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1.
J Hosp Infect ; 145: 77-82, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38145810

RESUMO

BACKGROUND: Nebulized therapy is the mainstay for treating obstructive airway diseases, but there is heightened concern about the potential risk for SARS-CoV-2 transmission during nebulization in COVID-19 patients. AIM: To investigate the effects of 0.9% saline nebulization on SARS-CoV-2 RNA spreading in 11 COVID-19 patients (five females, mean age 62.45 ± 9.31 years); also to ascertain whether saline nebulization changed the number of exhaled bio-aerosol particles in six out of the 11 patients. METHODS: Air samples were collected using suction pumps equipped with 0.45 µm PTFE filters and positioned around the patient's bed. Exhaled particles were quantified by using an optical particle counter. FINDINGS: At baseline (i.e. before nebulization) SARS-CoV-2 was detected more frequently in the pumps close to the patient than in those far away. After saline nebulization, the detection of SARS-CoV-2 in the pumps close to the patient was comparable to that observed at baseline. In the pumps far from the patient, saline nebulization slightly, but not significantly, increased SARS-CoV-2 RNA detection compared to baseline. Overall, no significant changes in the SARS-CoV-2 RNA detection were observed after saline nebulization. At baseline, exhaled particle emission varied among patients, with two of them showing higher emission of particles than the remaining patients. Saline nebulization induced a marked decrease in exhaled particles in the two patients who displayed high emission at baseline, whereas no changes were observed in the remaining patients. Saline nebulization did not significantly change SARS-CoV-2 RNA spreading. CONCLUSION: Saline nebulization does not significantly increase SARS-CoV-2 spreading.


Assuntos
COVID-19 , Feminino , Humanos , Pessoa de Meia-Idade , Idoso , SARS-CoV-2 , RNA Viral , Aerossóis e Gotículas Respiratórios , Solução Salina
2.
Phys Rev Lett ; 131(15): 151002, 2023 Oct 13.
Artigo em Inglês | MEDLINE | ID: mdl-37897756

RESUMO

We present the precision measurements of 11 years of daily cosmic positron fluxes in the rigidity range from 1.00 to 41.9 GV based on 3.4×10^{6} positrons collected with the Alpha Magnetic Spectrometer (AMS) aboard the International Space Station. The positron fluxes show distinctly different time variations from the electron fluxes at short and long timescales. A hysteresis between the electron fluxes and the positron fluxes is observed with a significance greater than 5σ at rigidities below 8.5 GV. On the contrary, the positron fluxes and the proton fluxes show similar time variation. Remarkably, we found that positron fluxes are modulated more than proton fluxes with a significance greater than 5σ for rigidities below 7 GV. These continuous daily positron fluxes, together with AMS daily electron, proton, and helium fluxes over an 11-year solar cycle, provide unique input to the understanding of both the charge-sign and mass dependencies of cosmic rays in the heliosphere.

3.
Phys Rev Lett ; 130(21): 211002, 2023 May 26.
Artigo em Inglês | MEDLINE | ID: mdl-37295095

RESUMO

We report the properties of primary cosmic-ray sulfur (S) in the rigidity range 2.15 GV to 3.0 TV based on 0.38×10^{6} sulfur nuclei collected by the Alpha Magnetic Spectrometer experiment (AMS). We observed that above 90 GV the rigidity dependence of the S flux is identical to the rigidity dependence of Ne-Mg-Si fluxes, which is different from the rigidity dependence of the He-C-O-Fe fluxes. We found that, similar to N, Na, and Al cosmic rays, over the entire rigidity range, the traditional primary cosmic rays S, Ne, Mg, and C all have sizeable secondary components, and the S, Ne, and Mg fluxes are well described by the weighted sum of the primary silicon flux and the secondary fluorine flux, and the C flux is well described by the weighted sum of the primary oxygen flux and the secondary boron flux. The primary and secondary contributions of the traditional primary cosmic-ray fluxes of C, Ne, Mg, and S (even Z elements) are distinctly different from the primary and secondary contributions of the N, Na, and Al (odd Z elements) fluxes. The abundance ratio at the source for S/Si is 0.167±0.006, for Ne/Si is 0.833±0.025, for Mg/Si is 0.994±0.029, and for C/O is 0.836±0.025. These values are determined independent of cosmic-ray propagation.


