Higher Radial Research Articles

Impairment of the locus coeruleus‐transentorhinal cortex pathway in persons at risk of Alzheimer’s disease

AbstractBackgroundRecent studies reported microstructural alterations in the locus coeruleus ‐ transentorhinal cortex (LC‐TEC) pathway in patients with Alzheimer’s disease (AD) but data in subjects at risk of AD (i.e., cognitively intact APOEe4 carriers) are missing. In this study, we apply in‐vivo diffusion weighted images (DWI) to study the effect of APOEe4 on the LC‐TEC pathway in cognitively unimpaired subjects.MethodForty‐five participants (14 APOEe4 carriers: age = 68±7 years, 45% females, MMSE score = 29±0.9; 31 non‐carriers: age = 68±6 years, 57% females, MMSE score = 30±0.6) underwent multimodal 3T MRI and multidomain neuropsychological exams. DWI were corrected for distortions with topup and eddy tools (part of FMRIB’s Software Library – FSL). Microstructural measures as fractional anisotropy (FA), mean (MD), axial (AxD), and radial (RD) diffusivities maps were estimated using the FMRIB’s Diffusion Toolbox (part of FSL) after the exclusion of cerebrospinal fluid voxels. Microstructural integrity of LC‐TEC was assessed using a thresholded probabilistic atlas non‐linearly warped on native maps with FNIRT (part of FSL). A Bonferroni multivariate generalized linear model, corrected for age and sex, was conducted to compare the diffusivity indexes between APOEe4 carriers and non‐carriers. Association with memory functioning (immediate and delayed recall) was also tested using Spearman’s rank correlations test.ResultAPOEe4 carriers and non‐carriers were comparable for cognitive performance (p>.246). Compared to non‐carriers, APOEe4 carriers showed lower FA (p = 0.048) and higher RD (p = 0.036) in the left LC‐TEC. In APOEe4 carriers, left RD negatively correlated with both immediate (rho = ‐0.808, p<0.001) and delayed (rho = ‐0.673, p = 0.025) memory recall.ConclusionMicrostructural alterations of the LC‐TEC pathway are detectable in subjects at‐risk for AD and correlate with lower memory performance. These preliminary results support the view that LC‐TEC impairment may play a role in AD pathophysiology since its early stages.

Impairment of the locus coeruleus‐transentorhinal cortex pathway in persons at risk of Alzheimer’s disease.

AbstractBackgroundRecent studies reported microstructural alterations in the locus coeruleus ‐ transentorhinal cortex (LC‐TEC) pathway in patients with Alzheimer’s disease (AD) but data in subjects at risk of AD (i.e., cognitively intact APOEε4 carriers) are missing. In this study, we apply in‐vivo diffusion weighted images (DWI) to study the effect of APOEε4 on the LC‐TEC pathway in cognitively unimpaired subjects.MethodForty‐five participants (14 APOEε4 carriers: age = 68±7 years, 45% females, MMSE score = 29±0.9; 31 non‐carriers: age = 68±6 years, 57% females, MMSE score = 30±0.6) underwent multimodal 3T MRI and multidomain neuropsychological exams. DWI were corrected for distortions with topup and eddy tools (part of FMRIB’s Software Library – FSL). Microstructural measures as fractional anisotropy (FA), mean (MD), axial (AxD), and radial (RD) diffusivities maps were estimated using the FMRIB’s Diffusion Toolbox (part of FSL) after the exclusion of cerebrospinal fluid voxels. Microstructural integrity of LC‐TEC was assessed using a thresholded probabilistic atlas non‐linearly warped on native maps with FNIRT (part of FSL). A Bonferroni multivariate generalized linear model, corrected for age and sex, was conducted to compare the diffusivity indexes between APOEε4 carriers and non‐carriers. Association with memory functioning (immediate and delayed recall) was also tested using Spearman’s rank correlations test.ResultAPOEε4 carriers and non‐carriers were comparable for cognitive performance (p>.246). Compared to non‐carriers, APOEε4 carriers showed lower FA (p = 0.048) and higher RD (p = 0.036) in the left LC‐TEC. In APOEε4 carriers, left RD negatively correlated with both immediate (rho = ‐0.808, p<0.001) and delayed (rho = ‐0.673, p = 0.025) memory recall.ConclusionMicrostructural alterations of the LC‐TEC pathway are detectable in subjects at‐risk for AD and correlate with lower memory performance. These preliminary results support the view that LC‐TEC impairment may play a role in AD pathophysiology since its early stages.

