Calculations of electric currents in Europa

Electrical currents should flow in the Galilean satellite, Europa, because it is located in Jupiter's corotating magnetosphere. The possible magnitudes of these currents are calculated by assuming that Europa is a differentiated body consisting of an outer H2O layer and a silicate core. Two types of models are considered here: one in which the water is completely frozen and a second in which there is an intermediate liquid layer. For the transverse electric mode (eddy currents), the calculated current density in a liquid layer is approximately 10 to the -5/Am. For the transverse magnetic mode (unipolar generator), the calculated current density in the liquid is severely constrained by the ice layer to a range of only 10 to the -10 to -11th power/ Am, for a total H2O thickness of 100 km, provided that neither layer is less than 4 km thick. The current density is less for a completely frozen H2O layer. If transient cracks were to appear in the ice layer, thereby exposing liquid, the calculated current density could rise to a range of 10 to the -6 to 10 to the -5/Am, depending on layer thicknesses, which would require an exposed area of 10 to the -9 to 10 to the -8 of the Europa surface. The corresponding total current of 2.3x10 to the 5th power A could in 1 yr. electrolyze 7x10 to the 5th power kg of water (and more if the cells were in series), and thereby store up to 10 the 8th power J of energy, but it is not clear how electrolysis can take place in the absence of suitable electrodes. Electrical heating would be significant only if the ice-layer thickness were on the order of 1 m, such as might occur if an exposed liquid surface were to freeze over; the heating under this condition could hinder the thickening of the ice layer

Review Essay--Reexamining the Early Career and Thought of Martin Luther King, Jr.: Volume I of the King Papers

Few figures in American history have inspired such an extraordinary amount of historical and biographical literature as Martin Luther King, Jr. Since his death in 1968, innumerable books have been written about King specifically or about his role in the civil rights movement. Four years ago David Garrow edited a series of eighteen volumes on King and the civil rights movement. 1 This past year witnessed the much anticipated publication of the first volume of a projected fourteen volumes of The Papers of Martin Luther King, Jr

Investigation of the sex determination mechanisms in summer flounder (Paralichthys dentatus) and black sea bass (Centropristis striata)

In many cultured finfish species, sexually dimorphic growth is observed, therefore, understanding the mechanisms of differentiation in fishes is necessary for successful aquaculture. Summer flounder (Paralichthys dentatus ) and black sea bass (Centropristis striata) are good candidate species for aquaculture because they easily adapt to culture conditions and have high market value. The production of monosex populations is advantageous in species exhibiting sexually dimorphic growth rates. The purpose of this research was to gain an understanding of the mechanisms involved in sex differentiation of summer flounder and black sea bass. In summer flounder, monosex female culture is beneficial because females grow two to three times larger than males. Like many teleosts with an XX/XY sex chromosome system, Paralichthid females are homogametic (XX) and males heterogametic (XY). Only homogametic individuals can be phenotypically sex reversed during sex differentiation. In the first part of this study, meiogynogenesis and temperature-dependent sex determination were used in the first steps towards the production of monosex female cultures of summer flounder. Meiogynogens were produced by applying a 6 minute pressure shock (8,500 psi) 2 minutes post-fertilization resulting in the production of 1,100 juveniles. For temperature-dependent sex determination, meiogynogens and control diploids were reared at a low temperature regime (12-20°C), 21, and 26°C for 376 days post hatch (DPH). Females were primarily produced at the low temperature regime (62.5% in meiogynogens and 22.6% in controls). The second part of this study examined the disruption of female-specific sex differentiation in black sea bass. Metamorphosed juveniles were reared at 17, 21, and 25°C for 279 DPH. While there was not a significant difference in sex ratios among treatments, the expected outcome of 100% female was not obtained in this protogynous species. Additionally, males were significantly larger than females by 275 DPH. This may provide a mechanism for future production of monosex (male) populations of this protogynous species. Understanding the control of sex in this species is crucial for broodstock maintenance. This research will increase our understanding of the reproductive biology of these species and improve their culture

Student Perceptions on the Community of Spiritual Formation at a Faith-Based University

Spiritual formation has always been of utmost importance in Christian education as faithbased institutions strive to educate the whole person; body, mind, and spirit. Because of this, Christian universities work to create programs and provide activities that challenge the minds and hearts of the students in order to promote spiritual growth. This study seeks to answer the following question: What does a phenomenological analysis of the lived experiences of students at a Council for Christian Colleges & Universities (CCCU) institution reveal about their perceptions of the spiritual formation priorities of the institution? Stated another way, what do students report about their lived experiences in relation to the spiritual formation practices at their institution? This research captured a glimpse of the spiritual formation programming at Pacific Northwest Christian University, or PNCU (pseudonym), as six students shared their experiences through a process of interviews. As the interview data and field notes were analyzed, four themes emerged from the research: Classes and professors impacted their spiritual growth, a sense of community was important to their well-being and spiritual formation, faculty and staff provided a platform for spiritual mentoring, and communal worship in various formats was meaningful. These themes proved consistent with the literature, and offered a snapshot of the overall health of the spiritual formation paradigm at the institution. As a result of this research, a few suggestions were formulated as to how the university could continue to improve its offerings of spiritually formative experiences, and offered insight into potential further study

Diurnal variations in optical depth at Mars: Observations and interpretations

Viking lander camera images of the Sun were used to compute atmospheric optical depth at two sites over a period of 1 to 1/3 martian years. The complete set of 1044 optical depth determinations is presented in graphical and tabular form. Error estimates are presented in detail. Optical depths in the morning (AM) are generally larger than in the afternoon (PM). The AM-PM differences are ascribed to condensation of water vapor into atmospheric ice aerosols at night and their evaporation in midday. A smoothed time series of these differences shows several seasonal peaks. These are simulated using a one-dimensional radiative convective model which predicts martial atmospheric temperature profiles. A calculation combining these profiles with water vapor measurements from the Mars Atmospheric Water Detector is used to predict when the diurnal variations of water condensation should occur. The model reproduces a majority of the observed peaks and shows the factors influencing the process. Diurnal variation of condensation is shown to peak when the latitude and season combine to warm the atmosphere to the optimum temperature, cool enough to condense vapor at night and warm enough to cause evaporation at midday

South Dakota Seed Quality: A Drillbox Survey

In a 1969 survey, a total of 450 samples of oats, barley, hard red spring wheat, durum wheat, and flax were taken during the spring planting season. These samples were collected in 23 eastern South Dakota counties. Several questions were asked the operator about each seed lot at the time the sample was collected. The samples were analyzed at the Seed Testing Laboratory at South Dakota State University for percent of pure seed, kind and number per pound of all crop seed, common weed seeds, noxious weed seeds, and germination. A copy of the analysis was sent to the cooperator

The Effects of Stacking on the Configurations and Elasticity of Single Stranded Nucleic Acids

Stacking interactions in single stranded nucleic acids give rise to configurations of an annealed rod-coil multiblock copolymer. Theoretical analysis identifies the resulting signatures for long homopolynucleotides: A non monotonous dependence of size on temperature, corresponding effects on cyclization and a plateau in the extension force law. Explicit numerical results for poly(dA) and poly(rU) are presented.Comment: 4 pages and 2 figures. Accepted in Phys. Rev. E Rapid Com