bluuebunny/crossref_metadata_2025 huggingface dataset:
Only iron-limited cells of the cyanobacteriumAnabaena flos-aquaeinhibit growth of the green algaChlamydomonas reinhardtii
Authors: Matz Carlyn J , Christensen Michael R , Bone Auralee D , Gress Courtney D , Widenmaier Scott B , Weger Harold G
Published: May 2004

Cocultivation of iron-limited cells of the cyanobacterium Anabaena flos-aquae (Lyng.) Brèb. and the green alga Chlamydomonas reinhardtii Dangeard resulted in growth of Anabaena but not Chlamydomonas, even in the presence of excess exogenous iron. This effect was also observed during the cultivation of Chlamydomonas in a medium in which iron-limited Anabaena cells had been growing, but were removed prior to culture of Chlamydomonas. Conversely, iron-limited Chlamydomonas cells grew very well in medium from iron (nutrient)-sufficient, phosphate-limited, and nitrogen-limited Anabaena cultures. Iron-limited Anabaena cultures produced siderophores, while the other types of Anabaena cultures did not. Treatment of Anabaena iron-limited medium with activated charcoal completely removed the inhibitory effect on Chlamydomonas growth, and boiling the medium removed most of the inhibitory effect. Both the charcoal and the boiling treatments also removed siderophores from the medium. Partially purified Anabaena siderophore preparations were also inhibitory to Chlamydomonas growth. The inhibitory effect of iron-limited Anabaena medium could be partially overcome by addition of excess micronutrients (especially cobalt copper) but not by addition of iron. We suggest that Anabaena-derived siderophores, present only in iron-limited Anabaena medium, inhibit the growth of Chlamydomonas cells via a previously uncharacterized toxicity. This effect is different from previously described experiments in which cyanobacterial siderophores suppressed green algal growth via competition for limiting amounts of iron.Key words: Anabaena, Chlamydomonas, cocultivation, iron limitation, micronutrients; siderophores.
Two new marine fungi from China and Singapore, with the description of a new genus,Sablecola(Halosphaeriales, Ascomycota)
Authors: Pang Ka-Lai , Jones EB Gareth , Vrijmoed Lilian LP
Published: May 2004

Two new marine fungi from woody substrata collected on sandy beaches of the Pearl River Estuary in southern China (brackish water) and the East Coast Beach in Singapore (fully saline seawater) are described. A new genus, Sablecola E.B.G. Jones, K.L. Pang & Vrijmoed, is introduced to accommodate Sablecola chinensis E.B.G. Jones, K.L. Pang & Vrijmoed, sp. nov, with ascospores having two polar and four equatorial, flattened, attenuate, strap-like appendages with parallel striations, which disintegrate into fine threads when mounted in seawater. Sablecola chinensis can be differentiated from other taxa with a similar ascospore appendage arrangement, such as Halosphaeria and Ocostaspora, by its ascospore appendage morphology. Remispora minuta E.B.G. Jones, K.L. Pang & Vrijmoed, sp. nov. has hyaline and membranous ascomata bearing ascospores with moustache-shaped appendages that are characteristic of Remispora species. This species cannot be accommodated in Haligena, a genus with spoon-shaped appendages at the point of attachment to the ascospores, which are attenuate and channelled.Key words: Haligena, marine fungi, Ocostaspora, Remispora, taxonomy.
Morphology and anatomy of chasmolithic versus epilithic growth: a taxonomic revision of inconspicuous saxicolousBuelliaspecies from the Sonoran Desert Region generally ascribed to the "Buellia punctata" group
Authors: Bungartz F , Nash III T H , Ryan B D
Published: May 2004

Six saxicolous species of Buellia, which were previously generally identified as Buellia punctata (Hoffm.) A. Massal., were examined from the Sonoran Desert. None of the species belongs to Beullia punctata s. str. Though inconspicuous, it can be demonstrated that the thallus morphology of these species is quite distinct and far less variable than previously assumed. Most species are epilithic, even though their thalli also show some degree of substrate penetration. Buellia sequax (Nyl.) Zahlbr., not previously reported from North America, is exclusively chasmolithic. Three new species with epilithic thalli, Beullia christophii Bungartz sp. nov., Beullia ryanii Bungartz sp. nov., and Beullia tergua Bungartz sp. nov., are described. Two species with filiform conidia are not treated in the genus Amandinea. We discuss why the current delimitation of this genus, based solely on conidial shape, is rejected: Buellia pullata Tuck., with filiform conidia, is consequently not transferred into Amandinea. Amandinea lecideina (H. Mayrhofer & Poelt) Scheid. & H. Mayrhofer is synonymized with Beullia prospersa (Nyl.) Riddle.Key words: North America, taxonomy, Physciaceae, Amandinea, conidia, thallus morphology, new species.
Spallation of 32S ions at ultra-relativistic energies in nuclear emulsion
Authors: El-Nadi M , Abdelsalam A , Shaat E A , Mossa N Ali , Moussa Z Abou , Kamel S , Rashed N , Osman W , Hafiz M E
Published: May 2004

