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Functional impairment in daily activities, such as work and socializing, is part of the diagnostic criteria for major depressive disorder and most anxiety disorders. Despite evidence that symptom severity and functional impairment are partially distinct, functional impairment is often overlooked. To assess whether functional impairment captures diagnostically relevant genetic liability beyond that of symptoms, we aimed to estimate the heritability of, and genetic correlations between, key measures of current depression symptoms, anxiety symptoms, and functional impairment.
Methods
In 17,130 individuals with lifetime depression or anxiety from the Genetic Links to Anxiety and Depression (GLAD) Study, we analyzed total scores from the Patient Health Questionnaire-9 (depression symptoms), Generalized Anxiety Disorder-7 (anxiety symptoms), and Work and Social Adjustment Scale (functional impairment). Genome-wide association analyses were performed with REGENIE. Heritability was estimated using GCTA-GREML and genetic correlations with bivariate-GREML.
Results
The phenotypic correlations were moderate across the three measures (Pearson’s r = 0.50–0.69). All three scales were found to be under low but significant genetic influence (single-nucleotide polymorphism-based heritability [h2SNP] = 0.11–0.19) with high genetic correlations between them (rg = 0.79–0.87).
Conclusions
Among individuals with lifetime depression or anxiety from the GLAD Study, the genetic variants that underlie symptom severity largely overlap with those influencing functional impairment. This suggests that self-reported functional impairment, while clinically relevant for diagnosis and treatment outcomes, does not reflect substantial additional genetic liability beyond that captured by symptom-based measures of depression or anxiety.
Accurate diagnosis of bipolar disorder (BPD) is difficult in clinical practice, with an average delay between symptom onset and diagnosis of about 7 years. A depressive episode often precedes the first manic episode, making it difficult to distinguish BPD from unipolar major depressive disorder (MDD).
Aims
We use genome-wide association analyses (GWAS) to identify differential genetic factors and to develop predictors based on polygenic risk scores (PRS) that may aid early differential diagnosis.
Method
Based on individual genotypes from case–control cohorts of BPD and MDD shared through the Psychiatric Genomics Consortium, we compile case–case–control cohorts, applying a careful quality control procedure. In a resulting cohort of 51 149 individuals (15 532 BPD patients, 12 920 MDD patients and 22 697 controls), we perform a variety of GWAS and PRS analyses.
Results
Although our GWAS is not well powered to identify genome-wide significant loci, we find significant chip heritability and demonstrate the ability of the resulting PRS to distinguish BPD from MDD, including BPD cases with depressive onset (BPD-D). We replicate our PRS findings in an independent Danish cohort (iPSYCH 2015, N = 25 966). We observe strong genetic correlation between our case–case GWAS and that of case–control BPD.
Conclusions
We find that MDD and BPD, including BPD-D are genetically distinct. Our findings support that controls, MDD and BPD patients primarily lie on a continuum of genetic risk. Future studies with larger and richer samples will likely yield a better understanding of these findings and enable the development of better genetic predictors distinguishing BPD and, importantly, BPD-D from MDD.
The identification of predictors of treatment response is crucial for improving treatment outcome for children with anxiety disorders. Machine learning methods provide opportunities to identify combinations of factors that contribute to risk prediction models.
Methods
A machine learning approach was applied to predict anxiety disorder remission in a large sample of 2114 anxious youth (5–18 years). Potential predictors included demographic, clinical, parental, and treatment variables with data obtained pre-treatment, post-treatment, and at least one follow-up.
Results
All machine learning models performed similarly for remission outcomes, with AUC between 0.67 and 0.69. There was significant alignment between the factors that contributed to the models predicting two target outcomes: remission of all anxiety disorders and the primary anxiety disorder. Children who were older, had multiple anxiety disorders, comorbid depression, comorbid externalising disorders, received group treatment and therapy delivered by a more experienced therapist, and who had a parent with higher anxiety and depression symptoms, were more likely than other children to still meet criteria for anxiety disorders at the completion of therapy. In both models, the absence of a social anxiety disorder and being treated by a therapist with less experience contributed to the model predicting a higher likelihood of remission.
Conclusions
These findings underscore the utility of prediction models that may indicate which children are more likely to remit or are more at risk of non-remission following CBT for childhood anxiety.
