bluuebunny/crossref_metadata_2025 huggingface dataset:
Distinctions between fetal and adult human platelet‐derived growth factor–responsive neural precursors
Authors: Chojnacki Andrew , Kelly John J. P. , Hader Walter , Weiss Samuel
Published: September 2008

Objective

Platelet‐derived growth factor (PDGF)–responsive neural precursors (PRPs; also known as oligodendrocyte progenitor cells) are one of the best characterized precursor cell populations of the rodent central nervous system. Yet little is known about the biology of human PRPs because of an apparent inability to culture and expand them in large numbers. This study was designed to establish an approach that allows direct comparisons between the biology of fetal and adult human PRPs, as a means to address potential differences in intrinsic myelin‐production capabilities.

Methods

We used the neurosphere culture system, under low plating density, to isolate, culture, and compare the properties of fetal and adult human PRPs.

Results

PDGF stimulated fetal human PRPs to generate neurospheres that differentiated primarily into oligodendrocytes, which acquired myelin basic protein expression, as well as neurons and a small number of astrocytes. Together with PDGF, fibroblast growth factor 2 promoted fetal human PRP expansion. In contrast, adult human PRPs isolated from the corpus callosum required twice the culture period to generate neurospheres, which contained oligodendrocytes, as well as astrocytes, but not neurons. Strikingly, fibroblast growth factor 2 did not promote adult human PRP self‐renewal.

Interpretation

Differences in the intrinsic proliferation, phenotype, and self‐renewal properties of fetal and adult human PRPs suggest they are distinct populations, which may result in distinct myelin‐production capabilities. Ann Neurol 2008;64:127–142
Crystalline morphology and dynamical crystallization of antibacterial β‐polypropylene composite
Authors: Chen Xin , Mai Kancheng
Published: September 2008

The crystalline morphology and dynamical crystallization of antibacterial polypropylene composite and pure polypropylene were investigated via differential scanning calorimeter (DSC), wide angle X‐ray diffraction (WAXD), and real‐time hot‐stage optical microscopy (OM). The results reveal that the crystalline morphology of antibacterial PP composites changes with variations of the crystallization conditions and compositions. The crystalline phase consists of both α‐PP and β‐PP crystals. The content of β‐PP decreases with the increase in antibacterial agent content and cooling rate. With the addition of β‐nucleating agent, the morphologies of all dynamically crystallized antibacterial PP composites show no obvious spherulitic morphology, and the decrease of crystal perfection and the increase of nucleation density of antibacterial PP composite system could be observed. With the increase of antibacterial agent content, the overall crystallization rates of the antibacterial PP composite increase dramatically, while the content of β‐PP in all antibacterial PP composite decrease distinctly under given cooling conditions. These results can be explained by the interruptive effect of antibacterial agent on interactions of β‐nucleating agent components and the obstructing effect of antibacterial agent on the mobility of PP chains in melts. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Business stakeholder analyzer: An experiment of classifying stakeholders on the Web
Authors: Chung Wingyan , Chen Hsinchun , Reid Edna
Published: September 2008

As the Web is used increasingly to share and disseminate information, business analysts and managers are challenged to understand stakeholder relationships. Traditional stakeholder theories and frameworks employ a manual approach to analysis and do not scale up to accommodate the rapid growth of the Web. Unfortunately, existing business intelligence (BI) tools lack analysis capability, and research on BI systems is sparse. This research proposes a framework for designing BI systems to identify and to classify stakeholders on the Web, incorporating human knowledge and machine‐learned information from Web pages. Based on the framework, we have developed a prototype called Business Stakeholder Analyzer (BSA) that helps managers and analysts to identify and to classify their stakeholders on the Web. Results from our experiment involving algorithm comparison, feature comparison, and a user study showed that the system achieved better within‐class accuracies in widespread stakeholder types such as partner/sponsor/supplier and media/reviewer, and was more efficient than human classification. The student and practitioner subjects in our user study strongly agreed that such a system would save analysts' time and help to identify and classify stakeholders. This research contributes to a better understanding of how to integrate information technology with stakeholder theory, and enriches the knowledge base of BI system design.
Secondary tearingmode in the nonlinear evolution of magnetorotational instability
Authors: Tatsuno T. , Dorland W.
Published: September 2008

Numerical investigation of the two‐dimensional magnetic reconnection is given in the context of the nonlinear evolution of the Magneto‐Rotational Instability (MRI). With a careful comparison to various theories using both one‐ and twodimensional analysis, it is found that a new stabilizing effect of the centrifugal force on tearing instability must be present in the specific geometry of the MRI.Magnetic reconnection might play a key role to the formation of the nonaxisymmetric structures observed in MRI experiments. The results may also be useful for the estimate of the accretion rate in various astrophysical objects. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nonhelical mean‐field dynamos in a sheared turbulence
Authors: Rogachevskii I. , Kleeorin N.
Published: September 2008

