New Generation (new + generation)

Distribution by Scientific Domains

Selected Abstracts


ABSTRACT A supercritical fluid extrusion (SCFX) process has been successfully developed for the production of a novel healthy snack containing 40,60 wt% protein with unique porous structure and texture. Supercritical carbon dioxide (SC-CO2) injection rate and product temperature at the die were found to be critical to control the expansion and texture of the final product. Maximum cross-sectional expansion was obtained at 0.3 wt% added SC-CO2, whereas more uniform internal structure was achieved at 0.7 wt% SC-CO2 level. As whey protein concentrate (80 wt%) concentration was increased from 52.8 to 78.2 wt% in the formulation, the cross-sectional expansion of baked and fried products increased by 65.8 and 44.4%, respectively. It was observed that lower viscosity of whey protein compared with starch decreased expansion but helped enhance further expansion during post-extrusion drying. The finding showed that an extrusion process at the temperature below protein denaturation temperature using SC-CO2 can help to prevent hard texture due to the thermosetting property of whey protein and to create a uniformly expanded structure. The textural properties of SCFX chips were comparable to commercial extruded or fried chip products. PRACTICAL APPLICATIONS The American snack market is one of fast-growing markets in the world as snacking becomes more popular. Because of the increasing concerns about health, there is also an increasing demand for new healthy snacks as an alternative for fried starch-based snacks with low nutrient density. This study shows the potential of supercritical fluid extrusion (SCFX) technology for healthy snack food production containing whey protein. SCFX chips had uniform cellular microstructure that cannot be obtained using conventional steam-based extrusion. As supercritical carbon dioxide can deliver certain flavors, an expanded snack not only with high nutrient density and unique texture but also with encapsulated flavors can be produced using the SCFX process and can be marketed as a novel healthy snack. [source]

Profiling a New Generation of Female Small Business Owners in New Zealand: Networking, Mentoring and Growth

Judy McGregor
The contribution of female small business owners to economic development in Western developed countries such as New Zealand, Australia, the United Kingdom, the United States and Canada, is generally under,researched and traditionally grounded in male norms. Increasingly policy,makers acknowledge that in countries like New Zealand where 85% of business employs five or less people, small business offers the greatest employment potential. Not enough is known, though, about the growth orientation and characteristics of female small business owners. This article reports findings from the largest empirical study of small business undertaken in New Zealand and provides inter,gender comparison between male and female small business owners and for intra,gender contrast between networked female small business owners and women who did not belong to a business network. The results showed that the networked women, who were in the main better educated and more affiliative by nature, were more expansionist than both other female small business owners and men. The networked women were also more likely to have a business mentor. The findings confound earlier research suggesting women are less growth,orientated and wish only to satisfy intrinsic needs from their businesses. The article concludes by discussing the need to acknowledge the heterogeneity of female small business and what this means for policy,makers when assessing their socio,economic potential. [source]

New Generation of Multifunctional Nanoparticles for Cancer Imaging and Therapy

Kyeongsoon Park
Abstract Advances in nanotechnology have contributed to the development of novel nanoparticles that enable the tumor-specific delivery of imaging probes and therapeutic agents in cancer imaging and therapy. Nanobiotechnology combines nanotechnology with molecular imaging, which has led to the generation of new multifunctional nanoparticles for cancer imaging and therapy. Multifunctional nanoparticles hold great promise for the future of cancer treatment because they can detect the early onset of cancer in each individual patient and deliver suitable therapeutic agents to enhance therapeutic efficacy. The combination of tumor-targeted imaging and therapy in an all-in-one system provides a useful multimodal approach in the battle against cancer. Novel multifunctional nanoparticles thus offer a new avenue in the application of personalized medicine in the near future. Herein, new trends and the significance of novel multifunctional nanoparticles in cancer imaging and therapy are reviewed. [source]

A New Generation of Catalytic Poly(vinylidene fluoride) Membranes: Coupling Plasma Treatment with Chemical Immobilization of Tungsten-Based Catalysts ,

