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A large fraction of atmospheric organic aerosol (OA) originates from natural emissions that are oxidized in the atmosphere to form secondary organic aerosol (SOA). Isoprene (IP) and monoterpenes (MT) are the most important precursors of SOA originating from forests. The climate impacts from OA are currently estimated through parameterizations of water uptake that drastically simplify the complexity of OA. We combine laboratory experiments, thermodynamic modeling, field observations, and climate modeling to (1) explain the molecular mechanisms behind RH‐dependent SOA water‐uptake with solubility and phase separation; (2) show that laboratory data on IP‐ and MT‐SOA hygroscopicity are representative of ambient data with corresponding OA source profiles; and (3) demonstrate the sensitivity of the modeled aerosol climate effect to assumed OA water affinity. We conclude that the commonly used single‐parameter hygroscopicity framework can introduce significant error when quantifying the climate effects of organic aerosol. The results highlight the need for better constraints on the overall global OA mass loadings and its molecular composition, including currently underexplored anthropogenic and marine OA sources. The interaction of airborne particulate matter (“aerosols”) with water is of critical importance for processes governing climate, precipitation, and public health. It also modulates the delivery and bioavailability of nutrients to terrestrial and oceanic ecosystems. We present a microphysical explanation to the humidity‐dependent water uptake behavior of organic aerosol, which challenges the highly simplified theoretical descriptions used in, e.g., present climate models. With the comprehensive analysis of laboratory data using molecular models, we explain the microphysical behavior of the aerosol over the range of humidity observed in the atmosphere, in a way that has never been done before. We also demonstrate the presence of these phenomena in the ambient atmosphere from data collected in the field. We further show, using two state‐of‐the‐art climate models, that misrepresenting the water affinity of atmospheric organic aerosol can lead to significant biases in the estimates of the anthropogenic influence on climate. Phase separation effects explain differences in water affinity of biogenic secondary organic aerosol (SOA) at subsaturation and supersaturationLaboratory data for monoterpene and isoprene SOA are representative of field observations with corresponding gas‐phase organic profilesImportance of organic aerosol‐water interactions for global climate is governed by highly uncertain organic aerosol budgets

Film insert moldings were produced from amorphous and crystalline polymers, i. e. PC + ABS and PET respectively. The vastly different characteristics of these polymers provide an interesting platform to study the mechanisms that are responsible for interfacial bond formation, particularly when these materials were molded at different molding conditions. It was observed that intermolecular diffusion between amorphous polymers takes place at virtually any temperature as long as it is kept above the glass transition temperature of the material, though higher temperatures are favorable to accelerate diffusion. As for crystalline polymers, there is an initial need to create free and mobile molecular chains by heating the materials to its melting temperature before any significant diffusion takes place. Certain criteria have to be met, irrespective of the materials used, before good interfacial bonding is achieved. Firstly, the injection molding parameters should be optimized to ensure intimacy between the surfaces of the film and injected resin. Once this is achieved, interdiffusion of molecules should be promoted to ensure extensive film-substrate molecular entanglements. The state of molecular entanglement should then be retained for a sufficient amount of time as the material solidifies in order to obtain good film-substrate adhesion.

The crystalline structure of the heat‐sealed part of oriented polypropylene (OPP) and cast polypropylene (CPP) films was investigated by differential scanning calorimetry, Fourier transform infrared spectroscopy, and thermal mechanical analysis (TMA). The relationship between the crystalline structure and the mechanical properties was analyzed. It was found that the high total crystallinity of both OPP and CPP gave rise to good mechanical properties and that the orientation of the crystalline structure in the OPP film also was an important factor. The optimum condition for heat sealing was the temperature at which total crystallinity was highest while still retaining the crystalline orientation of OPP. The assessment of crystalline orientation by TMA is an innovation initiated by the authors. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 513–519, 2006

The problem of obtaining the first and second derivatives of the profile of a pendant droplet is formulated as an integral equation of the first kind. This equation is solved by Tikhonov regularization in which the method of general cross validation is used to guide the selection of the regularization parameter. These derivatives are converted into mean curvature as a function of droplet height. Surface tension is then obtained by regression computation between the mean curvature and two possible algebraic expressions suggested by the Laplace−Young equation. This way of obtaining surface tension is demonstrated by applying it to a number of published droplet profiles. Some of the problems encountered are discussed and solutions suggested.

