310 research outputs found
Electron Pair Methods vs. Independent Particle Approximation: Quasiparticle Transformations
Some basic algebraic features of quasiparticle transformations are reviewed. Special nonlinear quasiparticle transformations are introduced leading to the second quantized counterparts of gerninal-type (correlated) wave functions. Algebraic representations of strong and weak orthogonality are discussed, and these issues are generalized to the case of non-orthogonal basis sets leading to the concepts of strong and weak biorthogonaltty
The Representation of the Chemical Bond in Quantum Chemical Calculations
The mathematical representation of chemical bonds in molecules
is discussed. The molecule is viewed as a system of weakly
interacting chemical bonds. The intrabond problems and the
averaged electrostatic interbond interactions are handled at the .
zeroth order, while the small interbond delocalization and dispersion
effects are taken into account on the basis of the perturbation
theory. A special diagrammatic technique is applied for
obtaining delocalization corrections for strictly localized orbitals.
A general second quantized theory is discussed in which the chemical
bonds are identified with two-electron local bond structures
characterized by composite-particle creation operators showing
Bose-type commutation rules. This approach accounts for intrabond
correlation already at the zeroth order
Conformation Analysis in Light of Localization and Delocalization
The role of electron delocalization in conformational effects,
especially in giving rise to barrier forces is discussed in the bond
orbital framework. Using orthogonal bond orbitals, the effects of
through space and through bond delocalization interactions is demonstrated;numerical examples show the predominant role of
through space delocalization. The total energy obtained by strictly
localized orthogonal bond orbitals is shown to be rather independent
of the relative orientations of the bonds. Second order perturbative
delocalization energy corrections are interpreted as bond-
bond pair potentials within the orthogonal basis. On the contrary,
nonorthogonal bond orbitals lead to an energy expression which
is very sensitive to the bond orientations even if one neglects completelyelectron delocalization. The origin of the barriers is discussed
in terms of nonempirical bond-bond pair potentials
Mars Atmospheric and Climatic Survey System
Before Mars can be explored by humans, its extreme climate and environment must be investigated. This can be achieved through the deployment of weather station probes capable of measuring Martian air temperature, atmospheric pressure, relative humidity, and wind speed. The Mars Atmospheric and Climatic Survey System (MACSS) aims to collect this data, allowing predictive models of global climate patterns on Mars to be developed. These models will aid NASA in providing the needed knowledge to prepare for long-term exposure to the conditions on Mars.
The probes are compact and lightweight; they have been designed to withstand Mars’ harsh environment: extreme temperatures, statically-charged dust particles, a thin atmosphere, and intense solar radiation. Considerations of deployment were also made, with the size and weight of each probe allowing for them to be deployed as-needed and as accessories in future missions rather than simultaneously in a single mission.
With regards to components, solar panels are to supply the probes with primary power. Data would be collected by sensors and stored on a solid-state drive. A low-gain antenna would establish communication between the probes, NASA’s Deep Space Network, and Mars’ rovers and orbiters. This data can then be evaluated on Earth, allowing models of Martian climate to be formed. In order to demonstrate the feasibility of MACSS, a mockup was designed, simulating data collection in real time with Earth-equivalent components. With continued collaboration, MACSS and its probes can be further optimized for deployment to and longevity on Mars.https://scholarscompass.vcu.edu/capstone/1202/thumbnail.jp
Intelectuals am Miroslav Krleža's and Woody Allen's films
U radu su uspoređivani životi i likovi intelektualca hrvatskog književnika Miroslava Krleže i američkog redatelja Woodyja Allena. Miroslav Krleža jedan je od najznačajnijih i najcjenjenijih hrvatskih književnika, a Woody Allen je jedan od najcjenjenijih živućih redatelja i komičara na svijetu. Uz sličnosti u životima i djelu navedenih umjetnika, postoje i sličnosti u njihovim likovima intelektualca. Komparativna analiza provedena je uz pomoć reprezentativnih likova iz njihovih najpoznatijih djela.This paper presents comparative analysis of Croatian literate Miroslav Krleža's and American director Woody Allen's lives as well as their intellectuals. Miroslav Krleža is one of the most significant Croatian authors, on the other hand, Woody Allen is one of the world's most respectful living directors. Along with some similarities in they lives and work, there are also similarities between their intellectuals. Comparative analysis is examined and conducted through readings and observing their most notable works
Clinicopathological study of postmenopausal bleeding in a tertiary hospital: a retrospective analysis
