Interferometric gravitational-wave detectors like LIGO need to be able to measure changes in their arm lengths of order 10−18 m or smaller. This requires very high laser power in order to raise the ...signal above shot noise. One significant limitation to increased laser power is an optomechanical interaction between the laser field and the detector's test masses that can form an unstable feedback loop. Such parametric instabilities have long been studied as a limiting effect at high power, and were first observed to occur in LIGO in 2014. Since then, passive and active means have been used to avoid these instabilities, though at power levels well below the final design value. Here we report on the successful implementation of tuned, passive dampers to tame parametric instabilities in LIGO. These dampers are applied directly to all interferometer test masses to reduce the quality factors of their internal vibrational modes, while adding a negligible amount of noise to the gravitational-wave output. In accordance with our model, the measured mode quality factors have been reduced by at least a factor of 10 with no visible increase in the interferometer's thermal noise level. We project that these dampers should remove most of the parametric instabilities in LIGO when operating at full power, while limiting the concomitant increase in thermal noise to approximately 1%.
Advanced LIGO and other ground-based interferometric gravitational-wave detectors use high laser power to minimize shot noise and suspended optics to reduce seismic noise coupling. This can result in ...an opto-mechanical coupling which can become unstable and saturate the interferometer control systems. The severity of these parametric instabilities scales with circulating laser power and first hindered LIGO operations in 2014. Static thermal tuning and active electrostatic damping have previously been used to control parametric instabilities at lower powers but are insufficient as power is increased. Here we report the first demonstration of dynamic thermal compensation to avoid parametric instability in an Advanced LIGO detector. Annular ring heaters that compensate central heating are used to tune the optical mode away from multiple problematic mirror resonance frequencies. We develop a single-cavity approximation model to simulate the optical beat note frequency during the central heating and ring heating transient. An experiment of dynamic ring heater tuning at the LIGO Livingston detector was carried out at 170 kW circulating power and, in agreement with our model, the third order optical beat note is controlled to avoid instability of the 15 and 15.5 kHz mechanical modes. We project that dynamic thermal compensation with ring heater input conditioning can be used in parallel with acoustic mode dampers to control the optical mode transient and avoid parametric instability of these modes up to Advanced LIGO's design circulating power of 750 kW. The experiment also demonstrates the use of three mode interaction monitoring as a sensor of the cavity geometry, used to maintain the g-factor product to g1g2 = 0.829 ± 0.004.
We report the outcomes of 20 patients (12 men, 8 women, 21 feet) with Charcot neuro-arthropathy who underwent correction of deformities of the ankle and hindfoot using retrograde intramedullary nail ...arthrodesis. The mean age of the patients was 62.6 years (46 to 83); their mean BMI was 32.7 (15 to 47) and their median American Society of Anaesthetists score was 3 (2 to 4). All presented with severe deformities and 15 had chronic ulceration. All were treated with reconstructive surgery and seven underwent simultaneous midfoot fusion using a bolt, locking plate or a combination of both. At a mean follow-up of 26 months (8 to 54), limb salvage was achieved in all patients and 12 patients (80%) with ulceration achieved healing and all but one patient regained independent mobilisation. There was failure of fixation with a broken nail requiring revision surgery in one patient. Migration of distal locking screws occurred only when standard screws had been used but not with hydroxyapatite-coated screws. The mean American Academy of Orthopaedic Surgeons Foot and Ankle (AAOS-FAO) score improved from 50.7 (17 to 88) to 65.2 (22 to 88), (p = 0.015). The mean Short Form (SF)-36 Health Survey Physical Component Score improved from 25.2 (16.4 to 42.8) to 29.8 (17.7 to 44.2), (p = 0.003) and the mean Euroqol EQ‑5D‑5L score improved from 0.63 (0.51 to 0.78) to 0.67 (0.57 to 0.84), (p = 0.012). Single-stage correction of deformity using an intramedullary hindfoot arthrodesis nail is a good form of treatment for patients with severe Charcot hindfoot deformity, ulceration and instability provided a multidisciplinary care plan is delivered.
The ability to predict and describe nonradiative processes in molecules via the identification and characterization of conical intersections is one of the greatest recent successes of theoretical ...chemistry. Only recently, however, has this concept been extended to materials science, where nonradiative recombination limits the efficiencies of materials for various optoelectronic applications. In this review, we present recent advances in the theoretical study of conical intersections in semiconductor nanomaterials. After briefly introducing conical intersections, we argue that specific defects in materials can induce conical intersections between the ground and first excited electronic states, thus introducing pathways for nonradiative recombination. We present recent developments in theoretical methods, computational tools, and chemical intuition for the prediction of such defect-induced conical intersections. Through examples in various nanomaterials, we illustrate the significance of conical intersections for nanoscience. We also discuss challenges facing research in this area and opportunities for progress.
