Determination of volatile polynuclear aromatic hydrocarbons in air from particulate profiles by means of partial least-squares regression

The possibility of estimating the total (particulate and gaseous) concentrations of volatile polynuclear aromatic hydrocarbons (PAH's) in air on the basis of measured concentrations of PAH's in particles by means of partial least-squares regression (PLS), is discussed. The results show that the estimation can be good for samples exposed to the same source and collected under similar weather conditions.     

Determination of mixed polynuclear aromatic hydrocarbons in the vapor phase by laser-induced fluorescence spectrometry

Laser-induced fluorescence spectromety is shown to be a viable technique for quantifying polynuclear aromatic hydrocarbons (PAH) in the vapor phase. Mixtures of anthracene, fluoranthene, and phenanthrene were analyzed in a vapor cell at temperatures ranging from 50° to 90°C. The individual concentrations of PAH's in these mixtures were calculated by a least-squares matrix technique and were accurate to within 3–5% at levels of about 5 × 10¹²?3 × 10¹⁵ molecules cm^?3.     

Potential methods in pattern recognition : Part 2. CLUPOT —an unsupervised pattern recognition technique

The applicability of potential functions in unsupervised pattern recognition is demonstrated on the basis of a new clustering technique called CLUPOT. CLUPOT is a centrotype sorting technique which means that for each detected cluster of objects a representative object can be selected. CLUPOT uses a reliability curve which permits the detection of significant clusters. Applications to four data sets (Kowalski's archeological artefact data, Ruspini's fuzzy set data. Fisher's Iris data and a part of Esbensen's meteorite data) show that CLUPOT yields significant clusterings.     

Simultaneous Removal of Polycyclic Aromatic Hydrocarbons and Soot Particles from flue Gas by Gliding arc Discharge Treatment

The removal of Polycyclic aromatic hydrocarbons (PAH’s) and soot particles from flue gas was studied using a gliding arc discharge reactor, and the flue gas was emitted from the polyethylene (PE) or polyvinyl chloride (PVC) combustion in a laboratory-scale drop tube furnace. The removal efficiencies have ranged from 70.3% up to 74.4%. The maximum removal efficiency of soot particles was up to 89.3%. Experimental results show that the technique can successfully remove PAH’s and soot particles from flue gas, a possible mechanism is proposed to explain the experimental observations.     

The one-particle green's function: The minimal basis set description of the two-electron bond

The ionization potential (IP), electron affinity (EA), one-matrix and correlation energy of a two-electron chemical bond are calculated in a minimal basis set using one-particle, many-body Green's function theory. Results obtained using the second-order self-energy (Σ) and higher-order Σ's proposed by (1) Pickup and Goscinski, (2) Tsui and Freed, (3) Simons and Smith are compared with each other and with the exact values in the basis. The relationship between these methods and with configuration interaction is discussed and the consequences of making approximations in the context of Green's function theory are clarified.     

Advances in Detection Methods of β-Amyloid Protein

Alzheimer's disease (AD) is a neurodegenerative disease with unknown etiology. β-amyloid protein (Aβ) is one of the specific biomarkers of AD, and many clinical studies suggest that abnormal levels of Aβ in blood, cerebrospinal fluid and brain tissue are closely related to the progression of AD. The analysis and evaluation of Aβ are important for early detection, tracking, prevention, and treatment of AD. In this paper, the present situations of the commonly used detection methods of Aβ at home and abroad were summarized and compared. Specifically, the latest application of new electrochemical biosensor in Aβ detection was mainly described, and the summary of its future directions and the potential applications was given.     

Neutral lipid enzyme electrode based on ion-sensitive field effect transistors

An enzyme electrode for neutral lipid determination based on hydrogen ion-sensitive field effect transistors (pH-FET's) is described. The electrode is composed of two pH-FET's with an immobilized lipase membrane on one pH-FET, and a platinum wire. Triglycerides are solubilized with 10% (v/v) Triton X-100. The electrode is used to determine triglycerides over wide concentration ranges with response times of ca. 2 min. Relations between signal and the logarithm of the concentration are linear over the ranges 100–400 mM triacetin, 3–50 mM tributylin and 0.6–3 mM triolein. In the case of triolein, the detection limit is 9 μg ml^?1 (signal/noise = 3:1). The effect of Triton X-100 on the electrode response is discussed.     

Performance and application of controlled temperature-gradient lamps in atomic absorption spectrometry

An improved design of controlled temperature-gradient lamp (CTGL) is suitable for arsenic, cadmium, phosphorus, potassium, rubidium, selenium, sodium, sulphur and zinc. Intensity and linewidth measurements indicate that the CTGL is significantly more intense than an electrodeless discharge lamp (EDL) at the same linewidth. CTGL's also compare favourably with EDL's when used as light sources for a.a.s. Arsenic and selenium can be determined at very low concentrations (ng ml^-1) by the hydride generation technique. Sulphur and phosphorus can be detected in the vacuum ultra-violet region using nitrogen-separated flames; the limits of detection are 13 and 10 μg ml^-1, respectively.     

