bluuebunny/crossref_metadata_2025 huggingface dataset:
A carbon cycle coupled climate model of Neoproterozoic glaciation: Influence of continental configuration on the formation of a “soft snowball”
Authors: Liu Yonggang , Peltier W. Richard
Published: September 2010

We examine the general conditions that must be satisfied by the configuration of the continents in order that steady state solutions for Neoproterozoic climate exist that are characterized by heavy continental glaciation but for which a substantial area of open water in the equatorial region persists. Such solutions have previously been termed “soft snowball” or “slush ball” to distinguish them from the “hard snowball” solutions that some have suggested be required to fit the observational constraints. It is found that three conditions are critical in this regard: (1) the continental area in high latitudes should be large enough that a massive ice sheet may develop even when pCO2 is relatively high, an ice sheet complex that is subsequently capable of flowing to lower latitude. (2) The continental fragments in low latitude must be connected (or separated only by continental shelves above which water depths are small) to a significant degree with those at higher latitudes. (3) A relatively simple supercontinental outline favors the formation of the “soft snowball” state. Although the latter requirement is important, we have nevertheless found that soft snowball solutions are realized for the realistic Sturtian continental configuration of Li et al. (2008) that existed at ∼720 Ma. However, in order for these states to exist, the positions of the individual continental fragments must be slightly adjusted so as to improve their connectivity. These adjustments are consistent with the error bars on the paleomagnetic inferences of paleolatitude and the even less well constrained paleolongitude. We also demonstrate that “soft snowball” solutions do not exist in models devoid of active continental ice sheets capable of flowing over the landscape. These results for Sturtian conditions extend our previously published results for the Marinoan period during which the supercontinent was centered upon much higher latitudes.
Tropical Composition, Cloud and Climate Coupling Experiment validation for cirrus cloud profiling retrieval using CloudSat radar and CALIPSO lidar
Authors: Deng Min , Mace Gerald G. , Wang Zhien , Okamoto Hajime
Published: September 2010

A profiling retrieval algorithm for ice cloud properties, such as effective radius (re), ice water content (IWC), and an extinction coefficient, has been developed to use combined CloudSat radar reflectivity factor (Ze) and CALIPSO attenuated backscattering coefficient measurements based on an optimal estimation framework. Developed as an operational standard data product for the CloudSat project, the algorithm can treat a wide range of ice cloud situations from optically tenuous cirrus in the upper troposphere to geometrically and optically thick anvil clouds. It is designed to consider the attenuation of thick clouds in the radar and lidar forward model equations and multiple scattering in the lidar data. An optimal estimation approach allows for inversion of the forward model equations so that the uncertainty due to the assumptions can be evaluated. A sensitivity study shows that lidar multiple scattering has to be accounted for carefully. As for all ice cloud retrieval algorithms, assumptions regarding particle habits and size distribution shapes are critical to the accuracy of the results. The deviation in simulated Ze among different size distribution assumptions is smaller than among different habit assumptions, which indicates that the uncertainty due to particle habits is larger than the size distribution assumption. Those uncertainties are included in the forward model error covariance matrix to analyze the retrieval error. The algorithm is applied to CloudSat‐CALIPSO data as well as lidar and radar data collected by the ER‐2 during the Tropical Composition, Cloud and Climate Coupling Experiment mission on 22 July 2007. The retrieved re, IWC, and extinction are shown to compare favorably with coincident in situ measurements collected by instruments on the NASA DC‐8. This algorithm is expected to be complementary to the set of standard data products that is already being produced by the CloudSat project.
Ensemble variational assimilation for the representation of background error covariances in a high‐latitude regional model
Authors: Storto A. , Randriamampianina R.
Published: September 2010

Statistical objective analysis requires the explicit specification of the observation and background error covariances. This paper deals with the estimation of the latter within a high‐latitude regional model. Four different approaches have been adopted to simulate the error evolution in the analysis and forecast steps of the model: i) the largely‐adopted NMC method, applied to both a winter and a summer season data set, ii) global ensemble analyses projected forward to the 6‐hour forecast range by the limited‐area model itself, iii) limited‐area ensemble variational assimilation with unperturbed lateral boundary conditions (LBCs) and iv) limited‐area ensemble variational assimilation with perturbed lateral boundary conditions. The structure of the four background error covariance matrices was extensively compared. It turned out that the NMC‐derived standard deviations had stronger amplitude at the large scales, especially in the lower troposphere, compared to those derived using the ensemble technique, and much broader horizontal and large‐scale vertical correlations. The contribution of lateral boundary perturbations is shown to be significant. Moreover, neglecting these LBCs perturbations contributes to unrealistic features, such as artificial small variances near the boundaries, which tend to spuriously propagate towards the inner area. Furthermore, humidity variances and associated cross‐covariances tend to be weaker in the ensemble assimilation experiments, in particular when lateral boundary conditions are not perturbed. A one‐month assimilation period allowed us to evaluate the impact of the different background error statistics on the forecasts: wind, geopotential and partly temperature are clearly benefiting from the use of ensemble‐based background error covariances; humidity skill scores are noticeably improved when background error covariances from limited‐area ensemble assimilation were used. The seasonality of the background error structures was also investigated, and it was found non‐negligible for the performance of the data assimilation and forecast systems.
Distribution and variation of plagioclase compositions on Mars
Authors: Milam Keith A. , McSween Harry Y. , Moersch Jeffrey , Christensen Philip R.
Published: September 2010

