Controls on lithium concentration and diffusion in zircon

This study was supported by ETH Research Grants ETH-34 15-2 (JS), ETH-14 16-1 (FM) and by Swiss National Science Foundation research grant 200020-153112/1 (NK).Thermal annealing of zircons prior to uranium-lead dating by laser ablation inductively coupled plasma mass spectrometry is a commonly-implemented procedure which improves data accuracy and precision by partially repairing radiation damage from the decay of uranium and thorium. However, it also leads to significantly higher concentrations of lithium in the zircon lattice, which become positively correlated with trivalent yttrium and rare earth elements. Prior to such treatments, zircons typically contain lithium below detection limits (typically <0.55 μg g−1), unless correlated with lanthanum and aluminum (i.e., melt/mineral inclusion tracer elements). This suggests that lithium in zircon is primarily sequestered within inclusions, and is able to permeate the crystal lattice to couple with yttrium and rare earth elements during the thermal annealing procedure. This process occurs 2–3 orders of magnitude faster than diffusion experiments have previously determined, indicating that another diffusion mechanism may apply. A model is proposed, whereby: (i) charge compensation of stoichiometrically over-abundant trivalent cations under water-rich magmatic conditions is likely accomplished by hydrogen, given the incompatibility of lithium in zircon and the abundance of hydrogen. However, (ii) conditions that are high temperature and low pressure (characteristic of both thermal annealing and the syn-eruptive environment), drive silicate melt inclusions to exsolve water, generating a motive force for both hydrogen and lithium from inclusions to permeate the lattice in order to reestablish electrochemical equilibrium between the interior and exterior of the zircon. To test the pressure dependency of lithium migration in the zircon lattice, thermal annealing experiments were performed at 850 °C and 1 bar, 2 kbar and 6 kbar using zircons from the Fish Canyon Tuff. The experiments demonstrate that thermal annealing at 2 and 6 kbar inhibits lithium mobility, with zircons registering lithium concentrations below detection limits similar to controls. The experimental results suggest that lithium concentrations in zircon are vulnerable to rapid perturbation by decompression (concurrent with high temperatures), which further indicate that lithium-in-zircon diffusion data should be interpreted with caution.Publisher PDFPeer reviewe

Eruption of Shallow Crystal Cumulates during Explosive Phonolitic Eruptions on Tenerife, Canary Islands

The recent eruptive history on the island of Tenerife is characterized in part by the presence of zoned phonolitic ignimbrites, some of which prominently display two types of juvenile clasts (i.e. light-colored, aphyric pumices alongside darker, more crystal-rich pumices, here dubbed ‘crystal-poor' and ‘crystal-rich', respectively). Petrographic observation of the crystal-rich pumices reveals intensely resorbed and intergrown mineral textures, consistent with the system reaching a high crystallinity, followed by perturbation and remobilization prior to eruption. Some trace elements show anomalous concentrations in such crystal-rich pumices (e.g. bulk Ba > 2000 ppm alongside low Zr and a positive Eu anomaly) indicative of crystal accumulation (of feldspar ± biotite). Many biotite and feldspar crystals are reversely zoned, with rim concentrations that are high in Ba but low in Sr, implying crystallization from an ‘enriched' melt, potentially derived from remobilization by partial melting of the aforementioned cumulate zones. Given (1) the presence of cumulates in the eruptive record on Tenerife and a bimodality of pumice textures, (2) the presence of three dominant compositions (basanite, phonotephrite, phonolite, separated by compositional gaps) in the volcanic record, and (3) abundant support for crystal fractionation as the dominant drive for magmatic evolution in Tenerife, it is hypothesized that crystal-poor magmas are extracted from mushy reservoirs in both the lower and upper crust. The thermodynamic software MELTS is used to test a polybaric differentiation model whereby phonolites (sensu lato) are generated by extraction of residual liquids from an intermediate-crystallinity phonotephritic mush in the upper crust, which is in turn generated from the residual liquids of an intermediate-crystallinity basanitic mush at deeper levels. Latent heat spikes following crystallization of successive phases in the upper crustal reservoir provide a thermal buffering mechanism to slow down cooling and crystallization, permitting enhanced melt extraction at a particular crystallinity interval (mostly ∼40-60 vol. % crystals). MELTS modeling typically fits the observed chemical data adequately, although some major elements (mostly Al2O3) also indicate partial ‘cannibalization' of feldspar along with some magma mixing (and potentially minor crustal contamination

