bluuebunny/crossref_metadata_2025 huggingface dataset:
Introduction to the POMME special section: Thermocline ventilation and biogeochemical tracer distribution in the northeast Atlantic Ocean and impact of mesoscale dynamics
Authors: Mémery L. , Reverdin G. , Paillet J. , Oschlies A.
Published: July 2005

Conducted in the northeast Atlantic Ocean (15°20′–21°20′W, 38°N–45°N), the Programme Océan Multidisciplinaire Méso Echelle (POMME) is a research project aimed at a better understanding of the biological production and the carbon budget of the region in relation to the formation mechanisms of the 11°–12°C mode water of the northeast Atlantic. With the help of two research vessels, several tens of floats and drifters, and nine moorings, the field experiment was carried out between autumn 2000 and autumn 2001, with a more intensive phase in the winter and early spring of 2001. The field experiment resolved small (several kilometers) to regional (several hundred kilometers) scales and daily to seasonal variability. A first analysis of the rich data set focused on the large‐scale and the mesoscale variability. It shows that the distribution of water mass characteristics and biological activity is strongly influenced by the mesoscales in this supposedly quiet transition zone between the subtropical and subpolar gyres. The seasonal variability, however, presents an imprint of the large‐scale structures with a clear north‐south gradient in properties and budgets. This region is found on an annual average to be a sink of atmospheric CO2. Smaller scales, associated with fronts and filaments, were clearly observed in many fields (temperature, but also chlorophyll, oxygen, biogenic particles, etc.), with modeling studies suggesting that they play a significant role in subduction, ventilation, and transport of biogeochemical tracers in the POMME region.
Molecular constituents of the postsynaptic density fraction revealed by proteomic analysis using multidimensional liquid chromatography‐tandem mass spectrometry
Authors: Yoshimura Yoshiyuki , Yamauchi Yoshio , Shinkawa Takashi , Taoka Masato , Donai Hitomi , Takahashi Nobuhiro , Isobe Toshiaki , Yamauchi Takashi
Published: July 2005

Protein constituents of the postsynaptic density (PSD) fraction were analysed using an integrated liquid chromatography (LC)‐based protein identification system, which was constructed by coupling microscale two‐dimensional liquid chromatography (2DLC) with electrospray ionization (ESI) tandem mass spectrometry (MS/MS) and an automated data analysis system. The PSD fraction prepared from rat forebrain was solubilized in 6 m guanidium hydrochloride, and the proteins were digested with trypsin after S‐carbamoylmethylation under reducing conditions. The tryptic peptide mixture was then analysed with the 2DLC‐MS/MS system in a data‐dependent mode, and the resultant spectral data were automatically processed to search a genome sequence database for protein identification. In triplicate analyses, the system allowed assignments of 5264 peptides, which could finally be attributed to 492 proteins. The PSD contained various proteins involved in signalling transduction, including receptors, ion channel proteins, protein kinases and phosphatases, G‐protein and related proteins, scaffold proteins, and adaptor proteins. Structural proteins, including membrane proteins involved in cell adhesion and cell–cell interaction, proteins involved in endocytosis, motor proteins, and cytoskeletal proteins were also abundant. These results provide basic data on a major protein set associated with the PSD and a basis for future functional studies of this important neural machinery.
Proteasome inhibition and aggregation in Parkinson's disease: a comparative study in untransfected and transfected cells
Authors: Biasini Emiliano , Fioriti Luana , Ceglia Ilaria , Invernizzi Roberto , Bertoli Alessandro , Chiesa Roberto , Forloni Gianluigi
Published: July 2005

Dysfunction of the ubiquitin‐proteasome system (UPS) has been implicated in Parkinson's disease (PD) and other neurodegenerative disorders. We have investigated the effect of UPS inhibition on the metabolism of α‐synuclein (SYN) and parkin, two proteins genetically and histopathologically associated to PD. Pharmacological inhibition of proteasome induced accumulation of both parkin and SYN in transfected PC12 cells. We found that this effect was caused by increased protein synthesis rather than impairment of protein degradation, suggesting that inhibition of the UPS might lead to non‐specific up‐regulation of cytomegalovirus (CMV)‐driven transcription. To investigate whether endogenous parkin and SYN can be substrate of the UPS, untransfected PC12 cells and primary mesencephalic neurones were exposed to proteasome inhibitors, and parkin and SYN expression was evaluated at both protein and mRNA level. Under these conditions, we found that proteasome inhibitors did not affect the level of endogenous parkin and SYN. However, we confirmed that dopaminergic neurones were selectively vulnerable to the toxicity of proteasome inhibitors. Our results indicate that studies involving the use of proteasome inhibitors, particularly those in which proteins are expressed from a heterologous promoter, are subjected to potential artefacts that need to be considered for the interpretation of the role of UPS in PD pathogenesis.
Up‐regulation of NMDAR1 subunit gene expression in cortical neurons via a PKA‐dependent pathway
Authors: Lau Garrick C. , Saha Shamol , Faris Ramona , Russek Shelley J.
Published: July 2005

