bluuebunny/crossref_metadata_2025 huggingface dataset:
Ultra‐thin barrier quaternary InAlGaN HEMTs with state of the art sheet resistance
Authors: Gao Xiang , Pan Ming , Gorka Daniel , Oliver Mark , Schuette Michael , Ketterson Andrew , Saunier Paul
Published: March 2014

We report transport properties measured from quaternary barrier InAlGaN high electron mobility transistor wafers on SiC substrates. With similar barrier thicknesses, higher mobility and sheet charge density were both demonstrated by a strained barrier quaternary In0.07Al0.75Ga0.18N HEMT comparing to a ternary In0.17Al0.83N HEMT with lattice matched barrier to the GaN buffer. With 1 nm AlN interlayer, sheet resistances of 218 Ω/□ and 228 Ω/□ were obtained from 4.8 nm and 4.4 nm barrier structures, respectively. Both structures also show excellent electron motilities. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Comparison of the physical, chemical and electrical properties of ALD Al2O3 on c‐ and m‐ plane GaN
Authors: Wei D. , Hossain T. , Nepal N. , Garces N. Y. , Hite J. K. , Meyer H. M. , Eddy C. R. , Edgar J. H.
Published: March 2014

This study compares the physical, chemical and electrical properties of Al2O3 thin films deposited on gallium polar c‐ and nonpolar m ‐plane GaN substrates by atomic layer deposition (ALD). Correlations were sought between the film's structure, composition, and electrical properties. The thickness of the Al2O3 films was 19.2 nm as determined from a Si witness sample by spectroscopic ellipsometry. The gate dielectric was slightly aluminum‐rich (Al:O=1:1.3) as measured from X‐ray photoelectron spectroscopy (XPS) depth profile, and the oxide‐semiconductor interface carbon concentration was lower on c ‐plane GaN. The oxide's surface morphology was similar on both substrates, but was smoothest on c ‐plane GaN as determined by atomic force microscopy (AFM). Circular capacitors (50‐300 μm diameter) with Ni/Au (20/100 nm) metal contacts on top of the oxide were created by standard photolithography and e‐beam evaporation methods to form metal‐oxide‐semiconductor capacitors (MOSCAPs). The alumina deposited on c ‐plane GaN showed less hysteresis (0.15 V) than on m ‐plane GaN (0.24 V) in capacitance‐voltage (CV) characteristics, consistent with its better quality of this dielectric as evidenced by negligible carbon contamination and smooth oxide surface. These results demonstrate the promising potential of ALD Al2O3 on c ‐plane GaN, but further optimization of ALD is required to realize the best properties of Al2O3 on m ‐plane GaN. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Growth of ternary wurtzite BAlN and BGaN by ENABLE‐MBE
Authors: Williamson Todd L. , Weisse‐Bernstein Nina R. , Hoffbauer Mark A.
Published: March 2014

The synthesis of dilute B content BAlN and BGaN has been performed by an advanced MBE technique called ENABLE. ENABLE is a direct chemical activation approach to film growth which uses an energetic beam of neutral N atoms to activate nitride thin film growth. Using the ENABLE‐MBE technology, up to 3.1% and 3.5% B has been incorporated in BAlN and BGaN, respectively. XRD scans indicate that the films are single phase and the crystalline quality is high. It has been shown in BAlN that a lower substrate temperature during growth leads to higher level of incorporation of B, with all other parameters held constant. Electrical measurements of BAlN shows reasonable breakdown voltage (∼25 V/µm) and leakage current (–9 nA at –20 V bias). (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
How do sustainability standards consider biodiversity?
Authors: Englund Oskar , Berndes Göran
Published: March 2014

Sustainability certification schemes and standards are meant to prevent a range of unacceptable socioeconomic and environmental consequences, such as threats to biodiversity. While there is wide support for conserving biodiversity, operationalizing this support in the form of guiding principles, criteria/indicators, and legislation is complicated. This study investigates how and to what extent 26 sustainability standards (eleven for forest management, nine for agriculture and six biofuel‐related) consider biodiversity, by assessing how they seek to prevent actions that can threaten biodiversity as well as how they support actions aimed at biodiversity conservation. For this purpose, a benchmark standard was developed, meant to represent a case with very high ambitions concerning biodiversity conservation. Of the assessed standards, the biofuel‐related standards demonstrated the highest level of compliance with the benchmark. On average, they complied with 72% of the benchmark's component criteria, compared to 61% for the agricultural standards and 60% for the forestry standards. Fairtrade, Sustainable Agriculture Network/Rainforest Alliance (SAN/RA), Roundtable on Sustainable Palm Oil (RSPO), and Roundtable on Responsible Soy (RTRS) were particularly stringent, while Green Gold Label S5 (GGLS5), PEOLG, Global Partnership for Good Agricultural Practices (GLOBALGAP), European Union Organic (EU Organic), National Organic Program (NOP), Green Gold Label S2 (GGLS2), and International Sustainability & Carbon Certification (ISCC) were particularly unstringent. All eleven forestry standards, six of the nine agricultural standards, and all six biofuel‐related standards addressed ecosystem conversion, ranging from requiring that high conservation value areas be identified and preserved to requiring full protection. Finally, key barriers to, and challenges for, certification schemes are discussed and recommendations are made for further development of sustainability standards. WIREs Energy Environ 2015, 4:26–50. doi: 10.1002/wene.118

