bluuebunny/crossref_metadata_2025 huggingface dataset:
A proline to glycine mutation in the Lck SH3‐domain affects conformational sampling and increases ligand binding affinity
Authors: Bauer Finn , Sticht Heinrich
Published: March 2007

Loop flexibility is discussed as a factor that affects ligand binding affinity of SH3 domains. To test this hypothesis, we designed a mutant in which a proline in the RT‐loop of the human Lck SH3‐domain is replaced by glycine. The dynamics and ligand binding properties of wild‐type and mutant LckSH3 were studied by fluorescence and NMR spectroscopy as well as molecular dynamics simulations. Although the mutated residue does not form direct contacts with the ligand, the mutation increases ligand affinity by a factor of eight. The mutant exhibits increased loop flexibility and enhanced sampling of binding‐competent conformations. This effect is expected to facilitate ligand binding itself and might also allow formation of tighter contacts in the complex thus resulting in an increased binding affinity.
Modulation of p300 binding by posttranslational modifications of the C‐terminal activation domain of hypoxia‐inducible factor‐1α
Authors: Cho Hyunju , Ahn Dae-Ro , Park Hyunsung , Yang Eun Gyeong
Published: March 2007

Posttranslational modifications of hypoxia‐inducible factor‐1α (HIF‐1α) influence HIF‐mediated transcription, likely by affecting binding to p300/cAMP‐response element‐binding protein (CBP). To systematically analyze the HIF‐1α–p300/CBP interaction, we developed a fluorescence polarization‐based binding assay, employing fluorescein‐labeled peptides derived from the C‐terminal transactivation domain (C‐TAD) of HIF‐1α. After optimized for effectively capturing p300/CBP, the assay was utilized for evaluating direct effects of posttranslational modifications of the HIF‐1α C‐TAD on p300 binding. The results demonstrated that asparagine hydroxylation and S‐nitrosylation of HIF‐1α decrease p300 binding, while its phosphorylation does not affect p300 binding, which was reconfirmed by competitive inhibition analyses using mutant peptides.
Genome‐wide screening of alpha‐tocopherol sensitive genes in heart tissue from alpha‐tocopherol transfer protein null mice (ATTP−/−)
Authors: Vasu Vihas T. , Hobson Brad , Gohil Kishorchandra , Cross Carroll E.
Published: March 2007

Alpha‐tocopherol transfer protein (ATTP) null mice (ATTP−/−) have a systemic deficiency of alpha‐tocopherol (AT). The heart AT levels of ATTP−/− are <10% of those in ATTP+/+ mice. The genomic responses of heart to AT deficiency were determined in 3 months old male ATTP−/− mice and compared with their ATTP+/+ littermate controls using Affymetrix 430A 2.0 high density oligonucleotide arrays. Differential analysis of ∼13 000 genes identified repression of genes related to immune system and activation of genes related to lipid metabolism and inflammation with no significant change in the expression of classical antioxidant genes (catalase, superoxide dismutase, glutathione peroxidase) in ATTP−/− as compared to ATTP+/+ mice. The present data identifies novel classes of AT sensitive genes in heart tissue.
Lipid rafts and membrane traffic
Authors: Hanzal-Bayer Michael F. , Hancock John F.
Published: March 2007

Membrane rafts are regions of increased lipid acyl chain order that differ in their lipid and protein composition from the surrounding membrane. By providing an additional level of compartmentalization they have been proposed to serve many functions in cellular signal transduction and trafficking. We will review their potential involvement in different forms of membrane traffic, explicitly excluding signalling, and discuss select aspects of the raft hypothesis in its current form.
Plant aquaporins: Novel functions and regulation properties
Authors: Maurel Christophe
Published: March 2007

Aquaporins are water channel proteins of intracellular and plasma membranes that play a crucial role in plant water relations. The present review focuses on the most recent findings concerning the molecular and cellular properties of plant aquaporins. The mechanisms of transport selectivity and gating (i.e. pore opening and closing) have recently been described, based on aquaporin structures at atomic resolution. Novel dynamic aspects of aquaporin subcellular localisation have been uncovered. Also, some aquaporin isoforms can transport, besides water, physiologically important molecules such as CO2, H2O2, boron or silicon. Thus, aquaporins are involved in many great functions of plants, including nutrient acquisition, carbon fixation, cell signalling and stress responses.
“Linking Up with the International Track” What's in a Slogan?
Authors: Wang Hongying
Published: March 2007

The rise of China as a major power in the world is an indisputable reality of world politics today. Less clear is whether China will abide by the prevailing international rules as it becomes more powerful. This article attempts to gauge China's evolving attitude toward international norms pertinent to domestic governance by studying a popular Chinese slogan – “link up with the international track” (yu guoji jiegui). It examines the rise of the slogan at different levels of the Chinese public discourse, analyses its meanings and applications in the Chinese discourse, and assesses the major controversies over the slogan. This study shows that Chinese thinking about international norms varies across time, secots and issue areas. It suggests the need for greater nuance in our understanding of current and future Chinese attitudes towards international rules.
From the Tax-for-Fee Reform to the Abolition of Agricultural Taxes: The Impact on Township Governments in North-west China
Authors: Kennedy John James
Published: March 2007

