Probabilistic Weibull behavior and mechanical properties of MEMS brittle materials

The objective of this work is to present a brief overview of a probabilistic design methodology for brittle structures, review the literature for evidence of probabilistic behavior in the mechanical properties of MEMS (especially strength), and to investigate whether evidence exists that a probabilistic Weibull effect exists at the structural microscale. Since many MEMS devices are fabricated from brittle materials, that raises the question whether these miniature structures behave similar to bulk ceramics. For bulk ceramics, the term Weibull effect is used to indicate that significant scatter in fracture strength exists, hence requiring probabilistic rather than deterministic treatment. In addition, the material's strength behavior can be described in terms of the Weakest Link Theory (WLT) leading to strength dependence on the component's size (average strength decreases as size increases), and geometry/loading configuration (stress distribution). Test methods used to assess the mechanical properties of MEMS, especially strength, are reviewed. Four materials commonly used to fabricate MEMS devices are reviewed in this report. These materials are polysilicon, single crystal silicon (SCS), silicon nitride, and silicon carbide.     

Effect of thermal treatment on ZnO substrate for epitaxial growth

ZnO is a highly efficient photon emitter, and has optical and piezoelectric properties that are attractive for a variety of applications in sensors and potentially optoelectronic devices such as emitters. Due to its identical stacking order and close lattice match to GaN, it is also being developed as a substrate material for GaN epitaxy. However, the surface finish of the ZnO is such that much of the damage induced by sawing and follow up mechanical polishing remains. We developed a thermal treatment method to eliminate surface damage on the 0 face of ZnO (0 0 0 1) to prepare it for epitaxial growth. Atomic force microscopy images of ZnO (0 0 0 1) annealed at 1050 °C for 3 h etc. show that residual scratches from mechanical polishing are removed and atomically flat, terrace-like surfaces are attained. In addition, low-temperature photoluminescence and high-resolution X-ray diffraction measurements have been employed to investigate the effect of annealing on ZnO substrates.     

PACAP-38 in Acute ST-Segment Elevation Myocardial Infarction in Humans and Pigs: A Translational Study

Acute myocardial infarction (MI) is one of the most common causes of death worldwide. Pituitary adenylate cyclase activating polypeptide (PACAP) is a cardioprotective neuropeptide expressing its receptors in the cardiovascular system. The aim of our study was to examine tissue PACAP-38 in a translational porcine MI model and plasma PACAP-38 levels in patients with ST-segment elevation myocardial infarction (STEMI). Significantly lower PACAP-38 levels were detected in the non-ischemic region of the left ventricle (LV) in MI heart compared to the ischemic region of MI-LV and also to the Sham-operated LV in porcine MI model. In STEMI patients, plasma PACAP-38 level was significantly higher before percutaneous coronary intervention (PCI) compared to controls, and decreased after PCI. Significant negative correlation was found between plasma PACAP-38 and troponin levels. Furthermore, a significant effect was revealed between plasma PACAP-38, hypertension and HbA1c levels. This was the first study showing significant changes in cardiac tissue PACAP levels in a porcine MI model and plasma PACAP levels in STEMI patients. These results suggest that PACAP, due to its cardioprotective effects, may play a regulatory role in MI and could be a potential biomarker or drug target in MI.     

“Those found responsible have been sacked”: some observations on the usefulness of error

Erik Hollnagel’s body of work in the past three decades has molded much of the current research approach to system safety, particularly notions of “error”. Hollnagel regards “error” as a dead-end and avoids using the term. This position is consistent with Rasmussen’s claim that there is no scientifically stable category of human performance that can be described as “error”. While this systems view is undoubtedly correct, “error” persists. Organizations, especially formal business, political, and regulatory structures, use “error” as if it were a stable category of human performance. They apply the term to performances associated with undesired outcomes, tabulate occurrences of “error”, and justify control and sanctions through “error”. Although a compelling argument can be made for Hollnagel’s view, it is clear that notions of “error” are socially and organizationally productive. The persistence of “error” in management and regulatory circles reflects its value as a means for social control.     