A previous study has shown that the adhesion between the film and substrate of film‐insert injection‐molded poly(propylene) (PP) film/PP substrate was evident with the increases in barrel temperature and injection holding pressure. In this second part of the research work, the crystallinity at the interfacial region (i.e., region between the film and the injected substrate) was extensively studied using FTIR imaging, polarized light microscopy, and DSC in an attempt to determine the level of influence that crystallinity has on the interface and bulk mechanical properties. Consequently, a more thorough and clearer picture of the influence of the inserted film on the interfacial crystallinity and subsequently the substrate mechanical properties, such as peel strength and impact strength, has been revealed. The initial proposition that crystallinity could enhance film–substrate interfacial bonding has been confirmed, judging from the higher peel strength with increasing crystallinity at the interfacial region. Nevertheless, the change in crystallinity was not only confined to the interfacial region. With the film acting as heat‐transfer inhibitor between the injected resin and the mold wall, the total crystal structure of the substrate was substantially altered, which subsequently affected the bulk mechanical properties. The lower impact strength of film‐insert injection‐molded samples compared to that of samples without film inserts provided evidence of how the film could impart inferior properties to the substrate. The difference in cooling rate between the substrate and film might also cause other defects such as warpage and/or residual stress build‐up within the product. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 294–301, 2005

Commercially available neoalkoxy titanate (Lica 12) and organosilane (3‐aminopropyltriethoxysilane) coupling agents were used to treat talc and calcium carbonate (CaCO3) to compare their effects with those of untreated fillers upon their incorporation into polypropylene (PP). Commercial stearic acid treated CaCO3 was also used to widen the scope of the study. Single‐filler PP composites (containing either talc or CaCO3) and hybrid‐filler composites (containing a mixture of talc and CaCO3) were compounded on a twin‐screw extruder and subsequently injection‐molded into dumbbells. The silane and titanate treatments dramatically increased the elongation at break for both the single‐filler and hybrid‐filler composites, whereas stearic acid did not. There was also a moderate improvement in the impact strength of the composites, particularly those treated with Lica 12. The hybrid composites, through the synergistic coalescence of positive characteristics from talc and CaCO3, had exceptionally good impact properties, more so with the aid of the coupling agents. For example, the impact strength value of a Lica 12 treated hybrid composite was the greatest for all the composites studied, overshadowing the superiority of the CaCO3‐filled PP composites, which predominantly had the highest impact properties. Further investigations of the thermal and morphological properties were also conducted to facilitate the determination of the coupling mechanisms and their interesting effects on the hybrid composites. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 98: 413–426, 2005

The mathematical problem of converting a normal spectrum into the corresponding first- and second-derivative spectra is formulated as an integral equation of the first kind. Tikhonov regularization is then applied to solve the spectral conversion problem. The end result is a set of linear algebraic equations that takes in as input the original spectrum and produces as output the second-derivative spectrum, which is then integrated to yield the first-derivative spectrum. Noise amplification is kept under control by adjusting the regularization parameter (guided by generalized cross-validation) in the algebraic equations. The performance of this procedure is demonstrated by applying it to different types of spectral data taken from the literature.

The main aim of this work was to study and compare the mechanical and thermal properties of hybrid polypropylene (PP) composites and single‐filler PP composites. With two main types of mineral fillers—calcium carbonate (CaCO3) and talc—PP composites of different filler weight ratios (talc/CaCO3) were compounded with a twin‐screw extruder and then injection‐molded into dumbbell specimens with an injection‐molding machine. Tensile, flexural, and impact tests were performed to determine and compare the mechanical properties of the hybrid and single‐filler PP composites. A synergistic hybridization effect was successfully achieved; the flexural strength and impact strength were highest among the hybrids when the PP/talc/CaCO3weight ratio was 70:15:15. The nucleating ability of the fillers and its effects on the mechanical properties were also studied with differential scanning calorimetry. Because of the influence of talc as the main nucleating agent, the hybrid fillers showed significant improvements in terms of the nucleating ability, and this contributed to the increase in or retention of the mechanical properties of the hybrid composites. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3327–3336, 2004

