Mechanistic alteration in micellar peptide esterolysis reactions

Buffer or CTACl-catalyzed basic cleavages of $\text{Z}$-$\text{D}$- or $\text{L}$-AA-$\text{L}$-Pro $\text{p}$-nitrophenyl esters proceed mainly via intramolecular cyclization to diketopiperazines. These reactions are more facile with $\text{DL}$ than with $\text{LL}$ substrates.     

Refinement of linear polymer crystal structures determined from electron diffraction data

The reliability of linear polymer structures determined by using electron diffraction data is investigated. The results of n-beam dynamical calculations and kinematic calculations which take account of crystal bending are compared with experimental structure factors for five published structures. In specific cases, both dynamical scattering and crystal bending effects are found to be important. Finally, guidelines are given for obtaining electron diffraction data which are optimal for structure solution.     

Arylmethyl radicals from arylmethoxybromodiazirines

[reaction: see text] Photolytic decompositions of 3-arylmethoxy-3-bromodiazirines afford arylmethyl radicals by homolyses of the diazirines' excited states.     

The bat head-related transfer function reveals binaural cues for sound localization in azimuth and elevation

Directional properties of the sound transformation at the ear of four intact echolocating bats, Eptesicus fuscus, were investigated via measurements of the head-related transfer function (HRTF). Contributions of external ear structures to directional features of the transfer functions were examined by remeasuring the HRTF in the absence of the pinna and tragus. The investigation mainly focused on the interactions between the spatial and the spectral features in the bat HRTF. The pinna provides gain and shapes these features over a large frequency band (20-90 kHz), and the tragus contributes gain and directionality at the high frequencies (60 to 90 kHz). Analysis of the spatial and spectral characteristics of the bat HRTF reveals that both interaural level differences (ILD) and monaural spectral features are subject to changes in sound source azimuth and elevation. Consequently, localization cues for horizontal and vertical components of the sound source location interact. Availability of multiple cues about sound source azimuth and elevation should enhance information to support reliable sound localization. These findings stress the importance of the acoustic information received at the two ears for sound localization of sonar target position in both azimuth and elevation.     

Loss of co-linearity by modular polyketide synthases: a mechanism for the evolution of chemical diversity

Modular polyketide synthases biosynthesise natural products through successive Claisen-type condensations, where one module is responsible for one round of chain extension. This review describes recent findings where this rule of co-linearity is broken, either by one module being bypassed (skipping) or through one module being used for multiple chain extension events (stuttering).     

Local Rules and Fitness Landscapes: A Catastrophe Model

This paper examines the imposition of local rules in five mail delivery centres of Australia Post. Local rules are patterns of behaviour used by subunits of an organization to optimise their payoff. These local rules may ultimately benefit the total organization. Fitness landscapes are used to examine the emergence of local rules in this workplace. This research examined the relationship between the time taken to sort the mail and the volume of this mail. Work rates show a clear catastrophe shift; that is, work rates suddenly drop when the volume of mail exceeds a certain level, as Postal Delivery Officers apply local rules to maximise gains inherent in the pay structures. Such behaviour is close to that predicted by Kauffman (1995) in computer simulations of lattices and may be indicative of the application of local rules in organizations. The implications of the use of local rules are that behaviour in social systems may be dictated by systemic and emergent processes which are outside immediate management control. A further implication is that organizations may be structured to a significant extent by such local rules.