Vertically aligned carbon nanotubes as cytocompatible material for enhanced adhesion and proliferation of osteoblast-like cells.

PubMed

Giannona, Suna; Firkowska, Izabela; Rojas-Chapana, José; Giersig, Michael

2007-01-01

In this study, we describe the spatial organization of CAL-72 osteoblast-like cells on arrays of vertically aligned multi-walled carbon nanotubes (VACNTs). It was observed that, unlike cell growth on non-patterned surfaces, the cell attachment and spreading process on VACNTs was significantly enhanced. Additionally, since carbon nanotubes are known to possess resilient mechanical properties and are chemically stable, the effect of periodic arrays of VACNTs on CAL-72 osteoblast-like cells was also studied. The periodicity and alignment of VACNTs considerably influenced growth, shape and orientation of the cells by steering toward the nanopattern. This situation is of great interest for the potential application of VACNTs in bone bioenginnering. This data provides evidence that CAL-72 osteoblast-like cells can sense physical features at the nanoscale. These results give a fascinating insight into the ways in which cell growth can be influenced by man-made nanostructures and could provide a framework for achieving controlled cell guidance with controlled organization and special physical properties.

People Interview: Materials unite physics and chemistry

NASA Astrophysics Data System (ADS)

2011-05-01

INTERVIEW Materials unite physics and chemistry Mark Miodownik is a materials scientist at King's College, London. David Smith talks to him about his career and his fascinating experiences of giving last year's Royal Institution Christmas Lectures.

Recent progress in boron nanomaterials

PubMed Central

Kondo, Takahiro

2017-01-01

Abstract Various types of zero, one, and two-dimensional boron nanomaterials such as nanoclusters, nanowires, nanotubes, nanobelts, nanoribbons, nanosheets, and monolayer crystalline sheets named borophene have been experimentally synthesized and identified in the last 20 years. Owing to their low dimensionality, boron nanomaterials have different bonding configurations from those of three-dimensional bulk boron crystals composed of icosahedra or icosahedral fragments. The resulting intriguing physical and chemical properties of boron nanomaterials are fascinating from the viewpoint of material science. Moreover, the wide variety of boron nanomaterials themselves could be the building blocks for combining with other existing nanomaterials, molecules, atoms, and/or ions to design and create materials with new functionalities and properties. Here, the progress of the boron nanomaterials is reviewed and perspectives and future directions are described. PMID:29152014

Nonlinear Optics with 2D Layered Materials.

PubMed

Autere, Anton; Jussila, Henri; Dai, Yunyun; Wang, Yadong; Lipsanen, Harri; Sun, Zhipei

2018-06-01

2D layered materials (2DLMs) are a subject of intense research for a wide variety of applications (e.g., electronics, photonics, and optoelectronics) due to their unique physical properties. Most recently, increasing research efforts on 2DLMs are projected toward the nonlinear optical properties of 2DLMs, which are not only fascinating from the fundamental science point of view but also intriguing for various potential applications. Here, the current state of the art in the field of nonlinear optics based on 2DLMs and their hybrid structures (e.g., mixed-dimensional heterostructures, plasmonic structures, and silicon/fiber integrated structures) is reviewed. Several potential perspectives and possible future research directions of these promising nanomaterials for nonlinear optics are also presented. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

On the topology of chromatin fibres

PubMed Central

Barbi, Maria; Mozziconacci, Julien; Victor, Jean-Marc; Wong, Hua; Lavelle, Christophe

2012-01-01

The ability of cells to pack, use and duplicate DNA remains one of the most fascinating questions in biology. To understand DNA organization and dynamics, it is important to consider the physical and topological constraints acting on it. In the eukaryotic cell nucleus, DNA is organized by proteins acting as spools on which DNA can be wrapped. These proteins can subsequently interact and form a structure called the chromatin fibre. Using a simple geometric model, we propose a general method for computing topological properties (twist, writhe and linking number) of the DNA embedded in those fibres. The relevance of the method is reviewed through the analysis of magnetic tweezers single molecule experiments that revealed unexpected properties of the chromatin fibre. Possible biological implications of these results are discussed. PMID:24098838

Floquet topological insulators for sound

NASA Astrophysics Data System (ADS)

Fleury, Romain; Khanikaev, Alexander B.; Alù, Andrea

2016-06-01

The unique conduction properties of condensed matter systems with topological order have recently inspired a quest for the similar effects in classical wave phenomena. Acoustic topological insulators, in particular, hold the promise to revolutionize our ability to control sound, allowing for large isolation in the bulk and broadband one-way transport along their edges, with topological immunity against structural defects and disorder. So far, these fascinating properties have been obtained relying on moving media, which may introduce noise and absorption losses, hindering the practical potential of topological acoustics. Here we overcome these limitations by modulating in time the acoustic properties of a lattice of resonators, introducing the concept of acoustic Floquet topological insulators. We show that acoustic waves provide a fertile ground to apply the anomalous physics of Floquet topological insulators, and demonstrate their relevance for a wide range of acoustic applications, including broadband acoustic isolation and topologically protected, nonreciprocal acoustic emitters.

Floquet topological insulators for sound

PubMed Central

Fleury, Romain; Khanikaev, Alexander B; Alù, Andrea

2016-01-01

The unique conduction properties of condensed matter systems with topological order have recently inspired a quest for the similar effects in classical wave phenomena. Acoustic topological insulators, in particular, hold the promise to revolutionize our ability to control sound, allowing for large isolation in the bulk and broadband one-way transport along their edges, with topological immunity against structural defects and disorder. So far, these fascinating properties have been obtained relying on moving media, which may introduce noise and absorption losses, hindering the practical potential of topological acoustics. Here we overcome these limitations by modulating in time the acoustic properties of a lattice of resonators, introducing the concept of acoustic Floquet topological insulators. We show that acoustic waves provide a fertile ground to apply the anomalous physics of Floquet topological insulators, and demonstrate their relevance for a wide range of acoustic applications, including broadband acoustic isolation and topologically protected, nonreciprocal acoustic emitters. PMID:27312175

Nitrogen-vacancy centers in diamond: nanoscale sensors for physics and biology.

PubMed

Schirhagl, Romana; Chang, Kevin; Loretz, Michael; Degen, Christian L

2014-01-01

Crystal defects in diamond have emerged as unique objects for a variety of applications, both because they are very stable and because they have interesting optical properties. Embedded in nanocrystals, they can serve, for example, as robust single-photon sources or as fluorescent biomarkers of unlimited photostability and low cytotoxicity. The most fascinating aspect, however, is the ability of some crystal defects, most prominently the nitrogen-vacancy (NV) center, to locally detect and measure a number of physical quantities, such as magnetic and electric fields. This metrology capacity is based on the quantum mechanical interactions of the defect's spin state. In this review, we introduce the new and rapidly evolving field of nanoscale sensing based on single NV centers in diamond. We give a concise overview of the basic properties of diamond, from synthesis to electronic and magnetic properties of embedded NV centers. We describe in detail how single NV centers can be harnessed for nanoscale sensing, including the physical quantities that may be detected, expected sensitivities, and the most common measurement protocols. We conclude by highlighting a number of the diverse and exciting applications that may be enabled by these novel sensors, ranging from measurements of ion concentrations and membrane potentials to nanoscale thermometry and single-spin nuclear magnetic resonance.

Photoaffinity Labeling Studies on a Promoter of Dendritic Spine Formation

NASA Astrophysics Data System (ADS)

Sibucao, Kevin Carlo Abril

The small molecule BTA-EG4 has been shown to be a promoter of dendritic spine formation. The mechanism behind this phenomenon, however, is not well understood. The work in this dissertation is motivated by this gap in knowledge. The first part of this dissertation focuses on photoaffinity labeling studies to identify the cellular targets of BTA-EG4. Chapter 1 provides a summary of Alzheimer's disease, the rational design of BTA-EG 4, and methods to determine targets of small molecules. In Chapter 2, the synthesis of a BTA-EG4-based photoaffinity labeling probe and photodegradation studies are presented. Kinetic studies demonstrate that the probe photolyzes rapidly under UV light. In Chapter 3, photoaffinity labeling studies and subsequent protein identification experiments are reported. Competition experiments with the photoaffinity labeling probe and BTA-EG4 demonstrate that the probe labels a 55-kDa protein specifically. Tandem mass spectrometry revealed that the 55-kDa protein is the actin binding protein fascin 1. The second part of this dissertation focuses on the major protein identified from photoaffinity labeling studies, fascin 1. Chapter 4 provides a brief survey of the structure and function of fascin 1. In Chapter 5, characterizations of the interaction between BTA-EG4 and fascin 1 are reported. Isothermal titration calorimetry confirms the physical binding between fascin 1 and BTA-EG6, a BTA-EG4 analog. Slow speed sedimentation assays reveal that BTA-EG4 does not affect the actin-bundling activity of fascin 1. However, GST pull-down experiments show that BTA-EG4 inhibits the binding of fascin 1 with the GTPase Rab35. In addition, this work demonstrates that BTA-EG4 may be mechanistically distinct from the known fascin inhibitor G2.

Demonstration Experiments in Physics

ERIC Educational Resources Information Center

Sutton, Richard M.

2003-01-01

This book represents a "cookbook" for teachers of physics, a book of recipes for the preparation of demonstration experiments to illustrate the principles that make the subject of physics so fascinating. Illustrations and explanations of each demonstration are done in an easy-to-understand format. Each can be adapted to be used as a demonstration…

Multinuclear metal-binding ability of a carotene

PubMed Central

Horiuchi, Shinnosuke; Tachibana, Yuki; Yamashita, Mitsuki; Yamamoto, Koji; Masai, Kohei; Takase, Kohei; Matsutani, Teruo; Kawamata, Shiori; Kurashige, Yuki; Yanai, Takeshi; Murahashi, Tetsuro

2015-01-01

Carotenes are naturally abundant unsaturated hydrocarbon pigments, and their fascinating physical and chemical properties have been studied intensively not only for better understanding of the roles in biological processes but also for the use in artificial chemical systems. However, their metal-binding ability has been virtually unexplored. Here we report that β-carotene has the ability to assemble and align ten metal atoms to afford decanuclear homo- and heterometal chain complexes. The metallo–carotenoid framework shows reversible metalation–demetalation reactivity with multiple metals, which allows us to control the size of metal chains as well as the heterobimetallic composition and arrangement of the carotene-supported metal chains. PMID:25857402

Teaching the Delightful Laws of Physics in a Survey Course

ERIC Educational Resources Information Center

Hewitt, Paul G.

2015-01-01

How physics can be made interesting is a question that needs no answer. That's because physics is interesting! It's a field of study jam-packed with fascination and wonder. The general public has an enormous thirst for physics knowledge, as indicated by the great numbers who purchase science magazines and books and watch "NOVA" and other…

Two-channel Kondo physics from arsenic bond oscillations in zirconium arsenide selenide

NASA Astrophysics Data System (ADS)

Kirchner, Stefan; Cichorek, Tomasz; Bochenek, L.; Schmidt, Marcus; Niewa, Rainer; Czulucki, A.; Auffermann, G.; Steglich, Frank; Kniep, Ruediger

2015-03-01

The two-channel Kondo effect is a fascinating but extremely fragile many-body state that has been theoretically discussed extensively. we address metallic compounds of a specific (PbFCl) structure for which a - AT 1 / 2 term to ρ (T) is frequently observed, in line with the two-channel Kondo effect. The origin of this anomalous behavior has remained enigmatic since here, solely the interaction between electrons may account for this behavior, and the two-channel Kondo state is not expected to occur. By combining chemical and structural investigations with various physical property measurements we show that the magnetic field-independent - AT 1 / 2 term to the low-T resistivity observed over two decades in ZrAsxSey with 1.90 <= x + y <= 1.99 originates from vacancies in the layer exclusively built up by As. Furthermore, we can trace back the two-channel Kondo effect in this material to a dynamic Jahn-Teller effect operating at these vacancies. All physical properties of the investigated compounds support this conclusion. Our findings will be relevant also for other metallic systems with pnictogen-pnictogen bondings, e.g., cage-forming compounds like the skutterudites.

A review on III-V core-multishell nanowires: growth, properties, and applications

NASA Astrophysics Data System (ADS)

Royo, Miquel; De Luca, Marta; Rurali, Riccardo; Zardo, Ilaria

2017-04-01

This review focuses on the emerging field of core-multishell (CMS) semiconductor nanowires (NWs). In these kinds of wires, a NW grown vertically on a substrate acts as a template for the coaxial growth of two or more layers wrapped around it. Thanks to the peculiar geometry, the strain is partially released along the radial direction, thus allowing the creation of fascinating heterostructures, even based on lattice mismatched materials that would hardly grow in a planar geometry. Enabling the unique bridging of the 1D nature of NWs with the exciting properties of 2D heterostructures, these novel systems are becoming attractive for material science, as well as fundamental and applied physics. We will focus on NWs made of III-V and III-V-based alloys as they represent a model system in which present growth techniques have reached a high degree of control on the material structural properties, and many physical properties have been assessed, from both the theoretical and experimental points of view. In particular, we provide an overview on the growth methods and structural properties of CMS NWs, on the modulation doping mechanisms enabled by these heterostructures, on the effects of a magnetic field, and on the phononic and optical properties typical of CMS NWs. Moreover, we review the main technological applications based on these systems, such as optoelectronic and photovoltaic devices.

A Presentation of the Black Hole Stretching Effect

ERIC Educational Resources Information Center

Kontomaris, Stylianos Vasileios; Malamou, Anna

2018-01-01

Black holes and the physics behind them is a fascinating topic for students of all levels. The exotic conditions which prevail near a black hole should be discussed and presented to undergraduate students in order to increase their interest in studying physics and to provide useful insights into basic physics concepts, such as non-uniform…

Advances in atomic physics

PubMed Central

El-Sherbini, Tharwat M.

2013-01-01

In this review article, important developments in the field of atomic physics are highlighted and linked to research works the author was involved in himself as a leader of the Cairo University – Atomic Physics Group. Starting from the late 1960s – when the author first engaged in research – an overview is provided of the milestones in the fascinating landscape of atomic physics. PMID:26425356

Once a physicist: Tony Hey

NASA Astrophysics Data System (ADS)

2008-01-01

Why did you originally choose to study physics? I was really interested in science at school, and I also read a couple of fascinating popular-science books about quantum mechanics and special relativity. My interest in these topics made me decide to study physics at Oxford University. Straight after I graduated in 1967 I did a theoretical-physics DPhil, also at Oxford.

Epitaxial strain effect on the physical properties of layered ruthenate and iridate thin films

NASA Astrophysics Data System (ADS)

Miao, Ludi

Transition metal oxides have attracted widespread attention due to their broad range of fascinating exotic phenomena such as multiferroicity, superconductivity, colossal magnetoresistance and metal-to-insulator transition. Due to the interplay between spin, charge, lattice and orbital degrees of freedom of strongly correlated d electrons, these physical properties are extremely sensitive to the external perturbations such as magnetic field, charge carrier doping and pressure, which provide a unique chance in search for novel exotic quantum states. Ruthenate systems are a typical strongly correlated system, with rich ordered states and their properties are extremely sensitive to external stimuli. Recently, the experimental observation of spin-orbit coupling induced Mott insulator in Sr2IrO4 as well as the theoretical prediction of topological insulating state in other iridates, have attracted tremendous interest in the physics of strong correlation and spin-orbit coupling in 4d/5d compounds. We observe an itinerant ferromagnetic ground state of Ca2 RuO4 film in stark contrast to the Mott-insulating state in bulk Ca2RuO4. We have also established the epitaxial strain effect on the transport and magnetic properties for the (Ca,Sr) 2RuO4 thin films. For Sr2IrO4 thin films, we will show that the Jeff = 1/2 moment orientation can be modulated by epitaxial strain. In addition, we discovered novel Ba 7Ir3O13+x thin films which exhibit colossal permittivity.

Advances in atomic physics: Four decades of contribution of the Cairo University - Atomic Physics Group.

PubMed

El-Sherbini, Tharwat M

2015-09-01

In this review article, important developments in the field of atomic physics are highlighted and linked to research works the author was involved in himself as a leader of the Cairo University - Atomic Physics Group. Starting from the late 1960s - when the author first engaged in research - an overview is provided of the milestones in the fascinating landscape of atomic physics.

Physics of the Kitaev Model: Fractionalization, Dynamic Correlations, and Material Connections

NASA Astrophysics Data System (ADS)

Hermanns, M.; Kimchi, I.; Knolle, J.

2018-03-01

Quantum spin liquids have fascinated condensed matter physicists for decades because of their unusual properties such as spin fractionalization and long-range entanglement. Unlike conventional symmetry breaking, the topological order underlying quantum spin liquids is hard to detect experimentally. Even theoretical models are scarce for which the ground state is established to be a quantum spin liquid. The Kitaev honeycomb model and its generalizations to other tricoordinated lattices are chief counterexamples - they are exactly solvable, harbor a variety of quantum spin liquid phases, and are also relevant for certain transition metal compounds including the polymorphs of (Na,Li)2IrO3 iridates and RuCl3. In this review, we give an overview of the rich physics of the Kitaev model, including two-dimensional and three-dimensional fractionalization as well as dynamic correlations and behavior at finite temperatures. We discuss the different materials and argue how the Kitaev model physics can be relevant even though most materials show magnetic ordering at low temperatures.

Teaching Elementary Particle Physics: Part I1

NASA Astrophysics Data System (ADS)

Hobson, Art

2011-01-01

I'll outline suggestions for teaching elementary particle physics, often called high energy physics, in high school or introductory college courses for non-scientists or scientists. Some presentations of this topic simply list the various particles along with their properties, with little overarching structure. Such a laundry list approach is a great way to make a fascinating topic meaningless. Students need a conceptual framework from which to view the elementary particles. That conceptual framework is quantum field theory (QFT). Teachers and students alike tend to quake at this topic, but bear with me. We're talking here about concepts, not technicalities. My approach will be conceptual and suitable for non-scientists and scientists; if mathematical details are added in courses for future scientists, they should be simple and sparse. Introductory students should not be expected to do QFT, but only to understand its concepts. Those concepts take some getting used to, but they are simple and can be understood by any literate person, be she plumber, attorney, musician, or physicist.

From astrophysics to mesoscopic physics: a sightseeing tour in the world of clusters and fullerenes

NASA Astrophysics Data System (ADS)

Rosen, Arne; Ostling, Daniel; Apell, P.; Tomanek, D.

1996-12-01

The discovery of the fullerenes in 1985 by Kroto, Heath, O'Brien, Curl and Smalley and the development of a method for production of macroscopic amounts in 1990 by Kraetschmer, Lamb, Fostiropoulos and Huffman opened a new area of carbon research with possible production of new materials with unique properties. The field has developed further later on with discoveries of nanotubes, metal filled nanotubes, carbon onions and more recently metal covered fullerenes. All these new discoveries show how cluster science opens approaches to the area of meososcopic physics. The general trend is here in the direction from small to large contrary to the general trend of modern meososcopic physics or micro-electronics where the movement is from large to small. It is especially fascinating how the whole area of fullerene research was initiated by problems in astrophysics. Originally Kraetschmer and Huffman had the intention to explain an observed strong extinction form interstellar dust and produced in experiments special carbon soot with a characteristics optical absorption known as 'the camel hump smoke'. This paper gives a short overview of some of our more recent theoretical work of the electronic properties of C60, metal covered C60 and nanotubes. In addition some results are also presented of optical properties of metal covered C60 as a function of metal coverage.

Chiral Superstructure Mesophases of Achiral Bent-Shaped Molecules - Hierarchical Chirality Amplification and Physical Properties.

PubMed

Le, Khoa V; Takezoe, Hideo; Araoka, Fumito

2017-07-01

Chiral mesophases in achiral bent-shaped molecules have attracted particular attention since their discovery in the middle 1990s, not only because of their homochirality and polarity, but also due to their unique physical/physicochemical properties. Here, the most intriguing results in the studies of such symmetry-broken states, mainly helical-nanofilament (HNF) and dark-conglomerate (DC) phases, are reviewed. Firstly, basic information on the typical appearance and optical activity in these phases is introduced. In the following section, the formation of mesoscopic chiral superstructures in the HNF and DC phases is discussed in terms of hierarchical chirality. Nanoscale phase segregation in mixture systems and gelation ability in the HNF phase are also described. In addition, some other related chiral phases of bent-shaped molecules are shown. Recent attempts to control such mesoscopic chiral structure and the alignment/confinement of HNFs are also discussed, along with several examples of their fascinating advanced physical properties, i.e. huge enhancement of circular dichroism, electro- and photo-tunable optical activities, chirality-induced nonlinear optics (second-harmonic-generation circular difference and electrogyration effect), enhanced hydrophobicity through the dual-scale surface morphological modulation, and photoconductivity in the HNF/fullerene binary system. Future prospects from basic science and application viewpoints are also indicated in the concluding section. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Experimental demonstration of anomalous Floquet topological insulator for sound

NASA Astrophysics Data System (ADS)

Peng, Yu-Gui; Qin, Cheng-Zhi; Zhao, De-Gang; Shen, Ya-Xi; Xu, Xiang-Yuan; Bao, Ming; Jia, Han; Zhu, Xue-Feng

2016-11-01

Time-reversal invariant topological insulator is widely recognized as one of the fundamental discoveries in condensed matter physics, for which the most fascinating hallmark is perhaps a spin-based topological protection, the absence of scattering of conduction electrons with certain spins on matter surface. Recently, it has created a paradigm shift for topological insulators, from electronics to photonics, phononics and mechanics as well, bringing about not only involved new physics but also potential applications in robust wave transport. Despite the growing interests in topologically protected acoustic wave transport, T-invariant acoustic topological insulator has not yet been achieved. Here we report experimental demonstration of anomalous Floquet topological insulator for sound: a strongly coupled metamaterial ring lattice that supports one-way propagation of pseudo-spin-dependent edge states under T-symmetry. We also demonstrate the formation of pseudo-spin-dependent interface states due to lattice dislocations and investigate the properties of pass band and band gap states.

Experimental demonstration of anomalous Floquet topological insulator for sound

PubMed Central

Peng, Yu-Gui; Qin, Cheng-Zhi; Zhao, De-Gang; Shen, Ya-Xi; Xu, Xiang-Yuan; Bao, Ming; Jia, Han; Zhu, Xue-Feng

2016-01-01

Time-reversal invariant topological insulator is widely recognized as one of the fundamental discoveries in condensed matter physics, for which the most fascinating hallmark is perhaps a spin-based topological protection, the absence of scattering of conduction electrons with certain spins on matter surface. Recently, it has created a paradigm shift for topological insulators, from electronics to photonics, phononics and mechanics as well, bringing about not only involved new physics but also potential applications in robust wave transport. Despite the growing interests in topologically protected acoustic wave transport, T-invariant acoustic topological insulator has not yet been achieved. Here we report experimental demonstration of anomalous Floquet topological insulator for sound: a strongly coupled metamaterial ring lattice that supports one-way propagation of pseudo-spin-dependent edge states under T-symmetry. We also demonstrate the formation of pseudo-spin-dependent interface states due to lattice dislocations and investigate the properties of pass band and band gap states. PMID:27834375

Moments in the Life of a Scientist

NASA Astrophysics Data System (ADS)

Rossi, Bruno

1990-08-01

Bruno Rossi has long been an influential figure in diverse areas of physics and in this volume he presents a fascinating account of his life and work as an experimental physicist. He discusses his scientific contributions, from experiments that played a major role in establishing the nature and properties of cosmic rays to those establishing the existence of a solar wind and others that laid the foundations of X-ray astronomy. Rossi provides close insight into his actual experiences as a scientist and the motivations that gave direction to his research, and he recounts the beginning of very significant stages in high energy physics and space research. He writes evocatively of the many places where he worked--of Florence, Arcetri, Padua, and Venice, of the mountains of Colorado and the deserts of New Mexico. His narrative also provides insight into the life of a Jewish family in fascist Italy. The text is accompanied by photographs taken throughout Rossi's career.

Manipulation of domain-wall solitons in bi- and trilayer graphene

NASA Astrophysics Data System (ADS)

Jiang, Lili; Wang, Sheng; Shi, Zhiwen; Jin, Chenhao; Utama, M. Iqbal Bakti; Zhao, Sihan; Shen, Yuen-Ron; Gao, Hong-Jun; Zhang, Guangyu; Wang, Feng

2018-01-01

Topological dislocations and stacking faults greatly affect the performance of functional crystalline materials1-3. Layer-stacking domain walls (DWs) in graphene alter its electronic properties and give rise to fascinating new physics such as quantum valley Hall edge states4-10. Extensive efforts have been dedicated to the engineering of dislocations to obtain materials with advanced properties. However, the manipulation of individual dislocations to precisely control the local structure and local properties of bulk material remains an outstanding challenge. Here we report the manipulation of individual layer-stacking DWs in bi- and trilayer graphene by means of a local mechanical force exerted by an atomic force microscope tip. We demonstrate experimentally the capability to move, erase and split individual DWs as well as annihilate or create closed-loop DWs. We further show that the DW motion is highly anisotropic, offering a simple approach to create solitons with designed atomic structures. Most artificially created DW structures are found to be stable at room temperature.

Strain, stabilities and electronic properties of hexagonal BN bilayers

NASA Astrophysics Data System (ADS)

Fujimoto, Yoshitaka; Saito, Susumu

Hexagonal boron nitride (h-BN) atomic layers have been regarded as fascinating materials both scientifically and technologically due to the sizable band gap. This sizable band-gap nature of the h-BN atomic layers would provide not only new physical properties but also novel nano- and/or opto-electronics applications. Here, we study the first-principles density-functional study that clarifies the biaxial strain effects on the energetics and the electronic properties of h-BN bilayers. We show that the band gaps of the h-BN bilayers are tunable by applying strains. Furthermore, we show that the biaxial strains can produce a transition from indirect to direct band gaps of the h-BN bilayer. We also discuss that both AA and AB stacking patterns of h-BN bilayer become feasible structures because h-BN bilayers possess two different directions in the stacking patterns. Supported by MEXT Elements Strategy Initiative to Form Core Research Center through Tokodai Institute for Element Strategy, JSPS KAKENHI Grant Numbers JP26390062 and JP25107005.

The Physics and Chemistry of Color: The Fifteen Causes of Color, 2nd Edition

NASA Astrophysics Data System (ADS)

Nassau, Kurt

2001-07-01

An updated and revised second edition of the acclaimed classic Have you ever wondered why the sky is blue, or a ruby red? This classic volume studies the physical and chemical origins of color by exploring fifteen separate causes of color and their varied and often subtle occurrences in biology, geology, mineralogy, the atmosphere, technology, and the visual arts. It covers all of the fundamental concepts at work and requires no specialized knowledge. Author Kurt Nassau includes hundreds of illustrations, tables, and photographs-as well as end-of-chapter problems-that aid in visualizing the concepts discussed. An updated bibliography permits readers to pursue their own particular interests and an expanded series of appendices cover advanced topics. The Physics and Chemistry of Color, Second Edition is a one-of-a-kind treatment of color that provides both detailed physical and chemical properties of color and a more general overview of the subject. It will prove highly useful to specialists and non-specialists alike-and fascinate those with varied interests from optics to art history.

Clash of Harmonics in Stravinsky's "The Rite of Spring"

ERIC Educational Resources Information Center

Ruiz, Michael J.

2018-01-01

This paper describes a fascinating connection between the physics of music and the famous chord in the dissonant rhythmic section of Stravinsky's "The Rite of Spring" (1913). The analysis of Stravinsky's chord will draw from the physics of harmonics, musical intervals, mathematics, and cognitive psychology. This highly interdisciplinary…

Few layer epitaxial germanene: a novel two-dimensional Dirac material

NASA Astrophysics Data System (ADS)

Dávila, María Eugenia; Le Lay, Guy

2016-02-01

Monolayer germanene, a novel graphene-like germanium allotrope akin to silicene has been recently grown on metallic substrates. Lying directly on the metal surfaces the reconstructed atom-thin sheets are prone to lose the massless Dirac fermion character and unique associated physical properties of free standing germanene. Here, we show that few layer germanene, which we create by dry epitaxy on a gold template, possesses Dirac cones thanks to a reduced interaction. This finding established on synchrotron-radiation-based photoemission, scanning tunneling microscopy imaging and surface electron diffraction places few layer germanene among the rare two-dimensional Dirac materials. Since germanium is currently used in the mainstream Si-based electronics, perspectives of using germanene for scaling down beyond the 5 nm node appear very promising. Other fascinating properties seem at hand, typically the robust quantum spin Hall effect for applications in spintronics and the engineering of Floquet Majorana fermions by light for quantum computing.

Few layer epitaxial germanene: a novel two-dimensional Dirac material.

PubMed

Dávila, María Eugenia; Le Lay, Guy

2016-02-10

Monolayer germanene, a novel graphene-like germanium allotrope akin to silicene has been recently grown on metallic substrates. Lying directly on the metal surfaces the reconstructed atom-thin sheets are prone to lose the massless Dirac fermion character and unique associated physical properties of free standing germanene. Here, we show that few layer germanene, which we create by dry epitaxy on a gold template, possesses Dirac cones thanks to a reduced interaction. This finding established on synchrotron-radiation-based photoemission, scanning tunneling microscopy imaging and surface electron diffraction places few layer germanene among the rare two-dimensional Dirac materials. Since germanium is currently used in the mainstream Si-based electronics, perspectives of using germanene for scaling down beyond the 5 nm node appear very promising. Other fascinating properties seem at hand, typically the robust quantum spin Hall effect for applications in spintronics and the engineering of Floquet Majorana fermions by light for quantum computing.

Few layer epitaxial germanene: a novel two-dimensional Dirac material

PubMed Central

Dávila, María Eugenia; Le Lay, Guy

2016-01-01

Monolayer germanene, a novel graphene-like germanium allotrope akin to silicene has been recently grown on metallic substrates. Lying directly on the metal surfaces the reconstructed atom-thin sheets are prone to lose the massless Dirac fermion character and unique associated physical properties of free standing germanene. Here, we show that few layer germanene, which we create by dry epitaxy on a gold template, possesses Dirac cones thanks to a reduced interaction. This finding established on synchrotron-radiation-based photoemission, scanning tunneling microscopy imaging and surface electron diffraction places few layer germanene among the rare two-dimensional Dirac materials. Since germanium is currently used in the mainstream Si-based electronics, perspectives of using germanene for scaling down beyond the 5 nm node appear very promising. Other fascinating properties seem at hand, typically the robust quantum spin Hall effect for applications in spintronics and the engineering of Floquet Majorana fermions by light for quantum computing. PMID:26860590

Ultrafast dynamics of electrons in ammonia.

PubMed

Vöhringer, Peter

2015-04-01

Solvated electrons were first discovered in solutions of metals in liquid ammonia. The physical and chemical properties of these species have been studied extensively for many decades using an arsenal of electrochemical, spectroscopic, and theoretical techniques. Yet, in contrast to their hydrated counterpart, the ultrafast dynamics of ammoniated electrons remained completely unexplored until quite recently. Femtosecond pump-probe spectroscopy on metal-ammonia solutions and femtosecond multiphoton ionization spectroscopy on the neat ammonia solvent have provided new insights into the optical properties and the reactivities of this fascinating species. This article reviews the nature of the optical transition, which gives the metal-ammonia solutions their characteristic blue appearance, in terms of ultrafast relaxation processes involving bound and continuum excited states. The recombination processes following the injection of an electron via photoionization of the solvent are discussed in the context of the electronic structure of the liquid and the anionic defect associated with the solvated electron.

News Education: Physics Education Networks meeting has global scale Competition: Competition seeks the next Brian Cox Experiment: New measurement of neutrino time-of-flight consistent with the speed of light Event: A day for all those who teach physics Conference: Students attend first Anglo-Japanese international science conference Celebration: Will 2015 be the 'Year of Light'? Teachers: Challenging our intuition in spectacular fashion: the fascinating world of quantum physics awaits Research: Science sharpens up sport Learning: Kittinger and Baumgartner: on a mission to the edge of space International: London International Youth Science Forum calls for leading young scientists Competition: Physics paralympian challenge needs inquisitive, analytical, artistic and eloquent pupils Forthcoming events

NASA Astrophysics Data System (ADS)

2012-05-01

Education: Physics Education Networks meeting has global scale Competition: Competition seeks the next Brian Cox Experiment: New measurement of neutrino time-of-flight consistent with the speed of light Event: A day for all those who teach physics Conference: Students attend first Anglo-Japanese international science conference Celebration: Will 2015 be the 'Year of Light'? Teachers: Challenging our intuition in spectacular fashion: the fascinating world of quantum physics awaits Research: Science sharpens up sport Learning: Kittinger and Baumgartner: on a mission to the edge of space International: London International Youth Science Forum calls for leading young scientists Competition: Physics paralympian challenge needs inquisitive, analytical, artistic and eloquent pupils Forthcoming events

Graphene: from synthesis to engineering to biosensor applications

NASA Astrophysics Data System (ADS)

Singh, Jagpreet; Rathi, Aditi; Rawat, Mohit; Gupta, Manoj

2018-03-01

Graphene is a fascinating material of recent origin whose first isolation was being made possible through micromechanical cleavage of a graphite crystal. Owing to its fascinating properties, graphene has garnered significant attention in the research community for multiple applications. A number of methods have been employed for the synthesis of single-layer and multi-layer graphene. The extraordinary properties of graphene such as its Hall effect at room temperature, high surface area, tunable bandgap, high charge mobility and excellent electrical, conducting and thermal properties allow for the development of sensors of various types and also opened the doors for its use in nanoelectronics, supercapacitors and batteries. Biological aspects of graphene have also been investigated with particular emphasis on its toxicity and drug delivery. In this review, many of the salient aspects of graphene, such as from synthesis to its applications, primarily focusing on sensor applications which are of current interest, are covered.

Fascinating functional properties of Mn:Gd2O3 nanocrystalline phosphor

NASA Astrophysics Data System (ADS)

Heiba, Zein K.; Imam, N. G.; Bakr Mohamed, Mohamed

2015-10-01

In the present work we through the light on some of the fascinating structural, magnetic and optical properties of Mn:Gd2O3 nanophosphor. Manganese substituted nanocrystalline Mn:Gd2O3 was prepared via a sol gel procedure. The prepared samples were characterized applying X-ray diffraction (XRD), infrared spectroscopy (IR), squid magnometer and photoluminance (PL). XRD and IR analysis revealed a single phase solid solution up to x = 0.2. The cation distribution of Mn and Gd between the crystallographically non-equivalent sites 8b and 24d of the space group Ia 3 bar is found to be preferentially for all samples. The lattice parameter decreases with composition x, accompanied with systematic variation in the r.m.s. microstrain < εL2 > 1 / 2 . The magnetic measurement showed negative values for curie paramagnetic temperatures, θ, which indicates an antiferromagnetic interaction between the magnetic ions in Mn:Gd2O3. PL spectra showed a series of emission lines in the room temperature fluorescence measurements under UV excitation (220 nm). The observed emission lines are stokes-shifted and the non-linearity optical phenomenon is confirmed. Further, the emission lines are slightly shifted with Mn concentration (x). The blue emission around (390-402) nm was appeared due to Mn doping. Because of its fascinating properties, Mn:Gd2O3 is recommended for fuel cells, photocatalytic, and biomedical applications.

Fascin- and α-Actinin-Bundled Networks Contain Intrinsic Structural Features that Drive Protein Sorting.

PubMed

Winkelman, Jonathan D; Suarez, Cristian; Hocky, Glen M; Harker, Alyssa J; Morganthaler, Alisha N; Christensen, Jenna R; Voth, Gregory A; Bartles, James R; Kovar, David R

2016-10-24

Cells assemble and maintain functionally distinct actin cytoskeleton networks with various actin filament organizations and dynamics through the coordinated action of different sets of actin-binding proteins. The biochemical and functional properties of diverse actin-binding proteins, both alone and in combination, have been increasingly well studied. Conversely, how different sets of actin-binding proteins properly sort to distinct actin filament networks in the first place is not nearly as well understood. Actin-binding protein sorting is critical for the self-organization of diverse dynamic actin cytoskeleton networks within a common cytoplasm. Using in vitro reconstitution techniques including biomimetic assays and single-molecule multi-color total internal reflection fluorescence microscopy, we discovered that sorting of the prominent actin-bundling proteins fascin and α-actinin to distinct networks is an intrinsic behavior, free of complicated cellular signaling cascades. When mixed, fascin and α-actinin mutually exclude each other by promoting their own recruitment and inhibiting recruitment of the other, resulting in the formation of distinct fascin- or α-actinin-bundled domains. Subdiffraction-resolution light microscopy and negative-staining electron microscopy revealed that fascin domains are densely packed, whereas α-actinin domains consist of widely spaced parallel actin filaments. Importantly, other actin-binding proteins such as fimbrin and espin show high specificity between these two bundle types within the same reaction. Here we directly observe that fascin and α-actinin intrinsically segregate to discrete bundled domains that are specifically recognized by other actin-binding proteins. Copyright © 2016 Elsevier Ltd. All rights reserved.

Coexistence of superconductivity and ferromagnetism in two dimensions.

PubMed

Dikin, D A; Mehta, M; Bark, C W; Folkman, C M; Eom, C B; Chandrasekhar, V

2011-07-29

Ferromagnetism is usually considered to be incompatible with conventional superconductivity, as it destroys the singlet correlations responsible for the pairing interaction. Superconductivity and ferromagnetism are known to coexist in only a few bulk rare-earth materials. Here we report evidence for their coexistence in a two-dimensional system: the interface between two bulk insulators, LaAlO(3) (LAO) and SrTiO(3) (STO), a system that has been studied intensively recently. Magnetoresistance, Hall, and electric-field dependence measurements suggest that there are two distinct bands of charge carriers that contribute to the interface conductivity. The sensitivity of properties of the interface to an electric field makes this a fascinating system for the study of the interplay between superconductivity and magnetism. © 2011 American Physical Society

Flexible Faraday Cage with a Twist: Surface Charge on a Möbius Strip

NASA Astrophysics Data System (ADS)

Stewart, Seán

2007-05-01

Once an intriguing topological novelty known only to mathematicians, the Möbius strip has become a source of fascination and inspiration to the layperson and artist alike. Principal among its features are the two strange properties that the Möbius strip is a surface with only one side and one edge. A Möbius strip is readily formed by taking a long rectangular strip of paper and giving one of its ends a half twist before joining it to its other end (see Fig. 1). Given its simplicity, I hoped to profit from its appealing yet counterintuitive nature by designing a simple demonstration experiment that would reveal the intrinsic physical difference between one- and two-sided surfaces.

Global Magnetohydrodynamic Modeling of the Solar Corona

NASA Technical Reports Server (NTRS)

Linker, Jon A.; Wagner, William (Technical Monitor)

2001-01-01

The solar corona, the hot, tenuous outer atmosphere of the Sun, exhibits many fascinating phenomena on a wide range of scales. One of the ways that the Sun can affect us here at Earth is through the large-scale structure of the corona and the dynamical phenomena associated with it, as it is the corona that extends outward as the solar wind and encounters the Earth's magnetosphere. The goal of our research sponsored by NASA's Supporting Research and Technology Program in Solar Physics is to develop increasingly realistic models of the large-scale solar corona, so that we can understand the underlying properties of the coronal magnetic field that lead to the observed structure and evolution of the corona. We describe the work performed under this contract.

Preface: Special Topic on Frontiers in Molecular Scale Electronics

NASA Astrophysics Data System (ADS)

Evers, Ferdinand; Venkataraman, Latha

2017-03-01

The electronic, mechanical, and thermoelectric properties of molecular scale devices have fascinated scientists across several disciplines in natural sciences and engineering. The interest is partially technological, driven by the fast miniaturization of integrated circuits that now have reached characteristic features at the nanometer scale. Equally important, a very strong incentive also exists to elucidate the fundamental aspects of structure-function relations for nanoscale devices, which utilize molecular building blocks as functional units. Thus motivated, a rich research field has established itself, broadly termed "Molecular Electronics," that hosts a plethora of activities devoted to this goal in chemistry, physics, and electrical engineering. This Special Topic on Frontiers of Molecular Scale Electronics captures recent theoretical and experimental advances in the field.

Lessons from life

NASA Astrophysics Data System (ADS)

Beck, Harold

2011-12-01

I was fascinated to read the descriptions of the careers of current-day physics graduates (October pp54-57), as I have recently been writing up an account of my own first job as a physicist at what was then the British Oxygen Company (BOC) way back in 1947, after I graduated with a degree in physics from King's College London.

Quantum technologies with hybrid systems

PubMed Central

Kurizki, Gershon; Bertet, Patrice; Kubo, Yuimaru; Mølmer, Klaus; Petrosyan, David; Rabl, Peter; Schmiedmayer, Jörg

2015-01-01

An extensively pursued current direction of research in physics aims at the development of practical technologies that exploit the effects of quantum mechanics. As part of this ongoing effort, devices for quantum information processing, secure communication, and high-precision sensing are being implemented with diverse systems, ranging from photons, atoms, and spins to mesoscopic superconducting and nanomechanical structures. Their physical properties make some of these systems better suited than others for specific tasks; thus, photons are well suited for transmitting quantum information, weakly interacting spins can serve as long-lived quantum memories, and superconducting elements can rapidly process information encoded in their quantum states. A central goal of the envisaged quantum technologies is to develop devices that can simultaneously perform several of these tasks, namely, reliably store, process, and transmit quantum information. Hybrid quantum systems composed of different physical components with complementary functionalities may provide precisely such multitasking capabilities. This article reviews some of the driving theoretical ideas and first experimental realizations of hybrid quantum systems and the opportunities and challenges they present and offers a glance at the near- and long-term perspectives of this fascinating and rapidly expanding field. PMID:25737558

Quantum technologies with hybrid systems.

PubMed

Kurizki, Gershon; Bertet, Patrice; Kubo, Yuimaru; Mølmer, Klaus; Petrosyan, David; Rabl, Peter; Schmiedmayer, Jörg

2015-03-31

An extensively pursued current direction of research in physics aims at the development of practical technologies that exploit the effects of quantum mechanics. As part of this ongoing effort, devices for quantum information processing, secure communication, and high-precision sensing are being implemented with diverse systems, ranging from photons, atoms, and spins to mesoscopic superconducting and nanomechanical structures. Their physical properties make some of these systems better suited than others for specific tasks; thus, photons are well suited for transmitting quantum information, weakly interacting spins can serve as long-lived quantum memories, and superconducting elements can rapidly process information encoded in their quantum states. A central goal of the envisaged quantum technologies is to develop devices that can simultaneously perform several of these tasks, namely, reliably store, process, and transmit quantum information. Hybrid quantum systems composed of different physical components with complementary functionalities may provide precisely such multitasking capabilities. This article reviews some of the driving theoretical ideas and first experimental realizations of hybrid quantum systems and the opportunities and challenges they present and offers a glance at the near- and long-term perspectives of this fascinating and rapidly expanding field.

Quantum technologies with hybrid systems

NASA Astrophysics Data System (ADS)

Kurizki, Gershon; Bertet, Patrice; Kubo, Yuimaru; Mølmer, Klaus; Petrosyan, David; Rabl, Peter; Schmiedmayer, Jörg

2015-03-01

An extensively pursued current direction of research in physics aims at the development of practical technologies that exploit the effects of quantum mechanics. As part of this ongoing effort, devices for quantum information processing, secure communication, and high-precision sensing are being implemented with diverse systems, ranging from photons, atoms, and spins to mesoscopic superconducting and nanomechanical structures. Their physical properties make some of these systems better suited than others for specific tasks; thus, photons are well suited for transmitting quantum information, weakly interacting spins can serve as long-lived quantum memories, and superconducting elements can rapidly process information encoded in their quantum states. A central goal of the envisaged quantum technologies is to develop devices that can simultaneously perform several of these tasks, namely, reliably store, process, and transmit quantum information. Hybrid quantum systems composed of different physical components with complementary functionalities may provide precisely such multitasking capabilities. This article reviews some of the driving theoretical ideas and first experimental realizations of hybrid quantum systems and the opportunities and challenges they present and offers a glance at the near- and long-term perspectives of this fascinating and rapidly expanding field.

Key advances in the chemical modification of nanocelluloses.

PubMed

Habibi, Youssef

2014-03-07

Nanocelluloses, including nanocrystalline cellulose, nanofibrillated cellulose and bacterial cellulose nanofibers, have become fascinating building blocks for the design of new biomaterials. Derived from the must abundant and renewable biopolymer, they are drawing a tremendous level of attention, which certainly will continue to grow in the future driven by the sustainability trend. This growing interest is related to their unsurpassed quintessential physical and chemical properties. Yet, owing to their hydrophilic nature, their utilization is restricted to applications involving hydrophilic or polar media, which limits their exploitation. With the presence of a large number of chemical functionalities within their structure, these building blocks provide a unique platform for significant surface modification through various chemistries. These chemical modifications are prerequisite, sometimes unavoidable, to adapt the interfacial properties of nanocellulose substrates or adjust their hydrophilic-hydrophobic balance. Therefore, various chemistries have been developed aiming to surface-modify these nano-sized substrates in order to confer to them specific properties, extending therefore their use to highly sophisticated applications. This review collocates current knowledge in the research and development of nanocelluloses and emphasizes more particularly on the chemical modification routes developed so far for their functionalization.

Interlayer electron-phonon coupling in WSe2/hBN heterostructures

NASA Astrophysics Data System (ADS)

Jin, Chenhao; Kim, Jonghwan; Suh, Joonki; Shi, Zhiwen; Chen, Bin; Fan, Xi; Kam, Matthew; Watanabe, Kenji; Taniguchi, Takashi; Tongay, Sefaattin; Zettl, Alex; Wu, Junqiao; Wang, Feng

2017-02-01

Engineering layer-layer interactions provides a powerful way to realize novel and designable quantum phenomena in van der Waals heterostructures. Interlayer electron-electron interactions, for example, have enabled fascinating physics that is difficult to achieve in a single material, such as the Hofstadter's butterfly in graphene/boron nitride (hBN) heterostructures. In addition to electron-electron interactions, interlayer electron-phonon interactions allow for further control of the physical properties of van der Waals heterostructures. Here we report an interlayer electron-phonon interaction in WSe2/hBN heterostructures, where optically silent hBN phonons emerge in Raman spectra with strong intensities through resonant coupling to WSe2 electronic transitions. Excitation spectroscopy reveals the double-resonance nature of such enhancement, and identifies the two resonant states to be the A exciton transition of monolayer WSe2 and a new hybrid state present only in WSe2/hBN heterostructures. The observation of an interlayer electron-phonon interaction could open up new ways to engineer electrons and phonons for device applications.

Strategies towards controlling strain-induced mesoscopic phase separation in manganite thin films

NASA Astrophysics Data System (ADS)

Habermeier, H.-U.

2008-10-01

Complex oxides represent a class of materials with a plethora of fascinating intrinsic physical functionalities. The intriguing interplay of charge, spin and orbital ordering in these systems superimposed by lattice effects opens a scientifically rewarding playground for both fundamental as well as application oriented research. The existence of nanoscale electronic phase separation in correlated complex oxides is one of the areas in this field whose impact on the current understanding of their physics and potential applications is not yet clear. In this paper this issue is treated from the point of view of complex oxide thin film technology. Commenting on aspects of complex oxide thin film growth gives an insight into the complexity of a reliable thin film technology for these materials. Exploring fundamentals of interfacial strain generation and strain accommodation paves the way to intentionally manipulate thin film properties. Furthermore, examples are given for an extrinsic continuous tuning of intrinsic electronic inhomogeneities in perovskite-type complex oxide thin films.

Anisotropic noble metal nanoparticles: Synthesis, surface functionalization and applications in biosensing, bioimaging, drug delivery and theranostics.

PubMed

Paramasivam, Gokul; Kayambu, Namitharan; Rabel, Arul Maximus; Sundramoorthy, Ashok K; Sundaramurthy, Anandhakumar

2017-02-01

Anisotropic nanoparticles have fascinated scientists and engineering communities for over a century because of their unique physical and chemical properties. In recent years, continuous advances in design and fabrication of anisotropic nanoparticles have opened new avenues for application in various areas of biology, chemistry and physics. Anisotropic nanoparticles have the plasmon absorption in the visible as well as near-infrared (NIR) region, which enables them to be used for crucial applications such as biological imaging, medical diagnostics and therapy ("theranostics"). Here, we describe the progress in anisotropic nanoparticles achieved since the millennium in the area of preparation including various shapes and modification of the particle surface, and in areas of application by providing examples of applications in biosensing, bio-imaging, drug delivery and theranostics. Furthermore, we also explain various mechanisms involved in cellular uptake of anisotropic nanoparticles, and conclude with our opinion on various obstacles that limit their applications in biomedical field. Anisotropy at the molecular level has always fascinated scientists and engineering communities for over a century, however, the research on novel methods through which shape and size of nanoparticles can be precisely controlled has opened new avenues for anisotropic nanoparticles in various areas of biology, chemistry and physics. In this manuscript, we describe progress achieved since the millennium in the areas of preparation of various shapes of anisotropic nanoparticles, investigate various methods involved in modifying the surface of these NPs, and provide examples of applications in biosensing and bio-imaging, drug delivery and theranostics. We also present mechanisms involved in cellular uptake of nanoparticles, describe different methods of preparation of anisotropic nanoparticles including biomimetic and photochemical synthesis, and conclude with our opinion on various obstacles that limit their applications in biomedical field. Copyright © 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Once a physicist: Umberto Guidoni

NASA Astrophysics Data System (ADS)

Guidoni, Umberto

2008-09-01

How did you first become interested in physics? As a teenager I was given a small telescope. It was only a toy but with it I could see the rings of Saturn. I was fascinated and decided I wanted to study space.

Coordination nano-space as stage of hydrogen ortho-para conversion.

PubMed

Kosone, Takashi; Hori, Akihiro; Nishibori, Eiji; Kubota, Yoshiki; Mishima, Akio; Ohba, Masaaki; Tanaka, Hiroshi; Kato, Kenichi; Kim, Jungeun; Real, José Antonio; Kitagawa, Susumu; Takata, Masaki

2015-07-01

The ability to design and control properties of nano-sized space in porous coordination polymers (PCPs) would provide us with an ideal stage for fascinating physical and chemical phenomena. We found an interconversion of nuclear-spin isomers for hydrogen molecule H2 adsorbed in a Hofmann-type PCP, {Fe(pz)[Pd(CN)4]} (pz=pyrazine), by the temperature dependence of Raman spectra. The ortho (o)-para (p) conversion process of H2 is forbidden for an isolated molecule. The charge density study using synchrotron radiation X-ray diffraction reveals the electric field generated in coordination nano-space. The present results corroborate similar findings observed on different systems and confirm that o-p conversion can occur on non-magnetic solids and that electric field can induce the catalytic hydrogen o-p conversion.

The success of recent land management efforts to reduce soil erosion in northern France

NASA Astrophysics Data System (ADS)

Frankl, Amaury; Prêtre, Vincent; Nyssen, Jan; Salvador, Pierre-Gil

2018-02-01

Soil erosion is an important problem in open-field agricultural landscapes. With almost no permanent vegetation in small headwater catchments, and with few physical obstacles to reduce runoff velocities, runoff concentration along linear landscape elements (plot boundaries) or thalwegs frequently causes ephemeral gullies to form - the latter reflecting the poor hydrogeomorphic condition of the land- and soilscape. To address this problem, and to remediate negative on- and off-site effects, land management efforts have multiplied over the past decades in many regions. This includes, amongst other measures, the implementation of vegetation barriers called 'fascines'. In the loess-dominated Aa River basin of northern France, where cropland accounts for 67% of the cover, we investigated the effect of fascines on ephemeral gully erosion dynamics, together with rainfall characteristics and cropland management. This was accomplished through a spatially explicit study of 269 sites prone to ephemeral gullying using a diachronic analysis of historical aerial photographs. Between 1947 and 2012, ephemeral gully densities at the scale of the Aa River basin (643 km2) varied between 0.39 and 1.31 m ha- 1 (long-term average of 0.68 m ha- 1 (with local maxima up to 9.35 m ha- 1). Densities are, however, much higher when only considering the most erosion-vulnerable municipalities (long-term average of 2.23-4.30 m ha- 1); those values should be used when comparing results from this study to other reports of ephemeral gully erosion. Fascines were introduced in 2001 and were present in 30% of the gully erosion sites by 2012. Although the presence of fascines has an effect on gully length reduction, spatial and temporal variations in gully length were mainly driven by cumulative precipitation. Measurement of sediment deposition at 29 fascines in 2016 showed that only 47% of the fascines functioned as sediment sinks. They stored on average 1.7 Mg of sediment per winter half-year, corresponding to 0.009 Mg ha- 1. The results suggest that fascines positively impact the landscape's resilience and reduce ephemeral gully erosion rates. The use of vegetation barriers such as fascines are increasingly implemented for erosion control in western Europe, but pose problems for the management of open-field landscapes.

Electronic transport in VO 2 —Experimentally calibrated Boltzmann transport modeling

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kinaci, Alper; Kado, Motohisa; Rosenmann, Daniel

2015-12-28

Materials that undergo metal-insulator transitions (MITs) are under intense study because the transition is scientifically fascinating and technologically promising for various applications. Among these materials, VO2 has served as a prototype due to its favorable transition temperature. While the physical underpinnings of the transition have been heavily investigated experimentally and computationally, quantitative modeling of electronic transport in the two phases has yet to be undertaken. In this work, we establish a density-functional-theory (DFT)-based approach to model electronic transport properties in VO2 in the semiconducting and metallic regimes, focusing on band transport using the Boltzmann transport equations. We synthesized high qualitymore » VO2 films and measured the transport quantities across the transition, in order to calibrate the free parameters in the model. We find that the experimental calibration of the Hubbard correction term can efficiently and adequately model the metallic and semiconducting phases, allowing for further computational design of MIT materials for desirable transport properties.« less

Silver Nanoparticles: Synthesis, Characterization, Properties, Applications, and Therapeutic Approaches.

PubMed

Zhang, Xi-Feng; Liu, Zhi-Guo; Shen, Wei; Gurunathan, Sangiliyandi

2016-09-13

Recent advances in nanoscience and nanotechnology radically changed the way we diagnose, treat, and prevent various diseases in all aspects of human life. Silver nanoparticles (AgNPs) are one of the most vital and fascinating nanomaterials among several metallic nanoparticles that are involved in biomedical applications. AgNPs play an important role in nanoscience and nanotechnology, particularly in nanomedicine. Although several noble metals have been used for various purposes, AgNPs have been focused on potential applications in cancer diagnosis and therapy. In this review, we discuss the synthesis of AgNPs using physical, chemical, and biological methods. We also discuss the properties of AgNPs and methods for their characterization. More importantly, we extensively discuss the multifunctional bio-applications of AgNPs; for example, as antibacterial, antifungal, antiviral, anti-inflammatory, anti-angiogenic, and anti-cancer agents, and the mechanism of the anti-cancer activity of AgNPs. In addition, we discuss therapeutic approaches and challenges for cancer therapy using AgNPs. Finally, we conclude by discussing the future perspective of AgNPs.

Novel electrochemiluminescence of silver nanoclusters fabricated on triplex DNA scaffolds for label-free detection of biothiols.

PubMed

Feng, Lingyan; Wu, Li; Xing, Feifei; Hu, Lianzhe; Ren, Jinsong; Qu, Xiaogang

2017-12-15

Electrochemiluminescence (ECL) of metal nanoclusters and their application have been widely reported due to the good biocompatibility, fascinating electrocatalytic activity and so on. Using DNA as synthesis template opens new opportunities to modulate the physical properties of AgNCs. Triplex DNA has been reported for the site-specific, homogeneous and highly stable silver nanoclusters (AgNCs) fabrication from our recent research. Here we further explore their extraordinary ECL properties and applications in biosensor utilization. By reasonable design of DNA sequence, AgNCs were obtained in the predefined position of CG.C + sites of triplex DNA, and the ECL emission at a low potential was observed with this novel DNA template. Finally, a simple and label-free method was developed for biothiols detection based on the enhanced catalytic reaction and a robust interaction between the triplex-AgNCs and cysteine, by influencing the microenvironment provided by DNA template. Copyright © 2017 Elsevier B.V. All rights reserved.

Design of Molecular Materials: Supramolecular Engineering

NASA Astrophysics Data System (ADS)

Simon, Jacques; Bassoul, Pierre

2001-02-01

This timely and fascinating book is destined to be recognised as THE book on supramolecular engineering protocols. It covers this sometimes difficult subject in an approachable form, gathering together information from many sources. Supramolecular chemistry, which links organic chemistry to materials science, is one of the fastest growth areas of chemistry research. This book creates a correlation between the structure of single molecules and the physical and chemical properties of the resulting materials. By making systematic changes to the component molecules, the resulting solid can be engineered for optimum performance. There is a clearly written development from synthesis of designer molecules to properties of solids and further on to devices and complex materials systems, providing guidelines for mastering the organisation of these systems. Topics covered include: Systemic chemistry Molecular assemblies Notions of symmetry Supramolecular engineering Principe de Curie Organisation in molecular media Molecular semiconductors Industrial applications of molecular materials This superb book will be invaluable to researchers in the field of supramolecular materials and also to students and teachers of the subject.

Solution-gated graphene transistors for chemical and biological sensors.

PubMed

Yan, Feng; Zhang, Meng; Li, Jinhua

2014-03-01

Graphene has attracted much attention in biomedical applications for its fascinating properties. Because of the well-known 2D structure, every atom of graphene is exposed to the environment, so the electronic properties of graphene are very sensitive to charged analytes (ions, DNA, cells, etc.) or an electric field around it, which renders graphene an ideal material for high-performance sensors. Solution-gated graphene transistors (SGGTs) can operate in electrolytes and are thus excellent candidates for chemical and biological sensors, which have been extensively studied in the recent 5 years. Here, the device physics, the sensing mechanisms, and the performance of the recently developed SGGT-based chemical and biological sensors, including pH, ion, cell, bacterial, DNA, protein, glucose sensors, etc., are introduced. Their advantages and shortcomings, in comparison with some conventional techniques, are discussed. Conclusions and challenges for the future development of the field are addressed in the end. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Statics and dynamics of DNA knotting

NASA Astrophysics Data System (ADS)

Orlandini, Enzo

2018-02-01

Knots and entanglement in polymers and biopolymers such as DNA and proteins constitute a timely topic that spans various scientific disciplines ranging from physics to chemistry, biology and mathematics. Although in the past many advancements have been made in understanding the equilibrium knotting probability and knot complexity of long polymer chains in solutions, many questions have been addressed in recent years by both experimental and theoretical means—for instance, how the knotting probability depends on the quality of the solvent, the elastic properties of the molecule and its degree of confinement. How knots form, evolve and eventually disappear in a fluctuating chain. Are the equilibrium and non-equilibrium properties of knotted molecules affected by the knot swelling/shrinking dynamics? Moreover, thanks to the great advance in nanotechnology and micromanipulation techniques, nowadays knots can be ‘manually’ tied in a single DNA molecule, followed during their motion along the chains, forced to pass through nanopores, or stretched by external forces or elongational flows. All these experimental approaches allow access to new information on the interplay of topology and polymer physics, and this has opened new perspectives in the field. Here, we provide an overview of the current knowledge of this topic, stressing the main results obtained, including the recent developments in experimental and computational approaches. Since almost all experiments on knotting involve DNA, the review will be mainly focused on the topological properties of this fascinating and biologically relevant molecule.

Fascinating Foam - Diverse Applications, Unexpected Properties, and Characterization Challenges (PD2P Talk)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kropka, Jamie M.

2009-09-24

Foam pervades our everyday lives: we use it to bathe and shave, it floats atop our beer, cappuccino and pie, and it can even infect our bodies in the form of viruses. Although we are able to manipulate foam in these and many other common practices, there is still much we do not know about this fascinatingly complex material. In this talk, some of the intriguing aspects of foam, which could not be predicted based on its constituent components, will be discussed. Some challenging aspects of foam characterization, which have impeded the development of a thorough understanding of the materialmore » despite over a century of investigations, will also be presented. Despite these challenges, there are some known aspects of foams and these will be outlined along with how today's modern tools are being utilized to tell us more about foam structure and dynamics. A brief introduction to Sandia's interest in foams will then be given, and some of the current research we are conducting to further those interests will be discussed. This work is focused on the preparation of 'model' organic foams for use in developing an understanding of how to tune their stability and rheological response. Finally, physical and chemical methods to stabilize the foam will be described and possible new directions for the work will be presented.« less

Equiangular Surfaces, Self-Similar Surfaces, and the Geometry of Seashells

ERIC Educational Resources Information Center

Boyadzhiev, Khristo N.

2007-01-01

Logarithmic spirals are among the most fascinating curves in the plane, being the only curves that are equiangular, and the only ones that are self-similar. In this article, we show that in three dimensions, these two properties are independent. Although there are surfaces that have both properties, there are some that are equiangular, but not…

Spin state switching in iron coordination compounds

PubMed Central

Gaspar, Ana B; Garcia, Yann

2013-01-01

Summary The article deals with coordination compounds of iron(II) that may exhibit thermally induced spin transition, known as spin crossover, depending on the nature of the coordinating ligand sphere. Spin transition in such compounds also occurs under pressure and irradiation with light. The spin states involved have different magnetic and optical properties suitable for their detection and characterization. Spin crossover compounds, though known for more than eight decades, have become most attractive in recent years and are extensively studied by chemists and physicists. The switching properties make such materials potential candidates for practical applications in thermal and pressure sensors as well as optical devices. The article begins with a brief description of the principle of molecular spin state switching using simple concepts of ligand field theory. Conditions to be fulfilled in order to observe spin crossover will be explained and general remarks regarding the chemical nature that is important for the occurrence of spin crossover will be made. A subsequent section describes the molecular consequences of spin crossover and the variety of physical techniques usually applied for their characterization. The effects of light irradiation (LIESST) and application of pressure are subjects of two separate sections. The major part of this account concentrates on selected spin crossover compounds of iron(II), with particular emphasis on the chemical and physical influences on the spin crossover behavior. The vast variety of compounds exhibiting this fascinating switching phenomenon encompasses mono-, oligo- and polynuclear iron(II) complexes and cages, polymeric 1D, 2D and 3D systems, nanomaterials, and polyfunctional materials that combine spin crossover with another physical or chemical property. PMID:23504535

Exploring the Yo-Yo: Filipino Physics Fun

ERIC Educational Resources Information Center

Murfin, Brian

2012-01-01

The yo-yo is a scientific toy that has fascinated young and old for thousands of years. According to yo-yo experts, the yo-yo is the second oldest toy in the world, after the doll. Yo-yo activities can be an excellent tool to help students explore many important physics concepts related to energy and motion. The rich history of the yo-yo offers…

Strong fascin expression promotes metastasis independent of its F-actin bundling activity.

PubMed

Heinz, Lisa S; Muhs, Stefanie; Schiewek, Johanna; Grüb, Saskia; Nalaskowski, Marcus; Lin, Yuan-Na; Wikman, Harriet; Oliveira-Ferrer, Leticia; Lange, Tobias; Wellbrock, Jasmin; Konietzny, Anja; Mikhaylova, Marina; Windhorst, Sabine

2017-12-15

High expression of the actin bundling protein Fascin increases the malignancy of tumor cells. Here we show that fascin expression is up-regulated in more malignant sub-cell lines of MDA-MB-231 cells as compared to parental cells. Since also parental MDA-MB-231 cells exhibit high fascin levels, increased fascin expression was termed as "hyperexpression". To examine the effect of fascin hyperexpression, fascin was hyperexpressed in parental MDA-MB-231 cells and metastasis was analyzed in NOD scid gamma (NSG) mice. In addition, the effect of fascin mutants with inactive or constitutively active actin bundling activity was examined. Unexpectedly, we found that hyperexpression of both, wildtype (wt) and mutant fascin strongly increased metastasis in vivo , showing that the effect of fascin hyperexpression did not depend on its actin bundling activity. Cellular assays revealed that hyperexpression of wt and mutant fascin increased adhesion of MDA-MB-231 cells while transmigration and proliferation were not affected. Since it has been shown that fascin controls adhesion by directly interacting with microtubules ( MTs), we analyzed if fascin hyperexpression affects MT dynamics. We found that at high concentrations fascin significantly increased MT dynamics in cells and in cell-free approaches. In summary our data show that strong expression of fascin in breast cancer cells increases metastasis independent of its actin bundling activity. Thus, it seems that the mechanism of fascin-stimulated metastasis depends on its concentration.

"I Fall Asleep in Class … but Physics Is Fascinating": The Use of Large-Scale Longitudinal Data to Explore the Educational Experiences of Aspiring Girls in Mathematics and Physics

ERIC Educational Resources Information Center

Mujtaba, Tamjid; Reiss, Michael J.

2016-01-01

This article explores how students' aspirations to study mathematics or physics in post-16 education are associated with their perceptions of their education, their motivations, and the support they feel they received. The analysis is based on the responses of around 10,000 students in England in Year 8 (age 12-13) and then in Year 10 (age 14-15).…

A presentation of the black hole stretching effect

NASA Astrophysics Data System (ADS)

Vasileios Kontomaris, Stylianos; Malamou, Anna

2018-01-01

Black holes and the physics behind them is a fascinating topic for students of all levels. The exotic conditions which prevail near a black hole should be discussed and presented to undergraduate students in order to increase their interest in studying physics and to provide useful insights into basic physics concepts, such as non-uniform gravitational fields. For this purpose, a simplified presentation of the stretching effect which is experienced by an object near a black hole is presented in this paper.

The Universe Untangled; Modern physics for everyone

NASA Astrophysics Data System (ADS)

Pillitteri, Abigail

2017-04-01

Physics has always been a tricky subject for the general public. Millions are fascinated by the laws of the physical world, but there has been a lack of books written specifically for general readers. The Universe Untangled is for those who are curious; yet do not have an extensive mathematical background. It uses images, analogies and comprehensible language to cover popular topics of interest including the evolution of the Universe, fundamental forces, the nature of space and time, and the quest for knowing the unknown.

Ultra-small plutonium oxide nanocrystals: an innovative material in plutonium science.