Background: Currently there are no disease modifying treatment for Synucleinopathies including Parkinson’s disease Dementia (PDD). Carrying a mutation in the GBA gene (beta-glucocerebrosidase/ GCAse) is a leading risk factor for synucleinopathies. Raising activity GCAse lowers α-synuclein levels in cells and animal models. Ambroxol is a pharmacological chaperone for GCAse and can raise GCAse levels. Our goal is to test Ambroxol as a disease-modifying treatment in PDD. Methods: We randomized fifty-five individuals with PDD to Ambroxol 1050mg/day, 525mg/day, or placebo for 52 weeks. Primary outcome measures included safety, Alzheimer’s disease Assessment Scale-cognitive (ADAS-Cog) subscale and the Clinician’s Global Impression of Change (CGIC). Secondary outcomes included pharmacokinetics, cognitive and motor outcomes and and plasma and CSF biomarkers. Results: Ambroxol was well tolerated. There were 7 serious adverse events (SAEs) none deemed related to Ambroxol. GCase activity was increased in white blood cells by ~1.5 fold. There were no differences between groups on primary outcome measures. Patients receiving high dose Ambroxol appeared better on the Neuropsychiatric Inventory. GBA carriers appeared to improve on some cognitive tests. pTau 181 was reduced in CSF. Conclusions: Ambroxol was safe and well-tolerated in PDD. Ambroxol may improve biomarkers and cognitive outcomes in GBA1 mutation carrie.rs Ambroxol improved some biomarkerss. ClinicalTrials.gov NCT02914366
Laser-driven X-rays as probes for high-energy-density physics spans an extremely large parameter space with laser intensities varying by 8 orders of magnitude. We have built and characterized a soft X-ray source driven by a modest intensity laser of 4 × 1013 W/cm2. Emitted X-rays were measured by diamond radiation detectors and a filtered soft X-ray camera. A material-dependence study on Al, Ti, stainless steel alloy 304, Fe, Cu and Sn targets indicated 5-μm-thick Cu foils produced the highest X-ray yield. X-ray emission in the laser direction and emission in the reverse direction depend strongly on the foil material and the thickness due to the opacity and hydrodynamic disassembly time. The time-varying X-ray signals are used to measure the material thinning rate and is found to be ∼1.5 μm/ns for the materials tested implying thermal temperature around 0.6 eV. The X-ray spectra from Cu targets peaks at ∼2 keV with no emission >4 keV and was estimated using images with eight different foil filters. One-dimensional hydrodynamic and spectral calculations using HELIOS-CR provide qualitative agreement with experimental results. Modest intensity lasers can be an excellent source for nanosecond bursts of soft X-rays.
Hydroxy-interlayered vermiculite (HIV) is a ubiquitous phyllosilicate in the <0.05-mm fraction of sandy soils on the U.S. southeastern coastal plain. Extensive areas of soils with abundant HIV (i.e., peninsular Florida) have no detectable mica; yet the coarseness, platy habit, and nonexchangeable K associated with HIV grains suggest a mica precursor. The objectives of this study were: (1) to probe for mica zones (1.0-nm) within HIV grains, using high-resolution transmission electron microscopy (HRTEM), and (2) to determine intragrain elemental distributions via electron microprobe analysis (EMA). HIV grains from a Quartzipsamment medium-silt fraction, which contained no detectable mica by X-ray diffraction (XRD), were concentrated via high-density liquid separation. EMA transects and X-ray dot maps showed zonation or trends of K depletion near edges of some grains, with K2O contents ranging from trace levels to >40 g kg-1. Elemental oxide data indicated a dioctahedral phyllosilicate structure, with some octahedral substitution of Fe and Mg for Al. Intermittent 1.0-nm lattice-fringe images obtained by HRTEM supported the presence of mica zones within grains. There were no detectable 1.4-nm fringes, despite the dominance of a 1.4-nm XRD peak, indicating the instability of the HIV specimen under the electron beam. Results support a transformational link between mica and HIV in these soils. Rapid incursion and polymerization of Al following loss of K from mica may limit the extent of the vermiculite intermediate. The latter idea is consistent with the paucity of vermiculite in Florida soils. Traces of occluded mica may be the last remnants of the precursor grain. A sand-sized mica precursor would likely have weathered in place during the period when colloidal components such as kaolinite illuviated to deeper zones. Thus, the transformation product (HIV) would comprise a significant proportion of the <0.05-mm fraction persisting in sandy eluvial horizons.
