensitivity for cardinal over diagonal orientations, which is referred to as the oblique effect. However, in the peripheral retina, the neural visual system becomes more sensitive to radially-oriented signals, a phenomenon known as the meridional effect. Here, we examined the relative contributions of optics and neural processing to the meridional effect in 10 participants at 0, 10, and 20 in the temporal retina. Optical anisotropy was quantified by measuring the eye's habitual wavefront aberrations. Alternatively, neural anisotropy was evaluated by measuring contrast sensitivity (at 2 and 4 cyc/deg) while correcting the eye's aberrations with an adaptive optics vision simulator, thus bypassing any optical factors. As eccentricity increased, optical and neural anisotropy increased in magnitude. The average ratio of horizontal to vertical optical MTF (at 2 and 4 cyc/deg) at 0, 10, and 20 was 0.96 0.14, 1.41 0.54 and 2.15 1.38, respectively. Similarly, the average ratio of horizontal to vertical contrast sensitivity with full optical correction at 0, 10, and 20 was 0.99 0.15, 1.28 0.28 and 1.75 0.80, respectively. These results indicate that the neural system's orientation sensitivity coincides with habitual blur orientation. These findings support the neural origin of the meridional effect and raise important questions regarding the role of peripheral anisotropic optical quality in developing the meridional effect and emmetropization. PMID:26928220

  16. Magnetic anisotropy in prismatic nickel nanowires

    NASA Astrophysics Data System (ADS)

    Sun, L.; Searson, P. C.; Chien, C. L.

    2001-12-01

    Nickel nanowire arrays with a diamond-shaped cross section and the same orientation have been fabricated in nanoporous single mica crystal membranes by electrodeposition. All wires are 5 ?m long with an effective diameter of 120 nm. The sample can be considered as a collection of laterally and vertically aligned identical micromagnetic prisms. We report on the magnetic anisotropy due to the quasi-one-dimensional wire shape and diamond cross section.

  17. Dynamical anisotropy of the optical propagation paths

    NASA Astrophysics Data System (ADS)

    Arsenyan, Tatiana I.; Pisklin, Maksim V.; Suhareva, Natalia A.; Zotov, Aleksey M.

    2015-11-01

    Dynamics of laser beam intensity profile spatial modulations over a model tropospheric path with the controlled meteorological parameters was studied. Influence of the underlying surface temperature as well as the side wind load were considered. The increase of dynamic anisotropic disturbances saturation with the path length was observed. Spatio-temporal correlation characteristics of the directivity pattern in the signal beam registration plane were obtained. Proposed method of the experimental samples analysis on the base of chronogram with the following definition of the dynamic structure tensors array allows to estimate local and averaged projections of the flow velocities over the chosen spatio-temporal region and to restore their geometry in the zone of intersection with the signal beam. Additional characteristics suggested for the diagonalized local structure tensors such as local energy capacity and local structuredness are informative for the estimation of the inhomogeneities spatial dimensions, time of access through the section considered, the dynamics of energetic jets. The concepts of rotational and translational dynamic anisotropy are introduced to discriminate the types of the changes of the local ellipsoids axes orientation as well as their values. Rotational anisotropy shows itself in the changes of the local ellipsoids orientation, thus characterizing the illumination variation over the beam cross-section. Translational anisotropy describes the difference between the axes values for local ellipsoids.

  18. Unveiling hidden patterns in CMB anisotropy maps

    SciTech Connect

    Ghosh, Tuhin; Souradeep, Tarun; Hajian, Amir

    2007-04-15

    Bianchi VII{sub h} models have been recently proposed to explain potential anomalies in the CMB anisotropy as observed by WMAP. We investigate the violation of statistical isotropy due to an embedded Bianchi VII{sub h} template in the CMB anisotropy maps to determine whether the existence of a hidden Bianchi template in the WMAP data is consistent with the previous null detection of the bipolar power spectrum in the WMAP first-year maps. We argue that, although correcting the WMAP maps for the Bianchi template may explain some features in the WMAP data, it may cause other anomalies such as preferred directions leading to detectable levels of violation of statistical isotropy in the Bianchi corrected maps. We compute the bipolar power spectrum for the low density Bianchi VII{sub h} models embedded in the background CMB anisotropy maps with the power spectrum that have been shown in recent literature to best fit the first-year WMAP data. By examining the statistical isotropy of these maps, we put a limit of (({sigma}/H)){sub 0}{<=}2.77x10{sup -10}(99% C.L.) on the shear parameter in Bianchi VII{sub h} models.

  19. Fluorescence Anisotropy Studies of Molecularly Imprinted Polymers

    SciTech Connect

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

    2006-01-01

    A molecularly imprinted polymer (MIP) is a biomimetic material that can be used as a biochemical sensing element. We studied the steady-state and time-resolved fluorescence and fluorescence anisotropy of anthracene imprinted polyurethane. We compared MIPs with imprinted analytes present, MIPs with the imprinted analytes extracted, MIPs with rebound analytes, non-imprinted control polymers (non-MIPs), and non-MIPs bound with analytes to understand MIPs binding behavior. MIPs and non-MIPs had similar steady-state fluorescence anisotropy in the range of 0.110.24. Anthracene rebound in MIPs and non-MIPs had a fluorescence lifetime _=0.64 ns and a rotational correlation time _F =1.21.5 ns, both of which were shorter than that of MIPs with imprinted analytes present (_=2.03 ns and _F =2.7 ns). The steady-state anisotropy of polymer solutions increased exponentially with polymerization time and might be used to characterize the polymerization extent in-situ.

  20. Seismic azimuthal anisotropy beneath the Pakistan Himalayas

    NASA Astrophysics Data System (ADS)

    Sandvol, Eric A.; Ni, James F.; Hearn, Thomas M.; Roecker, Steve

    1994-07-01

    Teleseismics S, SKS, and SKKS data, collected from a temporary broadband array across the Himalayan front in Pakistan, are analyzed for shear-wave splitting parameters. The SKS and SKKS phases have ray paths originating from both the South Pacific and Colombia which have azimuths approximately 40 deg apart with respect to the Pakistan array. If significant seismic azimuthal anisotropy is present we should observe splitting associated with one of these ray paths. No evidence was seen for any shear-wave splitting beneath any of the stations in the array. Teleseismic S waves were also used in order to provide better azimuthal coverage for the shear-wave splitting measurements. We were able to correct for any source-side anisotropy when needed. No receiver-side splitting was observed in any of the S wave data. The lack of shear-wave splitting beneath the Pakistan array indicates that there is no appreciable large-scale azimuthal anisotropy beneath this part of the Himalayas. Therefore, if there is any significant strain in the upper mantle beneath this area, it must either be vertically oriented, or, if horizontal, vertically vary in such a way that the integrated effect on S wave splitting is null.

  1. Paper Folding Fractions

    ERIC Educational Resources Information Center

    Pagni, David

    2007-01-01

    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.)

  2. Can Kindergartners Do Fractions?

    ERIC Educational Resources Information Center

    Cwikla, Julie

    2014-01-01

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

  3. An Appetite for Fractions

    ERIC Educational Resources Information Center

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

    2012-01-01

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

  4. Can Kindergartners Do Fractions?

    ERIC Educational Resources Information Center

    Cwikla, Julie

    2014-01-01

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

  5. (Carbon isotope fractionation inplants)

    SciTech Connect

    O'Leary, M.H.

    1990-01-01

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

  6. Seismic anisotropy beneath the Chinese mainland

    NASA Astrophysics Data System (ADS)

    Fu, Yuanyuan V.; Chen, Yongshun John; Li, Aibing

    2010-12-01

    We investigated the upper mantle anisotropy beneath China by applying teleseismic shear wave splitting measurements at 119 seismic stations from CDSN and GSN/IRIS networks in China. The splitting observations are characterized by apparent diversity of anisotropy pattern in adjacent tectonic domains, including the Tianshan orogenic belt, Tibetan plateau, the Yangtze craton, the North China craton and northeastern region. In western China (Tianshan orogenic belt and Tibetan plateau), fast polarization directions of split SKS waves coincide strikingly well with the dominating trend of deformational crustal features and delay times range from 0.5 s to 1.6 s. While in eastern China, seismic anisotropy deduced from shear wave splitting reveals a homogeneous NW-SE trending structure, almost perpendicular to the strike of large-scale surface structures. The observed delay times of 1.5 s to more than 2 s favor consistent mantle flow over large mantle thicknesses. Based upon the straightforward relationships between seismic anisotropy and the development of lattice preferred orientation of mineral in upper mantle rocks, we interpret the splitting results in terms of tectonic fabric within the upper mantle. Since the lithosphere is less than 100 km thick beneath eastern China and the observed fast directions are subparallel to the trend of the absolute plate motion (APM) of Eurasian plate, we propose that the asthenosphere may mainly contribute to the anisotropic effects beneath eastern China. However, the upper mantle anisotropy beneath western China may have developed more recently in the subcrustal lithosphere because of rather small delay times and thick lithosphere. We also use the opportunity of the dense geodetic measurements available in China to discuss the coupling between the crust and mantle. In the Eurasia-fixed reference frame, GPS and shear wave splitting both depict a similar trend beneath eastern China, suggesting a lithospheric block "escaping" toward the east that could orient olivine [001] axis in the upper mantle. There is a strong coupling between the crust and the mantle in eastern China. A different behavior is observed in western China. The GPS vectors trend NS-NE in Tibet and NW in Tianshan, close to the regional compression direction, whereas the fast directions trend EW in Tibet and NE in Tianshan, suggesting a tectonic regime close to a mode of axial shortening, generating the development of EW-trending foliation in Tibet and NE-trending foliation in Tianshan at depth. The crust and mantle deform independently in western China.

  7. Depth-dependent anisotropy in the Caribbean

    NASA Astrophysics Data System (ADS)

    Pinero, L.; Kendall, M.

    2001-12-01

    The tectonics of the Caribbean plate is controlled by its interaction with four other plates, the North American (NA), the South American (SA), the Nazca and the Cocos. Deformation along the east and the west boundaries is controlled by subduction - the Atlantic oceanic plate subducts beneath the Lesser Antilles trench in the east and the Cocos plate subducts beneath the Middle America trench in the west. The northern boundary is characterized by dextral strike-slip faulting to the east and a minor spreading center, the Cayman trough, in the west. The southern boundary zone is a complex and wide deformation zone consisting of a right-lateral transpressional fault connecting trench zones at either end where the Caribbean plate subducts beneath continental South America in the west and oceanic South America subducts beneath continental South America in the east. Our aim is to use observations of anisotropy to help characterise the style of mantle flow in the Caribbean region. We present preliminary estimates of seismic anisotropy obtained from shear-wave splitting analyses of SKS, SKKS and local S-phases. SKS and SKKS splitting has been analysed at the Caribbean IRIS stations, SDV (Santo Domingo, Venezuela), JTS (Costa Rica) and BOCO (Bogota, Colombia). The polarisation of the fast shear-wave correlates well with surface structural features, suggesting at first glance a continuity in mantle and crustal structures. However, a 90 degree periodicity in shear-wave splitting parameters with backazimuth is clearly observed at SJG, and to a lessor extent at SDV, implying depth-dependent variation in mantle anisotropy. Forward modelling suggest a 2-layer model of anisotropy with polarization directions of ? 1=246o and ? 2=270o and delay times of ? t1=1 s and ? t2=0.5 s. The lower layer aligns with the APM direction and the upper layer with the surface geology at the station. To gain further insight into variations in anisotropy with depth we analyse S--phases recorded on the Venezuelan Seismological Network in the northern eastern part of Venezuela. Given the limited number of stations but an abundance of seismicity, many events lie outside the shear-wave window. To better exploit this dataset we use a predictions of near-surface anisotropy and the associated free--surface effects to guide the interpretation of S-phases splitting outside the shear-wave window. Preliminary analysis suggests an average polarisation direction of 81 degrees, which corresponds well with the major structural features present in the area (e.g., the El Pilar fault) and with previous studies of SKS and SKKS phases done by Russo et al. (1993). The results to date suggest that the crust and mantle are coupled during deformation, but that deeper anisotropy may reflect current mantle flow patterns.

  8. Optical anisotropy in packed isotropic spherical particles: indication of nanometer scale anisotropy in packing structure.

    PubMed

    Yamaguchi, Kohei; Inasawa, Susumu; Yamaguchi, Yukio

    2013-02-28

    We investigated the origin of birefringence in colloidal films of spherical silica particles. Although each particle is optically isotropic in shape, colloidal films formed by drop drying demonstrated birefringence. While periodic particle structures were observed in silica colloidal films, no regular pattern was found in blended films of silica and latex particles. However, since both films showed birefringence, regular film structure patterns were not required to exhibit birefringence. Instead, we propose that nanometer-scale film structure anisotropy causes birefringence. Due to capillary flow from the center to the edge of a cast suspension, particles are more tightly packed in the radial direction. Directional packing results in nanometer-scale anisotropy. The difference in the interparticle distance between radial and circumferential axes was estimated to be 10 nm at most. Nanometer-scale anisotropy in colloidal films and the subsequent optical properties are discussed. PMID:23340745

  9. Fractional calculus in bioengineering.

    PubMed

    Magin, Richard L

    2004-01-01

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

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

    PubMed Central

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

    2012-01-01

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

  11. Aspects of anisotropic fractional quantum Hall effect in phosphorene

    NASA Astrophysics Data System (ADS)

    Ghazaryan, Areg; Chakraborty, Tapash

    2015-10-01

    We have analyzed the effects of the anisotropic energy bands of phosphorene on magnetoroton branches for electrons and holes in the two Landau levels close to the band edges. We have found that the fractional quantum Hall effect gap in the lowest (highest) Landau level in the conduction (valence) band is slightly larger than that for conventional semiconductor systems and therefore the effect should be experimentally observable in phosphorene. We also found that the magnetoroton mode for both electrons and holes consists of two branches with two minima due to the anisotropy. Most importantly, in the long-wavelength limit a second mode with upward dispersion, well separated from the magnetoroton mode was found to appear, that is entirely a consequence of the anisotropy in the system. These novel features of the collective mode, unique to phosphorene, can be observed in resonant inelastic light-scattering experiments.

