bluuebunny/crossref_metadata_2025 huggingface dataset:
Speed and Sensitivity of Phototransduction inDrosophilaDepend on Degree of Saturation of Membrane Phospholipids
Authors: Randall Alex S. , Liu Che-Hsiung , Chu Brian , Zhang Qifeng , Dongre Sidharta A. , Juusola Mikko , Franze Kristian , Wakelam Michael J.O. , Hardie Roger C.
Published: February 2015

Drosophilaphototransduction is mediated via a G-protein-coupled PLC cascade. Recent evidence, including the demonstration that light evokes rapid contractions of the photoreceptors, suggested that the light-sensitive channels (TRP and TRPL) may be mechanically gated, together with protons released by PLC-mediated PIP2hydrolysis. If mechanical gating is involved we predicted that the response to light should be influenced by altering the physical properties of the membrane. To achieve this, we used diet to manipulate the degree of saturation of membrane phospholipids. In flies reared on a yeast diet, lacking polyunsaturated fatty acids (PUFAs), mass spectrometry showed that the proportion of polyunsaturated phospholipids was sevenfold reduced (from 38 to ∼5%) but rescued by adding a single species of PUFA (linolenic or linoleic acid) to the diet. Photoreceptors from yeast-reared flies showed a 2- to 3-fold increase in latency and time to peak of the light response, without affecting quantum bump waveform. In the absence of Ca2+influx or intrpmutants expressing only TRPL channels, sensitivity to light was reduced up to ∼10-fold by the yeast diet, and essentially abolished in hypomorphic G-protein mutants (Gαq). PLC activity appeared little affected by the yeast diet; however, light-induced contractions measured by atomic force microscopy or the activation of ectopic mechanosensitive gramicidin channels were also slowed ∼2-fold. The results are consistent with mechanosensitive gating and provide a striking example of how dietary fatty acids can profoundly influence sensory performance in a classical G-protein-coupled signaling cascade.
Gain Modulation of Synaptic Inputs by Network State in Auditory CortexIn Vivo
Authors: Reig Ramon , Zerlaut Yann , Vergara Ramiro , Destexhe Alain , Sanchez-Vives Maria V.
Published: February 2015

The cortical network recurrent circuitry generates spontaneous activity organized into Up (active) and Down (quiescent) states during slow-wave sleep or anesthesia. These different states of cortical activation gain modulate synaptic transmission. However, the reported modulation that Up states impose on synaptic inputs is disparate in the literature, including both increases and decreases of responsiveness. Here, we tested the hypothesis that such disparate observations may depend on the intensity of the stimulation. By means of intracellular recordings, we studied synaptic transmission during Up and Down states in rat auditory cortexin vivo. Synaptic potentials were evoked either by auditory or electrical (thalamocortical, intracortical) stimulation while randomly varying the intensity of the stimulus. Synaptic potentials evoked by the same stimulus intensity were compared in Up/Down states. Up states had a scaling effect on the stimulus-evoked synaptic responses: the amplitude of weaker responses was potentiated whereas that of larger responses was maintained or decreased with respect to the amplitude during Down states. We used a computational model to explore the potential mechanisms explaining this nontrivial stimulus–response relationship. During Up/Down states, there is different excitability in the network and the neuronal conductance varies. We demonstrate that the competition between presynaptic recruitment and the changing conductance might be the central mechanism explaining the experimentally observed stimulus–response relationships. We conclude that the effect that cortical network activation has on synaptic transmission is not constant but contingent on the strength of the stimulation, with a larger modulation for stimuli involving both thalamic and cortical networks.
A Functional Link between MT Neurons and Depth Perception Based on Motion Parallax
Authors: Kim HyungGoo R. , Angelaki Dora E. , DeAngelis Gregory C.
Published: February 2015

As an observer translates, objects lying at different distances from the observer have differential image motion on the retina (motion parallax). It is well established psychophysically that humans perceive depth rather precisely from motion parallax and that extraretinal signals may be used to correctly perceive the sign of depth (near vs far) when binocular and pictorial depth cues are absent or weak. However, the neural basis for this capacity remains poorly understood. We have shown previously that neurons in the macaque middle temporal (MT) area combine retinal image motion with smooth eye movement command signals to signal depth sign from motion parallax. However, those studies were performed in animals that were required simply to track a visual target, thus precluding direct comparisons between neural activity and behavior. Here, we examine the activity of MT neurons in rhesus monkeys that were trained to discriminate depth sign based on motion parallax, in the absence of binocular disparity and pictorial depth cues. We find that the most sensitive MT neurons approach behavioral sensitivity, whereas the average neuron is twofold to threefold less sensitive than the animal. We also find that MT responses are predictive of perceptual decisions (independent of the visual stimulus), consistent with a role for MT in providing sensory signals for this behavior. Our findings suggest that, in addition to its established roles in processing stereoscopic depth, area MT is well suited to contribute to perception of depth based on motion parallax.
Posttraumatic Stress Disorder-Like Induction Elevates β-Amyloid Levels, Which Directly Activates Corticotropin-Releasing Factor Neurons to Exacerbate Stress Responses
Authors: Justice Nicholas J. , Huang Longwen , Tian Jin-Bin , Cole Allysa , Pruski Melissa , Hunt Albert J. , Flores Rene , Zhu Michael X. , Arenkiel Benjamin R. , Zheng Hui
Published: February 2015

