bluuebunny/crossref_metadata_2025_split huggingface dataset:
Antenna Radiation Patterns
Authors: Chryssomallis Michael , Christodoulou Christos 
Published: June 2015

The radiation pattern of an antenna is one of its basic properties since it shows the way the antenna distributes its energy in space. It generally consists of a number of lobes and if it is measured far away from the antenna it is independent of distance. It is a function of angles and can be expressed as field or power pattern. It usually can be completely specified from the patterns in two planes, perpendicular to each other, theEandHplanes, respectively. Related to the radiation pattern of an antenna, a number of important parameters exist, such as radiated power, radiation efficiency, directivity, gain, and antenna polarization.The aim of this article is to provide an introduction to radiation patterns and all the related important parameters. The content is organized in five sections. The second section introduces several antenna patterns, giving the necessary definitions and presenting the common types. The field regions of an antenna are also pointed out. In the third section, after the introduction of Poynting vector and radiation power density, radiation performance measures such as the beam solid angle, directivity, and gain of an antenna are defined. In the fourth section, the concepts of wave and antenna polarizations are discussed. Finally, in the fifth section, a general case of antenna pattern calculation is considered, and numerical solutions are suggested for radiation patterns that are not available in simple closed‐form expressions.
A community benchmark for viscoplastic thermal convection in a 2‐D square box
Authors: Tosi N. , Stein C. , Noack L. , Hüttig C. , Maierová P. , Samuel H. , Davies D. R. , Wilson C. R. , Kramer S. C. , Thieulot C. , Glerum A. , Fraters M. , Spakman W. , Rozel A. , Tackley P. J. 
Published: June 2015

AbstractNumerical simulations of thermal convection in the Earth's mantle often employ a pseudoplastic rheology in order to mimic the plate‐like behavior of the lithosphere. Yet the benchmark tests available in the literature are largely based on simple linear rheologies in which the viscosity is either assumed to be constant or weakly dependent on temperature. Here we present a suite of simple tests based on nonlinear rheologies featuring temperature, pressure, and strain rate‐dependent viscosity. Eleven different codes based on the finite volume, finite element, or spectral methods have been used to run five benchmark cases leading to stagnant lid, mobile lid, and periodic convection in a 2‐D square box. For two of these cases, we also show resolution tests from all contributing codes. In addition, we present a bifurcation analysis, describing the transition from a mobile lid regime to a periodic regime, and from a periodic regime to a stagnant lid regime, as a function of the yield stress. At a resolution of around 100 cells or elements in both vertical and horizontal directions, all codes reproduce the required diagnostic quantities with a discrepancy of at most
in the presence of both linear and nonlinear rheologies. Furthermore, they consistently predict the critical value of the yield stress at which the transition between different regimes occurs. As the most recent mantle convection codes can handle a number of different geometries within a single solution framework, this benchmark will also prove useful when validating viscoplastic thermal convection simulations in such geometries.
Driftcretions: The legacy impacts of driftwood on shoreline morphology
Authors: Kramer Natalie , Wohl Ellen 
Published: June 2015

AbstractThis research demonstrates how vegetation interacts with physical processes to govern landscape development. We quantify and describe interactions among driftwood, sedimentation, and vegetation for Great Slave Lake, which is used as proxy for shoreline dynamics and landforms before deforestation and wood removal along major waterways. We introduce driftcretion to describe large, persistent concentrations of driftwood that interact with vegetation and sedimentation to influence shoreline evolution. We report the volume and distribution of driftwood along shorelines, the morphological impacts of driftwood delivery throughout the Holocene, and rates of driftwood accretion. Driftcretions facilitate the formation of complex, diverse morphologies that increase biological productivity and organic carbon capture and buffer against erosion. Driftcretions should be common on shorelines receiving a large wood supply and with processes which store wood permanently. We encourage others to work in these depositional zones to understand the physical and biological impacts of large wood export from river basins.
On the evolution of Atlantic Meridional Overturning Circulation Fingerprint and implications for decadal predictability in the North Atlantic
Authors: Zhang Jinting , Zhang Rong 
Published: June 2015