Transcription mediated by protein kinase A and the cAMP response element binding protein (CREB) has been linked to the establishment of long‐term memory and cell survival. However, all of the major targets for activated CREB have yet to be identified. Given the fact that CREB‐mediated transcription is intimately involved in cellular processes of learning and memory and that CREB activity can be regulated by synaptic N‐methyl‐d‐aspartate receptors (NMDARs) and metabotropic GABA receptors, we have studied the role of the cAMP‐dependent signaling pathway in the regulation of the NMDA receptor subunit 1 (NMDAR1), a subunit required for functional receptor formation. We now report that levels of NMDAR1 subunit protein in primary neocortical cultures are increased 66% in response to forskolin, an activator of adenylyl cyclase. Up‐regulation of NMDAR1 is paralleled by a twofold increase in mRNA levels and an 83% increase in NMDAR1 promoter/luciferase reporter activity that is dependent on protein kinase A. Three cAMP regulatory elements (CREs) in the rat NMDAR1 promoter (− 228, − 67, and − 39) bind CREB in vitro and forskolin increases binding to two of the sites (− 228 and – 67). Chromatin immunoprecipitation of neuronal rat genomic DNA reveals that CREB is bound in vivo to the endogenous NMDAR1 gene. Increased presence of the activated Ser133 phosphorylated form is dependent on the length of exposure to forskolin. Taken together with the results of mutational analysis, the findings strongly suggest that transcription of NMDAR1 is regulated by the c‐AMP signaling pathway, most likely through the binding of CREB and its activation by signal‐dependent phosphorylation.
Reduced contribution from Na+/H+ exchange to acid extrusion during anoxia in adult rat hippocampal CA1 neurons
Authors: Sheldon Claire , Church John
Published: July 2005

The effect of anoxia on Na+/H+ exchange activity was examined in acutely isolated adult rat hippocampal CA1 neurons loaded with the H+‐sensitive fluorophore, BCECF. Five‐minute anoxia imposed under nominally HCO3–/CO2‐free conditions induced a fall in pHi, the magnitude of which was smaller following prolonged exposure to medium in which N‐methyl‐d‐glucamine (NMDG+) was employed as an extracellular Na+ (Na+o) substitute. Also consistent with the possibility that Na+/H+ exchange becomes inhibited soon after the induction of anoxia, rates of Na+o‐dependent pHi recovery from internal acid loads imposed during anoxia were slowed, compared to rates of Na+o‐dependent pHi recovery observed prior to anoxia. At the time at which rates of pHi recovery were reduced during anoxia, cellular adenosine triphosphate (ATP) levels had fallen to 35% of preanoxic levels, suggesting that ATP depletion might contribute to the observed inhibition of Na+/H+ exchange. In support, incubation of neurons with 2‐deoxyglucose and antimycin A under normoxic conditions induced a fall in cellular ATP levels that was also associated with reduced Na+o‐dependent rates of pHi recovery from imposed acid loads; conversely, pre‐treatment with 10 mm creatine attenuated the effects of anoxia to reduce both ATP levels and Na+o‐dependent rates of pHi recovery from internal acid loads. Taken together, the results are consistent with the possibility that functional Na+/H+ exchange activity in adult rat CA1 neurons declines soon after the onset of anoxia, possibly as a result of anoxia‐induced falls in intracellular ATP.
Secretion of locally synthesized neurohormone from neurites of peptidergic neurons
Authors: Lee Wenjau , Wayne Nancy L.
Published: July 2005

Local protein synthesis in neuronal processes is a common phenomenon and may play an important role in synaptic plasticity and hormonal regulation. We have used neuroendocrine bag cells of Aplysia californica as a model system to study local protein synthesis. In our previous work we found that bag cell neurites are capable of synthesizing and processing the prohormone of egg‐laying hormone (pro‐ELH). In the present study, we found that bag cell neurites are also capable of releasing locally synthesized pro‐ELH and ELH‐related products via both constitutive and regulated pathways. However, an electrical afterdischarge did not enhance local pro‐ELH synthesis, as it does in the bag cell soma. This is the first evidence that isolated neurites are capable of secreting locally synthesized proteins.
Endogenous mitochondrial oxidative stress: neurodegeneration, proteomic analysis, specific respiratory chain defects, and efficacious antioxidant therapy in superoxide dismutase 2 null mice
Authors: Hinerfeld Douglas , Traini Mathew D. , Weinberger Ron P. , Cochran Bruce , Doctrow Susan R. , Harry Jenny , Melov Simon
Published: July 2005

Oxidative stress and mitochondrial dysfunction have been linked to neurodegenerative disorders such as Parkinson's and Alzheimer's disease. However, it is not yet understood how endogenous mitochondrial oxidative stress may result in mitochondrial dysfunction. Most prior studies have tested oxidative stress paradigms in mitochondria through either chemical inhibition of specific components of the respiratory chain, or adding an exogenous insult such as hydrogen peroxide or paraquat to directly damage mitochondria. In contrast, mice that lack mitochondrial superoxide dismutase (SOD2 null mice) represent a model of endogenous oxidative stress. SOD2 null mice develop a severe neurological phenotype that includes behavioral defects, a severe spongiform encephalopathy, and a decrease in mitochondrial aconitase activity. We tested the hypothesis that specific components of the respiratory chain in the brain were differentially sensitive to mitochondrial oxidative stress, and whether such sensitivity would lead to neuronal cell death. We carried out proteomic differential display and examined the activities of respiratory chain complexes I, II, III, IV, V, and the tricarboxylic acid cycle enzymes alpha‐ketoglutarate dehydrogenase and citrate synthase in SOD2 null mice in conjunction with efficacious antioxidant treatment and observed differential sensitivities of mitochondrial proteins to oxidative stress. In addition, we observed a striking pattern of neuronal cell death as a result of mitochondrial oxidative stress, and were able to significantly reduce the loss of neurons via antioxidant treatment.
Cathepsin B mRNA and protein expression following contusion spinal cord injury in rats
Authors: Ellis Rebecca C. , Earnhardt J. Nicole , Hayes Ronald L. , Wang Kevin K.W. , Anderson Douglas K.
Published: July 2005