Evaluation of Bone Health Using High Resolution Peripheral Quantitative Computed Tomography in Survivors of Paediatric Acute Lymphoblastic Leukemia

Bone mass accrual, bone architecture, and strength may be impaired in children with a history of acute lymphoblastic leukemia (ALL) resulting in low bone mineral density (BMD) and fractures. The Children's Oncology Group recommends evaluating ALL survivors' bone health with dual-energy X-ray absorptiometry (DXA) testing. However, DXA testing may not accurately measure bone health in survivors due to low bone area for height, short stature, growth delays or decreased lean muscle mass. Further, it does not differentiate between trabecular and cortical bone, nor does it provide insights into bone microarchitecture and strength. High-resolution peripheral quantitative computed tomography (HR-pQCT) is a three-dimensional non-invasive imaging modality that provides a comprehensive assessment bone microarchitecture, volumetric BMD (vBMD) of both cortical and trabecular bone, and bone strength. In adult patients, HR-pQCT parameters have been shown to predict incident fractures. In this pilot study we utilized HR-pQCT to evaluate bone microarchitecture, vBMD, bone geometry and bone strength of peri-pubertal and pubertal survivors of ALL compared to healthy controls. Methods: We prospectively recruited ALL survivors (>1 year off therapy) with a DXA BMD Z-score between -2.0 to 0 within the proceeding six months, who were in early-late puberty (pre-pubertal patients excluded), and aged 11 to 18 years, along with healthy controls in the same age range at a single academic pediatric center in Canada. While a BMD Z-score of -2.0 to 0 has historically been considered normal, many children with Z-scores in this range have skeletal fragility and an increased fracture risk. Patients were excluded if they had comorbidity that impacts bone microarchitecture (ex. chronic kidney disease), were on a medication that impacts bone health (ex. corticosteroids) or had a genetic syndrome that increased their sensitivity to radiation (ex. Ataxia Telangiectasia). HR-pQCT of the distal radius and tibia was performed using the a standardized protocol. Bone mass was compared using total, trabecular and cortical vBMD, bone architecture was compared using cortical porosity and bone strength was compared using failure load. HR-pQCT derived variables were compared between ALL and control groups following stratification by sex. HR-pQCT values were summarized using medians and interquartile ranges and medians were compared using the Wilcoxon signed-rank test. Demographic and clinical characteristics were compared using the chi-square test. All tests were two tailed and p<0.05 was considered significant. Results: A total of 59 subjects were recruited (34 ALL survivors, 25 healthy controls). The sex of participants was male for 56.0% (n=14) of controls and 61.7% (n=21) of ALL survivors and female for 44.0% (n=11) of controls and 38.3% (n=13) of survivors. All survivors had received corticosteroids and methotrexate, and five (15%) had received cranial radiation. ALL survivors were not more likely than controls to report a history of a fracture (32.4%, n=11 vs. 16%, n=4). Additional data regarding the participants demographics is presented in Table 1. Male survivors had a lower radial trabecular vBMD, tibial total vBMD, and tibial trabecular vBMD, and a higher tibial failure load compared to healthy male controls. Female survivors had a lower radial total vBMD, radial trabecular vBMD, tibial total vBMD, and tibial trabecular vBMD. Female ALL survivors also had higher radial and tibial failure loads compared to healthy female controls. No differences in cortical porosity or cortical vBMD were identified between survivors and healthy controls. Complete HR-pQCT data is presented in Table 2. Conclusions: We demonstrated differences in the HR-pQCT parameters of peripubertal and pubertal ALL survivors compared to healthy controls. Survivors had reductions in key HR-pQCT parameters and an increased tibial failure load compared to healthy controls. In future studies HR-pQCT should be performed at a uniform time point post ALL therapy and used to predict future adverse bone health outcome such as fractures. Using this HR-pQCT guided approach ALL survivors at greatest risk of an adverse bone health outcome can be offered early interventions to prevent these outcomes.

Left ventricular myocardial deformation abnormalities in arrhythmic mitral valve prolapse: which comes first?