Mechanisms of nonhelical large‐scale dynamos (shear‐current dynamo and effect of homogeneous kinetic helicity fluctuations with zero mean) in a homogeneous turbulence with large‐scale shear are discussed. We have found that the shearcurrent dynamo can act even in random flows with small Reynolds numbers. However, in this case mean‐field dynamo requires small magnetic Prandtl numbers (i.e., when Pm < Pmcr< 1). The threshold in the magnetic Prandtl number, Pmcr= 0.24, is determined using second order correlation approximation (or first‐order smoothing approximation) for a background random flow with a scale‐dependent viscous correlation timeτc= (νk2)–1(whereνis the kinematic viscosity of the fluid andkis the wave number). For turbulent flows with large Reynolds numbers shear‐current dynamo occurs for arbitrary magnetic Prandtl numbers. This dynamo effect represents a very generic mechanism for generating large‐scale magnetic fields in a broad class of astrophysical turbulent systems with large‐scale shear. On the other hand, mean‐field dynamo due to homogeneous kinetic helicity fluctuations alone in a sheared turbulence is not realistic for a broad class of astrophysical systems because it requires a very specific random forcing of kinetic helicity fluctuations that contains, e.g., low‐frequency oscillations. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Helical magnetorotational instability of Taylor‐Couette flows in the Rayleigh limit and for quasi‐Kepler rotation
Authors: Rüdiger G. , Schultz M.
Published: September 2008

The magnetorotational instability (MRI) of differential rotation under the simultaneous presence of axial and azimuthal components of the (current‐free) magnetic field is considered. For rotation with uniform specific angular momentum the MHD equations for axisymmetric perturbations are solved in a local short‐wave approximation. All the solutions are overstable for Bz · Bϕ ≠ 0 with eigenfrequencies approaching the viscous frequency. For more flat rotation laws the results of the local approximation do not comply with the results of a global calculation of the MHD instability of Taylor‐Couette flows between rotating cylinders. – With Bϕ and Bz of the same order the traveling‐mode solutions are also prefered for flat rotation laws such as the quasi‐Kepler rotation. For magnetic Prandtl number Pm → 0 they scale with the Reynolds number of rotation rather than with the magnetic Reynolds number (as for standard MRI) so that they can easily be realized in MHD laboratory experiments. – Regarding the nonaxisymmetric modes one finds a remarkable influence of the ratio Bϕ/Bz only for the extrema. For Bϕ ≫ Bz and for not too small Pm the nonaxisymmetric modes dominate the traveling axisymmetric modes. For standard MRI with Bz ≫ Bϕ, however, the critical Reynolds numbers of the nonaxisymmetric modes exceed the values for the axisymmetric modes by many orders so that they are never prefered. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The dual role of shear in large‐scale dynamos
Authors: Brandenburg A.
Published: September 2008

The role of shear in alleviating catastrophic quenching by shedding small‐scale magnetic helicity through fluxes along contours of constant shear is discussed. The level of quenching of the dynamo effect depends on the quenched value of the turbulent magnetic diffusivity. Earlier estimates that might have suffered from the force‐free degeneracy of Beltrami fields are now confirmed for shear flows where this degeneracy is lifted. For a dynamo that is saturated near equipartition field strength those estimates result in a 5‐fold decrease of the magnetic diffusivity as the magnetic Reynolds number based on the wavenumber of the energy‐carrying eddies is increased from 2 to 600. Finally, the role of shear in driving turbulence and large‐scale fields by the magneto‐rotational instability is emphasized. New simulations are presented and the 3π /4 phase shift between poloidal and toroidal fields is confirmed. It is suggested that this phase shift might be a useful diagnostic tool in identifying mean‐field dynamo action in simulations and to distinguish this from other scenarios invoking magnetic buoyancy as a means to explain migration away from the midplane. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Meridional circulation and dynamo waves
Authors: Popova H. , Sokoloff D.
Published: September 2008

The effect of meridional circulation on spherical shell dynamos is considered in the Parker approximation. We demonstrate that the type of the exited solution crucially depend on the intensity of the meridional circulation. If the circulation is equatorward or if it is polarward however do not exceed some critical value, an oscillating solution in form of an equatorward traveling wave is excited. If the polarward meridional circulation becomes too intensive the solution becomes steady growing. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The price of oil in perspective
Authors: Bransby David
Published: September 2008

Soaring price of oil offers a huge opportunity for cellulosic biofuels © 2008 Society of Chemical Industry and John Wiley & Sons, Ltd
Influence of a Joining Helix on the BLUF Domain of the YcgF Photoreceptor from Escherichia coli
Authors: Schroeder Claudia , Werner Karla , Otten Harm , Krätzig Steffen , Schwalbe Harald , Essen Lars‐Oliver
Published: September 2008

BLUF‐domain‐comprising photoreceptors sense blue light by utilizing FAD as a chromophore. The ycgF gene product of Escherichia coli is composed of a N‐terminal BLUF domain and a C‐terminal EAL domain, with the latter postulated to catalyze c‐di‐GMP hydrolysis. The linkage between these two domains involves a predominantly helical segment. Its role on the function of the YcgF photoreceptor domain was examined by characterizing BLUF domains with and without this segment and reconstituting them with either FAD, FMN or riboflavin. The stability of the light‐adapted state of the YcgF BLUF domain depends on the presence of this joining, helical segment and the adenosine diphosphate moiety of FAD. In contrast to other BLUF domains, two‐dimensional 1H,15N and one‐dimensional 1H NMR spectra of isotope‐labeled YcgF‐(1–137) revealed large conformational changes during reversion from the light‐ to the dark‐adapted state. Based on these results the function of the joining helix in YcgF during signal transfer and the role of the BLUF domain in regulating c‐di‐GMP levels is discussed.
Glutathione Transferase: New Model for Glutathione Activation
Authors: Dourado Daniel F. A. R. , Fernandes Pedro Alexandrino , Mannervik Bengt , Ramos Maria João
Published: September 2008

