bluuebunny/crossref_metadata_2025 huggingface dataset:
Adaptive modulation with finite rate feedback for QR decomposition‐successive interference cancellation‐based multiple‐in multiple‐out systems
Authors: Wu Liang , Zhang Zaichen , Liu Huaping
Published: June 2013

This article studies adaptive modulation for QR decomposition and successive interference cancellation receivers in multiple‐input multiple‐output systems over slow‐ and fast‐fading channels. In slowly fading channels, adaptive modulation schemes with finite‐rate feedback under the constraints of a constant total transmit power, discrete‐rate and a target bit‐error‐rate (BER) are proposed. Specifically, the authors first develop adaptive modulation with modulation order feedback only. For power allocation and modulation order feedback, the authors establish an optimisation scheme that can be solved easily and analyse the effect of power‐level quantisation on the achievable data rates. For the fast fading channel case, the authors analyse the probability distribution of the ‘R’ matrix and derive a scheme that only requires feedback of the statistical information of the channel for adaptive modulation with optimal bit loading to guarantee that the BER target is met.
Cross‐layer resource allocation in orthogonal frequency multiple access systems based on channel distribution information
Authors: Navaie Keivan
Published: June 2013

In this study, the authors propose a cross‐layer resource allocation scheme for orthogonal frequency multiple access (OFDM) systems based on the subcarrier channel distribution information (CDI). Here, in contrast to most of the previous works, the authors consider practical discrete rate adaptation in which rate is adapted using a predefined set of modulation levels corresponding to fading regions. The OFDM system supports ‘streaming traffic’ that requires a minimum guaranteed average delay, as well as ‘elastic traffic’ with flexible rate requirements. The main objective is to maximise the total average transmission rate of elastic users, whereas the average delay is also guaranteed for streaming traffic, all subject to the maximum average transmission power constraint. The authors then propose an algorithm which finds suboptimal fading regions, as well as suboptimal subcarrier allocation based on dual decomposition method. In the proposed method, the solution of optimisation problem remains valid, until the channel distributions and/or the packet arrival and packet length distribution of the users are changed. This significantly reduces the computational complexity since there is no need to solve the optimisation problem for each channel side information (CSI) feedback. The proposed scheme also reduces the signalling overhead since corresponding to each user the CSI is required only for the assigned subcarriers. Particularly, the proposed method is suitable for cases in which wireless channel distributions is not changed, or can be simply estimated, for example, cases where a parametric distribution is fixed and only statistics such as average and variance is changed. Using simulations, the authors study the impact of number of fading regions and packet arrival rate on the achievable rate of elastic traffic.
Dynamic resource allocation with precoding and joint coding scheme for limited feedback‐based wireless multi‐antenna multicast system
Authors: Chen Lei , Wang Xiaoxiang , He Gaoning
Published: June 2013

In conventional multicast scheme (CMS), the total throughput of multicast group is constrained by the user with the worst channel quality. In order to overcome this problem of limited throughput, the authors introduce a resource allocation algorithm by exploiting layered coding combined with erasure correction coding for multicast services in the downlink of orthogonal frequency‐division multiple access‐based multi‐antenna system. To reduce the feedback overhead of uplink, the authors design a novel transmission scheme with limited feedback. Then, the joint subcarrier and power allocation problem for the data of base layer and enhancement layers are formulated, which is shown to be non‐deterministic polynomial‐ hard. Hence, in order to reduce the computational complexity, they propose a three‐phase suboptimal algorithm. The algorithm is designed to maximise the system throughput, whereas at the same time guarantee the quality of services (QoS) requirements of all multicast groups. It is composed of precoding scheme, proportional fairness subcarrier allocation algorithm and modified water‐filling power allocation algorithm with QoS guarantees (MWF‐Q). To further decrease the complexity of MWF‐Q, a power allocation algorithm with increased fixed power allocation algorithm with QoS guarantees is introduced. Simulation results show that the proposed algorithms based on limited feedback scheme significantly outperform CMS and any other existing algorithm with full feedback. Moreover, the proposed scheme can efficiently reduce 50% of the full feedback overhead.
Evaluation of the R&R and the compatibility index for non-independent measurements
Authors: Garcia-Benadí A. , Molino-Minero-Re E. , del Río-Fernández J. , Mànuel-Lázaro A.
Published: June 2013

This paper describes the methodology of the compatibility criteria
En and the methodology of repeatability
and reproducibility (R&R) throught the average and range method. With this paper
we will use the methodology R&R for the evaluation of the compatibility criteria
between the staff of the laboratories, where independent measurements are not insured.
Identities from infinite-dimensional symmetries of Herglotz variational functional
Authors: Georgieva Bogdana , Bodurov Theodore
Published: June 2013

This paper formulates and proves a theorem which provides the identities corresponding to infinite-dimensional symmetry groups of the functional defined by the generalized variational principle of Herglotz in the case of several independent variables. It contains the classical second Noether theorem as a special case. The equations satisfied by the extrema of this functional, when the Lagrangian density depends on first and second order partial derivatives of the argument functions, are found. We apply the theorem to find two new identities satisfied by the four-potential of the electromagnetic field propagating in a conductive medium. We also obtain an identity corresponding to a gauge symmetry of the Klein-Gordon equation with dissipation/generation. This identity becomes a continuity law when the wave function is a solution of this equation.
Structure determination of ultra dense magnesium borohydride: A first-principles study
Authors: Fan Jing , Duan Defang , Jin Xilian , Bao Kuo , Liu Bingbing , Cui Tian
Published: June 2013

