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71.
We present a velocity-map imaging (VMI) setup for photoelectron imaging that utilizes low electric extraction fields. This avoids any complications that could arise from electrostatic interactions between the extraction field and the molecular properties that are probed and has a minimal effect on the trajectory of ions in ion beam experiments. By using an attractive potential supplied to the detector, and keeping the electrodes at ground (zero) potential, we show that fringe fields between the VMI arrangement and the vacuum chamber can be eliminated, which is important in experiments on ions. 相似文献
72.
Aspects of transnationalism and identity in the period from the 1860s to the mid 1920s, which set in motion a form of globalization related to empire, are focused upon. The notion of 'regimes of representation' is adapted as a broad conceptual framework for exploring the role of colonial directories in establishing the identity of metropolitan commercial culture in Wellington, New Zealand. This outpost of empire is examined through a detailed analysis of the images presented in a series of directories by Kelly's and Wise. These reveal how British commerce established a strong and lasting identity in the colony through a variety of 'acts of representation'. It is concluded that colonial directories are a worthwhile but neglected source for exploring the geographies of empire. 相似文献
73.
74.
Distance-of-flight mass spectrometry (DOF-MS) has not yet been implemented, though it has many potential advantages in a variety of applications. Impeding the implementation of DOF-MS is the development of the required array detectors and working out the equivalents to the focusing methods now used in time-of-flight (TOF) mass analyzers. Ideally, a batch of ions composed of a variety of m/z values, despite initial distributions of space and energy, would be spatially focused at their respective flight distances at the same time. First-order energy focusing, including ion turnaround, is shown to be accomplished by the use of an ion mirror in conjunction with constant momentum acceleration of the initial ion packet. The initial spatial dispersion is maintained throughout the flight path. With zero initial spatial ion spread, energy focusing to achieve resolutions in the tens of thousands is shown to be feasible with ions from the elemental and isotope ratio mass regions through the extremely high m/z range. With moderate spatial spread taken into account, the DOF-MS approach is shown to achieve resolutions competitive with quadrupole and ion trap mass analyzers. Advantages of DOF-MS include all the advantages of TOF-MS plus simpler detector electronics and the improved signal-to-noise ratio and dynamic range afforded by array detection. 相似文献
75.
The incorporation of nanoparticles into engineering thermoplastics affords engineers an opportunity to synthesize polymer nanocomposites that potentially rival the most advanced materials in nature. Development of these materials is difficult because thermodynamic and kinetic barriers inhibit the dispersal of inorganic, often hydrophilic nanoparticles in hydrophobic polymer matrices. Using a new solvent-exchange approach, we preferentially reinforce the hard microdomains of thermoplastic elastomers with smectic clay of similar characteristic dimensions. The strong adhesion between the clay and the hard microdomains coupled with the formation of a percolative network not only stiffens and toughens, but increases the heat distortion temperature of the material and induces reversible thermotropic liquid-crystalline transitions. The discotic clay platelets induce morphological ordering over a range of length scales, which results in significant thermomechanical enhancement and expands high-temperature applications. Merging block-copolymer processing techniques with this method for preferential ordering of nanoparticle facilitates the development of new, hierarchically ordered materials. 相似文献
76.
The use of high intensity ultrasound to promote a number of reactions at the surface of solid poly(vinyl chloride) is reported. Substitution reactions involving a range of compounds, including dyes, can rapidly be carried out from aqueous solution under labile conditions. Sonochemically enhanced treatment with strong aqueous base produces dehydrochlorination even at room temperature to produce a thin layer of conjugated material at the surface which can then be grafted with a number of compounds. Some speculation as to the mechanistic features of the process as well as its potential utility is made. © 1999 Society of Chemical Industry 相似文献
77.
Buckley PR McKinley GH Wilson TS Small W Benett WJ Bearinger JP McElfresh MW Maitland DJ 《IEEE transactions on bio-medical engineering》2006,53(10):2075-2083
Presently, there is interest in making medical devices such as expandable stents and intravascular microactuators from shape memory polymer (SMP). One of the key challenges in realizing SMP medical devices is the implementation of a safe and effective method of thermally actuating various device geometries in vivo. A novel scheme of actuation by Curie-thermoregulated inductive heating is presented. Prototype medical devices made from SMP loaded with nickel zinc ferrite ferromagnetic particles were actuated in air by applying an alternating magnetic field to induce heating. Dynamic mechanical thermal analysis was performed on both the particle-loaded and neat SMP materials to assess the impact of the ferrite particles on the mechanical properties of the samples. Calorimetry was used to quantify the rate of heat generation as a function of particle size and volumetric loading of ferrite particles in the SMP. These tests demonstrated the feasibility of SMP actuation by inductive heating. Rapid and uniform heating was achieved in complex device geometries and particle loading up to 10% volume content did not interfere with the shape recovery of the SMP. 相似文献
78.
