bluuebunny/crossref_metadata_2025 huggingface dataset:
Is mannan-binding lectin (MBL) detectable on monocytes and monocyte-derived immature dendritic cells?
Authors: MacDonald Shirley L. , Downing Ian , Turner Marc , Kilpatrick David C.
Published: December 2008

MBL (mannan-binding lectin; also called mannose-binding lectin) is a circulating C-type lectin with a collagen-like region synthesized mainly by the liver. MBL may influence susceptibility to infection in recipients of stem cell transplants, and it has even been suggested that the MBL status of a donor can influence the recipient's susceptibility to post-transplant infections. We have previously reported that MBL can be detected on human monocytes and monocyte-derived dendritic cells, based on detection using biotinylated anti-MBL, suggesting that those cells could synthesize MBL. If true, permanent MBL replacement therapy could be achieved by stem cell infusions. However, two other groups independently failed to find mbl-2-derived mRNA in monocytes. Therefore, to confirm or refute our previous observations, we used an alternative experimental strategy. Instead of using biotinylated antibody and labelled streptavidin, detection of surface MBL was attempted using MBL-specific primary antibodies (131-1, 131-10 and 131-11) followed by fluorescein-labelled anti-IgG, and controlled by the use of non-specific IgG as primary antibody. Monocytes were counterstained with anti-CD14-PE before FACS analysis. Adherent monocytes were also cultured for 48 h in serum-free medium or converted into immature dendritic cells by culture with IL-4 (interleukin-4) and GM-CSF (granulocyte/monocyte colony-stimulating factor). During FACS analysis, the dendritic cells were gated after counter-staining with anti-CD1a-PE. MBL was readily detected on the surface of fresh monocytes using all three specific anti-MBL monoclonal antibodies, but specific anti-MBL binding was greatly diminished after monocytes had been cultured for 2 days in serum-free medium. Moreover, we could not detect any MBL present on the surface of monocyte-derived dendritic cells. We therefore conclude that MBL is indeed present on the surface of fresh human monocytes. However, in view of the mRNA findings of others and our own previous observation that no secretion of MBL took place in culture, we presume that the surface-bound MBL is derived from autologous plasma and not synthesized by the cells. This conclusion is consistent with our in vivo findings in stem cell transplant patients which provided evidence against significant extra-hepatic production of serum MBL. It provides no ready explanation for the remarkable observation of Mullighan, Heatley, Doherty, Szabo, Grigg, Hughes, Schwarer, Szer, Tait, Bik To and Bardy [(2002) Blood 99, 3524–3529] that the presence of variant alleles of mbl-2 in stem cell donors can influence susceptibility to serious infections in their recipients.
Organizational and Institutional Determinants of B2C Adoption under Shifting Environments
Authors: Jeyaraj Anand , Raiser Deborah B , Chowa Charles , Griggs Gary M
Published: December 2008

This study examines the adoption of business-to-consumer (B2C) e-commerce by bricks-and-mortar companies comprising the Standard & Poor's 500 (S&P 500) listings between 1992 and 2003. B2C represents a Type III information systems (IS) innovation that integrates IS with core business technologies. Extant studies on Type III innovations have examined organizational and institutional factors, solely or collectively, in explaining adoption, but not how their effects change under shifting environments over time. We develop an integrated model comprising organizational factors (i.e., espoused values and resources) and institutional factors (i.e., normative and mimetic pressures), as well as the moderating influence of shifting environments (i.e., early period and late period demarcated by changes in the environment). Using a piecewise event-history model specification, we examine the adoption of B2C innovations by 93 organizations over time. Our results show that both organizational and institutional factors influence B2C adoption; however, their effects varied with the environmental shifts. Specifically, senior IS executives influenced adoption in the early period whereas bandwagon mimetic pressures and business norms influenced adoption in the late period. The findings of our research demonstrate the importance of explicitly modeling environmental shifts in theorizing organizational adoption of innovations.
H
+
implanted channel waveguides in buried epitaxial crystalline YAG:Nd,Tm layers and infrared-to-blue upconversion characterization
Authors: Szachowicz Marta , Joubert Marie-France , Moretti Paul , Couchaud Maurice , Ferrand Bemard , Borca Camelia , Boudrioua Azzedine
Published: December 2008

Nd,Tm:YAG codoped single crystal waveguides were studied in order to discover if the presence of Nd3+ ions favors blue luminescence at 486 nm. Innovative implantation techniques were applied to locally change Δn and form varied H+ implanted channel structures in Nd,Tm:YAG buried epitaxial waveguiding layers. The guided blue luminescence due to the Tm3+ G14→H36 transition was studied under infrared excitation at 785 nm (Tm3+ absorption) and 808 nm (Nd3+ absorption) for the epitaxial planar waveguides of different Tm3+ and Nd3+ concentrations for all the implanted channel waveguide structures.
Crack problem in a long cylindrical superconductor
Authors: Yong Hua-Dong , Zhou You-He , Zeng Jun
Published: December 2008

