143 research outputs found
Effects of wind induced soil moisture stress on the germination and early growth of Pinus banksiana Lamb. on three soil texture types
A controlled environment wind tunnel was used to produce three wind speeds and hence three soil drying
rates in order to study the effects of soil moisture stress on seeds and germinants of Pinus banksiana
Lamb, planted in a sandy loam, loamy sand and sand. Osmotically primed and untreated seed were sown
when the soil was saturated and germination was monitored daily. Germinants at five stages of ontogeny,
the most advanced stage being the start of epicotyl growth, were placed into the wind tunnel with the soil
saturated. When 50% of the germinants were dead and/or wilted, final length and dry weight of the shoots
and roots were measured. All experiments were a split plot factorial design with wind speed as the main
plots and the soil and seed or ontogeny stage treatments as the subplots.
No seed germinated in the wind tunnel for any of the soil type and wind speed treatment combinations.
Therefore, seed were transfered from the soil surface to Petri-dishes in a germination cabinet where
germination was monitored daily. Compared to controls (primed and unprimed seed taken from cold
storage), germination of unprimed seed decreased with each increase in wind speed, the magnitude of the
decrease varying with soil type. A similar response was not noted for the primed seed; osmotic priming
appeared to negate the effects of the physical environment. The exact cause could not be determined from
these studies. The hypothesis that the unprimed seed did not imbibe some critical, minimum amount of
water before drying and that something inhibited germination when the seed was rehydrated is presented
and discussed.
The fewer number of macropores and the more rapid drying rate of the loamy sand and sandy loam soil
types was considered to be the cause of poorer establishment with increasing wind speed of the early
ontogeny stages (stages up to the point the radicle has penetrated the soil surface and the seed is slightly
elevated). The growth and survival of germinants once established was not affected by these factors. The
data suggests that the drying rate of the soil and the inability of root growth to keep up with this drying
was considered to be a major factor affecting growth and survival of the established germinants.
Additionally, the transpiration rate of the germinants probably played a significant role in the survival
time. The loamy sand and sandy loam soil types probably could not supply a sufficient quantity of water
to the germinant to keep pace with the transpirational demand. The sandy soil was better for growth and
survival than the finer soils probably because of the way water is held in the soil profile once the
capillaries are broken. Germinants began to die at soil moisture potentials above the permanent wilting
point (PWP) at the high wind speed. This supports the view that PWP is not a soil constant The increase
in some growth parameters with increasing wind speed supports the view that increasing wind speed is not
always detrimental to germinant growth. Application of the results to field conditions is discussed
New detectors for the kaon and hypernuclear experiments with KaoS at MAMI and with PANDA at GSI
The KaoS spectrometer at the Mainz Microtron MAMI, Germany, is perceived as
the ideal candidate for a dedicated spectrometer in kaon and hypernuclei
electroproduction. KaoS will be equipped with new read-out electronics, a
completely new focal plane detector package consisting of scintillating fibres,
and a new trigger system. First prototypes of the fibre detectors and the
associated new front-end electronics are shown in this contribution. The Mainz
hypernuclei research program will complement the hypernuclear experiments at
the planned FAIR facility at GSI, Germany. At the proposed antiproton storage
ring the spectroscopy of double Lambda hypernuclei is one of the four main
topics which will be addressed by the PANDA Collaboration. The experiments
require the operation of high purity germanium (HPGe) detectors in high
magnetic fields (B= 1T) in the presence of a large hadronic background. The
performance of high resolution Ge detectors in such an environment has been
investigated.Comment: Presentation at International Symposium on the Development of
Detectors for Particle, Astroparticle and Synchrotron Radiation Experiments,
Stanford, Ca (SNIC06), 6 pages, LaTeX, 11 eps figure
Determination of Sinapic Acid Derivatives in Canola Extracts Using High-Performance Liquid Chromatography
A high-performance liquid chromatographic (HPLC) method with diode array detection (DAD) was used to determine the total phenolics, including sinapic acid derivatives in canola. Ten Western Canadian canola seeds, six other commodity canola seeds, their corresponding press cakes and meals were analyzed. Seeds of European 00 rapeseed and Brassica Juncea (Indian mustard) were included for comparison. Phenolic compounds were separated using a gradient elution system of waterâmethanol-Îż-phosphoric acid solution with a flow rate of 0.8Â ml/min. In addition to sinapine (SP) and sinapic acid (SA), sinapoyl glucose (SG) is reported in the methanolic extracts. The detection and quantification limits of these compounds were 0.20â0.40 and 0.50â0.80Â ÎŒg/ml, respectively with recovery values over 98.0%. The content of total phenolics, SP, SA and SG in canola extracts ranged from 9.16 to 16.13, 6.39 to 12.28, 0.11 to 0.59 and 1.36 to 7.50Â mg/g, respectively with significant differences among varieties
Measurement of the recoil polarization in the p (\vec e, e' \vec p) pi^0 reaction at the \Delta(1232) resonance
The recoil proton polarization has been measured in the p (\vec e,e'\vec p)
pi^0 reaction in parallel kinematics around W = 1232 MeV, Q^2 = 0.121 (GeV/c)^2
and epsilon = 0.718 using the polarized c.w. electron beam of the Mainz
Microtron. Due to the spin precession in a magnetic spectrometer, all three
proton polarization components P_x/P_e = (-11.4 \pm 1.3 \pm 1.4) %, P_y =
(-43.1 \pm 1.3 \pm 2.2) %, and P_z/P_e = (56.2 \pm 1.5 \pm 2.6) % could be
measured simultaneously. The Coulomb quadrupole to magnetic dipole ratio CMR =
(-6.4\pm 0.7_{stat}\pm 0.8_{syst}) % was determined from P_x in the framework
of the Mainz Unitary Isobar Model. The consistency among the reduced
polarizations and the extraction of the ratio of longitudinal to transverse
response is discussed.Comment: 5 pages LaTeX, 1 table, 2 eps figure
Measurement of the Electric Form Factor of the Neutron at Q^2 = 0.3-0.8 (GeV/c)^2
The electric form factor of the neutron, G_En, has been measured at the Mainz
Microtron by recoil polarimetry in the quasielastic D(e_pol,e'n_pol)p reaction.
