Direct electrophilic borylation using Y2BCl (Y2 = Cl2 or o-catecholato) with equimolar AlCl3 and a tertiary amine has been applied to a wide range of arenes and heteroarenes. In situ ...functionalization of the ArBCl2 products is possible with TMS2MIDA, to afford bench-stable and easily isolable MIDA-boronates in moderate to good yields. According to a combined experimental and computational study, the borylation of activated arenes at 20 °C proceeds through an SEAr mechanism with borenium cations, Y2B(amine)+, the key electrophiles. For catecholato-borocations, two amine dependent reaction pathways were identified: (i) With CatB(NEt3)+, an additional base is necessary to accomplish rapid borylation by deprotonation of the borylated arenium cation (σ complex), which otherwise would rather decompose to the starting materials than liberate the free amine to effect deprotonation. Apart from amines, the additional base may also be the arene itself when it is sufficiently basic (e.g., N-Me-indole). (ii) When the amine component of the borocation is less nucleophilic (e.g., 2,6-lutidine), no additional base is required due to more facile amine dissociation from the boron center in the borylated arenium cation intermediate. Borenium cations do not borylate poorly activated arenes (e.g., toluene) even at high temperatures; instead, the key electrophile in this case involves the product from interaction of AlCl3 with Y2BCl. When an extremely bulky amine is used, borylation again does not proceed via a borenium cation; instead, a number of mechanisms are feasible including via a boron electrophile generated by coordination of AlCl3 to Y2BCl, or by initial (heteroarene)AlCl3 adduct formation followed by deprotonation and transmetalation.
Drought indicators are proliferating, but with little consideration of which are most meaningful for describing drought impacts. A number of recent reviews compare different drought indicators, but ...none assess which indicators are actually used in the many operational drought monitoring and early warning efforts, why they were selected, or whether they have been ‘ground‐truthed,’ i.e., compared with information representing local drought conditions and/or impacts. Also lacking is a comprehensive assessment of the state of monitoring drought impacts. To help fill this gap, we combine a review of drought indicators and impacts with a survey of 33 providers of operational drought monitoring and early warning systems from global to regional scales. Despite considerable variety in the indicators used operationally, certain patterns emerge. Both the literature review and the survey reveal that impact monitoring does exist but has rarely been systematized. Efforts to test drought indicators have mostly focused on agricultural drought. Our review points to a current trend towards the design and use of composite indicators, but with limited evaluation of the links between indicators and drought impacts. Overall, we find that much progress has been made both in research and practice on drought indicators, but monitoring and early warning systems are not yet strongly linked with the assessment of wider impacts on the environment and society. To understand drought impacts fully requires a better framing of drought as a coupled dynamic between the environment and society. WIREs Water 2016, 3:516–536. doi: 10.1002/wat2.1154
This article is categorized under:
Engineering Water > Planning Water
Science of Water > Methods
Science of Water > Water Extremes
Dechlorane (Dec) 602, Dechlorane (Dec) 603, Dechlorane (Dec) 604, and Dechlorane Plus (DP) are flame retardant substitutes for mirex. Dec 602, 603, and 604 were detected in sediment and fish from the ...Laurentian Great Lakes. Lake Ontario surface sediments had the highest concentrations of Dec 602 and 604 at 6.0 and 4.0 ng/g dry weight, respectively. Temporal analysis of a Lake Ontario sediment core indicates that Dec 602 and 604 trends are similar to DP peaking in the early 1980s. Lake trout and whitefish from Lake Ontario also had the highest concentrations of Dec 602 and 604 at 34 and 1.2 ng/g lipid. Concentrations of Dec 602 were higher than those of DP in all fish samples, indicating that Dec 602 is likely more bioavailable and/or more readily bioaccumulates than DP. Spatial trends for Dec 602 and 604 in sediment and fish indicate that manufacturing plants along the Niagara River upstream of Lake Ontario were important sources of Dec 602 and 604 to the Great Lakes, while Dec 603 in the Great Lakes is likely from atmospheric deposition. The findings of this first report of Dec 602, 603, and 604 in the Laurentian Great Lakes basin suggests further investigation of halogenated norbornene flame retardants in the environment is merited.
Persistent organic pollutants (POPs) are recognized as pollutants of global concern, but so far, information on the trends of legacy POPs in the waters of the world has been missing due to ...logistical, analytical, and financial reasons. Passive samplers have emerged as an attractive alternative to active water sampling methods as they accumulate POPs, represent time-weighted average concentrations, and can easily be shipped and deployed. As part of the AQUA-GAPS/MONET, passive samplers were deployed at 40 globally distributed sites between 2016 and 2020, for a total of 21 freshwater and 40 marine deployments. Results from silicone passive samplers showed α-hexachlorocyclohexane (HCH) and γ-HCH displaying the greatest concentrations in the northern latitudes/Arctic Ocean, in stark contrast to the more persistent penta (PeCB)- and hexachlorobenzene (HCB), which approached equilibrium across sampling sites. Geospatial patterns of polychlorinated biphenyl (PCB) aqueous concentrations closely matched original estimates of production and use, implying limited global transport. Positive correlations between log-transformed concentrations of Σ7PCB, ΣDDTs, Σendosulfan, and Σchlordane, but not ΣHCH, and the log of population density (p < 0.05) within 5 and 10 km of the sampling sites also supported limited transport from used sites. These results help to understand the extent of global distribution, and eventually time-trends, of organic pollutants in aquatic systems, such as across freshwaters and oceans. Future deployments will aim to establish time-trends at selected sites while adding to the geographical coverage.
