bluuebunny/crossref_metadata_2025 huggingface dataset:
Alzheimer's Disease: Presenilin 2-Sparing γ-Secretase Inhibition Is a Tolerable Aβ Peptide-Lowering Strategy
Authors: Borgegård Tomas , Gustavsson Susanne , Nilsson Charlotte , Parpal Santiago , Klintenberg Rebecka , Berg Anna-Lena , Rosqvist Susanne , Serneels Lutgarde , Svensson Samuel , Olsson Fredrik , Jin Shaobo , Yan Hongmei , Wanngren Johanna , Jureus Anders , Ridderstad-Wollberg Anna , Wollberg Patrik , Stockling Kenneth , Karlström Helena , Malmberg Åsa , Lund Johan , Arvidsson Per I. , De Strooper Bart , Lendahl Urban , Lundkvist Johan
Published: November 2012

γ-Secretase inhibition represents a major therapeutic strategy for lowering amyloid β (Aβ) peptide production in Alzheimer's disease (AD). Progress toward clinical use of γ-secretase inhibitors has, however, been hampered due to mechanism-based adverse events, primarily related to impairment of Notch signaling. The γ-secretase inhibitor MRK-560 represents an exception as it is largely tolerablein vivodespite displaying only a small selectivity between Aβ production and Notch signalingin vitro. In exploring the molecular basis for the observed tolerability, we show that MRK-560 displays a strong preference for the presenilin 1 (PS1) over PS2 subclass of γ-secretases and is tolerable in wild-type mice but causes dose-dependent Notch-related side effect in PS2-deficient mice at drug exposure levels resulting in a substantial decrease in brain Aβ levels. This demonstrates that PS2 plays an important role in mediating essential Notch signaling in several peripheral organs during pharmacological inhibition of PS1 and provide preclinicalin vivoproof of concept for PS2-sparing inhibition as a novel, tolerable and efficacious γ-secretase targeting strategy for AD.
Genetic Deletion ofgadd45b, a Regulator of Active DNA Demethylation, Enhances Long-Term Memory and Synaptic Plasticity
Authors: Sultan Faraz A. , Wang Jing , Tront Jennifer , Liebermann Dan A. , Sweatt J. David
Published: November 2012

Dynamic epigenetic mechanisms including histone and DNA modifications regulate animal behavior and memory. While numerous enzymes regulating these mechanisms have been linked to memory formation, the regulation of active DNA demethylation (i.e., cytosine-5 demethylation) has only recently been investigated. New discoveries aim toward the Growth arrest and DNA damage-inducible 45 (Gadd45) family, particularly Gadd45b, in activity-dependent demethylation in the adult CNS. This study found memory-associated expression ofgadd45bin the hippocampus and characterized the behavioral phenotype ofgadd45b−/−mice. Results indicate normal baseline behaviors and initial learning but enhanced persisting memory in mutants in tasks of motor performance, aversive conditioning and spatial navigation. Furthermore, we showed facilitation of hippocampal long-term potentiation in mutants. These results implicate Gadd45b as a learning-induced gene and a regulator of memory formation and are consistent with its potential role in active DNA demethylation in memory.
Distributed Representations of Rule Identity and Rule Order in Human Frontal Cortex and Striatum
Authors: Reverberi Carlo , Görgen Kai , Haynes John-Dylan
Published: November 2012

Humans are able to flexibly devise and implement rules to reach their desired goals. For simple situations, we can use single rules, such as “if traffic light is green then cross the street.” In most cases, however, more complex rule sets are required, involving the integration of multiple layers of control. Although it has been shown that prefrontal cortex is important for rule representation, it has remained unclear how the brain encodes more complex rule sets. Here, we investigate how the brain represents the order in which different parts of a rule set are evaluated. Participants had to follow compound rule sets that involved the concurrent application of two single rules in a specific order, where one of the rules always had to be evaluated first. The rules and their assigned order were independently manipulated. By applying multivariate decoding to fMRI data, we found that the identity of the current rule was encoded in a frontostriatal network involving right ventrolateral prefrontal cortex, right superior frontal gyrus, and dorsal striatum. In contrast, rule order could be decoded in the dorsal striatum and in the right premotor cortex. The nonhomogeneous distribution of information across brain areas was confirmed by follow-up analyses focused on relevant regions of interest. We argue that the brain encodes complex rule sets by “decomposing” them in their constituent features, which are represented in different brain areas, according to the aspect of information to be maintained.
Rac1 Controls Schwann Cell Myelination through cAMP and NF2/merlin
Authors: Guo Li , Moon Chandra , Niehaus Karen , Zheng Yi , Ratner Nancy
Published: November 2012

During peripheral nervous system development, Schwann cells (SCs) surrounding single large axons differentiate into myelinating SCs. Previous studies implicate RhoGTPases in SC myelination, but the mechanisms involved in RhoGTPase regulation of SC myelination are unknown. Here, we show that SC myelination is arrested in Rac1 conditional knock-out (Rac1-CKO) mice. Rac1 knock-out abrogated phosphorylation of the effector p21-activated kinase and decreased NF2/merlin phosphorylation. Mutation of NF2/merlin rescued the myelin deficit in Rac1-CKO micein vivoand the shortened processes in cultured Rac1-CKO SCsin vitro. Mechanistically, cAMP levels and E-cadherin expression were decreased in the absence of Rac1, and both were restored by mutation of NF2/merlin. Reduced cAMP is a cause of the myelin deficiency in Rac1-CKO mice, because elevation of cAMP by rolipram in Rac1-CKO micein vivoallowed myelin formation. Thus, NF2/merlin and cAMP function downstream of Rac1 signaling in SC myelination, and cAMP levels control Rac1-regulated SC myelination.
Fine-Grained Nociceptive Maps in Primary Somatosensory Cortex
Authors: Mancini Flavia , Haggard Patrick , Iannetti Gian Domenico , Longo Matthew R. , Sereno Martin I.
Published: November 2012

