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81.
    
Crosslinked oligosilylstyrene–poly(dimethylsiloxane) composite membranes were used to separate 1,2‐dimethoxyethane (1,2‐DME) from dilute aqueous solutions through a pervaporation process. The composite membranes were prepared through the casting of solutions of H‐terminated oligosilylstyrene and vinyl‐terminated poly(dimethylsiloxane) onto the surfaces of polysulfone ultrafiltration membranes. A crosslinked poly(dimethylsiloxane) gel was generated through the reaction of H‐terminated oligosilylstyrene and vinyl‐terminated poly(dimethylsiloxane), with a platinum complex used as a catalyst. The pervaporation characteristics of the composite membranes were investigated with respect to the feed composition of 1,2‐DME, the feed temperature, the downstream pressure, and the top‐layer thickness of the composite membranes. The composite membranes exhibited preferential selectivity to 1,2‐DME. Depending on the operation conditions, the separation factor and permeation rate of 1,2‐DME were 55–184 and 0.31–3.3 g/m2 h, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2284–2294, 2004  相似文献   
82.
    
The first synthesis of a chelating and reactive surfactant derived from citric acid and a short silicone as hydrophobic tail is described. Aqueous solutions of this reactive amphiphile spontaneously induce gold ion reduction, particle nucleation, and further direct crystal growth. The process, both pH and light dependent, occurs through lipid-directed assembly of metal ions, their reduction and subsequent lipid-directed growth to yield ultrathin (approximately 7 nm thick) quasi two-dimensional gold nanocrystals.  相似文献   
83.

In this paper, we propose an optimization model to support decisions related to the design of water distribution systems (WDS) that are subjected to interruptions caused by disruptive events, emphasizing their resilience capabilities, namely: absorption, adaptation, and recovery. Considering the exposure of WDS operation to random interruptions, we aim at minimizing the total investment considering the possibility of implementing actions that improve these capabilities, which can be put in place prior or posterior to the occurrence of a disruptive event. An application example is discussed as a way to understand the nature of the problem and to support the formulation of the proposed model. The results demonstrate the need to invest in resilient capacities adequate to each interruption probability associated to the disruptive scenarios, characterizing these considerations as of great importance to support managerial decisions, thus constituting a guideline for the allocation of investments before and/or after the occurrence of the event.

