Surface resistance investigations of the exchange of 3D monolayers with molecules self-assembled on planar gold surfaces

Simple four probe resistance measurements have been used to study the ligand exchange between monolayer protected clusters of Au and Ag with dithiol monolayers on planar gold surfaces. The decrease in in-plane resistance upon exposure of functionalized dithiol monolayer covered gold surfaces to monolayer protected cluster solutions is attributed to the attachment of free thiol groups of the monolayers on the gold surfaces to the clusters. This linking of clusters to monolayers results in screening of electron-adsorbate vibration interaction causing a decrease in resistance. There can also be additional factors determining the observed changes

Undetected locked-joint failures in kinematically redundant manipulators: a workspace analysis

Includes bibliographical references.Robots are frequently used for operations in hostile environments. The very nature of these environments, however, increases the likelihood of robot failures. Common failure tolerance techniques rely on effective failure detection. Since a failure may not always be successfully detected, or even if detected, may not be detected soon enough, it becomes important to consider the behavior of manipulators with undetected failures. This work focuses on developing techniques to analyze a manipulator's workspace and identify regions in which tasks, characterized by sequences of point-to-point moves, can be completed even with such failures. Measures of fault tolerance are formulated to allow for the evaluation of the workspace.This work was supported by Sandia National Labs under contract no. AL-3011 and by NSF under contract no. MIP-9708309

Analysis of the post-fault behavior of robotic manipulators, An

Includes bibliographical references.Operations in hazardous or remote environments are invariably performed by robots. The hostile nature of the environments, however, increase the likelihood of failures for robots used in such applications. The difficulty and delay in the detection and consequent correction of these faults makes the post-fault performance of the robots particularly important. This work investigates the behavior of robots experiencing undetected locked-joint failures in a general class of tasks characterized by point-to-point motion. The robot is considered to have "converged" to a task position and orientation if all its joints come to rest when the end-effector is at that position. It is seen that the post-fault behavior may be classified into three categories: 1) The robot converges to the task position; 2) the robot converges to a position other than the task position; or 3) the robot does not converge, but keeps moving forever. The specific conditions for convergence are identified, and the different behaviors illustrated with examples of simple planar manipulators.This work was supported by Sandia National Laboratories under contract number AL-3011

Antifungal Activity of Solventlessly Synthesized Organomercurials

A series of new barbituryl/thiobarbituryl substituted organomercurial derivatives 3a-i have been synthesised from pyrimidine derivatives 1a-c and arylmercuric chloride 2a-c over K2CO3 under microwave irradiations (MWI). This solventless synthesis apart from eliminating organic solvent from workup step, also gave improved yield as compared to the conventional heating, with reaction time reduced from hours to minutes. The prepared compounds were tested against A. niger and A. flavous for their antifungal activity and were found to posses good activity

The effect of graft function on FK506 plasma levels, dosages, and renal function, with particular reference to the liver

Plasma FK506 was studied in 49 liver, 13 heart, 3 double-lung or heart-lung, and 21 kidney recipients. The levels were correlated with the drug doses used, kidney function, and liver function. In all varieties of recipients, there was an early rise in the FK506 plasma levels that occurred at the time of intravenous administration of the drug. At the same time or shortly after, there were increases in serum creatinine that were transitory except in liver recipients with continuing suboptimal graft function. The quality of hepatic function dominated all aspects of FK506 management in the liver recipients. Those who received well-functioning grafts could be given about the same drug doses as recipients of kidneys and the thoracic organs. Liver recipients with defective grafts had astronomical rises in plasma FK506, a high incidence of renal failure, and probably increased neurotoxicity. In kidney transplant recipients, the FK506 plasma levels and doses were essentially the same in patients with prompt versus delayed renal function. These studies have highlighted the necessity, first, of close pharmacologic monitoring of patients who are given FK506 in the presence of abnormal liver function, and second, of using smaller intravenous induction doses than in past practice. © 1991 by Williams & Wilkins