Small Constituents Research Articles

Granular activated carbon adsorption process for removing trichloroethylene from groundwater

AbstractBatch adsorption capacity experiments and continuous flow breakthrough experiments were conducted to compare the effectiveness of seven granular activated carbons (GACs) in removing trichloroethylene (TCE) from groundwater. The order of GACs' adsorptive capacities for TCE was the same as their phenol numbers (indicator for <1 nm micropores). A small amount of methanol (0.05% v/v) did not affect the pure water TCE capacities, which were notably reduced by the small organic constituents of tap water. The breakthrough results show low utilization of the available adsorptive capacity due to both slow mass transport and the need to achieve a high degree of TCE removal, and that the serial bed mode of treatment is cost effective because a very high capacity utilization can be attained. The low‐cost, environmental friendly bamboo GAC is attractive as its competitive TCE capacity was readily used in actual treatment because of its favorable pore structure. © 2010 American Institute of Chemical Engineers AIChE J, 2011

Two step yielding in attractive colloids: transition from gels to attractive glasses

Steady and oscillatory rheology was utilized to study the mechanical response of colloidal glasses and gels with particular emphasis in their yielding behaviour. We used a suspension of hard sphere colloidal particles with short-range depletion attractions induced by the addition of non-adsorbing linear polymer. While high volume fraction hard sphere glasses exhibit a single yield point due to cage breaking, attraction dominated glasses show a two-step yielding reflecting bond and cage breaking, respectively. Here we investigated the yielding behaviour of frustrated colloid–polymer systems with equal attraction strength and range, varying the particle volume fraction, φ, spanning the region from an attractive glass (φ = 0.6) to a low volume fraction (φ = 0.1) attractive gel. Yielding throughout this range, probed both by oscillatory and steady shear, is found to remain a two step process until very low φ's. The first yield strain related with in-cage or inter-cluster bond braking remains constant for φ > 0.3 while the second yield strain, attributed to braking of cages or clusters into smaller constituents, increases as volume fraction is decreased due to enhancement of structural inhomogeneities in the gel. Steady shear tests indicated distinct shear rate regimes: At steady state, low and intermediate shear rates create denser or smaller flowing clusters, whereas high rates may lead to complete break-up into independent particles. When the range of attraction was increased, both yield strains increased scaling with the range of attraction and accompanied structural changes. Finally, ageing leads to an overall strengthening of both the gel and the attractive glass accompanied by an enhancement of the second stress overshoot in steady shear, while the attractive glass also becomes more brittle.

Phages in nature

Bacteriophages or phages are the most abundant organisms in the biosphere and they are a ubiquitous feature of prokaryotic existence. A bacteriophage is a virus which infects a bacterium. Archaea are also infected by viruses, whether these should be referred to as 'phages' is debatable, but they are included as such in the scope this article. Phages have been of interest to scientists as tools to understand fundamental molecular biology, as vectors of horizontal gene transfer and drivers of bacterial evolution, as sources of diagnostic and genetic tools and as novel therapeutic agents. Unraveling the biology of phages and their relationship with their hosts is key to understanding microbial systems and their exploitation. In this article we describe the roles of phages in different host systems and show how modeling, microscopy, isolation, genomic and metagenomic based approaches have come together to provide unparalleled insights into these small but vital constituents of the microbial world.

Polythiophene microspheres synthesized by transition metal mediated oxidative dispersion polymerization

INTRODUCTION In the past two decades, significant achievements have been made in the synthesis of soluble polythiophene (PT) derivatives. The incorporation of various functional side chains enables PT to be easily processed by solution method and gifts many interesting bonus properties as well. Nonetheless, these procedures are usually complex and expensive, which generally require stringent conditions and sometimes toxic solvents. Furthermore, for photovoltaic applications, the material stability under continuous illumination has to be taken into account. The solubilizing side chains may be passive in terms of light harvesting and charge transport, and they may also make the materials soft and allow for diffusion of small molecules and constituents. Recently, Bjerring et al. prepared unsubstituted PT films by solution processing thermocleaving method in which the solubilizing side chains were removed after the formation of polymer film.

