Maximum Diffusion Distance Research Articles

Study on Ratio Optimization and Diffusion-Gelation Process of Polymer Grouting Materials for Fracture Filling in Underground Mines.

The existence of fissures poses a serious threat to the safe production of underground mines, and this paper investigates a polymer grouting material for filling fissures in underground mines. To optimise the ratio of polymer grouting materials, this paper designed 16 test groups using the orthogonal test method to find the most reasonable slurry ratio. In order to study the gel diffusion process of polymer slurry in the fissure and to explore the changes of various parameters of the slurry after injection, simulated grouting tests were carried out, and the distribution laws of viscosity, pressure, and diffusion distance of the slurry were discussed. The findings indicate that when the proportion of ethylenediamine polypropylene oxide tetrol: glycerol polyether: catalyst: foam stabiliser is 10:8:0.5:0.4, the polymer grouting material has excellent compressive strength, and the maximum compressive strength can reach 12.31 MPa. Prior to reaching the gel time point, the viscosity of the polymer slurry was nearly constant, which is basically maintained at 0.772 Pa·s under normal temperature and pressure, but after reaching the gel time point, it abruptly rose. As the slurry mass increased, so did the penetration distance and pressure; in the simulated grouting test, when the slurry mass was 400 g, the maximum diffusion distance of the slurry reached 39 cm. Conversely, as the fracture pore size increased, the diffusion distance and pressure of the slurry decreased. Along the diffusion path, the slurry pressure progressively drops, but this change is not synchronised with the diffusion distance's change. This work can serve as a reference for the configuration of polymer slurry and aid in comprehending the diffusion law of the slurry within the fissure.

Study on Microstructure, Mechanical Performance and Thermal Shock Resistance of Diffusion Welded Joint of ODS-W and TZC Alloy

The diffusion welded joint of oxide dispersion strengthened tungsten (ODS-W) and Mo-Ti-Zr-C alloy (TZC) was successfully fabricated with the use of spark plasma sintering (SPS) at a vacuum level of 10 Pa. This study systematically investigates the microstructure, mechanical performance, and thermal shock resistance of the ODS-W/TZC connector at four different temperatures, ranging from 1300 to 1600 °C. The diffusion distance between the W and Mo atoms at the interface of ODS-W/TZC joint raises as the sintering temperature increases, with a maximum diffusion distance of up to 2 μm at 1500 °C, but then slightly decreases at 1600 °C. The ODS-W/TZC connector bonded at 1500 °C exhibits the best tensile performance, with tensile strengths of 459 MPa and 786 MPa at room temperature and 500 °C, respectively. A maximum hardness of 446 HV is obtained at the interface when the sample is sintered at 1600 °C. Thermal shock tests are conducted on the surface and interface of the ODS-W/TZC connector sintered at various temperatures. ODS-W/TZC samples prepared below 1500 °C were severely damaged, leading to exfoliation after laser thermal shock, while samples prepared above 1500 °C produced fewer damage cracks. Confocal laser scanning microscope (CLSM) analysis demonstrated that the ODS-W/TZC joint fabricated at 1500 °C exhibited substantially reduced height perturbation of both its surface and interface compared to that of ODS-W, providing evidence for its superior thermal shock resistance.

Characterizing and comparing microbial community and biofilm structure in three nitrifying moving bed biofilm reactors

This study investigated biofilm establishment, biofilm structure, and microbial community composition of biofilms in three laboratory-scale moving bed biofilm reactors. These reactors were filled with three types of plastic carriers with varied depths of living space for microbial growth. The reactors were operated under the same influent and operational conditions. Along with the operation, the results showed that carriers with grids of 50 μm in height delayed the biofilm development and formed the thinnest biofilm and a carpet-like structure with the lowest α-diversity. In comparison, another two carriers with grids of 200 and 400 μm in height formed thick biofilms and large colonies with more voids and channels. Quantified properties of biofilm thickness, biomass, heterogeneity, portion of the biofilm exposed to the nutrient, and maximum diffusion distance were examined, and the results demonstrated that they almost (except for heterogeneity) strongly correlated to the α-diversity of microbial community. These illustrate that depth of living space, as an important parameter for carrier, could drive the formation of biofilm structure and community composition. It improves understanding of influencing factors on biofilm establishment, structure and its microbial community, and would be helpful for the design of biofilm processes.

