A novel anionic surfactant templating route for synthesizing mesoporous silica with unique structure

Anionic surfactants are used in greater volume than any other surfactants because of their highly potent detergency and low cost of manufacture. However, they have not been used as templates for synthesizing mesoporous silica. Here we show a templating route for preparing mesoporous silicas based on self-assembly of anionic surfactants and inorganic precursors. We use aminosilane or quaternized aminosilane as co-structure-directing agent (CSDA), which is different from previous pathways. The alkoxysilane site of CSDA is co-condensed with inorganic precursors; the ammonium site of CSDA, attached to silicon atoms incorporated into the wall, electrostatically interacts with the anionic surfactants to produce well-ordered anionic-surfactant-templated mesoporous silicas (AMS). These have new structures with periodic modulations as well as two-dimensional hexagonal and lamellar phases. The periodic modulations may be caused by the coexistence of micelles that differ in size or curvature, possibly owing to local chirality. These mesoporous silicas provide a new family of mesoporous materials as well as shedding light on the structural behaviour of anionic surfactants.     

Effects of including a quantitative trait locus in selection under different waiting plans of young bulls

The advantage of using the genotype of a quantitative trait locus (QTL) in selection schemes of dairy cattle was quantified using stochastic simulation. Three selection plans were studied. In the first plan, young bulls waited for 3 yr until their sisters completed a lactation and then were evaluated and selected based on an animal model. In a second plan, young bulls waited for 5 yr until their daughters completed a lactation. An intermediate 4-yr waiting plan was also studied. Simulation was for 16 yr with overlapping generations. Population and model parameters were proportional to the U.S. Holstein population. The advantage of using a QTL was quantified as the percentage of superiority of QTL-assisted over QTL-free selection using cumulative genetic response. Percentage of superiority was reported for four selection pathways: active sires, young bulls, bull dams, and first lactation cows. A general trend was observed: low superiority in early years of selection that increased to a plateau in later years and then decreased. The superiority of the QTL information was greatest in the 3-yr waiting plan and least in the 4-yr waiting plan. Superiority at plateau for selection pathways ranged from 16 to 26% for the 3-yr waiting plan, from 3 to 12% for the 4-yr waiting plan, and from 5 to 13% for the 5-yr waiting plan. The contribution to selection response attributed to the QTL and the polygenes was quantified. The rate at which the favorable allele approached fixation and the accuracy of predicting breeding values on the percentage of superiority were studied.     

A factorial analysis of silanization conditions for the immobilization of oligonucleotides on glass surfaces

The modification of glass surfaces with (3-mercaptopropyl)trimethoxysilane and the application of this to DNA chip technology are described. A range of factors influencing the silanization method, and hence the number of surface-bound, chemically active thiol groups, were investigated using a design of experiment approach based on analysis of variance. The number of thiol groups introduced on glass substrates were measured directly using a specific radiolabel, [14C]cysteamine hydrochloride. For liquid-phase silanization, the number of surface-bound thiol groups was found to be dependent on both postsilanization thermal curing and silanization time and relatively independent of silane concentration, reaction temperature, and sample pretreatment. Depending on the conditions used in liquid-phase silanization, (1.3-9.0) x 10(12) thiol groups/cm2 on the glass samples were bound. The reliability and repeatability of liquid- and vacuum-phase silanization were also investigated. Eighteen-base oligonucleotide probes were covalently attached to the modified surfaces via a 3'-amino modification on the DNA and subsequent reaction with the cross-linking reagent N-(gamma-maleimidobutyryloxy) succinimide ester (GMBS). The resulting probe levels were determined and found to be stoichiometric with that of the introduced thiol groups. These results demonstrate that silanization of glass surfaces under specific conditions, prior to probe attachment, is of great importance in the development of DNA chips that use the simple concept of the covalent attachment of presynthesized oligonucleotides to silicon oxide surfaces.     

Attenuated total reflection design for in situ FT-IR spectroelectrochemical studies

A versatile spectroelectrochemical apparatus is introduced to study the changes in IR spectra of organic and inorganic compounds upon oxidation or reduction. The design is based on an attenuated total reflection device, which permits the study of a wide spectral range of 16,700 (600 nm)-250 cm(-1), with a small opaque region of 2250-1900 cm(-1). In addition, an IR data collection protocol is introduced to deal with electrochemically nonreversible background signals. This method is tested with ferrocene in acetonitrile; concentrations as low as 1 mM produce results that agree with those in the literature.     

