We consider Device-to-Device (D2D) communication underlaying cellular networks to improve local services. The system aims to optimize the throughput over the shared resources while fulfilling ...prioritized cellular service constraints. Optimum resource allocation and power control between the cellular and D2D connections that share the same resources are analyzed for different resource sharing modes. Optimality is discussed under practical constraints such as minimum and maximum spectral efficiency restrictions, and maximum transmit power or energy limitation. It is found that in most of the considered cases, optimum power control and resource allocation for the considered resource sharing modes can either be solved in closed form or searched from a finite set. The performance of the D2D underlay system is evaluated in both a single-cell scenario, and a Manhattan grid environment with multiple WINNER II A1 office buildings. The results show that by proper resource management, D2D communication can effectively improve the total throughput without generating harmful interference to cellular networks.
We studied the response of the ionosphere (F region) in the Brazilian sector during extreme space weather event of 17 March 2015 using a large network of 102 GPS‐ total electron content (TEC) ...stations. It is observed that the vertical total electron content (VTEC) was severely disturbed during the storm main and recovery phases. A wavelike oscillation with three peaks was observed in the TEC diurnal variation from equator to low latitudes during the storm main phase on 17–18 March 2015. The latitudinal extent of the wavelike oscillation peaks decreased from the beginning of the main phase toward the recovery phase. The first peak extended from beyond 0°S to 30°S, the second occurred from 6°S to 25°S, whereas the third diurnal peaks was confined from 13°S to 25°S. In addition, a strong negative phase in VTEC variations was observed during the recovery phase on 18–19 March 2015. This ionospheric negative phase was stronger at low latitudes than in the equatorial region. Also, two latitudinal chains of GPS‐TEC stations from equatorial region to low latitudes in the east and west Brazilian sectors are used to investigate the storm time behavior of the equatorial ionization anomaly (EIA) in the east and west Brazilian sectors. We observed an anomalous behavior in EIA caused by the wavelike oscillations during the storm main phase on 17 March, and suppression of the EIA, resulting from the negative phase in VTEC, in the storm recovery phase.
Key Points
The 17 March 2015 St. Patrick´s day geomagnetic storm
Extreme ionospheric space weather event over the Brazilian sector
Anomalous behavior in EIA during main phase and recovery phases
Aims/hypothesis
Supervised exercise programmes improve glycaemic control in type 2 diabetes, but training characteristics associated with reduction in HbA
1c
remain unclear. We conducted a systematic ...review with meta-regression analysis of randomised clinical trials (RCTs) assessing the association between intensity and volume of exercise training (aerobic, resistance or combined) and HbA
1c
changes in patients with type 2 diabetes.
Methods
Five electronic databases were searched (1980–2012) to retrieve RCTs of at least 12 weeks' duration, consisting of supervised exercise training vs no intervention, that reported HbA
1c
changes and exercise characteristics. Two independent reviewers conducted study selection and data extraction.
Results
Twenty-six RCTs (2,253 patients) met the inclusion criteria. In multivariate analysis, baseline HbA
1c
and exercise frequency explained nearly 58% of between-study variance. Baseline HbA
1c
was inversely correlated with HbA
1c
reductions after the three types of exercise training. In aerobic training, exercise volume (represented by frequency of sessions) was associated with changes in HbA
1c
(weighted
r
= −0.64), while no variables were correlated with glycaemic control induced by resistance training. In combined training, weekly volume of resistance exercise explained heterogeneity in multivariate analysis and was associated with changes in HbA
1c
levels (weighted
r
= −0.70).
Conclusions/interpretation
Reduction in HbA
1c
is associated with exercise frequency in supervised aerobic training, and with weekly volume of resistance exercise in supervised combined training. Therefore, exercise volume is a major determinant of glycaemic control in patients with type 2 diabetes.
As optical fibers revolutionize the way data is carried in telecommunications, the same is happening in the world of sensing. Fiber-optic sensors (FOS) rely on the principle of changing the ...properties of light that propagate in the fiber due to the effect of a specific physical or chemical parameter. We demonstrate the potentialities of this sensing concept to assess pressure in biomedical and biomechanical applications. FOSs are introduced after an overview of conventional sensors that are being used in the field. Pointing out their limitations, particularly as minimally invasive sensors, is also the starting point to argue FOSs are an alternative or a substitution technology. Even so, this technology will be more or less effective depending on the efforts to present more affordable turnkey solutions and peer-reviewed papers reporting in vivo experiments and clinical trials.