Recent studies have found that those who suffer from posttraumatic stress disorder (PTSD) are more likely to experience dementia as they age, most often Alzheimer's disease (AD). These findings suggest that the symptoms of PTSD might have an exacerbating effect on AD progression. AD and PTSD might also share common susceptibility factors such that those who experience trauma-induced disease were already more likely to succumb to dementia with age. Here, we explored these two hypotheses using a mouse model of PTSD in wild-type and AD model animals. We found that expression of human familial AD mutations in amyloid precursor protein and presenilin 1 leads to sensitivity to trauma-induced PTSD-like changes in behavioral and endocrine stress responses. PTSD-like induction, in turn, chronically elevates levels of CSF β-amyloid (Aβ), exacerbating ongoing AD pathogenesis. We show that PTSD-like induction and Aβ elevation are dependent on corticotropin-releasing factor (CRF) receptor 1 signaling and an intact hypothalamic–pituitary–adrenal axis. Furthermore, we show that Aβ species can hyperexcite CRF neurons, providing a mechanism by which Aβ influences stress-related symptoms and PTSD-like phenotypes. Consistent with Aβ causing excitability of the stress circuitry, we attenuate PTSD-like phenotypesin vivoby lowering Aβ levels during PTSD-like trauma exposure. Together, these data demonstrate that exposure to PTSD-like trauma can drive AD pathogenesis, which directly perturbs CRF signaling, thereby enhancing chronic PTSD symptoms while increasing risk for AD-related dementia.
The JAK/STAT3 Pathway Is a Common Inducer of Astrocyte Reactivity in Alzheimer's and Huntington's Diseases
Authors: Ben Haim Lucile , Ceyzériat Kelly , Carrillo-de Sauvage Maria Angeles , Aubry Fabien , Auregan Gwennaëlle , Guillermier Martine , Ruiz Marta , Petit Fanny , Houitte Diane , Faivre Emilie , Vandesquille Matthias , Aron-Badin Romina , Dhenain Marc , Déglon Nicole , Hantraye Philippe , Brouillet Emmanuel , Bonvento Gilles , Escartin Carole
Published: February 2015

Astrocyte reactivity is a hallmark of neurodegenerative diseases (ND), but its effects on disease outcomes remain highly debated. Elucidation of the signaling cascades inducing reactivity in astrocytes during ND would help characterize the function of these cells and identify novel molecular targets to modulate disease progression. The Janus kinase/signal transducer and activator of transcription 3 (JAK/STAT3) pathway is associated with reactive astrocytes in models of acute injury, but it is unknown whether this pathway is directly responsible for astrocyte reactivity in progressive pathological conditions such as ND. In this study, we examined whether the JAK/STAT3 pathway promotes astrocyte reactivity in several animal models of ND. The JAK/STAT3 pathway was activated in reactive astrocytes in two transgenic mouse models of Alzheimer's disease and in a mouse and a nonhuman primate lentiviral vector-based model of Huntington's disease (HD). To determine whether this cascade was instrumental for astrocyte reactivity, we used a lentiviral vector that specifically targets astrocytesin vivoto overexpress the endogenous inhibitor of the JAK/STAT3 pathway [suppressor of cytokine signaling 3 (SOCS3)]. SOCS3 significantly inhibited this pathway in astrocytes, prevented astrocyte reactivity, and decreased microglial activation in models of both diseases. Inhibition of the JAK/STAT3 pathway within reactive astrocytes also increased the number of huntingtin aggregates, a neuropathological hallmark of HD, but did not influence neuronal death. Our data demonstrate that the JAK/STAT3 pathway is a common mediator of astrocyte reactivity that is highly conserved between disease states, species, and brain regions. This universal signaling cascade represents a potent target to study the role of reactive astrocytes in ND.
Secreted Ectodomain of Sialic Acid-Binding Ig-Like Lectin-9 and Monocyte Chemoattractant Protein-1 Promote Recovery after Rat Spinal Cord Injury by Altering Macrophage Polarity
Authors: Matsubara Kohki , Matsushita Yoshihiro , Sakai Kiyoshi , Kano Fumiya , Kondo Megumi , Noda Mariko , Hashimoto Noboru , Imagama Shiro , Ishiguro Naoki , Suzumura Akio , Ueda Minoru , Furukawa Koichi , Yamamoto Akihito
Published: February 2015

