pinecone/core-2020-05-10-deduplication huggingface dataset:
Why does a metal-superconductor junction have a resistance?

This is a tutorial article based on a lecture delivered in June 1999 at the
NATO Advanced Study Institute in Ankara. The phenomenon of Andreev reflection
is introduced as the electronic analogue of optical phase-conjugation. In the
optical problem, a disordered medium backed by a phase-conjugating mirror can
become completely transparent. Yet, a disordered metal connected to a
superconductor has the same resistance as in the normal state. The resolution
of this paradox teaches us a fundamental difference between phase conjugation
of light and electrons.Comment: 12 pages, 5 postscript figures [v2: all figures inline
Soilborne Diseases and their Control

Seed and seedling diseases, root rots, and wilts are caused by a number of soilborne fungi, all of which are facultative saprophytes and can survive in soil for long periods in the absence of a susceptible host. In general, these diseases are serious yield constraints where short rotations or monoculture of legume crops are the rule. Seedling diseases and root rots are enhanced by poor seed vigor, poor seedbed preparation, and other biotic and abiotic stresses which predispose the host plant. Control of these diseases requires an integrated approach of genetic resistance/tolerance, cultural practices, appropriate seed treatments, and high seed vigor. The most economical and durable control of Fusarium wilt is to grow resistant varieties. New races of a wilt pathogen have arisen due to increased selection pressure from growing resistant varieties in short rotations but have not outpaced the development of resistant cultivars
Photon statistics of a random laser

A general relationship is presented between the statistics of thermal
radiation from a random medium and its scattering matrix S. Familiar results
for black-body radiation are recovered in the limit S to 0. The mean photocount
is proportional to the trace of 1-SS^dagger, in accordance with Kirchhoff's law
relating emissivity and absorptivity. Higher moments of the photocount
distribution are related to traces of powers of 1-SS^dagger, a generalization
of Kirchhoff's law. The theory can be applied to a random amplifying medium (or
"random laser") below the laser threshold, by evaluating the Bose-Einstein
function at a negative temperature. Anomalously large fluctuations are
predicted in the photocount upon approaching the laser threshold, as a
consequence of overlapping cavity modes with a broad distribution of spectral
widths.Comment: 26 pages, including 9 figure
Distances from the Correlation between Galaxy Luminosities and Rotation
  Rates

A large luminosity--linewidth template sample is now available, improved
absorption corrections have been derived, and there are a statistically
significant number of galaxies with well determined distances to supply the
zero point. A revised estimate of the Hubble Constant is H_0=77 +-4 km/s/Mpc
where the error is the 95% probability statistical error. Systematic
uncertainties are potentially twice as large.Comment: 21 pages, 9 figures. Invited chapter for the book `Post-Hipparcos
  Cosmic Candles', Eds. F. Caputo and A. Heck (Kluwer Academic Publishers,
  Dordrecht
The contribution of microlensing surveys to the distance scale

In the early nineties several teams started large scale systematic surveys of
the Magellanic Clouds and the Galactic Bulge to search for microlensing
effects. As a by product, these groups have created enormous time-series
databases of photometric measurements of stars with a temporal sampling
duration and accuracy which are unprecedented. They provide the opportunity to
test the accuracy of primary distance indicators, such as Cepheids, RRLyrae
stars, the detached eclipsing binaries, or the luminosity of the red clump. We
will review the contribution of the microlensing surveys to the understanding
of the physics of the primary distance indicators, recent differential studies
and direct distance determinations to the Magellanic Clouds and the Galactic
Bulge.Comment: Invited review article to appear in: `Post-Hipparcos Cosmic Candles',
  A. Heck & F. Caputo (Eds), Kluwer Academic Publ., Dordrecht, in press. 21
  pages; uses Kluwer's crckapb.sty LaTeX style file, enclose
Strong gravity and X-ray spectroscopy