Assuntos
Carbono , Magnésio , Neônio , Enxofre , Fenômenos Magnéticos
4.
Phys Rev Lett ; 130(16): 161001, 2023 Apr 21.
Artigo em Inglês | MEDLINE | ID: mdl-37154630

RESUMO

We present the precision measurements of 11 years of daily cosmic electron fluxes in the rigidity interval from 1.00 to 41.9 GV based on 2.0×10^{8} electrons collected with the Alpha Magnetic Spectrometer (AMS) aboard the International Space Station. The electron fluxes exhibit variations on multiple timescales. Recurrent electron flux variations with periods of 27 days, 13.5 days, and 9 days are observed. We find that the electron fluxes show distinctly different time variations from the proton fluxes. Remarkably, a hysteresis between the electron flux and the proton flux is observed with a significance of greater than 6σ at rigidities below 8.5 GV. Furthermore, significant structures in the electron-proton hysteresis are observed corresponding to sharp structures in both fluxes. This continuous daily electron data provide unique input to the understanding of the charge sign dependence of cosmic rays over an 11-year solar cycle.

6.
Phys Rev Lett ; 128(23): 231102, 2022 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-35749176

RESUMO

We present the precision measurement of 2824 daily helium fluxes in cosmic rays from May 20, 2011 to October 29, 2019 in the rigidity interval from 1.71 to 100 GV based on 7.6×10^{8} helium nuclei collected with the Alpha Magnetic Spectrometer (AMS) aboard the International Space Station. The helium flux and the helium to proton flux ratio exhibit variations on multiple timescales. In nearly all the time intervals from 2014 to 2018, we observed recurrent helium flux variations with a period of 27 days. Shorter periods of 9 days and 13.5 days are observed in 2016. The strength of all three periodicities changes with time and rigidity. In the entire time period, we found that below ∼7 GV the helium flux exhibits larger time variations than the proton flux, and above ∼7 GV the helium to proton flux ratio is time independent. Remarkably, below 2.4 GV a hysteresis between the helium to proton flux ratio and the helium flux was observed at greater than the 7σ level. This shows that at low rigidity the modulation of the helium to proton flux ratio is different before and after the solar maximum in 2014.

7.
Clin Nutr ESPEN ; 45: 351-355, 2021 10.
Artigo em Inglês | MEDLINE | ID: mdl-34620339

RESUMO

BACKGROUND & AIMS: The effect of the COVID-19 infection on nutritional status is not well established. Worldwide epidemiological studies have begun to investigate the incidence of malnutrition during hospitalization for COVID-19. The prevalence of malnutrition during follow-up after COVID-19 infection has not been investigated yet. The primary objective of the present study was to estimate the prevalence of the risk of malnutrition in hospitalized adult patients with COVID-19, re-evaluating their nutritional status during follow-up after discharge. The secondary objective was to identify factors that may contribute to the onset of malnutrition during hospitalization and after discharge. METHODS: We enrolled 142 COVID-19 patients admitted to Careggi University Hospital. Nutritional parameters were measured at three different timepoints for each patient: upon admission to hospital, at discharge from hospital and 3 months after discharge during follow-up. The prevalence of both the nutritional risk and malnutrition was assessed. During the follow-up, the presence of nutritional impact symptoms (NIS) was also investigated. An analysis of the association between demographic and clinical features and nutritional status was conducted. RESULTS: The mean unintended weight loss during hospitalization was 7.6% (p < 0.001). A positive correlation between age and weight loss during hospitalization was observed (r = 0.146, p = 0.08). Moreover, for elderly patients (>61 years old), a statistically significant correlation between age and weight loss was found (r = 0.288 p = 0.05). Patients admitted to an Intensive Care Unit (ICU) or Intermediate Care Unit (IMCU) had a greater unintended weight loss than patients who stayed in a standard care ward (5.46% vs 1.19%; p < 0.001). At discharge 12 patients were malnourished (8.4%) according to the ESPEN definition. On average, patients gained 4.36 kg (p < 0.001) three months after discharge. Overall, we observed a weight reduction of 2.2% (p < 0.001) from the habitual weight measured upon admission. Patients admitted to an ICU/IMCU showed a higher MUST score three months after discharge (Cramer's V 0.218, p = 0.035). With regard to the NIS score, only 7 patients (4.9%) reported one or more nutritional problems during follow-up. CONCLUSIONS: The identification of groups of patients at a higher nutritional risk could be useful with a view to adopting measures to prevent worsening of nutritional status during hospitalization. Admission to an ICU/IMCU, age and length of the hospital stay seem to have a major impact on nutritional status. Nutritional follow-up should be guaranteed for patients who lose more than 10% of their habitual weight during their stay in hospital, especially after admission to an ICU/IMCU.


