Morphology profiles generated by temperature gradient in PMMA modified epoxy system

A diglycidyl ether of bisphenol‐A (DGEBA) epoxy resin was modified with 15 wt% of poly(methylmethacrylate) (PMMA) and cured with a stoichiometric amount of 4,4′‐diamino diphenyl methane (DDM). The reactive mixture was cured in a heated mold with different gradients of temperature. Temperature profiles in the mold were imposed by generation of a heat flux from the base, supported on a hot plate, and the top, cooled with water; they were measured along the mold. Depending on the thermal history in each position of the mold, the competition between the phase‐separation process and reaction kinetics produces opaque or transparent zones. Phase separation can also occur in the postcure process while the gelation does not take place before. Therefore, a thermoset plate with gradient of morphology and properties was obtained. Mass fractions of PMMA dissolved in the matrix were calculated with the Fox equation from glass transition temperatures measured along the mold. They were related to morphologies developed during curing. The superposition of the phase diagrams with the conversion‐temperature trajectories during cure permitted an explanation of the morphology gradients generated.     

The View from the Top: Leaders' Perspectives on a Decade of Change in Engineering Education*

Researchers at The Pennsylvania State University's Center for the Study of Higher Education conducted 27 semi‐structured one‐hour interviews with the deans, chairs, faculty, industry leaders, and association officers who comprise the leadership of national engineering education societies and the Accreditation Board for Engineering and Technology. During the interviews, these leaders described what they believe are the two most significant changes in the in the field of engineering education during the last decade. This article discusses the sources and pervasiveness of each change, how each change has influenced policy or practice in engineering education, and the best ways to encourage faculty involvement in the change.     

Interface Functionalities in Multilayer Stack Organic Light Emitting Transistors (OLETs)

Herein is described a multidisciplinary approach to understand the performance limitations of small molecule organic light emitting transistors (OLETs) based on a layered architecture, an innovative architecture potentially competitive with the state of the art and more flexible for spectral emission control. The processes of charge injection and field‐effect transport at metal/organic and organic/organic interfaces are analysed using microscopic and spectroscopic techniques in coordination. Atomic force microscopy and ultrasonic force microscopy are employed to characterize the interface morphology and the initial growth stages of organic films where charge transport actually occurs. X‐ray diffraction and near edge X‐ray dichroic absorption with linearly polarised light allow to determine the unit cell packing and the molecular orientation at the active organic interfaces, as well as the amount of non‐ordered domains. Moreover, chemical reactivity at the interfaces is measured by X‐ray photoelectron spectroscopy. It is found that a strong reaction occurs at the metal‐organic interfaces, with molecular fragmentation. Additionally, the transport properties strongly depend on the nature of the materials forming the organic stack. Specifically, amorphous conjugated films as bottom layers can promote an increased molecular disorder in the upper active layer, with a concomitant deterioration of the conduction properties.     

A 3.3-V CMOS 10.7-MHz sixth-order bandpass ΣΔ modulatorwith 74-dB dynamic range

A 3.3-V bandpass ΣΔ modulator for IF sampling at 10.7 MHz in digital radio applications has been developed. The modulator presents a sixth-order single-loop architecture and features a 74-dB dynamic range in a 2OO-kHz signal bandwidth (FM signal), while for a 9-kHz signal bandwidth (AM signal) the dynamic range is 88 dB. The modulator has been integrated in a standard 0.35-μm CMOS technology using switched-capacitor technique and consumes 76 mW from a single 3.3V supply     

Vision-Based Measurement of Three-Dimensional Geometric Workpiece Properties

This paper documents a research program undertaken at the Industrial Research Institute of Swinburne University of Tech-nology (IRIS) in Melbourne Australia. The objective of the research was to investigate the potential for applying vision-based inspection of workpieces as a means of providing feed-back (i.e. compensation) for an industrial process. In this research, the emphasis was on high-accuracy identification and measurement of 3D properties from a 2D image. A number of techniques, for providing the transformation of the image, are documented. A common, sample process (i.e. the turning operation), and range of geometric entities were selected to demonstrate the methodology and to highlight various aspects of the proposed techniques. The paper concludes with a list of criteria that influence the accuracy of the final results.     

