“Erosion Control on Surface Mined Watersheds: a Modelling Approach”

ABSTRACT

This article describes the efforts of the Mexican government toward more efficient management of water resources. Inaccordance with the Mexican Constitution, municipal governments have been responsible for urban water and sanitation services. However; in practice most municipalities have weak finances and little expertise in managing water systems and the federal government still plays an important role in the management and financing of water infrastructure.

The article highlights the current state of the water sector in Mexico, including some of the main aspects of the legal and institutionalframework. It discusses the main difficulties faced by the municipalities in accomplishing their task. The strategy of the federal government, in order to achieve better urban water management, has focused on four main policies: changes in the legal and institutional framework for water management, further decentralization, new financing schemes, and greater private sector involvement. It concludes that flexible approaches should allow municipalities to find appropriate institutional, financial, and technical solutions.     

Reflection and transmission of a dielectric waveguide mirror

A numerical analysis of a generalized dielectric waveguide mirror of arbitrary structure angle is presented. A plane wave expansion technique is used to calculate output angle, power transmission, inter-waveguide and intra-waveguide coupling, far-field emission profile and losses of the waveguide mirror. In order to evaluate the effect of divergence, two methods are used and the result indicate that the effect is minimal. Furthermore, the introduction of a tilt in the mirror surface is examined and reveals a reduction in the inter-waveguide coupling as the tilt is increased. However, this coupling remains symmetric in tilt despite the asymmetry of the geometry due to the tilt. Results of the output angle and the FWHM (full-width half-maximum) of the emission profile are compared to experimental values obtained for a semiconductor triangular ring laser     

Comparison of auditory P300 habituation from active and passive conditions

The P3(00) event-related brain potential (ERP) was elicited using auditory stimuli and tasks in which the subject discriminated between standard and target tones or with passive task conditions in which the subject did not respond to either the standard or target stimuli. All stimulus presentations consisted of a series of ten-tone sequences in which the first six tones were always the standard and one of the last four tones was the target. The passive tasks were presented twice to assess for habituation effects. P3 amplitude was largest for the oddball task compared to the passive tasks, and repetition of the passive paradigm demonstrated a decrease in amplitude between conditions. P3 amplitude did not decrease across trials within any of the separate response conditions. P3 latency was shorter for the active discrimination relative to the passive tasks. The results suggest that the P3 component can be obtained reliably with passive procedures and does not habituate within a trial block. However, repeated blocks of passive stimulus presentations will cause the P3 ERP to diminish in size.     

Dynamic 3-D virtual fixtures for minimally invasive beating heart procedures

Two-dimensional or 3-D visual guidance is often used for minimally invasive cardiac surgery and diagnosis. This visual guidance suffers from several drawbacks such as limited field of view, loss of signal from time to time, and in some cases, difficulty of interpretation. These limitations become more evident in beating-heart procedures when the surgeon has to perform a surgical procedure in the presence of heart motion. In this paper, we propose dynamic 3-D virtual fixtures (DVFs) to augment the visual guidance system with haptic feedback, to provide the surgeon with more helpful guidance by constraining the surgeon's hand motions thereby protecting sensitive structures. DVFs can be generated from preoperative dynamic magnetic resonance (MR) or computed tomograph (CT) images and then mapped to the patient during surgery. We have validated the feasibility of the proposed method on several simulated surgical tasks using a volunteer's cardiac image dataset. Validation results show that the integration of visual and haptic guidance can permit a user to perform surgical tasks more easily and with reduced error rate. We believe this is the first work presented in the field of virtual fixtures that explicitly considers heart motion.     

Mode orthogonality in reciprocal and nonreciprocal waveguides

Using a general reciprocity theorem as a basis, the orthogonality relations for lossy reciprocal and nonreciprocal waveguides are discussed. To obtain a useful orthogonality relation which can extract a particular mode from a general mode expansion, a reciprocal waveguide must be bidirectional. A nonreciprocal waveguide, however, must be mutually bidirectional with its complementary waveguide (obtained by reversing the DC magnetic field applied to the gyrotropic media). For these bidirectionally conditions to be met, a waveguide must possess at least one of three symmetries: reflection, 180° rotation, or rotary reflection symmetry. In those cases warranted by the structure symmetry, simplified forms for the orthogonality relations are presented. The orthogonality relations for the special case of lossless reciprocal or nonreciprocal waveguides are discussed     

An estradiol‐inducible promoter enables fast,graduated control of gene expression in fission yeast

The fission yeast Schizosaccharomyces pombe lacks a diverse toolkit of inducible promoters for experimental manipulation. Available inducible promoters suffer from slow induction kinetics, limited control of expression levels and/or a requirement for defined growth medium. In particular, no S. pombe inducible promoter systems exhibit a linear dose–response, which would allow expression to be tuned to specific levels. We have adapted a fast, orthogonal promoter system with a large dynamic range and a linear dose response, based on β‐estradiol‐regulated function of the human oestrogen receptor, for use in S. pombe. We show that this promoter system, termed Z₃EV, turns on quickly, can reach a maximal induction of 20‐fold, and exhibits a linear dose response over its entire induction range, with few off‐target effects. We demonstrate the utility of this system by regulating the mitotic inhibitor Wee1 to create a strain in which cell size is regulated by β‐estradiol concentration. This promoter system will be of great utility for experimentally regulating gene expression in fission yeast. Copyright © 2017 John Wiley & Sons, Ltd.     

Modified Newton's method applied to potential field-based navigation for mobile robots

This paper investigates the inherent oscillation problem of potential field methods (PFMs) in the presence of obstacles and in narrow passages. These problems can cause slow progress and system instability in implementation. To overcome these two problems, in this paper, we propose a modification of Newton's method. The use of the modified Newton's method, which applies anywhere C/sub 2/ continuous navigation functions are defined, greatly improves system performance when compared to the standard gradient descent approach. To the best of our knowledge, ours is the first systematic approach to the oscillation problems in PFMs. We have validated this technique by comparing its performance with the gradient descent method in obstacle-avoidance tasks with different potential models and parameter changes.