5-Aminolaevulinic acid (ALA) induced formation of different fluorescent porphyrins: a study of the biosynthesis of porphyrins by bacteria of the human digestive tract

Aminolaevulinic acid (ALA) induces porphyrin formation in almost all living cells. The fluorescence spectra of porphyrins produced from a variety of 31 bacterial strains from the human oral cavity and other parts of digestive tract have been examined. Many of the bacteria exposed to ALA were able to induce protoporphyrin IX (PpIX) fluorescence, but under aerobic condition some bacteria can also produced different fluorescent porphyrins, in particular water-soluble porphyrins that can arise from an oxidation of the corresponding porphyrinogen precursors. The formation of fluorescent porphyrins can be different from one bacterial strain to another, but also one specific bacterium can form different fluorescent porphyrins. Irradiation of the ALA incubated cultures led to a rapid formation of water-soluble porphyrins exhibiting fluorescence maxima at wavelengths of 618-620 nm. This light induced formation of water-soluble porphyrins could be attributed to a photooxidation of the non-fluorescent (Uro/Copro)-porphyrinogen precursors. Addition of detergents to some of the bacterial cultures led to a strong PpIX fluorescence increase, indicating that some of the PpIX originally produced can be present in a non-fluorescent, probably aggregated, form. The large abundance of bacteria in the oral cavity and other parts of digestive tract, with their capacity to easily produce fluorescent porphyrins, indicates that such bacterial fluorescence should be suppressed during the ALA-based diagnosis of tumours in order to eliminate false positive results.     

Self-entrainment of air on stepped spillways

The pseudo-bottom-inception point related to air entrainment is located further upstream on stepped spillways than on smooth spillways, for otherwise identical conditions. Its position is relevant concerning cavitation aspects, flow losses and flow depths. This Paper presents and discusses visual observations made with a high-speed camera and air concentration measurements in the vicinity of the pseudo-bottom air inception point on a stepped model spillway. Insight into the bottom aeration processes is provided, pointing at the effects of dynamic and turbulent air-phase surface troughs instantaneously protruding to the pseudo-bottom. In addition, the measured data were analyzed with regard to the extensions of these surface troughs. The trough bases were found to reach approximately 70–80% of the mixture flow depth upstream of the inception point, to 60–70% at the inception point and to 40–50% at the equilibrium flow region downstream of the inception point. The highly-turbulent character of developed flow is described and the general air transport process specified on the basis of air concentrations and related parameters.     

Low-temperature light detectors: Neganov–Luke amplification and calibration

The simultaneous measurement of phonons and scintillation light induced by incident particles in a scintillating crystal such as CaWO₄ is a powerful technique for the active rejection of background induced by γ?s and β  ?s and even neutrons in direct Dark Matter searches. However, ?1%$?1\text{\%}$ of the energy deposited in a CaWO₄ crystal is detected as light. Thus, very sensitive light detectors are needed for an efficient event-by-event background discrimination. Due to the Neganov–Luke effect, the threshold of low-temperature light detectors based on semiconducting substrates can be improved significantly by drifting the photon-induced electron–hole pairs in an applied electric field. We present measurements with low-temperature light detectors based on this amplification mechanism. The Neganov–Luke effect makes it possible to improve the signal-to-noise ratio of our light detectors by a factor of ∼9 corresponding to an energy threshold of ∼21 eV$\sim 21\text{eV}$. We also describe a method for an absolute energy calibration using a light-emitting diode.     

Local canted spin behaviour in Co1.4−x Zn x Ge0.4Fe1.2O4 spinels: A macroscopic, mesoscopic and microscopic study

DC magnetization, neutron depolarization and neutron diffraction (with both polarized and unpolarized neutrons) measurements have been reported for the Co_1.1−x Zn _x Ge_0.1Fe_1.2O₁ spinels with x=0.5, 0.6 and 0.7. Neutron depolarization and neutron diffraction measurements confirm the presence of a long range ferrimagnetic ordering of the local canted spins in these ferrite samples. The observed features of low field magnetization have been explained under the framework of thermally activated domain wall movement of ferrimagnetic arrangement of local canted spins. An important role of magnetic anisotropy (due to the presence of Co²⁺ ions) in establishing the magnetic ordering and domain kinetics in these ferrites has been observed.     

