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1

The dawning era of polymer therapeutics  

Microsoft Academic Search

As we enter the twenty-first century, research at the interface of polymer chemistry and the biomedical sciences has given rise to the first nano-sized (5–100 nm) polymer-based pharmaceuticals, the 'polymer therapeutics'. Polymer therapeutics include rationally designed macromolecular drugs, polymer–drug and polymer–protein conjugates, polymeric micelles containing covalently bound drug, and polyplexes for DNA delivery. The successful clinical application of polymer–protein conjugates,

Ruth Duncan

2003-01-01

2

Nitinol-reinforced shape-memory polymers  

E-print Network

Reinforced shape-memory polymers have been developed from an acrylate based thermoset shape-memory polymer and nitinol wires. A rectangular shape-memory polymer measuring approximately 1 by 2 by 0.1 inches has a ten fold ...

Di Leo, Claudio V

2010-01-01

3

Porous Shape Memory Polymers  

PubMed Central

Porous shape memory polymers (SMPs) include foams, scaffolds, meshes, and other polymeric substrates that possess porous three-dimensional macrostructures. Porous SMPs exhibit active structural and volumetric transformations and have driven investigations in fields ranging from biomedical engineering to aerospace engineering to the clothing industry. The present review article examines recent developments in porous SMPs, with focus given to structural and chemical classification, methods of characterization, and applications. We conclude that the current body of literature presents porous SMPs as highly interesting smart materials with potential for industrial use. PMID:23646038

Hearon, Keith; Singhal, Pooja; Horn, John; Small, Ward; Olsovsky, Cory; Maitland, Kristen C.; Wilson, Thomas S.; Maitland, Duncan J.

2013-01-01

4

Shape-memory polymers for microelectromechanical systems  

Microsoft Academic Search

This paper investigates the use of shape-memory polymer thin films in microelectromechanical systems (MEMS). shape-memory polymers possess the capacity to recover large-strain deformations by the application of heat and are candidates for small-scale transduction. The key advantages of shape-memory polymers are their low material\\/fabrication cost coupled with their simplicity of integration\\/operation. In the present study, shape-memory polymers are spin coated

Ken Gall; Paul Kreiner; David Turner; Michael Hulse

2004-01-01

5

Memory as a new therapeutic target  

PubMed Central

This review aims to demonstrate how an understanding of the brain mechanisms involved in memory provides a basis for; (i) reconceptualizing some mental disorders; (ii) refining existing therapeutic tools; and (iii) designing new ones for targeting processes that maintain these disorders. First, some of the stages which a memory undergoes are defined, and the clinical relevance of an understanding of memory processing by the brain is discussed. This is followed by a brief review of some of the clinical studies that have targeted memory processes. Finally, some new insights provided by the field of neuroscience with implications for conceptualizing mental disorders are presented. PMID:24459414

Nader, Karim; Hardt, Oliver; Lanius, Ruth

2013-01-01

6

Shape-Memory Polymer Composites  

NASA Astrophysics Data System (ADS)

The development of shape-memory polymer composites (SMPCs) enables high recovery stress levels as well as novel functions such as electrical conductivity, magnetism, and biofunctionality. In this review chapter the substantial enhancement in mechanical properties of shape-memory polymers (SMPs) by incorporating small amounts of stiff fillers will be highlighted exemplarily for clay and polyhedral oligomeric silsesquioxanes (POSS). Three different functions resulting from adding functional fillers to SMP-matrices will be introduced and discussed: magnetic SMPCs with different types of magnetic nanoparticles, conductive SMPCs based on carbon nanotubes (CNTs), carbon black (CB), short carbon fiber (SCF), and biofunctional SMPCs containing hydroxyapatite (HA). Indirect induction of the shape-memory effect (SME) was realized for magnetic and conductive SMPCs either by exposure to an alternating magnetic field or by application of electrical current. Major challenges in design and fundamental understanding of polymer composites are the complexity of the composite structure, and the relationship between structural parameters and properties/functions, which is essential for tailoring SMPCs for specific applications. Therefore the novel functions and enhanced properties of SMPCs will be described considering the micro-/nanostructural parameters, such as dimension, shape, distribution, volume fraction, and alignment of fillers as well as interfacial interaction between the polymer matrix and dispersed fillers. Finally, an outlook is given describing the future challenges of this exciting research field as well as potential applications including automotive, aerospace, sensors, and biomedical applications.

Madbouly, Samy A.; Lendlein, Andreas

7

Shape memory alloy/shape memory polymer tools  

DOEpatents

Micro-electromechanical tools for minimally invasive techniques including microsurgery. These tools utilize composite shape memory alloy (SMA), shape memory polymer (SMP) and combinations of SMA and SMP to produce catheter distal tips, actuators, etc., which are bistable. Applications for these structures include: 1) a method for reversible fine positioning of a catheter tip, 2) a method for reversible fine positioning of tools or therapeutic catheters by a guide catheter, 3) a method for bending articulation through the body's vasculature, 4) methods for controlled stent delivery, deployment, and repositioning, and 5) catheters with variable modulus, with vibration mode, with inchworm capability, and with articulated tips. These actuators and catheter tips are bistable and are opportune for in vivo usage because the materials are biocompatible and convenient for intravascular use as well as other minimal by invasive techniques.

Seward, Kirk P.; Krulevitch, Peter A.

2005-03-29

8

Temperature-memory polymer actuators  

PubMed Central

Reading out the temperature-memory of polymers, which is their ability to remember the temperature where they were deformed recently, is thus far unavoidably linked to erasing this memory effect. Here temperature-memory polymer actuators (TMPAs) based on cross-linked copolymer networks exhibiting a broad melting temperature range (?Tm) are presented, which are capable of a long-term temperature-memory enabling more than 250 cyclic thermally controlled actuations with almost constant performance. The characteristic actuation temperatures Tacts of TMPAs can be adjusted by a purely physical process, guiding a directed crystallization in a temperature range of up to 40 °C by variation of the parameter Tsep in a nearly linear correlation. The temperature Tsep divides ?Tm into an upper Tm range (T > Tsep) forming a reshapeable actuation geometry that determines the skeleton and a lower Tm range (T < Tsep) that enables the temperature-controlled bidirectional actuation by crystallization-induced elongation and melting-induced contraction. The macroscopic bidirectional shape changes in TMPAs could be correlated with changes in the nanostructure of the crystallizable domains as a result of in situ X-ray investigations. Potential applications of TMPAs include heat engines with adjustable rotation rate and active building facades with self-regulating sun protectors. PMID:23836673

Behl, Marc; Kratz, Karl; Noechel, Ulrich; Sauter, Tilman; Lendlein, Andreas

2013-01-01

9

Post polymerization cure shape memory polymers  

DOEpatents

This invention relates to chemical polymer compositions, methods of synthesis, and fabrication methods for devices regarding polymers capable of displaying shape memory behavior (SMPs) and which can first be polymerized to a linear or branched polymeric structure, having thermoplastic properties, subsequently processed into a device through processes typical of polymer melts, solutions, and dispersions and then crossed linked to a shape memory thermoset polymer retaining the processed shape.

Wilson, Thomas S; Hearon, Michael Keith; Bearinger, Jane P

2014-11-11

10

Shape memory polymer actuator and catheter  

DOEpatents

An actuator system is provided for acting upon a material in a vessel. The system includes an optical fiber and a shape memory polymer material operatively connected to the optical fiber. The shape memory polymer material is adapted to move from a first shape for moving through said vessel to a second shape where it can act upon said material.

Maitland, Duncan J. (Pleasant Hill, CA); Lee, Abraham P. (Walnut Creek, CA); Schumann, Daniel L. (Concord, CA); Matthews, Dennis L. (Moss Beach, CA); Decker, Derek E. (Byron, CA); Jungreis, Charles A. (Pittsburgh, PA)

2007-11-06

11

Shape memory polymer actuator and catheter  

DOEpatents

An actuator system is provided for acting upon a material in a vessel. The system includes an optical fiber and a shape memory polymer material operatively connected to the optical fiber. The shape memory polymer material is adapted to move from a first shape for moving through said vessel to a second shape where it can act upon said material.

Maitland, Duncan J.; Lee, Abraham P.; Schumann, Daniel L.; Matthews, Dennis L.; Decker, Derek E.; Jungreis, Charles A.

2004-05-25

12

Release mechanism utilizing shape memory polymer material  

DOEpatents

Microfabricated therapeutic actuators are fabricated using a shape memory polymer (SMP), a polyurethane-based material that undergoes a phase transformation at a specified temperature (Tg). At a temperature above temperature Tg material is soft and can be easily reshaped into another configuration. As the temperature is lowered below temperature Tg the new shape is fixed and locked in as long as the material stays below temperature Tg. Upon reheating the material to a temperature above Tg, the material will return to its original shape. By the use of such SMP material, SMP microtubing can be used as a release actuator for the delivery of embolic coils through catheters into aneurysms, for example. The microtubing can be manufactured in various sizes and the phase change temperature Tg is determinate for an intended temperature target and intended use.

Lee, Abraham P. (Walnut Creek, CA); Northrup, M. Allen (Berkeley, CA); Ciarlo, Dino R. (Livermore, CA); Krulevitch, Peter A. (Pleasanton, CA); Benett, William J. (Livermore, CA)

2000-01-01

13

Partial shape memory effect of polymers  

NASA Astrophysics Data System (ADS)

A blend of PLA (80%) and PBS (20%) has been prepared first by extrusion, then by injection molding. Tensile, stress-relaxation and recovery tests have been performed on the samples at 70°C and 75°C. The results indicated that the blend can regain only 24% of its initial shape. This partial shape memory effect has been improved by successive cycles of shape memory tests. After a fourth cycle, the blend is able to regain 82% of its shape. These original results indicated that a polymer without (or with partial) shape memory effect may be transformed to a shape memory polymer without any chemical modification.

Tcharkhtchi, A.; Elhirisia, S. Abdallah; Ebrahimi, K. M.; Fitoussi, J.; Shirinbayan, M.; Farzaneh, S.

2014-05-01

14

Thermomechanical modeling of a shape memory polymer  

E-print Network

The aim of this work is to demonstrate a Helmholtz potential based approach for the development of the constitutive equations for a shape memory polymer undergoing a thermomechanical cycle. The approach is motivated by the use of a simple spring...

Ghosh, Pritha B.

2009-05-15

15

Medical applications of shape memory polymers  

NASA Technical Reports Server (NTRS)

Shape memory polymers are described here and major advantages in some applications are identified over other medical materials such as shape memory alloys (SMA). A number of medical applications are anticipated for shape memory polymers. Some simple applications are already utilized in medical world, others are in examination process. Lately, several important applications are being considered for CHEM foams for self-deployable vascular and coronary devices. One of these potential applications, the endovascular treatment of aneurysm was experimentally investigated with encouraging results and is described in this paper as well.

Sokolowski, Witold M.

2005-01-01

16

Temperature and electrical memory of polymer fibers  

SciTech Connect

We report in this work studies of the shape memory behavior of polymer fibers loaded with carbon nanotubes or graphene flakes. These materials exhibit enhanced shape memory properties with the generation of a giant stress upon shape recovery. In addition, they exhibit a surprising temperature memory with a peak of generated stress at a temperature nearly equal to the temperature of programming. This temperature memory is ascribed to the presence of dynamical heterogeneities and to the intrinsic broadness of the glass transition. We present recent experiments related to observables other than mechanical properties. In particular nanocomposite fibers exhibit variations of electrical conductivity with an accurate memory. Indeed, the rate of conductivity variations during temperature changes reaches a well defined maximum at a temperature equal to the temperature of programming. Such materials are promising for future actuators that couple dimensional changes with sensing electronic functionalities.

Yuan, Jinkai; Zakri, Cécile; Grillard, Fabienne; Neri, Wilfrid; Poulin, Philippe [Centre de Recherche Paul Pascal - CNRS, University of Bordeaux, Avenue Schweitzer, 33600 Pessac (France)

2014-05-15

17

Thermomechanical properties of polyurethane shape memory polymers  

NASA Astrophysics Data System (ADS)

Segmented polyurethanes containing soft segments with low molecular weight show shape-memorizing properties. In these materials the advantages of polyurethanes are combined with the features of smart material technology. Shape memory polymers can repeatedly transform their shape and hardness. The dependence of thermal and mechanical properties of shape memory polyurethanes on temperature were investigated experimentally by means of differential scanning calorimetry and static mechanical testing. The results show that as the thermal cycles progress, the residual strain increases and the recovery strain decreases even if these changes saturate after a suitable number of thermomechanical cycles. This kind of behavior suggest a possible training procedure in order to have a reproducible mechanical behavior when the shape memory polymer is introduced into an operating device. Some possible applications in the textile machinery are also shown.

Airoldi, Graziella; Corsi, Andrea

1998-10-01

18

Memory operation mechanism of fullerene-containing polymer memory  

NASA Astrophysics Data System (ADS)

The memory operation mechanism in fullerene-containing nanocomposite gate insulators was investigated while varying the kind of fullerene in a polymer gate insulator. It was cleared what kind of traps and which positions in the nanocomposite the injected electrons or holes are stored in. The reason for the difference in the easiness of programming was clarified taking the role of the charging energy of an injected electron into account. The dependence of the carrier dynamics on the kind of fullerene molecule was investigated. A nonuniform distribution of injected carriers occurred after application of a large magnitude programming voltage due to the width distribution of the polystyrene barrier between adjacent fullerene molecules. Through the investigations, we demonstrated a nanocomposite gate with fullerene molecules having excellent retention characteristics and a programming capability. This will lead to the realization of practical organic memories with fullerene-containing polymer nanocomposites.

Nakajima, Anri; Fujii, Daiki

2015-03-01

19

Macroscopic behaviour of magnetic shape-memory polycrystals and polymer  

E-print Network

polycrystals and composites of single-crystal magnetic shape-memory particles embedded in a soft polymer matrix, Germany Single crystals of magnetic shape-memory materials display a large spontaneous deformation for shape mem- ory devices is to embed small single-crystal shape- memory particles in a soft polymer matrix

Rumpf, Martin

20

Polyalkene-based shape-memory polymers  

NASA Astrophysics Data System (ADS)

A series of polymers showing shape memory properties were developed based on polyalkenes derived from cyclooctene and related structures. These polymeric systems were synthesized via ring-opening metathesis polymerization (ROMP) using a well-defined ruthenium catalyst (Grubbs' type) by varying reaction conditions and proportions. Control over molecular weight was achieved by the inclusion of a chain transfer agent (CTA) and its influence on the behaviour of the obtained materials was evaluated. In order to provide them with shape memory behaviour the compounds were subjected to suitable chemical-thermal treatments and its characterization was accomplished by means of several techniques: differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), etc. Thus polymers developed herein could become a different alternative to the most studied and commercially available polyurethane based systems.

Alonso, J.; Cuevas, J. M.; Dios, J. R.; Vilas, J. L.; León, L. M.

2007-07-01

21

Thermoviscoelastic shape memory behavior for epoxy-shape memory polymer  

NASA Astrophysics Data System (ADS)

There are various applications for shape memory polymer (SMP) in the smart materials and structures field due to its large recoverable strain and controllable driving method. The mechanical shape memory deformation mechanism is so obscure that many samples and test schemes have to be tried in order to verify a final design proposal for a smart structure system. This paper proposes a simple and very useful method to unambiguously analyze the thermoviscoelastic shape memory behavior of SMP smart structures. First, experiments under different temperature and loading conditions are performed to characterize the large deformation and thermoviscoelastic behavior of epoxy-SMP. Then, a rheological constitutive model, which is composed of a revised standard linear solid (SLS) element and a thermal expansion element, is proposed for epoxy-SMP. The thermomechanical coupling effect and nonlinear viscous flowing rules are considered in the model. Then, the model is used to predict the measured rubbery and time-dependent response of the material, and different thermomechanical loading histories are adopted to verify the shape memory behavior of the model. The results of the calculation agree with experiments satisfactorily. The proposed shape memory model is practical for the design of SMP smart structures.

Chen, Jianguo; Liu, Liwu; Liu, Yanju; Leng, Jinsong

2014-05-01

22

Electrically conducting shape memory polymer composites for electroactive actuator  

NASA Astrophysics Data System (ADS)

We have tried to apply electroactive shape memory polymer to smart actuator. Electroactive shape memory can be achieved by applying an electric field to shape memory polymer without any thermal heating as conventional shape memory polymers. For it, electrically conducting shape memory composites were prepared by incorporating carbon nanotube into polymer matrix. A segmented polyurethane block copolymer composed of 4,4'-methylene bis (phenylisocyanate), polycaprolactone, and 1,4-butanediol was synthesized to be used as shape memory polymer, and carbon nanotube was used after surface-modification by an acid. It was found that nanotube-reinforced composites could show high electrical conductivity with increased modulus at only several weight percentages of nanotube, and electroactive shape recovery effect more than 80% could be obtained. Consequently, electric field-stimulated shape memory could be demonstrated through combined composites of polyurethane and nanotube.

Jung, Yong Chae; Goo, Nam Seo; Cho, Jae Whan

2004-07-01

23

Thermomechanical Characterization and Modeling of Shape Memory Polymers  

E-print Network

This work focuses on the thermomechanical characterization and constitutive model calibration of shape memory polymers (SMPs). These polymers have the ability to recover seemingly permanent large deformations under the appropriate thermomechanical...

Volk, Brent L.

2010-01-16

24

Thermomechanical indentation of shape memory polymers.  

SciTech Connect

Shape memory polymers (SMPs) are receiving increasing attention because of their ability to store a temporary shape for a prescribed period of time, and then when subjected to an environmental stimulus, recover an original programmed shape. They are attractive candidates for a wide range of applications in microsystems, biomedical devices, deployable aerospace structures, and morphing structures. In this paper we investigate the thermomechanical behavior of shape memory polymers due to instrumented indentation, a loading/deformation scenario that represents complex multiaxial deformation. The SMP sample is indented using a spherical indenter at a temperature T{sub 1} (>T{sub g}). The temperature is then lowered to T{sub 2} (memory is then activated by increasing the temperature to T{sub 1} (>T{sub g}) during free recovery the indentation impression disappears and the surface of the SMP recovers to its original profile. A recently-developed three-dimensional finite deformation constitutive model for the thermomechanical behavior of SMPs is then used with the finite element method to simulate this process. Measurement and simulation results are compared for cases of free and constrained recovery and good agreement is obtained, suggesting the appropriateness of the simulation approach for complex multiaxial loading/deformations that are likely to occur in applications.

Long, Kevin N. (University of Colorado, Boulder, CO); Nguyen, Thao D.; Castro, Francisco (University of Colorado, Boulder, CO); Qi, H. Jerry (University of Colorado, Boulder, CO); Dunn, Martin L. (University of Colorado, Boulder, CO); Shandas, Robin (University of Colorado, Boulder, CO)

2007-04-01

25

Polymer therapeutics: Top 10 selling pharmaceuticals - what next?  

PubMed

At the time of the first issue of the Journal of Controlled Release (JCR), polymeric drugs, polymer-drug and protein conjugates and block copolymer micelles carrying bound drugs, i.e. polymer therapeutics, were still regarded as scientific curiosities with little or no prospect of generating practical to use medicines. How this perception has changed. Many major Pharma now have R&D programmes in this area and in 2013 two polymer therapeutics, Copaxone and Neulasta, are featured in the Top 10 US pharmaceutical sales list. Although there are a growing number of marketed products (e.g. PEGylated proteins, a PEG-aptamer and oral polymeric sequestrants), and the first follow-on (generic products) are emerging, the first polymer-drug conjugates and block copolymer micelle products (as covalent conjugates) have yet to enter routine clinical use. Industrial familiarity and recent advances in the underpinning scientific disciplines will no doubt accelerate the transfer of polymer therapeutics into clinically useful medicines and imaging agents. This short personal perspective reflects on the current status of polymer therapeutics and the future opportunities to improve their successful translation. It adds to recent and historical reviews that comprehensively document the evolution of the field since JCR was born. PMID:24818766

Duncan, Ruth

2014-09-28

26

Poly(2-oxazoline)s as Polymer Therapeutics  

PubMed Central

Poly(2-oxazoline)s (POx) are currently discussed as an upcoming platform for biomaterials design and especially for polymer therapeutics. POx meets several requirements needed for the development of next-generation polymer therapeutics such as biocompatibility, high modulation of solubility, variation of size, architecture as well as chemical functionality. Although in the early 1990s first and promising POx-based systems were presented but the field lay dormant for almost two decades. Only very recently, POx based polymer therapeutics came back into the focus of very intensive research. In this review, we give an overview on the chemistry and physicochemical properties of POx and summarize the research of POx-protein conjugates, POx-drug conjugates, POx-based polyplexes and POx micelles for drug delivery. PMID:22865555

Luxenhofer, Robert; Han, Yingchao; Schulz, Anita; Tong, Jing; He, Zhijian; Kabanov, Alexander V.; Jordan, Rainer

2013-01-01

27

Methods of Making and Using Shape Memory Polymer Composite Patches  

NASA Technical Reports Server (NTRS)

A method of repairing a composite component having a damaged area including: laying a composite patch over the damaged area: activating the shape memory polymer resin to easily and quickly mold said patch to said damaged area; deactivating said shape memory polymer so that said composite patch retains the molded shape; and bonding said composite patch to said damaged part.

Hood, Patrick J.

2011-01-01

28

Modeling and simulation of magnetic shape-memory polymer composites  

E-print Network

Composites of small magnetic-shape-memory (MSM) particles em- bedded in a polymer matrix have been proposed magnetic field. For single crystals one can achieve 1 #12;strains of order of magnitude 10% [41, 39, 27, 38Modeling and simulation of magnetic shape-memory polymer composites September 6, 2006 S. Conti1 , M

Rumpf, Martin

29

Memristive learning and memory functions in polyvinyl alcohol polymer memristors  

NASA Astrophysics Data System (ADS)

Polymer based memristive devices can offer simplicity in fabrication and at the same time promise functionalities for artificial neural applications. In this work, inherent learning and memory functions have been achieved in polymer memristive devices employing Polyvinyl Alcohol. The change in conduction in such polymer devices strongly depends on the pulse amplitude, duration and time interval. Through repetitive stimuli training, temporary short-term memory can transfer into consolidated long-term memory. These behaviors bear remarkable similarities to certain learning and memory functions of biological systems.

Lei, Yan; Liu, Yi; Xia, Yidong; Gao, Xu; Xu, Bo; Wang, Suidong; Yin, Jiang; Liu, Zhiguo

2014-07-01

30

High-Temperature Shape Memory Polymers  

NASA Technical Reports Server (NTRS)

physical conformation changes when exposed to an external stimulus, such as a change in temperature. Such materials have a permanent shape, but can be reshaped above a critical temperature and fixed into a temporary shape when cooled under stress to below the critical temperature. When reheated above the critical temperature (Tc, also sometimes called the triggering or switching temperature), the materials revert to the permanent shape. The current innovation involves a chemically treated (sulfonated, carboxylated, phosphonated, or other polar function group), high-temperature, semicrystalline thermoplastic poly(ether ether ketone) (Tg .140 C, Tm = 340 C) mix containing organometallic complexes (Zn++, Li+, or other metal, ammonium, or phosphonium salts), or high-temperature ionic liquids (e.g. hexafluorosilicate salt with 1-propyl-3- methyl imidazolium, Tm = 210 C) to form a network where dipolar or ionic interactions between the polymer and the low-molecular-weight or inorganic compound forms a complex that provides a physical crosslink. Hereafter, these compounds will be referred to as "additives". The polymer is semicrystalline, and the high-melt-point crystals provide a temporary crosslink that acts as a permanent crosslink just so long as the melting temperature is not exceeded. In this example case, the melting point is .340 C, and the shape memory critical temperature is between 150 and 250 C. PEEK is an engineering thermoplastic with a high Young fs modulus, nominally 3.6 GPa. An important aspect of the invention is the control of the PEEK functionalization (in this example, the sulfonation degree), and the thermal properties (i.e. melting point) of the additive, which determines the switching temperature. Because the compound is thermoplastic, it can be formed into the "permanent" shape by conventional plastics processing operations. In addition, the compound may be covalently cross - linked after forming the permanent shape by S-PEEK by applying ionizing radiation ( radiation, neutrons), or by chemical crosslinking to form a covalent permanent network. With respect to other shape memory polymers, this invention is novel in that it describes the use of a thermoplastic composition that can be thermally molded or solution-cast into complex "permanent" shapes, and then reheated or redissolved and recast from solution to prepare another shape. It is also unique in that the shape memory behavior is provided by a non-polymer additive.

Yoonessi, Mitra; Weiss, Robert A.

2012-01-01

31

Disruptions in autobiographical memory processing in depression and the emergence of memory therapeutics.  

PubMed

Depression is characterized by distinct profiles of disturbance in ways autobiographical memories are represented, recalled, and maintained. We review four core domains of difficulty: systematic biases in favor of negative material; impoverished access and responses to positive memories; reduced access to the specific details of the personal past; and dysfunctional processes of rumination and avoidance around personal autobiographical material. These difficulties drive the onset and maintenance of depression; consequently, interventions targeted at these maladaptive processes have clinical potential. Memory therapeutics is the development of novel clinical techniques, translated from basic research, that target memory difficulties in those with emotional disorders. We discuss prototypical examples from this clinical domain including MEmory Specificity Training, positive memory elaboration, memory rescripting, and the method-of-loci (MoL). PMID:25060510

Dalgleish, Tim; Werner-Seidler, Aliza

2014-11-01

32

Modeling and simulation of magnetic-shape-memory polymer composites  

Microsoft Academic Search

Composites of small magnetic-shape-memory (MSM) particles embedded in a polymer matrix have been proposed as an energy damping mechanism and as actuators. Compared to a single crystal bulk material, the production is simpler and more flexible, as both type of the polymer and geometry of the microstructure can be tuned. Compared to polycrystals, in composites the soft polymer matrix permits

S. Conti; M. Lenz; M. Rumpf

2007-01-01

33

Temperature memory effect in amorphous shape memory polymers.  

PubMed

Temperature memory effect (TME) refers to the ability of shape memory polymers (SMPs) to memorize the temperature at which pre-deformation was conducted. In the past few years, this TME was experimentally demonstrated by comparing the applied programming temperature (Td) with a characteristic recovery temperature (Tc), which corresponds to either the maximum recovery stress or free recovery speed. In these well-designed experiments, Tc was observed to be close to Td, which is consistent with the intuitive understanding of 'memorization'. However, since the polymer recovery behavior has been proved to be strongly dependent on various programming and recovery conditions, a new question that whether Tc is always equal to Td in any thermo-temporal conditions remains to be addressed. In this paper, we answered this question by examining the free recovery profile of an acrylate based amorphous SMP. The recovery Tc, which is the temperature with the maximum recovery speed, versus the recovery temperature is shown to be strongly dependent on both programming and recovery conditions. Their detailed influence could be explained by using the reduced time. During a thermomechanical working cycle of SMPs, in addition to the Td, any other thermo-temporal conditions, such as the holding time (th), cooling rate, recovery heating rate (q), etc., can affect the observed Tc by changing the reduced programming or recovery time. In this manner, the relationship between Tc and Td is not uniquely determined. Besides, the TME in SMPs can only be achieved within a given temperature range. Both onset and offset of this temperature range are shown to be influenced by the programming history, but are independent of the recovery conditions. PMID:25354272

Yu, Kai; Qi, H Jerry

2014-12-21

34

Photopolymerized Thiol-Ene Systems as Shape Memory Polymers  

PubMed Central

In this study we introduce the use of thiol-ene photopolymers as shape memory polymer systems. The thiol-ene polymer networks are compared to a commonly utilized acrylic shape memory polymer and shown to have significantly improved properties for two different thiol-ene based polymer formulations. Using thermomechanical and mechanical analysis, we demonstrate that thiol-ene based shape memory polymer systems have comparable thermomechanical properties while also exhibiting a number of advantageous properties due to the thiol-ene polymerization mechanism which results in the formation of a homogenous polymer network with low shrinkage stress and negligible oxygen inhibition. The resulting thiol-ene shape memory polymer systems are tough and flexible as compared to the acrylic counterparts. The polymers evaluated in this study were engineered to have a glass transition temperature between 30 and 40 °C, exhibited free strain recovery of greater than 96% and constrained stress recovery of 100%. The thiol-ene polymers exhibited excellent shape fixity and a rapid and distinct shape memory actuation response. PMID:21072253

Nair, Devatha P.; Cramer, Neil B.; Scott, Timothy F.; Bowman, Christopher N.; Shandas, Robin

2010-01-01

35

Nanoscale porosity in polymer films: fabrication and therapeutic applications  

PubMed Central

This review focuses on current developments in the field of nanostructured bulk polymers and their application in bioengineering and therapeutic sciences. In contrast to well-established nanoscale materials, such as nanoparticles and nanofibers, bulk nanostructured polymers combine nanoscale structure in a macroscopic construct, which enables unique application of these materials. Contemporary fabrication and processing techniques capable of producing nanoporous polymer films are reviewed. Focus is placed on techniques capable of sub-100 nm features since this range approaches the size scale of biological components, such as proteins and viruses. The attributes of these techniques are compared, with an emphasis on the characteristic advantages and limitations of each method. Finally, application of these materials to biofiltration, immunoisolation, and drug delivery are reviewed. PMID:22140398

Bernards, Daniel A.; Desai, Tejal A.

2011-01-01

36

Shape memory polymer (SMP) actuation technology  

NASA Astrophysics Data System (ADS)

Cornerstone Research Group Inc. (CRG) is developing low-cost, lightweight, shape memory polymer (SMP) actuators for use in the deployment of rigid aeroshells. The SMP actuator technology has been selected for use because of its ability to store energy, within a very small volume, and release that energy on demand with little requirement for power. During the Phase I SBIR effort, CRG demonstrated the feasibility of using a thermally activated SMP actuator for the deployment of a subscale, rigid, deployable aeroshell. The follow-on Phase II effort improved upon the Phase I actuator technology through the application of finite element analysis and testing. This work resulted in the fabrication of a full-scale actuator (0.127m long, 0.102m diameter) that was able to develop more than 40 ft-lb of torque during actuation. A conformal cartridge heater (CCH) was developed in parallel to solve the problem of efficiently transferring heat stimulus into the SMP materials. The CCH maintains surface contact with the walls of the SMP actuator throughout the actuator's range of motion to optimize the heat transfer between the heating surface and the SMP material surface. The SMP actuator also has the potential of moving or deploying mechanisms simply through environmental stimulus. Since CRG is able to custom tailor the material properties of the SMP, broad application of this technology is possible.

Auffinger, Frank; Fisher, Michael; Maddux, Michael

2010-04-01

37

Controlled Drug Release from Biodegradable Shape-Memory Polymers  

NASA Astrophysics Data System (ADS)

Biodegradable shape-memory polymers (SMPs) have attracted significant interest for biomedical applications. Modern concepts for biofunctional implants often comprise the controlled release of bioactive compounds to gain specific biofunctionalities. Therefore, a general strategy has been suggested for polymer systems combining degradability and shape-memory capability with controlled release of drugs. This chapter provides a detailed description of the molecular basis for such multifunctional SMPs including the selection of building blocks, the polymer morphology, and the three dimensional architecture. Moreover, drug loading and release, drug effects on thermomechanical properties of SMPs, and drug release patterns in a physiological environment are described and potential applications in minimally-invasive surgery are discussed.

Wischke, Christian; Neffe, Axel T.; Lendlein, Andreas

38

Resistive switching memory based on bioinspired natural solid polymer electrolytes.  

PubMed

A solution-processed, chitosan-based resistive-switching memory device is demonstrated with Pt/Ag-doped chitosan/Ag structure. The memory device shows reproducible and reliable bipolar resistive switching characteristics. A memory device based on natural organic material is a promising device toward the next generation of nonvolatile nanoelectronics. The memory device based on chitosan as a natural solid polymer electrolyte can be switched reproducibly between high and low resistance states. In addition, the data retention measurement confirmed the reliability of the chitosan-based nonvolatile memory device. The transparent Ag-embedded chitosan film showed an acceptable and comparable resistive switching behavior on the flexible plastic substrate as well. A cost-effective, environmentally benign memory device using chitosan satisfies the functional requirements of nonvolatile memory operations. PMID:25513838

Raeis Hosseini, Niloufar; Lee, Jang-Sik

2015-01-27

39

AC Electric Field Activated Shape Memory Polymer Composite  

NASA Technical Reports Server (NTRS)

Shape memory materials have drawn interest for applications like intelligent medical devices, deployable space structures and morphing structures. Compared to other shape memory materials like shape memory alloys (SMAs) or shape memory ceramics (SMCs), shape memory polymers (SMPs) have high elastic deformation that is amenable to tailored of mechanical properties, have lower density, and are easily processed. However, SMPs have low recovery stress and long response times. A new shape memory thermosetting polymer nanocomposite (LaRC-SMPC) was synthesized with conductive fillers to enhance its thermo-mechanical characteristics. A new composition of shape memory thermosetting polymer nanocomposite (LaRC-SMPC) was synthesized with conductive functionalized graphene sheets (FGS) to enhance its thermo-mechanical characteristics. The elastic modulus of LaRC-SMPC is approximately 2.7 GPa at room temperature and 4.3 MPa above its glass transition temperature. Conductive FGSs-doped LaRC-SMPC exhibited higher conductivity compared to pristine LaRC SMP. Applying an electric field at between 0.1 Hz and 1 kHz induced faster heating to activate the LaRC-SMPC s shape memory effect relative to applying DC electric field or AC electric field at frequencies exceeding1 kHz.

Kang, Jin Ho; Siochi, Emilie J.; Penner, Ronald K.; Turner, Travis L.

2011-01-01

40

Shape memory polymer foams for endovascular therapies  

DOEpatents

A system for occluding a physical anomaly. One embodiment comprises a shape memory material body wherein the shape memory material body fits within the physical anomaly occluding the physical anomaly. The shape memory material body has a primary shape for occluding the physical anomaly and a secondary shape for being positioned in the physical anomaly.

Wilson, Thomas S. (Castro Valley, CA); Maitland, Duncan J. (Pleasant Hill, CA)

2012-03-13

41

DESIGN OF A VARIABLE STIFFNESS LEG USING SHAPE MEMORY POLYMER COMPOSITES  

E-print Network

571 DESIGN OF A VARIABLE STIFFNESS LEG USING SHAPE MEMORY POLYMER COMPOSITES DUNCAN W. HALDANE State University 1. Introduction Biomechanical studies have shown that animals modify their leg materials called shape memory polymers. Shape Memory Polymers (SMPs) experience a several order of magnitude

Collins, Emmanuel

42

Targeting Angiogenesis-Dependent Calcified Neoplasms Using Combined Polymer Therapeutics  

PubMed Central

Background There is an immense clinical need for novel therapeutics for the treatment of angiogenesis-dependent calcified neoplasms such as osteosarcomas and bone metastases. We developed a new therapeutic strategy to target bone metastases and calcified neoplasms using combined polymer-bound angiogenesis inhibitors. Using an advanced “living polymerization” technique, the reversible addition-fragmentation chain transfer (RAFT), we conjugated the aminobisphosphonate alendronate (ALN), and the potent anti-angiogenic agent TNP-470 with N-(2-hydroxypropyl)methacrylamide (HPMA) copolymer through a Glycine-Glycine-Proline-Norleucine linker, cleaved by cathepsin K, a cysteine protease overexpressed at resorption sites in bone tissues. In this approach, dual targeting is achieved. Passive accumulation is possible due to the increase in molecular weight following polymer conjugation of the drugs, thus extravasating from the tumor leaky vessels and not from normal healthy vessels. Active targeting to the calcified tissues is achieved by ALN's affinity to bone mineral. Methods and Finding The anti-angiogenic and antitumor potency of HPMA copolymer-ALN-TNP-470 conjugate was evaluated both in vitro and in vivo. We show that free and conjugated ALN-TNP-470 have synergistic anti-angiogenic and antitumor activity by inhibiting proliferation, migration and capillary-like tube formation of endothelial and human osteosarcoma cells in vitro. Evaluation of anti-angiogenic, antitumor activity and body distribution of HPMA copolymer-ALN-TNP-470 conjugate was performed on severe combined immunodeficiency (SCID) male mice inoculated with mCherry-labeled MG-63-Ras human osteosarcoma and by modified Miles permeability assay. Our targeted bi-specific conjugate reduced VEGF-induced vascular hyperpermeability by 92% and remarkably inhibited osteosarcoma growth in mice by 96%. Conclusions This is the first report to describe a new concept of a narrowly-dispersed combined polymer therapeutic designed to target both tumor and endothelial compartments of bone metastases and calcified neoplasms at a single administration. This new approach of co-delivery of two synergistic drugs may have clinical utility as a potential therapy for angiogenesis-dependent cancers such as osteosarcoma and bone metastases. PMID:19381291

Segal, Ehud; Pan, Huaizhong; Ofek, Paula; Udagawa, Taturo; Kope?ková, Pavla; Kope?ek, Jind?ich; Satchi-Fainaro, Ronit

2009-01-01

43

Biomedical applications of thermally activated shape memory polymers  

PubMed Central

Shape memory polymers (SMPs) are smart materials that can remember a primary shape and can return to this primary shape from a deformed secondary shape when given an appropriate stimulus. This property allows them to be delivered in a compact form via minimally invasive surgeries in humans, and deployed to achieve complex final shapes. Here we review the various biomedical applications of SMPs and the challenges they face with respect to actuation and biocompatibility. While shape memory behavior has been demonstrated with heat, light and chemical environment, here we focus our discussion on thermally stimulated SMPs. PMID:21258605

Small, Ward; Singhal, Pooja; Wilson, Thomas S.

