Publications

Abstract A new photocrosslinkable polymer designed for application in second harmonic generation has been prepared and tested for frequency doubling of IR lasers. The polymer is based on a colorless polyurethane with pendant tolane nonlinear optical chromophores that carry a polymerizable styrene moiety at their extremities. Photocrosslinking is achieved by irradiation of films containing a small amount of a bleachable radical photoinitiator. The effect of photoinduced radical crosslinking on the mobility of the chromophores has been studied by recording the intensity of the frequency doubled light, generated by a poled sample, with increasing temperature. As expected, photocrosslinking leads to NLO materials with highly stable chromophore orientation.

We use the Cellular Neural Network (CNN) to study the pattern formation properties of large scale spatially distributed systems. We have found that the Cellular Neural Network can produce patterns similar to those found in Ising spin glass systems, discrete bistable systems, and the reaction-diffusion system. A thorough analysis of a 1-D CNN whose cells are coupled to immediate neighbors allows us to completely characterize the patterns that can exist as stable equilibria, and to measure their complexity thanks to an entropy function. In the 2-D case, we do not restrict the symmetric coupling between cells to be with immediate neighbors only or to have a special diffusive form. When larger neighborhoods and generalized diffusion coupling are allowed, it is found that some new and unique patterns can be formed that do not fit the standard ferro-antiferromagnetic paradigms. We have begun to develop a theoretical generalization of these paradigms which can be used to predict the pattern formation properties of given templates. We give many examples. It is our opinion that the Cellular Neural Network model provides a method to control the critical instabilities needed for pattern formation without obfuscating parameterizations, complex nonlinearities, or high-order cell states, and which will allow a general and convenient investigation of the essence of the pattern formation properties of these systems.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

We investigate the importance of parts for the tasks of action and attribute classification. We develop a part-based approach by leveraging convolutional network features inspired by recent advances in computer vision. Our part detectors are a deep version of poselets and capture parts of the human body under a distinct set of poses. For the tasks of action and attribute classification, we train holistic convolutional neural networks and show that adding parts leads to top-performing results for both tasks. We observe that for deeper networks parts are less significant. In addition, we demonstrate the effectiveness of our approach when we replace an oracle person detector, as is the default in the current evaluation protocol for both tasks, with a state-of-the-art person detection system.

Vibrations and Stability of Thin Structures: Eliza Haseganu's Analysis of Wrinkling in Pressurized Membranes (D J Steigmann) Buckling, Vibrations and Optimal Design of Ring-Stiffened Thin Cylindrical Shells (S B Filippov) Asymptotic Analysis of Thin Shell Buckling (A L Smirnov) Thin-Wall Structures Made of Materials with Variable Elastic Moduli (A L Smirnov & P E Tovstik) Asymptotic Integration of Free Vibration Equations of Cylindrical Shells by Symbolic Computation (E M Haseganu et al.) Vibrations and Stability in Continuum Mechanics: The Mechanics of Pre-Stressed and Pre-Polarized Piezoelectric Crystals (E Baesu) On the Stability of Transient Viscous Flow in an Annulus (A A Kolyshkin et al.) Biomechanics: Mechanical Models of the Development of Glaucoma (S M Bauer) A Micromechanical Model for Predicting Microcracking Induced Material Degradation in Human Cortical Bone Tissue (O Akkus et al.) Experimental and Computational Mechanics of Solids: An Evolution of Solid Elements for Thermal-Mechanical Finite Element Analysis (J Moyra & J McDill) Quantization Effects in Shallow Powder Bed Vibrations (J Pegna & J Zhu).

