Pseudospin anisotropy of trilayer semiconductor quantum Hall ferromagnets

When two Landau levels are brought to a close coincidence between them and with the chemical potential in the Integer Quantum Hall regime, the two Landau levels can just cross or collapse while the external or pseudospin field that induces the alignment changes. In this work, all possible crossings are analyzed theoretically for the particular case of semiconductor trilayer systems, using a variational Hartree-Fock approximation. The model includes tunneling between neighboring layers, bias, intra-layer and inter-layer Coulomb interaction among the electrons. We have found that the general pseudospin anisotropy classification scheme used in bilayers applies also to the trilayer situation, with the simple crossing corresponding to an easy-axis ferromagnetic anisotropy analogy, and the collapse case corresponding to an easy-plane ferromagnetic analogy. An isotropic case is also possible, with the levels just crossing or collapsing depending on the filling factor and the quantum numbers of the two nearby levels. While our results are valid for any integer filling factor $\nu$ (=1,2,3,...), we have analyzed in detail the crossings at $\nu=3$ and $4$, and we have given clear predictions that will help in their experimental search. In particular, the present calculations suggest that by increasing the bias, the trilayer system at these two filling factors can be driven from an easy-plane anisotropy regime to an easy-axis regime, and then can be driven back to the easy-plane regime. This kind of reentrant behavior is an unique feature of the trilayers, compared with the bilayers

Coulomb and tunneling coupled trilayer systems at zero magnetic field

The ground-state electronic configuration of three coupled bidimensional electron gases has been determined using a variational Hartree-Fock approach, at zero magnetic field. The layers are Coulomb coupled, and tunneling is present between neighboring layers. In the limit of small separation between layers, the tunneling becomes the dominant energy contribution, while for large distance between layers the physics is driven by the Hartree electrostatic energy. Transition from tunneling to hartree dominated physics is shifted towards larger layer separation values as the total bidimensional density of the trilayers decreases. The inter-layer exchange helps in stabilize a "balanced" configuration, where the three layers are approximately equally occupied; most of the experiments are performed in the vicinity of this balanced configuration. Several ground-state configurations are consequence of a delicate interplay between tunneling and inter-subband exchange

Accurate and robust image superresolution by neural processing of local image representations

Image superresolution involves the processing of an image sequence to generate a still image with higher resolution. Classical approaches, such as bayesian MAP methods, require iterative minimization procedures, with high computational costs. Recently, the authors proposed a method to tackle this problem, based on the use of a hybrid MLP-PNN architecture. In this paper, we present a novel superresolution method, based on an evolution of this concept, to incorporate the use of local image models. A neural processing stage receives as input the value of model coefficients on local windows. The data dimension-ality is firstly reduced by application of PCA. An MLP, trained on synthetic se-quences with various amounts of noise, estimates the high-resolution image data. The effect of varying the dimension of the network input space is exam-ined, showing a complex, structured behavior. Quantitative results are presented showing the accuracy and robustness of the proposed method

Validación de un instrumento de evaluación del comportamiento sexual de personas con discapacidad intelectual para padres (ECS-PA)