We provide the first data that cathepsin B (Cath B), a lysosomal cysteine protease, is up‐regulated following contusion‐spinal cord injury (SCI). Following T12 laminectomy and moderate contusion, Cath B mRNA and protein expression profiles were examined from 2 to 168 h post‐injury in rats using real‐time PCR and immunoblots, respectively. Contusion injury significantly increased [mRNA]Cath B in the injury site and adjacent segments over sham injury levels. While the largest [mRNA]Cath B induction (20‐fold over naive) was seen in the injury site, the caudal segment routinely yielded [mRNA]Cath B levels greater than 10‐fold over naive. Interestingly, sham injury animals also experienced mRNA induction at several time points at the injury site and in segments rostral and caudal to the injury site. Contusion injury also significantly elevated levels of Cath B proenzyme protein (37 kDa) over sham injury in the injury site (48, 72 and 168 h post‐injury). Furthermore, significant protein increases of single and double chain Cath B (both active forms) occurred at the injury site at 72 and 168 h post‐injury. Similar significant increases in Cath B protein levels were seen in areas adjacent to the injury site. The induction of Cath B mRNA and protein expression following contusion injury is previously undescribed and suggests that Cath B may potentially be involved in the secondary injury cascade, perhaps for as long as 1 week post‐injury.
Improvement of embryonic dopaminergic neurone survival in culture and after grafting into the striatum of hemiparkinsonian rats by CEP‐1347
Authors: Boll Jette Bisgaard , Geist Marie Aavang , Kaminski Schierle Gabriele S. , Petersen Karina , Leist Marcel , Vaudano Elisabetta
Published: July 2005

Transplantation of embryonic nigral tissue ameliorates functional deficiencies in Parkinson's disease (PD). A main constraint of neural grafting is the poor survival of dopaminergic neurones grafted into patients. Studies in rats indicated that many grafted neurones die by apoptosis. CEP‐1347 is a mixed‐lineage‐kinase (MLK) inhibitor with neuroprotective action in several in vitro and in vivo models of neuronal apoptosis. We studied the effect of CEP‐1347 on the survival of embryonic rat dopaminergic neurones in culture, and after transplantation in hemiparkinsonian rats. CEP‐1347 and the alternative MLK inhibitor CEP‐11004 significantly increased the survival of dopaminergic neurones in primary cultures from rat ventral mesencephalon and in Mn2+‐exposed PC12 cells, a surrogate model of dopaminergic lethal stress. Moreover, combined treatment of the grafting cell suspension and the host animal with CEP‐1347 significantly improved the long‐term survival of rat dopaminergic neurones transplanted into the striatum of hemiparkinsonian rats. Also, the protective effect of CEP‐1347 resulted in an increase in total graft size and in enhanced fibre outgrowth. Thus, treatment with CEP‐1347 improved dopaminergic cell survival under severe stress and might be useful to improve the positive outcome of transplantation therapy in PD and reduce the amount of human tissue required.
Morphological and biochemical changes of neurofilaments in aged rat sciatic nerve axons
Authors: Uchida Atsuko , Tashiro Tomoko , Komiya Yoshiaki , Yorifuji Hiroshi , Kishimoto Takeo , Hisanaga Shin‐ichi
Published: July 2005

We have made a detailed comparison of neurofilaments (NFs) in the axons of the sciatic nerves between young and aged rats. In young rats, NF density was similar between proximal and distal sciatic nerve, but it became higher in the proximal region of sciatic nerve of aged rats. In accordance with this morphological change, NF protein content decreased dramatically in the middle region of the sciatic nerves of aged rats. The ratio of NF‐M to NF‐H in aged rats was lower than that in young rats at the proximal region of sciatic nerves and further decreased in the distal region of sciatic nerve. We analyzed transcription and axonal transport of NF proteins in motor neurons in spinal cord which are the major constituents of sciatic nerve axons. Of the transcripts of the NF subunits, NF‐M mRNA was particularly reduced in aged rats. Examination of slow axonal transport revealed that the transport rate for NF‐M was slightly faster than that for NF‐H in young rats, but slightly slower in aged rats. A decrease in both the synthesis and transport rate of NF‐M with aging may contribute to the relative reduction in NF‐M in the aged rat sciatic nerve. Although the relationship between NF packing and reduced NF‐M is not clear at present, these changes in NFs may be associated with age‐dependent axonal degeneration diseases.
The contributions of excitotoxicity, glutathione depletion and DNA repair in chemically induced injury to neurones: exemplified with toxic effects on cerebellar granule cells
Authors: Fonnum F. , Lock E. A.
Published: July 2005

Six chemicals, 2‐halopropionic acids, thiophene, methylhalides, methylmercury, methylazoxymethanol (MAM) and trichlorfon (Fig. 1), that cause selective necrosis to the cerebellum, in particular to cerebellar granule cells, have been reviewed. The basis for the selective toxicity to these neurones is not fully understood, but mechanisms known to contribute to the neuronal cell death are discussed. All six compounds decrease cerebral glutathione (GSH), due to conjugation with the xenobiotic, thereby reducing cellular antioxidant status and making the cells more vulnerable to reactive oxygen species. 2‐Halopropionic acids and methylmercury appear to also act via an excitotoxic mechanism leading to elevated intracellular Ca2+, increased reactive oxygen species and ultimately impaired mitochondrial function. In contrast, the methylhalides, trichlorfon and MAM all methylate DNA and inhibit O6‐guanine‐DNA methyltransferase (OGMT), an important DNA repair enzyme. We propose that a combination of reduced antioxidant status plus excitotoxicity or DNA damage is required to cause cerebellar neuronal cell death with these chemicals. The small size of cerebellar granule cells, the unique subunit composition of their N‐methyl‐d‐aspartate (NMDA) receptors, their low DNA repair ability, low levels of calcium‐binding proteins and vulnerability during postnatal brain development and distribution of glutathione and its conjugating and metabolizing enzymes are all important factors in determining the sensitivity of cerebellar granule cells to toxic compounds.

