Letter from C. S. Sargent to John Muir, 1894 Jan 8.

ARNOLD ARBORETUM,HARVARD UNIVERSITY.Jamaica Plain Mass., January 8, 1894My dear Mr. Muir:Thank you. The Silva is coming on slowly. The fifth volume appeared in October and the sixth is fairly on the way. I am working hard at it in order to get it off my hands in time to pay you a visit this spring. I should have accomplished this easily if the grip had not got the best of me in December and caused me to lose nearly a month\u27s time. However, I still want to get away, if I can, in time to see something of the Spring vegetation of California which will be quite new to me.Planned it [illegible] a dozen years [illegible] - 1893When we meet we can talk over that trip to India which I am still keen for, and all the more so if I can have the pleasure of your company.We often think and speak of your visit to Brookline and I hope the time is not far distant when you will come and see us again. I am glad you had such a good time on the other side of the ocean.With kind regards,I am,always faithfully yours,C. S. Sargent.John Muir, Esq.,Martinez, Cal.0176

The quantum-classical crossover of a field mode

We explore the quantum-classical crossover in the behaviour of a quantum field mode. The quantum behaviour of a two-state system - a qubit - coupled to the field is used as a probe. Collapse and revival of the qubit inversion form the signature for quantum behaviour of the field and continuous Rabi oscillations form the signature for classical behaviour of the field. We demonstrate both limits in a single model for the full coupled system, for states with the same average field strength, and so for qubits with the same Rabi frequency.Comment: 6 pages, 3 figures (in this version the figures, text and references have all been expanded

Amadurecimento e aceitação sensorial de abacate tratado com solução aquosa de 1-MCP.

O abacate (Persea americana Mill.) é um fruto rico em óleo e compostos benéficos à saúde (Ding et al., 2007). O fitormônio etileno (C2H4) é essencial para o amadurecimento deste fruto climatérico (Zauberman et al., 1988) e controlar sua ação é fundamental para estender a vida útil pós-colheita deste fruto. O 1-metilciclopropeno, composto inibidor da ação do etileno, tem sido largamente usado em pesquisa e comercialização pós-colheita de produtos hortícolas (Huber, 2008; Watkins, 2008). Para o abacate, o 1-MCP gasoso foi efetivo em concentrações de 30 nL L-1 a 500 nL L-1 em tratamentos de 24 h a 20 °C (Feng et al., 2000; Kluge et al., 2002; Adkins et al., 2005). Este composto mostrou-se também efetivo em solução aquosa como tratamento pós-colheita de tomates e abacates ?Hass? (Choi et al., 2008) e 'Simmonds' (Pereira et al., 2010), com a vantagem de não necessitar de locais fechados para sua aplicação e de reduzir o tempo de aplicação em relação à formulação gasosa. No entanto, o 1-MCP pode afetar a aceitação sensorial do produto tratado (Marin et al., 2009). O objetivo deste trabalho foi avaliar parâmetros de amadurecimento e aceitação sensorial do abacate Beta tratado com solução aquosa de 1-MCP.pdf 160

Equilibrium counterfactuals

We incorporate structural modellers into the economy they model. Using traditional moment-matching, they treat policy changes as zero probability (or exogenous) ”counterfactuals.” Bias occurs since real-world agents understand policy changes are positive probability events guided by modellers. Downward, upward, or sign bias occurs. Bias is illustrated by calibrating the Leland model to the 2017 tax cut. The traditional identifying assumption, constant moment partial derivative sign, is incorrect with policy optimization. The correct assumption is constant moment total derivative sign accounting for estimation-policy feedback. Model agent expectations can be updated iteratively until policy advice converges to agent expectations, with bias vanishing

A Study of the Direct-Fitting Method for Measurement of Galaxy Velocity Dispersions

We have measured the central stellar velocity dispersions of 33 nearby spiral and elliptical galaxies, using a straightforward template-fitting algorithm operating in the pixel domain. The spectra, obtained with the Double Spectrograph at Palomar Observatory, cover both the Ca triplet and the Mg b region, and we present a comparison of the velocity dispersion measurements from these two spectral regions. Model fits to the Ca triplet region generally yield good results with little sensitivity to the choice of template star. In contrast, the Mg b region is more sensitive to template mismatch and to details of the fitting procedure such as the order of a polynomial used to match the continuum shape of the template to the object. As a consequence of the correlation of the [Mg/Fe] ratio with velocity dispersion, it is difficult to obtain a satisfactory model fit to the Mg b lines and the surrounding Fe blends simultaneously, particularly for giant elliptical galaxies with large velocity dispersions. We demonstrate that if the metallicities of the galaxy and template star are not well matched, then direct template-fitting results are improved if the Mg b lines themselves are excluded from the fit and the velocity dispersion is determined from the surrounding weaker lines.Comment: 14 pages. To appear in A

