bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photonic Crystals—A Step towards Integrated Circuits for Photonics
Authors: Thylén Lars , Qiu Min , Anand Srinivasan 
Published: September 2004

AbstractThe field of photonic crystals has, over the past few years, received dramatically increased attention. Photonic crystals are artificially engineered structures that exhibit a periodic variation in one, two, or three dimensions of the dielectric constant, with a period of the order of the pertinent light wavelength. Such structures in three dimensions should exhibit properties similar to solid‐state electronic crystals, such as bandgaps, in other words wavelength regions where light cannot propagate in any direction. By introducing defects into the periodic arrangement, the photonic crystals exhibit properties analogous to those of solid‐state crystals. The basic feature of a photonic bandgap was indeed experimentally demonstrated in the beginning of the 1990s, and sparked a large interest in, and in many ways revitalized, photonics research. There are several reasons for this attention. One is that photonic crystals, in their own right, offer a proliferation of challenging research tasks, involving a multitude of disciplines, such as electromagnetic theory, nanofabrication, semiconductor technology, materials science, biotechnology, to name a few. Another reason is given by the somewhat more down‐to‐earth expectations that photonics crystals will create unique opportunities for novel devices and applications, and contribute to solving some of the issues that have plagued photonics such as large physical sizes, comparatively low functionality, and high costs. Herein, we will treat some basics of photonic crystal structures and discuss the state‐of‐the‐art in fabrication as well give some examples of devices with unique properties, due to the use of photonic crystals. We will also point out some of the problems that still remain to be solved, and give a view on where photonic crystals currently stand.
Theoretical Study of the Reactions of CF3OCHF2 with the Hydroxyl Radical and the Chlorine Atom
Authors: Wu Jia‐yan , Liu Jing‐yao , Li Ze‐sheng , Sun Chia‐chung 
Published: September 2004

AbstractTheoretical investigations are carried out on the reaction mechanism of the reactions of CF3OCHF2 (HFOC‐125) with the OH radicals and Cl atoms, as well as the heats of formation of CF3OCHF2 and CF3OCF2. The electronic structure information on the potential energy surface for each reaction is obtained at the B3LYP/6–311G(d,p) level, and energetic information is further refined by G3(MP2) theory. The direct dynamics calculation of the hydrogen abstraction reactions are also performed at the G3(MP2)//B3LYP/6–311G(d,p) level. The classical energy profile is corrected by interpolated single‐point energies (ISPE) approach, incorporating the small‐curvature tunnelling effect (SCT) calculated by the variational transition‐state theory (VTST). The rate constants are in good agreement with the experimental data and are found to be k1=4.95×10−30 T5.40 exp(−347/T) and k2=1.86×10−23 T3.43 exp(−1579/T) cm3 molecule−1 s−1 over the temperature range 200–2000 K. The rate constants at 298 K for these two reactions are 3.38×10−16 and 2.80×10−17 cm3 molecule−1 s−1, respectively. Using group‐balanced isodesmic reactions as working chemical reactions, the standard enthalpies of formation for CF3OCHF2 and CF3OCF2 are −312.3±1.0 and −257.3±1.0 kcal mol−1, respectively, evaluated by G3(MP2) theory based on the B3LYP/6–311G(d,p) geometries. The theoretical studies provide rate constants of the title reactions and the enthalpies of the species, which are important parameters in determining the atmospheric lifetime and the feasible pathways for the loss of HFOC‐125.
The Origin of Aromaticity: Important Role of the Sigma Framework in Benzene
Authors: Kovačević Borislav , Barić Danijela , Maksić Zvonimir B. , Müller Thomas 
Published: September 2004

