bluuebunny/crossref_metadata_2025 huggingface dataset:
High sensitivity AlGaN/GaN lateral field‐effect rectifier for zero‐bias microwave detection
Authors: Zhou Q. , Chen W. , Zhou C. , Zhang B. , Chen K.J.
Published: October 2013

High sensitivity AlGaN/GaN lateral field‐effect rectifiers (L‐FERs) were realised that can be monolithically integrated with AlGaN/GaN high electron mobility transistors (HEMTs) circuitry. F− ion plasma treatment was optimised to achieve strong nonlinearity of the L‐FER at zero‐bias. The L‐FER treated by F− ion plasma at 120 W for 200 s exhibits a record level zero‐biased curvature coefficient, γ, of 69 V−1 at room temperature. The direct‐measured voltage sensitivity is as high as 6.75 mV/μW at 2 GHz. The high sensitivity and AlGaN/GaN HEMTs compatibility of the L‐FER make them very promising for zero‐bias square‐law detector applications.
Identification of static distortion by noise measurement
Authors: Gunn L.J. , Allison A. , Abbott D.
Published: October 2013

Many active devices exhibit gross nonlinearity, which is traditionally mitigated using negative feedback. In those cases where negative feedback is not desired, compensation for the distortion can be carried out at the postprocessing stage by inverting the transfer function of the device. A new technique is demonstrated where the inherent noise in the system is exploited to estimate the required transformation, thus reducing distortion without the need for an offline characterisation step. It is demonstrated that the proposed technique can reduce the total harmonic distortion of a common‐emitter amplifier from about 10% to < 1%.
Particle swarm against market‐based optimisation for obstacle avoidance
Authors: Palm R. , Bouguerra A.
Published: October 2013

A comparison of particle swarm optimisation (PSO) and market‐based optimisation (MBO) is presented when applied to obstacle avoidance by mobile robots using artificial potential fields and special traffic rules. Most notably, PSO and MBO are applied to optimise the motion of mobile robots when acting in a common confined workspace. Simulation results show that both methods perform equally well with slight advantage for PSO.
Radiofrequency identification of wireless devices based on RF fingerprinting
Authors: Padilla P. , Padilla J.L. , Valenzuela‐Valdés J.F.
Published: October 2013

A radiofrequency (RF) fingerprinting strategy for the proper identification of wireless devices in mobile and wireless networks is proposed. The main objective is the extraction of the main parameters of the RF signal of the device by means of the preamble in the communication in the wireless network. A complete procedure for RF fingerprint data extraction is provided, and some experimentation is conducted for its validation.
Classification of visual stimuli with different spatial patterns for single‐frequency, multi‐class SSVEP BCI
Authors: Han C.‐H. , Hwang H.‐J. , Im C.‐H.
Published: October 2013

A new approach for a multi‐class steady‐state visual‐evoked potential (SSVEP)‐based brain–computer interface (BCI) is proposed. It was demonstrated through preliminary experiments that spatial patterns of SSVEP responses recorded using high‐density electroencephalography while presenting pattern reversal checkerboard stimuli with different spatial patterns can be classified with fairly high accuracy. The average classification accuracies in two of the three subjects were 91.7% (12‐class) and 93.3% (15‐class), suggesting that the proposed visual stimulation can potentially be used for multi‐class SSVEP‐based BCI.
Influence of sympathetic inrush on voltage dips caused by transformer energisation
Authors: Peng Jinsheng , Li Haiyu , Wang Zhongdong , Ghassemi Foroozan , Jarman Paul
Published: October 2013

Energising a transformer with other adjacent transformers in service may induce sympathetic inrush that could lead to long duration voltage dips. This study addresses this issue through analysing voltage dip events observed on a 400/132 kV grid when energisations of several generator step‐up transformers were performed. With the help of a number of field measurements of voltage dips involving sympathetic inrush, a detailed network model in alternative transients program/electromagnetic transients program has been developed and validated. Based on the network model, comprehensive simulation studies have been performed. In addition, because of the nature of multiple controlling parameters, sensitivity assessment has been carried out to identify the key influential parameters. It is found that the sympathetic inrush, although does not affect voltage dip magnitude, can prolong voltage dip duration by 143% under the worst energisation condition. The sympathetic inrush occurring in substation transformers gives rise to a network‐wide sympathetic interaction, resulting in further prolonged voltage dips on the 132 kV grid. Finally, it is proven that application of static var compensator is able to speed up the voltage dip recovery.
Design and experimental verification of low cost plastic optical fibre transimpedance amplifiers
Authors: García del Pozo Jose María , Celma Santiago , Gimeno Cecilia , Camón Agustín
Published: October 2013

This study introduces a low‐cost transimpedance amplifier (TIA) suitable for plastic optical fibre front ends. The proposed TIA is designed with some novel principles and fabricated in a low‐cost 180‐nm CMOS technology. The power consumption is 24 mW supplying the block with 1.8 V. An electrical test allows characterising the block under ideal conditions reaching 1 GHz bandwidth and low noise levels. An optical measurement setup is also presented, allowing checking the block performance in a controlled test ambient. This optical setup allows validating the novel design criteria as well as obtaining valuable information for future works.
Energy storage for active network management on electricity distribution networks with wind power
Authors: Carr Stephen , Premier Giuliano C. , Guwy Alan J. , Dinsdale Richard M. , Maddy Jon
Published: October 2013