C. Lopez
Abstract A new generation of catalytically active membranes for secondary amine oxidation and phenol degradation has been developed by coupling the advantages of low-temperature plasma-modification processes with surface chemical immobilization reactions of catalysts. Poly(vinylidene fluoride) membranes have been modified with NH3 radiofrequency glow discharges in order to graft amino groups at their surface, providing active sites for stable immobilization of tungsten-based heterogeneous catalysts. Particular attention has been focused on tungstate, WO42,, and decatungstate, W10O324,, which act efficiently as catalysts for the oxidation of secondary amines and as photocatalysts for the degradation of organic pollutants, respectively. Plasma-modified membranes surface-tailored with WO42, have been used in catalytic membrane reactors to activate hydrogen peroxide for oxidizing secondary amines to nitrones; membranes modified with W10O324, have been used for the complete degradation of phenol. The obtained results, in terms of amine,nitrone conversion and phenol degradation, respectively, appear extremely promising; these modified membranes can be considered as a pioneering, successful example of heterogenization of W-based catalysts on plasma-treated membranes. [source]

"The New Generation": Mental Hygiene and the Portrayals of Children by the National Film Board of Canada, 1946,1967

Brian J. Low
That is the achievement of the psychologists. In our own society they are very kind, and do everything for our own good. The tales of what they do elsewhere are rather terrifying. ,Hilda Neatby So Little for the Mind (1953) [source]

Qatari Women: a New Generation of Leaders?

Louay Bahry

A New Generation of Women's Health Services

Growing Service Lines Beyond Reproductive Health
First page of article [source]

Strain and Hückel Aromaticity: Driving Forces for a Promising New Generation of Electron Acceptors in Organic Electronics,

G. Brunetti Dr.
Die Hauptmerkmale elektronenakzeptierender Materialien mit einem 9,9,-Bifluorenyliden-Gerüst sind verringerte Ringspannungen und ein Zugewinn an Aromatizität. Die Dimere (siehe Bild) zeigen eine Absorption nahe dem roten Spektralbereich (ca. 600,nm) sowie HOMO- (5.58,5.06,eV) und LUMO-Niveaus (3.37,3.09,eV), die die Materialien zusammen mit ihrer hohen Löslichkeit und thermischen Stabilität zu vielversprechenden Akzeptoren für Bulk-Heterojunction(BHJ)-Solarzellen machen. [source]

Pyrazolo[4,3-d]pyrimidines as New Generation of Cyclin-Dependent Kinase Inhibitors.

CHEMINFORM, Issue 51 2003
Daniela Moravcova
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

Bis-Tetrahydrofuran: a Privileged Ligand for Darunavir and a New Generation of HIV Protease Inhibitors That Combat Drug Resistance

CHEMMEDCHEM, Issue 9 2006

Two inhibitors that incorporate bis-THF as an effective high-affinity P2 ligand for the HIV-1 protease substrate binding site maintain impressive potency against mutant strains resistant to currently approved protease inhibitors. Crystallographic structures of protein,ligand complexes help to explain the superior antiviral property of these inhibitors and their potency against a wide spectrum of HIV-1 strains. [source]

New Generation of Gold Catalysts: Nanoporous Foams and Tubes,Is Unsupported Gold Catalytically Active?

CHEMPHYSCHEM, Issue 13 2007
Masatake Haruta Prof. Dr.
Gold fever: Gold turns out to be catalytically very active, provided that either one or two of the three conditions shown in the graphic are fulfilled. In CO oxidation at room temperature even unsupported gold is active in the presence of alkaline water. The active states of gold in the gold catalysts reported so far can be classified into four groups: bulk gold, nanoparticles, clusters or thin layers with specific sizes, and cations. [source]

