bluuebunny/crossref_metadata_2025 huggingface dataset:
Positron annihilation lifetime spectroscopy and diffusion studies of large molecule penetrants into a polyester
Authors: Ward Shelia A. , Pethrick Richard A.
Published: March 2012

Positron annihilation lifetime spectroscopy measurements are reported for a polyester and free volume characteristics determined as a function of temperature. The glass‐rubber transition was determined using DMTA. The diffusion behaviour of a series of large molecules; dioctyl phthalate, 2‐ethyl hexylbenzyl phthalate, nonyl phenol ethoxylate, isopropyl myristate, and oleic acid into the polyester were investigated using gravimetric measurements. The permeation does not follow simple Fickian type behaviour and the rate of diffusion of 2‐ethyl hexylbenzyl phthalate is surprisingly high in comparison to the other systems studied. At or above the Tg, the diffusion rates for all the systems studied increase substantially. The sizes of the permeant molecules in their lowest energy conformation were calculated theoretically. Comparison of the size of the molecules and that of the void size measured by positron annihilation lifetime spectroscopy measurements divides the molecules into two groups. Isopropylmyristate and oleic acid exhibits cross sections which would allow the molecules to slither into cavities. The remaining molecules have cross sections which are larger than the available void size and must swell the matrix before diffusion can occur. The permeation behaviour is influenced by the available free volume but dominated by the solubility characteristics of the permeants. POLYM. ENG. SCI., 52:1978–1984, 2012. © 2012 Society of Plastics Engineers
Design and fabrication of preshaped ionic polymer metal composite gripper by thermal treatment process
Authors: Kim Dong‐Ik , Seo Beom‐Ho , Lee Seung‐Ki , Park Jae‐Hyoung
Published: March 2012

This article proposes a new method to fabricate the ionic polymer metal composite (IPMC) actuator with a preshaped form by a simple thermal treatment process. The effects of the thermal treatment process on the properties of the actuator such as stiffness, displacement, resonance, and generating force are analyzed. To verify the effect of the thermal treatment process on the generation force of the actuator, the four‐fingered gripper using the proposed method is designed, fabricated, and compared with an unheated actuator. Experimental results show that thermally treated IPMC actuators have an improved generatingforce compared with that of unheated actuators. POLYM. ENG. SCI., 52:1991–1997, 2012. © 2012 Society of Plastics Engineers
An Analytical Approach for Fast Odour Evaluation of Recycled Food–Grade Paperboard Materials Using HS–SPME–MS‐Nose Technology
Authors: Caelenberg Tim Van , Leuven Isabelle Van , Dirinck Patrick
Published: March 2012

Recycled paperboard is frequently used as a raw material for food packaging. As consumers are becoming more sensitive to off‐flavours, paperboard packaging needs to contain a low‐odour potential when brought in contact with food products. As paperboard manufacturers, printing companies and food producers have a lack of time for solving off‐flavour problems, sensory testing and conventionally used gas chromatography–mass spectrometry (GC–MS) techniques are frequently too time consuming. To meet the needs of fast and reliable odour analysis of recycled paperboard, MS‐based electronic nose (MS‐nose) technology was evaluated in this study. As this technique is based on MS identification, chemical information of the volatiles could be obtained. A hyphenated configuration, consisting of a headspace solid phase microextraction (HS–SPME) autosampler coupled to an MS‐nose instrument, was discussed. The odorous volatiles of four recycled paperboard samples, obtained by GC–MS analysis, were used for feature selection of ion masses needed for statistical data analysis of the MS‐nose results. Besides, the sensitivity and the reliability of the HS–SPME technique were tested by the statistical correlation of the obtained GC–MS data with descriptive sensory test results. The HS–SPME–MS‐nose analysis of the paperboard samples resulted in an objective classification, based on differences between diagnostic mass fragments of lipid oxidation volatiles, volatiles formed by microbiological activity and residual ink and coating volatiles. On the basis of the obtained results, the MS‐nose approach could be used as a fast odour characterization technique for product quality control of cellulose‐based packaging materials. Copyright © 2012 John Wiley & Sons, Ltd.
A component model for welded beam‐to‐column joints with beams of unequal depth
Authors: Simões da Silva Luis , Jordão Sandra , Simões Rui
Published: March 2012

In many practical situations, internal nodes connect beams with unequal depth whenever the span lengths are not uniform. Following the methodology defined in EC 3‐1‐8, this paper presents a component model that is able to reproduce accurately the complex behavior of welded beam‐to‐column joints with beams of unequal height, which corresponds to a node configuration that is not yet covered in the EC 3 design rules. Based on an experimental program carried out at the University of Coimbra, the relevant components for the column web panel under a non‐uniform stress state are characterized, leading to the development of a new design procedure that extends the scope of EC 3‐1‐8.

