Presidents, Their Styles and Their Leadership

If one set out to design a democracy in which the personal qualities of the top leader could be expected to have an impact on political outcomes, the result might well resemble the political system of the United States. The separation of powers and the Constitutional provision for a president with autonomous powers such as the veto have enabled chief executives to place a personal stamp on the nation's policies since the founding of the Republic; but until the1930s, Congress typically took the lead in policy making, and the activities of the federal government had little impact on the nation and world

Standard, Meta-Standard: a framework for coding occupational data

Die Debatte über ein angemessenes Schema zur Codierung von beruflichen Daten dauert seit ungefähr 100 Jahren ohne befriedigende Ergebnisse an. Der vorliegende Beitrag geht den Gründen dieses mangelnden Konsens nach. Den entscheidenden Grund sieht der Autor darin, daß jedes entwickelte Schema unvermeidlich die spezifischen Forschungsinteressen und -annahmen mit ihren zeitbedingten Beschränkungen reflektiert. Der gleiche Datensatz führt deshalb zu unterschiedlichen Klassifikationen. Auf dem Hintergrund dieser Problemstellung entwickelt der Autor ein Codierungsschema, das der 'unvermeidlichen' Relativität besser gerecht zu werden sucht. (pmb)'Debate over appropriate schema for coding occupational data has been ongoing without satisfactory resolution since at least the late nineteenth century. It is fuelled by the fact that classifying occupational data whether they are collected by culling the historical record or through precise sociological survey, can never be exact. Some of the relevant data are nearly always ambiguous (when is a 'merchant' merely a small shopkeeper and when a multi-national shipper of luxury goods?). Moreover, any scheme will inevitably reflect its author's particular research interests and/or assumptions about social and occupational structures relevant to the period and place under investigation. Consequently, any two authors faced with the same dataset are likely to produce different and even incompatible coding schemes with which to catagorize occupational information. Authors concerned with similar phenomena which occur in different places or at different times are even more likely to generate incompatible schemes. These well-known problems have far reaching ramifications. If coding schemes are ultimately subjective, then can we ever truly verify the quantitative historical research which employ them? How, without some attempt to standardized coding practices, the quantitative data collected and computerized by others will never be usable in for secondary or comparative analyses?' (author's abstract

The Nature of Faint Blue Stars in the Halo. II

Spectra and colors of 189 hot (FB) stars selected colorimetrically and mostly within 30° of the galactic poles are analyzed quantitatively for surface gravity and effective temperatures. Palomar spectra give line intensities and Balmer line profiles, found in the Appendix tables. Using a network of model atmospheres, the g and θ so determined give directly the light-to-mass ratio, and eventually the luminosities. The high-latitude hot stars cover a range of 10^6 in luminosity, and are classifiable into various groups. Spectroscopically normal B stars make up 26 percent of the sample; they rotate and have nearly normal line spectra. Interpreted as Population I stars, on the mass-luminosity relation, they have relatively high luminosities and large z-coordinates. For some, the nuclear lifetimes at present luminosities are less than transit times from the plane. Their high velocities present a problem for galactic kinematics. A few are slightly helium rich, while others are highly evolved Population II stars, from details of the spectroscopy. Some of the Population I stars may be in not-understood, short-lived evolutionary phases of high luminosity and low mass. The (g, θ)-relation can be transformed into luminosity-temperature diagrams if masses are known. Many fall along a relation log gθ^4 = 2.35, have common properties of halo stars, and T_(eff) from 9500° to 40,000° K. The light-to-mass ratio for these is 68 (in solar units) ; most HB and sdB stars have weak metal and weak helium lines, i.e., are halo stars. We call this the extended horizontal branch (EHB). Quantitative classification gives 17 percent of the FB stars as horizontal-branch B and early A (HB) stars, and 16 percent subdwarf B (sdB) stars. There are 16 percent subdwarf O (sdO) stars, including planetary nuclei; these have strong, or very strong, helium lines. Assuming a constant mass, 0.66 m_⊙, the observed L/m gives Mb = +0.5. The EHB for field stars fits the globular cluster HB, and extends it to high T_(eff). The bolometric correction produces the change of M_v with color. The hot white dwarfs are 11 percent of the FB stars and appear as a bridge between the sdO stars and the ordinary DA white dwarfs. Composite stars are unresolved, noninteracting binaries with strange UBV colors; they require a faint Mv for the primary (e.g., sdO or sdB), and an unevolved G companion. The helium deficiency and the evolutionary problems are sharpest for the EHB stars. In a few, slightly stronger helium lines are accompanied by lines of peculiar elements (S III, P II seen at high dispersion. While the L/m ratio is closely the same for sdO as for sdB and HB, the He lines become strong. Evolutionary tracks avoid the region of the hot EHB stars; the hottest sdO stars approach the helium main sequence. The low surface helium is almost certainly not cosmological in origin. Gravitational diffusion in a nonrotating star in the absence of convection is plausible; in the sdO and the peculiar sdB stars convection and helium flashes may have occurred. Numerous radial velocities were measured. Where possible, proper motions, luminosities, and radial-velocity dispersions were used for space motions. The Population I normal stars have abnormally high space motions, not greatly different from Population II stars. The luminosities derived from spectroscopy are consistent with those from peculiar motions

