4,991 research outputs found
Electronic structure induced reconstruction and magnetic ordering at the LaAlOSrTiO interface
Using local density approximation (LDA) calculations we predict
GdFeO-like rotation of TiO octahedra at the -type interface between
LaAlO and SrTiO. The narrowing of the Ti bandwidth which results
means that for very modest values of , LDA calculations predict charge
and spin ordering at the interface. Recent experimental evidence for magnetic
interface ordering may be understood in terms of the close proximity of an
antiferromagnetic insulating ground state to a ferromagnetic metallic excited
state
Defining the Costs of an Outbreak of Karnal Bunt of Wheat
In determining the economic impact of a possible outbreak of the quarantinable wheat disease Karnal Bunt, an examination was made of the detailed components of the costs involved. The costs were classified as: (a) Direct costs (yield and quality losses); (b) Reaction costs (export bans, quality down-grading, seed industry costs); and (c) Control costs (quarantine zones, fungicides, spore destruction). The relative importance of each of these cost components is measured for a hypothetical outbreak of Karnal Bunt in the European Union, as a means of ensuring that the policy responses to such an outbreak are appropriate considering the costs involved.disease, quarantine, cost, wheat, Agricultural and Food Policy, Crop Production/Industries,
A unified first-principles study of Gilbert damping, spin-flip diffusion and resistivity in transition metal alloys
Using a formulation of first-principles scattering theory that includes
disorder and spin-orbit coupling on an equal footing, we calculate the
resistivity , spin flip diffusion length and the Gilbert damping
parameter for NiFe substitutional alloys as a function of
. For the technologically important NiFe alloy, permalloy, we
calculate values of Ohm-cm, nm,
and compared to experimental low-temperature values
in the range Ohm-cm for , nm for , and
for indicating that the theoretical formalism captures
the most important contributions to these parameters.Comment: Published in Physical Review Letter
SKS Splitting beneath Southern California
Measurements of SKS phase splitting were obtained from nineteen seismic stations in southern California. The fast polarization directions are 53° at the southern end of the Great Valley, 82 ± 8° in the western Transverse Ranges and northern Peninsular Ranges, 95 ± 4° in Mojave Desert, and 70° on San Clemente Island. The splitting time ranges from 0.8 to 1.8 seconds, which is consistent with an anisotropic layer of 100 to 200 km thick for 4% anisotropy
Enhancing CHO cell productivity through the stable depletion of microRNA-23
The Chinese hamster ovary cell (CHO) has been the “work horse” of the biopharmaceutical industry for the past 2 decades. Their preeminent position is due to their genetic tractability and capacity to produce high quality recombinant proteins with human-like post-translational modifications. Productivity limitations, however, have stimulated the application of various optimisation strategies to further improve therapeutic product yields. Despite the marked improvements in bioprocess design and media formulation, enhanced CHO cell performance is by no means routine. microRNAs (miRNAs) offer an attractive alternative to genetic engineering using a protein-coding gene due to their ability to regulate multiple molecular networks simultaneously in addition to reducing the cells translational burden.
Our lab identified various miRNAs whose expression was closely correlated with CHO cell growth rate including the oncogenic miR-17~92 cluster and the ribosome-enhancing miR-10a, as well as various growth-associated miRNAs such as miR-30e, miR-206, miR-451 and miR-639. Transient characterisation of a set of these candidates revealed several to negatively regulate growth and apoptosis such as miR-34a/34a* and miR-23b*; positively influence growth including miR-15a-16-1 and miR-532-5p and potentially enhance specific productivity in the case of miR-200a. CHO clones with enhanced growth attributes could achieve high cell densities early in culture prior to the induction of a temperature-shift, a process control strategy commonly used to enhance specific productivity but often at the cost of growth.
A common trade-off for enhanced growth is often the reduction in CHO cell specific productivity. Stable depletion of miR-23, implicated in B-cell differentiation, using a miR-sponge decoy was observed to enhance recombinant protein yield by ~3-fold without influencing CHO-SEAP cell growth in batch culture. Interestingly, these high producing clones also demonstrated a ~30% increase in oxidative metabolism, an energy state previously associated with productivity. The mitochondrial electron transport system components, Complex I and II, were observed to be responsible for this enhanced energy provision. Proteomic analysis identified potential targets of miR-23 involved in the TCA cycle e.g. IDH1 and MDHA/B and related to mitochondrial function e.g. LETM1.