Magnesium borohydride (Mg(BH4)2) is one of the potential hydrogen storage materials. Recently, two experiments [Y. Filinchuk, B. Richter, T. R. Jensen, V. Dmitriev, D. Chernyshov, and H. Hagemann, Angew. Chem., Int. Ed. 50, 11162 (2011);10.1002/anie.201100675 L. George, V. Drozd, and S. K. Saxena, J. Phys. Chem. C 113, 486 (2009)10.1021/jp807842t] found that α-Mg(BH4)2 can irreversibly be transformed to an ultra dense δ-Mg(BH4)2 under high pressure. Its volumetric hydrogen content at ambient pressure (147 g/cm3) exceeds twice of DOE's (U.S. Department of Energy) target (70 g/cm3) and that of α-Mg(BH4)2 (117 g/cm3) by 20%. In this study, the experimentally proposed P42nm structure of δ-phase has been found to be dynamically unstable. A new Fddd structure has been reported as a good candidate of δ-phase instead. Its enthalpy from 0 to 12 GPa is much lower than P42nm structure and the simulated X-ray diffraction spectrum is in satisfied agreement with previous experiments. In addition, the previously proposed P-3m1 structure, which is denser than Fddd, is found to be a candidate of ɛ-phase due to the agreement of Raman shifts.
Rota-Baxter 3-Lie algebras
Authors: Bai RuiPu , Guo Li , Li Jiaqian , Wu Yong
Published: June 2013

In this paper, we introduce the concepts of a Rota-Baxter operator and differential operator with weights on an n-algebra. We then focus on Rota-Baxter 3-Lie algebras and show that they can be derived from Rota-Baxter Lie algebras and pre-Lie algebras and from Rota-Baxter commutative associative algebras with derivations. We also establish the inheritance property of Rota-Baxter 3-Lie algebras.
On strongly interacting internal waves in a rotating ocean and coupled Ostrovsky equations
Authors: Alias A. , Grimshaw R. H. J. , Khusnutdinova K. R.
Published: June 2013

In the weakly nonlinear limit, oceanic internal solitary waves for a single linear long wave mode are described by the KdV equation, extended to the Ostrovsky equation in the presence of background rotation. In this paper we consider the scenario when two different linear long wave modes have nearly coincident phase speeds and show that the appropriate model is a system of two coupled Ostrovsky equations. These are systematically derived for a density-stratified ocean. Some preliminary numerical simulations are reported which show that, in the generic case, initial solitary-like waves are destroyed and replaced by two coupled nonlinear wave packets, being the counterpart of the same phenomenon in the single Ostrovsky equation.
Growth and characterization of co-evaporated Cu2ZnSnS4 thin films
Authors: Chalapathi U. , Uthanna S. , Sundara Raja V.
Published: June 2013

Thin films of Cu2ZnSnS4 (CZTS), a potential absorber layer for thin film heterojunction solar cells, have been successfully grown on soda-lime glass substrates held at 450 ∘C using co-evaporation technique. Cu, Sn, ZnS, and S, kept in molybdenum boats, are used as the source materials. The as-deposited films are annealed at 550 ∘C for an hour under sulphur atmosphere to improve the crystallinity and sulphur content. Films exhibited kesterite structure with (112) preferred orientation. The lattice parameters are found to be a = 0.544 nm and c = 1.098 nm. The crystallite size increased from 90 nm to 105 nm on annealing at 550 ∘C. Raman spectroscopy analysis of annealed films confirmed the CZTS phase formation with Cu2S as the secondary phase. The grain size is found to increase from 0.5 μm to 0.8 μm on annealing at 550 ∘C. The direct band gap of the annealed films is found to be 1.55 eV. The films are p-type in nature.
Synthesis and characterization of lead-free 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 ceramic
Authors: Coondoo Indrani , Panwar Neeraj , Amorín Harvey , Alguero Miguel , Kholkin A. L.
Published: June 2013

Polycrystalline sample of lead-free 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 ceramic has been synthesized by solid state reaction method. Single-phase perovskite structure with rhombohedral symmetry was confirmed by x-ray diffraction. Temperature dependent dielectric permittivity studies demonstrated frequency independent behavior, indicating that the studied sample was not a typical relaxor ferroelectric. A polymorphic phase transition between rhombohedral and tetragonal phase was noticed near room temperature followed by a tetragonal to cubic transition with 97 °C as the temperature of maximum permittivity. The macroscopic values of d33 and d31 were ∼350 pC/N and −141 pm/V, whereas the electromechanical coupling factors kp and kt were 44.5% and 41.6%, respectively. Bulk P-E hysteresis loop was obtained with saturation polarization 11 μC/cm2 and coercive field ∼4 kV/cm. Distinct polarization contrast with a complex mosaic-like domain structure was observed in the out-of-plane mode of piezoresponse force microscopy. The domain width and the correlation length were estimated to be nearly 2 μm and 827 nm, respectively. Local hysteresis loop with apparent coercive voltage, Vc = 15.8 V, was observed.
Doping and compensation in Nb-doped anatase and rutile TiO2
Authors: Lee Hsin-Yi , Robertson John
Published: June 2013