Ein Komponenten‐Modell für geschweißte Träger‐Stützen‐Verbindungen mit Trägern ungleicher Höhe. In vielen praktischen Situationen verbinden bei unterschiedlichen Spannweiten innere Knoten Träger ungleicher Höhe. Entsprechend der in EC 3‐1‐8 festgelegten Methodik stellt dieser Aufsatz ein Komponentenmodell für eine genaue Nachbildung des komplexen Verhaltens geschweißter Träger‐Stützen‐Verbindungen mit Trägern ungleicher Höhe vor, was einer Knotenkonfiguration entspricht, die durch die EC 3‐Bemessungsregeln noch nicht abgedeckt ist. Auf Grundlage umfangreicher Versuchsserien an der Universität von Coimbra werden die Komponenten für die Stützenstege unter ungleichmäßiger Belastung modelliert, was zur Formulierung eines neuen Bemessungsverfahrens führt, das den Umfang der im EC 3‐1‐8 dargestellten Möglichkeiten signifikant erweitert.
Francis Sibson (1814–1876): The Unsung Hero of Modern Surgery and Anesthesia
Authors: Osiro Stephen , Downs Erin , Grater Joanna , Loukas Marios
Published: March 2012

Francis Sibson (1814–1876) was a British physician and anatomist widely regarded as a true pioneer of the medical profession. He overcame a tragic and difficult childhood to become an avid educator at several medical schools and dedicated his life to research. For modern scientists, he is most remembered for describing Sibson’s fascia, his experimental use of curare in the treatment of hydrophobia and tetanus, and his detailed description of the positions and movements of internal organs. He died on September 7, 1876 at the age of 62 from complications of an aortic aneurysm.
Effect of Titanium Surface Calcium and Magnesium on Adhesive Activity of Epithelial-Like Cells and Fibroblasts
Authors: Okawachi Hideyuki , Ayukawa Yasunori , Atsuta Ikiru , Furuhashi Akihiro , Sakaguchi Mami , Yamane Koichi , Koyano Kiyoshi
Published: March 2012

In the present study, we investigated the hydrothermal treatment of titanium with divalent cation solutions and its effect in promoting the adhesion of gingival epithelial cells and fibroblasts in vitro. Gingival keratinocyte-like Sa3 cells or fibroblastic NIH3T3 cells were cultured for 1 h on experimental titanium plates hydrothermally-treated with CaCl2 (Ca) or MgCl2 (Mg) solution, or distilled water (DW). The number and adhesive strengths of attached cells on the substrata were then analyzed. The number of Sa3 cells adhering to the Ca- and Mg-treated plates was significantly larger than in the DW group, but the strength of this adhesion did not differ significantly between groups. In contrast, NIH3T3 cell adhesion number and strength were increased in both the Ca and Mg groups compared to the DW group. Fluorescent microscopic observation indicated that, in all groups, Sa3 had identical expression levels of integrin β4 and development of actin filaments, whereas NIH3T3 cells in the Ca and Mg groups displayed much stronger punctate cytoplasmic signals for vinculin and more bundle-shaped actin filaments than cells in the DW group. As a result, it was indicated that the hydrothermal treatment of titanium with Ca or Mg solution improved the integration of soft tissue cells with the substrata, which may facilitate the development of a soft tissue barrier around the implant.
Liouville-type theorems and decay estimates for solutions to higher order elliptic equations
Authors: Lu Guozhen , Wang Peiyong , Zhu Jiuyi
Published: March 2012

Liouville-type theorems are powerful tools in partial differential equations. Boundedness assumptions of solutions are often imposed in deriving such Liouville-type theorems. In this paper, we establish some Liouville-type theorems without the boundedness assumption of nonnegative solutions to certain classes of elliptic equations and systems. Using a rescaling technique and doubling lemma developed recently in Poláčik et al. (2007) [20], we improve several Liouville-type theorems in higher order elliptic equations, some semilinear equations and elliptic systems. More specifically, we remove the boundedness assumption of the solutions which is required in the proofs of the corresponding Liouville-type theorems in the recent literature. Moreover, we also investigate the singularity and decay estimates of higher order elliptic equations.
Classical non-mass-preserving solutions of coagulation equations
Authors: Escobedo M. , Velázquez J.J.L.
Published: March 2012

In this paper we construct classical solutions of a family of coagulation equations with homogeneous kernels that exhibit the behaviour known as gelation. This behaviour consists in the loss of mass due to the fact that some of the particles can become infinitely large in finite time.
Mean curvature flow with obstacles
Authors: Almeida L. , Chambolle A. , Novaga M.
Published: March 2012

We consider the evolution of fronts by mean curvature in the presence of obstacles. We construct a weak solution to the flow by means of a variational method, corresponding to an implicit time-discretization scheme. Assuming the regularity of the obstacles, in the two-dimensional case we show existence and uniqueness of a regular solution before the onset of singularities. Finally, we discuss an application of this result to the positive mean curvature flow.
SIGN CHANGES OF FOURIER COEFFICIENTS OF ENTIRE MODULAR INTEGRALS
Authors: CHOIE YOUNGJU , KOHNEN WINFRIED
Published: March 2012

Let f be a non-zero cusp form with real Fourier coefficients a(n) (n ≥ 1) of positive real weight k and a unitary multiplier system v on a subgroup Γ ⊂ SL2(ℝ) that is finitely generated and of Fuchsian type of the first kind. Then, it is known that the sequence (a(n))(n ≥ 1) has infinitely many sign changes. In this short note, we generalise the above result to the case of entire modular integrals of non-positive integral weight k on the group Γ0*(N) (N ∈ ℕ) generated by the Hecke congruence subgroup Γ0(N) and the Fricke involution $W_N:= \big(\scriptsize\begin{array}{c@{}c} 0 & -{1/\sqrt N} \\[3pt] \sqrt N & 0\\ \end{array}\big)$ provided that the associated period functions are polynomials.
ON THE DISTRIBUTION OF -FREE NUMBERS AND NON-VANISHING FOURIER COEFFICIENTS OF CUSP FORMS
Authors: MATOMÄKI KAISA
Published: March 2012

