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1.
Nature ; 605(7911): 659-662, 2022 05.
Artículo en Inglés | MEDLINE | ID: mdl-35614244

RESUMEN

The possibility to accelerate electron beams to ultra-relativistic velocities over short distances by using plasma-based technology holds the potential for a revolution in the field of particle accelerators1-4. The compact nature of plasma-based accelerators would allow the realization of table-top machines capable of driving a free-electron laser (FEL)5, a formidable tool to investigate matter at the sub-atomic level by generating coherent light pulses with sub-ångström wavelengths and sub-femtosecond durations6,7. So far, however, the high-energy electron beams required to operate FELs had to be obtained through the use of conventional large-size radio-frequency (RF) accelerators, bound to a sizeable footprint as a result of their limited accelerating fields. Here we report the experimental evidence of FEL lasing by a compact (3-cm) particle-beam-driven plasma accelerator. The accelerated beams are completely characterized in the six-dimensional phase space and have high quality, comparable with state-of-the-art accelerators8. This allowed the observation of narrow-band amplified radiation in the infrared range with typical exponential growth of its intensity over six consecutive undulators. This proof-of-principle experiment represents a fundamental milestone in the use of plasma-based accelerators, contributing to the development of next-generation compact facilities for user-oriented applications9.

2.
Nature ; 595(7866): 223-226, 2021 07.
Artículo en Inglés | MEDLINE | ID: mdl-34234332

RESUMEN

Neutron-star mergers were recently confirmed as sites of rapid-neutron-capture (r-process) nucleosynthesis1-3. However, in Galactic chemical evolution models, neutron-star mergers alone cannot reproduce the observed element abundance patterns of extremely metal-poor stars, which indicates the existence of other sites of r-process nucleosynthesis4-6. These sites may be investigated by studying the element abundance patterns of chemically primitive stars in the halo of the Milky Way, because these objects retain the nucleosynthetic signatures of the earliest generation of stars7-13. Here we report the element abundance pattern of the extremely metal-poor star SMSS J200322.54-114203.3. We observe a large enhancement in r-process elements, with very low overall metallicity. The element abundance pattern is well matched by the yields of a single 25-solar-mass magnetorotational hypernova. Such a hypernova could produce not only the r-process elements, but also light elements during stellar evolution, and iron-peak elements during explosive nuclear burning. Hypernovae are often associated with long-duration γ-ray bursts in the nearby Universe8. This connection indicates that similar explosions of fast-spinning strongly magnetized stars occurred during the earliest epochs of star formation in our Galaxy.

3.
Phys Rev Lett ; 132(21): 215001, 2024 May 24.
Artículo en Inglés | MEDLINE | ID: mdl-38856283

RESUMEN

We present a new approach that demonstrates the deflection and guiding of relativistic electron beams over curved paths by means of the magnetic field generated in a plasma-discharge capillary. We experimentally prove that the guiding is much less affected by the beam chromatic dispersion with respect to a conventional bending magnet and, with the support of numerical simulations, we show that it can even be made dispersionless by employing larger discharge currents. This proof-of-principle experiment extends the use of plasma-based devices, that revolutionized the field of particle accelerators enabling the generation of GeV beams in few centimeters. Compared to state-of-the-art technology based on conventional bending magnets and quadrupole lenses, these results provide a compact and affordable solution for the development of next-generation tabletop facilities.

