Comparing orthomagmatic and hydrothermal mineralization models for komatiite-hosted nickel deposits in Zimbabwe using multiple-sulfur, iron, and nickel isotope data

Trojan and Shangani mines are low-grade (<0.8 % Ni), komatiite-hosted nickel sulfide deposits associated with ca. 2.7 Ga volcano-sedimentary sequences of the Zimbabwe craton. At both mines, nickel sulfide mineralization is present in strongly deformed serpentinite bodies that are enveloped by a complex network of highly sheared, silicified, and sulfide-bearing metasedimentary rocks. Strong, polyphase structural–metamorphic–metasomatic overprints in both the Trojan and Shangani deposits make it difficult to ascertain if sulfide mineralization was derived from orthomagmatic or hydrothermal processes, or by a combination of both. Multiple S, Fe, and Ni isotope analyses were applied to test these competing models. Massive ores at Shangani Mine show mass-dependent fractionation of sulfur isotopes consistent with a mantle sulfur source, whereas S-isotope systematics of net-textured ore and disseminated ore in talcose serpentinite indicates mixing of magmatic and sedimentary sulfur sources, potentially via post-magmatic hydrothermal processes. A restricted range of strongly mass-independent Δ33S values in ore samples from Trojan Mine likely reflects high-temperature assimilation of sulfur from supracrustal rocks and later superimposed low-temperature hydrothermal remobilization. Iron isotope values for most Ni-bearing sulfides show a narrow range suggesting that, in contrast to sulfur, nearly all of iron was derived from an igneous source. Negative Ni isotope values also agree with derivation of Ni from ultramafic melt and a significant high-temperature fractionation of Ni isotopes. Fe isotope values of some samples from Shangani Mine are more fractionated than expected to occur in high-temperature magmatic systems, further suggesting that hydrothermal processes were involved in either low-grade ore formation (liberation of Ni from olivine by sulfur-bearing hydrothermal fluids) or remobilization of existing sulfides potentially inducing secondary Ni-sulfide mineralization

Prevalence of obstructive sleep apnea in suicidal patients with major depressive disorder.

In this paper, we report the rate of previously undiagnosed obstructive sleep apnea (OSA) in a randomized clinical trial (RCT) of suicidal patients with major depressive disorder (MDD). One hundred and twenty-five suicidal adults with MDD were recruited into a RCT. None were suspected to have OSA. Fourteen percent met diagnostic criteria for OSA. The Apnea Hypopnea Index (AHI) was predicted by increasing age, male sex, and higher Body Mass Index. However, neither the degree of daytime sleepiness nor the degree of insomnia predicted AHI severity. A high degree of suspicion is warranted for OSA in suicidal patients with MDD, and for patients with treatment-resistant depression. ClinicalTrials.gov identifier: NCT01689909

The relationship of person-specific eveningness chronotype, greater seasonality, and less rhythmicity to suicidal behavior: A literature review.

BackgroundEpidemiological data have demonstrated seasonal and circadian patterns of suicidal deaths. Several reviews and meta-analyses have confirmed the relationship between sleep disturbance and suicidality. However, these reviews/meta-analyses have not focused on seasonal and circadian dysfunction in relation to suicidality, despite the common presence of this dysfunction in patients with mood disorders. Thus, the current literature review analyzed studies investigating person-specific chronotype, seasonality, and rhythmicity in relation to suicidal thoughts and behaviors.MethodsStudy authors reviewed articles related to individual-level chronotype, seasonality, and rhythmicity and suicidality that were written in English and not case reports or reviews.ResultsThis review supports a relationship between an eveningness chronotype, greater seasonality, and decreased rhythmicity with suicidal thoughts and behaviors in those with unipolar depression, as well as in other psychiatric disorders and in children/adolescents.LimitationsThese findings need to be explored more fully in mood disordered populations and other psychiatric populations, in both adults and children, with objective measurement such as actigraphy, and with chronotype, seasonality, and rhythmicity as well as broader sleep disturbance measurement all included so the construct(s) most strongly linked to suicidality can be best identified.ConclusionsEveningness, greater seasonality, and less rhythmicity should be considered in individuals who may be at risk for suicidal thoughts and behaviors and may be helpful in further tailoring assessment and treatment to improve patient outcome

