Theoretical and practical aspects of selected fiber-blend color-formulation functions

Color matching blends of precolored fiber using three different methods was studied. Best color-matching accuracy was obtained using a two-constant Kubelka-Munk (KM) procedure. First-formula color differences averaged 1.6 CIELAB units and were found to be within the experimental error of 1.6 CIELAB units. Useful approximations were obtained using the methods proposed by Friele and by Stearns. First-formula color matches averaged 2.4 CIELAB units for the Stearns and 2.7 CIELAB units for the Friele methods. The methods are mathematically compared and the merits of each are discussed. Where possible, interpretation of the empirical parameters each method employs is attempted. It is pointed out that absorption and scattering constants calculated for fibers using the KM formalism are not true KM absorption and scattering constants. It is demonstrated that too literal an interpretation of these constants leads to apparent anomalies. It is shown that the fiber KM scattering constants which are normally considered unchanged as dye is applied cannot be considered unchanged if these same fibers are subsequently to be used in blends with other colored fibers.     

Boreal forests, aerosols and the impacts on clouds and climate

Previous studies have concluded that boreal forests warm the climate because the cooling from storage of carbon in vegetation and soils is cancelled out by the warming due to the absorption of the Sun's heat by the dark forest canopy. However, these studies ignored the impacts of forests on atmospheric aerosol. We use a global atmospheric model to show that, through emission of organic vapours and the resulting condensational growth of newly formed particles, boreal forests double regional cloud condensation nuclei concentrations (from approx. 100 to approx. 200 cm(-3)). Using a simple radiative model, we estimate that the resulting change in cloud albedo causes a radiative forcing of between -1.8 and -6.7 W m(-2) of forest. This forcing may be sufficiently large to result in boreal forests having an overall cooling impact on climate. We propose that the combination of climate forcings related to boreal forests may result in an important global homeostasis. In cold climatic conditions, the snow-vegetation albedo effect dominates and boreal forests warm the climate, whereas in warmer climates they may emit sufficiently large amounts of organic vapour modifying cloud albedo and acting to cool climate.     

Efficiently harvesting excitons from electronic type-controlled semiconducting carbon nanotube films

We have employed thin films of highly purified semiconducting carbon nanotubes as near-infrared optical absorbers in heterojunction photovoltaic and photodetector devices with the electron acceptor C(60). In comparison with previous implementations of more electrically heterogeneous carbon nanotube/C(60) devices, we have realized a 10× gain in zero-bias quantum efficiency (QE) and even more substantial gains in power conversion efficiency (η(p)). The semiconducting nanotube/C(60) heterojunctions are highly rectifying with a peak external QE, internal QE, and η(p) of 12.9 ± 1.3, 91 ± 22, and 0.6%, respectively, in the near-infrared. We show that the device efficiency is determined by the effective length scale for exciton migration in the nanotube films, confirm the high internal QE via photoluminescence quenching, and demonstrate that the driving force for exciton dissociation at the fullerene-fullerene heterointerface is optimized for diameters <1.0 nm. These results will guide the development of next-generation high-performance carbon nanotube-based solar cells and photosensitive devices.     

Semiconducting carbon nanotube/fullerene blended heterojunctions for photovoltaic near-infrared photon harvesting

We demonstrate that the near-infrared (NIR) absorptivity of semiconducting single-walled carbon nanotubes (s-SWCNTs) can be harnessed in blended heterojunctions with the fullerene derivative [6,6]-phenyl-C₆₁-butyric acid methyl ester (PCBM). Photogenerated charge separation is efficiently driven by the ultrahigh interfacial area of the blends and the favorable energy offsets between the two materials. NIR-sensitive photovoltaic and photodetector devices utilizing the stack (indium tin oxide/ca. 10 nm s-SWCNT:PCBM/100 nm C₆₀/10 nm 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP)/Ag) were fabricated with NIR power conversion efficiencies >1.3% and peak, zero bias external quantum efficiency of 18% at λ = 1205 nm.      