4.
Public Health ; 219: 117-123, 2023 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-37159976

RESUMEN

OBJECTIVES: This study aimed to perform a systematic review and meta-analysis to assess the scientific evidence of the relationship between vulnerability to access to safe drinking water, sanitation, and hygiene (WASH) practices on stunting in children aged <5 years in developing countries. STUDY DESIGN: This is a systematic review and meta-analysis article to assess the relationship between under-five stunting and WASH vulnerability in developing countries. METHODS: The systematic review with meta-analysis was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol methodology. The following databases were used: LILACS, MEDLINE (via PubMed), SciELO, Web of Science, ScienceDirect, SCOPUS, and Embase. All original studies identified that related WASH vulnerability to stunting in children aged <5 years in developing countries was included. Three authors performed independently the selection and extraction of data from the articles. The statistical software STATA version 11 was used. Cochran's Q test and Chi-square test (I2) with 95% significance were used to assess the heterogeneity of the studies. RESULTS: The search resulted in the initial identification of 2047 articles; after reading the abstracts, followed by the full articles, 14 articles were included in the systematic review and eight articles were included in the meta-analysis. The studies selected for the systematic review were published between the years 1992 and 2021 and conducted in eight countries, namely, Ethiopia, India, Indonesia, Bangladesh, Tanzania, Peru, China, and Lesotho. The studies assessed vulnerability to access to WASH on the growth of children aged <5 years. There was a significant difference when relating WASH vulnerability to children's height. The meta-analysis of this study showed that the impact of WASH on child stunting is significant when it comes to lack of sanitation in 72% of the studies. CONCLUSIONS: The study found that WASH vulnerability contributes to stunting in children aged <5 years in developing countries. Based on our findings, we recommend incorporating WASH strategies, especially sanitation, into the formulation of interventions integrating with health promotion policies for healthy early childhood development.


Asunto(s)
Saneamiento , Agua , Niño , Preescolar , Humanos , Países en Desarrollo , Trastornos del Crecimiento/epidemiología , Higiene , Saneamiento/métodos
5.
Br Poult Sci ; 64(1): 137-141, 2023 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-36129037

RESUMEN

1. This study evaluated the minimal inhibitory concentration (MIC) of ciprofloxacin and the presence of plasmid-mediated quinolone resistance (PMQR) mechanisms in 97 nontyphoidal Salmonella spp. isolated from broilers and carcases from three different regions in Brazil. The presence of mutations in quinolone resistance determination regions (QRDRS) was investigated in the ciprofloxacin-resistant strain by DNA sequencing.2. Most of the Salmonella spp. (85.6%) had intermediate resistance to ciprofloxacin and only one isolate was resistant. MIC breakpoints ranged from ≤0.03 to 1 µg/ml and 67.0% of the strains had a MIC of 0.25 µg/ml (n=65). Thirteen strains (13.4%) were susceptible to ciprofloxacin with MIC ≤0.06 µg/ml. The qnrB gene was detected in eight isolates with intermediate resistance and in two susceptible strains. The other PMQR genes, qnrA, qnrC, qnrD, qnrS, qnrVC, aac(6')-Ib, qepA, oqxAB and mutations in QRDR were not detected in any strain.3. There was a high frequency of ciprofloxacin intermediate resistant Salmonella from broiler and broiler carcases from Brazil. The presence of these strains in poultry and derived products poses a risk to public health.


Asunto(s)
Ciprofloxacina , Quinolonas , Animales , Ciprofloxacina/farmacología , Pollos , Brasil , Proteínas Bacterianas/genética , Salmonella , Quinolonas/farmacología , Pruebas de Sensibilidad Microbiana/veterinaria , Antibacterianos/farmacología , Farmacorresistencia Bacteriana/genética
6.
Med Intensiva ; 47(4): 212-220, 2023 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-35528275

