bluuebunny/crossref_metadata_2025 huggingface dataset:
Phenyl urea derivatives as organic stabilizers for rigid poly(vinyl chloride) against photo‐degradation
Authors: Sabaa Magdy W. , Mohamed Riham R.
Published: November 2006

Phenyl urea derivatives have been prepared and investigated as photostabilizers for rigid PVC by measuring the extent of weight loss (%), the amount of gel formation as well as the intrinsic viscosity of the soluble fractions of the degraded polymer. Moreover, the efficiency of these stabilizers was evaluated from the extent of discoloration of the degraded polymer in their presence. The results indicated a reasonable stabilizing effect of these derivatives when compared with the commercially used UV stabilizers: phenyl salicylate (Salol) and methanone, 2‐hydroxy‐4‐(octyloxy)‐phenyl‐benzophenone. A synergistic effect is achieved when the phenyl urea derivatives are mixed with the UV absorbers in the ratio (75 : 25%), respectively. A radical mechanism is proposed to account for the stabilizing action of the products investigated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 2217–2226, 2007
Virus‐PLoc: A fusion classifier for predicting the subcellular localization of viral proteins within host and virus‐infected cells
Authors: Shen Hong‐Bin , Chou Kuo‐Chen
Published: November 2006

Viruses can reproduce their progenies only within a host cell, and their actions depend both on its destructive tendencies toward a specific host cell and on environmental conditions. Therefore, knowledge of the subcellular localization of viral proteins in a host cell or virus‐infected cell is very useful for in‐depth studying of their functions and mechanisms as well as designing antiviral drugs. An analysis on the Swiss‐Prot database (version 50.0, released on May 30, 2006) indicates that only 23.5% of viral protein entries are annotated for their subcellular locations in this regard. As for the gene ontology database, the corresponding percentage is 23.8%. Such a gap calls for the development of high throughput tools for timely annotating the localization of viral proteins within host and virus‐infected cells. In this article, a predictor called “Virus‐PLoc” has been developed that is featured by fusing many basic classifiers with each engineered according to the K‐nearest neighbor rule. The overall jackknife success rate obtained by Virus‐PLoc in identifying the subcellular compartments of viral proteins was 80% for a benchmark dataset in which none of proteins has more than 25% sequence identity to any other in a same location site. Virus‐PLoc will be freely available as a web‐server at http://202.120.37.186/bioinf/virus for the public usage. Furthermore, Virus‐PLoc has been used to provide large‐scale predictions of all viral protein entries in Swiss‐Prot database that do not have subcellular location annotations or are annotated as being uncertain. The results thus obtained have been deposited in a downloadable file prepared with Microsoft Excel and named “Tab_Virus‐PLoc.xls.” This file is available at the same website and will be updated twice a year to include the new entries of viral proteins and reflect the continuous development of Virus‐PLoc. © 2006 Wiley Periodicals, Inc. Biopolymers 85: 233–240, 2007.

This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
High‐performance liquid chromatography and LC‐ESI‐MS method for the identification and quantification of two biologically active polyisoprenylated benzophenones xanthochymol and isoxanthochymol in different parts of Garcinia indica
Authors: Kumar Satyanshu , Chattopadhyay Sunil K.
Published: November 2006

A reverse‐phase high‐performance liquid chromatographic method was developed for qualitative and quantitative analysis of xanthochymol (1), and isoxanthochymol (2) in the fruit rinds, leaves and seed pericarps of Garcinia indica with confirmation using PDA detection and electrospray ionization MS. Absorption at 276 nm was chosen as the measuring wavelength at which resolution and baseline separation of compounds (1) and (2) could be obtained. The identity of the above two isomeric compounds (1) and (2) in the samples was unambiguously determined by their respective quasi‐molecular ion [M – H]− in ESI‐MS. Compounds (1) and (2) were qualitatively and quantitatively analyzed in the above three samples of Garcinia indica. The overall analytical procedure is rapid and reproducible and is considered for the analysis of the above two compounds. Copyright © 2006 John Wiley & Sons, Ltd.
Microlaryngoscopic repair of iatrogenic pharyngeal pouch perforations: Treatment of choice?
Authors: Paleri Vinidh , Najim Omar , Meikle David , Wilson Janet A.
Published: November 2006

Background.

Endoscopic stapled diverticulostomy (ESD) has become the preferred technique for managing pharyngeal pouches. Iatrogenic perforation, created during stapling, is a rare but serious complication with significant morbidity and mortality. The conventional management in these instances is to convert it to an external procedure and excise the pouch.

Methods.

Iatrogenic perforations were noticed after stapling in 3 cases in our series of 73 patients who underwent ESD. They were repaired using microlaryngoscopic techniques.

Results.

All patients had an unremarkable postoperative course.

Conclusions.

Selected cases with iatrogenic perforations can be repaired primarily and observed with excellent outcome, obviating the need for an external pouch excision. © 2006 Wiley Periodicals, Inc. Head Neck, 2007
Evaluation of recurrent nodal disease after definitive radiation therapy for nasopharyngeal carcinoma: Diagnostic value of fine‐needle aspiration cytology and CT scan
Authors: Tar Toh Song , Wai Yuen Heng , Hong Goh Yau , Hood Keng Goh Christopher
Published: November 2006

Background.

Recurrent nodal disease in patients with nasopharyngeal carcinoma (NPC) after definitive radiotherapy presents a difficult clinical problem. This cohort of patients poses a diagnostic challenge to the head and neck surgeon because evaluation of the post‐irradiated neck, both clinically and radiologically, is known to be difficult, and it is not uncommon for neck dissection specimen in suspected recurrent nodal disease to contain no viable tumor cells. Currently, there is no well‐accepted method for the preoperative determination of the presence of malignancy in these nodal diseases.