The substitutional Nb donor states in anatase and rutile TiO2 are calculated using the screened exchange hybrid density functional. The calculations find that Nb forms a shallow state in anatase and a deep state in rutile TiO2, as in experiment. Donors in anatase are found to become compensated in O-rich conditions because oxygen interstitial acceptors acquire a negative formation energy for Fermi energies high in the band gap. O-poor conditions permit doping, not by creating O vacancies but by inhibiting the formation of oxygen interstitials which compensate doping.
Spiral metamaterial for active tuning of optical activity
Authors: Kan Tetsuo , Isozaki Akihiro , Kanda Natsuki , Nemoto Natsuki , Konishi Kuniaki , Kuwata-Gonokami Makoto , Matsumoto Kiyoshi , Shimoyama Isao
Published: June 2013

We propose an electrostatically actuated spiral structure as a metamaterial for circularly polarized light in the terahertz (THz) frequency range. An array of planar spiral structures was fabricated with micro electro mechanical system technology, and the geometry of the structures can be changed by electrostatic actuation. The actuation transforms the planar spirals into three-dimensional helices, resulting in optical activity in which the differential polarization response of the material depends on whether the incident light is left- or right-circularly polarized. THz spectroscopy confirmed that the optical activity can be tuned with the proposed structures.
Role of intrinsic molecular dipole in energy level alignment at organic interfaces
Authors: Lindell Linda , Çakır Deniz , Brocks Geert , Fahlman Mats , Braun Slawomir
Published: June 2013

The energy level alignment in metal-organic and organic-organic junctions of the widely used materials tris-(8-hydroxyquinoline)aluminum (Alq3) and 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA) is investigated. The measured alignment schemes for single and bilayer films of Alq3 and NTCDA are interpreted with the integer charge transfer (ICT) model. Single layer films of Alq3 feature a constant vacuum level shift of ∼0.2–0.4 eV in the absence of charge transfer across the interface. This finding is attributed to the intrinsic dipole of the Alq3 molecule and (partial) ordering of the molecules at the interfaces. The vacuum level shift changes the onset of Fermi level pinning, as it changes the energy needed for equilibrium charge transfer across the interface.
Inhomogeneous Si-doping of gold-seeded InAs nanowires grown by molecular beam epitaxy
Authors: Rolland Chloé , Caroff Philippe , Coinon Christophe , Wallart Xavier , Leturcq Renaud
Published: June 2013

We have investigated in situ Si doping of InAs nanowires grown by molecular beam epitaxy from gold seeds. The effectiveness of n-type doping is confirmed by electrical measurements showing an increase of the electron density with the Si flux. We also observe an increase of the electron density along the nanowires from the tip to the base, attributed to the dopant incorporation on the nanowire facets whereas no detectable incorporation occurs through the seed. Furthermore, the Si incorporation strongly influences the lateral growth of the nanowires without giving rise to significant tapering, revealing the complex interplay between axial and lateral growth.
Direct measurement of piezoelectric shear coefficient
Authors: Malakooti Mohammad H. , Sodano Henry A.
Published: June 2013

Piezoelectric materials exhibit electromechanical coupling which has led to their widespread application for sensors, actuators, and energy harvesters. These materials possess anisotropic behavior with the shear coefficient, and have the largest electromechanical coupling coefficient. However, the shear mode is difficult to measure with existing techniques and thus has not been fully capitalized upon in recent devices. Better understanding of the full shear response with respect to the driving electric field would significantly help the design of optimized piezoelectric shear devices. Here, a simple and low cost direct measurement method based on digital image correlation is developed to characterize the shear response of piezoelectric materials and its nonlinear behavior as a function of external field. The piezoelectric shear coefficient (d15) of a commercial shear plate actuator is investigated in both bipolar and unipolar electric fields. Two different nonlinearities and hysteresis behaviors of the actuators were observed, and the relation between the driving field amplitude and the corresponding d15 coefficient is determined. Moreover, the measured transverse displacement of the plate actuator in simple shear condition is validated through a laser interferometry technique.
Acousto-electric transport in epitaxial monolayer graphene on SiC
Authors: Santos P. V. , Schumann T. , Oliveira M. H. , Lopes J. M. J. , Riechert H.
Published: June 2013

We report on the piezoelectric excitation and acoustic charge transport by gigahertz surface acoustic waves (SAWs) in epitaxial monolayer graphene (EG) on SiC. The GHz SAWs frequencies were generated by interdigital transducers fabricated on a piezoelectric island on the SiC substrate. Acoustic transport studies in a Hall bar geometry show that the propagating SAW field transports carriers in EG, the transport direction being determined by the direction of the acoustic beam. Carrier transport is driven by drift in the piezoelectric field induced by the SAW in EG.
Giant optical splitting in the spin-states assisting a sharp magnetic switching in GdN thin films
Authors: Vidyasagar R. , Kita T. , Sakurai T. , Ohta H.
Published: June 2013

