Long-Term (9-Year) Response of Two Semiarid Grasslands to Prescribed Fire in the Southwestern USA

Historically, arid grasslands of SW USA experienced fire return intervals of 5-10 years. During the last 100 years, however, fire has been a rare event. Recent expansion of woody plants in arid grasslands has prompted managers to re-introduce fire as a tool to reduce abundance of woody plants and maintain perennial grass cover. The use of fire in desert grasslands poses unique challenges, however, due to extreme variability in rainfall patterns. Our research examines vegetation response to repeat fire in 2 desert grassland ecotones near Albuquerque, New Mexico (35.05o N 106.60o W)

Infra-red fixed points in supersymmetry

Model independent constraints on supersymmetric models emerge when certain couplings are drawn towards their infra-red (quasi) fixed points in the course of their renormalization group evolution. The general principles are first reviewed and the conclusions for some recent studies of theories with R-parity and baryon and lepton number violations are summarized.Comment: 5 pages Latex with 2 figures embedded as eps files Talk given at WHEPP6, Chennai, India, January 3-15, 2000, to appear in special issue of Praman

Further Studies on the Nitrate Assimilating Power of Soils

In a paper read at the meeting last year it was pointed out that when a soluble form of organic matter was added to soils which were incubated in tumblers, a considerable quantity of nitrate nitrogen could be used by the micro-organisms of the soil. The amount of nitrate nitrogen assimilated was in a measure determined by the amount of nitrate present at the beginning, the form and amount of organic matter used, and the length of incubation period. Two percent of straw furnished sufficient carbon for the assimilation of 10 mgm. per 100 gms. of soil in one week, and for about 15 mgm. in 3 weeks. Two percent of soluble starch or dextrose permitted the assimilation of about 15 mgm. in 1 week

Studies on Methods of Measuring the Nitrate Assimilating Power of Soils

The work of many investigators has demonstrated the fact that nitrate nitrogen disappears from soils to which organic materials of a high carbon-nitrogen ratio have been added. Doryland in 1916 claimed that soils have a definite nitrate consuming power and that additions of organic matter such as straw, dextrose, or other soluble sugars stimulated the disappearance of the nitrates. He attributed this disappearance to the fact that the nitrates were assimilated by microorganisms but not lost from the soil

The BATSE experiment on the Compton Gamma Ray Observatory: Status and some early results

The Burst and Transient Source Experiment (BATSE) on the Compton Gamma Ray Observatory (GRO) is a sensitive all-sky detector system. It consists of eight uncollimated detectors at the corners of the spacecraft which have a total energy range of 15 keV to 100 MeV. The primary objective of BATSE is the detection, location, and study of gamma ray bursts and other transient sources. The instrement also has considerable capability for the study of pulsars, solar flares, and other discrete high energy sources. The experiment is now in full operation, detecting about one gamma ray burst per day. A brief description of the on-orbit performance of BATSE is presented, along with examples of early results from some of the gamma ray bursts

The Effects of Some Nitrogen Fertilizers on Nitrification

A number of investigations have shown the effects of certain nitrogen fertilizers on the nitrification process and it has generally been noted that nitrates would stimulate the production of nitrates. The work of Coleman, Brown and Gowda and Greaves may be referred to in this connection

Infrared Fixed Point Structure in Minimal Supersymmetric Standard Model with Baryon and Lepton Number Violation

We study in detail the renomalization group evolution of Yukawa couplings and soft supersymmetry breaking trilinear couplings in the minimal supersymmetric standard model with baryon and lepton number violation. We obtain the exact solutions of these equations in a closed form, and then depict the infrared fixed point structure of the third generation Yukawa couplings and the highest generation baryon and lepton number violating couplings. Approximate analytical solutions for these Yukawa couplings and baryon and lepton number violating couplings, and the soft supersymmetry breaking couplings are obtained in terms of their initial values at the unification scale. We then numerically study the infrared fixed surfaces of the model, and illustrate the approach to the fixed points.Comment: 16 pages REVTeX, figures embedded as epsfigs, replaced with version to appear in Physical Review D, minor typographical errors eliminated and references reordered, figures correcte