This study presents the first global compositional maps of plagioclase, the most abundant mineral in the Martian crust. Linear deconvolutions of spectra from the Thermal Emission Spectrometer (TES) allowed calculation of average plagioclase compositions for dust‐free areas on Mars ±60° of the equator (approximately 40% of the surface for this range of latitudes). As a whole, surface type 1 and 2 terrains are virtually identical with respect to their average plagioclase compositions, ∼An60. The majority of TES observations were modeled as labradorite and bytownite (between An50and An90), while fewer observations were modeled with other plagioclase compositions that did not correlate with specific geologic terrains. The lack of diversity in average plagioclase compositions across multiple geologic units may represent an upper Martian crust with minimal variation in plagioclase compositions. Alternatively, aeolian, fluvial, and/or impact activity may have redistributed heterogeneous crustal material forming a relatively homogeneous, global surface layer.
Macroscale hydrologic modeling of ecologically relevant flow metrics
Authors: Wenger Seth J. , Luce Charles H. , Hamlet Alan F. , Isaak Daniel J. , Neville Helen M.
Published: September 2010

Stream hydrology strongly affects the structure of aquatic communities. Changes to air temperature and precipitation driven by increased greenhouse gas concentrations are shifting timing and volume of streamflows potentially affecting these communities. The variable infiltration capacity (VIC) macroscale hydrologic model has been employed at regional scales to describe and forecast hydrologic changes but has been calibrated and applied mainly to large rivers. An important question is how well VIC runoff simulations serve to answer questions about hydrologic changes in smaller streams, which are important habitat for many fish species. To answer this question, we aggregated gridded VIC outputs within the drainage basins of 55 streamflow gages in the Pacific Northwest United States and compared modeled hydrographs and summary metrics to observations. For most streams, several ecologically relevant aspects of the hydrologic regime were accurately modeled, including center of flow timing, mean annual and summer flows and frequency of winter floods. Frequencies of high and low flows in the summer were not well predicted, however. Predictions were worse for sites with strong groundwater influence, and some sites showed errors that may result from limitations in the forcing climate data. Higher resolution (1/16th degree) modeling provided small improvements over lower resolution (1/8th degree). Despite some limitations, the VIC model appears capable of representing several ecologically relevant hydrologic characteristics in streams, making it a useful tool for understanding the effects of hydrology in delimiting species distributions and predicting the potential effects of climate shifts on aquatic organisms.
H Balmer lines in terrestrial aurora: Historical record and new observations by OSIRIS on Odin
Authors: Gattinger R. L. , Egeland A. , Bourassa A. E. , Lloyd N. D. , Degenstein D. A. , Stegman J. , Llewellyn E. J.
Published: September 2010

The H Balmer emissions were first identified in terrestrial aurora by Vegard (1939). The earliest photographic spectral observations are reviewed. In the subsequent decade, the intensity ratios for Hα, Hβ, and Hγ were measured, and the well‐known line broadening and blue shift were established. Recently, the Hα, Hγ, Hδ, and Hɛ features have been measured by OSIRIS on Odin. The Balmer components are resolved from other auroral features using sets of synthetic spectra. The measured intensity ratios are in good agreement with an extensive set of published model calculations. The presented observations are in the polar region averaged over limb tangent altitudes from 100 to 105 km, approximately perpendicular to the terrestrial magnetic field lines, for this geometry showing Doppler broadening without obvious Doppler shifts. The OSIRIS‐measured full‐width at half‐height of the Hα feature is 2.2 nm corresponding to an H atom velocity of 500 km s−1 and energy approximately 1.3 keV.
Astrocytes and Pericytes Differentially Modulate Blood—Brain Barrier Characteristics during Development and Hypoxic Insult
Authors: Ahmad Abraham Al , Taboada Carole Bürgi , Gassmann Max , Ogunshola Omolara O
Published: September 2010

Understanding regulation of blood–brain barrier (BBB) is crucial to reduce/prevent its disruption during injury. As high brain complexity makes interpretation of in vivo data challenging, BBB studies are frequently performed using simplified in vitro models. However, many models fail to address the three-dimensional (3D) cellular interactions that occur in vivo, an important feature that may explain discrepancies in translation of in vitro data to the in vivo situation. We have designed and characterized an innovative 3D model that reproduces morphological and functional characteristics of the BBB in vivo and used it to investigate cellular interactions and contribution of astrocytes and pericytes to BBB development. Our model shows that both astrocytes and pericytes significantly suppress endothelial proliferation. In contrast, differential effects on tubulogenesis were observed with astrocytes reducing the number of tubes formed but increasing diameters and length, whereas pericytes had the opposite effect. Pericytes also induce proper localization of barrier proteins, lumen polarization, and functional activity of ATP-binding cassette (ABC) transporters similar to astrocytes, but the presence of both cells is required to maintain optimal barrier characteristics during hypoxic exposure. This model is simple, dynamic, and convenient to study many aspects of BBB function and represents an exciting new tool to address open questions of BBB regulation.
Sustainable Water
Authors: Schwesig David
Published: September 2010