This article is categorized under:

Bioenergy > Economics and Policy

Bioenergy > Climate and Environment
Modeling stochastic noise in gene regulatory systems
Authors: Meister Arwen , Du Chao , Li Ye Henry , Wong Wing Hung
Published: March 2014

The Master equation is considered the gold standard for modeling the stochastic mechanisms of gene regulation in molecular detail, but it is too complex to solve exactly in most cases, so approximation and simulation methods are essential. However, there is still a lack of consensus about the best way to carry these out. To help clarify the situation, we review Master equation models of gene regulation, theoretical approximations based on an expansion method due to N.G. van Kampen and R. Kubo, and simulation algorithms due to D.T. Gillespie and P. Langevin. Expansion of the Master equation shows that for systems with a single stable steady‐state, the stochastic model reduces to a deterministic model in a first‐order approximation. Additional theory, also due to van Kampen, describes the asymptotic behavior of multistable systems. To support and illustrate the theory and provide further insight into the complex behavior of multistable systems, we perform a detailed simulation study comparing the various approximation and simulation methods applied to synthetic gene regulatory systems with various qualitative characteristics. The simulation studies show that for large stochastic systems with a single steady‐state, deterministic models are quite accurate, since the probability distribution of the solution has a single peak tracking the deterministic trajectory whose variance is inversely proportional to the system size. In multistable stochastic systems, large fluctuations can cause individual trajectories to escape from the domain of attraction of one steady‐state and be attracted to another, so the system eventually reaches a multimodal probability distribution in which all stable steady‐states are represented proportional to their relative stability. However, since the escape time scales exponentially with system size, this process can take a very long time in large systems.
Alt a 1 from Alternaria interacts with PR5 thaumatin‐like proteins
Authors: Gómez-Casado Cristina , Murua-García Amaya , Garrido-Arandia María , González-Melendi Pablo , Sánchez-Monge Rosa , Barber Domingo , Pacios Luis F. , Díaz-Perales Araceli
Published: March 2014

Alt a 1 is a protein found in Alternaria alternata spores related to virulence and pathogenicity and considered to be responsible for chronic asthma in children. We found that spores of Alternaria inoculated on the outer surface of kiwifruits did not develop hyphae. Nevertheless, the expression of Alt a 1 gene was upregulated, and the protein was detected in the pulp where it co‐localized with kiwi PR5. Pull‐down assays demonstrated experimentally that the two proteins interact in such a way that Alt a 1 inhibits the enzymatic activity of PR5. These results are relevant not only for plant defense, but also for human health as patients with chronic asthma could suffer from an allergic reaction when they eat fruit contaminated with Alternaria.
Drosophila melanogaster as a model system to study long‐chain fatty acid amide metabolism
Authors: Jeffries Kristen A. , Dempsey Daniel R. , Behari Anita L. , Anderson Ryan L. , Merkler David J.
Published: March 2014

Long‐chain fatty acid amides are cell‐signaling lipids identified in mammals and, recently, in invertebrates, as well. Many details regarding fatty acid amide metabolism remain unclear. Herein, we demonstrate that Drosophila melanogaster is an excellent model system for the study long‐chain fatty acid amide metabolism as we have quantified the endogenous levels of N‐acylglycines, N‐acyldopamines, N‐acylethanolamines, and primary fatty acid amides by LC/QTOF‐MS. Growth of D. melanogaster on media supplemented with [1‐13C]‐palmitate lead to a family of 13C‐palmitate‐labeled fatty acid amides in the fly heads. The [1‐13C]‐palmitate feeding studies provide insight into the biosynthesis of the fatty acid amides.
The control of partitioning between protein and fat during human starvation: its internal determinants and biological significance
Authors: Dulloo A. G. , Jacquet J.
Published: March 2014

Human subjects vary in the extent to which their body's protein and fat compartments are mobilized for fuel during starvation. Although an inverse association between the initial adiposity and the contribution of protein as fuel during starvation has been known for nearly a century, interest in the quantitative importance and functional significance of the initial percentage fat as a determinant of biological variation in energy-partitioning between protein and fat (and hence in determining the partitioning characteristic of the individual) is relatively recent. The present paper addresses these issues by revisiting the classic Minnesota experiment of semi-starvation and refeeding from a standpoint of system physiology. In a quantitative analysis of the relationship between the initial body composition (ratio FAT0:fat-free mass (FFM)0) and the composition of weight loss (ratio ΔFAT:ΔFFM) in the thirty-two men in the Minnesota study, the arguments are put forward that the fraction of FFM lost when the fat stores reach total depletion is independent of the initial percentage fat, and that this fraction represents the ‘dispensible’ component of the protein compartment that is compatible with life (i.e. the protein energy-reserve, rp). The concepts are developed that (1) the initial percentage body fat (which reflects the initial ratio FAT0:FFM0) provides a ‘memory of partitioning’ which dictates the control of partitioning between protein and fat in such a way that both the protein energy-reserve (rp) and the fat energy-reserve (rf) reach complete depletion simultaneously, a strategy that would ensure maximum length of survival during long-term food scarcity, and that (2) variability in the relative sizes of these two energy reserves (i.e. in rf:rp) could, in addition to the initial percentage fat, also contribute to human variability in energy-partitioning. The basic assumptions underlying this re-analysis of the Minnesota data, and the concepts that are derived from it, have been integrated in the simple mathematical model for predicting the partitioning characteristic of the individual. This model is used to explain how variability in the fraction of the protein compartment that could function as an energy reserve (rp) can be as important as the initial percentage fat in determining inter-individual variability in protein-sparing during the early phase of starvation, in fuel partitioning during prolonged starvation, or in the maximum percentage weight loss during starvation. The elucidation of factors underlying variability in the size of the protein energy-reserve may have important implications for our understanding of the pathophysiology of starvation and age-associated susceptibility to muscle wasting, and in the clinical management of cachexia and obesity.
NOTATION AS LIBERATION
Authors: Barrett Richard
Published: March 2014

