Effect of preemulsifying mercaptans on modification in emulsion polymerization systems

Preemulsifying modifiers, or their solutions in monomers, with soap and water prior to charging the remaining ingredients of an emulsion polymerization system markedly changes the reactivity of high molecular weight modifiers. The increased reactivity of a mercaptan is seen in a higher regulating index as measured by the rate of depletion of the mercaptan. The regulating index of tert-hexadecyl mercaptan for a styrene-butadiene copolymerization (SBR) increased from 0.3 for the control to 3.0 after preagitation, and thus approached the tert-dodecyl mercaptan control in efficiency on a molar basis. The regulating index of n-dodecyl mercaptan increased from 1.0 for the control to 16 for the experimental. The latter value is too high for efficient modification of SBR systems. This technique permits the attainment of a continuous range of regulating index values within limits based on the reactivity of the modifier and intensity and duration of preagitation. This paper presents solutions for two of the problems associated with the preagitation technique and proposes a mechanism to account for the changes in modification arising from preagitating modifiers in the soap solution. This report develops a variable in emulsion polymerization that has been little used and incompletely understood.     

3D modeling and motion parallax for improved videoconferencing

Computational Visual Media - We consider a face-to-face videoconferencing system that uses a Kinect camera at each end of the link for 3D modeling and an ordinary 2D display for output. The Kinect...     

Modification of emulsion polymerization by multiple addition of modifier

Model equations were used to determine approximately the optimum conditionneeded to obtain the lowest molecular weight, P?_v, with a fixed molar amount of modifier by the addition in three portions of modifiers with different regulating indexes. Simulated calculations were also conducted to determine the effect two- and three-portion additions of a modifier had on the P?_v/P?_n ratio. The simulated calculations served as guides for two-, three-, and manyfold incremental modifier addition experiments. The calculations and experiments establish the need for matching the portioning of the modifier to the regulating index in order to obtain efficient use of the modifier.     

Oligopeptidase B-dependent signaling mediates host cell invasion by Trypanosoma cruzi

Mammalian cell invasion by the intracellular protozoan parasite Trypanosoma cruzi is mediated by recruitment and fusion of host cell lysosomes, an unusual process that has been proposed to be dependent on the ability of parasites to trigger intracellular free calcium concentration ([Ca2+]i) transients in host cells. Previous work implicated the T.cruzi serine hydrolase oligopeptidase B in the generation of Ca2+-signaling activity in parasite extracts. Here we show that deletion of the gene encoding oligopeptidase B results in a marked defect in host cell invasion and in the establishment of infections in mice. The invasion defect is associated with the inability of oligopeptidase B null mutant trypomastigotes to mobilize Ca2+ from thapsigargin-sensitive stores in mammalian cells. Exogenous recombinant oligopeptidase B reconstitutes the oligopeptidase B-dependent Ca2+ signaling activity in null mutant parasite extracts, demonstrating that this enzyme is responsible for the generation of a signaling agonist for mammalian cells.     

Inhibition of potassium (KATP) channels reduces the short-circuit current response of rat colonic mucosa to acetylcholine

Intestinal secretion depends upon electrogenic chloride transport into the gut lumen, which requires maintenance of an electrically negative cell-membrane voltage. We have investigated whether secretory responses of rat colonic mucosa to acetylcholine were sensitive to inhibition of potassium channels and whether selective inhibition could indicate the nature of the channel involved. Rat colonic mucosa was set up in Ussing chambers, short-circuit current responses obtained to acetylcholine, and the sensitivity of such responses to inhibition of potassium channels was investigated. Non-selective potassium-channel blockade by barium induced concentration-dependent inhibition of responses to acetylcholine. Similar inhibitory effects were obtained using 4-aminopyridine and glibenclamide. 5-Hydroxydecanoate and phentolamine also inhibited the increase in short-circuit current. However, a combination of charybdotoxin plus apamin was without effect. We conclude that a basolateral outward movement of potassium ions is required for the secretory action of acetylcholine on rat colonic mucosa. The potassium channel involved seems to be ATP-dependent and calcium-insensitive.     

