bluuebunny/crossref_metadata_2025 huggingface dataset:
Rapid determination of double bond configuration and position along the hydrocarbon chain in cyclic fatty acid monomers
Authors: Mossoba M. M. , Yurawecz M. P. , Roach J. A. G. , Lin H. S. , McDonald R. E. , Flickinger B. D. , Perkins E. G.
Published: December 2006

This study reports the structural elucidation of diunsaturated 5‐ or 6‐membered ring cyclic fatty acid monomers (CFAM) isolated from heated flaxseed oil by complementary gas chromatography (GC)‐mass spectrometry (MS) and GC‐matrix isolation‐Fourier transform infrared spectroscopy (MI‐FTIR). Infrared measurements of CFAM were carried out on methyl ester derivatives as well‐resolved chromatograms were obtained on a polar 100% cyanopropyl polysiloxane capillary GC column. By contrast, electron ionization MS of methyl ester derivatives was of limited value because of double bond migration during the ionization process in the mass spectrometer. This communication reports definitive MS fragmentation patterns that can confirm ring position and double bond position along the fatty acid chain in 1,2‐disubstituted CFAM determined as 2‐alkenyl‐4,4‐dimethyloxazoline derivatives. Double bond configuration (cis, trans, or conjugatedcis,cis) in CFAM was confirmed by GC‐MI‐FTIR. The presence of CFAM, degradation products found in used frying oils, is a potential source of dietary toxicity.
UV Spectrophotometry of autoxidized lipid monolayers while on silica gel
Authors: Porter W. L. , Levasseur L. A. , Jeffers J. I. , Henick A. S.
Published: December 2006

Autoxidation reactions of linoleic acid and tocopherol and of mixtures of the two have been monitored in the dry monolayer state while adsorbed on silica gel, by means of silica slurry spectrophotometry and oxygen uptake measurements. The UV absorbance of the products of linoleic acid alone is similar to that of previously characterized compounds, but that from tocopherol is not referable to any oxidation products known to the authors, regardless of whether the determination is made while adsorbed on silica or on the extracted products. Two compounds, designated A and B, having absorbance in ethanol at 2610–2670 and 3000 A, respectively, are the major products of tocopherol oxidation detectable by UV above 2200 A. They are a tocopheryl quinone without a hydroxyl group and an adduct of linoleic acid and oxidized tocopherol. The product distribution suggests that tocopherol may have a restricted migration in this system.
Diet and the fatty acids in the plasma of lambs during the first eight days after birth
Authors: Noble R. C. , Steele W. , Moore J. H.
Published: December 2006

This study reports the plasma lipid changes in lambs receiving either ewes' milk or a reconstituted low fat milk powder during the first eight days after birth. The liveweight gains of the lambs on the artificial diet was less than half that observed in the lambs on the natural diet. The plasma lipid levels in the lambs on the natural diet increased considerably after birth due to large increases in the concentrations of the cholesteryl ester, triglyceride and phospholipid fractions. For the lambs on the artificial diet these fractions remained similar to those observed at birth. In both groups unesterified fatty acid fractions decreased after birth. The main difference between the two groups of lambs was the large increase in C18 polyunsaturated fatty acids observed after birth in the lambs on the natural diet. The triene‐tetraene ratio of the fatty acids in the lambs on the natural diet decreased from 1.0 at birth to 0.08 after eight days whereas in the lambs on the artificial diet the ratio increased to 2.9. These composition changes are discussed in relationship to the metabolism of essential fatty acids in monogastric animals.
Determination of plasma tocopherols by gas liquid chromatography
Authors: Lehmann Joanna , Slover Hal T.
Published: December 2006

A method is described for the separation and determination of plasma tocopherols by gas liquid chromatography (GLC). Proteins in 0.1 g samples of plasma were precipitated with ethanol containing a known amount of 5,7‐dimethyltocol which served as an internal standard. Tocopherols were extracted into petroleum ether, purified by thin layer chromatography and analyzed as trimethylsilyl ethers by gas liquid chromatography (GLC) on 0.5% Apiezon L. Recoveries of α‐ and γ‐tocopherols averaged 100% and 93%, respectively. The mean total tocopherol content of eight human plasma samples was 8.5 μg/g by GLC and 9.9 μg/g by a ferric chloride‐α,α′‐dipyridyl method. The α‐ and γ‐tocopherol contents of 16 human plasma samples ranged from 4.0 to 12.3 μg/g and 0.6 to 2.1 μg/g, respectively.
Mycobacterial sulfolipids: Spontaneous desulfation
Authors: Goren Mayer B.
Published: December 2006

A glycolipid sulfate elaborated in abundance by surface‐grown cultures ofMycobacterium tuberculosis has been characterized in earlier studies as a complex 2,3,6,6′‐tetraacyl α, α′ trehalose 2′‐sulfate. The purified ammonium salt undergoes rapid quantitative desulfation on mere dissolution in reagent grade anhydrous ether. The same reaction is observed in sulfolipids recovered from a number of human strains and one bovine strain. Experimental observations on the normal and acid‐catalyzed rates of the reaction and on the influence of other solvents and other cationic forms support a proposed mechanism, which is detailed. Structural criteria which may influence the proclivity for spontaneous desulfation are discussed.
Lipolysis in castor seeds: A reinvestigation of the neutral lipase
Authors: Ory Robert L. , Angelo Allen J. St.
Published: December 2006

