bluuebunny/crossref_metadata_2025 huggingface dataset:
Three-dimensional analysis of spontaneous surface instability and pattern formation of thin soft films
Authors: Huang Shi-Qing , Li Bo , Feng Xi-Qiao
Published: April 2008

For soft films with a thickness on the order of microns or nanometers, the long-range surface∕interface interaction can be sufficiently strong to induce their surface instability or even rupture. By using the bifurcation theory of elasticity, we here present a three-dimensional theoretical model to study the spontaneous surface instability of a soft elastic thin film supported by a rigid substrate. By accounting for the competition of van der Waals interaction energy with elastic strain energy and surface energy, we obtain the analytical solutions for the critical conditions of three-dimensional surface morphology instability. The effects of surface energy, thickness, and elastic properties of the film on the characteristic wavelength of surface wrinkling are examined. It is found that the characteristic wavelength of the deformation bifurcation mode depends on the film thickness via an exponential relation, with the power index in the range of 0.75–1.0, which mainly depends on the ratio between the surface energy and shear modulus of the film but not on the nature of the surface∕interface interaction. Furthermore, it is shown that the interface condition between the film and the substrate significantly influences the critical condition of surface bifurcation. The theoretical solution proves to be a good agreement with the corresponding experiment results.
Potential of mean force calculations of ligand binding to ion channels from Jarzynski’s equality and umbrella sampling
Authors: Baştuğ Turgut , Chen Po-Chia , Patra Swarna M. , Kuyucak Serdar
Published: April 2008

Potential of mean force (PMF) calculations provide a reliable method for determination of the absolute binding free energies for protein-ligand systems. The common method used for this purpose—umbrella sampling with weighted histogram analysis—is computationally very laborious, which limits its applications. Recently, a much simpler alternative for PMF calculations has become available, namely, using Jarzynski’s equality in steered molecular dynamics simulations. So far, there have been a few comparisons of the two methods and mostly in simple systems that do not reflect the complexities of protein-ligand systems. Here, we use both methods to calculate the PMF for ion permeation and ligand binding to ion channels. Comparison of results indicate that Jarzynski’s method suffers from relaxation problems in complex systems and would require much longer simulation times to yield reliable PMFs for protein-ligand systems.
Analysis of the exponential character of single molecule rotational correlation functions for large and small fluorescence collection angles
Authors: Vallée R. A. L. , Rohand T. , Boens N. , Dehaen W. , Hinze G. , Basché T.
Published: April 2008

Coarse-grained molecular dynamics simulations and single molecule fluorescence microscopy experiments have been performed in order to investigate the influence of the numerical aperture (NA) of the microscope objective on the exponential character of the rotational correlation functions of probes embedded in complex matrices. The results obtained by using either a dry lens (NA=0.95) or an oil objective (NA=1.4) show that, in the moderately (simulations) and deeply (experiment) supercooled melts, the rotational (linear dichroism) correlation functions of the single molecules (SMs) exhibit a nonexponential character. Furthermore, by fitting Kohlrausch–Williams–Watt functions to the correlation curves, the stretching parameters turn out to be very similar for both types of objectives. Our results demonstrate that the nonexponentiality is intrinsic to the complex rotational dynamics of the SM in the supercooled solid and point to the validity of the use of a high NA dry lens to perform such experiments.
Hardness and elastic properties of covalent/ionic solid solutions from first-principles theory
Authors: Hu Qing-Miao , Kádas Krisztina , Hogmark Sture , Yang Rui , Johansson Börje , Vitos Levente
Published: April 2008

Most of the engineering materials are alloys (solid solutions) and inevitably contain some impurities or defects such as vacancies. However, theoretical predictions of the hardness of this kind of materials have rarely been addressed in literature. In this paper, a hardness formula for multicomponent covalent solid solution is proposed based on the work of Šimůnek and Vackář [Phys. Rev. Lett. 96, 085501 (2006)]. With this formula, the composition dependence of the hardness is investigated for titanium nitrogencarbide (TiN1−xCx), off-stoichiometric transition-metal nitrides (TiN1−x and VN1−x), and B-doped semiconductors. The predicted hardness is in good agreement with experiments. To investigate the most frequently quoted correlation between hardness and elastic modulus, the elastic moduli of the systems involved in this paper have also been calculated. The results show that the elastic moduli cannot be used for rigorous predictions of the hardness of the solid solutions.
Spin-dependent dwell times of electron tunneling through double- and triple-barrier structures
Authors: Erić Marko , Radovanović Jelena , Milanović Vitomir , Ikonić Zoran , Indjin Dragan
Published: April 2008

We have analyzed the influence of Dresselhaus and Rashba spin-orbit couplings (caused by the bulk inversion asymmetry and the structural asymmetry, respectively) on electron tunneling through a double- and triple-barrier structures, with and without an externally applied electric field. The results indicate that the degree of structural asymmetry and external electric field can greatly affect the dwell times of electrons with opposite spin orientation. This opens up the possibilities of obtaining efficient spin separation in the time domain. The material system of choice is AlxGa1−xSb, and the presented model takes into account the position dependence of material parameters, as well as the effects of band nonparabolicity.
Magnetic-field-induced stress and magnetization in mechanically blocked Ni–Mn–Ga
Authors: Sarawate N. N. , Dapino M. J.
Published: April 2008