The recent normalization of sexuality and sexual rights among people with Intellectual Disability (ID) has led to an increase in the number of initiatives aimed at improving their knowledge and skills through sexual-affective education programs, but these programs require evaluation instruments reliable to identify their needs and may be sensitive to change after the intervention. In this assessment their perceptions must converge, those of the professionals who deal with them and those of their parents to ensure the veracity of the information obtained, but unfortunately we lack valid and reliable psychometric instruments, both self-reported, because in many cases they lack of verbal skills sufficient to express their desires and experiences, as heteroinformed, since the existing ones are fundamentally focused on the study of attitudes towards sexuality of this group. The objective of this work has been to construct and validate a questionnaire to obtain information from parents about the sexuality of people with mild or moderate ID. The instrument consisting of 32 items with different response formats was administered to 118 parents of adults with ID. The Exploratory Factor Analysis and de Confirmatory Factor Analysis offers a structure composed by 3 factors: (F1) Comprehension of the privacy and social rules (13 items), (F2) perception of knowledge about sexuality that your child has (10 items) and (F3) concern for inappropriate sexual behavior (9 items). The model obtained with these four factors presents a good adjustment as shown by the main indicators (Chi2 S-B/df = 1.14, RMSEA = 0.035, CFI = 0.910 y TLI = 0.902). The ECS-PA is shown as an instrument that allows obtaining valid and reliable information about the sexuality of people with mild or moderate ID.La reciente normalización de la sexualidad y de los derechos sexuales entre las personas conDiscapacidad Intelectual (DI) ha hecho que se incremente el número de iniciativas dirigidas a mejorar sus conocimientos y habilidades mediante programas de educación afectivo-sexual pero dichos programas requieren instrumentos de evaluación fiables que permitan identificar sus necesidades y puedan ser sensibles al cambio tras la intervención. En dicha valoración deben confluir sus percepciones, las de los profesionales que se ocupan de ellos y las de sus padres para asegurar la veracidad de la información obtenida, pero lamentablemente carecemos de instrumentos psicométricos válidos y fiables tanto autoinformados, debido a que en muchos casos carecen de habilidades verbales suficientes para expresar sus deseos y vivencias, como heteroinformados, pues los existentes se centran fundamentalmente en el estudio de las actitudes hacia la sexualidad de este colectivo. El objetivo de este trabajo ha sido construir y validar un cuestionario para obtener información de los padres acerca de la sexualidad de las personas con DI leve o moderada. El instrumento fue administrado a 118 padres de personas adultas con DI. Se realizó un Análisis Factorial Exploratorio  seguido de un Análisis Factorial Confirmatorio que ofreció una estructura compuesta de 3 factores: (F1) Comprensión de la privacidad y normas sociales (13 ítems), (F2) percepción de los conocimientos sobre sexualidad que tiene su hijo/a (10 ítems), y (F3) preocupación por un comportamiento sexual inadecuado (9 ítems). El modelo obtenido con estos tres factores presenta un buen ajuste como muestran los principales indicadores (Chi2 S-B/df = 1,14, RMSEA = 0,035, CFI = 0,910 y TLI = 0,902). El ECS-PA se muestra como un instrumento que permite obtener información válida y fiable sobre la sexualidad de las personas con DI leve o moderada.

Induced pluripotent stem cell-derived endothelial cells promote angiogenesis and accelerate wound closure in a murine excisional wound healing model

Chronic wounds are a major complication in patients with cardiovascular diseases. Cell therapies have shown potential to stimulate wound healing, but clinical trials using adult stem cells have been tempered by limited numbers of cells and invasive procurement procedures. Induced pluripotent stem cells (iPSCs) have several advantages of other cell types, for example they can be generated in abundance from patients’ somatic cells (autologous) or those from a matched donor. iPSCs can be efficiently differentiated to functional endothelial cells (iPSC-ECs). Here, we used a murine excisional wound model to test the pro-angiogenic properties of iPSC-ECs in wound healing. Two full-thickness wounds were made on the dorsum of NOD-SCID mice and splinted. iPSC-ECs (5 × 105) were topically applied to one wound, with the other serving as a control. Treatment with iPSC-ECs significantly increased wound perfusion and accelerated wound closure. Expression of endothelial cell (EC) surface marker, platelet endothelial cell adhesion molecule (PECAM-1) (CD31), and pro-angiogenic EC receptor, Tie1, mRNA was up-regulated in iPSC-EC treated wounds at 7 days post-wounding. Histological analysis of wound sections showed increased capillary density in iPSC-EC wounds at days 7 and 14 post-wounding, and increased collagen content at day 14. Anti-GFP fluorescence confirmed presence of iPSC-ECs in the wounds. Bioluminescent imaging (BLI) showed progressive decline of iPSC-ECs over time, suggesting that iPSC-ECs are acting primarily through short-term paracrine effects. These results highlight the pro-regenerative effects of iPSC-ECs and demonstrate that they are a promising potential therapy for intractable wounds.Zoë E. Clayton, Richard P. Tan, Maria M. Miravet, Katarina Lennartsson, John P. Cooke, Christina A. Bursill, Steven G. Wise, Sanjay Pate

