Modifying the adsorption behavior of polyamidoamine dendrimers at silica surfaces investigated by total internal reflection fluorescence correlation spectroscopy

Polyamidoamine (PAMAM) dendrimers were modified and tested for use as solution-phase diffusion probes in silica nanostructures. In order for the successful application of dendrimers as solution-phase probes, their interactions with silica surfaces must be understood and controlled, so that the motion of the probe is not influenced by adsorption. Adsorption/desorption kinetics of PAMAM dendrimers and their diffusion in solution near silica surfaces were investigated with total internal reflection fluorescence correlation spectroscopy (TIR-FCS). Dendrimers of generations 3, 5, and 7 were dye-labeled with carboxyrhodamine 6G. Because PAMAM dendrimers are positively charged in solution (having primary amines as end groups), significant adsorption of these molecules to the negatively charged silica surface was observed. Adsorption/desorption rates and the equilibrium constant for adsorption were determined by fitting the autocorrelation functions to a kinetic model. The desorption rate decreases and the absorption equilibrium constant increases with higher dendrimer generation. To reduce the adsorption of these probes to silica surfaces, the labeled dendrimers were reacted with succinic anhydride, converting the primary amine end groups to negatively charged carboxylic acid groups. These carboxylated dendrimers did not detectably adsorb to silica from aqueous solution. TIR-FCS was used to determine their free-solution diffusion constants near silica surfaces, and the corresponding hydrodynamic radii compare favorably with values reported from forced Rayleigh scattering measurements.     

Quantum Dot‐Based Thermal Spectroscopy and Imaging of Optically Trapped Microspheres and Single Cells

Laser‐induced thermal effects in optically trapped microspheres and single cells are investigated by quantum dot luminescence thermometry. Thermal spectroscopy has revealed a non‐localized temperature distribution around the trap that extends over tens of micrometers, in agreement with previous theoretical models besides identifying water absorption as the most important heating source. The experimental results of thermal loading at a variety of wavelengths reveal that an optimum trapping wavelength exists for biological applications close to 820 nm. This is corroborated by a simultaneous analysis of the spectral dependence of cellular heating and damage in human lymphocytes during optical trapping. This quantum dot luminescence thermometry demonstrates that optical trapping with 820 nm laser radiation produces minimum intracellular heating, well below the cytotoxic level (43 °C), thus, avoiding cell damage.     

Direct Reduction of Mixtures of Manganese Ore and Iron Ore

This paper presents recent results of direct reduction investigation of different combination of blends of manganese ore, iron ore and coal at the Department of Ferrous Metallurgy (IEHK) of RWTH Aachen University. A mixture of iron and manganese ore in a ratio of 75/25 is a good raw material for steelmaking of high Mn‐alloyed grades. The experimental studies consisting of reduction of (a) fine material and (b) agglomerated material (briquettes) were carried out in the range of 1273 to 1673 K. The behaviour of combined reduction of manganese ore and iron ore and the employment in the direct reduction on a coal and gas basis for production of steels with high Mn content were investigated. It was found that a high metallization degree for Mn can be reached at 1273 K with the reduction of manganese ore by hydrogen‐containing gas. Addition of carbon monoxide to the reducing gas retarded the reduction process. The addition of coal to manganese ore and iron ore blends increased the degree of reduction. The results of carbothermic reduction of briquettes consisting of a mixture of manganese ore and iron ore combined with coal as reducing agent show that a high temperature, a low Mn/Fe ratio and a high Fe₂O₃ content have a favourable effect on the degree of reduction. In order to obtain a high degree of metallization, the temperature should be higher than 1473 K. The reduction of briquettes at higher temperatures (up 1573 K) has shown a molten phase and the separation of slag and metal.     

Preliminary development of an interaction matrix for observation of client–therapist relationships in play therapy.