Photon correlation and scattering: introduction to the feature issue

This feature issue of Applied Optics contains 31 research papers on photon correlation and scattering, many of which were presented at an OSA Topical Meeting that was held 21-23 August 2000 in Whistler, British Columbia, Canada. These papers focus on research in dynamic light scattering, surface light scattering, photon correlation, and laser velocimetry and their applications to physical, chemical, and biological processes.     

Evidence against the non-enzymatic calcium theory of tenderization

The objective of the present study was to determine whether variation in the tenderization of lamb longissimus could be attributed to variations in the rise in free calcium postmortem and sarcomere lengthening post rigor. The longissimus muscle of 10 crossbred lambs (Romney×Coopworth) was sampled at 1 and 7 days postmortem for determination of MIRINZ shear force, myofibrillar fragmentation index (MFI), sarcomere length, free calcium, and proteolysis of troponin-T. Despite considerable variation in tenderness and tenderization of the muscles, sarcomere lengthening was not observed. The concentration of free calcium at 7 days postmortem correlated significantly with the MFI (r=0.640; P<0.05) and tended to correlate with the shear force (r=−0.596; P<0.1) and degradation of troponin-T (r=0.625; P<0.1). Degradation of troponin-T was significantly correlated with tenderization (r=0.664; P<0.05). Troponin-T is a calpain substrate, but reportedly is not degraded through a direct effect from calcium. The present results, therefore, suggest that the variation in free calcium in postmortem muscle affects tenderization through an effect on the calpain system and not through a direct effect of calcium on myofibrillar proteins. Consequently, the results of this study do not support the (calcium) theory that calcium directly affects tenderization.     

In vitro injury model for oligodendrocytes: development, injury, and recovery

In this study we investigated the effects of severe hypothermia (cryoinjury) on oligodendrocyte (OL) cell marker expression and morphological features. We used a chemically defined cell culture medium, glial development medium (GDM), which favored the optimal expression of the OL phenotype in CG4 cells. Experiments using CG4 cells cultured in 2% serum or in GDM were conducted in parallel. After severe hypothermia, cells were reanimated at 37 degrees C and 4.5% CO(2) and cultured in either GDM or in medium supplemented with 2% serum. In either medium, around 70% of the total number of cells detached within 2 to 4 hours following reanimation. Oligodendroglial markers such as A2B5, O4, Tf, ferritin, tubulin, and MBP were examined by double and triple immunofluorescence. All of these markers except MBP re-appeared at different times during the recovery period for up to 48 hours. Glial fibrillary acidic protein (GFAP) and heat shock protein 60 (HSP-60) were used as injury markers. The presence of serum induced HSP-60 expression, while GDM did not. All CG4 cells expressed HSP-60 in response to hypothermia independently of the cell culture medium used. Cryoinjury induced a spectrum of morphological changes in CG4 cells. The expression of OL specific markers was also influenced by hypothermia. Moreover both, serum and cryoinjury induced the expression of HSP-60 that colocalized with OL and myelin markers. The expression of GFAP by injured cells but not by normal cells corroborated the state of injury of CG4 cells.     

Interaction of Perchloroethylene with Cerium Oxide in Three-Way Catalysts

The role of cerium oxide on direct oxidation of perchloroethylene (PCE) by a three-way catalyst was explored. In the absence of an external oxidizing agent, PCE was oxidized over an alumina supported Pt/Rh three-way catalyst. We hypothesize that the chlorine atoms in the adsorbed PCE interact with oxygen in CeO(2), reducing the cerium to create CeCl(3).     

铂族金属的精炼法

由于铂族金属(PGM)的价格昂贵和尖端技术领域对它的需求量日益增加,激发了人们从一次物料和二次物料中回收和分离铂族金属的兴趣。一些传统的精炼法已逐渐被较新的、更为有效的分离方法,诸如溶剂萃取法和离子交换法所取代。本文对经典精炼法和现代精炼法作了评述,还分别讨论了与这些方法有关的溶液化学。着重介绍了现代分离法在技术上的各种优点,并提供了从一次物料和二次物料中回收PGM的参考文献。