bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of leaf‐to‐canopy upscaling methodologies against carbon flux data in North America
Authors: Sprintsin Michael , Chen Jing M. , Desai Ankur , Gough Christopher M.
Published: January 2012

Despite the wide acceptance of the “big‐leaf” upscaling strategy in evapotranspiration modeling (e.g., the Penman‐Monteith model), its usefulness in simulating canopy photosynthesis may be limited by the underlying assumption of homogeneous response of carbon assimilation light‐response kinetics through the canopy. While previous studies have shown that the separation of the canopy into sunlit and shaded parts (i.e., two‐leaf model) is typically more effective than big‐leaf models for upscaling photosynthesis from leaf to canopy, a systematic comparison between these two upscaling strategies among multiple ecosystems has not been presented. In this study, gross primary productivity was modeled using two‐leaf and big‐leaf upscaling approaches in the Boreal Ecosystem Productivity Simulator for shrublands, broadleaf, and conifer forest types. When given the same leaf‐level photosynthetic parameters, the big‐leaf approach significantly underestimated canopy‐level GPP while the two‐leaf approach more closely predicted both the magnitude and day‐to‐day variability in eddy covariance measurements. The underestimation by the big‐leaf approach is mostly caused by its exclusion of the photosynthetic contributions of shaded leaves. Tests of the model sensitivity to a foliage clumping index revealed that the contribution of shaded leaves to the total simulated productivity can be as high as 70% for highly clumped stands and seldom decreases below ∼40% for less‐clumped canopies. Our results indicate that accurate upscaling of photosynthesis across a broad array of ecosystems requires an accurate description of canopy structure in ecosystem models.
Net carbon accumulation of a high‐latitude permafrost palsa mire similar to permafrost‐free peatlands
Authors: Olefeldt David , Roulet Nigel T , Bergeron Onil , Crill Patrick , Bäckstrand Kristina , Christensen Torben R.
Published: January 2012

Palsa mires, nutrient poor permafrost peatlands common in subarctic regions, store a significant amount of carbon (C) and it has been hypothesized their net ecosystem C balance (NECB) is sensitive to climate change. Over two years we measured the NECB for Stordalen palsa mire and found it to accumulate 46 g C m−2 yr−1. While Stordalen NECB is comparable to nutrient poor peatlands without permafrost, the component fluxes differ considerably in magnitude. Specifically, Stordalen had both lower growing season CO2 uptake and wintertime CO2losses, but importantly also low dissolved organic carbon exports and hydrocarbon (mainly methane) emissions. Restricted C losses from palsa mires are likely to have facilitated C accumulation of unproductive subarctic permafrost peatlands. Continued climate change and permafrost thaw is likely to amplify several component fluxes, with an uncertain overall effect on NECB – highlighting the necessity for projections of high‐latitude C storage to consider all C fluxes.
Mixing in the western equatorial Pacific and its modulation by ENSO
Authors: Richards K. J. , Kashino Y. , Natarov A. , Firing E.
Published: January 2012

High vertical resolution measurements of the flow in the western equatorial Pacific reveal the vertical shear to be dominated by flow features that have a small vertical scale (O(10 m)). This is true for all the measurements we have taken over a 3 year period and differing ENSO states. Much of the measured turbulent activity is found to be associated with these small scale features, with the suggestion that mixing in the region is heavily influenced by the presence of this small scale activity. The level of mixing within and above the thermocline is strongly modulated by ENSO events, with the level of mixing being significantly greater during the observed La Niña event. Changes to the stratification above the thermocline during ENSO events play a major role in both changes to the level of turbulent activity and the effective vertical diffusion coefficient.
Initial results from a dynamic coupled magnetosphere‐ionosphere‐ring current model
Authors: Pembroke Asher , Toffoletto Frank , Sazykin Stanislav , Wiltberger Michael , Lyon John , Merkin Viacheslav , Schmitt Peter
Published: January 2012

In this paper we describe a coupled model of Earth's magnetosphere that consists of the Lyon‐Fedder‐Mobarry (LFM) global magnetohydrodynamics (MHD) simulation, the MIX ionosphere solver and the Rice Convection Model (RCM) and report some results using idealized inputs and model parameters. The algorithmic and physical components of the model are described, including the transfer of magnetic field information and plasma boundary conditions to the RCM and the return of ring current plasma properties to the LFM. Crucial aspects of the coupling include the restriction of RCM to regions where field‐line averaged plasma‐β≤ 1, the use of a plasmasphere model, and the MIX ionosphere model. Compared to stand‐alone MHD, the coupled model produces a substantial increase in ring current pressure and reduction of the magnetic field near the Earth. In the ionosphere, stronger region‐1 and region‐2 Birkeland currents are seen in the coupled model but with no significant change in the cross polar cap potential drop, while the region‐2 currents shielded the low‐latitude convection potential. In addition, oscillations in the magnetic field are produced at geosynchronous orbit with the coupled code. The diagnostics of entropy and mass content indicate that these oscillations are associated with low‐entropy flow channels moving in from the tail and may be related to bursty bulk flows and bubbles seen in observations. As with most complex numerical models, there is the ongoing challenge of untangling numerical artifacts and physics, and we find that while there is still much room for improvement, the results presented here are encouraging.
Forecasting the Dst index during corotating interaction region events using synthesized solar wind parameters
Authors: Andriyas T. , Spencer E. , Raj A. , Sojka J. , Mays M. L.
Published: January 2012

