1,505 research outputs found
Platts, John-Residence P.2
No full textJohn Platts home, 364 Quince, Salt Lake City, Utah. Used in Annual Report 1974-7
Electron Energy Distributions Produced by Gamma-Rays
No full textReproduced with permission from Platts. Platts holds all copyright to this article. For the original version, please refer to the print publication of Nucleonics Vol. 12 No. 10 (now Nucleonics Week).A DETAILED KNOWLEDGE of the number
and energies of the electrons set in
motion in a material when it is irradiated
by a continuous spectrum of
X-rays is very useful. Calculations of
energy abstracted from the beam and
absorbed by the material, and of the
ionization produced in a cavity within
the material, all depend on such
knowledge. Applications of these calculations
are described elsewhere.
Tables are presented that make it
possible to calculate the initial energy
distribution of the electrons set in
motion in an element of volume by
either monoenergetic radiation or continuous
spectra.
After being set in motion, these electrons of differing energy proceed
out of the volume in which they
originated and travel through the
absorbing material, losing energy at a
varying rate, until they are brought to
rest. It is useful to be able to determine
the electron flux passing through
an element of area at any point in the
material. From the initial volume
distribution, the energy distribution
of electrons passing through an element
of area is calculated in this article.The authors take pleasure in acknowledging
the financial support of the National Cancer
Institute of Canada. One of us (J. E. T.) is
indebted to the National Research Council of
Canada for financial assistance in the form
of a bursary
Insight into uranyl binding by cyclic peptides from molecular dynamics and density functional theory
No full textIt is a challenging task to develop uranyl-chelating agents based on peptide chemistry. A recently developed cationic dummy atom model of uranyl in conjunction with the classical molecular dynamics simulation presents a helpful utility to study the chelation of uranyl by peptides with a low computational cost. In the present study, it was used to describe the chelation of uranyl by the cyclic decapeptide with 4 Glu residues cycGluArgGluProGlyGluTrpGluProGly and its derivatives containing two phosphorylated serines in place of two Glu, termed pS16, pS18, pS38, and pS68. The obtained structures were further studied by density functional theory (DFT) and subsequent density analysis. We show that a combination of steered molecular dynamics and simulated annealing, using standard forcefields for peptide with the cationic dummy atom model of uranyl, can quickly and reliably obtain binding modes of uranyl-peptide complexes. Classical molecular dynamics simulation in explicit water produces geometry very close to the DFT-optimized structure. The presence of uranyl completely changes the conformation of these cyclic peptides from unstructured to organised. The simulation of a peptide with two uranyl units explained why only the 1:1 ratio of peptide and chelated-uranyl is observed experimentally in most cases, by the insufficiency of the anionic residues for the chelation of two UO 2 2 + units, but that pS16 can accommodate two such units
Computational evidence for structural consequences of kiteplatin damage on DNA
No full textThe reaction of the potential anticancer drug
kiteplatin, cis-[PtCl2(cis-1,4-DACH)], with oligomers of
single- and double-stranded DNA ranging from 2 to 12
base pairs in length was performed as a model for DNA
interaction. The potential for conformational flexibility of
single-stranded adducts was examined with density functional
theory (DFT) and compared with data from 1H-NMR
1D and 2D spectroscopy. This indicates the presence of
multiple conformations of an adduct with d(GpG), but only
one form of the adduct with d(TGGT). The importance of
a suitable theoretical model, and in particular basis set, in
reproducing experimental data is demonstrated. The DFT
theoretical model was extended to platinated base pair step
(GG/CC), allowing a comparison to the related compounds
cisplatin and oxaliplatin. Adducts of kiteplatin with larger
fragments of double-stranded DNA, including tetramer,
octamer, and dodecamer, were studied theoretically using
hybrid quantum mechanics/molecular mechanics methods.