Assuntos
COVID-19 , Desnutrição , Adulto , Idoso , Hospitalização , Humanos , Desnutrição/epidemiologia , Pessoa de Meia-Idade , Prevalência , SARS-CoV-2
9.
Phys Rev Lett ; 127(2): 021101, 2021 Jul 09.
Artigo em Inglês | MEDLINE | ID: mdl-34296911

RESUMO

We report the properties of sodium (Na) and aluminum (Al) cosmic rays in the rigidity range 2.15 GV to 3.0 TV based on 0.46 million sodium and 0.51 million aluminum nuclei collected by the Alpha Magnetic Spectrometer experiment on the International Space Station. We found that Na and Al, together with nitrogen (N), belong to a distinct cosmic ray group. In this group, we observe that, similar to the N flux, both the Na flux and Al flux are well described by the sums of a primary cosmic ray component (proportional to the silicon flux) and a secondary cosmic ray component (proportional to the fluorine flux). The fraction of the primary component increases with rigidity for the N, Na, and Al fluxes and becomes dominant at the highest rigidities. The Na/Si and Al/Si abundance ratios at the source, 0.036±0.003 for Na/Si and 0.103±0.004 for Al/Si, are determined independent of cosmic ray propagation.

10.
Actas urol. esp ; 45(4): 309-319, mayo 2021. tab, ilus
Artigo em Espanhol | IBECS | ID: ibc-216936

RESUMO

Introducción y objetivos: Tras el flujo migratorio procedente del África Subsahariana (ASS) en Europa, el número de diagnósticos de esquistosomiasis urogenital (EUG) es cada vez mayor. Este fenómeno representa un desafío para los urólogos que trabajan en zonas no endémicas. El objetivo de este estudio es describir el tratamiento urológico y los procedimientos quirúrgicos de los pacientes con EUG en un centro de referencia terciarioPacientesTodos los sujetos del ASS diagnosticados con EUG entre enero del 2011 y noviembre del 2018 fueron inscritos retrospectivamente. Se recogió y analizó la información detallada de los pacientes con EUG tratados mediante procedimientos urológicos.ResultadosTreinta pacientes fueron diagnosticados con EUG, 12 (42,8%) fueron tratados mediante cirugía. El procedimiento quirúrgico más común fue la resección transuretral de vejiga (RTUV) para las lesiones sospechosas persistentes después del tratamiento con praziquantel administrado en 7 casos (58%). Otros procedimientos quirúrgicos (realizados una vez) fueron RTUV combinada con ureteroscopia láser por sospecha de neoplasia de vejiga con cálculos renales, litotricia endoscópica y nefrolitotomía percutánea para cálculos vesicales y renales, nefrectomía laparoscópica para enfermedad renal terminal, colocación de nefrostomía bilateral para hidroureteronefrosis, cirugía testicular exploratoria por sospecha de torsión testicular. Cuatro pacientes (33%) se perdieron en el seguimiento.ConclusiónSe ha observado un número cada vez mayor de migrantes del ASS diagnosticados con EUG. Algunos pacientes requirieron intervención quirúrgica por sospecha de lesiones neoplásicas o daños en órganos en fase terminal. En varios pacientes fue particularmente difícil realizar un seguimiento regular. Se necesitan más estudios multicéntricos para lograr un manejo estándar en términos de diagnóstico, tratamiento y seguimiento de los sujetos con EUG. (AU)