1. There is a significant species difference in the toxicity of 2,4-dichlorophenoxyacetic acid (2,4-D). The oral no overall adverse effect level (NOAEL) for chronic toxicity of 2,4-D in rat is 5 mg ...kg − 1 day − 1 and in dog is 1 mg kg − 1 day − 1. The maximum tolerated dose (MTD) in rat is 150 and 75 kg − 1 day − 1 for male and females, respectively. The MTD in dog is 7.5 mg kg − 1 day − 1 for males and females. 2. In an attempt to explain the increased sensitivity to 2,4-D in dog, male and female rats and dogs were orally dosed with either 5 or 50 mg kg − 1 14 C-2,4-D. The rates and routes of excretion were investigated along with plasma toxicokinetics and biotransformation of the compound. 3. Elimination of the radioactive dose of 2,4-D from rat plasma was significantly faster than in dog. The approximate t ½ were 1.3-3.4 h for rat and 99-134 h for dog following a 5 or 50 mg kg − 1 dose, respectively. This led to large differences in the calculated AUC (0- ∝) 21-57 μ eq. h g − 1 for rat and 4889-5298 µg eq. h g − 1 for dog at 5 mg kg − 1, and 122-2358 µg eq. h g − 1 for rat and 34 110-44 296 µg eq. h g − 1 for dog at 50 mg kg − 1). 4. In rat, the major route of excretion was in the urine. Excretion was essentially complete after 24 h for the low dose and after 48 h for the high dose. For dog, elimination was incomplete over the sampling period with only about 50% of the dose recovered. Urine was the principal route of excretion at the low dose, but about equal amounts were excreted in urine and faeces at the high dose over 120 h. 5. In rat, 2,4-D was unmetabolized and excreted in urine as the parent compound. In dog, the dose was excreted mainly following metabolism. 2,4-D in dog was conjugated forming the taurine, serine, glycine, glutamic acid, cysteine, sulphate and glucuronide conjugates, plus an unidentified metabolite, which were excreted in urine. Plasma, however, only contained unmetabolized 2,4-D. 6. The results show that the body burden of 2,4-D in dog is significantly higher than in rat for an equivalent dose, which is consistent with the increased sensitivity of dog to 2,4-D toxicity.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
1. The oral no overall adverse effect level (NOAEL) for chronic toxicity of 4-chloro-2-methylphenoxyacetic acid (MCPA) in rat is ~1.3 mg kg-1 and in dog is 0.2 mgkg-1. In an attempt to explain the ...difference in toxicology between these species, rats and dogs were orally dosed with (14C)-MCPA at 5 or 100 mg kg-1 and plasma toxicokinetics, rates and routes of excretion and biotransformation were investigated. 2. Elimination of radioactivity in rat plasma was biphasic and in dog was monophasic. Rat eliminated radioactivity from plasma significantly faster than dog (approximate values based on total radioactivity: 5 mgkg-1 rat: t½dist 3.5 h, t½elim 17.2-36.2 h, AUC(0-∞) 230 µg equiv h g-1; 5 mgkg-1 dog: t½47 h, AUC(0-∞) 2500 µg equiv h g-1; 100mg kg-1 rat: t½dist 10 h, t½elim 10.27-25.4 h, AUC(0-∞) 5400 µg equiv h g-1; 100 mg kg-1 dog: t½41 h, AUC(0-∞) 20 500µg equiv h g-1). 3. For both species, the principal route of excretion was in urine but renal elimination was notably more rapid and more extensive in rat. 4. In both rat and dog, excretion of radioactivity was mainly as MCPA and its hydroxylated metabolite hydroxymethylphenoxyacetic acid (HMCPA). In rat, both were mainly excreted as the free acids although a small proportion was conjugated. In dog, the proportion of HMCPA was increased and the majority of both species was excreted as glycine or taurine conjugates. 5. These data, along with previously published accounts, indicate that renal elimination of MCPA in dog is substantially slower than in rat resulting in disproportionate elevation of AUC (based on total radioactivity) in dog compared with rat.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Data on 806 patients undergoing bone graft surgery for a scaphoid fracture nonunion were retrospectively collected at 19 centres in the United Kingdom. Each centre contributed at least 30 cases. ...Sufficient data were available in 462 cases to study factors that influenced the outcome of surgery. Overall union occurred in at least 69%, and nonunion in at least 22%, with 9% of cases having ‘uncertain union status’. Union appeared to be adversely influenced by smoking and the time between acute scaphoid fracture and nonunion surgery, with adjusted odds ratios of 1.8 and 2.4, respectively, but neither achieved the pre-determined significance level of 0.003. The type of bone graft (vascular vs non-vascular; iliac crest vs distal radius) did not appear to influence outcome. Further large multicentre prospective studies with clear definitions of ‘union’ and other factors are needed to clarify whether modification of surgical technique can influence union.
Level of evidence: IV
Urinary pyridinoline and deoxypyridinoline crosslinks (crosslink) are excreted when bone is resorbed. The aims of this study in healthy infants were to determine whether crosslinks a) could predict ...growth velocity, b) are variable due to circadian rhythm, and c) differ in infants who were either breast-fed or formula-fed. In 78 healthy infants (48 male; 30 female) urine samples were collected and anthropometric measurements were taken at 2, 3, 4, 5, 6, 8, 10 and 12 months of age. In addition, a total of 25 samples were collected during the day (0700-2000) in 5 of the infants to determine circadian rhythm of crosslink excretion. Crosslink excretion decreased (p < 0.001) with age between 2 and 12 months. Pyridinoline excretion showed a significant, but weak correlation (r > or = 0.21; p < 0.05) with linear growth velocity and weight velocity in the subsequent month until 6 months of age, and no correlation thereafter. Infants studied for circadian rhythm showed a 63% greater (p < 0.05) rate of pyridinoline excretion after a nap as compared to the 13-hour mean value. In a subset of infants whose energy intake was exclusively from breast milk (BF, n = 23) or formula (FF, n = 10), crosslink excretion was greater in BF infants at 3 months of age (p < 0.05). The correlations between crosslink excretion and growth parameters indicate that crosslinks may be useful as a marker of growth in infant populations. However sources of variation in crosslink excretion, such as circadian rhythm and diet may limit their utility to predict growth in an individual infant. These factors should be considered in future studies examining markers of bone turnover in infants.
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