Early metal-silicate differentiation during planetesimal formation revealed by acapulcoite and lodranite meteorites

International audienceIn order to establish the role and expression of silicate-metal fractionation in early planetesimal bodies, we have conducted a highly siderophile element (HSE: Os, Ir, Ru, Pt, Pd, Re) abundance and 187Re-187Os study of acapulcoite-lodranite meteorites. These data are reported with new petrography, mineral chemistry, bulk-rock major and trace element geochemistry, and oxygen isotopes for Acapulco, Allan Hills (ALHA) 81187, Meteorite Hills (MET) 01195, Northwest Africa (NWA) 2871, NWA 4833, NWA 4875, NWA 7474 and two examples of transitional acapulcoite-lodranites, Elephant Moraine (EET) 84302 and Graves Nunataks (GRA) 95209. These data support previous studies that indicate that these meteorites are linked to the same parent body and exhibit limited degrees (2 × CI chondrite) HSE abundances in transitional acapulcoite-lodranite meteorites (EET 84302, GRA 95209). All of the meteorites have chondritic Re/Os with measured 187Os/188Os ratios of 0.1271 ± 0.0040 (2 St. Dev.). These geochemical characteristics imply that the precursor material of the acapulcoites and lodranites was broadly chondritic in composition, and were then heated and subject to melting of metal and sulfide in the Fe-Ni-S system. This resulted in metallic melt removal and accumulation to form lodranites and transitional acapulcoite-lodranites. There is considerable variation in the absolute abundances of the HSE, both among samples and between aliquots of the same sample, consistent with both inhomogeneous distribution of HSE-rich metal, and of heterogeneous melting and incomplete mixing of silicate material within the acapulcoite-lodranite parent body. Oxygen isotope data for acapulcoite-lodranites are also consistent with inhomogeneous melting and mixing of accreted components from different nebular sources, and do not form a well-defined mass-dependent fractionation line. Modeling of HSE inter-element fractionation suggests a continuum of melting in the Fe-Ni-S system and partitioning between solid metal and sulfur-bearing mineral melt, where lower S contents in the melt resulted in lower Pt/Os and Pd/Os ratios, as observed in lodranites. The transitional meteorites, EET 84302 and GRA 95209, exhibit the most elevated HSE abundances and do not follow modelled Pt/Os and Pd/Os solid metal-liquid metal partitioning trends. We interpret this to reflect metal melt pooling into domains that were sampled by these meteorites, suggesting that they may originate from deeper within the acapulcoite-lodranite parent body, perhaps close to a pooled metallic 'core' region. Petrographic examination of transitional samples reveals the most extensive melting, pooling and networking of metal among the acapulcoite-lodranite meteorites. Overall, our results show that solid metal-liquid metal partitioning in the Fe-Ni-S system in primitive achondrites follows a predictable sequence of limited partial melting and metal melt pooling that can lead to significant HSE inter-element fractionation effects in proto-planetary materials

Hypnotic Medications and Suicide: Risk, Mechanisms, Mitigation, and the FDA

OBJECTIVE: Insomnia is associated with increased risk for suicide. The Food and Drug Administration (FDA) has warnings regarding suicide in the prescribing information of hypnotics. We conducted a review of the evidence for and against hypnotics increasing the risk of suicide. METHOD: This review focused on modern, FDA-approved hypnotics, beginning with the introduction of benzodiazepines, limiting its findings to adults. PubMed and Web of Science were searched, crossing the terms ‘suicide’ and ‘suicidal’ with each of the modern FDA-approved hypnotics. The FDA website was searched for post-marketing safety reviews, and the FDA was contacted to provide detailed case reports for hypnotic-related suicide deaths reported through its Adverse Event Report system. RESULTS: The epidemiological studies show that hypnotics are associated with increased risk for suicide. However, none of these studies adequately controlled for depression or other psychiatric disorders that may be linked with insomnia. Suicide deaths have been reported from single-agent hypnotic overdoses. A separate concern is that benzodiazepine receptor agonist hypnotics can cause parasomnias, which in rare cases may lead to suicidal ideation or suicidal behavior in persons who were not known to be previously suicidal. On the other hand, ongoing research is testing whether treatment of insomnia might reduce suicidality in depressed adults. CONCLUSIONS: This review indicates hypnotic medications are associated with suicidal ideation. Future studies should be designed to assess both types of possible effects: 1) an increase in suicidality due to central nervous system impairments from a given hypnotic medication; and 2) a decrease in suicidality due to improving insomnia

Reducing Suicidal Ideation Through Insomnia Treatment (REST-IT): A Randomized Clinical Trial.

