bluuebunny/crossref_metadata_2025 huggingface dataset:
Mapping the shape of the accretion disk of Hercules X‐1
Authors: Leahy D.A.
Published: March 2004

Hercules X‐1 is an x‐ray binary with a 1.7 day orbit and which exhibits a regular 35‐day intensity cycle, which comes in two types: 0.2 orbital phase turn‐on and 0.7 phase turn‐on. The cycle is well measured by the RXTE/ASM and is caused by a sequence of occultations by the inner and outer edges of the accretion disk. In addition to the 35‐day x‐ray cycle, the accretion disk shadows the companion star HZ Her to give the regular and well known optical modulation, and gives a modulation of the EUV emission from the system. The x‐ray modulation is most precisely measured and best for determination of the disk shape. Here disk and emission region models are used to derived the disk shape from the 0.2 turn‐on cycles and compared to a previous derivation based on 0.7 turn‐on cycles. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Surface images of the short period contact binary AE Phe
Authors: Barnes J. R. , Lister T. A. , Hilditch R. W. , Collier Cameron A.
Published: March 2004

We present high resolution Doppler images of the short period (P = 0.362 d) contact binary AE Phe. Using least squares deconvolution, we make use of the information content of the several thousand lines in each échelle spectrum to obtain the necessary S/N and time resolution required to resolve individual starspot features. A single pair of rotationally broadened profiles (free of sidelobes due to blending) with a typical S/N of 3000 ‐ 4000 per spectrum is thus obtained. With 300 sec exposures we achieve a cadence of 350 sec which is equivalent to sampling the rotation phase every 4°. We derive images for four nights of data which reveal starspots at most latitudes on both components of the common envelope system. Individual starspots evolve significantly on very short timescales, of order one day; significantly faster than the week timescales found on active single stars and the Sun. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Indirect imaging of polars
Authors: Schwope A.D. , Staude A. , Vogel J. , Schwarz R.
Published: March 2004

Tomographic techniques of different flavour offer enormous diagnostic power for the analysis of magnetic cataclysmic binaries, particularly those of AM Herculis type, the so‐called polars. The three main ingredients of such systems, the donor star, the accretor and the accretion stream between the two stars, are investigated by Doppler tomography, Roche tomography and eclipse mapping methods. The indirect imaging methods reveal the structure, extent and ionization conditions in the accretion stream, they reveal the extent of the irradiation zone on the secondary star and constrain the mass ratio and the orbital inclination of the binary. We describe a new code for Roche tomography, the achievements and limitations of straight Doppler tomography and a new mapping technique tentatively called curtain tomography. This new technique will map emission line profiles to an accretion curtain making full use of the velocity and the photometric information. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stellar surface imaging: mapping brightness and magnetic fields
Authors: Hussain G. A. J.
Published: March 2004

Rapidly rotating late‐type stars typically display signs of magnetic activity that exceed those seen on the Sun by over two orders of magnitude. The techniques of Doppler imaging and Zeeman Doppler imaging have been instrumental in unveiling magnetic activity patterns at the photospheres of these active stars. Essentially, these techniques work by inverting time‐series of high resolution spectra to produce temperature, brightness and/or magnetic field maps at the surfaces of stars. I will describe how these techniques work and review what they have taught us about the nature of magnetic activity in rapid rotators over the last 20 years. Finally, I will conclude by outlining the capabilities of these techniques in light of new instrumentation that is now becoming available. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Roche tomography of the secondary stars in CVs
Authors: Watson C. A. , Dhillon V. S.
Published: March 2004

The secondary stars in cataclysmic variables (CVs) are key to our understanding of the origin, evolution and behaviour of this class of interacting binary. In seeking a fuller understanding of these objects, the challenge for observers is to obtain images of the secondary star. This goal can be achieved through Roche tomography, an indirect imaging technique that can be used to map the Roche‐lobe‐filling secondary. The review begins with a description of the basic principles that underpin Roche tomography, including methods for determining the system parameters. Finally, we conclude with a look at the main scientific highlights to date, including the first unambiguous detection of starspots on AE Aqr B, and consider the future prospects of this technique. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Eclipse mapping of the hot circumstellar plasma in Algol binaries
Authors: Peters G.J. , Polidan R. S.
Published: March 2004

Phase‐resolved FUV observations of three Algol‐type interacting binaries (V356 Sgr, TT Hya, and RY Per) have been made during totality with the Far Ultraviolet Spectroscopic Explorer to map the location of the hot circumstellar plasma that produces emission lines of O VI, Si III,IV, S IV, C III, and N II. Since OVI shows very little variation in profile, strength, and velocity as the disk of the secondary occults the line formation region, we conclude that the emission originates in material that has a substantial flow perpendicular to the orbital plane (perhaps a bipolar jet). The behavior of the emission lines from the moderate‐ionization species suggests that the plasma producing these emission features has a large equatorial component. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Few projections astrotomography: 2‐CLEAN DSA reconstruction
Authors: Agafonov M. I.
Published: March 2004

2‐CLEAN DSA method of Determination of permissible Solutions Area created on the basis of the Radioastronomical approach to image reconstruction from few projections is presented as a component of astrotomography and also as a method of reconstruction, as it has good prospects for a wide range of remote sensing. Its basis was described and published before 1990 in the application to the reconstruction of 2D‐images. Later the method received its name and was thoroughly developed, in particular for 3‐D reconstruction from 2D and 1D‐projections. 2‐CLEAN DSA method allows to carry out 2D‐recognition in a wide space frequency band {0, ωb} constrained only by the upper frequency ωb when the number of 1D‐projections contains only ∼ 0.1 of the number needed for the usual tomographical approach. It easily adapts to the wide range of additional constraints. Some of the important points connected with 2D‐reconstruction of the images and sections of optically thin emissive objects are described. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Tomography of stellar non‐radial pulsations
Authors: Berdyugina S. V.
Published: March 2004