Methods.

Over a 7‐year period in a tertiary hospital, we systematically reviewed the clinical charts of 42 patients with NPC who were diagnosed with suspected recurrent nodal disease, after radical definitive radiotherapy. Fine‐needle aspiration cytology (FNAC) was performed on clinically palpable nodes and results were correlated with final histopathologic results. Findings on CT scan were also correlated with final histopathologic specimens.

Results.

The specificity and sensitivity of FNAC was 75.0% and 75.0%, respectively. The positive and negative predictive value of FNAC was 93.8% and 37.5%, respectively. CT scan had a positive predictive value of 78.6%. The negative predictive value for multilevel involvement on CT scan was 20%.

Conclusion.

Radiological imaging and FNAC are useful diagnostic modalities in assessing recurrent nodal disease in the post‐irradiated neck in patients with NPC. Although routine CT scan criteria for pathologic lymphadenopathy cannot be accurately applied in the post‐irradiated neck, it is a useful surveillance tool in the routine follow‐up of patients with post‐irradiated neck with NPC. Clinicians, however, must understand their limitations when assessing these patients. The possibility of negative neck dissection must be conveyed to the patients. © 2006 Wiley Periodicals, Inc. Head Neck, 2007
Academic application is not an oxymoron
Authors: Ulrich Dave
Published: November 2006

Commentary on “A Performance‐Based, Minimalist Human Resource Management Approach in Business Schools”
The synoptic climate controls on hydrology in the upper reaches of the Peace River Basin. Part I: snow accumulation
Authors: Romolo L. , Prowse T. D. , Blair D. , Bonsal B. R. , Martz L. W.
Published: November 2006

For most cold region rivers, winter snowpack accumulation is the main contributor to spring run‐off events. This study investigated the synoptic controls on snowpack variability in the upper reaches of the Peace River Basin. An examination of snowpack accumulation at Grande Prairie, Alberta, revealed considerable inter‐annual variability for the period 1963–1996. Moreover, a decadal‐scale shift was evident with the magnitude of the snowpack being significantly reduced after 1976.

An eigenvector‐based map‐pattern classification procedure identified 16 patterns, of which 10 are classified as dry (non‐efficient precipitators) and 6 as wet (efficient precipitators). A frequency analysis demonstrated that variances in the occurrence of synoptic patterns were significantly related to variances in the magnitude of the snowpack at Grande Prairie on both an inter‐annual and inter‐decadal basis. Further analysis revealed that variances in the Pacific/North American (PNA) pattern influenced the local synoptic regime with wet (dry) types dominating under the negative (positive) PNA or zonal (meridional) flow. Although the Southern Oscillation Index (SOI) was found to have a significant impact on wet/dry‐type occurrence, it was revealed that El Niño events were associated with average synoptic conditions, while La Niña events were associated with a significant increase (decrease) in wet (dry) type frequency. A storm track analysis further identified that the occurrence of the wet and dry synoptic patterns influences the magnitude and position of surface lows in and around the Peace River Basin, and western Canada. Copyright © 2006 John Wiley & Sons, Ltd.
The synoptic climate controls on hydrology in the upper reaches of the Peace River Basin. Part II: Snow ablation
Authors: Romolo L. , Prowse T. D. , Blair D. , Bonsal B. R. , Marsh P. , Martz L. W.
Published: November 2006

The timing and rate of spring snowmelt in the upper reaches of the Peace River Basin control the development of large upstream spring flood waves and subsequent downstream ice‐jam flooding events. Given that snowmelt is controlled by atmospheric processes, this study identified the mid‐tropospheric circulation patterns that control the timing and rate of the snowmelt season on a critical tributary of the Peace River Basin.

Results showed that the date of spring snowmelt initiation in the upper Peace has become significantly earlier over the study period (1963–1996). This was explained by a significant increasing (decreasing) trend in the occurrence of mid‐tropospheric ridging (troughing and zonal flow) patterns, which are associated with above (below) average mean daily temperatures and available melt energy at Grande Prairie. Further analysis revealed that variances in the timing and rate of melt at Grande Prairie could be explained by variances in the local synoptic regime.

Examination of the broad‐scale atmospheric controls identified that the variances in the occurrence of the synoptic patterns could be explained by variances in the Pacific/North American teleconnection pattern. Although El Niño events were associated with average synoptic and snow ablation conditions, La Niña events were found to significantly impact the March synoptic regime over western Canada, and subsequently, the melt timing at Grande Prairie. Copyright © 2006 John Wiley & Sons, Ltd.
Modelling climate change impacts in the Peace and Athabasca Catchment and delta: II—variations in flow and water levels with varying winter severity
Authors: Leconte Robert , Peters Daniel , Pietroniro Alain , Prowse Terry
Published: November 2006

