COMMENTS ON π-ELECTRON CONJUGATION IN THE FIVE-MEMBERED RING OF BENZO-DERIVATIVES OF CORANNULENE

Cyclic conjugation in corannulene and its benzo-derivatives is studied by means of the π-electron contents and the energy effects of individual rings, with particular attention to the structural effects influencing the magnitude of cyclic conjugation in the 5-membered ring. Two main general regularities were observed: (a) the PCP effect (6-membered rings connected by a single bond to the 5-membered ring increase in it the intensity of cyclic conjugation), and (b), the linear effect (6-membered rings separated from the 5-membered ring by another 6-membered ring, but not in PCP constellation, decrease the magnitude of cyclic conjugation in the 5-membered ring).     

Structural Analysis,Electrochemical Behavior,and Biocompatibility of Novel Quaternary Titanium Alloy with near β Structure

This article analyses the microstructure, electrochemical behavior, and biocompatibility of a novel Ti-20Nb-10Zr-5Ta alloy with low Young’s modulus (59 GPa) much closer to that of bone, between 10 and 30 GPa, than Ti and other Ti alloys used as implant biomaterial. XRD and SEM measurements revealed a near β crystalline microstructure containing β phase matrix and secondary α phase, with a typical grain size of around 200 μm. The corrosion behavior in neutral Ringer solution evidenced: self-passivation behavior characterizing a very resistant passive film; an easy passivation as a result of favorable influence of the alloying elements Nb, Zr, and Ta that participate with their passive oxides to the formation of the alloy passive film; low corrosion and ion release rates corresponding with very low toxicity. In MEM solution, the novel alloy demonstrated very high corrosion resistance and no susceptibility to localized corrosion. Biocompatibility was evaluated on in vitro human osteoblast-like and human immortalized pulmonary fibroblast cell (Wi-38) lines and the new Ti-20Nb-10Zr-5Ta alloy exhibited no cytotoxicity. The new Ti-20Nb-10Zr5Ta alloy is a promising material for implants due to combined properties of low elastic modulus, very low corrosion rate, and good biocompatibility.     

Diffusional System Based on Tolazoline Hydrochloride Included in a Reticulated Carboxymethylcellulose Hydrogel

This paper presents a diffusional system consisting of tolazoline hydrochloride included into a carboxymethylcellulose based hydrogel, showing a high swelling capacity in water. The process kinetics of the drug inclusion into hydrogel as well as of the drug releasing have been studied. The tolazoline hydrochloride release was performed by elution with a simulated biological fluid within the digestive tract, at the small intestine level (pH = 8.2) where the drug is mostly absorbed. The results make evident a zero-order kinetics over the 30–400 min range, which would place the system among those with ‘sustained’ release, with obvious advantages compared with the classical drug administration.     

Polymer-Biologically Active Principle Conjugates Obtained by Esterification of Poly(Vinyl Alcohol)

The paper deals with the study of some polymer-biologically active principle systems characterized by the controlled release of the bioactive component by hydrolyze followed by diffusion. The systems were obtained by coupling the 2-mercapto-benzotiazolyl-acetic acid and N-(m-nitrobenzoyl)-L-methionine on poly(vinyl alcohol) by means of esteric bonds in the presence of diciclohexylcarbodiimide as an activator. The influence of some coupling process parameters on the reaction efficiency was studied, such as the drug/support and activator/support ratios. The coupling products with a maximum content of biologically active compound were characterized by spectral measurements, also as regards the capacity of bioactive compound release under the conditions simulating those within the gastro-intestinal tract. The antibacterial activity of the conjugates against Staphylococcus aureus, Eschrichia coli, Sarcina lutea, and Bacillus subtilis was determined.     

Development of a stability intelligent control system for turning

This paper presents a stability control system based on a new strategy, with application in turning. It works by permanent assessment of the system operating point position relative to the stability limit, and process parameter permanent, in-process modification such as this point is always placed in the stable domain zone that gives the highest process performance. In the case of turning, here approached: (1) this zone is the stability limit proximity; (2) the system operating point position is determined by assessing a cutting force monitored signal feature; and (3) this position is changed by modifying the cutting edge setting angle, the feed rate, and the cutting speed, as it follows: when the risk of overpassing the stability limit is imminent, the setting angle is increased, followed by a feed rate diminishing and then by a worked piece rotation speed reduction, while immediately after surpassing the risk, the three variables modification is reversed, this way the chatter onset being permanently avoided and the performance kept in every moment at the highest possible level. The system was experimentally implemented on a transversal lathe. The results of tests on dedicatedly designed specimens are showing a machining productivity significant increase, in conditions of a stable cutting process. The system is simple, and it can be easily added to the existing CNC machine tools, without important modifications.     

