Brain tumor classification using the diffusion tensor image segmentation (D-SEG) technique.

BACKGROUND: There is an increasing demand for noninvasive brain tumor biomarkers to guide surgery and subsequent oncotherapy. We present a novel whole-brain diffusion tensor imaging (DTI) segmentation (D-SEG) to delineate tumor volumes of interest (VOIs) for subsequent classification of tumor type. D-SEG uses isotropic (p) and anisotropic (q) components of the diffusion tensor to segment regions with similar diffusion characteristics. METHODS: DTI scans were acquired from 95 patients with low- and high-grade glioma, metastases, and meningioma and from 29 healthy subjects. D-SEG uses k-means clustering of the 2D (p,q) space to generate segments with different isotropic and anisotropic diffusion characteristics. RESULTS: Our results are visualized using a novel RGB color scheme incorporating p, q and T2-weighted information within each segment. The volumetric contribution of each segment to gray matter, white matter, and cerebrospinal fluid spaces was used to generate healthy tissue D-SEG spectra. Tumor VOIs were extracted using a semiautomated flood-filling technique and D-SEG spectra were computed within the VOI. Classification of tumor type using D-SEG spectra was performed using support vector machines. D-SEG was computationally fast and stable and delineated regions of healthy tissue from tumor and edema. D-SEG spectra were consistent for each tumor type, with constituent diffusion characteristics potentially reflecting regional differences in tissue microstructure. Support vector machines classified tumor type with an overall accuracy of 94.7%, providing better classification than previously reported. CONCLUSIONS: D-SEG presents a user-friendly, semiautomated biomarker that may provide a valuable adjunct in noninvasive brain tumor diagnosis and treatment planning

Accretion of a satellite onto a spherical galaxy. II. Binary evolution and orbital decay

We study the dynamical evolution of a satellite orbiting outside of a companion spherical galaxy. The satellite is subject to a back-reaction force resulting from the density fluctuations excited in the primary stellar system. We evaluate this force using the linear response theory developed in Colpi and Pallavicini (1997). The force is computed in the reference frame comoving with the primary galaxy and is expanded in multipoles. To capture the relevant features of the physical process determining the evolution of the detached binary, we introduce in the Hamiltonian the harmonic potential as interaction potential among stars. The dynamics of the satellite is computed self-consistently. We determine the conditions for tidal capture of a satellite from an asymptotic free state. If the binary comes to existence as a bound pair, stability against orbital decay is lost near resonance. The time scale of binary coalescence is computed as a function of the eccentricity and mass ratio. In a comparison with Weinberg's perturbative technique we demonstrate that pinning the center of mass of the galaxy would induce a much larger torque on the satellite.Comment: 13 pages, Tex,+ 10 .ps figures Submitted to The Astrophysical Journa

Expanding the application space for piezoelectric materials

The long history of innovation in the field of piezoelectric devices has, over the last 65 years, been predominantly rooted in a single material, the Pb(Zr, Ti)O3 ceramic, known as lead zirconate titanate (PZT). Despite enormous resources being dedicated in the last 20 years to identifying lead-free alternatives to PZT and developing a thriving, but limited, market in PbTiO3-relaxor single crystals, most device developments are still PZT based. However, more recently, solid solutions based on BiFeO3 have opened up new applications for active piezoelectric devices at high temperatures (to 600 ○C) and under high stress (exceeding 250 MPa), with applications in industrial ultrasound, aerospace, automotive, and micro-actuators. This perspective article examines how new materials are expanding the application space for piezoelectric materials

Speech audiometry test with picture-related sentence lists in Modern Greek for partially hearing children

