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Search: WFRF:(Shekhar A.)

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1.
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2.
  • Aaltonen, T., et al. (author)
  • Combination of CDF and D0 W-Boson mass measurements
  • 2013
  • In: Physical Review D. - 1550-7998 .- 1550-2368. ; 88:5, s. 052018-
  • Journal article (peer-reviewed)abstract
    • We summarize and combine direct measurements of the mass of the W boson in root s = 1.96 TeV proton-antiproton collision data collected by CDF and D0 experiments at the Fermilab Tevatron Collider. Earlier measurements from CDF and D0 are combined with the two latest, more precise measurements: a CDF measurement in the electron and muon channels using data corresponding to 2.2 fb(-1) of integrated luminosity, and a D0 measurement in the electron channel using data corresponding to 4.3 fb(-1) of integrated luminosity. The resulting Tevatron average for the mass of the W boson is M-W = 80387 +/- 16 MeV. Including measurements obtained in electron-positron collisions at LEP yields the most precise value of M-W = 80385 +/- 15 MeV.
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4.
  • Jansen, Joachim, 1989-, et al. (author)
  • Monitoring of carbon-water fluxes at Eurasian meteorological stations using random forest and remote sensing
  • 2023
  • In: Scientific Data. - : Springer Nature. - 2052-4463. ; 10:1
  • Journal article (peer-reviewed)abstract
    • Simulating the carbon-water fluxes at more widely distributed meteorological stations based on the sparsely and unevenly distributed eddy covariance flux stations is needed to accurately understand the carbon-water cycle of terrestrial ecosystems. We established a new framework consisting of machine learning, determination coefficient (R2), Euclidean distance, and remote sensing (RS), to simulate the daily net ecosystem carbon dioxide exchange (NEE) and water flux (WF) of the Eurasian meteorological stations using a random forest model or/and RS. The daily NEE and WF datasets with RS-based information (NEE-RS and WF-RS) for 3774 and 4427 meteorological stations during 2002-2020 were produced, respectively. And the daily NEE and WF datasets without RS-based information (NEE-WRS and WF-WRS) for 4667 and 6763 meteorological stations during 1983-2018 were generated, respectively. For each meteorological station, the carbon-water fluxes meet accuracy requirements and have quasi-observational properties. These four carbon-water flux datasets have great potential to improve the assessments of the ecosystem carbon-water dynamics.
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5.
  • Rahnev, D, et al. (author)
  • The Confidence Database
  • 2020
  • In: Nature human behaviour. - : Springer Science and Business Media LLC. - 2397-3374. ; 4:3, s. 317-325
  • Journal article (peer-reviewed)
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6.
  • Ali, S., et al. (author)
  • Influence of the water–sediment interaction on the major ions chemistry and fluoride pollution in groundwater of the Older Alluvial Plains of Delhi, India
  • 2021
  • In: Journal of Earth System Science. - : Springer Nature. - 2347-4327 .- 0973-774X. ; 130:2
  • Journal article (peer-reviewed)abstract
    • Fluoride (F–) pollution in groundwater of the Older Alluvial Plain (OAP) of Delhi has been reported as a major problem. About 34% of the groundwater samples collected for this study had F– level beyond the permissible limit; with F– concentration in the range of 0.14–3.15 mg/L (average 1.20 mg/L). In this context, this article for the first time attempts on the genesis of major ions chemistry and F– pollution in groundwater of OAP Delhi by going beyond the statistical analysis to sediment geochemistry, chemical weathering processes and understanding of the processes using stable environmental isotopes (2H and 18O). The XRD of the OAP sediments revealed the dominance of fluor-biotite, albite, calcite, quartz, and chlorite. Whereas, the separated clay revealed the dominance of chlorite, kaolinite, and illite minerals. The saturation index (SI) values indicated that the groundwater chemistry is in the process of further F– enrichment by way of sediment groundwater interaction. With the given mineralogy of the sediments, the dominance of major ions like Na+, K+, Mg2+, Ca2+, Cl– and F– has been attributed to chemical weathering of biotites, phlogopites, albite, and calcite during sediment–water interaction. While the dominance of SO42– has been attributed to anthropogenic sources and confirmed by its association with heavier stable isotopes of hydrogen (δ2H: −50.44 to −40.02‰) and oxygen (δ18O: −7.19 to −5.62‰) indicating evaporative enrichment during isotopic fractionation.