Increasing amounts of variable renewable generation are likely to enter the UK's energy systems in the near future. To accommodate this generation onto electricity networks, the concept of active network management (ANM) has become a significant area of research interest. Network connected energy storage systems (ESS) are considered here as a means to actively control the network in order to increase the amount of generation that is possible to connect to a network. ESS is one of several potential methods of ANM, but has not been widely researched in this context. In this study, the ability of the ESS to increase the amount of wind energy accepted onto a network is assessed over a range of roundtrip storage efficiencies. An analysis is then conducted to determine the cost of energy produced through the ESS for a number of scenarios. The results show that the ESS is able to increase the energy accepted onto a distribution network, with the efficiency of the ESS, energy storage capacity, windfarm size, network losses and network characteristics being important in determining the relative effectiveness of the ESS and the cost at which electricity is produced.
Static synchronous compensator sizing for enhancement of fault ride‐through capability and voltage stabilisation of fixed speed wind farms
Authors: Mahfouz M.M.A , El‐Sayed Mohamed A.H.
Published: October 2013

High penetration level of wind energy affects the generation profile of the power systems, which impose more stringent connection requirements of wind farms. The ability of wind power plant to remain connected during grid faults is very important to avoid cascaded outages because of power deficit. FACT devices are considered to be a key technology to accomplish these requirements. The implementation of three‐level inverter based on a static synchronous compensator (STATCOM) for the improvement of the ride‐through and stability of fixed speed wind farms is analysed here. This brings the challenges for system planner to determine the appropriate STATCOM rating. This study provides a simple approach to evaluate the STATCOM rating for voltage‐level regulation at the point of common coupling around its pre‐specified value. Vector current control is used as robust control to inject the required reactive power from STATCOM. This study emphasizes also on the analysis of torque speed curve to evaluate the induction generator speed limit and for defining the critical clearing time of the fault according to the selected STATCOM rating. Simulation results under fault conditions are performed to validate the enhancement of wind farm low‐voltage ride‐through capability and increasing the critical clearing time by installing STATCOM.
Superhydrophobic polytetrafluoroethylene surface obtained using reactive ion etching and duplication with polydimethylsiloxane mould
Authors: Kim Bonghwan , Kim Hwamin , Kim Jongjae , Cho Chan Seob , Lee Jonghyun
Published: October 2013

The fabrication of a superhydrophobic surface by texturing of the polytetrafluoroethylene (PTFE) surface in the form of pyramidlike structures is demonstrated. In addition, the superhydrophobic surface is duplicated by using a polydimethylsiloxane (PDMS) mould. The hydrophobic properties were determined by measuring the contact angle and roughness of the PTFE surface on the pyramidal structure. The calculated roughness factor and root mean squares roughness ranged from 2.47 to 2.6 and 0.25 to 0.4 µm, respectively. The contact angle of a water droplet on the PTFE surface was greater than 150°, which was well maintained for over seven weeks. In the case of PDMS mould surface, the contact angle of a water droplet was greater than 130°.
Spin-polarized hydrogen and its isotopes: A rich class of quantum phases (Review Article)
Authors: Bešlić I. , Vranješ Markić L. , Boronat J.
Published: October 2013

We review the recent activity in the theoretical description of spin-polarized atomic hydrogen and its isotopes at very low temperatures. Spin-polarized hydrogen is the only system in nature that remains stable in the gas phase even in the zero temperature limit due to its small mass and weak interatomic interaction. Hydrogen and its heavier isotope tritium are bosons, the heavier mass of tritium producing a self-bound (liquid) system at zero temperature. The other isotope, deuterium, is a fermion with nuclear spin one making possible the study of three different quantum systems depending on the population of the three degenerate spin states. From the theoretical point of view, spin-polarized hydrogen is specially appealing because its interatomic potential is very accurately known making possible its precise quantum many-body study. The experimental study of atomic hydrogen has been very difficult due to its high recombination rate, but it finally led to its Bose-Einstein condensate state in 1998. Degeneracy has also been observed in thin films of hydrogen adsorbed on the 4He surface allowing for the possibility of observing the Berezinskii–Kosterlitz–Thouless superfluid transition.
Theory of superfluid states with singlet and triplet types of pairing in nuclear matter
Authors: Shul'ga S. N. , Slyusarenko Yu. V.
Published: October 2013