Uranium migration through the Swiss Opalinus Clay varies on the metre scale in response to differences of the stability constant of the aqueous, ternary uranyl complex Ca<sub>2</sub>UO<sub>2</sub>(CO<sub>3</sub>)<sub>3</sub>

Abstract. The simulation of uranium migration through the Swiss Opalinus Clay is used as an example to quantify the influence of varying values of a stability constant in the underlying thermodynamic database on the migration lengths for the repository scale. Values for the stability constant of the neutral, ternary uranyl complex Ca2UO2(CO3)3 differ in literature by up to one order of magnitude. Within the studied geochemical system, either the neutral or the anionic complex CaUO2(CO3)32- is the predominant one, depending on the chosen value for the neutral complex. This leads to a changed interaction with the diffuse double layers (DDL) enveloping the clay minerals and thus can potentially influence the diffusive transport of uranium. Hence, two identical scenarios only differing in the value for the stability constant of the Ca2UO2(CO3)3 complex were applied in order to quantify and compare the migration lengths of uranium on the host rock scale (50 m) after a simulation time of one million years. We ran multi-component diffusion simulations for the shaly and sandy facies in the Opalinus Clay. A difference in the stability constant of 1.33 log units changes the migration lengths by 5 to 7 m for the sandy and shaly facies, respectively. The deviation is caused by the anion exclusion effect. However, with a maximum diffusion distance of 22 m, the influence of the stability constant of the Ca2UO2(CO3)3 complex on uranium migration in the Opalinus Clay is negligible on the host rock scale.

A Study on the Prediction of Hazardous Areas of Sulfuric Acid Leakage

Sulfuric acid is used for various purposes in industry, but research on sulfuric acid accidents is lacking. Thus, to prepare safety measures, it is necessary to analyze the risk distance for such accidents, particularly sulfuric acid leaks. As part of this study, 112 scenarios of varying wind speeds and leakage amounts were prepared and a risk-distance analysis was carried out at an industrial plant. The scenarios were then analyzed based on hazard concentrations. The analysis revealed that if the entire amount of sulfuric acid leaked from the industrial plant, it spread up to 9,978 m at a wind speed of 6 m/s. Residential areas were also included within the maximum diffusion distance, and it was confirmed that the leak also affected neighboring administrative districts. Therefore, it is necessary to prepare a plan to prevent and respond to sulfuric acid leakage accidents in industrial complexes.

Fissure Grouting Mechanism Accounting for the Time-Dependent Viscosity of Silica Sol.

Subject to the complex hydrogeological environment where underground engineering is located, the grouting prevention and control of microfissure water ingress are increasingly strict. Silica sol grout has been increasingly used in field tests because of its fine particles and good injectability. Therefore, it is necessary to examine the time-dependent viscosity of silica sol grout and clarify its diffusion law in a rock fissure. In this study, the time dependence of the viscosity of silica sol grout was studied, and then the grout viscosity was subdivided into a slow growth period, accelerated growth period, and rapid curing period according to the growth rate. The effects of the concentration of colloidal silica suspension, the concentration of accelerant, and the mixing volume ratio of the two on the growth of the slurry viscosity were studied. A parameter λ was introduced to comprehensively characterize the influence of the three factors on the rheological properties of the slurry. The relationship between the gel induction time and λ and the accelerating growth stage of the slurry gel was obtained by data fitting. The time-dependent equation of the silica sol solution was established. The difference in the grouting diffusion law between silica sol grout and cement–sodium silicate grout (C-S grout) is compared and analyzed by a stepwise calculation method under two grouting modes (constant-pressure grouting and constant-rate grouting). The results show that under the condition of constant-pressure grouting, the silica sol grout migrates and diffuses continuously for a long time, while the C-S grout is close to the final diffusion form at 15–20 s, and the maximum diffusion distance is much smaller than that of silica sol grout. Under the condition of constant-rate grouting, the grouting pressure driving C-S grout increases sharply with time. Compared with C-S grout, silica sol grout has the obvious advantages of a longer effective diffusion time and lower energy consumption. The research results have certain theoretical significance and reference value for the engineering design of silica sol grouting.

