Preservation of systematic Ni and Cr heterogeneity in otherwise homogeneous mantle olivine: Implications for timescales of post-metasomatism re-equilibration

The flux of elements into Earth’s sub-continental lithospheric mantle is facilitated by the passage of small-fraction melts that either crystallise new phases or react with pre-existing minerals. Metasomatised peridotite records the end product of this exchange but rarely captures the process in the act due to subsolidus re-equilibration. We present the results of a systematic investigation of a metasomatic melt channel preserved in a mantle peridotite from the Late Cretaceous Bultfontein kimberlite (Kaapvaal craton) that shows rare direct evidence of the melt-rock reaction processes. We show that the metasomatic proto-kimberlite melt underwent variable crystallisation of clinopyroxene, sulfides, phlogopite, spinel and zircon together with interaction and diffusive exchange with the surrounding olivine-rich mantle. Element profiles across large olivine porphyroclasts (Fo88) show significant core-to-rim variations in Ni (NiO = 0.18-0.32 wt.%) and Cr (Cr = 35-60 ppm), while concentrations of all other elements (e.g. Mg, Fe, Mn, Co, V) are remarkably homogeneous. Electron backscatter diffraction analysis shows that the disequilibrium of Ni and Cr is greatest where the crystal contains large components of the [100] and [010] axes. The disequilibrium is preserved in certain orientations because diffusion of Ni and Cr in olivine is more anisotropic than Fe-Mg and Mn, and slower in the [100] and [010] directions. We present the first observations of Ni and Cr decoupling from other elements in mantle olivine and suggest that this is a consequence of: (i) changing mineral-melt concentration gradients associated with the reactive percolation of a precursory kimberlite melt; and (ii) late-stage sulfide and spinel precipitation. We use the diffusion limited re-equilibration of Ni in olivine to quantify the timing of metasomatism prior to xenolith entrainment by the host kimberlite. Our modelling indicates that reactive percolation occurred on the order of 103-105 years prior to entrainment; this provides an additional line of support for the hypothesis that a period of metasomatism by proto-kimberlite melts precedes the final kimberlite ascent to the surface. The broader implication of our finding of variable rates of minor element diffusion in natural olivine is that it highlights the importance of anisotropy and the impact of changing local concentration gradients during subsolidus re-equilibration.NER

Structure and dielectric properties of polar fluids with extended dipoles: results from numerical simulations

The strengths and short-comings of the point-dipole model for polar fluids of spherical molecules are illustrated by considering the physically more relevant case of extended dipoles formed by two opposite charges $\pm q$ separated by a distance $d$ (dipole moment $\mu=q d$). Extensive Molecular Dynamics simulations on a high density dipolar fluid are used to analyse the dependence of the pair structure, dielectric constant \eps and dynamics as a function of the ratio $d/\sigma$ (\sig is the molecular diameter), for a fixed dipole moment $\mu$. The point dipole model is found to agree well with the extended dipole model up to d/\sig \simeq 0.3. Beyond that ratio, \eps shows a non-trivial variation with d/\sig. When d/\sig>0.6, a transition is observed towards a hexagonal columnar phase; the corresponding value of the dipole moment, \mu^2/\sig^3 k T=3, is found to be substantially lower than the value of the point dipole required to drive a similar transition.Comment: 10 pages, 11 figures; Paper submitted to Molecular Physic

Unusual Formation of Point-Defect Complexes in the Ultrawide-Band-Gap Semiconductor β-Ga2 O3

Understanding the unique properties of ultra-wide band gap semiconductors requires detailed information about the exact nature of point defects and their role in determining the properties. Here, we report the first direct microscopic observation of an unusual formation of point defect complexes within the atomic-scale structure of β-Ga2O3 using high resolution scanning transmission electron microscopy (STEM). Each complex involves one cation interstitial atom paired with two cation vacancies. These divacancy-interstitial complexes correlate directly with structures obtained by density functional theory, which predicts them to be compensating acceptors in β-Ga2O3. This prediction is confirmed by a comparison between STEM data and deep level optical spectroscopy results, which reveals that these complexes correspond to a deep trap within the band gap, and that the development of the complexes is facilitated by Sn doping through increased vacancy concentration. These findings provide new insight on this emerging material's unique response to the incorporation of impurities that can critically influence their properties

