bluuebunny/crossref_metadata_2025 huggingface dataset:
The effects of fasting and streptozotocin diabetes on the triglyceride lipase activity of rat liver plasma membranes
Authors: Nomura Takahide , Iguchi Akihisa , Matsunaga Hitoshi , Sakamoto Nobuo
Published: December 2006

The activity of hepatic triglyceride lipase (H‐TGL) of plasma membranes isolated from rat liver is shown to be reduced by fasting. Refeeding restores the enzyme activity. The suppressed activity of H‐TGL in streptozotocin diabetic rats is restored by insulin treatment. The behavior of the enzyme activites in both situation coincides with that of plasma insulin levels. The results suggest that the H‐TGL of rat liver plasma membranes is under hormonal regulation by insulin.
Waxes and volatile oils inHypericum ericoides (Guttiferae)
Authors: Cardona M. L. , Marco J. A. , Sendra J. M. , Seoane E. , Ibañez J. Torres
Published: December 2006

A wax isolated from an hexane extract ofHypericum ericoides L. was shown to contain only an, aldehydic and an alcoholic fraction. The aldehydic fraction was found to be largelyn‐octacosanal (≈77%), with minor amounts of other linear homologous aldehydes, whereas the alcoholic fraction was almost puren‐octacosanol. From the same hexane extract, a volatile oil was also isolated and studied by combined gas chromatography‐mass spectrometry (GC‐MS). Monoterpene, sesquiterpene and aliphatic straight chain (C8–C11) hydrocarbons, sesquiterpene alcohols and aliphatic long‐chain acids (C8, C9, C10, C11, C12, C14, C16 and C18) were found. Biogenetic relationships are discussed.
Abnormal lipid composition of fat tissue in human mesenteric panniculitis
Authors: Cherayil G. D. , Scaria K. S. , Hensley G. T. , Elliott W. H.
Published: December 2006

Mesenteric fat tissue obtained at autopsy from 6 patients with mesenteric panniculitis (MP) were found to contain significant amounts of cholesteryl esters (CE). In addition, samples from 3 of these cases were found to contain 0.5–1.3% free cholesterol, 0.9–1.9% free fatty acids (FFA), 0.6–2.5% 1‐alkyl glyceryl ether diesters and small amounts of squalene. Two of these tissues also contained alk‐1‐enyl glyceryl ether diesters. The fatty acid compositions of the CE, FFA, triacylglycerides and glyceryl ether diesters (GEDE) were determined and oleic acid (18∶1) was found to be the major fatty acid. The alkyl group composition of the GEDE consisted essentially of 16∶0 and 18∶0 and 18∶1 carbon atoms in both types of ethers.
Quantitative estimation of C‐24 epimeric sterol mixtures by 220 MHz nuclear magnetic resonance spectroscopy
Authors: Chiu P. ‐L. , Patterson G. W.
Published: December 2006

Four pairs of 24‐alkyl epimeric sterols: 24α‐ and 24β‐methylcholesterol; 24α‐ and 24β‐ethylcholesterol; 24α‐ and 24β‐methyl‐5, 22‐E‐cholestadienol; and 24α‐ and 24β‐ethyl‐5, 22‐E‐cholestadienol, were mixed in known proportions (0, 20, 40, 50, 60, 80 and 100% of β‐epimer to α‐epimer). The 220 MHz nuclear magnetic resonance spectra of each of the mixtures were obtained and compared. Areas of these spectra useful in quantitative determinations were identified and discussed.
Seasonal changes in lipid and fatty acid composition of the freshwater mollusk,Diplodom patagonicus
Authors: Pollero R. J. , Brenner R. R. , Gros E. G.
Published: December 2006

Diplodom patagonicus is a freshwater bivalve mollusk living in lakes of the patagonian Andes mountains in Argentina. Lipid composition and seasonal changes in the mollusk were studied in the natural habitat. In addition to common nonpolar and polar lipids, small amounts of alk‐1‐enyldiacylglycerol ethers and significant quantities of ceramide aminoethyl phosphonate were present. Total lipid content changed during the year, primarily because of decreased triacylglycerols in winter. The fatty acid composition of the lipids, remarkably different from that of marine bivalves, and even from other fresh water animals, was especially rich in the ω6 fatty acids, linoleic and arachidonic (ca. 25%), and poor in the ω3 acids, 20∶5 and 22∶6. The ω6/ω3 acid ratio was ca. 2, which is very high compared to marine bivalves. The fatty acid composition and the ω6/ω3 acid ratio were constant during the whole year, suggesting a very stable diet, rich in vegetal detritus and poor in diatoms. The influence of environmental temperature fluctuation with season on fatty acid composition also was negible. Modest proportions of 22∶2 nonmethylene‐interrupted (NMI) acids were detected and confirmed by mass spectrometry. It was shown that 20∶2 NMI acids were absent.
Sterol ester hydrolase inFusarium oxysporum
Authors: Madhosingh Clarence , Orr Winson
Published: December 2006

