1,771 research outputs found
Titanium Nitride and Nitrogen Ion Implanted Coated Dental Materials
Titanium nitride and/or nitrogen ion implanted coated dental materials have been investigated since the mid-1980s and considered in various applications in dentistry such as implants, abutments, orthodontic wires, endodontic files, periodontal/oral hygiene instruments, and casting alloys for fixed restorations. Multiple methodologies have been employed to create the coatings, but detailed structural analysis of the coatings is generally lacking in the dental literature. Depending on application, the purpose of the coating is to provide increased surface hardness, abrasion/wear resistance, esthetics, and corrosion resistance, lower friction, as well as greater beneficial interaction with adjacent biological and material substrates. While many studies have reported on the achievement of these properties, a consensus is not always clear. Additionally, few studies have been conducted to assess the efficacy of the coatings in a clinical setting. Overall, titanium nitride and/or nitrogen ion implanted coated dental materials potentially offer advantages over uncoated counterparts, but more investigation is needed to document the structure of the coatings and their clinical effectiveness
The Diabetes Remission Clinical Trial (DiRECT): protocol for a cluster randomised trial
Background:
Despite improving evidence-based practice following clinical guidelines to optimise drug therapy, Type 2 diabetes (T2DM) still exerts a devastating toll from vascular complications and premature death. Biochemical remission of T2DM has been demonstrated with weight loss around 15kg following bariatric surgery and in several small studies of non-surgical energy-restriction treatments. The non-surgical Counterweight-Plus programme, running in Primary Care where obesity and T2DM are routinely managed, produces >15 kg weight loss in 33 % of all enrolled patients. The Diabetes UK-funded Counterpoint study suggested that this should be sufficient to reverse T2DM by removing ectopic fat in liver and pancreas, restoring first-phase insulin secretion.
The Diabetes Remission Clinical Trial (DiRECT) was designed to determine whether a structured, intensive, weight management programme, delivered in a routine Primary Care setting, is a viable treatment for achieving durable normoglycaemia. Other aims are to understand the mechanistic basis of remission and to identify psychological predictors of response.
Methods/Design:
Cluster-randomised design with GP practice as the unit of randomisation: 280 participants from around 30 practices in Scotland and England will be allocated either to continue usual guideline-based care or to add the Counterweight-Plus weight management programme, which includes primary care nurse or dietitian delivery of 12-20weeks low calorie diet replacement, food reintroduction, and long-term weight loss maintenance. Main inclusion criteria: men and women aged 20-65years, all ethnicities, T2DM 0-6years duration, BMI 27-45 kg/m2. Tyneside participants will undergo Magnetic Resonance (MR) studies of pancreatic and hepatic fat, and metabolic studies to determine mechanisms underlying T2DM remission. Co-primary endpoints: weight reduction ≥ 15 kg and HbA1c <48 mmol/mol at one year. Further follow-up at 2 years.
Discussion:
This study will establish whether a structured weight management programme, delivered in Primary Care by practice nurses or dietitians, is a viable treatment to achieve T2DM remission. Results, available from 2018 onwards, will inform future service strategy
Multicomponent kinematics in a massive filamentary IRDC
To probe the initial conditions for high-mass star and cluster formation, we
investigate the properties of dense filaments within the infrared dark cloud
G035.39-00.33 (IRDC G035.39) in a combined Very Large Array (VLA) and the Green
Bank Telescope (GBT) mosaic tracing the NH3 (1,1) and (2,2) emission down to
0.08 pc scales. Using agglomerative hierarchical clustering on multiple
line-of-sight velocity component fitting results, we identify seven extended
velocity-coherent components in our data, likely representing spatially
coherent physical structures, some exhibiting complex gas motions. The velocity
gradient magnitude distribution peaks at its mode of 0.35 km/s/pc and has a
long tail extending into higher values of 1.5 - 2 km/s/pc, and is generally
consistent with those found toward the same cloud in other molecular tracers
and with the values found towards nearby low-mass dense cloud cores at the same
scales. Contrary to observational and theoretical expectations, we find the
non-thermal ammonia line widths to be systematically narrower (by about 20%)
than those of N2H+ (1-0) line transition observed with similar resolution. If
the observed ordered velocity gradients represent the core envelope solid-body
rotation, we estimate the specific angular momentum to be about 2 x 10^21
cm^2/s, similar to the low-mass star-forming cores. Together with the previous
finding of subsonic motions in G035.39, our results demonstrate high levels of
similarity between kinematics of a high-mass star-forming IRDC and the low-mass
star formation regime.Comment: 22 pages, 14 figures, accepted to Ap
JWST reveals widespread CO ice and gas absorption in the Galactic Center cloud G0.253+0.016
We report JWST NIRCam observations of G0.253+0.016, the molecular cloud in
the Central Molecular Zone known as The Brick, with the F182M, F187N, F212N,
F410M, F405N, and F466N filters. We catalog 56,146 stars detected in all 6
filters using the crowdsource package. Stars within and behind The Brick
exhibit prodigious absorption in the F466N filter that is produced by a
combination of CO ice and gas. In support of this conclusion, and as a general
resource, we present models of CO gas and ice and CO ice in the F466N,
F470N, and F410M filters. Both CO gas and ice may contribute to the observed
stellar colors. We show, however, that CO gas does not absorb the Pf and
Hu lines in F466N, but that these lines show excess absorption,