Structural Basis of Fatty Acid Substrate Binding to Cyclooxygenase-2

The cyclooxygenases (COX-1 and COX-2) are membrane-associated heme-containing homodimers that generate prostaglandin H(2) from arachidonic acid (AA). Although AA is the preferred substrate, other fatty acids are oxygenated by these enzymes with varying efficiencies. We determined the crystal structures of AA, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA) bound to Co(3+)-protoporphyrin IX-reconstituted murine COX-2 to 2.1, 2.4, and 2.65 A, respectively. AA, EPA, and docosahexaenoic acid bind in different conformations in each monomer constituting the homodimer in their respective structures such that one monomer exhibits nonproductive binding and the other productive binding of the substrate in the cyclooxygenase channel. The interactions identified between protein and substrate when bound to COX-1 are conserved in our COX-2 structures, with the only notable difference being the lack of interaction of the carboxylate of AA and EPA with the side chain of Arg-120. Leu-531 exhibits a different side chain conformation when the nonproductive and productive binding modes of AA are compared. Unlike COX-1, mutating this residue to Ala, Phe, Pro, or Thr did not result in a significant loss of activity or substrate binding affinity. Determination of the L531F:AA crystal structure resulted in AA binding in the same global conformation in each monomer. We speculate that the mobility of the Leu-531 side chain increases the volume available at the opening of the cyclooxygenase channel and contributes to the observed ability of COX-2 to oxygenate a broad spectrum of fatty acid and fatty ester substrates.

Inhibition of Shiga Toxin 2 (Stx2) in Apple Juices and its Resistance to Pasteurization

In the present study, we evaluated Shiga toxin (Stx2) activity in apple juices by measuring a decrease in dehydrogenase activity of Vero cells with the microculture tetrazolium (MTT) assay. Freshly prepared juice from Red Delicious apples and Golden Delicious apples inhibited the biological activity of the bacterial toxin Stx2 produced by E. coli O157:H7 strains. Studies with immunomagnetic beads bearing specific antibodies against the toxin revealed that Stx2 activity was restored when removed from the apple juice. SDS gel electrophoresis revealed no difference (P < 0.05) in the densities or molecular weights between Stx2 in either PBS or apple juices. These results suggest that Stx2 may be reversibly bound to small molecular weight constituents in the juice. The Stx2 toxin was not inactivated on exposure to heat programs (63 degrees C for 30 min, 72 degrees C for 15 s, 89 degrees C for 1 s) commonly used to pasteurize apple juice, but lost all activity when exposed to 100 degrees C for 5 min. The results suggest that pasteurization of apple juice used to inactivate E. coli O157:H7 has no effect on Stx2, and that food-compatible and safe antitoxin compounds can be used to inhibit the biological activity of the Shiga toxin.

A protocol for enrichment of CD34+ stromal cell fraction through human skin disaggregation and magnetic separation

A protocol for enrichment of CD34+ stromal cell fraction through human skin disaggregation and magnetic separation

Thermal characterization of high temperature reactor particle layers by photothermal microscopy

Thermal diffusivity of particle pyrolytic carbon layers deposited on 500 μm diameter spherical particle before irradiation has been measured using photoreflectance microscopy (PM). This technique is used to characterize of such small constituents at a microscopic scale and temperature controlled up to 1000 °C. Nevertheless, one of the layers – buffer layer – needs a particular analysis due to its porous structure. Indeed, measurements by PM on this material only permit to obtain the thermal diffusivity of the solid skeleton. These require the use of a numerical homogenization technique to estimate an effective thermal conductivity. The effect of temperature is discussed. Mapping of the thermal diffusivity of coated fuel particles provides useful data for modelling fuel performance during the nuclear reactors operation.

Electoral rules of the authoritarian game: undemocratic effects of proportional representation in Rwanda

Much has been written about the special design of Rwanda's judiciary in order to handle the aftermath of the genocide in 1994. By contrast, other institutional elements of the 2003 constitution have rarely been addressed in research. The second (partial) parliamentary elections in September 2008 revealed some of the implications which the carefully designed electoral system has for Rwanda's political development. As a starting point, the paper emphasises the need to link the debate about institutional design in divided societies with the debate about elections in authoritarian regimes. Under different regime types, “institutional engineers” may pursue different goals. The paper argues that proportional representation (PR) can foster undemocratic outcomes: PR impedes the local accountability of politicians in a political environment in which the government is not held in check by a democratic opposition. Thus, the current PR system facilitates the maintenance of authoritarian power in Rwanda whereas small constituencies would establish closer links between the local populations and their representatives.