Attempts to study the neutral lipase reported in germinating castor seeds and to compare this enzyme to the acid lipase of dormant seeds were unsuccessful because of the inability to repeat the work described earlier (1). Activity of the proposed neutral lipase could not be detected, nor could appearance of the enzyme be hastened or affected by treating the germinating seeds with gibberellic acid or Actinomycin‐D. Possible explanations for the discrepancy between these findings and the early report are presented.
The relationship of milk phospholipids to membranes of the secretory cell
Authors: Patton Stuart , Keenan T. W.
Published: December 2006

Forty‐two per cent of the lipid phosphorus in milk was found in skim milk lipoprotein; the other 58% occurs in the milk fat globule membrane (MFGM). Investigation of these two sources of lipid phosphorus revealed that they involve the same individual phospholipids, in essentially the same proportions with similar fatty acid compositions. Both contain sphingomyelin and cerebrosides in levels characteristic of those found in plasma membranes. Other points of resemblance between MFGM and skim milk lipoprotein, have been shown previously. Infusion of (14C) palmitate into the mammary gland of a lactating goat produced more extensive labeling of all the phospholipid classes in the skim milk lipoproteins than in those in the MFGM during the following 24 hr. When (14C) palmitate was infused into the jugular vein of a lactating goat, a precusor‐product‐type relationship was observed between specific activities of the skim milk and MFGM polar lipids. These results render the MFGM an unlikely origin of the skim milk lipoprotein. Other possible sources of this latter lipoprotein are Golgi vesicle membranes or plasma membrane of the lactating cell.
Lipid composition and de novo lipid biosynthesis of human palmar fat in Dupuytren's disease
Authors: Rabinowitz Joseph L. , Ostermann Lee , Bora F. W. , Staeffen Jean
Published: December 2006

Seventy‐two surgically obtained Dupuytren's disease palmar‐fat (DDPF) specimens and 18 location‐matched speciments from patients not suffering from this disease (controls) were studied for their total lipid composition and de novo lipogenic activity. Incubation of “DDPF” with 1‐[14C]acetate in oxygen produced [14C]palmitate and [14C]stearate in approximately equal yields as those obtained from “controls”. No [14C]octanate was formed in any of the palmar‐fat preparations. The lipids and fatty acid analysis revealed differences; (a) DDPF specimens were richer in free fatty acids, methyl esters of fatty acids and freecholesterol than specimens of controls (b) DDPF specimens contained less phospholipids. (c) DDPF specimens showed a significantly higher content of octanoate and other short‐chain fatty acids than specimens of controls. The above findings are not incompatible with the results expected if some mild hypoxia occurred in DDPF; this has been suggested in the statistical correlations observed for this disease and alcoholism with liver involvement.
The synthesis and biological activity of thiolcarnitine and its thiolesters
Authors: Duhr Edward F. , Mauro J. Matthew , Clennan Edward L. , Barden Roland E.
Published: December 2006

Acetyl‐D,L‐thiolcarnitine was synthesized by the acid‐catalyzed addition of thiolacetic acid to 4‐trimethylammonio‐2‐butenoic acid. Acetyl‐D,L‐thiolcarnitine was the precursor of D,L‐thilcarnitine, which was prepared by base hydrolysis. Thiolcarnitine significantly enriched in the L‐isomer was prepared from acetyl‐D,L‐thiolcarnitine using carnitine acetyltransferase as the resolving agent. The C2, C8 and C16 carnitine thiolesters were obtained by acylating thiolcarnitine with the corresponding N‐hydroxysuccinimide esters. As a substrate for carnitine acetyltransferase, acetylthiolcarnitine gave the same kinetic constants as did acetylcarnitine; on the other hand, thiolcarnitine and carnitine gave the same Km but the Vmax with thiolcarnitine was less than 5% of the value obtained with carnitine. With thiolcarnitine and acetylthiolcarnitine as reactants, the measured Keq, at 30 C and pH 7.0, for the reaction catalyzed by carnitine acetyltransferase (see below) was 4.6±.1. acetylthiolcarnitine+CoA—acetyl‐CoA+thiolcarnitine
Regulation of the sequencing in sterol biosynthesis
Authors: Nes William R.
Published: December 2006

The evolutionary development and sequencing of events in the biosynthetic pathway leading to sterols is reviewed and illustrated by recent experiments from the author's laboratory.
Preparation of tritium‐labeled sterols and the synthesis of labeled‐24‐azacholesterol
Authors: Thompson Malcolm J. , Berngruber Otto W. , Klein Peter D.
Published: December 2006

A method is presented for the preparation of 2,4‐3H‐sterols (stigmasterol, β‐sitosterol, campesterol, fucosterol and 7‐dehydrocholesterol) via the technique of exchange‐labeling of keto steroids and their subsequent conversion to sterols. The preparation of tritium‐labeled 3β‐hydroxy‐24‐norchol‐5‐en‐23‐oic acid and the synthesis of 2,4‐3H‐24‐azacholesterol are reported. Some advantages of the exchange‐labeling method over the conventional catalytic exchange method are discussed.
The quantitative analysis of sphingolipids by determination of long chain base as the trinitrobenzene sulfonic acid derivative
Authors: Siakotos A. N. , Kulkarni S. , Passo S.
Published: December 2006

