bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthese von Polymethintetrathiafulvalenen durch Dimerisierung von ω‐(1,3‐Dithiol‐2‐yliden)polyenalen mit dem Lawesson‐Reagens: Carotinoide und supracarotinoide Tetrathiafulvalene
Authors: Märkl von Gottfried , Aschenbrenner Norbert , Baur Andreas , Rastorfer Corinna , Kreitmeier Peter
Published: August 2003

Synthesis of Polymethinetetrathiafulvalenes by Dimerization of ω‐(1,3‐Dithiol‐2‐ylidene)polyenals with the Lawesson Reagent: Carotenoid and Supracarotenoid Tetrathiafulvalenes

The dimerization of aldehydes via their unstable thioaldehydes giving 1,3‐dithietanes, which undergo sulfur extrusion to give alkenes (see Scheme 8) is used for a new, general synthesis of tetrahiafulvalenes with polymethine spacers. In the presence of the Lawesson reagent 19, the 2‐(ω‐oxopolyenylidene)‐1,3‐dithiol‐4,5‐dicarbonitriles 6 and 13 and the ω‐(1,3‐benzodithiol‐2‐yliden)polyenals 8 and 15 can be dimerized via the thioaldehydes. The aldehydes 6 and 13 are obtained by reaction of the unsaturated dialdehydes 4, 2,7‐dimethylocta‐2,4,6‐trienedial (14a) and crocetindialdehyde (14b) with 1 mol of 2‐thioxo‐1,3‐dithiole‐4,5‐dicarbonitrile (5) and 2 mol of triphenylphosphine (Schemes 5 and 6). The ω‐(1,3‐benzodithiol‐2‐yliden)polyenales 8 and 15 were prepared by the Wittig reaction of the dialdehydes with 1 mol of (1,3‐benzodithiol‐(2‐yl)tributylphosphoniumtetrafluoroborate (12) (Schemes 7 and 6).

Starting from the corresponding aldehydes 6 and 13, the polymethinetetrathiafulvalenes 7d, 16a, and 16b with conjugated 16 and 32 polymethine chains become available (Schemes 9 and 10), which we call carotinoid and supracarotinoid tetrathiafulvalenes. The (benzodithiol‐2‐yliden)acetaldehyde (8a) and ‐butenal (8b) are dimerized to give the tetrathiafulvalenes 9a and 9b with 4 and 8 methine C‐atoms, respectively (Scheme 11). In case of 15a und 15b, the Lawesson method fails, the dimer 17a with 16 methine C‐atoms can be obtained from 15a via the McMurry reaction (Scheme 13).

The intermediate thioaldehydes can be intercepted by the formation of Diels–Alder adducts with hexachlorocyclopentadiene and hexa‐2,4‐diene (Scheme 12). The redox potentials E1/2 of the described polymethinetetrathiafulvalenes are reported.
Synthese von neuen (Phenylalkyl)aminen zur Untersuchung von Struktur–Aktivitätsbeziehungen. Mitteilung 2
Authors: Trachsel Daniel
Published: August 2003

Synthesis of Novel (Phenylalkyl)amines for the Investigation of Structure–Activity Relationships. Part 21). 4‐Thio‐Substituted [2‐(2,5‐Dimethoxyphenyl)ethyl]amines (=2,5‐Dimethoxybenzeneethanamines)

The 4‐substituted [2‐(2,5‐dimethoxyphenyl)ethyl]amines (=2,5‐dimethoxybenzeneethanamines) and its α‐methyl analogs are known to act as potent 5‐HT2A/C ligands, which have, depending on their 4‐substituent, agonistic or antagonistic character. Generally, compounds with a small lipophilic substituent typically are agonists and those with a larger lipophilic substituent predominantly antagonists or at least partial agonists. Since little is known about the transition and more information is needed about the structural requirements of the 4‐substituent to control the functional activity, 12 novel 4‐thio‐substituted [2‐(2,5‐dimethoxyphenyl)ethyl]amines were synthesized and spectroscopically characterized. Thus 2,5‐dimethoxybenzenethiol (7) was converted to the thioether derivatives 8a–l with several alkyl, fluoroalkyl, alkenyl, and benzyl halides. Subsequent Vilsmeier‐formylation afforded the benzaldehydes 9a–l, condensation with MeNO2 the nitroethenyl derivatives 10a–l, and reduction with AlH3 the desired (2‐phenylethyl)amines 11a–l.
Allylic Sulfones Containing Triene Moieties as Key Synthons for Carotenoid Synthesis
Authors: Ji Minkoo , Choi Hojin , Jeong Young Cheol , Jin Jingquan , Baik Woonphil , Lee Sijoon , Kim Jeong Soo , Park Minsoo , Koo Sangho
Published: August 2003

An efficient synthetic method for the allylic sulfone 2 containing a conjugated triene moiety has been proposed involving i) coupling of allylic sulfones 4 with the C5 bromoallylic sulfide 5, ii) base‐promoted dehydrosulfonation in the presence of allylic sulfide, and iii) selective oxidation of the resulting trienyl sulfide to the corresponding sulfone. Total synthesis of lycopene starting from the C15 allylic sulfone 2b has been described, where the new C10 bis(chloroallylic) sulfone 11 proved to be a useful substitute for the C10 bis(chloroallylic) sulfide 3, which did not require the problematic chemoselective sulfur oxidation in a conjugated polyene.
Stereochemistry of the Conversion of 2‐Phenoxyethanol into Phenol and Acetaldehyde by Acetobacterium sp.
Authors: Speranza Giovanna , Mueller Britta , Orlandi Maximilian , Morelli Carlo F. , Manitto Paolo , Schink Bernhard
Published: August 2003