Observations from SOHO, STEREO, and ACE during the declining phase of the solar cycle toward the deep minimum in 2008 are analyzed to establish the timing of corotating interaction region (CIR) activity. This analysis is then employed to synthesize signals of the z component of the interplanetary magnetic field (IMF) Bz, solar wind radial velocity vx, and solar wind proton density Np at 1 AU. The synthesized signals are used as a substitute for ACE measurements to represent solar wind forcing due to coronal hole driven CIR events occurring during multiple Bartel rotations (BR 2381 to BR 2393). The signals drive a low‐order physics‐based model of the magnetosphere called WINDMI, one of whose outputs is the ground‐based measurement of the Dst index. Estimating the arrival of CIR events for future rotations using ACE and SOHO data during BR 2381 produced what we refer to as an uncalibrated yearly forecast. We next generated a video‐calibrated estimate of the arrival times of CIR events in addition to information from BR 2381 using SOHO and STEREO images of the Sun in order to produce a simulated 3.5 day ahead forecast of possible geomagnetic activity. The time of arrival of CIR events is taken to be the travel time of density compressions as seen in a noninertial frame according to a radial solar wind speed of 500 km/s and a distance of 1 AU. We were able to forecast the timing of CIR‐induced geomagnetic activity to within 12 h for 17 out of 28 events by using the expected recurrence of the events through multiple Bartel rotations together with SOHO and STEREO coronal hole sightings made 3.5 days before every event. The uncertainty in the IMF Bz led to a forecast of levels of geomagnetic activity on an ensemble basis, yielding a distribution of different possible Dst signatures. We used a 10‐sample ensemble and a 50‐sample ensemble to obtain typical representations of geomagnetic activity. Depending on the periodicity and intensity of fluctuations in Bz, we obtained higher or lower levels of activity and shorter or longer times for the recovery of the Dst to quiet levels.
Resolving vertical and east‐west horizontal motion from differential interferometric synthetic aperture radar: The L'Aquila earthquake
Authors: Dalla Via G. , Crosetto M. , Crippa B.
Published: January 2012

Analysis of surface coseismic displacement has already been obtained for the 6 April 2009 L'Aquila (central Italy) earthquake from differential interferometric synthetic aperture radar (DInSAR) data. Working jointly on ascending and descending DInSAR data makes for a step forward with respect to published preliminary estimates: we process data in order to retrieve a continuous displacement pattern, both in the vertical and horizontal directions, the latter being limited to the eastward component because of the low sensibility of the SAR images used to resolve northward motion. Our analysis provides new insights on the horizontal component of displacement, obtaining a clear picture of eastward displacement patterns over the epicentral area. This result is noteworthy, as until now little information has been available on horizontal displacement following normal‐fault events in the central Apennines (Umbria‐Marche, 1997, and L'Aquila, 2009), given the lack of dense GPS networks, the only available source of horizontal displacement data in this area. Inverted fault characteristics from such data also show noteworthy differences compared to previous studies, localizing the Paganica fault as the causative fault for the earthquake.
Climate model simulated changes in temperature extremes due to land cover change
Authors: Avila F. B. , Pitman A. J. , Donat M. G. , Alexander L. V. , Abramowitz G.
Published: January 2012

A climate model, coupled to a sophisticated land surface scheme, is used to explore the impact of land use induced land cover change (LULCC) on climate extremes indices recommended by the Expert Team on Climate Change Detection and Indices (ETCCDI). The impact from LULCC is contrasted with the impact of doubling atmospheric carbon dioxide (CO2). Many of the extremes indices related to temperature are affected by LULCC and the resulting changes are locally and field significant. Some indices are systematically affected by LULCC in the same direction as increasing CO2 while for others LULCC opposes the impact of increasing CO2. We suggest that assumptions that anthropogenically induced changes in temperature extremes can be approximated just by increasing greenhouse gases are flawed, as LULCC may regionally mask or amplify the impact of increasing CO2 on climate extremes. In some regions, the scale of the LULCC forcing is of a magnitude similar to the impact of CO2 alone. We conclude that our results complicate detection and attribution studies, but also offer a way forward to a clearer and an even more robust attribution of the impact of increasing CO2 at regional scales.
Effects on precipitation, clouds, and temperature from long‐range transport of idealized aerosol plumes in WRF‐Chem simulations
Authors: Zhao Zhan , Pritchard Michael S. , Russell Lynn M.
Published: January 2012

Using the Weather Research and Forecasting model with Chemistry (WRF‐Chem), we explored the impacts of nonlocal aerosol plumes transported at three different altitudes on a summertime convective system developed in a clean environment over the northeastern United States. Idealized aerosol plumes from forest fire and volcano emissions, which are known to be frequently transported in this region, were prescribed at three separate altitudes on the upstream boundary of WRF‐Chem. The low‐altitude (1.5–2.5 km) plume characteristic of forest fire emissions intersects the water clouds, resulting in optically thicker clouds and about a 30% decrease in accumulated precipitation. The precipitation response to the idealized aerosol plume is attributed to the aerosol “second indirect effect” and aerosol‐induced enhancement in evaporation efficiency. Convection also significantly impacted this low‐altitude aerosol plume because wet removal scavenges up to 70% of plume aerosols over regions where deep convection and precipitation occur. In stark contrast, midaltitude (5.6–6.6 km) and high‐altitude (11.5–12.5 km) plumes exerted a negligible effect on clouds and precipitation. The apparent highly nonlinear sensitivity of simulated convection to the vertical positioning of nonlocal aerosol plumes is explained in terms of the dominant controls influencing this convection regime and limitations in the microphysics currently implemented in WRF‐Chem.
Aircraft observation of the seasonal variation in the transport of CO2 in the upper atmosphere
Authors: Sawa Yousuke , Machida Toshinobu , Matsueda Hidekazu
Published: January 2012

