Very-high energy gamma-ray astronomy: A 23-year success story in high-energy astroparticle physics

Very-high energy (VHE) gamma quanta contribute only a minuscule fraction - below one per million - to the flux of cosmic rays. Nevertheless, being neutral particles they are currently the best "messengers" of processes from the relativistic/ultra-relativistic Universe because they can be extrapolated back to their origin. The window of VHE gamma rays was opened only in 1989 by the Whipple collaboration, reporting the observation of TeV gamma rays from the Crab nebula. After a slow start, this new field of research is now rapidly expanding with the discovery of more than 150 VHE gamma-ray emitting sources. Progress is intimately related with the steady improvement of detectors and rapidly increasing computing power. We give an overview of the early attempts before and around 1989 and the progress after the pioneering work of the Whipple collaboration. The main focus of this article is on the development of experimental techniques for Earth-bound gamma-ray detectors; consequently, more emphasis is given to those experiments that made an initial breakthrough rather than to the successors which often had and have a similar (sometimes even higher) scientific output as the pioneering experiments. The considered energy threshold is about 30 GeV. At lower energies, observations can presently only be performed with balloon or satellite-borne detectors. Irrespective of the stormy experimental progress, the success story could not have been called a success story without a broad scientific output. Therefore we conclude this article with a summary of the scientific rationales and main results achieved over the last two decades.Comment: 45 pages, 38 figures, review prepared for EPJ-H special issue "Cosmic rays, gamma rays and neutrinos: A survey of 100 years of research

Obesidade e sobrepeso em adolescentes: relação com atividade física, aptidão física, maturação biológica e "status" socioeconômico Obesity and overweight in adolescents: relationship among physical activity, physical fitness, biological maturity and socioeconomic status

Este estudo relaciona atividade física (AF), aptidão física (AptF), maturação biológica e "status" socioe-conômico (ESE) com as prevalências de risco ponderal de adolescentes. Foi desenvolvido no Concelho de Santo Tirso, região norte de Portugal e amostrou 961 alunos (463 meninos e 498 meninas) com idades variando entre os 11 e os 18 anos. O índice de massa corporal foi utilizado para estabelecer o "status" ponderal com base nos pontos de corte propostos por COLE et al. A AF foi avaliada através do questionário de Baecke e a AptF com quatro testes da bateria Fitnessgram. O ESE foi estimado a partir do acesso aos escalões atribuídos pela Ação Social Escolar e a maturação biológica a partir do "offset" maturacional. A análise estatística foi efetuada nos "softwares" Pepi versão 4.0 e SPSS 18.0. O nível de significância foi mantido em 5%. Seis por cento dos alunos eram obesos e 19,5% tinham sobrepeso; meninos e meninas têm prevalências semelhantes de sobrepeso e obesidade. Os níveis médios de AF foram baixos a moderados independentemente do sexo ou "status" ponderal. Os meninos eram mais ativos que as meninas (p < 0,001), mas não se registraram diferenças significativas entre os alunos com obesidade e sobrepeso e os normoponderais. Na AptF, um número superior a 50%, foi considerado inapto, i.e, não obtiveram taxas de sucesso em todos os testes. Os alunos com sobrepeso e obesidade foram mais inaptos. Alunos com "offset" maturacional mais avançado e os mais novos tinham mais chances de ter sobrepeso e obesidade, mas não houve relação significativa entre o ESE e o "status" ponderal. Concluímos que os jovens Tirsenses apresentam prevalências de obesidade e sobrepeso elevadas, são relativamente pouco ativos e, em grande medida, fisicamente inaptos.<br>The aim of this study was to relate physical activity, physical fitness, maturation and socioeconomic status with the prevalence of ponderal risk in adolescents. This was a transversal study made in the Council of Santo Tirso in the north of Portugal. The sample consisted of 961students (463 boys and 498 girls), aged 11 to 18. Body mass index was used to establish ponderal status based on the cut points from COLE et al. Physical activity was evaluated by Baecke's questionnaire and physical fitness with four tests from Fitnessgram battery. Socioeconomic status was ranked according to the grades assigned by state school subsidies, while biological maturation estimation was based on maturational offset. Software programs Pepi version 4.0 and SPSS 18.0 were used for statistical analysis. The level of significance was kept in 5%. Six percent of the target students were obese and 19.5% had overweight. The prevalences of overweight and obesity were similar between genders. The medium levels of physical activity were low or moderate, independent of gender or ponderal status. Boys were more active than girls (p < 0.001) but no significant differences were found between the students with obesity and overweight and normoponderal ones. On what concerns physical fitness, a high percentage of students (above 50%) were considered inapt and failed the tests. Students suffering from overweight and obesity were clearly more inapt. Students with more advanced maturational offset as well as the youngest ones were more likely to present overweight and obesity but no meaningful relationship was found between socioeconomic position and ponderal status. We concluded that young students from S. Tirso had high prevalences of obesity and overweight, were relatively inactive and largely physically unfit