White matter hyperintensity (WMH) burden is greater, has a frontal-temporal distribution, and is associated with proxies of exposure to repetitive head impacts (RHI) in former American football players. These findings suggest that in the context of RHI, WMH might have unique etiologies that extend beyond those of vascular risk factors and normal aging processes. The objective of this study was to evaluate the correlates of WMH in former elite American football players. We examined markers of amyloid, tau, neurodegeneration, inflammation, axonal injury, and vascular health and their relationships to WMH. A group of age-matched asymptomatic men without a history of RHI was included to determine the specificity of the relationships observed in the former football players.
Participants and Methods:
240 male participants aged 45-74 (60 unexposed asymptomatic men, 60 male former college football players, 120 male former professional football players) underwent semi-structured clinical interviews, magnetic resonance imaging (structural T1, T2 FLAIR, and diffusion tensor imaging), and lumbar puncture to collect cerebrospinal fluid (CSF) biomarkers as part of the DIAGNOSE CTE Research Project. Total WMH lesion volumes (TLV) were estimated using the Lesion Prediction Algorithm from the Lesion Segmentation Toolbox. Structural equation modeling, using Full-Information Maximum Likelihood (FIML) to account for missing values, examined the associations between log-TLV and the following variables: total cortical thickness, whole-brain average fractional anisotropy (FA), CSF amyloid ß42, CSF p-tau181, CSF sTREM2 (a marker of microglial activation), CSF neurofilament light (NfL), and the modified Framingham stroke risk profile (rFSRP). Covariates included age, race, education, APOE z4 carrier status, and evaluation site. Bootstrapped 95% confidence intervals assessed statistical significance. Models were performed separately for football players (college and professional players pooled; n=180) and the unexposed men (n=60). Due to differences in sample size, estimates were compared and were considered different if the percent change in the estimates exceeded 10%.
Results:
In the former football players (mean age=57.2, 34% Black, 29% APOE e4 carrier), reduced cortical thickness (B=-0.25, 95% CI [0.45, -0.08]), lower average FA (B=-0.27, 95% CI [-0.41, -.12]), higher p-tau181 (B=0.17, 95% CI [0.02, 0.43]), and higher rFSRP score (B=0.27, 95% CI [0.08, 0.42]) were associated with greater log-TLV. Compared to the unexposed men, substantial differences in estimates were observed for rFSRP (Bcontrol=0.02, Bfootball=0.27, 994% difference), average FA (Bcontrol=-0.03, Bfootball=-0.27, 802% difference), and p-tau181 (Bcontrol=-0.31, Bfootball=0.17, -155% difference). In the former football players, rFSRP showed a stronger positive association and average FA showed a stronger negative association with WMH compared to unexposed men. The effect of WMH on cortical thickness was similar between the two groups (Bcontrol=-0.27, Bfootball=-0.25, 7% difference).
Conclusions:
These results suggest that the risk factor and biological correlates of WMH differ between former American football players and asymptomatic individuals unexposed to RHI. In addition to vascular risk factors, white matter integrity on DTI showed a stronger relationship with WMH burden in the former football players. FLAIR WMH serves as a promising measure to further investigate the late multifactorial pathologies of RHI.
People with bipolar disorder (BPD) are more likely to die prematurely, which is partly attributed to comorbid cardiometabolic traits. Previous studies report cardiometabolic abnormalities in BPD, but their shared aetiology remains poorly understood. This study examined the phenotypic associations and shared genetic aetiology between BPD and various cardiometabolic traits.
Methods
In a subset of the UK Biobank sample (N = 61 508) we investigated phenotypic associations between BPD (ncases = 4186) and cardiometabolic traits, represented by biomarkers, anthropometric traits and cardiometabolic diseases. To determine shared genetic aetiology in European ancestry, polygenic risk scores (PRS) and genetic correlations were calculated between BPD and cardiometabolic traits.
Results
Several traits were significantly associated with increased risk for BPD, namely low total cholesterol, low high-density lipoprotein cholesterol, high triglycerides, high glycated haemoglobin, low systolic blood pressure, high body mass index, high waist-to-hip ratio; and stroke, coronary artery disease and type 2 diabetes diagnosis. BPD was associated with higher polygenic risk for triglycerides, waist-to-hip ratio, coronary artery disease and type 2 diabetes. Shared genetic aetiology persisted for coronary artery disease, when correcting PRS associations for cardiometabolic base phenotypes. Associations were not replicated using genetic correlations.
Conclusions
This large study identified increased phenotypic cardiometabolic abnormalities in BPD participants. It is found that the comorbidity of coronary artery disease may be based on shared genetic aetiology. These results motivate hypothesis-driven research to consider individual cardiometabolic traits rather than a composite metabolic syndrome when attempting to disentangle driving mechanisms of cardiometabolic abnormalities in BPD.
