399 research outputs found
An in vitro anatomic model of the human cerebral arteries with saccular arterial aneurysms
Summary: Anin vitro model of the main human cerebral arteries with or without saccular arterial aneurysms is presented. A cast of the cerebral arteries was obtained in a human specimen. Three aneurysms were simulated and added to the cast. Wax copies of the cast were produced, and embedded with liquid resin solidifying into solid blocks. After evacuation of the wax, a model consisting of a hollow reproduction of the cast within the resin block was obtained. The model is reproducible and anatomically accurate. Since it is transparent to visible light, and compatible with x-ray, magnetic resonance and transcranial doppler techniques, it should prove useful for a wide range of haemodynamic and radiologic investigations. The reported technique may be adapted to any structure with a hollow configuration, allowing for the preparation of arterial and venous models from other vascular areas, as well as models from other anatomic systems, such as the biliary or urinary tract
The Brazilian ethanol industry: an overview of its production, technology, location, land use, regulations, and futures prospects.
Brazilian ethanol has been used as biofuel since the 1970s, and currently is replacing approximately 40% of the gasoline that would be otherwise consumed in the country. Domestic demand for Brazilian ethanol is increasing as well as its exports since the biofuels are being promoted by governments around the world as an alternative to fossil fuel. In this context, the main objective of this paper is to do a descriptive and exploratory analysis of the Brazilian ethanol production system and the potential of biofuels in Brazil. We overview the recent developments in the ethanol industry with regard to ethanol technologies in Brazil (including new varieties, transgenic varieties, cellulosic technology), and the role of the Brazilian Agricultural Research Corporation (EMBRAPA) research in this area. We examine the government promoting policies and their impacts on land use such as the increase across time and space in sugar cane area planted in the states of São Paulo, Paraná, Minas Gerais, Goiás and Mato Grosso do Sul (the main producers) and its consequences for other crops in these producing areas and for food security
CCD and photon-counting photometric observations of asteroids carried out at Padova and Catania observatories
We present the results of observational campaigns of asteroids performed at
Asiago Station of Padova Astronomical Observatory and at M.G. Fracastoro
Station of Catania Astrophysical Observatory, as part of the large research
programme on Solar System minor bodies undertaken since 1979 at the Physics and
Astronomy Department of Catania University. Photometric observations of six
Main-Belt asteroids (27 Euterpe, 173 Ino, 182 Elsa, 539 Pamina, 849 Ara, and
984 Gretia), one Hungaria (1727 Mette), and two Near-Earth Objects (3199
Nefertiti and 2004 UE) are reported. The first determination of the synodic
rotational period of 2004 UE was obtained. For 182 Elsa and 1727 Mette the
derived synodic period of 80.23+/-0.08 h and 2.981+/-0.001 h, respectively,
represents a significant improvement on the previously published values. For
182 Elsa the first determination of the H-G magnitude relation is also
presented.Comment: 19 pages, 11 figures, accepted for publication in Planetary and Space
Scienc
The binary near-Earth asteroid (175706) 1996 FG3 - An observational constraint on its orbital evolution
Using our photometric observations taken between 1996 and 2013 and other
published data, we derived properties of the binary near-Earth asteroid
(175706) 1996 FG3 including new measurements constraining evolution of the
mutual orbit with potential consequences for the entire binary asteroid
population. We also refined previously determined values of parameters of both
components, making 1996 FG3 one of the most well understood binary asteroid
systems. We determined the orbital vector with a substantially greater accuracy
than before and we also placed constraints on a stability of the orbit.
Specifically, the ecliptic longitude and latitude of the orbital pole are
266{\deg} and -83{\deg}, respectively, with the mean radius of the uncertainty
area of 4{\deg}, and the orbital period is 16.1508 +/- 0.0002 h (all quoted
uncertainties correspond to 3sigma). We looked for a quadratic drift of the
mean anomaly of the satellite and obtained a value of 0.04 +/- 0.20 deg/yr^2,
i.e., consistent with zero. The drift is substantially lower than predicted by
the pure binary YORP (BYORP) theory of McMahon and Scheeres (McMahon, J.,
Scheeres, D. [2010]. Icarus 209, 494-509) and it is consistent with the theory
of an equilibrium between BYORP and tidal torques for synchronous binary
asteroids as proposed by Jacobson and Scheeres (Jacobson, S.A., Scheeres, D.