Introduction and objectives: An increasing number of urogenital schistosomiasis (UGS) is being diagnosed in Europe following the unprecedented migratory flux from Sub-Saharan Africa (SSA). This phenomenon represent a challenge for urologists working in a non-endemic area. The aim of this study is to describe the urological management and the surgical procedures of patients with UGS in a tertiary referral centre.PatientsAll subjects from SAA diagnosed with UGS from January 2011 to November 2018 were enrolled retrospectively. Detailed data of patients with UGS undergoing to urological procedures were collected and analysed.ResultsThirty patients were diagnosed with UGS, among them 12 (42.8%) were submitted to surgery. The most common surgical procedure was trans urethral resection of bladder (TURB) for suspected lesions persisted after praziquantel treatment performed in 7cases (58%). Other surgical procedure were TURB and concomitant ureteroscopy with laser fragmentation for suspected bladder neoplasm with renal stone, endoscopic lithotripsy and percutaneous nephrolithotomy for bladder and renal stones, laparoscopic nephrectomy for end-stage kidney disease, placement of bilateral nephrostomy for hydroureteronephrosis, explorative testicular surgery for a suspected testicular torsion in one case each. Four patients (33%) were lost at the follow up.ConclusionAn increasing number of migrants from SSA diagnosed with UGS has been observed. Some patients required a surgical intervention for suspected neoplastic lesions or end-stage organ damage. It was particularly difficult to perform a regular follow-up in several patients. Further multicentric studies are needed to reach a proper standard in diagnosis, treatment and follow-up of subjects with UGS. (AU)


Assuntos
Humanos , Cálculos Renais , Esquistossomose/tratamento farmacológico , Ureteroscopia , Medicina Tropical , Estudos Retrospectivos
11.
Phys Rev Lett ; 126(8): 081102, 2021 Feb 26.
Artigo em Inglês | MEDLINE | ID: mdl-33709764

RESUMO

Precise knowledge of the charge and rigidity dependence of the secondary cosmic ray fluxes and the secondary-to-primary flux ratios is essential in the understanding of cosmic ray propagation. We report the properties of heavy secondary cosmic ray fluorine F in the rigidity R range 2.15 GV to 2.9 TV based on 0.29 million events collected by the Alpha Magnetic Spectrometer experiment on the International Space Station. The fluorine spectrum deviates from a single power law above 200 GV. The heavier secondary-to-primary F/Si flux ratio rigidity dependence is distinctly different from the lighter B/O (or B/C) rigidity dependence. In particular, above 10 GV, the F/Si/B/O ratio can be described by a power law R^{δ} with δ=0.052±0.007. This shows that the propagation properties of heavy cosmic rays, from F to Si, are different from those of light cosmic rays, from He to O, and that the secondary cosmic rays have two classes.