To assess the relationship between food insecurity, sleep quality, and days with mental and physical health issues among college students.
Design:
An online survey was administered. Food insecurity was assessed using the ten-item Adult Food Security Survey Module. Sleep was measured using the nineteen-item Pittsburgh Sleep Quality Index (PSQI). Mental health and physical health were measured using three items from the Healthy Days Core Module. Multivariate logistic regression was conducted to assess the relationship between food insecurity, sleep quality, and days with poor mental and physical health.
Setting:
Twenty-two higher education institutions.
Participants:
College students (n 17 686) enrolled at one of twenty-two participating universities.
Results:
Compared with food-secure students, those classified as food insecure (43·4 %) had higher PSQI scores indicating poorer sleep quality (P < 0·0001) and reported more days with poor mental (P < 0·0001) and physical (P < 0·0001) health as well as days when mental and physical health prevented them from completing daily activities (P < 0·0001). Food-insecure students had higher adjusted odds of having poor sleep quality (adjusted OR (AOR): 1·13; 95 % CI 1·12, 1·14), days with poor physical health (AOR: 1·01; 95 % CI 1·01, 1·02), days with poor mental health (AOR: 1·03; 95 % CI 1·02, 1·03) and days when poor mental or physical health prevented them from completing daily activities (AOR: 1·03; 95 % CI 1·02, 1·04).
Conclusions:
College students report high food insecurity which is associated with poor mental and physical health, and sleep quality. Multi-level policy changes and campus wellness programmes are needed to prevent food insecurity and improve student health-related outcomes.
We live in a networked world. Online social networking platforms and the World Wide Web have changed how society thinks about connectivity. Because of the technological nature of such networks, their study has predominantly taken place within the domains of computer science and related scientific fields. But arts and humanities scholars are increasingly using the same kinds of visual and quantitative analysis to shed light on aspects of culture and society hitherto concealed. This Element contends that networks are a category of study that cuts across traditional academic barriers, uniting diverse disciplines through a shared understanding of complexity in our world. Moreover, we are at a moment in time when it is crucial that arts and humanities scholars join the critique of how large-scale network data and advanced network analysis are being harnessed for the purposes of power, surveillance, and commercial gain. This title is also available as Open Access on Cambridge Core.
Evidence is limited on how to synthesize and incorporate the views of stakeholders into a multisite pragmatic trial and how much academic teams change study design and protocol in response to stakeholder input. This qualitative study describes how stakeholders contributed to the design, conduct, and dissemination of findings of a multisite pragmatic clinical trial, the COMprehensive Post-Acute Stroke Services (COMPASS) Study. We engaged stakeholders as integral research partners by embedding them in study committees and community resource networks that supported local sites. Data stemmed from formal focus groups and continuous participation in working groups. Guided by Grounded Theory, we extracted themes from focus group and meeting notes. These were discussed as a team and with other stakeholder groups for feasibility. A consensus approach was used. Stakeholder input changed many aspects of the study including: the care model that treated stroke as a chronic condition after hospital discharge, training for hospital-based providers who often lacked awareness of the barriers to recovery that patients face, support for caregivers who were essential for stroke patients’ recovery, and for community-based health and social service providers whose services can support recovery yet often go underutilized. Stakeholders brought value to both pragmatic research and health service delivery. Future studies should test the impact of elements of study implementation informed by stakeholders vs those that are not.
22q11.2 deletion syndrome (22q11DS) associates with schizophrenia spectrum disorders (SSDs), autism spectrum disorders (ASDs), and other psychiatric disorders, but co-occurrence of diagnoses are not well described.
Methods
We evaluated the co-occurrence of SSDs, ASDs and other axis I psychiatric diagnoses in 31 adolescents and adults with 22q11DS, assessing ASDs using either stringent Collaborative Program for Excellence in Autism (ASD-CPEA) criteria, or less stringent DSM-IV criteria alone (ASD-DSM-IV).
Results
Ten (32%) individuals met criteria for an SSD, five (16%) for ASD-CPEA, and five others (16%) for ASD-DSM-IV. Of those with ASD-CPEA, one (20%) met SSD criteria. Of those with ASD-DSM-IV, four (80%) met SSD criteria. Depressive disorders (8 individuals; 26%) and anxiety disorders (7; 23%) sometimes co-occurred with SSDs and ASDs. SSDs, ASDs, and anxiety occurred predominantly among males and depression predominantly among females.
