An unusual 1,2-N→C acyl migration in urea derivatives of α-aminoorganolithiums

Transmetalation of urea derivatives of α-aminoorganostannanes with alkyllithiums provides α-aminoorganolithiums which undergo rapid N to C acyl migration to afford α-aminocarboxamides. The stereochemical course of the transmetalation/migration process depends on the substituents on the urea and varies from complete retention of configuration to complete racemization.     

Assessment of the Formant Frequencies in Normal and Laryngectomized Individuals Using Linear Predictive Coding

The objective of this study was to assess the difference in voice quality as defined by acoustical analysis using sustained vowel in laryngectomized patients in comparison with normal volunteers. This was designed as a retrospective single center cohort study. An adult tertiary referral unit formed the setting of this study. Fifty patients (40 males) who underwent total laryngectomy and 31 normal volunteers (18 male) participated. Group comparisons with the first three formant frequencies (F1, F2, and F3) using linear predictive coding (LPC) (Laryngograph Ltd, London, UK) was performed. The existence of any significant difference of F1, F2, and F3 between the two groups using the sustained vowel /i/ and the effects of other factors namely, tumor stage (T), chemoradiotherapy, pharyngectomy, cricothyroid myotomy, closure of pharyngoesophageal segment, and postoperative complication were analyzed. Formant frequencies F1, F2, and F3 were significantly different in male laryngectomees compared to controls: F1 (P<0.001, Mann-Whitney U test), F2 (P<0.001, Student's t test), and F3 (P=0.008, Student's t test). There was no significant difference between females in both groups for all three formant frequencies. Chemoradiotherapy and postoperative complications (pharyngocutaneous fistula) caused a significantly lower formant F1 in men, but showed little effect in F2 and F3. Laryngectomized males produced significantly higher formant frequencies, F1, F2, and F3, compared to normal volunteers, and this is consistent with literature. Chemoradiotherapy and postoperative complications significantly influenced the formant scores in the laryngectomee population. This study shows that robust and reliable data could be obtained using electroglottography and LPC in normal volunteers and laryngectomees using a sustained vowel.     

Composition of the Canadian Total Force: Issues and Findings for the Air Components

In 1987 the Canadian Department of National Defence enunciated the Total Force concept. The Total Force is comprised of Regular and Reserve components. The intention is to make maximum use of the Reserve to reduce defence expenditures and at the same time to ensure that military capability remains adequate to support national policy objectives. This paper discusses some of the governing parameters that affect the modelling of the composition of the Total Force and analyses the mix of regular and reserve forces. The interplay between the key factors and their marginal costs will be stressed. The models are employed to study two units in the Canadian Forces, a maintenance support unit and a tactical unit with high operational activity cost. The lessons drawn from these studies are highlighted.     

A FLASH of insight into cellular chemistry: genetically encoded labels for protein visualization in vivo

Genetically encoded fluorescent labels, such as green fluorescent protein, make it possible to visualize a protein's natural distribution and environment in living cells. A new approach to protein labeling in living cells has been devised in which a small, membrane-permeable ligand binds with high affinity and specificity to a short peptide motif that can be incorporated into the protein of interest; the ligand becomes brightly fluorescent after binding to the peptide.     

Bis(amino acid) derivatives of 1,4-diamino-2-butyne that adopt a C2-symmetric turn conformation

1,4-Diamino-2-butyne was prepared from 1,4-dichloro-2-butyne via 1,4-diazido-2-butyne. Bis(amino acid) derivatives of 1,4-diamino-2-butyne having the general structure (Boc-Xxx-NHCH2C[triple bond])2 (Xxx = Ala, Phe and Met) were prepared and examined by 1H NMR spectroscopy. Using chemical shift, coupling constant and DMSO titration data it is found that these compounds adopt a C2-symmetric turn conformation featuring two intramolecular hydrogen bonds.     

Application of stir bar sorptive extraction for wine analysis

Stir bar sorptive extraction (SBSE) coupled with gas chromatography/mass spectrometry (GC/MS) was used to analyse wine samples for three applications: flavour and compositional analysis; 2,4,6-trichloroanisole (TCA), a common off-aroma in wine; and agrochemicals. SBSE was found to be orders of magnitude more sensitive than modern conventional methodology, allowing for lower detection and quantitation levels, and improved confirmation of identity; SBSE often gave better signal to noise in scan mode than other methods in selective ion monitoring (SIM) mode. With the help of their characteristic mass spectra all agrochemicals could be identified unambiguously at concentrations of 10 microg L(-1) in wine and a further 100 constituents were detected in a Cabernet Sauvignon sample. Thus it is now possible to analyse complex samples such as wine by scan mode, with better confirmation of identity, and without sacrificing sensitivity, where previously SIM methodology had to be used.