This paper, originally the keynote address at a conference on notation in contemporary music held at Goldsmiths, University of London, in October 2013, examines the relationship between notation and improvisation in today's music. Starting from the position that improvisation is a method of composition, and that the two are in no way opposites, the author reflects on his dual practice as composer of often complexly notated scores and an improvising musician. The title subverts the familiar claim that it is improvisation that liberates the musician from the supposed tyranny of fixed notation, suggesting instead that notation may serve a valuable function in suggesting possible directions or points of focus in free improvisation.
Kreutzer Quartet, Wilton's Music Hall, London: Sadie Harrison, Edward Cowie and Michael Finnissy
Authors: Conway Paul
Published: March 2014

The Kreutzer Quartet's ‘Beethoven Begins’ series, based around the great German master's Op.18 string quartets, has included an example of new music in each of its six concerts, a tribute to the players’ eclectic tastes, versatility and accomplishment in diverse repertoire. Their generously filled programmes all take place within the flaky grandeur of Wilton's Music Hall, one of London's quirkiest and most bewitching venues.
Festival d'Automne 2013
Authors: Kaltenecker Martin
Published: March 2014

Since 1972, the Parisian Festival d'Automne has organised dozens of events every year in the field of theatre, dance and music. The list of premieres is impressive, and comprises all the major names in the realm of contemporary art. The concerts represent a kind of anthology of recent outstanding achievements, combined with commissions from younger composers, and a recapitulation of important works of twentieth-century music which may be mentioned in every music history but are rarely performed: this year, for instance, featured Karlheinz Stockhausen'sTrans. Offering a precious and vital complement to the other various Parisian seasons, the Festival has no venue of its own, so that, as quite a number of the concerts are co-produced with other institutions, the ‘visibility’ of the festival stems only from the quality of the programming, the excellence of the musicians, and the interaction with the overall artistic project.
Post-capture attitude control for a tethered space robot–target combination system
Authors: Huang Panfeng , Wang Dongke , Meng Zhongjie , Liu Zhengxiong
Published: March 2014

This paper presents a novel scheme for achieving attitude control of a tumbling combination system in the post-capture phase of a tethered space robot (TSR). Given the combination rotation characteristics, tether force is applied to provide greater control torques for stabilising the attitude. The proposed control scheme involves two attitude controllers, which coordinate the controller of the tether force and thruster force and the controller of single thruster force. The numerical simulations include a comparison between this coordinated control and the traditional thruster control and a sensitivity analysis on initial values of parameters. Simulation results validate the feasibility of the attitude control scheme for a tumbling combination system, and fuel consumption of the attitude control is efficiently reduced using the coordinated control strategies.
The acquisition of relative clauses in spontaneous child speech in Mandarin Chinese
Authors: CHEN JIDONG , SHIRAI YASUHIRO
Published: March 2014

This study investigates the developmental trajectory of relative clauses (RCs) in Mandarin-learning children's speech. We analyze the spontaneous production of RCs by four monolingual Mandarin-learning children (0;11 to 3;5) and their input from a longitudinal naturalistic speech corpus (Min, 1994). The results reveal that in terms of the syntactic role of the head noun in the matrix clause, isolated noun phrase RCs dominate, followed by those that modify the subject or object of the matrix clauses and predicate nominal relatives. This pattern differs from those observed in English (Diessel & Tomasello, 2000), German (Brandt, Diessel & Tomasello, 2008), and Japanese (Ozeki & Shirai, 2007). Regarding the syntactic role of the head noun inside the RC (i.e. subject, object, or oblique relatives), the early RCs are dominated by object relatives. This pattern also differs from those observed in English and Japanese. We propose a multifactorial usage-based learning account for the developmental patterns.
Some properties of weak solutions to the weighted p-Laplacian near an isolated singular point
Authors: Yin Jingxue , Song Huijuan
Published: March 2014

We study the weighted p-Laplacian with an isolated singular point, and discuss some properties of solutions near such a point, including removable singularities, boundedness and growth rate estimates. In particular, some relevant critical exponents are exactly determined.
Multiple solutions for a class of (p, q)-gradient elliptic systems via a fibering method
Authors: Vélin Jean
Published: March 2014

