bluuebunny/crossref_metadata_2025 huggingface dataset:
On the use of gradual dense–sparse discretizations in receding horizon control
Authors: Robinson John W.C. , Ögren Petter
Published: March 2013

A key factor to success in implementations of real time optimal control, such as receding horizon control (RHC), is making efficient use of computational resources. The main trade‐off is then between efficiency and accuracy of each RHC iteration, and the resulting overall optimality properties of the concatenated iterations, that is, how closely this represents a solution to the underlying infinite time optimal control problem (OCP). Both these issues can be addressed by adapting the RHC solution strategy to the expected form of the solution. Using gradual dense–sparse (GDS) node distributions in direct transcription formulations of the finite time OCP solved in each RHC iteration is a way of adapting the node distribution of this OCP to the fact that it is actually part of an RHC scheme. We have previously argued that this is reasonable, because the near future plan must be implemented now, but the far future plan can and will be revised later. In this paper, we investigate RHC applications where the asymptotic qualitative behavior of the OCP solution can be analyzed in advance. For some classes of systems, explicit exponential convergence rates of the solutions can be computed. We establish such convergence rates for a class of control affine nonlinear systems with a locally quadratic cost and propose to use versions of GDS node distributions for such systems because they will (eventually) be better adapted to the form of the solution. The advantages of the GDS approach in such settings is illustrated with simulations. Copyright © 2013 John Wiley & Sons, Ltd.
Feedback controller design for linear and a class of nonlinear optimal control problems
Authors: Shirazian Mohammad , Effati Sohrab
Published: March 2013

This paper presents a feedback controller designing approach for a large class of finite‐time optimal control problems. This approach involves a piecewise truncated variational iteration method (PTVIM) for solving the nonlinear Hamilton–Jacobi–Bellman equation. By using the finite iterations of PTVIM, an analytic approximate solution for value function and suboptimal feedback control law is obtained. Some illustrative examples are employed to demonstrate the accuracy and efficiency of the proposed approach. Copyright © 2013 John Wiley & Sons, Ltd.
Worry about one's own children, psychological well‐being, and interest in psychosocial intervention
Authors: Stinesen‐Kollberg Karin , Thorsteinsdottir Thordis , Wilderäng Ulrica , Steineck Gunnar
Published: March 2013

Background

This study investigated the association between worrying about own children and low psychological well‐being during the year that follows breast cancer.

Methods

In an observational population‐based study, we collected data from 313 women operated for breast cancer at Sahlgrenska University Hospital in Gothenburg, Sweden.

Results

Worrying about one's own children (3–7 on a 1–7 visual digital scale) was, among other variables, significantly associated with low psychological well‐being 1 year after breast cancer surgery (relative risk 2.63; 95% CI 1.77–3.90; posterior probability value 98.8%).

Conclusions

In this group of women operated for breast cancer, we found an association between worrying about one's own children and low psychological well‐being. In a healthcare system where resources are scarce, it becomes imperative to identify to whom resources should be directed. Therefore, we may consider prioritizing psychological interventions for mothers with younger children and develop effective means to communicate about issues related to the children to increase chances of an effective, successful rehabilitation. Copyright © 2013 John Wiley & Sons, Ltd.
Component‐Controlled Synthesis of Small‐Sized Pd‐Ag Bimetallic Alloy Nanocrystals and Their Application in a Non‐Enzymatic Glucose Biosensor
Authors: Liu Suli , Zhang Can , Yuan Lin , Bao Jianchun , Tu Wenwen , Han Min , Dai Zhihui
Published: March 2013

Small‐sized monodisperse Pd‐Ag alloy nanocrystals (NCs) are synthesized via a solid‐liquid and solid‐solid phase chemical route, i.e., sequential reduction of Pd(NO3)2 and AgNO3 solid precursors in the liquid mixture of dodecylamine and 1‐octadecene, followed by fusion of formed Pd and Ag NCs at 250 °C. By controlling the addition sequence and molar ratio of the metallic precursors, a series of Pd‐Ag alloy NCs, including Pd5Ag, Pd2Ag, PdAg, PdAg2, and PdAg5, is obtained. The alloy NCs are highly crystallized and exhibit a strong atomic ensemble in addition to component‐dependent electronic effects. Pd2Ag NCs have unique structure and electronic properties, showing a much faster electron transfer process at a modified glassy carbon electrode interface compared with that of other alloys. Therefore, the Pd2Ag NCs are chosen as the electrocatalyst to evaluate the performance of Pd‐Ag nanoalloy and a novel non‐enzymatic glucose biosensor is fabricated. The biosensor exhibits an acceptable reproducibility, a good stability and low interferences, which can be used to examine glucose in clinic blood serum samples. This work provides a simple multiphasic reaction system to synthesize binary alloy NCs with well‐controlled componential ratio and opens the avenue to utilize them in biosensing or other advanced technological fields.
Robust adaptive control for a class of cascaded nonlinear systems with applications to space interception
Authors: Zhang Feng , Duan Guang‐Ren , Zhou Bin
Published: March 2013