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8.
  • Ali, S., et al. (author)
  • Concentration of fluoride in groundwater of India : A systematic review, meta-analysis and risk assessment
  • 2019
  • In: Groundwater for Sustainable Development. - : Elsevier. - 2352-801X. ; 9
  • Research review (peer-reviewed)abstract
    • It is a well-known fact that the Indian groundwater is polluted by fluoride. However, for the first time in India, non-carcinogenic risk assessments and meta-analysis of fluoride exposure to humans were carried out due to consumption of groundwater. In this context, we collected fluoride concentration data in groundwater across India by systematic searches conducted in various international search engines databases. Here, we demonstrated a detailed meta-analysis and meta-regression of fluoride and evaluated health risk assessment. For this purpose, meta-analysis of 63 studies on fluoride in groundwater in India, comprising 57381 samples are included. We found that 1.) The pooled concentration of fluoride in India is around 2.37 mg/L with 95% confident interval (1.46–3.28 mg/L) which is higher than WHO and national standards limit of 1.5 mg/L. 2) The meta-analysis of data suggests that in rural parts of the country, fluoride concentration is 1.85 times higher than urban areas. 3) The concentration of fluoride in groundwater decreased significantly (p < 0.05) with increase in rainfall and longitude. The risk assessment via oral and dermal route exposure reveals that the consumers in majority of the regions are at considerable non-carcinogenic risk and children are at higher risk than adults (Total hazard quotient > 1). The findings are helpful in identifying the affected areas of India and we recommend that the safer options of drinking water should be adopted.
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9.
  • Ali, S., et al. (author)
  • Elevated fluoride in groundwater of Siwani Block, Western Haryana, India : A potential concern for sustainable water supplies for drinking and irrigation
  • 2018
  • In: Groundwater for Sustainable Development. - : Elsevier BV. - 2352-801X. ; 7, s. 410-420
  • Journal article (peer-reviewed)abstract
    • Groundwater pollution is a serious health concern in north-western India. In this study, we have reported very high concentration of fluoride i.e. 18.5 and 16.6 mg/l from Sainiwas locality in Siwani block of Bhiwani district, Haryana, India. The values are much higher than the permissible limit set by WHO and BIS. The evapotranspiration in the area leads to Ca2+ precipitation, which allows an increase in F- content in the groundwater. In addition, the replacement of hydroxyl of secondary clay mineral under alkaline condition is responsible for release of F-. In absence of alternative source, the fluoride polluted groundwater in some of these localities is also used for drinking. Further, the suitability of groundwater for irrigation is also evaluated by various parameters such as Sodium Adsorption Ratio (SAR), Sodium Percentage (Na%), Kelly's Ratio (KR), Magnesium Hazard (MH) and Residual Sodium Carbonate (RSC). It emerges out that in a few localities, groundwater is not suitable for irrigation and with respect to Magnesium Hazard (MH) almost all samples are unsuitable for irrigation. This article highlights groundwater quality of Siwani block in Haryana and proposes for immediate remedial measures. 
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10.