Biodegradable polymers applied in tissue engineering research: a review

Monique Martina
Abstract Typical applications and research areas of polymeric biomaterials include tissue replacement, tissue augmentation, tissue support, and drug delivery. In many cases the body needs only the temporary presence of a device/biomaterial, in which instance biodegradable and certain partially biodegradable polymeric materials are better alternatives than biostable ones. Recent treatment concepts based on scaffold-based tissue engineering principles differ from standard tissue replacement and drug therapies as the engineered tissue aims not only to repair but also regenerate the target tissue. Cells have been cultured outside the body for many years; however, it has only recently become possible for scientists and engineers to grow complex three-dimensional tissue grafts to meet clinical needs. New generations of scaffolds based on synthetic and natural polymers are being developed and evaluated at a rapid pace, aimed at mimicking the structural characteristics of natural extracellular matrix. This review focuses on scaffolds made of more recently developed synthetic polymers for tissue engineering applications. Currently, the design and fabrication of biodegradable synthetic scaffolds is driven by four material categories: (i) common clinically established polymers, including polyglycolide, polylactides, polycaprolactone; (ii) novel di- and tri-block polymers; (iii) newly synthesized or studied polymeric biomaterials, such as polyorthoester, polyanhydrides, polyhydroxyalkanoate, polypyrroles, poly(ether ester amide)s, elastic shape-memory polymers; and (iv) biomimetic materials, supramolecular polymers formed by self-assembly, and matrices presenting distinctive or a variety of biochemical cues. This paper aims to review the latest developments from a scaffold material perspective, mainly pertaining to categories (ii) and (iii) listed above. Copyright © 2006 Society of Chemical Industry [source]

Attenuation of pain and inflammation in adjuvant-induced arthritis by the proteasome inhibitor MG132

Aisha S. Ahmed
Objective In rheumatoid arthritis (RA), pain and joint destruction are initiated and propagated by the production of proinflammatory mediators. Synthesis of these mediators is regulated by the transcription factor NF-,B, which is controlled by the ubiquitin proteasome system (UPS). The present study explored the effects of the proteasome inhibitor MG132 on inflammation, pain, joint destruction, and expression of sensory neuropeptides as markers of neuronal response in a rat model of arthritis. Methods Arthritis was induced in rats by injection of heat-killed Mycobacterium butyricum. Arthritis severity was scored, and nociception was evaluated by mechanical pressure applied to the hind paw. Joint destruction was assessed by radiologic and histologic analyses. NF-,B DNA-binding activity was analyzed by electromobility shift assay, and changes in the expression of the p50 NF-,B subunit and the proinflammatory neuropeptides substance P (SP) and calcitonin gene-related peptide (CGRP) were detected by immunohistochemistry. Results Arthritic rats treated with MG132 demonstrated a marked reduction in inflammation, pain, and joint destruction. The elevated DNA-binding activity of the NF-,B/p50 homodimer and p50, as well as the neuronal expression of SP and CGRP, observed in the ankle joints of arthritic rats were normalized after treatment with MG132. Conclusion In arthritic rats, inhibition of proteasome reduced the severity of arthritis and reversed the pain behavior associated with joint inflammation. These effects may be mediated through the inhibition of NF-,B activation and may possibly involve the peripheral nervous system. New generations of nontoxic proteasome inhibitors may represent a novel pharmacotherapy for RA. [source]

Are Points the Better Graphics Primitives?

Markus Gross
Since the early days of graphics the computer based representation of three-dimensional geometry has been one of the core research fields. Today, various sophisticated geometric modelling techniques including NURBS or implicit surfaces allow the creation of 3D graphics models with increasingly complex shape. In spite of these methods the triangle has survived over decades as the king of graphics primitives meeting the right balance between descriptive power and computational burden. As a consequence, today's consumer graphics hardware is heavily tailored for high performance triangle processing. In addition, a new generation of geometry processing methods including hierarchical representations, geometric filtering, or feature detection fosters the concept of triangle meshes for graphics modelling. Unlike triangles, points have amazingly been neglected as a graphics primitive. Although being included in APIs since many years, it is only recently that point samples experience a renaissance in computer graphics. Conceptually, points provide a mere discretization of geometry without explicit storage of topology. Thus, point samples reduce the representation to the essentials needed for rendering and enable us to generate highly optimized object representations. Although the loss of topology poses great challenges for graphics processing, the latest generation of algorithms features high performance rendering, point/pixel shading, anisotropic texture mapping, and advanced signal processing of point sampled geometry. This talk will give an overview of how recent research results in the processing of triangles and points are changing our traditional way of thinking of surface representations in computer graphics - and will discuss the question: Are Points the Better Graphics Primitives? [source]