Topographic maps of the receptive surface are a fundamental feature of neural organization in many sensory systems. While touch is finely mapped in the cerebral cortex, it remains controversial how precise any cortical nociceptive map may be. Given that nociceptive innervation density is relatively low on distal skin regions such as the digits, one might conclude that the nociceptive system lacks fine representation of these regions. Indeed, only gross spatial organization of nociceptive maps has been reported so far. However, here we reveal the existence of fine-grained somatotopy for nociceptive inputs to the digits in human primary somatosensory cortex (SI). Using painful nociceptive-selective laser stimuli to the hand, and phase-encoded functional magnetic resonance imaging analysis methods, we observed somatotopic maps of the digits in contralateral SI. These nociceptive maps were highly aligned with maps of non-painful tactile stimuli, suggesting comparable cortical representations for, and possible interactions between, mechanoreceptive and nociceptive signals. Our findings may also be valuable for future studies tracking the time course and the spatial pattern of plastic changes in cortical organization involved in chronic pain.
Fife, aDrosophilaPiccolo-RIM Homolog, Promotes Active Zone Organization and Neurotransmitter Release
Authors: Bruckner Joseph J. , Gratz Scott J. , Slind Jessica K. , Geske Richard R. , Cummings Alexander M. , Galindo Samantha E. , Donohue Laura K. , O'Connor-Giles Kate M.
Published: November 2012

Neuronal communication depends on the precisely orchestrated release of neurotransmitter at specialized sites called active zones (AZs). A small number of scaffolding and cytoskeletal proteins comprising the cytomatrix of the active zone (CAZ) are thought to organize the architecture and functional properties of AZs. The majority of CAZ proteins are evolutionarily conserved, underscoring the fundamental similarities in neurotransmission at all synapses. However, core CAZ proteins Piccolo and Bassoon have long been believed exclusive to vertebrates, raising intriguing questions about the conservation of the molecular mechanisms that regulate presynaptic properties. Here, we present the identification of apiccolo-rim-related gene in invertebrates, together with molecular phylogenetic analyses that indicate the encoded proteins may represent Piccolo orthologs. In accordance, we find that theDrosophilahomolog, Fife, is neuronal and localizes to presynaptic AZs. To investigate thein vivofunction of Fife, we generated a deletion of thefifelocus. We find that evoked neurotransmitter release is substantially decreased infifemutants and loss offiferesults in motor deficits. Through morphological analysis offifesynapses, we identify underlying AZ abnormalities including pervasive presynaptic membrane detachments and reduced synaptic vesicle clustering. Our data demonstrate the conservation of a Piccolo-related protein in invertebrates and identify critical roles for Fife in regulating AZ structure and function. These findings suggest the CAZ is more conserved than previously thought, and open the door to a more complete understanding of how CAZ proteins regulate presynaptic structure and function through genetic studies in simpler model systems.
The Early Maturation of Visual Cortical Area MT is Dependent on Input from the Retinorecipient Medial Portion of the Inferior Pulvinar
Authors: Warner Claire E. , Kwan William C. , Bourne James A.
Published: November 2012

The hierarchical development of the primate visual cortex and associated streams remains somewhat of a mystery. While anatomical, physiological, and psychological studies have demonstrated the early maturation of the dorsal “where”/“how” or motion cortical stream, little is known about the circuitry responsible. The influence of the retinogeniculostriate pathway has been investigated, but little attention has been paid to the role of two more recently described disynaptic retinothalamic projections to the middle temporal (MT) area, an early maturing dorsal stream cortical field, and which bypass the primary visual cortex (V1). These pathways are via the koniocellular layers of the lateral geniculate nucleus (LGN) and the medial portion of the inferior pulvinar (PIm). Both have been demonstrated in the adult nonhuman primate, but their influence during the maturation of the visual cortex is unknown. We used a combination of neural tracing and immunohistochemistry to follow the development of LGN and PIm inputs to area MT in the marmoset monkey. Our results revealed that the early maturation of area MT is likely due to the disynaptic retinopulvinar input and not the retinogeniculate input or the direct projection from V1. Furthermore, from soon after birth to adulthood, there was a dynamic shift in the ratio of input from these three structures to area MT, with an increasing dominance of the direct V1 afference.
Chemosensory Convergence on Primary Olfactory Cortex
Authors: Maier Joost X. , Wachowiak Matt , Katz Donald B.
Published: November 2012