This paper proposes a robust H ∞ ‐based adaptive backstepping control scheme for the output stabilization of a special class of cascaded nonlinear systems. This kind of systems possess the feature that the first sub‐equation is a linear perturbed system, whereas the rest ones perform a general semi‐strict feedback form. Different from the conventional backstepping design approach, the special cascaded structure ensures to introduce the H ∞  technique to the backstepping procedure such that both the robust performance and the robust stability can be simultaneously guaranteed. Within the Lyapunov framework, the proposed control scheme is proved to guarantee (i) the uniformly ultimate boundedness of the system signals with a bound that can be made arbitrarily small by suitably choosing control parameters; (ii) asymptotic output stabilization as long as the uncertain nonlinearities and external disturbances vanish; and (iii) ‐performance of the closed‐loop system. A space interception scenario is utilized to demonstrate the effectiveness of the proposed control scheme. Copyright © 2013 John Wiley & Sons, Ltd.
The hybrid architecture of wireless and power line communications in HANs for Smart Grid security
Authors: Li Zhuo , Liang Qilian , Mu Jiasong , Wang Wei , Zhang Baoju
Published: March 2013

Traditionally, jamming to the wireless system is a fatal threat to the security of home area networks (HANs), which impedes the two‐way data transmission between electric devices and the smart meter, and thus deteriorates the reliability of the in‐home communication of Smart Grid. On the basis of this consideration, this paper incorporates the power line system into the HAN and proposes a hybrid architecture of orthogonal frequency‐division multiplexing‐based wireless communication and power line communication for the Smart Grid security application. With this new solution, the channel diversity of the HAN is realized, and the communication reliability is still guaranteed even when the wireless channel suffers from jamming. Simulation results validate the feasibility of the proposed hybrid architecture, and furthermore, as a receiver diversity scheme, selection combining is preferred to maximum ratio combining. Copyright © 2013 John Wiley & Sons, Ltd.
Functional silver nanostructured surfaces applied in SERS and SIMS
Authors: Škantárová Lenka , Oriňák Andrej , Oriňáková Renáta , Jerigová Monika , Stupavská Monika , Velič Dušan
Published: March 2013

Present article deals with functionality of silver nanostructured surfaces prepared by potentiostatic electrochemical deposition on the paraffin impregnated graphite electrode as template‐free substrates. The effect of the electrodeposition conditions on two silver surface functions: analytical signal enhancement in Surface‐enhanced Raman spectroscopy and pre‐ionization function, applied in secondary ion mass spectrometry (SIMS) is reported. Functional silver nanostructured substrate was prepared at a potential −850 mV with a deposition duration of 20 min. Analytical signal enhancement factors of 3.2 ×105 for Raman peak at 649 cm−1, 3.0×105 for peak at 810 cm−1 and 2.7×105 for peak at 1539 cm−1 were determined for Rhodamine 6G at deposited surface. Slight pre‐ionization effect has been observed in SIMS, and 1.2×105 fold signal enhancement was established for fragment of Rhodamine 6G with m/z 429 (M‐CH3‐Cl). Electrochemical preparation of nanostructures represents a step towards surface integration directly into miniaturized systems and sensors. Copyright © 2013 John Wiley & Sons, Ltd.
Widely Tunable Carrier Mobility of Boron Nitride‐Embedded Graphene
Authors: Wang Jinying , Zhao Ruiqi , Liu Zhongfan , Liu Zhirong
Published: March 2013

The carrier transport in boron nitride‐embedded graphene (BNG) is studied using density functional theory coupled with the Boltzmann transport equation. Under a phonon scattering mechanism, the intrinsic carrier mobility of BNG at room temperature is tunable from 1.7 × 103 to 1.1 × 105 cm2 V−1 s−1 when the bandgap is between 0.38 and 1.39 eV. Some specific BNG materials even show ultrahigh mobility up to 6.6 × 106 cm2 V−1 s−1, and the transport polarity (whether it is electron or hole transport) can be tailored by the application of a uniaxial strain. The wide mobility variation of BNG is attributed to the dependence of the effective mass and the deformation potential constant on the carbon concentration and width. The results indicate that BNG can have both a large on–off ratio and high carrier mobility and is thus a promising material for electronic devices.
Photo‐induced Free Radical Modification of Graphene
Authors: Zhang Liming , Zhou Lin , Yang Mingmei , Liu Zhirong , Xie Qin , Peng Hailin , Liu Zhongfan
Published: March 2013

Graphene has stimulated enormous interest due to its intriguing structure and fascinating properties. The extremely high carrier mobility, mechanical flexibility, and optical transparency as well as the versatility for band structure engineering make graphene a promising candidate for next‐generation carbon‐based electronic devices. Graphene chemistry, the covalent functionalization of graphene as a 2D giant molecule, offers a promising direction to controllably tailor its properties through the introduction of various chemical decorations. One of the great challenges for graphene functionalization originates from its strong chemical stability, thus highly reactive chemical species are needed as the reactants. In recent years, novel photochemical approaches have been developed to achieve efficient graphene modification and bandgap modulation, following a general concept of “Photochemical Bandgap Engineering of Graphene”. In this article, such kinds of photochemical graphene engineering are demonstrated, together with a brief discussion on the future directions, challenges, and opportunities in this fascinating research area.
Biosynthesis and pathway engineering of antifungal polyene macrolides in actinomycetes
Authors: Kong Dekun , Lee Mi-Jin , Lin Shuangjun , Kim Eung-Soo
Published: March 2013

