The energetics of melting fertile heterogeneities within the depleted mantle

To explore the consequences of mantle heterogeneity for primary melt production, we develop a mathematical model of energy conservation for an upwelling, melting body of recycled oceanic crust embedded in the depleted upper mantle. We consider the end‐member geometric cases of spherical blobs and tabular veins. The model predicts that thermal diffusion into the heterogeneity can cause a factor‐of‐ two increase in the degree of melting for bodies with minimum dimension smaller than ∼1 km, yielding melt fractions between 50 and 80%. The role of diffusion is quantified by an appropriately defined Peclet number, which represents the balance of diffusion‐driven and adiabatic melting. At intermediate Peclet number, we show that melting a heterogeneity can cool the ambient mantle by up to ∼20 K (spherical) or ∼60 K (tabular) within a distance of two times the characteristic size of the body. At small Peclet number, where heterogeneities are expected to be in thermal equilibrium with the ambient mantle, we calculate the energetic effect of pyroxenite melting on the surrounding peridotite; we find that each 5% of recycled oceanic crust diminishes the peridotite degree of melting by 1–2%. Injection of the magma from highly molten bodies of recycled oceanic crust into a melting region of depleted upper mantle may nucleate reactive‐dissolution channels that remain chemically isolated from the surrounding peridotite

Englacial Pore Water Localizes Shear in Temperate Ice Stream Margins

The margins of fast‐moving ice streams are characterized by steep velocity gradients. Some of these gradients cannot be explained by a temperature‐dependent viscosity alone. Laboratory data suggest that water in the ice‐grain matrix decreases the ice viscosity; we propose that this causes the strong localization of shear in temperate ice stream margins. However, the magnitude of weakening and its consequences for ice stream dynamics are poorly understood. Here we investigate how the coupling between temperate ice properties, ice mechanics, and drainage of melt water from the ice stream margin alters the dynamics of ice streams. We consider the steady‐state ice flow, temperature, water content, and subglacial water drainage in an ice stream cross section. Temperate ice dynamics are modeled as a two‐phase flow, with gravity‐driven water transport in the pores of a viscously compacting and deforming ice matrix. We find that the dependence of ice viscosity on meltwater content focuses the temperate ice region and steepens the velocity gradients in the ice stream margin. It provides a possible explanation for the steep velocity gradients observed in some ice stream shear margins. This localizes heat dissipation there, which in turn increases the amount of meltwater delivered to the ice stream bed. This process is controlled by the permeability of the temperate ice and the sensitivity of ice viscosity to meltwater content, both of which are poorly constrained properties

Magmatic intrusions control Io's crustal thickness

Io, the most volcanically active body in the solar system, loses heat through eruptions of hot lava. Heat is supplied by tidal heating and is thought to be transferred through the mantle by magmatic segregation, a mode of transport that sets it apart from convecting terrestrial planets. We present a model that couples magmatic transport of tidal heat to the volcanic system in the crust, in order to determine the controls on crustal thickness, magmatic intrusions, and eruption rates. We demonstrate that magmatic intrusions are a key component of Io's crustal heat balance; around 80% of the magma delivered to the base of the crust must be emplaced and frozen as plutons to match rough estimates of crustal thickness. As magma ascends from a partially molten mantle into the crust, a decompacting boundary layer forms, which can explain inferred observations of a high-melt-fraction region.Comment: Accepted to JGR:Planets. 24 pages inc appendices and references. 7 figure

Neighborhood Effects on Crime for Female and Male Youth: Evidence from a Randomized Housing Voucher Experiment

The Moving to Opportunity (MTO) demonstration assigned housing vouchers via random lottery to public housing residents in five cities. We use the exogenous variation in residential locations generated by MTO to estimate neighborhood effects on youth crime and delinquency. The offer to relocate to lower-poverty areas reduces arrests among female youth for violent and property crimes, relative to a control group. For males the offer to relocate reduces arrests for violent crime, at least in the short run, but increases problem behaviors and property crime arrests. The gender difference in treatment effects seems to reflect differences in how male and female youths from disadvantaged backgrounds adapt and respond to similar new neighborhood environments.

Experimental Analysis of Neighborhood Effects

Families, primarily female-headed minority households with children, living in high-poverty public housing projects in five U.S. cities were offered housing vouchers by lottery in the Moving to Opportunity program. Four to seven years after random assignment, families offered vouchers lived in safer neighborhoods that had lower poverty rates than those of the control group not offered vouchers. We find no significant overall effects of this intervention on adult economic self-sufficiency or physical health. Mental health benefits of the voucher offers for adults and for female youth were substantial. Beneficial effects for female youth on education, risky behavior, and physical health were offset by adverse effects for male youth. For outcomes exhibiting significant treatment effects, we find, using variation in treatment intensity across voucher types and cities, that the relationship between neighborhood poverty rate and outcomes is approximately linear.

Moving to Opportunity in Boston: Early Results of a Randomized Mobility Experiment

This paper examines the short-run impacts of a change in residential neighborhood on the well-being of low-income families, using evidence from the Moving To Opportunity (MTO) program in which eligibility for a housing voucher was determined by random lottery. Applicants in high poverty public housing projects were assigned by lottery to one of three groups: Experimental offered mobility counseling and a voucher valid only in a low-poverty Census tract; Section 8 Comparison offered a geographically unrestricted voucher; or Control offered no new assistance, but continued eligibility for public housing. Our quantitative analyses of program impacts at the Boston site of MTO uses data on 540 families approximately two years after program enrollment. 48 percent of the Experimental group and 62 percent of the Section 8 Comparison group moved through the MTO program. Households in both treatment groups experienced improvements in multiple measures of well-being relative to the Control group including increased safety, improved health among household heads, and fewer behavior problems among boys. There were no significant short-run impacts of either MTO treatment on employment, earnings, or welfare receipt. Experimental group children were less likely to be personally victimized by crime, to be injured, or to experience an asthma attack.

Sensitivity studies for the cubic-kilometre deep-sea neutrino telescope KM3NeT

The observation of high-energy neutrinos from astrophysical sources would substantially improve our knowledge and understanding of the non-thermal processes in these sources, and would in particular pinpoint the accelerators of cosmic rays. The sensitivity of different design options for a future cubic-kilometre scale neutrino telescope in the Mediterranean Sea is investigated for generic point sources and in particular for some of the galactic objects from which TeV gamma emmission has recently been observed by the H.E.S.S. atmospheric Cherenkov telescope. The effect of atmospheric background on the source detection probabilities has been taken into account through full simulation. The estimated event rates are compared to previous results and limits from present neutrino telescopes.Comment: 4 pages, 1 figure, contribution of the 30th International Cosmic Ray conferenc

Reciprocity relations between ordinary temperature and the Frieden-Soffer's Fisher-temperature

Frieden and Soffer conjectured some years ago the existence of a ``Fisher temperature" T_F that would play, with regards to Fisher's information measure I, the same role that the ordinary temperature T plays vis-a-vis Shannon's logarithmic measure. Here we exhibit the existence of reciprocity relations between T_F and T and provide an interpretation with reference to the meaning of T_F for the canonical ensemble.Comment: 3 pages, no figure

Experimental study of acoustic displays of flight parameters in a simulated aerospace vehicle

Evaluating acoustic displays of target location in target detection and of flight parameters in simulated aerospace vehicle