Over the last decade, there have been numerous reports of rural discontent and unrest over excessive local taxes and fees known as villagers' burdens. In response, the central government enacted the tax-for-fee reform (TFR) in 2002 that abolished local fees levied on individuals and rural households in favour of a single agricultural tax. In addition the central government has announced plans to eliminate the agricultural tax as well after 2006. The aim of the TFR is to streamline local revenue collection and establish a more transparent and efficient provision of services. The immediate result, however, is a dramatic reduction in the autonomy of township governments as well as the provision of local services. Poorer townships have become more dependent on county government for revenues, and these townships function more like county administrative units than local self-governments. Moreover, many services have also been cut due to a lack of local revenues. In north-west China, there has been a sharp decline in the provision of educational and medical services. The solution is an increase in county remittances, but these are slow and uneven, and the combination of reduced autonomy and services has produced a number of “administrative shells” at the township level. If the inefficacy continues, then there may be even greater rural discontent and unrest over the loss of basic services than there was over increasing villagers' burdens.
Gendered Pathways to Rural Schooling: The Interplay of Wealth and Local Institutions
Authors: Davis Deborah , Landry Pierre , Peng Yusheng , Xiao Jin
Published: March 2007

Using a 2004 survey of over 1,000 children in a multi-ethnic county of Yunnan province, this article demonstrates how household and village assets operate in gender distinct ways to promote school enrolment in an era of economic privatization and skewed sex ratios. As expected, parental and village wealth facilitate enrolment, but parental wealth is far more decisive for girls than boys. Similarly we find a gender difference in the impact of such parental cultural capitals as education and membership in the Communist Youth League. For a daughter, having a father with higher than average levels of education and past membership in the Youth League facilitates enrolment independent of household wealth; for sons the impact of father's cultural capital is positive but less decisive. Having a more educated mother or a mother who was in the Youth League also promotes a child's enrolment but not as significantly as father's assets. In conclusion, the article considers why parents' involvement in the Youth League during their own adolescence but not their current Communist Party membership facilitates school enrolment, and the broader social and political implications for the role of the Communist Party in rural society.
Regulating Intellectual Life in China: The Case of the Chinese Academy of Social Sciences
Authors: Sleeboom-Faulkner Margaret
Published: March 2007

This article explores why and how the Chinese Academy of Social Sciences (CASS), a PRC state research-institute, survived after its involvement with the June Fourth demonstrations in 1989 through research regulation. I show how the explicit ascription of an advisory role to CASS required an increase in freedom of research and an increase in political steering through regulation. I do this by comparing the institutional setting of CASS in the early 1990s with that during Li Tieying's leadership (1998 to 2003). The article traces a general trend in which organizational reforms at institutions of higher education increasingly entail giving political direction to the development of the social science debate. Radical political views are discouraged through regulation, guidelines, meetings, academic activities and financial, material and social encouragement. This institutional approach aims to yield insight into the functioning of CASS as producer of knowledge and as think-tank to the government.
How Do Chinese Civic Associations Respond to the Internet? Findings from a Survey
Authors: Yang Guobin
Published: March 2007

Based on survey data collected from October 2003 to January 2004, this article provides the first systematic empirical analysis of how civic associations in urban China have responded to the internet. It shows, first, that urban grassroots organizations are equipped with a minimal level of internet capacity. Secondly, for these organizations, the internet is most useful for publicity work, information dessemination, and networking with peer and international organizations. Thirdly, social change organizations, younger organizations and organizations in Beijing report more use of the internet than business associations, older organizations and organizations outside Beijing. Finally, organizations with bare-bone internet capacity report more active use of the internet than better-equipped organizations. These findings suggest that the internet has had special appeal to relatively new organizations oriented to social change and that a “web” of civic associations has emerged in China.
Frederic Wakeman, Jr., 1937–2006
Authors: Elliott Mark C.
Published: March 2007

Frederic Wakeman Jr., pre-eminent historian of modern China and Haas Professor of Asian Studies emeritus at the University of California, Berkeley, died of cancer on 14 September 2006 in Lake Oswego, Oregon, at the age of 68. He is survived by his wife, He Lea Wakeman, his sister, Sue Farquhar, three children, Frederic III, Matthew and Sarah, and two grandchildren.
Making Private Property: Enclosure, Common Right and the Work of Hedges
Authors: BLOMLEY NICHOLAS
Published: March 2007

Analyses of enclosure in late sixteenth and early seventeenth century England have tended to focus on the social work of representations, in particular estate maps. I depart from this emphasis, however, in my attempt to focus on the consequential and often contradictory role of material objects in producing enclosure. In particular, I emphasise the important work that hedges did, physically, symbolically and legally, in the dispossession of the commoner. Acting as an organic barbed wire, the hedge was increasingly put to work to protect the lands of the powerful. Disrupting the propertied spaces of the commoning economy, hedges were not surprisingly targeted by those who opposed privatisation. The hedge, as both a sign and material barrier, served complicated and sometimes opposing ends. It materialised private property's right to exclude, but thus came into conflict with common property's right not to be excluded. The hedge was both an edge to property and was itself property. Both the encloser and the commoner, however, had property interests in the hedge. If broken, the hedge could signal violence and riot, or the legitimate assertion of common right. The hedge served as an often formidable material barrier, yet this very materiality made it vulnerable to ‘breaking’ and ‘leveling’.
Estate Improvement and the Professionalisation of Land Agents on the Egremont Estates in Sussex and Yorkshire, 1770–1835
Authors: WEBSTER SARAH
Published: March 2007