In this work, the general problem of a center crack in a long cylindrical superconductor is studied. The dependence of the stress intensity factor on the parameters, including the crack length and the applied field, is investigated. We presented a simple model in which the effect of the crack on the critical current is taken into account. It is assumed that the crack forms a perfect barrier to the flow of current. The Bean model and the Kim model are considered for the critical state. Based on the complex potential and boundary collocation methods, the stress intensity factor under the magnetic field is obtained for a long cylindrical superconductor containing a central crack. The results show that the crack length and the applied field have significant effects on the fracture behavior of the superconductor.
Detection of spin current by electron spin resonance
Authors: Liang F. , Wang J. , Yang Y. H. , Chan K. S.
Published: December 2008

We propose an electrical scheme for detection of pure spin current without charge current by electron spin resonance (ESR). The pure spin current is flowing through a two-dimensional electron gas (2DEG) heterojunction consisting of two 2DEG electrodes with Rashba and/or Dresselhaus spin orbital interaction and a nonmagnetic narrow strip between them. When an ESR is introduced in the system, the interplay between ESR and spin current will lead to a nonzero charge current flowing due to breakdown of dynamic time reverse symmetry of the system. The induced charge current, not only its magnitude but also its direction, can be modulated by system parameters such as ESR frequency and gate voltage, because spin current itself fulfills the electron-hole inversion antisymmetry. Our proposal to use ESR pumping charge current may pave a new way to detect electrically pure spin current.
Light-emitting polymer space-charge-limited transistor
Authors: Chen Chun-Yu , Chao Yu-Chiang , Meng Hsin-Fei , Horng Sheng-Fu
Published: December 2008

Polymer light-emitting transistor is realized by vertically stacking a top-emitting polymer light-emitting diode on a polymer space-charge-limited transistor. The transistor modulates the current flow of the light-emitting diode by the metal-grid base voltage. The active semiconductor of the transistor is poly(3-hexylthiophene). Yellow poly(para-phenylene vinylene) derivative is used as the yellow emitting material. As the cathode is fixed at −12 V and the grid base voltage varies from 0.9 to −0.9 V the light emission is turned on and off with on luminance up to 1208 cd/m2. The current efficiency of the light-emitting transistor is 10 cd/A.
Shrinkage and expansion mechanisms of SiO2 elliptical membrane nanopores
Authors: Won Shin Jae , Lee Jeong Yong , Oh Do Hyun , Kim Tae Whan , Cho Woon Jo
Published: December 2008

20 nm SiO2 elliptical membrane nanopores with various thicknesses were directly formed in situ by using a focused electron beam with transmission electron microscopy (TEM). The shrinkage and the expansion behaviors of the SiO2 ellipse nanopores with different thicknesses were attributed to variations in their geometries, in particular their curvatures. The geometric mechanisms of elliptical nanopores with various thicknesses fabricated utilizing a SiO2 membrane with a thickness gradient by using an electron beam irradiation are described on the basis of TEM images, which depend on the electron beam irradiation time.
Numerical investigation of the magnetized plasma sheath characteristics in the presence of negative ions
Authors: Hatami M. M. , Shokri B. , Niknam A. R.
Published: December 2008

In this work, a planar and low-pressure discharge in a mixture of a noble gas (argon) and an electronegative gas (oxygen) is considered. It is assumed that the produced plasma consists of electrons, two species of positive ions, and one species of negative ion. The behavior of the density distribution and kinetic energy of these charged particles in the sheath region are studied. Also, it is assumed that a weak external magnetic field which is nearly perpendicular to the wall is exerted to the sheath region. The positive ion species are considered as a cold, collisionless fluid while both electron and negative ion densities obey the Boltzmann distribution. By using a hydrodynamic approach and ignoring ionization and recombination, it is shown numerically that by increasing the density of the negative ions in the plasma the density distribution of both positive ion species and the kinetic energy of these ion species decreases and increases, respectively. Also, it is shown that in the presence of the negative ions the normalized electrostatic potential of the sheath region changes and by increasing the negative ion densities the normalized electrostatic potential in the sheath increases. In addition, the effect of the density ratio of both positive ion species, density and temperature of the negative ions, and the magnitude of the external magnetic field are studied on the net density distribution of the charged particles in the sheath region. The obtained numerical results show that by decreasing the temperature of the negative ions the amplitude of the fluctuations of the net density distribution of the charged particles in the sheath region increases and the position of these fluctuations shifts toward the sheath edge. Finally, it is seen that in the absence of negative ions the net density distribution of charged particles in the sheath region is monotonic while in the presence of negative ions it is nonmonotonic.
Quasilinear theory of electron transport by radio frequency waves and nonaxisymmetric perturbations in toroidal plasmas
Authors: Kominis Y. , Ram A. K. , Hizanidis K.
Published: December 2008

