Moving live dissociated neurons with an optical tweezer

The use of an optical tweezer for moving dissociated neurons was studied. The main features of the tweezers are outlined as well as the general principles of its operation. Infrared beams at 980 and 1064 nm were used, focused so as to make a trap for holding neurons and moving them. Absorption by cells at those wavelengths is very small. Experiments were done to evaluate nonsticky substrate coatings, from which neurons could be easily lifted with the tweezers. The maximum speed of cell movement as a function of laser power was determined. Detailed studies of the damage to cells as a function of beam intensity and time of exposure were made. The 980 nm beam was much less destructive, for reasons that are not understood, and could be used to safely move cells through distances of millimeters in times of seconds. An illustrative application of the use of the tweezers to load neurons without damage into plastic cages on a glass substrate was presented. The conclusion is that optical tweezers are an accessible and practical tool for helping to establish neuron cultures of cells placed in specific locations

Pressure-Dependence Of The Hyperfine Field Of A Cd Probe In A Relaxed Trivacancy Complex In Ni

Perturbed gamma-gamma-angular-correlation experiments were carried out using extremely dilute Cd-111 probes to measure the pressure dependence of the magnetic hyperfine field at a vacancy-solute complex in Ni in which the Cd probe is relaxed to the center of a tetrahedron of vacancies. The pressure dependence of the hyperfine field of the defect-free substitutional site was found to be dH(hf)/dp = -0.038(6) kG/kbar, which agrees with a previous measurement. The pressure dependence of the hyperfine field associated with the vacancy complex was found to be dH(hf)/dp = -0.023(4) kG/kbar. Results are not found to be consistent with a simple picture of the hyperfine-field-production mechanism obtained from recent first-principles calculations

High-Risk Flood Control Dams on Difficult Soil Foundations

Addicks and Barker Dams are two flood risk management structures owned and operated by the U.S. Army Corps of Engineers (USACE) and recently classified as extremely high risk. These dams were built in the 1940’s in west Houston, Texas, upstream of a densely populated metropolitan area. The dams consist of 11 and 13 miles of rolled earth embankments, outlet structures with five barrel conduits, and uncontrolled spillways at both ends of both dams. The original design of both dams provided for four of the five outlet conduit barrels to be ungated, permitting a combined uncontrolled discharge from both dams of 15,700 cubic feet per second into Buffalo Bayou. Due to urban development throughout the 1940s and 50s, all conduit barrels of both dams were gated by 1963 to allow restricted discharge flows into Buffalo Bayou during normal operating conditions. These fundamental changes in operations together with the existence of erodible fine sand and silt foundation soil conditions led to the initiation of several potential failure modes at the outlet structures. These have been recently confirmed by the findings of voids beneath the conduits in both dams. Interim measures have temporarily stopped progression of the failures. This paper’s presentation mainly focuses on the history and issue evaluations of the outlet structures of these dams and the interim measures and long term solutions under consideration for reducing risks associated with these critical infrastructures

Development of a porcine skeletal muscle cDNA microarray: analysis of differential transcript expression in phenotypically distinct muscles

RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are.Abstract Background Microarray profiling has the potential to illuminate the molecular processes that govern the phenotypic characteristics of porcine skeletal muscles, such as hypertrophy or atrophy, and the expression of specific fibre types. This information is not only important for understanding basic muscle biology but also provides underpinning knowledge for enhancing the efficiency of livestock production. Results We report on the de novo development of a composite skeletal muscle cDNA microarray, comprising 5500 clones from two developmentally distinct cDNA libraries (longissimus dorsi of a 50-day porcine foetus and the gastrocnemius of a 3-day-old pig). Clones selected for the microarray assembly were of low to moderate abundance, as indicated by colony hybridisation. We profiled the differential expression of genes between the psoas (red muscle) and the longissimus dorsi (white muscle), by co-hybridisation of Cy3 and Cy5 labelled cDNA derived from these two muscles. Results from seven microarray slides (replicates) correctly identified genes that were expected to be differentially expressed, as well as a number of novel candidate regulatory genes. Quantitative real-time RT-PCR on selected genes was used to confirm the results from the microarray. Conclusion We have developed a porcine skeletal muscle cDNA microarray and have identified a number of candidate genes that could be involved in muscle phenotype determination, including several members of the casein kinase 2 signalling pathway.Peer Reviewe