Rural Pharmacy not delivering on its health promotion potential

Objective: To investigate the level and perceived quality of health promotion advice received from rural pharmacists.Design: Self-administered written survey on access to and quality of pharmacy services in rural Western Australia completed by rural residents.Setting: Rural Pharmacy.Participants: Four hundred and eighty-three respondents who regularly used a pharmacy.Outcome measures: Items in the survey included frequency of receiving prevention advice and satisfaction ratings on health and pharmacy services.Results: Eighty-eight per cent of respondents had never discussed exercise or diet with their pharmacist and 65% had never discussed preventing health problems. Receiving good prevention advice predicted satisfaction with health services in general but not satisfaction with pharmacy services.Conclusion: Pharmacies are being underutilised with respect to their capacity to deliver heath prevention advice and ways to capitalise on this potential need to be investigated

The Chiral Dipolar Hard Sphere Model

A simple molecular model of chiral molecules is presented in this paper : the chiral dipolar hard sphere model. The discriminatory interaction between enantiomers is represented by electrostatic (or magnetic) dipoles-dipoles interactions : short ranged steric repulsion are represented by hard sphere potential and, in each molecule, two point dipoles are located inside the sphere. The model is described in detail and some of its elementary properties are given ; in particular, it is shown that the that the knowledge of only three multipole spherical components (namely : $Q_{10}$, $Q_{21}$ and $Q_{22}$) allows to compute all multipole spherical components of the model. Despite, the simplicity of the model, it is shown also that the energy landscape of the interaction between two enantiomers is quite rich, this renders systems of chiral dipolar hard sphere very interesting and complicated to study. Few preliminary Monte Carlo simulation results are also reported in the paper. Last, but not least, this paper is dedicated to Jean-Jacques Weis.Comment: 28 pages, 14 Figures, 3 Tables. To appear in Molecular Physic

Religious Participation and DSM IV Major Depressive Disorder Among Black Caribbeans in the United States

This study examines the relationship between religious involvement and 12-month and lifetime DSM-IV major depressive disorder (MDD) within a nationally rep- resentative sample of Black Caribbean adults. MDD was assessed using the DSM-IV World Mental Health Com- posite International Diagnostic Interview (WMH-CIDI). Religious involvement included measures of religious coping, organizational and nonorganizational involvement, and subjective religiosity. Study findings indicate that religious involvement is associated with 12-month and lifetime prevalence of MDD. Multivariate relationships between religious involvement and MDD indicate lower prevalence of 12-month and lifetime MDD among persons who use religious coping and characterize themselves as being religious (for lifetime prevalence only); persons who frequently listen to religious radio programs report higher lifetime MDD. Lower rates of 12-month and lifetime MDD are noted for persons who attend religious services at least once a week (as compared to both higher and lower levels of attendance), indicating a curvilinear relationship. The findings are discussed in relation to previous research on religion and mental health concerns, conceptual models of the role of religion in mental health (e.g., prevention, resource mobilization) that specify multiple and often divergent pathways and mechanisms of religious effects on health outcomes, and the role of religion among Caribbean Blacks.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/107411/1/Religious Participation and DSM IV Major Depressive Disorder Among Black Caribbeans in the United States.pdfDescription of Religious Participation and DSM IV Major Depressive Disorder Among Black Caribbeans in the United States.pdf : Main articl

Development and Validation of the Behavioral Tendencies Questionnaire

At a fundamental level, taxonomy of behavior and behavioral tendencies can be described in terms of approach, avoid, or equivocate (i.e., neither approach nor avoid). While there are numerous theories of personality, temperament, and character, few seem to take advantage of parsimonious taxonomy. The present study sought to implement this taxonomy by creating a questionnaire based on a categorization of behavioral temperaments/tendencies first identified in Buddhist accounts over fifteen hundred years ago. Items were developed using historical and contemporary texts of the behavioral temperaments, described as “Greedy/Faithful”, “Aversive/Discerning”, and “Deluded/Speculative”. To both maintain this categorical typology and benefit from the advantageous properties of forced-choice response format (e.g., reduction of response biases), binary pairwise preferences for items were modeled using Latent Class Analysis (LCA). One sample (n1 = 394) was used to estimate the item parameters, and the second sample (n2 = 504) was used to classify the participants using the established parameters and cross-validate the classification against multiple other measures. The cross-validated measure exhibited good nomothetic span (construct-consistent relationships with related measures) that seemed to corroborate the ideas present in the original Buddhist source documents. The final 13-block questionnaire created from the best performing items (the Behavioral Tendencies Questionnaire or BTQ) is a psychometrically valid questionnaire that is historically consistent, based in behavioral tendencies, and promises practical and clinical utility particularly in settings that teach and study meditation practices such as Mindfulness Based Stress Reduction (MBSR)