A single-crystal Ni–Mn–Ga sample (AdaptaMat, Ltd.) is first compressed from its longest shape to a given bias strain and subsequently subjected to a slowly alternating magnetic field while being prevented from deforming. The tests are repeated for several bias strains. The available blocking stress, or maximum field-induced stress relative to the bias stress, is critical for quantifying the work capacity of a material. The largest available blocking stress for this material is 1.47 MPa at a bias strain of 3% and field amplitude of 640 kA/m. The work capacity calculated as the area under the available blocking stress versus bias strain curve is 72.4 kJ/m3. An existing continuum thermodynamics model for Ni–Mn–Ga sensors is augmented by incorporating the magnetoelastic energy as a source of stress generation when the material is mechanically blocked. The strain and magnetization are described by fixing the variant volume fraction.
Hopping conduction in zinc vanadate semiconducting glasses
Authors: Ghosh Aloka , Bhattacharya S. , Bhattacharya D. P. , Ghosh A.
Published: April 2008

In this paper, we have studied the electrical conductivity for different compositions of the zinc vanadate semiconducting glasses within a wide temperature range. We have analyzed the temperature dependence of the electrical conductivity within the framework of various models for the hopping conduction. We have observed that Mott’s phonon-assisted nearest neighbor hopping model of small polarons is appropriate for describing the conductivity data at high temperatures. We have further observed that at lower temperatures, Mott’s variable range hopping model is operative, while Greaves’ variable range hopping model is valid within the intermediate temperature range. The values of the density of states at the Fermi level, which are obtained from the analysis, are consistent with those for localized states.
Submicrometer polymer transistors fabricated by a mask-free photolithographic self-alignment process
Authors: Bürgi Lukas , Pfeiffer Reto , Winnewisser Carsten
Published: April 2008

A simple method for patterning down to 400nm gaps between two thin-film electrodes is presented. The edge of the first electrode defines the gap via a photolithographic step using off-normal through-substrate exposure. It is demonstrated that the gap width can be controlled simply by adjusting the exposure angle and/or photoresist thickness. Using this process, poly(3-hexylthiophene) field-effect transistors with a submicrometer channel and a large channel width to length ratio of up to 5000 have been fabricated. Since the process is mask free, contactless, highly parallel, and offers high resolution, it is potentially suited for the high-throughput, low-cost fabrication of electronic circuits.
Combined optical and electrical modeling of polymer:fullerene bulk heterojunction solar cells
Authors: Kotlarski Jan D. , Blom Paul W. M. , Koster Lambert. J. A. , Lenes Martijn , Slooff Lenneke H.
Published: April 2008

Optical interference effects are important for the total absorption as well as the profile of the exciton generation rate in polymer:fullerene bulk heterojunction solar cells. For solar cells with an active layer of poly[2-methoxy-5-(3′,7′-dimethyloctyloxy)-1,4-phenylenevinylene] as electron donor and [6,6]-phenyl C61 butyric acid methyl ester as electron acceptor, the total exciton generation rate can be directly extracted from the saturated photocurrent. It is demonstrated that for solar cells with an active layer thickness smaller than 250nm, a constant exciton generation profile, based on this extracted total rate, gives identical electrical characteristics as compared to exciton generation profiles from an optical model. For thicker cells interference effects have to be taken into account, since a uniform generation profile leads to an overestimation of recombination losses and space-charge formation.
Laser ablation in a liquid-confined environment using a nanosecond laser pulse
Authors: Kang Hyun Wook , Lee Ho , Welch Ashley J.
Published: April 2008

Laser ablation of aluminum metal with 1ns, 800nm pulse at low radiant exposures was investigated in air (dry) and water (wet) environments. Compared to dry ablation, an approximately eight times increase in material removal rate was associated with wet ablation. Based on optical reflectance and scanning electron microscope images, bubble formation/collapse was responsible for augmented acoustic pressure and ablation performance. Numerically simulated temperature distributions during wet ablation were consistent with the occurrence of explosive water vaporization near the critical temperature of water. Strong pressure emission during liquid vaporization and jet formation can account for enhanced ablation process. Radial expansion of bubbles minimized the redeposition of debris, leading to improvements in energy coupling to the target and ablation performance.
Distance dependence of fluorescence enhancement from photonic crystal surfaces
Authors: Ganesh Nikhil , Mathias Patrick C. , Zhang Wei , Cunningham Brian T.
Published: April 2008