The chemical formulae of the six xenobiotics and one metabolite dichlorvos discussed in the text.

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Phosphorylation of extracellular‐regulating kinase in NMDA receptor antagonist‐induced newly generated neurons in the adult rat dentate gyrus
Authors: Okuyama Noriko , Takagi Norio , Kawai Takayuki , Miyake‐Takagi Keiko , Takeo Satoshi
Published: July 2005

Neurogenesis in the adult brain is promoted by various stimulations. NMDA receptor blockade enhances neurogenesis in the hippocampal dentate gyrus. There is no agreed conclusion, however, as to whether newly generated neurons after NMDA receptor blockade obtain functional properties. We investigated the functional maturation of newly generated neurons after NMDA receptor blockade. In the dentate gyrus, 80% of newly generated cells differentiated into the phenotype of mature neurons at 29 days after the single intraperitoneal injection of an NMDA receptor antagonist MK‐801. The number of newly generated neurons after MK‐801 treatment was significantly greater than that in the saline‐treated group. The neurogenic basic helix‐loop‐helix transcription factor NeuroD protein in the dentate gyrus after MK‐801 treatment was expressed transiently in proliferative cells, but not in mature neurons. To determine functional properties of newly generated neurons, we administered NMDA to the lateral ventricle. As an in vivo response, we assessed extracellular‐regulating kinase (ERK) phosphorylation. The newly generated neurons showed ERK phosphorylation by NMDA administration as seen in surrounding mature neurons. The number of newly generated neurons, which responded to NMDA receptor stimulation, increased with time after MK‐801 treatment. The present study provides evidence that newly generated neurons in the adult hippocampus after NMDA receptor blockade acquire biochemical function in vivo.
Nonperiodic boundary conditions for solvated systems
Authors: Petraglio Gabriele , Ceccarelli Matteo , Parrinello Michele
Published: July 2005

The simulation of charged and/or strongly polar solutes represents a challenge for standard molecular-dynamics techniques. The use of periodic boundary conditions (PBCs) leads to artifacts due to the interaction between two replicas in the presence of the long-range Coulomb forces. A way to avoid these problems is the use of nonperiodic boundary conditions. A possible realization is to consider a finite system, a sphere, embedded in a reaction field described by the method of the images. In the present work the modified image approximation has been implemented in a molecular-dynamics code and optimized for the use of two standard solvents, water and acetonitrile. The methodology has then been applied to investigate the conformational changes in water-solvated alanine dipeptide. The free-energy surface calculated with this method is comparable to that obtained with PBC.
Density-functional study of two Fe4-based single-molecule magnets
Authors: Ribas-Arino Jordi , Baruah Tunna , Pederson Mark R.
Published: July 2005

We present the results of our all-electron density-functional calculations on the electronic structure and magnetic anisotropy energy of the [Fe4(OMe)6(dpm)6] and [Fe4(thme)2(dpm)6] molecular clusters, which are experimentally found to behave as single-molecule magnets. The calculated magnetic anisotropy energy barriers are 2.65 and 15.8K, respectively, which agree with the experimental data. We also present a density-functional study on the effect of the structure distortions on the magnetic anisotropy of the [Fe(H2O)6]3+ complex. This study, together with an analysis of the projected anisotropies of each iron ion in both molecular clusters, allows us to qualitatively understand why the magnetic anisotropy energy (MAE) barrier of the second single-molecule magnet (SMM) is larger than the MAE of the first SMM.
The structure of 4-methylphenol and its water cluster revealed by rotationally resolved UV spectroscopy using a genetic algorithm approach
Authors: Myszkiewicz Grzegorz , Meerts W. Leo , Ratzer Christian , Schmitt Michael
Published: July 2005

The structure of 4-methylphenol (p-cresol) and its binary water cluster have been elucidated by rotationally resolved laser-induced fluorescence spectroscopy. The electronic origins of the monomer and the cluster are split into four sub-bands by the internal rotation of the methyl group and of the hydroxy group in case of the monomer, and the water moiety in case of the cluster. From the rotational constants of the monomer the structure in the S1 state could be determined to be distorted quinoidally. The structure of the p-cresol-water cluster is determined to be trans linear, with a O–O hydrogen bond length of 290pm in the electronic ground state and of 285pm in the electronically excited state. The S1-state lifetime of p-cresol, p-cresol-d1, and the binary water cluster have been determined to be 1.6, 9.7, and 3.8ns, respectively.
Growth of GaMnAs under near-stoichiometric conditions
Authors: Avrutin V. , Humienik D. , Frank S. , Koeder A. , Schoch W. , Limmer W. , Sauer R. , Waag A.
Published: July 2005

