Ion-pairing ability,chemical stability,and selectivity behavior of halogenated dodecacarborane cation exchangers in neutral carrier-based ion-selective electrodes

Recently, it has been discovered that carba-closo-dodecaborates can be used as cation exchangers in neutral carrier-based ion-selective chemical sensors. Because of their inherent chemical stability and versatile functionalization chemistries, they offer many advantages that may potentially be exploited for ion analyses that require nontraditional sample conditions, including strongly acidic media. In this work, trimethylammonium salts of undecachlorinated (UCC), undecabrominated (UBC), hexabrominated (HBC), and undecaiodinated (UIC) carborane anions were prepared and evaluated for their potential use in solvent polymeric membrane-based sensors. Computational methods including Natural population analysis and electrostatic mapping were used to predict the ion-exchanging ability of each lipophilic anion. In addition, the sandwich membrane technique was used to evaluate the ion-pairing ability of each carborane anion in situ (i.e., within bis(2-ethylhexyl) sebacate (DOS)- and 2-nitrophenyl octyl ether (o-NPOE)-plasticized ISE membranes). The results of the computational and potentiometric studies found that binding affinity of the anions followed the generalized trend HBC > UCC > UBC > UIC. PVC-DOS bulk optode thin films containing the chromoionophore ETH 5315 and a respective anion were used to determine the chemical stability/lipophilicity of the carboranes and tetrakis[3,5-bis(trifluoromethyl)phenyl] borate (TFPB) in acidic media (0.2 M HOAc) under flowing conditions. The studies found that in terms of stability/lipophilicity UIC > UBC > TFPB approximately UCC > HBC. Electrodes containing a Pb(2+)-selective ionophore, tert-butylcalix[4]arene-tetrakis(N,N-dimethylthioacetamide)(lead IV), were used to evaluate the functionality of each cation exchanger. An evaluation of response characteristics such as slope and selectivity found that UIC and UBC were quite comparable to the behavior of TFPB. Interestingly, both UIC and UBC showed a marked selectivity improvement over cadmium, with log K(pot)(pb),(Cd) values of -7.19 and -7.29, respectively, with TFPB giving a value of -5.89. Demonstrating excellent stability and suitable electrostatic properties, the carboranes, UIC in particular, are a very promising alternative to the tetraphenylborates and should find widespread application in the field of chemical sensors.     

Experimental observation of rainbow scattering by a coated cylinder: twin primary rainbows and thin-film interference

We experimentally examine the primary rainbow created by the illumination of a coated cylinder. We present a simple technique for varying the coating thickness over a wide range of values, and we see evidence for two different scattering regimes. In one, where the coating thickness is large, twin rainbows are produced. In the second, where the coating is thin enough to act as a thin film, a single rainbow is produced whose intensity varies periodically as the coating thickness varies. We find good agreement with previous theoretical predictions.     

The Commercialization of Information Infrastructure as Technological Mediation: The Internet Access Market

The study interprets the geographic diffusion of Internet Service Providers (ISPs) and the expansion of ISPs product lines in terms of the market for technological mediation. A firm involved in technology mediation takes advantage of gaps between general technological opportunities and particular user needs in specific places at particular times. If the economic opportunities are fleeting, then so too is the business. If the economic opportunities are renewed frequently, then the business can grow and adapt to take advantage of them. The concept of technological mediation helps us understand business behavior accompanying the commercialization of internet access technology.     

