Microlensing and the Search for Extraterrestrial Life

Are microlensing searches likely to discover planets that harbor life? Given our present state of knowledge, this is a difficult question to answer. We therefore begin by asking a more narrowly focused question: are conditions on planets discovered via microlensing likely to be similar to those we experience on Earth? In this paper I link the microlensing observations to the well-known "Goldilocks Problem" (conditions on the Earth-like planets need to be "just right"), to find that Earth-like planets discovered via microlensing are likely to be orbiting stars more luminous than the sun. This means that light from the planetary system's central star may contribute a significant fraction of the baseline flux relative to the star that is lensed. Such blending of light from the lens with light from the lensed source can, in principle, limit our ability to detect these events. This turns out not to be a significant problem, however. A second consequence of blending is the opportunity to determine the spectral type of the lensed spectral type of the lensed star. This circumstance, plus the possibility that finite-source-size effects are important, implies that some meaningful follow-up observations are likely to be possible for a subset Earth-like planets discovered via microlensing. In addition, calculations indicate that reasonable requirements on the planet's density and surface gravity imply that the mass of Earth-like planets is likely to be within a factor of $\sim 15$ of an Earth mass.Comment: 15 pages, 2 figures. To be published in the Astrophysical Journa

On the Nature and Location of the Microlenses

This paper uses the caustic crossing events in the microlens data sets to explore the nature and location of the lenses. We conclude that the large majority of lenses, whether they are luminous or dark, are likely to be binaries. Further, we demonstrate that blending is an important feature of all the data sets. An additional interpretation suggested by the data, that the caustic crossing events along the directions to the Magellanic Clouds are due to lenses located in the Clouds, implies that most of the LMC/SMC events to date are due to lenses in the Magellanic Clouds. All of these conclusions can be tested. If they are correct, a large fraction of lenses along the direction to the LMC may be ordinary stellar binary systems, just as are the majority of the lenses along the direction to the Bulge. Thus, a better understanding of the larger-than-anticipated value derived for the Bulge optical depth may allow us to better interpret the large value derived for the optical depth to the LMC. Indeed, binarity and blending in the data sets may illuminate connections among several other puzzles: the dearth of binary-source light curves, the dearth of non-caustic-crossing perturbed binary-lens events, and the dearth of obviously blended point-lens events.Comment: 15 pages, 2 figures. Submitted to the Astrophysical Journal Letters, 4 January 199

An Additional Application of the Space Interferometry Mission to Gravitational Microlensing Experiments

Despite the detection of a large number of gravitational microlensing events, the nature of Galactic dark matter remains very uncertain. This uncertainty is due to two major reasons: the lens parameter degeneracy in the measured Einstein timescale and the blending problem in dense field photometry. Recently, consideration has been given to routine astrometric followup observations of lensing events using the {\it Space Interferometry Mission} (SIM) as a means of breaking the lens parameter degeneracy in microlensing events. In this paper, we show that in addition to breaking the lens parameter degeneracy, SIM observations can also be used to correct for nearly all types of blending. Therefore, by resolving both the problems of the lens parameter degeneracy and blending, SIM observations of gravitational lensing events will significantly better constrain the nature of Galactic dark matter.Comment: 17 pages, including 4 figures and no table, substantially modified from the original version, resubmitted to MNRA

Canopy flow and aspects of the response of plants protected by herbaceous shelterbelts and wood fences

Field experiments have been conducted in the semiarid southwest region of La Pampa, Argentina, in order to investigate the effect of different types of windbreak on wind characteristics and growth parameters of wheat (Triticum aestivum, Buck Charrua variety) within the sheltered region. Windbreaks decrease wind speed, reducing damage to the crop and improving yield and quality. Sheltering may improve microclimate conditions for plant growth and protects the soil from wind erosion. Aspects of the sheltering ability of four different windbreaks have been tested: single and double row herbaceous (Tritio secale) shelterbelts, and two different artificial wooden fences, with the same overall average porosity, but with different porosity distributions. Mean velocity, turbulence intensity, skewness distributions and spectral and wavelet analysis have been performed in order to characterise the turbulent flow downstream of the different windbreaks. Wheat grain yield and harvest index were compared with adjacent unsheltered plantations. The single and double row shelterbelts enhanced the grain yield and the harvest index of the protected plants. An influence of the turbulent structure on plant growth is suggested by the different response of plants sheltered by the two types of artificial fences.Facultad de Ingenierí

The large cosmological constant approximation to classical and quantum gravity: model examples