We experimentally verify the near-field nature of the fluorescence enhancement afforded by large area planar photonic crystal resonators. This is done by mapping the fluorescence enhancement factor for a fluorophore as a function of its distance above the device surface and comparing the results to numerical calculations. Experiments show that the decay of the enhancement factor is exponential as a function of distance from the device surface, and excellent agreement with the numerically calculated exponential decay length is obtained. In contrast to approaches involving surface plasmons on metal surfaces, we find that the maximum enhancement is obtained when the fluorophore is closest to the photonic crystal surface due to the absence of quenching at short distances. We also show that the decay length is largely controlled by the wavelength of light resonant in the device.
The use of a macroscopic formulation describing the effects of dynamic compaction and porosity on plasma sprayed copper
Authors: Arrigoni M. , Boustie M. , Bolis C. , Berthe L. , Barradas S. , Jeandin M.
Published: April 2008

Coatings processed by thermal deposition techniques involve porosity. The Laser adhesion test developed for testing bond strength of a coating on its substrate requires a good knowledge of shock wave propagation in such media. Experiments carried out on plasma sprayed copper samples, about 14% porous, with velocity interferometer system for any reflector measurements display the discrepancy of previously used models. Hence, a one-dimensional formulation of the compaction process, based on a simple P-α model, is proposed to improve the correlation between experimental and computed data signals obtained on a plasma sprayed copper under dynamic loading. Besides, this improvement allows the estimation of the bond strength of a plasma sprayed copper on aluminum substrate.
An ultrahigh vacuum system for in situ studies of thin films and nanostructures by nuclear resonance scattering of synchrotron radiation
Authors: Stankov Svetoslav , Rüffer Rudolf , Sladecek Marcel , Rennhofer Marcus , Sepiol Bogdan , Vogl Gero , Spiridis Nika , Slezak Tomasz , Korecki Jozef
Published: April 2008

A multifunctional ultrahigh vacuum (UHV) system has been set up at the nuclear resonance beamline ID18 of the European Synchrotron Radiation Facility (ESRF). Thin and ultrathin films, nanoislands and -wires, multilayers, and stoichiometric oxides can be prepared by molecular beam epitaxy and characterized by low-energy electron diffraction, Auger electron spectroscopy, and reflection high-energy electron diffraction. Upon characterization the sample is transferred under UHV conditions to the chamber for experiments with the synchrotron beam. Electronic and magnetic properties, vibrational dynamics, and diffusion phenomena can be investigated by several synchrotron radiation based techniques, such as nuclear forward scattering, nuclear inelastic and quasielastic scattering, synchrotron radiation based perturbed angular correlations, and nuclear and electronic reflectivity. In addition, two portable UHV chambers serve to transfer the sample to other beamlines profiting from the available experimental techniques at the ESRF.
Tunneling entity in different injection regimes of InGaN light emitting diodes
Authors: Reynolds C. L. , Patel A.
Published: April 2008

The forward I-V characteristics of InGaN-based light emitting diodes heteroepitaxially grown have previously been shown to be dominated by tunneling over a wide range of bias, as indicated by unrealistic values for the ideality factor. Comparison of the electrical characteristics in different bias regimes for InGaN light emitting diodes (LEDs) to expressions for the tunneling current enables one to achieve an understanding of the tunneling entities involved. At low bias for LEDs grown on sapphire, data are consistent with electron tunneling to deep levels in the vicinity of mixed/screw dislocations and are characterized by an energy near 200meV. This component is absent for those devices homoepitaxially grown. In the intermediate bias regime, LEDs both heteroepitaxially and homoepitaxially grown exhibit a tunneling component that is proposed to be associated with the heavy hole tunneling via intermediate states and to have a characteristic energy near 80meV.
Lasing from dye-doped photonic crystals with graded layers in dichromate gelatin emulsions
Authors: Kok Mang Hin , Lu Weixin , Lee Jeffrey Chi Wai , Tam Wing Yim , Wong George K. L. , Chan C. T.
Published: April 2008

We report on optically pumped lasing from dye-doped, graded-spacing layer structures of dichromate gelatin emulsions fabricated using two-beam holographic interference. The graded layers exhibited deep and wide photonic band gaps. Multimode lasing with both a low threshold and a high quality factor was observed at the band edge of the photonic band gap. We modeled the emissions from the dye-doped graded layer system using a finite difference time domain technique and achieved good agreement with experimental results.
Substantial pyroelectric effect enhancement in laminated composites
Authors: Chang H. H. S. , Huang Z.
Published: April 2008

A mathematical model has been developed to determine the pyroelectric coefficient (PY coef.) enhancement through secondary pyroelectric effect, utilizing a 2-2 connectivity of the pyroelectric lead zirconate titanate (PZT) and elastic laminate layers. Based on the prediction of this analysis, laminar stainless steel (St) PZT/St structures have been fabricated and more than 100% enhancement in PY coef. has been observed in these structures. Good agreement between the theoretical and experimental results was obtained by taking into account of the stain transfer loss at the St and PZT interface.
Extremely high thermal conductivity of graphene: Prospects for thermal management applications in nanoelectronic circuits
Authors: Ghosh S. , Calizo I. , Teweldebrhan D. , Pokatilov E. P. , Nika D. L. , Balandin A. A. , Bao W. , Miao F. , Lau C. N.
Published: April 2008

