Carbon nanotube (CNT) yarns are micron-size fibers that contain thousands of intertwined CNTs in their cross sections and exhibit piezoresistance characteristics that can be tapped for sensing purposes. Sensor yarns can be integrated into polymeric and composite materials to measure strain through resistance measurements without adding weight or altering the integrity of the host material. This paper includes the details of novel strain gauge sensor configurations comprised of CNT yarn, the numerical modeling of their piezoresistive response, and the parametric analysis schemes that determines the highest sensor sensitivity to mechanical loading. The effect of several sensor configuration parameters are discussed including the inclination and separation of the CNT yarns within the sensor, the mechanical properties of the CNT yarn, the direction and magnitude of the applied mechanical load, and the dimensions and shape of the sensor. The sensor configurations that yield the highest sensitivity are presented and discussed in terms of the mechanical and electrical properties of the CNT yarn. It is shown that strain gauge sensors consisting of CNT yarn are sensitive enough to measure strain, and could exhibit even higher gauge factors than those of metallic foil strain gauges.
Loss of heterozygosity on chromosome 9 has been reported in a variety of human cancers. The cyclin-dependent kinase inhibitor p16 gene, mapped on chromosome 9p21, is presumed to be the tumor-suppressor gene localized in this chromosome. The aim of our study was to determine, in 26 Barrett's adenocarcinomas and 20 squamous-cell carcinomas of the esophagus, the prevalence of loss of heterozygosity on chromosome 9 by typing of microsatellite loci and mutation of p16 by direct sequencing of exons 1 and 2. Allelic losses were found in 69% of adenocarcinomas, but only a microdeletion in exon 1 of p16 occurred in 1 tumor. Among squamouscell carcinomas, 65% had allelic losses and 5 tumors were mutated on the p16 gene (1 deletion, 3 nucleotide substitutions and 1 insertion). The relatively low rate of p16 mutation observed here coupled with the high frequency of loss of heterozygosity on chromosome 9 suggests that one or several tumor-suppressor gene(s) distinct from p16 may be the target(s) of allelic deletion in most esophageal cancers or that p16 is inactivated in another way. Int. J. Cancer 72:27-30, 1997.r 1997 Wiley-Liss, Inc.Cancer of the esophagus is among the most common and severe malignant neoplasms worldwide and occurs primarily in 2 forms: squamous-cell carcinoma (SCC) and adenocarcinoma arising in the context of Barrett's esophagus. The mechanisms underlying pathogenesis of the disease are unclear, though both environmental and genetic factors are suspected to play roles. Previously, no tumorsuppressor gene other than p53 (Gleeson et al., 1995;Muzeau et al., 1996) has been reported to play an important role during esophageal tumorigenesis.A high frequency of loss of heterozygosity (LOH) and/or homozygous deletion affecting chromosome 9p21-22 has been reported in a variety of primary tumors and cell lines (Holland et al., 1994;Cairns et al., 1994). Chromosome 9, therefore, is presumed to contain a tumor-suppressor gene(s) involved in the genesis of different human tumors.A new tumor-suppressor gene, p16 (also known as CDKN2A, INK4A or MTS1), has been identified and mapped on chromosome 9p21. It contains 3 coding exons (Serrano et al., 1993) and encodes a 156-amino-acid protein, previously identified as a cyclindependent kinase (CDK) inhibitor that has capacities to bind CDK4 and CDK6 and to inhibit cellular proliferation by preventing entry into the S phase of the cell cycle (Serrano et al., 1993;Lukas et al., 1995). This gene is homozygously deleted or mutated in a variety of cell lines derived from tumors and has been proposed to constitute a potential target of point mutations and deletions in primary human tumors (Pollock et al., 1996).There is a controversy regarding the implication of p16 gene alterations in the development of esophageal cancers (Mori et al., 1994;Okamoto et al., 1994;Zhou et al., 1994;Igaki et al., 1995;Liu et al., 1995;Suzuki et al., 1995; Esteve et al., 1996;Maesawa et al., 1996). The present study was thus undertaken to determine the prevalence of LOH on chromosome 9 and p16 mutatio...
Carbon nanotube yarns are micron-scale fibers comprised by tens of thousands of carbon nanotubes in their cross section and exhibiting piezoresistive characteristics that can be tapped to sense strain. This paper presents the details of novel foil strain gauge sensor configurations comprising carbon nanotube yarn as the piezoresistive sensing element. The foil strain gauge sensors are designed using the results of parametric studies that maximize the sensitivity of the sensors to mechanical loading. The fabrication details of the strain gauge sensors that exhibit the highest sensitivity, based on the modeling results, are described including the materials and procedures used in the first prototypes. Details of the calibration of the foil strain gauge sensors are also provided and discussed in the context of their electromechanical characterization when bonded to metallic specimens. This characterization included studying their response under monotonic and cyclic mechanical loading. It was shown that these foil strain gauge sensors comprising carbon nanotube yarn are sensitive enough to capture strain and can replicate the loading and unloading cycles. It was also observed that the loading rate affects their piezoresistive response and that the gauge factors were all above one order of magnitude higher than those of typical metallic foil strain gauges. Based on these calibration results on the initial sensor configurations, new foil strain gauge configurations will be designed and fabricated, to increase the strain gauge factors even more.
A linear acoustic levitation transportation system based on a ring-type vibrator is presented. The system is composed by two 21-kHz Langevin transducers connected to a ring-shaped structure formed by two semicircular sections and two flat plates. In this system, a flexural standing wave is generated along the ring structure, producing an acoustic standing wave between the vibrating ring and a plane reflector located at a distance of approximately a half wavelength from the ring. The acoustic standing wave in air has a series of pressure nodes, where small particles can be levitated and transported. The ring-type transportation system was designed and analyzed by using the finite element method. Additionally, a prototype was built and the acoustic levitation and transport of a small polystyrene particle was demonstrated.
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