784 research outputs found
Risico inventarisatie van schade door ethyleen bij tussenplanten : effecten van tomaat op tussengeplante komkommer en tomaat
Bij een herfstteelt van trostomaten op goten is het aantrekkelijk om in de winter tomaten of komkommers tussen te planten. Door het grotendeels weg laten zakken van het oude gewas onder de goot en het jonge gewas op de goot te zetten, kan de teeltwisseling met een minder groot gat in de productie verlopen. Omdat trostomaten aan de plant volledig doorkleuren bestaat in principe de kans dat de ethyleen die gevormd wordt door de rijpende vruchten schade kan geven aan het jonge tussengeplante gewas. Bij tomaat is in 2000 op enkele bedrijven trosrui geconstateerd bij het tussengeplante toma tengewas. Hierbij werd gedacht aan mogelijke ethyleenschade. Ethyleen is een gasvormige, planteigen stof die als groeiregulator (hormoon) bij zeer veel verschillende fysiologische processen betrokken is. Het beïnvloedt o.a. bloei, bladgroei en lengtegroei van de spruit (Abeles et al., 1992). Als er externe bronnen zijn van ethyleen dan is er al snel sprake van schade. Symptomen van ethyleenschade zijn o.a. afwijkende kiemplanten, bloemrui, trosrui, afwijkende bladstand, bladval en stagnatie van de vegetatieve groei. Ernstige ethyleenschade uit zich direct in bladvergeling, maar soms treedt er verdekt wat lichte schade op die toch blijkt te leiden tot productiederving. Ethyleen komt in de buitenlucht standaard voor in een concentratie van 1 – 5 ppb (Abeles et al., 1992), maar kan in stedelijke gebieden tot wel 100 keer hoger worden. Ethyleen kan dus als luchtvervuiling een kas binnenkomen, of ophopen ten gevolge van een slecht afgestelde brander (Hanan, 1973, Esmeijer, 1999). Een andere bron van ethyleen is een gewas met doorkleurende vruchten zoals tomaat (Reid, 1988). In het geval van tussenplanten in de winterperiode zou dit problemen kunnen opleveren. In het verleden werd ook wel tussengeplant, maar leidde dit nooit tot problemen, omdat de vruchten los geoogst werden en nooit zo lang doorgekleurd in het gewas aanwezig bleven. Bovendien werd er alleen tussengeplant in de zomermaanden als er relatief veel gelucht werd. Bij tussenplanten in de winter van komkommers bij tomaat gaat het om een situatie waarin de luchtramen vaak gesloten zijn en er weinig licht beschikbaar is. De meeste gewassen zijn in die omstandigheden gevoelig voor schade, en naar verwachting zullen jonge, snel groeiende komkommerplanten op die regel geen uitzondering zijn
Spin configuration in a frustrated ferromagnetic/antiferromagnetic thin film system
We have studied the magnetic configuration in ultrathin antiferromagnetic Mn
films grown around monoatomic steps on an Fe(001) surface by spin-polarized
scanning tunneling microscopy/spectroscopy and ab-initio-parametrized
self-consistent real-space tight binding calculations in which the spin
quantization axis is independent for each site thus allowing noncollinear
magnetism. Mn grown on Fe(001) presents a layered antiferromagnetic structure.
In the regions where the Mn films overgrows Fe steps the magnetization of the
surface layer is reversed across the steps. Around these defects a frustration
of the antiferromagnetic order occurs. Due to the weakened magnetic coupling at
the central Mn layers, the amount of frustration is smaller than in Cr and the
width of the wall induced by the step does not change with the thickness, at
least for coverages up to seven monolayers.Comment: 10 pages, 5 figure
Dust, Ice and Gas in Time (DIGIT) Herschel program first results: A full PACS-SED scan of the gas line emission in protostar DK Cha
DK Cha is an intermediate-mass star in transition from an embedded
configuration to a star plus disk stage. We aim to study the composition and
energetics of the circumstellar material during this pivotal stage. Using the
Range Scan mode of PACS on the Herschel Space Observatory, we obtained a
spectrum of DK Cha from 55 to 210 micron as part of the DIGIT Key Program.