The use of radio frequency waves to generate plasma current and to modify the current profile in magnetically confined fusion devices is well documented. The current is generated by the interaction of electrons with an appropriately tailored spectrum of externally launched rf waves. In theoretical and computational studies, the interaction of rf waves with electrons is represented by a quasilinear diffusion operator. The balance, in steady state, between the quasilinear operator and the collision operator gives the modified electron distribution from which the generated current can be calculated. In this paper the relativistic operator for momentum and spatial diffusion of electrons due to rf waves and nonaxisymmetric magnetic field perturbations is derived. Relativistic treatment is necessary for the interaction of electrons with waves in the electron cyclotron range of frequencies. The spatial profile of the rf waves is treated in general so that diffusion due to localized beams is included. The nonaxisymmetric magnetic field perturbations can be due to magnetic islands as in neoclassical tearing modes. The plasma equilibrium is expressed in terms of the magnetic flux coordinates of an axisymmetric toroidal plasma. The electron motion is described by guiding center coordinates using the action-angle variables of motion in an axisymmetric toroidal equilibrium. The Lie perturbation technique is used to derive a diffusion operator which is nonsingular and time dependent. The resulting action diffusion equation describes resonant and nonresonant momentum and spatial diffusion. Momentum space diffusion leads to current generation in the plasma and spatial diffusion describes the effect of rf waves and magnetic perturbations on spatial evolution of the current profile. Depending on the symmetry of the equilibrium and the corresponding relation of the action variables to the configuration space variables, in addition to diffusion along the radial direction, poloidal, and toroidal electron diffusion, is also described. In deriving the diffusion operator, no statistical assumption, such as, the Markovian assumption, for the underlying electron dynamics, is imposed. Consequently, the operator is time dependent and valid for a dynamical phase space that is a mix of correlated regular orbits and decorrelated chaotic orbits. The diffusion operator is expressed in a form suitable for implementation in a numerical code.
Density functional theory calculations of anisotropic constitutive relationships in alpha-cyclotrimethylenetrinitramine
Authors: Conroy M. W. , Oleynik I. I. , Zybin S. V. , White C. T.
Published: December 2008

Constitutive relationships in the crystalline energetic material α-cyclotrimethylenetrinitramine (α-RDX) have been investigated using first-principles density functional theory. The equilibrium properties of α-RDX including unit cell parameters and bulk modulus, as well as the hydrostatic equation of state (EOS), have been obtained and compared with available experimental data. The isotropic EOS has been extended to include the anisotropic response of α-RDX by performing uniaxial compressions normal to several low-index planes, {100}, {010}, {001}, {110}, {101}, {011}, and {111}, in the Pbca space group. The uniaxial-compression data exhibit a considerable anisotropy in the principal stresses, changes in energy, band gaps, and shear stresses, which might play a role in the anisotropic behavior of α-RDX under shock loading.
Raman scattering measurements of phonon anharmonicity in CuAlO2 thin films
Authors: Singh Manoj K. , Dussan S. , Sharma Ganpat L. , Katiyar Ram S.
Published: December 2008

CuAlO 2 thin films were grown on single crystalline sapphire substrates with c-axis orientation by rf sputtering method. The x-ray diffraction data indicate the formation of delafossite structure and tend to be oriented along (001). Temperature dependent Raman spectra of CuAlO2 thin films were measured from 80 to 1273 K, and we observed two optical modes at Eg (∼418 cm−1) and A1g(∼767 cm−1) showing anomalous frequency and linewidth shifts with temperature, which were interpreted as an experimental evidence of combined effect of lattice expansion and anharmonic phonon-phonon interaction in CuAlO2. At high temperature, polaronic state and change in effective mass due to lattice expansion also affect the frequency shift and the linewidth of the observed Raman modes.
Low write-current magnetic random access memory cell with anisotropy-varied free layers
Authors: Fukami S. , Honjo H. , Suzuki T. , Ishiwata N.
Published: December 2008

We propose a magnetic random access memory (MRAM) cell that utilizes field-induced switching and is applicable to high-speed memories. The MRAM cell, called the shape-varying MRAM cell, has three free layers, each having different shapes and functions, and achieves low write-current switching with high thermal stability and high external field robustness. We show analytically that one of the layers contributes to the low write-current switching and another contributes to the thermal stability. We also show the results of a micromagnetic simulation, in which write current of <0.5 mA, write time of <2 ns, energy barrier (ΔE/kBT)>100, and external field robustness of >32 Oe were obtained.
Nonlinear effects in thermoacoustic refrigerators driven by voltage-excited loudspeakers
Authors: Fan Li , Zhang Shu-yi , Zhang Hui
Published: December 2008

A nonlinear model of electrodynamic loudspeakers excited by voltages is used to study the influences of nonlinearities of loudspeakers on performances of thermoacoustic refrigerators. The theoretical simulated results demonstrate that the nonlinearities of the magnetic fields and vibration components of the loudspeakers change electroacoustic transfer efficiencies and acoustic output powers of the loudspeakers, and the nonlinearities of the vibration components also shift the resonance frequencies of the loudspeakers. In the voltage-excited systems, the product of the magnetic induction intensity and the length of the coil play an important part in the performances of the acoustic source because of the influence of the motional electromotive force exerted on the coil when it is moving in the magnetic field.
Self-fields in a free-electron laser with electromagnetic-wave wiggler and ion-channel guiding
Authors: Mehdian H. , Hasanbeigi A. , Jafari S.
Published: December 2008

A theory of self-fields in a free-electron laser with electromagnetic-wave wiggler and ion-channel guiding is presented. The equations of motion for an electron have been analyzed. This equation together with its numerical solutions shows that the first part of group I and II trajectories is unstable. The effects of self-fields on the gain for groups I and II orbits have also been investigated by deriving the gain formula and numerical calculation. A gain decrement is found due to the effects of self-fields for group I orbits, and the gain enhancement for group II orbits. The gain decrement (enhancement) arises from diamagnetic (paramagnetic) generated by the self-fields. The gain decrement (enhancement) increases by increasing the beam density.
Ultrathin AlN∕GaN heterostructure field-effect transistors with deposition of Si atoms on AlN barrier surface
Authors: Onojima Norio , Hirose Nobumitsu , Mimura Takashi , Matsui Toshiaki
Published: December 2008