The role of land agents in the management and improvement of English landed estates between 1770 and 1850 is examined in this paper. The focus is on the responsibilities of land agents, their contribution to agricultural improvement, and in particular the validity of a thesis of the professionalisation of agents during this period. The Petworth House archives are used to compare the work of two legal agents at Petworth in Sussex with that of a professional land agency firm in Yorkshire, both employed by the third Earl of Egremont (1751–1837). This study suggests that the role of land agents in agricultural improvement at Petworth was limited to the financial, legal and political aspects of these developments rather than practical management. It proposes that legal agents remained more influential than has been supposed, even on estates renowned for agricultural improvement, and despite contemporary criticism that emphasised the importance of applied agricultural expertise. The belated professionalisation of the Petworth agents and the significant differences in their roles when compared with contemporary and historical accounts suggests that estate management was therefore far more diverse than is suggested in some recent literature.
Landscape Parks and the Memorialisation of Empire: The Pierreponts' ‘Naval Seascape’ in Thoresby Park, Nottinghamshire during the French Wars, 1793–1815
Authors: SEYMOUR SUSANNE , CALVOCORESSI RUPERT
Published: March 2007

This paper engages with debates over estate and empire during the French Revolutionary and Napoleonic Wars through a focus on park landscaping. Drawing on Colley's (1992) idea of a ‘cult of the elite hero’ and work on life geographies (Daniels and Nash, 2004), it examines landscape and monument design commemorating naval service. Unlike most other studies of this period, the paper examines naval monuments in the private setting of a landscape park and considers the ways in which this disrupts a neat division between public and private spheres. At Thoresby Park in Nottinghamshire, Charles Pierrepont, a naval veteran active in landscape improvement, created a ‘naval seascape’ which promoted a sense of a ‘service elite’ (Colley, 1992). The paper examines the contested meanings of this seascape and the ways in which they help revision the nature of landscape parks during the French Wars and their public and private roles.
The Guano Voyages
Authors: CORDLE CELIA
Published: March 2007

This paper on guano stems from research into hop cultivation in Kent. Parliamentary Papers give fascinating accounts of voyages made during the nineteenth century to obtain this ‘wonder’ fertiliser. The efforts made on behalf of the agricultural community by naval officers and seamen were an important extension of rural history, and were considered vital at the time. The paper describes the effort that went into this cooperation between agriculture and the navy, as well as its global scope, at a time when agricultural chemistry was in its infancy. Although developments in chemistry would displace the need for guano within two decades, the desire for guano was then very striking. Naval personnel underwent considerable danger and physical hardship during these explorations to bring farmers the fertilisers that they wanted, and some features of this narrative are explored here.
Maurice Beresford, 1920–2005
Authors: Fox Harold
Published: March 2007

For his contribution to landscape history, Maurice Beresford may be compared to William Hoskins. His first book, The Lost Villages of England (1954), explored a subject which he initially chanced upon when surveying ridge and furrow in a Midland parish and found that there was a gap in the pattern somewhere near its centre. That gap, a deserted village, led him rapidly into a huge field of enquiry, embracing historical demography, social history and agrarian history, as well the history of the landscape. Many others have been drawn into this field, which was pioneered simultaneously by Hoskins, largely through the enthusiasm of Beresford's writing. It was Beresford, together with John Hurst, who initiated the long-running excavations of a deserted village at Wharram Percy, where fundamental techniques in medieval archaeology were developed and many innovative ideas emerged, on changing settlement morphology, for example, on types of peasant houses and, latterly, on peasant diet and disease. The influential group now called the Medieval Settlement Research Group was at first associated with the excavations at Wharram.
Flooding induces secondary dormancy in Setaria parviflora seeds
Authors: Mollard Federico P.O. , Insausti Pedro , Sánchez Rodolfo A.
Published: March 2007

The effect of flooding on the dormancy level of Setaria parviflora seeds from a non-flooded upland and a seasonally (winter–spring) flooded lowland in the Pampa grasslands of Argentina was investigated. Seeds from both communities were subjected to reciprocal burial treatments in the two habitats, and exhumed during and after the flooding season. Effect of immersion in water at 5°C was compared to incubation of seeds on the surface of water-saturated paper at the same temperature. After exhumation of the buried seeds or immersion treatments, germination was assayed at 25°C and at 20/30°C in the dark or in combination with light. Burial in the lowland, which was flooded in winter–spring, significantly reduced germination, while burial in the non-flooded upland did not reduce germination. Similarly, immersion in water at 5°C significantly reduced germination compared to non-immersed controls. During summer, seeds buried in the lowland showed increased capacity to germinate, particularly when exposed to fluctuating temperatures or light. Thus, flooding induced secondary dormancy in S. parviflora seeds, and it was broken during the non-flooding season. These responses of the seeds would prevent germination until there was no further risk of flooding. Remarkably, in S. parviflora seeds harvested from both habitats, we observed essentially the same germination requirements after flooding. However, some slight differences were detected between the seed populations exhumed from the lowland site, indicating that flooding had larger effects on the seeds from the upland community. This suggests some differentiation of these populations evident only after flooding in the field.
A model of biogeochemical cycles of carbon, nitrogen, and phosphorus including symbiotic nitrogen fixation and phosphatase production
Authors: Wang Y.‐P. , Houlton B. Z. , Field C. B.
Published: March 2007

