bluuebunny/crossref_metadata_2025 huggingface dataset:
The Distinct Role of Medium Spiny Neurons and Cholinergic Interneurons in the D2/A2AReceptor Interaction in the Striatum: Implications for Parkinson's Disease
Authors: Tozzi Alessandro , de Iure Antonio , Di Filippo Massimiliano , Tantucci Michela , Costa Cinzia , Borsini Franco , Ghiglieri Veronica , Giampà Carmen , Fusco Francesca Romana , Picconi Barbara , Calabresi Paolo
Published: February 2011

A2Aadenosine receptor antagonists are currently under investigation as potential therapeutic agents for Parkinson's disease (PD). However, the molecular mechanisms underlying this therapeutic effect is still unclear. A functional antagonism exists between A2Aadenosine and D2dopamine (DA) receptors that are coexpressed in striatal medium spiny neurons (MSNs) of the indirect pathway. Since this interaction could also occur in other neuronal subtypes, we have analyzed the pharmacological modulation of this relationship in murine MSNs of the direct and indirect pathways as well in striatal cholinergic interneurons. Under physiological conditions, endogenous cannabinoids (eCBs) play a major role in the inhibitory effect on striatal glutamatergic transmission exerted by the concomitant activation of D2DA receptors and blockade of A2Areceptors in both D2- and D1-expressing striatal MSNs. In experimental models of PD, the inhibition of striatal glutamatergic activity exerted by D2receptor activation did not require the concomitant inhibition of A2Areceptors, while it was still dependent on the activation of CB1receptors in both D2- and D1-expressing MSNs. Interestingly, the antagonism of M1 muscarinic receptors blocked the effects of D2/A2Areceptor modulation on MSNs. Moreover, in cholinergic interneurons we found coexpression of D2and A2Areceptors and a reduction of the firing frequency exerted by the same pharmacological agents that reduced excitatory transmission in MSNs. This evidence supports the hypothesis that striatal cholinergic interneurons, projecting to virtually all MSN subtypes, are involved in the D2/A2Aand endocannabinoid-mediated effects observed on both subpopulations of MSNs in physiological conditions and in experimental PD.
Maternal Influenza Viral Infection Causes Schizophrenia-Like Alterations of 5-HT2Aand mGlu2Receptors in the Adult Offspring
Authors: Moreno José L. , Kurita Mitsumasa , Holloway Terrell , López Javier , Cadagan Richard , Martínez-Sobrido Luis , García-Sastre Adolfo , González-Maeso Javier
Published: February 2011

Epidemiological studies indicate that maternal influenza viral infection increases the risk for schizophrenia in the adult offspring. The serotonin and glutamate systems are suspected in the etiology of schizophrenia, as well as in the mechanism of action of antipsychotic drugs. The effects of hallucinogens, such as psilocybin and mescaline, require the serotonin 5-HT2Areceptor, and induce schizophrenia-like psychosis in humans. In addition, metabotropic glutamate receptor mGlu2/3agonists show promise as a new treatment for schizophrenia. Here, we investigated the level of expression and behavioral function of 5-HT2Aand mGlu2receptors in a mouse model of maternal influenza viral infection. We show that spontaneous locomotor activity is diminished by maternal infection with the mouse-adapted influenza A/WSN/33 (H1N1) virus. The behavioral responses to hallucinogens and glutamate antipsychotics are both affected by maternal exposure to influenza virus, with increased head-twitch response to hallucinogens and diminished antipsychotic-like effect of the glutamate agonist. In frontal cortex of mice born to influenza virus-infected mothers, the 5-HT2Areceptor is upregulated and the mGlu2receptor is downregulated, an alteration that may be involved in the behavioral changes observed. Additionally, we find that the cortical 5-HT2Areceptor-dependent signaling pathways are significantly altered in the offspring of infected mothers, showing higherc-fos,egr-1, andegr-2expression in response to the hallucinogenic drug DOI. Identifying a biochemical alteration that parallels the behavioral changes observed in a mouse model of prenatal viral infection may facilitate targeting therapies for treatment and prevention of schizophrenia.
Absence of Large-Scale Dendritic Plasticity of Layer 5 Pyramidal Neurons in Peri-Infarct Cortex
Authors: Mostany Ricardo , Portera-Cailliau Carlos
Published: February 2011

When stroke or traumatic brain injury lead to cortical damage, how do surviving neurons rewire the brain to restore lost functionalities? Several Golgi studies have argued forde novogrowth and branching of dendrites of pyramidal neurons in the spared hemisphere, but the results could not always be replicated. Functional brain imaging studies in humans and rodents suggest that significant neuronal plasticity occurs in areas surrounding the cortical lesion, but whether dendritic rearrangements occur there has been less well studied, especially after stroke. We usedin vivotwo-photon microscopy in adult mice expressing green fluorescent protein to monitor longitudinally the length and branch complexity of entire apical dendritic arbors from layer 5 pyramidal neurons distributed over a large peri-infarct cortex region after middle cerebral artery occlusion. We find no evidence of growth of dendrites or addition of new branches to their arbors over a period of 3 months after stroke. Instead, we observed a two-step pruning process: an initial decrease in dendritic length, followed by a loss of dendritic branches. Importantly, the shortening of branch tips reflected a general shrinkage in the dendritic apical tree, suggesting that mechanical forces attributable to the involution of the infarct contributed to the changes in dendritic length. These results help resolve a long-standing debate regarding the role of large-scale dendritic plasticity of pyramidal neurons in functional recovery after cortical injury.
Ablation of CBP in Forebrain Principal Neurons Causes Modest Memory and Transcriptional Defects and a Dramatic Reduction of Histone Acetylation But Does Not Affect Cell Viability
Authors: Valor Luis M. , Pulopulos Matias M. , Jimenez-Minchan Maria , Olivares Roman , Lutz Beat , Barco Angel
Published: February 2011