We study properties of -free numbers, that is numbers that are not divisible by any member of a set . First we formulate the most-used procedure for finding them (in a given set of integers) as easy-to-apply propositions. Then we use the propositions to consider Diophantine properties of -free numbers and their distribution on almost all short intervals. Results on -free numbers have implications to non-vanishing Fourier coefficients of cusp forms, so this work also gives information about them.
ORBITS OF SEMIGROUPS OF TRUNCATED CONVOLUTION OPERATORS
Authors: SHKARIN STANISLAV
Published: March 2012

We prove that a semigroup generated by finitely many truncated convolution operators on Lp[0, 1] with 1 ≤ p < ∞ is non-supercyclic. On the other hand, there is a truncated convolution operator, which possesses irregular vectors.
ON THE DIOPHANTINE EQUATIONx2+d2l+ 1=yn
Authors: BÉRCZES ATTILA , PINK ISTVÁN
Published: March 2012

Letd> 0 be a squarefree integer and denote byh=h(−d) the class number of the imaginary quadratic field$\mathbb{Q}(\sqrt{-d})$. It is well known (see e.g. [25]) that for a given positive integerNthere are only finitely many squarefreed's for whichh(−d) =N. In [45], Saradha and Srinivasan and in [28] Le and Zhu considered the equation in the title and solved it completely under the assumptionh(−d) = 1 apart from the cased≡ 7 (mod 8) in which caseywas supposed to be odd. We investigate the title equation in unknown integers (x,y,l,n) withx≥ 1,y≥ 1,n≥ 3,l≥ 0 and gcd(x,y) = 1. The purpose of this paper is to extend the above result of Saradha and Srinivasan to the caseh(−d) ∈ {2, 3}.
GOLDIE*-SUPPLEMENTED MODULES – CORRIGENDUM
Authors: BIRKENMEIER G. F. , MUTLU F. TAKIL , NEBİYEV C. , SOKMEZ N. , TERCAN A.
Published: March 2012

In this corrigendum to the paper, “Goldie*-supplemented modules” [1], we present revised Propositions 3.7 and 3.12 and correct some typographical errors.
Tremella diploschistina (Tremellales, Basidiomycota, Fungi), a new lichenicolous species growing on Diploschistes
Authors: MILLANES A. M. , WESTBERG M. , WEDIN M. , DIEDERICH P.
Published: March 2012

Several specimens of a lichen-inhabiting Tremella, inducing the formation of pale yellow, dark brown or black galls on species of Diploschistes, have been collected in three localities in Sweden and in one locality in the USA. Morphological and molecular studies confirm that this material represents a single species, which differs from other described Tremella species in the combination of gall morphology, basidium morphology, basidium and basidiospore sizes, presence of thick-walled hyphidia, and a different host-selection. We consequently describe this fungus as Tremella diploschistina sp. nov., on the basis of morphology and phylogenetic analyses of ITS and nLSU sequences. The phylogenetic analyses reveal that the fungus clearly belongs in Tremella, although the relationships with other species in the genus remain unclear.
Calopadia erythrocephala, a new foliicolous lichenized fungus from Brazil
Authors: FARKAS Edit , ELIX John A. , FLAKUS Adam
Published: March 2012

The foliicolous lichenized fungus Calopadia erythrocephala Farkas, Elix & Flakus, is described as new to science from the Atlantic submontane rainforests in Brazil. The species is very similar to C. puiggarii, but is distinguished by the presence of a red pigment in the campylidia, the darker apothecial discs and larger conidia. Fusarubin, the red pigment produced by the new species, is reported for the first time from foliicolous lichens. A world-wide key to foliicolous species of Calopadia with single, muriform ascospores is presented.
A new corticolousOpegrapha(Opegraphaceae) species from India
Authors: JOSEPH Siljo , SINHA Gopal Prasad
Published: March 2012

A corticolous lichen species,Opegrapha granulosaSiljo & G. P. Sinha, with a UV+ pale yellow thallus, is described as new to science from the Sundarbans Biosphere Reserve, West Bengal, India.
The Auto Parts-Automotive Chain in Mexico and China: Co-operation Potential?
Authors: Peters Enrique Dussel
Published: March 2012

Mexico's economic relationship with China has intensified substantially in the last decade. Based on an increasing literature on the overall and aggregate relationship, this analysis proposes a detailed examination of the auto parts-automobile chain, which is of utmost importance for both countries and will be significant for understanding the future trade relationship between them. In order to understand the industrial organization of Mexico and China, the article first gives an overview of the international trade and industrial organization patterns. After establishing the characteristics of Mexico's and China's legal framework, production, employment and trade, the analysis concludes with a group of proposals to improve binational co-operation. Both countries – China interested in increasing its export platform based on Chinese parts brands and Mexico supplying parts and components and providing decades of experiences in international networks – can benefit from these suggestions and overcome current tensions.
Online Chinese Perceptions of Latin America: How They Differ from the Official View
Authors: Shen Simon
Published: March 2012

