Aspects for the design of sputtering systems

The factors causing problems in sputter deposition of thin films are analysed and possible design solutions are offered. ZnO sputtered films are used as a probe for studying problems. The physical parameters of the discharge that have influence on the sputtering processes are described and related to the sputtering parameters. A comparison of discharges used in Diode, Magnetron, and Triode arrangements with respect to their system performances results in the conclusion that Magnetrons are superior to Diodes and that Triodes are better than Magnetrons, in spite of the fact that Triodes' discharges are of the supported kind and their deposited layers are difficult to reproduce.     

Sustainability and recycle–reuse in process systems

We have only one planet in which to live. Because of accelerating use of limited natural resources, its attendant environmental degradation, and societal inequity that has resulted among groups of people as well as that which will result between present and future generations, we generally recognize that the current development patterns are not sustainable for the long term. This realization calls for satisfying our needs by judiciously using renewable resources, recycling wastes and end-of-life products for beneficial uses, and reversing environmental degradation in some areas and minimizing environmental impacts in others. As new scientific and technological innovations are exploited to implement these goals, tools and methods are needed to ascertain that the direction of economic development for meeting increasing standard of living is protective of human life and ecology. Countries that are economically developed, and therefore wealthy, are in a better position to protect the environment than are the developing countries. This situation calls for technologies that are not only benign but also affordable for the developing world. This is the grand challenge of this century. Some ideas on the elements of this grand challenge that are relevant to the practice of chemistry and engineering are discussed here.     

Polarization properties of Scarabaeidae

Beetles of the scarab family are known to reflect circularly polarized light from incident unpolarized light. They are unusual in that there are many animals that use polarized light in some form and several that actually create it, but there are few examples of the creation of circularly polarized light by animals. Scarabs have been measured with a spectropolarimetric reflectometer and are found to reflect light that is generally left-hand circularly polarized. Previous work is summarized, and what is believed to be new measurements of several scarab specimens are presented.     

To cite or not to cite: author self-citations and the impact factor

Author self-citations are another factor that affects the impact factor of a journal. Typically these self-citations are just counted as such. But to be more meaningful I suggest that when examining the contribution of authors?? self-citations to impact factors one should first count the number of citations in the text rather than in the reference list, and then discriminate between different kinds of author self-citations??from those that are informative to those that are self-enhancing??if these data are to be more credible.     

Physically correct penalty-like formulations for accurate pressure calculation in finite element algorithms of the Navier-Stokes equations

Finite element algorithms for incompressible fluids, in particular the penalty function method, are re-examined and re-formulated based on physically consistent approximations to the mass conservation equation. These approximations lead to methods that satisfy all fluid conditions under the assumption of slightly compressible flow and directly yield approximations to the pressure field that are free from spurious oscillations. Penalty function-type algorithms are developed for direct steady-state calculations and for time-dependent simulations of viscous incompressible flows that are based on the bilinear isoparametric quadrilateral element and circumvent the Ladyszhenskaya, Babuska and Brezzi (LBB) condition. Further-more, methods that eliminate pressure oscillations in the low Mach number region of high-speed compressible flows are obtained. These methods are tested in examples that show their superior performance in approximating the pressure field.     

Variational approach to moiré pattern synthesis

Moiré phenomena occur when two or more images are nonlinearly combined to create a new superposition image. Moiré patterns are patterns that do not exist in any of the original images but appear in the superposition image, for example as the result of a multiplicative superposition rule. The topic of moiré pattern synthesis deals with creating images that when superimposed will reveal certain desired moiré patterns. Conditions that ensure that a desired moiré pattern will be present in the superposition of two images are known; however, they do not specify these images uniquely. The freedom in choosing the superimposed images can be exploited to produce various degrees of visibility and ensure desired properties. Performance criteria for the images that measure when one superposition is better than another are introduced. These criteria are based on the visibility of the moire patterns to the human visual system and on the digitization that takes place when the images are presented on discrete displays. We propose to resolve the freedom in moire synthesis by choosing the images that optimize the chosen criteria.     

