Population Redistribution Research Articles

Laser-induced fluorescent cooling of rare-earth-doped fluoride glasses

Continual cooling of a material by anti-Stokes luminescence has been experimentally observed in a solid material. Net cooling was achieved by pumping to the lower levels of the 2F 5/2 manifold of Yb 3+, followed by population redistribution across this manifold via thermalization and fluorescence to the ground state. Fluoride glass hosts in the ZBLAN and BaF 2–InF 3–GaF 3 (BIG) families have been used in these experiments. Temperature decreases of 0.33 K in a bulk glass sample and 16 K in a fiber sample were obtained in ZBLANPb:Yb 3+. Net cooling was achieved when an electrochemical purification stage was incorporated into the glass fabrication process to decrease the extrinsic absorptive component of the host glass in the 1.0 μm region. Resonant laser ablation experiments showed the positive and negative effects of electrochemical processing on fluoride glasses in reducing transition metal content which is detrimental to successful fluorescent cooling. Reduction in copper, iron, and chromium content of 18, 4.2, and 5.5 were determined for the ZBLANPb sample via RLA. However, reductions in transition metal content were only 1.9 for copper and a negligible amount for iron and chromium in the BIG glasses.

Quantitative Analysis of Movement: Measuring and Modeling Population Redistribution in Animals and Plants. Peter Turchin

Previous articleNext article No AccessNew Biological BooksQuantitative Analysis of Movement: Measuring and Modeling Population Redistribution in Animals and Plants. Peter Turchin Jeannette YenJeannette Yen Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The Quarterly Review of Biology Volume 74, Number 2Jun., 1999 Published in association with Stony Brook University Article DOIhttps://doi.org/10.1086/393125 Views: 17Total views on this site Citations: 2Citations are reported from Crossref Copyright 1999 The University of ChicagoPDF download Crossref reports the following articles citing this article:Liang Wang, Foivos Diakogiannis, Scott Mills, Nigel Bajema, Ian Atkinson, Greg J. Bishop-Hurley, Ed Charmley A noise robust automatic radiolocation animal tracking system, Animal Biotelemetry 9, no.11 (Aug 2021).https://doi.org/10.1186/s40317-021-00248-wWenbo Yan, Zhigao Zeng, Huisheng Gong, Yan Duan, Leigang Zhao, Aliu Peng, Julia Molnar , PLOS ONE 15, no.77 ( 2020): e0235464.https://doi.org/10.1371/journal.pone.0235464

Environmental radiation effect of atomic Rydberg states

The interaction between Rydberg states of atoms and environmental radiation has been systematically studied. The experimental results show that the redistribution of populations of the Rydberg states of Na for ns( n=20–24), np( n=19–23) and nd( n=19–23) caused by environmental radiation is appreciable at room temperature and thereby affects the lifetime of the states. The theoretical calculations concerning the experiments exhibit that the influences of stimulated emission induced by environmental radiation on lifetimes of Rydberg states are weaker than those of stimulated absorption and a rise in energy level will lead to an increase of these influences in the energy-range studied. The relativity between liftimes of Rydberg atoms and environmental temperature has been calculated.

Fluorescent molecular hydrogen in the Eagle nebula

We used the University of New South Wales Infrared Fabry-Perot (UNSWIRF) to investigate the photodissociation region (PDR) associated with theelephant trunk' features in the M16 Hii region (the Eagle nebula). Images were made in the H2 1±0 S(1) and 2±1 S(1) lines at 2.122 and 2.248mm, respectively, and in the Hi Brg line at 2.166mm. The trunk-like features have an average H2 number density of ,10 4 cm y3 and are irradiated by a far-UV ®eld ,10 4 ´ the ambient interstellar value. The H2 intensity pro®le across the trunks is consistent with a simple model in which cylindrical columns of gas are illuminated externally, primarily by a direct component (the stars of NGC 6611), with an additional contribution from an isotropic component (scattered light). We ®nd that most of the H2 emission from the source is consistent with purelyuorescent excitation, however a signi®cant fraction of the H2 emission (,25 per cent) from the northernmost column shows evidence forcollisionaluorescence', i.e. redistribution of H2 level populations through collisions. This emission is con®ned to clumps up to ,0.01 pc in diameter, with densities >10 5 cm y3 , and perhaps > 10 6 cm y3 , ®lling at most a few per cent of the volume of the trunks. The line intensities and ratios are consistent with steady-state and not time-dependent PDR models.

