953 research outputs found
Surface recombination velocity measurements on surfaces of n-type germanium subjected to various gas cycles
Analysis of Amorphous Layers on Silicon by Backscattering and Channelling Effect Measurements
Gene up-regulation by DNA demethylation in 35S-gshI-transgenic poplars (Populus x canescens)
Gene expression levels of transgene 35S-gshI (γ-glutamylcysteine synthetase) cloned
from E. coli, and the endogenous gene gsh1 of poplar (Populus x canescens) were upregulated
by the DNA demethylating agent DHAC (5,6-dihydro-5'-azacytidine
hydrochloride) (10-4 M for 7 days) in aseptic leaf discs cultures. Two 35S-gshI-transgenic
(6lgl and 11ggs) and wild type (WT) poplar clones were used. The efficiency of gene
upregulation was also analyzed under herbicide paraquat stress (4 x 10-7 M). Levels of
gshI-mRNA and gsh1-mRNA were determined by RT-qPCR (reverse transcriptase
quantitative PCR) after cDNA synthesis. For internal control, the constitutively expressed
housekeeping poplar genes α-tubulin and actin were used, and the 2−HHCt method was
applied for data analysis. In long term DHAC treatment (21 days), a morphogenetic
response of de novo root development was observed on leaf discs in a wide concentration
range of DHAC (10-8 to 10-6 M). Adventitious shoots (11ggs clone) also emerged from
leaf discs after a combined treatment with DHAC (10-4 M) and paraquat (10-7 M). Shoots
were dissected, rooted and transplanted in glass houses for further analyses for
phytoremediation capacity. Since DNA methylation patterns are inherited (epigenetic
memory), these poplar plants with increased gene expression levels of both transgene
35S-gshI and endogenous gene gsh1 provide novel plant sources for in situ application
Surface disorder production during plasma immersion implantation and high energy ion implantation
High-depth-resolution Rutherford Backscattering Spectrometry (RBS) combined with channeling technique was used to analyze the surface layer formed during plasma immersion ion implantation (PIII) of single crystal silicon substrates. Single wavelength multiple angle of incidence ellipsometry (MAIE) was applied to estimate the thickness of the surface layer. The thickness of the disordered layer is much higher than the projected range of P ions and it is comparable with that of protons.\ud
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Another example of surface damage investigation is the analysis of anomalous surface disorder created by 900 keV and 1.4 MeV Xe implantation in 100 silicon. For the 900 keV implants the surface damage was also characterized with spectroellipsometry (SE). Evaluation of ellipsometric data yields thickness values for surface damage that are in reasonable agreement with those obtained by RBS
Non-destructive characterization of nitrogen-implanted silicon-on-insulator structures by spectroscopic ellipsometry
Silicon-on-insulator (SOI) structures implanted with 200 or 400 keV N+ ions at a dose of 7.5 × 1017cm−2 were studied by spectroscopic ellipsometry (SE). The SE measurements were carried out in the 300–700 nm wavelength (4.13-1.78 eV photon energy) range. The SE data were analysed by the conventional method of using appropriate optical models and linear regression analysis. We applied a seven-layer model (a surface oxide layer, a thick silicon layer, upper two interface layers, a thick nitride layer and lower two interface layers) with good results. The fitted parameters were the layer thickness and compositions. The results were compared with data obtained from Rutherford backscattering spectroscopy (RBS) and transmission electron microscopy. The sensitivity of our optical model and fitting technique was good enough to distinguish between the silicon-rich transition layers near the upper and lower interfaces of the nitride layer, which are unresolvable in RBS measurements
Ion-implantation-caused special damage profiles determined by spectroscopic ellipsometry in crystalline and in relaxed (annealed) amorphous silicon
We previously developed a fitting method of several parameters to evaluate ion-implantation-caused damage profiles from spectroscopic ellipsometry (SE) (M. Fried et al., J. Appl. Phys., 71 (1992) 2835). Our optical model consists of a stack of layers with fixed and equal thicknesses and damage levels described by a depth profile function (coupled half Gaussians). The complex refractive index of each layer is calculated from the actual damage level by Bruggeman effective medium approximation (EMA) using crystalline (c-Si) and amorphous (a-Si) silicon as end-points. Two examples are presented of the use of this method with modified optical models. First, we investigated the surface damage formed by room temperature B+ and N+ implantation into silicon. For the analysis of the SE data we added a near surface amorphous layer to the model with variable thickness. Second, we determined 20 keV B+ implantation-caused damage profiles in relaxed (annealed) amorphous silicon. In this special case, the complex refractive index of each layer was calculated from the actual damage level by the EMA using relaxed a-Si and implanted a-Si as end-points. The calculated profiles are compared with Monte Carlo simulations (TRIM code); good agreement is obtained
Comparative investigation of damage induced by diatomic and monoatomic ion implantation in silicon
The damaging effect of mono- and diatomic phosphorus and arsenic ions implanted into silicon was investigated by spectroscopic ellipsometry (SE) and high-depth-resolution Rutherford backscattering and channeling techniques. A comparison was made between the two methods to check the capability of ellipsometry to examine the damage formed by room temperature implantation into silicon. For the analysis of the spectroscopic ellipsometry data we used the conventional method of assuming appropriate optical models and fitting the model parameters (layer thicknesses and volume fractions of the amorphous silicon component in the layers) by linear regression. The depth dependence of the damage was determined by both methods. It was revealed that SE can be used to investigate the radiation damage of semiconductors together with appropriate optical model construction which can be supported or independently checked by the channeling method. However, in case of low level damage (consisting mainly of isolated point defects) ellipsometry can give false results, overestimating the damage using inappropriate dielectric functions. In that case checking by other methods like channeling is desirable
Feketenyár (Populus nigra) gametoklónok mikroszatellita változatossága; (TTCTGG)5 deléció a WPMS-20 lokuszon.
A nyárfajok (Populus ssp) extrém kis méretű genomja
(2n=4×=38; 5.5×108 bp; 2C=1.1 pg) nagyfokú genetikai
stabilitással párosul. Munkánk célja a feketenyár (Populus nigra)
genetikai variabilitásának növelése volt haploid (n) indukció
alkalmazásával, portoktenyészetben, két portok-donor klón (N-SL
és N-309) alkalmazásával. A felnevelt haploid utódok (1-35)
genetikai polimorfizmus elemzését öt SSR lokusz allél
diverzitásával jellemeztük. Összesen 20 SSR allél 280
szekvenciáját azonosÃtottuk, egy-egy lókuszon 1-6
allélgyakorisággal: WPMS-02 (5 allél), WPMS-04 (6 allél),
WPMS-06 (2 allél), WPMS-20 (6 allél) és PTR-04 (1 allél). Az
elemzést ALF (automatic laser fluorometer) módszerrel végeztük.
A WPMS-20 allél szekvencia elemzésével egy 5-szörös (TTCTGG)
deléciót mutattunk ki a (TTCTGG)8 lokuszon. Az SSR allélek léte,
illetve nemléte alapján dendrogramot készÃtettünk, amely alapján
elemeztük és meghatároztuk az új nemesÃtésű klónok genetikai
diverzitását. Az új SSR-klóntÃpusok jelentÅ‘s nemesÃtési
alapanyagot szolgáltatnak a nyárfanemesÃtés számára
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