RESUMEN

Objective: We examined weather a protocol for fraction of inspired oxygen (FiO2) adjustment can reduce hyperoxemia and excess oxygen use in COVID-19 patients mechanically ventilated. Design: Prospective cohort study. Setting: Two intensive care units (ICUs) dedicated to COVID-19 patients in Brazil. Patients: Consecutive patients with COVID-19 mechanically ventilated. Interventions: One ICU followed a FiO2 adjustment protocol based on SpO2 (conservative-oxygen ICU) and the other, which did not follow the protocol, constituted the control ICU. Main variables of interest: Prevalence of hyperoxemia (PaO2 >100 mmHg) on day 1, sustained hyperoxemia (present on days 1 and 2), and excess oxygen use (FiO2 > 0.6 in patients with hyperoxemia) were compared between the two ICUs. Results: Eighty two patients from the conservative-oxygen ICU and 145 from the control ICU were included. The conservative-oxygen ICU presented lower prevalence of hyperoxemia on day 1 (40.2% vs. 75.9%, p < 0.001) and of sustained hyperoxemia (12.2% vs. 49.6%, p < 0.001). Excess oxygen use was less frequent in the conservative-oxygen ICU on day 1 (18.3% vs. 52.4%, p < 0.001). Being admitted in the control ICU was independently associated with hyperoxemia and excess oxygen use. Multivariable analyses found no independent relationship between day 1 hyperoxemia, sustained hyperoxemia, or excess FiO2 use and adverse clinical outcomes. Conclusions: Following FiO2 protocol was associated with lower hyperoxemia and less excess oxygen use. Although those results were not associated with better clinical outcomes, adopting FiO2 protocol may be useful in a scenario of depleted oxygen resources, as was seen during the COVID-19 pandemic.


Objetivo: Evaluar si un protocolo para el ajuste de la FiO2 reduce la hiperoxemia y el uso excesivo de oxígeno en pacientes con COVID-19 en ventilación mecánica. Diseño: Estudio de cohorte prospectivo. Ámbito: Unidades de cuidados intensivos (UCI) dedicadas a pacientes con COVID-19 en Brasil. Pacientes: Pacientes con COVID-19. Intervenciones: Una UCI siguió un protocolo de ajuste de FiO2 basado en SpO2 (UCI de oxigenoterapia conservadora, N = 82) y la otra no siguió el protocolo (UCI control, N = 145). Principales variables de interés: Prevalencia de hiperoxemia (PaO2 > 100 mmHg) en el día 1, hiperoxemia sostenida (presente en los días 1 y 2) y exceso de uso de oxígeno (FiO2 > 0,6 en pacientes con hiperoxemia) entre las 2 UCI. Resultados: La UCI de oxigenoterapia conservadora presentó menor prevalencia de hiperoxemia en el día 1 (40,2 vs. 75,9%; p < 0,001) y de hiperoxemia sostenida (12,2 vs. 49,6%; p < 0,001). El uso excesivo de oxígeno fue menos frecuente en la UCI de oxigenoterapia conservadora el día 1 (18,3 vs. 52,4%; p < 0,001). El ingreso en la UCI control se asoció de forma independiente con la hiperoxemia y el uso excesivo de oxígeno. Los análisis multivariables no encontraron una relación independiente entre hiperoxemia o uso excesivo de FiO2 y resultados clínicos adversos. Conclusiones: Seguir el protocolo de FiO2 se asoció con menor hiperoxemia y menor consumo de oxígeno en exceso. Aunque esos resultados no se asociaron con mejores resultados clínicos, la adopción del protocolo FiO2 puede ser útil en un escenario de recursos de oxígeno agotados, como se vio durante la pandemia de COVID-19.

7.
Ann Surg Oncol ; 29(9): 5515-5524, 2022 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-35687176

RESUMEN

BACKGROUND: The histopathological growth pattern (HGP) of colorectal liver metastases (CLM) has been associated with prognosis. This study was designed to elucidate if the HGP is associated with local recurrence risk and impacts the adequate width of surgical margin. METHODS: All consecutive patients resected for CLM in 2018-2019 were considered. HGP was prospectively classified as follows: desmoplastic, pushing, and replacement. Surgical margin was classified as follows: R0 (margin ≥ 1 mm), R1vasc (0-mm margin, tumor detachment from intrahepatic vessels), and R1par (tumor exposure along transection plane). R0 resections were further distinguished in R0min (1-mm margin) and R0wide (> 1-mm margin). RESULTS: A total of 340 resection areas in 136 patients were analyzed (70 R0min, 143 R0wide, 31 R1vasc, 96 R1par). HGP was desmoplastic in 26 cases, pushing in 221, and replacement in 93. Thirty-six local recurrences occurred (11%, median follow-up 21 months): 1 after R0wide, 4 after R0min, 3 after R1vasc, and 28 after R1par resection. In R1par group, local recurrence rate was high independently of HGP (29%). In R1vasc and R0min groups, local recurrence risk was higher in the replacement group (R1vasc: 29% vs. 4% if pushing/desmoplastic; R0min: 11% vs. 4%). In R0wide group, local recurrence risk was low for all HGP ( < 1%). Independent predictors of local recurrence were replacement HGP (odds ratio = 1.654, P = 0.036), and R1par resection (odds ratio = 57.209, P < 0.001 vs. R0). CONCLUSIONS: Replacement HGP is associated with an increased risk of local recurrence. In these patients, a wide surgical margin should be pursued, because R1vasc and R0min resections could be insufficient. R1par resection is inadequate, independently of the HGP.