Partial production cross sections of electromagnetic breakup of 32S projectiles at two widely differing energies were measured using an emulsion target. The electromagnetic dissociation represents about 6% and 17% of the total number of nuclear events at Elab/A = 3.7 and 200 GeV, respectively. The experimental electromagnetic cross sections σexpEMD show an energy dependence that is well reproduced by the WeizsackerWilliams approximation. The value of σexpEMD at 200A GeV (with γ >> 1) shows a good agreement with that predicted by the combined model of Pshenichnov et al. Examination of the reactions (γ, p) and (γ, He) reveals that the ratio of 1 p/1 He cross sections is close to unity at Dubna energy (3.7A GeV), while it rapidly increases to 3.0 ± 0.6 at CERN energy (200A GeV). In most of the observed dissociation modes, the total kinetic energy of the fragments in the projectile rest frame is lower than 50 MeV. Nevertheless, it is possible that the contribution of excitation modes of the different multipolarities is determining in this region. PACS No.: 25.70
Longitudinal- and transverse-operators formalism for chiral media: Application to guided structures filled with chiral materials
Authors: Oussaid R , Haraoubia B
Published: May 2004

In this paper an approach based on the calculation of longitudinal and transverse operators is presented. The paper is devoted to the interesting topic of electromagnetic-wave propagation in complex (chiral) media. The studied process allows the analysis of guidedstructures with chiral-medium components. In this case the equations are continuously coupled. Using the longitudinal equations, we analyze wave propagation in a parallel-plate chirowaveguide consisting of two parallel perfectly conducting planes filled with a lossless, homogeneous, isotropic chiral material. The main feature of the guides is that the propagation modes are always hybrid. In addition, bifurcated modes exist with the same cutoff-frequency values and unequal propagation characteristics. We address here the issue of wave propagation in a rectangular chirowaveguide, by means of longitudinal and transverse operators. This topic was first addressed by Engheta and Pelet. (IEEE Trans. Antenna Propag. 38, 90 (1990)). We rederive their results, using a method based on a new mathematical approach that seems to be original.PACS Nos.: 41.20.Jb
E1, E2, M1, and M2 transitions in the nickel isoelectronicsequence
Authors: Hamasha S M , Shlyaptseva A S , Safronova U I
Published: May 2004

A relativistic many-body method is developed to calculate energy and transition rates for multipole transitions in many-electron ions. This method is based on relativistic many-body perturbation theory (RMBPT), agrees with MCDF calculations in lowest order, includes all second-order correlation corrections, and includes corrections from negative-energy states. Reduced matrix elements, oscillator strengths, and transition rates are calculated for electric-dipole (E1) and electric-quadrupole (E2) transitions, and magnetic-dipole (M1) and magnetic-quadrupole (M2) transitions in Ni-like ions with nuclear charges ranging from Z = 30 to 100. The calculations start from a 1s22s22p63s23p63d10 DiracFock potential. First-order perturbation theory is used to obtain intermediate-coupling coefficients, and second-order RMBPT is used to determine the matrix elements. The contributions from negative-energy states are included in the second-order E1, M1, E2, and M2 matrix elements. The resulting transition energies and transition rates are compared with experimental values and withresults from other recent calculations.PACS Nos.: 32.30.Rj, 32.70.Cs, 32.80.Rm, 34.70.+e
Clustering in some randomly occupied two- and three-dimensional lattices
Authors: Ulug A , Karakaplan M , Ulug B
Published: May 2004

Clustering in some two- and three-dimensional lattices is investigated using an algorithm similar to that of HoshenKopelman. The total number of clusters reveals a maximum at an occupation probability, pmax, where the average cluster size, 2.03 ± 0.07, is found to be independent of the size, dimension, coordination number, and the type of lattice. We discussed the fact that the clustering effectively begins at pmax. The percolation threshold, pc, and pmax are found to get closer to each other as the coordination number increases. PACS Nos.: 64.60.Ht, 64.60.Qb, 82.30.Nr
Calculation of the range of medium-energy F, Cs, and Ga ions in silicon carbide
Authors: Kabadayi Ö
Published: May 2004

We present simulation results for the implantation of fast F, Cs, and Ga ions into amorphous SiC using a technique that we developed in a previous work. Bragg's rule is employed to calculate the electronic and nuclear stopping powers in the compound. To find ion ranges, numerical solution of the first-order ODE have been performed by using Fehlberg fourth- and fifth-order RungeKutta method. The results are compared with experimental data, as well as with the result of the Monte Carlo program SRIM and other standard procedures such as PRAL. It is found that the agreement between our method and the literature is good. PACS Nos.: 61.72.Ww, 72.80.Jc, 61.80
Spectroscopic investigation of sensitized-Cs (62 P3/262P1/2) laser retrofluorescence in a pure optically thick vapour near a dissipative surface
Authors: Bris Karine Le , Assi Claude Kondo , Gagné Jean -Marie
Published: May 2004