  相似文献   
84.
The synthesis and grafting to glass or quartz of alkylalkoxysilane coupling agents (RSi(OR′) 3 ) that are susceptible/responsive to oxidation is described. Hydrosilylation of the inexpensive polyolefin squalene occurred efficiently once or twice with the silane HMe 2 SiOSiMe 2 (CH 2 ) 2 Si(OEt) 3 to give a silane coupling agent 3 that possesses several alkene groups. Once grafted to a silica surface Q-Sq using traditional means, the coupling agent was oxidized and further processed in several different ways. First, epoxidation using soluble peracids led to polyepoxides that could be further hydrolyzed to give polyalcohol surfaces Q-Sq-PAA-H 2 O . Alternatively, ozonolysis with gaseous O 3 led to the ozonides Q-Sq-O 3 , which could be decomposed to give either aldehyde/ketone Q-Sq-O 3 -redu , or ketone/carboxylic acid groups Q-Sq-O 3 -H 2 O 2 , respectively, bound to the surface. The aldehyde/ketone groups were characterized by condensation with dinitrophenylhydrazine to give the highly colored hydrazones Q-Sq-O 3 -redu-DNPH . These studies demonstrate the ready portability of organic chemistry to silica (or related) surfaces using judiciously chosen silane coupling agents and the possibility of controlling surface functionalization by postgrafting oxidation.  相似文献   
85.
The porosity of electrodeposited nickel has been measured by an autoradiographic technique after the surface of the copper basis had been prepared by a number of different methods. Statistical analysis of the results shows that porosity is independent of the method of preparation.  相似文献   
86.
In this study, the distinction between complicated and complex is used to shed some light on compliance with best practice guidelines. Data were gathered related to obstetric practice in labor wards and operating theaters at two Scandinavian hospitals, one of them being a university hospital, and in a training facility. The complexity of obstetrical intervention is analyzed in this paper, as is the potential of compliance-based routines in obstetrics. Complex situations are different from complicated ones and patient safety management efforts should recognize and enhance the sort of diversity that helps the emergence of resilience in complex situations.  相似文献   
87.
88.
Therapy with ofloxacin, ciprofloxacin, and lomefloxacin (alone or in combination with clindamycin) and therapy with sparfloxacin, clinafloxacin, and temafloxacin alone were given to mice with subcutaneous abscesses. The abscesses were caused by two Bacteroides fragilis isolates, one of which was susceptible and one of which was resistant to ofloxacin, ciprofloxacin, and lomefloxacin, alone or in combination with Escherichia coli. The abscesses were examined 5 days after inoculation. Numbers of B. fragilis organisms reached log10 10.2 to 11.8 per abscess, and numbers of E. coli organisms reached log10 10.6 to 11.8 per abscess. All of the quinolones reduced the number of susceptible B. fragilis isolates (log10 3.6 to 6.9) and E. coli isolates (log10 5.7 to 6.8). However, ciprofloxacin and lomefloxacin failed to reduce the number of resistant B. fragilis organisms in single-organism or mixed infections. The addition of clindamycin to either ofloxacin, ciprofloxacin, or lomefloxacin reduced the numbers of both susceptible and resistant B. fragilis organisms (log10 3.8 to 7.8). In contrast, sparfloxacin, clinafloxacin, and temafloxacin were effective as single therapy in eradicating B. fragilis resistant to ofloxacin, ciprofloxacin, and lomefloxacin. These in vivo data confirm the in vitro activity of these quinolones and suggest that although ofloxacin, ciprofloxacin, and lomefloxacin are occasionally effective as single agents in eradicating mixed infection by susceptible strains of B. fragilis and E. coli, addition of an agent with activity against anaerobic organisms will ensure their efficacy. Quinolones with good efficacy against B. fragilis may be effective as single-agent therapy of mixed infections.  相似文献   
89.
Opportunistic bacterial infections are the predominant cause of death following myelosuppressive radiation exposure. When used alone, a variety of immunomodulators and antibiotics have been reported to reduce radiation-induced death. In these studies, the combined therapeutic effects of the immunomodulator glucan and the quinolone antibiotic pefloxacin were evaluated for survival-enhancing effects in myelosuppressed C3H/HeN mice. Mice were exposed to 7.9 Gy of whole-body 60Co radiation and treated with saline, glucan (250 mg/kg of body weight intravenously, 1 h after irradiation), pefloxacin (64 mg/kg/day orally, days 3 to 24 after irradiation), or glucan plus pefloxacin. Survival 30 days after irradiation in mice receiving these respective treatments was 25, 48, 7, and 85%. Evaluation of granulocyte-macrophage progenitor cell (GM-CFC) recovery in mice receiving these treatments revealed that, compared with recovery in saline-treated mice, glucan stimulated GM-CFC recovery, pefloxacin suppressed GM-CFC recovery, and glucan administered in combination with pefloxacin could override pefloxacin's hemopoietic suppressive effect.  相似文献   
90.
We describe the design, development, and evaluation of a personal digital music library application designed to assist musicians in capturing, developing, and managing their musical ideas over time. The target user group is musicians who primarily use audio and text for composition and arrangement, rather than with formal music notation. The software design was guided by a formative user study which suggested five requirements for the software to support: capturing, overdubbing, developing, archiving, and organizing. This led to a spatial hypermedia approach forming the basis for the developed application. Furthermore, the underlying spatial data-model was exploited to give raw audio compositions a hierarchical structure, and—to aid musicians in retrieving previous ideas—a search facility was provided to support both query by humming and text-based queries. A user evaluation of the implemented environment indicated that the target musicians would find the hypermedia environment useful for capturing and managing their moments of musical creativity. More specifically, they would make use of the query by humming facility and the hierarchical track organization, but not the overdubbing facility as implemented.  相似文献   
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