The conversion of 2‐phenoxyethanol to phenol and acetate by the anaerobic bacterium Acetobacterium sp. strain LuPhet1 proceeds through acetaldehyde with concomitant migration of a H‐atom from C(1) to C(2) of the glycolic moiety. Separate feeding experiments with (R)‐ and (S)‐2‐phenoxy(1‐2H)ethanol, prepared via chemoenzymatic syntheses, indicate that the H‐atom involved in the 1,2‐shift is the pro‐S one of the enantiotopic couple of the alcohol function.
Design and Synthesis of Guanidinoglycosides Directed against the TAR RNA of HIV‐1
Authors: Wang Min , Tu Peng‐Fei , Xu Zhi‐Dong , Yu Xiao‐Lin , Yang Ming
Published: August 2003

Replication of human immunodeficiency virus type 1 (HIV‐1) requires specific interactions of the Tat protein with the transactivation responsive region (TAR) RNA. Tat‐TAR RNA Interaction is mediated by a short arginine‐rich domain of the protein. Disruption of this interaction could, in theory, create a state of complete viral latency. Here, four novel 6‐amino‐6‐deoxytrehalose guanidinoglycoside derivatives (10 and 13–15) as target molecules have been designed to bind to TAR RNA for blocking the interaction of Tat‐TAR RNA. They were obtained by coupling 6‐amino‐6‐deoxy‐α,α‐trehalose (6) with the protected amino acids, deprotection by catalytic hydrogenation, followed by guanidinylated with S‐methylisothiourea sulfate. Their abilities to inhibit Tat‐TAR RNA interaction were determined by a Tat‐dependent HIV‐1 long terminal repeats (LTR)‐driven chloramphenicol acetyltransferase (CAT) assays.
A Diterpenoid with a New Skeleton and Cytotoxic Terpenoids Isolated from Amentotaxus formosana
Authors: Su Huey‐Jen , Wang Li‐Wen , Lin Chun‐Nan , Day Shiow‐Hwa , Wei Bai‐Luh , Yang Sheng‐Zehn , Won Shen‐Jeu
Published: August 2003

The new diterpenoid 6α‐hydroxy‐ent‐kaur‐16‐en‐15‐one (1) and a diterpenoid with a new skeleton, i.e., amentotaxin BB (5), as well as three new lanostanoids, i.e., (3β,23R)‐3‐methoxy‐24‐methylenelanost‐8‐en‐23‐ol (6), (23S)‐23‐methoxy‐24‐methylenelanost‐8‐en‐3‐one (7), and (3β,24ξ)‐3‐methoxy‐24‐methyl‐9,19‐cyclolanostan‐25‐ol (8), were isolated from the bark and leaves of Amentotaxus formosana. Their structures, including the relative configurations, were elucidated from spectroscopic data. Compound 1 and a known compound, ent‐kaur‐16‐en‐15‐one (2), showed potent cytotoxic effects against a number of cancer cells in vitro.
Zn2+‐Complexation by a β‐Peptidic Helix and Hairpin Containing β3hCys and β3hHis Building Blocks: Evidence from CD Measurements. Preliminary Communication
Authors: Rossi Francesco , Lelais Gérald , Seebach Dieter
Published: August 2003

Two new β3‐homohistidine‐ and β3‐homocysteine‐containing β‐peptides have been prepared by solid‐phase synthesis. A β‐octapeptide (2) contains seven β3‐amino acids and one β2‐amino acid. The β2/β3 segment has been placed in the middle of this peptide, which contains β3‐amino acids of alternating configuration, to induce the formation of a hairpin secondary structure. A β‐decapeptide (3) has been designed to fold to a 314‐helical secondary structure with neighboring His side chains in 6‐ and 9‐positions. Circular‐dichroism (CD) measurements show the capability of both peptides to bind Zn2+ ions in aqueous solution. In the case of the β‐octapeptide, binding of Zn2+ causes a dramatic change of the CD spectrum, indicating a change or a stabilization of its secondary structure. Zn2+ Ions clearly stabilize the 314‐helix of the β‐decapeptide, in neutral and basic solution. For the construction of the two new β‐peptides, we needed to have a supply of the β‐amino acid derivatives Fmoc‐β3hCys(Trt)‐OH and Fmoc‐β3hHis(Trt)‐OH, the preparation of which is described herein.
Synthesis, Structure, and Physicochemical Studies of Hexakis(2,4‐dimethylanilinium) Cyclohexaphosphate Hexahydrate
Authors: Khedhiri Lamia , Nasr Cherif Ben , Rzaigui Mohamed , Lefebre Frederic
Published: August 2003

Chemical preparation, crystal structure, thermal analysis, IR absorption, and NMR studies are given for a new organic cyclohexaphosphate, the hexakis(2,4‐dimethylanilinium) cyclohexaphosphate hexahydrate ((2,4‐Me2C6H3NH3)6P6O18⋅6 H2O). This compound crystallizes in the monoclinic space group P21/n, with cell parameters a=10.914(4) Å, b=11.198(3) Å, c=25.670(2) Å, β=95.05(4)°, Z=2, and V=3124(2) Å3. Its crystal structure is determined and refined to a final R=0.054 for 4627 independent reflections. The atomic arrangement can be described as a layer organization built by P6O18‐ring anions and H2O molecules. Between these layers are located the organic groups that form H‐bonds with O‐atoms of the P6O18 rings and H2O molecules. Determination of the geometric characteristics of the H‐bonds show the existence in this structure of four particularly strong H‐bonding contacts (1.75, 1.76, 1.78, and 1.87 Å).
N‐(4‐Biphenylmethyl)imidazoles as Potential Therapeutics for the Treatment of Prostate Cancer: Metabolic Robustness Due to Fluorine Substitution?
Authors: Leroux Frédéric , Hutschenreuter Tilman U. , Charrière Céline , Scopelliti Rosario , Hartmann Rolf W.
Published: August 2003