  12. Symmetric continued fractions

    SciTech Connect

    Panprasitwech, Oranit; Laohakosol, Vichian; Chaichana, Tuangrat

    2010-11-11

    Explicit formulae for continued fractions with symmetric patterns in their partial quotients are constructed in the field of formal power series. Similar to the work of Cohn in 1996, which generalized the so-called folding lemma to {kappa}-fold symmetry, the notion of {kappa}-duplicating symmetric continued fractions is investigated using a modification of the 1995 technique due to Clemens, Merrill and Roeder.

  13. Thermodynamics in Fractional Calculus

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

    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.

  14. Intracellular Cadmium Isotope Fractionation

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    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.

  15. Anisotropies observed within ejecta during solar particle onsets

    NASA Technical Reports Server (NTRS)

    Richardson, I. G.; Cane, H. V.

    1995-01-01

    The observation of solar energetic particle onsets within ejecta material suggests that the magnetic field topology of these ejecta is more likely to be that of a 'magnetic bottle' rooted at the Sun than that of a detached plasmoid-like structure. Another possibility is that only open field lines are present. We examine the anisotropies of particle onsets which onset inside ejecta material. A striking feature of a significant fraction of these events is that they show, at onset, strong flows from the east of the Sun, in contrast to the flows from the west usually observed at the onset of solar particle events outside of ejecta. This observation confirms that magnetic field lines can be strongly distorted inside ejecta so as to lie nearly opposite to the Parker spiral direction. This conclusion is fully consistent with the presence of looped magnetic structures in ejecta. If only open field lines are present, it is unclear how these large field line distortions could have been produced.

  16. Fractional laser skin resurfacing.

    PubMed

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

    2012-11-01

    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

  17. Chromatographic methods of fractionation.

    PubMed

    Friesen, A D

    1987-01-01

    Chromatography's functional versatility, separation efficiency, gentle non-denaturing separating process and ease of automation and scale-up make it attractive for industrial scale protein purification. The Winnipeg Rh Institute's new Plasma Fractionation facility is an example of the use of chromatography for the large scale purification of plasma protein fractions. The fractionation facility has a capacity to process 800 litres of plasma per batch into blood clotting factor VIII and IX, albumin and intravenous immune serum globulin (i.v. ISG). Albumin and i.v. ISG are purified using ion exchange columns of DEAE-Sepharose (230 litre size), DEAE-Biogel (150 litre size) and CM-Sepharose (150 litre size). The chromatographic process is automated using a Modicon 584 Programmable Logic Controller to regulate valves, pumps and sensors which control plasma flow during fractionation. The stainless steel tanks and piping are automatically cleaned-in-place. The high degree of automation and cleaning provides efficient operation and sanitary processing. Chromatographic methods (DEAE-Sepharose and metal chelation) are also being used at the pilot scale to purify the human blood products superoxide dismutase and hemoglobin from outdated red blood cells. Characterization of the protein fractions produced by chromatography has shown them to be of equal or higher quality than fractions produced by other techniques. PMID:3609484

  18. Competing magnetic anisotropies in obliquely deposited thin permalloy film

    NASA Astrophysics Data System (ADS)

    Belyaev, B. A.; Izotov, A. V.; Solovev, P. N.

    2016-01-01

    Distribution of the magnetic anisotropy in thin film prepared by thermal vacuum oblique deposition of permalloy with small off-normal angle of incident in the presence of an external magnetic field has been studied by ferromagnetic resonance technique. On local area of the sample, a mutual compensation of near orthogonal in-plane uniaxial magnetic anisotropies induced by oblique deposition and by applied magnetic field has been found. Moreover, in addition to the uniaxial (twofold) magnetic anisotropy, fourfold and sixfold magnetic anisotropies have been observed in the sample. To explain the obtained high-order anisotropies, we assumed that the sample has exchange coupled adjacent regions or phases with different parameters of magnetic anisotropy. The results of the micromagnetic analysis of a two-layer model of the sample confirm the hypothesis.

  19. Structure and Anisotropy Beneath Southern Italy

    NASA Astrophysics Data System (ADS)

    Okeler, A.; Gu, Y. J.; Steckler, M. S.; Lerner-Lam, A.

    2007-12-01

    The crust and upper mantle structures beneath southern Italy are often associated with rollback and fragmentation of the Western Mediterranean subduction zone in the past 30 million years. In this study, we utilize broadband records from the Calabria-Apennine-Tyrrhenian/Subduction Collision-Accretion Network (CAT/SCAN) to probe the effect of the past and on-going plate motions beneath this region. Waveforms from two distinct frequency ranges are examined in detail using both forward and inverse waveform modeling approaches, and the resulting 1-D models for each path are subjected to a Monte-Carlo uncertainty test. By analyzing the Love and Rayleigh waves from two regional earthquakes during the temporary deployment between 2003 and 2005, we are able to retrieve information on the anisotropic seismic structure down to 200-km depth. Our study shows that the average seismic structure beneath Calabria/Apulia is significantly faster than that beneath the Apenninic mountain chain. Sharp changes in seismic velocities, regardless of wave polarizations, lend strong support for the distinct geologic histories of the major tectonic units. The difference between Love- and Rayleigh-wave models provides further constraints on the dynamic processes and crust/mantle fabric beneath the study area. Our preliminary results show relatively minor anisotropy beneath the southeastern Tyrrhenian Sea and Calabrian Arc region, which could be partially explained by the rapid changes in the alignment of olivine fast crystallographic-axes due to the complex arc geometry. The ray paths connecting the Ionian Sea and the Southern Apennines reveal strong anisotropy, where transversely polarized waves travel at higher speeds than vertically polarized waves. Both "frozen-in" and flow-induced anisotropy could contribute to the observed waveform differences between the Love and Rayleigh waves sampling this region.

  20. Detecting Mantle Anisotropy with Marine CSEM Sounding

    NASA Astrophysics Data System (ADS)

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

    2010-12-01

    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.

  1. CMB statistical anisotropy from noncommutative gravitational waves

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

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

  2. Programming magnetic anisotropy in polymeric microactuators

    NASA Astrophysics Data System (ADS)

    Kim, Jiyun; Chung, Su Eun; Choi, Sung-Eun; Lee, Howon; Kim, Junhoi; Kwon, Sunghoon

    2011-10-01

    Polymeric microcomponents are widely used in microelectromechanical systems (MEMS) and lab-on-a-chip devices, but they suffer from the lack of complex motion, effective addressability and precise shape control. To address these needs, we fabricated polymeric nanocomposite microactuators driven by programmable heterogeneous magnetic anisotropy. Spatially modulated photopatterning was applied in a shape-independent manner to microactuator components by successive confinement of self-assembled magnetic nanoparticles in a fixed polymer matrix. By freely programming the rotational axis of each component, we demonstrate that the polymeric microactuators can undergo predesigned, complex two- and three-dimensional motion.

  3. Programming magnetic anisotropy in polymeric microactuators.

    PubMed

    Kim, Jiyun; Chung, Su Eun; Choi, Sung-Eun; Lee, Howon; Kim, Junhoi; Kwon, Sunghoon

    2011-10-01

    Polymeric microcomponents are widely used in microelectromechanical systems (MEMS) and lab-on-a-chip devices, but they suffer from the lack of complex motion, effective addressability and precise shape control. To address these needs, we fabricated polymeric nanocomposite microactuators driven by programmable heterogeneous magnetic anisotropy. Spatially modulated photopatterning was applied in a shape-independent manner to microactuator components by successive confinement of self-assembled magnetic nanoparticles in a fixed polymer matrix. By freely programming the rotational axis of each component, we demonstrate that the polymeric microactuators can undergo predesigned, complex two- and three-dimensional motion. PMID:21822261

  4. Magnetic Edge Anisotropy in Graphenelike Honeycomb Crystals

    NASA Astrophysics Data System (ADS)

    Lado, J. L.; Fernndez-Rossier, J.

    2014-07-01

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

  5. Magnetic edge anisotropy in graphenelike honeycomb crystals.

    PubMed

    Lado, J L; Fernndez-Rossier, J

    2014-07-11

    The independent predictions of edge ferromagnetism and the quantum spin Hall phase in graphene have inspired the quest of other two-dimensional honeycomb systems, such as silicene, germanene, stanene, iridates, and organometallic lattices, as well as artificial superlattices, all of them with electronic properties analogous to those of graphene, but a larger spin-orbit coupling. Here, we study the interplay of ferromagnetic order and spin-orbit interactions at the zigzag edges of these graphenelike systems. We find an in-plane magnetic anisotropy that opens a gap in the otherwise conducting edge channels that should result in large changes of electronic properties upon rotation of the magnetization. PMID:25062225

  6. The Microwave Anisotropy Probe (MAP) Mission

    NASA Technical Reports Server (NTRS)

    Markley, F. Landis; Andrews, Stephen F.; ODonnell, James R., Jr.; Ward, David K.; Ericsson, Aprille J.; Bauer, Frank H. (Technical Monitor)

    2002-01-01

    The Microwave Anisotropy Probe mission is designed to produce a map of the cosmic microwave background radiation over the entire celestial sphere by executing a fast spin and a slow precession of its spin axis about the Sun line to obtain a highly interconnected set of measurements. The spacecraft attitude is sensed and controlled using an Inertial Reference Unit, two Autonomous Star Trackers, a Digital Sun Sensor, twelve Coarse Sun Sensors, three Reaction Wheel Assemblies, and a propulsion system. This paper describes the design of the attitude control system that carries out this mission and presents some early flight experience.

  7. The Microwave Anisotropy Probe (MAP) Mission

    NASA Technical Reports Server (NTRS)

    Markley, F. Landis; Andrews, Stephen F.; ODonnell, James R., Jr.; Ward, David K.; Bauer, Frank H. (Technical Monitor)

    2002-01-01

    The Microwave Anisotropy Probe mission is designed to produce a map of the cosmic microwave background radiation over the entire celestial sphere by executing a fast spin and a slow precession of its spin axis about the Sun line to obtain a highly interconnected set of measurements. The spacecraft attitude is sensed and controlled using an inertial reference unit, two star trackers, a digital sun sensor, twelve coarse sun sensors, three reaction wheel assemblies, and a propulsion system. This paper presents an overview of the design of the attitude control system to carry out this mission and presents some early flight experience.

  8. Knitted patterns as a model for anisotropy

    NASA Astrophysics Data System (ADS)

    ?epi?, Mojca

    2012-07-01

    Anisotropy is a difficult concept, although it is often met in everyday life. This paper describes a simple modelknitted patternshaving 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.

  9. Concave nanomagnets with widely tunable anisotropy

    DOEpatents

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

    2014-07-01

    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.

  10. Electro-mechanical anisotropy of phosphorene.

    PubMed

    Wang, Luqing; Kutana, Alex; Zou, Xiaolong; Yakobson, Boris I

    2015-06-01

    The applied uniaxial stress can break the original symmetry of a material, providing an experimentally feasible way to alter material properties. Here, we explore the effects of uniaxial stress along an arbitrary direction on mechanical and electronic properties of phosphorene, showing the enhancement of inherent anisotropy. Basic physical quantities including Young's modulus, Poisson's ratio, band gap, and effective carrier masses under external stress are all computed from first principles using density functional theory, while the final results are presented in compact analytical forms. PMID:25963326

  11. Fluorescence anisotropy measurements under shock compression

    NASA Astrophysics Data System (ADS)

    Wang, Jue; Bassett, Will; Banishev, Alexandr; Dlott, Dana

    2015-06-01

    Fluorescence anisotropy measurements, where the parallel and perpendicular polarized emissions from probe molecules are acquired simultaneously, provide direct measurement of molecular rotational dynamics. In our experiments, the fluorescence from rhodamine 6G dye in various materials under GPa shocks produced by laser-driven flyer plates is collected, separated into two orthogonally-polarized beams using a Wollaston prism and detected with a streak camera. In liquids, the molecular rotations result from rotational diffusion and in solids from shear flow. The rotation rates can be used to determine the viscosity of the shocked medium.

  12. Structural anisotropy of directionally dried colloids

    NASA Astrophysics Data System (ADS)

    Boulogne, François; Pauchard, Ludovic; Giorgiutti-Dauphiné, Frédérique; Botet, Robert; Schweins, Ralf; Sztucki, Michael; Li, Joaquim; Cabane, Bernard; Goehring, Lucas

    2014-02-01

    Aqueous colloidal dispersions of silica particles become anisotropic when they are dried through evaporation. This anisotropy is generated by a uniaxial strain of the liquid dispersions as they are compressed by the flow of water toward a solidification front. Part of the strain produced by the compression is relaxed, and part of it is stored and transferred to the solid. This stored elastic strain has consequences for the properties of the solid, where it may facilitate the growth of shear bands, and generate birefringence.

