bluuebunny/crossref_metadata_2025 huggingface dataset:
Oxidative Stress and Diabetes Mellitus: Unravelling the Intricate Connection: A Comprehensive Review
Authors: Rais Nadeem , Ved Akash , Ahmad Rizwan , Parveen Aashna
Published: January 2024

Background: Diabetes mellitus (DM) is often associated with oxidative stress (OS), which is defined as an imbalance between the body's antioxidant defense systems and the generation of reactive oxygen species (ROS). OS serves as a crucial factor in the intricate relationship between DM and cellular dysfunction, influencing the generation of ROS and subsequent DM complications such as retinopathy, cardiomyopathy, neuropathy, nephropathy, encephalopathy, and peripheral arteriopathy.

Objective: This comprehensive review aims to elucidate the complex interplay between OS and DM, providing a thorough understanding of the underlying mechanisms and highlighting emerging therapeutic interventions for the management of OS-related complications in DM. It also explores novel antioxidant-based therapies aiming at specific OS markers and developing personalized interventions, which represents a promising avenue for enhancing treatment efficacy in DM.

Method: The search was conducted on scientific databases and web portals such as PubMed, ScienceDirect, Web of Science, Embase, Google Scholar, EBSCO, DOAJ, etc.

Conclusion: In conclusion, OS and DM are related through a dynamic and intricate interaction involving genetic, molecular, and environmental variables. Interdisciplinary approaches hold the potential to uncover novel biomarkers for early detection, prognosis, and oriented therapeutic interventions, thereby revolutionizing the clinical management of DM-related complications. With research continuing to advance and customized treatments being more widely incorporated into clinical practice, there is hope that the impact of OS-related DM complications will be significantly mitigated in the future. Despite notable progress, certain unexplored facets necessitate deeper investigations into the precise mechanisms through which OS exacerbates the progression of DM.
KAFKASYA’DA BİR LİMANIN YÜKSELİŞİ: POTİ LİMANI (1856-1914)
Authors: Turan Resul
Published: January 2024

Poti, Osmanlı idaresinde Kafkas kıyıları ve iç kesimlerin güvenliğinin sağlamasında bir set görevi görmüştür. Bu fonksiyonu, XIX. yüzyılda Rusya’nın genişleme ile uluslararası ticareti Kafkasya’ya çekme yönündeki politikası neticesinde ticari açıdan daha fazla ön plana çıkmaya başlamıştır. Özellikle Poti, Trabzon-Tebriz ticaretinin Rus topraklarına çekilmesi ve sağlanan ticari kolaylıklarla hızlı bir gelişim seyri yakalamış, Kafkasya’nın idari merkezi Tiflis’in ana limanı haline gelmiştir. Bu bağlamda çalışmanın amacı Rusya’nın kuzeyden güneye doğru genişlemesine paralel olarak yeni limanların ortaya çıkışı, gelişimi ve gerileyişi şeklinde yaşanan değişim ile Redut Kale, Sohum, Batum ve Trabzon limanlarıyla rekabet çerçevesinde Poti’nin liman ve kentsel gelişim seyrini Rus ve Osmanlı kaynakları ışığında ele almaktır.
Strengthening and Embossment of Final Shape in NiTi Shape Memory Alloys (SMA)
Authors: Hornbogen E.
Published: April 2004

Shape memory alloys transform at low temperature by a martensitic reaction β → α , which implies formation of a domain structure (similar to ferromagnetic, ferroelectric transformations). This microstructure allows complex pseudo‐plastic deformability. A systematic approach is provided for the types of reverse reactions α → β, which are found between crystalographically reversible (martensitic) and diffusion controlled (combined reactions). Features of optimum microstructures for shaping and desired SM‐properties are discussed.
Titelbild: A Droplet‐Based, Composite PDMS/Glass Capillary Microfluidic System for Evaluating Protein Crystallization Conditions by Microbatch and Vapor‐Diffusion Methods with On‐Chip X‐Ray Diffraction (Angew. Chem. 19/2004)
Authors: Zheng Bo , Tice Joshua D. , Roach L. Spencer , Ismagilov Rustem F.
Published: April 2004

Proteinkristalle wachsen in Nanoliter‐Tröpfchen in einer Mikrofluidzelle aus Polydimethylsiloxan/Glas‐Komposit. R. F. Ismagilov und Mitarbeiter beschreiben in ihrer Zuschrift auf S. 2562 ff., wie mithilfe dieses Verfahrens die Kristallisationsbedingungen für Proteine in Microbatch‐ und Dampfdiffusionsansätzen optimiert werden können. Die Qualität der erhaltenen Kristalle wurde direkt anhand ihrer Röntgenbeugungsmuster bestimmt (im Hintergrund).
Controversy in Chemistry: What Counts as Evidence?—Two Studies in Molecular Structure
Authors: Labinger Jay A. , Weininger Steve J.
Published: April 2004

Hindsight is a wonderful thing: Controversies are always difficult to characterize while they are in progress; however, as shown for the cases of stereochemistry and bond‐stretch isomerization, it is much easier once all the evidence has been amassed. These two examples have demonstrated how important it is to consider all the experimental results before coming to a conclusion. The second example shows above all that some evidence is more equal than others—crystal‐structure analysis was considered at all stages to be the most reliable.
Fluorine Interactions at the Thrombin Active Site: Protein Backbone Fragments HCαCO Comprise a Favorable CF Environment and Interactions of CF with Electrophiles
Authors: Olsen Jacob A. , Banner David W. , Seiler Paul , Wagner Björn , Tschopp Thomas , Obst‐Sander Ulrike , Kansy Manfred , Müller Klaus , Diederich François
Published: April 2004