Global climate models have not yet considered the effects of nutrient cycles and limitation when forecasting carbon uptake by the terrestrial biosphere into the future. Using the principle of resource optimization, we here develop a new theory by which C, N, and P cycles interact. Our model is able to replicate the observed responses of net primary production to nutrient additions in N‐limited, N‐ and P‐colimited, and P‐limited terrestrial environments. Our framework identifies a new pathway by which N2 fixers can alter P availability: By investing in N‐rich, phosphorus liberation enzymes (phosphatases), fixers can greatly accelerate soil P availability and P cycling rates. This interaction is critical for the successful invasion and establishment of N2 fixers in an N‐limited environment. We conclude that our model can be used to examine nutrient limitation broadly, and thus offers promise for coupling the biogeochemical system of C, N, and P to broader climate‐system models.
Thermo‐rheological magma control on the impact of highly fluid lava flows at Mt. Nyiragongo
Authors: Giordano D. , Polacci M. , Longo A. , Papale P. , Dingwell D. B. , Boschi E. , Kasereka M.
Published: March 2007

In January 2002 Mount Nyiragongo erupted foiditic lavas that covered the Southern volcano flank devastating vast urban areas. Lava flows originated from vents at different heights on the eruptive fissure displayed different velocities, from tens of km/h at the highest vents to slow‐advance (0.1–1 km/h) in Goma town several km away from the volcano. To understand the different behavior of lava flows and their threat to the local population, we undertook a multidisciplinary study involving textural and rheological measurements and numerical simulations of heat transfer during magma ascent. We demonstrate that pre‐eruptive cooling and syn‐eruptive undercooling of magma determined the different rheological behavior of lava flows erupted from vents at diverse heights. Venting at lower altitudes is expected to produce viscous, slowly advancing lavas, although development of fluid, faster flows should be included among possible future eruptive scenarios.
Regional changes in precipitation in Europe under an increased greenhouse emissions scenario
Authors: Tapiador F. J. , Sánchez E. , Gaertner M. A.
Published: March 2007

Regional multi‐model ensembles are used to both increase the spatial resolution of the global simulations and to palliate uncertainties arising from different parameterizations and dynamical cores. Here, we present the simulated current (1960–1990) and future (2070–2100) precipitation climatologies using eight Regional Climate Models (RCM) over Europe for an increased greenhouse gases scenario. Analysis of the current climate simulations in terms of the Probability Distribution Functions (PDF) shows noticeable regional differences in the type of precipitation which are in agreement with known precipitation climatologies. For future climate we observe an overall decrease of mean precipitation in most of the Mediterranean regions. A rise in high monthly precipitation amounts appear for all the regions, except for the Iberian peninsula and the Alps. As our analysis embed both spatial and temporal uncertainties in the modeling, our results provide further evidence of a variety of regional patterns within Europe under an increased greenhouse emissions scenario.
Low‐latitude valley region irregularities studied using the Gadanki radar
Authors: Patra A. K. , Venkateswara Rao N.
Published: March 2007

A study of valley region irregularities (VRI) and structures utilizing a database of observations obtained by the Gadanki radar is presented. It is shown that VRI occur both in the presence and absence of equatorial spread F (ESF) activity. VRI are found to occur initially near 2000 LT at an altitude as high as 180 km and then descend with time. Notably, the occurrence pattern of VRI resembles closely to that of the low‐latitude intermediate layers. The above occurrence pattern is observed irrespective of the type of ESF event present. During ESF plume events, however, significant temporal structures in VRI with close relation to the ESF structures are observed, which are otherwise missing. VRI velocities in relation to ESF are in the range of −70 m s−1 to 100 m s−1 while in the absence of ESF, VRI velocities are in the range of ±50 m s−1. Further, SNR and spectral width are considerably higher when they are associated with ESF plumes. It is suggested that VRI are generated on the intermediate layers possibly through gradient drift instability. It is also suggested that the valley region ambient fields are quite capable of generating these irregularities. The role of the unstable F region electric fields on VRI is found to be important for structuring in VRI and may be critical for the generation of irregularities when the valley region is stable by itself.
Diurnal tides in mesosphere/low‐thermosphere during 2002 at Wuhan (30.6°N, 114.4°E) using canonical correlation analysis
Authors: Xue Xianghui , Wan Weixing , Xiong Jiangang , Dou Xiankang
Published: March 2007

