University of Colorado Boulder

About: University of Colorado Boulder is a education organization based out in Boulder, Colorado, United States. It is known for research contribution in the topics: Population & Galaxy. The organization has 48794 authors who have published 115151 publications receiving 5387328 citations. The organization is also known as: CU Boulder & UCB.

Soft-mode spectroscopy: Experimental studies of structural phase transitions

Abstract: This paper reviews the experimental studies of displacive phase transitions in solids. Primary emphasis is upon inelastic light scattering and neutron scattering; related infrared reflectivity measurements, as well as x-ray and EPR analyses are also summarized. Several prototype structures are considered in detail: (1) the rocksalt IV-VI semiconductors PbTe, SnTe, and GeTe; (2) the ferroelectric perovskites exemplified by PbTi${\mathrm{O}}_{3}$ and BaTi${\mathrm{O}}_{3}$; (3) perovskites which exhibit cell-doubling transitions, such as LaAl${\mathrm{O}}_{3}$, SrTi${\mathrm{O}}_{3}$, and KMn${\mathrm{F}}_{3}$; (4) crystals having the $\ensuremath{\alpha}$-quartz structure, including Ge${\mathrm{O}}_{2}$, Si${\mathrm{O}}_{2}$, and AlP${\mathrm{O}}_{4}$; (5) the "improper ferroelectrics" ${\mathrm{Gd}}_{2}$${(\mathrm{M}\mathrm{o}{\mathrm{O}}_{4})}_{3}$ and ${\mathrm{Tb}}_{2}$${(\mathrm{M}\mathrm{o}{\mathrm{O}}_{4})}_{3}$; (6) the V-VI-VII semiconductors typified by SbSI; (7) the hydrogen-bonded ferroelectrics of the K${\mathrm{H}}_{2}$P${\mathrm{O}}_{4}$ family; (8) Jahn-Teller systems such as DyV${\mathrm{O}}_{4}$ and RbCo${\mathrm{F}}_{3}$, in which structural distortions occur as secondary effects; (9) order-disorder systems such as NaN${\mathrm{O}}_{2}$ and the ammonium halides (N${\mathrm{H}}_{4}$Cl, N${\mathrm{H}}_{4}$Br), in which no "soft mode" occurs in the spectral region ($\ensuremath{\omega}g{10}^{11}$ Hz) probed by ir, Raman, and neutron spectroscopy; (10) $\ensuremath{\beta}$-tungsten ($A\ensuremath{-}15$) structures such as ${\mathrm{V}}_{3}$Si and ${\mathrm{Nb}}_{3}$Sn, which exhibit high-temperature superconductivity. These crystal categories are used to illustrate several phenomena of current physical interest: Specifically, we discuss harmonic and anharmonic mode coupling; "critical exponents" $\ensuremath{\beta}$ differing from one-half in the temperature dependences of the order parameter $\ensuremath{\phi}(T)={\ensuremath{\phi}}_{0}{(T\ensuremath{-}{T}_{0})}^{\ensuremath{\beta}}$ and of the soft-mode frequency $\ensuremath{\omega}(T)={\ensuremath{\omega}}_{0}{(T\ensuremath{-}{T}_{0})}^{\ensuremath{\beta}}$; and the recently discovered "central" modes centered at zero frequency, which grow in intensity as the transition temperature ${T}_{0}$ is approached from above or below. The review covers the period 1940-1972. A few 1973 works are mentioned for which the author had preprints in 1972 or very early 1973. This review is in no sense a comprehensive survey of ferroelectricity. Readers are referred to the following earlier reviews on that subject: Silverman (1966, 1969), Cochran and Cowley (1967), Blinc (1968), Murzin et al. (1968), Nettleton (1970), and Blinc and Zaks (1972).

Self-inhibition by dopaminergic neurons.