Conclusions
Individuals with 22q11DS can manifest SSDs in the presence or absence of ASDs and other axis I diagnoses. The results suggest that standard clinical care should include childhood screening for ASDs, and later periodic screening for all axis I diagnoses.
Stop the Bleed (STB) is a national initiative that provides lifesaving hemorrhagic control education. In 2019, pharmacists were added as health-care personnel eligible to become STB instructors. This study was conducted to evaluate the efficacy of pharmacist-led STB trainings for school employees in South Texas.
Methods:
Pharmacist-led STB trainings were provided to teachers and staff in Laredo, Texas. The 60-min trainings included a presentation followed by hands-on practice of tourniquet application, wound-packing, and direct pressure application. Training efficacy was assessed through anonymous pre- and postevent surveys, which evaluated changes in knowledge, comfort level, and willingness to assist in hemorrhage control interventions. Student volunteers (predominantly pharmacy and medical students) assisted in leading the hands-on portion, providing a unique interprofessional learning opportunity.
Results:
Participants with previous training (N = 98) were excluded, resulting in a final cohort of 437 (response rate 87.4%). Compared with baseline, comfort level using tourniquets (mean, 3.17/5 vs 4.20/5; P < 0.0001), opinion regarding tourniquet safety (2.59/3 vs 2.94/3; P < 0.0001), and knowledge regarding tourniquets (70.86/100 vs 75.84/100; P < 0.0001) and proper tourniquet placement (2.40/4 vs 3.15/4; P < 0.0001) significantly improved.
Conclusions:
Pharmacist-led STB trainings are efficacious in increasing school worker knowledge and willingness to respond in an emergency hemorrhagic situation.
Lieder and Griffiths rightly urge that computational cognitive models be constrained by resource usage, but they should go further. The brain's primary function is to regulate resource usage. As a consequence, resource usage should not simply select among algorithmic models of “aspects of cognition.” Rather, “aspects of cognition” should be understood as existing in the service of resource management.
Between 2010 and 2019 the international health care organization Partners In Health (PIH) and its sister organization Zanmi Lasante (ZL) mounted a long-term response to the 2010 Haiti earthquake, focused on mental health. Over that time, implementing a Theory of Change developed in 2012, the organization successfully developed a comprehensive, sustained community mental health system in Haiti's Central Plateau and Artibonite departments, directly serving a catchment area of 1.5 million people through multiple diagnosis-specific care pathways. The resulting ZL mental health system delivered 28 184 patient visits and served 6305 discrete patients at ZL facilities between January 2016 and September 2019. The experience of developing a system of mental health services in Haiti that currently provides ongoing care to thousands of people serves as a case study in major challenges involved in global mental health delivery. The essential components of the effort to develop and sustain this community mental health system are summarized.
The rocky shores of the north-east Atlantic have been long studied. Our focus is from Gibraltar to Norway plus the Azores and Iceland. Phylogeographic processes shape biogeographic patterns of biodiversity. Long-term and broadscale studies have shown the responses of biota to past climate fluctuations and more recent anthropogenic climate change. Inter- and intra-specific species interactions along sharp local environmental gradients shape distributions and community structure and hence ecosystem functioning. Shifts in domination by fucoids in shelter to barnacles/mussels in exposure are mediated by grazing by patellid limpets. Further south fucoids become increasingly rare, with species disappearing or restricted to estuarine refuges, caused by greater desiccation and grazing pressure. Mesoscale processes influence bottom-up nutrient forcing and larval supply, hence affecting species abundance and distribution, and can be proximate factors setting range edges (e.g., the English Channel, the Iberian Peninsula). Impacts of invasive non-native species are reviewed. Knowledge gaps such as the work on rockpools and host–parasite dynamics are also outlined.
