Organochlorine compounds in Lake Superior: chiral polychlorinated biphenyls and biotransformation in the aquatic food web

The enantiomeric composition of seven chiral PCB congeners was measured in the Lake Superior aquatic food web sampled in 1998, to determine the extent of enantioselective biotransformation in aquatic biota. All chiral PCB congeners studied (CBs 91, 95, 136, 149, 174, 176, and 183) biomagnified in the Lake Superior aquatic food web, based on biomagnification and food web magnification factors greater than unity. PCB atropisomers were racemic in phytoplankton and zooplankton, suggesting no biotransformation potential toward PCBs for these low trophic level organisms. However, Diporeia and mysids had significantly nonracemic residues for most chiral congeners studied. This observation suggests that these macrozooplankton can stereoselectively metabolize chiral congeners. Alternatively, macrozooplankton obtained nonracemic residues from feeding on organic-rich suspended particles and sediments, which would imply that stereoselective microbial PCB biotransformation may be occurring in Lake Superior sediments at PCB concentrations far lower than that previously associated with such activity. Widely nonracemic PCB residues in forage fish (lake herring, rainbow smelt, and slimy sculpin) and lake trout suggest a combination of both in vivo biotransformation and uptake of nonracemic residues from prey for these species. Minimum biotransformation rates, calculated from enantiomer mass balances between predators and prey, suggest metabolic half-lives on the order of 8 yr for CB 136 in lake trout and 2.6 yr for CB 95 in sculpins. This result suggests that significant biotransformation may occur for metabolizable PCB congeners over the lifespan of these biota. This study highlights the potential of chiral analysis to study biotransformation processes in food webs.     

Enhanced problem translation and short-term memory: Components of mathematical talent.

The performance of mathematically talented 12- and 13-year-olds on various cognitive tasks was compared with that of average-ability youth, verbally talented youth, and college students. In Experiment 1, the hypothesis that mathematical talent includes enhanced problem-translation skills was supported: The mathematically talented students were better than other groups at writing equations expressing complex relationships. Although the mathematically talented group outperformed their average-ability peers, they were no better than the verbally talented group or the college students in rewriting and recalling the propositions in an algebra story problem. In Experiment 2, the hypothesis that mathematical talent includes enhanced ability to represent and manipulate information in short-term memory was strongly supported: the mathematically talented youth outperformed the other youth and, in most cases, performed as well as or better than the college students. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Embedding deductive capabilities in relational database systems

The basic idea of our work is to include deductive capabilities in a relational database system by fully using the operands of relational algebra and without using any theorem prover. We present a deductive database system where the user can formulate deduction laws as logical formulas, but which works on an underlying relational database system by fully using the data manipulation routines of such a system. Generally, it is not possible to express the deduction laws by means of expressions of relational algebra (see Ref. 1). In our system, a relational algebra expression is associated with every database deduction law. The result of its evaluation (with respect to an underlying database) is the set of all database entries that can be deduced from the database by applying the respective law once (Theorem 1). By successively applying all these relational expressions for all the database deduction laws it is possible to generate the whole extensional database (i.e. all tuples deducible from the database).     

Fiber quality of emmer (Triticum dicoccumSchubler) and einkorn wheat (T monococcumL) landraces as determined by analytical pyrolysis

Hulled wheat grain is used mainly in the alternative or health food market. Most of the suggested beneficial effects of these cereals are due to specific characteristics of their fibre. Pyrolysis/gas-chromatography/mass-spectrometry (PY/GC/MS) has proved to be a reproducible analytical tool for fibre analysis applicable to the analysis of cereal fibre. Pericarp fibre of 10 emmer and einkorn wheat landraces were analysed by PY/GC/MS and compared to a test durum wheat variety. The pyrolysis fragments derived from the polysaccharide fraction were significantly more abundant in emmers than in the other genotypes, whereas the highest percentage of lignin-derived pyrolysis fragments was detected in durum wheat. The genotype groups (winter and spring emmers, einkorn and durum wheat) were satisfactorily discriminated on the basis of the molecular composition of the fibre, whereas a discrimination within groups was not possible due to the limited number of samples available. The results suggest that the native emmer genetic material may represent a source of high-value dietary fibre. Breeding should aim at preserving such characters. © 1998 Society of Chemical Industry     

Temperature Tunable 4D Polymeric Photonic Crystals

Photonic crystals owe their multitude of optical properties to the way their structure creates interference effects. It is therefore possible to influence the photonic response by acting on their physical structure. In this article, tunable photonic crystals made by elastic polymers that respond to their environment are explored, in particular with a physical deformation under temperature variation. This creates a feedback process in which the photonic response depends on its physical structure, which itself is influenced by the environmental changes. By using a multi-photon polymerization process specifically optimized for soft responsive polymers such as Liquid Crystalline Networks, highly resolved, reproducible, and mechanically self-standing photonic crystals are fabricated. The physical structure of the 3D woodpile can be tuned by an external temperature variation creating a reversible spectral tuning of 50 nm in the telecom wavelength range. By comparing these results with finite element calculations and temperature induced shape-change, it is confirmed that the observed tuning is due to an elastic deformation of the structure. The achieved nanometric patterning of tunable anisotropic photonic materials will further foster the development of reconfigurable photonic crystals with point defects acting as tunable resonant cavities and, more in general, of 4D nanostructures.     

