Existence and Nonlinear Stability of Stationary States of the Schrödinger–Poisson System

We consider the Schrödinger–Poisson system in the repulsive (plasma physics) Coulomb case. Given a stationary state from a certain class we prove its nonlinear stability, using an appropriately defined energy-Casimir functional as Lyapunov function. To obtain such states we start with a given Casimir functional and construct a new functional which is in some sense dual to the corresponding energy-Casimir functional. This dual functional has a unique maximizer which is a stationary state of the Schrödinger–Poisson system and lies in the stability class. The stationary states are parameterized by the equation of state, giving the occupation probabilities of the quantum states as a strictly decreasing function of their energy levels.     

Reexamination of the thermolytic rearrangement of 4-halophenyl azides to 2-aminophenols and other products

Summary The halogenation of derivatives of 2-aminophenol with N-chloro- and N-bromosuccinimides at ambient temperatures in acetic acid was studied. With the necessary compounds available, a reexamination of the thermolytic rearrangement of 2-halophenyl azides to 2-aminophenols and other products was undertaken. It is certain that the rearrangement of 4-halophenyl azides to 2-aminophenols occurs but the products identified in this study differ significantly from those reported previously by Suschitzky et al. (1963, 1966).

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Neuuntersuchung der thermolytischen Umlagerung von 4-Halogenphenylaziden zu 2-Aminophenolen und anderen Produkten

Zusammenfassung Es wurde die Halogenierung von 2-Aminophenol-Derivaten mit N-Chlor- und N-Bromsuccinimid bei Raumtemperatur in Essigsäure untersucht. Mit den zur Verfügung stehenden Verbindungen konnte eine Neuuntersuchung der thermolytischen Umlagerung von 4-Halogenphenylaziden zu 2-Aminophenolen und anderen Produkten unternommen werden. Diese Umlagerung findet sicherlich statt, allerdings differieren die dabei beobachteten Produkte signifikant von denen, die Suschitzky et al. 1963 und 1966 beschrieben.

     

Lithium and potassium isotope separation using radiofrequency spectroscopy

Separation of lithium and potassium isotopes has been achieved using the isotopic differences in the radiofrequency spectrum. The isotope separation was studied in a supersonic molecular beam magnetic resonance spectrometer, and enrichment factors up to 30 obtained.     

Supersonic jet spectroscopy of naphthalene–fluorene bichromophoric cluster

We have investigated the supersonic jet spectroscopy and photophysics of 1-methylnaphthalene–fluorene (1MN–FL) cluster, and looked for indications of intramolecular electronic energy transfer (Intra-EET) from the FL (donor, D) to 1MN (acceptor, A). The clusters were identified by their time of flight (TOF) mass spectra. We observed clusters bands in the LIF spectrum near the region of 1MN origin. We have also observed cluster TOF–resonance enhanced multi-photon ionization (REMPI) spectrum near the electronic origin of the fluorene moiety. However, this spectrum was almost independent of the excitation wavelength, and was not observed in the LIF spectrum. This is probably due to fast Intra-EET resulting in lifetime broadening of the donor chromophore cluster spectrum, similar to that observed previously for the naphthalene–anthracene bichromophoric system.     

Improved syntheses of some monochloro- and monobromo-8-quinolinols

Summary Procedures were developed for the preparation of the 2-, 3-, 4-, and 6-monosubstituted chloro and bromo 8-quinolinols which afforded greater yields and/or reduced the number of steps in the preparation. 100 MHz¹H-NMR spectra for the 12 possible monochloro and monobromo analogues are given.

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Verbesserte Synthese von Monochlor- und Monobrom-8-chinolinolen

Zusammenfassung Es wurden Verfahren entwickelt, um 2-, 3-, 4- und 6-Chlor bzw. -Brom-8-chinolinole in besseren Ausbeuten und/oder bei reduzierter Anzahl von Synthesestufen herzustellen. Die¹H-NMR-Spektren der 12 möglichen Monochlor- und Monobromverbindungen werden angegeben.

