12,182 research outputs found
Geology of the Snap Lake kimberlite intrusion, Northwest Territories, Canada: field observations and their interpretation
The Cambrian (523 Ma) Snap Lake hypabyssal kimberlite intrusion, Northwest Territories, Canada, is a complex segmented diamond-bearing ore-body. Detailed geological investigations suggest that the kimberlite is a multi-phase intrusion with at least four magmatic lithofacies. In particular, olivine-rich (ORK) and olivine-poor (OPK) varieties of hypabyssal kimberlite have been identified. Key observations are that the olivine-rich lithofacieshas a strong tendency to be located where the intrusion is thickest and that there is a good correlation between intrusion thickness, olivine crystal size and crystal content. Heterogeneities in the lithofacies are attributed to variations in intrusion thickness and structural complexities. The geometry and distribution of lithofacies points to magmaticco-intrusion, and flow segregation driven by fundamental rheological differences between the two phases. We envisage that the low-viscosity OPK magma acted as a lubricant for the highly viscous ORK magma. The presenceof such low-viscosity, crystal-poor magmas may explain how crystal-laden kimberlite magmas (>60 vol.%) are able to reach the surface during kimberlite eruptions. We also document the absence of crystal settling and the development of an unusual subvertical fabric of elongate olivine crystals, which are explained by rapid degassing-induced quench crystallization of the magmas during and after intrusio
The extended Main Sequence Turn Off cluster NGC1856: rotational evolution in a coeval stellar ensemble
Multiple or extended turnoffs in young clusters in the Magellanic Clouds have
recently received large attention. A number of studies have shown that they may
be interpreted as the result of a significant age spread (several 10^8yr in
clusters aged 1--2 Gyr), while others attribute them to a spread in stellar
rotation. We focus on the cluster NGC 1856, showing a splitting in the upper
part of the main sequence, well visible in the color m_{F336W}-m_{F555W}$, and
a very wide turnoff region. Using population synthesis available from the
Geneva stellar models, we show that the cluster data can be interpreted as
superposition of two main populations having the same age (~350Myr), composed
for 2/3 of very rapidly rotating stars, defining the upper turnoff region and
the redder main sequence, and for 1/3 of slowly/non-rotating stars. Since rapid
rotation is a common property of the B-A type stars, the main question raised
by this model concerns the origin of the slowly/non-rotating component. Binary
synchronization is a possible process behind the slowly/non-rotating
population; in this case, many slowly/non-rotating stars should still be part
of binary systems with orbital periods in the range from 4 to 500 days. Such
periods imply that Roche lobe overflow occurs, during the evolution of the
primary off the main sequence, so most primaries may not be able to ignite core
helium burning, consistently why the lack of a red clump progeny of the slowly
rotating population.Comment: 8 pages 4 figures, accepted for publication on Monthly Notices of the
R.A.
The investigation of time dependent flame structure by ionization probes
Ionization probes were used to measure mean ionization current and frequency spectra, auto-correlations and cross-correlations in jet flames with variation in the initial Reynolds numbers and equivalence ratios. Special attention was paid to the transitional region between the burner exit plane and the plane of onset of turbulence
Local delivery of doxorubicin nanocrystals from electrospun nanofibers
The objective of this study is to develop a novel system for local application of DOX either in surgical loci or in a topical application device enabling a controlled release of the drug. The developed system involves the encapsulation of DOX into electrospun polymeric nanofibers. Chosen polymers were polyoxyethilene (PEO) and polycaprolactone (PCL).This work was supported by the Portuguese Foundation for Science and
Technology (FCT) in the framework of the Strategic Funding UID/FIS/04650/2013.