A spectrophotometric procedure has been developed for the determination of microquantities of sphingolipids. The assay system involved includes the methanolysis of the fatty acid moiety of the sphingolipid with boron trifluoride in methanol to yield a long chain base containing a free amino group. The long chain amine, sphingosine, is then extracted into an organic phase and reacted with aqueous trinitrobenzene sulfonic acid to yield a product with an absorption maximum at 340 mμ. Lipid peroxidation products and silicic acid do not seriously interfere in the 340 region. A wide variety of pure sphingolipids yielded equivalent optical densities per mole of sphingolipid. Sphingolipids assayed included cerebroside, cerebroside sulfate, ganglioside and sphingomyelin.
Early recognition of bipolar disorder
Authors: Hauser Marta , Pfennig Andrea , Özgürdal Seza , Heinz Andreas , Bauer Michael , Juckel Georg
Published: December 2006

Bipolar disorders are frequently not diagnosed until long after their onset, leaving patients with no or correspondingly inadequate treatment. The course of the disorder is all the more severe and the negative repercussions for those affected all the greater. Concerted research effort is therefore going into learning how to recognize bipolar disorders at an early stage. Drawing on current research results, this paper presents considerations for an integrative Early Symptom Scale with which persons at risk can be identified and timely intervention initiated. This will require prospective studies to determine the predictive power of the risk factors integrated into the scale.
Validity of the EQ-5D in assessing and valuing health status in patients with schizophrenic, schizotypal or delusional disorders
Authors: König Hans-Helmut , Roick Christiane , Angermeyer Matthias C.
Published: December 2006

Purpose

The EQ-5D is a generic questionnaire generating a health profile and a single index score for health-related quality of life. This study aimed to analyse the discriminative ability and validity of the EQ-5D in patients with schizophrenic, schizotypal or delusional disorders.

Subjects and methods

One hundred sixty-six patients with schizophrenic, schizotypal or delusional disorders (ICD-10 F2) completed the EQ-5D. Measures of quality of life (WHOQOL-BREF), utility (TTO), subjective (SCL-90R) and objective (PANSS, CGI-S) psychopathology, and functioning (GAF, GARF, SOFAS, HoNOS) provided comparison. Discriminative ability was analysed by assessing frequency distributions of EQ-5D scores. Validity of the EQ-5D self-classifier was analysed by assessing differences in related other scores grouped by response levels of EQ-5D items. Validity of the visual analogue scale (EQ VAS) and the EQ-5D index (UK social tariff) was analysed by assessing their correlation with all other scores.

Results

Seventy-nine percent of respondents reported problems in at least one of the EQ-5D dimensions (anxiety/depression 57%, usual activities 45%, pain/discomfort 44%, self-care 29%, mobility 22%). The mean EQ VAS score/EQ-5D index was 65.7/0.71. The four most frequently reported EQ-5D health states covered 45% of all respondents. For almost all EQ-5D dimensions, different response levels were associated with significantly different scores of measures used for comparison. Correlation of EQ VAS score and EQ-5D index were largest with scores of subjective measures (SCL-90R: −0.50 and −0.73; WHOQOL mental subscore 0.62 and 0.58; alwaysP< 0.001).

Discussion and conclusion

The EQ-5D showed a moderate ceiling effect and seems to be reasonably valid in this patient group.
Increased risk of mental disorders among lifetime victims of stalking – Findings from a community study
Authors: Kuehner Christine , Gass Peter , Dressing Harald
Published: December 2006

Purpose

Population-based studies on the relationship between stalking and mental health outcomes in victims are scarce. The aim of the present study was to assess associations between stalking victimization and specific DSM-IV mental disorders in a community sample.

Method

A postal survey was conducted in a middle-sized German city (sample size = 675). Lifetime stalking victims and non-victims were compared regarding rates of any mental disorder, comorbid mental disorders, and specific disorders assessed by the Patient Health Questionnaire (PHQ).

Results

Victims had a higher incidence of mental disorders and comorbid mental disorders. Sex- and age-adjusted rates of specific disorders were increased, with the most robust associations identified for major depression (OR 4.8, 95% CI 1.8–12.8) and panic disorder (OR 4.1, 95% CI 1.1–14.9). Victims also reported higher current use of psychotropic medication (20.8% versus 5.6%).

Conclusions

Our study indicates substantial associations between stalking victimization and impaired mental health that can be quantified at diagnostic levels in the general population. To confirm these findings, larger community studies are needed, which also include an assessment of lifetime psychopathology and of factors potentially mediating the associations between stalking victimization and mental health.
Binding structure of the leucine aminopeptidase inhibitor microginin FR1
Authors: Kraft Manuel , Schleberger Christian , Weckesser Jürgen , Schulz Georg E.
Published: December 2006

Natural bioactive compounds are of general interest for pharmaceutical research because they may serve as leads in drug development campaigns. Among them, microginins are linear peptides known to inhibit various exopeptidases. The crystal structure of microginin FR1 from Microcystis sp. bound to bovine lens leucine aminopeptidase was established at 1.73 Å resolution. The observed binding structure could be beneficial for the design of potent aminopeptidase inhibitors.
Binding of Vac14 to neuronal nitric oxide synthase: Characterisation of a new internal PDZ‐recognition motif
Authors: Lemaire Jean-François , McPherson Peter S.
Published: December 2006