Describes the development of the Carmichael Therapist/Client Interaction Matrix (CTCIM) and presents preliminary findings on its use in supervision of therapists and for empirical study of therapist/client interactions. The purpose of the CTCIM is to graphically depict the relationship between the level of therapist's responses and the client's behaviors in therapy. The CTCIM was used to evaluate 32 sessions in a university play therapy laboratory. Five children (aged 6–10 yrs) were paired with 5 therapists. The 5 children represented a wide range of problems from physical abuse survivors to school adjustment difficulties. The 5 graduate student therapists varied from beginning to moderate counseling experience. A positive correlation was found between therapist's responses and client behavioral outcomes in the preliminary study. Based on the finding that the CTCIM met 4 of the 6 dimensions recommended by P. Howe and L. Silvern (1981) in investigating issues important to therapists and clients, it is concluded that the CTCIM demonstrates potential for empirical studies and for supervision of therapists. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Framing the construct of life satisfaction in terms of older adults' personal goals.

Older adults' life satisfaction can be better understood in light of their personal goals. This study of 179 elders examined (1) how goals correlate with satisfaction, (2) whether elders maintain satisfaction by accommodating goals to past losses, and (3) how correlations between satisfaction and key predictors differ among groups with different goals. Satisfaction was related positively to social maintenance and energetic lifestyle goals and negatively to concerns for improvement, disengagement, stability, and reduced activity. Past losses were correlated with current goals but not with satisfaction, consistent with the notion of accommodation. A cluster analysis identified 5 patterns of goals: high demand, age prescribed, self-focused, socially engaged, and low demand. Correlations between satisfaction and other predictors differed by cluster, suggesting that the determinants of elders' satisfaction depend on personal goals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Distinguishing anxiety and depression: Reexamination of the reconstructed Hamilton scales.

The discriminant validities of the original and the reconstructed Hamilton anxiety and depression scales (J. H. Riskind et al, 1987) were compared in patients who had principal Diagnostic and Statistical Manual of Mental Disorders-III—Revised (DSM-III—R) anxiety disorders with or without 1 or more comorbid mood disorders. The reconstructed anxiety and depression scales had better discriminant validity (scale intercorrelation?=?.61) than the original scales did (r?=?.78). However, the reconstructed scales shared considerable variance (about 37%), which was significantly higher than the shared variance (about 2%) reported by Riskind et al. Discriminant analyses showed that the reconstructed scales did not distinguish anxiety patients with comorbid mood disorders from those without comorbid mood disorders better than the original scales did. However, the reconstructed scales eliminate item overlap, an obvious source of artifactual correlations between scores on the Hamilton anxiety and depression scales. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Tribological performance of uncoated and TiCN-coated D2, M2 and M4 steels under lubricated condition

Hard coatings are used to improve the wear resistance of metals which largely depends on adhesion between substrate and coating.The wear and friction behavior of uncoated and TiCN-coated D2, M2 and M4 steels were evaluated by a pin-on-disk test under lubricated conditions.In order to evaluate the influence of lubricant on wear performance, dry friction tests were also performed.The results showed that friction coefficients were very similar for both uncoated and TiCN-coated steels.Under lubricated conditions, the uncoated D2 tool steel exhibited the lowest friction coefficient, but the TiCN-coated D2 steel presented the smallest wear rate.Abrasion was the main wear mechanism in all the tribocouples.Additionally, microhardness measurements were carried out, finding an influence of the steel substrate on the hardness of the coatings.Besides, adhesion test was conducted, suggesting a good adhesion of class 1 between substrates and TiCN coatings.     

A computational approach to modeling commodity markets

We build an agent based computational framework to study large commodity markets. A detailed representation of the consumers, producers and the market is used to study the micro level behavior of the market and its participants. The user can control players’ preferences, their strategies, assumptions of the model, its initial conditions, market elements and trading mechanisms. The first part of the paper describes the computational framework and its three main modules. The later part describes a case study that examines the decentralized market in detail, specifically the computational options available for matching the buyers and suppliers in a synthetic market. The study illustrates the sensitivity of the outcome of various economic variables, such as clearing price, quantity, profits and social welfare, to different matching schemes in a bilateral computational setting. Based on seven different matching orders for the buyers and suppliers, our study shows that the results can vary dramatically for different pairing orders.     

Stimuli-directed self-organized chiral superstructures for adaptive windows enabled by mesogen-functionalized graphene

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