This paper is devoted to the study of a typical (p, q)-gradient elliptic system. We discuss the existence of multiple non-trivial solutions. More precisely, we establish the existence of three non-trivial solutions, obtained by applying the fibering method introduced by Pohozaev.
Pregnancy-associated listeriosis in England and Wales
Authors: AWOFISAYO A. , AMAR C. , RUGGLES R. , ELSON R. , ADAK G. K. , MOOK P. , GRANT K. A.
Published: March 2014

Listeriosis is a rare but severe foodborne disease with low morbidity and high case-fatality rates. Pregnant women, unborn and newborn babies are among the high-risk groups for listeriosis. We examined listeriosis cases reported to the enhanced surveillance system in England and Wales from 1990 to 2010 to identify risk factors influencing outcome. Cases were defined as pregnancy-associated if Listeria monocytogenes was isolated from a pregnant woman or newborn infants aged <28 days. Of the 3088 cases reported, pregnancy-associated listeriosis accounted for 462 (15%) cases and 315 cases resulted in a live birth. Several factors were identified as affecting the severity and outcome of listeriosis in pregnancy in both mother and child including: presence or absence of maternal symptoms, gestational age at onset of symptoms, and clinical presentation in the infant (meningitis or septicaemia). Deprivation, ethnicity and molecular serotype had no effect on outcome.
Individualization of drug therapy in older people
Authors: Scibona P , Angriman F , Vazquez C , Ferreyro BL , Perelsztein AG , Simonovich VA , Jauregui JR , Musso CG , Belloso WH
Published: March 2014

Older people are high consumers of prescription drugs and are at increasing risk of polypharmacy and adverse reactions. Pharmacokinetic and pharmacodynamic modifications due to age and co-morbidities are an important consideration, but pharmacological background evidence to guide safe and effective therapeutic approaches are often inadequate since the older population is under-represented in clinical trials. We review the pharmacokinetic and pharmacodynamic changes that are characteristic in old age and consider evidence regarding potentially safer prescription and monitoring of drugs commonly used in older patients. We also introduce the possible role of pharmacogenomics and therapeutic drug monitoring as tools to guide the individualization of drug therapy.
National Study of Ambulance Transports to United States Emergency Departments: Importance of Mental Health Problems
Authors: Larkin Gregory Luke , Claassen Cynthia A. , Pelletier Andrea J. , Camargo Carlos A.
Published: March 2014

Introduction:

Understanding ambulance utilization patterns is essential to assessing prehospital system capacity and preparedness at the national level.

Objective:

To describe the characteristics of patients transported to US emergency departments (EDs) by ambulance and to determine predictors of ambulance utilization.

Methods:

Data were obtained from the National Hospital Ambulatory Medical Care Survey using mode of arrival, demographic and visit information, ICD-9-CM E and V-codes, and classified reasons for the visit.

Results:

The rates for ED visits of persons conveyed by ambulence were stable between 1997 and 2003, consisting of approximately one in every seven ED visits (14%). In 2003, there were 16.2 million ED visits for which an ambulance was used in the US. However, for patients with mental health visits, nearly one in three ED presentations (31%) arrived by ambulance. Significantly higher rates of ambulance use were associated with: (1) mental health visits; (2) older age; (3) African-Americans; (4) Medicare or self-pay insurance status; (5) urban ED location; (6) US regions outside of the South; (7) presentation between 12 midnight to 0800 hours; (8) injury-related visits; (9) urgent visit status; and/or (10) those resulting in hospital admission. Among mental health patients, older age, self-pay insurance status, urban ED location, regions outside the southern US, and urgent visit classification predicted ambulance use. Ambulance usage within the mental health group was highest for suicide and lowest for mood and anxiety disorder-related visits.

Conclusion:

Reliance on ambulance services varies by age, insurance status, geographic factors, time of day, urgency of visit, subsequent admission status, and type of mental health disorder. Even after controlling for many confounding factors, mental health problems remain an important predictor of ambulance use.
Molecular characterization of oil palmElaeis guineensisJacq. of different origins for their utilization in breeding programmes
Authors: Arias Diana , Ochoa Iván , Castro Fernando , Romero Hernán
Published: March 2014

Sustainable development of a breeding programme depends on having sufficient genetic variability to achieve genetic gains in each selection cycle. The aim of this study was to molecularly characterize families of the oil palm,Elaeis guineensisJacq., of different origins using microsatellite molecular markers. The value of the observed heterozygosity was higher than that of the expected heterozygosity in all of the progenies. The coefficients (GST= 0.207 andFST= 0.174) and AMOVA showed genotypic differences among the evaluated families. Likewise, this was reflected in the groups obtained by the dendrogram and principal coordinate analyses. This difference could have evolved due to the enrichment of some of the families with germplasm from different origins. Therefore, genetic relationships estimated from molecular data would be convenient to select families more distant from each group and palms more distant from each family selected to reserve genetic variability. This information will guide us in the decision-making process when planning breeding programmes focused on crosses to develop new populations with an acceptable broad genetic base and adaptability. In this way, sources of resistance to biotic and abiotic factors can be identified for the development of new varieties with competitive advantages for the sector.
Nanotubes for Energy Storage
Authors: Pan Hui
Published: March 2014