The authors reported on investigation of the thermal conductivity of graphene suspended across trenches in Si∕SiO2 wafer. The measurements were performed using a noncontact technique based on micro-Raman spectroscopy. The amount of power dissipated in graphene and corresponding temperature rise were determined from the spectral position and integrated intensity of graphene’s G mode. The extremely high thermal conductivity in the range of ∼3080–5150W∕mK and phonon mean free path of ∼775nm near room temperature were extracted for a set of graphene flakes. The obtained results suggest graphene’s applications as thermal management material in future nanoelectronic circuits.
Four point bending setup for characterization of semiconductor piezoresistance
Authors: Richter J. , Arnoldus M. B. , Hansen O. , Thomsen E. V.
Published: April 2008

We present a four point bending setup suitable for high precision characterization of piezoresistance in semiconductors. The compact setup has a total size of 635cm3. Thermal stability is ensured by an aluminum housing wherein the actual four point bending fixture is located. The four point bending fixture is manufactured in polyetheretherketon and a dedicated silicon chip with embedded piezoresistors fits in the fixture. The fixture is actuated by a microstepper actuator and a high sensitivity force sensor measures the applied force on the fixture and chip. The setup includes heaters embedded in the housing and controlled by a thermocouple feedback loop to ensure characterization at different temperature settings. We present three-dimensional finite element modeling simulations of the fixture and discuss the possible contributions to the uncertainty of the piezoresistance characterization. As a proof of concept, we show measurements of the piezocoefficient π44 in p-type silicon at three different doping concentrations in the temperature range from T=30°CtoT=80°C. The extracted piezocoefficients are determined with an uncertainty of 1.8%.
Photoemission measurement of extremely insulating materials: Capacitive photocurrent detection in photoelectron yield spectroscopy
Authors: Nakayama Yasuo , Machida Shinichi , Tsunami Daisuke , Kimura Yasuo , Niwano Michio , Noguchi Yutaka , Ishii Hisao
Published: April 2008

The electronic structures of various materials have been investigated using photoemission measurements. The sample charge-up problem, however, limits the application of these measurements to insulating materials. In this study, we propose a capacitive photocurrent detection method that permits photoelectron yield spectroscopy measurements of extremely insulating materials in both vacuum and ambient pressure conditions. The mechanism of detection is discussed, and the application to gold and rubrene films on mica substrates is demonstrated.
Modulations of photoinduced magnetoconductance for polymer diodes
Authors: Lee Tsung-Hsun , Guo Tzung-Fang , Huang J. C. A. , Wen Ten-Chin
Published: April 2008

This study elucidates the magnetoconductance (MC) response of polymer diodes, which can be modulated by photoillumination, varying the composition of the active layer and applying electrical bias. Under illumination, the short-circuit current of polymer diodes with active layers of regioregular poly(3-hexylthiophene) (P3HT) exhibits an MC response of approximately −4.0% in a magnetic field B=1000mT at room temperature. The MC response drastically reverses from negative to positive (−23.0% to 2.0%) as the electrical bias is increased from nearly below to above the open-circuit voltage. However, it is quenched (<0.1%) when the illumination is turned off or an electron acceptor material, [6,6]-phenyl C61-butyric acid methyl ester, is blended with P3HT as the active layer, suggesting that, in nature, the MC response is associated with the illumination and excitonic states. The annihilation of triplet excitons probably dominates the negative MC response.
Demonstration of magnetoelectric read head of multiferroic heterostructures
Authors: Zhang Yi , Li Zheng , Deng Chaoyong , Ma Jing , Lin Yuanhua , Nan Ce-Wen
Published: April 2008

Bilayered heterostructures of ferrites and BaTiO3, epitaxially grown on SrTiO3 single crystal substrate via pulsed laser deposition, showed an obvious magnetoelectric effect. Employing such simple bilayered thin films as a prototype magnetoelectric read head was demonstrated. The media field from the bits in a magnetic recording medium was modeled by an ac magnetic field. The output voltage waveforms of the bilayered thin films well followed the wave functions of the ac magnetic excitation signal, which illustrates utility of the bilayered heterostructures as magnetoelectric read head.
Excess carrier dynamics of InGaN∕GaN multiple-quantum-well light-emitting diodes with various silicon barrier doping profiles
Authors: Li Yun-Li , Lai Wei-Chih , Chang Yun-Chorng
Published: April 2008

This study investigates the carrier dynamics of InGaN∕GaN light-emitting diodes with various doping profiles in the active region by using time-resolved photoluminescence experiments. Excess carrier lifetime strongly depends on excitation intensity when the quantum wells in the active region comprise doped and undoped barriers. The measured lifetime is shorter when the excitation intensity is lower. Competition between radiative recombination in quantum wells with undoped barriers and carrier tunneling from quantum wells with undoped barriers to wells with doped barriers is responsible for this phenomenon. Reducing the excitation intensity causes more carriers to undergo faster recombination in doped quantum wells.
Macro and micro nutrient limitation of microbial productivity in oligotrophic subtropical Atlantic waters
Authors: Dixon Joanna L.
Published: April 2008

