11,990 research outputs found
Conformal Blocks for Arbitrary Spins in Two Dimensions
Conformal blocks for four point functions for fields with arbitrary spins in
two dimensions are obtained by evaluating an appropriate integral. The results
are just products of hypergeometric functions of the conformally invariant
cross ratios formed from the four complex coordinates. Results for scalars
previously obtained are a special case. Applications to four point functions
involving the energy momentum tensor are discussed.Comment: 7 pages, version 2 extra references and small changes, version 3
small corrections and extra material, version to be publishe
Toward High-Precision Measures of Large-Scale Structure
I review some results of estimation of the power spectrum of density
fluctuations from galaxy redshift surveys and discuss advances that may be
possible with the Sloan Digital Sky Survey. I then examine the realities of
power spectrum estimation in the presence of Galactic extinction, photometric
errors, galaxy evolution, clustering evolution, and uncertainty about the
background cosmology.Comment: 24 pages, including 11 postscript figures. Uses crckapb.sty (included
in submission). To appear in ``Ringberg Workshop on Large-Scale Structure,''
ed D. Hamilton (Kluwer, Amsterdam), p. 39
Physical limits of inference
I show that physical devices that perform observation, prediction, or
recollection share an underlying mathematical structure. I call devices with
that structure "inference devices". I present a set of existence and
impossibility results concerning inference devices. These results hold
independent of the precise physical laws governing our universe. In a limited
sense, the impossibility results establish that Laplace was wrong to claim that
even in a classical, non-chaotic universe the future can be unerringly
predicted, given sufficient knowledge of the present. Alternatively, these
impossibility results can be viewed as a non-quantum mechanical "uncertainty
principle". Next I explore the close connections between the mathematics of
inference devices and of Turing Machines. In particular, the impossibility
results for inference devices are similar to the Halting theorem for TM's.
Furthermore, one can define an analog of Universal TM's (UTM's) for inference
devices. I call those analogs "strong inference devices". I use strong
inference devices to define the "inference complexity" of an inference task,
which is the analog of the Kolmogorov complexity of computing a string. However
no universe can contain more than one strong inference device. So whereas the
Kolmogorov complexity of a string is arbitrary up to specification of the UTM,
there is no such arbitrariness in the inference complexity of an inference
task. I end by discussing the philosophical implications of these results,
e.g., for whether the universe "is" a computer.Comment: 43 pages, updated version of Physica D version, which originally
appeared in 2007 CNLS conference on unconventional computatio
Effects of antenatal betamethasone on preterm human and mouse ductus arteriosus: comparison with baboon data.
BackgroundAlthough studies involving preterm infants ≤34 weeks gestation report a decreased incidence of patent ductus arteriosus after antenatal betamethasone, studies involving younger gestation infants report conflicting results.MethodsWe used preterm baboons, mice, and humans (≤276/7 weeks gestation) to examine betamethasone's effects on ductus gene expression and constriction both in vitro and in vivo.ResultsIn mice, betamethasone increased the sensitivity of the premature ductus to the contractile effects of oxygen without altering the effects of other contractile or vasodilatory stimuli. Betamethasone's effects on oxygen sensitivity could be eliminated by inhibiting endogenous prostaglandin/nitric oxide signaling. In mice and baboons, betamethasone increased the expression of several developmentally regulated genes that mediate oxygen-induced constriction (K+ channels) and inhibit vasodilator signaling (phosphodiesterases). In human infants, betamethasone increased the rate of ductus constriction at all gestational ages. However, in infants born ≤256/7 weeks gestation, betamethasone's contractile effects were only apparent when prostaglandin signaling was inhibited, whereas at 26-27 weeks gestation, betamethasone's contractile effects were apparent even in the absence of prostaglandin inhibitors.ConclusionsWe speculate that betamethasone's contractile effects may be mediated through genes that are developmentally regulated. This could explain why betamethasone's effects vary according to the infant's developmental age at birth
Proboscis Morphology and Its Relationship to Feeding Habits in Noctuid Moths
This study describes proboscis morphology and identifies morphometric differences among five species of noctuid moths with different feeding habits (fruit versus nectar-feeding). Morphological and morphometric parameters were analyzed using scanning electron microscopy and light microscopy. Measurements included: galea height in ten sites from base to tip, total proboscis length, and length of the distal region that contains large sensilla styloconica and / or tearing hooks and erectible barbs. Both morphometric and morphological differences were identified among species within and between feeding guilds, and these results are discussed in light of the feeding habits of each species
Development and Sustainability of Eastern Mediterranean Region and South African National Food Composition Databases
Introduction:
The World Health Organization’s (WHO)-Eastern Mediterranean Region Office (EMRO) aims to reduce the consumption of sugar, fat (saturated fatty acids, trans fatty acids) and salt; and decrease the risk of obesity and non-communicable diseases in the Eastern Mediterranean Region (EMR). To address this Quadram Institute Bioscience is working jointly with WHO-EMRO in providing training and capacity development to national experts, leading to standardized, harmonized, comprehensive, open access Food Composition Data (FCD) to underpin food and nutrition programs and policies in these low- and middle-income countries (LMIC).