  • Anderson, Ian, et al. (author)
  • Indigenous and tribal peoples' health (The Lancet-Lowitja Institute Global Collaboration) : a population study
  • 2016
  • In: The Lancet. - : Elsevier. - 0140-6736 .- 1474-547X. ; 388:10040, s. 131-157
  • Journal article (peer-reviewed)abstract
    • Background: International studies of the health of Indigenous and tribal peoples provide important public health insights. Reliable data are required for the development of policy and health services. Previous studies document poorer outcomes for Indigenous peoples compared with benchmark populations, but have been restricted in their coverage of countries or the range of health indicators. Our objective is to describe the health and social status of Indigenous and tribal peoples relative to benchmark populations from a sample of countries.Methods: Collaborators with expertise in Indigenous health data systems were identified for each country. Data were obtained for population, life expectancy at birth, infant mortality, low and high birthweight, maternal mortality, nutritional status, educational attainment, and economic status. Data sources consisted of governmental data, data from non-governmental organisations such as UNICEF, and other research. Absolute and relative differences were calculated.Findings: Our data (23 countries, 28 populations) provide evidence of poorer health and social outcomes for Indigenous peoples than for non-Indigenous populations. However, this is not uniformly the case, and the size of the rate difference varies. We document poorer outcomes for Indigenous populations for: life expectancy at birth for 16 of 18 populations with a difference greater than 1 year in 15 populations; infant mortality rate for 18 of 19 populations with a rate difference greater than one per 1000 livebirths in 16 populations; maternal mortality in ten populations; low birthweight with the rate difference greater than 2% in three populations; high birthweight with the rate difference greater than 2% in one population; child malnutrition for ten of 16 populations with a difference greater than 10% in five populations; child obesity for eight of 12 populations with a difference greater than 5% in four populations; adult obesity for seven of 13 populations with a difference greater than 10% in four populations; educational attainment for 26 of 27 populations with a difference greater than 1% in 24 populations; and economic status for 15 of 18 populations with a difference greater than 1% in 14 populations.Interpretation: We systematically collated data across a broader sample of countries and indicators than done in previous studies. Taking into account the UN Sustainable Development Goals, we recommend that national governments develop targeted policy responses to Indigenous health, improving access to health services, and Indigenous data within national surveillance systems.
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11.
  • Belopolski, Ilya, et al. (author)
  • Observation of a linked-loop quantum state in a topological magnet
  • 2022
  • In: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 604:7907, s. 647-652
  • Journal article (peer-reviewed)abstract
    • Quantum phases can be classified by topological invariants, which take on discrete values capturing global information about the quantum state1–13. Over the past decades, these invariants have come to play a central role in describing matter, providing the foundation for understanding superfluids5, magnets6,7, the quantum Hall effect3,8, topological insulators9,10, Weyl semimetals11–13 and other phenomena. Here we report an unusual linking-number (knot theory) invariant associated with loops of electronic band crossings in a mirror-symmetric ferromagnet14–20. Using state-of-the-art spectroscopic methods, we directly observe three intertwined degeneracy loops in the material’s three-torus, T3, bulk Brillouin zone. We find that each loop links each other loop twice. Through systematic spectroscopic investigation of this linked-loop quantum state, we explicitly draw its link diagram and conclude, in analogy with knot theory, that it exhibits the linking number (2, 2, 2), providing a direct determination of the invariant structure from the experimental data. We further predict and observe, on the surface of our samples, Seifert boundary states protected by the bulk linked loops, suggestive of a remarkable Seifert bulk–boundary correspondence. Our observation of a quantum loop link motivates the application of knot theory to the exploration of magnetic and superconducting quantum matter.
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12.
  • Boyko, Andrey A., et al. (author)
  • Optical parametric oscillator pumped at similar to 1 mu m with intracavity mid-IR difference-frequency generation in OPGaAs
  • 2018
  • In: Optical Materials Express. - : Optical Society of America. - 2159-3930 .- 2159-3930. ; 8:3, s. 549-554
  • Journal article (peer-reviewed)abstract
    • Intracavity difference-frequency generation (DFG) between signal and idler pulses is investigated in orientation-patterned GaAs inside the cavity of a similar to 1 mu m pumped nanosecond optical parametric oscillator (OPO). Using two different samples and temperature tuning in the non-critical configuration, tunability between 7 and 9.2 mu m is demonstrated. The superior thermo-mechanical properties of OPGaAs enabled also for the first time operation of this cascaded scheme at kilohertz (1-3 kHz) repetition rates reaching average powers similar to 10 mW in the mid-IR.
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14.