It is predicted that climate change will result in big changes to the global distribution of rainfall, causing drought and desertification in some regions and floods in others. Already there are signs of such changes occurring, with particularly serious consequences for poorer countries. The need for international cooperation in managing the effects of climate change, and other influences on the hydrological cycle, is becoming urgent. Future wars may well be fought over water. This book is part of a series focusing on key issues in environmental science and technology. Focusing on the sustainability of water supplies to the growing populations throughout the world, this volume consists of articles contributed by a group of experts drawn from around the globe. Issues covered include: policy making in the European Union; rural water supplies in Africa; chemical monitoring and analytical methods; water use in agriculture; social justice in supplying water; potable water recycling, and sustainable water treatment. The book will be useful to those working in the water industry, policy makers and planners, researchers and environmental consultants, and students in environmental science, technology, engineering, and management. There is also much here to interest all concerned with major environmental issues such as climate change and the many other factors which influence the sustainability of water supplies.
Potential Impact of Climate Change on Improved and Unimproved Water Supplies in Africa
Authors: Bonsor Helen , MacDonald Alan , Calow Roger
Published: September 2010

With significant climate change predicted in Africa over the next century, this chapter explores a key question: how will rural water supplies in Africa be affected ? Approximately 550 million people in Africa live in rural communities and are reliant on water resources within walking distance of their community for drinking water. Less than half have access to improved sources (generally large diameter wells, springs or boreholes equipped with hand pumps); the majority rely on unimproved sources, such as open water and shallow wells. Major climate modelling uncertainties, combined with rapid socio-economic change, make predicting the future state of African water resources difficult; an appropriate response to climate change is to assume much greater uncertainty in climate and intensification of past climate variability. Based on this assumption the following should be considered:Those relying on unimproved water sources (300 million in rural Africa) are likely to be most affected by climate change because unimproved sources often use highly vulnerable water resources.Improved rural water supplies in Africa are overwhelmingly dependent on groundwater, due to the unreliability of other sources.Climate change is unlikely to lead to a continent-wide failure of improved rural water sources that access deeper groundwater (generally over 20 metres below ground surface) through boreholes or deep wells. This is because groundwater-based domestic supply requires little recharge, and the groundwater resources at depth will generally be of sufficient storage capacity to remain a secure water resource. However, a significant minority of people could be affected if the frequency and length of drought increases – particularly those in areas with limited groundwater storage.In most areas, the key determinants of water security will continue to be driven by access to water rather than absolute water availability. Extending access, and ensuring that targeting and technology decisions are informed by an understanding of groundwater conditions, will become increasingly important.Accelerating groundwater development for irrigation could increase food production, raise farm incomes and reduce overall vulnerability. However, ad hoc development could threaten domestic supplies and, in some areas, lead to groundwater depletion.

Although climate change will undoubtedly be important in determining future water security, other drivers (such as population growth and rising food demands) are likely to provide greater pressure on rural water supplies.
The European Water Framework Directive – Chemical Monitoring Programmes, Analytical Challenges and Results from an Irish Case Study
Authors: Borchers Ulrich , Schwesig David , O'Donnell Ciaran , Concannon Colman
Published: September 2010

The European Water Framework Directive (WFD) is one of the most important legislative instruments in the water field. The overarching objective of the policy is the achievement of a “good status” in all waters of European Member States by the end of 2015. Important milestones include the analysis of pressures and impacts, a characterisation of water bodies and monitoring programmes.

The effectiveness of these monitoring programmes and hence of the overall WFD implementation will depend highly on the ability of Member States’ laboratories to measure the status of water bodies. The chemical status of water bodies is linked to compliance with EU Environmental Quality Standards defined in a daughter directive. In order to assess the chemical status, a number of priority substances and priority hazardous substances have to be monitored. Requirements on the analytical methods to be used for chemical monitoring are laid down in terms of technical specifications by another daughter directive.

In some cases, the requirements on analytical methods (e.g. limit of quantification and measurement uncertainty) for chemical monitoring under WFD pose a real challenge, even for state-of-the-art analytical techniques. This has initiated a number of European activities in the development of guidance documents, harmonisation efforts and demand-driven research.

The main tasks, challenges and research needs related to chemical monitoring of water bodies under the WFD are presented, including an outlook on how these issues are tackled. This is completed by the presentation of actual chemical monitoring results from surface waters from the Republic of Ireland.
Social Justice and Water
Authors: McDonald Adrian , Clarke Martin , Boden Peter , Kay David
Published: September 2010

Social justice and water refers to fairness of access to water resources and equality of burden from poor water quality and water hazards. This chapter considers briefly the origins and definition of social justice, and ways in which social justice and water interact. Global scale water justice is considered mainly in respect of disease and the lack of progress towards effective provision of water and sanitation. A detailed case study of the links between water debt and deprivation in the UK is then examined, concluding with a consideration of the options available to resolve water debt issues whilst respecting social justice. We conclude with a consideration of the future constraints on water resources in the light of the latest UK climate projections, and recognise that difficult choices might be encountered in which social justice for people might have to have priority over environmental justice for river and land habitats.
The Reaction of Rhenium(V) Cores with a Tetradentate Schiff Base. The Isolation of '3+3' and '4+0' Complexes of Rhenium(V)
Authors: Potgieter Kim C. , Mayer Peter , Gerber Thomas I. A.
Published: September 2010

