Abstract
The repeating fast radio burst source FRB 121102 has been shown to have an exceptionally high and variable Faraday rotation measure (RM), which must be imparted within its host galaxy, ...likely by or within its local environment. In the redshifted (
z
= 0.193) source reference frame, the RM decreased from 1.46 × 10
5
rad m
−2
to 1.33 × 10
5
rad m
−2
between 2017 January and August, showing day-timescale variations of ∼200 rad m
−2
. Here we present 16 FRB 121102 RMs from burst detections with the Arecibo 305 m radio telescope, the Effelsberg 100 m, and the Karl G. Jansky Very Large Array, providing a record of FRB 121102’s RM over a 2.5 yr time span. Our observations show a decreasing trend in RM, although the trend is not linear, dropping by an average of 15% year
−1
and is ∼ 9.7 × 10
4
rad m
−2
at the most recent epoch of 2019 August. Erratic, short-term RM variations of ∼10
3
rad m
−2
week
−1
were also observed between MJDs 58215–58247. A decades-old neutron star embedded within a still-compact supernova remnant or a neutron star near a massive black hole and its accretion torus have been proposed to explain the high RMs. We compare the observed RMs to theoretical models describing the RM evolution for FRBs originating within a supernova remnant. FRB 121102’s age is unknown, and we find that the models agree for source ages of ∼6–17 yr at the time of the first available RM measurements in 2017. We also draw comparisons to the decreasing RM of the Galactic center magnetar, PSR J1745−2900.
Abstract
Sodium sulfur batteries require efficient sulfur hosts that can capture soluble polysulfides and enable fast reduction kinetics. Herein, we design hollow, polar and catalytic bipyramid ...prisms of cobalt sulfide as efficient sulfur host for sodium sulfur batteries. Cobalt sulfide has interwoven surfaces with wide internal spaces that can accommodate sodium polysulfides and withstand volumetric expansion. Furthermore, results from in/ex-situ characterization techniques and density functional theory calculations support the significance of the polar and catalytic properties of cobalt sulfide as hosts for soluble sodium polysulfides that reduce the shuttle effect and display excellent electrochemical performance. The polar catalytic bipyramid prisms sulfur@cobalt sulfide composite exhibits a high capacity of 755 mAh g
−1
in the second discharge and 675 mAh g
−1
after 800 charge/discharge cycles, with an ultralow capacity decay rate of 0.0126 % at a high current density of 0.5 C. Additionally, at a high mass loading of 9.1 mg cm
−2
, sulfur@cobalt sulfide shows high capacity of 545 mAh g
−1
at a current density of 0.5 C. This study demonstrates a hollow, polar, and catalytic sulfur host with a unique structure that can capture sodium polysulfides and speed up the reduction reaction of long chain sodium polysulfides to solid small chain polysulfides, which results in excellent electrochemical performance for sodium-sulfur batteries.
FRB 121102 is the only known repeating fast radio burst source. Here we analyze a wide-frequency-range (1-8 GHz) sample of high signal-to-noise, coherently dedispersed bursts detected using the ...Arecibo and Green Bank telescopes. These bursts reveal complex time-frequency structures that include subbursts with finite bandwidths. The frequency-dependent burst structure complicates the determination of a dispersion measure (DM); we argue that it is appropriate to use a DM metric that maximizes frequency-averaged pulse structure, as opposed to peak signal-to-noise, and find DM = 560.57 0.07 pc cm−3 at MJD 57,644. After correcting for dispersive delay, we find that the subbursts have characteristic frequencies that typically drift lower at later times in the total burst envelope. In the 1.1-1.7 GHz band, the ∼0.5-1 ms subbursts have typical bandwidths ranging from 100 to 400 MHz, and a characteristic drift rate of ∼200 MHz ms−1 toward lower frequencies. At higher radio frequencies, the subburst bandwidths and drift rate are larger, on average. While these features could be intrinsic to the burst emission mechanism, they could also be imparted by propagation effects in the medium local to the source. Comparison of the burst DMs with previous values in the literature suggests an increase of ΔDM ∼ 1-3 pc cm−3 in 4 yr; though, this could be a stochastic variation as opposed to a secular trend. This implies changes in the local medium or an additional source of frequency-dependent delay. Overall, the results are consistent with previously proposed scenarios in which FRB 121102 is embedded in a dense nebula.
Aims
To establish whether irrigant activation techniques (IATs) result in greater intracanal smear layer and debris removal than conventional needle irrigation (CNI).
