Characterization of hydrogen responsive nanoporous palladium films synthesized via a spontaneous galvanic displacement reaction.

A model is presented regarding the mechanistic properties associated with the interaction of hydrogen with nanoporous palladium (np-Pd) films prepared using a spontaneous galvanic displacement reaction (SGDR), which involves PdCl(2) reduction by atomic Ag. Characterization of these films shows both chemical and morphological factors, which influence the performance characteristics of np-Pd microcantilever (MC) nanomechanical sensing devices. Raman spectroscopy, uniquely complemented with MC response profiles, is used to explore the chemical influence of palladium oxide (PdO). These combined techniques support a reaction mechanism that provides for rapid response to H(2) and recovery in the presence of O(2). Post-SGDR processing via reduction of PdCl(2)(s) in a H(2) environment results in a segregated nanoparticle three-dimensional matrix dispersed in a silver layer. The porous nature of the reduced material is shown by high resolution scanning electron microscopy. Extended grain boundaries, typical of these materials, result in a greater surface area conducive to fast sorption/desorption of hydrogen, encouraged by the presence of PdO. X-ray diffraction and inductively coupled plasma-optical emission spectroscopy are employed to study changes in morphology and chemistry occurring in these nanoporous films under different processing conditions. The unique nature of chemical/morphological effects, as demonstrated by the above characterization methods, provides evidence in support of observed nanomechanical response/recovery profiles offering insight for catalysis, H(2) storage and improved sensing applications.

Infrared imaging using arrays of SiO2 micromechanical detectors.

In this Letter, we describe the fabrication of an array of bimaterial detectors for infrared (IR) imaging that utilize SiO(2) as a structural material. All the substrate material underneath the active area of each detector element was removed. Each detector element incorporates an optical resonant cavity layer in the IR-absorbing region of the sensing element. The simplified microfabrication process requires only four photolithographic steps with no wet etching or sacrificial layers. The thermomechanical deflection sensitivity was 7.9×10(-3) rad/K, which corresponds to a noise equivalent temperature difference (NETD) of 2.9 mK. In the present work, the array was used to capture IR images while operating at room temperature and atmospheric pressure without the need for vacuum packaging. The average measured NETD of our IR detector system was approximately 200 mK, but some sensing elements exhibited an NETD of 50 mK.

Oil-exporting status, quality of life, and fertility: a cross national study.

PIP: It has been suggested that unless the rapid increase in income in the oil-exporting countries is accompanied by more equitable distribution of modern goods and services, the impact on health, literacy, and fertility is likely to be negligible. This study represents an initial attempt to examine the possible effects of the oil-exporting status of nations on their income, quality of life, and fertility. Data from 150 countries were used, and the Physical Quality of Life Index (PQLI) was utilized instead of traditional measures of development. Some findings are: 1) the variable showing the strongest direct relationship to fertility was physical quality of life (p=-.756) which is consistent with the distributional hypothesis; 2) per capita gross national product (GNP) and oil-exporting status showed weaker paths to fertility and their signs were in opposite directions; 3) per capita GNP showed a moderate negative relationship to fertility (p=-.171) while oil-exporting status had a positive path of about the same size (p= .155), thus per capita income and oil-exporting status had only about 1/5 the net relationship to fertility as did physical quality of life; 4) the indirect relationship of income as channeled through PQLI was over twice as large as the measured direct relationship, so that the importance of per capita GNP for lower fertility is primarily through its influence on the physical quality of life within a nation; 5) oil-exporting status was associated with lower physical quality of life and the latter was strongly related to higher fertility; and 6) in the long run, the relationship between oil-exporting status and quality of life should be positive. If separate analyses are conducted, the division should be made along an oil-exporter/non-exporter dichotomy, rather than a more developed/less developed country categorization. It is concluded that nations with relatively high life expectancies high levels of literacy, and low levels of infant mortality exhibited lower fertility than did nations with poorer records on these dimensions. While higher per capita incomes were significantly related to lower fertility, the greater portion of the relationship was channeled through the quality of life. Once the effect of the oil-exporting nations is controlled, developed and underdeveloped countries do not differ widely in the relationships between per capita GNP, physical quality of life, and fertility.^ieng