In a systematic fluorine scan of a rigid inhibitor to map the fluorophilicity/fluorophobicity of the active site in thrombin, one or more F substituents were introduced into the benzyl ring reaching into the D pocket. The 4‐fluorobenzyl inhibitor showed a five to tenfold higher affinity than ligands with other fluorination patterns. X‐ray crystal‐structure analysis of the protein–ligand complex revealed favorable CF⋅⋅⋅HCαCO and CF⋅⋅⋅CO interactions of the 4‐F substituent of the inhibitor with the backbone HCαCO unit of Asn98. The importance of these interactions was further corroborated by the analysis of small‐molecule X‐ray crystal‐structure searches in the Protein Data Base (PDB) and the Cambridge Structural Database (CSD). In the CF⋅⋅⋅CO interactions that are observed for both aromatic and aliphatic CF units and a variety of carbonyl and carboxyl derivatives, the F atom approaches the CO C atom preferentially along the pseudotrigonal axis of the carbonyl system. Similar orientational preferences are also seen in the dipolar interactions CF⋅⋅⋅CN, CF⋅⋅⋅CF, and CF⋅⋅⋅NO2, in which the F atoms interact at sub‐van der Waals distances with the electrophilic centers.
Mikroverfahrenstechnik in der Lehre und Ausbildung an Hochschulen
Authors: Dietrich T. R. , Liauw M. A.
Published: April 2004

No abstracts.
MR microscopy and microspectroscopy of the intact kidney
Authors: Crozier Stuart , Cowin Gary , Endre Zoltan H.
Published: April 2004

Magnetic resonance (MR) techniques have become essential in clinical practice and a broad range of research areas. We begin with a review of the potential and limitations for resolution improvements by MR techniques. The kidney has distinct regional structural, functional and biochemical variability. The isolated perfused rat kidney (IPRK) retains renal function while eliminating movement and susceptibility boundaries which severely limit the potential of MR techniques. The IPRK, with a length of less than 20 mm in the longest axis, will be used to illustrate the potential resolution of different MR techniques and the different biological information that can be obtained. © 2004 Wiley Periodicals, Inc. Concepts Magn Reson 22A: 50–59, 2004.
Setting up 13C CP/MAS experiments
Authors: Taylor R.E.
Published: April 2004

The 13C cross‐polarization (CP) technique combined with magic angle spinning (MAS) has become one of the more commonly performed solid‐state nuclear magnetic resonance (NMR) experiments. The basics of initially setting up the experiment are given and used to illustrate such NMR phenomena as rotational echoes, homogeneous and inhomogeneous interactions, continuous wave 1H decoupling, and coupling of quadrupolar 14N nuclei to 13C nuclei. The polarization transfer from the protons to the carbons is described briefly with the usual thermodynamic and quantum mechanical models. The setup and use of the experiment for routine analyses are discussed. © 2004 Wiley Periodicals, Inc. Concepts Magn Reson 22A: 37–49, 2004.
The Hybrid Organic‐Inorganic 2‐D Material (CsNa2[{Sn(CH3)2}3(H2O)4(β‐XW9O33)]·7H2O)∞ (X = AsIII, SbIII) and Its Solution Properties
Authors: Hussain Firasat , Reicke Markus , Kortz Ulrich
Published: April 2004

We report on the hybrid organic‐inorganic 2‐D materials (CsNa2[{Sn(CH3)2}3(H2O)4(β‐AsW9O33)]·7H2O)∞ (1a) and the isomorphous (CsNa2[{Sn(CH3)2}3(H2O)4(β‐SbW9O33)]·7H2O)∞ (2a) which crystallize in the orthorhombic system, space group Pna21, with identical unit cell parameters a = 26.118(2) Å, b = 16.064(1) Å, c = 13.776(1) Å, and Z = 1. Compounds 1a and 2a have been synthesized in good yield by crystallization from a reaction mixture of dimethyltin dichloride and Na9[α‐XW9O33] (X = AsIII, SbIII) in aqueous, acidic medium. We have shown by multinuclear NMR spectroscopy (183W, 119Sn, 13C, 1H) that 1a and 2a decompose in solution leading to the monomeric species [{Sn(CH3)2(H2O)2}3(β‐XW9O33)]3− [X = AsIII (1), SbIII (2)]. Polyanions 1 and 2 consist of a (β‐XW9O33) fragment stabilized by three dimethyltin units. The dimethyltin groups are grafted onto the polyanion by two Sn−O(W) bonds on the side of the heteroatom lone pair. Compounds 1 and 2 are rare examples of discrete polyoxoanions which polymerize upon crystallization leading to a 2‐D solid‐state structure with inorganic and organic surface regions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Infertility due to intrauterine residual fetal bone fragments
Authors: Çepni İsmail , Kumbak Banu , Öcal Pelin , İdil Mehmet , Aksu Feridun
Published: April 2004

A case of intrauterine retention of fetal bone diagnosed 8 years after termination of a pregnancy is presented. The patient had a history of hypermenorrhea infertility, and persistent vaginal discharge beginning after the abortion. Transvaginal sonography demonstrated an intrauterine foreign body. Curettage was performed, and fetal bone fragments were found within the removed materials. © 2004 Wiley Periodicals, Inc. J Clin Ultrasound 32:253–255, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/jcu.20028
Late‐onset ureteric urinoma with intermittent jet flow as a complication of ureterolithotomy
Authors: Unal Birsen , Basar Halil , Karadeniz Bilgili Miyace Y. , Basar Murat , Batislam Ertan , Erdal Haydar Hüseyin , Kara Simay
Published: April 2004

