bluuebunny/crossref_metadata_2025 huggingface dataset:
Expulsion of Dust from Young Stellar Clusters
Authors: Grosbøl P. , Dottori H.
Published: March 2013

Young stellar clusters were identified on deep near-infrared images of 6 nearby, grand-design spirals observed with HAWK-I/VLT. A 90% completeness was reached for cluster complexes with MK = −11.5m (corresponding to masses around 104 M⊙) while the linear resolution was around 40 pc. The distribution of clusters in the (H-K)–(J-H) diagrams revealed two groups of clusters. Comparing with Starburst99 model tracks, the groups could be interpreted as one old population of clusters with low extinction and one consisting of young clusters with visual extinction as high as AV = 7m. The clear separation between the two groups suggests a rapid expulsion of dust from the young clusters.

Monte-Carlo models were made assuming a cluster distribution function g(Mc, τ) = Mc−a τ−γ where Mc and τ are cluster mass and age, respectively. Fitting such models to the observed NIR color distributions, it was concluded that the cluster mortality had to be significant with γ = 0.8-1.0. Further, the star formation phase of clusters has to extend over several Myr. Young clusters have high extinctions at least the first 3 Myr but then lose their reddening over a period of around 5 Myr, depending on the exact evolutionary tracks used.
When the Largest Spiral is Formed
Authors: Eufrasio Rafael T. , de Mello Duília F. , Urrutia-Viscarra Fernanda , de Oliveira Claudia Mendes , Dwek Eli
Published: March 2013

We used UV-to-IR archival data to investigate the nature of the giant spiral galaxy, NGC 6872, 65 Mpc away. It belongs to the southern Pavo group and is interacting with a small lenticular galaxy, IC4970. GALEX UV images show a very large part of the galaxy not seen before, making it one of the largest spiral galaxies known, with a physical size greater than 150 kpc. The SED of 17 regions (10 kpc of diameter) across the two arms show a remarkable spatial distribution, as if they were mirror images with respect to their stellar population. However, the last 40 kpc of the northeastern arm are much bluer than any other region of the southwestern one. There is a strong spatial correlation between the NUV luminosity and the distance to the nucleus. The UV data supports the scenario of an interaction at 130 Myr which triggered star formation all over the disk of NGC 6872. The tip of the northeastern arm resembles a tidal dwarf galaxy in the process of formation.
The Resolved Kennicutt-Schmidt Law in Nearby Galaxies
Authors: Momose R. , Koda J. , Kennicutt R. C. , Egusa F. , Okumura S. K. , Calzetti D. , Liu G. , Meyer J. Donovan , Scoville N. Z. , Sawada T. , Kuno N.
Published: March 2013

The Kennicutt-Schmidt law (Schmidt 1959; Kennicutt 1998, hereafter K-S law) is a power law correlation between area averaged star formation rate (ΣSFR) and gas surface density (Σgas). Despite its importance, the physics that underlie this correlation has remained unclear. The power law index, N, is a prime discriminator of the mechanisms that regulate star formation and form the K-S law (e.g. Leroy et al. 2008; Tan 2010). We present a study of the resolved K-S law for 10 nearby disk galaxies using our new CO(1-0) data at 750 and 500 pc resolutions. The CO(1-0) line emission is established as a tracer of the molecular gas column density, and results in a super-linear correlation (N = 1.3 and 1.8). We discuss the cause of the discrepancy between previous studies, and the mechanism of star formation indicated from our new results.
Radiation-driven Feedback to the ISM around AGNs
Authors: Wada Keiichi
Published: March 2013

Although the “donut-like” obscuring molecular torus is often postulated to explain the type-1 and -2 dichotomy in AGNs, its physical origin is still unclear. We propose a plausible mechanism to explain the formation of the geometrically and optically thick torus, i.e. radiation-driven fountain. Using 3-D hydrodynamic simulations including radiative feedback from the central source, taking into account the X-ray heating and radiation pressure on the gas, we found that a vertical circulation of gas is generated in the central few to tens parsecs. Interaction between the non-steady outflows and inflows causes the formation of a geometrically thick torus with internal turbulent motion. As a result, the AGN is obscured for a wide range of solid angles. In a quasi-steady state, the opening angles for the column density toward a black hole < 1023 cm−2 are approximately ± 30° and ± 50° for AGNs with 10% and 1% Eddington luminosity, respectively. Mass inflows through the torus coexist with the outflow and internal turbulent motion, although the average mass accretion rate to the central parsec region is about ten times smaller than the accretion rate required to maintain the assumed AGN luminosity. This implies that relatively luminous AGN activity is intrinsically intermittent or that there are other mechanisms, such as stellar energy feedback, that enhance the mass accretion to the center.
Quenching of Star Formation in Molecular Outflow Host NGC 1266
Authors: Alatalo K. , Nyland K. E. , Graves G. , Deustua S. , Young L. M. , Davis T. A. , Crocker A. F. , Bureau M. , Bayet E. , Blitz L. , Bois M. , Bournaud F. , Cappellari M. , Davies R. L. , de Zeeuw P. T. , Emsellem E. , Khochfar S. , Krajnovic D. , Kuntschner H. , McDermid R. M. , Morganti R. , Naab T. , Oosterloo T. , Sarzi M. , Scott N. , Serra P. , Weijmans A.
Published: March 2013