2011-01-01

44

Shape memory polymer cellular solid design for medical applications  

NASA Astrophysics Data System (ADS)

Shape memory polymers (SMPs) are an emerging class of active materials whose response can be easily tailored via modifications of the molecular parameters and optimization of the transformation processes. In this work, we originally demonstrated that a correct coupling of polymer transformation processes (co-extrusion with chemical blowing agents, salt co-extrusion/particulate leaching, solvent casting/particulate leaching) and SMPs allows one to obtain porous structures with a broad spectrum of morphological properties resulting in tunable thermo-mechanical and shape recovery properties. Such a wide range of properties could fulfil the specifications of medical applications in which the use of SMP-based foams can be envisaged.

De Nardo, L.; Bertoldi, S.; Tanzi, M. C.; Haugen, H. J.; Farè, S.

2011-03-01

45

Wafer-scale arrays of nonvolatile polymer memories with microprinted semiconducting small molecule/polymer blends.  

PubMed

Nonvolatile ferroelectric-gate field-effect transistors (Fe-FETs) memories with solution-processed ferroelectric polymers are of great interest because of their potential for use in low-cost flexible devices. In particular, the development of a process for patterning high-performance semiconducting channel layers with mechanical flexibility is essential not only for proper cell-to-cell isolation but also for arrays of flexible nonvolatile memories. We demonstrate a robust route for printing large-scale micropatterns of solution-processed semiconducting small molecules/insulating polymer blends for high performance arrays of nonvolatile ferroelectric polymer memory. The nonvolatile memory devices are based on top-gate/bottom-contact Fe-FET with ferroelectric polymer insulator and micropatterned semiconducting blend channels. Printed micropatterns of a thin blended semiconducting film were achieved by our selective contact evaporation printing, with which semiconducting small molecules in contact with a micropatterned elastomeric poly(dimethylsiloxane) (PDMS) mold were preferentially evaporated and absorbed into the PDMS mold while insulating polymer remained intact. Well-defined micrometer-scale patterns with various shapes and dimensions were readily developed over a very large area on a 4 in. wafer, allowing for fabrication of large-scale printed arrays of Fe-FETs with highly uniform device performance. We statistically analyzed the memory properties of Fe-FETs, including ON/OFF ratio, operation voltage, retention, and endurance, as a function of the micropattern dimensions of the semiconducting films. Furthermore, roll-up memory arrays were produced by successfully detaching large-area Fe-FETs printed on a flexible substrate with a transient adhesive layer from a hard substrate and subsequently transferring them to a nonplanar surface. PMID:24070419

Bae, Insung; Hwang, Sun Kak; Kim, Richard Hahnkee; Kang, Seok Ju; Park, Cheolmin

2013-11-13

46

Macroscopic Behaviour of Magnetic Shape-Memory Polycrystals and Polymer Composites Sergio Conti1  

E-print Network

in response to an applied magnetic field. For sin- gle crystals one can achieve strains of order of magnitudeMacroscopic Behaviour of Magnetic Shape-Memory Polycrystals and Polymer Composites Sergio Conti1-proposed alternative for shape memory devices is to embed small single-crystal shape-memory particles in a soft polymer

Sminchisescu, Cristian

47

Design of a deployable structure with shape memory polymers  

NASA Astrophysics Data System (ADS)

Auxetic (negative Poisson's ratio) configurations have recently been used to build prototypes of deployable structures using classical shape memory alloys (Nickel-Titanium-Copper). Chiral configurations, featuring three or more inter-connected spiral-wound hubs, exploit efficient tensile-rotational mechanisms. These structures offer high deployability ratios in structural elements with load-bearing characteristics. Shape memory polymers have the potential to replace these shape memory alloys and other stored-energy actuators, and have the attractive properties of low mass, high actuation strain, easy fabrication and tuneable thermal properties. In this work we discuss how shape memory polymers (SMP) integrated into a chiral core could offer enhanced deployable characteristics and increase the efficiency of the auxetic deformations in these unusual cellular structures. We consider the spiral-wound fundamental component needed for SMP n-chiral prototypes and present test results showing actuation motion of expanding SMP deployable structures. Applications likely to benefit from these structures include lightweight elements for structural engineering applications, deployable structures for space applications and implantable medical devices.

Rossiter, Jonathan; Scarpa, Fabrizio; Takashima, Kazuto; Walters, Peter

2012-04-01

48

Shape memory polymers based on uniform aliphatic urethane networks  

SciTech Connect

Aliphatic urethane polymers have been synthesized and characterized, using monomers with high molecular symmetry, in order to form amorphous networks with very uniform supermolecular structures which can be used as photo-thermally actuable shape memory polymers (SMPs). The monomers used include hexamethylene diisocyanate (HDI), trimethylhexamethylenediamine (TMHDI), N,N,N{prime},N{prime}-tetrakis(hydroxypropyl)ethylenediamine (HPED), triethanolamine (TEA), and 1,3-butanediol (BD). The new polymers were characterized by solvent extraction, NMR, XPS, UV/VIS, DSC, DMTA, and tensile testing. The resulting polymers were found to be single phase amorphous networks with very high gel fraction, excellent optical clarity, and extremely sharp single glass transitions in the range of 34 to 153 C. Thermomechanical testing of these materials confirms their excellent shape memory behavior, high recovery force, and low mechanical hysteresis (especially on multiple cycles), effectively behaving as ideal elastomers above T{sub g}. We believe these materials represent a new and potentially important class of SMPs, and should be especially useful in applications such as biomedical microdevices.

Wilson, T S; Bearinger, J P; Herberg, J L; Marion III, J E; Wright, W J; Evans, C L; Maitland, D J

2007-01-19

49

Initiation of shape-memory effect by inductive heating of magnetic nanoparticles in thermoplastic polymers  

Microsoft Academic Search

In shape-memory polymers, changes in shape are mostly induced by heating, and exceeding a specific switching temperature, Tswitch. If polymers cannot be warmed up by heat transfer using a hot liquid or gaseous medium, noncontact triggering will be required. In this article, the magnetically induced shape-memory effect of composites from magnetic nanoparticles and thermoplastic shape-memory polymers is introduced. A polyetherurethane

R. Mohr; K. Kratz; T. Weigel; M. Lucka-Gabor; M. Moneke; A. Lendlein

2006-01-01

50

High actuation properties of shape memory polymer composite actuator  

NASA Astrophysics Data System (ADS)

The shape memory polymers (SMPs) possess two shapes: permanent shape and temporary shape. This property leads to replacement of shape memory alloys by SMPs in various applications. In this work, two properties, namely structure activeness and the shape memory property of ‘controlled behavior composite material (CBCM)’ plate and its comparison with the conventional symmetrical composite plate (SYM), are studied. The SMPC plates (CBCM and SYM) are manufactured using epoxy resin with a thermal glass transition temperature (Tg) of 130?°C. The shape memory properties of these composites are investigated (under three-point bending test) and compared by deforming them to the same displacement. Three types of recoveries are conducted: unconstrained recovery, constrained recovery, and partial recovery under load. It is found that by coupling the structure activeness (due to its asymmetry) and its shape memory property, higher activated displacement is obtained during the unconstrained recovery. Also, at a lower recovery temperature (90?°C) than the fixing temperature, a recovery close to 100% is obtained for CBCM, whereas for SYM it is only 25%. During constrained recovery, CBCM produces five times larger recovery force than SYM. In addition, higher actuation properties are demonstrated by calculating recovered work and recovery percentages during partial recovery under load.

Basit, A.; L'Hostis, G.; Durand, B.

2013-02-01

51

Conducting polymer memory devices based on dynamic doping.  

PubMed

Molecular electronic junctions consisting of a 20 nm thick layer of polypyrrole (PPy) and 10 nm of TiO2 between conducting layers of carbon and gold were investigated as potential nonvolatile memory devices. By making the polymer layer much thinner than conventional polymer electronic devices, it is possible to dynamically oxidize and reduce the polypyrrole layer by an applied bias. When the electrode in contact with the PPy is biased positive, oxidation of the PPy occurs to yield a conducting polaron state. The junctions exhibit a large increase in conductance in response to the positive bias, which is reversed by a subsequent negatively biased pulse. Switching between the conducting and nonconducting state can occur for pulses at least as short as 10 micros, and the conducting state persists after a positive bias pulse for at least 1 week. The read/write/read/erase cycle may be repeated for at least 1700 cycles, although with an error rate of approximately 3% due mainly to an incomplete "erase" step. The speed and retention of the PPy/TiO2 junctions are far superior to those of the analogous fluorene/TiO2 devices lacking the polymer, and the conductance changes are absent if SiO2 is substituted for TiO2. The observations are consistent with "dynamic doping" of the solid-state polymer layer, with the possible involvement of adventitious mobile ions. Although the speed of the current polymer/TiO2 junctions is slower than commercial dynamic random access memory, their retention is approximately 5 orders of magnitude longer. PMID:18646749

Barman, Sudip; Deng, Fengjun; McCreery, Richard L

2008-08-20

52

Thiol-vinyl systems as shape memory polymers and novel two-stage reactive polymer systems  

NASA Astrophysics Data System (ADS)

The focus of this research was to formulate, characterize and tailor the reaction methodologies and material properties of thiol-vinyl systems to develop novel polymer platforms for a range of engineering applications. Thiol-ene photopolymers were demonstrated to exhibit several advantageous characteristics for shape memory polymer systems for a range of biomedical applications. The thiol-ene shape memory polymer systems were tough and flexible as compared to the acrylic control systems with glass transition temperatures between 30 and 40 °C; ideal for actuation at body temperature. The thiol-ene polymers also exhibited excellent shape fixity and a rapid and distinct shape memory actuation response along with free strain recoveries of greater than 96% and constrained stress recoveries of 100%. Additionally, two-stage reactive thiol-acrylate systems were engineered as a polymer platform technology enabling two independent sets of polymer processing and material properties. There are distinct advantages to designing polymer systems that afford two distinct sets of material properties -- an intermediate polymer that would enable optimum handling and processing of the material (stage 1), while maintaining the ability to tune in different, final properties that enable the optimal functioning of the polymeric material (stage 2). To demonstrate the range of applicability of the two-stage reactive systems, three specific applications were demonstrated; shape memory polymers, lithographic impression materials, and optical materials. The thiol-acrylate reactions exhibit a wide range of application versatility due to the range of available thiol and acrylate monomers as well as reaction mechanisms such as Michael Addition reactions and free radical polymerizations. By designing a series of non-stoichiometeric thiol-acrylate systems, a polymer network is initially formed via a base catalyzed 'click' Michael addition reaction. This self-limiting reaction results in a Stage 1 polymer with excess acrylic functional groups within the network. At a later point in time, the photoinitiated, free radical polymerization of the excess acrylic functional groups results in a highly crosslinked, robust material system. By varying the monomers within the system as well as the stoichiometery of thiol to acrylate functional groups, the ability of the two-stage reactive systems to encompass a wide range of properties at the end of both the stage 1 and stage 2 polymerizations was demonstrated. The thiol-acrylate networks exhibited intermediate Stage 1 rubbery moduli and glass transition temperatures that range from 0.5 MPa and -10 ºC to 22 MPa and 22 ºC respectively. The same polymer networks can then attain glass transition temperatures that range from 5 ºC to 195 ºC and rubbery moduli of up to 200 MPa after the subsequent photocure stage. Two-stage reactive polymer composite systems were also formulated and characterized for thermomechanical and mechanical properties. Thermomechanical analysis showed that the fillers resulted in a significant increase in the modulus at both stage 1 and stage 2 polymerizations without a significant change in the glass transition temperatures (Tg). The two-stage reactive matrix composite formed with a hexafunctional acrylate matrix and 20 volume % silica particles showed a 125% increase in stage 1 modulus and 101% increase in stage 2 modulus, when compared with the modulus of the neat matrix. Finally, the two-stage reactive polymeric devices were formulated and designed as orthopedic suture anchors for arthroscopic surgeries and mechanically characterized. The Stage 1 device was designed to exhibit properties ideal for arthroscopic delivery and device placement with glass transition temperatures 25 -- 30 °C and rubbery moduli ˜ 95 MPa. The subsequent photopolymerization generated Stage 2 polymers designed to match the local bone environment with moduli ranging up to 2 GPa. Additionally, pull-out strengths of 140 N were demonstrated and are equivalent to the pull-strengths achieved by other commercially availab

Nair, Devatha P.

2011-12-01

53

Thermal response of novel shape memory polymer-shape memory alloy hybrids  

NASA Astrophysics Data System (ADS)

Shape memory polymers (SMP) and shape memory alloys (SMA) have both been proven important smart materials in their own fields. Shape memory polymers can be formed into complex three-dimensional structures and can undergo shape programming and large strain recovery. These are especially important for deployable structures including those for space applications and micro-structures such as stents. Shape memory alloys on the other hand are readily exploitable in a range of applications where simple, silent, light-weight and low-cost repeatable actuation is required. These include servos, valves and mobile robotic artificial muscles. Despite their differences, one important commonality between SMPs and SMAs is that they are both typically activated by thermal energy. Given this common characteristic it is important to consider how these two will behave when in close environmental proximity, and hence exposed to the same thermal stimulus, and when they are incorporated into a hybrid SMA-SMP structure. In this paper we propose and examine the operation of SMA-SMP hybrids. The relationship between the two temperatures Tg, the glass transition temperature of the polymer, and Ta, the nominal austenite to martensite transition temperature of the alloy is considered. We examine how the choice of these two temperatures affects the thermal response of the hybrid. Electrical stimulation of the SMA is also considered as a method not only of actuating the SMA but also of inducing heating in the surrounding polymer, with consequent effects on actuator behaviour. Likewise by varying the rate and degree of thermal stimulation of the SMA significantly different actuation and structural stiffness can be achieved. Novel SMP-SMA hybrid actuators and structures have many ready applications in deployable structures, robotics and tuneable engineering systems.

Rossiter, Jonathan; Takashima, Kazuto; Mukai, Toshiharu

2014-03-01

54

Thermoset shape-memory polymer nanocomposite filled with nanocarbon powders  

NASA Astrophysics Data System (ADS)

A system of a thermoset styrene-based shape-memory polymer (SMP) filled with nanocarbon powders is investigated in this paper. The thermomechanical properties are characterized by thermal gravity analysis, differential scanning calorimetery and dynamic mechanical analysis. In addition, the distribution of CB is investigated by scanning electron microscope. To realize the electroactive stimuli of SMP, the electrical conductivity of SMP filled with various amounts of CB is characterized. The percolation threshold of electrically conductive SMP filled with CB is about 3.8 % (volume fraction of CB), which is much lower than many other electrically conductive polymers. When applying a voltage of 30V, the shape recovery process of SMP/CB (10 vol%) can be realized in about 100s.

Lan, Xin; Liu, Yanju; Leng, Jinsong

2009-07-01

55

Shape memory polymer filled honeycomb model and experimental validation  

NASA Astrophysics Data System (ADS)

An analytical model predicting the in-plane Young’s and shear moduli of a shape memory polymer filled honeycomb composite is presented. By modeling the composite as a series of rigidly attached beams, the mechanical advantage of the load distributed on each beam by the infill is accounted for. The model is compared to currently available analytical models as well as experimental data. The model correlates extremely well with experimental data for empty honeycomb and when the polymer is above its glass transition temperature. Below the glass transition temperature, rule of mixtures is shown to be more accurate as bending is no longer the dominant mode of deformation. The model is also derived for directions other than the typical x and y allowing interpolation of the stiffness of the composite in any direction.

Beblo, R. V.; Puttmann, J. P.; Joo, J. J.; Reich, G. W.

2015-02-01

56

Characterization of Nonlinear Rate Dependent Response of Shape Memory Polymers  

NASA Technical Reports Server (NTRS)

Shape Memory Polymers (SMPs) are a class of polymers, which can undergo deformation in a flexible state at elevated temperatures, and when cooled below the glass transition temperature, while retaining their deformed shape, will enter and remain in a rigid state. Upon heating above the glass transition temperature, the shape memory polymer will return to its original, unaltered shape. SMPs have been reported to recover strains of over 400%. It is important to understand the stress and strain recovery behavior of SMPs to better develop constitutive models which predict material behavior. Initial modeling efforts did not account for large deformations beyond 25% strain. However, a model under current development is capable of describing large deformations of the material. This model considers the coexisting active (rubber) and frozen (glass) phases of the polymer, as well as the transitions between the material phases. The constitutive equations at the continuum level are established with internal state variables to describe the microstructural changes associated with the phase transitions. For small deformations, the model reduces to a linear model that agrees with those reported in the literature. Thermomechanical characterization is necessary for the development, calibration, and validation of a constitutive model. The experimental data reported in this paper will assist in model development by providing a better understanding of the stress and strain recovery behavior of the material. This paper presents the testing techniques used to characterize the thermomechanical material properties of a shape memory polymer (SMP) and also presents the resulting data. An innovative visual-photographic apparatus, known as a Vision Image Correlation (VIC) system was used to measure the strain. The details of this technique will also be presented in this paper. A series of tensile tests were performed on specimens such that strain levels of 10, 25, 50, and 100% were applied to the material while it was above its glass transition temperature. After deforming the material to a specified applied strain, the material was then cooled to below the glass transition temperature (Tg) while retaining the deformed shape. Finally, the specimen was heated again to above the transition temperature, and the resulting shape recovery profile was measured. Results show that strain recovery occurs at a nonlinear rate with respect to time. Results also indicate that the ratio of recoverable strain/applied strain increases as the applied strain increases.

Volk, Brent; Lagoudas, Dimitris C.; Chen, Yi-Chao; Whitley, Karen S.

2007-01-01

57

Polymer Therapeutics: Polymers as Drugs, Drug and Protein Conjugates and Gene Delivery Systems: Past, Present and Future Opportunities  

Microsoft Academic Search

As the 21st century begins we are witnessing a paradigm shift in medical practice. Whereas\\u000a the use of polymers in biomedical materials applications -- for example, as prostheses, medical devices,\\u000a contact lenses, dental materials and pharmaceutical excipients -- is long established, polymer-based\\u000a medicines have only recently entered routine clinical practice [1,\\u000a 2,3,4]. Importantly, many of the innovative polymer-based therapeutics\\u000a once dismissed as

Ruth Duncan; Helmut Ringsdorf; Ronit Satchi-Fainaro

58

Shape memory polymer hexachiral auxetic structures with tunable stiffness  

NASA Astrophysics Data System (ADS)

Planar auxetic structures have the potential to impact on a wide range of applications from deployable and morphing structures to space-filling composite and medical treatments. The ability to fabricate auxetics from smart materials greatly enhances this facility by building in controllable actuation and deployment. A smart auxetic device can be compressed and fixed into a storage state. When deployment is required the device can be appropriately stimulated and the stored elastic energy is released, resulting in a marked structural expansion. Instead of using a conventional external actuator to drive deployment the material is made to undergo phase transition where one stimulus (e.g. heat) initiates a mechanical response. Here we show how smart material auxetics can be realized using a thermally responsive shape memory polymer composites. We show how a shape memory polymer auxetic hexachiral structure can be tailored to provide a tunable stiffness response in its fully deployed state by varying the angle of inter-hub connections, and yet is still able to undergo thermally stimulated deployment.

Rossiter, Jonathan; Takashima, Kazuto; Scarpa, Fabrizio; Walters, Peter; Mukai, Toshiharu

2014-04-01

59

Crossbar arrays of nonvolatile, rewritable polymer ferroelectric diode memories on plastic substrates  

NASA Astrophysics Data System (ADS)

In this paper, we demonstrate a scalable and low-cost memory technology using a phase separated blend of a ferroelectric polymer and a semiconducting polymer as data storage medium on thin, flexible polyester foils of only 25 µm thickness. By sandwiching this polymer blend film between rows and columns of metal electrode lines where each intersection makes up one memory cell, we obtained 1 kbit cross bar arrays with bit densities of up to 10 kbit/cm2.

van Breemen, Albert J. J. M.; van der Steen, Jan-Laurens; van Heck, Gert; Wang, Rui; Khikhlovskyi, Vsevolod; Kemerink, Martijn; Gelinck, Gerwin H.

2014-03-01

60

A macro-mechanical constitutive model for shape memory polymer  

NASA Astrophysics Data System (ADS)

It is of theoretical and engineering interest to establish a macro-mechanical constitutive model of the shape memory polymer (SMP), which includes the mechanical constitutive equation and the material parameter function, from the viewpoint of practical application. In this paper, a new three-dimensional macro-mechanical constitutive equation, which describes the mechanical behaviors associated with the shape memory effect of SMP, is developed based on solid mechanics and the viscoelasticity theorem. According to the results of the DMA test, a new material parameter function is established to express the relationship of the material parameters and temperature during the glass transition of SMP. The new macro-mechanical constitutive equation and material parameter function are used to numerically simulate the process producing the shape memory effect of SMP, which includes deforming at high temperature, stress freezing, unloading at low temperature and shape recovery. They are also used to investigate and analyze the influences of loading rate and temperature change rate on the thermo-mechanical behaviors of SMP. The numerical results and the comparisons with Zhou's material parameter function and Tobushi's mechanical constitutive equation illustrate that the proposed three-dimensional macro-mechanical constitutive model can effectively predict the thermo-mechanical behaviors of SMP under the state of complex stress.

Zhou, Bo; Liu, Yanju; Leng, Jinsong

2010-12-01

61

Modeling and simulation of magnetic-shape-memory polymer composites  

NASA Astrophysics Data System (ADS)

Composites of small magnetic-shape-memory (MSM) particles embedded in a polymer matrix have been proposed as an energy damping mechanism and as actuators. Compared to a single crystal bulk material, the production is simpler and more flexible, as both type of the polymer and geometry of the microstructure can be tuned. Compared to polycrystals, in composites the soft polymer matrix permits the active grains to deform to some extent independently; in particular the rigidity of grain boundaries arising from incompatible orientations is reduced. We study the magnetic-field-induced deformation of composites, on the basis of a continuous model incorporating elasticity and micromagnetism, in a reduced two-dimensional, plane-strain setting. The aim is to give conceptual guidance for the design of composite materials independent of the concrete macroscopic device. Thus, on the background of homogenization theory, we determine the macroscopic behavior by studying an affine-periodic cell problem. An energy descent algorithm is developed, whose main ingredients are a boundary element method for the computation of the elastic and magnetic field energies; and a combinatorial component reflecting the phase transition in the individual particles, which are assumed to be of single-domain type. Our numerical results demonstrate the behavior of the macroscopic material properties for different possible microstructures, and give suggestions for the optimization of the composite.

Conti, S.; Lenz, M.; Rumpf, M.

2007-07-01

62

Magnetic Resonance Flow Velocity and Temperature Mapping of a Shape Memory Polymer Foam Device  

SciTech Connect

Interventional medical devices based on thermally responsive shape memory polymer (SMP) are under development to treat stroke victims. The goals of these catheter-delivered devices include re-establishing blood flow in occluded arteries and preventing aneurysm rupture. Because these devices alter the hemodynamics and dissipate thermal energy during the therapeutic procedure, a first step in the device development process is to investigate fluid velocity and temperature changes following device deployment. A laser-heated SMP foam device was deployed in a simplified in vitro vascular model. Magnetic resonance imaging (MRI) techniques were used to assess the fluid dynamics and thermal changes associated with device deployment. Spatial maps of the steady-state fluid velocity and temperature change inside and outside the laser-heated SMP foam device were acquired. Though non-physiological conditions were used in this initial study, the utility of MRI in the development of a thermally-activated SMP foam device has been demonstrated.

Small IV, W; Gjersing, E; Herberg, J L; Wilson, T S; Maitland, D J

2008-10-29

63

Therapeutic synthetic polymers: a game of Russian roulette?  

Microsoft Academic Search

Synthetic polymer-based drug-delivery systems have been applied in drug delivery for the past 50 years. So why are there so few examples of these macromolecules being used successfully in the clinic? It is our view that many products are failing because of a neglect of the fundamental science surrounding the architectural control of the molecules present, their behaviour following in

A. Christy Hunter; S. Moein Moghimi

2002-01-01

64

Various shape memory effects of stimuli-responsive shape memory polymers  

NASA Astrophysics Data System (ADS)

One-step dual-shape memory polymers (SMPs) recover their original (permanent) shape upon small variation of environmental conditions such as temperature, electric field, light, magnetic field, and solvent/chemicals. For advanced applications such as aerospace and medical devices, complicated, multiple-step, spatially controllable, and two-way shape memory effects (SMEs) are required. In the past decade, researchers have devoted great effort to improve the versatility of the SME of SMPs to meet the needs of advanced applications. This paper is intended to review the up-to-date research endeavors on advanced SMEs. The problems facing the various SMPs are discussed. The challenges and opportunities for future research are discussed.

Meng, Harper; Mohamadian, Habib; Stubblefield, Michael; Jerro, Dwayne; Ibekwe, Samuel; Pang, Su-Seng; Li, Guoqiang

2013-09-01

65

Helix Generation, Amplification, Switching, and Memory of Chromophoric Polymers  

NASA Astrophysics Data System (ADS)

The origin of biomolecular handedness known as homochirality in the animate world may be one of the most puzzling issues among scientists. The cooperativity of amplification, switching, and memory in biopolymers and synthetic helical polymers might be shared with ideas of a scenario for the biomolecular homochirality, autocatalytic mechanism in chiral chemical synthesis, and bifurcation equilibrium mechanisms in crystallization of chiral crystals. This work focuses on several chiroptical amplification phenomena exemplified in optically active chromophoric helical polysilanes bearing chiral and achiral side groups, which exist in isotropic dilute solution, as aggregate forms dispersed in isotropic solution, in double layered films deposited onto a solid surface, in the thermotropic cholesteric liquid crystal film state, and ultimately by dictating invisible chiral weak and ultraweak interactions at subatomic, atomic, and molecular levels.

Fujiki, Michiya

66

Shape memory polymers: three-dimensional isotropic modeling  

NASA Astrophysics Data System (ADS)

This paper presents a comprehensive three-dimensional isotropic numerical simulation for a thermo-mechanical constitutive model of shape memory polymers (SMPs). In order to predict the thermo-mechanical behavior of SMPs, a one-dimensional rheological thermo-mechanical constitutive model is adopted, translated into a three-dimensional form and a time discrete form of the three-dimensional model is then presented. Numerical simulation of this model was developed using the UMAT subroutine capabilities of the finite element software ABAQUS. Evolution of the analysis was conducted by making use of the backward difference scheme, which was applied to all quantities within the model, including the material properties. A comparison of the numerical simulation results was carried out with the available experimental data. Numerical simulation results clearly exhibit the thermo-mechanical properties of the material which include shape fixity, shape recovery, and recovery stress. Finally, a prediction for the transverse and shear directions of the material is presented.

Balogun, Olaniyi; Mo, Changki

2014-04-01

67

Development of a shape memory polymer fastening system  

NASA Astrophysics Data System (ADS)

Traditional fastening systems exhibit various limitations that a next-generation shape memory polymer (SMP) system can overcome. Bolts and screws provide high-strength attachment but require permanent modification to the system and are typically visible, depending on the configuration. Adhesive bonding can provide high-strength attachment and low visibility, but it is irreversible. Hook and loop fasteners offer reversibility, but the fastened strength and the removal force are similar, limiting the applications. The unique properties of SMP enable a fastening system that offers advantages not currently available in any one fastening system, including reversibility, low visibility, and high-strength attachment. Cornerstone Research Group (CRG) designed a fastener system that consists of an array of SMP heads and stems that interlock. The high modulus of the SMP at room temperature provides rigid attachment, keeping the system interlocked. When activated above the glass transition temperature (Tg), the heads and stems become soft and flexible, reducing the force required during attachment and detachment of the system. The shape memory property of the SMP ensures all heads and stems return to their original position to allow proper alignment. The developed system provides shear and tensile strength in excess of 300 psi with tensile detachment requiring only 2 psi. The material selection, design, testing, and optimization of the SMP fastening system are discussed.

Cable, Kristin; Hermiller, Jason; Kirby, Brandon; Sunday, Matthew

2009-03-01

68

On a novel self-regulating shape memory polymer composite  

NASA Astrophysics Data System (ADS)

Polyurethane shape memory polymers (PU-SMPs) are active materials that can be transformed into complex shapes with the ability to recover their original shape even after undergoing large deformations. Because of their light weight, large recoverability, low cost, and high compliance, SMPs can be potentially employed as actuators, MEMS devices, temperature sensors, and damping elements to name a few. One of the key challenges in implementing SMPs is the response time which is limited by the method of heating and cooling and the material. Unlike shape memory alloys, SMPs can be activated by multiple stimuli including lasers, resistive heating, electric fields, and magnetic fields. While these methods may provide an efficient way of heating the SMP, they rely on the slow process of passive conduction for cooling. In this paper, a self regulating SMP (SR-SMP) composite is introduced, whereby a novel heating and cooling system consisting of embedded silica capillary tubes in the SMP (DiAPLEX® MP4510: SMP Technologies, Inc.) has been developed. The tubes are used to pump hot/cold fluid through the SMP membrane and hence provide a local temperature source. In order to show the effectiveness and efficiency of the mechanism, the thermomechanical response of the SR-SMP is compared experimentally to a SMP with "conventional" i.e. global heating and cooling mechanisms. It is shown that the SR-SMP has a faster thermomechanical response. It has been demonstrated previously that soft SMPs can be controlled by an electric field while in the rubbery phase, thus taking advantage of the Maxwell stress or electrostatic stress effect. Thermomechanical characterization of PU-SMPs is described for different weight percentages of resin (Diphenylmethane-4, 4'-diisocyanate) and hardener (1,4-Butanediol). Varying the percent hardener reduced the effective cross-link density of the polymer and hence the thermomechanical properties. The electromechanical response of pure SMP and SR-SMP is predicted numerically. The numerical computation indicates that the softer SMPs (resin:hardener = 5:4, 8:7, and 9:8) could be used as electroactive polymers.

Gao, Fei; Son, Seyul; Park, Kyungmook; Biggs, David; Andrews, Courtney; Mockensturm, Eric M.; Goulbourne, Nakhiah C.

2011-04-01

69

Inductively Heated Shape Memory Polymer for the Magnetic Actuation of Medical Devices  

E-print Network

Presently there is interest in making medical devices such as expandable stents and intravascular microactuators from shape memory polymer (SMP). One of the key challenges in realizing SMP medical devices is the implementation ...

Buckley, Patrick R.

2007-01-23

70

Assessment and preliminary model development of shape memory polymers mechanical counter pressure space suits  

E-print Network

This thesis seeks to assess the viability of a space qualified shape memory polymer (SMP) mechanical counter pressure (MCP) suit. A key development objective identified by the International Space Exploration Coordination ...

Wee, Brian (Brian J.)

2013-01-01

71

Actuation of shape memory polymer using magnetic fields for applications in medical devices  

E-print Network

A novel approach to the heating and actuation of shape memory polymer using dispersed Curie temperature thermo-regulated particles is proposed. Such a material has potential applications in medical devices which are delivered ...

Buckley, Patrick Regan, 1981-

2004-01-01

72

Inorganic-Organic Shape Memory Polymers and Foams for Bone Defect Repairs  

E-print Network

The ultimate goal of this research was to develop a “self-fitting” shape memory polymer (SMP) scaffold for the repair of craniomaxillofacial (CMF) bone defects. CMF defects may be caused by trauma, tumor removal or congenital abnormalities...

Zhang, Dawei

2013-04-16

73

Digital memory versatility of fully ?-conjugated donor-acceptor hybrid polymers.  

PubMed

The fully ?-conjugated donor-acceptor hybrid polymers Fl-TPA, Fl-TPA-TCNE, and Fl-TPA-TCNQ, which are composed of fluorene (Fl), triphenylamine (TPA), dimethylphenylamine, alkyne, alkyne-tetracyanoethylene (TCNE) adduct, and alkyne-7,7,8,8-tetracyanoquinodimethane (TCNQ) adduct, were synthesized. These polymers are completely amorphous in the solid film state and thermally stable up to 291-409 °C. Their molecular orbital levels and band gaps vary with their compositions. The TCNE and TCNQ units, despite their electron-acceptor characteristics, were found to enhance the ?-conjugation lengths of Fl-TPA-TCNE and Fl-TPA-TCNQ (i.e., to produce red shifts in their absorption spectra and significant reductions in their band gaps). These changes are reflected in the electrical digital memory behavior of the polymers. Moreover, the TCNE and TCNQ units were found to diversify the digital memory modes and to widen the active polymer layer thickness window. In devices with aluminum top and bottom electrodes, the Fl-TPA polymer exhibits stable unipolar permanent memory behavior with high reliability. The Fl-TPA-TCNE and Fl-TPA-TCNQ devices exhibit stable unipolar permanent memory behavior as well as dynamic random access memory behavior with excellent reliability. These polymer devices were found to operate by either hole injection or hole injection along with electron injection, depending on the polymer composition. Overall, this study demonstrated that the incorporation of ?-conjugated cyano moieties, which control both the ?-conjugation length and electron-accepting power, is a sound approach for the design and synthesis of high-performance digital memory polymers. The TCNE and TCNQ polymers synthesized in this study are highly suitable active materials for the low-cost mass production of high-performance, polarity-free, programmable, volatile, and permanent memory devices that can be operated with very low power consumption, high ON/OFF current ratios, and high reliability. PMID:24779635

Ko, Yong-Gi; Kim, Dong Min; Kim, Kyungtae; Jung, Sungmin; Wi, Dongwoo; Michinobu, Tsuyoshi; Ree, Moonhor

2014-06-11

74

Internal stress storage in shape memory polymer nanocomposites Ken Gall,a)  

E-print Network

shape memory polymer matrix. Although the shape memory effect is not inherent to the ceramic. Under 50% compression of the composite material, the nanoparticles store a finite compressive stress strain, by the inclusion of hard ceramic reinforcements.3 In the present study, we examine the storage

Balzar, Davor

75

Autonomous, hands-free shape memory in glassy, liquid crystalline polymer networks.  

PubMed

Repeatedly forming temporary shapes can be a limitation to the employment of shape memory polymers. This work utilizes glassy, liquid crystal polymer networks to spontaneously form 3D shapes that are independent of a user. These shapes are autonomously fixed with rapid temperature cycling. PMID:22535595

Lee, Kyung Min; Bunning, Timothy J; White, Timothy J

2012-06-01

76

Three-Dimensional Modeling of Shape Memory Polymers Considering Finite Deformations and Heat Transfer  

E-print Network

, and extensions of 10%, 15%, 20%, and 25% are applied in the constrained displacement recovery analyses. ..................................................................... 149 Figure 36 ? Prototype of a shape memory polymer neurovascular stent. Courtesy... panels on new commercial and military aircraft to shape changing metals being used for cardiovascular stents and aneurysm treatments . More recently, advances in new stimuli-responsive polymer systems ? including piezoelectric, electroactive...

Volk, Brent Louis 1985-

2012-10-16

77

Method for loading shape memory polymer gripper mechanisms  

DOEpatents

A method and apparatus for loading deposit material, such as an embolic coil, into a shape memory polymer (SMP) gripping/release mechanism. The apparatus enables the application of uniform pressure to secure a grip by the SMP mechanism on the deposit material via differential pressure between, for example, vacuum within the SMP mechanism and hydrostatic water pressure on the exterior of the SMP mechanism. The SMP tubing material of the mechanism is heated to above the glass transformation temperature (Tg) while reshaping, and subsequently cooled to below Tg to freeze the shape. The heating and/or cooling may, for example, be provided by the same water applied for pressurization or the heating can be applied by optical fibers packaged to the SMP mechanism for directing a laser beam, for example, thereunto. At a point of use, the deposit material is released from the SMP mechanism by reheating the SMP material to above the temperature Tg whereby it returns to its initial shape. The reheating of the SMP material may be carried out by injecting heated fluid (water) through an associated catheter or by optical fibers and an associated beam of laser light, for example.

Lee, Abraham P. (Walnut Creek, CA); Benett, William J. (Livermore, CA); Schumann, Daniel L. (Concord, CA); Krulevitch, Peter A. (Pleasanton, CA); Fitch, Joseph P. (Livermore, CA)

2002-01-01

78

Self-Deploying Trusses Containing Shape-Memory Polymers  

NASA Technical Reports Server (NTRS)

Composite truss structures are being developed that can be compacted for stowage and later deploy themselves to full size and shape. In the target applications, these smart structures will precisely self-deploy and support a large, lightweight space-based antenna. Self-deploying trusses offer a simple, light, and affordable alternative to articulated mechanisms or inflatable structures. The trusses may also be useful in such terrestrial applications as variable-geometry aircraft components or shelters that can be compacted, transported, and deployed quickly in hostile environments. The truss technology uses high-performance shape-memory-polymer (SMP) thermoset resin reinforced with fibers to form a helical composite structure. At normal operating temperatures, the truss material has the structural properties of a conventional composite. This enables truss designs with required torsion, bending, and compression stiffness. However, when heated to its designed glass transition temperature (Tg), the SMP matrix acquires the flexibility of an elastomer. In this state, the truss can be compressed telescopically to a configuration encompassing a fraction of its original volume. When cooled below Tg, the SMP reverts to a rigid state and holds the truss in the stowed configuration without external constraint. Heating the materials above Tg activates truss deployment as the composite material releases strain energy, driving the truss to its original memorized configuration without the need for further actuation. Laboratory prototype trusses have demonstrated repeatable self-deployment cycles following linear compaction exceeding an 11:1 ratio (see figure).

Schueler, Robert M.

2008-01-01

79

Micro devices using shape memory polymer patches for mated connections  

DOEpatents

A method and micro device for repositioning or retrieving miniature devices located in inaccessible areas, such as medical devices (e.g., stents, embolic coils, etc.) located in a blood vessel. The micro repositioning or retrieving device and method uses shape memory polymer (SMP) patches formed into mating geometries (e.g., a hoop and a hook) for re-attachment of the deposited medical device to a catheter or guidewire. For example, SMP or other material hoops are formed on the medical device to be deposited in a blood vessel, and SMP hooks are formed on the micro device attached to a guidewire, whereby the hooks on the micro device attach to the hoops on the medical device, or vice versa, enabling deposition, movement, re-deposit, or retrieval of the medical device. By changing the temperature of the SMP hooks, the hooks can be attached to or released from the hoops located on the medical device. An exemplary method for forming the hooks and hoops involves depositing a sacrificial thin film on a substrate, patterning and processing the thin film to form openings therethrough, depositing or bonding SMP materials in the openings so as to be attached to the substrate, and removing the sacrificial thin film.

