8,975 research outputs found
Does measurement technique explain the mismatch between European head size and WHO charts?
Objective To test whether different measuring techniques produce systematic differences in head size that could explain the large head circumferences found in Northern European children compared with the WHO standard.
Design: Cross-sectional observational study.
Setting: Scotland, UK.
Patients: Study 1: 68 healthy children aged 0.4–18 months from mother and baby groups and a medical students teaching session. Study 2: 81 children aged 0.4 to 25 months from hospital wards and neonatal follow-up clinics.
Interventions: Study 1: heads measured with plastic tape using both the WHO tight and UK loose technique. Study 2: heads measured using WHO research technique and a metal measuring tape and compared with routinely acquired measurements.
Main outcome measures: Mean difference in head z-scores using WHO standard between the two methods.
Results: The tight technique resulted in a mean (95% CI) z-score difference of 0.41 (0.27 to 0.54, p<0.001) in study 1 and 0.44 (0.36 to 0.53, p<0.001) in study 2. However, the mean WHO measurements in the healthy infants still produced a mean z-score that was two-third of a centile space (0.54 SD (0.28 to 0.79) p<0.001) above the 50th centile.
Conclusion: The WHO measurement techniques produced significantly lower measures of head size, but average healthy Scottish children still had larger heads than the WHO standard using this method
The use of isotopic carbon in a study of the metabolism of anthanilic acid in Neurospora
The finding by Tatum, Banner, and Beadle (l), that the tryptophanless Neurospora mutant strain 10575 accumulates anthranilic acid, which in turn can be utilized for growth of strain 40008, has provided evidence that anthranilic acid is a biochemical precursor of tryptophan in this organism. It has been further established that indole is an intermediate in this conversion (2-5).
More recent work with a number of mutants of Neurospora (6-8) has established that tryptophan is a biochemical precursor to niacin with kynurenine and hydroxyanthranilic acid as intermediates. The accumulated evidence has indicated the existence in the mold of the following series of reactions:
→ Anthranilic acid → indole → tryptophan → kynurenine → 3-hydroxyanthranilic acid → nicotinic acid
In the light of this evidence the present work was undertaken to trace the carbon in the carboxyl group of anthranilic acid in order to estimate its contribution as a structural unit in the formation of niacin and tryptophan. The organism chosen for this investigation was a biochemical mutant strain of Neurospora designated as strain 40008. This mutant utilizes anthranilic acid, indole, or tryptophan for growth.
The mutant was grown in the presence of anthranilic acid containing Cl4 in the carboxyl group. Niacin and tryptophan were isolated from the mold mycelium and tested for radioactivity
Copper, zinc, silver, and lead concentrations and distributions in mine waste ore at Keystone near Ely, Nevada
This paper investigates the concentrations and distributions of copper (Cu), zinc (Zn), silver (Ag), and lead (Pb) in the Keystone mining waste rock mound. This study employs flame atomic absorption spectrometry for the analysis of ore samples that were totally dissolved, water leaches of ore samples, and dissolved plant material. This study suggests that the Keystone mound contains low grade ore of about 0.08%, or approximately one fifth of the 0.4% established by the mining operations during the 1930s as unprofitable ore. The data show that Cu, Zn and Ag concentrations increase from the top of the mound to the bottom of the mound. The average concentrations are as follows (top and bottom, respectively): Cu - 590 ppm and 920 ppm, Zn - 25 ppm and 75 ppm, Ag - 1.8 ppm and 2.8 ppm. Lead, however, is fairly constant throughout the mound, around 48 ppm. The change in concentration levels for Cu, Zn, and Ag are probably due to natural leaching and past heap leaching during mining activities. The soil pH is acidic with a pH level of 3 to 4 throughout the mound. This low pH has mediated the transport of Cu, Zn, and Ag down the mound. The data for the plants show that the concentration of Cu, Zn, and Ag are elevated in plants growing on the mound
The Albedo Distribution of Near Earth Asteroids
The cryogenic WISE mission in 2010 was extremely sensitive to asteroids and
not biased against detecting dark objects. The albedos of 428 Near Earth
Asteroids (NEAs) observed by WISE during its fully cryogenic mission can be fit
quite well by a 3 parameter function that is the sum of two Rayleigh
distributions. The Rayleigh distribution is zero for negative values, and
follows for positive x. The peak
value is at x=\sigma, so the position and width are tied together. The three
parameters are the fraction of the objects in the dark population, the position
of the dark peak, and the position of the brighter peak. We find that 25.3% of
the NEAs observed by WISE are in a very dark population peaking at , while the other 74.7% of the NEAs seen by WISE are in a moderately dark
population peaking at . A consequence of this bimodal distribution
is that the Congressional mandate to find 90% of all NEAs larger than 140 m
diameter cannot be satisfied by surveying to H=22 mag, since a 140 m diameter
asteroid at the very dark peak has H=23.7 mag, and more than 10% of NEAs are
darker than p_V = 0.03.Comment: 7 pages LaTex, 4 figures, accepted for publication in the
Astronomical Journa
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Control of regioselectivity:oxidation and deprotection
Palladium is a highly versatile metal, capable of catalysing oxidations, reductions and a myriad of organic transformations. The inorganic chemistry of palladium, and the relation of this to the catalytic activity of the metal, is briefly discussed. A short survey of the range of palladiumcatalysed reactions is undertaken.