PubMed

Hudry, Damien; Apostolidis, Christos; Walter, Olaf; Janssen, Arne; Manara, Dario; Griveau, Jean-Christophe; Colineau, Eric; Vitova, Tonya; Prüssmann, Tim; Wang, Di; Kübel, Christian; Meyer, Daniel

2014-08-11

Apart from its technological importance, plutonium (Pu) is also one of the most intriguing elements because of its non-conventional physical properties and fascinating chemistry. Those fundamental aspects are particularly interesting when dealing with the challenging study of plutonium-based nanomaterials. Here we show that ultra-small (3.2±0.9 nm) and highly crystalline plutonium oxide (PuO2 ) nanocrystals (NCs) can be synthesized by the thermal decomposition of plutonyl nitrate ([PuO2 (NO3 )2 ]⋅3 H2 O) in a highly coordinating organic medium. This is the first example reporting on the preparation of significant quantities (several tens of milligrams) of PuO2 NCs, in a controllable and reproducible manner. The structure and magnetic properties of PuO2 NCs have been characterized by a wide variety of techniques (powder X-ray diffraction (PXRD), X-ray absorption fine structure (XAFS), X-ray absorption near edge structure (XANES), TEM, IR, Raman, UV/Vis spectroscopies, and superconducting quantum interference device (SQUID) magnetometry). The current PuO2 NCs constitute an innovative material for the study of challenging problems as diverse as the transport behavior of plutonium in the environment or size and shape effects on the physics of transuranium elements. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

50 Years of Fermilab

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lincoln, Don

America’s leading particle physics laboratory is turning 50 years old this year. Fermilab’s Dr. Don Lincoln remembers the laboratory’s first half century and looks forward to the fascinating research topics that Fermilab’s scientific staff are looking at as they leap forward into the future.

Towards Explaining the Water Siphon

ERIC Educational Resources Information Center

Jumper, William D.; Stanchev, Boris

2014-01-01

Many high school and introductory college physics courses cover topics in fluidics through the Bernoulli and Poiseuille equations, and consequently one might think that siphons should present an excellent opportunity to engage students in various laboratory measurement exercises incorporating these fascinating devices. However, the flow rates (or…

Riffing on the universe

NASA Astrophysics Data System (ADS)

Cox, Trevor

2016-05-01

Music and physics might seem like polar opposites, one having great emotional potency and the other being a cerebral subject of equations, theories and deductions. Both, however, benefit from improvisers - people who stand on the shoulders of giants, taking earlier triumphs and building on them to create something new. For me, analogies like these, which draw parallels between physicists and jazz musicians, are the most fascinating revelations in Stephon Alexander's book The Jazz of Physics.

Coordination nano-space as stage of hydrogen ortho–para conversion

PubMed Central

Kosone, Takashi; Hori, Akihiro; Nishibori, Eiji; Kubota, Yoshiki; Mishima, Akio; Ohba, Masaaki; Tanaka, Hiroshi; Kato, Kenichi; Kim, Jungeun; Real, José Antonio; Kitagawa, Susumu; Takata, Masaki

2015-01-01

The ability to design and control properties of nano-sized space in porous coordination polymers (PCPs) would provide us with an ideal stage for fascinating physical and chemical phenomena. We found an interconversion of nuclear-spin isomers for hydrogen molecule H2 adsorbed in a Hofmann-type PCP, {Fe(pz)[Pd(CN)4]} (pz=pyrazine), by the temperature dependence of Raman spectra. The ortho (o)–para (p) conversion process of H2 is forbidden for an isolated molecule. The charge density study using synchrotron radiation X-ray diffraction reveals the electric field generated in coordination nano-space. The present results corroborate similar findings observed on different systems and confirm that o–p conversion can occur on non-magnetic solids and that electric field can induce the catalytic hydrogen o–p conversion. PMID:26587262

Gold Nanoparticles for Biology and Medicine

PubMed Central

Giljohann, David A.; Seferos, Dwight S.; Daniel, Weston L.; Massich, Matthew D.; Patel, Pinal C.

2014-01-01

Gold colloids have fascinated scientists for over a century and are now heavily utilized in chemistry, biology, engineering, and medicine. Today these materials can be synthesized reproducibly, modified with seemingly limitless chemical functional groups, and, in certain cases, characterized with atomic-level precision. This Review highlights recent advances in the synthesis, bioconjugation, and cellular uses of gold nanoconjugates. There are now many examples of highly sensitive and selective assays based upon gold nanoconjugates. In recent years, focus has turned to therapeutic possibilities for such materials. Structures which behave as gene-regulating agents, drug carriers, imaging agents, and photoresponsive therapeutics have been developed and studied in the context of cells and many debilitating diseases. These structures are not simply chosen as alternatives to molecule-based systems, but rather for their new physical and chemical properties, which confer substantive advantages in cellular and medical applications. PMID:20401880

Rayleigh-Taylor instability-fascinating gateway to the study of fluid dynamics

NASA Astrophysics Data System (ADS)

Benjamin, Robert F.

1999-09-01

A series of low-cost simple, "kitchen-physics" experiments demonstrates Rayleigh-Taylor Instability (RTI), the growth of ripples at an interface between fluids when the higher-density fluid is on top. We also describe the importance of RTI in ocean dynamics and commercial products.

Fascin Overexpression Promotes Cholangiocarcinoma RBE Cell Proliferation, Migration, and Invasion.

PubMed

Zhao, Haiying; Yang, Fuquan; Zhao, Wenyan; Zhang, Chunjv; Liu, Jingang

2016-04-01

Fascin is overexpressed in various tumor tissues and is closely related to tumor metastasis and invasion. However, the role of fascin in cholangiocarcinoma RBE cells has not been clearly reported. This study aimed to establish a cholangiocarcinoma cell line with stable and high expression of fascin to observe the effect of fascin on cell proliferation, migration, and invasion. A fascin overexpression vector, pcDNA3.1-Fascin, was constructed and transfected into the human cholangiocarcinoma RBE cell line. The results of real-time polymerase chain reaction, Western blot, and immunofluorescence indicated that fascin was steadily and highly expressed in RBE cells. The results of 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide and colony formation assay indicated that upregulated fascin expression could enhance cholangiocarcinoma cell proliferation. The results of wound healing assay and transwell assay indicated that fascin could promote cholangiocarcinoma cell migration and invasion, and a further study found that the nuclear factor-κB signaling pathway was activated after upregulation of fascin, whereas E-cadherin expression in these cells was significantly decreased. Additionally, E-cadherin expression was significantly increased after inhibiting nuclear factor-κB activity using inhibitor or small interfering RNA, and E-cadherin expression was decreased by fascin overexpression after nuclear factor-κB inhibition, suggesting that nuclear factor-κB signaling pathway was not involved in the regulation of E-cadherin by fascin. In summary, the results of this study demonstrated that fascin effectively promoted cholangiocarcinoma RBE cell proliferation, migration, and invasion. This study provides evidence for fascin as a potential target in the treatment of cholangiocarcinoma. © The Author(s) 2015.

Hexaflexagons

ERIC Educational Resources Information Center

Gardner, Martin

2012-01-01

This article is a slightly condensed reprint of Martin Gardner's very first "Mathematical Games" column (which appeared December 1956 in "Scientific American"). Here Gardner introduces flexagons (paper polygons folded from straight or crooked strips of paper which have the fascinating property of changing their faces when they are "flexed"),…

Teaching the Delightful Laws of Physics in a Survey Course

NASA Astrophysics Data System (ADS)

Hewitt, Paul G.

2015-10-01

How physics can be made interesting is a question that needs no answer. That's because physics is interesting! It's a field of study jam-packed with fascination and wonder. The general public has an enormous thirst for physics knowledge, as indicated by the great numbers who purchase science magazines and books and watch NOVA and other science specials. A related question, how to make a physics course interesting, is something that we can answer. All we have to do is present physics at a proper pace in the language of the learner. My adage has always been that if the first course in physics is delightful, the rigor of a follow-up course will be welcomed.

Metal Thio- and Selenophosphates as Multifunctional van der Waals Layered Materials.

PubMed

Susner, Michael A; Chyasnavichyus, Marius; McGuire, Michael A; Ganesh, Panchapakesan; Maksymovych, Petro

2017-10-01

Since the discovery of Dirac physics in graphene, research in 2D materials has exploded with the aim of finding new materials and harnessing their unique and tunable electronic and optical properties. The follow-on work on 2D dielectrics and semiconductors has led to the emergence and development of hexagonal boron nitride, black phosphorus, and transition metal disulfides. However, the spectrum of good insulating materials is still very narrow. Likewise, 2D materials exhibiting correlated phenomena such as superconductivity, magnetism, and ferroelectricity have yet to be developed or discovered. These properties will significantly enrich the spectrum of functional 2D materials, particularly in the case of high phase-transition temperatures. They will also advance a fascinating fundamental frontier of size and proximity effects on correlated ground states. Here, a broad family of layered metal thio(seleno)phosphate materials that are moderate- to wide-bandgap semiconductors with incipient ionic conductivity and a host of ferroic properties are reviewed. It is argued that this material class has the potential to merge the sought-after properties of complex oxides with electronic functions of 2D and quasi-2D electronic materials, as well as to create new avenues for both applied and fundamental materials research in structural and magnetic correlations. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Nanomaterials for membrane fouling control: accomplishments and challenges.

PubMed

Yang, Qian; Mi, Baoxia

2013-11-01

We report a review of recent research efforts on incorporating nanomaterials-including metal/metal oxide nanoparticles, carbon-based nanomaterials, and polymeric nanomaterials-into/onto membranes to improve membrane antifouling properties in biomedical or potentially medical-related applications. In general, nanomaterials can be incorporated into/onto a membrane by blending them into membrane fabricating materials or by attaching them to membrane surfaces via physical or chemical approaches. Overall, the fascinating, multifaceted properties (eg, high hydrophilicity, superparamagnetic properties, antibacterial properties, amenable functionality, strong hydration capability) of nanomaterials provide numerous novel strategies and unprecedented opportunities to fully mitigate membrane fouling. However, there are still challenges in achieving a broader adoption of nanomaterials in the membrane processes used for biomedical applications. Most of these challenges arise from the concerns over their long-term antifouling performance, hemocompatibility, and toxicity toward humans. Therefore, rigorous investigation is still needed before the adoption of some of these nanomaterials in biomedical applications, especially for those nanomaterials proposed to be used in the human body or in contact with living tissue/body fluids for a long period of time. Nevertheless, it is reasonable to predict that the service lifetime of membrane-based biomedical devices and implants will be prolonged significantly with the adoption of appropriate fouling control strategies. Copyright © 2013 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.

Scaling in Theropod Dinosaurs: Femoral Bone Dimensions

ERIC Educational Resources Information Center

Lee, Scott A.

2014-01-01

Finding topics that inspire students is an important aspect of any physics course. Virtually everyone is fascinated by "Tyrannosaurus rex," and the excitement of the class is palpable when we explore scaling effects in "T. rex" and other bipedal theropod dinosaurs as part of our discussion of mechanics and elasticity. In this…

Teaching Oscillations by a Model of Nanoresonator

ERIC Educational Resources Information Center

Lindell, A.; Viiri, J.

2009-01-01

Nanoscience offers fascinating opportunities for science education as it links the achievements of modern technology to traditional models of science. In this article we present a nanotechnology orientated lesson on oscillations, suitable for physics courses at high schools and universities. The focus of the lesson is in forced oscillations on a…

Crocodiles and Alligators. Young Discovery Library Series.

ERIC Educational Resources Information Center

Farre, Marie

This book is written for children ages 5 through 10. Part of a series designed to develop their curiosity, fascinate them and educate them, this volume describes the physical characteristics, behavior, and peculiar habits of crocodiles, including how to distinguish them from close relatives such as alligators, cayman, and gharials. (YP)

Exploring Paper.

ERIC Educational Resources Information Center

Brand, Judith, Ed.

1999-01-01

Exploratorium Magazine communicates ideas that exhibits cannot easily demonstrate, extending the museum beyond its physical walls. This issue takes an in-depth look at the science and history of paper. Topics include: (1) Fascinating Facts about Paper; (2) A Closer Look at the Paper in This Magazine; (3) Handmade Paper; (4) Paper Airplanes; (5)…

Modern Gravitational Lens Cosmology for Introductory Physics and Astronomy Students

ERIC Educational Resources Information Center

Huwe, Paul; Field, Scott

2015-01-01

Recent and exciting discoveries in astronomy and cosmology have inspired many high school students to learn about these fields. A particularly fascinating consequence of general relativity at the forefront of modern cosmology research is gravitational lensing, the bending of light rays that pass near massive objects. Gravitational lensing enables…

Making Sense of Bell's Theorem and Quantum Nonlocality

NASA Astrophysics Data System (ADS)

Boughn, Stephen

2017-05-01

Bell's theorem has fascinated physicists and philosophers since his 1964 paper, which was written in response to the 1935 paper of Einstein, Podolsky, and Rosen. Bell's theorem and its many extensions have led to the claim that quantum mechanics and by inference nature herself are nonlocal in the sense that a measurement on a system by an observer at one location has an immediate effect on a distant entangled system (one with which the original system has previously interacted). Einstein was repulsed by such "spooky action at a distance" and was led to question whether quantum mechanics could provide a complete description of physical reality. In this paper I argue that quantum mechanics does not require spooky action at a distance of any kind and yet it is entirely reasonable to question the assumption that quantum mechanics can provide a complete description of physical reality. The magic of entangled quantum states has little to do with entanglement and everything to do with superposition, a property of all quantum systems and a foundational tenet of quantum mechanics.

Topotactic Metal-Insulator Transition in Epitaxial SrFeO x Thin Films

DOE PAGES

Khare, Amit; Shin, Dongwon; Yoo, Tae Sup; ...

2017-07-31

Multivalent transition metal oxides provide fascinating and rich physics related to oxygen stoichiometry. In particular, the adoptability of various valence states of transition metals enables perovskite oxides to display mixed (oxygen) ionic and electronic conduction and catalytic activity useful in many practical applications, including solid-oxide fuel cells (SOFCs), rechargeable batteries, gas sensors, and memristive devices. For proper realization of the ionic conduction and catalytic activity, it is essential to understand the reversible oxidation and reduction process, which is governed by oxygen storage/release steps in oxides. Topotactic phase transformation facilitates the redox process in perovskites with specific oxygen vacancy ordering bymore » largely varying the oxygen concentration of a material without losing the lattice framework. The concentration and diffusion of oxide ions (O 2–), the valence state of the transition metal cations, and the thermodynamic structural integrity together provide fundamental understanding and ways to explicitly control the redox reaction.[6] In addition, it offers an attractive route for tuning the emergent physical properties of transition metal oxides, via strong coupling between the crystal lattice and electronic structure.« less

Lab-on-Fiber devices as an all around platform for sensing

NASA Astrophysics Data System (ADS)

Ricciardi, A.; Consales, M.; Quero, G.; Crescitelli, A.; Esposito, E.; Cusano, A.

2013-12-01

"Lab-on-Fiber" technology is an emerging field envisioning a novel class of advanced, multifunctional photonic devices and components arising from the integration onto optical fibers of different materials at micro and nano-scale with suitable physical, chemical and biological properties. This new fascinating and intriguing research field thus proposes a new technological platform where functionalized materials, devices and components are constructed, embedded all together in a single optical fiber providing the necessary physical connections and light matter interaction, exploitable in both communication and sensing applications. This technological innovation would open the way for the creation of a novel technological world completely integrated in a single optical fiber conferring unique and unprecedented performances and functionality degree. Although, the benefits provided by such a technology can be easily understood, many research efforts are, however, required to translate the vision in a technological reality. Indeed, the main issue to address concerns the identification and definition of viable fabrication methodologies, routes and strategies enabling the integration of a large set of functional materials at sub wavelength scale onto non conventional substrates as the case of optical fibers.

Clash of Harmonics in Stravinsky's The Rite of Spring

NASA Astrophysics Data System (ADS)

Ruiz, Michael J.

2018-04-01

This paper describes a fascinating connection between the physics of music and the famous chord in the dissonant rhythmic section of Stravinsky's The Rite of Spring (1913). The analysis of Stravinsky's chord will draw from the physics of harmonics, musical intervals, mathematics, and cognitive psychology. This highly interdisciplinary approach will especially appeal to students typically found in a physics course for non-majors. A video accompanies this paper so that readers and students can hear the construction of Stravinsky's dissonant chord as well as an orchestra performing an excerpt of The Rite of Spring.

Metalinguistic Negation in English and Arabic

ERIC Educational Resources Information Center

Nedwick, Kelly M.

2014-01-01

Negation is a unique and fascinating property of human language which has been given extensive theoretical and typological treatment. One categorization divides negation use into metalinguistic negation and descriptive negation (Horn, 1985). Descriptive negation (DN) is the truth-functional semantic operator which has received the most attention…

Ab initio prediction of superdense tetragonal and monoclinic polymorphs of carbon

DOE PAGES

Li, Zhen -Zhen; Wang, Jian -Tao; Xu, Li -Fang; ...

2016-11-02

The design and synthesis of three-dimensional denser carbons are one of the hot issues in condensed matter physics because of their fascinating properties. Here we identify by ab initio calculations several tetragonal and monoclinic polymorphs of carbon that adopt the t32, t32*, m32, and m32* structures in P4¯2 1c, P4 32 12, P2 1/c, and C2 symmetry, respectively. These carbon polymorphs have large 32-atom unit cells in all-sp 3 bonding networks comprising five- and six-membered rings that are dynamically stable, as verified by a phonon mode analysis. Electronic band structure calculations show that they are insulators with band gaps inmore » the range of 5.19–5.41 eV, close to the calculated band gap of 5.34 eV for diamond. Remarkably, these carbon phases possess an extremely high atom number density exceeding that of diamond. Lastly, the present results establish different types of carbon phases and offer insights into their outstanding structural and electronic properties.« less

STM Studies of Spin-­Orbit Coupled Phases in Real-­ and Momentum-­Space

DOE Office of Scientific and Technical Information (OSTI.GOV)

Madhavan, Vidya

The recently discovered class of spin-orbit coupled materials with interesting topological character are fascinating both from fundamental as well as application point of view. Two striking examples are 3D topological insulators (TIs) and topological crystalline insulators (TCIs). These materials host linearly dispersing (Dirac like) surface states with an odd number of Dirac nodes and are predicted to carry a quantized half-integer value of the axion field. The non-trivial topological properties of TIs and TCIs arise from strong spin-orbit coupling leading to an inverted band structure; which also leads to the chiral spin texture in momentum space. In this project wemore » used low temperature scanning tunneling microscopy (STM) and spectroscopy (STS) to study materials with topological phases in real- and momentum-space. We studied both single crystals and thin films of topological materials which are susceptible to being tuned by doping, strain or gating, allowing us to explore their physical properties in the most interesting regimes and set the stage for future technological applications. .« less

Silver Nanoparticles: Synthesis, Characterization, Properties, Applications, and Therapeutic Approaches

PubMed Central

Zhang, Xi-Feng; Liu, Zhi-Guo; Shen, Wei; Gurunathan, Sangiliyandi

2016-01-01

Recent advances in nanoscience and nanotechnology radically changed the way we diagnose, treat, and prevent various diseases in all aspects of human life. Silver nanoparticles (AgNPs) are one of the most vital and fascinating nanomaterials among several metallic nanoparticles that are involved in biomedical applications. AgNPs play an important role in nanoscience and nanotechnology, particularly in nanomedicine. Although several noble metals have been used for various purposes, AgNPs have been focused on potential applications in cancer diagnosis and therapy. In this review, we discuss the synthesis of AgNPs using physical, chemical, and biological methods. We also discuss the properties of AgNPs and methods for their characterization. More importantly, we extensively discuss the multifunctional bio-applications of AgNPs; for example, as antibacterial, antifungal, antiviral, anti-inflammatory, anti-angiogenic, and anti-cancer agents, and the mechanism of the anti-cancer activity of AgNPs. In addition, we discuss therapeutic approaches and challenges for cancer therapy using AgNPs. Finally, we conclude by discussing the future perspective of AgNPs. PMID:27649147

Maximization of the connectivity repertoire as a statistical principle governing the shapes of dendritic arbors

PubMed Central

Wen, Quan; Stepanyants, Armen; Elston, Guy N.; Grosberg, Alexander Y.; Chklovskii, Dmitri B.

2009-01-01

The shapes of dendritic arbors are fascinating and important, yet the principles underlying these complex and diverse structures remain unclear. Here, we analyzed basal dendritic arbors of 2,171 pyramidal neurons sampled from mammalian brains and discovered 3 statistical properties: the dendritic arbor size scales with the total dendritic length, the spatial correlation of dendritic branches within an arbor has a universal functional form, and small parts of an arbor are self-similar. We proposed that these properties result from maximizing the repertoire of possible connectivity patterns between dendrites and surrounding axons while keeping the cost of dendrites low. We solved this optimization problem by drawing an analogy with maximization of the entropy for a given energy in statistical physics. The solution is consistent with the above observations and predicts scaling relations that can be tested experimentally. In addition, our theory explains why dendritic branches of pyramidal cells are distributed more sparsely than those of Purkinje cells. Our results represent a step toward a unifying view of the relationship between neuronal morphology and function. PMID:19622738

The Teaching Effectiveness of a Relevant Physics Course

NASA Astrophysics Data System (ADS)

Hobson, Art

1998-04-01

If America is to achieve the science literacy that is ssential to industrialized democracy, all students must study such topics as scientific methodology, pseudoscience, critical thinking, ozone depletion, technological risk, and global warming. My large-enrollment liberal-arts physics course covers the great principles of physics along with several such philosophical and societal topics. Students find these topics relevant and fascinating, leading to strong course evaluations and large enrollments by non-scientists even in courses labeled physics. I will describe this course and present some evidence indicating that the course is effective in communicating physics and its interdisciplinary connections. A textbook, Physics: Concepts and Connections (Prentice Hall, 1995, 2nd edition to appear in June 1998), is available.

The Tax-Inducible Actin-Bundling Protein Fascin Is Crucial for Release and Cell-to-Cell Transmission of Human T-Cell Leukemia Virus Type 1 (HTLV-1).

PubMed

Gross, Christine; Wiesmann, Veit; Millen, Sebastian; Kalmer, Martina; Wittenberg, Thomas; Gettemans, Jan; Thoma-Kress, Andrea K

2016-10-01

The delta-retrovirus Human T-cell leukemia virus type 1 (HTLV-1) preferentially infects CD4+ T-cells via cell-to-cell transmission. Viruses are transmitted by polarized budding and by transfer of viral biofilms at the virological synapse (VS). Formation of the VS requires the viral Tax protein and polarization of the host cytoskeleton, however, molecular mechanisms of HTLV-1 cell-to-cell transmission remain incompletely understood. Recently, we could show Tax-dependent upregulation of the actin-bundling protein Fascin (FSCN-1) in HTLV-1-infected T-cells. Here, we report that Fascin contributes to HTLV-1 transmission. Using single-cycle replication-dependent HTLV-1 reporter vectors, we found that repression of endogenous Fascin by short hairpin RNAs and by Fascin-specific nanobodies impaired gag p19 release and cell-to-cell transmission in 293T cells. In Jurkat T-cells, Tax-induced Fascin expression enhanced virus release and Fascin-dependently augmented cell-to-cell transmission to Raji/CD4+ B-cells. Repression of Fascin in HTLV-1-infected T-cells diminished virus release and gag p19 transfer to co-cultured T-cells. Spotting the mechanism, flow cytometry and automatic image analysis showed that Tax-induced T-cell conjugate formation occurred Fascin-independently. However, adhesion of HTLV-1-infected MT-2 cells in co-culture with Jurkat T-cells was reduced upon knockdown of Fascin, suggesting that Fascin contributes to dissemination of infected T-cells. Imaging of chronically infected MS-9 T-cells in co-culture with Jurkat T-cells revealed that Fascin's localization at tight cell-cell contacts is accompanied by gag polarization suggesting that Fascin directly affects the distribution of gag to budding sites, and therefore, indirectly viral transmission. In detail, we found gag clusters that are interspersed with Fascin clusters, suggesting that Fascin makes room for gag in viral biofilms. Moreover, we observed short, Fascin-containing membrane extensions surrounding gag clusters and clutching uninfected T-cells. Finally, we detected Fascin and gag in long-distance cellular protrusions. Taken together, we show for the first time that HTLV-1 usurps the host cell factor Fascin to foster virus release and cell-to-cell transmission.

The Future of Theoretical Physics and Cosmology

NASA Astrophysics Data System (ADS)

Gibbons, G. W.; Shellard, E. P. S.; Rankin, S. J.

2003-11-01

Based on lectures given in honor of Stephen Hawking's 60th birthday, this book comprises contributions from the world's leading theoretical physicists. Popular lectures progress to a critical evaluation of more advanced subjects in modern cosmology and theoretical physics. Topics covered include the origin of the universe, warped spacetime, cosmological singularities, quantum gravity, black holes, string theory, quantum cosmology and inflation. The volume provides a fascinating overview of the variety of subjects to which Stephen Hawking has contributed.

Kondo behavior and metamagnetic phase transition in the heavy-fermion compound CeBi2

NASA Astrophysics Data System (ADS)

Zhou, W.; Xu, C. Q.; Li, B.; Sankar, R.; Zhang, F. M.; Qian, B.; Cao, C.; Dai, J. H.; Lu, Jianming; Jiang, W. X.; Qian, Dong; Xu, Xiaofeng

2018-05-01

Heavy fermions represent an archetypal example of strongly correlated electron systems which, due to entanglement among different interactions, often exhibit exotic and fascinating physics involving Kondo screening, magnetism, and unconventional superconductivity. Here we report a comprehensive study on the transport and thermodynamic properties of a cerium-based heavy-fermion compound CeBi2 which undergoes an antiferromagnetic transition at TN˜3.3 K . Its high-temperature paramagnetic state is characterized by an enhanced heat capacity with Sommerfeld coefficient γ over 200 mJ mol-1K-2 . The magnetization in the magnetically ordered state features a metamagnetic transition. Remarkably, a large negative magnetoresistance associated with the magnetism was observed in a wide temperature and field-angle range. Collectively, CeBi2 may serve as an intriguing system to study the interplay between the f electrons and the itinerant Fermi sea.

The innovative applications of therapeutic nanostructures in dentistry.

PubMed

Elkassas, Dina; Arafa, Abla

2017-05-01

Nanotechnology has paved multiple ways in preventing, reversing or restoring dental caries which is one of the major health care problems. Nanotechnology aided in processing variety of nanomaterials with innovative dental applications. Some showed antimicrobial effect helping in the preventive stage. Others have remineralizing potential intercepting early lesion progression as nanosized calcium phosphate, carbonate hydroxyapatite nanocrystals, nanoamorphous calcium phosphate and nanoparticulate bioactive glass particularly with provision of self-assembles protein that furnish essential role in biomimetic repair. The unique size of nanomaterials makes them fascinating carriers for dental products. Thus, it is recentlyclaimedthat fortifying the adhesives with nanomaterials that possess biological meritsdoes not only enhance the mechanical and physical properties of the adhesives, but also help to attain and maintain a durable adhesive joint and enhanced longevity. Accordingly, this review will focus on the current status and the future implications of nanotechnology in preventive and adhesive dentistry. Copyright © 2017 Elsevier Inc. All rights reserved.

Magnetic polymer microcapsules loaded with Nile Red fluorescent dye

NASA Astrophysics Data System (ADS)

Bartel, Marta; Wysocka, Barbara; Krug, Pamela; Kępińska, Daria; Kijewska, Krystyna; Blanchard, Gary J.; Kaczyńska, Katarzyna; Lubelska, Katarzyna; Wiktorska, Katarzyna; Głowala, Paulina; Wilczek, Marcin; Pisarek, Marcin; Szczytko, Jacek; Twardowski, Andrzej; Mazur, Maciej

2018-04-01

Fabrication of multifunctional smart vehicles for drug delivery is a fascinating challenge of multidisciplinary research at the crossroads of materials science, physics and biology. We demonstrate a prototypical microcapsule system that is capable of encapsulating hydrophobic molecules and at the same time reveals magnetic properties. The microcapsules are prepared using a templated synthesis approach where the molecules to be encapsulated (Nile Red) are present in the organic droplets that are suspended in the polymerization solution which also contains magnetic nanoparticles. The polymer (polypyrrole) grows on the surface of organic droplets encapsulating the fluorescent dye in the core of the formed microcapsule which incorporates the nanoparticles into its wall. For characterization of the resulting structures a range of complementary physicochemical methodology is used including optical and electron microscopy, magnetometry, 1H NMR and spectroscopy in the visible and X-ray spectral ranges. Moreover, the microcapsules have been examined in biological environment in in vitro and in vivo studies.

Development and in vitro evaluation of carboxymethyl chitosan based drug delivery system for the controlled release of propranolol hydrochloride

NASA Astrophysics Data System (ADS)

Hernawan; Nur Hayati, Septi; Nisa, Khoirun; Wheni Indrianingsih, Anastasia; Darsih, Cici; Kismurtono, Muhammad

2017-12-01

Propranolol hydrochloride is a nonselective β-adrenergic drug and has been used as angina pectoris, antihypertensive, and that of many other cardiovascular disorders. It has a relatively short plasma half-life and duration of action are considered too short in certain circumstances. Thus, it’s fascinating to elongate the action. The tablet formula was based on extended-release by a propranolol hydrochloride based carboxymethyl chitosan matrix. Here we used direct compression technique with internal wet granulation to prepare the tablets. The tablets were evaluated for physical properties (hardness, weight variation test, friability) and in vitro release studies. There was no interaction observed between propranolol hydrochloride and excipients. Dissolution profiles of each formulation were followed zero order model. In conclusion, these results strongly suggest that in appropriate proportions carboxymethyl chitosan with internal granulation is suitable for formulating propranolol hydrochloride controlled release.

A new reversal mode in exchange coupled antiferromagnetic/ferromagnetic disks: distorted viscous vortex

DOE PAGES

Gilbert, Dustin A.; Ye, Li; Varea, Aïda; ...

2015-04-28

Magnetic vortices have generated intense interest in recent years due to their unique reversal mechanisms, fascinating topological properties, and exciting potential applications. In addition, the exchange coupling of magnetic vortices to antiferromagnets has also been shown to lead to a range of novel phenomena and functionalities. Here we report a new magnetization reversal mode of magnetic vortices in exchange coupled Ir 20Mn 80/Fe 20Ni 80 microdots: distorted viscous vortex reversal. In contrast to the previously known or proposed reversal modes, the vortex is distorted close to the interface and viscously dragged due to the uncompensated spins of a thin antiferromagnet,more » which leads to unexpected asymmetries in the annihilation and nucleation fields. Lastly, these results provide a deeper understanding of the physics of exchange coupled vortices and may also have important implications for applications involving exchange coupled nanostructures.« less

Topological Nodal-Net Semimetal in a Graphene Network Structure

NASA Astrophysics Data System (ADS)

Wang, Jian-Tao; Nie, Simin; Weng, Hongming; Kawazoe, Yoshiyuki; Chen, Changfeng

2018-01-01

Topological semimetals are characterized by the nodal points in their electronic structure near the Fermi level, either discrete or forming a continuous line or ring, which are responsible for exotic properties related to the topology of bulk bands. Here we identify by ab initio calculations a distinct topological semimetal that exhibits nodal nets comprising multiple interconnected nodal lines in bulk and have two coupled drumheadlike flat bands around the Fermi level on its surface. This nodal net semimetal state is proposed to be realized in a graphene network structure that can be constructed by inserting a benzene ring into each C- C bond in the bct-C4 lattice or by a crystalline modification of the (5,5) carbon nanotube. These results expand the realm of nodal manifolds in topological semimetals, offering a new platform for exploring novel physics in these fascinating materials.

Oh the Places You'll Go, with Graphene: A Chemist's Exploration of Two-Dimensions

NASA Astrophysics Data System (ADS)

Wassei, Jonathan Khalil

Graphene, the first two-dimensional crystal ever studied, has made such an impact in a myriad of fields ranging from physical science to engineering that its discovery earned Nobel recognition in 2010. Although it was initially lauded as the answer to the Moore's law limitation of silicon electronics, what really captivated scientists was the fact that it opened countless avenues of exploration. From a synthetic chemists perspective, it became imperative to find a more sensible way to isolate graphene if it were ever to become practical for industrial use. This thesis demonstrates several fascinating routes to synthesize graphene, such as: top down methods involving the solution processing of graphitic materials through redox chemistry and bottom-up approaches mainly using chemical vapor deposition (CVD). In addition, several device architectures were developed to exploit intrinsic properties of the derived graphene. These applications include: transparent electrodes, Flash memory devices and bio-electrodes for cell stimulation.

Revealing missing charges with generalised quantum fluctuation relations.

PubMed

Mur-Petit, J; Relaño, A; Molina, R A; Jaksch, D

2018-05-22

The non-equilibrium dynamics of quantum many-body systems is one of the most fascinating problems in physics. Open questions range from how they relax to equilibrium to how to extract useful work from them. A critical point lies in assessing whether a system has conserved quantities (or 'charges'), as these can drastically influence its dynamics. Here we propose a general protocol to reveal the existence of charges based on a set of exact relations between out-of-equilibrium fluctuations and equilibrium properties of a quantum system. We apply these generalised quantum fluctuation relations to a driven quantum simulator, demonstrating their relevance to obtain unbiased temperature estimates from non-equilibrium measurements. Our findings will help guide research on the interplay of quantum and thermal fluctuations in quantum simulation, in studying the transition from integrability to chaos and in the design of new quantum devices.

Resonant tunneling through discrete quantum states in stacked atomic-layered MoS2.

PubMed

Nguyen, Linh-Nam; Lan, Yann-Wen; Chen, Jyun-Hong; Chang, Tay-Rong; Zhong, Yuan-Liang; Jeng, Horng-Tay; Li, Lain-Jong; Chen, Chii-Dong

2014-05-14

Two-dimensional crystals can be assembled into three-dimensional stacks with atomic layer precision, which have already shown plenty of fascinating physical phenomena and been used for prototype vertical-field-effect-transistors.1,2 In this work, interlayer electron tunneling in stacked high-quality crystalline MoS2 films were investigated. A trilayered MoS2 film was sandwiched between top and bottom electrodes with an adjacent bottom gate, and the discrete energy levels in each layer could be tuned by bias and gate voltages. When the discrete energy levels aligned, a resonant tunneling peak appeared in the current-voltage characteristics. The peak position shifts linearly with perpendicular magnetic field, indicating formation of Landau levels. From this linear dependence, the effective mass and Fermi velocity are determined and are confirmed by electronic structure calculations. These fundamental parameters are useful for exploitation of its unique properties.

On the way to unveiling the atomic structure of superheavy elements

NASA Astrophysics Data System (ADS)

Laatiaoui, Mustapha

2016-12-01

Optical spectroscopy of the transfermium elements (atomic number Z > 100) is nowadays one of the most fascinating and simultaneously challenging tasks in atomic physics. On the one hand, key atomic and even nuclear ground-state properties may be obtained by studying the spectral lines of these heaviest elements. On the other hand, these elements have to be produced "online" by heavy-ion induced fusion-evaporation reactions yielding rates on the order of a few atoms per second at most, which renders their optical spectroscopy extremely difficult. Only recently, a first foray of laser spectroscopy into this heaviest element region was reported. Several atomic transitions in the element nobelium (Z = 102) were observed and characterized, using an ultra-sensitive and highly efficient resonance ionization technique. The findings confirm the predictions and additionally provide a benchmark for theoretical modelling. The work represents an important stepping stone towards experimental studies of the atomic structure of superheavy elements.

Wood-Derived Ultrathin Carbon Nanofiber Aerogels.

PubMed

Li, Si-Cheng; Hu, Bi-Cheng; Ding, Yan-Wei; Liang, Hai-Wei; Li, Chao; Yu, Zi-You; Wu, Zhen-Yu; Chen, Wen-Shuai; Yu, Shu-Hong

2018-06-11

Carbon aerogels with 3D networks of interconnected nanometer-sized particles exhibit fascinating physical properties and show great application potential. Efficient and sustainable methods are required to produce high-performance carbon aerogels on a large scale to boost their practical applications. An economical and sustainable method is now developed for the synthesis of ultrathin carbon nanofiber (CNF) aerogels from the wood-based nanofibrillated cellulose (NFC) aerogels via a catalytic pyrolysis process, which guarantees high carbon residual and well maintenance of the nanofibrous morphology during thermal decomposition of the NFC aerogels. The wood-derived CNF aerogels exhibit excellent electrical conductivity, a large surface area, and potential as a binder-free electrode material for supercapacitors. The results suggest great promise in developing new families of carbon aerogels based on the controlled pyrolysis of economical and sustainable nanostructured precursors. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

An Elementary Model of the Earth's Magnetic Field

ERIC Educational Resources Information Center

Watt, Jeanie I.; Roth, Bradley J.

2007-01-01

This article is intended as a guide for teaching geomagnetism in a high school or university introductory physics class. Many students find this subject fascinating. Instructors, however, often have a difficult time introducing this topic at an elementary level. Suggestions will be made on how to accomplish this using three electricity and…

Fun with Physics in the Elementary School.

ERIC Educational Resources Information Center

Ediger, Marlow

Primary grade pupils can become fascinated with simple machines. This paper suggests that teachers have simple machines in the classroom for a unit of study. It proposes some guidelines to create a unit of study for six simple machines that include the fulcrum, inclined plane, pulley, wheel and axle, wedge, and screw. Friction, gravity, force, and…

Tribology.

PubMed

Spencer, Nicholas D

2012-01-01

The 156th Faraday Discussion covered the field of tribology, focussing on the subtopics of biotribology, predictive modelling, smart surfaces, and future lubricated systems. The papers themselves covered topics that drew on the fields of biology, medicine, chemistry, physics, materials science and mechanical engineering, providing a challenging and fascinating insight into the current state of the field of tribology.

Motional Mechanisms of Homopolar Motors & Rollers

ERIC Educational Resources Information Center

Wong, H. K.

2009-01-01

The strong Nd[subscript 2]Fe[subscript 14]B permanent magnet has facilitated development of various fascinating yet simple homopolar motors. However, the physics of these devices is often not explained, or is explained incorrectly. A major concern is that Newton's third law was overlooked in some of the earlier articles. In this paper, I will…

Who was... John Henri Fabre?

PubMed

Malcolm, Alan D B

2002-04-01

The books of Jean Henri Fabre, replete with lively accounts of his observations on nature, inspired generations of children from all over the world. The detail in his study of insects and the entertaining presentation allowed readers to absorb his fascination. Yet, he was a physics teacher by profession and virtually self taught on matters of entomology.

Pattern Formation

NASA Astrophysics Data System (ADS)

Hoyle, Rebecca

2006-03-01

From the stripes of a zebra and the spots on a leopard's back to the ripples on a sandy beach or desert dune, regular patterns arise everywhere in nature. The appearance and evolution of these phenomena has been a focus of recent research activity across several disciplines. This book provides an introduction to the range of mathematical theory and methods used to analyse and explain these often intricate and beautiful patterns. Bringing together several different approaches, from group theoretic methods to envelope equations and theory of patterns in large-aspect ratio-systems, the book also provides insight behind the selection of one pattern over another. Suitable as an upper-undergraduate textbook for mathematics students or as a fascinating, engaging, and fully illustrated resource for readers in physics and biology, Rebecca Hoyle's book, using a non-partisan approach, unifies a range of techniques used by active researchers in this growing field. Accessible description of the mathematical theory behind fascinating pattern formation in areas such as biology, physics and materials science Collects recent research for the first time in an upper level textbook Features a number of exercises - with solutions online - and worked examples

Fascin regulates nuclear actin during Drosophila oogenesis

PubMed Central

Kelpsch, Daniel J.; Groen, Christopher M.; Fagan, Tiffany N.; Sudhir, Sweta; Tootle, Tina L.

2016-01-01

Drosophila oogenesis provides a developmental system with which to study nuclear actin. During Stages 5–9, nuclear actin levels are high in the oocyte and exhibit variation within the nurse cells. Cofilin and Profilin, which regulate the nuclear import and export of actin, also localize to the nuclei. Expression of GFP-tagged Actin results in nuclear actin rod formation. These findings indicate that nuclear actin must be tightly regulated during oogenesis. One factor mediating this regulation is Fascin. Overexpression of Fascin enhances nuclear GFP-Actin rod formation, and Fascin colocalizes with the rods. Loss of Fascin reduces, whereas overexpression of Fascin increases, the frequency of nurse cells with high levels of nuclear actin, but neither alters the overall nuclear level of actin within the ovary. These data suggest that Fascin regulates the ability of specific cells to accumulate nuclear actin. Evidence indicates that Fascin positively regulates nuclear actin through Cofilin. Loss of Fascin results in decreased nuclear Cofilin. In addition, Fascin and Cofilin genetically interact, as double heterozygotes exhibit a reduction in the number of nurse cells with high nuclear actin levels. These findings are likely applicable beyond Drosophila follicle development, as the localization and functions of Fascin and the mechanisms regulating nuclear actin are widely conserved. PMID:27535426

Can visco-elastic phase separation, macromolecular crowding and colloidal physics explain nuclear organisation?

PubMed

Iborra, Francisco J

2007-04-12

The cell nucleus is highly compartmentalized with well-defined domains, it is not well understood how this nuclear order is maintained. Many scientists are fascinated by the different set of structures observed in the nucleus to attribute functions to them. In order to distinguish functional compartments from non-functional aggregates, I believe is important to investigate the biophysical nature of nuclear organisation. The various nuclear compartments can be divided broadly as chromatin or protein and/or RNA based, and they have very different dynamic properties. The chromatin compartment displays a slow, constrained diffusional motion. On the other hand, the protein/RNA compartment is very dynamic. Physical systems with dynamical asymmetry go to viscoelastic phase separation. This phase separation phenomenon leads to the formation of a long-lived interaction network of slow components (chromatin) scattered within domains rich in fast components (protein/RNA). Moreover, the nucleus is packed with macromolecules in the order of 300 mg/ml. This high concentration of macromolecules produces volume exclusion effects that enhance attractive interactions between macromolecules, known as macromolecular crowding, which favours the formation of compartments. In this paper I hypothesise that nuclear compartmentalization can be explained by viscoelastic phase separation of the dynamically different nuclear components, in combination with macromolecular crowding and the properties of colloidal particles. I demonstrate that nuclear structure can satisfy the predictions of this hypothesis. I discuss the functional implications of this phenomenon.

Components of aesthetic experience: aesthetic fascination, aesthetic appraisal, and aesthetic emotion

PubMed Central

Marković, Slobodan

2012-01-01

In this paper aesthetic experience is defined as an experience qualitatively different from everyday experience and similar to other exceptional states of mind. Three crucial characteristics of aesthetic experience are discussed: fascination with an aesthetic object (high arousal and attention), appraisal of the symbolic reality of an object (high cognitive engagement), and a strong feeling of unity with the object of aesthetic fascination and aesthetic appraisal. In a proposed model, two parallel levels of aesthetic information processing are proposed. On the first level two sub-levels of narrative are processed, story (theme) and symbolism (deeper meanings). The second level includes two sub-levels, perceptual associations (implicit meanings of object's physical features) and detection of compositional regularities. Two sub-levels are defined as crucial for aesthetic experience, appraisal of symbolism and compositional regularities. These sub-levels require some specific cognitive and personality dispositions, such as expertise, creative thinking, and openness to experience. Finally, feedback of emotional processing is included in our model: appraisals of everyday emotions are specified as a matter of narrative content (eg, empathy with characters), whereas the aesthetic emotion is defined as an affective evaluation in the process of symbolism appraisal or the detection of compositional regularities. PMID:23145263

The Tax-Inducible Actin-Bundling Protein Fascin Is Crucial for Release and Cell-to-Cell Transmission of Human T-Cell Leukemia Virus Type 1 (HTLV-1)

PubMed Central

Wiesmann, Veit; Millen, Sebastian; Wittenberg, Thomas; Gettemans, Jan; Thoma-Kress, Andrea K.

2016-01-01

The delta-retrovirus Human T-cell leukemia virus type 1 (HTLV-1) preferentially infects CD4+ T-cells via cell-to-cell transmission. Viruses are transmitted by polarized budding and by transfer of viral biofilms at the virological synapse (VS). Formation of the VS requires the viral Tax protein and polarization of the host cytoskeleton, however, molecular mechanisms of HTLV-1 cell-to-cell transmission remain incompletely understood. Recently, we could show Tax-dependent upregulation of the actin-bundling protein Fascin (FSCN-1) in HTLV-1-infected T-cells. Here, we report that Fascin contributes to HTLV-1 transmission. Using single-cycle replication-dependent HTLV-1 reporter vectors, we found that repression of endogenous Fascin by short hairpin RNAs and by Fascin-specific nanobodies impaired gag p19 release and cell-to-cell transmission in 293T cells. In Jurkat T-cells, Tax-induced Fascin expression enhanced virus release and Fascin-dependently augmented cell-to-cell transmission to Raji/CD4+ B-cells. Repression of Fascin in HTLV-1-infected T-cells diminished virus release and gag p19 transfer to co-cultured T-cells. Spotting the mechanism, flow cytometry and automatic image analysis showed that Tax-induced T-cell conjugate formation occurred Fascin-independently. However, adhesion of HTLV-1-infected MT-2 cells in co-culture with Jurkat T-cells was reduced upon knockdown of Fascin, suggesting that Fascin contributes to dissemination of infected T-cells. Imaging of chronically infected MS-9 T-cells in co-culture with Jurkat T-cells revealed that Fascin’s localization at tight cell-cell contacts is accompanied by gag polarization suggesting that Fascin directly affects the distribution of gag to budding sites, and therefore, indirectly viral transmission. In detail, we found gag clusters that are interspersed with Fascin clusters, suggesting that Fascin makes room for gag in viral biofilms. Moreover, we observed short, Fascin-containing membrane extensions surrounding gag clusters and clutching uninfected T-cells. Finally, we detected Fascin and gag in long-distance cellular protrusions. Taken together, we show for the first time that HTLV-1 usurps the host cell factor Fascin to foster virus release and cell-to-cell transmission. PMID:27776189

Hydrogel Beads: The New Slime Lab?

ERIC Educational Resources Information Center

Brockway, Debra; Libera, Matthew; Welner, Heidi

2011-01-01

Creating slime fascinates students. Unfortunately, though intrigue is at its peak, the educational aspect of this activity is often minimal. This article describes a chemistry lab that closely relates to the slime lab and allows high school students to explore the concepts of chemical bonding, properties, and replacement reactions. It involves the…

Iron-based superconductors: Unity or diversity?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kivelson, S. A.

2010-02-24

Superconductivity is among the most fascinating properties that a material can show. On the fundamental level, it represents a direct, macroscopic manifestation of coherent quantum mechanical behaviour, and its potential practical importance is almost unlimited, especially if new superconductors can be synthesized or discovered with still higher transition temperatures, Tc.

Construction and Testing of Broadband High Impedance Ground Planes (HIGPS) for Surface Mount Antennas

DTIC Science & Technology

2008-03-01

Conductor PMC: Perfect Magnetic Conductor RF: Radio Frequency RH: Right-handed SNG : Single Negative TACAN: Tactical Air Navigation UAV: Unmanned Aerial...negative ( SNG ) and double-negative (DNG) materials, and their fascinating properties have driven the interest in MTMs (Engheta and Ziolkowski, 2006

PREFACE: Nanobiology: from physics and engineering to biology

NASA Astrophysics Data System (ADS)

Nussinov, Ruth; Alemán, Carlos

2006-03-01

Biological systems are inherently nano in scale. Unlike nanotechnology, nanobiology is characterized by the interplay between physics, materials science, synthetic organic chemistry, engineering and biology. Nanobiology is a new discipline, with the potential of revolutionizing medicine: it combines the tools, ideas and materials of nanoscience and biology; it addresses biological problems that can be studied and solved by nanotechnology; it devises ways to construct molecular devices using biomacromolecules; and it attempts to build molecular machines utilizing concepts seen in nature. Its ultimate aim is to be able to predictably manipulate these, tailoring them to specified needs. Nanobiology targets biological systems and uses biomacromolecules. Hence, on the one hand, nanobiology is seemingly constrained in its scope as compared to general nanotechnology. Yet the amazing intricacy of biological systems, their complexity, and the richness of the shapes and properties provided by the biological polymers, enrich nanobiology. Targeting biological systems entails comprehension of how they work and the ability to use their components in design. From the physical standpoint, ultimately, if we are to understand biology we need to learn how to apply physical principles to figure out how these systems actually work. The goal of nanobiology is to assist in probing these systems at the appropriate length scale, heralding a new era in the biological, physical and chemical sciences. Biology is increasingly asking quantitative questions. Quantitation is essential if we are to understand how the cell works, and the details of its regulation. The physical sciences provide tools and strategies to obtain accurate measurements and simulate the information to allow comprehension of the processes. Nanobiology is at the interface of the physical and the biological sciences. Biology offers to the physical sciences fascinating problems, sophisticated systems and a rich repertoire of shapes and materials. Inspection of the protein structure databank illustrates the breadth of scaffolds, shapes and properties that protein molecules and their building blocks can provide. Via a shape-guided self-assembly strategy, these can be put together toward a specific function. Further, by inserting synthetic non-natural residues at judiciously selected positions, or synthetic peptide linkers, we may selectively rigidify the construct, or obtain a totally new world of shapes and scaffolds. Such broadening of the chemical space may lead to an almost unlimited range of nanosystems and architectures. Merging computation with experiment will accelerate nanodesign. Computational modeling will enhance the application of nanotechnology to key areas such as drug delivery and biomaterial design. Nanobiology is a field where interdisciplinary collaborations are essential and disciplines converge. Discipline convergence should enable the quantitation, leading to a better understanding of the regulatory networks within cells and between cells of an organism. These networks dictate how a cell responds to external stimuli, which in turn activate signaling cascades. It should allow the addressing of a broad range of questions on the structure and function of the cytoskeleton; the nuclear envelope; signal transduction by membrane embedded receptors; the nanomechanical properties of the extracellular matrix; nuclear transport; and voltage induced channel gating. For successful nanostructure design, we need to figure out and be able to control the intermolecular associations. For a stable functional construct, there are two key elements: first, the conformations of the building blocks in the designed structure should follow their natural tendencies; and second, the associations should be favorable. Molecules interact through their surfaces. Thus, favorable associations derive from shape complementarity and contributions of the various physical components. Nanobiology is in its infancy. Yet, biology provides an enormous range of engaging and stimulating problems with many in vivo examples of intricate, complex, fascinating biological systems. Understanding, mimicking and controlling the devices which target these processes and which are constructed from these molecules is a tremendous challenge to the converging disciplines in nanobiology.

First-principles studies of electric field effects on the electronic structure of trilayer graphene

NASA Astrophysics Data System (ADS)

Wang, Yun-Peng; Li, Xiang-Guo; Fry, James N.; Cheng, Hai-Ping

2016-10-01

A gate electric field is a powerful way to manipulate the physical properties of nanojunctions made of two-dimensional crystals. To simulate field effects on the electronic structure of trilayer graphene, we used density functional theory in combination with the effective screening medium method, which enables us to understand the field-dependent layer-layer interactions and the fundamental physics underlying band gap variations and the resulting band modifications. Two different graphene stacking orders, Bernal (or ABC) and rhombohedral (or ABA), were considered. In addition to confirming the experimentally observed band gap opening in ABC-stacked and the band overlap in ABA-stacked trilayer systems, our results reveal rich physics in these fascinating systems, where layer-layer couplings are present but some characteristics features of single-layer graphene are partially preserved. For ABC stacking, the electric-field-induced band gap size can be tuned by charge doping, while for ABA band the tunable quantity is the band overlap. Our calculations show that the electronic structures of the two stacking orders respond very differently to charge doping. We find that in the ABA stacking hole doping can reopen a band gap in the band-overlapping region, a phenomenon distinctly different from electron doping. The physical origins of the observed behaviors were fully analyzed, and we conclude that the dual-gate configuration greatly enhances the tunability of the trilayer systems.

The success of recent land management efforts to tackle gully erosion in Northern France

NASA Astrophysics Data System (ADS)

Frankl, Amaury; Nyssen, Jan; Salvador, Pierre-Gil

2017-04-01

In the open-field agricultural landscapes of Europe, especially in the topographic-rolling loess-covered regions, soil erosion is an important problem. Here, small headwater catchments hold almost no permanent vegetation, and with few physical obstacles to reduce runoff velocities, runoff concentration along linear landscape elements (plot boundaries) or thalwegs frequently causes ephemeral gullies to occur - the latter reflecting the poor hydrogeomorphic condition of the land- and soilscape. To tackles this, and to remediate negative on- and off-site effects, land management efforts have multiplied over the past decades in many regions. This includes, amongst others measures, the implementation of vegetation barriers (French fascines, Dutch wilgenteendam). In the loess-dominated Aa river basin (640 km2) of northern France, where cropland accounts for 67% of the cover, mainly managed in open-field agro-industrial farming schemes, we investigated the effect of the implementation of vegetation barriers on ephemeral gully erosion dynamics, together with rainfall characteristics and cropland management. This was done from a spatially explicit study at the scale of 500 x 500 m grid cells using a diachronic analysis of historical aerial photographs (period 1947-2012). Fascines, introduced since 2001, were present in ca. 25% of the gully erosion sites. Spatio-temporal gully length variability was mainly driven by cumulative precipitation, and the presence of fascines could not significantly explain trends in decreasing gully lengths. In addition, the impact of fascines on mudflow hazards and on local sediment storage was also analysed. In sum, fascines clearly showed to have a local effect on the storage of sediment, but due to their limited implementation and poor maintenance, they did not decrease the landscape's vulnerability to gully erosion or mudflow hazards. Being increasingly implemented for erosion control in western Europe, this study points at the challenges encountered when managing vast open-field landscapes with vegetation barriers.

Cross-Linking Molecules Modify Composite Actin Networks Independently

NASA Astrophysics Data System (ADS)

Schmoller, K. M.; Lieleg, O.; Bausch, A. R.

2008-09-01

While cells make use of many actin binding proteins (ABPs) simultaneously to tailor the mechanical properties of the cytoskeleton, the detailed interplay of different ABPs is not understood. By a combination of macrorheological measurements and confocal microscopy, we show that the ABPs fascin and filamin modify the structural and viscoelastic properties of composite in vitro actin networks independently. The outnumbering ABP dictates the local network structure and therefore also dominates the macromechanical network response.

George Gamow: Scientific Amateur and Polymath

NASA Astrophysics Data System (ADS)

Harper, Eamon

George Gamow (1904-1968) was among the first of the many brilliant scientists who forsook Europe for the United States in the early 1930s. Although most were fleeing the fascist imperium of Hitler and Mussolini, Gamow was one of a few who managed to escape the burgeoning despotism of Stalin in the Soviet Union. His early application of quantum mechanics to the atomic nucleus and his subsequent insight into the role played by the physics of the atom and its nucleus in stars, galaxies, and the universe identifies him as a scientist of unusual genius. Gamow displayed a boisterous, infectious - almost Rutherfordian - interest in all aspects of pure science. His interests were broad and his industry prodigious. His scientific output covered areas as diverse as nuclear physics, astrophysics, cosmology, biological genetics, and the fascinating question of the relationship of the large-scale structure and development of the universe to the properties of elementary particles and fields. He also was an immensely imaginative and prolific author of popular expositions on scientific subjects. One who is as well-known for his authorship of the Mr. Tompkins series of science popularizations as for his contributions to the development of the physical consequences of the big-bang theory of the expanding universe and the prediction of the cosmic background radiation must be unique in the scientific pantheon.

TGF-β induces fascin expression in gastric cancer via phosphorylation of smad3 linker area.

PubMed

Li, Liling; Cao, Fang; Liu, Baoan; Luo, Xiaojuan; Ma, Xin; Hu, Zhongliang

2015-01-01

Fascin is an actin-bundling protein critical for tumor invasion. TGF-β could induce fascin expression in gastric cancer cells. In this study, we attempted to explore the role of p-smad3L in the expression of fascin induced by TGF-β in gastric cancer cells. Pseudopodia were evaluated by immunofluorescence. Fascin expression was detected by RT-PCR and western blot. Smad3 siRNA was used to repress the endogenous smad3. The phosphorylations of smad3 linker region at sites s204, s208 and s213 were detected by western blot. The fascin promoter reporter activity was measured by dual luciferase assay. TGF-β could increase the formation of pseudopodia and the expression of fascin in gastric cancer cells. Smad3 depletion abrogated the expression of fascin induced by TGF-β. The phosphorylation of smad3 linker region at serine 204, 208 and 213 was enhanced in gastric cancer cells after TGF-β treatment. The fascin promoter reporter activity was significantly enhanced with TGF-β treatment in both wild-type Smad3 group and Smad3EPSM group (P<0.05). Furthermore, the fascin promoter reporter activity in the wild-type Smad3 transfectant cells was significantly higher than that in Smad3EPSM cells (P<0.05). fascin expression induced by TGF-β depends on smad3, at least in part, depends on smad3 linker phosphorylation.

Shear bond strength and enamel fracture behavior of ceramic brackets Fascination® and Fascination®2.

PubMed

Gittner, Robert; Müller-Hartwich, Ralf; Engel, Sylvia; Jost-Brinkmann, Paul-Georg

2012-01-01

The purpose of this study was to compare the shear bond strength and incidence of enamel fractures of the ceramic brackets Fascination® and Fascination®2. A total of 360 teeth (180 first upper bicuspids and 180 lower incisors) were stored in 96% ethanol, while 360 other teeth (180 first upper bicuspids and 180 lower incisors) were stored in 0.1% thymol. All 720 teeth were bonded one-half each with Fascination® and Fascination®2 brackets using three different adhesives and three different light curing units. The teeth were debonded with a debonding-device according to DIN EN ISO 10477 using a universal testing machine with a crosshead speed of 1 mm per minute. The enamel surface was then examined stereomicroscopically (10x and 40x magnification). The non-parametric Mann-Whitney U test was used, since the data were not normally distributed. The Fascination®2 brackets provided significantly lower shear bond strength than Fascination® brackets (p = 0.003). Fascination® brackets demonstrated significantly fewer, smaller enamel fractures than Fascination®2 brackets (p = 0.012). The lower shear bond strength of the Fascination®2 brackets is clinically acceptable, but our study's experimental design did not enable us to prove whether this is clinically associated with a lower risk of enamel fracture.

Fascin 1 is dispensable for developmental and tumour angiogenesis

PubMed Central

Ma, Yafeng; Reynolds, Louise E.; Li, Ang; Stevenson, Richard P.; Hodivala-Dilke, Kairbaan M.; Yamashiro, Shigeko; Machesky, Laura M.

2013-01-01

Summary The actin bundling protein fascin 1 is not expressed in adult epithelial tissues, but during development it is transiently expressed in many different cell types, and later in adults it is expressed in a subset of immune cells, nervous tissues, endothelial cells, smooth muscle cells and pericytes. In contrast to the wealth of knowledge about the role of fascin 1 in cancer cell migration and invasion, little is known about the involvement of fascin 1 in angiogenesis. We speculated that as angiogenesis involves migration and invasion of tissues by endothelial cells, fascin 1 might have a role in both normal and tumour angiogenesis. Here, we provide evidence that loss of fascin 1 causes relatively minor reductions to angiogenesis during embryonic, postnatal and cancerous development by examining E12.5 hindbrains, postnatal retinas and B16F0 tumour cell allografts in fascin 1-null mice. We also find that in fascin 1 null tissues, endothelial cells display reduced filopodia formation during sprouting. We thus propose that fascin 1 expression promotes angiogenesis via filopodia formation, but is largely dispensable for both normal and tumour angiogenesis. PMID:24244855

Fascin 1 is dispensable for developmental and tumour angiogenesis.

PubMed

Ma, Yafeng; Reynolds, Louise E; Li, Ang; Stevenson, Richard P; Hodivala-Dilke, Kairbaan M; Yamashiro, Shigeko; Machesky, Laura M

2013-01-01

The actin bundling protein fascin 1 is not expressed in adult epithelial tissues, but during development it is transiently expressed in many different cell types, and later in adults it is expressed in a subset of immune cells, nervous tissues, endothelial cells, smooth muscle cells and pericytes. In contrast to the wealth of knowledge about the role of fascin 1 in cancer cell migration and invasion, little is known about the involvement of fascin 1 in angiogenesis. We speculated that as angiogenesis involves migration and invasion of tissues by endothelial cells, fascin 1 might have a role in both normal and tumour angiogenesis. Here, we provide evidence that loss of fascin 1 causes relatively minor reductions to angiogenesis during embryonic, postnatal and cancerous development by examining E12.5 hindbrains, postnatal retinas and B16F0 tumour cell allografts in fascin 1-null mice. We also find that in fascin 1 null tissues, endothelial cells display reduced filopodia formation during sprouting. We thus propose that fascin 1 expression promotes angiogenesis via filopodia formation, but is largely dispensable for both normal and tumour angiogenesis.

TOPICAL REVIEW Recent developments in inorganically filled carbon nanotubes: successes and challenges

NASA Astrophysics Data System (ADS)

Gautam, Ujjal K.; Costa, Pedro M. F. J.; Bando, Yoshio; Fang, Xiaosheng; Li, Liang; Imura, Masataka; Golberg, Dmitri

2010-10-01

Carbon nanotubes (CNTs) are a unique class of nanomaterials that can be imagined as rolled graphene sheets. The inner hollow of a CNT provides an extremely small, one-dimensional space for storage of materials. In the last decade, enormous effort has been spent to produce filled CNTs that combine the properties of both the host CNT and the guest filling material. CNTs filled with various inorganic materials such as metals, alloys, semiconductors and insulators have been obtained using different synthesis approaches including capillary filling and chemical vapor deposition. Recently, several potential applications have emerged for these materials, such as the measurement of temperature at the nanoscale, nano-spot welding, and the storage and delivery of extremely small quantities of materials. A clear distinction between this class of materials and other nanostructures is the existence of an enormous interfacial area between the CNT and the filling matter. Theoretical investigations have shown that the lattice mismatch and strong exchange interaction of CNTs with the guest material across the interface should result in reordering of the guest crystal structure and passivation of the surface dangling bonds and thus yielding new and interesting physical properties. Despite preliminary successes, there remain many challenges in realizing applications of CNTs filled with inorganic materials, such as a comprehensive understanding of their growth and physical properties and control of their structural parameters. In this article, we overview research on filled CNT nanomaterials with special emphasis on recent progress and key achievements. We also discuss the future scope and the key challenges emerging out of a decade of intensive research on these fascinating materials.

Immunohistochemical expression of Fascin-1 in colorectal cancer in relation to clinical and pathological parameters.

PubMed

Piskor, Barbara M; Pryczynicz, Anna; Lubowicka, Emilia; Miniewska, Katarzyna; Zinczuk, Justyna; Zareba, Konrad; Guzinska-Ustymowicz, Katarzyna

2018-06-11

Fascins are a group of proteins taking part in the maintenance of a proper structure of the cellular cytoskeleton. Fascin-1 is an actin-bundling protein present in neurons, fibroblasts, endothelial, smooth muscle, dendritic and mesenchymal cells whereas lack of its expression is characteristic of epithelial cells. Fascin-1 overexpression can be observed in neoplastic cells. Therefore, the aim of this study was to assess the expression of Fascin-1 protein in patients with colorectal cancer (CRC) and to analyze associations between Fascin-1 expression and clinical-pathological parameters. The study material included postoperative samples (tumor and unchanged colon tissue) obtained from 51 CRC patients. Fascin-1 expression was assessed in the paraffin sections by immunohistochemistry. A statistically significant correlation was found between the histological type of cancer and the expression of Fascin-1 (p = 0.012). Increased expression of Fascin-1 in CRC was more frequent in adenocarcinoma type without the mucosal component with a better prognosis and decreased expression of this protein correlated with infiltration of cancer cells to blood and lymphatic vessels (p = 0.038). Our findings indicate a potential role of Fascin-1 in the pathogenesis of colon cancer; however, further studies will show whether this protein plays a role in the infiltration of colorectal cancer cells.

Music through the Skin--Simple Demonstration of Human Electrical Conductivity

ERIC Educational Resources Information Center

Vollmer, M.; Möllmann, K. P.

2016-01-01

The conduction of electricity is an important topic for any basic physics course. Issues of safety often results in teacher demonstration experiments in front of the class or in extremely simple though--for students--not really fascinating (not to say boring) hands on activities for everybody using 1.5 V batteries, cables and light bulbs etc. Here…

Fueling the Car of Tomorrow: An Alternative Fuels Curriculum for High School Science Classes

ERIC Educational Resources Information Center

Schumack, Mark; Baker, Stokes; Benvenuto, Mark; Graves, James; Haman, Arthur; Maggio, Daniel

2010-01-01

It is no secret that many high school students are fascinated with automobiles. The activities in "Fueling the Car of Tomorrow"--a free high school science curriculum, available online--(see "On the web")--capitalize on this heightened awareness and provide relevant learning opportunities designed to reinforce basic physics, chemistry, biology,…

Fascin expression in cholesteatoma: correlation with destruction of the ossicular chain and extent of disease.

PubMed

Binnetoglu, A; Sari, M; Baglam, T; Erbarut Seven, I; Yumusakhuylu, A C; Topuz, M F; Batman, C

2015-08-01

Fascin is an actin-bundling protein found in cell membrane protrusions and increases cell motility. The expression of fascin in epithelial neoplasms has been described only recently. No data are available concerning the role of this protein in invasive cholesteatoma. Thus, we investigated the expression of fascin in cholesteatoma tissue and the relationship between fascin expression and intraoperative evaluation of the destruction of the ossicular chain and extent of disease. Cholesteatoma specimens of 28 patients and external auditory canal (EAC) skin specimens of the same patients (as the control group) were collected from mastoidectomies. Immunohistochemical technique was used to investigate the fascin expression in all cholesteatoma tissues and EAC skin specimens. Immunohistochemical staining was assessed semiquantitatively based on the thickness of epithelium. SPSS software version 16.0 (SPSS Inc., Chicago, IL, USA) was performed to statistically analyse the relationships between fascin expression and intraoperative evaluation destruction of ossicular chain and extent of the disease. Immunohistochemically, there was no or very low fascin expression observed in normal epithelial cells of EAC skin, while expressed in cholesteatoma tissue. Also, fascin expression in cholesteatoma tissues was significantly correlated with destruction of ossicular chain and extent of the disease. Fascin expression is usually found in cholesteatoma epithelium and is correlated with destruction of the ossicular chain and extent of disease. Considering all of the correlations between the clinical and histopathological findings, 'fascin immunoexpression scoring' may be used for histological grading of cholesteatoma. © 2015 John Wiley & Sons Ltd.