Using online Chinese communities as primary sources, this article studies public perceptions in China of Latin America in terms of how the region is seen as part of the Third World while also offering China a convenient backyard by which to access the First World United States. Codified online public opinion on four different Latin American topics is then analysed and compared with official opinion: how “Latin Americanization” becomes China's nightmare, how the Latin Americans should learn from the “China model,” how the Latin Americans were being discriminated in the H1N1 epidemic, and how the “Latin American card” to balance the United States is emphasized. The conclusion suggests that only when the stereotypes discussed in this article are dismissed will the true value of Latin America gradually obtain any standing in the eyes of ordinary Chinese and will the Latin American mission of the Chinese government be fully understood by its subjects.
The Intellectuals of Italian Catholic Action and the Sacralisation of Politics in 1930s Europe
Authors: DAGNINO JORGE
Published: March 2012

There has been a growing revival of interest in the subject of political religion in recent years. However, despite this tendency, the perspective of contemporary Italian Catholics on the subject has hardly been touched upon, except by Emilio Gentile and Renato Moro. This article addresses this gap, analysing the response to the phenomenon of political religions during the 1930s by the two intellectual branches of Italian Catholic Action, namely, the FUCI and the Movimento laureati. Indeed, it was during the 1930s that these intellectuals became most aware of the novelty and danger posed by the emergence of the political religions. The article follows the analyses provided by the FUCI and the Movimento laureati on Bolshevism, National Socialism and Italian Fascism. During the 1930s new concepts such as ‘political religions’, ‘religion of the blood’, ‘totalitarian religion’ and ‘new idols’, all expressed the effort of these Catholic intellectuals to come to terms with the new reality of the sacralisation of politics being carried out by the totalitarian experiments.
Heroism, Raison d'état, and National Communism: Red Nationalism in the Cinema of People's Poland
Authors: KUNICKI MIKOŁAJ
Published: March 2012

Using archival sources, film reviews, interviews, secondary sources and movies, this article examines a Polish nationalist-communist school of directors who supported the Communist Party regime in constructing a new ethos, which consisted of ethnocentric nationalism and authoritarian nation state ideology. It demonstrates how the party state tried to legitimise itself by endorsing popular culture, specifically mainstream cinema. It also argues that National Communism inevitably led to the nationalist-authoritarian fusion, which set up the conditions for a pluralist and polyphonic realm, outside, but also within the ruling camp.
Civic pride and redevelopment in the post-war British city
Authors: SHAPELY PETER
Published: March 2012

This article is concerned with civic pride in post-war urban Britain. While many of the development projects during 1945–79 proved to be design failures, suggesting the demise of civic pride, the ambitions of local authorities, planners and developers have largely been ignored or dismissed. Nevertheless, the development plans which emerged during this period reveal a desire to rebuild new, modern and vibrant cities. Moreover, the planning and financing of these new projects highlights the structure of local governance in post-war Britain, with a shift towards new partnerships consisting of the council, the technocrat and the developer. As such, civic pride continued to be evident in the post-war period, both as an aspiration for urban development and as a symbolic form of power.
Cities in late medieval Europe: the promise and the curse of modernity
Authors: BOONE MARC
Published: March 2012

This article examines how modern historiography has developed quite differentiated views on the way medieval cities have given expression to renewal and to creativity. ‘National’ traditions have played a highly influential role in modifying the general views articulated in the major syntheses produced by scholars such as Max Weber and Henri Pirenne at the beginning of the twentieth century. An almost jubilant way of looking at the city as the hotbed of modernity gave room, in the decades after the Great War, to pessimism and a negative view on urbanity, before a more nuanced and positive view has been re-established after World War II and in the course of recent paradigmatic changes.
Review of periodical articles
Authors: LIDDY CHRISTIAN D. , ELLIOTT PAUL , MISKELL LOUISE
Published: March 2012

The most striking feature of this year's publications is the large number of articles about the economic, financial and business history of medieval towns. ‘What was the Hanse?’ (Was war die Hanse?) sounds like the sort of question that might be asked in an undergraduate examination, designed to elicit a wide range of responses, from the purely descriptive to the more analytical. The question has, in fact, generated a substantial, if rather problematic, historiography, as two studies of the Hanse make clear. The tendency to define the Hanse as a ‘state’ or to see it as endowed with ‘state-like’ qualities does not do justice to the complexity of a more loosely framed and highly adaptable commercial and urban network.
The linear dependence of polar cap index on its controlling factors in solar wind and magnetotail
Authors: Gao Ye , Kivelson Margaret G. , Walker Raymond J.
Published: March 2012

The solar wind is coupled to the magnetosphere‐ionosphere system through various interactions, e.g., magnetic reconnection at the dayside magnetopause, and viscous interactions at the low latitude boundary layer. The polar cap, a region of open magnetic flux connecting the magnetic field of the Earth to that of the solar wind, is an ideal region in which to investigate how solar wind drives the magnetosphere‐ionosphere dynamo. For such studies, the polar cap (PC) index provides a useful characterization of the state of the polar ionosphere. A previous study by Gao et al. (2012a) found that polar cap dynamics, characterized by the PC index, responds to both solar wind driving quantified by the electric field (EK‐R) proposed by Kivelson and Ridley (2008) which is a representative of the electric field imposed on the ionosphere by magnetopause reconnection that takes cross polar cap potential saturation into account, and the energy release in the magnetotail, described by a modified AL index (ALU). In that study, the dependence of the PC index on EK‐R and ALU was investigated assuming a linear relationship. In this study, we test the assumption that the relationship is linear by performing a similar analysis applying a more general, nonlinear model to the events of the Gao et al. (2012a) study. A nonlinear relationship can be established by use of a statistical approach referred to as the additive model. We find that the more flexible additive model outperforms the linear model. However, the improvement is small. Provided that EK‐R is used to characterize the solar wind input, results obtained from the additive model are very similar to those from the linear model. This result indicates that the linear relation between the PC index and EK‐R, ALU obtained by Gao et al. (2012a) represents the data within fluctuations.
Inner magnetosphere convection and magnetotail structure of hot ions imaged by ENA during a HSS‐driven storm
Authors: Keesee A. M. , Elfritz J. G. , McComas D. J. , Scime E. E.
Published: March 2012

