Extreme precipitation and flood episodes in the Himalayas are oftentimes traced to synoptic situations involving connections between equatorward advancing upper level extratropical circulations and ...moisture-laden tropical monsoon circulation. While previous studies have documented precipitation characteristics in the Himalayan region during severe storm cases, a comprehensive understanding of circulation dynamics of extreme precipitation mechanisms is still warranted. In this study, a detailed analysis is performed using rainfall observations and reanalysis circulation products to understand the evolution of monsoon-extratropical circulation features and their interactions based on 34 extreme precipitation events which occurred in the Western Himalayas (WEH) during the period 1979–2013. Our results provide evidence for a common large-scale circulation pattern connecting the extratropics and the South Asian monsoon region, which is favorable for extreme precipitation occurrences in the WEH region. This background upper level large-scale circulation pattern consists of a deep southward penetrating midlatitude westerly trough, a blocking high over western Eurasia and an intensifying Tibetan anticyclone. It is further seen from our analysis that the key elements of monsoon-midlatitude interactions, responsible for extreme precipitation events over the WEH region, are: (1) midlatitude Rossby wave breaking, (2) west-northwest propagation of monsoon low-pressure system from the Bay of Bengal across the Indian subcontinent, (3) eddy shedding of the Tibetan anticyclone, (4) ageostrophic motions and transverse circulation across the Himalayas, and (5) strong moist convection over the Himalayan foothills. Furthermore, high-resolution numerical simulations indicate that diabatic heating and mesoscale ageostrophic effects can additionally amplify the convective motions and precipitation in the WEH region.
Poly(hydroxy acid)s are a family of biocompatible and (bio)degradable polyesters with various outcomes in different domains of application. To date, poly(hydroxy acid)s are best prepared by ...ring‐opening polymerization (ROP) of the corresponding cyclic esters. Using racemic chiral monomers featuring side‐chain groups enables to access, providing a stereoselective catalyst/initiator system is implemented, stereoregular functional polymers, thereby improving their physico–chemical properties, and ultimately, widening their range of uses. Here, we highlight a few important advances in metal‐mediated stereoselective ROP of cyclic esters towards the synthesis of (functional) stereoregular poly(hydroxy acid)s that have recently been disclosed, emphasizing on (functional) β‐ and γ‐lactones, diolide and O‐carboxyanhydride (OCA) monomers and yttrium‐based catalysis. Fine‐tuning of the substituents flanked on the catalyst ligand enables reaching poly(hydroxy acid)s with syndiotactic and also isotactic microstructures. The stereocontrol mechanisms at work and their probable origin, relying on steric but also electronic factors imparted in particular by the ligand substituents, are discussed. Taking advantage of such stereoselective ROPs, original copoly(hydroxy acid)s with gradient or alternated patterns then become accessible from the use of mixtures of chemically different, oppositely configured enantiopure monomers.
ROP under control: Recent advances in the stereoselective metal‐mediated ring‐opening polymerization of chiral cyclic esters to access original highly stereoregular homopolyesters or sequence‐controlled alternated or gradient copolyesters are reviewed, with an emphasis on stereocontrol factors and mechanisms.
This article reports world averages of measurements of
b
-hadron,
c
-hadron, and
τ
-lepton properties obtained by the Heavy Flavor Averaging Group using results available through summer 2016. For the ...averaging, common input parameters used in the various analyses are adjusted (rescaled) to common values, and known correlations are taken into account. The averages include branching fractions, lifetimes, neutral meson mixing parameters,
C
P
violation parameters, parameters of semileptonic decays, and Cabbibo–Kobayashi–Maskawa matrix elements.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
New zero valent iron magnetic biochar composites (ZVI-MBC) were synthesized by facile method using Eucalyptus globules bark waste. The as-prepared ZVI-MBC was used as an adsorbent for the removal of ...Pb(II) from aqueous solution. Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and energy-dispersive spectroscopy (EDS) were used for characterization of ZVI-MBC. Effect of variable parameters including pH, contact time and initial concentration of metal ions was studied. The ZVI-MBC exhibited good adsorption performance over the initial pH at 6. The adsorption isotherm data were fitted well to Langmuir isotherm then Freundlich model, and the adsorption capacity was found to be 60.8mg/g at 303K. The kinetic data were studied by applying two adsorption kinetic models, pseudo-first- and pseudo-second-order equations. The experimental kinetic data fitted very well to the pseudo-second-order model. The experimental results herein suggest that ZVI-MBC can be used as low cost-effective material for the removal of Pb(II) from water systems with a simple magnetic separation process.
