Agronomic and allelopathic effects of sequential cropping and tillage on tobacco and vegetable production

Production of vegetables and tobacco (Nicotiana tabacum L.) have traditionally been through monocrop, conventionally tilled systems. With the increasing importance of low input practices and conservation, and the declining number of producers, there is a need to develop reduced tillage systems and sequential cropping. This need prompted an investigation into the effects of reduced tillage and sequential cropping of tobacco, tomato (Lycopersicon esculentum Mill.) and broccoli (Brassica oleracea var. Italica L.) production systems. Three tillage systems (no-till, conventional till with a winter cover, and conventional till with no winter cover) and three cropping sequences (spring broccoli followed by tobacco or tomato; spring broccoli followed by tobacco or tomato, followed by fall broccoli; and tobacco or tomato followed by fall broccoli) were used in 1989 and 1990 at three locations in eastern Tennessee. Tobacco and tomato systems were evaluated separately. Also, since broccoli yields were suppressed by reduced tillage, field, greenhouse, and laboratory investigations were initiated to assess the possible allelopathic influences of wheat cover crops on the growth of tobacco, tomato, and broccoli. Field soil samples were evaluated for presence of five organic acids which are known to be allelochemicals produced from decaying wheat residue. Ferulic, p-hydroxybenzoic, p-coumaric, syringic and vanillic acids were applied to these crops individually at various concentrations. Methods of extraction and determination of concentrations of these acids from soils through high performance liquid chromatography were developed. Field samples were then evaluated for quantities of these acids. Broccoli yield and quality were reduced by minimum tillage but were not affected by cropping sequence. Tobacco was also adversely affected by reduced tillage. Tomato yield, however, was not affected by tillage, but fewer cull fruit occurred in no-till. Earlier planted tomatoes had somewhat higher yields and quality than those in later planted sequences. Allelochemicals had negligible effects on tomato and tobacco growth but retarded broccoli growth and dry weight accumulation. Greater concentrations of ferulic and p-coumaric acids were found in soils from no-till plots than from conventional till plots. Methods of extraction and analysis of organic acids were successfully developed and described in detail

Making long-term memories in minutes:a spaced learning pattern from memory research in education

Memory systems select from environmental stimuli those to encode permanently. Repeated stimuli separated by timed spaces without stimuli can initiate Long-TermPotentiation(LTP) and long-term memory (LTM encoding. These processes occur in time scales of minutes, and have been demonstrated in many species. This study reports on using a specific timed pattern of three repeated stimuli separated by 10min spaces drawn from both behavioral and laboratory studies of LTP and LTM encoding. A technique was developed based on this pattern to test whether encoding complex information into LTM in students was possible using the pattern within a very short timescale. In an educational context, stimuli were periods of highly compressed instruction, and spaces were created through 10min distractor activities. Spaced Learning in this form was used as the only means of instruction for a national curriculum Biology course, and led to very rapid LTM encoding as measured by the high-stakes test for the course. Remarkably, learning at a greatly increased speed and in a pattern that included deliberate distraction produced significantly higher scores than random answers (p<0.00001)and scores were not significantly different for experimental groups (one hour spaced learning) and control groups(four months teaching). Thus learning per hour of instruction, as measured by the test, was significantly higher for the spaced learning groups(p<0.00001). In a third condition, spaced learning was used to replace the end of course review for one of two examinations. Results showed significantly higher outcomes for the course using spaced learning(p<0.0005). The implications of these findings and further areas for research are briefly considered