TGF-β induces fascin expression in gastric cancer via phosphorylation of smad3 linker area

PubMed Central

Li, Liling; Cao, Fang; Liu, Baoan; Luo, Xiaojuan; Ma, Xin; Hu, Zhongliang

2015-01-01

Background: Fascin is an actin-bundling protein critical for tumor invasion. TGF-β could induce fascin expression in gastric cancer cells. In this study, we attempted to explore the role of p-smad3L in the expression of fascin induced by TGF-β in gastric cancer cells. Methods: Pseudopodia were evaluated by immunofluorescence. Fascin expression was detected by RT-PCR and western blot. Smad3 siRNA was used to repress the endogenous smad3. The phosphorylations of smad3 linker region at sites s204, s208 and s213 were detected by western blot. The fascin promoter reporter activity was measured by dual luciferase assay. Results: TGF-β could increase the formation of pseudopodia and the expression of fascin in gastric cancer cells. Smad3 depletion abrogated the expression of fascin induced by TGF-β. The phosphorylation of smad3 linker region at serine 204, 208 and 213 was enhanced in gastric cancer cells after TGF-β treatment. The fascin promoter reporter activity was significantly enhanced with TGF-β treatment in both wild-type Smad3 group and Smad3EPSM group (P<0.05). Furthermore, the fascin promoter reporter activity in the wild-type Smad3 transfectant cells was significantly higher than that in Smad3EPSM cells (P<0.05). Conclusions: fascin expression induced by TGF-β depends on smad3, at least in part, depends on smad3 linker phosphorylation. PMID:26269751

Spin reversal and ferroelectricity in perovskite Dy{sub 0.7}Sr{sub 0.3}MnO{sub 3} and Dy{sub 0.6}Sr{sub 0.4}MnO{sub 3}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jin, Y.; Cao, S. X.; Ren, W., E-mail: renwei@shu.edu.cn

2015-08-17

Multiferroic materials which simultaneously exhibit electric polarization and magnetism have attracted more and more attention due to their novel physical properties and promising applications. Here, we report the magnetic and ferroelectric properties of single phase perovskite manganites Dy{sub 0.7}Sr{sub 0.3}MnO{sub 3} and Dy{sub 0.6}Sr{sub 0.4}MnO{sub 3} by varying temperature and magnetic field. Our results reveal that there exist spin reversal and strong antiferromagnetic pinning effects in both compounds, as well as negative magnetization in Dy{sub 0.6}Sr{sub 0.4}MnO{sub 3}. Moreover, upon Sr-doping, spontaneous electric polarizations have been observed and the maximum polarization value of Dy{sub 0.7}Sr{sub 0.3}MnO{sub 3} is about 1000 μC/m{supmore » 2} while Dy{sub 0.6}Sr{sub 0.4}MnO{sub 3} reaches to 2000 μC/m{sup 2}. The onset of the ferroelectric transition temperature is enhanced to be around 60 K. Our results indicate that the antiferromagnetic coupling is relevant to the ferroelectric properties of these fascinating multiferroic systems.« less

A Deuterated Neutron Detector Array For Nuclear (Astro)Physics Studies

NASA Astrophysics Data System (ADS)

Almaraz-Calderon, Sergio; Asher, B. W.; Barber, P.; Hanselman, K.; Perello, J. F.

2016-09-01

The properties of neutron-rich nuclei are at the forefront of research in nuclear structure, nuclear reactions and nuclear astrophysics. The advent of intense rare isotope beams (RIBs) has opened a new door for studies of systems with very short half-lives and possible fascinating properties. Neutron spectroscopic techniques become increasingly relevant when these neutron rich nuclei are used in a variety of experiments. At Florida State University, we are developing a neutron detector array that will allow us to perform high-resolution neutron spectroscopic studies with stable and radioactive beams. The neutron detection system consists of 16 deuterated organic liquid scintillation detectors with fast response and pulse-shape discrimination capabilities. In addition to these properties, there is the potential to use the structure in the pulse-height spectra to extract the energy of the neutrons and thus produce directly excitation spectra. This type of detector uses deuterated benzene (C6D6) as the liquid scintillation medium. The asymmetric nature of the scattering between a neutron and a deuterium in the center of mass produces a pulse-height spectrum from the deuterated scintillator which contains useful information on the initial energy of the neutron. Work supported in part by the State of Florida and NSF Grant No. 1401574.

Synergistic Behavior of Tubes, Junctions, and Sheets Imparts Mechano-Mutable Functionality in 3D Porous Boron Nitride Nanostructures

PubMed Central

2015-01-01

One-dimensional (1D) boron nitride nanotube (BNNT) and 2D hexagonal BN (h-BN) are attractive for demonstrating fundamental physics and promising applications in nano-/microscale devices. However, there is a high anisotropy associated with these BN allotropes as their excellent properties are either along the tube axis or in-plane directions, posing an obstacle in their widespread use in technological and industrial applications. Herein, we report a series of 3D BN prototypes, namely, pillared boron nitride (PBN), by fusing single-wall BNNT and monolayer h-BN aimed at filling this gap. We use density functional theory and molecular dynamics simulations to probe the diverse mechano-mutable properties of PBN prototypes. Our results demonstrate that the synergistic effect of the tubes, junctions, and sheets imparts cooperative deformation mechanisms, which overcome the intrinsic limitations of the PBN constituents and provide a number of superior characteristics including 3D balance of strength and toughness, emergence of negative Poisson’s ratio, and elimination of strain softening along the armchair orientation. These features, combined with the ultrahigh surface area and lightweight structure, render PBN as a 3D multifunctional template for applications in graphene-based nanoelectronics, optoelectronics, gas storage, and functional composites with fascinating in-plane and out-of-plane tailorable properties. PMID:25289114

Algorithmic implementation of particle-particle ladder diagram approximation to study strongly-correlated metals and semiconductors

NASA Astrophysics Data System (ADS)

Prayogi, A.; Majidi, M. A.

2017-07-01

In condensed-matter physics, strongly-correlated systems refer to materials that exhibit variety of fascinating properties and ordered phases, depending on temperature, doping, and other factors. Such unique properties most notably arise due to strong electron-electron interactions, and in some cases due to interactions involving other quasiparticles as well. Electronic correlation effects are non-trivial that one may need a sufficiently accurate approximation technique with quite heavy computation, such as Quantum Monte-Carlo, in order to capture particular material properties arising from such effects. Meanwhile, less accurate techniques may come with lower numerical cost, but the ability to capture particular properties may highly depend on the choice of approximation. Among the many-body techniques derivable from Feynman diagrams, we aim to formulate algorithmic implementation of the Ladder Diagram approximation to capture the effects of electron-electron interactions. We wish to investigate how these correlation effects influence the temperature-dependent properties of strongly-correlated metals and semiconductors. As we are interested to study the temperature-dependent properties of the system, the Ladder diagram method needs to be applied in Matsubara frequency domain to obtain the self-consistent self-energy. However, at the end we would also need to compute the dynamical properties like density of states (DOS) and optical conductivity that are defined in the real frequency domain. For this purpose, we need to perform the analytic continuation procedure. At the end of this study, we will test the technique by observing the occurrence of metal-insulator transition in strongly-correlated metals, and renormalization of the band gap in strongly-correlated semiconductors.

Focal theoretical problems in modulated and martensitic transformations in alloys and perovskites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krumhansl, J.A.

Fundamental understanding of the microscopic physic of displacive transformations requires insight into the most remarkable and fascinating feature common to so many of the transformations; the formation of local distortive structures, modulations and more general patterns at the mesoscopic scale, far larger than atomic spacings, much smaller than typical specimen size. These have been extensively studied by metallurgists for some time; but also, they are are manifest in ferroelectrics, in such phenomena as the blue phases'' in chloesteric liquid crystals, and in turbulence. This commonality in such a wide range of materials challenges us to achieve a basic understanding ofmore » the physics of why such local, persistent mesostructures appear. In order to address some of the bigger questions -- microscopics of nucleation and growth, mesoscopic and transitional (precursor) structures, and properties of transformed materials -- we began addressing the limitations of traditional methods for describing the thermodynamics and (elastic) distortions of displacive transformations. Conventional phonon descriptions and linear elasticity (and their contribution of the free energy) are obviously limited to very small distortions and are intrinsically incapable of describing the larger, topology changing displacements that are of essence here.« less

The Dead Sea, The Lake and Its Setting

NASA Astrophysics Data System (ADS)

Brink, Uri ten

I cannot think of a subject more befitting the description of interdisciplinary research with societal relevance than the study of the Dead Sea, a terminal lake of the Jordan River in Israel and Jordan. The scientific study of the Dead Sea is intimately connected with politics, religion, archeology, economic development, tourism, and environmental change.The Dead Sea is a relatively closed geologic and limnologic system with drastic physical changes often occurring on human timescales and with a long human history to observe these changes. Research in this unique area covers diverse aspects such as active subsidence and deformation along strike-slip faults; vertical stratification and stability of the water column; physical properties of extremely saline and dense (1234 kg/m3) water; spontaneous precipitation of minerals in an oversaturated environment; origin of the unusual chemical composition of the brine; existence of life in extreme environments; use of lake level fluctuations as a paleoclimatic indicator; and effects on the environment of human intervention versus natural climatic variability. Although the Dead Sea covers a small area on a global scale, it is nevertheless one of the largest natural laboratories for these types of research on Earth. These reasons make the Dead Sea a fascinating topic for the curious mind.

Thickness-dependent carrier and phonon dynamics of topological insulator Bi2Te3 thin films.

PubMed

Zhao, Jie; Xu, Zhongjie; Zang, Yunyi; Gong, Yan; Zheng, Xin; He, Ke; Cheng, Xiang'ai; Jiang, Tian

2017-06-26

As a new quantum state of matter, topological insulators offer a new platform for exploring new physics, giving rise to fascinating new phenomena and new devices. Lots of novel physical properties of topological insulators have been studied extensively and are attributed to the unique electron-phonon interactions at the surface. Although electron behavior in topological insulators has been studied in detail, electron-phonon interactions at the surface of topological insulators are less understood. In this work, using optical pump-optical probe technology, we performed transient absorbance measurement on Bi 2 Te 3 thin films to study the dynamics of its hot carrier relaxation process and coherent phonon behavior. The excitation and dynamics of phonon modes are observed with a response dependent on the thickness of the samples. The thickness-dependent characteristic time, amplitude and frequency of the damped oscillating signals are acquired by fitting the signal profiles. The results clearly indicate that the electron-hole recombination process gradually become dominant with the increasing thickness which is consistent with our theoretical calculation. In addition, a frequency modulation phenomenon on the high-frequency oscillation signals induced by coherent optical phonons is observed.

Semimetallization of dielectrics in strong optical fields

PubMed Central

Kwon, Ojoon; Paasch-Colberg, Tim; Apalkov, Vadym; Kim, Bum-Kyu; Kim, Ju-Jin; Stockman, Mark I.; Kim, D.

2016-01-01

At the heart of ever growing demands for faster signal processing is ultrafast charge transport and control by electromagnetic fields in semiconductors. Intense optical fields have opened fascinating avenues for new phenomena and applications in solids. Because the period of optical fields is on the order of a femtosecond, the current switching and its control by an optical field may pave a way to petahertz optoelectronic devices. Lately, a reversible semimetallization in fused silica on a femtosecond time scale by using a few-cycle strong field (~1 V/Å) is manifested. The strong Wannier-Stark localization and Zener-type tunneling were expected to drive this ultrafast semimetallization. Wider spread of this technology demands better understanding of whether the strong field behavior is universally similar for different dielectrics. Here we employ a carrier-envelope-phase stabilized, few-cycle strong optical field to drive the semimetallization in sapphire, calcium fluoride and quartz and to compare this phenomenon and show its remarkable similarity between them. The similarity in response of these materials, despite the distinguishable differences in their physical properties, suggests the universality of the physical picture explained by the localization of Wannier-Stark states. Our results may blaze a trail to PHz-rate optoelectronics. PMID:26888147

Semimetallization of dielectrics in strong optical fields

DOE PAGES

Kwon, Ojoon; Paasch-Colberg, Tim; Apalkov, Vadym; ...

2016-02-18

At the heart of ever growing demands for faster signal processing is ultrafast charge transport and control by electromagnetic fields in semiconductors. Intense optical fields have opened fascinating avenues for new phenomena and applications in solids. Because the period of optical fields is on the order of a femtosecond, the current switching and its control by an optical field may pave a way to petahertz optoelectronic devices. Lately, a reversible semimetallization in fused silica on a femtosecond time scale by using a few-cycle strong field (~1 V/Å) is manifested. The strong Wannier-Stark localization and Zener-type tunneling were expected to drivemore » this ultrafast semimetallization. Wider spread of this technology demands better understanding of whether the strong field behavior is universally similar for different dielectrics. Here we employ a carrier-envelope-phase stabilized, few-cycle strong optical field to drive the semimetallization in sapphire, calcium fluoride and quartz and to compare this phenomenon and show its remarkable similarity between them. The similarity in response of these materials, despite the distinguishable differences in their physical properties, suggests the universality of the physical picture explained by the localization of Wannier-Stark states. Lastly, our results may blaze a trail to PHz-rate optoelectronics.« less

Semimetallization of dielectrics in strong optical fields.

PubMed

Kwon, Ojoon; Paasch-Colberg, Tim; Apalkov, Vadym; Kim, Bum-Kyu; Kim, Ju-Jin; Stockman, Mark I; Kim, D

2016-02-18

At the heart of ever growing demands for faster signal processing is ultrafast charge transport and control by electromagnetic fields in semiconductors. Intense optical fields have opened fascinating avenues for new phenomena and applications in solids. Because the period of optical fields is on the order of a femtosecond, the current switching and its control by an optical field may pave a way to petahertz optoelectronic devices. Lately, a reversible semimetallization in fused silica on a femtosecond time scale by using a few-cycle strong field (~1 V/Å) is manifested. The strong Wannier-Stark localization and Zener-type tunneling were expected to drive this ultrafast semimetallization. Wider spread of this technology demands better understanding of whether the strong field behavior is universally similar for different dielectrics. Here we employ a carrier-envelope-phase stabilized, few-cycle strong optical field to drive the semimetallization in sapphire, calcium fluoride and quartz and to compare this phenomenon and show its remarkable similarity between them. The similarity in response of these materials, despite the distinguishable differences in their physical properties, suggests the universality of the physical picture explained by the localization of Wannier-Stark states. Our results may blaze a trail to PHz-rate optoelectronics.

Can Carbon Nanotubes Deliver on Their Promise in Biology? Harnessing Unique Properties for Unparalleled Applications.

PubMed

Serpell, Christopher J; Kostarelos, Kostas; Davis, Benjamin G

2016-04-27

Carbon nanotubes (CNTs) are cylindrical sheets of hexagonally ordered carbon atoms, giving tubes with diameters on the order of a few nanometers and lengths typically in the micrometer range. They may be single- or multiwalled (SWCNTs and MWCNTs respectively). Since the seminal report of their synthesis in 1991, CNTs have fascinated scientists of all stripes. Physicists have been intrigued by their electrical, thermal, and vibrational potential. Materials scientists have worked on integrating them into ultrastrong composites and electronic devices, while chemists have been fascinated by the effects of curvature on reactivity and have developed new synthesis and purification techniques. However, to date no large-scale, real-life biotechnological CNT breakthrough has been industrially adopted and it is proving difficult to justify taking these materials forward into the clinic. We believe that these challenges are not the end of the story, but that a viable carbon nanotube biotechnology is one in which the unique properties of nanotubes bring about an effect that would be otherwise impossible. In this Outlook, we therefore seek to reframe the field by highlighting those biological applications in which the singular properties of CNTs provide some entirely new activity or biological effect as a pointer to "what could be".

Fascin-1 knock-down of human glioma cells reduces their microvilli/filopodia while improving their susceptibility to lymphocyte-mediated cytotoxicity

PubMed Central

Hoa, Neil T; Ge, Lisheng; Erickson, Kate L; Kruse, Carol A; Cornforth, Andrew N; Kuznetsov, Yurii; McPherson, Alex; Martini, Filippo; Jadus, Martin R

2015-01-01

Cancer cells derived from Glioblastoma multiforme possess membranous protrusions allowing these cells to infiltrate surrounding tissue, while resisting lymphocyte cytotoxicity. Microvilli and filopodia are supported by actin filaments cross-linked by fascin. Fascin-1 was genetically silenced within human U251 glioma cells; these knock-down glioma cells lost their microvilli/filopodia. The doubling time of these fascin-1 knock-down cells was doubled that of shRNA control U251 cells. Fascin-1 knock-down cells lost their transmigratory ability responding to interleukin-6 or insulin-like growth factor-1. Fascin-1 silenced U251 cells were more easily killed by cytolytic lymphocytes. Fascin-1 knock-down provides unique opportunities to augment glioma immunotherapy by simultaneously targeting several key glioma functions: like cell transmigration, cell division and resisting immune responses. PMID:25901196

Motional Mechanisms of Homopolar Motors & Rollers

NASA Astrophysics Data System (ADS)

Wong, H. K.

2009-10-01

The strong Nd2Fe14B permanent magnet has facilitated development of various fascinating yet simple homopolar motors However, the physics of these devices is often not explained, or is explained incorrectly. A major concern is that Newton's third law was overlooked in some of the earlier articles. In this paper, I will employ this law in explaining the motional mechanisms of these devices.

It Happened in Antarctica. A Collection of Observations Requiring Scientific Explanations.

ERIC Educational Resources Information Center

Yaxley, Murray

There are many reasons for studying Antarctica. It is the key element in the world's climate. Some of the secrets of the earth's past are locked beneath its icecap. It has a fascinating physical environment and a unique and fragile ecosystem. It is a frontier of scientific research and technological development. Its history is an important and…

Galilean Relativity and the Work-Kinetic Energy Theorem

ERIC Educational Resources Information Center

Tefft, Brandon J.; Tefft, James A.

2007-01-01

As the topic of relativity is developed in a first-year physics class, there seems to be a tendency to move as quickly as possible to the fascinating ideas set forth in Einstein's special theory of relativity. In this paper we linger a little with the Galilean side of relativity and discuss an intriguing problem and its solution to illustrate a…

Adapting to the Deep Sea: A Fun Activity with Bioluminescence

ERIC Educational Resources Information Center

Rife, Gwynne

2006-01-01

Over the past decade, much has been learned about the ocean's secrets and especially about the creatures of the deep sea. The deepest parts of the oceans are currently the focus of many new discoveries in both the physical and biological sciences. Middle school students find the deep sea fascinating and especially seem to enjoy its mysterious and…

Journey to Mars: the physics of travelling to the red planet

NASA Astrophysics Data System (ADS)

Stinner, Arthur; Begoray, John

2005-01-01

Mars has fascinated mankind since antiquity. The retrograde motion of the red planet provided the impetus for the Earth-centred solar system of Ptolemy, and 1500 years later, for the Sun-centred solar system of Copernicus. Kepler's laws of planetary motion were the result of his all-out 'war on Mars' that lasted for about 18 years. Fascination for Mars reappeared in the beginning of the last century with the astronomer Percival Lowell's well publicized claim that intelligent life was responsible for the 'canals' that were sighted with a new powerful telescope. We are seeing a resurgence of this interest in the wake of many successful attempts to land on Mars in the last 30 years to study the surface and the atmosphere of the planet. Indeed, the Canadian Space Agency (CSA) is now cooperating with NASA in the quest for a full scale scientific assault on the red planet. In response to this new interest, we wrote an interactive computer program (ICP), illustrating the physics of planetary motion, that we have used successfully in lecture-demonstrations and with students in classrooms. The main part of this article describes two missions to Mars, and a third one that illustrates the capabilities of the ICP.

Evolving images of the proton: Hadron physics over the past 40 years

DOE PAGES

Pennington, Michael R.

2016-04-05

Once upon a time, the world was simple: the proton contained three quarks, two ups and a down. How these give the proton its mass and its spin seemed obvious. Over the past 40 years the proton has become more complicated, and how even these most obvious of its properties is explained in a universe of quarks, antiquarks and gluons remains a challenge. That this should be so should come as no surprise. Quantum chromodynamics, the theory of the strong interaction, is seemingly simple, and its consequences are straightforward in the domain of hard scattering where perturbation theory applies. However,more » the beauty of the hadron world is its diversity. The existence of hadrons, their properties, and their binding into nuclei do not appear in the Lagrangian of QCD. They all emerge as a result of its strong coupling. Strong coupling QCD creates complex phenomena, much richer than known 40 years ago: a richness that ensures colour confinement and accounts for more than 95% of the mass of the visible Universe. How strong coupling QCD really works requires a synergy between experiment and theory. Furthermore, a very personal view of these fascinating developments in cold QCD is presented.« less

Theory of scanning tunneling spectroscopy: from Kondo impurities to heavy fermion materials

NASA Astrophysics Data System (ADS)

Morr, Dirk K.

2017-01-01

Kondo systems ranging from the single Kondo impurity to heavy fermion materials present us with a plethora of unconventional properties whose theoretical understanding is still one of the major open problems in condensed matter physics. Over the last few years, groundbreaking scanning tunneling spectroscopy (STS) experiments have provided unprecedented new insight into the electronic structure of Kondo systems. Interpreting the results of these experiments—the differential conductance and the quasi-particle interference spectrum—however, has been complicated by the fact that electrons tunneling from the STS tip into the system can tunnel either into the heavy magnetic moment or the light conduction band states. In this article, we briefly review the theoretical progress made in understanding how quantum interference between these two tunneling paths affects the experimental STS results. We show how this theoretical insight has allowed us to interpret the results of STS experiments on a series of heavy fermion materials providing detailed knowledge of their complex electronic structure. It is this knowledge that is a conditio sine qua non for developing a deeper understanding of the fascinating properties exhibited by heavy fermion materials, ranging from unconventional superconductivity to non-Fermi-liquid behavior in the vicinity of quantum critical points.

Evolving images of the proton: Hadron physics over the past 40 years

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pennington, Michael R.

Once upon a time, the world was simple: the proton contained three quarks, two ups and a down. How these give the proton its mass and its spin seemed obvious. Over the past 40 years the proton has become more complicated, and how even these most obvious of its properties is explained in a universe of quarks, antiquarks and gluons remains a challenge. That this should be so should come as no surprise. Quantum chromodynamics, the theory of the strong interaction, is seemingly simple, and its consequences are straightforward in the domain of hard scattering where perturbation theory applies. However,more » the beauty of the hadron world is its diversity. The existence of hadrons, their properties, and their binding into nuclei do not appear in the Lagrangian of QCD. They all emerge as a result of its strong coupling. Strong coupling QCD creates complex phenomena, much richer than known 40 years ago: a richness that ensures colour confinement and accounts for more than 95% of the mass of the visible Universe. How strong coupling QCD really works requires a synergy between experiment and theory. Furthermore, a very personal view of these fascinating developments in cold QCD is presented.« less

Photosensitive graphene transistors.

PubMed

Li, Jinhua; Niu, Liyong; Zheng, Zijian; Yan, Feng

2014-08-20

High performance photodetectors play important roles in the development of innovative technologies in many fields, including medicine, display and imaging, military, optical communication, environment monitoring, security check, scientific research and industrial processing control. Graphene, the most fascinating two-dimensional material, has demonstrated promising applications in various types of photodetectors from terahertz to ultraviolet, due to its ultrahigh carrier mobility and light absorption in broad wavelength range. Graphene field effect transistors are recognized as a type of excellent transducers for photodetection thanks to the inherent amplification function of the transistors, the feasibility of miniaturization and the unique properties of graphene. In this review, we will introduce the applications of graphene transistors as photodetectors in different wavelength ranges including terahertz, infrared, visible, and ultraviolet, focusing on the device design, physics and photosensitive performance. Since the device properties are closely related to the quality of graphene, the devices based on graphene prepared with different methods will be addressed separately with a view to demonstrating more clearly their advantages and shortcomings in practical applications. It is expected that highly sensitive photodetectors based on graphene transistors will find important applications in many emerging areas especially flexible, wearable, printable or transparent electronics and high frequency communications. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Smad4/Fascin index is highly prognostic in patients with diffuse type EBV-associated gastric cancer.

PubMed

Son, Byoung Kwan; Kim, Dong-Hoon; Min, Kyueng-Whan; Kim, Eun-Kyung; Kwon, Mi Jung

2018-04-01

Gastric cancer is a heterogeneous disorder for which predicting clinical outcomes is challenging, although various biomarkers have been suggested. The Smad4 and Fascin proteins are known prognostic indicators of different types of malignancy. Smad4 primarily functions as a key regulator of tumor suppression, whereas Fascin exhibits oncogenic function by enhancing tumor infiltration. A combined marker based on these opposing roles may improve prognostic accuracy in gastric cancer. Smad4 and Fascin expression was assessed in tissue microarrays obtained from 285 primary gastric adenocarcinoma, 201 normal tissue, and 51 metastatic adenocarcinoma samples. A Smad4/Fascin index based on the relative expression of each protein was divided into low- and high-expression groups using receiver operating characteristic curves. We compared normal tissue, primary adenocarcinoma, and metastatic adenocarcinoma in Smad4 and Fascin expression and the differences in clinicopathological findings between low Smad4/Fascin and high Smad4/Fascin expression in gastric adenocarcinoma. High Smad4/Fascin expression was significantly associated with worse outcomes, such as old age, advanced T and N category, large tumor size, high histological grade, lymphatic and vascular invasion, and presence of Epstein-Barr virus (EBV) (all p < 0.05). Univariate and multivariate analyses revealed a significant relationship between disease-free or overall survival and Smad4/Fascin index in diffuse-type or EBV-associated gastric cancer (all p < 0.05). A dual marker system using Smad4 and Fascin may be a reliable indicator for predicting clinical outcomes in patients with diffuse-type or EBV-associated gastric cancer. Copyright © 2018 Elsevier GmbH. All rights reserved.

Simple and Beautiful Experiments III by LADY CATS and Science Teachers' group

NASA Astrophysics Data System (ADS)

Tanemura, M.; Okiharu, F.; Ishii, K.; Onishi, H.; Taniguchi, M.; Uchida, T.; Yasuda, J.; Hoshino, T.; Yoshimura, T.; Hashimoto, T.; Wada, S.; Kinoshita, K.; Ebata, T.; Kawakatsu, H.

2010-07-01

LADY CATS (LADY Creators of Activities for Teaching Science) is an organization of science teachers. Our group includes a lot of female teachers, which is rather unusual in the field of physics. We would like to propose and exhibit beautiful and simple science experiments that can demonstrate the principles of physics to fascinate students' interest. These experiments are easily made and low-cost. It is also aimed to catch female and humanities students' eyes on physics from the view point of female teachers. Furthermore, we believe that these ideas help resolve gender problems and support non-specialist teachers in primary school.

Fascin Is Critical for the Maintenance of Breast Cancer Stem Cell Pool Predominantly via the Activation of the Notch Self-Renewal Pathway.

PubMed

Barnawi, Rayanah; Al-Khaldi, Samiyah; Majed Sleiman, Ghida; Sarkar, Abdullah; Al-Dhfyan, Abdullah; Al-Mohanna, Falah; Ghebeh, Hazem; Al-Alwan, Monther

2016-12-01

An emerging dogma shows that tumors are initiated and maintained by a subpopulation of cancer cells that hijack some stem cell features and thus referred to as "cancer stem cells" (CSCs). The exact mechanism that regulates the maintenance of CSC pool remains largely unknown. Fascin is an actin-bundling protein that we have previously demonstrated to be a major regulator of breast cancer chemoresistance and metastasis, two cardinal features of CSCs. Here, we manipulated fascin expression in breast cancer cell lines and used several in vitro and in vivo approaches to examine the relationship between fascin expression and breast CSCs. Fascin knockdown significantly reduced stem cell-like phenotype (CD44 hi /CD24 lo and ALDH + ) and reversal of epithelial to mesenchymal transition. Interestingly, expression of the embryonic stem cell transcriptional factors (Oct4, Nanog, Sox2, and Klf4) was significantly reduced when fascin expression was down-regulated. Functionally, fascin-knockdown cells were less competent in forming colonies and tumorspheres, consistent with lower basal self-renewal activity and higher susceptibility to chemotherapy. Fascin effect on CSC chemoresistance and self-renewability was associated with Notch signaling. Activation of Notch induced the relevant downstream targets predominantly in the fascin-positive cells. Limiting-dilution xenotransplantation assay showed higher frequency of tumor-initiating cells in the fascin-positive group. Collectively, our data demonstrated fascin as a critical regulator of breast CSC pool at least partially via activation of the Notch self-renewal signaling pathway and modification of the expression embryonic transcriptional factors. Targeting fascin may halt CSCs and thus presents a novel therapeutic approach for effective treatment of breast cancer. Stem Cells 2016;34:2799-2813 Video Highlight: https://youtu.be/GxS4fJ_Ow-o. © 2016 AlphaMed Press.

Once a physicist: Bruce McWilliams

NASA Astrophysics Data System (ADS)

McWilliams, Bruce

2009-07-01

Why did you choose to study physics? When I was about 11, I got some electronics kits; I made radios and circuits, and read about how the transistor works. I wanted to understand why things worked, and I remember being so fascinated by the TV set that I took it apart. My mother didn't like that! As a teenager, I had a very good high-school physics teacher who gave me lots of advanced books to read, including the Feynman Lectures. Back then, my favourite part was being able to estimate something or predict it.

Addressing the electronic properties of III-V nanowires by photoluminescence excitation spectroscopy

NASA Astrophysics Data System (ADS)

De Luca, M.

2017-02-01

Semiconductor nanowires (NWs) have been attracting an increasing interest in the scientific community. This is due to their peculiar filamentary shape and nanoscale diameter, which renders them versatile and cost-effective components of novel technological devices and also makes them an ideal platform for the investigation of a variety of fascinating physical effects. Absorption spectroscopy is a powerful and non-destructive technique able to provide information on the physical properties of the NWs. However, standard absorption spectroscopy is hard to perform in NWs, because of their small volume and the presence of opaque substrates. Here, we demonstrate that absorption can be successfully replaced by photoluminescence excitation (PLE). First, the use of polarization-resolved PLE to address the complex and highly-debated electronic band structure of wurtzite GaAs and InP NWs is shown. Then, PLE is used as a statistically-relevant method to localize the presence of separate wurtzite and zincblende NWs in the same InP sample. Finally, a variety of resonant exotic effects in the density of states of In x Ga1-x As/GaAs core/shell NWs are highlighted by high-resolution PLE. , which features invited work from the best early-career researchers working within the scope of J. Phys. D. This project is part of the Journal of Physics’ series 50th anniversary celebrations in 2017. Marta De Luca was selected by the Editorial Board of J. Phys. D as a Leader.

Perspective: Electrospray photoelectron spectroscopy: From multiply-charged anions to ultracold anions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Lai-Sheng, E-mail: Lai-Sheng-Wang@brown.edu

2015-07-28

Electrospray ionization (ESI) has become an essential tool in chemical physics and physical chemistry for the production of novel molecular ions from solution samples for a variety of spectroscopic experiments. ESI was used to produce free multiply-charged anions (MCAs) for photoelectron spectroscopy (PES) in the late 1990 s, allowing many interesting properties of this class of exotic species to be investigated. Free MCAs are characterized by strong intramolecular Coulomb repulsions, which create a repulsive Coulomb barrier (RCB) for electron emission. The RCB endows many fascinating properties to MCAs, giving rise to meta-stable anions with negative electron binding energies. Recent developmentmore » in the PES of MCAs includes photoelectron imaging to examine the influence of the RCB on the electron emission dynamics, pump-probe experiments to examine electron tunneling through the RCB, and isomer-specific experiments by coupling PES with ion mobility for biological MCAs. The development of a cryogenically cooled Paul trap has led to much better resolved PE spectra for MCAs by creating vibrationally cold anions from the room temperature ESI source. Recent advances in coupling the cryogenic Paul trap with PE imaging have allowed high-resolution PE spectra to be obtained for singly charged anions produced by ESI. In particular, the observation of dipole-bound excited states has made it possible to conduct vibrational autodetachment spectroscopy and resonant PES, which yield much richer vibrational spectroscopic information for dipolar free radicals than traditional PES.« less

Functional metasurfaces based on metallic and dielectric subwavelength slits and stripes array

NASA Astrophysics Data System (ADS)

Guo, Yinghui; Pu, Mingbo; Li, Xiong; Ma, Xiaoliang; Gao, Ping; Wang, Yanqin; Luo, Xiangang

2018-04-01

Starting with the early works of extraordinary optical transmission and extraordinary Young’s interference, researchers have been fascinated by the unusual optical properties displayed by metallic holes/slits and subsequently found similar abnormities in dielectric counterparts. Benefiting from the shrinking wavelength of surface plasmon polaritons excited in metallic slits and high refractive index of dielectric stripes, one can realize local phase modulation and approach desired dispersion by engineering the geometries of a slits and stripes array. In this review, we review recent developments in functional metasurfaces composed of various metallic and dielectric subwavelength slits and stripes arrays, with special emphasis on achromatic, ultra-broadband, quasi-continuous, multifunctional and reconfigurable metasurfaces. Particular attention is paid to provide insight into the design strategies for these devices. Finally, we give an outlook of the development in this fascinating area.

Fascination and Social Togetherness-Discussions about Spice Smoking on a Swedish Internet Forum.

PubMed

Kjellgren, Anette; Henningsson, Helena; Soussan, Christophe

2013-01-01

Spice is a smoking mixture containing synthetic cannabinoids with psychoactive effects similar to herbal cannabis. It is sold on the Internet and has become popular among young people. The purpose of the present study was to investigate experiences of intoxication induced by Spice, as described on a Swedish internet-based discussion forum. A systematic search yielded 40 reports, which were analyzed using phenomenological method. A total of 7 themes (composed of 27 categories) emerged from the analysis: 1. Spice use as social ritual; 2. Social secretiveness; 3. Intoxication remarks; 4. Well-being and elation; 5. Altered perception of reality; 6. Fears and coping; 7. Unpleasant physical effects. The results show that smoking was a social activity mostly carried out in small peer-groups, and that the substances induced strong intoxication with both positive and negative effects. Despite fears and unpleasant effects, the intoxication was often considered fascinating and rewarding.

Fascination and Social Togetherness—Discussions about Spice Smoking on a Swedish Internet Forum

PubMed Central

Kjellgren, Anette; Henningsson, Helena; Soussan, Christophe

2013-01-01

Spice is a smoking mixture containing synthetic cannabinoids with psychoactive effects similar to herbal cannabis. It is sold on the Internet and has become popular among young people. The purpose of the present study was to investigate experiences of intoxication induced by Spice, as described on a Swedish internet-based discussion forum. A systematic search yielded 40 reports, which were analyzed using phenomenological method. A total of 7 themes (composed of 27 categories) emerged from the analysis: 1. Spice use as social ritual; 2. Social secretiveness; 3. Intoxication remarks; 4. Well-being and elation; 5. Altered perception of reality; 6. Fears and coping; 7. Unpleasant physical effects. The results show that smoking was a social activity mostly carried out in small peer-groups, and that the substances induced strong intoxication with both positive and negative effects. Despite fears and unpleasant effects, the intoxication was often considered fascinating and rewarding. PMID:24324336

Novel Photovoltaic Devices Using Ferroelectric Material and Colloidal Quantum Dots

NASA Astrophysics Data System (ADS)

Paik, Young Hun

As the global concern for the financial and environmental costs of traditional energy resources increases, research on renewable energy, most notably solar energy, has taken center stage. Many alternative photovoltaic (PV) technologies for 'the next generation solar cell' have been extensively studied to overcome the Shockley-Queisser 31% efficiency limit as well as tackle the efficiency vs. cost issues. This dissertation focuses on the novel photovoltaic mechanism for the next generation solar cells using two inorganic nanomaterials, nanocrystal quantum dots and ferroelectric nanoparticles. Lead zirconate titanate (PZT) materials are widely studied and easy to synthesize using solution based chemistry. One of the fascinating properties of the PZT material is a Bulk Photovoltaic effect (BPVE). This property has been spotlighted because it can produce very high open circuit voltage regardless of the electrical bandgap of the materials. However, the poor optical absorption of the PZT materials and the required high temperature to form the ferroelectric crystalline structure have been obstacles to fabricate efficient photovoltaic devices. Colloidal quantum dots also have fascinating optical and electrical properties such as tailored absorption spectrum, capability of the bandgap engineering due to the wide range of material selection and quantum confinement, and very efficient carrier dynamics called multiple exciton generations. In order to utilize these properties, many researchers have put numerous efforts in colloidal quantum dot photovoltaic research and there has been remarkable progress in the past decade. However, several drawbacks are still remaining to achieve highly efficient photovoltaic device. Traps created on the large surface area, low carrier mobility, and lower open circuit voltage while increasing the absorption of the solar spectrum is main issues of the nanocrystal based photovoltaic effect. To address these issues and to take the advantages of the two materials, this dissertation focused on material synthesis for low cost solution process for both materials, fabrication of various device structures and electrical/optical characterization to understand the underlying physics. We successfully demonstrated lead sulfide quantum dots (PbS QDs) and lead zirconate titanate nanoparticles (PZT NPs) in an aqueous solution and fabricated a photosensitive device. Solution based low-temperature process was used to fabricate a PbS QD and a PZT NP device. We exhibited a superior photoresponse and ferroelectric photovoltaic properties with the novel PZT NP device and studied the physics on domain wall effect and internal polarity effect. PZT NP was mainly investigated because PZT NP device is the first report as a photosensitive device with a successful property demonstration, as we know of. PZT's crystalline structure and the size of the nanocrystals were studied using X-ray diffraction and TEM (Transmission electron microscopy) respectively. We observed < 100 nm of PZT NPs and this result matched with DLS (dynamic light scattering) measurement. We fabricated ferroelectric devices using the PZT NPs for the various optical and electrical characterizations and verified ferroelectric properties including ferroelectric hysteresis loop. We also observed a typical ferroelectric photovoltaic effect from a PZT NP based device which was fabricated on an ITO substrate. We synthesized colloidal quantum dots (CQD) with the inexpensive soluble process. Fabricated PbS QD was used for the hybrid device with PZT thin films. J-V measured and the result shows superior open circuit voltage characteristics compared to conventional PbS QD PV devices, and resulting the improvement of the solar cell efficiency. This Ferroelectrics and Quantum Dots (FE-QDs) device also the first trial and the success as we know of.

Transcending matter: physics and ultimate meaning.

PubMed

Paulson, Steve; Frank, Adam; Kaiser, David; Maudlin, Tim; Natarajan, Priyamvada

2015-12-01

From the discovery of new galaxies and nearly undetectable dark energy to the quantum entanglement of particles across the universe, new findings in physics naturally elicit a sense of awe and wonder. For the founders of modern physics-from Einstein and Bohr to Heisenberg, Pauli, and Bohm-a fascination with deeper questions of meaning and ultimate reality led some of them to explore esoteric traditions and metaphysics. More recently, however, physicists have largely shunned such philosophical and spiritual associations. What can contemporary physics offer us in the quest to understand our place in the universe? Has physics in some ways become a religion unto itself that rejects the search for existential meaning? Discussion of these and related questions is presented in this paper. © 2015 New York Academy of Sciences.

Explaining Today's Physics Through History and Biography

NASA Astrophysics Data System (ADS)

Lindley, David

2014-03-01

Quantum computers, string theory, holographic universes - to the general audience, today's physics can be as mystifying as it is fascinating. But modern ideas evolved from an earlier phase of physics - Newtonian mechanics, simple cause and effect - that is in principle easier for the non-expert to grasp. I have found that writing about physics from a historical and biographical perspective is an effective way to convey modern thinking by explaining where it comes from - it is a way of carrying the reader from concepts that make intuitive sense to ideas that seem, on first encounter, utterly bizarre. Smuggling explanations into stories satisfies the reader's desire for narrative - bearing in mind that narrative can include the evolution of ideas as well as tales about intriguing and original people.

More than the sum of its parts: Coarse-grained peptide-lipid interactions from a simple cross-parametrization

NASA Astrophysics Data System (ADS)

Bereau, Tristan; Wang, Zun-Jing; Deserno, Markus

2014-03-01

Interfacial systems are at the core of fascinating phenomena in many disciplines, such as biochemistry, soft-matter physics, and food science. However, the parametrization of accurate, reliable, and consistent coarse-grained (CG) models for systems at interfaces remains a challenging endeavor. In the present work, we explore to what extent two independently developed solvent-free CG models of peptides and lipids—of different mapping schemes, parametrization methods, target functions, and validation criteria—can be combined by only tuning the cross-interactions. Our results show that the cross-parametrization can reproduce a number of structural properties of membrane peptides (for example, tilt and hydrophobic mismatch), in agreement with existing peptide-lipid CG force fields. We find encouraging results for two challenging biophysical problems: (i) membrane pore formation mediated by the cooperative action of several antimicrobial peptides, and (ii) the insertion and folding of the helix-forming peptide WALP23 in the membrane.

Red blood cell-deformability measurement: review of techniques.

PubMed

Musielak, M

2009-01-01

Cell-deformability characterization involves general measurement of highly complex relationships between cell biology and physical forces to which the cell is subjected. The review takes account of the modern technical solutions simulating the action of the force applied to the red blood cell in macro- and microcirculation. Diffraction ektacytometers and rheoscopes measure the mean deformability value for the total red blood cell population investigated and the deformation distribution index of individual cells, respectively. Deformation assays of a whole single cell are possible by means of optical tweezers. The single cell-measuring setups for micropipette aspiration and atomic force microscopy allow conducting a selective investigation of deformation parameters (e.g., cytoplasm viscosity, viscoelastic membrane properties). The distinction between instrument sensitivity to various RBC-rheological features as well as the influence of temperature on measurement are discussed. The reports quoted confront fascinating possibilities of the techniques with their medical applications since the RBC-deformability has the key position in the etiology of a wide range of conditions.

Versatile ligands for high-performance liquid chromatography: An overview of ionic liquid-functionalized stationary phases.

PubMed

Zhang, Mingliang; Mallik, Abul K; Takafuji, Makoto; Ihara, Hirotaka; Qiu, Hongdeng

2015-08-05

Ionic liquids (ILs), a class of unique substances composed purely by cation and anions, are renowned for their fascinating physical and chemical properties, such as negligible volatility, high dissolution power, high thermal stability, tunable structure and miscibility. They are enjoying ever-growing applications in a great diversity of disciplines. IL-modified silica, transforming the merits of ILs into chromatographic advantages, has endowed the development of high-performance liquid chromatography (HPLC) stationary phase with considerable vitality. In the last decade, IL-functionalized silica stationary phases have evolved into a series of branches to accommodate to different HPLC modes. An up-to-date overview of IL-immobilized stationary phases is presented in this review, and divided into five parts according to application mode, i.e., ion-exchange, normal-phase, reversed-phase, hydrophilic interaction and chiral recognition. Specific attention is channeled to synthetic strategies, chromatographic behavior and separation performance of IL-functionalized silica stationary phases. Copyright © 2015 Elsevier B.V. All rights reserved.

Many-body exciton states in self-assembled quantum dots coupled to a Fermi sea

NASA Astrophysics Data System (ADS)

Kleemans, N. A. J. M.; van Bree, J.; Govorov, A. O.; Keizer, J. G.; Hamhuis, G. J.; Nötzel, R.; Silov, A. Yu.; Koenraad, P. M.

2010-07-01

Many-body interactions give rise to fascinating physics such as the X-ray Fermi-edge singularity in metals, the Kondo effect in the resistance of metals with magnetic impurities and the fractional quantum Hall effect. Here we report the observation of striking many-body effects in the optical spectra of a semiconductor quantum dot interacting with a degenerate electron gas. A semiconductor quantum dot is an artificial atom, the properties of which can be controlled by means of a tunnel coupling between a metallic contact and the quantum dot. Previous studies concern mostly the regime of weak tunnel coupling, whereas here we investigate the regime of strong coupling, which markedly modifies the optical spectra. In particular we observe two many-body exciton states: Mahan and hybrid excitons. These experimental results open the route towards the observation of a tunable Kondo effect in excited states of semiconductors and are of importance for the technological implementation of quantum dots in devices for quantum information processing.

Surface State-Dominated Photoconduction and THz Generation in Topological Bi2Te2Se Nanowires

PubMed Central

2017-01-01

Topological insulators constitute a fascinating class of quantum materials with nontrivial, gapless states on the surface and insulating bulk states. By revealing the optoelectronic dynamics in the whole range from femto- to microseconds, we demonstrate that the long surface lifetime of Bi2Te2Se nanowires allows us to access the surface states by a pulsed photoconduction scheme and that there is a prevailing bolometric response of the surface states. The interplay of the surface and bulk states dynamics on the different time scales gives rise to a surprising physical property of Bi2Te2Se nanowires: their pulsed photoconductance changes polarity as a function of laser power. Moreover, we show that single Bi2Te2Se nanowires can be used as THz generators for on-chip high-frequency circuits at room temperature. Our results open the avenue for single Bi2Te2Se nanowires as active modules in optoelectronic high-frequency and THz circuits. PMID:28081604

Experimental demonstration of the microscopic origin of circular dichroism in two-dimensional metamaterials

PubMed Central

Khanikaev, A. B.; Arju, N.; Fan, Z.; Purtseladze, D.; Lu, F.; Lee, J.; Sarriugarte, P.; Schnell, M.; Hillenbrand, R.; Belkin, M. A.; Shvets, G.

2016-01-01

Optical activity and circular dichroism are fascinating physical phenomena originating from the interaction of light with chiral molecules or other nano objects lacking mirror symmetries in three-dimensional (3D) space. While chiral optical properties are weak in most of naturally occurring materials, they can be engineered and significantly enhanced in synthetic optical media known as chiral metamaterials, where the spatial symmetry of their building blocks is broken on a nanoscale. Although originally discovered in 3D structures, circular dichroism can also emerge in a two-dimensional (2D) metasurface. The origin of the resulting circular dichroism is rather subtle, and is related to non-radiative (Ohmic) dissipation of the constituent metamolecules. Because such dissipation occurs on a nanoscale, this effect has never been experimentally probed and visualized. Using a suite of recently developed nanoscale-measurement tools, we establish that the circular dichroism in a nanostructured metasurface occurs due to handedness-dependent Ohmic heating. PMID:27329108

Mesopores induced zero thermal expansion in single-crystal ferroelectrics.

PubMed

Ren, Zhaohui; Zhao, Ruoyu; Chen, Xing; Li, Ming; Li, Xiang; Tian, He; Zhang, Ze; Han, Gaorong

2018-04-24

For many decades, zero thermal expansion materials have been the focus of numerous investigations because of their intriguing physical properties and potential applications in high-precision instruments. Different strategies, such as composites, solid solution and doping, have been developed as promising approaches to obtain zero thermal expansion materials. However, microstructure controlled zero thermal expansion behavior via interface or surface has not been realized. Here we report the observation of an impressive zero thermal expansion (volumetric thermal expansion coefficient, -1.41 × 10 -6  K -1 , 293-623 K) in single-crystal ferroelectric PbTiO 3 fibers with large-scale faceted and enclosed mesopores. The zero thermal expansion behavior is attributed to a synergetic effect of positive thermal expansion near the mesopores due to the oxygen-based polarization screening and negative thermal expansion from an intrinsic ferroelectricity. Our results show that a fascinating surface construction in negative thermal expansion ferroelectric materials could be a promising strategy to realize zero thermal expansion.

Minority-spin t 2gstates and the degree of spin polarization in ferromagnetic metallic La 2-2xSr 1+2xMn 2O 7 (x = 0.38)

DOE PAGES

Sun, Z.; Wang, Q.; Douglas, J. F.; ...

2013-11-07

In this paper, a half-metal is a material with conductive electrons of one spin orientation. This type of substance has been extensively searched for due to the fascinating physics as well as the potential applications for spintronics. Ferromagnetic manganites are considered to be good candidates, though there is no conclusive evidence for this notion. Here we show that the ferromagnet La 2–2xSr 1+2xMn 2O 7 (x = 0.38) possesses minority-spin states, challenging whether any of the manganites may be true half-metals. However, when electron transport properties are taken into account on the basis of the electronic band structure, we foundmore » that the La 2–2xSr 1+2xMn 2O 7 (x = 0.38) can essentially behave like a complete half metal.« less

The use of polyoxometalates in protein crystallography – An attempt to widen a well-known bottleneck

PubMed Central

Bijelic, Aleksandar; Rompel, Annette

2015-01-01

Polyoxometalates (POMs) are discrete polynuclear metal-oxo anions with a fascinating variety of structures and unique chemical and physical properties. Their application in various fields is well covered in the literature, however little information about their usage in protein crystallization is available. This review summarizes the impact of the vast class of POMs on the formation of protein crystals, a well-known (frustrating) bottleneck in macromolecular crystallography, with the associated structure elucidation and a particular emphasis focused on POM's potential as a powerful crystallization additive for future research. The Protein Data Bank (PDB) was scanned for protein structures with incorporated POMs which were assigned a PDB ligand ID resulting in 30 PDB entries. These structures have been analyzed with regard to (i) the structure of POM itself in the immediate protein environment, (ii) the kind of interaction and position of the POM within the protein structure and (iii) the beneficial effects of POM on protein crystallography apparent so far. PMID:26339074

Above 400-K robust perpendicular ferromagnetic phase in a topological insulator

PubMed Central

Tang, Chi; Chang, Cui-Zu; Zhao, Gejian; Liu, Yawen; Jiang, Zilong; Liu, Chao-Xing; McCartney, Martha R.; Smith, David J.; Chen, Tingyong; Moodera, Jagadeesh S.; Shi, Jing

2017-01-01

The quantum anomalous Hall effect (QAHE) that emerges under broken time-reversal symmetry in topological insulators (TIs) exhibits many fascinating physical properties for potential applications in nanoelectronics and spintronics. However, in transition metal–doped TIs, the only experimentally demonstrated QAHE system to date, the QAHE is lost at practically relevant temperatures. This constraint is imposed by the relatively low Curie temperature (Tc) and inherent spin disorder associated with the random magnetic dopants. We demonstrate drastically enhanced Tc by exchange coupling TIs to Tm3Fe5O12, a high-Tc magnetic insulator with perpendicular magnetic anisotropy. Signatures showing that the TI surface states acquire robust ferromagnetism are revealed by distinct squared anomalous Hall hysteresis loops at 400 K. Point-contact Andreev reflection spectroscopy confirms that the TI surface is spin-polarized. The greatly enhanced Tc, absence of spin disorder, and perpendicular anisotropy are all essential to the occurrence of the QAHE at high temperatures. PMID:28691097

European Science Notes Information Bulletin Reports on Current European and Middle Eastern Science

DTIC Science & Technology

1992-01-01

Overcash MATERIALS Research and Development in the Abbey-Polymer Processing and Properties ................... 574 J. Magill Corrosion and Protection Centre...gressi• ely pursuing the development of powerful "* Software Engineering and microprocessors and communication chips. The Information Processing ...differential equations, processing , Europe has a number of fascinating weather forecasting) that are to be developed by a projects in distributed

Flexible Faraday Cage with a Twist: Surface Charge on a Mobius Strip

ERIC Educational Resources Information Center

Stewart, Sean

2007-01-01

Once an intriguing topological novelty known only to mathematicians, the Mobius strip has become a source of fascination and inspiration to the layperson and artist alike. Principal among its features are the two strange properties that the Mobius strip is a surface with only one side and one edge. A Mobius strip is readily formed by taking a long…

Nanostructured materials with plasmonic nanobiosensors for early cancer detection: A past and future prospect.

PubMed

Sugumaran, Sathish; Jamlos, Mohd Faizal; Ahmad, Mohd Noor; Bellan, Chandar Shekar; Schreurs, Dominique

2018-02-15

Early cancer detection and treatment is an emerging and fascinating field of plasmonic nanobiosensor research. It paves to enrich a life without affecting living cells leading to a possible survival of the patient. This review describes a past and future prospect of an integrated research field on nanostructured metamaterials, microwave transmission, surface plasmonic resonance, nanoantennas, and their manifested versatile properties with nano-biosensors towards early cancer detection to preserve human health. Interestingly, (i) microwave transmission shows more advantages than other electromagnetic radiation in reacting with biological tissues, (ii) nanostructured metamaterial (Au) with special properties like size and shape can stimulate plasmonic effects, (iii) plasmonic based nanobiosensors are to explore the efficacy for early cancer tumour detection or single molecular detection and (iv) nanoantenna wireless communication by using microwave inverse scattering nanomesh (MISN) technique instead of conventional techniques can be adopted to characterize the microwave scattered signals from the biomarkers. It reveals that the nanostructured material with plasmonic nanobiosensor paves a fascinating platform towards early detection of cancer tumour and is anticipated to be exploited as a magnificent field in the future. Copyright © 2017 Elsevier B.V. All rights reserved.

Reviews Website: Online Graphing Calculator Video Clip: Learning From the News Phone App: Graphing Calculator Book: Challenge and Change: A History of the Nuffield A-Level Physics Project Book: SEP Sound Book: Reinventing Schools, Reforming Teaching Book: Physics and Technology for Future Presidents iPhone App: iSeismometer Web Watch

NASA Astrophysics Data System (ADS)

2011-01-01

WE RECOMMEND Online Graphing Calculator Calculator plots online graphs Challenge and Change: A History of the Nuffield A-Level Physics Project Book delves deep into the history of Nuffield physics SEP Sound Booklet has ideas for teaching sound but lacks some basics Reinventing Schools, Reforming Teaching Fascinating book shows how politics impacts on the classroom Physics and Technology for Future Presidents A great book for teaching physics for the modern world iSeismometer iPhone app teaches students about seismic waves WORTH A LOOK Teachers TV Video Clip Lesson plan uses video clip to explore new galaxies Graphing Calculator App A phone app that handles formulae and graphs WEB WATCH Physics.org competition finds the best websites

SETI: A good introductory physics topic

NASA Astrophysics Data System (ADS)

Hobson, Art

1997-04-01

If America is to achieve the science literacy that is essential to industrialized democracy, all students must study such topics as scientific methodology, pseudoscience, ozone depletion, and global warming. My large-enrollment liberal-arts physics course covers the great principles of physics along with several such philosophical and societal topics. It is easy to include the interdisciplinary context of physics in courses for non-scientists, because these courses are flexible, conceptual, and taught to students whose interests span a broad range. Students find these topics relevant and fascinating, leading to large enrollments by non-scientists even in courses labeled ''physics.'' I will discuss my approach to teaching the search for extra-terrestrial intelligence (SETI), a topic with lots of good physics and with connections to scientific methodology and pseudoscience. A textbook for this kind of course has been published, Physics: Concepts and Connections (Prentice-Hall, 1995).

The tumor marker Fascin is strongly induced by the Tax oncoprotein of HTLV-1 through NF-kappaB signals.

PubMed

Kress, Andrea K; Kalmer, Martina; Rowan, Aileen G; Grassmann, Ralph; Fleckenstein, Bernhard

2011-03-31

Oncogenic transformation of CD4(+) T cells by human T-cell lymphotropic virus type 1 (HTLV-1) is understood as the initial step to adult T-cell leukemia/lymphoma, a process that is mainly initiated by perturbation of cellular signaling by the viral Tax oncoprotein, a potent transcriptional regulator. In search of novel biomarkers with relevance to oncogenesis, we identified the tumor marker and actin-bundling protein Fascin (FSCN1) to be specifically and strongly up-regulated in both HTLV-1-transformed and adult T-cell leukemia/lymphoma patient-derived CD4(+) T cells. Fascin is important for migration and metastasis in various types of cancer. Here we report that a direct link can exist between a single viral oncoprotein and Fascin expression, as the viral oncoprotein Tax was sufficient to induce high levels of Fascin. Nuclear factor-κB signals were important for Tax-mediated transcriptional regulation of Fascin in T cells. This suggests that Fascin up-regulation by Tax contributes to the development of HTLV-1-associated pathogenesis.

Studies of Cave Sediments: Physical and Chemical Records of Paleoclimate (Revised Edition)

NASA Astrophysics Data System (ADS)

Baker, Andy

2007-10-01

Caves have long fascinated humankind, from prehistory to present-day tourism. Caves are also a subject for a range of scientific investigations, including cave biology, archaeology, paleoclimatology, geology, hydrology, and geomorphology. One of the benefits caves provide is their role as a repository of material that might not otherwise survive on the Earth's surface, due to caves' interiors being protected from physical erosion by nature of their underground locations. Studies of Cave Sediments focuses on this role as a repository, in particular on Quaternary (historic to 1.8 million years old) paleoclimate information preserved in cave sediments.

Weyl's search for a difference between 'physical' and 'mathematical' automorphisms

NASA Astrophysics Data System (ADS)

Scholz, Erhard

2018-02-01

During his whole scientific life Hermann Weyl was fascinated by the interrelation of physical and mathematical theories. From the mid 1920s onward he reflected also on the typical difference between the two epistemic fields and tried to identify it by comparing their respective automorphism structures. In a talk given at the end of the 1940s (ETH, Hs 91a:31) he gave the most detailed and coherent discussion of his thoughts on this topic. This paper presents his arguments in the talk and puts it in the context of the later development of gauge theories.

A Novel Approach to Anharmonicity for a Wealth of Applications in Nonlinear Science Technologies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hanusse, Patrick

2011-04-19

We present a new theory of the anharmonicity of nonlinear oscillations that are exhibited by many physical systems. New physical quantities are introduced that describe the departure from linear or harmonic behavior and as far as extremely anharmonic situations. In order to solve the nonlinear phase equation, the key notion of our theory, which controls the anharmonic behavior, a new and fascinating nonlinear trigonometry is designed. These results provide a general and accurate yet compact description of such signals, by far better than the Fourier description, both quantitatively and qualitatively and will benefit many application fields.

Hey hey hey hey, it was the DNA

NASA Astrophysics Data System (ADS)

Williams, Martin A. K.

2016-05-01

The investigation of the emergence of spatial patterning in the density profiles of the individual elements of multicomponent systems was perhaps first popularised in a biophysical context by Turing’s work on embryogenesis in 1952. How molecular-scale properties transpire to produce patterns at larger scales continues to fascinate today. Now a model DNA-nanotube system, whose assemblies have been reported recently by Glaser et al (2016 New J. Phys. 18 055001), promises to reveal insights by allowing the mechanical properties of the underlying macromolecular entities to be controlled independently of their chemical nature.

Cross-Linker Unbinding and Self-Similarity in Bundled Cytoskeletal Networks

NASA Astrophysics Data System (ADS)

Lieleg, O.; Bausch, A. R.

2007-10-01

The macromechanical properties of purely bundled in vitro actin networks are not only determined by the micromechanical properties of individual bundles but also by molecular unbinding events of the actin-binding protein (ABP) fascin. Under high mechanical load the network elasticity depends on the forced unbinding of individual ABPs in a rate dependent manner. Cross-linker unbinding in combination with the structural self-similarity of the network enables the introduction of a concentration-time superposition principle—broadening the mechanically accessible frequency range over 8 orders of magnitude.

The Odd Power of Dispersion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Peng

2014-12-01

In ancient China, water has been regarded as one of the five vital components of life. It has been observed that water has many fascinating properties: water is ‘soft’ yet it can penetrate a hard rock; water is ‘pure’ yet it can tolerate other beings. Because of its unique properties, water is often associated with good quality and has been given the highest praise by Laozi in his book Tao Te Ching saying: the highest/best quality that one can have is being like water. However, little did people understand why and how water possesses such fascinating properties. Modern scientific developmentsmore » made people realize that the macroscopic liquid water is made of a large number of water molecules held together via a network of hydrogen bonds. And those wonderful properties of water are merely the macroscopic manifestations of the interactions between water molecules and other molecules. For example, the dissolving ability of water is due to the fact that the interaction between a water molecule and the other molecular species is stronger than the interactions among their own molecular species. In fact the interactions between any two molecules are governed by the same physics and are termed intermolecular interaction (or intermolecular forces in some literature, although technically ‘force’ is incorrect usage here). Although the very existence of the intermolecular interactions is easily proved, e.g. the mere presence of the solid phase of matter, and scientists today have recognized that the seemingly weak intermolecular interactions essentially hold the world together through a delicate and cooperative process, the theoretical understanding of various intermolecular interactions is still far from satisfactory. On the practical side, theoreticians need to balance computational cost and accuracy. Because of the relatively small magnitudes of the intermolecular interactions, errors that appear tiny compared to the usual chemical (covalent) bonding may change conclusions qualitatively. High-level ab initio methods including explicit description of electron correlation can achieve the desired accuracy at very high computational cost. (Chapter 5 and 6) However the cooperative network of hundreds of thousands of molecules that reflects the true power of intermolecular interactions cannot be modeled easily by ab initio methods. Deeper understanding of intermolecular interactions yields better theoretical models; better theoretical models facilitate and even deepen the understanding of intermolecular interactions. With the aforementioned motivation in mind, a significant portion of this dissertation is dedicated to developing a method to describe the intermolecular interactions accurately with affordable computational resources.« less

Association of Fascin and matrix metalloproteinase-9 expression with poor prognostic parameters in breast carcinoma of Egyptian women.

PubMed

Youssef, Nermeen Salah; Hakim, Sarah Adel

2014-07-04

The effects of fascin on cell invasiveness involve changes in cell motility and matrix metalloproteinase-9 (MMP-9) activity. Previous studies on the prognostic value of fascin and MMP-9 in breast carcinoma revealed conflicting results. To date, no immunohistochemical studies have been performed to assess the possible association between them in breast carcinoma. This study is designed to correlate their expression with prognostic parameters in breast carcinoma and assess the relationship between them. Immunohistochemical expression of fascin and MMP-9 was evaluated semi quantitatively in 67 cases of breast carcinoma regarding the percentage of positive cells. Chi square test and Fisher's exact test were used to examine the relationship between categorical variables. Kappa statistics was used to compute the measure of agreement between two investigational methods. Fascin and MMP-9 expressions were detected in 43.28% and 50.75% of breast carcinomas (respectively). Regarding the normal breast tissue, fascin expression was observed in myoepithelial cells and luminal cells of few ducts and acini. However, normal tissue showed negative MMP-9 expression. A significant relationship was observed between fascin and MMP-9 expression and lymph node metastases (p = 0.001 and 0.002 respectively), advanced tumor stage (p = 0.004 and 0.005 respectively), estrogen receptor negative (p = 0.002 and 0.005 respectively), progesterone receptor negative (p = 0.001 and 0.003 respectively) hormonal status and molecular subtypes (p = 0.0007 and 0.014 respectively). A significant strong agreement was detected between fascin and MMP-9 expression (p = 0.0001). More intense immunostaining of fascin and MMP-9 was observed at the invasive fronts compared with other areas of the tumor. Moreover, a significant moderate agreement between fascin and MMP-9 was found regarding the site of predominant intensity. Fascin and MMP-9 proteins are associated with parameters of poor prognosis in breast cancer. The significant strong agreement between the two markers supports the role of fascin in cell invasiveness by activating matrix proteases besides increasing cell motility. Both proteins may represent potential therapeutic targets for patients with breast cancer especially those with hormone receptor-negative status. The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1421167695121127.

Butterfly in the Quantum World; The story of the most fascinating quantum fractal

NASA Astrophysics Data System (ADS)

Satija, Indubala I.

2016-08-01

``Butterfly in the Quantum World'' by Indu Satija, with contributions by Douglas Hofstadter, is the first book ever to tell the story of the ``Hofstadter butterfly'', a beautiful and fascinating graph lying at the heart of the quantum theory of matter. The butterfly came out of a simple-sounding question: What happens if you immerse a crystal in a magnetic field? What energies can the electrons take on? From 1930 onwards, physicists struggled to answer this question, until 1974, when graduate student Douglas Hofstadter discovered that the answer was a graph consisting of nothing but copies of itself nested down infinitely many times. This wild mathematical object caught the physics world totally by surprise, and it continues to mesmerize physicists and mathematicians today. The butterfly plot is intimately related to many other important phenomena in number theory and physics, including Apollonian gaskets, the Foucault pendulum, quasicrystals, the quantum Hall effect, and many more. Its story reflects the magic, the mystery, and the simplicity of the laws of nature, and Indu Satija, in a wonderfully personal style, relates this story, enriching it with a vast number of lively historical anecdotes, many photographs, beautiful visual images, and even poems, making her book a great feast, for the eyes, for the mind and for the soul.

Migration and invasion induced by linoleic acid are mediated through fascin in MDA-MB-231 breast cancer cells.

PubMed

Gonzalez-Reyes, Christian; Marcial-Medina, Cleofas; Cervantes-Anaya, Nancy; Cortes-Reynosa, Pedro; Salazar, Eduardo Perez

2018-06-01

Epidemiological studies strongly suggest an association between high levels of dietary fat intake and an increased risk of developing breast cancer. Linoleic acid (LA) is an essential omega-6 PUFA and the major fatty acid in occidental diets. In breast cancer cells, LA induces expression of plasminogen activator inhibitor-1, proliferation, migration, and invasion. Fascin is an actin crosslinker globular protein that generates actin bundles made of parallel actin filaments, which mediate formation and stability of microspikes, stress fibers, membrane ruffles, and filopodia. However, the role of fascin in migration and invasion induced by LA in MDA-MB-231 breast cancer cells remains to be studied. We demonstrate here that LA induces an increase of fascin expression in MDA-MB-231 and MCF12A mammary epithelial cells. Particularly, LA induces the formation of filopodia and lamellipodia and the localization of fascin in these actin structures in MDA-MB-231 breast cancer cells. However, LA only induces formation of microspikes and the localization of fascin in these actin structures in mammary non-tumorigenic epithelial cells MCF12A. In addition, LA induces migration, invasion, and matrix metalloproteinase-9 secretion through a fascin-dependent pathway in MDA-MB-231 cells. In summary, our findings demonstrate that fascin is required for migration and invasion induced by LA in MDA-MB-231 breast cancer cells.

Smart Materials in Architecture: Useful Tools with Practical Applications or Fascinating Inventions for Experimental Design?

NASA Astrophysics Data System (ADS)

Konarzewska, Bogusława

2017-10-01

For at least several decades smart or so-called intelligent materials, being the result of great advancements in material engineering, appear in architecture in different applications. Most of them are called “smart” because of their inherent properties: a real-time response to environmental stimuli. There are also those considered to be “smart” due to smart design: their original structure or the composition of their materials are in nanoscale, providing them with unique properties. Colour changes, physical states, temperature or shape-always repeatable and reversible - make these materials attractive to architects, both from a visual and a practical point of view. Their spectacular applications often inspire architects, scientists and artists to create, for instance, city displays revealing various shapes and figures according to daily weather conditions; thermochromics urban seats that reflect peoples’ presence; wallpaper with organic patterns that glow in darkness, and many others. On the other hand, more practical projects are being developed, such as “switchable” partition glass walls (that is, we can turn them on and they change their transparency while switching on or off: electrochromic glass is a good example). Other concepts include self-cleaning building envelopes; self-repairing concrete; phase-changing materials diminishing cooling loads in the buildings; energy-generating highways; materials that harden at the moment of impact thus withstanding exceptionally great forces; shape memory alloys playing the role of actuators-opening and - closing façade louvers or thin polymer films mimicking the function of living skin, adopted as a building envelope. All those projects result from the fascination of designers with the possibility to create materials and, in effect, a complex environment that is active, “flexible”, and adapts to changing conditions and users’ needs and is compatible with real, natural environments. Smart materials that serve this purpose make such projects not only more unique and beautiful but, as their inventors claim, their application may bring real environmental and financial gains in the future. This article presents the most crucial, selected examples of such materials and examines what benefits they could offer.