Polyene macrolides are a large family of natural products typically produced by soil actinomycetes. Polyene macrolides are usually biosynthesized by modular and large type I polyketide synthases (PKSs), followed by several steps of sequential post-PKS modifications such as region-specific oxidations and glycosylations. Although known as powerful antibiotics containing potent antifungal activities (along with additional activities against parasites, enveloped viruses and prion diseases), their high toxicity toward mammalian cells and poor distribution in tissues have led to the continuous identification and structural modification of polyene macrolides to expand their general uses. Advances in in-depth investigations of the biosynthetic mechanism of polyene macrolides and the genetic manipulations of the polyene biosynthetic pathways provide great opportunities to generate new analogues. Recently, a novel class of polyene antibiotics was discovered (a disaccharide-containing NPP) that displays better pharmacological properties such as improved water-solubility and reduced hemolysis. In this review, we summarize the recent advances in the biosynthesis, pathway engineering, and regulation of polyene antibiotics in actinomycetes.
Non‐methylene Interrupted and Hydroxy Fatty Acids in Polar Lipids of the Alga Grateloupia turuturu Over the Four Seasons
Authors: Kendel Melha , Barnathan Gilles , Fleurence Joël , Rabesaotra Vony , Wielgosz‐Collin Gaëtane
Published: March 2013

Phospholipids (PL) and glycolipids (GL) FA in the edible Rhodophyta Grateloupia turuturu, from Brittany, France, were investigated over four seasons. The major lipid class was GL in all seasons (around 45 %). More than 80 FA occurred in polar lipids, with chains from C12 to C26, identified as methyl esters and N‐acyl pyrrolidides by gas chromatography–mass spectrometry (GC–MS). PUFA occurred at up to 47.1 % (summer) in PL, and up to 43.6 % (summer) in GL. The major PUFA were 20:5n‐3 (12.2 % in PL and 29.0 % in GL) and 20:4n‐6 (25.6 % in PL and 10.4 % in GL). The unusual 18:3n‐7 acid was identified in PL up to 2.2 %. Several minor unsaturated FA were identified in PL and are previously unreported in seaweeds, namely 14‐tricosenoic, 15‐tetracosenoic, 5,11‐octadecadienoic and 5,9‐nonadecadienoic. Also unprecedented in seaweeds, ten 2‐hydroxy and three 3‐hydroxy FA occurred mainly in PL, 13.9 % in spring with the 3‐hydroxyhexadecanoic acid as the major one (8.1 % winter). Three n‐9 monounsaturated 2‐hydroxy FA occurred in PL. The 2‐hydroxy‐15‐tetracosenoic acid was characterized as the dimethyl disulfide adduct of its methyl ester. The 2‐hydroxy‐16‐pentacosenoic and 2‐hydroxy‐17‐hexacosenoic acids were identified by comparison of mass spectra and GC mobilities with those of the 2‐hydroxy‐15‐tetracosenoic acid, and of other homogeneous FA series. These rare n‐9 monounsaturated 2‐hydroxy FA are unprecedented in seaweeds.
Detection of 430 Fatty Acid Methyl Esters from a Transesterified Butter Sample
Authors: Schröder Markus , Vetter Walter
Published: March 2013

Milk fat is known to contain one of the highest number of fatty acids of all edible oils. Some of these fatty acids are known to be valuable (e.g. conjugated linoleic acids, furan fatty acid) and other as undesirable (e.g. saturated and some trans‐fatty acids) food ingredients. However, a comprehensive picture on the presence of many trace fatty acids has not been achieved. For this reason we have developed an analysis scheme based on the conversion of the fatty acids into methyl esters. The fatty acid methyl esters were then fractionated by urea complexation. Both the filtrate of the urea complexation (~4 % of the sample weight) and the original sample were fractionated by high‐speed counter‐current chromatography (HSCCC). The resulting fractions were analyzed by GC/MS analysis. With this method 430 fatty acids were detected in one single butter sample. More than 230 fatty acids had two or more double bonds. In addition to the widely known spectrum of fatty acids we also detected a range of cyclohexyl fatty acids (five homologues) and methyl‐branched fatty acids (including short chain and even‐numbered anteiso‐fatty acids), conjugated tetradecadienoic acids along with the novel ω‐oxo‐fatty acids (seven homologues). The reported relative retention time on the polar column may serve as a data base for the screening of other samples for this profusion of fatty acids.
cAMP signalling decreases p300 protein levels by promoting its ubiquitin/proteasome dependent degradation via Epac and p38 MAPK in lung cancer cells
Authors: Jeong Min-Jae , Kim Eui-Jun , Cho Eun-Ah , Ye Sang-Kyu , Kang Gyeong Hoon , Juhnn Yong-Sung
Published: March 2013

The transcriptional coactivator p300 functions as a histone acetyltransferase and a scaffold for transcription factors. We investigated the effect of cAMP signalling on p300 expression. The activation of cAMP signalling by the expression of constitutively active Gαs or by treatment with isoproterenol decreased the p300 protein expression in lung cancer cells. Isoproterenol promoted the ubiquitination and subsequent proteasomal degradation of p300 in an Epac‐dependent manner. Epac promoted p300 degradation by inhibiting the activity of p38 MAPK. It is concluded that cAMP signalling decreases the level of the p300 protein by promoting its ubiquitin–proteasome dependent degradation, which is mediated by Epac and p38 MAPK, in lung cancer cells.
Similarities and differences of clinical characteristics between Brugada syndrome and early repolarization syndrome
Authors: Watanabe Hiroshi , Minamino Tohru
Published: March 2013