Numerical modeling of diffusion of leaked soluble hazardous chemicals in the Daya Bay, China

Based on observation data and temperature diffusion experiment of soluble hazardous chemicals, propylene oxide was taken as a typical hazardous chemical to simulate diffusion after leakage in conditions of variable locations, source intensities, and tides in the Daya Bay by FVCOM model. The results show no unsafe concentration (0.02 mg/L) area after 24 hours for leakage of 100 tons occurring in channel and anchorage, and over 3 km2 unsafe area for the same amount of leakage occurring in port. There are more than 5 km2 and 10 km2 unsafe areas after 24 hours in all locations for 500 t and 1000 t leakage, respectively. Maximum diffusion distance and range increase with increasing diffusion space and current velocity, while the dilution effect becomes stronger, which results in maximum diffusion distance and range in channel, followed by anchorage and port, and reversed maximum concentration distribution. Current velocity acts more as a disincentive within 1 hour and an incentive for diffusion after 1 hour. Diffusion simulation of typical hazardous chemicals will provide technical supports to improve ability of handling environmental emergency in the Daya Bay.

Fabrication and laser performance of planar waveguide LuAG/Yb:LuAG/LuAG ceramics

Planar waveguide LuAG/10 at.%Yb:LuAG/LuAG laser ceramics were fabricated by the tape casting method combined with the vacuum pre-sintering and hot isostatic pressing (HIP) post-treatment. The morphologies of the raw materials, tapes and green bodies were observed. The microstructure, optical transmittance and the Yb3+ ions distribution of the LuAG/10 at.%Yb:LuAG/LuAG ceramics with different pre-sintering temperatures after HIP post-treatment were mainly studied. The experimental results showed that the average grain size and in-line transmittance of the HIPed ceramics increased with the increase of pre-sintering temperature. For the LuAG/10 at.%Yb:LuAG/LuAG ceramics pre-sintered at 1825 °C for 20 h and then HIPed at 1700 °C for 3 h under 200 MPa Ar atmosphere, the in-line transmittance of the sample with the thickness of 2 mm was about 74% at 1100 nm and the maximum diffusion distance of Yb3+ was about 166 μm. The bulk and grain boundary diffusion coefficients of Yb3+ ions for the samples pre-sintered at 1775 °C–1825 °C after HIP post-treatment were calculated by Fick's second law by using the LA-ICP-MS. What's more, CW laser at 1030 nm was demonstrated and the maximum output power of 0.4 W with a slop efficiency of 9.4% was achieved.

