Efficient and flexible sampling with blue noise properties of triangular meshes

This paper deals with the problem of taking random samples over the surface of a 3D mesh describing and evaluating efficient algorithms for generating different distributions. We discuss first the problem of generating a Monte Carlo distribution in an efficient and practical way avoiding common pitfalls. Then, we propose Constrained Poisson-disk sampling, a new Poisson-disk sampling scheme for polygonal meshes which can be easily tweaked in order to generate customized set of points such as importance sampling or distributions with generic geometric constraints. In particular, two algorithms based on this approach are presented. An in-depth analysis of the frequency characterization and performance of the proposed algorithms are also presented and discussed.     

Variable echo time imaging for detecting the short T2* components of the sciatic nerve: a validation study

Objective

The aim of this study was to develop and validate an MRI protocol based on a variable echo time (vTE) sensitive to the short T2* components of the sciatic nerve.

Materials and methods

15 healthy subjects (M/F: 9/6; age: 21–62) were scanned at 3T targeting the sciatic nerve at the thigh bilaterally, using a dual echo variable echo time (vTE) sequence (based on a spoiled gradient echo acquisition) with echo times of 0.98/5.37 ms. Apparent T2* (aT2*) values of the sciatic nerves were calculated with a mono-exponential fit and used for data comparison.

Results

There were no significant differences in aT2* related to side, sex, age, and BMI, even though small differences for side were reported. Good-to-excellent repeatability and reproducibility were found for geometry of ROIs (Dice indices: intra-rater 0.68–0.7; inter-rater 0.70–0.72) and the related aT2* measures (intra-inter reader ICC 0.95–0.97; 0.66–0.85) from two different operators. Side-related signal-to-noise-ratio non-significant differences were reported, while contrast-to-noise-ratio measures were excellent both for side and echo.

Discussion

Our study introduces a novel MR sequence sensitive to the short T2* components of the sciatic nerve and may be used for the study of peripheral nerve disorders.

     

A Series of 2-((1-Phenyl-1H-imidazol-5-yl)methyl)-1H-indoles as Indoleamine 2,3-Dioxygenase 1 (IDO1) Inhibitors

Indoleamine 2,3-dioxygenase 1 (IDO1) is a promising therapeutic target in cancer immunotherapy and neurological disease. Thus, searching for highly active inhibitors for use in human cancers is now a focus of widespread research and development efforts. In this study, we report the structure-based design of 2-(5-imidazolyl)indole derivatives, a series of novel IDO1 inhibitors which have been designed and synthesized based on our previous study using N1-substituted 5-indoleimidazoles. Among these, we have identified one with a strong IDO1 inhibitory activity (IC₅₀=0.16 μM, EC₅₀=0.3 μM). Structural-activity relationship (SAR) and computational docking simulations suggest that a hydroxyl group favorably interacts with a proximal Ser167 residue in Pocket A, improving IDO1 inhibitory potency. The brain penetrance of potent compounds was estimated by calculation of the Blood Brain Barrier (BBB) Score and Brain Exposure Efficiency (BEE) Score. Many compounds had favorable scores and the two most promising compounds were advanced to a pharmacokinetic study which demonstrated that both compounds were brain penetrant. We have thus discovered a flexible scaffold for brain penetrant IDO1 inhibitors, exemplified by several potent, brain penetrant, agents. With this promising scaffold, we provide herein a basis for further development of brain penetrant IDO1 inhibitors.     

Realization of an adaptive voltage driver for voice coil motor

In this paper we describe a head servo-positioning system for hard disk drives (HDDs), in which the usual current command for the voice coil motor has been replaced by a simpler voltage command. This solution has proven advantages in terms of cost, since the voltage driver does not require any resistive shunt for current measurement and phase-shaping passive networks for the current controller. Also, it requires a lower pin count and can be easily implemented with a PWM power stage. The voltage driver consists of a voltage-controlled power stage, with a pre-filter placed at its input, plus a back e.m.f. feed-forward compensator. The role of the pre-filter is to provide a transfer function between input signal and VCM current as close as possible to that of a standard current loop, so providing a one-to-one replacement to standard current drivers. To achieve this, it can be shown that the filter must cancel out the low-frequency pole of the VCM, located in a position which depends on the electrical impedance of the VCM itself. This, however, may change by ±30% during HDD operations, due to self-heating and consequent variation of the VCM resistance. Such variation may lead to an unsatisfactory performance of the voltage driver, so an adaptation mechanism, capable of tracking variations of VCM coil resistance, must be set up. This paper presents an on-line estimation procedure, based on an extended Kalman filter (EKF), capable of estimating the VCM coil resistance with a high degree of accuracy. EKF, however, usually brings a high computational load, making it unsuitable for real-time, low-cost embedded applications. The paper presents two reduced-order model of the VCM, for which the EKF can be implemented with 30 and 50% less computational effort, respectively, while maintaining a good estimate of the VCM coil resistance. The paper reports experimental results of VCM resistance estimation, obtained with the proposed algorithm, running in 30 μS on a 25 MHz, fixed-point DSP. Also, the on-line estimation is used to adapt the pre-filter. Experimental results show that the servo performance with adaptive voltage driver is not affected by resistance variation and equivalent to that of the standard current driver.     