Rubinstein-Taybi syndrome (RSTS) is an inheritable disease associated with mutations in the gene encoding the CREB (cAMP response element-binding protein)-binding protein (CBP) and characterized by growth impairment, learning disabilities, and distinctive facial and skeletal features. Studies in mouse models for RSTS first suggested a direct role for CBP and histone acetylation in cognition and memory. Here, we took advantage of the genetic tools for generating mice in which the CBP gene is specifically deleted in postmitotic principal neurons of the forebrain to investigate the consequences of the loss of CBP in the adult brain. In contrast to the conventional CBP knock-out mice, which exhibit very early embryonic lethality, postnatal forebrain-restricted CBP mutants were viable and displayed no overt abnormalities. We identified the dimer of histones H2A and H2B as the preferred substrate of the histone acetyltransferase domain of CBP. Surprisingly, the loss of CBP and subsequent histone hypoacetylation had a very modest impact in the expression of a number of immediate early genes and did not affect neuronal viability. In addition, the behavioral characterization of these mice dissociated embryonic and postnatal deficits caused by impaired CBP function, narrowed down the anatomical substrate of specific behavioral defects, and confirmed the special sensitivity of object recognition memory to CBP deficiency. Overall, our study provides novel insights into RSTS etiology and clarifies some of the standing questions concerning the role of CBP and histone acetylation in activity-driven gene expression, memory formation, and neurodegeneration.
Disrupting Function of FK506-Binding Protein 1b/12.6 Induces the Ca2+-Dysregulation Aging Phenotype in Hippocampal Neurons
Authors: Gant John C. , Chen Kuey-Chu , Norris Christopher M. , Kadish Inga , Thibault Olivier , Blalock Eric M. , Porter Nada M. , Landfield Philip W.
Published: February 2011

With aging, multiple Ca2+-associated electrophysiological processes exhibit increased magnitude in hippocampal pyramidal neurons, including the Ca2+-dependent slow afterhyperpolarization (sAHP), L-type voltage-gated Ca2+channel (L-VGCC) activity, Ca2+-induced Ca2+release (CICR) from ryanodine receptors (RyRs), and Ca2+transients. This pattern of Ca2+dysregulation correlates with reduced neuronal excitability/plasticity and impaired learning/memory and has been proposed to contribute to unhealthy brain aging and Alzheimer's disease. However, little is known about the underlying molecular mechanisms. In cardiomyocytes, FK506-binding protein 1b/12.6 (FKBP1b) binds and stabilizes RyR2 in the closed state, inhibiting RyR-mediated Ca2+release. Moreover, we recently found that hippocampalFkbp1bexpression is downregulated, whereasRyr2andFrap1/Mtor(mammalian target of rapamycin) expression is upregulated with aging in rats. Here, we tested the hypothesis that disrupting FKBP1b function also destabilizes Ca2+homeostasis in hippocampal neurons and is sufficient to induce the aging phenotype of Ca2+dysregulation in young animals. Selective knockdown ofFkbp1bwith interfering RNAin vitro(96 h) enhanced voltage-gated Ca2+current in cultured neurons, whereasin vivo Fkbp1bknockdown by microinjection of viral vector (3–4 weeks) dramatically increased the sAHP in hippocampal slice neurons from young-adult rats. Rapamycin, which displaces FKBP1b from RyRs in myocytes, similarly enhanced VGCC current and the sAHP and also increased CICR. Moreover, FKBP1b knockdownin vivowas associated with upregulation of RyR2 and mTOR protein expression. Thus, disruption of FKBP1b recapitulated much of the Ca2+-dysregulation aging phenotype in young rat hippocampus, supporting a novel hypothesis that declining FKBP function plays a major role in unhealthy brain aging.
Dynamic Changes in Superior Temporal Sulcus Connectivity during Perception of Noisy Audiovisual Speech
Authors: Nath Audrey R. , Beauchamp Michael S.
Published: February 2011

Humans are remarkably adept at understanding speech, even when it is contaminated by noise. Multisensory integration may explain some of this ability: combining independent information from the auditory modality (vocalizations) and the visual modality (mouth movements) reduces noise and increases accuracy. Converging evidence suggests that the superior temporal sulcus (STS) is a critical brain area for multisensory integration, but little is known about its role in the perception of noisy speech. Behavioral studies have shown that perceptual judgments are weighted by the reliability of the sensory modality: more reliable modalities are weighted more strongly, even if the reliability changes rapidly. We hypothesized that changes in the functional connectivity of STS with auditory and visual cortex could provide a neural mechanism for perceptual reliability weighting. To test this idea, we performed five blood oxygenation level-dependent functional magnetic resonance imaging and behavioral experiments in 34 healthy subjects. We found increased functional connectivity between the STS and auditory cortex when the auditory modality was more reliable (less noisy) and increased functional connectivity between the STS and visual cortex when the visual modality was more reliable, even when the reliability changed rapidly during presentation of successive words. This finding matched the results of a behavioral experiment in which the perception of incongruent audiovisual syllables was biased toward the more reliable modality, even with rapidly changing reliability. Changes in STS functional connectivity may be an important neural mechanism underlying the perception of noisy speech.
The Anterior Piriform Cortex Is Sufficient for Detecting Depletion of an Indispensable Amino Acid, Showing Independent Cortical Sensory Function
Authors: Rudell John B. , Rechs Adam J. , Kelman Todd J. , Ross-Inta Catherine M. , Hao Shuzhen , Gietzen Dorothy W.
Published: February 2011