Canal wall reconstruction and mastoid obliteration with composite multi-fractured osteoperiosteal flap

We used inferior pedicled composite multi-fractured osteoperiosteal flap (CMOF), our original and new surgical approach, to obliterate the mastoid cavity and reconstruct the external auditory canal (EAC) to prevent the open cavity problems. CMOF was used to obliterate the mastoid cavity and reconstruct the EAC in 24 patients (13 women, 11 men; age span 12–51 years) who underwent radical mastoidectomy to treat the chronic otitis media between 1998 and 2004. Small meatoplasty was done in all 24 patients to relive their aesthetical concerns. Temporal bone CT scanning was done to observe the neo-osteogenesis in the mastoidectomy cavity and the CMOF, and the EAC volume was measured postoperatively. All our patients were followed-up for 2 years. The epithelization of the new EAC in our patients was complete at the end of the second month. Cholesteatoma, granulation, and recurrence of osteitis did not occur in any of the patients. We saw the new bone formation filling the mastoid cavity in the postoperative temporal bone CT scanning images. The mean volume of the new EAC on the 24th month was 1.83 ± 0.56 cm(3). We had an almost natural EAC, which owed its existence to the neo-osteogenesis that grows behind the CMOF, which we use to obliterate the mastoid cavity and to reconstruct the EAC

Exercise twice-a-day potentiates markers of mitochondrial biogenesis in men

Endurance exercise begun with reduced muscle glycogen stores seems to potentiate skeletal muscle protein abundance and gene expression. However, it is unknown whether this greater signaling responses is due to performing two exercise sessions in close proximity-as a first exercise session is necessary to reduce the muscle glycogen stores. In the present study, we manipulated the recovery duration between a first muscle glycogen-depleting exercise and a second exercise session, such that the second exercise session started with reduced muscle glycogen in both approaches but was performed either 2 or 15 hours after the first exercise session (so-called twice-a-day and once-daily approaches, respectively). We found that exercise twice-a-day increased the nuclear abundance of transcription factor EB (TFEB) and nuclear factor of activated T cells (NFAT) and potentiated the transcription of peroxisome proliferator-activated receptor-ɣ coactivator 1-alpha (PGC-1α), peroxisome proliferator-activated receptor-alpha (PPARα), and peroxisome proliferator-activated receptor beta/delta (PPARβ/δ) genes, in comparison with the once-daily exercise. These results suggest that part of the elevated molecular signaling reported with previous train-low approaches might be attributed to performing two exercise sessions in close proximity. The twice-a-day approach might be an effective strategy to induce adaptations related to mitochondrial biogenesis and fat oxidation

Mutations in pericentrin cause Seckel syndrome with defective ATR-dependent DNA damage signaling

Large brain size is one of the defining characteristics of modern humans. Seckel syndrome (MIM 210600), a disorder of markedly reduced brain and body size, is associated with defective ATR-dependent DNA damage signaling. Only a single hypomorphic mutation of ATR has been identified in this genetically heterogeneous condition. We now report that mutations in the gene encoding pericentrin (PCNT)--resulting in the loss of pericentrin from the centrosome, where it has key functions anchoring both structural and regulatory proteins--also cause Seckel syndrome. Furthermore, we find that cells of individuals with Seckel syndrome due to mutations in PCNT (PCNT-Seckel) have defects in ATR-dependent checkpoint signaling, providing the first evidence linking a structural centrosomal protein with DNA damage signaling. These findings also suggest that other known microcephaly genes implicated in either DNA repair responses or centrosomal function may act in common developmental pathways determining human brain and body size