Unsteady Flow Predictions of Initial Surface Formation in Aluminum Strip Casting

A comprehensive multidomain computational fluid dynamics model is described for examining the unsteady thermal-fluid dynamic conditions at the early onset of surface formation in aluminum strip casting. By employing zones for the solidifying melt, substrate, high-speed water jets, and active film for thermal buffering between the melt and the substrate, a fully implicit in time solution is obtained. Furthermore, the melt domain transport equations are cast in an Eulerian–Lagrangian form to include the motion of a backward-facing compliant step and its associated contact line, both affecting the initial melt–substrate contact cooling conditions. The influence of the compliant step motion on the thermal-fluid history at the earliest stages of surface formation is examined. Results show a well-defined characteristic response between the contact line motion and the solid fraction/temperature history. Associated recirculation cells are affected profoundly by contact line motion and exhibit cyclical removal and reappearance. Coupled with large relative velocity between phases at the contact line, overall flow patterns suggest conditions for alloy segregation.     

Competing risks as a multi-state model

This paper deals with the competing risks model as a special case of a multi-state model. The properties of the model are reviewed and contrasted to the so-called latent failure time approach. The relation between the competing risks model and right-censoring is discussed and regression analysis of the cumulative incidence function briefly reviewed. Two real data examples are presented and a guide to the practitioner is given.     

Ein Planungsansatz zum Umgang mit Störungen bei der Produktion: Die flexible Produktionsfeinplanung mithilfe von Planungsschritten

Disruptions like the breakdown of machines or delays in the delivery of materials cause generated production plans to be useless, at least in some parts. A new planning approach for coping with this uncertainty caused by disruptions is presented. Planning steps that are described by properties, preconditions and consequences are used for material requirements planning and scheduling. If their preconditions are satisfied in a certain state of environment, planning steps will be applicable. The consequences of planning steps change the state of environment. Each customer order establishes a goal of a new planning problem to be achieved by applying planning steps. Plan execution concerns all planning steps applicable in a certain state of environment. In choosing among applicable planning steps and among available resources the flexibility of plan execution is preserved.     

A comparison of forearm and thumb muscle electromyographic responses to the use of laparoscopic instruments with either a finger grasp or a palm grasp

Laparoscopic techniques allow for less-invasive treatment of common surgical problems. Laparoscopic instruments are different from standard surgical instruments and generally incorporate a pistol-grip handle configuration with rings for the fingers. This handle configuration has been reported as being uncomfortable, leading to finger compression neuropathies in some cases. As an alternative, the surgeon can choose to grasp laparoscopic instruments using a more powerful palm grip during grasping motions. This study evaluates the hypothesis that the use of the palm grip requires less muscle tension than the finger-grip when grasping with laparoscopic instruments. Nine general surgeons used an Autosuture laparoscopic grasper with a ringed pistol-grip handle held in both a finger-in-ring (F) or palm (P) hand grip position to grasp and close two spring-loaded metal plates. The same task was performed with a surgical haemostat clamp (H) for comparison. Each subject performed the grasping task in a random sequence for the three instrument configurations at two grasping forces levels (0.7 and 4.2 N), and with the instrument at three angles to the subjects' sagittal plane (0 degree, 45 degrees and 90 degrees). Surface electromyographic (EMG) signals were acquired from the flexor carpi ulnaris (FCU), flexor digitorum profundus (FDP), flexor digitorum superficialis (FDS), extensor carpi ulnaris (ECU), extensor digitorum comunis (EDC) and the thenar compartment (TH). The peak root mean squared (RMS) EMG voltage was averaged for five repetitions at each instrument, force and angle condition. Statistical analysis was carried out by repeated measures ANOVA. The muscle EMG RMS amplitude while using the palm grip was decreased in the FDS, TH and EDC, was unchanged in the ECU and FCU, and was slightly higher in the FDP when compared with the finger grip. These differences were most prominent at 90 degrees to the sagittal plane where the subjects' wrists neared maximal flexion. It is concluded that the palm grip is more powerful than the finger grip when grasping with laparoscopic instruments, particularly at angles perpendicular to the surgeon's sagittal plane.     

Multiple interruptions of responding maintained by a fixed-interval schedule of electric-shock presentation in squirrel monkeys.

Recent experiments have demonstrated that the characteristic pattern of responding engendered by a fixed-interval (FI) schedule of food reinforcement can also be established and maintained by response-contingent electric shocks. Under an FI schedule of food presentation, the characteristic pattern of responding survives repeated interruption by stimulus conditons absent at the time of reinforcement. The present experiment, with 3 male squirrel monkeys, demonstrates a similar phenomenon under circumstances in which the sole consequence of FI responding was the delivery of response-contingent shocks. Several possible interpretations of FI performance maintained by electric-shock presentation are discussed. (15 ref.) (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Changes of physicochemical indicators during mastitis and the effects of milk ejection on their sensitivity

We examined the relationship between physicochemical indicators and somatic cells in the milk of dairy cows during experimentally induced mastitis and their significance as indicators for use in controlling udder health. We were concerned particularly with the effect of alveolar milk ejection on the sensitivity of these indicators. In Expt 1, Escherichia coli lipopolysaccharide (Esch. coli LPS) was injected into the left rear quarter to induce an inflammatory reaction in one quarter in each of six cows. The contralateral control quarter was injected with a solution of NaCl (9 g/l). Nine milk samples were taken from both quarters until 60 h after injection. In Expt 2, repeated milk samples were taken every 20 s from one quarter during a 120-s teat stimulation in 20 cows with different somatic cell counts (SCC). Quarters were clustered for low (<5.0 log cells/ml), mid (5.0-5.7 log cells/ml) and high (>5.7 log cells/ml) SCC of the sample taken at t=0 s. Samples were analysed for SCC, electrical conductivity (EC) and Na+ and Cl- concentrations. During the experimental inflammation SCC, EC, Na+ and Cl- peaked at 12 h from LPS administration and values in treated quarters (T) at this time were elevated to 7900, 157, 501 and 169% of the values in untreated quarters, respectively. In Expt 2, SCC, EC, Na+ and Cl- in high SCC quarters were 2520, 121, 283 and 141% of low SCC quarters at the start of stimulation (t=0 s), respectively. Highly significant (P<0.001) differences in EC, Na+ and Cl- between high and low SCC quarters disappeared owing to the onset of alveolar milk ejection 100 s after the first contact with the teat. In conclusion, SCC in cows' milk provided the strongest amplitude in the case of an intramammary inflammation. EC, Na+ or Cl- were useful tools only if the measurements were performed in cisternal milk before the start of alveolar milk ejection.     

Effective electrode configuration for selective stimulation with inner eye prostheses

The quality of visual perception with retinal prostheses strongly depends on the local selectivity. Electrode arrays at the surface of the retina should excite exclusively cells within a local area but they are expected to co-stimulate bypassing axons originating from ganglion cells of the outer regions. Long electrodes parallel to these axons are shown to be good candidates for avoiding the co-stimulation phenomenon. Efficiency of focal excitation depends on the length and resistance of the electrodes.     

The European Radiobiology Archives (ERA), present state and future developments

The European Radiobiology Archives (ERA) aims to collect most of the information still available in Europe on long-term animal experiments--including some selected human studies suitable for comparison with animal data--and to make them available to the scientific community for further analysis. ERA cooperates with the US (National Radiobiology Archives, NRA) and Japan (Japanese Radiobiology Archives, JRA) in the International Radiobiology Archives (IRA).