A large number of in situ carbon dioxide (CO2) measurements from 5224 flights were taken by commercial airliners from 2005 to 2010. We analyzed the seasonal cycles in tropospheric CO2 in wide areas of the world over the Eurasian continent, the North Pacific, Southeast Asia, and Oceania. In the Northern Hemisphere, large seasonal changes of CO2 in the upper troposphere are found from spring through summer at northern midlatitudes to high latitudes with significant longitudinal differences; seasonally low CO2 mixing ratios are vertically transported from the surface over the Eurasian continent and then transported eastward to the North Pacific. In the Southern Hemisphere, the CO2 in the upper troposphere increases rapidly from April to June, indicating clearly the interhemispheric transport of high CO2 from the Northern Hemisphere winter. The rapid increase in the upper southern lower latitudes is equivalent to about 0.2 Pg increase in carbon. This interhemispheric transport should be adequately represented in general circulation models for source/sink estimates by inverse methods, because it is comparable to the seasonal or net fluxes estimated for a current inversion area size or a typical subcontinental domain. Estimation for transport of CO2 through the high altitudes will be more important than ever with increasing data from aircraft observations.
Replies to comments on “A revisit of drawdown behavior during pumping in unconfined aquifers” by Neuman and Mishra
Authors: Yeh T.‐C. J. , Mao D. , Wan L. , Lee C.‐H. , Wen J.‐C. , Lu W.
Published: January 2012

Key Points

Transition of water release mechanisms

Heterogeneous, variably saturated flow equation

Unconfined aquifers
Characterisation of the Contribution of the GABA-Benzodiazepine α1 Receptor Subtype to [11C]Ro15-4513 PET Images
Authors: Myers James FM , Rosso Lula , Watson Ben J , Wilson Sue J , Kalk Nicola J , Clementi Nicoletta , Brooks David J , Nutt David J , Turkheimer Federico E , Lingford-Hughes Anne R
Published: January 2012

This positron emission tomography (PET) study aimed to further define selectivity of [11C]Ro15-4513 binding to the GABARα5 relative to the GABARα1 benzodiazepine receptor subtype. The impact of zolpidem, a GABARα1-selective agonist, on [11C]Ro15-4513, which shows selectivity for GABARα5, and the nonselective benzodiazepine ligand [11C]flumazenil binding was assessed in humans. Compartmental modelling of the kinetics of [11C]Ro15-4513 time-activity curves was used to describe distribution volume ( VT) differences in regions populated by different GABA receptor subtypes. Those with low α5 were best fitted by one-tissue compartment models; and those with high α5 required a more complex model. The heterogeneity between brain regions suggested spectral analysis as a more appropriate method to quantify binding as it does not a priori specify compartments. Spectral analysis revealed that Zolpidem caused a significant VT decrease (~10%) in [11C]flumazenil, but no decrease in [11C]Ro15-4513 binding. Further analysis of [11C]Ro15-4513 kinetics revealed additional frequency components present in regions containing both α1 and α5 subtypes compared with those containing only α1. Zolpidem reduced one component (mean ± s.d.: 71% ± 41%), presumed to reflect α1-subtype binding, but not another (13% ± 22%), presumed to reflect α5. The proposed method for [11C]Ro15-4513 analysis may allow more accurate selective binding assays and estimation of drug occupancy for other nonselective ligands.
Controlled synthesis of MDMO-PPV and block copolymers made thereof
Authors: Vandenbergh Joke , Cosemans Inge , Lutsen Laurence , Vanderzande Dirk , Junkers Tanja
Published: January 2012

Via CBr4-mediation bromine functional MDMO-PPVs with controlled molecular weight were obtained and chain extended in further ATRP reactions.
Early Language and Behavioral Regulation Skills as Predictors of Social Outcomes
Authors: Aro Tuija , Eklund Kenneth , Nurmi Jari-Erik , Poikkeus Anna-Maija
Published: January 2012

Purpose

In the present study, the authors examined the prospective associations among early language skills, behavioral regulation skills, and 2 aspects of school-age social functioning (adaptability and social skills).

Method

The study sample consisted of children with and without a familial risk for dyslexia. The authors analyzed the relations among children’s language (at age 2;6 [years;months] and age 5;0), behavioral regulation skills (at age 5;0), and social functioning (at age 8;0) using structural equation modeling. Subgroups of children with respect to language and behavioral regulation skills (at age 5;0) were identified through the use of mixture modeling.

Results

Among at-risk children, behavioral regulation skills mediated the association between early language skills and social outcomes. A subgroup of children with poor regulatory and weak language skills scored lower in adaptability, whereas a subgroup having only poor language skills (with normal behavioral regulation) did not differ from a group with age-appropriate skills.

