Structures and Electronic States of Nickel Rich Oxides for Lithium Ion Batteries

A new superstructure of layered pristine LiNiO2 (LNO) was obtained optimizing a large supercell of the 166 space group, the one observed experimentally by XRD, and relaxing both cell parameters and internal positions. The crystal structure shows size and charge disproportionation of the NiO6 octahedra instead of the Jahn-Teller distortion. The decrease of the internal energy obtained with the structural optimization of the supercell relative to the same structure in its primitive unit cell is much larger than the one obtained by relaxing similarly dimensioned supercells of monoclinic symmetry relative to their primitive unit cells, although the monoclinic phase remains more stable. The Ni-O bond length distribution of the new structure agree well with the experiments. Our results show that the choice of the simulation cell is important for determining the energetics of this class of oxide materials, proposed for cathodes in lithium ion batteries (LIBs). We used this new structure as a template for the study of the structural and electronic changes induced by the delithiation and Mn for Ni cation substitution, originating the solid solutions LiNiyMn(1-y)O2 (LNMO). Our results, surprisingly, agree well with the existing experiments and explain observed trends better than previous studies.Comment: Preprin

Structures and electronic states of nickel-rich oxides for lithium ion batteries

A new superstructure of layered pristine LiNiO2 (LNO) was obtained by first replicating 16 times the optimized structure of the 12-atom primitive cell of the R3m space group and then relaxing both cell parameters and internal positions. The structural optimization is accompanied by a very significant lowering of the internal energy. The R3m space group is the space group observed experimentally by XRD. In contrast to the structure commonly proposed in the literature, this new crystal structure, which still belongs to the R3m space group, shows size and charge disproportionation of the NiO6 octahedra. The charge disproportionation results in a change in the Ni oxidation state from Ni3+ calculated in the 12-atom primitive unit cell, to Ni4+ and almost Ni2+. This is the first time that such charge disproportionation has been calculated for the R3m crystal structure of LNO. The Ni-O bond length distribution of the new structure agrees well with experimental values. Our results show that the choice of the simulation unit cell is important for determining the energetics of this class of oxide material, proposed for cathodes in lithium ion batteries (LIBs). We used this new structure as a template for the study of the structural and electronic changes induced by delithiation and by Mn for Ni cation substitution, originating the solid solutions LiNiyMn(1-y)O2 (LNMO). Our results, surprisingly, agree well with existing experiments and explain observed trends better than previous studies.Correct atomistic models of LNO and LNMO (N = Nickel, M = Manganese) oxide materials are critical for a correct prediction of the charging and discharging behavior of Li-ion batteries with NMC cathodes

An Evidence-based Review: Efficacy of Safety Helmets in the Reduction of Head Injuries in Recreational Skiers and Snowboarders

BACKGROUND: Approximately 600,000 ski- and snowboarding-related injuries occur in North America each year, with head injuries accounting for up to 20% of all injuries. Currently, there are no major institutional recommendations regarding helmet use for skiers and snowboaders in the United States, in part owing to previous conflicting evidence regarding their efficacy. The objective of this review was to evaluate existing evidence on the efficacy of safety helmets during skiing and snowboarding, particularly in regard to head injuries, neck and cervical spine injuries, and risk compensation behaviors. These data will then be used for potential recommendations regarding helmet use during alpine winter sports. METHODS: The PubMed, Cochrane Library, and EMBASE databases were searched using the search string helmet OR head protective devices AND (skiing OR snowboarding OR skier OR snowboarder) for articles on human participants of all ages published between January 1980 and April 2011. The search yielded 83, 0, and 96 results in PubMed, Cochrane Library, and EMBASE, respectively. Studies published in English describing the analysis of original data on helmet use in relation to outcomes of interest, including death, head injury, severity of head injury, neck or cervical spine injury, and risk compensation behavior, were selected. Sixteen published studies met a priori inclusion criteria and were reviewed in detail by authors. RESULTS: Level I recommendation is that all recreational skiers and snowboarders should wear safety helmets to reduce the incidence and severity of head injury during these sports. Level II recommendation/observation is that helmets do not seem to increase risk compensation behavior, neck injuries, or cervical spine injuries among skiers and snowboarders. Policies and interventions to increase helmet use should be promoted to reduce mortality and head injury among skiers and snowboarders. CONCLUSION: Safety helmets clearly decrease the risk and severity of head injuries in skiing and snowboarding and do not seem to increase the risk of neck injury, cervical spine injury, or risk compensation behavior. Helmets are strongly recommended during recreational skiing and snowboarding