Glutathione transferases are enzymes of the cellular detoxification system that metabolize a vast spectrum of xenobiotic and endobiotic toxic compounds. They are homodimers or heterodimers and each monomer has an active center composed of a G‐site in which glutathione (GSH) binds and an H‐site for the electrophilic substrate. When GSH binds to the G‐site, the pKavalue of its thiol group drops by 2.5 units; this promotes its deprotonation and, therefore, produces a strong nucleophilic thiolate that is able to react with the electrophilic substrate. The mechanism behind the deprotonation of the thiol group is still unknown. Some studies point to the fact that the GSH glutamyl α‐carboxylate group is essential for GSH activation, whereas others indicate the importance of the active‐center water molecules. On the basis of QM/MM calculations, we propose a mechanism of GSH activation in which a water molecule, acting as a bridge, is able to assist in the transfer of the proton from the GSH thiol group to the GSH glutamyl α‐carboxylate group, after an initial GSH conformational rearrangement. We calculated the potential of mean force of this GSH structural rearrangement that would be necessary for the approach of both groups and we then performed a QM/MM ONIOM scan of water‐assisted proton transfer. The overall free‐energy barrier for the process is consistent with experimental studies of the enzyme kinetics.
Mixed‐Ligand Metal–Organic Frameworks with Large Pores: Gas Sorption Properties and Single‐Crystal‐to‐Single‐Crystal Transformation on Guest Exchange
Authors: Park Hye Jeong , Suh Myunghyun Paik
Published: September 2008

Two isomorphous 3D metal–organic frameworks, {[Cu2(BPnDC)2(bpy)]⋅8 DMF⋅6 H2O}n (1) and {[Zn2(BPnDC)2(dabco)]⋅13 DMF⋅3 H2O}n (2), have been prepared by the solvothermal reactions of benzophenone 4,4′‐dicarboxylic acid (H2BPnDC) with Cu(NO3)2⋅2.5 H2O and 4,4′‐bipyridine (bpy), and with Zn(NO3)2⋅6 H2O and 4‐diazabicyclo[2.2.2]octane (dabco), respectively. Compounds 1 and 2 are composed of paddle‐wheel {M2(O2CR)4} cluster units, and they generate 2D channels with two different large pores (effective size of larger pore: 18.2 Å for 1, 11.4 Å for 2). The framework structure of desolvated solid, [Cu2(BPnDC)2(bpy)]n (SNU‐6; SNU=Seoul National University), is the same as that of 1, as evidenced by powder X‐ray diffraction patterns. SNU‐6 exhibits high permanent porosity (1.05 cm3 g−1) with high Langmuir surface area (2910 m2 g−1). It shows high H2 gas storage capacity (1.68 wt % at 77 K and 1 atm; 4.87 wt % (excess) and 10.0 wt % (total) at 77 K and 70 bar) with high isosteric heat (7.74 kJ mol−1) of H2 adsorption as well as high CO2 adsorption capability (113.8 wt % at 195 K and 1 atm). Compound 2 undergoes a single‐crystal‐to‐single‐crystal transformation on guest exchange with n‐hexane to provide {[Zn2(BPnDC)2(dabco)]⋅6 (n‐hexane)⋅3 H2O}n (2hexane). The transformation involves dynamic motion of the molecular components in the crystal, mainly a bending motion of the square planes of the paddle‐wheel units resulting from rotational rearrangement of phenyl rings and carboxylate planes of BPnDC2−.
Fluorescent Magnesium(II) Coordination Polymeric Hydrogel
Authors: Leong Wei Lee , Batabyal Sudip K. , Kasapis Stefan , Vittal Jagadese J.
Published: September 2008

A pH and mechano‐responsive coordination polymeric gel was developed without the use of long chain hydrophobic groups. The hydrogel was synthesised by reacting the aqueous solution of Mg2+ with the basic aqueous solution of N‐(7‐hydroxyl‐4‐methyl‐8‐coumarinyl)‐alanine. The gelation is attributed to the self‐aggregation of 1D coordination polymers to form 3D nanostructures through non‐covalent interactions to entrap water molecules. The freeze‐dried hydrogel exhibits a fibrillar network structure with a uniform ribbon shape. UV/vis absorption studies illustrate that the hydrogel displays a typical π–π* transition. The fluorescence intensity of the hydrogel is enhanced drastically with a longer lifetime upon gel formation. Mechanical analysis including dynamic oscillation on shear, steady shear and creep (retardation‐relaxation) testing have been performed to elucidate the supramolecular nature of the 3D assembly. Together with the viscoelastic properties and biocompatibility, the Mg2+ hydrogel may find utility as a novel soft material in biomedical applications.
Chlorinated Derivatives of C78‐Fullerene Isomers with Unusually Short Intermolecular Halogen–Halogen Contacts
Authors: Simeonov Kalin S. , Amsharov Konstantin Yu. , Jansen Martin
Published: September 2008

The chlorinated fullerenes C78(2)Cl18 and C78(3)Cl18 were synthesized by highly selective chlorination of the individual isomers. They were crystallized as C78(2)Cl18⋅Br2⋅TiCl4 and solvent free C78(3)Cl18. The carbon connectivities of both isomers have been confirmed through X‐ray single‐crystal analysis. Studious investigation of both crystal packings together with the crystal structure of C78(4)Cl18 has revealed the presence of unusually short intermolecular halogen–halogen contacts, which provide evidence for attractive intermolecular interactions, the nature of which is discussed.
Inflammatory cytokines augments TGF‐β1‐induced epithelial‐mesenchymal transition in A549 cells by up‐regulating TβR‐I
Authors: Liu Xiangde
Published: September 2008