The reaction of the potentially tetradentate N4-donor ligand N,N?-bis[(2-aminophenyl)methylidene]ethane-1,2-diamine (H2ane) with various rhenium(V) precursors led to the formation of different rhenium(V) complexes. With trans-[ReOBr3(PPh3)2], the unusual ?3+3' complex cation [Re(tnn)(Htnn)]2+ (H2tnn = N-(2-aminophenylmethylidene)ethane-1,2-diamine) was isolated. With trans-[ReO2(py)4]Cl, the complex [ReO(dne)] was found (H3dne = N1-2-aminobenzyl-N2-2-aminobenzylideneethane-1,2-diamine), and the cationic complex [ReO(ane)]+ was formed from cis-[ReO2I(PPh3)2]. These products were characterized by 1H NMR and IR spectroscopy, and by X-ray diffraction.
3d - 4f Heterometallic Complexes for the Construction of POM-based Inorganic - Organic Hybrid Compounds: from Nanoclusters to One-Dimensional Ladder-Like Chains
Authors: Du Dongying , Qin Junsheng , Li Shunli , Lan Yaqian , Wang Xinlong , Su Zhongmin
Published: September 2010

Three polyoxometalate-based inorganic–organic hybrid compounds, namely nanoclusters [Cu(en)2H2O]3[(α-SiW11O39)Nd(H2O)(η2,μ-1,1)-CH3COO]·3.5H2O (1) and [Cu(en)2H2O]3[(α-SiW11O39)Sm(H2O)(η2,μ-1,1)-CH3COO]·3H2O (2), and 1D H2[Cu(en)2H2O]8[Cu(en)2]3[{(α-SiW11O39)Ce(H2O)(η2,μ-1,1)-CH3COO}4]·22H2O (3) (en = 1,2-ethylenediamine) have been isolated. 1 and 2 are isomorphic and consist of [(α-SiW11O39)Ln(H2O)(η2,μ-1,1)-CH3COO]6– polyanions modified by [Cu(en)2H2O]2+ fragments. In 3, [Cu(en)2H2O]2+ are grafted on [(α-SiW11O39)Ce(H2O)(η2,μ-1,1)-CH3COO]6– polyanions and further connected by [Cu(en)2]2+ groups, representing the first example in polyoxometalate chemistry of a 1D ladder-like polyanion chain consisting of monovacant Keggin-type polyanions, lanthanide complexes and transition metal complexes. In these compounds, copper complexes coordinate to not only terminal O atoms but also bridging O atoms of the polyanions. Magnetic studies of 1 and 3 reveal weak antiferromagnetic interactions exist in them.
Potential for reduced methane and carbon dioxide emissions from livestock and pasture management in the tropics
Authors: Thornton Philip K. , Herrero Mario
Published: September 2010

We estimate the potential reductions in methane and carbon dioxide emissions from several livestock and pasture management options in the mixed and rangeland-based production systems in the tropics. The impacts of adoption of improved pastures, intensifying ruminant diets, changes in land-use practices, and changing breeds of large ruminants on the production of methane and carbon dioxide are calculated for two levels of adoption: complete adoption, to estimate the upper limit to reductions in these greenhouse gases (GHGs), and optimistic but plausible adoption rates taken from the literature, where these exist. Results are expressed both in GHG per ton of livestock product and in Gt CO
2
-eq. We estimate that the maximum mitigation potential of these options in the land-based livestock systems in the tropics amounts to approximately 7% of the global agricultural mitigation potential to 2030. Using historical adoption rates from the literature, the plausible mitigation potential of these options could contribute approximately 4% of global agricultural GHG mitigation. This could be worth on the order of $1.3 billion per year at a price of $20 per t CO
2
-eq. The household-level and sociocultural impacts of some of these options warrant further study, however, because livestock have multiple roles in tropical systems that often go far beyond their productive utility.
Dimensionality of mate choice, sexual isolation, and speciation
Authors: Hohenlohe Paul A. , Arnold Stevan J.
Published: September 2010

Multiple cues, across multiple sensory modalities, are involved in mate choice in a wide range of animal taxa. This multiplicity leads to the prediction that, in adaptive radiations, sexual isolation results from divergence in multiple dimensions. However, difficulties in directly measuring preferences and detecting multiple effects limit our ability to empirically assess the number of independent traits contributing to mate choice and sexual isolation. We present an approach to estimate the dimensionality of sexual isolation using mating trials across groups of related populations. We analyze nine radiations: seven in fruit flies (Drosophila) and one each in salamanders (Desmognathus) and cichlid fishes (Pseudotropheus). We find strong evidence that multiple latent traits—linear combinations of phenotypic traits and preferences—are responsible for the patterns of sexual isolation in all nine radiations but that dimensionality has a strong upper limit. Just two latent traits are implicated in the majority of cases. Mapping along latent trait axes tests predictions of sexual-selection models and allows correlation with specific phenotypic traits and functional components of mate choice. We find support for the role of stabilizing natural selection on the sexually selected (male) traits. In the cichlids, latent-trait axes incorporate male-coloration patterns and exhibit convergence as well as divergence among populations. In the salamanders, temporal patterning in sensory modalities and male vs. female preferences are reflected in different latent-trait axes.
Sharp rates of decay of solutions to the nonlinear fast diffusion equation via functional inequalities
Authors: Bonforte M. , Dolbeault J. , Grillo G. , Vázquez J. L.
Published: September 2010