     

The mechanism of proton transfer between adjacent sites exposed to water

The surface of a protein, or a membrane, is spotted with a multitude of proton-binding sites, some of which are only a few angstroms apart. When a proton is released from one site, it propagates through the water by a random walk under the bias of the local electrostatic potential determined by the distribution of the charges on the protein. Some of the released protons disperse into the bulk, but during the first few nanoseconds, the released protons can be trapped by encounter with nearby acceptor sites. This process resembles a scenario which corresponds with the time-dependent Debye-Smoluchowski equation. In the present study, we investigated the mechanism of proton transfer between sites that are only a few angstroms apart, using as a model the proton exchange between sites on a small molecule, fluorescein, having two, spectrally distinguishable, proton-binding sites. The first site is the oxyanion on the chromophore ring structure. The second site is the carboxylate moiety on the benzene ring of the molecule. Through our experiments, we were able to reconstruct the state of protonation at each site and the velocity of proton transfer between them. The fluorescein was protonated by a few nanosecond long proton pulse under specific conditions that ensured that the dye molecules would be protonated only by a single proton. The dynamics of the protonation of the chromophore were measured under varying initial conditions (temperature, ionic strength, and different solvents (H(2)O or D(2)O)), and the velocity of the proton transfer between the two sites was extracted from the overall global analysis of the signals. The dynamics of the proton transfer between the two proton-binding sites of the fluorescein indicated that the efficiency of the site-to-site proton transfer is very sensitive to the presence of the screening electrolyte and has a very high kinetic isotope effect (KIE = 55). These two parameters clearly distinguish the mechanism from proton diffusion in bulk water. The activation energy of the reaction (E(a) = 11 kcal mol(-1)) is also significantly higher than the activation energy for proton dissociation in bulk water (E(a) approximately 2.5 kcal mol(-1)). These observations are discussed with respect to the effect of the solute on the water molecules located within the solvation layer.     

Preparation and fungitoxicity of 3,6-dichloro-and 3,6-dibromo-8-quinolinols

Summary 3,6-Dichloro- and 3,6-dibromo-8-quinolinols were prepared by direct halogenation of 8-nitroquinoline by N-halosuccinimide in acetic acid or by halogenation of the corresponding 6-halo-8-nitroquinoline prepared via aSkraup reaction. The nitro group was reduced to amino and the amine was hydrolyzed to the phenol in 70% sulfuric acid at 220°C. The fungitoxicity of 3,6-dichloro- and 3,6-dibromo-8-quinolinols, as well as intermediates in their preparation, againstAspergillus niger, Aspergillus oryzae, Myrothecium verrucaria, Trichoderma viride, andMucor cirinelloides was determined. 3,6-dichloro-8-quinolinol is the most fungitoxic analogue of this class of compounds observed to date.

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Herstellung und Fungitoxizität von 3,6-Dichlor- und 3,6-Dibrom-8-chinolinen

Zusammenfassung 3,6-Dichlor- und 3,6-Dibrom-8-chinoline wurden durch direkte Halogenierung von 8-Nitrochinolin mit N-Halogensuccinimid in Essigsäure oder durch Halogenierung der entsprechenden nachSkraup synthetisierten 6-Halogen-8-nitrochinoline hergestellt. Die Nitrogruppe wurde zum Amin reduziert und die Aminofunktion in 70% iger Schwefelsäure bei 220°C zum Phenol hydrolysiert. Die Fungitoxizität der 3,6-Dichlor- und 3,6-Dibrom-8-chinoline und jene der bei ihrer Herstellung auftretenden Zwischenstufen gegenAspergillus niger, Aspergillus oryzae, Myrothecium verrucaria, Trichoderma viride undMucor cirinelloides wurde bestimmt. 3,6-Dichlor-8-chinolin ist der derzeit stärkste bekannte fungitoxische Vertreter dieser Substanzklasse.

     

Evidence of steric factors in the fungitoxic mechanisms of 8-quinolinol and its 2-, 3-, 4-, 5-, 6-and 7-chloro and bromo analogues

Summary A study was made of the fungitoxicity of 2-, 3-, 4-, 5-, 6- and 7-chloro and bromo-8-quinolinols againstAspergillus niger,A. oryzae,Myrothecium verrucaria,Trichoderma viride andTrichophyton mentagrophytes in Sabouraud dextrose broth and in Yeast Nitrogen Base supplemented with 1%D-glucose and 0.088%L-asparagine. Based on the presence or absence of synergism between pairs of substituted 8-quinolinols and reversal or nonreversal of toxicity byL-cysteine or N-acetyl-L-cysteine, the following conclusions were reached: (1) substituents on the quinoline ring change the site(s) of action of the toxicant; (2) the sites of action of the 5-, 6-, and 7-chloro-8-quinolinols are different from each other and from 8-quinolinol and its 2-, 3-, and 4-chloro analogues, and the same is true for the corresponding bromo compounds; (3) 8-quinolinol and its 3- and 4-chloro and bromo analogues appear to share common sites of action; (4) for good antifungal activity the 2 position of the ring must not be substituted by sterically bulky groups; (5) the geometry of the binding sites of action are not so constrained that they cannot accommodate the analogously substituted chloro- and bromo-8-quinolinols.