Abstract Funding Acknowledgements Type of funding sources: None. Background. Arrhythmic mitral valve prolapse (MVP) is characterized by left ventricular (LV) fibrosis in the basal inferolateral wall and papillary muscles. We hypothesized that LV fibrosis are driven by excessive mechanical forces acting on myocardial susceptible cells, representing the last step in the MVP-induced myocardial stretch process. Purpose. We aimed to evaluate the LV myocardial deformation, using strain assessed with cardiac magnetic resonance (CMR), in arrhythmic MVP patients with normal LV ejection fraction (LVEF) and absent/trivial mitral regurgitation (MR) and its correlation with the presence of LV fibrosis, detected by late gadolinium enhancement (LGE) in post-contrast CMR images. Methods. We enrolled consecutive arrhythmic MVP patients with normal LVEF and no/trivial MR. Sixty-nine (39 female; median age: 40 years) patients without MVP, arrhythmias or cardiovascular history served as control group. All patients underwent CMR for identification of LGE and evaluation of LV myocardial deformation. Results. A total of 66 patients were enrolled (47 female; median age: 44 years). In the overall MVP population, LGE was present in 41 patients (62.1%). MVP patients without LGE (25 patients, 37.9%) presented a higher global radial (median: 42.19 vs 33; p: <0.0001) and higher global longitudinal strain (median: -21.61 vs -18.10; p: <0.0001), compared to the control group. A reduction of regional basal posterolateral radial (BPL median: 50.60 vs 67.30; p: 0.0015) and longitudinal strain (BPL median: -23.50 vs -26.70; p: 0.0186) were observed in the MVP patients as compared with controls (Figures A-D). Conversely to the basal region, mid anterolateral and posterolateral region presented a higher radial (MAL median: 52.60 vs 31.10; p: < 0.0001 and MPL median: 52.80 vs 21.50; p: < 0.0001) and longitudinal strain (MAL median: -24.80 vs -18.30; p: < 0.0001 and MPL median: -25.30 vs -14.80; p: < 0.0001), when compared to control group. MVP patients with LGE had a lower global radial (median: 36.48 vs 42.19; p: <0.0047), longitudinal (median: -19.18 vs -21.61; p: 0.0013) and circumferential strain (median: -17.80 vs -19.28; p: 0.0134) compared with those without fibrosis. According to MVP patients without LGE, the presence of fibrosis is associated with a lower regional radial (BAL median: 64.40 vs 82.80; p: 0.0481; MAL median: 42.60 vs 52.60; p: 0.0287) and circumferential strain (BAL median: -21.90 vs -24.20; p: 0.0174; BPL median: -16.80 vs -18.80; p: 0.0411; MPL median: -15.50 vs -19.40; p: 0.0077) in the LV basal-mid lateral walls (Figures E-I). Conclusions. Arrhythmic MVP patients with normal LV systolic function and absent/trivial MR presented an abnormal myocardial deformation pattern. The reduced strain in BPL wall of MVP patients without LGE could be considered as an early marker of MVP-induced myocardial stress, that could promote, time by time, LV fibrosis and arrhythmias in MVP patients.

A simplified model for transition prediction applicable to wind-turbine rotors

Abstract. This work aims to develop a simple framework for transition prediction over wind-turbine blades, including effects of the blade rotation and spanwise velocity without requiring fully three-dimensional simulations. The framework is based on a set of boundary-layer equations (BLEs) and parabolized stability equations (PSEs), including rotation effects. An important element of the developed BL method is the modeling of the spanwise velocity at the boundary-layer edge. The two analyzed wind-turbine geometries correspond to a constant airfoil and the DTU 10-MW Reference Wind Turbine blades. The BL model allows an accurate prediction of the chordwise velocity profiles. Further, for regions not too close to the stagnation point and root of the blade, profiles of the spanwise velocity agree with those from Reynolds-averaged Navier–Stokes (RANS) simulations. The model also allows predicting inflectional velocity profiles for lower radial positions, which may allow crossflow transition. Transition prediction is performed at several radial positions through an “envelope-of-envelopes” methodology. The results are compared with the eN method of Drela and Giles, implemented in the EllipSys3D RANS code. The RANS transition locations closely agree with those from the PSE analysis of a 2D mean flow without rotation. These results also agree with those from the developed model for cases with low 3D and rotation effects, such as at higher radial positions and geometries with strong adverse pressure gradients where 2D Tollmien–Schlichting (TS) waves are dominant. However, the RANS and PSE 2D models predict a later transition in the regions where 3D and rotation effects are non-negligible. The developed method, which accounts for these effects, predicted earlier transition onsets in this region (e.g., 19 % earlier than RANS at 26 % of the radius for the constant-airfoil geometry) and shows that transition may occur via highly oblique modes. These modes differ from 2D TS waves and appear in locations with inflectional spanwise velocity. However, except close to the root of the blade, crossflow transition is unlikely since the crossflow velocity is too low. At higher radial positions, where 3D and rotation effects are weaker and the adverse pressure gradient is more significant, modes with small wave angles (close to 2D) are found to be dominant. Finally, it is observed that an increase in the rotation speed modifies the spanwise velocity and increases the Coriolis and centrifugal forces, shifting the transition location closer to the leading edge. This work highlights the importance of considering the blade rotation and the three-dimensional flow generated by that in transition prediction, especially in the inner part of the blade.

