Determination of first-order molecular hyperpolarizability of EAADCy and EDMAADCy using steady-state spectroscopic data and quantum-chemical calculations

Ethyl 5-(4-aminophenyl)-3-amino-2,4-dicyanobenzoate (EAADCy) and ethyl 5-(4-dimethylaminophenyl)-3-amino-2,4-dicyanobenzoate (EDMAADCy) organic molecules containing separate electron donor and electron acceptor groups belong to biphenyl derivatives in which a large dipole moment change between ground (S₀) and the first intramolecular charge transfer excited (S₁) states, as well as a large transition moment have been noted. The existence of electronically excited states with a strong intermolecular charge transfer (ICT) character is an essential prerequisite for large non-linear optical properties. Therefore, in this paper, we present a scrupulous analysis of the first-order hyperpolarizabilities of the studied molecules using an equivalent internal field model of an organic molecule. The calculated (using semiempirical calculations, CAChe WS 5.04) additive part of the first-order hyperpolarizability, β_add, values are discussed in relationship to the experimental data of the charge transfer hyperpolarizability, β_CT, obtained from steady-state spectroscopic measurements.     

Why filtering surface profiles?

This position paper is to discuss the problems of assessing microgeometrical deviations at surfaces of geometrically defined bodies. The new ISO 4287:1996 defines a lot of parameters for the 2D-assessment of three different types of profiles, the primary profile, the roughness profile and the waviness profile. Concerning the microtopography, the standardized procedures of electrical filtering for separating roughness and waviness are a convention which was derived from the possibilities of the computer-aided evaluation of profiles, which does not necessarily refer to process and functional properties. To reduce the again proliferated number of parameters by the edition of the above-mentioned standard, it is proposed to omit the electrical filtering and to evaluate the primary profile with its superimposed roughness and waviness within the evaluation length lp only. In this case, lp is used as sampling length filter. The practicability and usefulness of this proposal are discussed, also regarding the increasing 3D-evaluation of surfaces to be expected. Concerning the amplitude parameters to be used for assessing, tolerancing and process supervising, the application of parameters based on a statistical consideration of the amplitude density curve is recommended.     

Stress corrosion cracking of alpha brass in a tarnishing ammoniacal environment: Fractography and chemical analysis

Alloy 260 brass specimens under stress were exposed at room temperature to 15 N aqueous ammonia solution with 8 g/1 of cupric copper predissolved. This environment causes tarnishing of the brass surface and intergranular stress corrosion cracking. Scanning electron microscopy, energy dispersive X-ray analysis, and Auger electron spectroscopy were employed to study fractography, corrosion product composition and distribution within the stress corrosion crack, and fracture surface chemistry characteristic of stress corrosion cracking in this system. A thin oxidized film was detected by Auger spectroscopy at the leading edge of the propagating crack. With continued exposure to the corrosive environment, deposits form on the fracture surface, then coalesce to form a continuous tarnish film that is depleted of zinc. No bulk depletion of zinc was detected in the alloy at the stress corrosion crack leading edge. No evidence of noncrystallographic crack arrest marks was found on the intergranular fracture surface.     

The behaviour of homogeneous AlCu4 and AlZn3 in weakly acid and in O2-saturated chloride solutions

The electrochemical behaviour of a homogeneous binary Al–4wt.%Cu and of a homogeneous binary Al–3wt.%Zn alloy in weakly acid chloride solutions, in O₂-saturated chloride and citrate buffer solution and in Fe²⁺/Fe³⁺-containing citrate buffer solution has been examined using a rotating disc electrode. In weakly acid and in O₂-containing solutions the behaviour of the AlCu and of the AlZn alloy differs from the behaviour of pure Al. H⁺ -and O₂-reduction at these alloys take place at a much higher rate. Under certain conditions, the reactions are even under transport control. Obviously, this is caused by the preceding selective dissolution of Al. Clusters from residual Cu and Zn, respectively, can pierce the passive layer and act as cathodic sites. In an electrolyte, where the passive layer is not dissolved, the AlZn and the AlCu alloy behave like pure Al. This is shown with the Fe²⁺/Fe³⁺ redox system in a neutral buffer solution.     