3,3′,5,5′‐ And 2,2′,6,6′‐tetrafluoro‐substituted 1‐[(1,1′‐biphenyl]‐4‐yl)methyl]‐1H‐imidazoles were synthesized as inhibitors of 17α‐hydroxylase‐C17,20‐lyase (P450 17, CYP 17). P450 17 is the key enzyme of androgen biosynthesis. Its inhibition is a novel therapeutic approach for treatment of prostate cancer. To increase the so‐far insufficientin vivolifetime of such compounds, the metabolically sensitive positions were blocked by F‐substitution. Themeta‐ andortho‐F‐substituted compounds were prepared by selective metallation or halogen/metal permutation reactions performed on symmetrically substituted 1,1′‐biphenyls. Compared with the halogen‐free compounds, theortho‐F‐substituted derivatives did not match the activity, whereas themeta‐F‐substituted isomers equaled or surpassed the latter.
Synthesis of Pyrano[3,2‐b]indole Derivatives Based on Intramolecular Hetero‐DielsAlder of 2‐Benzylidene‐2,3‐dihydro‐1H‐indol‐3‐ones
Authors: Davion Yann , Joseph Benoît , Bénéteau Valérie , Léger Jean‐Michel , Jarry Christian , Mérour Jean‐Yves
Published: August 2003

Pyrano[3,2‐b]indole derivatives 2–6 were synthesized in good yields from 1‐acetyl‐2‐benzylidene‐2,3‐dihydro‐1H‐indol‐3‐ones 8 and 13–15 by an intramolecular hetero‐DielsAlder reaction. The structures of compounds 2a, 3a, 4, 5, and 6 were unambiguously established by X‐ray analysis. Compounds 4 and 5 were further aromatized to the corresponding derivatives 16 and 17, respectively.
Enantioselectivity in Odor Perception: Synthesis and Olfactory Properties of Iso‐β‐Bisabolol, a New Natural Product
Authors: Braun Norbert A. , Meier Manfred , Schmaus Gerhard , Hölscher Bernd , Pickenhagen Wilhelm
Published: August 2003

The odorous trace constituent iso‐β‐bisabolol (4) was isolated from East Indian and Western Australian sandalwood oil and synthesized by using the (E/Z)‐triene 12 (iso‐γ‐bisabolene) as a key intermediate. Only one of four stereoisomeric forms of 4, (6R,7R)‐4a, is odor active, having a strong floral, muguet‐like, very pleasant scent.
Multicriteria second‐order neural networks approach to imaging through turbulence
Authors: Wang Yuanmei
Published: August 2003

Atmospheric turbulence can greatly limit the spatial resolution in optical images obtained of space objects when imaged with ground‐based telescopes. Two widely used algorithms to remove atmospheric turbulence in this class of images are blind de‐convolution and speckle imaging. Both algorithms are effective in removing atmospheric turbulence, but they use different types of prior knowledge and have different strengths and weaknesses. We have developed a multicriteria cross entropy minimization approach to imaging through atmospheric turbulence and a second‐order neural network implementations. Our simulations illustrated the efficiency of our method. © 2003 Wiley Periodicals, Inc. Int J Imaging Syst Technol 13, 146–151, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.10037
Wavelet energy spectrum for time‐frequency localization of earthquake energy
Authors: Zhou Ziqin , Adeli Hojjat
Published: August 2003

The authors recently developed a method for time‐frequency signal analysis of earthquake records using Mexican hat wavelets. Ground motions in earthquakes are postulated as a sequence of simple penny‐shaped ruptures at different locations along a fault line and occurring at different times. In this article, a wavelet energy spectrum is proposed for time‐frequency localization of the earthquake input energy. The ground acceleration generated by a simple penny‐shaped rupture is used as the basis to form the mother wavelet. The symmetric Mexican hat wavelet is chosen as the mother wavelet. The spectrum is presented pictorially in a two‐dimensional, time‐frequency domain. The proposed wavelet energy spectrum can be used to observe the evolution of the frequency contents of earthquake energy over time and distance of the site from the epicenter in a more accurate manner than the traditional time series (accelerogram) or frequency domain (Fourier amplitude spectrum) representation. It can be viewed as a microscope for looking into the time‐frequency characteristics of earthquake acceleration records. The wavelet energy spectrum provides frequency evolution information to be used in the structural design process. © 2003 Wiley Periodicals, Inc. Int J Imaging Syst Technol 13, 133–140, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.10038
Optimal data acquisition in fMRI using prolate spheroidal wave functions
Authors: Lindquist Martin A.
Published: August 2003

Functional magnetic resonance imaging (fMRI) is a technique that can be used to noninvasively study mental activity in a persons brain. fMRI has the potential to answer many interesting questions regarding the way the brain functions. Unfortunately, the drawback to fMRI studies, as they are traditionally performed, is that the temporal resolution is too low to effectively answer questions regarding what happens in an active region of the brain immediately following stimulation. Shepp and Zhang (2000) introduced a new method that could potentially lead to a significant increase in temporal resolution. Their method suggests a way to improve the time resolution in fMRI studies by sampling only a fraction of the points needed to recreate a full image. Instead of full image reconstruction, an optimal prolate spheroidal wave function filter is used to obtain a measurement over the total activity in a predefined region in the brain, B, at successive time points. The sampling region and filter are chosen in order to minimize the energy loss over the region of interest (ROI). The region they suggested to sample was chosen heuristically and corresponds to the scaled polar set of B. It was shown to be near optimal through extensive computer searches. In this article the optimal sampling region is found for the case when the ROI is circular or spherical and the sampling size is small. Based on this result, a new heuristic is introduced for other ROIs, which improves upon the results obtained using the polar set of B. © 2003 Wiley Periodicals, Inc. Int J Imaging Syst Technol 13, 126–132, 2003; Published online in Wiley Inter‐Science (www.interscience.wiley.com). DOI 10.1002/ima.10051
Fossil sister group of craniates: Predicted and found
Authors: Mallatt Jon , Chen Jun‐yuan
Published: August 2003

