532 research outputs found
Variations on the Deuteron
We consider few problems which are related to the deuteron and have simple
analytical solution. Relation is found between the deuteron electric quadrupole
moment and the -scattering amplitude. The degree of circular polarization
of photons is calculated for the radiative capture of longitudinally polarized
thermal neutrons. The anapole, electric dipole and magnetic quadrupole moments
of the deuteron are calculated.Comment: 14 pages, late
Topological network alignment uncovers biological function and phylogeny
Sequence comparison and alignment has had an enormous impact on our
understanding of evolution, biology, and disease. Comparison and alignment of
biological networks will likely have a similar impact. Existing network
alignments use information external to the networks, such as sequence, because
no good algorithm for purely topological alignment has yet been devised. In
this paper, we present a novel algorithm based solely on network topology, that
can be used to align any two networks. We apply it to biological networks to
produce by far the most complete topological alignments of biological networks
to date. We demonstrate that both species phylogeny and detailed biological
function of individual proteins can be extracted from our alignments.
Topology-based alignments have the potential to provide a completely new,
independent source of phylogenetic information. Our alignment of the
protein-protein interaction networks of two very different species--yeast and
human--indicate that even distant species share a surprising amount of network
topology with each other, suggesting broad similarities in internal cellular
wiring across all life on Earth.Comment: Algorithm explained in more details. Additional analysis adde
Primena reaktivnih siloksanskih pretpolimera za sintezu poli(ester-siloksana) i poli(ester-etar-siloksana)
Thermoplastic poly(ester-siloxane)s (TPES) and poly(ester-ether-siloxane)s, (TPEES), based on poly(butylene terephthalate) (PBT) as the hard segment and different siloxane-prepolymers as the soft segments, were prepared. The TPES and TPEES were synthesized by catalyzed two-step transesterification from dimethyl terephthalate, (DMT), 1,4-butanediol, (BD) and a siloxane-prepolymer. Incorporation of dicarboxypropyl- or disilanol-terminated poly(dimethylsiloxane) s (PDMS) into the polar poly(butylene terephthalate) chains resulted in rather inhomogeneous TPES copolymers, which was a consequence of a prononuced phase separation of the polar and non-polar reactants during synthesis. Two concepts were employed to avoid or reduce phase separation: 1) the use of siloxane-containing triblock prepolymers with hydrophilic terminal blocks, such as ethylene oxide (EO), poly(propylene oxide) (PPO) or poly(caprolactone) (PLC) when the terminal blocks serve as a compatibilizer between the extremely non-polar PDMS and the polar DMT and BD, and 2) the use of a high-boiling solvent (1,2,4-trichlorobenzene) during the first phase of the reaction. Homogeneity was significantly improved in the case of copolymers based on PCL-PDMS-PCL.U okviru ovog rada su sintetisani termoplastiÄni poli(estarāsiloksani) (TPES)
i poli(estarāetarāsiloksani) (TPEES), sa tvrdim segmentima na bazi poli(butilentereftalata)
(PBT) i mekim segmentima na bazi razliÄitih siloksanskih pretpolimera.
TPES i TPEES su sintetisani katalizovanom reakcijom dvostepene transesterifikacije,
iz dimetilterftalata (DMT), 1,4-butandiola (BD) i odgovarajuÄeg siloksanskog
pretpolimera. Pri ugradnji dikarboksipropil- ili disilanol-terminiranih
poli(dimetilsiloksana) (PDMS) u polarne poli(butilentereftalatne) lance dobijeni
su priliÄno nehomogeni TPES kopolimeri, Å”to je bila posledica loÅ”e menjivosti
reaktanata tokom odigravanja reakcije. Primenjena su dva koncepta da bi se izbeglo
ili smanjilo fazno razdvajanje reakcione smene tokom sinteze organoāsiloksanskih
kopolimera: 1) primena siloksanskih triblok-pretpolimera kod kojih su
hidrofilni terminalni blokovi, izgraÄeni od etilenoksida (EO), poli(propilenoksida)
(PPO) ili poli(kaprolaktona) (PLC), imali funkciju kompatibilizatora izmeÄu
nepolarnog PDMS-a i polarnih reaktanata, DMT-a i BD-a i 2) primena rastvaranja
visoke temperature kljuÄanja (1,2,4-trihlorbenzena) za vreme izvoÄenja prve
faze reakcije. ZnaÄajno poveÄanje homogenosti postignuto je kod kopolimera na bazi
PCLāPDMSāPCL segmenata
Synthesis and Application of Domestic Glassy Carbon TiO2 Nanocomposite for Electrocatalytic Triclosan Detection
Nanoparticles of TiO2 are suitable for many catalytic and photocatalytic applications due to their extraordinary properties such as superhydrophobicity, semiconductivity, electron-rich, and environmental compatibility. The main crystalline phases of TiO2, anatase, and rutile possess different crystal structures, crystallinity, crystalline sizes, and specific surface areas, and these characteristics directly affect the catalytic performance of TiO2. In the present study, domestic carbon material enhanced with TiO2 nanoparticles was synthesized and used for the construction of a modified carbon paste electrode. The electrocatalytic activity of the modified electrodes was investigated depending on the TiO2 crystalline phases in the electrode material. Furthermore, the obtained working electrode was utilized for triclosan detection. Under optimized experimental conditions, the developed electrode showed a submicromolar triclosan detection limit of 0.07 ĀµM and a wide linear range of 0.1 to 15 ĀµM. The relative standard deviations for repeatability and reproducibility were lower than 4.1%, and with satisfactory selectivity, the proposed system was successfully applied to triclosan monitoring in groundwater. All these results confirm that the sustainable production of new and domestically prepared materials is of great benefit in the field of electrocatalysis and that the morphology of such produced materials is strongly related to their catalytic properties