We present the case of a late‐onset urinoma in a 47‐year‐old man with a history of right ureterolithotomy performed 6 months previously, following 2 unsuccessful attempts at extracorporeal shock wave lithotripsy. The ipsilateral kidney was nonfunctional and hydronephrotic. The urinoma did not show enhancement on contrast‐enhanced CT and intravenous pyelography. Sonography revealed turbulence in the urinoma and jet flow from the ureter. Lab studies of fluid obtained by percutaneous puncture and aspiration yielded misleading findings for urine and revealed the presence of hemosiderin‐laden macrophages. The urinoma was surgically resected and ureteroneocystostomy was performed. © 2004 Wiley Periodicals, Inc. J Clin Ultrasound 32:264–266, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/jcu.20029
Mechanical characterization of new glass fiber reinforced epoxy composites
Authors: Ratna D. , Chongdar T. K. , Chakraborty B. C.
Published: April 2004

Glass fiber reinforced plastic (GFRP) composites were made using CTPEGA [carboxyl terminated poly(ethylene glycol) adipate] modified epoxy as a matrix and characterized for their flexural properties, impact strength and interlaminar shear stress (ILSS). The volume fraction of glass was about 0.45 for all the composites. The concentration of CTPEGA in the matrix was varied gradually from 0 to 40 phr (parts per hundred parts of resin), to investigate the effect of CTPEGA concentration on the mechanical properties of the composites. It was found that the flexural strength and ILSS gradually decreases with increase in CTPEGA concentration. However, the impact strength of the composites increases up to 20 phr of CTPEGA concentration and decreases thereafter. Scanning electron microscope (SEM) analysis of the fracture surface indicates massive plastic deformation in modified epoxy based composites. Polym. Compos. 25:165–171, 2004. © 2004 Society of Plastics Engineers.
Saturation transfer difference (STD) 1H‐NMR experiments and in silico docking experiments to probe the binding of N‐acetylneuraminic acid and derivatives to Vibrio cholerae sialidase
Authors: Haselhorst Thomas , Wilson Jennifer C. , Thomson Robin J. , McAtamney Sarah , Menting John G. , Coppel Ross L. , von Itzstein Mark
Published: April 2004

Saturation transfer difference (STD) 1H NMR experiments were used to probe the epitope binding characteristics of the sialidase [EC 3.2.1.18] from the bacterium Vibrio cholerae, the causative agent of cholera. Binding preferences were investigated for N‐acetylneuraminic acid (Neu5Ac, 1), the product of the sialidase catalytic reaction, for the known sialidase inhibitor 5‐acetamido‐2,6‐anhydro‐3,5‐dideoxy‐D‐glycero‐D‐galacto‐non‐2‐enoic acid (Neu5Ac2en, 2), and for the uronic acid‐based Neu5Ac2en mimetic iso‐propyl 2‐acetamido‐2,4‐dideoxy‐α‐L‐threo‐hex‐4‐enopyranosiduronic acid (3), in which the native glycerol side‐chain of Neu5Ac2en is replaced with an O‐iso‐propyl ether. The STD experiments provided evidence, supporting previous studies, that Neu5Ac (1) binds to the sialidase as the α‐anomer. Docking experiments using DOCK (version 4.0.1) revealed further information regarding the binding characteristics of the enzyme active site in complex with Neu5Ac2en (2) and the Neu5Ac2en mimetic (3), indicating an expected dominant interaction of the acetamide moiety with the protein. Proteins 2004. © 2004 Wiley‐Liss, Inc.
Distinguishing sources of N2O in European grasslands by stable isotope analysis
Authors: Wrage Nicole , Lauf Jutta , del Prado Agustin , Pinto Miriam , Pietrzak Stefan , Yamulki Sirwan , Oenema Oene , Gebauer Gerhard
Published: April 2004

Nitrifiers and denitrifiers are the main producers of the greenhouse gas nitrous oxide (N2O). Knowledge of the respective contributions of each of these microbial groups to N2O production is a prerequisite for the development of effective mitigation strategies for N2O. Often, the differentiation is made by the use of inhibitors. Measurements of the natural abundance of the stable isotopes of N and O in N2O have been suggested as an alternative for the often unreliable inhibition studies. Here, we tested the natural abundance incubation method developed by Tilsner et al.1 with soils from four European grasslands differing in long‐term management practices. Emission rates of N2O and stable isotope natural abundance of N2O and mineral N were measured in four different soil incubations: a control with 60% water‐filled pore space (WFPS), a treatment with 60% WFPS and added ammonium (NH4+) to support nitrifiers, a control with 80% WFPS and a treatment with 80% WFPS and added nitrate (NO3−) to support denitrifiers. Decreases in NH4+ concentrations, linked with relative 15N‐enrichment of residual NH4+ and production of 15N‐depleted NO3−, showed that nitrification was the main process for mineral N conversions. The N2O production, however, was generally dominated by reduction processes, as indicated by the up to 20 times larger N2O production under conditions favouring denitrification than under conditions favouring nitrification. Interestingly, the N2O concentration in the incubation atmospheres often levelled off or even decreased, accompanied by increases in δ15N and δ18O values of N2O. This points to uptake and further reduction of N2O to N2, even under conditions with small concentrations of N2O in the atmosphere. The measurements of the natural abundances of 15N and 18O proved to be a valuable integral part of the natural abundance incubation method. Without these measurements, nitrification would not have been identified as essential for mineral N conversions and N2O consumption could not have been detected. Copyright © 2004 John Wiley & Sons, Ltd.
Improved method for peak picking in matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry
Authors: Kempka Martin , Sjödahl Johan , Björk Anders , Roeraade Johan
Published: April 2004