  • Galbany, L., et al. (author)
  • Evidence for a Chandrasekhar-mass explosion in the Ca-strong 1991bg-like type la supernova 2016hnk
  • 2019
  • In: Astronomy and Astrophysics. - : EDP Sciences. - 0004-6361 .- 1432-0746. ; 630
  • Journal article (peer-reviewed)abstract
    • Aims. We present a comprehensive dataset of optical and near-infrared photometry and spectroscopy of type Ia supernova (SN) 2016hnk, combined with integral field spectroscopy (IFS) of its host galaxy, MCG -01-06-070, and nearby environment. Our goal with this complete dataset is to understand the nature of this peculiar object.Methods. Properties of the SN local environment are characterized by means of single stellar population synthesis applied to IFS observations taken two years after the SN exploded. We performed detailed analyses of SN photometric data by studying its peculiar light and color curves. SN 2016hnk spectra were compared to other 1991bg-like SNe Ia, 2002es-like SNe Ia, and Ca-rich transients. In addition, we used abundance stratification modeling to identify the various spectral features in the early phase spectral sequence and also compared the dataset to a modified non-LTE model previously produced for the sublumnious SN 1999by.Results. SN 2016hnk is consistent with being a subluminous (M-B = -16.7 mag, S-BV =0.43 +/- 0.03), highly reddened object. The IFS of its host galaxy reveals both a significant amount of dust at the SN location, residual star formation, and a high proportion of old stellar populations in the local environment compared to other locations in the galaxy, which favors an old progenitor for SN 2016hnk. Inspection of a nebular spectrum obtained one year after maximum contains two narrow emission lines attributed to the forbidden [Ca II] lambda lambda 7291,7324 doublet with a Doppler shift of 700 km s(-1). Based on various observational diagnostics, we argue that the progenitor of SN 2016hnk was likely a near Chandrasekhar-mass (M-Ch) carbon-oxygen white dwarf that produced 0.108 M-circle dot of Ni-56. Our modeling suggests that the narrow [Ca II] features observed in the nebular spectrum are associated with Ca-48 from electron capture during the explosion, which is expected to occur only in white dwarfs that explode near or at the M-Ch limit.
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15.
  • Harper, Karen A., et al. (author)
  • Edge influence on vegetation at natural and anthropogenic edges of boreal forests in Canada and Fennoscandia
  • 2015
  • In: Journal of Ecology. - : Wiley. - 0022-0477 .- 1365-2745. ; 103:3, s. 550-562
  • Journal article (peer-reviewed)abstract
    • Although anthropogenic edges are an important consequence of timber harvesting, edges due to natural disturbances or landscape heterogeneity are also common. Forest edges have been well studied in temperate and tropical forests, but less so in less productive, disturbance-adapted boreal forests. We synthesized data on forest vegetation at edges of boreal forests and compared edge influence among edge types (fire, cut, lake/wetland; old vs. young), forest types (broadleaf vs. coniferous) and geographic regions. Our objectives were to quantify vegetation responses at edges of all types and to compare the strength and extent of edge influence among different types of edges and forests. Research was conducted using the same general sampling design in Alberta, Ontario and Quebec in Canada, and in Sweden and Finland. We conducted a meta-analysis for a variety of response variables including forest structure, deadwood abundance, regeneration, understorey abundance and diversity, and non-vascular plant cover. We also determined the magnitude and distance of edge influence (DEI) using randomization tests. Some edge responses (lower tree basal area, tree canopy and bryophyte cover; more logs; higher regeneration) were significant overall across studies. Edge influence on ground vegetation in boreal forests was generally weak, not very extensive (DEI usually <20m) and decreased with time. We found more extensive edge influence at natural edges, at younger edges and in broadleaf forests. The comparison among regions revealed weaker edge influence in Fennoscandian forests.Synthesis. Edges created by forest harvesting do not appear to have as strong, extensive or persistent influence on vegetation in boreal as in tropical or temperate forested ecosystems. We attribute this apparent resistance to shorter canopy heights, inherent heterogeneity in boreal forests and their adaptation to frequent natural disturbance. Nevertheless, notable differences between forest structure responses to natural (fire) and anthropogenic (cut) edges raise concerns about biodiversity implications of extensive creation of anthropogenic edges. By highlighting universal responses to edge influence in boreal forests that are significant irrespective of edge or forest type, and those which vary by edge type, we provide a context for the conservation of boreal forests.