Tumor imaging in small animals with a combined micro-CT/micro-DSA system using iodinated conventional and blood pool contrast agents

Cristian T. Badea
Abstract X-ray based micro-computed tomography (CT) and micro-digital subtraction angiography (DSA) are important non-invasive imaging modalities for following tumorogenesis in small animals. To exploit these imaging capabilities further, the two modalities were combined into a single system to provide both morphological and functional data from the same tumor in a single imaging session. The system is described and examples are given of imaging implanted fibrosarcoma tumors in rats using two types of contrast media: (a) a new generation of blood pool contrast agent containing iodine with a concentration of 130,mg/mL (FenestraÔ VC, Alerion Biomedical, San Diego, CA, USA) for micro-CT and (b) a conventional iodinated contrast agent (Isovue®-370,mg/mL iodine, trademark of Bracco Diagnostics, Princeton, NJ, USA) for micro-DSA. With the blood pool contrast agent, the 3D vascular architecture is revealed in exquisite detail at 100,µm resolution. Micro-DSA images, in perfect registration with the 3D micro-CT datasets, provide complementary functional information such as mean transit times and relative blood flow through the tumor. This imaging approach could be used to understand tumor angiogenesis better and be the basis for evaluating anti-angiogenic therapies. Copyright © 2006 John Wiley & Sons Ltd. [source]

Mental health impact of Afghanistan and Iraq deployment: meeting the challenge of a new generation of veterans

Charles R. Marmar M.D.
First page of article [source]

Contrast Echocardiography: Clinical Utility

Gerald Maurer M.D.
This article reviews the advances made by the echocardiography contrast agents from their first appearance in the early 1970s with homemade preparations up to the new generation of transpul-monary contrast agents made of small microbubbles capable of transversing the lung's capillary bed. The great progress in contrast agent development has kept pace with the progress made by echocar-diographic equipment, thus making the study of myocardial perfusion in the clinical settings a near-future reality. This article also discusses the medical need that myocardial contrast echo has the potential to satisfy. [source]

High-throughput screening of kinase inhibitors by multiplex capillary electrophoresis with UV absorption detection

Yan He
Abstract Protein kinases play a major role in the transformation of cells and are often used as molecular targets for the new generation of anticancer drugs. We present a novel technique for high-throughput screening of inhibitors of protein kinases. The technique involves the use of multiplexed capillary electrophoresis (CE) for the rapid separation of the peptides, phosphopeptides, and various inhibitors. By means of UV detection, diversified peptides with native amino acid sequences and their phosphorylated counterparts can be directly analyzed without the need for radioactive or fluorescence labeling. The effects of different inhibitors and their IC50 value were determined using three different situations involving the use of a single purified kinase, two purified kinases, and crude cell extracts, respectively. The results suggest that multiplexed CE/UV may prove to be a straightforward and general approach for high-throughput screening of compound libraries to find potent and selective inhibitors of the various protein kinases. [source]

Going Public: Teaching Students to Speak Out in Public Contexts

Judith Baxter
Abstract Many students find speaking in large group, whole class or ,public' contexts intimidating. Over the last 30 years, a model of collaborative talk in small groups has been favoured within English teaching in British education but, with the new generation of GCSE syllabuses, students are required to speak effectively to larger audiences. This article explores what constitutes an effective ,public' speaker at GCSE level, and suggests various teaching strategies as starting points. [source]