Using cognitive artifacts to understand distributed cognition

Studies of patient safety have identified gaps in current work including the need for research about communication and information sharing among healthcare providers. They have also encouraged the use of decision support tools to improve human performance. Distributed cognition is the shared awareness of goals, plans, and details that no single individual grasps. Cognitive artifacts are objects such as: schedules, display boards, lists, and worksheets that form part of a distributed cognition. Cognitive artifacts that are related to operating room (OR) scheduling include: the availabilities sheet, master schedule, OR graph, and OR board. All provide a "way in" to understand how teams in the acute care setting dynamically plan and manage the balance between demand for care and the resources available to provide it. This work has import for the way that information technology supports the organization, management, and use of healthcare resources. Better computer-supported cognitive artifacts will benefit patient safety by making teamwork processes, planning, communications, and resource management more resilient.     

Healthcare groups at work: further lessons from research into large-scale coordination

The first special issue in Large-Scale Coordination earlier this year showed the breadth of application research from air traffic control to the military and multi-agency emergency response. This special issue shows depth of research at large scale in healthcare. These studies of large-scale coordination examine work between and across groups, beyond earlier conceptions of social human factors. Revealing the complexity of work domains and the subtle, yet effective, ways that workers negotiate its challenges opens the way to develop information and communications technology support tools that are grounded in a scientific understanding.     

Online frequency domain system identification based on a virtualinstrument

System identification is an inherently iterative process. Yet, limited attempts have been made so far to implement the whole identification loop in a single device. This paper discusses the difficulties of the task and presents a solution based on a Matlab toolbox and a set of virtual instruments. During the identification session, the obtained models may call for refinement or validation by new experiments. Using this integrated software-hardware tool, these subsequent experiments can be accomplished online with the identification procedure. As a demonstration, the modeling of a hairdryer is described. The universal applicability of this solution is believed to be guaranteed by the modular architecture of virtual instrumentation and the general definition of the software interface developed. The interface allows combining Matlab-based identification packages with virtual instruments or pure hardware interfaced to Matlab     

Exposure to dissent and recall of information.

Recent work on minority influence has led to a debate about whether majorities and minorities exercise different forms of influence. C. L. Nemeth (see record 1986-14271-001) has argued that consistent minorities induce different cognitive processes than do consistent majorities, with a resulting impact on the quality of the judgments rendered. Two experiments test this theory. In Experiment 1, Ss heard 3 tape-recorded lists of words and learned that either a minority or a majority differed in the category "first noticed." This feedback occurred either once or over 3 trials. When exposure was once, recall was not affected by the source; when it was consistent, Ss exposed to the minority view recalled more words than those exposed to the majority view. In Experiment 2, Ss were exposed to a minority view that was either consistent over time or inconsistent over time. Ss exposed to a consistent minority had better recall than control Ss. Exposure to an inconsistent minority did not improve recall. The results offer support for the Nemeth formulation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intercomparison of the Realizations of the ITS-90 from 83.8058 K to 692.677 K among European NMIs

The EUROMET.T-K3 comparison is the regional extension of CCT-K3. The comparison involved the six European national metrology institutes (NMIs) previously involved in CCT-K3 (LNE-INM/CNAM, SMU, INRiM, NMi-VSL, NPL, PTB) and 18 additional European national laboratories. The comparison was divided into five different loops, each coordinated by a co-pilot chosen from the laboratories having participated in the CCT-K3 comparison. LNE-INM/CNAM played the role of pilot in linking the five loops. In each loop, an artifact in the form of a standard platinum resistance thermometer (SPRT, 25 Ω) was circulated among the participating laboratories. To have sufficient information about the possible drift of the SPRTs, the co-pilots performed a calibration over the full temperature range at the beginning and at the end of the loop. A EUROMET reference value (ERV), taking into account the whole comparison, was defined, and the differences (T _Lab − T _ERV) were calculated with the associated uncertainties. The method for establishing the link between the participants in CCT-K3 and in EUROMET.T-K3 is described. Institut National de Métrologie (BNM-INM/CNAM at the time of the comparison, LNE-INM/CNAM since 1 January 2005), Paris, France.