Quantum mechanics explained

The physical motivation for the mathematical formalism of quantum mechanics is made clear and compelling by starting from an obvious fact - essentially, the stability of matter - and inquiring into its preconditions: what does it take to make this fact possible?Comment: 29 pages, 5 figures. v2: revised in response to referee comment

Hubble Space Telescope Spectroscopy of the Balmer lines in Sirius B

Sirius B is the nearest and brightest of all white dwarfs, but it is very difficult to observe at visible wavelengths due to the overwhelming scattered light contribution from Sirius A. However, from space we can take advantage of the superb spatial resolution of the Hubble Space Telescope to resolve the A and B components. Since the closest approach in 1993, the separation between the two stars has become increasingly favourable and we have recently been able to obtain a spectrum of the complete Balmer line series for Sirius B using HST?s Space Telescope Imaging Spectrograph (STIS). The quality of the STIS spectra greatly exceed that of previous ground-based spectra, and can be used to provide an important determination of the stellar temperature (Teff = 25193K) and gravity (log g = 8.556). In addition we have obtained a new, more accurate, gravitational red-shift of 80.42 +/- 4.83 km s-1 for Sirius B. Combining these results with the photometric data and the Hipparcos parallax we obtain new determinations of the stellar mass for comparison with the theoretical mass-radius relation. However, there are some disparities between the results obtained independently from log g and the gravitational redshift which may arise from flux losses in the narrow 50x0.2arcsec slit. Combining our measurements of Teff and log g with the Wood (1995) evolutionary mass-radius relation we get a best estimate for the white dwarf mass of 0.978 M. Within the overall uncertainties, this is in agreement with a mass of 1.02 M obtained by matching our new gravitational red-shift to the theoretical M/R relation.Comment: 11 pages, 6 figures, accepted for publication in the Monthly Notices of the Royal Astronomical Societ