We studied the effect of the V∕III flux ratio and substrate temperature on magnetotransport properties and lattice parameters of Ga0.96Mn0.04As grown by molecular-beam epitaxy. For all the substrate temperatures, the conductivities and Curie temperatures of the layers were found to increase as the V∕III flux ratio approaches 1. A Curie temperature as high as 95 K was achieved for the Ga0.96Mn0.04As samples grown at 240 °C and a V∕III ratio of about 1.5. The lattice parameter of Ga0.96Mn0.04As increased with decreasing V∕III ratio and/or increasing growth temperature. Possible reasons for the effect of the V∕III ratio on the magnetotransport properties and lattice parameter of GaMnAs are discussed.
Threshold properties of matrix-valued Schrödinger operators
Authors: Melgaard Michael
Published: July 2005

We present some results on the perturbation of eigenvalues embedded at a threshold for a two-channel Hamiltonian with three-dimensional Schrödinger operators as entries and with a small off-diagonal perturbation. In particular, we show how the threshold eigenvalue gives rise to discrete eigenvalues below the threshold and, moreover, we establish a criterion on existence of half-bound states associated with embedded pseudo eigenvalues.
Supersymmetric nonlocal gas equation
Authors: Das Ashok , Popowicz Z.
Published: July 2005

In this paper we study systematically the question of supersymmetrization of the nonlocal gas equation. We obtain both the N=1 and the N=2 supersymmetric generalizations of the system which are integrable. We show that both the systems are bi-Hamiltonian. While the N=1 supersymmetrization allows the hierarchy of equations to be extended to negative orders (local equations), we argue that this is not the case for the N=2 supersymmetrization. In the bosonic limit, however, the N=2 system of equations lead to a new coupled integrable system of equations.
Ballistic and pocket limitations of mobility in nanometer Si metal-oxide semiconductor field-effect transistors
Authors: Łusakowski J. , Knap W. , Meziani Y. , Cesso J.-P. , Fatimy A. El , Tauk R. , Dyakonova N. , Ghibaudo G. , Boeuf F. , Skotnicki T.
Published: July 2005

Room-temperature magnetoresistance of nanometer bulk Si n-type metal-oxide semiconductor field-effect transistors was measured at magnetic fields up to 10 T. The electron magnetoresistance mobility was determined for transistors with the gate length in 30 to 740 nm range and was shown to decrease with decreasing the gate length. We show that the mobility reduction is caused both by the ballistic and the pocket effect and that for the strong inversion these two effects are of a comparable magnitude.
Self-organized nanoscale Ge dots and dashes on SiGe/Si superlattices
Authors: Fitting L. , Ware M. E. , Haywood J. R. , Walter Jennifer J. H. , Nemanich R. J.
Published: July 2005

This study explores the self-organization of Ge nanostructures on SiGe/Si superlattices grown on Si substrates with the surface normal tilted from (001) towards (111) by up to 25°. Prior studies found two-dimensional ordering of Ge dots on nominally flat Si(001) surfaces with a very homogeneous size distribution. Our results show that the Ge islands are less ordered for tilted Si(001) substrates. For substrates with a miscut of 25°, Ge dots nucleate on top of the ripples that form approximately perpendicular to the [1-10]Si direction, i.e., perpendicular to the step direction. Additionally, we observe the formation of Ge dashes, which align preferentially along the [1-10]Si direction.
Simple cubic three-dimensional photonic crystals based on macroporous silicon and anisotropic posttreatment
Authors: Matthias Sven , Müller Frank , Gösele Ulrich
Published: July 2005

Three-dimensional structures for photonic crystal applications have been fabricated up to now either by pure bottom-up approaches such as colloidal self-assembly, by pure top-down approaches using very large scale integration technology, or by interference lithography. Here we evaluate a concept enabling large photonic band gaps in simple cubic structures, the manufacturing of which is based on photoelectrochemical etching of strongly modulated macroporous silicon. A subsequent anisotropic etching of the porous structure, which exploits the crystallographic nature of the substrate used, converts the former circular cross section of the pores into a squared one. We theoretically study the dispersion behavior of photonic crystals being fabricated by this developed technique. The band-structure calculations are compiled with respect to the relative pore arrangement and the dielectric volume fraction. We present experimentally realized structures and characterize the photonic crystal optically. The reflectance measurements are in good agreement with corresponding band-structure calculations. Moreover, the introduced process extends the variety of designing and sculpturing three-dimensional microstructures to meet the requirements of a multitude of micro- and nanotechnological applications.
No-cloning of nonorthogonal states does not require inner product preserving
Authors: Li Dafa , Li Xiangrong , Huang Hongtao , Li Xinxin
Published: July 2005

The no-cloning theorem says there is no quantum copy machine which can copy any one-qubit state. Inner product preserving was always used to prove the no-cloning of nonorthogonal states. In this paper we show that the no-cloning of nonorthogonal states does not require inner product preserving and discuss the minimal properties which a linear operator possesses to copy two different states at the same device. In this paper, we obtain the following necessary and sufficient condition. For any two different states ∣ψ⟩=a∣0⟩+b∣1⟩ and ∣φ⟩=c∣0⟩+d∣1⟩, assume that a linear operator L can copy them, that is, L(∣ψ,0⟩)=∣ψ,ψ⟩ and L(∣φ,0⟩)=∣φ,φ⟩. Then the two states are orthogonal if and only if L(∣0,0⟩) and L(∣1,0⟩) are unit length states. Thus we only need linearity and that L(∣0,0⟩) and L(∣1,0⟩) are unit length states to prove the no-cloning of nonorthogonal states. It implies that inner product preserving is not necessary for the no-cloning of nonorthogonal states.
High nitrogen incorporation in GaAsN epilayers grown by chemical beam epitaxy using radio-frequency plasma source
Authors: Pinault M.-A. , Freundlich A. , Coaquira J. A. H. , Fotkatzikis A.
Published: July 2005