We detail the rich molecular story of NGC 1266, its serendipitous discovery within the ATLAS3D survey (Cappellari et al. 2011) and how it plays host to an AGN-driven molecular outflow, potentially quenching all of its star formation (SF) within the next 100 Myr. While major mergers appear to play a role in instigating outflows in other systems, deep imaging of NGC 1266 as well as stellar kinematic observations from SAURON, have failed to provide evidence that NGC 1266 has recently been involved in a major interaction. The molecular gas and the instantaneous SF tracers indicate that the current sites of star formation are located in a hypercompact disk within 200 pc of the nucleus (Fig. 1; SF rate ≈ 2 M⊙ yr−1). On the other hand, tracers of recent star formation, such as the Hβ absorption map from SAURON and stellar population analysis show that the young stars are distributed throughout a larger area of the galaxy than current star formation. As the AGN at the center of NGC 1266 continues to drive cold gas out of the galaxy, we expect star formation rates to decline as the star formation is ultimately quenched. Thus, NGC 1266 is in the midst of a key portion of its evolution and continued studies of this unique galaxy may help improve our understanding of how galaxies transition from the blue to the red sequence (Alatalo et al. 2011).
Detecting Gas Outflows in Type-2 AGNs Selected from the Sloan Digital Sky Survey
Authors: Bae Hyun-Jin , Woo Jong-Hak , Oh Semyeong
Published: March 2013

Energetic outflow from active galactic nuclei (AGNs) may play a critical role in galaxy evolution (e.g., Silk & Rees 1998). We present a velocity diagnostic for detecting gas outflow in the narrow-line region of Type-2 AGNs using line-of-sight velocity offsets of the [O iii] λ5007 and Hα emission lines with respect to the systemic velocity of stars in host galaxies (See Figure 1). We apply the diagnostics to nearby galaxies at 0.02 < z < 0.05, 3775 AGN-host and 907 star-forming galaxies as a comparison sample, which are selected from the Sloan Digital Sky Survey DR7. After obtaining a best-fit stellar population model for the continuum and a systemic velocity based on stellar lines, we subtract the stellar component to measure velocity offsets of each emission line. We find a sample of 169 AGN-host galaxies with outflow signatures, displaying a larger velocity shift of [O iii] than that of Hα, as expected in a decelerating outflow model (Komossa et al. 2008). We find that the offset velocity of [O iii] increases with Eddington ratio, suggesting that gas outflow depends on the energetics of AGN.
AGN feedback on the ISM of 3C 236
Authors: Labiano A. , García-Burillo S. , Combes F. , Usero A. , Soria-Ruiz R. , Tremblay G. , Neri R. , Fuente A. , Morganti R. , Oosterloo T.
Published: March 2013

We have carried out 1mm/3mm continuum and 12CO(2−1) line high resolution observations to identify the footprints of AGN feedback on 3C 236. The CO emission comes from a spatially resolved disk characterized by a regular rotating pattern. Within the limits imposed by the sensitivity and velocity coverage of our data, we do not detect any outflow signatures in the cold molecular gas. Re-inspection of optical and IR spectra, shows the presence of a previously unknown ionized gas outflow. The star-formation efficiency in 3C 236, is consistent with the value measured in normal galaxies, which follow the canonical Kennicutt-Schmidt law. This result, confirmed to hold in other young radio sources examined in this work, is in stark contrast with the factor of 10–50 lower SFE that has been claimed to characterize evolved powerful radio galaxies. The recent reactivation of the AGN in 3C 236 is a likely explanation for the early evolutionary status of its molecular disk.
A 22μm selected sample from WISE and SDSS spectra catalogs
Authors: Wen Xiao-Qing , Yin Hong-Wei
Published: March 2013

We cross-matched Wide-field Infrared Survey Explorer sources with the Sloan Digital Sky Survey galaxy spectroscopic catalog within 6 arcsec to produce 182798 galaxies with 22 μm signal to noise > 3. The different redshift bins of the sample show that the rest-frame 22μm luminosities increase with redshift, for rest-frame 22μm luminosities in the range of 106 − 1012 L⊙. The infrared sample is located in the blue sequence. The Seyfert fraction increases with redshift more obviously in the IR sample than in an optical control sample. The Seyfert fraction increases significantly with increasing rest-frame 22 μm luminosity below 1011 L⊙.
Complexity and theories of change in international politics
Authors: Gunitsky Seva
Published: March 2013

This article examines how the principles of complex systems can illuminate recurring mechanisms of change in theories of international relations. It applies the logic of complex systems to two specific puzzles in international politics – the problem of theorizing change in structural realism, and the dynamics of cross-border democratic diffusion. In the first case, by shifting the analysis of anarchy's consequences from state behavior to state attributes, complex systems can illustrate the sources of domestic and international transformations embedded in structural theories. This approach offers a way to think about democratization as a global process of interstate competition and socialization driven by the pressures of anarchy. In the second case, the principles of co-adaptation in complex systems can help reframe diffusion not as the unilinear spread of democracy but as the interplay of self-reinforcing and self-dampening dynamics, whose interaction shapes both actor expectations and democratic outcomes. In both cases, complex systems serve a limited but useful role; although not conducive to theory creation, the approach provides a useful analytical prism for examining patterns of change and continuity in global processes, and highlights concrete ways of improving models of transformations in international politics.
TRANSITIVE PRIMAL INFON LOGIC
Authors: COTRINI CARLOS , GUREVICH YURI
Published: March 2013