Recent Advances in Childhood Arterial Ischemic Stroke

Although many underlying diseases have been reported in the setting of childhood arterial ischemic stroke, emerging research demonstrates that non-atherosclerotic intracerebral arteriopathies in otherwise healthy children are prevalent. Minor infections may play a role in arteriopathies that have no other apparent underlying cause. Although stroke in childhood differs in many aspects from adult stroke, few systematic studies specific to pediatrics are available to inform stroke management. Treatment trials of pediatric stroke are required to determine the best strategies for acute treatment and secondary stroke prevention. The high cost of pediatric stroke to children, families, and society demands further study of its risk factors, management, and outcomes. This review focuses on the recent findings in childhood arterial ischemic stroke

Gamma-Secretase-Dependent and -Independent Effects of Presenilin1 on β-Catenin·Tcf-4 Transcriptional Activity

Presenilin1 (PS1) is a component of the γ-secretase complex mutated in cases of Familial Alzheimer's disease (FAD). PS1 is synthesized as a 50 kDa peptide subsequently processed to two 29 and 20 kDa subunits that remain associated. Processing of PS1 is inhibited by several mutations detected in FAD patients. PS1 acts as negative modulator of β-catenin·Tcf-4 transcriptional activity. In this article we show that in murine embryonic fibroblasts (MEFs) the mechanisms of action of the processed and non-processed forms of PS1 on β-catenin·Tcf-4 transcription are different. Whereas non-processed PS1 inhibits β-catenin·Tcf-4 activity through a mechanism independent of γ-secretase and associated with the interaction of this protein with plakoglobin and Tcf-4, the effect of processed PS1 is prevented by γ-secretase inhibitors, and requires its interaction with E- or N-cadherin and the generation of cytosolic terminal fragments of these two cadherins, which in turn destabilize the β-catenin transcriptional cofactor CBP. Accordingly, the two forms of PS1 interact differently with E-cadherin or β-catenin and plakoglobin: whereas processed PS1 binds E-cadherin with high affinity and β-catenin or plakoglobin weakly, the non-processed form behaves inversely. Moreover, contrarily to processed PS1, that decreases the levels of c-fos RNA, non-processed PS1 inhibits the expression c-myc, a known target of β-catenin·Tcf-4, and does not block the activity of other transcriptional factors requiring CBP. These results indicate that prevention of PS1 processing in FAD affects the mechanism of repression of the transcriptional activity dependent on β-catenin

Tuning chelation by the surfactant-like peptide A6H using predetermined pH values

We examine the self-assembly of a peptide A6H comprising a hexa-alanine sequence A6 with a histidine (H) “head group”, which chelates Zn2+ cations. We study the self assembly of A6H and binding of Zn2+ ions in ZnCl2 solutions, under acidic and neutral conditions. A6H self-assembles into nanotapes held together by a β-sheet structure in acidic aqueous solutions. By dissolving A6H in acidic ZnCl2 solutions, the carbonyl oxygen atoms in A6H chelate the Zn2+ ions and allow for β-sheet formation at lower concentrations, consequently reducing the onset concentration for nanotape formation. A6H mixed with water or ZnCl2 solutions under neutral conditions produces short sheets or pseudocrystalline tapes, respectively. The imidazole ring of A6H chelates Zn2+ ions in neutral solutions. The internal structure of nanosheets and pseudocrystalline sheets in neutral solutions is similar to the internal structure of A6H nanotapes in acidic solutions. Our results show that it is possible to induce dramatic changes in the self-assembly and chelation sites of A6H by changing the pH of the solution. However, it is likely that the amphiphilic nature of A6H determines the internal structure of the self-assembled aggregates independent from changes in chelation

Self-assembly of bioactive peptides, peptide conjugates, and peptide-mimetic materials

Molecular self-assembly is a multi-disciplinary field of research, with potential chemical and biological applications. One of the main driving forces of self-assembly is molecular amphiphilicity, which can drive formation of complex and stable nanostructures. Self-assembling peptide and peptide conjugates have attracted great attention due to their biocompatibility, biodegradability and biofunctionality. Understanding assembly enables the better design of peptide amphiphiles which may form useful and functional nanostructures. This review covers self-assembly of amphiphilic peptides and peptide mimetic materials, as well as their potential applications