Phenomenological model for the remanent magnetization of dilute quasi-one-dimensional antiferromagnets

We present a phenomenological model for the remanent magnetization at low temperatures in the quasi-one-dimensional dilute antiferromagnets CH_{3}NH_{3}Mn_{1-x}Cd_{x} Cl_{3}\cdot 2H_{2}O and (CH_{3})_{2}NH_{2}Mn_{1-x}Cd_{x}Cl_{3}\cdot 2H_{2}O. The model assumes the existence of uncompensated magnetic moments induced in the odd-sized segments generated along the Mn(^{2+}) chains upon dilution. These moments are further assumed to correlate ferromagnetically after removal of a cooling field. Using a (mean-field) linear-chain approximation and reasonable set of model parameters, we are able to reproduce the approximate linear temperature dependence observed for the remanent magnetization in the real compounds.Comment: 5 pages, 2 figures; final version to appear in Physical Review

Magnon dispersion and thermodynamics in CsNiF_3

We present an accurate transfer matrix renormalization group calculation of the thermodynamics in a quantum spin-1 planar ferromagnetic chain. We also calculate the field dependence of the magnon gap and confirm the accuracy of the magnon dispersion derived earlier through an 1/n expansion. We are thus able to examine the validity of a number of previous calculations and further analyze a wide range of experiments on CsNiF_3 concerning the magnon dispersion, magnetization, susceptibility, and specific heat. Although it is not possible to account for all data with a single set of parameters, the overall qualitative agreement is good and the remaining discrepancies may reflect departure from ideal quasi-one-dimensional model behavior. Finally, we present some indirect evidence to the effect that the popular interpretation of the excess specific heat in terms of sine-Gordon solitons may not be appropriate.Comment: 9 pages 10 figure

The Origin of Intraspecific Variation of Virulence in an Eukaryotic Immune Suppressive Parasite

Occurrence of intraspecific variation in parasite virulence, a prerequisite for coevolution of hosts and parasites, has largely been reported. However, surprisingly little is known of the molecular bases of this variation in eukaryotic parasites, with the exception of the antigenic variation used by immune-evading parasites of mammals. The present work aims to address this question in immune suppressive eukaryotic parasites. In Leptopilina boulardi, a parasitic wasp of Drosophila melanogaster, well-defined virulent and avirulent strains have been characterized. The success of virulent females is due to a major immune suppressive factor, LbGAP, a RacGAP protein present in the venom and injected into the host at oviposition. Here, we show that an homologous protein, named LbGAPy, is present in the venom of the avirulent strain. We then question whether the difference in virulence between strains originates from qualitative or quantitative differences in LbGAP and LbGAPy proteins. Results show that the recombinant LbGAPy protein has an in vitro GAP activity equivalent to that of recombinant LbGAP and similarly targets Drosophila Rac1 and Rac2 GTPases. In contrast, a much higher level of both mRNA and protein is found in venom-producing tissues of virulent parasitoids. The F1 offspring between virulent and avirulent strains show an intermediate level of LbGAP in their venom but a full success of parasitism. Interestingly, they express almost exclusively the virulent LbGAP allele in venom-producing tissues. Altogether, our results demonstrate that the major virulence factor in the wasp L. boulardi differs only quantitatively between virulent and avirulent strains, and suggest the existence of a threshold effect of this molecule on parasitoid virulence. We propose that regulation of gene expression might be a major mechanism at the origin of intraspecific variation of virulence in immune suppressive eukaryotic parasites. Understanding this variation would improve our knowledge of the mechanisms of transcriptional evolution currently under active investigation

Remove Noise in Video with 3D Topological Maps

International audienceIn this paper we present a new method for foreground masks denoising in videos. Our main idea is to consider videos as 3D images and to deal with regions in these images. Denoising is thus simply achieved by merging foreground regions corresponding to noise with background regions. In this framework, the main question is the definition of a cri-terion allowing to decide if a region corresponds to noise or not. Thanks to our complete cellular description of 3D images, we can propose an advanced criterion based on Betti numbers, a topological invariant. Our results show the interest of our approach which gives better results than previous methods