Human osteology is the biomechanics science that deals with the study of minerals and non-collagenous organic components that shield human organs and aids in the production of blood cells. A bone ...follows a specific regenerative pattern after injury or defect. Direct healing ability is still a substantial medical challenge in pathological or nonunion conditions. Such bone defects often necessitate a choice of biomaterial matrix (polymer/ceramic/bioglasses/metallic implants) with the combinations of bioactive signaling molecules (drug molecules) in a spatiotemporal pattern. In this regard, we address the development of a drug delivery system and also outline the interactions of drug molecules with the scaffolding surface that could further trigger the regeneration process. Eventually, the review highlights the notion of drug embedded onto the three-dimensional scaffolds and the release profiles surface coated metallic implant that creates a new window for bone tissue engineering. Besides, a systematic review was performed for literature regarding the role of antibiotics and dual drug delivery strategies that would have a potential utilization of bone-related infection control.
Graphical abstract
Most high load-bearing implants are metallic alloys which contain toxic chemical components that might be released due to the corrosive environment of body fluids and load-bearing activity. Surface ...modification techniques do not guarantee biocompatibility. Hence, the bioactive surface of implants can be modified by coating the surface with a suitable material that addresses the needs of the patient. The choice and application process of the coatings should be determined based on the workability of the material and its physiochemical properties, such as the procedures involved and performance in avoiding removal of any desirable material properties that are helpful in the tissue regeneration process. Tailor-made coating materials prove very promising, as they might improve permanent implantations, make them more affordable and reduce the need for surgical revisions. The scope of the featured properties, such as addition of accelerated tissue regeneration, antibacterial properties and controlled release and removal of debris from the biological system to the metal implants makes coatings an ideal choice for surface modification of implants. This report reviews several options available for forming a biologically active layer over metallic surfaces that will interact with and produce desirable effects on host tissues.
Stereoselective ring-opening polymerization (ROP) of cyclic esters is the privileged strategy to access stereoregular polyesters that are widely applied in various domains, such as in particular the ...biomedical and packaging fields. The production of synthetic stereo-enriched polyhydroxyalkanoates (PHAs) derived from racemic β-lactones by ROP is still a challenge. In this context, linear, high molar mass, narrowly dispersed PHAs, namely PBPL CH 2 O i Pr , PBPL CH 2 O t Bu and PBPL CH 2 OTBDMS ( M n,SEC up to 94 300 g mol −1 ; Đ M = 1.06–1.18; TBDMS = Si t BuMe 2 ), with syndiotactic enrichment ( P r = 0.76–0.87) were successfully synthesized by stereoselective ROP of the corresponding functional racemic β-propiolactones, rac -BPL CH 2 O i Pr , rac -BPL CH 2 O t Bu and rac -BPL CH 2 OTBDMS , respectively, which are promoted by diverse achiral diamino-bis(phenolate) yttrium complexes featuring various R′/R′′ substituents (Y{ONNO R′,R′′ }, 2a–d). The influence of the steric hindrance of the BPL FG side-functionality, with FG = CH 2 O i Pr, CH 2 O t Bu, and CH 2 OTBDMS, on the ROP kinetics, stereoselectivity and thermal properties of the resulting PHAs, as a function of 2a–d catalysts, was compared to that of the previously reported similar but less hindered BPL FG monomers, with FG = CH 2 OMe, CH 2 OAllyl, CH 2 OBn, and CH 2 OPh. Overall, this study evidenced that, for the newly prepared rac -BPL CH 2 O i Pr , rac -BPL CH 2 O t Bu and rac -BPL CH 2 OTBDMS monomers, due to steric constraints induced by the monomer alkoxy/silyloxy side-functionality, all ROPs afforded syndio-enriched polyesters, regardless of the catalyst used. Conversely, only combinations of a BPL FG monomer containing two sets of methylene hydrogens within the side-functionality, i.e. with FG = C H 2 OC H 2 X with X = H, CH = CH 2 and C 6 H 5 as in BPL CH 2 OMe , BPL CH 2 OAllyl , and BPL CH 2 OBn , with a yttrium catalyst bearing ortho / para -chloro substituents (2a), gave isotactic functional PHAs. With the latter three monomers, a catalyst with highly sterically crowded substituents on the ligand platform (2a,b) was necessary to recover syndio-enriched PBPL CH 2 OMe,OAll,OBn .
