Giant and time-dependent magnetocaloric effect in high-spin molecular magnets

We have measured and calculated the magnetocaloric effect in macroscopic samples of oriented high-spin molecular clusters like Mn12 and Fe8 as a function of the temperature and both the intensity and the sweeping rate of the applied magnetic field. We have observed a high magnetic entropy variation around the blocking temperature of the magnetic moment of molecules and calculated the shift of the entropy variation and cooling temperature, with the sweeping rate of the magnetic field.Comment: 10 pages, 3 figure

Large Nonreciprocal Propagation of Surface Acoustic Waves in Epitaxial Ferromagnetic/Semiconductor Hybrid Structures

Nonreciprocal propagation of sound, that is, the different transmission of acoustic waves traveling in opposite directions, is a challenging requirement for the realization of devices such as acoustic isolators and circulators. Here, we demonstrate efficient nonreciprocal transmission of surface acoustic waves (SAWs) propagating in opposite directions in a GaAs substrate coated with an epitaxial Fe3Si film. The nonreciprocity arises from the acoustic attenuation induced by the magnetoelastic (ME) interaction between the SAW strain field and spin waves in the ferromagnetic film, which depends on the SAW propagation direction and can be controlled via the amplitude and orientation of an external magnetic field. The acoustic-transmission nonreciprocity, defined as the difference between the transmitted acoustic powers for forward and backward propagation at the ME resonance, reaches values of up to 20%, which are, to our knowledge, the largest values of nonreciprocity reported for SAWs traveling in a semiconducting piezoelectric substrate covered by a ferromagnetic film. The experimental results are well accounted for by a model for the ME interaction, which also shows that the nonreciprocity can be further enhanced by optimization of the sample design. These results make Fe3Si/GaAs a promising platform for the realization of efficient nonreciprocal SAW devices

Communicationsand Corporate Social Responsibility: A Canvas to Build its Strategy

El papel de las comunicaciones en el mundo empresarial evoluciona hacia un modelo más participativo y consensuado con los stakeholders, debido a que ellos son cruciales para generar impacto en responsabilidad social, mejorar la reputación y mantener vigente una organización en el futuro. Académicos reconocen que el desempeño financiero de la empresa, la relación con los inver- sores, los mercados de capital y la creación de imagen son aspectos en los que día a día tienen mayor influencia los grupos de interés; por esta razón, el propósito de este trabajo es el de crear una herra- mienta que facilite la construcción de un marco de comunicaciones con el fin de ajustarla alineación de la responsabilidad social corporativa (RSC) en la relación empresa-stakeholder. El modelo de “lienzo” propuesto es una formuladinámica para emprender un acercamiento de intereses con los grupos estratégicos de la organización para definir el mejor mecanismo participativo y así lograr esta- blecer una relación de beneficio mutuo dentro de las actividades propias de la RSCThe communication's role in the business world evolves towards a more participatory and consensual model with stakeholders, because they are crucial to generate impact on social res- ponsibility, improve reputation and remain being leaders in the future. Scholars have recognized that financial performance of the company, the investor relations, capital markets and build a brand image are aspects that day by day have greater influence the stakeholders; therefore, the purpose of this work is to create a tool that facilitates the construction of a communications framework to adjust the alignment of corporate social responsibility (CSR) in the company-stakeholder relationship. The canvas model proposed is a dynamic formula with the purpose of undertake a rapprochement of interests with strategic groups of the organization in order to define the best participatory mechanism and achieve a mutual benefit relationship within the activities of CS

Emergence of the stripe-domain phase in patterned permalloy films

The occurrence of stripe domains in ferromagnetic permalloy (Py = Fe20Ni80) is a well-known phenomenon which has been extensively observed and characterized. This peculiar magnetic configuration appears only in films with a thickness above a critical value (dcr), which is strongly determined by the sputtering conditions (i.e., deposition rate, temperature, magnetic field). So far, dcr has usually been presented as the boundary between the homogeneous (H) and stripe-domain (SD) regime, respectively, below and above dcr. In this work we study the transition from the H to the SD regime in thin films and microstructured bridges of Py with different thicknesses. We find there is an intermediate regime, over a quite significant thickness range below dcr, which is signaled in confined structures by a quickly changing domain-wall configuration and by a broadening of the magnetoresistance dip at the coercive field. We call this the emerging stripe-domain (ESD) regime. The transition from the ESD to the SD regime is accompanied by a sharp increase of the magnetoresistance ratio at the thickness where stripes appear in MFM

Propagation of Magnetic Avalanches in Mn12Ac at High Field Sweep Rates

Time-resolved measurements of the magnetization reversal in single crystals of Mn 12 Ac in pulsed magnetic fields, at magnetic field sweep rates from 1.5     kT / s up to 7     kT / s , suggest a new process that cannot be scaled onto a deflagrationlike propagation driven by heat diffusion. The sweep rate dependence of the propagation velocity, increasing from a few 100     m / s up to the speed of sound in Mn 12 Ac , indicates the existence of two new regimes at the highest sweep rates, with a transition around 4     kT / s that can be understood as a magnetic deflagration-to-detonation transition

Spin dynamics in single-molecule magnets combining surface acoustic waves and high frequency electron paramagnetic resonance

We report an experimental technique that integrates high-frequency surface acoustic waves (SAWs) with high-frequency electron paramagnetic resonance (HFEPR) spectroscopy in order to measure spin dynamics on fast time scales in single-molecule magnets. After the system is driven out of equilibrium by triggering magnetic avalanches, or simply by heating with short SAW pulses, the evolution of the spin populations within fixed energy levels is measured using HFEPR spectroscopy

Infección periprotésica aguda de rodilla por fusobacterium nucleatum. Revisión de la literatura a propósito de un caso.

Fusobacterium Nucleatum is an anaerobic commensal microorganism present in the oral cavity and some mucous membranes with great capacity to form biofilm. In the literature, only one case of acute periprosthetic infection of the knee by Fusobacterium Nucleatum has been reported, providing the second case. A 72-year-old man presented with an acute periprosthetic infection by fusobacterium nucleatum after a second time of a prosthetic knee replacement. Debridement and spacer changes were performed up to 4 times, associating parenteral antibiotic treatment. After ensuring the absence of infection, a modular revision knee prosthesis with stems was placed, with a satisfactory evolution after two years. Currently he has preserved ambulation, joint balance of 0º-50º and is free of infection. Fusobacterium Nucleatum infection is very rare, but aggressive and difficult to resolve, recommending two-stage replacement in acute infection and adequate antibiotic treatment to offer curative treatment

Azithromycin to Prevent Pertussis in Household Contacts, Catalonia and Navarre, Spain, 2012-2013

We retrospectively assessed the effectiveness of azithromycin in preventing transmission of pertussis to a patient's household contacts. We also considered the duration between symptom onset in the primary patient and azithromycin administration. We categorized contacts into 4 groups: those treated within 21 days after illness onset in the primary patient. We studied 476 primary index patients and their 1,975 household contacts, of whom 4.5% were later identified as having pertussis. When contacts started chemoprophylaxis within 14 days after primary patient's symptom onset was less effective. We recommend that contacts of persons with pertussis begin chemoprophylaxis within <14 days after primary patient's symptom onset