12.
Actas Urol Esp (Engl Ed) ; 45(4): 309-319, 2021 May.
Artigo em Inglês, Espanhol | MEDLINE | ID: mdl-33685664

RESUMO

INTRODUCTION AND OBJECTIVES: An increasing number of urogenital schistosomiasis (UGS) is being diagnosed in Europe following the unprecedented migratory flux from Sub-Saharan Africa (SSA). This phenomenon represent a challenge for urologists working in a non-endemic area. The aim of this study is to describe the urological management and the surgical procedures of patients with UGS in a tertiary referral centre. PATIENTS: All subjects from SAA diagnosed with UGS from January 2011 to November 2018 were enrolled retrospectively. Detailed data of patients with UGS undergoing to urological procedures were collected and analysed. RESULTS: Thirty patients were diagnosed with UGS, among them 12 (42.8%) were submitted to surgery. The most common surgical procedure was trans urethral resection of bladder (TURB) for suspected lesions persisted after praziquantel treatment performed in 7cases (58%). Other surgical procedure were TURB and concomitant ureteroscopy with laser fragmentation for suspected bladder neoplasm with renal stone, endoscopic lithotripsy and percutaneous nephrolithotomy for bladder and renal stones, laparoscopic nephrectomy for end-stage kidney disease, placement of bilateral nephrostomy for hydroureteronephrosis, explorative testicular surgery for a suspected testicular torsion in one case each. Four patients (33%) were lost at the follow up. CONCLUSION: An increasing number of migrants from SSA diagnosed with UGS has been observed. Some patients required a surgical intervention for suspected neoplastic lesions or end-stage organ damage. It was particularly difficult to perform a regular follow-up in several patients. Further multicentric studies are needed to reach a proper standard in diagnosis, treatment and follow-up of subjects with UGS.


Assuntos
Cálculos Renais , Esquistossomose Urinária , Migrantes , Humanos , Estudos Retrospectivos , Esquistossomose Urinária/tratamento farmacológico , Ureteroscopia
13.
Hum Reprod ; 36(6): 1520-1529, 2021 05 17.
Artigo em Inglês | MEDLINE | ID: mdl-33522572

RESUMO

STUDY QUESTION: How is the semen quality of sexually active men following recovery from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection? SUMMARY ANSWER: Twenty-five percent of the men with recent SARS-Cov-2 infections and proven healing were oligo-crypto-azoospermic, despite the absence of virus RNA in semen. WHAT IS KNOWN ALREADY: The presence of SARS-CoV-2 in human semen and its role in virus contagion and semen quality after recovery from coronavirus disease 2019 (COVID-19) is still unclear. So far, studies evaluating semen quality and the occurrence of SARS-CoV-2 in semen of infected or proven recovered men are scarce and included a limited number of participants. STUDY DESIGN, SIZE, DURATION: A prospective cross-sectional study on 43 sexually active men who were known to have recovered from SARS-CoV2 was performed. Four biological fluid samples, namely saliva, pre-ejaculation urine, semen, and post-ejaculation urine, were tested for the SARS-CoV-2 genome. Female partners were retested if any specimen was found to be SARS-CoV-2 positive. Routine semen analysis and quantification of semen leukocytes and interleukin-8 (IL-8) levels were performed. PARTICIPANTS/MATERIALS, SETTING, METHODS: Questionnaires including International Index of Erectile Function and Male Sexual Health Questionnaire Short Form were administered to all subjects. The occurrence of virus RNA was evaluated in all the biological fluids collected by RT-PCR. Semen parameters were evaluated according to the World Health Organization manual edition V. Semen IL-8 levels were evaluated by a two-step ELISA method. MAIN RESULTS AND THE ROLE OF CHANCE: After recovery from COVID-19, 25% of the men studied were oligo-crypto-azoospermic. Of the 11 men with semen impairment, 8 were azoospermic and 3 were oligospermic. A total of 33 patients (76.7%) showed pathological levels of IL-8 in semen. Oligo-crypto-azoospermia was significantly related to COVID-19 severity (P < 0.001). Three patients (7%) tested positive for at least one sample (one saliva; one pre-ejaculation urine; one semen and one post-ejaculation urine), so the next day new nasopharyngeal swabs were collected. The results from these three patients and their partners were all negative for SARS-CoV-2. LIMITATIONS, REASONS FOR CAUTION: Although crypto-azoospermia was found in a high percentage of men who had recovered from COVID-19, clearly exceeding the percentage found in the general population, the previous semen quality of these men was unknown nor is it known whether a recovery of testicular function was occurring. The low number of enrolled patients may limit the statistical power of study. WIDER IMPLICATIONS OF THE FINDINGS: SARS-CoV-2 can be detected in saliva, urine, and semen in a small percentage of men who recovered from COVID-19. One-quarter of men who recovered from COVID-19 demonstrated oligo-crypto-azoospermia indicating that an assessment of semen quality should be recommended for men of reproductive age who are affected by COVID-19. STUDY FUNDING/COMPETING INTEREST(S): None. TRIAL REGISTRATION NUMBER: N/A.