Objective: The aim of this study was to develop Greek Sentence Based Speech Audiometry Test in quiet test for Hearing Impaired (HI) children (G-SEBSAT). Methods: Seventy-six children were recruited following approval by the local ethics committee and after obtaining informed consent from their parents. The collection of vocabulary was based on showing pictures selected from popular reading materials in Greek to hearing impaired HI children. A grammatical content analysis was carried out to determine the average syntactic and morphological structures of the sentences used by the HI children. Ten picture related sentence lists were developed based on the vocabulary and the grammatical analysis, and recorded by a male native speaker of standard Modern Greek. These were presented to both normal hearing (NH) and HI children, and the average speech response threshold (SRT) as well as the slope of the SRT curve at the SRT level of 50% correct responses (S50) were recorded in both groups. Sentence lists were validated with respect to the variability of their difficulty within each group, as well the test-retest variability of the respective SRT scores. Results: The average speech response threshold (SRT) across all lists for HI children was 65.27 dB and the slope of the SRT curve at the SRT level of 50% correct responses was 3.11%/dB. The corresponding results across all lists for NH children were 17.66 dB and 9.7%/dB, respectively. The SRT of HI children were strongly positively correlated, in a statistically significant manner with the PTA in both the test and the retest sessions (test: r=0.750, P < 0.0005; retest: r=0.753, P < 0.0005). The Spearman correlation of the rankings of SRT values and the slope values was 0.998 and 0.997 respectively for the HI and 0.939 and 0.88, for the NH group, indicating very low variability across the test and retest sessions. In addition, the analysis of variance (ANOVA) of the average SRT in NH children and the SRT residuals in the HI group indicated that the different sentences were of the same difficulty within each group. ((F(9,81)=0.401, p=0.930 and (F(9,93)=2.241, p=0.025 respectively). Conclusions: A validated sentence based speech audiometry test was created in Greek for the first time. SRT and S50 values for both NH and HI children are comparable to similar tests developed in other languages

On the nonthermal X-ray emission in blazar jets

We consider particle acceleration to high energy via diffusive shock acceleration in a simple, self-consistent shock in jet model for blazars. Electrons are assumed to be accelerated at a shock front in relativistic jets and radiate synchrotron emission in a post-shock region. The full time, space and momentum dependence of the electron distribution function is used for a calculation of the nonthermal synchrotron spectra. We discuss the evolution of the spectral index by varying the rate at which particles enter the acceleration process. The results indicate that the synchrotron spectral index displays a characteristic looplike behaviour with intensity (as has been observed in several blazars), where the orientation of the loop depends on whether the acceleration time scale is comparable to the synchrotron cooling time scale or not. We show that our model provides a good fit to the observed evolution of the spectral index of Mkn 421 during a flare in 1994.Comment: 6 pages, 3 figures, conference proceedin

Gene silencing in tick cell lines using small interfering or long double-stranded RNA

Gene silencing by RNA interference (RNAi) is an important research tool in many areas of biology. To effectively harness the power of this technique in order to explore tick functional genomics and tick-microorganism interactions, optimised parameters for RNAi-mediated gene silencing in tick cells need to be established. Ten cell lines from four economically important ixodid tick genera (Amblyomma, Hyalomma, Ixodes and Rhipicephalus including the sub-species Boophilus) were used to examine key parameters including small interfering RNA (siRNA), double stranded RNA (dsRNA), transfection reagent and incubation time for silencing virus reporter and endogenous tick genes. Transfection reagents were essential for the uptake of siRNA whereas long dsRNA alone was taken up by most tick cell lines. Significant virus reporter protein knockdown was achieved using either siRNA or dsRNA in all the cell lines tested. Optimum conditions varied according to the cell line. Consistency between replicates and duration of incubation with dsRNA were addressed for two Ixodes scapularis cell lines; IDE8 supported more consistent and effective silencing of the endogenous gene subolesin than ISE6, and highly significant knockdown of the endogenous gene 2I1F6 in IDE8 cells was achieved within 48 h incubation with dsRNA. In summary, this study shows that gene silencing by RNAi in tick cell lines is generally more efficient with dsRNA than with siRNA but results vary between cell lines and optimal parameters need to be determined for each experimental system

Attribution of Atmospheric Sulfur Dioxide over the English Channel to Dimethylsulfide and Changing Ship Emissions