Structural parameters of all the base-paired models were
evaluated and binding energies calculated in gas phase and in solution; these are compared across the series and
also with the related complexes cisplatin and oxaliplatin,
thus revealing insights into how kiteplatin binds to DNA
and similarities and differences between this and related
compounds
Evaluating the Effectiveness of Selective Hedge-Based on Oil Product Trading Data in Platts Window
No full textThe crude oil and petroleum products pricing for international trading is based on benchmark oil prices assessed by Platts Energy, a price reporting agency. Platts provides an assessment of the value of various refined oil products by collecting bid, offer and deal details through Platts window. Since it is not as transparent and liquid as trades in futures market, Platts assessment is easier to be influenced by large trade volume. Oil companies or petroleum product consumers can follow the price fluctuation to do selective or cross hedging. This study takes statistical approach to show the leveraged profit of single trading company in Platts window from the past data, and try to find out price regularity to evaluate the hedge effectiveness of cross hedging and to prove the theory issued by Professor Howard and D\ue2Antonio.
The modern concept of risk management has evolved from simple risk reduction to pursuing better financial performance. A company can do the so-called selective hedge or dynamic hedge by different hedge ratio from its market view. In this study, the finding is that spread of Asian kerosene jet fuel and gasoil price, the regrade, can be influenced by large trading quantity from single company in Platts window. In turn, the assessed price can be leveraged to a larger profit in other physical or paper positions. The past 10-year regrade showed a regular pattern which oil companies or oil product consumers, such as airlines, can hedge effectively with better performance by taking advantage of the variation. In the paper by Charles T. Howard and Louis J. D\ue2Antonio, a derived mathematical model of hedge effectiveness shows the possibility of more profit by using the futures position while carrying the same risk. A set of parameters is also offered for trader to easily judge if long or short position should be taken, and how effective the profit will be. However, the measure is solely for speculation deals. For hedging purpose, paper positions must be opposite to physical positions for risk reduction
Investigation of steric influences on hydrogen-bonding motifs in cyclic ureas by using X-ray, neutron, and computational methods
No full textA series of urea-derived heterocycles, 5N-substituted hexahydro-1,3,5- triazin-2-ones, has been prepared and their structures have been determined for the first time. This family of compounds only differ in their substituent at the 5-position (which is derived from the corresponding primary amine), that is, methyl (1), ethyl (2), isopropyl (3), tert-butyl (4), benzyl (5), N,N-(diethyl)ethylamine (6), and 2-hydroxyethyl (7). The common heterocyclic core of these molecules is a cyclic urea, which has the potential to form a hydrogen-bonding tape motif that consists of self-associative R2 2(8) dimers. The results from X-ray crystallography and, where possible, Laue neutron crystallography show that the hydrogen-bonding motifs that are observed and the planarity of the hydrogen bonds appear to depend on the steric hindrance at the α-carbon atom of the N substituent. With the less-hindered substituents, methyl and ethyl, the anticipated tape motif is observed. When additional methyl groups are added onto the α-carbon atom, as in the isopropyl and tert-butyl derivatives, a different 2D hydrogen-bonding motif is observed. Despite the bulkiness of the substituents, the benzyl and N,N-(diethyl)ethylamine derivatives have methylene units at the α-carbon atom and, therefore, display the tape motif. The introduction of a competing hydrogen-bond donor/acceptor in the 2-hydroxyethyl derivative disrupts the tape motif, with a hydroxy group interrupting the N-H×××O-C interactions. The geometry around the hydrogen-bearing nitrogen atoms, whether planar or non-planar, has been confirmed for compounds 2 and 5 by using Laue neutron diffraction and rationalized by using computational methods, thus demonstrating that distortion of O-C-N-H torsion angles occurs to maintain almost-linear hydrogen-bonding interactions. The incredible bulk: A series of cyclic ureas has been studied to examine the influence of bulky substituents on the hydrogen-bonding motifs that form and the degree to which the urea group can be distorted to maintain strong intermolecular contacts.</p
Exploring the Reactivity and Biological Effects of Heteroleptic N-Heterocyclic Carbene Gold(I)-Alkynyl Complexes
No full textWith the aim to explore the effects of different organometallic ligands on the reactivity and biological properties of a series of twelve heteroleptic AuI complexes, of general formula [Au(NHC)(alkynyl)] (NHC = benzimidazolylidene or 1,3-dihydroimidazolylidene) were synthesized and characterized by 1H and 13C NMR and elemental analysis, and in some cases also by X-ray diffraction. The compounds were all stable in H2O/DMSO as established by NMR spectroscopy, while they could react with model thiols (EtSH) in the presence of water to undergo ligand-substitution reactions. 1H NMR experiments showed that dissociation of the more labile alkynyl ligand was possible for all compounds, while in the case of the benzimidazolylidene series also dissociation of the NHC ligand could be observed. DFT calculations suggest that, depending on the steric hindrance exerted by both the NHC wingtip groups and the alkynyl substituents, the reaction can proceed either via a π-stabilized intermediate or with the alkynyl ligand remaining purely σ-coordinated to the AuI center until completely dissociated. The most stable compounds in PBS buffer (pH 7.4), as assessed by UV-Visible spectrophotometry, were further investigated for their ability to stabilize G4 DNA by FRET DNA melting assay, showing only moderate activity. Moreover, two derivatives were tested in vitro for their anticancer activities in three different human cancer cell lines and showed cytotoxicity in the low micromolar range
Segmentation in Markov chain consumer behaviour models
No full textContents * A: Historical development of credit and behavioural scoring
* R W Johnson: Legal, social and economic issues in implementing scoring in the US
* R Eisenbeis: Problems in applying discriminant analysis in credit scoring models
* M A Hopper and E M Lewis: Behaviour scoring and adaptive control systems
* B: Objectives and measures in credit scoring
* A D Wilkie: Measures for comparing scoring systems
* G Wilkinson and J Tingay: The use of affordability data - does it add real value?