The stellar surface imaging technique is used for studying stellar non‐radial pulsations on the basis of inversions of time series of variable line profiles without making assumptions on the specific shape of the pulsations. The inversion results in an image of the stellar surface in which sectoral and tesseral modes can be distinguished in many cases and the pulsational degree and the azimuthal order can be determined. The capability of the technique is studied with simulated data. Then, the surface imaging technique is applied to high‐resolution spectra of the rapidly rotating Beta Cep‐type star ω1 Sco, which shows strong line‐profile variations. Stellar surface imaging is concluded to be a useful technique for pulsation‐mode identification. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Differential rotation of cool active stars
Authors: Petit P. , Donati J.‐F. , Collier Cameron A.
Published: March 2004

The surface differential rotation of active solar‐type stars can be investigated by means of Doppler and Zeeman‐Doppler Imaging, both techniques enabling one to estimate the short‐term temporal evolution of photospheric structures (cools spots or magnetic regions). After describing the main modeling tools recently developed to guarantee a precise analysis of differential rotation in this framework, we detail the main results obtained for a small number of active G and K fast rotating stars. We evoke in particular some preliminary trends that can be derived from this sample, bearing the promise that major advances in this field will be achieved with the new generation of spectropolarimeters (ESPaDOnS/CFHT, NARVAL/TBL). (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Tomographic studies of exoplanet atmospheres
Authors: Collier Cameron A. , Leigh Ch.
Published: March 2004

We review the current state of models for the optical and near‐infrared reflection spectra of exoplanetary atmospheres, with particular reference to the close‐orbiting giant planets that offer the best prospects for high‐resolution spectroscopic detection.We describe the main steps in the tomographic procedures that have been used in recent attempts to separate these faint signals from the direct spectra of the parent stars.We compare recent, deep upper limits on planetary albedos with model predictions, and discuss prospects for future attempts to detect and characterise the reflection, transmission and thermal emission spectra of these planets at optical and infrared wavelengths. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Doppler Tomography of X‐ray binaries
Authors: VrtíLek S.D. , Quaintrell H. , Boroson B. , Shields M.
Published: March 2004

The Space Telescope Imaging Spectrograph (STIS) on HST provides the first ultraviolet data that are of sufficient spectral and temporal resolution to generate Doppler tomograms of X‐ray binaries.We show both optical and ultraviolet maps constructed for the intermediate mass system Hercules X‐1/HZ Her and the massive wind‐fed system SMC X‐1/SK160. We have used the maps and corresponding lightcurves as diagnostics with which to test the validity of published models for Hercules X‐1. We find that although the models are mostly able to explain the light curves they are not consistent with the full phase maps. We present simulations of Doppler maps of X‐ray lines that will be possible with the spectral and temporal resolution and substantial effective area of the next major X‐ray mission, Con‐X. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Astrotomography
Authors: Cameron A.C. , Schwope A. , Vrielmann S.
Published: March 2004

Even in the new millenium, many astronomical objects cannot be resolved spatially with any available telescope. Most stars are too small and galaxies are too far away to be imaged directly or in detail in the foreseeable future. However, advances in data‐analysis techniques allow us now to create detailed indirect images using tomographic methods. These images provide unprecedented insights into fundamental processes that drive the evolution of stars and galaxies, such as accretion and magnetic‐field generation, on length scales that are of great physical importance but which are otherwise inaccessible. Here we present a collection of papers on recent progress in astrotomography, all of which were presented at Joint Discussion 09 of the XXV General Assembly of the IAU in Sydney, during July 2003. The online edition of the journal contains several illustrative movies for free download. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Chemoenzymatic Synthesis of (2S)‐ and (2R)‐2‐(1,3‐Dithian‐2‐ylmethyl)oxirane
Authors: Sundby Eirik , Holt Jarle , Vik Anders , Anthonsen Thorleif
Published: March 2004

Lipase‐catalyzed transesterifications and biological reductions were used to obtain the (S)‐enantiomers of 3‐chloro‐1‐(1,3‐dithian‐2‐yl)‐2‐propanol and 1‐(1,3‐dithian‐2‐yl)‐3‐fluoro‐2‐propanol and their (R)‐acetates. (S)‐3‐Chloro‐1‐(1,3‐dithian‐2‐yl)‐2‐propanol and (R)‐3‐chloro‐1‐(1,3‐dithian‐2‐yl)‐2‐propyl acetate were converted into the respective enantiomers of 2‐(1,3‐dithian‐2‐ylmethyl)oxirane. During this work we also isolated a new gem‐disubstituted epoxide, 2‐(chloromethyl)‐2‐(1,3‐dithian‐2‐yl)oxirane. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Chemical and Structural Properties of the Inclusion Complex of Euplotin C with Heptakis(2,6‐di‐O‐methyl)‐β‐cyclodextrin through NMR Spectroscopy, Electrospray Mass Spectrometry and Molecular Mechanics Investigations
Authors: Guella Graziano , Callone Emanuela , Mancini Ines , Uccello‐Barretta Gloria , Balzano Federica , Dini Fernando
Published: March 2004

