bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crystals and Life
Authors: Arrhenius Gustaf O. 
Published: June 2003

AbstractThe record of life's emergence on Earth has been thoroughly obliterated by the remelting and turnover of the crust, soggy and pliable from the water, retained by the planet's gravitational field. Provided that life existed on a smaller body such as Mars with an arrested crustal evolution, a protected sedimentary record there may give clues to the decisive events in the first 500 million years in the history of our solar system. Until such records become available, we have in our guesswork to rely on laboratory constructions that need to satisfy the demands both of chemical feasibility and environmental boundary conditions. The combination leaves few survivors among competing hypotheses.
As life entails a decrease in entropy and creation of order, the origin and propagation of crystalline order has become a guiding theoretical concept. Recognizing Jack Dunitz's fundamental contribution to this field of knowledge, I wish to dedicate my modest discourse to this great scientist upon his scoring of the fourth significant time mark on the staff of life.
Structural Effects of Group VI Metal Tricarbonyl Binding to Benzenoid Rings: Interruption of Conjugation or Enhanced Aromaticity?
Authors: Baldridge Kim K. , Nambu Mitch , Siegel Jay S. 
Published: June 2003

AbstractThe effect of tricarbonyl (group VI metal) complexation on the geometric aromatic character of benzenoid rings is studied as a function of bond‐length alternation (localization) in the parent arene. Good agreement between theory and experiment is established for (η6‐benzene) tricarbonylchromium, ‐molybdenum, and ‐tungsten. It is found that, whereas the electrons of benzene become slightly more localized upon tricarbonyl metal complexation, those of ‘cyclohexatriene' mimics, like in‐starphenylene, become more delocalized. A combination of ab initio quantum‐mechanical and high‐accuracy X‐ray methods leads to a linear structurestructure correlation between the free and metal‐bound arene bond‐alternation geometry. In all cases, the average bond length in the arene increases upon complexation. The computational observation that the average bond length increases more in benzene complexes than in in‐starphenylene implies stronger back bonding in the benzene complexes and coincides with the experimental observation that more‐delocalized arenes form thermodynamically favored complexes. The rotational barriers about the tricarbonylmetal‐to‐arene axis were computed for 1‐Cr, 1‐Mo, and 1‐W as well as for 5‐Cr, 5‐Mo, and 5‐W. Barriers for the former group are characteristically low, almost negligible (0.05 kcal/mol for 1‐Cr; 0.01 kcal/mol for 1‐Mo; 0.27 kcal/mol for 1‐W), whereas for the latter group they are substantial (11.2 kcal/mol for 5‐Cr; 15.2 kcal/mol for 5‐Mo; 13.6 kcal/mol for 5‐W). The higher barriers found in 5‐M compounds are consistent with previous findings.
Helicity‐Encoded Molecular Strands: Efficient Access by the Hydrazone Route and Structural Features
Authors: Schmitt Jean‐Louis , Stadler Adrian‐Mihail , Kyritsakas Nathalie , Lehn Jean‐Marie 
Published: June 2003

AbstractControl over the folding of molecular strands may be achieved by appropriate choice of the constituting subunits, in particular for chains of specific heterocycles such as sequences of directly connected pyridine (py) and pyrimidine (pym) rings, which are known to fold into extended helical structures. Since the hydrazone (hyz) group represents an isomorphic analogue of a py site, the condensation of hydrazine and carboxaldehyde derivatives of pym offers a very efficient approach to strands incorporating hyz instead of py units and constituted by sequences of alternating hyz and pym groups. A series of such strands of different lengths, up to ten hyz units, i.e., 1–7, were synthesized. Their spectral properties indicate that they fold indeed into helical shapes. Extensive characterization was performed in solution by 1HNMR spectroscopy and in the solid state by determination of the crystal structures of eight such strands. They all display the expected helical geometry with up to 3 1/3 turns and direct stacking contacts. The efficiency and flexibility of the synthetic approach as well as its wide potential for generation of diversity through lateral decoration make the (hyzpym) subunit a particularly attractive helicity codon.
Getting More out of Crystal‐Structure Analyses
Authors: Bürgi Hans‐Beat , Capelli Silvia C. 
Published: June 2003

