Black hole evaporation in a spherically symmetric non-commutative space-time

Recent work in the literature has studied the quantum-mechanical decay of a Schwarzschild-like black hole, formed by gravitational collapse, into almost-flat space-time and weak radiation at a very late time. The relevant quantum amplitudes have been evaluated for bosonic and fermionic fields, showing that no information is lost in collapse to a black hole. On the other hand, recent developments in noncommutative geometry have shown that, in general relativity, the effects of non-commutativity can be taken into account by keeping the standard form of the Einstein tensor on the left-hand side of the field equations and introducing a modified energy-momentum tensor as a source on the right-hand side. Relying on the recently obtained non-commutativity effect on a static, spherically symmetric metric, we have considered from a new perspective the quantum amplitudes in black hole evaporation. The general relativity analysis of spin-2 amplitudes has been shown to be modified by a multiplicative factor F depending on a constant non-commutativity parameter and on the upper limit R of the radial coordinate. Limiting forms of F have been derived which are compatible with the adiabatic approximation.Comment: 8 pages, Latex file with IOP macros, prepared for the QFEXT07 Conference, Leipzig, September 200

Deformation of continental crust along a transform boundary, Coast Mountains, British Columbia

New structural, paleomagnetic, and apatite (U-Th)/He results from the continental margin inboard of the Queen Charlotte fault (~54°N) delineate patterns of brittle faulting linked to transform development since ~50 Ma. In the core of the orogen, ~250 km from the transform, north striking, dip-slip brittle faults and vertical axis rotation of large crustal domains occurred after ~50 Ma and before intrusion of mafic dikes at 20 Ma. By 20 Ma, dextral faulting was active in the core of the orogen, but extension had migrated toward the transform, continuing there until <9 Ma. Local tilting in the core of the orogen is associated with glacially driven, post-4 Ma exhumation. Integration with previous results shows that post-50 Ma dextral and normal faulting affected a region ~250 km inboard of the transform and ~300 km along strike. Initially widespread, the zone of active extension narrowed and migrated toward the transform ~25 Ma after initiation of the transform, while dextral faulting continued throughout the region. Differential amounts of post-50 Ma extension created oroclines at the southern and northern boundaries of the deformed region. This region approximately corresponds to continental crust that was highly extended just prior to transform initiation. Variation in Neogene crustal tilts weakens interpretations relying on uniform tilting to explain anomalous paleomagnetic inclinations of mid-Cretaceous plutons. Similarities to the Gulf of California suggest that development of a transform in continental crust is aided by previous crustal extension and that initially widespread extension narrows and moves toward the transform as the margin develops

Cretaceous-to-recent record of elevated 3He/4He along the Hawaiian-Emperor volcanic chain

Helium isotopes are a robust geochemical tracer of a primordial mantle component in hot spot volcanism. The high 3He/4He (up to 35 RA, where RA is the atmospheric 3He/4He ratio of 1.39 × 10−6) of some Hawaiian Island volcanism is perhaps the classic example. New results for picrites and basalts from the Hawaiian-Emperor seamount chain indicate that the hot spot has produced high 3He/4He lavas for at least the last 76 million years. Picrites erupted at 76 Ma have 3He/4He (10–14 RA), which is at the lower end of the range for the Hawaiian Islands but still above the range of modern mid-ocean ridge basalt (MORB; 6–10 RA). This was at a time when hot spot volcanism was occurring on thin lithosphere close to a spreading ridge and producing lava compositions otherwise nearly indistinguishable from MORB. After the hot spot and spreading center diverged during the Late Cretaceous, the hot spot produced lavas with significantly higher 3He/4He (up to 24 RA). Although 3He/4He ratios stabilized at relatively high values by 65 Ma, other chemical characteristics such as La/Yb and 87Sr/86Sr did not reach and stabilize at Hawaiian-Island-like values until ~45 Ma. Our limited 3He/4He record for the Hawaiian hot spot shows a poor correlation with plume flux estimates (calculated from bathymetry and residual gravity anomalies [Van Ark and Lin, 2004]). If 3He is a proxy for the quantity of primordial mantle material within the plume, then the lack of correlation between 3He/4He and calculated plume flux suggests that variation in primordial mantle flux is not the primary factor controlling total plume flux

Sclerostin does not play a major role in the pathogenesis of skeletal complications in type 2 diabetes mellitus

