Gold nanocages: synthesis, properties, and applications

Noble-metal nanocages comprise a novel class of nanostructures possessing hollow interiors and porous walls. They are prepared using a remarkably simple galvanic replacement reaction between solutions containing metal precursor salts and Ag nanostructures prepared through polyol reduction. The electrochemical potential difference between the two species drives the reaction, with the reduced metal depositing on the surface of the Ag nanostructure. In our most studied example, involving HAuCl(4) as the metal precursor, the resultant Au is deposited epitaxially on the surface of the Ag nanocubes, adopting their underlying cubic form. Concurrent with this deposition, the interior Ag is oxidized and removed, together with alloying and dealloying, to produce hollow and, eventually, porous structures that we commonly refer to as Au nanocages. This approach is versatile, with a wide range of morphologies (e.g., nanorings, prism-shaped nanoboxes, nanotubes, and multiple-walled nanoshells or nanotubes) available upon changing the shape of the initial Ag template. In addition to Au-based structures, switching the metal salt precursors to Na(2)PtCl(4) and Na(2)PdCl(4) allows for the preparation of Pt- and Pd-containing hollow nanostructures, respectively. We have found that changing the amount of metal precursor added to the suspension of Ag nanocubes is a simple means of tuning both the composition and the localized surface plasmon resonance (LSPR) of the metal nanocages. Using this approach, we are developing structures for biomedical and catalytic applications. Because discrete dipole approximations predicted that the Au nanocages would have large absorption cross-sections and because their LSPR can be tuned into the near-infrared (where the attenuation of light by blood and soft tissue is greatly reduced), they are attractive materials for biomedical applications in which the selective absorption of light at great depths is desirable. For example, we have explored their use as contrast enhancement agents for both optical coherence tomography and photoacoustic tomography, with improved performance observed in each case. Because the Au nanocages have large absorption cross-sections, they are also effective photothermal transducers; thus, they might provide a therapeutic effect through selective hyperthermia-induced killing of targeted cancer cells. Our studies in vitro have illustrated the feasibility of applying this technique as a less-invasive form of cancer treatment.     

Estimation of the effect of food irradiation on total dietary vitamin availability as compared with dietary allowances: study for Argentina

The purpose of this work was to evaluate whether irradiation treatment of all foods, for which this treatment is of recognised technological usefulness, would have any detrimental effect on total dietary vitamin availability for consumption by the Argentinian population. Per capita availability of foods produced in or imported into Argentina that could be usefully irradiated and which are usually consumed in the country was recorded from FAO food balance sheets. The vitamin content of the foods and the vitamin losses occurring under good irradiation practices were gathered from the literature. The nutritional impact of vitamin losses due to irradiation was estimated by comparing results to the Recommended Dietary Allowances of the US National Research Council. The vitamins studied were: A, D, E, K, ascorbic acid, thiamine, riboflavin, niacin, pyridoxine, biotin, cyanocobalamin, folacin and pantothenic acid. Results showed that, even if irradiation was applied to every food which could be usefully treated, vitamin availabilities would exceed 100% of the respective RDA and so no adverse nutritional impact would be expected, except for folacin and vitamin D. However, typical availabilities of folate and vitamin D are less than the RDA. Synthesis of vitamin D in the skin from 7-dehydrocholesterol would suggest no nutritional problem. Available data on folic acid losses due to food irradiation are incomplete and suggest the need for further experimental research. © 1998 SCI.     

The stability of personality traits in individuals with borderline personality disorder.

Although stability and pervasive inflexibility are general criteria for Diagnostic and Statistical Manual of Mental Disorders, 4th edition (American Psychiatric Association, 1994) personality disorders (PDs), borderline PD (BPD) is characterized by instability in several domains, including interpersonal behavior, affect, and identity. The authors hypothesized that such inconsistencies notable in BPD may relate to instability at the level of the basic personality traits that are associated with this disorder. Five types of personality trait stability across 4 assessments over 6 years were compared for BPD patients (N = 130 at first interval) and patients with other PDs (N = 302). Structural stability did not differ across groups. Differential stability tended to be lower for 5-factor model (FFM) traits in the BPD group, with the strongest and most consistent effects observed for Neuroticism and Conscientiousness. Growth curve models suggested that these 2 traits also showed greater mean-level change, with Neuroticism declining faster and Conscientiousness increasing faster, in the BPD group. The BPD group was further characterized by greater individual-level instability for Neuroticism and Conscientiousness in these models. Finally, the BPD group was less stable in terms of the ipsative configuration of FFM facet-level profiles than was the other PD group over time. Results point to the importance of personality trait instability in characterizing BPD. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Information sharing and team performance: A meta-analysis.

Information sharing is a central process through which team members collectively utilize their available informational resources. The authors used meta-analysis to synthesize extant research on team information sharing. Meta-analytic results from 72 independent studies (total groups = 4,795; total N = 17,279) demonstrate the importance of information sharing to team performance, cohesion, decision satisfaction, and knowledge integration. Although moderators were identified, information sharing positively predicted team performance across all levels of moderators. The information sharing–team performance relationship was moderated by the representation of information sharing (as uniqueness or openness), performance criteria, task type, and discussion structure by uniqueness (a 3-way interaction). Three factors affecting team information processing were found to enhance team information sharing: task demonstrability, discussion structure, and cooperation. Three factors representing decreasing degrees of member redundancy were found to detract from team information sharing: information distribution, informational interdependence, and member heterogeneity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On fracture testing of piezoelectric ceramics