Food perception and preference formation relies on the ability to combine information from both the taste and olfactory systems. Accordingly, psychophysical investigations in humans and behavioral work in animals has shown that the taste system plays an integral role in odor processing. However, the neural basis for the influence of taste (gustation) on odor (olfaction) remains essentially unknown. Here we tested the hypothesis that gustatory influence on olfactory processing occurs at the level of primary olfactory cortex. We recorded activity from single neurons in posterior olfactory (piriform) cortex (pPC) of awake rats while presenting basic taste solutions directly to the tongue. A significant portion of pPC neurons proved to respond selectively to taste stimuli. These taste responses were significantly reduced by blockade of the gustatory epithelium, were unaffected by blockade of the olfactory epithelium, and were independent of respiration behavior. In contrast, responses to olfactory stimuli, recorded from the same area, were reduced by nasal epithelial deciliation and phase-locked to the respiration cycle. These results identify pPC as a likely site for gustatory influences on olfactory processing, which play an important role in food perception and preference formation.
Prioritized Maps of Space in Human Frontoparietal Cortex
Authors: Jerde Trenton A. , Merriam Elisha P. , Riggall Adam C. , Hedges James H. , Curtis Clayton E.
Published: November 2012

Priority maps are theorized to be composed of large populations of neurons organized topographically into a map of gaze-centered space whose activity spatially tags salient and behaviorally relevant information. Here, we identified four priority map candidates along human posterior intraparietal sulcus (IPS0–IPS3) and two along the precentral sulcus (PCS) that contained reliable retinotopically organized maps of contralateral visual space. Persistent activity increased from posterior-to-anterior IPS areas and from inferior-to-superior PCS areas during the maintenance of a working memory representation, the maintenance of covert attention, and the maintenance of a saccade plan. Moreover, decoders trained to predict the locations on one task (e.g., working memory) cross-predicted the locations on other tasks (e.g., attention) in superior PCS and IPS2, suggesting that these patterns of maintenance activity may be interchangeable across the tasks. Such properties make these two areas in frontal and parietal cortex viable priority map candidates.
Numb is Required for the Production of Terminal Asymmetric Cell Divisions in the Developing Mouse Retina
Authors: Kechad Amel , Jolicoeur Christine , Tufford Adele , Mattar Pierre , Chow Renee W.Y. , Harris William A. , Cayouette Michel
Published: November 2012

In the developing nervous system, cell diversification depends on the ability of neural progenitor cells to divide asymmetrically to generate daughter cells that acquire different identities. While much work has recently focused on the mechanisms controlling self-renewing asymmetric divisions producing a differentiating daughter and a progenitor, little is known about mechanisms regulating how distinct differentiating cell types are produced at terminal divisions. Here we study the role of the endocytic adaptor protein Numb in the developing mouse retina. Using clonalnumbinactivation in retinal progenitor cells (RPCs), we show that Numb is required for normal cell-cycle progression at early stages, but is dispensable for the production of self-renewing asymmetric cell divisions. At late stages, however, Numb is no longer required for cell-cycle progression, but is critical for the production of terminal asymmetric cell divisions. In the absence of Numb, asymmetric terminal divisions that generate a photoreceptor and a non-photoreceptor cell are decreased in favor of symmetric terminal divisions generating two photoreceptors. Using live imaging in retinal explants, we show that a Numb fusion protein is asymmetrically inherited by the daughter cells of some late RPC divisions. Together with our finding that Numb antagonizes Notch signaling in late-stage RPCs, and that blocking Notch signaling in late RPCs almost completely abolishes the generation of terminal asymmetric divisions, these results suggest a model in which asymmetric inheritance of Numb in sister cells of terminal divisions might create unequal Notch activity, which in turn drives the production of terminal asymmetric divisions.
The Niño Jesús Doctor
Authors: Hughes Jennifer Scheper
Published: November 2012

The last two decades have seen an accelerated production of novel devotions at the margins of the Catholic Church in Mexico. Celebration of Santo Niño Jesús Doctor, the infant Jesus dressed as a medical doctor, is one of the fastest-growing new religious expressions in contemporary Mexico. This paper takes this particularly productive moment as an opportunity to theorize novelty and innovation in Mexican religion. In spite of the increase in non-Catholic religious alternatives, including most importantly a range of novel Protestant expressions, I suggest the possibility that at the beginning of the twenty-first century Roman Catholicism is the primary field of religious innovation in Mexico, and that it frequently has been an important locus of innovation since its arrival in the New World. An analysis of devotion to this new manifestation of the infant Jesus reveals the cultural mechanisms that allow for and sustain religious innovation in Mexico.
Adsorption of influenza A and B viruses on detonation nanodiamonds materials
Authors: Ivanova Marina V. , Burtseva Elena I. , Ivanova Valeria T. , Trushakova Svetlana V. , Isaeva Elena I. , Shevchenko Elena S. , Isakova Aleksandra A. , Manykin Anatoly A. , Spitsyn Boris V.
Published: November 2012

This paper presents the data on sorption efficiency of nanodiamonds, detonation soot and its complexes with polyaniline for nano size biological objects: fragments of cDNA and epidemic influenza viruses, including A(H1N1, H3N2) and B strains, isolated in 1999-2010, pandemic strain A(H1N1)pdm09, influenza avian A(H5N2) viruses and reassortants A(H5N2) and A(H5N1). As the result of the sorption on detonation nanodiamonds (DND), detonation soot and their complexes with polyaniline, hemagglutination (HA) titers of virus solutions decreased by ≤ 4000 times for concentrated viruses, suspended in saline and by ≤8 times for allantoic viruses. The detonation soot was approximately 2.5 times more effective than DND. Detonation nanodiamond materials proved to be efficient sorbents for cDNA fragments of >190 bp size. No desorption of viruses from nanodiamonds and soot into saline was revealed (observation time 48 h). DND and soot at concentrations ≤ 1 mg/ml were not toxic for MDCK cells. A moderate increase of monocytes was registrated in blue rats after intra-abdominal immunization with DND+ virus complexes.
Nanodiamond-based Nanolubricants: polyester oil based formulations
Authors: Ivanov M. , Ivanov D. , Pavlyshko S.V. , Koscheev A. , Shenderova Olga A.
Published: November 2012