A method for peak picking for matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOFMS) is described. The method is based on the assumption that two sets of ions are formed during the ionization stage, which have Gaussian distributions but different velocity profiles. This gives rise to a certain degree of peak skewness. Our algorithm deconvolutes the peak and utilizes the fast velocity, bulk ion distribution for peak picking. Evaluation of the performance of the new method was conducted using peptide peaks from a bovine serum albumin (BSA) digest, and compared with the commercial peak‐picking algorithms Centroid and SNAP. When using the new two‐Gaussian algorithm, for strong signals the mass accuracy was equal to or marginally better than the results obtained from the commercial algorithms. However, for weak, distorted peaks, considerable improvement in both mass accuracy and precision was obtained. This improvement should be particularly useful in proteomics, where a lack of signal strength is often encountered when dealing with weakly expressed proteins. Finally, since the new peak‐picking method uses information from the entire signal, no adjustments of parameters related to peak height have to be made, which simplifies its practical use. Copyright © 2004 John Wiley & Sons, Ltd.
Photoinhibition in lichens depends on cortical characteristics and hydration
Authors: GAUSLAA Yngvar , SOLHAUG Knut Asbjørn
Published: April 2004

Two shade-adapted (Lobaria pulmonaria and Cetraria islandica) and two sun-adapted lichen populations (Xanthoria parietina and Cetraria nivalis) were exposed to three irradiance regimes (1: photosynthetic radiation—PAR, 2: PAR+UV-A, 3: PAR+UV-A+UV-B) and two hydration regimes (1: no hydration, 2: daily hydration) in a growth cabinet for three weeks. Shade-adapted thalli had transparent upper cortices without coloured pigments, whereas sun-adapted thalli had coloured UV-B absorbing cortical pigments masking the photobiont. Manipulation of pigment concentration was the third factor used in the factorial design (1: pigments intact, 2: pigments non-destructively extracted from air-dry living thalli by acetone). Inhibition of the photobiont due to PAR alone was severe in the two shade-adapted populations, but no applied UV wavelength bands caused additional aggravation of photoinhibition. Shade-adapted thalli of the ubiquitous C. islandica were more PAR-susceptible than of the rare old forest lichen L. pulmonaria, suggesting that screening by the mycobiont rather than photobiont characteristics, account for their different success in sun-exposed localities. Hydration of shade-adapted species during exposure reduced their photoinhibition substantially, probably because of moisture-activated repair mechanisms. On the contrary, the sun-adapted X. parietina was most phototolerant in the desiccated state, whereas hydration caused increased photoinhibition. When removing the orange cortical pigment parietin, the photoinhibition in moist thalli was aggravated, confirming a PAR-protective function of parietin. No effects of irradiance treatment, pigment extraction (usnic acid), or hydration level were observed in C. nivalis.
Vernon Ahmadjian introduced the term ‘chlorolichen’
Authors: Lange Otto L. , Wagenitz Gerhard
Published: April 2004

In a recent article (Lange & Wagenitz 2003) we analysed the variation and historical changes in the meaning of the old lichenological term ‘phycolichen’. We came to the conclusion that the word is not suited for use as a name for green algal lichens because of the considerable ambiguity generated by its previous usage. Instead we recommended the name ‘chlorolichen’, a term that appeared to have been used rarely in the lichenological literature; we found it only in publications by Sillett & Goslin (1999) and Ellyson & Sillett (2003). At the time we were not able to determine its origin but this puzzle has, in the meantime, been solved. It was Vernon Ahmadjian who introduced this word as a counterpart for cyanolichens (V. Ahmadjian in litt). He first used the term in 1989 when he wrote “… enough species of lichens with green photobionts (chlorolichens) have been synthesized …” (p. 29), and he also applied the term in his book ‘The Lichen Symbiosis’ (Ahmadjian 1993: 123). Thus, it is to the credit and innovation of Vernon Ahmadjian that we have available the short forms ‘chlorolichens’ and ‘cyanolichens’ for the two functional groups of lichens with either green algae or with cyanobacteria, respectively, as their main photobionts.
THE GESNERIACEAE OF SULAWESI I: AN INTRODUCTION
Authors: MENDUM M. , ATKINS H. J.
Published: April 2004

Sulawesi (Celebes) is the largest island in the biogeographic region of Wallacea. The Gesneriaceae of the island are represented by 11 genera, some of which show a very high degree of endemism. Knowledge of the origin and affinities of the flora of this island is important for an understanding of the biogeography of the area. The Gesneriaceae promise to be excellent models for phytogeographic analysis, but before this, basic taxonomic studies must be carried out. A list of the currently known genera and species is provided, and descriptions of new taxa will be published over the coming months.
THE GENUS CYRTANDRA (GESNERIACEAE) IN PENINSULAR MALAYSIA AND SINGAPORE
Authors: BRAMLEY G. L. C. , WEBER A. , CRONK Q. C. B. , BOKHARI M. H.
Published: April 2004

Nine species of Cyrtandra (Gesneriaceae) are recognized in Peninsular Malaysia. Three (C. cupulata, C. pendula and C. wallichii) are common and occur more or less throughout the area; C. pendula is also recorded from Singapore. Four (C. dispar, C. gimlettei, C. patula and C. suffruticosa) have more restricted distributions, and two (C. lanceolata and C. stonei) are local endemics. Three species and one variety originally described by Ridley are here reduced to synonymy: C. barbata (=C. cupulata), C. falcata (=C. suffruticosa) and C. rotundifolia (=C. pendula), and C. cupulata var. minor (=C. cupulata). Keys for fieldwork and herbarium use are presented and general information is provided. The appendix by M.H. Bokhari contains descriptions of leaf anatomy for eight of the nine species recognized and a key based on anatomical characters.
A REVISION OF CHIRITA SECT. LIEBIGIA (GESNERIACEAE)
Authors: HILLIARD O. M.
Published: April 2004