The spin-states splitting and spin ordering in the band structure of GdN thin films have been studied using optical absorbance spectroscopy and magnetometer. Remarkably, the optical absorbance measurements indicate a giant splitting in the spin-states near-infrared frequency regime, through which the spin-up and spin-down states of the GdN films have been evaluated. Both the spin-up and spin-down states split subsequently wider, which attributes to a combining effect from the nitrogen vacancies, and the population of electronic states pertaining to the spins associated with 4f states of Gd3+ ions. While spin-splitting energy enhances, magnetic-hysteresis loops suggest a sharp magnetic switching feature.
Possibilities and challenges in regional forest biomass utilization
Authors: Laihanen M. , Karhunen A. , Ranta T.
Published: June 2013

In Finland, it is estimated that forest biomass will be the main source of bioenergy when meeting the national target of 38% renewable from final energy consumption by 2020. Achieving this target means that concrete actions on increasing the use of renewable energy have to take place in regional level. The aim of this was to introduce a questionnaire study, which highlights concrete local possibilities and challenges in utilization of forest biomass. Volume of regional forest biomass business and production prices was also studied. The questionnaire was sent for actual participants operating in forest biomass production, supply, and end-use. This study gives information about operation methods and bottlenecks in forest biomass markets for all stakeholder groups interested in use and production of forest biomass. Opinions, valuable references, and concrete examples could be applied into practice by actual actors working with forest biomass. Background information for this kind of study is sufficient data about regional use and availability of forest biomass.
Spontaneous B-site order and metallic ferrimagnetism in LaSrVMoO6 grown by pulsed laser deposition
Authors: Chakraverty S. , Yu X. Z. , Kawasaki M. , Tokura Y. , Hwang H. Y.
Published: June 2013

We have investigated the structure and physical properties of single phase LaSrVMoO6 thin films grown by pulsed-laser deposition on (111) perovskite substrates. Despite the use of a mixed target, a high degree of ordering of V and Mo ions in the double perovskite structure has been observed using x-ray diffraction, reflection high-energy electron diffraction, and high-angle annular dark-field scanning transmission electron microscopy. Unlike previous reports, we find ferrimagnetic ordering of V and Mo spins at ∼25 K, with saturation magnetization ∼0.7 μB/formula unit. Furthermore, the films are highly metallic with resistivity ∼78 μΩ cm at 2 K.
Development of interspecies testicular germ-cell transplantation in flatfish
Authors: Pacchiarini Tiziana , Sarasquete Carmen , Cabrita Elsa
Published: June 2013

Interspecific testicular germ cell (TGC) transplantation was investigated in two commercial flatfish species. Testes from donor species (Senegalese sole) were evaluated using classical histological techniques (haematoxylin–eosin staining and haematoxylin–light green–orange G–acid fuchsine staining), in situ hybridisation and immunohistochemical analysis. Both Ssvasa1–2 mRNAs and SsVasa protein allowed the characterisation of TGCs, confirming the usefulness of the vasa gene in the detection of Senegalese sole TGCs. Xenogenic transplants were carried out using TGCs from one-year-old Senegalese sole into turbot larvae. Propidium iodide–SYBR-14 and 4′,6′-diamidino-2-phenylindole (DAPI) staining showed that 87.98% of the extracted testicular cells were viable for microinjection and that 15.63% of the total recovered cells were spermatogonia. The vasa gene was characterised in turbot recipients using cDNA cloning. Smvasa mRNA was confirmed as a germ cell-specific molecular marker in this species. Smvasa expression analysis during turbot ontogeny was carried out before Senegalese sole TGC transplants into turbot larvae. Turbot larvae at 18 days after hatching (DAH) proved to be susceptible to manipulation procedures. High survival rates (83.75 ± 15.90 – 100%) were obtained for turbot larvae at 27, 34 and 42 DAH. These data highlight the huge potential of this species for transplantation studies. Quantitative PCR was employed to detect Senegalese sole vasa mRNAs (Ssvasa1–2) in the recipient turbot larvae. The Ssvasa mRNAs showed a significant increase in relative expression in 42-DAH microinjected larvae three weeks after treatment, showing the proliferation of Senegalese sole spermatogonia in transplanted turbot larvae.
Dust storms – what do they really cost?
Authors: Tozer P. , Leys J.
Published: June 2013

Dust storms are frequent in Australia and can have a large impact on the soil resource, the economy and people. There have been few economic studies of the impact of wind erosion worldwide and only one in Australia before this study. While wind erosion impacts on the soil resource at the point of the erosion, the level of economic impact rises as the population and associated infrastructure affected by dust increases. This study estimates the impact on the economy of the state of New South Wales of a single large dust storm called Red Dawn that passed over the eastern coast of Australia on 23 September 2009. Estimates for rural and urban areas are presented with both on- and off-site costs evaluated. The estimated cost is A$299 million (with a range of A$293–A$313 million) with most of the cost being associated with household cleaning and associated activities. The dust storm also impacted on many cities on the coast of the state of Queensland, but their costs are not included in this study. This study demonstrates some, but not all, of the major economic costs associated with wind erosion in Australia. Given the annual average cost of dust storms it is suggested that A$9 million per year would be a conservative estimate of the level of investment required in rural areas for dust mitigation strategies, based on improved land management that could be justified to achieve a positive impact on soil condition and reduce economic losses in rural towns and the more populous coastal cities.
Andrographolide derivatives inhibit guanine nucleotide exchange and abrogate oncogenic Ras function
Authors: Hocker Harrison J. , Cho Kwang-Jin , Chen Chung-Ying K. , Rambahal Nandini , Sagineedu Sreenivasa Rao , Shaari Khozirah , Stanslas Johnson , Hancock John F. , Gorfe Alemayehu A.
Published: June 2013