Imaging tests in determination of brain death

In this issue, an excellent review is published on the imaging findings in non-neonatal hypoxic-ischemic encephalopathy [1]. The authors also go into detail on imaging “brain death”, an entity that is currently causing debate as far as the imaging approach is concerned. Brain death refers to the irreversible end of all brain activity due to necrosis of neurons. The diagnosis of brain death allows organ donation for transplantation or withdrawal of life support. Legal standard and/or practice guidelines are currently present in most countries. There is uniform agreement on the clinical neurological examination to evaluate absence of brain function. This examination includes the assessment of coma, the absence of brain reflexes, and the assessment of apnea. Some guidelines require a confirmatory test for the diagnosis o

Nonlinear excitations in CsNiF3 in magnetic fields perpendicular to the easy plane

Experimental and numerical studies of the magnetic field dependence of the specific heat and magnetization of single crystals of CsNiF3 have been performed at 2.4 K, 2.9 K, and 4.2 K in magnetic fields up to 9 T oriented perpendicular to the easy plane. The experimental results confirm the presence of the theoretically predicted double peak structure in the specific heat arising from the formation of nonlinear spin modes. The demagnetizing effects are found to be negligible, and the overall agreement between the data and numerical predictions is better than reported for the case when the magnetic field was oriented in the easy plane. Demagnetizing effects might play a role in generating the difference observed between theory and experiment in previous work analyzing the excess specific heat using the sine-Gordon model.Comment: 6 pages, 5 figures, submitted to Phys. Rev.

Deciding case by case on family presence in the emergency care service

Objective: To understand how physicians and nurses experience and perceive the presence of families in the emergency care service. Methods: This was a qualitative study that used symbolic interactionism as a theoretical reference, and grounded theory as a methodological reference. Twenty professionals participated – equally representing physicians and nurses - working in two emergency rooms located in the south of Brazil. Data were collected between October of 2016 and February of 2017, by means of interviews. Results: The existence of a social culture of family exclusion was identifi ed, widely diffused and practiced by professionals. However, families sometimes remain with their loved ones in the emergency room, since professionals analyze and decide “case by case”, considering different aspects throughout the care process. Conclusion: Multiple aspects are related in determining family presence during emergency care for physicians and nurses. Thus, a single directive on the presence of the family is not prudent. In fact, it is suggested that each health unit develop its protocols, considering local particularities.Objetivo: Compreender como médicos e enfermeiros vivenciam e percebem a presença da família no serviço de atendimento emergencial. Métodos: Estudo qualitativo que utilizou o Interacionismo Simbólico como referencial teórico e a Teoria Fundamentada nos Dados como referencial metodológico. Participaram 20 profi ssionais – divididos equitativamente entre médicos e enfermeiros – que atuavam em duas Salas de Emergência localizadas no Sul do Brasil. Os dados foram coletados entre outubro de 2016 e fevereiro de 2017, por meio de entrevistas. Resultados: Identifi cou-se a existência de uma cultura social de exclusão familiar, amplamente difundida e praticada pelos profi ssionais. Contudo, às vezes, as famílias permanecem com seus entes queridos na Sala de Emergência, visto que os profi ssionais analisam e decidem “caso a caso”, considerando diferentes aspectos ao longo do processo assistencial. Conclusão: Para médicos e enfermeiros múltiplos aspectos estão relacionados na determinação da presença familiar durante o atendimento emergencial. Assim, não é aconselhável uma diretiva única para a presença da família. Em realidade, sugere-se que cada unidade de saúde elabore seus protocolos considerando as particularidades locais.Objetivo: Comprender cómo médicos y enfermeros experimentan y perciben la presencia familiar en el servicio de atención de urgencias. Métodos: Estudio cualitativo, aplicando el Interaccionismo Simbólico como referencial teórico, y la Teoría Fundamentada en los Datos como referencial metodológico. Participaron 20 profesionales –equitativamente divididos entre médicos y enfermeros– actuantes en dos Servicios de Urgencias del Sur de Brasil. Datos recolectados de octubre 2016 a febrero 2017 mediante entrevistas. Resultados: Se identifi có la existencia de una cultura social de exclusión familiar, ampliamente difundida y practicada por los profesionales. Igualmente, a veces, las familias permanecen con sus seres queridos en el Servicio de Urgencias, dado que los profesionales analizan y deciden “caso por caso”, considerando diferentes aspectos a lo largo del proceso de atención. Conclusión: Para médicos y enfermeros, múltiples aspectos se relacionan con la determinación de la presencia familiar durante la atención de urgencia. Por ello, no es aconsejable una directiva única sobre presencia familiar. En realidad, se sugiere que cada unidad de salud elabore sus protocolos considerando sus propias características