Chirita sect. Liebigia (Gesneriaceae), endemic to Sumatra, Java and Bali, is revised, paying particular attention to inflorescence and anther characters, the latter being illustrated. Whereas a previous worker considered the section to consist of the single species C. asperifolia, the present revision recognizes 12 species. Six are newly described (C. adenonema, C. dissimilis, C. leuserensis, C. praeterita, C. tenuipes and C. tobaënsis), and C. blumei var. cordifolia is given specific rank as C. neoforbesii. Notes on the history and nomenclature of sect. Liebigia are given in an appendix by B.L. Burtt.
FACTORS CONTROLLING INITIATION AND ORIENTATION OF THE MACROCOTYLEDON IN ANISOCOTYLOUS GESNERIACEAE
Authors: SAUEREGGER J. , WEBER A.
Published: April 2004

Anisocotyly, the prolonged meristematic growth of one of the two cotyledons, is a distinctive feature of Gesneriaceae subfam. Cyrtandroideae. The larger cotyledon, the macrocotyledon, often grows to resemble a normal foliage leaf, and in some taxa may be the only foliar organ of the plant. This raises a number of questions. Which cotyledon becomes the macrocotyledon? Is this pre-determined in the embryo or differentiated after germination? Which external factors such as gravity and light are involved? The observation that the macrocotyledons of unifoliate Gesneriaceae growing on steep rocks mostly point downwards suggests that gravity is involved, but it is not clear whether it plays an initial determinant role or merely later influences orientation. In order to identify possible controlling factors, several experiments were performed, mostly on material of Chirita lavandulacea and Streptocarpus rexii. All seedlings responded significantly to light, the cotyledon further from the light source becoming the macrocotyledon. Seedlings growing in inclined pots with the light source below the pots mostly developed an upper macrocotyledon. The explanation proposed is that this cotyledon receives more light when the two cotyledons unfold after germination. Later on, apparently due to gravity, Chirita seedlings showed re-orientation with the macrocotyledons ultimately pointing downwards, though in Streptocarpus no such downwards re-orientation was observed. This difference is probably correlated to a difference in hypocotyl structure. Our conclusion is that while light is the initial factor controlling macrocotyledon development, gravity may cause re-orientation in some species.
CYANIXIA, A NEW GENUS FOR THE SOCOTRAN ENDEMIC BABIANA SOCOTRANA (IRIDACEAE–CROCOIDEAE)
Authors: GOLDBLATT P. , MANNING J. C. , DAVIES J. , SAVOLAINEN V. , REZAI S.
Published: April 2004

The sub-Saharan and mainly western southern African genus Babiana (Iridaceae–Crocoideae) is morphologically diverse, containing some 80 species. The Socotran B. socotrana, which differs from all other members of the genus inter alia in its trisulcate pollen grains, basic chromosome number, x=10, corms of axillary origin, and globose, colliculate–tuberculate seeds, is here excluded from Babiana and referred to the new genus Cyanixia. Other Babiana species have monosulcate pollen grains with a two-banded operculum, a basic chromosome number of x=7, terminal corm ontogeny, and derived pear-shaped seeds with a smooth glossy surface. Cyanixia socotrana was previously assigned to Babiana because of superficial similarities in morphology, including plicate leaves and blue flowers, thought at the time to be bilabiate, although now known to be actinomorphic and rotate. DNA sequence analysis using the chloroplast gene matK confirms that Babiana is a monophyletic assemblage, whereas B. socotrana is sister to the Lapeirousia/Savannosiphon clade of sub-Saharan Africa. The latter shares axillary corm ontogeny with the southern African Micranthus, Thereianthus, and Watsonia, in contrast to the more common situation in Crocoideae (including Babiana) in which the corm develops from the base of the flowering stem. The tropical African Zygotritonia, which also has axillary corm development, shares with Cyanixia a trisulcate pollen grain, but it differs markedly from that genus in its small, zygomorphic flower, undivided style, and basic chromosome number x=8. Cyanixia is here described as a new monotypic genus of Crocoideae, probably most closely allied to Savannosiphon, also a monospecific genus.
Carbonate dissolution and precipitation in coastal environments: Laboratory analysis and theoretical consideration
Authors: Singurindy Olga , Berkowitz Brian , Lowell Robert P.
Published: April 2004

We have conducted laboratory experiments to examine CaCO3 dissolution and precipitation in saltwater‐freshwater mixing zones, with a view to understanding and predicting porosity changes in coastal environments. Mixing of seawater or saline subsurface water with fresh water can be of major importance in the chemical diagenesis of carbonate rocks and sediments. We used artificial seawater and NaCl solutions of different concentrations under different CO2 partial pressures and with different mixing ratios. Two‐dimensional flow cells filled with glass beads and crushed calcium carbonate rock were used to measure calcium carbonate precipitation and dissolution, respectively. An important feature of these experiments is that the results are shown to agree well with a relatively simple transport theory describing mineral precipitation/dissolution that results from the nonlinear dependence of CaCO3 saturation upon electrolyte concentration. The theory demonstrates that the rate of dissolution or precipitation depends on the curvature (and sign) of the solubility as a function of salinity, the square of the salinity gradient, and the macroscopic dispersion coefficient. The theory is largely scale independent and depends upon field parameters that can be determined. Analysis of data from three field sites (Yucatan peninsula, Bermuda, and Mallorca) demonstrates excellent agreement between field observations and theory.
Multi-instrument observations of ULF wave-driven discrete auroral arcs propagating sunward and equatorward from the poleward boundary of the duskside auroral oval
Authors: Mathews J. T. , Mann I. R. , Rae I. J. , Moen J.
Published: April 2004