  13. Seismic anisotropy above a subducting plate

    SciTech Connect

    Shih, X.R.; Meyer, R.P. ); Schneider, J.F. )

    1991-08-01

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

  14. Anisotropies in the gravitational-wave stochastic background

    SciTech Connect

    Ölmez, S.; Mandic, V.; Siemens, X. E-mail: mandic@physics.umn.edu

    2012-07-01

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

  15. Cosmic ray north-south anisotropy 1961 - 1983

    NASA Technical Reports Server (NTRS)

    Bieber, J. W.; Pomerantz, M. A.

    1985-01-01

    Measurements from neutron monitors in Thule (Greenland) and McMurdo (Antarctica) were used to determine yearly values of the cosmic ray north-south anisotropy over the period 1961-1983. The results strongly suggest that superposed upon the mean anisotropy of 0.05% is a solar cycle variation of amplitude 0.03%. No evidence for a dependence of the anisotropy upon polarity of the solar poloidal magnetic field is found.

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

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

    The development of anisotropy in an initially isotropic spectrum is studied numerically for two-dimensional magnetohydrodynamic turbulence. The anisotropy develops due to the combined effects of an externally imposed dc magnetic field and viscous and resistive dissipation at high wave numbers. The effect is most pronounced at high mechanical and magnetic Reynolds numbers. The anisotropy is greater at the higher wave numbers. Previously announced in STAR as N83-12998

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

    PubMed Central

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

    2013-01-01

    Corpus callosum (CC) area abnormalities have been reported in magnetic resonance imaging (MRI) studies of adults and youths with bipolar disorder (BPD), suggesting interhemispheric communication may be abnormal in BPD and may be present early in the course of illness and affect normal neuromaturation of this structure throughout the lifecycle. Neuroimaging scans from 44 youths with DSM-IV BPD and 22 healthy controls (HC) were analyzed using cross-sectional area measurements and a novel method of volumetric parcellation. Univariate analyses of variance were conducted on CC subregions using both volume and traditional area measurements. Youths with BPD had smaller middle and posterior callosal regions, and reduced typical age-related increases in CC size. The cross-sectional area and novel volumetric methodologies resulted in similar findings. Future longitudinal assessments of CC development would track the evolution of callosal abnormalities in youths with BPD and allow exploration of the functional significance of these findings. PMID:20686873

  18. Software pipeline for midsagittal corpus callosum thickness profile processing : automated segmentation, manual editor, thickness profile generator, group-wise statistical comparison and results display.

    PubMed

    Adamson, Chris; Beare, Richard; Walterfang, Mark; Seal, Marc

    2014-10-01

    This paper presents a fully automated pipeline for thickness profile evaluation and analysis of the human corpus callosum (CC) in 3D structural T 1-weighted magnetic resonance images. The pipeline performs the following sequence of steps: midsagittal plane extraction, CC segmentation algorithm, quality control tool, thickness profile generation, statistical analysis and results figure generator. The CC segmentation algorithm is a novel technique that is based on a template-based initialisation with refinement using mathematical morphology operations. The algorithm is demonstrated to have high segmentation accuracy when compared to manual segmentations on two large, publicly available datasets. Additionally, the resultant thickness profiles generated from the automated segmentations are shown to be highly correlated to those generated from the ground truth segmentations. The manual editing tool provides a user-friendly environment for correction of errors and quality control. Statistical analysis and a novel figure generator are provided to facilitate group-wise morphological analysis of the CC. PMID:24968872

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

    SciTech Connect

    Stone, Kevin H.

    2014-07-14

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

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

    NASA Astrophysics Data System (ADS)

    Stone, Kevin H.; Kortright, Jeffrey B.

    2014-09-01

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

  1. Axial Magnetic Anisotropy from Two Systems Fe2B and Co2B with Planar Anisotropy

    NASA Astrophysics Data System (ADS)

    Taufour, Valentin; Lamichhane, Tej; Bud'Ko, Sergey L.; Jesche, Anton; Goldman, Alan I.; Dennis, Kevin W.; McCallum, R. William; Antropov, Vladimir; Canfield, Paul C.

    2015-03-01

    Growth of single crystals of (Fe1-xCox)2B (0 <= x <= 1) and detailed characterization of their magnetic properties will be presented. Despite the fact that both Fe2B and Co2B show a planar anisotropy at room temperature, we observe a uniaxial anisotropy at intermediate doping which makes (Fe,Co)2B a promising system for permanent magnet applications in a system without rare-earth element. Comparison with recent band structure calculations will be presented. The temperature dependence of the anisotropy measured on single crystals from 2 K to 1000 K shows some unusual variations with an increase of the magnetic anisotropy with increasing temperature at some specific substitution. This work is supported by the Critical Materials Institute, an Energy Innovation Hub funded by the US DOE and by the Office of Basic Energy Science, Division of Materials Science and Engineering. Ames Laboratory is operated for the US DOE by Iowa State University under Contract No. DE-AC02-07CH11358.

  2. Electrical resistivity characterization of anisotropy in the Biscayne Aquifer.

    PubMed

    Yeboah-Forson, Albert; Whitman, Dean

    2014-01-01

    Electrical anisotropy occurs when electric current flow varies with azimuth. In porous media, this may correspond to anisotropy in the hydraulic conductivity resulting from sedimentary fabric, fractures, or dissolution. In this study, a 28-electrode resistivity imaging system was used to investigate electrical anisotropy at 13 sites in the Biscayne Aquifer of SE Florida using the rotated square array method. The measured coefficient of electrical anisotropy generally ranged from 1.01 to 1.12 with values as high as 1.36 found at one site. The observed electrical anisotropy was used to estimate hydraulic anisotropy (ratio of maximum to minimum hydraulic conductivity) which ranged from 1.18 to 2.83. The largest values generally were located on the Atlantic Coastal Ridge while the lowest values were in low elevation areas on the margin of the Everglades to the west. The higher values of anisotropy found on the ridge may be due to increased dissolution rates of the oolitic facies of the Miami formation limestone compared with the bryozoan facies to the west. The predominate trend of minimum resistivity and maximum hydraulic conductivity was E-W/SE-NW beneath the ridge and E-W/SW-NE farther west. The anisotropy directions are similar to the predevelopment groundwater flow direction as indicated in published studies. This suggests that the observed anisotropy is related to the paleo-groundwater flow in the Biscayne Aquifer. PMID:24033332

  3. Deciphering the human brain proteome: characterization of the anterior temporal lobe and corpus callosum as part of the Chromosome 15-centric Human Proteome Project.

    PubMed

    Martins-de-Souza, Daniel; Carvalho, Paulo C; Schmitt, Andrea; Junqueira, Magno; Nogueira, Fbio C S; Turck, Christoph W; Domont, Gilberto B

    2014-01-01

    Defining the proteomes encoded by each chromosome and characterizing proteins related to human illnesses are among the goals of the Chromosome-centric Human Proteome Project (C-HPP) and the Biology and Disease-driven HPP. Following these objectives, we investigated the proteomes of the human anterior temporal lobe (ATL) and corpus callosum (CC) collected post-mortem from eight subjects. Using a label-free GeLC-MS/MS approach, we identified 2454 proteins in the ATL and 1887 in the CC through roughly 7500 and 5500 peptides, respectively. Considering that the ATL is a gray-matter region while the CC is a white-matter region, they presented proteomes specific to their functions. Besides, 38 proteins were found to be differentially expressed between the two regions. Furthermore, the proteome data sets were classified according to their chromosomal origin, and five proteins were evidenced at the MS level for the first time. We identified 70 proteins of the chromosome 15 - one of them for the first time by MS - which were submitted to an in silico pathway analysis. These revealed branch point proteins associated with Prader-Willi and Angelman syndromes and dyskeratosis congenita, which are chromosome-15-associated diseases. Data presented here can be a useful for brain disorder studies as well as for contributing to the C-HPP initiative. Our data are publicly available as resource data to C-HPP participant groups at http://yoda.iq.ufrj.br/Daniel/chpp2013. Additionally, the mass spectrometry proteomics data have been deposited to the ProteomeXchange with identifier PXD000547 for the corpus callosum and PXD000548 for the anterior temporal lobe. PMID:24274931

  4. Fractional Noether Theorem Based on Extended Exponentially Fractional Integral

    NASA Astrophysics Data System (ADS)

    Long, Zi-Xuan; Zhang, Yi

    2013-10-01

    Based on the new type of fractional integral definition, namely extended exponentially fractional integral introduced by EI-Nabulsi, we study the fractional Noether symmetries and conserved quantities for both holonomic system and nonholonomic system. First, the fractional variational problem under the sense of extended exponentially fractional integral is established, the fractional d'Alembert-Lagrange principle is deduced, then the fractional Euler-Lagrange equations of holonomic system and the fractional Routh equations of nonholonomic system are given; secondly, the invariance of fractional Hamilton action under infinitesimal transformations of group is also discussed, the corresponding definitions and criteria of fractional Noether symmetric transformations and quasi-symmetric transformations are established; finally, the fractional Noether theorems for both holonomic system and nonholonomic system are explored. What's more, the relationship between the fractional Noether symmetry and conserved quantity are revealed.

  5. Anomalous work function anisotropy in ternary acetylides

    NASA Astrophysics Data System (ADS)

    Terdik, Joseph Z.; Nmeth, Kroly; Harkay, Katherine C.; Terry, Jeffrey H., Jr.; Spentzouris, Linda; Velzquez, Daniel; Rosenberg, Richard; Srajer, George

    2012-07-01

    Anomalous anisotropy of work function values in ternary alkali metal transition metal acetylides is reported. Work function values of some characteristic surfaces in these emerging semiconducting materials may differ by more than 2 eV as predicted by density functional theory calculations. This large anisotropy is a consequence of the relative orientation of rodlike [MC2]? negatively charged polymeric subunits and the surfaces, with M being a transition metal or metalloid element and C2 refers to the acetylide ion C22-, with the rods embedded into an alkali cation matrix. It is shown that the conversion of the seasoned Cs2Te photoemissive material to ternary acetylide Cs2TeC2 results in substantial reduction of its ?3 eV work function down to 1.71-2.44 eV on the Cs2TeC2(010) surface, while its high quantum yield is preserved. Similar low work function values are predicted for other ternary acetylides as well, allowing for a broad range of applications from improved electron and light sources to solar cells, field emission displays, detectors, and scanners.

  6. Extrinsic response anisotropy in ferroelectric perovskite polycrystals

    NASA Astrophysics Data System (ADS)

    Garcia, J. E.; Perez, R.; Albareda, A.; Eiras, J. A.

    2007-10-01

    A study on the anisotropy of the nonlinear dielectric response in donor- and acceptor-doped Pb(Zr 0.6Ti 0.4)O 3 ceramics is presented. They have been tested in two directions, parallel to and normal to the poling direction. The results reveal a noticeable anisotropic behavior related to a different movement of domain walls when the field is applied in either direction. A simple model for the domain wall movement, which can be applied to any perovskite ceramic, is developed in order to explain this behavior. It is supposed that the grains are monocrystals with a lamellar structure of non- 180 ? domains. It is proved that in such a structure, the extrinsic contribution is greater in the direction normal to the poling direction than in that parallel to this direction. Moreover, acceptor-doped ceramics show a higher anisotropy than donor-doped ceramics. This fact can be explained by taking into account that the complex defects show a preferential orientation, so they produce a stronger domain wall pinning in the poling direction than in the normal one.

  7. Reflectance anisotropy spectroscopy of magnetite (110) surfaces

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

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

  8. Electro-mechanical anisotropy of phosphorene

    NASA Astrophysics Data System (ADS)

    Wang, Luqing; Kutana, Alex; Zou, Xiaolong; Yakobson, Boris I.

    2015-05-01

    The applied uniaxial stress can break the original symmetry of a material, providing an experimentally feasible way to alter material properties. Here, we explore the effects of uniaxial stress along an arbitrary direction on mechanical and electronic properties of phosphorene, showing the enhancement of inherent anisotropy. Basic physical quantities including Young's modulus, Poisson's ratio, band gap, and effective carrier masses under external stress are all computed from first principles using density functional theory, while the final results are presented in compact analytical forms.The applied uniaxial stress can break the original symmetry of a material, providing an experimentally feasible way to alter material properties. Here, we explore the effects of uniaxial stress along an arbitrary direction on mechanical and electronic properties of phosphorene, showing the enhancement of inherent anisotropy. Basic physical quantities including Young's modulus, Poisson's ratio, band gap, and effective carrier masses under external stress are all computed from first principles using density functional theory, while the final results are presented in compact analytical forms. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr00355e

  9. Cosmic microwave anisotropies from BPS semilocal strings

    SciTech Connect

    Urrestilla, Jon; Bevis, Neil; Hindmarsh, Mark; Kunz, Martin; Liddle, Andrew R E-mail: n.bevis@imperial.ac.uk E-mail: martin.kunz@physics.unige.ch

    2008-07-15

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

  10. Results from the Wilkinson Microwave Anisotropy Probe

    NASA Technical Reports Server (NTRS)

    Komatsu, E.; Bennett, Charles L.; Komatsu, Eiichiro

    2015-01-01

    The Wilkinson Microwave Anisotropy Probe (WMAP) mapped the distribution of temperature and polarization over the entire sky in five microwave frequency bands. These full-sky maps were used to obtain measurements of temperature and polarization anisotropy of the cosmic microwave background with the unprecedented accuracy and precision. The analysis of two-point correlation functions of temperature and polarization data gives determinations of the fundamental cosmological parameters such as the age and composition of the universe, as well as the key parameters describing the physics of inflation, which is further constrained by three-point correlation functions. WMAP observations alone reduced the flat ? cold dark matter (Lambda Cold Dark Matter) cosmological model (six) parameter volume by a factor of > 68, 000 compared with pre-WMAP measurements. The WMAP observations (sometimes in combination with other astrophysical probes) convincingly show the existence of non-baryonic dark matter, the cosmic neutrino background, flatness of spatial geometry of the universe, a deviation from a scale-invariant spectrum of initial scalar fluctuations, and that the current universe is undergoing an accelerated expansion. The WMAP observations provide the strongest ever support for inflation; namely, the structures we see in the universe originate from quantum fluctuations generated during inflation.