This study investigates whether the recently described Cambrian fossil Haikouella (and the very similar Yunnanozoon) throws light on the longstanding problem of the origin of craniates. In the first rigorous cladistic analysis of the relations of this animal, we took 40 anatomical characters from Haikouella and other taxa (hemichordates, tunicates, cephalochordates, conodont craniates and other craniates, plus protostomes as the outgroup) and subjected these characters to parsimony analysis. The characters included several previously unrecognized traits of Haikouella, such as upper lips resembling those of larval lampreys, the thick nature of the branchial bars, a mandibular branchial artery but no mandibular branchial bar, muscle fibers defining the myomeres, a dark fibrous sheath that defines the notochord, conclusive evidence for paired eyes, and a large hindbrain and diencephalon in the same positions as in the craniate brain. The cladistic analysis produced this tree: (protostomes, hemichordates (tunicates, (cephalochordates, (Haikouella, (conodonts + other craniates))))), with the “Haikouella + craniate” clade supported by bootstrap values that ranged from 81–96%, depending on how the analysis was structured. Thus, Haikouella is concluded to be the sister group of the craniates. Alternate hypotheses that unite Haikouella with hemichordates or cephalochordates, or consider it a basal deuterostome, received little or no support. Although it is the sister group of craniates, Haikouella is skull‐less and lacks an ear, but it does have neural‐crest derivatives in its branchial bars. Its craniate characters occur mostly in the head and pharynx; its widely spaced, robust branchial bars indicate it ventilated with branchiomeric muscles, not cilia. Despite its craniate mode of ventilation, Haikouella was not a predator but a suspension feeder, as shown by its cephalochordate‐like endostyle, and tentacles forming a screen across the mouth. Haikouella was compared to pre‐craniates predicted by recent models of craniate evolution and was found to fit these predictions closely. Specifically, it fits Northcutt and Gans' prediction that the change from ciliary to muscular ventilation preceded the change from suspension feeding to predatory feeding; it fits Butler's claim that vision was the first craniate sense to start elaborating; it is consistent with the ideas of Donoghue and others about the ancestor of conodont craniates; and, most strikingly, it resembles Mallatt's prediction of the external appearance of the ancestral craniate head. By contrast, Haikouella does not fit the widespread belief that ancestral craniates resembled hagfishes, because it has no special hagfish characters. Overall, Haikouella agrees so closely with recent predictions about pre‐craniates that we conclude that the difficult problem of craniate origins is nearly solved. J. Morphol. 258:1–31, 2003. © 2003 Wiley‐Liss, Inc.
Architectural properties of distal forelimb muscles in horses,Equus caballus
Authors: Brown Nicholas A.T. , Kawcak Christopher E. , McIlwraith C. Wayne , Pandy Marcus G.
Published: August 2003

Articular injuries in athletic horses are associated with large forces from ground impact and from muscular contraction. To accurately and noninvasively predict muscle and joint contact forces, a detailed model of musculoskeletal geometry and muscle architecture is required. Moreover, muscle architectural data can increase our understanding of the relationship between muscle structure and function in the equine distal forelimb. Muscle architectural data were collected from seven limbs obtained from five thoroughbred and thoroughbred‐cross horses. Muscle belly rest length, tendon rest length, muscle volume, muscle fiber length, and pennation angle were measured for nine distal forelimb muscles. Physiological cross‐sectional area (PCSA) was determined from muscle volume and muscle fiber length. The superficial and deep digital flexor muscles displayed markedly different muscle volumes (227 and 656 cm3, respectively), but their PCSAs were very similar due to a significant difference in muscle fiber length (i.e., the superficial digital flexor muscle had very short fibers, while those of the deep digital flexor muscle were relatively long). The ulnaris lateralis and flexor carpi ulnaris muscles had short fibers (17.4 and 18.3 mm, respectively). These actuators were strong (peak isometric force, Fmax= 5,814 and 4,017 N, respectively) and stiff (tendon rest length to muscle fiber length, LT:LMF= 5.3 and 2.1, respectively), and are probably well adapted to stabilizing the carpus during the stance phase of gait. In contrast, the flexor carpi radialis muscle displayed long fibers (89.7 mm), low peak isometric force (Fmax= 555 N), and high stiffness (LT:LMF= 1.6). Due to its long fibers and low Fmax, flexor carpi radialis appears to be better adapted to flexion and extension of the limb during the swing phase of gait than to stabilization of the carpus during stance. Including muscle architectural parameters in a musculoskeletal model of the equine distal forelimb may lead to more realistic estimates not only of the magnitudes of muscle forces, but also of the distribution of forces among the muscles crossing any given joint. J. Morphol. 258:106–114, 2003. © 2003 Wiley‐Liss, Inc.
Differential mesowear in occluding upper and lower molars: Opening mesowear analysis for lower molars and premolars in hypsodont horses
Authors: Kaiser Thomas M. , Fortelius Mikael
Published: August 2003