Physics Reality Show

NASA Astrophysics Data System (ADS)

Erukhimova, Tatiana

The attention span of K-12 students is very short; they are used to digesting information in short snippets through social media and TV. To get the students interested in physics, we created the Physics Reality Show: a series of staged short videos with duration no longer than a few minutes. Each video explains and illustrates one physics concept or law through a fast-paced sequence of physics demonstrations and experiments. The cast consists entirely of physics undergraduate students with artistic abilities and substantial experience in showing physics demonstrations at current outreach events run by the department: Physics Shows and Physics & Engineering Festival. Undergraduate students are of almost the same age as their high-school audience. They are in the best position to connect with kids and convey their fascination with physics. The PI and other faculty members who are involved in the outreach advise and coach the cast. They help students in staging the episodes and choosing the most exciting and relevant demonstrations. Supported by the APS mini-outreach Grant.

Reviews

NASA Astrophysics Data System (ADS)

2005-07-01

WE RECOMMEND When Physics Became King This book delves into the history of science since the 18th century. The History of the Laser An interesting read that will teach you far more than its title suggests. History of Physics Selected Reprints A fascinating collection of physics papers spanning four decades. Datalogging set-ups Five great products from Leybold Didactic’s CASSY range. Videocom Measure motion and convert it to graphs with this great device. Basic Raybox This simple piece of equipment offers great performance. WORTH A LOOK Virtual Physics Lab John Nunn’s software demystifies science using clear illustrations. HANDLE WITH CARE Microchem Electricity Kit This box of equipment for introducing electricity lacks quality. Raymond the Raybox A disappointing raybox. The basic version reviewed on p389 is better. WEB WATCH A rough guide to e-learning.

Majorana Fermions in Particle Physics, Solid State and Quantum Information

NASA Astrophysics Data System (ADS)

Borsten, L.; Duff, M. J.

This review is based on lectures given by M. J. Duff summarising the far reaching contributions of Ettore Majorana to fundamental physics, with special focus on Majorana fermions in all their guises. The theoretical discovery of the eponymous fcrmion in 1937 has since had profound implications for particlc physics, solid state and quantum computation. The breadth of these disciplines is testimony to Majorana's genius, which continues to permeate physics today. These lectures offer a whistle-stop tour through some limited subset of the key ideas. In addition to touching on these various applications, we will draw out some fascinating relations connecting the normed division algebras R, ℂ, H, O to spinors, trialities. K-theory and the classification of stable topological states of symmetry-protected gapped free-fermion systems.

Regulation of the tumor marker Fascin by the viral oncoprotein Tax of human T-cell leukemia virus type 1 (HTLV-1) depends on promoter activation and on a promoter-independent mechanism.

PubMed

Mohr, Caroline F; Gross, Christine; Bros, Matthias; Reske-Kunz, Angelika B; Biesinger, Brigitte; Thoma-Kress, Andrea K

2015-11-01

Adult T-cell leukemia/lymphoma is a highly infiltrative neoplasia of CD4(+) T-lymphocytes that occurs in about 5% of carriers infected with the deltaretrovirus human T-cell leukemia virus type 1 (HTLV-1). The viral oncoprotein Tax perturbs cellular signaling pathways leading to upregulation of host cell factors, amongst them the actin-bundling protein Fascin, an invasion marker of several types of cancer. However, transcriptional regulation of Fascin by Tax is poorly understood. In this study, we identified a triple mode of transcriptional induction of Fascin by Tax, which requires (1) NF-κB-dependent promoter activation, (2) a Tax-responsive region in the Fascin promoter, and (3) a promoter-independent mechanism sensitive to the Src family kinase inhibitor PP2. Thus, Tax regulates Fascin by a multitude of signals. Beyond, using Tax-expressing and virus-transformed lymphocytes as a model system, our study is the first to identify the invasion marker Fascin as a novel target of PP2, an inhibitor of metastasis. Copyright © 2015 Elsevier Inc. All rights reserved.

Neuronal avalanches and learning

NASA Astrophysics Data System (ADS)

de Arcangelis, Lucilla

2011-05-01

Networks of living neurons represent one of the most fascinating systems of biology. If the physical and chemical mechanisms at the basis of the functioning of a single neuron are quite well understood, the collective behaviour of a system of many neurons is an extremely intriguing subject. Crucial ingredient of this complex behaviour is the plasticity property of the network, namely the capacity to adapt and evolve depending on the level of activity. This plastic ability is believed, nowadays, to be at the basis of learning and memory in real brains. Spontaneous neuronal activity has recently shown features in common to other complex systems. Experimental data have, in fact, shown that electrical information propagates in a cortex slice via an avalanche mode. These avalanches are characterized by a power law distribution for the size and duration, features found in other problems in the context of the physics of complex systems and successful models have been developed to describe their behaviour. In this contribution we discuss a statistical mechanical model for the complex activity in a neuronal network. The model implements the main physiological properties of living neurons and is able to reproduce recent experimental results. Then, we discuss the learning abilities of this neuronal network. Learning occurs via plastic adaptation of synaptic strengths by a non-uniform negative feedback mechanism. The system is able to learn all the tested rules, in particular the exclusive OR (XOR) and a random rule with three inputs. The learning dynamics exhibits universal features as function of the strength of plastic adaptation. Any rule could be learned provided that the plastic adaptation is sufficiently slow.

Emergent properties of magnetic materials

NASA Astrophysics Data System (ADS)

Ratcliff, William Davis, II

In Tolstoy's War and Peace, history is presented as a tapestry spun from the daily interactions of large numbers of individuals. Even if one understands individuals, it is very difficult to predict history. Similarly, the interactions of large numbers of electrons give rise to properties that one would not initially guess from their microscopic interactions. During the course of my dissertation, I have explored emergent phenomena in a number of contexts. In ZnCr2O4, geometric frustration gives rise to a plethora of equivalent ground states. From these, a lower dimensional set of collinear spins on hexagons are selected to form the building blocks of the lattice. In MgTi2O4, quantum spins dimerize and form a unique chiral ordering pattern on the spinel lattice. Descending into two dimensions, differences in size and charge give rise to an ordering between triangular layers of magnetic and nonmagnetic ions. This triangular lattice allows for the possibility of observing the RVB spin liquid state, or perhaps a valence bond crystal and initial measurements are promising. Also, on the spinel lattice, ionic ordering gives rise to one dimensional chains with their own interesting physics. Finally, in the SrCoxTi1-x O3, system we find that upon reduction, tiny clusters of Co metal precipitate out and chemical inhomogeneity on the microscale may determine much of the physics. This has relevance to a number of recent claims of room temperature ferromagnism in dilute magnetic systems. In all of these systems, complex behavior emerges from well understood microscopic behavior. For me, this is the fascination of strongly correlated electronic systems.

Atomic Covalent Functionalization of Graphene

PubMed Central

Johns, James E.; Hersam, Mark C.

2012-01-01

Conspectus Although graphene’s physical structure is a single atom thick, two-dimensional, hexagonal crystal of sp2 bonded carbon, this simple description belies the myriad interesting and complex physical properties attributed to this fascinating material. Because of its unusual electronic structure and superlative properties, graphene serves as a leading candidate for many next generation technologies including high frequency electronics, broadband photodetectors, biological and gas sensors, and transparent conductive coatings. Despite this promise, researchers could apply graphene more routinely in real-world technologies if they could chemically adjust graphene’s electronic properties. For example, the covalent modification of graphene to create a band gap comparable to silicon (~1 eV) would enable its use in digital electronics, and larger band gaps would provide new opportunities for graphene-based photonics. Towards this end, researchers have focused considerable effort on the chemical functionalization of graphene. Due to its high thermodynamic stability and chemical inertness, new methods and techniques are required to create covalent bonds without promoting undesirable side reactions or irreversible damage to the underlying carbon lattice. In this Account, we review and discuss recent theoretical and experimental work studying covalent modifications to graphene using gas phase atomic radicals. Atomic radicals have sufficient energy to overcome the kinetic and thermodynamic barriers associated with covalent reactions on the basal plane of graphene but lack the energy required to break the C-C sigma bonds that would destroy the carbon lattice. Furthermore, because they are atomic species, radicals substantially reduce the likelihood of unwanted side reactions that confound other covalent chemistries. Overall, these methods based on atomic radicals show promise for the homogeneous functionalization of graphene and the production of new classes of two-dimensional materials with fundamentally different electronic and physical properties. Specifically, we focus on recent studies of the addition of atomic hydrogen, fluorine, and oxygen to the basal plane of graphene. In each of these reactions a high energy, activating step initiates the process, breaking the local π structure and distorting the surrounding lattice. Scanning tunneling microscopy experiments reveal that substrate mediated interactions often dominate when the initial binding event occurs. We then compare these substrate effects with the results of theoretical studies that typically assume a vacuum environment. As the surface coverage increases, clusters often form around the initial distortion, and the stoichiometric composition of the saturated end product depends strongly on both the substrate and reactant species. In addition to these chemical and structural observations, we review how covalent modification can extend the range of physical properties that are achievable in two-dimensional materials. PMID:23030800

Towards an aerogel-based coating for aerospace applications: reconstituting aerogel particles via spray drying

NASA Astrophysics Data System (ADS)

Bheekhun, N.; Abu Talib, A. R.; Mustapha, S.; Ibrahim, R.; Hassan, M. R.

2016-10-01

Silica aerogel is an ultralight and highly porous nano-structured ceramic with its thermal conductivity being the lowest than any solids. Although aerogels possess fascinating physical properties, innovative solutions to tackle today's problems were limited due to their relative high manufacturing cost in comparison to conventional materials. Recently, some producers have brought forward quality aerogels at competitive costs, and thereby opening a panoply of applied research in this field. In this paper, the feasibility of spray-drying silica aerogel to tailor its granulometric property is studied for thermal spraying, a novel application of aerogels that is never tried before in the academic arena. Aerogel-based slurries with yttria stabilised zirconia as a secondary ceramic were prepared and spray-dried according to modified T aguchi experimental design in order to appreciate the effect of both the slurry formulation and drying conditions such as the solid content, the ratio of yttria stabilised zirconia:aerogel added, the amount of dispersant and binder, inlet temperature, atomisation pressure and feeding rate on the median particle size of the resulting spray-dried powder. The latter was found to be affected by all the aforementioned independent variables at different degree of significance and inclination. Based on the derived relationships, an optimised condition to achieve maximum median particle size was then predicted.

Development of "fragility" in relaxor ferroelectrics

NASA Astrophysics Data System (ADS)

Wang, Yi-zhen; Chen, Lan; Wang, Hai-yan; Frank Zhang, X.; Fu, Jun; Xiong, Xiao-min; Zhang, Jin-xiu

2014-02-01

Relaxor ferroelectrics (RFs), a special class of the disordered crystals or ceramics, exhibit a pronounced slowdown of their dynamics upon cooling as glass-forming liquids, called the "Super-Arrhenius (SA)" relaxation. Despite great progress in glass-forming liquids, the "fragility" property of the SA relaxation in RFs remains unclear so far. By measuring the temperature-dependent dielectric relaxation in the typical relaxor Pb(Mg1/3Nb2/3)O3-x%PbTiO3 (PMN - x%PT) with 0 ≤ x ≤ 20.0, we in-depth study the "fragility" properties of the SA relaxation in PMN - x%PT. Such fascinating issues as the mechanism of the "fragility" at an atomic scale, the roles of the systematic configurational entropy change and interaction among relaxing units (RUs, including polar nanoregions and free dipoles) and the relation between "fragility" and ferroelectric order are investigated. Our results show that both the "fragility" of the temperature-dependent SA relaxation and ferroelectric order in the PMN - x%PT systems investigated arise thermodynamically from the configurational-entropy loss due to the attractive interaction among RUs, and develops as a power law, possibly diverging at the finite critical temperature Tc. A reasonable physical scenario, based on our "configurational-entropy-loss" theory and Nowick's "stress-induced-ordering" theory, was proposed.

Electronic properties of novel topological quantum materials studied by angle-resolved photoemission spectroscopy (ARPES)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Yun

The discovery of quantum Hall e ect has motivated the use of topology instead of broken symmetry to classify the states of matter. Quantum spin Hall e ect has been proposed to have a separation of spin currents as an analogue of the charge currents separation in quantum Hall e ect, leading us to the era of topological insulators. Three-dimensional analogue of the Dirac state in graphene has brought us the three-dimensional Dirac states. Materials with three-dimensional Dirac states could potentially be the parent compounds for Weyl semimetals and topological insulators when time-reversal or space inversion symmetry is broken. Inmore » addition to the single Dirac point linking the two dispersion cones in the Dirac/Weyl semimetals, Dirac points can form a line in the momentum space, resulting in a topological node line semimetal. These fascinating novel topological quantum materials could provide us platforms for studying the relativistic physics in condensed matter systems and potentially lead to design of new electronic devices that run faster and consume less power than traditional, silicon based transistors. In this thesis, we present the electronic properties of novel topological quantum materials studied by angle-resolved photoemission spectroscopy (ARPES).« less

Multidimensional Generalized Functions in Aeroacoustics and Fluid Mechanics. Part 1; Basic Concepts and Operations

NASA Technical Reports Server (NTRS)

Farassat, Fereidoun; Myers, Michael K.

2011-01-01

This paper is the first part of a three part tutorial on multidimensional generalized functions (GFs) and their applications in aeroacoustics and fluid mechanics. The subject is highly fascinating and essential in many areas of science and, in particular, wave propagation problems. In this tutorial, we strive to present rigorously and clearly the basic concepts and the tools that are needed to use GFs in applications effectively and with ease. We give many examples to help the readers in understanding the mathematical ideas presented here. The first part of the tutorial is on the basic concepts of GFs. Here we define GFs, their properties and some common operations on them. We define the important concept of generalized differentiation and then give some interesting elementary and advanced examples on Green's functions and wave propagation problems. Here, the analytic power of GFs in applications is demonstrated with ease and elegance. Part 2 of this tutorial is on the diverse applications of generalized derivatives (GDs). Part 3 is on generalized Fourier transformations and some more advanced topics. One goal of writing this tutorial is to convince readers that, because of their powerful operational properties, GFs are absolutely essential and useful in engineering and physics, particularly in aeroacoustics and fluid mechanics.

Intrinsic phonon bands in high quality monolayer T' molybdenum ditelluride

NASA Astrophysics Data System (ADS)

Chen, Shao-Yu; Naylor, Carl; Goldstein, Thomas; Johnson, Charlie; Yan, Jun

Distorted octahedral (T') transition metal dichalcogenide (TMDC) is a type of layered semimetal that has attracted significant recent attention because of its fascination physical, chemical and nontrivial topological properties. Unlike its hexagonal counterpart, monolayer (1L) T'-TMDC is challenging to work with due to rapid sample degradation in air. In this talk, I will discuss well-protected 1L-T' - MoTe2 that exhibits sharp and robust intrinsic Raman bands, with intensities about one order of magnitude stronger than those from bulk T'-MoTe2. The high quality samples enable us to reveal for the first time the set of all nine even-parity zone-center optical phonons. Crystal angle and light polarization resolved measurements further indicate that all the intrinsic Raman modes belong to either z-mode (vibrating along the zigzag Mo atomic chain) or m-modes (vibrating in the mirror plane). Moreover, with the knowledge of vibrational symmetry, we can effectively distinguish the intrinsic modes from Te-metalloid-like modes with energy around 122 and 141 cm-1 which are associated to the sample degradation. Our studies offer a powerful non-destructive method for assessing sample quality, providing the fingerprint as well as key insights in understanding the fundamental properties of 1L T'-TMDCs.

Epitaxial growth and properties of doped transition metal and complex oxide films.

PubMed

Chambers, Scott A

2010-01-12

The detailed science and technology of crystalline oxide film growth using vacuum methods is reviewed and discussed with an eye toward gaining fundamental insights into the relationships between growth process and parameters, film and interface structure and composition, and electronic, magnetic and photochemical properties. The topic is approached first from a comparative point of view based on the most widely used growth methods, and then on the basis of specific material systems that have generated very high levels of interest. Emphasis is placed on the wide diversity of structural, electronic, optical and magnetic properties exhibited by oxides, and the fascinating results that this diversity of properties can produce when combined with the degrees of freedom afforded by heteroepitaxy.

A fascinating adventure: astronomical activities for people with disabilities during IYA 2009

NASA Astrophysics Data System (ADS)

Ortiz-Gil, A.; Blay, P.; Gallego Calvente, A. T.; Gómez Collado, M.; Guirado, J. C.; Lanzara, M.; Martínez Núñez, S.

2011-11-01

Here we give a brief outline of the activities developed during the International Year of Astronomy specifically addressed to people with various disabilities, both physical and/or intellectual. Among the different activities that we carried out we wish to highlight the publication of an astronomy book in Braille, astronomy talks for the intellectually disabled, a software for people with motor disabilities, and a planetarium show for the blind and visually impaired

Natural Language Interfaces to Database Systems

DTIC Science & Technology

1988-10-01

the power was nff to avoid re-entering data for each run of the calculations. External physical devices were developed such as punched tape and...given rise to more powerful or faster tools. Today, operations with the latest fifth generation database management system are not going to be any faster...database does not represent an evolution of greater power or speed. The fascinating aspect is that it represents an evolution of usability and more

WKB approximation and tunneling in theories with noncanonical kinetic terms

NASA Astrophysics Data System (ADS)

González, Mariana Carrillo; Masoumi, Ali; Solomon, Adam R.; Trodden, Mark

2017-09-01

Tunneling is a fascinating aspect of quantum mechanics that renders the local minima of a potential meta-stable, with important consequences for particle physics, for the early hot stage of the universe, and more speculatively, for the behavior of the putative multiverse. While this phenomenon has been studied extensively for systems which have canonical kinetic terms, many theories of fundamental physics contain fields with noncanonical kinetic structures. It is therefore desirable to have a detailed framework for calculating tunneling rates and initial states after tunneling for these theories. In this work we present such a rigorous formulation and illustrate its use by applying it to a number of examples.

Physics of smectic membranes

NASA Astrophysics Data System (ADS)

Pieranski, P.; Beliard, L.; Tournellec, J.-Ph.; Leoncini, X.; Furtlehner, C.; Dumoulin, H.; Riou, E.; Jouvin, B.; Fénerol, J.-P.; Palaric, Ph.; Heuving, J.; Cartier, B.; Kraus, I.

1993-03-01

Due to their layered structure, smectic liquid crystals can form membranes, similar to soap bubbles, that can be spanned on frames. Such smectic membranes have been used extensively as samples in many structural X-ray studies of smectic liquid crystals. In this context they have been considered as very convenient and highly perfect samples but little attention has been paid to the reasons for their existence and to the process of their formation. Our aim here is to address a first list of questions, which are the most urgent to answer. We will also describe experiments and models that have been conceived especially in order to understand the physics of these fascinating systems.

Neutrinos: Nature's Ghosts?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lincoln, Don

2013-06-18

Dr. Don Lincoln introduces one of the most fascinating inhabitants of the subatomic realm: the neutrino. Neutrinos are ghosts of the microworld, almost not interacting at all. In this video, he describes some of their properties and how they were discovered. Studies of neutrinos are expected to be performed at many laboratories across the world and to form one of the cornerstones of the Fermilab research program for the next decade or more.

The emergence of mirror-like response properties from domain-general principles in vision and audition.

PubMed

Saygin, Ayse P; Dick, Frederic

2014-04-01

Like Cook et al., we suggest that mirror neurons are a fascinating product of cross-modal learning. As predicted by an associative account, responses in motor regions are observed for novel and/or abstract visual stimuli such as point-light and android movements. Domain-specific mirror responses also emerge as a function of audiomotor expertise that is slowly acquired over years of intensive training.

Neutrinos: Nature's Ghosts?

ScienceCinema

Lincoln, Don

2018-06-07

Dr. Don Lincoln introduces one of the most fascinating inhabitants of the subatomic realm: the neutrino. Neutrinos are ghosts of the microworld, almost not interacting at all. In this video, he describes some of their properties and how they were discovered. Studies of neutrinos are expected to be performed at many laboratories across the world and to form one of the cornerstones of the Fermilab research program for the next decade or more.

Nuclear Physics of neutron stars

NASA Astrophysics Data System (ADS)

Piekarewicz, Jorge

2015-04-01

One of the overarching questions posed by the recent community report entitled ``Nuclear Physics: Exploring the Heart of Matter'' asks How Does Subatomic Matter Organize Itself and What Phenomena Emerge? With their enormous dynamic range in both density and neutron-proton asymmetry, neutron stars provide ideal laboratories to answer this critical challenge. Indeed, a neutron star is a gold mine for the study of physical phenomena that cut across a variety of disciplines, from particle physics to general relativity. In this presentation--targeted at non-experts--I will focus on the essential role that nuclear physics plays in constraining the dynamics, structure, and composition of neutron stars. In particular, I will discuss some of the many exotic states of matter that are speculated to exist in a neutron star and the impact of nuclear-physics experiments on elucidating their fascinating nature. This material is based upon work supported by the U.S. Department of Energy Office of Science, Office of Nuclear Physics under Award Number DE-FD05-92ER40750.

Photo-fluorescent and magnetic properties of iron oxide nanoparticles for biomedical applications

NASA Astrophysics Data System (ADS)

Shi, Donglu; Sadat, M. E.; Dunn, Andrew W.; Mast, David B.

2015-04-01

Iron oxide exhibits fascinating physical properties especially in the nanometer range, not only from the standpoint of basic science, but also for a variety of engineering, particularly biomedical applications. For instance, Fe3O4 behaves as superparamagnetic as the particle size is reduced to a few nanometers in the single-domain region depending on the type of the material. The superparamagnetism is an important property for biomedical applications such as magnetic hyperthermia therapy of cancer. In this review article, we report on some of the most recent experimental and theoretical studies on magnetic heating mechanisms under an alternating (AC) magnetic field. The heating mechanisms are interpreted based on Néel and Brownian relaxations, and hysteresis loss. We also report on the recently discovered photoluminescence of Fe3O4 and explain the emission mechanisms in terms of the electronic band structures. Both optical and magnetic properties are correlated to the materials parameters of particle size, distribution, and physical confinement. By adjusting these parameters, both optical and magnetic properties are optimized. An important motivation to study iron oxide is due to its high potential in biomedical applications. Iron oxide nanoparticles can be used for MRI/optical multimodal imaging as well as the therapeutic mediator in cancer treatment. Both magnetic hyperthermia and photothermal effect has been utilized to kill cancer cells and inhibit tumor growth. Once the iron oxide nanoparticles are up taken by the tumor with sufficient concentration, greater localization provides enhanced effects over disseminated delivery while simultaneously requiring less therapeutic mass to elicit an equal response. Multi-modality provides highly beneficial co-localization. For magnetite (Fe3O4) nanoparticles the co-localization of diagnostics and therapeutics is achieved through magnetic based imaging and local hyperthermia generation through magnetic field or photon application. Here, Fe3O4 nanoparticles are shown to provide excellent conjugation bases for entrapment of therapeutic molecules, fluorescent agents, and targeting ligands; enhancement of solid tumor treatment is achieved through co-application of local hyperthermia with chemotherapeutic agents.

C. V. Raman and Colonial Physics: Acoustics and the Quantum

NASA Astrophysics Data System (ADS)

Banerjee, Somaditya

2014-06-01

Presenting the social and historical context of Chandrasekhara Venkata Raman, this paper clarifies the nature and development of his work in early twentieth-century colonial India. Raman's early fascination with acoustics became the basis of his later insights into the nature of the light quantum. His work on light scattering played an important role in the experimental verification of quantum mechanics. In general, Raman's worldview corrects certain Orientalist stereotypes about scientific practice in Asia.

Voyage dans le noir. Trous noirs, matière noire, énergie noire et antimatière [Journey in the dark. Black holes, dark matter, dark energy and antimatter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Alvarez-Gaume, Luis; Doser, Michael; Grojean, Chri

2009-11-26

Et si nous faisions avec les physiciens un voyage dans le noir ? De l'astrophysique à la physique des particules les trois noirs, la matière noire, l'énergie noire ou l’antimatière intriguent et fascinent. Que sont ces objets qui bousculent nos idées et qui véhiculent parfois des craintes irraisonnées? Luis Alvarez-Gaume, Michael Doser et Christophe Grojean, physiciens du CERN vous invitent à mettre en lumière (!) les constituants de base de la matière et à explorer les mystères de la physique contemporaine. Une soirée lumineuse pour éclairer des concepts et ne plus avoir peur du noir. [ What if we mademore » a trip to the physicists in the dark? From astrophysics to particle physics the three blacks, dark matter, dark energy or antimatter intrigue and fascinate. What are these objects that jostle our ideas and sometimes convey irrational fears? Luis Alvarez-Gaume, Michael Doser and Christophe Grojean, CERN physicists invite you to highlight (!) The basic constituents of matter and to explore the mysteries of contemporary physics. A bright evening to illuminate concepts and not be afraid of the dark.]« less

A One-Dimensional Organic Lead Chloride Hybrid with Excitation-Dependent Broadband Emissions

DOE PAGES

Wu, Guanhong; Zhou, Chenkun; Ming, Wenmei; ...

2018-05-23

Organic–inorganic metal halide hybrids have emerged as a new class of materials with fascinating optical and electronic properties. The exceptional structure tunability has enabled the development of materials with various dimensionalities at the molecular level, from three-dimensional (3D) to 2D, 1D, and 0D. Here, we report a new 1D lead chloride hybrid, C 4N 2H 14PbCl 4, which exhibits unusual inverse excitation-dependent broadband emission from bluish-green to yellow. Density functional theory calculations were performed to better understand the mechanism of this excitation-dependent broadband emission. This 1D hybrid material is found to have two emission centers, corresponding to the self-trapped excitonsmore » (STEs) and vacancy-bound excitons. The excitation-dependent emission is due to different populations of these two types of excitons generated at different excitation wavelengths. Furthermore, this work shows the rich chemistry and physics of organic–inorganic metal halide hybrids and paves the way to achieving novel light emitters with excitation-dependent broadband emissions at room temperature.« less

A New Method for Studying the Atom: Optical spectra for multiply ionized atoms are produced by means of nuclear-physics techniques.

PubMed

Bashkin, S

1965-05-21

The new spectroscopy is in its infancy, and many fascinating aspects are yet to be studied. The properties of thin films may be studied by means of the excitation they induce in a given kind of beam. The production of ions with but a single electron offers a means of carefully mapping the nuclear charge distribution without the complications introduced by the normal complement of electrons. The study of high-purity, multiply ionized particles should make for better temperature determinations in hot plasmas. Possibly the data on lifetimes and modes of decay of excited energy levels may assist in the quantitative assignment of element abundances in the stars. One can even attempt to use the glowing beams as sources for absorption spectroscopy. The method seems to permit study of every stage of excitation for every stage of ionization for every element in the periodic table. Practical problems may interfere with so complete a study, but a major extension of our knowledge of atomic structure seems to be at hand.

Surface state-dominated photoconduction and THz-generation in topological Bi2Te2Se-nanowires

NASA Astrophysics Data System (ADS)

Seifert, Paul; Vaklinova, Kristina; Kern, Klaus; Burghard, Marko; Holleitner, Alexander

Topological insulators constitute a fascinating class of quantum materials with non-trivial, gapless states on the surface and trivial, insulating bulk states. In revealing the optoelectronic dynamics in the whole range from femto- to microseconds, we demonstrate that the long surface lifetime of Bi2Te2Se-nanowires allows to access the surface states by a pulsed photoconduction scheme and that there is a prevailing bolometric response of the surface states. The interplay of the surface state dynamics on the different timescales gives rise to a surprising physical property of Bi2Te2Se-nanowires: their pulsed photoconductance changes polarity as a function of laser power. Moreover, we show that single Bi2Te2Se-nanowires can be used as THz-generators for on-chip high-frequency circuits at room temperature. Our results open the avenue for single Bi2Te2Se-nanowires as active modules in optoelectronic high-frequency and THz-circuits. We acknowledge financial support by the ERC Grant NanoReal (n306754).

Electric field effect in multilayer Cr2Ge2Te6: a ferromagnetic 2D material

NASA Astrophysics Data System (ADS)

Xing, Wenyu; Chen, Yangyang; Odenthal, Patrick M.; Zhang, Xiao; Yuan, Wei; Su, Tang; Song, Qi; Wang, Tianyu; Zhong, Jiangnan; Jia, Shuang; Xie, X. C.; Li, Yan; Han, Wei

2017-06-01

The emergence of two-dimensional (2D) materials has attracted a great deal of attention due to their fascinating physical properties and potential applications for future nano-electronic devices. Since the first isolation of graphene, a Dirac material, a large family of new functional 2D materials have been discovered and characterized, including insulating 2D boron nitride, semiconducting 2D transition metal dichalcogenides and black phosphorus, and superconducting 2D bismuth strontium calcium copper oxide, molybdenum disulphide and niobium selenide, etc. Here, we report the identification of ferromagnetic thin flakes of Cr2Ge2Te6 (CGT) with thickness down to a few nanometers, which provides a very important piece to the van der Waals structures consisting of various 2D materials. We further demonstrate the giant modulation of the channel resistance of 2D CGT devices via electric field effect. Our results illustrate the gate voltage tunability of 2D CGT and the potential of CGT, a ferromagnetic 2D material, as a new functional quantum material for applications in future nanoelectronics and spintronics.

A One-Dimensional Organic Lead Chloride Hybrid with Excitation-Dependent Broadband Emissions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Guanhong; Zhou, Chenkun; Ming, Wenmei

Organic–inorganic metal halide hybrids have emerged as a new class of materials with fascinating optical and electronic properties. The exceptional structure tunability has enabled the development of materials with various dimensionalities at the molecular level, from three-dimensional (3D) to 2D, 1D, and 0D. Here, we report a new 1D lead chloride hybrid, C 4N 2H 14PbCl 4, which exhibits unusual inverse excitation-dependent broadband emission from bluish-green to yellow. Density functional theory calculations were performed to better understand the mechanism of this excitation-dependent broadband emission. This 1D hybrid material is found to have two emission centers, corresponding to the self-trapped excitonsmore » (STEs) and vacancy-bound excitons. The excitation-dependent emission is due to different populations of these two types of excitons generated at different excitation wavelengths. Furthermore, this work shows the rich chemistry and physics of organic–inorganic metal halide hybrids and paves the way to achieving novel light emitters with excitation-dependent broadband emissions at room temperature.« less

Nonlinear coherent structures in granular crystals

NASA Astrophysics Data System (ADS)

Chong, C.; Porter, Mason A.; Kevrekidis, P. G.; Daraio, C.

2017-10-01

The study of granular crystals, which are nonlinear metamaterials that consist of closely packed arrays of particles that interact elastically, is a vibrant area of research that combines ideas from disciplines such as materials science, nonlinear dynamics, and condensed-matter physics. Granular crystals exploit geometrical nonlinearities in their constitutive microstructure to produce properties (such as tunability and energy localization) that are not conventional to engineering materials and linear devices. In this topical review, we focus on recent experimental, computational, and theoretical results on nonlinear coherent structures in granular crystals. Such structures—which include traveling solitary waves, dispersive shock waves, and discrete breathers—have fascinating dynamics, including a diversity of both transient features and robust, long-lived patterns that emerge from broad classes of initial data. In our review, we primarily discuss phenomena in one-dimensional crystals, as most research to date has focused on such scenarios, but we also present some extensions to two-dimensional settings. Throughout the review, we highlight open problems and discuss a variety of potential engineering applications that arise from the rich dynamic response of granular crystals.

Reviews Book: Sustainable Energy—Without the Hot Air Equipment: Doppler Effect Unit Book: The Physics of Rugby Book: Plastic Fantastic: How the Biggest Fraud in Physics Shook the Scientific World Equipment: Brunel Eyecam Equipment: 200x Digital Microscope Book: The Atom and the Apple: Twelve Tales from Contemporary Physics Book: Physics 2 for OCR Web Watch

NASA Astrophysics Data System (ADS)

2009-09-01

WE RECOMMEND Sustainable Energy—Without the Hot Air This excellent book makes sense of energy facts and figures Doppler Effect Unit Another simple, effective piece of kit from SEP Plastic Fantastic: How the Biggest Fraud in Physics Shook the Scientific World Intriguing and unique write-up of an intellectual fraud case Brunel Eyecam An affordable digital eyepiece for your microscope 200x Digital Microscope An adjustable digital flexcam for classroom use The Atom and the Apple: Twelve Tales from Contemporary Physics A fascinating round-up of the recent history of physics WORTH A LOOK The Physics of Rugby Book uses sport analogy and context to teach physics concepts Physics 2 for OCR Essential textbook for the course but otherwise pointless WEB WATCH Some free teaching materials are better than those you'd pay for

Fascin and EMMPRIN expression in primary mucinous tumors of ovary: a tissue microarray study.

PubMed

Alici, Omer; Kefeli, Mehmet; Yildiz, Levent; Baris, Sancar; Karagoz, Filiz; Kandemir, Bedri

2014-12-01

The aim of this study was to compare the expressions of fascin and EMMPRIN in primary malignant, borderline and benign mucinous ovarian tumors, and to investigate the relationship of these markers with tumor progression and their applicability to differential diagnosis. An immunohistochemical study was performed for fascin and EMMPRIN using the tissue microarray technique. Eighty-one cases were included in the study; there were 37 benign, 25 borderline and 19 malignant primary mucinous ovarian tumors. For each case, a total staining score was determined, consisting of scores for extent of staining and intensity of staining. The cases were allocated to negative, weakly positive and strongly positive staining categories, according to the total staining score. Both of the markers were significantly negative in benign tumors as compared with borderline and malignant tumors. There was no significant difference between borderline and malignant groups for both markers. Sixty-eight percent of malignant tumors were stained positive by fascin, while this rate was 40% for borderline mucinous tumors. All malignant tumors were strongly stained positive for EMMPRIN, while this rate was 92% for borderline mucinous tumors. The rest of the cases stained weakly positive. No significant difference in staining score was found between fascin and EMMPRIN expression. In ovarian primary mucinous tumors, fascin and EMMPRIN may play an important role in tumor progression from benign tumor to carcinoma. In that context, EMMPRIN and fascin expression may have potential application in the differential diagnosis of some diagnostically problematic mucinous ovarian tumors. However, the differential diagnostic applicability of EMMPRIN appears to be more limited than that of fascin due to its wide spectrum of staining in mucinous ovarian tumors. Copyright © 2014 Elsevier GmbH. All rights reserved.

Light for the quantum. Entangled photons and their applications: a very personal perspective

NASA Astrophysics Data System (ADS)

Zeilinger, Anton

2017-07-01

The quantum physics of light is a most fascinating field. Here I present a very personal viewpoint, focusing on my own path to quantum entanglement and then on to applications. I have been fascinated by quantum physics ever since I heard about it for the first time in school. The theory struck me immediately for two reasons: (1) its immense mathematical beauty, and (2) the unparalleled precision to which its predictions have been verified again and again. Particularly fascinating for me were the predictions of quantum mechanics for individual particles, individual quantum systems. Surprisingly, the experimental realization of many of these fundamental phenomena has led to novel ideas for applications. Starting from my early experiments with neutrons, I later became interested in quantum entanglement, initially focusing on multi-particle entanglement like GHZ states. This work opened the experimental possibility to do quantum teleportation and quantum hyper-dense coding. The latter became the first entanglement-based quantum experiment breaking a classical limitation. One of the most fascinating phenomena is entanglement swapping, the teleportation of an entangled state. This phenomenon is fundamentally interesting because it can entangle two pairs of particles which do not share any common past. Surprisingly, it also became an important ingredient in a number of applications, including quantum repeaters which will connect future quantum computers with each other. Another application is entanglement-based quantum cryptography where I present some recent long-distance experiments. Entanglement swapping has also been applied in very recent so-called loophole-free tests of Bell’s theorem. Within the physics community such loophole-free experiments are perceived as providing nearly definitive proof that local realism is untenable. While, out of principle, local realism can never be excluded entirely, the 2015 achievements narrow down the remaining possibilities for local realistic explanations of the quantum phenomenon of entanglement in a significant way. These experiments may go down in the history books of science. Future experiments will address particularly the freedom-of-choice loophole using cosmic sources of randomness. Such experiments confirm that unconditionally secure quantum cryptography is possible, since quantum cryptography based on Bell’s theorem can provide unconditional security. The fact that the experiments were loophole-free proves that an eavesdropper cannot avoid detection in an experiment that correctly follows the protocol. I finally discuss some recent experiments with single- and entangled-photon states in higher dimensions. Such experiments realized quantum entanglement between two photons, each with quantum numbers beyond 10 000 and also simultaneous entanglement of two photons where each carries more than 100 dimensions. Thus they offer the possibility of quantum communication with more than one bit or qubit per photon. The paper concludes discussing Einstein’s contributions and viewpoints of quantum mechanics. Even if some of his positions are not supported by recent experiments, he has to be given credit for the fact that his analysis of fundamental issues gave rise to developments which led to a new information technology. Finally, I reflect on some of the lessons learned by the fact that nature cannot be local, that objective randomness exists and about the emergence of a classical world. It is suggestive that information plays a fundamental role also in the foundations of quantum physics.

Study of the Warm Dense Matter with XANES spectroscopy - Applications to planetary interiors

NASA Astrophysics Data System (ADS)

Denoeud, Adrien

With the recent discovery of many exoplanets, modelling the interior of these celestial bodies is becoming a fascinating scientific challenge. In this context, it is crucial to accurately know the equations of state and the macroscopic and microscopic physical properties of their constituent materials in the Warm Dense Matter regime (WDM). Moreover, planetary models rely almost exclusively on physical properties obtained using first principles simulations based on density functional theory (DFT) predictions. It is thus of paramount importance to validate the basic underlying mechanisms occurring for key planetary constituents (metallization, dissociation, structural modifications, phase transitions, etc....) as pressure and temperature both increase. In this work, we were interested in two materials that can be mainly found in the Earth-like planets: silica, or SiO2, as a model compound of the silicates that constitute the major part of their mantles, and iron, which is found in abundance in their cores. These two materials were compressed and brought to the WDM regime by using strong shock created by laser pulses during various experiments performed on the LULI2000 (Palaiseau, France) and the JLF (Livermore, US) laser facilities and on the LCLS XFEL (Stanford, US). In order to penetrate this dense matter and to have access to its both ionic and electronic structures, we have probed silica and iron with time-resolved X-ray Absorption Near Edge Structure (XANES). In parallel with these experiments, we performed quantum molecular dynamics simulations based on DFT at conditions representative of the region investigated experimentally so as to extract the interesting physical processes and comprehend the limits of the implemented models. In particular, these works allowed us to highlight the metallization processes of silica in temperature and the structural changes of its liquid in density, as well as to more constrain the melting curve of iron at very high pressures.

Microfluidics as a functional tool for cell mechanics.

PubMed

Vanapalli, Siva A; Duits, Michel H G; Mugele, Frieder

2009-01-05

Living cells are a fascinating demonstration of nature's most intricate and well-coordinated micromechanical objects. They crawl, spread, contract, and relax-thus performing a multitude of complex mechanical functions. Alternatively, they also respond to physical and chemical cues that lead to remodeling of the cytoskeleton. To understand this intricate coupling between mechanical properties, mechanical function and force-induced biochemical signaling requires tools that are capable of both controlling and manipulating the cell microenvironment and measuring the resulting mechanical response. In this review, the power of microfluidics as a functional tool for research in cell mechanics is highlighted. In particular, current literature is discussed to show that microfluidics powered by soft lithographic techniques offers the following capabilities that are of significance for understanding the mechanical behavior of cells: (i) Microfluidics enables the creation of in vitro models of physiological environments in which cell mechanics can be probed. (ii) Microfluidics is an excellent means to deliver physical cues that affect cell mechanics, such as cell shape, fluid flow, substrate topography, and stiffness. (iii) Microfluidics can also expose cells to chemical cues, such as growth factors and drugs, which alter their mechanical behavior. Moreover, these chemical cues can be delivered either at the whole cell or subcellular level. (iv) Microfluidic devices offer the possibility of measuring the intrinsic mechanical properties of cells in a high throughput fashion. (v) Finally, microfluidic methods provide exquisite control over drop size, generation, and manipulation. As a result, droplets are being increasingly used to control the physicochemical environment of cells and as biomimetic analogs of living cells. These powerful attributes of microfluidics should further stimulate novel means of investigating the link between physicochemical cues and the biomechanical response of cells. Insights from such studies will have implications in areas such as drug delivery, medicine, tissue engineering, and biomedical diagnostics.

Bilateral substrate effect on the thermal conductivity of two-dimensional silicon

NASA Astrophysics Data System (ADS)

Zhang, Xiaoliang; Bao, Hua; Hu, Ming

2015-03-01

Silicene, the silicon-based counterpart of graphene, has received exceptional attention from a wide community of scientists and engineers in addition to graphene, due to its unique and fascinating physical and chemical properties. Recently, the thermal transport of the atomic thin Si layer, critical to various applications in nanoelectronics, has been studied; however, to date, the substrate effect has not been investigated. In this paper, we present our nonequilibrium molecular dynamics studies on the phonon transport of silicene supported on different substrates. A counter-intuitive phenomenon, in which the thermal conductivity of silicene can be either enhanced or suppressed by changing the surface crystal plane of the substrate, has been observed. This phenomenon is fundamentally different from the general understanding of supported graphene, a representative two-dimensional material, in which the substrate always has a negative effect on the phonon transport of graphene. By performing phonon polarization and spectral energy density analysis, we explain the underlying physics of the new phenomenon in terms of the different impacts on the dominant phonons in the thermal transport of silicene induced by the substrate: the dramatic increase in the thermal conductivity of silicene supported on the 6H-SiC substrate is due to the augmented lifetime of the majority of the acoustic phonons, while the significant decrease in the thermal conductivity of silicene supported on the 3C-SiC substrate results from the reduction in the lifetime of almost the entire phonon spectrum. Our results suggest that, by choosing different substrates, the thermal conductivity of silicene can be largely tuned, which paves the way for manipulating the thermal transport properties of silicene for future emerging applications.

Iron vacancy in tetragonal Fe1-xS crystals and its effect on the structure and superconductivity.

PubMed

Guo, Zhongnan; Sun, Fun; Han, Bingling; Lin, Kun; Zhou, Liang; Yuan, Wenxia

2017-03-29

Understanding the effects of non-stoichiometry on the structure and physical properties of tetragonal Fe chalcogenides is of great importance, especially for developing fascinating superconductivity in this system, which might be very sensitive to the non-stoichiometry. In this study, a series of Fe 1-x S single crystals were synthesized by a hydrothermal method, which show varying concentrations of Fe vacancies (0 ≤ x ≤ 0.1) in the structure. Based on the crystal samples, the effects of vacancies on the crystal structure and physical properties were studied. The vacancy-free sample (x = 0) showed a metallic state in resistance and superconductivity below 4.5 K, whereas for the samples with Fe vacancies (x ≥ 0.05), the SC was degraded and the sample exhibited semiconducting behavior. Structural analysis showed that the Fe vacancy decreases the lattice parameter a, but elongates c, leading to enhanced tetragonality in Fe 1-x S. Selected-area electron diffraction showed that the vacancy in Fe 1-x S was disordered, which is different from the scenario in FeSe-based materials. On combining the abovementioned results with the first-principles calculations, it was speculated that the disappearance of SC in non-stoichiometric Fe 1-x S resulted from the localization of the 3d electrons of Fe. Moreover, the accompanied metal-insulator transition induced by Fe vacancy mainly belonged to the Mott mechanism because the vacancy did not significantly alter the band structure. These results not only provide deep insight into the effect of Fe vacancy in Fe chalcogenides, but also provide a basis to effectively induce SC in Fe sulfides by decreasing the number of Fe vacancies.

The New Physics and Cosmology - Dialogues with the Dalai Lama

NASA Astrophysics Data System (ADS)

Zajonc, Arthur; Houshmand, Zara

2004-03-01

What happens when the Dalai Lama meets with leading physicists and a historian? This book is the carefully edited record of the fascinating discussions at a Mind and Life conference in which five leading physicists and a historian (David Finkelstein, George Greenstein, Piet Hut, Arthur Zajonc, Anton Zeilinger, and Tu Weiming) discussed with the Dalai Lama current thought in theoretical quantum physics, in the context of Buddhist philosophy. A contribution to the science-religion interface, and a useful explanation of our basic understanding of quantum reality, couched at a level that intelligent readers without a deep involvement in science can grasp. In the tradition of other popular books on resonances between modern quantum physics and Zen or Buddhist mystical traditions--notably The Dancing Wu Li Masters and The Tao of Physics , this book gives a clear and useful update of the genuine correspondences between these two rather disparate approaches to understanding the nature of reality.

The Entangled Histories of Physics and Computation

NASA Astrophysics Data System (ADS)

Rodriguez, Cesar

2007-03-01

The history of physics and computation intertwine in a fascinating manner that is relevant to the field of quantum computation. This talk focuses of the interconnections between both by examining their rhyming philosophies, recurrent characters and common themes. Leibniz not only was one of the lead figures of calculus, but also left his footprint in physics and invented the concept of a universal computational language. This last idea was further developed by Boole, Russell, Hilbert and G"odel. Physicists such as Boltzmann and Maxwell also established the foundation of the field of information theory later developed by Shannon. The war efforts of von Neumann and Turing can be juxtaposed to the Manhattan Project. Professional and personal connections of these characters to the development of physics will be emphasized. Recently, new cryptographic developments lead to a reexamination of the fundamentals of quantum mechanics, while quantum computation is discovering a new perspective on the nature of information itself.

Investigating water transport through the xylem network in vascular plants.

PubMed

Kim, Hae Koo; Park, Joonghyuk; Hwang, Ildoo

2014-04-01

Our understanding of physical and physiological mechanisms depends on the development of advanced technologies and tools to prove or re-evaluate established theories, and test new hypotheses. Water flow in land plants is a fascinating phenomenon, a vital component of the water cycle, and essential for life on Earth. The cohesion-tension theory (CTT), formulated more than a century ago and based on the physical properties of water, laid the foundation for our understanding of water transport in vascular plants. Numerous experimental tools have since been developed to evaluate various aspects of the CTT, such as the existence of negative hydrostatic pressure. This review focuses on the evolution of the experimental methods used to study water transport in plants, and summarizes the different ways to investigate the diversity of the xylem network structure and sap flow dynamics in various species. As water transport is documented at different scales, from the level of single conduits to entire plants, it is critical that new results be subjected to systematic cross-validation and that findings based on different organs be integrated at the whole-plant level. We also discuss the functional trade-offs between optimizing hydraulic efficiency and maintaining the safety of the entire transport system. Furthermore, we evaluate future directions in sap flow research and highlight the importance of integrating the combined effects of various levels of hydraulic regulation.

Of Linear Colliders, the GDE Workshop at Bangalore, Mughals, Camels, Elephants and Sundials

DOE Office of Scientific and Technical Information (OSTI.GOV)

Loew, Greg

In this colloquium, the speaker will give a summary of the recent International Linear Collider (ILC) Global Design Effort (GDE) Workshop at Bangalore and how the High Energy Physics community converged to this meeting after many years of electron-positron linear collider design and experimental work. Given that this workshop for the first time took place in India, the speaker will also show a few pictures and talk briefly about what he learned in that fascinating country.

Amateur versus professional: the search for Bigfoot.

PubMed

Regal, Brian

2008-06-01

Those who would seek monsters not as metaphors, but as flesh and blood organisms have gone largely overlooked by the history of science. Starting in the 1950s and 1960s a group of amateur monster hunters and physical anthropologists began to pursue such creatures as Sasquatch, Bigfoot and the Yeti as living species. Whether or not such creatures exist, the monster hunters themselves are fascinating subjects for study, illustrating the tensions that are all too common between amateur naturalists and professional scientists.

Electron-Poor Polar Intermetallics: Complex Structures, Novel Clusters, and Intriguing Bonding with Pronounced Electron Delocalization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lin, Qisheng; Miller, Gordon J.

Intermetallic compounds represent an extensive pool of candidates for energy related applications stemming from magnetic, electric, optic, caloric, and catalytic properties. The discovery of novel intermetallic compounds can enhance understanding of the chemical principles that govern structural stability and chemical bonding as well as finding new applications. Valence electron-poor polar intermetallics with valence electron concentrations (VECs) between 2.0 and 3.0 e –/atom show a plethora of unprecedented and fascinating structural motifs and bonding features. Furthermore, establishing simple structure-bonding-property relationships is especially challenging for this compound class because commonly accepted valence electron counting rules are inappropriate.

Electron-Poor Polar Intermetallics: Complex Structures, Novel Clusters, and Intriguing Bonding with Pronounced Electron Delocalization

DOE PAGES

Lin, Qisheng; Miller, Gordon J.

2017-12-18

Intermetallic compounds represent an extensive pool of candidates for energy related applications stemming from magnetic, electric, optic, caloric, and catalytic properties. The discovery of novel intermetallic compounds can enhance understanding of the chemical principles that govern structural stability and chemical bonding as well as finding new applications. Valence electron-poor polar intermetallics with valence electron concentrations (VECs) between 2.0 and 3.0 e –/atom show a plethora of unprecedented and fascinating structural motifs and bonding features. Furthermore, establishing simple structure-bonding-property relationships is especially challenging for this compound class because commonly accepted valence electron counting rules are inappropriate.

Remote monitoring of vibrational information in spider webs.

PubMed

Mortimer, B; Soler, A; Siviour, C R; Vollrath, F

2018-05-22

Spiders are fascinating model species to study information-acquisition strategies, with the web acting as an extension of the animal's body. Here, we compare the strategies of two orb-weaving spiders that acquire information through vibrations transmitted and filtered in the web. Whereas Araneus diadematus monitors web vibration directly on the web, Zygiella x-notata uses a signal thread to remotely monitor web vibration from a retreat, which gives added protection. We assess the implications of these two information-acquisition strategies on the quality of vibration information transfer, using laser Doppler vibrometry to measure vibrations of real webs and finite element analysis in computer models of webs. We observed that the signal thread imposed no biologically relevant time penalty for vibration propagation. However, loss of energy (attenuation) was a cost associated with remote monitoring via a signal thread. The findings have implications for the biological use of vibrations by spiders, including the mechanisms to locate and discriminate between vibration sources. We show that orb-weaver spiders are fascinating examples of organisms that modify their physical environment to shape their information-acquisition strategy.

Remote monitoring of vibrational information in spider webs

NASA Astrophysics Data System (ADS)

Mortimer, B.; Soler, A.; Siviour, C. R.; Vollrath, F.

2018-06-01

Spiders are fascinating model species to study information-acquisition strategies, with the web acting as an extension of the animal's body. Here, we compare the strategies of two orb-weaving spiders that acquire information through vibrations transmitted and filtered in the web. Whereas Araneus diadematus monitors web vibration directly on the web, Zygiella x-notata uses a signal thread to remotely monitor web vibration from a retreat, which gives added protection. We assess the implications of these two information-acquisition strategies on the quality of vibration information transfer, using laser Doppler vibrometry to measure vibrations of real webs and finite element analysis in computer models of webs. We observed that the signal thread imposed no biologically relevant time penalty for vibration propagation. However, loss of energy (attenuation) was a cost associated with remote monitoring via a signal thread. The findings have implications for the biological use of vibrations by spiders, including the mechanisms to locate and discriminate between vibration sources. We show that orb-weaver spiders are fascinating examples of organisms that modify their physical environment to shape their information-acquisition strategy.

Drops in Space: Super Oscillations and Surfactant Studies

NASA Technical Reports Server (NTRS)

Apfel, Robert E.; Tian, Yuren; Jankovsky, Joseph; Shi, Tao; Chen, X.; Holt, R. Glynn; Trinh, Eugene; Croonquist, Arvid; Thornton, Kathyrn C.; Sacco, Albert, Jr.;

From isolated light-harvesting complexes to the thylakoid membrane: a single-molecule perspective

NASA Astrophysics Data System (ADS)

Gruber, J. Michael; Malý, Pavel; Krüger, Tjaart P. J.; Grondelle, Rienk van

2018-01-01

The conversion of solar radiation to chemical energy in plants and green algae takes place in the thylakoid membrane. This amphiphilic environment hosts a complex arrangement of light-harvesting pigment-protein complexes that absorb light and transfer the excitation energy to photochemically active reaction centers. This efficient light-harvesting capacity is moreover tightly regulated by a photoprotective mechanism called non-photochemical quenching to avoid the stress-induced destruction of the catalytic reaction center. In this review we provide an overview of single-molecule fluorescence measurements on plant light-harvesting complexes (LHCs) of varying sizes with the aim of bridging the gap between the smallest isolated complexes, which have been well-characterized, and the native photosystem. The smallest complexes contain only a small number (10-20) of interacting chlorophylls, while the native photosystem contains dozens of protein subunits and many hundreds of connected pigments. We discuss the functional significance of conformational dynamics, the lipid environment, and the structural arrangement of this fascinating nano-machinery. The described experimental results can be utilized to build mathematical-physical models in a bottom-up approach, which can then be tested on larger in vivo systems. The results also clearly showcase the general property of biological systems to utilize the same system properties for different purposes. In this case it is the regulated conformational flexibility that allows LHCs to switch between efficient light-harvesting and a photoprotective function.

Interface structure and mechanics between graphene and metal substrates: a first-principles study

NASA Astrophysics Data System (ADS)

Xu, Zhiping; Buehler, Markus J.

2010-12-01

Graphene is a fascinating material not only for technological applications, but also as a test bed for fundamental insights into condensed matter physics due to its unique two-dimensional structure. One of the most intriguing issues is the understanding of the properties of graphene and various substrate materials. In particular, the interfaces between graphene and metal substrates are of critical importance in applications of graphene in integrated electronics, as thermal materials, and in electromechanical devices. Here we investigate the structure and mechanical interactions at a graphene-metal interface through density functional theory (DFT)-based calculations. We focus on copper (111) and nickel (111) surfaces adhered to a monolayer of graphene, and find that their cohesive energy, strength and electronic structure correlate directly with their atomic geometry. Due to the strong coupling between open d-orbitals, the nickel-graphene interface has a much stronger cohesive energy with graphene than copper. We also find that the interface cohesive energy profile features a well-and-shoulder shape that cannot be captured by simple pair-wise models such as the Lennard-Jones potential. Our results provide a detailed understanding of the interfacial properties of graphene-metal systems, and help to predict the performance of graphene-based nanoelectronics and nanocomposites. The availability of structural and energetic data of graphene-metal interfaces could also be useful for the development of empirical force fields for molecular dynamics simulations.

FAIR - Cosmic Matter in the Laboratory

NASA Astrophysics Data System (ADS)

Stöcker, Horst; Stöhlker, Thomas; Sturm, Christian

2015-06-01

To explore cosmic matter in the laboratory - this fascinating research prospect becomes available at the Facility for Antiproton and Ion Research, FAIR. The new facility is being constructed within the next five years adjacent to the existing accelerator complex of the GSI Helmholtz Centre for Heavy Ion Research at Darmstadt/Germany, expanding the research goals and technical possibilities substantially. This includes new insights into the dynamics of supernovae depending on the properties of short-lived neutron-rich nuclei which will be investigated with intense rare isotope beams. New insights will be provided into the interior of stars by exploring dense plasmas with intense heavy-ion beams combined with a high-performance laser - or into neutron star cores by probing the highest baryon densities in relativistic nucleus-nucleus collisions at unprecedented collision rates. To the latter, the properties of hadrons play an important part which will be systematically studied by high precision hadron spectroscopy with antiproton beams at unmatched intensities. The worldwide unique accelerator and experimental facilities of FAIR will open the way for a broad spectrum of unprecedented fore-front research supplying a large variety of experiments in hadron, nuclear, atomic and plasma physics as well as biomedical and material science which will be briefly described in this article. This article is based on the FAIR Green Paper [4] and gives an update of former publications [5] - [12].

Stacking sequence determines Raman intensities of observed interlayer shear modes in 2D layered materials – A general bond polarizability model

PubMed Central

Luo, Xin; Lu, Xin; Cong, Chunxiao; Yu, Ting; Xiong, Qihua; Ying Quek, Su

2015-01-01

2D layered materials have recently attracted tremendous interest due to their fascinating properties and potential applications. The interlayer interactions are much weaker than the intralayer bonds, allowing the as-synthesized materials to exhibit different stacking sequences, leading to different physical properties. Here, we show that regardless of the space group of the 2D materials, the Raman frequencies of the interlayer shear modes observed under the typical configuration blue shift for AB stacked materials, and red shift for ABC stacked materials, as the number of layers increases. Our predictions are made using an intuitive bond polarizability model which shows that stacking sequence plays a key role in determining which interlayer shear modes lead to the largest change in polarizability (Raman intensity); the modes with the largest Raman intensity determining the frequency trends. We present direct evidence for these conclusions by studying the Raman modes in few layer graphene, MoS2, MoSe2, WSe2 and Bi2Se3, using both first principles calculations and Raman spectroscopy. This study sheds light on the influence of stacking sequence on the Raman intensities of intrinsic interlayer modes in 2D layered materials in general, and leads to a practical way of identifying the stacking sequence in these materials. PMID:26469313

Stacking sequence determines Raman intensities of observed interlayer shear modes in 2D layered materials--A general bond polarizability model.

PubMed

Luo, Xin; Lu, Xin; Cong, Chunxiao; Yu, Ting; Xiong, Qihua; Quek, Su Ying

2015-10-15

2D layered materials have recently attracted tremendous interest due to their fascinating properties and potential applications. The interlayer interactions are much weaker than the intralayer bonds, allowing the as-synthesized materials to exhibit different stacking sequences, leading to different physical properties. Here, we show that regardless of the space group of the 2D materials, the Raman frequencies of the interlayer shear modes observed under the typical z(xx)z configuration blue shift for AB stacked materials, and red shift for ABC stacked materials, as the number of layers increases. Our predictions are made using an intuitive bond polarizability model which shows that stacking sequence plays a key role in determining which interlayer shear modes lead to the largest change in polarizability (Raman intensity); the modes with the largest Raman intensity determining the frequency trends. We present direct evidence for these conclusions by studying the Raman modes in few layer graphene, MoS2, MoSe2, WSe2 and Bi2Se3, using both first principles calculations and Raman spectroscopy. This study sheds light on the influence of stacking sequence on the Raman intensities of intrinsic interlayer modes in 2D layered materials in general, and leads to a practical way of identifying the stacking sequence in these materials.

Analysis of magic lengths in growth of supported metallic nanowires

NASA Astrophysics Data System (ADS)

Han, Yong

2014-12-01

Metallic nanowires can exhibit fascinating physical properties. These unique properties often originate primarily from the quantum confinement of free electrons in a potential well, while electron-electron interactions do not play a decisive role. A recent experimental study shows that self-assembled Ir nanowires grown on Ge(001) surface have a strong length preference: the nanowire lengths are an integer multiple of 4.8 nm. In this paper, a free-electron-gas model for geometries corresponding to the nanowires is used to analyze the selection of these preferred or magic lengths. The model shows that the inclusion of even numbers of free electrons in an Ir nanowire produces these magic lengths once an electron spillage effect is taken into account. The model also shows that the stability of the nanowire diminishes with its increasing length, and consequently suggests why no long nanowires are observed in experiments. It is also shown that applying generic results for quantum size effects in a nanofilm geometry is not adequate to accurately describe the length selection in the rather different nanowire geometry, where the transverse dimensions are smaller than the electron Fermi wavelength. Finally, monatomic Au chain growth on Ge(001) surface is also analyzed. In contrast to Ir nanowires, the model shows that the stability of an Au chain depends strongly on the extent of electron spillage.

Recent advance in the pharmacology of dihydropyrimidinone.

PubMed

Wan, J-P; Pan, Y

2012-04-01

Dihydropyrimidinones (DHPMs) are a series of highly valuable small molecules possessing versatile pharmaceutical properties. Although the first one-pot synthesis of DHPMs had been reported more than 100 years ago, the fascinating achievement in DHPMs-based pharmacology during the past century promoted durative interests to the pharmacological and related studies of the scaffold, which lead to the discovery of many new biological functions of DHPMs. Recent pharmacological development on DHPMs-based molecules have been summarized in this review.

Gymnastics in Phase Space

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chao, Alexander Wu; /SLAC

2012-03-01

As accelerator technology advances, the requirements on accelerator beam quality become increasingly demanding. Facing these new demands, the topic of phase space gymnastics is becoming a new focus of accelerator physics R&D. In a phase space gymnastics, the beam's phase space distribution is manipulated and precision tailored to meet the required beam qualities. On the other hand, all realization of such gymnastics will have to obey accelerator physics principles as well as technological limitations. Recent examples of phase space gymnastics include Emittance exchanges, Phase space exchanges, Emittance partitioning, Seeded FELs and Microbunched beams. The emittance related topics of this listmore » are reviewed in this report. The accelerator physics basis, the optics design principles that provide these phase space manipulations, and the possible applications of these gymnastics, are discussed. This fascinating new field promises to be a powerful tool of the future.« less

Voyage dans le noir. Trous noirs, matière noire, énergie noire et antimatière [Journey in the dark. Black holes, dark matter, dark energy and antimatter

ScienceCinema

Alvarez-Gaume, Luis; Doser, Michael; Grojean, Chri

2018-05-24

Et si nous faisions avec les physiciens un voyage dans le noir ? De l'astrophysique à la physique des particules les trois noirs, la matière noire, l'énergie noire ou l’antimatière intriguent et fascinent. Que sont ces objets qui bousculent nos idées et qui véhiculent parfois des craintes irraisonnées? Luis Alvarez-Gaume, Michael Doser et Christophe Grojean, physiciens du CERN vous invitent à mettre en lumière (!) les constituants de base de la matière et à explorer les mystères de la physique contemporaine. Une soirée lumineuse pour éclairer des concepts et ne plus avoir peur du noir. [ What if we made a trip to the physicists in the dark? From astrophysics to particle physics the three blacks, dark matter, dark energy or antimatter intrigue and fascinate. What are these objects that jostle our ideas and sometimes convey irrational fears? Luis Alvarez-Gaume, Michael Doser and Christophe Grojean, CERN physicists invite you to highlight (!) The basic constituents of matter and to explore the mysteries of contemporary physics. A bright evening to illuminate concepts and not be afraid of the dark.

Surface chemistry of Au/TiO2: Thermally and photolytically activated reactions

NASA Astrophysics Data System (ADS)

Panayotov, Dimitar A.; Morris, John R.

2016-03-01

The fascinating particle size dependence to the physical, photophysical, and chemical properties of gold has motivated thousands of studies focused on exploring the ability of supported gold nanoparticles to catalyze chemical transformations. In particular, titanium dioxide-supported gold (Au/TiO2) nanoparticles may provide the right combination of electronic structure, structural dynamics, and stability to affect catalysis in important practical applications from environmental remediation to selective hydrogenation to carbon monoxide oxidation. Harnessing the full potential of Au/TiO2 will require a detailed atomic-scale understanding of the thermal and photolytic processes that accompany chemical conversion. This review describes some of the unique properties exhibited by particulate gold before delving into how those properties affect chemistry on titania supports. Particular attention is given first to thermally driven reactions on single crystal system. This review then addresses nanoparticulate samples in an effort begin to bridge the so-called materials gap. Building on the foundation provided by the large body of work in the field of thermal catalysis, the review describes new research into light-driven catalysis on Au/TiO2. Importantly, the reader should bear in mind throughout this review that thermal chemistry and thermal effects typically accompany photochemistry. Distinguishing between thermally-driven stages of a reaction and photo-induced steps remains a significant challenge, but one that experimentalists and theorists are beginning to decipher with new approaches. Finally, a summary of several state-of-the-art studies describes how they are illuminating new frontiers in the quest to exploit Au/TiO2 as an efficient catalyst and low-energy photocatalyst.

Functional materials from cellulose-derived liquid-crystal templates.

PubMed

Giese, Michael; Blusch, Lina K; Khan, Mostofa K; MacLachlan, Mark J

2015-03-02

Cellulose nanocrystals (CNCs), known for more than 50 years, have attracted attention because of their unique properties such as high specific strength and modulus, high surface area, and fascinating optical properties. Just recently, however, their potential in supramolecular templating was identified by making use of their self-assembly behavior in aqueous dispersions in the presence of compatible precursors. The combination of the mesoporosity, photonic properties, and chiral nematic order of the materials, which are available as freestanding films, has led to a significant number of interesting and promising discoveries towards new functional materials. This Review summarizes the use of cellulose derivatives, especially CNCs, as novel templates and gives an overview of the recent developments toward new functional materials. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fascin 1 is an actin filament-bundling protein that regulates ectoplasmic specialization dynamics in the rat testis

PubMed Central

Gungor-Ordueri, N. Ece; Celik-Ozenci, Ciler

2014-01-01

In the testis, spermatids are polarized cells, with their heads pointing toward the basement membrane during maturation. This polarity is crucial to pack the maximal number of spermatids in the seminiferous epithelium so that millions of sperms can be produced daily. A loss of spermatid polarity is detected after rodents are exposed to toxicants (e.g., cadmium) or nonhormonal male contraceptives (e.g., adjudin), which is associated with a disruption on the expression and/or localization of polarity proteins. In the rat testis, fascin 1, an actin-bundling protein found in mammalian cells, was expressed by Sertoli and germ cells. Fascin 1 was a component of the ectoplasmic specialization (ES), a testis-specific anchoring junction known to confer spermatid adhesion and polarity. Its expression in the seminiferous epithelium was stage specific. Fascin 1 was localized to the basal ES at the Sertoli cell-cell interface of the blood-testis barrier in all stages of the epithelial cycle, except it diminished considerably at late stage VIII. Fascin 1 was highly expressed at the apical ES at stage VII–early stage VIII and restricted to the step 19 spermatids. Its knockdown by RNAi that silenced fascin 1 by ∼70% in Sertoli cells cultured in vitro was found to perturb the tight junction-permeability barrier via a disruption of F-actin organization. Knockdown of fascin 1 in vivo by ∼60–70% induced defects in spermatid polarity, which was mediated by a mislocalization and/or downregulation of actin-bundling proteins Eps8 and palladin, thereby impeding F-actin organization and disrupting spermatid polarity. In summary, these findings provide insightful information on spermatid polarity regulation. PMID:25159326

Fascin-1 is released from proximal tubular cells in response to calcineurin inhibitors (CNIs) and correlates with isometric vacuolization in kidney transplanted patients

PubMed Central

Jacobs-Cachá, Conxita; Torres, Irina B; López-Hellín, Joan; Cantarell, Carme; Azancot, María A; Román, Antonio; Moreso, Francesc; Serón, Daniel; Meseguer, Anna; Sarró, Eduard

2017-01-01

Immunosuppression based on calcineurin inhibitors (CNIs) has greatly improved organ transplantation, although subsequent nephrotoxicity significantly hinders treatment success. There are no currently available specific soluble biomarkers for CNI-induced nephrotoxicity and diagnosis relies on renal biopsy, which is costly, invasive and may cause complications. Accordingly, identification of non-invasive biomarkers distinguishing CNI-induced kidney tubular damage from that of other etiologies would greatly improve diagnosis and enable more precise dosage adjustment. For this purpose, HK-2 cells, widely used to model human proximal tubule, were treated with CNIs cyclosporine-A and FK506, or staurosporine as a calcineurin-independent toxic compound, and secretomes of each treatment were analyzed by proteomic means. Among the differentially secreted proteins identified, only fascin-1 was specifically released by both CNIs but not by staurosporine. To validate fascin-1 as a biomarker of CNI-induced tubular toxicity, fascin-1 levels were analyzed in serum and urine from kidney-transplanted patients under CNIs treatment presenting or not isometric vacuolization (IV), which nowadays represents the main histological hallmark of CNI-induced tubular damage. Patients with chronic kidney disease (CKD) and healthy volunteers were used as controls. Our results show that urinary fascin-1 was only significantly elevated in the subset of CNI-treated patients presenting IV. Moreover, fascin-1 anticipated the rise of sCr levels in serially collected urine samples from CNI-treated pulmonary-transplanted patients, where a decline in kidney function and serum creatinine (sCr) elevation was mainly attributed to CNIs treatment. In conclusion, our results point towards fascin-1 as a putative soluble biomarker of CNI-induced damage in the kidney tubular compartment. PMID:28979691

Fascin-1 is released from proximal tubular cells in response to calcineurin inhibitors (CNIs) and correlates with isometric vacuolization in kidney transplanted patients.