Assuntos
COVID-19 , SARS-CoV-2 , Estudos Transversais , Feminino , Humanos , Masculino , Estudos Prospectivos , RNA Viral , Sêmen , Análise do Sêmen
14.
Phys Rev Lett ; 126(4): 041104, 2021 Jan 29.
Artigo em Inglês | MEDLINE | ID: mdl-33576661

RESUMO

We report the observation of new properties of primary iron (Fe) cosmic rays in the rigidity range 2.65 GV to 3.0 TV with 0.62×10^{6} iron nuclei collected by the Alpha Magnetic Spectrometer experiment on the International Space Station. Above 80.5 GV the rigidity dependence of the cosmic ray Fe flux is identical to the rigidity dependence of the primary cosmic ray He, C, and O fluxes, with the Fe/O flux ratio being constant at 0.155±0.006. This shows that unexpectedly Fe and He, C, and O belong to the same class of primary cosmic rays which is different from the primary cosmic rays Ne, Mg, and Si class.

15.
Phys Rev Lett ; 127(27): 271102, 2021 Dec 31.
Artigo em Inglês | MEDLINE | ID: mdl-35061443

RESUMO

We present the precision measurement of the daily proton fluxes in cosmic rays from May 20, 2011 to October 29, 2019 (a total of 2824 days or 114 Bartels rotations) in the rigidity interval from 1 to 100 GV based on 5.5×10^{9} protons collected with the Alpha Magnetic Spectrometer aboard the International Space Station. The proton fluxes exhibit variations on multiple timescales. From 2014 to 2018, we observed recurrent flux variations with a period of 27 days. Shorter periods of 9 days and 13.5 days are observed in 2016. The strength of all three periodicities changes with time and rigidity. The rigidity dependence of the 27-day periodicity is different from the rigidity dependences of 9-day and 13.5-day periods. Unexpectedly, the strength of 9-day and 13.5-day periodicities increases with increasing rigidities up to ∼10 GV and ∼20 GV, respectively. Then the strength of the periodicities decreases with increasing rigidity up to 100 GV.

16.
Phys Rev Lett ; 124(21): 211102, 2020 May 29.
Artigo em Inglês | MEDLINE | ID: mdl-32530660

RESUMO

We report the observation of new properties of primary cosmic rays, neon (Ne), magnesium (Mg), and silicon (Si), measured in the rigidity range 2.15 GV to 3.0 TV with 1.8×10^{6} Ne, 2.2×10^{6} Mg, and 1.6×10^{6} Si nuclei collected by the Alpha Magnetic Spectrometer experiment on the International Space Station. The Ne and Mg spectra have identical rigidity dependence above 3.65 GV. The three spectra have identical rigidity dependence above 86.5 GV, deviate from a single power law above 200 GV, and harden in an identical way. Unexpectedly, above 86.5 GV the rigidity dependence of primary cosmic rays Ne, Mg, and Si spectra is different from the rigidity dependence of primary cosmic rays He, C, and O. This shows that the Ne, Mg, and Si and He, C, and O are two different classes of primary cosmic rays.

17.
Clin Microbiol Infect ; 26(9): 1151-1154, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32289479

RESUMO

BACKGROUND: Congenital cytomegalovirus (CMV) infection is the leading infectious cause of neurological impairment for which, currently, there are no approved antenatal treatment options. OBJECTIVES: The aim of this article was to summarize the available evidence on the use of valacyclovir during pregnancy to prevent and treat congenital CMV infection and disease. SOURCES: Two databases (PubMed and ClinicalTrial.gov) were reviewed. CONTENT: Six relevant documents were identified, namely one observational study, three clinical trials, two case reports. Most relevant findings were those from two clinical trials. A phase 2/3 placebo-controlled study showed a decrease of 71% (5 of 45 vs 14 of 47) in rate of CMV vertical transmission in women treated with 8 g/day valacyclovir following primary CMV infection in pregnancy. A phase 2, single-arm clinical trial, showed that 8 g/day valacyclovir administered to mothers of symptomatic infected foetuses increased the portion of asymptomatic neonates to 82% (34 of 41), compared with 43% (20 of 47) in untreated pregnancies from a historical cohort. IMPLICATIONS: Studies in favour of using valacyclovir during pregnancy for prevention and treatment of congenital CMV infection are emerging but are still few. Randomized clinical trials on large cohorts of patients investigating the efficacy on prevention and treatment of congenital CMV are required. Unfortunately, this will be probably not be feasible at least in the short period. In the meantime, data on the 'off label' use of valacyclovir for CMV in pregnancy could be collected within a multicentre observational study.