Engrafted mesenchymal stem cells from human deciduous dental pulp (SHEDs) support recovery from neural insults via paracrine mechanisms that are poorly understood. Here we show that the conditioned serum-free medium (CM) from SHEDs, administered intrathecally into rat injured spinal cord during the acute postinjury period, caused remarkable functional recovery. The ability of SHED-CM to induce recovery was associated with an immunoregulatory activity that induced anti-inflammatory M2-like macrophages. Secretome analysis of the SHED-CM revealed a previously unrecognized set of inducers for anti-inflammatory M2-like macrophages: monocyte chemoattractant protein-1 (MCP-1) and the secreted ectodomain of sialic acid-binding Ig-like lectin-9 (ED-Siglec-9). Depleting MCP-1 and ED-Siglec-9 from the SHED-CM prominently reduced its ability to induce M2-like macrophages and to promote functional recovery after spinal cord injury (SCI). The combination of MCP-1 and ED-Siglec-9 synergistically promoted the M2-like differentiation of bone marrow-derived macrophagesin vitro, and this effect was abolished by a selective antagonist for CC chemokine receptor 2 (CCR2) or by the genetic knock-out of CCR2. Furthermore, MCP-1 and ED-Siglec-9 administration into the injured spinal cord induced M2-like macrophages and led to a marked recovery of hindlimb locomotor function after SCI. The inhibition of this M2 induction through the inactivation of CCR2 function abolished the therapeutic effects of both SHED-CM and MCP-1/ED-Siglec-9. Macrophages activated by MCP-1 and ED-Siglec-9 extended neurite and suppressed apoptosis of primary cerebellar granule neurons against the neurotoxic effects of chondroitin sulfate proteoglycans. Our data suggest that the unique combination of MCP-1 and ED-Siglec-9 repairs the SCI through anti-inflammatory M2-like macrophage induction.
Photoreceptor Ablation Initiates the Immediate Loss of Glutamate Receptors in Postsynaptic Bipolar Cells in Retina
Authors: Dunn Felice A.
Published: February 2015

Structural changes underlying neurodegenerative diseases include dismantling of synapses, degradation of circuitry, and even massive rewiring. Our limited understanding of synapse dismantling stems from the inability to control the timing and extent of cell death. In this study, selective ablation of cone photoreceptors in live mouse retina and tracking of postsynaptic partners at the cone-to-ON cone bipolar cell synapse reveals that early reaction to cone loss involves rapid and local changes in postsynaptic glutamate receptor distribution. Glutamate receptors disappear with a time constant of 2 h. Furthermore, binding of glutamate receptors by agonists and antagonists is insufficient to rescue glutamate receptor loss, suggesting that receptor allocation depends on the physical presence of cones. These findings demonstrate that the initial step in synapse disassembly involves postsynaptic receptor loss rather than dendritic retraction, providing insight into the early stages of neurodegenerative disease.
Mammalian gonocyte and spermatogonia differentiation: recent advances and remaining challenges
Authors: Manku Gurpreet , Culty Martine
Published: February 2015

The production of spermatozoa relies on a pool of spermatogonial stem cells (SSCs), formed in infancy from the differentiation of their precursor cells, the gonocytes. Throughout adult life, SSCs will either self-renew or differentiate, in order to maintain a stem cell reserve while providing cells to the spermatogenic cycle. By contrast, gonocytes represent a transient and finite phase of development leading to the formation of SSCs or spermatogonia of the first spermatogenic wave. Gonocyte development involves phases of quiescence, cell proliferation, migration, and differentiation. Spermatogonia, on the other hand, remain located at the basement membrane of the seminiferous tubules throughout their successive phases of proliferation and differentiation. Apoptosis is an integral part of both developmental phases, allowing for the removal of defective cells and the maintenance of proper germ–Sertoli cell ratios. While gonocytes and spermatogonia mitosis are regulated by distinct factors, they both undergo differentiation in response to retinoic acid. In contrast to postpubertal spermatogenesis, the early steps of germ cell development have only recently attracted attention, unveiling genes and pathways regulating SSC self-renewal and proliferation. Yet, less is known on the mechanisms regulating differentiation. The processes leading from gonocytes to spermatogonia have been seldom investigated. While the formation of abnormal gonocytes or SSCs could lead to infertility, defective gonocyte differentiation might be at the origin of testicular germ cell tumors. Thus, it is important to better understand the molecular mechanisms regulating these processes. This review summarizes and compares the present knowledge on the mechanisms regulating mammalian gonocyte and spermatogonial differentiation.
Redox behavior of Dicerium trioxide and the Possible Formation of Sesquioxide- C for Fuel cells
Authors: Yue Yang , Santhanam K.S.V. , Reed K. , Allston T.
Published: February 2015

Cerium oxide is an important electrode material in fuel cells. It has been interconverted in the gaseous phase at high temperatures or in the presence of oxygen and more recently in the solid state by applying an electric field. In the dynamic change that occurs, the migration of oxygen vacancies have been initiated at a critical potential of 2.8 V. We wish to report here an electrochemical method where the conversion of cerium oxides is brought out in aqueous medium where hydrogen ion is assisting the process of conversion. Keeping dissolved oxygen level negligible, the conversion of Ce2O3 to CeO2 occurs at 0.72 V vs saturated calomel electrode (SCE) with hydrogen ion assisting the process and the reversible conversion at 0.15 V (SCE). The hydrogen ion assisted conversion is compared with the solid state conversion that operates on oxygen vacancy creation.
Influence of Ga Substitution on the Nature of Glasses in Zr69.5Al7.5-xGaxCu12Ni11 and Ce75Al25-xGax Metallic Glass Compositions
Authors: Mandal R.K. , Tiwari R.S. , Singh Devinder , Singh Dharmendra
Published: February 2015

