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1.
Braz J Biol ; 84: e278758, 2024.
Artículo en Inglés | MEDLINE | ID: mdl-39140498

RESUMEN

Natural products, specifically plant extracts with biological activity and the ability to act as botanical biopesticides are often mistakenly considered nontoxic. Scientific evidence indicates the contrary, and for this reason, the objective of this work was to evaluate the toxicity of extracts obtained from Petiveria alliacea L. (Caryophyllales, Phytolaccaceae) using Daphnia magna Straus (Cladocera, Daphniidae) as a bioindicator to identify the plant extracts and the respective concentrations that present the highest toxicity. Leaves of P. alliacea were collected in the Peruvian amazone. From this material, three types of extract (hexane, ethanolic and aqueous) were prepared, which were used in the bioassays with D. magna to find the least toxic extract. Acute toxicity bioassays with D. magna during 48 h of exposure to hexane, ethanolic, and aqueous extracts yielded median lethal concentration (LC50) values of 26.9, 230.6, and 657.9 mg L-1, respectively. The aqueous extract presented the lowest toxicity, causing minimal D. magna mortality in the range of 6.67 to 13.33% at concentrations of 10 and 100 mg L-1. This result enables the efficient use of this plant species in a sustainable manner with a minimal environmental impact for the future development of natural products for pest control.


Asunto(s)
Daphnia , Extractos Vegetales , Animales , Extractos Vegetales/farmacología , Extractos Vegetales/química , Daphnia/efectos de los fármacos , Dosificación Letal Mediana , Perú , Pruebas de Toxicidad Aguda , Daphnia magna
2.
Food Res Int ; 181: 114109, 2024 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-38448097

RESUMEN

Microplastics are a complex mix of chemicals containing polymers and certain plastic additives such as bisphenols and phthalates. These particles are porous materials that can also sorb contaminants from their surroundings, and leach chemicals from the particle under certain circumstances. Aquatic animals can ingest microplastic particles, which mostly bioaccumulate in the gastrointestinal tract of animals. In terms of dietary exposure, small animals consumed whole such as mussels, contribute more to the dietary intake of microplastic particles. Plastic additives and contaminants are not chemically bound to the polymers, and certain processing methods or cooking processes result in the release of these chemicals that leach from the plastic particles, leaving them more available for absorption when ingested. Analytical methods are crucial for a better understanding of the occurrence of plastic additives and contaminants in aquatic products, and to know certain circumstances and treatments that influence human exposure. This study uses an MSPD-HPLC methodology for the simultaneous determination of 9 analytes (BPA, BPF, BPS, DEP, DBP, DEHP, DDD, DDT, and DDE) analyzing, for the first time, the occurrence of these chemicals in raw, steamed and canned mussels of two different harvesting areas (Atlantic and the Mediterranean), becoming one of the most efficient methodologies for determining the presence of these analytes in very complex food matrices, able to define the changes in cooking and processing activities. The results showed that the heat and pressure treatment could influence the migration of plastic additives from microplastic particles present in mussels to the cooking liquids.


Asunto(s)
Bivalvos , Plásticos , Animales , Humanos , Cromatografía Líquida de Alta Presión , Microplásticos , Alimentos Marinos , Vapor
3.
Phys Rev Lett ; 131(5): 051201, 2023 Aug 04.
Artículo en Inglés | MEDLINE | ID: mdl-37595214

RESUMEN

We report the first detection of a TeV γ-ray flux from the solar disk (6.3σ), based on 6.1 years of data from the High Altitude Water Cherenkov (HAWC) observatory. The 0.5-2.6 TeV spectrum is well fit by a power law, dN/dE=A(E/1 TeV)^{-γ}, with A=(1.6±0.3)×10^{-12} TeV^{-1} cm^{-2} s^{-1} and γ=3.62±0.14. The flux shows a strong indication of anticorrelation with solar activity. These results extend the bright, hard GeV emission from the disk observed with Fermi-LAT, seemingly due to hadronic Galactic cosmic rays showering on nuclei in the solar atmosphere. However, current theoretical models are unable to explain the details of how solar magnetic fields shape these interactions. HAWC's TeV detection thus deepens the mysteries of the solar-disk emission.