A low-power, monochromatic, tunable diode laser is used to selectively populate the cesium 62P3/2 (Fe = 2, 3, 4, 5) hyperfine-structure levels in a pure optically thick vapour in the presence of a dissipative surface. The integrated retrofluorescence intensities for the 852 nm (62P3/2 → 62S1/2), 894 nm (62P1/2 → 62S1/2)> and 455 nm (72P3/2 → 62S1/2) lines have been measured and analyzed. When the laser frequency is scanned through the [62S1/2(Fg) → 62P3/2(Fe)] hyperfine resonance line, the sensitized retrofluorescence spectral signal corresponding to the 894 nm line has a profile significantly different from the retrofluorescence signal at the 852 nm line, but rather similar to the profiles of the lines associated with the energy-pooling collisions. The population of the 62P1/2 atomic level in an optically thick vapour cannot be explained only by the fine-structure excitation transfer process [Cs (62P3/2) + Cs (62S1/2) ↔ Cs (62P1/2) + Cs (62S1/2)] usually accepted in an optically thin vapour. We have investigated inelastic collisions in the populating mechanisms of 62P1/2 level starting from the 62P3/2 level exited by the monochromatic laser taking into account the presence of an electrically conductive surface. It appears from our experimental and theoretical investigations that, the spectral properties of the laser-induced Cs 894 nm sensitized retrofluorescence in a pure optically thick vapour near a dissipative surface cannot be explained by both the conventional mechanism and cascade collisions. The satisfactory interpretation of the experimental results is an open problem of atomic spectroscopy.PACS Nos.: 32.30, 32.50, 32.70, 32.80, 34.10, 34.50, 42.62
3-Amino-1-hydroxyacetone
Authors: Ullah Nisar , Fali Clara Nanfe , Spenser Ian D
Published: May 2004

3-Amino-1-hydroxypropan-2-one (3-amino-1-hydroxyacetone) was prepared in an overall yield of 52% in 6 steps starting with N-phthaloylglycine. This synthesis is readily adaptable for the preparation of bond-labeled samples, i.e., samples that are labeled intramolecularly at contiguous sites.Key words: 3-amino-1-hydroxyacetone, 3-amino-1-hydroxypropan-2-one.
Cyclization of 2-(2-bromoethoxy)-acetophenones and 5-(ω-haloalkoxy)-1,5-dihydro-2H-pyrrol-2-ones  Formation of five- to eight-membered oxygen-containing heterocycles via intramolecular alkylation
Authors: Nikitin Kirill V , Andryukhova Nonna P
Published: May 2004

Under basic conditions (lithium diisopropylamide or sodium hydride in THF) 2-(2-bromoethoxy)-acetophenones were transformed to 3,4-dihydro[1]benzoxepin-5(2H)-ones (homochromanones) in high yields. The preparation of novel tetrahydropyrano[2,3-b]pyrrol-6(2H)-ones and 3,4-dihydro-2H-pyrrolo[2,1-b][1,3]oxazin-6(8aH)-ones and spiro compounds was performed using similar cyclization in moderate to good yields.Key words: cyclization, lithiation, spiro heterocycles.
Novel mixed-ligand Pt(II) complexes: Synthesis, multinuclear magnetic resonance, and crystal structures of cis- and trans-Pt(R2SO)(pyrazine)Cl2
Authors: Rochon Fernande D , Priqueler Julien RL
Published: May 2004

A new type of mixed-ligand Pt(II) complexes, Pt(R2SO)(pyrazine)Cl2, was synthesized from the aqueous reaction of K[Pt(R2SO)Cl3] with pyrazine. The compounds were characterized mainly by IR and multinuclear magnetic resonance spectroscopies (1H, 13C, and 195Pt) and crystallography. Compounds with dimethylsulfoxide, tetramethylenesulfoxide, di-n-propylsulfoxide, di-n-butylsulfoxide, dibenzylsulfoxide, and diphenylsulfoxide were studied. IR spectroscopy suggested a cis geometry for the di-n-propylsulfoxide complex and trans geometry for the other compounds. The 195Pt NMR resonances of the complexes were observed between 3042 and 3121 ppm, with that of the diphenylsulfoxide complex being at higher field than those of the others. The pyrazine 3J(195Pt-1H) coupling constant was observed for the DMSO compound (33 Hz), suggesting a trans geometry. No J(195Pt-13C) coupling could be detected. The crystal structures of trans-Pt(tetramethylenesulfoxide)(pyrazine)Cl2 and of cis-Pt(di-n-propylsulfoxide)(pyrazine)Cl2 were determined and confirmed the geometry suggested by IR and NMR spectroscopies. The compound with di-n-butylsulfoxide could not be isolated, because it rapidly formed the pyrazine-bridged dimer. Key words: platinum, sulfoxide, pyrazine, crystal structure, NMR, IR.
A novel self-complementary three-dimensional inorganic network organized by H-bond dimers of inorganic chains  Synthesis and crystal structure of (C6H16N2)[Zn(HPO4)2]
Authors: Zhang Xian-Ming , Bai Chan-Juan , Zhang Yan-Li , Wu Hai-Shun
Published: May 2004

A novel organic-templated zincophosphate, namely (C6H16N2)[Zn(HPO4)2], was hydrothermally synthesized and X-ray single-crystal structural analysis reveals that the anions [Zn(HPO4)2]2, which have square-twisted chains containing corner-sharing four-rings of alternating ZnO4 and PO4 tetrahedra, are assemblied via self-complementary strong and symmetrical hydrogen-bonding R22(8) synthons between the phosphate groups into three-dimensional hydrogen bond frameworks featuring three-dimensional intersecting pseudochannels. The doubly protonated 2,5-dimethylpiperazinium cations are attached to the three-dimensional inorganic framework via N-H···O hydrogen bonds to strengthen the 3-D network.
Stereoselective synthesis of naturally occurring unsaturated amide alkaloids by a modified RambergBäcklund reaction
Authors: Li Yang , Zhang Yu , Huang Zhi , Cao Xiaoping , Gao Kun
Published: May 2004