Nanotubes (NTs) are promising candidates as energy storage materials for hydrogen, electricity, and lithium because of their unique structural, mechanical, and electrical properties. The performance of NT-based energy storage materials is considerably improved compared to the conventional bulk-based materials. In addition, the open structure of NTs can help to improve the storage capacity. In this review, we systematically discuss the applications of NTs in energy storage, and the influence of their structures and morphologies on their performance for hydrogen storage, supercapacitor, and lithium battery. We show that the modification of NTs (functionalization, doping, defect control, and structure engineering) and the design of NT-based composite structures (hybrid and ternary composites including NTs, graphene, oxides, polymers, and metal) provide strategies to improve the performance of NT-based energy storage materials.
Lamellar nickel hydroxy-halides: anionic exchange synthesis, structural characterization and magnetic behavior
Authors: Taibi Mostafa , Jouini Noureddine , Rabu Pierre , Ammar Souad , Fiévet Fernand
Published: March 2014

The structural and magnetic investigation of new nickel-layered hydroxy-halides LHS-Ni-X (X = Cl, Br, and I) gives new insight into the magnetic interaction mechanisms in two-dimensional α-Ni(OH)2 systems.
The grab-and-drop protocol: a novel strategy for membrane protein isolation and reconstitution from single cells
Authors: Schrems Angelika , Phillips John , Casey Duncan , Wylie Douglas , Novakova Mira , Sleytr Uwe B. , Klug David , Neil Mark A. A. , Schuster Bernhard , Ces Oscar
Published: March 2014

Samples of cell membrane were non-destructively removed from individual, live cells using optically trapped beads, and deposited into a supported lipid bilayer mounted on an S-layer protein-coated substrate.
Structure analysis on the nanoscale: closed WS2 nanoboxes through a cascade of topo- and epitactic processes
Authors: Hoshyargar Faegheh , Mugnaioli Enrico , Branscheid Robert , Kolb Ute , Panthöfer Martin , Tremel Wolfgang
Published: March 2014

Closed WS2 nanoboxes were formed by topotactic sulfidization of a WO3/WO3·⅓H2O intergrowth phase. The box-like morphology can be traced back to a topotactic dehydration reaction of the precursor followed by an epitactic induction of intermediate hexagonal WO3.
Adsorptive separation on metal–organic frameworks in the liquid phase
Authors: Van de Voorde Ben , Bueken Bart , Denayer Joeri , De Vos Dirk
Published: March 2014

While much attention of the MOF community has been devoted to adsorption and purification of gases, there is now also a vast body of data on the capability of MOFs to separate and purify liquid mixtures.
Thermomechanical properties, antibiotic release, and bioactivity of a sterilized cyclodextrin drug delivery system
Authors: Halpern Jeffrey M. , Gormley Catherine A. , Keech Melissa A. , von Recum Horst A.
Published: March 2014

We examine the effect that commercial sterilization techniques have on the physical, mechanical, and drug delivery properties of polyurethane polymers.
In search of ligands and receptors of the pollen tube: the missing link in pollen tube perception
Authors: Hafidh Said , Potěšil David , Fíla Jan , Feciková Jana , Čapková Věra , Zdráhal Zbyněk , Honys David
Published: March 2014

The journey undertaken by the pollen tube in angiosperms to reach the deeply embedded female gametophyte for fertilization involves persistent guidance by the female gametophyte and accurate perception of the signals by the pollen tube. Several ovule-secreted peptides have been identified. Nevertheless, there are no exact findings on how these signals are perceived by the pollen tube. As a novel approach, we have improvised a modified SIV (semi-in vivo) technique, SIV-PS (SIV pollen tube secretome), to perform gel-free LC–MS/MS for high-throughput analysis of pollen-tube-secreted proteins. Our approach has led to the identification of over 1400 protein groups. Among them are pollen-tube-secreted ligands and receptor proteins representing potential male components in perceiving ovule-emitted cues for guidance. The present article reviews the missing link in pollen tube perception and showcases the improvised SIV-PS as a tool for high-throughput and targeted study of the pollen tube secretome.
Genetic control of identity and growth in the early Arabidopsis embryo
Authors: Weijers Dolf
Published: March 2014

Plants can grow complex and elaborate structures, in some species for thousands of years. Despite the diversity in form and shape, plants are built from a limited number of fundamental tissue types, and their arrangement is deeply conserved in the plant kingdom. A key question in biology is how these fundamental tissues, i.e. epidermal, ground and vascular tissue, are specified and organized in time and space. In the present paper, I discuss the use of the early Arabidopsis embryo as a model system to dissect the control of tissue formation and patterning, as well as the specification of the stem cells that sustain post-embryonic growth. I present recent insights into the molecules and mechanisms that control both the specification and the subsequent growth of the different cell types within the embryonic root. Finally, I discuss major unanswered questions and future challenges in using the embryo as a model to decipher the regulatory logic of plant development.
Glyoxalases and stress tolerance in plants
Authors: Kaur Charanpreet , Ghosh Ajit , Pareek Ashwani , Sopory Sudhir K. , Singla-Pareek Sneh L.
Published: March 2014