Atmospheric sulfur dioxide (SO2) was measured continuously from the Penlee Point Atmospheric Observatory(PPAO) near Plymouth, United Kingdom between May 2014 and November 2015. This coastal site is exposed to marine air across a wide wind sector. The predominant southwesterly winds carry relatively clean background Atlantic air. In contrast, air from the southeast is heavily influenced by exhaust plumes from ships in the English Channel as well as near the Plymouth Sound. New International Maritime Organization (IMO) regulation came into force in January 2015 to reduce sulfur emissions tenfold in Sulfur Emission Control Areas such as the English Channel. Our observations suggest a three-fold reduction from 2014 to 2015 in ship-emitted SO2 from that direction. Apparent fuel sulfur content calculated from coincidental SO2 and carbon dioxide (CO2) peaks from local ship plum es show a high level of compliance to the IMO regulation (> 95 %) in both years. Dimethylsulfide (DMS) is an important source of atmospheric SO2 even in this semi-polluted region. The relative contribution of DMS oxidation to the SO2 burden over the English Channel increased from ~ 1/3 in 2014 to ~ 1/2 in 2015 due to the reduction in ship sulfur emissions. Our diel analysis suggests that SO2 is removed from the marine atmospheric boundary layer in about half a day, with dry deposition to the ocean accounting for a quarter of the total loss

Lower Left Ventricular Ejection Fraction Relates to Cerebrospinal Fluid Biomarker Evidence of Neurodegeneration in Older Adults

BACKGROUND: Subclinical cardiac dysfunction is associated with decreased cerebral blood flow, placing the aging brain at risk for Alzheimer's disease (AD) pathology and neurodegeneration. OBJECTIVE: This study investigates the association between subclinical cardiac dysfunction, measured by left ventricular ejection fraction (LVEF), and cerebrospinal fluid (CSF) biomarkers of AD and neurodegeneration. METHODS: Vanderbilt Memory & Aging Project participants free of dementia, stroke, and heart failure (n = 152, 72±6 years, 68% male) underwent echocardiogram to quantify LVEF and lumbar puncture to measure CSF levels of amyloid-β42 (Aβ42), phosphorylated tau (p-tau), and total tau (t-tau). Linear regressions related LVEF to CSF biomarkers, adjusting for age, sex, race/ethnicity, education, Framingham Stroke Risk Profile, cognitive diagnosis, and apolipoprotein E ɛ4 status. Secondary models tested an LVEF x cognitive diagnosis interaction and then stratified by diagnosis (normal cognitive (NC), mild cognitive impairment (MCI)). RESULTS: Higher LVEF related to decreased CSF Aβ42 levels (β= -6.50, p = 0.04) reflecting greater cerebral amyloid accumulation, but this counterintuitive result was attenuated after excluding participants with cardiovascular disease and atrial fibrillation (p = 0.07). We observed an interaction between LVEF and cognitive diagnosis on CSF t-tau (p = 0.004) and p-tau levels (p = 0.002), whereas lower LVEF was associated with increased CSF t-tau (β= -9.74, p = 0.01) and p-tau in the NC (β= -1.41, p = 0.003) but not MCI participants (p-values>0.13). CONCLUSIONS: Among cognitively normal older adults, subclinically lower LVEF relates to greater molecular evidence of tau phosphorylation and neurodegeneration. Modest age-related changes in cardiovascular function may have implications for pathophysiological changes in the brain later in life

Stellar Disk Truncations: Where do we stand ?

In the light of several recent developments we revisit the phenomenon of galactic stellar disk truncations. Even 25 years since the first paper on outer breaks in the radial light profiles of spiral galaxies, their origin is still unclear. The two most promising explanations are that these 'outer edges' either trace the maximum angular momentum during the galaxy formation epoch, or are associated with global star formation thresholds. Depending on their true physical nature, these outer edges may represent an improved size characteristic (e.g., as compared to D_25) and might contain fossil evidence imprinted by the galaxy formation and evolutionary history. We will address several observational aspects of disk truncations: their existence, not only in normal HSB galaxies, but also in LSB and even dwarf galaxies; their detailed shape, not sharp cut-offs as thought before, but in fact demarcating the start of a region with a steeper exponential distribution of starlight; their possible association with bars; as well as problems related to the line-of-sight integration for edge-on galaxies (the main targets for truncation searches so far). Taken together, these observations currently favour the star-formation threshold model, but more work is necessary to implement the truncations as adequate parameters characterising galactic disks.Comment: LaTeX, 10 pages, 6 figures, presented at the "Penetrating Bars through Masks of Cosmic Dust" conference in South Africa, proceedings published by Kluwer, and edited by Block, D.L., Freeman, K.C., Puerari, I., & Groess, R; v3 to match published versio