White Matter Matters: Unraveling Violence in Psychosis and Psychopathy

Abstract Individuals with psychotic disorders have an increased risk of committing acts of violence. Neurobiological support for the extent to which violence in psychosis is driven by psychotic symptoms and/or antisocial traits could have clinical and legal implications. Neuroimaging studies have reported white matter (WM) abnormalities in individuals with psychosis and in those with antisocial traits. However, it is unknown whether WM abnormalities in psychosis patients with a history of violence (violent-PSY) resemble those found in nonviolent psychosis patients (nonviolent PSY), violent nonpsychotic individuals (violent non-PSY), or both. Diffusion tensor imaging scans from 301 males including violent-PSY (n = 28), violent non-PSY (n = 20), nonviolent PSY (n = 58), and healthy controls (HC, n = 195) were analyzed with tract-based spatial statistics. Fractional anisotropy (FA), mean, axial and radial (RD) diffusivity were compared between groups. Psychopathic traits in the violent groups were measured with Psychopathy Checklist-revisited (PCL-R). Violent-PSY had globally lower FA and higher RD, compared with nonviolent PSY. Both psychosis groups and violent non-PSY group had widespread disruptions in WM compared with HC. There were no significant WM differences between violent-PSY and violent non-PSY. PCL-R scores did not differ between the violence groups and were associated with higher RD in corpus callosum. Here we demonstrate a widespread pattern of reduced WM integrity in violent-PSY compared with nonviolent PSY. The lack of significant WM and PCL-R differences between the violence groups, together with the positive association between PCL-R and WM deficits in violent-PSY and violent non-PSY may indicate shared neurobiological underpinnings of trait violence.

Abstract 15877: Chamber Volumes and Deformation Measures are Abnormal in Chemotherapy-Naïve Cancer Patients: Potential Implications for Surveillance and Definitions of Cardiotoxicity

Background: Cancer Therapeutics-related Cardiac Dysfunction (CTRCD) is defined by an interval drop in contractile performance to below reference lower limits of normal. This definition assumes healthy reference data appropriately represent referral populations with active cancer. However, the influence of active cancer on cardiac chamber volumes and contractile performance has not been established. Using cardiac magnetic resonance (CMR), we studied chamber volume- and deformation-based markers in ~400 cancer patients with comparison to ~100 healthy controls. Methods: 394 active cancer patients referred for first-time anthracycline-based chemotherapy and 102 healthy volunteers (HV) were recruited. Both underwent identical CMR protocols with quantification of chamber volumes and ejection fraction (EF). Left ventricular (LV) mechanics were also assessed by 3D myocardial deformation analysis (3D-MDA), providing global longitudinal, circumferential, radial and principal peak-systolic strain amplitude and rate. Results: The mean age was 53.8±13 years (78% female), with 64% having breast cancer and 36% lymphoma. Table 1 summarizes CMR findings of cancer patients versus HV, stratified by sex. Chamber volumes were significantly smaller while LV mass was significantly greater versus HV. LV EF and global longitudinal (GLS) were similar. However, cancer patients demonstrated significantly higher radial, circumferential and maximal principal strain amplitude. Peak-systolic strain rates were also consistently elevated. Conclusion: Chemotherapy-naïve cancer patients have smaller chamber volumes, greater LV mass, and higher radial, circumferential, and maximal principal strain versus healthy subjects. LV EF and peak GLS remain similar, and therefore are most appropriate to define CTRCD. However, an altered state of cardiac health is apparent by all other CMR-based markers, reflecting a unique cardiac phenotype of patients with active cancer.