In this paper, we use canonical correlation analysis (CCA) method to investigate the mesosphere/low thermosphere (MLT) diurnal tidal winds during the year 2002 observed by a newly installed meteor radar at Wuhan (30.6°N, 114.4°E). In general, six effective diurnal tidal pairs of patterns are obtained, which represent over 90% total variances of the origin data set. These patterns are expected to correspond to the atmospheric oscillations within diurnal frequency band excited or modulated by different sources, namely, the seasonal variations and the modulations by semiannual‐like variations, solar 27‐day rotation and the planetary wave oscillations. Among all of the patterns, the first pattern is the most notable, which represents ∼40% of total variances. Its amplitudes show maximum values in spring and autumn as well as sudden phase transit near equinox month, which is in line with the results obtained from traditional harmonic analysis. The vertical wavelengths (∼30 km) suggest the classic tidal mode S(1,1) is dominant, and the preceding phases (∼5–6 hours) of the meridional components of the diurnal tidal wind show right‐rotating circular polarization may be the main characteristic in tidal wind.
Use of proper orthogonal decomposition for the reduction of atmospheric chemical kinetics
Authors: Sportisse Bruno , Djouad Rafik
Published: March 2007

We investigate in this article a method based on proper orthogonal decompositions (POD) in order to reduce atmospheric chemical mechanisms. In a preliminary test, we apply this algorithm to the reduction of the CBM IV mechanism in a box model. The reduced basis computed with POD gives accurate results in its domain of validity while the CPU time needed for integration has been drastically lowered. The number of degrees of freedom of the local reduced model is 2 or 3. Moreover, we investigate some numerical strategies and a sensitivity analysis related to the choice of the reduced basis. This reducing technique is applied to three different scenarios for initial conditions: rural, urban, and polluted. Our tests indicate the deep relation with the slow‐fast behavior of chemical kinetics.
Representing a new MODIS consistent land surface in the Community Land Model (CLM 3.0)
Authors: Lawrence Peter J. , Chase Thomas N.
Published: March 2007

Recently a number of studies have found significant differences between Moderate Resolution Imaging Spectroradiometer (MODIS) land surface mapping and the land surface parameters of the Community Land Model (CLM) of the Community Climate System Model (CCSM). To address these differences in land surface description, we have developed new CLM 3.0 land surface parameters that reproduce the physical properties described in the MODIS land surface data while maintaining the multiple Plant Functional Type (PFT) canopy and herbaceous layer representation used in CLM. These new parameters prescribe crop distributions directly from historical crop mapping allowing cropping to be described in CLM for any year from 1700 to current day. The new model parameters are calculated at 0.05 degrees resolution so they can be aggregated and used over a wider range of model grid resolutions globally. Compared to the current CLM 3.0 parameters, the new parameters have an increase in bare soil fraction of 10% which is realized through reduced tree, shrub, and crop cover. The new parameters also have area average increases of 10% for leaf area index (LAI) and stem area index (SAI) values, with the largest increases in tropical forests. The new land surface parameters have strong repeatable impacts on the climate simulated in CCSM 3.0 with large improvements in surface albedo compared to MODIS values. In many cases the improvements in surface albedo directly resulted in improved simulation of precipitation and near‐surface air temperature; however, for the most part the existing biases of CCSM 3.0 remained with the new parameters. Further analysis of changes in surface hydrology revealed that the increased LAI of the new parameters resulted in lower overall evapotranspiration with reduced precipitation in CCSM 3.0. This was an unexpected result given that other research into the impacts of vegetation change suggests that the new parameters should have the opposite impact. This suggests that while the new parameters significantly improve the climate simulated in CLM 3.0 and CCSM 3.0, the new surface parameters have limited success in rectifying surface hydrology biases that result from the parameterizations within the CLM 3.0.
Understanding coronal heating and solar wind acceleration: Case for in situ near‐Sun measurements
Authors: McComas D. J. , Velli M. , Lewis W. S. , Acton L. W. , Balat‐Pichelin M. , Bothmer V. , Dirling R. B. , Feldman W. C. , Gloeckler G. , Habbal S. R. , Hassler D. M. , Mann I. , Matthaeus W. H. , McNutt R. L. , Mewaldt R. A. , Murphy N. , Ofman L. , Sittler E. C. , Smith C. W. , Zurbuchen T. H.
Published: March 2007

The solar wind has been measured directly from 0.3 AU outward, and the Sun's atmosphere has been imaged from the photosphere out through the corona. These observations have significantly advanced our understanding of the influence of the Sun's varying magnetic field on the structure and dynamics of the corona and the solar wind. However, how the corona is heated and accelerated to produce the solar wind remains a mystery. Answering these fundamental questions requires in situ observations near the Sun, from a few solar radii (RS) out to ∼20 RS, where the internal, magnetic, and turbulent energy in the coronal plasma is channeled into the bulk energy of the supersonic solar wind. A mission to make such observations has long been a top priority of the solar and space physics community. The recent Solar Probe study has proven that such a mission is technically feasible and can be accomplished within reasonable resources.
Relative importance of the day‐night asymmetry in Schumann resonance amplitude records
Authors: Pechony O. , Price C. , Nickolaenko A. P.
Published: March 2007

Computations of Schumann resonance (SR) field amplitudes from a point source in the uniform and nonuniform cavities are performed to estimate the relative importance of the day‐night asymmetry in observed SR amplitudes. Additional simulations with globally distributed sources, representing diurnal and seasonal variations of global lightning activity, are performed in uniform and nonuniform cavities to evaluate the impact of the day‐night asymmetry on the diurnal and seasonal amplitude variations. The results show that the effect of diurnal ionosphere changes on the first mode SR amplitudes is ∼10%. Model results indicate that the source properties (the level of activity and proximity to the observer) play the dominant role in the diurnal variations observed in SR field records, with the day‐night asymmetry being secondary in importance.
Retroviral oncoprotein Tax deregulates NF‐κB by activating Tak1 and mediating the physical association of Tak1–IKK
Authors: Wu Xuefeng , Sun Shao‐Cong
Published: March 2007