This paper presents the results of investigation of the superfluid states in a two-component Fermi liquid within the framework of the Fermi liquid approach. Particular attention is paid to the superfluid states in nuclear matter which are characterized by the superposition of singlet and triplet types of pairing in spin and isospin spaces. The fundamental principles of the Fermi liquid approach are formulated and further used in the study of superfluidity in nuclear matter with the superposition of singlet and triplet types of pairing. The system of self-consistency equations is derived and its solutions are presented. The conditions of existence of the considered states are determined. These conditions impose certain constraints on the interaction potential and particle density in the system. It is shown that the states with a complete set of nonzero order parameters are realized only in a narrow density range, the width and position of which on the density scale depend on the actual parametrization of the Skyrme potential employed. We considered 18 different parameterizations and indicated for which of them the studied types of superfluid states may appear. The problem of stability of the states with the superposition of singlet and triplet pairing is studied. It is shown that the lowest value of the thermodynamic potential corresponds to purely triplet states. Then, in the order of increasing, follow the thermodynamic potentials of purely singlet states and mixed singlet-triplet states. Separately, we consider the case of unitary states, for which the solutions of the self-consistency equations are also analyzed. It is shown that the density range in which such states can be realized is different from that corresponding to the nonunitary states. The problem of existence of the unitary superfluid states with the superposition of singlet and triplet superfluidity is considered in the case of asymmetrical nuclear matter. It is shown that the appearance of asymmetry in nuclear matter breaks the unitarity of superfluid states in nuclear matter with regard to isospin.
Chemical oscillator as a generalized Rayleigh oscillator
Authors: Ghosh Shyamolina , Ray Deb Shankar
Published: October 2013

We derive the conditions under which a set of arbitrary two dimensional autonomous kinetic equations can be reduced to the form of a generalized Rayleigh oscillator which admits of limit cycle solution. This is based on a linear transformation of field variables which can be found by inspection of the kinetic equations. We illustrate the scheme with the help of several chemical and bio-chemical oscillator models to show how they can be cast as a generalized Rayleigh oscillator.
Analysis and design of triple-band high-impedance surface absorber with periodic diversified impedance
Authors: Rui Zhang Guo , Heng Zhou Pei , Bin Zhang Hui , Bo Zhang Lin , Liang Xie Jian , Jiang Deng Long
Published: October 2013

In this paper, a triple-band planar absorber with high-impedance surface (HIS) is designed and fabricated. The absorber structure is composed of polyurethane foam sandwiched between a lossy sheet of frequency selective surfaces (FSS) and a perfect electric conductor. The lossy FSS possesses different resistances in a periodic composite unit as compared with typical HIS absorber. Losses in the FSS are introduced by printing the periodic composite square ring pattern on blank stickers using various resistive inks. Physical mechanism of the HIS absorbers is analyzed by equivalent circuit model and electric field distribution studies. The proposed absorber with periodic composite units offers superimposed triple-band absorption as compared with that of the single units having single- or dual-band absorption characteristics. The reflection loss measurements show that the 90% absorption bandwidth of the HIS absorber is increased by 42% by the proposed composite periodic units.
Raman frequency shift induced by photorefractive effect on Fe–doped lithium niobate
Authors: Bazzan M. , Kokanyan N. , Zaltron A. , Argiolas N. , Chapron D. , Fontana M. D.
Published: October 2013

We report on the observation of a time dependent frequency shift of the Raman modes in photorefractive Fe:LiNbO3. The origin of this shift is attributed primarily to the space charge field which builds up due to photo-induced charge transport by the excitation beam, and to the subsequent piezo-induced strain. This phenomenon can be regarded as the Raman analogous of the photorefractive effect, in which the space charge field is detected by an electro-optic variation of the refractive index. It should be possible therefore to analyze it using standard models for photorefractivity. In this paper, we verify this claim discussing its validity.
Work function engineering of single layer graphene by irradiation-induced defects
Authors: Kim Jong-Hun , Hwang Jin Heui , Suh Joonki , Tongay Sefaattin , Kwon Sangku , Hwang C. C. , Wu Junqiao , Young Park Jeong
Published: October 2013

We report the tuning of electrical properties of single layer graphene by α-beam irradiation. As the defect density increases upon irradiation, the surface potential of the graphene changes, as determined by Kelvin probe force microscopy and Raman spectroscopy studies. X-ray photoelectron spectroscopy studies indicate that the formation of C/O bonding is promoted as the dose of irradiation increases when at atmospheric conditions. Our results show that the surface potential of the graphene can be engineered by introducing atomic-scale defects via irradiation with high-energy particles.
Nanoscale mapping of oxygen vacancy kinetics in nanocrystalline Samarium doped ceria thin films
Authors: Doria Sandra , Yang Nan , Kumar Amit , Jesse Stephen , Tebano Antonello , Aruta Carmela , Di Bartolomeo Elisabetta , Arruda Thomas M. , Kalinin Sergei V. , Licoccia Silvia , Balestrino Giuseppe
Published: October 2013

The position-dependent oxygen vacancy dynamics induced by a biased scanning probe microscopy tip in Samarium doped ceria thin films grown on MgO (100) substrates is investigated. The granularity of the samples gives rise to spatially dependent local electrochemical activity, as explored by electrochemical strain microscopy. The kinetics of the oxygen vacancy relaxation process is investigated separately for grain boundaries and grains. Higher oxygen vacancy concentration variation and slower diffusion are observed in the grain boundary regions as compared to the grains.
Heteroepitaxial reflector for the fabrication of Si thin film photovoltaic devices
Authors: Asante Kofi , Cross Michael , Varhue Walter
Published: October 2013