PDZ domains mediate protein interactions primarily through either classical recognition of carboxyl‐terminal motifs or PDZ/PDZ domain associations. Several studies have also described internal modes of PDZ recognition, most of which depend on β‐finger structures. Here, we describe a novel interaction between the PDZ domain of nNOS and Vac14, the activator of the PtdIns(3)P 5‐kinase PIKfyve. Binding assays using various Vac14 deletion constructs revealed a β‐finger independent interaction that is based on a novel internal motif. Mutational analyses reveal essential residues within the motif allowing us to define a new type of PDZ domain interaction.
Alternative splicing of human and mouse NPFF2 receptor genes: Implications to receptor expression
Authors: Änkö Minna-Liisa , Östergård Maria , Lintunen Minnamaija , Panula Pertti
Published: December 2006

Alternative splicing has an important role in the tissue‐specific regulation of gene expression. Here we report that similar to the human NPFF2 receptor, the mouse NPFF2 receptor is alternatively spliced. In human the presence of three alternatively spliced receptor variants were verified, whereas two NPFF2 receptor variants were identified in mouse. The alternative splicing affected the 5′ untranslated region of the mouse receptor and the variants in mouse were differently distributed. The mouse NPFF system may also have species‐specific features since the NPFF2 receptor mRNA expression differs from that reported for rat.
Choosing a suitable analytical model for aerosol extinction spectra in the retrieval of UV/visible satellite occultation measurements
Authors: Vanhellemont F. , Fussen D. , Dodion J. , Bingen C. , Mateshvili N.
Published: December 2006

In the retrieval of satellite occultation experiments the optical extinction by atmospheric gases can be adequately modeled as the product of an extinction cross section with the number density. For aerosols the situation is more complex. Usually, the extinction spectrum is modeled by some analytical function of wavelength, controlled by a small number of parameters. However, a consensus about which function to use does not exist. The goal of this paper is to find out which analytical function is most suitable and how many parameters are necessary to capture the background aerosol extinction behavior. To do this, we first retrieve atmospheric constituent altitude profiles from a set of simulated spectra, measured by a virtual instrument of which the characteristics are based on the ones from the Global Ozone Monitoring by Occultation of Stars (GOMOS) instrument. Several aerosol extinction models are used in the retrieval. The effect of the aerosol model choice on the retrieval error and bias is then calculated by comparing the retrieved profiles with the ones that were used in the simulation. The results show that the use of a second‐degree polynomial leads to good retrievals of aerosol extinction coefficients, while simpler models already give very acceptable results for the other species.
Seasonal changes in the age and structure of dissolved organic carbon in Siberian rivers and streams
Authors: Neff J. C. , Finlay J. C. , Zimov S. A. , Davydov S. P. , Carrasco J. J. , Schuur E. A. G. , Davydova A. I.
Published: December 2006

We examined the age and structural composition of dissolved organic carbon (DOC) transported in the Kolyma River, two large tributaries and several small upland and lowland streams in 2003. The sampling took place under ice through the winter and included the spring flood period. Radiocarbon measurements of the DOC indicated that the bulk of the annual DOC flux was modern in origin (Δ14C > 100‰) and pyrolysis‐gas chromatography/mass spectroscopy techniques showed high concentration of terrestrial lignin monomers consistent with vigorous leaching of surface horizons during the spring thaw. By September 2003 however, little terrestrial lignin was present and the radiocarbon age became significantly older (Δ14C < 0‰) indicating that the mechanism of DOC generation transitions from surface to deeper soils or other terrestrial sources of old, previously stabilized C.
Digisonde spread F and GPS phase fluctuations in the equatorial ionosphere during solar maximum
Authors: Chen W. S. , Lee C. C. , Liu J. Y. , Chu F. D. , Reinisch B. W.
Published: December 2006

The Jicamarca (11.95°S, 76.87°W) digisonde and the Arequipa (16.47°S, 71.49°W) GPS receiver observed the equatorial F region irregularities on the western South America from April 1999 to March 2000. The spread F measured by the digisonde were classified into four types, and the GPS phase fluctuations derived from the temporal variation of total electron content were divided into three levels to represent the irregularity strength. The observation shows that the occurrences of all four types of spread F are higher in the D months (January, February, November, and December) than in the E months (March, April, September, and October). For the GPS phase fluctuations, both seasonal and nighttime variations show that the occurrences of strong level irregularities are higher than moderate level irregularities in the E months, but the situation is reversed in the D months. Moreover, the occurrence sequences of four types of spread F and three levels of GPS phase fluctuations all can be explained by the E × B drift variations and the generalized Rayleigh‐Taylor instability. For the comparisons between the GPS phase fluctuations and the digisonde spread F/plasma bubbles, results show that the GPS phase fluctuations can represent the appearances of the digisonde spread F, and the strong level of GPS phase fluctuations are associated with the occurrence of topside plasma bubbles. These results imply that the greater GPS phase fluctuation is related to the larger altitudinal range distribution of irregularities.
On determination of the Curie point from thermomagnetic curves
Authors: Petrovský E. , Kapička A.
Published: December 2006