An investigation into how discrete frequency fast mode waves propagating sunward from the magnetotail may drive field line resonant Alfvén waves on closed field lines on the afternoon flank of the Earth’s magnetosphere is presented. Due to the morphology of the magnetic field lines on the flank, higher latitude poleward boundary auroral field lines map deeper into the magnetotail, implying that phase lags from mode coupling to sunward propagating fast mode waves in this stretched field geometry can overcome the standard poleward phase propagation of typical field line resonances, producing resonant Alfvén wave-driven discrete auroral arcs that propagate equatorward on closed field lines. A comparison is made between the predicted results and magnetometer, all sky camera and meridian scanning photometer observations of multiple east–west aligned discrete auroral arcs that propagate equatorward and sunward from the poleward boundary of the dayside auroral oval between 1400 and 1500 UT (approximately 1600 to 1700 MLT) on 3 January 1998. From this comparison, the conclusion is reached that the observations are consistent with the theoretical picture of discrete auroral arcs being driven by Alfvénic waves on closed field lines, the Alfvén waves being excited by discrete frequency fast mode waves propagating sunward from the magnetotail in the flank waveguide of the outer magnetosphere.
High harmonic fields in a rotamak plasma
Authors: Zhong Fangchuan , Petrov Yuri , Huang Tian-Sen
Published: April 2004

High harmonic oscillations of the magnetic fields in a rotamak plasma are measured for the first time in experiments. Experimental results indicate that besides the fundamental rotating magnetic field, harmonic fields are stimulated simultaneously. The features of the harmonics in the discharges with and without toroidal field are compared. In the case without toroidal field the harmonics are dominated by odd orders, as expected by theory. The presence of toroidal field enhances the even harmonics greatly. The ratio of amplitudes of second harmonic and the fundamental one can be as high as 45% in this case. Numerical simulation confirms that the Hall term J×B is the cause of the harmonic generation.
Alfvén wave propagation in a partially ionized plasma
Authors: Watts Christopher , Hanna Jeremy
Published: April 2004

Results from a laboratory study of the dispersion relation of Alfvén waves propagating through a partially ionized plasma are presented. The plasma is generated using a helicon source, creating a high density, current-free discharge, where the source can be adjusted to one of several modes with varying neutral fraction. Depending on the neutral fraction, the measured dispersion curve of shear Alfvén waves can change significantly. Measurement results are compared with theoretical predictions of the effect of neutral particles on Alfvén wave propagation. In fitting the theory, the neutral fraction is independently estimated using two simple particle transport models, one collisionless, the other collisional. The two models predict comparable neutral fractions, and agree well with the neutral fraction required for the Alfvén dispersion theory.
GEKKO/HIPER-driven shock waves and equation-of-state measurements at ultrahigh pressures
Authors: Ozaki N. , Tanaka K. A. , Ono T. , Shigemori K. , Nakai M. , Azechi H. , Yamanaka T. , Wakabayashi K. , Yoshida M. , Nagao H. , Kondo K.
Published: April 2004

The GEKKO/HIPER-laser [N. Miyanaga et al., in Proceedings of the 18th International Conference on Fusion Energy (IAEA, Sorrento, Italy, 2001), IAEA-CN-77] driven shock experiments were characterized in detail for studies on equation-of-state (EOS) at ultrahigh pressures. High-quality shock waves were produced with the bundled 9 laser beams optically smoothed by spectral dispersion technique and Kinoform phase plates. The laser beams were directly focused on targets at up to an intensity of 1014 W/cm2 or higher with a wavelength of 351 nm and a duration of 2.5 ns. Key issues on dynamic EOS research; the spatial uniformity and temporal steadiness of shock wave were estimated, and the preheating problem was also investigated by measurements of the self-emission and reflectivity from target rear surface. The experimental and analytical methods were validated by using double-step targets consisting of two Hugoniot standard metals. Extreme pressures only accessed in nuclear explosion experiments were generated with reproducibility and good accuracy using the laser direct-drive experimental system, for Al, Cu, polystyrene, and Ta. It was indicated that new and reliable EOS data at the ultrahigh pressures could be provided for materials ranging from low to high initial density by the laser direct-drive experimental technique.
Dependence of up–down asymmetry on the edge safety factor in the Saha Institute of Nuclear Physics–Tokamak (SINP–Tokamak)
Authors: Ghosh Joydeep , Pal Rabindranath , Basu Debjyoti
Published: April 2004

Inside the limiter of Saha Institute of Nuclear Physics–Tokamak (SINP–Tokamak) [A. N. Sekar Iyengar, S. K. Majumdar, J. Basu, R. K. Paul, R. Pal, and S. Chowdhury, Pramana, J. Phys. 39, 181 (1992)] plasma potential was investigated using Langmuir probe arrays with poloidal and radial resolution and as a function of the safety factor at the limiter. A poloidal asymmetry was observed in floating potential in the edge region. Quantitatively, its up–down difference exhibits an almost square of safety factor divided by toroidal magnetic field-like scaling. A radial electric field, also observed in this region, was seen to increase with the edge safety factor. The plasma seems to be collisional here with the mean free path shorter than the connection length, where Pfirsch–Schluter current causes a qualitatively similar up–down asymmetry. However, its magnitude was seen to be much lower than the observed results. It has been shown that the presence of radial and/or toroidal component of the electric and magnetic fields in SINP–Tokamak can contribute significantly to the observed asymmetry.
The comparison of the penetration process of running and standing waves into a plasma with resonance surface
Authors: Zhukov V. , de Blank H. J. , Kobayashi M. , Schwab I.
Published: April 2004