Asunto(s)
Neoplasias Colorrectales , Neoplasias Hepáticas , Neoplasias Colorrectales/patología , Neoplasias Colorrectales/cirugía , Hepatectomía , Humanos , Neoplasias Hepáticas/secundario , Neoplasias Hepáticas/cirugía , Márgenes de Escisión , Recurrencia Local de Neoplasia/patología , Recurrencia Local de Neoplasia/cirugía
8.
Phys Rev Lett ; 129(23): 234801, 2022 Dec 02.
Artículo en Inglés | MEDLINE | ID: mdl-36563228

RESUMEN

The breakthrough provided by plasma-based accelerators enabled unprecedented accelerating fields by boosting electron beams to gigaelectronvolt energies within a few centimeters [1-4]. This, in turn, allows the realization of ultracompact light sources based on free-electron lasers (FELs) [5], as demonstrated by two pioneering experiments that reported the observation of self-amplified spontaneous emission (SASE) driven by plasma-accelerated beams [6,7]. However, the lack of stability and reproducibility due to the intrinsic nature of the SASE process (whose amplification starts from the shot noise of the electron beam) may hinder their effective implementation for user purposes. Here, we report a proof-of-principle experiment using plasma-accelerated beams to generate stable and reproducible FEL light seeded by an external laser. FEL radiation is emitted in the infrared range, showing the typical exponential growth of its energy over six consecutive undulators. Compared to SASE, the seeded FEL pulses have energies 2 orders of magnitude larger and stability that is 3 times higher.

9.
Int Arch Occup Environ Health ; 95(8): 1763-1773, 2022 10.
Artículo en Inglés | MEDLINE | ID: mdl-35511292

RESUMEN

OBJECTIVE: The association between adverse working conditions and mental disorders is well established. In addition to psychopathological symptoms, this study aimed at investigating anger and personality traits in a clinical sample of subjects referring negative interpersonal experiences in workplaces. METHODS: 1676 workers attending a Centre for Occupational Stress in Milan (from 2014 to 2016) were administered an assessment protocol including SCL-90 for general psychopathology, STAXI for anger intensity and expression, and MMPI-2 for personality traits. A qualitative checklist was used to collect negative experiences in workplaces. RESULTS: Patients reported they were exposed to "threats to the task or the professional career" more than to "attacks to the person". Over 80% scored above the cutoff in all the subscales of the SCL-90, with highest scores in Depression, Obsessive-Compulsive Disorder, Anxiety, Somatization and Paranoia. 60% scored above the 90th percentile in the AX/in subscale, showing intense anger feelings that they mostly suppress. Abnormal elevations at the MMPI scales of Hypochondria, Depression, Hysteria, and Paranoia were found in over 50% of the sample. Women reported higher psychological difficulties and internalized anger than men. Anger towards objects and people, instead, was more common in males. No differences were observed by work sector or employment status. CONCLUSIONS: In addition to severe psychological difficulties, individuals reporting negative interpersonal experiences in workplaces have high levels of internalized anger and a distinctive profile of personality traits. While a deeper investigation is needed, anger expression should be considered in future treatment programs.