A convenient and rapid approach for the synthesis of naturally occurring unsaturated amide alkaloids 1a1n by the recently developed one-flask RambergBäcklund reaction is described. The starting material was alcohol 3, which was transformed into thiolacetate 4 using the Mitsunobu reaction. In situ cleavage of acetyl moiety of 4, followed by alkylation of the resulting thiol with appropriate chloroacetamide 5, provided the sulfide 6. Oxidation of sulfide 6 gave the corresponding sulfone 2. Treatment of the sulfone 2 with the dibromodifluoromethane in the presence of alumina-supported potassium hydroxide in dichloromethane solution afforded unsaturated amide alkaloids 1a1n. To the best of our knowledge, the synthesis of 1e and 1i was reported for the first time.Key words: synthesis, unsaturated amide alkaloids, RambergBäcklund reaction.
A new method of syntheses of 18-membered macrocyclic diphenyltin(IV) compounds and crystal structures of {Ph2Sn[S(C6H3NO)O]}3·Y (Y = 2H2O or 4C6H6) and {Ph3Sn[S(C6H3NO)O]SnPh3(EtOH)}·[EtOH]
Authors: Ma Chunlin , Jiang Qin , Zhang Rufen
Published: May 2004

Two diphenyltin(IV) compounds: {Ph2Sn[S(C6H3NO)O]}3·Y (Y = 2H2O, 1; 4C6H6, 2) have been unexpectedly obtained by the reactions of triphenyltin chloride with 2-mercaptonicotinic acid in the presence of Et3N. However, by the reaction of the same reactants in the presence of EtONa, only a new triphenyltin(IV) compound ({Ph3Sn[S(C6H3NO)O]SnPh3(EtOH)}·[EtOH], 3) was obtained. The X-ray analyses reveal that compounds 1 and 2 are trinuclear, 18-membered macrocyclic compounds while 3 is a dinuclear compound. Specially, π-π stacking interaction was recognized in crystals of compound 1, which makes it a dimer. Co-crystallization was found in the crystals of all the three compounds 1, 2, and 3, the co-crystallized solvent molecules are water, benzene, and ethanol molecules, respectively. A possible dephenylation mechanism of 1 and 2 was illustrated in detail.Key words: triphenyltin, 2-mercaptonicotinic acid, dephenylation, macrocyclic, π-π stacking interaction, co-crystallization, crystal structure.
A study of the electrochemical behaviour of cobalt in aqueous H2CO3/HCO3/CO32 solutions at pH 79
Authors: Simard Stéphan , Gallant Danick
Published: May 2004

The electrochemical behaviour of a cobalt rotating electrode in H2CO3/HCO3/CO32 aqueous solutions was investigated in the pH region from 7 to 9. The effects of H2CO3/HCO3/CO32 concentration, pH, and the presence of phosphates as inhibitors was explored using a rotating disc electrode at 1000 rpm. Some potentiodynamic experiments indicate that for pH 8.5 and higher, carbonate and bicarbonate species play a key role on the rate of electrooxidation of cobalt. For pH lower than 8.5, the electrochemical behaviour of cobalt changes drastically and very aggressive corrosion is observed. The involvement of carbonic acid must be considered in the corrosion process of cobalt in this pH region. The study of passive film potential decay under open circuit potential and galvanostatic reduction was performed on preanodized cobalt electrodes in solutions of various compositions. These experiments indicated the phenomena occurring at the electrodesolution interface during the corrosion process. A mechanism involving competitive adsorption of different species is suggested on the basis of the experimental evidence.Key words: cobalt, bicarbonate, phosphate, carbonic acid, corrosion.
MODELING PRIVATE EQUITY FUNDS AND PRIVATE EQUITY COLLATERALISED FUND OBLIGATIONS
Authors: de Malherbe Etienne
Published: May 2004

The recent development of the securitisation of funds of private equity funds poses the question of the individual and joint modelling of the underlying funds. Private equity funds are different from other managed funds because of their particular bounded life cycle: when the fund starts, the investment partners make an initial capital commitment, the fund managers gradually draw down the committed capital into investments, returns and proceeds are distributed as the investments are realised and the fund is eventually liquidated as the final investment horizon is reached. Modelling private equity funds therefore requires three stages: the modelling of the commitment drawdowns, the modelling of the investment value and the modelling of the return repayments. A standard lognormal process is utilised for the dynamics of the investment value. Squared Bessel processes are utilised for the dynamics of the rates of drawdowns and repayments.

Résumé: Le récent développement de la titrisation de fonds de fonds de placements privés pose la question de la modélisation individuelle et jointe des fonds sous-jacents. Les fonds de placements privés sont différents des autres sociétés d'investissement à cause de leur cycle de vie particulier et limité: au démarrage du fonds, les associés s'engagent sur un apport initial en capital; puis les gérants du fonds opèrent des tirages progressifs sur le capital apporté pour procéder à des investissements; les revenus et les profits sont distribués à mesure que les investissements sont réalisés; enfin, le fonds est liquidé lorsque l'horizon d'investissement est atteint. La modélisation d'un fonds doit donc se faire en trois étapes: la modélisation des tirages sur l'apport en capital, la modélisation de la valeur des investissements et enfin la modélisation des paiements et remboursements des dividendes et retours sur investissements. Un processus lognormal standard est utilisé pour la dynamique de la valeur des investissements. Des processus de Bessel carré sont utilisés pour la dynamique des taux de tirage et de remboursement.
TESTING FOR "PURE" CONTAGION EFFECTS IN INTERNATIONAL BANKING: THE CASE OF BCCI'S FAILURE
Authors: KANAS ANGELOS
Published: May 2004

