Chemical Processors Research Articles

Multifunctional acrylic fibers prepared via in-situ formed silver nanoparticles: Physicochemical, UV radiation protection, and antistatic properties

A single treatment that makes textiles multifunctional is very attractive to the textile chemical processors. In this study, multifunctional acrylic fibers were produced by in situ forming silver (Ag) nanoparticles at various concentrations of Ag and trisodium citrate (TSC). The exhaustion of silver into acrylic fibers and the reduction of Ag to Ag nanoparticles were carried out at 90 °C, well above the glass transition temperature (Tg) of this fiber in water. The effect of the concentration of Ag, Ag to TSC ratio, pH, and reaction time on the color strength, ultraviolet (UV) radiation absorption, surface electrical resistance and mechanical properties of the treated fibers were systematically investigated. It was found that if the concentration of Ag was less than 1% on the weight of acrylic fibers or the Ag to TSC ratio was less than 1:2, no color was produced. The color strength and UV radiation absorption capacity of the treated acrylic fibers increased with an increase in the concentration of Ag, and Ag to TSC ratio, and also with a decrease in the pH. On the other hand, the surface resistance of the treated acrylic fibers decreased with an increase in the concentration of Ag and a decrease in the treatment pH. The treated fibers showed excellent antibacterial activity, UV radiation absorption capacity, and also very good antistatic properties along with an excellent colorfastness to washing. Moreover, the developed treatment is highly durable to washing as after 20 washes the treated fibers lost their antibacterial activity only marginally.

Soft tubular microfluidics for 2D and 3D applications

Microfluidics has been the key component for many applications, including biomedical devices, chemical processors, microactuators, and even wearable devices. This technology relies on soft lithography fabrication which requires cleanroom facilities. Although popular, this method is expensive and labor-intensive. Furthermore, current conventional microfluidic chips precludes reconfiguration, making reiterations in design very time-consuming and costly. To address these intrinsic drawbacks of microfabrication, we present an alternative solution for the rapid prototyping of microfluidic elements such as microtubes, valves, and pumps. In addition, we demonstrate how microtubes with channels of various lengths and cross-sections can be attached modularly into 2D and 3D microfluidic systems for functional applications. We introduce a facile method of fabricating elastomeric microtubes as the basic building blocks for microfluidic devices. These microtubes are transparent, biocompatible, highly deformable, and customizable to various sizes and cross-sectional geometries. By configuring the microtubes into deterministic geometry, we enable rapid, low-cost formation of microfluidic assemblies without compromising their precision and functionality. We demonstrate configurable 2D and 3D microfluidic systems for applications in different domains. These include microparticle sorting, microdroplet generation, biocatalytic micromotor, triboelectric sensor, and even wearable sensing. Our approach, termed soft tubular microfluidics, provides a simple, cheaper, and faster solution for users lacking proficiency and access to cleanroom facilities to design and rapidly construct microfluidic devices for their various applications and needs.

Calculating Voronoi Diagrams Using Simple Chemical Reactions

This paper overviews work on the use of simple chemical reactions to calculate Voronoi diagrams and undertake other related geometric calculations. This work highlights that this type of specialised chemical processor is a model example of a parallel processor. For example increasing the complexity of the input data within a given area does not increase the computation time. These processors are also able to calculate two or more Voronoi diagrams in parallel. Due to the specific chemical reactions involved and the relative strength of reaction with the substrate (and cross-reactivity with the products) these processors are also capable of calculating Voronoi diagrams sequentially from distinct chemical inputs. The chemical processors are capable of calculating a range of generalised Voronoi diagrams (either from circular drops of chemical or other geometric shapes made from adsorbent substrates soaked in reagent) , skeletonisation of planar shapes and weighted Voronoi diagrams (e.g., additively weighted Voronoi diagrams, Multiplicitavely weighted Crystal growth Voronoi diagrams). The paper will also discuss some limitations of these processors. These chemical processors constitute a class of pattern forming reactions which have parallels with those observed in natural systems. It is possible that specialised chemical processors of this general type could be useful for synthesising functional structured materials.

CXS chemical dry vacuum pump brings smart vacuum to the process industry

AbstractDry vacuum pumps are now well established around the world as an efficient, reliable option for demanding chemical processing industry applications. Chemical processors are placing new demands on the market, driving an emerging trend for vacuum to be seen as a utility; highly reliable, flexible, and available on demand in a ′plug and pump′ system that requires minimum set up and maintenance. CXS dry vacuum pump systems from Edwards have been in operation worldwide for several years now, and are providing ′utilitarian′ high performing, highly controllable vacuum equipment allowing processors to minimise running costs and reduce environmental performance.

