Most-probable-number procedures for enumerating ruminal bacteria, including the simultaneous estimation of total and cellulolytic numbers in one medium.

Based on results from eight experiments, no overall difference was found between roll tube and three- and five-tube most-probable-number (MPN) methods for estimating total numbers of ruminal bacteria. However, standard errors for the replicate means within an experiment were higher with the MPN procedures. Visual growth and pH were the criteria used for scoring the MPN tubes. Total numbers were significantly higher in MPN medium containing 40% ruminal fluid, as compared with a complete medium without ruminal fluid. By using a broth medium containing ball-milled cellulose and soluble carbohydrates as energy sources, it was possible to estimate both total and cellulolytic ruminal bacterial numbers in the same MPN series. Disappearance of cellulose and decrease in pH were used to determine growth. Values did not differ from those obtained in separate MPN assays. By using this method, diurnal changes in total and cellulolytic bacterial numbers were estimated in sheep fed forage or a concentrate-type diet

SCALE MODELS FOR THE EXPERIMENTAL ANALYSIS OF THE COLLAPSE MECHANISMS OF MASONRY BAY WINDOWS UNDER HORIZONTAL ACTIONS

The present contribution illustrates a first set of results obtained within the framework of currently on-going research aimed at evaluating the seismic vulnerability of masonry buildings in Boston’s Back Bay area. In particular, the study focuses on the collapse mechanisms of "bay windows", a typical late 19th century architectural element of the Victori- an style that characterizes the facades of Back Bay’s old buildings. With the aim of investigating the main features of bay windows response to horizontal loads, the analysis is focused on a single bay window considering it isolated from the rest of the building and resting on a rigid basement. A series of experimental tests has been conduct- ed on five scale-model bay windows of varying height free from openings. A system of hori- zontal actions proportional to the model mass density distribution has been imposed during the test by placing the model on a "tilting-table". The recordings of two digital video cameras allowed the identification of the collapse mechanisms. The results obtained are described in terms of determination of the horizontal loads col- lapse multiplier and identification of the actual collapse mechanisms. In addition, a first in- terpretation of the experimental results is provided by means of some simple mechanical schemes that use the typical tools of limit analysis. The agreement between experimental and theoretical results is more than satisfactory, and the proposed theoretical schemes seem able to provide useful information for assessing the mechanical response of bay windows

Muscular forearm activation in hand-grip tasks with superimposition of mechanical vibrations

The purpose of this paper is to evaluate the muscular activation of the forearm, with or without vibration stimuli at different frequencies while performing a grip tasks of 45 s at various level of exerted force. In 16 individuals, 9 females and 7 males, the surface electromyogram (EMG) of extensor carpi radialis longus and the flexor carpi ulnari muscles were assessed. At a short latency from onset EMG, RMS and the level of MU synchronization were assessed to evaluate the muscular adaptations. Whilst a trend of decay of EMG Median frequency (MDFd) was employed as an index of muscular fatigue. Muscular tasks consists of the grip of an instrumented handle at a force level of 20%, 30%, 40%, 60% of the maximum voluntary force. Vibration was supplied by a shaker to the hand in mono-frequential waves at 20, 30, 33 and 40 Hz. In relation to EMG, RMS and MU synchronization, the muscular activation does not seem to change with the superimposition of the mechanical vibrations, on the contrary a lower MDFdwas observed at 33 Hz than in absence of vibration. This suggests an early muscular fatigue induced by vibration due to the fact that 33 Hz is a resonance frequency for the hand-arm system