AbstractThe physical nature of aromaticity is addressed at a high ab initio level. It is conclusively shown that the extrinsic aromatic stabilization energy of benzene E(ease)B, estimated relative to its linear polyene counterpart(s), is very well‐reproduced at the Hartree–Fock (HF) level. This is a consequence of the fact that the contributions arising from the zero‐point vibrational energy (ZPVE) and electron correlation are rather small. More specifically, they yield together 2.0 kcal mol−1 to the destabilization of benzene. A careful scrutiny of the HF energies by virial theorem shows further that the kinetic energies of the σ and π electrons E(T)${{{\sigma \hfill \atop HF\hfill}}}$ and E(T)${{{{\rm \pi} \hfill \atop HF\hfill}}}$ are strictly additive in the gauge linear zig‐zag polyenes, which also holds for their sum Et(T)HF. This finding has the important corollary that E(ease)B is little dependent on the choice of the homodesmic reactions involving zig‐zag polyenes. A detailed physical analysis of the σ‐ and π‐electron contributions to extrinsic aromaticity requires explicit introduction of the potential energy terms Vne, Vee, and Vnn, which signify Coulomb interactions between the electrons and the nuclei. The Vee term involves repulsive interaction V${{{{\rm \sigma} {\rm \pi} \hfill \atop ee\hfill}}}$ between the σ and π electrons, which cannot be unequivocally resolved into σ and π contributions. The same holds for the Vnn energy, which implicitly depends on the electron density distribution via the Born–Oppenheimer (BO) potential energy surface. Several possibilities for partitioning V${{{{\rm \sigma} {\rm \pi} \hfill \atop ee\hfill}}}$ and Vnn terms into σ and π components are examined. It is argued that the stockholder principle is the most realistic, which strongly indicates that E(ease)B is a result of favorable σ‐framework interactions. In contrast, the π‐electron framework prefers the open‐chain linear polyenes.
Quantum Dynamics Study of the Excited‐State Double‐Proton Transfer in 2,2′‐Bipyridyl‐3,3′‐diol
Authors: Gelabert Ricard , Moreno Miquel , Lluch José M. 
Published: September 2004

AbstractDensity functional theory and quantum dynamics simulations have been used to study the double‐proton transfer reaction in 2,2′‐bipyridyl‐3,3′‐diol in the first singlet excited electronic state. This process is experimentally known to be branched: It consists of a fast, concerted reaction mechanism (τ≈100 fs) and a stepwise reaction mechanism [with a fast initial step (τ≈100 fs) and a slower final step (τ≈10 ps)]. Quantum dynamics simulations on a two‐dimensional model reveal that the concerted reaction occurs despite the nonexistence of a concerted reaction path, but they fail to explain the relative slowness of the stepwise mechanism. A qualitative simulation using a three‐dimensional model suggests that internal vibrational relaxation (IVR) might be the reason why the second stage of the stepwise mechanism is so slow.
Local Dense Structural Heterogeneities in Liquid Water from Ambient to 300 MPa Pressure: Evidence for Multiple Liquid–Liquid Transitions
Authors: Khoshtariya Dimitri E. , Zahl Achim , Dolidze Tina D. , Neubrand Anton , van Eldik Rudi 
Published: September 2004

AbstractDifference and double‐difference near‐infrared DO–D and HO–H stretching overtone (2νOD and 2νOH) spectroscopy and a rigorous (physically substantiated) band deconvolution technique were applied to reveal three different kinds of inherent (interstitial) structures of liquid water, which determine its high density (compared to ice Ih under ambient conditions), its compressibility (under hydrostatic pressure, up to 300 MPa), and its high fragility (manifested under temperature variation). Our data processing allowed the rigorous discrimination of up to six vibrational components. On the basis of an extensive comparative analysis combined with available structural data (X‐ray and neutron scattering) and molecular dynamics (MD) simulations for liquid water, as well as with experimental and computed data for small non‐tetrahedrally arranged water clusters, the major four components could be ascribed to: i) The basic Ih icelike substructure; ii) the temperature‐dependent remote interstitial “defects” due to tetrahedral displacements (primarily responsible for transport properties); iii) the interstitial “defects” most probably arranged in quasiplanar noncyclic tetramers (totally absent in the ice structure); and iv) the interstitial “defects” formed with increasing pressure, probably arranged in cubic water octamers and composed of two pairs of noncyclic and cyclic tetramer fragments. The latter structures include, essentially, bent hydrogen bonds stabilized by resonance effects.
A comparison of CBT and EMDR for sexually‐abused Iranian girls
Authors: Jaberghaderi Nasrin , Greenwald Ricky , Rubin Allen , Zand Shahin Oliaee , Dolatabadi Shiva 
Published: September 2004