Assessing fuel cell vehicle innovation and the role of policy in Japan,Korea, and China 总被引:1,自引:0,他引:1
Despite intensive public and private research efforts into developing fuel cell vehicles (FCV), the global number of FCV remains small and they are unavailable for commercial purchase. We use an in-depth literature review, and bibliometric and patent analysis to analyse FCV technology within the conceptual framework of Rogers' innovation diffusion curve and suggest how the particular innovation systems and policies adopted in three key Asian car-manufacturing countries (Japan, Korea, and China) have influenced the development of FCV. Such analysis may capture trends not indicated by technical measures such as increases in efficiency or decreases in unit cost. Although Japan continues to lead in terms of number of patents and quality of academic research, Korea and China have been successful in developing fuel cell programs. Korean academics patent more frequently than their Japanese and Chinese peers, producing 18% of FC patents, with 16% of those filed also naming a private company. The 2008 financial crisis and ongoing economic uncertainty appears to have had some effect on patent activity whilst academic research appears unaffected. Diffusion curve analysis suggests that FCVs have not reached technological maturity. 相似文献
79.
Chhatre SS Guardado JO Moore BM Haddad TS Mabry JM McKinley GH Cohen RE 《ACS applied materials & interfaces》2010,2(12):3544-3554
The design of robust omniphobic surfaces, which are not wetted by low-surface-tension liquids such as octane (γlv=21.6 mN/m) and methanol (γlv=22.7 mN/m), requires an appropriately chosen surface micro/nanotexture in addition to a low solid-surface energy (γsv). 1H,1H,2H,2H-Heptadecafluorodecyl polyhedral oligomeric silsesquioxane (fluorodecyl POSS) offers one of the lowest solid-surface energy values ever reported (γsv≈10 mN/m) and has become the molecule of choice for coating textured surfaces. In this work, we synthesize and evaluate a series of related molecules that either retain the POSS cage and differ in fluoroalkyl chain length or that retain the fluorodecyl chains surrounding a linear or cyclic molecular structure. The solid-surface energy (γsv) of these molecules was estimated using contact angle measurements on flat spin-coated silicon wafer surfaces. Zisman analysis was performed using a homologous series of n-alkanes (15.5≤γlv≤27.5 mN/m), whereas Girifalco-Good analysis was performed using a set of polar and nonpolar liquids with a wider range of liquid surface tension (15.5≤γlv≤72.1 mN/m). The hydrogen-bond-donating, hydrogen-bond-accepting, polar, and nonpolar (dispersion) contributions to the solid-surface energy of each compound were determined by probing the surfaces using a set of three liquid droplets of either acetone, chloroform, and dodecane or diiodomethane, dimethyl sulfoxide, and water. 相似文献
80.
Analysis of lower carbon power systems has tended to focus on the operational carbon dioxide (CO2) emissions from power stations. However, to achieve the large cuts required it is necessary to understand the whole-life contribution of all sectors of the electricity industry. Here, a preliminary assessment of the life cycle carbon emissions of the transmission network in Great Britain is presented. Using a 40-year period and assuming a static generation mix it shows that the carbon equivalent emissions (or global warming potential) of the transmission network are around 11 gCO2-eq/kWh of electricity transmitted and that almost 19 times more energy is transmitted by the network than is used in its construction and operation. Operational emissions account for 96% of this with transmission losses alone totalling 85% and sulphur hexafluoride (SF6) emissions featuring significantly. However, the CO2 embodied within the raw materials of the network infrastructure itself represents a modest 3%. Transmission investment decisions informed by whole-life cycle carbon assessments of network design could balance higher financial and carbon ‘capital’ costs of larger conductors with lower transmission losses and CO2 emissions over the network lifetime. This will, however, necessitate new regulatory approaches to properly incentivise transmission companies. 相似文献