Abstract A brief historical perspective relating the discovery of dendrimers and other dendritic polymers is presented. Dendritic polymers are recognized as the fourth major class of macromolecular architecture consisting of four sub‐ classes, namely, (1) random hyperbranched, (2) dendrigrafts, (3) dendrons, and (4) dendrimers. The previous literature is reviewed with anecdotal events leading to implications for dendrimers in the emerging science of nanotechnology. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 2719–2728, 2002

The fracture of bone is a health concern of increasing significance as the population ages. It is therefore of importance to understand the mechanics and mechanisms of how bone fails, both from a perspective of outright (catastrophic) fracture and from delayed/time‐dependent (subcritical) cracking. To address this need, there have been many in vitro studies to date that have attempted to evaluate the relevant fracture and fatigue properties of human cortical bone; despite these efforts, however, a complete understanding of the mechanistic aspects of bone failure, which spans macroscopic to nanoscale dimensions, is still lacking. This paper seeks to provide an overview of the current state of knowledge of the fracture and fatigue of cortical bone, and to address these issues, whenever possible, in the context of the hierarchical structure of bone. One objective is thus to provide a mechanistic interpretation of how cortical bone fails. A second objective is to develop a framework by which fracture and fatigue results in bone can be presented. While most studies on bone fracture have relied on linear‐elastic fracture mechanics to determine a single‐value fracture toughness (e.g., K c or G c ), more recently, it has become apparent that, as with many composites or toughened ceramics, the toughness of bone is best described in terms of a resistance‐curve (R‐curve), where the toughness is evaluated with increasing crack extension. Through the use of the R‐curve, the intrinsic and extrinsic factors affecting its toughness are separately addressed, where ‘intrinsic’ refers to the damage processes that are associated with crack growth ahead of the tip, and ‘extrinsic’ refers to the shielding mechanisms that primarily act in the crack wake. Furthermore, fatigue failure in bone is presented from both a classical fatigue life ( S/N ) and fatigue‐crack propagation (d a /d N ) perspective, the latter providing for an easier interpretation of fatigue micromechanisms. Finally, factors, such as age, species, orientation, and location, are discussed in terms of their effect on fracture and fatigue behaviour and the associated mechanisms of bone failure.

Este artigo elabora uma cartografia analítica do programa de pesquisa perseguido ao longo dos três livros do autor: Urban outcasts (2008), Punishing the poor (2009) e Deadly symbiosis: race and the rise of the penal State (no prelo). Nessa trilogia, são desfeitos os nexos triangulares entre fragmentação de classe, divisão étnica e remodelagem do Estado na cidade polarizada, na virada do século, para explicar a produção política, a distribuição socioespacial e a gestão punitiva da marginalidade mediante o acoplamento de políticas sociais disciplinares e de justiça criminal neutralizante. Indico como utilizei noções-chave de Pierre Bourdieu (espaço social, campo burocrático, poder simbólico) para clarificar categorias que permaneceram fluidas (como a de gueto) e forjar novos conceitos (estigmatização territorial e marginalidade avançada, contenção punitiva e paternalismo liberal, hiperencarceramento e sociodiceia negativa) como ferramentas para uma sociologia comparada da gênese inconclusa do precariado pós-industrial, da regulação penal da pobreza na era da insegurança social difusa e da construção do Leviatã neoliberal.

The considerable importance of microporous solids such as zeolites in shape-selective catalysis, ion-exchange processes, and molecular sieving applications has inspired the recent extensive efforts to produce analogous materials that are based on metal sulfide,1 metal-organic,2 and organic3 frameworks. A wide variety of molecular building units such as inorganic clusters, metal-organic complexes, porphyrin, organic macrocyles, and cyclic peptides have been linked by either metal ligation or hydrogen bonding to yield diverse extended assemblies having open frameworks. The voids present within these frameworks are usually in the form of channels or chambers where a guest molecule that was introduced during the synthesis resides. At least three issues pose a challenge to those embarking on the designed synthesis of crystalline microporous materials of this kind. First, the large open space within the constructed framework is often found to be occupied by other frameworks that are copies of the original to give an interpenetrating framework structure leaving either little or no voided space in the crystal. Second, since most of the assembly reactions are performed at or near room temperature, the formation of the ultimate product in crystalline form is usually found to be more an art than a science. This is due to the absence of a temperature gradient that allows for slow nucleation and consequently single crystal formation. Third, attempts to evaluate the porosity in these materials by exchanging or decomposing the guest species have in most cases resulted in destruction of the assembled frameworks leading to nonporous solids. This chapter describes our recent research efforts to address these issues. The molecular building block approach for the achievement of these materials will be outlined.