Lee, Abraham P. (Walnut Creek, CA); Fitch, Joseph P. (Livermore, CA)

2000-01-01

80

Component assembly with shape memory polymer fastener for microrobots  

NASA Astrophysics Data System (ADS)

Adhesives are generally used for the assembly of microrobots, whereas bolts, screws, or rivets are used for larger robots. Although adhesives are easy to apply, lightweight, and small, they cannot be used for repeated assembly and disassembly of parts. In this paper, we present a novel microfastener composed of a polyurethane-based shape memory polymer (SMP) that is lightweight and small but that is easily detached for disassembly. This was achieved by using the shape recovery and modulus change of the SMP. A sheet of macromolded SMP was laser machined into an I-beam-shaped rivet, and notches were added to the structure to prevent stress concentration. Pull-off tests showed that, as the notch radius increased, the disengagement strength of the rivet fastener decreased and the reusability increased. Through the elastoplastic model, a single SMP rivet was calculated to have maximum disengagement strength of 150 N cm-2 in the elastic range, depending on the notch radius. The fasteners were applied to a jumping microrobot. The legs and body were assembled with ten fasteners, which showed no permanent deformation after impact during jumping movements. The legs were easily replaced with ones of different stiffness by heating the engaged sites to make the fasteners compliant and detachable. The proposed detachable SMP microfasteners are particularly useful for testing the isolated performance of microrobot components to determine the optimal designs for these components.

Kim, Ji-Suk; Lee, Dae-Young; Koh, Je-Sung; Jung, Gwang-Pil; Cho, Kyu-Jin

2014-01-01

81

Therapeutic polymers for dental adhesives: Loading resins with bio-active components  

PubMed Central

Objectives Many recent adhesives on the market exhibit reasonable clinical performance. Future innovations in adhesive materials should therefore seek out novel properties rather than simply modifying existing technologies. It is proposed that adhesive materials that are “bio-active” could contribute to better prognosis of restorative treatments. Methods This review examines the recent approaches used to achieve therapeutic polymers for dental adhesives by incorporating bio-active components. A strategy to maintain adhesive restorations is the focus of this paper. Results Major trials on therapeutic dental adhesives have looked at adding antibacterial activities or remineralization effects. Applications of antibacterial resin monomers based on quaternary ammonium compounds have received much research attention, and the loading of nano-sized bioactive particles or multiple ion-releasing glass fillers have been perceived as advantageous since they are not expected to influence the mechanical properties of the carrier polymer. Significance The therapeutic polymer approaches described here have the potential to provide clinical benefits. However, not many technological applications in this category have been successfully commercialized. Clinical evidence as well as further advancement of these technologies can be a driving force to make these new types of materials clinically available. PMID:23899387

Imazato, Satoshi; Ma, Sai; Chen, Ji-hua; Xu, Hockin H.K.

2014-01-01

82

Demonstration of a multiscale modeling technique: prediction of the stress-strain response of light activated shape memory polymers  

Microsoft Academic Search

Presented is a multiscale modeling method applied to light activated shape memory polymers (LASMPs). LASMPs are a new class of shape memory polymer (SMPs) being developed for adaptive structures applications where a thermal stimulus is undesirable. LASMP developmental emphasis is placed on optical manipulation of Young's modulus. A multiscale modeling approach is employed to anticipate the soft and hard state

Richard V. Beblo; Lisa Mauck Weiland

2010-01-01

83

Conductivity switching and electronic memory effect in polymers with pendant azobenzene chromophores.  

PubMed

Electronic memory devices having the indium-tin oxide/polymer/Al sandwich structure were fabricated from polymers containing pendant azobenzene chromophores in donor-acceptor structures. The reversibility, or rewritability, of the high-conductivity (ON) state was found to be dependent on the terminal moiety of the azobenzene chromophore. While the polymers with electron-accepting terminal moieties (-Br or -NO2) in the pendant azobenzene exhibit write-once, read-many-times (WORM) type memory behavior, those with electron-donating terminal moieties (-OCH3) exhibit rewritable (FLASH) memory behavior. The WORM memory devices have low switching ("write") voltages below -2 V and high ON/OFF current ratios of about 10(4)-10(6). The polarity of the "write" voltage can be reversed by using an electrode with a higher work function than Al, thus excluding metallic filamentary conduction as a cause of the bistable switching phenomenon. The FLASH memory devices have low "write" and "erase" voltages of about -1.7 to -1.8 V and 2.0 to 2.2 V, respectively, and ON/OFF current ratios of about 10(3)-10(4). The electrical bistability observed can be attributed to charge trapping at the azobenzene chromophores, resulting in the charge-separated, high-conductivity state. The proposed mechanism is supported experimentally by a red shift and peak broadening in the UV-visible absorption spectra of the polymer films resulting from the OFF-to-ON electrical transition. PMID:20355755

Lim, Siew Lay; Li, Na-Jun; Lu, Jian-Mei; Ling, Qi-Dan; Zhu, Chun Xiang; Kang, En-Tang; Neoh, Koon Gee

2009-01-01

84

Shape recovery of nanoscale imprints in a thermoset ``shape memory'' polymer  

NASA Astrophysics Data System (ADS)

This letter reports temperature-dependent recovery of atomic force microscope tip-formed indentations in a thermoset shape memory polymer. The indentations are made at both room temperature and 69°C, and then recovered at temperatures between 40°C and 70°C. The shape recovery is more complete for higher anneal temperatures, and is relatively independent of time for 102-104s. The experiments show shape memory in the 1-100nm size scale.

Nelson, Brent A.; King, William P.; Gall, Ken

2005-03-01

85

Sugar-based amphiphilic polymers for biomedical applications: from nanocarriers to therapeutics.  

PubMed

Various therapeutics exhibit unfavorable physicochemical properties or stability issues that reduce their in vivo efficacy. Therefore, carriers able to overcome such challenges and deliver therapeutics to specific in vivo target sites are critically needed. For instance, anticancer drugs are hydrophobic and require carriers to solubilize them in aqueous environments, and gene-based therapies (e.g., siRNA or pDNA) require carriers to protect the anionic genes from enzymatic degradation during systemic circulation. Polymeric micelles, which are self-assemblies of amphiphilic polymers (APs), constitute one delivery vehicle class that has been investigated for many biomedical applications. Having a hydrophobic core and a hydrophilic shell, polymeric micelles have been used as drug carriers. While traditional APs are typically comprised of nondegradable block copolymers, sugar-based amphiphilic polymers (SBAPs) synthesized by us are comprised of branched, sugar-based hydrophobic segments and a hydrophilic poly(ethylene glycol) chain. Similar to many amphiphilic polymers, SBAPs self-assemble into polymeric micelles. These nanoscale micelles have extremely low critical micelle concentrations offering stability against dilution, which occurs with systemic administration. In this Account, we illustrate applications of SBAPs for anticancer drug delivery via physical encapsulation within SBAP micelles and chemical conjugation to form SBAP prodrugs capable of micellization. Additionally, we show that SBAPs are excellent at stabilizing liposomal delivery systems. These SBAP-lipid complexes were developed to deliver hydrophobic anticancer therapeutics, achieving preferential uptake in cancer cells over normal cells. Furthermore, these complexes can be designed to electrostatically complex with gene therapies capable of transfection. Aside from serving as a nanocarrier, SBAPs have also demonstrated unique bioactivity in managing atherosclerosis, a major cause of cardiovascular disease. The atherosclerotic cascade is usually triggered by the unregulated uptake of oxidized low-density lipoprotein, a cholesterol carrier, in macrophages of the blood vessel wall; SBAPs can significantly inhibit oxidized low-density lipoprotein uptake in macrophages and abrogate the atherosclerotic cascade. By modification of various functionalities (e.g., branching, stereochemistry, hydrophobicity, and charge) in the SBAP chemical structure, SBAP bioactivity was optimized, and influential structural components were identified. Despite the potential of SBAPs as atherosclerotic therapies, blood stability of the SBAP micelles was not ideal for in vivo applications, and means to stabilize them were pursued. Using kinetic entrapment via flash nanoprecipitation, SBAPs were formulated into nanoparticles with a hydrophobic solute core and SBAP shell. SBAP nanoparticles exhibited excellent physiological stability and enhanced bioactivity compared with SBAP micelles. Further, this method enables encapsulation of additional hydrophobic drugs (e.g., vitamin E) to yield a stable formulation that releases two bioactives. Both as nanoscale carriers and as polymer therapeutics, SBAPs are promising biomaterials for medical applications. PMID:25141069

Gu, Li; Faig, Allison; Abdelhamid, Dalia; Uhrich, Kathryn

2014-10-21

86

All organic memory devices utilizing fullerene molecules and insulating polymers  

NASA Astrophysics Data System (ADS)

The convergence of mobile technologies combined with stricter power requirements and increasing demands have strained the current memory technology. Newer technologies such as phase changing, ferroelectric, and magnetic random access memories are unsatisfactory in meeting the new requirements. We propose a new memory technology based on our initial discovery of charge storage in C60 molecules within poly (4-vinyl phenol) (PVP). To understand the memory potential, we created single-layer devices consisting of ˜30nm films of PVP+C60 sandwiched between aluminum (Al) electrodes. Current versus voltage (I-V) sweeps showed a significant hysteresis of 75nA, with distinguishable memory states. Room temperature charging of C60 was confirmed indirectly through capacitance versus voltage measurements and directly by monitoring the A1g characteristic peak of C60 during Raman measurements. We demonstrated memory operations by applying read-write-erase (RWE) pulses. The PVP+C60 devices exhibited memory retention for over 1 hour and response times of around 10ns. Characteristic hysteresis was demonstrated at the nanoscale. Conduction models were fitted at room temperature to the I-V curves. It was found that combination of direct and Fowler-Nordheim tunneling were the principle conduction mechanisms. For a more technologically viable memory device, we developed a multi-layer device structure, consisting of a polystyrene (PS) capping layer. The resulting asymmetrical I-V curve exhibited a hysteresis ratio of 103 . RWE cycles were measured with clearly distinguishable states. The memory retentions were measured over 2 hours and the response time around 10ns. The stability of the multi-layer devices was improved. I-V measurements at temperatures varying from 4.2 K to 298 K were performed to construct a theoretical model. The I-V curves were found to be temperature independent and exhibited similar tunneling behaviors as the single-layer devices. A simple model for conduction and memory operation is proposed based on the I-V fits. These devices exhibit the characteristics needed to satisfy the new demands for memory application and have the potential of becoming the first universal memory technology. They possess the high speed, non-volatility, thermal stability, and potentially high memory densities to make them ideal for use in laptops, iPhones, mp3 players, portable video players, GPS systems, and other mobile devices.

Kanwal, Alokik Paul

87

Investigation of interfacial shear stresses, shape fixity, and actuation strain in composites incorporating shape memory polymers and shape memory alloys  

NASA Astrophysics Data System (ADS)

Shape memory composites (SMCs) based on shape memory alloys (SMAs) and shape memory polymers (SMPs) allow many design possibilities due to their controllable temperature-dependent mechanical properties. The complementary characteristics of SMAs and SMPs can be utilized in systems with shape recovery created by the SMA and shape fixity provided by the SMP. In this research, three SMC operating regimes are identified and the behavior of SMC structures is analyzed by focusing on composite shape fixity and interfacial stresses. Analytical models show that SMPs can be used to adequately fix the shape of SMA actuators and springs. COMSOL finite element simulations are in agreement with analytical expressions for shape fixity and interfacial stresses. Analytical models are developed for an end-coupled linear SMP-SMA two-way actuator and the predicted strain is shown to be in good agreement with experimental test results.

Park, Jungkyu; Headings, Leon; Dapino, Marcelo; Baur, Jeffery; Tandon, Gyaneshwar

2015-03-01

88

The dynamics of polymers in solution with hydrodynamic memory  

E-print Network

The theory of the dynamics of polymers in solution is developed coming from the hydrodynamic theory of the Brownian motion (BM) and the Rouse-Zimm (RZ) model. It is shown that the time correlation functions describing the polymer motion essentially differ from those in the previous RZ models based on the Einstein theory of BM. The MSD of the polymer coil is at short times proportional to t^2 (instead of t). At long times it contains additional (to the Einstein term) contributions, the leading of which is ~ t^{1/2}. The relaxation of the internal normal modes of the polymer differs from the traditional exponential decay. This is displayed in the tails of their correlation functions, the longest-lived being ~ t^{-3/2} in the Rouse limit and t^{-5/2} in the Zimm case when the hydrodynamic interaction is strong. It is discussed that the found peculiarities, in particular a slower diffusion of the coil, should be observable in dynamic scattering experiments. The dynamic structure factor and the first cumulant of the polymer coil are calculated. The theory is extended to the situation when the dynamics of the studied polymer is influenced by the presence of other polymers in dilute solution.

V. Lisy; J. Tothova; B. Brutovsky; A. V Zatovsky

2005-09-15

89

RFID Tag Antenna Based Temperature Sensing Using Shape Memory Polymer Actuation  

E-print Network

RFID Tag Antenna Based Temperature Sensing Using Shape Memory Polymer Actuation Rahul Bhattacharyya sensor using the UHF RFID tag antenna as a sensing mechanism. Permanent changes are induced in the tag of UHF RFID tags to serve as ultra-low cost temperature alarm sensors which are capable of detecting

Entekhabi, Dara

90

Electrochromic conductive polymer fuses for hybrid organic/inorganic semiconductor memories  

NASA Astrophysics Data System (ADS)

We demonstrate a nonvolatile, write-once-read-many-times (WORM) memory device employing a hybrid organic/inorganic semiconductor architecture consisting of thin film p-i-n silicon diode on a stainless steel substrate integrated in series with a conductive polymer fuse. The nonlinearity of the silicon diodes enables a passive matrix memory architecture, while the conductive polyethylenedioxythiophene:polystyrene sulfonic acid polymer serves as a reliable switch with fuse-like behavior for data storage. The polymer can be switched at ˜2 ?s, resulting in a permanent decrease of conductivity of the memory pixel by up to a factor of 103. The switching mechanism is primarily due to a current and thermally dependent redox reaction in the polymer, limited by the double injection of both holes and electrons. The switched device performance does not degrade after many thousand read cycles in ambient at room temperature. Our results suggest that low cost, organic/inorganic WORM memories are feasible for light weight, high density, robust, and fast archival storage applications.

Möller, Sven; Forrest, Stephen R.; Perlov, Craig; Jackson, Warren; Taussig, Carl

2003-12-01

91

Multi-stimulus-responsive shape-memory polymer nanocomposite network cross-linked by cellulose nanocrystals.  

PubMed

In this study, we developed a thermoresponsive and water-responsive shape-memory polymer nanocomposite network by chemically cross-linking cellulose nanocrystals (CNCs) with polycaprolactone (PCL) and polyethylene glycol (PEG). The nanocomposite network was fully characterized, including the microstructure, cross-link density, water contact angle, water uptake, crystallinity, thermal properties, and static and dynamic mechanical properties. We found that the PEG[60]-PCL[40]-CNC[10] nanocomposite exhibited excellent thermo-induced and water-induced shape-memory effects in water at 37 °C (close to body temperature), and the introduction of CNC clearly improved the mechanical properties of the mixture of both PEG and PCL polymers with low molecular weights. In addition, Alamar blue assays based on osteoblasts indicated that the nanocomposites possessed good cytocompatibility. Therefore, this thermoresponsive and water-responsive shape-memory nanocomposite could be potentially developed into a new smart biomaterial. PMID:25647407

Liu, Ye; Li, Ying; Yang, Guang; Zheng, Xiaotong; Zhou, Shaobing

2015-02-25

92

Programmable polymer-based supramolecular temperature sensor with a memory function.  

PubMed

A new class of polymeric thermometers with a memory function is reported that is based on the supramolecular host-guest interactions of poly(N-isopropylacrylamide) (PNIPAM) with side-chain naphthalene guest moieties and the tetracationic macrocycle cyclobis(paraquat-p-phenylene) (CBPQT(4+)) as the host. This supramolecular thermometer exhibits a memory function for the thermal history of the solution, which arises from the large hysteresis of the thermoresponsive LCST phase transition (LCST = lower critical solution temperature). This hysteresis is based on the formation of a metastable soluble state that consists of the PNIPAM-CBPQT(4+) host-guest complex. When heated above the transition temperature, the polymer collapses, and the host-guest interactions are disrupted, making the polymer more hydrophobic and less soluble in water. Aside from providing fundamental insights into the kinetic control of supramolecular assemblies, the developed thermometer with a memory function might find use in applications spanning the physical and biological sciences. PMID:24711257

Sambe, Léna; de La Rosa, Victor R; Belal, Khaled; Stoffelbach, François; Lyskawa, Joel; Delattre, François; Bria, Marc; Cooke, Graeme; Hoogenboom, Richard; Woisel, Patrice

2014-05-12

93

Estimation of aneurysm wall stresses created by treatment with a shape memory polymer foam device  

PubMed Central

In this study, compliant latex thin-walled aneurysm models are fabricated to investigate the effects of expansion of shape memory polymer foam. A simplified cylindrical model is selected for the in-vitro aneurysm, which is a simplification of a real, saccular aneurysm. The studies are performed by crimping shape memory polymer foams, originally 6 and 8 mm in diameter, and monitoring the resulting deformation when deployed into 4-mm-diameter thin-walled latex tubes. The deformations of the latex tubes are used as inputs to physical, analytical, and computational models to estimate the circumferential stresses. Using the results of the stress analysis in the latex aneurysm model, a computational model of the human aneurysm is developed by changing the geometry and material properties. The model is then used to predict the stresses that would develop in a human aneurysm. The experimental, simulation, and analytical results suggest that shape memory polymer foams have potential of being a safe treatment for intracranial saccular aneurysms. In particular, this work suggests oversized shape memory foams may be used to better fill the entire aneurysm cavity while generating stresses below the aneurysm wall breaking stresses. PMID:21901546

Hwang, Wonjun; Volk, Brent L.; Akberali, Farida; Singhal, Pooja; Criscione, John C.

2012-01-01

94

Non-volatile ferroelectric memory with position-addressable polymer semiconducting nanowire.  

PubMed

One-dimensional nanowires (NWs) have been extensively examined for numerous potential nano-electronic device applications such as transistors, sensors, memories, and photodetectors. The ferroelectric-gate field effect transistors (Fe-FETs) with semiconducting NWs in particular in combination with ferroelectric polymers as gate insulating layers have attracted great attention because of their potential in high density memory integration. However, most of the devices still suffer from low yield of devices mainly due to the ill-control of the location of NWs on a substrate. NWs randomly deposited on a substrate from solution-dispersed droplet made it extremely difficult to fabricate arrays of NW Fe-FETs. Moreover, rigid inorganic NWs were rarely applicable for flexible non-volatile memories. Here, we present the NW Fe-FETs with position-addressable polymer semiconducting NWs. Polymer NWs precisely controlled in both location and number between source and drain electrode were achieved by direct electrohydrodynamic NW printing. The polymer NW Fe-FETs with a ferroelectric poly(vinylidene fluoride-co-trifluoroethylene) exhibited non-volatile ON/OFF current margin at zero gate voltage of approximately 10(2) with time-dependent data retention and read/write endurance of more than 10(4) seconds and 10(2) cycles, respectively. Furthermore, our device showed characteristic bistable current hysteresis curves when being deformed with various bending radii and multiple bending cycles over 1000 times. PMID:24644019

Hwang, Sun Kak; Min, Sung-Yong; Bae, Insung; Cho, Suk Man; Kim, Kang Lib; Lee, Tae-Woo; Park, Cheolmin

2014-05-28

95

Influence of Holding Time on Shape Recovery in a Polyurethane Shape-Memory Polymer  

NASA Astrophysics Data System (ADS)

Shape-memory polymers have attracted a lot of interest in recent years. A shape-memory polymer can be deformed and fixed into a temporary shape and subsequently made to recover its original shape when a suitable stimulus is applied. This is accomplished by means of a thermomechanical cycle called programming. Programming can be performed in a stress- or strain-controlled mode. The thermomechanical conditions of the programming affect shape-memory properties differently in each programming mode. One of the parameters which significantly affects shape-memory properties in a stress-controlled procedure is stress-holding time ( t H) at high temperature. This paper studies how stress-holding time affects the most significant shape-memory properties under successive thermomechanical cycles. The experiments were conducted using two different programming temperatures in the vicinity of the T g. The shape-recovery ratio decreased dramatically with cycling even when the holding time was just a few seconds, however, the impact of the stress-holding time depends on the temperature at which it has been applied. Shape-fixity ratio and switching temperature were also studied, but stress-holding time and successive cycles do not seem to affect either of these factors.

Santiago, David; Ferrando, Francesc; De la Flor, Silvia

2014-07-01

96

Gold nanoparticle charge trapping and relation to organic polymer memory devices.  

PubMed

Nanoparticle-based polymer memory devices (PMDs) are a promising technology that could replace conventional silicon-based electronic memory, offering fast operating speeds, simple device structures and low costs. Here we report on the current state of nanoparticle PMDs and review some of the problems that are still present in the field. We also present new data regarding the charging of gold nanoparticles in metal-insulator-semiconductor capacitors, showing that charging is possible under the application of an electric field with a trapped charge density due to the nanoparticles of 3.3 x 10(12) cm(-2). PMID:19770145

Prime, D; Paul, S; Josephs-Franks, P W

2009-10-28

97

Electron Beam Crosslinked Polyurethane Shape Memory Polymers with Tunable Mechanical Properties.  

PubMed

Novel electron beam crosslinked polyurethane shape memory polymers with advanced processing capabilities and tunable thermomechanical properties have been synthesized and characterized. We demonstrate the ability to manipulate crosslink density in order to finely tune rubbery modulus, strain capacity, ultimate tensile strength, recovery stress, and glass transition temperature. This objective is accomplished for the first time in a low-molecular-weight polymer system through the precise engineering of thermoplastic resin precursors suitable for mass thermoplastic processing. Neurovascular stent prototypes were fabricated by dip-coating and laser machining to demonstrate processability. PMID:25411531

Hearon, Keith; Nash, Landon D; Volk, Brent L; Ware, Taylor; Lewicki, James P; Voit, Walter E; Wilson, Thomas S; Maitland, Duncan J

2013-06-01

98

Electron Beam Crosslinked Polyurethane Shape Memory Polymers with Tunable Mechanical Properties  

PubMed Central

Novel electron beam crosslinked polyurethane shape memory polymers with advanced processing capabilities and tunable thermomechanical properties have been synthesized and characterized. We demonstrate the ability to manipulate crosslink density in order to finely tune rubbery modulus, strain capacity, ultimate tensile strength, recovery stress, and glass transition temperature. This objective is accomplished for the first time in a low-molecular-weight polymer system through the precise engineering of thermoplastic resin precursors suitable for mass thermoplastic processing. Neurovascular stent prototypes were fabricated by dip-coating and laser machining to demonstrate processability. PMID:25411531

Hearon, Keith; Nash, Landon D.; Volk, Brent L.; Ware, Taylor; Lewicki, James P.; Voit, Walter E.; Wilson, Thomas S.

2014-01-01

99

Polymer ferroelectric field-effect memory device with SnO channel layer exhibits record hole mobility  

PubMed Central

Here we report for the first time a hybrid p-channel polymer ferroelectric field-effect transistor memory device with record mobility. The memory device, fabricated at 200°C on both plastic polyimide and glass substrates, uses ferroelectric polymer P(VDF-TrFE) as the gate dielectric and transparent p-type oxide (SnO) as the active channel layer. A record mobility of 3.3?cm2V?1s?1, large memory window (?16?V), low read voltages (??1?V), and excellent retention characteristics up to 5000?sec have been achieved. The mobility achieved in our devices is over 10 times higher than previously reported polymer ferroelectric field-effect transistor memory with p-type channel. This demonstration opens the door for the development of non-volatile memory devices based on dual channel for emerging transparent and flexible electronic devices. PMID:24912617

Caraveo-Frescas, J. A.; Khan, M. A.; Alshareef, H. N.

2014-01-01

100

Current tissue engineering and novel therapeutic approaches to axonal regeneration following spinal cord injury using polymer scaffolds?  

PubMed Central

This review highlights current tissue engineering and novel therapeutic approaches to axonal regeneration following spinal cord injury. The concept of developing 3-dimensional polymer scaffolds for placement into a spinal cord transection model has recently been more extensively explored as a solution for restoring neurologic function after injury. Given the patient morbidity associated with respiratory compromise, the discrete tracts in the spinal cord conveying innervation for breathing represent an important and achievable therapeutic target. The aim is to derive new neuronal tissue from the surrounding, healthy cord that will be guided by the polymer implant through the injured area to make functional reconnections. A variety of naturally derived and synthetic biomaterial polymers have been developed for placement in the injured spinal cord. Axonal growth is supported by inherent properties of the selected polymer, the architecture of the scaffold, permissive microstructures such as pores, grooves or polymer fibres, and surface modifications to provide improved adherence and growth directionality. Structural support of axonal regeneration is combined with integrated polymeric and cellular delivery systems for therapeutic drugs and for neurotrophic molecules to regionalize growth of specific nerve populations. PMID:19737633

Madigan, Nicolas N.; McMahon, Siobhan; O’Brien, Timothy; Yaszemski, Michael J.; Windebank, Anthony J.

2010-01-01

101

Study on the shape memory effects of poly( l -lactide-co-?-caprolactone) biodegradable polymers  

Microsoft Academic Search

The thermal properties, crystalline structure and shape memory effects of poly(l-lactide) (PLLA) and poly(l-lactide-co-?-caprolactone) (PCLA) copolymers are systematically investigated by differential scanning calorimetry (DSC),\\u000a X-ray diffraction (XRD) and tensile tests. The effects of the deformation strain on the shape recovery rate and recovery stress\\u000a are also revealed. The polymers have the PLLA crystal and the amorphous phase, which are served

X. L. Lu; Z. J. Sun; W. Cai; Z. Y. Gao

2008-01-01

102

Directed water shedding on high-aspect-ratio shape memory polymer micropillar arrays.  

PubMed

A reconfigurable, droplet-directing surface is developed based on high-aspect-ratio shape-memory polymer (SMP) pillars. The water droplet on the original or recovered SMP pillars can slide off the surface at a finite angle of inclination while being fully pinned on the deformed pillar array. This wettability contrast allows directed water shredding from the straight pillars to the deformed ones. PMID:24293288

Chen, Chi-Mon; Yang, Shu

2014-02-26

103

Constitutive model for photo-mechanical behaviors of photo-induced shape memory polymers  

NASA Astrophysics Data System (ADS)

Light-activated polymers are an exciting class of materials that respond mechanically when irradiated at particular wavelengths. Recent demonstrations include two novel polymers developed by Scott et al (2006) and Lendlein et al (2005). In these polymers, photochemistry alters the microstructure of the cross-linked polymer network, which is further translated as light-induced deformation and when properly used light-induced shape memory effect. In this work, we develop a model framework to simulate the photomechanical response of light-activated polymer systems. This framework breaks down the observed macroscopic photomechanical phenomenon into four coupled sets of underlying physics, which occur throughout the material during irradiation and mechanical deformation. In the context of this framework, a basic photomechanical phenomenon involves simultaneously modeling photophysics, photochemistry, chemomechanical coupling, and mechanical behavior. Furthermore, network alteration are accounted for through the parallel decomposition of the cross-linked network into two components, an original network and a photochemically altered network, which allows to capture the observed photomechanical behaviors demonstrated in these materials. One of the principal strengths of this model framework is its generality as it can be applied to light activated polymer systems with fundamentally different of photophysics, photochemistry, and chemomechanical behaviors simply by choosing different field equations for the four sets of physics specific to a material system.

Long, Kevin N.; Scott, Timothy F.; Qi, H. Jerry; Dunn, Martin L.; Bowman, Christopher N.

2009-03-01

104

Thermally responsive polymer systems for self-healing, reversible adhesion and shape memory applications  

NASA Astrophysics Data System (ADS)

Responsive polymers are "smart" materials that are capable of performing prescribed, dynamic functions under an applied stimulus. In this dissertation, we explore several novel design strategies to develop thermally responsive polymers and polymer composites for self-healing, reversible adhesion and shape memory applications. In the first case described in Chapters 2 and 3, a thermally triggered self-healing material was prepared by blending a high-temperature epoxy resin with a thermoplastic polymer, poly(epsilon-caprolactone) (PCL). The initially miscible system undergoes polymerization induced phase separation (PIPS) during the curing of epoxy and yields a variety of compositionally dependent morphologies. At a particular PCL loading, the cured blend displays a "bricks-and-mortar" morphology in which epoxy exists as interconnected spheres ("bricks") within a continuous PCL matrix ("mortar"). A heat induced "bleeding" phenomenon was observed in the form of spontaneous wetting of all free surfaces by the molten PCL, and is attributed to the volumetric thermal expansion of PCL above its melting point in excess of epoxy brick expansion, which we term differential expansive bleeding (DEB). This DEB is capable of healing damage such as cracks. In controlled self-healing experiments, heating of a cracked specimen led to PCL bleeding from the bulk that yields a liquid layer bridging the crack gap. Upon cooling, a "scar" composed of PCL crystals was formed at the site of the crack, restoring a significant portion of mechanical strength. We further utilized DEB to enable strong and thermally-reversible adhesion of the material to itself and to metallic substrates, without any requirement for macroscopic softening or flow. After that, Chapters 4--6 present a novel composite strategy for the design and fabrication of shape memory polymer composites. The basic approach involves physically combining two or more functional components into an interpenetrating fiber/matrix structure, allowing them to function in a synergistic fashion yet remain physically separated. This latter aspect is critical since it enables the control of overall composite properties and functions by separately tuning each component. Utilizing the intrinsic versatility of this approach, composites with novel properties and functions (in addition to "regular" shape memory) have been developed, including (1) shape memory elastomeric composites (SMECs; Chapter 4), (2) triple-shape polymeric composites (TSPCs; Chapter 5), and (3) electrically conductive nanocomposites (Chapter 6). Then in Chapter 7, by combining the success in both thermoplastic based self-healing and shape memory polymer composites, we demonstrate a thermally triggered self-healing coating. This coating features a unique "shape memory assisted self-healing" mechanism in which crack closure (via shape memory) and crack re-bonding (via melting and diffusion of the thermoplastic healing agent) are achieved simultaneously upon a single heating step, leading to both structural and functional (corrosion resistance) recovery. Finally, Chapter 8 presents for the first time the preparation of functionally graded shape memory polymers (SMPs) that, unlike conventional SMPs, have a range of glass transition temperatures that are spatially graded. This was achieved using a temperature gradient curing method that imposes different vitrification limits at different positions along the gradient. The resulting material is capable of responding to a wide range of thermal triggers and a good candidate for low-cost, material based temperature sensors. All the aforementioned materials and methods show great potential for practical applications due to their high performance, low cost and broad applicability. Some recommendations for future research and development are given in Chapter 9.

Luo, Xiaofan

105

Charge transfer and trapping properties in polymer gate dielectrics for non-volatile organic field-effect transistor memory applications  

Microsoft Academic Search

We investigate here charge transfer and trapping characteristics of various chargeable polymer dielectric layers, polystyrene (PS), poly(4-vinyl naphthalene) (PVN), and amorphous fluoropolymer (Teflon® AF) in non-volatile pentacene field-effect transistor (FET) memory devices. Non-volatile memory properties, i.e., the degree of threshold voltage (VTh) shifts (memory window), the programming and erasing bias, and the retention time, strongly depended on the selection of

Kang-Jun Baeg; Yong-Young Noh; Dong-Yu Kim

2009-01-01

106

Shape memory polymer (SMP) gripper with a release sensing system  

DOEpatents

A system for releasing a target material, such as an embolic coil from an SMP located at the end of a catheter utilizing an optical arrangement for releasing the material. The system includes a laser, laser driver, display panel, photodetector, fiber optics coupler, fiber optics and connectors, a catheter, and an SMP-based gripper, and includes a release sensing and feedback arrangement. The SMP-based gripper is heated via laser light through an optic fiber causing the gripper to release a target material (e.g., embolic coil for therapeutic treatment of aneurysms). Various embodiments are provided for coupling the laser light into the SMP, which includes specific positioning of the coils, removal of the fiber cladding adjacent the coil, a metal coating on the SMP, doping the SMP with a gradient absorbing dye, tapering the fiber optic end, coating the SMP with low refractive index material, and locating an insert between the fiber optic and the coil.

Maitland, Duncan J. (Pleasant Hill, CA); Lee, Abraham P. (Walnut Creek, CA); Schumann, Daniel L. (Concord, CA); Silva, Luiz Da (Danville, CA)

2000-01-01

107

Improved delivery of polymer therapeutics to prostate tumors using plasmonic photothermal therapy  

NASA Astrophysics Data System (ADS)

When a patient is presented with locally advanced prostate cancer, it is possible to provide treatment with curative intent. However, once the disease has formed distant metastases, the chances of survival drops precipitously. For this reason, proper management of the disease while it remains localized is of critical importance. Treating these malignant cells with cytotoxic agents is effective at cell killing; however, the nonspecific toxicity profiles of these drugs often limit their use until the disease has progressed and symptom palliation is required. Incorporation of these drugs in nanocarriers such as polymers help target them to tumors with a degree of specificity, though major vascular barriers limit their effective delivery. In this dissertation, it is shown that plasmonic photothermal therapy (PPTT) can be used to help overcome some of these barriers and improve delivery to prostate tumors. First, the concept of using PPTT to improve the delivery of macromolecules to solid tumors was validated. This was done by measuring the tumor uptake of albumin. Next, the concept of targeting gold nanorods (GNRs) directly to the tumor's vasculature to better modulate vascular response to heating was tested. Surface conjugation of cyclic RGD (Arg-Gly-Asp) to GNRs improved their binding and uptake to endothelial cells in vitro, but not in vivo. Nontargeted GNRs and PPTT were then utilized to guide the location of polymer therapeutic delivery to prostate tumors. N-(2-hydroxypropyl)methacrylamide (HPMA) copolymers, which were designed to be targeted to cells previously exposed to heat shock, were used in this study. Treatment of tumors with PPTT facilitated a burst accumulation of the copolymers over 4 hours, and heat shock targeting to cells allowed them to be retained for an extended period of time. Finally, the tumor localization of the HPMA copolymers following PPTT was evaluated by magnetic resonance imaging (MRI). These results show that PPTT may be a useful tool to enhance delivery of polymeric drug carriers to locally advanced prostate tumors.

Gormley, Adam Joseph

108

Towards Therapeutic Applications of Arthropod Venom K+-Channel Blockers in CNS Neurologic Diseases Involving Memory Acquisition and Storage  

PubMed Central

Potassium channels are the most heterogeneous and widely distributed group of ion channels and play important functions in all cells, in both normal and pathological mechanisms, including learning and memory processes. Being fundamental for many diverse physiological processes, K+-channels are recognized as potential therapeutic targets in the treatment of several Central Nervous System (CNS) diseases, such as multiple sclerosis, Parkinson's and Alzheimer's diseases, schizophrenia, HIV-1-associated dementia, and epilepsy. Blockers of these channels are therefore potential candidates for the symptomatic treatment of these neuropathies, through their neurological effects. Venomous animals have evolved a wide set of toxins for prey capture and defense. These compounds, mainly peptides, act on various pharmacological targets, making them an innumerable source of ligands for answering experimental paradigms, as well as for therapeutic application. This paper provides an overview of CNS K+-channels involved in memory acquisition and storage and aims at evaluating the use of highly selective K+-channel blockers derived from arthropod venoms as potential therapeutic agents for CNS diseases involving learning and memory mechanisms. PMID:22701481

Gati, Christiano D. C.; Mortari, Márcia R.; Schwartz, Elisabeth F.

2012-01-01

109

Synthesis and Characterization of Polymer Nanocarriers for the Targeted Delivery of Therapeutic Enzymes  

PubMed Central

Protein drugs, such as recombinant enzymes useful for detoxification and replacement therapies, have extraordinary specificity and potency. However, inherently inadequate delivery to target sites and rapid inactivation limit their medical utility. Using chaperone polymeric particles designed within an injectible size range (sub-micron) may help solve these shortcomings. Such nanocarriers would (i) prevent premature inactivation of encapsulated therapeutic protein cargoes, (ii) provide a carrier that can be surface decorated by targeting ligands, and (iii) optimize sub-cellular localization of the drug. This chapter describes the techniques successfully employed for the preparation of polymer nanocarriers (PNC) loaded with the antioxidant enzyme, catalase, and targeted to endothelial cells. Methods of PNC synthesis, loading with catalase, characterization, coupling of a targeting moiety, and in vitro testing of the enzymatic and targeting activities are provided here. Advantages and disadvantages of specific designs are discussed. Due to the modular nature of the targeting methodology employed, it is believed that these protocols will provide a solid foundation for the formulation of a wide variety of enzymatic drug targeting strategies. PMID:20013177

Simone, Eric; Dziubla, Thomas; Shuvaev, Vladimir; Muzykantov, Vladimir R.

2011-01-01

110

New design strategy for reversible plasticity shape memory polymers with deformable glassy aggregates.  

