Vapor-deposited platinum as a fuel-cell catalyst

Electrodes are prepared by vacuum deposition of platinum on nickel substrate with conventional vapor-deposition apparatus. Amount of platinum loaded on substrate can be veried by changing exposure time during deposition. These electrodes are significantly more effective than conventional oxygen electrodes

Origin of the unusual dependence of Raman D band on excitation wavelength in graphite-like materials

We have revisited the still unresolved puzzle of the dispersion of the Raman disordered-induced D band as a function of laser excitation photon energy E$_L$ in graphite-like materials. We propose that the D-mode is a combination of an optic phonon at the K-point in the Brillioun zone and an acoustic phonon whose momentum is determined uniquely by the double resonance condition. The fit of the experimental data with the double-resonance model yields the reduced effective mass of 0.025m$_{e}$ for the electron-hole pairs corresponding to the A$_{2}$ transition, in agreement with other experiments. The model can also explain the difference between $\omega_S$ and $\omega_{AS}$ for D and D$^{\star}$ modes, and predicts its dependence on the Raman excitation frequency.Comment: 4 figures in eps forma

Searching for the Common Suprathermal Power Law Tail in Parker Solar Probe\u27s ISOIS Data

Results from the Advanced Composition Explorer (ACE) and the Ulysses spacecraft suggested the existence of a pervasive power-law spectrum of suprathermal ions in the solar wind with a spectral index of -3/2. This distribution is of particular interest to humanity because the suprathermal ions it describes can serve as the seed population for large, destructive events that can harm ground- and air-based equipment. It has been suggested that various statistical mechanisms can produce the observed spectrum, however the underlying physical phenomena are not yet known. The spectrum of suprathermal ions is relatively unstudied closer to the Sun than 1 au. I investigate the first year and a half of Parker Solar Probe\u27s data to find evidence of this spectrum in this previously unstudied region. I find weak evidence to suggest the existence of a common spectrum of protons from 60 to 200 keV inside the region being studied. Naive fits to all of the events fail to produce the expected -3/2, yet some relationship between magnetic turbulence and spectral index is found, as is an apparent relationship between radial distance and spectral index, suggesting some type of asymptotic approach to index -3/2 as radial distance increases. Additionally, my results are not incompatible with recent adaptations to some statistical models that yield softer spectra. Further work is required to uncover the phenomena in this region that determine the shape of the solar wind spectrum

Covariant quantum measurements may not be optimal

Quantum particles, such as spins, can be used for communicating spatial directions to observers who share no common coordinate frame. We show that if the emitter's signals are the orbit of a group, then the optimal detection method may not be a covariant measurement (contrary to widespread belief). It may be advantageous for the receiver to use a different group and an indirect estimation method: first, an ordinary measurement supplies redundant numerical parameters; the latter are then used for a nonlinear optimal identification of the signal.Comment: minor corrections, to appear in J. Mod. Opt. (proc. of Gdansk conf.

Division of labour and risk taking in the dinosaur ant, Dinoponera quadriceps

The success of social insects can be largely attributed to division of labour. In contrast to most social insects, many species with simple societies contain workers which are capable of sexual reproduction. Headed by one or a few reproductive individuals, subordinate workers form a dominance hierarchy, queuing to attain the reproductive role. In these species task allocation may be influenced by individual choice based on future reproductive prospects. Individuals with a better chance of inheriting the colony may be less likely to take risks and high-ranking workers that spend a greater amount of time in proximity to the brood may be able to increase the ability to police egg-laying by cheating subordinates. We investigated division of labour and risk taking in relation to dominance rank in the queenless ponerine ant, Dinoponera quadriceps, a species with relatively simple societies. Using behavioural observations, we show that high-ranking workers spend more time performing egg care, less time foraging and are less likely to defend the nest against attack. High-rankers also spent a greater amount of time guarding and inspecting eggs, behaviours which are likely to improve detection of egg laying by cheating subordinates. We also show that high-ranking workers spend a greater amount of time idle, which may help increase lifespan by reducing energy expenditure. Our results suggest that both risk-taking and egg-care behaviours are related to future reproductive prospects in D. quadriceps. This highlights a mechanism by which effective division of labour could have been achieved during the early stages of eusocial evolution