Mantle melting as a function of water content beneath back-arc basins

Subduction zone magmas are characterized by high concentrations of H_(2)O, presumably derived from the subducted plate and ultimately responsible for melting at this tectonic setting. Previous studies of the role of water during mantle melting beneath back-arc basins found positive correlations between the H_(2)O concentration of the mantle (H_(2)O_o ) and the extent of melting (F), in contrast to the negative correlations observed at mid-ocean ridges. Here we examine data compiled from six back-arc basins and three mid-ocean ridge regions. We use TiO_2 as a proxy for F, then use F to calculate H_(2)O_o from measured H_(2)O concentrations of submarine basalts. Back-arc basins record up to 0.5 wt % H_(2)O or more in their mantle sources and define positive, approximately linear correlations between H_(2)O_o and F that vary regionally in slope and intercept. Ridge-like mantle potential temperatures at back-arc basins, constrained from Na-Fe systematics (1350°–1500°C), correlate with variations in axial depth and wet melt productivity (∼30–80% F/wt % H_(2)O_o ). Water concentrations in back-arc mantle sources increase toward the trench, and back-arc spreading segments with the highest mean H_(2)O_o are at anomalously shallow water depths, consistent with increases in crustal thickness and total melt production resulting from high H_(2)O. These results contrast with those from ridges, which record low H_(2)O_o (<0.05 wt %) and broadly negative correlations between H_(2)O_o and F that result from purely passive melting and efficient melt focusing, where water and melt distribution are governed by the solid flow field. Back-arc basin spreading combines ridge-like adiabatic melting with nonadiabatic mantle melting paths that may be independent of the solid flow field and derive from the H_(2)O supply from the subducting plate. These factors combine significant quantitative and qualitative differences in the integrated influence of water on melting phenomena in back-arc basin and mid-ocean ridge settings

Evidence of Fragmenting Dust Particles from Near-Simultaneous Optical and Near-IR Photometry and Polarimetry of Comet 73P/Schwassmann-Wachmann 3

We report imaging polarimetry of segments B and C of the Jupiter-family Comet 73P/Schwassmann-Wachmann 3 in the I and H bandpasses at solar phase angles of approximately 35 and 85deg. The level of polarization was typical for active comets, but larger than expected for a Jupiter-family comet. The polarimetric color was slightly red (dP/dL = +1.2 +/- 0.4) at a phase angle of ~ 35deg and either neutral or slightly blue at a phase angle of ~ 85deg. Observations during the closest approach from 2006 May 11-13 achieved a resolution of 35 km at the nucleus. Both segments clearly depart from a 1/rho surface brightness for the first 50 - 200 km from the nucleus. Simulations of radiation driven dust dynamics can reproduce some of the observed coma morphology, but only with a wide distribution of initial dust velocities (at least a factor of 10) for a given grain radius. Grain aggregate breakup and fragmentation are able to reproduce the observed profile perpendicular to the Sun-Comet axis, but fit the observations less well along this axis (into the tail). The required fragmentation is significant, with a reduction in the mean grain aggregate size by about a factor of 10. A combination of the two processes could possibly explain the surface brightness profile of the comet.Comment: 40 pages including 11 figure

Dust in Comet C/2007 N3 (Lulin)

We report optical imaging, optical and near-infrared polarimetry, and Spitzer mid-infrared spectroscopy of comet C/2007 N3 (Lulin). Polarimetric observations were obtained in R (0.676 micron) at phase angles from 0.44 degrees to 21 degrees with simultaneous observations in H (1.65 micron) at 4.0 degrees, exploring the negative branch in polarization. Comet C/2007 N3 (Lulin) shows typical negative polarization in the optical as well as a similar negative branch near-infrared wavelengths. The 10 micron silicate feature is only weakly in emission and according to our thermal models, is consistent with emission from a mixture of silicate and carbon material. We argue that large, low-porosity (akin to Ballistic Particle Cluster Aggregates) rather absorbing aggregate dust particles best explain both the polarimetric and the mid-infrared spectral energy distribution.Comment: 18 pages, 9 figures, 3 table