Fluid-kinetics enhanced selective etching process of NiPt film by piranha chemistry in silicide formation for complementary metal oxide semiconductor fabrication

NiPtSi is a prime candidate for the complementary metal-oxide-semiconductors CMOS self-aligned silicidation process beyond the 22nm node. The formation of NiPt silicide in smaller geometries demands more Platinum (Pt) additive to control the silicide quality and a more capable NiPt selective etching process to remove surface residual metals for complementing the formation of silicide. Both higher Pt selective etch rate and lower surface material loss are desired in NiPt selective etching process.High temperature (>150°C) sulfuric acid base piranha chemistry in fresh dispensing on wafer can etch Pt with less damage to the exposed wafer surface. By using (1) a larger mass-to-charge density Pt redox reaction zone in the electrochemistry spectrum of the Pt redox behavior, (2) stronger chemical fluid kinetics and (3) intensified voltammetric cycles, the Pt selective removal rate can be boosted. Two types of wet chemical processors are used to examine the fluid-chemical kinetics effect on the Pt selective etching rate. It is shown that higher chemical flow rates and stronger fluid-kinetics can enhance the Pt transport behavior. The collateral wafer surface material loss rate also increases by higher chemical flow rates, but the amount of total material loss actually reduces due to a greater reduction in the required process time. The fluid-kinetics enhanced selective etching process can cover a wider range of NiPt film conditions (5% Pt, up to 200Å, 10% Pt up to 180Å).

Facile fabrication of nanofluidic diode membranes using anodic aluminium oxide

Active control of ion transport plays important roles in chemical and biological analytical processes. Nanofluidic systems hold the promise for such control through electrostatic interaction between ions and channel surfaces. Most existing experiments rely on planar geometry where the nanochannels are generally very long and shallow with large aspect ratios. Based on this configuration the concepts of nanofluidic gating and rectification have been successfully demonstrated. However, device minimization and throughput scaling remain significant challenges. We report here an innovative and facile realization of hetero-structured Al(2)O(3)/SiO(2) (Si) nanopore array membranes by using pattern transfer of self-organized nanopore structures of anodic aluminum oxide (AAO). Thanks to the opposite surface charge states of Al(2)O(3) (positive) and SiO(2) (negative), the membrane exhibits clear rectification of ion current in electrolyte solutions with very low aspect ratios compared to previous approaches. Our hetero-structured nanopore arrays provide a valuable platform for high throughput applications such as molecular separation, chemical processors and energy conversion.

Gated proton transport in aligned mesoporous silica films

Modulated proton transport plays significant roles in biological processes such as ATP synthesis as well as in technologically important applications including, for example, hydrogen fuel cells. The state-of-the-art proton-exchange membrane is the sulphonated tetrafluoroethylene copolymer Nafion developed by DuPont in the late 1960s, with a high proton conductivity. However, actively switchable proton conduction, a functional mimic of the ion transport within a cell membrane, has yet to be realized. Herein, we report the electrostatic gating of proton transport within aligned mesoporous silica thin film. It is observed that surface-charge-mediated transport is dominant at low proton concentrations. We have further demonstrated that the proton conduction can be actively modulated by two-fourfold with a gate voltage as low as 1 V. Such artificial gatable ion transport media could have potential applications in nanofluidic chemical processors, biomolecular separation and electrochemical energy conversion.

Optimizing total system cost by balancing unit cost against real cost

Both pump manufacturers and chemical processors are reporting significant long-term savings from making initial investment in perfluoroelastomer seals, the most fluid resistant of elastomeric sealing materials, due to benefits in greatly reduced downtime and longer seal life. This can lead to increased productivity and lower environmental risk. This feature discusses how this may be approached and provides some examples of user experience.

THE FORMATION OF VORONOI DIAGRAMS IN CHEMICAL AND PHYSICAL SYSTEMS: EXPERIMENTAL FINDINGS AND THEORETICAL MODELS

The work discusses the formation of Voronoi diagrams in spatially extended nonlinear systems taking experimental and theoretical results into account. Concerning experimental systems a number of chemical systems used previously as prototype chemical processors and a barrier gas-discharge system are investigated. Although the underlying microscopic processes are very different, both types of systems show self-organized Voronoi diagrams for suitable parameters. Indeed certain chemical systems exhibit Voronoi diagrams as an output state for two distinct sets of parameters one that corresponds to the interaction of stable forced trigger waves and the other that corresponds to the spontaneous initiation and interaction of waves due to point instabilities in the system. In the case of the chemical systems front initiation, propagation and interaction (annihilation) are the primary mechanisms for Voronoi diagram formation, in the case of the barrier gas-discharge system regions of vanishing electric field define the medial axes of the Voronoi diagram. On the basis of cellular automata models the general concept of the formation of Voronoi diagrams has been explained, and related mechanisms have been simulated. Another intuitive approach towards the understanding of self-organized Voronoi diagrams has been given on the basis of reaction–diffusion models explaining the formation of Voronoi diagrams as a result of the mutual interactions of trigger fronts. The variety of systems exhibiting Voronoi diagrams as stationary states indicates that Voronoi diagrams are a generic and natural pattern formation phenomenon.