Methodology
Six electronic ...databases were searched to identify scanning electron microscopy studies evaluating smear layer and/or debris removal following the use of manual dynamic activation (MDA), passive ultrasonic irrigation (PUI), sonic irrigation (SI) or apical negative pressure (ANP) IATs in mature permanent teeth. Meta‐analyses were performed for each canal segment (coronal, middle, apical and apical 1 mm) in addition to subgroup analyses for individual IATs with respect to CNI. Outcomes were presented as standardized mean differences (SMD) alongside 95% confidence intervals (95% CI) and chi‐squared analysis.
Results
From 252 citations, 16 studies were identified. The meta‐analyses demonstrated significant improvements in coronal (SMD: 1.15, 95% CI: 0.72–1.57 / SMD: 0.54, 95% CI: 0.29–0.80), middle (SMD: 1.30, 95% CI: 0.59–2.53 / SMD: 0.8, 95% CI: 0.58–1.13) and apical thirds (SMD: 1.22, 95% CI: 0.83–1.62 / SMD: 1.86, 95% CI: 0.76–2.96) for smear layer and debris removal, respectively. In the apical 1 mm IATs improved cleanliness; however, differences were insignificant (SMD: 1.15, 95% CI: ‐0.47–2.77). Chi‐squared analysis revealed heterogeneity scores of 79.3–92.8% and 0.0–93.5% for smear layer and debris removal, respectively.
Conclusions
IATs improve intracanal cleanliness across a substantial portion of the canal, and therefore, their use is recommended throughout root canal preparation. However, current data is too heterogeneous to compare and identify superiority of an individual technique highlighting the need to standardize experimental protocols and develop a more representative research model to investigate the in vivo impact of IATs on clinical outcomes and periapical healing following root canal treatment.
Cation order, with a local structure related to γ-LiFeO2, is observed in the nominally cation-disordered Li-excess rocksalt Li1.25Nb0.25Mn0.5O2via X-ray diffraction, neutron pair distribution ...function analysis, magnetic susceptibility and NMR spectroscopy. The correlation length of ordering depends on synthesis conditions and has implications for the electrochemistry of these phases.
Inclusion of urea in dairy cattle diets is often limited by negative effects of high levels of feed urea on dry matter intake (DMI) and efficiency of rumen N utilization. We hypothesized that ...supplying urea postruminally would mitigate these limitations and allow greater inclusion of urea in dairy cattle diets. Four rumen-fistulated Holstein-Friesian dairy cows (7 ± 2.1 lactations, 110 ± 30.8 d in milk; mean ± standard deviation) were randomly assigned to a 4 × 4 Latin square design to examine DMI, milk production and composition, digestibility, rumen fermentation, N balance, and plasma constituents in response to 4 levels of urea continuously infused into the abomasum (0, 163, 325, and 488 g/d). Urea doses were targeted to linearly increase the crude protein (CP) content of total DMI (diet plus infusion) by 0%, 2%, 4%, and 6% and equated to 0%, 0.7%, 1.4%, and 2.1% of expected DMI, respectively. Each 28-d infusion period consisted of a 7-d dose step-up period, 14 d of adaptation, and a 7-d measurement period. The diet was fed ad libitum as a total mixed ration 10.9% CP, 42.5% corn silage, 3.5% grass hay, 3.5% wheat straw, and 50.5% concentrate (dry matter basis) and was formulated to meet 100%, 82%, and 53% of net energy, metabolizable protein, and rumen-degradable protein requirements, respectively. Linear, quadratic, and cubic effects of urea dose were assessed using polynomial regression assuming the fixed effect of treatment and random effects of period and cow. Dry matter intake and energy-corrected milk yield responded quadratically to urea dose, and milk urea content increased linearly with increasing urea dose. Apparent total-tract digestibility of CP increased linearly with increasing urea dose and ruminal NH
-N concentration responded quadratically to urea dose. Mean total VFA concentration was not affected by urea dose. The proportion of N intake excreted in feces decreased linearly and that excreted in urine increased linearly in response to increasing urea dose. The proportion of N intake excreted in milk increased linearly with increasing urea dose. Urinary urea excretion increased linearly with increasing urea dose. Microbial N flow responded cubically to urea dose, but the efficiency of microbial protein synthesis was not affected. Plasma urea concentration increased linearly with increasing urea dose. Regression analysis estimated that when supplemented on top of a low-CP diet, 179 g/d of postruminal urea would maximize DMI at 23.4 kg/d, corresponding to a dietary urea inclusion level of 0.8% of DMI, which is in line with the current recommendations for urea inclusion in dairy cattle diets. Overall, these results indicate that postruminal delivery of urea does not mitigate DMI depression as urea dose increases.