Nitrogen incorporation in GaAsN epilayers grown by chemical beam epitaxy using a radio-frequency (rf) plasma source as nitrogen precursor was studied as a function of growth conditions. For higher growth temperatures (∼460°C), only higher rf power values yield significant incorporation of nitrogen. The nitrogen incorporation exhibits two behaviors with the growth rate: metal-organic-chemical-vapor-deposition and molecular-beam-epitaxy like behaviors at low and high growth rate, respectively. The highest nitrogen compositions are obtained at rates of about 1 μm/h. Despite a significant reduction of the N incorporation with increasing growth temperature, the optimization of the growth conditions allowed us to reach nitrogen concentrations up to 7.1% for samples fabricated at 460 °C. Films with higher nitrogen content exhibit low-temperature luminescence at energies higher than those predicted using the band-anticrossing model and an extrapolation of the literature data for smaller N composition.
Controlling fluorescence lifetime of rare-earth element in amorphous inorganic solids via very small compositional adjustments
Authors: Choi Yong Gyu , Curry Richard J. , Park Bong Je , Kim Kyong Hon , Heo Jong , Hewak Dan W.
Published: July 2005

Fluorescence lifetime of hypersensitive 4f-4f transitions of rare-earth elements embedded in amorphous inorganic solids can be dramatically modified by compositional adjustment of the hosts tantamount to not more than 1 mol % without any elaborated thermal treatments. It is possible to modify a spontaneous emission rate of Dy3+:(F11∕26,H9∕26)→H15∕26 transition in chalcogenide Ge–As–S glasses through selective addition of low levels of Ga and CsBr. Along with the change of the spontaneous emission rate, multiphonon relaxation rate involved in the (F11∕26,H9∕26) state also significantly varies upon the minute compositional adjustment. The combination of these effects results in the measured lifetime of the fluorescing (F11∕26,H9∕26) level being greatly enhanced. Such behaviors are attributed to the hypersensitive nature associated with the H15∕26↔F11∕26 transition and preferential coordination of bromine in the nearest-neighboring shell of the Dy3+ ions, which is formed spontaneously during the vitrification process of the host materials. These experimental observations show the most extreme dependence of the fluorescence lifetime on small compositional changes reported compared to any other noncrystalline solid-state dielectric. As such coutilization of many hypersensitive transitions of rare-earth elements and those host materials used in this study may present a unique opportunity to control absorption and emission properties, especially fluorescence lifetimes, through a minute compositional adjustment.
A multiphase flow model for the unstable mixing of incompressible layered materials
Authors: Cheng Baolian , Glimm J. , Sharp D. H. , Yu Y.
Published: July 2005

In this paper, a model for the unstable mixing of n parallel or concentric incompressible fluid layers is proposed. The approach in constructing this model is pairwise, based on a known two-incompressible-fluid mixing model. The problem complexity increases significantly in going from two to three fluids, but the increase in complexity is relatively small thereafter. We present a detailed study of the n=3 problem, which displays all of the difficult modeling issues applicable to arbitrary n⩾3 while still being reasonably tractable.
Optical vibration sensor fabricated by femtosecond laser micromachining
Authors: Kamata Masanao , Obara Minoru , Gattass Rafael R. , Cerami Loren R. , Mazur Eric
Published: July 2005

We fabricated an optical vibration sensor using a high-repetition rate femtosecond laser oscillator. The sensor consists of a single straight waveguide written across a series of three pieces of glass. The central piece is mounted on a suspended beam to make it sensitive to mechanical vibration, acceleration, or external forces. Displacement of the central piece is detected by measuring the change in optical transmission through the waveguide. The resulting sensor is small, simple, and requires no alignment. The sensor has a linear response over the frequency range 20 Hz–2 kHz, can detect accelerations as small as 0.01m∕s2, and is nearly temperature independent.
Giant field enhancement at carbon nanotube tips induced by multistage effect
Authors: Huang J. Y. , Kempa K. , Jo S. H. , Chen S. , Ren Z. F.
Published: July 2005

Recently, we have reported an extremely strong field emission from carbon nanotubes grown on carbon cloth, with the field-enhancement factor of up to 18 800. In this paper, we study the origins of this effect, by investigating field emission from individual carbon nanotubes, in a transmission electron microscope equipped with a piezo manipulator. Microscopic analysis reveals a multistage structure of some of the nanotubes, characterized by an order of magnitude smaller nanotubes branching off the tips of bigger nanotubes (or carbon fibers). The multistage structure causes a macroscopic enhancement of the electric field, which can match that of a single macroscopically long nanotube with length equal to the combined length of all stages, and the tip radius equal to that of the thinnest nanotube in the structure. This not only explains the observed giant field enhancement, but also provides important clues for the design of nanotube emitters for electronic applications.
Mechanical elasticity of single and double clamped silicon nanobeams fabricated by the vapor-liquid-solid method
Authors: San Paulo A. , Bokor J. , Howe R. T. , He R. , Yang P. , Gao D. , Carraro C. , Maboudian R.
Published: July 2005

