Two results on exact boundary control of parabolic equations

(1) The known nullcontrollability result for boundary control ofu _t = u_xx + q(x)u is generalized to consider a time-dependent coefficientq. (2) For boundary control ofu _t =Au (where it is known thatC _T : (initial data) (optimal nullcontrol for timeT) exists for allT>0) it is shown that logC _T =145-1 asT 0.     

Semiclassical approach to collision-induced emission in the presence of intense laser radiation: An aspect in the study of cooperative chemical and optical pumping

Collion-induced emission in molecular systems in an intense laser field is studied using the semiclassical approach, with a view towards cooperative chemical and optical pumping in laser production. The formalism is developed with the electronic-field representation, which treats collision and radiative interaction on the same footing. Electronic-field surfaces can be regarded as forming spectra for spontaneous emission; and particular emission events can be accounted for by propagating classical trajectories on emission electronic-field surfaces. Pre-emission loss from the excited state is dealt with by propagating classical trajectories on a loss surface along a complex contour of emission branch points. This loss surface is derived on the basis of localized radiative couplings between electronic-field states and provides a framework to treat the general problem of discrete state-continuum interactions. The formalism is applied to a two-state, collinear exponential model to compute S-matrix elements and transition probabilities between asymptotic states.     

Selective targeting of DNA for cleavage within DNA-histone assemblies by a spermine-[CpW(CO)3Ph]2 conjugate

In contrast to the histone-modifying action of other complexes of the type CpML(n)R, the compound obtained by linking the phenyl rings of two CpW(CO)(3)Ph moieties to the DNA-binding agent spermine selectively cleaves DNA in DNA-histone assemblies.     

Detection of phosphoproteins on electroblot membranes using a small-molecule organic fluorophore

A new formulation of the small-molecule organic fluorophore, Pro-Q Diamond dye, has been developed that permits rapid and simple detection of phosphoproteins directly on polyvinylidene difluoride (PVDF) or nitrocellulose membranes (electroblots). Protein samples are first separated by electrophoresis and then electroblotted to membranes, stained and destained, in an analogous manner as typically performed with Amido Black or Ponceau S dye staining of total protein profiles. After staining, blots are imaged using any of a variety of laser-based gel scanners, xenon-arc lamp-based gel scanners or charge-coupled device (CCD) camera-based imaging devices equipped with UV trans- or epi-illumination. The uncomplicated and reliable staining protocol delivers results in as little as 1 h and the limit of detection for the stain is typically 2-4 ng of phosphoprotein with a linear dynamic range of approximately 15-fold. Compared with traditional radiolabeling and antibody-based approaches, the new method offers significant advantages, including avoidance of radioactivity, no need for expensive antibodies, no requirement for blocking unoccupied sites on the membrane with protein or detergent solutions, no sequence context-specific binding to phosphorylated amino acid residues and the ability to analyze the native, steady-state phosphorylation of proteins obtained directly from tissue specimens or body fluids. Pro-Q Diamond dye binds directly and exclusively to the phosphate moiety, allowing it to detect the broadest spectrum of phosphorylated proteins possible. The stain binds noncovalently to phosphoproteins and is thus fully compatible with matrix-assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS) or Edman sequencing. The blot stain is also compatible with standard colorimetric, fluorogenic, and chemiluminescent detection techniques employed in immunoblotting.     

Potential non-steroidal estrogens and antiestrogens,IV Organic azides in heterocyclic synthesis,part 13: Synthesis of aza- and diazacoumestrols via azido derivatives

Summary 4-Chloro-3-aryl-coumarins and quinolones2 a–e undergo thermolytic ring closure by reaction with sodium azide in refluxing dimethyl formamide to yield indolo[3,2-c]coumarins and indolo[3,2-c]quinolin-6(5H)-ones6 a–e. In the case of the coumarin2 a the azido coumarin5 can be isolated. The mono- and diazacoumestrol-dimethylethers6 a–c are converted into the coumestrol analogues7 a–c and their diacetyl derivatives8 a–c.

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Potentielle nichtsteroidale Östrogene und Antiöstrogene, 4. Mitt.: Organische Azide in der Heterocyclensynthese, Teil 13: Synthese von Aza- und Diazacumöstrolen über Azidzwischenstufen

Zusammenfassung 4-Chlor-3-arylcumarine und-chinolone2 a–e reagieren thermolytisch mit Natriumazid in siedendem Dimethylfomamid unter Ringschluß zu Indolo[3,2-c]cumarinen und Indolo[3,2-c]chinolin-6(5H)-onen6 a–e. Nur aus dem Cumarinderivat2 a kann das zwischenzeitlich gebildete Azidocumarin5 isoliert werden. Die so erhaltenen Mono- und Diazacumöstroldimethylether6 a–c werden in die entsprechenden Cumöstrole7 a–c und ihre Diacetylderivate8 a–c umgewandelt.