Early repolarization (or J wave) is a common electrocardiographic finding that occurs in 1% to 10% of healthy persons. It has been generally considered benign for decades. However, there is increasing evidence showing that early repolarization is associated with the susceptibility to ventricular fibrillation and sudden cardiac death. Therefore, early repolarization syndrome, or J‐wave syndrome, has recently been proposed as a new disease entity. Brugada syndrome is characterized by ST‐segment elevation in the right precordial leads (V1 to V3) of a 12‐lead electrocardiogram, and is another form of idiopathic ventricular fibrillation associated with J‐point elevation. Brugada syndrome and early repolarization syndrome share genetic, clinical, and electrophysiological characteristics, such as causative genes, male dominance, pause‐dependent augmentation of J‐point elevation, and response to drugs. However, these two diseases also have certain differences. This review focuses on the similarities and differences between Brugada syndrome and early repolarization syndrome, both of which are associated with J‐point elevation and sudden cardiac death.
Hölder continuity of the Lyapunov exponent for analytic quasiperiodic Schrödinger cocycle with weak Liouville frequency
Authors: YOU JIANGONG , ZHANG SHIWEN
Published: March 2013

For analytic quasiperiodic Schrödinger cocycles, Goldshtein and Schlag [Hölder continuity of the integrated density of states for quasi-periodic Schrödinger equations and averages of shifts of subharmonic functions.Ann. of Math.(2)154(2001), 155–203] proved that the Lyapunov exponent is Hölder continuous provided that the base frequency$\omega $satisfies a strong Diophantine condition. In this paper, we give a refined large deviation theorem, which implies the Hölder continuity of the Lyapunov exponent for all Diophantine frequencies$\omega $, even for weak Liouville$\omega $, which improves the result of Goldshtein and Schlag.
Revealing the state space of turbulent pipe flow by symmetry reduction
Authors: Willis A. P. , Cvitanović P. , Avila M.
Published: March 2013

Symmetry reduction by the method of slices is applied to pipe flow in order to obtain a quotient of the streamwise translation and azimuthal rotation symmetries of turbulent flow states. Within the symmetry-reduced state space, all travelling wave solutions reduce to equilibria, and all relative periodic orbits reduce to periodic orbits. Projections of these solutions and their unstable manifolds from their infinite-dimensional symmetry-reduced state space onto suitably chosen two- or three-dimensional subspaces reveal their interrelations and the role they play in organizing turbulence in wall-bounded shear flows. Visualizations of the flow within the slice and its linearization at equilibria enable us to trace out the unstable manifolds, determine close recurrences, identify connections between different travelling wave solutions and find, for the first time for pipe flows, relative periodic orbits that are embedded within the chaotic saddle, which capture turbulent dynamics at transitional Reynolds numbers.
EVOLUTION OF A COST-UTILITY MODEL OF DONEPEZIL FOR ALZHEIMER'S DISEASE
Authors: Peters Jaime L. , Anderson Rob , Hoyle Martin , Hyde Chris
Published: March 2013

Objectives: The aim of this study was to describe the evolution of a cost-utility model used to inform the UK National Institute for Health and Clinical Excellence's (NICE) most recent decisions on the cost-utility of drug treatments for Alzheimer's disease (AD), and to explore the impact of structural assumptions on the cost-utility results.

Methods: Changes informed by noted limitations of the decision model used in NICE's previous decisions (in 2006) were made cumulatively to the original decision model for donepezil compared with best supportive care (for patients with mild to moderate AD). Deterministic and probabilistic analyses were undertaken for each cumulative change of the model. The expected value of perfect information (EVPI) of parameter estimates and structural assumptions was also calculated.

Results: Cumulative changes to the decision model highlighted how the results of the original model (incremental cost-effectiveness ratio of £81,000 per quality-adjusted life-year gained) related to those of the new model (where donepezil was estimated to be cost-saving), mainly due to uncertainty in the incremental cost of donepezil treatment over best supportive care (ranging from -£600 to £3,000 per patient). The partial EVPI analysis reflected this finding where further information on treatment discontinuations and cost parameter estimates were shown to be valuable in terms of reducing decision uncertainty.

Conclusions: Assessing the evolution of the cost-utility model helped to identify and explore structural differences between cohort-based models and is likely to be useful for decision models in other disease areas. This approach makes the structural uncertainty explicit, forcing decision makers to address structural uncertainty in addition to parameter uncertainty.
IMPROVING ACCESS TO SKILLED ATTENDANCE AT DELIVERY: A POLICY BRIEF FOR UGANDA
Authors: Nabudere Harriet , Asiimwe Delius , Amandua Jacinto
Published: March 2013

Objective:This study describes the process of production, findings for a policy brief on Increasing Access to Skilled Birth Attendance, and subsequent use of the report by policy makers and others from the health sector in Uganda.

Methods:The methods used to prepare the policy brief use the SUPPORT Tools for evidence-informed health policy making. The problem that this evidence brief addresses was identified through an explicit priority setting process involving policy makers and other stakeholders, further clarification with key informant interviews of relevant policy makers, and review of relevant documents. A working group of national stakeholder representatives and external reviewers commented on and contributed to successive drafts of the report. Research describing the problem, policy options, and implementation considerations was identified by reviewing government documents, routinely collected data, electronic literature searches, contact with key informants, and reviewing the reference lists of relevant documents that were retrieved.