Pressure-induced changes on the optical properties and microstructure of silica-gel matrices doped with rhodamine 6G

Sol–gel method and high-pressure technique were associated to produce silica compacts with low porosity and doped with rhodamine 6G (R6G). Acid catalyzed solutions of tetraethyl orthosilicate mixed with dye previously dissolved in ethanol were used for the synthesis of doped silica gel. The monolith obtained was comminuted and the powder was compacted between 3.0 and 7.7 GPa, at room temperature, using a toroidal-type high-pressure chamber. Excitation–emission fluorescence spectroscopy was used to investigate the optical properties of R6G embedded in the closed pores of the silica matrix. Measurements of surface areas and pore size distribution for the powders and compacts, using the N₂ isotherms were performed, showing a great reduction in surface area and porosity, after compaction. The dye entrapped in the compacted silica maintains its optical properties similar to that in ethanolic solutions, meaning that the dye is dispersed in a molecular level. Additionally, these samples are optically transparent, hard and resistant to dye leaching and to chemical attacks, being a promising material to be used in optical devices.     

Studies on enzymatic activity and conformational stability of muscle acylphosphatase mutated at conserved lysine residues

An oligonucleotide-directed mutagenesis study was carried out on the five acylphosphatase conserved lysine residues to assess their possible participation in enzyme active site formation and their contribution to the enzyme conformational stability. The study was designed to eliminate the ambiguity arising from the presence of a sulfate ion, an enzyme competitive inhibitor, bound to lysine 32 and 68 in the crystal structure of the erythrocyte isoenzyme. Furthermore, previous kinetic studies suggested the presence of residues with pKa=7.9 and 11, tentatively identified as two lysines. The kinetic parameters for the mutants under investigation are not significantly different from those of the wild-type enzyme, demonstrating that none of the lysine residues are involved in catalysis or in substrate binding. In addition, thermal and urea denaturation experiments performed by circular dichroism indicate that the mutated lysine residues do not play a significant role in the enzyme structural stabilization, as the destabilizing energy averages 1.40 kJ/mol. Such results are in agreement with those obtained with other proteins indicating that lysine residues make little contribution to the stability of the native structure.      

Protein Folding and Misfolding on Surfaces

Protein folding, misfolding and aggregation, as well as the way misfolded and aggregated proteins affects cell viability are emerging as key themes in molecular and structural biology and in molecular medicine. Recent advances in the knowledge of the biophysical basis of protein folding have led to propose the energy landscape theory which provides a consistent framework to better understand how a protein folds rapidly and efficiently to the compact, biologically active structure. The increased knowledge on protein folding has highlighted its strict relation to protein misfolding and aggregation, either process being in close competition with the other, both relying on the same physicochemical basis. The theory has also provided information to better understand the structural and environmental factors affecting protein folding resulting in protein misfolding and aggregation into ordered or disordered polymeric assemblies. Among these, particular importance is given to the effects of surfaces. The latter, in some cases make possible rapid and efficient protein folding but most often recruit proteins/peptides increasing their local concentration thus favouring misfolding and accelerating the rate of nucleation. It is also emerging that surfaces can modify the path of protein misfolding and aggregation generating oligomers and polymers structurally different from those arising in the bulk solution and endowed with different physical properties and cytotoxicities.     

Run by run advanced process control of metal sputter deposition

Metal sputter deposition processes for semiconductor manufacturing are characterized by a decrease in deposition rate from run to run as the sputter target degrades. The goal is to maintain a desired deposition thickness from wafer to wafer and lot to lot. Run by run (RbR) model-based process control (MBPC) has been applied to metal sputter deposition processes at Texas Instruments. RbR MBPC, based on the exponentially weighted moving-average filter, provides the ability to track and compensate for process drifts without a priori assumptions on their magnitude or consistency (from sputter target to sputter target or collimator to collimator). The application of RbR MBPC resulted in an improved C_pk of 44% for aluminum sputter deposition, while reducing the number of lot-based monitor wafers by a factor of three. The application of RbR MBPC to the titanium sputter deposition process eliminated look-ahead test runs and reduced the number of monitor wafers by a factor of three. At the same time, C_pk was improved by 10% with the application of RbR MBPC     

A programming model and system infrastructure for real-timesynchronization in distributed multimedia systems

One of the major requirements of distributed multimedia applications is the need to maintain often complex, real-time synchronization constraints. More specifically, it is necessary to be able to manage arbitrary intra- and inter-media synchronization across activities in the distributed environment. Furthermore, it is important that such developments are integrated into emerging object-oriented standards for distributed computing. This paper presents an object-oriented programming model and associated implementation to meet these requirements. The main concepts behind the proposed approach are, firstly, the use of reactive objects for real-time control and synchronization and, secondly, quality of service controlled bindings for predictable communication between objects. The flexibility of the approach is demonstrated by three contrasting examples of real-time synchronization. The implementation extends the real-time capabilities of the Chorus micro-kernel by introducing the concepts of rtports, rthandlers and quality of service controlled connections. The paper demonstrates how reactive objects and bindings are realized on this infrastructure