The remotely measured increase in plasma sheet ion temperatures during high speed stream‐driven storms is greater than that of ICME‐driven storms. These hot ions are convected to the inner magnetosphere where they drive the ring current. On 22 July 2009, a high speed stream yielded a moderate (minimum Dst of −79 nT) storm, one of the largest that occurred during the extended solar minimum between January 2007 and September 2010. We present measurements obtained with an energetic neutral atom (ENA) imager of the TWINS mission during the main phase of the storm. Ion temperatures calculated from the ENA measurements show storm‐time increase in ion temperature and a subsequent convection of hot ions into the inner magnetosphere. In the magnetotail, a region of hot ions near local midnight is observed that may be associated with substorm‐related bursty bulk flows.
Three‐dimensional numerical simulation of turbidity currents in a submarine channel on the seafloor of the Niger Delta slope
Authors: Abd El‐Gawad S. , Cantelli A. , Pirmez C. , Minisini D. , Sylvester Z. , Imran J.
Published: March 2012

In the present work, we use a three‐dimensional numerical model to simulate turbidity currents in a large‐scale submarine environment. The model solves the Reynolds Averaged Navier–Stokes equations, along with a two‐equation turbulence closure model, the sediment conservation equations for multiple grain‐size classes and the Exner equation of bed sediment conservation. Four different grain‐size classes (30, 64, 125, and 250μm) are considered. The model is applied to a modern seafloor environment in the continental slope of the Niger Delta where bathymetric data and seven piston cores were collected in and around a sinuous channel. Detailed analyses show the grain‐size distribution for different beds within each core. Since the flow events responsible for the formation of this modern depository are unknown, we perform simulations with different inflow conditions in order to match the grain‐size data. The model realistically predicts the flow field and its evolution over the complex topography and shows the spatial distribution of different grain‐size classes. A strong lateral flow from the inner to the outer bank is observed at the bends of the low‐relief channel. From the computed deposition rate, we obtain the fraction of each grain‐size class at the core locations and compareD50 and D90 predicted from the model with the core data. The discrete values predicted from the model fall within the range of D50 and D90observed in different beds in the cores. The results demonstrates that a 3‐D numerical model can be a useful tool for understanding the distribution pattern, thickness, and grain size of the turbidity currents and their deposits at the field scale and can help constrain the variabilities of reservoir architecture.
Introducing a disturbance ionosphere index
Authors: Jakowski N. , Borries C. , Wilken V.
Published: March 2012

Although ionospheric perturbations such as traveling ionospheric disturbances have a strong impact on Global Navigation Satellite Systems (GNSS) and other space‐based radio systems, the description of individual perturbations is difficult. To overcome this problem, it is suggested to use a disturbance ionosphere index (DIX) that describes the perturbation degree of the ionosphere in a less specific form as a proxy. Although such an index does not describe the exact propagation conditions at the measurement site, the estimated index number indicates the probability of a potential impact on radio systems used in communication, navigation, and remote sensing. The definition of such a DIX must take into account the following major requirements: relevance to practical needs, objective measure of ionospheric conditions, easy and reproducible computation, and availability of a reliable database. Since the total electron content has been shown in many publications to act as an outstanding parameter for quantifying the range error and also the strength of ionospheric perturbations, we propose a DIX that is based on GNSS measurements. To illustrate the use of the index, recent storms monitored in 2011 and the Halloween storm are discussed. The proposed index is a robust and objective measure of the ionospheric state, applicable to radio systems which are impacted by a highly variable perturbed ionosphere.
Stochastic and deterministic assembly processes in subsurface microbial communities
Authors: Stegen James C , Lin Xueju , Konopka Allan E , Fredrickson James K
Published: March 2012

A major goal of microbial community ecology is to understand the forces that structure community composition. Deterministic selection by specific environmental factors is sometimes important, but in other cases stochastic or ecologically neutral processes dominate. Lacking is a unified conceptual framework aiming to understand why deterministic processes dominate in some contexts but not others. Here we work toward such a framework. By testing predictions derived from general ecological theory we aim to uncover factors that govern the relative influences of deterministic and stochastic processes. We couple spatiotemporal data on subsurface microbial communities and environmental parameters with metrics and null models of within and between community phylogenetic composition. Testing for phylogenetic signal in organismal niches showed that more closely related taxa have more similar habitat associations. Community phylogenetic analyses further showed that ecologically similar taxa coexist to a greater degree than expected by chance. Environmental filtering thus deterministically governs subsurface microbial community composition. More importantly, the influence of deterministic environmental filtering relative to stochastic factors was maximized at both ends of an environmental variation gradient. A stronger role of stochastic factors was, however, supported through analyses of phylogenetic temporal turnover. Although phylogenetic turnover was on average faster than expected, most pairwise comparisons were not themselves significantly non-random. The relative influence of deterministic environmental filtering over community dynamics was elevated, however, in the most temporally and spatially variable environments. Our results point to general rules governing the relative influences of stochastic and deterministic processes across micro- and macro-organisms.
Viral clones from the GOS expedition with an unusual photosystem-I gene cassette organization
Authors: Béjà Oded , Fridman Svetlana , Glaser Fabian
Published: March 2012