  11. Topological signatures in CMB temperature anisotropy maps

    SciTech Connect

    Hipolito-Ricaldi, W.S.; Gomero, G.I.

    2005-11-15

    We propose an alternative formalism to simulate cosmic microwave background (CMB) temperature maps in {lambda}CDM universes with nontrivial spatial topologies. This formalism avoids the need to explicitly compute the eigenmodes of the Laplacian operator in the spatial sections. Instead, the covariance matrix of the coefficients of the spherical harmonic decomposition of the temperature anisotropies is expressed in terms of the elements of the covering group of the space. We obtain a decomposition of the correlation matrix that isolates the topological contribution to the CMB temperature anisotropies out of the simply connected contribution. A further decomposition of the topological signature of the correlation matrix for an arbitrary topology allows us to compute it in terms of correlation matrices corresponding to simpler topologies, for which closed quadrature formulas might be derived. We also use this decomposition to show that CMB temperature maps of (not too large) multiply connected universes must show ''patterns of alignment,'' and propose a method to look for these patterns, thus opening the door to the development of new methods for detecting the topology of our Universe even when the injectivity radius of space is slightly larger than the radius of the last scattering surface. We illustrate all these features with the simplest examples, those of flat homogeneous manifolds, i.e., tori, with special attention given to the cylinder, i.e., T{sup 1} topology.

  12. Effects of pressure anisotropy on plasma transport

    SciTech Connect

    Zawaideh, E.; Najmabadi, F.; Conn, R.W.

    1986-03-01

    In a recent paper a new set of generalized two-field equations is derived which describes plasma transport along the field lines of a space and time dependent magnetic field. These equations are valid for collisional to weakly collisional plasmas; they reduce to the conventional fluid equations of Braginskii for highly collisional plasmas. An important feature of these equations is that the anisotropy in the ion pressure is explicitly included. In this paper, these generalized transport equations are applied to a model problem of plasma flow through a magnetic mirror field. The profiles of the plasma parameters (density, flow speed, and pressures) are numerically calculated for plasma in different collisionality regimes. These profiles are explained by examining the competing terms in the transport equation. The pressure anisotropy is found to profoundly impact the plasma flow behavior. As a result, the new generalized equations predict flow behavior more accurately than the conventional transport equations. A large density and pressure drop is predicted as the flow passes through a magnetic mirror. Further, the new equations uniquely predict oscillations in the density profile, an effect missing in results from the conventional equations.

  13. Spintronic anisotropy: proximity-induced superparamagnetism

    NASA Astrophysics Data System (ADS)

    Misiorny, Maciej; Hell, Michael; Wegewijs, Maarten

    2014-03-01

    Superparamagnetism of molecular magnets, i.e. the preferential alignment of their spins along an easy axis, is a useful effect for nanoscale applications as it prevents undesired spin reversals. In these systems such a stabilization of axial spin states is ensured by the magnetic anisotropy barrier stemming from intrinsic spin-orbit coupling. Here we demonstrate that any spin-isotropic high-spin quantum dot coupled to ferromagnets can in fact acquire such superparamagnetic properties in a spintronic way, even though spin-orbit interaction is negligible. We predict a proximity-induced spin-anisotropy barrier, which has hallmarks of a spintronic exchange-field of quadrupolar nature: it is highly localized, electrically controllable, increases with tunnel coupling and spin-polarization. Such a field is a generalization of the dipolar exchange field that relates to a current-induced spin-torque, effect well established in spintronics. We acknowledge the financial support from the DFG (FOR 912), the Foundation for Polish Science (M.M.) and the Alexander von Humboldt Foundation (M.M.).

  14. A large anisotropy in the sky distribution of 3CRR quasars and other radio galaxies

    NASA Astrophysics Data System (ADS)

    Singal, Ashok K.

    2015-06-01

    We report the presence of large anisotropies in the sky distributions of powerful extended quasars as well as some other sub-classes of radio galaxies in the 3CRR survey, the most reliable and most intensively studied complete sample of strong steep-spectrum radio sources. The anisotropies lie about a plane passing through the equinoxes and the north celestial pole. Out of a total of 48 quasars in the sample, 33 of them lie in one half of the observed sky and the remaining 15 in the other half. The probability that in a random distribution of 3CRR quasars in the sky, statistical fluctuations could give rise to an asymmetry in observed numbers up to this level is only ˜1 %. Also only about 1/4th of Fanaroff-Riley 1 (FR1) type of radio galaxies lie in the first half of the observed sky and the remainder in the second half. If we include all the observed asymmetries in the sky distributions of quasars and radio galaxies in the 3CRR sample, the probability of their occurrence by a chance combination reduces to ˜2×10-5. Two pertinent but disturbing questions that could be raised here are—firstly why should there be such large anisotropies present in the sky distribution of some of the strongest and most distant discrete sources, implying inhomogeneities in the universe at very large scales (covering a fraction of the universe)? Secondly why should such anisotropies lie about a great circle decided purely by the orientation of earth's rotation axis and/or the axis of its revolution around the sun? It seems yet more curious when we consider the other anisotropies, e.g., an alignment of the four normals to the quadrupole and octopole planes in the CMBR with the cosmological dipole and the equinoxes. Then there is the other recently reported large dipole anisotropy in the NVSS radio source distribution differing in magnitude from the CMBR dipole by a factor of four, and therefore not explained as due to the peculiar motion of the Solar system, yet aligned with the CMBR dipole which itself lies close to the line joining the equinoxes. Are these alignments a mere coincidence or do they imply that these axes have a preferential placement in the larger scheme of things, implying an apparent breakdown of the Copernican principle or its more generalization, cosmological principle, upon which the standard cosmological model is based upon?

  15. Snow anisotropy enables more precise determination of thermal conductivity via second-order bounds

    NASA Astrophysics Data System (ADS)

    Loewe, H.; Riche, F.; Schneebeli, M.

    2012-12-01

    The evolution of macroscopic physical properties of snow and their relation to microstructural parameters is a key aspect for virtually all applications in cryospheric sciences. Snow properties are usually parametrized phenomenologically, e.g. in terms of the density (ice volume fraction) as the most important microstructural parameter which correlates well with physical properties. However, a large scatter usually remains if properties are solely constrained on density. We show that the broad range of anisotropy in natural snow, if formalized by appropriate means, can be exploited to reduce the scatter. To this end we address the effective thermal conductivity tensor of snow via known rigorous, second-order bounds. The bounds predict the relevance of a microstructural anisotropy parameter Q which is given by an integral over the two-point correlation function and thereby unambiguously defined for arbitrary microstructures. For validation we compiled a comprehensive data set of 167 snow samples. These comprise individual samples of various seasonal snow types and several time series of metamorphism experiments under isothermal conditions (duration: one year) and temperature gradient conditions (duration: weeks to months) with emphasis on depth hoar. All samples were reconstructed by micro-computed tomography to facilitate a comparison of the theory with microstructure-based Finite Element simulations of conductive heat transport. Compared to purely density based parametrizations, the incorporation of Q yields a considerably smaller error. Our systematic approach quantifies the influence of snow anisotropy and constitutes a generalizable route to incorporate snow microstructure into macroscopic snow models. By mathematical analogy, we indicate the expected impact of anisotropy on the dielectric tensor, permeability and the adsorption rate of diffusing species in the pore space.

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

    NASA Astrophysics Data System (ADS)

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

    2013-12-01

    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.

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

    SciTech Connect

    Cooray, Asantha; Gong Yan; Smidt, Joseph; Santos, Mario G.

    2012-09-01

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

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

    SciTech Connect

    Linden, Tim; Profumo, Stefano

    2013-07-20

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

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

    NASA Astrophysics Data System (ADS)

    Linden, Tim; Profumo, Stefano

    2013-07-01

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

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

    PubMed Central

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

    2010-01-01

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

  1. FRACTIONAL CRYSTALLIZATION FEED ENVELOPE

    SciTech Connect

    HERTING DL

    2008-03-19

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

  2. Release Fraction Evaluation

    SciTech Connect

    Bamberger, Judith A.; Glissmeyer, John A.

    2004-01-01

    This document presents results of experiments conducted to measure release fractions during certain tank retrieval processes. The tests were performed in a 1/4 scale model of a waste storage tank. The retrieval processes simulated were: (1) Discharging liquid or slurry from the mouth of a vertically oriented two-in. Schedule 40 pipe. The discharging material was in free-fall from the mouth of the pipe near the top of the tank into a liquid or slurry pool at the bottom of the tank. (2) The jet from a 9/16-in.-diameter nozzle transferring liquid or slurry waste from one side of the tank to the other. The discharging liquid was aimed at the opposite side of the tank from the nozzle and either impacted the tank wall or fell into a liquid or slurry pool in the bottom of the tank. (3) A high pressure fan jet of liquid striking a steel plate or simulated waste from a stand-off distance of a few inches. For each process, a water-soluble fluorescent dye was added to the liquid fraction as a tracer. Kaolin clay was used to represent the solids. The tank was covered and there was no forced ventilation in the tank during the tests. Six air samples were collected during each test. The air samples were collected at fixed positions in the tank. The air sample filters were dried and weighed to determine the solids collection. The fluorescent dye was then leached from each filter and quantified with a fluorometer to determine the collection of liquid. Samples of the slurry and liquid simulants were also collected to determine the quantities of simulant used in each test. To calculate the release fraction, the quantity collected on each air sample was adjusted for the fraction of the tank volume sampled and divided by the quantity of material exposed in the simulation. The method was not as sensitive for the solids content as it was for the liquid content, but in those instances where a solids release fraction was determined, it was in relatively good agreement with that of the liquid phase. Release fractions are commonly used to make conservative estimates of emissions from processes. Usually, rather gross assumptions are made in such estimates, such as the total failure of abatement equipment and the use of maximum inventory values. Consequently, it is common practice to report bounding release fraction values with single digit accuracy. The release fractions for the top of the unventilated tank ranged from 9 x 10{sup -7} to 8 x 10{sup -5} depending on the process simulated.

  3. Multipartite Fully Entangled Fraction

    NASA Astrophysics Data System (ADS)

    Xu, Jianwei

    2016-01-01

    Fully entangled fraction is a definition for bipartite states, which is tightly related to bipartite maximally entangled states, and has clear experimental and theoretical significance. In this work, we generalize it to multipartite case, we call the generalized version multipartite fully entangled fraction (MFEF). MFEF measures the closeness of a state to GHZ states. The analytical expressions of MFEF are very difficult to obtain except for very special states, however, we show that, the MFEF of any state is determined by a system of finite-order polynomial equations. Therefore, the MFEF can be efficiently numerically computed.

  4. CMB statistical anisotropy from noncommutative gravitational waves

    SciTech Connect

    Shiraishi, Maresuke; Ricciardone, Angelo; Mota, David F.; Arroja, Frederico E-mail: d.f.mota@astro.uio.no E-mail: arroja@pd.infn.it

    2014-07-01

    Primordial statistical anisotropy is a key indicator to investigate early Universe models and has been probed by the cosmic microwave background (CMB) anisotropies. In this paper, we examine tensor-mode CMB fluctuations generated from anisotropic gravitational waves, parametrised by P{sub h}(k) = P{sub h}{sup (0)}(k) [ 1 + ∑{sub LM} f{sub L}(k) g{sub LM} Y{sub LM} ( k-circumflex )], where P{sub h}{sup (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 f{sub 0}(k) = f{sub 2}(k) ∝ k{sup -2} are created and hence highly red-tilted off-diagonal components arise in the CMB power spectra, namely ℓ{sub 2} = ℓ{sub 1} ± 2 in TT, TE, EE and BB, and ℓ{sub 2} = ℓ{sub 1} ± 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 g{sub 00} = 30 and g{sub 2M} = 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.

  5. LOCAL ANISOTROPY, HIGHER ORDER STATISTICS, AND TURBULENCE SPECTRA

    SciTech Connect

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

    2012-05-10

    Correlation anisotropy emerges dynamically in magnetohydrodynamics (MHD), producing stronger gradients across the large-scale mean magnetic field than along it. This occurs both globally and locally, and has significant implications in space and astrophysical plasmas, including particle scattering and transport, and theories of turbulence. Properties of local correlation anisotropy are further documented here by showing through numerical experiments that the effect is intensified in more localized estimates of the mean field. The mathematical formulation of this property shows that local anisotropy mixes second-order with higher order correlations. Sensitivity of local statistical estimates to higher order correlations can be understood in connection with the stochastic coordinate system inherent in such formulations. We demonstrate this in specific cases, and illustrate the connection to higher order statistics by showing the sensitivity of local anisotropy to phase randomization, after which the global measure of anisotropy is recovered at all scales of averaging. This establishes that anisotropy of the local structure function is not a measure of anisotropy of the energy spectrum. Evidently, the local enhancement of correlation anisotropy is of substantial fundamental interest and must be understood in terms of higher order correlations, specifically fourth-order and above.

  6. OBSERVATIONAL SCAN-INDUCED ARTIFICIAL COSMIC MICROWAVE BACKGROUND ANISOTROPY

    SciTech Connect

    Liu Hao; Li Tipei E-mail: litp@tsinghua.edu.cn

    2011-05-10

    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.