Primal infon logic was introduced in 2009 in connection with access control. In addition to traditional logic constructs, it contains unary connectives p said indispensable in the intended access control applications. Propositional primal infon logic is decidable in linear time, yet suffices for many common access control scenarios. The most obvious limitation on its expressivity is the failure of the transitivity law for implication: $x \to y$ and $y \to z$ do not necessarily yield $x \to z$. Here we introduce and investigate equiexpressive “transitive” extensions TPIL and TPIL* of propositional primal infon logic as well as their quote-free fragments TPIL0 and TPIL0* respectively. We prove the subformula property for TPIL0* and a similar property for TPIL*; we define Kripke models for the four logics and prove the corresponding soundness-and-completeness theorems; we show that, in all these logics, satisfiable formulas have small models; but our main result is a quadratic-time derivation algorithm for TPIL*.
Regulation of cytochrome P450 2e1 expression by ethanol: role of oxidative stress-mediated pkc/jnk/sp1 pathway
Authors: Jin M , Ande A , Kumar A , Kumar S
Published: March 2013

CYP2E1 metabolizes ethanol leading to production of reactive oxygen species (ROS) and acetaldehyde, which are known to cause not only liver damage but also toxicity to other organs. However, the signaling pathways involved in CYP2E1 regulation by ethanol are not clear, especially in extra-hepatic cells. This study was designed to examine the role of CYP2E1 in ethanol-mediated oxidative stress and cytotoxicity, as well as signaling pathways by which ethanol regulates CYP2E1 in extra-hepatic cells. In this study, we used astrocytic and monocytic cell lines, because they are important cells in central nervous system . Our results showed that 100 mM ethanol significantly induced oxidative stress, apoptosis, and cell death at 24 h in the SVGA astrocytic cell line, which was rescued by a CYP2E1 selective inhibitor, diallyl sulfide (DAS), CYP2E1 siRNA, and antioxidants (vitamins C and E). Further, we showed that DAS and vitamin C abrogated ethanol-mediated (50 mM) induction of CYP2E1 at 6 h, as well as production of ROS at 2 h, suggesting the role of oxidative stress in ethanol-mediated induction of CYP2E1. We then investigated the role of the protein kinase C/c-Jun N-terminal kinase/specificity protein1 (PKC/JNK/SP1) pathway in oxidative stress-mediated CYP2E1 induction. Our results showed that staurosporine, a non-specific inhibitor of PKC, as well as specific PKCζ inhibitor and PKCζ siRNA, abolished ethanol-induced CYP2E1 expression. In addition, inhibitors of JNK (SP600125) and SP1 (mithramycin A) completely abrogated induction of CYP2E1 by ethanol in SVGA astrocytes. Subsequently, we showed that CYP2E1 is also responsible for ethanol-mediated oxidative stress and apoptotic cell death in U937 monocytic cell lines. Finally, our results showed that PKC/JNK/SP1 pathway is also involved in regulation of CYP2E1 in U937 cells. This study has clinical implications with respect to alcohol-associated neuroinflammatory toxicity among alcohol users.
Mesoscale distribution and functional diversity of picoeukaryotes in the first-year sea ice of the Canadian Arctic
Authors: Piwosz Kasia , Wiktor Józef Maria , Niemi Andrea , Tatarek Agnieszka , Michel Christine
Published: March 2013

Sea ice, a characteristic feature of polar waters, is home to diverse microbial communities. Sea-ice picoeukaryotes (unicellular eukaryotes with cell size <3 μm) have received little attention compared with diatoms that dominate the spring bloom in Arctic first-year sea ice. Here, we investigated the abundance of all picoeukaryotes, and of 11 groups (chlorophytes, cryptophytes, bolidophytes, haptophytes, Pavlovaphyceae, Phaeocystis spp., pedinellales, stramenopiles groups MAST-1, MAST-2 and MAST-6 and Syndiniales Group II) at 13 first-year sea-ice stations localized in Barrow Strait and in the vicinity of Cornwallis Island, Canadian Arctic Archipelago. We applied Catalyzed Reporter Deposition–Fluorescence In Situ Hybridization to identify selected groups at a single cell level. Pavlovaphyceae and stramenopiles from groups MAST-2 and MAST-6 were for the first time reported from sea ice. Total numbers of picoeukaryotes were significantly higher in the vicinity of Cornwallis Island than in Barrow Strait. Similar trend was observed for all the groups except for haptophytes. Chlorophytes and cryptophytes were the dominant plastidic, and MAST-2 most numerous aplastidic of all the groups investigated. Numbers of total picoeukaryotes, chlorophytes and MAST-2 stramenopiles were positively correlated with the thickness of snow cover. All studied algal and MAST groups fed on bacteria. Presence of picoeukaryotes from various trophic groups (mixotrophs, phagotrophic and parasitic heterotrophs) indicates the diverse ecological roles picoeukaryotes have in sea ice. Yet, >50% of total sea-ice picoeukaryote cells remained unidentified, highlighting the need for further study of functional and phylogenetic sea-ice diversity, to elucidate the risks posed by ongoing Arctic changes.
Diverse populations of lake water bacteria exhibit chemotaxis towards inorganic nutrients
Authors: Dennis Paul G , Seymour Justin , Kumbun Kimber , Tyson Gene W
Published: March 2013