indicating that CO ice is also present and contributes to observed F466N
absorption. The most strongly absorbed stars in F466N are extincted by 2
magnitudes, corresponding to 80\% flux loss. This high observed absorption
requires very high column densities of CO, requiring total CO column that is in
tension with standard CO abundance and/or gas-to-dust ratios. There is
therefore likely to be a greater CO/H ratio (X) and more
dust per H molecule () in the Galactic Center than the Galactic
disk. Ice and/or gas absorption is observed even in the cloud outskirts,
implying that additional caution is needed when interpreting stellar photometry
in filters that overlap with ice bands throughout our Galactic Center. The
widespread CO absorption in our Galactic Center hints that significant ice
absorption is likely present in other galactic centers.Comment: Submitted to ApJ. Revised after second referee report. 16 pages, 11
figure
Changes in the Treatment Responses to Artesunate-Mefloquine on the Northwestern Border of Thailand during 13 Years of Continuous Deployment
Background: Artemisinin combination treatments (ACT) are recommended as first line treatment for falciparum malaria throughout the malaria affected world. We reviewed the efficacy of a 3-day regimen of mefloquine and artesunate regimen (MAS ), over a 13 year period of continuous deployment as first-line treatment in camps for displaced persons and in clinics for migrant population along the Thai-Myanmar border. Methods and Findings: 3,264 patients were enrolled in prospective treatment trials between 1995 and 2007 and treated with MAS. The proportion of patients with parasitaemia persisting on day-2 increased significantly from 4.5% before 2001 to 21.9% since 2002 (p<0.001). Delayed parasite clearance was associated with increased risk of developing gametocytaemia (AOR = 2.29; 95% CI, 2.00-2.69, p = 0.002). Gametocytaemia on admission and carriage also increased over the years (p = 0.001, test for trend, for both). MAS efficacy has declined slightly but significantly (Hazards ratio 1.13; 95% CI, 1.07-1.19, p<0.001), although efficacy in 2007 remained well within acceptable limits: 96.5% (95% CI, 91.0-98.7). The in vitro susceptibility of P. falciparum to artesunate increased significantly until 2002, but thereafter declined to levels close to those of 13 years ago (geometric mean in 2007: 4.2 nM/l; 95% CI, 3.2-5.5). The proportion of infections caused by parasites with increased pfmdr1 copy number rose from 30% (12/ 40) in 1996 to 53% (24/45) in 2006 (p = 0.012, test for trend). Conclusion: Artesunate-mefloquine remains a highly efficacious antimalarial treatment in this area despite 13 years of widespread intense deployment, but there is evidence of a modest increase in resistance. Of particular concern is the slowing of parasitological response to artesunate and the associated increase in gametocyte carriage. © 2009 Carrara et al
Hidden Gems on a Ring: Infant Massive Clusters and Their Formation Timeline Unveiled by ALMA, HST, and JWST in NGC 3351
We use 0.1″ observations from the Atacama Large Millimeter Array (ALMA), Hubble Space Telescope (HST), and JWST to study young massive clusters (YMCs) in their embedded “infant” phase across the central starburst ring in NGC 3351. Our new ALMA data reveal 18 bright and compact (sub-)millimeter continuum sources, of which 8 have counterparts in JWST images and only 6 have counterparts in HST images. Based on the ALMA continuum and molecular line data, as well as ancillary measurements for the HST and JWST counterparts, we identify 14 sources as infant star clusters with high stellar and/or gas masses (∼105 M ⊙), small radii (≲ 5 pc), large escape velocities (6–10 km s−1), and short freefall times (0.5–1 Myr). Their multiwavelength properties motivate us to divide them into four categories, likely corresponding to four evolutionary stages from starless clumps to exposed H ii region–cluster complexes. Leveraging age estimates for HST-identified clusters in the same region, we infer an evolutionary timeline, ranging from ∼1–2 Myr before cluster formation as starless clumps, to ∼4–6 Myr after as exposed H ii region–cluster complexes. Finally, we show that the YMCs make up a substantial fraction of recent star formation across the ring, exhibit a nonuniform azimuthal distribution without a very coherent evolutionary trend along the ring, and are capable of driving large-scale gas outflows
CMZoom: Survey Overview and First Data Release
We present an overview of the CMZoom survey and its first data release.
CMZoom is the first blind, high-resolution survey of the Central Molecular Zone
(CMZ; the inner 500 pc of the Milky Way) at wavelengths sensitive to the
pre-cursors of high-mass stars. CMZoom is a 500-hour Large Program on the
Submillimeter Array (SMA) that mapped at 1.3 mm all of the gas and dust in the
CMZ above a molecular hydrogen column density of 10^23 cm^-2 at a resolution of
~3" (0.1 pc). In this paper, we focus on the 1.3 mm dust continuum and its data
release, but also describe CMZoom spectral line data which will be released in
a forthcoming publication. While CMZoom detected many regions with rich and
complex substructure, its key result is an overall deficit in compact
substructures on 0.1 - 2 pc scales (the compact dense gas fraction: CDGF). In
comparison with clouds in the Galactic disk, the CDGF in the CMZ is
substantially lower, despite having much higher average column densities. CMZ
clouds with high CDGFs are well-known sites of active star formation. The
inability of most gas in the CMZ to form compact substructures is likely
responsible for the dearth of star formation in the CMZ, surprising considering
its high density. The factors responsible for the low CDGF are not yet
understood but are plausibly due to the extreme environment of the CMZ, having
far-reaching ramifications for our understanding of the star formation process
across the cosmos.Comment: Accepted for Publication in ApJ
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