Parabolic Focal Conics and Polygonal Textures in Lipid Liquid Crystals

Polygonal defect arrays in lipid liquid crystals prepared from dipalmitoyl-, dimyristoyl-, and dilaurylphosphatidylcholine with various concentrations of water have been observed and characterized using optical microscopy. These arrays appear similar to the polygonal arrays previously observed in thermotropic smectic and cholesteric liquid crystals. The parabolic focal conic model proposed by Rosenblatt, Pindak, Clark and Meyer for the polygonal arrays in thermotropic smectic liquid crystals also describes the observed properties in the smectic A phase of lipid liquid crystals. The polygonal arrays become progressively more birefringent as the strains inducing them are increased. The parabolic focal conic model does not completely describe the details of the more birefringent polygonal arrays.Engineering and Applied Science

Treaties and Congressional-Executive or Presidential Agreements: Interchangeable Instruments of National Policy: II

The existence under our Constitution of the variety of interchangeable techniques, described in the previous Sections of this article, for perfecting international agreements has obviously served the nation well in the past. It may in the future, if the facts of variety and interchangeability are fully recognized and acted upon by the public and by all branches of the Government, provide a system for the conduct of our foreign relations which is adequate both to cope with the imperatives of survival and to secure our other national interests in the contemporary world—that is, a system whereby policy is quickly and easily formed by democratic means for the nation as a whole, and whereby the execution of policy is prompt and efficient, without being subjected to the adventitious whims and disintegrating attacks of obstructionist minority control. The flexibility and dispatch which such a system may require are available in the President\u27s powers to make the initial decision as to how any particular agreement is to be perfected and to make and perform, on his own responsibility, all agreements needed to meet war and other emergencies. Conversely, ample check upon any arbitrary or unwise exercise of executive power, beyond what is imposed by public opinion and the President\u27s unique responsibility to the voters of the whole nation, is insured by the fact that, without the aid of the Congress, the powers of the President, or even of the President and the Senate, to perform important international agreements are in the long run severely limited. Sooner or later, and in most instances sooner, a President who is engaged in important international undertakings must secure funds and supplementary legislation and must, therefore, submit his negotiations to the scrutiny and approval or disapproval of a majority of the elected representatives of the people. Full and free responsiveness to democratic control and to the national interest can be made certain by use of the Congressional-Executive agreement as a functional alternative to the treaty, enabling the President to go to both houses of the Congress for confirmation of any particular agreement, either in the first instance, or after it has become apparent that an agreement previously submitted to the Senate will be blocked by a minority obdurate in opposing majority will. In such a system the survival, as a sort of constitutional vermiform appendix, of an additional undemocratic mode of validating international agreements by the two-thirds vote of a single house, can do no harm to the national interest, if it is agreed by all parties that this mode of validation is not exclusive of the more democratic mode and that its continued existence is not to be used to obfuscate issues of substantive policy by the invocation of procedural subtleties

Hydration of Single Crystals of Dipalmitoylphosphatidylcholine

Optical birefringence and x-ray measurements are reported for single crystals $(0.5 mm \times 2 mm \times 5 \mu m)$ of dipalmitoylphosphatidylcholine as a function of temperature and relative humidity. Large single crystals grown in $CHCl_3$/acetone at a low water concentration undergo an irreversible phase transformation at $20^{\circ}C$ and 70% relative humidity or at $60^{\circ}C$ and 65% relative humidity. After this transformation occurs, the crystals can be made to undergo a reversible transformation into and out of the $L_{\alpha}$ phase. The x-ray-determined mosaic spread in the hydrated crystal is less than $\approx 0.04^{\circ}$ both above and below the main transition.Engineering and Applied Science