The goal of this paper is to state the optimal decay rate for solutions of the nonlinear fast diffusion equation and, in self-similar variables, the optimal convergence rates to Barenblatt self-similar profiles and their generalizations. It relies on the identification of the optimal constants in some related Hardy–Poincaré inequalities and concludes a long series of papers devoted to generalized entropies, functional inequalities, and rates for nonlinear diffusion equations.
High-resolution forest carbon stocks and emissions in the Amazon
Authors: Asner Gregory P. , Powell George V. N. , Mascaro Joseph , Knapp David E. , Clark John K. , Jacobson James , Kennedy-Bowdoin Ty , Balaji Aravindh , Paez-Acosta Guayana , Victoria Eloy , Secada Laura , Valqui Michael , Hughes R. Flint
Published: September 2010

Efforts to mitigate climate change through the Reduced Emissions from Deforestation and Degradation (REDD) depend on mapping and monitoring of tropical forest carbon stocks and emissions over large geographic areas. With a new integrated use of satellite imaging, airborne light detection and ranging, and field plots, we mapped aboveground carbon stocks and emissions at 0.1-ha resolution over 4.3 million ha of the Peruvian Amazon, an area twice that of all forests in Costa Rica, to reveal the determinants of forest carbon density and to demonstrate the feasibility of mapping carbon emissions for REDD. We discovered previously unknown variation in carbon storage at multiple scales based on geologic substrate and forest type. From 1999 to 2009, emissions from land use totaled 1.1% of the standing carbon throughout the region. Forest degradation, such as from selective logging, increased regional carbon emissions by 47% over deforestation alone, and secondary regrowth provided an 18% offset against total gross emissions. Very high-resolution monitoring reduces uncertainty in carbon emissions for REDD programs while uncovering fundamental environmental controls on forest carbon storage and their interactions with land-use change.
Selective viral vector transduction of ErbB4 expressing cortical interneurons in vivo with a viral receptor–ligand bridge protein
Authors: Choi Jiwon , Young John A. T. , Callaway Edward M.
Published: September 2010

Both treatment of disease and basic studies of complex tissues can benefit from directing viral vector infection to specific cell types. We have used a unique cell targeting method to direct viral vector transduction to cerebral cortical neurons expressing the neuregulin (NRG) receptor ErbB4; both NRG and ErbB4 have been implicated in schizophrenia, and ErbB4 expression in cerebral cortex is known to be restricted to inhibitory neurons. We find that a bridge protein composed of the avian viral receptor TVB fused to NRG, along with EnvB-psuedotyped virus, is able to direct infection selectively to ErbB4-expressing inhibitory cortical neurons in vivo. Interestingly, although ErbB4 is expressed in a broad range of cortical inhibitory cell types, NRG-dependent infection is restricted to a more selective subset of inhibitory cell types. These results demonstrate a tool that can be used for further studies of NRG and ErbB receptors in brain circuits and demonstrate the feasibility for further development of related bridge proteins to target gene expression to other specific cell types in complex tissues.
Real-time single-cell response to stiffness
Authors: Mitrossilis Démosthène , Fouchard Jonathan , Pereira David , Postic François , Richert Alain , Saint-Jean Michel , Asnacios Atef
Published: September 2010

Living cells adapt to the stiffness of their environment. However, cell response to stiffness is mainly thought to be initiated by the deformation of adhesion complexes under applied force. In order to determine whether cell response was triggered by stiffness or force, we have developed a unique method allowing us to tune, in real time, the effective stiffness experienced by a single living cell in a uniaxial traction geometry. In these conditions, the rate of traction force buildup
dF
/
dt
was adapted to stiffness in less than 0.1 s. This integrated fast response was unambiguously triggered by stiffness, and not by force. It suggests that early cell response could be mechanical in nature. In fact, local force-dependent signaling through adhesion complexes could be triggered and coordinated by the instantaneous cell-scale adaptation of
dF
/
dt
to stiffness. Remarkably, the effective stiffness method presented here can be implemented on any mechanical setup. Thus, beyond single-cell mechanosensing, this method should be useful to determine the role of rigidity in many fundamental phenomena such as morphogenesis and development.
Hippocampal long-term depression is required for the consolidation of spatial memory
Authors: Ge Yuan , Dong Zhifang , Bagot Rosemary C. , Howland John G. , Phillips Anthony G. , Wong Tak Pan , Wang Yu Tian
Published: September 2010

