Fast pyrolysis of cellulose with reactive methane gas in a single-pulse shock tube

A shock tube technique was employed to study the fast pyrolysis of cellulose with methane under conditions of high temperature, high heating rate, short reaction time, and rapid quenching. The effects of temperature, methane atmosphere, and reaction time are investigated. Experiments were carried out at temperatures between 700 and 2200°C in 1% methane (diluted in argon), and comparisons in the yields of major gas products are made with the results obtained in pure argon atmosphere. The total gas yield decreased about 25–30% in methane. The principal gas products—carbon monoxide, carbon dioxide, and acetylene, except ethylene—were significantly decreased in methane as compared to the yields in pure argon. An increase of about 25% in ethylene yield in methane over argon was observed. The onset of the decomposition of cellulose and the evolution of major pyrolysis products were changed with the reaction times, which also affected the amplitude and the distribution of the pyrolysis products. © 1994 John Wiley & Sons, Inc.     

Transistors Formed from a Single Lithography Step Using Information Encoded in Topography

This paper describes a strategy for the fabrication of functional electronic components (transistors, capacitors, resistors, conductors, and logic gates but not, at present, inductors) that combines a single layer of lithography with angle‐dependent physical vapor deposition; this approach is named topographically encoded microlithography (abbreviated as TEMIL). This strategy extends the simple concept of ‘shadow evaporation’ to reduce the number and complexity of the steps required to produce isolated devices and arrays of devices, and eliminates the need for registration (the sequential stacking of patterns with correct alignment) entirely. The defining advantage of this strategy is that it extracts information from the 3D topography of features in photoresist, and combines this information with the 3D information from the angle‐dependent deposition (the angle and orientation used for deposition from a collimated source of material), to create ‘shadowed’ and ‘illuminated’ regions on the underlying substrate. It also takes advantage of the ability of replica molding techniques to produce 3D topography in polymeric resists. A single layer of patterned resist can thus direct the fabrication of a nearly unlimited number of possible shapes, composed of layers of any materials that can be deposited by vapor deposition. The sequential deposition of various shapes (by changing orientation and material source) makes it possible to fabricate complex structures—including interconnected transistors—using a single layer of topography. The complexity of structures that can be fabricated using simple lithographic features distinguishes this procedure from other techniques based on shadow evaporation.     

Systems in development: Motor skill acquisition facilitates three-dimensional object completion.

How do infants learn to perceive the backs of objects that they see only from a limited viewpoint? Infants’ 3-dimensional object completion abilities emerge in conjunction with developing motor skills—independent sitting and visual–manual exploration. Infants at 4.5 to 7.5 months of age (n = 28) were habituated to a limited-view object and tested with volumetrically complete and incomplete (hollow) versions of the same object. Parents reported infants’ sitting experience, and infants’ visual–manual exploration of objects was observed in a structured play session. Infants’ self-sitting experience and visual–manual exploratory skills predicted looking at the novel, incomplete object on the habituation task. Further analyses revealed that self-sitting facilitated infants’ visual inspection of objects while they manipulated them. The results are framed within a developmental systems approach, wherein infants’ sitting skill, multimodal object exploration, and object knowledge are linked in developmental time. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Formation and destruction of H2S in the short residence time pyrolysis of pulverized coal and model compounds

The evolution of sulphur as H₂S from three US bituminous coals, L-cystine, and thianthrene has been studied in the reflected shock region of a chemical shock tube. With heating rates of approximately 3 × 10⁶Ks^?1, to temperatures in the range 1000–2000K, ultimate yields of sulphur from 7 to 70% as H₂S are observed in as little as 1.5 ms. The most important influence on ultimate yields may be the H/S molar ratio in the fuel which corresponds in the hydrocarbons studied with the H₂S yields. Inherent mineral matter may also influence the evolution, as H₂S formation precedes light hydrocarbon formation from the two model compounds, but occurs nearly simultaneously from the coals. The overall rate of H₂S formation for the three coals is adequately described by a reaction, first order with respect to remaining sulphur, with a rate constant $\text{k=8.1 × 10}{}^7\text{exp}\text{(?}\text{15 960}\text{T}\text{) s}{}^{\mathrm{?1}}$. In the pyrolysis of all five solids, the H₂S yields are decreased to below detectable limits at temperatures >1500K. The path for destruction of the H₂S appears to be by reaction with hydrocarbons such as C₂H₂, the concentration of which becomes similar to the H₂S concentration in the temperature range 1500–1600K.     

The relationship between cigarette use, nicotine dependence, and craving in laboratory volunteers.

Data from epidemiological studies suggest that individual differences in cigarettes per day (CPD) and duration of smoking account for only a small portion of the variance in Diagnostic and Statistical Manual of Mental Disorders (4th ed.) (DSM-IV) nicotine dependence. However, DSM-IV may be an insensitive measure of nicotine dependence; other measures might better reflect the true nature of the relationship between use and dependence. This paper describes the relationship between cigarettes per day (CPD) and years smoking and the severity of nicotine dependence as measured by the Nicotine Dependence Syndrome Scale (NDSS). Furthermore, we assessed the validity of individual differences in nicotine dependence by determining whether they related to cue-evoked craving during abstinence. Data were pooled from five laboratory studies of 489 regular (i.e., 15+ CPD) smokers. In contrast to previously reported data demonstrating a relatively strong relationship between CPD and dependence in chippers (Shiffman & Sayette, 2005), CPD and years smoking accounted for a statistically significant, but small (<6%), portion of the variance in nicotine dependence in daily smokers. Individual differences in both CPD and years smoking had little or no relationship with craving. However, the magnitude of craving was significantly related to the degree of nicotine dependence even after controlling for use variables and excluding craving-related items on the NDSS. These data suggest that among moderate to heavy daily smokers, meaningful individual differences in nicotine dependence are observed independent of differences in current daily cigarette consumption and duration of smoking. Further research into the sources of this variance is critical to understanding the process of and risk for nicotine dependence.     