Polymorphisms of the dna base excision repair gene mutyh in head and neck cancer

Background: Head and neck squamous cell carcinomas (HNSCC) comprise about 6% of all malignant neoplasms. The major risk factors of HNSCC are smoking and alcohol consumption. Genetic polymorphisms of DNA repair enzymes may lead to genetic instability and carcinogenesis. MUTYH gene encodes a DNA glycosylase that can initiate the base excision repair (BER) pathway and prevent G:C > T:A transversion by excising adenine mispaired with 8-hydroxyguanine produced by reactive oxygen species (ROS). Aim: to perform a case-control study to test the association between polymorphism in the MUTYH gene: Tyr165Cys and head and neck cancer risk progression. Methods: Genotypes were determined in DNA from peripheral blood lymphocytes of 193 patients (among them 97 subjects with precancerous hyperplastic laryngeal lesions and 96 subjects with head and neck cancer) and 140 age, sex and ethnic-matched cancer-free controls by tetra-primer amplification refractory mutation system PCR (T-ARMS-PCR). Results: We found an association between head and neck cancer risk and the Tyr165Tyr variant of the MUTYH gene (OR 2.18; 95% CI 1.19–3.97). For Tyr165Tyr genotype we also observed positive correlation with cancer progression assessed by tumor size (OR 4.56; 95% CI 1.60–12.95). We did not observe any correlation between Tyr165Cys polymorphism of MUTYHgene and precancerous hyperplastic laryngeal lesions risk. Conclusion: The Tyr165Tyr polymorphic variant of the MUTYHgene may be associated with head and neck cancer in Polish population

Exploring the Role of Relational Practices in Water Governance Using a Game-Based Approach

The growing complexity and interdependence of water management processes requires the involvement of multiple stakeholders in water governance. Multi-party collaboration is increasingly vital at both the strategy development and implementation levels. Multi-party collaboration involves a process of joint decision-making among key stakeholders in a problem domain directed towards the future of that domain. However, the common goal is not present from the beginning; rather, the common goal emerges during the process of collaboration. Unfortunately, when the conflicting interests of different actors are at stake, the large majority of environmental multi-party efforts often do not reliably deliver sustainable improvements to policy and/or practice. One of the reasons for this, which has been long established by many case studies, is that social learning with a focus on relational practices is missing. The purpose of this paper is to present the design and initial results of a pilot study that utilized a game-based approach to explore the effects of relational practices on the effectiveness of water governance. This paper verifies the methods used by addressing the following question: are game mechanisms, protocols for facilitation and observation, the recording of decisions and results, and participant surveys adequate to reliably test hypotheses about behavioral decisions related to water governance? We used the “Lords of the Valley” (LOV) game, which focuses on the local-level management of a hypothetical river valley involving many stakeholders. We used an observation protocol to collect data on the quality of relational practices and compared this data with the quantitative outcomes achieved by participants in the game. In this pilot study, we ran the game three times with different groups of participants, and here we provide the outcomes within the context of verifying and improving the methods

