Exponential behavior of the interlayer exchange coupling across non-magnetic metallic superlattices

It is shown that the coupling between magnetic layers separated by non-magnetic metallic superlattices can decay exponentially as a function of the spacer thickness $N$, as opposed to the usual $N^{-2}$ decay. This effect is due to the lack of constructive contributions to the coupling from extended states across the spacer. The exponential behavior is obtained by properly choosing the distinct metals and the superlattice unit cell composition.Comment: To appear in Phys. Rev.

Permeability of the blood-brain barrier through the phases of ischaemic stroke and relation with clinical outcome: protocol for a systematic review

Introduction: Ischaemic stroke is the most prevalent type of stroke and is characterised by a myriad of pathological events triggered by a vascular arterial occlusion. Disruption of the blood-brain barrier (BBB) is a key pathological event that may lead to fatal outcomes. However, it seems to follow a multiphasic pattern that has been associated with distinct biological substrates and possibly contrasting outcomes. Addressing the BBB permeability (BBBP) along the different phases of stroke through imaging techniques could lead to a better understanding of the disease, improved patient selection for specific treatments and development of new therapeutic modalities and delivery methods. This systematic review will aim to comprehensively summarise the existing evidence regarding the evolution of the BBBP values during the different phases of an acute ischaemic stroke and correlate this event with the clinical outcome of the patient. Methods and analysis: We will conduct a computerised search on Medline, EMBASE, Cochrane Central Register of Controlled Trials, Scopus and Web of Science. In addition, grey literature and ClinicalTrials.gov will be scanned. We will include randomised controlled trials, cohort, cross-sectional and case-controlled studies on humans that quantitatively assess the BBBP in stroke. Retrieved studies will be independently reviewed by two authors and any discrepancies will be resolved by consensus or with a third reviewer. Reviewers will extract the data and assess the risk of bias of the selected studies. If possible, data will be combined in a quantitative meta-analysis following the guidelines provided by Cochrane Handbook for Systematic Reviews of Interventions. We will assess cumulative evidence using the Grading of Recommendations, Assessment, Development and Evaluation approach. Ethics and dissemination: Ethical approval is not needed. All data used for this work are publicly available. The result obtained from this work will be published in a peer-reviewed journal and disseminated in relevant conferences.info:eu-repo/semantics/publishedVersio

Locally advanced adenocarcinoma of the rectum presenting with necrotising fasciitis of the perineum: successful management with early aggressive surgery and multimodal therapy

Colorectal cancer is a common malignant neoplasm and its treatment usually involves surgery associated, in some cases, depending on the staging, with chemoradiotherapy. Necrotising fasciitis of the perineum is a highly lethal infection of the perineum, perirectal tissues and genitals, requiring emergency surgical debridement, broad-spectrum antibiotics and control of sepsis. We present the case of a 59-year-old man with necrotising fasciitis of the perineum as the first clinical manifestation of locally advanced adenocarcinoma of the rectum, in which successful management consisted of early and aggressive surgical debridement, followed by multimodal therapy with curative intent. 2 years and 6 months after surgery the patient is well, with no evidence of local or systemic relapse.info:eu-repo/semantics/publishedVersio

Giant Cell Arteritis Presenting as Simultaneous Bilateral Critical Upper Limb Ischemia - Clinical Case

Introdução: A arterite de células gigantes (ACG), de etiologia desconhecida, é a vasculite sistémica mais comum nos adultos e pode ter uma ampla variedade de apresentações clínicas. Atinge mais frequentemente os ramos extracranianos da artéria carótida mas, em 10-15% dos casos, pode ocorrer o envolvimento das artérias subclávia, axilar e braquial. Caso clínico: Tratava-se de uma doente do sexo feminino, de 80 anos, com antecedentes de HTA e doença cerebrovascular. Foi observada no serviço de urgência por arrefecimento e dor em repouso nos membros superiores, com evidências de cianose digital distal bilateral. As queixas tinham tido início 2 meses antes e agravamento progressivo desde então. Realizou um angio-TC que mostrou a existência de oclusão de ambas as artérias axilares/braquiais proximais e imagens sugestivas de vasculite ao nível de ambas as artérias subclávias, aorta e artérias femorais comuns. Foi medicada com corticoterapia; contudo, por não apresentar melhoria significativa após 5 dias, optou-se por realizar um bypass carotídeo-umeral bilateral. Após a cirurgia, ocorreu resolução completa das queixas e a doente apresentava pulso radial palpável bilateralmente. Seis meses após a cirurgia, a doente encontrava-se assintomática e os bypasses permeáveis. Conclusão: O presente trabalho pretende expor o caso de uma doente com o diagnóstico inaugural e ACG,que se apresentou com isquemia crítica bilateral e simultânea. Este quadro clínico exigiu a realização de um procedimento de revascularização raro