4.
JRSM Cardiovasc Dis ; 12: 20480040231178585, 2023.
Artículo en Inglés | MEDLINE | ID: mdl-37346383

RESUMEN

Background: In Mexico less than half of the treated hypertensive patients reach blood pressure (BP) targets. Most hypertensive individuals rely on the standard medical care (SMC) to achieve the BP control goals; however, the efficacy of BP telemonitoring (BPT) to achieve BP targets has been poorly studied. Aim: To compare the efficacy of BPT versus SMC to achieve BP goals in patients with uncontrolled hypertension. Methods: A two-arm, open-label clinical trial was conducted in patients ≥18 years with uncontrolled hypertension. The participants were randomized to 2 arms (BPT vs SMC) and followed for 12 weeks. For the statistical analysis, the chi-squared test and covariance were used. Results: One hundred and seventy-eight participants were included, BPT (n = 94) and SMC (n = 84), after 12 weeks of follow up, we observed a baseline-adjusted reduction in systolic BP with both BPT (-13.5 [1.3] mmHg) and the SMC (-5.9 [1.4] mmHg; p < 0.001) but a greater decrease with BPT (p < 0.001). Likewise, we found a baseline-adjusted reduction of diastolic BP with BPT (-6.9 [0.9] mmHg) and SMC (-2.7 [0.9] mmHg) (p = 0.007) with a more significant percentage change from baseline with BPT (-6.8% [1.0] vs 2.5% [1.1]; p = 0.007). In the BPT arm, a larger proportion of patients achieved the BP target versus SMC (30.5% vs 12.8%; p = 0.005). Conclusion: BPT showed a greater proportion of patients achieving office BP control goals (<140/90 mmHg), compared to standard medical care.

6.
Rev. cir. (Impr.) ; 75(2)abr. 2023.
Artículo en Español | LILACS-Express | LILACS | ID: biblio-1441459

RESUMEN

La diverticulitis apendicular es una enfermedad poco frecuente, con una incidencia aproximada de 1%. Se define por la presencia de divertículos verdaderos o falsos en la pared del apéndice cecal. Durante la fase aguda posee una clínica indistinguible a la apendicitis, sin embargo en ocasiones presenta características clínicas particulares que la distinguen de la apendicitis aguda, tales como la presencia de dolor abdominal insidioso o intermitente y/o ausencia de sintomatología gastrointestinal (náuseas, vómitos o anorexia). En la diverticulitis apendicular las técnicas imagenológicas son de utilidad limitada al otorgar información inespecífica, por lo que el diagnóstico tiende a realizarse mediante el estudio anatomopatológico del apéndice posterior a una intervención quirúrgica en paciente con cuadro clínico compatible con apendicitis aguda. El tratamiento de elección corresponde a la apendicectomía, lo que permite evitar complicaciones futuras como por ejemplo perforación apendicular, neoplasias, entre otros. Se obtuvieron los datos de fuentes como Pubmed y Scielo. Específicamente la búsqueda de artículos originales y de revisiones sistemáticas, preferentemente menores a 15 años de publicación en revistas científicas de alto índice de impacto, con las palabras "diverticulitis apendicular", "diverticulosis" y "complicaciones diverticulares".


Appendiceal diverticulitis is a rare disease with an incidence of approximately 1%. It is defined by the presence of true or false diverticula in the wall of the cecal appendix. During the acute phase, it has symptoms that are indistinguishable from appendicitis, however, it sometimes presents particular clinical characteristics that distinguish it from acute appendicitis, such as the presence of insidious or intermittent abdominal pain and/or the absence of gastrointestinal symptoms (nausea, vomiting, or anorexia). In appendiceal diverticulitis, imaging techniques are of limited utility as they provide non-specific information, so the diagnosis tends to be made through the pathology study of the treatment after surgery in a patient with a clinical picture compatible with acute appendicitis. The treatment of choice corresponds to appendectomy, which allows avoiding future complications such as appendiceal perforation, neoplasms, among others. Data were obtained from sources such as Pubmed and Scielo, specifically searching for original articles and systematic reviews with the words "apendicular diverticulitis", "diverticulosis" and "diverticular complications". The criteria used were articles mainly under 5 years of publication in high-impact scientific journals.