Higher Radial Harmonics of Sausage Oscillations in Coronal Loops

Abstract Impulsively excited sausage oscillations of a plasma cylinder with a smooth radial profile of Alfvén speed are analyzed with a numerical solution of the initial-value problem for a partial differential equation of the Klein–Gordon type, describing linear magnetoacoustic oscillations with a fixed axial wavelength and an azimuthal mode number. The range of analyzed ratios of Alfvén speeds outside and inside the cylinder is from 2 to 10. Both trapped and leaky regimes of the oscillations are considered. It is shown that even in the long-wavelength limit, i.e., for axial wavenumbers much smaller than the cutoff values, damping times of higher radial sausage harmonics could be significantly greater than the oscillation periods, i.e., several oscillation cycles could be present in the signal. The quality factors decrease with decfreasing ratios of Alfvén speeds outside and inside the cylinder. Oscillation periods of the second and third radial harmonics remain practically independent of the axial wavelength even when the wavelength is shorter than the radius of the cylinder. The ratios of oscillation periods of fundamental and higher radial and axial harmonics are found to be significantly different, up to a factor of two in the long-wavelength limit. It is concluded that higher radial harmonics could be responsible for the departure of observed sausage oscillation signals from a harmonic shape, especially during the first several cycles of the oscillation. Even in the absence of spatially resolved data, higher axial and radial harmonics can be distinguished from each other by the period ratios.

Assessment of left ventricular function in horses with aortic regurgitation by 2D speckle tracking

BackgroundAortic regurgitation (AR) may lead to left ventricular (LV) dilatation, cardiac arrhythmias and heart failure. Close follow-up of horses with AR is therefore paramount to detect onset of cardiac decompensation. The aim of this study was to examine whether two-dimensional speckle tracking (2DST) can be used to detect altered myocardial function in horses with chronic AR compared to control horses. Speckle tracking was performed on short axis and long axis images of the LV in 29 healthy Warmblood horses and 57 Warmblood horses with AR. Radial, circumferential and longitudinal strain, strain rate and displacement were measured for each segment separately and the average was calculated over all segments. Data generated from the apical segments were not included in the analysis.ResultsRadial (SR) and circumferential (SC) strain were significantly higher in horses with moderate AR (average SR 75.5 ± 24.3%, SC 19.3 ± 3.2%) but not in horses with severe AR (SR 65.5 ± 26.2%, SC 16.3 ± 3.5%), compared to control horses (SR 54.5 ± 18.0%, SC 16.8 ± 3.0%). Longitudinal strain did not show significant differences, but longitudinal displacement (DL) was larger in horses with moderate (average DL 29.5 ± 4.1 cm) and severe AR (DL 32.4 ± 6.1 cm) compared to control horses (DL 25.7 ± 4.0 cm), especially in the interventricular septum. Diastolic longitudinal strain rate was lower in early diastole in horses with severe AR (0.93 ± 0.18/s) compared to controls (1.13 ± 0.13/s).Conclusions2DST is able to detect altered myocardial motion in horses with AR, which showed significantly higher radial and circumferential strain. Further research is needed to determine whether these findings contribute to a more accurate diagnosis and prognosis in clinical cases.

Magnetic Resonance-based Assessment of Myocardial 2-Dimensional Strain Using Feature Tracking: Association With Cardiovascular Risk Factors in a Population-based Cohort Free of Cardiovascular Disease.

Myocardial strain analysis is a promising tool for the detection of subtle but relevant alterations of left ventricular function, also in asymptomatic subjects. Thus, we determined the feasibility of cardiac magnetic resonance-based 2D global strain analysis using feature tracking and its association with cardiovascular risk factors in a sample from the general population. Subjects without a history of cardiocerebrovascular disease were enrolled in a substudy of the population-based KORA (Cooperative Health Research in the Region of Augsburg) cohort. In all participants with the absence of late gadolinium enhancement, longitudinal and circumferential global strains were measured on Cine SSFP imaging (TR: 29.97 ms, TE: 1.46 ms, ST: 8 mm), using a semiautomatic segmentation algorithm (CVI42, Circle, Canada). Differences in strain values according to age, sex, body mass index, hypertension, diabetes mellitus, and hyperlipidemia were derived using linear regression analysis. Among 360 subjects (mean age, 56.2±9.2 y, 57% male), the average global systolic radial strain was 40.1±8.2%, circumferential 19.9±2.7%, and longitudinal 19.8±3.2%. Male sex was associated with decreased global strain values, independent of the strain direction (all P<0.001). Although many cardiovascular risk factors were correlated with strain in univariate analysis, mainly waist-to-hip ratio and HbA1c remained associated with decreased radial and circumferential strains in fully adjusted models. Similarly, higher radial and circumferential strains were observed in older subjects (β=0.14, P=0.01 and β=0.11, P=0.04, respectively). Strain analysis using magnetic resonance feature tracking is feasible in population-based cohort studies and shows differences with respect to age and sex as well as an independent association with markers of metabolic syndrome.