The inclusion complex of heptakis(2,6‐di‐O‐methyl)‐β‐cyclodextrin (DIMEB) with euplotin C (EC), a cytotoxic metabolite isolated from the protistan strains composing the marine ciliate Euplotes crassus, has been investigated by 1H NMR techniques, electrospray ionization mass spectrometry (ESI/MS) and molecular mechanics (MM) calculations. The results suggest that DIMEB preferentially includes the side chain of this sesquiterpenoid with the terminal methyl groups exposed at the narrower rim of the cyclodextrin (CD). The dihydropyranic ring of EC is also well enclosed in the host cavity, whereas the acetyl group and the ring protons at C‐4 and C‐5 lie outside the larger rim. A kinetic degradation study of EC and its inclusion complex (EC‐DIMEB) in aqueous solution has been performed by HPLC‐UV‐MS measurements obtaining structural data for the hydrolysis end‐products. A significant increase in the chemical stability of complexed EC compared with free EC has also been determined. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Oxidative Fragmentation of the Bridged β‐Triketone Core of Hyperforin
Authors: Verotta Luisella , Lovaglio Erminio , Sterner Olov , Appendino Giovanni , Bombardelli Ezio
Published: March 2004

The β‐triketone core of the antidepressant phloroglucinol hyperforin (1) undergoes a series of peroxide‐induced oxidative rearrangements leading to compound 5, which is formed by opening of ring A, and compound 6, which is formed by removal of the C‐1 carbonyl bridge. A mechanistic rationale for this process is proposed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
A Novel Synthesis of 2‐Alkoxy‐3‐hydroxytropones and 2,7‐Dihydroxytropones from Dialkoxy‐8‐oxabicyclo[3.2.1]oct‐6‐en‐3‐ones
Authors: Zinser Hartmut , Henkel Sonja , Föhlisch Baldur
Published: March 2004

Trichloro‐substituted 8‐oxabicyclo[3.2.1]oct‐6‐en‐3‐ones 6 and 7 are solvolysed by methanolic sodium methoxide to form the bicyclo[3.2.1] α,α‐dimethoxy ketones 13 and 14, with preservation of one chloro substituent. In the case of 6a, prolonged reaction time with an excess of methanolic sodium methoxide provides a trimethoxy‐substituted oxanorbornene aldehyde 19 through ring contraction. Treatment of the mixture of 13 and 14 with zinc and aqueous acetic acid affords dechlorinated α‐oxo acetals 15 and 16. Starting with the [4+3] cycloadducts derived from 2‐methylfuran and tetrachloroacetones (6b and 7b), the same procedure, but with use of ethanol or trifluoroethanol, results in the corresponding ethoxy‐ and trifluoroethoxy acetals. These compounds can be converted into the oxabicyclic compounds 15, which undergo cleavage of the ether bridge on heating with KOH in methanol, thus providing 2‐alkoxy‐3‐hydroxytropones 20, which can be dealkylated to give the 2,7‐dihydroxytropones (7‐hydroxytropolones) 29. The lithium enolate generated from the α‐oxo acetal 15a can be exo‐alkylated with methyl iodide. Michael addition with 2‐nitro‐1‐butene followed by a Nef reaction furnishes the bicyclic dioxo acetal 5. Treatment of 5 with basic methanol results in an epoxyazulenone derivative 26, and a hydroxytropone 20f, which is in equilibrium with the cyclic hemiacetal form 28. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Reactions of Levulinic Acid with Norbornane/ene Amino Acids and Diamines
Authors: Stájer Géza , Szabó Angela E. , Csámpai Antal , Sohár Pál
Published: March 2004

Whereas the cyclizations of di‐endo‐3‐aminobicyclo[2.2.1]heptane‐2‐carboxylic acid (2) and di‐endo‐3‐aminobicyclo[2.2.1]hept‐5‐ene‐2‐carboxylic acid (3) with 4‐oxopentanoic acid (1) yield methanodioxopyrrolo[1,2‐a][3,1]benzoxazines 6 and 7, the di‐exo analogues give either the pyrrolo[1,2‐a]pyridine 8 as sole product (in the case of 4), or 10 together with the methyl‐substituted derivative 9 (in the case of 5). Compound 1 reacts with di‐exo‐3‐aminobicyclo[2.2.1]heptane‐2‐methanamine (11) and di‐exo‐3‐aminobicyclo[2.2.1]hept‐5‐ene‐2‐methanamine (12) to give the methylene‐bridged pyrrolo[2,1‐b]quinazolinones 13 and 14 respectively; a pentacyclic product containing a dipyrrolodiazepine moiety 15 was also isolated. The structures and stereochemistry were elucidated by means of IR and NMR spectroscopy, including COSY, DIFFNOE, DEPT, HMQC and HMBC techniques.
Chemoselective Acylation of Amines in Aqueous Media
Authors: Naik Sarala , Bhattacharjya Gitalee , Talukdar Bandana , Patel Bhisma K.
Published: March 2004

Amines are efficiently acylated by both cyclic and acyclic anhydrides by dissolving them in an aqueous medium with the help of a surfactant, sodium dodecyl sulfate (SDS). Cyclic and acyclic anhydrides react with equal ease with an amine, and amines with various stereo‐electronic factors react at the same rates with an anhydride. Chemoselective acylation of amines in the presence of phenols and thiols and of thiols in the presence of phenols has been achieved. No acidic or basic reagents are used during the reaction. No chromatographic separation is required for isolation of the acylated products. Reactions in a neutral aqueous medium, easy isolation of products, and innocuous by‐products make the present method a green chemical process. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Carrier‐Mediated Transport of Toxic Heavy Metal Ions in Bulk Liquid Membranes
Authors: Brinchi Lucia , Germani Raimondo , Mancini Maria Vincenza , Savelli Gianfranco , Spreti Nicoletta
Published: March 2004