Protein synthesis requires a continuous supply of all of the indispensable (essential) amino acids (IAAs). If any IAA is deficient, animals must obtain the limiting amino acid by diet selection. Sensing of IAA deficiency requires an intact anterior piriform cortex (APC), but does it act alone? Shortly after rats begin eating an IAA-deficient diet, the meal ends and EPSPs are activated in the APC; from there, neurons project to feeding circuits; the meal ends within 20 min. Within the APCin vivo, uncharged tRNA activates the general amino acid control non-derepressing 2 (GCN2) enzyme system increasing phosphorylation of eukaryotic initiation factor (P-eIF2α), which blocks general protein synthesis. If this paleocortex is sufficient for sensing IAA depletion, both neuronal activation and P-eIF2α should occur in an isolated APC slice. We used standard techniques for electrophysiology and immunohistochemistry. After rats ate IAA-devoid or -imbalanced diets, their depleted slices responded to different stimuli with increased EPSP amplitudes. Slices from rats fed a control diet were bathed in artificial CSF replete with all amino acids with or without the IAA, threonine, or a tRNA synthetase blocker,l-threoninol, or its inactive isomer,d-threoninol. Thr depletionin vitroincreased both EPSP amplitudes and P-eIF2α.l(but notd)-threoninol also increased EPSP amplitudes relative to control. Thus, we show independent excitation of the APC with responses parallel to those knownin vivo. These data suggest a novel idea: in addition to classical processing of peripheral sensory input, direct primary sensing may occur in mammalian cortex.
Subregional Specification of Embryonic Stem Cell-Derived Ventral Telencephalic Tissues by Timed and Combinatory Treatment with Extrinsic Signals
Authors: Danjo Teruko , Eiraku Mototsugu , Muguruma Keiko , Watanabe Kiichi , Kawada Masako , Yanagawa Yuchio , Rubenstein John L. R. , Sasai Yoshiki
Published: February 2011

During early telencephalic development, the major portion of the ventral telencephalic (subpallial) region becomes subdivided into three regions, the lateral (LGE), medial (MGE), and caudal (CGE) ganglionic eminences. In this study, we systematically recapitulated subpallial patterning in mouse embryonic stem cell (ESC) cultures and investigated temporal and combinatory actions of patterning signals. In serum-free floating culture, the dorsal-ventral specification of ESC-derived telencephalic neuroectoderm is dose-dependently directed by Sonic hedgehog (Shh) signaling. Early Shh treatment, even before the expression onset of Foxg1 (also Bf1; earliest marker of the telencephalic lineage), is critical for efficiently generating LGE progenitors, and continuous Shh signaling until day 9 is necessary to commit these cells to the LGE lineage. When induced under these conditions and purified by fluorescence-activated cell sorter, telencephalic cells efficiently differentiated into Nolz1+/Ctip2+LGE neuronal precursors and subsequently, both in culture and afterin vivografting, into DARPP32+medium-sized spiny neurons. Purified telencephalic progenitors treated with high doses of the Hedgehog (Hh) agonist SAG (Smoothened agonist) differentiated into MGE- and CGE-like tissues. Interestingly, in addition to strong Hh signaling, the efficient specification of MGE cells requires Fgf8 signaling but is inhibited by treatment with Fgf15/19. In contrast, CGE differentiation is promoted by Fgf15/19 but suppressed by Fgf8, suggesting that specific Fgf signals play different, critical roles in the positional specification of ESC-derived ventral subpallial tissues. We discuss a model of the antagonistic Fgf8 and Fgf15/19 signaling in rostral-caudal subpallial patterning and compare it with the roles of these molecules in cortical patterning.
Calcitonin Gene-Related Peptide in the Bed Nucleus of the Stria Terminalis Produces an Anxiety-Like Pattern of Behavior and Increases Neural Activation in Anxiety-Related Structures
Authors: Sink Kelly S. , Walker David L. , Yang Yong , Davis Michael
Published: February 2011

Calcitonin gene-related peptide (CGRP) evokes anxiety-like responses when infused into the lateral ventricle of rats. Because the bed nucleus of the stria terminalis (BNST) lies immediately adjacent to the lateral ventricle, is rich in CGRP receptors, and has itself been implicated in anxiety, we evaluated the hypothesis that these effects are attributable to stimulation of CGRP receptors within the BNST itself. Bilateral intra-BNST, but not dorsal, CGRP infusions (0, 200, 400, 800 ng/side) enhanced startle amplitude in a dose-dependent manner, and produced an anxiety-like response on the elevated plus maze. Intra-BNST infusion of the CGRP antagonist, αCGRP8-37, blocked the effect of CGRP on startle, and also blocked startle potentiation produced by exposure to trimethylthiazoline (a component of fox feces that induces anxiety-like behavior in rats). Intra-BNST, but not dorsal, CGRP infusions also increased c-Fos immunoreactivity in a number of anxiety-related brain areas (central nucleus of the amygdala, locus ceruleus, ventrolateral septal nucleus, paraventricular hypothalamic nucleus, lateral hypothalamus, lateral parabrachial nucleus, dorsal raphe nucleus, and nucleus accumbens shell), all of which receive direct projections from the BNST. Together, the results indicate that the activation of BNST CGRP receptors is both necessary and sufficient for some anxiety responses and that these effects may be mediated by activation of a wider network of BNST efferent structures. If so, inhibition of CGRP receptors may be a clinically useful strategy for anxiety reduction.
CRMP5 (Collapsin Response Mediator Protein 5) Regulates Dendritic Development and Synaptic Plasticity in the Cerebellar Purkinje Cells
Authors: Yamashita Naoya , Mosinger Bedrich , Roy Arpita , Miyazaki Mari , Ugajin Kozue , Nakamura Fumio , Sasaki Yukio , Yamaguchi Kazuhiko , Kolattukudy Pappachan , Goshima Yoshio
Published: February 2011