Temperature-induced conformational changes of native lysozyme in aqueous solution studied by dielectric spectroscopy

We report dielectric measurements at radiofrequencies on lysozyme in aqueous solution at two values of pH (3.5 and 6) as a function of temperature in the interval 5–55°C. From the analysis of the dielectric relaxation of the protein solution, the effective hydrodynamic radius r and the electric dipole moment μ of the protein were calculated. The results show that temperature causes continuous gradual changes of r and μ with a maximum at 25–30°C where the Gibbs free energy for native lysozyme shows an analogous trend. We suggest that the gradual variations of r and μ are the manifestation of a redistribution of microscopic state populations of the protein within the same macroscopic native state.

Japan's population redistribution: A comparison with the United States

The purposes of this paper are, first, to analyze population distribution changes 1965-95 in Japan by four categories-the existing metropolitan area; new suburbs; new metropolitan area; and non-metropolitan area-by using the Hoover index, and, second, to compare the results obtained for Japan with those for the US presented in Nucci and Long (1995) and Long and Nucci (1997). To clarify the temporal changes in population distribution, the delineation of metropolitan areas needs to employ a floating principle rather than a fixed one, and the definition of metropolitan areas should be similar to that of Standard Metropolitan Statistical Areas (SMSA) used in the US. To meet these conditions, the Standard Metropolitan Employment Areas (SMEA) advocated by H. Yamada and K. Tokuoka are used in this article.In Japan, during the period 1965-75, there occurred a considerable population concentration due to a marked population increase in the old suburbs located in the core regions (such as Kanto, Tokai and Kinki) and to a large population decrease in non-metropolitan areas in the peripheral regions (such as Hokkaido, Tohoku, Hokuriku, Chugoku, Shikoku and Kyushu). During the period 1975-85, the difference between the population change rates of the core and the periphery levelled off. However, in the peripheral regions, the main category of population growth was the old central cities and depopulation in non-metropolitan areas continued. In the core regions, the category showing the largest rate of increase shifted from the old suburbs to the newly-added suburbs, implying population deconcentration from the old SMEAs. During 1985-95, deconcentration proceeded further in the core portion of the country. Meanwhile, in the peripheral regions, whereas the category showing the largest rate of increase finally shifted from the old SMEAs to the newer suburbs, non-metropolitan areas returned to recording a heavy population decrease.With respect to the 1965-95 period as a whole, the population increase in the newer SMEAs created in the non-metropolitan areas was negligible. Bearing in mind the depopulation of the non-SMEAs, this means that we cannot regard the overall trend of population redistribution as being counterurbanization.With regard to the Japan-US comparison, population deconcentration in the old metropolitan areas is common to both countries, but the following remarkable differences can be noted. First, in the US, the contribution of the new metropolitan areas created in the non-metropolitan areas to urbanization is more conspicuous than that of the new suburbs added to the old metropolitan areas. Second, whereas a clean break with the past in terms of population redistribution was found in the US, such a phenomenon was not observed in Japan. Third, in Japan, population growth in the core regions and depopulation in the peripheral regions are found throughout the period, whereas in the US, both types of region take on different change aspects and the spatial patterns of population redistribution are far more complicated.

Raman mixing of Rydberg angular momenta probed by photoelectron angular distributions

Because of the orbital degeneracy, the optical pulse induced redistribution of the initial single-state population over different-l Rydberg states in the hydrogen atom cannot be probed by, e.g., the traditional ramped-field ionization or the combination of this technique with the two-pulse Ramsey interferometry. The model calculations performed by us for the ionization from a low-lying hydrogenic state via high Rydberg states suggest that such a probe for the different-l spreading could be the photoelectron angular distributions measured versus laser intensity.