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16.
  • Krieger, Jonas A., et al. (author)
  • Weyl spin-momentum locking in a chiral topological semimetal
  • 2024
  • In: Nature Communications. - 2041-1723. ; 15:1
  • Journal article (peer-reviewed)abstract
    • Spin-orbit coupling in noncentrosymmetric crystals leads to spin-momentum locking – a directional relationship between an electron’s spin angular momentum and its linear momentum. Isotropic orthogonal Rashba spin-momentum locking has been studied for decades, while its counterpart, isotropic parallel Weyl spin-momentum locking has remained elusive in experiments. Theory predicts that Weyl spin-momentum locking can only be realized in structurally chiral cubic crystals in the vicinity of Kramers-Weyl or multifold fermions. Here, we use spin- and angle-resolved photoemission spectroscopy to evidence Weyl spin-momentum locking of multifold fermions in the chiral topological semimetal PtGa. We find that the electron spin of the Fermi arc surface states is orthogonal to their Fermi surface contour for momenta close to the projection of the bulk multifold fermion at the Γ point, which is consistent with Weyl spin-momentum locking of the latter. The direct measurement of the bulk spin texture of the multifold fermion at the R point also displays Weyl spin-momentum locking. The discovery of Weyl spin-momentum locking may lead to energy-efficient memory devices and Josephson diodes based on chiral topological semimetals.
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17.
  • McDermott, Constance L., et al. (author)
  • Governance for REDD+, forest management and biodiversity: existing approaches and future options
  • 2012
  • In: Understanding Relationships between Biodiversity, Carbon, Forests and People: The Key to Achieving REDD+ Objectives. A Global Assessment Report.. ; , s. 115-115
  • Book chapter (peer-reviewed)abstract
    • This chapter examines the evolution of REDD+ governance and identifies policy options to increase synergies among REDD+, the sustainable management of forests and biodiversity conservation. REDD+ emerged at the international level as a point of convergemnce acorss the 'institutional complexes' of forests, climate and biodiversity. This convergence attracted the engagement of a wide range of institutions in REDD+ activities, which together have drawn on three primary sources of authority to influence REDD+ rule-making: government sovereignty, contingent finance and voluntary carbon markets. Intergovernmental processes, which represent the primary articulation of governmental authority at the global level, have generated few binding commitments to the sustainable management of forests or biodiversity due to conflicting country interests. These efforts instead have favoured normative guidance, monitoring and reporting, and legality verification initiatives that reinforce sovereign authority. Bilateral and multi-lateral finance initiatives have exerted ‘fund-based’ authority through the application of operational safeguards protecting indigenous and local communities and biodiversity, but limited funding and low capacity of REDD+ countries to absorb those funds have constrained their influence. Finally, non-state actors have developed voluntary certification schemes for forest and carbon as a ’fast track’ approach to elaborating more substantive international standards for environmentally- and socially-responsible forest practices. While the small size and voluntary nature of markets for forest carbon have greatly constrained the impact of these approaches, this could change if a significant regulatory market for REDD+ develops.Furthermore, the governance of REDD+, forest management and biodiversity is pluralistic, involving multiple institutions and actors. Efforts to promote REDD+ safeguarding at the international level exist in tension with national sovereignty and local autonomy. This complexity is taken into consideration in the suite of policy options provided in this chapter, which suggest the need to draw on a range of institutions and approaches and to consider how together they influence the balance of power and incentives across actors and scales.
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18.
  • Tapasvi, S, et al. (author)
  • Discoid lateral meniscus: current concepts
  • 2021
  • In: Journal of ISAKOS : joint disorders & orthopaedic sports medicine. - : Elsevier BV. - 2059-7762. ; 6:1, s. 14-21
  • Journal article (peer-reviewed)
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