Three types of mineral fillers—talc, calcium carbonate (CaCO3), and kaolin (10–40 wt % filler loadings)—were compounded with polypropylene (PP) with a twin‐screw extruder. The composites were injection‐molded, and the effects of the filler loading on the mechanical, flow, and thermal properties for the three different types of filled composites were investigated. The aim was to compare their properties and to deduce prospective filler combinations that would yield hybrid PP composites in following studies. The results showed that in most cases, the strength and stiffness of the talc‐filled PP composites was significantly higher than those of the CaCO3‐ and kaolin‐filled PP composites. However, CaCO3, being a nonreactive filler, increased the toughness of PP. The kaolin‐filled PP composites also showed some improvement in terms of strength and stiffness, although the increases in these properties were not as significant as those of the talc‐filled PP composites. The effects of interfacial interactions between the fillers and PP on the mechanical properties were also evaluated with semiempirical equations. The nucleating ability of all three fillers was studied with differential scanning calorimetry, and the strongest nucleating agent of the three was talc, followed by CaCO3and kaolin. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91: 3315–3326, 2004

A method based on Tikhonov regularisation is used to convert the Couette viscometry data of a number of liquid foods into shear stress vs shear rate relationships. For liquid foods that have a yield stress and if the viscometry data cover the appropriate range of shear stress, Tikhonov regularisation is used to compute simultaneously the yield stress. The versatility of Tikhonov regularisation is demonstrated by applying it to process data from wide as well as narrow gap Couette viscometers. The results generated by Tikhonov regularisation are compared against that obtained by methods currently employed by rheologists.

There has been little published work on the statistical features of breath times in postoperative patients. We applied extreme value theory (a statistical method) to the variation in the timing of postoperative breathing.

Abstract: The molecular weight (Mw) effect of polystyrene sulphonate (PSS) on the yield stress of ZrO2 dispersion was evaluated. Three “monodispersed” samples with Mw of 1430, 9960 and 130,000, and two broad distribution samples of Mw 70,000 and 1.0 million were investigated. Adsorbed PSS gave rise to charged patch attraction that enhanced the maximum yield stress, τ y max, of dispersions at charge neutral condition [3]. As a PSS patch consists of only one molecule, the patch size should increase with increasing Mw. For PSS of Mw 1430 with just only seven repeating units the patch formed would be rectangular (linear) and small with a high charge density. For Mw of 9960 and higher, the patch would be irregular in shape with a smaller charge density. At a moderate surface coverage of ˜20%, the τ y max increases quite sharply from Mw 9960 to 130,000 and very gradually from 130,000 to 1.0 million. From Mw 9960 to 130,000, the strength of the patch attraction increases quite strongly with increasing patch size. From Mw 130,000 to 1million, the small increase in τ y max reflected a limiting patch size effect. At the limiting size, the attraction is at maximum strength. At the same coverage, PSS of Mw 1430 also displayed a strong charge patch attraction. This was attributed to a higher number of charged patch interactions at the closest point of separation and also to the high charge density of the PSS patch. The low surface coverage of 6% revealed no significant molecular weight effect on τ y max. The network structure consisted of a mixture of charge patch and bare surface interactions.

Abstract:  The effects of 2-hydroxyethyl cellulose (HEC) of weight-average molecular weight 15,000, 90,000 and 7,20,000 on the rheological properties of TiO2 dispersions were evaluated. For all three HECs, the maximum yield stress, τymax, (occurred at zero zeta potential), decreased with increasing HEC concentration. Interestingly, the largest reduction in τymax was observed with the HEC with the highest molecular weight. This reduction was attributed to steric interaction arising from adsorbed HEC. Adsorbed high-molecular-weight HEC formed an effectively thicker steric barrier because of its larger size and higher adsorption capacity. Bridging interactions that were expected to be important for the high-molecular-weight HEC were found to be unimportant here. In the flocculated regime, HEC enhanced the shear-thinning characteristics of the TiO2 dispersions.

