526 research outputs found
Alternatieve groeiremming kuipplanten : alternatieven voor chemische groeiremming bij Solanum en Heliotropium
Solanum rantonnettii en Heliotropium peruvianum opgepot in week 41 2001 zijn in 4 kasafdelingen geplaatst waarbij, naast de als standaard ingestelde temperatuur van 15oC, DIF+kouval, natte kouval door middel van dagelijkse besproeiing met gekoeld water en belichting met SL-lampen is toegepast. Deze behandelingen zijn gecombineerd met het gebruik van standaard potgrond geschikt voor een eb/vloed watergeefsysteem en met potgrond waaraan 20% klei is toegevoegd. Bij alle behandelingscombinaties zijn 3 bespuitingsregimes toegepast waarbij 0, 10, 20 of 30 gram Alar per 100 planten is gebruikt tijdens 4 tot 11 bespuitingen. Bij een eindbeoordeling door 18 kuipplantenkwekers bleek, dat vooral de bespuitingen waarbij 20 of 30 gram Alar per 100 planten was toegepast, een positief effect hadden op de kwaliteit van het eindproduct. De toevoeging van klei aan de potgrond kan een positieve bijdrage leveren bij het gewas Heliotropium. De alternatieve maatregelen om groei te remmen door tijdelijke temperatuursverlaging gedurende het etmaal door luchten of beregenen met gekoeld water en het belichten met lampen met een kortgolvig spectrum leverden onvoldoende bijdragen voor het gewenste resultaat
Distinction between clouds and ice/snow covered surfaces in the identification of cloud-free observations using SCIAMACHY PMDs
SCIAMACHY on ENVISAT allows measurement of different trace gases including those most abundant in the troposphere (e.g. CO<sub>2</sub>, NO<sub>2</sub>, CH<sub>4</sub>, BrO, SO<sub>2</sub>). However, clouds in the observed scenes can severely hinder the observation of tropospheric gases. Several cloud detection algorithms have been developed for GOME on ERS-2 which can be applied to SCIAMACHY. The GOME cloud algorithms, however, suffer from the inadequacy of not being able to distinguish between clouds and ice/snow covered surfaces because GOME only covers the UV, VIS and part of the NIR wavelength range (240-790 nm). As a result these areas are always flagged as clouded, and therefore often not used. Here a method is presented which uses the SCIAMACHY measurements in the wavelength range between 450 nm and 1.6 µm to make a distinction between clouds and ice/snow covered surfaces. The algorithm is developed using collocated MODIS observations. The algorithm presented here is specifically developed to identify cloud-free SCIAMACHY observations. The SCIAMACHY Polarisation Measurement Devices (PMDs) are used for this purpose because they provide higher spatial resolution compared to the main spectrometer measurements
Evidence of photospheric vortex flows at supergranular junctions observed by FG/SOT (Hinode)
Twisting motions of different nature are observed in several layers of the
solar atmosphere. Chromospheric sunspot whorls and rotation of sunspots or even
higher up in the lower corona sigmoids are examples of the large scale twisted
topology of many solar features. Nevertheless, their occurrence at large scale
in the quiet photosphere has not been investigated. The present study reveals
the existence of vortex flows located at the supergranular junctions of the
quiet Sun. We use a 1-hour and a 5-hour time series of the granulation in Blue
continuum and G-band images from FG/SOT to derive the photospheric flows. A
feature tracking technique called Balltracking is performed to track the
granules and reveal the underlying flow fields. In both time series we identify
long-lasting vortex flow located at supergranular junctions. The first vortex
flow lasts at least 1 hour and is ~20-arcsec-wide (~15.5 Mm). The second vortex
flow lasts more than 2 hours and is ~27-arcsec-wide (~21 Mm).Comment: 4 pages, 10 figure
Inter-network regions of the Sun at millimetre wavelengths
The continuum intensity at wavelengths around 1 mm provides an excellent way
to probe the solar chromosphere. Future high-resolution millimetre arrays, such
as the Atacama Large Millimeter Array (ALMA), will thus produce valuable input
for the ongoing controversy on the thermal structure and the dynamics of this
layer. Synthetic brightness temperature maps are calculated on basis of
three-dimensional radiation (magneto-)hydrodynamic (MHD) simulations. While the
millimetre continuum at 0.3mm originates mainly from the upper photosphere, the
longer wavelengths considered here map the low and middle chromosphere. The
effective formation height increases generally with wavelength and also from
disk-centre towards the solar limb. The average intensity contribution
functions are usually rather broad and in some cases they are even
double-peaked as there are contributions from hot shock waves and cool
post-shock regions in the model chromosphere. Taking into account the