Although NMDA receptor (NMDAR)-dependent long-term potentiation (LTP) and long-term depression (LTD) of glutamatergic transmission are candidate mechanisms for long-term spatial memory, the precise contributions of LTP and LTD remain poorly understood. Here, we report that LTP and LTD in the hippocampal CA1 region of freely moving adult rats were prevented by NMDAR 2A (GluN2A) and 2B subunit (GluN2B) preferential antagonists, respectively. These results strongly suggest that NMDAR subtype preferential antagonists are appropriate tools to probe the roles of LTP and LTD in spatial memory. Using a Morris water maze task, the LTP-blocking GluN2A antagonist had no significant effect on any aspect of performance, whereas the LTD-blocking GluN2B antagonist impaired spatial memory consolidation. Moreover, similar spatial memory deficits were induced by inhibiting the expression of LTD with intrahippocampal infusion of a short peptide that specifically interferes with AMPA receptor endocytosis. Taken together, our findings support a functional requirement of hippocampal CA1 LTD in the consolidation of long-term spatial memory.
Self-catalyzed growth of S layers via an amorphous-to-crystalline transition limited by folding kinetics
Authors: Chung Sungwook , Shin Seong-Ho , Bertozzi Carolyn R. , De Yoreo James J.
Published: September 2010

The importance of nonclassical, multistage crystallization pathways is increasingly evident from theoretical studies on colloidal systems and experimental investigations of proteins and biomineral phases. Although theoretical predictions suggest that proteins follow these pathways as a result of fluctuations that create unstable dense-liquid states, microscopic studies indicate these states are long-lived. Using in situ atomic force microscopy to follow 2D assembly of S-layer proteins on supported lipid bilayers, we have obtained a molecular-scale picture of multistage protein crystallization that reveals the importance of conformational transformations in directing the pathway of assembly. We find that monomers with an extended conformation first form a mobile adsorbed phase, from which they condense into amorphous clusters. These clusters undergo a phase transition through S-layer folding into crystalline clusters composed of compact tetramers. Growth then proceeds by formation of new tetramers exclusively at cluster edges, implying tetramer formation is autocatalytic. Analysis of the growth kinetics leads to a quantitative model in which tetramer creation is rate limiting. However, the estimated barrier is much smaller than expected for folding of isolated S-layer proteins, suggesting an energetic rationale for this multistage pathway.
Targeting botulinum neurotoxin persistence by the ubiquitin-proteasome system
Authors: Tsai Yien Che , Maditz Rhyan , Kuo Chueh-ling , Fishman Paul S. , Shoemaker Charles B. , Oyler George A. , Weissman Allan M.
Published: September 2010

Botulinum neurotoxins (BoNTs) are the most potent natural toxins known. The effects of BoNT serotype A (BoNT/A) can last several months, whereas the effects of BoNT serotype E (BoNT/E), which shares the same synaptic target, synaptosomal-associated protein 25 (SNAP25), last only several weeks. The long-lasting effects or persistence of BoNT/A, although desirable for therapeutic applications, presents a challenge for medical treatment of BoNT intoxication. Although the mechanisms for BoNT toxicity are well known, little is known about the mechanisms that govern the persistence of the toxins. We show that the recombinant catalytic light chain (LC) of BoNT/E is ubiquitylated and rapidly degraded in cells. In contrast, BoNT/A LC is considerably more stable. Differential susceptibility of the catalytic LCs to ubiquitin-dependent proteolysis therefore might explain the differential persistence of BoNT serotypes. In this regard we show that TRAF2, a RING finger protein implicated in ubiquitylation, selectively associates with BoNT/E LC and promotes its proteasomal degradation. Given these data, we asked whether BoNT/A LC could be targeted for rapid proteasomal degradation by redirecting it to characterized ubiquitin ligase domains. We describe chimeric SNAP25-based ubiquitin ligases that target BoNT/A LC for degradation, reducing its duration in a cellular model for toxin persistence.
Statistical tests for whether a given set of independent, identically distributed draws comes from a specified probability density
Authors: Tygert Mark
Published: September 2010

We discuss several tests for determining whether a given set of independent and identically distributed (i.i.d.) draws does not come from a specified probability density function. The most commonly used are Kolmogorov–Smirnov tests, particularly Kuiper’s variant, which focus on discrepancies between the cumulative distribution function for the specified probability density and the empirical cumulative distribution function for the given set of i.i.d. draws. Unfortunately, variations in the probability density function often get smoothed over in the cumulative distribution function, making it difficult to detect discrepancies in regions where the probability density is small in comparison with its values in surrounding regions. We discuss tests without this deficiency, complementing the classical methods. The tests of the present paper are based on the plain fact that it is unlikely to draw a random number whose probability is small, provided that the draw is taken from the same distribution used in calculating the probability (thus, if we draw a random number whose probability is small, then we can be confident that we did not draw the number from the same distribution used in calculating the probability).
Photophoretic levitation of engineered aerosols for geoengineering
Authors: Keith David W.
Published: September 2010