  7. Studying the Interstellar Magnetic Field from Anisotropies in Velocity Channels

    NASA Astrophysics Data System (ADS)

    Esquivel, A.; Lazarian, A.; Pogosyan, D.

    2015-11-01

    Turbulence in the interstellar medium is anisotropic due to the ubiquitous magnetic fields. This anisotropy depends on the strength of the magnetic field and leaves an imprint on observations of spectral line maps. We use a grid of ideal magnetohydrodynamic simulations of driven turbulence and produce synthetic position-position-velocity maps to study the turbulence anisotropy in velocity channels of various resolutions. We found that the average structure function of velocity channels is aligned with the projection of the magnetic field on the plane of the sky. We also found that the degree of such anisotropy increases with the magnitude of the magnetic field. For thick velocity channels (low velocity resolution), the anisotropy is dominated by density, and the degree of anisotropy in these maps allows one to distinguish sub-Alfvnic and super-Alfvnic turbulence regimes, but it also depends strongly on the sonic Mach number. For thin channels (high velocity resolution), we find that the anisotropy depends less on the sonic Mach number. An important limitation of this technique is that it only gives a lower limit on the magnetic field strength because the anisotropy is related only to the magnetic field component on the plane of the sky. It can, and should, be used in combination with other techniques to estimate the magnetic field, such as the Fermi-Chandrasekhar method, anisotropies in centroids, Faraday rotation measurements, or direct line-of-sight determinations of the field from Zeeman effect observations.

  8. Ramping up on Fractions

    ERIC Educational Resources Information Center

    Stephens, Ana C.; Bottge, Brian A.; Rueda, Enrique

    2009-01-01

    This article describes a technology-based and hands-on instructional intervention designed to advance middle school students' understandings of fractions. This problem-solving experience is based on the principles of Enhanced Anchored Instruction (EAI) and proved instructionally worthwhile and motivating to teachers and students in both inclusive

  9. Sweet Work with Fractions

    ERIC Educational Resources Information Center

    Vinogradova, Natalya; Blaine, Larry

    2013-01-01

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

  10. Understanding Equivalent Fractions.

    ERIC Educational Resources Information Center

    Hunting, Robert P.

    1984-01-01

    Twenty-nine students in grades four, six, and eight were asked to find solutions to fraction equivalence problems and to verify their solutions using discrete material. Discontinuities were observed between strategies students used for producing solutions and supporting knowledge grounded in physical reality. (Author/MNS)

  11. Field-Flow Fractionation.

    ERIC Educational Resources Information Center

    Caldwell, Karin D.

    1988-01-01

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

  12. Fraction collector for electrophoresis

    NASA Technical Reports Server (NTRS)

    Bier, M.

    1977-01-01

    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.

  13. Fractionation of Soil Phosphorus

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An understanding of the qualitative and quantitative information provided by soil phosphorus (P) fractionation methods is important for addressing agronomic and water quality problems, as well as evaluating P biogeochemistry in extreme environments. This chapter provides a schematic overview of and ...

  14. Sweet Work with Fractions

    ERIC Educational Resources Information Center

    Vinogradova, Natalya; Blaine, Larry

    2013-01-01

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

  15. On Difficulties with Fractions.

    ERIC Educational Resources Information Center

    Hasemann, Klaus

    1981-01-01

    Students recognized as less successful individuals in mathematics are tested for their understanding of fractions. The data reveals that most were only able to apply remembered rules to problems without actually knowing if the rule worked for the given situation. (MP)

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

    NASA Astrophysics Data System (ADS)

    Canon-Tapia, E.

    2013-05-01

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

  17. Geomechanics and elastic anisotropy of the Bakken Formation, Williston Basin

    NASA Astrophysics Data System (ADS)

    Ostadhassan, Mehdi

    Many of the earth's rocks exhibit anisotropic characteristics. Anisotropy is particularly common in many sedimentary rocks, such as shales. Anisotropy is defined as the spatial alignment of mineral grains, layers, fractures and stresses which causes elastic wave velocity and other elastic properties to vary with direction. There are two types of anisotropy: intrinsic and stress-induced. Intrinsic anisotropy is caused by beddings, microstructures or aligned fractures formed during deposition. Stress-induced anisotropy is caused by strain associated with external stresses. Intrinsic anisotropy originates in the absence of external stresses, while stress-induced anisotropy results from tectonic and overburden stresses. The style of earth material alignment causes two simplified, but convenient models of anisotropy: vertically transverse isotropy (VTI), like shale, and horizontally transverse isotropy (HTI), like vertically fractured medium. These models have been used to describe how physical properties of rock vary in a medium. Identifying the anisotropy in a formation is important in reservoir characterization seismic data processing and oil-field development. Deep shales are the most abundant yet least characterized sedimentary rocks in the Williston Basin of North Dakota. They are significant sources of hydrocarbon unconventional resources in this basin. This dissertation aims to fulfill an investigation of anisotropy in this rock type in several different facets through exploiting of field data. I seek to generate key information for better interplay of field in-situ stress and the existing natural fracture systems for the purpose of drilling, well completion, perforating, hydraulic fracturing and defining reservoir properties. In this study advanced sonic logging data has been processed and interpreted to calculate three independent shear moduli. These parameters then will be used to estimate Thomsen (1986) anisotropy parameters, elastic stiffness coefficients and principal stresses of deep shales in the Williston Basin. The parameters then will be used to generate shear radial profiles and slowness-frequency plots analyze formation anisotropy type and origin as well as reservoir quality. The next step will be to evaluate direction and magnitude of the minimum and maximum anisotropic principal horizontal stresses as the governing element in geomechanical modeling. I will analyze wellbore stability and predict wellbore behavior under stress alteration caused by drilling. Elastic anisotropy of the formation will be included in the 3-D numerical models. In addition the effects of local geological features on the mode of anisotropy both in the far-field and around the borehole to get an in-depth insight of the fractures will be studied. Finally, by generating stress polygons for the reservoir, before and after production and pressure decline, I will try to study how reservoir depletion may cause future geological natural hazards such as faulting and induced seismic events in the region.

  18. Primordial statistical anisotropy generated at the end of inflation

    SciTech Connect

    Yokoyama, Shuichiro; Soda, Jiro E-mail: jiro@tap.scphys.kyoto-u.ac.jp

    2008-08-15

    We present a new mechanism for generating primordial statistical anisotropy of curvature perturbations. We introduce a vector field which has a non-minimal kinetic term and couples with a waterfall field in a hybrid inflation model. In such a system, the vector field gives fluctuations of the end of inflation and hence induces a subcomponent of curvature perturbations. Since the vector has a preferred direction, the statistical anisotropy could appear in the fluctuations. We present the explicit formula for the statistical anisotropy in the primordial power spectrum and the bispectrum of curvature perturbations. Interestingly, there is the possibility that the statistical anisotropy does not appear in the power spectrum but does appear in the bispectrum. We also find that the statistical anisotropy provides the shape dependence to the bispectrum.

  19. Magnetisation reversal in anisotropy graded Co/Pd multilayers

    NASA Astrophysics Data System (ADS)

    Barton, C. W.; Thomson, T.

    2015-08-01

    We demonstrate high precision controllability of the magnetization reversal nucleation process in [Co/Pd]8 multilayer films consisting of two sets of bilayers with high and low perpendicular anisotropy, respectively. The anisotropy of the entire film is set by the degree of Co/Pd interfacial mixing during deposition which provides fine control of the anisotropy of an individual bilayer in the multilayer stack. The relative number of each type of bilayer is used to select the magnetisation reversal behavior such that changing one bilayer changes the properties of the entire multilayer through anisotropy averaging. A simple extension to the sputtering protocol would provide multilayer films with fully graded anisotropy, while maintaining a constant saturation magnetization opening new possibilities for the creation of highly engineered multilayer structures for spin torque devices and future magnetic recording media.

  20. Tuning the Magnetic Anisotropy at a Molecule-Metal Interface

    NASA Astrophysics Data System (ADS)

    Bairagi, K.; Bellec, A.; Repain, V.; Chacon, C.; Girard, Y.; Garreau, Y.; Lagoute, J.; Rousset, S.; Breitwieser, R.; Hu, Yu-Cheng; Chao, Yen Cheng; Pai, Woei Wu; Li, D.; Smogunov, A.; Barreteau, C.

    2015-06-01

    We demonstrate that a C60 overlayer enhances the perpendicular magnetic anisotropy of a Co thin film, inducing an inverse spin reorientation transition from in plane to out of plane. The driving force is the C60/Co interfacial magnetic anisotropy that we have measured quantitatively in situ as a function of the C60 coverage. Comparison with state-of-the-art ab initio calculations show that this interfacial anisotropy mainly arises from the local hybridization between C60 pz and Co dz2 orbitals. By generalizing these arguments, we also demonstrate that the hybridization of C60 with a Fe(110) surface decreases the perpendicular magnetic anisotropy. These results open the way to tailor the interfacial magnetic anisotropy in organic-material-ferromagnet systems.

  1. Anisotropy of strong pinning in multi-band superconductors

    SciTech Connect

    van der Beek, C.J.; Konczykowski, M.; Prozorov, Ruslan

    2012-07-17

    The field-angular dependence and anisotropy of the critical current density in iron-based superconductors is evaluated using a phenomenological approach featuring distinct anisotropy factors for the penetration depth and the coherence length. Both the weak collective pinning limit and the strong pinning limit relevant for iron-based superconductors at low magnetic fields are considered. It is found that in the more anisotropic materials, such as SmFeAsO and NdFeAsO, the field-angular dependence is completely dominated by the coherence length (upper critical field) anisotropy, thereby explaining recent results on the critical current in these materials. In less anisotropic superconductors, strong pinning can lead to an apparent inversion of the anisotropy. Finally, it is shown that, under all circumstances, the ratio of the c-axis and ab-plane critical current densities for the magnetic field along the ab-plane directly yields the coherence length anisotropy factor ??.

  2. Vortex polarity switching in magnets with surface anisotropy

    NASA Astrophysics Data System (ADS)

    Pylypovskyi, Oleksandr V.; Sheka, Denis D.; Kravchuk, Volodymyr P.; Gaididei, Yuri

    2015-05-01

    Vortex core reversal in magnetic particle is essentially influenced by a surface anisotropy. Under the action of a perpendicular static magnetic field the vortex core undergoes a shape deformation of pillow- or barrel-shaped type, depending on the type of the surface anisotropy. This deformation plays a key point in the switching mechanism: We predict that the vortex polarity switching is accompanied (i) by a linear singularity in case of Heisenberg magnet with bulk anisotropy only and (ii) by a point singularities in case of surface anisotropy or exchange anisotropy. We study in details the switching process using spin-lattice simulations and propose a simple analytical description using a wired core model, which provides an adequate description of the Bloch point statics, its dynamics and the Bloch point mediated switching process. Our analytical predictions are confirmed by spin-lattice simulations for Heisenberg magnet and micromagnetic simulations for nanomagnet with account of a dipolar interaction.

  3. How to build molecules with large magnetic anisotropy.

    PubMed

    Cirera, Jordi; Ruiz, Eliseo; Alvarez, Santiago; Neese, Frank; Kortus, Jens

    2009-01-01

    Predicting single-molecule magnets? Magnetic anisotropy, a property that plays a key role in single-molecule magnets (SMMs), has been analyzed by using theoretical methods. Mononuclear complexes and the dependence of the magnetic anisotropy on their geometrical and electronic structure, as well as how such mononuclear complexes must be combined as building blocks to obtain polynuclear complexes with large anisotropy (see figure) are considered.The magnetic anisotropy of mononuclear transition-metal complexes has been studied by means of electronic structure calculations based on density functional theory. The variation of the zero-field splitting (ZFS) parameters has been analyzed for the following characteristic distortions: a tetragonal Jahn-Teller distortion, the Bailar twist, the Berry pseudorotation, and the planarization of tetrahedral complexes. Finally, the coupling of mononuclear building blocks in polynuclear complexes to obtain a large negative magnetic anisotropy necessary to improve their single-molecule-magnet (SMM) behavior has been studied. PMID:19248077

  4. Magnetic stress anisotropy field in plated cylindrical Permalloy films.

    NASA Technical Reports Server (NTRS)

    Lutes, O. S.

    1971-01-01

    An analysis is made of the magnetic stress anisotropy field (Hks) arising from internal and external stress sources in plated-wire memory elements. The analysis takes into consideration circumferential composition variation and cylindrical geometry of the Permalloy film. Expressions are derived relating Hks to uniaxial film stress, average composition, and amplitude of composition variation. A result of particular importance is that even for average zeromagnetostrictive composition (ZMC) films, Hks may still make an appreciable contribution to the total anisotropy field if the composition is not uniform. Calculated Hks characteristics are shown to correlate with anisotropy field changes observed in annealing experiments. Examples are given to show the importance of composition uniformity in determining the stability of the anisotropy field. The utility of the analysis is extended by the inclusion of data expressing the inverse relation between anisotropy field and easy-axis dispersion in the film.

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

    PubMed Central

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

    2014-01-01

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

  6. Orientational anisotropy and interfacial transport in polycrystals

    NASA Astrophysics Data System (ADS)

    Moghadam, M. M.; Rickman, J. M.; Harmer, M. P.; Chan, H. M.