Thin film crystalline Si diodes are a viable solution to the goal of fabricating economical photovoltaic (PV) cells. A functional, light trapping, thin film PV was fabricated with a heteroepitaxial (YSZ) reflecting layer which also served as a complaint layer for the growth of crystalline Si or SiGe active layers. X-ray analysis confirmed that the deposited semiconductor layers were crystalline. It was observed that the light trapping PV cell formed with the YSZ reflector layer increased the short circuit current under illumination by 22% over that fabricated without the YSZ reflector layer. It was further observed that the surface texture in the YSZ layer contributed to both the ability to grow crystalline semiconductor layers and to act as an effective light trapping structure.
Atomic-level functional model of dengue virus Envelope protein infectivity
Authors: Christian Elizabeth A. , Kahle Kristen M. , Mattia Kimberly , Puffer Bridget A. , Pfaff Jennifer M. , Miller Adam , Paes Cheryl , Davidson Edgar , Doranz Benjamin J.
Published: October 2013

Significance

Dengue virus (DENV) infects nearly 400 million people annually, and approximately 40% of the world’s population lives at risk for infection. Without a therapeutic or vaccine available, DENV remains a major public health burden. Our studies provide a comprehensive structure–function analysis of the DENV Envelope protein, integrating information from numerous Envelope structures with our functional data into a cohesive mechanistic model. This model describes the dynamic processes by which specific residue interactions within Envelope mediate infectivity—from fusion-loop triggering to hinge movement to membrane fusion—and may also apply to related class II viral fusion proteins. Because of the importance of the specific amino acids identified, our results also identify new functional residue targets for DENV vaccines and therapeutics.
Inhibition of Return Affects Contrast Sensitivity
Authors: Sapir Ayelet , Jackson Kevin , Butler Joe , Paul Matthew A. , Abrams Richard A.
Published: October 2013

Inhibition of return (IOR)—a slow response to targets at recently attended locations, is believed to play an important role in guiding behaviour. In the attention literature it has been shown that attentional capture by an exogenous cue affects contrast sensitivity so that it alters the appearance of low-contrast stimuli. Despite a significant amount of work over the last quarter century on IOR, it is not yet clear whether IOR operates in the same way. In the current study we examined the effect of IOR on contrast sensitivity—a very early, low-level perceptual process. We found in both a detection task and an orientation discrimination task that lower contrast was needed to detect the stimulus (Experiment 1) and determine its orientation (Experiment 2) at the cued location than at the uncued location, at short cue–target delays, while higher contrast was needed at long delays—reflecting IOR. These results clearly demonstrate that IOR affects contrast sensitivity in a similar way as attentional capture does and suggest that IOR increases perceived contrast of an object in the uncued location.
Pharyngeal Function and Breathing Pattern during Partial Neuromuscular Block in the Elderly
Authors: Cedborg Anna I. Hårdemark , Sundman Eva , Bodén Katarina , Hedström Hanne Witt , Kuylenstierna Richard , Ekberg Olle , Eriksson Lars I.
Published: October 2013

Background:

Intact pharyngeal function and coordination of breathing and swallowing are essential for airway protection and to avoid respiratory complications. Postoperative pulmonary complications caused by residual effects of neuromuscular-blocking agents occur more frequently in the elderly. Moreover, elderly have altered pharyngeal function which is associated with increased risk of aspiration. The purpose of this study was to evaluate effects of partial neuromuscular block on pharyngeal function, coordination of breathing and swallowing, and airway protection in individuals older than 65 yr.

Methods:

Pharyngeal function and coordination of breathing and swallowing were assessed by manometry and videoradiography in 17 volunteers, mean age 73.5 yr. After control recordings, rocuronium was administered to obtain steady-state train-of-four ratios of 0.70 and 0.80 followed by spontaneous recovery to greater than 0.90.

Results:

Pharyngeal dysfunction increased significantly at train-of-four ratios 0.70 and 0.80 to 67 and 71%, respectively, compared with 37% at control recordings, and swallowing showed a more severe degree of dysfunction during partial neuromuscular block. After recovery to train-of-four ratio of greater than 0.90, pharyngeal dysfunction was not significantly different from the control state. Resting pressure in the upper esophageal sphincter was lower at all levels of partial neuromuscular block compared with control recordings. The authors were unable to demonstrate impaired coordination of breathing and swallowing.

Conclusion:

Partial neuromuscular block in healthy elderly individuals causes an increased incidence of pharyngeal dysfunction from 37 to 71%, with impaired ability to protect the airway; however, the authors were unable to detect an effect of partial neuromuscular block on coordination of breathing and swallowing.
High-mobility Group Box 1 Protein Initiates Postoperative Cognitive Decline by Engaging Bone Marrow–derived Macrophages
Authors: Vacas Susana , Degos Vincent , Tracey Kevin J. , Maze Mervyn
Published: October 2013

Background:

Aseptic trauma engages the innate immune response to trigger a neuroinflammatory reaction that results in postoperative cognitive decline. The authors sought to determine whether high-mobility group box 1 protein (HMGB1), an ubiquitous nucleosomal protein, initiates this process through activation and trafficking of circulating bone marrow–derived macrophages to the brain.

Methods:

The effects of HMGB1 on memory (using trace fear conditioning) were tested in adult C57BL/6J male mice; separate cohorts were tested after bone marrow–derived macrophages were depleted by clodrolip. The effect of anti-HMGB1 neutralizing antibody on the inflammatory and behavioral responses to tibial surgery were investigated.