Three data points have been extracted at squared four-momentum transfers Q^2 =
0.3, 0.6 and 0.8 (GeV/c)^2. Corrections for nuclear binding effects have been
applied.Comment: 9 pages, 7 figures, 2 tables. Accepted for publication in EPJ
Measurement of the LT-asymmetry in \pi^0 electroproduction at the energy of the \Delta (1232) resonance
The reaction p(e,e'p)pi^0 has been studied at Q^2=0.2 (GeV/c)^2 in the region
of W=1232 MeV. From measurements left and right of q, cross section asymmetries
\rho_LT have been obtained in forward kinematics \rho_LT(\theta_\pi^0=20deg) =
(-11.68 +/- 2.36_stat +/- 2.36_sys)$ and backward kinematics
\rho_LT(\theta_\pi^0=160deg) =(12.18 +/- 0.27_stat +/- 0.82_sys). Multipole
ratios \Re(S_1+^* M_1+)/|M_1+|^2 and \Re(S_0+^* M_1+)/|M_1+|^2 were determined
in the framework of the MAID2003 model. The results are in agreement with older
data. The unusally strong negative \Re(S_0+^* M_1+)/|M_1+|^2 required to bring
also the result of Kalleicher et al. in accordance with the rest of the data is
almost excluded.Comment: 7 pages, 7 figures, 4 tables. Changed content. Accepted for
publication in EPJ
High-precision Studies of the He(e,ep) Reaction at the Quasielastic Peak
Precision studies of the reaction He(e,ep) using the
three-spectrometer facility at the Mainz microtron MAMI are presented. All data
are for quasielastic kinematics at MeV/c. Absolute cross
sections were measured at three electron kinematics. For the measured missing
momenta range from 10 to 165 MeV/c, no strength is observed for missing
energies higher than 20 MeV. Distorted momentum distributions were extracted
for the two-body breakup and the continuum. The longitudinal and transverse
behavior was studied by measuring the cross section for three photon
polarizations. The longitudinal and transverse nature of the cross sections is
well described by a currently accepted and widely used prescription of the
off-shell electron-nucleon cross-section. The results are compared to modern
three-body calculations and to previous data.Comment: 4 pages, 3 figures. Submitted for publication in Phys. Rev. Let
Efficient method for rapid multiplication of clean and healthy willow clones via in vitro propagation with broad genotype applicability
Willow is a versatile crop with considerable potential as a source of renewable biomass for bioenergy. Although breeding new varieties takes less time compared with some other tree species, producing new willow varieties is still a slow, labour-intensive process, partly because clonally propagating the results of each cross is a bottleneck early in the breeding scheme. In this paper, we describe a facile, rapid method for the in vitro culture of a wide range of willow genotypes. We have developed a combination of media and methods for efficient tissue-culture propagation to rapidly multiply individual plants and simultaneously produce clean, stock germplasm applicable to a wide range of willow genotypes that can be phytosanitary tested to demonstrate their disease-free status. The micropropagation method described could generate in the order of 5000 viable, transplantable clones from a single plant in just 24 weeks and was used to produce phytosanitary tested breeding material for export to overcome restriction on the international transport of woody cuttings. This method could represent a valuable biotechnology adjunct to willow breeding programmes and could accommodate early selection via molecular or biochemical markers
Single-shot divergence measurements of a laser-generated relativistic electron beam
Copyright 2010 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Physics of Plasmas, 17(11), 113106_1-113106_7, 2010 and may be found at http://dx.doi.org/10.1063/1.351459
- âŠ