Conclusions

The present findings indicate that behavioral regulation skills play an important role in predicting social outcomes among children at risk for language difficulties. Furthermore, it is suggested that various aspects of social functioning may be influenced differently by self-regulation skills and that predictive relationships vary with the degree of language development deficits and accompanying risks.
Influence of solute-solvent coordination on the orientational relaxation of ion assemblies in polar solvents
Authors: Ji Minbiao , Hartsock Robert W. , Sung Zheng , Gaffney Kelly J.
Published: January 2012

We have investigated the rotational dynamics of lithium thiocyanate (LiNCS) dissolved in various polar solvents with time and polarization resolved vibrational spectroscopy. LiNCS forms multiple distinct ionic structures in solution that can be distinguished with the CN stretch vibrational frequency of the different ionic assemblies. By varying the solvent and the LiNCS concentration, the number and type of ionic structures present in solution can be controlled. Control of the ionic structure provides control over the volume, shape, and dipole moment of the solute, critical parameters for hydrodynamic and dielectric continuum models of friction. The use of solutes with sizes comparable to or smaller than the solvent molecules also helps amplify the sensitivity of the measurement to the short-ranged solute-solvent interaction. The measured orientational relaxation dynamics show many clear and distinct deviations from simple hydrodynamic behavior. All ionic structures in all solvents exhibit multi-exponential relaxation dynamics that do not scale with the solute volume. For Lewis base solvents such as benzonitrile, dimethyl carbonate, and ethyl acetate, the observed dynamics strongly show the effect of solute-solvent complex formation. For the weak Lewis base solvent nitromethane, we see no evidence for solute-solvent complex formation, but still see strong deviation from the predictions of simple hydrodynamic theory.
Stochastic simulation of chemically reacting systems using multi-core processors
Authors: Gillespie Colin S.
Published: January 2012

In recent years, computer simulations have become increasingly useful when trying to understand the complex dynamics of biochemical networks, particularly in stochastic systems. In such situations stochastic simulation is vital in gaining an understanding of the inherent stochasticity present, as these models are rarely analytically tractable. However, a stochastic approach can be computationally prohibitive for many models. A number of approximations have been proposed that aim to speed up stochastic simulations. However, the majority of these approaches are fundamentally serial in terms of central processing unit (CPU) usage. In this paper, we propose a novel simulation algorithm that utilises the potential of multi-core machines. This algorithm partitions the model into smaller sub-models. These sub-models are then simulated, in parallel, on separate CPUs. We demonstrate that this method is accurate and can speed-up the simulation by a factor proportional to the number of processors available.
Composite parameterization and Haar measure for all unitary and special unitary groups
Authors: Spengler Christoph , Huber Marcus , Hiesmayr Beatrix C.
Published: January 2012

We adopt the concept of the composite parameterization of the unitary group $\mathcal {U}(d)$U(d) to the special unitary group $\mathcal {SU}(d)$SU(d). Furthermore, we also consider the Haar measure in terms of the introduced parameters. We show that the well-defined structure of the parameterization leads to a concise formula for the normalized Haar measure on $\mathcal {U}(d)$U(d) and $\mathcal {SU}(d)$SU(d). With regard to possible applications of our results, we consider the computation of high-order integrals over unitary groups.
Calibrated nanoscale dopant profiling using a scanning microwave microscope
Authors: Huber H. P. , Humer I. , Hochleitner M. , Fenner M. , Moertelmaier M. , Rankl C. , Imtiaz A. , Wallis T. M. , Tanbakuchi H. , Hinterdorfer P. , Kabos P. , Smoliner J. , Kopanski J. J. , Kienberger F.
Published: January 2012

The scanning microwave microscope is used for calibrated capacitance spectroscopy and spatially resolved dopant profiling measurements. It consists of an atomic force microscope combined with a vector network analyzer operating between 1–20 GHz. On silicon semiconductor calibration samples with doping concentrations ranging from 1015 to 1020 atoms/cm3, calibrated capacitance-voltage curves as well as derivative dC/dV curves were acquired. The change of the capacitance and the dC/dV signal is directly related to the dopant concentration allowing for quantitative dopant profiling. The method was tested on various samples with known dopant concentration and the resolution of dopant profiling determined to 20% while the absolute accuracy is within an order of magnitude. Using a modeling approach the dopant profiling calibration curves were analyzed with respect to varying tip diameter and oxide thickness allowing for improvements of the calibration accuracy. Bipolar samples were investigated and nano-scale defect structures and p-n junction interfaces imaged showing potential applications for the study of semiconductor device performance and failure analysis.
Subthreshold characteristics of ballistic electron emission spectra
Authors: Qin H. L. , Goh K. E. J. , Bosman M. , Pey K. L. , Troadec C.
Published: January 2012

We report upon a comprehensive investigation of the subthreshold characteristics of the ballistic electron emission microscopy (BEEM) current in ballistic electron emission spectroscopy. Starting from the Bell-Kaiser model, we derive an analytical equation to describe the subthreshold behavior of the BEEM current. It is found that the BEEM current in this region should exhibit a subthreshold swing of ∼60 mV/decade at room temperature, which we experimentally verified. This finding provides a rule of thumb for the detectability of the subthreshold behavior in a spectrum. For spectra where the subthreshold behavior is discernible above the signal noise, it is demonstrated that significant deviations in the near-threshold region can occur when fitting with a simple quadratic model that ignores the subthreshold behavior. To take the subthreshold behavior into account, a simple analytical model is proposed. This model not only fits significantly better in the near threshold region than the square model, but also gives a barrier height closer to the one extracted from the Bell-Kaiser model. More significantly, this model provides a quick method to estimate the subthreshold BEEM current amplitude based on the BEEM current above the barrier height.
Ultra-thin plasmonic optical vortex plate based on phase discontinuities
Authors: Genevet Patrice , Yu Nanfang , Aieta Francesco , Lin Jiao , Kats Mikhail A. , Blanchard Romain , Scully Marlan O. , Gaburro Zeno , Capasso Federico
Published: January 2012