AbstractFourteen randomly assigned Iranian girls ages 12–13 years who had been sexually abused received up to 12 sessions of CBT or EMDR treatment. Assessment of post‐traumatic stress symptoms and problem behaviours was completed at pre‐treatment and 2 weeks post‐treatment. Both treatments showed large effect sizes on the post‐traumatic symptom outcomes, and a medium effect size on the behaviour outcome, all statistically significant. A non‐significant trend on self‐reported post‐traumatic stress symptoms favoured EMDR over CBT. Treatment efficiency was calculated by dividing change scores by number of sessions; EMDR was significantly more efficient, with large effect sizes on each outcome. Limitations include small N, single therapist for each treatment condition, no independent verification of treatment fidelity, and no long‐term follow‐up. These findings suggest that both CBT and EMDR can help girls to recover from the effects of sexual abuse, and that structured trauma treatments can be applied to children in Iran. Copyright © 2004 John Wiley & Sons, Ltd
Treatment of flying phobia using virtual reality: data from a 1‐year follow‐up using a multiple baseline design
Authors: Botella C. , Osma J. , Garcia‐Palacios A. , Quero S. , Baños R.M. 
Published: September 2004

AbstractThe present work is a new contribution about the short‐ and long‐term efficacy of virtual reality (VR) exposure therapy for the treatment of flying phobia (FP). We present data from pre‐treatment, post‐treatment and 1‐year follow‐up assessments in a sample of nine participants using a multiple baseline design. The treatment programme included a main therapeutic component: VR exposure (six sessions), accompanied by one session of education about anxiety, flying and exposure. The VR software developed by our team is described. Our software included, besides the virtual scenario used by most researchers, the plane, two new scenarios: the room and the airport, developed to work with the patients anticipatory anxiety. The results obtained, at post‐treatment and 1 year after the completion of the treatment, support the efficacy of VR in the treatment of flying phobia. VR produced an activation of the fear and avoidance structures and a progressive decrement of fear, avoidance and belief in catastrophic thoughts. The scores in other specific self‐report meaures of flying phobia confirm these findings. After the treatment, all participants flew. Our data support the efficacy of VR for the treatment of flying phobia achieved by other studies. Our contribution to this field is the use of VR exposure as the only therapeutic component, the long‐term efficacy data, and the use of VR software for the treatment of anticipatory anxiety. Copyright © 2004 John Wiley & Sons, Ltd.
Effects of control loop delay on the stability of a rate control algorithm
Authors: Aweya James , Montuno Delfin Y. , Ouellette Michel 
Published: September 2004

AbstractThis paper presents exact stability analysis of a rate control algorithm described inPerform. Eval.2001;43(2–3):63–94;Int. J. Commun. Systems2001;14(6):593–618. The stability regions of the rate control process in the presence of control loop delay are analysed. The rate control process is represented by delay‐difference equation and the criteria for asymptotic stability are derived in terms of the control parameters and control loop delay. The analysis shows that the approximate upper bound of the control gain derived in Aweyaet al.is very close to the exact bound developed here. Using theoretical calculations performed in the discrete‐time domain, we show that as the feedback time delaydincreases, the intensity of control (i.e. the control gain α) must decrease in order for the system to remain stable. Copyright © 2004 John Wiley & Sons, Ltd.
Neuropilin‐1 is required for endothelial tip cell guidance in the developing central nervous system
Authors: Gerhardt Holger , Ruhrberg Christiana , Abramsson Alexandra , Fujisawa Hajime , Shima David , Betsholtz Christer 
Published: September 2004

AbstractRecent evidence indicates that sprouting angiogenesis in the central nervous system (CNS) is a guided process similar to the guidance of axons and insect tracheal tubes. Specialized tip cells of vessel sprouts navigate in response to local depots or gradients of vascular endothelial growth factor (VEGF‐A). Neuropilin‐1 (Nrp‐1) is a transmembrane receptor with a repulsive function in axon guidance. Nrp‐1 also binds the VEGF‐A splice isoform VEGF165, stimulates angiogenesis, and is necessary for vascular development in the mouse. However, the morphogenetic events controlled by Nrp‐1 in angiogenesis have not been defined. Here, we analyzed endothelial tip cell guidance in the CNS of Nrp‐1–deficient mice. We focused our attention on the developing hindbrain, which is normally vascularized in a stereotyped manner. Initially, angiogenic sprouts extend along radial glia from the pial surface toward the ventricles, but in the subventricular zone (SVZ), they leave the radial path, turn laterally, and fuse to form a capillary plexus. Radial sprout elongation correlated with tip cell filopodia extensions along nestin‐positive radial glial processes, but in the SVZ, the tip cell filopodia also extended perpendicular to the glial tracks and made contact with filopodia of the neighboring sprouts. In Nrp‐1–deficient mice, the tip cell filopodia remained associated with the radial glia in the SVZ, which correlated with a failure of sprout turning and elongation across this region. As a result, the sprouts remained blind‐ended forming glomeruloid tufts in the SVZ. These observations suggest that Nrp‐1 plays an important role in allowing the endothelial tip cell filopodia to switch substrate and protrude in a new direction at a specific location in the developing brain. Developmental Dynamics 231:503–509, 2004. © 2004 Wiley‐Liss, Inc.
Analysis of the Tcf‐3 promoter during early development of Xenopus
Authors: Spieker Nicole , Peterson Josi , Reneman Stefan , Destrée Olivier 
Published: September 2004

