Bias in Aggregations of Subjective Probability and Utility

Subjective estimates of probability or utility are prone to two kinds of error: random and systematic (bias). The usual approach to reducing random error is averaging. How to reduce systematic error is not clear. This paper deals with the question of bias propagation when the estimates that are averaged are bias prone. Both simple and weighted averages are examined. The idea of using averaging as a bias reduction technique is explored. When the weights used in the averaging process are themselves biased, the random error in the average is also affected, possibly adversely. A balance has to be struck between bias reduction requirements and random error reduction requirements.     

Synthesis,spectral characterization,catalytic and antibacterial activity of macrocyclic Cu<Superscript>II</Superscript> compounds

Macrocyclic Cu^II compounds of the type Cu(L₄)Cl₂ (where L₄ = N₄ or N₂O₂ donor macrocyclic ligand) have been synthesized by treating the corresponding macrocycles with copper chloride in methanol. These compounds were characterized with the help of elemental analysis, i.r., mass, ESR, electronic spectra, conductance, magnetic and thermal studies. Distorted octahedral geometry has been proposed for all of these compounds. These compounds were found to be efficient in the catalytic oxidation of ascorbic acid and the percentage yields of oxidation products were determined spectrophotometrically. The biological activities of these compounds have been tested against gram +ve and gram −ve bacteria and found to be more active when compared with commercially available antibacterials like streptomycin and ampicillin.     

Evaluating UV-B effects and EDU protection in soybean leaves using fluorescence

A growth-chamber experiment was conducted to evaluate whether ethylenenediurea (EDU), a chemical shown to be protective against ozone pollution, could ameliorate foliar damage induced by ultraviolet-B (UV-B) radiation exposure in 'Roanoke' soybean (Glycine max L.), a UV-B-sensitive cultivar, and whether these effects could be discriminated using fluorescence (F) observations. The experiment had four treatment groups: control; biologically effective UV-B (18 kJ m(-2) day(-1)); EDU (500 micromol mol(-1)); and both UV-B and EDU (UV/EDU). Measurements included photosynthetic pigments, F image system (FIS) images of adaxial surfaces in four spectral regions (blue, green, red and far-red) and F emission spectra of the pigment extracts produced at two excitation wavelengths, 280 nm (280EX) and 380 nm (380EX). Several F ratios from 280EX, 380EX and the FIS images successfully separated the low UV vs high EDU group responses based on means alone, with intermediate values for controls and the combined UV/EDU groups. A UV-B/blue emission ratio, F315/F420 (280EX), was correlated with chlorophyll content (microg cm(-2))(R = 0.88, P < 0.001), as was a ratio of emissions at two UV-A wavelengths: F330/F385 (280EX) (R = 0.87). These two 280EX ratios were also linearly correlated with emission ratios produced by 380EX, such as the far-red/green ratio, F730/F525 (380EX) (R = 0.92, P < 0.001), and clearly distinguished the UV-B and EDU groups separately, and which bracketed the similar intermediate responses of the UV/EDU and control groups. The FIS images additionally captured the following anatomical spatial patterns across the leaf surfaces: (1) emissions of UV-B-irradiated leaves were more uniform but lower in intensity than those of other groups; and (2) emissions of EDU-treated leaves exhibited the greatest variation in spatial patterns because veins had elevated blue F and leaf edges had enhanced red and far-red F. This experiment supports the hypothesis that EDU substantially ameliorated UV-B damage to foliage, a result that relied on the combined use of FIS images and emission spectra.     

Intermolecular Dipole–Dipole Relaxation of Xe Dissolved in Water

Intermolecular ¹²⁹Xe–¹H nuclear Overhauser effects and ¹²⁹Xe longitudinal relaxation time measurements were used to demonstrate that the dipole–dipole coupling is the dominant relaxation mechanism for ¹²⁹Xe in water, at room temperature. ¹²⁹Xe–¹H cross-relaxation rates were derived to be ς_XeH 3.2 ± 0.3 × 10⁻³ s⁻¹, independent of xenon pressure (in the range of 1–10 bar) and of the presence of oxygen. Corresponding xenon–proton internuclear distances were calculated to be 2.69 ± 0.12 Å. Using the magnitude of the dipole–dipole coupling and the spin density ratio between dissolved xenon and bulk water, it is estimated that ¹²⁹Xe–¹H spin polarization-induced nuclear Overhauser effects would yield little net proton signal enhancement in water.     

Lithium diisopropylamide solvated by hexamethylphosphoramide: substrate-dependent mechanisms for dehydrobrominations

Lithium diisopropylamide-mediated dehydrobrominations of exo-2-bromonorbornane, 1-bromocyclooctene, and cis-4-bromo-tert-butylcyclohexane were studied in THF solutions and THF solutions with added hexamethylphosphoramide (HMPA). Rate studies reveal a diverse array of mechanisms based on mono-, di-, and trisolvated monomers as well as triple ions. The results are contrasted with analogous eliminations in THF in the absence of HMPA.     

The design of efficient and selective routes to a key 1,4-cis-substituted cyclohexylamide intermediate

This Letter describes the synthetic challenges in synthesising key 1,4-cis-substituted cyclohexylamide intermediate 1 for our research programme. Five different routes address the major issues of selectivity to afford the cis product in isomerically pure form and in high yield. Major purification issues were also encountered upon scaling some of the routes. The merits of the diverse routes are assessed and the reasoning given for which one was ultimately used for large-scale synthesis of 1.     

Robust mixed 10/12 helices promoted by "alternating chirality" in a new family of C-linked carbo-beta-peptides

The C-linked carbo-beta-peptides, oligomers of a new class of C-linked carbo-beta3-amino acids, have been shown to generate mixed 12/10 and 10/12 helices. The design involves use of "alternating chirality" of the epimeric (at the amine center) monomers to control the stability of these helices. The observation of stable 12/10 helix in a tripeptide and 10/12 helix in a tetrapeptide is unprecedented.     

Two new macrocyclic diaryl ether heptanoids from Boswellia ovalifoliolata

The stems of Boswellia ovalifoliolata BAL. & HENRY (Burseraceae) afforded two new macrocyclic diaryl ether heptanoids, ovalifoliolatin A (1) and B (2) together with three known compounds; acerogenin C (3), 3 alpha-hydroxyurs-12-ene (4), and sitost-4-en-3-one (5). The structures were established by means of spectroscopic analysis and compounds 1, 3-5 were evaluated for their antibacterial activity.     

Copper(II), zinc(II) and mixed metal copper(II)-zinc(II) peroxocomplexes containing 2,2′,6′,2″-terpyridine

Summary Facile reaction of 2,2,6,2-terpyridine (L; terpy) with copper or zinc powders or their mixtures, in the presence of an excess of H₂O₂, leads to novel complexes [Cu(L)-(O₂ ^2–)]·3H₂O, [Zn(L)(O ₂ ^2– )]·H₂O and [Cu,Zn(L)₂(O ₂ ^2– )₂]· 4H₂O, respectively, which were isolated and characterized by elemental and micro- analysis, e.s.r., electronic, i.r. and thermogravimetric analysis in air and argon.