In this presentation, results of our recent investigations on the role of Ga on Al site in Zr69.5Al7.5-xGaxCu12Ni11 and Ce75Al25-xGax metallic glass compositions will be discussed. Ga like Al is normally expected to be in trivalent state. However, it may go in monovalent state depending on other alloying elements. The rapidly solidified melt spun ribbons of above two alloys gave rise to two important conclusions. The Zr69.5Al7.5-xGaxCu12Ni11 system displayed metallic glass formation in the range of x=0 to 7.5. In this process, we have come out with a new composition of glass without Al corresponding to x=7.5. In contrast to the above, for Ce-Al(Ga) system, we have observed phase separation in glass after dilute substitution of Ga. It seems that such a phase separation in this system cannot be understood in terms of summation of enthalpy of mixing of the various possible binaries in this system. The substitution of Ga in different valence states might have created chemical pressure leading to creation of two types of distinct major clusters. The phase separation may be due to this. This has also given rise to excursion of Ce 4f-states of the alloy. This and aforesaid ‘chemical pressure’ will be corroborated based on results of binary Ce-Al system under pressure by other investigators.
Thermoelectric properties control of Half-Heusler compounds by lattice defects and interfaces introduced based on the close relationship with Heusler compounds
Authors: Kimura Yoshisato , Chai Yaw-Wang , Oniki Toshinori , Itagaki Takahiko , Otani Shinya
Published: February 2015

Half-Heusler MNiSn (M=Ti, Zr, Hf) compounds are well-known, excellent n-type thermoelectric materials. The n-type Seebeck coefficients of ZrNiSn are reduced because of the precipitation of the metallic Heusler ZrNi2Sn phase. An excellent n-type Seebeck coefficient can be converted to p-type based on the vacancy site occupation by the solute Co atoms in the half-Heusler TiNiSn phase as well as ZrNiSn. The Heusler phase precipitates, including their precursor nano-structure in the half-Heusler matrix and the vacancy site occupation of the half-Heusler phase, are regarded as lattice defects based on the crystallographically and thermodynamically close relationship between half-Heusler and Heusler phases.
Electrically Tunable Ultra-specific Zinc Oxide Biosensor
Authors: Munje Rujuta D. , Wangzhou Andi , Selvam Anjan Panneer , Muthukumar Sriram , Prasad Shalini
Published: February 2015

Zinc oxide surface states can be utilized for ultra-specific detection of biomolecules. The major challenges in using ZnO for bio-sensing are attaining enhanced sensitivity and specificity. In this study, we explore the functionalization of zinc in ZnO through utilizing the thiol bond. The purpose of this study is to demonstrate that the ZnO based sensor is capable of achieving high specificity in presence of competitive surface binding through the thiol bond. The final goal is to design an ultra-specific biosensor to detect low occurring biomolecules. In this study, we have selected cortisol as a stress marker to demonstrate quantification and detection from synthetic sweat. In order to demonstrate ultra-specificity, we have used two competitive thiol based molecules binding to zinc, a linker Dithiobis succinimidyl propionate (DSP) and reducing agent of DSP, Dithiothreitol (DTT). Electrochemical impedance spectroscopy (EIS) is used to quantify the signal obtained through various ratiometric concentrations of DSP and DTT. To validate the EIS study results, inherent fluorescence studies are done by mapping changes in green emission spectrum of ZnO before and after linker functionalization. The optimal combination in terms of highest signal is identified to be of 25mM DTT and 50mM DSP. This is implemented in the experiments performed to calibrate the cortisol concentration in synthetic sweat. This study demonstrates the detection of cortisol antigen in synthetic sweat present within the physiological levels of 8 ng/mL to 140 ng/mL.
Using Cell-Free Expression to Create Light-Activated Proteins In Situ in Droplet Interface Bilayer Networks
Authors: Taylor Graham J. , Sarles Stephen A.
Published: February 2015

Droplet interface bilayers (DIBs) are physical lipid bilayers that mimic real membranes in living cells, and they are formed quickly using droplets of water and lipids in oil (Fig. 1A). DIBs allow biomolecular sensing and direct detection of transmembrane proteins or peptides and small molecules such as drugs, anesthetics, or even ions. Cell-free expression systems allow in vitro protein synthesis using actual natural machinery extracted from organisms (Fig. 1B). Previous attempts to combine DIBs with cell-free extracts (CFE) encountered bilayer destabilization due to components in the expression system. This study evaluates incorporation of Promega’s T7 S30 High Yield (HY) Expression system with DIBs to pave the way for future in situ expression of light-activated bacteriorhodopsin (BR) and other complex transmembrane proteins in DIBs. A secondary output includes establishing a method for real-time monitoring and modeling of CF expression reactions using minimal volume. The ability to quantify CF output in such small volumes reduces cost per reaction from $20 to around $0.40, and synthesized protein levels reach tens to hundreds of micrograms per milliliter in less than 1 hour at 37°C.
Development of Novel Magnetostrictive Fe-Co-B Thin Films as a High Frequency Sensor Platform
Authors: Sheng Zhizhi , Cheng Z.-Y.
Published: February 2015