Epithelial‐mesenchymal transition (EMT) is believed to play an important role in fibrosis and tumor invasion. EMT can be induced in vitro cell culture by various stimuli including growth factors and matrix metalloproteinases. In this study, we report that cytomix (a mixture of IL‐1β, TNF‐α and IFN‐γ) significantly enhances TGF‐β1‐induced EMT in A549 cells as evidenced by acquisition of fibroblast‐like cell shape, loss of E‐cadherin, and reorganization of F‐actin. IL‐1β or TNF‐α alone can also augment TGF‐β1‐induced EMT. However, a combination of IL‐1β and TNF‐α or the cytomix is more potent to induce EMT. Cytomix, but not individual cytokine of IL‐1β, TNF‐α or IFN‐γ, significantly up‐regulates expression of TGF‐β receptor type I (TβR‐I). Suppression of TβR‐I, Smad2 or Smad3 by siRNA partially blocks EMT induction by cytomix plus TGF‐β1, indicating cytomix augments TGF‐β1‐induced EMT through enhancing TβR‐I and Smad signaling. These results indicate that inflammatory cytokines together with TGF‐β1 may play an important role in the development of fibrosis and tumor progress via the mechanism of epithelial‐mesenchymal transition. Cell Motil. Cytoskeleton 2008. © 2008 Wiley‐Liss, Inc.
Benzimidazolium Salts as Small, Nonpeptidic and BBB‐Permeable Human Prolyl Oligopeptidase Inhibitors
Authors: Tarragó Teresa , Masdeu Carme , Gómez Elena , Isambert Nicolás , Lavilla Rodolfo , Giralt Ernest
Published: September 2008

Prolyl oligopeptidase (POP) is a cytosolic serine peptidase that hydrolyzes proline‐containing peptides at the carboxy terminus of proline residues. This peptidase has gained importance as a target for the treatment of cognitive disturbances of patients with neuropsychiatric diseases. Our research addresses the identification of POP inhibitors from a small focused library of polar heterocyclic compounds arising from multicomponent reactions. Two selective POP‐specific inhibitors were identified on the basis of their inhibition of dipeptidyl peptidase IV. The most active compounds were evaluated for their in vitro transport through the blood–brain barrier (BBB) using a parallel artificial membrane permeability assay. Our results show for the first time that benzimidazolium salts are new POP‐inhibitory scaffolds with properties of solubility, specificity, and lipophilicity that may allow them to cross the BBB by passive diffusion. These findings constitute an excellent starting point to synthesize new POP inhibitors with enhanced properties.
Temozolomide, thalidomide, and whole brain radiation therapy for patients with brain metastasis from metastatic melanoma
Authors: Atkins Michael B. , Sosman Jeffrey A. , Agarwala Sanjiv , Logan Theodore , Clark Joseph I. , Ernstoff Marc S. , Lawson David , Dutcher Janice P. , Weiss Geoffrey , Curti Brendan , Margolin Kim A.
Published: September 2008

BACKGROUND.

The combination of temozolomide (TMZ) and thalidomide was reported to produce a high response rate, including shrinkage of brain metastases, in patients with metastatic melanoma. The authors tested the efficacy of a regimen including TMZ, thalidomide, and whole brain radiation therapy (WBRT) in patients with brain (CNS) metastases from melanoma.

METHODS.

Patients with melanoma, CNS metastases documented by magnetic resonance imaging, and no prior systemic chemotherapy received WBRT, 30 Gray in 10 fractions, Days 1 to 5 and 8 to 12; TMZ, 75 mg/m2/day, Weeks 1 to 6; and thalidomide, 100 mg/day, Weeks 1 to 4, then escalated by 100 mg/day at Weeks 5, 7, and 9 as tolerated to a maximum of 400 mg/day. CNS and systemic tumor response was assessed at Week 10. Patients without CNS or clinically significant systemic disease progression received additional cycles of TMZ at 10‐week intervals.

RESULTS.

Thirty‐nine patients received treatment, and 3 exhibited CNS response (1 complete response, 2 partial responses) (response rate, 7.6%; 95% confidence interval, 0.7%‐16.1%), all unconfirmed by repeat imaging. Seven patients had stable CNS disease at 10 weeks. No patient exhibited a systemic response. Only 4 patients received 2 cycles of therapy, and just 1 received 3. Median time to progression was 7 weeks, and median overall survival was 4 months. Grade 3‐4 side effects included deep venous thrombosis (3), pulmonary embolism (1), and CNS events (12). Eighteen (45%) patients required admission for side effects (7) and/or symptomatic disease progression (11).

CONCLUSIONS.

The efficacy of TMZ, thalidomide, and WBRT in the treatment of CNS metastatic melanoma is low. Other treatment approaches should be considered for this patient population. Cancer 2008. © 2008 American Cancer Society.
Currently used criteria for active surveillance in men with low‐risk prostate cancer
Authors: Suardi Nazareno , Capitanio Umberto , Chun Felix K. H. , Graefen Markus , Perrotte Paul , Schlomm Thorsten , Haese Alexander , Huland Hartwig , Erbersdobler Andreas , Montorsi Francesco , Karakiewicz Pierre I.
Published: September 2008

BACKGROUND.

Active surveillance (AS) represents a treatment option for select patients with low‐risk, organ‐confined prostate cancer (PCa). In this report, the authors addressed the rates of misclassification associated with the use of 5 different clinical criteria for AS. Misclassification was defined as the presence of either nonorgan‐confined disease or high‐grade PCa.