Aberrant signaling by oncogenic mutant rat sarcoma (Ras) proteins occurs in ∼15% of all human tumors, yet direct inhibition of Ras by small molecules has remained elusive. Recently, several small-molecule ligands have been discovered that directly bind Ras and inhibit its function by interfering with exchange factor binding. However, it is unclear whether, or how, these ligands could lead to drugs that act against constitutively active oncogenic mutant Ras. Using a dynamics-based pocket identification scheme, ensemble docking, and innovative cell-based assays, here we show that andrographolide (AGP)—a bicyclic diterpenoid lactone isolated from
Andrographis paniculata
—and its benzylidene derivatives bind to transient pockets on Kirsten-Ras (K-Ras) and inhibit GDP–GTP exchange. As expected for inhibitors of exchange factor binding, AGP derivatives reduced GTP loading of wild-type K-Ras in response to acute EGF stimulation with a concomitant reduction in MAPK activation. Remarkably, however, prolonged treatment with AGP derivatives also reduced GTP loading of, and signal transmission by, oncogenic mutant K-RasG12V. In sum, the combined analysis of our computational and cell biology results show that AGP derivatives directly bind Ras, block GDP–GTP exchange, and inhibit both wild-type and oncogenic K-Ras signaling. Importantly, our findings not only show that nucleotide exchange factors are required for oncogenic Ras signaling but also demonstrate that inhibiting nucleotide exchange is a valid approach to abrogating the function of oncogenic mutant Ras.
Isaac: ultra-fast whole-genome secondary analysis on Illumina sequencing platforms
Authors: Raczy Come , Petrovski Roman , Saunders Christopher T. , Chorny Ilya , Kruglyak Semyon , Margulies Elliott H. , Chuang Han-Yu , Källberg Morten , Kumar Swathi A. , Liao Arnold , Little Kristina M. , Strömberg Michael P. , Tanner Stephen W.
Published: June 2013

Summary: An ultrafast DNA sequence aligner (Isaac Genome Alignment Software) that takes advantage of high-memory hardware (>48 GB) and variant caller (Isaac Variant Caller) have been developed. We demonstrate that our combined pipeline (Isaac) is four to five times faster than BWA + GATK on equivalent hardware, with comparable accuracy as measured by trio conflict rates and sensitivity. We further show that Isaac is effective in the detection of disease-causing variants and can easily/economically be run on commodity hardware.

Availability: Isaac has an open source license and can be obtained at https://github.com/sequencing.

Contact:  craczy@illumina.com

Supplementary information:  Supplementary data are available at Bioinformatics online.
Whole-Genome rVISTA: a tool to determine enrichment of transcription factor binding sites in gene promoters from transcriptomic data
Authors: Dubchak Inna , Munoz Matthew , Poliakov Alexandre , Salomonis Nathan , Minovitsky Simon , Bodmer Rolf , Zambon Alexander C.
Published: June 2013

Summary: We have developed a web-based query tool, Whole-Genome rVISTA (WGRV), that determines enrichment of transcription factors (TFs) and associated target genes in sets of co-regulated genes. WGRV enables users to query databases containing pre-computed genome coordinates of evolutionarily conserved transcription factor binding sites in the proximal promoters (from 100 bp to 5 kb upstream) of human, mouse and Drosophila genomes. TF binding sites are based on position-weight matrices from the TRANSFAC Professional database. For a given set of co-regulated genes, WGRV returns statistically enriched and evolutionarily conserved binding sites, mapped by the regulatory VISTA (rVISTA) algorithm. Users can then retrieve a list of genes from the query set containing the enriched TF binding sites and their location in the query set promoters. Results are exported in a BED format for rapid visualization in the UCSC genome browser. Flat files of mapped conserved sites and their genomic coordinates are also available for analysis with stand-alone software.

Availability:  http://genome.lbl.gov/cgi-bin/WGRVistaInputCommon.pl.

Contact:  azambon@ucsd.edu or ildubchak@lbl.gov

Supplementary information:  Supplementary data are available at Bioinformatics online.
How to (or not to) … measure performance against the Abuja target for public health expenditure
Authors: Witter Sophie , Jones Alex , Ensor Tim
Published: June 2013

In 2001, African heads of state committed ‘to set a target of allocating at least 15% of our annual budget to the improvement of the health sector’. This target has since been used as a benchmark to hold governments accountable. However, it was never followed by a set of guidelines as to how it should be measured in practice. This article sets out some of the areas of ambiguity and argues for an interpretation which focuses on actual expenditure, rather than budgets (which are theoretical), and which captures areas of spending that are subject to government discretion. These are largely domestic sources, but include budget support, which is externally derived but subject to Ministry of Finance sectoral allocation. Theoretical and practical arguments in favour of this recommendation are recommended using a case study from Sierra Leone. It is recommended that all discretionary spending by government is included in the numerator and denominator when calculating performance against the target, including spending by all ministries on health, social health insurance payments, debt relief funds and budget support. Conversely, all forms of private payment and earmarked aid should be excluded. The authors argue that the target, while an important vehicle for tracking political commitment to the sector, should be assessed intelligently by governments, which have legitimate wider public finance objectives of maximizing overall social returns, and should be complemented by a wider range of indicators, to avoid distortions.
Acute Normovolemic Hemodilution in the Pig Is Associated with Renal Tissue Edema, Impaired Renal Microvascular Oxygenation, and Functional Loss
Authors: Konrad Franziska M. , Mik Egbert G. , Bodmer Sander I. A. , Ates N. Bahar , Willems Henriëtte F. E. M. , Klingel Karin , de Geus Hilde R. H. , Stolker Robert Jan , Johannes Tanja
Published: June 2013

Background:

The authors investigated the impact of acute normovolemic hemodilution (ANH) on intrarenal oxygenation and its functional short-term consequences in pigs.