     

Studies of the Reaction Behavior of Nitryl Compounds Towards Azides: Evidence for Tetranitrogen Dioxide,N4O2

The reaction behavior of NaN₃, AgN₃, and Me₃SiN₃ towards FNO₂, CINO₂, NO₂SbF₆, and NO₂BF₄ was investigated. At -30°C or below in a solvent-free system sodium azide did not react with CINO₂, NO₂BF₄, or NO₂SbF₆. Below -30°C silver azide did not react either with neat C1NO₂. Treatment of Me₃SiN₃ with pure C1NO₂ led to the formation of C1N₃, N₂O, and Me₃SiOSiMe₃. A mechanism for this reaction has been proposed. Pure chlorine azide was isolated by fractional condensation and identified by its low-temperature Raman spectrum (liquid state). The reaction of Cp₂Ti(N₃)₂ with C1NO₂ also yielded C1N₃ as the only azide-containing reaction product. Treatment of FNO₂ with NaN₃ at temperatures as low as -78°C always ended in an explosion which was probably due to the formation of FN₃ as one of the reaction products. The reaction of NO₂SbF₆ with NaN₃ in liquid CO₂ (-55°C· T· -35°C) as the solvent afforded a new azide species which was stable at low temperature in solution only and was investigated by means of low-temperature Raman spectroscopy. The obtained vibrational data give strong evidence for the presence of tetranitrogen dioxide, N₄O₂, which can be regarded as nitryl azide (NO₂N₃). The structure and vibrational frequencies of N₄O₂ were computed ab initio at correlated level (MP2/6-31 + G^*). In liquid xenon (-100°C· T· -60°C) NaN₃ did not react with NO₂SbF₆. A previous literature report on the preparation of N₄O₂ could not be established.     

Supramolecular framework adducts constructed of hexamethylenetetramine,aquated alkali metal cationic clusters,and hexacyanoferrates(II/III)

The reaction of alkali metal hexacyanoferrate(II/III) with (CH₂)₆N₄ (hexamethylenetetramine, abbreviated HMT) in an acidic medium yielded crystalline compounds of stoichiometries HK₂[Fe¹¹¹(CN)₆]·2HMT·4H₂O, H₂K₂[Fe¹¹(CN)₆]·2HMT·4H₂O, and HNa₂[Fe¹¹¹(CN)₆]· 2HMT·5H₂O. Their crystal structures are based on a packing of three molecular components: neutral and/orprotonated HMT, hexacyanoferrate, and an alkali metal ion-water cluster. The resulting three-dimensional supramolecular framework is constructed from the coordination of the alkali metal ion by aqua ligands as well as [Fe(CN)₆]{n–} and HMT units, and further stabilization is achieved by hydrogen bonding between water molecules and the noncoordinated nitrogen atoms of HMT and hexacyanoferrate.     

Matrix-dependent instability of selenium(IV) stored in teflon containers

Solutions of selenium(IV) standards with different acid matrices were stored in containers constructed of boosilicate glass, conventional polyethylene, and fluorinated ethylenepropylene (teflon FEP). After 50 days of storage in FEP, there were highly significant losses of Se(IV) from standards in either 5% HCl/5% H₂SO₄, or 5% H₂SO₄. Increasing the hydrochloric acid concentration, e.g., 15% HCl/5% H₂SO₄, greatly reduced this loss. Addition of selenium-75 (selenate-free) indicated that the losses did not result from physical adsorption onto container surfaces. It is shown that the losses were caused by oxidation of Se(IV) to Se(VI).     

A new palladium catalyst system for the cyanation of aryl chlorides with K4[Fe(CN)6]

The development of a novel Pd-catalyzed synthesis of (hetero)aromatic nitriles from the corresponding aryl chlorides and potassium hexacyanoferrate(II) is described. This novel protocol avoids the use of highly toxic alkali cyanides and proceeds in the presence of small amounts of palladium catalysts. High yields and selectivities of the corresponding aryl nitriles were achieved applying di(1-adamantyl)-1-butylphosphine (cataCXium^® A) as the ligand.     

A simple cobalt catalyst system for the efficient and regioselective cyclotrimerisation of alkynes

The intermolecular cyclotrimerisation of terminal and internal alkynes can be catalysed by simple cobalt complexes such as a CoBr2(diimine) under mild reaction conditions when treated with zinc and zinc iodide with high regioselectivity in excellent yields.