PubMed

Jacobs-Cachá, Conxita; Torres, Irina B; López-Hellín, Joan; Cantarell, Carme; Azancot, María A; Román, Antonio; Moreso, Francesc; Serón, Daniel; Meseguer, Anna; Sarró, Eduard

2017-01-01

Immunosuppression based on calcineurin inhibitors (CNIs) has greatly improved organ transplantation, although subsequent nephrotoxicity significantly hinders treatment success. There are no currently available specific soluble biomarkers for CNI-induced nephrotoxicity and diagnosis relies on renal biopsy, which is costly, invasive and may cause complications. Accordingly, identification of non-invasive biomarkers distinguishing CNI-induced kidney tubular damage from that of other etiologies would greatly improve diagnosis and enable more precise dosage adjustment. For this purpose, HK-2 cells, widely used to model human proximal tubule, were treated with CNIs cyclosporine-A and FK506, or staurosporine as a calcineurin-independent toxic compound, and secretomes of each treatment were analyzed by proteomic means. Among the differentially secreted proteins identified, only fascin-1 was specifically released by both CNIs but not by staurosporine. To validate fascin-1 as a biomarker of CNI-induced tubular toxicity, fascin-1 levels were analyzed in serum and urine from kidney-transplanted patients under CNIs treatment presenting or not isometric vacuolization (IV), which nowadays represents the main histological hallmark of CNI-induced tubular damage. Patients with chronic kidney disease (CKD) and healthy volunteers were used as controls. Our results show that urinary fascin-1 was only significantly elevated in the subset of CNI-treated patients presenting IV. Moreover, fascin-1 anticipated the rise of sCr levels in serially collected urine samples from CNI-treated pulmonary-transplanted patients, where a decline in kidney function and serum creatinine (sCr) elevation was mainly attributed to CNIs treatment. In conclusion, our results point towards fascin-1 as a putative soluble biomarker of CNI-induced damage in the kidney tubular compartment.

DOE Office of Scientific and Technical Information (OSTI.GOV)

DiMasi,E.

Biominerals, the mineralized tissues of animals, plants, and microorganisms, have inspired humanity with their properties and forms since prehistory. Bones and shells have been used for tools, for currency, for symbolic objects and for art in every culture. Both the fascination and the importance that biominerals present for science are made clear in Darwin's nineteenth-century writings, and in D'Arcy Wentworth Thompson's 1917 On Growth and Form, with its memorable cover illustration of the multi-chambered calcium carbonate nautilus shell. Biomineralization is now a field of study in its own right.

Dual-enhanced photothermal conversion properties of reduced graphene oxide-coated gold superparticles for light-triggered acoustic and thermal theranostics

NASA Astrophysics Data System (ADS)

Lin, Li-Sen; Yang, Xiangyu; Niu, Gang; Song, Jibin; Yang, Huang-Hao; Chen, Xiaoyuan

2016-01-01

A rational design of highly efficient photothermal agents that possess excellent light-to-heat conversion properties is a fascinating topic in nanotheranostics. Herein, we present a facile route to fabricate size-tunable reduced graphene oxide (rGO)-coated gold superparticles (rGO-GSPs) and demonstrate their dual-enhanced photothermal conversion properties for photoacoustic imaging and photothermal therapy. For the first time, graphene oxide (GO) was directly used as an emulsifying agent for the preparation of gold superparticles (GSPs) with near-infrared absorption by the emulsion method. Moreover, GO spontaneously deposited on the surface of GSPs could also act as the precursor of the rGO shell. Importantly, both the plasmonic coupling of the self-assembled gold nanoparticles and the interaction between GSPs and rGO endow rGO-GSPs with enhanced photothermal conversion properties, allowing rGO-GSPs to be used for sensitive photoacoustic detection and efficient photothermal ablation of tumours in vivo. This study provides a facile approach to prepare colloidal superparticles-graphene hybrid nanostructures and will pave the way toward the design and optimization of photothermal nanomaterials with improved properties for theranostic applications.A rational design of highly efficient photothermal agents that possess excellent light-to-heat conversion properties is a fascinating topic in nanotheranostics. Herein, we present a facile route to fabricate size-tunable reduced graphene oxide (rGO)-coated gold superparticles (rGO-GSPs) and demonstrate their dual-enhanced photothermal conversion properties for photoacoustic imaging and photothermal therapy. For the first time, graphene oxide (GO) was directly used as an emulsifying agent for the preparation of gold superparticles (GSPs) with near-infrared absorption by the emulsion method. Moreover, GO spontaneously deposited on the surface of GSPs could also act as the precursor of the rGO shell. Importantly, both the plasmonic coupling of the self-assembled gold nanoparticles and the interaction between GSPs and rGO endow rGO-GSPs with enhanced photothermal conversion properties, allowing rGO-GSPs to be used for sensitive photoacoustic detection and efficient photothermal ablation of tumours in vivo. This study provides a facile approach to prepare colloidal superparticles-graphene hybrid nanostructures and will pave the way toward the design and optimization of photothermal nanomaterials with improved properties for theranostic applications. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07552a

An efficient strategy for designing ambipolar organic semiconductor material: Introducing dehydrogenated phosphorus atoms into pentacene core

NASA Astrophysics Data System (ADS)

Tang, Xiao-Dan

2017-09-01

The charge transport properties of phosphapentacene (P-PEN) derivatives were systematically explored by theoretical calculation. The dehydrogenated P-PENs have reasonable frontier molecular orbital energy levels to facilitate both electron and hole injection. The reduced reorganization energies of dehydrogenated P-PENs could be intimately connected to the bonding nature of phosphorus atoms. From the idea of homology modeling, the crystal structure of TIPSE-4P-2p is constructed and fully optimized. Fascinatingly, TIPSE-4P-2p shows the intrinsic property of ambipolar transport in both hopping and band models. Thus, introducing dehydrogenated phosphorus atoms into pentacene core could be an efficient strategy for designing ambipolar material.

Electrochemical synthesis of mesoporous gold films toward mesospace-stimulated optical properties

NASA Astrophysics Data System (ADS)

Li, Cuiling; Dag, Ömer; Dao, Thang Duy; Nagao, Tadaaki; Sakamoto, Yasuhiro; Kimura, Tatsuo; Terasaki, Osamu; Yamauchi, Yusuke

2015-03-01

Mesoporous gold (Au) films with tunable pores are expected to provide fascinating optical properties stimulated by the mesospaces, but they have not been realized yet because of the difficulty of controlling the Au crystal growth. Here, we report a reliable soft-templating method to fabricate mesoporous Au films using stable micelles of diblock copolymers, with electrochemical deposition advantageous for precise control of Au crystal growth. Strong field enhancement takes place around the center of the uniform mesopores as well as on the walls between the pores, leading to the enhanced light scattering as well as surface-enhanced Raman scattering (SERS), which is understandable, for example, from Babinet principles applied for the reverse system of nanoparticle ensembles.

Mechanical Properties in Metal-Organic Frameworks: Emerging Opportunities and Challenges for Device Functionality and Technological Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Burtch, Nicholas C.; Heinen, Jurn; Bennett, Thomas D.

We report that some of the most remarkable recent developments in metal–organic framework (MOF) performance properties can only be rationalized by the mechanical properties endowed by their hybrid inorganic–organic nanoporous structures. While these characteristics create intriguing application prospects, the same attributes also present challenges that will need to be overcome to enable the integration of MOFs with technologies where these promising traits can be exploited. In this review, emerging opportunities and challenges are identified for MOF-enabled device functionality and technological applications that arise from their fascinating mechanical properties. This is discussed not only in the context of their more well-studiedmore » gas storage and separation applications, but also for instances where MOFs serve as components of functional nanodevices. Recent advances in understanding MOF mechanical structure–property relationships due to attributes such as defects and interpenetration are highlighted, and open questions related to state-of-the-art computational approaches for quantifying their mechanical properties are critically discussed.« less

Mechanical Properties in Metal-Organic Frameworks: Emerging Opportunities and Challenges for Device Functionality and Technological Applications

DOE PAGES

Burtch, Nicholas C.; Heinen, Jurn; Bennett, Thomas D.; ...

2017-11-17

We report that some of the most remarkable recent developments in metal–organic framework (MOF) performance properties can only be rationalized by the mechanical properties endowed by their hybrid inorganic–organic nanoporous structures. While these characteristics create intriguing application prospects, the same attributes also present challenges that will need to be overcome to enable the integration of MOFs with technologies where these promising traits can be exploited. In this review, emerging opportunities and challenges are identified for MOF-enabled device functionality and technological applications that arise from their fascinating mechanical properties. This is discussed not only in the context of their more well-studiedmore » gas storage and separation applications, but also for instances where MOFs serve as components of functional nanodevices. Recent advances in understanding MOF mechanical structure–property relationships due to attributes such as defects and interpenetration are highlighted, and open questions related to state-of-the-art computational approaches for quantifying their mechanical properties are critically discussed.« less

Mechanical Properties in Metal-Organic Frameworks: Emerging Opportunities and Challenges for Device Functionality and Technological Applications.

PubMed

Burtch, Nicholas C; Heinen, Jurn; Bennett, Thomas D; Dubbeldam, David; Allendorf, Mark D

2017-11-17

Some of the most remarkable recent developments in metal-organic framework (MOF) performance properties can only be rationalized by the mechanical properties endowed by their hybrid inorganic-organic nanoporous structures. While these characteristics create intriguing application prospects, the same attributes also present challenges that will need to be overcome to enable the integration of MOFs with technologies where these promising traits can be exploited. In this review, emerging opportunities and challenges are identified for MOF-enabled device functionality and technological applications that arise from their fascinating mechanical properties. This is discussed not only in the context of their more well-studied gas storage and separation applications, but also for instances where MOFs serve as components of functional nanodevices. Recent advances in understanding MOF mechanical structure-property relationships due to attributes such as defects and interpenetration are highlighted, and open questions related to state-of-the-art computational approaches for quantifying their mechanical properties are critically discussed. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Physics is …; The Physicist explores attributes of physics

NASA Astrophysics Data System (ADS)

Baker, F. Todd

2016-12-01

He's back! 'The physicist'returns with an entirely new compilation of questions and answers from his long-lived website where laypeople can ask questions about anything physics related. This book focuses on adjectives (practical, beautiful, surprising, cool, frivolous) instead of nouns like the first two books (atoms, photons, quanta, mechanics, relativity). The answers within 'Physics Is' are responses to people looking for answers to fascinating (and often uninformed) questions. It covers topics such as sports, electromagnetism, gravitational theory, special relativity, superheroes, videogames, and science fiction. These books are designed for laypeople and rely heavily on concepts rather than formalism. That said, they keep the physics correct and don't water down, so expert physicists will find this book and its two companion titles fun reads. They may actually recognize similar questions posed to them by friends and family. As with the first two books, 'Physics Is' ends with a chapter with questions from people who think that 'The physicist' is a psychic and from people who think they have the answers to life, the universe and everything.

Garden greenery and the health of older people in residential care facilities: a multi-level cross-sectional study.

PubMed

Dahlkvist, Eva; Hartig, Terry; Nilsson, Annika; Högberg, Hans; Skovdahl, Kirsti; Engström, Maria

2016-09-01

To test the relationship between greenery in gardens at residential facilities for older people and the self-perceived health of residents, mediated by experiences of being away and fascination when in the garden and the frequency of visitation there. To examine how these indirect effects vary with the number of physical barriers to visiting the garden. Many older people in residential facilities suffer from complex health problems. Access to a green outdoor environment may enable psychological distance, engage effortless attention, encourage more frequent visitation and promote resident health. A multi-level, cross-sectional, correlational design. Questionnaires were administered June-August, 2011 to convenience samples of residents at 72 facilities for older people with complex healthcare needs. One to 10 eligible residents were sampled during self-motivated garden visits at each facility (n = 290). They reported on their garden experiences and health. Facility staff reported on objective garden characteristics and barriers to access. A serial mediation model was tested with multiple linear regression analysis. The total indirect effect of greenery on self-perceived health was positive and significant. Garden greenery appears to affect health by enhancing a sense of being away, affording possibilities to experience the outdoor environment as interesting and encouraging visitation. Among residents in homes with multiple barriers, only fascination mediated the relationship between greenery and self-perceived health. Ample greenery in outdoor space at residential facilities for older people appears to promote experiences of being away and fascination, more frequent visitation and better health. © 2016 The Authors. Journal of Advanced Nursing Published by John Wiley & Sons Ltd.

Peppytides: Interactive Models of Polypeptide Chains

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zuckermann, Ron; Chakraborty, Promita; Derisi, Joe

2014-01-21

Peppytides are scaled, 3D-printed models of polypeptide chains that can be folded into accurate protein structures. Designed and created by Berkeley Lab Researcher, Promita Chakraborty, and Berkeley Lab Senior Scientist, Dr. Ron Zuckermann, Peppytides are accurate physical models of polypeptide chains that anyone can interact with and fold intro various protein structures - proving to be a great educational tool, resulting in a deeper understanding of these fascinating structures and how they function. Build your own Peppytide model and learn about how nature's machines fold into their intricate architectures!

Peppytides: Interactive Models of Polypeptide Chains

ScienceCinema

Zuckermann, Ron; Chakraborty, Promita; Derisi, Joe

2018-06-08

Peppytides are scaled, 3D-printed models of polypeptide chains that can be folded into accurate protein structures. Designed and created by Berkeley Lab Researcher, Promita Chakraborty, and Berkeley Lab Senior Scientist, Dr. Ron Zuckermann, Peppytides are accurate physical models of polypeptide chains that anyone can interact with and fold intro various protein structures - proving to be a great educational tool, resulting in a deeper understanding of these fascinating structures and how they function. Build your own Peppytide model and learn about how nature's machines fold into their intricate architectures!

Electro-Mechanical Resonance Curves

NASA Astrophysics Data System (ADS)

Greenslade, Thomas B.

2018-03-01

Recently I have been investigating the frequency response of galvanometers. These are direct-current devices used to measure small currents. By using a low-frequency function generator to supply the alternating-current signal and a stopwatch smartphone app to measure the period, I was able to take data to allow a resonance curve to be drawn. This is the sort of project that should provide a fascinating research experience for the introductory physics student. In this article I will discuss the galvanometers that I used in this work, and will show a resonance curve for one of them.

An environmentally benign route for the development of compressible, thermally insulating and fire retardant aerogels through self-assembling the silk fibroin biopolymer inside the silica structure - An approach towards 3D printing of aerogels.

PubMed

Maleki, Hajar; Montes, Susan; Hayati-Roodbari, Nastaran; Putz, Florian; Huesing, Nicola

2018-06-04

Thanks to the exceptional materials properties of silica aerogels, this fascinating highly porous material has found high performance and real-life applications in various modern industries. However, a requirement for a broadening of these applications is based on the further improvement of their properties especially with regard to mechanical strength and post-synthesis processability with minimum compromise to the other physical properties. Here, we report an entirely novel, simple and aqueous based synthesis approach to prepare mechanically robust aerogel hybrids by co-gelation of silk fibroin (SF) biopolymer, extracted from silkworm cocoons. The synthesis is based on a one-step sequential processes of acid catalysis (physical) crosslinking of the SF biopolymer and simultaneous polycondensation of tetramethyl orthosilicate (TMOS), in the presence of 5-(trimethoxysilyl)pentanoic acid (TMSPA) as a coupling agent and subsequent solvent exchange and supercritical drying. Extensive characterizations by solid-state 1H-NMR, 29Si-NMR, and 2D 1H-29Si heteronuclear correlation (HETCOR) MAS NMR spectroscopy as well as various microscopic techniques (SEM, TEM) and mechanical assessment, confirmed the molecular-level homogeneity of the hybrid nanostructure. The developed silica-SF aerogel hybrids contained an improved set of material properties, such as low density (ρb, average = 0.11 - 0.2 g cm-3), high porosity (~90%), high specific surface area (~ 400-800 m2 g-1), excellent flexibility in compression (up to 80% of strain) with three-order of magnitude improvement in the Young's modulus over that of pristine silica aerogels. In addition, the silica-SF hybrid aerogels are fire retardant and demonstrated excellent thermal insulation performance with thermal conductivities (λ) of (0.033-0.039 Wm-1 K-1). As a further advantage, the formulated hybrid silica-SF aerogel showed an excellent printability in the wet state using a micro-extrusion based 3D printing approach. The printed structures had comparable properties to their monolith counterparts, improving post-synthesis processing or shaping of the silica aerogels significantly. Finally, the hybrid silica-SF aerogels reported in here represents significant progress for mechanically customized and robust aerogel for multi-purpose applications namely as customized thermal insulation material or as dual porous open-cell biomaterial used in regenerative medicine.

Understanding the Magic of the Bicycle; Basic scientific explanations to the two-wheeler's mysterious and fascinating behavior

NASA Astrophysics Data System (ADS)

Connolly, Joseph W.

The bicycle is a common, yet unique mechanical contraption in our world. In spite of this, the bike's physical and mechanical principles are understood by a select few. You do not have to be a genius to join this small group of people who understand the physics of cycling. This is your guide to fundamental principles (such as Newton's laws) and the book provides intuitive, basic explanations for the bicycle's behaviour. Each concept is introduced and illustrated with simple, everyday examples. Although cycling is viewed by most as a fun activity, and almost everyone acquires the basic skills at a young age, few understand the laws of nature that give magic to the ride. This is a closer look at some of these fun, exhilarating, and magical aspects of cycling. In the reading, you will also understand other physical principles such as motion, force, energy, power, heat, and temperature.

'Pro et contra' ionic liquid drugs - Challenges and opportunities for pharmaceutical translation.

PubMed

Balk, Anja; Holzgrabe, Ulrike; Meinel, Lorenz

2015-08-01

Ionic liquids (ILs) are organic salts with a melting point below 100°C. Active pharmaceutical ingredients (APIs) are transformed into ILs by combining them with typically large yet charged counterions. ILs hold promise to build a large design space for relevant pharmaceutical parameters, particularly for poorly water soluble drugs. It is for this wide design space that ILs may be the entry into the fascinating vision of modifying physico-chemical properties without the need to structurally modify the active pharmaceutical ingredient itself. This extremely intriguing pharmaceutical option is critically discussed including its potential and limitations. The review is starting off with an introduction to the metathesis and characterization of ILs, and leads over to examples for pharmaceutical application, including enhancement of dissolution rate and kinetic solubility and hygroscopicity adaptation, respectively. Tuning biopharmaceutics and toxicology by proper IL design is another focus. The review connects the interrelated chemical, physical, pharmaceutical, and toxicological outcome of API-ILs, serving as guidance for the formulation scientist who aims at expanding ones armamentarium for poorly water soluble APIs while avoiding structural modification, thereof. Copyright © 2015 Elsevier B.V. All rights reserved.

Broadband atomic-layer MoS₂ optical modulators for ultrafast pulse generations in the visible range.

PubMed

Zhang, Yuxia; Yu, Haohai; Zhang, Rui; Zhao, Gang; Zhang, Huaijin; Chen, Yanxue; Mei, Liangmo; Tonelli, Mauro; Wang, Jiyang

2017-02-01

Visible lasers are a fascinating regime, and their significance is illustrated by the 2014 Noble prizes in physics and chemistry. With the development of blue laser diodes (LDs), the LD-pumped solid-state visible lasers become a burgeoning direction today. Constrained by the scarce visible optical modulators, the solid-state ultrafast visible lasers are rarely realized. Based on the bandgap structure and optoelectronic properties of atomic-layer MoS₂, it can be proposed that MoS₂ has the potential as a visible optical modulator. Here, by originally revealing layer-dependent nonlinear absorption of the atomic-layer MoS₂ in the visible range, broadband atomic-layer MoS₂ optical modulators for the visible ultrafast pulse generation are developed and selected based on the proposed design criteria for novel two-dimensional (2D) optical modulators. By applying the selected MoS₂ optical modulators in the solid-state praseodymium lasers, broadband mode-locked ultrafast lasers from 522 to 639 nm are originally realized. We believe that this Letter should promote the development of visible ultrafast photonics and further applications of 2D optoelectronic materials.

Striated Acto-Myosin Fibers Can Reorganize and Register in Response to Elastic Interactions with the Matrix

PubMed Central

Friedrich, Benjamin M.; Buxboim, Amnon; Discher, Dennis E.; Safran, Samuel A.

2011-01-01

The remarkable striation of muscle has fascinated many for centuries. In developing muscle cells, as well as in many adherent, nonmuscle cell types, striated, stress fiberlike structures with sarcomere-periodicity tend to register: Based on several studies, neighboring, parallel fibers at the basal membrane of cultured cells establish registry of their respective periodic sarcomeric architecture, but, to our knowledge, the mechanism has not yet been identified. Here, we propose for cells plated on an elastic substrate or adhered to a neighboring cell, that acto-myosin contractility in striated fibers close to the basal membrane induces substrate strain that gives rise to an elastic interaction between neighboring striated fibers, which in turn favors interfiber registry. Our physical theory predicts a dependence of interfiber registry on externally controllable elastic properties of the substrate. In developing muscle cells, registry of striated fibers (premyofibrils and nascent myofibrils) has been suggested as one major pathway of myofibrillogenesis, where it precedes the fusion of neighboring fibers. This suggests a mechanical basis for the optimal myofibrillogenesis on muscle-mimetic elastic substrates that was recently observed by several groups in cultures of mouse-, human-, and chick-derived muscle cells. PMID:21641316

Vapourisers: Physical Principles and Classification

PubMed Central

Dhulkhed, Vithal; Shetti, Akshaya; Naik, Shraddha; Dhulkhed, Pavan

2013-01-01

Vapourisers have evolved from rudimentary inhalers to the microprocessor controlled, temperature compensated and flow sensing devices, which are universal today. The improvements in the design was influenced by the development of potent inhalational anaesthetics, unique properties of some agents, a deeper understanding of their mechanism of action, inherent flaws in the older vapourisers, mechanical problems due to thymol deposition, factors influencing their output such as temperature and pressure variations. It is important to review the principles governing the design of the vapouriser to gain insight into their working. It is fascinating to know how some of the older vapourisers, popularly used in the past, functioned. The descendant of Oxford Miniature Vapourizer, the Triservice vapouriser is still a part of the military anaesthesia draw over equipment meant for field use whereas the Copper Kettle the first precision device is the fore-runner of the Tec 6 and Aladdin cassette vapouriser. Anaesthesia trainees if exposed to draw over techniques get a deeper understanding of equipment and improved skills for disaster situations. In the recent advanced versions of the vapouriser a central processing unit in the anaesthetic machine controls the operation by continuously monitoring and adjusting fresh gas flow through the vapouriser to maintain desired concentration of the vapour. PMID:24249878

PdCo/Pd-Hexacyanocobaltate Hybrid Nanoflowers: Cyanogel-Bridged One-Pot Synthesis and Their Enhanced Catalytic Performance

NASA Astrophysics Data System (ADS)

Liu, Zhen-Yuan; Fu, Geng-Tao; Zhang, Lu; Yang, Xiao-Yu; Liu, Zhen-Qi; Sun, Dong-Mei; Xu, Lin; Tang, Ya-Wen

2016-08-01

Elaborate architectural manipulation of nanohybrids with multi-components into controllable 3D hierarchical structures is of great significance for both fundamental scientific interest and realization of various functionalities, yet remains a great challenge because different materials with distinct physical/chemical properties could hardly be incorporated simultaneously into the synthesis process. Here, we develop a novel one-pot cyanogel-bridged synthetic approach for the generation of 3D flower-like metal/Prussian blue analogue nanohybrids, namely PdCo/Pd-hexacyanocobaltate for the first time. The judicious introduction of polyethylene glycol (PEG) and the formation of cyanogel are prerequisite for the successful fabrication of such fascinating hierarchical nanostructures. Due to the unique 3D hierarchical structure and the synergistic effect between hybrid components, the as-prepared hybrid nanoflowers exhibit a remarkable catalytic activity and durability toward the reduction of Rhodamine B (RhB) by NaBH4. We expect that the obtained hybrid nanoflowers may hold great promises in water remediation field and beyond. Furthermore, the facile synthetic strategy presented here for synthesizing functional hybrid materials can be extendable for the synthesis of various functional hybrid nanomaterials owing to its versatility and feasibility.

PdCo/Pd-Hexacyanocobaltate Hybrid Nanoflowers: Cyanogel-Bridged One-Pot Synthesis and Their Enhanced Catalytic Performance.

PubMed

Liu, Zhen-Yuan; Fu, Geng-Tao; Zhang, Lu; Yang, Xiao-Yu; Liu, Zhen-Qi; Sun, Dong-Mei; Xu, Lin; Tang, Ya-Wen

2016-08-30

Elaborate architectural manipulation of nanohybrids with multi-components into controllable 3D hierarchical structures is of great significance for both fundamental scientific interest and realization of various functionalities, yet remains a great challenge because different materials with distinct physical/chemical properties could hardly be incorporated simultaneously into the synthesis process. Here, we develop a novel one-pot cyanogel-bridged synthetic approach for the generation of 3D flower-like metal/Prussian blue analogue nanohybrids, namely PdCo/Pd-hexacyanocobaltate for the first time. The judicious introduction of polyethylene glycol (PEG) and the formation of cyanogel are prerequisite for the successful fabrication of such fascinating hierarchical nanostructures. Due to the unique 3D hierarchical structure and the synergistic effect between hybrid components, the as-prepared hybrid nanoflowers exhibit a remarkable catalytic activity and durability toward the reduction of Rhodamine B (RhB) by NaBH4. We expect that the obtained hybrid nanoflowers may hold great promises in water remediation field and beyond. Furthermore, the facile synthetic strategy presented here for synthesizing functional hybrid materials can be extendable for the synthesis of various functional hybrid nanomaterials owing to its versatility and feasibility.

PdCo/Pd-Hexacyanocobaltate Hybrid Nanoflowers: Cyanogel-Bridged One-Pot Synthesis and Their Enhanced Catalytic Performance

PubMed Central

Liu, Zhen-Yuan; Fu, Geng-Tao; Zhang, Lu; Yang, Xiao-Yu; Liu, Zhen-Qi; Sun, Dong-Mei; Xu, Lin; Tang, Ya-Wen

2016-01-01

Elaborate architectural manipulation of nanohybrids with multi-components into controllable 3D hierarchical structures is of great significance for both fundamental scientific interest and realization of various functionalities, yet remains a great challenge because different materials with distinct physical/chemical properties could hardly be incorporated simultaneously into the synthesis process. Here, we develop a novel one-pot cyanogel-bridged synthetic approach for the generation of 3D flower-like metal/Prussian blue analogue nanohybrids, namely PdCo/Pd-hexacyanocobaltate for the first time. The judicious introduction of polyethylene glycol (PEG) and the formation of cyanogel are prerequisite for the successful fabrication of such fascinating hierarchical nanostructures. Due to the unique 3D hierarchical structure and the synergistic effect between hybrid components, the as-prepared hybrid nanoflowers exhibit a remarkable catalytic activity and durability toward the reduction of Rhodamine B (RhB) by NaBH4. We expect that the obtained hybrid nanoflowers may hold great promises in water remediation field and beyond. Furthermore, the facile synthetic strategy presented here for synthesizing functional hybrid materials can be extendable for the synthesis of various functional hybrid nanomaterials owing to its versatility and feasibility. PMID:27573057

Eukaryotic and Prokaryotic Cytoskeletons: Structure and Mechanics

NASA Astrophysics Data System (ADS)

Gopinathan, Ajay

2013-03-01

The eukaryotic cytoskeleton is an assembly of filamentous proteins and a host of associated proteins that collectively serve functional needs ranging from spatial organization and transport to the production and transmission of forces. These systems can exhibit a wide variety of non-equilibrium, self-assembled phases depending on context and function. While much recent progress has been made in understanding the self-organization, rheology and nonlinear mechanical properties of such active systems, in this talk, we will concentrate on some emerging aspects of cytoskeletal physics that are promising. One such aspect is the influence of cytoskeletal network topology and its dynamics on both active and passive intracellular transport. Another aspect we will highlight is the interplay between chirality of filaments, their elasticity and their interactions with the membrane that can lead to novel conformational states with functional implications. Finally we will consider homologs of cytoskeletal proteins in bacteria, which are involved in templating cell growth, segregating genetic material and force production, which we will discuss with particular reference to contractile forces during cell division. These prokaryotic structures function in remarkably similar yet fascinatingly different ways from their eukaryotic counterparts and can enrich our understanding of cytoskeletal functioning as a whole.

Localization Transport in Granular and Nanoporous Carbon Systems.

NASA Astrophysics Data System (ADS)

Fung, Alex Weng Pui

Porous carbon materials have long since been used in industry to make capacitors and adsorption agents because of their high specific surface area. Although their adsorption properties have been extensively studied, we have not seen the same vigor in the investigation of their physical properties, which are important not only for providing complementary characterization methods, but also for understanding the physics which underlies the manufacturing process and motivates intelligent design of these materials. The study of the new physics in these novel nanoporous materials also straddles the scientific forefronts of nanodimensional and disordered systems. In this thesis, we study the structural and electrical properties of two nanoporous carbons, namely activated carbon fibers and carbon aerogels. Specifically, we perform Raman scattering, x-ray diffraction, magnetic susceptibility, electrical transport and magnetotransport experiments. Results from other experiments reported in the literature or communicated to us by our collaborators, such as porosity and surface area measurements by adsorption methods, electron spin resonance, transmission electron microscopy, mechanical properties measurements and so on, are also frequently used in this thesis for additional characterization information. By correlating all the relevant results, we obtain the structure -property relationships in these nanoporous materials. This study shows that the transport properties of these porous materials can be used on one hand for sensitive characterization of complex materials, and on the other hand, for observing interesting and unusual physical phenomena. For example, as-prepared nanoporous carbon systems, exhibit in their low-temperature electrical conductivity a universal temperature dependence which is characteristic of a granular metallic system, despite their morphological differences. By studying further the magnetoresistance in these carbon materials, it is found that the variable-range hopping mechanism cannot be totally disregarded in the understanding of the low-temperature conduction process in some granular metals having a similar morphology. In the transport study of the heat-treated activated carbon fibers, the surprising observation of a negative magnetoresistance at room temperature has also provided some insight into the weak localization phenomenon in the percolation limit. In particular, the effects of anomalous diffusion in a percolating system is now included in the calculations of the weak-localization corrections to the conductivity and magnetoresistance, yielding a new temperature dependence of the dephasing distance. These localization phenomena in the nanoporous carbon structures studied here are mostly understandable in terms of the existing theories for disordered systems, but their detailed interpretations often indicate problems and shortcomings in some of these theories, at times because the physical properties of the nanoporous carbon materials studied here are unique among disordered materials. Hence, nanoporous carbons belong to a distinct class of disordered systems in their own rights. In the field of transport in disordered systems, porous media also seem to have been an oversight of the general research community, although theoretical percolation studies have often touched upon systems with similar morphologies. This thesis presents a study of the transport behavior in nanoporous carbons over the full spectrum of disorder, controlled by heat treatment, starting from the strong localization regime, then crossing the metal-insulator transition, and finally to the weak localization limit. In each regime of disorder, the existing theories are either adapted, and when necessary, extended to explain the observed transport behavior in these fascinating materials. (Copies available exclusively from MIT Libraries, Rm. 14-0551, Cambridge, MA 02139-4307. Ph. 617 -253-1690.).

Molecular Approach to Conjugated Polymers with Biomimetic Properties.

PubMed

Baek, Paul; Voorhaar, Lenny; Barker, David; Travas-Sejdic, Jadranka

2018-06-13

The field of bioelectronics involves the fascinating interplay between biology and human-made electronics. Applications such as tissue engineering, biosensing, drug delivery, and wearable electronics require biomimetic materials that can translate the physiological and chemical processes of biological systems, such as organs, tissues. and cells, into electrical signals and vice versa. However, the difference in the physical nature of soft biological elements and rigid electronic materials calls for new conductive or electroactive materials with added biomimetic properties that can bridge the gap. Soft electronics that utilize organic materials, such as conjugated polymers, can bring many important features to bioelectronics. Among the many advantages of conjugated polymers, the ability to modulate the biocompatibility, solubility, functionality, and mechanical properties through side chain engineering can alleviate the issues of mechanical mismatch and provide better interface between the electronics and biological elements. Additionally, conjugated polymers, being both ionically and electrically conductive through reversible doping processes provide means for direct sensing and stimulation of biological processes in cells, tissues, and organs. In this Account, we focus on our recent progress in molecular engineering of conjugated polymers with tunable biomimetic properties, such as biocompatibility, responsiveness, stretchability, self-healing, and adhesion. Our approach is general and versatile, which is based on functionalization of conjugated polymers with long side chains, commonly polymeric or biomolecules. Applications for such materials are wide-ranging, where we have demonstrated conductive, stimuli-responsive antifouling, and cell adhesive biointerfaces that can respond to external stimuli such as temperature, salt concentration, and redox reactions, the processes that in turn modify and reversibly switch the surface properties. Furthermore, utilizing the advantageous chemical, physical, mechanical and functional properties of the grafts, we progressed into grafting of the long side chains onto conjugated polymers in solution, with the vision of synthesizing solution-processable conjugated graft copolymers with biomimetic functionalities. Examples of the developed materials to date include rubbery and adhesive photoluminescent plastics, biomolecule-functionalized electrospun biosensors, thermally and dually responsive photoluminescent conjugated polymers, and tunable self-healing, adhesive, and stretchable strain sensors, advanced functional biocidal polymers, and filtration membranes. As outlined in these examples, the applications of these biomimetic, conjugated polymers are still in the development stage toward truly printable, organic bioelectronic devices. However, in this Account, we advocate that molecular engineering of conjugated polymers is an attractive approach to a versatile class of organic electronics with both ionic and electrical conductivity as well as mechanical properties required for next-generation bioelectronics.

Field-induced superconducting phase of FeSe in the BCS-BEC cross-over

PubMed Central

Kasahara, Shigeru; Watashige, Tatsuya; Hanaguri, Tetsuo; Kohsaka, Yuhki; Yamashita, Takuya; Shimoyama, Yusuke; Mizukami, Yuta; Endo, Ryota; Ikeda, Hiroaki; Aoyama, Kazushi; Terashima, Taichi; Uji, Shinya; Wolf, Thomas; von Löhneysen, Hilbert; Shibauchi, Takasada; Matsuda, Yuji

2014-01-01

Fermi systems in the cross-over regime between weakly coupled Bardeen–Cooper–Schrieffer (BCS) and strongly coupled Bose–Einstein-condensate (BEC) limits are among the most fascinating objects to study the behavior of an assembly of strongly interacting particles. The physics of this cross-over has been of considerable interest both in the fields of condensed matter and ultracold atoms. One of the most challenging issues in this regime is the effect of large spin imbalance on a Fermi system under magnetic fields. Although several exotic physical properties have been predicted theoretically, the experimental realization of such an unusual superconducting state has not been achieved so far. Here we show that pure single crystals of superconducting FeSe offer the possibility to enter the previously unexplored realm where the three energies, Fermi energy εF, superconducting gap Δ, and Zeeman energy, become comparable. Through the superfluid response, transport, thermoelectric response, and spectroscopic-imaging scanning tunneling microscopy, we demonstrate that εF of FeSe is extremely small, with the ratio Δ/εF∼1(∼0.3) in the electron (hole) band. Moreover, thermal-conductivity measurements give evidence of a distinct phase line below the upper critical field, where the Zeeman energy becomes comparable to εF and Δ. The observation of this field-induced phase provides insights into previously poorly understood aspects of the highly spin-polarized Fermi liquid in the BCS-BEC cross-over regime. PMID:25378706

Analytical methods in the high conversion reactor core design

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zeggel, W.; Oldekop, W.; Axmann, J.K.

High conversion reactor (HCR) design methods have been used at the Technical University of Braunschweig (TUBS) with the technological support of Kraftwerk Union (KWU). The present state and objectives of this cooperation between KWU and TUBS in the field of HCRs have been described using existing design models and current activities aimed at further development and validation of the codes. The hard physical and thermal-hydraulic boundary conditions of pressurized water reactor (PWR) cores with a high degree of fuel utilization result from the tight packing of the HCR fuel rods and the high fissionable plutonium content of the fuel. Inmore » terms of design, the problem will be solved with rod bundles whose fuel rods are adjusted by helical spacers to the proposed small rod pitches. These HCR properties require novel computational models for neutron physics, thermal hydraulics, and fuel rod design. By means of a survey of the codes, the analytical procedure for present-day HCR core design is presented. The design programs are currently under intensive development, as design tools with a solid, scientific foundation and with essential parameters that are widely valid and are required for a promising optimization of the HCR core. Design results and a survey of future HCR development are given. In this connection, the reoptimization of the PWR core in the direction of an HCR is considered a fascinating scientific task, with respect to both economic and safety aspects.« less

Resource letter SH-1: superfluid helium

NASA Astrophysics Data System (ADS)

Hallock, Robert B.

1982-03-01

The resource letter covers the general subject of superfluid helium and treats 3He and 3He-4He mixtures as well as 4He. No effort has been made to include the fascinating experiments on either solid helium or the equally fascinating work on adsorbed helium where the helium coverage is below that necessary for superfluidity. An earlier resource letter by C. T. Lane [Am. J. Phys. 35, 367 (1967)] may be consulted for additional comments on some of the cited earlier manuscripts, but the present work is self-contained and may be used independently. Many high-quality research reports have not been cited here. Rather, the author has tried in most cases to include works particularly readable or relevant. There is a relatively heavy emphasis on experimental references. The primary reason is that these works tend to be more generally readable. No doubt some works that might have been included, have not, and for this the author takes responsibility with apology. Articles selected for incorporation in a reprint volume (to be published separately by the American Association of Physics Teachers) are marked with an asterisk(*). Following each referenced work the general level of difficulty is indicated by E, I, or A for elementary, intermediate, or advanced.

Transforming Matter: A History of Chemistry from Alchemy to the Buckyball by Trevor H. Levere

NASA Astrophysics Data System (ADS)

Truman Schwartz, A.

2001-08-01

By and large, the chemistry is presented in a logical and comprehensible form. People and ideas are emphasized. However, because of Transforming Matter's brevity and its intended audience, there are inevitable oversimplifications and sins of omission. There were also a few sins of commission in the uncorrected proof that I read. On page 159 there is an implication that equilibrium does not exist in "irreversible" processes such as the precipitation of silver chloride. The author rushes through electron orbitals in one paragraph (page 178) in which he mistakenly refers to something he calls "Planck's equation" and appears to identify p orbitals with n = 2. On the next page we are told that "overlapping p orbitals produced a pi bond." True, but they can also produce a sigma bond. And on page 198 we learn that "a single Freon molecule can cause the decomposition of millions of ozone molecules." The most frequently cited estimate is 100,000 ozone molecules decomposed per Freon molecule. This may be the nit picking of a physical chemist, but it does reflect some of the hazards of trying to achieve an admirable goal--introducing readers to the fascinating history of our fascinating science.

Rotational Properties of Jupiter Trojan 1173 Anchises

NASA Astrophysics Data System (ADS)

Chatelain, Joseph; Henry, Todd; French, Linda; Trilling, David

2015-11-01

Anchises (1173) is a large Trojan asteroid librating about Jupiter’s L5 Lagrange point. Here we examine its rotational and lightcurve properties by way of data collected over a 3.5 year observing campaign. The length of the campaign means that data were gathered for more than a quarter of Anchises' full orbital revolution which allows for accurate determinations of pole orientation and bulk shape properties for the asteroid that can then be compared to results of previous work (i.e. French 1987, Horner et al. 2012). In addition to light curves, photometric data taken during this campaign could potentially detect color differences between hemispheres as the viewing geometry changes over time. Understanding these details about a prominent member of the Jupiter Trojans may help us better understand the history of this fascinating and important group of asteroids.

Duality of two pairs of double-walled nanotubes consisting of S=1 and S=3/2 spins probed by means of a quantum simulation approach

NASA Astrophysics Data System (ADS)

Liu, Zhaosen; Ian, Hou

2017-01-01

Using a quantum simulation approach, we investigate in the present work the spontaneous magnetic properties of two pairs of double-walled cylindrical nanotubes consisting of different spins. Our simulated magnetic and thermodynamic properties for each pair of them are precisely identical, exhibiting a fascinating property of the nature world and demonstrating the correctness of our simulation approach. The second pair of nanotubes are frustrated, two magnetic phases of distinct spin configurations appear in the low temperature region, but only the inner layer consisting of small spins is frustrated evidently, its magnetization is considerably suppressed in the high temperature phase. Moreover, the nanosystems exhibit typical Ising-like behavior due to the uniaxial anisotropy along the z-direction, and evident finite-size effects as well.

Image processing analysis of traditional Gestalt vision experiments

NASA Astrophysics Data System (ADS)

McCann, John J.

2002-06-01

In the late 19th century, the Gestalt Psychology rebelled against the popular new science of Psychophysics. The Gestalt revolution used many fascinating visual examples to illustrate that the whole is greater than the sum of all the parts. Color constancy was an important example. The physical interpretation of sensations and their quantification by JNDs and Weber fractions were met with innumerable examples in which two 'identical' physical stimuli did not look the same. The fact that large changes in the color of the illumination failed to change color appearance in real scenes demanded something more than quantifying the psychophysical response of a single pixel. The debates continues today with proponents of both physical, pixel-based colorimetry and perceptual, image- based cognitive interpretations. Modern instrumentation has made colorimetric pixel measurement universal. As well, new examples of unconscious inference continue to be reported in the literature. Image processing provides a new way of analyzing familiar Gestalt displays. Since the pioneering experiments by Fergus Campbell and Land, we know that human vision has independent spatial channels and independent color channels. Color matching data from color constancy experiments agrees with spatial comparison analysis. In this analysis, simple spatial processes can explain the different appearances of 'identical' stimuli by analyzing the multiresolution spatial properties of their surrounds. Benary's Cross, White's Effect, the Checkerboard Illusion and the Dungeon Illusion can all be understood by the analysis of their low-spatial-frequency components. Just as with color constancy, these Gestalt images are most simply described by the analysis of spatial components. Simple spatial mechanisms account for the appearance of 'identical' stimuli in complex scenes. It does not require complex, cognitive processes to calculate appearances in familiar Gestalt experiments.

Physics and Religion

NASA Astrophysics Data System (ADS)

Finegold, Leonard; Thomson-Hohl, Timothy; Tyagi, Som

2010-02-01

Aspects of religion with science/religion have been covered in the pages of Physics Today and Physics News. They reflect wide student interest in these topics. For a decade, two physicists and a campus minister have taught a writing-intensive course ``Issues in Science and Religion'' Physics/Sociology 137. Here we outline our course (open to all students), to encourage others contemplating similar courses. Many students escape an exposure to the basics of science, and so we capture them. We discuss inter alia relativity and uncertainties (both quantum and classical, which fascinate students), including their controversial relationships with religion. One of us (LF), as a biophysicist, was asked to cover evolution, which topic has proved to be rather popular: Various scientific organizations have publicly defended evolution against intelligent design and creationism. To keep the quality of the course, we have restricted enrollment. Here we discuss only the science/physics part of the course. Visiting speakers (covering the gamut from religious to non-religious) have included a Vatican astronomer, a Sloan survey cosmologist, the director of SETI, a neuropsychologist, a sociologist, historians of science and theologians. )

Molecular structure of bottlebrush polymers in melts

PubMed Central

Paturej, Jarosław; Sheiko, Sergei S.; Panyukov, Sergey; Rubinstein, Michael

2016-01-01

Bottlebrushes are fascinating macromolecules that display an intriguing combination of molecular and particulate features having vital implications in both living and synthetic systems, such as cartilage and ultrasoft elastomers. However, the progress in practical applications is impeded by the lack of knowledge about the hierarchic organization of both individual bottlebrushes and their assemblies. We delineate fundamental correlations between molecular architecture, mesoscopic conformation, and macroscopic properties of polymer melts. Numerical simulations corroborate theoretical predictions for the effect of grafting density and side-chain length on the dimensions and rigidity of bottlebrushes, which effectively behave as a melt of flexible filaments. These findings provide quantitative guidelines for the design of novel materials that allow architectural tuning of their properties in a broad range without changing chemical composition. PMID:28861466

Two-dimensional MoTe2 materials: From synthesis, identification, and charge transport to electronics applications

NASA Astrophysics Data System (ADS)

Chang, Yuan-Ming; Lin, Che-Yi; Lin, Yen-Fu; Tsukagoshi, Kazuhito

2016-11-01

We present a review of recent developments in the synthesis, thickness identification, electronic properties, and possible applications of layered MoTe2 flakes. Special emphasis is made on two-dimensional (2D) MoTe2 semiconductors and the extensive research in recent years on their applications in electronics. Layered MoTe2 flakes have been the focus of substantial interest in the research community because of their fascinating characteristics, including an appropriate band gap and a simple fabrication method (exfoliation) to form layered nanomaterials. Our aim is to provide the readers an overview of layered MoTe2 flakes and to understand their properties, which may lead to their applications in micro- and nanoelectronics.

Few-Layered Black Phosphorus: From Fabrication and Customization to Biomedical Applications.

PubMed

Wang, Huaiyu; Yu, Xue-Feng

2018-02-01

As a new kind of 2D material, black phosphorus has gained increased attention in the past three years. Although few-layered black phosphorus nanosheets (BPs) degrade quickly under ambient conditions to phosphate anions, which greatly hampers their optical and electronic applications, this property also makes BPs highly biocompatible and biodegradable, and is regarded as an advantage for various biomedical applications. This Concept summarizes the state-of-art progresses of BPs, from fabrication and surface modification to biomedical applications. It is expected that BPs with such fascinating properties will encourage more scientists to engage in expanding its biomedical applications by tackling the scientific challenges involved in their development. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Coherent-Interface-Assembled Ag2O-Anchored Nanofibrillated Cellulose Porous Aerogels for Radioactive Iodine Capture.

PubMed

Lu, Yun; Liu, Hongwei; Gao, Runan; Xiao, Shaoliang; Zhang, Ming; Yin, Yafang; Wang, Siqun; Li, Jian; Yang, Dongjiang

2016-10-26

Nanofibrillated cellulose (NFC) has received increasing attention in science and technology because of not only the availability of large amounts of cellulose in nature but also its unique structural and physical features. These high-aspect-ratio nanofibers have potential applications in water remediation and as a reinforcing scaffold in composites, coatings, and porous materials because of their fascinating properties. In this work, highly porous NFC aerogels were prepared based on tert-butanol freeze-drying of ultrasonically isolated bamboo NFC with 20-80 nm diameters. Then nonagglomerated 2-20-nm-diameter silver oxide (Ag 2 O) nanoparticles (NPs) were grown firmly onto the NFC scaffold with a high loading content of ∼500 wt % to fabricate Ag 2 O@NFC organic-inorganic composite aerogels (Ag 2 O@NFC). For the first time, the coherent interface and interaction mechanism between the cellulose I β nanofiber and Ag 2 O NPs are explored by high-resolution transmission electron microscopy and 3D electron tomography. Specifically, a strong hydrogen between Ag 2 O and NFC makes them grow together firmly along a coherent interface, where good lattice matching between specific crystal planes of Ag 2 O and NFC results in very small interfacial straining. The resulting Ag 2 O@NFC aerogels take full advantage of the properties of the 3D organic aerogel framework and inorganic NPs, such as large surface area, interconnected porous structures, and supreme mechanical properties. They open up a wide horizon for functional practical usage, for example, as a flexible superefficient adsorbent to capture I - ions from contaminated water and trap I 2 vapor for safe disposal, as presented in this work. The viable binding mode between many types of inorganic NPs and organic NFC established here highlights new ways to investigate cellulose-based functional nanocomposites.

Recent advances of ionic liquids and polymeric ionic liquids in capillary electrophoresis and capillary electrochromatography.

PubMed

Tang, Sheng; Liu, Shujuan; Guo, Yong; Liu, Xia; Jiang, Shengxiang

2014-08-29

Ionic liquids (ILs) and polymeric ionic liquids (PILs) with unique and fascinating properties have drawn considerable interest for their use in separation science, especially in chromatographic techniques. In this article, significant contributions of ILs and PILs in the improvement of capillary electrophoresis and capillary electrochromatography are described, and a specific overview of the most relevant examples of their applications in the last five years is also given. Accordingly, some general conclusions and future perspectives in these areas are discussed. Copyright © 2014 Elsevier B.V. All rights reserved.

The comparative study of bulk magneto-phonon and magnetic polaritons of lateral antiferromagnetic superlattices for potential THz applications

NASA Astrophysics Data System (ADS)

Ta, Jin-Xing; Han, Yu; Lan, Cheng

2016-02-01

Bulk magneto-phonon and magnetic polaritons of lateral antiferromagnetic superlattices for potential THz applications have been investigated in the framework of the effective medium theory. The dispersion relations applied for the system are displayed. In contrast with lateral FeF2/SiO2 superlattice, some fascinating polariton modes with negative group velocity signifying photonic band gap scenarios and attractive optical properties are observed from the numerical results presented with the example, lateral FeF2/TlBr superlattice.

From coupled elementary units to the complexity of the glass transition.

PubMed

Rehwald, Christian; Rubner, Oliver; Heuer, Andreas

2010-09-10

Supercooled liquids display fascinating properties upon cooling such as the emergence of dynamic length scales. Different models strongly vary with respect to the choice of the elementary subsystems as well as their mutual coupling. Here we show via computer simulations of a glass former that both ingredients can be identified via analysis of finite-size effects within the continuous-time random walk framework. The subsystems already contain complete information about thermodynamics and diffusivity, whereas the coupling determines structural relaxation and the emergence of dynamic length scales.

Experimental reconstruction of the Berry curvature in a topological Bloch band

NASA Astrophysics Data System (ADS)

Weitenberg, Christof; Flaeschner, Nick; Rem, Benno; Tarnowski, Matthias; Vogel, Dominik; Luehmann, Dirk-Soeren; Sengstock, Klaus

2016-05-01

Topological properties lie at the heart of many fascinating phenomena in solid state systems such as quantum Hall systems or Chern insulators. The topology can be captured by the distribution of Berry curvature, which describes the geometry of the eigenstates across the Brillouin zone. Employing fermionic ultracold atoms in a hexagonal optical lattice, we engineer the Berry curvature of the Bloch bands using resonant driving and measure it with full momentum resolution. Our results pave the way to explore intriguing phases of matter with interactions in topological band structures.

Two dimensional layered materials: First-principle investigation

NASA Astrophysics Data System (ADS)

Tang, Youjian

Two-dimensional layered materials have emerged as a fascinating research area due to their unique physical and chemical properties, which differ from those of their bulk counterparts. Some of these unique properties are due to carriers and transport being confined to 2 dimensions, some are due to lattice symmetry, and some arise from their large surface area, gateability, stackability, high mobility, spin transport, or optical accessibility. How to modify the electronic and magnetic properties of two-dimensional layered materials for desirable long-term applications or fundamental physics is the main focus of this thesis. We explored the methods of adsorption, intercalation, and doping as ways to modify two-dimensional layered materials, using density functional theory as the main computational methodology. Chapter 1 gives a brief review of density functional theory. Due to the difficulty of solving the many-particle Schrodinger equation, density functional theory was developed to find the ground-state properties of many-electron systems through an examination of their charge density, rather than their wavefunction. This method has great application throughout the chemical and material sciences, such as modeling nano-scale systems, analyzing electronic, mechanical, thermal, optical and magnetic properties, and predicting reaction mechanisms. Graphene and transition metal dichalcogenides are arguably the two most important two-dimensional layered materials in terms of the scope and interest of their physical properties. Thus they are the main focus of this thesis. In chapter 2, the structure and electronic properties of graphene and transition metal dichalcogenides are described. Alkali adsorption onto the surface of bulk graphite and metal intecalation into transition metal dichalcogenides -- two methods of modifying properties through the introduction of metallic atoms into layered systems -- are described in chapter 2. Chapter 3 presents a new method of tuning the electronic properties of 2D materials: resonant physisorption. An example is given for adsorption of polycyclic aromatic hydrocarbon molecules onto graphene. The energy levels of these molecules were fine tuned to make them resonate with the graphene Fermi level, thus enhancing the strength of their effect on the graphene electronic structure. Chapter 4 develops the idea of coupling two distinct surface adsorption systems across a suspended atomically thin membrane. We examine a system of dual-sided adsorption of potassium onto a graphene membrane. The sequence of adsorption patterns predicted undergoes a striking devil's staircase of intermediate coverage fractions as the difference in adsorbate chemical potential between the two sides of the membrane varies. Chapter 5 is devoted to magnetic and band structure engineering of transition metal dichalcogenides through introduction of magnetic atoms into the lattice. Semiconducting transition metal dichalcogenide systems such as MoS2 and WS2 have band gaps suitable for electronic and optoelectronic applications, but are not magnetic. By intercalating and doping in a carefully designed stoichiometric ratio that precisely controls the occupation and relative placement of the dopant and host levels, we can convert a semiconducting transition metal dichalcogenide system into a half-metal or -- more surprisingly -- a half-semiconductor, where the conduction band is fully spin polarized and the energy scale for magnetism is the band gap.

Microfabrication of SrRuO3 thin films on various oxide substrates using LaAlO3/BaOx sacrificial bilayers

NASA Astrophysics Data System (ADS)

Harada, Takayuki; Tsukazaki, Atsushi

2018-02-01

Oxides provide various fascinating physical properties that could find use in future device applications. However, the physical properties of oxides are often affected by formation of oxygen vacancies during device fabrication processes. In this study, to develop a damage-free patterning process for oxides, we focus on a lift-off process using a sacrificial template layer, by which we can pattern oxide thin films without severe chemical treatment or plasma bombardment. As oxides need high thin-film growth temperature, a sacrificial template needs to be made of thermally stable and easily etchable materials. To meet these requirements, we develop a sacrificial template with a carefully designed bilayer structure. Combining a thermally and chemically stable LaAlO3 and a water-soluble BaOx, we fabricated a LaAlO3/BaOx sacrificial bilayer. The patterned LaAlO3/BaOx sacrificial bilayers were prepared on oxide substrates by room-temperature pulsed laser deposition and standard photolithography process. The structure of the sacrificial bilayer can be maintained even in rather tough conditions needed for oxide thin film growth: several hundred degrees Celsius under high oxygen pressure. Indeed, the LaAlO3/BaOx bilayer is easily removable by sonication in water. We applied the lift-off method using the LaAlO3/BaOx sacrificial bilayer to a representative oxide conductor SrRuO3 and fabricated micron-scale Hall-bar devices. The SrRuO3 channels with the narrowest line width of 5 μm exhibit an almost identical transport property to that of the pristine film, evidencing that the developed process is beneficial for patterning oxides. We show that the LaAlO3/BaOx lift-off process is applicable to various oxide substrates: SrTiO3, MgO, and Al2O3. The new versatile patterning process will expand the range of application of oxide thin films in electronic and photonic devices.

EDITORIAL: Carbon-based nanoscience and nanotechnology: where are we, where are we heading? Carbon-based nanoscience and nanotechnology: where are we, where are we heading?

NASA Astrophysics Data System (ADS)

Soukiassian, Patrick G.; Ramachandra Rao, M. S.

2010-09-01

'Without carbon, life cannot exist', the saying goes, and not only life. For technological development, carbon was the ultimate material of the 19th century. It allowed the beginnings of the industrial revolution, enabling the rise of the steel and chemical industries, it made the railways run, and it played a major role in the development of naval transportation. Silicon, another very interesting material which makes up a quarter of the earth's crust, became the material of the 20th century in its turn. It gave us the development of high performance electronics and photovoltaics with large fields of applications and played a pivotal role in the evolution of computer technology. The increased device performance of information and data processing systems is changing our lives on a daily basis, producing scientific innovations for a new industrial era. However, success breeds its own problems, and there is ever more data to be handled—which requires a nanoscience approach. This cluster aims to address various aspects, prospects and challenges in this area of great interest for all our futures. Carbon exists in various allotropic forms that are intensively investigated for their unusual and fascinating properties, from both fundamental and applied points of view. Among them, the sp2 (fullerenes, nanotubes and graphene) and sp3 (diamond) bonding configurations are of special interest since they have outstanding and, in some cases, unsurpassed properties compared to other materials. These properties include very high mechanical resistance, very high hardness, high resistance to radiation damage, high thermal conductivity, biocompatibility and superconductivity. Graphene, for example, possesses very uncommon electronic structure and a high carrier mobility, with charge carriers of zero mass moving at constant velocity, just like photons. All these characteristics have put carbon and carbon-related nanomaterials in the spotlight of science and technology research. The main challenges for future understanding include i) material growth, ii) fundamental properties, and iii) developing advanced applications. The reviews in this Cluster Issue of Journal of Physics D: Applied Physics cover carbon nanoparticles and nanotubes, graphene, nano-diamond and films. They address the most current aspects and issues related to their fundamental and outstanding properties, and describe various classes of high-tech applications based on these promising materials. Future prospects, difficulties and challenges are addressed. Important issues include growth, morphology, atomic and electronic structure, transport properties, superconductivity, doping, nanochemistry using hydrogen, chemical and bio-sensors, and bio-imaging, allowing readers to evaluate this very interesting topic and draw perspectives for the future.

The neural representation of typical and atypical experiences of negative images: comparing fear, disgust and morbid fascination

PubMed Central

Lindquist, Kristen A.; Adebayo, Morenikeji; Barrett, Lisa Feldman

2016-01-01

Negative stimuli do not only evoke fear or disgust, but can also evoke a state of ‘morbid fascination’ which is an urge to approach and explore a negative stimulus. In the present neuroimaging study, we applied an innovative method to investigate the neural systems involved in typical and atypical conceptualizations of negative images. Participants received false feedback labeling their mental experience as fear, disgust or morbid fascination. This manipulation was successful; participants judged the false feedback correct for 70% of the trials on average. The neuroimaging results demonstrated differential activity within regions in the ‘neural reference space for discrete emotion’ depending on the type of feedback. We found robust differences in the ventrolateral prefrontal cortex, the dorsomedial prefrontal cortex and the lateral orbitofrontal cortex comparing morbid fascination to control feedback. More subtle differences in the dorsomedial prefrontal cortex and the lateral orbitofrontal cortex were also found between morbid fascination feedback and the other emotion feedback conditions. This study is the first to forward evidence about the neural representation of the experimentally unexplored state of morbid fascination. In line with a constructionist framework, our findings suggest that neural resources associated with the process of conceptualization contribute to the neural representation of this state. PMID:26180088

Archimedes meets Einstein: a millennial geometric bridge

NASA Astrophysics Data System (ADS)

Prado, Xabier; Area, Iván; Paredes, Angel; Domínguez Castiñeiras, José Manuel; Edelstein, José D.; Mira, Jorge

2018-07-01

This contribution explores some analogies between special relativity and geometrical tools developed by the ancient Greeks. The kinematics of one-dimensional elastic collisions is solved with simple ruler-and-compass constructions on conic sections. Then, a thought-provoking relation involving Lorentz transformations, Archimedes’ law of the lever and Einstein’s formula for the relativistic mass is put forward. The familiarity with classical geometry is useful in developing intuitions on deep concepts of modern physics and can be profitable for high school or basic undergraduate teaching. Moreover, it is fascinating to establish a bridge connecting beautiful ideas separated by two millennia.

Music through the skin—simple demonstration of human electrical conductivity

NASA Astrophysics Data System (ADS)

Vollmer, M.; Möllmann, K. P.

2016-05-01

The conduction of electricity is an important topic for any basic physics course. Issues of safety often results in teacher demonstration experiments in front of the class or in extremely simple though—for students—not really fascinating (not to say boring) hands on activities for everybody using 1.5 V batteries, cables and light bulbs etc. Here we briefly review some basic facts about conduction of electricity through the human body and report a simple, safe, and awe inspiring electrical conduction experiment which can be performed with little preparation by a teacher involving the whole class of say 20 students.

Scaling in Theropod Dinosaurs: Femoral Bone Dimensions

NASA Astrophysics Data System (ADS)

Lee, Scott A.

2014-05-01

Finding topics that inspire students is an important aspect of any physics course. Virtually everyone is fascinated by Tyrannosaurus rex, and the excitement of the class is palpable when we explore scaling effects in T. rex and other bipedal theropod dinosaurs as part of our discussion of mechanics and elasticity. In this paper, we explore the role of longitudinal stress in the femur bones due to the weight of the dinosaur in determining how the geometry of the femur changes with size of the theropod. This is one area of allometry the study of how different biological characteristics scale with size.

Fabrication and magnetic properties of Ni nanospheres encapsulated in a fullerene-like carbon.

PubMed

Pol, S V; Pol, V G; Frydman, A; Churilov, G N; Gedanken, A

2005-05-19

A very simple, efficient, and economical synthetic technique, which produces fascinating fullerene-like Ni-C (graphitic) core-shell nanostructures at a relatively low temperature, is reported. The thermal dissociation of Ni acetylacetonate is carried out in a closed vessel cell (Swagelok) that was heated at 700 degrees C for 3 h. The encapsulation of ferromagnetic Ni nanospheres into the onion structured graphitic layers is obtained in a one-stage, single precursor reaction, without a catalyst, that possesses interesting magnetic properties. The magnetoresistance (MR) property of Ni nanospheres encapsulated in a fullerene-like carbon was measured, which shows large negative MR, of the order of 10%. The proposed mechanism for the formation of the Ni-C core-shell system is based on the segregation and the surface flux formed in the Ni and carbon particles during the reaction under autogenic pressure at elevated temperature.

Magnetic field controlled graphene oxide-based origami with enhanced surface area and mechanical properties.

PubMed

Park, Ok-Kyung; Tiwary, Chandra Sekhar; Yang, Yang; Bhowmick, Sanjit; Vinod, Soumya; Zhang, Qingbo; Colvin, Vicki L; Asif, S A Syed; Vajtai, Robert; Penev, Evgeni S; Yakobson, Boris I; Ajayan, Pulickel M

2017-06-01

One can utilize the folding of paper to build fascinating 3D origami architectures with extraordinary mechanical properties and surface area. Inspired by the same, the morphology of 2D graphene can be tuned by addition of magnetite (Fe 3 O 4 ) nanoparticles in the presence of a magnetic field. The innovative 3D architecture with enhanced mechanical properties also shows a high surface area (∼2500 m 2 g -1 ) which is utilized for oil absorption. Detailed microscopy and spectroscopy reveal rolling of graphene oxide (GO) sheets due to the magnetic field driven action of magnetite particles, which is further supported by molecular dynamics (MD) simulations. The macroscopic and local deformation resulting from in situ mechanical loading inside a scanning electron microscope reveals a change in the mechanical response due to a change internal morphology, which is further supported by MD simulation.

Nanomechanical strength mechanisms of hierarchical biological materials and tissues.

PubMed

Buehler, Markus J; Ackbarow, Theodor

2008-12-01

Biological protein materials (BPMs), intriguing hierarchical structures formed by assembly of chemical building blocks, are crucial for critical functions of life. The structural details of BPMs are fascinating: They represent a combination of universally found motifs such as alpha-helices or beta-sheets with highly adapted protein structures such as cytoskeletal networks or spider silk nanocomposites. BPMs combine properties like strength and robustness, self-healing ability, adaptability, changeability, evolvability and others into multi-functional materials at a level unmatched in synthetic materials. The ability to achieve these properties depends critically on the particular traits of these materials, first and foremost their hierarchical architecture and seamless integration of material and structure, from nano to macro. Here, we provide a brief review of this field and outline new research directions, along with a review of recent research results in the development of structure-property relationships of biological protein materials exemplified in a study of vimentin intermediate filaments.

Spectroscopically forbidden infra-red emission in Au-vertical graphene hybrid nanostructures

NASA Astrophysics Data System (ADS)

Sivadasan, A. K.; Parida, Santanu; Ghosh, Subrata; Pandian, Ramanathaswamy; Dhara, Sandip

2017-11-01

Implementation of Au nanoparticles (NPs) is a subject for frontier plasmonic research due to its fascinating optical properties. Herein, the present study deals with plasmonic assisted emission properties of Au NPs-vertical graphene (VG) hybrid nanostructures. The influence of effective polarizability of Au NPs on the surface enhanced Raman scattering and luminescence properties is investigated. In addition, a remarkable infra-red emission in the hybrid nanostructures is observed and interpreted on the basis of intra-band transitions in Au NPs. The flake-like nanoporous VG structure is invoked for the generation of additional confined photons to impart additional momentum and a gradient of confined excitation energy towards initiating the intra-band transitions of Au NPs. Integrating Au plasmonic materials in three-dimensional VG nanostructures enhances the light-matter interactions. The present study provides a new adaptable plasmonic assisted pathway for optoelectronic and sensing applications.

