4,654 research outputs found
Channeling of electrons and positrons in straight and periodically bent diamond(110) crystals
In this paper we present the results of a systematic numerical analysis of
the channeling properties of electrons and positrons in oriented straight and
periodically bent diamond(110) crystals. We analyse dependence of the intensity
of the radiation emitted on the projectile energy as well as on the bending
amplitude. The analysis presented is based on the grounds of accurate numerical
simulations of the channeling process. The simulation parameters, such as the
crystal orientation, thickness and bending parameters of the crystals as well
as the energy of the projectiles, were chosen to match those used in past and
ongoing experiments. The peculiarities which appear in the radiation spectra
are attributed to the interplay of various radiation mechanisms. The analysis
performed can be used to predict and explain future experimental results.Comment: 14 pages, 8 figures, 1 tabl
A Linear Programming Approach to Weak Reversibility and Linear Conjugacy of Chemical Reaction Networks
15 páginas, 2 figuras.-- The final publication is
available at www.springerlink.comA numerically effective procedure for determining weakly reversible
chemical reaction networks that are linearly conjugate to a known reaction network is
proposed in this paper. The method is based on translating the structural and algebraic
characteristics of weak reversibility to logical statements and solving the obtained
set of linear (in)equalities in the framework of mixed integer linear programming.
The unknowns in the problem are the reaction rate coefficients and the parameters of
the linear conjugacy transformation. The efficacy of the approach is shown through
numerical examples.Matthew D. Johnston and David Siegel acknowledge the support of D. Siegel’s Natural
Sciences and Engineering Research Council of Canada Discovery Grant. Gàbor Szederkényi acknowledges
the support of the Hungarian National Research Fund through grant no. OTKA K-83440 as well as
the support of project CAFE (Computer Aided Process for Food Engineering) FP7-KBBE-2007-1 (Grant
no: 212754).Peer reviewe
Pathway analysis and transcriptomics improve protein identification by shotgun proteomics from samples comprising small number of cells - a benchmarking study
BACKGROUND: Proteomics research is enabled with the high-throughput technologies, but our ability to identify expressed proteome is limited in small samples. The coverage and consistency of proteome expression are critical problems in proteomics. Here, we propose pathway analysis and combination of microproteomics and transcriptomics analyses to improve mass-spectrometry protein identification from small size samples.
RESULTS: Multiple proteomics runs using MCF-7 cell line detected 4,957 expressed proteins. About 80% of expressed proteins were present in MCF-7 transcripts data; highly expressed transcripts are more likely to have expressed proteins. Approximately 1,000 proteins were detected in each run of the small sample proteomics. These proteins were mapped to gene symbols and compared with gene sets representing canonical pathways, more than 4,000 genes were extracted from the enriched gene sets. The identified canonical pathways were largely overlapping between individual runs. Of identified pathways 182 were shared between three individual small sample runs.
CONCLUSIONS: Current technologies enable us to directly detect 10% of expressed proteomes from small sample comprising as few as 50 cells. We used knowledge-based approaches to elucidate the missing proteome that can be verified by targeted proteomics. This knowledge-based approach includes pathway analysis and combination of gene expression and protein expression data for target prioritization. Genes present in both the enriched gene sets (canonical pathways collection) and in small sample proteomics data correspond to approximately 50% of expressed proteomes in larger sample proteomics data. In addition, 90% of targets from canonical pathways were estimated to be expressed. The comparison of proteomics and transcriptomics data, suggests that highly expressed transcripts have high probability of protein expression. However, approximately 10% of expressed proteins could not be matched with the expressed transcripts.The cost of this publication was funded by Vladimir Brusic. (Vladimir Brusic)Published versio
On the nature of ferromagnetism in diluted magnetic semiconductors: GaAs:Mn, GaP:Mn
A microscopic Hamiltonian for interacting manganese impurities in diluted
magnetic semiconductors (DMS) is derived. It is shown that in p -type III-V DMS
the indirect exchange between Mn impurities has similarities with the Zener
mechanism in transition metal oxides. Here the mobile holes and localized
states near the top of the valence band play the role of unoccupied oxygen
orbitals which induce ferromagnetism. The Curie temperature estimated from the
proposed kinematic exchange agrees with recent experiments on GaAs:Mn. The
model is also applicable to the GaP:Mn system.Comment: 10 pages, 3 figures. Submitted to Europhysics Letters, June 25, 200
Synthesis of inorganic dyes based on plasmonic silver nanoparticles for the visible and infrared regions of the spectrum
The effect of various technological factors during the multistage synthesis of plasmonic silver particles in aqueous solutions on nanoparticle size, morphology, and color is studied. The synthesized suspensions are found to contain tabular silver nanoparticles of hexagonal and triangular shape. The foundations of the technology for synthesizing stable silver colloids with a high silver concentration for the visible and nearinfrared regions of the spectrum are developed
Effects caused by glutamic acid and hydrogen peroxide on the morphology of hydroxyapatite, calcium hydrogen phosphate, and calcium pyrophosphate
Reacting hydroxyapatite with H2O2 vapor at 10°C and brushite CaHPO4 · 2H2O with 90% H2O2 solution at 0°C (the hydroxyapatite and brushite were both prepared in the presence of glutamic acid) yielded the relevant peroxo solvates containing up to 18% hydrogen peroxide. The peroxo compounds and their degradation products obtained at 170–960°C were morphologically studied (using SEM). The factors influencing particle sizes are considered
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