Anatomy of cosmic tidal reconstruction

Abstract 21-cm intensity surveys aim to map neutral hydrogen atoms in the universe through hyper-fine emission. Unfortunately, long-wavelength (low-wavenumber) radial modes are highly contaminated by smooth astrophysical foregrounds that are six orders of magnitude brighter than the cosmological signal. This contamination also leaks into higher radial and angular wavenumber modes and forms a foreground wedge. Cosmic tidal reconstruction aims to extract the large-scale signal from anisotropic features in the local small-scale power spectrum through non-linear tidal interactions; losing small-scale modes to foreground wedge will impair its performance. In this paper, we review tidal interaction theory and estimator construction, and derive the theoretical expressions for the reconstructed spectra. We show the reconstruction is robust against peculiar velocities. Removing low line-of-sight k modes, we demonstrate cross-correlation coefficient r is greater than 0.7 on large scales (k ≲ 0.1 h Mpc−1) even with a cut-off value $k^c_{\Vert }=0.1$h Mpc−1. Discarding wedge modes yields 0.3 ≲ r ≲ 0.5 and completely removes the dependency on $k^c_{\Vert }$. Our theoretical predictions agree with these numerical simulations.

Exploring the multiple-hit hypothesis of preterm white matter damage using diffusion MRI.

BackgroundPreterm infants are at high risk of diffuse white matter injury and adverse neurodevelopmental outcome. The multiple hit hypothesis suggests that the risk of white matter injury increases with cumulative exposure to multiple perinatal risk factors. Our aim was to test this hypothesis in a large cohort of preterm infants using diffusion weighted magnetic resonance imaging (dMRI).MethodsWe studied 491 infants (52% male) without focal destructive brain lesions born at < 34 weeks, who underwent structural and dMRI at a specialist Neonatal Imaging Centre. The median (range) gestational age (GA) at birth was 30+ 1 (23+ 2–33+ 5) weeks and median postmenstrual age at scan was 42+ 1 (38–45) weeks. dMRI data were analyzed using tract based spatial statistics and the relationship between dMRI measures in white matter and individual perinatal risk factors was assessed. We tested the hypothesis that increased exposure to perinatal risk factors was associated with lower fractional anisotropy (FA), and higher radial, axial and mean diffusivity (RD, AD, MD) in white matter. Neurodevelopmental performance was investigated using the Bayley Scales of Infant and Toddler Development, Third Edition (BSITD-III) in a subset of 381 infants at 20 months corrected age. We tested the hypothesis that lower FA and higher RD, AD and MD in white matter were associated with poorer neurodevelopmental performance.ResultsIdentified risk factors for diffuse white matter injury were lower GA at birth, fetal growth restriction, increased number of days requiring ventilation and parenteral nutrition, necrotizing enterocolitis and male sex. Clinical chorioamnionitis and patent ductus arteriosus were not associated with white matter injury. Multivariate analysis demonstrated that fetal growth restriction, increased number of days requiring ventilation and parenteral nutrition were independently associated with lower FA values. Exposure to cumulative risk factors was associated with reduced white matter FA and FA values at term equivalent age were associated with subsequent neurodevelopmental performance.ConclusionThis study suggests multiple perinatal risk factors have an independent association with diffuse white matter injury at term equivalent age and exposure to multiple perinatal risk factors exacerbates dMRI defined, clinically significant white matter injury. Our findings support the multiple hit hypothesis for preterm white matter injury.