In the current work tribological properties of different compositions of lubricant additives based on detonation nanodiamond (DND) particles are reported. As compared to the previous findings using polyalphaolefin oil as a base oil for the additives, it is demonstrated that polymer esters are also a valuable base oil for the additive preparation. It is also demonstrated that synergistic compositions of DND with organic molybdenum provide significant improvement of the polyalphaolephin and mineral oils lubricating properties. Treatment of of DND with fluorine containing gases is an additional possibility toward reduced friction and wear of the DND-based nanolubricants.
Development of Zinc Phosphide as an Absorber Using Chemical Reflux Technique.
Authors: Adusumilli Siva P , Vasekar Parag , VanHart Daniel , Dhakal Tara , Westgate Charles R. , Desu Seshu
Published: November 2012

Recent trend in thin film solar cells is to use earth abundant materials such as zinc and iron. Zinc phosphide (Zn3P2) has been has been explored as a choice for solar cell absorber and is currently reviving attention. Zinc phosphide is synthesized from earth-abundant constituents. We have already optimized zinc phosphide phase both in nanocrystalline and bulk thin film form. The purpose of this study is to study growth conditions at different temperatures. In this study, Trioctylphosphine (TOP) is used as a source of phosphorous which reacts with zinc and results in the growth of Zn3P2. The synthesized zinc phosphide phase has been characterized using SEM, EDS, XRD and XPS. We report a simple and repeatable process for synthesis of Zn3P2 phase.
Durability of Materials in a Stress-Response Framework: Acrylic Materials for Photovoltaic Systems
Authors: Murray Myles P. , Bruckman Laura S. , French Roger H.
Published: November 2012

In the development of novel materials for enhanced photovoltaic (PV) performance, it is critical to have quantitative knowledge of the initial performance, as well as the performance of these materials over the required 25-year lifetime of the PV system. Lifetime and degradation science (L&DS) allows for the development of new metrology and metrics, coupled to degradation mechanisms and rates. Induced absorbance to dose (IAD), a new metric being developed for solar radiation durability studies of solar and environmentally exposed photovoltaic materials, is defined as the rate of photodarkening or photobleaching of a material as a function of total absorbed solar radiation dose. In a reliability engineering framework, these quantitative degradation rates can be determined at various solar irradiances making possible real time and accelerated testing. The potential to predict power losses in a photovoltaic system over time caused by the accumulation of this kind of degradation can be calculated for real time applications or extrapolated for accelerated exposure conditions. Three formulations of poly (methyl methacrylate) (PMMA) used for mirror augmented PV systems were analyzed for the changes in IAD after accelerated testing.
Enhancing Materials Research Through Innovative 3D Environments and Interactive Manuals for Data Visualization and Analysis
Authors: Flores Claudia , Matlock Teenie , Dávila Lilian P.
Published: November 2012

Spatial intelligence plays an important role in the success of nanoscience students specific to their visual ability to perceive structures in three dimensions. The NSF-funded IDEAS project makes use of a unique interactive 3D visualization system, based on immersive environment technology, for research and learning in Materials Science and Engineering (MSE) at UC Merced. In order to determine the effectiveness of the immersive system on nanoscience learning, a pilot project was conducted with undergraduate students, which showed the success of immersive systems in the science learning process. Overall, the immersive environment provided complete control in the construction and analysis of carbon-based nanostructure models. Results also showed the 3D visualization system benefited students with low spatial abilities. To facilitate a better understanding of the structure and properties of nanostructures, the IDEAS project has recently been expanded to allow accelerated simulations for materials research. It is important to integrate these new applications into undergraduate level courses in order to strengthen materials science education, recruit and retain future students, and to adapt modern technologies for future materials science educators. The expansion of the IDEAS project relies on the flexibility of this system to serve as a research tool as well as an innovative resource for science education. To adapt the 3D visualization and computing system and help engage students early in engineering research, our research group gathered practical technical documentation geared towards education of science users, based on both Cognitive Science and MSE Education (MSE-Ed) research. The work presented here involves developing educational resources through the design of audio-visual manuals for effective nanoscience learning. The manuals are being created using commercial software to produce interactive electronic books (ebooks). During the planning of the audio-visual manuals, we discovered that it is imperative to provide adequate educational tools as well as efficient guiding principles for the large number of visual, inductive, and active learners in general engineering education. This interdisciplinary project combines fundamental concepts from materials science and cognitive science, particularly project-based learning and active processing, while considering the concepts of overloading, and the unreliability of natural language, among other topics. This investigation will serve society by enhancing materials science research and education, as well as influencing engineering, chemistry, computer science and cognitive science fields, among others.
Plasma graft polymerization of Acrylic Acid and immobilization of Heparin to improve blood compatibility of Polyethylene terephthalate (PET).
Authors: Eftekhari Samin , Mirzadeh Hamid
Published: November 2012