Rhetoric and Practice in English Teaching

Mary Bousted
Abstract The empirical data collected for this article are derived from an analysis of the ideology and practice of English teachers working in three contrasting secondary schools. The analysis of the data reveals the following findings. The concept of personal growth, expressed in the pedagogy advocated by the London School, retains its ability to provide, for contemporary teachers of English, an underpinning rationale for their work. The pedagogical practices advocated by the London School writers - the use of oracy, the reading of contemporary children's literature and the drafting process - are supported by the respondents. Observation of lessons reveals that the respondents, through their use of mediating practices, are able to ,deliver' the cultural products of standard English and the literary canon in ways which retain elements of the process-based pedagogy advocated by the London School writers. The respondents do not, however, recognise this aspect of their classroom practice in their rhetorical representation of their work. The article concludes with the argument that the demand, by powerful external agencies, for the subject of English to furnish each new generation with icons of cultural stability in the form of spoken and written standard English and a knowledge of the literary heritage, has not declined. A less oppositional response on the part of English teachers to the demand that the subject deliver the cultural products outlined above, based upon a recognition of their use of mediating practices, may, it is argued, provide a means whereby the practitioners of the subject gain more control over its present condition and its future direction. [source]

Seasonal changes in wing dimorphism of the lygaeid bug Dimorphopterus japonicus (Heteroptera: Lygaeidae) in relation to environmental factors

Abstract The lygaeid bug Dimorphopterus japonicus Hidaka, which mainly feeds on a eulalia, Miscanthus sinensis, shows marked wing dimorphism of brachyptery and macroptery. Its production of macropters is stimulated in rearing conditions such as high temperature, long photoperiod and crowding during the nymphal stage. In this study, we investigated the seasonal prevalence in occurrence and the seasonal change in incidence of macroptery in D. japonicus for field populations in Okayama, western Japan. The results demonstrated that nymphal density was a key factor in determining the proportion of macropters, indicating an escape strategy from crowded populations. The field surveys also revealed that this bug has a univoltine life cycle in Okayama. There was a seasonal change in the incidence of macroptery in the new generation. The combined effects of temperature and photoperiod on wing-form determination explained this seasonality trait. [source]

Dynamic zone topology routing protocol for MANETs

Mehran Abolhasan
The limited scalability of the proactive and reactive routing protocols have resulted in the introduction of new generation of routing in mobile ad hoc networks, called hybrid routing. These protocols aim to extend the scalability of such networks beyond several hundred to thousand of nodes by defining a virtual infrastructure in the network. However, many of the hybrid routing protocols proposed to date are designed to function using a common pre-programmed static zone map. Other hybrid protocols reduce flooding by grouping nodes into clusters, governed by a cluster-head, which may create performance bottlenecks or a single point of failures at each cluster-head node. We propose a new routing strategy in which zones are created dynamically, using a dynamic zone creation algorithm. Therefore, nodes are not restricted to a specific region. Additionally, nodes perform routing and data forwarding in a cooperative manner, which means that in the case failure, route recalculation is minimised. Routing overheads are also further reduced by introducing a number of GPS-based location tracking mechanisms, which reduces the route discovery area and the number of nodes queried to find the required destination. Copyright © 2006 AEIT [source]


EVOLUTION, Issue 1 2009
Scott V. Edwards
The advent and maturation of algorithms for estimating species trees,phylogenetic trees that allow gene tree heterogeneity and whose tips represent lineages, populations and species, as opposed to genes,represent an exciting confluence of phylogenetics, phylogeography, and population genetics, and ushers in a new generation of concepts and challenges for the molecular systematist. In this essay I argue that to better deal with the large multilocus datasets brought on by phylogenomics, and to better align the fields of phylogeography and phylogenetics, we should embrace the primacy of species trees, not only as a new and useful practical tool for systematics, but also as a long-standing conceptual goal of systematics that, largely due to the lack of appropriate computational tools, has been eclipsed in the past few decades. I suggest that phylogenies as gene trees are a "local optimum" for systematics, and review recent advances that will bring us to the broader optimum inherent in species trees. In addition to adopting new methods of phylogenetic analysis (and ideally reserving the term "phylogeny" for species trees rather than gene trees), the new paradigm suggests shifts in a number of practices, such as sampling data to maximize not only the number of accumulated sites but also the number of independently segregating genes; routinely using coalescent or other models in computer simulations to allow gene tree heterogeneity; and understanding better the role of concatenation in influencing topologies and confidence in phylogenies. By building on the foundation laid by concepts of gene trees and coalescent theory, and by taking cues from recent trends in multilocus phylogeography, molecular systematics stands to be enriched. Many of the challenges and lessons learned for estimating gene trees will carry over to the challenge of estimating species trees, although adopting the species tree paradigm will clarify many issues (such as the nature of polytomies and the star tree paradox), raise conceptually new challenges, or provide new answers to old questions. [source]