Environmental context. The subtropical oceans comprise ~70% of the world’s ocean surface and profoundly affect global biogeochemistry and climate. They are characteristically low-nutrient regions, but, owing to their large extent and often rapid nutrient turnover, may contribute to greater than 30% of the total marine primary production. However, there remains long-standing uncertainty as to what individual or combination of resources, e.g. macro (N, P) and micro (trace metals) nutrients, limit or co-limit marine productivity and thus total carbon fixation in these spatially dominant gyre systems.
Abstract. The subtropical oceans are characteristically low-nutrient low-chlorophyll regions, but owing to their geographical dominance and rapid nutrient cycling may contribute >30% of the total marine primary production. The present study investigates the addition of P, Fe, Co and Zn on rates of primary production and heterotrophic bacterial production, through a combination of mesoscale in situ (P, and P + Fe) and in vitro (Co or Zn) bioassay incubation experiments.
Results from the bioassay incubation experiments suggest that primary production and chlorophyll a biomass are limited by N and P in this oligotrophic region. However, both were increased further after addition of trace metal micronutrients in the order Fe + Zn ≥ Fe + Co > Fe ≈ Co. In contrast, rates of heterotrophic bacterial production did not appear to be P, or significantly, P + Fe limited, although in situ rates did increase during the first 12 h of mesoscale P fertilisation (which were not mirrored in the mesoscale P + Fe addition). The addition of Co to unfertilised waters increased heterotrophic bacterial production and the numbers of heterotrophic bacteria, Prochlorococcus spp. and Synechococcus spp., suggesting Co limitation. Prochlorococcus spp. were the most abundant autotrophs. The highest increases in both heterotrophic and autotrophic carbon assimilation were shown after in vitro addition of either Co or Zn to mesoscale enriched P + Fe waters, suggesting multiple limitation of microbial growth rates in the subtropical oligotrophic north-east Atlantic.
Corrigendum to: Trace metal dynamic speciation studied by scanned stripping chronopotentiometry (SSCP)
Authors: Domingos Rute F. , Lopez Rócio , Pinheiro José P.
Published: April 2008

Environmental context. Natural aquatic systems are subject to changing conditions and practically never reach chemical equilibrium. Therefore, a quantitative understanding of the interaction of the trace metals with heterogeneous samples and their kinetic characteristics requires the dynamic characterisation of trace metal speciation. We show that scanned stripping chronopotentiometry (SSCP) is able to discriminate the dynamic nature of the complexes, although it still overestimates the average stability constants obtained from the SSCP wave characteristics using the Freundlich isotherm to account for the chemical heterogeneity.
Abstract. The ability of scanned stripping chronopotentiometry (SSCP) to obtain dynamic information for metal complexation with heterogeneous colloidal ligands was evaluated by measurements of lead(II) and cadmium(II) complexation by humic and fulvic acids extracted from an ombrotrophic peat bog. Average stability constants were calculated, using a first order chemical heterogeneity approach, and compared with those obtained by an ion selective electrode (ISE). SSCP average stability constants were overestimated in comparison to those obtained by the ISE, which suggests that the first order heterogeneity approach did not fully account for the ligand heterogeneity. However, the comparison of the stability constants obtained from the two SSCP signals (the shift of the half-wave potential and the decrease of transition time) provides information about the dynamic nature of the metal complexes formed with the humic matter. These results were in reasonable agreement with the theoretical predictions of the dynamic theory for colloidal systems.
Chasing quicksilver northward: mercury chemistry in the Arctic troposphere
Authors: Hedgecock Ian M. , Pirrone Nicola , Sprovieri Francesca
Published: April 2008

Environmental Context. ‘Mercurial storms rage over the Arctic’ wrote Fred Pearce in New Scientist in June of 1997: he was referring to the recent discovery by Bill Schroeder and his colleagues (Nature, Vol. 394, 1998) of periods soon after Arctic dawn when the concentration of mercury in the atmosphere literally plummets to levels so low that they can be undetectable, even by the most sensitive of modern instruments. A decade and many measurement campaigns later, we think we understand how these so-called depletion events occur, if not all the mechanisms that go towards providing the conditions for them to happen. Nor do we really know what happens to the mercury removed from the atmosphere; the fear is that it is deposited and enters the Arctic ecosystem, where it is potentially extremely harmful. The present study questions whether that fear is grounded.
Abstract. The tropospheric boundary layer chemistry of Hg has been simulated using a two-phase photochemical box model to see if our current (experimental and theoretical) understanding of Hg(g)0 reaction rates can account for the depletion events seen during Arctic spring, when the so-called ‘bromine explosion’ in the model is constrained by the measured ozone depletion rate. The simulations reveal that the observed rate of Hg(g)0 depletion can be accounted for; however, the measured concentrations of gas-phase oxidised Hg and HgP (Hg associated with particulate matter) cannot. Simulating the emission of Hg(g)0 from the snow pack to mimic the observed concentration recovery after a depletion event suggests the net Hg deposition from a depletion event is all but irrelevant.
Intrinsic noise, dissipation cost, and robustness of cellular networks: The underlying energy landscape of MAPK signal transduction
Authors: Lapidus Saul , Han Bo , Wang Jin
Published: April 2008