AbstractIt has been suggested previously that the Atlantic Meridional Overturning Circulation (AMOC) anomaly associated with changes in the North Atlantic Deep Water formation propagates southward with an advection speed north of 34°N. In this study, using Geophysical Fluid Dynamics Laboratory Coupled Model version 2.1 (GFDL CM2.1), we show that this slow southward propagation of the AMOC anomaly is crucial for the evolution and the enhanced decadal predictability of the AMOC fingerprint—the leading mode of upper ocean heat content (UOHC) in the extratropical North Atlantic. A positive AMOC anomaly in northern high latitudes leads to a convergence/divergence of the Atlantic meridional heat transport (MHT) anomaly in the subpolar/Gulf Stream region, thus warming in the subpolar gyre (SPG) and cooling in the Gulf Stream region after several years. Recent decadal prediction studies successfully predicted the observed warm shift in the SPG in the mid‐1990s. Our results here provide the physical mechanism for the enhanced decadal prediction skills in the SPG UOHC.
A quantitative assessment of the relationship between precipitation deficits and air temperature variations
Authors: He B. , Wang H. L. , Wang Q. F. , Di Z. H. 
Published: June 2015

AbstractPrevious studies have reported precipitation deficits related to temperature extremes. However, how and to what extent precipitation deficits affect surface air temperatures is still poorly understood. In this study, the relationship between precipitation deficits and surface temperatures was examined in China from 1960 to 2012 based on monthly temperature and precipitation records from 565 stations. Significant negative correlations were identified in each season, with the strongest relationships in the summer, indicating that higher temperatures usually accompanied water‐deficient conditions and lower temperatures usually accompanied wet conditions. The examination of the correlations based on 30 year moving windows suggested that the interaction between the two variables has declined over the past three decades. Further investigation indicated a higher impact of extreme dry conditions on temperature than that of extreme wet conditions. In addition, a new simple index (Dry Temperature Index, DTI) was developed and used to quantitatively describe the relationship between water deficits and air temperature variations. We tested and compared the DTI in the coldest month (January) and the hottest month (July) of the year, station by station. In both months, the number of stations with a DThighI ≥ 50% was greater than those with a DThighI < 50%, indicating that a greater proportion of higher temperatures occurred during dry conditions. Based on the results, we conclude that water deficits in China are usually correlated to high temperatures but not to low temperatures.
Haematopoiesis
Authors: Kumar Ritu , Evans Todd 
Published: June 2015

Abstract

Haematopoiesis generates a variety of distinct blood cell types from a common stem cell. Secreted signalling molecules called cytokines modulate the survival, proliferation and differentiation of all the blood cell lineages, mediated by defined sets of transcription factors. Haematopoiesis is also influenced by external cues such as oxygen concentration. Haematopoiesis is an ongoing process continuing throughout lifetime, although the location of stem cells, and the specific cell types derived from them, changes during embryonic, foetal and early postnatal development. In the adult, haematopoiesis occurs primarily in the bone marrow, in association with a supportive niche. Haematopoietic stem cells are derived from cells bipotential for blood and endothelial cells, or directly from specialised endothelium. Blood lineages have a hierarchical relationship, but there is some flexibility among progenitors for deriving specific fates. Defects in haematopoiesis result in common and serious human diseases including anaemia and leukaemia.

Key Concepts

Haematopoiesis is the process of forming blood cells, which occurs during embryogenesis and throughout life.

Defects in haematopoiesis can result in some of the most common and serious human diseases, including anaemia and leukaemia.

Blood consists of many different kinds of cells with a diverse range of functions, controlling gaseous exchange and clotting and comprising the immune system.

All blood cells are derived from a common progenitor, the haematopoietic stem cell.

The sites where haematopoiesis occurs change during embryonic development, but in adult mammals, the bone marrow is the major site of haematopoiesis.

Haematopoietic stem cells in the bone marrow reside in a specialised microenvironment known as the haematopoietic stem cell niche, composed of osteoblasts, mesenchymal cells and sinusoidal vessels.

Growth factors called cytokines control the survival, self‐renewal and differentiation of haematopoietic stem cells and their progeny.

Blood cells have a close developmental relationship with endothelial cells, and haematopoietic stem cells appear to derive from ‘haemogenic endothelium’.

Haematopoiesis is also regulated by external factors. For example, hypoxia results in a compensatory increase in the number of erythrocytes.

Much effort is currently focused on generating and manipulating haematopoietic stem cells in vitro, to develop new regenerative therapies.
Ribosomal Proteins: Role in Ribosomal Functions
Authors: Nikolay Rainer , van den Bruck David , Achenbach John , Nierhaus Knud H 
Published: June 2015

Abstract

The assignment of specific ribosomal functions to individual ribosomal proteins is difficult due to the enormous cooperativity of the ribosome; however, important roles for distinct ribosomal proteins are becoming evident. Although ribosomal ribonucleic acid (rRNA) has the major claim to certain aspects of ribosome function, such as decoding and peptidyltransferase activity, there are also protein‐dominated functional hot‐spots on the ribosome such as the messenger RNA (mRNA) entry pore, the translation factor‐binding site and the exit of the ribosomal tunnel. The latter is binding site for both chaperones and complexes associated with protein transport through membranes. Furthermore, the contribution of ribosomal proteins is essential for the assembly and optimal functioning of the ribosome.