啮齿动物对秦岭松栎混交林建群种种子扩散格局的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 啮齿动物对秦岭松栎混交林建群种种子扩散格局的影响 DOI: 10.5846/stxb201804140859 作者: 作者单位: 西北农林科技大学林学院,西北农林科技大学林学院,西北农林科技大学林学院,西北农林科技大学林学院,河南师范大学生命科学学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金项目（31470644） Effects of rodents on seed dispersal patterns of constructive species in the pine-oak mixed forests of the Qinling Mountains, Shaanxi Province, China Author: Affiliation: College of Forestry,Northwest A & F University,College of Forestry,Northwest A & F University,College of Forestry,Northwest A & F University,College of Forestry,Northwest A F University,College of Life Science,Henan Normal University Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:森林群落中的啮齿动物对林木种子存在着一定的取食偏好性，这种偏好性会使啮齿动物形成不同的捕食和贮藏策略，从而导致林木种子形成不同的扩散格局。以秦岭中段松栎混交林建群种锐齿槲栎、油松、华山松为研究对象，采用塑料标签标记种子方法，研究啮齿动物对种子传播和扩散格局的影响。结果表明：（1）种子特征是影响啮齿动物对其进行扩散的重要因子，油松种子以其质量小、种皮薄等特点吸引啮齿动物大量捕食，其原地取食率达到83.33%，显著高于华山松和锐齿槲栎种子。（2）锐齿槲栎和华山松种子大部分被搬运一定距离后再被取食和埋藏，其中，扩散距离在1 m以内、1-3 m和5-8 m的锐齿槲栎种子分别占59.12%、18.23%和13.26%，最远扩散距离达12 m处；华山松种子扩散距离主要介于在1-3 m（37.85%）和3-5 m（23.73%），在距离5-8 m（13.56%）、8-10 m（11.86%）和大于10 m（11.30%）区间也有一定的分布，最大扩散距离为12 m。（3）啮齿动物倾向于将锐齿槲栎种子搬运至松林内取食，而将华山松种子搬运至栎林内埋藏，说明不同林分类型及其环境因素对林木种子扩散后的分布格局具有重要影响。（4）3种类型种子被啮齿动物捕食的比例以油松最大（96.90%），锐齿槲栎次之（73.57%），华山松最小（50%）；次年调查时，未被捕食的种子大部分已经被取食，仅有极少数锐齿槲栎种子萌发成幼苗（1.67%）。啮齿动物的捕食和贮藏行为对林木种子扩散及其成功更新都至关重要。 Abstract:Rodents in forest communities have a feeding preference for tree seeds. This preference will lead to different predation and storage strategies for rodents, resulting in different diffusion patterns of tree seeds. In this study, the seed fate of Quercus aliena var. acuteserrata, Pinus armandii, and Pinus tabuliformis was studied to analyze the seed dispersal patterns of constructive species in the pine-oak mixed forests of the Qinling Mountains, Shaanxi Province, China. The results demonstrated that seed traits are the main factor affecting their removal by rodents. The in-situ seed predation rate of P. tabuliformis seeds was 83.33%, which was notably higher than that of other seed types, indicating that rodents preferentially fed on the small P. tabuliformis seeds. Q. aliena var. acuteserrata seeds and P. armandii seeds were transported to distant locations for feeding and burying. The Q. aliena var. acuteserrata seeds with diffusion distances of less than 1 m, 1-3 m and 5-8 m accounted for 59.12%, 18.23%, and 13.26% of predated seeds, respectively; the farthest diffusion distance was 12 m. The seed diffusion distance of P. armandii was mainly between 1-3 m (37.85%) and 3-5 m (23.73%), and was within the range of 5-8 m (13.56%), 8-10 m (11.86%), and greater than 10 m (11.30%);the maximum diffusion distance of P. armandii seeds was also 12 m. Rodents tended to transport Q. aliena var. acuteserrata seeds to the pine forest for feeding, while transporting the seeds of P. armandii to the oak forest, indicating that different forest types are an important factor in seed dispersal. P. tabuliformis seeds were the most predated on by rodents (96.90%), followed by Q. aliena var. acuteserrata seeds (73.57%), and P. armandii seeds (50%). In the following year's survey, most of the predated seeds had been consumed, and only a handful of Q. aliena var. acuteserrata seeds had sprouted into seedlings (1.67%). Rodent predation and storage behaviors are critical for the spread of forest seeds and their successful renewal. 参考文献 相似文献 引证文献

Evaluation of a mitigation system for leakage accidents using mathematical modeling

Chemical accidents generated during maintenance, repair, and normal operation, such as dispersion, fire, and explosions, can cause massive losses within and outside workplaces. Since a 2012 hydro fluorine leak in Gumi, South Korea, many studies have investigated mitigation systems for reducing accident impact. However, due to potential costs, and lack time and expertise, most companies have hesitated to install mitigation systems without accurate impact evaluations. Therefore, it is essential to analyze mitigation system efficacy under various possible accident scenarios. We considered a mitigation system incorporating a reserve vessel installed next to a storage vessel. When a leakage accident occurs, the chemical in the main vessel is transferred to the reserve vessel by a pump. Simulation results based on Torricellis’ theorem indicate that this mitigation system could significantly reduce leakage, and reduce leakage consequences in terms of maximum diffusion distance and hazardous gas concentrations based on consequence analysis.