We develop a probabilistic method for analyzing global features of a cellular network under intrinsic statistical fluctuations, which is important when there are finite numbers of molecules. By making a self-consistent mean field approximation of splitting the variables in order to reduce the large number of degrees of freedom, which is reasonable for a not very strongly interacting network, we discovered that the underlying energy landscape of the mitogen-activated protein kinases (MAPKs) signal transduction network (with experimentally measured or inferred parameters such as chemical reaction rate coefficients in the network) is funneled toward a global minimum characterized by the nonequilibrium steady-state fixed point of the system at the end of the signal transduction process. For this system, we also show that the energy landscape is robust against intrinsic fluctuations and random perturbation to the inherent chemical reaction rates. The ratio of the slope versus the roughness of the energy landscape becomes a quantitative measure of robustness and stability of the network. Furthermore, we quantify the dissipation cost of this nonequilibrium system through entropy production, caused by the nonequilibrium flux in the system. We found that a lower dissipation cost corresponds to a more robust network. This least dissipation property might provide a design principle for robust and functional networks. Finally, we find the possibility of bistable and oscillatory-like solutions, which are important for cell fate decisions, upon perturbations. The method described here can be used in a variety of biological networks.
Cardiogenic small molecules that enhance myocardial repair by stem cells
Authors: Sadek Hesham , Hannack Britta , Choe Elizabeth , Wang Jessica , Latif Shuaib , Garry Mary G. , Garry Daniel J. , Longgood Jamie , Frantz Doug E. , Olson Eric N. , Hsieh Jenny , Schneider Jay W.
Published: April 2008

The clinical success of stem cell therapy for myocardial repair hinges on a better understanding of cardiac fate mechanisms. We have identified small molecules involved in cardiac fate by screening a chemical library for activators of the signature gene
Nkx2.5
, using a
luciferase
knockin bacterial artificial chromosome (BAC) in mouse P19CL6 pluripotent stem cells. We describe a family of sulfonyl-hydrazone (Shz) small molecules that can trigger cardiac mRNA and protein expression in a variety of embryonic and adult stem/progenitor cells, including human mobilized peripheral blood mononuclear cells (M-PBMCs). Small-molecule-enhanced M-PBMCs engrafted into the rat heart in proximity to an experimental injury improved cardiac function better than control cells. Recovery of cardiac function correlated with persistence of viable human cells, expressing human-specific cardiac mRNAs and proteins. Shz small molecules are promising starting points for drugs to promote myocardial repair/regeneration by activating cardiac differentiation in M-PBMCs.
Partitioned expression of duplicated genes during development and evolution of a single cell in a polyploid plant
Authors: Hovav Ran , Udall Joshua A. , Chaudhary Bhupendra , Rapp Ryan , Flagel Lex , Wendel Jonathan F.
Published: April 2008

Polyploidy is an important driver of eukaryotic evolution, evident in many animals, fungi, and plants. One consequence of polyploidy is subfunctionalization, in which the ancestral expression profile becomes partitioned among duplicated genes (termed homoeologs). Subfunctionalization appears to be a common phenomenon insofar as it has been studied, at the scale of organs. Here, we use a high-resolution methodology to investigate the expression of thousands of pairs of homoeologs during the development of a single plant cell, using as a model the seed trichomes (“cotton fiber”) of allopolyploid (containing “A” and “D” genomes) cotton (
Gossypium
). We demonstrate that ≈30% of the homoeologs are significantly A- or D-biased at each of three time points studied during fiber development. Genes differentially biased toward the A or D genome belong to different biological processes, illustrating the functional partitioning of genomic contributions during cellular development. Interestingly, expression of the biased genes was shifted strongly toward the agronomically inferior D genome. Analyses of homoeologous gene expression during development of this cell showed that one-fifth of the genes exhibit changes in A/D ratios, indicating that significant alteration in duplicated gene expression is fairly frequent even at the level of development and maturation of a single cell. Comparing changes in homoeolog expression in cultivated versus wild cotton showed that most homoeolog expression bias reflects polyploidy rather than domestication. Evidence suggests, however, that domestication may increase expression bias in fibers toward the D genome, potentially implicating D-genome recruitment under human selection during domestication.
Representation, Interaction, and Intersubjectivity
Authors: Alterman Richard
Published: April 2008