Atomic force microscopy has been used to characterize the mechanical elasticity of Si nanowires synthesized by the vapor-liquid-solid method. The nanowires are horizontally grown between the two facing Si(111) sidewalls of microtrenches prefabricated on a Si(110) substrate, resulting in suspended single and double clamped nanowire-in-trench structures. The deflection of the nanowires is induced and measured by the controlled application of normal forces with the microscope tip. The observed reversibility of the nanowire deflections and the agreement between the measured deflection profiles and the theoretical behavior of single and double clamped elastic beams demonstrate the overall beamlike mechanical behavior and the mechanical rigidity of the clamping ends of the nanowire-in-trench structures. These results demonstrate the potential of the nanowire-in-trench fabrication approach for the integration of VLS grown nanostructures into functional nanomechanical devices.
Vertically oriented GaN-based air-gap distributed Bragg reflector structure fabricated using band-gap-selective photoelectrochemical etching
Authors: Sharma R. , Haberer E. D. , Meier C. , Hu E. L. , Nakamura S.
Published: July 2005

A three-period vertically oriented GaN-based air-gap distributed Bragg reflector structure was fabricated using band-gap-selective photoelectrochemical (PEC) etching. The epitaxial structure consisted of an Al0.08Ga0.92N∕(In0.04Ga0.96N∕In0.07Ga0.93N) superlattice structure, wherein the InGaN layers served as sacrificial layers during PEC etching. Microreflectance measurements yielded an average enhancement in the reflected signal of ∼12-fold over the wavelength range of 550–650 nm, when compared with the signal from a dry-etched GaN surface.
ASAP, a human microtubule-associated protein required for bipolar spindle assembly and cytokinesis
Authors: Saffin Jean-Michel , Venoux Magali , Prigent Claude , Espeut Julien , Poulat Francis , Giorgi Dominique , Abrieu Ariane , Rouquier Sylvie
Published: July 2005

We have identified a unique human microtubule-associated protein (MAP) named ASAP for
AS
ter-
A
ssociated
P
rotein. ASAP localizes to microtubules in interphase, associates with the mitotic spindle during mitosis, localizes to the central body during cytokinesis and directly binds to purified microtubules by its COOH-terminal domain. Overexpression of ASAP induces profound bundling of cytoplasmic microtubules in interphase cells and aberrant monopolar spindles in mitosis. Depletion of ASAP by RNA interference results in severe mitotic defects: it provokes aberrant mitotic spindle, delays mitotic progression, and leads to defective cytokinesis or cell death. These results suggest a crucial role for ASAP in the organization of the bipolar mitotic spindle, mitosis progression, and cytokinesis and define ASAP as a key factor for proper spindle assembly.
Mutation of Gly-94 in transmembrane segment M1 of Na
+
,K
+
-ATPase interferes with Na
+
and K
+
binding in E
2
P conformation
Authors: Einholm Anja Pernille , Toustrup-Jensen Mads , Andersen Jens Peter , Vilsen Bente
Published: July 2005

The importance of Gly-93 and Gly-94 in transmembrane segment M1 of the Na
+
,K
+
-ATPase for interaction with Na
+
and K
+
was demonstrated by functional analysis of mutants Gly-93-Ala and Gly-94-Ala. In the crystal structures of the Ca
2+
-ATPase, the corresponding residues, Asp-59 and Leu-60, are located exactly where M1 bends. Rapid kinetic measurements of K
+
-induced dephosphorylation allowed determination of the affinity of the
E
2
P phosphoenzyme intermediate for K
+
. In Gly-94-Ala, the K
+
affinity was reduced 9-fold, i.e., to the same extent as seen for mutation of the cation-binding residue Glu-329. Furthermore, Gly-94-Ala showed strongly reduced sensitivity of the
E
1
P-
E
2
P equilibrium to Na
+
, with accumulation of
E
2
P even at 600 mM Na
+
, indicating that interaction of
E
2
P with extracellular Na
+
is impaired. On the contrary, in Gly-93-Ala, the affinity for K
+
was slightly increased, and the
E
1
P-
E
2
P equilibrium was displaced in favor of
E
1
P. In both mutants, the affinity of the cytoplasmically facing sites of
E
1
for Na
+
was reduced, but this effect was relatively small compared with the effects seen for
E
2
P in Gly-94-Ala. Comparison with Ca
2+
-ATPase mutagenesis data suggests that the role of M1 in binding of the transported ions is universal among P-type ATPases, despite the low sequence homology in this region. Structural modeling of Na
+
,K
+
-ATPase mutant Gly-94-Ala on the basis of the Ca
2+
-ATPase crystal structures indicates that the alanine side chain comes close to Ile-287 of M3, particularly in
E
2
P, thus resulting in a steric clash that may explain the present observations.
Emergent patterns of growth controlled by multicellular form and mechanics
Authors: Nelson Celeste M. , Jean Ronald P. , Tan John L. , Liu Wendy F. , Sniadecki Nathan J. , Spector Alexander A. , Chen Christopher S.
Published: July 2005

Spatial patterns of cellular growth generate mechanical stresses that help to push, fold, expand, and deform tissues into their specific forms. Genetic factors are thought to specify patterns of growth and other behaviors to drive morphogenesis. Here, we show that tissue form itself can feed back to regulate patterns of proliferation. Using microfabrication to control the organization of sheets of cells, we demonstrated the emergence of stable patterns of proliferative foci. Regions of concentrated growth corresponded to regions of high tractional stress generated within the sheet, as predicted by a finite-element model of multicellular mechanics and measured directly by using a micromechanical force sensor array. Inhibiting actomyosin-based tension or cadherin-mediated connections between cells disrupted the spatial pattern of proliferation. These findings demonstrate the existence of patterns of mechanical forces that originate from the contraction of cells, emerge from their multicellular organization, and result in patterns of growth. Thus, tissue form is not only a consequence but also an active regulator of tissue growth.
Anorectal Malformations: Does Healthcare Meet the Needs?
Authors: Hartman Esther E , Sprangers Mirjam A. G , Visser Mechteld R. M , Oort Frans J , Hanneman Marianne J. G , van Heurn L W. Ernest , de Langen Zacharias J , Madern Gerard C , Rieu Paul N. M. A , van der Zee David C , Looyaard N , Aronson Daniel C
Published: July 2005