Process adaptation to complement inherent clonal attributes can be exploited to enhance production yields as evident in the case of a miR-23b*-depleted clone achieving a 50% improved SEAP yield in a fed-batch culture with temperature shift (31°C). Exploiting the role of miRNAs in the regulation of bioprocess-related phenotypes (e.g. miR-34a and its role in antibody fucosylation) highlights the versatility of these small molecules for industrial application, a prospect further explored within this thesis
Indications of a sub-linear and non-universal Kennicutt-Schmidt relationship
We estimate the parameters of the Kennicutt-Schmidt (KS) relationship,
linking the star formation rate (Sigma_SFR) to the molecular gas surface
density (Sigma_mol), in the STING sample of nearby disk galaxies using a
hierarchical Bayesian method. This method rigorously treats measurement
uncertainties, and provides accurate parameter estimates for both individual
galaxies and the entire population. Assuming standard conversion factors to
estimate Sigma_SFR and Sigma_mol from the observations, we find that the KS
parameters vary between galaxies, indicating that no universal relationship
holds for all galaxies. The KS slope of the whole population is 0.76, with the
2sigma range extending from 0.58 to 0.94. These results imply that the
molecular gas depletion time is not constant, but varies from galaxy to galaxy,
and increases with the molecular gas surface density. Therefore, other galactic
properties besides just Sigma_mol affect Sigma_SFR, such as the gas fraction or
stellar mass. The non-universality of the KS relationship indicates that a
comprehensive theory of star formation must take into account additional
physical processes that may vary from galaxy to galaxy.Comment: 7 pages, 2 figures, 1 table. Updated to match MNRAS accepted versio
First-principles calculations of magnetization relaxation in pure Fe, Co, and Ni with frozen thermal lattice disorder
The effect of the electron-phonon interaction on magnetization relaxation is
studied within the framework of first-principles scattering theory for Fe, Co,
and Ni by displacing atoms in the scattering region randomly with a thermal
distribution. This "frozen thermal lattice disorder" approach reproduces the
non-monotonic damping behaviour observed in ferromagnetic resonance
measurements and yields reasonable quantitative agreement between calculated
and experimental values. It can be readily applied to alloys and easily
extended by determining the atomic displacements from ab initio phonon spectra
Comparing attitudes about legal sanctions and teratogenic effects for cocaine, alcohol, tobacco and caffeine: A randomized, independent samples design
BACKGROUND: Establishing more sensible measures to treat cocaine-addicted mothers and their children is essential for improving U.S. drug policy. Favorable post-natal environments have moderated potential deleterious prenatal effects. However, since cocaine is an illicit substance having long been demonized, we hypothesized that attitudes toward prenatal cocaine exposure would be more negative than for licit substances, alcohol, nicotine and caffeine. Further, media portrayals about long-term outcomes were hypothesized to influence viewers' attitudes, measured immediately post-viewing. Reducing popular crack baby stigmas could influence future policy decisions by legislators. In Study 1, 336 participants were randomly assigned to 1 of 4 conditions describing hypothetical legal sanction scenarios for pregnant women using cocaine, alcohol, nicotine or caffeine. Participants rated legal sanctions against pregnant women who used one of these substances and risk potential for developing children. In Study 2, 139 participants were randomly assigned to positive, neutral and negative media conditions. Immediately post-viewing, participants rated prenatal cocaine-exposed or non-exposed teens for their academic performance and risk for problems at age18. RESULTS: Participants in Study 1 imposed significantly greater legal sanctions for cocaine, perceiving prenatal cocaine exposure as more harmful than alcohol, nicotine or caffeine. A one-way ANOVA for independent samples showed significant differences, beyond .0001. Post-hoc Sheffe test illustrated that cocaine was rated differently from other substances. In Study 2, a one-way ANOVA for independent samples was performed on difference scores for the positive, neutral or negative media conditions about prenatal cocaine exposure. Participants in the neutral and negative media conditions estimated significantly lower grade point averages and more problems for the teen with prenatal cocaine exposure than for the non-exposed teen beyond .0001 alpha level. The positive media program closed estimated grade point average differences and risks of later problems to a non-statistically significant margin, p >.05. CONCLUSION: Ratings for prenatal cocaine were more negative than comparable ratings for alcohol, nicotine or caffeine exposure. Stereotypes can be reduced, showing viewers that positive postnatal environments ameliorate potential teratogenic effects of cocaine. Reducing negative stereotypes for crack babies may be a requisite for substantive changes in current policy
The Genome Sequence of the Metal-Mobilizing, Extremely Thermoacidophilic Archaeon \u3ci\u3eMetallosphaera sedula\u3c/i\u3e Provides Insights into Bioleaching-Associated Metabolism
Despite their taxonomic description, not all members of the order Sulfolobales are capable of oxidizing
reduced sulfur species, which, in addition to iron oxidation, is a desirable trait of biomining microorganisms.
However, the complete genome sequence of the extremely thermoacidophilic archaeon Metallosphaera sedula
DSM 5348 (2.2 Mb, _2,300 open reading frames [ORFs]) provides insights into biologically catalyzed metal
sulfide oxidation. Comparative genomics was used to identify pathways and proteins involved (directly or
indirectly) with bioleaching. As expected, the M. sedula genome contains genes related to autotrophic carbon
fixation, metal tolerance, and adhesion. Also, terminal oxidase cluster organization indicates the presence of
hybrid quinol-cytochrome oxidase complexes. Comparisons with the mesophilic biomining bacterium Acidithiobacillus
ferrooxidans ATCC 23270 indicate that the M. sedula genome encodes at least one putative rusticyanin,
involved in iron oxidation, and a putative tetrathionate hydrolase, implicated in sulfur oxidation. The
fox gene cluster, involved in iron oxidation in the thermoacidophilic archaeon Sulfolobus metallicus, was also
identified. These iron- and sulfur-oxidizing components are missing from genomes of nonleaching members of
the Sulfolobales, such as Sulfolobus solfataricus P2 and Sulfolobus acidocaldarius DSM 639. Whole-genome
transcriptional response analysis showed that 88 ORFs were up-regulated twofold or more in M. sedula upon
addition of ferrous sulfate to yeast extract-based medium; these included genes for components of terminal
oxidase clusters predicted to be involved with iron oxidation, as well as genes predicted to be involved with
sulfur metabolism. Many hypothetical proteins were also differentially transcribed, indicating that aspects of
the iron and sulfur metabolism of M. sedula remain to be identified and characterized
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