[2011]. ApJ Letters, 736, L19). Based on the assumption of equilibrium, we
derived a ratio of the quality factor and tidal Love number of Q/k = 2.4 x 10^5
uncertain by a factor of five. We also derived a product of the rigidity and
quality factor of mu Q = 1.3 x 10^7 Pa using the theory that assumes an elastic
response of the asteroid material to the tidal forces. This very low value
indicates that the primary of 1996 FG3 is a 'rubble pile', and it also calls
for a re-thinking of the tidal energy dissipation in close asteroid binary
systems.Comment: Many changes based on referees comment
Why Agricultural Technological Transfers to Developing Countries Should be Deregulated
Formation of asteroid pairs by rotational fission
Asteroid pairs sharing similar heliocentric orbits were found recently.
Backward integrations of their orbits indicated that they separated gently with
low relative velocities, but did not provide additional insight into their
formation mechanism. A previously hypothesized rotational fission process4 may
explain their formation - critical predictions are that the mass ratios are
less than about 0.2 and, as the mass ratio approaches this upper limit, the
spin period of the larger body becomes long. Here we report photometric
observations of a sample of asteroid pairs revealing that primaries of pairs
with mass ratios much less than 0.2 rotate rapidly, near their critical fission
frequency. As the mass ratio approaches 0.2, the primary period grows long.
This occurs as the total energy of the system approaches zero requiring the
asteroid pair to extract an increasing fraction of energy from the primary's
spin in order to escape. We do not find asteroid pairs with mass ratios larger
than 0.2. Rotationally fissioned systems beyond this limit have insufficient
energy to disrupt. We conclude that asteroid pairs are formed by the rotational
fission of a parent asteroid into a proto-binary system which subsequently
disrupts under its own internal system dynamics soon after formation.Comment: 12 pages, 2 figures, 1 table + Supplementary Informatio
Production efficiency of the bacterial non-ribosomal peptide indigoidine relies on the respiratory metabolic state in <i>S. cerevisiae</i>
Abstract Background Beyond pathway engineering, the metabolic state of the production host is critical in maintaining the efficiency of cellular production. The biotechnologically important yeast Saccharomyces cerevisiae adjusts its energy metabolism based on the availability of oxygen and carbon sources. This transition between respiratory and non-respiratory metabolic state is accompanied by substantial modifications of central carbon metabolism, which impact the efficiency of metabolic pathways and the corresponding final product titers. Non-ribosomal peptide synthetases (NRPS) are an important class of biocatalysts that provide access to a wide array of secondary metabolites. Indigoidine, a blue pigment, is a representative NRP that is valuable by itself as a renewably produced pigment. Results Saccharomyces cerevisiae was engineered to express a bacterial NRPS that converts glutamine to indigoidine. We characterize carbon source use and production dynamics, and demonstrate that indigoidine is solely produced during respiratory cell growth. Production of indigoidine is abolished during non-respiratory growth even under aerobic conditions. By promoting respiratory conditions via controlled feeding, we scaled the production to a 2Â L bioreactor scale, reaching a maximum titer of 980Â mg/L. Conclusions This study represents the first use of the Streptomyces lavendulae NRPS (BpsA) in a fungal host and its scale-up. The final product indigoidine is linked to the activity of the TCA cycle and serves as a reporter for the respiratory state of S. cerevisiae. Our approach can be broadly applied to investigate diversion of flux from central carbon metabolism for NRPS and other heterologous pathway engineering, or to follow a population switch between respiratory and non-respiratory modes
GMOs: Non-Health Issues
The controversy over genetically modified [GM] organisms is often framed in terms of possible hazards for human health. Articles in a previous volume of this *Encyclopedia* give a general overview of GM crops [@Mulvaney2014] and specifically examine human health [@Nordgard2014] and labeling [@Bruton2014] issues surrounding GM organisms. This article explores several other aspects of the controversy: environmental concerns, political and legal disputes, and the aim of "feeding the world" and promoting food security. Rather than discussing abstract, hypothetical GM organisms, this article explores the consequences of the GM organisms that have actually been deployed in the particular contexts that they have been deployed, on the belief that there is little point in discussing GM organisms in an idealized or context-independent way
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