AbstractMotion and disorder in the crystal structures of benzene, (D6)benzene, and the clathrate C60⋅(HQ)3 (HQ=hydroquinone=benzene‐1,4‐diol) are studied. The observed temperature evolution of their atomic displacement parameters (ADPs) is analyzed in terms of a physical model that explicitly accounts for effects of temperature. The major part of the ADPs of (D6)benzene is explained by rigid‐body normal modes. The small but significant fraction that remains is shown to be due to zero‐point intramolecular motion. Comparison of the ADPs of D‐ and H‐isotopomers of benzene confirms the expected isotopic relationship. These findings, which leave no room for disorder between two Kekulé structures, corroborate the validity of the physical model. An analogous treatment of the ADPs of the hydroquinone part of the clathrate compound reveals a distinctive disposition of displacements related neither to rigid‐body nor to zero‐point motion. The pattern is interpreted nearly quantitatively in terms of orientational and positional disorder of the hydroquinone molecule amounting to a few degrees and hundredths of an Ångström, respectively. The model of disorder accounts for unusual bond angles in the average structure and suggests a chemically sensible pattern of locally ordered H‐bonds.
The RE M E Phases
Authors: Bojin Mihaela D. , Hoffmann Roald 
Published: June 2003

AbstractThere are more than 2000 compounds with RE/M/E 1 : 1 : 1 stoichiometry, where RE is a rare earth, actinide, or from groups 1–4, E is a late transition metal from groups 8–12, and E belongs to groups 13–15. In the first paper of a series, we describe the primary structural characteristics of this large class of compounds, focusing on the geometries and bonding in the [ME]n− anionic sublattices. We start with a detailed description of the EuAuSn lattice, by emphasizing its essential building blocks and the symmetry operations connecting them, in order to set up a way of describing systematically the geometric features of other RE M E frameworks. Nearly all these phases have eclipsed hexagonal layered arrangements (with only ME bonds within these slabs) in the ME sublattice. In most cases, stacking the puckered layers in the third dimension gives rise to ME, MM, or EE bonds, alternating in certain patterns. We point to several interesting sets of RE M E compounds, of like structure, but whose electron counts vary significantly. The structures of nonlayered networks and their most‐common electron counts are also introduced.
The RE M E Phases
Authors: Bojin Mihaela D. , Hoffmann Roald 
Published: June 2003

AbstractIn the second contribution on the RE M E phases, we enumerate the distinct networks resulting from the stacking in an eclipsed fashion of graphitic and puckered layers. Specifically, we derive all the distinct hypothetical lattices for up to N=7 layers per unit cell for planar (graphitic) sheets, and up to N=10 for slightly puckered layers. For the networks with slightly puckered layers, there can be only an even number of layers/unit cell, N. Additionally, we formulate an empirical rule for network stability: the structure should have either a mirror plane or a twin operation (mirror plane, followed by a color change) bisecting it half‐way up the stacking axis. Using these simple principles, from the original multitude of 2N−1 structures for a given N, we are able to significantly narrow down the number of potential combinations. Thus, for N=2, we find two nets, for N=4, one, for N=6, two, for N=8, there are no such viable arrangements, and for N=10, we exclude all but two distinct lattices. We sketch further guidelines to continue the enumeration for higher Ns. We also propose an ‘overlapping' Aufbau, by which more‐complex structures are derived from the smaller, basic ones. In the last part, we analyze the eclipsed stacking of diamond‐type layers; the resulting networks are analogous (in sequencing) to those determined for slightly puckered sheets. The networks formed from staggered diamond‐type layers are briefly discussed in the context of the related SiC polytypes.
Any Scalene Triangle Is the Most Chiral Triangle
Authors: Rassat André , Fowler Patrick W. 
Published: June 2003