Fast pyrolysis of cellulose in a single pulse shock tube

A shock tube technique was employed to study the thermal decomposition of cellulose in an inert argon gas under the conditions of high temperature, high heating rate, and short reaction times. The influence of temperature and reaction times on product yields and their distribution were investigated. A clean, tar and char free gas consisting mainly of CO, CO₂, C₂H₂, C₂H₄ and CH₄ were produced throughout the course of this investigation. A mass conversion of cellulose to gas exceeding 90 wt% has been realized between the temperatures 700 and 2200°C for the reaction times examined. Carbon monoxide is the major product and attains a yield in excess of 65 wt% for temperatures above 1300°C. Global kinetic parameters for the decomposition of cellulose and its principal gas products were obtained by fitting the experimental data to a single, first order kinetic model. The energy of activation for the decomposition of cellulose was found to be 130.5 kJ/mol. The material balances made for the total mass, carbon and oxygen are good.     

Infrastructure epistemologies: water,wastewater and displaced persons in Germany

Recent years have seen historically unprecedented global disaster migration; in 2016 Germany received 1.3 million displaced individuals. Regardless of past resources and future potential, disaster migrants are a new, vulnerable population. This new population increases demand for water and wastewater infrastructure services, despite being temporarily unable to pay for services. As such, this kind of sudden population increase is a resiliency challenge for the receiving infrastructure systems. Qualitative analysis of 1,884 open-ended survey responses was blended with a statistical analysis to discover how and why the German public perceives water and sanitation services have been provided to the disaster migrants. Unprompted, 36% (112/314) of respondents referenced at least one of three infrastructure epistemologies, including water and wastewater as a service, as a basic need, and as a human right. These epistemologies share statistically significant relationships with how long respondents feel water and wastewater should be provided to displaced persons. A temporally limited, normative perception of water and sanitation as a humanitarian good functions to enable water and wastewater infrastructure to deliver a high level of service despite the significant disruption of the large and vulnerable population influx, and has practical implications for the structure of cost recovery.     

pH‐responsive polyzwitterions: A comparative study of acrylamide‐based polyampholyte terpolymers and polybetaine copolymers

A comparative study of pH‐responsive polyzwitterions (PZs) with polyampholyte or polybetaine architectures was conducted with well‐defined model polymer systems. Low‐charge‐density PZs, including ampholytic terpolymers composed of acrylamide (AM), sodium 3‐acrylamido‐3‐methylbutanoate, and (3‐acrylamidopropyl)trimethylammonium chloride and carboxybetaine copolymers composed of AM and 3‐(3‐acrylamidopropyldimethylammonio)propionate, were prepared via free‐radical polymerization in 0.5M NaCl to yield ter‐ and copolymers with random termonomer and comonomer distributions. Sodium formate was used as a chain‐transfer agent during the polymerizations to eliminate the effects of the monomer feed composition on the degree of polymerization (DP) and to suppress gel effects and broadening of the molecular weight distributions. The polymer compositions were determined via ¹³C‐NMR spectroscopy, and the residual counterion content was determined via elemental analysis for Na⁺ and Cl^?. The molecular weights (MWs) and polydispersity indices (PDIs) were determined via size exclusion chromatography/multi‐angle laser light scattering (SEC–MALLS); the polymer MWs ranged from 1.4 to 1.5 × 10⁶ g/mol, corresponding to DPs of 1.6–1.9 × 10⁴ repeat units, with all the polymers exhibiting PDIs less than or equal to 2.1. The intrinsic viscosities determined from SEC–MALLS data and the Flory–Fox relationship agreed with the intrinsic viscosities determined via low‐shear dilute‐solution viscometry. Data from the SEC–MALLS analysis were used to analyze the radius of gyration/molecular weight (R_g–M) relationships and the Mark–Houwink–Sakurada intrinsic viscosity/molecular weight ([η]–M) relationships for the PZs. The R_g–M and [η]–M relationships and viscometric data revealed that under size exclusion chromatography conditions, the poly[acrylamide‐co‐3‐(3‐acrylamidopropyldimethylammonio)propionate] betaine copolymers had more open, random‐coil conformations and greater polymer–solvent interactions than the ampholytic poly[acrylamide‐co‐sodium 3‐acrylamido‐3‐methylbutanoate‐co‐(3‐acrylamidopropyl)trimethylammonium chloride] terpolymers. The pH‐ and salt‐responsive dilute‐solution viscosity behavior of the PZs was examined to assess the effects of the polymer structure and composition on the solution properties. The polyampholyte terpolymers had greater solution viscosities and more pronounced stimuli‐responsiveness than the polybetaine copolymers because of their stronger intramolecular interactions and increased chain stiffness. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 24–39, 2004     

Temperature‐Sensitive Hydrogel‐Particle Films from Evaporating Drops

A simple method to prepare temperature‐sensitive films composed of micrometer‐sized colloidal hydrogel particles using evaporating drops of colloidal suspensions is demonstrated. The films range in thickness from a monolayer to approximately fifty particle diameters depending on initial particle volume fraction. Sessile droplets of hydrogel‐particle suspensions are evaporated on silicon wafers. The film is formed from particles spread densely over the air–water interface which then cross‐link and are deposited on the surface during the evaporation process. The resultant thin films exhibit a temperature‐responsiveness characteristic of the individual particles permitting modulation of size, shape, porosity, and optical transmission.