Synchrotron Phase Tomography: An Emerging Imaging Method for Microvessel Detection in Engineered Bone of Craniofacial Districts.

The engineering of large 3D constructs, such as certain craniofacial bone districts, is nowadays a critical challenge. Indeed, the amount of oxygen needed for cell survival is able to reach a maximum diffusion distance of ~150–200 μm from the original vascularization vector, often hampering the long-term survival of the regenerated tissues. Thus, the rapid growth of new blood vessels, delivering oxygen and nutrients also to the inner cells of the bone grafts, is mandatory for their long-term function in clinical practice. Unfortunately, significant progress in this direction is currently hindered by a lack of methods with which to visualize these processes in 3D and reliably quantify them. In this regard, a challenging method for simultaneous 3D imaging and analysis of microvascularization and bone microstructure has emerged in recent years: it is based on the use of synchrotron phase tomography. This technique is able to simultaneously identify multiple tissue features in a craniofacial bone site (e.g., the microvascular and the calcified tissue structure). Moreover, it overcomes the intrinsic limitations of both histology, achieving only a 2D characterization, and conventional tomographic approaches, poorly resolving the vascularization net in the case of an incomplete filling of the newly formed microvessels by contrast agents. Indeed, phase tomography, being based on phase differences among the scattered X-ray waves, is capable of discriminating tissues with similar absorption coefficients (like vessels and woven bone) in defined experimental conditions. The approach reviewed here is based on the most recent experiences applied to bone regeneration in the craniofacial region.

Quantitative image analysis to characterize the dynamics of Listeria monocytogenes biofilms

This work shows that the combination of two-dimensional (2D) and three-dimensional (3D) analyses of images acquired by confocal laser scanning microscopy facilitates the quantitative spatiotemporal characterization of architectures formed by Listeria monocytogenes biofilms. In particular, the analysis of structural features such as maximum thickness, biovolume, areal porosity and maximum diffusion distance allowed elucidating differences in biofilm formation of three L. monocytogenes strains (L1A1, CECT5873 and CECT4032).The analysis showed a common sequence for all strains. In the first phase, independent clusters evolve to interconnected clusters and honeycomb-like structures. Flat biofilms characterized the second phase. The structures disappear in the third phase.Nevertheless, the duration of the phases differed from strain to strain. L1A1 strain exhibited the slowest dynamics and the thickest biofilms while the strain CECT4032 presented the faster dynamics and the thinnest biofilms. Also, the number of dead cells varies significantly from strain to strain.From the results of the analysis, it can be concluded that 2D parameters are critical to differentiating morphological features while 3D parameters ease the interpretation and comparative study of the different phases during the life cycle of biofilms.

Application of an integrated biomarker response index to assess ground water contamination in the vicinity of a rare earth mine tailings site.

We utilized a multi-biomarker approach (Integrated Biomarker Response version 2, IBRv2) to investigate the scope and dispersion of groundwater contamination surrounding a rare earth mine tailings impoundment. Parameters of SD rat included in our IBRv2 analyses were glutathione levels, superoxide dismutase, catalase, and glutathione peroxidase activities, total anti-oxidative capacity, chromosome aberration, and micronucleus formation. The concentration of 20 pollutants including Cl(-), SO4 (2-), Na(+), K(+), Mg(2+), Ca(2+), TH, CODMn, As, Se, TDS, Be, Mn, Co, Ni, Cu, Zn, Mo, Cd, and Pb in the groundwater were also analyzed. The results of this study indicated that groundwater polluted by tailings impoundment leakage exhibited significant ecotoxicological effects. The selected biomarkers responded sensitively to groundwater pollution. Analyses showed a significant relationship between IBRv2 values and the Nemerow composite index. IBRv2 could serve as a sensitive ecotoxicological diagnosis method for assessing groundwater contamination in the vicinity of rare earth mine tailings. According to the trend of IBRv2 value and Nemerow composite index, the maximum diffusion distance of groundwater pollutants from rare earth mine tailings was approximately 5.7km.