Participation and pay

A distinction is made between the technical details of pay plans and the decision process that is used in developing and administering them. Data are presented which show that pay plans which are identical in technical details can produce quite different results in terms of motivation and satisfaction. It appears that when employees are active participants in the development and administration of pay plans, plans are more likely to be successful. Several studies are cited which support this point and it is argued that the reasons for this include the fact that participation increases employee trust of a pay plan. Finally, it is pointed out that pay can serve as a change agent in organization development efforts if the efforts begin with and involve employees participating in pay decisions.     

Adaptation and perceptual norms in color vision

Many perceptual dimensions are thought to be represented relative to an average value or norm. Models of norm-based coding assume that the norm appears psychologically neutral because it reflects a neutral response in the underlying neural code. We tested this assumption in human color vision by asking how judgments of "white" are affected as neural responses are altered by adaptation. The adapting color was varied to determine the stimulus level that did not bias the observer's subjective white point. This level represents a response norm at the stages at which sensitivity is regulated by the adaptation, and we show that these response norms correspond to the perceptually neutral stimulus and that they can account for how the perception of white varies both across different observers and within the same observer at different locations in the visual field. We also show that individual differences in perceived white are reduced when observers are exposed to a common white adapting stimulus, suggesting that the perceptual differences are due in part to differences in how neural responses are normalized. These results suggest a close link between the norms for appearance and coding in color vision and illustrate a general paradigm for exploring this link in other perceptual domains.     

Nitrosamines and water

This paper provides an overview of all current issues that are connected to the presence of nitrosamines in water technology. N-nitrosodimethylamine (NDMA) is the most frequently detected member of this family. Nitrosamines became the hottest topic in drinking water science when they were identified as disinfection by-products (DBPs) in chloraminated waters. The danger that they pose to consumer health seems to be much higher than that from chlorinated DBPs. This review summarizes our contemporary knowledge of these compounds in water, their occurrence, and precursors of nitrosamines in drinking and wastewaters, in addition to attempts to remove nitrosamines from water. The paper also reviews our knowledge of the mechanisms of nitrosamine formation in water technology. The current, commonly accepted mechanism of NDMA formation during chloramination of drinking waters assumes that dichloramine reacts with dimethylamine, forms unsymmetrical dimethylhydrazine and further oxidizes to NDMA. The question to answer is which precursors are responsible for delivering the DMA moiety for the reaction since the presence of DMA in water cannot explain the quantities of NDMA that are formed. There are also reports that other oxidants that are commonly used in water technology may generate NDMA. However, the mechanisms of such transformations are unknown. Methods for the removal of nitrosamines from water are described briefly. However, the research that has been undertaken on such methods seems to be at an early stage of development. It is predicted that photolytic methods may have the greatest potential for technological application.     

International standards for radiation protection

International standards for radiation protection are issued by many bodies. These bodies differ to a large extent in their organisation, in the way the members are designated and in the way the international standards are authorised by the issuing body. Large differences also exist in the relevance of the international standards. One extreme is that the international standards are mandatory in the sense that no conflicting national standard may exist, the other extreme is that national and international standards conflict and there is no need to resolve that conflict. Between these extremes there are some standards or documents of relevance, which are not binding by any formal law or contract but are de facto binding due to the scientific reputation of the issuing body. This paper gives, for radiation protection, an overview of the main standards issuing bodies, the international standards or documents of relevance issued by them and the relevance of these documents.     

An equilibrium model for the crystallization of high silica zeolites

A simple equilibrium model is proposed to explain the change in pH which occurs when high silica zeolites are crystallized from gels. The model shows that for a given concentration of quaternary ammonium ions the highest increases in pH are associated with the most stable zeolite, and that the yields depend primarily on the stoichiometry of the reaction mixture. For reaction mixtures which are buffered by amines the model shows that the increase in pH is reduced and the yields are substantially increased.     