Two electrophoretically different forms of sterol ester hydrolase (EC 3.1.1.13) were obtained from the cytoplasmic extract of the mycelia ofFusarium oxysporum. The entities, estimated at 60,000 (I) and 15,000 (II) molecular weights, were obtained in Sephadex G100 column chromatography of the ammonium sulfate precipitate from the cytoplasmic extract. A third form III, 75,000 MW, was obtained from the culture filtrate. The activity of the enzyme was increased by Triton X‐100 and was not inhibited byp‐chloromercuribenzoate (PCMB), a sulfhydryl reagent. The enzymes I and II were inhibited differentially by NaCl. The optimal activities of forms I, II and III occurred at pH 4.8, pH 8.0 and pH 7.0, respectively. the apparent Km values of 7.7×10−5, 8.3×10−5 and 10.5×10−5, respectively, indicate a similar order of affinity for cholesteryl oleate at pH 7.1. The rate of hydrolysis of cholesteryl esters were in the order: linoleate>oleate>valerate>butyrate > acetate. Cholesteryl benzoate and palmitate were not hydrolyzed. The properties of the microbial enzyme are discussed in relation.
Mitochondrial membrane fatty acid composition in the marmoset monkey following dietary lipid supplementation
Authors: McMurchie Edward J. , Gibson Robert A. , Charnock John S. , McIntosh Graeme H.
Published: December 2006

Diets supplemented with high levels of saturated fatty acids derived from sheep kidney (perirenal) fat or unsaturated fatty acids derived from sunflowerseed oil were fed to marmoset monkeys for 22 wk. The effect of such diets on plasma, red blood cell phospholipids, and liver, heart, kidney and brain mitochondrial phospholipid fatty acids was determined. Despite large differences in the level and type of lipid present in the experimental diets, there was little effect on the proportion of saturated to unsaturated fatty acids in the phospholipids of the membranes examined. The diets did, however, alter the proportion of the various classes of polyunsaturated fatty acids in the membrane phospholipids, with the sunflower‐seed oil diet elevating and the sheep kidney fat diet reducing the n−6/n−3 unsaturated fatty acid ratio, relative to a low (mixed fat) reference diet. This change occurred in all membranes except brain, in which only a small response to altered dietary lipid intake was observed. Elevation of dietary linoleic acid led to an increase in membrane linoleic acid and a marked decrease in membrane arachidonic acid, such that the membranes from animals fed the sunflowerseed oil diet exhibited the lowest proportion of arachidonic acid. In this latter respect, the response of the marmoset monkey to dietary lipid supplementation differs markedly from the rat. Our inability to alter significantly membrane lipid saturation/unsaturation supports the notion that a homeostatic mechanism is in some way responsible for buffering membranes from the effects of significant changes in the nature of the dietary lipid intake.
Elongation of (n−9) and (n−7)cis‐monounsaturated and saturated fatty acids in seeds ofsinapis alba
Authors: Mukherjee Kumar D.
Published: December 2006

Lipids in developing seeds ofSinapis alba contain appreciable proportions of (n−7)octadecenoic (vaccenic) acid besides its (n−9) isomer (oleic acid), whereas the constituent very long chain (>C18) monounsaturated fatty acids of these lipids are overwhelmingly composed of the (n−9) isomers. Cotyledons of developingSinapis alba seed use [1‐14C]acetate, [1‐14C]malonate or [1,3‐14C]malonyl‐CoA for de novo synthesis of palmitic, stearic and oleic acids and for elongation of preformed oleic, vaccenic and stearic acids to their higher (n−9), (n−7) and saturated homologs, respectively. Moreover, elongation of preformed (n−7)palmitoleic acid to vaccenic acid is observed. Stepwise C2‐additions to preformed oleoyl‐CoA by acetyl‐CoA or malonyl‐CoA yielding (n−9)icosenoyl‐CoA, (n−9)docosenoyl‐CoA and (n−9)tetracosenoyl‐CoA are by far the most predominant reactions catalyzed by the elongase system, which seems to have a preference for oleoyl‐CoA over vaccenoyl‐CoA as the primer. The pattern of14C‐labeling of the very long chain fatty acids formed from either acetate or malonate shows a close analogy in the mode of elongation of monounsaturated and saturated fatty acids.
Cholesterol and phospholipid composition of erythroblasts isolated from Mouse Spleen after Rauscher Leukemia virus infection
Authors: Montfoort A. , Boere W. A. M.
Published: December 2006

Erythroblasts (more than 95% pure) were isolated from MuLV‐R infected mouse spleen. The cholesterol, phospholipid, and fatty acid composition of the diacyl and plasma logen derivatives of the choline and ethanolamine phosphoglycerides of mouse erythroblasts, red blood cells enriched with reticulocytes, and mature erythrocytes have been compared. It was demonstrated that during maturation of the mouse red blood cells, the following relative changes in the lipid composition occur: (a) The cholesterol/phospholipid molar ratio increases from 0.35 to 0.77 (b) The sphingomyelin concentration increases from 3.0 to 12.1 and the phosphatidylserine concentration from 5.3 to 11.2 as percentage of the total phospholipid. (c) Phosphatidylcholine decreases from 52.0 to 46.2% and phosphatidylinositol from 6.7 to 3.1%, respectively. (d) The percentage of linoleic acid in the phosphatidylcholine fraction increases more than two fold and is predominantly found at the 2‐position. However, molecules containing linoleic acid at the 1‐position are found to be more abundant in erythroblasts than in mature erythrocytes. (e) Phosphatidylethanolamine has been found to contain a high percentage of arachidonic acid, which was mainly found at the 2‐position. The percentage of arachidonic acid at the 1‐position increases during maturation, while the percentage at the 2‐position decreses. (f) The plasmalogen derivatives of the choline phosphoglycerides were found to be almost absent in mouse red blood cells (<0.5%), while the ethanolamine plasmalogen phosphoglycerides represented about 8% of the phospholipids.
Acid triacylglycerol lipase from bovine thyroid gland
Authors: De Wolf M. , Lagrou A. , Hilderson H. J. , Dierick W.
Published: December 2006