Chemotaxis allows microorganisms to rapidly respond to different environmental stimuli; however, understanding of this process is limited by conventional assays, which typically focus on the response of single axenic cultures to given compounds. In this study, we used a modified capillary assay coupled with flow cytometry and 16S rRNA gene amplicon pyrosequencing to enumerate and identify populations within a lake water microbial community that exhibited chemotaxis towards ammonium, nitrate and phosphate. All compounds elicited chemotactic responses from populations within the lake water, with members of Sphingobacteriales exhibiting the strongest responses to nitrate and phosphate, and representatives of the Variovorax, Actinobacteria ACK-M1 and Methylophilaceae exhibiting the strongest responses to ammonium. Our results suggest that chemotaxis towards inorganic substrates may influence the rates of biogeochemical processes.
Co-operative roles for DNA supercoiling and nucleoid-associated proteins in the regulation of bacterial transcription
Authors: Dorman Charles J.
Published: March 2013

DNA supercoiling and NAPs (nucleoid-associated proteins) contribute to the regulation of transcription of many bacterial genes. The horizontally acquired SPI (Salmonella pathogenicity island) genes respond positively to DNA relaxation, they are activated and repressed by the Fis (factor for inversion stimulation) and H-NS (histone-like nucleoid-structuring) NAPs respectively, and are positively controlled by the OmpR global regulatory protein. The ompR gene is autoregulated and responds positively to DNA relaxation. Binding of the Fis and OmpR proteins to their targets in DNA is differentially sensitive to its topological state, whereas H-NS binds regardless of the topological state of the DNA. These data illustrate the overlapping and complex nature of NAP and DNA topological contributions to transcription control in bacteria.
Effect of DNA conformation on facilitated diffusion
Authors: Brackley Chris A. , Cates Mike E. , Marenduzzo Davide
Published: March 2013

Within a living cell, site-specific DNA-binding proteins need to search the whole genome to find a target of ~10–20 bp. That they find the target, and do so quickly, is vital for the correct functioning of the DNA, and of the cell as a whole. The current understanding is that this search is performed via facilitated diffusion, i.e. by combining three-dimensional bulk diffusion within the cytoplasm or nucleoplasm, with one-dimensional diffusion along the DNA backbone, to which the protein binds non-specifically. After reviewing the standard theory of facilitated diffusion, we discuss in the present article the still rather rare direct computer simulations of this process, focusing on the three-dimensional part of the search, and the effect of DNA looping and the general DNA conformation on its efficiency. We close by highlighting some open questions in this field.
New biologically motivated knot table
Authors: Brasher Reuben , Scharein Rob G. , Vazquez Mariel
Published: March 2013

The knot nomenclature in common use, summarized in Rolfsen's knot table [Rolfsen (1990) Knots and Links, American Mathematical Society], was not originally designed to distinguish between mirror images. This ambiguity is particularly inconvenient when studying knotted biopolymers such as DNA and proteins, since their chirality is often significant. In the present article, we propose a biologically meaningful knot table where a representative of a chiral pair is chosen on the basis of its mean writhe. There is numerical evidence that the sign of the mean writhe is invariant for each knot in a chiral pair. We review numerical evidence where, for each knot type K, the mean writhe is taken over a large ensemble of randomly chosen realizations of K. It has also been proposed that a chiral pair can be distinguished by assessing the writhe of a minimal or ideal conformation of the knot. In all cases examined to date, the two methods produce the same results.
Studies of bacterial topoisomerases I and III at the single-molecule level
Authors: Terekhova Ksenia , Marko John F. , Mondragón Alfonso
Published: March 2013

Topoisomerases are the enzymes responsible for maintaining the supercoiled state of DNA in the cell and also for many other DNA-topology-associated reactions. Type IA enzymes alter DNA topology by breaking one DNA strand and passing another strand or strands through the break. Although all type IA topoisomerases are related at the sequence, structure and mechanism levels, different type IA enzymes do not participate in the same cellular processes. We have studied the mechanism of DNA relaxation by Escherichia coli topoisomerases I and III using single-molecule techniques to understand their dissimilarities. Our experiments show important differences at the single-molecule level, while also recovering the results from bulk experiments. Overall, topoisomerase III relaxes DNA using fast processive runs followed by long pauses, whereas topoisomerase I relaxes DNA through slow processive runs followed by short pauses. These two properties combined give rise to the overall relaxation rate, which is higher for topoisomerase I than for topoisomerase III, as expected from many biochemical observations. The results help us to understand better the role of these two topoisomerases in the cell and also serve to illustrate the power of single-molecule experiments to uncover new functional characteristics of biological molecules.
The impact of hypoxia on cell death pathways
Authors: Lenihan Colin R. , Taylor Cormac T.
Published: March 2013

Hypoxia is a frequently encountered feature of the cellular microenvironment in a number of pathophysiological processes in which programmed cell death (apoptosis) affects disease progression including, but not limited to, cancer, chronic inflammation, myocardial infarction, stroke and ischaemic acute kidney injury. In these diseases, the presence of hypoxia can significantly affect the rate of cell death and thus may make a significant contribution to disease progression. In the present review, we discuss the complex relationship that exists between the presence of hypoxia and the regulation of cell death pathways.
Insights into chromatin fibre structure by in vitro and in silico single-molecule stretching experiments
Authors: Collepardo-Guevara Rosana , Schlick Tamar
Published: March 2013