Clinical Phenotypes and Comorbidity in European Sleep Apnoea Patients

BackgroundClinical presentation phenotypes of obstructive sleep apnoea (OSA) and their association with comorbidity as well as impact on adherence to continuous positive airway pressure (CPAP) treatment have not been established.MethodsA prospective follow-up cohort of adult patients with OSA (apnoea-hypopnoea index (AHI) of >= 5/h) from 17 European countries and Israel (n = 6,555) was divided into four clinical presentation phenotypes based on daytime symptoms labelled as excessive daytime sleepiness ("EDS") and nocturnal sleep problems other than OSA (labelled as "insomnia"): 1) EDS (daytime+/nighttime-), 2) EDS/insomnia (daytime+/nighttime+), 3) non-EDS/noninsomnia (daytime-/nighttime-), 4) and insomnia (daytime-/nighttime+) phenotype.ResultsThe EDS phenotype comprised 20.7%, the non-EDS/non-insomnia type 25.8%, the EDS/insomnia type 23.7%, and the insomnia phenotype 29.8% of the entire cohort. Thus, clinical presentation phenotypes with insomnia symptoms were dominant with 53.5%, but only 5.6% had physician diagnosed insomnia. Cardiovascular comorbidity was less prevalent in the EDS and most common in the insomnia phenotype (48.9% vs. 56.8%, p<0.001) despite more severe OSA in the EDS group (AHI 35.0 +/- 25.5/h vs. 27.9 +/- 22.5/h, p<0.001, respectively). Psychiatric comorbidity was associated with insomnia like OSA phenotypes independent of age, gender and body mass index (HR 1.5 (1.188-1.905), p<0.001). The EDS phenotype tended to associate with higher CPAP usage (22.7 min/d, p = 0.069) when controlled for age, gender, BMI and sleep apnoea severity.ConclusionsPhenotypes with insomnia symptoms comprised more than half of OSA patients and were more frequently linked with comorbidity than those with EDS, despite less severe OSA. CPAP usage was slightly higher in phenotypes with EDS

Polymorphisms in RAD51, XRCC2 and XRCC3 genes of the homologous recombination repair in colorectal cancer—a case control study

XRCC2 and XRCC3 proteins are structurally and functionally related to RAD51 which play an important role in the homologous recombination, the process frequently involved in cancer transformation. In our previous work we show that the 135G>C polymorphism (rs1801320) of the RAD51 gene can modify the effect of the Thr241Met polymorphism (rs861539) of the XRCC3 gene. We tested the association between the 135G>C polymorphism of the RAD51 gene, the Thr241Met polymorphism of the XRCC3 gene and the Arg188His polymorphism (rs3218536) of the XRCC2 gene and colorectal cancer risk and clinicopathological parameters. Polymorphisms were evaluated by restriction fragment length polymorphism polymerase chain reaction (RFLP-PCR) in 100 patients with invasive adenocarcinoma of the colon and in 100 sex, age and ethnicity matched cancer–free controls. We stratified the patients by genotypes, tumour Duke’s and TNM stage and calculated the linkage of each genotype with each stratum. Carriers of Arg188Arg/Me241tMet, His188His/Thr241Thr and His188His/G135G genotypes had an increased risk of colorectal cancer occurrence (OR 5.70, 95% CI 1.10–29.5; OR 12.4, 95% CI 1.63–94.9; OR 5.88, 95% CI 1.21–28.5, respectively). The C135C genotype decreased the risk of colorectal cancer singly (OR 0.06, 95% CI 0.02–0.22) as well as in combination with other two polymorphisms. TNM and Duke’s staging were not related to any of these polymorphisms. Our results suggest that the 135G>C polymorphism of the RAD51 gene can be an independent marker of colorectal cancer risk. The Thr241Met polymorphism of the XRCC3 gene and the Arg188His polymorphism of the XRCC2 gene can modify the risk of colorectal cancer

Arterial bicarbonate is associated with hypoxic burden and uncontrolled hypertension in obstructive sleep apnea - The ESADA cohort

Objective: Blood bicarbonate concentration plays an important role for obstructive sleep apnea (OSA) patients to maintain acid-base balance. We investigated the association between arterial standard bicarbonate ([HCO3-]) and nocturnal hypoxia as well as comorbid hypertension in OSA. Methods: A cross-sectional analysis of 3329 patients in the European Sleep Apnea Database (ESADA) was performed. Arterial blood gas analysis and lung function test were performed in conjunction with polysomnographic sleep studies. The 4% oxygen desaturation index (ODI), mean and minimum oxygen saturation (SpO2), and percentage of time with SpO2 below 90% (T90%) were used to reflect nocturnal hypoxic burden. Arterial hypertension was defined as a physician diagnosis of hypertension with ongoing antihypertensive medication. Hypertensive patients with SBP/DBP below or above 140/90 mmHg were classified as controlled-, uncontrolled hypertension, respectively. Results: The [HCO3-] level was normal in most patients (average 24.0 ± 2.5 mmol/L). ODI, T90% increased whereas mean and minimum SpO2 decreased across [HCO3-] tertiles (ANOVA, p = 0.030, &lt;0.001, &lt;0.001, and &lt;0.001, respectively). [HCO3-] was independently associated with ODI, mean SpO2, minimum SpO2, and T90% after adjusting for confounders (β value [95%CI]: 1.21 [0.88–1.54], −0.16 [-0.20 to −0.11], −0.51 [-0.64 to −0.37], 1.76 [1.48–2.04], respectively, all p &lt; 0.001). 1 mmol/L elevation of [HCO3-] was associated with a 4% increased odds of uncontrolled hypertension (OR: 1.04 [1.01–1.08], p = 0.013). Conclusion: We first demonstrated an independent association between [HCO3-] and nocturnal hypoxic burden as well as uncontrolled hypertension in OSA patients. Bicarbonate levels as an adjunctive measure provide insight into the pathophysiology of hypertension in OSA