Cyanobacteria have a key role in marine photosynthesis, which contributes to the global carbon cycle and to the world oxygen supply. Genes encoding for photosystem-II (PSII) and photosystem-I (PSI) reaction centers are found in different cyanophage genomes, and it was suggested that the horizontal transfer of these genes might be involved in increasing phage fitness. We have further analyzed a rare viral Global Ocean Sampling (GOS) clone containing PSI genes. This clone contains the unusual PSI gene organization psaD->C->A, as opposed to the more frequently observed viral psaJF->C->A->B->K->E->D organization, and was detected only once in the GOS metagenome. Our analyses identified more occurrences with similar arrangement and indicate that this PSI viral gene organization (now psaD->C->A->B), although rare, is authentic and represents a new PSI gene arrangement.
Metabolic Syndrome Is Linked to Chromosome 7q21 and Associated With Genetic Variants in CD36 and GNAT3 in Mexican Americans
Authors: Farook Vidya S. , Puppala Sobha , Schneider Jennifer , Fowler Sharon P. , Chittoor Geetha , Dyer Thomas D. , Allayee Hooman , Cole Shelley A. , Arya Rector , Black Mary H. , Curran Joanne E. , Almasy Laura , Buchanan Thomas A. , Jenkinson Christopher P. , Lehman Donna M. , Watanabe Richard M. , Blangero John , Duggirala Ravindranath
Published: March 2012

The prevalence of metabolic syndrome (MS) has been rising alarmingly worldwide, including in the United States, but knowledge on specific genetic determinants of MS is very limited. Therefore, we planned to identify the genetic determinants of MS as defined by National Cholesterol Education Program/Adult Treatment Panel III (NCEP/ATPIII) criteria. We performed linkage screen for MS using data from 692 Mexican Americans, who participated in the San Antonio Family Diabetes/Gallbladder Study (SAFDGS). We found strong evidence for linkage of MS on chromosome 7q (LOD = 3.6, empirical P = 6.0 × 10−5), between markers D7S2212 and D7S821. In addition, six chromosomal regions exhibited potential evidence for linkage (LOD ≥1.2) with MS. Furthermore, we examined 29 single‐nucleotide polymorphisms (SNPs) from the fatty acid translocase (FAT or CD36, 18 SNPs) gene and guanine nucleotide binding protein, α transducing 3 (GNAT3, 11 SNPs) gene, located within the 1‐LOD support interval region for their association with MS and its related traits. Several SNPs were associated with MS and its related traits. Remarkably, rs11760281 in GNAT3 and rs1194197 near CD36 exhibited the strongest associations with MS (P = 0.0003, relative risk (RR) = 1.6 and P = 0.004, RR = 1.7, respectively) and several other related traits. These two variants explained ∼18% of the MS linkage evidence on chromosome 7q21, and together conferred approximately threefold increase in MS risk (RR = 2.7). In conclusion, our linkage and subsequent association studies implicate a region on chromosome 7q21 to influence MS in Mexican Americans.
DNAJB6 governs a novel regulatory loop determining Wnt/β-catenin signalling activity
Authors: Menezes Mitchell E. , Mitra Aparna , Shevde Lalita A. , Samant Rajeev S.
Published: March 2012

DKK1 (dickkopf 1 homologue) is a secreted inhibitor of the Wnt signalling pathway and a critical modulator of tumour promotion and the tumour microenvironment. However, mechanisms regulating DKK1 expression are understudied. DNAJB6 {DnaJ [HSP40 (heat-shock protein 40 kDa)] homologue, subfamily B, member 6} is an HSP40 family member whose expression is compromized during progression of breast cancer and melanoma. Inhibition of the Wnt/β-catenin signalling pathway by up-regulation of DKK1 is one of the key mechanisms by which DNAJB6 suppresses tumour metastasis and EMT (epithelial–mesenchymal transition). Analysis of the DKK1 promoter to define the cis-site responsible for its up-regulation by DNAJB6 revealed the presence of two binding sites for a transcriptional repressor, MSX1 (muscle segment homeobox 1). Our investigations showed that MSX1 binds the DKK1 promoter and inhibits DKK1 transcription. Interestingly, silencing DNAJB6 resulted in up-regulation of MSX1 concomitant with increased stabilization of β-catenin. ChIP (chromatin immunoprecipitation) studies revealed that β-catenin binds the MSX1 promoter and stabilization of β-catenin elevates MSX1 transcription, indicating that β-catenin works as a transcription co-activator for MSX1. Functionally, exogenous expression of MSX1 in DNAJB6-expressing cells promotes the mesenchymal phenotype by suppression of DKK1. Thus we have identified a novel regulatory mechanism of DNAJB6-mediated DKK1 transcriptional up-regulation that can influence EMT. DKK1 is a feedback regulator of β-catenin levels and thus our studies also define an additional negative control of this β-catenin/DKK1 feedback loop by MSX1, which may potentially contribute to excessive stabilization of β-catenin.
The Bioreductive Alkylation of DNA by Kalafungin: A Theoretical Investigation
Authors: Hume Paul A. , Brimble Margaret A. , Reynisson Jóhannes
Published: March 2012

