Gel formation in diimide‐hydrogenated polymers

The hydrogenation of diene‐based polymers via diimide is a very attractive alternative to the conventional catalytic hydrogenation route based on gaseous molecular hydrogen. However, serious crosslinking always accompanies it and limits the end‐use properties of the polymers. Gel formation in polymers that are hydrogenated via diimide has been investigated in detail through an inspection of all the chemical reactions involved in the process. The results indicate that hydrogen peroxide decomposition, some reactions related to oxygen, and the redox reaction between hydrogen peroxide and hydrazine are capable of generating radicals. However, radicals generated in the aqueous phase do not appear to initiate the crosslinking of diene‐based polymers in the latex form. It is proposed that the primary radicals giving rise to crosslinking are generated in the polymer phase in situ, and the step responsible for generating these organic radicals is possibly the diimide disproportionation reaction. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 1122–1125, 2005     

Hydrogenation of natural rubber latex in the presence of OsHCl(CO)(O2)(PCy3)2

Hydrogenation is an important method of chemical modification, which improves the physical, chemical, and thermal properties of diene elastomers. Natural rubber latex (NRL) can be quantitatively hydrogenated to provide a strictly alternating ethylene–propylene copolymer using a homogeneous osmium catalyst OsHCl(CO)(O₂)(PCy₃)₂. A detailed kinetic investigation was carried out by monitoring the amount of hydrogen consumption during the reaction using a gas‐uptake apparatus. The kinetic results of NRL hydrogenation indicated that this system had a second‐order dependence of the hydrogenation rate on hydrogen pressure and then decreased toward a zero‐order dependence for hydrogen pressures above 13.8 bar. The hydrogenation was also observed to be first‐order with respect to catalyst concentration and inverse first‐order on rubber concentration due to impurities present in the rubber latex. Additions of a controlled amount of acid demonstrated a beneficial effect on the hydrogenation rate of NRL. The temperature dependence of the hydrogenation rate was investigated and an apparent activation energy (over the range of 120–160°C) was calculated as 57.6 kJ/mol. Mechanistic aspects of this catalytic process are discussed on the basis of kinetic results. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 640–655, 2006     

Effects of cashew nut shell liquid as a plasticizer on cure characteristics,processability, and mechanical properties of 50 : 50 NR/EPDM blends: A comparison with paraffin oil

50 : 50 natural rubber (NR) and ethylene–propylene–diene monomer rubber (EPDM) blends were prepared with different contents of cashew nut shell liquid (CNSL), a natural product obtained from the shells of the cashew nut, as a plasticizer. For comparison, a commercial paraffin oil plasticizer was also used. The effect of plasticizer content on the cure characteristics, processability, and mechanical properties such as tensile strength, elongation at break, and Young's modulus before and after ageing was investigated. Scanning electron microscopy (SEM) was used to observe the blend morphology. The results indicated that the CNSL plasticizer resulted in lower Mooney viscosity and lower cure time of the 50 : 50 NR/EPDM blends. The incorporation of CNSL into 50 : 50 NR/EPDM blends improved tensile strength and elongation at break but decreased Young's modulus. On addition of CNSL the resistance of the blends to heat and weathering ageing improved. Scanning electron micrographs revealed that the morphology of the blend plasticized with CNSL is finer and more homogeneous compared with the blend plasticized with paraffin oil. Overall results indicate that CNSL can be used as a cheaper plasticizer to replace paraffin oil in NR/EPDM blends with improved processability and mechanical properties. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Using Courseware Discussion Boards to Engage Graduate Students in Online Library Workshops

ABSTRACT

Librarians at Oregon State University (OSU) Libraries used the discussion board features of Blackboard courseware to create an interactive experience for graduate students at a distance who could not attend the on-campus “Literature Review Workshops.” These recently developed workshops have been extremely popular with graduate students across the disciplines and have generated a growing demand from distance education graduate students and faculty to offer similar information online. Reluctant to simply deliver content via an online tutorial, librarians sought to duplicate the workshop atmosphere by making the sessions available for a short time-period online, asking participants to respond to discussion questions at specific points in the workshop, and offering audio-mediated online demonstrations of tools and resources. Student feedback and follow-up requests for more workshops support the perception that this approach offered a rewarding learning experience that addressed their specific adult learning needs.     

The split keyboard: an ergonomics success story

OBJECTIVE: The author reviews the paper by Kroemer (1972) on the design of the split geometry keyboard and the subsequent 35 years of research on the topic. BACKGROUND: It was first suggested in the 1920s that arm strain in the typist could be reduced by splitting the keyboard into two halves and inclining the two halves laterally. The first systematic research on the split keyboard was conducted by Kroemer in the 1960s and published in his 1972 article. METHODS: The literature on split geometry keyboards was identified, and the progression of the research was reviewed. RESULTS: The Kroemer article marked the beginning of a prolonged, worldwide research effort to determine whether and how the split keyboard design might improve comfort and prevent pain in keyboard users. CONCLUSIONS: In the early 1990s, split keyboard designs began to be broadly commercially available. Clear evidence of a health benefit of the split keyboards emerged in the late 1990s. By 2006, a split keyboard was the number one-selling keyboard, of all keyboards sold, in the U.S. retail market. APPLICATION: The history of research on this topic, the challenges to changing the conventional design, and the broader acceptance of the split design are a success story with lessons for all of us.     