Methods:

Renal microvascular oxygenation (µPo
2) was measured in cortex, outer and inner medulla via three implanted optical fibers by oxygen-dependent quenching of phosphorescence. Besides systemic hemodynamics, renal function, histopathology, and hypoxia-inducible factor-1α expression were determined. ANH was performed in n = 18 pigs with either colloids (hydroxyethyl starch 6% 130/0.4) or crystalloids (full electrolyte solution), in three steps from a hematocrit of 30% at baseline to a hematocrit of 15% (H3).

Results:

ANH with crystalloids decreased µPo
2 in cortex and outer medulla approximately by 65% (P < 0.05) and in inner medulla by 30% (P < 0.05) from baseline to H3. In contrast, µPo
2 remained unaltered during ANH with colloids. Furthermore, renal function decreased by approximately 45% from baseline to H3 (P < 0.05) only in the crystalloid group. Three times more volume of crystalloids was administered compared with the colloid group. Alterations in systemic and renal regional hemodynamics, oxygen delivery and oxygen consumption during ANH, gave no obvious explanation for the deterioration of µPo
2 in the crystalloid group. However, ANH with crystalloids was associated with the highest formation of renal tissue edema and the highest expression of hypoxia-inducible factor-1α, which was mainly localized in distal convoluted tubules.

Conclusions:

ANH to a hematocrit of 15% statistically significantly impaired µPo
2 and renal function in the crystalloid group. Less tissue edema formation and an unimpaired renal µPo
2 in the colloid group might account for a preserved renal function.
Relationship between Volume and Survival in Closed Intensive Care Units Is Weak and Apparent Only in Mechanically Ventilated Patients
Authors: Fernández Rafael , Altaba Susana , Cabre Lluis , Lacueva Victoria , Santos Antonio , Solsona Jose-Felipe , Añon Jose-Manuel , Catalan Rosa-Maria , Gutierrez Maria-Jose , Fernandez-Cid Ramon , Gomez-Tello Vicente , Curiel Emilio , Fernandez-Mondejar Enrique , Oliva Joan-Carles
Published: June 2013

Background:

Recent studies have found an association between increased volume and increased intensive care unit (ICU) survival; however, this association might not hold true in ICUs with permanent intensivist coverage. Our objective was to determine whether ICU volume correlates with survival in the Spanish healthcare system.

Methods:

Post hoc analysis of a prospective study of all patients admitted to 29 ICUs during 3 months. At ICU discharge, the authors recorded demographic variables, severity score, and specific ICU treatments. Follow-up variables included ICU readmission and hospital mortality. Statistics include logistic multivariate analyses for hospital mortality according to quartiles of volume of patients.

Results:

The authors studied 4,001 patients with a mean predicted risk of death of 23% (range at hospital level: 14–46%). Observed hospital mortality was 19% (range at hospital level: 11–35%), resulting in a standardized mortality ratio of 0.81 (range: 0.5–1.3). Among the 1,923 patients needing mechanical ventilation, the predicted risk of death was 32% (14–60%) and observed hospital mortality was 30% (12–61%), resulting in a standardized mortality ratio of 0.96 (0.5–1.7). The authors found no correlation between standardized mortality ratio and ICU volume in the entire population or in mechanically ventilated patients. Only mechanically ventilated patients in very low-volume ICUs had slightly worse outcome.

Conclusion:

In the currently studied healthcare system characterized by 24/7 intensivist coverage, the authors found wide variability in outcome among ICUs even after adjusting for severity of illness but no relationship between ICU volume and outcome. Only mechanically ventilated patients in very low-volume centers had slightly worse outcomes.
Environmental transmission of a personality trait: foster parent exploration behaviour predicts offspring exploration behaviour in zebra finches
Authors: Schuett Wiebke , Dall Sasha R. X. , Wilson Alastair J. , Royle Nick J.
Published: June 2013

Consistent behavioural differences among individuals are common in many species and can have important effects on offspring fitness. To understand such ‘personality’ variation, it is important to determine the mode of inheritance, but this has been quantified for only a few species. Here, we report results from a breeding experiment in captive zebra finches,
Taeniopygia guttata
, in which we cross-fostered offspring to disentangle the importance of genetic and non-genetic transmission of behaviour. Genetic and foster-parents’ exploratory type was measured in a novel environment pre-breeding and offspring exploratory type was assessed at adulthood. Offspring exploratory type was predicted by the exploratory behaviour of the foster but not the genetic parents, whereas offspring size was predicted by genetic but not foster-parents’ size. Other aspects of the social environment, such as rearing regime (uni- versus biparental), hatching position, brood size or an individual's sex did not influence offspring exploration. Our results therefore indicate that non-genetic transmission of behaviour can play an important role in shaping animal personality variation.
Spermatophore consumption in a cephalopod
Authors: Wegener Benjamin J. , Stuart-Fox Devi , Norman Mark D. , Wong Bob B. M.
Published: June 2013