The processes of penetration of running and standing waves into magnetized plasma with a resonance surface are compared. It is shown, that at a sufficiently large amplitude of the wave (here the amplitude can be much less of the initial magnetic field) the penetrations of the running and standing waves are of absolutely different character. The picture of flow is determined in many respects by the ratio between a wave phase velocity in case of a running wave (product of a wave frequency and length in case of a standing wave) and by a typical Alfvén velocity.
Laboratory evidence of a supersonic ion beam generated by a current-free “helicon” double-layer
Authors: Charles C. , Boswell R. W.
Published: April 2004

An electric double-layer is generated near the open end of a high-density low pressure helicon sustained radio frequency (13.56 MHz) plasma source which expands into a diffusion chamber. Ion energy distribution functions measured with a retarding field energy analyzer placed in the diffusion chamber with its aperture facing the double-layer show the presence of a low energy peak (∼29 V) around the local plasma potential and a high energy peak (∼47 V) corresponding to a supersonic ion beam (∼2.1cs). At an axial distance 12 cm downstream of the double-layer, the beam density is 14% of the local density at that position and the ion energy gain is approximately 70% of the potential drop of the double-layer. The ion beam is observed from the center out to a radius corresponding to that of the plasma source tube (−6.8 cm⩽r⩽+6.8 cm) and is not greatly affected by the expanding magnetic field. A depression in the total ion flux just downstream of the double-layer—previously measured on the main z-axis of the reactor—is also present across the chamber diameter. Evidence of an electron beam near the closed end of the source tube, generated via “backwards” acceleration through the double-layer, has been observed on a Langmuir probe trace.
Comment on “The superposition of rotating and stationary magnetic sources: Implications for the auroral region” [Phys. Plasmas 10, 2971 (2003)]
Authors: Vasyliūnas Vytenis M.
Published: April 2004

The claim by Rothwell [Phys. Plasmas 10, 2971 (2003)] that electric fields parallel to the magnetic field can be produced just by the rotation of the Earth’s magnetic dipole in an external field arises from a misinterpretation of the generalized Ohm’s law and is incorrect.
Low mode surface perturbation tolerance of ignition capsule implosions for the National Ignition Facility
Authors: Strobel George L. , Haan Steven W. , Dittrich Thomas R.
Published: April 2004

The stability of a capsule intended to produce ignition on the National Ignition Facility (NIF) [J. A. Paisner, J. D. Boyes, S. A. Kumpan, W. H. Lowdermilk, and M. S. Sorem, Laser Focus World 30, 75 (1994)] is examined. Sensitivity to target fabrication defects in spherical harmonics modes L⩽12 is quantified in terms of a mode dependent tolerance to surface perturbations. Simulations of NIF capsule implosions with single mode perturbations on a single surface allow the determination of modal growth factors. Simulations with large initial perturbations were also done to determine how large a final perturbation could be tolerated. Combining the growth factors and tolerances determines specifications on initial perturbations. This allows an estimate of modal tolerance for each capsule surface and thickness variation for a polyimide ablator capsule design with central gas fills of 0.3 or 0.6 mg/cm3.
Neutrino (antineutrino) effective charge in a magnetized electron–positron plasma
Authors: Serbeto A. , Rios L. A. , Mendonça J. T. , Shukla P. K.
Published: April 2004

Using dynamical techniques of the plasma physics, the neutrino (antineutrino) effective charge in a magnetized dense electron–positron plasma is determined here. It shown that its value, which is determined by the plasma collective processes, depends mainly on the propagation direction of plasma waves and neutrinos against the external magnetic field direction. The direction dependence of the effective charge occurs due to the fact that the magnetic field breaks the plasma isotropy. The present theory gives a unified picture of the problem which is valid for an external magnetic field below the Landau–Schwinger critical value. Comparison with some of the results from the quantum field theory has been made.
Stability analysis of H-mode pedestal and edge localized modes in a Joint European Torus power scan
Authors: Onjun Thawatchai , Kritz Arnold H. , Bateman Glenn , Parail Vassili , Wilson Howard , Lönnroth Johnny , Huysmans Guido , Dnestrovskij Alex
Published: April 2004

Simulations of three Joint European Torus [P. H. Rebut et al., Nucl. Fusion 25, 1011 (1985)] type I ELMy high-confinement discharges in a power scan are carried out using the JETTO integrated modeling code [M. Erba et al., Plasma Phys. Controlled Fusion 39, 261 (1997)] with predictive core and pedestal models, which include the effect of edge localized modes (ELMs). It is found that current-driven peeling modes trigger the ELM crashes in these discharges and, as a result, yield an explanation of the experimentally observed increase in pedestal height with heating power. After each ELM crash, the pressure gradient and the related bootstrap current density at the edge of plasma rapidly increase with increasing heating power, while the total current density rises only slowly because the total current density is impeded by a back electromotive force. Hence, as the heating power is increased, the pedestal pressure can rise to higher values during an ELM cycle before the current density reaches the level required for destabilization of the current-driven peeling modes. In addition, a stability analysis using the HELENA and MISHKA codes [A. B. Mikhailovskii et al., Plasma Phys. Rep. 23, 713 (1997)] is carried out in conjunction with these simulations. The analysis includes infinite-n ideal ballooning, finite-n ballooning, and low-n kink/peeling modes.
Trapped electron effects in a magnetic filter field of the plasma source
Authors: Kumar T. A. Santhosh , Mattoo S. K. , Jha R.
Published: April 2004