The thermochemical cascades for the bioreductive alkylation of DNA by kalafungin were calculated using density functional theory (DFT). Guanine (G) was used as a model nucleotide. According to the calculations both one- and two-electron reduction of kalafungin is possible in vivo. Furthermore, a clear pathway was found for both mono- and bis-alkylations of G with the former favoured. Alkylation at C-8 position of G is considerably more exothermic than on the N2-exocyclic amine. In the absence of experimentally identified adduct structures of kalafungin, the results presented here support the idea that this compound readily forms covalent bonds with DNA resulting in pro-mutagenic lesions.
Dynamic and transient interactions of Atg9 with autophagosomes, but not membrane integration, are required for autophagy
Authors: Orsi A. , Razi M. , Dooley H. C. , Robinson D. , Weston A. E. , Collinson L. M. , Tooze S. A.
Published: March 2012

Autophagy is a catabolic process essential for cell homeostasis, at the core of which is the formation of double-membrane organelles called autophagosomes. Atg9 is the only known transmembrane protein required for autophagy and is proposed to deliver membrane to the preautophagosome structures and autophagosomes. We show here that mammalian Atg9 (mAtg9) is required for the formation of DFCP1-positive autophagosome precursors called phagophores. mAtg9 is recruited to phagophores independent of early autophagy proteins, such as ULK1 and WIPI2, but does not become a stable component of the autophagosome membrane. In fact, mAtg9-positive structures interact dynamically with phagophores and autophagosomes without being incorporated into them. The membrane compartment enriched in mAtg9 displays a unique sedimentation profile, which is unaltered upon starvation-induced autophagy. Correlative light electron microscopy reveals that mAtg9 is present on tubular–vesicular membranes emanating from vacuolar structures. We show that mAtg9 resides in a unique endosomal-like compartment and on endosomes, including recycling endosomes, where it interacts with the transferrin receptor. We propose that mAtg9 trafficking through multiple organelles, including recycling endosomes, is essential for the initiation and progression of autophagy; however, rather than acting as a structural component of the autophagosome, it is required for the expansion of the autophagosome precursor.
c-Jun N-terminal kinase–mediated Rad18 phosphorylation facilitates Polη recruitment to stalled replication forks
Authors: Barkley Laura R. , Palle Komaraiah , Durando Michael , Day Tovah A. , Gurkar Aditi , Kakusho Naoko , Li Jianying , Masai Hisao , Vaziri Cyrus
Published: March 2012

The E3 ubiquitin ligase Rad18 chaperones DNA polymerase η (Polη) to sites of UV-induced DNA damage and monoubiquitinates proliferating cell nuclear antigen (PCNA), facilitating engagement of Polη with stalled replication forks and promoting translesion synthesis (TLS). It is unclear how Rad18 activities are coordinated with other elements of the DNA damage response. We show here that Ser-409 residing in the Polη-binding motif of Rad18 is phosphorylated in a checkpoint kinase 1–dependent manner in genotoxin-treated cells. Recombinant Rad18 was phosphorylated specifically at S409 by c-Jun N-terminal kinase (JNK) in vitro. In UV-treated cells, Rad18 S409 phosphorylation was inhibited by a pharmacological JNK inhibitor. Conversely, ectopic expression of JNK and its upstream kinase mitogen-activated protein kinase kinase 4 led to DNA damage–independent Rad18 S409 phosphorylation. These results identify Rad18 as a novel JNK substrate. A Rad18 mutant harboring a Ser → Ala substitution at S409 was compromised for Polη association and did not redistribute Polη to nuclear foci or promote Polη−PCNA interaction efficiently relative to wild-type Rad18. Rad18 S409A also failed to fully complement the UV sensitivity of Rad18-depleted cells. Taken together, these results show that Rad18 phosphorylation by JNK represents a novel mechanism for promoting TLS and DNA damage tolerance.
Postlipolytic insulin-dependent remodeling of micro lipid droplets in adipocytes
Authors: Ariotti Nicholas , Murphy Samantha , Hamilton Nicholas A. , Wu Lizhen , Green Kathryn , Schieber Nicole L. , Li Peng , Martin Sally , Parton Robert G.
Published: March 2012

Despite the lipolysis–lipogenesis cycle being a fundamental process in adipocyte biology, very little is known about the morphological changes that occur during this process. The remodeling of lipid droplets to form micro lipid droplets (mLDs) is a striking feature of lipolysis in adipocytes, but once lipolysis ceases, the cell must regain its basal morphology. We characterized mLD formation in cultured adipocytes, and in primary adipocytes isolated from mouse epididymal fat pads, in response to acute activation of lipolysis. Using real-time quantitative imaging and electron tomography, we show that formation of mLDs in cultured adipocytes occurs throughout the cell to increase total LD surface area by ∼30% but does not involve detectable fission from large LDs. Peripheral mLDs are monolayered structures with a neutral lipid core and are sites of active lipolysis. Electron tomography reveals preferential association of mLDs with the endoplasmic reticulum. Treatment with insulin and fatty acids results in the reformation of macroLDs and return to the basal state. Insulin-dependent reformation of large LDs involves two distinct processes: microtubule-dependent homotypic fusion of mLDs and expansion of individual mLDs. We identify a physiologically important role for LD fusion that is involved in a reversible lipolytic cycle in adipocytes.
Stretch-induced actin remodeling requires targeting of zyxin to stress fibers and recruitment of actin regulators
Authors: Hoffman Laura M. , Jensen Christopher C. , Chaturvedi Aashi , Yoshigi Masaaki , Beckerle Mary C.
Published: March 2012