Constructive Chemical Processors — Experimental Evidence that Shows this Class of Programmable Pattern Forming Reactions Exist at the Edge of a Highly Nonlinear Region

An adapted chemical processor for the computation of a mixed cell Voronoi diagram has been fabricated. A novel copper ferrocyanide based system was combined with a ferric ferrocyanide based system. At higher substrate loading the predictable (programmable) pattern forming structure is lost as the copper system is subject to a chemical instability. The unstable copper system and analogous systems constitute a new class of pattern forming reactions.

On some limitations of reaction–diffusion chemical computers in relation to Voronoi diagram and its inversion

A reaction–diffusion chemical computer in this context is a planar uniform chemical reactor, where data and results of a computation are represented by concentration profiles of reactants and the computation itself is implemented via the spreading and interaction of diffusive and phase waves. This class of chemical computers are efficient at solving problems with a ‘natural’ parallelism where data sets are decomposable onto a large number of geographically neighboring domains which are then processed in parallel. Typical problems of this type include image processing, geometrical transformations and optimisation. When chemical based devices are used to solve such problems questions regarding their reproducible, efficiency and the accuracy of their computations arise. In addition to these questions what are the limitations of reaction–diffusion chemical processors—what type of problems cannot currently and are unlikely ever to be solved? To answer the questions we study how a Voronoi diagram is constructed and how it is inverted in a planar chemical processor. We demonstrate that a Voronoi diagram is computed only partially in the chemical processor. We also prove that given a specific Voronoi diagram it is impossible to reconstruct the planar set (from which diagram was computed) in the reaction–diffusion chemical processor. In the Letter we open the first ever line of enquiry into the computational inability of reaction–diffusion chemical computers.

ON MULTITASKING IN PARALLEL CHEMICAL PROCESSORS: EXPERIMENTAL FINDINGS

A parallel chemical processor is a thin-layer of a reagent mixture which reacts to changes in its concentration — data configuration — in a predictable way to form a stationary pattern corresponding to the concentration of the reagent — result configuration. A computation in the chemical processor is implemented via the spreading and interaction of diffusive or phase waves. We design chemical processors that solve a classical problem of computational geometry — computation of a Voronoi diagram. Namely, we study the possibility of designing a multitasking chemical processor that independently and simultaneously computes Voronoi diagrams of two different data planar sets. We define a two-tasking chemical processor as two distinct reactant–substrate couples within a reaction–diffusion processor that solve separate tasks but share the same physical space. A micro-volume of the physical space is an elementary processor of a massively parallel chemical processor, therefore two reaction–diffusion systems occupying the same space are considered to be a single chemical processor. We found that when a single reactant is on a gel layer containing either one or two substrates the same single Voronoi diagram corresponding to the original location of the reactant drops is constructed. However, when two reactants are on a gel containing two substrates and where there is extremely limited cross reactivity between the separate reactant-substrate couples then two Voronoi diagrams of the data planar points (two sets of drops of separate reactants) are constructed; the third "complementary" pattern is also constructed. The first Voronoi diagram constructed is identical at least in position to the one constructed where one reactant was with one substrate (with the same original configuration of reactant drops). After the formation of the first diagram is completed the diffusion fronts corresponding to unlike reactants cross and are only annihilated where they meet another reactant front composed of the same reactant. The result is the computation of two additional Voronoi diagrams pertaining to the spatial positions of the two sets of reactant drops. The outcomes of this experiment albeit in a simple chemical system are significant because the system constitutes the first class of a synthetic chemical parallel processor capable of at least two computations at the same time.

