An electrothermal carbon nanotube gas sensor

We show both gas pressure and species sensing capabilities based on the electrothermal effect of a multiwalled carbon nanotube (MWCNT). Upon exposure to gaseous environments, the resistance of a heated MWCNT is found to change following the conductive heat-transfer variances of gas molecules. To realize this mechanism, a suspended MWCNT is constructed by synthesis and assembly in localized chemical vapor deposition that is accomplished within seconds via real-time electrical feedback control. Vacuum pressure sensitivity and gas species differentiability are observed and analyzed. Such MWCNT electrothermal sensors are compact, fast and reversible in responses, and fully integratable with microelectronics.     

The quantitative measurement of magnetic moments from phase images of nanoparticles and nanostructures—I. Fundamentals

An approach that can be used to measure the magnetic moment of a magnetized nanoparticle or nanostructure from an electron-optical phase image is introduced. The measurement scheme is based on integration of the gradient of the measured phase image within a circular boundary that contains the structure of interest. The quantity obtained is found to be directly proportional to the magnetic moment of the particle, with a constant of proportionality that does not depend on the particle's shape or magnetization state. The measurement of magnetic moments from both simulated and experimental phase images is demonstrated, and strategies are presented that can be utilized to overcome sources of error associated with, for example, the presence of neighboring magnetic particles and the perturbation of the holographic reference wave.     

Dynamic study of intramembranous particles in human fresh erythrocytes using an "in vitro cryotechnique"

For analyses of dynamic ultrastructures of erythrocyte intramembranous particles (IMPs) in situ, a quick-freezing method was used to stabilize the flow behavior of erythrocytes embedded in vitreous ice. Fresh human blood was jetted at various pressures through artificial tubes, in which the flowing erythrocytes were elongated from biconcave discoid shapes to elliptical ones, and quickly frozen in liquid isopentane-propane cryogen (-193 degrees C). They were freeze-fractured using a scalpel in liquid nitrogen, and routinely prepared for replica membranes. Many IMPs were observed on the protoplasmic freeze-fracture face (P-face) of the erythrocyte membranes. Some control erythrocytes under nonflowing or stationary conditions showed IMPs with their random distribution. However, other jetted erythrocytes under flowing conditions showed variously sized IMPs with much closer distribution. They were also arranged into parallel rows in some parts, and aggregated together. This quick-freezing method enabled for the first time the visualization of time-dependent topology and the molecular alteration of IMPs in dynamically flowing erythrocytes.     

EUV Optical Design-Reflective and Diffractive Optics

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Organic air pollutants inside and outside residences in Shimizu, Japan: levels, sources and risks

Concentrations of 38 organic air pollutants including aromatic hydrocarbons (AHCs), carbonyl compounds (CCs), volatile organic halogenated compounds (VOHCs), and organophosphorus compounds (OPCs) were measured in indoor and outdoor air in an industrial city, Shimizu, Shizuoka Prefecture, Japan. Levels of pollutants tended to be higher indoors than outdoors in both summer and winter except for benzene, carbon tetrachloride, trichloroethylene, tetrachloroethylene, and dichlorvos (DDVP). This trend was especially pronounced for CCs such as formaldehyde and acetaldehyde. For the organic air pollutants, the concentrations of AHCs and VOHCs substantially increased in winter, but not those of CCs and OPCs; the trends were similar for both indoors and outdoors. We investigated possible indoor sources of pollutants statistically. Multiple regression analysis of corresponding indoor and outdoor concentrations and the responses to our questionnaire showed that indoor concentrations of certain AHCs were significantly affected by their outdoor concentrations and cigarette smoking. For formaldehyde, indoor concentrations were significantly affected by house age and the presence of carpet or pets. For p-dichlorobenzene (pDCB), the concentrations in bedroom trended to be higher than those in other indoors and outdoors, suggested that mothballs for clothes present in bedrooms are the principal indoor source of pDCB. We compared indoor and outdoor pollutant concentrations to acceptable risk limits for 11 organic air pollutants. In indoors without smoking samples, the geometric mean concentrations of benzene, formaldehyde, acetaldehyde, carbon tetrachloride, pDCB, and DDVP exceeded the equivalent concentration representing the upper bound of one-in-one-hundred-thousand (1x10(-5)) excess risk over a lifetime of exposure.     

Strength and deformation characteristics and small strain properties of undisturbed gravelly soils

A series of medium-scale and large-scale triaxial and unconfined compression tests was conducted in order to evaluate the strength and deformation characteristics and small strain properties of undisturbed well-graded gravelly soils retrieved from three tunnel excavation sites in Toyama prefecture, Japan. Undisturbed gravelly soils were taken by means of a new sampling method using thick water-soluble polymer solutions. The strength and deformation characteristics were evaluated mainly by performing sustained loading and large amplitude unloading and reloading cycles during otherwise monotonic loading at a constant strain rate in drained triaxial compression tests. During isotropic consolidation and shearing, at several stress states, eleven very small vertical cycles were applied to evaluate the quasi-elastic deformation property at small strain levels around 0.001% by static measurement. Dynamic measurements using a pair of accelerometers attached to the side surface of the specimen and wave sources attached to the top cap were also conducted at the same stress levels as static measurements in a single test. Several effects including grading characteristics and pressure level on the difference between the moduli measured statically and dynamically were discussed. The relationship between the small strain and strength properties of undisturbed gravelly soils was evaluated. The small strain properties of air-dried dense Toyoura sand in large-scale triaxial compression tests were also investigated in this study to compare the results of undisturbed gravelly soils.     

Low cycle fatigue assessments of corner welded joints based on local strain approach

Low cycle fatigue strengths of corner welded joints with single bevel groove welding were studied. Low cycle fatigue tests were performed with three types of specimens which have different sizes of weld root face. The test results indicated that the low cycle fatigue strength of the corner welded joints strongly depends on the weld root size. Then, the fatigue strength of the corner joints was evaluated based on the effective notch strain at the weld root tip which was calculated by elasto-plastic finite element analyses. A unique relationship between the effective notch strain and the fatigue life of the joint was observed regardless of the weld root size. Therefore, it was revealed that the effective notch strain approach is applicable to evaluate the low cycle fatigue strength of the corner welded joints.     

Numerical study on post-fracture redundancy of the two-girder steel-concrete composite highway bridges

As the Japan bridge inventory ages and traffic volumes increase, the government is spending more on maintaining their existing structures to extend the service life of the current bridge inventory. This includes two-girder bridges that are classified as fracture critical and non-redundant. Owing to the increased inspection costs associated with these fracture-critical bridges, there is a need to evaluate alternate load paths and to implement retrofit methods on existing bridge structures to avoid bridge replacement. In this paper, fracture redundancy of the two-girder bridge is investigated through a case study for a three-span continuous twin I-girder bridge. The finite element analysis is carried out to evaluate the load-carrying capacity after fracture of a girder of the two-girder bridge. Damage of studs near the moment contra-flexure regions are also considered in this study. Spacing between the transverse beams is discussed as possible techniques to improve redundancy and reduce the fracture potential of two-girder bridge structures. The concrete slab is indicated to be a significant member for guarantying the redundancy of the two-girder steel-concrete composite bridges.     

Kinetic model of algal growth incorporating intracellular carbohydrate and phosphorus pools

A series of studies on a kinetic model of photosynthesis, nutrient ingestion, and metabolism for algal growth were conducted. Coefficients included in the proposed model were examined referring to experimental data on growth of Chlorella sp. It was shown that the proposed model can simulate the mechanism of algal growth, change of intracellular phosphorus content, change of intracellular carbohydrate content, and effects of nutrients on algal growth.