Polymeric materials have been attracted the attention of researchers in various R&D applications. In this research, attempts were made to evaluate the changes in blood compatibility of polyethylene terephthalate (PET) by grafting acrylic acid (AAc) and immobilizing heparin by employing two-step plasma treatment. The PET surface was modified by using a novel method named “two-step plasma treatments” (TSPT). While first plasma is creating active sites for grafting, the second plasma polymerizing pre-adsorbed reactive monomer onto the surface of films. Finally, heparin immobilization was performed in the presence of 1-ethyl-3-(dimethylaminopropyl) carbodiimide. All films were characterized by attenuated total reflection Fourier transformed infrared (ATR-FTIR) spectroscopy and scanning electron microscopy (SEM). The surface hydrophilicity of films was studied by water contact angle test and blood compatibility evaluated by Lactate dehydrogenase method (LDH Test). In vitro studies based on LDH results demonstrared that platelet adhesion onto the modified surfaces with heparin was drastically reduced in comparison with unmodified PET.
Characterization of Li7La3Zr2O12 Thin Films Prepared by Pulsed Laser Deposition
Authors: Tan Jiajia , Tiwari Ashutosh
Published: November 2012

A pulsed laser deposition system was employed to fabricate thin films of Li7La3Zr2O12 solid electrolyte. The deposition process was carried out at room-temperature, resulting in amorphous films. These as-deposited films had a large optical band gap of 5.13 eV, and exhibited a lithium-ion conductivity of 3.35×10-7 S/cm. The films were then annealed, and the effect of annealing on the optical and electrical properties of the films was examined. After annealing at 1000 °C, the films were found to be cubic with a narrower band gap of 3.64 eV. In addition, these annealed films showed an inferior ionic conductivity than the as-deposited ones.
Efficient Upconverting Nanophosphors for Imaging and Photodynamic Therapy
Authors: Yust Brian G. , Kumar Gangadharan Ajith , Mimun Lawrence C. , Sardar Dhiraj K.
Published: November 2012

Erbium-Ytterbium codoped nanophosphor systems are explored for high efficiency upconversion. The NIR to visible upconversion from 1550 nm and 980 nm excitation are of particular interest to us for biomedical applications such as imaging, sensing, and photodynamic therapy. Variations in synthesis method and rare earth concentration are carried out in sodium, potassium, and transition metal based phosphor materials. The spectroscopic properties of the material dry and in biologically appropriate solution are taken. After bioconjugation, these particles will be used in a mouse model to demonstrate that cancer imaging with a near-infrared excitation source is possible.
Rare Earth Based Upconverting Materials for Solar Cell Application
Authors: Pokhrel Madhab , Kumar G. A. , Sardar Dhiraj K.
Published: November 2012

Basic spectroscopic studies of Yb and Er-doped M2O2S (M= Gd, La,Y) phosphor was reported with particular attention to its upconversion properties under 1550 nm excitation. Since the absorption spectra of Co2+overlaps with Er3+(4I13/2→4I15/2) at near infrared (NIR) region, we are proposing the concept of an efficiency enhancement of infrared upconverting phosphors as an energy converting material that could potentially improve the efficiency of Si solar cells in bifacial configuration. Different concentrations of Er3+/Co2+ phosphors were synthesized by solid state flux fusion method. The phosphor powders were well crystallized in a hexagonal shape with an average size 4 mm. Preliminary upconversion analysis of singly Er3+ and doubly Co2+/Er3+ doped Y2O2S under 980 and 1550 nm excitation indicates that the composition has to be optimized to understand the role of Co2+ in the system.
Nanometer Resolution XANES Imaging of Individual PC-RAM Devices
Authors: Richter Jan H. , Krbal Milos , Kolobov Alexander V. , Fons Paul , Wang Xiaomin , Mitrofanov Kirill V. , Simpson Robert E. , Tominaga Junji , Osawa Hitoshi , Suzuki Motohiro
Published: November 2012

We introduce a technique to permit x-ray absorption spectroscopy studies focusing on individual phase-change (Ge2Sb2Te5) memory cells in fully integrated PC-RAM structures. Devices were investigated employing an x-ray nanobeam of only about 300 nm diameter, which could be fully contained within the spatial extent of the active area within a single device cell and enabled us to investigate individual devices without interference from non-switching material surrounding the area of interest. By monitoring the fluorescence signals of tungsten and germanium at a photon energy corresponding to the Ge K-edge absorption edge white line position, we were successful in producing 2D area maps of the active cell region, which clearly show the imbedded tungsten heater element and the switched region of the phase change material. Additionally, position dependent changes in the phase change material could be traced by taking an array of XANES spectra at the Ge K-edge on and in the vicinity of individual devices.
Nonlinear Two-Photon Photocurrent Spectroscopy of CdS Nanosheets
Authors: Kumar Parveen , Wade Aaron , Smith Leigh Morris , Jackson Howard E , Yarrison-Rice Jan M , Choi Young-Jin , Park Jae-Gwan
Published: November 2012