What the participants share, their common “sense” of the world, creates a foundation, a framing, an orientation that enables human actors to see and act in coordination with one another. For recurrent activities, the methods the participants use to understand each other as they act change, making the intersubjective space in which actors operate richer and easier to produce. This article works through some of the issues that emerge from a close examination of intersubjectivity as it is managed through representation and interaction. The data that are presented document, in detail, a sequence of related interactions, within and across episodes of cooperation, where continuity and change can be observed. The emergence of conversational structure and coordinating representations are significant milestones in the long‐term development of a representational practice that support the runtime co‐construction of intersubjective space. Conversational structures emerge interactively to mediate recurrent points of coordination in the domain activity, and only secondarily the conversation itself. Coordinating representations change the representational practice of the participants by making it easier to manage their “shared view” of the collective work, enabling the participants to make progress, expand the field of the common activity, while exhibiting more control of if and when explicit grounding occurs.
The Dossettiani and the Concept of the Secular State in the Constitutional Debates: 1946–7
Authors: Bedani Gino
Published: April 2008

It is now generally accepted that the members of the Constituent Assembly who were charged with drafting the Constitution concentrated their efforts on formulating the ideals to be expressed in it at the expense of the institutional arrangements of the new Republic. This has generally been viewed as resulting from a combination of two factors: their weak grasp of the liberal principles underpinning liberal parliamentary democracy, and a concomitant error of judgement in assuming that sufficient stress on the ideals of the Constitution would guarantee the basis of a healthy democracy. This article sets out to examine the input of the most influential Catholic group, the dossettiani, and argues, against the error of judgement thesis, that in fact their rejection of the concept of the secular state was a more fundamental denial of important principles of a pluralist democracy than has usually been supposed. The article also places their contribution within the context of the Church's aim to create a ‘Christian civilization’, and further suggests that the model of Catholic Action which inspired its collateral vision of Catholic forces was corrosive of a pluralist vision of correct institutional arrangements. The article ends by suggesting that these factors may have weighed more heavily on subsequent distortions of Italian democracy than has so far been supposed.
An end to Collective Identities? Political Culture and Voting Behaviour in Sesto San Giovanni and Erba
Authors: Bull Anna
Published: April 2008

This paper addresses the question of the demise or resilience of political subcultures in Italy today, focusing on two areas, Sesto San Giovanni and Erba, characterized until recently by a socialist/communist subculture and a Catholic/interclassist one. The voting behaviour and political values of key social groups, above all industrial workers, in these two towns provides evidence of the persistence and indeed revival of political subcultures in Italy. The paper argues that their function has changed, though. Whereas in the past a political subculture encompassed the whole spatial community, nowadays it appears to represent the interests and needs of specific groups within a territory, thus becoming one of many political instruments and choices open to social actors and voters.
The tale of San Vittore: prisons, politics, crime and Fascism in Milan, 1943–1946
Authors: Foot John
Published: April 2008

The prison system under Fascism was used to house both common and political prisoners. After 25 July 1943, the prisons were opened, only to be closed once again in occupied Italy as the Nazis took over the system. San Vittore prison in Milan was theatre to a series of changes over the period from 1943 to 1946, culminating in the famous riots of April 1946. This article analyses the changes in the prison system, the mix of prisoners inside the institution and the continuation of the civil war inside San Vittore after liberation. This micro-focus allows reflections on a number of key issues regarding the post-war state: legitimacy, legality, repression and amnesty. The post-liberation regime's failure to keep order both inside and outside of the prison system was a key test of its legitimacy among those who had gone along with Fascism and were worried about what was to come: The article centres on the extraordinary and contested events surrounding the ‘revolt’ of 1946 in San Vittore and argues that accounts thus far provided are neither accurate nor particularly insightful about this key post-war moment. The amnesty of 1946, so long attributed to Togliatti's personal sense of responsibility was, in reality, forced upon the justice minister by the chaos in the prisons right across the peninsula.
Transforming Italy's institutions? The bicameral committee on institutional reform
Authors: Gilbert Mark
Published: April 2008

In 1997, Italy's leading politicians began the overdue process of revising the existing constitution. The bicameral commission of parliament charged with this task has proposed significant alterations to the country's institutional structure. Innovations include a directly elected presidency, an end to bicameralism and a greater role for sub-national tiers of administration. However, this article argues that the suggested changes are in fact less sweeping than they seem, and do not address the country's urgent need to move towards a more competitive form of democracy.
Pasolini contro Calvino: culture, the canon and the millennium
Authors: Gordon Robert S. C.
Published: April 2008

This article offers an account of a recent debate in the cultural pages of the Italian press on a polemical work of literary criticism entitled Pasolini contro Calvino, in which the two authors are shown to represent emblematically different attitudes towards literature, cultural institutions and the culture industry in post-war Italy. The debate surrounding this claim is examined in substance, but also as an illustration of the workings of culture in 1990s Italy.
The organization of industrial interests in Italy, 1906–1925
Authors: Morris Jonathan
Published: April 2008

Franklin Hugh Adler,Italian Industrialists from Liberalism to Fascism. The Political Development of the Industrial Bourgeoisie, Cambridge University Press, Cambridge, 1996, xv + 458 pp., ISBN 0–521–433406–8 hbk, £40.00