7.
Heliyon ; 9(2): e13567, 2023 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-36865471

RESUMEN

After replacing asbestos with other types of fibers used as reinforcement of cementitious matrices, it has been found that rice husk, an agro-industrial waste with high silica content, can be used to improve the properties of fibercement. In this work, the effect of adding different forms of silica (rice husk, rice husk ash, and silica microparticles) on fibercement's physicochemical and mechanical properties was investigated. Rice husk ash and silica microparticles were extracted from the rice husk incineration and acid leaching process. The chemical composition of silica was determined by X-Ray Fluorescence, and the ash leached with hydrochloric acid was found to contain more than 98% silica. Cement, fiberglass, additives, and different forms of silica were used to manufacture fibercement specimens in their different forms. Concentrations of 0%, 3%, 5%, and 7% were taken for each form of silica, and four replicates were performed. The setting time was 28 days, during which absorption, density, and humidity tests were performed. Experiments were statistically analyzed at a 95% confidence value, and it was determined that there are significant differences in the compressive resistance, density, and absorption in relation to the type of additive and the interaction between the type of additive and its percentage of addition, but not whit percentage of addition. It was found that the fibercement specimens with 3% of rice husk present a modulus of elasticity of 9.4% higher than de control sample. The use of rice husk as an additive in fibercement composites seems to be interesting because these agro-industrial wastes are inexpensive and easily available everywhere to utilize in the cement industry and also helpful in reducing environmental pollution due to their cost and the positive effect on their properties.

9.
J Stroke Cerebrovasc Dis ; 31(6): 106412, 2022 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-35354109

RESUMEN

Easter Island (Rapa Nui), Chile, is remote, located in the Polynesian Triangle in Oceania. The closest continental point is Chile, 3,512 km east. It has a population of 7,750 inhabitants, who are Chilean citizens, and receives more than 60,000 tourists a year. For this entire population, there is a medium complexity hospital without a neurology specialist. In 2019, local professionals were trained in a Telestroke program with remote clinical support conducted by neurologists located on mainland Chile. We present a 50-year-old native male, with unknown medical history, who suddenly presented right-half-body weakness and aphasia. He was evaluated via Telestroke consultation, and thrombolysis with tenecteplase was indicated. The patient improved rapidly and 45 min later the NIHSS score was 0 points. To our knowledge, this is the first reported case of Telestroke treatment in such a remote area, highlighting the importance of telemedicine to overcome geographical and technological stroke care barriers and to improve patients' outcome, no matter where they live.


Asunto(s)
Neurología , Accidente Cerebrovascular , Telemedicina , Hospitales , Humanos , Masculino , Persona de Mediana Edad , Accidente Cerebrovascular/diagnóstico , Accidente Cerebrovascular/tratamiento farmacológico , Terapia Trombolítica
10.
Exp Parasitol ; 231: 108172, 2021 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-34774533

RESUMEN

The nematophagous fungus Duddingtonia flagrans is used in integrated management of gastrointestinal nematodes in ruminants. The chlamydospores of the fungus, orally administered, pass through the segments of the ruminant digestive tract and, in the feces, capture the nematodes preventing their migration to grasslands. The drastic conditions of the gastrointestinal segments can negatively affect the fungus' biocontrol activity. The aim of this study was to assess the effect of in vitro conditions of the sheep's main gastrointestinal segments on the concentration, viability and nematode predatory ability of D. flagrans chlamydospores. The segments evaluated separately in vitro were the oral cavity, rumen, abomasum, and small intestine. The results showed that chlamydospores concentration was not affected by exposure to the different segments. The viability of the chlamydospores after exposure to the oral cavity (2.53 × 106 CFU/mL) and small intestine (1.24 × 105 CFU/mL) was significantly lower than its control treatment, with values of 6.67 × 106 CFU/mL and 2.31 × 105 CFU/mL respectively. Nematode predatory ability after rumen exposure was reduced by 7% compared to the control treatment, by 25% after abomasum exposure and by 17% after small intestine. This study revealed the individual in vitro effect of each segment of ovine gastrointestinal tract on the integrity of this strain of the fungus D. flagrans affecting its viability and nematode predatory ability under the evaluated conditions. Delivery systems could be designed to protect chlamydospores considering the impact of each gastrointestinal segment.


Asunto(s)
Ascomicetos/fisiología , Enfermedades Gastrointestinales/prevención & control , Tracto Gastrointestinal/microbiología , Infecciones por Nematodos/prevención & control , Abomaso/microbiología , Abomaso/parasitología , Análisis de Varianza , Animales , Ascomicetos/crecimiento & desarrollo , Heces/parasitología , Enfermedades Gastrointestinales/microbiología , Enfermedades Gastrointestinales/parasitología , Tracto Gastrointestinal/parasitología , Intestino Delgado/microbiología , Intestino Delgado/parasitología , Boca/microbiología , Boca/parasitología , Infecciones por Nematodos/microbiología , Control Biológico de Vectores/métodos , Rumen/microbiología , Rumen/parasitología , Ovinos , Esporas Fúngicas/crecimiento & desarrollo
12.
Vet World ; 14(2): 393-404, 2021 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-33776304