The Role of Binder Content on Microstructure and Properties of a Cu-base Active Brazing Filler Metal for Diamond and cBN

R. Elsener
Melting experiments of Cu-Sn-Ti-Zr filler metal powder containing cellulose nitrate and graphite, respectively, resulted in the formation of nanosized TiC particles in both Cu-rich phase and CuSn3Ti5 intermetallic regions of the alloy (see figure). The variation of the binder type and content allows to tailor the properties of the filler metals in terms of erosion resistance, decisive for a new generation of superabrasive tools. [source]

Supramolecular Soft Adhesive Materials

Jérémie Courtois
Abstract The rheological and adhesive properties of bis-urea functionalized low-molecular-weight polyisobutylenes (PIBUT) are investigated. The polymers, which can interact through supramolecular hydrogen bonds, can self-organize over times of the order of days at room temperature. This organized structure has been identified by small angle X-ray scattering (SAXS) and its rheological properties indicate the behaviour of a soft viscoelastic gel. The ordered structure can be disrupted by temperature and shear so that at 80,°C, the material behaves as a highly viscoelastic fluid and no SAXS peak is observed. When cooled back at room temperature, the PIBUT retrieves its ordered structure and gel properties after 20 h of annealing. This very slow molecular dynamics gives PIBUT a highly dissipative nature upon deformation, which combined with strongly interacting moieties results in very interesting adhesive properties both on steel surfaces but more importantly on typical low adhesion surfaces such as silicone. A strategy based on the controlled incorporation of supramolecular bonds in a covalently crosslinked network appears promising for the development of a new generation of highly interacting and dissipative soft adhesives. [source]

The barefoot ecologist goes fishing

Jeremy D Prince
Abstract Haliotid (abalone) fisheries are comprised of small-scale (<5 km2) stocks and serve as a model for many such fisheries. Extremely valuable to local fishing communities in aggregate, these micro-stocks are myriad and complex to study, monitor, assess and manage. Micro-stocks need assessment and management at local scales to prevent small components from suffering the tragedy of commons. This paper asks how can we ever hope to address the research and management needs of so many small resources? Community-based and territorial rights-based systems may help in sustaining these resources, but servicing the technical needs of many small communities of stakeholders raises problems. A new generation of ,barefoot ecologists' is envisaged to perform this task. [source]

Cell Imaging: (Generic Strategy of Preparing Fluorescent Conjugated-Polymer-Loaded Poly(DL -lactide- co -Glycolide) Nanoparticles for Targeted Cell Imaging) Adv.

A generic strategy for the fabrication of highly fluorescent poly(DL -lactide- co -glycolide) nanoparticles loaded with conjugated polymers is reported by B. Liu et al. This method may serve to produce a new generation of biocompatible, surface-functionalizable probes for targeted cancer cell imaging and diagnostics, as described on page 3535. [source]

Generic Strategy of Preparing Fluorescent Conjugated-Polymer-Loaded Poly(DL -lactide- co -Glycolide) Nanoparticles for Targeted Cell Imaging