In many rock magnetic studies, information on magnetic mineralogy is of crucial importance. Besides standard analytical methods, such as X‐ray spectroscopy, more sensitive thermomagnetic analyses are often used. Temperature dependence of magnetic parameters can serve as basis for determination of magnetic second‐order phase transition temperatures. Although limited by several drawbacks, the most serious being thermally induced transformations of the original minerals, this method provides useful information not only about the presence of magnetic minerals, but also additional knowledge on, e.g., the prevailing grain size distribution or degree of substitution. In thermomagnetic analysis, temperature dependence of two parameters, induced magnetization and magnetic susceptibility, is mostly used. However, let us say because of historical reasons, the same approach for the Curie point determination has been often used in analyzing the two parameters. In our contribution, we discuss the physical principles of the two parameters, showing that the methods developed and used for induced magnetization cannot be used also for temperature dependence of magnetic susceptibility because there is no physical justification to do so. Otherwise, the error in determining the Curie point can be some few degrees but can reach also several tens of degrees. Such an error has serious consequences for further interpretation of the data, e.g., in terms of degree of Ti substitution in Ti magnetite.
Mars Orbiter Camera observations of Martian dust devils and their tracks (September 1997 to January 2006) and evaluation of theoretical vortex models
Authors: Cantor Bruce A. , Kanak Katharine M. , Edgett Kenneth S.
Published: December 2006

A multiyear, planet‐wide survey of Martian dust devils was conducted using observations from Mars Global Surveyor Mars Orbiter Camera, acquired through 21 January 2006. A total of 223,350 images were surveyed and 11,456 dust devils were seen in 0.4% of the images, 11.5% in the Southern and 88.5% in the Northern Hemisphere. Dust devils were observed at latitudes from 71.9°S to 62.2°N, over a range of surface albedos (Am∼0.11–0.22) and elevations from Hellas (−8750 m) to Arsia Mons (+17,250 m). The light‐ and dark‐toned streaks created by dust devils were observed from 80°S to 80°N and changed on timescales as short as 1 month. At mid‐to‐high latitudes, seasonal changes in streak patterns contribute to the seasonal “wave of darkening” observed telescopically from Earth. Dust devils were observed in all seasons in both hemispheres with the exception of Ls = 202.8°–281.5° in the north. Peak activity occurred during midsummer in each hemisphere. Five regions in Amazonis, Syria‐Claritas, Meridiani, and Gusev were monitored regularly. Amazonis had the largest dust devils and was the most active planet‐wide, with annual activity occurring from Ls∼8.5°–197°. Interannual variability resulted from dust storms and planet‐encircling dust hazes, which were observed to initiate and abate dust devil activity. There was no evidence suggesting dust devils cause or lead to initiation of dust storms. Model‐derived tangential wind speeds of large vortices were >20 m s−1 at 20 m above the surface. Dust flux calculations suggest that dust devils are a contributor to the background dust opacity observed through northern spring and summer.
Salmonella, the host and disease: a brief review
Authors: Coburn Bryan , Grassl Guntram A , Finlay B B
Published: December 2006

Salmonella species cause substantial morbidity, mortality and burden of disease globally. Infections with Salmonella species cause multiple clinical syndromes. Central to the pathophysiology of all human salmonelloses is the induction of a strong host innate immune/inflammatory response. Whether this ultimately reflects an adaptive advantage to the host or pathogen is not clear. However, it is evident that both the host and pathogen have evolved mechanisms of triggering host responses that are detrimental to the other. In this review, we explore some of the host and pathogenic mechanisms mobilized in the two predominant clinical syndromes associated with infection with Salmonella enterica species: enterocolitis and typhoid.
Immunopathology of flavivirus infections
Authors: King Nicholas J C , Getts Daniel R , Getts Meghann T , Rana Sabita , Shrestha Bimmi , Kesson Alison M
Published: December 2006

With the recent emergence of the flavivirus, West Nile virus (WNV), in particular, the New York strain of Lineage I WNV in North America in 1999, there has been a significant increase in activity in neurotropic flavivirus research. These viruses cause encephalitis that can result in permanent neurological sequelae or death. Attempts to develop vaccines have made progress, but have been variably successful, despite considerable commercial underwriting. Thus, the discovery of ways and means to combat disease is no less urgent. As such, most recent work has been directed towards dissecting and understanding the pathogenesis of disease, as a way of informing possible approaches to abrogation or amelioration of illness. Whether inherent to flaviviruses or because humans are incidental, dead‐end hosts, it is clear that these viruses interact with their human hosts in extremely complex ways. This occurs from the cellular level, at which infection must be established to produce disease, to its interaction with the adaptive immune response, which may result in its eradication, with or without immunopathological and consequent neurological sequelae. As human proximity to and contact with flavivirus insect vectors and amplifying hosts cannot practically be eliminated, our understanding of the pathogenesis of flavivirus‐induced diseases, especially with regard to possible targets for treatment, is imperative.
Balancing immunity and pathology in visceral leishmaniasis
Authors: Stanley Amanda C , Engwerda Christian R
Published: December 2006

Experimental visceral leishmaniasis (VL) caused by infection withLeishmania donovaniresults in the development of organ‐specific immunity in the two main target tissues of infection, the spleen and the liver. The liver is the site of an acute resolving infection associated with the development of inflammatory granulomas around infected Kupffer cells, and resistance to reinfection. Paradoxically, the spleen is an initial site for the generation of cell‐mediated immune responses, but ultimately becomes a site of parasite persistence with associated immunopathological changes. These include splenomegaly and a breakdown in tissue architecture that is postulated to contribute to the immunocompromized status of the host. The progressive development of splenic pathology is largely associated with high levels of TNF and interleukin (IL)‐10. Follicular dendritic cell (DC) networks are lost, whereas TNF mediates the destruction of marginal zone macrophages and gp38+stromal cells, and IL‐10 promotes impaired DC migration into T‐cell areas with consequent ineffective T‐cell priming. Splenic stromal cell function is also altered, promoting the selective development of IL‐10‐producing DC with immunoregulatory properties. Ultimately, a fine immunological balance determines responses that effectively promote parasite clearance in the liver and those that promote pathology in the spleen, and future investigation aims to separate these responses to offer further means of parasite control in chronically infected VL patients.
Nonlinear piezoelectric resonance: A theoretically rigorous approach to constant I−V measurements
Authors: Blackburn John F. , Cain Markys G.
Published: December 2006