PubMed

Reversible plasticity shape memory (RPSM) is a new concept in the study of shape memory performance behavior and describes a phenomenon in which shape memory polymers (SMPs) can undergo a large plastic deformation at room temperature and subsequently recover their original shape upon heating. To date, RPSM behavior has been demonstrated in only a few polymers. In the present study, we implement a new design strategy, in which deformable glassy hindered phenol (AO-80) aggregates are incorporated into an amorphous network of epoxidized natural rubber (ENR) cured with zinc diacrylate (ZDA), in order to achieve RPSM properties. We propose that AO-80 continuously tunes the glass transition temperature (Tg) and improves the chain mobility of the SMP, providing traction and anchoring the ENR chains by intermolecular hydrogen bonding interactions. The RPSM behavior of the amorphous SMPs is characterized, and the results demonstrate good fixity at large deformations (up to 300%) and excellent recovery upon heating. Large energy storage capacities at Td in these RPSM materials are demonstrated compared with those achieved at elevated temperature in traditional SMPs. Interestingly, the further revealed self-healing properties of these materials are closely related to their RPSM behavior. PMID:25389952

Lin, Tengfei; Tang, Zhenghai; Guo, Baochun

2014-12-10

111

Ordered arrays of a defect-modified ferroelectric polymer for non-volatile memory with minimized energy consumption  

NASA Astrophysics Data System (ADS)

Ferroelectric polymers are among the most promising materials for flexible electronic devices. Highly ordered arrays of the defect-modified ferroelectric polymer P(VDF-TrFE-CFE) (poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene)) are fabricated by nanoimprint lithography for nonvolatile memory application. The defective CFE units reduce the coercive field to one-fifth of that of the un-modified P(VDF-TrFE), which can help minimize the energy consumption and extend the lifespan of the device. The nanoimprint process leads to preferable orientation of polymer chains and delicately controlled distribution of the defects, and thus a bi-stable polarization that makes the memory nonvolatile, as revealed by the pulsed polarization experiment.Ferroelectric polymers are among the most promising materials for flexible electronic devices. Highly ordered arrays of the defect-modified ferroelectric polymer P(VDF-TrFE-CFE) (poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene)) are fabricated by nanoimprint lithography for nonvolatile memory application. The defective CFE units reduce the coercive field to one-fifth of that of the un-modified P(VDF-TrFE), which can help minimize the energy consumption and extend the lifespan of the device. The nanoimprint process leads to preferable orientation of polymer chains and delicately controlled distribution of the defects, and thus a bi-stable polarization that makes the memory nonvolatile, as revealed by the pulsed polarization experiment. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr03866e

Chen, Xiang-Zhong; Chen, Xin; Guo, Xu; Cui, Yu-Shuang; Shen, Qun-Dong; Ge, Hai-Xiong

2014-10-01

112

Reticulation of low density shape memory polymer foam with an in vivo demonstration of vascular occlusion.  

PubMed

Predominantly closed-cell low density shape memory polymer (SMP) foam was recently reported to be an effective aneurysm filling device in a porcine model (Rodriguez et al., Journal of Biomedical Materials Research Part A 2013: (http://dx.doi.org/10.1002/jbm.a.34782)). Because healing involves blood clotting and cell migration throughout the foam volume, a more open-cell structure may further enhance the healing response. This research sought to develop a non-destructive reticulation process for this SMP foam to disrupt the membranes between pore cells. Non-destructive mechanical reticulation was achieved using a gravity-driven floating nitinol pin array coupled with vibratory agitation of the foam and supplemental chemical etching. Reticulation resulted in a reduced elastic modulus and increased permeability, but did not impede the shape memory behavior. Reticulated foams were capable of achieving rapid vascular occlusion in an in vivo porcine model. PMID:25222869

Rodriguez, Jennifer N; Miller, Matthew W; Boyle, Anthony; Horn, John; Yang, Cheng-Kang; Wilson, Thomas S; Ortega, Jason M; Small, Ward; Nash, Landon; Skoog, Hunter; Maitland, Duncan J

2014-12-01

113

Efficient tristable resistive memory based on single layer graphene/insulating polymer multi-stacking layer  

NASA Astrophysics Data System (ADS)

Tristable resistive memories based on single layer graphene (SLG)/insulating polymer multi-stacking layer were fabricated. By using the traditional transfer method, the chemical vapor deposition-synthesized SLG serving as charging layers were combined with poly(methyl methacrylate) (PMMA) layers and polystyrene (PS) layers to form charge traps with various depth. Based on the PS/SLG/PMMA/SLG/PMMA multi-stacking layer, the devices exhibited efficient tristable memory performances. The ratios as large as 104 between different resistive states were maintained for a retention time of more than 104 s. The operation mechanisms of stepping-charging in the multi-stacking layer for the tristable resistive switching were proposed on the basis of the current-voltage analysis.

Wu, Chaoxing; Li, Fushan; Guo, Tailiang

2014-05-01

114

Temperature dependence of anisotropic diffraction in holographic polymer-dispersed liquid crystal memory.  

PubMed

Grating devices using photosensitive organic materials play an important role in the development of optical and optoelectronic systems. High diffraction efficiency and polarization dependence achieved in a holographic polymer-dispersed liquid crystal (HPDLC) grating are expected to provide polarization-controllable optical devices, such as a holographic memory for optically reconfigurable gate arrays (ORGAs). However, the optical property is affected by the thermal modulation around the transition temperature (T(ni)) where the liquid crystal (LC) changes from nematic to isotropic phases. The temperature dependence of the diffraction efficiency in HPDLC grating is investigated using four types of LC composites comprised of LCs and monomers having different physical properties such as T(ni) and anisotropic refractive indices. The holographic memory formed by the LC with low anisotropic refractive index and LC diacrylate monomer implements optical reconfiguration for ORGAs at a high temperature beyond T(ni) of LC. PMID:24085129

Ogiwara, Akifumi; Watanabe, Minoru; Moriwaki, Retsu

2013-09-10

115

Recovery torque modeling of carbon fiber reinforced shape memory polymer nanocomposites  

NASA Astrophysics Data System (ADS)

Carbon fiber and carbon nanofiber paper (CF&CNFP) can be incorporated into shape memory polymers (SMPs) to increase electrical conductivity and allow high speed electrical actuation with a low power. This paper studies the interactions among the recovery torques of CF&CNFP and SMP and the gravity torque during the shape recovery process. The proposed recovery torque model in a SMP CF&CNFP based structure is validated by experimental data obtained using a recently developed low cost, non-contact measurement testbed.

Shen, He; Xu, Yunjun; Liang, Fei; Gou, Jihua; Mabbott, Bob

2013-11-01

116

Graphite-polymer coatings for electrically induced thermal actuation of shape memory alloys  

NASA Astrophysics Data System (ADS)

Electrically conductive graphite-polymer coatings on electrically insulated nichrome wires are used as electrical resistors to heat the coating-wire assemblage. Preliminary experiments have demonstrated steady state surface temperatures of about 160 deg C. Further, the electrical power input for the coated wires is almost 1/2 that of the power input for uncoated wires. Experiments and analytical modeling indicate the power reduction is, in large part, due to reduced convective losses to the environment. This work is a first step in the development of efficient electrical resistors for shape memory alloys.

Liu, Bo; Bourdo, Shawn; Dervishi, Enkeleda; Berry, Brian; Kim, Han; Bhattacharyya, Abhijit; Viswanathan, Tito

2004-07-01

117

Feasibility study of polyurethane shape-memory polymer actuators for pressure bandage application  

NASA Astrophysics Data System (ADS)

The feasibility of laboratory-synthesized polyurethane-based shape-memory polymer (SMPU) actuators has been investigated for possible application in medical pressure bandages where gradient pressure is required between the ankle and the knee for treatment of leg ulcers. In this study, using heat as the stimulant, SMPU strip actuators have been subjected to gradual and cyclic stresses; their recovery force, reproducibility and reusability have been monitored with respect to changes in temperature and circumference of a model leg, and the stress relaxation at various temperatures has been investigated. The findings suggest that SMPU actuators can be used for the development of the next generation of pressure bandages.

Ahmad, Manzoor; Luo, Jikui; Miraftab, Mohsen

2012-02-01

118

Organic one-transistor-type nonvolatile memory gated with thin ionic liquid-polymer film for low voltage operation.  

PubMed

As one of the most emerging next-generation nonvolatile memories, one-transistor (1T)-type nonvolatile memories are of great attention due to their excellent memory performance and simple device architecture suitable for high density memory arrays. In particular, organic 1T-type memories containing both organic semiconductors and insulators are further beneficial because of their mechanical flexibility with low cost fabrication. Here, we demonstrate a new flexible organic 1T-type memory operating at low voltage. The low voltage operation of a memory less than 10 V was obtained by employing a polymer gate insulator solution blended with ionic liquid as a charge storage layer. Ionic liquid homogeneously dissolved in a thin poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) film gave rise to low voltage operation of a device due to its high capacitance. Simultaneously, stable charge trapping of either anions or cations efficiently occurred in the polymer matrix, dependent upon gate bias. Optimization of ionic liquid in PVDF-TrFE thus led to an air-stable and mechanically flexible organic 1T-type nonvolatile memory operating at programming voltage of ±7 V with large ON/OFF current margin of approximately 10(3), reliable time-dependent data retention of more than 10(4) seconds, and write/read endurance cycles of 80. PMID:25341965

Hwang, Sun Kak; Park, Tae Joon; Kim, Kang Lib; Cho, Suk Man; Jeong, Beom Jin; Park, Cheolmin

2014-11-26

119

Role of Space Charge in a Memory-Type Organic Photoreceptor Coated on an Organic Polymer Electrode  

Microsoft Academic Search

Role of photo-generated space charges on the memory effect, observed in an iodine-doped conductive polymer\\/poly(N-vinylcarbazole) (PVK)-trinitrofluorenone (TNF) double-layered system, was investigated by means off voltage-current measurements. The results were consistent with the previous conclusion obtained by the xerographic technique. The memory effect was found to come from space charges formed at the electrode-photoreceptor interface containing iodine. The space charge formation

Yusuke Nakazawa; Katsuyoshi Hoshino; Jun-ichi Hanna; Hiroshi Kokado

1991-01-01

120

Electroactive polymer and shape memory alloy actuators in biomimetics and humanoids  

NASA Astrophysics Data System (ADS)

There is a strong need to replicate natural muscles with artificial materials as the structure and function of natural muscle is optimum for articulation. Particularly, the cylindrical shape of natural muscle fiber and its interconnected structure promote the critical investigation of artificial muscles geometry and implementation in the design phase of certain platforms. Biomimetic robots and Humanoid Robot heads with Facial Expressions (HRwFE) are some of the typical platforms that can be used to study the geometrical effects of artificial muscles. It has been shown that electroactive polymer and shape memory alloy artificial muscles and their composites are some of the candidate materials that may replicate natural muscles and showed great promise for biomimetics and humanoid robots. The application of these materials to these systems reveals the challenges and associated technologies that need to be developed in parallel. This paper will focus on the computer aided design (CAD) models of conductive polymer and shape memory alloys in various biomimetic systems and Humanoid Robot with Facial Expressions (HRwFE). The design of these systems will be presented in a comparative manner primarily focusing on three critical parameters: the stress, the strain and the geometry of the artificial muscle.

Tadesse, Yonas

2013-04-01

121

Self-healing nanocomposite using shape memory polymer and carbon nanotubes  

NASA Astrophysics Data System (ADS)

Carbon fiber reinforced composites are used in a wide range of applications in aerospace, mechanical, and civil structures. Due to the nature of material, most damage in composites, such as delaminations, are always barely visible to the naked eye, which makes it difficult to detect and repair. The investigation of biological systems has inspired the development and characterization of self-healing composites. This paper presents the development of a new type of self-healing material in order to impede damage progression and conduct in-situ damage repair in composite structures. Carbon nanotubes, which are highly conductive materials, are mixed with shape memory polymer to develop self-healing capability. The developed polymeric material is applied to carbon fiber reinforced composites to automatically heal the delamination between different layers. The carbon fiber reinforced composite laminates are manufactured using high pressure molding techniques. Tensile loading is applied to double cantilever beam specimens using an MTS hydraulic test frame. A direct current power source is used to generate heat within the damaged area. The application of thermal energy leads to re-crosslinking in shape memory polymers. Experimental results showed that the developed composite materials are capable of healing the matrix cracks and delaminations in the bonded areas of the test specimens. The developed self-healing material has the potential to be used as a novel structural material in mechanical, civil, aerospace applications.

Liu, Yingtao; Rajadas, Abhishek; Chattopadhyay, Aditi

2013-04-01

122

Polymer (PTFE) and shape memory alloy (NiTi) intercalated nano-biocomposites  

NASA Astrophysics Data System (ADS)

Engineering on a nano-scale has been undertaken to mimic a biomaterial by forming an intercalated nano-composite structure by PVD sputtering of a polymer with a nickel-titanium (NiTi) shape memory alloy (SMA). A PTFE polymer has been selected due to its elastic properties, low interactions with water, optimum surface energies, stability and chemical resistance. NiTi SMAs allow the coatings to be energy absorbent and thus suitable in load bearing situations. The coatings are aimed to constantly withstand variable adverse biological environments whilst maintaining their characteristics. The nano-intercalated structures have been characterised for their wettability, friction coefficients, chemical composition, and morphology. Intercalation of a polymer with energy-absorbing alloys uncovers a set of material systems that will offer characteristics such as self-healing of hierarchal tissue in the body. The reformation of PTFE following sputter deposition was confirmed by FTIR spectra. According to SEM analysis PTFE shows a promising surface interaction with NiTi, forming stable coatings. Surface interactions are evident by the hydrophobic behaviour of films as the composite's water contact angle is around 86° which lies in-between that of PTFE and NiTi. The nano composite films are lubricious and have a measured CoF below 0.2 which does not vary with layer thickness.

Anjum, S. S.; Rao, J.; Nicholls, J. R.

2012-09-01

123

Study on the activation of styrene-based shape memory polymer by medium-infrared laser light  

SciTech Connect

This paper demonstrates the feasibility of shape memory polymer (SMP) activation by medium-infrared laser light. Medium-infrared light is transmitted by an optical fiber embedded in the SMP matrix, and the shape recovery process and temperature distribution are recorded by an infrared camera. Light-induced SMP exhibits potential applications in biomedicines and flexible displays.

Leng Jinsong; Yu Kai; Lan Xin [Center for Composite Materials and Structures, Harbin Institute of Technology, HeiLongJiang 150001 (China); Zhang Dawei [Center for Composite Materials and Structures, Harbin Institute of Technology, HeiLongJiang 150001 (China); Material Science and Engineering College, Northeast Forestry University, HeiLongJiang 150040 (China); Liu Yanju [Department of Astronautical Science and Mechanics, Harbin Institute of Technology, HeiLongJiang 150001 (China)

2010-03-15

124

A Shape Memory Polymer Dialysis Needle Adapter for the Reduction of Hemodynamic Stress within Arteriovenous Grafts  

SciTech Connect

A deployable, shape memory polymer adapter is investigated for reducing the hemodynamic stress caused by a dialysis needle flow within an arteriovenous graft. Computational fluid dynamics simulations of dialysis sessions with and without the adapter demonstrate that the adapter provides a significant decrease in the wall shear stress. In vitro flow visualization measurements are made within a graft model following delivery and actuation of a prototype shape memory polymer adapter. Vascular access complications resulting from arteriovenous (AV) graft failures account for over $1 billion per year in the health care costs of dialysis patients in the U.S.[1] The primary mode of failure of arteriovenous fistulas (AVF's) and polytetrafluoroethylene (PTFE) grafts is the development of intimal hyperplasia (IH) and the subsequent formation of stenotic lesions, resulting in a graft flow decline. The hemodynamic stresses arising within AVF's and PTFE grafts play an important role in the pathogenesis of IH. Studies have shown that vascular damage can occur in regions where there is flow separation, oscillation, or extreme values of wall shear stress (WSS).[2] Nevaril et al.[3] show that exposure of red blood cells to WSS's on the order of 1500 dynes/cm2 can result in hemolysis. Hemodynamic stress from dialysis needle flow has recently been investigated for the role it plays in graft failure. Using laser Doppler velocimetry measurements, Unnikrishnan et al.[4] show that turbulence intensities are 5-6 times greater in the AV flow when the needle flow is present and that increased levels of turbulence exist for approximately 7-8cm downstream of the needle. Since the AVF or PTFE graft is exposed to these high levels of hemodynamic stress several hours each week during dialysis sessions, it is quite possible that needle flow is an important contributor to vascular access occlusion.[4] We present a method for reducing the hemodynamic stress in an AV graft by tailoring the fluid dynamics of the dialysis needle flow using a deployable shape memory polymer (SMP) dialysis needle adapter. Such an adapter is deployed through the needle into the graft where it is actuated into an expanded shape using thermal energy. The expanded adapter has a tube-like shape, in which the distal end has a larger cross-sectional area than that of the needle. When the dialysis session is completed, the adapter is retracted through the needle. In this initial study, we conduct computational fluid dynamics (CFD) simulations to assess the changes in the hemodynamic stress on a graft wall when the SMP adapter is utilized. Additionally, we fabricate a prototype SMP adapter and deploy it in an in vitro model of an AV graft.

Ortega, J M; Small, W; Wilson, T S; Benett, W; Loge, J; Maitland, D J

2006-08-16

125

Coarse-grained simulation of molecular mechanisms of recovery in thermally activated shape-memory polymers  

NASA Astrophysics Data System (ADS)

Thermally actuated shape-memory polymers (SMPs) are capable of being programmed into a temporary shape and then recovering their permanent reference shape upon exposure to heat, which facilitates a phase transition that allows dramatic increase in molecular mobility. Experimental, analytical, and computational studies have established empirical relations of the thermomechanical behavior of SMPs that have been instrumental in device design. However, the underlying mechanisms of the recovery behavior and dependence on polymer microstructure remain to be fully understood for copolymer systems. This presents an opportunity for bottom-up studies through molecular modeling; however, the limited time-scales of atomistic simulations prohibit the study of key performance metrics pertaining to recovery. In order to elucidate the effects of phase fraction, recovery temperature, and deformation temperature on shape recovery, here we investigate the shape-memory behavior in a copolymer model with coarse-grained potentials using a two-phase molecular model that reproduces physical crosslinking. Our simulation protocol allows observation of upwards of 90% strain recovery in some cases, at time-scales that are on the order of the timescale of the relevant relaxation mechanism (stress relaxation in the unentangled soft-phase). Partial disintegration of the glassy phase during mechanical deformation is found to contribute to irrecoverable strain. Temperature dependence of the recovery indicates nearly full elastic recovery above the trigger temperature, which is near the glass-transition temperature of the rubbery switching matrix. We find that the trigger temperature is also directly correlated with the deformation temperature, indicating that deformation temperature influences the recovery temperatures required to obtain a given amount of shape recovery, until the plateau regions overlap above the transition region. Increasing the fraction of glassy phase results in higher strain recovery at low to intermediate temperatures, a widening of the transition region, and an eventual crossover at high temperatures. Our results corroborate experimental findings on shape-memory behavior and provide new insight into factors governing deformation recovery that can be leveraged in biomaterials design. The established computational methodology can be extended in straightforward ways to investigate the effects of monomer chemistry, low-molecular-weight solvents, physical and chemical crosslinking, different phase-separation morphologies, and more complicated mechanical deformation toward predictive modeling capabilities for stimuli-responsive polymers.

Abberton, Brendan C.; Liu, Wing Kam; Keten, Sinan

2013-12-01

126

Synergic effect of carbon black and short carbon fiber on shape memory polymer actuation by electricity  

NASA Astrophysics Data System (ADS)

This paper presents a study on the effect of carbon black (CB) and short carbon fibers (SCFs) on shape memory polymer (SMP) actuation by applying electric current. The coexistence of CB and SCF electrically conductive networks, supporting each other, resulting in significant improvement of electrical properties, was supported by optical microscopy, while the roles of particulate and fibrous fillers were distinguished by scanning electron microscopy. In sequence, the volume resistivity curves of one filler systems and two fillers systems were figured out and compared. Moreover, experimental results substantiated that the actuation voltage of two-filler SMP composites' shape recovery was prominently lower in comparison with that of one-filler systems at the same filler content. Additional, the response of glass transition temperature (Tg) and thermomechanical properties to filler content and two fillers' synergic effect were characterized and illuminated experimentally.

Leng, Jinsong; Lv, Haibao; Liu, Yanju; Du, Shanyi

2008-11-01

127

Fabrication and Characterization of Cylindrical Light Diffusers Comprised of Shape Memory Polymer  

SciTech Connect

We have developed a technique for constructing light diffusing devices comprised of a flexible shape memory polymer (SMP) cylindrical diffuser attached to the tip of an optical fiber. Devices were fabricated by casting an SMP rod over the cleaved tip of an optical fiber and media blasting the SMP rod to create a light diffusing surface. The axial and polar emission profiles and circumferential (azimuthal) uniformity were characterized for various blasting pressures, nozzle-to-sample distances, and nozzle translation speeds. The diffusers were generally strongly forward-directed and consistently withstood over 8 W of incident infrared laser light without suffering damage when immersed in water. These devices are suitable for various endoluminal and interstitial biomedical applications.

Small IV, W; Buckley, P R; Wilson, T S; Loge, J M; Maitland, K D; Maitland, D J

2007-01-29

128

Thermomechanical Properties, Collapse Pressure, and Expansion of Shape Memory Polymer Neurovascular Stent Prototypes  

PubMed Central

Shape memory polymer stent prototypes were fabricated from thermoplastic polyurethane. Commercial stents are generally made of stainless steel or other alloys. These alloys are too stiff and prevent most stent designs from being able to navigate small and tortuous vessels to reach intracranial lesions. A solid tubular model and a high flexibility laser etched model are presented. The stents were tested for collapse in a pressure chamber. At 37°C, the full collapse pressure was comparable to that of commercially available stents, and higher than the estimated maximum pressure exerted by intracranial arteries. However, there is a potential for onset of collapse, which needs further study. The stents were crimped and expanded, the laser-etched stent showed full recovery with an expansion ratio of 2.7 and a 1% axial shortening. PMID:19107804

Baer, Géraldine M.; Wilson, Thomas S.; Small, Ward; Hartman, Jonathan; Benett, William J.; Matthews, Dennis L.; Maitland, Duncan J.

2011-01-01

129

A constitutive theory for shape memory polymers: coupling of small and large deformation  

NASA Astrophysics Data System (ADS)

At high temperatures, SMPs share attributes like rubber and exhibit long-range reversibility. In contrast, at low temperatures they become very rigid and are susceptible to plastic, only small strains are allowable. But there relatively little literature has considered the unique small stain (rubber phase) and large stain (glass phase) coupling in SMPs when developing the constitutive modeling. In this work, we present a 3D constitutive model for shape memory polymers in both low temperature small strain regime and high temperature large strain regime. The theory is based on the work of Liu et al. [15]. Four steps of SMP's thermomechanical loadings cycle are considered in the constitutive model completely. The linear elastic and hyperelastic effects of SMP in different temperatures are also fully accounted for in the proposed model by adopt the neo-Hookean model and the Generalized Hooke's laws.

Tan, Qiao; Liu, Liwu; Liu, Yanju; Leng, Jinsong; Yan, Xiangqiao; Wang, Haifang

2013-04-01

130

Laser Chemosensor with Rapid Responsivity and Inherent Memory Based on a Polymer of Intrinsic Microporosity  

PubMed Central

This work explores the use of a polymer of intrinsic microporosity (PIM-1) as the active layer within a laser sensor to detect nitroaromatic-based explosive vapors. We show successful detection of dinitrobenzene (DNB) by monitoring the real-time photoluminescence. We also show that PIM-1 has an inherent memory, so that it accumulates the analyte during exposure. In addition, the optical gain and refractive index of the polymer were studied by amplified spontaneous emission and variable-angle ellipsometry, respectively. A second-order distributed feedback PIM-1 laser sensor was fabricated and found to show an increase in laser threshold of 2.5 times and a reduction of the laser slope efficiency by 4.4 times after a 5-min exposure to the DNB vapor. For pumping at 2 times threshold, the lasing action was stopped within 30 s indicating that PIM-1 has a very fast responsivity and as such has a potential sensing ability for ultra-low-concentration explosives. PMID:22163750

Wang, Yue; McKeown, Neil B.; Msayib, Kadhum J.; Turnbull, Graham A.; Samuel, Ifor D. W.

2011-01-01

131

An approach to predict the shape-memory behavior of amorphous polymers from Dynamic Mechanical Analysis (DMA) data  

NASA Astrophysics Data System (ADS)

The prediction of shape-memory behavior is essential regarding the design of a smart material for different applications. This paper proposes a simple and quick method for the prediction of shape-memory behavior of amorphous shape memory polymers (SMPs) on the basis of a single dynamic mechanical analysis (DMA) temperature sweep at constant frequency. All the parameters of the constitutive equations for linear viscoelasticity are obtained by fitting the DMA curves. The change with the temperature of the time-temperature superposition shift factor ( a T ) is expressed by the Williams-Landel-Ferry (WLF) model near and above the glass transition temperature ( T g ), and by the Arrhenius law below T g . The constants of the WLF and Arrhenius equations can also be determined. The results of our calculations agree satisfactorily with the experimental free recovery curves from shape-memory tests.

Kuki, Ákos; Czifrák, Katalin; Karger-Kocsis, József; Zsuga, Miklós; Kéki, Sándor

2015-02-01

132

Demonstration of a multiscale modeling technique: prediction of the stress-strain response of light activated shape memory polymers  

NASA Astrophysics Data System (ADS)

Presented is a multiscale modeling method applied to light activated shape memory polymers (LASMPs). LASMPs are a new class of shape memory polymer (SMPs) being developed for adaptive structures applications where a thermal stimulus is undesirable. LASMP developmental emphasis is placed on optical manipulation of Young's modulus. A multiscale modeling approach is employed to anticipate the soft and hard state moduli solely on the basis of a proposed molecular formulation. Employing such a model shows promise for expediting down-selection of favorable formulations for synthesis and testing, and subsequently accelerating LASMP development. An empirical adaptation of the model is also presented which has applications in system design once a formulation has been identified. The approach employs rotational isomeric state theory to build a molecular scale model of the polymer chain yielding a list of distances between the predicted crosslink locations, or r-values. The r-values are then fitted with Johnson probability density functions and used with Boltzmann statistical mechanics to predict stress as a function of the strain of the phantom polymer network. Empirical adaptation for design adds junction constraint theory to the modeling process. Junction constraint theory includes the effects of neighboring chain interactions. Empirical fitting results in numerically accurate Young's modulus predictions. The system is modular in nature and thus lends itself well to being adapted to other polymer systems and development applications.

Beblo, Richard V.; Mauck Weiland, Lisa

2010-09-01

133

Inorganic-organic shape memory polymers and foams for bone defect repairs  

NASA Astrophysics Data System (ADS)

The ultimate goal of this research was to develop a "self-fitting" shape memory polymer (SMP) scaffold for the repair of craniomaxillofacial (CMF) bone defects. CMF defects may be caused by trauma, tumor removal or congenital abnormalities and represent a major class of bone defects. Their repair with autografts is limited by availability, donor site morbidity and complex surgical procedures. In addition, shaping and positioning of these rigid grafts into irregular defects is difficult. Herein, we have developed SMP scaffolds which soften at T > ˜56 °C, allowing them to conformally fit into a bone defect. Upon cooling to body temperature, the scaffold becomes rigid and mechanically locks in place. This research was comprised of four major studies. In the first study, photocrosslinkable acrylated (AcO) SMP macromers containing a poly(epsilon-caprolactone) (PCL) segment and polydimethylsiloxane (PDMS) segments were synthesized with the general formula: AcO-PCL40-block-PDMS m-block-PCL40-OAc. By varying the PDMS segment length (m), solid SMPs with highly tunable mechanical properties and excellent shape memory abilities were prepared. In the second study, porous SMP scaffolds were fabricated based on AcO-PCL 40-block-PDMS37-block-PCL 40-OAc via a revised solvent casting particulate leaching (SCPL) method. By tailoring scaffold parameters including salt fusion, macromer concentration and salt size, scaffold properties (e.g. pore features, compressive modulus and shape memory behavior) were tuned. In the third study, porous SMP scaffolds were produced from macromers with variable PDMS segment lengths (m = 0 -- 130) via an optimized SCPL method. The impact on pore features, thermal, mechanical, and shape memory properties as well as degradation rates were investigated. In the final study, a bioactive polydopamine coating was applied onto pore surfaces of the SMP scaffold prepared from PCL diacrylate. The thin coating did not affect intrinsic bulk properties of the scaffold. However, the coating significantly increased its bioactivity, giving rise to the formation of "bone-bonding" hydroxyapatite (HAp) when exposed to simulated body fluid (SBF). It was also shown that the coating largely enhanced the scaffold's capacities to support osteoblasts adhesion, proliferation and osteogenesis. Thus, the polydopamine coating should enhance the performance of the "self-fitting" SMP scaffolds for the repair of bone defects.

Zhang, Dawei

134

Lipid-polymer hybrid nanoparticles as a new generation therapeutic delivery platform: a review.  

PubMed

Lipid-polymer hybrid nanoparticles (LPNs) are core-shell nanoparticle structures comprising polymer cores and lipid/lipid-PEG shells, which exhibit complementary characteristics of both polymeric nanoparticles and liposomes, particularly in terms of their physical stability and biocompatibility. Significantly, the LPNs have recently been demonstrated to exhibit superior in vivo cellular delivery efficacy compared to that obtained from polymeric nanoparticles and liposomes. Since their inception, the LPNs have advanced significantly in terms of their preparation strategy and scope of applications. Their preparation strategy has undergone a shift from the conceptually simple two-step method, involving preformed polymeric nanoparticles and lipid vesicles, to the more principally complex, yet easier to perform, one-step method, relying on simultaneous self-assembly of the lipid and polymer, which has resulted in better products and higher production throughput. The scope of LPNs' applications has also been extended beyond single drug delivery for anticancer therapy, to include combinatorial and active targeted drug deliveries, and deliveries of genetic materials, vaccines, and diagnostic imaging agents. This review details the current state of development for the LPNs preparation and applications from which we identify future research works needed to bring the LPNs closer to its clinical realization. PMID:23872180

Hadinoto, Kunn; Sundaresan, Ajitha; Cheow, Wean Sin

2013-11-01

135

Polymer-Based Therapeutics: Nanoassemblies and Nanoparticles for Management of Atherosclerosis  

PubMed Central

Coronary arterial disease, one of the leading causes of adult mortality, is triggered by atherosclerosis. A disease with complex etiology, atherosclerosis results from the progressive long-term combination of atherogenesis, the accumulation of modified lipoproteins within blood vessel walls, along with vascular and systemic inflammatory processes. The management of atherosclerosis is challenged by the localized flare-up of several multipronged signaling interactions between activated monocytes, atherogenic macrophages and inflamed or dysfunctional endothelial cells. A new generation of approaches is now emerging founded on multifocal, targeted therapies that seek to reverse or ameliorate the athero-inflammatory cascade within the vascular intima. This article reviews the various classes and primary examples of bioactive configurations of nanoscale assemblies. Of specific interest are polymer-based or polymer-lipid micellar assemblies designed as multimodal receptor-targeted blockers or drug carriers whose activity can be tuned by variations in polymer hydrophobicity, charge, and architecture. Also reviewed are emerging reports on multifunctional nanoassemblies and nanoparticles for improved circulation and enhanced targeting to athero-inflammatory lesions and atherosclerotic plaques. PMID:21523920

Lewis, Daniel R.; Kamisoglu, Kubra; York, Adam; Moghe, Prabhas V.

2012-01-01

136

Development of a liver-targeted siRNA delivery platform with a broad therapeutic window utilizing biodegradable polypeptide-based polymer conjugates.  

PubMed

The greatest challenge standing in the way of effective in vivo siRNA delivery is creating a delivery vehicle that mediates a high degree of efficacy with a broad therapeutic window. Key structure-activity relationships of a poly(amide) polymer conjugate siRNA delivery platform were explored to discover the optimized polymer parameters that yield the highest activity of mRNA knockdown in the liver. At the same time, the poly(amide) backbone of the polymers allowed for the metabolism and clearance of the polymer from the body very quickly, which was established using radiolabeled polymers to demonstrate the time course of biodistribution and excretion from the body. The fast degradation and clearance of the polymers provided for very low toxicity at efficacious doses, and the therapeutic window of this poly(amide)-based siRNA delivery platform was shown to be much broader than a comparable polymer platform. The results of this work illustrate that the poly(amide) platform has a promising future in the development of a siRNA-based drug approved for human use. PMID:24657948

Barrett, Stephanie E; Burke, Rob S; Abrams, Marc T; Bason, Carol; Busuek, Marina; Carlini, Edward; Carr, Brian A; Crocker, Louis S; Fan, Haihong; Garbaccio, Robert M; Guidry, Erin N; Heo, Jun H; Howell, Bonnie J; Kemp, Eric A; Kowtoniuk, Robert A; Latham, Andrew H; Leone, Anthony M; Lyman, Michael; Parmar, Rubina G; Patel, Mihir; Pechenov, Sergey Y; Pei, Tao; Pudvah, Nicole T; Raab, Conrad; Riley, Sean; Sepp-Lorenzino, Laura; Smith, Sheri; Soli, Eric D; Staskiewicz, Steven; Stern, Melissa; Truong, Quang; Vavrek, Marissa; Waldman, Jacob H; Walsh, Eileen S; Williams, J Michael; Young, Stephanie; Colletti, Steven L

2014-06-10

137

Fabrication and static characterization of carbon-fiber-reinforced polymers with embedded NiTi shape memory wire actuators  

Microsoft Academic Search

In this work, unidirectional carbon-fiber-reinforced polymers (CFRP) with embedded NiTi shape memory alloy (SMA) wire actuators were manufactured using a universal testing machine equipped with a thermally controlled chamber. Beam specimens containing cold-worked, annealed and trained NiTi SMA wires distributed along their neutral plane were fabricated. Several tests in a three-point bending mode at different constant temperatures were performed. To

C J de Araújo; L F A Rodrigues; J F Coutinho Neto; R P B Reis

2008-01-01

138

Improved adhesion between nickel–titanium shape memory alloy and a polymer matrix via silane coupling agents  

Microsoft Academic Search

NiTi wires were functionalized with silane coupling agents to improve interfacial adhesion between the inorganic constituent and a host matrix for composite applications. Surface derivatization was characterized by X-ray Photoelectron Spectroscopy, and mechanical pullout tests were performed to quantify the increase in adhesion between the NiTi shape memory alloy wires and polymer matrix. Improvements of roughly 100% in the adhesion

N. A. Smith; G. G. Antoun; A. B. Ellis; W. C. Crone

2004-01-01

139

Demonstrating the importance of polymer-conjugate conformation in solution on its therapeutic output: Diethylstilbestrol (DES)-polyacetals as prostate cancer treatment.  

PubMed

The design of improved polymeric carriers to be used in the next generation of polymer therapeutics is an ongoing challenge. Biodegradable systems present potential advantages regarding safety benefit apart from the possibility to use higher molecular weight (Mw) carriers allowing PK optimization, by exploiting the enhanced permeability and retention (EPR)-mediated tumor targeting. Within this context, we previously designed pH-responsive polyacetalic systems, tert-polymers, where a drug with the adequate diol-functionality was incorporated within the polymer mainchain. The synthetic, non-steroidal estrogen, diethylstilboestrol (DES) clinically used for the treatment of advanced prostate cancer was chosen as drug. In order to improve the properties of this tert-polymer, novel polyacetalic systems as block-co-polymers, with more defined structure have been obtained. This second generation polyacetals allowed higher drug capacity than the tert-polymer, a biphasic DES release profile at acidic pH and due to its controlled amphiphilic character readily formed micelle-like structures in solution. These features result in an enhancement of conjugate therapeutic value in selected prostate cancer cell models. Exhaustive physico-chemical characterization focusing on nanoconjugate solution behavior and using advanced techniques, such as, pulsed-gradient spin-echo NMR (PGSE-NMR) and small-angle neutron scattering (SANS), has been carried out in order to demonstrate this hypothesis. Clear evidence of significantly different conformation in solution has been obtained for both polyacetals. These results demonstrate that an adequate control on molecular or supramolecular conformation in solution with polymer therapeutics is crucial in order to achieve the desired therapeutic output. PMID:22230343

Giménez, Vanessa; James, Craig; Armiñán, Ana; Schweins, Ralf; Paul, Alison; Vicent, María J

2012-04-30

140

Strong electroactive biodegradable shape memory polymer networks based on star-shaped polylactide and aniline trimer for bone tissue engineering.  

PubMed

Preparation of functional shape memory polymer (SMP) for tissue engineering remains a challenge. Here the synthesis of strong electroactive shape memory polymer (ESMP) networks based on star-shaped polylactide (PLA) and aniline trimer (AT) is reported. Six-armed PLAs with various chain lengths were chemically cross-linked to synthesize SMP. After addition of an electroactive AT segment into the SMP, ESMP was obtained. The polymers were characterized by (1)H NMR, GPC, FT-IR, CV, DSC, DMA, tensile test, and degradation test. The SMP and ESMP exhibited strong mechanical properties (modulus higher than GPa) and excellent shape memory performance: short recovery time (several seconds), high recovery ratio (over 94%), and high fixity ratio (almost 100%). Moreover, cyclic voltammetry test confirmed the electroactivity of the ESMP. The ESMP significantly enhanced the proliferation of C2C12 cells compared to SMP and linear PLA (control). In addition, the ESMP greatly improved the osteogenic differentiation of C2C12 myoblast cells compared to PH10 and PLA in terms of ALP enzyme activity, immunofluorescence staining, and relative gene expression by quantitative real-time polymerase chain reaction (qRT-PCR). These intelligent SMPs and electroactive SMP with strong mechanical properties, tunable degradability, good electroactivity, biocompatibility, and enhanced osteogenic differentiation of C2C12 cells show great potential for bone regeneration. PMID:25742188

Xie, Meihua; Wang, Ling; Ge, Juan; Guo, Baolin; Ma, Peter X

2015-04-01

141

Invading target cells: multifunctional polymer conjugates as therapeutic nucleic acid carriers  

Microsoft Academic Search

Polymer-based conjugates are an interesting option and challenge for the design of nano-sized drug-delivery systems, as they\\u000a require advanced conjugation chemistry and precise engineering. In the case of nucleic acid therapy, non-viral carriers face\\u000a several biological barriers during the delivery process, namely 1) protection of the cargo from extracellular degradation,\\u000a 2) avoidance of non-specific interactions with non-targeted tissues, 3) efficient

Ulrich Lächelt; Ernst Wagner

2011-01-01

142

Fabrication and In Vitro Deployment of a Laser-Activated Shape Memory Polymer Vascular Stent  

SciTech Connect

Vascular stents are small tubular scaffolds used in the treatment of arterial stenosis (narrowing of the vessel). Most vascular stents are metallic and are deployed either by balloon expansion or by self-expansion. A shape memory polymer (SMP) stent may enhance flexibility, compliance, and drug elution compared to its current metallic counterparts. The purpose of this study was to describe the fabrication of a laser-activated SMP stent and demonstrate photothermal expansion of the stent in an in vitro artery model. A novel SMP stent was fabricated from thermoplastic polyurethane. A solid SMP tube formed by dip coating a stainless steel pin was laser-etched to create the mesh pattern of the finished stent. The stent was crimped over a fiber-optic cylindrical light diffuser coupled to an infrared diode laser. Photothermal actuation of the stent was performed in a water-filled mock artery. At a physiological flow rate, the stent did not fully expand at the maximum laser power (8.6 W) due to convective cooling. However, under zero flow, simulating the technique of endovascular flow occlusion, complete laser actuation was achieved in the mock artery at a laser power of {approx}8 W. We have shown the design and fabrication of an SMP stent and a means of light delivery for photothermal actuation. Though further studies are required to optimize the device and assess thermal tissue damage, photothermal actuation of the SMP stent was demonstrated.