We have recently introduced an approach for studying perturbatively classical and quantum canonical general relativity. The perturbative technique appears to preserve many of the attractive features of the non-perturbative quantization approach based on Ashtekar's new variables and spin networks. With this approach one can find perturbatively classical observables (quantities that have vanishing Poisson brackets with the constraints) and quantum states (states that are annihilated by the quantum constraints). The relative ease with which the technique appears to deal with these traditionally hard problems opens several questions about how relevant the results produced can possibly be. Among the questions is the issue of how useful are results for large values of the cosmological constant and how the approach can deal with several pathologies that are expected to be present in the canonical approach to quantum gravity. With the aim of clarifying these points, and to make our construction as explicit as possible, we study its application in several simple models. We consider Bianchi cosmologies, the asymmetric top, the coupled harmonic oscillators with constant energy density and a simple quantum mechanical system with two Hamiltonian constraints. We find that the technique satisfactorily deals with the pathologies of these models and offers promise for finding (at least some) results even for small values of the cosmological constant. Finally, we briefly sketch how the method would operate in the full four dimensional quantum general relativity case.Comment: 21 pages, RevTex, 2 figures with epsfi

Convolutional LSTM Networks for Subcellular Localization of Proteins

Machine learning is widely used to analyze biological sequence data. Non-sequential models such as SVMs or feed-forward neural networks are often used although they have no natural way of handling sequences of varying length. Recurrent neural networks such as the long short term memory (LSTM) model on the other hand are designed to handle sequences. In this study we demonstrate that LSTM networks predict the subcellular location of proteins given only the protein sequence with high accuracy (0.902) outperforming current state of the art algorithms. We further improve the performance by introducing convolutional filters and experiment with an attention mechanism which lets the LSTM focus on specific parts of the protein. Lastly we introduce new visualizations of both the convolutional filters and the attention mechanisms and show how they can be used to extract biological relevant knowledge from the LSTM networks

Leuprolide Acetate 1-Month Depot for Central Precocious Puberty: Hormonal Suppression and Recovery

Methods. This prospective US multicenter trial of leuprolide acetate 1-month depot (7.5–15 mg) for central precocious puberty utilized an open-label treatment period, long-term follow-up, and adult callback. Forty-nine females <9 years old with Tanner breast stage ≥2 before 8 years and 6 males <10 years old with Tanner genital stage ≥2 before 9 years with stimulated LH ≥10 IU/L and bone age advance ≥1 year were enrolled. Results. Subjects were treated for 3.9 ± 2.0 years. Mean peak GnRH-stimulated LH and FSH were prepubertal after the first dose and remained suppressed throughout treatment. During treatment, mean estradiol decreased to the limit of detection and mean testosterone decreased but remained above prepubertal norms. During posttreatment follow-up (3.5 ± 2.2 years), all patients achieved a pubertal hormonal response within 1 year and menses were reported in all females ≥12 years old. No impairment of reproductive function was observed at adulthood (mean age: 24.8 years)

Imaging Gold Nanoparticles in Living Cells Environments using Heterodyne Digital Holographic Microscopy

This paper describes an imaging microscopic technique based on heterodyne digital holography where subwavelength-sized gold colloids can be imaged in cell environment. Surface cellular receptors of 3T3 mouse fibroblasts are labeled with 40 nm gold nanoparticles, and the biological specimen is imaged in a total internal reflection configuration with holographic microscopy. Due to a higher scattering efficiency of the gold nanoparticles versus that of cellular structures, accurate localization of a gold marker is obtained within a 3D mapping of the entire sample's scattered field, with a lateral precision of 5 nm and 100 nm in the x,y and in the z directions respectively, demonstrating the ability of holographic microscopy to locate nanoparticles in living cells environments

Frictional Instabilities and Carbonation of Basalts Triggered by Injection of Pressurized H2O- and CO2- Rich Fluids

The safe application of geological carbon storage depends also on the seismic hazard associated with fluid injection. In this regard, we performed friction experiments using a rotary shear apparatus on precut basalts with variable degree of hydrothermal alteration by injecting distilled H2O, pure CO2, and H2O + CO2 fluid mixtures under temperature, fluid pressure, and stress conditions relevant for large-scale subsurface CO2 storage reservoirs. In all experiments, seismic slip was preceded by short-lived slip bursts. Seismic slip occurred at equivalent fluid pressures and normal stresses regardless of the fluid injected and degree of alteration of basalts. Injection of fluids caused also carbonation reactions and crystallization of new dolomite grains in the basalt-hosted faults sheared in H2O + CO2 fluid mixtures. Fast mineral carbonation in the experiments might be explained by shear heating during seismic slip, evidencing the high chemical reactivity of basalts to H2O + CO2 mixtures