Spin-Orbit Torques and Magnetization Switching in (Bi,Sb)2Te3/Fe3GeTe2 Heterostructures Grown by Molecular Beam Epitaxy.

Topological insulators (TIs) hold promise for manipulating the magnetization of a ferromagnet (FM) through the spin-orbit torque (SOT) mechanism. However, integrating TIs with conventional FMs often leads to significant device-to-device variations and a broad distribution of SOT magnitudes. In this work, we present a scalable approach to grow a full van der Waals FM/TI heterostructure by molecular beam epitaxy, combining the charge-compensated TI (Bi,Sb)2Te3 with 2D FM Fe3GeTe2 (FGT). Harmonic magnetotransport measurements reveal that the SOT efficiency exhibits a non-monotonic temperature dependence and experiences a substantial enhancement with a reduction of the FGT thickness to 2 monolayers. Our study further demonstrates that the magnetization of ultrathin FGT films can be switched with a current density of Jc ∼ 1010 A/m2, with minimal device-to-device variations compared to previous investigations involving traditional FMs.

Face-to-face and online teaching experience on experimental animals and alternative methods with nursing students: a research study.

BACKGROUND: Animal models are increasingly used in Nursing science to study care approaches. Despite the scientific relevance and the ethical debate surrounding the use of experimental animals, there is a scarcity of scholarly literature exploring this topic in Nursing Schools. AIM: To evaluate perceptions and attitudes of nursing students enrolled in a Pharmacology course on the use of experimental animals and implementation of alternative methods, by comparing the experience for two academic years. An interdisciplinary collaboration has also been developed. METHODS: A descriptive cross-sectional, quantitative study was developed. Undergraduate nursing students were enrolled in the Pharmacology subject at the University of Leon (Spain). The study was carried out in the Pharmacology facilities. Students followed a two-session practical class regarding experimental animals and alternative methods in the Pharmacology course (Degree in Nursing) in two different academic years (2019-20/2020-21). At the end of the activity, they answered a questionnaire to assess their opinions on the use of experimental animals and alternative methods in Pharmacology and the 3Rs principle. RESULTS: A comparison of the students' perception with and without direct participation in the evaluation of promazine effects in mice was made. A total of 190 students participated in the teaching experience, providing high scores in all items (4-5 out of 5 points) regarding the teaching experience. Students became also aware of the advantages and disadvantages on the use of experimental animals, as well as the ethical considerations to bear in mind for their use and the need for alternative methods. CONCLUSIONS: In the students' opinion, the total replacement of animals by alternative techniques was very difficult, and they preferred to do the practice face-to-face. The alternative method designed was useful for the students to accept the employment of experimental animals in biomedical research and education, and know the legislation applied in the protection of animals.

Van der Waals heterostructures for spintronics and opto-spintronics.

The large variety of 2D materials and their co-integration in van der Waals heterostructures enable innovative device engineering. In addition, their atomically thin nature promotes the design of artificial materials by proximity effects that originate from short-range interactions. Such a designer approach is particularly compelling for spintronics, which typically harnesses functionalities from thin layers of magnetic and non-magnetic materials and the interfaces between them. Here we provide an overview of recent progress in 2D spintronics and opto-spintronics using van der Waals heterostructures. After an introduction to the forefront of spin transport research, we highlight the unique spin-related phenomena arising from spin-orbit and magnetic proximity effects. We further describe the ability to create multifunctional hybrid heterostructures based on van der Waals materials, combining spin, valley and excitonic degrees of freedom. We end with an outlook on perspectives and challenges for the design and production of ultracompact all-2D spin devices and their potential applications in conventional and quantum technologies.

Immediate feeding tolerance in patients with mild acute biliary pancreatitis.