As freshwater ice is known to significantly affect flows and water levels within the Peace–Athabasca Delta (PAD), a winter severity sensitivity analysis using a one‐dimensional open channel hydraulic model was performed for four climate scenarios (from mild to severe), and was examined under three differing flow conditions (low, average, and high hydraulic regimes), in an effort to better understand the multiple interactions between ice cover and the hydrodynamic regime of this complex system characterized by overbank flooding and flow reversal episodes. In general, a reduction of winter severity lowered lake levels and river flows. While the winter severity effect is of relatively short duration in the rivers, the subsequent reduction in lake levels extends over the summer months. High river flows predispose flow reversal conditions, and water enters the lakes at the outlet as the water levels in the rivers feeding the PAD increase significantly over a short period of time. This flow reversal effect is suppressed during milder winters. Numerical modelling results indicate that extending the ice‐cover season (severe winter) by 14 days resulted in an increase of up to 5 cm in water level of large lakes in the PAD, while reducing it by 28 days lowered the levels by almost 10 cm. Short‐term variations in river levels reached up to 1·5 m as a result of varying the extent of the ice‐cover season. As the simulation runs did not consider ice‐jam events and neglected the effect of ice thickness on water levels, the reported quantitative results must be interpreted with prudence. Copyright © 2006 Crown in the right of Canada, and John Wiley & Sons, Ltd.
Single photon correlation measurements in a study of excitation process of individual CdTe/ZnTe quantum dots
Authors: Suffczyński J. , Kazimierczuk T. , Goryca M. , Trajnerowicz A. , Kowalik K. , Kossacki P. , Golnik A. , Nawrocki M. , Gaj J. A. , Karczewski G.
Published: November 2006

We present the results of systematic autocorrelation and cross‐correlation measurements performed on photons originating from various excitonic transitions in a single CdTe/ZnTe quantum dot (QD). Excitation power dependence of photoluminescence intensity was also measured on the same dot under the same experimental conditions. Recorded correlation histograms have provided evidence for memory effects in QD photoluminescence extending over a few excitation periods. Rate equation model assuming a ladder of states and excitation through a single carrier and exciton capture, is fitted to the data. As a consequence, simultaneous quantitative description of the results of both, correlation and power dependence, is obtained. Strong evidence is presented for a QD excitation by capture of single carriers rather than entire excitons. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Controlling spontaneous emission from quantum dots using photonic crystal microcavities
Authors: Gevaux D. G. , Atkinson P. , Anderson D. , Bennett A. J. , Bremner S. P. , Griffiths J. , Ellis D. J. P. , Stevenson R. M. , Jones G. A. C. , Ritchie D. A. , Shields A. J.
Published: November 2006

Controlling the radiative lifetime of quantum dot excitons by using microcavities provides a means of improving the performance of single photon sources. By manipulating the density of optical states in the environment of the quantum dot, the rate of spontaneous recombination can be altered by the Purcell effect. The emitted light can also be concentrated into a smaller extraction cone, improving efficiency. We investigate the use of temperature to spectrally tune an InAs self‐assembled quantum dot exciton and the mode of a photonic crystal defect cavity. A Purcell enhancement of the spontaneous emission rate of up to a factor of 11.4 is seen on‐resonance, while suppression by up to a factor of 4.4 is seen off‐resonance. Also, a two orders of magnitude increase in the intensity of light detected is measured when compared to quantum dots in bulk GaAs. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
InAs/InP(001) quantum dots and quantum sticks grown by MOVPE: shape, anisotropy and formation process
Authors: Michon A. , Patriarche G. , Sagnes I. , Beaudoin G. , Saint‐Girons G.
Published: November 2006

This contribution presents a thermodynamical analysis of the formation process of InAs/InP(001) quantum dots (QDs) or quantum sticks (QSs) grown by metalorganic vapor phase epitaxy. This study, based on an analytical model of Tersoff et al. adapted to our QD geometry, describes the origin of QD shape anisotropy and size dispersion. It also explains the shape transition from QDs to QSs under As‐poor growth conditions. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Emission lineshape in strain free quantum dot
Authors: Poliani E. , Bonfanti M. , Sanguinetti S. , Grilli E. , Guzzi M. , Gurioli M. , Abbarchi M. , Koguchi N.
Published: November 2006

We present a detailed study of the temperature dependence of the single quantum dot emission lineshape in strain free, GaAs/AlGaAs quantum dots. In particular, we analyze the emission lineshape in terms of linewidth, peak energy and sidebands. These quantities are all connected with the nature of the electron–phonon interaction. We conclude that the line broadening in quantum dots is due to pure dephasing processes driven by GaAs‐LO phonons. In addition, there is a lack of quantum size effect on the excitonic energy renormalization with the temperature. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Vertical homonuclear quantum ring molecules
Authors: Malet F. , Pi M. , Mayol R. , Barranco M. , Lipparini E. , Climente J. I. , Planelles J.
Published: November 2006

Within Local Spin Density Functional Theory, we have investigated the structure of homonuclear, fewelectron circular vertical semiconductor double quantum rings artificial molecules at zero magnetic field, and have obtained the addition spectrum as a function of inter‐ring distance. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
High precision numerical estimates of acoustic phonon frequencies of nonspherical nanoparticles
Authors: Murray Daniel B. , Laarakker Avra S. , Saviot Lucien
Published: November 2006

We introduce an adapted method for calculating the acoustic vibrational frequencies of arbitrarily shaped nanoparticles to high precision. Molecular dynamics simulation results are tested against exact solutions for a free sphere, a hollow sphere and a spheroid. This permits theoretical predictions of the frequencies of peaks in low frequency Raman spectra. Our results demonstrate that vibrational frequencies can be calculated for a wide range of low frequency modes with accuracies on the order of a tenth of a percent. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Pressure‐induced optoelectronic properties of InP nanocrystals: Tight‐binding approach
Authors: Díaz J. G. , Jaskólski W. , Zieliński M. , Bryant G. W.
Published: November 2006