Fe-Co-B was identified as a potential candidate for the development of high-frequency sensors and high-frequency actuators. To fabricate high-frequency magnetostrictive resonators, Fe-Co-B magetostrictive thin films were prepared by combining electrochemical deposition and microfabrication processes. It is crucial to obtain thin films with proper microstructure and composition. Results showed that Fe-rich Fe-Co-B thin films exhibited better resonance behavior than those with Co-rich and equiatomic Fe and Co compositions. It is also found that the deposition condition plays an important role on the performance of the films. Fe55Co28B17 thin films were fabricated under the same current density for different times. The films exhibited nanocrystalline structure, circular nodules as surface morphology and good resonance behavior. Fe/Co ratio on surface and cross section slightly decreased with increasing the deposition time. The resonance frequency slightly increased and the Q value was found to decrease with increasing deposition time.
Determination of Diffusion Length of Carriers in Graphene Using Contactless Photoelectromagnetic Method of Investigations
Authors: Nowak Marian , Solecka Barbara , Jesionek Marcin
Published: February 2015

The photoelectromagnetic (PEM) investigations are proposed for determination of diffusion length of carriers in graphene. The presented measurements are performed in Corbino configuration using noncontact technique. The circular PEM currents are detected in an outer coil by induction if illumination intensity is periodically varied. The theoretical dependence of PEM response on magnetic field induction, intensity and spatial distribution of illumination as well as on frequency of illumination chopping is presented. Experimental PEM data are presented for graphene films grown by CVD processing on a cooper foil and transferred onto a glass substrate. The presented method of investigations should be essential for development of graphene electronic and optoelectronic devices.
First-principles study of electronic transport properties of graphene nanoribbons with pentagon-heptagon (5-7) line defects
Authors: Nishida Yasutaka , Yoshida Takashi , Aiga Fumihiko , Yamazaki Yuichi , Miyazaki Hisao , Kajita Akihiro , Sakai Tadashi
Published: February 2015

In this study, we investigated the influence of line defects consisting of pentagon-heptagon (5-7) pairs on the electronic transport properties of zigzag-edged and armchair-edged graphene nanoribbons (GNRs). Using the first-principles density functional theory, we study their electronic properties. To investigate their current-voltage (I-V) characteristics at low bias voltage (∼ 1 meV), we use the nonequilibrium Green’s function method. As a result, we found that the conductance of the GNRs having a connected line defect between source and drain shows better performance than that of the ideal zigzag-edged GNRs (ZGNRs). A detailed investigation of the transmission spectra and the wave function around the Fermi level reveals that the line defects arranged along the transport direction work similar to an edge state of the ZGNRs and can be an additional conduction channel. Our results suggest that such a line defect can be effective for low-resistance GNR interconnects.
A Facile Synthesis of Graphene Quantum Dots via Size-Selective Precipitation and Their Application in GQD-layer Modified DSSC
Authors: Ryu Jaehoon , Jang Jyongsik
Published: February 2015

A novel approach to synthesize highly luminescent graphene quantum dots (GQDs) with well-defined sizes was explored based on simple oxidation of herringbone-type carbon nanofibers (HCNFs) and size-selective precipitation. In addition, the upconversion properties of GQD were investigated by applying GQD in working electrode of dye-sensitized solar cells (DSSCs).
The Fabrication of High-Performance Flexible Mercury Aptasensor Based on Graphene
Authors: An Ji Hyun , Jang Jyongsik
Published: February 2015

Liquid-ion gated FET-type flexible graphene-based aptasensor was fabricated for Hg detection in real world samples. Single-layer graphene was grown and transferred onto a flexible substrate and integrated into the liquid-ion gated FET system via surface engineerging process. Field-induced responses to Hg2+ ions in real world samples were highly rapid, sensitive and selective, leading to the high-perfromance graphene aptasensor. The aptasensor also displayed excellent flexibility and mechanical durability.
nanoHUB.org: A Gateway to Undergraduate Simulation-Based Research in Materials Science and Related Fields
Authors: Faltens Tanya A. , Bermel Peter , Buckles Amanda , Douglas K. Anna , Strachan Alejandro , Zentner Lynn K. , Klimeck Gerhard
Published: February 2015

Our future engineers and scientists will likely be required to use advanced simulations to solve many of tomorrow's challenges in nanotechnology. To prepare students to meet this need, the Network for Computational Nanotechnology (NCN) provides simulation-focused research experiences for undergraduates at an early point in their educational path, to increase the likelihood that they will ultimately complete a doctoral program. The NCN summer research program currently serves over 20 undergraduate students per year who are recruited nationwide, and selected by NCN and the faculty for aptitude in their chosen field within STEM, as well as complementary skills such as coding and written communication. Under the guidance of graduate student and faculty mentors, undergraduates modify or build nanoHUB simulation tools for exploring interdisciplinary problems in materials science and engineering, and related fields. While the summer projects exist within an overarching research context, the specific tasks that NCN undergraduate students engage in range from modifying existing tools to building new tools for nanoHUB and using them to conduct original research. Simulation tool development takes place within nanoHUB, using nanoHUB’s workspace, computational clusters, and additional training and educational resources. One objective of the program is for the students to publish their simulation tools on nanoHUB. These tools can be accessed and executed freely from around the world using a standard web-browser, and students can remain engaged with their work beyond the summer and into their careers. In this work, we will describe the NCN model for undergraduate summer research. We believe that our model is one that can be adopted by other universities, and will discuss the potential for others to engage undergraduate students in simulation-based research using free nanoHUB resources.
Experimental and Theoretical Investigation of Minimization of Forming-Induced Variability in Resistive Memory Devices
Authors: Geist Brian L. , Strukov Dmitri , Kochergin Vladimir
Published: February 2015

