bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractThe 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

AbstractWe 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

AbstractWe 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

AbstractSingle 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

AbstractInAs 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

AbstractAmphibian 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

AbstractAlkyl 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

AbstractMale 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

AbstractA 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

AbstractFollowing 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

AbstractThe 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

AbstractAnalysis 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

AbstractThe 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

AbstractThe 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

AbstractRat 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

AbstractThe 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

AbstractPhospholipids 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

AbstractGlucosyl 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

AbstractThe 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

AbstractA 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

AbstractThe 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

AbstractQuantitative 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

AbstractThree 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

AbstractThe 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.