Aerosols could be injected into the upper atmosphere to engineer the climate by scattering incident sunlight so as to produce a cooling tendency that may mitigate the risks posed by the accumulation of greenhouse gases. Analysis of climate engineering has focused on sulfate aerosols. Here I examine the possibility that engineered nanoparticles could exploit photophoretic forces, enabling more control over particle distribution and lifetime than is possible with sulfates, perhaps allowing climate engineering to be accomplished with fewer side effects. The use of electrostatic or magnetic materials enables a class of photophoretic forces not found in nature. Photophoretic levitation could loft particles above the stratosphere, reducing their capacity to interfere with ozone chemistry; and, by increasing particle lifetimes, it would reduce the need for continual replenishment of the aerosol. Moreover, particles might be engineered to drift poleward enabling albedo modification to be tailored to counter polar warming while minimizing the impact on equatorial climates.
A small molecule accelerates neuronal differentiation in the adult rat
Authors: Wurdak Heiko , Zhu Shoutian , Min Kyung Hoon , Aimone Lindsey , Lairson Luke L. , Watson James , Chopiuk Gregory , Demas James , Charette Bradley , Halder Rajkumar , Weerapana Eranthie , Cravatt Benjamin F. , Cline Hollis T. , Peters Eric C. , Zhang Jay , Walker John R. , Wu Chunlei , Chang Jonathan , Tuntland Tove , Cho Charles Y. , Schultz Peter G.
Published: September 2010

Adult neurogenesis occurs in mammals and provides a mechanism for continuous neural plasticity in the brain. However, little is known about the molecular mechanisms regulating hippocampal neural progenitor cells (NPCs) and whether their fate can be pharmacologically modulated to improve neural plasticity and regeneration. Here, we report the characterization of a small molecule (KHS101) that selectively induces a neuronal differentiation phenotype. Mechanism of action studies revealed a link of KHS101 to cell cycle exit and specific binding to the TACC3 protein, whose knockdown in NPCs recapitulates the KHS101-induced phenotype. Upon systemic administration, KHS101 distributed to the brain and resulted in a significant increase in neuronal differentiation in vivo. Our findings indicate that KHS101 accelerates neuronal differentiation by interaction with TACC3 and may provide a basis for pharmacological intervention directed at endogenous NPCs.
Mutations in mouse
Aspm
(abnormal spindle-like microcephaly associated) cause not only microcephaly but also major defects in the germline
Authors: Pulvers Jeremy N. , Bryk Jarosław , Fish Jennifer L. , Wilsch-Bräuninger Michaela , Arai Yoko , Schreier Dora , Naumann Ronald , Helppi Jussi , Habermann Bianca , Vogt Johannes , Nitsch Robert , Tóth Attila , Enard Wolfgang , Pääbo Svante , Huttner Wieland B.
Published: September 2010

Mutations in
ASPM
(abnormal spindle-like microcephaly associated) cause primary microcephaly in humans, a disorder characterized by a major reduction in brain size in the apparent absence of nonneurological anomalies. The function of the Aspm protein in neural progenitor cell expansion, as well as its localization to the mitotic spindle and midbody, suggest that it regulates brain development by a cell division-related mechanism. Furthermore, evidence that positive selection affected
ASPM
during primate evolution has led to suggestions that such a function changed during primate evolution. Here, we report that in
Aspm
mutant mice, truncated Aspm proteins similar to those causing microcephaly in humans fail to localize to the midbody during M-phase and cause mild microcephaly. A human
ASPM
transgene rescues this phenotype but, interestingly, does not cause a gain of function. Strikingly, truncated Aspm proteins also cause a massive loss of germ cells, resulting in a severe reduction in testis and ovary size accompanied by reduced fertility. These germline effects, too, are fully rescued by the human
ASPM
transgene, indicating that ASPM is functionally similar in mice and humans. Our findings broaden the spectrum of phenotypic effects of
ASPM
mutations and raise the possibility that positive selection of
ASPM
during primate evolution reflects its function in the germline.
Notch signaling contributes to proliferation and tumor formation of human T-cell leukemia virus type 1–associated adult T-cell leukemia
Authors: Pancewicz Joanna , Taylor John M. , Datta Abhik , Baydoun Hicham H. , Waldmann Thomas A. , Hermine Olivier , Nicot Christophe
Published: September 2010

The Notch signaling pathway plays an important role in cellular proliferation, differentiation, and apoptosis. Unregulated activation of Notch signaling can result in excessive cellular proliferation and cancer. Human T-cell leukemia virus type 1 (HTLV-I) is the etiological agent of adult T-cell leukemia (ATL). The disease has a dismal prognosis and is invariably fatal. In this study, we report a high frequency of constitutively activated Notch in ATL patients. We found activating mutations in Notch in more than 30% of ATL patients. These activating mutations are phenotypically different from those previously reported in T-ALL leukemias and may represent polymorphisms for activated Notch in human cancers. Compared with the exclusive activating frameshift mutations in the proline, glutamic acid, serine, and threonine (PEST) domain in T-ALLs, those in ATLs have, in addition, single-substitution mutations in this domain leading to reduced CDC4/Fbw7-mediated degradation and stabilization of the intracellular cleaved form of Notch1 (ICN1). Finally, we demonstrated that inhibition of Notch signaling by γ-secretase inhibitors reduced tumor cell proliferation and tumor formation in ATL-engrafted mice. These data suggest that activated Notch may be important to ATL pathogenesis and reveal Notch1 as a target for therapeutic intervention in ATL patients.
Freeing the Serial Mechanism Designer from Inverse Kinematic Solvability Constraints
Authors: Friedman Diana C. W. , Kowalewski Tim , Jovanovic Radivoje , Rosen Jacob , Hannaford Blake
Published: September 2010