The detailed structure and dynamics of the chromatin fibre and their relation to gene regulation represent important open biological questions. Recent advances in single-molecule force spectroscopy experiments have addressed these questions by directly measuring the forces that stabilize and alter the folded states of chromatin, and by investigating the mechanisms of fibre unfolding. We present examples that demonstrate how complementary modelling approaches have helped not only to interpret the experimental findings, but also to advance our knowledge of force-induced events such as unfolding of chromatin with dynamically bound linker histones and nucleosome unwrapping.
Parallels between embryo and cancer cell metabolism
Authors: Smith Danielle G. , Sturmey Roger G.
Published: March 2013

A key characteristic of cancer cells is the ability to switch from a predominantly oxidative metabolism to glycolysis and the production of lactate even when oxygen is plentiful. This metabolic switch, known as the Warburg effect, was first described in the 1920s, and has fascinated and puzzled researchers ever since. However, a dramatic increase in glycolysis in the presence of oxygen is one of the hallmarks of the development of the early mammalian embryo; a metabolic switch with many parallels to the Warburg effect of cancers. The present review provides a brief overview of this and other similarities between the metabolism in tumours and early embryos and proposes whether knowledge of early embryo metabolism can help us to understand metabolic regulation in cancer cells.
Influence of chain stiffness on knottedness in single polymers
Authors: Virnau Peter , Rieger Florian C. , Reith Daniel
Published: March 2013

In the present article, we investigate and review the influence of chain stiffness on self-entanglements and knots in a single polymer chain with Monte Carlo simulations spanning good solvent, theta and globular phases. The last-named are of particular importance as a model system for DNA in viral capsids. Intriguingly, the dependence of knot occurrence and complexity with increasing stiffness is non-trivial, but can be understood with a few simple concepts outlined in the present article.
mTORC1 regulates CD8+ T-cell glucose metabolism and function independently of PI3K and PKB
Authors: Finlay David K.
Published: March 2013

Given that inflammatory T-cells have a highly glycolytic metabolism, whereas regulatory T-cells rely more on oxidative glucose metabolism, there is growing interest in understanding how T-cell metabolism relates to T-cell function. The mTORC1 (mammalian target of rapamycin complex 1) has a crucial role to determine the balance between effector and regulatory T-cell differentiation, but is also described as a key regulator of metabolism in non-immune cell systems. The present review explores the relationship between these diverse functions of mTORC1 with regard to T-cell function. In many cell systems, mTORC1 couples PI3K (phosphoinositide 3-kinase) and PKB (protein kinase B), also known as Akt, with the control of glucose uptake and glycolysis. However, this is not the case in activated CD8+ CTLs (cytotoxic T-lymphocytes) where PI3K/PKB signalling is dispensable for the elevated levels of glycolysis that is characteristic of activated T-cells. Nevertheless, mTORC1 is still essential for glycolytic metabolism in CD8+ T-cells, and this reflects the fact that mTORC1 does not lie downstream of PI3K/PKB signalling in CD8+ T-cells, as is the case in many other cell systems. mTORC1 regulates glucose metabolism in CTLs through regulating the expression of the transcription factor HIF1α (hypoxia-inducible factor 1α). Strikingly, HIF1α functions to couple mTORC1 with a diverse transcriptional programme that extends beyond the control of glucose metabolism to the regulation of multiple key T-cell functions. The present review discusses the idea that mTORC1/HIF1α signalling integrates the control of T-cell metabolism and T-cell function.
Determining the topology of stable protein–DNA complexes
Authors: Darcy Isabel K. , Vazquez Mariel
Published: March 2013

Difference topology is an experimental technique that can be used to unveil the topological structure adopted by two or more DNA segments in a stable protein–DNA complex. Difference topology has also been used to detect intermediates in a reaction pathway and to investigate the role of DNA supercoiling. In the present article, we review difference topology as applied to the Mu transpososome. The tools discussed can be applied to any stable nucleoprotein complex.
Maximum likelihood estimation of depth field for trinocular images
Authors: Neri A. , Carli M. , Battisti F.
Published: March 2013

In this reported work, the maximum likelihood estimation of the depth field from a trinocular imaging system is considered. Conventional stereo pairs are able to extract depth information from image changes only along the epipolar line, but the use of three cameras in an ‘L’ shape allows one to utilise any change, irrespective of its orientation. The estimate is obtained by maximising the sum of the cross‐correlations computed along the orthogonal epipolar lines. Theoretical assessment of the achievable performance based on Fisher's information is also included. Simulation results have validated the mathematical framework and the performance analysis.
Electronic approach for enhancing impedance phase sensitivity of GMI magnetic sensors
Authors: Silva E.C. , Gusmão L.A.P. , Barbosa C.R.H. , Monteiro E.C.
Published: March 2013

Over the last decade, giant magnetoimpedance (GMI) sensors have been intensively studied as a new possibility for measuring ultra‐weak magnetic fields. Presented is a newly developed method that allows the enhancement of the impedance phase sensitivity of GMI sensors and, consequently, increases the sensitivity of phase‐based GMI magnetometers. The electronic circuit that implements the proposed method is presented and discussed, and the obtained experimental results indicating its effectiveness are shown.
Time‐domain performance of patch‐loaded band‐reject UWB antenna
Authors: Koohestani M. , Pires N. , Skrivervik A.K. , Moreira A.A.
Published: March 2013