An experiment is carried out to ascertain the role of energetic electrons in the excitation of plasma turbulence, near the inhomogeneity of a magnetic filter field. This is done in two steps. First, a magnetic filter arrangement is used to eliminate energetic electrons from the plasma. Second, electrons of 0–20 eV energy are deliberately introduced between the main filter and an additional filter located in the target chamber. It is observed that plasma near the additional filter is quiescent in the absence of energetic electrons. When the energetic electrons are introduced, the plasma near the additional filter becomes turbulent. The frequency spectrum of the turbulent fluctuation is broad, with a peak around 100 kHz which lies in the lower hybrid frequency range.
Multicomponent dynamical nucleation theory and sensitivity analysis
Authors: Kathmann Shawn M. , Schenter Gregory K. , Garrett Bruce C.
Published: April 2004

Vapor to liquid multicomponent nucleation is a dynamical process governed by a delicate interplay between condensation and evaporation. Since the population of the vapor phase is dominated by monomers at reasonable supersaturations, the formation of clusters is governed by monomer association and dissociation reactions. Although there is no intrinsic barrier in the interaction potential along the minimum energy path for the association process, the formation of a cluster is impeded by a free energy barrier. Dynamical nucleation theory provides a framework in which equilibrium evaporation rate constants can be calculated and the corresponding condensation rate constants determined from detailed balance. The nucleation rate can then be obtained by solving the kinetic equations. The rate constants governing the multistep kinetics of multicomponent nucleation including sensitivity analysis and the potential influence of contaminants will be presented and discussed.
Ab initio study of the electronic and structural properties of the crystalline polyethyleneimine polymer
Authors: Herlem Guillaume , Lakard Boris
Published: April 2004

Polyethyleneimine is a very interesting polymer, not only for its extensive use in biological applications, but also for its crystal structure as a double-stranded helix in the anhydrous state. In order to elucidate the electronic bulk properties of the crystalline (or linear) polyethyleneimine built from ethylenediamine molecules in anhydrous conditions, we performed ab initio density functional theory calculations on water-free molecular crystal structures. The resulting polymer is a semiconductor with a small band gap: Eg=0.40 eV.
The approximation of geometrical optics for bulk spin waves in spatially inhomogeneous ferromagnetic insulators with an exchange defect
Authors: Reshetnyak S. A.
Published: April 2004

The refractive index for bulk spin waves propagating in a ferromagnetic medium with an inhomogeneous distribution of exchange interaction parameters and uniaxial anisotropy is calculated in the spin density formalism. The reflection and transmission coefficients for spin waves at the boundary between two homogeneous magnets with different exchange interaction constants, uniaxial magnetic anisotropy, and saturation magnetization are calculated with allowance for a δ-function-like exchange at the interface. The dependence of the reflected wave intensity and the refractive index on the frequency of the wave and the value of a homogeneous external dc magnetic field is obtained.
Electronic structure and x-ray magnetic circular dichroism in uranium monochalcogenides
Authors: Antonov V. N. , Harmon B. N. , Andryushchenko O. V. , Bekenev L. V. , Yaresko A. N.
Published: April 2004

The electronic structure and x-ray magnetic circular dichroism (XMCD) spectra of US, USe, and UTe are investigated theoretically from first principles, using the fully relativistic Dirac LMTO band structure method. The electronic structure is obtained with the local spin-density approximation (LSDA), as well as with a generalization of the LSDA+U method which takes into account that in the presence of spin–orbit coupling, the occupation matrix of localized electrons becomes nondiagonal in the spin indices. The origin of the XMCD spectra in the compounds is examined.
Low-temperature anomalies of the mobility and Shubnikov–de Haas oscillations due to electron resonance scattering on donor impurities in semiconductors. Explanation based on the Friedel approach
Authors: Okulov V. I. , Sabirzyanova L. D. , Sazonova K. S. , Paranchich S. Yu.
Published: April 2004

Manifestations of electron resonance scattering by donor impurities in the low-temperature conductivity of semiconductors are investigated in the case when the donor resonance energy level of the impurities lies in the conduction band. It is shown that the application of resonance scattering theory in the framework of the Friedel approach can explain the stabilization of the electron density, the maximum of the electron mobility, and the minimum of the Dingle temperature as a function of the concentration of donor impurities and also the anomalous temperature dependence of the mobility due to the resonance. New experimental data are obtained on the concentration, mobility, and Dingle temperature of electrons in mercury selenide crystals containing iron impurities, and it is found that these new results, like those known previously, are in complete agreement with the behavior predicted in the proposed approach. The relation of this approach to the previous interpretation of the concentration maximum of the mobility is discussed, and arguments for its applicability are presented.
Structural mechanisms of low-temperature work hardening and fracture of cryogenic metallic materials
Authors: Pokhyl Yu. A.
Published: April 2004

On the basis of the results of original research, various physical aspects of work hardening and fracture of metallic materials at low temperatures (the macroscopic behavior, microstructural processes governing plastic flow and work hardening, the mechanisms of nucleation and propagation of fracture in the final stage of plastic deformation) are analyzed from a unified point of view: the evolution of the microstructural state during plastic deformation of different groups of structural metallic materials in the temperature range 300–4.2 K. The characteristic physical situations realized in low-temperature plastic deformation and fracture of solids are generalized and classified.