We deposited Si atoms on the AlN barrier surface of an ultrathin AlN∕GaN heterostructure field-effect transistor (HFET). This induced a remarkable change in the electrical properties of the two-dimensional electron gas. A 2-nm-thick Si layer reduced the sheet resistance of an AlN∕GaN HFET (AlN barrier, 2nm) from 60356to388Ω∕sq. The effect on the Ohmic contact was also significant: the presence of an undermost layer of Si atoms under Ohmic contacts produced a low specific contact resistance of 1.7×10–6Ωcm2. A 50-nm-gate AlN∕GaN HFET with a Si layer exhibited excellent device characteristics with a current-gain cutoff frequency of 106GHz.
Lateral-driven continuous magnetophoretic separation of blood cells
Authors: Jung Jinhee , Han Ki-Ho
Published: December 2008

We present a method for the lateral-driven continuous magnetophoretic separation of red and white blood cells from peripheral whole blood, based on their native magnetic properties. The separation is achieved using a high-gradient magnetic field, caused by a ferromagnetic wire array inlaid on glass substrate. The wire array creates an even lateral magnetophoretic force on the whole area of the microchannel, improving the separation efficiency and throughput. When the flow rate and external magnetic flux were 20 μl/h and 0.3 T, respectively, the microseparator continuously separated out 93.9% of red blood cells and 89.2% of white blood cells from the whole blood.
New versatile and linear optical sensor based on electro-optical modulation and compensation
Authors: Claverie Rémy , Salvestrini Jean Paul , Fontana Marc D. , Ney Pascal
Published: December 2008

This paper is devoted to the description and characterization of a new electro-optic sensor based on a polarimetric device operating in reflection mode, and on a closed-loop controller. The main features of the proposed sensor are versatility, insensitivity to the laser beam optical power fluctuation, and fully linear working mode. The resolution of the sensor, in terms of phase shift, is shown to be better than ±20 mrad and its accuracy to ±50 mrad.
Ground-state charge-transfer complex formation in hybrid poly(3-hexyl thiophene):titanium dioxide solar cells
Authors: Haeldermans I. , Vandewal K. , Oosterbaan W. D. , Gadisa A. , D’Haen J. , Van Bael M. K. , Manca J. V. , Mullens J.
Published: December 2008

The existence of a ground-state charge-transfer (CT) complex in a conjugated polymer:metal oxide nanoparticle bulk heterojunction photovoltaic cell is demonstrated by Fourier-transform photocurrent spectroscopy (FTPS). The CT complex between poly(3-hexylthiophene) (P3HT) and titanium dioxide (TiO2) is characterized by a weak additional photocurrent band (onset 1eV) in the FTPS spectra, situated below the conjugated polymer bandgap of 2eV. The presence of CT interaction between P3HT and TiO2 in relation to frontier orbital alignment is discussed, as well as the contribution of a sub-bandgap interfacial CT state to the electron transfer process in P3HT:TiO2 solar cells.
Physics Nobel Prize to Nambu, Kobayashi, and Maskawa for theories of symmetry breaking
Authors: Schwarzschild Bertram
Published: December 2008

In particle physics, some symmetries are so severely broken that they’re hard to recognize. Others are so slightly broken that the imperfection is hard to find.
Trampoline model of vertical earthquake ground motion
Authors: Matthews Jermey N. A.
Published: December 2008

These items, with supplementary material, first appeared at http://www.physicstoday.org.
Batteries and electrochemical capacitors
Authors: Abruña Héctor D. , Kiya Yasuyuki , Henderson Jay C.
Published: December 2008

Present and future applications of electrical energy storage devices are stimulating research into innovative new materials and novel architectures.
Who is listening? What do they hear?
Authors: Benka Stephen G.
Published: December 2008

In communicating our science, have we put too much emphasis on the information we want to convey? Perhaps there is another way to think about it.
Traffic and tillage effects on wheat production on the Loess Plateau of China: 1. Crop yield and SOM
Authors: Chen Hao , Bai Yuhua , Wang Qingjie , Chen Fu , Li Hongwen , Tullberg J. N. , Murray J. R. , Gao Huanwen , Gong Yuanshi
Published: December 2008

Challenges for dryland farming on the Loess Plateau of China are continuous nutrient loss, low soil organic matter and crop yield, and soil degradation. Controlled traffic, combined with zero or minimum tillage and residue cover, has been proposed to improve soil structure and crop yield. From 1998 to 2006, we conducted a field experiment comparing soil organic matter and wheat productivity between controlled traffic and conventional tillage farming systems. The field experiment was conducted using 2 controlled traffic treatments (zero tillage with residue cover and no compaction, shallow tillage with residue cover and no compaction) and a conventional tillage treatment. Results showed that controlled traffic treatments significantly increased soil organic matter and microbial biomass in the 0–0.30 m soil profile. Controlled traffic with zero tillage significantly increased total N in the 0–0.05 m soil profile. The mean yield over 8 years of controlled traffic treatments was >10% greater than that of conventional tillage. Controlled traffic farming appears to be a solution to the cropping problems faced on the Loess Plateau of China.
Carbon and N turnover in moist sandy soil following short exposure to a range of high soil temperature regimes
Authors: Luxhøi J. , Fillery I. R. P. , Recous S. , Jensen L. S.
Published: December 2008