Methods for piezoelectric characterization include the standard resonance test. At higher powers, however, the material’s inherent nonlinearity acts to significantly affect the expected resonance response. High-power resonance methods have previously been developed to describe piezoelectric nonlinearity. In this article we specify and describe the approximations adopted in the current theory and propose a more rigorous theory derived from fundamental principles. We first use thermodynamics to derive the form of the constitutive equations. In particular, we propose that the envelope rather than instantaneous values of stress, strain, and electric field must appear in these equations to yield a type of nonlinearity which, nonetheless, yields a sinusoidal current for sinusoid applied voltage. An alternative approach is set out describing the highly nonlinear experimental data by fitting just one adjustable material parameter to the entire impedance response measured around resonance. Theoretical descriptions for conventional constant-voltage and modified constant-current excitation are developed and compared with experiments for soft and hard compositions of a piezoelectric ceramic (PZT-5H and PZT-4D). The theory is able to match whole families of constant-voltage and constant-current curves with only one adjustable parameter. These models may be used to characterize the high-power properties of piezoelectric materials.
Energy transfer processes and heat generation in Yb3+-doped phosphate glasses
Authors: Jacinto C. , Oliveira S. L. , Nunes L. A. O. , Catunda T. , Bell M. J. V.
Published: December 2006

In this work we present a study of energy transfer processes in Yb3+-doped phosphate glasses with different OH− contents and Yb3+ concentrations. Fluorescence and thermal lens (TL) techniques were used in order to analyze the Yb3+–OH− and Yb3+-other impurity interactions. The role of OH− groups is also presented and discussed. The results show that in the low concentration region up to ∼3×1020Ybions∕cm3, the interaction between Yb3+ and OH radicals is the dominant process reducing the lifetime, increasing the TL dioptric power, and then endangering the performance of the system. For the high Yb3+ concentration limit, the Yb3+-other impurity interaction, which is favored by energy migration, is comparable to the Yb3+–OH− energy transfer, even for high OH− concentration. The nonradiative decay rate due to hydroxyl groups follows Förster-Dexter theory [Ann. Phys. 2, 55 (1948); J. Chem. Phys. 21, 836 (1953)] except at low Yb3+ concentration, being more active at low OH− levels, where quenching rate is probably due to several impurities.
Influence of annealing on B-site order and dielectric properties of (0.4)Pb(In1∕2Nb1∕2)O3:(0.6)Pb(Mg1∕3Nb2∕3)O3 relaxor ceramics
Authors: Tai Cheuk W. , Baba-Kishi K. Z.
Published: December 2006

The structural long-range B-site ordered domains and dielectric properties of the as-sintered and postannealed ceramics (0.4)Pb(In1∕2Nb1∕2)O3:(0.6)Pb(Mg1∕3Nb2∕3)O3 have been characterized. Transmission electron microscopy studies show an increase in the size of the ordered domains following annealing. In the low-field dielectric measurements, the longer the annealing time, the narrower is the diffuse phase transition. A high-temperature dielectric anomaly at low frequency in the as-sintered sample significantly weakens following postannealing. The annealed samples retained their exceptionally slim ferroelectric hysteresis loops.
Generating loop graphs via Hopf algebra in quantum field theory
Authors: Mestre Ângela , Oeckl Robert
Published: December 2006

We use the Hopf algebra structure of the time-ordered algebra of field operators to generate all connected weighted Feynman graphs in a recursive and efficient manner. The algebraic representation of the graphs is such that they can be evaluated directly as contributions to the connected n-point functions. The recursion proceeds by loop order and vertex number.
Bayesian analog of Gleason’s theorem
Authors: Marlow Thomas
Published: December 2006

We introduce a novel notion of probability within quantum history theories and give a Gleasonesque proof for these assignments. This involves introducing a tentative novel axiom of probability. We also discuss how we are to interpret these generalized probabilities as partially ordered notions of preference, and we introduce a tentative generalized notion of Shannon entropy. A Bayesian approach to probability theory is adopted throughout; thus the axioms we use will be minimal criteria of rationality rather than ad hoc mathematical axioms.
Efficiency of the shock wave generation caused by underwater electrical wire explosion
Authors: Grinenko A. , Efimov S. , Fedotov A. , Krasik Ya. E. , Schnitzer I.
Published: December 2006

Shearing interferometry, together with shadowgraph and Schlieren photography techniques, has been applied for the visualization of the cylindrical water flow behind the shock wave generated by high-power 6 GW nanosecond time-scale underwater electrical discharge. The flow was visualized during the first microsecond of the wire explosion process in the region between the expanding exploding wire discharge channel and the shock wave. The optical methods, combined with the hydrodynamic calculation, enable an accurate estimation of the energy transferred from the discharge to the water flow. The estimated efficiency of the transformation of the electrical dissipated energy to the mechanical energy of the generated compressed water flow is ∼15%.
High spatial resolution picosecond cathodoluminescence of InGaN quantum wells
Authors: Sonderegger S. , Feltin E. , Merano M. , Crottini A. , Carlin J. F. , Sachot R. , Deveaud B. , Grandjean N. , Ganière J. D.
Published: December 2006