AbstractThe shape space of all possible triangles is represented by a triangular diagram, an analogue of the phase diagram for ternary mixtures. Each point of its interior corresponds to the angle set of a pair of (2D) enantiomeric physical triangles and, with appropriate conventions, to just one member of the pair. Points on median lines represent achiral triangles, those on sides represent degenerate chiral triangles, and those on vertices achiral degenerate linear triangles. A chirality index for triangles must vanish on these lines, but nowhere else within the six compartments of the diagram, and should alternate in sign between them. The archetype is the lowest A2‐symmetric eigenfunction of the Schrödinger equation for the particle confined to an equilateral triangular box. Within the constraints, the extrema of an acceptable function may be pushed onto any D3h‐symmetric hexagonal set of points in the diagram, thereby verifying a conjecture of Dunitz that any scalene triangle is the most‐chiral triangle for some legal 2D‐chirality index.
Face alignment using view‐based direct appearance models
Authors: Yan Shuicheng , Hou Xinwen , Li Stan Z. , Zhang Hongjiang , Cheng Qiansheng 
Published: June 2003

AbstractAccurate face alignment is the prerequisite for many computer vision problems, such as face recognition, synthesis and 3D face modeling. In this article, a novel appearance model, called direct appearance model (DAM), is proposed and its extended view‐based models are applied for multiview face alignment. Similar to the active appearance model (AAM), DAM also makes ingenious use of both shape and texture constraints; however, it does not combine them as in AAM; texture information is used directly to predict the shape and estimate the position and appearance (hence the name DAM). The way that DAM models shapes and textures has the following advantages as compared with AAM: (1) DAM subspaces include admissible appearances previously unseen in AAM, (2) it can converge more quickly and has higher accuracy, and (3) the memory requirement is cut down to a large extent. Extensive experiments are presented to evaluate the DAM alignment in comparison with AAM. © 2003 Wiley Periodicals, Inc. Int J Imaging Syst Technol 13: 106–112, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.10039
How we detect a face: A survey of psychological evidence
Authors: Lewis Michael B. , Ellis Hadyn D. 
Published: June 2003

AbstractScientists strive to build systems than can detect and recognize faces. One such system already exists: the human brain. How this system operates, however, is far from being fully understood. In this article, we review the psychological evidence regarding the process of face detection in particular. Evidence is collated from a variety of face‐processing tasks including stimulus detection; face categorization, visual search, first saccade analysis, and face detection itself. Together, the evidence points towards a multistage‐processing model of face detection. These stages involve preattentive processing, template fitting, and template evaluation. Comparisons are made with automatic face‐detection systems. © 2003 Wiley Periodicals, Inc. Int J Imaging Syst Technol 13, 3–7, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.10040
Modeling and animation of individualized faces for 3D facial expression synthesis
Authors: Zhang Yu , Prakash Edmond C. , Sung Eric 
Published: June 2003

AbstractThis article presents new methods for realistic and fast 3D facial expression synthesis based on an individualized face model constructed from the anatomical perspective. The face model has a 3D structure of anatomically motivated facial skin, muscles, and skull. We start from a highly accurate facial mesh reconstructed from the individual face measurements. By taking as input a collection of reflectance images covering the face, the view‐based texture blending method automatically generates a comprehensive texture map for photorealistic rendering. Based on the reconstructed facial mesh, a deformable multilayer skin model is developed to simulate the dynamic behavior of the skin by taking into account the nonlinear stress‐strain relationship and incompressibility of the skin. We develop a muscle modeling process that includes three kinds of force‐based facial muscle model to simulate facial muscle contraction. The 3D face model incorporates a skull structure which extends the scope of facial motion, facilitates facial muscle construction and constrains skin deformation. Based on the facial action coding system, various facial expressions are synthesized by the contraction of a set of facial muscles. Lagrangian mechanics governs the dynamics, dictating the deformation of facial skin in response to the contraction of muscles. For computational efficiency, we devise an adaptive computation algorithm for the numerical simulation. It uses either a semi‐implicit integration scheme or a quasi‐static solver to compute the relaxation of the facial mesh by traversing the designed data structures in a breadth‐first order. The resulting system enables us to construct realistic face models of living humans and to synthesize facial expressions in real time. © 2003 Wiley Periodicals, Inc. Int J Imaging Syst Technol 13: 42–64, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.10041
Face tracking for model‐based coding and face animation
Authors: Ahlberg Jörgen , Forchheimer Robert 
Published: June 2003