Listeria monocytogenes-carrying consortia in food industry. Composition, subtyping and numerical characterisation of mono-species biofilm dynamics on stainless steel

In order to find out how real Listeria monocytogenes-carrying biofilms are in industrial settings, a total of 270 environmental samples belonging to work surfaces from fish (n=123), meat (n=75) and dairy industries (n=72) were analysed in order to detect L. monocytogenes. 12 samples were positive for L. monocytogenes and a total of 18 different species were identified as accompanying microbiota in fish and meat industry. No L. monocytogenes was found in samples from dairy industry. Molecular characterisation combining results of AscI and ApaI macrorestriction PFGE assays yielded 7 different subtypes of L. monocytogenes sharing in 71.43% of cases the same serogroup (1/2a–3a). Results from dynamic numerical characterisation between L. monocytogenes monospecies biofilms on stainless steel (SS) using MATLAB-based tool BIOFILMDIVER demonstrated that except in isolate A1, in which a significant increase in the percentage of covered area (CA), average diffusion distance (ADD) and maximum diffusion distance (MDD) was observed after 120h of culture, no significant differences were observed in the dynamics of the rest of the L. monocytogenes isolates. Quantitative dual-species biofilm association experiments performed on SS indicated that L. monocytogenes cell counts presented lower values in mixed-species cultures with certain species at 24 and 48h compared with mono-species culture. However, they remained unaltered after 72h except when co-cultured with Serratia fonticola which presented differences in all sampling times and was also the dominant species within the dual-species biofilm. When considering frequency of appearance of accompanying species, an ecological distribution was demonstrated as Escherichia coli appeared to be the most abundant in fish industry and Carnobacterium spp. in meat industry.

Solute Diffusion Characteristics of a Rapid Hardening Al-Cu-Mg Alloy during the Early Stages of Age Hardening

The heat-transfer characteristics of a rapid hardening Al-1.1Cu-1.7Mg at. pct alloy during the early stages of age hardening have been tested, both by experiment and finite element modeling, for a typical laboratory-scale sample, and subsequently a maximum diffusion distance by random walk has been calculated for the solute atom species. It is found that due to small diffusion distances compared to the average dislocation loop interspacing, the dislocation-locking hardness mechanism is not likely, and rather, the cluster hardening model is more accurate.

Numerical modelling and experimental investigation of diffusion brazing SS304/BNi-2/SS304 joint

The kinetics of dissolution and isothermal solidification at the bonding temperature during diffusion brazing SS304/BNi-2/SS304 has been studied through a combination of analytical modelling and experimental investigations. The modelling is based on the diffusion theory and the consideration of transient motion of liquid/solid interface. A set of coupled finite differential equations has been programmed to track the motion of liquid/solid interface during the isothermal solidification of liquid filler. Four parameters can be mathematically determined from the analytical modelling including the evolution of solute concentration profile, the maximum diffusion distance, and the maximum liquid thickness as well as the time to complete the isothermal solidification. These analyses are helpful to understanding the joining mechanism during diffusion brazing. The temperature dependent diffusion coefficient used in the modelling is derived together with the experimental data from brazing the wedge shaped joint specimen of SS304/BNi-2/SS304. The effects of bonding temperature and initial joint thickness on the joining process have also been investigated.

漁港漁場整備事業における浚渫土砂海洋投入に関する実態調査とＳＳ拡散予測について

To obtain figures and tables for environmental assessment on diffusion caused by dumping dredged materials from fishery ports into the ocean, study on past records on volume of dredging and dumping materials were carried out. The cases for numerical simulation on diffusion were selected by examining the study on past records. The simulation was conducted for conditions of three types of dredged materials, three water depths, three current speeds and one representative median diameter.As the results of the simulation, figures of maximum concentration, maximum diffusion distance, affecting time on diffusion for 2mg/L and 10mg/L conditions were obtained.After specifying sorts of fish around the dumping area and fishing time, a trial of prediction on diffusion and assessment for dumping dredged material were conducted by using those figures.

Oxygen Consumption Rates and Metabolic Enzyme Activities of Oceanic California Medusae in Relation to Body Size and Habitat Depth.

