Metal Mixing and Ejection in Dwarf Galaxies is Dependent on Nucleosynthetic Source

Using a high resolution simulation of an isolated dwarf galaxy, accounting for multi-channel stellar feedback and chemical evolution on a star-by-star basis, we investigate how each of 15 metal species are distributed within our multi-phase interstellar medium (ISM) and ejected from our galaxy by galactic winds. For the first time, we demonstrate that the mass fraction probability distribution functions (PDFs) of individual metal species in the ISM are well described by a piecewise log-normal and power-law distribution. The PDF properties vary within each ISM phase. Hot gas is dominated by recent enrichment, with a significant power-law tail to high metal fractions, while cold gas is predominately log-normal. In addition, elements dominated by asymptotic giant branch (AGB) wind enrichment (e.g. N and Ba) mix less efficiently than elements dominated by supernova enrichment (e.g. $\alpha$ elements and Fe). This result is driven by the differences in source energetics and source locations, particularly the higher chance compared to massive stars for AGB stars to eject material into cold gas. Nearly all of the produced metals are ejected from the galaxy (only 4% are retained), but over 20% of metals dominated by AGB enrichment are retained. In dwarf galaxies, therefore, elements synthesized predominately through AGB winds should be both overabundant and have a larger spread compared to elements synthesized in either core collapse or Type Ia supernovae. We discuss the observational implications of these results, their potential use in developing improved models of galactic chemical evolution, and their generalization to more massive galaxies.Comment: 18 pages, 7 figures (plus 2 page, 2 figure appendix). Accepted to Ap

5-HT obesity medication efficacy via POMC activation is maintained during aging

Peer reviewedPublisher PD

Synthesis and structure of sterically overloaded tetra-coordinated yttrium and lanthanum disiloxides

The NSF is thanked for purchase of a JEOL ECS-400 NMR Spectrometer (CRIF-MU CHE-1048553).The synthesis, structures and reactivity of the spirocyclic yttrium and lanthanum disiloxides {[(CH2R2SiO)2]2M}H [M = Ln, Y; R = SiMe(SiMe3)2] 3 and 4 are reported. Compounds 3 and 4 were prepared from reactions of two equivalents of [CH2(R)2SiOH]2 [R = Si(SiMe3)2Me] ( 1 ) with one equivalent of M[N(SiMe3)2]2 (M = Y, La), respectively.PostprintPeer reviewe

General Issues Connecting Flavor Symmetry and Supersymmetry

We motivate and construct supersymmetric theories with continuous flavor symmetry, under which the electroweak Higgs doublets transform non-trivially. Flavor symmetry is spontaneously broken at a large mass scale in a sector of gauge-singlet fields; the light Higgs multiplets naturally emerge as special linear combinations that avoid acquiring the generic large mass. Couplings of the light Higgs doublets to light moduli fields from the singlet sector could lead to important effects in the phenomenology of the Higgs sector.Comment: 5 page

Mapping Change Management: A Co-citation Analysis

Today\u27s organizations are continually undergoing changes to make improvements in their efficiency and effectiveness. The ability of organizations to effectively implement and sustain successful change, however, has been limited, with most change initiatives failing to attain the desired success. To counter this trend, researchers across several disciplines have worked to provide practitioners better insight into how to facilitate change within their organizations. This research has resulted in many theories as to what constitutes change and how best to implement it, but it lacks a unifying theory that encompasses all aspects of change research. This effort takes a step toward a better understanding of the change management field and its nature. Using a co-citation methodology, 141 influential authors from the field of change management were identified. Their works were then categorized into identifiable sub-groups within the field and mapped, providing insight into the level of integration that has occurred within the field and across the disciplines that have explored change. Also, the extent to which the existing theories have begun to converge toward a unifying theory is observed. The purpose of this effort is to point future researchers in a direction that will lead to a unifying theory of change management. This unifying theory can then be translated into practices that will enable organizations to successfully transition through needed change initiatives

Contribution of Endogenous Glucocorticoids and Their Intravascular Metabolism by 11β-HSDs to Postangioplasty Neointimal Proliferation in Mice

Exogenous glucocorticoids inhibit neointimal proliferation in animals. We aime to test the hypothesis that endogenous glucocorticoids influence neointimal proliferation; this may be mediated by effects on systemic risk factors or locally in vessels, and modulated either by adrenal secretion or by enzymes expressed in vessels which mediate local inactivation (11β-HSD2 in endothelium) or regeneration (11β-HSD1 in smooth muscle) of glucocorticoids. Femoral artery wire-angioplasty was conducted in C57Bl/6J, Apo-E(−/−), 11β-HSD1(−/−), Apo-E, 11β-HSD1(−/−) (double knockout) and 11β-HSD2(−/−) mice following glucocorticoid administration, adrenalectomy, glucocorticoid or mineralocorticoid receptor antagonism, or selective 11β-HSD1 inhibition. In C57Bl/6J mice, neointimal proliferation was reduced by systemic or local glucocorticoid administration, unaffected by adrenalectomy, reduced by the mineralocorticoid receptor antagonist eplerenone, and increased by the glucocorticoid receptor antagonist RU38486. 11β-HSD2 deletion had no effect on neointimal proliferation, with or without eplerenone. 11β-HSD1 inhibition or deletion had no effect in chow-fed C57Bl/6J mice, but reduced neointimal proliferation in Apo-E(−/−) mice on Western diet. Reductions in neointimal size were accompanied by reduced macrophage and increased collagen content. We conclude that pharmacological administration of glucocorticoid receptor agonists or of mineralocorticoid receptor antagonists may be useful in reducing neointimal proliferation. Endogenous corticosteroids induce beneficial glucocorticoid receptor activation and adverse mineralocorticoid receptor activation. However, manipulation of glucocorticoid metabolism has beneficial effects only in mice with exaggerated systemic risk factors, suggesting effects mediated primarily in liver and adipose rather than intra-vascular glucocorticoid signalling. Reducing glucocorticoid action with 11β-HSD1 inhibitors that are being developed for type 2 diabetes appears not to risk enhanced neointimal proliferation