Marlene LĂșcio acknowledges the exploratory project funded by FCT with the reference IF/00498/2012.info:eu-repo/semantics/publishedVersio
The near-IR counterpart of IGR J17480-2446 in Terzan 5
Some globular clusters in our Galaxy are noticeably rich in low-mass X-ray
binaries. Terzan 5 has the richest population among globular clusters of X- and
radio-pulsars and low-mass X-ray binaries. The detection and study of
optical/IR counterparts of low-mass X-ray binaries is fundamental to
characterizing both the low-mass donor in the binary system and investigating
the mechanisms of the formation and evolution of this class of objects. We aim
at identifying the near-IR counterpart of the 11 Hz pulsar IGRJ17480-2446
discovered in Terzan 5. Adaptive optics (AO) systems represent the only
possibility for studying the very dense environment of GC cores from the
ground. We carried out observations of the core of Terzan 5 in the near-IR
bands with the ESO-VLT NAOS-CONICA instrument. We present the discovery of the
likely counterpart in the Ks band and discuss its properties both in outburst
and in quiescence. Archival HST observations are used to extend our discussion
to the optical bands. The source is located at the blue edge of the turn-off
area in the color-magnitude diagram of the cluster. Its luminosity increase
from quiescence to outburst, by a factor 2.5, allows us to discuss the nature
of the donor star in the context of the double stellar generation population of
Terzan 5 by using recent stellar evolution models.Comment: 7 pages, 4 figure
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Dynamic interpersonal therapy for moderate to severe depression: A pilot randomized controlled and feasibility trial
Background: Improving Access to Psychological Therapies (IAPT) services treat most patients in England who present to primary care with major depression. Psychodynamic psychotherapy is one of the psychotherapies offered. Dynamic Interpersonal Therapy (DIT) is a psychodynamic and mentalization-based treatment for depression. 16 sessions are delivered over approximately 5 months. Neither DIT's effectiveness relative to low-intensity treatment (LIT), nor the feasibility of randomizing patients to psychodynamic or cognitive-behavioural treatments (CBT) in an IAPT setting has been demonstrated.
Methods: 147 patients were randomized in a 3:2:1 ratio to DIT (n = 73), LIT (control intervention; n = 54) or CBT (n = 20) in four IAPT treatment services in a combined superiority and feasibility design. Patients meeting criteria for major depressive disorder were assessed at baseline, mid-treatment (3 months) and post-treatment (6 months) using the Hamilton Rating Scale for Depression (HRSD-17), Beck Depression Inventory-II (BDI-II) and other self-rated questionnaire measures. Patients receiving DIT were also followed up 6 months post-completion.
Results: The DIT arm showed significantly lower HRSD-17 scores at the 6-month primary end-point compared with LIT (d = 0.70). Significantly more DIT patients (51%) showed clinically significant change on the HRSD-17 compared with LIT (9%). The DIT and CBT arms showed equivalence on most outcomes. Results were similar with the BDI-II. DIT showed benefit across a range of secondary outcomes.ConclusionsDIT delivered in a primary care setting is superior to LIT and can be appropriately compared with CBT in future RCTs
Processing The Interspecies Quorum-Sensing Signal Autoinducer-2 (AI-2) Characterization Of Phospho-(S)-4,5-Dihydroxy-2,3-Pentanedione Isomerization By LsrG Protein
The molecule (S)-4,5-dihydroxy-2,3-pentanedione (DPD) is produced by many different species of bacteria and is the precursor of the signal molecule autoinducer-2 (AI-2). AI-2 mediates interspecies communication and facilitates regulation of bacterial behaviors such as biofilm formation and virulence. A variety of bacterial species have the ability to sequester and process the AI-2 present in their environment, thereby interfering with the cell-cell communication of other bacteria. This process involves the AI-2-regulated lsr operon, comprised of the Lsr transport system that facilitates uptake of the signal, a kinase that phosphorylates the signal to phospho-DPD (P-DPD), and enzymes (like LsrG) that are responsible for processing the phosphorylated signal. Because P-DPD is the intracellular inducer of the lsr operon, enzymes involved in P-DPD processing impact the levels of Lsr expression. Here we show that LsrG catalyzes isomerization of P-DPD into 3,4,4-trihydroxy-2-pentanone-5-phosphate. We present the crystal structure of LsrG, identify potential catalytic residues, and determine which of these residues affects P-DPD processing in vivo and in vitro. We also show that an lsrG deletion mutant accumulates at least 10 times more P-DPD than wild type cells. Consistent with this result, we find that the lsrG mutant has increased expression of the lsr operon and an altered profile of AI-2 accumulation and removal. Understanding of the biochemical mechanisms employed by bacteria to quench signaling of other species can be of great utility in the development of therapies to control bacterial behavior
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