16,431 research outputs found
Extractives From Grand Fir [Abies Grandis (DOUGL.) LINDL.] Bark
The neutral fraction of the petroleum-ether-soluble bark extract contains a homologous series of normal alkanes (C19 to C42), free β-sitosterol, behenyl and lignoceryl alcohols, esters of these three compounds with arachidic, behenic, and lignoceric acids, and a major fraction comprising a mixture of behenyl and lignoceryl ferulates. The triterpene lactones cyclograndisolide and epicyclograndisolide are minor components
Radar studies of the planets
The radar measurements phase of the lunar studies involving reflectivity and topographic mapping of the visible lunar surface was ended in December 1972, but studies of the data and production of maps have continued. This work was supported by Manned Spacecraft Center, Houston. Topographic mapping of the equatorial regions of Mars has been carried out during the period of each opposition since that of 1967. The method comprised extended precise traveling time measurements to a small area centered on the subradar point. As measurements continued, planetary motions caused this point to sweep out extensive areas in both latitude and longitude permitting the development of a fairly extensive topographical map in the equatorial region. Radar observations of Mercury and Venus have also been made over the past few years. Refinements of planetary motions, reflectivity maps and determinations of rotation rates have resulted
Autocatalytic plume pinch-off
A localized source of buoyancy flux in a non-reactive fluid medium creates a
plume. The flux can be provided by either heat, a compositional difference
between the fluid comprising the plume and its surroundings, or a combination
of both. For autocatalytic plumes produced by the iodate-arsenous acid
reaction, however, buoyancy is produced along the entire reacting interface
between the plume and its surroundings. Buoyancy production at the moving
interface drives fluid motion, which in turn generates flow that advects the
reaction front. As a consequence of this interplay between fluid flow and
chemical reaction, autocatalytic plumes exhibit a rich dynamics during their
ascent through the reactant medium. One of the more interesting dynamical
features is the production of an accelerating vortical plume head that in
certain cases pinches-off and detaches from the upwelling conduit. After
pinch-off, a new plume head forms in the conduit below, and this can lead to
multiple generations of plume heads for a single plume initiation. We
investigated the pinch-off process using both experimentation and simulation.
Experiments were performed using various concentrations of glycerol, in which
it was found that repeated pinch-off occurs exclusively in a specific
concentration range. Autocatalytic plume simulations revealed that pinch-off is
triggered by the appearance of accelerating flow in the plume conduit.Comment: 10 figures. Accepted for publication in Phys Rev E. See also
http://www.physics.utoronto.ca/nonlinear/papers_chemwave.htm
Mainstreaming of genomic medicine in gastroenterology, present and future: a nationwide survey of UK gastroenterology trainees
Objective: Genomics and personalised medicine are increasingly relevant for patients with gastroenterological conditions. We aim to capture the current state of genomics training in gastroenterology to review current understanding, clinical experience and long-term educational needs of UK trainees. //
Design and setting: A web-based nationwide survey of all UK gastroenterology specialty trainees was conducted in 2017. //
Results: 100 trainees (14% of UK gastroenterology trainees) completed this survey. Only 9% and 16% of respondents believe that their local training programme adequately prepares them for the future clinical practice using genomic medicine and personalised medicine, respectively. Barriers identified include the need for greater trainee education (95%), inadequate clinical guidance to base interventions on the results of genomic testing (53%), concerns over misinterpretation by patients (43%) and overuse/misuse of testing by clinicians (34%).
Survey respondents felt prepared to perform HFE genotyping (98%), assess TPMT status (97%) and interpret HLA subtyping for suspected coeliac disease (85%). However, only a minority felt prepared to perform the following investigations: polyposis screening (34%), hereditary pancreatitis screening (30%), testing for Lynch yndrome (33%) and KRAS testing for colorectal cancer (20%).
Most respondents would support holding dedicated training days on genomic medicine (83%), formal training provisions for the mainstreaming of genomic testing (64%), an update to the UK gastroenterology specialty training curriculum and examinations (57%) and better-defined referral pathways for local genomic services (91%). //
Conclusion: Most gastroenterology trainees in this survey feel ill equipped to practise genomic and personalised medicine as consultants. We propose specific revisions to the UK gastroenterology specialty curriculum that addresses trainees needs
Mainstreaming of genomic medicine in gastroenterology, present and future: a Nationwide Survey of UK Gastroenterology Trainees
Objective: Genomics and personalised medicine are increasingly relevant for patients with gastroenterological conditions. We aim to capture the current state of genomics training in gastroenterology to review current understanding, clinical experience and long-term educational needs of UK trainees.Design & Setting: A web-based nationwide survey of all UK gastroenterology specialty trainees was conducted in 2017.Results: 100 trainees (14% of UK gastroenterology trainees) completed this survey. Only 9% and 16% of respondents believe that their local training programme adequately prepares them for future clinical practice utilising genomic medicine and personalised medicine respectively. Barriers identified include the need for greater trainee education (95%), inadequate clinical guidance to base interventions on the results of genomic testing (53%), concerns over misinterpretation by patients (43%) and overuse/misuse of testing by clinicians (34%).Survey respondents felt prepared to perform HFE genotyping (98%), assess TPMT status (97%), and interpret HLA-subtyping for suspected coeliac disease (85%). However, only a minority felt prepared to perform the following investigations: polyposis screening (34%), hereditary pancreatitis screening (30%), testing for Lynch Syndrome (33%), and KRAS testing for colorectal cancer (20%).Most respondents would support holding dedicated training days on genomic medicine (83%), formal training provisions for the mainstreaming of genomic testing (64%), an update to the UK gastroenterology specialty training curriculum and examinations (57%), and better-defined referral pathways for local genomic services (91%).Conclusion: Most gastroenterology trainees in this survey feel ill-equipped to practice genomic and personalised medicine as consultants. We propose specific revisions to the UK gastroenterology specialty curriculum that address trainees needs
Reactamole: Functional Reactive Molecular Programming
Chemical reaction networks (CRNs) are an important tool for molecular programming, a field that is rapidly expanding our ability to deploy computer programs into biological systems for a variety of applications. However, CRNs are also difficult to work with due to their massively parallel nature, leading to the need for higher-level languages that allow for easier computation with CRNs. Recently, research has been conducted into a variety of higher-level languages for deterministic CRNs but modeling CRN parallelism, managing error accumulation, and finding natural CRN representations are ongoing challenges.