AbstractWe present a face and facial feature tracking system able to extract animation parameters describing the motion and articulation of a human face in real‐time on consumer hardware. The system is based on a statistical model of face appearance and a search algorithm for adapting the model to an image. Speed and robustness is discussed, and the system evaluated in terms of accuracy. © 2003 Wiley Periodicals, Inc. Int J Imaging Syst Technol 13: 8–22, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.10042
Synthetic faces: Analysis and applications
Authors: Kshirsagar Sumedha , Garchery Stephane , Sannier Gael , Magnenat‐Thalmann Nadia 
Published: June 2003

AbstractFacial animation has been a topic of intensive research for more than three decades. Still, designing realistic facial animations remains to be a challenging task. Several models and tools have been developed so far to automate the design of faces and facial animations synchronized with speech, emotions, and gestures. In this article, we take a brief overview of the existing parameterized facial animation systems. We then turn our attention to facial expression analysis, which we believe is the key to improving realism in animated faces. We report the results of our research regarding the analysis of the facial motion capture data. We use an optical tracking system that extracts the 3D positions of markers attached at specific feature point locations. We capture the movements of these face markers for a talking person. We then form a vector space representation by using the principal component analysis of this data. We call this space “expression and viseme space.” As a result, we propose a new parameter space for sculpting facial expressions for synthetic faces. Such a representation not only offers insight into improving realism of animated faces, but also gives a new way of generating convincing speech animation and blending between several expressions. Expressive facial animation finds a variety of applications ranging from virtual environments to entertainment and games. With the advances in Internet technology, the development of online sales assistants, Web navigation aides and Web‐based interactive tutors is promising than ever before. We overview the recent advances in the field of facial animation on the Web, with a detailed look at the requirements for Web‐based facial animation systems and various applications. © 2003 Wiley Periodicals, Inc. Int J Imaging Syst Technol 13: 65–73, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.10043
Audiovisual localization of multiple speakers in a video teleconferencing setting
Authors: Kapralos Bill , Jenkin Michael R. M. , Milios Evangelos 
Published: June 2003

AbstractAttending to multiple speakers in a video teleconferencing setting is a complex task. From a visual point of view, multiple speakers can occur at different locations and present radically different appearances. From an audio point of view, multiple speakers may be speaking at the same time, and background noise may make it difficult to localize sound sources without somea prioriestimate of the sound source locations. This article presents a novel sensor and corresponding sensing algorithms to address the task of attending, simultaneously, to multiple speakers for video teleconferencing. A panoramic visual sensor is used to capture a 360° view of the speakers in the environment and from this view potential speakers are identified via a color histogram approach. A directional audio system based on beamforming is then used to confirm potential speakers and attend to them. Experimental evaluation of the sensor and its algorithms are presented including sample performance of the entire system in a teleconferencing setting. © 2003 Wiley Periodicals, Inc. Int J Imaging Syst Technol 13: 95–105, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.10045
Face as an index: Knowing who is who using a PDA
Authors: Yang Jie , Chen Xilin , Kunz William , Kundra Harsh 
Published: June 2003