Results:The proportion of pregnant women delivering from public and private non-profit facilities was low at 34 percent in 2008/09. The three policy options discussed in the report could be adopted independently or complementary to the other to increase access to skilled care. The Ministry of Health in deliberating to provide intrapartum care at first level health facilities from the second level of care, requested for research evidence to support these decisions. Maternal waiting shelters and working with the private-for-profit sector to facilitate deliveries in health facilities are promising complementary interventions that have been piloted in both the public and private health sector. A combination of strategies is needed to effectively implement the proposed options as discussed further in this article.

Conclusions:The policy brief report was used as a background document for two stakeholder dialogue meetings involving members of parliament, policy makers, health managers, researchers, civil society, professional organizations, and the media.
Stable isotope analysis of ancient and modern gentoo penguin egg membrane and the krill surplus hypothesis in Antarctica
Authors: Emslie Steven D. , Polito Michael J. , Patterson William P.
Published: March 2013

The ‘krill surplus’ hypothesis in Antarctica posits that the historic depletion of krill-eating whales and seals in the 18–20th centuries provided a surplus of krill in the Southern Ocean that benefited penguins. A previous study which examined stable isotopes in ancient and modern tissues of Adélie penguin (Pygoscelis adeliae) provides support for this hypothesis. Specifically, a significant decrease in δ13C and δ15N values occurred in modern versus ancient tissues from an apparent dietary shift from fish to krill associated with the purported krill surplus. Here, we present new data on gentoo penguin (Pygoscelis papua) tissues from active and abandoned colonies at three locations in the Antarctic Peninsula. We found an overall, but weak, decrease in modern versus fossil δ15N and δ13C values of gentoo penguin egg membrane with considerable variation across three breeding sites. Dietary mixing models suggest that shifts between fish and krill in gentoo penguins were likely not as strong as those previously observed in Adélie penguins. This weaker signal probably results from the greater reliance on fish in their diets, past and present, though we cannot rule out declines in primary productivity or other ecosystem shifts which also could account for declines in δ13C and δ15N values.
Structure and ecology of freshwater benthic diatom communities from Byers Peninsula, Livingston Island, South Shetland Islands
Authors: Kopalová Kateřina , van de Vijver Bart
Published: March 2013

Diatom and water chemistry samples were collected from 49 lakes, pools and rivers on Byers Peninsula (Livingston Island, South Shetland Islands) during the summer of 2009. A diverse diatom flora of 143 taxa was found. Fragilaria capucina s.l., Psammothidium papilio, Navicula dobrinatemniskovae and several Nitzschia taxa dominated the flora. The biogeographical analysis showed that more than 55% of all observed taxa presented a restricted Antarctic biogeographic distribution and only 30% had a cosmopolitan distribution, contrary to previously published data. Cluster analysis and Principal Components Analysis were used to classify the samples based on their chemical characteristics, revealing that nutrients and specific conductance were the main factors dividing the samples into four groups: young lakes, coastal lakes, larger lakes on the central plateau and smaller, temporary pools. Diatom communities corresponded well to this division and were strongly influenced by salinity and nutrients.
Geochemistry of streams from Byers Peninsula, Livingston Island
Authors: Lyons W. Berry , Welch K.A. , Welch S.A. , Camacho A. , Rochera C. , Michaud L. , deWit R. , Carey A.E.
Published: March 2013

In January and February 2009, a series of water samples were collected from streams on Byers Peninsula. These samples were analysed for major elements and δ18O to determine the role of lithology and landscape position on stream geochemistry, and to understand better the hydrology (i.e. residence time of water) of these systems. Precipitation chemistry is enriched in Na+, as are the streams located close to the coast. Streams originating from inland locations have much higher percentages of Ca2+. In contrast, Mg2+ varied little, though streams that are in greater contact with volcanic-derived soils have slightly higher concentrations. Anion percentages varied greatly between streams with SO42- ranging from 5% to 45% of the anion composition. Dissolved Si concentrations as high as 141 μM were observed. All these data suggest that active chemical weathering is occurring in this region. A time series over 13 days at one stream showed little variation in major element geochemistry. The δ18O of precipitation samples collected over this same period varied by ∼10‰ while the majority of stream samples varied less than ∼1.5‰. These data indicate that the stream waters represent mixtures of precipitation events, melting snow and water from the subsurface that had gained solutes through chemical weathering.
Interannual active layer variability at the Limnopolar Lake CALM site on Byers Peninsula, Livingston Island, Antarctica
Authors: de Pablo M.A. , Blanco J.J. , Molina A. , Ramos M. , Quesada A. , Vieira G.
Published: March 2013

In order to monitor the evolution of the active layer in the South Shetland Islands, in February 2009 we established a new Circumpolar Active Layer Monitoring (CALM) site in the Limnopolar Lake basin on Byers Peninsula, Livingston Island. We monitored air, surface and ground (two boreholes of 135 and 80 cm deep) temperatures and Active Layer Thickness (ALT) was measured by mechanical probing in early February 2009, 2010 and 2011. The mean ALT was 44 cm with a range of about 92 cm, but where permafrost existed it was deeper than 1.0 m, as could be inferred from the borehole temperatures. ALT at this site was very dependent on air temperature and snow cover thickness, the ALT spatial distribution presenting the same pattern as soil penetration resistance, and higher values ALT coinciding with sites where patterned ground, ponds, and a near surface ground water saturation were observed. Additionally, ground temperature data provided an excellent tool for understanding the relationship between the ALT measured during the thaw season and the thermal evolution of the ground throughout the year.
Heterogeneous vertical structure of the bacterioplankton community in a non-stratified Antarctic lake
Authors: Villaescusa Juan A. , Casamayor Emilio O. , Rochera Carlos , Quesada Antonio , Michaud Luigi , Camacho Antonio
Published: March 2013