We introduce Reactamole, a higher-level language for deterministic CRNs that utilizes the functional reactive programming (FRP) paradigm to represent CRNs as a reactive dataflow network. Reactamole equates a CRN with a functional reactive program, implementing the key primitives of the FRP paradigm directly as CRNs. The functional nature of Reactamole makes reasoning about molecular programs easier, and its strong static typing allows us to ensure that a CRN is well-formed by virtue of being well-typed. In this paper, we describe the design of Reactamole and how we use CRNs to represent the common datatypes and operations found in FRP. We also demonstrate the potential of this functional reactive approach to molecular programming by giving an extended example where a CRN is constructed using FRP to modulate and demodulate an amplitude modulated signal
Global data for ecology and epidemiology: a novel algorithm for temporal Fourier processing MODIS data
Background. Remotely-sensed environmental data from earth-orbiting satellites are increasingly used to model the distribution and abundance of both plant and animal species, especially those of economic or conservation importance. Time series of data from the MODerate-resolution Imaging Spectroradiometer (MODIS) sensors on-board NASA's Terra and Aqua satellites offer the potential to capture environmental thermal and vegetation seasonality, through temporal Fourier analysis, more accurately than was previously possible using the NOAA Advanced Very High Resolution Radiometer (AVHRR) sensor data. MODIS data are composited over 8- or 16-day time intervals that pose unique problems for temporal Fourier analysis. Applying standard techniques to MODIS data can introduce errors of up to 30% in the estimation of the amplitudes and phases of the Fourier harmonics. Methodology/Principal Findings. We present a novel spline-based algorithm that overcomes the processing problems of composited MODIS data. The algorithm is tested on artificial data generated using randomly selected values of both amplitudes and phases, and provides an accurate estimate of the input variables under all conditions. The algorithm was then applied to produce layers that capture the seasonality in MODIS data for the period from 2001 to 2005. Conclusions/Significance. Global temporal Fourier processed images of 1 km MODIS data for Middle Infrared Reflectance, day- and night-time Land Surface Temperature (LST), Normalised Difference Vegetation Index (NDVI), and Enhanced Vegetation Index (EVI) are presented for ecological and epidemiological applications. The finer spatial and temporal resolution, combined with the greater geolocational and spectral accuracy of the MODIS instruments, compared with previous multi-temporal data sets, mean that these data may be used with greater confidence in species' distribution modelling
Pricing and hedging of Asian options: Quasi-explicit solutions via Malliavin calculus
We use Malliavin calculus and the Clark-Ocone formula to derive the hedging strategy of an arithmetic Asian Call option in general terms. Furthermore we derive an expression for the density of the integral over time of a geometric Brownian motion, which allows us to express hedging strategy and price of the Asian option as an analytic expression. Numerical computations which are based on this expression are provided
Space Climate Manifestation in Earth Prices - from Medieval England Up to Modern Usa
In this study we continue to search for possible manifestations of space
weather influence on prices of agricultural products and consumables. We note
that the connection between solar activity and prices is based on the causal
chain that includes several nonlinear transition elements. These non-linear
elements are characterized by threshold sensitivity to external parameters and
lead to very inhomogeneous local sensitivity of the price to space weather
conditions. It is noted that "soft type" models are the most adequate for
description of this class of connections. Two main observational effects
suitable for testing causal connections of this type of sensitivity are
considered: burst-like price reactions on changes in solar activity and price
asymmetry for selected phases of the sunspot cycle. The connection, discovered
earlier for wheat prices of Medieval England, is examined in this work on the
basis of another 700-year data set of consumable prices in England. Using the
same technique as in the previous part of our work (Pistilnik and Yom Din 2004)
we show that statistical parameters of the interval distributions for price
bursts of consumables basket and for sunspot minimum states are similar one to
another, like it was reported earlier for wheat price bursts. Possible sources
of these consistencies between three different multiyear samples are discussed.
For search of possible manifestations of the "space weather - wheat market"
connection in modern time, we analyze dynamics of wheat prices in the USA in
the twentieth century. We show that the wheat prices revealed a maximum/minimum
price asymmetry consistent with the phases of the sunspot cycle. We discuss
possible explanations of this observed asymmetry, unexpected under conditions
of globalization of the modern wheat market.Comment: First International Symposium on Space Climate: Direct and Indirect
Observations of Long-Term Solar Activity, 20-23 June 2004, Oulu, Finlan
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