Asunto(s)
Trastornos Mentales , Estrés Laboral , Ira , Femenino , Humanos , Masculino , Personalidad , Lugar de Trabajo
10.
Lett Appl Microbiol ; 75(1): 45-50, 2022 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-35342967

RESUMEN

Purpureocillium lilacinum is a filamentous and hyaline fungus cosmopolitan, saprophytic, largely used in the biological control of plant-parasitic nematodes and insects, also considered an emerging and opportunistic human pathogen. The standard treatment for hyalohyphomycosis caused by P. lilacinum is not yet defined, since this fungus is resistant to different antifungals, in vitro and in vivo. The aim of this study was to evaluate and compare in vitro antifungal activity against environmental and clinical P. lilacinum isolates and our results demonstrated that these isolates can be resistant to newer generation triazoles, such as voriconazole, and to caspofungin, a drug of the echinocandin class. In summary, we highlight the importance of knowing the different susceptibility profiles of P. lilacinum isolates, and besides that, the emergence of uncommon human and animal opportunistic fungi, such P. lilacinum, especially during COVID-19, highlight the need for antifungal susceptibility testing of isolates since empirical therapy with different treatment schedules failed in great number of patients.


Asunto(s)
COVID-19 , Hypocreales , Animales , Antifúngicos/farmacología , Equinocandinas/farmacología
11.
Differentiation ; 120: 36-47, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-34229995

RESUMEN

Seminiferous tubules physically connect to the rete testis through short segments called the transition region (TR). During fetal development, this specialized junction is considered the initial site where testis cords begin to form and to grow in length well beyond birth and into adulthood and form convoluted tubular cores. Mitotic activity of the Sertoli cell, the somatic cell of the epithelium, ceases before puberty, but modified Sertoli cells in the TR remain immature and capable of proliferation. This review presents what is known about this specialized region of the testis, with an emphasis on the morphological, molecular and physiological features, which support the hypothesis that this short region of epithelial transition serves as a specialized niche for undifferentiated Sertoli cells and spermatogonial stem cells. Also, the region is populated by an elevated number of immune cells, suggesting an important activity in monitoring and responding to any leakage of autoantigens, as sperm enter the rete testis. Several structure/function characteristics of the transition region are discussed and compared across species.


Asunto(s)
Células de Sertoli/citología , Espermatogonias/citología , Nicho de Células Madre , Animales , Masculino , Células de Sertoli/metabolismo , Espermatogénesis , Espermatogonias/metabolismo , Uniones Estrechas/metabolismo , Uniones Estrechas/ultraestructura
12.
Cell Tissue Res ; 386(1): 173-190, 2021 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-34296344

RESUMEN

The monocyte chemoattractant protein 1 (MCP-1) belongs to the CC chemokine family and acts in the recruitment of C-C motif chemokine receptor 2 (CCR2)-positive immune cell types to inflammation sites. In testis, the MCP-1/CCR2 axis has been associated with the macrophage population's functional regulation, which presents significant functions supporting germ cell development. In this context, herein, we aimed to investigate the role of the chemokine receptor CCR2 in mice testicular environment and its impact on male sperm production. Using adult transgenic mice strain that had the CCR2 gene replaced by a red fluorescent protein gene, we showed a stage-dependent expression of CCR2 in type B spermatogonia and early primary spermatocytes. Several parameters related to sperm production were reduced in the absence of CCR2 protein, such as Sertoli cell efficiency, meiotic index, and overall yield of spermatogenesis. Daily sperm production decreased by almost 40%, and several damages in the seminiferous tubules were observed. Significant reduction in the expression of important genes related to the Sertoli cell function (Cnx43, Vim, Ocln, Spna2) and meiosis initiation (Stra8, Pcna, Prdm9, Msh5) occurred in comparison to controls. Also, the number of macrophages significantly decreased in the absence of CCR2 protein, along with a disturbance in Leydig cell steroidogenic activity. In summary, our results show that the non-activation of the MCP-1/CCR2 axis disturbs the testicular homeostasis, interfering in macrophage population, meiosis initiation, blood-testis barrier function, and androgen synthesis, leading to the malfunction of seminiferous tubules, decreased testosterone levels, defective sperm production, and lower fertility index.