METHODS.

Between 1992 and 2007, 4885 patients underwent radical prostatectomy (RP) at 1 of 2 European academic centers, and the patients were identified who fulfilled the criteria for AS according to 5 different investigational groups (Hardie et al, Roemeling et al, Choo et al, Klotz, and D'Amico and Coleman). Statistics targeted the rates of misclassification for each of the 5 definitions.

RESULTS.

Four thousand three hundred eight patients, 4047 patients, 3993 patients, 2455 patients, and 2345 patients fulfilled the AS criteria of Hardie et al, Roemeling et al, Choo et al, Klotz, and D'Amico and Coleman, respectively. Extracapsular extension was reported in 13.5% to 26% of patients, and seminal vesicle invasion was reported in 2.9% to 8.2% of patients. When PCa with Gleason scores from 8 to 10 at RP was considered high grade, the misclassification rates were 27%, 25%, 25%, 15%, and 14% for the 5 studies, respectively. Conversely, when PCa with Gleason scores from 7 to 10 was considered high grade, the misclassification rates increased to 56%, 55%, 45%, 42%, and 39%, respectively.

CONCLUSIONS.

The currently available AS criteria are limited by a high rate of misclassification. The use of more selective AS criteria may reduce the rate of misclassification but also may reduce significantly the percentage of patients who may be considered for AS. Cancer 2008. © 2008 American Cancer Society.
Rhinal and dorsolateral prefrontal cortex lesions produce selective impairments in object and spatial learning and memory in canines
Authors: Christie Lori‐Ann , Saunders Richard C. , Kowalska Danuta M. , MacKay William A. , Head Elizabeth , Cotman Carl W.
Published: September 2008

To examine the effects of rhinal and dorsolateral prefrontal cortex lesions on object and spatial recognition memory in canines, we used a protocol in which both an object (delayed nonmatching to sample, or DNMS) and a spatial (delayed nonmatching to position or DNMP) recognition task were administered daily. The tasks used similar procedures such that only the type of stimulus information to be remembered differed. Rhinal cortex (RC) lesions produced a selective deficit on the DNMS task, both in retention of the task rules at short delays and in object recognition memory. By contrast, performance on the DNMP task remained intact at both short and long delay intervals in RC animals. Subjects who received dorsolateral prefrontal cortex (dlPFC) lesions were impaired on a spatial task at a short, 5‐second delay, suggesting disrupted retention of the general task rules; however, this impairment was transient, and long‐term spatial memory performance was unaffected in dlPFC subjects. The present results provide support for the involvement of the RC in object, but not visuospatial, processing and recognition memory, whereas the dlPFC appears to mediate retention of a nonmatching rule. These findings support theories of functional specialization within the medial temporal lobe and frontal cortex and suggest that rhinal and dorsolateral prefrontal cortices in canines are functionally similar to analogous regions in other mammals. J. Comp. Neurol. 511:257–270, 2008. © 2008 Wiley‐Liss, Inc.
Nucleosome Immobilization Strategies for Single‐Pair FRET Microscopy
Authors: Koopmans Wiepke J. A. , Schmidt Thomas , van Noort John
Published: September 2008

All genomic transactions in eukaryotes take place in the context of the nucleosome, the basic unit of chromatin, which is responsible for DNA compaction. Overcoming the steric hindrance that nucleosomes present for DNA‐processing enzymes requires significant conformational changes. The dynamics of these have been hard to resolve. Single‐pair Fluorescence Resonance Energy Transfer (spFRET) microscopy is a powerful technique for observing conformational dynamics of the nucleosome. Nucleosome immobilization allows the extension of observation times to a limit set only by photobleaching, and thus opens the possibility of studying processes occurring on timescales ranging from milliseconds to minutes. It is crucial however, that immobilization itself does not introduce artifacts in the dynamics. Here we report on various nucleosome immobilization strategies, such as single‐point attachment to polyethylene glycol (PEG) or surfaces coated with bovine serum albumin (BSA), and confinement in porous agarose or polyacrylamide gels. We compare the immobilization specificity and structural integrity of immobilized nucleosomes. A crosslinked star polyethylene glycol coating performs best with respect to tethering specificity and nucleosome integrity, and enables us to reproduce for the first time bulk nucleosome unwrapping kinetics in single nucleosomes without immobilization artifacts.
Load‐regulated CSMA
Authors: Ashraf Manzur , Jayasuriya Aruna , Perreau Sylvie
Published: September 2008

In this paper, we derive throughput of a threshold‐based transmission policy, namely load‐regulated carrier sense multiple access (CSMA), taking into account the propagation delay of the medium and the offered load at different probabilities of the fading channel. In case of the saturated load‐regulated CSMA, a trivial relationship between deterministic offered load to the channel at a particular fading channel condition and the maximum possible offered load has been shown. We further extend the load regulation concept into multi‐channel domain. Both single and multi‐channel load‐regulated CSMA improves the throughput of the system compared with the existing CSMA system, which does not consider channel fading to control the packet transmissions. Copyright © 2008 John Wiley & Sons, Ltd.
Throughput analysis for interference limited TDMA and TDMA/CDMA wirelessad hocnetworks
Authors: Wang Jui Teng
Published: September 2008