Bacterial community composition during summer was analysed in surface and bottom waters of the oligotrophic shallow (4.5 m) Lake Limnopolar (Livingston Island, South Shetland Islands, Antarctica), using 16S rRNA gene clone libraries and sequencing. Up to 61% of the 16S rDNA sequences found were closely related to sequences retrieved from lakes, glaciers or polar systems. The distribution of these sequences was not homogeneous, with vertical differences found in both bacterial taxa composition and isolation source of the closest match from GenBank. In the surface sample 86% of the sequences were related to bacteria found in soils, seawater or gut microbiota, probably explained by waterborne transport from the catchment, by wind through sea sprays, or local bird activity. Conversely, in the deep samples, 95% of the sequences were closer to bacteria typically described for lakes, glaciers or polar systems. The presence of benthic mosses covering the bottom of the lake favours a more stable deep layer leading to the existence of this biological heterogeneity through the water column, although the lake does not show physical-chemical stratification in summer. This study illustrates a strong influence of external factors on the microbial ecology of this model Antarctic lake.
Distribution and reproductive capacity of Deschampsia antarctica and Colobanthus quitensis on Byers Peninsula, Livingston Island, South Shetland Islands, Antarctica
Authors: Vera María Luisa , Fernández-Teruel Teresa , Quesada Antonio
Published: March 2013

The Maritime Antarctic is one of the regions where regional climate change is most intense and the reproductive performance of plants may be enhanced. Reporting the distribution of Deschampsia antarctica and Colobanthus quitensis on Byers Peninsula (Livingston Island, South Shetland Islands), our results confirm that D. antarctica is more widespread than C. quitensis. Flower and seed development of both species varied between sites. Deschampsia antarctica produced more viable seeds than C. quitensis, although fully developed seeds were not found at all locations. Seed production in C. quitensis was low in comparison with other Antarctic locations. The largest cushions of Colobanthus observed in 2002 were 15 cm in diameter, suggesting that the populations may have established at least 50 years ago. Deschampsia antarctica tussocks were very often 20 cm in diameter, although turf areas up to 1.5 m across were also observed, probably due to coalesced aggregates of individuals. This study shows that, although seed production is low, the presence of seedlings and young individuals suggests an expansion process.
A review of scientific research trends within ASPA No. 126 Byers Peninsula, South Shetland Islands, Antarctica
Authors: Benayas J. , Pertierra L. , Tejedo P. , Lara F. , Bermudez O. , Hughes K.A. , Quesada A.
Published: March 2013

Byers Peninsula, Livingston Island, was one of the first sites in Antarctica designated for environmental conservation and scientific protection. Research on Byers Peninsula has been predominantly international, with 88 indexed publications (93% of them published during last 20 years) from 209 authors affiliated to 110 institutions from 22 nations, all of which are signatories to the Antarctic Treaty. Palaeontological research represented 20% of the published articles. The variety of freshwater bodies within the area has made Byers Peninsula a reference site for limnological studies (24% of papers). The site also contains numerous outcrops and periglacial features relevant to geology, stratigraphy and geomorphology (29%). Terrestrial biodiversity is extraordinarily high for lichens, bryophytes and invertebrates (15% of articles). Only 5% of the publications concern research on human activities, including both archaeology and impact monitoring. Glaciology, meteorology and climatology studies represent only 7% of papers. This work highlights the international and multidisciplinary nature of science conducted on Byers Peninsula in order to promote international cooperation and to provide information relevant for environmental management and conservation.
Environmental management of a scientific field camp in Maritime Antarctica: reconciling research impacts with conservation goals in remote ice-free areas
Authors: Pertierra Luis R. , Hughes Kevin A. , Benayas Javier , Justel Ana , Quesada Antonio
Published: March 2013

Currently, a substantial proportion of Antarctic research is carried out through deployment of field camps, but little detailed information on the running of these facilities is often available. The remoteness of camps and the fragility of local Antarctic terrestrial ecosystems make the running of sustainable, low impact field science and logistics in ice-free areas a challenge for environmental managers. In this study we examined the environmental management at the Spanish camp within Antarctic Specially Protected Area (ASPA) No. 126 Byers Peninsula, Livingston Island, South Shetland Islands. Firstly, the input of materials and generation of pollution associated with the camp during a ten year period of operation was quantified. Examination of greenhouse gas emissions shows a mean of 14 t CO2equivalent per researcher associated with transportation of people to the site, plus 44 t CO2equivalent per researcher, associated with transportation of cargo to the field site. Secondly, the cumulative trampling footprint across Byers Peninsula and associated local impacts were recorded. Results showed the pattern of human movement within the ASPA and how activities concentrated around the field camp site. At the same time every effort was taken to ensure scientific outputs from research activities within the ASPA were maximized. Practical recommendations on operational logistics are discussed to minimize environmental impacts and optimize scientific benefits.
Mapping snow cover and snow depth across the Lake Limnopolar watershed on Byers Peninsula, Livingston Island, Maritime Antarctica
Authors: Fassnacht S.R. , López-Moreno J.I. , Toro M. , Hultstrand D.M.
Published: March 2013