A flat optical device that generates optical vortices with a variety of topological charges is demonstrated. This device spatially modulates light beams over a distance much smaller than the wavelength in the direction of propagation by means of an array of V-shaped plasmonic antennas with sub-wavelength separation. Optical vortices are shown to develop after a sub-wavelength propagation distance from the array, a feature that has major potential implications for integrated optics.
Growth, optical, and electrical properties of nonpolar m-plane ZnO on p-Si substrates with Al2O3 buffer layers
Authors: Wang T. , Wu H. , Chen C. , Liu C.
Published: January 2012

Nonploar m-plane ZnO films were grown on p-Si (111) substrates by using atomic layer deposition. X-ray diffraction and high resolution tunneling electron microscopy measurements showed that the ZnO films were 〈101¯0〉 oriented, and the crystalline quality of ZnO films was improved with an Al2O3 buffer layer, which significantly enhances the photoluminescence and reduces the reverse leakage current of ZnO/Si heterojuction.
Probing local surface conductance using current sensing atomic force microscopy
Authors: Liu Yucong , He Jiayu , Kwon Osung , Zhu Da-Ming
Published: January 2012

We have analyzed correlations between surface morphology and current sensing images obtained using a current sensing atomic force microscope (CSAFM) and the implication of surface conductivity derived from the current sensing images. We found that in cases where the diameter of a CSAFM probe tip is much smaller than the correlation length of the surface morphological features, the current detected using the probe should have little correlation with the surface features imaged by the same probe. If the sample thickness is much larger than the tip size, the surface conductivity distribution of a sample can be derived from a current sensing image using the Holm resistance relation, and the current probed using a CSAFM reflects the conductance variations in a layer on the surface with the thickness comparable to the probe diameter. However, if the thickness of a sample is comparable to or smaller than the tip diameter, CSAFM measures the conductance across the entire portion of the sample sandwiched between the tip and the electrode.
Photoluminescence and secondary ion mass spectrometry investigation of unintentional doping in epitaxial germanium thin films grown on III-V compound by metal-organic chemical vapor deposition
Authors: Bai Yu , Bulsara Mayank T. , Fitzgerald Eugene A.
Published: January 2012

High quality epitaxial germanium (Ge) thin films grown on lattice matched and mismatched III-V compound may lead to development of new electronic and optoelectronic devices. Understanding the doping and electronic properties of these Ge thin films is the first step in this development. In this paper, we report on high-quality epitaxial Ge thin films grown on GaAs and AlAs by metal-organic chemical vapor deposition. Cross-sectional transmission electron microscopy and atomic force microscopy reveal the high structural quality of the Ge thin films. Using photoluminescence, secondary ion mass spectrometry, and spreading resistance analysis, we investigated the unintentional doping characteristics of the fabricated Ge-on-III-V thin films. We found that arsenic (n-type doping) concentration is determined by the background partial pressure of volatile As-species (e.g., As2 and As4), which incorporate into the Ge thin films via gas phase transport during the growth. Group III element (p-type doping) incorporation in the Ge thin films occurs during the growth through a surface exchange process. There exists a trade-off between Ge film structural quality and group III element “auto-doping.” III-V compound surfaces that are group III element-rich facilitate the initiation of Ge thin films with high crystalline quality and low surface roughness. However, the group-III-rich surfaces also result in high group III element (p-type doping) concentrations in the Ge thin films.
The infrared fingerprint signals of silica nanoparticles and its application in immunoassay
Authors: Ding Yadan , Chu Xueying , Hong Xia , Zou Peng , Liu Yichun
Published: January 2012

Infrared absorption properties of silica nanoparticles were studied. The transverse optical and the longitudinal optical phonon modes from the silica were proved to be the characteristic spectroscopic fingerprint signals. Based on this, a sandwich-structured immunoassay was performed, and the detection of the analyte (human IgG) was achieved by using biofunctional silica nanoparticles as infrared probes. The immunoassay based on Fourier transform infrared reflection absorption spectroscopy of silica nanoparticles shows significant value for potential applications in many areas, such as biomedicine, food safety, and waste treatment.
Spin transfer torque programming dipole coupled nanomagnet arrays
Authors: Lyle Andrew , Harms Jonathan , Klein Todd , Lentsch August , Martens Daniel , Klemm Angeline , Wang Jian-Ping
Published: January 2012