The node throughput, which is defined as the total rate received at each node, is evaluated for the interference limited TDMA and TDMA/CDMA wirelessad hocnetworks. In the TDMA wirelessad hocnetwork, there is only one transmission link connected to each node in the same time slot, whereas in the TDMA/CDMA wirelessad hocnetwork there are multiple transmission links connected to each node in the same time slot. We first derive the node throughput for these two wirelessad hocnetworks and then make a comparison of the node throughput between them. The theoretical results and simulation results both reveal that the TDMA wirelessad hocnetwork outperforms the TDMA/CDMA wirelessad hocnetwork in the node throughput. Copyright © 2008 John Wiley & Sons, Ltd.
Transplanted neurons form both normal and ectopic projections in the adult brain
Authors: Magavi Sanjay S.P. , Lois Carlos
Published: September 2008

Transplantation of embryonic or stem cell derived neurons has been proposed as a potential therapy for several neurological diseases. Previous studies reported that transplanted embryonic neurons extended long‐distance projections through the adult brain exclusively to appropriate targets. We transplanted E14 lateral ganglionic eminence (LGE) and E15 cortical precursors from embryonic mice into the intact adult brain and analyzed the projections formed by transplanted neurons. In contrast to previous studies, we found that transplanted embryonic neurons formed distinct long‐distance projections to both appropriate and ectopic targets. LGE neurons transplanted into the adult striatum formed projections not only to the substantia nigra, a normal target, but also to the claustrum and through all layers of fronto‐orbital cortex, regions that do not normally receive striatal input. In some cases, inappropriate projections outnumbered appropriate projections. To examine the relationship between the donor cells and host brain in establishing the pattern of projections, we transplanted cortical precursors into the adult striatum. Despite their heterotopic location, cortical precursors not only predominantly formed projections appropriate for cortical neurons, but they also formed projections to inappropriate targets. Transplantation of GFP‐expressing cells into β‐galactosidase‐expressing mice confirmed that the axonal projections were not created by the fusion of donor and host cells. These results suggest that repairing the brain using transplantation may be more complicated than previously expected, because exuberant ectopic projections could result in brain dysfunction. Understanding the signals regulating axonal extension in the adult brain will be necessary to harness stem cells or embryonic neurons for effective neuronal‐replacement therapies. © 2008 Wiley Periodicals, Inc. Develop Neurobiol, 2008.
Calcium signaling: A common thread in vertebrate left–right axis development
Authors: Langenbacher Adam , Chen Jau‐Nian
Published: September 2008

The establishment of a left–right axis during vertebrate development is essential for coordinating the relative positions of the internal organs to ensure that they function appropriately. Studies in numerous model organisms have revealed differences in regulative mechanisms upstream of nodal signaling, a conserved pathway in left–right axis specification. This review will summarize the diverse pathways involved in the break of left–right symmetry and explore in depth the multiple roles of calcium in vertebrate left–right axis specification. Developmental Dynamics 237:3491–3496, 2008. © 2008 Wiley‐Liss, Inc.
Development of human plasmacytoid dendritic cells depends on the combined action of the basic helix‐loop‐helix factor E2‐2 and the Ets factor Spi‐B
Authors: Nagasawa Maho , Schmidlin Heike , Hazekamp Mark G. , Schotte Remko , Blom Bianca
Published: September 2008

Plasmacytoid dendritic cells (pDC) are central players in the innate and adaptive immune response against viral infections. The molecular mechanism that underlies pDC development from progenitor cells is only beginning to be elucidated. Previously, we reported that the Ets factor Spi‐B and the inhibitors of DNA binding protein 2 (Id2) or Id3, which antagonize E‐protein activity, are crucially involved in promoting or impairing pDC development, respectively. Here we show that the basic helix‐loop‐helix protein E2‐2 is predominantly expressed in pDC, but not in their progenitor cells or conventional DC. Forced expression of E2‐2 in progenitor cells stimulated pDC development. Conversely, inhibition of E2‐2 expression by RNA interference impaired the generation of pDC suggesting a key role of E2‐2 in development of these cells. Notably, Spi‐B was unable to overcome the Id2 enforced block in pDC development and moreover Spi‐B transduced pDC expressed reduced Id2 levels. This might indicate that Spi‐B contributes to pDC development by promoting E2‐2 activity. Consistent with notion, simultaneous overexpression of E2‐2 and Spi‐B in progenitor cells further stimulated pDC development. Together our results provide additional insight into the transcriptional network controlling pDC development as evidenced by the joint venture of E2‐2 and Spi‐B.
Structural Peculiarities and Electrophysical Properties of Lithium Ion Conducting Lanthanum Niobate Prepared by Solid‐State Reaction and Precipitation from Solution
Authors: Belous Anatolii , Gavrilenko Oksana , Pashkova Olena , Bohnké Odile , Bohnké Claude
Published: September 2008

Synthesis of lithium ion conducting niobate was carried out by a conventional solid‐state reaction (SSR) and by precipitation from solution (PS). X‐ray powder diffraction was used to determine both intermediate phases that are formed during the preparation of these niobate from powder precursors and to determine the structure of sintered ceramics. It is shown that the PS technique leads to the formation of a perovskite phase at a lower temperature relative to the temperature required for the SSR technique. The electrophysical properties of the sintered ceramics were investigated by ac impedance spectroscopy. It is shown that not only the resistance but also the capacitance of the grain boundary are strongly affected by the method of synthesis used. It was found for the first time that the ceramic obtained from powders prepared by precipitation from solution can be used as pH sensors with good sensitivity (48 mV/pH) in the pH range from 4 to 10 and with a fast response time.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Stability Constants and Dissociation Rates of the EDTMP Complexes of Samarium(III) and Yttrium(III)
Authors: Kálmán Ferenc Krisztián , Király Róbert , Brücher Ernő
Published: September 2008