Intercalation of solvent and polymer in galleries of mobile clay platelets by a Monte Carlo simulation

AbstractThe intercalation of solvent particles and polymer chains of concentration Cw = 0.2 and Cp = 0.2, respectively, in a layer of (4) clay platelets is studied by a Monte Carlo simulation on a cubic lattice. Polymer chains and platelets are modeled by bond fluctuations. Besides the excluded volume, a set of polymer‐clay (cs) and solvent‐clay (ws) interactions with (i) cs = 1, ws = −2, (ii) cs = −2, ws = 1 and (iii) cs = ws = −2 are considered. The global dynamics of platelets is constrained due to the presence of three components, i.e., solvent, polymer, and platelets, which retain their interstitial spacing with well‐defined galleries. Intercalation of solvent particles and polymer chains (low molecular weight) occurs with their attractive interaction with the platelets, which further reinforces the layered clay morphology. The density profiles of the solvent particles are similar to previous studies with platelets in a mobile solvent. The density profile of polymer chains differs considerably from the platelets in a polymer matrix alone, particularly with its attractive interaction (ii). For the same attractive interaction of solvent and polymer chains with the clay platelets (iii), the solvent particles (the smallest constituents) intercalate the fastest in the clay galleries, whereas the intercalation of polymer chains decreases with their molecular weight. The polymer density profiles, both longitudinal (x) and transverse (y), show maxima peaks around outer platelets (surface) of the layer and decay sharply both in the adjacent galleries and in the bulk. The amplitude of oscillation in the transverse density profiles, a measure of the degree of intercalation, decreases with increasing molecular weight of the polymer. The intercalation of the polymer is driven by its attractive interaction at the low molecular weight, but reduces considerably at high molecular weight because of both entanglement and larger radius of gyration. Variations of the gyration radius of the diffusing polymer chains with molecular weight and interaction with the clay are consistent with the results of their corresponding density profiles. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2487–2500, 2009

The Effects of Electoral Institutions in Rwanda: Why Proportional Representation Supports the Authoritarian Regime

While much has been written about the special design of Rwanda’s judiciary in order to handle the aftermath of the genocide in 1994, other institutional actions resulting from the 2003 constitution have rarely been addressed in research. However, the second (partial) parliamentary elections in September 2008 revealed some of the implications which the carefully designed electoral system has for Rwanda’s political development. As a starting point, the paper emphasises the need to link the debates on institutional design in divided societies with elections in authoritarian regimes. Under different regime types, 'institutional engineers' may pursue different goals. The paper concludes that in the case of Rwanda proportional representation (PR) has been implemented to support undemocratic goals. PR limits the local accountability of politicians in a political environment in which the government is not controlled by a democratic opposition. Thus, Rwanda’s current PR system facilitates the maintenance of authoritarian power in the country, whereas small constituencies would establish closer links between the local populations and their representatives.

Party Coalitions and Interest Group Networks

We analyze affiliation networks of interest groups that endorse the same candidates in primary elections, donate to the same candidates in general elections, and voice support for the same legislative proposals. Patterns of interest group ties resemble two competing party coalitions in elections but not in legislative debate. Campaign endorsement and financial contribution ties among interest groups are consistently correlated but legislative ties do not follow directly from electoral alliances. The results challenge the consensus in the emerging literature on the expanded party organization; interest groups have distinct incentives to join together in a party coalition in elections but also to build bipartisan grand coalitions to pursue legislative goals. We also modify conventional views on party differences. The Democratic coalition is not fractured into many small constituencies. The Democratic campaign and legislative networks are denser than equivalent Republican networks, with a core of labor organizations occupying central positions.

Master techniques in orthopaedic surgery

Paediatric orthopaedics as a specialty is a rather small constituency ( vide infra ) with a limited, some would say austere, textbook literature. For this reason any new material is stimulating. This volume comprises one of the set entitled ‘Master Techniques in Orthopaedic Surgery’. The main

The Semantics and Pragmatics of Clausal Question-Answer Pairs in ASL

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Analysis of the Nucleation and Growth of Amorphous CaCO3by Means of Time-Resolved Static Light Scattering

The formation of amorphous calcium carbonate particles from supersaturated aqueous solution is relevant to many processes in nature and industry. The present work introduces time-resolved static light scattering as a new tool to investigate the initial stage of this process. The process is initiated by mixing a solution of Na(2)CO(3) with a CaCl(2) solution or, alternatively, by mixing solutions of the dimethyl ester of carbonic acid and CaCl(2) with solutions of NaOH. Particle formation was analyzed by recording scattering curves as a function of time. Scattering data indicate the formation of compact spheres with diameters close to 360 nm. In the case of particle formation induced by ester hydrolysis, nucleation sets in after a certain lag time. Particle size is homogeneous, and the growth mechanism corresponds to an addition of ions or small constituent particles to a constant number of growing spheres. An increase of the NaOH concentration, which triggers ester hydrolysis, decreases the lag period prior to the onset of particle formation. An increase of the solution temperature also decreases this lag period. The temperature and NaOH dependent duration of the lag time could successfully be interpreted in terms of the kinetics of the ester hydrolysis. The work establishes time-resolved static light scattering as an efficient tool to investigate the particle formation process of amorphous calcium carbonate.