Objectives:

The first aim was to identify the types of healthcare services used by children, adolescents, and adults with anorectal malformation (ARM) in relation to the severity of their disease and to examine whether additional care was needed. The second aim was to evaluate specific areas in the healthcare system, including provided information, transfer from pediatric to adult care, and satisfaction with the provided care.

Methods:

Three hundred eighty‐six (61%) patients with ARM, ages 6 to 52, completed a questionnaire that assessed their use of healthcare services and the need for additional services. Also, questions were asked about specific areas in the healthcare system. Clinical and sociodemographic characteristics were extracted from medical records.

Results:

In the preceding 6 months 50% of the children, 24% of the adolescents, and 24% of the adults consulted a medical specialist. Compared with patients with a mild form of ARM in the age range of 6 to 16 years, the more severely afflicted patients visited medical professionals more often (18% vs. 32%). Particularly, adolescents in the age range of 12 to 16 years with a severe form of the disease more often visited the pediatric surgeon than their peers with a mild form (2% vs. 16%). Twenty‐three percent of the children, 7% of the adolescents, and 8% of the adults consulted a nonmedical professional. Twenty percent of the children, 13% of the adolescents, and 17% of the adults would have liked additional or more treatment of a nonmedical professional. In 6 months, 40% of the children, 24% of the adolescents, and 20% of the adults received treatment information. One third of the adult patients who were transferred to “adult” surgeons encountered transfer problems. Almost all patients were satisfied with the care provided.

Conclusions:

There is good access to medical healthcare services, especially for children. However, more psychosocial and paramedical care is considered necessary. As could be expected, children and adolescents with a severe form of the disease reported to have visited a medical specialist more often. Although healthcare for patients with ARM may be improved at certain points, most parents and patients were very satisfied with the care provided.
Human Hepatic Mitochondria Generate Reactive Oxygen Species and Undergo the Permeability Transition in Response to Hydrophobic Bile Acids
Authors: Sokol Ronald J , Dahl Rolf , Devereaux Michael W , Yerushalmi Baruch , Kobak Gregory E , Gumpricht Eric
Published: July 2005

Objectives:

Hydrophobic bile acids accumulate in the liver during cholestasis and are believed to cause hepatocellular necrosis and apoptosis in part through induction of the mitochondrial permeability transition (MPT) and the mitochondrial generation of oxidative stress. The purpose of this study was to determine if human hepatic mitochondria respond to bile acids in this manner.

Methods:

The MPT was measured spectrophotometrically and morphologically in normal human liver mitochondria exposed to glycochenodeoxycholic acid (GCDC) with and without cyclosporin A, an inhibitor of the MPT, antioxidants, and tauroursodeoxycholic acid (TUDC). Hydroperoxide generation was measured by dichlorofluorescein fluorescence. Cytochrome c and apoptosis‐inducing factor were assessed by immunoblotting.

Results:

GCDC induced the MPT in a dose‐dependent manner, which was inhibited by cyclosporin A, alpha‐tocopherol, beta‐carotene, idebenone, and TUDC. GCDC stimulated reactive oxygen species generation and release of cytochrome c and apoptosis‐inducing factor, which were significantly inhibited by the antioxidants, cyclosporin A, and TUDC.

Conclusions:

Mitochondrial pathways of cell death are stimulated in human hepatic mitochondria exposed to GCDC consistent with the role of mitochondrial dysfunction in the pathogenesis of cholestatic liver injury. These results parallel those reported in rodents, supporting the extrapolation of mechanistic studies of bile acid toxicity from rodent to humans.
Are There Psychosocial Differences in Diagnostic Subgroups of Children with Recurrent Abdominal Pain?
Authors: Robins Paul M , Glutting Joseph J , Shaffer Stephen , Proujansky Roy , Mehta Devendra
Published: July 2005

Objectives:

To examine psychosocial differences in diagnostic subgroups of children with recurrent abdominal pain (RAP).

Methods:

Children meeting Apley's 1975 definition of RAP were divided according to physician ratings into three subgroups, based on the Rome II diagnostic criteria of functional gastrointestinal disorders: functional dyspepsia (n = 17), irritable bowel syndrome (n = 18), and functional abdominal pain (n = 27). Groups were compared using measures of (a) child psychopathology, (b) parent psychopathology, and (c) child pain, somatization, and functional disability.

Results:

Multivariate results from a discriminant function analysis demonstrated that children classified according to these criteria could not be differentiated with respect to parent reported child psychopathology or child pain, somatization, and functional disability. There were significant univariate differences, however, between groups on parental psychopathology (F = 4.39, P = 0.02); parents of children with functional dyspepsia reported greater parental psychopathology symptoms than the other two groups.

Conclusions:

This study provides a preliminary comparison of pain, somatization, functional impact, and psychopathology ratings in the Rome II diagnostic subclassifications of children with RAP. Further investigation utilizing larger sample sizes, pain measures specifying pain location, and parental modeling of somatic behavior is indicated to better understand potential similarities and differences between these subgroups.