The Tax oncoprotein of human T‐cell leukaemia virus type I (HTLV‐I) persistently activates nuclear factor‐κB (NF‐κB), which is required for HTLV‐I‐mediated T‐cell transformation. Tax activates NF‐κB by stimulating the activity of IκB kinase (IKK), but the underlying mechanism remains elusive. Here, we show that Tax functions as an intracellular stimulator of an IKK‐activating kinase, Tak1 (TGF‐β‐activating kinase 1). In addition, Tax physically interacts with Tak1 and mediates the recruitment of IKK to Tak1. In HTLV‐I‐infected T cells, Tak1 is constitutively activated and complexed with both Tax and IKK. We provide genetic evidence that Tak1 is essential for Tax‐induced IKK activation. Furthermore, unlike cellular stimuli, the Tax‐specific NF‐κB signalling does not require the ubiquitin‐binding function of IKKγ. These findings show a pathological mechanism of IKK activation by Tax and provide an example for how IKK is persistently activated in cancer cells.
Mechanism of arachidonic acid action on syntaxin–Munc18
Authors: Connell Emma , Darios Frédéric , Broersen Kerensa , Gatsby Naomi , Peak‐Chew Sew‐Yeu , Rickman Colin , Davletov Bazbek
Published: March 2007

Syntaxin and Munc18 are, in tandem, essential for exocytosis in all eukaryotes. Recently, it was shown that Munc18 inhibition of neuronal syntaxin 1 can be overcome by arachidonic acid, indicating that this common second messenger acts to disrupt the syntaxin–Munc18 interaction. Here, we show that arachidonic acid can stimulate syntaxin 1 alone, indicating that it is syntaxin 1 that undergoes a structural change in the syntaxin 1–Munc18 complex. Arachidonic acid is incapable of dissociating Munc18 from syntaxin 1 and, crucially, Munc18 remains associated with syntaxin 1 after arachidonic‐acid‐induced syntaxin 1 binding to synaptosomal‐associated protein 25 kDa (SNAP25). We also show that the same principle operates in the case of the ubiquitous syntaxin 3 isoform, highlighting the conserved nature of the mechanism of arachidonic acid action. Neuronal soluble N‐ethyl maleimide sensitive factor attachment protein receptors (SNAREs) can be isolated from brain membranes in a complex with endogenous Munc18, consistent with a proposed function of Munc18 in vesicle docking and fusion.
Non‐invasive imaging of firefly luciferase reporter gene expression using bioluminescence imaging in human prostate cancer models
Authors: Li Hongwei , Li Jin Zhong , Helm Gregory A. , Pan Dongfeng
Published: March 2007

Monitoring the expression of therapeutic genes in targeted tissues in disease models is important to assess the effectiveness and safety of systems of gene therapy delivery. In the present study, we employed a CCD (charge‐coupled‐device) imaging system to monitor how a prostate‐specific adenovirus vector (AdPSA‐Luc) mediated the long‐term, sustained expression of firefly luciferase (Luc) in living human prostate cancer mouse models. The in vivo bioluminescence imaging revealed significantly high levels of luciferase expression up to 1 month, not only in prostate tumours, but also in lungs after intratumoural injection. Systemic tail vein injection of AdPSA‐Luc revealed significant luciferase expression in lungs of both human prostate cancer mouse models and naïve mice, but significantly higher in the former, while the control virus, AdCMV‐Luc, containing CMV (cytomegalovirus) promoter and luciferase gene, just restricted expression in the livers. Our findings demonstrate the ability of the cooled CCD camera to sensitively and non‐invasively track the location, magnitude and persistence of luciferase gene expression in human prostate cancer mouse models. Monitoring of gene therapy studies in small animals may be aided considerably with further extensions of this technique.
Expression and characterization of human growth hormone–Fc fusion proteins for transcytosis induction
Authors: Lee Chang Hoon , Woo Jung Hee , Cho Kwang Keun , Kang Seung Ha , Kang Sang Kee , Choi Yun Jaie
Published: March 2007

The major obstacle for oral delivery of administered therapeutic proteins is malabsorption in the intestine. This malabsorption could be overcome by induction of neonatal FcRn [Fc (CH2 and CH3 domains of human IgG1 antibody) receptor]‐mediated transcytosis in the intestine using recombinant fusion of CH2 and CH3 moieties of human IgG to a therapeutic protein. To this end we developed recombinant hGH (human growth hormone) fused to the N‐terminus of Fc moieties [CH2‐CH3 or h (hinge)‐CH2‐CH3] from human IgG1. These recombinant proteins secreted by the methylotrophic yeast Pichia pastoris functionally induced secretion of insulin‐like growth factor 1 by HepG2 cells in the response to hGH moiety in the fusion proteins. In a transport study using polarized T84 cells, 3.7% of added dimeric hGH–h‐Fc was transported in the apical‐to‐basolateral direction within 1 h by FcRn‐mediated transcytosis of 1 cm2 monolayers. However, transport of monomeric hGH–Fc (only 0.43%) was much less effective, yet its transport was 2.3 times higher than that of hGH. Finally, we concluded that, upon recombinant fusion, maintenance of dimeric structure of Fc moieties is crucial for the induction of FcRn‐mediated transcytosis.
Strain relaxation in heteroepitaxial films by misfit twinning. I. Critical thickness
Authors: Liu Lilin , Zhang Yousheng , Zhang Tong-Yi
Published: March 2007