Resistive memory materials and devices (often called memristors) are an area of intense research, with metal/metal oxide/metal resistive elements a prominent example of such devices. Electroforming (the formation of a conductive filament in the metal oxide layer) represents one of the often necessary steps of resistive memory device fabrication that results in large and poorly controlled variability in device performance. In this contribution we present a numerical investigation of the electroforming process. In our model, drift and Ficks and Soret diffusion processes are responsible for movement of vacancies in the oxide material. Simulations predict filament formation and qualitatively agreed with a reduction of the forming voltage in structures with a top electrode. The forming and switching results of the study are compared with numerical simulations and show a possible pathway toward more repeatable and controllable resistive memory devices.
Effects of morphology of buffer layers on ZnO/sapphire heteroepitaxial growth by RF magnetron sputtering
Authors: Ide Tomoaki , Matsushima Koichi , Shimizu Ryota , Yamashita Daisuke , Seo Hynwoong , Koga Kazunori , Shiratani Masaharu , Itagaki Naho
Published: February 2015

Effects of surface morphology of buffer layers on ZnO/sapphire heteroepitaxial growth have been investigated by means of “nitrogen mediated crystallization (NMC) method”, where the crystal nucleation and growth are controlled by absorbed nitrogen atoms. We found a strong correlation between the height distribution profile of NMC-ZnO buffer layers and the crystal quality of ZnO films. On the buffer layer with a sharp peak in height distribution, a single-crystalline ZnO film with atomically-flat surface was grown. Our results indicate that homogeneous and high-density nucleation at the initial growth stages is critical in heteroepitaxy of ZnO on lattice mismatched substrates.
High Pressure Induced Binding Between Linear Carbon Chains and Nanotubes
Authors: Brunetto Gustavo , Andrade Nádia F. , Galvão Douglas S. , Souza Filho Antônio G.
Published: February 2015

Recent studies of single-walled carbon nanotubes (CNTs) in aqueous media have showed that water can significantly affect the tube mechanical properties. CNTs under hydrostatic compression can preserve their elastic properties up to large pressure values, while exhibiting exceptional resistance to mechanical loadings. It was experimentally observed that CNTs with encapsulated linear carbon chains (LCCs), when subjected to high hydrostatic pressure values, present irreversible red shifts in some of their vibrational frequencies. In order to address the cause of this phenomenon, we have carried out fully atomistic reactive (ReaxFF) molecular dynamics (MD) simulations for model structures mimicking the experimental conditions. We have considered the cases of finite and infinite (cyclic boundary conditions) CNTs filled with LCCs (LCC@CNTs) of different lengths (from 9 up to 40 atoms). Our results show that increasing the hydrostatic pressure causes the CNT to be deformed in an inhomogeneous way due to the LCC presence. The LCC/CNT interface regions exhibit convex curvatures, which results in more reactive sites, thus favoring the formation of covalent chemical bonds between the chain and the nanotube. This process is irreversible with the newly formed bonds continuing to exist even after releasing the external pressure and causing an irreversibly red shift in the chain vibrational modes from 1850 to 1500 cm−1.
Carrier Volume is More Likely to Impact Trifluralin Efficiency than Crop Residue
Authors: Borger Catherine P. D. , Riethmuller Glen P. , Ashworth Michael , Minkey David , Hashem Abul
Published: February 2015

PRE herbicides are generally less effective in conservation farming systems because of high levels of crop residue. However, performance can be improved if the herbicides are applied with a high carrier volume. This research investigated the interaction of carrier volume and row spacing or height of crop residue on the control of rigid ryegrass with trifluralin, at Cunderdin and Wongan Hills Western Australia. To create plots with varying residue row spacing in 2011, wheat was seeded in 2010 using a narrow row spacing (25 or 22 cm at Cunderdin and Wongan Hills), wide spacing (50 or 44 cm), or not planted to wheat. Narrow or wide row spacing or no crop plots had an average residue biomass of 4480, 3560, and 2430 kg ha−1at Cunderdin and 1690, 1910, and 1030 kg ha−1at Wongan Hills. To vary residue height, the wheat was harvested to produce tall, medium, or short crop residue (22, 13, and 5 cm at Cunderdin and 27, 22, and 17 cm at Wongan Hills). Rigid ryegrass seeds were broadcast onto each site in 2011 and trifluralin was sprayed using 50, 75, or 100 L ha−1carrier volume (directly prior to seeding). Increased carrier volume increased spray coverage at both sites (average cover of 9, 15, and 26% at 50, 75, and 100 L ha−1), leading to improved control of rigid ryegrass (68, 75, and 82% control at Cunderdin and 23, 41, and 68% control at Wongan Hills). Reduced crop residue height or increased row spacing led to reduced rigid ryegrass density at Cunderdin but had no impact at Wongan Hills. Therefore, carrier volume has a more consistent impact on the performance of trifluralin than crop residue row spacing or height.
Serious Games for Mobile Devices: the InTouch Project Case Study
Authors: Imbellone Alfredo , Botte Brunella , Medaglia Carlo Maria
Published: February 2015