The authors have studied InxGa1−xN∕GaN (x≈15%) quantum wells (QWs) using atomic force microscopy (AFM) and picosecond time resolved cathodoluminescence (pTRCL) measurements. They observed a contrast inversion between monochromatic CL maps corresponding to the high energy side (3.13eV) and the low energy side (3.07eV) of the QW luminescence peak. In perfect correlation with CL images, AFM images clearly show regions where the QW thickness almost decreases to zero. Pronounced spectral diffusion from high energy thinner regions to low energy thicker regions is observed in pTRCL, providing a possible explanation for the hindering of nonradiative recombination at dislocations.
Carrier dynamics and electrostatic potential variation in InGaN quantum wells grown on {112¯2} GaN pyramidal planes
Authors: Srinivasan S. , Stevens M. , Ponce F. A. , Omiya H. , Mukai T.
Published: December 2006

InGaN quantum wells grown in the conventional [0001] direction are known to exhibit long carrier lifetimes that are attributed to strong internal electric fields due to spontaneous and piezoelectric polarization. These fields are expected to be considerably reduced in other crystal geometries. In this work, the authors have investigated the carrier dynamics of InGaN single quantum wells grown parallel to {112¯2} planes. The carrier lifetimes, measured by time-resolved cathodoluminescence, are considerably smaller than for quantum wells grown in the conventional c-plane geometry. In addition, the lifetime does not change significantly with varying indium composition or increasing well width. Electron holography measurements of the electrostatic potential across these quantum wells confirm that the internal fields in this geometry are negligible. These results are of interest for the development of higher-efficiency light-emitting diodes using alternative substrate orientations.
Electroluminescence efficiency of blue InGaN∕GaN quantum-well diodes with and without an n-InGaN electron reservoir layer
Authors: Otsuji N. , Fujiwara K. , Sheu J. K.
Published: December 2006

The temperature dependence of the electroluminescence (EL) spectral intensity has been investigated in detail between T=20 and 300K at various injection current levels for a set of two blue InGaN∕GaN multiple-quantum-well (MQW) light-emitting diodes (LEDs) with and without an additional n-doped In0.18Ga0.82N electron reservoir layer (ERL). The radiative recombination efficiency of the main blue emission band (∼480nm) is found to be significantly improved at all temperature regions and current levels when the additional ERL is introduced. For high injection currents If, i.e., large forward bias voltages Vf, a quenching of the EL intensity is observed for T<100K for both LED structures, accompanying appearance of short-wavelength satellite emissions around 380–430nm. Furthermore, the low-temperature intensity reduction of the main EL band is stronger for the LED without the ERL than with the ERL. For low If, i.e., small Vf, however, no quenching of the EL intensity is observed for both LEDs even below 100K and the short-wavelength satellite emissions are significantly reduced. These results of the main blue emission and the short-wavelength satellite bands imply that the unusual evolution of the EL intensity with temperature and current is caused by variations of the actual potential field distribution due to both internal and external fields. They significantly influence the carrier capture efficiency by radiative recombination centers within the active MQW layer and the carrier escape out of the active regions into high-energy recombination centers responsible for the short-wavelength satellite emissions.
Lateral wavelength control of InAs∕InGaAsP∕InP (100) quantum dots in the 1.55μm region by selective-area metal organic vapor-phase epitaxy
Authors: Zhou D. , Anantathanasarn S. , van Veldhoven P. J. , van Otten F. W. M. , Eijkemans T. J. , de Vries T. , Smalbrugge E. , Nötzel R.
Published: December 2006

We report lateral wavelength control of InAs quantum dots (QDs) embedded in InGaAsP on InP (100) substrates by selective-area metal organic vapor-phase epitaxy (SA MOVPE). The technologically important 1.55μm telecommunications wavelength region is assessed by the combination of ultrathin GaAs interlayers beneath the QDs with proper SiNx mask design. Atomic force microscopy and microphotoluminescence reveal evolution of the QDs formed by 2 ML InAs as a function of growth rate enhancement with pronounced height and density increase, resulting in a wide wavelength tuning range of 110nm. Saturation of QD formation is observed for 3 ML InAs supply producing a much smaller tuning range of only 25nm which is supported by the increasing GaAs interlayer thickness. Hence, two regimes are identified allowing either wide wavelength tuning or wavelength stability of QDs in the 1.55μm region offering complementary applications of the monolithic integration of optoelectronic devices by SA MOVPE.
Tunable full-color-emitting La0.827Al11.9O19.09:Eu2+,Mn2+ phosphor for application to warm white-light-emitting diodes
Authors: Won Yu-Ho , Jang Ho Seong , Im Won Bin , Jeon Duk Young , Lee Jeong Soo
Published: December 2006