An acid lipase has been detected in bovine thyroid tissue using triolein as a substrate. The activity, probably associated with the lysosomes, displays a rather broad pH‐optimum in the pH 4 to pH 6.5 range. The lipase activity can be partially purified by cosedimentation with lysosomes followed by solubilization through detergent and chromatography on Sephadex G‐200 and carboxymethyl cellulose. The elution profile on Sephadex G‐200 shows one peak (moleculare weight 67,000±2,000). In the final CM‐cellulose step, two lipase peaks (lipase LA and lipase LB) are found. Sulhydryl reagents (iodoacetate, iodoacetamide, and N‐ethylmaleimide) as well as mercuric ions markedly reduce both enzyme activities. Calcium ions, EDTA, and heparin have no effect. Sodium fluoride and diisopropylfluorophosphate are only slightly inhibitory. Sodium chloride causes a slight increase in both lipase activities. Anionic phospholipids such as cardiolipin and phosphatidylserine are not essential for enzyme activity.
Effects of three dietary fats on plasma lipids and lipoproteins in fasting and post‐prandial humans after a short‐term diet
Authors: Baudet M. F. , Esteva O. , Delplanque B. , Winchenne N. , Jacotot B.
Published: December 2006

The effects of 3 dietary fats (olive oil, canbra oil and butter) on the fatty acids of blood lipids and on serum lipoproteins were compared in 6 healthy adult outpatients, after a 6‐day normocaloric diet including 35% of the studied fat. Important, although incomplete, changes appeared in the fatty acid composition of the various serum lipids and in the composition and distribution of serum lipoproteins. These changes probably result from the degree of saturation of the fat ingested. Moreover, differences were observed among individual subjects. Genetic differences, which are important in clinical practice, are stressed in connection with risks of vascular diseases and hyperlipidemia and affect intestinal fat absorption and lipoprotein metabolism.
Metabolism of erucic acid in adipocytes isolated from rat epididymal fat
Authors: Christophersen Bjorn , Krogstad Torild , Norseth Jon
Published: December 2006

The metabolism of [14‐14C]erucic acid and [U‐14C]palmitic acid has been investigated in adipocytes isolated from rat epididymal fat. The rate of acylation of [14C]erucic acid in cellular lipids and oxidation to CO2 and acid‐soluble activity was ca. 1/3 of the rate with [14C]palmitic acid as substrate. A maximal incorporation of fatty acids in triacylglycerol was found at a fatty acid concentration of 0.8 mM in the medium, both with [14C]erucic acid and [14C]palmitic acid as substrate. Glucose added to the medium increased the esterification and decreased the oxidation of both fatty acids. No significant chain‐shortening of [14C]erucic acid to shorter monoenes was identified in the fat cells. Increasing concentrations of unlabeled palmitic acid in the incubation medium markedly inhibited the esterification of [14C]erucic acid, whereas unlabeled erucic acid had little effect on the rate of esterification of [14C]palmitic acid.
Absence of wax esters in pelagic lake baikal fauna
Authors: Morris R. J.
Published: December 2006

The absence of wax esters in meso‐ and bathypelagic organisms from Lake Baikal may be a clue to the historical development of wax ester metabolism in the marine ecosystem.
Levels of polyunsaturated fatty acids in tissues from zinc‐deficient rats fed a linseed oil diet
Authors: Eder Klaus , Kirchgessner Manfred
Published: December 2006

The effect of zinc deficiency on the levels of n−6 and n−3 polyunsaturated fatty acids (PUFA) in lipids from tissues of rats fed a diet containing linseed oil was investigated. Rats were fed either a control diet (25 mg Zn/kg) or a zinc‐deficient diet (0.8 mg Zn/kg) for 10 d. To avoid energy and nutrient deficiency, 11.6 g of diet per day was administered by gastric tube. At the end of the experiment, rats fed the zinc‐deficient diet had drastically reduced plasma zinc concentration and alkaline phosphatase activity consistent with severe zinc deficiency in these rats. Zinc‐deficient rats had higher levels of n−3 PUFA, in particular eicosapentaenoic acid (EPA), and lower levels of n−6 PUFA, in particular linoleic acid, in liver and plasma phosphatidylcholine (PC) and in erythrocyte membrane total lipids than did control rats. By contrast, the levels of n−3 PUFA in PC from testes and heart, and in phosphatidylethanolamine (PE) from liver, testes and heart, were only slightly different between zinc‐deficient and control rats. The study suggests that desaturation of α‐linolenic acid is not inhibited by zinc deficiency, and that in zinc‐deficient rats, n−3 PUFA preferentially incorporated into phospholipids at the expense of n−6 PUFA, especially EPA into PC. The study also shows that the effect of zinc deficiency on PUFA levels is different for PC and PE in rat tissues.
Reactions of diazomethane with glycerolipids in the presence of serum or inorganic salts
Authors: Schmid Patricia C. , Schmid Harald H. O.
Published: December 2006

Diazomethane is widely used for the selective methylation of nonesterified fatty acids in the presence of other lipids. However, when the reaction is carried out directly with plasma or serum, substantial methanolysis of phospholipid acyl groups occurs. Because of the importance of rigorous selectivity in the assay of unesterified fatty acids which are present only in trace amounts in cells and body fluids, we have investigated the diazomethane procedure in detail and reached the following conclusions: (i) When diazomethane reacts with lipid extracts in organic solvent, no ester hydrolysis occurs. (ii) In the presence of serum or plasma, diazomethane reacts with water and inorganic salts, causing the solution to become basic (CH2N2+NaCl+HOH→CH3Cl+Na++OH−+N2); methoxide ions are formed from methanol (CH3OH+OH−→CH3O−+HOH) causing extensive methanolysis (CH3O−+RO−CO−R′→CH3O−CO−R′+RO−). An analogous reaction takes place with ethanol. All esters of glycerol are transesterified in aqueous salt solution by this mechanism. It is therefore essential to prepare a lipid extract prior to the assay of unesterified fatty acids when using the diazomethane procedure.
The influence of exogenous cholesterol on the fatty acid composition of liver lipids in the rats given linoleate and γ‐linolenate
Authors: Takayasu Ken , Yoshikawa Iwao
Published: December 2006