We find evidence of "pure" contagion effects in international banking arising from the collapse of BCCI. A Markov regime-switching approach is employed to allow for the uncertainty surrounding the date of BCCI's collapse. The results indicate that there are shortcomings in the supervision of internationally spread banking groups like BCCI, and carry implications for the EU single market programme in financial services.
DECISION MAKING FOR NETWORK HEALTH ASSESSMENT IN AN INTELLIGENT INTRUSION DETECTION SYSTEM ARCHITECTURE
Authors: SIRAJ AMBAREEN , VAUGHN RAYFORD B. , BRIDGES SUSAN M.
Published: May 2004

This paper describes the use of artificial intelligence techniques in the creation of a network-based decision engine for decision support in an Intelligent Intrusion Detection System (IIDS). In order to assess overall network health, the decision engine fuses outputs from different intrusion detection sensors serving as "experts" and then analyzes the integrated information to present an overall security view of the system for the security administrator. This paper reports on the workings of a decision engine that has been successfully embedded into the IIDS architecture being built at the Center for Computer Security Research, Mississippi State University. The decision engine uses Fuzzy Cognitive Maps (FCM)s and fuzzy rule-bases for causal knowledge acquisition and to support the causal knowledge reasoning process.
COMPUTING HIGHLY SPECIFIC AND NOISE-TOLERANT OLIGOMERS EFFICIENTLY
Authors: YAMADA TOMOYUKI , MORISHITA SHINICHI
Published: May 2004

The sequencing of the genomes of a variety of species and the growing databases containing expressed sequence tags (ESTs) and complementary DNAs (cDNAs) facilitate the design of highly specific oligomers for use as genomic markers, PCR primers, or DNA oligo microarrays. The first step in evaluating the specificity of short oligomers of about 20 units in length is to determine the frequencies at which the oligomers occur. However, for oligomers longer than about fifty units this is not efficient, as they usually have a frequency of only 1. A more suitable procedure is to consider the mismatch tolerance of an oligomer, that is, the minimum number of mismatches that allows a given oligomer to match a substring other than the target sequence anywhere in the genome or the EST database. However, calculating the exact value of mismatch tolerance is computationally costly and impractical. Therefore, we studied the problem of checking whether an oligomer meets the constraint that its mismatch tolerance is no less than a given threshold. Here, we present an efficient dynamic programming algorithm solution that utilizes suffix and height arrays. We demonstrated the effectiveness of this algorithm by efficiently computing a dense list of numerous oligo-markers applicable to the human genome. Experimental results show that the algorithm runs faster than well-known Abrahamson's algorithm by orders of magnitude and is able to enumerate 65%~76% of qualified oligomers.
Women Lenders as Sources of Land Credit in Nineteenth-Century Michigan
Authors: Heller Charles F. , Houdek John T.
Published: May 2004

Individuals held almost all of the rural mortgages in nineteenth-century Kalamazoo County, Michigan. The women among their ranks were responsible for one of every six loans in the study's townships. Most women lenders, some of whom were socially prominent, lived within the County's limits; they varied considerably in age and marital status. Their role as sources of rural credit, however, is valuable evidence of women's early financial activity.
Statistical Machine Translation with Scarce Resources Using Morpho-syntactic Information
Authors: Nießen Sonja , Ney Hermann
Published: May 2004

In statistical machine translation, correspondences between the words in the source and the target language are learned from parallel corpora, and often little or no linguistic knowledge is used to structure the underlying models. In particular, existing statistical systems for machine translation often treat different inflected forms of the same lemma as if they were independent of one another. The bilingual training data can be better exploited by explicitly taking into account the interdependencies of related inflected forms. We propose the construction of hierarchical lexicon models on the basis of equivalence classes of words. In addition, we introduce sentence-level restructuring transformations which aim at the assimilation of word order in related sentences. We have systematically investigated the amount of bilingual training data required to maintain an acceptable quality of machine translation. The combination of the suggested methods for improving translation quality in frameworks with scarce resources has been successfully tested: We were able to reduce the amount of bilingual training data to less than 10% of the original corpus, while losing only 1.6% in translation quality. The improvement of the translation results is demonstrated on two German-English corpora taken from the Verbmobil task and the Nespole! task.
The Australian Air Quality Forecasting System. Part III: Case Study of a Melbourne 4-Day Photochemical Smog Event
Authors: Tory K. J. , Cope M. E. , Hess G. D. , Lee S. , Puri K. , Manins P. C. , Wong N.
Published: May 2004

A 4-day photochemical smog event in the Melbourne, Victoria, Australia, region (6–9 March 2001) is examined to assess the performance of the Australian Air Quality Forecasting System (AAQFS). Although peak ozone concentrations measured during this period did not exceed the 1-h national air quality standard of 100 ppb, elevated maximum ozone concentrations in the range of 50–80 ppb were recorded at a number of monitoring stations on all four days. These maximum values were in general very well forecast by the AAQFS. On all but the third day the system predicted the advection of ozone precursors over Port Phillip (the adjacent bay) during the morning, where, later in the day, relatively high ozone concentrations developed. The ozone was advected back inland by bay and sea breezes. On the third day, a southerly component to the background wind direction prevented the precursor drainage over the bay, and the characteristic ozone cycle was disrupted. The success of the system's ability to predict peak ozone at individual monitoring stations was largely dependent on the direction and penetration of the sea and bay breezes, which in turn were dependent on the delicate balance between these winds and the opposing synoptic flow.
The Australian Air Quality Forecasting System. Part I: Project Description and Early Outcomes
Authors: Cope M. E. , Hess G. D. , Lee S. , Tory K. , Azzi M. , Carras J. , Lilley W. , Manins P. C. , Nelson P. , Ng L. , Puri K. , Wong N. , Walsh S. , Young M.
Published: May 2004