We experimentally demonstrated spin transfer torque (STT) programming of dipole coupled nanomagnets using magnetic tunnel junctions. The STT write operations were performed in conjunction with a clock field used in magnetic quantum cellular automata (MQCA) operations. The spacing and number of nanomagnets in the transmission line strongly affected the STT programming of the individual pillars. These MQCA transmission lines ranged in length from 2 elements to 20 elements, while device sizes ranged between 50 nm × 80 nm and 70 nm × 100 nm with spacing between 10 nm and 15 nm. With the application of the clock field, currents of 100-200 μA are sufficient to STT program the device. The demonstration of STT programming of individual nanomagnets in a dipole coupled array marks a significant step forward for applications such as MQCA logic device.
Influence of piezoceramic to fused silica plate thickness on the radii of curvature of piezoelectric bimorph mirror
Authors: Libu M. , Susanth S. , Vasanthakumari K. G. , Dileep Kumar C. J. , Raghu N.
Published: January 2012

Piezoelectric based bimorph mirrors (PBM) find extensive use in focusing of x-ray beams. Many optical instruments require use of PBM whose radii of curvature can be tuned precisely. The 100 mm and 300 mm PBMs were fabricated with varying piezoelectric to fused silica plate thicknesses. The radii of curvature of free standing mirrors were measured as a function of voltage and it was found to decrease with increasing voltage. For a given piezoelectric plate thickness, as the fused silica thickness increases, the radii of curvature was found to increase owing to increase in stiffness of the mirror. On the other hand, for a given fused silica plate thickness, when the piezoelectric plate thickness is increased, the radii of curvature are decreased for a given electric field, due to increase in generated force. This study brings out the influence of piezoceramic to fused silica plate thickness on the radii of curvature of PBM.
Reduction of charge injection barrier by 1-nm contact oxide interlayer in organic field effect transistors
Authors: Darmawan Peter , Minari Takeo , Kumatani Akichika , Li Yun , Liu Chuan , Tsukagoshi Kazuhito
Published: January 2012

The enhancement of the charge injection process by the insertion of an ultrathin (∼1 nm) contact oxide interlayer (COI) at the metal/organic material interface in organic field effect transistors (OFETs) is reported. Six different oxides were used as COI, and Al2O3 was found to exhibit the highest OFET mobility with a reduction in the average contact resistance (Rc) from 19.9 to 1.9 kΩ·cm. Photoelectron yield spectroscopy analysis revealed that the insertion of COI increases the work function of an Au contact and reduces the charge injection barrier at the interface, which lowers Rc and, therefore, results in enhanced device performance.
Relaxor ferroelectric characteristics of Ba5LaTi3Nb7O30 tungsten bronze ceramics
Authors: Li Kun , Li Zhu Xiao , Qiang Liu Xiao , Ming Chen Xiang
Published: January 2012

Ba5LaTi3Nb7O30 tungsten-bronze ferroelectric ceramics were synthesized and characterized. The tetragonal tungsten bronze structure in space group P4/mbm was confirmed, and a broad permittivity peak with strong frequency dispersion was observed around 250 K where the peak points well fitted the Vogel-Fulcher relationship [H. Vogel, Phys. Zeit. 22, 645 (1921); G. S. Fulcher, J. Am. Ceram. Soc. 8, 339 (1925)]. The temperature dependence of the ferroelectric hysteresis indicated the paraelectric to ferroelectric phase transition in the temperature range between 153 and 273 K. The high temperature permittivity curve deviated from the Curie-Weiss law in quite a narrow temperature region above Tmax, which reflected the weak correlations between the polar nanoregions. The Curie-Weiss constant (C) was 1.218 × 105 K, which was consistent with that for the displacive type ferroelectric. No DSC peak was detected over the temperature region investigated here. Moreover, the Curie-Weiss constant below Tmax (C′) was just two times of C, and the second order phase transition was confirmed for Ba5LaTi3Nb7O30.
Observation of nonlinear absorption and visible photoluminescence emission in chemically synthesized Cu2+ doped ZnS nanoparticles
Authors: Kole A. K. , Kumbhakar P. , Chatterjee U.
Published: January 2012

Nonlinear optical properties of chemically synthesized ZnS and Cu2+ doped ZnS nanoparticles of average sizes ∼2.5 nm are reported by using open aperture z-scan technique with the Nd:YAG laser second harmonic radiation at 532 nm. Tunable photoluminescence emissions in the visible region due to the increase in concentration of Cu2+ doping in ZnS are observed at room temperature. By analyzing the experimental z-scan data, it is found that three photon absorptions (3PA) are taking place in all the samples. The extracted values of 3PA coefficients of the samples are ∼109 times higher than that of bulk ZnS.
Dependence of thermal conductivity on structural parameters in porous samples
Authors: Miettinen L. , Kekäläinen P. , Turpeinen T. , Hyväluoma J. , Merikoski J. , Timonen J.
Published: January 2012

The in-plane thermal conductivity of porous sintered bronze plates was studied both experimentally and numerically. We developed and validated an experimental setup, where the sample was placed in vacuum and heated while its time-dependent temperature field was measured with an infrared camera. The porosity and detailed three-dimensional structure of the samples were determined by X-ray microtomography. Lattice-Boltzmann simulations of thermal conductivity in the tomographic reconstructions of the samples were used to correct the contact area between bronze particles as determined by image analysis from the tomographic reconstructions. Small openings in the apparent contacts could not be detected with the imaging resolution used, and they caused an apparent thermal contact resistance between particles. With this correction included, the behavior of the measured thermal conductivity was successfully explained by an analytical expression, originally derived for regular structures, which involves three structural parameters of the porous structures. There was no simple relationship between heat conductivity and porosity.
Accelerated ion beams for art forensics
Authors: Collon Philippe , Wiescher Michael
Published: January 2012