A previous study of a novel technique to design a band‐reject UWB monopole antenna by using patch loading is extended. Frequency‐domain measurements have confirmed that the antenna designed using this technique rejects the interfering signal at the two intended narrowband frequency ranges. Moreover, the antenna radiation pattern distortion is negligible except at the notched bands. A study of time‐domain characteristics based on the antenna pulse response and system fidelity factor is presented. The time performance has been extracted from frequency‐domain measurements using a standard method. The obtained time‐domain results promise the suitability of the proposed technique to design band‐reject antennas useful for future UWB system applications.
Cramér‐Rao bound for joint estimation problems
Authors: Ijyas V.P. Thafasal , Sameer S.M.
Published: March 2013

A new Cramér‐Rao bound (CRB) is derived for projection/separation based joint estimation problems. The determination of bounds for the achievable performance of signal projection/separation methods, which specifically take into account the separated signal premise, is not an adequately addressed one, given the booming relevance of such methods in signal processing and wireless communication applications. In this reported work such a bound is derived, which is robust to variations in noise variances. This bound is evaluated for an important wireless communication application pertaining to parameter estimation in the uplink of OFDMA proposed for 4G communication. The features of the proposed CRB have been substantiated through computer simulation studies.
DFT based phasor estimation algorithm for numerical digital relaying
Authors: Silva K.M. , Küsel B.F.
Published: March 2013

A novel phasor estimation algorithm is proposed, by means of an innovative modification of the traditional full cycle discrete Fourier transformer (FCDFT) algorithm. The main idea is to combine the FCDFT outputs for even and odd sample‐setsobtained for one cycle data window decimated by two and by four. Its performance was compared with the ones of other full cycle algorithms reported in the late literature on the subject. The obtained results reveal the proposed algorithm leads to the best performance, even considering both the decaying DC component of the fault current and the one caused by the current transformer secondary circuit.
Application of series resonant converters to reduce ripple transmission to LED arrays in offline drivers
Authors: Almeida P.S. , Costa M.A. Dalla , Alonso J.M. , Braga H.A.C.
Published: March 2013

Proposed is a novel approach to reduce low‐frequency ripple in light‐emitting diode (LED) arrays that are supplied from the AC grid. The proposal employs a series resonant DC–DC converter connected to the output of the power factor correction (PFC) stage so that the low‐frequency ripple transmitted from the PFC stage to the LEDs can be minimised. This solution achieves two goals: (i) reduction of the bulk capacitance used at the output of the PFC stage so that long‐life film capacitors can be employed, and (ii) increasing the efficiency of the LED driver owing to the low switching losses of the resonant converter. Experimental results are provided to validate this proposal.
3–10 GHz self‐biased resistive‐feedback LNA with inductive source degeneration
Authors: Feng C. , Yu X. P. , Lu Z. H. , Lim W. M. , Sui W. Q.
Published: March 2013

A 3–10 GHz self‐biased low‐noise amplifier (LNA) implemented in Global Foundries 65 nm CMOS process is presented. A novel input‐matching network employing the resistive feedback and inductive source degeneration techniques is proposed to achieve the wideband matching as well as low noise figure. The LNA exhibits a power gain of 17 ± 1 dB over 3–10 GHz with noise figure ranging from 3.5 to 4.3 dB. The fabricated LNA occupies an area of 0.15 mm2 and draws 12 mA from 1.2 V power supply.
SAR image despeckling in directionlet domain based on edge detection
Authors: Sethunadh R. , Thomas T.
Published: March 2013

Presented is a novel directionally adaptive despeckling algorithm for a SAR image using a multi‐direction anisotropic wavelet transform, called a directionlet. It efficiently extracts edge information along dominant directions from the spatially segmented SAR image. Then an optimal scale dependent subband adaptive threshold, based on the generalised cross‐validation technique, is applied to the edge removed image. The despeckled image is finally synthesised using the extracted edge information to preserve the sharpness of edges and the texture. The proposed scheme outperforms many of the traditional despeckling schemes such as the Lee filter and the wavelet and bandlet based edge detection methods in terms of numeric and perceptual quality.
Unbalance and harmonic voltage compensation for a stand‐alone variable speed constant frequency double‐output induction generator supplying non‐linear and unbalanced loads
Authors: Pattnaik Monalisa , Kastha Debaprasad
Published: March 2013

This study presents an improved control algorithm for a stand‐alone double‐output induction machine‐based variable speed constant frequency generator. The algorithm ensures sinusoidal load voltage and machine stator current for all types of loads such as balanced, unbalanced, linear and non‐linear in any arbitrary combination. This is achieved by incorporating harmonic and unbalanced load compensation function to the stator side converter. Unlike other control strategies reported in the literature for this purpose, the proposed algorithm does not require extraction or compensation of individual harmonic/unbalance components of the load voltage/stator current. Harmonic compensation performance of the algorithm is thoroughly analysed theoretically and design guidelines provided. The experimental results obtained from a laboratory prototype demonstrate excellent load voltage regulation property during severe transient operating conditions. Total harmonic distortion and unbalance of the load voltage and stator current even with large unbalanced non‐linear loads are also found to be much smaller compared with similar systems reported earlier in the literature.
Control of a hybrid excitation synchronous generator connected to a diode bridge rectifier supplying a DC bus in embedded applications
Authors: Mbayed Rita , Salloum Georges , Vido Lionel , Monmasson Eric , Gabsi Mohamed
Published: March 2013

