Towards real CAD

Present-day computer-aided design (CAD) packages play only a small part in the area of mechanical engineering design, which involves the synthesis and embodiment of physical components to perform a pre-determined function without unwanted side effects. The computer cannot properly help the designer in this task until it is able to capture and process the function requirements of the design. This paper describes the computer system being developed for this purpose at the Engineering Design Centre at Cambridge University Engineering Department. The paper also explores some of the geometrical and programming implications raised.     

Developing and fully developed turbulent flow of drag reducing fluids in an annular duct

Velocity profiles for the inner and outer flow regions of annuli are proposed for the turbulent flow of drag reducing fluids. Theoretical expressions for friction factors are developed. From the shear stress equations and the velocity profiles, estimates for the entrance lengths are given.     

Crystal growth of selected II–VI semiconducting alloys by directional solidification: Part I Ground-based experiments

A series of Hg_0.84Zn_0.16 Te crystal ingots have been grown from pseudobinary melts by the Bridgmam–Stockbarger type directional solidification using a Marshall Space Flight Center/Space Science Laboratory heat-pipe furnace and the ground control experiment laboratory furnace of the crystal growth furnace which was flown on the first United States Microgravity Mission. A number of translation rates and a series of hot- and cold-zone temperatures were employed to assess the influence of growth parameters on the crystal properties for the purpose of optimizing the in-flight growth conditions. This revised version was published online in November 2006 with corrections to the Cover Date.     

Artefactual cleavage of E coli H-NS by OmpT

In the bacterium Escherichia coli, H-NS-(H1, H1a) is a heat-stable protein with a molecular mass of 15.5 kDa involved in nucleoid organisation and gene regulation linked to certain signal transduction pathways. We have shown that, following addition of preparations of everted inner membrane vesicles, heat-stable cleavage products of approximately 10 kDa of H-NS are formed in vitro from newly synthesised, radio-labelled H-NS and from purified H-NS. The 15.5 kDa protein and its cleavage products were also recovered from a minicell system. These results raised the possibility that cleavage of H-NS is physiologically significant. However, the cleavage of H-NS observed appears to occur during cell breakage and to depend on the method of protein extraction and the presence of the outer membrane protease, OmpT. Nevertheless, the results indicate that H-NS may contain at least two separate domains with cleavage occurring between these domains at a preferred OmpT site. Failure to take account of H-NS cleavage in sample preparation and analysis can lead to serious underestimation of H-NS levels.     

Unfavorable mechanical effects of heat and moisture exchangers in ventilated patients

OBJECTIVE: To investigate the mechanical effects of artificial noses. SETTING: A general intensive care unit of a university hospital. PATIENTS: 10 patients in pressure support ventilation for acute respiratory failure. INTERVENTIONS: The following three conditions were randomly tested on each patient: the use of a heated humidifier (control condition), the use of a heat and moisture exchanger without filtering function (HME), and the use of a combined heat and moisture exchanger and mechanical filter (HMEF). The pressure support level was automatically adapted by means of a closed-loop control in order to obtain constancy, throughout the study, of patient inspiratory effort as evaluated from airway occlusion pressure at 0.1 s (P0.1). Patient's ventilatory pattern, P0.1, work of breathing, and blood gases were recorded. MEASUREMENTS AND MAIN RESULTS: The artificial noses increased different components of the inspiratory load: inspiratory resistance, ventilation requirements (due to increased dead space ventilation), and dynamic intrinsic positive end-expiratory pressure (PEEP). The additional load imposed by the artificial noses was entirely undertaken by the ventilator, being the closed-loop control of P0.1 effective to maintain constancy of patient inspiratory work by means of adequate increases in pressure support level. CONCLUSIONS: The artificial noses cause unfavorable mechanical effects by increasing inspiratory resistance, ventilation requirements, and dynamic intrinsic PEEP. Clinicians should consider these effects when setting mechanical ventilation and when assessing patients' ability to breathe spontaneously.     

Modulation of cAMP-dependent protein kinase by derivatives of chondroitin sulfate

Here, we report investigations about the direct effect of glycosaminoglycans, such as dermatan sulfate, chondroitin 4- and 6-sulfate upon cAMP-dependent protein kinase activity. The results indicate that glycosaminoglycans strongly influence the phosphorylation activity of this enzyme against histone type IIa and [Val6, Ala7]-kemptide. While chondroitin 4-sulfate and dermatan sulfate exhibit inhibitory effects, chondroitin 6-sulfate shows a stimulating effect. In addition, the chondroitin 6-sulfate is also able to reduce the chondroitin 4-sulfate and dermatan sulfate specific inhibition.     

Study of the nutrient distribution in root tips of the tropical forage Brachiaria

A Brachiaria breeding project is being conducted at CIAT, Colombia to combine acid soil adaptation of B. decumbens with other favourable traits of Brachiaria species that are less adapted to acid soils. Micro-PIXE was applied to investigate nutrient uptake and distribution in root tips of different species grown in hydroponic culture under control and simulated acid soil stress conditions. Different sample measurement approaches were evaluated, including: (1) linear scans with single point measurements along the root axis; (2) mapping of whole root tips; and (3) mapping of root cross sections. Different tissue types could be distinguished on the base of differences in nutrient concentrations and/or Al stress. Al, if supplied under nutrient stress conditions, increased P accumulation in the central vascular tissue of the meristematic and elongation zone of B. decumbens and B. brizantha. Furthermore, a negative correlation was found between Al and Cl accumulation in the root cap of B. decumbens.