Mantle Melting as a Function of Water Content beneath the Mariana Arc

Subduction zone magmas are characterized by high concentrations of pre-eruptive H_2O, presumably as a result of an H_2Oflux originating from the dehydrating, subducting slab. The extent of mantle melting increases as a function of increasing water content beneath back-arc basins and is predicted to increase in a similar manner beneath arc volcanoes. Here, we present new data for olivine-hosted, basaltic melt inclusions from the Mariana arc that reveal pre-eruptive H_2O contents of ~1•5-6•0 wt %, which are up to three times higher than concentrations reported for the Mariana Trough back-arc basin. Major element systematics of arc and back-arc basin basalts indicate that the back-arc basin melting regime does not simply mix with wet, arc-derived melts to produce the observed range of back-arc magmatic H_2O concentrations. Simple melting models reveal that the trend of increasing extents of melting with increasing H_2O concentrations of the mantle source identified in the Mariana Trough generally extends beneath the Mariana volcanic front to higher mantle water contents and higher extents of melting. In detail, however, each Mariana volcano may define a distinct relationship between extent of melting and the H_2O content of the mantle source. We develop a revised parameterization of hydrous melting, incorporating terms for variable pressure and mantle fertility, to describe the distinct relationships shown by each arc volcano. This model is used in combination with thermobarometry constraints to show that hydrous melts equilibrate at greater depths (34-87 km) and temperatures (>1300°C) beneath the Mariana arc than beneath the back-arc basin (21-37 km), although both magma types can form from a mantle of similar potential temperature (~1350°C).The difference lies in where the melts form and equilibrate. Arc melts are dominated by those that equilibrate within the hot core of the mantle wedge, whereas back-arc melts are dominated by those that equilibrate within the shallow zone of decompression melting beneath the spreading center. Despite higher absolute melting temperatures (>1300°C), Mariana arc melts reflect lower melt productivity as a result of wet melting conditions and a more refractory mantle source

Molecular characterization of the genes encoding the tungsten-containing aldehyde ferredoxin oxidoreductase from Pyrococcus furiosus and formaldehyde ferredoxin oxidoreductase from Thermococcus litoralis

The hyperthermophilic archaea Pyrococcus furiosus and Thermococcus litoralis contain the tungstoenzymes aldehyde ferredoxin oxidoreductase, a homodimer, and formaldehyde ferredoxin oxidoreductase, a homotetramer. herein we report the cloning and sequencing of the P. furiosus gene aor (605 residues; M_r, 66,630) and the T. litoralis gene for (621 residues; M_r, 68,941)

Outflows from Luminous YSOs: An Infrared Polarimetric Study

e present Near Infrared imaging polarimetry of three regions of massive star formation, G$192.16 - 3.82$, Cepheus A, and W42. In W42 we have discovered a new bipolar nebula located at the far side of the HII region behind the visible cluster of exciting stars. The axis of this new nebula is aligned with the magnetic field threading the entire cluster region. Polarization in the bipolar outflow nebulosity associated with G192.16 is consistent with a single illuminating source, too faint to be detected at 2 \micron. Polarization in the reflection nebulosity associated with Ceph A requires more than one illuminating source, although HW2 is clearly dominant. In all three objects, the magnetic field in the outflow at distances greater than $\sim 0.2$ pc is radial. In G192.16 the magnetic field geometry closer than $\sim 0.2$ pc to the embedded star appears chaotic. For G192.16 the outflow is not aligned with the surrounding magnetic field, which lies in the galactic plane. In Ceph A, the outflow axis could be interpreted as being aligned with the galactic plane, but the magnetic field threading the region is not. Only in the case of W42 is the magnetic field threading the HII region aligned with the mean field in the surrounding galactic plane.Comment: 1 LaTeX file, 10 figure

The Grizzly, February 14, 2008

Writer\u27s Strike May See a Silver Lining • Ellison Unveils Art Exhibit in Berman • Relief for Students? College Endowments Skyrocket • Ursinus Designs New Certificate for International Studies • Is Everybody Really Doing It? The Indictment of the Greek Community at Ursinus College Surprises Many • Ursinus Community Shares its Dirty Little Secrets • Focus the Nation and Environmentalism: No Longer Just for Hippies • UC Study Abroad Helpful Hints • Opinions: Lessons from Super Tuesday; Does The Times Need Bill Kristol?; Lessons from the Hormuz Strait • Ursinus Wrestlers Clinch Dual Meet • UC Indoor Track Teams Make Big Moves, Heat Up Competitionhttps://digitalcommons.ursinus.edu/grizzlynews/1755/thumbnail.jp