What role do lay beliefs about hypertension etiology play in perceptions of medication effectiveness?

Background: Some people take the disease label hypertension literally; leading to the belief that increasing relaxation instead of medication is the best treatment for this condition. We experimentally tested the effect of such underlying beliefs on ratings of interventions for hypertension and compared alternative communication strategies to increase medication effectiveness ratings. Methods: Outpatients (N = 152) with a known diagnosis of hypertension read a vignette describing an asymptomatic condition and recommended treatment. Experimental factors were the disease label (Hypertension vs. Korotkoff's Syndrome) and type of argument designed to persuade the reader that medication is most effective (Causal vs. Correlational). Measures: Background measures included demographics, beliefs that stress causes health problems and trust in physicians. Outcomes were effectiveness ratings for interventions to treat the condition. Results: Participants who read a vignette describing Hypertension rated relaxing more as significantly more effective than participants exposed to the same condition but with the unfamiliar Korotkoff's Syndrome label, [F(1, 141) = 5.22, p = .024]. However, medication, reducing salty foods and losing weight were rated as more effective than relaxing more. Intervention ratings did not differ by type of argument presented. There was a significant interaction of disease label and trust in physicians [F(1, 125) = 7.01, p = .009]. Individuals with low trust rated medication as significantly less effective when exposed to an unfamiliar disease label. Conclusions: This study confirms the effect of the hypertension disease label on ratings of different interventions for the condition. However, participants rated biomedically recommended interventions as more effective than those not endorsed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Associations between tobacco smoking and illicit drug use among methadone-maintained opiate-dependent individuals.

Tobacco chippers are individuals who smoke regularly yet are not nicotine dependent. In the present study, the authors examined the prevalence of tobacco chipping among methadone-maintained opiate abusers. Furthermore, the authors examined associations between tobacco and illicit substance use by comparing heavy smokers, tobacco chippers, and nonsmokers. Results demonstrate that tobacco chipping occurs among methadone-maintained individuals. Illicit substance use, measured through urine toxicology, was found to increase in a stepwise fashion from nonsmokers, to chippers, to heavy smokers. Smoking status (nonsmoker, chipper, heavy smoker) proved a more powerful predictor of cocaine and opiate use than daily methadone dose. Findings lend support to existing evidence suggesting associations between tobacco and opiate and cocaine use and strongly suggest that smoking cessation should be offered to all methadone-maintained individuals. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Mechanism of a Standalone β-Lactone Synthetase: New Continuous Assay for a Widespread ANL Superfamily Enzyme

Enzyme-catalyzed β-lactone formation from β-hydroxy acids is a crucial step in bacterial biosynthesis of β-lactone natural products and membrane hydrocarbons. We developed a novel, continuous assay for β-lactone synthetase activity using synthetic β-hydroxy acid substrates with alkene or alkyne moieties. β-Lactone formation is followed by rapid decarboxylation to form a conjugated triene chromophore for real-time evaluation by UV/Vis spectroscopy. The assay was used to determine steady-state kinetics of a long-chain β-lactone synthetase, OleC, from the plant pathogen Xanthomonas campestris. Site-directed mutagenesis was used to test the involvement of conserved active site residues in Mg²⁺ and ATP binding. A previous report suggested OleC adenylated the substrate hydroxy group. Here we present several lines of evidence, including hydroxylamine trapping of the AMP intermediate, to demonstrate the substrate carboxyl group is adenylated prior to making the β-lactone final product. A panel of nine substrate analogues were used to investigate the substrate specificity of X. campestris OleC by HPLC and GC-MS. Stereoisomers of 2-hexyl-3hydroxyoctanoic acid were synthesized and OleC preferred the (2R,3S) diastereomer consistent with the stereo-preference of upstream and downstream pathway enzymes. This biochemical knowledge was used to guide phylogenetic analysis of the β-lactone synthetases to map their functional diversity within the acyl-CoA synthetase, NRPS adenylation domain, and luciferase superfamily.