The glyoxalase pathway is required for detoxification of cytotoxic metabolite MG (methylglyoxal) that would otherwise increase to lethal concentrations under adverse environmental conditions. Since its discovery 100 years ago, several roles have been assigned to glyoxalases, but, in plants, their involvement in stress response and tolerance is the most widely accepted role. The plant glyoxalases have emerged as multigene family and this expansion is considered to be important from the perspective of maintaining a robust defence machinery in these sessile species. Glyoxalases are known to be differentially regulated under stress conditions and their overexpression in plants confers tolerance to multiple abiotic stresses. In the present article, we review the importance of glyoxalases in plants, discussing possible roles with emphasis on involvement of the glyoxalase pathway in plant stress tolerance.
Poly(dimethylsiloxane)-based microdevices for studying plant reproduction
Authors: Arata Hideyuki , Higashiyama Tetsuya
Published: March 2014

Long-term holding and precise handling of growing plant tissues during in vitro cultivation has been a major hurdle for experimental studies related to plant development and reproduction. In the present review, we introduce two of our newly developed poly(dimethylsiloxane)-based microdevices: a T-shaped microchannel device for pollen tube chemoattraction and a microcage array for long-term live imaging of ovules. Their design, usage and advantages are described, and future prospects of experimental approaches to plant reproduction using such microdevices are discussed.
Hormonal responses during early embryogenesis in maize
Authors: Chen Junyi , Lausser Andreas , Dresselhaus Thomas
Published: March 2014

Plant hormones have been shown to regulate key processes during embryogenesis in the model plant Arabidopsis thaliana, but the mechanisms that determine the peculiar embryo pattern formation of monocots are largely unknown. Using the auxin and cytokinin response markers DR5 and TCSv2 (two-component system, cytokinin-responsive promoter version #2), as well as the auxin efflux carrier protein PIN1a (PINFORMED1a), we have studied the hormonal response during early embryogenesis (zygote towards transition stage) in the model and crop plant maize. Compared with the hormonal response in Arabidopsis, we found that detectable hormone activities inside the developing maize embryo appeared much later. Our observations indicate further an important role of auxin, PIN1a and cytokinin in endosperm formation shortly after fertilization. Apparent auxin signals within adaxial endosperm cells and cytokinin responses in the basal endosperm transfer layer as well as chalazal endosperm are characteristic for early seed development in maize. Moreover, auxin signalling in endosperm cells is likely to be involved in exogenous embryo patterning as auxin responses in the endosperm located around the embryo proper correlate with adaxial embryo differentiation and outgrowth. Overall, the comparison between Arabidopsis and maize hormone response and flux suggests intriguing mechanisms in monocots that are used to direct their embryo patterning, which is significantly different from that of eudicots.
TGR5 in inflammation and cardiovascular disease
Authors: Pols Thijs W.H.
Published: March 2014

TGR5 (Takeda G-protein-coupled receptor 5) [also known as GPBAR1 (G-protein-coupled bile acid receptor 1), M-BAR (membrane-type receptor for bile acids) or GPR131 (G-protein-coupled receptor 131)] is a G-protein-coupled receptor that was discovered as a bile acid receptor. TGR5 has specific roles in several tissues, among which are the regulation of energy expenditure, GLP-1 (glucagon-like peptide 1) secretion and gall bladder filling. An accumulating body of evidence now demonstrates that TGR5 also acts in a number of processes important in inflammation. Most striking in this context are several observations that TGR5 signalling curbs the inflammatory response of macrophages via interfering with NF-κB (nuclear factor κB) activity. In line with this, recent animal studies also suggest that TGR5 could be exploited as a potential target for intervention in a number of inflammation-driven diseases, including atherosclerosis. In the present paper, I review our current understanding of TGR5 with a strong focus on its potential as target for intervention in inflammation-driven diseases.
Tapping the translation potential of cAMP signalling: molecular basis for selectivity in cAMP agonism and antagonism as revealed by NMR
Authors: Boulton Stephen , Akimoto Madoka , VanSchouwen Bryan , Moleschi Kody , Selvaratnam Rajeevan , Giri Rajanish , Melacini Giuseppe
Published: March 2014

Eukaryotic CBDs (cAMP-binding domains) control multiple cellular functions (e.g. phosphorylation, guanine exchange and ion channel gating). Hence the manipulation of cAMP-dependent signalling pathways has a high translational potential. However, the ubiquity of eukaryotic CBDs also poses a challenge in terms of selectivity. Before the full translational potential of cAMP signalling can be tapped, it is critical to understand the structural basis for selective cAMP agonism and antagonism. Recent NMR investigations have shown that structurally homologous CBDs respond differently to several CBD ligands and that these unexpected differences arise at the level of either binding (i.e. affinity) or allostery (i.e. modulation of the autoinhibitory equilibria). In the present article, we specifically address how the highly conserved CBD fold binds cAMP with markedly different affinities in PKA (protein kinase A) relative to other eukaryotic cAMP receptors, such as Epac (exchange protein directly activated by cAMP) and HCN (hyperpolarization-activated cyclic-nucleotide-modulated channel). A major emerging determinant of cAMP affinity is hypothesized to be the position of the autoinhibitory equilibrium of the apo-CBD, which appears to vary significantly across different CBDs. These analyses may assist the development of selective CBD effectors that serve as potential drug leads for the treatment of cardiovascular diseases.
Glutamatergic pathways as a target for the treatment of dyskinesias in Parkinson's disease
Authors: Cenci M. Angela
Published: March 2014

