Distribution of polychlorinated dibenzo-p-dioxins and dibenzofurans in various sizes of airborne particles

We investigated the particle size distribution of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) in atmospheric samples collected at four sites. The largest amounts of particle-bound PCDD/F were found on small particles with aerodynamic diameters (dae) of less than 1.1 microns that accounted for over 50% of the total PCDD/F, contributing mostly to the toxicity and providing over 47% of the total TEQs (Toxicity Equivalents) loading. PCDF showed about twice the concentration of the PCDD in the total TEQs. The total PCDD/F concentration for accumulation mode particles (dae < 1.1 microns) ranged from 8.2 to 16 pg/m3 and that on coarse particles (dae > 1.1 microns) from 3.5 to 8.6 pg/m3. Five to eight percent of the total PCDD/F was found on large particles of dae > 7 microns. It was observed that the PCDD/F homologue profiles on large particles were different from the small particles and the fraction of less chlorinated PCDD/F in the homologue groups increased with increasing particle size. The reentrainment of soil particles including PCDD/F did not significantly influence the PCDD/F on the large particles. Two plausible mechanisms, the mass transfer of the gas phase PCDD/F on the particle surface and the contribution of the large size fly ash emitted from incinerators are proposed to explain the observed PCDD/F homologues partitioning among particle size fractions.     

氯酸钠浸金试验及应用

本文介绍了用氯酸钠浸出银电解阳极泥中金的试验情况,讨论了影响金浸出率的因素,提出了氯酸钠浸金的最佳技术条件以及在生产应用中出现的问题和解决的办法,对氯气和氯酸钠浸金经济技术指标作了对比,认为用氯酸钠代替氯气,技术上是可行的,经济上是合理的。     

Studies on gold elution and electrowinning using sodium carbonate media

Laboratory-scale experiments on gold elution and electrolysis in sodium carbonate media were performed. The effect of solution composition, flow rate, and acid washing on the elution of gold from loaded carbons was studied. Both laboratory and plant loaded carbons were evaluated for their elution behaviour. It was found that the percent of gold eluted was greatly influenced by the temperature, acid concentration, and residence time of the acid washing step.The concentration of sodium carbonate affects the elution of the gold. In some cases, a mixture of sodium carbonate and sodium hydroxide was more effective than sodium carbonate alone.The electrolysis behaviour of some plant was studied to ascertain whether problems with anode corrosion, scale formation and poor gold deposition kinetics were associated with the medium properties or the process practice. It was found that the solution composition had to be compatible with both elution and electrowinning to avoid disruption of the gold mill circuit.     

用氢氧化钠提高泡塑富集金能力的探讨

研究了用氢氧化钠处理的泡塑在分离富集金过程中回收率，吸附范围及金在分析过程中的分布情况，研究表明用氢氧化钠处理的泡塑回收率高，富集能力强，并据金的分布情况对影响泡塑富集能力的原因进行了探讨，为泡塑分离富集金的分析提供了一种新的泡塑预处理方法。     

Optical slicing and 3-D characterization of hippocampal capillaries in the rat visualized by autometallographic silver enhancement of colloidal gold particles

In order to visualize the vascular system of the rat brain, 10 Wistar rats were perfused transcardially with glutaraldehyde and a 40 degrees C gold-gelatine solution. The brains were post-fixed with glutaraldehyde and vibratomized into 100-micron-thick slices, and the gold particles were developed by autometallography. In this way, the colloidal gold particles in the vessels became encased in silver and thereby made visible. The developed gold staining is stable and does not interfere with further dehydration and counterstaining. Images were frame grabbed during optical slicing, and classic stereograms and 'shadow' 3-D images were produced. We found a high variation of capillary density in the hippocampal region reflecting known subregional structures. The silver-enhanced vessels acted as natural markers and made it possible to study and measure aspects of the complexity of dehydration and staining artifacts. We found a non-linear shrinking of 13-17% in the x- and y-directions and a spatial shrinking up to 50% in some regions after the dehydration and staining process. This observation may be of interest not only in relation to tissue subjected to this fixation protocol but also to other fixation procedures. The gold-gelatine autometallographic technique and the present stereograms can release data for stereological use as well.     

