The effects of feedback provided by a person versus that provided by a computer on performance, motivation, and feedback seeking were studied. Employing a 2 x 3 experimental design, subjects were assigned to one of three feedback conditions: (a) no feedback, (b) feedback only upon request, and (c) automatic feedback with feedback provided either by a person or a computer The results indicate that (a) subjects are more likely to seek feedback from a computer than from another person; (b) feedback from a person causes a decline in performance relative to a condition where a person is present but does not deliver feedback; (c) both human- and computer-mediated feedback reduce motivation in comparison to a control group that receives no feedback; and (d) personality - in this case, self-esteem and public and private self-consciousness -interacts with the receipt of person-mediated feedback to negatively affect performance.
The two successive fluid-fluid phase transitions in surfactant Langmuir monolayers are described using a highly simplified molecular model: a `reactive' mixture of inter-converting squares of two different sizes. The model is solved by a mean-field lattice approach and by Monte Carlo simulations. The mean-field scheme involves a re-division of the original lattice into `cells' which can contain either one large square representing the (projection on the lattice of) an amphiphilic molecule in a conformationally disordered ('expanded') state, or clusters consisting of 1-4 small squares, each representing an ordered ('stretched') molecule. This procedure circumvents some of the difficulties associated with the size disparity of the adsorbed particles. In spite of its simplicity, the model can explain some major, as well as some subtle, characteristics of experimental monolayer phase diagrams. These include the conditions under which the monolayer exhibits one phase transition, two or none; the decrease of the triple point temperature with increasing chain length, and the gradual decrease with temperature of the liquid-condensed phase density.
Speech detection and matching simultaneously presented printed and spoken words were used to examine phonologic and phonetic processing of Hebrew heterophonic homographs. Subjects detected a correspondence between an ambiguous letter string and the amplitude envelopes of both dominant and subordinate phonological alternatives. Similar effects were obtained when the homographs were phonologically disambiguated by adding vowel marks. The matching of the unpointed printed forms of heterophonic homographs to the dominant and subordinate spoken alternatives presented auditorily was as fast as matching the pointed unambiguous forms to the respective spoken words. This outcome was not obtained when print and speech were not presented simultaneously. These results suggest that printed heterophonic homographs activate the two spoken alternatives they represent and provide further confirmation for fast phonetic recoding in reading.
Previous studies have shown that the streptococcal hemolysin, streptolysin S, is capable of interacting with hydrogen peroxide (H2O2) to injure vascular endothelial cells (Free Radic. Biol. Med. 7:369-376; 1989). To extend these observations, intact group A streptococci (strain 203S) were examined for ability to injure endothelial cells alone and for ability to injure the same cells in the presence of sublethal concentrations of H2O2 (generated from glucose/glucose oxidase). While neither control bacteria nor bacteria that had been pretreated with poly-L-histidine to render them cationic were cytotoxic to endothelial cells by themselves under the conditions of the experiment, endothelial cells were injured by combinations of streptococcal cells and sublytic amounts of H2O2. Taken together, these data suggest that the sequelae which often occur following primary infection with group A streptococci may be the result of a combined assault of host inflammatory cells and the invading bacteria on the vascular lining cells of the host.
51Chromium-labeled rat pulmonary artery endothelial cells (EC) cultivated in MEM medium were killed, in a synergistic manner, by mixtures of subtoxic amounts of glucose oxidase-generated H2O2 and subtoxic amounts of the following agents: the cationic substances, nuclear histone, defensins, lysozyme, poly-L-arginine, spermine, pancreatic ribonuclease, polymyxin B, chlorhexidine, cetyltrimethyl ammonium bromide, as well as by the membrane-damaging agents phospholipases A2 (PLA2) and C (PLC), lysolecithin (LL), and by streptolysin S (SLS) of group A streptococci. Cytotoxicity induced by such mixtures was further enhanced by subtoxic amounts either of trypsin or of elastase. Glucose-oxidase cationized by complexing to poly-L-histidine proved an excellent deliverer of membrane-directed H2O2 capable of enhancing EC killing by other agonists. EC treated with rabbit anti-streptococcal IgG were also killed, in a synergistic manner, by H2O2, suggesting the presence in the IgG preparation of cross-reactive antibodies. Killing of EC by the various mixtures of agonists was strongly inhibited by scavengers of hydrogen peroxide (catalase, dimethylthiourea, MnCl2), by soybean trypsin inhibitor, by polyanions, as well as by putative inhibitors of phospholipases. Strong inhibition of cell killing was also observed with tannic acid and by extracts of tea, but less so by serum. On the other hand, neither deferoxamine, HClO, TNF, nor GTP gamma S had any modulating effects on the synergistic cell killing. EC exposed either to 6-deoxyglucose, puromycin, or triflupromazin became highly susceptible to killing by mixtures of hydrogen peroxide with several of the membrane-damaging agents. While maximal synergistic EC killing was achieved by mixtures of H2O2 with either PLA2, PLC, LL, or with SLS, a very substantial release of [3H]arachidonic acid (AA), PGE2, and 6-keto-PGF occurred only if a proteinase was also added to the mixture of agonists. The release of AA from EC was markedly inhibited either by scavengers of H2O2, by proteinase inhibitors, by cationic agents, by HClO, by tannic acid, and by quinacrin. We suggest that cellular injury induced in inflammatory and infectious sites might be the result of synergistic effects among leukocyte-derived oxidants, lysosomal hydrolases, cytotoxic cationic polypeptides, proteinases, and microbial toxins, which might be present in exudates. These "cocktails" not only kill cells, but also solubilize AA and several of its metabolites. However, AA release by the various agonists can be also achieved following attack by leukocyte-derived agonists on dead cells. It is proposed that treatment by "cocktails" of adequate antagonists might be beneficial to protect against cellular injury in vivo.