The worlds of art and archaeology have adapted techniques developed in nuclear physics laboratories to learn where and when an artwork or artifact was created.
Silicon carbide defects hold promise for device-friendly qubits
Authors: Smart Ashley G.
Published: January 2012

Commercial-grade wafers of the popular semiconductor harbor spin states that can be coherently manipulated at room temperature.
Historical contingency affects signaling strategies and competitive abilities in evolving populations of simulated robots
Authors: Wischmann Steffen , Floreano Dario , Keller Laurent
Published: January 2012

One of the key innovations during the evolution of life on earth has been the emergence of efficient communication systems, yet little is known about the causes and consequences of the great diversity within and between species. By conducting experimental evolution in 20 independently evolving populations of cooperatively foraging simulated robots, we found that historical contingency in the occurrence order of novel phenotypic traits resulted in the emergence of two distinct communication strategies. The more complex foraging strategy was less efficient than the simpler strategy. However, when the 20 populations were placed in competition with each other, the populations with the more complex strategy outperformed the populations with the less complex strategy. These results demonstrate a tradeoff between communication efficiency and robustness and suggest that stochastic events have important effects on signal evolution and the outcome of competition between distinct populations.
Serum amyloid A opposes lipoxin A4to mediate glucocorticoid refractory lung inflammation in chronic obstructive pulmonary disease
Authors: Bozinovski Steven , Uddin Mohib , Vlahos Ross , Thompson Michelle , McQualter Jonathan L. , Merritt Anne-Sophie , Wark Peter A. B. , Hutchinson Anastasia , Irving Louis B. , Levy Bruce D. , Anderson Gary P.
Published: January 2012

Chronic obstructive pulmonary disease (COPD) will soon be the third most common cause of death globally. Despite smoking cessation, neutrophilic mucosal inflammation persistently damages the airways and fails to protect from recurrent infections. This maladaptive and excess inflammation is also refractory to glucocorticosteroids (GC). Here, we identify serum amyloid A (SAA) as a candidate mediator of GC refractory inflammation in COPD. Extrahepatic SAA was detected locally in COPD bronchoalveolar lavage fluid, which correlated with IL-8 and neutrophil elastase, consistent with neutrophil recruitment and activation. Immunohistochemistry detected SAA was in close proximity to airway epithelium, and in vitro SAA triggered release of IL-8 and other proinflammatory mediators by airway epithelial cells in an ALX/FPR2 (formyl peptide receptor 2) receptor-dependent manner. Lipoxin A4(LXA4) can also interact with ALX/FPR2 receptors and lead to allosteric inhibition of SAA-initiated epithelial responses (pA213 nM). During acute exacerbation, peripheral blood SAA levels increased dramatically and were disproportionately increased relative to LXA4. Human lung macrophages (CD68+) colocalized with SAA and GCs markedly increased SAA in vitro (THP-1, pEC5043 nM). To determine its direct actions, SAA was administered into murine lung, leading to induction of CXC chemokine ligand 1/2 and a neutrophilic response that was inhibited by 15-epi-LXA4but not dexamethasone. Taken together, these findings identify SAA as a therapeutic target for inhibition and implicate SAA as a mediator of GC-resistant lung inflammation that can overwhelm organ protective signaling by lipoxins at ALX/FPR2 receptors.
Silkworms transformed with chimeric silkworm/spider silk genes spin composite silk fibers with improved mechanical properties
Authors: Teulé Florence , Miao Yun-Gen , Sohn Bong-Hee , Kim Young-Soo , Hull J. Joe , Fraser Malcolm J. , Lewis Randolph V. , Jarvis Donald L.
Published: January 2012

The development of a spider silk-manufacturing process is of great interest. However, there are serious problems with natural manufacturing through spider farming, and standard recombinant protein production platforms have provided limited progress due to their inability to assemble spider silk proteins into fibers. Thus, we used
piggyBac
vectors to create transgenic silkworms encoding chimeric silkworm/spider silk proteins. The silk fibers produced by these animals were composite materials that included chimeric silkworm/spider silk proteins integrated in an extremely stable manner. Furthermore, these composite fibers were, on average, tougher than the parental silkworm silk fibers and as tough as native dragline spider silk fibers. These results demonstrate that silkworms can be engineered to manufacture composite silk fibers containing stably integrated spider silk protein sequences, which significantly improve the overall mechanical properties of the parental silkworm silk fibers.
Stabilization of hepatitis C virus RNA by an Ago2–miR-122 complex
Authors: Shimakami Tetsuro , Yamane Daisuke , Jangra Rohit K. , Kempf Brian J. , Spaniel Carolyn , Barton David J. , Lemon Stanley M.
Published: January 2012