BACKGROUND: Both psychological and physiological disturbances have been implicated in the aetiopathogenesis of irritable bowel syndrome (IBS). AIMS: To investigate how the psychological factors act, and the involvement of infective and physiological factors. METHODS: Consecutive patients hospitalised for gastroenteritis reported life events for the previous 12 months, and past illness experiences on standardised questionnaires. They also completed psychometric questionnaires for anxiety, neuroticism, somatisation, and hypochondriasis. In some patients, rectal biopsy specimens were obtained during the acute illness and at three months postinfection. RESULTS: Ninety four patients completed all questionnaires: 22 patients were diagnosed with IBS after their gastroenteritis (IBS+), and 72 patients returned to normal bowel habits (IBS-). IBS+ patients reported more life events and had higher hypochondriasis scores than IBS- patients. The predictive value of the life event and hypochondriasis measures was highly significant and independent of anxiety, neuroticism, and somatisation scores, which were also elevated in IBS+ patients. Rectal biopsy specimens from 29 patients showed a chronic inflammatory response in both IBS+ and IBS- patients. Three months later, specimens from IBS+ patients continued to show increased chronic inflammatory cell counts but those from IBS- patients had returned to normal levels. IBS+ and IBS- patients exhibited rectal hypersensitivity and hyper-reactivity and rapid colonic transit compared with normal controls, but there were no significant differences between IBS+ and IBS- patients for these physiological measurements. CONCLUSION: Psychological factors most clearly predict the development of IBS symptoms after gastroenteritis but biological mechanisms also contribute towards the expression of symptoms.

Abstract: Adsorbed polystyrene sulphonate (PSS) shifts the pH of the zero zeta potential, pHς = 0, of ZrO2 to a lower pH. The positive charge density of ZrO2 at pH = pHς=0 determined from the amount of PSS adsorbed was in excellent agreement with that obtained from charge titration. Polystyrene sulphonic acid shifts pHς=0 to a greater degree compared with polyacrylic acid because it is a much stronger acid. A patch is likely to just consist of one adsorbed molecule. The patch is negative when the charges of the molecule exceed the underlying positive surface charge. Attraction between the negative patch and the bare positive surface of a second particle is responsible for increasing the yield stress of concentrated ZrO2 dispersions at pHς=0. Its magnitude is only of the order of the van der Waals attraction. Increasing ionic strength and patch misalignment diminish the attraction. The upper limit of the patch area was estimated from the radius of gyration of the molecule in solution. With a known patch area, the patch charged density can be calculated. With the selection of an appropriate patch area, the yield stress due to charged patch attraction increases linearly with the product of the negative and positive patch densities.

Techniques for measuring the fundamental flow properties of as-mined Victorian brown coal suspensions are developed. Flow properties are presented for Morwell, Yallourn and Loy Yang coals as a function of concentration for fixed particle size distribution. Even at the relatively low solids concentration of 20 to 30 percent by weight, the suspensions exhibit complex non-Newtonian characteristics. Generally at high concentration, the suspensions are thixotropic with a shear rate dependent viscosity and exhibit a yield stress. The inherent thixotropy of the coals can be exploited and it is technically but perhaps not economically feasible to transport the as-mined coals in a pipeline. The power requirement to pump the coals in a pipeline is found to be 10 to 30 times that required to pump black coal in the Black Mesa pipeline in the U.S.A. The differences in the rheological properties of the three coals is related to the surface properties of the coal particle — expressed in terms of carboxylate and inorganic cation content, and to differences in the pore volume of the coals. The flow characteristics of one coal can be converted to that of another simply by varying either the carboxylate or ionic content of the suspension.

The effects of alkyl chain length and concentration of surfactant on the yield stress–pH behavior of a 57 wt% ZrO2suspension were evaluated. An alkyl chain lengthnof between 5 to 12 carbons was used. For chain lengthn≥ 7, a much larger maximum yield stress (at zero zeta potential) than that without additive was recorded. The increase in the maximum yield stress is as much as sixfold. Generally, a higher surfactant concentration leads to a higher yield stress. The increase in the maximum yield stress is quite insensitive to surfactant chain length. Ionic strength appears to have no effect on the yield stress–pH behavior of suspensions with a surfactant. The data are consistent with the observation of a long-range attractive (hydrophobic) force measured in surface force experiments.