Transport through a dichloromethane liquid membrane has been studied to investigate the ability of 1,1,7,7‐tetraethyl‐4‐tetradecyldiethylenetriamine (TE14DT), previously tested for the transport of copper, to act as a carrier for toxic heavy metal ions such as Cd2+, Pb2+ and Hg2+. The carrier displayed a remarkable capability to extract all the metal ions from the source to the organic phases but only cadmium was efficiently transported across the membrane. The experimental conditions optimised for the transport of copper are inadequate for lead and mercury. In fact, the inefficacy of their transport could be due, as regards lead, to the slow diffusion of the complex through the membrane, while mercury remained in the organic phase because of the high stability of the mercury‐carrier complex. Selectivity tests using binary mixtures of the metal ions showed TE14DT’s capability to transport copper or cadmium also in the presence of lead in the source phase. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Synthesis and Enantioselective Gas Chromatography of Stereoisomers of 7,11‐Dimethylheptadecane − A Pheromone Component of Lambdina Species
Authors: Chow Sharon , Koenig Wilfried A. , Kitching William
Published: March 2004

The stereoisomers of 7,11‐dimethylheptadecane exhibit a useful level of separation under enantioselective gas chromatographic conditions, using a modified cyclodextrin phase. Synthesis of the (7R,11R) isomer and coinjection studies establish the order of elution as (7S,11S), (7R,11R), and finally the meso form, the latter being a sex‐pheromone component of Lambdina species. Enantiomeric assays of natural samples containing this hydrocarbon system will now be possible. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Synthesis of a 2,3‐Di‐O‐substituted Heptose Structure by Regioselective 3‐O‐Silylation of a 2‐O‐Substituted Heptose Derivative
Authors: Ishii Kazuyuki , Esumi Yasuaki , Iwasaki Youhei , Yamasaki Ryohei
Published: March 2004

A 3,4‐diol derivative of 2‐O‐benzyl (Bn) heptose (Hep), methyl 6,7‐di‐O‐acetyl‐2‐O‐benzyl‐L‐glycero‐α‐D‐manno‐heptopyranoside (3), was treated with both triethylsilyl (TES) andtert‐butyldimethylsilyl (TBDMS) chlorides to regioselectively form the 3‐O‐silyl ethers4and6, respectively. To examine whether silylation of the 3,4‐diol of a 2‐O‐substituted disaccharide also gives the corresponding 3‐O‐silylated disaccharide, we synthesized α‐GlcN3‐(1⇄2)‐Hep11aby coupling a Hep 2‐OH acceptor9with a GlcN3trichloroacetimidate10. As expected from the results obtained using the 2‐O‐Bn Hep3, treatment of α‐GlcN3‐(1⇄2)‐Hep‐3,4‐diol14with TESCl followed by acetylation gave only the 3‐O‐TES15. Compound14was converted into the 3‐OH acceptor16by silylation/acetylation — without isolating15— and subsequent acid hydrolysis. By coupling the disaccharide 3‐OH acceptor16with per‐O‐benzylated β‐lactosyl trichloroacetimidate17, we obtained the desired 2,3‐branched tetrasaccharide, α‐Lac‐(1⇄3)‐[α‐GlcN3‐(1⇄2)]‐Hep18a. Hydrogenation of18a, followed byN‐acetylation, gave α‐Lac‐(1⇄3)‐[α‐GlcNAc‐(1⇄2)]‐Hep22. Thus, we synthesized the 2,3‐dibranched Hep by utilizing the 2‐O‐substituted Hep. This regioselectiveO‐3‐silylation of the 2‐O‐substituted Hep provides an intermediate that can be utilized for the synthesis of not only 2,3‐ and 3,4‐dibranched Hep but also the 2,3,4‐tribranched Hep structures present in lipooligo‐ and lipopolysaccharides produced by pathogenic Gram‐negative bacteria. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
The Stereoselective Synthesis of Alkenyl‐β‐lactams by Palladium‐Catalyzed [2+2] Carbonylative Cycloaddition
Authors: Troisi Luigino , De Vitis Luisella , Granito Catia , Epifani Erbana
Published: March 2004

Allyl halides of different structures, under CO pressure, in the presence of Et3N, a catalytic amount of Pd(OAc)2, and triphenylphosphane as ligand, undergo a [2+2] cycloaddition reaction with various imines. The reaction is highly regio‐ and stereoselective: β‐lactams are formed in good yields and with trans diastereoselectivity in both the β‐lactam ring and the vinylic moiety. New and important information is suggested regarding the known reaction mechanism. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Reactivity of β‐Carbolines and Cyclopenta[b]indolones Prepared from the Intramolecular Cyclization of 5(4H)‐Oxazolones Derived from L‐Tryptophan
Authors: Condie Glenn C. , Bergman Jan
Published: March 2004