Asunto(s)
Proteínas de Ciclo Celular/metabolismo , Macrófagos/metabolismo , Receptores de Quimiocina/metabolismo , Espermatogénesis/fisiología , Testículo/fisiología , Animales , Femenino , Humanos , Masculino , Ratones
13.
Nature ; 527(7579): 484-7, 2015 Nov 26.
Artículo en Inglés | MEDLINE | ID: mdl-26560034

RESUMEN

The first stars are predicted to have formed within 200 million years after the Big Bang, initiating the cosmic dawn. A true first star has not yet been discovered, although stars with tiny amounts of elements heavier than helium ('metals') have been found in the outer regions ('halo') of the Milky Way. The first stars and their immediate successors should, however, preferentially be found today in the central regions ('bulges') of galaxies, because they formed in the largest over-densities that grew gravitationally with time. The Milky Way bulge underwent a rapid chemical enrichment during the first 1-2 billion years, leading to a dearth of early, metal-poor stars. Here we report observations of extremely metal-poor stars in the Milky Way bulge, including one star with an iron abundance about 10,000 times lower than the solar value without noticeable carbon enhancement. We confirm that most of the metal-poor bulge stars are on tight orbits around the Galactic Centre, rather than being halo stars passing through the bulge, as expected for stars formed at redshifts greater than 15. Their chemical compositions are in general similar to typical halo stars of the same metallicity although intriguing differences exist, including lower abundances of carbon.

14.
Tech Coloproctol ; 25(4): 371-383, 2021 04.
Artículo en Inglés | MEDLINE | ID: mdl-33230649

RESUMEN

BACKGROUND: The laparoscopic approach for colorectal surgery has gradually become widely accepted for the treatment of both benign and malignant diseases thanks to its several advantages over the open approach. However, it is associated with the same potential postoperative complications. Some recent studies have analyzed the potential role of laparoscopy in early diagnosis and management of complications following laparoscopic colorectal surgery. The aim of this systematic review was to investigate the outcomes of redo-laparoscopy (RL) for the management of early postoperative complications following laparoscopic colorectal surgery, focusing on length of stay, morbidity and mortality. METHODS: A systematic review of the literature was performed according to the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines through MEDLINE (PubMed), Embase and Google Scholar from January 1990 to December 2019. The main outcomes examined were conversion rate, length of hospital stay, postoperative morbidity and mortality rates. A meta-analysis of all eligible studies was then conducted and forest plots were generated. RESULTS: A total of 19 studies involving 1394 patients who required reoperation after laparoscopic colorectal resection were included. In 539 (38.2%) of these patients, a laparoscopic approach was adopted. The most common indication for returning to the operating theater was anastomotic leakage (64.4% of all redo-surgeries, 67.7% of RL) and the most common type of intervention performed in RL was diverting stoma with or without anastomotic repair/redo (47.1%). Nine studies were included in the pooled analysis. The mean length of stay was significantly shorter in the RL group than in the redo-open one (WMD = - 0.90; 95% CI - 1.04 to - 0.76; Z = - 12,6; p < 0.001). A significantly lower risk of mortality was observed in the RL cohort (OR = - 0.91; 95% CI - 1.58 to - 0.23; Z = - 2.62; p = 0.009). CONCLUSIONS: Laparoscopy is a valid and effective approach for the treatment of complications following laparoscopic primary colorectal surgery thanks to it is well-established advantages over the open approach, which remain noticeable even in redo-surgeries.