Three groups of rats were given cholesterol and cholic acid for four weeks, and then fed a diet with 20% lard (group 1), a diet with 4% of the lard substituted by methyl linoleate (group 2), and a diet with 2% substituted by methyl linoleate and another 2% by methyl γ‐linolenate (group 3) during the same period. Two control groups (4 and 5) received the same diets as did groups 2 and 3, respectively, but without cholesterol and cholic acid. The hepatic cholesterol accumulation was significantly less in group 3 than in groups 1 and 2, and distinct differences in the degree of plasma cholesterol elevation were found among the cholesterol fed groups (1>2>3). Supplement of γ‐linolenate resulted in a reduction of the ratio of arachidonate to homo‐γ‐linolenate in both the cholesterol‐fed group and the control group, but the ratio was much lower in the former. Incorporation of 1‐14C‐linoleate and 1‐14C‐γ‐linolenate into the liver lipids of groups 2 and 4, and groups 3 and 5 was observed respectively at 1 and 3 hr after the intravenous injection. The specific activity of arachidonate from both of the labeled acids in phospholipid and triglyceride was apparently lower in groups 2 and 3 than in groups 4 and 5, respectively. The distribution rate of radioactivities in tetraenoic acids was also low in groups 2 and 3 among the fatty acids of phospholipid and triglyceride. The results indicated impairment of conversion of homo‐γ‐linolenate into arachidonate in the cholesterol‐fed rats.
Effect of 6‐substituted sterols on sterol‐induced reproduction inPhytophthora cactorum
Authors: Elliott C. G. , Math V. B.
Published: December 2006

6‐Methylcholesterol and 6‐ketocholestanol do not promote oospore development inPhytophthora cactorum when added as sole sterol supplement of media, and they inhibit development induced by cholesterol. 6‐Fluorocholesterol promotes oospore formation; 6‐chlorocholesterol does not, and neither inhibits cholesterol‐induced development. A strain ofP. cactorum has been found which is exceptional among Phytophthoras or Pythiums examined hitherto in forming numberous oospores with cholestanol. In this strain, 6‐ketocholestanol inhibits cholestanol‐induced oospore formation. These results indicate the importance of C‐6 as a point of interaction with cellular sites controlling oospore formation.
Iodination of arachidonic acid by the iron/H2O2/iodide system
Authors: Henderson William R. , Hubbard Walter C. , Klebanoff Seymour J.
Published: December 2006

The newly described iron/hydrogen peroxide (H2O2)/iodide antimicrobial system iodinates arachidonic acid to form the same products which are generated by peroxidase/H2O2/iodide systems. Arachidonic acid is multiply iodinated with the formation ofbis‐iodohydrins and monoiodinated products which were identified as iodolactones by their high performance liquid chromatography elution patterns and by gas chromatography‐mass spectrometric analysis. Iodination of arachidonic acid by the iron/H2O2/iodide system appears to proceed via the formation of hydroxyl radicals as an intermediate species. Iodination of unsaturated lipids may contribute to the cytotoxicity of the iron/H2O2/iodide system.
Serum lipoprotein hydrolysis by purified lipases
Authors: Fried Melvin , Chorvath Branko
Published: December 2006

Purified lipases from pork pancreas,Rhizopus arrhizus andLeptospira biflexa hydrolyze the triglycerides of pork very low density lipoproteins (VLDL), while higher density lipoproteins are not affected significantly. The velocity versus substrate curves for the VLDL were sigmoid.
Chromatin supraorganization, DNA fragmentation, and cell death in erythrocytes of the rattlesnake, Crotalus durissus terrificus (Serpentes, Viperidae), infected with the protozoan, Hepatozoon spp. (Apicomplexa, Hepatozoidae)
Authors: Miyamoto Maristela , Mello Maria Luiza S.
Published: December 2006

Forms of the protozoan of the Hepatozoon genus are detected free in the circulation and also within some of the erythrocytes of infected snakes. In healthy snakes, DNA fragmentation and cell death usually affect a few circulating erythrocytes in agreement with the long life span expected for these cells. In the present study we investigated whether infection by Hepatozoon spp. affected the incidence of DNA fragmentation and cell death in erythrocytes from the rattlesnake, Crotalus durissus terrificus. Methods such as the kinetics of Feulgen‐DNA hydrolysis, and the TUNEL and comet assays, previously used for the study of chromatin organization and DNA fragmentation in erythrocytes of healthy snakes, were used. The results indicated that Hepatozoon spp. increased the DNA fragmentation and chromatin condensation typical of cell death in circulating erythrocytes of C. d. terrificus, including cells that do not harbour the parasite. The Hepatozoon infection is thus suggested to accelerate destruction of erythrocytes in the rattlesnake, not only affecting cells harbouring the parasite, but also in those without it.
Inhibition of prolyl 4‐hydroxylase prevents left ventricular remodelling in rats with thoracic aortic banding
Authors: Fielitz Jens , Philipp Sebastian , Herda Lars Roman , Schuch Evelyn , Pilz Bernhard , Schubert Carola , Günzler Volkmar , Willenbrock Roland , Regitz‐Zagrosek Vera
Published: December 2006

Background:

Pressure overload leads to myocardial remodelling with collagen accumulation, left ventricular hypertrophy (LVH), neurohormonal activation and myocardial dysfunction. Prolyl 4‐hydroxylases (P4H) are involved in collagen maturation. Inhibition of P4H has been shown to prevent LV remodelling and improve survival post‐myocardial infarction.