Widely Tunable Continuous-Wave Mid-Infrared Laser Source Based on Difference-Frequency Generation in AgGaS(2)

We demonstrate difference-frequency generation in the 6.8-12.5-mum range by mixing two high-power single-frequency laser diodes in a type II AgGaS(2) crystal. This compact all-solid-state scheme provides maximum output powers that exceed 1 muW and permits continuous adjustment-free scans larger than 2 cm(-1) across the entire tuning range.     

Kinetic and mechanistic study of FeS dissolution in aqueous sulfur dioxide solution

FeS leaching was carried out in aqueous sulfur dioxide solution at low temperature and pressure (T = 60°CC;P_SO2 = 51.7 kPa) using both a constant-pressure gas-uptake apparatus and conventional glass-leaching equipment. In the initial stages of the leaching reaction the ratio [SO₂]/[Fe²⁺] was found equal to 1.3. This suggests a stoichiometry given by the following sequence of equations

$\text{FeS + SO}{}_2\text{·H}{}_2\text{O ? FeS + H}{}^{\mathrm{+}}$

$\text{FeS · HSO}{}_3{}^{\mathrm{?}}\text{+ H}{}^{\mathrm{+}}\text{→ Fe}{}^{\mathrm{2+}}\text{+ H}{}_2\text{S + SO}{}_3{}^{\mathrm{2?}}$

As the reactions progressed a build up of various oxy-sulfur species was observed.The leaching process appears to proceed by two concurrent dissolution paths, namely acid dissolution and aquated sulfur dioxide dissolution. In both cases the rate determining step (r.d.s.) involves a surface desorption reaction. In the constant leaching region, the kinetics can be represented by the following rate expression:

At low [H+] relative to [SO₂-H₂O], path I predominates. This can be represented by:

$\text{|}{}_{\mathrm{s}}\text{FeS +SO}{}_2\text{· H}{}_2\text{O ? |}{}_2\text{FeS SO}{}_2\text{· H}{}_2\text{O}$

$\text{|}{}_{\mathrm{s}}\text{FeS SO}{}_2\text{· H}{}_2\text{O ? |}{}_{\mathrm{s}}\text{FeS HSO}{}_3{}^{\mathrm{?}}\text{+ H}{}^{\mathrm{+}}$

$\text{|}{}_{\mathrm{s}}\text{FeS HSO}{}_3{}^{\mathrm{?}}\text{→ Fe}{}^{\mathrm{2+}}{}_{\mathrm{(aq)}}\text{r.d.s.}$

At high [H⁺] relative to [SO₂·H₂O], path II predominates. This can be represented by:

$\text{|}{}_{\mathrm{s}}\text{FeS + H}{}^{\mathrm{+}}\text{? |}{}_{\mathrm{s}}\text{FeS H}{}^{\mathrm{+}}$

$\text{|}{}_{\mathrm{s}}\text{FeS H}{}^{\mathrm{+}}\text{→ Fe}{}^{\mathrm{2+}}{}_{\mathrm{(aq)}}\text{r.d.s.}$

The apparent activation energy was found to be 41.6 kJ per mole.     

'It's the end of the world as we know it': Threat and the spatial-symbolic self": Correction to Burris and Rempel (2004).

Reports an error in 'It's the End of the World as We Know It': Threat and the Spatial-Symbolic Self" by Christopher T. Burris and John K. Rempel (Journal of Personality and Social Psychology, 2004[Jan], Vol 86[1], 19-42). The article contained two errors. On page 35, second column, line 14, two of the word fragments are notated incorrectly. The word shown as s[k]ull should be sk[u]ll, and the word shown as as[h]es should be as[h]e[s]. (The following abstract of the original article appeared in record 2003-11198-002.) According to amoebic self theory, the boundary defining the self encompasses 3 levels of self-representation--bodily, social, and spatial-symbolic. Study 1 related a newly developed measure of individual differences in sensitivity to boundary threat across these 3 domains to values and disgust sensitivity. Four subsequent studies focused on spatial-symbolic threat sensitivity and related it to right-wing authoritarianism, aversive reactions to unfamiliar out-groups, and revulsion to vermin. A final experiment illustrates how a salient spatial-symbolic threat (dust mites) can elicit reactions toward out-groups that closely parallel mortality salience effects observed in research inspired by terror management theory, even though dust mites do not elicit mortality concerns. The importance of preserving the familiar in order to preserve the self is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of the size and charge of nonstoichiometric silver sulfide nanoparticles on their interaction with blood cells

Silver sulfide (Ag₂S) nanoparticles synthesized using different precursors have been characterized by dynamic light scattering measurements and high-resolution transmission electron microscopy. In addition to Ag₂S nanoparticles, we have detected Ag₂S/Ag heterostructures. Using optical microscopy, we have examined interaction of the nanoparticles with red cells of peripheral blood. The results of the interaction have been shown to depend on the particle size and charge. A red cell solution containing large, negatively charged particles coagulated, whereas small, positively charged Ag₂S nanoparticles were concentrated around red cells.     

Synthesis and optical properties of glass with cadmium sulfide nanoparticles

A new approach to the synthesis of silicate glass with cadmium sulfide (CdS) nanoparticles has been developed. It has been demonstrated that replacement of cadmium sulfide with cadmium oxide and zinc sulfide used as sources of cadmium and sulfur allows a substantial reduction of sulfur volatilization during the melting. The produced samples have been investigated by the methods of spectrophotometry in the ultraviolet and visible ranges of the optical range. Thermal treatment of the samples at temperatures exceeding the glass formation point initiates the growth of CdS nanoparticles, which results in the increase of their average size from 3 to 5.2 nm and a significant shift of the fundamental absorption edge to the longer wavelength range from 380 to 480 nm.