The Wacker reaction, the palladium(II)-catalysed oxidation of alkenes to carbonyls, is considered in detail. In the absence of heteroatoms, the Wacker reaction of terminal alkenes is known to produce methyl ketones. However, it is shown that the Wacker reaction of styrenes is unusual; under reoxidant-free conditions, the reaction proceeds to give aldehydes as the major products. The scope of this transformation is probed with a series of ring-substituted styrenes: it is found to be general for all substituents studied. The mechanism responsible for this anti-Markovnikov regioselectivity is investigated. Palladium(0) is eliminated as a possible cause of unusual reactivity. NMR studies and reactions of suitable substrates are used to suggest a side-on complex of either an agostic or 4-type. Kinetic studies show no evidence of an agostic interaction, and thus an 4-complex is more likely. Attempts at achieving catalytic activity in the formation of aldehydes are unsuccessful with small-molecule reoxidants. However, the use of heteropolyacids is found to lead to a catalytic reaction. A second source of unexpected regioselectivity in the Wacker reaction is the agostic interaction of hydrogens on the allylic position with the palladium centre. Some new evidence is obtained for this effect in the reaction of 1-phenylbut-1-ene and 1-phenyl-3-methylbut-1-ene. Attempts are made to gain additional insight by seeking a kinetic isotope effect in the Wacker reaction of dec-1-ene and a partially-deuterated analogue. Some evidence of a kinetic isotope effect is found.
The use of benzyl (Bn) groups is one of the most common methods used in synthesis to protect alcohols and amines. The method of choice for the removal of Bn groups is hydrogenolysis over a palladium catalyst. Oxidative deprotection methods are also available, particularly when the MPM (4-methoxybenzyl) group is used in place of Bn. The NAP (2-naphthylmethyl) protective group has recently been introduced and has been shown to be removed by hydrogenolysis more readily than Bn groups. The usefulness of the NAP group is extended: it is demonstrated that NAP is less sensitive to oxidative cleavage with CAN [hexa-amminecerium(IV) nitrate(V)] than MPM. A series of glucose-based substrates are prepared, and used to demonstrate this oxidative selectivity
A comprehensive and absolute corporate sustainability assessment and enhanced input output life cycle assessment
Stresses due to economic activity are threatening to exceed environmental and societal limits with the potential to jeopardize local communities and create global crises. This research proposes new methodologies and analytic techniques to comprehensively assess corporate sustainability and enhance the efficiency of estimating environmental and social impacts with Input Output Life Cycle Assessment (IOLCA).
Sustainability assessments and management require consideration of both social and environmental impacts as outflows of economic activity. There are a number of assessment tools available to gain insight into environmental and social impacts; but in most cases, these approaches lack essential components for a comprehensive and absolute sustainability assessment.
This dissertation proposes a new quantitative method for assessing sustainability across all the interrelationships within multiple domains of sustainability—economic, social, environmental, and potentially others. The comprehensive sustainability target method (CSTM) is a novel extension to an existing environmental burden sustainability technique. CSTM applies the science-based targets and concept of absolute sustainability to social burdensome and beneficial impacts, environmental beneficial impacts, and the interdependencies between the sustainability domains. CSTM is contrasted with an example of the relative assessments that appear in many sustainability disclosures. In addition to science-based targets for environmental burdens, companies should attempt to meet science-based targets for social and beneficial impacts.
Another area of research is focused on IOLCA, a widely used method of estimating environmental impacts based on economic sector level data and analysis. These IOLCA models rely on sector averages and require practitioners to combine impact estimation models to describe specific companies or “custom products”. This research presents a novel extension to environmental input-output modeling that increases the usability and responsiveness of the technique to perform custom product-specific assessments.
This enhancement models direct impacts from emissions (and other stressors) attributable to direct spending on commodities across the economy that cause those impacts. The proposed extension directly calculates the internal impact (II); hence, the model implemented is referred to as the IOLCA-II. The IOLCA-II extension directly produces impact estimates in the categories typically used to manage and report greenhouse gas (GHG) emissions: Scope 1, Scope 2, and Scope 3. In addition to the IOLCA-II enhancement for environmental assessment, selected social impacts are incorporated into the extended model to permit social impact estimation. IOLCA-II impacts are estimated for two scenarios: first, a solar energy application at a university; and second, driverless operation of a long-haul trucking company. The baseline and scenarios are modeled using IOLCA-II and compared to explore the impacts and consequences of the proposed scenarios. These case studies reveal the advantages of using the new methodology and the efficiency of the input-output model results compared to conventional IOLCA hybrid/custom product assessment
Design and Optimization of a Wind Deflector for Round-Nose MD-500 Series Helicopters
This thesis examines the problem experienced by the numerous rotary wing operators whose operations require flight with personnel seated outside the fuselage or with doors off. This investigation is specific to the round nose configured MD-500 series aircraft due to test aircraft availability and the wide range of missions it conducts worldwide. During cruise flight, personnel exposed to the aircraft slipstream are subjected to high wind loads and extreme wind chill effects, compromising their ability to perform required tasks. External passengers also add to the overall helicopter parasite drag, decreasing its performance as well as interfering with the crew through increased noise, wind and turbulence in the cockpit. Prior research indicates that attachment of wind deflectors to the helicopter forward fuselage diverts the wind away from the fuselage, reducing overall parasite drag and slipstream effects on external passengers. The purpose of this investigation is threefold, identification of the structural requirements for airframe integration, design and fabrication of airworthy test deflectors, and evaluation of effects of the devices on external passengers, helicopter performance and pilot interface. Seven full-scale wind deflector configurations were flight tested at airspeeds of 0 to 80 knots. The deflector configured with a sweep angle of 50˚and width of 8 inches with Gurney flap provided for reductions of 52% in external passenger load, 2 psi main rotor torque in 80 knot cruise and significantly less wind, noise and turbulence in the cockpit
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