Collapsin response mediator protein 5 (CRMP5) is one of the CRMP members that expresses abundantly in the developing brain. To examine thein vivofunction of CRMP5, we generatedcrmp5-deficient (crmp5−/−) mice. Anti-calbindin immunofluorescence studies ofcrmp5−/−mice revealed aberrant dendrite morphology; specifically, a decrease in the size of soma and diameter of primary dendrite of the cerebellar Purkinje cells at postnatal day 21 (P21) and P28, but not at P14. Coincidentally, CRMP5 is detected in Purkinje cells at P21 and P28 fromcrmp5+/−mice. In cerebellar slices ofcrmp5−/−mice, the induction of long-term depression of excitatory synaptic transmission between parallel fibers and Purkinje cells was deficient. Given that brain-derived neurotrophic factor (BDNF) plays major roles in dendritic development, we tried to elucidate the possible roles of CRMP5 in BDNF signaling. The effect of BDNF to induce dendritic branching was markedly attenuated in culturedcrmp5−/−neurons. Furthermore, CRMP5 was tyrosine phosphorylated when coexpressed with neurotrophic tyrosine kinase receptor type 2 (TrkB), a receptor for BDNF, in HEK293T cells. These findings suggest that CRMP5 is involved in the development, maintenance and synaptic plasticity of Purkinje cells.
Cocaine-Induced Plasticity in the Nucleus Accumbens Is Cell Specific and Develops without Prolonged Withdrawal
Authors: Dobi Alice , Seabold Gail K. , Christensen Christine H. , Bock Roland , Alvarez Veronica A.
Published: February 2011

Cocaine induces plasticity at glutamatergic synapses in the nucleus accumbens (NAc). Withdrawal was suggested to play an important role in the development of this plasticity by studies showing that some changes only appear several weeks after the final cocaine exposure. In this study, the requirement for prolonged withdrawal was evaluated by comparing the changes in glutamatergic transmission induced by two different noncontingent cocaine treatments: a short treatment followed by prolonged withdrawal, and a longer treatment without prolonged withdrawal. Recordings were performed from mouse medium spiny neurons (MSNs) in the NAc at the same time after the first cocaine injection under both treatments. A similar increase in the frequency of glutamate-mediated miniature EPSCs was observed in D1-expressing MSNs after both cocaine treatments, demonstrating that prolonged withdrawal was not required. Furthermore, larger AMPA receptor-to-NMDA receptor ratios, higher spine density, and enlarged spine heads were observed in the absence of withdrawal after a long cocaine treatment. These synaptic adaptations expressed in D1-containing MSNs of the NAc core were not further enhanced by protracted withdrawal. In conclusion, a few repeated cocaine injections are enough to trigger adaptations at glutamatergic synapses in D1-expressing MSNs, which, although they take time to develop, do not require prolonged cocaine withdrawal.
Unterstützung von Softwareanpassungen in Kleinen und Mittelständischen Unternehmen: Wege zu einer Anpassungskultur
Authors: Yetim Fahri , Dörner Christian , Pipek Volkmar
Published: February 2011

Moderne Softwaresysteme sollten in erheblichem Umfang auch während der Benutzung noch an neue oder geänderte Anwendungspraktiken angepasst werden können. Neben der notwendigen technischen Flexibilität von Softwaresystemen und dem Vorhalten der notwendigen Anpassungsinterfaces ist die Etablierung einer ”Anpassungskultur“ ein wesentliches Merkmal einer erfolgreichen Anpassungsunterstützung. Dieser Beitrag präsentiert die Ergebnisse einer qualitativen empirischen Studie in fünf kleinen- und mittelständischen Unternehmen. Die Studie hatte das Ziel, die Effekte verschiedener Anpassungswerkzeuge und ihren Beitrag zur Etablierung einer ”Anpassungskultur“ zu verstehen. Die Interpretation der Ergebnisse aus der Perspektive der Technologie-Akzeptanzforschung liefert einige Hinweise darauf, welche Maßnahmen in der Praxis in Unternehmen getroffen werden müssen, um die Akzeptanz und Übernahme von innovativen Technologien zu erleichtern bzw. zu fördern. Die meisten Befragten gaben fehlende Zeit und mangelndes Wissens als Barrieren für die Nutzung von Anpassungsunterstützungstools an.
Relationships among thermomechanical treatments, microstructure, and tensile properties of a near beta-titanium alloy: β-CEZ: Part II. Relationships between thermomechanical treatments and tensile properties
Authors: Mora L. , Quesne C. , Penelle R.
Published: February 2011

