Weep hole inspection by circumferential creeping waves

This paper reports the development of a novel ultrasonic inspection technique that detects radial fatigue cracks on the far side of thin airframe stiffener ‘weep’ holes. These cracks are located on the upper part of the weep hole (12 o'clock position), away from the lower skin of the wing. Cracks in this position are not readily detectable by conventional ultrasonic inspection techniques, particularly for short cracks. A special technique using circumferential creeping waves was adapted to inspect for these cracks. The conventional creeping wave technique experiences a strong specular reflection from the near surface of the hole that masks the creeping wave signal that arrives later in time. In order to overcome this difficulty, a split-aperture (two-element) transducer was used that resulted in the specular and creeping wave echoes being approximately equal in magnitude. The two separate transducers allowed us to alternate between pulse-echo and pitch-catch modes of operation with a resulting improvement in detection sensitivity. In the case of 0.25-inch-diameter weep holes, optimum sensitivity was calculated to be around 5 MHz. The detection threshold was found to be approximately 0.003 inches and the signal saturated at crack lengths in excess of 0.020 inches. The original paint and surface finish had no substantial adverse effects on the technique's sensitivity. Similarly, changing the weep hole diameter or chamfer conditions did not significantly affect the technique's performance. These results were obtained using specimens with both machined notches and real fatigue cracks.     

Tourism as tragedy? Common problems with water in post-revolutionary Nicaragua

This paper examines the increased demand placed on limited water resources by a rapidly growing tourism sector in Playa Gigante, Nicaragua. Results from field campaigns suggest that recharge of the local aquifer may not meet burgeoning tourism demands for water. This paper also points to initial conflicts over water between locals and tourism operations, which are further complicated by ineffective implementation of national water policies and the common pool nature of groundwater. The conclusion discusses the need for more extensive research and better implementation of water policy through community governance and collaboration.     

Mass spectrometric immunoassay and MRM as targeted MS-based quantitative approaches in biomarker development: Potential applications to cardiovascular disease and diabetes

Type 2 diabetes mellitus (T2DM) is an important risk factor for cardiovascular disease (CVD)—the leading cause of death in the United States. Yet not all subjects with T2DM are at equal risk for CVD complications; the challenge lies in identifying those at greatest risk. Therapies directed toward treating conventional risk factors have failed to significantly reduce this residual risk in T2DM patients. Thus newer targets and markers are needed for the development and testing of novel therapies. Herein we review two complementary MS-based approaches—mass spectrometric immunoassay (MSIA) and MS/MS as MRM—for the analysis of plasma proteins and PTMs of relevance to T2DM and CVD. Together, these complementary approaches allow for high-throughput monitoring of many PTMs and the absolute quantification of proteins near the low picomolar range. In this review article, we discuss the clinical relevance of the high density lipoprotein (HDL) proteome and Apolipoprotein A-I PTMs to T2DM and CVD as well as provide illustrative MSIA and MRM data on HDL proteins from T2DM patients to provide examples of how these MS approaches can be applied to gain new insight regarding cardiovascular risk factors. Also discussed are the reproducibility, interpretation, and limitations of each technique with an emphasis on their capacities to facilitate the translation of new biomarkers into clinical practice.     

Quantitative mass spectrometry for colorectal cancer proteomics

This review documents the uses of quantitative MS applied to colorectal cancer (CRC) proteomics for biomarker discovery and molecular pathway profiling. Investigators are adopting various labeling and label-free MS approaches to quantitate differential protein levels in cells, tumors, and plasma/serum. We comprehensively review recent uses of this technology to examine mouse models of CRC, CRC cell lines, their secretomes and subcellular fractions, CRC tumors, CRC patient plasma/serum, and stool samples. For biomarker discovery these approaches are uncovering proteins with potential diagnostic and prognostic utility, while in vitro cell culture experiments are characterizing proteomic and phosphoproteomic responses to disrupted signaling pathways due to mutations or to inhibition of drugable enzymes.     

Quantitative calcium resistivity based method for accurate and scalable water vapor transmission rate measurement

The development of flexible organic light emitting diode displays and flexible thin film photovoltaic devices is dependent on the use of flexible, low-cost, optically transparent and durable barriers to moisture and/or oxygen. It is estimated that this will require high moisture barriers with water vapor transmission rates (WVTR) between 10(-4) and 10(-6) g/m(2)/day. Thus there is a need to develop a relatively fast, low-cost, and quantitative method to evaluate such low permeation rates. Here, we demonstrate a method where the resistance changes of patterned Ca films, upon reaction with moisture, enable one to calculate a WVTR between 10 and 10(-6) g/m(2)/day or better. Samples are configured with variable aperture size such that the sensitivity and/or measurement time of the experiment can be controlled. The samples are connected to a data acquisition system by means of individual signal cables permitting samples to be tested under a variety of conditions in multiple environmental chambers. An edge card connector is used to connect samples to the measurement wires enabling easy switching of samples in and out of test. This measurement method can be conducted with as little as 1 h of labor time per sample. Furthermore, multiple samples can be measured in parallel, making this an inexpensive and high volume method for measuring high moisture barriers.     

Evaluation of realtime people tracking for indoor environments using ubiquitous motion sensors and limited wireless network infrastructure

We present the development and evaluation of a realtime indoor localisation system for tracking people. Our aim was to track a person’s indoor position using dead-reckoning, while limiting position error without depending on extensive wireless network infrastructure. The Indoor People Tracker used wearable motion sensors, a floor-plan map and a limited wireless sensor network for proximity ranging. We evaluated how the position accuracy of the Indoor People Tracker was affected by floor-plan map features, wireless proximity range and motion information. The advantage of the Indoor People Tracker was found; it was able to achieve accurate position resolution with minimal error, while not depending on wireless proximity.