4‐(1H‐Indol‐3‐ylmethyl)‐2‐trichloromethyl‐1,3‐oxazol‐5(4H)‐one (4) was shown to undergo an intramolecular reaction in the presence of TFA, to afford a β‐carboline 5 and a cyclopenta[b]indolone 6 by nucleophilic addition at C‐2 and C‐5, respectively. The distribution of these two products was found to be dependent on the reaction temperature, with lower temperatures favouring the formation of the β‐carboline 5. Subsequent reactions performed on the β‐carboline 5 led to the formation of canthine and canthin‐6‐one derivatives. These syntheses both involved methyl 1‐formyl‐β‐carboline‐3‐carboxylate (20), a useful precursor which was prepared in 54% yield, by a four‐step procedure, from readily available L‐tryptophan. The cyclopenta[b]indolone 6 readily underwent oxidative deamidation to afford cyclopenta[b]indole‐2,3‐dione (37), while substitution by alcohols afforded the alkoxy derivatives 40 and 41. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
1‐(Phenylethynyl)pyrene and 9,10‐Bis(phenylethynyl)anthracene, Useful Fluorescent Dyes for DNA Labeling: Excimer Formation and Energy Transfer
Authors: Malakhov Andrei D. , Skorobogatyi Mikhail V. , Prokhorenko Igor A. , Gontarev Sergei V. , Kozhich Dmitry T. , Stetsenko Dmitry A. , Stepanova Irina A. , Shenkarev Zakhar O. , Berlin Yuri A. , Korshun Vladimir A.
Published: March 2004

A series of novel modifying reagents, including phosphoramidites and solid supports, have been synthesized, and used for the introduction of 1‐(phenylethynyl)pyrene (PEPy) and 9,10‐bis(phenylethynyl)anthracene (BPEA) fluorescent dyes into predetermined positions of synthetic oligonucleotides. These two fluorophores have been shown to constitute an energy donor−acceptor pair, and can be used as such in fluorescent oligonucleotide probes, designed for the detection and structural studies of nucleic acids. The sensitivity of the probe to duplex formation is demonstrated. The formation of the PEPy and BPEA excimers is reported for the first time on nucleic acids. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
cycloSaligenyl‐mannose‐1‐monophosphates as a New Strategy in CDG‐Ia Therapy: Hydrolysis, Mechanistic Insights and Biological Activity
Authors: Muus Ulrike , Kranz Christian , Marquardt Thorsten , Meier Chris
Published: March 2004

Phosphomannomutase 2 (PMM‐2) deficiency leads to an inefficient intracellular formation of mannose‐1‐phosphate (1), which causes an inherited metabolic disease with multisystemic abnormalities (Congenital Disorder of Glycosylation type Ia, CDG‐Ia). In order to circumvent this metabolic deficiency, the cycloSal approach was applied for the intracellular delivery of mannose‐1‐monophosphate (1). cycloSaligenyl‐pyranose‐1‐monophosphates 6−11 were obtained by a phosphitylation/oxidation procedure starting from appropriately protected D‐pyranoses. The chemical hydrolysis data and the involved hydrolysis mechanisms of cyclosaligenyl‐mannose‐1‐monophosphates 6−9 and their epimeric glucose analogues 10, 11 are reported. Furthermore, the biological activity of cycloSal‐mannose‐1‐phosphates 6−9 was tested in vitro in PMM‐2‐deficient fibroblasts. 3‐Methyl‐cycloSal‐2,3,4,6‐tetra‐O‐acetyl‐α‐D‐mannopyranose‐1‐monophosphate (8) showed a total correction of the phenotype, thus proving the delivery of mannose‐1‐phosphate. This may offer a suitable possibility for a therapy of CDG‐Ia. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Diastereoisomeric Molecular Knots by Combination of Central and Topological Chiralities
Authors: Lukin Oleg , Yoneva Albena , Vögtle Fritz
Published: March 2004

We report an unprecedented example of diastereoisomerism created by reaction of topologically chiral molecular knots (knotanes) bearing hydroxy groups with centrochiral (1S)‐(+)‐camphor‐10‐sulfonyl chloride. The diastereoisomers of knotanes bearing on their periphery one and three camphorsulfonyl units have been completely separated using commercial silica gel (Kromasil) and chiral (Chiralpak AD) HPLC columns respectively. The circular dichroisms of the separated samples have been measured and consequences of the chiral induction discussed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Is the North Atlantic oscillation a random walk? A comment with further results
Authors: Mills Terence C.
Published: March 2004

Time series on the North Atlantic oscillation (NAO) have been subject to considerable analysis in recent years, with the consensus emerging that the data are not characterized by a random walk process. However, no consensus has yet emerged concerning the short run correlation structure of the data. This comment explores the time series properties of the NAO in more detail, using testing and modelling procedures that have found wide application in areas such as economics and finance. A structural time series model provides a comprehensive explanation of the index's rich dynamics, there being a slowly changing level component and a cyclical component having a period of approximately 7.5 years. These are dominated, however, by an irregular component, whose presence makes accurate forecasting of the index problematic. Copyright © 2004 Royal Meteorological Society
Modification of growing‐season surface temperature records in the northern great plains due to land‐use transformation: verification of modelling results and implication for global climate change
Authors: Mahmood Rezaul , Hubbard Kenneth G. , Carlson Christy
Published: March 2004