Aim:

To evaluate the role of P4H in pressure overload‐induced myocardial remodelling.

Methods:

Male Wistar rats underwent thoracic aortic banding (AoB) and were treated with a P4H inhibitor (P4HI) or vehicle (control). Echocardiography and haemodynamic measurements were performed after 4 weeks. Collagens, matrix metalloproteinases (MMP), tissue inhibitors of MMPs (TIMP), growth factors and neurohormonal markers were quantitated in LV samples.

Results:

AoB led to LVH, increased LV enddiastolic pressure (LVEDP) and decreased contractility compared to sham. P4HI reversed these effects. AoB increased collagen I and III expression, which was normalized by P4HI. AoB led to deregulation of matrix remodelling enzymes, enhanced expression of growth factors and activation of the endothelin system. P4HI partially prevented deregulation of the MMP/TIMP system, inhibited upregulation of growth factors and normalized AoB‐induced ECE‐1 and ETB expression.

Conclusions:

P4HI leads to an improvement of AoB‐associated LV dysfunction and reduces imbalance of extracellular matrix turnover and hypertrophy‐associated gene expression. P4H inhibition could therefore be of value in treatment of myocardial remodelling accompanying pressure overload hypertrophy.
The plant‐specific VIMAG domain of Glutamine Dumper1 is necessary for the function of the protein in arabidopsis
Authors: Pratelli Réjane , Pilot Guillaume
Published: December 2006

The over‐expression of the arabidopsis GLUTAMINE DUMPER1 gene (GDU1) leads to increased amino acid content and transport. In a screening for mutations suppressing this phenotype, a mutant was isolated. The mutation leads to a glycine to arginine substitution in one of the two conserved domains of the protein, the VIMAG domain. More detailed structure function relationship analyses showed that the presence of this domain and the membrane localisation are both necessary for the function of the GDU1 protein. These results shed light on the function of the GDU1 protein whose family is specific to plants.
Model variations of Schumann resonance based on Optical Transient Detector maps of global lightning activity
Authors: Nickolaenko A. P. , Pechony O. , Price C.
Published: December 2006

We present model computations of global electromagnetic resonance (Schumann resonance) based on the monthly worldwide distribution of thunderstorm activity collected by the Optical Transient Detector satellite. To obtain diurnal and seasonal variations of electromagnetic signals produced by the thunderstorms worldwide, we apply masks that “activate” definite parts of global thunderstorms and move around the planet with the Sun. Three types of masks are discussed: The first one triggers the activity at the dayside of the globe; the second one activates its afternoon sector; and the third one switches on the thunderstorms within a hot spot, a circular area of a fixed radius. We perform computations of Schumann resonance spectra and demonstrate that numerical models are a useful tool for studying and interpreting resonance features.
Mixing times in the mantle of the early Earth derived from 2‐D and 3‐D numerical simulations of convection
Authors: Coltice N. , Schmalzl J.
Published: December 2006

The Earth's mantle is chemically heterogeneous at all scales, as shown by elemental and isotopic analysis of oceanic basalts. This heterogeneity is continuously destroyed by convective stirring and slow diffusion. It has been argued that 3‐D time‐dependent convection is less efficient than 2‐D convection, except in the presence of a toroidal component. In this study we question this conclusion with numerical simulations and show that mixing in 3‐D time‐dependent convection is as efficient as in 2‐D, and only depends on convective vigor. We compute mixing times of thermal and chemical heterogeneities in the early Earth of 10 and 100 Myrs respectively.
Space‐based near‐infrared CO2 measurements: Testing the Orbiting Carbon Observatory retrieval algorithm and validation concept using SCIAMACHY observations over Park Falls, Wisconsin
Authors: Bösch H. , Toon G. C. , Sen B. , Washenfelder R. A. , Wennberg P. O. , Buchwitz M. , de Beek R. , Burrows J. P. , Crisp D. , Christi M. , Connor B. J. , Natraj V. , Yung Y. L.
Published: December 2006

Space‐based measurements of reflected sunlight in the near‐infrared (NIR) region promise to yield accurate and precise observations of the global distribution of atmospheric CO2. The Orbiting Carbon Observatory (OCO) is a future NASA mission, which will use this technique to measure the column‐averaged dry air mole fraction of CO2 with the precision and accuracy needed to quantify CO2 sources and sinks on regional scales (∼1000 × 1000 km2) and to characterize their variability on seasonal timescales. Here, we have used the OCO retrieval algorithm to retrieve and surface pressure from space‐based Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) measurements and from coincident ground‐based Fourier transform spectrometer (FTS) measurements of the O2 A band at 0.76 μm and the 1.58 μm CO2 band for Park Falls, Wisconsin. Even after accounting for a systematic error in our representation of the O2 absorption cross sections, we still obtained a positive bias between SCIAMACHY and FTS retrievals of ∼3.5%. Additionally, the retrieved surface pressures from SCIAMACHY systematically underestimate measurements of a calibrated pressure sensor at the FTS site. These findings lead us to speculate about inadequacies in the forward model of our retrieval algorithm. By assuming a 1% intensity offset in the O2 A band region for the SCIAMACHY retrieval, we significantly improved the spectral fit and achieved better consistency between SCIAMACHY and FTS retrievals. We compared the seasonal cycle of at Park Falls from SCIAMACHY and FTS retrievals with calculations of the Model of Atmospheric Transport and Chemistry/Carnegie‐Ames‐Stanford Approach (MATCH/CASA) and found a good qualitative agreement but with MATCH/CASA underestimating the measured seasonal amplitude. Furthermore, since SCIAMACHY observations are similar in viewing geometry and spectral range to those of OCO, this study represents an important test of the OCO retrieval algorithm and validation concept using NIR spectra measured from space. Finally, we argue that significant improvements in precision and accuracy could be obtained from a dedicated CO2 instrument such as OCO, which has much higher spectral and spatial resolutions than SCIAMACHY. These measurements would then provide critical data for improving our understanding of the carbon cycle and carbon sources and sinks.
Crystalline Ni nanoparticles as the origin of ferromagnetism in Ni implanted ZnO crystals
Authors: Zhou Shengqiang , Potzger K. , Zhang Gufei , Eichhorn F. , Skorupa W. , Helm M. , Fassbender J.
Published: December 2006

