Ion radial diffusion in an electrostatic impulse model for stormtime ring current formation

Guiding-center simulations of stormtime transport of ring-current and radiation-belt ions having first adiabatic invariants mu is approximately greater than 15 MeV/G (E is approximately greater than 165 keV at L is approximately 3) are surprisingly well described (typically within a factor of approximately less than 4) by the quasilinear theory of radial diffusion. This holds even for the case of an individual model storm characterized by substorm-associated impulses in the convection electric field, provided that the actual spectrum of the electric field is incorporated in the quasilinear theory. Correction of the quasilinear diffusion coefficient D(sub LL)(sup ql) for drift-resonance broadening (so as to define D(sub LL)(sup ql)) reduced the typical discrepancy with the diffusion coefficients D(sub LL)(sup sim) deduced from guiding-center simulations of representative-particle trajectories to a factor of approximately 3. The typical discrepancy was reduced to a factor of approximately 1.4 by averaging D(sub LL)(sup sim), D(sub LL)(sup ql), and D(sub LL)(sup rb) over an ensemble of model storms characterized by different (but statistically equivalent) sets of substorm-onset times

Neoselachians from the Danian (early Paleocene) of Denmark

A diverse elasmobranch fauna was collected from the early Danian Rødvig Formation and the early to middle Danian Stevns Klint Formation at Stevns Klint and from the middle Danian Faxe Formation at Faxe, Denmark. Teeth from 27 species of sharks are described including the earliest records of Chlamydoselachus and Heptranchias howelli from Europe. The fauna collected at the Faxe quarry is rich in large species of shark including Sphenodus lundgreni and Cretalamna appendiculata and includes no fewer than four species of Hexanchiformes. The species collected yield an interesting insight into shark diversity in the Boreal Sea during the earliest Paleogene. The early Danian fauna recorded from the Cerithium Limestone represents an impoverished Maastrichtian fauna, whereas the fauna found in the slightly younger bryozoan limestone is representative of a pronounced cold water fauna. Several species that hitherto have only been known from the Late Cretaceous have been identified, clearly indicating that the K–T boundary was not the end of the Cretaceous fauna; it lingered and survived into the early Danian

Cellular excitability and the regulation of functional neuronal identity: from gene expression to neuromodulation

The intrinsic properties of a neuron determine the translation of synaptic input to axonal output. It is this input– output relationship that is the heart of all nervous system activity. As such, the overall regulation of the intrinsic excitability of a neuron directly determines the output of that neuron at a given point in time, giving the cell a unique “functional identity.” To maintain this distinct functional output, neurons must adapt to changing patterns of synaptic excitation. These adaptations are essential to prevent neurons from either falling silent as synaptic excitation falls or becoming saturated as excitation increases. In the absence of stabilizing mechanisms, activity-dependent plasticity could drive neural activity to saturation or quiescence. Furthermore, as cells adapt to changing patterns of synaptic input, presumably the overall balance of intrinsic conductances of the cell must be maintained so that reliable output is achieved (Daoudal and Debanne, 2003; Turrigiano and Nelson, 2004; Frick and Johnston, 2005). Although these regulatory phenomena have been well documented, the molecular and physiological mechanisms involved are poorly understood

The Coronal X-ray Spectrum of the Multiple Weak-Lined T Tauri Star System HD 98800

We present high-resolution X-ray spectra of the multiple (hierarchical quadruple) weak-lined T Tauri star system HD 98800, obtained with the High Energy Transmission Gratings Spectrograph (HETGS) aboard the Chandra X-ray Observatory (CXO). In the zeroth-order CXO/HETGS X-ray image, both principle binary components of HD 98800 (A and B, separation 0.8'') are detected; component A was observed to flare during the observation. The infrared excess (dust disk) component, HD 98800B, is a factor ~4 fainter in X-rays than the apparently ``diskless'' HD 98800A, in quiescence. The line ratios of He-like species (e.g., Ne IX, O VII) in the HD 98800A spectrum indicate that the X-ray-emitting plasma around HD 98800 is in a typical coronal density regime (log n <~ 11). We conclude that the dominant X-ray-emitting component(s) of HD 98800 is (are) coronally active. The sharp spectral differences between HD 98800 and the classical T Tauri star TW Hya demonstrate the potential utility of high-resolution X-ray spectroscopy in providing diagnostics of pre-main sequence accretion processes.Comment: 11 pages, 5 figures; to appear in the Astrophysical Journal (Letters

Correlated Levels of mRNA and Soma Size in Single Identified Neurons: Evidence for Compartment-specific Regulation of Gene Expression

In addition to the overall complexity of transcriptional regulation, cells also must take into account the subcellular distribution of these gene products. This is particularly challenging for morphologically complex cells such as neurons. Yet the interaction between cellular morphology and gene expression is poorly understood. Here we provide some of the first evidence for a relationship between neuronal compartment size and maintenance of mRNA levels in neurons. We find that single-cell transcript levels of 18S rRNA, GAPDH, and EF1-alpha, all gene products with primary functions in the cell soma, are strongly correlated to soma size in multiple distinct neuronal types. Levels of mRNA for the K+ channel shal, which is localized exclusively to the soma, are negatively correlated with soma size, suggesting that gene expression does not simply track positively with compartment size. Conversely, levels of beta-actin and beta-tubulin mRNA, which are major cytoskeletal proteins of neuronal processes, do not correlate with soma size, but are strongly correlated with one another. Additionally, actin/tubulin expression levels correlate with voltage-gated ion channels that are uniquely localized to axons. These results suggest that steady-state transcript levels are differentially regulated based on the subcellular compartment within which a given gene product primarily acts