Background: Postmenopausal bleeding is bleeding from the genital tract one year after menopause. The incidence is 4-11%. It is one of the cardinal signs of endometrial carcinoma. There is 10% risk of genital cancer and 10% risk of significant pathology and needs evaluation. In majority of them, it is due to benign condition such as endometrial atrophy or polyp. The aim of the present study was to evaluate the endometrial thickness by transvaginal ultrasound and to correlate with the histopathological pattern of the material obtained by hysteroscopic guided biopsy or curettage.Methods: A retrospective analysis of all the patients attending the outpatient department from January 2017 to December 2019 was done. This study was undertaken at M.S. Ramaiah Medical College and Hospitals. All patients with postmenopausal bleeding were evaluated clinically, then they underwent PAP smear, transvaginal ultrasound for endometrial thickness. This was followed by hysteroscopic guided biopsy and curettage. The material obtained was sent for histopathological examination as it is the gold standard for further management.Results: A total of 89 patients were enrolled for the study. The final results revealed atrophic endometrium in 35.95%, hyperplasia without atypia in 20.2%, polyps in 11.2% and endometrial carcinoma in 6.7%.Conclusions: In postmenopausal bleeding assessing endometrial thickness by transvaginal ultrasound is ideal. Hysteroscopy is a simple technique to evaluate the uterine cavity and take biopsy for histopathological examination, which is the gold standard
Analiza djelotvornosti i sigurnosti analgetika za migrenu kod djece na listi osnovnih lijekova Svjetske zdravstvene organizacije : diplomski rad
Uvod: Acetaminofen i ibuprofen su jedini analgetici s Osnovne liste lijekova Svjetske zdravstvene organizacije indicirani za akutne napadaje migrene kod djece. Cilj ovog istraživanja bio je sustavno analizirati randomizirane kontrolirane pokuse (RCTs) i sustavne preglede (SRs) o acetaminofenu i ibuprofenu za liječenje akutnog napada migrene kod djece. Metode: Pretražene su baze podataka MEDLINE, CDSR, DARE i CENTRAL. Dva su autora, neovisno, provjeravali rezultate pretraživanja literature te izvlačili podatke iz uključenih studija. Opisna analiza je provedena. Kvaliteta studija analizirana je korišteći Cochraneovu ljestvicu za procjenu rizika od pristranosti za randomizirane kontrolirane pokuse i AMSTAR ljestvicu za procjenu kvalitete sustavnih pregleda.
Rezultati: Uključena su tri RCTa i 10 sustavnih pregleda. O djelotvornosti acetaminofena pronađen je 1 RCT, ukriženog ustroja. Uključivao je 88 pacijenata podijeljenih u tri skupine koje su primale acetaminofen, ibuprofen ili placebo. Zaključak studije je da su acetaminofen i ibuprofen učinkoviti kod umjerenih do ozbiljnih napada migrene kod djece te da ibuprofen najbolje ublažava bol. Osim te studije još dva RCT-a analizirala su djelotvornost ibuprofena, s ukupno s ukupno 201 djece. Sve studije zaključuju da je ibuprofen djelotvoran. Deset sustavnih pregleda analizirali su razne terapije za liječenje migrene kod djece, a objavljeni su između 2004. i 2015. godine. Uključenje pronađenih RCT-ova bilo je varijabilno u tim sustavnim pregledima. Kvaliteta pronađenih dokaza procijenjena je kao srednje do niska. Zaključak: Do sada je objavljen samo jedan randomizirani kontrolirani pokus o acetaminofenu, a tri o ibuprofenu za akutne napade migrene kod djece. Istraživanja su nezadovoljavajuće kvalitete i u njih je bio uključen mali broj djece. Dokazi o djelotvornosti acetaminofena i ibuprofena kao terapije za akutne migrenske napadaje kod djece su slabi stoga je upitna opravdanost uključivanja paracetamola i ibuprofena na SZO EML kao antimigrenika za djecu.Background: Acetaminophen and ibuprofen were the only analgesic indicated on the World Health Organization Essential Medicines List (WHO EML) as antimigraine medicines for acute attacks in children. The aim of this study was to systematically analyze randomized controlled trials (RCTs) and systematic reviews (SRs) about acetaminophen and ibuprofen for treatment of acute migraine attack in children.
Methods: Databases MEDLINE, CDSR, DARE and CENTRAL were searched. Two
reviewers independently screened literature search results and extracted data from included studies. Descriptive analysis was conducted. Quality of studies was analyzed using Cochrane risk of bias tool for RCTs and AMSTAR for SRs.
Results: Three RCT and 10 systematic reviews were included. The only RCT that was found about acetaminophen had a cross-over design and included 88 children, divided into three groups that received paracetamol, ibuprofen or placebo. Study concluded that both paracetamol and ibuprofen were effective treatments for severe of moderate migraine attacks in children, and that ibuprofen gave the best relief. This one RCT and two more RCTs analyzed ibuprofen, with a total of 201 children included in all 3. Conclusion of all was that ibuprofen is effective medication for migraine in children. The 10 SRs analyzed various therapies for migraine in children, and were published between 2004 and 2015. Inclusion of the 3 RCT varied in those systematic reviews. Quality of evidence was medium to low. Conclusion: Only one RCT about paracetamol and 3 RCTs about ibuprofen for migraine attacks for children have been published thus far; they included small number of children and studies were of questionable quality. Evidence-base for effectiveness of acetaminophen and paracetamol as treatments for migraine attacks in children is weak and inclusion of acetaminophen and ibuprofen as antimigraine medicine for children in the WHO EML is questionable
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