Baer, G M; Small IV, W; Wilson, T S; Benett, W J; Matthews, D L; Hartman, J; Maitland, D J

2007-04-25

143

Thermomechanical properties of polyurethane shape memory polymer–experiment and modelling  

NASA Astrophysics Data System (ADS)

In this paper extensive research on the polyurethane shape memory polymer (PU-SMP) is reported, including its structure analysis, our experimental investigation of its thermomechanical properties and its modelling. The influence of the effects of thermomechanical couplings on the SMP behaviour during tension at room temperature is studied using a fast and sensitive infrared camera. It is shown that the thermomechanical behaviour of the SMP significantly depends on the strain rate: at a higher strain rate higher stress and temperature values are obtained. This indicates that an increase of the strain rate leads to activation of different deformation mechanisms at the micro-scale, along with reorientation and alignment of the molecular chains. Furthermore, influence of temperature on the SMP’s mechanical behaviour is studied. It is observed during the loading in a thermal chamber that at the temperature 20 °C below the glass transition temperature (Tg) the PU-SMP strengthens about six times compared to the material above Tg but does not exhibit the shape recovery. A finite-strain constitutive model is formulated, where the SMP is described as a two-phase material composed of a hyperelastic rubbery phase and elastic-viscoplastic glassy phase. The volume content of phases is governed by the current temperature. Finally, model predictions are compared with the experimental results.

Pieczyska, E. A.; Maj, M.; Kowalczyk-Gajewska, K.; Staszczak, M.; Gradys, A.; Majewski, M.; Cristea, M.; Tobushi, H.; Hayashi, S.

2015-04-01

144

Opacification of Shape Memory Polymer Foam Designed for Treatment of Intracranial Aneurysms  

PubMed Central

Shape memory polymer (SMP) foam possesses structural and mechanical characteristics that make them very promising as an alternative treatment for intracranial aneurysms. Our SMP foams have low densities, with porosities as high as 98.8%; favorable for catheter delivery and aneurysm filling, but unfavorable for attenuating X-rays. This lack of contrast impedes the progression of this material becoming a viable medical device. This paper reports on increasing radioopacity by incorporating a high-Z element, tungsten particulate filler to attenuate X-rays, while conserving similar physical properties of the original non-opacified SMP foams. The minimal amount of tungsten for visibility was determined and subsequently incorporated into SMP foams, which were then fabricated into samples of increasing thicknesses. These samples were imaged through a pig’s skull to demonstrate radio-opacity in situ. Quantification of the increase in image contrast was performed via image processing methods and standard curves were made for varying concentrations of tungsten doped solid and foam SMP. 4% by volume loading of tungsten incorporated into our SMP foams has proven to be an effective method for improving radio-opacity of this material while maintaining the mechanical, physical and chemical properties of the original formulation. PMID:22101759

Rodriguez, Jennifer N.; Yu, Ya-Jen; Miller, Matthew W.; Wilson, Thomas S.; Hartman, Jonathan; Clubb, Fred J.; Gentry, Brandon; Maitland, Duncan J.

2012-01-01

145

Facile 3D Metal Electrode Fabrication for Energy Applications via Inkjet Printing and Shape Memory Polymer  

NASA Astrophysics Data System (ADS)

This paper reports on a simple 3D metal electrode fabrication technique via inkjet printing onto a thermally contracting shape memory polymer (SMP) substrate. Inkjet printing allows for the direct patterning of structures from metal nanoparticle bearing liquid inks. After deposition, these inks require thermal curing steps to render a stable conductive film. By printing onto a SMP substrate, the metal nanoparticle ink can be cured and substrate shrunk simultaneously to create 3D metal microstructures, forming a large surface area topology well suited for energy applications. Polystyrene SMP shrinkage was characterized in a laboratory oven from 150-240°C, resulting in a size reduction of 1.97-2.58. Silver nanoparticle ink was patterned into electrodes, shrunk, and the topology characterized using scanning electron microscopy. Zinc-Silver Oxide microbatteries were fabricated to demonstrate the 3D electrodes compared to planar references. Characterization was performed using 10M potassium hydroxide electrolyte solution doped with zinc oxide (57g/L). After a 300s oxidation at 3Vdc, the 3D electrode battery demonstrated a 125% increased capacity over the reference cell. Reference cells degraded with longer oxidations, but the 3D electrodes were fully oxidized for 4 hours, and exhibited a capacity of 5.5mA-hr/cm2 with stable metal performance.

Roberts, R. C.; Wu, J.; Hau, N. Y.; Chang, Y. H.; Feng, S. P.; Li, D. C.

2014-11-01

146

Shape memory polymers and their composites in aerospace applications: a review  

NASA Astrophysics Data System (ADS)

As a new class of smart materials, shape memory polymers and their composites (SMPs and SMPCs) can respond to specific external stimulus and remember the original shape. There are many types of stimulus methods to actuate the deformation of SMPs and SMPCs, of which the thermal- and electro-responsive components and structures are common. In this review, the general mechanism of SMPs and SMPCs are first introduced, the stimulus methods are then discussed to demonstrate the shape recovery effect, and finally, the applications of SMPs and SMPCs that are reinforced with fiber materials in aerospace are reviewed. SMPC hinges and booms are discussed in the part on components; the booms can be divided again into foldable SMPC truss booms, coilable SMPC truss booms and storable tubular extendible member (STEM) booms. In terms of SMPC structures, the solar array and deployable panel, reflector antenna and morphing wing are introduced in detail. Considering the factors of weight, recovery force and shock effect, SMPCs are expected to have great potential applications in aerospace.

Liu, Yanju; Du, Haiyang; Liu, Liwu; Leng, Jinsong

2014-02-01

147

Electro-induced shape-memory polymer nanocomposite containing conductive particles and short fibers  

NASA Astrophysics Data System (ADS)

This present paper is focused on the effect of conductive particulate and fibrous fillers on the characterized property of styrene-based shape memory polymer incorporating carbon black (CB) and short carbon fiber (SCF). It was shown that the particulate additives are dispersed homogeneously within matrix and served as interconnections between the fibers, while the fibrous additives may be considered as a rigid long aggregate of carbon, leading to easy formation of continuous conductive networks. The glass transition temperature of nanocomposites drops sharply as compared with that of pure SMP from the differential scanning calorimetry (DSC). For the composite containing 5 wt% CB and 2 wt% SCF, the storage modulus increases by 16.2% compared to that of the composite containing 5 wt% CB and 1 wt% SCF; the peak of tangent delta curve is an alternative definition of T g, thus T g defined in such a way is determined as 69.44°C from Dynamic Mechanical Analyzer (DMA) test which is higher than 25.78°C obtained from DSC test. The electrical conductivity of the composite achieves 3 S/cm by four-point Van De Pauw method, and the shape recovery can be activated with a constant voltage of 25 V through them.

Lv, Haibao; Leng, Jinsong; Du, Shanyi

2008-03-01

148

Modelling of loading, stress relaxation and stress recovery in a shape memory polymer.  

PubMed

A multi-element constitutive model for a lactide-based shape memory polymer has been developed that represents loading to large tensile deformations, stress relaxation and stress recovery at 60, 65 and 70°C. The model consists of parallel Maxwell arms each comprising neo-Hookean and Eyring elements. Guiu-Pratt analysis of the stress relaxation curves yields Eyring parameters. When these parameters are used to define the Eyring process in a single Maxwell arm, the resulting model yields at too low a stress, but gives good predictions for longer times. Stress dip tests show a very stiff response on unloading by a small strain decrement. This would create an unrealistically high stress on loading to large strain if it were modelled by an elastic element. Instead it is modelled by an Eyring process operating via a flow rule that introduces strain hardening after yield. When this process is incorporated into a second parallel Maxwell arm, there results a model that fully represents both stress relaxation and stress dip tests at 60°C. At higher temperatures a third arm is required for valid predictions. PMID:24878964

Sweeney, J; Bonner, M; Ward, I M

2014-09-01

149

Shape recovery performances of a deployable hinge fabricated by fiber-reinforced shape-memory polymer  

NASA Astrophysics Data System (ADS)

A new type of fiber reinforced thermoset styrene-based shape-memory polymer composite (SMPC) is developed and analyzed. The main objective is to systematically characterize the shape recovery properties of SMPC, which is a foundation for SMPC used in deployable structures. Firstly, the deployment dynamics of cured SMPC shell is presented. Then, the shape recovery performance is investigated by finite element analysis (FEA). The deployment process of curved SMPC shell (from 0-180 degree) is simulated by the geometrically nonlinear analysis. The deployment moment increases with the increase of the thickness of curved shell, and the strain show somewhat uniform in the central part of the curved shell. Furthermore, a hinge made of SMPC is fabricated, which consists of two curved SMPC shells in opposite directs. The deployment of hinge can be achieved in about100s by applying a 20V voltage. The deployment ratio approaches approximate 100 %. Finally the deployment of a prototype of solar array actuated by the hinge is demonstrated.

Lan, Xin; Wang, Xiaohua; Lu, Haibao; Liu, Yanju; Leng, Jinsong

2009-03-01

150

Structural design of flexible Au electrode to enable shape memory polymer for electrical actuation  

NASA Astrophysics Data System (ADS)

An effective resistive Joule heating approach was conducted to improve the electrical actuation and shape-recovery performance of a shape memory polymer (SMP) nanocomposite. Two types of gold (Au) film patterns were deposited to be used as electrodes to drive thermal-responsive SMPs and achieve a uniform temperature distribution during electro-activated shape recovery. Furthermore, the sensing capability of the Au electrode to both mechanical and thermal stimuli applied to the SMP nanocomposite was experimentally investigated and theoretically analyzed. It was found that the change in the electrical resistance of the Au electrode could be used as an indication of shape-recovery performance. The linear response of the electrical resistance to strain was identified mainly due to the opening/closing of microcracks and their propagations in the Au electrodes during out-of-plane deformations. With an increment of thermomechanical bending cycles, the electrical resistance was increased exponentially, but it returned back to the original reading when the SMP nanocomposite returned back to its permanent shape. Finally, the flexible Au electrode enabled the actuation of the SMP nanocomposite under an electric voltage of 13.4 V, with an improved shape-recovery performance and temperature distribution.

Lu, Haibao; Lei, Ming; Zhao, Chao; Xu, Ben; Leng, Jinsong; Fu, Y. Q.

2015-04-01

151

[Therapeutic case of general paresis manifested by bradykinesia and recent memory loss].  

PubMed

We reported a 32-year-old man with general paresis. He showed slowly progressive bradykinesia and recent memory loss. Argyll Robertson pupils were not present. Muscle strength and sensations were normal except for slight vibratory disturbance. Tendon reflexes were slightly exaggerated. MMSE, HDS-R and WAIS-R scores showed the intellectual impairment. His laboratory investigations revealed elevated both TPHA and FTA-ABS titers in the serum and the CSF. The CSF contained leukocytosis (25/mm3) and protein 80 mg/dl. Cranial CT and MRI demonstrated diffuse cortical atrophy. SPECT revealed marked reduction of the blood flow in bilateral cerebral hemisphere. Cerebral angiography revealed moderate stenosis of the major vessels. The diagnosis of neurosyphilis (general paresis) was made and the treatment of intravenous benzyl penicillin potassium 24 million units per day was started. After 6 weeks of the treatment, the clinical signs (includes MMSE, HDS-R and WAIS-R scores) and the findings of SPECT and cerebral angiography showed improvement. Although the cell count and protein in the CSF became decreased, the titers of TPHA and FTA-ABS in the serum and the CSF were not decreased. Neurosyphilis should always be considered in a etiologically unknown case with bradykinesia and dementia. PMID:10614161

Iwasaki, Y; Sakakibara, Y; Sone, M; Kato, T; Yoshida, E; Indo, T

1999-09-01

152

Tumor cells and memory T cells converge at glycolysis: therapeutic implications.  

PubMed

In the immune system, activation of naïve T (Tn) cells into effector T cells (Teff) involves a metabolic switch to glycolysis to promote rapid proliferation and differentiation. In the October issue of The Journal of Clinical Investigation, Sukumar et al. have demonstrated that in CD8(+) memory T (Tems) cells glycolytic phenotype contributes to the shortened lifespan of Tems. Conversely, inhibition of glycolysis in Tems not only extended their viability but also augmented desirable properties. Notably, they also demonstrate that glycolytic inhibition during the ex vivo clonal expansion of tumor-specific Tems enhanced their antitumor function. Overall, the data suggest that an antiglycolytic strategy targeting the Tems could enhance antitumor immune response. On the other hand, cancer cells have long been known to exhibit metabolic reprogramming which involves a shift toward glycolysis (the conversion of glucose into lactate) to facilitate uninterrupted growth. Interestingly, antiglycolytic treatment of cancer cells has been known to trigger antitumor immune response as well. Taken together, it is probable that a strategy involving concurrent inhibition of glycolysis in tumor cells and Tems could promote a dual attack on cancer by inducing an effective antitumor immune response and an immunogenic chemotherapy. PMID:24556820

Karthikeyan, Swathi; Geschwind, Jean-Francois; Ganapathy-Kanniappan, Shanmugasundaram

2014-05-01

153

Therapeutic Vaccination Expands and Improves the Function of the HIV-Specific Memory T-Cell Repertoire  

PubMed Central

Background.?The licensing of herpes zoster vaccine has demonstrated that therapeutic vaccination can help control chronic viral infection. Unfortunately, human trials of immunodeficiency virus (HIV) vaccine have shown only marginal efficacy. Methods.?In this double-blind study, 17 HIV-infected individuals with viral loads of <50 copies/mL and CD4+ T-cell counts of >350 cells/µL were randomly assigned to the vaccine or placebo arm. Vaccine recipients received 3 intramuscular injections of HIV DNA (4 mg) coding for clade B Gag, Pol, and Nef and clade A, B, and C Env, followed by a replication-deficient adenovirus type 5 boost (1010 particle units) encoding all DNA vaccine antigens except Nef. Humoral, total T-cell, and CD8+ cytotoxic T-lymphocyte (CTL) responses were studied before and after vaccination. Single-copy viral loads and frequencies of latently infected CD4+ T cells were determined. Results.?Vaccination was safe and well tolerated. Significantly stronger HIV-specific T-cell responses against Gag, Pol, and Env, with increased polyfunctionality and a broadened epitope-specific CTL repertoire, were observed after vaccination. No changes in single-copy viral load or the frequency of latent infection were observed. Conclusions.?Vaccination of individuals with existing HIV-specific immunity improved the magnitude, breadth, and polyfunctionality of HIV-specific memory T-cell responses but did not impact markers of viral control. Clinical Trials Registration.?NCT00270465 PMID:23482645

Casazza, Joseph P.; Bowman, Kathryn A.; Adzaku, Selorm; Smith, Emily C.; Enama, Mary E.; Bailer, Robert T.; Price, David A.; Gostick, Emma; Gordon, Ingelise J.; Ambrozak, David R.; Nason, Martha C.; Roederer, Mario; Andrews, Charla A.; Maldarelli, Frank M.; Wiegand, Ann; Kearney, Mary F.; Persaud, Deborah; Ziemniak, Carrie; Gottardo, Raphael; Ledgerwood, Julie E.; Graham, Barney S.; Koup, Richard A.

2013-01-01

154

Porous media properties of reticulated shape memory polymer foams and mock embolic coils for aneurysm treatment  

PubMed Central

Background Shape memory polymer (SMP) foams are being investigated as an alternative aneurysm treatment method to embolic coils. The goal of both techniques is the reduction of blood flow into the aneurysm and the subsequent formation of a stable thrombus, which prevents future aneurysm rupture. The purpose of this study is to experimentally determine the parameters, permeability and form factor, which are related to the flow resistance imposed by both media when subjected to a pressure gradient. Methods The porous media properties—permeability and form factor—of SMP foams and mock embolic coils (MECs) were measured with a pressure gradient method by means of an in vitro closed flow loop. We implemented the Forchheimer-Hazen-Dupuit-Darcy equation to calculate these properties. Mechanically-reticulated SMP foams were fabricated with average cell sizes of 0.7E-3 and 1.1E-3 m, while the MECs were arranged with volumetric packing densities of 11-28%. Results The permeability of the SMP foams was an order of magnitude lower than that of the MECs. The form factor differed by up to two orders of magnitude and was higher for the SMP foams in all cases. The maximum flow rate of all samples tested was within the inertial laminar flow regime, with Reynolds numbers ranging between 1 and 35. Conclusions The SMP foams impose a greater resistance to fluid flow compared to MECs, which is a result of increased viscous and inertial losses. These results suggest that aneurysms treated with SMP foam will have flow conditions more favorable for blood stasis than those treated with embolic coils having packing densities???28%. PMID:24120254

2013-01-01

155

Electrical switching and memory behaviors in organic diodes based on polymer blend films treated by ultraviolet ozone  

NASA Astrophysics Data System (ADS)

Resistive memory devices with resistive switching characteristics were fabricated based on poly (3,4-ethylene-dioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) doping with polyvinyl alcohol. It has been demonstrated that the resistive switching characteristics in the memory device was strongly dependent on the treatment of the polymer blend film by ultraviolet ozone (UV-ozone). The UV-ozone treated device exhibited improved performance with the ON/OFF current ratio of more than 102, and its ON and OFF states can be maintained over 96 h without deterioration. The resistive switching behavior in the UV-ozone treated device was attributed to the formation and rupture of the PEDOT:PSS filaments as well as the narrow conducting paths through the native oxide of aluminum.

Huang, Jinying; Ma, Dongge

2014-09-01

156

A phenomenological model for simulating the chemo-responsive shape memory effect in polymers undergoing a permeation transition  

NASA Astrophysics Data System (ADS)

We present a phenomenological model for studying the constitutive relations and working mechanism of the chemo-responsive shape memory effect (SME) in shape memory polymers (SMPs). On the basis of the solubility parameter equation, diffusion model and permeation transition model, a phenomenological model is derived for quantitatively identifying the influential factors in the chemically induced SME in SMPs. After this, a permeability parallel model and series model are implemented in order to couple the constitutive relations of the permeability coefficient, stress and relaxation time as a function of stretch, separately. The inductive effect of the permeability transition on the transition temperature is confirmed as the driving force for the chemo-responsive SME. Furthermore, the analytical result from the phenomenological model is compared with the available experimental results and the simulation of a semi-empirical model reported in the literature for verification.

Lu, Haibao; Huang, Wei Min; Leng, Jinsong

2014-04-01

157

Production of bioinspired and rationally designed polymer hydrogels for controlled delivery of therapeutic proteins  

NASA Astrophysics Data System (ADS)

Hydrogel systems for controlled delivery therapeutic growth factors have been developed in a wide spectrum of strategies: these systems aim for the release of growth factors via a passive diffusion, electrostatic interaction, degradation of hydrogels, and responsiveness to external stimuli. Heparin, a highly sulfated glycosaminoglycan (GAG), was employed for a targeted delivery system of vascular endothelial growth factor (VEGF) to endothelial cells overexpressing a relevant receptor VEGFR-2. Addition of dimeric VEGF to 4-arm star-shaped poly(ethylene glycol) (PEG) immobilized with low-molecular weight heparin (LMWH) afforded a non-covalently assembled hydrogel via interaction between heparin and VEGF, with storage modulus 10 Pa. The release of VEGF and hydrogel erosion reached maximum 100 % at day 4 in the presence of VEGFR-2 overexpressing pocine aortic endothelial cell (PAE/KDR), while those of 80% were achieved via passive release at day 5 in the presence of PAE cell lacking VEGFR-2 or in the absence of cell, indicating that the release of VEGF was in targeted manner toward cell receptor. The proliferation of PAE/KDR in the presence of [PEG-LMWH/VEGF] hydrogel was greater by ca. 30% at day 4 compared to that of PAE, confirming that the release of VEGF was in response to the cellular demand. The phosphorylation fraction of VEGFR-2 on PAE/KDR was greater in the presence of [PEG-LMWH/VEGF] hydrogel, increasing from 0.568 at day 1 to 0.790 at day 4, whereas it was maintained at 0.230 at day 4 in the presence of [PEG-LMWH] hydrogel. This study has proven that this hydrogel, assembled via bio-inspired non-covalent interaction, liberating VEGFon celluar demand to target cell, eroding upon VEGF release, and triggering endothelial cell proliferation, could be used in multiple applications including targeted delivery and angiogenesis. Heparin has been widely exploited in growth factor delivery systems owing to its ability to bind many growth factors through the flexible patterns of functional groups. However, heterogeneity in the composition and in the polydispersity of heparin has been problematic in controlled delivery system and thus motivated the development of homogeneous heparin mimics. Peptides of appropriate sequence and chemical function have therefore recently emerged as potential replacements for heparin in select applications. Studied was the assessment of the binding affinities of multiple sulfated peptides (SPs) for a set of heparin-binding peptides (HBPs) and for VEGF; these binding partners have application in the selective immobilization of proteins and in hydrogel formation through non-covalent interactions. Sulfated peptides were produced via solid-phase methods, and their affinity for the HBPs and VEGF was assessed via affinity liquid chromatography (ALC), surface plasmon resonance (SPR), and in select cases, isothermal titration calorimetry (ITC). The shortest peptide, SPa, showed the highest affinity binding of HBPs and VEGF165 in both ALC and SPR measurements, with slight exceptions. Of the investigated HBPs, a peptide based on the heparin-binding domain of human platelet factor 4 showed greatest binding affinities toward all of the SPs, consistent with its stronger binding to heparin. The affinity between SPa and PF4ZIP was indicated via SPR ( KD = 5.27 muM) and confirmed via ITC (KD = 8.09 muM). The binding by SPa of both VEGF and HBPs suggests its use as a binding partner to multiple species, and the use of these interactions in assembly of materials. Given that the peptide sequences can be varied to control binding affinity and selectivity, opportunities are also suggested for the production of a wider array of matrices with selective binding and release properties useful for biomaterials applications. Hydrogel consisting of SPa was formed via a covalent Michael Addition reaction between maleimide- and thiol-terminated multi-arm PEGs and Cys-SPa. The mechanical property of hydrogel was tunable from ca. 186 to 1940 Pa. by varing the cross-linking density, suggesting its flexible applications depending

Kim, Sung Hye

158

Nonvolatile organic thin film transistor memory devices based on hybrid nanocomposites of semiconducting polymers: gold nanoparticles.  

PubMed

We report the facile fabrication and characteristics of organic thin film transistor (OTFT)-based nonvolatile memory devices using the hybrid nanocomposites of semiconducting poly(9,9-dioctylfluorene-alt-bithiophene) (F8T2) and ligand-capped Au nanoparticles (NPs), thereby serving as a charge storage medium. Electrical bias sweep/excitation effectively modulates the current response of hybrid memory devices through the charge transfer between F8T2 channel and functionalized Au NPs trapping sites. The electrical performance of the hybrid memory devices can be effectively controlled though the loading concentrations (0-9 %) of Au NPs and organic thiolate ligands on Au NP surfaces with different carbon chain lengths (Au-L6, Au-L10, and Au-L18). The memory window induced by voltage sweep is considerably increased by the high content of Au NPs or short carbon chain on the ligand. The hybrid nanocomposite of F8T2:9% Au-L6 provides the OTFT memories with a memory window of ~41 V operated at ± 30 V and memory ratio of ~1 × 10(3) maintained for 1 × 10(4) s. The experimental results suggest that the hybrid materials of the functionalized Au NPs in F8T2 matrix have the potential applications for low voltage-driven high performance nonvolatile memory devices. PMID:24224739

Chang, Hsuan-Chun; Liu, Cheng-Liang; Chen, Wen-Chang

2013-12-26

159

Memory device applications of a conjugated polymer: Role of space charges  

Microsoft Academic Search

Conjugated polymers have been used in data-storage devices. A ``state'' has been written by applying a voltage pulse. The state of the device has been ``read'' from the current under a small probe voltage (0.2 V). The polymer retained the state for more than 1 h which can be refreshed or erased at will. The stored space charges under a

Himadri S. Majumdar; Anirban Bandyopadhyay; Alberto Bolognesi; Amlan J. Pal

2002-01-01

160

Memory device applications of a conjugated polymer: Role of space charges  

Microsoft Academic Search

Conjugated polymers have been used in data-storage devices. A “state” has been written by applying a voltage pulse. The state of the device has been “read” from the current under a small probe voltage (0.2 V). The polymer retained the state for more than 1 h which can be refreshed or erased at will. The stored space charges under a

Himadri S. Majumdar; Anirban Bandyopadhyay; Alberto Bolognesi; Amlan J. Pal

2002-01-01

161

Thermomechanical and shape-memory properties of epoxy-based shape-memory polymer using diglycidyl ether of ethoxylated bisphenol-A  

NASA Astrophysics Data System (ADS)

A series of epoxy-based shape-memory polymers (SMPs) was prepared by using diglycidyl ether of ethoxylated bisphenol-A containing two oxyethylene units and the curing agents iso-phorone diamine and Jeffamine D230. The thermal properties, dynamic mechanical properties, mechanical properties and shape-memory properties of the epoxy-based SMPs were systematically studied by DSC, DMTA, universal tester and fold-deploy experiments, respectively. The results showed that as the content of D230 increased, the glass transition temperature of the SMPs decreased from 77.5 ± 1.1 to 40 ± 0.7?°C according to DSC, the rubber modulus decreased gradually according to DMTA, and the tensile strength at room temperature (RT) decreased from 58.5 ± 0.3 to 27.0 ± 3.3 MPa according to tensile tests. Tensile tests above RT showed that the tensile stress and elongation at break depended heavily on the experimental temperature, and fold-deploy experiments showed that these SMPs had shape retention ratios higher than 95% and shape recovery ratios close to 100%.

Fan, Mengjin; Yu, Heng; Li, Xiangyuan; Cheng, Jue; Zhang, Junying

2013-05-01

162

Microfabricated therapeutic actuators  

DOEpatents

Microfabricated therapeutic actuators are fabricated using a shape memory polymer (SMP), a polyurethane-based material that undergoes a phase transformation at a specified temperature (Tg). At a temperature above temperature Tg material is soft and can be easily reshaped into another configuration. As the temperature is lowered below temperature Tg the new shape is fixed and locked in as long as the material stays below temperature Tg. Upon reheating the material to a temperature above Tg, the material will return to its original shape. By the use of such SMP material, SMP microtubing can be used as a release actuator for the delivery of embolic coils through catheters into aneurysms, for example. The microtubing can be manufactured in various sizes and the phase change temperature Tg is determinate for an intended temperature target and intended use. 8 figs.

Lee, A.P.; Northrup, M.A.; Ciarlo, D.R.; Krulevitch, P.A.; Benett, W.J.

1999-06-15

163

Microfabricated therapeutic actuators  

DOEpatents

Microfabricated therapeutic actuators are fabricated using a shape memory polymer (SMP), a polyurethane-based material that undergoes a phase transformation at a specified temperature (Tg). At a temperature above temperature Tg material is soft and can be easily reshaped into another configuration. As the temperature is lowered below temperature Tg the new shape is fixed and locked in as long as the material stays below temperature Tg. Upon reheating the material to a temperature above Tg, the material will return to its original shape. By the use of such SMP material, SMP microtubing can be used as a release actuator for the delivery of embolic coils through catheters into aneurysms, for example. The microtubing can be manufactured in various sizes and the phase change temperature Tg is determinate for an intended temperature target and intended use.

Lee, Abraham P. (Walnut Creek, CA); Northrup, M. Allen (Berkeley, CA); Ciarlo, Dino R. (Livermore, CA); Krulevitch, Peter A. (Pleasanton, CA); Benett, William J. (Livermore, CA)

1999-01-01

164

Polymers.  

ERIC Educational Resources Information Center

Presents an open-ended experiment which has students exploring polymer chemistry and reverse osmosis. This activity involves construction of a polymer membrane, use of it in a simple osmosis experiment, and application of its principles in solving a science-technology-society problem. (ML)

Tucker, David C.

1986-01-01

165

Memories.  

ERIC Educational Resources Information Center

This theme issue of the journal "Exploring" covers the topic of "memories" and describes an exhibition at San Francisco's Exploratorium that ran from May 22, 1998 through January 1999 and that contained over 40 hands-on exhibits, demonstrations, artworks, images, sounds, smells, and tastes that demonstrated and depicted the biological,…

Brand, Judith, Ed.

1998-01-01

166

ZnO-based nonvolatile memory thin-film transistors with polymer dielectric/ferroelectric double gate insulators  

NASA Astrophysics Data System (ADS)

The authors report on the fabrication of a top-gate ZnO thin-film transistor (TFT) with a polymer dielectric/ferroelectric double-layer gate insulator that was formed on patterned ZnO through a sequential spin-casting process of 450-nm-thick poly-4-vinylphenol (PVP) and 200-nm-thick poly(vinylidene fluoride/trifluoroethylene) [P(VDF/TrFE)]. Compared to the single P(VDF/TrFE) layer, double layer shows remarkably reduced leakage current with the aid of the PVP buffer. TFT with the PVP/P(VDF/TrFE) double layer exhibits a field effect mobility of 0.36cm2/V and a large memory hysteresis in the transfer characteristics due to the ferroelectric P(VDF/TrFE). The retention of the device lasted over 2h.

Noh, Seok Hwan; Choi, Wonjun; Oh, Min Suk; Hwang, D. K.; Lee, Kimoon; Im, Seongil; Jang, Sungjin; Kim, Eugene

2007-06-01

167

Spatial profile of charge storage in organic field-effect transistor nonvolatile memory using polymer electret  

NASA Astrophysics Data System (ADS)

Spatial profile of the charge storage in the pentacene-based field-effect transistor nonvolatile memories using poly(2-vinyl naphthalene) electret is probed. The electron trapping into the electret after programming can be space dependent with more electron storage in the region closer to the contacts, and reducing the channel length is an effective approach to improve the memory performance. The deficient electron supply in pentacene is proposed to be responsible for the inhomogeneous electron storage in the electret. The hole trapping into the electret after erasing is spatially homogeneous, arising from the sufficient hole accumulation in the pentacene channel.

She, Xiao-Jian; Liu, Jie; Zhang, Jing-Yu; Gao, Xu; Wang, Sui-Dong

2013-09-01

168

Biobased poly(propylene sebacate) as shape memory polymer with tunable switching temperature for potential biomedical applications.  

PubMed

From the point of better biocompatibility and sustainability, biobased shape memory polymers (SMPs) are highly desired. We used 1,3-propanediol, sebacic acid, and itaconic acid, which have been industrially produced via fermentation or extraction with large quantities as the main raw materials for the synthesis of biobased poly(propylene sebacate). Diethylene glycol was used to tailor the flexibility of the polyester. The resulted polyesters were found to be promising SMPs with excellent shape recovery and fixity (near 100% and independent of thermomechanical cycles). The switching temperature and recovery speed of the SMPs are tunable by controlling the composition of the polyesters and their curing extent. The continuously changed switching temperature ranging from 12 to 54 °C was realized. Such temperature range is typical for biomedical applications in the human body. The molecular and crystalline structures were explored to correlate to the shape memory behavior. The combination of potential biocompatibility and biodegradability of the biobased SMPs makes them suitable for fabricating biomedical devices. PMID:21381645

Guo, Baochun; Chen, Yongwen; Lei, Yanda; Zhang, Liqun; Zhou, Wen You; Rabie, A Bakr M; Zhao, Jianqing

2011-04-11

169

Improving the electrical conductivity by forming Ni powder chains in a shape-memory polymer filled with carbon black  

NASA Astrophysics Data System (ADS)

We demonstrate a simple approach to significantly reduce the electrical resistivity of thermo-responsive shape-memory polymers (SMPs), so that they can be easily triggered for shape recovery by Joule heating at a low electrical voltage. After adding a small amount of Ni micro particles into a polyurethane SMP filled with carbon black (CB), the electrical resistivity is slightly reduced. However, if these Ni particles are aligned into chains (by applying a low magnetic field on SMP/CB/Ni solution and then drying to fix the conductive chains), the drop of electrical resistivity is significant. This kind of SMP composites is suitable for cyclic operation as only micro/nano particles are used. A sample (40×15×1mm) with 10vol% of CB and 0.5vol% of chained Ni can be heated to 80°C for shape recovery at 30 V (1.2 W) of power. This approach is generic and applicable for producing other conductive polymers.

Lan, Xin; Huang, Wei Min; Liu, Na; Phee, Sy; Leng, Jin Song; Du, Shan Yi

2008-03-01

170

Radiation-crosslinking of shape memory polymers based on poly(vinyl alcohol) in the presence of carbon nanotubes  

NASA Astrophysics Data System (ADS)

Shape memory polymers based on poly(vinyl alcohol) (SM-PVA) in the presence of 2-carboxyethyl acrylate oligomers (CEA) and multi-wall carbon nanotubes (MWCNTs) crosslinked by ionizing radiation were investigated. Chemical-crosslinking of PVA by glutaraldehyde in the presence of CEA and MWCNTs was also studied. The swelling and gel fraction of the radiation-crosslinked SM-PVA and chemically crosslinked systems were evaluated. Analysis of the swelling and gel fraction revealed a significant reduction in swelling and an increase in the gel fraction of the material that was chemically crosslinked with glutaraldehyde. The radiation-crosslinked SM-PVA demonstrated 100% gelation at an irradiation dose of 50 kGy. In addition, radiation-crosslinked SM-PVA exhibited good temperature responsive shape-memory behavior. A scanning electron microscopy (SEM) analysis was performed. The thermal properties of radiation-crosslinked SM-PVA were investigated by a thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). The ability of the material to return or store energy (E?), to its ability to lose energy (E?), and the ratio of these effects (Tan?), which is called damping were examined via DMA. The temperature of Tan? in the radiation-crosslinked SM-PVA decreased significantly by 6 and 13 °C as a result of the addition of MWCNTs. In addition, the temperature of Tan? for SM-PVA increased as the irradiation dose increased. These radiation-crosslinked SM-PVA materials show promising shape-memory behavior based on the range of temperatures at which Tan? appears.

Basfar, A. A.; Lotfy, S.

2015-01-01

171

A Shape Memory Polymer with Improved Shape Recovery* Changdeng Liu1  

E-print Network

's thermal conductivity with the heat transfer time, , also defined as a shape memory induction time the heat transfer progress. A mathematical was worked out that quantitatively relates the material for most SMPs involve the transfer of heat from an external source to the SMP. Compared with its cousin

Mather, Patrick T.

172

Are herbal compounds the next frontier for alleviating learning and memory impairments? An integrative look at memory, dementia and the promising therapeutics of traditional chinese medicines.  

PubMed

Recent advances in neuroscience have revealed a greater, in-depth understanding of the complexities associated with memory. Contemporary theories hold that an integral relationship between memory formation, stabilization and consolidation revolve around plasticity of neuronal networks. The associated requisite receptors ?-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) and N-methyl-d-aspartate (NMDA) and cellular mechanisms surrounding plasticity (posed to incite molecular functionality), also display strong correlations in the pathogenesis of dementias. When the brain is in a diseased state as a result of malignant neurotransmission (i.e. in Alzheimer's disease; AD), the homeostatic balance required for normal neuronal processes is disrupted, which leads to degeneration of neural circuitry. Present efforts to find new treatments aimed at reversing or halting neurodegeneration are immense, with increasing attention being placed on investigating various herbal medicines. A wide variety of herbal plants (i.e. Panax ginseng, Polygala tenuifolia, Acorus gramineus and Huperzia serrata, examined here within), extracts and compounds have, to date, already presented advantageous results when tested against known pathogenic markers related to AD-associated dementia. The efficaciousness of herbal medicines appears to be a modulatory effect on neurotrophins, kinases and their substrates that, in turn, initiate or take part in intracellular cascades related to memory processes. PMID:21305632

Jesky, Robert; Hailong, Chen

2011-08-01

173

Spider-silk-like shape memory polymer fiber for vibration damping  

NASA Astrophysics Data System (ADS)

In this study, the static and dynamic properties of shape memory polyurethane (SMPU) fiber are reported and compared to those of spider dragline silk. Although the polymeric fiber has a lower strength compared to spider dragline silks (0.2–0.3 GPa versus 1.1 GPa), it possesses much higher toughness (276–289 MJ m?3 versus 160 MJ m?3), due to its excellent extensibility. The dynamic mechanical tests reveal that SMPU fiber has a high damping capacity (tan ? = 0.10–0.35) which is comparable to or even higher than that of spider silks (tan ? = 0.15). In addition, we found that, different programming methods change the shape memory and damping properties of the fiber in different ways and cold-drawing programming is more advocated in structural applications. These results suggest that the SMPU fiber has similar vibration damping and mechanical properties as spider silk, and may find applications in lightweight engineering structures.