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Nachweis sterischer Faktoren bei der Fungitoxizität von 8-Chinolinol und seinen 2-, 3-, 4-, 5-, 6- und 7-Chlor- und -Brom-Analogen

Zusammenfassung Es wurde eine Studie der Fungitoxizität von 2-, 3-, 4-, 5-, 6- und 7-Chlor- und-Brom-8-chinolinol gegenüberAspergillus niger,A. oryzae,Myrothecium verrucaria,Trichoderma viride undTrichphyton mentagrophytes in Sabouraud Dextrose Nährmedium und in Hefe-N-Base mit 1%D-Glucose und 0.088%L-Asparagin unternommen. Auf der Basis des Zutreffens oder der Abwesenheit eines Synergismus zwischen Paaren von substituierten 8-Chinolinolen und der Umkehrung oder Nichtumkehrung der Toxizität durchL-Cystein oder N-Acetyl-L-cystein wurden folgende Schlußfolgerungen abgeleitet: (1) Substituenten am Chinolin-Ring ändern die Aktionsstelle(n) des Toxikans; (2) Die Angriffsstellen der 5-, 6- und 7-Chlor-8-chinolinole sind untereinander und von 8-Chinolinol und seinen 2-, 3- und 4-Chlor-Analogen verschieden, wobei das auch für die entsprechenden Brom-Verbindungen gilt; (3) 8-Chinolinol und seine 3- und 4-Chlor- und -Brom-Analogen scheinen gemeinsame Aktionsstellen zu teilen; (4) für eine gute antifungale Aktivität darf die 2-Position des Rings nicht mit sterisch anspruchsvollen Gruppen besetzt sein; (5) Die Geometrie des Bindungsstellen der Wirkung ist nicht so gespannt, daß nicht sowohl analoge Chlor- oder Brom-8-chinolinole Platz finden.

     

Inverse deuterium isotope effect on radiationless electronic transitions

Fluorescence quantum yields, Y, front photoselected vibrational states in the S₁ manifold of anthracene and of perdeuterated anthracene in planar supersonic jets reveal a large inverse deuterium isotope effect on the non-radiative relaxation from the S₁ origin (Y_H/Y_D = 5), while for high (1500 cm⁻¹) excess energies above the S₁ origin the inverse isotope effect is eroded (Y_H/Y_D ≈ 1). Novel information emerges on intermediating states involved in intersystem crossing.     

Extending the range of compounds amenable for gas chromatography-mass spectrometric analysis

Gas chromatography-mass spectrometry (GC-MS) suffers from a major limitation in that an expanding number of thermally labile or low volatility compounds of interest are not amenable for analysis. We found that the elution temperatures of compounds from GC can be significantly lowered by reducing the column length, increasing the carrier gas flow rate, reducing the capillary column film thickness and lowering the temperature programming rate. Pyrene is eluted at 287 degrees C in standard GC-MS with a 30 m x 0.25 mm I.D. column with 1-microm DB5ms film and 1-ml/min He column flow rate. In contrast, pyrene is eluted at 79 degrees C in our "Supersonic GC-MS" system using a 1 m x 0.25 mm I.D. column with 0.1-microm DB5ms film and 100-ml/min He column flow rate. A simple model has been invoked to explain the significantly (up to 208 degrees C) lower elution temperatures observed. According to this model, every halving of the temperature programming rate, or number of separation plates (either through increased flow rate or due to reduced column length), results in approximately 20 degrees C lower elution temperature. These considerably lower elution temperatures enable the analysis of an extended range of thermally labile and low volatility compounds, that otherwise could not be analyzed by standard GC-MS. We demonstrate the analysis of large polycyclic aromatic hydrocarbons (PAHs) such as decacyclene with ten fused rings, well above the current GC limit of PAHs with six rings. Even a metalloporphirin such as magnesiumoctaethylporphin was easily analyzed with elution temperatures below 300 degrees C. Furthermore, a range of thermally labile compounds were analyzed including carbamates such as methomyl, aldicarb, aldicarbsulfone and oxamyl, explosives such as pentaerythritol tetranitrate, Tetryl and HMX, and drugs such as reserpine (608 a.m.u.). Supersonic GC-MS was used, based on the coupling of a supersonic molecular beam (SMB) inlet and ion sources with a bench-top Agilent 6890 GC plus 5972 MSD. The Supersonic GC-MS provides enhanced molecular ion without any ion source related peak tailing. Thus, the lower GC separation power involved in the analysis of thermally labile and low volatility compounds is compensated by increased separation power of the MS gained from the enhanced molecular ion. Several implications of these findings are discussed, including our conclusion that slower chromatography leads to better analysis of thermally labile compounds.