Land‐use and land‐cover change can modify near‐surface atmospheric condition. Mesoscale modelling studies have shown that modification in land use affects near‐surface soil moisture storage and energy balance. Such a study in the Great Plains showed that changes in land use from natural grass to irrigated agriculture enhanced soil water storage in the root zone and increased latent energy flux. This increase in latent energy flux would correspond to a decrease in sensible heat flux and, therefore, modify near‐surface temperature records. To verify this deduction, we have investigated the changes in the historical near‐surface temperature records in Nebraska, USA. We have analysed the long‐term mean monthly maximum, minimum, and monthly mean air temperature data from five irrigated and five non‐irrigated sites. The cooperative weather observation (coop) network is the source of the data. We have found that there is a clear trend in decreasing mean maximum and average temperature data for irrigated sites. For example, York, NE, reports that the mean maximum growing season temperature is decreasing at the rate −0.01°C year−1. The results from non‐irrigated sites indicated an increasing trend for the same parameters. The data from Halsey, NE, indicate a +0.01°C year−1 increase in this century. In addition, we have conducted similar analyses of temperature data for the National Climatic Data Center's Historical Climatic Network data set for the same locations. The results are similar to that obtained with the coop data set. Further investigation of dew‐point temperature records for irrigated and non‐irrigated sites also show an increasing and decreasing trend respectively. Therefore, we conclude that the land‐use change in the Great Plains has modified near‐surface temperature records. Copyright © 2004 Royal Meteorological Society
A 3 year climatology of rainfall characteristics over tropical and subtropical South America based on tropical rainfall measuring mission precipitation radar data
Authors: de Angelis Carlos F. , Mcgregor Glenn R. , Kidd Chris
Published: March 2004

Tropical Rainfall Measuring Mission precipitation radar data acquired during the period 1 January 1998 to 31 December 2000 over tropical and subtropical South America were used to evaluate the ability of the PR2A25 algorithm in estimating and modelling some rainfall characteristics near the surface. Harmonic analysis applied to the 3 h mean rain rate images successfully modelled the rainfall dynamics over the study area and revealed the extent and propagation of rain bands from the western and eastern Amazon towards its interior, and from western subtropical South America towards the east. It is suggested that rain bands that originate along the eastern slopes of the Andes Cordillera during the first hours of the day and then propagate towards the Amazon interior are possibly due to the convergence of cold katabatic flows from the Andes with warm and moist air present in the foothills of the mountains. This contrasts with previous studies that propose the propagation of precipitation systems from the eastern Amazon towards the Andes Mountains. As study results are based on precipitation radar data with a low sampling rate this bears significant implications for the conclusions drawn. Therefore, study results should be considered as exploratory more than as definitive. Copyright © 2004 Royal Meteorological Society
Assessing two different climatic models and the NCEP–NCAR reanalysis data for the description of winter precipitation in the Iberian Peninsula
Authors: Nieto Susana , Dolores Frías M. , Rodríguez‐Puebla Concepción
Published: March 2004

The main questions motivating this study are: Can climate simulations describe the observations? To what extent can we use climate models to predict climate change? For this purpose, an analysis was made of the correspondences and/or discrepancies between observed winter precipitation data and the data from the National Centers for Environmental Prediction–National Center for Atmospheric Research (NCEP–NCAR) reanalysis project, and from two global climatic models: ECHAM4/OPYC3 and HadCM3. The data used correspond to the accumulated winter precipitation for the period 1949–2000, and comparisons of the mean and variability patterns were made. The methods used were principal components analysis, to break down variability and reduce the dimensions of the fields, and correlation and cross‐spectrum analyses for comparison of the time series. For all these, we studied the suitability of their average distributions, as well as their modes of spatial and spectral variability. The results for the Iberian Peninsula show good agreement between the precipitation data of the NCEP–NCAR reanalysis and the observations, both in the average analysis and in the main modes of spatial and time variability. Therefore, the reanalysis data were proved to be a good resource for interpreting climate variations. As regards the climatic models considered, in general the results point to their suitability for describing the spatial distribution of winter precipitation, whereas the spectral association is less appropriate. The variability of the precipitation data was related to circulation patterns and teleconnection indices, such as the North Atlantic oscillation and the Arctic oscillation. The results allow us to conclude that the discrepancies between the two models and observations must be due to a weak representation of the interannual variability. Copyright © 2004 Royal Meteorological Society
Guided‐wave characteristics of periodic microstrip lines with inductive loading: Slow‐wave and bandstop behaviors
Authors: Zhu Lei
Published: March 2004

Guided‐wave characteristics of planar periodic microstrip lines with inductive loading are investigated by resorting to the unit‐length transmission parameters of an equivalent transmission line. By applying the SOC de‐embedding technique, the above two quantities are effectively extracted from the full‐wave MoM modeling of a microstrip line with finite periodic cells. Extensive results at first confirm the slow‐wave behavior such that both real parts of such two quantities rise up slowly and then rapidly with frequency. Further, they demonstrate, for the first time, the guided‐wave bandstop characteristic with non‐zero attenuation constant and imaginary characteristic impedance. Five‐cell periodic microstrip circuits are then designed and fabricated for theoretical and experimental verification. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 77–79, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20052
A new class of improved‐efficiency THz filters for on‐chip detection of biomaterials
Authors: Stewing F. , Kleine‐Ostmann T. , Koch M.
Published: March 2004

In a recent breakthrough experiment, the marker‐free on‐chip analysis of DNA using THz voltage pulses propagating along a resonant thin‐film microstrip line was demonstrated. However, the large area of standard filters used in this experiment requires amounts of DNA material that exceed the amount used in state‐of‐the‐art biochip readers. Based on numerical simulations, in this paper we present a new class of filters with increased sensitivity, which require much less DNA material, and propose a new improved measurement scheme. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 79–82, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20053
Variable‐gain amplifier for adaptive antenna control at the 2.4‐GHz ISM‐band
Authors: Multanen Miikka , Salonen Pekka , Kivikoski Markku
Published: March 2004