This study deals with the modelling and the control of the hybrid excitation synchronous machine connected to a diode bridge rectifier. The set operates as a DC generator that supplies an isolated grid in embedded applications such as aircraft electrical power generation. The elaborated model includes the magnetic circuit saturation effect. The aim of the control is to maintain the DC bus voltage constant when the load and/or the speed of the rotor vary. Simulation results and experiments validate the approach. The electrical parameters of the laboratory prototype machine are identified prior to the control test.
Experimental study of induction motor misalignment and its online detection through data fusion
Authors: Chaudhury Subimal Bikash , Sengupta Mainak , Mukherjee Kaushik
Published: March 2013

Most of the induction motor (IM) fault detection schemes are based on one sensor with one detection logic which are generally incapable of bringing out any consistent feature related to rotor misalignment. Moreover, these logics do not consider simultaneously the asymmetric load condition with variable speed operation. In this study, a data fusion‐based misalignment related fault identification algorithm is presented, which isolates fault features from similar features generated because of other operating conditions. In the proposed scheme, the feature vector is constructed by using signatures created from frequency‐domain characteristics obtained from stator vibration and line current measurements. Thereafter, the feature fusion technology, by means of the weighted linear combination concept, is adopted to take advantage of the best features from both sensors and to discern the pattern of misalignment with other signatures. The technique is validated experimentally on a 5.5 hp IM and the results are presented.
Specific absorption rate and path loss in specific body location in heterogeneous human model
Authors: Kurup Divya , Joseph Wout , Vermeeren Günter , Martens Luc
Published: March 2013

A multi‐implant scenario is considered using insulated dipole antennas for specific locations such as the liver, heart, spleen and the kidneys where implants communicate with a pacemaker acting as a central hub. Wireless communication within human body experiences loss in the form of attenuation and absorption, and to identify these losses, the path loss is studied in this paper for an adult and child heterogeneous human model. Link performance is calculated to investigate the applicability of in‐body communication. The specific absorption rate for all these locations is also studied to verify compliance with international safety guidelines.
Body‐centric ultra‐wideband multi‐channel characterisation and spatial diversity in the indoor environment
Authors: Catherwood Philip A. , Scanlon William G.
Published: March 2013

This study presents the findings of an empirical channel characterisation for an ultra‐wideband off‐body optic fibre‐fed multiple‐antenna array within an office and corridor environment. The results show that for received power experiments, the office and corridor were best modelled by lognormal and Rician distributions, respectively [for both line of sight (LOS) and non‐LOS (NLOS) scenarios]. In the office, LOS measurements for tmean and tRMS were both described by the Normal distribution for all channels, whereas NLOS measurements for tmean and tRMS were Nakagami and Weibull distributed, respectively. For the corridor measurements, LOS for tmean and tRMS were either Nakagami or normally distributed for all channels, with NLOS measurements for tmean and tRMS being Nakagami and normally distributed, respectively. This work also shows that achievable diversity gain was influenced by both mutual coupling and cross‐correlation co‐efficients. Although the best diversity gains were 1.8 dB for three‐channel selective diversity combining, the authors present recommendations for improving these results.
Dual band‐notched small monopole antenna with novel W‐shaped conductor backed‐plane and novel T‐shaped slot for UWB applications
Authors: Ojaroudi Nasser , Ojaroudi Mohammad , Ghadimi Noradin
Published: March 2013

In this study, a novel method for designing a new monopole antenna with dual band‐notched characteristic for UWB applications has been presented. The proposed antenna consists of a square radiating patch with a modified T‐shaped slot, and a ground plane with two E‐shaped slots and a W‐shaped conductor backed‐plane. By cutting two E‐shaped slots in the ground plane, additional resonance is excited and hence much wider impedance bandwidth can be produced, especially at the higher band, which results in a wide usable fractional bandwidth of more than 130% (2.73–13.3 GHz). In order to generate single band‐notched characteristic, the authors use a W‐shaped conductor backed‐plane structure on the other side of the substrate. In addition, by cutting a modified T‐shaped slot in the radiating patch and microstrip feed‐line, a dual band‐notched function is achieved. The measured results reveal that the presented dual notch band monopole antenna offers a very wide bandwidth with two notched bands, covering all the 5.2/5.8 GHz wireless local area network, 3.5/5.5 GHz WiMAX and 4 GHz C bands. The designed antenna has a small size of 12 × 18 mm2. Good voltage standing wave ratio (VSWR) and radiation pattern characteristics are obtained in the frequency band of interest. Simulated and measured results are presented to validate the usefulness of the proposed antenna structure for ultra‐wideband (UWB) applications.
Design and analysis of a decade bandwidth 180° hybrid coupler
Authors: Chan Kevin K.M. , Tan Adrian E.C. , Rambabu Karumudi
Published: March 2013

The design and analysis of a decade bandwidth 3 dB 180° hybrid coupler using tandem connection of two similar wideband 8.34 dB hybrids is presented. The designed coupler has return loss better than 12 dB over a decade bandwidth, insertion loss below 6 dB, amplitude balance within ± 1 dB, phase balance of ± 20° and isolation above 18 dB. Gap and overlap ground patterns at the junction of the tightly coupled to uncoupled region are introduced to improve isolation by preventing odd‐mode field coupling and preserving equal even‐ and odd‐mode phase velocities across the junction.
Investigation on structural colours in wing scales of butterfly Papilio peranthus Fabricius
Authors: Li J. , Han Q. , Chen Y. , Zhu Z. , Huang W.
Published: March 2013