Asunto(s)
Cirugía Colorrectal , Procedimientos Quirúrgicos del Sistema Digestivo , Laparoscopía , Humanos , Laparoscopía/efectos adversos , Tiempo de Internación , Complicaciones Posoperatorias/etiología , Complicaciones Posoperatorias/cirugía , Reoperación , Resultado del Tratamiento
15.
Opt Lett ; 45(19): 5575-5578, 2020 Oct 01.
Artículo en Inglés | MEDLINE | ID: mdl-33001957

RESUMEN

The interaction of an ultra-intense laser with a solid state target allows the production of multi-MeV proton and ion beams. This process is explained by the target normal sheath acceleration (TNSA) model, predicting the creation of an electric field on the target rear side, due to an unbalanced positive charge. This process is related to the emission of relativistic ultrafast electrons, occurring at an earlier time. In this work, we highlight the correlations between the ultrafast electron component and the protons by their simultaneous detection by means of an electro-optical sampling and a time-of-flight diagnostics, respectively, supported by numerical simulations showing an excellent agreement.

16.
J Phys Chem A ; 124(52): 10977-10988, 2020 Dec 31.
Artículo en Inglés | MEDLINE | ID: mdl-33348984

RESUMEN

Dissociation processes involving phosphorus cations were investigated during laser-assisted atom probe tomography of crystalline indium phosphide (InP). This technique not only allows the formation of medium-sized phosphorus cations by means of femtosecond laser pulses under ultrahigh vacuum and high electric field conditions but also allows one to study the time-resolved dissociation dynamics. Data reveal the formation of cations up to P232+ and their subsequent dissociation into two smaller Pk+ cations (k > 2). The use of a time- and position-sensitive detector combined with numerical calculations provided information related to the molecule orientation, decay time, and kinetic energy release during dissociation phenomena. Results suggest that the dissociation processes are most likely due to the emission of Pk2+ cations in excited states and their subsequent decay in low field regions during their flight toward the detector. This study provides operative guidelines to obtain information on dissociation processes using a tomographic atom probe as a reaction microscope and indicates the current capabilities and limitations of such an approach.

17.
Nature ; 506(7489): 463-6, 2014 Feb 27.
Artículo en Inglés | MEDLINE | ID: mdl-24509711

RESUMEN

The element abundance ratios of four low-mass stars with extremely low metallicities (abundances of elements heavier than helium) indicate that the gas out of which the stars formed was enriched in each case by at most a few--and potentially only one--low-energy supernova. Such supernovae yield large quantities of light elements such as carbon but very little iron. The dominance of low-energy supernovae seems surprising, because it had been expected that the first stars were extremely massive, and that they disintegrated in pair-instability explosions that would rapidly enrich galaxies in iron. What has remained unclear is the yield of iron from the first supernovae, because hitherto no star has been unambiguously interpreted as encapsulating the yield of a single supernova. Here we report the optical spectrum of SMSS J031300.36-670839.3, which shows no evidence of iron (with an upper limit of 10(-7.1) times solar abundance). Based on a comparison of its abundance pattern with those of models, we conclude that the star was seeded with material from a single supernova with an original mass about 60 times that of the Sun (and that the supernova left behind a black hole). Taken together with the four previously mentioned low-metallicity stars, we conclude that low-energy supernovae were common in the early Universe, and that such supernovae yielded light-element enrichment with insignificant iron. Reduced stellar feedback both chemically and mechanically from low-energy supernovae would have enabled first-generation stars to form over an extended period. We speculate that such stars may perhaps have had an important role in the epoch of cosmic reionization and the chemical evolution of early galaxies.

18.
Ann Ig ; 32(3): 245-253, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-32266362

RESUMEN

BACKGROUND: Although the benefits and importance of vaccination before and right after pregnancy, are well known, vaccination coverage among pregnant women remains very low. The aim of our study was to evaluate pregnant women's knowledge and attitude towards vaccination. STUDY DESIGN: A cross sectional study was performed from October 2018 to June 2019 at the University of Messina. METHODS: We gave pregnant women >18 years old a non-self-compiling paper questionnaire. We stratified the sample according to age (<30 and >30 years old), marital status (single/divorced, in a relationship and married) and level of education (<8 and >8 years of school attendance). All possible correlations between collected data were analysed using software R. RESULTS: The sample included 156 women (mean age 32±0.49 years old). Only 1.4% of the subjects were aware of all the vaccines indicated for children. Luckily, 86.7% of the sample had a positive attitude, believing in the effectiveness and safety of immunization, despite a limited lack of confidence and a belief in false myths was expressed by some of the subjects. Interestingly, results showed that information about vaccination were more frequently obtained from family/friends (52.6%), mass media (49.1%), blogs/forums (19.3%), rather than from medical institutions (only 17.5%) or the family physician (only 35.0%), reflecting the quality of the information obtained. CONCLUSIONS: Our results proved that a general positive attitude emerged among our sample towards vaccination, however, correct information was not always provided to women, making it a crucial issue for public health in the future.


