Basic Strategies (basic + strategy)

Distribution by Scientific Domains

Selected Abstracts

Ontogenetic switches from plant resistance to tolerance: minimizing costs with age?

Karina Boege
Abstract Changes in herbivory and resource availability during a plant's development should promote ontogenetic shifts in resistance and tolerance, if the costs and benefits of these basic strategies also change as plants develop. We proposed and tested a general model to detect the expression of ontogenetic tradeoffs for these two alternative anti-herbivory strategies in Raphanus sativus. We found that ontogenetic trajectories occur in both resistance and tolerance but in opposite directions. The juvenile stage was more resistant but less tolerant than the reproductive stage. The ontogenetic switch from resistance to tolerance was consistent with the greater vulnerability of young plants to leaf damage and with the costs of resistance and tolerance found at each stage. We posit that the ontogenetic perspective presented here will be helpful in resolving the current debate on the existence and detection of a general resistance,tolerance tradeoff. [source]

Enzymatic activation of sulfur for incorporation into biomolecules in prokaryotes

Dorothea Kessler
Abstract Sulfur is a functionally important element of living matter. Incorporation into biomolecules occurs by two basic strategies. Sulfide is added to an activated acceptor in the biosynthesis of cysteine, from which methionine, coenzyme A and a number of biologically important thiols can be constructed. By contrast, the biosyntheses of iron sulfur clusters, cofactors such as thiamin, molybdopterin, biotin and lipoic acid, and the thio modification of tRNA require an activated sulfur species termed persulfidic sulfur (R-S-SH) instead of sulfide. Persulfidic sulfur is produced enzymatically with the IscS protein, the SufS protein and rhodanese being the most prominent biocatalysts. This review gives an overview of sulfur incorporation into biomolecules in prokaryotes with a special emphasis on the properties and the enzymatic generation of persulfidic sulfur as well as its use in biosynthetic pathways. [source]

Optimizing patient flow in a large hospital surgical centre by means of discrete-event computer simulation models

Rodrigo B. Ferreira MSc
Abstract Objective, This study used the discrete-events computer simulation methodology to model a large hospital surgical centre (SC), in order to analyse the impact of increases in the number of post-anaesthetic beds (PABs), of changes in surgical room scheduling strategies and of increases in surgery numbers. Methods, The used inputs were: number of surgeries per day, type of surgical room scheduling, anaesthesia and surgery duration, surgical teams' specialty and number of PABs, and the main outputs were: number of surgeries per day, surgical rooms' use rate and blocking rate, surgical teams' use rate, patients' blocking rate, surgery delays (minutes) and the occurrence of postponed surgeries. Two basic strategies were implemented: in the first strategy, the number of PABs was increased under two assumptions: (a) following the scheduling plan actually used by the hospital (the ,rigid' scheduling , surgical rooms were previously assigned and assignments could not be changed) and (b) following a ,flexible' scheduling (surgical rooms, when available, could be freely used by any surgical team). In the second, the same analysis was performed, increasing the number of patients (up to the system ,feasible maximum') but fixing the number of PABs, in order to evaluate the impact of the number of patients over surgery delays. Conclusion, It was observed that the introduction of a flexible scheduling/increase in PABs would lead to a significant improvement in the SC productivity. [source]

Differences in chewing strategies used by edentate people

Aim:, To examine, in detail, the different masticatory measures that contribute to individual chewing strategies of edentate people. Measures:, Variables relating to displacement and force were derived using a new three dimensional implant force transducer, a mucosal pressure transducer and measurements of mandibular movements. Materials:, Five edentate subjects with conventional upper dentures and lower dentures stabilized on two dental implants. The subjects chewed unilaterally on their preferred chewing side. Seven foods were chewed , almond, fruit pastille, chewing gum and four different meats. Analysis:, The data were analysed by separating each sequence into cycles and ,phases' of cycles for which variables were derived. Results:, As expected, the results showed greater differences between subjects than between foods. From the five subjects, four basic strategies were identified in response to the different foods: one subject primarily modulated force, one subject modulated the number of cycles, two subjects modulated force and the number of cycles and one subject showed little modulation at all. As part of these strategies many striking differences between subjects were observed, e.g. one subject showed little modulation of her ,default' chewing pattern for different foods, yet one subject modulated the number of force and manipulation cycles, the force strategy (forces increasing through sequences) and swallow thresholds. Conclusion:,People appear to develop different strategies to compensate for chewing difficulty by modulating speed, the number of cycles and/or penetration forces. [source]

Statistical prediction of global sea-surface temperature anomalies

A. W. Colman
Abstract Sea-surface temperature (SST) is one of the principal factors that influence seasonal climate variability, and most seasonal prediction schemes make use of information regarding SST anomalies. In particular, dynamical atmospheric prediction models require global gridded SST data prescribed through the target season. The simplest way of providing those data is to persist the SST anomalies observed at the start of the forecast at each grid point, with some damping, and this strategy has proved to be quite effective in practice. In this paper we present a statistical scheme that aims to improve that basic strategy by combining three individual methods together: simple persistence, canonical correlation analysis (CCA), and nearest-neighbour regression. Several weighting schemes were tested: the best of these is one that uses equal weight in all areas except the east tropical Pacific, where CCA is preferred. The overall performance of the combined scheme is better than the individual schemes. The results show improvements in tropical ocean regions for lead times beyond 1 or 2 months, but the skill of simple persistence is difficult to beat in the extratropics at all lead times. Aspects such as averaging periods and grid size were also investigated: results showed little sensitivity to these factors. The combined statistical SST prediction scheme can also be used to improve statistical regional rainfall forecasts that use SST anomaly patterns as predictors. Copyright Crown Copyright 2003. Published by John Wiley & Sons, Ltd. [source]

Laboratory diagnosis of Mycoplasma pneumoniae infection

F. Daxboeck
Diagnosis of Mycoplasma pneumoniae infection is challenging due to the fastidious nature of the pathogen, the considerable seroprevalence, and the possibility of transient asymptomatic carriage. During recent years, various new techniques have been adapted for the diagnosis of M. pneumoniae infection, notably in the field of molecular biology. Standard polymerase chain reaction (PCR) is currently the method of choice for direct pathogen detection, but several PCR-related methods provide enhanced sensitivity or more convenient handling procedures, and have been successfully applied for research purposes. Among these techniques are real-time PCR, nested PCR, reverse transcriptase PCR (RT-PCR) and multiplex PCR. Generally, amplification-based methods have replaced hybridization assays and direct antigen detection. Serology, which is the basic strategy for mycoplasma diagnosis in routine clinical practice, has been improved by the widespread availability of sensitive assays for separate detection of different antibody classes. For the diagnosis of mycoplasma pneumonia, serology and direct pathogen detection should be combined. Extrapulmonary diseases may be diagnosed by direct pathogen detection alone, but the value of this diagnostic approach is limited by the probably immunologically mediated pathogenesis of some manifestations. This review summarizes the current state of Mycoplasma pneumoniae diagnosis, with special reference to molecular techniques. The value of different methods for routine diagnosis and research purposes is discussed. [source]