An experimental study of a confined and submerged impinging jet heat transfer using Al2O3-water nanofluid

An experimental investigation was performed to study the heat transfer performance of a 36 nm-Al₂O₃-particle–water nanofluid in a confined and submerged impinging jet on a flat, horizontal and circular heated surface. The tests were realized for the following ranges of the governing parameters: the nozzle diameter is 3 mm and the distance nozzle-to-heated-surface was set to 2, 5 and 10 mm; the flow Reynolds number varies from 3800 to 88 000, the Prandtl number from 5 to 10, and the particle volume fraction is ranging from 0 to 6%. Experimental data, obtained for both laminar and turbulent flow regimes, have clearly shown that, depending upon the combination of nozzle-to-heated surface distance and particle volume fraction, the use of a nanofluid can provide a heat transfer enhancement in some cases; conversely, for other combinations, an adverse effect on the convective heat transfer coefficient may occur. Within the experimental parameters used, it has been observed that highest surface heat transfer coefficients can be achieved using an intermediate nozzle-to-surface distance of 5 mm and a 2.8% particle volume fraction nanofluid. Nanofluids with high particle volume fractions, say 6% or higher, have been found not appropriate for the heat transfer enhancement purpose under the confined impinging jet configuration. On the other hand, for a very small and a large distance of nozzle-to-heated-surface, it has been observed that the nanofluid use does not provide a perceptible heat transfer enhancement and has, for some particular cases, produced a clear decrease of the convective heat transfer coefficient while compared to that obtained using distilled water.     

On heat transfer in external natural convection flows using two nanofluids

In the present work, a theoretical model based on the integral formalism approach for both laminar and turbulent external natural convection is extended to nanofluids. By using empirical models based on experimental data for computing viscosity and thermal conductivity of water–alumina and water–CuO suspensions, a close attention is first focused on the influence due to increasing the volume fraction of nanoparticles on the heat transfer and then to the transition threshold between laminar and turbulent regimes. The heat transfer is shown to strongly depend on the flow regime and on particle volume fraction. A clear degradation of heat transfer is observed using nanofluids while compared to that of the base-fluid. Moreover, the fact of increasing the particle volume fraction tends to delay the occurrence of the flow transition to turbulence.     

Long-term memory for the terrorist attack of September 11: Flashbulb memories, event memories, and the factors that influence their retention.

More than 3,000 individuals from 7 U.S. cities reported on their memories of learning of the terrorist attacks of September 11, as well as details about the attack, 1 week, 11 months, and/or 35 months after the assault. Some studies of flashbulb memories examining long-term retention show slowing in the rate of forgetting after a year, whereas others demonstrate accelerated forgetting. This article indicates that (a) the rate of forgetting for flashbulb memories and event memory (memory for details about the event itself) slows after a year, (b) the strong emotional reactions elicited by flashbulb events are remembered poorly, worse than nonemotional features such as where and from whom one learned of the attack, and (c) the content of flashbulb and event memories stabilizes after a year. The results are discussed in terms of community memory practices. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Expedient Immobilization of TEMPO by Copper‐Catalyzed Azide‐Alkyne [3+2]‐Cycloaddition onto Polystyrene Resin

TEMPO was readily grafted by copper(I)‐catalyzed azide‐alkyne cycloaddition onto polystyrene. Starting with commercially available Merrifield resin (4.3 mmol/ g) almost quantitative loading of TEMPO onto the polymer was achieved (≥ 4 mmol/ g). The so obtained PS‐CLICK‐TEMPO allowed the oxidation of alcohols to aldehydes with bleach or molecular oxygen as the terminal oxidant with high yields and selectivity in multiple cycles without loss of activity.     

Comparative Antimicrobial Activity of Silver Nanoparticles Obtained by Wet Chemical Reduction and Solvothermal Methods

The synthesis of nanoparticles from noble metals has received high attention from researchers due to their unique properties and their wide range of applications. Silver nanoparticles (AgNPs), in particular, show a remarkable inhibitory effect against microorganisms and viruses. Various methods have been developed to obtain AgNPs, however the stability of such nanostructures over time is still challenging. Researchers attempt to obtain particular shapes and sizes in order to tailor AgNPs properties for specific areas, such as biochemistry, biology, agriculture, electronics, medicine, and industry. The aim of this study was to design AgNPs with improved antimicrobial characteristics and stability. Two different wet chemical routes were considered: synthesis being performed (i) reduction method at room temperatures and (ii) solvothermal method at high temperature. Here, we show that the antimicrobial properties of the obtained AgNPs, are influenced by their synthesis route, which impact on the size and shape of the structures. This work analyses and compares the antimicrobial properties of the obtained AgNPs, based on their structure, sizes and morphologies which are influenced, in turn, not only by the type or quantities of precursors used but also by the temperature of the reaction. Generally, AgNPs obtained by solvothermal, at raised temperature, registered better antimicrobial activity as compared to NPs obtained by reduction method at room temperature.