Asunto(s)
Actitud Frente a la Salud , Conocimientos, Actitudes y Práctica en Salud , Mujeres Embarazadas/psicología , Vacunación , Adulto , Niño , Estudios Transversales , Femenino , Humanos , Embarazo , Autoinforme
19.
Phys Rev Lett ; 122(11): 114801, 2019 Mar 22.
Artículo en Inglés | MEDLINE | ID: mdl-30951354

RESUMEN

The development of compact accelerator facilities providing high-brightness beams is one of the most challenging tasks in the field of next-generation compact and cost affordable particle accelerators, to be used in many fields for industrial, medical, and research applications. The ability to shape the beam longitudinal phase space, in particular, plays a key role in achieving high-peak brightness. Here we present a new approach that allows us to tune the longitudinal phase space of a high-brightness beam by means of plasma wakefields. The electron beam passing through the plasma drives large wakefields that are used to manipulate the time-energy correlation of particles along the beam itself. We experimentally demonstrate that such a solution is highly tunable by simply adjusting the density of the plasma and can be used to imprint or remove any correlation onto the beam. This is a fundamental requirement when dealing with largely time-energy correlated beams coming from future plasma accelerators.

20.
Gen Comp Endocrinol ; 273: 163-171, 2019 03 01.
Artículo en Inglés | MEDLINE | ID: mdl-29966660

RESUMEN

Undifferentiated spermatogonia (Aund) or spermatogonial stem cells (SSCs) are committed to the establishment and maintenance of spermatogenesis and fertility throughout a male's life and are located in a highly specialized microenvironment called niche that regulates their fate. Although several studies have been developed on SSCs in mammalian testis, little is known about other vertebrate classes. The present study is the first to perform a more detailed investigation on the spermatogonial cells and their niche in a reptilian species. Thus, we characterized Aund/SSCs and evaluated the existence of SSCs niche in the Kinosternon scorpioides, a freshwater turtle found from Mexico to northern and central South America. Our results showed that, in this species, Aund/SSCs exhibited a nuclear morphological pattern similar to those described for other mammalian species already investigated. However, in comparison to other spermatogonial cell types, Aund/SSCs presented the largest nuclear volume in this turtle. Similar to some mammalian and fish species investigated, both GFRA1 and CSF1 receptors were expressed in Aund/SSCs in K. scorpioides. Also, as K. scorpioides Aund/SSCs were preferentially located near blood vessels, it can be suggested that this niche characteristic is a well conserved feature during evolution. Besides being valuable for comparative reproductive biology, our findings represent an important step towards the understanding of SSCs biology and the development of valuable systems/tools for SSCs culture and cryopreservation in turtles. Moreover, we expect that the above-mentioned results will be useful for reproductive biotechnologies as well as for governmental programs aiming at reptilian species conservation.


Asunto(s)
Escorpiones/citología , Espermatogonias/citología , Nicho de Células Madre , Tortugas/metabolismo , Animales , Biomarcadores/metabolismo , Forma de la Célula , Tamaño de la Célula , Receptores del Factor Neurotrófico Derivado de la Línea Celular Glial/metabolismo , Masculino , Receptores de Factor Estimulante de Colonias de Granulocitos y Macrófagos/metabolismo , Escorpiones/metabolismo , América del Sur , Espermatogonias/metabolismo , Células Madre/citología , Células Madre/metabolismo
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