The stability constants of Sm(EDTMP) (log KML = 20.71) and Y(EDTMP) (log KML = 19.19) were determined by a competition reaction between the Ln3+ ion (Ln3+ = Sm3+ or Y3+) and Cu2+ for the EDTMP ligand by spectrophotometry at pH ≈ 10, in the presence of an excess amount of citrate (0.15 M NaCl, 25 °C). For determining the stability constants of Cu(EDTMP) (log KML = 19.36) and Ca(EDTMP) (log KML = 8.71) pH–potentiometry was used. In the pH range 4–9 the EDTMP complexes are present in the form of nonprotonated and mono‐, di‐ and triprotonated species. The Ca2+ ion forms a dinuclear complex with Ln(EDTMP). In a simplified blood plasma model consisting of Sm3+, Ca2+ and Zn2+ metal ions, EDTMP, citrate, cysteine and histidine ligands, Sm3+ is practically present in the form of [Sm(HEDTMP)Ca]2–, whereas Zn2+ predominantly forms [Zn(HEDTMP)]5– and [Zn(H2EDTMP)]4– complexes. For studying the dissociation rates of the complexes, the kinetics of the metal exchange (transmetallation) reactions between the Ln(EDTMP) complexes and Cu2+–citrate were investigated in the pH range 7–9 by the stopped‐flow method. The rates of the exchange reactions are independent of the Cu2+ concentration and increase with the H+ concentration. The rate constants, characterizing the proton‐assisted dissociation of the Ln(EDTMP) complexes, are several orders of magnitude higher than those of the similar Ln(EDTA) complexes, because the protonation constants of Ln(EDTMP) are high and the protonated Ln(HEDTMP) and Ln(H2EDTMP) species are present in higher concentration. The half‐times of dissociation of Sm(EDTMP) and Y(EDTMP) at pH = 7.4 and 25 °C are 4.9 and 7.5 s, respectively. These relatively short dissociation half‐time values do not predict the deposition of Ln3+ ions in bones in the form of intact Ln(EDTMP) complexes. It is more probable that sorption of the EDTMP ligand and Sm3+ or Y3+ ions occurs independently after the dissociation of complexes.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Synthesis, Structures and Reactions of Isolable Terminal Aryl/Biaryl‐butadiynes (Ar–C≡C–C≡CH)
Authors: West Kara , Hayward Laura N. , Batsanov Andrei S. , Bryce Martin R.
Published: September 2008

The synthesis and isolation is reported of five terminal aryl/biaryl‐butadiynes, Ar–C≡C–C≡CH, (5a–c, 10a and 10b) from 2‐methyl‐6‐aryl/biaryl‐hexa‐3,5‐diyn‐2‐ol precursors [Ar–C≡C–C≡C–C(Me)2OH; Ar = 2‐MeOC6H4, 3‐MeOC6H4, 4‐MeOC6H4, 2‐phenylpyridin‐5‐yl, 3‐phenylpyridin‐2‐yl, respectively]. The X‐ray crystal structures have been obtained for compounds 5c and 10a. Surprisingly, no ≡C–H···X (X = N or O) hydrogen bonds exist in the crystals of 5c and 10a. These structures illustrate the fact that ≡C–H···X hydrogen bonds are not always reliable tools for crystal engineering. Palladium‐catalysed cross‐coupling of 5c with 2‐iodopyrimidine gave the unsymmetrical 1,4‐diarylbutadiyne derivative 12; copper‐catalysed reactions of 5c and 10a with benzyl azide proceeded regioselectively to give alkynyltriazoles 13 and 14.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
Digital cellular mobile‐radio system ECR900
Authors: Ballard M. , Issenmann E.
Published: September 2008

In Europe, second generation equipment for mobile telecommunications will operate in the WMHz band as defined by the Groupe Spécial Mobile (GSM) of the European Conference of Posts and Telecommunications (CEPT). By contributing to and complying with these recommendations, Alcatel, in cooperation with Nokia and AEG, has contributed in developing a pan‐European digital Cellular mobile‐Radio system, the ECR900.

This system is based on the Intelligent Network (IN) concept. The Alcatel E10 and the System 12 digital switches are compatible IN components and naturally accommodate the ECR900 system.

Outside these digital exchanges, specific mobile functions are concentrated at mobile‐radio service control points, built on ALCATEL8300 telecommunication processors.

The ECR900 system has already been ordered in France for the GSM Mobile‐Radio network, in the Federal Republic of Germany and in the Netherlands.
Large vocabulary hidden markov model based speech recognition
Authors: Rigoll Cerhard
Published: September 2008

This paper gives an introduction to the use of Hidden Markov Models and Information Theory principles for speech recognition. The use of these techniques has led to powerful large vocabulary speech recognition systems developed in the recent years. The use of Hidden Markov Models for stochastic modeling of speech and the basic modules of a Hidden Markov Model based speech recognition system are explained. It is shown how the speech waveform can be transformed into acoustic features and into prototypes which characterize the acoustic state space of the given speaker. The phonemes of the language can be represented by Hidden Markov Models. The statistical parameters of these Markov models can be obtained during a training session. During recognition the input to the linguistic decoder is the acoustic label string resulting from the speech signal of a spoken sentence. The decoder picks the sentence which maximizes the probability of the word sequence of this sentence if the given label stream is seen. The paper concludes with a more detailed explanation of the acoustic processor of the speech recognition system and some proposed algorithms for its improvement which can lead to a better system performance.
Optimum reception in digital communication systems
Authors: Othmer F. E.
Published: September 2008