The paper presents the InTouch project and discusses design principles, implementation and evaluation of serious mobile games for the development of soft skills. 30 serious games for mobile devices were produced to be tested and evaluated during Learning Labs participated by SMEs professionals operating in different business sectors from seven European countries. The games describe situational learning cases related to 10 non routine skills, and use different types of interaction. Evaluation results are described, showing an overall positive impact deriving from the choice of the serious game approach and the use of mobile devices. When analyzing the role of different dimensions of the games, the most relevant elements influencing players’ satisfaction and their willingness to play again were found to be the levels of fun and difficulty associated with the games, the interest, the sense of reality and the adequacy of duration of the games.
State-of-the-art in Business Games
Authors: Petridis Panagiotis , Hadjicosta Kyriaki , Shi Guang Victor , Dunwell Ian , Baines Tim , Bigdeli Ali , Bustinza Oscar F. , Uren Victoria
Published: February 2015

The use of digital games and gamification has demonstrated potential to improve many aspects of how businesses provide training to staff, and communicate with consumers. However, there is still a need for better understanding of how the adoption of games and gasification would influence the process of decision-making in organisations across different industry. This article provides a structured review of existing literature on the use of games in the business environment, and seeks to consolidate findings to address research questions regarding their perception, proven efficacy, and identifies key areas for future work. The findings highlight that serious games can have positive and effective impacts in multiple areas of a business, including training, decision-support, and consumer outreach. They also emphasise the challenges and pitfalls of applying serious games and gamification principles within a business context, and discuss the implications of development and evaluation methodologies on the success of a game-based solution.
Game elements improve performance in a working memory training task
Authors: Ninaus Manuel , Pereira Gonçalo , Stefitz René , Prada Rui , Paiva Ana , Neuper Christa , Wood Guilherme
Published: February 2015

The utilization of game elements in a non-game context is currently used in a vast range of different domains. However, research on game elements’ effects in cognitive tasks is still sparse. Thus, in this study we implemented three game elements, namely, progress bar, level indicator, and a thematic setting, in a working memory training task. We evaluated the impact of game elements on user performance and perceived state of flow when compared to a conventional version of the task. Participants interacting with game elements showed higher scores in the working memory training task than participants from a control group who completed the working memory training task without the game elements. Moreover, game elements facilitated the individuals’ performance closer to their maximum working memory capacity. Finally, the perceived flow did not differ between the two groups, which indicates that game elements can induce better performance without changing the perception of being “in the zone”, that is without an increase in anxiety or boredom. This empirical study indicates that certain game elements can improve the performance and efficiency in a working memory task by increasing users’ ability and willingness to train at their optimal performance level.
Special Issue on Digital Games for Learning Mathematics
Authors: De Gloria Alessandro
Published: February 2015

Given the huge relevance of mathematics, for both reasoning and applications, it is important to develop more engaging and effective methods that can be used to enhance children’s conceptual understanding of mathematics, develop mathematical thinking processes and improve arithmetical skills. Digital games provide interesting possibilities to support these goals and one can easily find great deal of online games and apps targeted for learning mathematics. This spoecial issue is devoted to present leading-edge research and perspectives in the field.
Variación en grados de latencia en semillas entre colectas de chile piquín ( Capsicum annuum var. glabriusculum )
Authors: Cano-Vázquez Anaid , López-Peralta Ma. Cristina , Zavaleta-Mancera Hilda A. , Cruz-Huerta Nicacio , Ramírez-Ramírez Iván , Gardea-Béjar Alfonso , González-Hernández Víctor A.
Published: February 2015

El chile piquín ( Capsicum annuum var. glabriusculum ) que se consume en México es, en su mayoría, recolectado de plantas silvestres. Esta actividad podría amenazar la diversidad genética de la especie. Idealmente, el chile piquín debería producirse intensivamente para proteger la población silvestre y satisfacer la demanda; sin embargo, la baja germinación de semillas de esta especie de chile ha sido tradicionalmente un problema para su establecimiento a nivel comercial. Las causas de lo anterior son desconocidas. Identificar las causas de la baja germinación y la diversidad entre colectas es, por tanto, de importancia. Se evaluaron 16 diferentes colectas de chile piquín provenientes de siete estados del país y del sur de Estados Unidos. Un estudio morfológico determinó que en las colectas evaluadas no existen diferencias ni barreras morfológicas que impidan la germinación apropiada de las semillas. Una cinética de imbibición determinó que no existen impedimentos físicos para el paso apropiado de agua al interior de las semillas; sin embargo, la germinación de las 16 colectas fue muy variable (0 a 66%), con un promedio de 15%. El pretratamiento de las semillas con la hormona AG3 (5,000 ppm), elevó la tasa promedio de germinación a 59% en 14 de las 16 colectas, mientras que los tratamientos de acondicionamiento con peróxido de hidrógeno y nitrato de potasio solamente mejoraron la germinación de semillas en dos y cuatro colectas, respectivamente. El presente trabajo corrobora que la limitante de germinación en semillas de chile piquín se debe a un fenómeno de latencia fisiológica, la cual puede romperse con aplicación exógena de AG3 a 5,000 ppm, cuyos efectos varían entre colectas.
Using kernels and ecological niche modeling to delineate conservation areas in an endangered patch‐breeding phenotype
Authors: Denoël Mathieu , Ficetola Gentile Francesco
Published: February 2015