In contrast to previously reported elevations in serum sclerostin levels in diabetic patients, the present study shows that the impaired bone microarchitecture and cellular turnover associated with type 2 diabetes mellitus (T2DM)-like conditions in ZDF rats are not correlated with changes in serum and bone sclerostin expression. INTRODUCTION: T2DM is associated with impaired skeletal structure and a higher prevalence of bone fractures. Sclerostin, a negative regulator of bone formation, is elevated in serum of diabetic patients. We aimed to relate changes in bone architecture and cellular activities to sclerostin production in the Zucker diabetic fatty (ZDF) rat. METHODS: Bone density and architecture were measured by micro-CT and bone remodelling by histomorphometry in tibiae and femurs of 14-week-old male ZDF rats and lean Zucker controls (n = 6/group). RESULTS: ZDF rats showed lower trabecular bone mineral density and bone mass compared to controls, due to decreases in bone volume and thickness, along with impaired bone connectivity and cortical bone geometry. Bone remodelling was impaired in diabetic rats, demonstrated by decreased bone formation rate and increased percentage of tartrate-resistant acid phosphatase-positive osteoclastic surfaces. Serum sclerostin levels (ELISA) were higher in ZDF compared to lean rats at 9 weeks (+40 %, p < 0.01), but this difference disappeared as their glucose control deteriorated and by week 14, ZDF rats had lower sclerostin levels than control rats (-44 %, p < 0.0001). Bone sclerostin mRNA (qPCR) and protein (immunohistochemistry) were similar in ZDF, and lean rats at 14 weeks and genotype did not affect the number of empty osteocytic lacunae in cortical and trabecular bone. CONCLUSION: T2DM results in impaired skeletal architecture through altered remodelling pathways, but despite altered serum levels, it does not appear that sclerostin contributes to the deleterious effect of T2DM in rat bone

A Cenozoic-style scenario for the end-Ordovician glaciation

The end-Ordovician was an enigmatic interval in the Phanerozoic, known for massive glaciation potentially at elevated CO2 levels, biogeochemical cycle disruptions recorded as large isotope anomalies and a devastating extinction event. Ice-sheet volumes claimed to be twice those of the Last Glacial Maximum paradoxically coincided with oceans as warm as today. Here we argue that some of these remarkable claims arise from undersampling of incomplete geological sections that led to apparent temporal correlations within the relatively coarse resolution capability of Palaeozoic biochronostratigraphy. We examine exceptionally complete sedimentary records from two, low and high, palaeolatitude settings. Their correlation framework reveals a Cenozoic-style scenario including three main glacial cycles and higher-order phenomena. This necessitates revision of mechanisms for the end-Ordovician events, as the first extinction is tied to an early phase of melting, not to initial cooling, and the largest δ13C excursion occurs during final deglaciation, not at the glacial apex

Screening for Traumatic Brain Injury in Prostituted Women

Violence is pervasive in prostitution and can cause traumatic brain injury (TBI). This study estimated the prevalence and demographic correlates of TBI among 66 women and transwomen in prostitution. Ninety-five percent had sustained head injuries, either by being hit in the head with objects and/or having their heads slammed into objects. Sixty-one percent had sustained head injuries in prostitution. The women described acute and chronic symptoms resulting from head injury and/or concussions. These included dizziness, depressed mood, headache, sleep difficulty, poor concentration, memory problems, difficulty following directions, low frustration tolerance, fatigue, and appetite and weight changes. Screening for TBI is crucial to the care of prostituted women

Developing a practice-driven research agenda in implementation science: Perspectives from experienced implementation support practitioners

Background Attention is being placed on the “ironic gap” or “secondary” research-to-practice gap in the field of implementation science. Among several challenges posited to exacerbate this research-to-practice gap, we call attention to one challenge in particular—the relative dearth of implementation research that is tethered intimately to the lived experiences of implementation support practitioners (ISPs). The purpose of this study is to feature a qualitative approach to engaging with highly experienced ISPs to inform the development of a practice-driven research agenda in implementation science. In general, we aim to encourage ongoing empirical inquiry that foregrounds practice-driven implementation research questions. Method Our analytic sample was comprised of 17 professionals in different child and family service systems, each with long-term experience using implementation science frameworks to support change efforts. Data were collected via in-depth, semi-structured interviews. Our analysis followed a qualitative content analysis approach. Our focal conceptual category centered on the desired areas of future research highlighted by respondents, with subcategories reflecting subsets of related research question ideas. Results Interviews yielded varying responses that could help shape a practice-driven research agenda for the field of implementation science. The following subcategories regarding desired areas for future research were identified in respondents’ answers: (a) stakeholder engagement and developing trusting relationships, (b) evidence use, (c) workforce development, and (d) cost-effective implementation. Conclusions There is significant promise in bringing implementation research and implementation practice together more closely and building a practice-informed research agenda to shape implementation science. Our findings point not only to valuable practice-informed gaps in the literature that could be filled by implementation researchers, but also topics for which dissemination and translation efforts may not have yielded optimal reach. We also highlight the value in ISPs bolstering their own capacity for engaging with the implementation science literature to the fullest extent possible.Plain Language Summary In the field of implementation science, increasing attention is being placed on the “ironic gap” or “secondary” research-to-practice gap. This gap reflects a general lag or disconnect between implementation research and implementation practice, often stemming from knowledge generated by implementation research not being accessible to or applied by professionals who support implementation efforts in various service-delivery systems. Several explanations for the research-to-practice gap in implementation science have been offered in recent years; the authors highlight one notable challenge that may be exacerbating the research-to-practice gap in this field, namely that implementation research often remains disconnected from the lived experiences of implementation support practitioners. In this paper, the authors demonstrate the promise of developing a practice-drive research agenda in implementation science, with specific research question ideas offered by highly experienced implementation support practitioners. The paper concludes by expressing enthusiasm for future efforts to bring implementation research and implementation practice together more closely, empirically foreground practice-driven implementation research questions, translate and disseminate existing implementation research findings more widely, and build the capacity of implementation support practitioners to fully engage with the implementation science literature