Bonding the superalkali M3O (M = Li and K): An effective strategy to improve the electronic and nonlinear optical properties of the inorganic B40 nanocage

NASA Astrophysics Data System (ADS)

Li, Zhipeng; Yu, Guangtao; Zhang, Xueying; Huang, Xuri; Chen, Wei

2017-10-01

Inspired by the fascinating finding of all-boron fullerene B40 (Nat Chem, 2014, 6, 727), we propose a new and effective strategy to construct a series of typical Donor-Acceptor (D-A) frameworks via linking the superalkali M3O (M = Li and K) unit with the low ionization potential to the B40 nanocage with large electron affinity. By means of the density functional theory computations, we have systematically investigated the structures, electronic properties, the first and second hyperpolarizabilities of these modified B40 nanocage systems. Owing to the formation of a B-O chemical bond, these composite systems (M3O)n-B40 (M = Li and K, n = 1 and 2) can possess the considerably large binding energy ranging from 57.0 to 99.8 kcal/mol, indicating their high structure stabilities. Compared with the pristine B40 nanocage, linking the superalkali M3O can effectively narrow the wide energy gap from the original 2.86 eV to 0.61-1.11 eV, and significantly increase the first and second hyperpolarizabilities to as large as 5.00 × 104-2.46 × 105 au and 1.48 × 107-4.85 × 108 au, respectively, owing to the occurrence of evident electron transfer process in this kind of typical D-A framework. These fascinating findings will be advantageous for promoting the potential applications of the inorganic boron-based nanosystems in the new type of electronic nanodevices and high-performance nonlinear optical materials.

Towards ab initio Calculations with the Dynamical Vertex Approximation

NASA Astrophysics Data System (ADS)

Galler, Anna; Kaufmann, Josef; Gunacker, Patrik; Pickem, Matthias; Thunström, Patrik; Tomczak, Jan M.; Held, Karsten

2018-04-01

While key effects of the many-body problem — such as Kondo and Mott physics — can be understood in terms of on-site correlations, non-local fluctuations of charge, spin, and pairing amplitudes are at the heart of the most fascinating and unresolved phenomena in condensed matter physics. Here, we review recent progress in diagrammatic extensions to dynamical mean-field theory for ab initio materials calculations. We first recapitulate the quantum field theoretical background behind the two-particle vertex. Next we discuss latest algorithmic advances in quantum Monte Carlo simulations for calculating such two-particle quantities using worm sampling and vertex asymptotics, before giving an introduction to the ab initio dynamical vertex approximation (AbinitioDΓA). Finally, we highlight the potential of AbinitioDΓA by detailing results for the prototypical correlated metal SrVO3.

Thermoacoustics of solids: A pathway to solid state engines and refrigerators

NASA Astrophysics Data System (ADS)

Hao, Haitian; Scalo, Carlo; Sen, Mihir; Semperlotti, Fabio

2018-01-01

Thermoacoustic oscillations have been one of the most exciting discoveries of the physics of fluids in the 19th century. Since its inception, scientists have formulated a comprehensive theoretical explanation of the basic phenomenon which has later found several practical applications to engineering devices. To date, all studies have concentrated on the thermoacoustics of fluid media where this fascinating mechanism was exclusively believed to exist. Our study shows theoretical and numerical evidence of the existence of thermoacoustic instabilities in solid media. Although the underlying physical mechanism exhibits some interesting similarities with its counterpart in fluids, the theoretical framework highlights relevant differences that have important implications on the ability to trigger and sustain the thermoacoustic response. This mechanism could pave the way to the development of highly robust and reliable solid-state thermoacoustic engines and refrigerators.

Managing Meetings

ERIC Educational Resources Information Center

Hay, Susan

2010-01-01

Meetings are a means of giving people a chance to contribute. Meetings are also the nursery where the people's skills of listening, speaking, and building good working relationships are honed. They are where people practice being courteously challenging and confident, and they are where people are fascinated and fascinating. Meetings are where…

Functional surface engineering of C-dots for fluorescent biosensing and in vivo bioimaging.

PubMed

Ding, Changqin; Zhu, Anwei; Tian, Yang

2014-01-21

Nanoparticles are promising scaffolds for applications such as imaging, chemical sensors and biosensors, diagnostics, drug delivery, catalysis, energy, photonics, medicine, and more. Surface functionalization of nanoparticles introduces an additional dimension in controlling nanoparticle interfacial properties and provides an effective bridge to connect nanoparticles to biological systems. With fascinating photoluminescence properties, carbon dots (C-dots), carbon-containing nanoparticles that are attracting considerable attention as a new type of quantum dot, are becoming both an important class of imaging probes and a versatile platform for engineering multifunctional nanosensors. In order to transfer C-dots from proof-of-concept studies toward real world applications such as in vivo bioimaging and biosensing, careful design and engineering of C-dot probes is becoming increasingly important. A comprehensive knowledge of how C-dot surfaces with various properties behave is essential for engineering C-dots with useful imaging properties such as high quantum yield, stability, and low toxicity, and with desirable biosensing properties such as high selectivity, sensitivity, and accuracy. Several reviews in recent years have reported preparation methods and properties of C-dots and described their application in biosensors, catalysis, photovoltatic cells, and more. However, no one has yet systematically summarized the surface engineering of C-dots, nor the use of C-dots as fluorescent nanosensors or probes for in vivo imaging in cells, tissues, and living organisms. In this Account, we discuss the major design principles and criteria for engineering the surface functionality of C-dots for biological applications. These criteria include brightness, long-term stability, and good biocompatibility. We review recent developments in designing C-dot surfaces with various functionalities for use as nanosensors or as fluorescent probes with fascinating analytical performance, and we emphasize applications in bioimaging and biosensing in live cells, tissues, and animals. In addition, we highlight our work on the design and synthesis of a C-dot ratiometric biosensor for intracellular Cu(2+) detection, and a twophoton fluorescent probe for pH measurement in live cells and tissues. We conclude this Account by outlining future directions in engineering the functional surface of C-dots for a variety of in vivo imaging applications, including dots with combined targeting, imaging and therapeutic-delivery capabilities, or high-resolution multiplexed vascular imaging. With each application C-dots should open new horizons of multiplexed quantitative detection, high-resolution fluorescence imaging, and long-term, real-time monitoring of their target.

Fluid Dynamics of Human Phonation and Speech

NASA Astrophysics Data System (ADS)

Mittal, Rajat; Erath, Byron D.; Plesniak, Michael W.

2013-01-01

This article presents a review of the fluid dynamics, flow-structure interactions, and acoustics associated with human phonation and speech. Our voice is produced through the process of phonation in the larynx, and an improved understanding of the underlying physics of this process is essential to advancing the treatment of voice disorders. Insights into the physics of phonation and speech can also contribute to improved vocal training and the development of new speech compression and synthesis schemes. This article introduces the key biomechanical features of the laryngeal physiology, reviews the basic principles of voice production, and summarizes the progress made over the past half-century in understanding the flow physics of phonation and speech. Laryngeal pathologies, which significantly enhance the complexity of phonatory dynamics, are discussed. After a thorough examination of the state of the art in computational modeling and experimental investigations of phonatory biomechanics, we present a synopsis of the pacing issues in this arena and an outlook for research in this fascinating subject.

PREFACE: 1st-2nd Young Researchers Meetings in Rome - Proceedings

NASA Astrophysics Data System (ADS)

YRMR Organizing Committee; Cannuccia, E.; Mazzaferro, L.; Migliaccio, M.; Pietrobon, D.; Stellato, F.; Veneziani, M.

2011-03-01

Students in science, particularly in physics, face a fascinating and challenging future. Scientists have proposed very interesting theories, which describe the microscopic and macroscopic world fairly well, trying to match the quantum regime with cosmological scales. Between the extremes of this scenario, biological phenomena in all their complexity take place, challenging the laws we observe in the atomic and sub-atomic world. More and more accurate and complex experiments have been devised and these are now going to test the paradigms of physics. Notable experiments include: the Large Hadronic Collider (LHC), which is going to shed light on the physics of the Standard Model of Particles and its extensions; the Planck-Herschel satellites, which target a very precise measurement of the properties of our Universe; and the Free Electron Lasers facilities, which produce high-brilliance, ultrafast X-ray pulses, allowing the investigation of the fundamental processes of solid state physics, chemistry, and biology. These projects are the result of huge collaborations spread across the world, involving scientists belonging to different and complementary research fields: physicists, chemists, biologists and others, keen to make the best of these extraordinary laboratories. Even though each branch of science is experiencing a process of growing specialization, it is very important to keep an eye on the global picture, remaining aware of the deep interconnections between inherent fields. This is even more crucial for students who are beginning their research careers. These considerations motivated PhD students and young post-docs connected to the Roman scientific research area to organize a conference, to establish the background and the network for interactions and collaborations. This resulted in the 1st and 2nd Young Researchers Meetings in Rome (http://ryrm.roma2.infn.it), one day conferences aimed primarily at graduate students and post-docs, working in physics in Italy and abroad. In its first two editions, the meeting was held at the Universities of Roma "Tor Vergata" (July 2009) and "LaSapienza" (February 2010), and organized in sections dedicated to up-to-date topics spanning broad research fields: Astrophysics-Cosmology, Soft-Condensed Matter Physics, Theoretical-Particle Physics, and Medical Physics. In these proceedings we have collected some of the contributions which were presented during the meetings.

Invited review current progress and limitations of spider silk for biomedical applications.

PubMed

Widhe, Mona; Johansson, Jan; Hedhammar, My; Rising, Anna

2012-06-01

Spider silk is a fascinating material combining remarkable mechanical properties with low density and biodegradability. Because of these properties and historical descriptions of medical applications, spider silk has been proposed to be the ideal biomaterial. However, overcoming the obstacles to produce spider silk in sufficient quantities and in a manner that meets regulatory demands has proven to be a difficult task. Also, there are relatively few studies of spider silk in biomedical applications available, and the methods and materials used vary a lot. Herein we summarize cell culture- and in vivo implantation studies of natural and synthetic spider silk, and also review the current status and future challenges in the quest for a large scale production of spider silk for medical applications. Copyright © 2011 Wiley Periodicals, Inc.

Magnetic enhancement of photoluminescence from blue-luminescent graphene quantum dots

NASA Astrophysics Data System (ADS)

Chen, Qi; Shi, Chentian; Zhang, Chunfeng; Pu, Songyang; Wang, Rui; Wu, Xuewei; Wang, Xiaoyong; Xue, Fei; Pan, Dengyu; Xiao, Min

2016-02-01

Graphene quantum-dots (GQDs) have been predicted and demonstrated with fascinating optical and magnetic properties. However, the magnetic effect on the optical properties remains experimentally unexplored. Here, we conduct a magneto-photoluminescence study on the blue-luminescence GQDs at cryogenic temperatures with magnetic field up to 10 T. When the magnetic field is applied, a remarkable enhancement of photoluminescence emission has been observed together with an insignificant change in circular polarization. The results have been well explained by the scenario of magnetic-field-controlled singlet-triplet mixing in GQDs owing to the Zeeman splitting of triplet states, which is further verified by temperature-dependent experiments. This work uncovers the pivotal role of intersystem crossing in GQDs, which is instrumental for their potential applications such as light-emitting diodes, photodynamic therapy, and spintronic devices.

Cellulosic Biomass-Reinforced Polyvinylidene Fluoride Separators with Enhanced Dielectric Properties and Thermal Tolerance.

PubMed

Li, Lei; Yu, Miao; Jia, Chao; Liu, Jianxin; Lv, Yanyan; Liu, Yanhua; Zhou, Yi; Liu, Chuanting; Shao, Ziqiang

2017-06-21

Safety issues are critical barriers to large-scale energy storage applications of lithium-ion batteries (LIBs). Using an ameliorated, thermally stable, shutdown separator is an effective method to overcome the safety issues. Herein, we demonstrate a novel, cellulosic biomass-material-blended polyvinylidene fluoride separator that was prepared using a simple nonsolvent-induced phase separation technique. This process formed a microporous composite separator with reduced crystallinity, uniform pore size distribution, superior thermal tolerance, and enhanced electrolyte wettability and dielectric and mechanical properties. In addition, the separator has a superior capacity retention and a better rate capability compared to the commercialized microporous polypropylene membrane. This fascinating membrane was fabricated via a relatively eco-friendly and cost-effective method and is an alternative, promising separator for high-power LIBs.

One hundred years of helicene chemistry. Part 1: non-stereoselective syntheses of carbohelicenes.

PubMed

Gingras, Marc

2013-02-07

Carbohelicenes belong to a class of fascinating, chiral, and helicoidal molecules, which have a rich history in chemistry since the very beginning of the 20th century. A renewed interest in polyaromatic chemistry and new synthetic challenges toward the search for innovative physical, biological, chemical and opto-electronic properties have brought high motivation in this field of studies. Theoretical insights gained from polyaromatic, chiral, conjugated and distorted π-systems are also responsible for this development. Several synthetic avenues were originally reported for making lower helicenes, but for many years, photochemical synthesis has remained a major method for producing small amount of helicenes. High-dilution conditions is still a limiting factor in their synthesis. The fulgurous impact of organometallic chemistry, novel synthetic methods, and recent catalytic systems has promoted the development of helicene chemistry, toward a library of tailor-made and highly functionalized helicene molecules. Helicene chemistry is being considered as an expanding and modern field, leading to several applications in supramolecular chemistry, in nanosciences, in chemical-biology, in polymers and materials science. This first part of a series of three reviews on carbohelicenes will be devoted to a comprehensive report on non-stereoselective reactions and methods for producing helicenes, along with their functionalization.

Sound and vision: visualization of music with a soap film

NASA Astrophysics Data System (ADS)

Gaulon, C.; Derec, C.; Combriat, T.; Marmottant, P.; Elias, F.

2017-07-01

A vertical soap film, freely suspended at the end of a tube, is vibrated by a sound wave that propagates in the tube. If the sound wave is a piece of music, the soap film ‘comes alive’: colours, due to iridescences in the soap film, swirl, split and merge in time with the music (see the snapshots in figure 1 below). In this article, we analyse the rich physics behind these fascinating dynamical patterns: it combines the acoustic propagation in a tube, the light interferences, and the static and dynamic properties of soap films. The interaction between the acoustic wave and the liquid membrane results in capillary waves on the soap film, as well as non-linear effects leading to a non-oscillatory flow of liquid in the plane of the film, which induces several spectacular effects: generation of vortices, diphasic dynamical patterns inside the film, and swelling of the soap film under certain conditions. Each of these effects is associated with a characteristic time scale, which interacts with the characteristic time of the music play. This article shows the richness of those characteristic times that lead to dynamical patterns. Through its artistic interest, the experiments presented in this article provide a tool for popularizing and demonstrating science in the classroom or to a broader audience.

Biomass derived Ni(OH)2@porous carbon/sulfur composites synthesized by a novel sulfur impregnation strategy based on supercritical CO2 technology for advanced Li-S batteries

NASA Astrophysics Data System (ADS)

Xia, Yang; Zhong, Haoyue; Fang, Ruyi; Liang, Chu; Xiao, Zhen; Huang, Hui; Gan, Yongping; Zhang, Jun; Tao, Xinyong; Zhang, Wenkui

2018-02-01

The rational design and controllable synthesis of sulfur cathode with high sulfur content, superior structural stability and fascinating electrochemical properties is a vital step to realize the large-scale application of rechargeable lithium-sulfur (Li-S) batteries. However, the electric insulation of elemental sulfur and the high solubility of lithium polysulfides are two intractable obstacles to hinder the success of Li-S batteries. In order to overcome aforementioned issues, a novel strategy combined supercritical CO2 fluid technology and biotemplating method is developed to fabricate Ni(OH)2 modified porous carbon microspheres as sulfur hosts to ameliorate the electronic conductive of sulfur and enhance simultaneously the physical and chemical absorptions of polysulfides. This elaborately designed Ni(OH)2@PYC/S composite cathode exhibits high reversible discharge capacity (1335 mAh g-1 at 0.1 C), remarkable cyclic stability (602 mAh g-1 after 200 cycles at 0.2 C) and superior rate capability, which is much better than its PYC/S counterpart. These results clearly demonstrate that the advanced porous carbon with good conductivity and the polar Ni(OH)2 coating layer with strong trapping ability of polysulfides are responsible for the enhanced electrochemical performance.

Latest research results on the effects of nanomaterials on humans and the environment: DaNa - Knowledge Base Nanomaterials

NASA Astrophysics Data System (ADS)

Marquardt, C.; Kühnel, D.; Richter, V.; Krug, H. F.; Mathes, B.; Steinbach, C.; Nau, K.

2013-04-01

Nanotechnology is considered one of the key technologies of the 21st century. The success of this fascinating technology is based on its versatility. It will bring about fundamental changes of basic research as well as of many sectors of industry and also of daily life from electronics to the health care system. However, consumers often miss reliable and understandable information on nanomaterials and all aspects of this versatile technology. A huge body of data on the potential hazards of nanoobjects towards human and environmental health already exists, but is either not easily accessible for a broad audience or presented unprocessable for nonexperts. But risk communication is an essential and thus integral component of risk management. For that purpose, the DaNa-Project aims at filling this gap by collecting and evaluating scientific results in an interdisciplinary approach with scientists from different research areas, such as human and environmental toxicology, biology, physics, chemistry, and sociology. Research findings from the field of human and environmental nanotoxicology are being prepared and presented together with material properties and possible applications for interested laymen and stakeholders. For the evaluation of literature a "Literature Criteria Checklist" has been developed as well as a Standard Operation Procedure template (SOP) based on careful scientific practice.

High-Performance Few-layer Mo-doped ReSe2 Nanosheet Photodetectors

PubMed Central

Yang, Shengxue; Tongay, Sefaattin; Yue, Qu; Li, Yongtao; Li, Bo; Lu, Fangyuan

2014-01-01

Transition metal dichalcogenides (TMDCs) have recently been the focus of extensive research activity owing to their fascinating physical properties. As a new member of TMDCs, Mo doped ReSe2 (Mo:ReSe2) is an octahedral structure semiconductor being optically biaxial and highly anisotropic, different from most of hexagonal layered TMDCs with optically uniaxial and relatively high crystal symmetry. We investigated the effects of physisorption of gas molecule on the few-layer Mo:ReSe2 nanosheet based photodetectors. We compared the photoresponse of the as-exfoliated device with annealed device both in air or ammonia (NH3) environment. After annealing at sub-decomposition temperatures, the Mo:ReSe2 photodetectors show a better photoresponsivity (~55.5 A/W) and higher EQE (10893%) in NH3 than in air. By theoretical investigation, we conclude that the physisorption of NH3 molecule on Mo:ReSe2 monolayer can cause the charge transfer between NH3 molecule and Mo:ReSe2 monolayer, increasing the n-type carrier density of Mo:ReSe2 monolayer. The prompt photoswitching, high photoresponsivity and different sensitivity to surrounding environment from the few-layer anisotropic Mo:ReSe2 can be used to design multifunctional optoelectronic and sensing devices. PMID:24962077

Configuration of ripple domains and their topological defects formed under local mechanical stress on hexagonal monolayer graphene.

PubMed

Park, Yeonggu; Choi, Jin Sik; Choi, Taekjib; Lee, Mi Jung; Jia, Quanxi; Park, Minwoo; Lee, Hoonkyung; Park, Bae Ho

2015-03-24

Ripples in graphene are extensively investigated because they ensure the mechanical stability of two-dimensional graphene and affect its electronic properties. They arise from spontaneous symmetry breaking and are usually manifested in the form of domains with long-range order. It is expected that topological defects accompany a material exhibiting long-range order, whose functionality depends on characteristics of domains and topological defects. However, there remains a lack of understanding regarding ripple domains and their topological defects formed on monolayer graphene. Here we explore configuration of ripple domains and their topological defects in exfoliated monolayer graphenes on SiO2/Si substrates using transverse shear microscope. We observe three-color domains with three different ripple directions, which meet at a core. Furthermore, the closed domain is surrounded by an even number of cores connected together by domain boundaries, similar to topological vortex and anti-vortex pairs. In addition, we have found that axisymmetric three-color domains can be induced around nanoparticles underneath the graphene. This fascinating configuration of ripple domains may result from the intrinsic hexagonal symmetry of two-dimensional graphene, which is supported by theoretical simulation using molecular dynamics. Our findings are expected to play a key role in understanding of ripple physics in graphene and other two-dimensional materials.

Phosphorene: Fabrication, properties, and applications

DOE PAGES

Kou, Liangzhi; Chen, Changfeng; Smith, Sean C.

2015-06-24

Phosphorene, the single- or few-layer form of black phosphorus, was recently rediscovered as a two-dimensional layered material holding great promise for applications in electronics and optoelectronics. Research into its fundamental properties and device applications has since seen exponential growth. In this Perspective, we review recent progress in phosphorene research, touching upon topics on fabrication, properties, and applications; we also discuss challenges and future research directions. We highlight the intrinsically anisotropic electronic, transport, optoelectronic, thermoelectric, and mechanical properties of phosphorene resulting from its puckered structure in contrast to those of graphene and transition-metal dichalcogenides. The facile fabrication and novel properties ofmore » phosphorene have inspired design and demonstration of new nanodevices; however, further progress hinges on resolutions to technical obstructions like surface degradation effects and nonscalable fabrication techniques. We also briefly describe the latest developments of more sophisticated design concepts and implementation schemes that address some of the challenges in phosphorene research. As a result, it is expected that this fascinating material will continue to offer tremendous opportunities for research and development for the foreseeable future.« less

Electronic properties and gas adsorption behaviour of pristine, silicon-, and boron-doped (8, 0) single-walled carbon nanotube: A first principles study.

PubMed

Azam, Mohd Asyadi; Alias, Farizul Muiz; Tack, Liew Weng; Seman, Raja Noor Amalina Raja; Taib, Mohamad Fariz Mohamad

2017-08-01

Carbon nanotubes (CNTs) have received enormous attention due to their fascinating properties to be used in various applications including electronics, sensing, energy storage and conversion. The first principles calculations within density functional theory (DFT) have been carried out in order to investigate the structural, electronic and optical properties of un-doped and doped CNT nanostructures. O 2 , CO 2 , and CH 3 OH have been chosen as gas molecules to study the adsorption properties based on zigzag (8,0) SWCNTs. The results demonstrate that the adsorption of O 2 , CO 2, and CH 3 OH gas molecules on pristine, Si-doped and B-doped SWCNTs are either physisorption or chemisorption. Moreover, the electronic properties indicating SWCNT shows significant improvement toward gas adsorption which provides the impact of selecting the best gas sensor materials towards detecting gas molecule. Therefore, these pristine, Si-, and B-doped SWCNTs can be considered to be very good potential candidates for sensing application. Copyright © 2017 Elsevier Inc. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Quigg, C.

The author sketches some pressing questions in several active areas of particle physics and outline the challenges they present for the design and operation of detectors. His assignment at the 1999 ICFA Instrumentation School is to survey some current developments in particle physics, and to describe the kinds of experiments they would like to do in the near future and illustrate the demands their desires place on detectors and data analysis. Like any active science, particle physics is in a state of continual renewal. Many of the subjects that seem most fascinating and most promising today simply did not existmore » as recently as twenty-five years ago. Other topics that have preoccupied physicists for many years have been reshaped by recent discoveries and insights, and transformed by new techniques in accelerator science and detector technology. To provide some context for the courses and laboratories at this school, he has chosen three topics that are of high scientific interest, and that place very different demands on instrumental techniques. He hopes that you will begin to see the breadth of opportunities in particle physics, and that you will also look beyond the domain of particle physics for opportunities to apply the lessons you learn here in Istanbul.« less

Pattern Formation in Langmuir Monolayers Due to Long-Range Electrostatic Interactions

NASA Astrophysics Data System (ADS)

Fischer, Thomas M.; Lösche, Mathias

A distinctive characteristic of Langmuir monolayers that bears important consequences for the physics of structure formation within membranes is the uniaxial orientation of the constituent dipolar molecules, brought about by the symmetry break which is induced by the surface of the aqueous substrate. The association of oriented molecular dipoles with the interface leads to the formation of image dipoles within the polarizeable medium - the subphase - such that the effective dipole orientation of every of the individual molecules is strictly normal to the surface, even within molecularly disordered phases. As a result, dipole-dipole repulsions play an eminently important role for the molecular interactions within the system - independent of the state of phase (while the dipole area density does of course depend on the state of phase) - and control the morphogenesis of the phase boundaries in their interplay with the one-dimensional (1D) line tension between coexisting phases. The physics of these phenomena is only now being explored and is particularly exciting for systems within a three-phase coexistence region where complete or partial wetting, as well as dewetting between the coexisting phases may be experimentally observed by applying fluorescence microscopy to the monolayer films. It is revealed that the wetting behavior depends sensitively on the details of the electrostatic interactions, in that the apparent contact angles observed at three-phase contact points depends on the sizes of the coexisting phases. This is in sharp contrast to the physics of wetting in conventional 3D systems where the contact angle is a materials property, independent of the local details. In 3D systems, this leads to Youngs equation - which has been established more than two centuries ago. We report recent progress in the understanding of this unusual and rather unexpected behavior of a quasi-2D system by reviewing recent experimental results from optical microscopy on equilibrium phase shapes, non-equilibrium phenomena - such as relaxation of the shapes after distortions inferred by Laser tweezers or local impulse heating - and rheological properties of the system. The theoretical analysis of the underlying molecular interactions leads to a comprehension of the observed phenomena and reveals microscopic properties of the system in quantitative terms. In view of the recently proposed lipid raft hypothesis, a particularly fascinating implication of our results is the possibility that biochemical reactions which depend on complex interactions between membrane-bound proteins might be controlled by the non-conventional physics of the 2D system: As an electrogenic event - such as ion transfer across the membrane - changes the electrostatic properties of the membrane surface it might concurrently infer wetting between 2D phases and thus lead to the conjunction of membrane areas that were originally separated within the plane. If two reactants (e.g., membrane-bound enzymes) are dissolved in distinct phases, such a colloidal reorganization might rearrange the micro-evironment to bring them into close vicinity - and thus trigger the biochemical reaction.

FAST TRACK COMMUNICATION Quantum entanglement: the unitary 8-vertex braid matrix with imaginary rapidity

NASA Astrophysics Data System (ADS)

Chakrabarti, Amitabha; Chakraborti, Anirban; Jedidi, Aymen

2010-12-01

We study quantum entanglements induced on product states by the action of 8-vertex braid matrices, rendered unitary with purely imaginary spectral parameters (rapidity). The unitarity is displayed via the 'canonical factorization' of the coefficients of the projectors spanning the basis. This adds one more new facet to the famous and fascinating features of the 8-vertex model. The double periodicity and the analytic properties of the elliptic functions involved lead to a rich structure of the 3-tangle quantifying the entanglement. We thus explore the complex relationship between topological and quantum entanglement.

Advances in graphene-based semiconductor photocatalysts for solar energy conversion: fundamentals and materials engineering.

PubMed

Xie, Xiuqiang; Kretschmer, Katja; Wang, Guoxiu

2015-08-28

Graphene-based semiconductor photocatalysis has been regarded as a promising technology for solar energy storage and conversion. In this review, we summarized recent developments of graphene-based photocatalysts, including preparation of graphene-based photocatalysts, typical key advances in the understanding of graphene functions for photocatalytic activity enhancement and methodologies to regulate the electron transfer efficiency in graphene-based composite photocatalysts, by which we hope to offer enriched information to harvest the utmost fascinating properties of graphene as a platform to construct efficient graphene-based composite photocatalysts for solar-to-energy conversion.

The search for anti-aging interventions: From elixirs to fasting regimens

PubMed Central

de Cabo, Rafael; Carmona-Gutierrez, Didac; Bernier, Michel; Hall, Michael N.; Madeo, Frank

2014-01-01

The phenomenon of aging is an intrinsic feature of life. Accordingly, the possibility to manipulate it has fascinated humans likely since time immemorial. Recent evidence is shaping a picture where low caloric regimes and exercise may improve healthy senescence, and several pharmacological strategies have been suggested to counteract aging. Surprisingly, the most effective interventions proposed to date converge on only a few cellular processes, in particular nutrient signaling, mitochondrial efficiency, proteostasis, and autophagy. Here, we critically examine drugs and behaviors to which life- or healthspan-extending properties have been ascribed and discuss the underlying molecular mechanisms. PMID:24949965

Experimental reconstruction of the Berry curvature in a Floquet Bloch band

NASA Astrophysics Data System (ADS)

Fläschner, N.; Rem, B. S.; Tarnowski, M.; Vogel, D.; Lühmann, D.-S.; Sengstock, K.; Weitenberg, C.

2016-05-01

Topological properties lie at the heart of many fascinating phenomena in solid-state systems such as quantum Hall systems or Chern insulators. The topology of the bands can be captured by the distribution of Berry curvature, which describes the geometry of the eigenstates across the Brillouin zone. Using fermionic ultracold atoms in a hexagonal optical lattice, we engineered the Berry curvature of the Bloch bands using resonant driving and show a full momentum-resolved measurement of the ensuing Berry curvature. Our results pave the way to explore intriguing phases of matter with interactions in topological band structures.

Development of Drug Delivery Systems Based on Layered Hydroxides for Nanomedicine

PubMed Central

Barahuie, Farahnaz; Hussein, Mohd Zobir; Fakurazi, Sharida; Zainal, Zulkarnain

2014-01-01

Layered hydroxides (LHs) have recently fascinated researchers due to their wide application in various fields. These inorganic nanoparticles, with excellent features as nanocarriers in drug delivery systems, have the potential to play an important role in healthcare. Owing to their outstanding ion-exchange capacity, many organic pharmaceutical drugs have been intercalated into the interlayer galleries of LHs and, consequently, novel nanodrugs or smart drugs may revolutionize in the treatment of diseases. Layered hydroxides, as green nanoreservoirs with sustained drug release and cell targeting properties hold great promise of improving health and prolonging life. PMID:24802876

Fabrication and nanoscale characterization of magnetic multilayer nanowires

NASA Astrophysics Data System (ADS)

Elawayeb, Mohamed

Magnetic multilayers nanowires are scientifically fascinating and have potential industrial applications in many areas of advanced nanotechnology. These applications arise due to the nanoscale dimensions of nanostructures that lead to unique physical properties. Magnetic multilayer nanowires have been successfully produced by electrodeposition into templates. Anodic Aluminium Oxide (AAO) membranes were used as templates in this process; the templates were fabricated by anodization method in acidic solutions at a fixed voltage. The fabrication method of a range of magnetic multilayer nanowires is described in this study and their structure and dimensions were analyzed using scanning electron microscope (SEM), Transmission electron microscope (TEM) and scanning transmission electron microscopy (STEM). This study is focused on the first growth of NiFe/Pt and NiFe/Fe magnetic multilayer nanowires, which were successfully fabricated by pulse electrodeposition into the channels of porous anodic aluminium oxide (AAO) templates, and characterized at the nanoscale. Individual nanowires have uniform structure and regular periodicity. The magnetic and nonmagnetic layers are polycrystalline, with randomly oriented fcc lattice structure crystallites. Chemical compositions of the individual nanowires were analyzed using TEM equipped with energy-dispersive x-ray analysis (EDX) and electron energy loss spectrometry (EELS). The electrical and magnetoresistance properties of individual magnetic multilayer nanowires have been measured inside a SEM using two sharp tip electrodes attached to in situ nanomanipulators and a new electromagnet technique. The giant magnetoresistance (GMR) effect of individual magnetic multilayer nanowires was measured in the current - perpendicular to the plane (CPP) geometry using a new in situ method at variable magnetic field strength and different orientations..

Daam1 regulates fascin for actin assembly in mouse oocyte meiosis.

PubMed

Lu, Yujie; Zhang, Yu; Pan, Meng-Hao; Kim, Nam-Hyung; Sun, Shao-Chen; Cui, Xiang-Shun

2017-07-18

As a formin protein, Daam1 (Dishevelled-associated activator of morphogenesis 1) is reported to regulate series of cell processes like endocytosis, cell morphology and migration via its effects on actin assembly in mitosis. However, whether Daam1 plays roles in female meiosis remains uncertain. In this study, we investigated the expression and functions of Daam1 during mouse oocyte meiosis. Our results indicated that Daam1 localized at the cortex of oocytes, which was similar with actin filaments. After Daam1 morpholino (MO) microinjection, the expression of Daam1 significantly decreased, which resulted in the failure of oocyte polar body extrusion. These results might be due to the defects of actin assembly, since the decreased fluorescence intensity of actin filaments in oocyte cortex and cytoplasm were observed. However, Daam1 knockdown seemed not to affect the meiotic spindle movement. In addition, we found that fascin might be the down effector of Daam1, since the protein expression of fascin decreased after Daam1 knockdown. Thus, our data suggested that Daam1 affected actin assembly during oocyte meiotic division via the regulation of fascin expression.

Bioinformatics by Example: From Sequence to Target

NASA Astrophysics Data System (ADS)

Kossida, Sophia; Tahri, Nadia; Daizadeh, Iraj

2002-12-01

With the completion of the human genome, and the imminent completion of other large-scale sequencing and structure-determination projects, computer-assisted bioscience is aimed to become the new paradigm for conducting basic and applied research. The presence of these additional bioinformatics tools stirs great anxiety for experimental researchers (as well as for pedagogues), since they are now faced with a wider and deeper knowledge of differing disciplines (biology, chemistry, physics, mathematics, and computer science). This review targets those individuals who are interested in using computational methods in their teaching or research. By analyzing a real-life, pharmaceutical, multicomponent, target-based example the reader will experience this fascinating new discipline.

Magnetosphere-Ionosphere Coupling in the Auroral Zone

NASA Technical Reports Server (NTRS)

Schriver, David

2004-01-01

The visual light display at high latitudes referred to as the aurora fascinates casual observers and researchers alike. The natural question is what causes the aurora? We know that energized electrons streaming along the Earth's ambient magnetic field and colliding with atmospheric particles produce aurora. We do not know for certain, however, how these electrons are accelerated to high energies primarily in the field-aligned direction toward the Earth, or what the drivers of this acceleration are. As such, the goal of this Guest Investigator research project was to examine the physical processes that can cause field-aligned acceleration of plasma particles in the auroral region.

Studies of the Stability and Dynamics of Levitated Drops

NASA Technical Reports Server (NTRS)

Anikumar, A.; Lee, Chun Ping; Wang, T. G.

1996-01-01

This is a review of our experimental and theoretical studies relating to equilibrium and stability of liquid drops, typically of low viscosity, levitated in air by a sound field. The major emphasis here is on the physical principles and understanding behind the stability of levitated drops. A comparison with experimental data is also given, along with some fascinating pictures from high-speed photography. One of the aspects we shall deal with is how a drop can suddenly burst in an intense sound field; a phenomenon which can find applications in atomization technology. Also, we are currently investigating the phenomenon of suppression of coalescence between drops levitated in intense acoustic fields.

Actin Cross-link Assembly and Disassembly Mechanics for α-Actinin and Fascin*

PubMed Central

Courson, David S.; Rock, Ronald S.

2010-01-01

Self-assembly of complex structures is commonplace in biology but often poorly understood. In the case of the actin cytoskeleton, a great deal is known about the components that include higher order structures, such as lamellar meshes, filopodial bundles, and stress fibers. Each of these cytoskeletal structures contains actin filaments and cross-linking proteins, but the role of cross-linking proteins in the initial steps of structure formation has not been clearly elucidated. We employ an optical trapping assay to investigate the behaviors of two actin cross-linking proteins, fascin and α-actinin, during the first steps of structure assembly. Here, we show that these proteins have distinct binding characteristics that cause them to recognize and cross-link filaments that are arranged with specific geometries. α-Actinin is a promiscuous cross-linker, linking filaments over all angles. It retains this flexibility after cross-links are formed, maintaining a connection even when the link is rotated. Conversely, fascin is extremely selective, only cross-linking filaments in a parallel orientation. Surprisingly, bundles formed by either protein are extremely stable, persisting for over 0.5 h in a continuous wash. However, using fluorescence recovery after photobleaching and fluorescence decay experiments, we find that the stable fascin population can be rapidly competed away by free fascin. We present a simple avidity model for this cross-link dissociation behavior. Together, these results place constraints on how cytoskeletal structures assemble, organize, and disassemble in vivo. PMID:20551315

The Continuing Saga of the Marine Polyether Biotoxins

PubMed Central

Nicolaou, K. C.; Frederick, Michael O.; Aversa, Robert J.

2009-01-01

Lead-in Brevetoxin B emerged from the sea and into the laboratories of Nakanishi and Clardy who, in 1981, reported its magnificent and unprecedented structure. With its ladder-like fused polyether molecular architecture, potent toxicity, and fascinating voltage-sensitive sodium channel-based mechanism of action, it immediately captured the imagination of chemists around the world. Their synthetic escapades resulted in numerous new synthetic methods and strategies for the construction of cyclic ethers, and culminated in several impressive total syntheses of this imposing molecule and some of its equally challenging siblings that followed. Indeed, many more brevetoxin-type marine polyethers have been reported since 1981 with maitotoxin being not only the most complex and most toxic of the class, but also the largest non-polymeric natural product known to date. In this article, we begin with a brief history of these biotoxins and the phenomena that led to their isolation and highlight their biological properties and mechanism of action. We then review the chemical synthesis endeavors so far published in this long running saga, placing particular emphasis on the new synthetic methods and technologies discovered, developed and applied to their total syntheses over the last few decades. Finally, we conclude with a discussion of the, as yet unfinished, story of maitotoxin, and project into the future of this fascinating area of research. PMID:18763702

New Results on Short-Range Correlations in Nuclei

DOE PAGES

Fomin, Nadia; Higinbotham, Douglas; Sargsian, Misak; ...

2017-10-12

Nuclear dynamics at short distances is one of the most fascinating topics of strong interaction physics. The physics of it is closely related to the understanding of the role of the QCD in generating nuclear forces at short distances, as well as of the dynamics of the superdense cold nuclear matter relevant to the interior of neutron stars. The emergence of high-energy electron and proton beams has led to significant recent progress in high-energy nuclear scattering experiments investigating the short-range structure of nuclei. These experiments, in turn, have stimulated new theoretical studies resulting in the observation of several new phenomenamore » specific to the short-range structure of nuclei. In this article, we review recent theoretical and experimental progress in studies of short-range correlations in nuclei and discuss their importance for advancing our understanding of the dynamics of nuclear interactions at short distances.« less

New Results on Short-Range Correlations in Nuclei

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fomin, Nadia; Higinbotham, Douglas; Sargsian, Misak

Nuclear dynamics at short distances is one of the most fascinating topics of strong interaction physics. The physics of it is closely related to the understanding of the role of the QCD in generating nuclear forces at short distances, as well as of the dynamics of the superdense cold nuclear matter relevant to the interior of neutron stars. The emergence of high-energy electron and proton beams has led to significant recent progress in high-energy nuclear scattering experiments investigating the short-range structure of nuclei. These experiments, in turn, have stimulated new theoretical studies resulting in the observation of several new phenomenamore » specific to the short-range structure of nuclei. In this article, we review recent theoretical and experimental progress in studies of short-range correlations in nuclei and discuss their importance for advancing our understanding of the dynamics of nuclear interactions at short distances.« less

Model-Free Views of Deep Inelastic Scattering

NASA Astrophysics Data System (ADS)

Schwinger, Julian

2014-11-01

Perhaps I should point out first that my choice of topic was dictated by the injunction that the nature of this symposium should revolve around subjects that might be conceivably of interest to Viki. Viki has, along with most high energy physicists been very interested in the subject of deep inelastic electron scattering. With his characteristic attention to directly visualizable approaches to physical phenomena, he has dealt with this in terms of rather specific models, attempting then to give very elementary explanations of these fascinating phenomena. I thought he might be interested to see the other side of the coin, namely, the extent to which one can correlate and comprehend these physical effects without the use of specific models. I think this may lend a certain useful balance to the way things are looked at these days. So my remarks are directed to Viki but you're all welcome to eavesdrop...

Electrically tunable tunneling rectification magnetoresistance in magnetic tunneling junctions with asymmetric barriers.

PubMed

Wang, Jing; Huang, Qikun; Shi, Peng; Zhang, Kun; Tian, Yufeng; Yan, Shishen; Chen, Yanxue; Liu, Guolei; Kang, Shishou; Mei, Liangmo

2017-10-26

The development of multifunctional spintronic devices requires simultaneous control of multiple degrees of freedom of electrons, such as charge, spin and orbit, and especially a new physical functionality can be realized by combining two or more different physical mechanisms in one specific device. Here, we report the realization of novel tunneling rectification magnetoresistance (TRMR), where the charge-related rectification and spin-dependent tunneling magnetoresistance are integrated in Co/CoO-ZnO/Co magnetic tunneling junctions with asymmetric tunneling barriers. Moreover, by simultaneously applying direct current and alternating current to the devices, the TRMR has been remarkably tuned in the range from -300% to 2200% at low temperature. This proof-of-concept investigation provides an unexplored avenue towards electrical and magnetic control of charge and spin, which may apply to other heterojunctions to give rise to more fascinating emergent functionalities for future spintronics applications.

Recent Advancements in the Global Understanding of what Drives Heatwaves

NASA Astrophysics Data System (ADS)

Perkins-Kirkpatrick, S.

2016-12-01

Heatwaves, defined as prolonged periods of extreme heat, are disastrous events that impact human, natural and industrial systems all over the world. In recent years, the global research effort has greatly increased our understanding on quantifying heatwaves and how they have changed, what drives them, and their future projections. This talk will summarize critical developments made in this field, with particular emphasis on the physical driving mechanisms and the role of internal climate variability. Case studies from various global regions will illustrate both similarities and differences in the physical set-ups of these fascinating events. Future projections of heatwaves and the human contribution behind specific observed heatwave events will be briefly discussed. The talk will conclude by highlighting research priorities such that future investigation is targeted, and closes existing knowledge gaps on what drives heatwaves as effectively as possible. Such developments will ultimately aid in the predictability of heatwaves, thus aiding in reducing their devastating impacts.

Reviews

NASA Astrophysics Data System (ADS)

2008-07-01

WE RECOMMEND Geyser Tube A simple plastic tube makes a great difference to an old trick Field Trip to the Moon This DVD postulates what the next Moon mission will be like Plutonium: A History of the World's Most Dangerous Element A fascinating account of the people and the science behind atomic bombs Solar Energy Modules A series of units ideal for use with 7-14-year-olds Photocopiable Practical Science New teaching resource is clear, straightforward and flexible Joseph Rotblat: Visionary for Peace Biography that is thorough, well-told and worth the telling WORTH A LOOK Applied Biophysics: A Molecular Approach for Physical Scientists This book explains why physics is essential to biology William's Words in Science Classroom dictionary of scientific terms can be hit and miss HANDLE WITH CARE Zero Time Space This story of quantum mechanics loses its thread in translation WEB WATCH A whizz around the pole-related science tools that are available

The Shape of a Ponytail and the Statistical Physics of Hair Fiber Bundles

NASA Astrophysics Data System (ADS)

Goldstein, Raymond E.; Warren, Patrick B.; Ball, Robin C.

2012-02-01

From Leonardo to the Brothers Grimm our fascination with hair has endured in art and science. Yet, a quantitative understanding of the shapes of a hair bundles has been lacking. Here we combine experiment and theory to propose an answer to the most basic question: What is the shape of a ponytail? A model for the shape of hair bundles is developed from the perspective of statistical physics, treating individual fibers as elastic filaments with random intrinsic curvatures. The combined effects of bending elasticity, gravity, and bundle compressibility are recast as a differential equation for the envelope of a bundle, in which the compressibility enters through an ``equation of state.'' From this, we identify the balance of forces in various regions of the ponytail, extract the equation of state from analysis of ponytail shapes, and relate the observed pressure to the measured random curvatures of individual hairs.

Gran Sasso National Laboratory: Outreach and communication activities

NASA Astrophysics Data System (ADS)

Antolini, R.; Di Giovanni, A.; Galeota, M.; Sebastiani, S.

2010-01-01

Due to its fascinating structures, the Gran Sasso National Laboratory (LNGS) offers huge opportunities for communication and outreach activities conceived for students and general public. A great effort is devoted to the organisation of the "OPEN DAY", in which the scientific staff of Gran Sasso introduces non expert people to the main relevant research topics of the laboratory through interactive demonstrations and particle detectors. In particular, a portable cosmic rays telescope has been realized: the detector is used by LNGS team in pubblic events as well as to promote the scientific activities of the Laboratory. In order to point out the importance of the scientific culture for young people, LNGS is involved in the organisation of several training courses for students and teachers focused on the improvement of the knowledge on modern physics topics. Since May 2008 is operating in Teramo the "Galileium", an interactive museum for physics and astrophysics.

Keep trophy records honest: Identifying whitetail/mule deer hybrids

Treesearch

Jim Heffelfinger; Renee Prive; David Paetkau; Carlos Alcala-Galvan; Roy Lopez; Irv Kornfield; Eldon Buckner

2012-01-01

Humans have always been fascinated by hybrids. Consider such classic monsters as Wolfman, Dracula, and Mothmanor heroes such as Spiderman, Batman, and Catwoman. This trend pre-dates Hollywood by millennia; the "Minotaur" in Greek mythology was half man and half bull. Our fascination with creatures that are half one thing and half another extends to wildlife....

British Female Converts to Islam: Choosing Islam as a Rejection of Individualism

ERIC Educational Resources Information Center

Soutar, Louise

2010-01-01

Voluntary religious conversion is a topic of great interest and fascination. However, this fascination is increased when the religion is Islam and the convert is female. Through the use of three in-depth interviews, this research hopes to answer the following questions: how much does a dissatisfaction with typical British individualism contribute…

Urban Indians: Patterns and Transformations.

ERIC Educational Resources Information Center

Higgins, Bryan

For centuries American Indians have been an object of Western fascination. All too often this fascination has been an invented view of Indian people. This is especially evident with the recent movement of Indian people to urban areas within the United States and Canada. Not only has this movement been ignored by society in general, but it has also…

How to?Identify Fingerprints and Animal Tracks

ERIC Educational Resources Information Center

Lindroth, Linda

2005-01-01

Caught by a fingerprint - or is it an animal track? This paper suggests investigating with these science projects for Earth Day. Students love spy mysteries, and the popularity of TV shows such as CSI and Unsolved Mysteries indicates the fascination is not only limited to our students. Why not capture this fascination for your science classroom.…

Observation of Topological Links Associated with Hopf Insulators in a Solid-State Quantum Simulator

NASA Astrophysics Data System (ADS)

Yuan, X.-X.; He, L.; Wang, S.-T.; Deng, D.-L.; Wang, F.; Lian, W.-Q.; Wang, X.; Zhang, C.-H.; Zhang, H.-L.; Chang, X.-Y.; Duan, L.-M.

2017-06-01

Hopf insulators are intriguing three-dimensional topological insulators characterized by an integer topological invariant. They originate from the mathematical theory of Hopf fibration and epitomize the deep connection between knot theory and topological phases of matter, which distinguishes them from other classes of topological insulators. Here, we implement a model Hamiltonian for Hopf insulators in a solid-state quantum simulator and report the first experimental observation of their topological properties, including fascinating topological links associated with the Hopf fibration and the integer-valued topological invariant obtained from a direct tomographic measurement. Our observation of topological links and Hopf fibration in a quantum simulator opens the door to probe rich topological properties of Hopf insulators in experiments. The quantum simulation and probing methods are also applicable to the study of other intricate three-dimensional topological model Hamiltonians.

Fabrication and characterization of nanowalls CdS/dye sensitized solar cells

NASA Astrophysics Data System (ADS)

Abdulelah, Haider; Ali, Basil; Mahdi, M. A.; Hassan, J. J.; Al-Taay, H. F.; Jennings, P.

2017-06-01

A microwave assisted chemical bath deposition (MA-CBD) was adopted to fabricate nanowalls CdS nanocrystalline thin film. Nanomaterials (such as nanowalls structure) have attracted significant attention due to their fascinating properties and unique applications, especially in optoelectronic nanodevices. Here we describe the fabrication of dye sensitized solar cells (DSSCs) based nanowalls cadmium sulfide (CdS) nanocrystalline thin films. The surface morphology, crystalline structure, and optical properties of the prepared nanocrystalline thin films are investigated. Rhodamine B, Malachite green, Eosin methylene blue, and Cresyl violet perchlorate dyes are used to fabricate the DSSCS devices. Current-voltage (I-V) characteristics show that the nanowall CdS/Eosin methylene blue device is the highest conversion efficiency of 0.89% under 100 mW/cm2. However, heat treatment of the fabricated solar cells causes significant enhancement in the output of all devices.

Size Dependent Mechanical Properties of Monolayer Densely Arranged Polystyrene Nanospheres.

PubMed

Huang, Peng; Zhang, Lijing; Yan, Qingfeng; Guo, Dan; Xie, Guoxin

2016-12-13

In contrast to macroscopic materials, the mechanical properties of polymer nanospheres show fascinating scientific and application values. However, the experimental measurements of individual nanospheres and quantitative analysis of theoretical mechanisms remain less well performed and understood. We provide a highly efficient and accurate method with monolayer densely arranged honeycomb polystyrene (PS) nanospheres for the quantitatively mechanical characterization of individual nanospheres on the basis of atomic force microscopy (AFM) nanoindentation. The efficiency is improved by 1-2 orders, and the accuracy is also enhanced almost by half-order. The elastic modulus measured in the experiments increases with decreasing radius to the smallest nanospheres (25-35 nm in radius). A core-shell model is introduced to predict the size dependent elasticity of PS nanospheres, and the theoretical prediction agrees reasonably well with the experimental results and also shows a peak modulus value.

Cherenkov sound on a surface of a topological insulator

NASA Astrophysics Data System (ADS)

Smirnov, Sergey

2013-11-01

Topological insulators are currently of considerable interest due to peculiar electronic properties originating from helical states on their surfaces. Here we demonstrate that the sound excited by helical particles on surfaces of topological insulators has several exotic properties fundamentally different from sound propagating in nonhelical or even isotropic helical systems. Specifically, the sound may have strictly forward propagation absent for isotropic helical states. Its dependence on the anisotropy of the realistic surface states is of distinguished behavior which may be used as an alternative experimental tool to measure the anisotropy strength. Fascinating from the fundamental point of view backward, or anomalous, Cherenkov sound is excited above the critical angle π/2 when the anisotropy exceeds a critical value. Strikingly, at strong anisotropy the sound localizes into a few forward and backward beams propagating along specific directions.

Organic-Inorganic Hybrid Ruddlesden-Popper Perovskites: An Emerging Paradigm for High-Performance Light-Emitting Diodes.

PubMed

Liu, Xiao-Ke; Gao, Feng

2018-05-03

Recently, lead halide perovskite materials have attracted extensive interest, in particular, in the research field of solar cells. These materials are fascinating "soft" materials with semiconducting properties comparable to the best inorganic semiconductors like silicon and gallium arsenide. As one of the most promising perovskite family members, organic-inorganic hybrid Ruddlesden-Popper perovskites (HRPPs) offer rich chemical and structural flexibility for exploring excellent properties for optoelectronic devices, such as solar cells and light-emitting diodes (LEDs). In this Perspective, we present an overview of HRPPs on their structural characteristics, synthesis of pure HRPP compounds and thin films, control of their preferential orientations, and investigations of heterogeneous HRPP thin films. Based on these recent advances, future directions and prospects have been proposed. HRPPs are promising to open up a new paradigm for high-performance LEDs.

A novel method for a multi-level hierarchical composite with brick-and-mortar structure

PubMed Central

Brandt, Kristina; Wolff, Michael F. H.; Salikov, Vitalij; Heinrich, Stefan; Schneider, Gerold A.

2013-01-01

The fascination for hierarchically structured hard tissues such as enamel or nacre arises from their unique structure-properties-relationship. During the last decades this numerously motivated the synthesis of composites, mimicking the brick-and-mortar structure of nacre. However, there is still a lack in synthetic engineering materials displaying a true hierarchical structure. Here, we present a novel multi-step processing route for anisotropic 2-level hierarchical composites by combining different coating techniques on different length scales. It comprises polymer-encapsulated ceramic particles as building blocks for the first level, followed by spouted bed spray granulation for a second level, and finally directional hot pressing to anisotropically consolidate the composite. The microstructure achieved reveals a brick-and-mortar hierarchical structure with distinct, however not yet optimized mechanical properties on each level. It opens up a completely new processing route for the synthesis of multi-level hierarchically structured composites, giving prospects to multi-functional structure-properties relationships. PMID:23900554

A novel method for a multi-level hierarchical composite with brick-and-mortar structure.

PubMed

Brandt, Kristina; Wolff, Michael F H; Salikov, Vitalij; Heinrich, Stefan; Schneider, Gerold A

2013-01-01

The fascination for hierarchically structured hard tissues such as enamel or nacre arises from their unique structure-properties-relationship. During the last decades this numerously motivated the synthesis of composites, mimicking the brick-and-mortar structure of nacre. However, there is still a lack in synthetic engineering materials displaying a true hierarchical structure. Here, we present a novel multi-step processing route for anisotropic 2-level hierarchical composites by combining different coating techniques on different length scales. It comprises polymer-encapsulated ceramic particles as building blocks for the first level, followed by spouted bed spray granulation for a second level, and finally directional hot pressing to anisotropically consolidate the composite. The microstructure achieved reveals a brick-and-mortar hierarchical structure with distinct, however not yet optimized mechanical properties on each level. It opens up a completely new processing route for the synthesis of multi-level hierarchically structured composites, giving prospects to multi-functional structure-properties relationships.

A novel method for a multi-level hierarchical composite with brick-and-mortar structure

NASA Astrophysics Data System (ADS)

Brandt, Kristina; Wolff, Michael F. H.; Salikov, Vitalij; Heinrich, Stefan; Schneider, Gerold A.

2013-07-01

The fascination for hierarchically structured hard tissues such as enamel or nacre arises from their unique structure-properties-relationship. During the last decades this numerously motivated the synthesis of composites, mimicking the brick-and-mortar structure of nacre. However, there is still a lack in synthetic engineering materials displaying a true hierarchical structure. Here, we present a novel multi-step processing route for anisotropic 2-level hierarchical composites by combining different coating techniques on different length scales. It comprises polymer-encapsulated ceramic particles as building blocks for the first level, followed by spouted bed spray granulation for a second level, and finally directional hot pressing to anisotropically consolidate the composite. The microstructure achieved reveals a brick-and-mortar hierarchical structure with distinct, however not yet optimized mechanical properties on each level. It opens up a completely new processing route for the synthesis of multi-level hierarchically structured composites, giving prospects to multi-functional structure-properties relationships.

Arrays of Ultrathin CdS Nanoflakes with High-Energy Surface for Efficient Gas Detection.

PubMed

Liu, Xiao-Hua; Yin, Peng-Fei; Kulinich, Sergei A; Zhou, Yu-Zhu; Mao, Jing; Ling, Tao; Du, Xi-Wen

2017-01-11

It is fascinating and challenging to endow conventional materials with unprecedented properties. For instance, cadmium sulfide (CdS) is an important semiconductor with excellent light response; however, its potential in gas-sensing was underestimated owing to relatively low chemical activity and poor electrical conductivity. Herein, we demonstrate that an ideal architecture, ultrathin nanoflake arrays (NFAs), can improve significantly gas-sensing properties of CdS material. The CdS NFAs are grown directly on the interdigitated electrode to expose large surface area. Their thickness is reduced below the double Debye length of CdS, permitting to achieve a full depletion of carriers. Particularly, the prepared CdS nanoflakes are enclosed with high-energy {0001} facets exposed, which provides more active sites for gas adsorption. Moreover, the NFAs exhibit the light-trapping effect, which further enhances their gas sensitivity. As a result, the as-prepared CdS NFAs demonstrate excellent gas-sensing and light-response properties, thus being capable of dual gas and light detection.

First-principles simulations of Graphene/Transition-metal-Dichalcogenides/Graphene Field-Effect Transistor

NASA Astrophysics Data System (ADS)

Li, Xiangguo; Wang, Yun-Peng; Zhang, X.-G.; Cheng, Hai-Ping

A prototype field-effect transistor (FET) with fascinating properties can be made by assembling graphene and two-dimensional insulating crystals into three-dimensional stacks with atomic layer precision. Transition metal dichalcogenides (TMDCs) such as WS2, MoS2 are good candidates for the atomically thin barrier between two layers of graphene in the vertical FET due to their sizable bandgaps. We investigate the electronic properties of the Graphene/TMDCs/Graphene sandwich structure using first-principles method. We find that the effective tunnel barrier height of the TMDC layers in contact with the graphene electrodes has a layer dependence and can be modulated by a gate voltage. Consequently a very high ON/OFF ratio can be achieved with appropriate number of TMDC layers and a suitable range of the gate voltage. The spin-orbit coupling in TMDC layers is also layer dependent but unaffected by the gate voltage. These properties can be important in future nanoelectronic device designs. DOE/BES-DE-FG02-02ER45995; NERSC.

New Methods for Assessing the Fascinating Nature of Nature Experiences

PubMed Central

Joye, Yannick; Pals, Roos; Steg, Linda; Evans, Ben Lewis

2013-01-01

In recent years, numerous environmental psychology studies have demonstrated that contact with nature as opposed to urban settings can improve an individual’s mood, can lead to increased levels of vitality, and can offer an opportunity to recover from stress. According to Attention Restoration Theory (ART) the restorative potential of natural environments is situated in the fact that nature can replenish depleted attentional resources. This replenishment takes place, in part, because nature is deemed to be a source of fascination, with fascination being described as having an “attentional”, an “affective” and an “effort” dimension. However, the claim that fascination with nature involves these three dimensions is to a large extent based on intuition or derived from introspection-based measurement methods, such as self-reports. In three studies, we aimed to more objectively assess whether these three dimensions indeed applied to experiences related to natural environments, before any (attentional) depletion has taken place. The instruments that were used were: (a) the affect misattribution procedure (Study 1), (b) the dot probe paradigm (Study 2) and (c) a cognitively effortful task (Study 3). These instrument were respectively aimed at verifying the affective, attentional and effort dimension of fascination. Overall, the results provide objective evidence for the claims made within the ART framework, that natural as opposed to urban settings are affectively positive (cfr., affective dimension) and that people have an attentional bias to natural (rather than urban) environments (cfr., attentional dimension). The results regarding the effort dimension are less straightforward, and suggest that this dimension only becomes important in sufficiently difficult cognitive tasks. PMID:23922645

New methods for assessing the fascinating nature of nature experiences.

PubMed

Joye, Yannick; Pals, Roos; Steg, Linda; Evans, Ben Lewis

2013-01-01

In recent years, numerous environmental psychology studies have demonstrated that contact with nature as opposed to urban settings can improve an individual's mood, can lead to increased levels of vitality, and can offer an opportunity to recover from stress. According to Attention Restoration Theory (ART) the restorative potential of natural environments is situated in the fact that nature can replenish depleted attentional resources. This replenishment takes place, in part, because nature is deemed to be a source of fascination, with fascination being described as having an "attentional", an "affective" and an "effort" dimension. However, the claim that fascination with nature involves these three dimensions is to a large extent based on intuition or derived from introspection-based measurement methods, such as self-reports. In three studies, we aimed to more objectively assess whether these three dimensions indeed applied to experiences related to natural environments, before any (attentional) depletion has taken place. The instruments that were used were: (a) the affect misattribution procedure (Study 1), (b) the dot probe paradigm (Study 2) and (c) a cognitively effortful task (Study 3). These instrument were respectively aimed at verifying the affective, attentional and effort dimension of fascination. Overall, the results provide objective evidence for the claims made within the ART framework, that natural as opposed to urban settings are affectively positive (cfr., affective dimension) and that people have an attentional bias to natural (rather than urban) environments (cfr., attentional dimension). The results regarding the effort dimension are less straightforward, and suggest that this dimension only becomes important in sufficiently difficult cognitive tasks.

2D transition metal dichalcogenides

NASA Astrophysics Data System (ADS)

Manzeli, Sajedeh; Ovchinnikov, Dmitry; Pasquier, Diego; Yazyev, Oleg V.; Kis, Andras

2017-08-01

Graphene is very popular because of its many fascinating properties, but its lack of an electronic bandgap has stimulated the search for 2D materials with semiconducting character. Transition metal dichalcogenides (TMDCs), which are semiconductors of the type MX2, where M is a transition metal atom (such as Mo or W) and X is a chalcogen atom (such as S, Se or Te), provide a promising alternative. Because of its robustness, MoS2 is the most studied material in this family. TMDCs exhibit a unique combination of atomic-scale thickness, direct bandgap, strong spin-orbit coupling and favourable electronic and mechanical properties, which make them interesting for fundamental studies and for applications in high-end electronics, spintronics, optoelectronics, energy harvesting, flexible electronics, DNA sequencing and personalized medicine. In this Review, the methods used to synthesize TMDCs are examined and their properties are discussed, with particular attention to their charge density wave, superconductive and topological phases. The use of TMCDs in nanoelectronic devices is also explored, along with strategies to improve charge carrier mobility, high frequency operation and the use of strain engineering to tailor their properties.

Improving surface and defect center chemistry of fluorescent nanodiamonds for imaging purposes--a review.

PubMed

Nagl, Andreas; Hemelaar, Simon Robert; Schirhagl, Romana

2015-10-01

Diamonds are widely used for jewelry owing to their superior optical properties accounting for their fascinating beauty. Beyond the sparkle, diamond is highly investigated in materials science for its remarkable properties. Recently, fluorescent defects in diamond, particularly the negatively charged nitrogen-vacancy (NV(-)) center, have gained much attention: The NV(-) center emits stable, nonbleaching fluorescence, and thus could be utilized in biolabeling, as a light source, or as a Förster resonance energy transfer donor. Even more remarkable are its spin properties: with the fluorescence intensity of the NV(-) center reacting to the presence of small magnetic fields, it can be utilized as a sensor for magnetic fields as small as the field of a single electron spin. However, a reproducible defect and surface and defect chemistry are crucial to all applications. In this article we review methods for using nanodiamonds for different imaging purposes. The article covers (1) dispersion of particles, (2) surface cleaning, (3) particle size selection and reduction, (4) defect properties, and (5) functionalization and attachment to nanostructures, e.g., scanning probe microscopy tips.

Lab-in-a-box @ school: Exiting hands-on experiments in soft matter physics

NASA Astrophysics Data System (ADS)

Jacobs, Karin; Brinkmann, Martin; Müller, Frank

2015-03-01

Soft materials like liquids and polymers are part of everyday life, yet at school, this topic is rarely touched. Within the priority program SPP 1064 'Nano- and Microfluidics' of the German Science Foundation, we designed an outreach project that allows pupils (age 14 to 18) to perform hands-on experiments (www.labinabox.de). The experiments allow them e.g. to feel viscosity and viscoelasticity, experience surface tension or see structure formation. We call the modus operandi 'subjective experiments' to contrast them with the scientifically objective experiments, which pupils often describe as being boring. Over a dozen different experiments under the topic 'physics of fluids' are collected in a big box that travels to the school. Three other topics of boxes are available, 'physics of light, 'physics of liquid crystals', and 'physics of adhesion and friction'. Each experiment can be performed by 1-3 pupils within 10 - 20 min. That way, each scholar can perform 6 to 8 different small experiments within one topic. 'Subjective experiments' especially catch the attention of girls without disadvantaging boys. Both are fascinated by the hands-on physics experience and are therefore eager to perform also 'boring' objective experiments. Morover, before/after polls reveal that their interest in physics has greatly advanced. The project can easily be taken over and/or adapted to other topics in the natural sciences. Financial support of the German Science Foundation DFG is acknowledged.

Motions of Celestial Bodies; Computer simulations

NASA Astrophysics Data System (ADS)

Butikov, Eugene

2014-10-01

This book is written for a wide range of graduate and undergraduate students studying various courses in physics and astronomy. It is accompanied by the award winning educational software package 'Planets and Satellites' developed by the author. This text, together with the interactive software, is intended to help students learn and understand the fundamental concepts and the laws of physics as they apply to the fascinating world of the motions of natural and artificial celestial bodies. The primary aim of the book is the understanding of the foundations of classical and modern physics, while their application to celestial mechanics is used to illustrate these concepts. The simulation programs create vivid and lasting impressions of the investigated phenomena, and provide students and their instructors with a powerful tool which enables them to explore basic concepts that are difficult to study and teach in an abstract conventional manner. Students can work with the text and software at a pace they can enjoy, varying parameters of the simulated systems. Each section of the textbook is supplied with questions, exercises, and problems. Using some of the suggested simulation programs, students have an opportunity to perform interesting mini-research projects in physics and astronomy.

The search for antiaging interventions: from elixirs to fasting regimens.

PubMed

de Cabo, Rafael; Carmona-Gutierrez, Didac; Bernier, Michel; Hall, Michael N; Madeo, Frank

2014-06-19

The phenomenon of aging is an intrinsic feature of life. Accordingly, the possibility to manipulate it has fascinated humans likely since time immemorial. Recent evidence is shaping a picture where low caloric regimes and exercise may improve healthy senescence, and several pharmacological strategies have been suggested to counteract aging. Surprisingly, the most effective interventions proposed to date converge on only a few cellular processes, in particular nutrient signaling, mitochondrial efficiency, proteostasis, and autophagy. Here, we critically examine drugs and behaviors to which life- or healthspan-extending properties have been ascribed and discuss the underlying molecular mechanisms. Copyright © 2014 Elsevier Inc. All rights reserved.

Epoxide-Opening Cascades in the Synthesis of Polycyclic Polyether Natural Products

PubMed Central

2009-01-01

The group of polycyclic polyether natural products is of special interest due to the fascinating structure and biological effects displayed by its members. The latter includes potentially therapeutic antibiotic, antifungal, and anticancer properties, as well as extreme lethality. The polycyclic structural features of this family can, in some cases, be traced to their biosynthetic origin, but in others that are less well understood, only to proposed biosynthetic pathways that feature dramatic, yet speculative, epoxide–opening cascades. In this review we summarize how such epoxide–opening cascade reactions have been used in the synthesis of polycyclic polyethers and related natural products. PMID:19572302

Nickel antimony oxide (NiSb2O6): A fascinating nanostructured material for gas sensing application

NASA Astrophysics Data System (ADS)

Singh, Archana; Singh, Ajendra; Singh, Satyendra; Tandon, Poonam

2016-02-01

Fabrication of nanocrystalline NiSb2O6 thin films via sol-gel spin coating method towards the development of liquefied petroleum gas (LPG) sensor operable at room temperature (25 °C) is being reported. Nanostructural, surface morphological and optical properties of trirutile-type NiSb2O6 have been investigated in order to explore the parameters of interest. The crystallite size has been found to be 19 nm. A detailed sensing performance (sensitivity, sensor response, response and recovery times, reproducibility and long term stability) of NiSb2O6 nanostructures grown on alumina substrate has been investigated.