Kai Li
Abstract A general strategy for the preparation of highly fluorescent poly(DL-lactide- co -glycolide) (PLGA) nanoparticles (NPs) loaded with conjugated polymers (CPs) is reported. The process involves encapsulation of organic-soluble CPs with PLGA using a modified solvent extraction/evaporation technique. The obtained NPs are stable in aqueous media with biocompatible and functionalizable surfaces. In addition, fluorescent properties of the CP-loaded PLGA NPs (CPL NPs) could be fine-tuned by loading different types of CPs into the PLGA matrix. Four types of CPL NPs are prepared with a volume-average hydrodynamic diameter ranging from 243 to 272,nm. The application of CPL NPs for bio-imaging is demonstrated through incubation with MCF-7 breast cancer cells. Confocal laser scanning microscopy studies reveal that the CPL NPs are internalized in cytoplasm around the nuclei with intense fluorescence. After conjugation with folic acid, cellular uptake of the surface-functionalized CPL NPs is greatly enhanced via receptor-mediated endocytosis by MCF-7 breast cancer cells, as compared to that for NIH/3T3 fibroblast cells, which indicates a selective targeting effect of the folate-functionalized CPL NPs in cellular imaging. The merits of CPL NPs, such as low cytotoxicity, high fluorescence, good photostability, and feasible surface functionalization, will inspire extensive study of CPL NPs as a new generation of probes for specific biological imaging and detection. [source]

Aliovalent Substitutions in Olivine Lithium Iron Phosphate and Impact on Structure and Properties

Nonglak Meethong
Abstract Lithium transition metal phosphate olivines are enabling a new generation of high power, thermally stable, long-life rechargeable lithium batteries that may prove instrumental in the worldwide effort to develop cleaner and more sustainable energy. Nanoscale (<100,nm) derivatives of the olivine family LiMPO4 (M,=,Fe, Mn, Co, Ni) are being adopted in applications ranging in size scale from hybrid and plug-in hybrid electric vehicles to utilities-scale power regulation. Following the previous paradigm set with intercalation oxides, most studies have focused on the pure ordered compounds and isovalent substitutions. In contrast, even the possibility for, and role of, aliovalent doping has been widely debated. Here, critical tests of plausible defect compensation mechanisms using compositions designed to accommodate Mg2+, Al3+, Zr4+, Nb5+ ions on the M1,and/or M2 sites of LiFePO4 with appropriate charge-compensating defects are carried out, and conclusive crystallographic evidence for lattice doping, e.g., up to at least 12 atomic percent added Zr, is obtained. Structural and electrochemical analyses show that doping can reduce the lithium miscibility gap, increase phase transformation kinetics during cycling, and expand Li diffusion channels in the structure. Aliovalent modifications may be effective for introducing controlled atomic disorder into the ordered olivine structure to improve battery performance. [source]

How does the Schwann cell lineage form tumors in NF1?

GLIA, Issue 14 2008
Steven L. Carroll
Abstract Neurofibromas are benign tumors of peripheral nerve that occur sporadically or in patients with the autosomal dominant tumor predisposition syndrome neurofibromatosis type 1 (NF1). Multiple neurofibroma subtypes exist which differ in their site of occurrence, their association with NF1, and their tendency to undergo transformation to become malignant peripheral nerve sheath tumors (MPNSTs), the most common malignancy associated with NF1. Most NF1 patients carry a constitutional mutation of the NF1 tumor suppressor gene. Neurofibromas develop in these patients when an unknown cell type in the Schwann cell lineage loses its remaining functional NF1 gene and initiates a complex series of interactions with other cell types; these interactions may be influenced by aberrant expression of growth factors and growth factor receptors and the action of modifier genes. Cells within certain neurofibroma subtypes subsequently accumulate additional mutations affecting the p19ARF -MDM2-TP53 and p16INK4A-Rb signaling cascades, mutations of other as yet unidentified genes, and amplification of growth factor receptor genes, resulting in their transformation into MPNSTs. These observations have been validated using a variety of transgenic and knockout mouse models that recapitulate neurofibroma and MPNST pathogenesis. A new generation of mouse models is also providing important new insights into the identity of the cell type in the Schwann cell lineage that gives rise to neurofibromas. Our improving understanding of the mechanisms underlying the pathogenesis of neurofibromas and MPNSTs raises intriguing new questions about the origin and pathogenesis of these neoplasms and establishes models for the development of new therapies targeting these neoplasms. © 2008 Wiley-Liss, Inc. [source]