Inequity in equity: How "equity" can lead to inequity for high-potential students.

Over the past three decades, the achievement of waves of American students with high intellectual potential has declined as a result of inequity in educational treatment. This inequity is the result of an extreme form of egalitarianism within American society and schools, which involves the pitting of equity against excellence rather than promoting both equity and excellence, anti-intellectualism, the "dumbing down" of the curriculum, equating aptitude and achievement testing with elitism, the attraction to fads by schools, and the insistence of schools to teach all students from the same curriculum at the same level. In this article we provide recommendations for creating positive change--recommendations that emphasize excellence for all, that call for responsiveness to individual differences, and that suggest basing educational policies on well-grounded research findings in psychology and education. Educational policies that fail to take into account the vast range of individual differences among students--as do many that are currently in us--are doomed to be ineffective. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Antibacterial agents and cystic fibrosis: synthesis and antimicrobial evaluation of a series of N-thiomethylazetidinones

The increasing emergence of multidrug-resistant microorganisms is one of the greatest challenges in the clinical management of infectious disease. New antimicrobial agents are therefore urgently required, particularly in the treatment of chronic and recurrent infections often associated with antibiotic-resistant pathogens, as in the case of cystic fibrosis (CF) patients. This study reports the antibacterial activity of a series of monocyclic β-lactams with an alkylidenecarboxyl chain or electron-withdrawing groups such as 4-OAc, 4-SAc, and 4-SO(2)Ph at the C4 position of the ring. N-Unsubstituted and N-thiomethyl derivatives were compared. A total of 33 azetidinones were tested for their activity against Gram-positive and Gram-negative bacterial clinical isolates. The combination of an N-thiomethyl group and a benzyl ester on the 4-alkylidene side chain were found to increase the potency against Gram-positive bacteria. The N-thiomethyl group clearly elevated the activity of 4-acetoxyazetidinones relative to the corresponding NH derivatives. The most active compounds showed minimum inhibitory concentration (MIC) values of 4 and 8 mg L(-1) against methicillin-resistant Staphylococcus aureus isolated from pediatric patients with CF.     

Easily accessible oxygen‐containing derivatives of niobium pentachloride as catalytic precursors for ethylene polymerization

The low catalytic activity of NbCl₅ as an ethylene polymerization catalyst was significantly increased by the addition of a series of oxygen donors. The novel niobium derivatives NbCl₅(OPh₂) (1), NbCl₅(OEt₂) (3), NbCl₅(O?CPh₂) (5), NbCl₅(O?CHPh) (6), NbCl₅(O?CHMe) (7) and [NbCl₄(dppe)₂](NbCl₆) (18) (dppe is 1,2‐bis(diphenylphosphino)ethane) and the previously reported derivatives NbCl₅(OMePh) (2), NbCl₅(thf) (4) (thf is tetrahydrofuran), NbCl₅(O?CHOMe) (8), NbCl₅(O?CHNMe₂) (9), NbCl₅[O?C(NMe₂)₂] (10), NbCl₅(NCMe) (11), NbCl₄(κ²‐1,2‐OC₆H₄OMe) (12), NbCl₄[κ²‐O?C(Me)CH₂C(Me₂)O] (13), (14), [NbCl₄(O₂CMe)]₂ (15), NbCl₃(dme)(µ‐O)NbCl₅ (16) (dme is 1,2‐dimethoxyethane), [NbCl₄(κ²‐dmm)₂](NbCl₆) (17) (dmm is dimethylmaleate), TaCl₅(O?CMe₂) (19) and [TaCl₄(O₂CMe)]₂ (20) were tested as catalytic precursors in the ethylene polymerization reaction using AlMe₃‐depleted methylaluminoxane as co‐catalyst. Highly linear polyethylene was obtained. Compounds 1, 3, 5, 6 and 8–13 showed catalytic activities in the range 89–116 kg_polymer mol_Nb^?1 h^?1 bar^?1, i.e. comparable with the best performances reached with niobium pre‐catalysts up to now. However, the dinuclear compounds 14–16 and 18 were found to be less active, whereas17 and the tantalum derivatives 19 and 20 did not produce polymer. Relatively high molecular weights were achieved with the mononuclear compounds 1, 2, 8, 9, 10 and 12, the dinuclear 16 and the phosphine ionic 18. Copyright © 2011 Society of Chemical Industry