This paper reviews the effects of general relativity in an X-ray spectrum reflected from a cold matter accreting onto a black hole. The spectrum consists of the iron K$\alpha$ line and the Compton reflection. We sketch the overall picture of radiative processes in the central parts of the accretion flow with relation to the relativistic effects derived from the discrete features in the X-ray spectrum. We discuss implications for detection of relativistic effects and computational tools of spectral analysis
Accretion Disks Around Black Holes: Twenty Five Years Later

We study the progress of the theory of accretion disks around black holes in
last twenty five years and explain why advective disks are the best bet in
explaining varied stationary and non-stationary observations from black hole
candidates. We show also that the recently proposed advection dominated flows
are incorrect.Comment: 30 Latex pages including figures. Kluwer Style files included.
  Appearing in `Observational Evidence for Black Holes in the Universe', ed.
  Sandip K. Chakrabarti, Kluwer Academic Publishers (DORDRECHT: Holland
Nucleosynthesis in Advective Accretion Disks Around Galactic and
  Extra-Galactic Black Holes

We compute the nucleosynthesis of materials inside advective disks around
black holes. We show that composition of incoming matter can change
significantly depending on the accretion rate and accretion disks. These works
are improvements on the earlier works in thick accretion disks of Chakrabarti,
Jin & Arnett (1987) in presence of advection in the flow.Comment: Latex pages including figures. Kluwer Style files included. Appearing
  in `Observational Evidence for Black Holes in the Universe', ed. Sandip K.
  Chakrabarti, Kluwer Academic Publishers (DORDRECHT: Holland
The Effect of Self-gravity of Gas on Gas Fueling in Barred Galaxies with
  a Supermassive Black Hole

In our previous paper, we have shown that a gas disk in the nuclear region of
a barred galaxy which contains a central supermassive black hole (SMBH) rapidly
evolves into a nuclear gas ring by the effect of an additional inner Lindblad
resonance caused by the SMBH. In this paper, we investigate the fate of the gas
ring, involving self-gravity of gas, using two-dimensional hydrodynamical
simulations. We find that the gas ring becomes gravitationally unstable for a
gas surface density of gas above a critical value, and fragments into several
gas clumps. Some denser clumps increase their mass via the accretion of the
surrounding gas and collisions with other clumps, and finally a very massive
gas clump (10^7 M_sun) is formed. Due to the torque from the most massive
clump, a part of the gas in the ring loses its angular momentum and falls into
the galactic center. As a result, a nuclear gas disk (50 pc) is formed around
the SMBH. The accretion rate for $R<50$ pc attains about 1 M_sun/yr for
3.5*10^7 yr. At the final phase of the bar-driven fueling, self-gravity is
crucial for the angular momentum transfer of the gas. This is a new mechanism
for gas fueling to the vicinity of the SMBH.Comment: 14 pages, 7 figures, AASTeX, submitted to Ap
Spiral Structure in IP Peg: Confronting Theory and Observations

The first convincing piece of evidence of spiral structure in the accretion
disc in IP Pegasi was found by Steeghs et al. (1997). We performed two kinds of
2D hydrodynamic simulations, a SFS finite volume scheme and a SPH scheme, with
a mass ratio of 0.5. Both results agreed well with each other. We constructed
Doppler maps and line flux-binary phase relations based on density
distributions, the results agreeing well with those obtained by observation.Comment: 4 pages, LaTeX with 2 ps figures using crckapb.sty. To appear in the
  Proceedings of Numerical Astrophysics 1998, Tokyo, Japan, 10-13 March, 1998,
  eds. S. M. Miyama, K. Tomisaka and T. Hanawa (Kluwer Academic Publishers
Uncertain future preferences and conservation

An important problem in environmental economics arises from te irreversibility of consuming or destroying certain resources. Extractive resources like oil are a clear example. Even for environmental resources the same seems to be true in a number of environmental cases, for example biodiversity, current climate conditions, or complex ecological systems. Irreversibility imposes a sever externality across different generations; future generations will suffer from the destruction of a unique asset like Amazonia, and it is not clear how such a loss could be compensated in terms of other goods. If such an asset is destroyed, then it is not possible to subsequently restore it. In contrast, if the asset is preserved, then it is possible to "use" the asset at a subsequent date. If there is uncertainty about future preferences or valuations, then preservation provides a type of insurance which is not available if the irreversible decision is carried out.
Sustainable use of renewable resources, Chapter 2.1

