The Height of a Giraffe

A minor modification of the arguments of Press and Lightman leads to an estimate of the height of the tallest running, breathing organism on a habitable planet as the Bohr radius multiplied by the three-tenths power of the ratio of the electrical to gravitational forces between two protons (rather than the one-quarter power that Press got for the largest animal that would not break in falling over, after making an assumption of unreasonable brittleness). My new estimate gives a height of about 3.6 meters rather than Press's original estimate of about 2.6 cm. It also implies that the number of atoms in the tallest runner is very roughly of the order of the nine-tenths power of the ratio of the electrical to gravitational forces between two protons, which is about 3 x 10^32.Comment: 12 pages, LaTe

Influence of Off-Sun-Earth Line Distance on the Accuracy of L1 Solar Wind Monitoring

Upstream solar wind measurements from near the L1 Lagrangian point are commonly used to investigate solar wind-magnetosphere coupling. The off-Sun-Earth line distance of such solar wind monitors can be large, up to 100 RE. We investigate how the correlation between measurements of the interplanetary magnetic field and associated ionospheric responses deteriorates as the off-Sun-Earth line distance increases. Specifically, we use the magnitude and polarity of the dayside region 0 field-aligned currents (R0 FACs) as a measure of interplanetary magnetic field (IMF) BY-associated magnetic tension effects on newly-reconnected field lines, related to the Svalgaard-Mansurov effect. The R0 FACs are derived from Advanced Magnetosphere and Planetary Electrodynamics Response Experiment measurements by a principal component analysis, for the years 2010–2016. We perform cross-correlation analyses between time-series of IMF BY, measured by the Wind spacecraft and propagated to the nose of the bow shock by the OMNI technique, and these R0 FAC measurements. Typically, in the summer hemisphere, cross-correlation coefficients between 0.6 and 0.9 are found. However, there is a reduction of order 0.1–0.15 in correlation coefficient between periods when Wind is close to (within 45 RE) and distant from (beyond 70 RE) the Sun-Earth line. We find a time-lag of around 17 min between predictions of the arrival of IMF features at the bow shock and their effect in the ionosphere, irrespective of the location of Wind.publishedVersio

Lobe Reconnection and Cusp-Aligned Auroral Arcs

Following the St. Patrick's Day (17 March) geomagnetic storm of 2013, the interplanetary magnetic field had near-zero clock angle for almost two days. Throughout this period multiple cusp-aligned auroral arcs formed in the polar regions; we present observations of, and provide a new explanation for, this poorly understood phenomenon. The arcs were observed by auroral imagers onboard satellites of the Defense Meteorological Satellite Program. Ionospheric flow measurements and observations of energetic particles from the same satellites show that the arcs were produced by inverted-V precipitation associated with upward field-aligned currents (FACs) at shears in the convection pattern. The large-scale convection pattern revealed by the Super Dual Auroral Radar Network and the corresponding FAC pattern observed by the Active Magnetosphere and Planetary Electrodynamics Response Experiment suggest that dual-lobe reconnection was ongoing to produce significant closure of the magnetosphere. However, we propose that once the magnetosphere became nearly closed complicated lobe reconnection geometries arose that produced interleaving of regions of open and closed magnetic flux and spatial and temporal structure in the convection pattern that evolved on timescales shorter than the orbital period of the DMSP spacecraft. This new model naturally explains many features of cusp-aligned arcs, including why they focus in from the nightside toward the cusp region.publishedVersio

Using Media Messaging to Promote Healthful Eating and Physical Activity among Urban Youth

National trends show consistent increases, as well as racial and ethnic dis- parities, in the prevalence of overweight children and adolescents. Such disparity is evident regarding behaviors such as a poor diet and a lack of physical activity and in the prevalence and outcomes of associated health problems. It has been suggested that grounding interventions in cultural traditions and norms are critical for preventing obesity among ethnic and racial minority youth; however, with some notable exceptions, few community interventions have used this approach. Moreover, urban minority youth may face additional barriers to healthful eating and physical activity behaviors, such as limited environmental and social support systems. Thus, there is a great need for culturally rele- vant community-based programs to serve them

The Effect of Furrow Irrigation Erosion on Crop Productivity

Furrow irrigation erosion redistributes topsoil by eroding upper ends of fields and depositing sediment on downslope portions causing a several fold topsoil depth difference on individual fields. This investigation was conducted to evaluate the effects of this erosion and deposition process on crop yield and to develop crop yield-topsoil depth relationships. Studies were conducted on 14 farmer-operated fields and on field plots with a continuous topsoil depth gradient from 10 to 66 cm. Severe erosion on the upper ends of fields combined with tillage has mixed light-colored subsoil with topsoil and caused these areas to become whitish in color. Crop yields have sharply decreased on these whitish areas compared to areas where the topsoil depth is 38 cm, or the original depth. Yields were increased, but less sharply, where sediment deposition has increased topsoil depth above 38 cm up to a depth of about 66 cm. Yield-topsoil depth relationships followed the equation Y = a+b 1nX with significant correlation coefficients for wheat (Triticum aestivum L.), sweet corn (Zea mays L.), barley (Hordeum vulgare L.), alfalfa (Medicago sativa L.), dry beans (Phaseolus sap.) and sugarbeets (Beta vulgaris L.). Yield decreases per unit loss of topsoil were greatest for wheat and sweet corn and least for sugarbeets. Yields on whitish soil areas could not be improved more than indicated by these relationships by adding additional fertilizer phosphorus or potassium