Key Concepts

A universal nomenclature for the ribosomal proteins was introduced in 2014, which terminates the babylonic chaos of the various nomenclature systems.

About two thirds of the bacterial ribosomal proteins have counterparts in archaeal and eukaryotic ribosomes.

Both rRNA and ribosomal proteins are essential for assembly, structure and function of the ribosomes.

A few ribosomal proteins are essential for the assembly, but lack a function in the mature ribosome.

In addition to rRNA‐dominated functional hot‐spots such as the decoding centre and the peptidyl‐transferase centre, there are also protein‐dominated functional hot‐spots such as the entry pore for the mRNA on the 30S subunit, the docking site for G‐protein factors and the exit of the tunnel harbouring the nascent peptide chain.
Xenopus
Embryo: Neural Induction
Authors: Pla Patrick , Monsoro‐Burq Anne‐Hélène 
Published: June 2015

Abstract

In embryos, the prospective nervous system forms during early development by a series of molecular events named neural induction. This includes the early action of mesoderm‐derived fibroblast growth factors (FGFs), followed by the blockade of bone morphogenetic protein (BMP) signalling by the dorsal mesoderm during gastrulation, and finally comprises the regionalisation of the neural plate along the anterior‐posterior and medial‐lateral axes, under the complex and combined actions of FGFs, retinoids and Wnts. Founding experiments using frog embryos have initiated intensive research on neural induction 90 years ago. Molecular approaches combined to classical experimental embryology strategies provide a powerful way of deciphering those complex regulations in frogs and more recently in other vertebrates. This article describes the current model of neural induction in the frog model system
Xenopus,
a model largely conserved between aquatic species and amniotes.

Key Concepts

The formation of neural precursors from the embryonic ectoderm is one of the earliest embryonic inductions.

Neural induction results in the formation of a neural plate regionalised along its anterior‐posterior and medial‐lateral axis.

Neural induction is subdivided into at least three steps: acquisition of neural competence, induction of anterior neural tissue, and posteriorisation of the neural tissue.

Almost a century after the discovery of the Spemann–Mangold organiser in frogs, the exploration of the molecular mechanisms driving neural induction remains a very active field of research.

The models and molecular mechanisms discovered in frogs are largely conserved in other vertebrates including amniotes.
T‐Lymphocyte Responses: Development
Authors: Cosmi Lorenzo , Liotta Francesco , Annunziato Francesco 
Published: June 2015

AbstractCD4+ T cells can be subdivided from a functional point of view into two main subsets: effector cells, which provide protection against exogenous agents, and regulatory T (Treg) cells whose function is to avoid autoimmune reactions and to stop the effector response against exogenous antigens, when the response itself becomes dangerous for the host.Human effector T helper (Th) lymphocytes can be additionally classified into lineages based mainly on their immunological functions that are supported by distinct profile of cytokine, transcription factor and homing receptor expression. Recently, beyond the well‐known Th1 and Th2 cells, other populations have been discovered. These include the Th17 subset, which is certainly the most intensively studied, but also Th22, Th9 and T follicular helper (Tfh) lymphocytes. T effector lymphocytes are not only responsible for different types of protective responses but also for the pathogenesis of many disorders.Regarding Treg cells, there are two main categories, one emerging from the thymus as a population already planned to suppress the response against self antigens and another population which also emerges from the thymus, but acquires its suppressive activity in the periphery and is devoted to regulating the response towards non‐self antigens.Key ConceptsCD4+ Th cells exist in two main functional subsets: effector cells that fight with exogenous agents and regulatory cells that protect from the damage induced by immune response.Effector Th lymphocytes can be distinguished into three main phenotypes based on their immunological functions, the Th1, Th2 and Th17 subsets.Cytokines produced by cells of innate immunity at the moment of the encounter of the naive Th cell with the specific antigen are crucial in the acquisitions of the different effector phenotypes.T effector lymphocytes are also responsible for the pathogenesis of many disorders, Th1 and Th17 cells playing a role in chronic inflammatory diseases and Th2 cells in atopic diseases.T regulatory cells provide protection from autoimmune phenomena and from the potential damage induced by persisting of the immune response.T regulatory cells that achieve the regulatory phenotype in the thymus protect from self‐reactions, while the ones that acquire the regulatory properties in the periphery suppress the responses to exogenous antigens, when they may become dangerous for the host.
Human Genome Project, Personalised Medicine and Future Health Care
Authors: Tempini Niccolò , Leonelli Sabina 
Published: June 2015