AbstractXTcf‐3 functions as a transcriptional regulator in the canonical Wnt signaling cascade and can repress or activate downstream target genes. Expression of XTcf‐3 is differentially regulated in time and place during development (Molenaar et al. [1998] Mech Dev. 75:151–154), but little is known about the mechanisms that control transcriptional activation and repression. A 15‐kb genomic fragment of Tcf‐3 sequences from Xenopus tropicalis was cloned, including the 5′ untranslated region; exons 1, 2, and 3; and intron sequences. We used 5′ deletion constructs for transgenesis and episomal luciferase assays in Xenopus to examine temporal and spatial regulation of the promoter during early development. A −3054/+34‐bp Tcf‐3 upstream region was identified that drives a green fluorescent protein (GFP) reporter transgene in a pattern similar to endogenous expression of XtTcf‐3 from gastrula to tail bud stages. At stage 12, expression of the reporter is restricted to the middle and posterior neurectoderm. At stage 22, expression is strongest in the neural plate, the eye anlagen and branchial arches. At stage 35/36, expression is found in the head mesenchyme, the branchial arches, the heart, the mesencephalon, eyes, otic vesicles, notochord, somites and the lateral plate mesoderm. Part of the cis‐acting elements driving this GFP reporter transgene expression map between −372 and −95 bp of the transcription start site. Furthermore, two TCF/LEF sites are necessary for full activity of the promoter during gastrula stages in episomal luciferase assays. Developmental Dynamics 231:510–517, 2004. © 2004 Wiley‐Liss, Inc.
Mouse orthologue of ARX, a gene mutated in several X‐linked forms of mental retardation and epilepsy, is a marker of adult neural stem cells and forebrain GABAergic neurons
Authors: Colombo Elena , Galli Rossella , Cossu Giulio , Gécz Jozef , Broccoli Vania 
Published: September 2004

AbstractMutations in the human ARX gene show unusually heterogeneous clinical presentations, including syndromic and nonsyndromic mental retardation, myoclonic epilepsy with spasticity, and lissencephaly with abnormal genitalia, that are believed to arise from an impairment of the embryonic mechanisms building the anterior central nervous system structures. Here, we show that the murine ortholog Arx has a highly dynamic expression pattern during both early shaping of the forebrain vesicle and later major events of neural migrations and cell‐type specification. Early on, the Arx gene is specifically activated in anterior forebrain anlage. Afterward, Arx expression is confined to the telencephalic vesicles and is enhanced during differentiation of the subpallial structures of the ganglionic eminences, overlapping with Dlx2, Dlx5, and Gad1 transcriptional domains. Tangentially migrating neurons reaching the cortical plate are also Arx‐positive at all embryonic stages analyzed. RNA–protein colabeling staining shows that Arx expression is maintained in the mature cortical interneurons, suggesting its involvement in the different functions of the γ‐aminobutyric acid (GABA)ergic neurons settled into the adult cerebral cortex. Finally, Arx expression is detected in the anterior subventricular layer of the adult brain, where neural stem cells have been shown to be located. Of interest, Arx expression is highly up‐regulated during in vitro differentiation of pure neural stem cell cultures retrieved from adult brain. All together, these findings suggest Arx as a gene involved in the commitment of proliferating neuroblasts into a GABAergic neuronal fate. In conclusion, our mouse Arx expression data provide important further insights into the puzzling complexity of the human ARX mutation pleiotropy. Developmental Dynamics 231:631–639, 2004. © 2004 Wiley‐Liss, Inc.
Histone deacetylase 1 (HDAC‐1) required for the normal formation of craniofacial cartilage and pectoral fins of the zebrafish
Authors: Pillai Renjitha , Coverdale Louise E. , Dubey Gaytri , Martin C. Cristofre 
Published: September 2004

