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A bubble-assisted electroosmotic (EO) micropump is proposed as a miniaturized actuating element to be integrated in a microfluidic chemical sensing system. In this device, a bubble is generated in a narrow channel to form a thin water sheet between the bubble and the wall. Due to the high surface-to-volume ratio of the water sheet, an efficient EO flow is realized at relatively low pumping voltages of 20–60 V without using a porous material. The direction and the flow rate of the EO flow depended on the polarity and the magnitude of the pumping voltage, and the highest flow rate of about ±500 pL/s was obtained at ±60 V. A bubble-assisted EO micropump was combined with a LAPS for measuring the pH value of a droplet with a volume of 1 nL.

An on-chip electroosmotic (EO) micropump (EOP) was integrated in a microfluidic channel combined with a light-addressable potentiometric sensor (LAPS). The movement of EO flow towards right and left directions can be clearly observed in the microfluidic channel. The characteristics of photocurrent-time and photocurrent-bias voltage are obtained when buffer solution passes through the sensing region. The results demonstrate that the combination of an on-chip EOP with an LAPS is feasible.

A rigid rotor dynamic balance model was established to analyze the vibration form of a rigid rotor under unbalance inertia force. The principle of two-plane correction with the influence coefficient method had been conducted, and the principle of the cross-correlation method calculating amplitude and phase of unbalance vibration signal was introduced. The method was found to be effective and practical. A dynamic balance test program was performed on a rigid rotor vibration simulation instrument and a dynamic balancing analyzer based on LabVIEW, which showed that rigid rotor dynamic balancing by two-plane correction with the influence coefficient method could satisfy the performance and required precision.

In smoothing of Class A surfaces for auto-body, the whole surface is firstly divided into many base surfaces, and then blended them into a whole surface. The base surface is often not big enough to meet the blending requirements, so it should be extended. The paper discussed the extension of Bézier curves and surfaces, and analyzed the relationships between extended curves/surfaces and vertexes. The result shows that the arrangement of control vertexes is closely related to the quality of extended curves/surfaces.

The polarized Brillouin scattering spectra were systematically measured to study the elastic properties of bulk hexagonal close-packed (hcp) ZnO single crystal in this paper. The peak polarizations of all modes in spectra were analyzed firstly. The elastic properties, such as the whole set of Elastic constants were accordingly calculated and compared with the previous literatures. Also investigated were the effects of the rotation of the sample in the (0001) plane perpendicular to the z axis on different acoustic modes. The results show that the quasi-longitudinal and quasi-transverse modes perpendicular to the (0001) plane act as the expected trigonometric function of the rotation angle, while the longitudinal and transverse modes on the (0001) plane remain constant.

1. Root life span regulates the quantity and quality of root-derived organic matter transferred to the soil organic matter pool. However, poor understanding of the rates and controls of root life span has hindered the prediction of carbon (C) flow and nutrient cycling dynamics at the ecosystem scale. 2. We examined the effects of root branch order, root diameter, mycorrhizal colonization, season of birth, depth in the soil, nitrogen (N) fertilization and foliage removal on root life span in a longleaf pine (Pinus palustris Mill.) forest from 2001 to 2004 using minirhizotron and soil monolith sampling. 3. Among all factors, root branch order had the strongest and most consistent effect on life span, with higher order roots having a 46% longer life span than roots one order lower. 4. Within first order roots, mycorrhizal colonization significantly increased root life span by > 45% in 2 of 3 years. 5. Roots born in winter and spring generally lived longer than roots born in summer and autumn. Root life span was positively correlated with depth in the soil and root diameter, but the correlations were weaker than with order, year and season. Neither N fertilization nor foliage removal had a significant impact on root life span. 6. When biomass mortality and associated N flux were estimated based on order-specific mean life span, N concentration and ecosystem-scale biomass estimates, first order roots constituted approximately 50% of the total biomass mortality and > 60% of the N flux for the first three root orders combined. 7. Synthesis. Our results show that (i) root branch order was the strongest predictor of life span among all covariates and can effectively partition the distal longleaf pine root systems into three or more populations with different turnover rates; (ii) only a fraction of fine roots turns over annually, whereas models of C cycles assume an annual turnover for the entire fine root system. We conclude that an order-based approach holds greater promise than the traditional diameter class approach for evaluating the role of different fine root populations in C flow and nutrient cycling.

Among tree fine roots, the distal small-diameter lateral branches comprising first- and second-order roots lack secondary (wood) development. Therefore, these roots are expected to decompose more rapidly than higher order woody roots. But this prediction has not been tested and may not be correct. Current evidence suggests that lower order roots may decompose more slowly than higher order roots in tree species associated with ectomycorrhizal (EM) fungi because they are preferentially colonized by fungi and encased by a fungal sheath rich in chitin (a recalcitrant compound). In trees associated with arbuscular mycorrhizal (AM) fungi, lower order roots do not form fungal sheaths, but they may have poorer C quality, e.g. lower concentrations of soluble carbohydrates and higher concentrations of acid-insolubles than higher order roots, thus may decompose more slowly. In addition, litter with high concentrations of acid insolubles decomposes more slowly under higher N concentrations (such as lower order roots). Therefore, we propose that in both AM and EM trees, lower order roots decompose more slowly than higher order roots due to the combination of poor C quality and high N concentrations. To test this hypothesis, we examined decomposition of the first six root orders in Fraxinus mandshurica (an AM species) and Larix gmelinii (an EM species) using litterbag method in northeastern China. We found that lower order roots of both species decomposed more slowly than higher order roots, and this pattern appears to be associated mainly with initial C quality and N concentrations. Because these lower order roots have short life spans and thus dominate root mortality, their slow decomposition implies that a substantial fraction of the stable soil organic matter pool is derived from these lower order roots, at least in the two species we studied.

With global changes such as increasing temperature and enhanced N deposition, soil nitrogen (N) availability is predicted to increase substantially, and how fine root dynamics responds to the altered soil N has become one of the key questions in terrestrial ecology. As such, a number of hypotheses have been proposed to explain the relationship between increasing soil N availability and fine root production, mortality, and turnover. This article considered four major hypotheses: with increasing soil N availability, 1) both fine root production and turnover rate would increase, 2) both fine root production and turnover rate would decrease, 3) fine root production would decrease while fine root turnover rate would increase, and 4) fine root production would increase while fine root turnover rate would decrease. Current evidence suggests that the patterns depicted in hypothesis 1) and 2) could both occur in nature and may reflect characteristics of different species. Hypotheses 3) and 4) were thought to characterize only a transient stage of the responses of fine root dynamics to increasing N availability. To better understand the response of root dynamics to increasing soil N, future studies should consider: 1) the definition of fine roots and heterogeneity in fine root structure and function; 2) methods used in estimating fine root production and turnover rate; 3) changes of soil N availability both in space and time. More attention should also be paid to the influences of mycorrhizal infection on root dynamic responses to soil N availability.