Laboratory experiments were undertaken to examine the effects of high soil temperatures on N biotransformations in sandy soils. Soils were incubated at 30°, 40°, 50°, and 60°C for 2 days, before all treatments were kept at 30°C for up to 41 days. Another laboratory experiment evaluated the effect of different cycles of exposure to 50° and 30°C, including frequency and duration of exposure to 50°C, to assess the sensitivity of N biotransformations to temporary increases in temperature in the high range. CO2-C production, soil microbial biomass-C, gross N mineralisation, gross N immobilisation, and potential gross nitrification were measured. Gross N mineralisation and CO2-C production increased with temperature (in the range 30°−50°C) and exhibited a Q10-relationship close to 2. Between 50° and 60°C, Q10 was closer to 2.8. The increase in gross N mineralisation and CO2-C production after exposure to 50° and 60°C is attributed to the decomposition of dead microbial biomass by the viable microbial population but this flush in activity was short-lived. Immobilisation rate was always low and remained unaffected by the temperature regime, probably because the growth of the microbial biomass was inhibited at the higher temperatures. This imbalance between gross N mineralisation and immobilisation resulted in rapid increases in mineral N in soil. Two 6-h cycles of 50°C interspersed with 30°C were equally as effective as a single 48-h exposure at stimulating CO2 production. Evidence of uncoupling CO2 production and gross N mineralisation was observed in one study where soil was incubated at 50°C, but this response was not universal. The nitrification process was totally suppressed by exposure to temperature higher than 40°C, probably due to thermal denaturation of enzymes. The relevance of findings to field conditions is discussed.
Increased survival of western corn rootworm on transgenic corn within three generations of on-plant greenhouse selection
Authors: Meihls Lisa N. , Higdon Matthew L. , Siegfried Blair D. , Miller Nicholas J. , Sappington Thomas W. , Ellersieck Mark R. , Spencer Terence A. , Hibbard Bruce E.
Published: December 2008

To delay evolution of insect resistance to transgenic crops producingBacillus thuringiensis(Bt) toxins, nearby “refuges” of host plants not producing Bt toxins are required in many regions. Such refuges are expected to be most effective in slowing resistance when the toxin concentration in Bt crops is high enough to kill all or nearly all insects heterozygous for resistance. However, Bt corn,Zea mays, introduced recently does not meet this “high-dose” criterion for control of western corn rootworm (WCR),Diabrotica virgifera virgifera. A greenhouse method of rearing WCR on transgenic corn expressing the Cry3Bb1 protein was used in which approximately 25% of previously unexposed larvae survived relative to isoline survival (compared to 1–4% in the field). After three generations of full larval rearing on Bt corn (Constant-exposure colony), WCR larval survival was equivalent on Bt corn and isoline corn in greenhouse trials, and the LC50was 22-fold greater for the Constant-exposure colony than for the Control colony in diet bioassays with Cry3Bb1 protein on artificial diet. After six generations of greenhouse selection, the ratio of larval recovery on Bt corn to isoline corn in the field was 11.7-fold greater for the Constant-exposure colony than the Control colony. Removal from selection for six generations did not decrease survival on Bt corn in the greenhouse. The results suggest that rapid response to selection is possible in the absence of mating with unexposed beetles, emphasizing the importance of effective refuges for resistance management.
Membrane shape as a reporter for applied forces
Authors: Lee Heun Jin , Peterson Eric L. , Phillips Rob , Klug William S. , Wiggins Paul A.
Published: December 2008

Recent advances have enabled 3-dimensional reconstructions of biological structures in vivo, ranging in size and complexity from single proteins to multicellular structures. In particular, tomography and confocal microscopy have been exploited to capture detailed 3-dimensional conformations of membranes in cellular processes ranging from viral budding and organelle maintenance to phagocytosis. Despite the wealth of membrane structures available, there is as yet no generic, quantitative method for their interpretation. We propose that by modeling these observed biomembrane shapes as fluid lipid bilayers in mechanical equilibrium, the externally applied forces as well as the pressure, tension, and spontaneous curvature can be computed directly from the shape alone. To illustrate the potential power of this technique, we apply an axial force with optical tweezers to vesicles and explicitly demonstrate that the applied force is equal to the force computed from the membrane conformation.
Storage of cellular 5′ mRNA caps in P bodies for viral cap-snatching
Authors: Mir M. A. , Duran W. A. , Hjelle B. L. , Ye C. , Panganiban A. T.
Published: December 2008