We study the photocurrent from photoexcited charged carriers excited with lasers of energy both above and below the energy gap in CdS nanostructures. We observe non-linear photocurrents in CdS nanosheet devices in the metal-semiconductor-metal configuration with Schottky contacts for sub-band gap excitations. Analysis of two-photon absorption dominated photocurrents reveals a nonlinear coefficient of β = 2 cm/GW for these nanosheet devices, which is comparable to those of bulk CdS. We demonstrate the use of the photocurrent polarization measurements to determine the orientation of atoms in the nanosheet.
Fabrication and antimicrobial effects of silver nanoparticle-poly(N-isopropylacrylamide)-poly(ferrocenylsilane) hydrogel composites
Authors: Sui Xiaofeng , Feng Xueling , Di Luca Andrea , van Blitterswijk Clemens A. , Moroni Lorenzo , Hempenius Mark A. , Vancso G. Julius
Published: November 2012

Novel hydrogels composed of thermo-responsive poly(N-isopropylacrylamide) (PNIPAM) and redox-responsive poly(ferrocenylsilane) (PFS) macromolecules were formed by photopolymerization. PFS chains bearing acrylate side groups were copolymerized with NIPAM and N,N’-methylenebisacrylamide in tetrahydrofuran in a predetermined ratio under ultraviolet light-emitting diode (UV-LED) irradiation at a wavelength of 365 nm, in the presence of a photoinitiator. Crosslinking occurred smoothly, providing homogeneous hydrogels. The equilibrium swelling ratio, rheology and morphology of these hybrid PNIPAM-PFS-based hydrogels were investigated. In-situ fabrication of silver nanoparticles inside the hydrogel network via reduction of silver nitrate by the PFS chains led to hydrogel composites. These composites showed strong antimicrobial activity while maintaining a high biocompatibility with cells.
Phosphors as Sensors for Radiation-Induced Displacement Damage
Authors: Gollub S. L. , Harl R. R. , Weeden-Wright S. L. , Rogers B. R. , Walker D. G.
Published: November 2012

The radiation-induced displacement damage in yttrium borate (YBO3) is studied under X-ray, proton, and alpha irradiation. The photoluminescence (PL) was tested before and after irradiation to determine whether damage occurred and whether it could be queried by examining the PL spectrum. Two different dopants (cerium and europium) were used to activate the phosphor because each provides not only a different spectral signature but also a different mechanism for altering the spectrum between the pre- and post-PL measurements. X-rays, being primarily ionizing radiation, did not show any significant change between the pre and post measurements. We expected protons and alphas to damage the crystal structure, evidence of which could be seen in the change in the spectra before and after irradiation. However, we found no change under alpha exposure (3.6 × 1010 particles/cm2) and a significant change after proton exposure (5 × 1015 particles/cm2). While the material appears to be sensitive to protons, we cannot rule out its sensitivity to alphas because the alpha fluence may be too low to show an effect. This result provides strong indication that our materials are being damaged by particle radiation and that the radiation effects can be quantified.
Matrices of inkjet printed OFETs for the realization of artificial robotic skin
Authors: Loi Alberto , Basiricò Laura , Cosseddu Piero , Lai Stefano , Maiolino Perla , Baglini Emanuele , Denei Simone , Mastrogiovanni Fulvio , Cannata Giorgio , Palomba Chiara , Barbaro Massimo , Bonfiglio Annalisa
Published: November 2012

In this paper we introduce a novel, flexible, system for mechanical deformation detection. The core of the system is based on an Organic Thin Film Transistor (OTFT) which has been assembled on a flexible PET substrate and patterned by means of inkjet printing. OTFT-based mechanical sensors were fabricated employing two different organic semiconductors, namely a small molecule (pentacene) deposited by thermal evaporation and its solution-processable derivative 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS-pentacene) deposited by drop casting. It will be shown that the surface deformation induced by an external mechanical stimulus gives rise in both cases to a marked, reproducible and reversible (within a certain rage of surface deformation) variation of the device output current. Starting from these results, more complex structures such as arrays and matrices of OTFT-based mechanical sensors have been fabricated by means of inkjet printing. Thanks to the flexibility of the introduced structure, we will show that the presented system can be transferred on different surfaces (hard and soft) and employed for a wide range of applications. In particular, we have designed and fabricated a fully functional system based on a matrix of 64 elements that can be employed for detecting mechanical stimuli over larger areas, and will demonstrate that such a system can be successfully employed for tactile transduction in the realization of artificial “robot skins”.
High Speed Surface Modification in Fine-Pitch Package Substrate Manufacturing Process with High Density 60 Hz Nonequilibrium Atmospheric Pressure Plasma
Authors: Iwata Yoshiyuki , Sakamoto Hajime , Takeda Keigo , Hori Masaru
Published: November 2012

This study examined surface modification of solder resist and dry film resist using 60 Hz nonequilibrium atmospheric pressure plasma with O2/N2 mixing gas. Results show that the plasma discharge condition at O2/N2 mixing ratio of 0.1% was the best for surface modification for both materials, and the surfaces were modified sufficiently at 0.45 m/min package substrate transportation speed. From the plasma diagnostics by Vacuum Ultraviolet Absorption Spectroscopy (VUVAS) and Optical Emission Spectroscopy (OES), it was found that the behaviors of the oxygen radical density and NO-γ emission intensity correlate strongly with surface modification. The extremely high oxygen radical density around 4.7 × 1013 cm-3 was obtained at O2/N2 mixing ratio of 0.1%. The electron density was 2.5 × 1015 cm-3 that is two digits more than that of the conventional atmospheric pressure plasma such as Dielectric Barrier Discharge (DBD). The solder resist surface with the plasma treatment was analyzed by X-ray Photoelectron Spectroscopy (XPS), and it was clarified that material surface was modified by hydrophilic group generation owing polymer chain oxidation with oxygen radical.
Role of Enthalpy and Relative Electric Permittivity in Electric Field Induced Nucleation
Authors: Kohary K. , Vazquez-Diosdado J. , Ashwin P. , Wright C. D.
Published: November 2012