    2016-04-01

    Interfacial diffusion is governed to a large degree by geometric parameters that are determined by crystallographic orientation. In this study, we assess the impact of orientational anisotropy on mass transport at internal interfaces, focusing on the role of preferred crystallographic orientation (i.e., texture) on mass diffusion in a polycrystal. More specifically, we perform both numerical and analytical studies of steady-state diffusion for polycrystals having various grain-orientation distributions. By relating grain misorientation to grain-boundary energies and, via the Borisov relation, to the diffusivity, we link microstructure variability to kinetics. Our aim is to correlate shape features of the orientation distribution, such as the location and shapes of peaks, with the calculated effective diffusivity. Finally, we discuss the role of crystallographic constraints, such as those associated with grain junctions, in determining the effective diffusivity of a polycrystal.

  7. Absolute Plate Velocities from Seismic Anisotropy

    NASA Astrophysics Data System (ADS)

    Kreemer, Corné; Zheng, Lin; Gordon, Richard

    2015-04-01

    The orientation of seismic anisotropy inferred beneath plate interiors may provide a means to estimate the motions of the plate relative to the sub-asthenospheric mantle. Here we analyze two global sets of shear-wave splitting data, that of Kreemer [2009] and an updated and expanded data set, to estimate plate motions and to better understand the dispersion of the data, correlations in the errors, and their relation to plate speed. We also explore the effect of using geologically current plate velocities (i.e., the MORVEL set of angular velocities [DeMets et al. 2010]) compared with geodetically current plate velocities (i.e., the GSRM v1.2 angular velocities [Kreemer et al. 2014]). We demonstrate that the errors in plate motion azimuths inferred from shear-wave splitting beneath any one tectonic plate are correlated with the errors of other azimuths from the same plate. To account for these correlations, we adopt a two-tier analysis: First, find the pole of rotation and confidence limits for each plate individually. Second, solve for the best fit to these poles while constraining relative plate angular velocities to consistency with the MORVEL relative plate angular velocities. The SKS-MORVEL absolute plate angular velocities (based on the Kreemer [2009] data set) are determined from the poles from eight plates weighted proportionally to the root-mean-square velocity of each plate. SKS-MORVEL indicates that eight plates (Amur, Antarctica, Caribbean, Eurasia, Lwandle, Somalia, Sundaland, and Yangtze) have angular velocities that differ insignificantly from zero. The net rotation of the lithosphere is 0.25±0.11° Ma-1 (95% confidence limits) right-handed about 57.1°S, 68.6°E. The within-plate dispersion of seismic anisotropy for oceanic lithosphere (σ=19.2° ) differs insignificantly from that for continental lithosphere (σ=21.6° ). The between-plate dispersion, however, is significantly smaller for oceanic lithosphere (σ=7.4° ) than for continental lithosphere (σ=14.7° ). Two of the slowest-moving plates, Antarctica (vRMS=4 mm a-1, σ=29° ) and Eurasia (vRMS=3 mm a-1, σ=33° ), have two of the largest within-plate dispersions, which may indicate that a plate must move faster than ˜5 mm a-1 to result in seismic anisotropy useful for estimating plate motion. We will investigate if these relationships still hold with the new expanded data set and with the alternative set of relative plate angular velocities. We have found systematic differences between the SKS orientations and our predicted plate motion azimuths underneath the Arabia plate, which suggests to us either plate-scale mantle flow process not directly associated with that plate's absolute motion or intrinsic lithospheric anisotropy. We will discuss more of such discrepancies underneath other plates using the enlarged data set.

  8. Fluid substitution effects on seismic anisotropy

    NASA Astrophysics Data System (ADS)

    Huang, Long; Stewart, Robert R.; Sil, Samik; Dyaur, Nikolay

    2015-02-01

    We derive equations for HTI and orthorhombic symmetries to analyze fluid substitution effects in porous fractured media. The derivations are based on the anisotropic Gassmann equation and linear slip theory. We assess the influence of fluid substitution (gas, brine, and oil) on elastic moduli, velocities, anisotropy, and azimuthal amplitude variations. We find that in the direction normal to fractures, P-wave moduli increase as much as 56% and P-wave velocity increases up to 19% for gas-to-brine substitution. For the direction parallel to fractures, P-wave velocity remains almost constant when porosity is low (5%) but can increase up to 4% if porosity is high (25%). Since P-waves in two different directions have different sensitivities to fluids and fractures, the Thomsen's parameters (defined for HTI and orthorhombic symmetries), ? and ?, are sensitive to fluid types and fractures. We also found that ? is sensitive to porosity for liquid saturation but insensitive to porosity for the case of gas saturation. Gassmann assumes (and as has been observed) that shear modulus does not depend on fluids. And we observe no changes in shear-wave splitting (?) for different fluids. The azimuthal amplitude variation is dependent on fluid types, fractures, and porosity. We observe up to 12% increase in azimuthal amplitude variation for low porosity gas sands after brine saturation and 6% decrease for high porosity gas sands. We find that the percentage changes in gas-to-oil substitution are about half that of the gas-to-brine case. The equations we have derived provide a useful tool to quantitatively evaluate the effects of fluid substitution on seismic anisotropy.

  9. Microwave anisotropy probe scientific instrument metrology

    NASA Astrophysics Data System (ADS)

    Crane, J. Allen; Herrera, Acey; Dahya, Neil; Sampler, Henry P.; Mule, Pete; Hill, Mike; Aviado, Carlos; Osgood, Dean; Bereczky, Alex

    2004-01-01

    The Wilkinson Microwave Anisotropy Probe (WMAP) measures anisotropy or temperature differences in the Cosmic Microwave Background (CMB) radiation with high angular resolution and sensitivity, yielding unprecedented accuracy. To achieve this measurement, WMAP"s back-to-back Gregorian telescopes focus microwave radiation into 20 feed horns connected to 10 differential microwave radiometers. Proper alignment of the telescope reflectors, feed horns, and radiometers at flight temperatures was essential to the mission success. This paper will present the WMAP instrument metrology requirements and associated challenges, discuss the opto-mechanical tooling utilized to accomplish these objectives, and then give an overview of the metrology effort. The WMAP instrument integration effort included the following key metrology tasks: alignment and clocking of 20 microwave feed horns and mating microwave differencing assemblies within a focal plane assembly; alignment of a pair of primary and secondary reflectors composing back-to-back Gregorian telescopes; and the placement of the focal plane assembly and reflector system relative to each other, and as a unit on the spacecraft. WMAP environmental test metrology efforts included: reflector and truss thermal stability at 80 K; reflector and feed horn position verification at 90 K, and pre and post vibration and acoustic test reflector and feed horn position verification. The WMAP instrument integration and test objectives required the use of a photogrammetric camera, a laser tracker, a portable coordinate measuring machine (PCMM), and theodolites utilizing an electronic theodolite metrology system (ETMS) and autocollimation. The synergy of these metrology systems facilitated the successful characterization of the WMAP scientific instrument mechanical performance data at room temperature and flight temperatures, and correlation of the data to the analytical model. WMAP was launched on July 1, 2001, and flight data has confirmed the proper on-orbit instrument alignment was achieved.

  10. Dark matter annihilation or unresolved astrophysical sources? Anisotropy probe of the origin of the cosmic gamma-ray background

    SciTech Connect

    Ando, Shin'ichiro; Komatsu, Eiichiro; Narumoto, Takuro; Totani, Tomonori

    2007-03-15

    The origin of the cosmic gamma-ray background (CGB) is a longstanding mystery in high-energy astrophysics. Possible candidates include ordinary astrophysical objects such as unresolved blazars, as well as more exotic processes such as dark matter annihilation. While it would be difficult to distinguish them from the mean intensity data alone, one can use anisotropy data instead. We investigate the CGB anisotropy both from unresolved blazars and dark matter annihilation (including contributions from dark matter substructures), and we find that the angular power spectra from these sources are very different. We then focus on detectability of dark matter annihilation signals using the anisotropy data by treating the unresolved blazar component as a known background. We find that the dark matter signature should be detectable in the angular power spectrum of the CGB from two-year all-sky observations with the Gamma Ray Large Area Space Telescope (GLAST), as long as the dark matter annihilation contributes to a reasonable fraction, e.g., > or approx. 0.3, of the CGB at around 10 GeV. We conclude that the anisotropy measurement of the CGB with GLAST should be a powerful tool for revealing the CGB origin, and potentially for the first detection of dark matter annihilation.

  11. Seismic anisotropy and mantle creep in young orogens

    USGS Publications Warehouse

    Meissner, R.; Mooney, W.D.; Artemieva, I.

    2002-01-01

    Seismic anisotropy provides evidence for the physical state and tectonic evolution of the lithosphere. We discuss the origin of anisotropy at various depths, and relate it to tectonic stress, geotherms and rheology. The anisotropy of the uppermost mantle is controlled by the orthorhombic mineral olivine, and may result from ductile deformation, dynamic recrystallization or annealing. Anisotropy beneath young orogens has been measured for the seismic phase Pn that propagates in the uppermost mantle. This anisotropy is interpreted as being caused by deformation during the most recent thermotectonic event, and thus provides information on the process of mountain building. Whereas tectonic stress and many structural features in the upper crust are usually orientated perpendicular to the structural axis of mountain belts, Pn anisotropy is aligned parallel to the structural axis. We interpret this to indicate mountain-parallel ductile (i.e. creeping) deformation in the uppermost mantle that is a consequence of mountain-perpendicular compressive stresses. The preferred orientation of the fast axes of some anisotropic minerals, such as olivine, is known to be in the creep direction, a consequence of the anisotropy of strength and viscosity of orientated minerals. In order to explain the anisotropy of the mantle beneath young orogens we extend the concept of crustal 'escape' (or 'extrusion') tectonics to the uppermost mantle. We present rheological model calculations to support this hypothesis. Mountain-perpendicular horizontal stress (determined in the upper crust) and mountain-parallel seismic anisotropy (in the uppermost mantle) require a zone of ductile decoupling in the middle or lower crust of young mountain belts. Examples for stress and mountain-parallel Pn anisotropy are given for Tibet, the Alpine chains, and young mountain ranges in the Americas. Finally, we suggest a simple model for initiating mountain parallel creep.

  12. Modal investigation of elastic anisotropy in shallow-water environments: anisotropy beyond vertical transverse isotropy.

    PubMed

    Soukup, Darin J; Odom, Robert I; Park, Jeffrey

    2013-07-01

    Theoretical and numerical results are presented for modal characteristics of the seismo-acoustic wavefield in anisotropic range-independent media. General anisotropy affects the form of the elastic-stiffness tensor, particle-motion polarization, the frequency and angular dispersion curves, and introduces near-degenerate modes. Horizontally polarized particle motion (SH) cannot be ignored when anisotropy is present for low-frequency modes having significant bottom interaction. The seismo-acoustic wavefield has polarizations in all three coordinate directions even in the absence of any scattering or heterogeneity. Even weak anisotropy may have a significant impact on seismo-acoustic wave propagation. Unlike isotropic and transversely isotropic media with a vertical symmetry axis where acoustic signals comprise P-SV modes alone (in the absence of any scattering), tilted TI media allow both quasi-P-SV and quasi-SH modes to carry seismo-acoustic energy. Discrete modes for an anisotropic medium are best described as generalized P-SV-SH modes with polarizations in all three Cartesian directions. Conversion to SH is a loss that will mimic acoustic attenuation. An in-water explosion will excite quasi-SH. PMID:23862797

  13. Effects of pore structure and fractures on velocity anisotropy and permeability anisotropy in Ellenburger carbonate, Central Texas

    NASA Astrophysics Data System (ADS)

    Unomah, Gabriel

    The effects of pore structure and fractures on seismic velocity anisotropy and permeability anisotropy in dry core samples from Ellenburger carbonate, Central Texas are investigated using P-wave velocity (Vp), polarized orthogonal S-wave velocities (Vs1 and Vs2), and permeability (Kh and K v) parallel and perpendicular to the dominant fracture direction. The presence of cracks influences the seismic, elastic and anisotropic parameters under applied stress. The stronger relationship between seismic, petrophysical and petrographic properties parallel than perpendicular to the dominant fracture is because the rock appears to be homogenous parallel to the aligned cracks. The strong correlation of P-wave anisotropy (0.87) and maximum shear anisotropy (0.52) with permeability anisotropy is because of the preferred orientation caused by the fractures. The empirical relationships may be useful in reservoir characterization, mapping fractures and hydraulic fracturing.

  14. What is a fractional derivative?

    NASA Astrophysics Data System (ADS)

    Ortigueira, Manuel D.; Tenreiro Machado, J. A.

    2015-07-01

    This paper discusses the concepts underlying the formulation of operators capable of being interpreted as fractional derivatives or fractional integrals. Two criteria for required by a fractional operator are formulated. The Grnwald-Letnikov, Riemann-Liouville and Caputo fractional derivatives and the Riesz potential are accessed in the light of the proposed criteria. A Leibniz rule is also obtained for the Riesz potential.

  15. An Introduction to Continued Fractions.

    ERIC Educational Resources Information Center

    Moore, Charles G.