There is community concern about the treatment of farm animals post-farm gate, particularly animal transport and slaughter. Relationships between lamb behavioural and physiological variables on farm, stockperson, dog and lamb behavioural variables pre-slaughter and plasma cortisol, glucose and lactate in lambs post-slaughter were studied in 400 lambs. The lambs were observed in three behavioural tests, novel arena, flight distance to a human and temperament tests, before transport for slaughter. Closed-circuit television video footage was used to record stockperson, dog and lamb behaviour immediately before slaughter. Blood samples for cortisol, glucose and lactate analyses were collected on farm following the three behavioural tests and immediately post-slaughter. The regression models that best predicted plasma cortisol, glucose and lactate concentrations post-slaughter included a mixture of stockperson and dog behavioural variables as well as lamb variables both on-farm and pre-slaughter. These regression models accounted for 33%, 34% and 44% of the variance in plasma cortisol, glucose and lactate concentrations post-slaughter, respectively. Some of the stockperson and dog behaviours pre-slaughter that were predictive of the stress and metabolic variables post-slaughter included the duration of negative stockperson behaviours such as fast locomotion and lifting/pulling lambs, and the duration of dog behaviours such as lunging and barking at the lamb, while some of the predictive lamb behaviour variables included the durations of jumping and fleeing. Some of the physiological and behavioural responses to the behavioural tests on farm were also predictive of the stress and metabolic variables post-slaughter. These relationships support the well-demonstrated effect of handling on fear and stress responses in livestock, and although not direct evidence of causal relationships, highlight the potential benefits of training stockpeople to reduce fear and stress in sheep at abattoirs.
The soluble metal sulphate salts melanterite, rozenite, rhomboclase, szomolnokite, copiapite, coquimbite, hexahydrite and halotrichite, together with gypsum, have been identified, some for the first time, on the banks of the Rio Tinto, SW Spain. Secondary Fe-sulphate minerals can form directly from evaporating, acid, sulphate-rich solutions as a result of pyrite oxidation. Chemical analyses of mixtures of these salt minerals indicate concentrations of Fe (up to 31 wt.%), Mg (up to 4 wt.%), Cu (up to 2 wt.%) and Zn (up to 1 wt.%). These minerals are shown to act as transient storage for metals and can store on average up to 10% (9.5 — 11%) and 22% (20—23%), Zn and Cu respectively, of the total discharge of the Rio Tinto during the summer period.
Melanterite and rozenite precipitates at Rio Tinto are only found in association with very acidic drainage waters (pH <1.0) draining directly from pyritic waste piles. Copiapite precipitates abundantly on the banks of the Rio Tinto by (1) direct evaporation of the river water; or (2) as part of a paragenetic sequence with the inclusion of minor halotrichite, indicating natural dehydration and decomposition. The natural occurrences are comparable with the process of paragenesis from the evaporation of Rio Tinto river water under laboratory experiments resulting in the formation of aluminocopiapite, halotrichite, coquimbite, voltaite and gypsum.
Toxic trace elements present an environmental hazard in the vicinity of mining and smelting activities. However, the processes of transfer of these elements to groundwater and to plants are not always clear. Tharsis mine, in the Iberian pyrite belt (SW Spain), has been exploited since 2500 BC, with extensive smelting taking place from the 1850s until the 1920s. Sixty four soil (mainly topsoils) and vegetation samples were collected in February 2001 and analysed by ICP-AES for 23 elements. Concentrations are 6—6300 mg kg-1 As and 14—24800 mg kg-1 Pb in soils, and 0.20—9 mg kg-1 As and 2—195 mg kg-1 Pb in vegetation. Trace element concentrations decrease rapidly away from the mine, with As and Pb concentrations in the range 6—1850 mg kg—1 (median 22 mg kg—1) and 14—31 mg kg—1 (median 43 mg kg—1), respectively, 1 km away from the mine. These concentrations are low when compared to other well-studied mining and smelting areas (e.g. 600 mg kg—1 As at 8 km from Yellowknife smelter, Canada; >100 mg kg—1 Pb over 270 km2 around the Pb-Zn Port Pirie smelter, South Australia; mean of 1419 mg kg—1 Pb around Aberystwyth smelter, Wales, UK). The high metal content of the vegetation and the low soil pH (mean pH 4.93) indicate the potential for trace element mobility which could explain the relatively low concentration of metals in Tharsis topsoils and cause threats to plans to redevelop the Tharsis area as an orange plantation.
We present results of evolutionary simulations based on density functional calculations of a potentially new type of energetic materials called extended solids: P-N and N-H. High-density structures with covalent bonds generated using variable and fixed concentration methods were analysed in terms of thermo-dynamical stability and agreement with experimental X-ray diffraction (XRD) spectra. X-ray diffraction spectra were calculated using a virtual diffraction algorithm that computes kinematic diffraction intensity in three-dimensional reciprocal space before being reduced to a two-theta line profile. Calculated XRD patterns were used to search for the structure of extended solids present at experimental pressures by optimizing data according to experimental XRD peak position, peak intensity and theoretically calculated enthalpy. Elastic constants has been calculated for thermodynamically stable structures of P-N system.