Oxygen consumption rates were measured in 14 species of hydromedusae and 5 species of bathypelagic coronate scyphomedusae. Analysis of all individuals of all species of medusae showed the familiar pattern of decreasing specific oxygen consumption rate with increasing wet weight of animals. Citrate synthase (CS), lactate dehydrogenase (LDH), malate dehydrogenase (MDH), and pyruvate kinase (PK) activities were measured in more than 30 species of medusae. Octopine dehydrogenase, strombine dehydrogenase, and alanopine dehydrogenase were not detected in either hydromedusae or scyphomedusae. The allometric scaling phenomenon of decreasing activity in larger individuals was observed in Krebs cycle enzyme activities. LDH activities, on the other hand, increased with increasing wet weight. Most medusae were aerobically poised, with higher CS activities than LDH activities. However, several meso- and bathypelagic medusae, including the coronate scyphozoans Periphylla periphylla and Nausitho{e2dot} rubra, were anaerobically poised, possibly as a mechanism to assist in vertical migrations at low oxygen concentrations in the oxygen minimum layer. There is poor correlation between CS activities and oxygen consumption rates in these medusae when compared to previously investigated animals. To account for this poor correlation, we propose the hypothesis that medusan CS at the periphery of the maximum diffusion distance may be oxygen-limited and does not function at the normal in vivo rate. For pelagic medusae, there is no apparent decline in metabolic rate and metabolic potential, as determined by enzymatic activity, with increasing depth of occurrence, beyond the declines caused by the decrease in temperature with depth. These patterns are in contrast to the rapid declines in metabolic rates and metabolic potentials with depth that have been observed for pelagic fishes and crustaceans. Deep-living medusae have metabolic rates of a magnitude similar to those of bathypelagic fishes and crustaceans.

Aluminum surface mobility on two types of silicon oxide during ionized cluster beam deposition

AbstractAn ionized cluster beam (ICB) source was used to deposit A1 onto two types of silicon oxides. One was a thermal oxide generated by steam oxidation of Si at 900°C. The other was a P‐doped oxide deposited on Si at 425°C. During Al deposition, 60 μm diameter wires were held at the substrates to serve as masks. After A1 deposition, the wires were removed and the masked areas were examined by scanning electron microscopy (SEM) and by scanning Auger microprobe (SAM). The ICB source was operated at 0, 3 and 6 kV accleration voltages. The substrates were held at 80, 200 and 400°C during A1 depositions. The A1 deposition rate averaged 24 nm min.−1 The chamber pressure during deposition was 3 × 10−4 Pa. The diffusion distance of A1l under a mask edge was determined from the SEM micrographs and SAM line scans. The maximum diffusion distance occurred at 200°C for both substrates, with the exception of the 0 kV A1 beam deposited on the low‐temperature oxide (LTO). On the high‐temperature oxide (HTO), the maximum diffusion distance was 29 μm at 6 kV acceleration voltage. The minimum diffusion distance was 8 μm at 70–80°C on the LTO for acceleration voltages of 0 and 3 kV.

Aluminum Atom Surface Mobility on SiO2 During Ionized Cluster Beam Deposition

ABSTRACTAn ionized cluster beam (ICB) source was used to deposit Al onto SiO2 substrates. A 60 gtm diameter wire held at the substrate served as a mask. After Al deposition, the wire was removed and the masked area was examined by scanning electron microscopy (SEM) and by scanning Auger microprobe (SAM). The ICB source was operated at 0, 3, and 6 kV acceleration voltages. The substrate was held at 80°, 200°, and 400°C during Al depositions. The Al deposition rate averaged 240 A per min. The chamber pressure during deposition was 2×10-6 Torr. The diffusion distance of Al under the mask edge was determined from the SEM micrographs and SAM line scans. The maximum diffusion distance for all acceleration voltages occured at a substate temperature of 200°C. The maximum diffusion distance at 200°C was 29 μm at 6 kV acceleration voltage. The minimum diffusion distance was 12 μm at 400°C for an acceleration voltage of 6 kV.