903 research outputs found
Modelling optical micro-machines
A strongly focused laser beam can be used to trap, manipulate and exert
torque on a microparticle. The torque is the result of transfer of angular
momentum by scattering of the laser beam. The laser could be used to drive a
rotor, impeller, cog wheel or some other microdevice of a few microns in size,
perhaps fabricated from a birefringent material. We review our methods of
computationally simulating the torque and force imparted by a laser beam. We
introduce a method of hybridizing the T-matrix with the Finite Difference
Frequency Domain (FDFD) method to allow the modelling of materials that are
anisotropic and inhomogeneous, and structures that have complex shapes. The
high degree of symmetry of a microrotor, such as discrete or continuous
rotational symmetry, can be exploited to reduce computational time and memory
requirements by orders of magnitude. This is achieved by performing
calculations for only a given segment or plane that is repeated across the
whole structure. This can be demonstrated by modelling the optical trapping and
rotation of a cube.Comment: 4 pages, 3 figure
Effect of cactus pear cultivation after Mediterranean maquis on soil carbon stock, Ī“13C spatial distribution and root turnover
croplands and orchards leading to strong soil degradation. Organic carbon is usually accumulated in soils under
maquis leading to partial regeneration of fertility for future agricultural use. The aim of this work was to investigate
the effect of land use change from maquis to agriculture on soil organic carbon (SOC) stock and its spatial
distribution in a Mediterranean system. Three Mediterranean land use systems (seminatural vegetation, cactus
pear crop and olive grove) were selected in Sicily and analysed for soil C stocks and their Ī“13C. Total SOC and
Ī“13C were measured up to 75 cm soil depth within and between the rows of cactus pear and olive grove and
along a similar transect in maquis, in order to evaluate the distribution of new and old C derived from roots.
The land use change from Mediterranean maquis (C3 plant) to cactus pear (CAM plant) lead to a SOC decrease
of 65% after 28 years of cultivation, and a further decrease for 14% after 7 years after the change from cactus
pear to olive grove (C3 plant). Considering these SOC losses as well as the periods after the land use changes
we calculated the mean residence time (MRT) of soil organic matter. TheMRT of C under Mediterranean maquis
was about 142 years, but was just 10 years under cactus pear. Root biomass of cactus pear was used for a new
approach to estimate root turnover. The root turnover rate of cactus decreased along the soil profile from 7.1%
per year in 0ā15 cm to 3.7% in 60ā75 cm soil depth. Along the transect, the average of root turnover values
was highest in the middle of the intra-row. Root turnover and C inputwere correlated with SOC stocks to evaluate
C sequestration potential of soils depending on land use and managements. Weconclude that the SOC under maquis
is higher and has longer residence time compared to permanent agricultural crops like cactus pear and
olives
Phylogenetic analysis of planarian collagens and their roles in regeneration
Poster Presentation - Theme 3: Development & stem cellsStem cells are regulated by the microenvironment or niche they reside in, which consists of growth factors, niche cells and the extracellular matrix. The ECM acts as both a structural component and as a reservoir for growth factors that are released upon degradation. During regeneration, stem cells in the planarian are activated to migrate and proliferate; however, the role of the ECM in stem cell regulation is still unclear. Analysis of an EST library of planarian transcripts revealed nine fibrillar-related collagen chains (DjCol1-9). Sequence and structural analysis ...postprin
Phosphate coordination and movement of DNA in the Tn5 synaptic complex: role of the (R)YREK motif
Bacterial DNA transposition is an important model system for studying DNA recombination events such as HIV-1 DNA integration and RAG-1-mediated V(D)J recombination. This communication focuses on the role of proteināphosphate contacts in manipulating DNA structure as a requirement for transposition catalysis. In particular, the participation of the nontransferred strand (NTS) 5ā² phosphate in Tn5 transposition strand transfer is analyzed. The 5ā² phosphate plays no direct catalytic role, nonetheless its presence stimulates strand transfer ā¼30-fold. X-ray crystallography indicates that transposaseāDNA complexes formed with NTS 5ā² phosphorylated DNA have two properties that contrast with structures formed with complexes lacking the 5ā² phosphate or complexes generated from in-crystal hairpin cleavage. Transposase residues R210, Y319 and R322 of the (R)YREK motif coordinate the 5ā² phosphate rather than the subterminal NTS phosphate, and the 5ā² NTS end is moved away from the 3ā² transferred strand end. Mutation R210A impairs the 5ā² phosphate stimulation. It is posited that DNA phosphate coordination by R210, Y319 and R322 results in movement of the 5ā² NTS DNA away from the 3ā²-end thus allowing efficient target DNA binding. It is likely that this role for the newly identified RYR triad is utilized by other transposase-related proteins
Velocity-resolved high-J CO emission from massive star-forming clumps
(Abridged) Context. Massive star formation is associated with energetic
processes, which result in significant gas cooling via far-infrared (IR) lines.