Design for Testability for Highly Reconfigurable Component-Based Systems

Highly-reconfigurable component-based systems, i.e., systems that are built form existing components and are distributed in many versions and configurations, are becoming increasingly popular.The design and verification of such systems presents new challenges. In this paper we propose a design approach that facilitates analysis and testing of different configurations by identifying and tracking relations among requirements, logic components and resources. The approach proposed in the paper allows for easily identifying different dependencies among resources, components and requirements and thus spotting the tests that must be re-executed to assure the desired level of quality.     

Toward a comprehensive treatment of temporal constraints about periodic events

In this article, we propose an Allen‐like approach to deal with different types of temporal constraints about periodic events. We consider the different components of such constraints (thus, unlike Allen, we also take into account quantitative constraints) including frame times, user‐defined periods, qualitative temporal constraints, and numeric quantifiers and the interactions between such components. We propose a specialized high‐level formalism to represent temporal constraints about periodic events; temporal reasoning on the formalism is performed by a path‐consistency algorithm repeatedly applying our operations of inversion, intersection, and composition and by a specialized reasoner about periods and numeric quantification. The high‐level formalism has been designed in such a way that different types of temporal constraints about periodic events can be represented in a compact and (hopefully) user‐friendly way and path‐consistency‐based temporal reasoning on the formalism can be performed in polynomial time. We also prove that our definitions of inversion, intersection, and composition and, thus, of our path‐consistency algorithm, are correct. This article also sketches the general architecture of the temporal manager for periodic events (TeMP⁺), that has been designed on the basis of our approach. As a working example, we show an application of our approach to scheduling in a school. © 2003 Wiley Periodicals, Inc.     

Low frequency noise and technology induced mechanical stress in MOSFETs

A detailed experimental investigation of low frequency noise as a function of technology-induced mechanical stress in MOSFET devices is presented. Both n- and p-MOSFETs have been studied. Strain in the channel region is obtained by the Shallow Trench Isolation (STI) technique. An increasing of 1/f noise intensity when compressive mechanical stress increases has been detected in p-channel transistor. A critical discussion of this experimental finding has been proposed in the scenario of advanced generation CMOS technologies.     

DYNAMIC SCHEDULING FOR A SINGLE MACHINE SYSTEM UNDER DIFFERENT SETUP AND BUFFER CAPACITY SCENARIOS

The problem of dynamic scheduling for single machine manufacturing systems has been extensively studied in the past under different setup scenarios, mainly for systems with infinite buffer capacity. This paper addresses a general framework and investigates similarities and differences between policies optimal if setup times and costs are or are not negligible, if buffers have a finite or an infinite capacity. The cost function takes into account of backlog and surplus, but also includes a demand loss component if buffers have a finite capacity and a setup cost if not negligible. Both a steady state and a transient optimization problem are considered and already known results are compared and extended to complete the analysis.     

Multi‐template approach to realize central pattern generators for artificial locomotion control

Biologically inspired control of artificial locomotion often makes use of the concept of central pattern generator (CPG), a network of neurons establishing the locomotion pattern within a lattice of neural activity. In this paper a new approach, based on cellular neural networks (CNNs), for the design of CPGs is presented. From a biological point of view this new approach includes an approximated chemical synapse realized and implemented in a CNN structure. This allows to extend the results, previously obtained with a reaction‐diffusion‐CNN (RD‐CNN) for the locomotion control of a hexapod robot, to a more general class of artificial CPGs in which the desired locomotion pattern and the switching among patterns are realized by means of a spatio‐temporal algorithm implemented in the same CNN structure. Copyright © 2002 John Wiley & Sons, Ltd.     

Microscopic Description of Nanostructures Grown on (N11) Surfaces

We report on a theoretical study of GaAs/InGaAs based nanostructures grown along the [N11] direction. The elastic deformations of the structures were calculated by means of the continuum elasticity theory, taking into account commensurability constraints at the interfaces. The strained atomic positions were derived, as well as the strain induced piezoelectric polarizations and electric fields. These data were used as an input for the calculation of the fundamental electronic transitions of our systems within the empirical tight-binding approach. These results are compared with the envelope function methods. We applied our approach to a (211) oriented InAs quantum dot embedded in a GaAs matrix, and to a (311) oriented InGaAs quantum wire, embedded in AlGaAs barriers. In both cases, we obtained a non-symmetric elastic deformation due to the lower symmetry of (N11)-oriented structures. Moreover, the atomic displacements and the strain induced piezoelectric potential induce a separation of the hole and electron wave functions, which are shifted from the dot center.