Nonreciprocal Wavefront Engineering with Time-Modulated Gradient Metasurfaces

We propose a paradigm to realize nonreciprocal wavefront engineering using time-modulated gradient metasurfaces. The essential building block of these surfaces is a subwavelength unit cell whose reflection coefficient oscillates at low frequency. We demonstrate theoretically and experimentally that such modulation permits tailoring the phase and amplitude of any desired nonlinear harmonic and determines the behavior of all other emerging fields. By appropriately adjusting the phase delay applied to the modulation of each unit cell, we realize time-modulated gradient metasurfaces that provide efficient conversion between two desired frequencies and enable nonreciprocity by (i) imposing drastically different phase gradients during the up/down conversion processes and (ii) exploiting the interplay between the generation of certain nonlinear surface and propagative waves. To demonstrate the performance and broad reach of the proposed platform, we design and analyze metasurfaces able to implement various functionalities, including beam steering and focusing, while exhibiting strong and angle-insensitive nonreciprocal responses. Our findings open an alternative direction in the field of gradient metasurfaces, in which wavefront control and magnetic-free nonreciprocity are locally merged to manipulate the scattered fields

On the embedding of spacetime in five-dimensional Weyl spaces

We revisit Weyl geometry in the context of recent higher-dimensional theories of spacetime. After introducing the Weyl theory in a modern geometrical language we present some results that represent extensions of Riemannian theorems. We consider the theory of local embeddings and submanifolds in the context of Weyl geometries and show how a Riemannian spacetime may be locally and isometrically embedded in a Weyl bulk. We discuss the problem of classical confinement and the stability of motion of particles and photons in the neighbourhood of branes for the case when the Weyl bulk has the geometry of a warped product space. We show how the confinement and stability properties of geodesics near the brane may be affected by the Weyl field. We construct a classical analogue of quantum confinement inspired in theoretical-field models by considering a Weyl scalar field which depends only on the extra coordinate.Comment: 16 pages, new title and references adde

Inverting Adversarially Robust Networks for Image Synthesis

Recent research in adversarially robust classifiers suggests their representations tend to be aligned with human perception, which makes them attractive for image synthesis and restoration applications. Despite favorable empirical results on a few downstream tasks, their advantages are limited to slow and sensitive optimization-based techniques. Moreover, their use on generative models remains unexplored. This work proposes the use of robust representations as a perceptual primitive for feature inversion models, and show its benefits with respect to standard non-robust image features. We empirically show that adopting robust representations as an image prior significantly improves the reconstruction accuracy of CNN-based feature inversion models. Furthermore, it allows reconstructing images at multiple scales out-of-the-box. Following these findings, we propose an encoding-decoding network based on robust representations and show its advantages for applications such as anomaly detection, style transfer and image denoising

Making Vision Transformers Truly Shift-Equivariant

For computer vision, Vision Transformers (ViTs) have become one of the go-to deep net architectures. Despite being inspired by Convolutional Neural Networks (CNNs), ViTs' output remains sensitive to small spatial shifts in the input, i.e., not shift invariant. To address this shortcoming, we introduce novel data-adaptive designs for each of the modules in ViTs, such as tokenization, self-attention, patch merging, and positional encoding. With our proposed modules, we achieve true shift-equivariance on four well-established ViTs, namely, Swin, SwinV2, CvT, and MViTv2. Empirically, we evaluate the proposed adaptive models on image classification and semantic segmentation tasks. These models achieve competitive performance across three different datasets while maintaining 100% shift consistency

History, synthesis, properties, applications and regulatory issues of prebiotic oligosaccharides

In this chapter, the health promoting effects of carbohydrate prebiotics are addressed. A brief description of their synthesis, thermo-physical properties, mechanisms of action, technological applications and current regulatory issues are presented

Assignments and competencies of nursing managers: a descriptive exploratory research

INTRODUCTION The teaching hospitals (HE – from the Portuguese Hospitais de Ensino) are important institutions for the country that provide highly complex assistance, training of human resources in health, the development of clinical research and the evaluation of new technologies. The Teaching Hospitals Restructuring Program (PRHE – from the Portuguese Programa de Reestruturação de Hospitais de Ensino) was created in 2003 to certify these institutions in teaching, research, assistance and management (1). The achievement of quantitative and qualitative goals for HE(1) based on specific directives, were established by local managers of the Unified Health System (SUS – Sistema Único de Saúde), and included an increase in medium and high complexity procedures, urgency and emergency, and education and research network (2). In this research, we focus on the nursing manager who occupies the highest nursing position in the HE and is committed to developing his role in teaching, research, care and management. He has a voice and a seat in the upper levels of the HE, and he opines, discusses and influences the decisions of the hospital, considers human resources and different ways of conducting nursing care and materials used by the team, and acts as a mediator between nursing and other categories, all of which requires specific skills. After almost ten years of the PRHE, and in view of the small amount of literature on this subject, we expected to find out how these changes were absorbed by the nursing managers and to identify the attributes and competencies of HE nursing managers from the state of Paraná in relation to teaching, research, care and management.Aim: to identify the attributes and competencies of nursing managers in the teaching hospitals in the state of Paraná, in relation to their teaching, research, care and management. Method: a descriptive, exploratory, qualitative approach, carried out in 12 teaching hospitals in Paraná, through semi-structured interviews with 13 nurses who occupy the top position in nursing. The interviews included identification data of the participants, their positions and their attributes and competencies. Results: the attributes were; institutional representation, nursing care management, human resources management and teaching. The skills that stood out after content analysis were; conflict management, leadership, decision making and policy. Conclusions: although the research was carried out in teaching hospitals, the most frequent assignments and competencies of managers relate to the managerial dimension to the detriment of the teaching and research dimensions

Mucosal varicosities : case report treated with monoethanolamine oleate

We reported a case of varicosities in the buccal mucosa treated with sclerotherapy. The sclerosant agent used was the monoethanolamine oleate. After three sessions the lesions disappeared and the patient is follow-up