Die Strahlensterilisation zur Bekämpfung von Pflanzensehädlingen in der Landwirtsehaft

Eines der wichtigstcn Probleme der landwirtschaftlichen Produktion ist der Schutz der Pflanzen vor Schadlingen, Erkrankungen und Unkraut. An der Lösung dieses äußerst wichtigen und gleichzeitig kompliziortcn Problems arbeiten viele Wissenschaftler und Praktiker, und es wurden auf diesem Gebiet bedeutende Erfolge erziclt.

Die Amvendung verschiedener Bekampfungsmethoden (agrotechnischer, biologischer,chemiseherusw.)führt zueiner wesentlichen Verringerung der Verluste, die der Lantlwirtschaft durch Scbädlinge zngefügt werden.

Ungeachtet desscn, daß auf dem Gebiet des Pflanzensehutzes große Fortschritte gemacht wurden, sind die Ernteverluste durch Schädlinge in der Landwirtschaft noch groß. So gehen der Landwirtschaft unseres Landes allein bei 8 Hauptkulturen jährlich Produkte im Wert von einigen Milliarden Rubel verloren. Nach statistischen Angaben der FAO der UNO vernichten Insekten und Nagetiero im Weltmaßstab jährlich eine solche Menge an Getreide, die zur Ernährung von 200 Millionen enschen fiber em Jahr ausreichen würde.

Daraus folgt, daß der Schutz der Pflanzen vor Schädlingen, Krankhcitcn und Unkraut eine der wichtigsten Quellen für die Ertragssteigerung landivirtschaftlicher Kulturen ist.     

Influence of spectral phase on cross-polarized wave generation with short femtosecond pulses

In this paper we present the first comprehensive study of the role of spectral phase on cross-polarized wave (XPW) generation using sub-30 femtosecond (fs) laser pulses. XPW generation improves the temporal contrast and shortens the pulse duration of fs chirped pulse amplification (CPA) lasers. For Ti:Sa lasers, compression below 30?fs is non-trivial and therefore never perfect. We therefore systematically analyze the effect of an arbitrary input spectral phase on the output spectrum and efficiency of the XPW process, both theoretically and experimentally. We derive the maximum acceptable value of residual phase for a given initial pulse duration in order to efficiently drive the XPW process for pulse shortening and contrast improvement.     

Über eine neue Form des Jaminschen Interferenzrefraktometers

Zeitschrift für Physik A Hadrons and nuclei -     

Crystal and molecular structure of tetrapyridyl-copper(II)-bis-nitrato-bis-pyridine

The crystal and molecular structure of a pyridine complex of anhydrous copper(II)nitrate is described. The structure has been solved by vector search methods and refined by least-squares methods to R₁=0.049 [I>2(I)]. The complex lies on a twofold axis parallel toa, and two solvent pyridine molecules lie on twofold axes parallel toc. The copper atom is coordinated by four pyridyl groups and two monodentate NO₃ groups. Crystal data: C₃₀H₃₀N₈O₆Cu, orthorhombic, space group Pnna(52),a=14.446(7),b=12.154(5),c=16.881(4) Å,V=2964(2) ų,Z=4.     

Dynamic and controlled rate thermal analysis of hydrozincite and smithsonite

The understanding of the thermal stability of zinc carbonates and the relative stability of hydrous carbonates including hydrozincite and hydromagnesite is extremely important to the sequestration process for the removal of atmospheric CO₂. The hydration-carbonation or hydration-and-carbonation reaction path in the ZnO-CO₂-H₂O system at ambient temperature and atmospheric CO₂ is of environmental significance from the standpoint of carbon balance and the removal of green house gases from the atmosphere. The dynamic thermal analysis of hydrozincite shows a 22.1% mass loss at 247°C. The controlled rate thermal analysis (CRTA) pattern of hydrozincite shows dehydration at 38°C, some dehydroxylation at 170°C and dehydroxylation and decarbonation in a long isothermal step at 190°C. The CRTA pattern of smithsonite shows a long isothermal decomposition with loss of CO₂ at 226°C. CRTA technology offers better resolution and a more detailed interpretation of the decomposition processes of zinc carbonate minerals via approaching equilibrium conditions of decomposition through the elimination of the slow transfer of heat to the sample as a controlling parameter on the process of decomposition. The CRTA technology offers a mechanism for the study of the thermal decomposition and relative stability of minerals such as hydrozincite and smithsonite.     