A variable‐gain amplifier for an adaptive antenna at the ISM band is presented. The amplifier consists of three stages and has a digital control. The device is made on a printed circuit board. The amplifier's maximum gain, noise figure, and output compression point are 31.2 dB, 5 dB, and 8.6 dBm, respectively. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 82–85, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20054
A compact and low‐loss 1 × 2 wavelength MUX/DEMUX based on a multimode‐interference coupler using quasi state
Authors: Sam Y. L. , Won Y. H.
Published: March 2004

In this paper, we propose a compact multimode‐interference‐based wavelength MUX/DEMUX. By using the quasi‐output state, the device length can be greatly reduced. The device performances are numerically investigated by using the finite‐difference beam‐propagation method (FD‐BPM). Simulation results show that the device performances, in terms of coupling loss and extinction ratio, are enhanced. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 86–88, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20055
A novel superstrate gain‐enhanced antenna with lateral metallic walls
Authors: Bernard L. , Loison R. , Gillard R. , Lucidarme T.
Published: March 2004

Based on gain‐enhancement methods, a narrow single‐superstrate antenna with metallic walls is proposed. The associated resonance conditions are established and a high‐gain antenna with a wide H‐plane beamwidth is designed at 2 GHz. Both simulated and measured results are presented. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 93–96, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20058
A novel dual‐band printed‐dipole antenna using CRC structure
Authors: Liu Y. F. , Xue Q. , Chan C. H.
Published: March 2004

This paper presents a new approach to the realization of dual‐band operation in a single printed‐dipole antenna by incorporating compact resonant cell (CRC) structures. A dual‐band antenna that operates at 900 MHz and 2.4 GHz is constructed to illustrate the design methodology. The overall length of the proposed antenna is reduced by 12%, in comparison with that of the conventional design. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 105–106, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20061
Modeling of light propagation through step‐like discontinuities in slab dielectric waveguides
Authors: Romanova E. A. , Gaal S. B.
Published: March 2004

One‐way light propagation through a steplike discontinuity of dielectric‐slab waveguide is simulated by using the finite‐difference beam‐propagation method (FD‐BPM) and the Green's function method. The validity of the slowly varying envelope approximation in modeling of the total field distribution and the radiation‐field distribution is analyzed. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 108–114, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20063
A simple theoretical model for rectangular microstrip resonator with stubs
Authors: da Costa Karlo Q. , Dmitriev Victor
Published: March 2004

In this work, we present a simple theoretical analysis of a compact rectangular microstrip resonator with stubs. The analytical model is based on a recursive algorithm for a transmission line loaded with capacitive stubs. We calculate the input impedance and the resonant frequency of this resonator and analyse the dependence of these parameters on the number and dimensions of the stubs. The numerical results are compared with those obtained by other methods and with experimental data. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 119–123, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20066
Reduced conditions for the constitutive parameters of lossy bi‐anisotropic media
Authors: Tan Eng Leong
Published: March 2004

This paper presents reduced conditions for the constitutive parameters of lossy bi‐anisotropic media. It is shown that only two separate dyadic conditions, in contrast to the previously reported four, will be necessary and sufficient to characterize a medium as lossy. For the gyrotropic bi‐anisotropic case revisited, it is found that these media call for merely two scalar conditions for their constitutive parameters, in contrast to the nine (reducible to seven) conditions formulated previously. The reduced dyadic and scalar conditions will simplify analysis of the physical realizability and the valid range of parameter values for new composite media. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 133–135, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20070
Angle of arrival measurement using an ultra fast transient analyzer and music algorithm
Authors: Benlarbi‐Delaï Aziz , Rolland Nathalie , Ghis Anne , Rolland Paul‐Alain
Published: March 2004

This paper describes a cross‐fertilization approach between a novel sub‐nanosecond transient analyzer based on nonsimultaneous spatial sampling and a high‐resolution algorithm based on subspace decomposition and the eigen‐analysis method. Our targeted goal is the real‐time measurement of the angle of arrival (AOA) devoted to a connected vehicle in the field of intelligent transport systems (ITS). © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 141–144, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20073
On‐vehicle low‐profile metal‐plate antenna for AMPS/GSM/DCS/PCS/UMTS multiband operations
Authors: Liu Yung‐Tao , Su Saou‐Wen , Tang Chia‐Luan , Chen Hong‐Twu , Wong Kin‐Lu
Published: March 2004

A novel low‐profile metal‐plate antenna capable of generating two wide resonant modes for covering the AMPS/GSM (824–894 MHz/890–960 MHz) bands and the DCS/PCS/UMTS (1710–1880 MHz/1850–1990 MHz/1920–2170 MHz) bands for mobile communications in vehicles is presented. The proposed antenna is easily achieved by folding a stamped metal plate into a swanlike shape and then feeding it by using a matching‐bridge technique. The proposed antenna has a low profile of 27 mm (about 8% of the free‐space wavelength at 900 MHz) above the ground plane and shows conical radiation patterns for frequencies across the operating bands. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 144–146, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20074
New compact configuration of a stepped‐impedance ceramic bandpass filter
Authors: Wang Xuedong , Liu Peitao , Liu Xiangyang , Li Ying
Published: March 2004

A new compact configuration of a stepped‐impedance comb‐line filter is proposed. By reversing one of the two resonators, the size of the filter becomes much smaller than that of the former. The impedance ratio has a small effect on the filter's size. The filter is made of low‐temperature co‐fired ceramic (LTCC). The simulated frequency characteristics are compared with the measured data of the fabricated filter and good agreement is reported. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 146–149, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20075
Novel low‐loss wide‐angle Y‐junctions of optical waveguides with graded‐index profiles
Authors: Yongjun Yang , Fushen Chen
Published: March 2004