We consider here optimal use patterns for renewable resources and address the problem of optimal use of renewable resources under a variety of assumptions both about the nature of the economy in which these resources are embedded and about the objective of that economy. Although we focus here on the technical economic issues of defining and characterizing paths which are optimal in various senses, in the presence of renewable resources, one should not loose sight of the very real motivation underlying these exercises: many of the earth's most important biological and ecological resources are renewable, so that in their management we confront the fundamental choice which underlies this paper, namely their extinction, or their preservation as viable species.
North-South trade and the dynamics of the environment, Chapter 2.2

This paper develops a dynamic model of North-South trade in which environment plays an important role. Our model is based on Chichilnisky North-South model for the macroeconomic interaction between two sectors of the world economy. The latter was introduced in a static context. We introduce dynamics in the original North-South model by allowing endogenous accumulation of capital. As a second extension of [1], we introduce here a variable which represents the system of property rights on the environmental asset which is used as an input to production. This could represent, for example, the property rights on forests from which wood is extracted to be used as an input to the production of traded goods or the property rights on water which is similarly used, perhaps for agricultural goods for export. The paper explains mathematically and through simulations the dynamics of a two-region world. There are two produced goods and two inputs to production.  We show that as we vary the property rights of the environment the dynamics of the system changes. The less well defined are the property rights, the more chaotic are the model's dynamics.
Trade, migration, and environment: a general equilibrium analysis, Chapter 2.3

Two major trends in the world economy are international migration and environmental degradation. The object of the paper is to analyze the connection between these two trends, which have generally been analyzed in isolation. Here we represent a world economy in which the exploitation of natural 
resources as well as the migration of labor have a global character. We discuss the welfare impact of migration and exploitation of natural resources and policies to address these issues.

The main results of the paper are as follows. Migration is prompted by wage differentials as technology is different across countries. We show that migration from the South induces a decrease in the exploitation of the resource in the South. This increases the welfare of the South but can decrease that of the North. Migration can lead to higher prices ofresources in the North and in the South, setting up a process of induced technical change in the North and better terms of trade for the South, altogether a positive outcome. As is intuitively obvious, migration reduces the wage differential between North and South in a model where, contrary to Heckscher-Ohlin assumptions, technologies differ between countries. Finally, we show that it is possible that a tax on the use of the resource in the South induces an increase in its extraction rather than a decrease. Trade policies could have a positive impact on resource extraction, could reduce the wage gap and therefore decrease the economic incentive to the mobility of labour.
Linear Redshift Distortions: A Review

Redshift maps of galaxies in the Universe are distorted by the peculiar velocities of galaxies along the line of sight. The amplitude of the distortions on large, linear scales yields a measurement of the linear redshift distortion parameter, which is $\beta \approx \Omega_0^{0.6}/b$ in standard cosmology with cosmological density $\Omega_0$ and light-to-mass bias $b$. All measurements of $\beta$ from linear redshift distortions published up to mid 1997 are reviewed. The average and standard deviation of the reported values is bias is $b_{optical}/b_{IRAS} \approx 1.5$. If optical galaxies are unbiased, then $\Omega_0 = 0.33^{+0.32}_{-0.22}$, while if IRAS galaxies are unbiased, then $\Omega_0 = 0.63^{+0.35}_{-0.27}$
Analyzing redshift surveys to measure the power spectrum on large scales

Upcoming large redshift surveys potentially allow precision measurements of the galaxy power spectrum. To accurately measure P(k) on the largest scales, comparable to the depth of the survey, it is crucial that finite volume effects are accurately corrected for in the data analysis. Here we derive analytic expressions for the one such effect that has not previously been worked out exactly: that of the so-called integral constraint. We also show that for data analysis methods based on counts in cells, multiple constraints can be included via simple matrix operations, thereby rendering the results less sensitive to galactic extinction and misestimates of the shape of the radial selection function
Properties of Galaxies in and around Voids