Few parts of Antarctica are not permanently covered in ice. The retreat of the ice sheet from Byers Peninsula on western Livingston Island, Maritime Antarctica, has provided a new area of seasonal snow cover. Snow surveys were conducted in late November 2008 at the time of peak accumulation across the 1 km2Lake Limnopolar watershed. Topographic variables were derived from a digital elevation model to determine the variables controlling the presence or absence of snow and the distribution of snow depth. Classification with binary regression trees showed that wind related variables dominated the presence and depth of snow. The product of the sine of aspect and the sine of slope was the first variable in both regression trees. Density profiles were also measured and illustrated a relatively homogeneous snowpack over space at peak snow accumulation.
Serological and virological surveys of the influenza A viruses in Antarctic and sub-Antarctic penguins
Authors: Abad F. Xavier , Busquets Núria , Sanchez Azucena , Ryan Peter G. , Majó Natàlia , Gonzalez-Solís Jacob
Published: March 2013

To evaluate the avian influenza virus (AIV) circulation in Antarctic and sub-Antarctic penguins we carried out a serosurvey on six species from Livingston, Marion and Gough islands. Seropositivity against AIV was performed on serum samples using a competitive enzyme-linked immunosorbent assay and haemagglutination and neuraminidase inhibition assays. Some oropharyngeal and cloacal swabs were also assayed to detect influenza virus genomes by real time reverse transcription-polymerase chain reaction. Overall, 12.1% (n= 140) penguins were seropositive to AIV. By species, we detected 5% (n= 19) and 11% (n= 18) seroprevalence in sub-Antarctic rockhopper penguins (Eudyptesspp.) from Gough and Marion islands, respectively, 42% (n= 33) seroprevalence in macaroni penguins (Eudyptes chysolophusBrandt), but no positives in the three other species, gentoo (Pygoscelis papuaForster;n= 25) and chinstrap penguins (P. antarcticaForster;n= 16), from Livingston Island and king penguins (Aptenodytes patagonicusMiller;n= 27) from Marion Island. While seropositivity reflected previous exposure to the AIV, the influenza genome was not detected. Our results indicate that AIV strains have circulated in penguin species in the sub-Antarctic region, but further studies are necessary to determine the precise role that such penguin species play in AIV epidemiology and if this circulation is species (or genus) specific.
Conducting the deepest all-sky pulsar survey ever: the all-sky High Time Resolution Universe survey
Authors: Ng Cherry ,   the HTRU Collaboration
Published: March 2013

The extreme conditions found in and around pulsars make them fantastic natural laboratories, providing insights to a rich variety of fundamental physics and astronomy. To discover more pulsars we have begun the High Time Resolution Universe (HTRU) survey: a blind survey of the northern sky with the 100-m Effelsberg radio telescope in Germany and a twin survey of the southern sky with the 64-m Parkes radio telescope in Australia. The HTRU is an international collaboration with expertise shared among the MPIfR in Germany, ATNF/CASS and Swinburne University of Technology in Australia, University of Manchester in the UK and INAF in Italy. The HTRU survey uses multi-beam receivers and backends constructed with recent advancements in technology, providing unprecedentedly high time and frequency resolution, allowing us to probe deeper into the Galaxy than ever before. While a general overview of HTRU has been given by Keith at this conference, here we focus on three further aspects of HTRU discoveries and highlights. These include the ‘Diamond-planet pulsar’ binary J1719-1438 and a second similar system recently discovered. In addition, we provide specifications of the HTRU-North survey and an update of its status. In the last section we give an overview of the search for highly-accelerated binaries in the Galactic plane region. We discuss the computational challenges arising from the processing of the petabyte-sized HTRU survey data. We present an innovative segmented search technique which aims to increase our chances of discovering highly accelerated relativistic binary systems, potentially including pulsar-black-hole binaries.
Neutron star structure: what we learn from their masses and radii
Authors: Özel Feryal
Published: March 2013

Neutron stars possess the densest matter and strongest gravitational fields that are accessible to observations. In this talk, I will discuss how precise measurements of neutron star radii, masses, and spins not only open a window onto the poorly known neutron star interior but can also be used to probe their formation mechanism, their recycling to millisecond periods, and their connection to the formation of low-mass black holes.
Radio counterparts of gamma-ray pulsars
Authors: Guillemot L.
Published: March 2013

Observations of pulsars with the Large Area Telescope (LAT) on the Fermi satellite have revolutionized our view of the gamma-ray pulsar population. For the first time, a large number of young gamma-ray pulsars have been discovered in blind searches of the LAT data. More generally, the LAT has discovered many new gamma-ray sources whose properties suggest that they are powered by unknown pulsars. Radio observations of gamma-ray sources have been key to the success of pulsar studies with the LAT. For example, radio observations of LAT-discovered pulsars provide constraints on the relative beaming fractions, which are crucial for pulsar population studies. Also, radio searches of LAT sources with no known counterparts have been very efficient, with the discovery of over forty millisecond pulsars. I review radio follow-up studies of LAT-discovered pulsars and unidentified sources, and discuss some of the implications of the results.
X-ray properties of rotation-powered pulsars
Authors: Pavlov George , Kargaltsev Oleg
Published: March 2013