This paper presents a fast numerical solution for the inverse kinematics of a serial manipulator. The method is implemented on the C‐arm, a manipulator designed for use in robotic surgery. The inverse kinematics solution provides all possible solutions for any six degree‐of‐freedom serial manipulator, assuming that the forward kinematics are known and that it is possible to solve for the remaining joint angles if one joint angle’s value is known. With a fast numerical method and the current levels of computing power, designing a manipulator with closed‐form inverse kinematics is no longer necessary. When designing the C‐arm, we therefore chose to weigh other factors, such as actuator size and patient safety, more heavily than the ability to find a closed‐form inverse kinematics solution.
Tunable magnetic and electrical properties of polycrystalline and epitaxial NixFe3−xO4 thin films prepared by reactive co-sputtering
Authors: Jin C , Zhang Q , Mi W B , Jiang E Y , Bai H L
Published: September 2010

Polycrystalline and epitaxial Ni
x
Fe3−x
O4 (0 ⩽ x ⩽ 1.03) thin films were fabricated by reactively co-sputtering Fe and Ni targets in a mixed Ar + O2 atmosphere, and the structure, magnetic and magnetotransport properties were investigated systematically. The saturation magnetization and resistivity can be tuned over a wide range. The room-temperature saturation magnetization for the polycrystalline thin films decreases linearly with x from 440 to 230 emu cm−3, due to Ni substitution. For the epitaxial thin films, the saturation magnetization and the resistivity can be tuned in the range 195–340 emu cm−3 and 10−4–10−2 Ω m by Ni substitution and the introduction of Fe vacancies, because both Ni substitution and Fe vacancies can influence the charge carrier density and the double exchange on the B sublattice.
ReOx charge injection/blocking layers in organic electronic devices
Authors: Luo Jiaxiu , Xiao Lixin , Chen Zhijian , Qu Bo , Gong Qihuang
Published: September 2010

The charge transport of rhenium oxide (ReO
x
) in organic electronic devices was investigated. The hole injection/transport was blocked and the electron injection/transport was enhanced with doping of ReO
x
in organic electronic devices. Thus the charge balance and efficiency of organic light-emitting diodes were improved; current efficiency of 2.7 cd A−1 at 20 mA cm−2 for the device with ReO
x
was higher than 1.5 cd A−1 for the device without it. In the case of organic photovoltaic cells, the open-circuit voltage (V
oc), 0.58 V, was higher compared with the device without ReO
x
(0.44 V) due to the improvement of interface properties. The power conversion efficiency was increased to 2.27% by the combination of ReO
x
(increases V
oc) with poly(3,4-ethylenedioxythiophene) : poly(styrene-sulfonate) (improves hole transport to increase J
sc) on the modification of the anode, higher than 1.85% for the device without ReO
x
.
Theoretical analysis of a nanoscale plasmonic filter based on a rectangular metal–insulator–metal waveguide
Authors: Yun Binfeng , Hu Guohua , Cui Yiping
Published: September 2010

A compact and nanometric surface plasmon polariton (SPP) band-pass filter based on a rectangular ring resonator composed of metal–insulator–metal waveguides is proposed. Using the finite difference time domain method, the effects of the structure parameters on the transmission characteristics of this SPP band-pass filter are analysed in detail. The results show that the proposed SPP filter has narrow transmission peaks and the corresponding resonance wavelengths can be linearly tuned by altering the resonator's cavity length. Moreover, the transmission ratios of the pass bands can be tuned by changing the coupling gaps between the input/output MIM waveguides and the resonator. Also the metal loss and dispersion effects on the filter responses are included. The simple band-pass SPP filter is very promising for high-density SPP waveguide integrations.
Barium transport in the hot spot region of fluorescent lamps
Authors: Sigeneger F , Rackow K , Uhrlandt D , Ehlbeck J , Lieder G
Published: September 2010

The transport of barium atoms and ions in the vicinity of the hot spot in fluorescent lamps operating at 25 kHz is investigated by a combined experimental and theoretical approach. By laser-induced fluorescence, the particle densities of barium atoms and ions were measured time-resolved at different distances from the spot centre. In addition, the time-dependent cathode fall voltage was measured using an improved band method. The model combines a kinetic part for the electrons with a fluid part for the barium atoms and ions. Both parts are spatially resolved in spherically symmetric geometry. The space-dependent electron Boltzmann equation yields the electron density and the ionization rate coefficient of barium as functions of the cathode fall voltage. These results are used to solve the time-dependent particle balance equations of barium atoms and ions which include the ionization of barium as gain and loss terms, respectively. Good agreement between the measured and calculated particle densities of barium atoms is obtained. A sensitive dependence of the ionization frequency and of the barium particle densities on the cathode fall voltage was found.
Surface-plasmon voltammetry using a gold grating
Authors: Jory M J , Cann P S , Sambles J R
Published: September 2010

Using a sensitive optical wavelength modulation technique the surface-plasmon excited on a gold grating surface immersed in sulfuric acid is studied at the same time as cyclic voltammetry is undertaken. Because of the optical sensitivity of the modulation technique significant optical effects are observed at potentials well below those at which any gross oxidation effects occur.