MicroRNAs (miRNAs) are small noncoding RNAs that regulate eukaryotic gene expression by binding to regions of imperfect complementarity in mRNAs, typically in the 3′ UTR, recruiting an Argonaute (Ago) protein complex that usually results in translational repression or destabilization of the target RNA. The translation and decay of mRNAs are closely linked, competing processes, and whether the miRNA-induced silencing complex (RISC) acts primarily to reduce translation or stability of the mRNA remains controversial. miR-122 is an abundant, liver-specific miRNA that is an unusual host factor for hepatitis C virus (HCV), an important cause of liver disease in humans. Prior studies show that it binds the 5′ UTR of the messenger-sense HCV RNA genome, stimulating translation and promoting genome replication by an unknown mechanism. Here we show that miR-122 binds HCV RNA in association with Ago2 and that this slows decay of the viral genome in infected cells. The stabilizing action of miR-122 does not require the viral RNA to be translationally active nor engaged in replication, and can be functionally substituted by a nonmethylated 5′ cap. Our data demonstrate that a RISC-like complex mediates the stability of HCV RNA and suggest that Ago2 and miR-122 act coordinately to protect the viral genome from 5′ exonuclease activity of the host mRNA decay machinery. miR-122 thus acts in an unconventional fashion to stabilize HCV RNA and slow its decay, expanding the repertoire of mechanisms by which miRNAs modulate gene expression.
Novelty exposure overcomes foot shock-induced spatial-memory impairment by processes of synaptic-tagging in rats
Authors: Almaguer-Melian William , Bergado-Rosado Jorge , Pavón-Fuentes Nancy , Alberti-Amador Esteban , Mercerón-Martínez Daymara , Frey Julietta U.
Published: January 2012

Novelty processing can transform short-term into long-term memory. We propose that this memory-reinforcing effect of novelty could be explained by mechanisms outlined in the “synaptic tagging hypothesis.” Initial short-term memory is sustained by a transient plasticity change at activated synapses and sets synaptic tags. These tags are later able to capture and process the plasticity-related proteins (PRPs), which are required to transform a short-term synaptic change into a long-term one. Novelty is involved in inducing the synthesis of PRPs [Moncada D, et al. (2011)
Proc Natl Acad Sci USA
108:12937–12936], which are then captured by the tagged synapses, consolidating memory. In contrast to novelty, stress can impair learning, memory, and synaptic plasticity. Here, we address questions as to whether novelty-induced PRPs are able to prevent the loss of memory caused by stress and if the latter would not interact with the tag-setting process. We used water-maze (WM) training as a spatial learning paradigm to test our hypothesis. Stress was induced by a strong foot shock (FS; 5 × 1 mA, 2 s) applied 5 min after WM training. Our data show that FS reduced long-term but not short-term memory in the WM paradigm. This negative effect on memory consolidation was time- and training-dependent. Interestingly, novelty exposure prevented the stress-induced memory loss of the spatial task and increased BDNF and Arc expression. This rescuing effect was blocked by anisomycin, suggesting that WM-tagged synapses were not reset by FS and were thus able to capture the novelty-induced PRPs, re-establishing FS-impaired long-term memory.
Player preferences among new and old violins
Authors: Fritz Claudia , Curtin Joseph , Poitevineau Jacques , Morrel-Samuels Palmer , Tao Fan-Chia
Published: January 2012

Most violinists believe that instruments by Stradivari and Guarneri “del Gesu” are tonally superior to other violins—and to new violins in particular. Many mechanical and acoustical factors have been proposed to account for this superiority; however, the fundamental premise of tonal superiority has not yet been properly investigated. Player's judgments about a Stradivari's sound may be biased by the violin's extraordinary monetary value and historical importance, but no studies designed to preclude such biasing factors have yet been published. We asked 21 experienced violinists to compare violins by Stradivari and Guarneri del Gesu with high-quality new instruments. The resulting preferences were based on the violinists’ individual experiences of playing the instruments under double-blind conditions in a room with relatively dry acoustics. We found that (
i
) the most-preferred violin was new; (
ii
) the least-preferred was by Stradivari; (
iii
) there was scant correlation between an instrument's age and monetary value and its perceived quality; and (
iv
) most players seemed unable to tell whether their most-preferred instrument was new or old. These results present a striking challenge to conventional wisdom. Differences in taste among individual players, along with differences in playing qualities among individual instruments, appear more important than any general differences between new and old violins. Rather than searching for the “secret” of Stradivari, future research might best focused on how violinists evaluate instruments, on which specific playing qualities are most important to them, and on how these qualities relate to measurable attributes of the instruments, whether old or new.
Glycosyl transferases in family 61 mediate arabinofuranosyl transfer onto xylan in grasses
Authors: Anders Nadine , Wilkinson Mark D. , Lovegrove Alison , Freeman Jacqueline , Tryfona Theodora , Pellny Till K. , Weimar Thilo , Mortimer Jennifer C. , Stott Katherine , Baker John M. , Defoin-Platel Michael , Shewry Peter R. , Dupree Paul , Mitchell Rowan A. C.
Published: January 2012

Xylan, a hemicellulosic component of the plant cell wall, is one of the most abundant polysaccharides in nature. In contrast to dicots, xylan in grasses is extensively modified by α-(1,2)– and α-(1,3)–linked arabinofuranose. Despite the importance of grass arabinoxylan in human and animal nutrition and for bioenergy, the enzymes adding the arabinosyl substitutions are unknown. Here we demonstrate that knocking-down glycosyltransferase (GT) 61 expression in wheat endosperm strongly decreases α-(1,3)–linked arabinosyl substitution of xylan. Moreover, heterologous expression of wheat and rice GT61s in Arabidopsis leads to arabinosylation of the xylan, and therefore provides gain-of-function evidence for α-(1,3)-arabinosyltransferase activity. Thus, GT61 proteins play a key role in arabinoxylan biosynthesis and therefore in the evolutionary divergence of grass cell walls.