RESUMEN

The anesthetic-surgical stress response consists of metabolic, neuroendocrine, hemodynamic, immunological, and behavioral adaptations through chemical mediators such as the adrenocorticotropic hormone, growth hormone, antidiuretic hormone, cortisol, aldosterone, angiotensin II, thyroid-stimulating hormone, thyroxine, triiodothyronine, follicle-stimulating hormone, luteinizing hormone, catecholamines, insulin, interleukin (IL)-1, IL-6, tumor necrosis factor-alpha, and prostaglandin E-2. Behavioral changes include adopting the so-called prayer posture, altered facial expressions, hyporexia or anorexia, drowsiness, sleep disorders, restriction of movement, licking or biting the injured area, and vocalizations. Overall, these changes are essential mechanisms to counteract harmful stimuli. However, if uncontrolled surgical stress persists, recovery time may be prolonged, along with increased susceptibility to infections in the post-operative period. This review discusses the neurobiology and most relevant organic responses to pain and anesthetic-surgical stress in dogs and cats. It highlights the role of stress biomarkers and their influence on autonomous and demeanor aspects and emphasizes the importance of understanding and correlating all factors to provide a more accurate assessment of pain and animal welfare in dogs and cats throughout the surgical process.

13.
Odontol. sanmarquina (Impr.) ; 24(2): 71-77, abr.-jun. 2021.
Artículo en Español, Inglés | LILACS-Express | LILACS | ID: biblio-1178076

RESUMEN

El mixoma odontogénico es una neoplasia benigna, localmente agresiva, con una baja prevalencia (frecuencia del 2% al 5% de los tumores odontogénicos) en los maxilares. Este tumor a menudo se presenta como una lesión expansiva asintomática sin cambios nerviosos sensoriales. El objetivo del presente trabajo es detallar el caso de un paciente masculino de 42 años quien acude al servicio de Cirugía Bucal y Maxilofacial del Hospital Nacional Hipólito Unanue por presentar una tumoración de crecimiento lento en maxilar superior, que fue aumentando de tamaño con el tiempo y desplazando órganos dentarios, y que se extiende al paladar duro y parte de paladar blando, el diagnóstico anatomopatológico fue de mixoma odontogénico y recibió un tratamiento radical (hemimaxilectomia) por la naturaleza agresiva del tumor. En este trabajo discutimos la presentación del mixoma odontogénico en el maxilar superior, los enfoques de trata- miento; detallando la importancia de plantear alternativas de tratamiento que permitan la reconstrucción inmediata generando la menor morbilidad posible.


Odontogenic myxoma is a locally aggressive benign neoplasm with a low prevalence (frequency 2% to 5% of odontogenic tumors) in the jaws. This tumor often presents as an asymptomatic expansive lesion without sensory nerve changes. The aim of this study is to detail the case of a 42-year-old male patient who attends the Oral and Maxillofacial Surgery service of the Hipólito Unanue National Hospital due to a slow-growing tumor in the upper jaw, which increased in size over time and displacing dental organs, and extending to the hard palate and part of the soft palate, the pathological diagnosis was odontogenic myxoma and received radical treatment (hemimaxilectomy) due to the aggressive nature of the tumor. In this work we discuss the presentation of odontogenic myxoma in the maxilla, treatment approaches; detailing the importance of proposing treatment alternatives that allow immediate reconstruction generating the least possible morbidity.