The Greenland Ice Sheet has been a major contributor to global sea-level rise in recent decades
, and it is expected to continue to be so
. Although increases in glacier flow
and surface melting
have ...been driven by oceanic
and atmospheric
warming, the magnitude and trajectory of the ice sheet's mass imbalance remain uncertain. Here we compare and combine 26 individual satellite measurements of changes in the ice sheet's volume, flow and gravitational potential to produce a reconciled estimate of its mass balance. The ice sheet was close to a state of balance in the 1990s, but annual losses have risen since then, peaking at 345 ± 66 billion tonnes per year in 2011. In all, Greenland lost 3,902 ± 342 billion tonnes of ice between 1992 and 2018, causing the mean sea level to rise by 10.8 ± 0.9 millimetres. Using three regional climate models, we show that the reduced surface mass balance has driven 1,964 ± 565 billion tonnes (50.3 per cent) of the ice loss owing to increased meltwater runoff. The remaining 1,938 ± 541 billion tonnes (49.7 per cent) of ice loss was due to increased glacier dynamical imbalance, which rose from 46 ± 37 billion tonnes per year in the 1990s to 87 ± 25 billion tonnes per year since then. The total rate of ice loss slowed to 222 ± 30 billion tonnes per year between 2013 and 2017, on average, as atmospheric circulation favoured cooler conditions
and ocean temperatures fell at the terminus of Jakobshavn Isbræ
. Cumulative ice losses from Greenland as a whole have been close to the rates predicted by the Intergovernmental Panel on Climate Change for their high-end climate warming scenario
, which forecast an additional 70 to 130 millimetres of global sea-level rise by 2100 compared with their central estimate.
This review is based on a presentation that was made at a meeting concerning hydration. It summarizes the epidemiological evidence for selected beverages in relation to cardiovascular and/or ...metabolic health. The review focuses on tea, cocoa, milk, orange juice, alcohol, and beverages sweetened with sugars. These beverage types were chosen because of their widespread consumption, with tea, cocoa, orange juice, and milk being of potential benefit while alcohol and sugars may be detrimental. There is reasonably consistent evidence of reduced risk of cardiovascular disease (CVD) in association with high consumption of tea, with the tea flavonoids appearing to be responsible for these benefits. There is also a growing evidence base for cocoa flavanols to have beneficial cardiovascular effects. The bulk of the evidence supporting these conclusions is epidemiological and needs to be confirmed with randomized controlled trials. Milk is associated with reduced risk of CVD, particularly in relation to blood pressure, with certain milk tripeptides being implicated in having effects to reduce angiotensin action. Further work is needed to confirm these potentially beneficial effects. There is some evidence of potentially beneficial effects of orange juice on aspects of cardiovascular function, but this is by no means convincing, and further evidence is needed from randomized controlled trials, together with the elucidation of whether any benefits are linked to the citrus flavanones or simply to the vitamin C content. While there is some evidence that red wine may convey some health benefits, there is also clear evidence that alcoholic beverages can have undesirable effects on blood pressure and increase the risk of CVD. It is possible that low to moderate intakes of alcoholic beverages may be beneficial. There is some evidence that beverages sweetened with sugars may contribute to increased energy intake and weight gain, and there is also an indication from longitudinal cohort studies that they are associated with an increased risk of developing type 2 diabetes. The mechanism of this latter association has not been explained. In conclusion, there is a substantial amount of epidemiological evidence for benefits of tea and cocoa in relation to cardiovascular health. There is a growing literature describing randomized controlled trials, but more evidence is needed. Potential cardiovascular and metabolic health benefits of milk and orange juice needs further investigation. The associations of higher alcohol intakes and consumption of beverages sweetened with sugars and their increased health risks are of concern, and more attention should be focused on this area.
Previous studies of radiological damage in rheumatoid arthritis (RA) have used candidate-gene approaches, or evaluated single genome-wide association studies (GWAS). We undertook the first ...meta-analysis of GWAS of RA radiological damage to: (1) identify novel genetic loci for this trait; and (2) test previously validated variants.
Seven GWAS (2,775 RA cases, of a range of ancestries) were combined in a meta-analysis. Radiological damage was assessed using modified Larsen scores, Sharp van Der Heijde scores, and erosive status. Single nucleotide polymophsim (SNP) associations with radiological damage were tested at a single time-point using regression models. Primary analyses included age and disease duration as covariates. Secondary analyses also included rheumatoid factor (RF). Meta-analyses were undertaken in trans-ethnic and European-only cases.
In the trans-ethnic primary meta-analysis, one SNP (rs112112734) in close proximity to HLA-DRB1, and strong linkage disequilibrium with the shared-epitope, attained genome-wide significance (P = 4.2x10-8). In the secondary analysis (adjusting for RF) the association was less significant (P = 1.7x10-6). In both trans-ethnic primary and secondary meta-analyses 14 regions contained SNPs with associations reaching P<5x10-6; in the European primary and secondary analyses 13 and 10 regions contained SNPs reaching P<5x10-6, respectively. Of the previously validated SNPs for radiological progression, only rs660895 (tagging HLA-DRB1*04:01) attained significance (P = 1.6x10-5) and had a consistent direction of effect across GWAS.
Our meta-analysis confirms the known association between the HLA-DRB1 shared epitope and RA radiological damage. The lack of replication of previously validated non-HLA markers highlights a requirement for further research to deliver clinically-useful prognostic genetic markers.
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