Results:

A single injection of HMGB1 caused memory decline, as evidenced by a decrease in freezing time (52 ± 11% vs. 39 ± 5%; n = 16–17); memory decline was prevented when bone marrow–derived macrophages were depleted (39 ± 5% vs. 50 ± 9%; n = 17). Disabling HMGB1 with a blocking monoclonal antibody, before surgery, reduced postoperative memory decline (52 ± 11% vs. 29 ± 5%; n = 15–16); also, hippocampal expression of monocyte chemotactic protein-1 was prevented by the neutralizing antibody (n = 6). Neither the systemic nor the hippocampal inflammatory responses to surgery occurred in mice pretreated with anti-HMGB1 neutralizing antibody (n = 6).

Conclusion:

Postoperative neuroinflammation and cognitive decline can be prevented by abrogating the effects of HMGB1. Following the earlier characterization of the resolution of surgery-induced memory decline, the mechanisms of its initiation are now described. Together, these data may be used to preoperatively test the risk to surgical patients for the development of exaggerated and prolonged postoperative memory decline that is reflected in delirium and postoperative cognitive dysfunction, respectively.
A limited host immune range facilitates the creation and maintenance of diversity in parasite virulence
Authors: Best Alex , Hoyle Andy
Published: October 2013

A vast theoretical literature has explored the evolutionary dynamics of parasite virulence. The classic result from this modelling work is that, assuming a saturating transmission–virulence trade-off, there is a single evolutionary optimum where the parasite optimizes the epidemiological
R
0
. However, there are an increasing number of models that have shown how ecological and epidemiological feedbacks to evolution can instead result in the creation and maintenance of multiple parasite strains. Here, we fully explore one such example, where recovered hosts have a limited ‘immune range’ resulting in partial cross-immunity to parasite strains that they have not previously encountered. Taking an adaptive dynamics approach, we show that, provided this immune range is not too wide, high levels of diversity can evolve and be maintained through multiple branching events. We argue that our model provides a more realistic picture of disease dynamics in vertebrate host populations and may be a key explanatory factor in the high levels of parasite diversity seen in natural systems.
The canonical equation of adaptive dynamics for Mendelian diploids and haplo-diploids
Authors: Metz Johan A. J. , de Kovel Carolien G. F.
Published: October 2013

One of the powerful tools of adaptive dynamics is its so-called canonical equation (CE), a differential equation describing how the prevailing trait vector changes over evolutionary time. The derivation of the CE is based on two simplifying assumptions, separation of population dynamical and mutational time scales and small mutational steps. (It may appear that these two conditions rarely go together. However, for small step sizes the time-scale separation need not be very strict.) The CE was derived in 1996, with mathematical rigour being added in 2003. Both papers consider only well-mixed clonal populations with the simplest possible life histories. In 2008, the CE's reach was heuristically extended to locally well-mixed populations with general life histories. We, again heuristically, extend it further to Mendelian diploids and haplo-diploids. Away from strict time-scale separation the CE does an even better approximation job in the Mendelian than in the clonal case owing to gene substitutions occurring effectively in parallel, which obviates slowing down by clonal interference.
First passage time to allopatric speciation
Authors: Yamaguchi Ryo , Iwasa Yoh
Published: October 2013

Allopatric speciation is a mechanism to evolve reproductive isolation; it is caused by the accumulation of genetic differences between populations while they are geographically isolated. Here, we studied a simple stochastic model for the time until speciation caused by geographical isolation in fragmented populations that experience recurrent but infrequent migration between subpopulations. We assumed that mating incompatibility is controlled by a number of loci that behave as neutral characters in the accumulation of novel mutations within each population. Genetic distance between populations was defined as the number of incompatibility-controlling loci that differ between them. Genetic distance increases through the separate accumulation of mutations in different populations, but decreases after a successful migration event followed by genetic mixing between migrants and residents. We calculated the time to allopatric speciation, which occurs when the genetic distance exceeds a specified threshold. If the number of invasive individuals relative to the resident population is not very large, diffusion approximation provides an accurate prediction. There is an intermediate optimal rate of migration that maximizes the rate of species creation by recurrent invasion and diversification. We also examined cases that involved more than two populations.
Collective animal decisions: preference conflict and decision accuracy
Authors: Conradt Larissa
Published: October 2013

Social animals frequently share decisions that involve uncertainty and conflict. It has been suggested that conflict can enhance decision accuracy. In order to judge the practical relevance of such a suggestion, it is necessary to explore how general such findings are. Using a model, I examine whether conflicts between animals in a group with respect to preferences for avoiding false positives versus avoiding false negatives could, in principle, enhance the accuracy of collective decisions. I found that decision accuracy nearly always peaked when there was maximum conflict in groups in which individuals had different preferences. However, groups with no preferences were usually even more accurate. Furthermore, a relatively slight skew towards more animals with a preference for avoiding false negatives decreased the rate of expected false negatives versus false positives considerably (and vice versa), while resulting in only a small loss of decision accuracy. I conclude that in ecological situations in which decision accuracy is crucial for fitness and survival, animals cannot ‘afford’ preferences with respect to avoiding false positives versus false negatives. When decision accuracy is less crucial, animals might have such preferences. A slight skew in the number of animals with different preferences will result in the group avoiding that type of error more that the majority of group members prefers to avoid. The model also indicated that knowing the average success rate (‘base rate’) of a decision option can be very misleading, and that animals should ignore such base rates unless further information is available.
Biological information: why we need a good measure and the challenges ahead
Authors: van Baalen Minus
Published: October 2013