Experimental Reaction–Diffusion Chemical Processors for Robot Path Planning

In this paper we discuss the experimental implementation of a chemical reaction–diffusion processor for robot motion planning in terms of finding the shortest collision-free path for a robot moving in an arena with obstacles. These reaction–diffusion chemical processors for robot navigation are not designed to compete with existing silicon-based controllers. These controllers are intended for the incorporation into future generations of soft-bodied robots built of electro- and chemo-active polymers. In this paper we consider the notion of processing as being implicit in the physical medium constituting the body of a ‘soft’ robot. This work therefore represents some early steps in the employment of excitable media controllers. An image of the arena in which the robot is to navigate is mapped onto a thin-layer chemical medium using a method that allows obstacles to be represented as local changes in the reactant concentrations. Disturbances created by the ‘objects’ generate diffusive and phase wave fronts. The spreading waves approximate to a repulsive field generated by the obstacles. This repulsive field is then inputted into a discrete model of an excitable reaction–diffusion medium, which computes a tree of shortest paths leading to a selected destination point. Two types of chemical processors are discussed: a disposable palladium processor, which executes arena mapping from a configuration of obstacles, given before an experiment and, a reusable Belousov–Zhabotinsky processor which allows for online path planning and adaptation for dynamically changing configurations of obstacles.

Occupational lung cancer risk for men in Germany: results from a pooled case-control study.

Occupational exposures such as crystalline silica, diesel engine exhaust, polycyclic aromatic hydrocarbons, and man-made mineral fibers are strongly suspected to increase lung cancer risk. Two case-control studies in Germany conducted between 1988 and 1996 were pooled for a joint analysis. A total of 3,498 male cases and 3,541 male population controls, frequency matched for age and region, were included in the study. The lifelong history of all jobs and industries was coded and occupational exposures were evaluated by expert rating. Odds ratios, crude and adjusted for smoking and asbestos exposure, were calculated by conditional logistic regression. Job-related evaluation showed a statistically significant increased odds ratio adjusted for smoking among farmers; forestry workers, fishermen, and livestock workers; miners and quarrymen; chemical processors; cabinet makers and related wood workers; metal producers and processors; bricklayers and carpenters; road construction workers, pipelayers and well diggers; plasterers, insulators, and upholsterers; painters and lacquerers; stationary engine and heavy equipment operators; transport workers and freight handlers; and service workers. With regard to specific occupational exposures, elevated odds ratios (OR) (95% confidence intervals (CI)) for lung cancer risk adjusted for smoking and asbestos exposure were observed for man-made mineral fibers (OR = 1.48, 95% CI 1.17, 1.88); crystalline silica (OR = 1.41, 95% CI 1.22, 1.62); diesel engine exhaust (OR = 1.43, 95% CI 1.23, 1.67); and polycyclic aromatic hydrocarbons (OR = 1.53, 95% CI 1.14, 2.04). The risk of asbestos exposure, adjusted for smoking was also increased (OR = 1.41, 95% CI 1.24, 1.60).

Chronic bronchitis, shortness of breath, and airway obstruction by occupation in New Zealand.

The objectives of this study were to measure the population prevalence of symptoms of chronic obstructive lung disease and mild airway obstruction and to compare these between occupational groups. There were 1,609 subjects (63.9% response rate) who completed a respiratory questionnaire. Of these, 1,132 (70.4%) underwent pulmonary function testing (FEV1 and FVC). Twenty-one categories of current occupation were used for analysis. Four definitions of chronic obstructive pulmonary disease (COPD) were used: (1) chronic bronchitis, (2) chronic bronchitis with airway obstruction, (3) shortness of breath, and (4) shortness of breath with airway obstruction. For chronic bronchitis, adjusted prevalence odds ratios were significantly elevated for food processors other than bakers (OR = 2.83; 95% CI, 1.27 to 6.29) and chemical processors (OR = 18.84; 3.71 to 95.64). The combination of chronic bronchitis and mild airway obstruction (FEV1/FVC < 0.75) was associated with bakers (OR = 25.5; 3.86 to 168.53) and spray painters (OR = 14.40; 2.85-72.69). Shortness of breath was associated with hairdressers (OR = 2.75; 0.80 to 9.42) and bakers (OR = 6.72; 0.57 to 79.66), and nursing was associated with lower levels of shortness of breath (OR = 0.42; 0.16 to 1.15). Working ever with vapors, gases, dust, or fumes was significantly associated with chronic bronchitis and airway obstruction (OR = 3.13; 1.07 to 9.12). This population-based study has identified certain occupations with increased prevalence of chronic bronchitis and COPD.