Efficient delineation of conservation areas is a great challenge in maintaining biodiversity. Kernel density estimators (KDEs) are a powerful tool in this perspective, but they have not been applied at the population level on patch‐distributed organisms. This would be particularly worthy for species that need broad habitats beyond those where they can be sampled; such as terrestrial lands for pond‐breeding amphibians. The aim of this study was to compare different approaches for the identification of suitable areas for conservation: KDE, ecological niche modelling, and a combination of KDE and niche models. Paedomorphosis was chosen as a model system because this is an important form of intraspecific variation that is present in numerous taxa, but geographically localized within species and globally endangered. 277 ponds were sampled in one of the hotspots of paedomorphosis to determine the abundance and distribution of paedomorphs (i.e., individuals retaining gills at the adult stage) of the palmate newt (Lissotriton helveticus), with emphasis on the connections between the most valuable populations. KDEs gave insights into the surface areas required to balance the maintenance of certain number of connected ponds and the respective number of disjoint areas in which the whole population is divided. The inclusion of barriers in the models helped in accurately designing the limits of the areas to protect. Alone, habitat models were not able to successfully delineate the area to protect, but the integration between terrestrial suitable areas or barriers and KDE allowed an objective identification of areas required for conservation. Overall, the best performance was observed by the KDE integrating ecological barriers, and by the combination between KDE and niche modelling. In a broader perspective, KDEs are thus a pertinent tool in providing quantitative spatial measurements to delineate conservation areas based on patch‐abundance data with a specific focus to connectivity.
Relationships Among Providing Maternal, Child, and Adolescent Health Services; Implementing Various Financial Strategy Responses; and Performance of Local Health Departments
Authors: Issel L. Michele , Olorunsaiye Comfort , Snebold Laura , Handler Arden
Published: February 2015

Objectives. We explored the relationships between local health department (LHD) structure, capacity, and macro-context variables and performance of essential public health services (EPHS).

Methods. In 2012, we assessed a stratified, random sample of 195 LHDs that provided data via an online survey regarding performance of EPHS, the services provided or contracted out, the financial strategies used in response to budgetary pressures, and the extent of collaborations. We performed weighted analyses that included analysis of variance, pairwise correlations by jurisdiction population size, and linear regressions.

Results. On average, LHDs provided approximately 13 (36%) of 35 possible services either directly or by contract. Rather than cut services or externally consolidating, LHDs took steps to generate more revenue and maximize capacity. Higher LHD performance of EPHS was significantly associated with delivering more services, initiating more financial strategies, and engaging in collaboration, after adjusting for the effects of the Affordable Care Act and jurisdiction size.

Conclusions. During changing economic and health care environments, we found that strong structural capacity enhanced local health department EPHS performance for maternal, child, and adolescent health.
Sulfide/Calcium Carbonate Scale Coprecipitation
Authors: Denney Dennis
Published: February 2015

This article, written by Dennis Denney, contains highlights of paper SPE 168182, ’Sulfide Scale Coprecipitation With Calcium Carbonate,’ by C. Okocha and K.S. Sorbie, SPE, Heriot-Watt University, prepared for the 2014 SPE International Symposium and Exhibition on Formation Damage Control, Lafayette, Louisiana, 26-28 February. The paper has not been peer reviewed.

Mixed carbonate-/sulfide-scale problems have been reported when water is produced from carbonate reservoirs. This study presents interactions of lead sulfide and zinc sulfide coprecipitating with calcite. The relationship between bulk precipitation and deposition on a metal surface of the mixed carbonate/sulfide scales was examined when the mixed scales began to nucleate, agglomerate, and grow. The nature of these mixed crystals may indicate that mixed sulfide scales tend to prefer forming in solution rather than adhering to metal surfaces in protected zones. Thus, the mixed sulfide scale may be controlled in one zone but be unprotected in other regions.

Introduction

Carbonate reservoirs contain approximately 60% of the world’s remaining oil and gas reserves. Scale precipitation during oil and gas production is costly. Conventional scales, such as sulfate and carbonate, are well-known and have been researched and reported extensively. Sulfide scales are less studied, and their effect on conventional scales (formation and inhibition) is relatively unknown.

The effects of carbonate/sulfide coprecipitation in bulk solution and on metal surfaces are presented. Sulfide was coprecipitated with barium sulfate (BaSO4), and the effects on formation and inhibition of the BaSO4 crystals were monitored. The relationship between bulk precipitation and surface deposition of the mixed carbonate/ sulfide scales was examined also. Both carbonate- and sulfide-scale problems have been reported when water is produced from carbonate reservoirs, and the use of scale inhibitors to control this problem is relatively common.