Furrow Erosion Reduces Crop Yields

Furrow irrigation erosion redistributes topsoil within fields and causes serious topsoil losses from farms. Erosion occurs on the upper portions of fields where the furrow streams are largest and the energy greatest. The furrow stream must be large enough at the head end of the furrow to supply sufficient water for infiltration over the entire furrow length

Producing no-till cereal or corn following alfalfa on furrow-irrigated land

Improved cropping systems are needed to reduce production inputs, increase production efficiency, protect water quality, and reduce soil erosion on furrow-irrigated land. Five field studies were conducted to evaluate the feasibility of producing cereal or corn (Zea Mays L.) without tillage following alfalfa (Medicago sativa L.) on furrow-irrigated land. The primary purposes of these studies were to reduce tillage costs and use N that becomes available through decomposition and mineralization following killing of alfalfa. Results demonstrated that no-till crops can be successfully irrigated with a high degree of water application uniformity, and with less water than for traditionally tilled crops. Production costs were lower resulting in higher net income for the no-till produced crops in all studies. Corn can be produced successfully with all of its required N being supplied from the decomposing alfalfa roots and nodules. The rate at which NO3–N is formed from this source parallels the N-requirements of corn. All of the N requirements for cereals can be supplied from the alfalfa source if the alfalfa is killed in the early fall so that there will be ample time at soil temperatures sufficiently high to permit some accumulation of NO3–N in the soil before the rapid N uptake period required by cereals. If this regime is not followed, cereals may need to be supplemented with added N to assure adequacy. The use of N by corn or cereal following alfalfa reduces the potential for nitrate leaching as compared to conditions when low N requiring crops are grown after alfalfa

Seasonal and diurnal variations in AMPERE observations of the Birkeland currents compared to modeled results

We reduce measurements made by the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) to give the total Birkeland (field-aligned) current flowing in both hemispheres in monthly and hourly bins. We analyze these totals using 6 years of data (2010–2015) to examine solar zenith angle-driven variations in the total Birkeland current flowing in both hemispheres, simultaneously, for the first time. A diurnal variation is identified in the total Birkeland current flowing, consistent with variations in the solar zenith angle. A seasonal variation is also identified, with more current flowing in the Northern (Southern) Hemisphere during Bartels rotations in northern (southern) summer. For months close to equinox, more current is found to flow in the Northern Hemisphere, contrary to our expectations. We also conduct the first test of the Milan (2013) model for estimating Birkeland current magnitudes, with modifications made to account for solar contributions to ionospheric conductance based on the observed variation of the Birkeland currents with season and time of day. The modified model, using the value of ?D averaged by Bartels rotation (scaled by 1.7), is found to agree with the observed AMPERE currents, with a correlation of 0.87 in the Northern Hemisphere and 0.86 in the Southern Hemisphere. The improvement over the correlation with dayside reconnection rate is demonstrated to be a significant improvement to the model. The correlation of the residuals is found to be consistent with more current flowing in the Northern Hemisphere. This new observation of systematically larger current flowing in the Northern Hemisphere is discussed in the context of previous results which suggest that the Northern Hemisphere may react more strongly to dayside reconnection than the Southern Hemisphere

Predictions from Quantum Cosmology

The world view suggested by quantum cosmology is that inflating universes with all possible values of the fundamental constants are spontaneously created out of nothing. I explore the consequences of the assumption that we are a `typical' civilization living in this metauniverse. The conclusions include inflation with an extremely flat potential and low thermalization temperature, structure formation by topological defects, and an appreciable cosmological constant.Comment: (revised version), 15 page

Effect of Nitrogen and Irrigation on Sugarbeet Production in Southern Idaho

Most of the nitrogen fertilizer is applied to sugarbeet fields in southern Idaho before planting. During the early stages of plant growth the soil and fertilizer N is subject to leaching because the NO?-N concentrations in the soil usually are higher than later in the season. The rate of N uptake in this area, under conditions where N does not limit plant growth, increases rapidly beginning early in June, reaches a peak early in July, and begins to decrease in late July. If inadequate N is available to meet crop needs then the addition of N fertilizer just prior to the period when the demand rate increases should increase the efficiency of sucrose production and N fertilizer use. The practice of supplemental, midseason application of N in irrigation water is increasing in southern Idaho. It is not known whether this practice is resulting in more efficient use of N fertilizer, increasing yields, or whether or not midseason applications have an adverse net effect on sucrose production. The objective of this study was to evaluate current N fertilizer practices and the effect of irrigation management on root and sucrose yields. Major emphasis was placed on the effects of N and irrigation management on petiole NO?-N concentrations to refine the use of petiole analysis as a diagnostic tool in managing N fertilizer