The tensile properties of the β-CEZ titanium alloy (Ti Al, 2Sn, 4Zr, 4Mo, 2Cr, 1Fe wt. %) have been investigated at intermediate temperatures as a function of the thermomechanical treatments. the strength and ductility have been correlated with the microstructural changes caused by the various heat treatments. It is found that the highest yield strength is associated with a structure containing a small area fraction, a small size, and a high density of primary α platelets (αp). Moreover, the size of the secondary α phase (αs) has been found to affect the yield strength. It is concluded that the ductility is enhanced by a high area fraction of αp platelets and is also sensitive to the density and the morphological orientation of the αp platelets. The interfaces between the αp and β phases play a dominant role in β-CEZ tensile behavior, and transgranular fracture is the main failure feature of this alloy.
Develop and follow your own passion
Authors: Nix William D.
Published: February 2011

What follows is a commencement speech given to the graduating class of the School of Engineering at San Jose State University in December of 2005. Eminent materials researcher and educator, William D. Nix, offered his insights on finding one’s own passion and internal compass.
MAKING STUFF premieres in January on PBS
Authors: Jones Kevin , Larese Jennifer
Published: February 2011

Watch MAKING STUFF with David Pogue on your local PBS station.This is a four-part series exploring the materials that will shape the future. Premieres January 19, 2011 at 9:00 pm ET/PT (check local listings)
Thermal-Spray Processing of Materials
Authors: Sampath S. , McCune R.
Published: February 2011

The enhancement of engineering materials by surface modification has extended the operational envelope for many structures in terms of resistance to corrosion, wear, fatigue, and other forms of surface degradation and has made feasible the introduction of novel materials into high-performance applications. Surface engineering, using thermal-spray coatings, represents a pragmatic and highly costeffective means of satisfying stringent design criteria (e.g., in aerospace applications), operating under extreme environments (e.g., high temperatures, wear, and corrosion), and introducing a multiplicity of functions (e.g., thermal barriers, biomedical implants, and electronic multilayers). Thermal-spray technology as a family of processes is distinguished by its ability to deposit overlays of metals, ceramics, polymers, and composites of these materials in layers of substantial thickness (e.g., >25 µm) for engineering applications, often with equipment that can operate in the atmosphere and can be portable for use in the field. While traditional applications of thermal-spray coatings have addressed issues of surface protection, there is a growing activity in the use of the basic technology concepts for producing engineered functional surfaces and devices that offer the materials engineer a new scale of construction between thin films and macroscopic structures.
Defects and Diffusion in Silicon Technology
Authors: Haynes Tony E.
Published: February 2011

The silicon at the heart of highperformance integrated circuits (ICs) is the most precisely engineered material in mass production today. Crystalline silicon, purified to the level required for manufacturing modern, high-performance microelectronics (better than parts-per-billion purity), is arguably the most perfect material known. It is produced in large quantities and very economically. Continuing progress in basic silicon materials science has been central to this achievement. At the same time, access to such a perfect material and detailed knowledge of silicon's properties have provided the experimentalist with excellent opportunities to devise rather elegant experiments in whichthe parameters can be controlled very precisely. Silicon has similarly provided condensed-matter theorists with a nearly ideal test bed for new theoretical approaches. This issue of MRS Bulletin is dedicated to the materials physics that has both enabled the development of such a highly perfect material and benefited from its availability.
The Dynamics of Deposit Formation in Thermal-Spray Processes
Authors: Vardelle Armelle , Moreau Christian , Fauchais Pierre
Published: February 2011

In thermal spraying, coatings are formed by particles flattening and piling up on the substrate. At impact, the sudden deceleration of the particle causes a pressure buildup at the particle-surface interface; the high pressure inside the particle forces melted material to flow laterally and ductile material to deform. The particle spreads outward from the point of impact and forms a “splat.” The arresting of spreading results from the conversion of particle kinetic energy into work of viscous deformation and surface energy. Solidification constraint (when the solidification front is advancing from the substrate surface fast enough to interact with the liquid during spreading) and mechanical constraint (due to the roughness of the substrate surface) can interfere with the flattening process.
Thermal-Barrier Coatings for Advanced Gas-Turbine Engines
Authors: Zhu Dongming , Miller Robert A.
Published: February 2011

Ceramic thermal-barrier coatings (TBCs) have received increasing attention for gasturbine engine applications. The advantages of using TBCs include increased fuel efficiency by allowing higher gas temperatures and improved durability and reliability from lower component temperatures. As illustrated in Figure 1, TBCs can provide effective heat insulation to engine components, thus allowing higher operating temperatures and reduced cooling requirements. Atypical two-layer TBC system consists of a porous ZrO2-Y2O3 ceramic top coat and an oxidation-resistant metallic bond coat. These TBC systems can be applied to the metal substrate either by plasma spray or by electron-beam physical vapor deposition (EB-PVD) techniques.
Thermal-Spraying of Polymers and Polymer Blends
Authors: Brogan J. A.
Published: February 2011

Thermal-spraying of polymers can be traced back to the 1940s, when polyethylene (PE) was first produced by E.I. du Pont de Nemours & Company. Early work with flame-spraying guns was unsuccessful because the equipment, designed for spraying metals, produced a flame that was both too hot and too short to melt the PE without degradation. The technology has advanced considerably in the past 20 years. Flame-spray equipment and hardware accessories have been designed by numerous companies (PFS Thermoplastics, Alamo, Eutectic + Castolin, etc.) specifically for polymeric materials. The new equipment provides either a lower flame temperature or uses special cooling shrouds to cool the center of the flame, providing a longer residence time at a lower temperature. Many plastics can now be completely melted in-flight and allow heat-sensitive components to be coated with plastic.
Science and Technology of Solid-Oxide Fuel Cells
Authors: Singhal S. C.
Published: February 2011