Evolution can be characterized as a process that shapes and maintains information across generations. It is also widely acknowledged that information may play a pivotal role in many other ecological processes. Most of the ecologically relevant information (and some important evolutionary information too) is of a very subjective and analogue kind: individuals use cues that may carry information useful only to them but not to others. This is a problem because most information theory has been developed for objective and discrete information. Can information theory be extended to this theory to incorporate multiple forms of information, each with its own (physical) carriers and dynamics? Here, I will not review all the possible roles that information can play, but rather what conditions an appropriate theory should satisfy. The most promising starting point is provided by entropy measures of conditional probabilities (using the so-called Kullback–Leibler divergence), allowing an assessment of how acquiring information can lead to an increase in fitness. It is irrelevant (to a certain extent) where the information comes from—genes, experience or culture—but it is important to realize that information is not merely subjective but its value should be evaluated in fitness terms, and it is here that evolutionary theory has an enormous potential. A number of important stumbling points remain, however; namely, the identification of whose fitness it concerns and what role the spatio-temporal dynamics plays (which is tightly linked to the nature of the physical carriers of the information and the processes that impact on it).
Co-infection and super-infection models in evolutionary epidemiology
Authors: Alizon Samuel
Published: October 2013

Multiple infections are intensively studied because of their consequences for the health of the host but also because they can radically alter the selective pressures acting on parasites. I discuss how multiple infections have been modelled in evolutionary epidemiology. First, I briefly mention within-host models, which are at the root of these epidemiological models. Then, I present the super-infection framework, with an original focus on how the definition of the super-infection function can lead to evolutionary branching. There are several co-infection models and, for each of them, I briefly go through the underlying mathematics (especially the invasion fitness of a mutant strain) and I discuss the biological assumptions they make and the questions they consequently may ask. In particular, I show that a widely used co-infection model should not be invoked for invasion analyses because it confers a frequency-dependent advantage to rare neutral mutants. Finally, I present more recent frameworks, such as the Price equation framework in epidemiology, that can account for increased parasite diversity. To conclude, I discuss some perspectives for the study of multiple infections in evolutionary epidemiology.
Methanospirillum psychrodurum sp. nov., isolated from wetland soil
Authors: Zhou Liguang , Liu Xiaoli , Dong Xiuzhu
Published: October 2013

A psychrotolerant methanogenic strain, X-18T, was isolated from the soil of the Madoi wetland at Qinghai, Tibetan plateau, China. Cells were wavy rods (11–62 µm long) with blunt tapered ends and Gram-stain-negative. Strain X-18Tgrew strictly anaerobically and produced methane exclusively from H2/CO2. Growth occurred in the temperature range of 4–32 °C and optimally at 25 °C. Growth pH ranged from 6.5 to 8.0 and the optimum was 7.0. The G+C content of the genomic DNA of strain X-18Twas 44.4 mol%. Phylogenetic analysis based on 16S rRNA gene sequences and the alpha subunit of methyl-coenzyme M reductase indicated that strain X-18Twas affiliated to the genusMethanospirillumand was most closely related toMethanospirillum lacunaeKi8-1T, with 96.3 % 16S rRNA gene sequence similarity. However, strain X-18Tcould be distinguished from the existing species of the genusMethanospirillumby its lower growth temperature and obligate hydrogenotrophic methanogenesis. On the basis of phenotypic characteristics and phylogenetic analysis, strain X-18Trepresents a novel species of the genusMethanospirillum, for which the nameMethanospirillum psychrodurumsp. nov. is proposed and strain X-18Tis assigned as the type strain ( = CGMCC 1.5186T = JCM 19216T).
Falsiporphyromonas endometrii gen. nov., sp. nov., isolated from the post-partum bovine uterus, and emended description of the genus Porphyromonas Shah and Collins 1988
Authors: Wagener K. , Drillich M. , Baumgardt S. , Kämpfer P. , Busse H.-J. , Ehling-Schulz M.
Published: October 2013

Two black-pigmented, anaerobic bacterial strains, designated LMM 40T and LMM 41, were isolated from the bovine post-partum endometrium of two Holstein cows. The 16S rRNA gene sequences of the two strains were identical and showed the highest similarity to the 16S rRNA gene sequence of the type strain of

Porphyromonas crevioricanis

(90.2 %) but only 85.1 % 16S rRNA gene sequence similarity to the type strain of the type species of the genus

Porphyromonas

,

Porphyromonas asaccharolytica

. The major fatty acid profiles of the two strains were similar to those of species of the genus