A new approach of reconstructing ungulate diet, the mesowear method, was recently introduced by Fortelius and Solounias ([2000] Am Mus Novitat 3301:1–36). Mesowear is based on facet development on the occlusal surfaces of the teeth. Restricting mesowear investigation to maxillary cheek teeth would allow mesowear investigation only in assemblages of large numbers of individuals and therefore would generally restrict this method to relatively few assemblages of recent and fossil ungulates. Most of the fossil, subfossil, and recent ungulate osteological assemblages that may be assigned to a single taxon have smaller numbers of individuals. This results in a demand to extend the mesowear method to further tooth positions in order to obtain stable dietary classifications of fossil taxa. The focus of this article is to test if a consistent mesowear classification is obtainable for mandibular as well as for maxillary teeth. For statistical testing, large assemblages of isolated cheek teeth of the Vallesian hipparionine horse Hippotherium primigenium and of the recent zebra Equus burchelli were employed as models. The upper tooth positions P4, M1, M2, and M3 as suggested by Kaiser and Solounias (2003) as the model for the “extended” mesowear method and the lower tooth positions P4–M3 were tested for their consistency in classification of the mesowear variables. We found a considerable shift of the mesowear signature towards the grazing edge of the mesowear continuum in lower cheek teeth. In order to adjust the signal of lower teeth to the signal of the upper teeth, a calibration factor was introduced which allowed incorporation of lower cheek teeth into the same model of mesowear investigation together with upper cheek teeth. We propose that this model is particularly suited for the reconstruction of paleodiets in hypsodont hipparionine and equine equids. We further investigated the functional relation between the mesowear profiles and the distribution of dental tissues along the course of the occlusal contact. We therefore correlated mesowear profiles with enamel distribution profiles and found the mesowear profile to be strongly controlled by the attritional environment encountered by a given apex area. The differential signal observed in cusp apex morphology between upper and lower cheek teeth was found to be more closely related to attrition by the antagonistic tooth than to the distribution of dental tissues in the tooth under consideration. The results suggest a general extension of the mesowear method of paleodiet reconstruction and a basic scenario for the evolution of anisodont dentitions. J. Morphol. 258:67–83, 2003. © 2003 Wiley‐Liss, Inc.
Cranial osteology in momotidae (Aves: Coraciiformes)
Authors: Pascotto Márcia C. , Donatelli Reginaldo J.
Published: August 2003

Momotidae (motmots) is found throughout Latin America between Mexico and northern Argentina. Given the absence of detailed studies of cranial osteology of Momotidae in the literature, this article presents a comprehensive description of the variation of the cranial osteology in all nine species of Momotidae and compares the results with published studies of other families of Coraciiformes and families in other orders. In addition, the cranial structures described are related to ecological and behavioral aspects of Momotidae. The cranial osteology of Baryphthengus ruficapillus is described in detail and compared with other species of Momotidae. The results indicate the presence in Momotidae of modified cranial structures, among which the most conspicuous are the frontal, lacrimal, squamosal, orbital, and laterosphenoid regions, as well as the palatine, upper jaw, pterygoid, and mandible. J. Morphol. 258:32–48, 2003. © 2003 Wiley‐Liss, Inc.
Structural peculiarities of the tubercles in the skin of the turbot, Scophthalmus maximus (L., 1758) (Osteichthyes, Pleuronectiformes, Scophthalmidae)
Authors: Zylberberg Louise , Chanet Bruno , Wagemans France , Meunier François J.
Published: August 2003

The structure of the bony tubercles of the turbot, Scophthalmus maximus (L., 1758), was examined using ground sections, microradiography, SEM, and TEM. The tubercles are small, isolated, mineralized conical plates randomly distributed in the eyed side of the body. They are composed of three layers: the outer limiting layer, the external layer, and the basal plate, which make up the thin and flat elasmoid scales of Teleostei. The main difference between regular elasmoid scales and bony tubercles lies in the organization and the growth of the basal plate. Indeed, the conical shape of the tubercle is the result of a prominent thickening of the central part of the basal plate where the collagen matrix is organized in a complicated three‐dimensional network. Densely packed thick collagen fibrils form superimposed plies organized in a plywood‐like structure that resembles that of the elasmoid scales but it is criss‐crossed by numerous vertical sheets of thin collagen fibrils. The tubercles originate from thin and flat plates located in the skin of larvae and juveniles, whose structure is that of regular‐developing elasmoid scales. Thus, the tubercles of Scophthalmus maximus could be considered as modified elasmoid scales rather than bony structures. They might be the result of specific arrangements related to the general trend of reduction of the dermal skeleton in the teleostean lineage. J. Morphol. 258:84–96, 2003. © 2003 Wiley‐Liss, Inc.
Formation of cartilage in the heart of the Spanish terrapin, Mauremys leprosa (Reptilia, Chelonia)
Authors: López David , Durán Ana C. , de Andrés A. Victoria , Guerrero Alejandro , Blasco Manuel , Sans‐Coma Valentín
Published: August 2003

Cartilaginous deposits are regularly present in the heart of several reptilian, avian, and mammalian species. The formation of these extraskeletal cartilages has been studied in birds and mammals, but not in reptiles. The aim here was to elucidate this question in the Spanish terrapin. Hearts from 23 embryos belonging to Yntema (1968) developmental stages 17 to 26 and eight terrapins age 3 months to 10 years were examined using histological, histochemical, and immunohistochemical techniques. In the heart of the Spanish terrapin (Mauremys leprosa), chondrogenesis can start during embryonic life. Cartilaginous tissue develops from a mesenchymal cellular condensation that extends along the aorticopulmonary septum and the incipient pars fibrosa of the ventricular horizontal septum. This cellular condensation, which is smooth muscle α‐actin (SMα‐actin)‐negative and type II collagen‐negative during stages 17 to 22, acts as a prechondrogenic condensation. In stage 23, production of type II collagen begins in the central core of the condensation and gradually spreads toward its periphery. The type II collagen‐positive (chondrogenic) cellular condensation remains devoid of perichondrium prior to birth. Thereafter, it converts into hyaline cartilage that extends along the proximal part of the aorticopulmonary septum and the pars fibrosa of the horizontal septum. Our findings are consistent with the assumption that, as in birds and mammals, the precursors of the cardiac chondrocytes in chelonians are neural crest‐derived cells of nonmuscular nature. In addition, they point to the possibility that cells from the neural crest populate the embryonic pars fibrosa of the horizontal septum, thereby contributing to its alignment with the aorticopulmonary septum. In the present species, a second cartilaginous deposit of a hyaline nature extends along the sinus wall of the right semilunar valve of the right aorta, penetrating the fibrous cushion that constitutes the proximal support of the corresponding valve leaflet. This cartilage develops after birth, between the third and eighteenth month of life; its morphogenetic origin is unclear. The cartilaginous foci occurring in hearts of Spanish terrapin appear to act as pivots resisting mechanical tensions generated during the cardiac cycle. In the specimens examined there was no sign of replacement of the cardiac cartilages by bone tissue. J. Morphol. 258:97–105, 2003. © 2003 Wiley‐Liss, Inc.
The role of the oceans in climate
Authors: Bigg G. R. , Jickells T. D. , Liss P. S. , Osborn T. J.
Published: August 2003