Emerging phase-change electrical memory technologies rely on the fast amorphous to crystalline transition, which is usually characterized by an ‘S-shape’ current-voltage curve. We investigate the possibility that electric field induced nucleation may play a dominant role in defining this characteristic electrical switching behavior. We derive quantitative crystallization maps to study the kinetics of the amorphous to crystalline transition in the presence of electric field contribution to the free energy and we investigate how the prediction of the electric field induced nucleation model is affected by material properties such as enthalpy and relative electric permittivity.
Graphene Electromechanical Actuation; Origins, Optimization and Applications
Authors: Rogers Geoffrey W. , Liu Jefferson Z.
Published: November 2012

Graphene-based materials have emerged as exceptional candidates for the development of novel, high performance actuators. Developing such an actuation material requires an in depth knowledge of the physics of operation and, therefrom, how to best optimize its performance. We investigate the electromechanical actuation of pristine monolayer graphene to elucidate the origin of this material’s exceptional electromechanical actuation performance. It is shown that the electrostatic double-layer (EDL) effect is dominant compared to the quantum-mechanical (QM) effect upon charging and electrolyte immersion. Seeking to optimize the QM actuation performance, we preliminarily investigate graphene oxide (GO) as a potential graphene-based actuation material, and find that it exhibits both unique and high performance responses. Having demonstrated huge stresses (~100 GPa) and high strains (~0.4%), graphene-based materials are uniquely positioned to address future industrial actuation challenges.
Modified Polylactide Microfiber Scaffolds for Tissue Engineering
Authors: Vera-Graziano R. , Maciel-Cerda A. , Moreno-Rondon E.V. , Ospina A. , Gomez-Pachon E.Y.
Published: November 2012

Physical properties of porous membranes made of biocompatible and biodegradable polymers have been studied. The membranes are intended to be used as scaffolds for the regeneration of soft and hard tissues. Polylactides, polycaprolactone and some of their derivates are biocompatible as well as biodegradable materials, and are used for the preparation of nanofibers and nanoporous membranes. These membranes also have comparative advantages as cellular scaffolds for tissue engineering since they can be prepared to mimic the morphology of the extra cellular matrix.

Chemical, physical, and biological properties of microfibers and scaffolds of polylactic acid (PLLA), as well as PLLA modified with hydroxyapatite nanoparticles and collagen (Col) are reported in this paper. The microfibers and the scaffolds were prepared by electrospinning. Morphology, diameter and porosity of the scaffold were determined by scanning electron microscopy and an image analyzer program. The microfibers are semicrystalline showing a shell of crystalline nanofibrils. The diameter of the fibers varied between 100 and 800 nm and the porous area of the membrane is between 60 and 80%. The mechanical properties of the microfibers and scaffolds were evaluated by microtensile tests and their behavior was simulated by using an original multiscale asymptotic homogenization model. Cultures of mesenchymal stem cells were used to evaluate their biological activity. Cell adhesion was observed in the modified PLLA scaffolds with grafted hydroxyapatite.
Biocompatibility of Polyurethane Urea Elastomers for Cardiac Tissue Engineering
Authors: Paredes-Puerto A. , Dashti D. , Yeghiazarians Y. , Healy K.E. , Hernández-Sánchez F.
Published: November 2012

Cardiac disease is the main cause of death in men and women in México and the U.S.A. When heart muscle suffers an injury, i.e. cardiac infarction, the tissue dies and is replaced by a fibrotic scar that does not allow for normal organ function. To alleviate scar tissue, the objective of this work was to investigate and synthesize polyurethane ureas from polycaprolactone diol, methylene bis(4-cyclohexilisocyanate), and butanediamine with different hard segment contents, characterize them, and prove their biocompatibility by seeding SCA-1+/CD45-cardiac progenitor cells obtained from mice cardiospheres. Ultimately, this work aims to explore how polyurethane urea elastomers can aid in therapeutic cardiac tissue regeneration.
Photoluminescence transformation of core/shell CdSe/ZnS quantum dots at the conjugation to biomolecules
Authors: Torchynska T. V. , Ballardo Rodríguez I. Ch. , Shcherbyna Ye.
Published: November 2012

The paper presents the results of PL spectrum analysis of CdSe/ZnS QDs covered by PEG polymer with and without bioconjugation to bio-molecules .– the Osteopontin antibodies. Commercial CdSe/ZnS QDs used in the study are characterized by the color emission with the maximum at 640 nm (1.96 eV) at 300K. It is shown that PL spectra of nonconjugated QDs can be presented as a superposition of PL bands related to exciton emission in the CdSe core (1.96 eV) and some high energy PL bands (in the spectral range 2.37 .– 3.00 eV). The comparative study of PL spectrum at high (300K) and low (10K) temperatures has testified that high energy PL bands deal with electronhole emission via interface states at the CdSe/ZnS/polymer interfaces.