Assuntos
Antivirais/uso terapêutico , Infecções por Citomegalovirus/tratamento farmacológico , Transmissão Vertical de Doenças Infecciosas/prevenção & controle , Complicações Infecciosas na Gravidez/tratamento farmacológico , Complicações Infecciosas na Gravidez/virologia , Valaciclovir/uso terapêutico , Feminino , Humanos , Gravidez
18.
Phys Rev Lett ; 123(18): 181102, 2019 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-31763896

RESUMO

Precision measurements by the Alpha Magnetic Spectrometer (AMS) on the International Space Station of ^{3}He and ^{4}He fluxes are presented. The measurements are based on 100 million ^{4}He nuclei in the rigidity range from 2.1 to 21 GV and 18 million ^{3}He from 1.9 to 15 GV collected from May 2011 to November 2017. We observed that the ^{3}He and ^{4}He fluxes exhibit nearly identical variations with time. The relative magnitude of the variations decreases with increasing rigidity. The rigidity dependence of the ^{3}He/^{4}He flux ratio is measured for the first time. Below 4 GV, the ^{3}He/^{4}He flux ratio was found to have a significant long-term time dependence. Above 4 GV, the ^{3}He/^{4}He flux ratio was found to be time independent, and its rigidity dependence is well described by a single power law ∝R^{Δ} with Δ=-0.294±0.004. Unexpectedly, this value is in agreement with the B/O and B/C spectral indices at high energies.

19.
Phys Rev Lett ; 122(10): 101101, 2019 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-30932626

RESUMO

Precision results on cosmic-ray electrons are presented in the energy range from 0.5 GeV to 1.4 TeV based on 28.1×10^{6} electrons collected by the Alpha Magnetic Spectrometer on the International Space Station. In the entire energy range the electron and positron spectra have distinctly different magnitudes and energy dependences. The electron flux exhibits a significant excess starting from 42.1_{-5.2}^{+5.4} GeV compared to the lower energy trends, but the nature of this excess is different from the positron flux excess above 25.2±1.8 GeV. Contrary to the positron flux, which has an exponential energy cutoff of 810_{-180}^{+310} GeV, at the 5σ level the electron flux does not have an energy cutoff below 1.9 TeV. In the entire energy range the electron flux is well described by the sum of two power law components. The different behavior of the cosmic-ray electrons and positrons measured by the Alpha Magnetic Spectrometer is clear evidence that most high energy electrons originate from different sources than high energy positrons.

20.
Phys Rev Lett ; 122(4): 041102, 2019 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-30768313

RESUMO

Precision measurements of cosmic ray positrons are presented up to 1 TeV based on 1.9 million positrons collected by the Alpha Magnetic Spectrometer on the International Space Station. The positron flux exhibits complex energy dependence. Its distinctive properties are (a) a significant excess starting from 25.2±1.8 GeV compared to the lower-energy, power-law trend, (b) a sharp dropoff above 284_{-64}^{+91} GeV, (c) in the entire energy range the positron flux is well described by the sum of a term associated with the positrons produced in the collision of cosmic rays, which dominates at low energies, and a new source term of positrons, which dominates at high energies, and (d) a finite energy cutoff of the source term of E_{s}=810_{-180}^{+310} GeV is established with a significance of more than 4σ. These experimental data on cosmic ray positrons show that, at high energies, they predominantly originate either from dark matter annihilation or from other astrophysical sources.

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