The ocean is increasingly seen as a vital component of the climate system. It exchanges with the atmosphere large quantities of heat, water, gases, particles and momentum. It is an important part of the global redistribution of heat from tropics to polar regions keeping our planet habitable, particularly equatorward of about 30°. In this article we review recent work examining the role of the oceans in climate, focusing on research in the Third Assessment Report of the IPCC and later. We discuss the general nature of oceanic climate variability and the large role played by stochastic variability in the interaction of the atmosphere and ocean. We consider the growing evidence for biogeochemical interaction of climatic significance between ocean and atmosphere. Air–sea exchange of several radiatively important gases, in particular CO2, is a major mechanism for altering their atmospheric concentrations. Some more reactive gases, such as dimethyl sulphide, can alter cloud formation and hence albedo. Particulates containing iron and originating over land can alter ocean primary productivity and hence feedbacks to other biogeochemical exchanges. We show that not only the tropical Pacific Ocean basin can exhibit coupled ocean–atmosphere interaction, but also the tropical Atlantic and Indian Oceans. Longer lived interactions in the North Pacific and Southern Ocean (the circumpolar wave) are also reviewed. The role of the thermohaline circulation in long‐term and abrupt climatic change is examined, with the freshwater budget of the ocean being a key factor for the degree, and longevity, of change. The potential for the Mediterranean outflow to contribute to abrupt change is raised. We end by examining the probability of thermohaline changes in a future of global warming. Copyright © 2003 Royal Meteorological Society
Seasonal and secular variations of sunshine duration and natural seasons in Japan
Authors: Inoue Tomoshige , Matsumoto Jun
Published: August 2003

Seasonal transitions of sunshine duration and their secular changes in Japan are investigated for the period 1951–2000, and the influence of climatic variations on seasonal weather tendencies is discussed. Two seasons with little sunshine in the Baiu and the Akisame seasons are recognized in central and western Japan (CW Japan). In northern Japan, however, only one season with little sunshine in summer is seen. Another season with little sunshine is recognized for the Sea of Japan side and the Southwest Islands during the winter monsoon season.

The sunshine duration from spring to autumn in northern Japan decreased in the late 1980s and the 1990s, and the period of little sunshine in summer has become longer since the mid 1980s. In CW Japan, sunshine in late spring in the 1950s and the early 1960s was less than that in other years. A rapid increase in sunshine duration which corresponds with the end of the Baiu rainy season has been delayed since 1980. The period in midsummer with little sunshine has also appeared more frequently than it did before 1980. In the Southwest Islands, sunshine duration has been decreasing almost all through the year. When comparing the differences between the Sea of Japan side and the Pacific Ocean side in winter, the sunshine contrast between them has intensified recently.

By using sunshine duration, an objective classification of six natural seasons in CW Japan is conducted. Then, the long‐term change of seasonal march in CW Japan is investigated. The end dates of the Baiu season after 1980 have been delayed by about 5 days compared with those before 1980. From the viewpoint of sunshine contrasts between the Sea of Japan side and the Pacific Ocean side, the winter monsoon season in Japan has become longer in recent years, even under the warming trend of winter temperature. Copyright © 2003 Royal Meteorological Society
Urbanization and seasonal temperature trends: observational evidence from a data‐sparse part of North America
Authors: Englehart Phil J. , Douglas Arthur V.
Published: August 2003

Viewed from the continental or hemispheric perspective, the evidence of warming trends in surface temperatures continues to accumulate. Here, we focus on the detection of seasonal temperature trends at regional and sub‐regional space scales. The study region is transnational, extending from the border areas of New Mexico and Texas in the USA, southward into the altiplano of north central Mexico. The analysis considers maximum and minimum temperature records (1941–2000) from 21 stations located in a variety of land‐use environments ranging from large urban settings to rural areas. The analysis demonstrates that a significant part of the variability in minimum temperatures for stations located in large urban areas is captured by positive linear trend, and thus is likely associated with rapid urbanization within the region. A similar, but comparatively minor, urban effect is also apparent in the maximum temperature records for the warm season (June–September). Aside from the urban influence, the most consistent feature emerging from the analysis is the tendency for station records to exhibit a recent (post—1970) warming trend. It is present across all place sizes, i.e. from large urban to rural stations, and is particularly pronounced for cool‐ and warm‐season minimum temperatures and for warm‐season maximum temperatures. This behaviour generally mirrors the temperature trends detected on continental and hemispheric space scales, and thus the onset of this warming regime is broadly consistent with documented changes in large‐scale climate modes such as the North Atlantic oscillation and the Atlantic multi‐decadal oscillation. Copyright © 2003 Royal Meteorological Society
The annual cycle and interannual variability of atmospheric pressure in the vicinity of the North Pole
Authors: Cullather Richard I. , Lynch Amanda H.
Published: August 2003

A comparison of National Centers for Environmental Prediction–National Center for Atmospheric Research reanalysis six‐hourly sea‐level pressure data with former Soviet drifting station observations over the central Arctic Basin reveals high monthly correlations throughout the period 1950–91, but also a preferred winter season negative bias of about 1.4 hPa. Using the reanalysis, supplemented by Arctic Ocean Buoy Program fields and in situ observations, a generalized depiction of the annual cycle of pressure fields over the Arctic may be constructed. Above the Canada Basin–Laptev Sea side of the Arctic, the annual cycle of surface pressure is dominated by the first harmonic, which has an amplitude of about 5 hPa and maximum pressure occurring in March. Along the periphery of northern Greenland and extending to the North Pole, a weak semiannual cycle is found in surface pressure with maxima in May and November. The presence of the semiannual variation over time is highly variable.