Comparing aging and fitness effects on brain anatomy

Recent studies suggest that cardiorespiratory fitness (CRF) mitigates the brain’s atrophy typically associated with aging, via a variety of beneficial mechanisms. One could argue that if CRF is generally counteracting the negative effects of aging, the same regions that display the greatest age-related volumetric loss should also show the largest beneficial effects of fitness. To test this hypothesis we examined structural MRI data from 54 healthy older adults (ages 55–87), to determine the overlap, across brain regions, of the profiles of age and fitness effects. Results showed that lower fitness and older age are associated with atrophy in several brain regions, replicating past studies. However, when the profiles of age and fitness effects were compared using a number of statistical approaches, the effects were not entirely overlapping. Interestingly, some of the regions that were most influenced by age were among those not influenced by fitness. Presumably, the age-related atrophy occurring in these regions is due to factors that are more impervious to the beneficial effects of fitness. Possible mechanisms supporting regional heterogeneity may include differential involvement in motor function, the presence of adult neurogenesis, and differential sensitivity to cerebrovascular, neurotrophic and metabolic factors

Episodic X-ray Emission Accompanying the Activation of an Eruptive Prominence: Evidence of Episodic Magnetic Reconnection

We present an X-ray imaging and spectroscopic study of a partially occulted C7.7 flare on 2003 April 24 observed by RHESSI that accompanied a prominence eruption observed by TRACE. (1) The activation and rise of the prominence occurs during the preheating phase of the flare. The initial X-ray emission appears as a single coronal source at one leg of the prominence and it then splits into a double source. Such a source splitting happens three times, each coinciding with an increased X-ray flux and plasma temperature, suggestive of fast reconnection in a localized current sheet and an enhanced energy release rate. In the late stage of this phase, the prominence displays a helical structure. These observations are consistent with the tether-cutting and/or kink instability model for triggering solar eruptions. (2) The eruption of the prominence takes place during the flare impulsive phase. Since then, there appear signatures predicted by the classical CSHKP model of two-ribbon flares occurring in a vertical current sheet trailing an eruption. These signatures include an EUV cusp and current-sheet-like feature (or ridge) above it. There is also X-ray emission along the EUV ridge both below and above the cusp, which in both regions appears closer to the cusp at higher energies in the thermal regime. This trend is reversed in the nonthermal regime. (3) Spectral analysis indicates thermal X-rays from all sources throughout the flare, while during the impulsive phase there is additional nonthermal emission which primarily comes from the coronal source below the cusp. This source also has a lower temperature, a higher emission measure, and a much harder nonthermal spectrum than the upper sources.Comment: 8 pages, 5 figures, submitted to Ap

Exploring the Higgs Portal with 10/fb at the LHC

We consider the impact of new exotic colored and/or charged matter interacting through the Higgs portal on Standard Model Higgs boson searches at the LHC. Such Higgs portal couplings can induce shifts in the effective Higgs-gluon-gluon and Higgs-photon-photon couplings, thus modifying the Higgs production and decay patterns. We consider two possible interpretations of the current LHC Higgs searches based on ~ 5/fb of data at each detector: 1) a Higgs boson in the mass range (124-126) GeV and 2) a `hidden' heavy Higgs boson which is underproduced due to the suppression of its gluon fusion production cross section. We first perform a model independent analysis of the allowed sizes of such shifts in light of the current LHC data. As a class of possible candidates for new physics which gives rise to such shifts, we investigate the effects of new scalar multiplets charged under the Standard Model gauge symmetries. We determine the scalar parameter space that is allowed by current LHC Higgs searches, and compare with complementary LHC searches that are sensitive to the direct production of colored scalar states.Comment: 27 pages, 11 figures; v2: references added, correction to scalar form factor, numerical results updated with Moriond 2012 data, conclusions unchange

A Cellular Mechanism for Dendritic Spine Loss Following Traumautic Brain Injury in Rat

Traumatic brain injury is a leading cause of death and disability in the United States. The injury is often composed of two processes: the primary injury, which can involve irreversible loss of tissue, and the secondary injury, which involves a cascade of reactive processes such as excitotoxicity that occur in the hours and days after the initial insult. Excitotoxic stimulation of neuronal circuits can lead to cellular dysfunction and modulation of neuronal sensitivity. One mechanism of dysfunction involves the calcium-regulated phosphatase, calcineurin. Calcineurin has been shown to be involved in the modulation of the neuronal post-synaptic structures known as dendritic spines. One means by which CaN regulates spine structure is through the dephosphorylation of the down-stream effector proteins such as, cofilin. This study tracks the changes in CaN activity levels as well as the phosphorylation state of cofilin in the cortex and hippocampus in each hemisphere of the laterally injured brain. We report that the lateral brain injury causes an increase in CaN activity in the hippocampus with a corresponding dephosphorylation of cofilin. Trauma-induced changes in CaN follow a slightly different time course in cortical tissue, as there is a biphasic modulation of cofilin that begins with an increased phosphorylation which is followed by an extended dephosphorylation. This dephosphorylation is partially prevented by a single post-injury injection of FK506, a calcineurin inhibitor. Since dephosphorylation of cofilin is a rate-limiting step in dendritic spine collapse, the results of this study demonstrate a potential cellular mechanism through which traumatic brain injury results in altered neuronal function