Thermogravimetric analysis of wheatleyite Na<Subscript>2</Subscript>Cu<Superscript>2+</Superscript>(C<Subscript>2</Subscript>O<Subscript>4</Subscript>)<Subscript>2</Subscript>·2H<Subscript>2</Subscript>O

Evidence for the existence of primitive life forms such as lichens and fungi can be based upon the formation of oxalates. These oxalates form as a film like deposit on rocks and other host matrices. The anhydrous oxalate mineral moolooite CuC₂O₄ as the natural copper(II) oxalate mineral is a classic example. Another example of a natural oxalate is the mineral wheatleyite Na₂Cu²⁺(C₂O₄)₂·2H₂O. High resolution thermogravimetry coupled to evolved gas mass spectrometry shows decomposition of wheatleyite at 255°C. Two higher temperature mass losses are observed at 324 and 349°C. Higher temperature mass losses are observed at 819, 833 and 857°C. These mass losses as confirmed by mass spectrometry are attributed to the decomposition of tennerite CuO. In comparison the thermal decomposition of moolooite takes place at 260°C. Evolved gas mass spectrometry for moolooite shows the gas lost at this temperature is carbon dioxide. No water evolution was observed, thus indicating the moolooite is the anhydrous copper(II) oxalate as compared to the synthetic compound which is the dihydrate.     

Synthesis, characterization of mono, di and tri alkyl surfactant intercalated Wyoming montmorillonite for the removal of phenol from aqueous systems

Organoclays were synthesized by the ion exchange of cationic surfactants containing single, double and triple alkyl chains for sodium ions in an aqueous suspension of Wyoming Na-montmorillonite. The characterization of organoclays with and without adsorbed phenol was determined by X-ray diffraction, TEM and thermal analysis. Differences in the surfaces and in the interlayer of the mono, di and tri alkyl chain organoclays resulted in differences in the adsorption efficiency for phenol with tri > di > mono > Na-Mt. The results prove that organoclays can be effective for the removal of phenol from an aqueous solution and this removal is a function of the surfactant molecule and its concentration. In general, the higher the concentration as measured by the CEC value and the greater the number of alkyl chains in the surfactant molecule, the greater the percentage of the phenol that is removed.     

Raman spectroscopic study of the molecular structure of the uranyl mineral zippeite from Jáchymov (Joachimsthal), Czech Republic

Raman spectra at 298 and 77K and infrared spectra of the uranyl sulfate mineral zippeite from Jáchymov (Joachimsthal), Czech Republic, K(0.6)(H(3)O)0.4[(UO(2))6(SO(4))3(OH)7].8H2O, were studied. Observed bands were tentatively attributed to the (UO(2))2+ and (SO(4))2- stretching and bending vibrations, the OH stretching vibrations of water molecules, hydroxyls and oxonium ions, and H(2)O, oxonium, and delta U-OH bending vibrations. Empirical relations were used for the calculation of U-O bond lengths in uranyl R (A)=f(nu(3) or nu(1)(UO(2))2+). Calculated U-O bond lengths are in agreement with U-O bond lengths from the single crystal structure analysis and those inferred for uranyl anion sheet topology of uranyl pentagonal dipyramidal coordination polyhedra. The number of observed bands supports the conclusion from single crystal structure analysis that at least two symmetrically distinct U6+ (in uranyls) and S6+ (in sulfates), water molecules and hydroxyls may be present in the crystal structure of the zippeite studied. Strong to very weak hydrogen bonds present in the crystal structure of zippeite studied were inferred from the IR spectra.     

Using thermally activated hydrotalcite for the uptake of phosphate from aqueous media

Hydrotalcites of formula Mg₆A₁₂(OH)₁₆(PO₄)·4H₂O formed by intercalation with the phosphate anion as a function of pH show variation in the d-spacing attributed to the size of the hydrated anion in the interlayer. The value changes from 11.91 Å for pH 9.3, to 7.88 Å at pH 12.5. No crystalline hydrotalcites with phosphate in the interlayer were formed at pH 9.3. Thermal decomposition identifies three steps namely dehydration, dehydroxylation and some loss of carbonate during the thermal treatment. The addition of a thermally activated ZnAl-HT to a phosphate solution resulted in the uptake of the phosphate and the reformation of the hydrotalcite. The technology has the potential for water purification through anion removal.