The minus strand and ambisense segmented RNA viruses include multiple important human pathogens and are divided into three families, theOrthomyxoviridae, theBunyaviridae, and theArenaviridae. These viruses all initiate viral transcription through the process of “cap-snatching,” which involves the acquisition of capped 5′ oligonucleotides from cellular mRNA. Hantaviruses are emerging pathogenic viruses of theBunyaviridaefamily that replicate in the cytoplasm of infected cells. Cellular mRNAs can be actively translated in polysomes or physically sequestered in cytoplasmic processing bodies (P bodies) where they are degraded or stored for subsequent translation. Here we show that the hantavirus nucleocapsid protein binds with high affinity to the 5′ cap of cellular mRNAs, protecting the 5′ cap from degradation. We also show that the hantavirus nucleocapsid protein accumulates in P bodies, where it sequesters protected 5′ caps. P bodies then serve as a pool of primers during the initiation of viral mRNA synthesis by the viral polymerase. We propose that minus strand segmented viruses replicating in the cytoplasm have co-opted the normal degradation machinery of P bodies for storage of cellular caps. Our data also indicate that modification of the cap-snatching model is warranted to include a role for the nucleocapsid protein in cap acquisition and storage.
Extracellular proteolysis by matrix metalloproteinase-9 drives dendritic spine enlargement and long-term potentiation coordinately
Authors: Wang Xiao-bin , Bozdagi Ozlem , Nikitczuk Jessica S. , Zhai Zu Wei , Zhou Qiang , Huntley George W.
Published: December 2008

Persistent dendritic spine enlargement is associated with stable long-term potentiation (LTP), and the latter is thought to underlie long-lasting memories. Extracellular proteolytic remodeling of the synaptic microenvironment could be important for such plasticity, but whether or how proteolytic remodeling contributes to persistent modifications in synapse structure and function is unknown. Matrix metalloproteinase-9 (MMP-9) is an extracellular protease that is activated perisynaptically after LTP induction and required for LTP maintenance. Here, by monitoring spine size and excitatory postsynaptic potentials (EPSPs) simultaneously with combined 2-photon time-lapse imaging and whole-cell recordings from hippocampal neurons, we find that MMP-9 is both necessary and sufficient to drive spine enlargement and synaptic potentiation concomitantly. Both structural and functional MMP-driven forms of plasticity are mediated through β1-containing integrin receptors, are associated with integrin-dependent cofilin inactivation within spines, and require actin polymerization. In contrast, postsynaptic exocytosis and protein synthesis are both required for MMP-9-induced potentiation, but not for initial MMP-9-induced spine expansion. However, spine expansion becomes unstable when postsynaptic exocytosis or protein synthesis is blocked, indicating that the 2 forms of plasticity are expressed independently but require interactions between them for persistence. When MMP activity is eliminated during theta-stimulation-induced LTP, both spine enlargement and synaptic potentiation are transient. Thus, MMP-mediated extracellular remodeling during LTP has an instructive role in establishing persistent modifications in both synapse structure and function of the kind critical for learning and memory.
Functional network reorganization during learning in a brain-computer interface paradigm
Authors: Jarosiewicz Beata , Chase Steven M. , Fraser George W. , Velliste Meel , Kass Robert E. , Schwartz Andrew B.
Published: December 2008

Efforts to study the neural correlates of learning are hampered by the size of the network in which learning occurs. To understand the importance of learning-related changes in a network of neurons, it is necessary to understand how the network acts as a whole to generate behavior. Here we introduce a paradigm in which the output of a cortical network can be perturbed directly and the neural basis of the compensatory changes studied in detail. Using a brain-computer interface, dozens of simultaneously recorded neurons in the motor cortex of awake, behaving monkeys are used to control the movement of a cursor in a three-dimensional virtual-reality environment. This device creates a precise, well-defined mapping between the firing of the recorded neurons and an expressed behavior (cursor movement). In a series of experiments, we force the animal to relearn the association between neural firing and cursor movement in a subset of neurons and assess how the network changes to compensate. We find that changes in neural activity reflect not only an alteration of behavioral strategy but also the relative contributions of individual neurons to the population error signal.
S layer protein A of
Lactobacillus acidophilus
NCFM regulates immature dendritic cell and T cell functions
Authors: Konstantinov Sergey R. , Smidt Hauke , de Vos Willem M. , Bruijns Sven C. M. , Singh Satwinder Kaur , Valence Florence , Molle Daniel , Lortal Sylvie , Altermann Eric , Klaenhammer Todd R. , van Kooyk Yvette
Published: December 2008

Dendritic cells (DCs) are antigen-presenting cells that play an essential role in mucosal tolerance. They regularly encounter beneficial intestinal bacteria, but the nature of these cellular contacts and the immune responses elicited by the bacteria are not entirely elucidated. Here, we examined the interactions of
Lactobacillus acidophilus
NCFM and its cell surface compounds with DCs.
L. acidophilus
NCFM attached to DCs and induced a concentration-dependent production of IL-10, and low IL-12p70. We further demonstrated that the bacterium binds to DC-specific ICAM-3-grabbing nonintegrin (DC-SIGN), a DC- specific receptor. To identify the DC-SIGN ligand present on the bacterium, we took advantage of a generated array of
L. acidophilus
NCFM mutants. A knockout mutant of
L. acidophilus
NCFM lacking the surface (S) layer A protein (SlpA) was significantly reduced in binding to DC-SIGN. This mutant incurred a chromosomal inversion leading to dominant expression of a second S layer protein, SlpB. In the SlpB-dominant strain, the nature of the interaction of this bacterium with DCs changed dramatically. Higher concentrations of proinflammatory cytokines such as IL-12p70, TNFα, and IL-1β were produced by DCs interacting with the SlpB-dominant strain compared with the parent NCFM strain. Unlike the SlpA-knockout mutant, T cells primed with
L. acidophilus
NCFM stimulated DCs produced more IL-4. The SlpA–DC-SIGN interaction was further confirmed as purified SlpA protein ligated directly to the DC-SIGN. In conclusion, the major S layer protein, SlpA, of
L. acidophilus
NCFM is the first probiotic bacterial DC-SIGN ligand identified that is functionally involved in the modulation of DCs and T cells functions.
Shadow of the Fatwa
Authors: Malik Kenan
Published: December 2008