    Provided is an introduction to the properties of continued fractions for the intellectually curious high school student. Among the topics included are (1) Expansion of Rational Numbers into Simple Continued Fractions, (2) Convergents, (3) Continued Fractions and Linear Diophantine Equations of the Type am + bn = c, (4) Continued Fractions and

  16. Representing Fractional Distributions in Chemistry

    ERIC Educational Resources Information Center

    Ault, Addison

    2008-01-01

    Many phenomena in chemistry involve fractional distributions. Sometimes it is a chemical substance that is fractionally distributed, other times it is a chemical process that is fractionally distributed. The purpose of this paper is to present a common approach to the representation of all fractional distributions. Using a common approach provides

  17. Hydrodynamic and magnetic fractionation of superparamagnetic nanoparticles for magnetic particle imaging

    NASA Astrophysics Data System (ADS)

    Lwa, Norbert; Knappe, Patrick; Wiekhorst, Frank; Eberbeck, Dietmar; Thnemann, Andreas F.; Trahms, Lutz

    2015-04-01

    Resovist originally developed as a clinical liver contrast agent for Magnetic Resonance Imaging exhibits also an outstanding performance as a tracer in Magnetic Particle Imaging (MPI). In order to study the physical mechanism of the high MPI performance of Resovist, we applied asymmetric flow field-flow fractionation (A4F) and static magnetic fractionation (SMF) to separate Resovist into a set of fractions with defined size classes. As A4F based on an elution method separates MNP according to their hydrodynamic size, SMF fractionates a particle distribution by its magnetic moment. The obtained fractions of both separation techniques were then magnetically characterized by magnetorelaxometry measurements to extract the corresponding effective magnetic anisotropy and hydrodynamic size distribution parameters. Additionally, the MPI performance of each fraction was assessed using magnetic particle spectroscopy. With both separation techniques fractions (normalized to their iron amount) an MPI signal gain of a factor of two could be obtained, even though the distribution of effective anisotropy and hydrodynamic size were significantly different. Relating these findings to the results from magnetic characterization allows for a better understanding of the underlying mechanisms of MPI performance of Resovist. This knowledge may help to improve the design of novel MPI tracers and development of separation methods.

  18. Fractional Simple Harmonic Oscillator

    NASA Astrophysics Data System (ADS)

    Narahari Achar, B. N.; Hanneken, John W.; Clarke, Ted J.; Skaggs, Jeremy M.

    2000-03-01

    Applications of fractional calculus to physics have received considerable attention recently, including generalization of the simple harmonic oscillator problem. This paper presents a survey of several approaches that have been proposed and discusses the advantages and disadvantages thereof. An approach to be preferred is based on the generalization of the integral equation of the simple harmonic oscillator that involves physically meaningful initial conditions. A complete formal solution to the equation of motion together with graphical display will be presented.

  19. Coronary fractional flow reserve.

    PubMed

    Shantouf, Ronney S; Mehra, Anil

    2015-03-01

    OBJECTIVE. This article presents the basic definitions and concepts of fractional flow reserve (FFR), a focused understanding of the need for hyperemia during assessment, key clinical studies supporting its use, and an introduction to newer noninvasive methods using FFR CT. CONCLUSION. Although it is still a new procedure, FFR CT may prove to be of tremendous use as the computational processing improves to reduce calculation times and enhance accuracy. PMID:25714310

  20. New Dry Fractionation Methods

    NASA Technical Reports Server (NTRS)

    McKay, David S.; Cooper, Bonnie L.

    2010-01-01

    This slide presentation describes new fractionation methods that are used to create dust that is respirable for testing the effects of inhalation of lunar dust in preparation for future manned lunar exploration. Because lunar dust is a very limited commodity, a method that does not result in loss of the material had to be developed. The dust separation system that is described incorporates some traditional methods, while preventing the dust from being contaminated or changed in reactivity properties while also limiting losses.

  1. Optical chromatographic sample fractionation

    NASA Astrophysics Data System (ADS)

    Terray, Alex; Taylor, Joseph D.; Hart, Sean J.

    2009-08-01

    Optical Chromatography involves the elegant combination of opposing optical and fluid drag forces on colloidal samples within microfluidic environments to both measure analytical differences and fractionate injected samples. Particles that encounter the focused laser beam are trapped axially along the beam and are pushed upstream from the laser focal point to rest at a point where the optical and fluid forces on the particle balance. In our recent devices particles are pushed into a region of lower microfluidic flow, where they can be retained and fractionated. Because optical and fluid forces are sensitive to differences in the physical and chemical properties of a sample, differences between samples and thus separations are possible. An optical chromatography beam focused to completely fill a fluid channel is operated as an optically tunable filter for the separation of polymeric/colloidal and biological samples. We demonstrate this technique coupled with an advanced microfluidic platform and show how it can be used as an effective method to fractionate particles in an injected multi-component sample. Our advanced microfluidic design accommodates three lasers simultaneously to effectively create a sequential cascade optical chromatographic separation system.

  2. Both Rare and De Novo Copy Number Variants Are Prevalent in Agenesis of the Corpus Callosum but Not in Cerebellar Hypoplasia or Polymicrogyria

    PubMed Central

    Sajan, Samin A.; Fernandez, Liliana; Nieh, Sahar Esmaeeli; Rider, Eric; Bukshpun, Polina; Wakahiro, Mari; Christian, Susan L.; Rivière, Jean-Baptiste; Sullivan, Christopher T.; Sudi, Jyotsna; Herriges, Michael J.; Paciorkowski, Alexander R.; Barkovich, A. James; Glessner, Joseph T.; Millen, Kathleen J.; Hakonarson, Hakon; Dobyns, William B.; Sherr, Elliott H.

    2013-01-01

    Agenesis of the corpus callosum (ACC), cerebellar hypoplasia (CBLH), and polymicrogyria (PMG) are severe congenital brain malformations with largely undiscovered causes. We conducted a large-scale chromosomal copy number variation (CNV) discovery effort in 255 ACC, 220 CBLH, and 147 PMG patients, and 2,349 controls. Compared to controls, significantly more ACC, but unexpectedly not CBLH or PMG patients, had rare genic CNVs over one megabase (p = 1.48×10−3; odds ratio [OR] = 3.19; 95% confidence interval [CI] = 1.89–5.39). Rare genic CNVs were those that impacted at least one gene in less than 1% of the combined population of patients and controls. Compared to controls, significantly more ACC but not CBLH or PMG patients had rare CNVs impacting over 20 genes (p = 0.01; OR = 2.95; 95% CI = 1.69–5.18). Independent qPCR confirmation showed that 9.4% of ACC patients had de novo CNVs. These, in comparison to inherited CNVs, preferentially overlapped de novo CNVs previously observed in patients with autism spectrum disorders (p = 3.06×10−4; OR = 7.55; 95% CI = 2.40–23.72). Interestingly, numerous reports have shown a reduced corpus callosum area in autistic patients, and diminished social and executive function in many ACC patients. We also confirmed and refined previously known CNVs, including significantly narrowing the 8p23.1-p11.1 duplication present in 2% of our current ACC cohort. We found six novel CNVs, each in a single patient, that are likely deleterious: deletions of 1p31.3-p31.1, 1q31.2-q31.3, 5q23.1, and 15q11.2-q13.1; and duplications of 2q11.2-q13 and 11p14.3-p14.2. One ACC patient with microcephaly had a paternally inherited deletion of 16p13.11 that included NDE1. Exome sequencing identified a recessive maternally inherited nonsense mutation in the non-deleted allele of NDE1, revealing the complexity of ACC genetics. This is the first systematic study of CNVs in congenital brain malformations, and shows a much higher prevalence of large gene-rich CNVs in ACC than in CBLH and PMG. PMID:24098143

  3. Both rare and de novo copy number variants are prevalent in agenesis of the corpus callosum but not in cerebellar hypoplasia or polymicrogyria.

    PubMed

    Sajan, Samin A; Fernandez, Liliana; Nieh, Sahar Esmaeeli; Rider, Eric; Bukshpun, Polina; Wakahiro, Mari; Christian, Susan L; Rivière, Jean-Baptiste; Sullivan, Christopher T; Sudi, Jyotsna; Herriges, Michael J; Paciorkowski, Alexander R; Barkovich, A James; Glessner, Joseph T; Millen, Kathleen J; Hakonarson, Hakon; Dobyns, William B; Sherr, Elliott H

    2013-01-01

    Agenesis of the corpus callosum (ACC), cerebellar hypoplasia (CBLH), and polymicrogyria (PMG) are severe congenital brain malformations with largely undiscovered causes. We conducted a large-scale chromosomal copy number variation (CNV) discovery effort in 255 ACC, 220 CBLH, and 147 PMG patients, and 2,349 controls. Compared to controls, significantly more ACC, but unexpectedly not CBLH or PMG patients, had rare genic CNVs over one megabase (p = 1.48×10⁻³; odds ratio [OR] = 3.19; 95% confidence interval [CI] = 1.89-5.39). Rare genic CNVs were those that impacted at least one gene in less than 1% of the combined population of patients and controls. Compared to controls, significantly more ACC but not CBLH or PMG patients had rare CNVs impacting over 20 genes (p = 0.01; OR = 2.95; 95% CI = 1.69-5.18). Independent qPCR confirmation showed that 9.4% of ACC patients had de novo CNVs. These, in comparison to inherited CNVs, preferentially overlapped de novo CNVs previously observed in patients with autism spectrum disorders (p = 3.06×10⁻⁴; OR = 7.55; 95% CI = 2.40-23.72). Interestingly, numerous reports have shown a reduced corpus callosum area in autistic patients, and diminished social and executive function in many ACC patients. We also confirmed and refined previously known CNVs, including significantly narrowing the 8p23.1-p11.1 duplication present in 2% of our current ACC cohort. We found six novel CNVs, each in a single patient, that are likely deleterious: deletions of 1p31.3-p31.1, 1q31.2-q31.3, 5q23.1, and 15q11.2-q13.1; and duplications of 2q11.2-q13 and 11p14.3-p14.2. One ACC patient with microcephaly had a paternally inherited deletion of 16p13.11 that included NDE1. Exome sequencing identified a recessive maternally inherited nonsense mutation in the non-deleted allele of NDE1, revealing the complexity of ACC genetics. This is the first systematic study of CNVs in congenital brain malformations, and shows a much higher prevalence of large gene-rich CNVs in ACC than in CBLH and PMG. PMID:24098143

  4. Characteristics of Two-Way Cosmic-Ray Diurnal Anisotropy

    NASA Astrophysics Data System (ADS)

    Sabbah, I.; Darwish, A. A.; Bishara, A. A.

    1998-08-01

    We examine the deviation of the solar diurnal anisotropy vector from the 18 LT direction during the positive state of the solar cycle by assuming two anisotropies in free space. We use two detectors characterized by two linearly independent coupling functions. The median primary rigidity of response of these detectors covers the range 16 GV <= R_m <= 331 GV. Amplitude, direction, spectrum exponent, and the upper cut-off rigidity of each anisotropy have been calculated using the least-squares method over the time interval 1968-1988. This period covers a complete solar magnetic cycle. Only one anisotropy is dominant during each magnetic state of the solar cycle. The upper cut-off rigidity at which the dominant anisotropy vanishes varies between 50-250 GV. The direction of the dominant anisotropy vector points toward the 18 LT direction during the negative state of the solar cycle and toward earlier hours than 18 LT during the positive state. The non-dominant anisotropy is characterized by very high upper cut-off rigidity and sharper energy spectral.

  5. Relationship between Anisotropy in Soil Hydraulic Conductivity and Saturation

    SciTech Connect

    Zhang, Z. Fred

    2014-01-01

    Anisotropy in unsaturated hydraulic conductivity is saturation-dependent. Accurate characterization of soil anisotropy is very important in simulating flow and contaminant (e.g., radioactive nuclides in Hanford) transport. A recently developed tensorial connectivity-tortuosity (TCT) concept describes the hydraulic conductivity tensor of the unsaturated anisotropic soils as the product of a scalar variable, the symmetric connectivity tortuosity tensor, and the hydraulic conductivity tensor at saturation. In this study, the TCT model is used to quantify soil anisotropy in unsaturated hydraulic conductivity. The TCT model can describe different types of soil anisotropy; e.g., the anisotropy coefficient, C, can be monotonically increase or decrease with saturation and can vary from greater than unity to less than unity and vice versa. Soil anisotropy is independent of soil water retention properties and can be characterized by the ratio of the saturated hydraulic conductivities and the difference of the tortuosity-connectivity coefficients in two directions. ln(C) is linearly proportional to ln(Se) with Se being the effective saturation. The log-linear relationship between C and Se allows the saturation-dependent anisotropy to be determined using linear regression with the measurements of the directional hydraulic conductivities at a minimum of two water content levels, of which one may be at full saturation. The model was tested using measurements of directional hydraulic conductivities.

  6. Laboratory measurements of the viscous anisotropy of olivine aggregates.

    PubMed

    Hansen, L N; Zimmerman, M E; Kohlstedt, D L

    2012-12-20

    A marked anisotropy in viscosity develops in Earth's mantle as deformation strongly aligns the crystallographic axes of the individual grains that comprise the rocks. On the basis of geodynamic simulations, processes significantly affected by viscous anisotropy include post-glacial rebound, foundering of lithosphere and melt production above subduction zones. However, an estimate of the magnitude of viscous anisotropy based on the results of deformation experiments on single crystals differs by three orders of magnitude from that obtained by grain-scale numerical models of deforming aggregates with strong crystallographic alignment. Complicating matters, recent experiments indicate that deformation of the uppermost mantle is dominated by dislocation-accommodated grain-boundary sliding, a mechanism not activated in experiments on single crystals and not included in numerical models. Here, using direct measurements of the viscous anisotropy of highly deformed polycrystalline olivine, we demonstrate a significant directional dependence of viscosity. Specifically, shear viscosities measured in high-strain torsion experiments are 15 times smaller than normal viscosities measured in subsequent tension tests performed parallel to the torsion axis. This anisotropy is approximately an order of magnitude larger than that predicted by grain-scale simulations. These results indicate that dislocation-accommodated grain-boundary sliding produces an appreciable anisotropy in rock viscosity. We propose that crystallographic alignment imparts viscous anisotropy because the rate of deformation is limited by the movement of dislocations through the interiors of the crystallographically aligned grains. The maximum degree of anisotropy is reached at geologically low shear strain (of about ten) such that deforming regions of the upper mantle will exhibit significant viscous anisotropy. PMID:23257885

  7. Crustal Anisotropy in a Subduction Zone Forearc: Northern Cascadia

    NASA Astrophysics Data System (ADS)

    Bostock, M. G.; Matharu, G.; Christensen, N. I.; Tromp, J.