The high oxygen-ion conductivity over wide ranges of temperature and oxygen pressure in stabilized cubic zirconia has led to its use as a solid-oxide electrolyte in a variety of electrochemical applications. Zirconia-based oxygen sensors are widely used for combustion control, especially in automobiles, for atmosphere control in furnaces, and as monitors of oxygen concentration in molten metals. Other applications include electrochemical pumps for control of oxygen potential, steam electrolyzers, and high-temperature solidoxide fuel cells (SOFCs). High-temperature SOFCs offer a clean, pollution-free technology to electrochemically generate electricity at high efficiencies. These fuel cells provide many advantages over traditional energy-conversion systems, including high efficiency, reliability, modularity, fuel adaptability, and very low levels of NOx and SOx emissions. The quiet, vibrationfree operation of SOFCs also eliminates the noise usually associated with conventional power-generation systems. Furthermore, because of the high temperature of operation (~1000°C) of SOFCs, naturalgas fuel can be reformed within the cell stack, eliminating the need for an expensive external reformer system. Also, pressurized SOFCs can be successfully used as replacements for combustors in gas turbines; such hybrid SOFC/gas-turbine power systems are expected to reach efficiencies approaching 70%.
New n-Type Transparent Conducting Oxides
Authors: Minami Tadatsugu
Published: February 2011

Most research to develop highly transparent and conductive thin films has focused on n-type semiconductors consisting of metal oxides. Historically, transparent conducting oxide (TCO) thin films composed of binary compounds such as SnO2 and In2O3 were developed by means of chemical- and physical-deposition methods. Impurity-doped SnO2 (Sb- or F-doped SnO2, e.g., SnO2:Sb or SnO2: F) and In2O3: Sn (indium tin oxide, ITO) films are in practical use. In addition to binary compounds, ternary compounds such as Cd2SnO4, CdSnO3, and CdIn2O4 were developed prior to 1980, but their TCO films have not yet been used widely.
Criteria for Choosing Transparent Conductors
Authors: Gordon Roy G.
Published: February 2011

Transparent, electrically conductive films have been prepared from a wide variety of materials. These include semiconducting oxides of tin, indium, zinc, and cadmium, and metals such as silver, gold, and titanium nitride. In this article, the physical properties of these materials are reviewed and compared.
A Soft Solution Processing Technique for Preparing Ferrite Films and Their Applications
Authors: Abe Masanori
Published: February 2011

“Ferrite plating” is a typical “soft solution processing” (SSP) application; it enables the formation of oxide ferromagnetic films from an aqueous solution atT24−100°C under atmospheric pressure. Using ferrite plating, we can grow crystallized ferrite films of spinel-type (MFe)3O4(where M = Fe, Co, Ni, Zn, Al, Cr, etc.) in one step, requiring no heat treatment. This opens the door to fabricating novel ferritefilm devices using substrates of such nonheat-resistant materials as plastics and GaAs integrated circuits; conventional ferrite-film preparation techniques, such as sputtering, vacuum evaporation, molecularbeam epitaxy, liquid-phase epitaxy, and so on, require high temperatures (>∼600°C) for the crystallization of ferrites, which deteriorates the non-heat-resistant substrates. Ferrite plating is a unique technique that allows us to synthesize ferrite “films” by means of a wet chemical process. There are many techniques, for synthesizing ferrite “particles” from aqueous solutions, but no technique, to our knowledge, enables ferrite-film synthesis by a wet chemical process.
Single-Molecule Magnets
Authors: Christou George , Gatteschi Dante , Hendrickson David N. , Sessoli Roberta
Published: February 2011

Magnets are widely used in a large number of applications, and their market is larger than that of semiconductors. Information storage is certainly one of the most important uses of magnets, and the lower limit to the size of the memory elements is provided by the superparamagnetic size, below which information cannot be permanently stored because the magnetization freely fluctuates. This occurs at room temperature for particles in the range of 10–100 nm, owing to the nature of the material. However, even smaller particles can in principle be used either by working at lower temperatures or by taking advantage of the onset of quantum size effects, which can make nanomagnets candidates for the construction of quantum computers.
High-Amylose Starches: From Biosynthesis to Their Use as Food Ingredients
Authors: Richardson Paul H. , Jeffcoat Roger , Shi Yong-Cheng
Published: February 2011

Starch is a versatile food ingredient and is widely used in numerous food and industrial applications. Whether in its native form, or modified1 through chemical substitution and/or physical modification (e.g., annealing), starch is used as a texturizer, gelling agent, thickener, adhesive, and moisture-retainer. Starches also provide an essential carbohydrate energy source and are obtained from roots, rootlike or tuberous plants, and cereals, all of which possess unique starch chemistries that impact their properties and function as food ingredients.
New Approaches to Characterizing Food Microstructures
Authors: Hermansson Anne-Marie , Langton Maud , Lorén Niklas
Published: February 2011