The Australian Air Quality Forecasting System (AAQFS) is the culmination of a 3-yr project to develop a numerical primitive equation system for generating high-resolution (1–5 km) short-term (24–36 h) forecasts for the Australian coastal cities of Melbourne and Sydney. Forecasts are generated 2 times per day for a range of primary and secondary air pollutants, including ozone, nitrogen dioxide, carbon monoxide, sulfur dioxide, and particles that are less than 10 μm in diameter (PM10). A preliminary assessment of system performance has been undertaken using forecasts generated over a 3-month demonstration period. For the priority pollutant ozone it was found that AAQFS achieved a coefficient of determination of 0.65 and 0.57 for forecasts of peak daily 1-h concentration in Melbourne and Sydney, respectively. The probability of detection and false-alarm rate were 0.71 and 0.55, respectively, for a 60-ppb forecast threshold in Melbourne. A similar level of skill was achieved for Sydney. System performance is also promising for the primary gaseous pollutants. Further development is required before the system can be used to forecast PM10 confidently, with a systematic overprediction of 24-h PM10 concentration occurring during the winter months.
Assessment of the Aviation Weather Center Global Forecasts of Mesoscale Convective Systems*
Authors: Ziv Baruch , Yair Yoav , Presman Karin , Füllekrug Martin
Published: May 2004

This paper examines the precision of location and top height of mesoscale convective systems, as forecast by the Aviation Weather Center (AWC). The examination was motivated by the Mediterranean Israeli Dust Experiment (MEIDEX) on the space shuttle Columbia, aimed to image transient luminous events (TLEs), such as sprites, jets, and elves, from orbit. Mesoscale convective systems offer a high probability for the occurrence of TLEs above active thunderstorms. Because the operational methodology was planned around a 24-h cycle, there was a need for a global forecast of areas with a high probability of massive thunderstorms that are prone to exhibit TLE activity. The forecast was based on the high-level significant weather (SIGWX) maps, commonly used for civil aviation, provided by the AWC on the Internet. To estimate the operational skill of this forecast for successfully detecting clouds with a high probability for producing TLEs, predictions for selected dates were compared with satellite observations. The locations of 66 mesoscale cloud systems on Significant Weather Maps, produced for eight different dates in August 2001, were compared with satellite global IR images for these dates. Operational skill was determined as the percentage of observed cloud systems found within a 5° range in the regions that appeared on the forecast maps as having the potential to contain thunderclouds and was found to be 92%. No consistent error was found in location. The predicted size of the convective system was typically larger than the observed size. Cloud-top heights of 53 systems were examined on four dates in October–November 2001, using IR radiances converted to brightness temperatures. For each convective system, the coldest cloud-top temperature was converted to height, using the NCEP–NCAR reanalysis data for the respective location and time. The standard error in the forecast heights was 2516 m. Because the purpose was to get true alerts of potential TLE occurrences, operational forecast skill was defined as the percentage of forecasts that were accurate within 1000 m or higher than observed. The 1000-m tolerance was allowed because of inevitable uncertainties underlying this method of analysis. Operational skill was found to be only 43%. During the “STS-107” mission flown in January 2003, the forecasted areas of main convective centers were transmitted daily to the crew and helped them in pointing the cameras and targeting thunderstorms. This ensured the success of the MEIDEX sprite observations that recorded numerous events in many different geographical locations.
Can generic paediatric mortality scores calculated 4 hours after admission be used as inclusion criteria for clinical trials?
Authors: Leteurtre Stéphane , Leclerc Francis , Wirth Jessica , Noizet Odile , Magnenant Eric , Sadik Ahmed , Fourier Catherine , Cremer Robin
Published: May 2004

Introduction

Two generic paediatric mortality scoring systems have been validated in the paediatric intensive care unit (PICU). Paediatric RISk of Mortality (PRISM) requires an observation period of 24 hours, and PRISM III measures severity at two time points (at 12 hours and 24 hours) after admission, which represents a limitation for clinical trials that require earlier inclusion. The Paediatric Index of Mortality (PIM) is calculated 1 hour after admission but does not take into account the stabilization period following admission. To avoid these limitations, we chose to conduct assessments 4 hours after PICU admission. The aim of the present study was to validate PRISM, PRISM III and PIM at the time points for which they were developed, and to compare their accuracy in predicting mortality at those times with their accuracy at 4 hours.

Methods

All children admitted from June 1998 to May 2000 in one tertiary PICU were prospectively included. Data were collected to generate scores and predictions using PRISM, PRISM III and PIM.

Results

There were 802 consecutive admissions with 80 deaths. For the time points for which the scores were developed, observed and predicted mortality rates were significantly different for the three scores (P < 0.01) whereas all exhibited good discrimination (area under the receiver operating characteristic curve ≥0.83). At 4 hours after admission only the PIM had good calibration (P = 0.44), but all three scores exhibited good discrimination (area under the receiver operating characteristic curve ≥0.82).