14.
Clin Transl Oncol ; 23(7): 1415-1428, 2021 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-33537865

RESUMEN

AIMS: To report toxicity of a hypofractionated scheme of whole-breast (WB) intensity-modulated radiotherapy (IMRT) with simultaneous integrated boost (SIB) to the tumor bed (TB) using Tomotherapy® with Direct modality. METHODS: Patients with early breast cancer, undergoing radiotherapy (RT) in 15 daily fractions to WB (prescription dose 40.05 Gy) and SIB to the TB (48 Gy), between 2013 and 2017, was analyzed. Primary endpoint was acute and intermediate toxicity assessed at the end and within 6 months from RT, according to Radiation Therapy Oncology Group (RTOG) scale. Secondary endpoints included early chronic toxicity at 12-months follow-up, using the Late Effects Normal Tissue Task Subjective, Objective, Management, and Analytic (LENT-SOMA) scale, and cosmesis using Harvard criteria. RESULTS: The study population was of 287 patients. Acute and intermediate toxicity was collected among 183 patients with data available at the end of RT and within 6 months, 85 (46%) experienced G2 toxicity and 84 (46%) G1 toxicity, while 14 (8%) did not report toxicity at any time. A significant reduction of any grade toxicity was observed between the two time points, with the majority of patients reporting no clinically relevant toxicity at 6 months. At univariate analysis, age < 40 years, breast volume > 1000 cm3 and Dmax ≤ 115% of prescription dose were predictive factors of clinically relevant acute toxicity (G ≥ 2) at any time. At multivariable analysis, only age and breast volume were confirmed as predictive factors, with Relative Risks (95% Confidence Intervals): 2.02 (1.13-3.63) and 1.84 (1.26-2.67), respectively. At 12-month follow-up, 113 patients had complete information on any toxicity with 53% of toxicity G < 2, while cosmetic evaluation, available for 102 patients, reported a good-excellent result for 86% of patients. CONCLUSIONS: Hypofractionated WB IMRT with a SIB to the TB, delivered with TomoDirect modality, is safe and well-tolerated. Most patients reported no toxicity after 6 months and good-excellent cosmesis. Predictive factors of clinically relevant toxicity might be considered during treatment planning in order to further reduce side effects.


Asunto(s)
Neoplasias de la Mama/radioterapia , Hipofraccionamiento de la Dosis de Radiación , Radioterapia de Intensidad Modulada/efectos adversos , Enfermedad Aguda , Adulto , Anciano , Neoplasias de la Mama/patología , Femenino , Humanos , Persona de Mediana Edad , Estudios Prospectivos , Traumatismos por Radiación/etiología , Radioterapia de Intensidad Modulada/métodos , Factores de Tiempo
15.
Vet World ; 14(11): 2984-2995, 2021 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-35017848

RESUMEN

Pain and anxiety are two of the most important concerns in clinical veterinary medicine because they arise as consequences of multiple factors that can severely affect animal welfare. The aim of the present review was to provide a description and interpretation of the physiological and behavioral alterations associated with pain and anxiety in equines. To this end, we conducted an extensive review of diverse sources on the topic. The article begins by describing the neurophysiological pathway of pain, followed by a discussion of the importance of the limbic system in responses to pain and anxiety, since prolonged exposure to situations that cause stress and pain generates such physiological changes as tachycardia, tachypnea, hypertension, hyperthermia, and heart rate variability (HRV), often accompanied by altered emotional states, deficient rest, and even aggressiveness. In the long term, animals may show deficiencies in their ability to deal with changes in the environment due to alterations in the functioning of their immune, nervous, and endocrinologic systems. In conclusion, pain and anxiety directly impact the homeostasis of organisms, so it is necessary to conduct objective evaluations of both sensations using behavioral scales, like the horse grimace scale, complemented by assessments of blood biomarkers to analyze their correlation with physiological parameters: Heart rate, respiratory rate, HRV, theparasympathetic tone activity index, lactate and glucose levels, and temperature. Additional tools - infrared thermography, for example - can also be used in these efforts to improve the quality of life and welfare of horses.

16.
Food Funct ; 11(10): 8768-8779, 2020 Oct 21.
Artículo en Inglés | MEDLINE | ID: mdl-32955071

RESUMEN

The physicochemical, nutritional and sensory properties of flours, doughs and tortillas made with traditional nixtamalization (TN) and ecological nixtamalization (EN) and enriched (9%) with the traditional maguey mushroom (Pleurotus agaves) were analysed. EN resulted in flours and tortillas having a greater content of bioactive compounds than that of TN flours, which represents a production process of maize tortillas containing high amounts of antioxidants. The addition of mushrooms to EN flours improved their sensory properties, whereas the addition of mushrooms to TN flours decreased them. The amount of P. agaves added to tortillas was equivalent to 3% enrichment with ß-glucans. The edible mushroom P. agaves, highly appreciated in many Mexican regions, improved the nutritional and sensory quality of blue maize tortillas when added to flours prepared by EN. A new product was developed using local traditional foods of complementary nutritional value.