Positive airway pressure (PAP) treatment reduces glycated hemoglobin (HbA1c) levels in obstructive sleep apnea patients with concomitant weight loss: Longitudinal data from the ESADA

Patients with obstructive sleep apnea (OSA) are at increased risk of developing metabolic disease such as diabetes. The effects of positive airway pressure on glycemic control are contradictory. We therefore evaluated the change in glycated hemoglobin (HbA1c) in a large cohort of OSA patients after long-term treatment with positive airway pressure. HbA1c levels were assessed in a subsample of the European Sleep Apnea Database [n=1608] at baseline and at long-term follow up with positive airway pressure therapy (mean 378.9±423.0 days). In a regression analysis, treatment response was controlled for important confounders. Overall, HbA1c decreased from 5.98±1.01% to 5.93±0.98% (p=0.001). Patient subgroups with a more pronounced HbA1c response included patients with diabetes (−0.15±1.02, p=0.019), those with severe OSA baseline (−0.10±0.68, p=0.005), those with morbid obesity (−0.20±0.81, p&lt;0.001). The strongest HbA1c reduction was observed in patients with a concomitant weight reduction &gt;5 kilos (−0.38±0.99, p&lt;0.001). In robust regression analysis, severe OSA (p=0.038) and morbid obesity (p=0.005) at baseline, and weight reduction &gt;5 kilos (p&lt;0.001) during follow up were independently associated with a reduction of HbA1c following PAP treatment. In contrast, PAP treatment alone without weight reduction was not associated with significant Hb1Ac reduction. In conclusion, positive airway pressure therapy is associated with HbA1c reduction in patients with severe OSA, in morbidly obese patients. and most obviously in those with significant weight lost during the follow-up. Our study underlines the importance to combine positive airway pressure use with adjustments in lifestyle to substantially modify metabolic complications in OSA

Expression Profiling of CYP1B1 in Oral Squamous Cell Carcinoma: Counterintuitive Downregulation in Tumors

Oral Squamous Cell Carcinoma (OSCC) has a very flagitious treatment regime. A prodrug approach is thought to aid in targeting chemotherapy. CYP1B1, a member of cytochrome P450 family, has been implicated in chemical carcinogenesis. There exists a general accordance that this protein is overexpressed in a variety of cancers, making it an ideal candidate for a prodrug therapy. The activation of the prodrug facilitated by CYP1B1 would enable the targeting of chemotherapy to tumor tissues in which CYP1B1 is specifically overexpressed as a result reducing the non-specific side effects that the current chemotherapy elicits. This study was aimed at validating the use of CYP1B1 as a target for the prodrug therapy in OSCC. The expression profile of CYP1B1 was analysed in a panel of 51 OSCC tumors, their corresponding normal tissues, an epithelial dysplasia lesion and its matched normal tissue by qRT-PCR, Western blotting and Immunohistochemistry. CYP1B1 was found to be downregulated in 77.78% (28/36) tumor tissues in comparison to their corresponding normal tissues as well as in the epithelial dysplasia lesion compared to its matched normal tissue at the transcriptional level, and in 92.86% (26/28) of tumor tissues at the protein level. This report therefore clearly demonstrates the downregulation of CYP1B1 at the transcriptional and translational levels in tumor tissues in comparison to their corresponding normal tissues. These observations indicate that caution should be observed as this therapy may not be applicable universally to all cancers and also suggest the possibility of a prophylactic therapy for oral cancer