Graphene oxide derived from palm kernel shells (rGOPKS) and polyacrylonitrile (PAN) were electrospun into composite fiber mats and evaluated as supercapacitor electrode materials. Their morphologies ...and crystalline properties were examined, and chemical interactions between rGOPKS and PAN were investigated. The diameters of individual fibers in the rGOPKS/PAN composite mats ranged from 1.351 to 1506 μm and increased with increasing rGOPKS content. A broad peak centered near 23° in the X-ray diffraction (XRD) pattern of rGOPKS corresponded to the (002) planes in graphitic carbon. Characteristic rGOPKS and PAN peaks were observed in the XRD patterns of all the composite fibers, and their Fourier-transform infrared (FTIR) spectra indicated hydrogen bond formation between rGOPKS and PAN. The composite fiber mats had smooth and homogeneous surfaces, and they exhibited excellent flexibility and durability. Their electrochemical performance as electrodes was assessed, and a maximum specific capacitance of 203 F g
−1
was achieved. The cycling stability of this electrode was excellent, and it retained over 90% of its capacitance after 5000 cycles. The electrode had an energy density of 17 W h kg
−1
at a power density of 3000 W kg
−1
. Dielectric results showed a nanofiber composite dielectric constant of 72.3 with minor leakage current (tan
δ
)
i.e.
, 0.33 at 51 Hz. These results indicate that the rGOPKS/PAN composite fibers have great promise as supercapacitor electrode materials.
Graphene oxide derived from palm kernel shells (rGOPKS) and polyacrylonitrile (PAN) were electrospun into composite fiber mats and evaluated as supercapacitor electrode materials.
Immigrants typically have more favorable health outcomes than their U.S.-born counterparts of the same race-ethnicity. However, little is known about how race-ethnicity and region of birth moderate ...the health outcomes of different immigrant groups as their tenure of U.S. residence increases. We study the association between time spent in the United States and health outcomes among non-Hispanic Black, non-Hispanic White, Asian, and Hispanic immigrants using National Health Interview Survey data. Although all immigrant groups initially report better health outcomes than their U.S.-born counterparts, the association between U.S. tenure and reported health outcomes varies among immigrants by race-ethnicity and region of birth. Black immigrants have the worst hypertension profiles, and Black and Hispanic immigrants have the worst obesity profiles. The results suggest that acculturation cannot fully explain racial-ethnic differences in the association between U.S. tenure and health outcomes. We advance a more complete sociological theory of immigrant integration to better explain disparate immigrant health profiles.
The nationwide lockdown was imposed over India from 25 March to 31 May 2020 with varied relaxations from phase I to phase IV to contain the spread
of COVID-19. Thus, emissions from industrial and ...transport sectors were halted during lockdown (LD), which has resulted in a significant reduction of
anthropogenic pollutants. The first two lockdown phases were strictly implemented (phase I and phase II) and hence were considered to be total lockdown
(TLD) in this study. Satellite-based tropospheric columnar nitrogen dioxide (TCN) from the years 2015 to 2020, tropospheric columnar carbon monoxide
(TCC) during 2019/20, and aerosol optical depth (AOD550) from the years 2014 to 2020 during phase I and phase II LD and pre-LD periods
were investigated with observations from Aura OMI, Sentinel-5P TROPOMI, and Aqua and Terra MODIS. To quantify lockdown-induced changes in TCN, TCC, and
AOD550, detailed statistical analysis was performed on de-trended data using the Student paired statistical t test. Results indicate
that mean TCN levels over India showed a dip of 18 % compared to the previous year and also against the 5-year mean TCN levels during the
phase I lockdown, which was found to be statistically significant (p value < 0.05) against the respective period. Furthermore, drastic changes in
TCN levels were observed over hotspots, namely eastern region and urban cities. For example, there was a sharp decrease of 62 % and 54 % in
TCN levels compared to 2019 and against 5-year mean TCN levels over New Delhi with a p value of 0.0002 (which is statistically significant)
during total LD. The TCC levels were high in the northeast (NE) region during the phase I LD period, which is mainly attributed to the active fire
counts in this region. However, lower TCC levels are observed in the same region due to the diminished fire counts during phase II. Further,
AOD550 is reduced over the country by ∼ 16 % (Aqua and Terra) from the 6-year (2014–2019) mean AOD550 levels, with
a significant reduction (Aqua MODIS 28 %) observed over the Indo-Gangetic Plain (IGP) region with a p value of ≪ 0.05. However, an
increase in AOD550 levels (25 % for Terra MODIS, 15 % for Aqua MODIS) was also observed over central India during LD compared to
the preceding year and found significant with a p value of 0.03. This study also reports the rate of change of TCN levels and AOD550
along with statistical metrics during the LD period.
PDF
