Noise transmission through flat rectangular panels into a closed cavity

Five panels backed by a closed cavity were studied experimentally and analytically to determine the noise transmission characteristics of the coupled panel-cavity system. The closed cavity was studied both with and without fiber-glass lining to provide either an absorbent or a reverberant acoustic space. The effects on noise reduction of cavity absorption, measurement location within the cavity, panel mass, and panel stiffness were examined. Results indicated that both measurement location and absorption in the cavity have significant effects on the noise reduction. Increasing panel mass improves the noise reduction at almost all frequencies, and increasing panel stiffness improves nose reduction below the fundamental resonance frequency. A simple, one dimensional analytical model was developed which provided good agreement with the experimental results

DNA sensing by electrocatalysis with hemoglobin

Electrocatalysis offers a means of electrochemical signal amplification, yet in DNA-based sensors, electrocatalysis has required high-density DNA films and strict assembly and passivation conditions. Here, we describe the use of hemoglobin as a robust and effective electron sink for electrocatalysis in DNA sensing on low-density DNA films. Protein shielding of the heme redox center minimizes direct reduction at the electrode surface and permits assays on low-density DNA films. Electrocatalysis with methylene blue that is covalently tethered to the DNA by a flexible alkyl chain linkage allows for efficient interactions with both the base stack and hemoglobin. Consistent suppression of the redox signal upon incorporation of a single cytosine-adenine (CA) mismatch in the DNA oligomer demonstrates that both the unamplified and the electrocatalytically amplified redox signals are generated through DNA-mediated charge transport. Electrocatalysis with hemoglobin is robust: It is stable to pH and temperature variations. The utility and applicability of electrocatalysis with hemoglobin is demonstrated through restriction enzyme detection, and an enhancement in sensitivity permits femtomole DNA sampling

Shear-invariant Sliding Contact Perception with a Soft Tactile Sensor

Manipulation tasks often require robots to be continuously in contact with an object. Therefore tactile perception systems need to handle continuous contact data. Shear deformation causes the tactile sensor to output path-dependent readings in contrast to discrete contact readings. As such, in some continuous-contact tasks, sliding can be regarded as a disturbance over the sensor signal. Here we present a shear-invariant perception method based on principal component analysis (PCA) which outputs the required information about the environment despite sliding motion. A compliant tactile sensor (the TacTip) is used to investigate continuous tactile contact. First, we evaluate the method offline using test data collected whilst the sensor slides over an edge. Then, the method is used within a contour-following task applied to 6 objects with varying curvatures; all contours are successfully traced. The method demonstrates generalisation capabilities and could underlie a more sophisticated controller for challenging manipulation or exploration tasks in unstructured environments. A video showing the work described in the paper can be found at https://youtu.be/wrTM61-pieUComment: Accepted in ICRA 201

Ohio and South Carolina Business Attitudes Toward Biotechnology

Author Institution: Science Communications Director, Monsanto CompanyRecent developments in biotechnology have resulted in an increased interest in the monitoring of public attitudes and perceptions of this area of science. The audiences of interest have broadened to include not only the general public, but also various public opinion leadership groups and groups involved in decision-making

Optimum Slenderness Ratio of a Stable Low-Drag Body

This paper presents a theoretical and experimental method of selecting the optimum slenderness ratio of a body with cylindrical midsection. Whether such a body is a large submarine or its arch enemy, the depth charge, the problem rem a ins to find a slenderness ratio which will permit the fastest possible velocity consistent with the power or sinking weight available. Considerable research has been done to determine the hydrodynamic characteristics of nose shapes both alone and combined with various afterbodies. In one of our reports we have pointed out that any one of several different nose shapes could be used on a particular body with little change in the total drag coefficient, and tests for certain afterbody shapes would probably bring similar results. Due to practical considerations, most bodies have a cylindrical midsection. Therefore, a typical underwater body of axial symmetry consists of arbitrarily selected nose and afterbody shapes separated by a cylindrical midsection. For dynamic stability, any underwater body must have fins which increase the surface area and, to some degree, the residual drag. We must necessarily consider the effect of such fins on slenderness ratio. In the following discussion of a particular concrete example, the emphasis has been placed on a body with a nose and afterbody with fins, of the same geometrical shape as the MK 13-1 torpedo (less shroud ring). The MK 13-1 torpedo is dynamically stable, has a cylindrical midsection, and has been tested with other nose shapes. After examination of the factors affecting the optimum slenderness ratio, it is found that a reasonably large variation from the theoretical optimum value will have little practical effect on the velocity of the body. Because of practical factors involved in the design of an undersea body, it may be desirable from the designer's point of view to have a relatively large slenderness ratio. This investigation shows that as far as drag per unit volume is concerned, the designer will will pay very little, if any, penalty if he disregards the drag factor and bases his selection of slenderness ratio entirely on such items as tactical requirements of maneuverability, structural design and utilization of internal space

A review of residual stress analysis using thermoelastic techniques

Thermoelastic Stress Analysis (TSA) is a full-field technique for experimental stress analysis that is based on infra-red thermography. The technique has proved to be extremely effective for studying elastic stress fields and is now well established. It is based on the measurement of the temperature change that occurs as a result of a stress change. As residual stress is essentially a mean stress it is accepted that the linear form of the TSA relationship cannot be used to evaluate residual stresses. However, there are situations where this linear relationship is not valid or departures in material properties due to manufacturing procedures have enabled evaluations of residual stresses. The purpose of this paper is to review the current status of using a TSA based approach for the evaluation of residual stresses and to provide some examples of where promising results have been obtained

Environments of Redshift Survey Compact Groups of Galaxies

Redshift Survey Compact Groups (RSCGs) are tight knots of N >= 3 galaxies selected from the CfA2+SSRS2 redshift survey. The selection is based on physical extent and association in redshift space alone. We measured 300 new redshifts of fainter galaxies within 1 h^{-1} Mpc of 14 RSCGs to explore the relationship between RSCGs and their environments. 13 of 14 RSCGs are embedded in overdense regions of redshift space. The systems range from a loose group of 5 members to an Abell cluster. The remaining group, RSCG 64, appears isolated. RSCGs are isolated and distinct from their surroundings to varying degrees, as are the Hickson Compact Groups. Among the 13 embedded RSCGs, 3 are distinct from their general environments (RSCG 9, RSCG 11 and RSCG 85).Comment: 35 pages, including 10 figures and 5 tables, accepted for publication in the Astronomical Journa