Numerical versus analytical models of laser-induced population redistribution in Rydberg atoms

Our recent approximate analytical results on the evolution of the initial state and the excitation from this state of a band of high Rydberg states by an optical pulse @Phys. Rev. A 55, 2144 ~1997!# are compared with more exact numerical results. The difference between the two approaches is that the approximations of representative atom-field couplings and equidistant spacing of high Rydberg states, applied in the analytical model, are removed in the numerical model. We find that the approximate analytical model is not able to reproduce all the results of the more exact numerical model, if the laser pulse is very short ~i.e., much shorter that the Kepler period of the resonantly excited high Rydberg state! or very intense ~i.e., when the Rabi period for the resonant transition is substantially shorter than the above Kepler period!. This mainly concerns the redistribution of the population over different Rydberg states. The analytical model predicts a symmetric distribution centered around the resonantly excited Rydberg state, irrespective of the pulse duration and intensity, while the numerical model allows an asymmetric distribution with its maximum shifted towards lower Rydberg states. Despite the above-stated difference, the analytical model is able to give preliminary results for the total population of all the excited Rydberg states and the evolution of the initial state, imitating at least qualitatively the results of the numerical model in certain time and intensity scales. @S1050-2947~99!06301-5#

Nationality Population Distribution, Redistribution and Degree of Separation in Moscow, 1979–1989

Despite the fact that the former Soviet Union was perhaps the most multinational state in the world, until recently data were not available to undertake a systematic investigation of patterns of nationality population, distribution, redistribution and segregation within Soviet cities. However, nationality data were recently published for the 32 rayons of Moscow for the last two census years of 1979 and 1989.

SPECTROSCOPY AND NON-EQUILIBRIUM DISTRIBUTION OF VIBRATIONALLY EXCITED METHANE IN A SUPERSONIC JET

High-resolution spectra of supersonic jets of vibrationally excited methane have been recorded by diode laser in the 8 μm region. A formalism for the description of energy distribution is proposed. It allows to estimate populations of vibrational polyads. Under these non-equilibrium conditions, translational temperature is also measured from line profiles. For relaxation, it is shown that vibrational relaxation between polyads is negligible whereas strong redistribution of population arises inside each polyad. Spectroscopically, observed lines involving the first four excited polyads allows cross-checked tests for energy level analysis.

Extremely Large Enhancement Factors in Surface-Enhanced Raman Scattering for Molecules on Colloidal Gold Clusters

In agreement with previous results reported for colloidal silver clusters, effective surface-enhanced Raman cross sections of about 10-16 cm2 per molecule, corresponding to enhancement factors on the order of 1014, have also been obtained for molecules attached to colloidal gold clusters. Spatially isolated nearly spherical colloidal gold particles of about 60 nm size show maximum enhancement factors on the order of 103 at 514 nm excitation, close to the single plasmon resonance. The enhancement factor increases by eleven orders of magnitude when colloidal gold clusters are formed by aggregation of the gold colloids and when near-infrared excitation is applied. The large effective surface-enhanced Raman cross section has been estimated by a straightforward method based on steady-state population redistribution due to the pumping of molecules to the first excited vibrational state via the strongly enhanced Raman process. Our experimental finding confirms the important role of colloidal clusters for extremely large surface-enhanced Raman scattering (SERS) enhancement factors. Simultaneously, it suggests colloidal gold clusters as a substrate for high-sensitivity surface-enhanced Raman scattering, which can provide an enhancement level sufficient for Raman single molecule detection. Due to its chemical inactivity, gold might have some advantages compared to silver, particularly in biomedical spectroscopy.

Interference stabilization of Rydberg atoms enhanced by multiple V-type resonances

We introduce a model of laser pulse ionization of a high Rydberg state whose core is a chain of coupled V-type transitions with exact resonance in each arm of the V. Through this chain the population is allowed to migrate resonantly from the initial state of low angular momentum to other bound states of higher angular momenta, both of low and high energy. Along with the redistribution of the initial population over different bound states, we discuss the effect of the redistribution on atomic stabilization, exploiting an analytical solution of the model that holds in a limiting case. The resonant migration mentioned is shown to be able to enhance atomic stabilization against ionization by an optical-frequency pulse.