Diabatic molecular states and the shielded diatomic orbital method. Evolution of two-interacting state systems for molecular hydrogen

Within Lichten's method, shielded diatomic orbitals (SDO's) are proposed as a basis for building-up diabatic molecular states in the single configurati approximation. The determination of SDO's i.e. eigenfunctions in prolate spheroidal coordinates of the two-center problem with a parametric shielding potential is extended to mono-excited states of many-electron diatomic systems, the shielding potential being obtained from simple electrostatic considerations. Four diabatic molecular states of H₂ are investigated i.e. ¹Σ_g⁺ (2pσ², 1Σ_g⁺ (1s,σ 2sσ), ¹Σ_u⁺(1sσ,4Pσ), ¹Σ_u⁺ (1sσ, 4fσ) using a minimal basis of SDO'S. The dynamical evolution of the nuclei for the two sets ¹Σ_g and ¹Σ_u⁺ of two interacting states is described in both the diabatic and the corresponding adiabatic representation.     

Field-theoretical approach to vibrational excitation in atom—diatom collinear collisions

The field-theoretical atom—diatom scattering equations of Csanak have been tested numerically, assuming a collinear collision model, with an exponential repulsive interaction potential and with a harmonic oscillator approximation for the molecule. Dyson's equation, in its integral form, has been solved obtaining orbitals representing the elastic scattering of an atom off the target and these Dyson's orbitals have been used to evaluate a matrix element containing a transition potential. This has been obtained by approximating Bethe—Salpeter's equation and yields directly the transition amplitudes for inelastic scattering. The results for single and multiple-jumps compare favourably with the exact values of Secrest and Johnson, and refinements of the model are suggested for further improvements.     

Experimental and computational modeling of the biological activity of benzaldehyde sulphur trioxide as a potential drug for the treatment of Alzheimer disease

Alzheimer's disease is a major public brain infection that has resulted in many deaths as revealed by the world health organization (WHO). Conventional Alzheimer treatments such as chemotherapy, surgery, and radiotherapy are not very effective and are usually associated with several adverse effects. Therefore, it is necessary to find new therapeutic approach that completely treat Alzheimer disease without much side effects. In this research work, we report the experimental and in silico molecular modeling of the biological activity of a novel azo-based compound as potential candidate for Alzheimer's disease. The synthesized compound was obtained by coupling reactions with 4-amino-3-nitrobenzaldehyde. Suitable purification and characterization techniques were employed and density functional theory (DFT) computational approach as well as in-silico molecular modeling has been employed to assess the electronic properties and anti-Alzheimer's potency. Suitable protein targets often regarded as target sites for most therapeutic vaccines for the said disease (4EY7, 1QTN, 4EY7, and 6EUE) have been selected for molecular docking investigation. For proper valuation of the drug candidacy, molecular docking studies were compared with conventional Alzheimer drug (donepezil). Also, the spectroscopic properties of the studied compound were investigated and compared with experimental data. Our findings show that the studied structure is relatively stable and expresses greater binding affinities of ?6.10, ?9.01, ?5.90, and ?11.20 kcal/mol than donepezil which had binding affinities of: 5.30, ?6.30, 5.90, and ?10.70 kcal/mol for each protein target. Thus, demonstrating the efficacy of the studied compound as potential candidate for Alzheimer's disease.     

Determination of vanadium in petroleum crudes and fuel oils by gas chromatography

A method is described for determining levels of vanadium as low as 0.1 μg g^-1 in petroleum oils by gas chromatography with flame-ionization detection. The method involves decomposition of the oils, derivatization and solvent extraction of vanadium as the chelate, [2,2,2',2'-tetramethyl-5,5'-(ethane-1,2-diyldiimino)bis(hex-4-en-3-onato)-(2-)] oxovanadium(IV), followed by gas chromatography on a non-polar (SE-30) column. The procedure is applied to a variety of samples, including standard reference and fuel oils used in an interlaboratory study. The results are compared with those of emission spectrography and two standard methods. The new procedure can be extended to the selective, simultaneous detection of copper, nickel and vanadium in such samples.     

Transferability of intensity parameters

The transferability of different kinds of intensity parameters is discussed. In order to transfer dipole moment derivatives with respect to internal or symmetry coordinates (dmd's) among similar modes in different molecules they must be split up into a mode-specific part (the dmd with respect to rotation-free reference coordinates) and a molecule-specific part (the rotational contribution). The calculation of reference coordinates and rotational contributions is discussed. The dmd's with respect to reference coordinates can be expressed in terms of first-order intensity parameters (bcp's or aop's). Expressions are given for CH₃X, propyne, butyne-2 and acetylene. The transferability of bcp's (or eop's) is tested by searching for a common set of bcp's for the following molecules: C₂H₂, C₂D₂, CH₃CCH, CD₃CCH, CH₃CCCH₃, CD₃CCCD₃. The final results are discussed in relation to the basic assumptions and the adopted constraints.     