Yang, Qianxi; Li, Guoqiang

2014-10-01

174

Polymers  

NSDL National Science Digital Library

This page contains two documents explaining ring and cross link polymers. The topic is covered at an advanced level in relation to nanotechnology and requires background knowledge in eight grade science. A powerpoint with illustrations and instructor guide (available as both a Microsoft Word Document and PDF) containing activities are included to aid in teaching this subject.

175

Memory effect in a junction-like CdS nanocomposite/conducting polymer poly[2-methoxy-5-(2-ethylhexyloxy)1,4-phenylene-vinylene] heterostructure.  

PubMed

The operation of a nonvolatile memory device is demonstrated using junction-like CdS nanocomposites embedded in a polymer matrix. The capacitance-voltage characteristics of Al/conducting polymer poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylene-vinylene]/CdS nanocomposites in a polyvinyl alcohol matrix/indium tin oxide device exhibit hysteresis, which is attributed to the trapping, storage, and emission of holes in the quantized valence band energy levels of isolated CdS nanoneedles. The characteristics at different operating frequencies show that the hysteresis is due to trapping of charge carriers in CdS nanocomposites rather than in the interfacial states. The memory behavior in the inorganic/organic heterostructure is explained on the basis of a simple energy band diagram. PMID:21730573

Mondal, S P; Reddy, V S; Das, S; Dhar, A; Ray, S K

2008-05-28

176

Vapor-phase testing of the memory-effects in benzene- and toluene-imprinted polymers conditioned at elevated temperature.  

PubMed

The preparation of polymers imprinted with common aromatic solvents such as benzene and toluene is an under-exploited subject of research. The present study was aimed at the understanding of whether true solvent memory effects can be achieved by molecular imprinting, as well as if they are stable at elevated temperature. A set of copolymers, comprising low and high cross-linking levels, was prepared from four different combinations of functional monomer and cross-linker, namely methacrylic acid (MAA)/ethylene glycol dimethacrylate (EGDMA), methyl methacrylate (MMA)/EGDMA, MAA/divinyl benzene (DVB) and MMA/DVB. Each possible combination was prepared separately in benzene, toluene and acetonitrile. The obtained materials were applied as coatings onto nickel-titanium (Ni-Ti) alloy wires which were incorporated into solid-phase microextraction devices and finally tested for their ability to competitively adsorb vapors from the headspace of an aqueous solution containing a few volatile organic compounds. Porosity analysis showed that, regardless of the solvent used, only a high cross-linking level permitted the preparation of mesoporous copolymers (BJH radius typically in the range 13-15 nm), a requirement for providing accessibility to the targeted nanoscale-imprinted cavities. A noticeable exception was, however, observed for the MMA/DVB copolymers which exhibited much diminished BJH radius. The porosity data correlated well with the extraction profiles found, which suggested the presence of benzene-imprinted sites in all the highly cross-linked copolymers prepared in benzene, except for the MMA/DVB copolymers. Concerning the effect of an elevated conditioning temperature on the memory-effects created by the imprinting process, the results were clearly indicative that the tested copolymers, including the more robust highly cross-linked ones, are not suitable for high temperature applications such as solid-phase microextraction coupled to gas chromatography. PMID:24176503

Azenha, Manuel; Schillinger, Eric; Sanmartin, Esther; Regueiras, M Teresa; Silva, Fernando; Sellergren, Börje

2013-11-13

177

The effect of free radical inhibitor on the sensitized radiation crosslinking and thermal processing stabilization of polyurethane shape memory polymers.  

PubMed

The effects of free radical inhibitor on the electron beam crosslinking and thermal processing stabilization of novel radiation crosslinkable polyurethane shape memory polymers (SMPs) blended with acrylic radiation sensitizers have been determined. The SMPs in this study possess novel processing capabilities-that is, the ability to be melt processed into complex geometries as thermoplastics and crosslinked in a secondary step using electron beam irradiation. To increase susceptibility to radiation crosslinking, the radiation sensitizer pentaerythritol triacrylate (PETA) was solution blended with thermoplastic polyurethane SMPs made from 2-butene-1,4-diol and trimethylhexamethylene diisocyanate (TMHDI). Because thermoplastic melt processing methods such as injection molding are often carried out at elevated temperatures, sensitizer thermal instability is a major processing concern. Free radical inhibitor can be added to provide thermal stabilization; however, inhibitor can also undesirably inhibit radiation crosslinking. In this study, we quantified both the thermal stabilization and radiation crosslinking inhibition effects of the inhibitor 1,4-benzoquinone (BQ) on polyurethane SMPs blended with PETA. Sol/gel analysis of irradiated samples showed that the inhibitor had little to no inverse effects on gel fraction at concentrations of 0-10,000 ppm, and dynamic mechanical analysis showed only a slight negative correlation between BQ composition and rubbery modulus. The 1,4-benzoquinone was also highly effective in thermally stabilizing the acrylic sensitizers. The polymer blends could be heated to 150°C for up to five hours or to 125°C for up to 24 hours if stabilized with 10,000 ppm BQ and could also be heated to 125°C for up to 5 hours if stabilized with 1000 ppm BQ without sensitizer reaction occurring. We believe this study provides significant insight into methods for manipulation of the competing mechanisms of radiation crosslinking and thermal stabilization of radiation sensitizers, thereby facilitating further development of radiation crosslinkable thermoplastic SMPs. PMID:23226930

Hearon, Keith; Smith, Sarah E; Maher, Cameron A; Wilson, Thomas S; Maitland, Duncan J

2013-02-01

178

The effect of free radical inhibitor on the sensitized radiation crosslinking and thermal processing stabilization of polyurethane shape memory polymers  

PubMed Central

The effects of free radical inhibitor on the electron beam crosslinking and thermal processing stabilization of novel radiation crosslinkable polyurethane shape memory polymers (SMPs) blended with acrylic radiation sensitizers have been determined. The SMPs in this study possess novel processing capabilities—that is, the ability to be melt processed into complex geometries as thermoplastics and crosslinked in a secondary step using electron beam irradiation. To increase susceptibility to radiation crosslinking, the radiation sensitizer pentaerythritol triacrylate (PETA) was solution blended with thermoplastic polyurethane SMPs made from 2-butene-1,4-diol and trimethylhexamethylene diisocyanate (TMHDI). Because thermoplastic melt processing methods such as injection molding are often carried out at elevated temperatures, sensitizer thermal instability is a major processing concern. Free radical inhibitor can be added to provide thermal stabilization; however, inhibitor can also undesirably inhibit radiation crosslinking. In this study, we quantified both the thermal stabilization and radiation crosslinking inhibition effects of the inhibitor 1,4-benzoquinone (BQ) on polyurethane SMPs blended with PETA. Sol/gel analysis of irradiated samples showed that the inhibitor had little to no inverse effects on gel fraction at concentrations of 0-10,000 ppm, and dynamic mechanical analysis showed only a slight negative correlation between BQ composition and rubbery modulus. The 1,4-benzoquinone was also highly effective in thermally stabilizing the acrylic sensitizers. The polymer blends could be heated to 150°C for up to five hours or to 125°C for up to 24 hours if stabilized with 10,000 ppm BQ and could also be heated to 125°C for up to 5 hours if stabilized with 1000 ppm BQ without sensitizer reaction occurring. We believe this study provides significant insight into methods for manipulation of the competing mechanisms of radiation crosslinking and thermal stabilization of radiation sensitizers, thereby facilitating further development of radiation crosslinkable thermoplastic SMPs. PMID:23226930

Hearon, Keith; Smith, Sarah E.; Maher, Cameron A.; Wilson, Thomas S.; Maitland, Duncan J.

2012-01-01

179

Anti-corrosive properties of an electropolymerized polymer coating on a shape memory alloy surface  

SciTech Connect

Acrylonitrile electropolymerization (in an aprotic and anhydrous medium) has been used as a way to build thin, homogeneous and covering polyacrylonitrile layers grafted on the surface of usual metals and specially on copper-based shape memory alloy: Cu-Zn-Al. The results of the study first confirm the possibility of grafting thin and covering polyacrylonitrile layers on Cu-Zn-Al surface. The morphology of the films however is influenced by the geometry of the polycristalline structure of the alloy and its superficial defects. Samples obtained after grafting polyacrylonitrile films were submitted to corrosion tests based on Electrochemical Impedance Spectroscopy (EIS) measurements in a NaCl/H{sub 2}O medium. Results show that some post-treatments of the grafted films are necessary to improve their protective role, while preserving the strong interfacial bondings. Actually, thermal and mechanical cycling of the shape memory alloy covered by electropolymerized polyacrylonitrile show that the adhesion of the film is better than for simply dipped films, and thus show the relevance of grafting. {copyright} {ital 1996 American Institute of Physics.}

de Cayeux, S. [CEA-DSM/DRECAM/SRSIM, 91191 Gif-sur-Yvette (France)]|[IMAGO SA, 13600 La Ciotat (France); Tanguy, J.; Lecayon, G. [CEA-DSM/DRECAM/SRSIM, 91191 Gif-sur-Yvette (France)

1996-01-01

180

Caspase-9 mediates synaptic plasticity and memory deficits of Danish dementia knock-in mice: caspase-9 inhibition provides therapeutic protection  

PubMed Central

Background Mutations in either A? Precursor protein (APP) or genes that regulate APP processing, such as BRI2/ITM2B and PSEN1/PSEN2, cause familial dementias. Although dementias due to APP/PSEN1/PSEN2 mutations are classified as familial Alzheimer disease (FAD) and those due to mutations in BRI2/ITM2B as British and Danish dementias (FBD, FDD), data suggest that these diseases have a common pathogenesis involving toxic APP metabolites. It was previously shown that FAD mutations in APP and PSENs promote activation of caspases leading to the hypothesis that aberrant caspase activation could participate in AD pathogenesis. Results Here, we tested whether a similar mechanism applies to the Danish BRI2/ITM2B mutation. We have generated a genetically congruous mouse model of FDD, called FDDKI, which presents memory and synaptic plasticity deficits. We found that caspase-9 is activated in hippocampal synaptic fractions of FDDKI mice and inhibition of caspase-9 activity rescues both synaptic plasticity and memory deficits. Conclusion These data directly implicate caspase-9 in the pathogenesis of Danish dementia and suggest that reducing caspase-9 activity is a valid therapeutic approach to treating human dementias. PMID:23217200

2012-01-01

181

A Structural Approach to Establishing a Platform Chemistry for the Tunable, Bulk Electron Beam Cross-Linking of Shape Memory Polymer Systems.  

PubMed

The synthetic design and thermomechanical characterization of shape memory polymers (SMPs) built from a new polyurethane chemistry that enables facile, bulk and tunable cross-linking of low-molecular weight thermoplastics by electron beam irradiation is reported in this study. SMPs exhibit stimuli-induced geometry changes and are being proposed for applications in numerous fields. We have previously reported a polyurethane SMP system that exhibits the complex processing capabilities of thermoplastic polymers and the mechanical robustness and tunability of thermomechanical properties that are often characteristic of thermoset materials. These previously reported polyurethanes suffer practically because the thermoplastic molecular weights needed to achieve target cross-link densities severely limit high-throughput thermoplastic processing and because thermally unstable radiation-sensitizing additives must be used to achieve high enough cross-link densities to enable desired tunable shape memory behavior. In this study, we demonstrate the ability to manipulate cross-link density in low-molecular weight aliphatic thermoplastic polyurethane SMPs (M w as low as ~1.5 kDa) without radiation-sensitizing additives by incorporating specific structural motifs into the thermoplastic polymer side chains that we hypothesized would significantly enhance susceptibility to e-beam cross-linking. A custom diol monomer was first synthesized and then implemented in the synthesis of neat thermoplastic polyurethane SMPs that were irradiated at doses ranging from 1 to 500 kGy. Dynamic mechanical analysis (DMA) demonstrated rubbery moduli to be tailorable between 0.1 and 55 MPa, and both DMA and sol/gel analysis results provided fundamental insight into our hypothesized mechanism of electron beam cross-linking, which enables controllable bulk cross-linking to be achieved in highly processable, low-molecular weight thermoplastic shape memory polymers without sensitizing additives. PMID:25411511

Hearon, Keith; Besset, Celine J; Lonnecker, Alexander T; Ware, Taylor; Voit, Walter E; Wilson, Thomas S; Wooley, Karen L; Maitland, Duncan J

2013-11-26

182

A Structural Approach to Establishing a Platform Chemistry for the Tunable, Bulk Electron Beam Cross-Linking of Shape Memory Polymer Systems  

PubMed Central

The synthetic design and thermomechanical characterization of shape memory polymers (SMPs) built from a new polyurethane chemistry that enables facile, bulk and tunable cross-linking of low-molecular weight thermoplastics by electron beam irradiation is reported in this study. SMPs exhibit stimuli-induced geometry changes and are being proposed for applications in numerous fields. We have previously reported a polyurethane SMP system that exhibits the complex processing capabilities of thermoplastic polymers and the mechanical robustness and tunability of thermomechanical properties that are often characteristic of thermoset materials. These previously reported polyurethanes suffer practically because the thermoplastic molecular weights needed to achieve target cross-link densities severely limit high-throughput thermoplastic processing and because thermally unstable radiation-sensitizing additives must be used to achieve high enough cross-link densities to enable desired tunable shape memory behavior. In this study, we demonstrate the ability to manipulate cross-link density in low-molecular weight aliphatic thermoplastic polyurethane SMPs (Mw as low as ~1.5 kDa) without radiation-sensitizing additives by incorporating specific structural motifs into the thermoplastic polymer side chains that we hypothesized would significantly enhance susceptibility to e-beam cross-linking. A custom diol monomer was first synthesized and then implemented in the synthesis of neat thermoplastic polyurethane SMPs that were irradiated at doses ranging from 1 to 500 kGy. Dynamic mechanical analysis (DMA) demonstrated rubbery moduli to be tailorable between 0.1 and 55 MPa, and both DMA and sol/gel analysis results provided fundamental insight into our hypothesized mechanism of electron beam cross-linking, which enables controllable bulk cross-linking to be achieved in highly processable, low-molecular weight thermoplastic shape memory polymers without sensitizing additives. PMID:25411511

Hearon, Keith; Besset, Celine J.; Lonnecker, Alexander T.; Ware, Taylor; Voit, Walter E.; Wilson, Thomas S.; Wooley, Karen L.; Maitland, Duncan J.

2014-01-01

183

Polarization memory decay spectroscopy of photoexcitations in ? -conjugated polymers: Evidence for excimers  

NASA Astrophysics Data System (ADS)

We used the technique of ultrafast transient polarized photomodulation in the visible/near-infrared range and polarization memory decay (PMD) spectroscopy to study the primary photoexcitations in films and solutions of two poly(phenylene-vinylene) (PPV) derivatives, namely, 2-methoxy-5-( 2' -ethylhexyloxy) PPV (MEH-PPV) and 2,5-dioctyloxy PPV (DOO-PPV). We found that the primary photoexcitations in DOO-PPV films and solutions and MEH-PPV solutions are intrachain singlet excitons that show the same PMD across the entire spectrum. In contrast, the ultrafast photoexcitations in MEH-PPV films are of two kinds; these are intrachain excitons with fast PMD kinetics and interchain species with very slow PMD kinetics, which is the property that identifies these photoexcitations as excimers (or interchain charge transfer exciton). We attribute the excimers in MEH-PPV films to the increased interchain coupling due to the tightly packed nanomorphology, which also explains the photoluminescence efficiency decrease and its odd kinetics.

Singh, Sanjeev; Drori, Tomer; Vardeny, Z. Valy

2008-05-01

184

Examination of nanoformulated crosslinked polymers complexed with copper/zinc superoxide dismutase as a therapeutic strategy for angiotensin II-mediated hypertension  

NASA Astrophysics Data System (ADS)

Excessive generation of superoxide (O2·-) has been extensively implicated as a signaling molecule in cardiovascular pathologies, including hypertension. As a major risk factor for myocardial infarction, stroke, and heart failure, the morbidity and mortality associated with hypertension is a worldwide epidemic. Although there are several standard therapies that effectively lower blood pressure, many hypertensive patients have uncontrolled blood pressure despite taking available medications. Thus, there is a necessity to develop new pharmacotherapies that target novel molecular effectors (e.g. O2·-) that have been implicated to be integral in the pathogenesis of hypertension. To overcome the failed therapeutic impact of currently available antioxidants in cardiovascular disease, we developed a nanomedicine-based delivery system for the O2 ·- scavenging enzyme, copper/zinc superoxide dismutase (CuZnSOD), in which CuZnSOD protein is electrostatically bound to poly-L-lysine (PLL 50)-polyethylene glycol (PEG) block co-polymer to form CuZnSOD nanozyme. Different formulations of CuZnSOD nanozyme are covalently stabilized by either reducible or non-reducible crosslinked bonds between the PLL50-PEG polymers. Herein, we tested the overall hypothesis that PLL50-PEG CuZnSOD nanozyme delivers active CuZnSOD protein to neurons and decreases blood pressure in a model of Angll-dependent hypertension. As determined by electron paramagnetic resonance (EPR) spectroscopy, nanozymes retain full SOD enzymatic activity. Furthermore, non-reducible crosslinked nanozyme delivers active CuZnSOD protein to central neurons in culture (CATH.a neurons) without inducing significant neuronal toxicity. In vivo studies conducted in Angll-mediated hypertensive adult male C57BL/6 mice demonstrate that the non-reducible crosslinked nanozyme significantly attenuates blood pressure when given directly into the brain and prevents the further increase in hypertension when intravenously (IV) administered. While these physiologic data are promising, it was essential to determine the biological distribution of our nanozymes. The experimental data provided herein implicate the proximal tubules in the kidney cortex as a primary target for CuZnSOD nanozyme following IV administration. Collectively, these studies support the further development of PLL50 -PEG CuZnSOD nanozyme as an antioxidant-based therapeutic option for the improved treatment of hypertension. Furthermore, the therapeutic impact of CuZnSOD nanozyme could be investigated in additional pathologies in which there are excessive levels of O2·- present in the kidney.

Savalia, Krupa

185

Memory-like behavior as a feature of electrical signal transmission in melanin-like bio-polymers  

NASA Astrophysics Data System (ADS)

The memory-like behavior of melanin biopolymer under electrical stimuli is shown through electrical transport characterization performed on melanin based metal insulator semiconductor structures on silicon. The presence of a memory window and retention behavior is verified by capacitance-voltage read outs before and after the application of voltage pulses. Interestingly, these phenomena occur without the presence of metallic nanoclusters enclosed in the melanin matrix. Charge trapping is considered the main mechanism responsible for the melanin memory-like character. The inability to erase the memory window has been ascribed to the permanent polarization effect during the application of the voltage pulse.

Ambrico, M.; Ambrico, P. F.; Ligonzo, T.; Cardone, A.; Cicco, S. R.; Lavizzera, A.; Augelli, V.; Farinola, G. M.

2012-06-01

186

Integrating a novel shape memory polymer into surgical meshes to improve device performance during laparoscopic hernia surgery  

NASA Astrophysics Data System (ADS)

About 600,000 hernia repair surgeries are performed each year. The use of laparoscopic minimally invasive techniques has become increasingly popular in these operations. Use of surgical mesh in hernia repair has shown lower recurrence rates compared to other repair methods. However in many procedures, placement of surgical mesh can be challenging and even complicate the procedure, potentially leading to lengthy operating times. Various techniques have been attempted to improve mesh placement, including use of specialized systems to orient the mesh into a specific shape, with limited success and acceptance. In this work, a programmed novel Shape Memory Polymer (SMP) was integrated into commercially available polyester surgical meshes to add automatic unrolling and tissue conforming functionalities, while preserving the intrinsic structural properties of the original surgical mesh. Tensile testing and Dynamic Mechanical Analysis was performed on four different SMP formulas to identify appropriate mechanical properties for surgical mesh integration. In vitro testing involved monitoring the time required for a modified surgical mesh to deploy in a 37°C water bath. An acute porcine model was used to test the in vivo unrolling of SMP integrated surgical meshes. The SMP-integrated surgical meshes produced an automated, temperature activated, controlled deployment of surgical mesh on the order of several seconds, via laparoscopy in the animal model. A 30 day chronic rat model was used to test initial in vivo subcutaneous biocompatibility. To produce large more clinical relevant sizes of mesh, a mold was developed to facilitate manufacturing of SMP-integrated surgical mesh. The mold is capable of manufacturing mesh up to 361 cm2, which is believed to accommodate the majority of clinical cases. Results indicate surgical mesh modified with SMP is capable of laparoscopic deployment in vivo, activated by body temperature, and possesses the necessary strength and biocompatibility to function as suitable ventral hernia repair mesh, while offering a reduction in surgical operating time and improving mesh placement characteristics. Future work will include ball-burst tests similar to ASTM D3787-07, direct surgeon feedback studies, and a 30 day chronic porcine model to evaluate the SMP surgical mesh in a realistic hernia repair environment, using laparoscopic techniques for typical ventral hernia repair.

Zimkowski, Michael M.

187

Response of the medial temporal lobe network in amnestic mild cognitive impairment to therapeutic intervention assessed by fMRI and memory task performance  

PubMed Central

Studies of individuals with amnestic mild cognitive impairment (aMCI) have detected hyperactivity in the hippocampus during task-related functional magnetic resonance imaging (fMRI). Such elevated activation has been localized to the hippocampal dentate gyrus/CA3 (DG/CA3) during performance of a task designed to detect the computational contributions of those hippocampal circuits to episodic memory. The current investigation was conducted to test the hypothesis that greater hippocampal activation in aMCI represents a dysfunctional shift in the normal computational balance of the DG/CA3 regions, augmenting CA3-driven pattern completion at the expense of pattern separation mediated by the dentate gyrus. We tested this hypothesis using an intervention based on animal research demonstrating a beneficial effect on cognition by reducing excess hippocampal neural activity with low doses of the atypical anti-epileptic levetiracetam. In a within-subject design we assessed the effects of levetiracetam in three cohorts of aMCI participants, each receiving a different dose of levetiracetam. Elevated activation in the DG/CA3 region, together with impaired task performance, was detected in each aMCI cohort relative to an aged control group. We observed significant improvement in memory task performance under drug treatment relative to placebo in the aMCI cohorts at the 62.5 and 125 mg BID doses of levetiracetam. Drug treatment in those cohorts increased accuracy dependent on pattern separation processes and reduced errors attributable to an over-riding effect of pattern completion while normalizing fMRI activation in the DG/CA3 and entorhinal cortex. Similar to findings in animal studies, higher dosing at 250 mg BID had no significant benefit on either task performance or fMRI activation. Consistent with predictions based on the computational functions of the DG/CA3 elucidated in basic animal research, these data support a dysfunctional encoding mechanism detected by fMRI in individuals with aMCI and therapeutic intervention using fMRI to detect target engagement in response to treatment.

Bakker, Arnold; Albert, Marilyn S.; Krauss, Gregory; Speck, Caroline L.; Gallagher, Michela

2015-01-01

188

Laser-induced nondestructive patterning of a thin ferroelectric polymer film with controlled crystals using Ge8Sb2Te11 alloy layer for nonvolatile memory.  

PubMed

We present a simple but robust nondestructive process for fabricating micropatterns of thin ferroelectric polymer films with controlled crystals. Our method is based on utilization of localized heat arising from thin Ge(8)Sb(2)Te(11) (GST) alloy layer upon exposure of 650 nm laser. The heat was generated on GST layer within a few hundred of nanosecond exposure and subsequently transferred to a thin poly(vinylidene fluoride-co-trifluoroethylene) film deposited on GST layer. By controlling exposure time and power of the scanned laser, ferroelectric patterns of one or two microns in size are fabricated with various shape. In the micropatterned regions, ferroelectric polymer crystals were efficiently controlled in both degree of the crystallinity and the molecular orientations. Nonvolatile memory devices with laser scanned ferroelectric polymer layers exhibited excellent device performance of large remnant polarization, ON/OFF current ratio and data retention. The results are comparable with devices containing ferroelectric films thermally annealed at least for 2 h, making our process extremely efficient for saving time. Furthermore, our approach can be conveniently combined with a number of other functional organic materials for the future electronic applications. PMID:25127181

Bae, Insung; Kim, Richard Hahnkee; Hwang, Sun Kak; Kang, Seok Ju; Park, Cheolmin

2014-09-10

189

Preprint submitted to International Journal of Solids and Structures 1 PREDICTING THERMAL SHAPE MEMORY OF CROSSLINKED POLYMER NETWORKS FROM LINEAR  

E-print Network

and temperature were measured by dynamic mechanical analysis. The resulting thermo- mechanical behavior was modeled and implemented in a commercial finite element code. The ability of the resulting thermomechanical was evaluated by comparison with experimental shape memory thermomechanical torsion data in a large deformation

Paris-Sud XI, Université de

190

Electrospun biomimetic fibrous scaffold from shape memory polymer of PDLLA-co-TMC for bone tissue engineering.  

PubMed

Multifunctional fibrous scaffolds, which combine the capabilities of biomimicry to the native tissue architecture and shape memory effect (SME), are highly promising for the realization of functional tissue-engineered products with minimally invasive surgical implantation possibility. In this study, fibrous scaffolds of biodegradable poly(d,l-lactide-co-trimethylene carbonate) (denoted as PDLLA-co-TMC, or PLMC) with shape memory properties were fabricated by electrospinning. Morphology, thermal and mechanical properties as well as SME of the resultant fibrous structure were characterized using different techniques. And rat calvarial osteoblasts were cultured on the fibrous PLMC scaffolds to assess their suitability for bone tissue engineering. It is found that by varying the monomer ratio of DLLA:TMC from 5:5 to 9:1, fineness of the resultant PLMC fibers was attenuated from ca. 1500 down to 680 nm. This also allowed for readily modulating the glass transition temperature Tg (i.e., the switching temperature for actuating shape recovery) of the fibrous PLMC to fall between 19.2 and 44.2 °C, a temperature range relevant for biomedical applications in the human body. The PLMC fibers exhibited excellent shape memory properties with shape recovery ratios of Rr > 94% and shape fixity ratios of Rf > 98%, and macroscopically demonstrated a fast shape recovery (?10 s at 39 °C) in the pre-deformed configurations. Biological assay results corroborated that the fibrous PLMC scaffolds were cytocompatible by supporting osteoblast adhesion and proliferation, and functionally promoted biomineralization-relevant alkaline phosphatase expression and mineral deposition. We envision the wide applicability of using the SME-capable biomimetic scaffolds for achieving enhanced efficacy in repairing various bone defects (e.g., as implants for healing bone screw holes or as barrier membranes for guided bone regeneration). PMID:24476093

Bao, Min; Lou, Xiangxin; Zhou, Qihui; Dong, Wen; Yuan, Huihua; Zhang, Yanzhong

2014-02-26

191

Stronger and faster degradable biobased poly(propylene sebacate) as shape memory polymer by incorporating boehmite nanoplatelets.  

PubMed

Boehmite (BM) nanoplatelets were adopted to compound with fully biobased poly(propylene sebacate) (PPSe) to form the shape memory composites. The PPSe/BM composites kept excellent shape memory properties as previously reported PPSe. Compared to neat PPSe, the composites possess much higher mechanical properties above the melting point and faster biodegradation rate, which was demonstrated via tensile test at elevated temperature and in vitro degradation experiments in phosphate buffer saline (PBS), respectively. The obviously improved mechanical properties at elevated temperature are attributed to the uniform dispersion of the reinforcing boehmite nanoplatelets, which was facilitated by the interfacial interaction between BM and PPSe as revealed by FTIR, XPS, and XRD results. The faster degradation is correlated to accelerated hydrolysis by basic boehmite with surface aluminols. The potential biocompatibility, as substantiated by the outstanding cell viability and cell attachment, together with the realization of transformation temperature close to body temperature makes the PPSe/BM composites suitable for the biomedical applications, such as stents, in human body. PMID:22817474

Guo, Wenshan; Kang, Hailan; Chen, Yongwen; Guo, Baochun; Zhang, Liqun

2012-08-01

192

Application of a novel 3-fluid nozzle spray drying process for the microencapsulation of therapeutic agents using incompatible drug-polymer solutions.  

PubMed

The aim of this study was to evaluate a novel 3-fluid concentric nozzle (3-N) spray drying process for the microencapsulation of omeprazole sodium (OME) using Eudragit L100 (EL100). Feed solutions containing OME and/or EL100 in ethanol were assessed visually for OME stability. Addition of OME solution to EL100 solution resulted in precipitation of OME followed by degradation of OME reflected by a colour change from colourless to purple and brown. This was related to the low pH of 2.8 of the EL100 solution at which OME is unstable. Precipitation and progressive discoloration of the 2-fluid nozzle (2-N) feed solution was observed over the spray drying time course. In contrast, 3-N solutions of EL100 or OME in ethanol were stable over the spray drying period. Microparticles prepared using either nozzle showed similar characteristics and outer morphology however the internal morphology was different. DSC showed a homogenous matrix of drug and polymer for 2-N microparticles while 3-N microparticles had defined drug and polymer regions distributed as core and coat. The results of this study demonstrate that the novel 3-N spray drying process can allow the microencapsulation of a drug using an incompatible polymer and maintain the drug and polymer in separate regions of the microparticles. PMID:24170510

Sunderland, Tara; Kelly, John G; Ramtoola, Zebunnissa

2015-04-01

193

Scope of nanotechnology in ovarian cancer therapeutics  

Microsoft Academic Search

This review describes the use of polymer micelle nanotechnology based chemotherapies for ovarian cancer. While various chemotherapeutic agents can be utilized to improve the survival rate of patients with ovarian cancer, their distribution throughout the entire body results in high normal organ toxicity. Polymer micelle nanotechnology aims to improve the therapeutic efficacy of anti-cancer drugs while minimizing the side effects.

Murali M Yallapu; Meena Jaggi; Subhash C Chauhan

2010-01-01

194

Electrical stimulation during skill training with a therapeutic glove enhances the induction of cortical plasticity and has a positive effect on motor memory.  

PubMed

To examine whether afferent stimulation of hand muscles has a facilitating effect on motor performance, learning and cortical excitability, healthy subjects were trained on the grooved pegboard test (GTP) while wearing a mesh glove (MG) with incorporated electrical stimulation. Three study groups (n=12) were compared in a between subjects design, the bare handed (BH), gloved (MG) and gloved with electrical stimulation (MGS) groups. Motor performance was assessed by the GPT completion time across 4 training blocks, and further one block was retested 7 days later to determine the off-line effects. On-line learning was obtained by normalizing the completion time values to the first training block, and off-line learning was obtained by normalizing the retest values to the last training block. Cortical excitability was assessed via single and paired-pulse transcranial magnetic stimulation (TMS) at pre-training, post-training and 30 min post-training. Motor evoked potential recruitment curve, short-latency intracortical inhibition and intracortical facilitation were estimated from the TMS assessments. Motor performance across all 4 training blocks was poor in the MG and MGS groups, while on-line learning was not affected by wearing the glove or by afferent stimulation. However, off-line learning, tested 7 days after training, was improved in the MGS group compared to the MG group. In addition, post-training corticospinal excitability was increased in the MGS group. It can be concluded that afferent stimulation improves off-line learning and thus has a positive effect on motor memory, likely due to LTP-like cortical plasticity in the consolidation phase. PMID:24844752

Christova, Monica; Rafolt, Dietmar; Golaszewski, Stefan; Nardone, Raffaele; Gallasch, Eugen

2014-08-15

195

A rapamycin-binding protein polymer nanoparticle shows potent therapeutic activity in suppressing autoimmune dacryoadenitis in a mouse model of Sjögren's syndrome.  

PubMed

Sjögren's syndrome (SjS) is a chronic autoimmune disease characterized initially by lymphocytic infiltration and destruction of exocrine glands, followed by systemic organ damage and B-cell lymphoma. Conventional treatment is based on management of symptoms and there is a shortage of therapies that address the underlying causes of inflammation at source exocrine tissue. The aim of this study was to test a novel protein polymer-based platform consisting of diblock copolymers composed from Elastin-like Polypeptides (ELPs) fused with FKBP12, to deliver a potent immunosuppressant with dose-limiting toxicity, rapamycin (Rapa) also known as Sirolimus, and evaluate its effects on the inflamed lacrimal gland (LG) of non-obese diabetic mouse (NOD), a classic mouse model of SjS. Both soluble and diblock copolymer ELPs were fused to FKBP12 and characterized with respect to purity, hydrodynamic radii, drug entrapment and release. Both formulations showed successful association with Rapa; however, the nanoparticle formulation, FSI, released drug with nearly a 5 fold longer terminal half-life of 62.5h. The strong interaction of FSI nanoparticles with Rapa was confirmed in vivo by a shift in the monoexponential pharmacokinetic profile for free drug to a biexponential profile for the nanoparticle formulation. When acutely administered by injection into NOD mice via the tail vein, this FSI formulation significantly suppressed lymphocytic infiltration in the LG relative to the control group while reducing toxicity. There was also a significant effect on inflammatory and mammalian target of Rapamycin (mTOR) pathway genes in the LG and surprisingly, our nanoparticle formulation was significantly better at decreasing a proposed tear biomarker of SjS, cathepsin S (CATS) compared to free drug. These findings suggest that FSI is a promising tool for delivering Rapa for treatment of SjS in a murine model and may be further explored to meet the unmet medical challenge of SjS. PMID:23892265

Shah, Mihir; Edman, Maria C; Janga, Srikanth R; Shi, Pu; Dhandhukia, Jugal; Liu, Siyu; Louie, Stan G; Rodgers, Kathleen; Mackay, J Andrew; Hamm-Alvarez, Sarah F

2013-11-10

196

A rapamycin-binding protein polymer nanoparticle shows potent therapeutic activity in suppressing autoimmune dacryoadenitis in a mouse model of Sjögren’s syndrome  

PubMed Central

Sjögren’s syndrome (SjS) is a chronic autoimmune disease characterized initially by lymphocytic infiltration and destruction of exocrine glands, followed by systemic organ damage and B-cell lymphoma. Conventional treatment is based on management of symptoms and there is a shortage of therapies that address the underlying causes of inflammation at source exocrine tissue. The aim of this study was to test a novel protein polymer-based platform consisting of diblock copolymers composed from Elastin-like Polypeptides (ELPs) fused with FKBP12, to deliver a potent immunosuppressant with dose-limiting toxicity, rapamycin (Rapa) also known as Sirolimus, and evaluate its effects on the inflamed lacrimal gland (LG) of non-obese diabetic mouse (NOD), a classic mouse model of SjS. Both soluble and diblock copolymer ELPs were fused to FKBP12 and characterized with respect to purity, hydrodynamic radii, drug entrapment and release. Both formulations showed successful association with Rapa; however, the nanoparticle formulation, FSI, released drug with nearly a 5 fold longer terminal half-life of 62.5h. The strong interaction of FSI nanoparticles with Rapa was confirmed in vivo by a shift in the monoexponential pharmacokinetic profile for free drug to a biexponential profile for the nanoparticle formulation. When acutely administered by injection into NOD mice via the tail vein, this FSI formulation significantly suppressed lymphocytic infiltration in the LG relative to the control group while reducing toxicity. There was also a significant effect on inflammatory and mammalian target of Rapamycin (mTOR) pathway genes in the LG and surprisingly, our nanoparticle formulation was significantly better at decreasing a proposed tear biomarker of SjS, cathepsin S (CATS) compared to free drug. These findings suggest that FSI is a promising tool for delivering Rapa for treatment of SjS in a murine model and may be further explored to meet the unmet medical challenge of SjS. PMID:23892265

Shah, Mihir; Edman, Maria C.; Janga, Srikanth R.; Shi, Pu; Dhandhukia, Jugal; Liu, Siyu; Louie, Stan G.; Rodgers, Kathleen; MacKay, J. Andrew; Hamm-Alvarez, Sarah F.

2013-01-01

197

Microfabricated therapeutic actuators and release mechanisms therefor  

DOEpatents

Microfabricated therapeutic actuators are fabricated using a shape memory polymer (SMP), a polyurethane-based material that undergoes a phase transformation at a specified temperature (Tg). At a temperature above temperature Tg material is soft and can be easily reshaped into another configuration. As the temperature is lowered below temperature Tg the new shape is fixed and locked in as long as the material stays below temperature Tg. Upon reheating the material to a temperature above Tg, the material will return to its original shape. By the use of such SMP material, SMP microtubing can be used as a retaining/release actuator for the delivery of material, such as embolic coils, for example, through catheters into aneurysms, for example. The microtubing can be manufactured in various sizes and the phase change temperature Tg is determinate for an intended temperature target and intended use. The SMP microtubing can be positioned around or within an end of a deposit material. Various heating arrangements can be utilized with the SMP release mechanism, and the SMP microtubing can include a metallic coating for enhanced light absorption.

Lee, Abraham P. (Walnut Creek, CA); Fitch, Joseph P. (Livermore, CA); Schumann, Daniel L. (Concord, CA); Da Silva, Luiz (Danville, CA); Benett, William J. (Livermore, CA); Krulevitch, Peter A. (Pleasanton, CA)

2000-01-01

198

Microfabricated therapeutic actuators and release mechanisms therefor  

SciTech Connect

Microfabricated therapeutic actuators are fabricated using a shape memory polymer (SMP), a polyurethane-based material that undergoes a phase transformation at a specified temperature (Tg). At a temperature above temperature Tg material is soft and can be easily reshaped into another configuration. As the temperature is lowered below temperature Tg the new shape is fixed and locked in as long as the material stays below temperature Tg. Upon reheating the material to a temperature above Tg, the material will return to its original shape. By the use of such SMP material, SMP microtubing can be used as a retaining/release actuator for the delivery of material, such as embolic coils, for example, through catheters into aneurysms, for example. The microtubing can be manufactured in various sizes and the phase change temperature Tg is determinate for an intended temperature target and intended use. The SMP microtubing can be positioned around or within an end of a deposit material. Various heating arrangements can be utilized with the SMP release mechanism, and the SMP microtubing can include a metallic coating for enhanced light absorption.