The isomorphism problem for finite groups of odd order and nilpotency class 2 with cyclic centre will be solved using some results of Brady [1], [2]. Since a finite nilpotent group is the direct product of its Sylow subgroups, we only need to consider finite q-groups where qis a prime. It has been shown in [1] and [2] that a finite q-group of nilpotency class 2 with cyclic centre is a central product either of two-generator subgroups with cyclic centre or of two-generator subgroups with cyclic centre and a cyclic subgroup, and that the q-groups of class 2 on two generators with cyclic centre comprise the following list: , and if q = 2 we have as well .

AbstractIn conjunction with an earlier work by Leong (1974a), this paper completes the solution of the isomorphism problem for finite nilpotent groups of class two with cyclic centre. A canonical decomposition for 2-groups of such type is obtained and proved.

Optical microscopy and X-ray diffraction studies reveal the presence of highly swollen mesophases in four-component systems containing amphiphilic triblock copolymers. According to the composition of the system, lamellar phases or hexagonal structures are produced. The polymeric mesophases exhibit textures very similar to those encountered in low molecular weight liquid crystalline phases.

The effect of pH on the flow behavior of ZrO2suspensions containing polyacrylic and octanoic acids was evaluated. In the flocculated pH regime, the flow behavior is highly shearthinning and can be described by a power-law model. The shearthinning behavior increases with increasing degree of flocculation. Maximum shearthinning was observed at the zero zeta potential condition. Hydrophobic interaction arising from adsorbed octanoic acid was found to enhance the shearthinning behavior. No such enhancement was observed for adsorbed polyacrylic acid. It was also illustrated that the viscosity-pH behavior is a mirror image of the yield stress-pH behavior. A quantitative particle-pair interactions model incorporating steric and hydrophobic interactions was proposed to explain the effects of polyacrylic and octanoic acids on the maximum yield stress.

The paper describes how the theology of low concentration brown coal suspensions can be exploited to produce high concentration, low viscosity suspensions which are attractive as a potential coal-water fuel. Brown coal suspensions with solid concentrations approaching those of bituminous black coal have been prepared. The high inherent water content (˜ 60 wt %) and macroporosity of the brown coal have been reduced by thermal and chemical means. The hydrophobicity of the coal surface has been increased sufficiently to reduce the tendency for swelling and water uptake. This, together with densification, has allowed the solids content to be progressively improved from 30 wt % solids with raw coal to 65 wt% solids with modified coals while maintaining the viscosity of the suspension at a low level. The high solid concentration was achieved without additives.

Nine tetranucleotide short tandem repeat (STR) loci, D3S1358, vWA, FGA TH01, TPOX, CSF1PO, D5S818, D13S317 and D7S820, were analyzed in the Japanese population with a newly released kit for personal identification using multiplex PCR with fluorescent-labeled primers following capillary electrophoresis. The observed heterozygosities were 0.67, 0.77, 0.82, 0.61, 0.62, 0.73, 0.78, 0.81 and 0.74, respectively, and the combined discrimination power of the nineplex was 0.9999999991. None of the nine loci deviated from Hardy-Weinberg equilibrium expectations using the chi-square test, homozygosity test, likelihood ratio test and exact test after the grouping of the alleles. The nine STR loci allele frequencies were significantly different from those of other ethnic populations.

The nature of effector cells which mediate delayed-type hypersensitivity (DTH) to dengue type 2 virus and the influence of the H-2 complex on the cellular transfer of DTH was investigated. The DTH effector cells appeared to consist of two types of T cells, one Lyt-1.1+, the other Lyt-2.1+ or, alternatively, an interaction between these two T cell subsets may be required for maximal expression of DTH. Cellular transfer of DTH reactivity also required compatibility at the K and D or I region of the H-2 complex. Compatibility at the D region alone was not sufficient for transfer of DTH. The significance and implications of these findings are discussed.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.