Engineering Low Dimensional Materials with van der Waals Interaction

NASA Astrophysics Data System (ADS)

Jin, Chenhao

Two-dimensional van der Waals materials grow into a hot and big field in condensed matter physics in the past decade. One particularly intriguing thing is the possibility to stack different layers together as one wish, like playing a Lego game, which can create artificial structures that do not exist in nature. These new structures can enable rich new physics from interlayer interaction: The interaction is strong, because in low-dimension materials electrons are exposed to the interface and are susceptible to other layers; and the screening of interaction is less prominent. The consequence is rich, not only from the extensive list of two-dimensional materials available nowadays, but also from the freedom of interlayer configuration, such as displacement and twist angle, which creates a gigantic parameter space to play with. On the other hand, however, the huge parameter space sometimes can make it challenging to describe consistently with a single picture. For example, the large periodicity or even incommensurability in van der Waals systems creates difficulty in using periodic boundary condition. Worse still, the huge superlattice unit cell and overwhelming computational efforts involved to some extent prevent the establishment of a simple physical picture to understand the evolution of system properties in the parameter space of interlayer configuration. In the first part of the dissertation, I will focus on classification of the huge parameter space into subspaces, and introduce suitable theoretical approaches for each subspace. For each approach, I will discuss its validity, limitation, general solution, as well as a specific example of application demonstrating how one can obtain the most important effects of interlayer interaction with little computation efforts. Combining all the approaches introduced will provide an analytic solution to cover majority of the parameter space, which will be very helpful in understanding the intuitive physical picture behind the consequence of interlayer interaction, as well as its systematic evolution in the parameter space. Experimentally, optical spectroscopy is a powerful tool to investigate properties of materials, owing to its insusceptibility to extrinsic effects like defects, capability of obtaining information in large spectral range, and the sensitivity to not only density of states but also wavefunction through transition matrix element. Following the classification of interlayer interaction, I will present optical spectroscopy studies of three van der Waals systems: Two-dimensional few layer phosphorene, one-dimensional double-walled nanotubes, and two-dimensional graphene/hexagonal Boron Nitride heterostructure. Experimental results exhibit rich and distinctively different effects of interlayer interaction in these systems, as a demonstration of the colorful physics from the large parameter space. On the other hand, all these cases can be well-described by the methods developed in the theory part, which explains experimental results quantitatively through only a few parameters each with clear physical meaning. Therefore, the formalism given here, both from theoretical and experimental aspects, offers a generally useful methodology to study, understand and design van der Waals materials for both fascinating physics and novel applications.

Europium mixed-valence, long-range magnetic order, and dynamic magnetic response in EuCu 2 ( Si x Ge 1 - x ) 2

DOE PAGES

Nemkovski, Krill S.; Kozlenko, D. P.; Alekseev, Pavel A.; ...

2016-11-01

In mixed-valence or heavy-fermion systems, the hybridization between local f orbitals and conduction band states can cause the suppression of long-range magnetic order, which competes with strong spin uctuations. Ce- and Yb-based systems have been found to exhibit fascinating physical properties (heavy-fermion superconductivity, non-Fermi-liquid states, etc.) when tuned to the vicinity of magnetic quantum critical points by use of various external control parameters (temperature, magnetic eld, chemical composition). Recently, similar effects (mixed-valence, Kondo uctuations, heavy Fermi liquid) have been reported to exist in some Eu-based compounds. Unlike Ce (Yb), Eu has a multiple electron (hole) occupancy of its 4f shell,more » and the magnetic Eu 2+ state (4f 7) has no orbital component in the usual LS coupling scheme, which can lead to a quite different and interesting physics. In the EuCu 2(Si xGe 1-x) 2 series, where the valence can be tuned by varying the Si/Ge ratio, it has been reported that a significant valence uctuation can exist even in the magnetic order regime. This paper presents a detailed study of the latter material using different microscopic probes (XANES, Mossbauer spectroscopy, elastic and inelastic neutron scattering), in which the composition dependence of the magnetic order and dynamics across the series is traced back to the change in the Eu valence state. In particular, the results support the persistence of valence uctuations into the antiferromagnetic state over a sizable composition range below the critical Si concentration x c ≈ 0:65. In conclusion, the sequence of magnetic ground states in the series is shown to re ect the evolution of the magnetic spectral response.« less

Acoustic perfect absorber based on metasurface with deep sub-wavelength thickness (Conference Presentation)

NASA Astrophysics Data System (ADS)

Assouar, Badreddine; Li, Yong

2016-04-01

The concept of the coiling up space, based on which artificial structures could exhibit extreme acoustic properties, such as high refractive index, double negativity, near-zero index, etc., have been investigated intensively recently due to the fascinating underlying physics and diverse potential applications [1-3]. One of the most important functionality is the ability to shrink bulky structures into deep sub-wavelength scale. It is therefore intuitive to prospect that the concept of coiling up space, if could be extended into the perforated system, will benefit to significantly reduce the total thickness while keeping total absorption. Conventional acoustic absorbers require a structure with a thickness comparable to the working wavelength, resulting major obstacles in real applications in low frequency range. We present a metasurface-based perfect absorber capable of achieving the total absorption of acoustic wave in extremely low frequency region. The metasurface possessing a deep sub-wavelength thickness down to a feature size of ~ lambda/223 is composed of a perforated plate and a coiled coplanar air chamber. Simulations based on fully coupled acoustic with thermodynamic equations and theoretical impedance analysis are utilized to reveal the underlying physics and the acoustic performances, showing an excellent agreement. Our realization should have high impact on amount of applications due to the extremely thin thickness, easy fabrication and high efficiency of the proposed structure. References 1. Z. Liang and J. Li, Phys. Rev. Lett. 108, 114301 (2012). 2. Y. Li, B. Liang, X. Tao, X. F. Zhu, X. Y. Zou, and J. C. Cheng, Appl. Phys. Lett. 101, 233508 (2012). 3. Y. Xie, W. Wang, H. Chen, A. Konneker, B. I. Popa, and S. A. Cummer, Nat. Commun. 5, 5553 (2014).

Radiation sensors for medical, industrial and environmental applications: how to engage with schools and the general public

NASA Astrophysics Data System (ADS)

Seitz, B.; Campos Rivera, N.; Gray, R.; Powell, A.; Thomson, F.

2018-01-01

Radiation, radiation detection and radiation protection are topics in physics and its applications which generate a wide interest in the public. This interest is either generated through medical procedures, applications of nuclear energy or nuclear accidents. The technical nature of these topics usually means that they are not well covered in the normal education stream, opening many opportunities to engage with schools and the general public to showcase the latest developments and their applications. The detection of radiation is at the very heart of understanding radiation, its fascination and associated fears. The outreach group of the nuclear physics group at the University of Glasgow demonstrates a number of successful outreach activities centred around radiation detection and described in this paper, focusing on activities delivered to a variety of audiences and related to applied nuclear physics work within our group. These concentrate on the application of novel sensor technologies for nuclear decommissioning, medical imaging modalities and the monitoring of environmental radioactivity. The paper will provide some necessary background material as well as practical instructions for some of the activities developed.

DNA confinement in nanochannels: physics and biological applications

NASA Astrophysics Data System (ADS)

Reisner, Walter; Pedersen, Jonas N.; Austin, Robert H.

2012-10-01

DNA is the central storage molecule of genetic information in the cell, and reading that information is a central problem in biology. While sequencing technology has made enormous advances over the past decade, there is growing interest in platforms that can readout genetic information directly from long single DNA molecules, with the ultimate goal of single-cell, single-genome analysis. Such a capability would obviate the need for ensemble averaging over heterogeneous cellular populations and eliminate uncertainties introduced by cloning and molecular amplification steps (thus enabling direct assessment of the genome in its native state). In this review, we will discuss how the information contained in genomic-length single DNA molecules can be accessed via physical confinement in nanochannels. Due to self-avoidance interactions, DNA molecules will stretch out when confined in nanochannels, creating a linear unscrolling of the genome along the channel for analysis. We will first review the fundamental physics of DNA nanochannel confinement—including the effect of varying ionic strength—and then discuss recent applications of these systems to genomic mapping. Apart from the intense biological interest in extracting linear sequence information from elongated DNA molecules, from a physics view these systems are fascinating as they enable probing of single-molecule conformation in environments with dimensions that intersect key physical length-scales in the 1 nm to 100 µm range.

DNA confinement in nanochannels: physics and biological applications.

PubMed

Reisner, Walter; Pedersen, Jonas N; Austin, Robert H

2012-10-01

DNA is the central storage molecule of genetic information in the cell, and reading that information is a central problem in biology. While sequencing technology has made enormous advances over the past decade, there is growing interest in platforms that can readout genetic information directly from long single DNA molecules, with the ultimate goal of single-cell, single-genome analysis. Such a capability would obviate the need for ensemble averaging over heterogeneous cellular populations and eliminate uncertainties introduced by cloning and molecular amplification steps (thus enabling direct assessment of the genome in its native state). In this review, we will discuss how the information contained in genomic-length single DNA molecules can be accessed via physical confinement in nanochannels. Due to self-avoidance interactions, DNA molecules will stretch out when confined in nanochannels, creating a linear unscrolling of the genome along the channel for analysis. We will first review the fundamental physics of DNA nanochannel confinement--including the effect of varying ionic strength--and then discuss recent applications of these systems to genomic mapping. Apart from the intense biological interest in extracting linear sequence information from elongated DNA molecules, from a physics view these systems are fascinating as they enable probing of single-molecule conformation in environments with dimensions that intersect key physical length-scales in the 1 nm to 100 µm range.

Dual-enhanced photothermal conversion properties of reduced graphene oxide-coated gold superparticles for light-triggered acoustic and thermal theranostics†

PubMed Central

Lin, Li-Sen; Yang, Xiangyu; Niu, Gang

2017-01-01

A rational design of highly efficient photothermal agents that possess excellent light-to-heat conversion properties is a fascinating topic in nanotheranostics. Herein, we present a facile route to fabricate size-tunable reduced graphene oxide (rGO)-coated gold superparticles (rGO-GSPs) and demonstrate their dual-enhanced photothermal conversion properties for photoacoustic imaging and photothermal therapy. For the first time, graphene oxide (GO) was directly used as an emulsifying agent for the preparation of gold superparticles (GSPs) with near-infrared absorption by the emulsion method. Moreover, GO spontaneously deposited on the surface of GSPs could also act as the precursor of the rGO shell. Importantly, both the plasmonic coupling of the self-assembled gold nanoparticles and the interaction between GSPs and rGO endow rGO-GSPs with enhanced photothermal conversion properties, allowing rGO-GSPs to be used for sensitive photoacoustic detection and efficient photothermal ablation of tumours in vivo. This study provides a facile approach to prepare colloidal superparticles–graphene hybrid nanostructures and will pave the way toward the design and optimization of photothermal nanomaterials with improved properties for theranostic applications. PMID:26726809

Engaging space: extraterrestrial architecture and the human psyche

NASA Astrophysics Data System (ADS)

Marie Seguin, Angel

2005-05-01

The human fascination with exploring and inhabiting the space that lies beyond Earth's atmosphere continues to grow. Nevertheless, 40 years of experience to date have clearly established that humans in outer space routinely suffer significant psychological impairment arising from their stressful extraterrestrial living conditions. This paper explores those extraterrestrial conditions through the interactions between the extraordinarily harsh environment of outer space, the sensations that humans encounter in space, and the qualities of a habitat that physically interposes itself between the two. The objective of this paper is to develop a habitat that expresses the extraterrestrial condition while supporting the mental health of its inhabitants, so as to augment the success of prolonged extraterrestrial residence and interplanetary travel.

Bioinspired Functional Materials

DOE PAGES

Zheng, Yongmei; Wang, Jingxia; Hou, Yongping; ...

2014-11-25

This special issue is focused on the nanoscale or micro-/nanoscale structures similar to the biological features in multilevels or hierarchy and so on. Research by mimicking biological systems has shown more impact on many applications due to the well-designed micro-/nanostructures inspired from the biological surfaces or interfaces; therefore, the materials may achieve the fascinating functionality. In conclusion, the bioinspired functional materials may be fabricated by developing novel technology or methods such as synthesis, self-assembly, and soft lithography at micro- or nanolevel or multilevels and, in addition, the multidisciplinary procedures of physical or chemical methods and nanotechnology to mimic the biologicalmore » multiscale micro-/nanostructures onto one-/two-dimensional surface materials.« less

Binaries in globular clusters

NASA Technical Reports Server (NTRS)

Hut, Piet; Mcmillan, Steve; Goodman, Jeremy; Mateo, Mario; Phinney, E. S.; Pryor, Carlton; Richer, Harvey B.; Verbunt, Frank; Weinberg, Martin

1992-01-01

Recent observations have shown that globular clusters contain a substantial number of binaries most of which are believed to be primordial. We discuss different successful optical search techniques, based on radial-velocity variables, photometric variables, and the positions of stars in the color-magnitude diagram. In addition, we review searches in other wavelengths, which have turned up low-mass X-ray binaries and more recently a variety of radio pulsars. On the theoretical side, we give an overview of the different physical mechanisms through which individual binaries evolve. We discuss the various simulation techniques which recently have been employed to study the effects of a primordial binary population, and the fascinating interplay between stellar evolution and stellar dynamics which drives globular-cluster evolution.

Cajal and consciousness. Introduction.

PubMed

Marijuán, P C

2001-04-01

One hundred years after Santiago Ramón Cajal established the bases of modern neuroscience in his masterpiece Textura del sistema nervioso del hombre y de los vertebrados, the question is stated again: What is the status of consciousness today? The responses in this book, by contemporary leading figures of neuroscience, evolution, molecular biology, computer science, and quantum physics, collectively compose a fascinating conceptual landscape. Both the evolutionary emergence of consciousness and its development towards the highest level may be analyzed by a wealth of new theories and hypotheses, including Cajal's prescient ones. Some noticeable gaps remain, however. Celebrating the centennial of Textura is a timely occasion to reassess how close--and how far--our system of the sciences is to explaining consciousness.

Video game induced knuckle pad.

PubMed

Rushing, Mary E; Sheehan, Daniel J; Davis, Loretta S

2006-01-01

Controversy and concern surround the video game playing fascination of children. Scientific reports have explored the negative effects of video games on youth, with a growing number recognizing the actual physical implications of this activity. We offer another reason to discourage children's focus on video games: knuckle pads. A 13-year-old black boy presented with an asymptomatic, slightly hyperpigmented plaque over his right second distal interphalangeal joint. A punch biopsy specimen confirmed knuckle pad as the diagnosis, and a traumatic etiology from video game playing was suspected. Knuckle pads can be painful, cosmetically unappealing, and refractory to treatment. They can now be recognized as yet another potential adverse consequence of chronic video game playing.

Distinguishing Majorana bound states and Andreev bound states with microwave spectra

NASA Astrophysics Data System (ADS)

Zhang, Zhen-Tao

2018-04-01

Majorana fermions are a fascinating and not yet confirmed quasiparticles in condensed matter physics. Here we propose using microwave spectra to distinguish Majorana bound states (MBSs) from topological trivial Andreev bound states. By numerically calculating the transmission and Zeeman field dependence of the many-body excitation spectrum of a 1D Josephson junction, we find that the two kinds of bound states have distinct responses to variations in the related parameters. Furthermore, the singular behaviors of the MBSs spectrum could be attributed to the robust fractional Josephson coupling and nonlocality of MBSs. Our results provide a feasible method to verify the existence of MBSs and could accelerate its application to topological quantum computation.

Effect of Secondary Doping Using Sorbitol on Structure and Transport Properties of PEDOT-PSS Thin Films

NASA Astrophysics Data System (ADS)

Khasim, Syed; Pasha, Apsar; Roy, Aashish S.; Parveen, Ameena; Badi, Nacer

2017-07-01

Poly(3,4-ethylene dioxythiophene):poly(styrenesulphonate) (PEDOT-PSS) in the recent past has emerged as one of the most fascinating conducting polymers for many device applications. The unique feature of PEDOT-PSS is its transparency in the entire visible spectrum with excellent thermal stability. The PEDOT-PSS as prepared as an aqueous dispersion has very low conductivity, and it hinders the performance of a device. In this work we report the conductivity enhancement of PEDOT-PSS thin films through secondary doping using a polar organic solvent such as sorbitol. The mechanism of conductivity enhancement was studied through various physical and chemical characterizations. The effect of sorbitol concentration on structure and transport properties of PEDOT-PSS thin films was investigated in detail. The structural and morphological modifications in PEDOT-PSS due to the addition of sorbitol was studied through Fourier transform spectroscopy, Ultra Violet-visible spectroscopy, theromogravimetric analysis, scanning electron microscopy and atomic force microscopy. The interactions resulting from conformational changes of PEDOT chains that changes from coiled to linear structure due to the sorbitol treatment significantly improves the conductivity of PEDOT-PSS films. The secondary doping of sorbitol reduces the energy barrier that facilitates the charge carrier hopping leading to enhanced conductivity. We have observed that the conductivity of PEDOT-PSS thin films was increased by two fold due to sorbitol treatment when compared to conductivity of pure PEDOT-PSS. We have carried out detailed analysis of dielectric parameters of sorbitol-treated PEDOT-PSS films and found that sorbitol treatment has a significant effect on various dielectric attributes of PEDOT-PSS films. Hence, secondary doping using sorbitol could be a useful way to effectively tailor the conductivity and dielectric properties of PEDOT-PSS thin films that can be used as flexible electrodes in optoelectronic devices.

Ultrafast interfacial energy transfer and interlayer excitons in the monolayer WS2/CsPbBr3 quantum dot heterostructure.

PubMed

Li, Han; Zheng, Xin; Liu, Yu; Zhang, Zhepeng; Jiang, Tian

2018-01-25

The idea of fabricating artificial solids with band structures tailored to particular applications has long fascinated condensed matter physicists. Heterostructure (HS) construction is viewed as an effective and appealing approach to engineer novel electronic properties in two dimensional (2D) materials. Different from common 2D/2D heterojunctions where energy transfer is rarely observed, CsPbBr 3 quantum dots (0D-QDs) interfaced with 2D materials have become attractive HSs for exploring the physics of charge transfer and energy transfer, due to their superior optical properties. In this paper, a new 0D/2D HS is proposed and experimentally studied, making it possible to investigate both light utilization and energy transfer. Specifically, this HS is constructed between monolayer WS 2 and CsPbBr 3 QDs, and exhibits a hybrid band alignment. The dynamics of energy transfer within the investigated 0D/2D HS is characterized by femtosecond transient absorption spectrum (TAS) measurements. The TAS results reveal that ultrafast energy transfer caused by optical excitation is observed from CsPbBr 3 QDs to the WS 2 layer, which can increase the exciton fluence within the WS 2 layer up to 69% when compared with pristine ML WS 2 under the same excitation fluence. Moreover, the formation and dynamics of interlayer excitons have also been investigated and confirmed in the HS, with a calculated recombination time of 36.6 ps. Finally, the overall phenomenological dynamical scenario for the 0D/2D HS is established within the 100 ps time region after excitation. The techniques introduced in this work can also be applied to versatile optoelectronic devices based on low dimensional materials.

Real-time detection of metal ions using conjugated polymer composite papers.

PubMed

Lee, Ji Eun; Shim, Hyeon Woo; Kwon, Oh Seok; Huh, Yang-Il; Yoon, Hyeonseok

2014-09-21

Cellulose, a natural polymeric material, has widespread technical applications because of its inherent structural rigidity and high surface area. As a conjugated polymer, polypyrrole shows practical potential for a diverse and promising range of future technologies. Here, we demonstrate a strategy for the real-time detection and removal of metal ions with polypyrrole/cellulose (PPCL) composite papers in solution. Simply, the conjugated polymer papers had different chemical/physical properties by applying different potentials to them, which resulted in differentiable response patterns and adsorption efficiencies for individual metal ions. First, large-area PPCL papers with a diameter of 5 cm were readily obtained via vapor deposition polymerization. The papers exhibited both mechanical flexibility and robustness, in which polypyrrole retained its redox property perfectly. The ability of the PPCL papers to recognize metal ions was examined in static and flow cells, in which real-time current change was monitored at five different applied potentials (+1, +0.5, 0, -0.5, and -1 V vs. Ag/AgCl). Distinguishable signals in the PPCL paper responses were observed for individual metal ions through principal component analysis. Particularly, the PPCL papers yielded unique signatures for three metal ions, Hg(ii), Ag(i), and Cr(iii), even in a real sample, groundwater. The sorption of metal ions by PPCL papers was examined in the flow system. The PPCL papers had a greatly superior adsorption efficiency for Hg(ii) compared to that of the other metal ions. With the strong demand for the development of inexpensive, flexible, light-weight, and environmentally friendly devices, the fascinating characteristics of these PPCL papers are likely to provide good opportunities for low-cost paper-based flexible or wearable devices.

Dilution-Induced Formation of Hybrid Perovskite Nanoplatelets.

PubMed

Tong, Yu; Ehrat, Florian; Vanderlinden, Willem; Cardenas-Daw, Carlos; Stolarczyk, Jacek K; Polavarapu, Lakshminarayana; Urban, Alexander S

2016-12-27

Perovskite nanocrystals (NCs) are an important extension to the fascinating field of hybrid halide perovskites. Showing significantly enhanced photoluminescence (PL) efficiency and emission wavelengths tunable through halide content and size, they hold great promise for light-emitting applications. Despite the rapid advancement in this field, the physical nature and size-dependent excitonic properties have not been well investigated due to the challenges associated with their preparation. Herein we report the spontaneous formation of highly luminescent, quasi-2D organic-inorganic hybrid perovskite nanoplatelets (NPls) upon dilution of a dispersion of bulk-like NCs. The fragmentation of the large NCs is attributed to osmotic swelling induced by the added solvent. An excess of organic ligands in the solvent quickly passivates the newly formed surfaces, stabilizing the NPls in the process. The thickness of the NPls can be controlled both by the dilution level and by the ligand concentration. Such colloidal NPls and their thin films were found to be extremely stable under continuous UV light irradiation. Full tunability of the NPl emission wavelength is achieved by varying the halide ion used (bromide, iodide). Additionally, time-resolved PL measurements reveal an increasing radiative decay rate with decreasing thickness of the NPls, likely due to an increasing exciton binding energy. Similarly, measurements on iodide-containing NPls show a transformation from biexponential to monoexponential PL decay with decreasing thickness, likely due to an increasing fraction of excitonic recombination. This interesting phenomenon of change in fluorescence upon dilution is a result of the intricate nature of the perovskite material itself and is uncommon in inorganic materials. Our findings enable the synthesis of halide perovskite NCs with high quantum efficiency and good stability as well as a tuning of both their optical and morphological properties.

An RNAi based screen in Drosophila larvae identifies fascin as a regulator of myoblast fusion and myotendinous junction structure.

PubMed

Camuglia, Jaclyn M; Mandigo, Torrey R; Moschella, Richard; Mark, Jenna; Hudson, Christine H; Sheen, Derek; Folker, Eric S

2018-04-06

A strength of Drosophila as a model system is its utility as a tool to screen for novel regulators of various functional and developmental processes. However, the utility of Drosophila as a screening tool is dependent on the speed and simplicity of the assay used. Here, we use larval locomotion as an assay to identify novel regulators of skeletal muscle function. We combined this assay with muscle-specific depletion of 82 genes to identify genes that impact muscle function by their expression in muscle cells. The data from the screen were supported with characterization of the muscle pattern in embryos and larvae that had disrupted expression of the strongest hit from the screen. With this assay, we showed that 12/82 tested genes regulate muscle function. Intriguingly, the disruption of five genes caused an increase in muscle function, illustrating that mechanisms that reduce muscle function exist and that the larval locomotion assay is sufficiently quantitative to identify conditions that both increase and decrease muscle function. We extended the data from this screen and tested the mechanism by which the strongest hit, fascin, impacted muscle function. Compared to controls, animals in which fascin expression was disrupted with either a mutant allele or muscle-specific expression of RNAi had fewer muscles, smaller muscles, muscles with fewer nuclei, and muscles with disrupted myotendinous junctions. However, expression of RNAi against fascin only after the muscle had finished embryonic development did not recapitulate any of these phenotypes. These data suggest that muscle function is reduced due to impaired myoblast fusion, muscle growth, and muscle attachment. Together, these data demonstrate the utility of Drosophila larval locomotion as an assay for the identification of novel regulators of muscle development and implicate fascin as necessary for embryonic muscle development.

High expression of SALL4 and fascin, and loss of E-cadherin expression in undifferentiated/dedifferentiated carcinomas of the endometrium

PubMed Central

Onder, Semen; Taskin, Orhun Cig; Sen, Fatma; Topuz, Samet; Kucucuk, Seden; Sozen, Hamdullah; Ilhan, Ridvan; Tuzlali, Sitki; Yavuz, Ekrem

2017-01-01

Abstract Undifferentiated/dedifferentiated endometrial carcinomas (UCE/DCEs) of the endometrium are rare tumors with poor prognosis. There are few clinicopathologic studies with detailed immunohistochemical analysis regarding UCE/DCEs. We evaluated the diagnostic value of a selected tumor stem-cell marker and epithelial-mesenchymal transition (EMT) markers, in addition to previously studied markers in identifying UCE/DCEs from other types of high-grade endometrial carcinomas. Eleven cases of UCE/DCEs with complete clinical follow-up that were diagnosed between 2006 and 2015 were included in the study. For immunohistochemical comparison, 11 clinically matched cases for each type of other high-grade endometrial carcinomas (high-grade endometrioid (F3-EC), serous [SC], and clear cell carcinoma [CCC]) were used as a control group. An immunohistochemical analysis including fascin, SALL4, E-cadherin, and β-catenin, in addition to epithelial and neuroendocrine markers was performed in each case. The majority of UCE/DCEs displayed diffuse expression of fascin (81.9%) and loss of E-cadherin expression (54.5%). SALL4 expression was detected in 36.3% of the UCE/DCE cases. SALL4 expression was significantly more frequent in UCE/DCEs than all other high-grade carcinomas (P < 0.001). Loss of E-cadherin and fascin expression was significantly more frequent in UCE/DCEs than high-grade endometrioid and clear cell adenocarcinomas (P = 0.012, 0.014 and P = 0.01, 0.003, respectively). We suggest that loss of E-cadherin expression together with fascin and SALL4 immunopositivity in addition to morphologic features have an impact in differential diagnosis of UCE/DCEs from other high-grade endometrial carcinomas. PMID:28272224

Cellulose-Based Biomimetics and Their Applications.

PubMed

Almeida, Ana P C; Canejo, João P; Fernandes, Susete N; Echeverria, Coro; Almeida, Pedro L; Godinho, Maria H

2018-05-01

Nature has been producing cellulose since long before man walked the surface of the earth. Millions of years of natural design and testing have resulted in cellulose-based structures that are an inspiration for the production of synthetic materials based on cellulose with properties that can mimic natural designs, functions, and properties. Here, five sections describe cellulose-based materials with characteristics that are inspired by gratings that exist on the petals of the plants, structurally colored materials, helical filaments produced by plants, water-responsive materials in plants, and environmental stimuli-responsive tissues found in insects and plants. The synthetic cellulose-based materials described herein are in the form of fibers and films. Fascinating multifunctional materials are prepared from cellulose-based liquid crystals and from composite cellulosic materials that combine functionality with structural performance. Future and recent applications are outlined. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Polysaccharide based nanogels in the drug delivery system: Application as the carrier of pharmaceutical agents.

PubMed

Debele, Tilahun Ayane; Mekuria, Shewaye Lakew; Tsai, Hsieh-Chih

2016-11-01

Polysaccharide-based nanoparticles have fascinated attention as a vesicle of different pharmaceutical agents due to their unique multi-functional groups in addition to their physicochemical properties, including biocompatibility and biodegradability. The existence of multi-functional groups on the polysaccharide backbone permits facile chemical or biochemical modification to synthesize polysaccharide based nanoparticles with miscellaneous structures. Polysaccharide-based nanogels have high water content, large surface area for multivalent bioconjugation, tunable size, and interior network for the incorporation of different pharmaceutical agents. These unique properties offer great potential for the utilization of polysaccharide-based nanogels in the drug delivery systems. Hence, this review describes chemistry of certain common polysaccharides, several methodologies used to synthesize polysaccharide nanoparticles and primarily focused on the polysaccharide (or polysaccharide derivative) based nanogels as the carrier of pharmaceutical agents. Copyright © 2016 Elsevier B.V. All rights reserved.

Electrospray ionization mass spectrometry: a technique to access the information beyond the molecular weight of the analyte.

PubMed

Banerjee, Shibdas; Mazumdar, Shyamalava

2012-01-01

The Electrospray Ionization (ESI) is a soft ionization technique extensively used for production of gas phase ions (without fragmentation) of thermally labile large supramolecules. In the present review we have described the development of Electrospray Ionization mass spectrometry (ESI-MS) during the last 25 years in the study of various properties of different types of biological molecules. There have been extensive studies on the mechanism of formation of charged gaseous species by the ESI. Several groups have investigated the origin and implications of the multiple charge states of proteins observed in the ESI-mass spectra of the proteins. The charged analytes produced by ESI can be fragmented by activating them in the gas-phase, and thus tandem mass spectrometry has been developed, which provides very important insights on the structural properties of the molecule. The review will highlight recent developments and emerging directions in this fascinating area of research.

Advances in applications of rhamnolipids biosurfactant in environmental remediation: A review.

PubMed

Liu, Guansheng; Zhong, Hua; Yang, Xin; Liu, Yang; Shao, Binbin; Liu, Zhifeng

2018-04-01

The objective of this review is to provide a comprehensive overview of the advances in the applications of rhamnolipids biosurfactants in soil and ground water remediation for removal of petroleum hydrocarbon and heavy metal contaminants. The properties of rhamnolipids associated with the contaminant removal, that is, solubilization, emulsification, dispersion, foaming, wetting, complexation, and the ability to modify bacterial cell surface properties, were reviewed in the first place. Then current remediation technologies with integration of rhamnolipid were summarized, and the effects and mechanisms for rhamnolipid to facilitate contaminant removal for these technologies were discussed. Finally rhamnolipid-based methods for remediation of the sites co-contaminated by petroleum hydrocarbons and heavy metals were presented and discussed. The review is expected to enhance our understanding on environmental aspects of rhamnolipid and provide some important information to guide the extending use of this fascinating chemical in remediation applications. © 2017 Wiley Periodicals, Inc.

Simulation and Modeling in High Entropy Alloys

NASA Astrophysics Data System (ADS)

Toda-Caraballo, I.; Wróbel, J. S.; Nguyen-Manh, D.; Pérez, P.; Rivera-Díaz-del-Castillo, P. E. J.

2017-11-01

High entropy alloys (HEAs) is a fascinating field of research, with an increasing number of new alloys discovered. This would hardly be conceivable without the aid of materials modeling and computational alloy design to investigate the immense compositional space. The simplicity of the microstructure achieved contrasts with the enormous complexity of its composition, which, in turn, increases the variety of property behavior observed. Simulation and modeling techniques are of paramount importance in the understanding of such material performance. There are numerous examples of how different models have explained the observed experimental results; yet, there are theories and approaches developed for conventional alloys, where the presence of one element is predominant, that need to be adapted or re-developed. In this paper, we review of the current state of the art of the modeling techniques applied to explain HEAs properties, identifying the potential new areas of research to improve the predictability of these techniques.

Design of Tribologically Enhanced Polymeric Materials for Biomedical Applications

NASA Astrophysics Data System (ADS)

Osaheni, Allen O.

Anytime two surfaces are in normal contact, accompanied by tangential motion, there is potential for deterioration of one or both surfaces. Gradual wear, or the removal of surface material, is typically an undesirable event. Therefore, the need for lubrication arises to minimize the amount of shear stress that develops between opposing surfaces. This reduction in shear stress is characterized by the coefficient of friction (COF). Friction is one of the primary subjects of interest in tribology, the science of the friction and wear of articulating surfaces. A number of fascinating tribological systems can be found in nature. One example which has drawn a considerable interest is articular cartilage. This smooth white tissue lines the articulating surfaces of our joints and sustains a tremendous amount of stress while maintaining smooth joint motion and low COF. The low COF exhibited by articular cartilage is unmatched by any man-made material. The phenomenal tribological properties of this biphasic material are attributed to a combination of a unique boundary lubrication mechanism and its ability to support interstitial fluid pressurization. This dissertation details the synthesis and characterization of novel tribologically enhanced polymeric materials which show great potential for several biomedical applications. Design of these material relied on the use of biomimetic tribological mechanisms. The overarching characterization described in this investigation provides valuable insight into the physical and mechanical characteristics of these unique materials.

Tunable Micro- and Nanomechanical Resonators

PubMed Central

Zhang, Wen-Ming; Hu, Kai-Ming; Peng, Zhi-Ke; Meng, Guang

2015-01-01

Advances in micro- and nanofabrication technologies have enabled the development of novel micro- and nanomechanical resonators which have attracted significant attention due to their fascinating physical properties and growing potential applications. In this review, we have presented a brief overview of the resonance behavior and frequency tuning principles by varying either the mass or the stiffness of resonators. The progress in micro- and nanomechanical resonators using the tuning electrode, tuning fork, and suspended channel structures and made of graphene have been reviewed. We have also highlighted some major influencing factors such as large-amplitude effect, surface effect and fluid effect on the performances of resonators. More specifically, we have addressed the effects of axial stress/strain, residual surface stress and adsorption-induced surface stress on the sensing and detection applications and discussed the current challenges. We have significantly focused on the active and passive frequency tuning methods and techniques for micro- and nanomechanical resonator applications. On one hand, we have comprehensively evaluated the advantages and disadvantages of each strategy, including active methods such as electrothermal, electrostatic, piezoelectrical, dielectric, magnetomotive, photothermal, mode-coupling as well as tension-based tuning mechanisms, and passive techniques such as post-fabrication and post-packaging tuning processes. On the other hand, the tuning capability and challenges to integrate reliable and customizable frequency tuning methods have been addressed. We have additionally concluded with a discussion of important future directions for further tunable micro- and nanomechanical resonators. PMID:26501294

Shining Light on Chitosan: A Review on the Usage of Chitosan for Photonics and Nanomaterials Research.

PubMed

Marpu, Sreekar B; Benton, Erin N

2018-06-17

Chitosan (CS) is a natural polymer derived from chitin that has found its usage both in research and commercial applications due to its unique solubility and chemical and biological attributes. The biocompatibility and biodegradability of CS have helped researchers identify its utility in the delivery of therapeutic agents, tissue engineering, wound healing, and more. Industrial applications include cosmetic and personal care products, wastewater treatment, and corrosion protection, to name a few. Many researchers have published numerous reviews outlining the physical and chemical properties of CS, as well as its use for many of the above-mentioned applications. Recently, the cationic polyelectrolyte nature of CS was found to be advantageous for stabilizing fascinating photonic materials including plasmonic nanoparticles (e.g., gold and silver), semiconductor nanoparticles (e.g., zinc oxide, cadmium sulfide), fluorescent organic dyes (e.g., fluorescein isothiocyanate (FITC)), luminescent transitional and lanthanide complexes (e.g., Au(I) and Ru(II), and Eu(III)). These photonic systems have been extensively investigated for their usage in antimicrobial, wound healing, diagnostics, sensing, and imaging applications. Highlighted in this review are the different works involving some of the above-mentioned molecular-nano systems that are prepared or stabilized using the CS polymer. The advantages and the role of the CS for synthesizing and stabilizing the above-mentioned optically active materials have been illustrated.

Reversible solvatomagnetic switching in a single-ion magnet from an entatic state† †Electronic supplementary information (ESI) available: Preparation methods and physical characterization data. Crystallographic refinement and computational details. Additional figures (Fig. S1–S12) and tables (Tables S1–S5). CCDC 952077 and 938463. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c6sc05188j Click here for additional data file. Click here for additional data file.

PubMed Central

Vallejo, J.; Viciano-Chumillas, M.; Castro, I.; Amorós, P.; Déniz, M.; Ruiz-Pérez, C.; Yuste-Vivas, C.; Krzystek, J.; Julve, M.; Lloret, F.

2017-01-01

A vast impact on molecular nanoscience can be achieved using simple transition metal complexes as dynamic chemical systems to perform specific and selective tasks under the control of an external stimulus that switches “ON” and “OFF” their electronic properties. While the interest in single-ion magnets (SIMs) lies in their potential applications in information storage and quantum computing, the switching of their slow magnetic relaxation associated with host–guest processes is insufficiently explored. Herein, we report a unique example of a mononuclear cobalt(ii) complex in which geometrical constraints are the cause of easy and reversible water coordination and its release. As a result, a reversible and selective colour and SIM behaviour switch occurs between a “slow-relaxing” deep red anhydrous material (compound 1) and its “fast-relaxing” orange hydrated form (compound 2). The combination of this optical and magnetic switching in this new class of vapochromic and thermochromic SIMs offers fascinating possibilities for designing multifunctional molecular materials. PMID:28580105

Configuration of ripple domains and their topological defects formed under local mechanical stress on hexagonal monolayer graphene

DOE PAGES

Park, Yeonggu; Choi, Jin Sik; Choi, Taekjib; ...

2015-03-24

Ripples in graphene are extensively investigated because they ensure the mechanical stability of two-dimensional graphene and affect its electronic properties. They arise from spontaneous symmetry breaking and are usually manifested in the form of domains with long-range order. It is expected that topological defects accompany a material exhibiting long-range order, whose functionality depends on characteristics of domains and topological defects. However, there remains a lack of understanding regarding ripple domains and their topological defects formed on monolayer graphene. Here we explore configuration of ripple domains and their topological defects in exfoliated monolayer graphenes on SiO₂/Si substrates using transverse shear microscope.more » We observe three-color domains with three different ripple directions, which meet at a core. Furthermore, the closed domain is surrounded by an even number of cores connected together by domain boundaries, similar to topological vortex and anti-vortex pairs. In addition, we have found that axisymmetric three-color domains can be induced around nanoparticles underneath the graphene. This fascinating configuration of ripple domains may result from the intrinsic hexagonal symmetry of two-dimensional graphene, which is supported by theoretical simulation using molecular dynamics. Our findings are expected to play a key role in understanding of ripple physics in graphene and other two-dimensional materials.« less

Configuration of ripple domains and their topological defects formed under local mechanical stress on hexagonal monolayer graphene

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Yeonggu; Choi, Jin Sik; Choi, Taekjib

Ripples in graphene are extensively investigated because they ensure the mechanical stability of two-dimensional graphene and affect its electronic properties. They arise from spontaneous symmetry breaking and are usually manifested in the form of domains with long-range order. It is expected that topological defects accompany a material exhibiting long-range order, whose functionality depends on characteristics of domains and topological defects. However, there remains a lack of understanding regarding ripple domains and their topological defects formed on monolayer graphene. Here we explore configuration of ripple domains and their topological defects in exfoliated monolayer graphenes on SiO₂/Si substrates using transverse shear microscope.more » We observe three-color domains with three different ripple directions, which meet at a core. Furthermore, the closed domain is surrounded by an even number of cores connected together by domain boundaries, similar to topological vortex and anti-vortex pairs. In addition, we have found that axisymmetric three-color domains can be induced around nanoparticles underneath the graphene. This fascinating configuration of ripple domains may result from the intrinsic hexagonal symmetry of two-dimensional graphene, which is supported by theoretical simulation using molecular dynamics. Our findings are expected to play a key role in understanding of ripple physics in graphene and other two-dimensional materials.« less

Using Computational and Mechanical Models to Study Animal Locomotion

PubMed Central

Miller, Laura A.; Goldman, Daniel I.; Hedrick, Tyson L.; Tytell, Eric D.; Wang, Z. Jane; Yen, Jeannette; Alben, Silas

2012-01-01

Recent advances in computational methods have made realistic large-scale simulations of animal locomotion possible. This has resulted in numerous mathematical and computational studies of animal movement through fluids and over substrates with the purpose of better understanding organisms’ performance and improving the design of vehicles moving through air and water and on land. This work has also motivated the development of improved numerical methods and modeling techniques for animal locomotion that is characterized by the interactions of fluids, substrates, and structures. Despite the large body of recent work in this area, the application of mathematical and numerical methods to improve our understanding of organisms in the context of their environment and physiology has remained relatively unexplored. Nature has evolved a wide variety of fascinating mechanisms of locomotion that exploit the properties of complex materials and fluids, but only recently are the mathematical, computational, and robotic tools available to rigorously compare the relative advantages and disadvantages of different methods of locomotion in variable environments. Similarly, advances in computational physiology have only recently allowed investigators to explore how changes at the molecular, cellular, and tissue levels might lead to changes in performance at the organismal level. In this article, we highlight recent examples of how computational, mathematical, and experimental tools can be combined to ultimately answer the questions posed in one of the grand challenges in organismal biology: “Integrating living and physical systems.” PMID:22988026

Generalized Low-Temperature Fabrication of Scalable Multi-Type Two-Dimensional Nanosheets with a Green Soft Template.

PubMed

Wang, Lanfang; Song, Chuang; Shi, Yi; Dang, Liyun; Jin, Ying; Jiang, Hong; Lu, Qingyi; Gao, Feng

2016-04-11

Two-dimensional nanosheets with high specific surface areas and fascinating physical and chemical properties have attracted tremendous interests because of their promising potentials in both fundamental research and practical applications. However, the problem of developing a universal strategy with a facile and cost-effective synthesis process for multi-type ultrathin 2 D nanostructures remains unresolved. Herein, we report a generalized low-temperature fabrication of scalable multi-type 2 D nanosheets including metal hydroxides (such as Ni(OH)2, Co(OH)2, Cd(OH)2, and Mg(OH)2), metal oxides (such as ZnO and Mn3O4), and layered mixed transition-metal hydroxides (Ni-Co LDH, Ni-Fe LDH, Co-Fe LDH, and Ni-Co-Fe layered ternary hydroxides) through the rational employment of a green soft-template. The synthesized crystalline inorganic nanosheets possess confined thickness, resulting in ultrahigh surface atom ratios and chemically reactive facets. Upon evaluation as electrode materials for pseudocapacitors, the Ni-Co LDH nanosheets exhibit a high specific capacitance of 1087 F g(-1) at a current density of 1 A g(-1), and excellent stability, with 103% retention after 500 cycles. This strategy is facile and scalable for the production of high-quality ultrathin crystalline inorganic nanosheets, with the possibility of extension to the preparation of other complex nanosheets. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Meteorites

NASA Astrophysics Data System (ADS)

Jenniskens, Peter

2015-08-01

Meteorites have long been known to offer a unique window into planetary formation processes at the time of solar system formation and into the materials that rained down on Earth at the time of the origin of life. Their material properties determine the impact hazard of Near Earth Asteroids. Some insight into how future laboratory studies of meteorites and laboratory astrophysics simulations of relevant physical processes can help address open questions in these areas and generate new astronomical observations, comes from what was learned from the recent laboratory studies of freshly fallen meteorites. The rapid recovery of Almahata Sitta (a polymict Ureilite), Sutter's Mill (a CM chondrite regolith breccia), Novato (an L6 chondrite), and Chelyabinsk (an LL5 chondrite) each were followed by the creation of a meteorite consortium, which grew to over 50 researchers in the case of Chelyabinsk. New technologies were used to probe the organic content of the meteorites as well as their magnetic signatures, isotopic abundances, trapped noble gasses, and cosmogenic radio nucleides, amongst others. This has resulted in fascinating insight into the nature of the Ureilite parent body, the likely source region of the CM chondrites in the main asteroid belt, and the collisional environment of the CM parent body. This work has encouraged follow-up in the hope of catching more unique materials. Rapid response efforts are being developed that aim to recover meteorites as pristinely as possible from falls for which the approach orbit was measured. A significant increase in the number of known approach orbits for different meteorite types will help tie meteorite types to their asteroid family source regions. Work so far suggests that future laboratory studies may recognize multiple source regions for iron-rich ordinary chondrites, for example. Hope is that these source regions will give insight into the material properties of impacting asteroids. At least some future laboratory astrophysics experiments are expected to focus on clarifying the physical conditions during small asteroid impacts such as the one responsible for the Chelyabinsk airburst and the over 1200 injured who needed medical attention.

Coupling between crystal structure and magnetism in transition-metal oxides

NASA Astrophysics Data System (ADS)

Barton, Phillip Thomas

Transition-metal oxides exhibit a fascinating array of phenomena ranging from superconductivity to negative thermal expansion to catalysis. This dissertation focuses on magnetism, which is integral to engineering applications such as data storage, electric motors/generators, and transformers. The investigative approach follows structure-property relationships from materials science and draws on intuition from solid-state chemistry. The interplay between crystal structure and magnetic properties is studied experimentally in order to enhance the understanding of magnetostructural coupling mechanisms and provide insight into avenues for tuning behavior. A combination of diffraction and physical property measurements were used to study structural and magnetic phase transitions as a function of chemical composition, temperature, and magnetic field. The systems examined are of importance in Li-ion battery electrochemistry, condensed-matter physics, solid-state chemistry, and p-type transparent conducting oxides. The materials were prepared by solid-state reaction of powder reagents at high temperatures for periods lasting tens of hours. The first project discussed is of a solid solution between NiO, a correlated insulator, and LiNiO2, a layered battery cathode. Despite the deceptive structural and compositional simplicity of this system, a complete understanding of its complex magnetic properties has remained elusive. This study shows that nanoscale domains of chemical order form at intermediate compositions, creating interfaces between antiferromagnetism and ferrimagnetism that give rise to magnetic exchange bias. A simple model of the magnetism is presented along with a comprehensive phase diagram. The second set of investigations focus on the Ge-Co-O system where the spin-orbit coupling of Co(II) plays a significant role. GeCo2O 4 is reported to exhibit unusual magnetic behavior that arises from Ising spin in its spinel crystal structure. Studies by variable-temperature synchrotron X-ray diffraction reveal a magnetostructural transition and capacitance measurements show evidence for magnetodielectric behavior. The above work uncovered a Co10Ge3O16 phase that had a known structure but whose physical properties were largely uncharacterized. This project examined its metamagnetic properties using detailed magnetometry experiments. Upon the application of a magnetic field, this material goes through a first-order phase transition from a noncollinear antiferromagnet to an unknown ferrimagnetic state. Lastly, this thesis explored the chemical dilution of magnetism in some perovskite and delafossite solid solutions. In the perovskite structure, compositions intermediate to the endmembers SrRuO3, a ferromagnetic metal, and LaRhO3, a diamagnetic semiconductor, were investigated. While the magnetism of this system is poised between localized and itinerant behavior, a compositionally-driven metal to insulator transition, revealed by electrical resistivity measurements, did not strongly impact the magnetic properties. Instead, both octahedral tilting and magnetic dilution had strong effects, and comparison of this characterization to Sr1-- x CaxRuO3 reinforces the important role of structural distortions in determining magnetic ground state. The final materials studied were of composition CuAl1-- xCrxO2 (0 < x < 1) in the delafossite structure. The primary interest was the geometric frustration of antiferromagnetism in CuCrO 2 and significant short-range correlations were observed above TN. The analysis found that reducing the number of degenerate states through Al substitution did not enhance magnetic ordering because of the weakening of magnetic exchange.

European Scientific Notes. Volume 35, Number 5,

DTIC Science & Technology

1981-05-31

Mr. Y.S. Wu Information Systems ESN 35-5 (1981) COMPUTER Levrat himself is a fascinating Dan SCIENCE who took his doctorate at the Universitv of...fascinating Computer Science Department reports for project on computer graphics. Text nurposes of teaching and research di- processing by computer has...water batteries, of offshore winds and lighter support alkaline batterips, lead-acid systems , structures, will be carried out before metal/air batteries

The Mystery of The Moon Illusion - Exploring Size Perception

NASA Astrophysics Data System (ADS)

Ross, Helen; Plug, Cornelis

2002-09-01

For thousands of years, one scientific puzzle has fascinated and perplexed the greatest philosophers, mathematicians, physicists, and psychologists -- why do the moon and sun appear so much larger on the horizon than when high up in the sky? Exploring the theories from antiquity to now, the 'Mystery of the Moon Illusion' is the definitive book on a mystery that has fascinated and tested the greatest minds throughout the ages.

Depletion force induced collective motion of microtubules driven by kinesin

NASA Astrophysics Data System (ADS)

Inoue, Daisuke; Mahmot, Bulbul; Kabir, Arif Md. Rashedul; Farhana, Tamanna Ishrat; Tokuraku, Kiyotaka; Sada, Kazuki; Konagaya, Akihiko; Kakugo, Akira

2015-10-01

Collective motion is a fascinating example of coordinated behavior of self-propelled objects, which is often associated with the formation of large scale patterns. Nowadays, the in vitro gliding assay is being considered a model system to experimentally investigate various aspects of group behavior and pattern formation by self-propelled objects. In the in vitro gliding assay, cytoskeletal filaments F-actin or microtubules are driven by the surface immobilized associated biomolecular motors myosin or dynein respectively. Although the F-actin/myosin or microtubule/dynein system was found to be promising in understanding the collective motion and pattern formation by self-propelled objects, the most widely used biomolecular motor system microtubule/kinesin could not be successfully employed so far in this regard. Failure in exhibiting collective motion by kinesin driven microtubules is attributed to the intrinsic properties of kinesin, which was speculated to affect the behavior of individual gliding microtubules and mutual interactions among them. In this work, for the first time, we have demonstrated the collective motion of kinesin driven microtubules by regulating the mutual interaction among the gliding microtubules, by employing a depletion force among them. Proper regulation of the mutual interaction among the gliding microtubules through the employment of the depletion force was found to allow the exhibition of collective motion and stream pattern formation by the microtubules. This work offers a universal means for demonstrating the collective motion using the in vitro gliding assay of biomolecular motor systems and will help obtain a meticulous understanding of the fascinating coordinated behavior and pattern formation by self-propelled objects.Collective motion is a fascinating example of coordinated behavior of self-propelled objects, which is often associated with the formation of large scale patterns. Nowadays, the in vitro gliding assay is being considered a model system to experimentally investigate various aspects of group behavior and pattern formation by self-propelled objects. In the in vitro gliding assay, cytoskeletal filaments F-actin or microtubules are driven by the surface immobilized associated biomolecular motors myosin or dynein respectively. Although the F-actin/myosin or microtubule/dynein system was found to be promising in understanding the collective motion and pattern formation by self-propelled objects, the most widely used biomolecular motor system microtubule/kinesin could not be successfully employed so far in this regard. Failure in exhibiting collective motion by kinesin driven microtubules is attributed to the intrinsic properties of kinesin, which was speculated to affect the behavior of individual gliding microtubules and mutual interactions among them. In this work, for the first time, we have demonstrated the collective motion of kinesin driven microtubules by regulating the mutual interaction among the gliding microtubules, by employing a depletion force among them. Proper regulation of the mutual interaction among the gliding microtubules through the employment of the depletion force was found to allow the exhibition of collective motion and stream pattern formation by the microtubules. This work offers a universal means for demonstrating the collective motion using the in vitro gliding assay of biomolecular motor systems and will help obtain a meticulous understanding of the fascinating coordinated behavior and pattern formation by self-propelled objects. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr02213d

Menstruation in Ulysses.

PubMed

Mullin, Katherine

2008-01-01

This article investigates James Joyce's fascination with a wide variety of medical texts, sexual folklores, religious beliefs, and persistent superstitions about menstruation. That fascination finds its way into Ulysses, which draws upon a number of intertexts to inform a curiosity about the female body most strikingly articulated by Bloom, Molly, and Gerty MacDowell. These intertexts are not simply imported into the novel but are dismantled and interrogated, as Joyce exposes, rather than endorses, clichés of essential femininity.

The Manhattan Project; A very brief introduction to the physics of nuclear weapons

NASA Astrophysics Data System (ADS)

Reed, B. Cameron

2017-05-01

The development of nuclear weapons by the Manhattan Project during World War II was one of the most dramatic scientific/technological episodes in human history. This book, prepared by a recognized expert on the Manhattan Project, offers a concise survey of the essential physics concepts underlying fission weapons. The text describes the energetics and timescales of fast-neutron chain reactions, why only certain isotopes of uranium and plutonium are suitable for use in fission weapons, how critical mass and bomb yield can be estimated, how the efficiency of nuclear weapons can be enhanced, how the fissile forms of uranium and plutonium were obtained, some of the design details of the 'Little Boy' and 'Fat Man' bombs, and some of the thermal, shock, and radiation effects of nuclear weapons. Calculation exercises are provided, and a Bibliography lists authoritative print and online sources of information for readers who wish to pursue more detailed study of this fascinating topic.

Optical trapping of nanoparticles by ultrashort laser pulses.

PubMed

Usman, Anwar; Chiang, Wei-Yi; Masuhara, Hiroshi

2013-01-01

Optical trapping with continuous-wave lasers has been a fascinating field in the optical manipulation. It has become a powerful tool for manipulating micrometer-sized objects, and has been widely applied in physics, chemistry, biology, material, and colloidal science. Replacing the continuous-wave- with pulsed-mode laser in optical trapping has already revealed some novel phenomena, including the stable trap, modifiable trapping positions, and controllable directional optical ejections of particles in nanometer scales. Due to two distinctive features; impulsive peak powers and relaxation time between consecutive pulses, the optical trapping with the laser pulses has been demonstrated to have some advantages over conventional continuous-wave lasers, particularly when the particles are within Rayleigh approximation. This would open unprecedented opportunities in both fundamental science and application. This Review summarizes recent advances in the optical trapping with laser pulses and discusses the electromagnetic formulations and physical interpretations of the new phenomena. Its aim is rather to show how beautiful and promising this field will be, and to encourage the in-depth study of this field.

Atomic-scale observation of structural and electronic orders in the layered compound α-RuCl3

NASA Astrophysics Data System (ADS)

Ziatdinov, M.; Banerjee, A.; Maksov, A.; Berlijn, T.; Zhou, W.; Cao, H. B.; Yan, J.-Q.; Bridges, C. A.; Mandrus, D. G.; Nagler, S. E.; Baddorf, A. P.; Kalinin, S. V.

2016-12-01

A pseudospin-1/2 Mott phase on a honeycomb lattice is proposed to host the celebrated two-dimensional Kitaev model which has an elusive quantum spin liquid ground state, and fascinating physics relevant to the development of future templates towards topological quantum bits. Here we report a comprehensive, atomically resolved real-space study by scanning transmission electron and scanning tunnelling microscopies on a novel layered material displaying Kitaev physics, α-RuCl3. Our local crystallography analysis reveals considerable variations in the geometry of the ligand sublattice in thin films of α-RuCl3 that opens a way to realization of a spatially inhomogeneous magnetic ground state at the nanometre length scale. Using scanning tunnelling techniques, we observe the electronic energy gap of ~0.25 eV and intra-unit cell symmetry breaking of charge distribution in individual α-RuCl3 surface layer. The corresponding charge-ordered pattern has a fine structure associated with two different types of charge disproportionation at Cl-terminated surface.

The Key Ingredients of the Electronic Structure of FeSe

NASA Astrophysics Data System (ADS)

Coldea, Amalia I.; Watson, Matthew D.

2018-03-01

FeSe is a fascinating superconducting material at the frontier of research in condensed matter physics. Here, we provide an overview of the current understanding of the electronic structure of FeSe, focusing in particular on its low-energy electronic structure as determined from angle-resolved photoemission spectroscopy, quantum oscillations, and magnetotransport measurements of single-crystal samples. We discuss the unique place of FeSe among iron-based superconductors, as it is a multiband system exhibiting strong orbitally dependent electronic correlations and unusually small Fermi surfaces and is prone to different electronic instabilities. We pay particular attention to the evolution of the electronic structure that accompanies the tetragonal-orthorhombic structural distortion of the lattice around 90 K, which stabilizes a unique nematic electronic state. Finally, we discuss how the multiband multiorbital nematic electronic structure impacts our understanding of the superconductivity, and show that the tunability of the nematic state with chemical and physical pressure helps to disentangle the role of different competing interactions relevant for enhancing superconductivity.

NEWS: Web's wonders!

NASA Astrophysics Data System (ADS)

2000-07-01

Introducing this month's collection of useful websites for physics teachers. If you have any suggestions for this column then please send them to us at ped@ioppublishing.co.uk Dave Pickersgill has drawn our attention to the following: www.sheffcol.ac.uk/links/ which has annotated, classified and searchable links to over 1700 educational sites. Included are around 500 science links. Members of the American Association of Physics Teachers were recently informed of a website for those hoping to arouse interest and knowledge of astronomy in their students. Space.com, a comprehensive space news website, had launched `spaceKids', a new channel specifically targeted at children complete with a gallery of space images, space and science news, stories, a space question and answer section hosted by a team of science teachers, interactive games, weekly polls and competitions. The website can be found at www.spacekids.com Those fascinated by all aspects of nuclear fusion should take a look at the General Atomics educational site: FusionEd.gat.com as well as the national site fusion.gat.com/PlasmaOutreach

Complex networks with large numbers of labelable attractors

NASA Astrophysics Data System (ADS)

Mi, Yuanyuan; Zhang, Lisheng; Huang, Xiaodong; Qian, Yu; Hu, Gang; Liao, Xuhong

2011-09-01

Information storage in many functional subsystems of the brain is regarded by theoretical neuroscientists to be related to attractors of neural networks. The number of attractors is large and each attractor can be temporarily represented or suppressed easily by corresponding external stimulus. In this letter, we discover that complex networks consisting of excitable nodes have similar fascinating properties of coexistence of large numbers of oscillatory attractors, most of which can be labeled with a few nodes. According to a simple labeling rule, different attractors can be identified and the number of labelable attractors can be predicted from the analysis of network topology. With the cues of the labeling association, these attractors can be conveniently retrieved or suppressed on purpose.

Thiopeptide Antibiotics: Retrospective and Recent Advances

PubMed Central

Just-Baringo, Xavier; Albericio, Fernando; Álvarez, Mercedes

2014-01-01

Thiopeptides, or thiazolyl peptides, are a relatively new family of antibiotics that already counts with more than one hundred different entities. Although they are mainly isolated from soil bacteria, during the last decade, new members have been isolated from marine samples. Far from being limited to their innate antibacterial activity, thiopeptides have been found to possess a wide range of biological properties, including anticancer, antiplasmodial, immunosuppressive, etc. In spite of their ribosomal origin, these highly posttranslationally processed peptides have posed a fascinating synthetic challenge, prompting the development of various methodologies and strategies. Regardless of their limited solubility, intensive investigations are bringing thiopeptide derivatives closer to the clinic, where they are likely to show their veritable therapeutic potential. PMID:24445304

Quantum games of opinion formation based on the Marinatto-Weber quantum game scheme

NASA Astrophysics Data System (ADS)

Deng, Xinyang; Deng, Yong; Liu, Qi; Shi, Lei; Wang, Zhen

2016-06-01

Quantization has become a new way to investigate classical game theory since quantum strategies and quantum games were proposed. In the existing studies, many typical game models, such as the prisoner's dilemma, battle of the sexes, Hawk-Dove game, have been extensively explored by using quantization approach. Along a similar method, here several game models of opinion formations will be quantized on the basis of the Marinatto-Weber quantum game scheme, a frequently used scheme of converting classical games to quantum versions. Our results show that the quantization can fascinatingly change the properties of some classical opinion formation game models so as to generate win-win outcomes.

Responsive Boronic Acid-Decorated (Co)polymers: From Glucose Sensors to Autonomous Drug Delivery.

PubMed

Vancoillie, Gertjan; Hoogenboom, Richard

2016-10-19

Boronic acid-containing (co)polymers have fascinated researchers for decades, garnering attention for their unique responsiveness toward 1,2- and 1,3-diols, including saccharides and nucleotides. The applications of materials that exert this property are manifold including sensing, but also self-regulated drug delivery systems through responsive membranes or micelles. In this review, some of the main applications of boronic acid containing (co)polymers are discussed focusing on the role of the boronic acid group in the response mechanism. We hope that this summary, which highlights the importance and potential of boronic acid-decorated polymeric materials, will inspire further research within this interesting field of responsive polymers and polymeric materials.

Intrinsic two-dimensional states on the pristine surface of tellurium

NASA Astrophysics Data System (ADS)

Li, Pengke; Appelbaum, Ian

2018-05-01

Atomic chains configured in a helical geometry have fascinating properties, including phases hosting localized bound states in their electronic structure. We show how the zero-dimensional state—bound to the edge of a single one-dimensional helical chain of tellurium atoms—evolves into two-dimensional bands on the c -axis surface of the three-dimensional trigonal bulk. We give an effective Hamiltonian description of its dispersion in k space by exploiting confinement to a virtual bilayer, and elaborate on the diminished role of spin-orbit coupling. These intrinsic gap-penetrating surface bands were neglected in the interpretation of seminal experiments, where two-dimensional transport was otherwise attributed to extrinsic accumulation layers.

Demystified … Nitric oxide

PubMed Central

Stuart-Smith, K

2002-01-01

The discovery of nitric oxide (NO) demonstrated that cells could communicate via the manufacture and local diffusion of an unstable lipid soluble molecule. Since the original demonstration of the vascular relaxant properties of endothelium derived NO, this fascinating molecule has been shown to have multiple, complex roles within many biological systems. This review cannot hope to cover all of the recent advances in NO biology, but seeks to place the discovery of NO in its historical context, and show how far our understanding has come in the past 20 years. The role of NO in mitochondrial respiration, and consequently in oxidative stress, is described in detail because these processes probably underline the importance of NO in the development of disease. PMID:12456772

Linked supramolecular building blocks for enhanced cluster formation

DOE PAGES

McLellan, Ross; Palacios, Maria A.; Beavers, Christine M.; ...

2015-01-09

Methylene-bridged calix[4]arenes have emerged as extremely versatile ligand supports in the formation of new polymetallic clusters possessing fascinating magnetic properties. Metal ion binding rules established for this building block allow one to partially rationalise the complex assembly process. The ability to covalently link calix[4]arenes at the methylene bridge provides significantly improved control over the introduction of different metal centres to resulting cluster motifs. Clusters assembled from bis-calix[4]arenes and transition metal ions or 3d-4f combinations display characteristic features of the analogous calix[4]arene supported clusters, thereby demonstrating an enhanced and rational approach towards the targeted synthesis of complex and challenging structures.

Flavonoid transport mechanisms: how to go, and with whom.

PubMed

Zhao, Jian

2015-09-01

Subcellular flavonoid transport and its underlying regulatory mechanisms are still poorly understood, but are fascinating research frontiers in plant science. Recent studies support and further extend previous hypotheses indicating that vacuolar sequestration of flavonoids involves vesicle trafficking, membrane transporters, and glutathione S-transferase (GST). However, the question remains to be addressed of how three distinct but nonexclusive mechanisms are functionally integrated into diverse but redundant transport routes for vacuolar sequestration or extracellular secretion of flavonoids. In this review, I highlight recent progress in understanding flavonoid-transporting vesicle behavior and properties, GST and membrane transporter functions and mechanisms, and flavonoid transport substrate specificity and preference. Copyright © 2015 Elsevier Ltd. All rights reserved.

Responsive Boronic Acid-Decorated (Co)polymers: From Glucose Sensors to Autonomous Drug Delivery

PubMed Central

Vancoillie, Gertjan; Hoogenboom, Richard

2016-01-01

Boronic acid-containing (co)polymers have fascinated researchers for decades, garnering attention for their unique responsiveness toward 1,2- and 1,3-diols, including saccharides and nucleotides. The applications of materials that exert this property are manifold including sensing, but also self-regulated drug delivery systems through responsive membranes or micelles. In this review, some of the main applications of boronic acid containing (co)polymers are discussed focusing on the role of the boronic acid group in the response mechanism. We hope that this summary, which highlights the importance and potential of boronic acid-decorated polymeric materials, will inspire further research within this interesting field of responsive polymers and polymeric materials. PMID:27775572

Coherent perfect absorption in one-sided reflectionless media

PubMed Central

Wu, Jin-Hui; Artoni, M.; La Rocca, G. C.

2016-01-01

In optical experiments one-sided reflectionless (ORL) and coherent perfect absorption (CPA) are unusual scattering properties yet fascinating for their fundamental aspects and for their practical interest. Although these two concepts have so far remained separated from each other, we prove that the two phenomena are indeed strictly connected. We show that a CPA–ORL connection exists between pairs of points lying along lines close to each other in the 3D space-parameters of a realistic lossy atomic photonic crystal. The connection is expected to be a generic feature of wave scattering in non-Hermitian optical media encompassing, as a particular case, wave scattering in parity-time (PT) symmetric media. PMID:27759020

How Do Enzymes 'Meet' Nanoparticles and Nanomaterials?

PubMed

Chen, Ming; Zeng, Guangming; Xu, Piao; Lai, Cui; Tang, Lin

2017-11-01

Enzymes are fundamental biological catalysts responsible for biological regulation and metabolism. The opportunity for enzymes to 'meet' nanoparticles and nanomaterials is rapidly increasing due to growing demands for applications in nanomaterial design, environmental monitoring, biochemical engineering, and biomedicine. Therefore, understanding the nature of nanomaterial-enzyme interactions is becoming important. Since 2014, enzymes have been used to modify, degrade, or make nanoparticles/nanomaterials, while numerous nanoparticles/nanomaterials have been used as materials for enzymatic immobilization and biosensors and as enzyme mimicry. Among the various nanoparticles and nanomaterials, metal nanoparticles and carbon nanomaterials have received extensive attention due to their fascinating properties. This review provides an overview about how enzymes meet nanoparticles and nanomaterials. Copyright © 2017 Elsevier Ltd. All rights reserved.

