An engineering assessment of probabilistic structural reliability analyses

The application of probabilistic structural reliability analyses to complex structural components and/or systems involves a multitude of engineering problems or decisions, many of which are outside the experience of conventional engineering analysts. The purpose of this paper is to provide some practical perspective on such applications so that the methodology can be more effectively utilized as input to design decisions. Specifically, the discussion covers the most important considerations in applying structural reliability methodology, the limitations and implied development needs of structural reliability analysis state of the art, and some practical guidance on the level of detail in applying the methods to engineering problems. Specific examples are presented.     

The application of methods of non-linear dynamics for the improved and predictive recognition of patients threatened by sudden cardiac death

OBJECTIVES: This study introduces new methods of non-linear dynamics (NLD) and compares these with traditional methods of heart rate variability (HRV) and high resolution ECG (HRECG) analysis in order to improve the reliability of high risk stratification. METHODS: Simultaneous 30 min high resolution ECG's and long-term ECG's were recorded from 26 cardiac patients after myocardial infarction (MI). They were divided into two groups depending upon the electrical risk, a low risk group (group 2, n = 10) and a high risk group (group 3, n = 16). The control group consisted of 35 healthy persons (group 1). From these electrocardiograms we extracted standard measures in time and frequency domain as well as measures from the new non-linear methods of symbolic dynamics and renormalized entropy. RESULTS: Applying discriminant function techniques on HRV analysis the parameters of non-linear dynamics led to an acceptable differentiation between healthy persons and high risk patients of 96%. The time domain and frequency domain parameters were successful in less than 90%. The combination of parameters from all domains and a stepwise discriminant function separated these groups completely (100%). Use of this discriminant function classified three patients with apparently low (no) risk into the same cluster as high risk patients. The combination of the HRECG and HRV analysis showed the same individual clustering but increased the positive value of separation. CONCLUSIONS: The methods of NLD describe complex rhythm fluctuations and separate structures of non-linear behavior in the heart rate time series more successfully than classical methods of time and frequency domains. This leads to an improved discrimination between a normal (healthy persons) and an abnormal (high risk patients) type of heart beat generation. Some patients with an unknown risk exhibit similar patterns to high risk patients and this suggests a hidden high risk. The methods of symbolic dynamics and renormalized entropy were particularly useful measures for classifying the dynamics of HRV.     

A new protein conjugate that replaces the use of secondary antibodies engineered from the two staphylococcal enzymes protein A and 6-phospho-{beta}-galactosidase

The lacG gene encoding the 6-phospho-ß-galactosidase(E.C.3.2.1.85) of Staphylococcus aureus was fused to the proteinA gene in the plasmid pRIT2T. Escherichia coli cells containingthis plasmid produce a fusion protein with both IgG bindingand 6-phospho-ß-galactosidase activities after heatinduction. The recombinant gene was overexpressed and the hybridprotein was purified to homogeneity in high yield. The chimericprotein was shown to have almost identical enzymatic characteristicsto pure 6-phospho-ß-galactosidase. This result leadsto the conclusion that a free N-terminus of the 6-phospho-ß-galactosidaseis not required for biological activity. The hybrid proteinof protein A and 6-phospho-ß-galactosidase was usedas an enzyme conjugate in enzyme-linked immunosorbent assays(ELISA). The experiments presented demonstrate that the 6-phospho-ß-galactosidaseis a suitable fusion partner in various diagnostic applicationswhere an unique biological activity is required.     

Children's involvement in intervention selection: Acceptability of interventions for misbehaving peers.

Examined children's acceptance of a variety of common school-based methods for dealing with misbehaving peers in 2 experiments in which 102 6th-graders served as Ss. Ss were surveyed for their suggestions for treating peers' classroom misbehaviors and their acceptance of different teacher-implemented interventions for modifying 2 behavior problems. The main finding was that Ss differentially rated the acceptability of 12 common interventions. From among 3 categories of interventions, Ss rated private teacher–student interactions, group reinforcement, and negative sanctions for the misbehaving children as most acceptable. Public reprimand and negative group contingencies were rated as unacceptable interventions. Behavior problem severity did not have a significant impact on Ss' ratings of intervention acceptability except for traditional interventions. Methodological, theoretical, and developmental considerations in treatment acceptability are discussed. (23 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The interactive effect of leader-member exchange and communication frequency on performance ratings.

The authors tested the hypothesis that communication frequency moderates the relationship between leader-member exchange (LMX) and job-performance ratings. In a study of 188 private sector workers, they found that LMX was more strongly related to job-performance ratings among individuals reporting frequent communication with the supervisor than among those reporting infrequent communication. At high levels of LMX, workers reporting frequent communication with the supervisor received more favorable job-performance ratings than did workers reporting infrequent communication. In contrast, at low levels of LMX, workers reporting frequent communication with the supervisor received less favorable job-performance ratings than workers reporting infrequent communication. The authors conducted a 2nd study of 153 public sector workers to provide a constructive replication and found similar results. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Taking a hands-on approach: Apparent grasping ability scales the perception of object size.

We examined whether the apparent size of an object is scaled to the morphology of the relevant body part with which one intends to act on it. To be specific, we tested if the visually perceived size of graspable objects is scaled to the extent of apparent grasping ability for the individual. Previous research has shown that right-handed individuals perceive their right hand as larger and capable of grasping larger objects than their left. In the first 2 experiments, we found that objects looked smaller when placed in or judged relative to their right hand compared to their left. In the third experiment, we directly manipulated apparent hand size by magnifying the participants' hands. Participants perceived objects to be smaller when their hand was magnified than when their hand was unmagnified. We interpret these results as demonstrating that perceivers use the extent of their hands' grasping abilities as “perceptual rulers” to scale the apparent size of graspable objects. Furthermore, hand size manipulations did not affect the perceived size of objects too big to be grasped, which suggests that hand size is only used as a scaling mechanism when the object affords the relevant action, in this case, grasping. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

In defense of controversy.

Discovering truth is not the sole agenda for every scientist. The rewards of achieving paradigm hegemony are huge and serve to justify all manner of strategies and tactics. In this issue and some that have preceded it, scientific paradigm clashes have been brought into the bright light of public scrutiny. I believe a science that is critical progresses faster than one driven solely by induction. Debate is undeniably a part of science, one from which spectators (practitioners and researchers) benefit. A greater understanding of each position is made easier by a direct and clear statement of that position and of what its proponents view as problems with the opposing paradigm. It is not expected that those who read an extreme position will adopt it; however, they may come to understand it better and draw their own conclusions accordingly. Controversy, properly understood and used, can serve the scientific community by sharpening the focus on the true issues where research is most vital to further our understanding of human behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)