We report the structural and magnetic properties of ZnO single crystals implanted at 623K with up to 10at.% of Ni. As revealed by x-ray diffraction, crystalline fcc-Ni nanoparticles were formed inside ZnO. The magnetic behavior (magnetization with field reversal and with different temperature protocols) of all samples is well explained by a magnetic Ni-nanoparticle system. Although the formation of Ni:ZnO based diluted magnetic semiconductor cannot be ruled out, the major contribution to the magnetic properties stems from crystalline nanoparticles synthesized under these implantation conditions.
Investigation of carbon contaminations in SiO2 films on 4H-SiC(0001)
Authors: Schürmann Mark , Dreiner Stefan , Berges Ulf , Westphal Carsten
Published: December 2006

Si O 2 films can be grown on SiC by oxidation of the clean SiC surfaces. During the oxidation process carbon atoms have to leave the crystal. This occurs by outdiffusion of CO molecules from the reaction front through the growing film. Carbon atoms remaining at the interface or in the oxide film lead to an increased density of states in the band gap, and therefore lower the quality of the SiO2∕SiC interface. In this work photoemission spectroscopy and photoelectron diffraction were used to study the carbon contamination in ultrathin SiO2 films on 4H-SiC(0001). The contaminations were produced during oxidation at high temperatures and low oxygen pressure. Due to their chemical shift carbon atoms from the contaminations and from the substrate can be distinguished in the C 1s photoemission spectrum. A combined photoelectron spectroscopy and photoelectron diffraction study shows that these carbon agglomerations are similar to carbon enrichments observed after heating of clean SiC surfaces and that they are either amorphous clusters or have no preferential orientation with respect to the SiC substrate.
Investigations of GaN surface quantum well in AlGaN∕GaN transistor heterostructures by contactless electroreflectance spectroscopy
Authors: Motyka M. , Syperek M. , Kudrawiec R. , Misiewicz J. , Rudziński M. , Hageman P. R. , Larsen P. K.
Published: December 2006

Al Ga N ∕ Ga N transistor heterostructures, caped by ∼2nm GaN layer, were investigated by contactless electroreflectance (CER) spectroscopy at room temperature. Below the AlGaN-related transition CER spectra have shown a clear resonance at the energy of ∼3.7eV, i.e., at much higher energy than the GaN band gap energy. The observed feature has been connected with the optical transition within the GaN cap layer. It was concluded that a surface GaN quantum well has been created by the deposition of nominally undoped (or Si-doped) GaN cap layer on AlGaN∕GaN transistor heterostructures.
High-spatial-resolution Raman microscopy of stress in shallow-trench-isolated Si structures
Authors: Poborchii Vladimir , Tada Tetsuya , Kanayama Toshihiko
Published: December 2006

Stress in single and periodic shallow-trench-isolated Si structures was examined by 364nm excitation confocal resonance Raman microscopy, laser penetration being restricted to the near-surface region. Using a 1.3 numerical aperture microobjective lens with a theoretical ∼140nm spatial resolution, the authors show that the configuration with both incident and scattered lights polarized parallel to each other and perpendicular to Si stripes is favorable for stress detection in the middle of the stripes, suppressing contributions from their edges. The stresses located in different areas of the structures were identified and analyzed.
Tunable single photonic defect-mode in cholesteric liquid crystals with laser-induced local modifications of helix
Authors: Yoshida Hiroyuki , Lee Chee Heng , Fujii Akihiko , Ozaki Masanori
Published: December 2006

The authors demonstrate a tunable single photonic defect-mode in a single cholesteric liquid crystal material based on a structural defect introduced by local modification of the helix. An unpolymerized region of cholesteric liquid crystal acting as the defect was left between two polymerized regions via a two-photon excitation laser-lithography process. Upon polymerization, the cholesteric liquid crystal helix elongated and became thermally stable, and a single photonic defect mode was exhibited due to the contrast in the helix pitch at the defect. The defect mode showed tunability upon heating, and a 36nm redshift was seen over a temperature range of 30°C.
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relationship and effective capacitance in external electrode fluorescent lamp
Authors: Lee Tae Il , Hwang Hyeon Seok , Park Ki Wan , Baik Hong Koo
Published: December 2006

The authors derived an analytical relationship between rms tube current and input power for various capacitances of the external electrode part and measured their effective capacitances in an external electrode fluorescent lamp. From the fitting derived relation in the measured data, the reliability of the authors’ derivation was certain and effective capacitances were measured. Consequently, it is confirmed that the derived relationship is very useful in estimating the effective capacitance of the external electrode part for any shape of glass tube and electrodes during the lamp operation.
Nonequilibrium molecular dynamics simulation study on the orientation transition in the amphiphilic lamellar phase under shear flow
Authors: Guo Hongxia
Published: December 2006