Modification of Kagan's amide for improved activity as Chiral Solvating Agent in enantiodiscrimination during NMR analysis

A modification is proposed in Kagan's amide in order to improve its ability to offer stronger hydrogen bonding and hence better ability to bind with substrates. Introduction of chlorine in the amide aromatic ring along with the two nitro groups, increases the acidic character of amide hydrogen and makes the hydrogen bond stronger, the concept is tested by making three derivatives of Kagan's amide and the effect is confirmed by nmr analysis. The modified chlorinated Kagan's amides were then tested as chiral solvating agents for detection of optical purity of several types of substrates where the supramolecular recognition is measured by in situ nmr analysis. Several guest molecules such as amide, sulfoxide, epoxy-keto, hydroxy acid, diacid and phosphoric acid were scanned for this study and its efficiency is further established by comparison with samples of known optical purity.     

An attempt to approach the solutions of the N-electron CNDO hamiltonian for conformational studies of conjugated systems

While dealing with the same N-electron hamiltonian, the SCF approximation and the third order PCILO results completely disagree about the conformation of conjugated systems. An attempt is made, using the CIPSI algorithm, to approach the exact solution of the N-electron CNDO hamiltonian for the butadiene molecule starting from either a priori localized, SCF localized or SCF delocalized MO's. The partial CI's performed from SCF delocalized MO's give arbitrary results when increasing the number of doubly excited determinants and Pancir?'s recent results is fortuitous; on the contrary the results obtained from a priori and SCF localized MO's have better convergence and consistence; from our best calculations the final solution seems to be a rather flat potential curve, the stable minimum being the trans planar minimum, with a second gauche minimum for θ = 120-150° (ΔH ≈ 1 kcal/mole), separated by a weak barrier (ΔH ≈ 2 kcal/mole). The third order PCILO solution is in much better agreement with this estimate of the exact solution than the SCF one.     

Why is azulene blue and anthracene white? a simple mo picture

In spite of their almost identical ionization potentials (IP's) and electron affinities (EA's), azulene and anthracene differ considrably in their lowest singlet-singlet excitation energies. This is hard to understand in the simple Hückel picture in which excitation energies are expressed as orbital energy differences, if orbital energies are taken from IP's and EA's. The difficulty is removed when electron repulsion is introduced explicitly. This is shown using simple inuitive concepts, which also account for the magnitude of singlet-triplet splitting and single out the structural features responsible for the difference between azulene and anthracene, so that generalizations are possible     

Transport studies of water and aqueous—dioxane through a pyrex sintered disc impregnated with cellulose acetate

Experimental results for the measurements of hydrodynamic permeability, electroosmotic velocity and streaming potential of water and dioxane—water (DH₂O) mixtures (10, 20, 30 and 40% by mass of dioxane) using a pyrex sintered disc (G₂) impregnated with cellulose acetate at 30°C and at voltages up to 40 V are reported. The data have been analysed in the light of non-equilibrium thermodynamics. Onsager's reciprocity relation for all compositions of aqueous—dioxane has been found to hold true. It has been found that the concentration dependence of the phenomenological coefficients conform to the Spiegler's frictional model. Efficiencies of electrokinetic energy conversion, i.e. electroosmosis and streaming potential, have been determined and the results are in accordance with the theory of non-equilibrium thermodynamics. The maximum value of the efficiency of energy conversion for both the modes has been found to be independent of the input force. Membrane characteristics such as pore radius and number of pores have been determined, whereas the membrane—permeant interface is characterised in term of the zeta potential.     

Electronegativity based on the simple bond charge model

A single physical interpretation of the various electronegativity scales of Pauling, Mulliken and Gordy is suggested, based on the simple bond charge (SBC) model of Parr and Borkman for the covalent bond. With a charge partition determined from vibrational frequencies, the SBC model is shown to account for the covalent bond energy in single-bonded homonuclear diatomic molecules and diamond-type crystals. The binding energy to the atom of a bond-electron in the single-bonded homonuclear diatomic molecules agrees with Mulliken's electroaffinity, and provides a definition for electronegativity. Gordy's empirical relation between the bond-stretching force constant and electronegativity is explained. It is then suggested that the physical effect underlying Pauling's thermochemical formula for electronagativity is the location of the bond charge in the heteronuclear molecule. The deviation of Pauling's formula from experiment in the case of the alkali hydrides can then be explained.     

Single- and double-gaussian FSGO model and compton profiles

Compton profiles (CP's) calculated from single- and double-gaussian versions of the floating spherical gaussian orbital (FSGO) model are compared with experiment. The CP's calculated from the single-gaussian version die out faster than the experimental CP's due to ill-presented inner shell. The double-gaussian version improves the agreement with the experimental CP's substantially. A remarkable empirical correlation between the molecular energy and the J(0) value as well as the width of the CP, J_0.5, has been observed for the ten-electron series of molecules within the double-gaussian frameworks.