AbstractIn this article, we present a PDA‐based system for extending human memory or/and information retrieval using a human face as the lookup index. The system can help a user to remember names of people whom he/she has met before and find useful information, such as names and research interests, about people whom he/she is interested in talking to. The system uses a captured face image as the lookup index to retrieve information from some available resource such as departmental directory, web sites, personal homepages, etc. We describe the development of a PDA‐based face recognition system and introduce algorithms for image preprocessing to enhance the quality of the image by sharpening focus and normalizing both lighting condition and head rotation. We use a unified LDA/PCA algorithm for face recognition. We address design issues of the interface to assist in visualization and comprehension of retrieved information. We present user study and experiment results to demonstrate the feasibility of the proposed system. © 2003 Wiley Periodicals, Inc. Int J Imaging Syst Technol 13: 33–41, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.10046
Face recognition based on face‐specific subspace
Authors: Shan Shiguang , Gao Wen , Zhao Debin 
Published: June 2003

AbstractIn this article, we present an individual appearance model based method, named face‐specific subspace (FSS), for recognizing human faces under variation in lighting, expression, and viewpoint. This method derives from the traditional Eigenface but differs from it in essence. In Eigenface, each face image is represented as a point in a low‐dimensional face subspace shared byallfaces; however, the experiments conducted show one of the demerits of such a strategy: it fails to accurately represent the most discriminanting features of a specific face. Therefore, we propose to model each face with one individual face subspace, named Face‐Specific Subspace. Distance from the face‐specific subspace, that is, the reconstruction error, is then exploited as the similarity measurement for identification. Furthermore, to enable the proposed approach to solve the single example problem, a technique to derive multisamples from one single example is further developed. Extensive experiments on several academic databases show that our method significantly outperforms Eigenface and template matching, which intensively indicates its robustness under variation in illumination, expression, and viewpoint. © 2003 Wiley Periodicals, Inc. Int J Imaging Syst Technol 13: 23–32, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ima.10047
Erratum: Pyramid‐based super‐resolution of the undersampled and subpixel image sequence, vol. 12, no. 6, pp. 254–263, 2002
Authors: Lu Yao , Inamura Minoru 
Published: June 2003

AbstractThe original article to which this Erratum refers was published in International Journal of Imaging Systems and Technology (2002) 12(6) 254–263
An error was made in the spelling of the second author's name for the online version of the above article. Please note the correct spelling should be as above: Inamura. We apologize to the author for this error.
Putative role of proteolysis and inﬂammatory response in the toxicity of nerve and blister chemical warfare agents: implications for multi‐threat medical countermeasures
Authors: Cowan F. M. , Broomﬁeld C. A. , Lenz D. E. , Smith W. J. 
Published: June 2003

AbstractDespite the contrasts in chemistry and toxicity, for blister and nerve chemical warfare agents there may be some analogous proteolytic and inﬂammatory mediators and pathological pathways that can be pharmacological targets for a single‐drug multi‐threat medical countermeasure. The dermal–epidermal separation caused by proteases and bullous diseases compared with that observed following exposure to the blister agent sulfur mustard (2,2′‐dichlorodiethyl sulﬁde) has fostered the hypothesis that sulfur mustard vesication involves proteolysis and inﬂammation. In conjunction with the paramount toxicological event of cholinergic crisis that causes acute toxicity and precipitates neuronal degeneration, both anaphylactoid reactions and pathological proteolytic activity have been reported in nerve‐agent‐intoxicated animals. Two classes of drugs already have demonstrated multi‐threat activity for both nerve and blister agents. Serine protease inhibitors can prolong the survival of animals intoxicated with the nerve agent soman and can also protect against vesication caused by the blister agent sulfur mustard. Poly (ADP‐ribose) polymerase (PARP) inhibitors can reduce both soman‐induced neuronal degeneration and sulfur‐mustard‐induced epidermal necrosis. Protease and PARP inhibitors, like many of the other countermeasures for blister and nerve agents, have potent primary or secondary anti‐inﬂammatory pharmacology. Accordingly, we hypothesize that drugs with anti‐inﬂammatory actions against either nerve or blister agent might also display multi‐threat efﬁcacy for the inﬂammatory pathogenesis of both classes of chemical warfare agent. Published in 2003 by John Wiley & Sons, Ltd.