By the extensive large-scale nonequilibrium molecular dynamics simulation on an effective generic model-A2B2 tetramer for amphiphiles, we investigate the shear-induced parallel to perpendicular orientation transition in the lamellar phase as a function of segregation degree and shear rate. Under low rate shear flow the evolution of parallel lamellar configurations at different segregation strengths shows a similar kinetic pathway independent of the segregation degree. While under high rate shear flow in which the lifetime of undulation instability exceeds the characteristic time of the applied shear flow, the kinetic pathway of the shear-induced parallel-to-perpendicular orientation transition in lamellar systems is the segregation degree dependent. Comparing the temporal mesoscopic domain morphology, the microscopic chain conformation, and macroscopic observable-viscosity changes with the experimentally proposed mechanisms, we find that the undulation instability, partial breakup of monodomain, grain rotation, and recombination combined with defect migration and annihilation are the kinetic pathway for the parallel-to-perpendicular orientation transition in the lamellar phase in or near the intermediate segregation limit, and that the undulation instability, domain dissolution, and reformation along the preferred direction combined with defect migration and annihilation are the kinetic pathway for the parallel-to-perpendicular orientation transition in the lamellar phase close to the order-to-disorder phase transition point. A detailed underlying microscopic picture of the alignment process illustrates that the orientation transition is driven by the alignment of molecules with shear flow. The orientation diagram that characterizes the steady-state orientations as a function of shear rate and attractive potential depth is built, in which the attractive potential depth takes the role of an inverse temperature, somewhat like the Flory-Huggins interaction parameter. The microscopic mechanism of the critical orientation transition condition is discussed.
Arrays of high-Tc Josephson junctions in open millimeter wave resonators
Authors: Klushin A. M. , He M. , Yan S. L. , Klein N.
Published: December 2006

The authors have explored the coupling mechanism of a millimeter wave radiation to bicrystal Josephson junction arrays embedded in a hemispherical Fabry-Pérot resonator. The authors have found that their high-temperature superconductor array can be modeled as a thin film grid polarizer. In agreement with this model, a strong dependence of the coupling of the Josephson junctions on the polarization of the electric filed in the resonator was observed. The authors achieved a maximum Josephson voltage of 28mV for an array of 182 bicrystal junctions at a temperature of 75K and a frequency of 74.4GHz.
Tuning the intersubband absorption in strained AlAsSb∕InGaAs quantum wells towards the telecommunications wavelength range
Authors: Cristea P. , Fedoryshyn Y. , Holzman J. F. , Robin F. , Jäckel H. , Müller E. , Faist J.
Published: December 2006

We study the intersubband absorption in Si doped AlAsSb∕InGaAs quantum wells (QWs) grown on InP substrates by molecular beam epitaxy. The investigated multiple QW structures contain strained In0.78Ga0.22As layers and additional AlAs layers for strain compensation. By varying the nominal QW width from 3 to 9 ML (monolayer) a minimum central absorption wavelength of 1.76μm is found for a 5 ML thick QW. Simulations of these experimental results using a self-consistent Schrödinger-Poisson solver show a deviation from the perfect squarelike potential caused by intermixing effects at the interfaces. These blurred interfaces are also revealed by transmission electron microscopy measurements.
Ferroelectric behavior of Al substituted InP
Authors: Park C. S. , Lee S. J. , Kang T. W. , Fu D. J.
Published: December 2006

InP:Al was grown by the liquid phase epitaxy method on InP (100)substrates. X-ray diffraction confirmed the epitaxial growth along (100) of AlInP. Photoluminescence spectra showed the evident effect of Al content. Ferroelectric characterization of the sample revealed a clear hysteresis in its polarization-voltage curves. The remnant polarization of InP:Al amounts to 1.99μC∕cm2 at 300Hz, and it decreases with increasing temperature in a continuous and diffusive manner. Resistance measurement demonstrated a maximum resistance at 160°C, tentatively consistent with the transition temperature of remnant polarization. The ferroelectricity is accounted by the collective interaction between nuclei having the microscopic instability from the cation size difference in InP:Al.
Quantum dot manipulation in a single-walled carbon nanotube using a carbon nanotube gate
Authors: Lee Dong Su , Park Seung Joo , Park Sang Deok , Park Yung Woo , Kemell Marianna , Ritala Mikko , Svensson Johannes , Jonson Mats , Campbell Eleanor E. B.
Published: December 2006

Cross junctions of carbon nanotubes (CNTs) separated by thin oxide layers have been fabricated, in which the top CNT is used as a local gate to control the electron transport through the lower CNT. Coulomb oscillation was observed in the lower CNTs at low temperatures. The gating field from the upper CNTs is seen to modulate the band structure in the lower CNTs, producing double quantum dot systems. The ability to modulate the electronic structure of CNTs in such a way opens up many possibilities for future electronic and logical nanodevices.
Dynamic exploration and editing of KEGG pathway diagrams
Authors: Klukas Christian , Schreiber Falk
Published: December 2006

Motivation: The Kyoto Encyclopedia of Genes and Genomes (KEGG) Pathway database is a very valuable information resource for researchers in the fields of life sciences. It contains metabolic and regulatory processes in the form of wiring diagrams, which can be used for browsing and information retrieval as well as a base for modeling and simulation. Thus it helps in understanding biological processes and higher-order functions of biological systems.

Currently the KEGG website uses semi-static visualizations for the presentation and navigation of its pathway information. While this visualization style offers a good pathway presentation and navigation, it does not provide some of the possibilities related to dynamic visualizations, most importantly, the creation and visualization of user-specific pathways.