    2014-12-01

    S-wave splitting analyses using high SNR low frequency earthquake (LFE) templates at 3-component stations across northern Cascadia indicate the presence of a heterogeneous distribution of crustal anisotropy in the North American plate. On southern Vancouver Island (SVI), we investigate the contribution to anisotropy from the Leech River Complex (LRC), an allochthonous terrane comprising strongly foliated greenschist-facies phyllites and amphibolite-facies schists with steeply dipping foliations striking E-W. Estimates of initial S-wave polarization direction are consistent with radiation patterns predicted from LFE focal mechanisms, providing corroboration for thrust along the plate boundary. Fast directions across mainland SVI are subparallel to the dominant foliation direction in the LRC. An eastward increase in depth normalized delay times combined with small-scale azimuthal variations in fast directions suggest a heterogeneous distribution of anisotropy. We test azimuthally anisotropic LRC models constrained by surface geology and seismic reflection studies using 3D spectral element method simulations. The preferred model of a NNE shallowly dipping wedge of LRC material with varying orientation of anisotropy terminating at mid crustal levels is able to recreate mean and azimuthal variations in fast directions along with variations in delay times, supporting the hypothesis of the LRC as a primary contributor to crustal anisotropy beneath SVI. For select stations where anisotropic LRC models do not recreate observations, fast directions are subparallel to local estimates of maximal compressive horizontal stress, suggesting fluid-filled cracks could be a source of anisotropy. We refute the idea that anisotropy along mainland SVI is primarily due to stress related cracks as has been suggested by prior studies. Fast directions at northern Washington stations exhibit variations with azimuth and incidence angle suggesting complex anisotropy interpreted as due to a combination of cracks and preferred mineral orientation of metamorphosed slates of the Olympic core rocks. These slates may also underlie stations on SVI and represent another source of anisotropy.

  8. Picosecond fluorescence studies of polypeptide dynamics: fluorescence anisotropies and lifetimes

    NASA Astrophysics Data System (ADS)

    Chen, Lin X.-Q.; Petrich, Jacob W.; Fleming, Graham R.; Perico, Angelo

    1987-08-01

    Fluorescence lifetimes and anisotropies for single tryptophan-containing polypeptide hormones ACTH and glucagon, and a series of their fragments are reported. The anisotropy data are discussed in the context of the theory of Perico and Guenza (J. Chem. Phys. 84 (1986) 510). A persistence length of about 7 to 10 residues is obtained for the mobilities in the two hormones. The theory is able to account for chain length and probe location effects, but the calculated time dependence of the anisotropy does not fit the experimental curve well at short times.

  9. Cosmic ray anisotropies late in a solar flare event

    NASA Technical Reports Server (NTRS)

    Allum, F. R.; Mccracken, K. G.; Rao, U. R.; Palmeira, R. A. R.; Fairfield, D. H.; Gleeson, L. J.

    1974-01-01

    The detailed relationship between the anisotropy characteristics observed during late times in the decay of a solar flare event and the interplanetary magnetic field parameters is investigated. The anisotropy always is from 45 deg east of the earth-sun line. This direction is approximately perpendicular to the nominal Archimedean spiral, independent of the particle energy. The amplitude of the anisotropy increases as the magnetic field azimuthal direction shows greater departure from the radial direction. These results are discussed in terms of current ideas about solar particle propagation in the interplanetary space.

  10. Solitary structures with ion and electron thermal anisotropy

    NASA Astrophysics Data System (ADS)

    Khusroo, Murchana; Bora, Madhurjya P.

    2015-11-01

    The formation of electrostatic solitary structures is analysed for a magnetised plasma with ion and electron thermal anisotropies. The ion thermal anisotropy is modelled with the help of the Chew-Goldberger-Low (CGL) double adiabatic equations of state while the electrons are treated as inertia-less species with an anisotropic bi-Maxwellian velocity distribution function. A negative electron thermal anisotropy ?ft({{T}e\\bot}/{{T}e\\parallel}>1\\right) is found to help form large amplitude solitary structures which are in agreement with observational data.

  11. Size and anisotropy effects on magnetic properties of antiferromagnetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Wesselinowa, J. M.

    2010-01-01

    Based on the Heisenberg model taking into account single-ion anisotropy and using a Green's function technique we have studied the influence of size and anisotropy effects on magnetization M, Neel temperature TN, coercive field Hc and spin excitation energy of antiferromagnetic nanoparticles. The properties are compared with those of ferromagnetic nanoparticles. We have shown that the enhanced magnetization M and coercive field Hc of antiferromagnetic nanoparticles is a surface effect, which is due to uncompensated surface spins. Moreover, the shape of the coercive field curve can be significantly influenced by surface magnetic anisotropy.

  12. Statistical anisotropies in gravitational waves in solid inflation

    SciTech Connect

    Akhshik, Mohammad; Emami, Razieh; Firouzjahi, Hassan; Wang, Yi E-mail: emami@ipm.ir E-mail: yw366@cam.ac.uk

    2014-09-01

    Solid inflation can support a long period of anisotropic inflation. We calculate the statistical anisotropies in the scalar and tensor power spectra and their cross-correlation in anisotropic solid inflation. The tensor-scalar cross-correlation can either be positive or negative, which impacts the statistical anisotropies of the TT and TB spectra in CMB map more significantly compared with the tensor self-correlation. The tensor power spectrum contains potentially comparable contributions from quadrupole and octopole angular patterns, which is different from the power spectra of scalar, the cross-correlation or the scalar bispectrum, where the quadrupole type statistical anisotropy dominates over octopole.

  13. Small-scale Anisotropies of Cosmic Rays from Relative Diffusion

    NASA Astrophysics Data System (ADS)

    Ahlers, Markus; Mertsch, Philipp

    2015-12-01

    The arrival directions of multi-TeV cosmic rays show significant anisotropies at small angular scales. It has been argued that this small-scale structure can naturally arise from cosmic ray scattering in local turbulent magnetic fields that distort a global dipole anisotropy set by diffusion. We study this effect in terms of the power spectrum of cosmic ray arrival directions and show that the strength of small-scale anisotropies is related to properties of relative diffusion. We provide a formalism for how these power spectra can be inferred from simulations and motivate a simple analytic extension of the ensemble-averaged diffusion equation that can account for the effect.

  14. Review of the anisotropy working group at UHECR-2012

    NASA Astrophysics Data System (ADS)

    Deligny, O.; de Mello Neto, J.; Sommers, P.; Sagawa, H.; Tinyakov, P.; Tkachev, I.; Ivanov, A.; Timofeev, L.

    2013-06-01

    The study of ultra-high energy cosmic rays (UHECRs) has recently experienced a jump in statistics as well as improved instrumentation. This has allowed a better sensitivity in searching for anisotropies in the arrival directions of cosmic rays. In this written version of the presentation given by the inter-collaborative "Anisotropy Working Group" at the International Symposium on Future Directions in UHECR physics at CERN in February 2012, we report on the current status for anisotropy searches in the arrival directions of UHECRs.

  15. Cellular automaton modeling of alloy solidification using local anisotropy rules

    SciTech Connect

    Napolitano, R.E.; Sanders, T.H. Jr.

    1998-12-31

    The evolution of dendritic morphology is simulated for a binary alloy using a two-dimensional cellular automaton growth algorithm. Solute diffusion is modeled with an alternate-direction implicit finite difference technique. Interface curvature and kinetic anisotropy are implemented through configurational terms which are incorporated into the growth potential used by the automaton. The weighting of the anisotropy term is explored and shown to be essential for overcoming grid-induced anisotropy, permitting more realistic development of dendritic morphologies. Dendritic structures are generated for both uniform and directional cooling conditions.

  16. Marginal Anisotropy in Layered Aperiodic Ising Systems

    NASA Astrophysics Data System (ADS)

    Berche, P. E.; Berche, B.; Turban, L.

    1996-05-01

    Two-dimensional layered aperiodic Ising systems are studied in the extreme anisotropic limit where they correspond to quantum Ising chains in a transverse field. The modulation of the couplings follows an aperiodic sequence gererated through substitution. According to Luck's criterion, such a perturbation becomes marginal when the wandering exponent of the sequence vanishes. Three marginal sequences are considered: the period-doubling, paper-folding and three-folding sequences. They correspond to bulk perturbations for which the critical temperature is shifted. The surface magnetization is obtained exactly for the three sequences. The scaling dimensions of the local magnetization on both surfaces, x_{m_s} and bar x_{m_s}, vary continuously with the modulation factor. The low-energy excitations of the quantum chains are found to scale as Lz with the size L of the system. This is the behaviour expected for a strongly anisotropic system, where z is the ratio of the exponents of the correlation lengths in the two directions. the anisotropy exponent z is here simply equal to x_{m_s}+bar x_{m_s}. The anisotropic scaling behaviour is verified numerically for other surface and bulk critical properties as well. On tudie des systmes d'Ising apriodiques en couches deux dimensions dans la limite anisotrope extrme o ils correspondent des chanes quantiques d'Ising en champ transverse. La modulation des interactions est engendre par une suite apriodique obtenue par substitution. D'aprs le critre de Luck, une telle perturbation devient marginale lorsque l'exposant de divagation associ la suite s'annule. Trois suites marginales sont examines : doublement de priode, pliage de papier et pliage ternaire. Elles correspondent des perturbations de volume entrainant un changement de temprature critique. Des expressions exactes de l'aimantation de surface sont obtenues pour les trois suites. Les dimensions anormales de l'aimantation locale sur les deux surfaces, x_{m_s} et bar x_{m_s}, varient continment avec le facteur de modulation. Les excitations de basse nergie des chanes quantiques varient en Lz avec la taille L du systme. C'est l le comportement attendu pour un systme fortement anisotrope o z est le rapport des exposants associs aux longueurs de corrlation dans les deux directions. L'exposant d'anisotropie z s'exprime simplement comme la somme des exposants magntiques x_{m_s}+bar x_{m_s}. Le comportement d'chelle anisotrope est vrifi numriquement pour d'autres propits critiques de surface et de volume.

  17. Fractional channel multichannel analyzer

    DOEpatents

    Brackenbush, L.W.; Anderson, G.A.

    1994-08-23

    A multichannel analyzer incorporating the features of the present invention obtains the effect of fractional channels thus greatly reducing the number of actual channels necessary to record complex line spectra. This is accomplished by using an analog-to-digital converter in the asynchronous mode, i.e., the gate pulse from the pulse height-to-pulse width converter is not synchronized with the signal from a clock oscillator. This saves power and reduces the number of components required on the board to achieve the effect of radically expanding the number of channels without changing the circuit board. 9 figs.

  18. Solvent Fractionation of Lignin

    SciTech Connect

    Chatterjee, Sabornie; Saito, Tomonori

    2014-01-01

    Lignin is a highly abundant source of renewable carbon that can be considered as a valuable sustainable source of biobased materials. The major issues for the commercial production of value added high performance lignin products are lignin s physical and chemical heterogenities. To overcome these problems, a variety of procedures have been developed to produce pure lignin suitable for high performace applications such as lignin-derived carbon materials. However, most of the isolation procedures affect lignin s properties and structure. In this chapter, a short review of the effect of solvent fractionation on lignin s properties and structure is presented.

  19. Fractional channel multichannel analyzer

    DOEpatents

    Brackenbush, Larry W. (Richland, WA); Anderson, Gordon A. (Benton City, WA)

    1994-01-01

    A multichannel analyzer incorporating the features of the present invention obtains the effect of fractional channels thus greatly reducing the number of actual channels necessary to record complex line spectra. This is accomplished by using an analog-to-digital converter in the asynscronous mode, i.e., the gate pulse from the pulse height-to-pulse width converter is not synchronized with the signal from a clock oscillator. This saves power and reduces the number of components required on the board to achieve the effect of radically expanding the number of channels without changing the circuit board.

  20. Anisotropy of the magnetic susceptibility of gallium

    USGS Publications Warehouse

    Pankey, T., Jr.

    1960-01-01

    The bulk magnetic susceptibilities of single gallium crystals and polycrystalline gallium spheres were measured at 25??C. The following anisotropic diamagnetic susceptibilities were found: a axis (-0.119??0. 001)??10-6 emu/g, b axis (-0.416??0.002)??10 -6 emu/g, and c axis (-0.229??0.001) emu/g. The susceptibility of the polycrystalline spheres, assumed to be the average value for the bulk susceptibility of gallium, was (-0.257??0.003)??10-6 emu/g at 25??C, and (-0.299??0.003)??10-6 emu/g at -196??C. The susceptibility of liquid gallium was (0.0031??0.001) ??10-6 emu/g at 30??C and 100??C. Rotational diagrams of the susceptibilities in the three orthogonal planes of the unit cell were not sinusoidal. The anisotropy in the single crystals was presumably caused by the partial overlap of Brillouin zone boundaries by the Fermi-energy surface. The large change in susceptibility associated with the change in state was attributed to the absence of effective mass influence in the liquid state. ?? 1960 The American Institute of Physics.