Lee, A.P.; Fitch, J.P.; Schumann, D.L.; Da Silva, L.; Benett, W.J.; Krulevitch, P.A.

2000-05-09

199

New and Notable How Polymers Translocate  

E-print Network

New and Notable How Polymers Translocate Through Pores: Memory is Important Anatoly B. Kolomeisky cellular membranes, involve the motion of polymer molecules across nar- row channels (1). Translocation the entropic barriers. These barriers ap- pear due to the decrease in the number of available polymer

200

Therapeutic ultrasound  

Microsoft Academic Search

The use of ultrasound in medicine is now quite commonplace, especially with the recent introduction of small, portable and relatively inexpensive, hand-held diagnostic imaging devices. Moreover, ultrasound has expanded beyond the imaging realm, with methods and applications extending to novel therapeutic and surgical uses. These applications broadly include: tissue ablation, acoustocautery, lipoplasty, site-specific and ultrasound mediated drug activity, extracorporeal lithotripsy,

Lawrence A Crum

2004-01-01

201

Therapeutic Nanodevices  

NASA Astrophysics Data System (ADS)

Therapeutic nanotechnology offers minimally invasive therapies with high densities of function concentrated in small volumes, features that may reduce patient morbidity and mortality. Unlike other areas of nanotechnology, novel physical properties associated with nanoscale dimensionality are not the raison d'être of therapeutic nanotechnology, whereas the aggregation of multiple biochemical (or comparably precise) functions into controlled nanoarchitectures is. Multifunctionality is a hallmark of emerging nanotherapeutic devices, and multifunctionality can allow nanotherapeutic devices to perform multistep work processes, with each functional component contributing to one or more nanodevice subroutine such that, in aggregate, subroutines sum to a cogent work process. Cannonical nanotherapeutic subroutines include tethering (targeting) to sites of disease, dispensing measured doses of drug (or bioactive compound), detection of residual disease after therapy and communication with an external clinician/operator. Emerging nanotherapeutics thus blur the boundaries between medical devices and traditional pharmaceuticals. Assembly of therapeutic nanodevices generally exploits either (bio)material self-assembly properties or chemoselective bioconjugation techniques, or both. Given the complexity, composition, and the necessity for their tight chemical and structural definition inherent in the nature of nanotherapeutics, their cost of goods (COGs) might exceed that of (already expensive) biologics. Early therapeutic nanodevices will likely be applied to disease states which exhibit significant unmet patient need (cancer and cardiovascular disease), while application to other disease states well-served by conventional therapy may await perfection of nanotherapeutic design and assembly protocols.

Lee, Stephen; Ruegsegger, Mark; Barnes, Philip; Smith, Bryan; Ferrari, Mauro

202

Therapeutic Nanodevices  

NASA Astrophysics Data System (ADS)

Therapeutic nanotechnology offers minimally invasive therapies with high densities of function concentrated in small volumes, features that may reduce patient morbidity and mortality. Unlike other areas of nanotechnology, novel physical properties associated with nanoscale dimensionality are not the raison d'etre of therapeutic nanotechnology, whereas the aggregation of multiple biochemical (or comparably precise) functions into controlled nanoarchitectures is. Multifunctionality is a hallmark of emerging nanotherapeutic devices, and multifunctionality can allow nanotherapeutic devices to perform multi-step work processes, with each functional component contributing to one or more nanodevice subroutine such that, in aggregate, subroutines sum to a cogent work process. Cannonical nanotherapeutic subroutines include tethering (targeting) to sites of disease, dispensing measured doses of drug (or bioactive compound), detection of residual disease after therapy and communication with an external clinician/operator. Emerging nanotherapeutics thus blur the boundaries between medical devices and traditional pharmaceuticals. Assembly of therapeutic nanodevices generally exploits either (bio)material self assembly properties or chemoselective bioconjugation techniques, or both. Given the complexity, composition, and the necessity for their tight chemical and structural definition inherent in the nature of nanotherapeutics, their cost of goods (COGs) might exceed that of (already expensive) biologics. Early therapeutic nanodevices will likely be applied to disease states which exhibit significant unmet patient need (cancer and cardiovascular disease), while application to other disease states well-served by conventional therapy may await perfection of nanotherapeutic design and assembly protocols.

Lee, Stephen C.; Ruegsegger, Mark; Barnes, Philip D.; Smith, Bryan R.; Ferrari, Mauro

203

A large-deformation thermo-mechanically coupled elastic-viscoplastic theory for amorphous polymers : modeling of micro-scale forming and the shape memory phenomenon  

E-print Network

Amorphous polymers are important engineering materials; however, their nonlinear, strongly temperature- and rate-dependent elastic-viscoplastic behavior is still not very well understood, and is modeled by existing ...

Srivastava, Vikas

2010-01-01

204

Mechanical memory  

DOEpatents

A first-in-first-out (FIFO) microelectromechanical memory apparatus (also termed a mechanical memory) is disclosed. The mechanical memory utilizes a plurality of memory cells, with each memory cell having a beam which can be bowed in either of two directions of curvature to indicate two different logic states for that memory cell. The memory cells can be arranged around a wheel which operates as a clocking actuator to serially shift data from one memory cell to the next. The mechanical memory can be formed using conventional surface micromachining, and can be formed as either a nonvolatile memory or as a volatile memory.

Gilkey, Jeffrey C. (Albuquerque, NM); Duesterhaus, Michelle A. (Albuquerque, NM); Peter, Frank J. (Albuquerque, NM); Renn, Rosemarie A. (Albuquerque, NM); Baker, Michael S. (Albuquerque, NM)

2006-05-16

205

Mechanical memory  

DOEpatents

A first-in-first-out (FIFO) microelectromechanical memory apparatus (also termed a mechanical memory) is disclosed. The mechanical memory utilizes a plurality of memory cells, with each memory cell having a beam which can be bowed in either of two directions of curvature to indicate two different logic states for that memory cell. The memory cells can be arranged around a wheel which operates as a clocking actuator to serially shift data from one memory cell to the next. The mechanical memory can be formed using conventional surface micromachining, and can be formed as either a nonvolatile memory or as a volatile memory.

Gilkey, Jeffrey C. (Albuquerque, NM); Duesterhaus, Michelle A. (Albuquerque, NM); Peter, Frank J. (Albuquerque, NM); Renn, Rosemarie A. (Alburquerque, NM); Baker, Michael S. (Albuquerque, NM)

2006-08-15

206

Therapeutic mammaplasty.  

PubMed

Therapeutic mammaplasty is a term for the oncoplastic application of breast reduction and mastopexy techniques to treat selected breast tumours by breast conserving surgery (BCS). It has the potential to increase the indications for BCS as well as achieve more acceptable aesthetic results from it in suitable women. Now an established technique in the range of oncoplastic options for women with breast cancer, it finds common application and is associated with good oncological and quality of life outcomes. PMID:24889526

Macmillan, R D; James, R; Gale, K L; McCulley, S J

2014-07-01

207

Longevity pathways and memory aging  

PubMed Central

The aging process has been associated with numerous pathologies at the cellular, tissue, and organ level. Decline or loss of brain functions, including learning and memory, is one of the most devastating and feared aspects of aging. Learning and memory are fundamental processes by which animals adjust to environmental changes, evaluate various sensory signals based on context and experience, and make decisions to generate adaptive behaviors. Age-related memory impairment is an important phenotype of brain aging. Understanding the molecular mechanisms underlying age-related memory impairment is crucial for the development of therapeutic strategies that may eventually lead to the development of drugs to combat memory loss. Studies in invertebrate animal models have taught us much about the physiology of aging and its effects on learning and memory. In this review we survey recent progress relevant to conserved molecular pathways implicated in both aging and memory formation and consolidation. PMID:24926313

Gkikas, Ilias; Petratou, Dionysia; Tavernarakis, Nektarios

2014-01-01

208

Nanoreinforced shape memory polyurethane  

NASA Astrophysics Data System (ADS)

Shape memory polymers (SMPs) are functional materials, which find applications in a broad range of temperature sensing elements and biological micro-electro-mechanical systems (MEMS). These polymers are capable of fixing a transient shape and recovering to their original shape after a series of thermo-mechanical treatments. Generally, these materials are thermoplastic segmented polyurethanes composed of soft segments, usually formed by a polyether macroglycol, and hard segments formed from the reaction of a diisocyanate with a low molecular mass diol. The hard segment content is a key parameter to control the final properties of the polymer, such as rubbery plateau modulus, melting point, hardness, and tensile strength. The long flexible soft segment largely controls the low temperature properties, solvent resistance, and weather resistance properties. The morphology and properties of polyurethanes (PU) are greatly influenced by the ratio of hard and soft block components and the average block lengths. However, in some applications, SMPs may not generate enough recovery force to be useful. The reinforcement of SMPs using nanofillers represents a novel approach of enhancing the performance of these materials. The incorporation of these fillers into SMPs can produce performance enhancements (particularly elastic modulus) at small nanoparticle loadings (˜1-2 wt %). An optimal performance of nanofiller-polymer nanocomposites requires uniform dispersion of filler in polymers and good interfacial adhesion. The addition of nanofillers like cellulose nanofibers (CNF), conductive cellulose nanofibers (C-CNF), and carbon nanotubes (CNTs) allows for the production of stiffer materials with deformation capacity comparable to that of the unfilled polymer. Additionally, the use of conductive nanoreinforcements such as C-CNF and CNTs leads to new pathways for actuation of the shape memory effect. During this work, thermoplastic shape memory polyurethanes were synthesized with varying chemical composition and molecular weight. This was achieved by controlling the moles of reactants used, by using polyols with different molecular weights, and by using different diisocyanates. Using these controls, polymer matrices with different but controlled structures were synthesized and then reinforced with CNF, C-CNF, and CNTs in order to study the influence of chemical structure and polymer-nanoreinforcement interactions on polymer nanocomposite morphology, thermal and mechanical properties, and shape memory behavior.

Richardson, Tara Beth

209

Polymer films  

DOEpatents

A film contains a first polymer having a plurality of hydrogen bond donating moieties, and a second polymer having a plurality of hydrogen bond accepting moieties. The second polymer is hydrogen bonded to the first polymer.

Granick, Steve; Sukhishvili, Svetlana A.

2004-05-25

210

Polymer films  

DOEpatents

A film contains a first polymer having a plurality of hydrogen bond donating moieties, and a second polymer having a plurality of hydrogen bond accepting moieties. The second polymer is hydrogen bonded to the first polymer.

Granick, Steve (Champaign, IL); Sukhishvili, Svetlana A. (Maplewood, NJ)

2008-12-30

211

[Therapeutic endosonography].  

PubMed

Endoscopic ultrasonography (EUS)-guided interventions are an essential tool for complex (such as combined or subsequent) therapeutic measures and are, in current as well as future endoscopy, an indispensable part of modern gastroenterology. Longitudinal EUS scanners allow one to puncture transluminally both mediastinal and abdominal lesions which cannot be approached with other techniques. Using the EUS-guided puncture of such pathological lesions, it becomes possible to perform further, more advanced endoscopic interventions which thus become safer as well as more efficient and are associated with a lower complication rate compared with conventional endoscopic or even surgical interventions. A crucial aspect in interventional EUS is the adequate, less traumatic treatment of pancreatic pseudocysts. The transluminal route for interventions spanning from the approach to the placement of a drainage for abscesses and/or necroses is considerably easier under EUS-guidance, including better outcomes. Novel approaches and interventions are the internal EUS-guided insertion of a transluminal (from the upper GI tract) I) cholangiodrainage in patients with malignant obstruction of the bile duct but no option to achieve sufficient conventional cholangiodrainage with ERC or PTC, II) pancreaticodrainage in symptomatic patients with enlarged pancreatic duct -/+ pancreatic fistula postoperatively or in patients with chronic pancreatitis, which may be considered new therapeutic strategies with non-operative intentions and/or low invasiveness. PMID:18537083

Will, U

2008-06-01

212

Cache Memories  

Microsoft Academic Search

Cache memories are used in modern, medium and high-speed CPUs to hold temporarily those portions of the contents of main memory which are {believed to be) currently in use. Since instructions and data in cache memories can usually be referenced in 10 to 25 percent of the time required to access main memory, cache memories permit the executmn rate of

Alan Jay Smith

1982-01-01

213

Therapeutic immunization for HIV.  

PubMed

Vaccines have entered into human clinical trials against infectious diseases and as therapies against cancer. The HIV virus establishes a latent infection at a very early stage and the T cell memory of the infected patient is rapidly destroyed. However, results of immunotherapy after DNA and protein immunization show that vaccine-induced immune responses might be present for a long period of time. Patients subjected to therapeutic immunization appear to do well, and to have a small immunological advantage, which, however, will have to be improved. The vaccine therapy should start early, while adequate reservoirs of appropriate T helper cells are available and still inducible. The DNA vaccines induce a relatively long-lived immunological memory, and gene-based immunization is effective in inducing cytotoxic CD8(+) T cells and CD4+ helper cells. Protein vaccines, on the other hand, primarily give T cell help. It thus appears that DNA and protein approaches to HIV immunization complement each other. A surprisingly broad reactivity to peptides from different subtypes of HIV was identified in individuals infected with several subtypes of HIV. PMID:17031650

Gudmundsdotter, Lindvi; Sjödin, Anna; Boström, Ann-Charlotte; Hejdeman, Bo; Theve-Palm, Rebecca; Alaeus, Annette; Lidman, Knut; Wahren, Britta

2006-11-01

214

DNA Polymerases as Therapeutic Targets  

PubMed Central

Numerous pathological states including cancer, autoimmune diseases, and viral/bacterial infections are often attributed to uncontrollable DNA replication. Inhibiting this essential biological process provides an obvious therapeutic target against these diseases. A logical target is the DNA polymerase, the enzyme responsible for catalyzing the addition of mononucleotides into a growing polymer using a DNA or RNA template as a guide for directing each incorporation event. This review provides a summary of therapeutic agents that target polymerase activity. A discussion of the biological function and mechanism of polymerases is first provided to illustrate the strategy for therapeutic intervention as well as the rational design of various nucleoside analogs that inhibit various polymerases associated with viral infections and cancer. The development of nucleoside and non-nucleoside inhibitors as anti-viral agents is discussed with particular emphasis on their mechanism of action, structure-activity relationships, toxicity, and mechanism of resistance. In addition, commonly used anti-cancer agents are described to illustrate the similarities and differences associated with various nucleoside analogs as therapeutic agents. Finally, new therapeutic approaches are discussed that include the inhibition of selective polymerases involved in DNA repair and/or translesion DNA synthesis as anti-cancer agents. PMID:18642851

Berdis, Anthony J.

2009-01-01

215

Corrective Emotional Experience in the Therapeutic Process  

Microsoft Academic Search

While we are using Alexander's work as a beginning point for this analysis of corrective emotional experience in the therapeutic process, we extend the concept beyond the level of ego experience (emotion, memory, and cognition) to that of Self or Soul experience (the transpersonal realms of collective unconscious, subtle energy, and the spirit world). Our analysis is grounded on the

David Hartman; Diane Zimberoff; Catherine Ponder

2004-01-01

216

Microgravity Polymers  

NASA Technical Reports Server (NTRS)

A one-day, interactive workshop considering the effects of gravity on polymer materials science was held in Cleveland, Ohio, on May 9, 1985. Selected programmatic and technical issues were reviewed to introduce the field to workshop participants. Parallel discussions were conducted in three disciplinary working groups: polymer chemistry, polymer physics, and polymer engineering. This proceedings presents summaries of the workshop discussions and conclusions.

1986-01-01

217

Memory Matters  

MedlinePLUS

... blood vessel (which carries the blood) bursts. Continue Brain Injuries Affect Memory At any age, an injury to ... with somebody's memory. Some people who recover from brain injuries need to learn old things all over again, ...

218

Virtual Memory  

Microsoft Academic Search

\\\\The need for automatic storage allocation arises from desires for program modularity, machine independence, and resource sharing. Virtual memory is an elegant way of achieving these objectives. In a virtual memory, the addresses a program may use to identify information are distinguished from the addresses the memory system uses to identify physical storage sites, and program-generated addresses are translated automatically

Peter J. Denning

1970-01-01

219

Polymers Presentation  

NSDL National Science Digital Library

This 15 page PowerPoint contains the presentation for the polymers module from Nano-Link. This lesson requires a background in eight grade science. Various details of polymers are discussed including molecular structures, cross-linked polymers, and ringed polymers. Lastly, an activity to explore cross-linked polymers is included. Visitors must complete a quick and free registration to access the materials.

220

Self-assembling materials for therapeutic delivery?  

PubMed Central

A growing number of medications must be administered through parenteral delivery, i.e., intravenous, intramuscular, or subcutaneous injection, to ensure effectiveness of the therapeutic. For some therapeutics, the use of delivery vehicles in conjunction with this delivery mechanism can improve drug efficacy and patient compliance. Macromolecular self-assembly has been exploited recently to engineer materials for the encapsulation and controlled delivery of therapeutics. Self-assembled materials offer the advantages of conventional crosslinked materials normally used for release, but also provide the ability to tailor specific bulk material properties, such as release profiles, at the molecular level via monomer design. As a result, the design of materials from the “bottom up” approach has generated a variety of supramolecular devices for biomedical applications. This review provides an overview of self-assembling molecules, their resultant structures, and their use in therapeutic delivery. It highlights the current progress in the design of polymer- and peptide-based self-assembled materials. PMID:19010748

Branco, Monica C.; Schneider, Joel P.

2009-01-01

221

Memory protection  

NASA Technical Reports Server (NTRS)

Accidental overwriting of files or of memory regions belonging to other programs, browsing of personal files by superusers, Trojan horses, and viruses are examples of breakdowns in workstations and personal computers that would be significantly reduced by memory protection. Memory protection is the capability of an operating system and supporting hardware to delimit segments of memory, to control whether segments can be read from or written into, and to confine accesses of a program to its segments alone. The absence of memory protection in many operating systems today is the result of a bias toward a narrow definition of performance as maximum instruction-execution rate. A broader definition, including the time to get the job done, makes clear that cost of recovery from memory interference errors reduces expected performance. The mechanisms of memory protection are well understood, powerful, efficient, and elegant. They add to performance in the broad sense without reducing instruction execution rate.

Denning, Peter J.

1988-01-01

222

Quantum memory Quantum memory  

NASA Astrophysics Data System (ADS)

Interaction of quantum radiation with multi-particle ensembles has sparked off intense research efforts during the past decade. Emblematic of this field is the quantum memory scheme, where a quantum state of light is mapped onto an ensemble of atoms and then recovered in its original shape. While opening new access to the basics of light-atom interaction, quantum memory also appears as a key element for information processing applications, such as linear optics quantum computation and long-distance quantum communication via quantum repeaters. Not surprisingly, it is far from trivial to practically recover a stored quantum state of light and, although impressive progress has already been accomplished, researchers are still struggling to reach this ambitious objective. This special issue provides an account of the state-of-the-art in a fast-moving research area that makes physicists, engineers and chemists work together at the forefront of their discipline, involving quantum fields and atoms in different media, magnetic resonance techniques and material science. Various strategies have been considered to store and retrieve quantum light. The explored designs belong to three main—while still overlapping—classes. In architectures derived from photon echo, information is mapped over the spectral components of inhomogeneously broadened absorption bands, such as those encountered in rare earth ion doped crystals and atomic gases in external gradient magnetic field. Protocols based on electromagnetic induced transparency also rely on resonant excitation and are ideally suited to the homogeneous absorption lines offered by laser cooled atomic clouds or ion Coulomb crystals. Finally off-resonance approaches are illustrated by Faraday and Raman processes. Coupling with an optical cavity may enhance the storage process, even for negligibly small atom number. Multiple scattering is also proposed as a way to enlarge the quantum interaction distance of light with matter. The quest for higher efficiency, better fidelity, broader bandwidth, multimode capacity and longer storage lifetime is pursued in all those approaches, as shown in this special issue. The improvement of quantum memory operation specifically requires in-depth study and control of numerous physical processes leading to atomic decoherence. The present issue reflects the development of rare earth ion doped matrices offering long lifetime superposition states, either as bulk crystals or as optical waveguides. The need for quantum sources and high efficiency detectors at the single photon level is also illustrated. Several papers address the networking of quantum memories either in long-haul cryptography or in the prospect of quantum processing. In this context, much attention has been paid recently to interfacing quantum light with superconducting qubits and with nitrogen-vacancy centers in diamond. Finally, the quantum interfacing of light with matter raises questions on entanglement. The last two papers are devoted to the generation of entanglement by dissipative processes. It is shown that long lifetime entanglement may be built in this way. We hope this special issue will help readers to become familiar with the exciting field of ensemble-based quantum memories and will stimulate them to bring deeper insights and new ideas to this area.

Le Gouët, Jean-Louis; Moiseev, Sergey

2012-06-01

223

Modulating b-Lapachone Release from Polymer Millirods through Cyclodextrin Complexation  

E-print Network

complexation; b-lapachone; drug-polymer interac- tions; poly(lactic/glycolic) acid (PLGA); drug deliveryModulating b-Lapachone Release from Polymer Millirods through Cyclodextrin Complexation FANGJING its therapeutic applications. Herein we describe the development of poly

Gao, Jinming

224

Piezoelectric Polymers  

NASA Technical Reports Server (NTRS)

The purpose of this review is to detail the current theoretical understanding of the origin of piezoelectric and ferroelectric phenomena in polymers; to present the state-of-the-art in piezoelectric polymers and emerging material systems that exhibit promising properties; and to discuss key characterization methods, fundamental modeling approaches, and applications of piezoelectric polymers. Piezoelectric polymers have been known to exist for more than forty years, but in recent years they have gained notoriety as a valuable class of smart materials.

Harrison, J. S.; Ounaies, Z.; Bushnell, Dennis M. (Technical Monitor)

2001-01-01

225

Coordination polymers  

Microsoft Academic Search

1.The properties of the beryllium-containing internal-complex polymer derived from bis-p-acetoacetylphenyl ether were investigated.2.The polymer is stable to heat: appreciable decomposition sets in only after long heating above 280°. The rate and extent of the degradation of the polymer at high temperatures are higher in air than in nitrogen. The internal-complex polymer undergoes no substantial change in properties as a result

M. G. Vinogradov; S. V. Vinogradova; Yu. A. Davidovich; V. V. Korshak

1963-01-01

226

Virtual memory  

NASA Technical Reports Server (NTRS)

Virtual memory was conceived as a way to automate overlaying of program segments. Modern computers have very large main memories, but need automatic solutions to the relocation and protection problems. Virtual memory serves this need as well and is thus useful in computers of all sizes. The history of the idea is traced, showing how it has become a widespread, little noticed feature of computers today.

Denning, P. J.

1986-01-01

227

American Therapeutic Recreation Association  

MedlinePLUS

American Therapeutic Recreation Association Promoting Health & Wellness Services New Feature for Members Only ~ Network with Members Become a part ... Proposals for 2015 Annual Conference Join thousands of Therapeutic Recreation specialists today Join Now Renew your membership ...

228

Characterization of Therapeutic Coatings on Medical Devices  

NASA Astrophysics Data System (ADS)

Therapeutic coatings on medical devices such as catheters, guide wires, and stents improve biocompatibility by favorably altering the chemical nature of the device/tissue or device/blood interface. Such coatings often minimize tissue damage (reduce friction), decrease chances for blood clot formation (prevent platelet adsorption), and improve the healing response (deliver drugs). Confocal Raman microscopy provides valuable information about biomedical coatings by, for example, facilitating the measurement of the thickness and swelling of frictionreducing hydrogel coatings on catheters and by determining the distribution of drug within a polymer-based drug-eluting coatings on stents. This chapter explores the application of Raman microscopy to the imaging of thin coatings of cross-linked poly(vinyl pyrrolidone) gels, parylene films, mixtures of dexamethasone with various polymethacrylates, and mixtures of rapamycin with hydrolysable (biodegradable) poly(lactide-co-glycolide) polymers. Raman microscopy measures the thickness and swelling of coatings, reveals the degree of mixing of drug and polymer, senses the hydrolysis of biodegradable polymers, and determines the polymorphic forms of drug present within thin therapeutic coatings on medical devices.

Wormuth, Klaus

229

Are polymer melts “ideal”?  

NASA Astrophysics Data System (ADS)

It is commonly accepted that in concentrated solutions or melts high-molecular weight polymers display random-walk conformational properties without long-range correlations between subsequent bonds. This absence of memory means, for instance, that the bond-bond correlation function, P(s), of two bonds separated by s monomers along the chain should exponentially decay with s. Presenting numerical results and theoretical arguments for both monodisperse chains and self-assembled (essentially Flory size-distributed) equilibrium polymers we demonstrate that some long-range correlations remain due to self-interactions of the chains caused by the chain connectivity and the incompressibility of the melt. Suggesting a profound analogy with the well-known long-range velocity correlations in liquids we find, for instance, P(s) to decay algebraically as s. Our study suggests a precise method for obtaining the statistical segment length b in a computer experiment.

Wittmer, J. P.; Beckrich, P.; Crevel, F.; Huang, C. C.; Cavallo, A.; Kreer, T.; Meyer, H.

2007-07-01

230

Episodic Memories  

ERIC Educational Resources Information Center

An account of episodic memories is developed that focuses on the types of knowledge they represent, their properties, and the functions they might serve. It is proposed that episodic memories consist of "episodic elements," summary records of experience often in the form of visual images, associated to a "conceptual frame" that provides a…

Conway, Martin A.

2009-01-01

231

Pittsburgh Memories.  

ERIC Educational Resources Information Center

By studying the painting "Pittsburgh Memories" by the Black artist Romare Bearden, student in grades K-3 learn that artists use their visual memories of real places and people when they make art. The students also learn how various types of space are depicted in a semi-abstract style. (RM)

Judson, Bay

1986-01-01

232

Collaging Memories  

ERIC Educational Resources Information Center

Even middle school students can have memories of their childhoods, of an earlier time. The art of Romare Bearden and the writings of Paul Auster can be used to introduce ideas about time and memory to students and inspire works of their own. Bearden is an exceptional role model for young artists, not only because of his astounding art, but also…

Wallach, Michele

2011-01-01

233

Practical memory checking with Dr. Memory  

Microsoft Academic Search

Memory corruption, reading uninitialized memory, using freed memory, and other memory-related errors are among the most difficult programming bugs to identify and fix due to the delay and non-determinism linking the error to an observable symptom. Dedicated memory checking tools are invaluable for finding these errors. However, such tools are difficult to build, and because they must monitor all memory

Derek Bruening; Qin Zhao

2011-01-01

234

Targeted delivery of therapeutics to endothelium  

PubMed Central

The endothelium is a target for therapeutic and diagnostic interventions in a plethora of human disease conditions including ischemia, inflammation, edema, oxidative stress, thrombosis and hemorrhage, and metabolic and oncological diseases. Unfortunately, drugs have no affinity to the endothelium, thereby limiting the localization, timing, specificity, safety, and effectiveness of therapeutic interventions. Molecular determinants on the surface of resting and pathologically altered endothelial cells, including cell adhesion molecules, peptidases, and receptors involved in endocytosis, can be used for drug delivery to the endothelial surface and into intracellular compartments. Drug delivery platforms such as protein conjugates, recombinant fusion constructs, targeted liposomes, and stealth polymer carriers have been designed to target drugs and imaging agents to these determinants. We review endothelial target determinants and drug delivery systems, describe parameters that control the binding of drug carriers to the endothelium, and provide examples of the endothelial targeting of therapeutic enzymes designed for the treatment of acute vascular disorders including ischemia, oxidative stress, inflammation, and thrombosis. PMID:18815813

Simone, Eric; Ding, Bi-Sen

2009-01-01

235

Simulations of Polymer Translocation  

NASA Astrophysics Data System (ADS)

Transport of molecules across membranes is an essential mechanism for life processes. These molecules are often long, and the pores in the membranes are too narrow for the molecules to pass through as a single unit. In such circumstances, the molecules have to squeeze -- i.e., translocate -- themselves through the pores. DNA, RNA and proteins are such naturally occuring long molecules in a variety of biological processes. Understandably, the process of translocation has been an active topic of current research: not only because it is a cornerstone of many biological processes, but also due to its relevance for practical applications. Translocation is a complicated process in living organisms -- the presence of chaperone molecules, pH, chemical potential gradients, and assisting molecular motors strongly influence its dynamics. Consequently, the translocation process has been empirically studied in great variety in biological literature. Study of translocation as a biophysical process is more recent. Herein, the polymer is simplified to a sequentially connected string of N monomers as it passes through a narrow pore on a membrane. The quantities of interest are the typical time scale for the polymer to leave a confining cell (the ``escape of a polymer from a vesicle'' time scale), and the typical time scale the polymer spends in the pore (the ``dwell'' time scale) as a function of N and other parameters like membrane thickness, membrane adsorption, electrochemical potential gradient, etc. Our research is focused on computer simulations of translocation. Since our main interest is in the scaling properties, we use a highly simplified description of the translocation process. The polymer is described as a self-avoiding walk on a lattice, and its dynamics consists of single-monomer jumps from one lattice site to another neighboring one. Since we have a very efficient program to simulate such polymer dynamics, which we decribe in Chapter 2, we can perform long simulations in which long polymers creep through tiny pores. In Chapter 3 we study pore blockage times for a translocating polymer of length N, driven by a field E across te pore. In three dimensions we find that the typical time the pore remains blocked during a translocation event scales as N^{1.37}/E We show that the scaling behavior stems from the polymer dynamics at the immediate vicinity of the pore -- in particular, the memory effects in the polymer chain tension imbalance across the pore. Chapter 4 studies the unbiased translocation of a polymer with length N, surrounded by equally long polymers, through a narrow pore in a membrane. We show that in dense polymeric systems a relaxation time exists that scales as N^{2.65}, much longer than the Rouse time N^2. If the polymers are well entangled, we find that the mean dwell times scales as N^{3.3}, while for shorter, less entangled polymers, we measure dwell times scaling as N^{2.7}. In Chapter 5 we study the translocation of an RNA molecule, pulled through a nanopore by an optical tweezer, as a method to determine its secondary structure. The resolution with which the elements of the secondary structure can be determined is limited by thermal fluctuations, ruling out single-nucleotide resolution under normal experimental conditions.

Vocks, H.

2008-07-01

236

Electrochemical Sensors Based on Organic Conjugated Polymers  

PubMed Central

Organic conjugated polymers (conducting polymers) have emerged as potential candidates for electrochemical sensors. Due to their straightforward preparation methods, unique properties, and stability in air, conducting polymers have been applied to energy storage, electrochemical devices, memory devices, chemical sensors, and electrocatalysts. Conducting polymers are also known to be compatible with biological molecules in a neutral aqueous solution. Thus, these are extensively used in the fabrication of accurate, fast, and inexpensive devices, such as biosensors and chemical sensors in the medical diagnostic laboratories. Conducting polymer-based electrochemical sensors and biosensors play an important role in the improvement of public health and environment because rapid detection, high sensitivity, small size, and specificity are achievable for environmental monitoring and clinical diagnostics. In this review, we summarized the recent advances in conducting polymer-based electrochemical sensors, which covers chemical sensors (potentiometric, voltammetric, amperometric) and biosensors (enzyme based biosensors, immunosensors, DNA sensors).

Rahman, Md. Aminur; Kumar, Pankaj; Park, Deog-Su; Shim, Yoon-Bo

2008-01-01

237

Natural Polymers  

NSDL National Science Digital Library

Polymers that exist in nature, called biopolymers , include a large and diverse range of compounds. This chapter discusses the most important types of natural polymers--their chemical makeup, key properties, and where they are found. The focus will be more on the chemical and physical properties of natural polymers and less on their biological synthesis or physiological function. The references at the end of the chapter provide additional information.

David Teegarden

2004-01-01

238

Polymer Chemistry  

NASA Technical Reports Server (NTRS)

This viewgraph presentation describes new technologies in polymer and material chemistry that benefits NASA programs and missions. The topics include: 1) What are Polymers?; 2) History of Polymer Chemistry; 3) Composites/Materials Development at KSC; 4) Why Wiring; 5) Next Generation Wiring Materials; 6) Wire System Materials and Integration; 7) Self-Healing Wire Repair; 8) Smart Wiring Summary; 9) Fire and Polymers; 10) Aerogel Technology; 11) Aerogel Composites; 12) Aerogels for Oil Remediation; 13) KSC's Solution; 14) Chemochromic Hydrogen Sensors; 15) STS-130 and 131 Operations; 16) HyperPigment; 17) Antimicrobial Materials; 18) Conductive Inks Formulations for Multiple Applications; and 19) Testing and Processing Equipment.

Williams, Martha; Roberson, Luke; Caraccio, Anne

2010-01-01

239

Memory Technologies Vivek Asthana  

E-print Network

Disk Memory 32KB -4MB 4 ns 2GB 60 ns 200 GB 8 ms SoC Board Computer memory Hierarchy USB Flash DriveMemory Technologies Vivek Asthana 13th Mar 2013 #12;13-Mar-13 2 Memory Usage (2025) #12;13-Mar-13 3 Outline What is a Memory Current Memory technologies · SRAM · DRAM · Flash Upcoming Memory technologies

Kumar, M. Jagadesh

240

Specification state space memory  

E-print Network

Specification state space memory 1/116 #12;Specification state space memory state memory contents 2/116 #12;Specification state space memory int; (0,..20); char; rat state memory contents 3/116 #12;Specification state space memory int; (0,..20); char; rat state memory contents ­2; 15; "A"; 3.14 4/116 #12

Hehner, Eric C.R.

241

Fullerene Embedded Shape Memory Nanolens Array  

NASA Astrophysics Data System (ADS)

Securing fragile nanostructures against external impact is indispensable for offering sufficiently long lifetime in service to nanoengineering products, especially when coming in contact with other substances. Indeed, this problem still remains a challenging task, which may be resolved with the help of smart materials such as shape memory and self-healing materials. Here, we demonstrate a shape memory nanostructure that can recover its shape by absorbing electromagnetic energy. Fullerenes were embedded into the fabricated nanolens array. Beside the energy absorption, such addition enables a remarkable enhancement in mechanical properties of shape memory polymer. The shape memory nanolens was numerically modeled to impart more in-depth understanding on the physics regarding shape recovery behavior of the fabricated nanolens. We anticipate that our strategy of combining the shape memory property with the microwave irradiation feature can provide a new pathway for nanostructured systems able to ensure a long-term durability.

Jeon, Sohee; Jang, Jun Young; Youn, Jae Ryoun; Jeong, Jun-Ho; Brenner, Howard; Song, Young Seok

2013-11-01

242

Fullerene embedded shape memory nanolens array.  

PubMed

Securing fragile nanostructures against external impact is indispensable for offering sufficiently long lifetime in service to nanoengineering products, especially when coming in contact with other substances. Indeed, this problem still remains a challenging task, which may be resolved with the help of smart materials such as shape memory and self-healing materials. Here, we demonstrate a shape memory nanostructure that can recover its shape by absorbing electromagnetic energy. Fullerenes were embedded into the fabricated nanolens array. Beside the energy absorption, such addition enables a remarkable enhancement in mechanical properties of shape memory polymer. The shape memory nanolens was numerically modeled to impart more in-depth understanding on the physics regarding shape recovery behavior of the fabricated nanolens. We anticipate that our strategy of combining the shape memory property with the microwave irradiation feature can provide a new pathway for nanostructured systems able to ensure a long-term durability. PMID:24253423

Jeon, Sohee; Jang, Jun Young; Youn, Jae Ryoun; Jeong, Jun-Ho; Brenner, Howard; Song, Young Seok

2013-01-01

243

Fullerene Embedded Shape Memory Nanolens Array  

PubMed Central

Securing fragile nanostructures against external impact is indispensable for offering sufficiently long lifetime in service to nanoengineering products, especially when coming in contact with other substances. Indeed, this problem still remains a challenging task, which may be resolved with the help of smart materials such as shape memory and self-healing materials. Here, we demonstrate a shape memory nanostructure that can recover its shape by absorbing electromagnetic energy. Fullerenes were embedded into the fabricated nanolens array. Beside the energy absorption, such addition enables a remarkable enhancement in mechanical properties of shape memory polymer. The shape memory nanolens was numerically modeled to impart more in-depth understanding on the physics regarding shape recovery behavior of the fabricated nanolens. We anticipate that our strategy of combining the shape memory property with the microwave irradiation feature can provide a new pathway for nanostructured systems able to ensure a long-term durability. PMID:24253423

Jeon, Sohee; Jang, Jun Young; Youn, Jae Ryoun; Jeong, Jun-ho; Brenner, Howard; Song, Young Seok

2013-01-01

244

POW Memory  

NSDL National Science Digital Library

Most people think eyewitness testimony is the best possible evidence against an alleged criminal -- especially when that testimony comes from the victim. But people who survive terrifying situations may actually have surprisingly unreliable memories of who or what caused them.

Science Update

2004-07-12

245

Polymers All Around You!  

ERIC Educational Resources Information Center

Background information on natural polymers, synthetic polymers, and the properties of polymers is presented as an introduction to this curriculum guide. Details are provided on the use of polymer products in consumer goods, polymer recycling, polymer densities, the making of a polymer such as GLUEP, polyvinyl alcohol, dissolving plastics, polymers

Gertz, Susan

246

Ferroelectric memories  

Microsoft Academic Search

In the past year it has become possible to fabricate ferroelectric thin-film memories onto standard silicon integrated circuits that combine very high speed (30-nanosecond read\\/erase\\/rewrite operation), 5-volt standard silicon logic levels, very high density (2 by 2 micrometer cell size), complete nonvolatility (no standby power required), and extreme radiation hardness. These ferroelectric random-access memories are expected to replace magnetic core

J. F. Scott; C. A. Paz de Araujo

1989-01-01

247

Memory Solitaire  

NSDL National Science Digital Library

In this online game, learners practice memory recall. They are shown a collage of pictures for two minutes, then have to write down everything they remember and check how they did. After, they learn a memory-improving method of "tell yourself a story" to help train their brain, and try again. Although this activity is designed to be done online and individually, it can easily be adapted to be done using a printout and in a group setting.