ANTECEDENTES: La pancreatitis aguda leve es una inflamación local del páncreas sin complicaciones locales ni falla orgánica. Su manejo consiste en tres elementos básicos: hidratación, analgesia y ayuno. La realimentación se inicia cuando el paciente no tiene dolor y refiere apetito, pero el momento exacto para iniciarla no está previamente documentado. OBJETIVO: Determinar la tolerancia a la alimentación oral inmediata (8 horas posterior al inicio del manejo) en comparación con la alimentación temprana (48 horas) en los pacientes con pancreatitis aguda biliar leve. MÉTODO: Se incluyeron pacientes con pancreatitis aguda biliar leve y se aleatorizaron en dos grupos: A) alimentación temprana a las 48 horas (30 pacientes) y B) alimentación inmediata a las 8 horas de inicio del manejo (29 pacientes). Fueron evaluados por un tercer observador ciego (no involucrado en el estudio) para documentar síntomas como náusea, vómito, reactivación del dolor abdominal, síndrome de respuesta inflamatoria sistémica, tolerancia alimentaria y estancia hospitalaria. RESULTADOS: No se encontraron diferencias significativas entre los grupos en cuanto a datos clínicos y bioquímicos. La estancia hospitalaria disminuyó significativamente en el grupo B (5.4 vs. 7.8 días; p < 0.003). CONCLUSIÓN: La alimentación inmediata en las primeras 8 horas del manejo de los pacientes con pancreatitis aguda biliar leve es bien tolerada y segura, y reduce la estancia hospitalaria. BACKGROUND: Mild acute pancreatitis is defined as pancreatic edema, without organic failure and without local complications. Its management consists in three basic elements: hydration, analgesia and fasting. Start refeeding when the patient haven´t pain and referring hungry, but exact time for this is not previously documented. OBJECTIVE: To determine the tolerance to immediate oral feeding (8 hours after the start of management) compared to early feeding (48 hours) in patients with mild acute biliary pancreatitis. METHOD: Included all patient with mild acute biliary pancreatitis, and they were randomized in to two groups: A) early oral feeding (n = 30) and B) immediate oral feeding (n = 29). They were evaluated by a third blind observer (not involved in the study) for documented symptoms like nausea, vomiting, reactivation of abdominal pain, systemic inflammatory response syndrome, food tolerance and hospital stay. RESULTS: There were no significant differences between both groups in the clinical data or in the biochemical studies. The hospital stay was significantly less in the group B (5.4 vs. 7.8 days; p < 0.003). CONCLUSION: Immediate oral feeding is well tolerated and secure in patients with mild acute biliary pancreatitis.

Therapeutic Use of Silver Nanoparticles in the Prevention and Arrest of Dental Caries.

Dental caries is one of the major diseases of the oral cavity affecting humans worldwide. Different alternatives have been used for its control, but its incidence and prevalence are still high. On the other hand, silver has been used for centuries due to its antimicrobial properties. With advances in nanotechnology, the use and research in nanomaterials has increased, recently, and silver nanoparticles have become an essential part of the dental practice, giving materials physical and chemical improvements in their properties, used for their antibacterial capacity preventing and arresting dental caries. The objective of this review was to examine the use of silver nanoparticles, in the treatment of dental caries in the remineralization of teeth hard tissues, as well as the antimicrobial potential, cytotoxicity, and long-term effectiveness.

Control of Spin-Orbit Torques by Interface Engineering in Topological Insulator Heterostructures.

(Bi1-xSbx)2Te3 topological insulators (TIs) are gathering increasing attention owing to their large charge-to-spin conversion efficiency and the ensuing spin-orbit torques (SOTs) that can be used to manipulate the magnetization of a ferromagnet (FM). The origin of the torques, however, remains elusive, while the implications of hybridized states and the strong material intermixing at the TI/FM interface are essentially unexplored. By combining interface chemical analysis and spin-transfer ferromagnetic resonance (ST-FMR) measurements, we demonstrate that intermixing plays a critical role in the generation of SOTs. By inserting a suitable normal metal spacer, material intermixing is reduced and the TI properties at the interface are largely improved, resulting in strong variations in the nature of the SOTs. A dramatic enhancement of a field-like torque, opposing and surpassing the Oersted-field torque, is observed, which can be attributed to the non-equilibrium spin density in Rashba-split surface bands and to the suppression of spin memory loss. These phenomena can play a relevant role at other interfaces, such as those comprising transition metal dichalcogenides.

Tunable room-temperature spin galvanic and spin Hall effects in van der Waals heterostructures.