Velocity-resolved observations can constrain the kinematics of the gas,
allowing the identification of the physical mechanisms responsible for gas
heating. Aims. Our aim is to quantify far-infrared CO line emission toward
high-mass star-forming regions, identify the high-velocity gas component
associated with outflows, and estimate the physical conditions required for the
excitation of the observed lines. Methods. Velocity-resolved SOFIA/GREAT
spectra of 13 high-mass star forming clumps of various luminosities and
evolutionary stages are studied using CO 11-10 and 16-15 lines. Results. All
targets show strong high-J CO emission in the far-IR, characterized by broad
line wings associated with outflows, thereby significantly increasing the
sample of sources with velocity-resolved high-J CO spectra. The contribution of
the emission in the line wings does not correlate with the envelope mass or
evolutionary stage. Gas rotational temperatures cover a narrow range of 120-220
K for the line wings. The non-LTE radiative transfer models indicate gas
densities of 1e5-1e7 cm-3 and N(CO) of 1e17- 1e18 cm-2, similar to physical
conditions in deeply-embedded low- and high-mass protostars. The
velocity-integrated CO line fluxes correlate with the bolometric luminosity
over 7 orders of magnitude including data on the low-mass protostars,
suggesting similar processes are responsible for the high-J CO excitation over
a significant range of physical scales. Conclusions. Velocity-resolved line
profiles allow the detection of outflows toward massive star-forming clumps
spanning a broad range of evolutionary stages. The lack of clear evolutionary
trends suggest that mass accretion and ejection prevail during the entire
lifetime of star-forming clumps.Comment: 21 pages, 19 figures, accepted to A&
T-cell subpopulations Ī±Ī² and Ī³Ī“ in cord blood of very preterm infants : The influence of intrauterine infection
Open Access: This article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution, and reproduction in any medium, provided the original author(s) and the source are creditedPreterm infants are very susceptible to infections. Immune response mechanisms in this group of patients and factors that influence cord blood mononuclear cell populations remain poorly understood and are considered insufficient. However, competent immune functions of the cord blood mononuclear cells are also described. The aim of this work was to evaluate the T-cell population (CD3+) with its subpopulations bearing T-cell receptor (TCR) Ī±Ī² or TCR Ī³Ī“ in the cord blood of preterm infants born before 32 weeks of gestation by mothers with or without an intrauterine infection. Being a pilot study, it also aimed at feasibility check and assessment of an expected effect size. The cord blood samples of 46 infants age were subjected to direct immunofluorescent staining with monoclonal antibodies and then analyzed by flow cytometry. The percentage of CD3+ cells in neonates born by mothers with diagnosis of intrauterine infection was significantly lower than in neonates born by mothers without infection (p = 0.005; Mann-Whitney U test). The number of cells did not differ between groups. Infection present in the mother did not have an influence on the TCR Ī±Ī² or TCR Ī³Ī“ subpopulations. Our study contributes to a better understanding of preterm infants' immune mechanisms, and sets the stage for further investigations.Peer reviewedFinal Published versio
Trends in antithrombotic management of patients with atrial fibrillation:A report from the Polish part of the EURObservational Research Programme - Atrial Fibrillation General Long-Term Registry
Postglacial expansion of the arctic keystone copepod calanus glacialis
Calanus glacialis, a major contributor to zooplankton biomass in the Arctic shelf seas, is a key link between primary production and higher trophic levels that may be sensitive to climate warming. The aim of this study was to explore genetic variation in contemporary populations of this species to infer possible changes during the Quaternary period, and to assess its population structure in both space and time. Calanus glacialis was sampled in the fjords of Spitsbergen (Hornsund and Kongsfjorden) in 2003, 2004, 2006, 2009 and 2012. The sequence of a mitochondrial marker, belonging to the ND5 gene, selected for the study was 1249 base pairs long and distinguished 75 unique haplotypes among 140 individuals that formed three main clades. There was no detectable pattern in the distribution of haplotypes by geographic distance or over time. Interestingly, a Bayesian skyline plot suggested that a 1000-fold increase in population size occurred approximately 10,000 years before present, suggesting a species expansion after the Last Glacial Maximum.GAME from the National Science Centre, the Polish Ministry of Science and Higher Education Iuventus Plus [IP2014 050573]; FCT-PT [CCMAR/Multi/04326/2013]; [2011/03/B/NZ8/02876
Ī²-delayed Ī³-proton decay in 56Zn: analysis of the charged-particle spectrum
A study of the beta decay of the proton-rich T-z = 2 nucleus Zn-56 has been reported in a recent publication. A rare and exotic decay mode, beta-delayed gamma-proton decay, has been observed there for the first time in the fp shell. Here, we expand on some of the details of the data analysis, focussing on the charged particle spectrum
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