CONTROLLED DELIVERY OF ANTIRETROVIRAL DRUG-LOADED CROSS-LINKED MICROSPHERES BY IONIC GELATION METHOD

Objective: Lamivudine (LVD) is a nucleoside reverse transcriptase inhibitor originally developed as an antiretroviral drug and primarily used in thetreatment of most common chronic disease of the planet, acquired immune deficiency syndrome and hepatitis B. The main objective of the study is todevelop controlled drug delivery system to increase the efficacy of antiretroviral drug, LVD against human immunodeficiency virus infections.Methods: The microencapsulation of LVD in gelatin microspheres was carried out by cross-linking process with glutaraldehyde saturated tolueneusing ionic-gelation method. The prepared microspheres were evaluated for particle size analysis, % yield value, % drug content, drug entrapmentefficiency, scanning electron microscopy for surface morphology, swelling index, accelerated stability studies, Fourier transform infrared radiationspectroscopy (FT-IR) and differential scanning calorimetry (DSC) for polymer drug compatibility, in vitro dissolution efficiency and release kineticstudies.Results: The obtained microspheres showed very smooth surface and exhibited regular spherical geometry due to higher crosslinking density. FT-IRand DSC revealed the absence of drug polymer interactions. The percentage yield, entrapment efficiency and drug content for F6 LVD microsphereswas found to be 79.31%, 65.55% and 96.25% respectively. The particle size was ranged from 34.61% to 51.45 μm sizes and in vitro release profileshowed that cross-linking density of gelatin microspheres effectively controlled the release of LVD.Conclusion: The findings of our investigation demonstrated that F6 of gelatin-LVD microspheres had good controlled release profile with maximumentrapment efficiency and prolonged drug release for 24 hrs or longer and this formulation would be capable of overcoming the drawbacks andlimitations of LVD conventional dosage forms.Keywords: Lamivudine, Microspheres, Controlled release, Gelatin, Fourier transform infrared, Differential scanning calorimetry, In vitro releasekinetics

Razvoj normaliziranog indeksa tla za urbane studije upotrebom podataka daljinskih mjerenja

This paper presents two novel spectral soil area indices to identify bare soil area and distinguish it more accurately from the urban impervious surface area (ISA). This study designs these indices based on medium spatial resolution remote sensing data from Landsat 8 OLI dataset. Extracting bare soil or urban ISA is more challenging than extracting water bodies or vegetation in multispectral Remote Sensing (RS). Bare soil and the urban ISA area often were mixed because of their spectral similarity in multispectral sensors. This study proposes Normalized Soil Area Index 1 (NSAI1) and Normalized Soil Area Index 2 (NSAI2) using typical multispectral bands. Experiments show that these two indices have an overall accuracy of around 90%. The spectral similarity index (SDI) shows these two indices have higher separability between soil area and ISA than previous indices. The result shows that percentile thresholds can effectively classify bare soil areas from the background. The combined use of both indices measured the soil area of the study area over 71 km2. Most importantly, proposed soil indices can refine urban ISA measurement accuracy in spatiotemporal studies.Ovaj rad prikazuje dva nova spektralna indeksa tla kako bi se identificiralo golo tlo te kako bi se bolje razlikovalo od urbanih nepropusnih površina (ISA). Ti indeksi su definirani na temelju srednje prostorne rezolucije daljinskih podataka Landsat 8 OLI skupa podataka. U multispektralnim daljinskim mjerenjima (RS) prepoznavanje golog tla ili urbane ISA podloge je složenije od prepoznavanja vodenih tijela ili podloge s vegetacijom. Zbog sličnosti spektara dobivenih multispektralnim senzorima golo tlo i urbana ISA površina često se ne razlučuju. Ova studija predlaže dva normalizirana indeksa tla (NSAI1 i NSAI2) korištenjem tipičnih multispektralnih pojaseva. Eksperimenti pokazuju da ta dva indeksa imaju sveukupnu točnost od približno 90%. Indeks spektralne sličnosti (SDI) pokazuje da ta dva indeksa razlikuju golo tlo od urbane ISA podloge bolje nego dosadašnji indeksi. Rezultati pokazuju da percentilni pragovi mogu efikasno razlučiti površine s golim tlom od pozadine. Kombiniranom upotrebom oba indeksa izmjerena je površina tla veća od 71 km2. Najznačajniji rezultat je taj da predloženi indeksi tla mogu poboljšati točnost mjerenja urbanih ISA u u prostorno-vremenskim studijama