The Immigration Debate: Studies on the Economic, Demographic, and Fiscal Effects of Immigration

1 Front Matter 2 1 Introduction 3 2 An Economic Framework for Assessing the Fiscal Impacts of Immigration 4 3 Fiscal Impacts of Immigrant and Native Households: A New Jersey Case Study 5 4 The Fiscal Impacts of Immigrants: A California Case Study 6 5 The Current Fiscal Impact of Immigrants and Their Descendants: Beyond the Immigrant Household 7 6 Immigrants and Natives in General Equilibrium Trade Models 8 7 Labor Market Outcomes of Female Immigrants in the United States 9 8 Historical Background to Current Immigration Issues 10 9 Immigration and Crime in the United States 11 10 The Impact of Recent Immigration on Population Redistribution Within the United States 12 Index

Blue satellite structure near He α and He β and redistribution of level populations

For a wide class of ions a mechanism for the emission of blue satellites close to the He-like resonance line in dense plasmas is proposed. It is based on the collisional transfer of population between autoionising levels. Detailed collisional radiative calculations involving all J-split autoionising levels are carried out for Al and may serve as a benchmark. A general consideration of redistribution effects inside the autoionising levels discovered diagnostically attractive density effects for laser-produced plasmas for both the He α and He β satellite structure.

Detecting Differences in Interstate Migration Streams Using An Enhanced Gravity Model

Southeastern Geographer Vol. XXXVIII, No. 1, M ay 1998, pp. 22-40 DETECTING DIFFERENCES IN INTERSTATE MIGRATION STREAMS USING AN ENHANCED GRAVITY MODEL i Alexander C. Vias Over the last 30 years, most statistical studies modeling population redistribution in the United States have focused on patterns and processes o f migration at the national and regional scale. However, the very nature o f these generalized studies results in a loss o f inform ation on indi­ vidual migration streams. This paper represents a prelim inary attem pt to rem edy this problem by focusing on two o f the m ost im portant m igration streams in the United States— the m ove­ m ent o f people to Arizona and Florida. In particular, an enhanced version o f the gravity model (utilizing ordinary least squares regression) is used to detect differences in the m igration stream s to each state during the five-year period o f 1985-1990. Results show that the structure o f movem ent into each o f these states is different, highlighting that m igration to the Sunbelt is far from homogenous, and that studies using m igration flows to and from every state may hide these im portant differences. INTRODUCTION. Migration processes have long fascinated social scientists from a number of disciplines including geography, economics, and sociology. One of the most common goals of researchers has been to detect, explore, and model patterns of migration. In the United States, a great deal of interest has been stimu­ lated by the massive Snowbelt-to-Sunbelt migration stream (Berry and Dahmann, 1977; Greenwood, 1985). Since World War II, millions of Americans have left the colder and more economically distressed regions of the United States and moved to areas in the southern and western portions of the nation. As a result of intense scrutiny by researchers, much more is known today about what motivates the decision to move and what factors determine the migrant’s final destination. In addition, researchers now have a clearer picture of the streams of migration that have dominated movement around the country. While these macro-level analyses have offered valuable insights on migration processes at the national scale, the very nature of these generalized studies results in a loss of information on individual migration streams. For example, migration models that utilize data on every migration stream in the U.S. may not offer much information on the specific characteristics of migration to a particular state. This paper represents a preliminary attempt to remedy this problem by focusing on two of the most important migration streams in the U.S.—the movement of people to Arizona and Florida. In particular, the well-known gravity model is used in an or­ dinary least squares (OLS) regression to define differences in the migration streams to each state during the five-year period of 1985-1990. Results show that Mr. Vias is a graduate student in the Department o f Geography and Regional Development, University o f Arizona, Tucson, AZ 85721. V o l . X X X V I I I , N o . 1 23 the movement of people into each of these states is in fact quite different and that generalized studies that use a cross-section of every state’s migration flows may hide these important differences. The first section of this paper provides a brief review ofthe literature on recent migration patterns in the U.S. and on the determinants of migration. This section is followed by a discussion of recent migration patterns to the two states that are the focus ofthis study, Arizona and Florida. In the next section a model is developed that can differentiate characteristics of the migration that took place to Arizona and Florida during the time in question. Besides the basic model, a number of other variables are also introduced, along with discussion of the data. Finally, the regression results for each of the model specifications are presented, along with a discussion of these results. The last section summarizes the goals and findings of this paper and outlines areas for further research. RECENT RESEARCH ON INTERSTATE MIGRATION. Over the past 50 years, thousands of papers have appeared...

