Blood pressure and indices of glomerular filtration area in hypertensive and normotensive Prague rats

The involvement of the kidney in the pathogenesis of hypertension has long been recognised, although the specific renal mechanisms underlying this phenomenon are still unknown. A current hypothesis attributes hyper tension to a reduction in glomerular filtration area by glomerular loss, The present study analyses the relationship between glomerular number and volume and conscious systolic blood pressure (SBP) in 4- to 53-week-old hypertensive (PHR) and normotensive (PNR) rats of the Prague strain. Adult PHRs had higher SEP, were larger and had larger kidneys than PNRs, but 20% fewer glomeruli, A significant negative correlation between SEP and glomerular number was found in PHR males, but not in PHR females or PNRs. There was no correlation at all between glomerular volume and SEP and, in young animals, both SEP and glomerular number were higher in PHRs than in PNRs. In addition, in adult PHRs, glomerular volume and SEP were higher in males than in females. In summary, a generally valid, causal relation-ship linking raised blood pressure to decreased glomerular number or volume could not be demonstrated in the Prague rat model of genetically determined hypertension. The nature of the renal mechanism(s) determining the hypertension in this model remains unknown. Copyright (C) 2000 S. Karger AG, Basel

The National Park Service at 100

In its first century, the National Park Service was transformed from an agency that managed a small number of western parks to one responsible for over 400 sites across the country. The management of these park sites has changed as well, with many new parks structured as a partnership effort between the National Park Service and surrounding cities and towns, as well as non-profit organizations and friends groups. The Park Service has had its work extended by Congress to reach beyond park boundaries in order to help states and local governments with resource preservation and the development of recreational opportunities in neighborhoods where people live and work. The Park Service has also been given a leadership role in providing technical assistance to other countries in creating national parks and preserving their natural and cultural resources. As the National Park Service enters its second century, it faces many of the same challenges as other federal agencies. The two primary challenges facing the National Park Service as it moves forward are ensuring sufficient funding for the national park system from Congress and other revenue sources and keeping the national parks relevant to succeeding generations of Americans. National parks remain popular with the American public for the way they connect us to the land and the story of our country. Perhaps former National Park Service Director George Hartzog stated it best when he said: “The national park idea has been nurtured by each succeeding generation of Americans. Today, across our land, the National Park System represents America at its best. Each park contributes to a deeper understanding of the history of the United States and our way of life; of the natural processes which have given form to our land, and to the enrichment of the environment in which we live.

The Path of the Presidio Trust Legislation

Creating the Presidio Trust and enacting the other land protection measures in the Omnibus Parks Act was not been simple. The park service had originally envisioned in the general management plan for the Presidio that a partnership institution would be created to assist the National Park Service with management of the area. The park service\u27s partnership idea would be changed substantially when the trust legislation emerged from Congress. This article will examine how the Presidio first became part of the National Park System, the efforts undertaken to provide the park service with the authority needed to manage the area, and the controversies and compromises that surrounded the enactment of the Presidio Trust legislation

The Path of the Presidio Trust Legislation

Creating the Presidio Trust and enacting the other land protection measures in the Omnibus Parks Act was not been simple. The park service had originally envisioned in the general management plan for the Presidio that a partnership institution would be created to assist the National Park Service with management of the area. The park service\u27s partnership idea would be changed substantially when the trust legislation emerged from Congress. This article will examine how the Presidio first became part of the National Park System, the efforts undertaken to provide the park service with the authority needed to manage the area, and the controversies and compromises that surrounded the enactment of the Presidio Trust legislation

Magnetism in 2D BN1−x_{1-x}Ox_x and B1−x_{1-x}Six_xN: polarized itinerant and local electrons

We use density functional theory based first-principles methods to study the magnetism in a 2D hexagonal BN sheet induced by the different concentrations of oxygen and silicon atoms substituting for nitrogen (O$_\mathrm{N}$) and boron (Si$_\mathrm{B}$) respectively. We demonstrate the possible formation of three distinct phases based on the magnetization energy calculated self-consistently for the ferromagnetic (ME$_{\mathrm{FM}}$) and antiferromagnetic (ME$_{\mathrm{AFM}}$) states, i.e. the paramagnetic phase with ME$_{\mathrm{FM}}$=ME$_{\mathrm{AFM}}$, the ferromagnetic phase with ME$_{\mathrm{FM}}$$>$ME$_{\mathrm{AFM}}$ and finally the polarized itinerant electrons with finite ME$_{\mathrm{FM}}$ but zero ME$_{\mathrm{AFM}}$. While the O$_\mathrm{N}$ system was found to exist in all three phases, no tendency towards the formation of the polarized itinerant electrons was observed for the Si$_\mathrm{B}$ system though the existence of the other two phases was ascertained. The different behavior of these two systems is associated with the diverse features in the magnetization energy as a function of the oxygen and silicon concentrations. Finally, the robustness of the polarized itinerant electron phase is also discussed with respect to the O substitute atom distributions and the applied strains to the system.Comment: accepted by RP

Entanglement and Quantum Phase Transition Revisited

We show that, for an exactly solvable quantum spin model, a discontinuity in the first derivative of the ground state concurrence appears in the absence of quantum phase transition. It is opposed to the popular belief that the non-analyticity property of entanglement (ground state concurrence) can be used to determine quantum phase transitions. We further point out that the analyticity property of the ground state concurrence in general can be more intricate than that of the ground state energy. Thus there is no one-to-one correspondence between quantum phase transitions and the non-analyticity property of the concurrence. Moreover, we show that the von Neumann entropy, as another measure of entanglement, can not reveal quantum phase transition in the present model. Therefore, in order to link with quantum phase transitions, some other measures of entanglement are needed.Comment: RevTeX 4, 4 pages, 1 EPS figures. some modifications in the text. Submitted to Phys. Rev.

Influence of a magnetic field on the viscosity of a dilute gas consisting of linear molecules.

The viscomagnetic effect for two linear molecules, N2 and CO2, has been calculated in the dilute-gas limit directly from the most accurate ab initio intermolecular potential energy surfaces presently available. The calculations were performed by means of the classical trajectory method in the temperature range from 70 K to 3000 K for N2 and 100 K to 2000 K for CO2, and agreement with the available experimental data is exceptionally good. Above room temperature, where no experimental data are available, the calculations provide the first quantitative information on the magnitude and the behavior of the viscomagnetic effect for these gases. In the presence of a magnetic field, the viscosities of nitrogen and carbon dioxide decrease by at most 0.3% and 0.7%, respectively. The results demonstrate that the viscomagnetic effect is dominated by the contribution of the jj¯ polarization at all temperatures, which shows that the alignment of the rotational axes of the molecules in the presence of a magnetic field is primarily responsible for the viscomagnetic effect

Ab initio Studies of the Possible Magnetism in BN Sheet by Non-magnetic Impurities and Vacancies

We performed first-principles calculations to investigate the possible magnetism induced by the different concentrations of non-magnetic impurities and vacancies in BN sheet. The atoms of Be, B, C, N, O, Al and Si are used to replace either B or N in the systems as impurities. We discussed the changes in density of states as well as the extent of the spatial distributions of the defect states, the possible formation of magnetic moments, the magnitude of the magnetization energies and finally the exchange energies due to the presence of these defects. It is shown that the magnetization energies tend to increase as the concentrations of the defects decreases in most of the defect systems which implies a definite preference of finite magnetic moments. The calculated exchange energies are in general tiny but not completely insignificant for two of the studied defect systems, i.e. one with O impurities for N and the other with B vacancies.Comment: 8 pages, 10 figures, submitted to Phys. Rev.