Prescribing patterns for upper respiratory tract infections : a prescription-review of primary care practice in Kedah, Malaysia and the implications

Introduction and aims: It is necessary to ascertain current prescribing of antibiotics for upper respiratory tract infections (URTIs) to address potential overuse. A retrospective analysis was conducted of all prescriptions for URTIs among ten public primary healthcare centres in Kedah, Malaysia from 1st January to 31st March 2014. Results: A total of 123,524 prescriptions were screened and analysed. Of these, 7129 prescriptions were for URTI, with 31.8% (n=2269) containing antibiotics. Macrolides were the most commonly prescribed antibiotic constituting 61% (n=1403) of total antibiotics prescribed. There was a statistically significant association between different prescribers and diagnoses (p=0•001) and a weak positive trend suggesting family medicine specialists are more competent in antibiotic prescribing, followed by medical officers and assistant medical officers (τ=0•122).. Conclusions: Prescribing practices of some prescribers were inconsistent with current guidelines encouraging resistance development. National antimicrobial stewardship programmes and further educational initiatives are ongoing in Malaysia to improve antibiotic us

Relationship between Stock Market Volatility, Stock Market Liquidity and Financial Performance of Non-Financial Firms Listed on Pakistan Stock Exchange

This paper analyzed the empirical relationship between different measures of stock market volatility, traded volume, market and accounting measures of financial performance of 260 firms panel data listed on Pakistan Stock Exchange using Generalized Autoregressive Conditional heteroskedasticity (GARCH) and Generalized moments methods (GMM). The study found that financial performance has significant positive relation with traded volume and significant negative relationship with stock market volatility both in two measures. The study used both microeconomic and macroeconomic measures to calculate stock market volatility and both measures have significant effects on financial performance

Unusual Case of Pump Thrombosis in LVAD Patient with COVID-19 — Diagnostic Challenges

We present the first reported case of left ventricular assist device (LVAD) pump thrombosis in the setting of the coronavirus pandemic. We describe the clinical features of the case which helped to differentiate coronavirus disease 19 (COVID-19) from LVAD pump thrombosis. The patient is 56-year-old female supported by destination LVAD therapy. She was originally implanted with a HeartMate II device in 2015 and underwent two pump exchanges in 2017 and 2019 for pump thrombosis, despite medication adherence. Shortly after routine lab work revealed near doubling of her lactate dehydrogenase (LDH) levels, she tested positive for COVID-19. She then developed power spikes and symptomatic heart failure, which prompted hospital admission. An initial computed tomography (CT) scan showed bilateral ground glass opacities, but repeat testing was negative for COVID-19. Her LVAD pump thrombosis was treated with aspirin, unfractionated heparin, and cangrelor, which was guided by thromboelastogram. Over several weeks, her LDH returned to baseline, and she was transitioned from cangrelor to ticagrelor and from heparin to warfarin. A repeat CT scan after several days of IV diuresis showed resolution of the ground glass opacities