Based on the dislocation theory of twinning, an analytical solution is given to determine the critical thickness of the misfit twin formation in an epilayer with different elastic constants from its substrate. For a given epilayer thickness and lattice mismatch strain, the twin formation energy should reach its minimum to determine the twin width and a zero minimum formation energy determines the critical thickness for misfit twinning. The effect of elastic mismatch between the epilayer and the substrate on the critical thickness is studied comprehensively, revealing that an elastically soft epilayer has a large critical thickness. Moreover, a misfit-twin-and-perfect-dislocation predominance chart is constructed to predict the predominant regions of misfit twinning and perfect dislocation in the mismatch strain and the specific twin-boundary energy domain.
Strain relaxation in heteroepitaxial films by misfit twinning: II. Equilibrium morphology
Authors: Zhang Yousheng , Liu Lilin , Zhang Tong-Yi
Published: March 2007

The equilibrium morphology of misfit twins in an epilayer with different elastic constants from its substrate is systematically investigated by energy minimization based on the dislocation mechanism of twinning. Explicit formulas for period arrays of misfit twins with the same orientation and with alternating orientations are derived by superposition of the solutions reported in Part I of this series. The equilibrium morphology for a periodic array of misfit twins is characterized by the twin width and the twin mean spacing. The effects of elastic mismatches between the epilayer and the substrate on the equilibrium morphology of twins are also studied comprehensively. The theoretical predictions agree with experimental observations.
Raman scattering spectra and ferroelectric properties of Bi1−xNdxFeO3 (x=–0.2) multiferroic ceramics
Authors: Yuan G. L. , Or Siu Wing , Chan Helen Lai Wa
Published: March 2007

Single-phase Bi1−xNdxFeO3 (BNFOx) (x=0–0.2) multiferroic ceramics were prepared to study the effects of Nd substitution on their crystal structures, Raman scattering spectra, and ferroelectric properties. Rietveld refinement of x-ray diffraction data showed a gradual change in crystal structure from rhombohedral to pseudotetragonal via triclinic with increasing x. The evolvement of Raman normal modes with increasing x suggested that such structural change is accompanied by the weakening of long-range ferroelectric order. The simultaneous occurrence of abrupt mode evolvement and ferroelectric-paraelectric transition in BNFOx=0.175 and BNFOx=0.2 was explained according to the change of Bi–O covalent bonds as a result of the decline in the stereochemical activity of the Bi lone electron pair at 0.175⩽x⩽0.2.
Density functional simulation of spontaneous formation of vesicle in block copolymer solutions
Authors: Uneyama Takashi
Published: March 2007

The author carries out numerical simulations of vesicle formation based on the density functional theory for block copolymer solutions. It is shown by solving the time evolution equations for concentrations that a polymer vesicle is spontaneously formed from the homogeneous state. The vesicle formation mechanism obtained by this simulation agrees with the results of other simulations based on the particle models as well as experiments. By changing parameters such as the volume fraction of polymers or the Flory-Huggins interaction parameter between the hydrophobic subchains and solvents, the spherical micelles, cylindrical micelles, or bilayer structures can also be obtained. The author also shows that the morphological transition dynamics of the micellar structures can be reproduced by controlling the Flory-Huggins interaction parameter.
Vibration-rotation energy pattern in acetylene: C13HC12H up to 6750cm−1
Authors: Fayt A. , Robert S. , Di Lonardo G. , Fusina L. , Tamassia F. , Herman M.
Published: March 2007

All known vibration-rotation absorption lines of C13HC12H accessing levels up to 6750cm−1 were gathered from the literature. They were fitted simultaneously to J-dependent Hamiltonian matrices exploiting the well known vibrational polyad or cluster block diagonalization, in terms of the pseudo-quantum-numbers Ns=v1+v2+v3 and Nr=5v1+3v2+5v3+v4+v5, and accounting also for l parity and e∕f symmetry properties. The anharmonic interaction coupling terms known to occur from a pure vibrational fit in this acetylene isotopologue [Robert et al., J. Chem. Phys. 123, 174302 (2005)] were included in the model. A total of 12 703 transitions accessing 158 different (v1v2v3v4v5,l4l5) vibrational states was fitted with a dimensionless standard deviation of 0.99, leading to the determination of 216 vibration-rotation parameters. The experimental data included very weak vibration-rotation transitions accessing 18 previously unreported states, some of them forming Q branches with very irregular patterns.
Probing the limits of accuracy in electronic structure calculations: Is theory capable of results uniformly better than “chemical accuracy”?
Authors: Feller David , Peterson Kirk A.
Published: March 2007