Conclusions

Among the three scores calculated at 4 hours after admission, all had good discriminatory capacity but only the PIM score was well calibrated. Further studies are required before the PIM score at 4 hours can be used as an inclusion criterion in clinical trials.
Field tests of an experimental helicopter time‐domain electromagnetic system for unexploded ordnance detection
Authors: Beard Les P. , Doll William E. , Holladay J. Scott , Gamey T. Jeffrey , Lee James L.C. , Bell David T.
Published: May 2004

Field trials of a low‐flying time‐domain helicopter electromagnetic system designed for detection of unexploded ordnance have yielded positive and encouraging results. The system is able to detect ordnance as small as 60‐mm rounds at 1‐m sensor height. We examined several transmitter and receiver configurations. Small loop receivers gave superior signal‐to‐noise ratios in comparison to larger receiver loops at low heights. Base frequencies of 90 Hz and 270 Hz were less affected than other base frequencies by noise produced by proximity to the helicopter and by vibration of the support structure. For small ordnance, a two‐lobed, antisymmetric transmitter loop geometry produced a modest signal‐to‐noise enhancement compared with a large single rectangular loop, presumably because the antisymmetric transmitter produces smaller eddy currents in the helicopter body, thereby reducing this source of noise. In most cases, differencing of vertically offset receivers did not substantially improve signal‐to‐noise ratios at very low sensor altitudes. Signal attenuation from transmitter to target and from target to receiver causes signals from smaller ordnance to quickly become indistinguishable from geological background variations, so that above a sensor height of about 3 m only large ordnance items (e.g., bombs and large caliber artillery rounds) were consistently detected.
A practical method for estimating effective parameters of anisotropy from reflection seismic data
Authors: Isaac J. Helen , Lawton Don C.
Published: May 2004

The location of any event imaged by P‐wave reflection seismic data beneath a tilted transversely isotropic (TTI) overburden is shifted laterally if isotropic velocities are used during data processing. The magnitude of the shift depends on five independent parameters: overburden thickness, angle of tilt, symmetry‐axis velocity, and the Thomsen anisotropy parameters and δ. The shift also varies with source–receiver offset.

We have developed a procedure to estimate these five parameters when the tilt of the symmetry axis from the vertical is equal to the dip of the TTI layer (except in the special cases transverse isotropy with vertical or horizontal axis of symmetry). We observe three attributes of seismic data processed using isotropic velocities: the zero‐offset arrival time of a selected reflection, the difference in arrival time between a near‐offset and a far‐offset arrival, and the difference in imaged location (smear) of this target event between the same offsets. We then perform a cascaded scan of the five parameters to determine those combinations of the five that result in calculated attributes equivalent to the observed attributes. The multiple solutions are averaged to give the parameter estimates.

Application of this method to synthetic and physical model reflection data results in multiple solutions, which are constrained and averaged to obtain the effective imaging parameters. These effective parameters are close estimates of the true model parameters in both cases. For field seismic data this procedure requires that there be a suitable observable event below the TTI overburden and assumes that the measured times and shifts are reasonably accurate.
Processing of anisotropic data in the τ‐pdomain: I—Geometric spreading and moveout corrections
Authors: van der Baan Mirko
Published: May 2004

Stacking of seismic data is conventionally done in the time‐offset domain. This has the disadvantage that geometric spreading must be removed before true‐amplitude processing can be attempted. This inconvenience arises since wave motion in the time‐offset domain is determined by spherical waves. Plane waves in layered media, on the other hand, are not subject to geometric spreading. Hence, processing of both isotropic and anisotropic data in such media benefits from first applying a plane‐wave decomposition such as a proper τ‐p transform. The resulting τ‐p gathers can be flattened and stacked over slowness. Subsequent time differentiation is needed to counter the loss of high frequencies during stacking. This approach has the advantage that the geometric spreading is removed without prior knowledge of the actual (an)isotropic velocity field and without any need to pick traveltimes or moveout velocities. Subsequent moveout corrections naturally require knowledge of the velocityfield.

The proposed methodology is exact for 3D data volumes and arbitrary anisotropy in laterally homogeneous media or for 2D acquisition lines over 1D, isotropic media or over 1D, transversely isotropic media with vertical axis of symmetry (VTI). It relies on the same principles as more conventional geometric spreading corrections and time‐offset stacking. In many respects, it is even more flexible. For instance, geometric spreading has been correctly removed for all present wave modes and types simultaneously (primary, multiple, pure‐mode, and converted waves), and nonhyperbolic moveout resulting from isotropic layering is also taken into account. In addition, head waves may now contribute constructively to the stacked section. Moreover, both multiple elimination and predictive deconvolution are straightforward and known to yield very good results in the τ‐p domain. The resulting stacked section can then be used for any poststack processing such as time migration.
Efficient automatic denoising of gravity gradiometry data
Authors: de Oliveira Lyrio Julio Cesar Soares , Tenorio Luis , Li Yaoguo
Published: May 2004

Gravity gradiometry data are prized for the high frequency information they provide. However, as any other geophysical data, gravity gradient measurements are contaminated by high‐frequency noise. Separation of the high‐frequency signal from noise is a crucial component of data processing. The separation can be performed in the frequency domain, which usually requires tuning filter parameters at each survey line to obtain optimal results. Because a modern gradiometry survey generates more data than a traditional gravity survey, such time‐consuming manual operations are not very practical. In addition, they may also introduce subjectivity into the process.

