Metal catalyzed rearrangement of a 2,2'-bipyridine Schiff-base ligand to a quaterpyridine-type complex

A Co(II) quaterpyridine-type complex has been prepared via a one-pot transformation of a 2,2'-bipyridine Schiff-base ligand in the presence of a Lewis acidic metal salt.     

Assessment of heavy metals emission from traffic on road surfaces

This study aims to analyse RDS heavy metal concentrations on road deposited sediment (RDS) using Riccarton Campus of Heriot-Watt University, Edinburgh, Scotland as a study site. RDS samples were collected at two transverse positions from different sites over a 4 month period in order to describe the influence of traffic on heavy metal emissions. The heavy metal concentrations of the RDS were determined by strong nitric acid digestion and atomic absorption spectrometry. The mean concentrations for Zn, Cu, Cd, Cr, Ni, Pb and Fe were found to be 213, 57, 1, 16, 15, 118, and 13497 mg kg-1 from samples near to the curb and 211, 79, 2, 15, 9, 35, and 14276 mg kg⁻¹ from samples 1 m from the curb respectively. Furthermore for both positions the highest concentrations for all metals were associated with the finer fraction (<63 μm) and stronger correlations between the metals were found further from the curb than near the curb, indicating that metals accumulating on the road surface further from the curb may likely be from the same source (traffic), while the sources of metals near the curb are more diverse.     

Effects of ligand tuning on dinuclear indium catalysts for lactide polymerization

Functionalized diaminophenols, H(N(R1R2)N(R3)O), were investigated as ligands for indium catalysts in the ring-opening polymerization of racemic lactide. Precursor complexes (N(Me2)N(Me)O)InCl(2) (1), (N(Pr2)NO)InCl(2) (2), and (N(Mes)NO)InCl(2) (3) were synthesized and fully characterized by (1)H and (13)C NMR spectroscopy, elemental analysis, and single-crystal X-ray crystallography. Complexes 1 and 2 were used to synthesize alkoxy-bridged complexes [(N(Me2)N(Me)O)InCl](2)(μ-Cl)(μ-OEt) (4) and [(N(Pr2)NO)InCl](2)(μ-Cl)(μ-OEt) (5). These complexes catalysed the polymerization of racemic lactide at different rates, with complex 5 being substantially more active than complex 4. The dissociation behaviour of these catalysts in the presence of lactide was also studied and used to make comparisons with previously reported catalyst systems.     

A novel and highly stereoselective route for the synthesis of non-racemic 3-substituted isoindolin-1-one targets

A new, versatile and highly stereoselective approach for the synthesis of non-racemic 3-substituted isoindolin-1-ones is described from a readily available chiral template. The potential of this new protocol is demonstrated through the synthesis of an enantiomerically enriched 3-alkyl N-H isoindolin-1-one target with an e.e. of 98%.     

Construction of Williamson type matrices

Recent advances in the construction of Hadamard matrices have depeaded on the existence of Baumert-Hall arrays and four (1, ?1) matrices A B C Dof order m which are of Williamson type, that is they pair-wise satisfy

i) MN^T = NM^T , ∈ {A B C D} and

ii) AA^T + BB^T + CC^T + DD^T = 4mI_m .

It is shown that Williamson type matrices exist for the orders m = s(4 ? 1)m = s(4s + 3) for s∈ {1, 3, 5, …, 25} and also for m = 93. This gives Williamson matrices for several new orders including 33, 95,189.

These results mean there are Hadamard matrices of order

i) 4s(4s ?1)t, 20s(4s ? 1)t,s ∈ {1, 3, 5, …, 25};

ii) 4s(4:s + 3)t, 20s(4s + 3)t s ∈ {1, 3, 5, …, 25};

iii) 4.93t, 20.93t

for

t ∈ {1, 3, 5, … , 61} ∪ {1 + 2 ^a 10 ^b 26 ^c a b c nonnegative integers}, which are new infinite families.

Also, it is shown by considering eight-Williamson-type matrices, that there exist Hadamard matrices of order 4(p + 1)(2p + l)r and 4(p + l)(2p + 5)r when p ≡ 1 (mod 4) is a prime power, 8ris the order of a Plotkin array, and, in the second case 2p + 6 is the order of a symmetric Hadamard matrix. These classes are new.     

Theory of the effect of a dc current on surface polaritons in n-type silicon

A theoretical investigation has been made of the effect of a drift current on surface polaritons in n-type silicon. The current direction is taken to be the same as the propagation direction of the surface polaritons. Retardation is included, but damping is neglected. In obtaining the dispersion relation, the specular-reflection/mirror-image technique of Kliewer and Fuchs is used to handle the boundary conditions. The results indicate that an interaction takes place between the current and polaritons which gives rise to polariton instabilities for certain frequency ranges. These instabilities are a consequence of the presence of the surface.     

Vocal fold nodule vs. vocal fold polyp: answer from surgical pathologist and voice pathologist point of view

Vocal fold polyps and nodules are caused by inflammation caused by stress or irritation. Our study involved looking retrospectively at 30 patients. A clinical diagnosis was established by an otolaryngologist and voice pathologist through videostroboscopic analysis. Histological sections after removal of the vocal fold lesion were available for microscopic examination. All of these cases have also been previously evaluated and photographed. A clinical diagnosis of either a polyp or a laryngeal nodule have been made and documented. Two pathologists made the histological evaluation separately initially unaware of the clinical diagnosis. Their impression was recorded. After the clinical diagnosis become available and comparison between the clinical and pathological diagnosis were made, a retrospective review of the tissue was attempted to reconcile the differences. In conclusion, after careful histological evaluation, no definitive histological distinction can be made between laryngeal nodules and polyps. Our data showed no distinction between the two entities when compared for the presence of edema, fibrin, inflammation, and amyloid-like material. A statistically significant difference was found in the size of the specimen and the presence of telangiectasias. Based on our data, a biopsy larger than 0.3 cm could be a polyp and a biopsy less than 0.3 cm could be a nodule.