A low‐loss wide‐angle Y‐junction with graded‐index optical waveguides which can change the optical propagation direction, is proposed. The optical power is divided equally into two branching waveguides with a wide angle. Device performance is examined numerically by the finite‐difference beam propagation method (FDBPM). The simulated results show that the output optical power can be more than 96%, even if a branching angle is as large as 53.1°. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 156–159, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20078
Präzise Dichtemessungen mit schwebenden Festkörpern: Flotation
Authors: Toth Hans , Fehlauer Heinz
Published: March 2004

Die Druckflotationsapparatur der Physikalisch‐Technischen Bundesanstalt kann relative Dichtedifferenzen von Siliziumproben mit sehr hoher Präzision messen. Dazu taucht die Probe vollständig in eine schwere Flüssigkeit ein. Sie wird darin frei schwebend austariert, indem die Dichte der Flüssigkeit gesteuert wird: Dazu variiert ein höhenverstellbares Ausgleichsgefäß den hydrostatischen Druck auf die Flüssigkeitssäule. Die Druckflotationsapparatur kann auch kleine und geometrisch nicht perfekte Festkörper messen. Solche hoch präzisen Dichtemessungen eröffnen eine neue Möglichkeit, Dichtenormale aus Silizium auf die SI‐Einheiten Kilogramm und Meter mit kleinstmöglicher Messunsicherheit zurückzuführen. Auch im Alltag werden Flotationsverfahren für verschiedenste Dichtemessungen eingesetzt.
Eier im Wellensalat: Experimente mit der Haushaltsmikrowelle
Authors: Karstädt Detlef , Möllmann Klaus‐Peter , Vollmer Michael
Published: March 2004

Haushaltsmikrowellen bieten ein interessantes Feld für einfache, teilweise spektakuläre Vorführexperimente. Mit Thermofaxpapier und Infrarotkamera lassen sich zum Beispiel die Modenverteilungen des Zentimeterwellenfeldes im Garraum sichtbar machen. Eine Reihe von Versuchen kann die Absorption durch Metalle zeigen, besonders interessant sind dabei dünne Drähte und Drahtspitzen: Lampenbirnen glühen und Wunderkerzen zünden von selbst. Mikrowellen können auch Entladungslampen starten, Wasser im Eisblock erhitzen und Eier explodieren lassen.
Photovoltaik auf Glas: CIS‐Dünnschicht‐Solarzellen
Authors: Meyer Nikolaus
Published: March 2004

Heutige Solarmodule bestehen aus kristallinem Silizium. Ihre Herstellung benötigt eine aufwändige Prozesstechnik und verbraucht viel Material und Energie. Das Hahn‐Meitner‐Institut (HMI) in Berlin hat als interessante Alternative eine Dünnschichttechnologie entwickelt. Bei ihr wirkt Kupfer‐Indium‐Disulfid (CIS) als direkter Halbleiter: Er kann die Energie auftreffender Photonen direkt in freie Ladungsträger und damit elektrischen Strom umsetzen. Deshalb brauchen CISSolarmodule nur eine sehr dünne Halbleiterschicht von etwa 1 μm Dicke, die auf Glas aufgebracht ist. CIS‐Module können geschätzt etwa 50 % billiger als heutige Silizium‐Solarzellen hergestellt werden. Die aus dem HMI heraus gegründete Sulfurcell Solartechnik GmbH baut nun eine Pilotproduktion auf.
Einsteins politische Akte: Physikgeschichte
Authors: Hoffmann Dieter
Published: March 2004

Einstein war nicht nur der geniale Physiker, der die Relativitätstheorie entwickelt und der Quantentheorie den Weg bereitet hat. Er war auch ein Mann, der wegen seiner politischen Überzeugungen vielfachen Anfeindungen, Missgunst und Gesinnungsschnüffelei ausgesetzt war. Insbesondere sein demokratisches und pazifistisches Engagement machte ihn in Deutschland für viele zum Feind. Sein Eintreten für Menschenrechte und gegen Rassismus ließ ihn später auch in den USA ins Visier des Geheimdienste und des FBI geraten.
Röntgenbilder von Kristallen
Authors: Loos Andreas
Published: March 2004

„Mit dem Fahrrad war er gekommen, sportlich und mit Rucksack”︁, erinnert sich ein Zeitgenosse an sein erstes Treffen mit dem ebenso unkonventionellen wie einflussreichen Physiker. Das war wohlgemerkt mitten im Winter. Und der Radfahrer war bereits 60 Jahre alt.
Kann auch Kohlenstoff magnetisch sein?
Authors: Esquinazi Pablo D.
Published: March 2004

Magnetische Ordnung war bislang nur in bestimmten Stoffen bekannt, die Atome mit 3d‐ oder 4f‐Elektronen enthalten. Einer Gruppe an der Universität Leipzig gelang es durch Protonenimplantation auch in reinem Graphit eine ferromagnetische Ordnung zu erzeugen.
Organische Dünnschichttransistoren entwickelt
Authors: Leute Angelika
Published: March 2004

Organische Halbleiter, die sich in gelöster Form verarbeiten lassen, haben in den vergangenen Jahren große Fortschritte gemacht und werden bereits in Displays eingesetzt. Eine neue Anwendung, die zur Zeit von Wissenschaftlern der Siemens AG in Erlangen und der Universität Oldenburg erforscht wird, sind Dünnschichttransistoren auf der Basis eines organischen Halbleiters [1]. Elektronische Eigenschaften und Stabilität reichen für erste technische Anwendungen aus.