Solving shortest paths efficiently on nearly acyclic directed graphs

Shortest path problems can be solved very efficiently when a directed graph is nearly acyclic. Earlier results defined a graph decomposition, now called the 1-dominator set, which consists of a unique collection of acyclic structures with each single acyclic structure dominated by a single associated trigger vertex. In this framework, a specialised shortest path algorithm only spends delete-min operations on trigger vertices, thereby making the computation of shortest paths through non-trigger vertices easier. A previously presented algorithm computed the 1-dominator set in O(mn) worst-case time, which allowed it to be integrated as part of an O(mn+nrlogr) time all-pairs algorithm. Here m and n respectively denote the number of edges and vertices in the graph, while r denotes the number of trigger vertices. A new algorithm presented in this paper computes the 1-dominator set in just O(m) time. This can be integrated as part of the O(m+rlogr) time spent solving single-source, improving on the value of r obtained by the earlier tree-decomposition single-source algorithm. In addition, a new bidirectional form of 1-dominator set is presented, which further improves the value of r by defining acyclic structures in both directions over edges in the graph. The bidirectional 1-dominator set can similarly be computed in O(m) time and included as part of the O(m+rlogr) time spent computing single-source. This paper also presents a new all-pairs algorithm under the more general framework where r is defined as the size of any predetermined feedback vertex set of the graph, improving the previous all-pairs time complexity from O(mn+nr²) to O(mn+r³).     

Laboratory and self-report assessments of impulsive behavior in adolescent daily smokers and nonsmokers.

This research compared adolescent daily smokers (n = 25) and nonsmokers (n = 26) on different measures of impulsivity. Assessments included question-based measures of delay (DDQ) and probability (PDQ) discounting, a measure of behavioral disinhibition (go-stop task), and a self-report measure of impulsivity (Barratt Impulsiveness Scale-Adolescent). Adolescent smokers were more impulsive on the DDQ and Barratt Impulsiveness Scale--Adolescent but not on the PDQ or the go-stop task. However, there was a significant interaction between smoking status and gender on the go-stop task, with male smokers performing less impulsively on this measure than male nonsmokers--an effect not observed with the female adolescents. These findings indicate that adolescents who smoke cigarettes are more impulsive with respect to some, but not all, types of impulsivity than are adolescents who do not smoke. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Antimicrobial coatings produced by “tethering” biocides to the coating matrix: A comprehensive review

Covalently attached, non-leaching biocidal-moieties are being explored as an environmentally friendly option for replacing antimicrobial coatings that release biocides. This review highlights studies on antimicrobial surface treatments and coatings in which the antimicrobial agent is covalently bound (i.e. tethered) to the surface or coating matrix. In addition, test methods for measuring antimicrobial surface activity are reviewed, and a discussion of advantages and disadvantages of the various methods is provided.     

The Hysteresis Characteristics of Some Industrial PRTs

Hysteresis in industrial platinum resistance thermometers (IPRT) is caused by tension and compression induced in the wire due to differential thermal expansion of the platinum wire and the substrate. This article reports the measurement of hysteresis in a wide range of IPRTs including thin-film, glass-encapsulated, ceramic-encapsulated, and low-hysteresis partially-supported sensors, over the temperature range from ?20 °C to 180 °C. The study confirms previous findings that the amount of hysteresis is very dependent on the design of the sensing element and the temperature range. In addition, some sensors exhibit a large change in resistance on first use, whereas others showed a slow increase in resistance with use. The observed hysteresis ranged between 0.2 % of the temperature range for one glass-encapsulated sensor and 0.002 % for the best of the partially-supported ceramic sensors.     

Thermoelastic assessment of damage growth in composites

This paper examines, experimentally and numerically, the use of thermal emission measurements as a means of assessing severity of damage and monitoring damage growth in composite materials. In contrast to most traditional methods the thermal emission profile reflects the interaction of load, geometry, material and damage in a non-destructive fashion. It represents a possible method for the scaling of test data, obtained from coupon tests, to tests on full scale structures.     

The Therapeutic Bond Scales: Psychometric characteristics and relationship to treatment effectiveness.

The Therapeutic Bond Scales assess the quality of the therapeutic relationship from the patient's perspective. The therapeutic bond is composed of 3 aspects: working alliance, empathic resonance, and mutual affirmation. Scales were developed to measure these aspects and the therapeutic bond as a whole. The correlations between these scales and 2 measures of outcome (session quality assessed by the patient and termination outcome evaluated by nonparticipant raters) were examined. All scales were significantly correlated with session quality. Therapeutic bond was significantly correlated with termination outcome in both a linear and a curvilinear fashion, suggesting that, at least in the initial phase of therapy, the therapeutic bond can be too high as well as too low. (PsycINFO Database Record (c) 2010 APA, all rights reserved)