Morphological transition between diffusion-limited and ballistic aggregation growth patterns

In this work, the transition between diffusion-limited and ballistic aggregation models was revisited using a model in which biased random walks simulate the particle trajectories. The bias is controlled by a parameter $\lambda$, which assumes the value $\lambda=0$ (1) for ballistic (diffusion-limited) aggregation model. Patterns growing from a single seed were considered. In order to simulate large clusters, a new efficient algorithm was developed. For $\lambda \ne 0$, the patterns are fractal on the small length scales, but homogeneous on the large ones. We evaluated the mean density of particles $\bar{\rho}$ in the region defined by a circle of radius $r$ centered at the initial seed. As a function of $r$, $\bar{\rho}$ reaches the asymptotic value $\rho_0(\lambda)$ following a power law $\bar{\rho}=\rho_0+Ar^{-\gamma}$ with a universal exponent $\gamma=0.46(2)$, independent of $\lambda$. The asymptotic value has the behavior $\rho_0\sim|1-\lambda|^\beta$, where $\beta= 0.26(1)$. The characteristic crossover length that determines the transition from DLA- to BA-like scaling regimes is given by $\xi\sim|1-\lambda|^{-\nu}$, where $\nu=0.61(1)$, while the cluster mass at the crossover follows a power law $M_\xi\sim|1 -\lambda|^{-\alpha}$, where $\alpha=0.97(2)$. We deduce the scaling relations \beta=\n u\gamma and $\beta=2\nu-\alpha$ between these exponents.Comment: 7 pages, 8 figure

Fabrication of calcium phosphates with controlled properties using a modular oscillatory flow reactor

Several technologies and synthesis routes have been implemented to produce calcium phosphates (CaPs) with distinct characteristics for biomedical applications. However, produce CaPs in a controlled way still represents a challenge. Oscillatory flow reactors (OFRs) are a technology ready to deliver in terms of mixing intensification in multiphase systems. In particular, continuous processes in OFRs improve control over the reaction conditions and can be implemented at an industrial scale. The aim of this work was to study for the first time the influence of the oscillation amplitude (x0: 4, 8 and 18 mm) and frequency (f: 1.9, 4 and 6 Hz) as well as residence time (τ: 3.3, 6.6 min) on the final CaP particles’ physicochemical properties using a continuous precipitation process in a novel modular oscillatory flow plate reactor (MOFPR). Furthermore, other parameters such as the initial reagents concentration, initial Ca/P molar ratio (Ca/P = 1.67, 1.33) and temperature (T = 37, 54 ºC) were also assessed. The synthesized particles and overall process were compared with particles obtained using the same methodology in conventional reactors, evidencing the potential of this technology to fabricate CaPs with tailored properties for potential application as nano or microcarriers for biomedical applications.info:eu-repo/semantics/publishedVersio

External Corrosion of the bottom plate of Petroleum and Derivative Storage tanks on Compacted Soils

Inspections carried out on petroleum and derivative storage tanks on compacted soils have shown external corrosion on the bottom plates of the tanks despite cathodic protection by an impressed current. The holes or cavities in the outer plates of the bottom of the tank (in contact with the soil) result in oil leakage, thereby having significant environmental impacts. The objective of this paper is to show, in laboratory experiments, that cathodic protection is not reliable when there are voids or spaces between the plates and the soil. In addition, it proposes the application of a thermal spray with aluminium in the parts of the bottom plates that are in contact with the soil to protect these plates from localised corrosion. It is important to note that the welding temperature was 320°C, without affecting the aluminium coating applied by the thermal spray