Reinforcement of actin stress fibers in response to mechanical stimulation depends on a posttranslational mechanism that requires the LIM protein zyxin. The C-terminal LIM region of zyxin directs the force-sensitive accumulation of zyxin on actin stress fibers. The N-terminal region of zyxin promotes actin reinforcement even when Rho kinase is inhibited. The mechanosensitive integrin effector p130Cas binds zyxin but is not required for mitogen-activated protein kinase–dependent zyxin phosphorylation or stress fiber remodeling in cells exposed to uniaxial cyclic stretch. α-Actinin and Ena/VASP proteins bind to the stress fiber reinforcement domain of zyxin. Mutation of their docking sites reveals that zyxin is required for recruitment of both groups of proteins to regions of stress fiber remodeling. Zyxin-null cells reconstituted with zyxin variants that lack either α-actinin or Ena/VASP-binding capacity display compromised response to mechanical stimulation. Our findings define a bipartite mechanism for stretch-induced actin remodeling that involves mechanosensitive targeting of zyxin to actin stress fibers and localized recruitment of actin regulatory machinery.
Pancreatic Autoantibodies and Autoantibodies Against Goblet Cells in Pediatric Patients With Inflammatory Bowel Disease
Authors: Kovacs Marta , Lakatos Peter Laszlo , Papp Maria , Jacobsen Silvia , Nemes Eva , Polgar Marianne , Solyom Eniko , Bodi Piroska , Horvath Agnes , Muller Katalin Eszter , Molnar Kriszta , Szabo Doloresz , Cseh Aron , Dezsofi Antal , Arato Andras , Veres Gabor
Published: March 2012

Background:

Significance of pancreatic autoantibodies determined by using exocrine pancreas (PAB) and antibodies against recombinant pancreas antigen (rPAB), as well as the importance of autoantibodies against goblet cells (GAB), is not known in pediatric patients with inflammatory bowel disease (IBD). Our aim was to determine the complex analysis of PAB, rPAB, GAB, antibodies against Saccharomyces cerevisiae, and perinuclear components of neutrophils in pediatric patients with IBD. Moreover, association with NOD2/CARD15 and disease phenotype was determined.

Methods:

A total of 152 pediatric patients (median age 13.9 years) with IBD (103 patients with Crohn disease [CD] and 49 patients with ulcerative colitis [UC]) and 104 controls were included. Serum autoantibodies were determined by indirect immunofluorescence assay. NOD2/CARD15 variants were tested by polymerase chain reaction/restriction fragment length polymorphism.

Results:

The presence of PAB and rPAB was significantly higher in CD (34% and 35.9%) and in UC (20.4% and 24.5%) compared with pediatric control cohort (0% and 0%, P < 0.0001). In addition, GAB positivity was significantly increased in patients with UC in comparison with CD and controls, respectively (UC, 12.2%; CD, 1.9%; controls, 1.9%; P = 0.02). Specificity of PAB and rPAB was 100%; however, sensitivity was low. The combination of PAB and/or antibodies against Saccharomyces cerevisiae/perinuclear components of neutrophils improved the sensitivity of serological markers in CD (87.4%) and in UC (79.6%); specificities were 89.3% and 93.2%, respectively. Pancreatic autoantibodies (PAB, rPAB) and GAB were not related to clinical presentation, medical therapy, or need for surgery in CD or in UC.

Conclusions:

Pancreatic autoantibodies and GAB were specific for IBD, but the sensitivity was limited as well because there was lack of correlation with clinical phenotype. Combinations of these antibodies have shown increased sensitivity; therefore, it may be recommended in the diagnostic procedure of IBD.
The overlooked greatwall: a new perspective on mitotic control
Authors: Glover David M.
Published: March 2012

The role of the dual specificity protein phosphatase, Cdc25, in activating the cyclin-dependent kinase-cyclin B complex (Cdk1-CycB) by overcoming the inhibitory Wee1 kinase is a long-established principle for mitotic entry. Recently, however, evidence has emerged of a regulatory network that facilitates Cdk1-CycB activity by inhibiting the form of protein phosphatase 2A having a B55 regulatory subunit (PP2A-B55). Here, I review the genetic and biochemical evidence for Greatwall kinase and its substrate Endosulphine as the key components of this previously obscure regulatory network. Not only is the inhibition of PP2A-B55 by phospho-endosulphine required to prevent dephosphorylation of Cdk1-CycB substrates until mitotic exit, but it is also required to promote Cdc25 activity and inhibit Wee1 at mitotic entry. I discuss how these alternating states of preferential PP2A-B55 or Cdk1-CycB activity can have an impact upon the regulation of Polo kinase and its ability to bind different partner proteins as mitosis progresses.