deviations from ionisation equilibrium for hydrogen gives a less strong
variation of the electron density and with it of the optical depth. The result
is a narrower formation height range. The average brightness temperature
increases with wavelength and towards the limb. The relative contrast depends
on wavelength in the same way as the average intensity but decreases towards
the limb. The dependence of the brightness temperature distribution on
wavelength and disk-position can be explained with the differences in formation
height and the variation of temperature fluctuations with height in the model
atmospheres.Comment: 15 pages, 10 figures, accepted for publication in A&A (15.05.07
PCNA Ubiquitination Is Important, But Not Essential for Translesion DNA Synthesis in Mammalian Cells
Translesion DNA synthesis (TLS) is a DNA damage tolerance mechanism in which specialized low-fidelity DNA polymerases bypass replication-blocking lesions, and it is usually associated with mutagenesis. In Saccharomyces cerevisiae a key event in TLS is the monoubiquitination of PCNA, which enables recruitment of the specialized polymerases to the damaged site through their ubiquitin-binding domain. In mammals, however, there is a debate on the requirement for ubiquitinated PCNA (PCNA-Ub) in TLS. We show that UV-induced Rpa foci, indicative of single-stranded DNA (ssDNA) regions caused by UV, accumulate faster and disappear more slowly in Pcna(K164R/K164R) cells, which are resistant to PCNA ubiquitination, compared to Pcna(+/+) cells, consistent with a TLS defect. Direct analysis of TLS in these cells, using gapped plasmids with site-specific lesions, showed that TLS is strongly reduced across UV lesions and the cisplatin-induced intrastrand GG crosslink. A similar effect was obtained in cells lacking Rad18, the E3 ubiquitin ligase which monoubiquitinates PCNA. Consistently, cells lacking Usp1, the enzyme that de-ubiquitinates PCNA exhibited increased TLS across a UV lesion and the cisplatin adduct. In contrast, cells lacking the Rad5-homologs Shprh and Hltf, which polyubiquitinate PCNA, exhibited normal TLS. Knocking down the expression of the TLS genes Rev3L, PolH, or Rev1 in Pcna(K164R/K164R) mouse embryo fibroblasts caused each an increased sensitivity to UV radiation, indicating the existence of TLS pathways that are independent of PCNA-Ub. Taken together these results indicate that PCNA-Ub is required for maximal TLS. However, TLS polymerases can be recruited to damaged DNA also in the absence of PCNA-Ub, and perform TLS, albeit at a significantly lower efficiency and altered mutagenic specificity
Basic opto-electronics on silicon for sensor applications
A general platform for integrated opto-electronic sensor systems on silicon is proposed. The system is based on a hybridly integrated semiconductor laser, ZnO optical waveguides and monolithic photodiodes and electronic circuiry
Frequent germ-line succinate dehydrogenase subunit D gene mutations in patients with apparently sporadic parasympathetic paraganglioma
PURPOSE: Recently, familial paraganglioma (PGL) was shown to be caused
bymutations in the gene encoding succinate dehydrogenase subunit D (SDHD).
However, the prevalence of SDHD mutations in apparently sporadic PGL is
unknown. We studied the frequency and spectrum of germ-line and somatic
SDHD mutations in patients with parasympathetic PGL. EXPERIMENTAL DESIGH:
We studied 57 unselected patients who developed parasympathetic PGLs (n =
105 tumors) and who were treated between 1987 and 1999 at the Erasmus MC
(Rotterdam, the Netherlands). Thirty-eight (67%) of these patients (n = 51
tumors) lacked a family history of parasympathetic PGL. We used
conformation-dependent gel electrophoresis and sequence determination
analysis of germ-line and tumor DNA to identify SDHD mutations. We
compared the clinical and molecular characteristics of sporadic and
hereditary PGLs. RESULTS: Three different SDHD germ-line mutations were
identified in 32 of the 57 (56%) patients. These included 19 of 19 (100%)
patients with familial PGL and also 13 of 38 (34%) patients with
apparently sporadic PGL. All three mutations were characterized as
missense mutations (D92Y, L95P, and L139P) in highly conserved regions of
the SDHD gene and were not observed in 200 control alleles. No somatic
mutations were found. CONCLUSIONS: Germ-line mutations of the SDHD gene
are present in a significant number of patients with apparently sporadic
parasympathetic PGL. Somatic SDHD mutations do not play a significant role
in the sporadic form of this tumor. Genetic testing for SDHD germ-line
mutations should be considered for every patient presenting with this
tumor, even if a personal or family history of PGL is absent, to allow
appropriate clinical management
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