An empirical tight‐binding theory is used to investigate pressure effects on the electronic and optical properties of InP nanocrystals. For bulk InP, our model predicts the Γ–X crossing of the conduction band minima at exactly the same lattice contraction as measured in the experiment. For small InP nanocrystals, the model correctly predicts the pressure dependence of the fundamental energy gap and luminescence intensity. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dephasing of orbital and spin degrees of freedom in semiconductor quantum dots due to phonons and magnons
Authors: Jacak W. , Krasnyj J. , Jacak J. , Gonczarek R. , Jacak L.
Published: November 2006

Phonon‐induced decoherence of orbital degrees of freedom in quantum dots (QDs) (GaAs/InAs) is studied and the relevant time‐scales are estimated versus dot dimension. Dephasing of excitons due to acoustic phonons and optical phonons, including enhancement of the effective Fröhlich constant caused by localization, is assessed for the state‐of‐art QDs. Temporal inefficiency of Pauli blocking in QDs due to lattice inertia is additionally predicted. For QD placed in a diluted magnetic semiconductor medium a magnon induced dephasing of spin is estimated in accordance with experimental results for Zn(Mn)Se/CdSe. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
InAs/InP quantum dot photonic crystal microcavities
Authors: Frédérick Simon , Dalacu Dan , Poole Philip J. , Lapointe Jean , Aers Geof C. , Williams Robin L.
Published: November 2006

We examine the optical mode structure of two‐dimensional, photonic crystal microcavities based on triple missing hole defects in hexagonal symmetry, etched air‐hole, suspended InP membranes. Polarisation dependent photoluminescence from InAs/InP quantum dots embedded within the cavities is used to explore mode energies and quality factors, Q, as a function of cavity design parameters. Optimised Q values are in excess of 7,500 for the modified y‐dipole mode. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Pure dephasing of two charge qubits in coupled quantum dots
Authors: Ben Chouikha W. , Jaziri S. , Bennaceur R.
Published: November 2006

We study the pure dephasing of two electrons confined in vertically coupled quantum dots, in which the presence of one electron confined in the double dot represents one qubit. We numerically evaluated the dephasing rates due to electrons coupling to both acoustic and optical phonons. Our numerically results show that the pure dephasing rates dependent on the separation between dots and the strength of electrons confinement. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photoreflectance investigations of energy level structure of InAs quantum dashes embedded in InGaAs/InGaAlAs quantum well grown on InP substrate
Authors: Rudno‐Rudziński W. , Kudrawiec R. , Sęk G. , Misiewicz J. , Somers A. , Schwertberger R. , Reithmaier J. P. , Forchel A.
Published: November 2006

Photoreflectance (PR) and photoluminescence measurements have been performed on molecular beam epitaxy grown InAs quantum dashes (QDash) of various sizes, embedded in In0.53Ga0.47As/In0.53Ga0.23Al0.24As quantum well (QW), grown on InP substrate. PR response from all relevant parts of the structure, i.e InAs/In0.53Ga0.47As QDashes, InAs/In0.53Ga0.47As/In0.53Ga0.23Al0.24As QW, and In0.53Ga0.23Al0.24As barriers, has been obtained. The lowest energy transition related to the ground state transition in QDashes shifts towards red with the increase in QDash sizes (amount of deposited InAs material) reaching wavelengths longer than for structures without the intermediate QW. The experimental data on the energies of optical transitions combined with the numerical calculation within the effective mass approximation has allowed determining the energy level structure of the entire system, including the values of conduction band offset between InGaAs and InGaAlAs layers. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Carrier relaxation in multi‐stacked InAs/GaAs quantum dots
Authors: Jang D.‐J. , Lu S.‐K. , Lee M.‐E. , Lai C. M. , Wang J. S. , Hsie K. Y.
Published: November 2006

The dependence of photoluminescence (PL) decay time on the thickness of spacer in InAs/GaAs multi‐stacked QDs (MSQDs) has been studied using time‐resolved PL upconversion. The decay time of PL increases with decreasing spacer thickness and indicates that vertical coupling in MSQD is significant. The separation of the two peaks of PL for 30 nm QDs results from excited and ground states indicates that the QDs sizes may be different from those of QDs with 10, 15, and 20 nm spacer thicknesses. The band filling effect is evident in MSQD from the study of time‐resolved photoluminescence. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Femtosecond photoluminescence spectroscopy of silicon nanocrystals
Authors: Trojánek F. , Neudert K. , Žídek K. , Dohnalová K. , Pelant I. , Malý P.
Published: November 2006

We report on the ultrafast photoluminescence dynamics in silicon nanocrystals measured by femtosecond up‐conversion technique. The samples were prepared by embedding porous silicon grains in a sol‐gel derived SiO2 matrix. Efficient initial relaxation of the excess energy of photoexcited carriers with the effective rate ≥4 eV/ps was observed. The ultrafast photoluminescence decay (about 400 fs) was interpreted in terms of quenching the interior exciton radiative recombination by fast carrier trapping on the nanocrystal surface. We also present the observation of the photoluminescence excited by two‐photon absorption at 830 nm and open aperture Z‐scan measurements to demonstrate a strong optical nonlinearity in silicon nanocrystals. We have found the value of two‐photon absorption coefficient β = 1.7 m/GW which corresponds to the imaginary part of the third‐order nonlinear susceptibility Im χ (3) = – 1 × 10–10 esu. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamics of coherent phonons in CsPbCl3 nanocrystals studied by femtosecond laser spectroscopy
Authors: Němec P. , Malý P.
Published: November 2006