Porphyromonas

, containing iso-C15 : 0 as the major component and moderate amounts of anteiso-C15 : 0, iso-C13 : 0, C15 : 0 and C16 : 0. Hydroxylated fatty acids, such as iso-C14 : 0 3-OH, iso-C16 : 0 3-OH and iso-C17 : 0 3-OH, were also detected. The quinone profiles were dominated by the menaquinones MK-8 and MK-9, while spermidine was the major polyamine. The polar lipid profiles contained major amounts of phosphatidylethanolamine, an unidentified phospholipid, an unidentified aminophospholipid and two unidentified lipids and minor amounts of phosphatidylglycerol, an unidentified aminolipid, a second unidentified aminophospholipid and an unidentified glycolipid. The cell-wall peptidoglycan contained meso-diaminopimelic acid. The genomic DNA G+C contents of LMM 40T and LMM 41 were 40.7 and 41.3 mol%, respectively. Based on a polyphasic approach, including phylogenetic analysis, physiological and biochemical tests as well as metabolic fingerprinting, it is proposed that the two strains are members of a novel genus and species, for which the name Falsiporphyromonas endometrii gen. nov., sp. nov. is proposed. The type strain of Falsiporphyromonas endometrii is LMM 40T ( = DSM 27210T = CCUG 64267T). An emended description of the genus

Porphyromonas

is also presented.
Hopper-like framework growth evolution in a cubic system: a case study of Cu2O
Authors: Chen Kunfeng , Song Shuyan , Xue Dongfeng
Published: October 2013

Crystallization of hopper-like Cu2O cubes is demonstrated in alkaline citrate–copper solution upon the equilibrium between complexation, precipitation and redox reactions. The complexation reactions of Na3cit and NaOH with Cu2+manipulate the current chemical reaction routes, phase transformation, and thus crystallization morphologies and compositions. During the crystallization of Cu2O variations of mother solution such as pH and the concentration of Cu2+(Cu+) are monitored byex situpH measurement and UV–Vis absorption spectroscopy. The shape evolution of Cu2O hopper cubes is consistent with the chemical reaction routes, which demonstrates the interplay between chemical reactions and crystal growth. The appropriate reaction concentration, Na3cit:Cu2+> 2 and 1 < NaOH:Cu2+< 2, has been identified for the growth of these hopper cubes. The current reaction-controllable crystal growth may further the synthesis chemistry toward rational control over crystallization.
The interpretation of polycrystalline coherent inelastic neutron scattering from aluminium
Authors: Roach Daniel L. , Ross D. Keith , Gale Julian D. , Taylor Jon W.
Published: October 2013

A new approach to the interpretation and analysis of coherent inelastic neutron scattering from polycrystals (poly-CINS) is presented. This article describes a simulation of the one-phonon coherent inelastic scattering from a lattice model of an arbitrary crystal system. The one-phonon component is characterized by sharp features, determined, for example, by boundaries of the (Q, ω) regions where one-phonon scattering is allowed. These features may be identified with the same features apparent in the measured total coherent inelastic cross section, the other components of which (multiphonon or multiple scattering) show no sharp features. The parameters of the model can then be relaxed to improve the fit between model and experiment. This method is of particular interest where no single crystals are available. To test the approach, the poly-CINS has been measured for polycrystalline aluminium using the MARI spectrometer (ISIS), because both lattice dynamical models and measured dispersion curves are available for this material. The models used include a simple Lennard-Jones model fitted to the elastic constants of this material plus a number of embedded atom method force fields. The agreement obtained suggests that the method demonstrated should be effective in developing models for other materials where single-crystal dispersion curves are not available.
Combined neutron reflectometry and rheology
Authors: Wolff M. , Kuhns P. , Liesche G. , Ankner J. F. , Browning J. F. , Gutfreund P.
Published: October 2013

Neutron reflectometry has been combined with rheology in order to investigate the solid boundary of liquids and polymers under shear deformation. This approach allows one to apply a controlled stress to a material while resolving the structural arrangements on the sub-nanometre length scale with neutron reflectivity, off-specular scattering and small-angle scattering at the same time. The specularly reflected neutron intensity of a 20% by weight solution of Pluronic F127 in deuterated water in contact with an octadecyl trichlorosilane-covered and a piranha-treated silicon wafer is evaluated. A pronounced difference is found in the structure formed by the polymer micelles at the two surfaces, which is explained by the difference in the affinity of the micellar shell to the solid interfaces. Under deformation, the near interface structure changes at deformations of about 2, 30 and 900%. The structural changes are correlated with changes in the storage and loss modulus of the polymer solution, revealing a transition from more solid to more liquid like properties.
Determination of the structure of liquids: an asymptotic approach
Authors: Mayo Martin , Yahel Eyal , Greenberg Yaron , Caspi El'ad N. , Beuneu Brigitte , Makov Guy
Published: October 2013

Accurate determination of a liquid structure, especially at high temperatures, remains challenging, as reflected in the scatter between different measurements. The experimental challenge is compounded by the process of the numerical transformation from the structure factor to the radial distribution function. The resulting uncertainty is often greater than that required to resolve issues associated with changes in the short-range order of the liquid, such as the existence of liquid–liquid phase transitions or correlations between thermophysical properties and structure. In the present contribution it is demonstrated for liquid bismuth as a model system that the structure factor can be obtained to high accuracy, by comparing several independent measurements in different setups. A simple method is proposed for improving the accuracy of the radial distribution functions, based on the extension of the finite range of momentum transfer,q, in the measured data by analytical asymptotic expressions. A unified mathematical formalism for the asymptotic dependence of the structure factor is developed and the asymptotic form of the Percus–Yevick hard-sphere solution is obtained as a special limiting case. The multiple expressions in the literature are shown to reflect uncertainty in the nature of the repulsive interatomic interaction at short separation distances. Applying this asymptotic method, it is shown that it enables access to details of the fine structure of the liquid and its temperature dependence.
A robust tangent procedure
Authors: Burla M. C. , Giacovazzo C. , Polidori G.
Published: October 2013