Many food-processing operations are designed to create the microstructure that gives the food product its characteristic properties. From milk we can produce different cheeses, yogurts, spreads, or whipped products where the properties are determined by the structure. Other examples of fabricated foods are cereal products such as pasta, meat products such as sausages, and so on. All of these products are based on colloidal structures such as gels, emulsions, foams, or combinations thereof. Microscopy provides the tools for describing how a particular structure is engineered, and, therefore, how it relates to the properties of the product.
The Materials Science of Eating and Food Breakdown
Authors: Lillford Peter J
Published: February 2011

Most of the process of eating is a learned skill. While an infant readily puts most things in its mouth, the ability to distinguish food from any other material has
to be taught, and even then it is several years before the whole range of foods can be consumed efficiently. Yet by the time we are 5–10 years old, our mastery of the complex set of mechanical actions involving tongue, teeth, and swallowing is so complete that we do not consciously note what we are doing or how we do it.
Supramolecular Aufbau: Folded Polymers as Building Blocks for Adaptive Organic Materials
Authors: Mio Matthew J. , Moore Jeffrey S.
Published: February 2011

The design of inorganic and organic solids with novel structures and properties has long been the object of materials research. The classical examples of porous materials (i.e., involving reversible guest passage) are zeolites. First discovered in the mid-1700s, zeolites are hydrated, crystalline aluminosilicates that organize into stable, discrete frameworks. Basic structures employ tetrahedral atoms (silicon or aluminum) bridged by oxygen atoms, where each oxygen is shared between two metalloid tetrahedra. Resulting covalent lattices can be neutral or negatively charged (as a result of bridging oxides) and often employ alkali metal or alkalineearth counterions. As a consequence of this ordered structure, zeolites both benefit from and are limited by their highly geometrical nature: their rigid structures are inherently robust, yet they are difficult to process. In addition, while natural and unnatural zeolites have been characterized, harsh synthetic conditions are common to both and lead to limitations in design and processability. Even so, these impediments have not prevented constructing a myriad of architectures on zeolite host lattices. Strengths and weaknesses aside, zeolites demonstrate a major objective of materials chemistry: the ability to manifest macroscopic physical properties based on embedded microscopic structure.
Self-Assembly of Organic Nano-Objects into Functional Materials
Authors: Stupp Samuel I. , Pralle Martin U. , Tew Gregory N. , Li Leiming , Sayar Mehmet , Zubarev Eugene R.
Published: February 2011

One of the goals of contemporary science is the atomic or molecular design of materials in order to achieve specific properties. There is special interest in imitating with these designed materials the remarkable integrated functionality we see in biology. Soft matter offers a particularly good opportunity to realize these goals because of the vast structural space offered by organic systems.
A Dislocation Model for the Directional Anisotropy of Grain-Boundary Fracture
Authors: Beltz Glenn E. , Lipkin Don M.
Published: February 2011

That fracture is governed by processes occurring over a wide range of length scales has been recognized since the earliest developments of modern fracture mechanics. Griffitha's study of the strength of cracked solids 1,2 is perhaps the earliest example of such multiscale thinking, predating by several decades the first attempts to apply atomistically grounded traction-separation laws to fracture (e.g., the Orowan-Gilman model3,4). Griffith recognized the critical condition for crack extension to be a statement of thermodynamic equilibrium of a cracked solid, representing a balance between the mechanical energy decrease upon crack extension and the corresponding increase in energy due to the newly created crack surface. Griffith determined the elastic strain energy of the cracked body using the continuum solution of the stress field about an ellipse5 and recognized that the potential energy associated with the cleavage surfaces of the crack was directly proportional to the surface energy, the latter deriving from the cohesive molecular forces of the solid. The Irwin-Orowan extension of Griffith mechanics to include plastic dissipation,6-9 which is known to occur on the mesoscopic length scale (~1–100 μm), provides yet a further example of multiscale thinking in the early community of fracture researchers. In fact, the interaction of length scales is of central importance in most problems of fracture.
Dynamic Fracture of Silicon: Concurrent Simulation of Quantum Electrons, Classical Atoms, and the Continuum Solid
Authors: Abraham Farid F. , Bernstein Noam , Broughton Jeremy Q. , Hess Daryl
Published: February 2011

Our understanding of materials phenomena is based on a hierarchy of physical descriptions spanning the space-time regimes of electrons, atoms, and matter and given by the theories of quantum mechanics, statistical mechanics, and continuum mechanics. The pioneering work of Clementi and co-workers provides a lucid example of the traditional approach to incorporating multiscale phenomena associated with these three mechanics. Using quantum mechanics, they evaluated the interactions of several water molecules. From this data base, they created an empirical potential for use in atomistic mechanics and evaluated the viscosity of water. From this computed viscosity, they performed a fluid-dynamics simulation to predict the tidal circulation in Buzzard's Bay. This is a powerful example of the sequential coupling of length and time scales: a series of calculations is used as input to the next rung up the length/time-scale ladder.
Intrinsic Point Defects and Their Control in Silicon Crystal Growth and Wafer Processing
Authors: Falster R. , Voronkov V. V.
Published: February 2011

Silicon produced for the microelectronics industry is far and away the purest and most perfect crystalline material manufactured today. It is fabricated routinely and in very large volumes. Many of the advances in integrated-circuit (IC) manufacturing achieved in recent years would not have been possible without parallel advances in silicon-crystal quality and defect engineering. Transition-metal contamination is a case in point. Essentially all practical problems (minority carrier lifetime, metal precipitation, stacking faults, etc.) associated with metal contaminants have largely been solved through advances in crystal purity.
Advanced Gettering Techniques in ULSI Technology
Authors: Istratov A. A. , Hieslmair H. , Weber E. R.
Published: February 2011