Two surveys for intrinsically faint galaxies towards nearby voids have been conducted at the MPI für Astronomie, Heidelberg. One selected targets from a new diameter limited ($\Phi \ge 5''$) catalog with morphological criteria while the other used digitized objective prism Schmidt plates to select mainly HII dwarf galaxies. For some 450 galaxies, redshifts and other optical data were obtained. We studied the spatial distribution of the sample objects, their luminosity function, and their intrinsic properties. Most of the galaxies belong to already well known sheets and filaments. But we found about a dozen highly isolated galaxies in each sample (nearest neighborhood distance $\ge 3 h_{75}^{-1} Mpc$). These tend to populate additional structures and are not distributed homogeneously throughout the voids. As our results on 'void galaxies' still suffer from small sample statistics, I also tried to combine similar existing surveys of nearby voids to get further hints on the larger structure and on the luminosity function of the isolated galaxies. No differences in the luminosity function of sheet and void galaxies could be found. The optical and infrared properties of both samples are in the normal range for samples dominated by late-type dwarfs. Follow-up HI studies show that the isolated dwarfs in both samples have unusual high amount of neutral gas for a given luminosity
Large-Scale Structures Behind the Milky Way from Near-IR Surveys

About 25% of the optical extragalactic sky is obscured by the dust and stars of our Milky Way. Dynamically important structures might still lie hidden in this zone. Various approaches are presently being employed to uncover the galaxy distribution in the Zone of Avoidance (ZOA) but all suffer from (different) limitations and selection effects. We investigated the potential of using the DENIS NIR survey for studies of galaxies behind the obscuration layer of our Milky Way and for mapping the Galactic extinction. As a pilot study, we recovered DENIS I, J and K band images of heavily obscured but optically still visible galaxies. We determined the I, J and K band luminosity functions of galaxies on three DENIS strips that cross the center of the nearby, low-latitude, rich cluster Abell 3627. The extinction-corrected I-J and J-K colours of these cluster galaxies compare well with that of an unobscured cluster. We searched for and identified galaxies at latitudes where the Milky Way remains fully opaque (|b| < 5deg and A_B > 4-5mag) - in a systematic search as well as around positions of galaxies detected with the blind HI survey of the ZOA currently conducted with the Multibeam Receiver of the Parkes Radiotelescope
Effects of convection on the mean solar structure

The overall framework for the study of solar convection and oscillations is the spherically symmetric component of solar structure. I discuss those properties of the solar interior which depend on convection and other possible hydrodynamical motion and the increasingly detailed information about the structure which is provided by helioseismic data. The most basic dependence of solar models on convection is the calibration to fix the solar radius. The dominant causes for differences in oscillation frequencies between the Sun and solar models seem to be located near the top of the convection zone. However, there is also evidence for possible weak mixing below the convection zone and perhaps in the solar core. The former, at least, might be induced by penetration of convective motion into the stable layers below
Current Status of Radio Source Databases

We review the history and present status of radio-source catalogue archiving and on-line retrieval of radio source data. Large efforts were spent by the first author in collecting and restoring electronic versions of new and old source catalogues. Some 67 catalogues with ~520,000 entries were searchable via the "Einstein On-line Service" (EOLS). When EOLS lost maintenance support in 1994 a group at SAO (Russia) started building software tools to search and cross-identify objects between the major radio catalogues, maintained as the "CATalog supporting System" (CATS) at the Special Astrophysical Observatory (SAO, Russia). The independent efforts in east and west have recently been joined. Almost 400 different source lists with ~2,000,000 entries have been archived (and partly prepared) by us. All 5C and Penticton "P"-surveys and many of the published WSRT survey lists are now available. CATS has been developed by O. Verkhodanov, S. Trushkin, V. Chernenkov at SAO primarily to support RATAN-600 radio observations. CATS runs under LINUX and can process requests on the basis of various net protocols and via email. Almost 70 well-known radio source catalogues and tables with about 1.3 Mrecords are now available via ftp from CATS, as well as their documentation files. Twenty of the larger tables may be searched simultaneously for objects in rectangular boxes of coordinates. New routines for cross-matching are in progress. More and more catalogues are being folded into CATS. CATS is supported by RFBR grant 96-07-89075
Searching (the) FIRST radio arcs near ACO clusters