Current limitations in electronic structure methods are discussed from the perspective of their potential to contribute to inherent uncertainties in predictions of molecular properties, with an emphasis on atomization energies (or heats of formation). The practical difficulties arising from attempts to achieve high accuracy are illustrated via two case studies: the carbon dimer (C2) and the hydroperoxyl radical (HO2). While the HO2 wave function is dominated by a single configuration, the carbon dimer involves considerable multiconfigurational character. In addition to these two molecules, statistical results will be presented for a much larger sample of molecules drawn from the Computational Results Database. The goal of this analysis will be to determine if a combination of coupled cluster theory with large 1-particle basis sets and careful incorporation of several computationally expensive smaller corrections can yield uniform agreement with experiment to better than “chemical accuracy” (±1kcal∕mol). In the case of HO2, the best current theoretical estimate of the zero-point-inclusive, spin-orbit corrected atomization energy (ΣD0=166.0±0.3kcal∕mol) and the most recent Active Thermochemical Table (ATcT) value (165.97±0.06kcal∕mol) are in excellent agreement. For C2 the agreement is only slightly poorer, with theory (D0=143.7±0.3kcal∕mol) almost encompassing the most recent ATcT value (144.03±0.13kcal∕mol). For a larger collection of 68molecules, a mean absolute deviation of 0.3kcal∕mol was found. The same high level of theory that produces good agreement for atomization energies also appears capable of predicting bond lengths to an accuracy of ±0.001Å.
Practicable enhancement of spontaneous emission using surface plasmons
Authors: Sun Greg , Khurgin Jacob B. , Soref Richard A.
Published: March 2007

The authors develop a rigorous theory of the enhancement of spontaneous emission from a light emitting device via coupling the radiant energy in and out of surface plasmon polaritons (SPPs) on the metal-dielectric interface. Using the GaN∕Ag system as an example, the authors show that using SPP pays off only for emitters that have a low luminescence efficiency.
Interactions between radical growth precursors on plasma-deposited silicon thin-film surfaces
Authors: Bakos Tamas , Valipa Mayur S. , Maroudas Dimitrios
Published: March 2007

We present a detailed analysis of the interactions between growth precursors, SiH3 radicals, on surfaces of silicon thin films. The analysis is based on a synergistic combination of density functional theory calculations on the hydrogen-terminated Si(001)-(2×1) surface and molecular-dynamics (MD) simulations of film growth on surfaces of MD-generated hydrogenated amorphous silicon (a-Si:H) thin films. In particular, the authors find that two interacting growth precursors may either form disilane (Si2H6) and desorb from the surface, or disproportionate, resulting in the formation of a surface dihydride (adsorbed SiH2 species) and gas-phase silane (SiH4). The reaction barrier for disilane formation is found to be strongly dependent on the local chemical environment on the silicon surface and reduces (or vanishes) if one/both of the interacting precursors is/are in a “fast diffusing state,” i.e., attached to fivefold coordinated surface Si atoms. Finally, activation energy barriers in excess of 1eV are obtained for two chemisorbed (i.e., bonded to a fourfold coordinated surface Si atom) SiH3 radicals. Activation energy barriers for disproportionation follow the same tendency, though, in most cases, higher barriers are obtained compared to disilane formation reactions starting from the same initial configuration. MD simulations confirm that disilane formation and disproportionation reactions also occur on a-Si:H growth surfaces, preferentially in configurations where at least one of the SiH3 radicals is in a “diffusive state.” Our results are in agreement with experimental observations and results of plasma process simulators showing that the primary source for disilane in low-power plasmas may be the substrate surface.
Crystalline ice growth on Pt(111) and Pd(111): Nonwetting growth on a hydrophobic water monolayer
Authors: Kimmel Greg A. , Petrik Nikolay G. , Dohnálek Zdenek , Kay Bruce D.
Published: March 2007

The growth of crystalline ice films on Pt(111) and Pd(111) is investigated using temperature programed desorption of the water films and of rare gases adsorbed on the water films. The water monolayer wets both Pt(111) and Pd(111) at all temperatures investigated [e.g., 20–155K for Pt(111)]. However, crystalline ice films grown at higher temperatures (e.g., T>135K) do not wet the monolayer. Similar results are obtained for crystalline ice films of D2O and H2O. Amorphous water films, which initially wet the surface, crystallize and dewet, exposing the water monolayer when they are annealed at higher temperatures. Thinner films crystallize and dewet at lower temperatures than thicker films. For samples sputtered with energetic Xe atoms to prepare ice crystallites surrounded by bare Pt(111), subsequent annealing of the films causes water molecules to diffuse off the ice crystallites to reform the water monolayer. A simple model suggests that, for crystalline films grown at high temperatures, the ice crystallites are initially widely separated with typical distances between crystallites of ∼14nm or more. The experimental results are consistent with recent theory and experiments suggesting that the molecules in the water monolayer form a surface with no dangling OH bonds or lone pair electrons, giving rise to a hydrophobic water monolayer on both Pt(111) and Pd(111).
Semiclassical coherent-state propagator for many particles
Authors: Braun Carol , Garg Anupam
Published: March 2007

We obtain the semiclassical coherent-state propagator for a many-particle system with an arbitrary Hamiltonian.