CONTEXT Regular exercise improves glucose control in diabetes, but the association of different exercise training interventions on glucose control is unclear. OBJECTIVE To conduct a systematic review ...and meta-analysis of randomized controlled clinical trials (RCTs) assessing associations of structured exercise training regimens (aerobic, resistance, or both) and physical activity advice with or without dietary cointervention on change in hemoglobin A1c (HbA1c) in type 2 diabetes patients. DATA SOURCES MEDLINE, Cochrane-CENTRAL, EMBASE, ClinicalTrials.gov, LILACS, and SPORTDiscus databases were searched from January 1980 through February 2011. STUDY SELECTION RCTs of at least 12 weeks' duration that evaluated the ability of structured exercise training or physical activity advice to lower HbA1c levels as compared with a control group in patients with type 2 diabetes. DATA EXTRACTION Two independent reviewers extracted data and assessed quality of the included studies. DATA SYNTHESIS Of 4191 articles retrieved, 47 RCTs (8538 patients) were included. Pooled mean differences in HbA1c levels between intervention and control groups were calculated using a random-effects model. Overall, structured exercise training (23 studies) was associated with a decline in HbA1c level (−0.67%; 95% confidence interval CI, −0.84% to −0.49%; I2, 91.3%) compared with control participants. In addition, structured aerobic exercise (−0.73%; 95% CI, −1.06% to −0.40%; I2, 92.8%), structured resistance training (−0.57%; 95% CI, −1.14% to −0.01%; I2, 92.5%), and both combined (−0.51%; 95% CI, −0.79% to −0.23%; I2, 67.5%) were each associated with declines in HbA1C levels compared with control participants. Structured exercise durations of more than 150 minutes per week were associated with HbA1c reductions of 0.89%, while structured exercise durations of 150 minutes or less per week were associated with HbA1C reductions of 0.36%. Overall, interventions of physical activity advice (24 studies) were associated with lower HbA1c levels (−0.43%; 95% CI, −0.59% to −0.28%; I2, 62.9%) compared with control participants. Combined physical activity advice and dietary advice was associated with decreased HbA1c (−0.58%; 95% CI, −0.74% to −0.43%; I2, 57.5%) as compared with control participants. Physical activity advice alone was not associated with HbA1c changes. CONCLUSIONS Structured exercise training that consists of aerobic exercise, resistance training, or both combined is associated with HbA1c reduction in patients with type 2 diabetes. Structured exercise training of more than 150 minutes per week is associated with greater HbA1c declines than that of 150 minutes or less per week. Physical activity advice is associated with lower HbA1c, but only when combined with dietary advice.
Forest edges influence more than half of the world's forests and contribute to worldwide declines in biodiversity and ecosystem functions. However, predicting these declines is challenging in ...heterogeneous fragmented landscapes. Here we assembled a global dataset on species responses to fragmentation and developed a statistical approach for quantifying edge impacts in heterogeneous landscapes to quantify edge-determined changes in abundance of 1,673 vertebrate species. We show that the abundances of 85% of species are affected, either positively or negatively, by forest edges. Species that live in the centre of the forest (forest core), that were more likely to be listed as threatened by the International Union for Conservation of Nature (IUCN), reached peak abundances only at sites farther than 200-400 m from sharp high-contrast forest edges. Smaller-bodied amphibians, larger reptiles and medium-sized non-volant mammals experienced a larger reduction in suitable habitat than other forest-core species. Our results highlight the pervasive ability of forest edges to restructure ecological communities on a global scale.
To provide a comprehensive picture of mental health problems (MHPs) in Brazilian medical students by documenting their prevalence and association with co-factors.
We systematically searched the ...MEDLINE/PubMed, SciELO, LILACS, and PsycINFO databases for cross-sectional studies on the prevalence of MHPs among medical students in Brazil published before September 29, 2016. We pooled prevalences using a random-effects meta-analysis, and summarized factors associated with MHP.
We included 59 studies in the analysis. For meta-analyses, we identified the summary prevalence of different MHPs, including depression (25 studies, prevalence 30.6%), common mental disorders (13 studies, prevalence 31.5%), burnout (three studies, prevalence 13.1%), problematic alcohol use (three studies, prevalence 32.9%), stress (six studies, prevalence 49.9%), low sleep quality (four studies, prevalence 51.5%), excessive daytime sleepiness (four studies, prevalence 46.1%), and anxiety (six studies, prevalence 32.9%). Signs of lack of motivation, emotional support, and academic overload correlated with MHPs.
Several MHPs are highly prevalent among future physicians in Brazil. Evidence-based interventions and psychosocial support are needed to promote mental health among Brazilian medical students.
Synthesising evidence on the long-term vaccine effectiveness of COVID-19 vaccines (BNT162b2 Pfizer-BioNTech, mRNA-1273 Moderna, ChAdOx1 nCoV-19 AZD1222; Oxford-AstraZeneca, and Ad26.COV2.S Janssen) ...against infections, hospitalisations, and mortality is crucial to making evidence-based pandemic policy decisions.