Mapping the Road from Childhood Trauma to Adult Somatization: The Role of Attachment

Objective: This study tested whether insecure attachment mediates the link between childhood trauma and adult somatization. Methods: A community sample of 101 couples completed self-report measures including the Relationship Scales Questionnaire, the Childhood Trauma Questionnaire, the Somatic Symptom Inventory, the Beck Depression Inventory, and the Conflict Tactics Scale. Results: Childhood trauma was associated with higher levels of somatization and insecure attachment. Insecure attachment style was also associated with higher levels of somatization. Controlling for age, income, and recent intimate partner violence, analyses showed that fearful attachment fully mediated the link between childhood trauma and somatization for women. For men there was no such mediation, but both childhood trauma and insecure attachment styles made independent contributions to predicting levels of somatization. Conclusions: Findings are consistent with the hypothesis that, for women, childhood trauma influences adult levels of somatization by fostering insecure adult attachment. For men, findings suggest that trauma and attachment are both important independent predictors of adult somatization. Study results support the idea that childhood trauma shapes patients’ styles of relating to others in times of need and these styles in turn influence the somatization process and how patients respond to providers. Screening for attachment style may provide information that could allow health care providers to tailor treatment more effectively. Key words: Attachment style, somatization, childhood trauma, interpersonal models. Abbreviations: CTQ = Childhood Trauma Questionnaire; CTS2 = Conflict Tactics Scale version 2; SSI = Somatic Symptom Inventory; RSQ = Relationship Scales Questionnaire; BDI = Beck Depression Inventory

Mapping the Road from Childhood Trauma to Adult Somatization: The Role of Attachment

Objective: This study tested whether insecure attachment mediates the link between childhood trauma and adult somatization. Methods: A community sample of 101 couples completed self-report measures including the Relationship Scales Questionnaire, the Childhood Trauma Questionnaire, the Somatic Symptom Inventory, the Beck Depression Inventory, and the Conflict Tactics Scale. Results: Childhood trauma was associated with higher levels of somatization and insecure attachment. Insecure attachment style was also associated with higher levels of somatization. Controlling for age, income, and recent intimate partner violence, analyses showed that fearful attachment fully mediated the link between childhood trauma and somatization for women. For men there was no such mediation, but both childhood trauma and insecure attachment styles made independent contributions to predicting levels of somatization. Conclusions: Findings are consistent with the hypothesis that, for women, childhood trauma influences adult levels of somatization by fostering insecure adult attachment. For men, findings suggest that trauma and attachment are both important independent predictors of adult somatization. Study results support the idea that childhood trauma shapes patients’ styles of relating to others in times of need and these styles in turn influence the somatization process and how patients respond to providers. Screening for attachment style may provide information that could allow health care providers to tailor treatment more effectively. Key words: Attachment style, somatization, childhood trauma, interpersonal models. Abbreviations: CTQ = Childhood Trauma Questionnaire; CTS2 = Conflict Tactics Scale version 2; SSI = Somatic Symptom Inventory; RSQ = Relationship Scales Questionnaire; BDI = Beck Depression Inventory

X-ray Variability in the Young Massive Triple theta2 Ori A

Massive stars rarely show intrinsic X-ray variability. The only O-stars credited to be intrinsically variable are theta1 Ori C due to effects from magnetic confinement of its wind, and theta2 Ori A suspected of similar activity. Early Chandra observations have shown that the most massive star system in the Orion Trapezium Cluster, theta2 Ori A, shows rapid variability on time scales of hours. We determine X-ray fluxes and find that the star shows very strong variability over the last 5 years. We observed a second large X-ray outburst in November 2004 with the high resolution transmission grating spectrometer on-board Chandra. In the low state X-ray emissivities indicate temperatures well above 25 MK. In the high state we find an extended emissivity distribution with high emissivities in the range from 3 MK to over 100 MK. The outburst event in stellar terms is one of the most powerful ever observed and the most energetic one in the ONC with a lower total energy limit of 1.5x10^37 ergs. The line diagnostics show that under the assumption that the line emitting regions in the low states are as close as within 1 -- 2 stellar radii from the O-star's photosphere, whereas the hard states suggest a distance of 3 -- 5 stellar radii. The two outbursts are very close to the periastron passage of the stars. We argue that the high X-ray states are possibly the result of reconnection events from magnetic interactions of the primary and secondary stars of the spectroscopic binary. Effects from wind collisions seem unlikely for this system. The low state emissivity and R-ratios strengthen the predicament that the X-ray emission is enhanced by magnetic confinement of the primary wind. We also detect Fe fluorescence indicative of the existence of substantial amounts of neutral Fe in the vicinity of the X-ray emission.Comment: 11 pages, 8 figures, accepted for publication in The Astrophysical Main Journa

Two dimensional anisotropic non Fermi-liquid phase of coupled Luttinger liquids

We show using bosonization techniques, that strong forward scattering interactions between one dimensional spinless Luttinger liquids (LL) can stabilize a phase where charge-density wave, superconducting and transverse single particle hopping perturbations are irrelevant. This new phase retains its LL like properties in the directions of the chains, but with relations between exponents modified by the transverse interactions, whereas, it is a perfect insulator in the transverse direction. The mechanism that stabilizes this phase are strong transverse charge density wave fluctuations at incommensurate wavevector, which frustrates crystal formation by preventing lock-in of the in-chain density waves.Comment: (4 pages, 2 figures