Does the uncanny valley exist? An empirical test of the relationship between eeriness and the human likeness of digitally created faces

The uncanny valley theory (UVT) (Mori, 1970) proposes that when stimuli are defined by a near-perfect resemblance to humans they cause people to experience greater negative affect relative to when they have perfect human likeness (HL) or little to no HL. Empirical research to support this non-linear relationship between negative affect and HL has been inconclusive, however, and a satisfactory causal explanation has not yet emerged to explain existing findings. In two studies, we examined the relationship between HL and eeriness using digital human faces. First, we examined the relationship between HL and eeriness while controlling for extraneous variation in stimulus appearance. We created two HL continua by manipulating the facial proportions and polygon count of several digital human models. Second, we proposed and tested two causal hypotheses regarding the uncanny valley phenomenon that we refer to as category conflict and feature atypicality. We created two additional HL continua by manipulating the skin coloration and category membership of models. Across these continua we introduced an atypical feature. Our results suggest that HL is linearly related to emotional response, except under conditions where HL varies by category membership, suggesting that previous empirical findings might be explained as a category conflict.     

Modification of butadiene–acrylonitrile and styrene–acrylonitrile copolymerizations in emulsion systems

Modification of acrylonitrile in copolymerizations with butadiene and with styrene in hot and cold emulsion recipes has been studied. Series of primary, secondary, and tertiary mercaptans in addition to several miscellaneous modifiers were tested. Kinetically the rate data for the monomer pairs containing acrylonitrile better fit first-order plots than the curves obtained for an ideal emulsion polymerization. In this study all modifier depletions in nitrile systems were plotted as log mercaptan versus log conversion and the slope of the curve was taken as the transfer constant. Normal mercaptans were inefficient modifiers in nitrile systems as determined in polymerization and depletion experiments. Secondary mercaptans, 2-nonyl, 2-decyl, and mixtures in this molecular weight range, were promising modifiers for low temperature (5°C.) nitrile systems. 2-Nonyl mercaptan gave enhanced modification by incremental addition of the modifier indicating this procedure could be used to advantage in preparing nitrile rubbers. The series of tertiary mercaptans from C₁₃ to C₇ showed an improvement in modification of low temperature nitrile systems as the molecular weight decreased. A plot of the data on a molar basis shows that the optimum modifier falls in the C₉–C₈ range. The optimum transfer constant for the most efficient modification of 70/30 and of 80/20 butadiene–acrylonitrile polymerizations at 5°C. terminated at 60% conversion is 2. Depletion data show that the transfer constant for a mercaptan decreases as the nitrile content in mixtures with butadiene increases. The properties of the vulcanizates of the 70/30 and 80/20 butadiene–acrylonitrile polymers prepared in the presence of low molecular weight mercaptans were equivalent to or better than those of the controls. These data show that nitrile polymers could be modified with a lower molecule weight mercaptan with no loss of properties but with a considerable saving in amount of modifier. Mercaptans are essential for the initiation of butadiene–acrylonitrile in the presence of persulfate at 50°C. For the hot nitrile rubber preparations, the series of mercaptan from t-C₁₀ to t-C₇ are efficient modifiers. However, the heptyl and octyl mercaptans are retarders, and the t-C₉ and t-C₁₀ are the preferred modifiers for efficiency and unretarded polymerization. The modification with a series of mercaptans ranging from t-C_13.2 to t-C₈ of 75/25 styreneacrylonitrile at 50°C. in presence of persulfate–bisulfite showed a consistent behavior. The transfer constant decreased in a regular manner as the molecular weight of the mercaptan increased, and for the series of tertiary modifiers the t-C₁₀ mercaptan was the most efficient as judged by a melt flow test.     

Biomolecular swarms – <Emphasis Type="Italic">an agent-based model of the lactose operon</Emphasis>

We present our latest version of a swarm-based, 3-dimensional model of the lactose (lac) operon gene regulatory system. The lac operon is a well-understood genetic switch capable of self-regulation dependent on the energy source of lactose. Our model includes a 3D visualisation which simulates proteins as agents with physical properties that interact with DNA, molecules, and other proteins, incorporating many of the important aspects of a genetic regulatory system. Our model utilizes a decentralized swarm approach with multiple agents acting independently – according to local interaction rules – to exhibit complex emergent behaviours, which constitute the externally observable and measurable switching behaviour.