Radiation of most of the known pulsars is powered by the loss of their rotational energy and angular momentum. Thanks to the Chandra and XMM-Newton observatories, X-ray emission has been detected from over 100 rotation-powered pulsars in the last 12 years. I will overview the current results of X-ray observations of rotation-powered pulsars, including the evolution of the X-ray properties, thermal and magnetospheric components of X-ray emission, and connection between the X-ray emission and emission at other wavelengths.
Quasi-Periodic Oscillations in magnetars: linking variability and emission
Authors: D'Angelo Caroline
Published: March 2013

I present recent results studying flare emission in magnetars. Strong quasi-periodic oscillations observed in the tail of giant magnetar flares are frequently interpreted as evidence for global seismic oscillations. I demonstrate that such a global oscillation is not directly observable in the lightcurve. New work suggests the amplitude for the strongest QPO stays nearly constant in the rotation phases where it is observed, which I argue suggests it is produced by an additional emission process from the star.
The superslow pulsation X-ray pulsars in high mass X-ray binaries
Authors: Wang Wei
Published: March 2013

There exists a special class of X-ray pulsars that exhibit very slow pulsation of Pspin > 1000 s in the high mass X-ray binaries (HMXBs). We have studied the temporal and spectral properties of these superslow pulsation neutron star binaries in hard X-ray bands with INTEGRAL observations. Long-term monitoring observations find spin period evolution of two sources: spin-down trend for 4U 2206+54 (Pspin ~ 5560 s with Ṗspin ~ 4.9 × 10−7 s s−1) and long-term spin-up trend for 2S 0114+65 (Pspin ~ 9600 s with Ṗspin ~ −1 × 10−6 s s−1) in the last 20 years. A Be X-ray transient, SXP 1062 (Pspin ~ 1062 s), also showed a fast spin-down rate of Ṗspin ~ 3 × 10−6 s s−1 during an outburst. These superslow pulsation neutron stars cannot be produced in the standard X-ray binary evolution model unless the neutron star has a much stronger surface magnetic field (B > 1014 G). The physical origin of the superslow spin period is still unclear. The possible origin and evolution channels of the superslow pulsation X-ray pulsars are discussed. Superslow pulsation X-ray pulsars could be younger X-ray binary systems, still in the fast evolution phase preceding the final equilibrium state. Alternatively, they could be a new class of neutron star system – accreting magnetars.
Pulsars as excellent probes for the magnetic structure in our Milky Way
Authors: Han JinLin
Published: March 2013

In this invited talk, I first discuss the advantages and disadvantages of many probes for the magnetic fields of the Milky Way. I conclude that pulsars are the best probes for the magnetic structure in our Galaxy, because magnetic field strength and directions can be derived from their dispersion measures (DMs) and rotation measures (RMs). Using the pulsars as probes, magnetic field structures in the Galactic disk, especially the field reversals between the arms and interarm regions, can be well revealed from the distribution of RM data. The field strengths on large scales and small scales can be derived from RM and DM data. RMs of extragalactic radio sources can be used as the indication of magnetic field directions in the spiral tangential regions, and can be used as probes for the magnetic fields in the regions farther away than pulsars when their median RMs are compared with pulsar RMs.
Pulsar Wind Nebulae: On their growing diversity and association with highly magnetized neutron stars
Authors: Safi-Harb Samar
Published: March 2013

The 1968 discovery of the Crab and Vela pulsars in their respective supernova remnants (SNRs) confirmed Baade and Zwicky's 1934 prediction that supernovae form neutron stars. Observations of Pulsar Wind Nebulae (PWNe), particularly with the Chandra X-ray Observatory, have in the past decade opened a new window to focus on the neutron stars' relativistic winds, study their interaction with their hosting SNRs, and find previously missed pulsars. While the Crab has been thought for decades to represent the prototype of PWNe, we now know of different classes of neutron stars and PWNe whose properties differ from the Crab. In this talk, I review the current status of neutron stars/PWNe-SNRs associations, and highlight the growing diversity of PWNe with an X-ray eye on their association with highly magnetized neutron stars. I conclude with an outlook to future high-energy studies.
Radio pulsar variability
Authors: Keane E. F.
Published: March 2013

Pulsars are potentially the most remarkable physical laboratories we will ever use. Although in many senses they are extremely clean systems there are a large number of instabilities and variabilities seen in the emission and rotation of pulsars. These need to be recognised in order to both fully understand the nature of pulsars, and to enable their use as precision tools for astrophysical investigations. Here I describe these effects, discuss the wide range of timescales involved, and consider the implications for precision pulsar timing.
Pulsars in gamma rays: What Fermi is teaching us
Authors: Kerr Matthew ,   the Fermi-LAT Collaboration
Published: March 2013

The 2nd Fermi-LAT pulsar catalog includes 117 γ-ray pulsars, of which roughly one third are millisecond pulsars (MSPs) while the remaining two thirds split evenly into young radio-loud and radio-quiet pulsars. Although this large population will enable future, detailed studies of emission mechanisms and the evolution of the underlying neutron star population, some nearly-universal properties are already clear and unequivocal. We discuss some of these aspects below, including the altitude of the γ-ray emission site, the shape of the γ-ray spectrum, and the implications of the latter for the radiation mechanism.