Fracture tests carried out on unpoled and poled PZT-5H four-point bend specimens are presented in this paper. The crack faces were parallel to the poling direction. Both mechanical loads and electric fields were applied to the poled specimens. The experimental results were analyzed by means of the finite element method and a conservative M-integral including the crack face boundary conditions. Fracture tests on four-point bend PIC-151 specimens with the crack faces perpendicular to the poling directions were also analyzed here; the experimental results were taken from the literature. A mixed mode fracture criterion is proposed for piezoelectric ceramics. This criterion is based upon the energy release rate and two phase angles. This criterion was implemented with experimental results from the literature and from this investigation. Excellent agrement was found between the fracture curve and the experimental results of the specimens with the crack faces perpendicular to the poling direction. With some scatter, reasonable agreement was observed between the fracture curve and the experimental results of the specimens with crack faces parallel to the poling direction.     

Fatty acid composition of macrophage phospholipids in mice fed fish or borage oil

The polyunsaturated fatty acid (PUFA) composition of murine peritoneal macrophage phospholipids was dramatically altered in vivo following the four-wk feeding of specific dietary oils. Fish oil (containing 20∶5n–3 and 22∶6n−3) feeding significantly increased macrophage 20∶5n−3, 22∶5n−3, and 22∶6n−3 (P<0.05), while borage oil (containing 18∶2n−6 and 18∶3n−6) increased (P<0.05) the macrophage 20∶3n−6/20∶4n−6 ratio, relative to safflower oil (containing 18∶2n−6) and hydrogenated coconut oil (containing 12∶0)-fed animals. The macrophage phospholipid PUFA profiles were compared with those of the liver, lung and spleen. The significance of the PUFA alterations is discussed.     

Sorghum Allelopathy—From Ecosystem to Molecule

Sorghum allelopathy has been reported in a series of field experiments following sorghum establishment. In recent years, sorghum phytotoxicity and allelopathic interference also have been well-described in greenhouse and laboratory settings. Observations of allelopathy have occurred in diverse locations and with various sorghum plant parts. Phytotoxicity has been reported when sorghum was incorporated into the soil as a green manure, when residues remained on the soil surface in reduced tillage settings, or when sorghum was cultivated as a crop in managed fields. Allelochemicals present in sorghum tissues have varied with plant part, age, and cultivar evaluated. A diverse group of sorghum allelochemicals, including numerous phenolics, a cyanogenic glycoside (dhurrin), and a hydrophobic p-benzoquinone (sorgoleone) have been isolated and identified in recent years from sorghum shoots, roots, and root exudates, as our capacity to analyze and identify complex secondary products in trace quantities in the plant and in the soil rhizosphere has improved. These allelochemicals, particularly sorgoleone, have been widely investigated in terms of their mode(s) of action, specific activity and selectivity, release into the rhizosphere, and uptake and translocation into sensitive indicator species. Both genetics and environment have been shown to influence sorgoleone production and expression of genes involved in sorgoleone biosynthesis. In the soil rhizosphere, sorgoleone is released continuously by living root hairs where it accumulates in significant concentrations around its roots. Further experimentation designed to study the regulation of sorgoleone production by living sorghum root hairs may result in increased capacity to utilize sorghum cover crops more effectively for suppression of germinating weed seedlings, in a manner similar to that of soil-applied preemergent herbicides like trifluralin.     

专业精神与行业竞争力:以香港为例谈如何确立风景园林行业之专业地位

自20世纪末以来,我国内地的风景园林行业正在经历着快速和深远的专业化变革.试图探讨在风景园林行业和风景园林教育的专业化进程中如何逐步确立行业的专业地位和专业精神,制订专业操守和行为准则,并保证专业教育中的课程设置和教学模式既务实,又能实现风景园林学科在学术和知识体系上的进步.以香港为例,说明了行业竞争力和专业精神之间的关系,以及如何通过制订园境师专业操守、教学评估制度和园境师注册考试制度,加强行业规范,提升行业的国际竞争力.     

Alkaline hydrothermal zeolites synthesized from high SiO2 and Al2O3 co-disposal fly ash filtrates

A co-disposal reaction was used wherein fly ash (FA) was reacted with acid mine drainage (AMD), to collect filtrates for zeolite synthesis. Raw fly ash as well as fly ash leached with HCl were subjected to the same alkaline hydrothermal zeolite synthesis conditions, as for the co-disposal filtrates, in order to evaluate the zeolitic material obtained. The Si and Al contents of the fly ash (FA) filtrates were used as precursor species for the alkaline hydrothermal conversion of the fly ash filtrates into zeolites. These filtrates were then analysed by XRF spectrometry for quantitative determination of SiO₂ and Al₂O₃. The [SiO₂]/[Al₂O₃] ratio obtained in the filtrates range from 1.4 to 2.5. The [SiO₂]/[Al₂O₃] ratio was used to predict whether the fly ash filtrates could successfully be converted into faujasite zeolitic material by the adopted synthesis procedures. If the [SiO₂]/[Al₂O₃] ratio is higher than 1.5 in the co-disposal filtrates, it favours the formation of faujasite. The zeolite synthesis included an alkaline fusion of the co-disposal filtrates, followed by aging for 8 hours and hydrothermal conversion by crystallisation at 100 °C. Different variables were investigated during the synthesis of zeolite to ascertain their influence on the end product. These variables include adding different amounts of deionised water to the FA-related starting material, using different compositions of FA related starting material and different FA:NaOH ratios in fusing the starting material.