To address this difficulty, we propose an automatic, data‐adaptive 1D wavelet filtering technique specially designed to process gravity gradiometry data. The method is based on the thresholding of the wavelet coefficients to filter out high‐frequency noise while preserving localized sharp signal features. We use an energy analysis across scales (specific for gravity gradiometry data) to select denoising thresholds and to identify sharp features of interest. We compare the proposed method with traditional Fourier‐domain filters by applying them to synthetic data sets contaminated with either correlated or uncorrelated noise. The results demonstrate that the proposed filter is efficient and, when applied in the fully automated mode, produces results that are comparable to the best results achievable through frequency‐domain filters. We further illustrate the method by applying it to a set of gravity gradiometry data acquired in the Gulf of Mexico and by characterizing the removed noise. Both synthetic and field examples show that the proposed method is an efficient and better alternative to other traditional frequency domain methods.
Improvement in GPR coherent noise attenuation using τ‐p and wavelet transforms
Authors: Nuzzo Luigia , Quarta Tatiana
Published: May 2004

We present a new application of modern filtering techniques to ground‐penetrating radar (GPR) data processing for coherent noise attenuation. We compare the performance of the discrete wavelet transform (DWT) and the linear Radon transform (τ‐p) to classical time‐space and Fourier domain methods using a synthetic model and real data. The synthetic example simulates problems such as system ringing and surface scattering, which are common in real cases. The field examples illustrate the removal of nearly horizontal but variable‐amplitude noise features. In such situations, classical space‐domain techniques require several trials before finding an appropriate averaging window size. Our comparative analysis indicates that the DWT method is better suited for local filtering than are 2D frequency‐domain (f‐f) techniques, although the latter are computationally efficient. Radon‐based methods are slightly superior than the techniques previously used for local directional filtering, but they are slow and quite sensitive to the p‐sampling rate, p‐range, and sizes of the muting zone. Our results confirm that Radon and wavelet methods are effective in removing noise from GPR images with minimal distortions of the signal.
Finite‐difference modeling of viscoelastic materials with quality factors of arbitrary magnitude
Authors: Asvadurov Sergey , Knizhnerman Leonid , Pabon Jahir
Published: May 2004

To minimize acoustic noise, designers of sonic logging tools often consider coatings of viscoelastic materials with very high attenuation properties. Efficient finite‐difference modeling of viscoelastic materials is a topic of current research.

To model viscoelastic materials in the time domain through finite differences efficiently, one needs to replace the time convolution, which enters in the stress–strain relations, by a set of first‐order differential equations. This procedure is equivalent to computing a rational approximation of a certain form to the frequency‐dependent complex modulus of viscoelasticity. Known schemes for computing such approximations are designed to treat materials with low attenuation, such as underground formations, but fail to produce accurate or even physically meaningful results for highly attenuative materials.

We propose a novel scheme that allows one to construct, for a given frequency range, a uniformly optimal rational approximation for the most widely used model of materials with constant quality (Q‐) factors of arbitrary magnitude. We present the proof of convergence and demonstrate it on numerical finite‐difference examples. These examples also demonstrate the effective transparency of a simple tool modeled as a pipe of highly viscoelastic material.

For frequency‐dependent quality factors we present a modified numerical scheme to compute a nearly optimal rational approximation of the viscoelastic modulus.
Clinical trial design in systemic lupus erythematosus: lessons learned and future directions
Authors: Strand V
Published: May 2004

Designing successful randomized controlled trials (RCTs) in systemic lupus erythematosus (SLE) poses many challenges. It remains difficult to correlate alterations in biologic markers with clinical outcome, especially when signs and symptoms are intermittent and broadly variable between patients. Disease activity indices were not designed specifically as outcome measures in RCTs, as they were developed in the context of longitudinal observational studies. Although all disease activity indices have been validatedagainsteach other and demonstratedto show change, organ system manifestations are variably weighted; fatigue and autoantibodytiters are scored in some and not in others. Due to the variability of the underlying disease course an assessment of disease activity may most accurately be portrayed as change over time, such as an area under the curve analysis. Another lesson learned is that ’responder indices’ proposed in the absence of prospective validation in RCTs do not function well. The argument can always be made that any response criteria will work if the treatment is effective;but without the precedent of a product specifically approved for use in SLE, this is hard to prove. The ACR/Systemic Lupus International Cooperating Clinics (SLICC) damage index was designed to score irreversible manifestations of disease or consequences of its treatment, provided they had been present for at least six months. The damage index may best be utilized to stratify patients or balance randomization at baseline. It may also be incorporated into an endpoint analysis, to ensure that treatment or disease associated deterioration in organ system function (that may be overlooked in scoring disease activity alone) has not occurred. Patient cohort data have demonstrated that the medical outcomes survey short form-36 (SF-36) reflected the effects of SLE better than other patient reported measures. Worsening SF-36 domain scores best correlate with higher disease activity, increased glucocorticoid doses and use of cytotoxic agents. It has been shown sensitive to change in RCTs and observationalcohorts, and reflects the impact of treatment with high dose glucocorticoids and immunosuppressiveagents, as well as end stage renal disease. There is now a body of data derived from RCTs in SLE. Albeit limited, yet to result in an approved therapy, evidence is accumulating that indicate ’early markers’ of response can be defined which may correlate with longer term clinical outcomes. This should inform us in our ongoing efforts to clinically test a broad variety of promising interventions.