The nature of the predominant acceptors in high quality zinc telluride

We report very sharp bound exciton luminescence spectra in high quality melt-grown very lightly compensated ZnTe, p-type with N_A-N_D in the low 10⁺¹⁵ cm^-3. Bound exciton localisation energies at seven shallow neutral acceptors with E_A between ~55 and ~150 meV are very insensitive to E_A. Optical absorption and dye laser luminescence excitation spectroscopy were necessary to obtain a full separation of the transitions due to different acceptors, together with a study of certain ‘two-hole’ luminescence satellites in which the acceptor is left in a series of orbital states after bound exciton decay. Two shallow acceptors are P_Te and As_Te, a third possibly Li_Zn while a fourth, relatively prominent in our best undoped crystals, may be a complex. A deeper, 150 meV acceptor, frequently reported in the ZnTe literature and electrically dominant in most of our undoped crystals has the Zeeman character of a point defect. We present clear evidence from our spectra that this energy does not represent the binding of a single hole at a doubly ionized cation vacancy, a popular attribution since 1963. This acceptor may be covered by another impurity, possibly Cu_Zn. We also report bound phonon effects, lifetime broadening of excited bound exciton states and observe a single unidentified donor with E_D ~18.5 meV. This energy is determined using selective dye laser excitation at the weak neutral donor bound exciton line and from the onset of valence band to ionized donor photo-absorption.     

Phase transitions in the Ashkin-Teller model

For some values of the coupling constants, a proof of the existence of two phase transitions in the Ashkin-Teller model is given. Only correlation inequalities are used.     

Spin waves,vortices, and the structure of equilibrium states in the classicalXY model

We prove that, for spin systems with a continuous symmetry group on lattices of arbitrary dimension, the surface tension vanishes at all temperatures. For the classicalXY model in zero magnetic field, this result is shown to imply absence of interfaces in the thermodynamic limit, at arbitrary temperature. We show that, at values of the temperature at which the free energy of that model is continuously differentiable, i.e. at all except possibly countably many temperatures, there iseither aunique translation-invariant equilibrium state, or all such states are labelled by the elements of the symmetry group, SO(2). Moreover, there areno non-translation-invariant, but periodic equilibrium states. We also reconsider the representation of theXY model as a gas of spin waves and vortices and discuss the possibility that, in four or more dimensions, translation invariance may be broken by imposing boundary conditions which force an (open) vortex sheet through the system. Among our main tools are new correlation inequalities.     

A new HPLC method for the simultaneous determination of fluazifop-butyl and fluazifop in soil samples

Summary The analytical method presented here enables the extraction of fluazifop-butyl and fluazifop from soil samples avoiding hydrolysis of the ester and allowing a better release of the acid form. Then the quantitative determination of both the compounds can be performed in one run by means of RP-HPLC. This is achieved by using a phenyl phase and an ion-pair reagent (tetrabutylammonium hydrogensulfate).     

Synthesis and reactions of 2H-Benzothieno[3,2-d][1,3]oxazine-2,4(1H)-dione

The title compound 5 is synthesized by the reaction of the potassium salt of 3-aminobenzo[b]thiophene-2-carboxylic acid with phosgene. Compound 5 is readily alkylated to give 6 with methyl iodide, benzyl bromide, or propargyl bromide in the presence of sodium hydride. Reaction of 5 and 6 with nucleophiles follows specifically different pathways. Compound 5 is readily ionized to the isocycanate species 13 and subsequently reacts with methanol or methylamine to produce exclusively the carbamate 7 or ureido acid 9 . The N-substituted derivative 6 , in analogous reactions with methanol or methylamine, produce exclusively the amino ester 8 or the amino amide 10 . The N-benzyl derivative 6b reacts with the cyclic S-methylthiopseudourea 11 to give the tetracycle 12 , a new ring system.     

The Synthesis of n,n-Dimethyl-2-(1-phenyl-2,5-cyclohexadien-1-yl)-ethylamine and of Mesembrine-Like Metabolites of this Potential Analgesic

The synthesis of the analgesic compound N,N-dimethyl-2-(1-phenyl-2,5-cyclohexadien-1-yl)ethylamine ( 1 ) is described. Its structural relation to morphine and its pharmacological activity is shortly discussed. The isolation of three mesembrinelike metabolites of 1 from the plasma of rats is reported along with synthetic work permitting the determination of the relative configuration of these metabolites.