Salman Rushdie’s critics lost the battle, but they won the war against free speech, says Kenan Malik
Legislating in the Dark
Authors: Keefe Patrick Radden
Published: December 2008

Patrick Radden Keefe considers how oversight got overlooked when Bush went wiretapping
Emblem of Darkness
Authors: Lévy Bernard-Henri , Lehrer Natasha
Published: December 2008

The fatwa marked a new era: a retreat from the ideal of tolerance and the spirit of the Enlightenment, says Bernard-Henri Lévy
Category length produces an inverted-U discriminability function in episodic recognition memory
Authors: Neely James H. , Tse Chi-Shing
Published: December 2008

Four experiments used signal detection analyses to assess recognition memory for lists of words consisting of differing numbers of exemplars from different semantic categories. The results showed that recognition memory performance, measured by d a, (a) increased as category length (CL, the number of study-list items selected from the same semantic category) increased from 1 to 8 but then decreased as CL further increased from 8 to 14, (b) was greater when 2 studied items from the same category occurred back to back, rather than being separated by 5–11 items from other categories, and (c) was greater for the first studied 2 exemplars than for the last studied 2 exemplars from blocked categories with CLs of 8 or 14. For all CLs, all z-coordinate receiver operating characteristic ( z-ROC) functions were linear with slopes significantly less than 1.0, and none had a significant quadratic component. These results pose a challenge for three major classes of recognition memory models: item-noise, context-noise, and dual-process models.
Generality of the Summation Effect in Human Causal Learning
Authors: Soto Fabian A. , Vogel Edgar H. , Castillo Ramón D. , Wagner Allan R.
Published: December 2008

Considerable research has examined the contrasting predictions of the elemental and configural association theories proposed by Rescorla and Wagner (1972) and Pearce (1987), respectively. One simple method to distinguish between these approaches is the summation test, in which the associative strength attributed to a novel compound of two separately trained cues is examined. Under common assumptions, the configural view predicts that the strength of the compound will approximate to the average strength of its components, whereas the elemental approach predicts that the strength of the compound will be greater than the strength of either component. Different studies have produced mixed outcomes. In studies of human causal learning, Collins and Shanks (2006) suggested that the observation of summation is encouraged by training, in which different stimuli are associated with different submaximal outcomes, and by testing, in which the alternative outcomes can be scaled. The reported experiments further pursued this reasoning. In Experiment 1, summation was more substantial when the participants were trained with outcomes identified as submaximal than when trained with simple categorical (presence/absence) outcomes. Experiments 2 and 3 demonstrated that summation can also be obtained with categorical outcomes during training, if the participants are encouraged by instruction or the character of training to rate the separately trained components with submaximal ratings. The results are interpreted in terms of apparent performance constraints in evaluations of the contrasting theoretical predictions concerning summation.
Examining the influence of action on spatial working memory: The importance of selection
Authors: Dodd Michael D. , Shumborski Sarah
Published: December 2008

We report three experiments that examine the influence of pointing-to relative to passively viewing an array of objects that participants are attempting to memorize. Recently, Chum, Bekkering, Dodd, and Pratt (2007) provided evidence that pointing to objects enhanced memory relative to passively viewing objects when pointing instruction was manipulated within trial (e.g., point to one array but passively view the other). We replicate this result but also demonstrate that when pointing instruction is blocked (e.g., participants point to or passively view all items in an array as opposed to pointing to some while passively viewing others), pointing to an array of objects actually decreases memory relative to passively viewing that array. Moreover, when pointing is manipulated within trial, the influence of action on working-memory performance appears to be attributable to an enhancement of processing of the pointed-to items as well as a subsequent inhibition of the passively viewed array. These results demonstrate that while action can enhance working memory under conditions where a subset of items is actively selected for additional processing, when selection is not a requirement (e.g., either point to everything or passively view everything), action decreases working-memory performance. Thus, the relationship between action and spatial working memory is complex and context dependent. These results are also discussed as they relate to other similar phenomena (e.g., retrieval-induced forgetting, Corsi Blocks test) in which selection during processing may be critical, and collectively these results provide important insight into spatial working memory and the factors that influence it.
Core verbal working-memory capacity: The limit in words retained without covert articulation
Authors: Chen Zhijian , Cowan Nelson
Published: December 2008

Verbal working memory may combine phonological and conceptual units. We disentangle their contributions by extending a prior procedure (Chen & Cowan, 2005) in which items recalled from lists of previously seen word singletons and of previously learned word pairs depended on the list length in chunks. Here we show that a constant capacity of about 3 chunks holds across list lengths and list types, provided that covert phonological rehearsal is prevented. What remains is a core verbal working-memory capacity.
Short article: Impaired context maintenance in mild to moderately depressed students
Authors: Msetfi Rachel M. , Murphy Robin A. , Kornbrot Diana E. , Simpson Jane
Published: December 2008