Foreword

NASA Astrophysics Data System (ADS)

1997-03-01

The field of nanoscale physics is now widely regarded both as a frontier of science and as a generic foundation for a wide range of new technologies in sectors as diverse as optics, electronics, chemicals, magnetics and sensors. The development of a body of good science in this field depends on the careful preparation and characterization of well-defined nanometre-scale structures. The development of genuine and viable nanotechnologies requires that scientists are alert to the connections between their model systems and the practical requirements of technological applications. This is the domain of applied physics, and it is fitting that in this issue Journal of Physics D should play host to a set of papers which reviews some of the frontiers of this exciting field. The subject of the first paper, by Perez et al from Lyon, concerns a new method for the controlled fabrication of novel nanostructures which are rich in potential - cluster assembled materials. This `bottom-up' approach defines a series of nanoscale building blocks, atomic clusters of a specific size, and assembles a thin film by the deposition of the clusters onto a surface. The paper discusses both the nature of the growth process and some of the intriguing physical properties of the films so formed - structural, optical and magnetic. Structural characterization of these and other nanosystems is one of the foundation issues in the development of a science of nanostructures, and the second paper in the set, by Castle and Zhdan from Surrey, is concerned with two of the principal scientific tools which are employed, i.e. the scanning electron microscope (SEM) and the (whole array of) scanning probe microscopes (in this case, the scanning force microscope (SFM)). Interest in truly nanometre-scale structures is pushing the veritable old SEM to its limits, though it has the advantage over its younger cousins, illustrated by the SFM, to whom atomic resolution is a mere trifle, of a much wider scan range as well as chemical analysis. The paper presents a careful analysis of what these complementary techniques can offer, and includes parallel images of the same regions of the same samples - precisely the kind of investigation which is required to develop a reliable metrology on the nanometre scale. But nanostructures need not be static; indeed, there is already a whole industry, heterogeneous catalysis, which depends on the evolution of the structural and electronic properties of supported nanoscale particles. The third paper, by Leibsle et al from Liverpool, shows how the scanning tunnelling microscope (STM) provides some searching insights into the spatial evolution of nanostructures during a chemical reaction in model surface systems. The paper also explores the fascinating domain of spontaneous (`self-organized') nanostructures (in this case, at oxide surfaces), a topic which may come to assume considerable importance for the large-scale production of nanostructured systems. It is to be hoped that this short series of articles will allow readers to take stock of a fast moving, if somewhat `hyped', field. Genuine advances are taking place as a result of imaginative and careful experiments, and a coherent level of understanding of the distinctive properties of nanometre-scale structures is taking shape. R E Palmer Nanoscale Physics Research Laboratory School of Physics and Space Research University of Birmingham, UK 31 December 1996

Chemical studies of elements with Z ⩾ 104 in gas phase

NASA Astrophysics Data System (ADS)

Türler, Andreas; Eichler, Robert; Yakushev, Alexander

2015-12-01

Chemical investigations of superheavy elements in the gas-phase, i.e. elements with Z ≥ 104, allow assessing the influence of relativistic effects on their chemical properties. Furthermore, for some superheavy elements and their compounds quite unique gas-phase chemical properties were predicted. The experimental verification of these properties yields supporting evidence for a firm assignment of the atomic number. Prominent examples are the high volatility observed for HsO4 or the very weak interaction of Cn with gold surfaces. The unique properties of HsO4 were exploited to discover the doubly-magic even-even nucleus 270Hs and the new isotope 271Hs. The combination of kinematic pre-separation and gas-phase chemistry allowed gaining access to a new class of relatively fragile compounds, the carbonyl complexes of elements Sg through Mt. A not yet resolved issue concerns the interaction of Fl with gold surfaces. While competing experiments agree on the fact that Fl is a volatile element, there are discrepancies concerning its adsorption on gold surfaces with respect to its daughter Cn. The elucidation of these and other questions amounts to the fascination that gas-phase chemical investigations exert on current research at the extreme limits of chemistry today.

Effect of Varying Pnictogen Elements (Pn=N, P, As, Sb, Bi) on the Optoelectronic Properties of SrZn2Pn2

NASA Astrophysics Data System (ADS)

Murtaza, G.; Yousaf, N.; Laref, A.; Yaseen, M.

2018-03-01

Pnictogen-based Zintl compounds have fascinating properties. Nowadays these compounds have gained exceptional interest in thermoelectric and optoelectronic fields. Therefore, in this work the structural, electronic and optical properties of SrZn2Pn2 (Pn=N, P, As, Sb, Bi) compounds were studied using state-of-the-art density functional theory. The optimised lattice parameters (ɑ, c, c/ɑ and bond lengths) are consistent with the experimental results. The bulk moduli and c/a showed a decrease when changing the Pnictogen (Pn) anion from N to Bi in SrZn2Pn2 (Pn=N, P, As, Sb, Bi). The modified Becke-Johnson potential is used for band structure calculations. All compounds show semiconducting behaviour except SrZn2Bi2, which is metallic. Pn-p, Zn-d and Sr-d play an important role in defining the electronic structure of the compounds. The optical conductivity and absorption coefficient strength are high in visible and ultraviolet regions. These band structures and optical properties clearly show that SrZn2Pn2 compounds are potential candidates in the fields of optoelectronic and photonic devices.

Soft exfoliation of 2D SnO with size-dependent optical properties

NASA Astrophysics Data System (ADS)

Singh, Mandeep; Della Gaspera, Enrico; Ahmed, Taimur; Walia, Sumeet; Ramanathan, Rajesh; van Embden, Joel; Mayes, Edwin; Bansal, Vipul

2017-06-01

Two-dimensional (2D) materials have recently gained unprecedented attention as potential candidates for next-generation (opto)electronic devices due to their fascinating optical and electrical properties. Tin monoxide, SnO, is an important p-type semiconductor with applications across photocatalysis (water splitting) and electronics (transistors). However, despite its potential in several important technological applications, SnO remains underexplored in its 2D form. Here we present a soft exfoliation strategy to produce 2D SnO nanosheets with tunable optical and electrical properties. Our approach involves the initial synthesis of layered SnO microspheres, which are readily exfoliated through a low-power sonication step to form high quality SnO nanosheets. We demonstrate that the properties of 2D SnO are strongly dependent on its dimensions. As verified through optical absorption and photoluminescence studies, a strong size-dependent quantum confinement effect in 2D SnO leads to substantial variation in its optical and electrical properties. This results in a remarkable (>1 eV) band gap widening in atomically thin SnO. Through photoconductivity measurements, we further validate a strong correlation between the quantum-confined properties of 2D SnO and the selective photoresponse of atomically thin sheets in the high energy UV light. Such tunable semiconducting properties of 2D SnO could be exploited for a variety of applications including photocatalysis, photovoltaics and optoelectronics in general.

A cryofuge for cold-collision experiments with slow polar molecules

NASA Astrophysics Data System (ADS)

Wu, Xing; Gantner, Thomas; Koller, Manuel; Zeppenfeld, Martin; Chervenkov, Sotir; Rempe, Gerhard

2017-11-01

Ultracold molecules represent a fascinating research frontier in physics and chemistry, but it has proven challenging to prepare dense samples at low velocities. Here, we present a solution to this goal by means of a nonconventional approach dubbed cryofuge. It uses centrifugal force to bring cryogenically cooled molecules to kinetic energies below 1 K × kB in the laboratory frame, where kB is the Boltzmann constant, with corresponding fluxes exceeding 1010 per second at velocities below 20 meters per second. By attaining densities higher than 109 per cubic centimeter and interaction times longer than 25 milliseconds in samples of fluoromethane as well as deuterated ammonia, we observed cold dipolar collisions between molecules and determined their collision cross sections.

Probing quantum effects in lithium

NASA Astrophysics Data System (ADS)

Deemyad, Shanti; Zhang, Rong

2018-05-01

In periodic table lithium is the first element immediately after helium and the lightest metal. While fascinating quantum nature of condensed helium is suppressed at high densities, lithium is expected to adapt more quantum solid behavior under compression. This is due to the presence of long range interactions in metallic systems for which an increase in the de-Boer parameter (λ/σ, where σ is the minimum interatomic distance and λ is the de-Broglie wavelength) is predicted at higher densities [1,2]. Physics of dense lithium offers a rich playground to look for new emergent quantum phenomena in condensed matter and has been subject of many theoretical and experimental investigations. In this article recent progress in studying the quantum nature of dense lithium will be discussed.

Horst Meyer and Quantum Evaporation

NASA Astrophysics Data System (ADS)

Balibar, S.

2016-11-01

With their 1963 article in Cryogenics Horst Meyer and his collaborators triggered intense research activity on the evaporation of superfluid helium. Discussing this subject with him in 1975 was enlightening. Fifty years later, the analogy between the photoelectric effect and the evaporation of superfluid helium in the low temperature limit is not yet clear, although remarkable progress has been made in its observation and its understanding. This special issue of the Journal of Low Temperature Physics is an opportunity to recall the history of quantum evaporation, and to express my gratitude to Horst Meyer. It describes quickly most of the experimental and theoretical works which have been published on quantum evaporation during the last 50 years, but it is not a comprehensive review of this fascinating subject.

Self-Assembled Magnetic Surface Swimmers: Theoretical Model

NASA Astrophysics Data System (ADS)

Aranson, Igor; Belkin, Maxim; Snezhko, Alexey

2009-03-01

The mechanisms of self-propulsion of living microorganisms are a fascinating phenomenon attracting enormous attention in the physics community. A new type of self-assembled micro-swimmers, magnetic snakes, is an excellent tool to model locomotion in a simple table-top experiment. The snakes self-assemble from a dispersion of magnetic microparticles suspended on the liquid-air interface and subjected to an alternating magnetic field. Formation and dynamics of these swimmers are captured in the framework of theoretical model coupling paradigm equation for the amplitude of surface waves, conservation law for the density of particles, and the Navier-Stokes equation for hydrodynamic flows. The results of continuum modeling are supported by hybrid molecular dynamics simulations of magnetic particles floating on the surface of fluid.

Engaging space: extraterrestrial architecture and the human psyche.

PubMed

Sequin, Angel Marie

2005-01-01

The human fascination with exploring and inhabiting the space that lies beyond Earth's atmosphere continues to grow. Nevertheless, 40 years of experience to date have clearly established that humans in outer space routinely suffer significant psychological impairment arising from their stressful extraterrestrial living conditions. This paper explores those extraterrestrial conditions through the interactions between the extraordinarily harsh environment of outer space, the sensations that humans encounter in space, and the qualities of a habitat that physically interposes itself between the two. The objective of this paper is to develop a habitat that expresses the extraterrestrial condition while supporting the mental health of its inhabitants, so as to augment the success of prolonged extraterrestrial residence and interplanetary travel. c2005 Elsevier Ltd. All rights reserved.

The Great Beyond: Higher Dimensions, Parallel Universes and the Extraordinary Search for a Theory of Everything

NASA Astrophysics Data System (ADS)

Halpern, Paul

2005-08-01

Praise for The Great Beyond "A marvelous book-very clear, very readable. A brilliant introduction to the math and physics of higher dimensions, from Flatland to superstrings. Its greatest strength is a wealth of fascinating historical narrative and anecdote. I enjoyed it enormously." -Ian Stewart, author of Flatterland "A remarkable journey from Plato's cave to the farthest reaches of human thought and scientific knowledge. This mind-boggling book allows readers to dream strange visions of hyperspace, chase light waves, explore Klein's quantum odyssey and Kaluza's cocoon, leap through parallel universes, and grasp the very essence of conscience and cosmos. Buy this book and feed your head." -Clifford Pickover, author of A Passion for Mathematics "Halpern looks with a bemused eye at the wildest ideas currently afoot in physics. He takes us into the personal world of those who relish and explore seemingly outlandish notions, and does it with a light, engaging style." -Gregory Benford, author of Foundation's Fear "An informative, stimulating, and thoughtful presentation at the very frontiers of contemporary physics. It is quite on a par with Brian Greene's The Elegant Universe or his more recent The Fabric of the Cosmos, and as such, deserves to receive wide non-specialist coverage among an intelligent, curious, thinking public." -Professor E. Sheldon, Contemporary Physics

Reversible optical control of macroscopic polarization in ferroelectrics

NASA Astrophysics Data System (ADS)

Rubio-Marcos, Fernando; Ochoa, Diego A.; Del Campo, Adolfo; García, Miguel A.; Castro, Germán R.; Fernández, José F.; García, José E.

2018-01-01

The optical control of ferroic properties is a subject of fascination for the scientific community, because it involves the establishment of new paradigms for technology1-9. Domains and domain walls are known to have a great impact on the properties of ferroic materials1-24. Progress is currently being made in understanding the behaviour of the ferroelectric domain wall, especially regarding its dynamic control10-12,17,19. New research is being conducted to find effective methodologies capable of modulating ferroelectric domain motion for future electronics. However, the practical use of ferroelectric domain wall motion should be both stable and reversible (rewritable) and, in particular, be able to produce a macroscopic response that can be monitored easily12,17. Here, we show that it is possible to achieve a reversible optical change of ferroelectric domains configuration. This effect leads to the tuning of macroscopic polarization and its related properties by means of polarized light, a non-contact external control. Although this is only the first step, it nevertheless constitutes the most crucial one in the long and complex process of developing the next generation of photo-stimulated ferroelectric devices.

Modulating optical rectification, second and third harmonic generation of doped quantum dots: Interplay between hydrostatic pressure, temperature and noise

NASA Astrophysics Data System (ADS)

Ganguly, Jayanta; Saha, Surajit; Bera, Aindrila; Ghosh, Manas

2016-10-01

We examine the profiles of optical rectification (OR), second harmonic generation (SHG) and third harmonic generation (THG) of impurity doped QDs under the combined influence of hydrostatic pressure (HP) and temperature (T) in presence and absence of Gaussian white noise. Noise has been incorporated to the system additively and multiplicatively. In order to study the above nonlinear optical (NLO) properties the doped dot has been subjected to a polarized monochromatic electromagnetic field. Effect of application of noise is nicely reflected through alteration of peak shift (blue/red) and variation of peak height (increase/decrease) of above NLO properties as temperature and pressure are varied. All such changes again sensitively depends on mode of application (additive/multiplicative) of noise. The remarkable influence of interplay between noise strength and its mode of application on the said profiles has also been addressed. The findings illuminate fascinating role played by noise in tuning above NLO properties of doped QD system under the active presence of both hydrostatic pressure and temperature.

Unusual phonon behavior and ultra-low thermal conductance of monolayer InSe.

PubMed

Zhou, Hangbo; Cai, Yongqing; Zhang, Gang; Zhang, Yong-Wei

2017-12-21

Monolayer indium selenide (InSe) possesses numerous fascinating properties, such as high electron mobility, quantum Hall effect and anomalous optical response. However, its phonon properties, thermal transport properties and the origin of its structural stability remain unexplored. Using first-principles calculations, we show that the atoms in InSe are highly polarized and such polarization causes strong long-range dipole-dipole interaction (DDI). For acoustic modes, DDI is essential for maintaining its structural stability. For optical modes, DDI causes a significant frequency shift of its out-of-phase vibrations. Surprisingly, we observed that there were two isolated frequency regimes, which were completely separated from other frequency regimes with large frequency gaps. Within each frequency regime, only a single phonon mode exists. We further reveal that InSe possesses the lowest thermal conductance among the known two-dimensional materials due to the low cut-off frequency, low phonon group velocities and the presence of large frequency gaps. These unique behaviors of monolayer InSe can enable the fabrication of novel devices, such as thermoelectric module, single-mode phonon channel and phononic laser.

Advanced composite alloys for constructional parts of robots

NASA Astrophysics Data System (ADS)

Issin, D. K.; Zholdubayeva, Zh D.; Neshina, Y. G.; Alkina, A. D.; Khuangan, N.; Rahimova, G. M.

2018-05-01

In recent years all over the world special attention has been paid to the development and implementation of nanostructured materials possessing unique properties and opening fascinating prospects for the development of technical progress in various fields of human activities. A special place can be given to the development of service robots, the market of which is actively developing. There is problem associated mainly with the lack of heat-strengthened alloys which consists in low thermal stability of the alloy properties under the conditions of elevated variable temperatures and loads. The article presents studies to assess the effect of composition, the amounts of refractory nanoscale particles and methods for their introduction into the melt on the structure and properties in nanostructured composite aluminum alloys. The powders of metals, alloys, as well as silicon carbide and aluminum oxide were used to produce the nanostructured powder composite materials. As a result of the research, NPCM compositions containing micro-size particles of transition metals that are carriers of nanosized reinforcing particles and initiators of the formation of an intermetallide of endogenous origin in a melt.

EDITORIAL: Gas plasmas in biology and medicine

NASA Astrophysics Data System (ADS)

Stoffels, Eva

2006-08-01

It is my great pleasure to introduce this special cluster devoted to recent developments in biomedical plasma technology. It is an even greater pleasure to behold the enormous progress which has been made in this area over the last five years. Research on biomedical plasma applications proceeds hand in hand with the development of new material processing technologies, based on atmospheric plasma sources. In the beginning, major research effort was invested in the development and control of new plasma sources—in this laborious process, novel devices were constructed and characterized, and also new plasma physical phenomena were discovered. Self-constriction of micro-plasmas, pattern formation, filamentation of glow discharges and various mode transitions are just a few examples. It is a real challenge for theorists to gain an understanding of these complex phenomena. Later, the devices had to be thoroughly tested and automated, and various safety issues had to be addressed. At present, many atmospheric plasma sources are ready to use, but not all fundamental and technical problems have been resolved by far. There is still plenty of room for improvement, as in any dynamic area of research. The recent trends are clear: the application area of plasmas expands into processing of unconventional materials such as biological scaffolds, and eventually living human, animal and plant tissues. The gentle, precise and versatile character of cold plasmas simply invites this new application. Firstly, non-living surfaces have been plasma-treated to attain desired effects in biomedical research; tissue engineering will soon fully profit from this powerful technique. Furthermore, studies on cultured plant and animal cells have provided many findings, which are both fundamentally interesting and potentially applicable in health care, veterinary medicine and agriculture. The most important and hitherto unique property of plasma treatment is that it can evade accidental cell death and its attendant complications, such as inflammation and scarring. Another substantial research direction makes use of the bactericidal properties of the plasma. The number of findings on plasma inactivation of bacteria and spores is growing; plasma sterilization has already achieved some commercial success. In future, bacteriostatic properties of cold plasmas will even facilitate non-contact disinfection of human tissues. At this moment, one cannot explicitly list all the medical procedures in which cold plasmas will be involved. My personal intuition predicts widespread use of plasma treatment in dentistry and dermatology, but surely more applications will emerge in the course of this multi-disciplinary research. In fact, some plasma techniques, such as coagulation and coblation, are already used in clinical practice—this is another image of plasma science, which is so far unfamiliar to plasma physicists. Therefore, this particular topic forms a perfect platform for contacts between physicists and medical experts. Our colleagues from the medical scientific community will continue giving us feedback, suggestions or even orders. Biomedical plasmas should not become an isolated research area—we must grow together with medical research, listen to criticism, and eventually serve the physicians. Only then will this new field grow, flourish and bear fruit. All the above-mentioned topics meet in this issue of Journal of Physics D: Applied Physics, comprising the most significant examples of modern biomedical plasma research. Browsing through the contributions, the reader can trace back the progress in this field: from fundamental physical (numerical) studies, through phenomenology and physics of new discharges, studies on plasma-surface modification, bacterial inactivation tests, fundamental cell biological investigations, to final in vivo applications. One may ask why this selection has found its place in a purely physical journal—many contributions are concerned with (micro)-biology rather than physics. To me, the answer is clear: it is important to maintain the visibility of this fascinating and growing cross-disciplinary field within the (plasma) physical community. This is not the `physics we are used to', but one we will eventually get used to and accept.

Recent Progress on Stability and Passivation of Black Phosphorus.

PubMed

Abate, Yohannes; Akinwande, Deji; Gamage, Sampath; Wang, Han; Snure, Michael; Poudel, Nirakar; Cronin, Stephen B

2018-05-11

From a fundamental science perspective, black phosphorus (BP) is a canonical example of a material that possesses fascinating surface and electronic properties. It has extraordinary in-plane anisotropic electrical, optical, and vibrational states, as well as a tunable band gap. However, instability of the surface due to chemical degradation in ambient conditions remains a major impediment to its prospective applications. Early studies were limited by the degradation of black phosphorous surfaces in air. Recently, several robust strategies have been developed to mitigate these issues, and these novel developments can potentially allow researchers to exploit the extraordinary properties of this material and devices made out of it. Here, the fundamental chemistry of BP degradation and the tremendous progress made to address this issue are extensively reviewed. Device performances of encapsulated BP are also compared with nonencapsulated BP. In addition, BP possesses sensitive anisotropic photophysical surface properties such as excitons, surface plasmons/phonons, and topologically protected and Dirac semi-metallic surface states. Ambient degradation as well as any passivation method used to protect the surface could affect the intrinsic surface properties of BP. These properties and the extent of their modifications by both the degradation and passivation are reviewed. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The TSS-1R Results - the Physics of Current Collection in Magnetized Plasmas Revised

NASA Astrophysics Data System (ADS)

Papadopoulos, Konstantinos

1996-11-01

The Tethered Satellite System (TSS-1R) was deployed from the space shuttle "Columbia" (STS-75 Mission) on February 24, 1996. The satellite was deployed to a distance of 19.7 km above the shuttle. The system operated nominally over its deployment phase which lasted 5.5 hours. A defect in the tether insulation inside the orbiter caused a local discharge which led to a tether break. Data collected before and during the break revealed a host of new physics phenomena concerning the current collection by charged bodies in space moving at orbital velocities. The maximum EMF observed during the mission was 3.8 kV and the maximum current exceeded 1A. Power generation of several kW's was demonstrated. The current collected was significantly larger than expected by space charged limited flow in magnetized and even unmagnetized plasmas. For example the 1A current was collected with less than 1 kV potential instead of the 20 kV given by previous theories. The presentation will review the fascinating results of the TSS-1R and will discuss the ongoing physics analysis of the observed phenomena. *In collaboration with A. Drobot and C.L. Chang of SAIC.

Fear, fascination and the sperm donor as 'abjection' in interviews with heterosexual recipients of donor insemination.

PubMed

Burr, Jennifer

2009-07-01

The background to this article is the medical regulation of sperm donation in the UK and the recent policy change so that children born from sperm, eggs or embryos donated after April 2005 have the right to know their donor's identity. I draw upon data from interviews with ten women and seven joint interviews with couples who received donor insemination from an anonymous sperm donor and were the parents of donor insemination children. I explore the symbolic presence of the donor and his potential to disrupt social and physical boundaries using the theoretical conceptions of boundaries and pollution as articulated by Mary Douglas and Julia Kristeva. I present data to argue that the anonymous donor manifests in various figures; the shadowy and ambiguous figure of 'another man'; the intelligent medical student; the donor as a family man, with children of his own who wants to help infertile men father children. In addition participants perceive the donor's physical characteristics, but also see their husband's physical characteristics, in their children. In conclusion I argue that anonymisation preserves features of conventional family life, maintains the idea of exclusivity within the heterosexual relationship and affirms the legal father's insecurity about his infertility.

Dynamically encircling an exceptional point for asymmetric mode switching.

PubMed

Doppler, Jörg; Mailybaev, Alexei A; Böhm, Julian; Kuhl, Ulrich; Girschik, Adrian; Libisch, Florian; Milburn, Thomas J; Rabl, Peter; Moiseyev, Nimrod; Rotter, Stefan

2016-09-01

Physical systems with loss or gain have resonant modes that decay or grow exponentially with time. Whenever two such modes coalesce both in their resonant frequency and their rate of decay or growth, an 'exceptional point' occurs, giving rise to fascinating phenomena that defy our physical intuition. Particularly intriguing behaviour is predicted to appear when an exceptional point is encircled sufficiently slowly, such as a state-flip or the accumulation of a geometric phase. The topological structure of exceptional points has been experimentally explored, but a full dynamical encircling of such a point and the associated breakdown of adiabaticity have remained out of reach of measurement. Here we demonstrate that a dynamical encircling of an exceptional point is analogous to the scattering through a two-mode waveguide with suitably designed boundaries and losses. We present experimental results from a corresponding waveguide structure that steers incoming waves around an exceptional point during the transmission process. In this way, mode transitions are induced that transform this device into a robust and asymmetric switch between different waveguide modes. This work will enable the exploration of exceptional point physics in system control and state transfer schemes at the crossroads between fundamental research and practical applications.

Tsikavytys' neznanym: uchnivs'kyi zoshyt (Fascination with the Unknown: Student Activity Book) [and] Tsikavytys' neznanym: vidpovidi do uchnivs'koho zoshyta (Fascination with the Unknown: Answer Key to Student Activity Book). Collage 2: A Ukrainian Language Development Series.

ERIC Educational Resources Information Center

Boruszczak, Bohdan, Comp.; Wozniak, Odarka, Comp.

One of four intermediate- to advanced-level activity books in a series, this student workbook offers a selection of exercises, vocabulary builders, dialogs, and writing exercises for language skill development. It is intended for use in the instruction of native speakers, heritage language learners, or second language learners of Ukrainian. Also…

Recent advances in magnetic nanoparticles with bulk-like properties

NASA Astrophysics Data System (ADS)

Batlle, Xavier

2013-03-01

Magnetic nanoparticles (NP) are an excellent example of nanostructured materials and exhibit fascinating properties with applications in high-density recording and biomedicine. Controlling the effects of the nanostructure and surface chemistry and magnetism at the monolayer level have become relevant issues. As the size is reduced below 100 nm, deviations from bulk behavior have been attributed to finite-size effects and changes in the magnetic ordering at the surface, thus giving rise to a significant decrease in the magnetization and increase in the magnetic anisotropy. The existence of a surface spin glass-like state due to magnetic frustration has been widely suggested in ferrimagnetic NP. However, in this talk, we will show that high crystal quality magnetite Fe3-xO4 NP of about a few nanometers in diameter and coated with different organic surfactants display bulk-like structural, magnetic and electronic properties. Magnetic measurements, transmission electron microscopy, X-ray absorption and magnetic circular dichroism and Monte Carlo simulations, evidenced that none of the usual particle-like behavior is observed in high quality NP of a few nm. Consequently, the magnetic and electronic disorder phenomena typically observed in those single-phase ferrimagnetic NP should not be considered as an intrinsic effect. We also performed a real-space characterization at the sub-nanometer scale, combining scanning transmission electron microscopy, electron energy loss spectroscopy and electron magnetic chiral dichroism. For the first time, we found that the surface magnetization is as high as about 70% of that of the core. The comparison to density functional theory suggested the relevance of the strong surface bond between the Fe ions and the organic surfactant. All the foregoing demonstrates the key role of both the crystal quality and surface bond on the physical properties of ferrimagnetic NP and paves the way to the fabrication of the next generation of NP with optimal magnetic properties. Some bio-applications will also be discussed. In collaboration with A Labarta, N Perez, O Iglesias, A Fraile, C Moya(U Barcelona); A Roca, MP Morales, CJ Serna (ICMM-CSIC); F Bartolome, LM Garcia, J. Bartolome (CSIC-U Zaragoza); R Mejias, DF Barber (CNB-CSIC); M Varela, J Gazquez, J Salafranca, SJ Pennycook (ORNL), ST Pantelides (Vanderbilt U).

Role of Anions Associated with the Formation and Properties of Silver Clusters.

PubMed

Wang, Quan-Ming; Lin, Yu-Mei; Liu, Kuan-Guan

2015-06-16

Metal clusters have been very attractive due to their aesthetic structures and fascinating properties. Different from nanoparticles, each cluster of a macroscopic sample has a well-defined structure with identical composition, size, and shape. As the disadvantages of polydispersity are ruled out, informative structure-property relationships of metal clusters can be established. The formation of a high-nuclearity metal cluster involves the organization of metal ions into a complex entity in an ordered way. To achieve controllable preparation of metal clusters, it is helpful to introduce a directing agent in the formation process of a cluster. To this end, anion templates have been used to direct the formation of high nuclearity clusters. In this Account, the role of anions played in the formation of a variety of silver clusters has been reviewed. Silver ions are positively charged, so anionic species could be utilized to control the formation of silver clusters on the basis of electrostatic interactions, and the size and shape of the resulted clusters can be dictated by the templating anions. In addition, since the anion is an integral component in the silver clusters described, the physical properties of the clusters can be modulated by functional anions. The templating effects of simple inorganic anions and polyoxometales are shown in silver alkynyl clusters and silver thiolate clusters. Intercluster compounds are also described regarding the importance of anions in determining the packing of the ion pairs and making contribution to electron communications between the positive and negative counterparts. The role of the anions is threefold: (a) an anion is advantageous in stabilizing a cluster via balancing local positive charges of the metal cations; (b) an anion template could help control the size and shape of a cluster product; (c) an anion can be a key factor in influencing the function of a cluster through bringing in its intrinsic properties. Properties including electron communication, luminescent thermochromism, single-molecule magnet, and intercluster charge transfer associated with anion-directed silver clusters have been discussed. We intend to attract chemists' attention to the role that anions could play in determining the structures and properties of metal complexes, especially clusters. We hope that this Account will stimulate more efforts in exploiting new role of anions in various metal cluster systems. Anions can do much more than counterions for charge balance, and they should be considered in the design and synthesis of cluster-based functional materials.

The rising star of 2D black phosphorus beyond graphene: synthesis, properties and electronic applications

NASA Astrophysics Data System (ADS)

Chen, Pengfei; Li, Neng; Chen, Xingzhu; Ong, Wee-Jun; Zhao, Xiujian

2018-01-01

Black phosphorus, which is a relatively rare allotrope of phosphorus, was first discovered by Bridgman in 1914. Since the advent of two-dimensional (2D) black phosphorus (which is known as phosphorene due to its resembling graphene sheets) in early 2014, research interest in the arena of black phosphorus was reignited in the scientific and technological communities. Henceforth, a myriad of research studies on this new member of the 2D world have been extensively emerged. Fascinatingly, 2D black phosphorus exhibits a distinctive wrinkled structure with the high hole mobility up to 1000 cm2 V-1 s-1, excellent mechanical properties, tunable band structures, anisotropic thermal, electrical and optical properties, thus leading to its marvelous prospects in device applications. This review firstly introduces the state-of-the-art development, structural properties and preparation routes of black phosphorus. In particular, anisotropy involved in mechanical properties, thermal conductivity, carrier transport as well as optical properties is comprehensively discussed. Apart from discussing the recent progress in black phosphorus which is applied to devices (i.e. field effect transistors and optoelectronic), the review also highlights the bottlenecks encountered by the society and finally casts an invigorating perspective and insightful outlook on the future direction of the next-generation 2D black phosphorus by harnessing its remarkable characteristics for energy production.

Lectures from the European RTN Winter School on Strings, Supergravity and Gauge Theories, CERN, 16 20 January, 2006

NASA Astrophysics Data System (ADS)

Derendinger, J.-P.; Scrucca, C. A.; Uranga, A. M.

2006-11-01

This special issue is devoted to the proceedings of the conference 'Winter School on Strings, Supergravity and Gauge Theories', which took place at CERN, the European Centre for Nuclear Research, in Geneva, Switzerland, from the 16 to the 20 of January 2006. This event was organized in the framework of the European Mobility Research and Training Network entitled 'Constituents, Fundamental Forces and Symmetries of the Universe'. It is part of a yearly series of scientific schools which have become a traditional rendezvous for young researchers of the community. The previous one was held at SISSA, in Trieste, Italy, in February 2005, and the next one will take place again at CERN, in January 2007. The school was primarily meant for young doctoral students and postdoctoral researchers working in the area of string theory. It consisted of five general lectures of four hours each, whose notes are published in the present proceedings, and five working group discussion sessions, focused on specific topics of the network research program. It was attended by approximately 250 participants. The topics of the lectures were chosen to provide an introduction to some of the areas of recent progress and to the open problems in string theory. String theory is expected to provide insights into the description of systems where the role of gravity is crucial. One prominent example of such systems are time-dependent backgrounds with big bang singularities, whose status in string theory is reviewed in the lecture notes by Ben Craps. In another main problem in quantum gravity, string theory gives a fascinating microscopic description of black holes and their properties. The lectures by Shiraz Minwalla review the thermal properties of black holes from their microscopic description in terms of a holographically dual large N field theory. Progress in the description of black hole microstates, and its interplay with the macroscopic description in terms of supergravity solutions via the attractor mechanism, are covered by the lectures by Atish Dabholkar and Boris Pioline. A final important mainstream topic in string theory, being a higher-dimensional theory, is its compactification to four dimensions, and the computation of four-dimensional physical properties in terms of the properties of the internal space. The lectures by Mariana Graña review recent progress in the classification of the most general supersymmetric backgrounds describing the compactified dimensions, and their role in determining the number of massless scalar moduli fields in four dimensions. The conference was financially supported by the European Commission under contract MRTN-CT-2004-005104 and by CERN. It was jointly organized by the Physics Institute of the University of Neuchâtel and the Theory Unit of the Physics Division of CERN. It is a great pleasure for us to warmly thank the Theory Unit of CERN for its very kind hospitality and for the high quality of the services and infrastructure that it has provided. We also acknowledge helpful administrative assistance from the Physics Institute of the University of Neuchâtel. Special thanks go finally to Denis Frank for his very valuable help in preparing the conference web pages, and to J Rostant, A-M Perrin and M-S Vascotto for their continuous and very reliable assistance.

Therapeutic horticulture in clinical depression: a prospective study of active components.

PubMed

Gonzalez, Marianne Thorsen; Hartig, Terry; Patil, Grete Grindal; Martinsen, Egil W; Kirkevold, Marit

2010-09-01

This paper is a report of a study conducted to assess change in depression severity, perceived attentional capacity and rumination (brooding) in individuals with clinical depression during a therapeutic horticulture programme and to investigate if the changes were mediated by experiences of being away and fascination. Individuals with clinical depression suffer from distortion of attention and rumination. Interventions can help to disrupt maladaptive rumination and promote restoration of depleted attentional capacity. A single-group study was conducted with a convenience sample of 28 people with clinical depression in 2009. Data were collected before, twice during, and immediately after a 12-week therapeutic horticulture programme, and at 3-month follow-up. Assessment instruments were the Beck Depression Inventory, Attentional Function Index, Brooding Scale, and Being Away and Fascination subscales from the Perceived Restorativeness Scale. Mean Beck Depression Inventory scores declined by 4.5 points during the intervention (F = 5.49, P = 0.002). The decline was clinically relevant for 50% of participants. Attentional Function Index scores increased (F = 4.14, P = 0.009), while Brooding scores decreased (F = 4.51, P = 0.015). The changes in Beck Depression Inventory and Attentional Function Index scores were mediated by increases in Being Away and Fascination, and decline in Beck Depression Inventory scores was also mediated by decline in Brooding. Participants maintained their improvements in Beck Depression Inventory scores at 3-month follow-up. Being away and fascination appear to work as active components in a therapeutic horticulture intervention for clinical depression.

Nanoscale superconducting memory based on the kinetic inductance of asymmetric nanowire loops

NASA Astrophysics Data System (ADS)

Murphy, Andrew; Averin, Dmitri V.; Bezryadin, Alexey

2017-06-01

The demand for low-dissipation nanoscale memory devices is as strong as ever. As Moore’s law is staggering, and the demand for a low-power-consuming supercomputer is high, the goal of making information processing circuits out of superconductors is one of the central goals of modern technology and physics. So far, digital superconducting circuits could not demonstrate their immense potential. One important reason for this is that a dense superconducting memory technology is not yet available. Miniaturization of traditional superconducting quantum interference devices is difficult below a few micrometers because their operation relies on the geometric inductance of the superconducting loop. Magnetic memories do allow nanometer-scale miniaturization, but they are not purely superconducting (Baek et al 2014 Nat. Commun. 5 3888). Our approach is to make nanometer scale memory cells based on the kinetic inductance (and not geometric inductance) of superconducting nanowire loops, which have already shown many fascinating properties (Aprili 2006 Nat. Nanotechnol. 1 15; Hopkins et al 2005 Science 308 1762). This allows much smaller devices and naturally eliminates magnetic-field cross-talk. We demonstrate that the vorticity, i.e., the winding number of the order parameter, of a closed superconducting loop can be used for realizing a nanoscale nonvolatile memory device. We demonstrate how to alter the vorticity in a controlled fashion by applying calibrated current pulses. A reliable read-out of the memory is also demonstrated. We present arguments that such memory can be developed to operate without energy dissipation.

Tuned, driven, and active soft matter

NASA Astrophysics Data System (ADS)

Menzel, Andreas M.

2015-02-01

One characteristic feature of soft matter systems is their strong response to external stimuli. As a consequence they are comparatively easily driven out of their ground state and out of equilibrium, which leads to many of their fascinating properties. Here, we review illustrative examples. This review is structured by an increasing distance from the equilibrium ground state. On each level, examples of increasing degree of complexity are considered. In detail, we first consider systems that are quasi-statically tuned or switched to a new state by applying external fields. These are common liquid crystals, liquid crystalline elastomers, or ferrogels and magnetic elastomers. Next, we concentrate on systems steadily driven from outside e.g. by an imposed flow field. In our case, we review the reaction of nematic liquid crystals, of bulk-filling periodically modulated structures such as block copolymers, and of localized vesicular objects to an imposed shear flow. Finally, we focus on systems that are "active" and "self-driven". Here our range spans from idealized self-propelled point particles, via sterically interacting particles like granular hoppers, via microswimmers such as self-phoretically driven artificial Janus particles or biological microorganisms, via deformable self-propelled particles like droplets, up to the collective behavior of insects, fish, and birds. As we emphasize, similarities emerge in the features and behavior of systems that at first glance may not necessarily appear related. We thus hope that our overview will further stimulate the search for basic unifying principles underlying the physics of these soft materials out of their equilibrium ground state.

Role of nanotopography in the development of tissue engineered 3D organs and tissues using mesenchymal stem cells.

PubMed

Salmasi, Shima; Kalaskar, Deepak M; Yoon, Wai-Weng; Blunn, Gordon W; Seifalian, Alexander M

2015-03-26

Recent regenerative medicine and tissue engineering strategies (using cells, scaffolds, medical devices and gene therapy) have led to fascinating progress of translation of basic research towards clinical applications. In the past decade, great deal of research has focused on developing various three dimensional (3D) organs, such as bone, skin, liver, kidney and ear, using such strategies in order to replace or regenerate damaged organs for the purpose of maintaining or restoring organs' functions that may have been lost due to aging, accident or disease. The surface properties of a material or a device are key aspects in determining the success of the implant in biomedicine, as the majority of biological reactions in human body occur on surfaces or interfaces. Furthermore, it has been established in the literature that cell adhesion and proliferation are, to a great extent, influenced by the micro- and nano-surface characteristics of biomaterials and devices. In addition, it has been shown that the functions of stem cells, mesenchymal stem cells in particular, could be regulated through physical interaction with specific nanotopographical cues. Therefore, guided stem cell proliferation, differentiation and function are of great importance in the regeneration of 3D tissues and organs using tissue engineering strategies. This review will provide an update on the impact of nanotopography on mesenchymal stem cells for the purpose of developing laboratory-based 3D organs and tissues, as well as the most recent research and case studies on this topic.

Current driven dynamics of magnetic domain walls in permalloy nanowires

NASA Astrophysics Data System (ADS)

Hayashi, Masamitsu

The significant advances in micro-fabrication techniques opened the door to access interesting properties in solid state physics. With regard to magnetic materials, geometrical confinement of magnetic structures alters the defining parameters that govern magnetism. For example, development of single domain nano-pillars made from magnetic multilayers led to the discovery of electrical current controlled magnetization switching, which revealed the existence of spin transfer torque. Magnetic domain walls (DWs) are boundaries in magnetic materials that divide regions with distinct magnetization directions. DWs play an important role in the magnetization reversal processes of both bulk and thin film magnetic materials. The motion of DW is conventionally controlled by magnetic fields. Recently, it has been proposed that spin polarized current passed across the DW can also control the motion of DWs. Current in most magnetic materials is spin-polarized, due to spin-dependent scattering of the electrons, and thus can deliver spin angular momentum to the DW, providing a "spin transfer" torque on the DW which leads to DW motion. In addition, owing to the development of micro-fabrication techniques, geometrical confinement of magnetic materials enables creation and manipulation of a "single" DW in magnetic nanostructures. New paradigms for DW-based devices are made possible by the direct manipulation of DWs using spin polarized electrical current via spin transfer torque. This dissertation covers research on current induced DW motion in magnetic nanowires. Fascinating effects arising from the interplay between DWs with spin polarized current will be revealed.

Neutron stars interiors: Theory and reality

NASA Astrophysics Data System (ADS)

Stone, J. R.

2016-03-01

There are many fascinating processes in the universe which we observe in more detail thanks to increasingly sophisticated technology. One of the most interesting phenomena is the life cycle of stars, their birth, evolution and death. If the stars are massive enough, they end their lives in a core-collapse supernova explosion, one of the most violent events in the universe. As a result, the densest objects in the universe, neutron stars and/or black holes, are created. The physical basis of these events should be understood in line with observation. Unfortunately, available data do not provide adequate constraints for many theoretical models of dense matter. One of the most open areas of research is the composition of matter in the cores of neutron stars. Unambiguous fingerprints for the appearance and evolution of particular components, such as strange baryons and mesons, with increasing density, have not been identified. In particular, the hadron-quark phase transition remains a subject of intensive research. In this contribution we briefly survey the most promising observational and theoretical directions leading to progress in understanding high density matter in neutron stars. A possible way forward in modeling high-density matter is outlined, exemplified by the quark-meson-coupling model (QMC). This model makes connection between hadronic structure and the underlying quark make-up. It offers a natural explanation for the saturation of nuclear force and treats high-density matter, containing the full baryon octet, in terms of four uniquely defined parameters adjusted to properties of symmetric nuclear matter at saturation.

Transition disks: four candidates for ongoing giant planet formation in Ophiuchus

NASA Astrophysics Data System (ADS)

Orellana, M.; Cieza, L. A.; Schreiber, M. R.; Merín, B.; Brown, J. M.; Pellizza, L. J.; Romero, G. A.

2012-03-01

Among the large set of Spitzer-selected transitional disks that we have examined in the Ophiuchus molecular, four disks have been identified as (giant) planet-forming candidates based on the morphology of their spectral energy distributions (SEDs), their apparent lack of stellar companions, and evidence of accretion. Here we characterize the structures of these disks modeling their optical, infrared, and (sub)millimeter SEDs. We use the Monte Carlo radiative transfer package RADMC to construct a parametric model of the dust distribution in a flared disk with an inner cavity and calculate the temperature structure that is consistent with the density profile, when the disk is in thermal equilibrium with the irradiating star. For each object, we conducted a Bayesian exploration of the parameter space generating Monte Carlo Markov chains (MCMC) that allow the identification of the best-fit model parameters and to constrain their range of statistical confidence. Our calculations imply that evacuated cavities with radii ~2-8 AU are present that appear to have been carved by embedded giant planets. We found parameter values that are consistent with those previously given in the literature, indicating that there has been a mild degree of grain growth and dust settling, which deserves to be investigated with further modeling and follow-up observations. Resolved images with (sub)millimeter interferometers would be required to break some of the degeneracies of the models and more tightly constrain the physical properties of these fascinating disks.

Electrospray Ionization Mass Spectrometry: A Technique to Access the Information beyond the Molecular Weight of the Analyte

PubMed Central

Banerjee, Shibdas; Mazumdar, Shyamalava

2012-01-01

The Electrospray Ionization (ESI) is a soft ionization technique extensively used for production of gas phase ions (without fragmentation) of thermally labile large supramolecules. In the present review we have described the development of Electrospray Ionization mass spectrometry (ESI-MS) during the last 25 years in the study of various properties of different types of biological molecules. There have been extensive studies on the mechanism of formation of charged gaseous species by the ESI. Several groups have investigated the origin and implications of the multiple charge states of proteins observed in the ESI-mass spectra of the proteins. The charged analytes produced by ESI can be fragmented by activating them in the gas-phase, and thus tandem mass spectrometry has been developed, which provides very important insights on the structural properties of the molecule. The review will highlight recent developments and emerging directions in this fascinating area of research. PMID:22611397

Enhanced fluorescence norfloxacin substituted naphthalimide derivatives: Molecular docking and antibacterial activity

NASA Astrophysics Data System (ADS)

Kumar, Santosh; Kumar, Gaurav; Tripathi, Amit Kumar; Seena, Sahadevan; Koh, Joonseok

2018-04-01

Hybrid derivatives are a fascinating and challenging process in the area of drug discovery. Naphthalimide derivatives with modified norfloxacin moiety were designed and synthesized. Docking simulations were done to assess the interactions of the derivatives with the E. coli type II topoisomerases Gyrase B and ParE ATP-binding pocket by taking novobiocin as a standard molecule. Results suggested that the norfloxacin substituted naphthalimide derivatives indicate red-shift emission maxima when compared to 4-bromo 1,8-naphthalic anhydride. The molecular docking simulation study revealed that the derivatives have similar interaction but a different mode of binding with the gyrase B ATP-binding pocket as compare to novobiocin. However, they bound to ParE ATP-binding pocket similarly to novobiocin. The antibacterial property was confirmed with disc diffusion method. Our study indicated that the norfloxacin substituted naphthalimide novel derivatives have pronounced fluorescence, anti-topoisomerase activity, and antibacterial properties; therefore, they could be developed into new drug candidates.

Effect of the tetrahedral groups on the optical properties of LaBRO{sub 5} (R = Si and Ge): A first-principles study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Linping; School of Physics Science and Technology, Xinjiang University, Urumqi 830046; Jing, Qun

2015-09-21

As potential candidates for deep-UV nonlinear optical (NLO) crystals, borosilicates and borogermanates, which contain NLO-active groups such as B-O, Si-O, and Ge-O groups, have fascinated many material scientists' research enthusiasm. In this paper, the electronic structures and optical properties of two isostructural noncentrosymmetric crystals LaBRO{sub 5} (R = Si and Ge) have been studied by the first-principles method. Combined with the analyses of the SHG-density and the localized electron-density difference, contributions of the constituent tetrahedra to the total NLO responses are investigated. Eventually, BO{sub 4} and GeO{sub 4} groups give nearly equal contributions to the SHG effect of LaBGeO{sub 5}, but formore » LaBSiO{sub 5}, SiO{sub 4} groups express stronger SHG response than that of BO{sub 4}. Such interesting conclusion is consistent with the distortion index analyses and dipole moment.« less

A Review on the Modification of Polysaccharide Through Graft Copolymerization for Various Potential Applications

PubMed Central

Kumar, Deepak; Pandey, Jyoti; Raj, Vinit; Kumar, Pramendra

2017-01-01

Introduction: Graft copolymerization is one of the most promising technique uses to modify the properties of naturally available polymers with a minimum loss in their native characteristics. Methods and Materials: Graft copolymerization is a very significant technique to add hybrid properties in backbone of polymers. The grafting generally initiated through the formation of free radical centers on the polymer backbone as well as monomer. Results: Grafted polysaccharides have various applications in different important scientific areas such as drug delivery, pharmaceutical field, plastic industry, waste water treatment, tannery effluent treatment, textile industry, agriculture area, etc. all of this fascinated us to summarize the major research articles over the last two decades outlining different methods of grafting, surface modification, graft copolymerization of synthetic and natural polymers. Conclusion: Various redox initiator systems viz. Ceric ammonium nitrate, per sulfate, Irradiation, FAS-H2O2 etc. is also explored for grafting of vinyl through conventional and non-conventional techniques. PMID:29151987

Ionic Liquid/Metal-Organic Framework Composites: From Synthesis to Applications.

PubMed

Kinik, Fatma Pelin; Uzun, Alper; Keskin, Seda

2017-07-21

Metal-organic frameworks (MOFs) have been widely studied for different applications owing to their fascinating properties such as large surface areas, high porosities, tunable pore sizes, and acceptable thermal and chemical stabilities. Ionic liquids (ILs) have been recently incorporated into the pores of MOFs as cavity occupants to change the physicochemical properties and gas affinities of MOFs. Several recent studies have shown that IL/MOF composites show superior performances compared with pristine MOFs in various fields, such as gas storage, adsorption and membrane-based gas separation, catalysis, and ionic conductivity. In this review, we address the recent advances in syntheses of IL/MOF composites and provide a comprehensive overview of their applications. Opportunities and challenges of using IL/MOF composites in many applications are reviewed and the requirements for the utilization of these composite materials in real industrial processes are discussed to define the future directions in this field. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Armored MOFs: enforcing soft microporous MOF nanocrystals with hard mesoporous silica.

PubMed

Li, Zheng; Zeng, Hua Chun

2014-04-16

Metal-organic frameworks (MOFs) are a class of fascinating supramolecular soft matters but with relatively weak mechanical strength. To enforce MOF materials for practical applications, one possible way seems to be transforming them into harder composites with a stronger secondary phase. Apparently, such a reinforcing phase must possess larger porosity for ionic or molecular species to travel into or out of MOFs without altering their pristine physicochemical properties. Herein we report a general synthetic approach to coat microporous MOFs and their derivatives with an enforcing shell of mesoporous silica (mSiO2). Four well-known MOFs (ZIF-8, ZIF-7, UiO-66, and HKUST-1), representing two important families of MOFs, have served as a core phase in nanocomposite products. We show that significant enhancement in mechanical properties (hardness and toughness) can indeed be achieved with this "armoring approach". Excellent accessibility of the mSiO2-wrapped MOFs and their metal-containing nanocomposites has also been demonstrated with catalytic reduction of 4-nitrophenol.

Recent progress in cellulose nanocrystals: sources and production.

PubMed

Trache, Djalal; Hussin, M Hazwan; Haafiz, M K Mohamad; Thakur, Vijay Kumar

2017-02-02

Cellulose nanocrystals, a class of fascinating bio-based nanoscale materials, have received a tremendous amount of interest both in industry and academia owing to its unique structural features and impressive physicochemical properties such as biocompatibility, biodegradability, renewability, low density, adaptable surface chemistry, optical transparency, and improved mechanical properties. This nanomaterial is a promising candidate for applications in fields such as biomedical, pharmaceuticals, electronics, barrier films, nanocomposites, membranes, supercapacitors, etc. New resources, new extraction procedures, and new treatments are currently under development to satisfy the increasing demand of manufacturing new types of cellulose nanocrystals-based materials on an industrial scale. Therefore, this review addresses the recent progress in the production methodologies of cellulose nanocrystals, covering principal cellulose resources and the main processes used for its isolation. A critical and analytical examination of the shortcomings of various approaches employed so far is made. Additionally, structural organization of cellulose and nomenclature of cellulose nanomaterials have also been discussed for beginners in this field.

Pharmaceutical aspects of salt and cocrystal forms of APIs and characterization challenges.

PubMed

Cerreia Vioglio, Paolo; Chierotti, Michele R; Gobetto, Roberto

2017-08-01

In recent years many efforts have been devoted to the screening and the study of new solid-state forms of old active pharmaceutical ingredients (APIs) with salification or co-crystallization processes, thus modulating final properties without changing the pharmacological nature. Salts, hydrates/solvates, and cocrystals are the common solid-state forms employed. They offer the intriguing possibility of exploring different pharmaceutical properties for a single API in the quest of enhancing the final drug product. New synthetic strategies and advanced characterization techniques have been recently proposed in this hot topic for pharmaceutical companies. This paper reviews the recent progresses in the field particularly focusing on the characterization challenges encountered when the nature of the solid-state form must be determined. The aim of this article is to offer the state-of-the-art on this subject in order to develop new insights and to promote cooperative efforts in the fascinating field of API salt and cocrystal forms. Copyright © 2017 Elsevier B.V. All rights reserved.

Removal of organic compounds from water by using a gold nanoparticle-poly(dimethylsiloxane) nanocomposite foam.

PubMed

Gupta, Ritu; Kulkarni, Giridhar U

2011-06-20

A low density, highly compressible, porous foam of poly(dimethylsiloxane) (PDMS) incorporated with Au nanoparticles (10-50 nm) has been synthesized by using a single-step process with water as a medium. It exhibits high swelling ability (≈600%) against benzene, toluene, ethylbenzene, and xylene (BTEX)-a property that has been exploited in the removal of oil spills from water. It is resistant to harsh chemical environments. It is also effective against odorous sulfur containing contaminants such as thioanisole. It works repeatedly and efficiently over many cycles. The regeneration of the foam is rather simple: heating in air to 300 °C for short time brings back its original activity. The fascinating properties of Au nanoparticles could be mingled with those of PDMS to provide a sustainable and practical solution for water treatment. It is also demonstrated to work effectively for deodorizing garlic extract with a promise as a food packaging material. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Mechanical and Electrical Properties of Organogels with Multiwall Carbon Nanotubes

NASA Astrophysics Data System (ADS)

Moniruzzaman, Mohammad; Winey, Karen

2008-03-01

Organogels are fascinating thermally reversible viscoelastic materials that are comprised of an organic liquid and low concentrations (typically <2 wt %) of low molecular mass organic gelators. We have fabricated the first organogel/carbon nanotube composites using 12-hydroxystearic acid (HSA) as the gelator molecule and pristine and carboxylated multi-wall carbon nanotubes as the nanofillers and 1,2-dichlorobenzene as the organic solvent. We have achieved significant improvements in the mechanical and electrical properties of organogels by incorporating these carbon nanotubes. For example, the linear viscoelastic regime of the HSA organogel, an indicator of the strength of the gel, extends by a factor of 4 with the incorporation of 0.2 wt% of the carboxylated nanotubes. Also, the carbon nanotubes (specially the pristine tubes) improve the electrical conductivity of the organogels, e.g. six orders of magnitude enhancement in electrical conductivity with 0.2 wt% of pristine tubes. Differential scanning calorimetry experiments indicate that the nanotubes do not affect the thermoreversibility of the organogels.

A Generic Wet Impregnation Method for Preparing Substrate-Supported Platinum Group Metal and Alloy Nanoparticles with Controlled Particle Morphology.

PubMed

Zhang, Changlin; Oliaee, Shirin Norooz; Hwang, Sang Youp; Kong, Xiangkai; Peng, Zhenmeng

2016-01-13

Mass production of shape-controlled platinum group metal (PGM) and alloy nanoparticles is of high importance for their many fascinating properties in catalysis, electronics, and photonics. Despite of successful demonstrations at milligram scale using wet chemistry syntheses in many fundamental studies, there is still a big gap between the current methods and their real applications due to the complex synthetic procedures, scale-up difficulty, and surface contamination problem of the made particles. Here we report a generic wet impregnation method for facile, surfactant-free, and scalable preparation of nanoparticles of PGMs and their alloys on different substrate materials with controlled particle morphology and clean surface, which bridges the outstanding properties of these nanoparticles to practical important applications. The underlying particle growth and shape formation mechanisms were investigated using a combination of ex situ and in situ characterizations and were attributed to their different interactions with the applied gas molecules.

Controllable lasing performance in solution-processed organic-inorganic hybrid perovskites.

PubMed

Kao, Tsung Sheng; Chou, Yu-Hsun; Hong, Kuo-Bin; Huang, Jiong-Fu; Chou, Chun-Hsien; Kuo, Hao-Chung; Chen, Fang-Chung; Lu, Tien-Chang

2016-11-03

Solution-processed organic-inorganic perovskites are fascinating due to their remarkable photo-conversion efficiency and great potential in the cost-effective, versatile and large-scale manufacturing of optoelectronic devices. In this paper, we demonstrate that the perovskite nanocrystal sizes can be simply controlled by manipulating the precursor solution concentrations in a two-step sequential deposition process, thus achieving the feasible tunability of excitonic properties and lasing performance in hybrid metal-halide perovskites. The lasing threshold is at around 230 μJ cm -2 in this solution-processed organic-inorganic lead-halide material, which is comparable to the colloidal quantum dot lasers. The efficient stimulated emission originates from the multiple random scattering provided by the micro-meter scale rugged morphology and polycrystalline grain boundaries. Thus the excitonic properties in perovskites exhibit high correlation with the formed morphology of the perovskite nanocrystals. Compared to the conventional lasers normally serving as a coherent light source, the perovskite random lasers are promising in making low-cost thin-film lasing devices for flexible and speckle-free imaging applications.

Theory, simulations and the design of functionalized nanoparticles for biomedical applications: A Soft Matter Perspective

NASA Astrophysics Data System (ADS)

Angioletti-Uberti, Stefano

2017-11-01

Functionalised nanoparticles for biomedical applications represents an incredibly exciting and rapidly growing field of research. Considering the complexity of the nano-bio interface, an important question is to what extent can theory and simulations be used to study these systems in a realistic, meaningful way. In this review, we will argue for a positive answer to this question. Approaching the issue from a "Soft Matter" perspective, we will consider those properties of functionalised nanoparticles that can be captured within a classical description. We will thus not concentrate on optical and electronic properties, but rather on the way nanoparticles' interactions with the biological environment can be tuned by functionalising their surface and exploited in different contexts relevant to applications. In particular, we wish to provide a critical overview of theoretical and computational coarse-grained models, developed to describe these interactions and present to the readers some of the latest results in this fascinating area of research.

Polar Elastomers as Novel Materials for Electromechanical Actuator Applications.

PubMed

Opris, Dorina M

2018-02-01

Dielectric elastomer actuators are stretchable capacitors capable of a musclelike actuation when charged. They will one day be used to replace malfunctioning muscles supposing the driving voltage can be reduced below 24 V. This focus here is on polar dielectric elastomers and their behavior under an electric field. Emphasis is placed on all the features that are correlated with the molecular structure, its synthetic realization, and its impact on properties. Regarding the polymer class, the focus, to some degree, is on polysiloxanes because of their attractively low glass transition temperatures. This enables introduction of highly polar groups to the backbone while maintaining soft elastic properties. The goal is to provide a few guidelines for future research in this emerging field that may be useful for those considering entering this fascinating endeavor. Because of the large number of materials available, a few restrictions in the selection have to be applied. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Real-Time Observation of Organic Cation Reorientation in Methylammonium Lead Iodide Perovskites.

PubMed

Bakulin, Artem A; Selig, Oleg; Bakker, Huib J; Rezus, Yves L A; Müller, Christian; Glaser, Tobias; Lovrincic, Robert; Sun, Zhenhua; Chen, Zhuoying; Walsh, Aron; Frost, Jarvist M; Jansen, Thomas L C

2015-09-17

The introduction of a mobile and polarized organic moiety as a cation in 3D lead-iodide perovskites brings fascinating optoelectronic properties to these materials. The extent and the time scales of the orientational mobility of the organic cation and the molecular mechanism behind its motion remain unclear, with different experimental and computational approaches providing very different qualitative and quantitative description of the molecular dynamics. Here we use ultrafast 2D vibrational spectroscopy of methylammonium (MA) lead iodide to directly resolve the rotation of the organic cations within the MAPbI3 lattice. Our results reveal two characteristic time constants of motion. Using ab initio molecular dynamics simulations, we identify these as a fast (∼300 fs) "wobbling-in-a-cone" motion around the crystal axis and a relatively slow (∼3 ps) jump-like reorientation of the molecular dipole with respect to the iodide lattice. The observed dynamics are essential for understanding the electronic properties of perovskite materials.

Continuing fascination of exploration in natural substances from microorganisms.

PubMed

Takahashi, Yoko

2017-01-01

In the search for novel organic compounds, I think it is of paramount importance not to overlook the pursuit of microorganism diversity and the abilities those microorganisms hold as a resource. In commemoration of Professor Satoshi Ōmura's Nobel Prize in Physiology or Medicine, I will briefly describe the microorganism that produces avermectin and then discuss how innovating isolation methods and pioneering isolation sources have opened the door to numerous new microorganism resources. Furthermore, as exploratory research of substances views the world from many different angles-from biological activity to a compound's physiochemical properties-it is possible to discover a novel compound from a well-known microorganism. Based on this, I will discuss the future prospects of exploratory research.

Tightening slip knots in raw and degummed silk to increase toughness without losing strength.

PubMed

Pantano, Maria F; Berardo, Alice; Pugno, Nicola M

2016-02-12

Knots are fascinating topological elements, which can be found in both natural and artificial systems. While in most of the cases, knots cannot be loosened without breaking the strand where they are tightened, herein, attention is focused on slip or running knots, which on the contrary can be unfastened without compromising the structural integrity of their hosting material. Two different topologies are considered, involving opposite unfastening mechanisms, and their influence on the mechanical properties of natural fibers, as silkworm silk raw and degummed single fibers, is investigated and quantified. Slip knots with optimized shape and size result in a significant enhancement of fibers energy dissipation capability, up to 300-400%, without affecting their load bearing capacity.

Tightening slip knots in raw and degummed silk to increase toughness without losing strength

PubMed Central

Pantano, Maria F.; Berardo, Alice; Pugno, Nicola M.

2016-01-01

Knots are fascinating topological elements, which can be found in both natural and artificial systems. While in most of the cases, knots cannot be loosened without breaking the strand where they are tightened, herein, attention is focused on slip or running knots, which on the contrary can be unfastened without compromising the structural integrity of their hosting material. Two different topologies are considered, involving opposite unfastening mechanisms, and their influence on the mechanical properties of natural fibers, as silkworm silk raw and degummed single fibers, is investigated and quantified. Slip knots with optimized shape and size result in a significant enhancement of fibers energy dissipation capability, up to 300–400%, without affecting their load bearing capacity. PMID:26868855

Structure and Biophysics of CBFβ/RUNX and Its Translocation Products.

PubMed

Tahirov, Tahir H; Bushweller, John

2017-01-01

The core binding factor (CBF) transcription factor is somewhat unique in that it is composed of a DNA binding RUNX subunit (RUNX1, 2, or 3) and a non-DNA binding CBFβ subunit, which modulates RUNX protein activity by modulating the auto-inhibition of the RUNX subunits. Since the discovery of this fascinating transcription factor more than 20 years ago, there has been a robust effort to characterize the structure as well as the biochemical properties of CBF. More recently, these efforts have also extended to the fusion proteins that arise from the subunits of CBF in leukemia. This chapter highlights the work of numerous labs which has provided a detailed understanding of the structure and function of this transcription factor and its fusion proteins.

Note: Mechanical in situ exfoliation of van der Waals materials

NASA Astrophysics Data System (ADS)

Pásztor, Á.; Scarfato, A.; Renner, Ch.

2017-07-01

Exfoliation, namely, the peeling of layered materials down to a single unit-cell thin foil, opens promising avenues to fabricate novel electronic materials. New properties and original functionalities emerge in the single and few layer configurations of a number of layered compounds, in particular in transition metal dichalcogenides. However, many of these thin exfoliated materials are very sensitive to ambient conditions impeding the exploration of this new and fascinating parameter space. Here we describe a method of mechanical exfoliation in ultra-high vacuum (UHV). This technique is easily adaptable to any UHV system and allows preparing and studying air sensitive nanoflakes in situ. We present the basic design and proof-of-concept scanning tunneling microscopy imaging of VSe2 nanoflakes.

Van der Waals Epitaxy of Functional Oxide Heterostructures

NASA Astrophysics Data System (ADS)

Chu, Ying-Hao

In the diligent pursuit of low-power consumption, multifunctional, and environmentally friendly electronics, more sophisticated requirements on functional materials are on demand. Recently, the discovery of 2D layered materials has created a revolution to this field. Pioneered by graphene, these new 2D materials exhibit abundant unusual physical phenomena that is undiscovered in bulk forms. These materials are characterized with their layer form and almost pure 2D electronic behavior. The confinement of charge and heat transport at such ultrathin planes offers possibilities to overcome the bottleneck of present device development in thickness limitation, and thus push the technologies into next generation. Van der Waals epitaxy, an epitaxial growth method to combine 2D and 3D materials, is one of current reliable manufacturing processes to fabricate 2D materials by growing these 2D materials epitaxially on 3D materials. Then, transferring the 2D materials to the substrates for practical applications. In the mean time, van der Waals epitaxy has also been used to create free-standing 3D materials by growing 3D materials on 2D materials and then removing them from 2D materials since the interfacial boding between 2D and 3D materials should be weak van der Waals bonds. In this study, we intend to take the same concept, but to integrate a family of functional materials in order to open new avenue to flexible electronics. Due to the interplay of lattice, charge, orbital, and spin degrees of freedom, correlated electrons in oxides generate a rich spectrum of competing phases and physical properties. Recently, lots of studies have suggested that oxide heterostructures provide a powerful route to create and manipulate the degrees of freedom and offer new possibilities for next generation devices, thus create a new playground for researchers to investigate novel physics and the emergence of fascinating states of condensed matter. In this talk, we use a 2D layered material as the substrate. And we take several oxides as examples to demonstrate a pathway to integrate 3D functional oxides on 2D layered materials.

Dynamical Evolution of the Recent Jet in CH Cyg

NASA Astrophysics Data System (ADS)

Karovska, Margarita

2011-10-01

We propose to carry out Chandra ACIS-S observations combined with HST/WFC3multi-wavelength imaging of the powerful, multi-component jet which was detectedin 2008 in the nearby symbiotic CH Cyg. CH Cyg is a fascinating system containing an evolved giant and a wind-accreting white dwarf, and it is one of the few symbiotics showing jet activity, especially in X-rays. Our goal is to measure the physical characteristics of the individual jet components, from the central source to the region of interaction with the circumbinary environment, reaching to within a few AU from the source of the jet. We will determine the characteristics of the central source, and of the inner and the outer jet, and the dynamical evolution, including precession, and kinematics of the ejecta.

Dynamical Evolution of the Recent Jet in CH Cyg

NASA Astrophysics Data System (ADS)

Karovska, Margarita

2011-09-01

We propose to carry out Chandra ACIS-S observations combined with HST/WFC3 multi-wavelength imaging of the powerful, multi-component jet which was detected in 2008 in the nearby symbiotic CH Cyg. CH Cyg is a fascinating system containing an evolved giant and a wind-accreting white dwarf, and it is one of the few symbiotics showing jet activity, especially in X-rays. Our goal is to measure the physical characteristics of the individual jet components, from the central source to the region of interaction with the circumbinary environment, reaching to within a few AU from the source of the jet. We will determine the characteristics of the central source, and of the inner and the outer jet, and the dynamical evolution, including precession, and kinematics of the ejecta.

Curved trajectories of actin-based motility in two dimensions

NASA Astrophysics Data System (ADS)

Wen, Fu-Lai; Leung, Kwan-tai; Chen, Hsuan-Yi

2012-05-01

Recent experiments have reported fascinating geometrical trajectories for actin-based motility of bacteria Listeria monocytogenes and functionalized beads. To understand the physical mechanism for these trajectories, we constructed a phenomenological model to study the motion of an actin-propelled disk in two dimensions. In our model, the force and actin density on the surface of the disk are influenced by the translation and rotation of the disk, which in turn is induced by the asymmetric distributions of those densities. We show that this feedback can destabilize a straight trajectory, leading to circular, S-shape and other geometrical trajectories observed in the experiments through bifurcations in the distributions of the force and actin density. The relation between our model and the models for self-propelled deformable particles is emphasized and discussed.

The Ring of Fire: The Effects of Slope upon Pattern Formation in Simulated Forest Fire Systems

NASA Astrophysics Data System (ADS)

Morillo, Robin; Manz, Niklas

We report about spreading fire fronts under sloped conditions using the general cellular automaton model and data from physical scaled-down experiments. Punckt et al. published experimental and computational results for planar systems and our preliminary results confirmed the expected speed-slope dependence of fire fronts propagating up or down the hill with a cut-off slope value above which no fire front can exist. Here we focus on two fascinating structures in reaction-diffusion systems: circular expanding target pattern and rotating spirals. We investigated the behaviors of both structures with varied values for the slope of the forest and the homogeneity of the trees. For both variables, a range of values was found for which target pattern or spiral formation was possible.

STS-73 Mission Insignia

NASA Technical Reports Server (NTRS)

1995-01-01

The crew patch of STS-73, the second flight of the United States Microgravity Laboratory (USML-2), depicts the Space Shuttle Columbia in the vastness of space. In the foreground are the classic regular polyhedrons that were investigated by Plato and later Euclid. The Pythagoreans were also fascinated by the symmetrical three-dimensional objects whose sides are the same regular polygon. The tetrahedron, the cube, the octahedron, and the icosahedron were each associated with the Natural Elements of that time: fire (on this mission represented as combustion science); Earth (crystallography), air and water (fluid physics). An additional icon shown as the infinity symbol was added to further convey the discipline of fluid mechanics. The shape of the emblem represents a fifth polyhedron, a dodecahedron, which the Pythagoreans thought corresponded to a fifth element that represented the cosmos.