We report on the generation of coherent optical phonons in CsPbCl3 nanocrystals in CsCl by femtosecond laser‐pulse illumination. The oscillations of four confined phonon modes were identified and their properties (amplitude, frequency, and phase) in dependence on the excitation laser pulse wavelength were studied. The results are interpreted in terms of spectral dependence of the phonon generation mechanism. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Shape and size effects on multi‐exciton complexes in single InAs quantum dots grown on InP(001) substrate
Authors: Chauvin N. , Bremond G. , Bru‐Chevallier C. , Dupuy E. , Regreny P. , Gendry M.
Published: November 2006

Single InAs/InP quantum dots and dashes are studied using micro‐photoluminescence spectroscopy. At low temperature exciton and biexciton are identified. An increase of the biexciton binding energy is observed with decreasing the quantum dot size. Moreover, the asymmetric confinement causes a pronounced linearly polarized splitting of the exciton for quantum dots. Such a splitting is not observed for the quantum dashes despite their strong asymmetrical shape. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
InAs quantum dots grown by molecular beam epitaxy on GaAs (211)B polar substrates
Authors: Zervos M. , Xenogianni C. , Deligeorgis G. , Androulidaki M. , Savvidis P. G. , Hatzopoulos Z. , Pelekanos N. T.
Published: November 2006

InAs nanostructures were grown by molecular beam epitaxy on GaAs (211)B at temperatures between 400‐530 °C and growth rates that were varied between 0.1 to 0.02 mono‐layers (ML) per second. For temperatures up to 500 °C we obtain pyramidal‐shaped InAs quantum dots with average heights between 3 and 7 nm while at 530 °C the dots become elongated, higher and are self organized into dashes along a specific crystallographic direction. Photoluminescence (PL) spectra taken at 18 K reveal in the QD samples grown at 500 °C a broad (55 meV FWHM) PL peak at 1.27 eV, associated with the QD layer. The PL peak blue shifts noticeably (∼7 meV) upon increasing power of excitation, as a consequence of the strain induced electric field that exists in the (211)B direction. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bradykinin‐related peptides from Phyllomedusa hypochondrialis azurea: mass spectrometric structural characterisation and cloning of precursor cDNAs
Authors: Thompson Alan Hunter , Bjourson Anthony John , Shaw Chris , McClean Stephen
Published: November 2006

Amphibian skin secretions contain a plethora of bioactive compounds, many of which are understood to act to deter ingestion by predators. Bradykinins in particular are constitutively expressed in many amphibian skin secretions, mediating a variety of effects including hyperalgesia and contraction of gastric smooth muscle. Using a variety of proteomic techniques (high‐performance liquid chromatography (HPLC) separation, matrix‐assisted laser desorption/ionisation time‐of‐flight mass spectrometry (MALDI‐TOFMS), and quadrupole time‐of‐flight tandem mass spectrometry (Q‐TOF‐MS/MS)) the current study identified 13 bradykinin‐like peptides in the skin secretions of Phyllomedusa hypochondrialis azurea, including several new C‐terminally extended isoforms (VPPGFTPFRLT, VHypPGFTPFRQT) and a novel phyllokinin‐like peptide (RPPGFTPFRVY). Identification of the cDNA sequences encoding these peptides led to the deduction that the peptides were derived from differential post‐translational processing and modification of five different precursors. Such an event emphasises the metabolic efficiency of peptide production in amphibian venom, with multiple products perhaps selective to different receptors in a variety of predators generated from a single precursor. An unusual modification was also recognised in the present study, with several bradykinin‐like peptides featuring hydroxyprolination of the first proline residue rather than the commonly targeted second. This alteration may be mediated by the structural organisation of N‐terminal amino acids prior to precursor processing. Copyright © 2006 John Wiley & Sons, Ltd.
Glyceryl ethers in insects: identification of alkyl and alk‐1‐enyl glyceryl ether phospholipids
Authors: Lambremont E. N. , Wood Randall
Published: November 2006

Alkyl and alk‐1‐enyl glyceryl ethers have been identified in the phospholipids of three insect species, the American cockroach (Periplaneta americana), the tobacco budworm (Heliothis virescens), and the boll weevil (Anthonomus grandis). Glyceryl ethers were not detected in the neutral lipids. The ethers were found in the phospholipid fraction of whole insects and in isolated fat body tissue. The ether content varied among the three insect species, and fluctuated during various developmental stages. Gas liquid chromatographic analysis of the alkyl glyceryl ethers and aldehydes derived from the alk‐1‐enyl glyceryl ethers of the cockroach and budworm whowed striking differences in chain length. However, the hydrocarbon side‐chain of the two ether fractions were similar in length for each species. Preliminary evidence indicates that 1‐14C‐acetate can be incorporated into alkyl ethers but not into alk‐1‐enyl ethers ofHeliothis pupae.
Autoxidation of tissue lipids. I. Incorporation of dietary fatty acids and formation of monocarbonyl compounds in adipose tissue lipids of the vitamin E‐deficient rat
Authors: Derrick Nancy M. , Wishner Lawrence A.
Published: November 2006

Male weanling rats were fed vitamin E‐deficient and vitamin E‐supplemented diets containing 5% corn oil or cod‐liver oil for 16 weeks, after which their adipose tissue lipids were extracted and analyzed in a nitrogen atmosphere for carbonyl compounds and fatty acids.

The vitamin E‐deficient cod‐liver oil‐fed rats, exhibiting incisor depigmentation and darkened adipose tissue, yielded lipids which had a lower iodine value, contained less polyunsaturated fatty acids, and contained more carbonyl compounds, particularly alkanals and alk‐2‐enals, than the lipids from the animals fed the vitamin E‐supplemented cod‐liver oil diet. The tissues of the vitamin E‐deficient corn oil‐fed rats contained less linoleate and more monocarbonyl compounds than those of the vitamin E‐supplemented corn oil‐fed animals.