Carbon Diffusion Between the Layers in Modern Pattern-Welded Damascus Blades

Pattern-welded Damascus steel blades are made by forge welding together pairs of steels having low- and high-carbon compositions. It is often assumed that these blades consist of hard and soft layers owing to the carbon variations of the original steels and that it is this difference in hardness that produces the etching characteristics that give the surface patterns. Theoretical arguments are presented that show that, with the modern forging techniques used to make these blades, carbon diffusion should be adequate to homogenize the C level between the layers of the blades, which predicts no hardness difference between layers. Experiments are presented on several modern blades, showing that there are no hardness differences found between layers. Arguments are presented for a theory that it is the difference in alloying elements between the layers that produces the differential etching characteristics that give rise to the visual surface patterns of most contemporary pattern-welded Damascus steels.     

Ground-based differential absorption lidar for water-vapor and temperature profiling: methodology

A comprehensive formulation of the differential absorption lidar (DIAL) methodology is presented that explicitly includes details of the spectral distributions of both the transmitted and the backscattered light. The method is important for high-accuracy water-vapor retrievals and in particular for temperature measurements. Probability estimates of the error that is due to Doppler-broadened Rayleigh scattering based on an extended experimental data set are presented, as is an analytical treatment of errors that are due to averaging in the nonlinear retrieval scheme. System performance requirements are derived that show that water-vapor retrievals with an accuracy of better than 5% and temperature retrievals with an accuracy of better than 1 K in the entire troposphere are feasible if the error that results from Rayleigh-Doppler correction can be avoided. A modification of the DIAL technique, high-spectral-resolution DIAL avoids errors that are due to Doppler-broadened Rayleigh backscatter and permits simultaneous water-vapor and wind measurements with the same system.     

Proton-Conductive Melanin-Like Fibers through Enzymatic Oxidation of a Self-Assembling Peptide

Melanin pigments have various properties that are of technological interest including photo- and radiation protection, rich coloration, and electronic functions. Nevertheless, laboratory-based synthesis of melanin and melanin-like materials with morphologies and chemical structures that are specifically optimized for these applications, is currently not possible. Here, melanin-like materials that are produced by enzymatic oxidation of a supramolecular tripeptide structures that are rich in tyrosine and have a 1D morphology are demonstrated, that are retained during the oxidation process while conducting tracks form through oxidative tyrosine crosslinking. Specifically, a minimalistic self-assembling peptide, Lys–Tyr–Tyr (KYY) with strong propensity to form supramolecular fibers, is utilized. Analysis by Raman spectroscopy shows that the tyrosines are pre-organized inside these fibers and, upon enzymatic oxidation, result in connected catechols. These form 1D conducting tracks along the length of the fiber, which gives rise to a level of internal disorder, but retention of the fiber morphology. This results in highly conductive structures demonstrated to be dominated by proton conduction. This work demonstrates the ability to control oxidation but retain a well-defined fibrous morphology that does not have a known equivalent in biology, and demonstrate exceptional conductivity that is enhanced by enzymatic oxidation.     

Special Features in Powder Preparation, Pressing, and Sintering of Uranium Dioxide

Nuclear ceramic grade UO₂ powders are usually prepared by the wet chemical ammonium diuranate route. The powders are pressed and sintered before incorporation into nuclear fuel assemblies. The processing is complex at all stages and the specifications are stringent. In powder preparation, slow addition of the precipitating reagent at a low temperature is recommended. The conditions for the drying of the precipitate, calcination and reduction are chosen to result in an agglomerate free, fine and porous powder that does not require milling or binder addition and is capable of being compacted and sintered to desired density with a homogeneous microstructure. The pressing conditions are chosen to give compacts that are free from defects such as cracking, chipping and end-capping. Sintering conditions are such that desintering, bloating, weathering and nitriding are avoided. Some insights that have been gained in powder preparation, pressing and sintering are presented in this paper. The relationship between powder characteristics and pressing and sintering properties is described.     