OBJECTIVES: To evaluate the attitudes of first‐ and fourth‐year medical students toward older people and the relationship between these attitudes and possible career choice. To examine the effects of ...an intensive geriatric medicine (GM) teaching program on these attitudes and career aspirations.
DESIGN: Observational study.
SETTING: University of Aberdeen.
PARTICIPANTS: Medical students.
MEASUREMENTS: In September 2005, first‐year students (n=163) at the start of their undergraduate training completed a questionnaire based on the University of California at Los Angeles Geriatrics Attitudes Scale. Students were asked how likely they were to consider a career in GM in the future on a 5‐point Likert scale. From the beginning of the academic year 2005/06, fourth‐year students completed the same questionnaire before and after an intensive 8‐day GM teaching program.
RESULTS: First‐year medical students had a mean attitude score±standard deviation of 3.69±0.39. A more‐positive attitude increased the likelihood of considering a career in GM (P<.001). Fourth‐year students had better attitude scores than first‐year students (3.86±0.36, P=.002). The GM teaching program did not significantly affect attitude scores but significantly increased the willingness to consider a career in GM by a mean 0.52 points (95% confidence interval=0.35–0.70, P<.001).
CONCLUSION: Attitudes toward older people were better in fourth‐year than first‐year medical students. A more‐positive attitude toward older people increased the likelihood of considering a career in GM. An intensive 8‐day course in GM had no significant effect on attitudes but increased the likelihood of fourth‐year students considering a career in GM.
Introduction: the ACMEplus project aims to devise a standardised system for measuring case-mix and outcome in older patients admitted to hospitals in different parts of Europe for primarily ‘medical’ ...(i.e. not surgical or psychiatric) reasons. As a first step in this project, a systematic review was carried out to identify factors which had a significant influence on outcome in such patients. Methods: the systematic search used Medline 1966–2000, Cinahl 1982–2000, Web of Science 1981–2000, reference lists of relevant papers and a hand search of Age and Ageing 1974–2000. A six-category grading system was devised to classify the 313 identified papers with regard to their relevance to the ACMEplus project, study design and power. The analysis of the 14 ‘category 1’ papers is presented. Results: the main areas of assessment of case-mix were function, cognition, depression, illness severity, nutrition, social elements, aspects of diagnosis and demographic details. Statistically significant predictors, for the four outcome measures, listed below were: For length of stay: functional status score, illness severity, cognitive score, poor nutrition, comorbidity score, diagnosis or presenting illness, polypharmacy, age and gender. For mortality: functional status score, illness severity, cognitive score, comorbidity score, diagnosis or presenting illness, polypharmacy, age and gender. For discharge destination: functional status score, cognitive score, diagnosis or presenting illness and age. For readmission rate: functional status score, illness severity, co-morbidity, polypharmacy, diagnosis or presenting illness and age. Conclusions: factors affecting outcome in older medical patients are complex. When looking at outcomes of hospital admission in older people it is important not just to look at routinely available statistics such as age, gender and diagnosis but also to take into account multifaceted aspects such as functional status and cognitive function.
ε-LiVOPO4, a multi-electron cathode material for Li-ion batteries, suffers from structural disorder upon nanosizing by high-energy ball-milling, which impedes kinetics and promotes undesirable ...interfacial side reactions. This work presents a feasible way to decrease the disorder in the ball-milled composite of ε-LiVOPO4/C by post-annealing at 450 °C in an Ar atmosphere, with no reduction reaction caused by carbon and no particle growth. The post-annealed material shows recovered voltage plateaus, enhanced kinetics of Li diffusivity, and suppressed interfacial reactions. As a result, a high-performance solid-state synthesized ε-LiVOPO4 can be obtained, delivering a capacity of 270 mAh g−1 at C/5 with less than 4% degradation upon 100 cycles.
Display omitted
•High, stable capacity at high rate is achieved in the annealed LiVOPO4/C composite.•Post-annealing of LiVOPO4/C composite heals disorder introduced by ball-milling.•NMR and pair-distribution function data reveal the degree of disorder in LiVOPO4.
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