The microstructure and geometrical dimensions of the scales on a butterfly Papilio peranthus Fabricius wing are obtained using scanning electron microscopy and transmission electron microscopy. Two kinds of scales are found in a butterfly wing and the structural colour mainly comes from the cover scale. Different structural models of cover scale that are related to ridge and concavity are constructed and their corresponding optical properties are investigated using the finite‐difference time‐domain method. It is concluded that the structural colour on the cover scale mainly comes from the sculpted multilayer structure and the ridge on the scale has few effects on the structural colour. When the curvature of the sculpted multilayer structure decreases, the dominant wavelength of colour will shift to a longer wavelength and move slower and slower. The two‐dimensional planar multilayer model can be used to calculate the structural colour when the curvature exceeds a certain value.
Surface electrode configurations for quartz MEMS double‐ended tuning fork resonator
Authors: Liang Jinxing , Chai Yanli , Meng Guangchan , Chen Xueying
Published: March 2013

The quartz double‐ended tuning fork (DETF) resonator is well known to be sensitive to longitudinal force and is widely used as the sensing element in modern accelerometer, force and pressure sensors. The quartz DETF resonator works in‐plane, with anti‐phase flexural mode vibration, which is driven into oscillation by internal strains created by AC voltages applied to electrode patterns on the beams. The DETF vibration modes and vibration characteristics are determined by the electrode pattern and its electromechanical coupling efficiency. Presented are three kinds of electrode patterns for different applications, and the effect of electrode patterns on the vibration performances are investigated experimentally. With the fundamental frequency at 65 KHz, the DETF resonator is designed and fabricated using the wet etching‐based quartz MEMS technique. The vibration characteristics including Q‐ value, and equivalent parameters, are evaluated using a 4294 A impedance analyser. Experimental results demonstrated that the vibration characteristics of quartz DETFs are affected by the electrode patterns including pattern location and widths. These results are expected to be useful for designing quartz DETF based devices.
Electrokinetic microchip‐based sample loading for surface plasmon resonance detection
Authors: Chen Xing , Zhang LuLu , Cai Haoyuan , Li Hui , Sun Jianhai , Cui Dafu
Published: March 2013

In this reported work, a microfluidic‐based fluid electrokinetic force has been used for surface plasmon resonance or surface plasmon resonance image (SPRI) detection. In this device, a modified rectangular microarray of Au instead of previous reported square or circular gold segments was designed and microfabricated with gold segment geometries and characterised by surface morphology studies. A voltage drop of maximal 400 V/cm was applied without gold erosion to drive fluorescein isothiocyanate isomer I in a high‐conductivity medium on the bare gold surface layer, enabling SPRI detection.
Tin oxide nanoparticle‐modified commercial PtRu catalyst for methanol oxidation
Authors: Wang Wei , Li Yong , Wang Hui
Published: March 2013

The electrocatalytic performance of commercial PtRu/C is significantly enhanced by directly mixing a few SnO2 nanoparticles. The composite catalysts show enhanced CO oxidation, higher activity and better stability than commercial PtRu/C. Among the different ratios of SnO2 nanoparticles (10–40%), the SnO2–PtRu/C (20%) composite catalyst shows the best catalytic activity for methanol oxidation. The effect of temperature on methanol oxidation was also investigated and the apparent activation energy (Ea) value of catalyst was obtained. The results here suggest a simple route to enhance the catalytic efficiency for commercial PtRu/C catalyst.
Comparative study on the freezing temperature synthesised CdSe nanoparticles before and after annealing
Authors: Sinha Subhojyoti , Chatterjee Sanat Kumar , Ghosh Jiten , Meikap Ajit Kumar
Published: March 2013

Thiyoglycolic acid‐capped CdSe nanoparticles have been synthesised at 273–279 K. A comparative study on the structural and optical characteristics of the as‐synthesised and annealed samples is done using state‐of‐the art instruments and software. Based on these studies here the authors report a colossal change in crystallinity, particle size and red shift in the absorption spectra upon annealing. Lattice strain is also found to increase by 18.77% upon annealing. Excitation wavelength‐dependent photoluminescence with giant Stokes shift and narrow full‐width at half‐maxima of both the samples is also reported, which may be useful for device application.
Simple process for 60 nm patterned nickel stamp replication
Authors: Zhang Ran , Chu Jinkui , Min Jian , Wang Haixiang , Wang Zhiwen
Published: March 2013

A simple process for nickel nanoimprint stamp replication is proposed. Based on this process, the replication of a 15 × 20 mm nickel nanoimprint stamp with 60 nm grating structures was carried out. First, the nanograting structures on the master silicon stamp were transferred to a polymer substrate using the hot embossing process; then, a layer of nickel was sputtered to fill the nanostructures on the substrate surface and form the seed layer for the electroforming process; finally, the back plane of the replica is electroformed. The observation results show good correlation between the dimensions of the master stamp's features and the corresponding replicated features. The performance test result of the replicated stamp demonstrated that the mechanical strength of the replica is sufficient for the hot embossing process.