Evaluation of a program to motivate impaired driving offenders to install ignition interlocks

Approximately 30,000 alcohol ignition interlocks, which are designed to prevent the operation of a vehicle if the driver has been drinking, are in use in the US and Canada. Ignition interlock programs are also being initiated in Sweden and Australia. The best-controlled studies that are currently available suggest that ignition interlocks are effective in reducing impaired driving recidivism while on the vehicle. However, in the US, the practical effectiveness of these devices is limited because only a small number of offenders are willing to install them in order to drive legally. This paper reports on a study of a court policy that created a strong incentive for impaired driving offenders to install interlocks by making traditional penalties, such as jail or electronically monitored house arrest, the alternative to participation in an interlock program. Comparison of the recidivism rates of offenders subject to this policy with offenders in similar, nearby courts, not using interlocks, indicated that the policy was producing substantial reductions in DUI recidivism.     

Optimizing Response Surface Experiments with Noise Factors Using Confidence Regions

One way to improve quality is to reduce the impact of variation. Taguchi emphasized that quality is improved by minimizing the effect of variables that are difficult or impossible to control. In robust design experiments, settings of design variables that are controllable are sought that are insensitive to the effects of the noise factors. A summary of methods for using confidence statements in the optimization of a product or process during the design phase is given. In addition, confidence regions for determining control factor settings that optimize the mean and variance simultaneously are discussed. An example is used to illustrate the advantages of characterizing the uncertainty in the optimal factor settings.     

Two-point, high-repetition-rate Rayleigh thermometry in flames: techniques to correct for apparent dissipation induced by noise

High-repetition-rate, two-point Rayleigh thermometry is used to measure the thermal dissipation in turbulent nonpremixed jet flames. Scalar-dissipation measurements are very important in turbulent combustion but are often strongly influenced by noise effects. Dissipation is proportional to the squared gradient of the scalar, and noise produces an "apparent dissipation" that can dominate the measured dissipation, particularly at high resolution. Two independent techniques are presented that enable correction for the apparent thermal dissipation, provided that the smallest spatial scales are resolved. A model for shot-noise-limited data is developed that predicts the magnitude of the apparent dissipation at any measurement location and gives the minimum value of the apparent dissipation for measurements that are not shot-noise limited. These techniques are applied to the Rayleigh thermometry data, and they are shown to be largely self-consistent and consistent with theoretical expectations. The apparent dissipation is significantly larger than the true dissipation, demonstrating the importance of data correction in this noise-limited, fully spatially resolved regime.     

Violation of Mermin–Ardehali–Belinksii–Klyshko inequality in the three-Jaynes–Cummings model

In this paper, we consider the situation that three identical two-level atoms are separately trapped in the three single-mode cavities. Each atom resonantly interacts with cavity via a one-photon hopping. The dynamics of nonlocality in the system is investigated via Mermin–Ardehali–Belinksii–Klyshko inequality. The results show that when three atoms are initially in W state and three-cavity fields are in vacuum states both the quantum state of three atoms and that of three cavities all display nonlocality On the other hand, when three atoms are initially in Greenberger–Horne–Zeilinger state and three-cavity fields are in vacuum states, the quantum state of three atoms and that of three cavities all do not display nonlocality.     

Assessing the peak capacity of IMS-IMS separations of tryptic peptide ions in He at 300 K

Two-dimensional ion mobility spectrometry (IMS-IMS) coupled with mass spectrometry is examined as a means of separating mixtures of tryptic peptides (from myoglobin and hemoglobin). In this study, we utilize two distinct drift regions that are identical in that each contains He buffer gas at 300 K. The two-dimensional advantage is realized by changing the structures of the ions. As ions arrive at the end of the first drift region, those of a specified mobility are selected, exposed to energizing collisions, and then introduced into a second drift region. Upon collisional activation, some ions undergo structural transitions, leading to substantial changes in their mobilities; others undergo only slight (or no) mobility changes. Examination of peak positions and shapes for peptides that are separated in the first IMS dimension indicates experimental peak capacities ranging from approximately 60 to 80; the peak shapes and range of changes in mobility that are observed in the second drift region (after activation) indicate a capacity enhancement ranging from a factor of approximately 7 to 17. Thus, experimental (and theoretical) evaluation of the peak capacity of IMS-IMS operated in this fashion indicates that capacities of approximately 480 to 1360 are accessible for peptides. Molecular modeling techniques are used to simulate the range of structural changes that would be expected for tryptic peptide ions and are consistent with the experimental shifts that are observed.