It is revealed that the QD bioconjugation to the anti Osteopontin antibody is accompanied by the change dramatically in PL spectra. Main features of PL spectrum transformstions deal with decreasing the PL intensity of interface related PL bands and the rise of intensity of CdSe core related PL bands. The explanation of mentioned effects has been proposed on the base of re-charging of interface related states at the bioconjugation process.
Stress Analysis of Molars Restored with Full Cast Metal Crowns
Authors: Porojan S. , Sandu L. , Topală F. , Babeş V.
Published: November 2012

The incomplete fit of full cast crown restorations remains a critical problem for dentists, leading many researchers to study this problem. Marginal and internal accuracy of fit is valued as one of the most important criteria for the clinical quality and success of complete crowns. The geometry of tooth preparation has been the subject of many debates without clear evidence that one type of tooth preparation or method of fabrication provides consistently superior marginal fit. The objective of this study was to evaluate, by finite element analysis, the influence of different marginal geometries (shoulderless, chamfer, shoulder) on the stress distribution in teeth prepared for cast metal crowns.

A 3D model of a molar was created: intact teeth, unrestored teeth different marginal geometries: shoulderless, with chamfer, with shoulder preparations; the same tooth restored full cast metal crowns. These were exported in Ansys finite element analysis software for structural simulations.

The values of the maximal equivalent stress were higher for the shoulder preparations, but distributed under the preparation line. Regarding the stress distribution for the other two preparation designs, the largest area is present for the chamfer preparation, followed by the shoulderless preparation.

Within the limitations of the present study, the shoulder preparation is the recommended preparation design from biomechanical point of view. It is followed by the shoulderless preparation. Chamfer margins are less favorable only from this point of view. In light of these results, consideration should be given to the designs from prophylactic and biological points of view, with emphasis on conserving tooth structure and preventing preparation trauma.
Auger Recombination of Biexcitons and Charged Excitons in CdSe/CdS core/shell Nanocrystals
Authors: Marceddu Marco , Saba Michele , Quochi Francesco , Lai Adriano , Huang Jing , Talapin Dmitri V. , Mura Andrea , Bongiovanni Giovanni
Published: November 2012

CdSe/CdS colloidal nanocrystals are light-emitting nanoparticles with remarkable optical properties such as suppressed fluorescence blinking and enhanced emission from multiexciton states. These properties have been attributed to the suppression of non-radiative Auger recombination. In this work we employ ultrafast spectroscopy techniques to identify optical signatures of neutral and charged excitonic and multiexcitonic states.
“Design of Poly(ethylene glycol)-Polycaprolactone Diblock Micelles with RGD Targeting Ligands and Embedded Iron Oxide Nanoparticles for Thermally-activated Release”
Authors: Brazel Christopher S. , Bennett James B. , Glover Amanda L. , Nikles Jacqueline A. , Everts Maaike , Glasgow Joel N. , Nikles David E.
Published: November 2012

A thermally-activated micelle consisting of a crystallizable poly(caprolactone), PCL, core and a poly(ethylene glycol), PEG, corona was developed to contain magnetic nanoparticles and anti-cancer agent doxorubicin as well as display a targeting RGD peptide. This system has the potential to target cancer cells, deliver combination hyperthermia and chemotherapy, and offer magnetic resonance imaging contrast. The micelles self-assemble in aqueous solutions and form a crystalline core with a melting transition ranging from 40 to 50 °C, depending on the length of the PCL blocks, with dynamic light scattering showing micelle sizes typically ranging from 20 to 100 nm, depending on block lengths and added drug or nanoparticles. The micelles become unstable as they are heated above their melting point, creating a thermally-activated drug release mechanism. By adding magnetite (Fe3O4) nanoparticles into the PCL core, the micelles can be heated using an externally applied AC magnetic field to induce hyperthermia in combination with the thermally-activated drug release. The polymers and magnetic nanoparticles (MNPs) were synthesized and characterized in our laboratories. The melting transitions of the PCL micelle cores were investigated using microcalorimetry. The heating of nanoparticles and magnetomicelles was conducted using a custom-built hyperthermia coil capable of generating fields of several hundred Oersteds at frequencies ranging from 50 to 450 kHz. Heating of MNPs was maximized at high field intensities. RGD peptides were attached to the PEG corona using maleimide chemistry, and the ability of the RGD-derivatized micelles to target integrin-expressing cells was investigated using fluorescent dye PKH26 to identify the localization of micelles in cultured human kidney (293) cells in vitro. The crystallizable (and meltable) cores in these micelles were designed to overcome drug leakage common in liposome systems and release the drug on demand after a period of time for localization to integrin receptors.
Composite nanosilver structures suitable for plasmonic biosensors
Authors: Sotiriou Georgios A. , Blattmann Christoph O. , Pratsinis Sotiris E.
Published: November 2012

Silver (Ag) nanoparticles dispersed in an amorphous silica (SiO2) matrix or coated by a SiO2 layer were synthesized by flame spray pyrolysis (FSP). The coated nanoparticles were produced by using a modified enclosed FSP setup, in which the SiO2 precursor was injected through a ring above the FSP nozzle at various burner-ring-distances (BRDs), after the core Ag nanoparticles had been formed. The produced nanoparticles were characterized by XRD, BET, TEM and UV/vis analysis. The Ag particle size was possible to be controlled by tuning the FSP parameters. For the SiO2 coated nanoparticles, larger Ag core sizes were obtained for higher BRDs. All the produced nanoparticles exhibited the characteristic plasmon resonance frequency of Ag nanoparticles.