Progress in silicon technology has been phenomenal since the invention of the transistor some 50 years ago. Device performance has improved by at least a factor of a million in every respect. As the minimum feature size on chips decreases toward 0.1 μm, which should be reached on a mass-production scale in a few years, the device yield is becoming ever more sensitive to defects and impurities. Transition metals, particularly iron, nickel, and copper, are the most common and most detrimental contaminants on a process line, and they can be unintentionally introduced in nearly every process step, including ingot growth, wafer handling, ion implantation, wet-chemical cleaning, high-temperature anneals, or oxidation. To avoid yield losses, the silicon industry has to be very strict with respect to metal-contamination levels on the production line. For instance, for iron, the Semiconductor Industry Association (SIA) Roadmap presently specifies 2.5 ϗ 1010 cm−2 as the maximum tolerable surface concentration, decreasing to 5 ϗ 109 cm−2 by 2004.
High Thermal Conductivity Materials
Authors: Watari Koji , Shinde Subhash L.
Published: February 2011

Every university student becomes familiar with the concept of thermal conductivity, a fundamental physical property of materials, through his or her textbooks. Initial work on high thermal conductivity was carried out in 1911 by Eucken, who discovered that diamond was a reasonably good conductor for heat at room temperature. Theoretical support for this discovery was established by Debye in 1914.
High Thermal Conductivity Silicon Nitride Ceramic
Authors: Hirao Kiyoshi , Watari Koji , Hayashi Hiroyuki , Kitayama Mikito
Published: February 2011

Since the confirmation that nonmetallic single crystals with a diamond-like structure, such as SiC, BP, and AlN, have high intrinsic thermal conductivities of over 300 W m−1 K−1,1,2 a great deal of effort has been focused on the development of nonoxide polycrystalline ceramics with high thermal conductivity.
Chemical-Vapor-Deposited Materials for High Thermal Conductivity Applications
Authors: Goela Jitendra S. , Brese Nathaniel E. , Pickering Michael A. , Graebner John E.
Published: February 2011

Chemical vapor deposition (CVD) is an attractive method for producing bulk and thin-film materials for a variety of applications. In this method, gaseous reagents condense onto a substrate and then react to produce solid materials. The materials produced by CVD are theoretically dense, highly pure, and have other superior properties.
Metallization of High Thermal Conductivity Materials
Authors: Imanaka Yoshihiko , Notis Michael R.
Published: February 2011

Great progress in LSI (large-scale integration) has been made over the past 10 years, and more rapid progress is expected in the future. In recent years, the increased circuit density in LSI devices has led to remarkable heat generation, thereby creating thermalmanagement issues for microelectronics packaging. In order to develop highperformance LSI effectively, packaging and system-level configuration of the computer must be modified to handle the heat.
Materials and the Global Environment: Waste Mining in the 21st Century
Authors: Ayres Robert U. , Holmberg John , Andersson Björn
Published: February 2011

Sustainability is supposed to be the watchword of the coming century. Kenneth Boulding characterized the economic system of the 19th century as a “cowboy economy,” meaning that resources were essentially not a limiting factor. In contrast, he noted that in the future we must prepare to live in a “spaceship economy,” adopting Barbara Ward's famous metaphor of “Spaceship Earth.” In a spaceship, all materials must be recycled (or discarded into space).
Precise Polymer Micro-Optical Systems
Authors: Braeuer Andreas , Dannberg Peter , Mann Gunnar , Popall Michael
Published: February 2011

The demand for precise micro-optical elements and subsystems is increasing drastically, influenced mainly by the exploding information and communications markets. For many applications, technologies capable of high-volume production of these elements are needed. Favored methods are replication technologies such as injection molding, hot embossing, or UV molding. The challenge for materials scientists is to synthesize materials that can be formed into micro-optical structures and that can resist extreme environmental conditions during operation and stocking (e.g., temperature changes from −45°C to +125°C).
Rubber Stamping for Plastic Electronics and Fiber Optics
Authors: Rogers John A.
Published: February 2011

Microcontact printing (μCP) is a low-cost technique for rubber stamping that combines the high spatial resolution of sophisticated forms of photolithography with capabilities (e.g., single-step patterning of large areas and nonplanar surfaces) that are not present in other approaches. μCP will be useful for applications where established methods are ineffective. Two areas are particularly promising: (1) plastic electronics, where the chemical incompatibility of the constituent materials with common photoresists and developers can preclude the use of photolithography, and where μCP with rotating cylindrical stamps forms an excellent match with the type of reel-to-reel processing that is envisioned for these systems; and (2) new classes of optical-fiber and microcapillarybased devices, where μCP allows highresolution (∼0.2 μm) circuits, photomasks, and actuators to be printed directly on the highly curved surfaces of cylinders with submillimeter diameters. This article describes some highlights of our work in these and related areas.
Preserving Art through the Ages
Authors: Vandiver Pamela B.
Published: February 2011

Preserving art through the ages is more than placing a designated object in a museum, properly storing and exhibiting it. Preservation involves more than preventing the destruction and looting of sites or the theft of and illicit trade in antiquities. It is more than conservation—that is, the assessment, documentation, and stabilization of an artifact's condition, and, if necessary, the skill and judgment to rescue an artifact, to intervene using a reversible treatment, and to follow with a program of monitoring stability.