AbstractHistone deacetylases interact with nucleosomes to facilitate the formation of transcriptionally repressed chromatin. In the present study, we show that histone deacetylase 1 (hdac‐1) is expressed throughout embryonic development of the zebrafish. The expression of hdac‐1 is ubiquitous in early embryos (2–16 hr postfertilization), but at later stages (36 and 48 hr postfertilization), it is primarily restricted to the branchial arches, fin bud mesenchyme, and hindbrain. We report the phenotypes of hdac‐1 homozygous mutant embryos and embryos injected with an hdac‐1 antisense morpholino. These embryos possess a complex phenotype affecting several embryonic structures. We observed developmental abnormalities in the heart and neural epithelial structures, including the retina and the loss of craniofacial cartilage and pectoral fins. Developmental Dynamics 231:647–654, 2004. © 2004 Wiley‐Liss, Inc.
Analysis of Mlc‐lacZ Met mutants highlights the essential function of Met for migratory precursors of hypaxial muscles and reveals a role for Met in the development of hyoid arch‐derived facial muscles
Authors: Prunotto Chiara , Crepaldi Tiziana , Forni Paolo E. , Ieraci Alessandro , Kelly Robert G. , Tajbakhsh Shahragim , Buckingham Margaret , Ponzetto Carola 
Published: September 2004

AbstractThe Pax3 and c‐met genes are necessary for the development of tongue, diaphragm, and limb muscles. These hypaxial muscles derive from precursors that migrate out of the ventrolateral lip of the somites at occipital, cervical, and limb levels. In this work, we re‐examined primary myogenesis in c‐met signaling mutants using a skeletal muscle‐specific lacZ transgene (Mlc3f‐nlacZ‐2E). This strategy allowed us to identify precisely the shoulder, limb, tongue, and dermal muscles that need Met for development and to confirm that the morphological structure of epaxial and body wall muscles was normal, even in the most severe c‐met mutant. Surprisingly, however, X‐gal staining showed that, in this mutant, hyoid arch‐derived facial muscles were either reduced or absent, thus revealing that Met also contributes to the development of muscles in the head. Developmental Dynamics 231:582–591, 2004. © 2004 Wiley‐Liss, Inc.
Development of the lymphatic vascular system: A mystery unravels
Authors: Hong Young‐Kwon , Shin Jay W. , Detmar Michael 
Published: September 2004

AbstractThe blood vascular and the lymphatic system play complementary roles in tissue perfusion and fluid reabsorption. Despite its critical role in mediating tissue fluid homeostasis, intestinal lipid absorption, and the immune response, the lymphatic system has not received as much attention as the blood vascular system, largely due to a lack of lymphatic‐specific markers and to the dearth of knowledge about the molecular regulation of lymphatic development and function. A series of recent landmark studies now significantly has advanced our understanding of the lymphatic system. Based upon the discovery and characterization of lymphatic‐specific growth factors, receptors, and transcriptional regulators, the mystery of lymphatic vascular system development begins to be unraveled. The successful isolation and cultivation of blood vascular and lymphatic endothelial cells has enabled comparative molecular and cellular analyses of these two genetically and developmentally closely related cell lineages. Moreover, studies of several genetic mouse models have set the framework for a new molecular model of embryonic lymphatic vascular development and have identified molecular pathways whose mutational inactivation leads to human diseases associated with lymphedema. Although these rapid advances already have led to development of the first lymphatic‐targeted molecular therapies, there still remain many unanswered questions regarding almost every aspect of lymphatic vascular biology, making the lymphatic system a highly exciting and rewarding field of study. Developmental Dynamics 231:462–473, 2004. © 2004 Wiley‐Liss, Inc.
Microfabricated fractal branching networks
Authors: Vozzi G. , Previti A. , Ciaravella G. , Ahluwalia A. 
Published: September 2004

AbstractIn this article, we demonstrate how a combination of engineering and biological techniques could lead to the realization of branched microstructures that can be used for the repair of damaged vascularized tissue. Recursive “treelike” networks were first generated by using fractal algorithms based on Murray's equation for vascular branching as well as allometric scaling rules. Two‐ and three‐dimensional branching patterns with different levels of complexity were then microfabricated from poly‐lactide‐co‐glycolide (PLGA) by using the pressure‐assisted microsyringe (PAM) system developed in our laboratory. Human endothelial cells isolated from umbilical cords were seeded on the microfabricated branched scaffolds to evaluate their effectiveness in supporting site‐specific cell adhesion. The results show that cell densities on the networks increase with complexity up to the sixth level and are then constant independent of branching level. The implications of this finding are discussed in terms of contact inhibition of “capillaries.” © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 71A: 326–333, 2004