Asunto(s)
Pan/análisis , Harina/análisis , Alimentos Fortificados/análisis , Pleurotus , Zea mays , Manipulación de Alimentos/métodos , Humanos , México , Valor Nutritivo
17.
Vet Immunol Immunopathol ; 228: 110100, 2020 Oct.
Artículo en Inglés | MEDLINE | ID: mdl-32871408

RESUMEN

Mesenchymal stem cells (MSC) are modern tools in regenerative therapies of humans and animals owed to their immunomodulatory properties, which are activated in a pro-inflammatory environment. Different preconditioning strategies had been devised to enhance the immunomodulatory properties of MSC. In this research, we evaluated the immunological attributes of equine adipose MSC (eAMSC) before and after preconditioning in vitro with prostaglandin E2 (PGE2), substance P (SP), their combination and IFNγ. PGE2/SP was the best combination to keep or enhance the mesodermal lineage differentiation of eAMSC. Alongside with this, preconditioning of eMSC with PGE2 and SP did not affect expression of stemness MSC surface phenotype: CD90+, CD44+, MHC class I+, MHC class II- and CD45-, assessed by cytometry. Both naïve and preconditioned eAMSC expressed genes related with immune properties, such as MHC-I, PTGES, IL6, IL1A, TNFα and IL8 assessed by qPCR. Only TNFα was under expressed in treated cells, while the other markers were either overexpressed or not changed. In no cases MHC-II expression was detected. The antiproliferative effect of preconditioned eAMSC exposed to activated peripheral blood mononuclear cells (PBMC) showed that SP treatment significantly inhibited proliferation of LPS stimulated PBMC. When eAMSC were stimulated with Poly I:C, all the treatments significantly inhibited proliferation of stimulated PBMC (p < 0.05). Direct contact (coculture) between the preconditioned eAMSC and PBMC, induced a shift of significantly more (CD4/CD25/FOXP3)+ T-regulatory PBMC than naïve eAMSC. In the experiments of this research, we investigated the secreted proteomic profile of naïve and preconditioned eAMSC, 42 up-regulated and 40 down-regulated proteins were found in the proteomic assay. Our proteomic data revealed profound changes in the secretory pattern of MSC exposed to different treatments, compared to naïve eAMSC as well as among treatments. In overall, compared to naïve cells, the protein profile of preconditioned cells resembled the mesenchymal-epithelial transition (MET). Here we showed that the combined use of PGE2 and SP provoked in overall the highest expression of anti-inflammatory markers as well as lead to an increased acquisition of a T-regulatory phenotype in preconditioned eAMSC without affecting their "stemness".


Asunto(s)
Dinoprostona/inmunología , Caballos/inmunología , Células Madre Mesenquimatosas/inmunología , Proteínas/metabolismo , Sustancia P/inmunología , Animales , Biomarcadores/metabolismo , Diferenciación Celular/inmunología , Proliferación Celular , Citometría de Flujo/veterinaria , Interferón gamma/inmunología , Masculino , Células Madre Mesenquimatosas/metabolismo , Mesodermo/citología , Proteoma , Vías Secretoras/inmunología
19.
Nanomaterials (Basel) ; 10(6)2020 Jun 05.
Artículo en Inglés | MEDLINE | ID: mdl-32516996

RESUMEN

A series of GdCu 2 nanoparticles with controlled sizes ranging from 7 nm to 40 nm has been produced via high-energy inert-gas ball milling. Rietveld refinements on the X-ray diffraction measurements ensure that the bulk crystalline I m m a structure is retained within the nanoparticles, thanks to the employed low milling times ranging from t = 0.5 to t = 5 h. The analysis of the magnetic measurements shows a crossover from Superantiferromagnetism (SAF) to a Super Spin Glass state as the size decreases at NP size of 〈 D 〉 ≈ 18 nm. The microstrain contribution, which is always kept below 1%, together with the increasing surface-to-core ratio of the magnetic moments, trigger the magnetic disorder. Additionally, an extra contribution to the magnetic disorder is revealed within the SAF state, as the oscillating RKKY indirect exchange achieves to couple with the aforementioned contribution that emerges from the size reduction. The combination of both sources of disorder leads to a maximised frustration for 〈 D 〉 ≈ 25 nm sized NPs.

20.
Phys Rev Lett ; 124(13): 131101, 2020 Apr 03.
Artículo en Inglés | MEDLINE | ID: mdl-32302173

RESUMEN

Because of the high energies and long distances to the sources, astrophysical observations provide a unique opportunity to test possible signatures of Lorentz invariance violation (LIV). Superluminal LIV enables the decay of photons at high energy. The high altitude water Cherenkov (HAWC) observatory is among the most sensitive gamma-ray instruments currently operating above 10 TeV. HAWC finds evidence of 100 TeV photon emission from at least four astrophysical sources. These observations exclude, for the strongest of the limits set, the LIV energy scale to 2.2×10^{31} eV, over 1800 times the Planck energy and an improvement of 1 to 2 orders of magnitude over previous limits.

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