Affinities and differences between Giovanni Pascoli and English and French poets

Part I: The poet's life, character and spiritual development, 1855-1891. Life at Bologna, 1873-1882 - family tragedy - anarchism -Pascoli's sentimental mysticism begins to assert itself against the positivistic tendencies of his environment - cultural atmosphere of Bologna alien to him - spiritual isolation -condemnation of contemporary ideas. Affinities with Leopardi - differences in temperament and art - reasons why his inspiration could not have guided Pascoli to complete poetical expression - affinities between Pascoli and mystical romantic poets - interest in foreign literature - shares dominant characteristics of romanticism - differences between his qualities and ideals and those of many romantic poets. Foreign influence disputed by critics - inspiration of Poe and Galletti's assertion that Pascoli guided by him to foreign poets - evidence to support this theory, Part II : Affinities and differences between Pascoli and English and French poets: possible reminiscences from their poetry. Pascoli's conception of poetry, spontaneous expression of the poet's purest self revealed to him by emotion. Identification of "fanciullino" with "Imagination" of English romantic poets - found also in Baudelaire and Rimbaud - neo-platonism in Pascoli and other poets. Poetry of childhood in Blake, Wordsworth, Coleridge, Coppee, Hugo and Pascoli. Broad conception of poetry - language - attitude towards nature. "Cosmic" poetry of Shelley, Lamartine, Byron, Wordsworth, Baudelaire, Hugo, Rimbaud - affinities, differences, possible reminiscences in Pascoli - preoccupation with evil in Pascoli and Hugo -obsession with death in Pascoli, Poe, Hugo, Baudelaire, Carducci, Maeterlinck - "romantic" atmosphere in Pascoli - mystic awe in poetry - Wordsworth Poetry, objectified dreams in Pascoli, German, English and French poets. Mystery and super-natural elements in Pascoli, Coleridge, Novalis, Baudelaire, French symbolists, Shelley, Poe, Maeterlinck, Hugo. Intuitions of mystery conveyed by symbol and music. Resemblance between Pascoli's use of symbolism and that of Rossetti and Hugo. Conclusion Pascoli has less affinity with French symbolists than with English romantic poets - nearest in spirit to Poe and Hugo -Pascoli's originality.<p

Current Renormalisation Constants with an O(a)-improved Fermion Action

Using chiral Ward identities, we determine the renormalisation constants of bilinear quark operators for the Sheikholeslami-Wohlert action lattice at beta=6.2. The results are obtained with a high degree of accuracy. For the vector current renormalisation constant we obtain Z_V=0.817(2)(8), where the first error is statistical and the second is due to mass dependence of Z_V. This is close to the perturbative value of 0.83. For the axial current renormalisation constant we obtain Z_A = 1.045(+10 -14), significantly higher than the value obtained in perturbation theory. This is shown to reduce the difference between lattice estimates and the experimental values for the pseudoscalar meson decay constants, but a significant discrepancy remains. The ratio of pseudoscalar to scalar renormalisation constants, Z_P/Z_S, is less well determined, but seems to be slightly lower than the perturbative value.Comment: 8 pages uuencoded compressed postscript file. Article to be submitted to Phys.Rev.

Modeling Porous Dust Grains with Ballistic Aggregates. II. Light Scattering Properties

We study the light scattering properties of random ballistic aggregates constructed in Shen et al. (Paper I). Using the discrete-dipole-approximation, we compute the scattering phase function and linear polarization for random aggregates with various sizes and porosities, and with two different compositions: 100% silicate and 50% silicate-50% graphite. We investigate the dependence of light scattering properties on wavelength, cluster size and porosity using these aggregate models. We find that while the shape of the phase function depends mainly on the size parameter of the aggregates, the linear polarization depends on both the size parameter and the porosity of the aggregates, with increasing degree of polarization as the porosity increases. Contrary to previous studies, we argue that monomer size has negligible effects on the light scattering properties of ballistic aggregates, as long as the constituent monomer is smaller than the incident wavelength up to 2*pi*a_0/lambda\sim 1.6 where a_0 is the monomer radius. Previous claims for such monomer size effects are in fact the combined effects of size parameter and porosity. Finally, we present aggregate models that can reproduce the phase function and polarization of scattered light from the AU Mic debris disk and from cometary dust, including the negative polarization observed for comets at scattering angles 160<theta<180 deg. These aggregates have moderate porosities, P\sim 0.6, and are of sub-micron-size for the debris disk case, or micron-size for the comet case.Comment: Submitted to ApJ. Scattering properties can be downloaded at http://www.astro.princeton.edu/~draine/SDJ2009.html Target geometries are at http://www.astro.princeton.edu/~draine/agglom.htm