An individual's gametes can represent a nourishing food source for a manipulative mate. Here, we provide evidence of ejaculate and sperm consumption in a cephalopod. Through labelling male spermatophores with
14
C radiolabel, we found that female squid,
Sepiadarium austrinum
, consumed the spermatophores of their partners and directed the nutrients received into both somatic maintenance and egg production. We further show that in this species—where fertilization occurs externally in the female's buccal cavity—sperm storage is short-term (less than 21 days). The combination of female spermatophore consumption and short-term external sperm storage has the potential to exert strong selection on male ejaculates and reproductive strategies.
Genome-wide evolutionary response to a heat wave in
Drosophila
Authors: Rodríguez-Trelles Francisco , Tarrío Rosa , Santos Mauro
Published: June 2013

Extreme climatic events can substantially affect organismal performance and Darwinian fitness. In April 2011, a strong heat wave struck extensive geographical areas of the world, including Western Europe. At that time, we happened to resume and extend a long-term time series of seasonal genetic data in the widespread fly
Drosophila subobscura
, which provided a unique opportunity to quantify the intensity of the genetic perturbation caused by the heat wave. We show that the spring 2011 genetic constitution of the populations transiently shifted to summer-like frequencies, and that the magnitude of the genetic anomaly quantitatively matched the temperature anomaly. The results provide compelling evidence that direct effects of rising temperature are driving adaptive evolutionary shifts, and also suggest a strong genetic resilience in this species.
The effect of sampling rate on observed statistics in a correlated random walk
Authors: Rosser G. , Fletcher A. G. , Maini P. K. , Baker R. E.
Published: June 2013

Tracking the movement of individual cells or animals can provide important information about their motile behaviour, with key examples including migrating birds, foraging mammals and bacterial chemotaxis. In many experimental protocols, observations are recorded with a fixed sampling interval and the continuous underlying motion is approximated as a series of discrete steps. The size of the sampling interval significantly affects the tracking measurements, the statistics computed from observed trajectories, and the inferences drawn. Despite the widespread use of tracking data to investigate motile behaviour, many open questions remain about these effects. We use a correlated random walk model to study the variation with sampling interval of two key quantities of interest: apparent speed and angle change. Two variants of the model are considered, in which reorientations occur instantaneously and with a stationary pause, respectively. We employ stochastic simulations to study the effect of sampling on the distributions of apparent speeds and angle changes, and present novel mathematical analysis in the case of rapid sampling. Our investigation elucidates the complex nature of sampling effects for sampling intervals ranging over many orders of magnitude. Results show that inclusion of a stationary phase significantly alters the observed distributions of both quantities.
Predator confusion is sufficient to evolve swarming behaviour
Authors: Olson Randal S. , Hintze Arend , Dyer Fred C. , Knoester David B. , Adami Christoph
Published: June 2013

Swarming behaviours in animals have been extensively studied owing to their implications for the evolution of cooperation, social cognition and predator–prey dynamics. An important goal of these studies is discerning which evolutionary pressures favour the formation of swarms. One hypothesis is that swarms arise because the presence of multiple moving prey in swarms causes confusion for attacking predators, but it remains unclear how important this selective force is. Using an evolutionary model of a predator–prey system, we show that predator confusion provides a sufficient selection pressure to evolve swarming behaviour in prey. Furthermore, we demonstrate that the evolutionary effect of predator confusion on prey could in turn exert pressure on the structure of the predator's visual field, favouring the frontally oriented, high-resolution visual systems commonly observed in predators that feed on swarming animals. Finally, we provide evidence that when prey evolve swarming in response to predator confusion, there is a change in the shape of the functional response curve describing the predator's consumption rate as prey density increases. Thus, we show that a relatively simple perceptual constraint—predator confusion—could have pervasive evolutionary effects on prey behaviour, predator sensory mechanisms and the ecological interactions between predators and prey.
Buckling morphology of an elastic beam between two parallel lateral constraints: implication for a snake crawling between walls
Authors: Xiao Junfeng , Chen Xi
Published: June 2013

A snake crawling on horizontal surfaces between two parallel walls exhibits a unique wave-like shape, which is different from the normal shape of a snake crawling without constraints. We propose that this intriguing system is analogous to a buckled beam under two lateral constraints. A new theoretical model of beam buckling, which is verified by numerical simulation, is firstly developed to account for the special boundary conditions. Under this theoretical model, the effect of geometrical parameters on the deformation shape, such as the distance between walls, length of the snake and radius of the snake, is examined. The buckling beam model is then applied to explain qualitatively the wave-like shape of the snake.
Self-similar hierarchical honeycombs
Authors: Haghpanah Babak , Oftadeh Ramin , Papadopoulos Jim , Vaziri Ashkan
Published: June 2013

