Experimentally Validated Added Mass Identification Algorithm Based on Frequency Response Functions

A methodology is presented for detecting added mass in structural systems maintaining a linear response. A single frequency response function measured at several frequencies along with a correlated analytical model of the structure in its original state are used to detect and quantify the added mass. A computationally efficient method of recalculating a single frequency response function is utilized in the identification algorithm. Experimental results from a frame structure are presented to validate and assess the proposed approach.     

Metallocene QACs: The Incorporation of Ferrocene Moieties into monoQAC and bisQAC Structures

Inspired by the incorporation of metallocene functionalities into a variety of bioactive structures, particularly antimicrobial peptides, we endeavored to broaden the structural variety of quaternary ammonium compounds (QACs) by the incorporation of the ferrocene moiety. Accordingly, 23 ferrocene-containing mono- and bisQACs were prepared in high yields and tested for activity against a variety of bacteria, including Gram-negative strains and a panel of clinically isolated MRSA strains. Ferrocene QACs were shown to be effective antiseptics with some displaying single-digit micromolar activity against all bacteria tested, demonstrating yet another step in the expansion of structural variety of antiseptic QACs.     

Diazepam's impact on self-stimulation but not stimulation-escape suggests hedonic modulation.

In rats that self-administered lateral hypothalamic (LH) stimulation through chronically implanted electrodes, ip diazepam (DZ) increased rates and decreased thresholds of self-stimulation (SS) in a dose-related manner. Stimulation-escape (SE), however, was refractory to the drug. There was a complete dichotomy in electrode placements along the anterior/posterior plane. Every pure-reward electrode location was posterior to every reward-escape electrode. DZ-sensitive SS appears to be mediated by a reward substrate common to both pure-reward and reward-escape rats, whereas SE is supported by an aversive system unaffected by DZ and stimulated only in those rats with anterior placements. The lack of control over SE suggests that the drug's effect on stimulation-induced conduct is to increase reward rather than to decrease aversion. This hypothesis is discussed in the context of DZ's interactions with drugs of abuse. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Socially mediated reduction of isolation distress in rat pups is blocked by naltrexone but not by Ro 15-1788.

[Correction Notice: An erratum for this article was reported in Vol 104(4) of Behavioral Neuroscience (see record 2008-10515-001). On page 462, the last paragraph of the first column was incorrect. The corrected paragraph is provided in the erratum.] The presence of a single anesthetized littermate significantly reduced the rate of ultrasonic vocalization by 10-day-old pups isolated in a novel environment. Naltrexone (1.0 mg/kg) returned the vocalization rate to the level of pups tested alone and disrupted the maintenance of body contact between the test pup and a companion. This suggests that the companion exerts comforting effects through endogenous opioid mechanisms. Although chlordiazepoxide is as effective as morphine in the quieting of isolation distress, the benzodiazepine (BDZ) antagonist Ro 15-1788 (5, 10, or 20 mg/kg) was ineffective in blocking the comfort effect and facilitated quiet contact with the companion. In isolated pups, Ro 15-1788 caused a significant, but not a dose-related, decrease in vocalization, a possible indication of the displacement of an endogenous anxiogenic ligand at the BDZ receptor complex. [An erratum for this article will appear in Behavioral Neuroscience, 1990 (Aug), Vol 104:4. The erratum concerns an error in the last paragraph of the first column on page 462.] (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Selected subunits of the cytosolic chaperonin associate with microtubules assembled in vitro

The molecular chaperone activities of the only known chaperonin in the eukaryotic cytosol (cytosolic chaperonin containing T-complex polypeptide 1 (CCT)) appear to be relatively specialized; the main folding substrates in vivo and in vitro are identified as tubulins and actins. CCT is unique among chaperonins in the complexity of its hetero-oligomeric structure, containing eight different, although related, gene products. In addition to their known ability to bind to and promote correct folding of newly synthesized and denatured tubulins, we show here that CCT subunits alpha, gamma, zeta, and theta also associated with in vitro assembled microtubules, i.e. behaved as microtubule-associated proteins. This nucleotide-dependent association between microtubules and CCT polypeptides (Kd approximately 0.1 microM CCT subunit) did not appear to involve whole oligomeric chaperonin particles, but rather free CCT subunits. Removal of the tubulin COOH termini by subtilisin digestion caused all eight CCT subunits to associate with the microtubule polymer, thus highlighting the non-chaperonin nature of the selective CCT subunit association with normal microtubules.     

Physical, chemical and energy aspects of underground hydrogen storage

Large scale energy storage is becoming an important consideration as we turn more towards nuclear power and the utilization of renewable sources such as solar energy. Underground storage of hydrogen in aquifers has been suggested as an inexpensive method of providing the required energy storage. With this theme in mind, the losses associated with gas storage in aquifers are discussed. These losses include physical leakage of gas, loss of gas through underground chemical reactions and the energy requirements associated with storing and recovering the gas.

Although underground storage of hydrogen appears a most promising solution to the problem of large scale energy storage it is shown that much work remains to be done to confirm this. For example, better estimates of hydrogen diffusion through water saturated porous media are required.     

Phase Error Characteristics of a Second-Order Phase-Lock Loop

An analytical expression for the phase error characteristics of a second-order phase-lock loop (PLL) is determined using the results of a previous nonlinear analysis. The characteristics determined are for sinusoidal FM in the absence of noise. Theoretical and experimental results are compared and are in close agreement. The theoretical results are useful as a design aid and in determining the proper parameters for the operation of a second-order PLL.