PD (Parkinson's disease) is characterized by some typical motor features that are caused by striatal dopamine depletion and respond well to dopamine-replacement therapy with L-dopa. Unfortunately, the majority of PD patients treated with L-dopa develop abnormal involuntary movements (dyskinesias) within a few years. The mechanisms underlying the development of LIDs (L-dopa-induced dyskinesias) involve, on one hand, a presynaptic dysregulation of dopamine release and clearance and, on the other hand, an abnormal postsynaptic response to dopamine in the brain. There is a large amount of evidence that these dopamine-dependent mechanisms are modulated by glutamatergic pathways and glutamate receptors. The present article summarizes the pathophysiological role of glutamatergic pathways in LID and reviews pre-clinical and clinical results obtained using pharmacological modulators of different classes and subtypes of glutamate receptors to treat parkinsonian dyskinesias.
Dicarbonyl stress and glyoxalases in ovarian function
Authors: Tatone Carla , Eichenlaub-Ritter Ursula , Amicarelli Fernanda
Published: March 2014

The ovary is the main regulator of female fertility. Changes in maternal health and physiology can disrupt intraovarian homoeostasis thereby compromising oocyte competence and fertility. Research has only recently devoted attention to the involvement of dicarbonyl stress in ovarian function. On this basis, the present review focuses on clinical and experimental research supporting the role of dicarbonyl overload and AGEs (advanced glycation end-products) as key contributors to perturbations of the ovarian microenvironment leading to lower fertility. Particular emphasis has been given to oocyte susceptibility to methylglyoxal, a powerful glycating agent, whose levels are known to increase during aging and metabolic disorders. According to the literature, the ovary and the oocyte itself can rely on the glyoxalase system to counteract the possible dicarbonyl overload such as that which may occur in reproductive-age women and patients with PCOS (polycystic ovarian syndrome) or diabetes. Overall, although biochemical methods for proper evaluation of dicarbonyl stress in oocytes and the ovarian microenvironment need to be established, AGEs can be proposed as predictive markers and/or therapeutic targets in new strategies for improving reproductive counselling and infertility therapies.
Epac proteins: specific ligands and role in cardiac remodelling
Authors: Bisserier Malik , Blondeau Jean-Paul , Lezoualc’h Frank
Published: March 2014

Epacs (exchange proteins directly activated by cAMP) act as guanine-nucleotide-exchange factors for the Ras-like small G-proteins Rap1 and Rap2, and are now recognized as incontrovertible factors leading to complex and diversified cAMP signalling pathways. Given the critical role of cAMP in the regulation of cardiac function, several studies have investigated the functional role of Epacs in the heart, providing evidence that Epacs modulate intracellular Ca2+ and are involved in several cardiac pathologies such as cardiac hypertrophy and arrhythmia. The present review summarizes recent data on the Epac signalling pathway and its role in cardiac pathophysiology. We also discuss recent advances in the discovery of novel pharmacological modulators of Epacs that were identified by high-throughput screening and their therapeutic potential for the treatment of cardiac disorders.
Same same but different: sperm-activating EC1 and ECA1 gametogenesis-related family proteins
Authors: Sprunck Stefanie , Hackenberg Thomas , Englhart Maria , Vogler Frank
Published: March 2014

During double fertilization in Arabidopsis thaliana, the egg cell secretes small cysteine-rich EC1 (egg cell 1) proteins, which enable the arriving sperm pair to rapidly interact with the two female gametes. EC1 proteins are members of the large and unexplored group of ECA1 (early culture abundant 1) gametogenesis-related family proteins, characterized by a prolamin-like domain with six conserved cysteine residues that may form three pairs of disulfide bonds. The distinguishing marks of egg-cell-expressed EC1 proteins are, however, two short amino acid sequence motifs present in all EC1-like proteins. EC1 genes appear to encode the major CRPs (cysteine-rich proteins) expressed by the plant egg cell, and they are restricted to flowering plants, including the most basal extant flowering plant Amborella trichopoda. Many other ECA1 gametogenesis-related family genes are preferentially expressed in the synergid cell. Functional diversification among the ECA1 gametogenesis-related family is suggested by the different patterns of expression in the female gametophyte and the low primary sequence conservation.
Flavonoids and the regulation of seed size in Arabidopsis
Authors: Doughty James , Aljabri Maha , Scott Rod J.
Published: March 2014