Gravitational lensing (GL) of distant radio sources by galaxy clusters should produce radio arc(let)s. We extracted radio sources from the FIRST survey near Abell cluster cores and found their radio position angles to be uniformly distributed with respect to the cluster centres. This result holds even when we restrict the sample to the richest or most centrally condensed clusters, and to sources with high S/N and large axial ratio. Our failure to detect GL with statistical methods may be due to poor cluster centre positions. We did not find convincing candidates for arcs either. Our result agrees with theoretical estimates predicting that surveys much deeper than FIRST are required to detect the effect. This is in apparent conflict with the detection of such an effect claimed by Bagchi & Kapahi (1995)
Cosmology with redshift surveys of radio sources

We use the K-z relation for radio galaxies to illustrate why it has proved difficult to obtain definitive cosmological results from studies based entirely on catalogues of the brightest radio sources, e.g. 3C. To improve on this situation we have been undertaking redshift surveys of complete samples drawn from the fainter 6C and 7C radio catalogues. We describe these surveys, and illustrate the new studies they are allowing. We also discuss our `filtered' 6C redshift surveys: these have led to the discovery of a radio galaxy at z=4.4, and are sensitive to similar objects at higher redshift provided the space density of these objects is not declining too rapidly with z. There is currently no direct evidence for a sharp decline in the space density of radio galaxies for z > 4, a result only barely consistent with the observed decline of flat-spectrum radio quasars
Searches for High Redshift Radio Galaxies

We have started a search for High Redshift Radio Galaxies (HZRGs) in an area covering 7 sr by selecting a sample of Ultra Steep Spectrum (USS) sources with a low flux density cut-off S(1400 MHz) > 10 mJy and a steep spectral index cut-off of alpha < -1.3 (S ~ nu**alpha) from the WENSS, NVSS and TEXAS surveys. Our first results for 27 sources show that we are almost twice as effective in finding HZRGs than than surveys of relatively bright radio sources with a spectral index cut-off of alpha < -1.0. The redshift distribution is consistent with an extension of the z - alpha relation to alpha < -1.3, but a large fraction of our sample (40%) consists of objects which are too faint to observe with 3-4m class telescopes. Our search is aimed at increasing the number of very high redshift radio galaxies for further detailed studies of the formation and evolution of massive galaxies and their environment
Observed Redshift Distributions and Cosmological Evolution of Radio Sources

It is shown that the new observed redshift distributions of various flux-limited samples of radio sources in general are consistent with the predictions of two basic evolutionary models published by Condon (1984) and Dunlop and Peacock (1990), i.e. none of them can be rejected at the confidence level of about 95 per cent. However, the models allowing a free-form evolution and suggesting both density and luminosity evolution are more consistent with the observational data at lower redshifts, while the 'pure luminosity evolution' model fits better the data at higher redshifts. This leads to a suspicion that the same evolution governing all radio sources, suggested by Condon (1984), might not be the case
A complete sample of quasars from the 7C redshift survey

We present details of a new sample of radio-loud quasars drawn from 0.013 sr of the 7C Redshift Survey. This sample is small (21 quasars) but complete in that every object with an unresolved nucleus and/or broad emission lines with S(151MHz) > 0.5 Jy has been discovered. The dependence of the quasar fraction with redshift and radio luminosity is investigated, providing new evidence supporting the unification of radio-loud quasars and powerful radio galaxies. This 7C sample is compared with optically-selected quasars, in order to determine whether there are systematic biases in the different selection techniques. There are no lightly reddened (Av approx. 1) quasars in our sample amongst the 14 with z < 2. The discovery of a reddened quasar at z = 2.034 and its implications are discussed. A tight correlation between radio luminosity and optical/near infrared continuum luminosity for a subset of the sample is also found