Almost 50 molecular and atomic lines were detected, many more than the 7 lines
detected in ISO-LWS. Nearly the entire ladder of CO from J=14-13 to 38-37
(E_u/k = 4080 K), water from levels as excited as E_u/k = 843 K, and OH lines
up to E_u/k = 290 K were detected. The continuum emission in our PACS SED scan
matches the flux expected from a model consisting of a star, a surrounding disk
of 0.03 Solar mass, and an envelope of a similar mass, supporting the
suggestion that the object is emerging from its main accretion stage.
Molecular, atomic, and ionic emission lines in the far-infrared reveal the
outflow's influence on the envelope. The inferred hot gas can be photon-heated,
but some emission could be due to C-shocks in the walls of the outflow cavity.Comment: 4 Page letter, To appear in A&A special issue on Hersche
MICROBE-MEDIATED PLANT–SOIL FEEDBACK CAUSES HISTORICAL CONTINGENCY EFFECTS IN PLANT COMMUNITY ASSEMBLY
The metabolism in vitro of human low-density lipoprotein by the human hepatoma cell line Hep G2
Investigation of Time-Frequency Features for GPR Landmine Discrimination
科研費報告書収録論文(課題番号:14102024/研究代表者:佐藤源之/ポーラリメトリック・インターフェロメトリックレーダによる地雷検知に関する研究
Erratum to: Circulating tumor DNA as a biomarker for monitoring early treatment responses of patients with advanced lung adenocarcinoma receiving immune checkpoint inhibitors.
The following error appeared in Section 3.5 in Ref. [1]. Instead of ‘Progressive disease-L1 expression data were available for 87 patients’, the text should read ‘PD-L1 expression data were available for 87 patients’. We apologize for this error.</p
On the single mode approximation in spinor-1 atomic condensate
We investigate the validity conditions of the single mode approximation (SMA)
in spinor-1 atomic condensate when effects due to residual magnetic fields are
negligible. For atomic interactions of the ferromagnetic type, the SMA is shown
to be exact, with a mode function different from what is commonly used.
However, the quantitative deviation is small under current experimental
conditions (for Rb atoms). For anti-ferromagnetic interactions, we find
that the SMA becomes invalid in general. The differences among the mean field
mode functions for the three spin components are shown to depend strongly on
the system magnetization. Our results can be important for studies of beyond
mean field quantum correlations, such as fragmentation, spin squeezing, and
multi-partite entanglement.Comment: Revised, newly found analytic proof adde
Methanol maps of low-mass protostellar systems: the Serpens Molecular Core
Observations of Serpens have been performed at the JCMT using Harp-B. Maps
over a 4.5'x5.4' region were made in a frequency window around 338 GHz,
covering the 7-6 transitions of methanol. Emission is extended over each
source, following the column density of H2 but showing up also particularly
strongly around outflows. The rotational temperature is low, 15-20 K, and does
not vary with position within each source. The abundance is typically 10^-9 -
10^-8 with respect to H2 in the outer envelope, whereas "jumps" by factors of
up to 10^2 -10^3 inside the region where the dust temperature exceeds 100 K are
not excluded. A factor of up to ~ 10^3 enhancement is seen in outflow gas. In
one object, SMM4, the ice abundance has been measured to be ~ 3x10^-5 with
respect to H2 in the outer envelope, i.e., a factor of 10^3 larger than the
gas-phase abundance. Comparison with C18O J=3-2 emission shows that strong CO
depletion leads to a high gas-phase abundance of CH3OH not just for the Serpens
sources, but for a larger sample of protostars. The observations illustrate the
large-scale, low-level desorption of CH3OH from dust grains, extending out to
and beyond 7500 AU from each source, a scenario which is consistent with
non-thermal (photo-)desorption from the ice. The observations also illustrate
the usefulness of CH3OH as a tracer of energetic input in the form of outflows,
where methanol is sputtered from the grain surfaces. Finally, the observations
provide further evidence of CH3OH formation through CO hydrogenation proceeding
on grain surfaces in low-mass envelopes.Comment: Accepted for publication in A&A
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