On the metallicity dependence of crystalline silicates in oxygen-rich asymptotic giant branch stars and red supergiants

We investigate the occurrence of crystalline silicates in oxygen-rich evolved stars across a range of metallicities and mass-loss rates. It has been suggested that the crystalline silicate feature strength increases with increasing mass-loss rate, implying a correlation between lattice structure and wind density. To test this, we analyse Spitzer IRS and Infrared Space Observatory SWS spectra of 217 oxygen-rich asymptotic giant branch stars and 98 red supergiants in the Milky Way, the Large and Small Magellanic Clouds and Galactic globular clusters. These encompass a range of spectral morphologies from the spectrally-rich which exhibit a wealth of crystalline and amorphous silicate features to 'naked' (dust-free) stars. We combine spectroscopic and photometric observations with the GRAMS grid of radiative transfer models to derive (dust) mass-loss rates and temperature. We then measure the strength of the crystalline silicate bands at 23, 28 and 33 microns. We detect crystalline silicates in stars with dust mass-loss rates which span over 3 dex, down to rates of ~10^-9 solar masses/year. Detections of crystalline silicates are more prevalent in higher mass-loss rate objects, though the highest mass-loss rate objects do not show the 23-micron feature, possibly due to the low temperature of the forsterite grains or it may indicate that the 23-micron band is going into absorption due to high column density. Furthermore, we detect a change in the crystalline silicate mineralogy with metallicity, with enstatite seen increasingly at low metallicity.Comment: Accepted for publication in MNRAS, 24 pages, 16 figure

Large-Scale Correlations in the Lyman-alpha Forest at z = 3-4

We present a study of the spatial coherence of the intergalactic medium toward two pairs of high-redshift quasars with moderate angular separations observed with Keck/ESI, Q1422+2309A/Q1424+2255 (z_em = 3.63, theta = 39") and Q1439-0034A/B (z_em = 4.25, theta = 33"). The crosscorrelation of transmitted flux in the Lyman-alpha forest shows a 5-7 sigma peak at zero velocity lag for both pairs. This strongly suggests that at least some of the absorbing structures span the 230-300/h_70 proper kpc transverse separation between sightlines. We also statistically examine the similarity between paired spectra as a function of transmitted flux, a measure which may be useful for comparison with numerical simulations. In investigating the dependence of the correlation functions on spectral characteristics, we find that photon noise has little impact for S/N >~ 10 per resolution element. However, the agreement between the autocorrelation along the line sight and the crosscorrelation between sightlines, a potential test of cosmological geometry, depends significantly on instrumental resolution. Finally, we present an inventory of metal lines. These include a a pair of strong C IV systems at z ~ 3.4 appearing only toward Q1439B, and a Mg II + Fe II system present toward Q1439 A and B at z = 1.68.Comment: 33 pages, 13 figures, submitted to Ap

Temperature and Kinematics of CIV Absorption Systems

We use Keck HIRES spectra of three intermediate redshift QSOs to study the physical state and kinematics of the individual components of CIV selected heavy element absorption systems. Fewer than 8 % of all CIV lines with column densities greater than 10^{12.5} cm^{-2} have Doppler parameters b < 6 km/s. A formal decomposition into thermal and non-thermal motion using the simultaneous presence of SiIV gives a mean thermal Doppler parameter b_{therm}(CIV) = 7.2 km/s, corresponding to a temperature of 38,000 K although temperatures possibly in excess of 300,000 K occur occasionally. We also find tentative evidence for a mild increase of temperature with HI column density. Non-thermal motions within components are typically small (< 10 km/s) for most systems, indicative of a quiescent environment. The two-point correlation function (TPCF) of CIV systems on scales up to 500 km/s suggests that there is more than one source of velocity dispersion. The shape of the TPCF can be understood if the CIV systems are caused by ensembles of objects with the kinematics of dwarf galaxies on a small scale, while following the Hubble flow on a larger scale. Individual high redshift CIV components may be the building blocks of future normal galaxies in a hierarchical structure formation scenario.Comment: submitted to the ApJ Letters, March 16, 1996 (in press); (13 Latex pages, 4 Postscript figures, and psfig.sty included