The Nature of Faint Blue Stars in the Halo. II

Spectra and colors of 189 hot (FB) stars selected colorimetrically and mostly within 30° of the galactic poles are analyzed quantitatively for surface gravity and effective temperatures. Palomar spectra give line intensities and Balmer line profiles, found in the Appendix tables. Using a network of model atmospheres, the g and θ so determined give directly the light-to-mass ratio, and eventually the luminosities. The high-latitude hot stars cover a range of 10^6 in luminosity, and are classifiable into various groups. Spectroscopically normal B stars make up 26 percent of the sample; they rotate and have nearly normal line spectra. Interpreted as Population I stars, on the mass-luminosity relation, they have relatively high luminosities and large z-coordinates. For some, the nuclear lifetimes at present luminosities are less than transit times from the plane. Their high velocities present a problem for galactic kinematics. A few are slightly helium rich, while others are highly evolved Population II stars, from details of the spectroscopy. Some of the Population I stars may be in not-understood, short-lived evolutionary phases of high luminosity and low mass. The (g, θ)-relation can be transformed into luminosity-temperature diagrams if masses are known. Many fall along a relation log gθ^4 = 2.35, have common properties of halo stars, and T_(eff) from 9500° to 40,000° K. The light-to-mass ratio for these is 68 (in solar units) ; most HB and sdB stars have weak metal and weak helium lines, i.e., are halo stars. We call this the extended horizontal branch (EHB). Quantitative classification gives 17 percent of the FB stars as horizontal-branch B and early A (HB) stars, and 16 percent subdwarf B (sdB) stars. There are 16 percent subdwarf O (sdO) stars, including planetary nuclei; these have strong, or very strong, helium lines. Assuming a constant mass, 0.66 m_⊙, the observed L/m gives Mb = +0.5. The EHB for field stars fits the globular cluster HB, and extends it to high T_(eff). The bolometric correction produces the change of M_v with color. The hot white dwarfs are 11 percent of the FB stars and appear as a bridge between the sdO stars and the ordinary DA white dwarfs. Composite stars are unresolved, noninteracting binaries with strange UBV colors; they require a faint Mv for the primary (e.g., sdO or sdB), and an unevolved G companion. The helium deficiency and the evolutionary problems are sharpest for the EHB stars. In a few, slightly stronger helium lines are accompanied by lines of peculiar elements (S III, P II seen at high dispersion. While the L/m ratio is closely the same for sdO as for sdB and HB, the He lines become strong. Evolutionary tracks avoid the region of the hot EHB stars; the hottest sdO stars approach the helium main sequence. The low surface helium is almost certainly not cosmological in origin. Gravitational diffusion in a nonrotating star in the absence of convection is plausible; in the sdO and the peculiar sdB stars convection and helium flashes may have occurred. Numerous radial velocities were measured. Where possible, proper motions, luminosities, and radial-velocity dispersions were used for space motions. The Population I normal stars have abnormally high space motions, not greatly different from Population II stars. The luminosities derived from spectroscopy are consistent with those from peculiar motions

Secreted phospholipase A2 activity in experimental autoimmune encephalomyelitis and multiple sclerosis

BACKGROUND: There is increased interest in the contribution of the innate immune system to multiple sclerosis (MS), including the activity of acute inflammatory mediators. The purpose of this study was to test the involvement of systemic secreted phospholipase A2 (sPLA2) enzymes in experimental autoimmune encephalomyelitis (EAE), an MS model, and to determine if enzyme activity is elevated in MS patients. METHODS: A non-invasive urinary assay was developed in order to monitor enzymatically active sPLA2 levels in Dark Agouti rats after induction of EAE. Some Rats were treated with nonapeptide CHEC-9, an uncompetitive sPLA2 enzyme inhibitor, during the initial rise in urinary enzyme levels. Body weight and clinical EAE score were measured for 18 days post immunization (PI), after which the rats were sacrificed for H&E and myelin staining, and for ED-1 immunocytochemistry, the latter to quantify macrophages and activated microglia. The urinary sPLA2 assay was also applied to un-timed samples collected from a cross section of 44 MS patients and 14 healthy controls. RESULTS: Mean levels of enzymatically active sPLA2 in the urine increased following immunization and peaked between days 8–10 PI which was just prior to the onset of EAE symptoms. At this time, a transient attenuation of activity was detected in the urine of CHEC-9 treated rats consistent with the activity-dependent properties of the inhibitor. The peptide also reduced or abolished EAE symptoms compared to vehicle-injected controls. Histopathological changes in the spinal cords of the EAE rats correlated generally with clinical score including a significant reduction in ED-1+ cells after peptide treatment. Multiple Sclerosis patients also showed elevations in sPLA2 enzyme activity. Mean levels of sPLA2 were increased 6-fold in the urine of patients with active disease and 4-fold for patients in remission, regardless of immunomodulating therapy. CONCLUSION: The results suggest that sPLA2 enzymes, traditionally thought to be part the acute phase inflammatory response, are therapeutic targets for MS

Understanding light quanta: First quantization of the free electromagnetic field

The quantization of the electromagnetic field in vacuum is presented without reference to lagrangean quantum field theory. The equal time commutators of the fields are calculated from basic principles. A physical discussion of the commutators suggest that the electromagnetic fields are macroscopic emergent properties of more fundamental physical system: the photons