Giuseppe Berta,Il governo degli interessi. Industriali, rappresentanza e politica nell'Italia del nord-ovest 1906–1924, Marsilio, Venice, 1996, xv + 175 pp., ISBN 88–317–6342–3 pbk, 32,000 Lire

Giorgio FioccaStoria della Confindustria 1900–1914, Marsilio, Venice, 1994, 266 pp., ISBN 88–317–5850–0 hbk, 70,000 Lire

The three books under review trace the organization of industrial interests in Italy from the foundation of the Lega industrial di Torino (LIT) in 1906 to the insertion of Confindustria into the Fascist totalitarian state. As Franklin Hugh Adler's ambitious and detailed account relates the Lega (LIT) begat first a Federazione Industriali Piemontesi (1908) and then the Confederazione Italiana dell'Industria (CIDI) in 1910 which was relaunched as the Confederazione generale dell'industria Italiana (Confindustria) in 1919. All of these organizations came under the effective direction of Gino Olivetti, the first secretary of the Lega who emerges from Adler's analysis as the principal theorist of a liberalproductionist ideology that the author regards as the central value system of the Italian industrial bourgeoisie. The slimmer volumes (in both scope and size) of Giuseppe Berta and Giorgio Fiocca diverge from Adler's account in stressing the discontinuities in the process of association which are attributed to the triumph of one industrial faction over another, and the changes in direction consequent upon this. By presenting these organizations within the broader context of entrepreneurial and associational activity, their accounts also call into question the extent to which the positions of Confindustria can be assumed to be representative of Italian industrialists as a whole.
Mussolini's charisma
Authors: Gentile Emilio
Published: April 2008

Mussolini was the prototype of twentieth-century charismatic dictators. His personal charisma antedated the founding of Fascism and the formal construction of collective charisma through the movement and the personality cult. First forged in the socialist movement, Mussolini's charisma assumed a new guise when he became a supporter of Italy's intervention in the First World War. He acquired an aura for the third time as Fascist leader. There were always tensions between the Duce and Fascism as the latter embodied the collective charisma of a movement. Nevertheless, Fascist ideology and culture incorporated the idea of the charismatic leader as a focus and source of authority on the model of the Catholic Church. Although it was difficult by the 1930s to distinguish between the believer's exaltation and courtly adulation, Mussolini exercised a personal charisma for many Fascists even after his death.
Political leadership in Italy: towards a plebiscitary democracy?
Authors: Donovan Mark
Published: April 2008

Following the collapse of the ‘First Republic’, political leadership has become both more technocratic and more charismatic. Constitutional reform of a presidential type, which would reinforce this dual trend, has come near to being effected. This paper argues that organizational changes in the main political parties bring them close to being able to participate in such a system. It also argues that a plebiscitary form of constitutional democracy, namely some form of presidentialism, could reinforce the consolidation of the nascent two-bloc party system. Finally, it argues that a political system based on two competitive party blocs could be of great benefit to the Italian polity.
Face Familiarity, Distinctiveness, and Categorical Perception
Authors: Angeli Adriana , Davidoff Jules , Valentine Tim
Published: April 2008

Four experiments with faces support the original interpretation of categorical perception (CP) as only present for familiar categories. Unlike in the results of Levin and Beale (2000), no evidence is found for face identity CP with unfamiliar faces. Novel face identities were shown to be capable of encoding for immediate sorting purposes but the representations utilized do not have the format of perceptual categories. One possibility explored was that a choice of a distinctive face as an end-point in a morphed continuum can spuriously produce effects that resemble CP. Such morphed continua provided unequal psychological responses to equal physical steps though much more so in a better likeness paradigm than for forced-choice recognition. Thus, researchers doing almost the same experiments may produce very different results and come to radically different conclusions.
A comparative analysis of métiers and catch profiles for some French demersal and pelagic fleets
Authors: Marchal Paul
Published: April 2008

Marchal, P. 2008. A comparative analysis of métiers and catch profiles for some French demersal and pelagic fleets. – ICES Journal of Marine Science, 65: 674–686. A quantitative comparison between métiers and resulting catch profiles was carried out for seven French demersal and pelagic fleets operating in the North Sea, the eastern Channel, and the Bay of Biscay. Typologies for four métiers have been attempted, based on different factors (gear, mesh size, fishing ground, and/or a priori target species), data sources (logbooks or harbour enquiries), and aggregation levels. Catch profiles were selected through cluster analysis. The linkage between métiers and catch profiles was quantified using uncertainty coefficients, which depended on the métier typology being used and the fleet under consideration, but were not subject to substantial inter- or intra-annual fluctuations. Future catch profiles and métiers were forecast in 2005 based on the 2001–2004 métier/catch profile correlations. When contrasted with the 2005 observations, the forecasting score was greatest (80–85%) for pelagic trawlers and gillnetters, and lowest for demersal trawlers (5–60%).