High-Efficiency Resonant RF Spin Rotator with Broad Phase Space Acceptance for Pulsed Polarized Cold Neutron Beams
We have developed a radio-frequency resonant spin rotator to reverse the
neutron polarization in a 9.5 cm x 9.5 cm pulsed cold neutron beam with high
efficiency over a broad cold neutron energy range. The effect of the spin
reversal by the rotator on the neutron beam phase space is compared
qualitatively to RF neutron spin flippers based on adiabatic fast passage. The
spin rotator does not change the kinetic energy of the neutrons and leaves the
neutron beam phase space unchanged to high precision. We discuss the design of
the spin rotator and describe two types of transmission-based neutron spin-flip
efficiency measurements where the neutron beam was both polarized and analyzed
by optically-polarized 3He neutron spin filters. The efficiency of the spin
rotator was measured to be 98.0+/-0.8% on resonance for neutron energies from
3.3 to 18.4 meV over the full phase space of the beam. As an example of the
application of this device to an experiment we describe the integration of the
RF spin rotator into an apparatus to search for the small parity-violating
asymmetry A_gamma in polarized cold neutron capture on para-hydrogen by the
NPDGamma collaboration at LANSCE
X-ray structural analysis and antitumor activity of new salicylic acid derivatives
This Thesis project is going to be situated in my home town Ćstersund, 600 kilometers north from Stockholm.ItĀ“s a small town with 60 000 people and it is the only city of the region JƤmtland in Norrland, Sweden.In the city centre of Ćstersund there is one existing bus terminal station where the buses arrive with people from the entire region.The task for this Thesis project is to rebuild the existing bus station in Ćstersund where the actual terminal building is going to be completely demolished and the entire block within the current bus stops is going to be rearranged.The topography of the terminal area is now dividing the regional buses that arrives on the upper level from the city buses that stops at the lower level. Therefore the main challenge of the new proposal is how one would strengthen the junction between these two flows of people and how a new architecture could enable the encounter between the countryside and the urban city.Detta examensprojekt kommer att vara belƤgen i min hemstad Ćstersund, 600 kilometer norr om Stockholm. Det Ƥr en liten stad med 60 000 personer och det Ƥr den enda staden i regionen JƤmtland, Norrland. I centrum av Ćstersund finns en befintlig bussterminalen dƤr bussarna anlƤnder med folk frĆ„n hela regionen. Uppgiften fƶr detta projekt Ƥr att bygga om den befintliga busstationen i Ćstersund topografin pĆ„ terminalomrĆ„det i dagslƤget separerar de regionala bussarna som anlƤnder pĆ„ den ƶvre nivĆ„n frĆ„n stadsbussarna som stannar pĆ„ en lƤgre nivĆ„. Den stƶrsta utmaningen i det nya fƶrslaget Ƥr hur man istƤllet skulle kunna stƤrka fƶrbindelsen mellan dessa tvĆ„ flƶden av mƤnniskor och hur en ny arkitektur kan mƶjliggƶra mƶtet mellan glesbyggd och den urbana staden
Associations of Plasma Selenium with Arsenic and Genomic Methylation of Leukocyte DNA in Bangladesh
Background
Global hypomethylation of DNA is thought to constitute an early event in some cancers and occurs in response to arsenic (As) exposure and/or selenium (Se) deficiency in both in vitro and animal models. In addition, antagonism between As and Se, whereby each reduces toxicity of the other, has been well documented in animal models. Se status may therefore modify the health effects of As in As-exposed populations.
Objective
The primary objectives of our study were to test the hypothesis that Se deficiency is associated with genomic hypomethylation of lymphocyte DNA and to determine whether Se levels are associated with blood As (bAs) and urinary As (uAs) concentrations in adults exposed to As-contaminated groundwater in Bangladesh. A secondary objective was to explore the relationships between plasma Se and As metabolites.
Design
We assessed plasma Se concentrations, As metabolite profiles in blood and urine, and genomic methylation of leukocyte DNA in a cross-sectional study of 287 adults.
Results
After adjustment for potential confounders, we observed an inverse association between Se (micrograms per liter) and genomic DNA methylation (disintegrations per minute per 1-Ī¼g/L increase in Se): Ī² = 345.6; 95% confidence interval (CI), 59ā632. Se concentrations were inversely associated with total As concentrations (micrograms per liter) in blood (Ī² = ā0.04; 95% CI, ā0.08 to ā0.01) and urine (Ī² = ā20.1; 95% CI, ā29.3 to ā10.9). Se levels were negatively associated with the percentage of monomethylarsinic acid (Ī² = ā0.59; 95% CI, ā1.04 to ā0.13) and positively associated with the percentage of dimethylarsinic acid (Ī² = 0.53; 95% CI, 0.04 to 1.01) in blood.
Conclusions
Our results suggest that Se is inversely associated with genomic DNA methylation. The underlying mechanisms and implications of this observation are unclear and warrant further investigation. In addition, Se may influence bAs and uAs concentrations, as well as relative proportions of As metabolites in blood
Photocatalytic activity of TiO2 nanoparticles modified with dopamine
Photocatalytic activity of bare colloidal TiO2 nanoparticles (NPs, d~45Ć
) and
surface modified with dopamine was obtained following degradation reaction of
herbicide RS-2-(4-chloro-o-tolyloxy)propionic acid (mecoprop, MCPP, C10H11ClO3)
under UV light irradiation. Results indicated that inner sphere charge transfer (CT)
complex is formed on the surface of TiO2 NPs due to modification with dopamine
which induced decreasing of the photocatalytic efficacy of TiO2 NPs
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