Hardness and grain size relations for thick chromium films deposited by hallow cathode discharge

Chromium films deposited by hollow cathode discharge show a variety of hardness, wear resistance and anti-corrosion characteristics. To find the relation between these properties and the film structure, investigations using X-ray diffraction, transmission electron microscopy and Auger electron spectroscopy were carried out for a variety of substrate bias voltages.Films deposited by hollow cathode discharge at 190°C and biased at 0 V and ?50 V and an electrochemically plated hard chromium film were compared by measurements of the Vickers microhardness and the line broadening of the (222)Cr line of X-ray diffraction after vacuum annealing at several temperatures. The hardness is approximately proportional to the square root of the line broadening.All the deposited films show a similar relation between hardness and line broadening. The square root of the grain size of these films as observed by TEM is inversely proportional to the hardness. This relation supports an empirical equation obtained by Agarwal et al. who worked with vacuum-deposited NiCr films. The grain size of the films as observed by TEM is several times larger than that calculated from line broadening.     

Assessment of global nitrogen pollution in rivers using an integrated biogeochemical modeling framework

This study has analyzed the global nitrogen loading of rivers resulting from atmospheric deposition, direct discharge, and nitrogenous compounds generated by residential, industrial, and agricultural sources. Fertilizer use, population distribution, land cover, and social census data were used in this study. A terrestrial nitrogen cycle model with a 24-h time step and 0.5° spatial resolution was developed to estimate nitrogen leaching from soil layers in farmlands, grasslands, and natural lands. The N-cycle in this model includes the major processes of nitrogen fixation, nitrification, denitrification, immobilization, mineralization, leaching, and nitrogen absorption by vegetation. The previously developed Total Runoff Integrating Pathways network was used to analyze nitrogen transport from natural and anthropogenic sources through river channels, as well as the collecting and routing of nitrogen to river mouths by runoff. Model performance was evaluated through nutrient data measured at 61 locations in several major world river basins. The dissolved inorganic nitrogen concentrations calculated by the model agreed well with the observed data and demonstrate the reliability of the proposed model. The results indicate that nitrogen loading in most global rivers is proportional to the size of the river basin. Reduced nitrate leaching was predicted for basins with low population density, such as those at high latitudes or in arid regions. Nitrate concentration becomes especially high in tropical humid river basins, densely populated basins, and basins with extensive agricultural activity. On a global scale, agriculture has a significant impact on the distribution of nitrogenous compound pollution. The map of nitrate distribution indicates that serious nitrogen pollution (nitrate concentration: 10-50 mg N/L) has occurred in areas with significant agricultural activities and small precipitation surpluses. Analysis of the model uncertainty also suggests that the nitrate export in most rivers is sensitive to the amount of nitrogen leaching from agricultural lands.     

In vitro heat generation by ferrimagnetic maghemite microspheres for hyperthermic treatment of cancer under an alternating magnetic field

Ferrimagnetic materials can be expected to be useful as thermo seeds for hyperthermic treatment of cancer, especially where the cancer is located in deep parts of body, as they can generate heat by magnetic hysteretic loss when they are placed in an alternating magnetic field. Recently, it was reported that ferrimagnetic maghemite (γ-Fe₂O₃) microspheres 20–30 μm in diameter prepared in aqueous solution can show excellent heat generating ability. However, these microspheres have many cracks on their surfaces. In this study, the preparation conditions for the microspheres was further optimized in order to obtain crack-free ferrimagnetic microspheres, and the in vitro heat generation of the obtained microspheres was measured in an agar phantom under an alternating magnetic field. Crack-free γ-Fe₂O₃ microspheres 20–30 μm in diameter were obtained successfully. Their saturation magnetization and coercive force were 68 emu g⁻¹ and 198 Oe, respectively. Their heat generation under an alternating magnetic field of 300 Oe at 100 kHz was estimated to be 42 W g⁻¹. The microspheres showed in vitro heat generation when they were dispersed in an agar phantom and placed under an alternating magnetic field. It is believed that these microspheres may be useful for the in situ hyperthermic treatment of cancer.     

River Floods in the Changing Climate—Observations and Projections

River flood damages, worldwide, have increased dynamically in the last few decades, so that it is necessary to interpret this change. River flooding is a complex phenomenon which can be affected by changes coupled to terrestrial, socio-economic and climate systems. The climate track in the observed changes is likely, even if human encroaching into the harm’s way and increase in the damage potential in floodplains can be the dominating factors in many river basins. Increase in intense precipitation has already been observed, with consequences to increasing risk of rain-induced flooding. Projections for the future, based on climate model simulations, indicate increase of flood risks in many areas, globally. Over large areas, a 100-year flood in the control period is projected to become much more frequent in the future time horizon. Despite the fact that the degree of uncertainty in model-based projections is considerable and difficult to quantify, the change in design flood frequency has obvious relevance to flood risk management practice. The number of flood-affected people is projected to increase with the amount of warming. For a 4°C warming the number of flood-affected people is over 2.5 times higher than for a 2°C warming. The present contribution addresses the climate track in an integrated way, tackling issues related to multiple factors, change detection, projections, and adaptation to floods.     

Photocurrent in and miscibility of poly(N-vinylcarbazole)/poly(methyl methacrylate) blends

Summary Steady-state photocurrent in poly(N-vinylcarbazole)(PVCz) (26,48 wt%)/poly(methyl methacrylate)(PMMA) blends is for the first time measured. The PVCz(26,48 wt%)/PMMA blends showed almost the same carrier-generation efficiencies at electric fields higher than 1 × 10⁵ V · cm⁻¹. The results are explained by high miscibility of the PVCz(26,48 wt%)/PMMA blends, suggesting the existence of PVCz chains in continous PMMA-rich phase in the phase-separated structure. The miscibility is also evaluated by means of excimer fluorescence of PVCz in these blends and fluorescence microscopy. Received: 26 December 2000/Revised version: 16 January 2001/Accepted: 19 January 2001     

Thickness uniformity of HDPE blown film: Relation to rheological properties and density

Previous work has elucidated that the wall slip velocity and viscosity of polymer melts influence the thickness uniformity of blown film. The present study investigates the effects of the stress dependence of wall slip, the shear thinning and the density on the uniformity. We have prepared high‐density polyethylenes with a variety of molecular weight distributions, which have different rheological properties. Examination of the thickness uniformity of their blown film has shown that the uniformity is correlated with wall slip velocity, the stress dependence of the velocity, melt viscosity, shear thinning and density; the coefficient of the correlation is determined to be 0.990. The reason why the stress dependence of wall slip and the shear thinning affect the uniformity is explained in terms of polymer melt flow behavior in a die, while the effect of density is interpreted considering bubble fluctuation in the blow‐up process. Polym. Eng. Sci. 44:965–972, 2004. © 2004 Society of Plastics Engineers.