Spin-orbit coupling stands as a powerful tool to interconvert charge and spin currents and to manipulate the magnetization of magnetic materials through spin-torque phenomena. However, despite the diversity of existing bulk materials and the recent advent of interfacial and low-dimensional effects, control of this interconversion at room temperature remains elusive. Here, we demonstrate strongly enhanced room-temperature spin-to-charge interconversion in graphene driven by the proximity of WS2. By performing spin precession experiments in appropriately designed Hall bars, we separate the contributions of the spin Hall and the spin galvanic effects. Remarkably, their corresponding conversion efficiencies can be tailored by electrostatic gating in magnitude and sign, peaking near the charge neutrality point with an equivalent magnitude that is comparable to the largest efficiencies reported to date. Such electric-field tunability provides a building block for spin generation free from magnetic materials and for ultra-compact magnetic memory technologies.

Thermoelectric spin voltage in graphene.

In recent years, new spin-dependent thermal effects have been discovered in ferromagnets, stimulating a growing interest in spin caloritronics, a field that exploits the interaction between spin and heat currents 1,2 . Amongst the most intriguing phenomena is the spin Seebeck effect 3-5 , in which a thermal gradient gives rise to spin currents that are detected through the inverse spin Hall effect 6-8 . Non-magnetic materials such as graphene are also relevant for spin caloritronics, thanks to efficient spin transport 9-11 , energy-dependent carrier mobility and unique density of states 12,13 . Here, we propose and demonstrate that a carrier thermal gradient in a graphene lateral spin valve can lead to a large increase of the spin voltage near to the graphene charge neutrality point. Such an increase results from a thermoelectric spin voltage, which is analogous to the voltage in a thermocouple and that can be enhanced by the presence of hot carriers generated by an applied current 14-17 . These results could prove crucial to drive graphene spintronic devices and, in particular, to sustain pure spin signals with thermal gradients and to tune the remote spin accumulation by varying the spin-injection bias.

Determination of the spin-lifetime anisotropy in graphene using oblique spin precession.

We determine the spin-lifetime anisotropy of spin-polarized carriers in graphene. In contrast to prior approaches, our method does not require large out-of-plane magnetic fields and thus it is reliable for both low- and high-carrier densities. We first determine the in-plane spin lifetime by conventional spin precession measurements with magnetic fields perpendicular to the graphene plane. Then, to evaluate the out-of-plane spin lifetime, we implement spin precession measurements under oblique magnetic fields that generate an out-of-plane spin population. We find that the spin-lifetime anisotropy of graphene on silicon oxide is independent of carrier density and temperature down to 150 K, and much weaker than previously reported. Indeed, within the experimental uncertainty, the spin relaxation is isotropic. Altogether with the gate dependence of the spin lifetime, this indicates that the spin relaxation is driven by magnetic impurities or random spin-orbit or gauge fields.

Hot-Carrier Seebeck Effect: Diffusion and Remote Detection of Hot Carriers in Graphene.

We investigate hot carrier propagation across graphene using an electrical nonlocal injection/detection method. The device consists of a monolayer graphene flake contacted by multiple metal leads. Using two remote leads for electrical heating, we generate a carrier temperature gradient that results in a measurable thermoelectric voltage V(NL) across the remaining (detector) leads. Due to the nonlocal character of the measurement, V(NL) is exclusively due to the Seebeck effect. Remarkably, a departure from the ordinary relationship between Joule power P and V(NL), V(NL) ∼ P, becomes readily apparent at low temperatures, representing a fingerprint of hot-carrier dominated thermoelectricity. By studying V(NL) as a function of bias, we directly determine the carrier temperature and the characteristic cooling length for hot-carrier propagation, which are key parameters for a variety of new applications that rely on hot-carrier transport.

Epidemiology of Bordetella pertussis in San Luis Potosí, Mexico.

We analyzed data from 147 patients with suspected pertussis in San Luis Potosí, Mexico. Bordetella pertussis was detected by real-time polymerase chain reaction in 59 (40.1%) cases. The incidence of B. pertussis infection was 2.3 per 100,000 population. There were 6 deaths among the study patients. We conclude that the impact of pertussis in our state is significantly higher than previously estimated.