Development of a Nanostructual Microwave Probe Based on GaAs

With the development of nanotechnology, the measurement of electrical properties in local area of materials and devices has become a great need. Although a lot kind of scanning probe microscope have been developed for satisfying the requirement of nanotechnology, a microscope technique which can determine electrical properties in local area of materials and devices is not yet developed. Recently, microwave microscope has been an interest to many researchers, due to its potential in the evaluation of electrical properties of materials and devices. The advance of microwave is that the response of materials is directly relative to the electromagnetic properties of materials. However, because of the problem of the structure of probes, nanometer-scale resolution has not been successful. To achieve the goal, a new structure microwave probe is required. In this paper, we report a nanostructural microwave probe. To restrain the attenuation of microwave in the probe, GaAs was used as the substrate of the probe. To obtain the desired structure, wet etching was used to fabricate the probe. Different with the dry etching, a side-etching will occur under the etching mask. Utilizing this property, a micro tip can be fabricated by etching a wafer, of which a small mask was introduced on the surface in advance.Comment: Submitted on behalf of EDA Publishing Association (http://irevues.inist.fr/EDA-Publishing

Modeling the impact of drought on canopy carbon and water fluxes for a subtropical evergreen coniferous plantation in southern China through parameter optimization using an ensemble Kalman filter

Soil and atmospheric water deficits have significant influences on CO<sub>2</sub> and energy exchanges between the atmosphere and terrestrial ecosystems. Model parameterization significantly affects the ability of a model to simulate carbon, water, and energy fluxes. In this study, an ensemble Kalman filter (EnKF) and observations of gross primary productivity (GPP) and latent heat (LE) fluxes were used to optimize model parameters significantly affecting the calculation of these fluxes for a subtropical coniferous plantation in southeastern China. The optimized parameters include the maximum carboxylation rate (<i>Vc</i><sub>max</sub>), the slope in the modified Ball-Berry model (<i>M</i>) and the coefficient determining the sensitivity of stomatal conductance to atmospheric water vapor deficit (<i>D</i><sub>0</sub>). Optimized <i>Vc</i><sub>max</sub> and <i>M</i> showed larger variations than <i>D</i><sub>0</sub>. Seasonal variations of <i>Vc</i><sub>max</sub> and <i>M</i> were more pronounced than the variations between the two years. <i>Vc</i><sub>max</sub> and <i>M</i> were associated with soil water content (SWC). During dry periods, SWC at the 20 cm depth explained 61% and 64% of variations of <i>Vc</i><sub>max</sub> and <i>M</i>, respectively. EnKF parameter optimization improved the simulations of GPP, LE and SH, mainly during dry periods. After parameter optimization using EnKF, the variations of GPP, LE and SH explained by the model increased by 1% to 4% at half-hourly steps and by 3% to 5% at daily time steps. Further efforts are needed to differentiate the real causes of parameter variations and improve the ability of models to describe the change of stomatal conductance with net photosynthesis rate and the sensitivity of photosynthesis capacity to soil water stress under different environmental conditions

In Situ SiRNA Assembly in Living Cells for Gene Therapy with MicroRNA Triggered Cascade Reactions Templated by Nucleic Acids

The in situ generation of siRNAs in living cells can greatly enhance the specificity and efficiency of gene therapy. Inspired by the natural molecular machines that organize different compartments sequentially in a limited space to facilitate cellular process, this work constructs a DNA nanomachine (DNM) by alternately hybridizing two pairs of DNA/RNA hybrids to a DNA scaffold generated by rolling circle amplification for highly efficient in situ siRNA assembly in living cells. After target cell-specific delivery of DNM, intracellular specific microRNA can work as a trigger to operate the DNM by initiating DNA cascade displacement reaction between DNA/RNA hybrids along the scaffold for continuous generation of siRNAs. Using miR-21 as a model, efficient siRNAs generation is achieved via DNA templated cascade reaction, which demonstrated impressive suppressions to VEGF mRNA and protein expressions in cells and in vivo tumor growth and indicated promising application of the designed strategy in gene therapy

The Effect of MyD88 Deficiency During Graft-Versus-Host Disease

Graft-versus-host disease is the onset of an un- wanted immune response in patients who have undergone bone marrow transplantation [1]. The effect of this unwanted immune response is lethal in many cases. The goal of this research is to reduce the effect of graft-versus-host disease which can possibly reduce the waiting time for an eligible bone marrow donor to appear. This paper focused on the MyD88 adaptor protein, which triggers biochemical signals that can initiate, maintain, expand, or terminate inflammatory sites [2]. Inflammatory sites are the areas where the immune cells are gathered to fight foreign pathogens [1]. Experiments were carried out wherein stem cells were extracted from C57BL/6 mice and injected into BALB.B mice. This experiment design establishes the allogeneic bone marrow transplantation because the minor histocompatibility complex gene is un-matched between the two strains of mice while the major histocompatibility complex gene is matched. We focused on the effect of MyD88 protein deficiency in transplan- tation recipient. The positive/negative controls for the allogeneic bone marrow transplantation and MyD88 knockout allogeneic bone marrow transplantation group were carefully observed for 28 days and assessed for survival, weight, and immune cell fraction changes. We found that MyD88 protein deficiency yields prolonged survival in graft-versus-host disease. Data also suggests that innate immunity is the dominant factor in graft-versus- host disease, not adaptive immunity. Future experiments with cytokine analysis in a similar experiment design will provide more information about the relationship between the innate immunity and the severity of graft versus host disease

Does Antarctic Krill Employ Body Shrinkage as an Overwintering Strategy?

To determine if Antarctic krill employ body shrinkage as one of its overwintering mechanisms in the field, Euphausia superba and Euphausia crystallorophias were collected during fall and winter in and around Marguerite Bay through US Southern Ocean GLOBEC field programs during fall and winter 2001 and 2002. The relationships between the body length and weight of both krill species were exponentially correlated with no significant differences between the two species (p\u3e0.05). The ratio between eye diameter and body length of individual krill was examined in an expectation that it could be used as an indicator of the body shrinkage as previously suggested by Shin and Nicol (2002). These ratios were significantly different between the two krill species. Especially, E. crystallorophias had bigger eyes than E. superba. In both krill species, eye diameters were highly correlated with body lengths (regression coefficients ≥ 0.70). For E. crystallorophias, no significant differences of the ratio of eye diameter/body length were detected between fall and winter. Even though the ratios for E. superba were seasonally varied, it was not clear whether body shrinkage was an actual and critical overwintering mechanism for the krill population found in this study area. These results suggest that some individuals of E. superba might experience the body shrinkage during a part of their life, but this morphological index alone (eye diameter/body length) may be insufficient to unambiguously separate the shrunk krill from the non-shrunk ones in the field-collected animals