Magnetohydrodynamic sausage waves in current-carrying coronal tubes

Magnetohydrodynamic (MHD) sausage waves in a coronal loop consisting of a core with longitudinal magnetic field and a current-carrying annulus with azimuthal magnetic field in the presence of plasma pressure are studied. As the plasma pressure is introduced to the loop a narrow band of infinite slow waves appear in the dispersion diagram, and the oscillation frequency of the fast sausage waves increases. In the loops with thinner annulus, more fast sausage waves with higher radial mode numbers are supported by the loop, and the fast sausage waves have smaller cut off wave numbers. The eigenfunction of the long wavelength fast sausage wave supported by the current-carrying loop, in the case of low density contrast, is similar to the eigenfunction of the slow sausage wave in a straight homogeneous loop with the maximum frequency of the frequency band. Other slow sausage waves both in a straight homogeneous loop and a current-carrying loop do not perturb the surrounding environment substantially.

Higher Radial Suspension Force of Magnetic Bearing on Centrifugal Compressor for HVAC

Higher Radial Suspension Force of Magnetic Bearing on Centrifugal Compressor for HVAC

Th17 cells correlate positively to the structural and functional integrity of the brain in bipolar depression and healthy controls

Abnormalities of T cell-mediated immune activation, in the absence of active somatic immune diseases, have consistently been reported in mood disorders. Apart from being important players in the regulation of cells of the immune system, T cells are essential for normal brain development. We here report studies on the relationship between circulating levels of T helper cells and structural and functional brain imaging in depressed bipolar patients. Since the CCL20-CCR6 axis is an important entry to the brain we differentiated the various T helper cell subpopulations on the basis of their chemokine receptor expression. MethodsFACS staining was performed for Th1, Th2, Th17, Th22 and T regulatory cells on frozen leukocytes of 25 consecutively admitted inpatients affected by a major depressive episode, without psychotic features, in the course of Bipolar Disorder I and 21 healthy controls. The frequency of the T helper populations was associated with DTI and fMRI data acquired on a Philips 3.0 Tesla scanner. Tract based spatial statistic was used to obtain measures of white matter integrity (fractional anisotropy, axial, radial and mean diffusivity) from a standard DTI sequence with 35 directions. Patients were also studied for fMRI through a moral valence decision task were subjects had to decide whether morally tuned stimuli were positive or negative. ResultsThe percentage of circulating Th17 (CCR6+CXCR3negCCR4+CCR10neg) cells correlated positively with higher fractional anisotropy in fiber tracts contributing to the functional integrity of the brain both in patients and healthy controls, while the frequency of circulating T regulatory (CD4+CD25+FOXP3+) cells correlated positively with higher radial and mean diffusivity in patients. The frequency of circulating T regulatory cells also correlated to lower neuronal responses to negative versus positive morally tuned stimuli in the right dorsolateral prefrontal cortex of patients. Th1 cells correlated negatively with white matter integrity in several tracts (healthy controls), while the cells showed a positive correlation to the levels of pro-inflammatory cytokines (patients). ConclusionThis study shows a new putative role for Th17 cells. Th17 cells are not only playing a role in inducing autoimmunity and auto-inflammation, but might also play a counter intuitive anabolic role in the maintenance of the functional and structural integrity of the brain.

The effect of the number of impeller blades on granular flow in a bladed mixer

Simulations of granular flow of monodisperse, cohesionless spherical glass beads in a cylindrical bladed mixer agitated by an impeller were performed using the discrete element method (DEM). The number of impeller blades was varied from 1 to 4 blades, and the impact of the number of blades on granular flow and mixing kinetics was investigated. It was found that particle velocities were influenced by the number of the blades used in the mixing system. Higher radial and vertical velocities of particles were observed in the 1- and 2-bladed mixers, which led to more pronounced three-dimensional recirculation patterns. However, the tangential velocity components of particles in the 3- and 4-bladed cases were larger. Additionally, it was found that using two or three impeller blades provided better mixing performance than using one or four blades, as evaluated by calculation of the relative standard deviation (RSD) and the Lacey index of the systems. Granular temperature and particle diffusivities obtained for the 2- and 3-bladed cases were also higher than those for the 1- and 4-bladed mixers. Solids fraction analysis showed that dilation of the particle bed occurred to the greatest extent in the 2-bladed mixer. Contact force network data and blade-particle force calculations showed that using different numbers of impeller blades led to significant differences in the force distribution. Finally, the effect of scaling up was evaluated by varying the mixer diameter to particle diameter ratio. Increasing the mixer diameter to particle diameter ratio was found to have little impact on flow and mixing behaviors.