We test the hypothesis that people with depression experience difficulties in maintaining task-relevant context information over longer periods of time using the AX version of the continuous performance task (AX-CPT). The AX-CPT requires that participants maintain a context cue (A) in an active state in order to respond correctly to a target cue (X) presented after a short delay. A total of 40 nondepressed and mild to moderately depressed students completed versions of the task with short (1-s) or long (10-s) interstimulus intervals (ISIs). Mildly depressed participants made significantly more context-dependent (BX) errors, unlike controls who made more errors on trials where good context processing would impair performance (AY). This pattern of errors was only evident in the long ISI condition, suggesting poor maintenance of contextual information.
Deriving a germinal center lymphocyte migration model from two-photon data
Authors: Figge Marc Thilo , Garin Alexandre , Gunzer Matthias , Kosco-Vilbois Marie , Toellner Kai-Michael , Meyer-Hermann Michael
Published: December 2008

Recently, two-photon imaging has allowed intravital tracking of lymphocyte migration and cellular interactions during germinal center (GC) reactions. The implications of two-photon measurements obtained by several investigators are currently the subject of controversy. With the help of two mathematical approaches, we reanalyze these data. It is shown that the measured lymphocyte migration frequency between the dark and the light zone is quantitatively explained by persistent random walk of lymphocytes. The cell motility data imply a fast intermixture of cells within the whole GC in approximately 3 h, and this does not allow for maintenance of dark and light zones. The model predicts that chemotaxis is active in GCs to maintain GC zoning and demonstrates that chemotaxis is consistent with two-photon lymphocyte motility data. However, the model also predicts that the chemokine sensitivity is quickly down-regulated. On the basis of these findings, we formulate a novel GC lymphocyte migration model and propose its verification by new two-photon experiments that combine the measurement of B cell migration with that of specific chemokine receptor expression levels. In addition, we discuss some statistical limitations for the interpretation of two-photon cell motility measurements in general.
Skin and Environmental Contamination With Vancomycin-Resistant Enterococci in Patients Receiving Oral Metronidazole or Oral Vancomycin Treatment forClostridium difficile–Associated Disease
Authors: Sethi Ajay K. , Al-Nassir Wafa N. , Nerandzic Michelle M. , Donskey Curtis J.
Published: December 2008

Background.

Oral metronidazole has been recommended for treatment of mild-to-moderateClostridium difficile–associated disease (CDAD), in part because of concern that use of vancomycin may be more likely to promote colonization and transmission of vancomycin-resistant enterococci (VRE). The objective of our study was to compare the frequency of skin and environmental VRE contamination associated with metronidazole treatment for CDAD with such frequency associated with vancomycin treatment for CDAD.

Design.

Prospective, observational study. This study was performed at the Cleveland Veterans Affairs Medical Center (Cleveland, OH). For patients with CDAD who had concurrent VRE colonization, stool, skin, and environmental samples were cultured for VRE before, during, and up to 3 weeks after therapy with metronidazole or vancomycin. The proportions of skin and environmental contamination were compared before and after resolution of diarrhea and during treatment with metronidazole or vancomycin.

Results.

Of the 34 patients, 17 were treated with vancomycin and 17 were treated with metronidazole. The proportion of environmental cultures that were positive for VRE was significantly higher during resolution of diarrhea than it was after resolution of diarrhea (38% vs 28%;P= .025), whereas the proportion of skin cultures positive was not different during and after resolution of diarrhea (78% vs 71%;P= .60). There were no differences between patients who received metronidazole and patients who received vancomycin in the proportions of skin culture results (73% vs 77%;P= .80) or environmental culture results (37% vs 32%;P= .359) that were positive for VRE. Eleven patients (32%) had chronic fecal incontinence, and 28 (82%) had incontinence at least once during their CDAD episode.

Conclusions.

In VRE-colonized patients with CDAD who experienced frequent fecal incontinence, skin and environmental VRE contamination was common during and after resolution of diarrhea. The frequency of VRE contamination was similar between patients treated with metronidazole and patients treated with vancomycin.
Review of Current Literature on the Economic Burden ofClostridium difficileInfection
Authors: Dubberke Erik R. , Wertheimer Albert I.
Published: December 2008

Clostridium difficileis well recognized as the most common infectious cause of healthcare-associated diarrhea. Since 2000, this pathogen has demonstrated an increased propensity to cause more frequent and virulent illness that is often refractory to treatment. An analysis by the Centers for Disease Control and Prevention revealed that, in the United States, the number of patients discharged from hospitals who received theInternational Classification of Diseases, Ninth Revisiondischarge diagnosis code forC. difficileinfection (CDI) more than doubled from 2000 to 2003. Unpublished data indicate that this trend has continued and that more than 250,000 US hospitalizations were associated with CDI in 2005. A previously uncommon hypervirulent strain ofC. difficileis thought to contribute, in part, to the dramatic increase in the incidence and severity of the infection. Although the economic impact of the disease is believed to be profound and is expected to increase, data on the costs associated with CDI are scarce. To more completely assess its economic burden, we performed a review of available literature that reported costs associated with the infection.