MR angiography of aneurysm models of various shapes and neck sizes

PURPOSE: To investigate the signal intensity of lateral and terminal saccular aneurysm models with differing neck sizes using three-dimensional time-of-flight (TOF) MR angiography with various imaging parameters. METHODS: The study included four lateral and four terminal saccular aneurysm models with pulsatile flow. The height and fundus diameter were 10 mm; the neck diameters were 2.5 mm, 5 mm, 7.5 mm, and 10 mm, respectively. Each aneurysm model was examined with fast imaging with steady-state precession MR sequences with parameters of 20-140/7 (repetition time/echo time) and flip angles of 10 degrees to 30 degrees. Signal intensity was measured and compared among the models. RESULTS: Three-dimensional TOF MR angiography with the shorter repetition time and/or larger flip angle showed weaker signal intensity in the aneurysm models. Stronger signal intensity was obtained in the terminal saccular aneurysm models and/or the models with a wider neck than in the lateral saccular aneurysm models and/or the models with a narrower neck. In some aneurysm models, longer repetition times produced greater signal intensity than that of background brain models, but not in aneurysms with narrow necks. CONCLUSION: Noncontrast 3-D TOF MR angiography delineated terminal saccular aneurysms and/or aneurysms with wider necks and did not delineate lateral saccular aneurysms and/or aneurysms with narrower necks. Longer repetition times are recommended to allow the spins flowing into the aneurysms to recover.     

Graphical and statistical comparison of various size distribution measurement systems using metal powders of a range of sizes and shapes

Abstract

The purpose of this paper was to describe the results of particle size analysis from image analysis, sieving analysis and dry or wet dispersion laser diffraction and compare these techniques. Measurements were made on particle systems of different morphological characteristics, size and particle size distribution widths using the most common metal powders. The results show reasonably good agreement between the different techniques concerning the shape of the distribution. However, there is a discrepancy regarding the absolute values, which can be explained by the fact that the techniques used are based on different measuring principles. The study suggests that image analysis is a powerful tool in characterising non-spherical particles, especially elongated particles and that caution needs to be taken when evaluating the sizing results of non-spherical particles using laser diffraction.     

添加亚硫酸钠焙烧-氰化提高金、银回收率的试验研究

进行了添加亚硫酸钠焙烧—氰化浸出金、银的工艺试验研究。试验结果表明，在矿样中加入1％～3％亚硫酸钠进行焙烧。可使焙烧一氰化工艺金、银的浸出率分别提高2％和25％以上。     

含锑难处理金精矿加压氧化法制备焦锑酸钠的工艺研究

锑及其化合物是重要的战略物资,焦锑酸钠被广泛应用于玻璃行业。锑金矿是难处理金矿的一种,直接氰化浸出时金的浸出率极低,需要进行预处理后才能提取金。针对某矿山含锑较低的难处理金精矿的特点,并结合目前难处理金矿的各种预处理方法的优缺点,研究确定了该类难处理金精矿适宜采用先回收锑再回收金的思路,即以含锑难处理金矿为原料,采用硫化钠浸出法优先分离锑,使锑以硫代亚锑酸钠形式进入滤液,然后采用加压氧化新工艺以焦锑酸钠产品的形式回收锑,氧化后的滤液经过净化和浓缩结晶后产出硫代硫酸钠产品,脱除锑后的浸出渣用细菌氧化预处理,最后用氰化法从细菌氧化渣中提取金,从而实现难处理金精矿中锑、硫、金的综合回收。     

Preparation and properties of polymeric colloidal crystals containing rare earth complexes

Rare earth organic complexes were introduced into the polymerization system, and the polymeric colloidal nanospheres containing rare earth complexes were prepared by emulsion copolymerization. The characterization results indicated that the polymeric spheres were small at nanometer size and the diameter was monodisperse, particularly the nanospheres possessed good fluorescent properties. Moreover, the polymeric nanospheres were self-assembled to fabricate the colloidal crystals, which were three-dimensional regular multilayer films. The polymeric colloidal crystal films exhibited excellent luminescent and novel optical properties.