ObjectiveThe authors sought to determine whether targeted treatment of insomnia with controlled-release zolpidem (zolpidem-CR) in suicidal adults with insomnia would provide a reduction in suicidal ideation superior to placebo.MethodsReducing Suicidal Ideation Through Insomnia Treatment was an 8-week three-site double-blind placebo-controlled parallel-group randomized controlled trial of zolpidem-CR hypnotic therapy compared with placebo, in conjunction with an open-label selective serotonin reuptake inhibitor. Participants were medication-free 18- to 65-year-olds with major depressive disorder, insomnia, and suicidal ideation. Suicidal ideation was the main outcome, measured first by the Scale for Suicide Ideation and second by the Columbia-Suicide Severity Rating Scale (C-SSRS).ResultsA total of 103 participants were randomly assigned to receive zolpidem-CR (N=51) or placebo (N=52) (64 women and 39 men; mean age=40.5 years). Zolpidem-CR had a robust anti-insomnia effect, especially in patients with the most severe insomnia symptoms. No significant treatment effect was observed on the Scale for Suicide Ideation (least squares mean estimate=-0.56, SE=0.83, 95% CI=-2.19, 1.08), but the reduction in scores was significantly positively related to improvement in insomnia after accounting for the effect of other depression symptoms. The C-SSRS indicated that zolpidem-CR had a significant treatment effect (least squares mean estimate=-0.26, SE=0.12, 95% CI=-0.50, -0.02). The advantage for zolpidem-CR in reducing suicidal ideation on the C-SSRS was greater in patients with more severe insomnia. No deaths or suicide attempts occurred.ConclusionsAlthough the results do not support the routine prescription of hypnotic medication for mitigating suicidal ideation in all depressed outpatients with insomnia, they suggest that coprescription of a hypnotic during initiation of an antidepressant may be beneficial in suicidal outpatients, especially in patients with severe insomnia

A multi-site randomized clinical trial to reduce suicidal ideation in suicidal adult outpatients with Major Depressive Disorder: Development of a methodology to enhance safety.

Background/aimsSuicide is a major public health concern, yet there are very few randomized clinical trials that have been conducted to reduce suicidal ideation in patients at risk of suicide. We describe the rationale and refinements of such a trial that is designed to assess the effect of a hypnotic medication on suicidal ideation in adult outpatients currently experiencing suicidal ideation.Methods"Reducing Suicidal Ideation Through Insomnia Treatment" is a multi-site randomized clinical trial that includes three recruiting sites and one data management site. This 4-year study is in its second year of recruitment. The purpose of the study is to compare hypnotic medication versus placebo as an add-on treatment to a selective serotonin reuptake inhibitor as a means of reducing suicidal ideation in depressed adult outpatients with insomnia and suicidal ideation. The safety features of the study follow the 2001 National Institutes of Health guidelines for studies that include patients at risk of suicide.ResultsIn total, 584 potential participants have undergone telephone screening; 67% of these failed the phone screen, most often due to an absence of expressed suicidal ideation (26% of the telephone screen fails). A total of 115 people appeared for a face-to-face baseline assessment, and 40 of these had completed a taper off of their ineffective psychotropic medications before the baseline assessments. In all, 64% of those who completed baseline assessments failed to proceed to randomization, most commonly because of no clinically significant suicidal ideation (51% of those excluded at baseline). One participant was offered and accepted voluntary psychiatric hospitalization in lieu of study participation. Thus far, 40 participants have been randomized into the study and 88.7% of scheduled visits have been attended, with 93.8% adherence to the selective serotonin reuptake inhibitor and 91.6% adherence to the randomized hypnotic versus placebo. None of the randomized participants have required hospitalization or had a suicide attempt.ConclusionBy carefully considering the inclusion and exclusion criteria and other safety features, the safe conduct of randomized clinical trials in suicidal adult patients is possible, including the inclusion of participants who have undergone a prescribed tapering off of psychotropic medications prior to baseline assessment