Dynamically, this progression of the annual cycle may be attributed to the transfer of atmospheric mass from Eurasia and into the Canadian Archipelago in spring and the reverse condition in autumn. Over the central Arctic Basin, springtime pressure increases result from an enhanced poleward mass transport from Eurasia. An increase of equatorward transport over the Canadian Archipelago in May and June results in central Arctic pressure decreases into summer. A less distinct temporal separation between the poleward Canadian transport and the equatorward Eurasian transport results in the weaker second pressure maximum in autumn.

On interannual time‐scales, atmospheric mass over the central Arctic is exchanged with the storm track centres of action in the North Atlantic and North Pacific. In particular, the large decrease in central Arctic Basin sea‐level pressure during the late 1980s is due to a large transfer of atmospheric mass into the North Pacific. Copyright © 2003 Royal Meteorological Society
The role of alloying elements in commercial alloys for corrosion resistance in oxidizing‐chloridizing atmospheres. Part I: Literature evaluation and thermodynamic calculations on phase stabilities
Authors: Bender R. , Schütze M.
Published: August 2003

In several high temperature processing environments the presence of chlorine may significantly reduce the life‐time of the components. Although metallic materials have been widely used under such conditions there is still a need for data on the role of the different alloying elements in commercial alloys. In the present work this role was investigated in detail at temperatures between 650 and 1000°C in synthetic air containing up to 2 vol.% Cl2. Before starting the experimental investigation a detailed literature evaluation on chlorine high temperature corrosion was performed followed by a thermodynamic assessment of the stability and the partial pressures of the phases formed by the reaction between alloy and environment. The results of this “theoretical approach” are presented in the following first part of the publication while the experimental work will be reported in the second part appearing in a later issue of this journal. Already the results of the “theoretical approach” yield a clear picture of which alloying elements play a detrimental role and which elements are beneficial. These results can be used as a tool for a general assessment of metallic alloys with regard to their performance in oxidizing/chloridizing high temperature environments. In the second part of this work the results from this “theoretical approach” will be compared with the behavior of 14 commercial materials, where the content of the major alloying elements was varied in a systematic manner.
The influence of NaCl and CO2 on the atmospheric corrosion of magnesium alloy AZ91
Authors: Lindström R. , Johansson L.‐G. , Svensson J.‐E.
Published: August 2003

The influence of NaCl and CO2 on the atmospheric corrosion of magnesium alloy AZ91 is studied in the laboratory. Samples were exposed under carefully controlled air and flow conditions; the relative humidity was 95%, the temperature was 22.0°C and the concentration of CO2 was < 1 ppm or 350 ppm. Different amounts of sodium chloride (0–70 μg/cm2) were added before exposure. The corrosion products were analyzed by gravimetry, ion chromatography, X‐ray diffraction and scanning electron microscopy. Mass gain and metal loss results are reported. The combination of high humidity and NaCl is very corrosive towards AZ91. However, the NaCl‐induced corrosion is inhibited by ambient concentrations of CO2. Exposure in the absence of CO2 gives rise to heavy pitting, with brucite, Mg(OH)2, being the dominant corrosion product. In the presence of CO2 a layer of hydrated magnesium hydroxy carbonate, Mg5(CO3)4(OH)2 · 5 H2O forms. A tentative corrosion mechanism is presented that explains the behavior in the two environments.
Prediction of the remaining lifetime of stainless steels under conditions of stress corrosion cracking
Authors: Tandler M. , Vehovar L. , Doleček V. , Rotnik U.
Published: August 2003

The prediction of the lifetime of metal structures and equipment under conditions of stress corrosion is very complicated because of the complexity of this process of degradation. Recently a new method, based on the so‐called corrosion elongation curves, has been found, which can be used to predict the time to failure under these conditions. By upgrading of these curves (and thus obtaining Upgraded Corrosion Elongation Curves – UCEC's) it has been possible to obtain a precise definition of the time needed for the initiation of the corrosion crack, and for its stable growth. It is upon this basis that diagrams for the prediction of remaining lifetime (DPRL's) have been developed. DPRL's can also be used to predict the values of various critical parameters which have to be achieved if a stress corrosion crack is to occur.
Carbon and stainless steel in solutions of lithium nitrate in ammonia at moderate temperatures
Authors: Heard C. L. , Ayala R.
Published: August 2003

The lithium nitrate in ammonia solution has been proposed and demonstrated as a thermodynamically attractive working mixture for absorption heat pumps. A literature search failed to find corrosion studies of said solution. The corrosion of carbon and stainless steel in solutions of lithium nitrate in ammonia was studied for a series of concentrations and temperatures from 50 to 150°C. The materials studied were found to be suitable for construction of absorption heat pump process equipment for this working mixture.
Charakterisierung von Randentkohlungsvorgängen bei der Austenitisierung des Wälzlagerstahls 100Cr6. Teil 1: Korrelation zwischen Randschichteigenschaften und Kohlenstoff‐Tiefenverlauf
Authors: Gegner J. , Nierlich W. , Wilbrandt P.‐J. , Kirchheim R. , Öchsner A.
Published: August 2003