Global impact of COVID-19 on stroke care

Background: The COVID-19 pandemic led to profound changes in the organization of health care systems worldwide. Aims: We sought to measure the global impact of the COVID-19 pandemic on the volumes for mechanical thrombectomy, stroke, and intracranial hemorrhage hospitalizations over a three-month period at the height of the pandemic (1 March–31 May 2020) compared with two control three-month periods (immediately preceding and one year prior). Methods: Retrospective, observational, international study, across 6 continents, 40 countries, and 187 comprehensive stroke centers. The diagnoses were identified by their ICD-10 codes and/or classifications in stroke databases at participating centers. Results: The hospitalization volumes for any stroke, intracranial hemorrhage, and mechanical thrombectomy were 26,699, 4002, and 5191 in the three months immediately before versus 21,576, 3540, and 4533 during the first three pandemic months, representing declines of 19.2% (95%CI, −19.7 to −18.7), 11.5% (95%CI, −12.6 to −10.6), and 12.7% (95%CI, −13.6 to −11.8), respectively. The decreases were noted across centers with high, mid, and low COVID-19 hospitalization burden, and also across high, mid, and low volume stroke/mechanical thrombectomy centers. High-volume COVID-19 centers (−20.5%) had greater declines in mechanical thrombectomy volumes than mid- (−10.1%) and low-volume (−8.7%) centers (p &lt; 0.0001). There was a 1.5% stroke rate across 54,366 COVID-19 hospitalizations. SARS-CoV-2 infection was noted in 3.9% (784/20,250) of all stroke admissions. Conclusion: The COVID-19 pandemic was associated with a global decline in the volume of overall stroke hospitalizations, mechanical thrombectomy procedures, and intracranial hemorrhage admission volumes. Despite geographic variations, these volume reductions were observed regardless of COVID-19 hospitalization burden and pre-pandemic stroke/mechanical thrombectomy volumes. © 2021 World Stroke Organization

Global Impact of the COVID-19 Pandemic on Stroke Volumes and Cerebrovascular Events: One-Year Follow-up.

Declines in stroke admission, intravenous thrombolysis, and mechanical thrombectomy volumes were reported during the first wave of the COVID-19 pandemic. There is a paucity of data on the longer-term effect of the pandemic on stroke volumes over the course of a year and through the second wave of the pandemic. We sought to measure the impact of the COVID-19 pandemic on the volumes of stroke admissions, intracranial hemorrhage (ICH), intravenous thrombolysis (IVT), and mechanical thrombectomy over a one-year period at the onset of the pandemic (March 1, 2020, to February 28, 2021) compared with the immediately preceding year (March 1, 2019, to February 29, 2020). We conducted a longitudinal retrospective study across 6 continents, 56 countries, and 275 stroke centers. We collected volume data for COVID-19 admissions and 4 stroke metrics: ischemic stroke admissions, ICH admissions, intravenous thrombolysis treatments, and mechanical thrombectomy procedures. Diagnoses were identified by their ICD-10 codes or classifications in stroke databases. There were 148,895 stroke admissions in the one-year immediately before compared to 138,453 admissions during the one-year pandemic, representing a 7% decline (95% confidence interval [95% CI 7.1, 6.9]; p&lt;0.0001). ICH volumes declined from 29,585 to 28,156 (4.8%, [5.1, 4.6]; p&lt;0.0001) and IVT volume from 24,584 to 23,077 (6.1%, [6.4, 5.8]; p&lt;0.0001). Larger declines were observed at high volume compared to low volume centers (all p&lt;0.0001). There was no significant change in mechanical thrombectomy volumes (0.7%, [0.6,0.9]; p=0.49). Stroke was diagnosed in 1.3% [1.31,1.38] of 406,792 COVID-19 hospitalizations. SARS-CoV-2 infection was present in 2.9% ([2.82,2.97], 5,656/195,539) of all stroke hospitalizations. There was a global decline and shift to lower volume centers of stroke admission volumes, ICH volumes, and IVT volumes during the 1st year of the COVID-19 pandemic compared to the prior year. Mechanical thrombectomy volumes were preserved. These results suggest preservation in the stroke care of higher severity of disease through the first pandemic year. This study is registered under NCT04934020