Understanding how seed size is regulated in angiosperms is a key goal for plant science as seed size is an important component of overall seed yield. Angiosperm seeds comprise three clearly defined components, i.e. the embryo, endosperm and seed coat, with each having a distinct genetic composition which exerts different influences on seed development. Complex cross-talk and integration of signals from these different regions of the seed together determine its final size. The present review considers some of the major regulators of seed size, with a particular emphasis on the role of the seed coat in modulating endosperm proliferation and cellularization. The innermost layer of the seed coat, the endothelium, synthesizes flavonoids which are held to provide a defensive function against microbes, act as feeding deterrents, provide UV protection and to have a role in seed dormancy. A growing body of data suggests that flavonoids may also play a fundamental role in regulating communication between the seed coat and the endosperm. In the present review, we discuss how this may be achieved in the light of the fact that several flavonoids are known to be potent auxin transport regulators.
Regulation of fertilization and early seed development
Authors: Dresselhaus Thomas , Doughty James
Published: March 2014

Plant reproduction meetings often deal either with pre-fertilization processes such as flowering and pollen biology or post-fertilization processes such as embryogenesis and seed development. The Biochemical Society Focused Meeting entitled ‘Regulation of Fertilization and Early Seed Development’ was organized to close this gap and to discuss mechanistic similarities and future research directions in the reproductive processes shortly before, during and after fertilization. As an outcome of the workshop, invited speakers and a few selected oral communication presenters contributed focused reviews and technical articles for this issue of Biochemical Society Transactions. We provide here a short overview of the contents and highlights of the various articles.
Controlling microtube permeability via grafted polymers and solvent quality
Authors: Suo Tongchuan , Whitmore Mark D.
Published: March 2014

We examine pressure-driven flow through a microtube with grafted polymers using a “doubly self-consistent field” steady-state theory. Our focus is on the structure of the polymer layer, the tube permeability, and the effects of solvent quality, for different regimes of open and closed tubes. We find that, within experimentally attainable pressure gradients, the flow has very little effect on the grafted layer. However, the polymers, and in particular variations in the solvent quality and cylinder radii, can have large effects on the flow. We find that the permeability can either increase or decrease with either the radius or solvent quality, and we identify the regimes for different behaviors in terms of general parameters that can be used to generalize to other systems. This allows us to identify regimes where the systems are most sensitive to these “tuning” parameters, and we find that they correspond to the boundaries between open and closed tubes identified earlier.
The influence of inertia and contact angle on the instability of partially wetting liquid strips: A numerical analysis study
Authors: Ubal Sebastián , Grassia Paul , Campana Diego M. , Giavedoni María D. , Saita Fernando A.
Published: March 2014

The stability of a thread of fluid deposited on a flat solid substrate is studied numerically by means of the Finite Element Method in combination with an Arbitrary Lagrangian-Eulerian technique. A good agreement is observed when our results are compared with predictions of linear stability analysis obtained by other authors. Moreover, we also analysed the influence of inertia for different contact angles and found that inertia strongly affects the growth rate of the instability when contact angles are large. By contrast, the wave number of the fastest growing mode does not show important variations with inertia. The numerical technique allows us to follow the evolution of the free surface instability until comparatively late stages, where the filament begins to break into droplets. The rupture pattern observed for several cases shows that the number of principal droplets agrees reasonably well with an estimation based on the fastest growing modes.
Spatial resolution in vector potential photoelectron microscopy
Authors: Browning R.
Published: March 2014

The experimental spatial resolution of vector potential photoelectron microscopy is found to be much higher than expected because of the cancellation of one of the expected contributions to the point spread function. We present a new calculation of the spatial resolution with support from finite element ray tracing, and experimental results.
Switching efficiency improvement in spin torque majority gates
Authors: Nikonov Dmitri E. , Manipatruni Sasikanth , Young Ian A.
Published: March 2014

Spin torque majority gate (STMG) is one of the promising options for beyond complementary metal-oxide-semiconductor logic. Improvement of its performance—switching speed vs. required current—is critical for its competitiveness. In this paper, (a) we identify an optimized layout of the gate comprised of thin magnetic wires with in-plane magnetization; (b) we optimize geometries of perpendicular magnetization spin torque majority gates. Micromagnetic simulations demonstrate an improvement in switching current for in-plane magnetization (with less than 1 ns switching time) from 6 mA in the original scheme to 1.5 mA in the present one. Additionally, failures of switching caused by vortex formation are eliminated and desired output magnetization is achieved. Various geometries of STMG with perpendicular magnetization are explored. The scheme with a straight cross proves to be the most advantageous. It is predicted to operate with the switching current of 50 μA and less than 4 ns switching time.
High quality factor integrated gigahertz magnetic transformers with FeGaB/Al2O3 multilayer films for radio frequency integrated circuits applications
Authors: Gao Y. , Zare S. , Yang X. , Nan T. X. , Zhou Z. Y. , Onabajo M. , O'Brien Kevin P. , Jalan Umesh , EI-tatani Mohammed , Fisher Paul , Liu M. , Aronow A. , Mahalingam K. , Howe B. M. , Brown G. J. , Sun N. X.
Published: March 2014

This work report new integrated high quality factor (Q) GHz magnetic transformers based on solenoid structures with FeGaB/Al2O3 multilayer films. These transformers show excellent high-frequency performance with a wide operation frequency range of 0.5–5 GHz, in which primary, secondary, and mutual inductances are flat, and the peak quality factor can reach around 14 at frequency of 1.2 GHz. High mutual coupling and low insertion loss are also demonstrated. These novel GHz transformers with high Q and mutual coupling show great promise for applications in radio frequency integrated circuits.