Der Einfluss einer Randentkohlung bei der Austenitisierung des durchhärtenden Wälzlagerstahls 100Cr6 (SAE 52100) auf die Randschichteigenschaften des martensitisch durchgehärteten Werkstoffs wurde mittels Materialanalytik und Diffusionsrechnungen untersucht. Dazu wurde in zwei Proben nach definierter Wärmebehandlung die oberflächennahe Kohlenstoffverteilung mikrochemisch mittels Sekundärionenmassenspektrometrie (SIMS) bestimmt. In Teil 1 der vorliegenden Arbeit werden diese Konzentrationsprofile mit den Tiefenverläufen der Kleinlasthärte sowie der durch Röntgenbeugung gemessenen Eigenspannungen und Halbwertsbreiten ({211} α'‐Fe Beugungslinie) verglichen. Zusätzlich wurden Gefügeuntersuchungen durchgeführt. In Teil 2 wird ein auf der Finite‐Elemente‐Methode (FEM) beruhendes verfeinertes Kinetikmodell für eine diffusionsgesteuerte Reaktion auf die Randentkohlung angewendet, um die erhaltenen Kohlenstoffverteilungen zu beschreiben.
Charakterisierung von Randentkohlungsvorgängen bei der Austenitisierung des Wälzlagerstahls 100Cr6. Teil 2: Modellierung des Kohlenstoff‐Tiefenverlaufs mit Hilfe der Methode der Finiten Elemente
Authors: Gegner J. , Nierlich W. , Öchsner A. , Wilbrandt P.‐J. , Kirchheim R.
Published: August 2003

Die quantitative Messung von Kohlenstoff‐Tiefenverläufen stellt eine wesentliche Voraussetzung zur werkstoffkundlichen Beurteilung von Randschichteigenschaften bei Entkohlungsvorgängen dar. Dies wurde in Teil 1 der vorliegenden Arbeit an zwei in unterschiedlich oxidierender Atmosphäre austenitiserten Proben aus durchhärtendem Wälzlagerstahl 100Cr6 (SAE 52100) durch abstandsabhängige Bestimmung der Härte, Eigenspannungen und röntgenographischen Halbwertsbreiten ({211} α’‐Fe Beugungslinie) gezeigt. In der Praxis ist es wichtig, Kohlenstoff‐Konzentrationsverläufe unter herrschenden Wärmebehandlungsbedingungen vorherzusagen oder darauf anhand von Profilmessungen zurückzuschließen. Deshalb stellt Teil 2 ein mit Hilfe der Finite‐Elemente‐Methode (FEM) entwickeltes Simulationswerkzeug vor, das auf einem verfeinerten Kinetikmodell für einen diffusionsgesteuerten Prozess beruht. Es berücksichtigt neben der Konzentrationsabhängigkeit des Diffusionskoeffizienten auch die entkohlungsbedingte Austenit‐Ferrit‐Phasenumwandlung, den zeitlich veränderlichen Einfluss der Verzunderung und variierende Atmosphärenverhältnisse. Die Interpretation der mittels Sekundärionenmassenspektrometrie (SIMS) in der Randschicht der beiden 100Cr6‐Proben sehr genau gemessenen Kohlenstoff‐Tiefenverläufe bestätigt die Anwendungsmöglichkeiten des neuen numerischen Werkzeugs.
Mikrostrukturelle Veränderungen von Magnesium‐Druckgusslegierungen nach langzeitiger thermischer Beanspruchung
Authors: Regener D. , Schick E. , Heyse H.
Published: August 2003

Die Erweiterung des Anwendungsbereiches von Magnesium‐Druckgusslegierungen im Automobilbau erfordert die Entwicklung neuer Legierungen, aber auch die umfassende Beurteilung vorhandener Legierungen unter verschärften Beanspruchungsbedingungen. Unter derartigen Bedingungen ist auch der Einsatz bei höheren Temperaturen zu verstehen, bei dem ein Kriechen des Werkstoffs zum Versagen des Bauteils führen kann.

Da die Gefügestabilität der Werkstoffe maßgeblich von der thermischen Belastung abhängt, werden im vorliegenden Beitrag die Legierungen AZ91, AM50 und AE42 einer 1000 h‐Langzeitglühung bei 150 °C und 200 °C unterworfen und die Veränderungen des Gefüges und der Härte im Vergleich zum druckgegossenen Ausgangszustand untersucht.

Die Ergebnisse zeigen starke Unterschiede in der Gefügestabilität der Legierungen AZ91 und AM50 einerseits und der Legierung AE42 andererseits. In den Legierungen AZ91 und AM50 wird infolge des Langzeitglühens bei 150 °C vor allem eine intensive Ausscheidung von Mg17Al12 aus der Al‐reichen eutektischen α‐Phase, bei 200 °C darüber hinaus auch die Koagulation und Vergröberung dieser Ausscheidungen beobachtet, die mit einer Erweichung des Werkstoffes einhergehen. In der Legierung AE42 sind die Veränderungen im Ausscheidungszustand weniger intensiv und führen unter den genannten Untersuchungsbedingungen noch nicht zur Gefügeerweichung.
Practicability and Limitations of Finite Element Simulation of the Dilation Behaviour of Coronary Stents
Authors: Stolpmann J. , Brauer H. , Stracke H.‐J. , Erbel R. , Fischer A.
Published: August 2003

After first implantation of a metallic stent into cardiac vessels in 1986 stent implantation has become a standard technique for treatment of coronary heart disease. During implantation of balloon‐expandable stents, the structure of the stent undergoes high plastic deformation. Despite the fact, that stents are used for more than 15 years nearly no information about the mechanical and micro structural process during dilation are known. The present paper presents a detailed study and comparison of the experimental and the simulated expansion behaviour of metallic stents. Used material models are discussed and crystallographic details are presented. Dilation curves describe the behaviour of balloon‐expandable coronary stents. The dilation behaviour depends on both the materials properties and the design of the stent. A numerical simulation of the dilation process by means of FE is suitable. A comparison of the experimental measurement and the numerical simulation demonstrates, that a Cauchy stress‐strain material model should be used for numerical simulations. A local failure criterion is introduced, which considers void initiation as a criterion for mechanical failure.