Cycle-averaged dynamics of a periodically driven, closed-loop circulation model

Time-varying elastance models have been used extensively in the past to simulate the pulsatile nature of cardiovascular waveforms. Frequently, however, one is interested in dynamics that occur over longer time scales, in which case a detailed simulation of each cardiac contraction becomes computationally burdensome. In this paper, we apply circuit-averaging techniques to a periodically driven, closed-loop, three-compartment recirculation model. The resultant cycle-averaged model is linear and time invariant, and greatly reduces the computational burden. It is also amenable to systematic order reduction methods that lead to further efficiencies. Despite its simplicity, the averaged model captures the dynamics relevant to the representation of a range of cardiovascular reflex mechanisms.     

The presence of a ferrocenyl unit on an estrogenic molecule is not always sufficient to generate in vitro cytotoxicity

We recently reported the dual (antihormonal and cytotoxic) functionality of ferrocifens, which are organometallic complexes derived from hydroxytamoxifen, the standard molecule in the treatment of hormone-dependent breast cancers. To test the hypothesis that the presence of a ferrocenyl substituent on molecules with an affinity for the estrogen receptor is sufficient to give them cytotoxic properties in vitro, we prepared complexes derived from estradiol with a ferrocenyl substituent at positions 7alpha and 17alpha. The complexes thus obtained retain a satisfactory level of affinity for the estrogen receptor (RBA values higher than 12 %). At low concentrations (0.1-1 microM) the complexes show an estrogenic effect in vitro equivalent to that of estradiol on hormone-dependent (MCF-7) breast cancer cells, and no cytotoxic effect on hormone-independent (MDA-MB-231) breast cancer cells. At high concentrations (up to 50 microM) the 17alpha-ethynylferrocenyl estradiol and 7alpha-ferrocenylmethylthio estradiol become cytotoxic (IC(50)=13.2 microM and 18.8 microM, respectively) while the 17alpha-ferrocenylestradiol remains non toxic. The low toxicity of these compounds support our hypothesis that electronic communication between the ferrocenyl and phenol moieties in the hydroxyferrocifens series is a key parameter in the generation of cytotoxic effects at submicromolar concentrations.     

Posttraining lesions of the amygdala interfere with fear-potentiated startle to both visual and auditory conditioned stimuli in C57BL/6J mice.

The fear-potentiated startle paradigm has been used with great success to examine conditioned fear in both rats and humans. The purpose of the present experiment was to extend the authors' previous findings and further validate the fear-potentiated startle paradigm in mice. In Experiments 1 and 2, C57BL/6J mice were given Pavlovian fear conditioning with either an auditory or a visual conditioned stimulus. Similar to data collected with rats, fear-potentiated startle was observed for both stimulus modalities. In Experiment 3, posttraining lesions of the amygdala disrupted fear-potentiated startle in both conditioned stimulus modalities. These data are consistent with amygdala lesion studies in rats and suggest that fear-potentiated startle in mice requires an intact amygdala. Together, these results extend the authors' previous results and provide the basis for using this well-understood behavioral paradigm for examining the molecular mechanisms of conditioned fear in transgenic and knockout mice. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Further observations of SCC in alpha-beta brass: Considerations regarding the appearance of crack arrest markings during SCC

A series of constant displacement and constant extension rate SCC tests was performed on an alpha-beta brass alloy in 1 N Na₂SO₄ solutions. The chosen mechanical and electrochemical conditions resulted in predominantly transgranular, cleavage-like failure at high (≈8 to ≈50 μm· s^•1) average crack propagation rates. Crack arrest markings were observed on selected transgranular facets which almost exclusively bordered regions of ductile overload failure. It is proposed that the observed crack velocities and the specific nature of the arrest mark appearance are most consistent with a cracking mechanism involving adsorption or some other interaction with a damaging environmental species. Formerly with Michigan Tech.