Inflammatory cytokines influence measures of white matter integrity in Bipolar Disorder

BackgroundBipolar Disorder (BD) is associated with elevated biomarkers of cell-mediated immune activation and inflammation and with signs of widespread disruption of white matter (WM) integrity in adult life. Consistent findings in animal models link WM damage in inflammatory diseases of the brain and serum levels of cytokines. MethodsWith an exploratory approach, we tested the effects of 22 serum analytes, including pro- and anti-inflammatory cytokines and neurotrophic/hematopoietic factors, on DTI measures of WM microstructure in a sample of 31 patients with a major depressive episode in course of BD. We used whole brain tract-based spatial statistics in the WM skeleton with threshold-free cluster enhancement of DTI measures of WM microstructure: axial (AD), radial (RD), and mean diffusivity (MD), and fractional anisotropy (FA). ResultsThe inflammation-related cytokines TNF-α, IL-8, IFN-γ and IL-10, and the growth factors IGFBP2 and PDGF-BB, shared the same significant associations with lower FA, and higher MD and RD, in large overlapping networks of WM fibers mostly located in the anterior part of the brain and including corpus callosum, cingulum, superior and inferior longitudinal fasciculi, inferior fronto-occipital fasciculi, uncinate, forceps, corona radiata, thalamic radiation, internal capsule. ConclusionsHigher RD is thought to signify increased space between fibers, suggesting demyelination or dysmyelination. The pattern of higher RD and MD with lower FA suggests that inflammation-related cytokine and growth factor levels inversely associate with integrity of myelin sheaths. The activated inflammatory response system might contribute to BD pathophysiology by hampering structural connectivity in critical cortico-limbic networks.

Effect of piston bowl shape on the in-cylinder flow characteristics of IC engines

Numerical simulation of the in-cylinder flow for internal combustion (IC) engine with different bowl shapes has been performed. The LES models are applied to a piston-cylinder assembly with a stationary valve and a harmonically moving piston. Gas motion inside the engine cylinder determines the thermal efficiency of an IC engine, and combustion chamber geometry affects the performance of the IC engine. Comparison of the flow characteristics inside the engine cylinder equipped with different piston geometries shows that the squish flow affects the turbulence generation process near the top dead center during compression stroke. The A-type combustion chamber with reentrant shape is shown to have higher radial velocity and turbulence intensity in the piston bowl compared with other types. Results of these simulations aid in the improved understanding of the effect of intake and compression process of piston geometry on the in-cylinder flow. The detailed flow characteristics inside the in-cylinder for different piston bowl shapes can offer basic guidelines to improve the combustion process.

Laguerre-Gaussian beam scintillation on slant paths

Scintillation evaluations for Laguerre-Gaussian (LG) beams for slant paths are made using Rytov approximation. On- and off-axis scintillation is formulated and calculated up to several tens of kilometers of slant distances for different zenith angles. Scintillation index variations against radial receiver point and different source sizes are also investigated. In all cases evaluated, it is found that LG beams with higher radial mode numbers result in less scintillation than Gaussian beam. Kolmogorov spectrum function is utilized in the scintillation calculations.

Reference Data for Bone Speed of Sound in Portuguese Girls and Boys Aged 9–13 Years

The objective of this study was to provide reference data for quantitative ultrasound (QUS, Sunlight Omnisense; BeamMed Ltd., Petach-Tikva, Israel) of the radius and tibia in Portuguese subjects. The evaluation was conducted with QUS in 430 healthy participants (213 girls and 217 boys) aged between 9 and 13 yr. The results indicate that 13-yr-old girls had higher radial and tibial speed of sound (SOS) than younger girls and higher tibial SOS than boys of the same age ( p < 0.05). Regression analysis revealed positive associations between radial and tibial SOS and skeletal maturity in girls and negative association between tibial SOS and fat mass in both sexes and average intensity of physical activity in girls ( p < 0.01). The young Portuguese subjects showed an age-related variation in SOS similar to that seen in some of the eastern Mediterranean countries. Children with a history of fracture of lower (n = 24) or upper limbs (n = 43) did not show a significant decrease of SOS values in any of the bone sites evaluated (tibia Z-score: −0.23 standard deviations [SDs]; radius Z-score: −0.21 SDs; p > 0.05).