Results: This paper presents methods for the dynamic visualization, interactive navigation and editing of KEGG pathway diagrams. These diagrams, given as KEGG Markup Language (KGML) files, can be visually explored using novel approaches combining semi-static and dynamic visualization, but also edited or even newly created and then exported into KGML files.

Availability: KGML-ED, a program implementing the presented methods, is available free of charge to the scientific community at

Contact:  schreibe@ipk-gatersleben.de
How internal waves influence the vertical distribution of zooplankton
Authors: RINKE KARSTEN , HÜBNER INA , PETZOLDT THOMAS , ROLINSKI SUSANNE , KÖNIG‐RINKE MARIE , POST JOHANNES , LORKE ANDREAS , BENNDORF JÜRGEN
Published: December 2006

1. We present data with a high spatio‐temporal resolution from a 72‐h field survey in Bautzen Reservoir (Saxony, Germany). The aims of this survey were to observe hydrophysical processes during a period of unstable stratification in spring and investigate the effect of wind‐induced internal waves on the vertical distribution of zooplankton.

2. Wind velocities up to 10 m s−1 caused a strong downwelling event of warm water at the sampling site and led to the generation of internal waves with an amplitude of 4 m.

3. The zooplankton community, which was dominated by Daphnia galeata, inhabited epilimnetic waters. Downwelling enlarged the thickness of the epilimnetic layer and, hence, led to high zooplankton abundances down to relatively deep water strata indicating lateral transport of zooplankton. As a consequence, area‐specific zooplankton abundances increased considerably (max. fourfold) during downwelling.

4. We conclude that classical limnological field sampling, such as for monitoring purposes, can lead to severely biased estimates of zooplankton abundance due to the interfering effects of hydrophysical processes like internal waves.

5. Backscattering strengths measured by a simultaneously deployed Acoustic Doppler Current Profiler (600 kHz) were found to be correlated with estimated zooplankton abundances based on plankton samples.
Detection and visualization of spatial genetic structure in continuous Eucalyptus globulus forest
Authors: JONES TIM H. , VAILLANCOURT RENÉ E. , POTTS BRAD M.
Published: December 2006

Visualizing the pattern of variation using microsatellites within a Eucalyptus globulus forest on the island of Tasmania provided surprising insights into the complex nature of the fine‐scale spatial genetic structure that resides in these forests. We used spatial autocorrelation and principal coordinate analysis to compare fine‐scale genetic structure between juvenile and mature cohorts in a study area, 140 m in diameter, located within a typical, continuous E. globulus forest. In total, 115 juvenile and 168 mature individuals were genotyped with eight highly polymorphic microsatellite loci. There was no significant difference in the level of genetic diversity between cohorts. However, there were differences in the spatial distribution of the genetic variation. Autocorrelation analysis provided clear evidence for significant spatial genetic structure in the mature cohort and significant, but weaker, structure in the juvenile cohort. The spatial interpolation of principal coordinate axes, derived from ordination of the genetic distance matrix between individuals, revealed a spatially coherent family group which was evident in both cohorts. Direct comparison of the genetic structure within each cohort allowed visualization of a shift in the spatial distribution of genetic variation within the population of approximately 10 m. As the shift coincided with the direction of prevailing winds, it is hypothesized that this phenomenon is due to downwind dispersal of seeds and is indicative of the important role of prevailing winds in forcing eastward gene flow in these high‐latitude forests.
Cytoskeletal protein P41 is required to anchor the terminal organelle of the wall‐less prokaryote Mycoplasma pneumoniae
Authors: Hasselbring Benjamin M. , Krause Duncan C.
Published: December 2006

The cell wall‐less prokaryote Mycoplasma pneumoniae approaches the minimal requirements for a cell yet produces a complex terminal organelle that mediates cytadherence and gliding motility. Here we explored the molecular nature of the M. pneumoniae gliding machinery, utilizing fluorescent protein fusions and digital microcinematography to characterize gliding‐altered mutants having transposon insertions in MPN311, encoding the cytoskeletal protein P41. Disruption of MPN311 resulted in loss of P41 and P24, the downstream gene product. Gliding ceases in wild‐type M. pneumoniae during terminal organelle development, which occurs at the cell poles adjacent to an existing structure. In contrast, terminal organelle development in MPN311 mutants did not necessarily coincide with gliding cessation, and new terminal organelles frequently formed at lateral sites. Furthermore, new terminal organelles exhibited gliding capacity quickly, unlike wild‐type M. pneumoniae. P41 and P24 localize at the base of the terminal organelle; in their absence this structure detached from the cell body of motile and dividing cells but retained gliding capacity and thus constitutes the gliding apparatus. Recombinant wild‐type P41 restored cell integrity, establishing a role for this protein in anchoring the terminal organelle to the cell body.
Recombination is suppressed and variability reduced in a nascent Y chromosome
Authors: BERSET‐BRÄNDLI L. , JAQUIÉRY J. , PERRIN N.
Published: December 2006

Several hypotheses have been elaborated to account for the evolutionary decay commonly observed in full‐fledged Y chromosomes. Enhanced drift, background selection and selective sweeps, which are expected to result from reduced recombination, may all share responsibilities in the initial decay of proto‐Y chromosomes, but little empirical information has been gathered so far. Here we take advantage of three markers that amplify on both of the morphologically undifferentiated sex chromosomes of the European tree frog (Hyla arborea) to show that recombination is suppressed in males (the heterogametic sex) but not in females. Accordingly, genetic variability is reduced on the Y, but in a way that can be accounted for by merely the number of chromosome copies per breeding pair, without the need to invoke background selection or selective sweeps.