The results indicate that vitamin E protection is necessary for the incorporation of C20 and C22 fatty acids into the tissues from the diet and that in the deficiency of vitamin E, a low level of autoxidation occurs in the tissues.
Determination of the structure of lecithins via the formation of acetylated 1,2‐diglycerides
Authors: Privett O. S. , Nutter L. J.
Published: November 2006

A detailed procedure for quantitative determinations of molecular species of lecithins is described and applied to several lecithins isolated from natural sources. The method is based on the conversion of lecithin to acetylated 1,2‐diglycerides and analysis of these compounds by methodology used for the determination of triglyceride structure.

The preparation of the acetylated 1,2‐diglycerides was carried out via hydrolysis with phospholipase C and acetylation of the resultant, 1,2‐diglycerides with pyridine‐acetic anhydride. Preparation of acetylated 1,2‐diglycerides from lecithin by acetolysis with acetic acid‐acetic anhydride was shown to be accompanied by intermolecular as well as intramolecular rearrangement of the fatty acids.

The structure of the acetylated 1,2‐diglycerides was determined by a combination of argentation‐TLC and pancreatic lipase hydrolysis using internal standards for quantification. The method was applied to lecithins isolated from milk serum, egg, soybean, safflower seed and wheat germ lipids.
Metabolism of chimyl alcohol and phosphatidyl ethanolamine in the rat brain
Authors: Bickerstaffe Roy , Mead James F.
Published: November 2006

Following intracerebral injection of14C‐phosphatidylethanolamine and3H‐chimyl alcohol into 18 day old rats, the ethanolamine phosphoglycerides were isolated and analyzed. The14C and3H activities in the dimethyl acetals derived from alkenyl acyl ethanolamine phosphoglycerides and in the glyceryl ethers derived from the alkyl acyl ethanolamine phosphoglycerides were measured. The absence of14C in the dimethyl acetals indicates that phosphatidyl ethanolamine is not transformed into phosphatidal ethanolamine under these circumstances. The increase with time of the3H content of the glyceryl ethers and dimethyl acetals indicates that chimyl alcohol was a precursor of both types of phospholipids.
The hypolipidemic effect of SU‐13,437 in rats with natural endogenous hypertriglyceridemia
Authors: Lenz Paul H. , Fleischman Alan I.
Published: November 2006

The oral administration of 25 mg 2‐methyl‐2‐[p‐(1,2,3,4‐tetrahydro‐1‐naphthyl)‐phenoxy] propionic acid (SU‐13,437) per kilogram body weight per day in two‐month‐old female rats with naturally occurring hypertriglyceridemia resulted in a 31% decrease (P<0.01) in the serum triglyceride concentration after 14 days of treatment, compared with littermate controls receiving diluent (Polyethylene glycol‐300) only. Phospholipid, cholesterol, free fatty acid, glucose, red blood cell and white blood cell concentrations were similar in the blood of treated and control animals after 14 days of treatment. Liver total and relative weight was increased as a result of SU‐13,437 treatment (P<0.01). The liver total lipid concentration per 10 gm liver decreased (P<0.05) due to a decrease in triglyceride (P<0.01), cholesterol (P<0.01), and free fatty acid (P<0.05) concentration following treatment. The relative liver glycogen concentration was elevated in treated rats at 7 (P<0.01) and 14 (P<0.05) days of treatment.
The lipids of the oriental hornet,Vespa orientalis F.
Authors: Ishay Jacob , Goldberg Sarah , Ikan Raphael
Published: November 2006

Analysis of the hornet's hemolymph revealed the presence of C16 and C18 fatty acids (70%), which were accompanied by minor quantities (ranging from 0.1% to 0.6%) of the following acids: C10∶0, C11∶0, C12∶0, C13∶0, C14∶0, C15∶0, C16∶0, and C17∶0. The hemolymph of the queen larvae contained more C18∶1 than the hemolymph of the worker larvae, and the percentage of C16∶1 was higher in the fat body and the midgut than in the hemolymph. The significance of these results is discussed.
Fatty acid composition of triglycerides and phosphoglycerides during growth inGlomerella cingulata
Authors: Anekwe Gregory E. , Dubal Bharat C.
Published: November 2006

The fatty acid composition of triglycerides and phosphoglycerides accumulated at selected ages during the growth ofGlomerella cingulata was investigated. Glyceride accumulation was taken as mg glyceride/mg N and the nitrogen content of the fungus at the ages investigated was used as an index of growth. The fatty acids produced were identified by comparing their retention times on gas liquid chromatography with that of known standards. The results showed that whereas total glyceride and fatty acid content varied from age to age, the fatty acid composition at the various ages remained the same.
The effects of biliary obstruction on the rates of uptake, synthesis and secretion of14C‐labeled cholesterol by isolated perfused rat livers
Authors: Ferris R. M. , Jacobj H. P. , Barak A. J.
Published: November 2006