AbstractAt the turn of the millennium, the Human Genome Project and the upcoming publication of the human genome sequence promised to open an entirely new approach to healthcare, based on the genotype of the individual. This approach was dubbed personalised medicine (PM). However, the analysis of sequencing results revealed that the complexity of the biological world had been underestimated. The major project of revolutionising medicine through genomics requires a more sophisticated and multilevel understanding of living systems, which in turn demands new data, models and modes of intervention on humans and non‐human organisms. Thus, the most advanced applications of PM involve a complex interweaving of biological and medical knowledge, as well as increasing attention to the technical systems through which data about any specific individual could be processed. Further, the development of PM needs to include consideration of several key ethical issues, ranging from privacy and data control to the risk that dependence on sophisticated technologies will widen the gap between haves and have‐nots both globally and within any one country.Key ConceptsPersonalised medicinedescribes the direction medical solutions are expected to evolve, towards personalisation and individual tailoring of therapies and treatment regimes that will cut and divide through patient populations. The motor of this promised innovation will be genomic profiling techniques, of nuclear DNA but also ones of latter development such as proteomics, metabolomics, transcriptomics and so on.Biomedicineis an interdisciplinary space involving biological and medical knowledge/expertise as well as IT, where scientific knowledge about biological phenomena is mobilised in order to devise solutions to medical problems.Data‐intensive sciencedescribes the mode of scientific research that is emerging as paramount in an age characterised by the increasing reliance and dependence of researchers on the development of complex, distributed infrastructures for data sharing and analysis.Postgenomicsindicates efforts at creating and understanding models of life and disease that put genomic science and other biosciences at all levels of complexity in relation to each other.Translational medicineindicates the fast‐developing domain of efforts and debate aimed at improving the translatability of discoveries and techniques from the lab into solutions, drugs and therapies that can be effectively implemented at the point of healthcare delivery.
Gamete Donation and ‘Race’
Authors: Hudson Nicky 
Published: June 2015

Abstract

Examining processes of gamete donation offers an opportunity to expose ideas about ‘race’ and examine perceptions about the racial substance that is ‘passed on’ from donor to offspring. Racial categories are of interest in the context of gamete donation because established ideas about the transmission of racial markers between generations and within racialised communities infuse the way in which donation is organised in clinical settings. The use and maintenance of these categories in donation practice has wider political implications because it reinscribes and re‐legitimises problematic and contested categories. This short article begins with an overview of the conceptual challenges associated with categorisations of race, considers the subsequent complexities of differentiating gamete donors in racial terms and concludes with a discussion of the implications of these debates for clinical practice, kinship relations and beyond.

Key Concepts

Ideas about the existence of discrete racial groups have been largely resigned to the history of scientific racism and colonialism.

Despite their contested nature, racial categories endure as a powerful visible signifier for relatedness and belonging in biological terms as well as carrying ideas about cultural and social relatedness, which are highly pertinent in understanding kinship.

Gamete donation, a form of assisted reproduction, offers a useful lens through which to expose ideas about race and examine perceptions about the racial substance that is ‘passed on’ from donor to offspring.

The ways people think about and select donors based on their racial or ethnic identities are often flexible and contingent and can therefore be at odds with commonly understood or clinically defined racial categories.

Whilst it is unlikely that racial categorisation will be omitted from use in assisted reproduction practices, we should remain cautious about the value that is attributed to such characteristics, particularly in relation to the growing globalised market in fertility treatment.
Structural Proteomics: Large‐Scale Studies
Authors: Ewing Rob M , Doyle Declan A 
Published: June 2015

Abstract

Proteins have many different functions in biological systems, and the molecular functions of proteins are dependent on their three‐dimensional structures. Mapping protein structures is therefore an important strategy in understanding gene and protein function. Structural proteomics or structural genomics refers to systematic efforts to functionally annotate protein molecular structures of whole or selected parts of genomes and/or proteomes. Structural proteomics studies have significantly added to our knowledge of protein structures over the past few years and a large fraction of available protein structures in public databases result from high‐throughput structural proteomics studies. Although structural proteomics techniques are continually being improved, significant challenges remain in protein expression and crystallisation and in particular for solving protein structures for challenging classes of protein such as membrane proteins.

Key Concepts

Protein function is directly linked to the three‐dimensional structure of the protein.

Structural proteomics refers to large‐scale mapping of protein structures.

Techniques such as protein crystallisation and X‐ray bombardment allow the three‐dimensional arrangement of atoms in protein molecules to be determined.

Technical and biological challenges remain in structural proteomics – in particular for certain classes of proteins such as proteins that span membranes. Large‐scale structural proteomics is an enabling technology for systems biology.