* R L Keeney and R M Oliver: Improving lender offers using consumer preferences
* C: Practical implementation of scoring systems
* A Lucas: Updating scorecards: Removing the mystique
* R M Oliver and E Wells: Efficient frontier cut-off policies in credit portfolios
* D: Features of scoring
* D J Hand and W E Henley: Can reject inference ever work?
* G A Overstreet Jr, E L Bradley, and R S Kemp Jr: The flat-maximum effect and generic linear scoring models: a test
* J N Crook, L C Thomas, and R Hamilton: The degradation of the scorecard over the business cycle
* G Bennett, G Platts, and J Crossley: Inferring the inferred
* E: Other applications of scoring in credit risk
* K J Leonard: Detecting credit card fraud using expert systems
* G Platts and I Howe: A single European scorecard
* A Lucas and J Powell: Small sample scoring
* F: Alternative approaches to scoring systems
* B Narain: Survival analysis and the credit granting decision
* P Sewart and J Whittaker: Graphical models in credit scoring
* M B Yobas, J N Crook, and P Ross: Credit scoring using neural and evolutionary techniques
* J Ho, L C Thomas, T A Pomrey, and W T Scherer: Segmenting in Markov chain consumer credit behaviour model
How to obtain Pt(IV) complexes suitable for conjugation to nanovectors from the oxidation of [PtCl(terpyridine)]+
No full textOxidation of [Pt(II)Cl(terpy)]+ (terpy = 2,2′:6′,2′′-terpyridine) has been attempted with several oxidizing agents and under different experimental conditions in order to obtain a Pt(IV) complex suitable for the conjugation to nanovectors to be used in drug delivery targeting for anticancer therapy. The best compromise in terms of yield and purity of the final complex was obtained by microwave-assisted reaction at 70 °C in 50% aqueous H2O2 for 2 h. Under these conditions the quantitative formation of [Pt(IV)Cl(OH)2(terpy)]+ was observed. The subsequent synthetic steps were, (i) functionalization of [Pt(IV)Cl(OH)2(terpy)]+ in the axial position with succinic anhydride to obtain [Pt(IV)Cl(OH)(succinato)(terpy)]+ and (ii) reaction of the latter with nonporous silica nanoparticles (SNPs) with an external shell containing primary amino groups to obtain a nanovector able to transport the Pt(IV) antitumor prodrug in the form of a conjugate Pt-SNP. Finally, the antiproliferative activity and cell accumulation of [Pt(II)Cl(terpy)]+, [Pt(IV)Cl(OH)2(terpy)]+, and the Pt-SNP conjugate were measured on three cancer cell lines. Despite highly effective accumulation of Pt-SNP in cells, a modest increase in activity was observed with respect to the molecular species. Further experiments showed that the Pt-SNP conjugate can release [Pt(II)Cl(terpy)]+ upon reduction, but this metabolite may undergo hydrolysis, and the resulting aquo complex could coordinate once again the free amino groups of the SNPs. In the resulting tetraamine form, the Pt(ii) complex conjugated to the SNPs cannot completely perform its antiproliferative activity. © 2017 The Royal Society of Chemistry
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