Abstract: Animals and Plants, L. E. Gilbert and P. H. Raven, Eds. (Univ. ofTexas Press, Austin, 1975), p. 3. 76. J. W. Hanover, Annu Rev. Entomol. 20,75 (1975). 77. R. H. Smith, U.S. For. Serv. Gen. Tech. Rep. PSW-I (1972); A. A. Berryman, BioScience 22, 598 (1972). 78. V. 1. Grimal'skii, L. T. Krushev, V. P. Gorlushkina, Lesn. Khoz. 12, 54 (1971); W. P. Smeljanez and L. A. Chursin, Anz. Schaedlingskd. 45, 33 (1972). 79. C. M. McKell, J. P. Blaisdell, J. R. Goodin, Eds., Wildland Shrubs-Their Biology and Utilization (General Technical Report INT-1, U.S. Forest Service, Washington, D.C., 1972). 80. C. H. A. Little, Can. J. Bot. 48, 1995 (1970). 81. S. J. Dina and L. G. Klikoff, J. Range Manage. 26, 207 (1973); J. D. Hodges and P. L. Lorio, Jr., Can. J. Bot. 47, 1651 (1969); see also Parker (84). 82. D. Otto, Arch. Forstwes. 19, 135 (1970). 83. W. Schwenke, Z. Angew. Entomol. 61, 365 (1968). 84. J. Parker, in Water Deficits and Plant Growth, T. T. Kozlowski, Ed. (Academic Press, New York, 1972), vol. 3, p. 125. 85. A. W. Naylor, in ibid., p. 241; R. E. Saunier, H. M. Hull, J. H. Ehrenreich, Plant Physiol. 43, 401 (1968). 86. T. C. R. White, Oecologia 16,279 (1974). 87. G. T. Harvey, Can. Entomol. 106, 353 (1974); see also Otto (82) and Schwenke (83). 88. T. T. Kozlowski, J. For. 67, 118 (1969); H. 0. Batzer, Environ. Entomol. 2, 727 (1973). 89. D. H. Janzen, Am. Nat. 104, 501 (1970); C. B. Huffaker, in Dynamics of Populations, P. J. denBoer and G. R. Gradwell, Eds. (Centre for Agricultural Publishing and Documentation, Wageningen, Netherlands, 1971), p. 327; J. R. Blais, For. Chron. 44 (1968).

The coarse Baum–Connes conjecture for spaces which admit a uniform embedding into Hilbert space

Abstract: Corollary 1.2. Let Γ be a finitely generated group. If Γ, as a metric space with a word-length metric, admits a uniform embedding into Hilbert space, and its classifying space BΓ has the homotopy type of a finite CW complex, then the strong Novikov conjecture holds for Γ, i.e. the index map from K∗(BΓ) to K∗(C∗ r (Γ)) is injective. Corollary 1.2 follows from Theorem 1.1 and the descent principle [23]. By index theory, the strong Novikov conjecture implies the Novikov conjecture on the homotopy invariance of higher signatures (cf. [8] for an excellent

Herbivores and nutrients control grassland plant diversity via light limitation

Abstract: Human alterations to nutrient cycles and herbivore communities are affecting global biodiversity dramatically. Ecological theory predicts these changes should be strongly counteractive: nutrient addition drives plant species loss through intensified competition for light, whereas herbivores prevent competitive exclusion by increasing ground-level light, particularly in productive systems. Here we use experimental data spanning a globally relevant range of conditions to test the hypothesis that herbaceous plant species losses caused by eutrophication may be offset by increased light availability due to herbivory. This experiment, replicated in 40 grasslands on 6 continents, demonstrates that nutrients and herbivores can serve as counteracting forces to control local plant diversity through light limitation, independent of site productivity, soil nitrogen, herbivore type and climate. Nutrient addition consistently reduced local diversity through light limitation, and herbivory rescued diversity at sites where it alleviated light limitation. Thus, species loss from anthropogenic eutrophication can be ameliorated in grasslands where herbivory increases ground-level light.

THE CARDIAC FIBROBLAST: Therapeutic Target in Myocardial Remodeling and Failure

Abstract: Cardiac fibroblasts play a central role in the maintenance of extracellular matrix in the normal heart and as mediators of inflammatory and fibrotic myocardial remodeling in the injured and failing heart. In this review, we evaluate the cardiac fibroblast as a therapeutic target in heart disease. Unique features of cardiac fibroblast cell biology are discussed in relation to normal and pathophysiological cardiac function. The contribution of cardiac fibrosis as an independent risk factor in the outcome of heart failure is considered. Candidate drug therapies that derive benefit from actions on cardiac fibroblasts are summarized, including inhibitors of angiotensin-aldosterone systems, endothelin receptor antagonists, statins, anticytokine therapies, matrix metalloproteinase inhibitors, and novel antifibrotic/anti-inflammatory agents. These findings point the way to future challenges in cardiac fibroblast biology and pharmacotherapy.