Third-generation direct methods programs are based on a phasing algorithm (e.g.the tangent or the parameter shift method) and on dual space refinement techniques. The two spaces may be alternated during the phasing procedure or used in a sequential way: for example, first phase and after extend and refine. The tangent approach inSIR2011belongs to the second category: phases are first estimated by the tangent formula, then their extension and refinement is performed in direct spaceviaelectron density modification techniques. In this article a number of new algorithms are described, with the aim of improving theSIR2011tangent step and allowing more efficient phase extension and refinement. New criteria were chosen for defining the number of reflections to phase, for modifying the tangent weighting scheme, and for fixing the active use of the psi-0 triplets and of the quartet invariants. Each tangent trial may now be submitted to the RELAX procedure, a tool for moving to the correct position a well oriented but misplaced structural model. The resulting procedure shows surprising efficiency, testified by a wide set of applications. The experimental results have been compared with the tangent and VLD (vive la différence) approaches implemented inSIR2011.
Octanol-rich and water-rich domains in dynamic equilibrium in the pre-ouzo region of ternary systems containing a hydrotrope
Authors: Diat Olivier , Klossek Michael L. , Touraud Didier , Deme Bruno , Grillo Isabelle , Kunz Werner , Zemb Thomas
Published: October 2013

Ternary mixtures of medium-chain fatty alcohols, water and a hydrotrope (such as ethanol), near the immiscibility gap, make stable single phases at constant temperature. Interestingly, in this `pre-ouzo region' these single phases consist of two distinct nanoscopic pseudo-phases, one octanol-rich and one water-rich. This domain of composition, which is known to produce strong light scattering and to separate under ultracentrifugation into two phases, has been studied using contrast variation in small-angle neutron scattering (SANS) combined with small- and wide-angle X-ray scattering (SWAXS). The existence of fatty alcohol-rich domains of well defined size of the order of 2 nm radius is proven. The scattering can be approximated by an Ornstein–Zernike function, which is close to the general expression of Choi, Chen, Sottmann & Strey [Physica B, (1998),241–243, 976–978] with vanishing quadratic Porod term. Exploitation of the relative intensities at the vanishing scattering angle in SANS demonstrates that the distribution coefficient of ethanol between the octanol-rich and the water-rich domains is close to one. WAXS of the two coexisting pseudo-phases is compared with the corresponding binary water–ethanol and octanol–ethanol samples.
Poly[(μ6-benzene-1,3,5-tricarboxylato-κ6O1:O1′:O3:O3′:O5:O5′)tris(N,N-dimethylformamide-κO)tris(μ3-formato-κ3O:O:O′)trizinc(II)]
Authors: Sim Jaeung , Kim Taemin , Yang Jin Kuk
Published: October 2013

The asymmetric unit of the title compound, [Zn3(HCO2)3(C9H3O6)(C3H7NO)3]n, contains one Zn ion, one formate ligand, oneN,N-dimethylformamide (DMF) ligand and one-third of a benzene-1,3,5-tricarboxylate (btc) ligand situated on a crystallographic 3 axis. Each ZnIIatom is coordinated by one O atom from a DMF ligand, two O atoms from two btc ligands and three O atoms from three formate ligands in a distorted octahedral geometry. The ZnIIatoms are connected by the formate and btc ligands, forming hexanuclear cores, which are linked by btc ligands, constructing a two-dimensional layered network along theabplane.
(E)-13-(4-Aminophenyl)parthenolide
Authors: Penthala Narsimha Reddy , Janganati Venumadhav , Parkin Sean , Varughese Kottayil I. , Crooks Peter A.
Published: October 2013

The title compound, C21H25NO3[systematic name: (3aS,9aR,10aR,10bS,E)-3-[(E)-4-(4-aminobenzylidene)-6,9a-dimethyl-3a,4,5,8,9,9a,10a,10b-octahydrooxireno[2′,3′:9,10]cyclodeca[1,2-b]furan-2(3H)-one] was obtained from the reaction of parthenolide [synonym: 4,5-epoxygermacra-1(10),11(13)-dieno-12,6-lactone] with 4-iodoaniline under Heck reaction conditions. It was identified as theE-isomer (conformation about the exocyclic methylidene C=C bond; the conformation about the C=C bond in the ten-membered ring is alsoE). The molecule is built up from fused ten-, five- (lactone) and three-membered (epoxide) rings with a 4-aminophenyl group as a substituent. The ten-membered ring displays an approximate chair–chair conformation, while the lactone ring has an envelope conformation with the C atom bonded to the ring O atom as the flap. The dihedral angle between the benzene ring of the 4-aminophenyl moiety and the lactone ring mean plane is 23.50 (8)°. In the crystal, molecules are linkedviaN—H...O hydrogen bonds, between the amine group and the lactone and epoxide ring O atoms, forming chains propagating along theb-axis direction. Adjacent chains are linkedviaC—H...O interactions, forming an undulating two-dimensional network lying parallel to the plane (001). The absolute structure of the molecule in the crystal was confirmed by resonance scattering [Flack parameter = 0.03 (3)].