The isolated perfused rat liver technique was utilized to study the effect of biliary obstruction on the rates of uptake, synthesis and secretion of14C‐labeled cholesterol in an effort to elucidate the mechanism of hypercholesterolemia in this condition. By perfusing normal and biliary obstructed livers with a medium containing14C‐labeled acetate or14C‐labeled lipoprotein cholesterol and by measuring cholesterol biosynthesis in vitro, it was possible to clarify some of the questions concerning these aspects of lipid metabolism. The results of these studies revealed that the uptake of cholesterol was not altered in biliary obstruction. Instead the hypercholesterolemia of biliary obstruction arises from an increased rate of secretion of cholesterol from liver, which is accompanied by an increased rate of hepatic cholesterolgenesis. Evidence is also presented to suggest that a substance is present in biliary obstructed blood which is capable of initiating increased cholesterolgenesis in normal livers.
Composition, particle size and role in dietary fat transport of two different lipoproteins of the intestinal lymph
Authors: Boquillon Micheline , Paris Roger , Clement Jacqueline
Published: November 2006

Rat intestinal lymph very low density lipoproteins have been separated by cellulose acetate electrophoresis. After administration of a meal including natural fats and labeled fatty acids, two labeled bands were detected on the electrophoregraphs. Further separations of these two kinds of particles were performed by density gradient zonal centrifugation. The isolated lipoproteins were analyzed for chemical composition and investigated by electron microscopy and electrophoresis. The moving particles had a higher protein and cholesterol content and a smaller diameter than the particles which remained at the origin. It has also been shown that the major part of the labeled lymph lipids were transported by the smaller particles.
Total, polar and neutral lipids ofRhizopus arrhizus fischer
Authors: Gunasekaran M. , Weber D. J. , Hess S. L.
Published: November 2006

The changes in total lipid content, neutral and polar lipids, total fatty acids, and free fatty acids were investigated over a 4 day period in the zygomycete,Rhizopus arrhizus Fischer. The highest concentration of lipids occurred at the 72 hr period. The degree of unsaturation in the total fatty acid fraction increased during the growth period, whereas the degree of unsaturation decreased in the free fatty acid fraction during the same time period. The ratios of neutral to polar lipids over the 4 day period were: 0.75, 0.22, 1.94 and 0.94. The major components of polar lipids were phosphatidyl ethanolamine, lecithin, lysolecithin, and fatty acids. The fatty acids in the mono‐ and diglycerides were predominately saturated (67–96%). The fatty acids in the triglycerides shifted from a predominately unaturated (69%, 24 hr) to a more saturated pattern (62%, 96 hr).
Fatty acid composition of milk phospholipids. III. Camel, ass, and pig milks
Authors: Morrison W. R.
Published: November 2006

Phospholipids were isolated from camel, ass, and pig milks, and their fatty acid compositions were determined by gasliquid chromatography. The specific distributions of fatty acids in phosphatidyl choline (PC) and phosphatidyl ethanolamine (PE) were determined. The results are compared with previous results for bovine, sheep, Indian buffalo, and human milks. The milk phospholipids which were studied can be grouped, on the basis of their fatty acid compositions, into those from ruminant herbivores, nonruminant herbivores, and nonherbivores. The phospholipids of camel milk however have features typical of all groups as well as 15% plasmalogen in the PE fraction.
Sphingolipid metabolism in leucocytes. I. Incorporation of14C‐glucose and14C‐galactose into glycosphingolipids by intact human leucocytes
Authors: Kampine John P. , Martensson Eric , Yankee Ronald A. , Kanfer Julian N.
Published: November 2006

Glucosyl ceramide and lactosyl ceramide have been isolated from intact human leucocytes. Incubation of intact white blood cells with either14C‐glucose or14C‐galactose resulted in the incorporation of these tracers into the glycosphingolipids. The products were extracted by conventional procedures and purified by combined silicic acid column and thin‐layer chromatography. The bulk of the radioactivity was found in the monohexoside and dihexoside ceramide fractions.

Acid hydrolysis yielded glucose as the principal carbohydrate of the monohexoside ceramide, regardless of the sugar precursor employed. In the dihexoside ceramide fraction, galactose was liberated as the major sugar component. The specific activities of the lactosyl ceramide was found to be greater than that of the corresponding glucosyl ceramide.
Characterization of naturally occurring α‐hydroxylinolenic acid
Authors: Smith C. R. , Wolff I. A.
Published: November 2006

The seed oil ofThymus vulgaris L. (Labiatae) contains 13% of a new unsaturated hydroxy fatty acid which has been characterized as α‐hydroxylinolenic acid. This oil also contains the previously unknown norlinolenic (all‐cis‐8,11,14‐heptadecatrienoic) acid (2%) and linolenic acid (55%). The co‐occurrence of these three acids suggests that the C17 acid is biosynthesized by α‐oxidation of linolenic acid.
Comparison of lipoprotein analysis by agarose gel and paper electrophoresis with analytical ultracentrifugation
Authors: Noble R. P. , Hatch F. T. , Marzimas J. A. , Lindgren F. T. , Jensen L. C. , Adamson G. L.
Published: November 2006

A comparison has been made of human serum lipoprotein analysis by agarose gel and paper electrophoresis with a standard method of analytical ultracentrifugation. Samples were obtained from 28 patients with various disorders of lipoprotein metabolism. Correspondence was shown between the following electrophoretic and ultracentrifugal fractions: β and Sf 0–20; pre‐β and Sf 20–400; α1 and total HDL. The deviations observed with the electrophoretic methods, though sizable, were smaller than the usual clinically significant abnormalities. Semiquantitative application is there fore justified. Agarose gel electrophoresis is slightly more difficult than paper electrophoresis, but gives improved resolution of pre‐β‐ and β‐lipoproteins and better densitometric scans. Evidence was also presented that the agarose method, when used in conjuction which ultracentrifugation, may be a valuable research technique for the study of lipoprotein properties.
Phospholipids of the pulmonate land snailCepaea nemoralis (L.)
Authors: Van Der Horst D. J. , Kingma F. J. , Oudejans R. C. H. M.
Published: November 2006