La 0.827 Al 11.9 O 19.09 : Eu 2 + , Mn 2 + showed three emission bands when excited by ultraviolet light. A blue emission originates from Eu2+, whereas both green and red emissions originate from Mn2+. The luminescent mechanism is explained invoking the energy transfer of Eu2+→Mn2+ and Mn2+(tetrahedralsite)→Mn2+(octahedralsite). This energy transfer was confirmed by faster decay times of the blue and green emissions as energy donors. The emitted color of La0.827Al11.9O19.09:Eu2+,Mn2+ can be easily tailored from blue to red through variations of the Mn2+ content. The white-light-emitting diode fabricated via a combination of an ultraviolet light-emitting diode (λpeak=385nm) with La0.827Al11.9O19.09:Eu2+,Mn2+ showed a warm white light (Tc=3559K).
Photoexcitation dynamics in thin films of insulated molecular wires
Authors: Chang M. H. , Frampton M. J. , Anderson H. L. , Herz L. M.
Published: December 2006

A study is presented on how encapsulation of conjugated polymer chains affects the motion of photoexcitations and the formation of interchain aggregates in solid films. It is shown that threading of a poly(diphenylene vinylene) backbone inside insulating cyclodextrins (rotaxination) and/or complexation of the chains with poly(ethylene oxide) are effective means of preventing the diffusion of excitons to nonradiative defect sites. Ultrafast time-resolved photoluminescence data reveal that excitation transfer between encapsulated chains is still possible and, for the case of rotaxination, is likely to be facilitated through close packing of end groups belonging to adjacent chains.
Generalized cascaded model to assess noise transfer in scintillator-based x-ray imaging detectors
Authors: Kim Ho Kyung
Published: December 2006

For a scintillator-based x-ray imaging detector, the conventional cascaded model is generalized to describe the direct x-ray induced quantum noise. The direct x rays are those that are unattenuated from a scintillator and that directly interact with photosensitive elements. The developed model is applied for an analysis of a photodiode array in conjunction with a phosphor screen and shows a good agreement with the measured noise-power spectrum.
Pulsed-laser deposition and growth studies of Bi3Fe5O12 thin films
Authors: Lux Robert , Heinrich Andreas , Leitenmeier Stephan , Körner Timo , Herbort Michael , Stritzker Bernd
Published: December 2006

Magneto-optical garnets are attractive because of their high Faraday rotation and low optical loss in the near infrared. Therefore their use is generally in nonreciprocal devices, i.e., as optical isolators in optical communication. In this paper we present data concerning the deposition of Bi3Fe5O12 (BIG) thin films on (100) and (111) Gd3Ga5O12 substrates using pulsed-laser deposition. Laser-induced processes on the surface of the oxide target used for ablation were analyzed and numerous films were deposited. We found the BIG film quality to be strongly affected by oxygen pressure, laser energy density, and the Bi∕Fe film ratio, whereas temperature had a minor influence. We also investigated the BIG-film deposition using a target pressed from metallic Bi and Fe powders and found information on the growth behavior of BIG. We report on details of the film deposition and film properties determined by environmental scanning electron microscopy, energy dispersive x-ray analysis, Rutherford backscattering spectroscopy, and x-ray diffraction. In addition, we determined the Faraday rotation of the films.
Nucleation, growth, percolation, and amorphous to crystalline transition of ultrathin molybdenum films
Authors: Nayak Maheswar , Lodha G. S. , Nandedkar R. V.
Published: December 2006

We report on the nucleation, growth, percolation, and crystalline transition of ultrathin layers of molybdenum deposited on float glass substrate by in situ electrical properties. The transition from insulating to metallic state (I-M) is shown as a function of molybdenum film thickness and sheet resistance. In the island growth regime, the electrical conductance (G) has two exponential dependencies on thickness (t), namely, logG−B1∝t and logG−B2∝t, explained as the anisotropic and isotropic growth of islands, respectively. In the I-M transition region, the electrical conductance of the films follows the scaling law G∝(t−tc)q. The value of critical exponent q determined from the present experiments agrees well with the theoretically predicted values for the critical exponent of conductivity in a two-dimensional percolating system. The amorphous to crystalline transition is also observed. The microscopic picture of film growth, derived from in situ sheet resistance measurements shows good agreement with that predicted by the percolation theory.
InAs nanowire formation on InP(001)
Authors: Parry H. J. , Ashwin M. J. , Jones T. S.
Published: December 2006

The heteroepitaxial growth of InAs on InP(001) by solid source molecular beam epitaxy has been studied for a range of different growth temperatures and annealing procedures. Atomic force microscopy images show that nanowires are formed for deposition in the temperature range of 400–480°C, and also following high temperature annealing (480°C) after deposition at 400°C. The wires show preferential orientation along ⟨11¯0⟩ and often exhibit pronounced serpentine behavior due to the presence of kinks, an effect that is reduced at increasing growth temperature. The results suggest that the serpentine behavior is related to the degree of initial surface order. Kinks in the wires appear to act as nucleation centers for In adatoms migrating along the wires during annealing, leading to the coexistence of large three-dimensional islands.
Photoluminescence properties: Catalyst-free ZnO nanorods and layers versus bulk ZnO
Authors: Al-Suleiman M. , Che Mofor A. , El-Shaer A. , Bakin A. , Wehmann H.-H. , Waag A.
Published: December 2006

In this contribution, we compare the photoluminescence properties of ZnO nanorods and epilayers with those of bulk ZnO. Owing to the high aspect ratio (length of 4–14μm, diameter of 80–500nm), the characterized ZnO nanorods show very good optical properties. Due to the high surface-to-volume ratio in ZnO nanorods, surface excitons dominate at low temperature. The optical properties of nanorod ensembles improve with increasing nanorod length. The photoluminescence emission from free A excitons was intense in the ZnO layer at 13K.