Hierarchical structures are observed in nature, and can be shown to offer superior efficiency. However, the potential advantages of structural hierarchy are not well understood. We extensively explored a bending-dominated model material (i.e. transversely loaded hexagonal honeycomb) which is susceptible to improvement by simple iterative refinement that replaces each three-edge structural node with a smaller hexagon. Using a blend of analytical and numerical techniques, both elastic and plastic properties were explored over a range of loadings and iteration parameters. A wide variety of specific stiffness and specific strengths (up to fourfold increase) were achieved. The results offer insights into the potential value of iterative structural refinement for creating low-density materials with desired properties and function.
Added mass of a circular cylinder oscillating in a free stream
Authors: Konstantinidis Efstathios
Published: June 2013

The fundamental understanding of the added mass phenomenon associated with the motion of a solid body relative to a fluid is revisited. This paper focuses on the two-dimensional flow around a circular cylinder oscillating transversely in a free stream. A virtual experiment reveals that the classical approach to this problem leads to a paradox. The inertial force is derived afresh based on analysis of the motion in a frame of reference attached to the cylinder centroid, which overcomes the paradox in the classical formulation. It is shown that the inertial force depends not only on the acceleration of the cylinder
per se
, but also on the relative motion between body and fluid embodied in a parameter called alpha,
α
, which represents the ratio of the maximum transverse velocity of the cylinder to the free-stream velocity; the induced inertial force is directionally varying and non-harmonic in time depended on the alpha parameter. It is further shown that the component of the inertial force in the transverse direction is negligible for
α
<0.1, increases quadratically for
α
<0.5, and tends asymptotically to the classical result as

, i.e. in still fluid.
Optimal behaviour can violate the principle of regularity
Authors: Trimmer Pete C.
Published: June 2013

Understanding decisions is a fundamental aim of behavioural ecology, psychology and economics. The regularity axiom of utility theory holds that a preference between options should be maintained when other options are made available. Empirical studies have shown that animals violate regularity but this has not been understood from a theoretical perspective, such decisions have therefore been labelled as irrational. Here, I use models of state-dependent behaviour to demonstrate that choices can violate regularity even when behavioural strategies are optimal. I also show that the range of conditions over which regularity should be violated can be larger when options do not always persist into the future. Consequently, utility theory—based on axioms, including transitivity, regularity and the independence of irrelevant alternatives—is undermined, because even alternatives that are never chosen by an animal (in its current state) can be relevant to a decision.
Toxin constraint explains diet choice, survival and population dynamics in a molluscivore shorebird
Authors: van Gils Jan A. , van der Geest Matthijs , Leyrer Jutta , Oudman Thomas , Lok Tamar , Onrust Jeroen , de Fouw Jimmy , van der Heide Tjisse , van den Hout Piet J. , Spaans Bernard , Dekinga Anne , Brugge Maarten , Piersma Theunis
Published: June 2013

Recent insights suggest that predators should include (mildly) toxic prey when non-toxic food is scarce. However, the assumption that toxic prey is energetically as profitable as non-toxic prey misses the possibility that non-toxic prey have other ways to avoid being eaten, such as the formation of an indigestible armature. In that case, predators face a trade-off between avoiding toxins and minimizing indigestible ballast intake. Here, we report on the trophic interactions between a shorebird (red knot,
Calidris canutus canutus
) and its two main bivalve prey, one being mildly toxic but easily digestible, and the other being non-toxic but harder to digest. A novel toxin-based optimal diet model is developed and tested against an existing one that ignores toxin constraints on the basis of data on prey abundance, diet choice, local survival and numbers of red knots at Banc d'Arguin (Mauritania) over 8 years. Observed diet and annual survival rates closely fit the predictions of the toxin-based model, with survival and population size being highest in years when the non-toxic prey is abundant. In the 6 of 8 years when the non-toxic prey is not abundant enough to satisfy the energy requirements, red knots must rely on the toxic alternative.
A Suppressor Screen of the Chimeric AtCNGC11/12 Reveals Residues Important for Intersubunit Interactions of Cyclic Nucleotide-Gated Ion Channels
Authors: Abdel-Hamid Huda , Chin Kimberley , Moeder Wolfgang , Shahinas Dea , Gupta Deepali , Yoshioka Keiko
Published: June 2013

To investigate the structure-function relationship of plant cyclic nucleotide-gated ion channels (CNGCs), we identified a total of 29 mutant alleles of the chimeric AtCNGC11/12 gene that induces multiple defense responses in the Arabidopsis (Arabidopsis thaliana) mutant, constitutive expresser of PR genes22 (cpr22). Based on computational modeling, two new alleles, S100 (AtCNGC11/12:G459R) and S137 (AtCNGC11/12:R381H), were identified as counterparts of human CNGA3 (a human CNGC) mutants. Both mutants lost all cpr22-mediated phenotypes. Transient expression in Nicotiana benthamiana as well as functional complementation in yeast (Saccharomyces cerevisiae) showed that both AtCNGC11/12:G459R and AtCNGC11/12:R381H have alterations in their channel function. Site-directed mutagenesis coupled with fast-protein liquid chromatography using recombinantly expressed C-terminal peptides indicated that both mutations significantly influence subunit stoichiometry to form multimeric channels. This observation was confirmed by bimolecular fluorescence complementation in planta. Taken together, we have identified two residues that are likely important for subunit interaction for plant CNGCs and likely for animal CNGCs as well.