Oxygen-derived species are implicated in the pathogenesis of tissue
damage in experimental models such as ethanol-induced gastric injury as
well as in certain clinical conditions. The aim of this study was to
examine the protective effect of manganese and glycine, previously shown
to act as H202 scavengers, on ethanol-induced gastric lesions in
the rat: MnCl2 and glycine (12.5-50mg/rat) were injected s.c up to 6
hours prior to oral administration of 96% ethanol and the extent of
mucosal damage was evaluated 1 hour later by gross and microscopic
score. Mn and glycine pre-treatment induced a dose-dependent
inhibition of lesion formation. Maximal protection was observed when
agents were applied 4 hours prior to the insult. Gross damage was also
markedly prevented by pre-treatment with dimethyl-thiourea
(DHTU,75mg/Kg), but not by allopurinol. Mixtures of subtoxic
concentrations of ethanol and H202 were highly lethal for monkey
kidney epithelial cells in culture. Cell killing in this model was
markedly attenuated by catalase and DMTU and to a lesser degree by
Mn+2 . These results imply that ethanol-induced gastric damage may in
part, involve generation of oxygen derived species, independent of the
xanthine oxidase system. Mn+2 and glycine provide marked gastro-
protection, acting possibly as oxygen radical scavengers.
A hybrid quantum/semiclassical simulation method is applied to the photodissociation dynamics of HCI in the Ar-HCI cluster. The method treats the hydrogen quantum mechanically, and the heavy atoms by semiclassical wavepackets. The dynamics of the H atoms if found to show resonances where the H atom rattles between the Ar and Cl atoms before leaving. Particularly interesting is the kinetic energy distribution of the H atom which shows a structure of pronounced peaks, associated with the resonance levels, while the absorption spectrum is structureless. The dynamics of the process is discussed.
A cross-linked polymer composed of polyethylenimine (PEI) reacted with 1,4-dibromobutane coated on a glassy C electrode (GCE) and contg. neg. charged ions, Fe(CN)63-/4-, is proposed as a ref. electrode in org. solvents. The system exhibits a relatively stable potential (±10 mV) over a period of several days in MeCN and a reasonable potential stability for several hours in DMF and CH2Cl2. The different parameters that affect the behavior of the GCE/PEI/Fe(CN)63-/4- are characterized. [on SciFinder(R)]
The photodissociation of HCl in the Ar-HCl cluster is studied theoretically, with the focus on the angular distribution of the H atom photofragments. Excited state resonances, in which the H atom rattles between the heavy atoms, contribute to the process. It is found that for excitation into a resonance state, the measurable angular distribution of H atoms from Ar-HCl clusters oriented in space provides a mapping of the resonance wave function. This predicts the possibility of imaging resonance wave functions in such processes.
Reprinted in Short Story Criticism: Criticism of the Works of Short Fiction Writers 92, ed. Jelena Krstovíc. Farmington Hills: Thomson Gale, 2006, pp. 74–79.
Self-assembled monolayers of ω-mercapto carboxylic acids, HS(CH2)nCO2H (n = 2, 5, 10), Cm on gold electrodes were used as a means to induce electrochem. differentiation between a neurotransmitter, dopamine, and ascorbic acid. Optimum differentiation is found for n = 5, and it is attributed to a compromise between a well-organized system that requires long ω-mercapto carboxylic acids and a reasonable rate of electron transfer which is obsd. with short ω-mercapto carboxylic acids. [on SciFinder(R)]
On the Relationship Between Mutation Rates and Growth Rates in a Changing Environment
with with E. Dekel and A. Rustichinni
The paper examines the relationship between the mutation rate and the rate of growth of the population when the environment is changing. It is shown that while the global maximum of the growth rate is attained at a non-zero mutation rate, zero is always a local maximum. This suggests that a population with an initially low mutation rate will evolve to a zero mutation rate.
The paper examines the asymptotic behavior of the set of equilibrium payoffs in a repeated game when there are bounds on the complexity of the strategies players may select. The complexity of a strategy is measured by the size of the minimal automaton that can implement it. The main result is that in a zero-sum game, when the size of the automata of both players go together to infinity, the sequence of values converges to the value of the one-shot game. This is true even if the size of the automata of one player is a polynomial of the size of the automata of the other player. The result for the zero-sum games gives an estimate for the general case.
New ethoxylated monofatty acid esters are obtained by esterification of 10-undecenoic acid chloride with several well defined polyethylene glycol mono-Me ethers. The monomeric surfactants show interesting surface properties, and they are characterized and compared to other known ethoxylated alcs. (Brijs) and acids (Mirjs). The crit. micelle concn. and area per mol. at the air-water interface are much higher than the similar com. Brijs, due to the special structure of the new surfactant allowing preferred orientation at the interface. [on SciFinder(R)]