Computer-based training versus traditional lecture: Effect on learning and retention

This study investigated the effectiveness of computer-based training (CBT) versus the standard or traditional lecture method. The study was conducted at a large pharmaceutical manufacturing site located in Eastern North Carolina. Subjects were chemical processors in the bulk chemical production division (N=54). All subjects completed a comprehensive hazardous chemicals safety training program, with one treatment group completing the course via a self-directed computer program (n=27) and one completing the course via traditional instructor-led sessions (n=27). Both delivery formats were identical relative to learning objectives and content. Level of learning was assessed via a 33-item pretest and posttest. Subjects were also administered a 33-item retention test one month following completion of the program. Subject biographical data, including educational level, were collected by questionnaire and the Computer Anxiety Index (CAIN) was administered to assess subjects' level of computer anxiety within the CBT group. Satisfaction with training was assessed in both treatment groups. Results indicated 1) both groups demonstrated significant learning following training, 2) there was no significant difference in level of learning between the two groups, 3) retention after one month was significantly higher in the CBT groups, 4) there was no correlation between educational level or computer anxiety and learning, and 5) there was no significant difference between the two groups on satisfaction with the training experience.

Reported incidence of occupational asthma in the United Kingdom, 1989-90.

To estimate the incidence of occupational asthma seen by respiratory and occupational physicians in the UK in 1989 and 1990. New cases of occupational asthma were taken from a national reporting scheme, the Surveillance of Work-related and Occupational Respiratory Disease Project (SWORD). Estimates of the working population from the Labour Force Survey were used to calculate reported incidence by age group, sex, occupation, and region. The SWORD project is a scheme for the reporting of new cases of work-related respiratory disease by thoracic and occupational physicians from throughout the UK which began in 1989. In 1989 and 1990, of 4229 cases reported, 1085 (26%) were in patients with occupational asthma. Only half the reported cases were attributed to agents prescribed under the Industrial Injuries Scheme. There was considerable diversity in risk by occupation, with highest annual rates in welders, solderers, and electronic assemblers (175/million), laboratory workers (188/million), metal treaters (267/million), bakers (334/million), plastics workers (337/million), chemical processors (364/million), and spray painters (658/million). Crude rates in men were higher than in women, but rates within occupations were similar in both sexes. Rates of disease rose with age; adjustment for occupation increased the gradient. Regional differences were only partly explained by diversity of industry and were probably mainly due to variation in levels of ascertainment and reporting. Asthma is the most commonly reported occupational lung disease in the UK. The incidence in the general population is unknown, but it was estimated that the incidence of new cases seen by respiratory and occupational physicians was about three times that reported. High relative risks were found in a number of occupations in which effective control of the work environment is urgently required.

Occupational risks for primary liver cancer in Shanghai, China.

Using occupational data for over 3,400 primary liver cancer cases diagnosed between 1980 and 1984 reported to the Shanghai Cancer Registry, and employment information from the 1982 census for the Shanghai population, standardized incidence ratios were computed to generate leads to occupational risks of liver cancer. Among men, a statistically significant excess number of cases was observed for chemical processors, textile workers, wood workers, blacksmiths and machine-tool operators, and material handlers and dock workers. Increased incidence of liver cancer also was observed among female transport equipment operators. These findings indicate that a number of similar occupations are associated with increased risk of primary liver cancer in western countries and China. Although causal inferences cannot be drawn from these data, our study adds to the limited evidence of the potential role of occupational exposures in liver carcinogenesis.

Institute Gathers Chemical Engineering Data

Chemical engineers have begun savoring the first fruits of a massive effort to gather, determine, and evaluate data on physical properties and predictive methods for large numbers of compounds and mixtures processed in the chemical industry. This centralized data source may lead to economic benefits for chemical processors, whose engineers no longer will need to spend so much time in search of design data or to build excessive safety factors into plants. The first beneficiaries of this effort are engineers from the 52 firms that are members of the Design Institute for Physical Property Data (DIPPR), organized under the American Institute of Chemical Engineers to carry out the project. Under terms of their membership, these firms will receive newly evaluated data and predictive methods one year before they are released to the chemical engineering community at large. Petroleum refining engineers have enjoyed access to similarly collected data and predictive methods, thanks to an effort begun ...

Use of electrochemical techniques for corrosion prevention and control in the process industries

Electrochemical techniques are described of direct use to chemical processors for optimum material selection in designing and maintaining new plants as well as corrosion monitoring and control in operating existing plants. Reference is made to the three corrosion forms most responsible for failures in chemical equipment, i.e.: general corrosion, localised corrosion, and stress‐corrosion cracking. Practical examples are given of successful industrial application of electrochemical methods: 1) for controlling active corrosion of a stainless alloy in pressure reactors operated with hot sulphuric acid solution and 2) for preventing stress corrosion cracking of a low‐alloy steel in a pressure absorption tower operated with hot alkali carbonate solution.