The phospholipids of the snailCepaea nemoralis, comprising the major lipid fraction (65%) in this terrestrial pulmonate, were investigated by thin‐layer and column chromatography. Detailed gas chromatographic analyses of liberated fatty acid fractions and amino acid analyses of the water soluble moieties of isolated phospholipid classes were carried out. Phosphatidyl choline (47%) and phosphatidyl ethanolamine (21%) were found to be the predominant phospholipid classes, while phosphatidyl serine (8%), phosphatidyl inositol (6%), diphosphatidyl glycerol (3%), ceramide amino‐ethylphosphonate (7%), lysophosphatidyl choline (1%), and phosphatidic acid (1%) were present in lesser amounts. In the phosphatidyl ethanolamine and phosphatidyl serine fractions, minor quantities of plasmalogen analogues were detected. Fatty acid profiles of the various phospholipid classes appeared to be strikingly diverse, e.g. a characteristic component, such as linoleic (18∶2ω6) acid, ranging from 3–54%. In vivo radioisotope studies using 1‐14C‐acetate demonstrated the high biosynthetic rate of all phospholipid classes and their respective fatty acid fractions. Results are discussed in relation to data on the phospholipids from other invertebrate species.
Gas‐liquid chromatography of triglyceride mixtures containing both odd and even carbon number fatty acids
Authors: Litchfield Carter , Harlow R. D. , Reiser Raymond
Published: November 2006

Quantitative GLC of triglycerides has been extended to natural fats containing both odd and even carbon number fatty acids. A 1.83‐m glass column containing 3.0% JXR silicone on 100/120 mesh Gas‐Chrom Q resolved triglycerides differing by only one carbon number. Peak resolution was significantly improved by hydrogenating each triglyceride sample prior to GLC analysis.

The triglycerides of four fish oils (mullet, tuna, menhaden, and pilchard) and one seed fat (Acanthosyris spinescens) containing odd carbon number fatty acids were analyzed by this technique. The method was also useful for determining the triglyceride composition of the cyclopentene fatty acid oil fromHydnocarpus wightiana seeds.
Comparison of column chromatographic methods for the quantitative determination of mono‐ and digalactodiglycerides in fresh alfalfa (Medicago sativa)
Authors: van der Veen J. , Hirota K. , Olcott H. S.
Published: November 2006

Three column chromatographic procedures for separating and recovering the galactolipids in fresh alfalfa extracts were compared. Silicic acid chromatography yielded pure fractions by thin‐layer chromatography, infrared absorption, and chemical analysis. The carbon‐Celite column gave the highest yield of monogalactodiglyceride. Of the 1.2% total lipids of fresh alfalfa, approximately 12% was monogalactodiglyceride and 8% was digalactodiglyceride. Linolenic acid accounted for about 90% of the total fatty acids in these components.
Mass spectra of prostaglandins: II. Trimethylsilyl and alkyloxime‐trimethylsilyl derivatives of prostaglandins B1 and B2
Authors: Middleditch B. S. , Desiderio D. M.
Published: November 2006

The mass spectra of the trimethylsilyl ester trimethylsilyl ether derivatives of prostaglandins B1 and B2, and of their O‐ethyl and O‐methyl oximes are reported and discussed. The high resolution spectra of these compounds are also considered. These spectra are compared with those of the corresponding d9‐trimethylsilyl derivatives and of the selectively labeled trimethylsilyl ester d9‐trimethylsilyl ethers. The base peaks of the spectra of the trimethylsilyl derivatives are formed by sequential loss of C5H11 (by cleavage of C‐15/6) and of CO (from the ring). The spectra of the oxime‐trimethylsilyl derivatives are dominated by ions resulting from loss of the alkoxy group of the oxime moiety.
Lipid composition ofChaetomium cochliodes: Effect of media
Authors: Safe S. , Brewer D.
Published: November 2006

The fatty acid and lipid compositions ofChaetomium cochliodes grown on three different media are compared. Although the growth media effects dramatic changes in the antibiotic production, only minor alterations in the lipid patterns are observed. γ‐Linolenic acid was identified for the first time from an ascomycete, and the phylogenetic consequences of this are discussed. In addition, ergosterol was shown to be the major sterol component (95%), the minor sterol being identified as ergosta‐5,7,9(11),22‐tetraen‐3β‐ol.
Deposition of dietary epoxides in tissues of rats
Authors: Fioriti J. A. , Buide N. , Sims R. J.
Published: November 2006

Epididymal fat pad lipids from rats fed trivernolin at the 4.8% level in the diet for 90 days were found to contain 6.1% epoxyoleic acid. No epoxides were detected in the serum lipids and only trace amounts were found in the liver lipids. TLC, GLC and a specific color reaction with picric acid were used to identify this fatty epoxide in the tissues. Epoxyoleic acid was shown to be present as a mixture of predominately monovernoloyl triglycerides with some divernoloyl triglycerides and small amounts of trivernolin. Lipase hydrolysis of the first two triglycerides has demonstrated that the vernoloyl groups are present mostly in the 1,3 positions. In a separate experiment, rats were fed cholesterol epoxide at the 0.5% and 1.5% levels in the diet for 90 days. TLC and GLC examination of lipids from these rats failed to reveal the presence of any cholesterol epoxide. Only one‐half of the sterol fed could be accounted for in the fecal lipids.