Materials and Methods:
By identifying specific regional needs for FCD compilation, detailed training workshops were developed to enable the production of vital high-quality harmonised data in the EMR including: Iran, Iraq, Pakistan, Kuwait, Tunisia, Morocco, Sudan, Egypt, and Jordan. Training on standardized methodologies for food composition and dietary intake methods, biomarkers, analytical methods and FCD tools were provided by experts from UK, Serbia, Portugal and WHO-EMRO, via knowledge exchange workshops and short-term training exchange of researchers.
Results:
A total of 45 FCD expert compilers from 13 countries attended 2 workshops and 3 training exchanges. Knowledge transfer consisted of: value documentation; quality assessment; online food composition data tools; food classification and description of composite dishes; recipe calculation; yield and retention factors; and laboratory food analysis (vitamins A, B1, B2, C, D2, D3 and E, fatty acids, amino acids, minerals, fibre). FCD from 6 countries was standardized using the EuroFIR data template and Theasuri (standardised vocabularies). The final datasets from Iran, Iraq, Pakistan, Kuwait, Tunisia and Morocco were made available via FoodExplorer an innovative interface for FCD which allows users to search information from food composition data simultaneously across many countries.
Discussion:
The use of improved standardized methodologies for food composition and dietary intake will produce robust measurements that will reinforce dietary monitoring and policy in LMIC. The capacity building from this project has led to searchable national food composition data from LMIC being made available as open access form for the first time. WHO-EMRO, is funding further updates of FCD tables in Jordan, Lebanon, Oman, Sudan, Tunisia, Morocco, Pakistan, Iran, Egypt, and UAE, with the focus on identifying TFA, SFA, salt and sugar in addition to micronutrients.Project supported by Global Challenges Research Funds (UK) and Medical Research Council (MR/R019576/1), is grateful to WHO EMRO.info:eu-repo/semantics/publishedVersio
Mikrosfere ropinirol hidroklorida za polagano oslobađanje: Utjecaj procesnih parametara
An emulsion solvent evaporation method was employed to prepare microspheres of ropinirole hydrochloride, a highly water soluble drug, by using ethylcellulose and PEG with the help of 32 full factorial design. The microspheres were made by incorporating the drug in a polar organic solvent, which was emulsified using liquid paraffin as an external oil phase. Effects of various process parameters such as viscosity of the external phase, selection of the internal phase, surfactant selection and selection of stirring speed were studied. Microspheres were evaluated for product yield, encapsulation efficiency and particle size. Various drug/ethylcellulose ratios and PEG concentrations were assayed. In vitro dissolution profiles showed that ethylcellulose microspheres were able to control release of the drug for a period of 12 h.Mikrosfere ropinirol hidroklorida, ljekovite tvari vrlo dobro topljive u vodi, pripravljene su metodom isparavanja otapala, koristeći etilcelulozu i PEG te 32 potpuno faktorijalno dizajniranje. Mikrosfere su pripravljene na sljedeći način: otopina ljekovite tvari u polarnom organskom otapalu emulgirana je s tekućim parafinom kao vanjskom uljnom fazom. Ispitivan je utjecaj različitih procesnih parametara poput viskoznosti vanjske faze, vrste interne faze i površinski aktivne tvari te brzine miješanja. Za pripravljene mikrosfere određeno je iskorištenje, učinkovitost inkapsuliranja i veličina čestica. Isprobavani su različiti odnosi ljekovite tvari i etilceluloze te koncentracija PEG-a. In vitro pokusi su pokazali da je oslobađanje ljekovite tvari kontrolirano tijekom 12 h
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