In this rapid living systematic evidence synthesis and meta-analysis, we searched EMBASE and the US National Institutes of Health's iSearch COVID-19 Portfolio, supplemented by manual searches of COVID-19-specific sources, until Dec 1, 2022, for studies that reported vaccine effectiveness immediately and at least 112 days after a primary vaccine series or at least 84 days after a booster dose. Single reviewers assessed titles, abstracts, and full-text articles, and extracted data, with a second reviewer verifying included studies. The primary outcomes were vaccine effectiveness against SARS-CoV-2 infections, hospitalisations, and mortality, which were assessed using three-level meta-analytic models. This study is registered with the National Collaborating Centre for Methods and Tools, review 473.
We screened 16 696 records at the title and abstract level, appraised 832 (5·0%) full texts, and initially included 73 (0·4%) studies. Of these, we excluded five (7%) studies because of critical risk of bias, leaving 68 (93%) studies that were extracted for analysis. For infections caused by any SARS-CoV-2 strain, vaccine effectiveness for the primary series reduced from 83% (95% CI 80-86) at baseline (14-42 days) to 62% (53-69) by 112-139 days. Vaccine effectiveness at baseline was 92% (88-94) for hospitalisations and 91% (85-95) for mortality, and reduced to 79% (65-87) at 224-251 days for hospitalisations and 86% (73-93) at 168-195 days for mortality. Estimated vaccine effectiveness was lower for the omicron variant for infections, hospitalisations, and mortality at baseline compared with that of other variants, but subsequent reductions occurred at a similar rate across variants. For booster doses, which covered mostly omicron studies, vaccine effectiveness at baseline was 70% (56-80) against infections and 89% (82-93) against hospitalisations, and reduced to 43% (14-62) against infections and 71% (51-83) against hospitalisations at 112 days or later. Not enough studies were available to report on booster vaccine effectiveness against mortality.
Our analyses indicate that vaccine effectiveness generally decreases over time against SARS-CoV-2 infections, hospitalisations, and mortality. The baseline vaccine effectiveness levels for the omicron variant were notably lower than for other variants. Therefore, other preventive measures (eg, face-mask wearing and physical distancing) might be necessary to manage the pandemic in the long term.
Canadian Institutes of Health Research and the Public Health Agency of Canada.
Abstract
We compare the sizes and luminosities of faint
z
= 6–8 galaxies magnified by the Hubble Frontier Fields clusters with star-forming regions, as well as more evolved objects, in the nearby ...universe. Our high-redshift comparison sample includes 330
z
= 6–8 galaxies, for which size measurements were made as part of a companion study where lensing magnifications were estimated from various public models. Accurate size measurements for these sources are complicated by the lens model uncertainties, but other results and arguments suggest that faint galaxies are small, as discussed in a companion study. The measured sizes for sources in our comparison sample range from <50 pc to ∼500 pc. For many of the lowest-luminosity sources, extremely small sizes are inferred, reaching individual sizes as small as 10–30 pc, with several sources in the 10–15 pc range with our conservative magnification limits. The sizes and luminosities are similar to those of single star cluster complexes like 30 Doradus in the lower-redshift universe and—in a few cases—super star clusters. The identification of these compact, faint star-forming sources in the
z
∼ 6–8 universe also allows us to set upper limits on the proto-globular cluster luminosity function at
z
∼ 6. By comparisons of the counts and sizes with recent models, we rule out (with some caveats) proto-globular cluster formation scenarios favoring substantial (
ξ
= 10) post-formation mass loss and set useful upper limits on others. Our size results suggest we may be very close to discovering a bona fide population of forming globular clusters at high redshift.
Abstract
We assemble a large comprehensive sample of 2534
z
∼ 2, 3, 4, 5, 6, 7, 8, and 9 galaxies lensed by the six clusters from the Hubble Frontier Fields (HFF) program. Making use of the ...availability of multiple independent magnification models for each of the HFF clusters and alternatively treating one of the models as the “truth,” we show that the median magnification factors from the v4 parametric models are typically reliable to values of 30–50, and in one case to 100. Using the median magnification factor from the latest v4 models, we estimate the UV luminosities of the 2534 lensed
z
∼ 2–9 galaxies, finding sources as faint as −12.4 mag at
z
∼ 3 and −12.9 mag at
z
∼ 7. We explicitly demonstrate the power of the surface density–magnification relations Σ(
z
) versus
μ
in the HFF clusters to constrain both distant galaxy properties and cluster lensing properties. Based on the Σ(
z
) versus
μ
relations, we show that the median magnification estimates from existing public models must be reliable predictors of the true magnification
μ
to
μ
< 15 (95% confidence). We also use the observed Σ(
z
) versus
μ
relations to derive constraints on the evolution of the luminosity function faint-end slope from
z
∼ 7 to
z
∼ 2, showing that faint-end slope results can be consistent with blank-field studies if, and only if, the selection efficiency shows no strong dependence on the magnification factor
μ
. This can only be the case if very low-luminosity galaxies are very small, being unresolved in deep lensing probes.
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