A multi-site randomized clinical trial to reduce suicidal ideation in suicidal adult outpatients with Major Depressive Disorder: Development of a methodology to enhance safety

BACKGROUND/AIMS: Suicide is a major public health concern, yet there are very few randomized clinical trials that have been conducted to reduce suicidal ideation in patients at risk for suicide. We describe the rationale and refinements of such a trial that is designed to assess the effect of a hypnotic medication on suicidal ideation in adult outpatients currently experiencing suicidal ideation. METHODS: “Reducing Suicidal Ideation Through Insomnia Treatment (REST-IT)” is a multi-site randomized clinical trial that includes 3 recruiting sites and one data management site. This 4-year study is in its second year of recruitment. The purpose of the study is to compare hypnotic medication versus placebo as an add-on treatment to a selective serotonin reuptake inhibitor as a means of reducing suicidal ideation in depressed adult outpatients with insomnia and suicidal ideation. The safety features of the study follow the 2001 NIH guidelines for studies that include patients at risk of suicide. RESULTS: Five hundred and eighty-four potential participants have undergone telephone screening; 67% of these failed the phone screen, most often due to an absence of expressed suicidal ideation (26% of the telephone screen fails). One hundred and twelve persons appeared for a face-to-face baseline assessment, and 40 of these had completed a taper of their ineffective psychotropic medications before the baseline assessments. Sixty-four% of those who completed baseline assessments failed to proceed to randomization, most commonly because of no clinically significant suicidal ideation (51% of those excluded at baseline). One participant was offered and accepted voluntary psychiatric hospitalization in lieu of study participation. Thus far, 40 participants have been randomized into the study, 88.7% of scheduled visits have been attended, with 93.8% adherence for the SSRI and 91.6% adherence for the randomized hypnotic versus placebo. None of the randomized participants have required hospitalization or had a suicide attempt. CONCLUSIONS: By carefully considering the inclusion and exclusion criteria and other safety features, the safe conduct of randomized clinical trials in suicidal adult patients is possible, including the inclusion of participants who have undergone a prescribed tapering of psychotropic medications prior to baseline assessment

The JCMT Gould Belt Survey : evidence for radiative heating in Serpens MWC 297 and its influence on local star formation

We present SCUBA-2 450 and 850 μm observations of the Serpens MWC 297 region, part of the James Clerk Maxwell Telescope (JCMT) Gould Belt Survey of nearby star-forming regions. Simulations suggest that radiative feedback influences the star formation process and we investigate observational evidence for this by constructing temperature maps. Maps are derived from the ratio of SCUBA-2 fluxes and a two-component model of the JCMT beam for a fixed dust opacity spectral index of β = 1.8.Within 40 arcsec of the B1.5Ve Herbig star MWC 297, the submillimetre fluxes are contaminated by free–free emission with a spectral index of 1.03 ± 0.02, consistent with an ultracompact HII region and polar winds/jets. Contamination accounts for 73 ± 5 per cent and 82 ± 4 per cent of peak flux at 450 μm and 850 μm, respectively. The residual thermal disc of the star is almost undetectable at these wavelengths. Young stellar objects (YSOs) are confirmed where SCUBA-2 850 μm clumps identified by the FELLWALKER algorithm coincide with Spitzer Gould Belt Survey detections. We identify 23 objects and use Tbol to classify nine YSOs with masses 0.09 to 5.1M_. We find two Class 0, one Class 0/I, three Class I and three Class II sources. The mean temperature is 15 ± 2 K for the nine YSOs and 32 ± 4 K for the 14 starless clumps. We observe a starless clump with an abnormally high mean temperature of 46 ± 2 K and conclude that it is radiatively heated by the star MWC 297. Jeans stability provides evidence that radiative heating by the star MWC 297 may be suppressing clump collapse