The reception problem in digital communication is stated in general terms and the corresponding optimum decision rule which minimizes a prescribed performance criterion, called average loss, is derived in general form. The general investigations are specialized to a class of performance criteria containing average symbol and average bit error probability as special cases. Assuming that the cascade connection of transmitter, channel, and (perhaps) some receiver front‐end can be modeled as a discrete‐time, finite‐state probabilistic machine, a receiver structure is derived which minimizes the average symbol (bit) error probability by making optimum decisions on the basis of the entire receiver input sequence and which has only a linearly growing complexity with growing sequence length. It is shown that the probabilistic‐machine assumption is fulfiled in a wide range of practically important transmission situations. It is also shown that in some special cases the optimum receiver structure is independent of the sequence length.
Performance limitations for distributed amplifiers
Authors: Carlin Herbert J. , Civalleri Pier Paolo
Published: September 2008

The model of a distributed amplifier as two cascaded chains coupled at discrete points by active devices is considered from a network theoretic point of view. The active devices are represented by a simplified equivalent circuit, consisting of a current source and of input and output capacitances. The connecting structures are assumed to be lossless, but no initial assumption of image parameter lines is made. This mode of operation is deduced as an optimum from the network equations. The chains can be identified as gate and drain lines formed using a number of MESFET's, if these are assumed to be representable by the equivalent circuits described above. The objective is to sum the gains of the individual devices with maximum gain bandwidth product (GBW) as limited by the parasitic capacitances. If each chain operates with a single resistor, i.e. source in the gate line, load in the drain line, it is shown that with two resistor (input and output) terminations per line, maximum GBW is the sum of individual element GBW's, and requires constant‐k image parameter operation of the lines. Under these conditions the gain must peak sharply at the edge of the band. Any deviation from this mode of operation, e.g. to suppress the peak, will result in a reduction of GBW, and one of the illustrative examples consists of two simple non‐image LC ladder chains designed so the response peak is suppressed with nominal deviation from maximum GBW. The above results strictly hold only under the simplifying assumptions that the whole structure is lossless: although the assumptions of the paper represent ideal operating conditions, the results still provide an upper bound for the limits of reachable gain.
On assessing robustness of recursive digital filters
Authors: Fettweis Alfred
Published: September 2008

In a recursive digital filter the need for applying rounding/truncation and overflow corrections to the signal (data) at appropriate locations causes the filter behaviour to differ in a more or less noticeable way from the desired one. The filter is said to be the more robust the less such differences are pronounced. For assessing robustness, a list of specific effects are proposed which can individually be tested. If the filter behaves properly with respect to all these tests it can be expected to behave properly also in any of the situations it will encounter during its operation. The possibility of guaranteeing robustness is discussed.
Comparison of near‐field and far‐field methods for fiber‐optic DMA measurements
Authors: Behles Manfred , Unrau Udo
Published: September 2008

The near‐field and the modified far‐field techniques to measure the mode power distribution in a multimode optical fiber with graded‐index profile are analyzed for their sensitivity to measurement errors by computer simulation and are directly compared by measurements on a biconically fused coupler. It is found that the near‐field technique is quite insensitive against various measurement errors except of an incorrect determination of the core‐cladding boundary. In contrast to this the modified far‐field method needs high‐precision measurement equipment and measurement results appear unreliable. Therefore, the near‐field or the ordinary far‐field technique are recommended for mode transition matrix measurements.
Interconnections technologies for VLSI circuits
Authors: Santi Giorgio De
Published: September 2008

VLSI technologies led to the possibility of integration of more than a million of active devices on a single silicon chip. A significant part of the effort in the geometrical circuitry shrinkage was set in development of suitable interconnection technologies. The goals persued were the improvement of the electrical properties (conductivity and contact resistance) with the simultaneous improvement of reliability performances.
IC packaging and interconnections‐status and trends
Authors: Pfahnl Arnold
Published: September 2008

This paper first presents an overview of present packaging technologies and their market shares for simple and complex (VLSI‐type) IC's, and the resulting trends and driving forces for future packaging developments. Then some of the limiting parameters of packaging of high performance IC's are outlined. The importance and cost of reability evaluations, trends in component qualification procedures, and their combined effects on device manufacturing technology are discussed. Finally, interconnection methods to the next packaging level (PWB etc.), the related assembly technologies, and the subsystem performance factors are described.
VLSI reliability: Contributions from a three year national research program
Authors: Soncini Giovanni , Canali Claudio , Zanoni E. , Cors Francrsco , Diligenti Alessandro , Fantini Fausto , Monaco Vito A. , Masetti Guido , Morandi Carlo
Published: September 2008

The continuous trend to further I.C. miniaturization implies increased local electric field strength and power dissipation density, and a perverse scaling, behaviour of metal interconnections and contacts. This will result in new failure mechanisms while old ones, non under control, may become a threat again.

This work reports on the most relevant results, related to VLSI reliability, obtained by the seven University Research Teams involved in a three years Research Program sponsored by the Italian Ministero Pubblica Istruzione.

In particular new methods to investigate electromigration and to localize latch‐up phenomena have been successfully developed. Also test and diagnosis techniques to analyze faults in digital I.C. with emphasis on ECL and custom VLSI have been studied, and electromagnetic interference effects, in operational amplifiers have been modelled and simulated.