Persistent Spectral Hole Burning of Eu3+ Ions in Silicate Glasses

Measurements of spectral hole burning have been carried out for glasses with compositions of (75 - x)SiO2·xAlO3/2· 25NaO1/2·1.0EuO3/2(x = 0, 10, 15, 20, 25, 35) at 4.2 K. A persistent spectral hole can only be burned in silicate glass containing Al2O3. The hole burning is accompanied with no antiholes and lasts for 30 min to 1 h. This phenomenon is in contrast to the hole shape and lifetime observed in an optical pumping mechanism due to population redistribution among the hyperfine levels previously reported for Eu3+-doped silicate glass. With an increase in Al2O3content, the hole linewidth becomes narrower and the hole depth increases. The variation in the hole linewidth can be explained in terms of the structural changes in the aluminosilicate glass.

Dynamics of Excited Solvated Electrons in Aqueous Solution Monitored with Femtosecond-Time and Polarization Resolution

Transient pump−probe spectroscopy of equilibrated solvated electrons is carried out in aqueous NaCl solution (5.9 M) in the visible and near-infrared using pulses of 100−170 fs duration and polarization resolution. Excitation is performed by a pump pulse at 620 nm in the blue wing of the electronic absorption band. Transient bleaching occurs in a broad interval around the maximum of the e- absorption at 705 nm, accompanied by induced absorption at longer wavelengths. No hole-burning features are observed within our experimental time resolution suggesting a time constant τ1 < 80 fs for rapid solvent relaxation and/or population redistribution among the excited electronic states. The relaxation dynamics involves a first intermediate, a frequency-shifted excited-state p‘ with lifetime τ2 = 190 ± 40 fs. A further time constant τ3 = 1.2 ± 0.4 ps accounts for the recovery of the ground state. The latter process involves a second intermediate that is assigned as a modified ground-state s‘‘. Evidence for stimulated emission suggests a distinct red shift of the transition p‘→ ground state to 800 ± 20 nm, while the transient absorption band of electrons in the s‘‘-level is centered at 780 ± 20 nm. The negligible anisotropy <0.01 of the probe absorption measured during and after the excitation process indicates that the observed distribution of solvent cavities of hydrated electrons is close to spherical symmetry.

Internal migration and urban change in Poland.

The paper investigates population change and migration over the period 1984–1994 for communes. There are important conclusions emerging from this study. The first is that we are watching now a profound change of population redistribution patterns in Poland. We observed that direct upwards hierarchical mobility has been markedly modified. The first modification is the substantial reduction of migration from rural to urban locations. There were important changes in the role of cities and towns. Largest cities, massive gainers of the seventies and eighties, have tended to lose population in the mid-nineties. It is likely that they lose population mainly to the neighbouring communes. We believe that a suburbanization process has been put into motion. Medium to large sized towns and cities, in the range between 50,000 and 500,000 as well as small, but not the smallest, towns attract substantial parts of the migration pool.

Vibrational energy redistribution of ethanol oligomers and dissociation of hydrogen bonds after ultrafast infrared excitation

2-color infrared spectroscopy of associated ethanol molecules is carried out with subpicosecond time resolution in the solvent carbon tetrachloride (1.2 M) at room temperature. After excitation of the CH-vibration at 2974 cm −1 rapid population redistribution with a time constant <0.5 ps is observed within the CH-stretching region in agreement with earlier observations, while an effective population lifetime of 12±2 ps is measured. In addition, amazingly fast dissociation of H-bonds occurs, the dominant component of which is governed by a time constant of approximately 2 ps and proposed to be of thermal origin. Further spectral features are discussed, e.g. energy transfer between CH- and OH-vibrations.

Continuities in Size of Place Preferences in the United States, 1972–19921

AbstractThe directions of net migration and population redistribution in the U.S. have switched from nonmetropolitan deconcentration during the 1970s, to metropolitan concentration during the 1980s, and back to deconcentration once again in the early 1990s. The complex causes of these distribution shifts are thought to involve both structural reconfigurations of economic activities that affect the location of opportunities and residential preferences that are tied more closely to amenities and quality of life considerations. This paper uses comparable data from three representative sample surveys of the U.S. population to update and extend earlier research on the preferential basis of redistribution trends. Our analysis does not support the view that shifts in the direction of residential preferences during 1972–1992 tend to coincide with shifts in metropolitan‐nonmetropolitan net migration and population redistribution. Rather, a consistent finding across all three surveys is that most people prefer their current residence type, and those who do not are almost twice as likely to prefer lower rather than higher density settings. These findings support the importance of preferences to explanations of recent population trends, but these preferences are not in isolation from the economic contexts in which they occur.