22 research outputs found
Effect of flame weed control on various weed species at various developmental stages
ArticlePhysical methods of weed control as
solarization, mulching, use of electricity, steam
and flame are now an alternative in the organically grown crop. Flame weeder already has a wide
range of practical use
,
particularly in the cultivation of vegetables in alternative form without any
chemical
treatment. Compared to chemical spraying, the use of flame weeder is more expensive,
but we can compensate the costs by the added value of bioproducts. The issue of costs affects the
wider use of the method in practice, but it may be offset by increased e
fficiency of weed control.
The correct parameters of flame weeder, such as burner angle, burner height, the gas pressure,
speed of weeder as well as the growth stage of the weed, weed species, climate conditions etc.,
can increase the effectiveness of weed
control. Field and laboratory tests carried out in Canada
and Slovakia were aimed at verifying the influence of parameters on the effectiveness of flame
weed control
The Development of Transport in the Czech Republic
Before 1989, transport in the former Czechoslovakia met its tasks based on the controlling principles of
planned economy, focused eastwards and oriented on cooperation between the Eastern Bloc countries
within COMECOM. Due to the preference for raw material extraction and heavy industry, the transport
sector dealt mainly with transporting commodities of these branches with high demands in volume. The
planned economic principles were also reflected by the consistent division of transport work with a
preference for stack substrate transport by rail.
The change of the political and economic circumstances in November 1989 influenced the life and
needs of society substantially. A market economy has come, focused on the market of developed
European countries and having an impact on the transport sector as such, individual transport systems,
transport preferences and transported commodities [2].
As at 1 January 1993, Czechoslovakia has been divided into two independent countries, i.e. the Czech
Republic and Slovakia. Therefore the following data from the Transport Statistics of the Czech Republic
[1] are comparable starting from 1994. The authors of the article had data available until 2006
Quark Condensate in the Deuteron
We study the changes produced by the deuteron on the QCD quark condensate by
means the Feynman-Hellmann theorem and find that the pion mass dependence of
the pion-nucleon coupling could play an important role. We also discuss the
relation between the many body effect of the condensate and the meson exchange
currents, as seen by photons and pions. For pion probes, the many-body term in
the physical amplitude differs significantly from that of soft pions, the one
linked to the condensate. Thus no information about the many-body term of the
condensate can be extracted from the pion-deuteron scattering length. On the
other hand, in the Compton amplitude, the relationship with the condensate is a
more direct one.Comment: to appear in Physics Review C (19 pages, 3 figures
Towards an understanding of isospin violation in pion-nucleon scattering
We investigate isospin breaking in low-energy pion-nucleon scattering in the
framework of chiral perturbation theory. This work extends the systematic
analysis of [1] to the energy range above threshold. Various relations, which
identically vanish in the limit of isospin symmetry, are used to quantify
isospin breaking effects. We study the energy dependence of the S- and P-wave
projections of these ratios and find dramatic effects in the S-waves of those
two relations which are given in terms of isoscalar quantities only. This
effect drops rather quickly with growing center-of-mass energy.Comment: 12 pp, REVTeX, 8 figs, FZJ-IKP(TH)-2000-2
Preventive Effects of Flavonoids on Alloxan-Induced Diabetes Mellitus in Rats
The aim of the present study was the evaluation of possible protective effects of quercetin and chrysin in experimental alloxan-induced diabetes in rats. Alloxan was injected at a single dose of 60 mg/kg (into the tail vein) for diabetes induction. Quercetin (50 and 100 mg/kg; orally) and chrysin (50 and 100 mg/kg; orally) were administered daily for 3 days prior and 7 days after alloxan injection. Alloxan induced a significant increase of glycaemia (p p p p < 0.01). On the other hand, glycosuria was increased in all groups of animals receiving alloxan. We suggest that the protective effect of the used flavonoids in experimental diabetes mellitus may be related to their antioxidative/chelatory properties. Increased glycosuria indicated that inhibition of renal glucose reabsorption may also play a role in the hypoglycaemic effect of both flavonoids
Mechanochemical Synthesis and Characterization of II-VI Nanocrystals: Challenge for Cytotoxicity Issues
CdSe@ZnS nanocrystals have been prepared by a two-step solid state mechanochemical synthesis. CdSe prepared from elements in the first step is mixed with ZnS synthesized from zinc acetate and sodium sulfide in the second step. The crystallite size of the new type CdSe@ZnS nanocrystals determined by X-ray diffraction Rietveld refined method was 35 nm and 10 nm for CdSe and ZnS, respectively. Energy dispersive/transmission electron microscopy/energy dispersive spectroscopy methods show good crystallinity of the nanoparticles and scanning electron microscopy elemental mapping illustrate consistent distribution of Cd, Se, Zn and S elements in the bulk of samples. UV-VIS spectra show an onset at 320 nm with calculated bandgap 3.85 eV. This absorption arises from the vibration modes of Zn-S bonds. The nanocrystals show the blue shift from the bandgap of bulk ZnS (3.66 eV). The synthesized CdSe@ZnS nanocrystals have been tested for dissolution, cytotoxicity and L-cysteine conjugation. The dissolution of Cd was less than 0.05 μg (in comparison with 0.8 μg which was evidenced for CdSe alone). The very low cytotoxic activity for selected cancer cell lines has been evidenced. CdSe@ZnS nanocrystals coated with L-cysteine are water-soluble and have a great potential in biomedical engineering as fluorescent labels