Parenting Online and Lay Literature on Infant Spanking: Information Readily Available to Parents

ABSTRACT Professional consensus exists against the spanking of infants based on the risk of escalation and injury. Moreover, infants are unable to recognize connections between their behavior and punishment and to modify their behavior in response. However, pediatricians and other health care professionals do not frequently discuss the issue of infant spanking with parents. Meanwhile, parents are increasingly seeking parenting information from other sources including the Internet and lay parenting books. Using content analysis methodology, online parenting sites and popular “how to” parenting books were reviewed with regard to the advisability of corporal punishment with infants. Results reveal that although the vast majority of online and popular print literature on infant parenting is developmentally sound, a small constituency of spanking advocates does exist. Given that some of the information available to parents contradicts professional consensus against the spanking of infants, it seems important for professionals concerned with the well being of infants to address the gaps in information and inherent dangers of infant spanking.

On the Topic of Pseudoclefts

Abstract. This paper presents arguments in favor of a pseudocleft analysis of a certain class of sentences in Malagasy, despite the lack of an overt wh‐element. It is shown that voice morphology on the verb creates an operator‐variable relationship much like the one created by wh‐movement in free relatives in English and other languages. The bulk of the paper argues in favor of an inversion analysis of specificational pseudoclefts in Malagasy: a predicate DP is fronted to a topic position from within a small clause constituent. Moreover, it is shown that the same inversion occurs in equative and specificational sentences in Malagasy, which suggests that these types of sentences share the same syntactic structure. The proposed analysis also provides support for the view that specificational pseudoclefts have a topic &gt; focus structure, where the wh‐clause has been overtly topicalized.

Characterization of micro-flocs of NOM coagulated by PACl, alum and polysilicate-iron in terms of molecular weight and floc size

Micro-flocs of NOM coagulated by polyaluminium chloride (PACl), alum and polysilicate-iron (PSI) were characterized by flocs size, HPSEC-based molecular weight and the captured content of coagulants-based aluminium and iron. Changes in floc composition with respect to the mass ratios of captured NOM to Al and Fe were examined. Lowering water pH to optimum levels was found to be capable of removing small NOM constituents that are generally difficult to be precipitated at neutral pH levels. For PACl and PSI, the distribution of micro flocs (0.1-5.0 microm) reached steady stage after rapid mixing for 30 seconds, with NOM being found existent within the non-coagulated fraction (d<0.1 microm) and the coagulated fraction with floc sizes above 5.0 microm (d >5.0 microm). For alum, however, the existence of NOM inside intermediate floc fractions of d = 0.1-1.0 microm, 1.0-3.0microm and 3.0-5.0 microm was confirmed.

Nanoscale spinel ferrites prepared by mechanochemical route

Among the many types of preparation and processing techniques, the nonconventional mechanochemical route has been recognized as a powerful method for the production of novel, high-performance, and low-cost nanomaterials. Because of their small constituent sizes and disordered structural state, nanoscale materials prepared by mechanochemical route are inherently unstable with respect to structural changes at elevated temperatures. Taking into account the considerable relevance of the thermal stability of nanoscale complex oxides to nanoscience and nanotechnology, in the present work, results on the response of mechanochemically prepared MgFe2O4 and NiFe2O4 to changes in temperature will be presented. Several interesting features are involved in the work, e.g., a relaxation of the mechanically induced cation distribution towards its equilibrium configuration, a disappearance of the superparamagnetism on heating, an increase of both the saturation magnetization and the Neel temperature with increasing particle size, and a core-shell structure of nanoparticles.

DSC approach for the investigation of mobile water fractions in aqueous solutions of NaCl and Tris buffer

The fraction of mobile (unfrozen) water during phase transitions of NaCl–H 2O solution and tris(hydroxymethyl)aminomethane (Tris) buffer solution has been determined by differential scanning calorimetry (DSC). Measurements were carried out in the temperature range between −50 and +30 °C with a heating rate of 2 K min −1. The fraction of mobile water was estimated from the enthalpy of melting of the different frozen phases present in aqueous solution samples. Results are supplemented by proton NMR intensity measurements in the same temperature range. A small endothermic peak was detected in the DSC curves at the same temperature where the change in the NMR intensity occurs. We assume that activation/deactivation of rotational molecular motion of hydration water molecules occurs at the steps of the NMR intensity at higher and lower temperatures during heating and cooling, respectively. The rotational motion is probably the initial stage of the eutectic phase separation. Tris additive to NaCl solution causes thermal shifts of the small endothermic peak and in the related NMR intensity. These qualitative differences indicate interactions of Na + and Cl − ions with the small organic molecule constituents.