Exploratorium

2000-01-01

248

Memorial Sloan-Kettering Cancer Center  

Cancer.gov

Research at Memorial Sloan-Kettering Cancer Center is focused on cancer diagnosis and enhancing responses of tumor to treatment with a goal of curing cancer. Animal studies of novel cancer therapeutics, while imperfect as a treatment model, have utility, both in studying therapeutic efficacy and toxicity. Because tumors are heterogenous, both between individuals and within a single tumor, non-invasive imaging studies are necessary to provide information about variation in response.

249

Affect and the therapeutic action of psychoanalysis.  

PubMed

In connection with controversial IJP articles by Stern et al. and Fonagy on the interpretation of the repressed and the recovery of past memories, the author maintains that the affect that is inherent in positive transference is at the heart of therapeutic action. Points of view put forward in the controversy (based on neurobiological knowledge) are related to Freudian metapsychology, as well as to their precursors whose scope was necessarily limited by a lack of access to more recent scientific discoveries. The author demonstrates metapsychological elements of therapeutic action inherent in the intersubjective relationship, especially identification, manifested in introjection and empathy. He describes cognitive development as spontaneously blossoming from the affective nucleus, and he explains the neuroscientific bases of this step forward. The classic (interpretative) psychoanalytic method makes up the cognitive superstructure necessary for the organisation of the mind that has sprung from the affective substructure. As a primary factor in psychic change, interpretation is limited in effectiveness to pathologies arising from the verbal phase, related to explicit memories, with no effect in the pre-verbal phase where implicit memories are to be found. Interpretation--the method used to the exclusion of all others for a century--is only partial; when used in isolation it does not meet the demands of modern broad-spectrum psychoanalysis, as the clinical material presented illustrates. PMID:16096070

Andrade, Victor Manoel

2005-06-01

250

Polymers Guide  

NSDL National Science Digital Library

This 21 page document contains an instructor guide for the polymers module from Nano-Link. The activity requires a background in eight grade science. The document includes background information on polymers, a hands-on learning activity, questions to check understanding, links to multimedia resources, and further readings. Visitors must complete a quick and free registration to access the materials.

251

Polymers & People  

ERIC Educational Resources Information Center

Each Tuesday during the fall of 2002, teams of high school students from three South Carolina counties conducted a four-hour polymer institute for their peers. In less than two months, over 300 students visited the Charleston County Public Library in Charleston, South Carolina, to explore DNA, nylon, rubber, gluep, and other polymers. Teams of…

Lentz, Linda; Robinson, Thomas; Martin, Elizabeth; Miller, Mary; Ashburn, Norma

2004-01-01

252

A coarse grained model of polymer networks focusing on the intermediate length scales  

E-print Network

We propose a coarse-grained model for polymer chains and polymer networks based on the meso-scale dynamics. The model takes the internal degrees of freedom of the constituent polymer chains into account using memory functions and colored noises. We apply our model to dilute polymer solutions and polymer networks. A numerical simulation on a dilute polymer solution demonstrates the validity of the assumptions on the dynamics of our model. By applying this model to polymer networks, we find a transition in the dynamical behavior from an isolated chain state to a network state.

Takashi Shibata; Hidemitsu Furukawa; Toshihiro Kawakatsu

2008-03-29

253

Worthington Memory  

NSDL National Science Digital Library

This Online Scrapbook of Worthington History is a collaborative project between the Worthington (Ohio) Libraries and the Worthington Historical Society to present local history materials. Visitors can search or browse the digitized collection, currently over 117 photographs and documents. Those unfamiliar with Worthington can use the browse feature to retrieve collection items organized into broad categories such as Arts, Architecture, Agriculture, Business and Commerce, or by decade from 1800 to 2002. Documentation, such as selection criteria, and a 36-page manual "Worthington Memory Digital Imaging Workflow" is provided, making Worthington Memory a handy resource for other public libraries wishing to begin a local history digitization project.

254

Memory clinics  

PubMed Central

Memory clinics were first described in the 1980s. They have become accepted worldwide as useful vehicles for improving practice in the identification, investigation, and treatment of memory disorders, including dementia. They are provided in various settings, the setting determining clientele and practice. All aim to facilitate referral from GPs, other specialists, or by self referral, in the early stages of impairment, and to avoid the stigma associated with psychiatric services. They bring together professionals with a range of skills for the benefit of patients, carers, and colleagues, and contribute to health promotion, health education, audit, and research, as well as service to patients. PMID:16517802

Jolley, D; Benbow, S M; Grizzell, M

2006-01-01

255

Nitric Oxide Release Part II. Therapeutic Applications  

PubMed Central

Summary A wide range of nitric oxide (NO)-releasing materials have emerged as potential therapeutics that exploit NO’s vast biological roles. Macromolecular NO-releasing scaffolds are particularly promising due to their ability to store and deliver larger NO payloads in a more controlled and effective manner compared to low molecular weight NO donors. While a variety of scaffolds (e.g., particles, dendrimers, and polymers/films) have been cleverly designed, the ultimate clinical utility of most NO-releasing macromolecules remains unrealized. Although not wholly predictive of clinical success, in vitro and in vivo investigations have enabled a preliminary evaluation of the therapeutic potential of such materials. Herein, we review the application of macromolecular NO therapies for cardiovascular disease, cancer, bacterial infections, and wound healing. PMID:22362384

Carpenter, Alexis W.; Schoenfisch, Mark H.

2012-01-01

256

Towards Therapeutic Arteriogenesis  

Cancer.gov

Arteriogenesis or the formation of arterial conduits is a promising therapeutic approach to the treatment of a number of ischemic vascular diseases. However, the molecular basis of this process remains poorly understood.

257

Therapeutics for Bowel Disorders  

Cancer.gov

The National Cancer Institute''s Laboratory of Metabolism is seeking statements of capability or interest from parties interested in collaborative research to further develop, evaluate, or commercialize therapeutics that ameliorate bowel disorders.

258

Branched Polymers  

E-print Network

Building on and from the work of Brydges and Imbrie, we give an elementary calculation of the volume of the space of branched polymers of order $n$ in the plane and in 3-space. Our development reveals some more general identities, and allows exact random sampling. In particular we show that a random 3-dimensional branched polymer of order $n$ has diameter of order $\\sqrt{n}$.

Richard Kenyon; Peter Winkler

2007-09-14

259

Polymer Synthesis  

NSDL National Science Digital Library

In the first four chapters, we have seen that many different kinds of polymers exist and that they have an extremely wide range of properties. Some are stiff, others are soluble, while still others are rubbery. There are plastics, and fibers, and adhesives, and foams. The structure and composition of the macromolecule dictate the ultimate properties. Structure and composition are determined when the macromolecule is synthesized. In this chapter we want to understand how monomers react together to form long polymer chains.

David Teegarden

2004-01-01

260

Therapeutic development in psoriasis.  

PubMed

Advances in molecular biology have provided the basis for development of new therapeutic approaches to psoriasis. New, more effective therapies target specific molecules in the inflammatory cascade involved in the pathogenesis of psoriasis.The biologic era of psoriasis therapy began with inhibitors of T-cell activation, tumor necrosis factor-?, and interleukin (IL)-12/23. Continued investigation has led to therapies and therapeutic candidates that target IL-17, IL-23, phosphodiesterase-4, and isomers of Janus kinase. PMID:25268599

Sobell, Jeffrey M; Leonardi, Craig L

2014-06-01

261

Therapeutic Endoscopic Ultrasound  

PubMed Central

Endoscopic ultrasound (EUS) is a viable and often preferred alternative to interventional and radiologic procedures, and the therapeutic applications of EUS continue to evolve. This evolution was catalyzed by the introduction of linear echoendoscopes that provide continuous imaging and observation of needles and by therapeutic devices that pass through large-caliber working channels. In this paper, we will discuss the spectrum of EUS-guided interventions that are currently available and in development. PMID:23293554

Abu Dayyeh, Barham K.

2012-01-01

262

Triboelectric activation of ferroelectric liquid crystal memory devices  

NASA Astrophysics Data System (ADS)

The switching of ferroelectric liquid crystal (FLC) memory device is achieved by triboelectric effect of externally connected insulator to the sample through a conductor. The positive and negative charges are induced by triboelectrification of polymers, depending on the nature of materials, and utilized to get the bright and dark states of the FLC memory device. These switching states are analyzed by electro-optical studies. This technique of polarization switching proves to be powerful for FLC devices exhibiting long-term memory. The charges, developed on the electrodes by this nonconventional technique, generate enough potential to switch the FLC molecules in memory state.

Choudhary, A.; Joshi, T.; Biradar, A. M.

2010-09-01

263

Super Memory  

NSDL National Science Digital Library

In this activity (pages 26-29 of the PDF), learners investigate how they can develop super memories by using mnemonic devices. In the first part of the activity, learners use mnemonic devices to memorize a group of random objects. In the second part, learners use mnemonic devices to memorize a phone number.

2012-06-08

264

Hollow memories  

NASA Astrophysics Data System (ADS)

A hollow-core optical fibre filled with warm caesium atoms can temporarily store the properties of photons. Michael Sprague from the University of Oxford, UK, explains to Nature Photonics how this optical memory could be a useful building block for fibre-based quantum optics.

2014-04-01

265

Memory Loss  

Microsoft Academic Search

In the wake of the current storm over what constitutes truth – non-fiction – and what is “made up” – fictional – my fascination with the flexibility of memory is suddenly more than a little apropos. Current literary events notwithstanding, I grew up under a dark veil of depression, which seemingly “erased” my childhood. It wasn’t until I delved into

Anne M. McDermott

2006-01-01

266

Memory psychophysics  

Microsoft Academic Search

The relationship between perceptual and cognitive processes has been a topic of increasing interest. This review focuses on the use of techniques and theory drawn from classical psychophysics and applied to the study of mental representation. Several issues including examination of the functions that relate remembered and perceived magnitude to physical intensity, the relationship of memorial to perceptual functions, the

Timothy L. Hubbard

1994-01-01

267

Semi-permeable coatings fabricated from comb-polymers efficiently protect proteins in vivo  

NASA Astrophysics Data System (ADS)

In comparison to neutral linear polymers, functional and architecturally complex (that is, non-linear) polymers offer distinct opportunities for enhancing the properties and performance of therapeutic proteins. However, understanding how to harness these parameters is challenging, and studies that capitalize on them in vivo are scarce. Here we present an in vivo demonstration that modification of a protein with a polymer of appropriate architecture can impart low immunogenicity, with a commensurably low loss of therapeutic activity. These combined properties are inaccessible by conventional strategies using linear polymers. For the model protein L-asparaginase, a comb-polymer bio-conjugate significantly outperformed the linear polymer control in terms of lower immune response and more sustained bioactivity. The semi-permeability characteristics of the coatings are consistent with the phase diagram of the polymer, which will facilitate the application of this strategy to other proteins and with other therapeutic models.

Liu, Mi; Johansen, Pål; Zabel, Franziska; Leroux, Jean-Christophe; Gauthier, Marc A.

2014-11-01

268

Milestoning with coarse memory.  

PubMed

Milestoning is a method used to calculate the kinetics of molecular processes occurring on timescales inaccessible to traditional molecular dynamics (MD) simulations. In the method, the phase space of the system is partitioned by milestones (hypersurfaces), trajectories are initialized on each milestone, and short MD simulations are performed to calculate transitions between neighboring milestones. Long trajectories of the system are then reconstructed with a semi-Markov process from the observed statistics of transition. The procedure is typically justified by the assumption that trajectories lose memory between crossing successive milestones. Here we present Milestoning with Coarse Memory (MCM), a generalization of Milestoning that relaxes the memory loss assumption of conventional Milestoning. In the method, milestones are defined and sample transitions are calculated in the standard Milestoning way. Then, after it is clear where trajectories sample milestones, the milestones are broken up into distinct neighborhoods (clusters), and each sample transition is associated with two clusters: the cluster containing the coordinates the trajectory was initialized in, and the cluster (on the terminal milestone) containing trajectory's final coordinates. Long trajectories of the system are then reconstructed with a semi-Markov process in an extended state space built from milestone and cluster indices. To test the method, we apply it to a process that is particularly ill suited for Milestoning: the dynamics of a polymer confined to a narrow cylinder. We show that Milestoning calculations of both the mean first passage time and the mean transit time of reversal-which occurs when the end-to-end vector reverses direction-are significantly improved when MCM is applied. Finally, we note the overhead of performing MCM on top of conventional Milestoning is negligible. PMID:23614410

Hawk, Alexander T

2013-04-21

269

The past, the future and the biology of memory storage.  

PubMed Central

We here briefly review a century of accomplishments in studying memory storage and delineate the two major questions that have dominated thinking in this area: the systems question of memory, which concerns where in the brain storage occurs; and the molecular question of memory, which concerns the mechanisms whereby memories are stored and maintained. We go on to consider the themes that memory research may be able to address in the 21st century. Finally, we reflect on the clinical and societal import of our increasing understanding of the mechanisms of memory, discussing possible therapeutic approaches to diseases that manifest with disruptions of learning and possible ethical implication of the ability, which is on the horizon, to ameliorate or even enhance human memory. PMID:10670023

Kandel, E R; Pittenger, C

1999-01-01

270

Shape-memory surfaces for cell mechanobiology  

NASA Astrophysics Data System (ADS)

Shape-memory polymers (SMPs) are a new class of smart materials, which have the capability to change from a temporary shape ‘A’ to a memorized permanent shape ‘B’ upon application of an external stimulus. In recent years, SMPs have attracted much attention from basic and fundamental research to industrial and practical applications due to the cheap and efficient alternative to well-known metallic shape-memory alloys. Since the shape-memory effect in SMPs is not related to a specific material property of single polymers, the control of nanoarchitecture of polymer networks is particularly important for the smart functions of SMPs. Such nanoarchitectonic approaches have enabled us to further create shape-memory surfaces (SMSs) with tunable surface topography at nano scale. The present review aims to bring together the exciting design of SMSs and the ever-expanding range of their uses as tools to control cell functions. The goal for these endeavors is to mimic the surrounding mechanical cues of extracellular environments which have been considered as critical parameters in cell fate determination. The untapped potential of SMSs makes them one of the most exciting interfaces of materials science and cell mechanobiology.

Ebara, Mitsuhiro

2015-02-01

271

Engineered therapeutic-releasing nanoporous anodic alumina-aluminum wires with extended release of therapeutics.  

PubMed

In this study, we present a nanoengineered therapeutic-releasing system based on aluminum wires featuring nanoporous anodic alumina layers and chitosan coatings. Nanoporous anodic alumina layers are produced on the surface of aluminum wires by electrochemical anodization. These nanoporous layers with precisely engineered nanopore geometry are used as nanocontainers for bovine serum albumin molecules labeled with fluorescein isothiocyanate (BSA-FITC), which is selected as a model drug. The surface of these therapeutic-releasing implants is coated with a biocompatible and biodegradable polymer, chitosan, in order to achieve a sustained release of protein over extended periods of time. The performance of this therapeutic-releasing device is systematically assessed through a series of experiments under static and dynamic flow conditions. In these experiments, the effect of such parameters as the number of layers of chitosan coating and the temperature and pH of the eluting medium is established. The obtained results reveal that the proposed therapeutic-releasing system based on nanoporous aluminum wires can be engineered with sustained release performance for up to 6.5 weeks, which is a critical factor for medical treatments using sensitive therapeutics such as proteins and genes when a localized delivery is desired. PMID:25625878

Law, Cheryl Suwen; Santos, Abel; Kumeria, Tushar; Losic, Dusan

2015-02-18

272

Effects of oxytocin on the fear memory reconsolidation.  

PubMed

Oxytoxin (OT) promotes social behavior and reduces anxiety. A great number of studies suggest that OT plays a role in learning and memory processes in animals and humans. Fear memories are rendered labile and prone to modification after reactivation and a restabilization and reconsolidation process is necessary for future memory conservation. This process is crucial for modulation of an existing memory and forms a promising therapeutic target for pathological memory disorders. In this study, we investigated whether a single systemic injection of OT has effects on reconsolidation of fear memories. We found post-reactivation administration of OT impairs reconsolidation of these memories and the impairment effect is reactivation-dependent. Postreactivation short-term fear memories and the learning of new fear memory were unaffected by OT. The study demonstrates the effectiveness of OT in persistently impairing fear memory retention by blocking reconsolidation in rats. OT administration after retrieval of fear memories may open a new avenue to treat pathological memory-related disorders. PMID:25796180

Hou, Yu; Zhao, Liyan; Zhang, Genai; Ding, Lixiang

2015-05-01

273

Injectable preformed scaffolds with shape-memory properties  

PubMed Central

Injectable biomaterials are increasingly being explored to minimize risks and complications associated with surgical implantation. We describe a strategy for delivery via conventional needle–syringe injection of large preformed macroporous scaffolds with well-defined properties. Injectable 3D scaffolds, in the form of elastic sponge-like matrices, were prepared by environmentally friendly cryotropic gelation of a naturally sourced polymer. Cryogels with shape-memory properties may be molded to a variety of shapes and sizes, and may be optionally loaded with therapeutic agents or cells. These scaffolds have the capability to withstand reversible deformations at over 90% strain level, and a rapid volumetric recovery allows the structurally defined scaffolds to be injected through a small-bore needle with nearly complete geometric restoration once delivered. These gels demonstrated long-term release of biomolecules in vivo. Furthermore, cryogels impregnated with bioluminescent reporter cells provided enhanced survival, higher local retention, and extended engraftment of transplanted cells at the injection site compared with a standard injection technique. These injectable scaffolds show great promise for various biomedical applications, including cell therapies. PMID:23150549

Bencherif, Sidi A.; Sands, R. Warren; Bhatta, Deen; Arany, Praveen; Verbeke, Catia S.; Edwards, David A.; Mooney, David J.

2012-01-01

274

Polymer inflation  

E-print Network

We consider the semi-classical dynamics of a free massive scalar field in a homogeneous and isotropic cosmological spacetime. The scalar field is quantized using the polymer quantization method assuming that it is described by a gaussian coherent state. For quadratic potentials, the semi-classical equations of motion yield a universe that has an early "polymer inflation" phase which is generic and almost exactly de Sitter, followed by a epoch of slow-roll inflation. We compute polymer corrections to the slow roll formalism, and discuss the probability of inflation in this model using a physical Hamiltonian arising from time gauge fixing. We also show how in this model, it is possible to obtain a significant amount of slow-roll inflation from sub-Planckain initial data, hence circumventing some of the criticisms of standard scenarios. These results show the extent to which a quantum gravity motivated quantization method affects early universe dynamics.

Syed Moeez Hassan; Viqar Husain; Sanjeev S. Seahra

2015-03-05

275

Polymer inflation  

E-print Network

We consider the semi-classical dynamics of a free massive scalar field in a homogeneous and isotropic cosmological spacetime. The scalar field is quantized using the polymer quantization method assuming that it is described by a gaussian coherent state. For quadratic potentials, the semi-classical equations of motion yield a universe that has an early "polymer inflation" phase which is generic and almost exactly de Sitter, followed by a epoch of slow-roll inflation. We compute polymer corrections to the slow roll formalism, and discuss the probability of inflation in this model using a physical Hamiltonian arising from time gauge fixing. These results show the extent to which a quantum gravity motivated quantization method affects early universe dynamics.

Hassan, Syed Moeez; Seahra, Sanjeev S

2014-01-01

276

Polymer inflation  

NASA Astrophysics Data System (ADS)

We consider the semiclassical dynamics of a free massive scalar field in a homogeneous and isotropic cosmological spacetime. The scalar field is quantized using the polymer quantization method assuming that it is described by a Gaussian coherent state. For quadratic potentials, the semiclassical equations of motion yield a universe that has an early "polymer inflation" phase which is generic and almost exactly de Sitter, followed by an epoch of slow-roll inflation. We compute polymer corrections to the slow-roll formalism, and discuss the probability of inflation in this model using a physical Hamiltonian arising from time gauge fixing. We also show how in this model, it is possible to obtain a significant amount of slow-roll inflation from sub-Planckian initial data, hence circumventing some of the criticisms of standard scenarios. These results show the extent to which a quantum gravity motivated quantization method affects early universe dynamics.

Hassan, Syed Moeez; Husain, Viqar; Seahra, Sanjeev S.

2015-03-01

277

Antimocrobial Polymer  

DOEpatents

A polymeric composition having antimicrobial properties and a process for rendering the surface of a substrate antimicrobial are disclosed. The composition comprises a crosslinked chemical combination of (i) a polymer having amino group-containing side chains along a backbone forming the polymer, (ii) an antimicrobial agent selected from quaternary ammonium compounds, gentian violet compounds, substituted or unsubstituted phenols, biguanide compounds, iodine compounds, and mixtures thereof, and (iii) a crosslinking agent containing functional groups capable of reacting with the amino groups. In one embodiment, the polymer is a polyamide formed from a maleic anhydride or maleic acid ester monomer and alkylamines thereby producing a polyamide having amino substituted alkyl chains on one side of the polyamide backbone; the crosslinking agent is a phosphine having the general formula (A)3P wherein A is hydroxyalkyl; and the antimicrobial agent is chlorhexidine, dimethylchlorophenol, cetyl pyridinium chloride, gentian violet, triclosan, thymol, iodine, and mixtures thereof.

McDonald, William F. (Utica, OH); Huang, Zhi-Heng (Walnut Creek, CA); Wright, Stacy C. (Columbus, GA)

2005-09-06

278

Pancreatic Pseudocyst: Therapeutic Dilemma  

PubMed Central

Pancreatic pseudocyst develops in both acute and chronic pancreatitis. It is an entity likely to either remain asymptomatic or develop devastating complications. Despite being diagnosed easily, treatment exercise is still at crossroads whether in the form of internal or external drainage or endoscopic, laparoscopic, or open intervention with a good radiological guidance. The therapeutic dilemma whether to treat a patient with a pancreatic pseudocyst, as well as when and with what technique, is a difficult one. This paper is intended to get information about diagnostic and therapeutic exercises most appropriate for acute and chronic pancreatic pseudocyst. PMID:22577595

Khanna, A. K.; Tiwary, Satyendra K.; Kumar, Puneet

2012-01-01

279

Therapeutic Antioxidant Medical Gas  

PubMed Central

Medical gases are pharmaceutical gaseous molecules which offer solutions to medical needs and include traditional gases, such as oxygen and nitrous oxide, as well as gases with recently discovered roles as biological messenger molecules, such as carbon monoxide, nitric oxide and hydrogen sulphide. Medical gas therapy is a relatively unexplored field of medicine; however, a recent increasing in the number of publications on medical gas therapies clearly indicate that there are significant opportunities for use of gases as therapeutic tools for a variety of disease conditions. In this article, we review the recent advances in research on medical gases with antioxidant properties and discuss their clinical applications and therapeutic properties. PMID:19177183

Nakao, Atsunori; Sugimoto, Ryujiro; Billiar, Timothy R; McCurry, Kenneth R

2009-01-01

280

DELIVERY OF THERAPEUTIC PROTEINS  

PubMed Central

The safety and efficacy of protein therapeutics are limited by three interrelated pharmaceutical issues, in vitro and in vivo instability, immunogenicity and shorter half-lives. Novel drug modifications for overcoming these issues are under investigation and include covalent attachment of poly(ethylene glycol) (PEG), polysialic acid, or glycolic acid, as well as developing new formulations containing nanoparticulate or colloidal systems (e.g. liposomes, polymeric microspheres, polymeric nanoparticles). Such strategies have the potential to develop as next generation protein therapeutics. This review includes a general discussion on these delivery approaches. PMID:20049941

Pisal, Dipak S.; Kosloski, Matthew P.; Balu-Iyer, Sathy V.

2009-01-01

281

In vitro cytotoxicity testing of AB-polymer networks based on oligo(epsilon-caprolactone) segments after different sterilization techniques.  

PubMed

Recently developed versatile biodegradable polymeric biomaterial offer new therapeutic options in numerous medical fields. Biocompatibility is a crucial requirement for the biomedical application of biomaterials, including the sterilization of these materials with the use of accepted protocols. Ethylene-oxide (EO) and low-temperature plasma (LTP) sterilization are frequently used low-temperature sterilization technologies for heat-sensitive materials. The agarose diffusion assay is a recommended cell-screening test to assess the cytotoxicity of biomaterials in vitro. The sensitivity of the agarose assay can be increased by using a modified computer-based image-analysis system. The influence of EO and LTP sterilization on the cytotoxicity of a versatile polymer system of shape-memory polymer networks based on oligo (epsilon-caprolactone) dimethacrylate and n-butyl acrylate was investigated. Statistically significant differences in the rate of cell lysis after EO and LTP sterilization of the polymer samples were detected by using this modified quantification system. The influence of the different sterilization techniques on the cytotoxicity of the polymeric material, as well as the clinical relevance of the described differences, are discussed. PMID:14598399

Rickert, Dorothee; Lendlein, A; Schmidt, A M; Kelch, S; Roehlke, W; Fuhrmann, R; Franke, R P

2003-11-15

282

Glue Polymer  

NSDL National Science Digital Library

What is a polymer, and what are some of its properties? This material is part of a series of hands-on science activities designed to arouse student interest. In this discovery activity students use white glue, water, and borax to make a vinyl polymer and study its properties. The activity includes a description, a list of science process skills and complex reasoning strategies being used, and a compilation of applicable K-12 national science education standards. Also provided are content topics, a list of necessary supplies, instructions, and presentation techniques. The content of the activity is explained, and assessment suggestions are provided.

Mid-continent Research for Education and Learning (McREL)

2004-01-01

283

Predictors of sustained therapeutic change  

Microsoft Academic Search

The authors integrate explorations by Blatt and colleagues of contributions of patient personality, therapeutic relationship, and change in mental representation to sustained therapeutic change. A pretreatment personality characteristic, self-critical perfectionism, a negative self-schema, significantly interfered with therapeutic progress in manual-directed, brief outpatient treatment for depression. The therapeutic relationship, however, facilitated changes in this negative self-representation, leading to sustained therapeutic change.

Sidney J. Blatt; David C. Zuroff; Lance L. Hawley; John S. Auerbach

2010-01-01

284

Protein-polymer nanoreactors for medical applications.  

PubMed

Major challenges that confront nanoscience in medicine today include the development of efficacious therapies with minimum side effects, diagnostic methods featuring significantly higher sensitivities and selectivities, and personalized diagnostics and therapeutics for theragnostic approaches. With these goals in mind, combining biological molecules and synthetic carriers/templates, such as polymer supramolecular assemblies, represents a very promising strategy. In this critical review, we present protein-polymer systems as reaction spaces at the nano-scale in which the enzymatic reactions take place inside polymer supramolecular assembly, at its interface with the environment or in a combination of both. The location of the protein(s) with respect to the polymer assembly generates a diversity of systems ranging from nanoreactors to active enzymatic polymer surfaces. We describe these both in terms of general modelling and addressing the specific conditions and requirements related to the medical domain. We will particularly present protein-polymer nanoreactors that provide protected spaces for enzymatic reactions. We also show how polymer supramolecular structures, such as micelles, capsules, dendrimers and vesicles, can accommodate sensitive biomolecules to mimic natural systems and functions, and to serve as avenues for new medical approaches. Even though not yet on the market, we will emphasize possible applications of protein-polymer systems that generate reaction nanospaces-as novel ways to advanced medicine (264 references). PMID:22085991

Palivan, Cornelia G; Fischer-Onaca, Ozana; Delcea, Mihaela; Itel, Fabian; Meier, Wolfgang

2012-04-01

285

Therapeutic Recombinant Monoclonal Antibodies  

ERIC Educational Resources Information Center

During the last two decades, the rapid growth of biotechnology-derived techniques has led to a myriad of therapeutic recombinant monoclonal antibodies with significant clinical benefits. Recombinant monoclonal antibodies can be obtained from a number of natural sources such as animal cell cultures using recombinant DNA engineering. In contrast to…

Bakhtiar, Ray

2012-01-01

286

AMUM LECTURE: Therapeutic ultrasound  

Microsoft Academic Search

The use of ultrasound in medicine is now quite commonplace, especially with the recent introduction of small, portable and relatively inexpensive, hand-held diagnostic imaging devices. Moreover, ultrasound has expanded beyond the imaging realm, with methods and applications extending to novel therapeutic and surgical uses. These applications broadly include: tissue ablation, acoustocautery, lipoplasty, site-specific and ultrasound mediated drug activity, extracorporeal lithotripsy,

Lawrence A. Crum

2004-01-01

287

Therapeutic Human Papillomavirus Vaccination  

Microsoft Academic Search

Despite impressive progress in prevention and therapy of premalignant and malignant dysplasia the worldwide burden of cancer is relatively unchanged. Supplementation of the therapeutic arsenal by immunotherapeutic methods would have the potential to make a significant impact. Dysplastic lesions and cancer of the cervix show strong association with human papillomaviruses (HPV), as do tumours of other mucosal epithelia like squamous

Andreas E. Albers; Andreas M. Kaufmann

2009-01-01

288

Controversies in therapeutic touch  

Microsoft Academic Search

One of the most puzzling areas covered under the umbrella of integrative medicine is the field of energy healing. Based on the notion of a subtle vital force which is presumed to be the source of health, many ancient healing techniques have been evolved within this paradigm, including the modern American variant called Therapeutic Touch (TT). This article reviews the

Eric Leskowitz

2003-01-01

289

Polymer solutions  

DOEpatents

There is provided a method of making a polymer solution comprising polymerizing one or more monomer in a solvent, wherein said monomer comprises one or more ethylenically unsaturated monomer that is a multi-functional Michael donor, and wherein said solvent comprises 40% or more by weight, based on the weight of said solvent, one or more multi-functional Michael donor.

Krawczyk, Gerhard Erich (Bremen, DE); Miller, Kevin Michael (West Dundee, IL)

2011-07-26

290

Polymer Blends  

Microsoft Academic Search

The concept of appropriately combining two or more different polymers to obtain a new material system with the desirable features of its constituents is not new. Over the years, numerous systems based on the chemical combination of different monomers through random, block, and graft copolymerization methods have been developed with this goal in mind. For similar reasons, the coatings and

D. R. Paul; J. W. Barlow

1980-01-01

291

Antimicrobial polymers.  

PubMed

Better health is basic requirement of human being, but the rapid growth of harmful pathogens and their serious health effects pose a significant challenge to modern science. Infections by pathogenic microorganisms are of great concern in many fields such as medical devices, drugs, hospital surfaces/furniture, dental restoration, surgery equipment, health care products, and hygienic applications (e.g., water purification systems, textiles, food packaging and storage, major or domestic appliances etc.) Antimicrobial polymers are the materials having the capability to kill/inhibit the growth of microbes on their surface or surrounding environment. Recently, they gained considerable interest for both academic research and industry and were found to be better than their small molecular counterparts in terms of enhanced efficacy, reduced toxicity, minimized environmental problems, resistance, and prolonged lifetime. Hence, efforts have focused on the development of antimicrobial polymers with all desired characters for optimum activity. In this Review, an overview of different antimicrobial polymers, their mechanism of action, factors affecting antimicrobial activity, and application in various fields are given. Recent advances and the current clinical status of these polymers are also discussed. PMID:25408272

Jain, Anjali; Duvvuri, L Sailaja; Farah, Shady; Beyth, Nurit; Domb, Abraham J; Khan, Wahid

2014-12-01

292

How Memory Works  

MedlinePLUS

Memory functions through three steps: acquisition, consolidation and retrieval. 347126 InteliHealth 2010-02-10 f InteliHealth/Harvard Medical Content 2012-08-24 How Memory Works Memory functions through three steps: Acquisition Consolidation ...

293

Types of Memory  

MedlinePLUS

... can be further divided into explicit, implicit and semantic memory. Explicit memories are facts that you made ... as driving a car or riding a bicycle. Semantic memories are facts that are so deeply ingrained ...

294

Effects of selective phosphodiesterases-4 inhibitors on learning and memory: a review of recent research.  

PubMed

Phosphodiesterase-4 (PDE-4) regulates the intracellular level of cyclic adenosine monophosphate. Recent studies demonstrated that PDE-4 inhibitors can counteract deficits in long-term memory caused by aging or increased expression of mutant forms of human amyloid precursor proteins, and can influence the process of memory function and cognitive enhancement. Therapeutics, such as ketamine, a drug used in clinical anesthesia, can also cause memory deficits as adverse effects. Targeting PDE-4 with selective inhibitors may offer a novel therapeutic strategy to prevent, slow the progress, and, eventually, treat memory deficits. PMID:24699857

Peng, Sheng; Sun, Haiyan; Zhang, Xiaoqing; Liu, Gongjian; Wang, Guanglei

2014-09-01

295

Polyphenols: Multipotent Therapeutic Agents in Neurodegenerative Diseases  

PubMed Central

Aging leads to numerous transitions in brain physiology including synaptic dysfunction and disturbances in cognition and memory. With a few clinically relevant drugs, a substantial portion of aging population at risk for age-related neurodegenerative disorders require nutritional intervention. Dietary intake of polyphenols is known to attenuate oxidative stress and reduce the risk for related neurodegenerative diseases such as Alzheimer's disease (AD), stroke, multiple sclerosis (MS), Parkinson's disease (PD), and Huntington's disease (HD). Polyphenols exhibit strong potential to address the etiology of neurological disorders as they attenuate their complex physiology by modulating several therapeutic targets at once. Firstly, we review the advances in the therapeutic role of polyphenols in cell and animal models of AD, PD, MS, and HD and activation of drug targets for controlling pathological manifestations. Secondly, we present principle pathways in which polyphenol intake translates into therapeutic outcomes. In particular, signaling pathways like PPAR, Nrf2, STAT, HIF, and MAPK along with modulation of immune response by polyphenols are discussed. Although current polyphenol researches have limited impact on clinical practice, they have strong evidence and testable hypothesis to contribute clinical advances and drug discovery towards age-related neurological disorders. PMID:23840922

Bhullar, Khushwant S.; Rupasinghe, H. P. Vasantha

2013-01-01

296

Polymers Pushing Polymers: Polymer Mixtures in Thermodynamic Equilibrium with a Pore  

E-print Network

Polymers Pushing Polymers: Polymer Mixtures in Thermodynamic Equilibrium with a Pore R. Podgornik, 1000 Ljubljana, Slovenia Polymer Science and Engineering Department, University of Massachusetts, Amherst, Massachusetts 01003, United States ABSTRACT: We investigate polymer partitioning from polymer

Podgornik, Rudolf

297

Solid Tumor-Targeting Theranostic Polymer Nanoparticle in Nuclear Medicinal Fields  

PubMed Central

Polymer nanoparticles can be prepared by self-assembling of amphiphilic polymers, and various types of molecular assemblies have been reported. In particular, in medicinal fields, utilization of these polymer nanoparticles as carriers for drug delivery system (DDS) has been actively tried, and some nanoparticulate drugs are currently under preclinical evaluations. A radionuclide is an unstable nucleus and decays with emission of radioactive rays, which can be utilized as a tracer in the diagnostic imaging systems of PET and SPECT and also in therapeutic purposes. Since polymer nanoparticles can encapsulate most of diagnostic and therapeutic agents with a proper design of amphiphilic polymers, they should be effective DDS carriers of radionuclides in the nuclear medicinal field. Indeed, nanoparticles have been recently attracting much attention as common platform carriers for diagnostic and therapeutic drugs and contribute to the development of nanotheranostics. In this paper, recent developments of solid tumor-targeting polymer nanoparticles in nuclear medicinal fields are reviewed. PMID:25379530

Makino, Akira; Kimura, Shunsaku

2014-01-01

298

Solid tumor-targeting theranostic polymer nanoparticle in nuclear medicinal fields.  

PubMed

Polymer nanoparticles can be prepared by self-assembling of amphiphilic polymers, and various types of molecular assemblies have been reported. In particular, in medicinal fields, utilization of these polymer nanoparticles as carriers for drug delivery system (DDS) has been actively tried, and some nanoparticulate drugs are currently under preclinical evaluations. A radionuclide is an unstable nucleus and decays with emission of radioactive rays, which can be utilized as a tracer in the diagnostic imaging systems of PET and SPECT and also in therapeutic purposes. Since polymer nanoparticles can encapsulate most of diagnostic and therapeutic agents with a proper design of amphiphilic polymers, they should be effective DDS carriers of radionuclides in the nuclear medicinal field. Indeed, nanoparticles have been recently attracting much attention as common platform carriers for diagnostic and therapeutic drugs and contribute to the development of nanotheranostics. In this paper, recent developments of solid tumor-targeting polymer nanoparticles in nuclear medicinal fields are reviewed. PMID:25379530

Makino, Akira; Kimura, Shunsaku

2014-01-01

299

POLYMER PROGRAM SEMINAR "Nanomanufacturing with Polymers"  

E-print Network

POLYMER PROGRAM SEMINAR "Nanomanufacturing with Polymers" Prof. Joey Mead University Lowell has developed a suite of processes to enable the nanomanufacturing of polymer based products of properties (e.g. biocompatibility, polarity, and modulus). Polymer materials can be used as substrates

Alpay, S. Pamir

300

Clinical holistic medicine: how to recover memory without "implanting" memories in your patient.  

PubMed

Every therapeutic strategy and system teach us the philosophy of the treatment system to the patient, but often this teaching is subliminal and the philosophical impact must be seen as "implanted philosophy", which gives distorted interpretations of past events called "implanted memories". Based on the understanding of the connection between "implanted memory" and "implanted philosophy" we have developed a strategy for avoiding implanting memories arising from one of the seven most common causes of implanted memories in psychodynamic therapy: 1) Satisfying own expectancies, 2) pleasing the therapist, 3) transferences and counter transferences, 4) as source of mental and emotional order, 5) as emotional defence, 6) as symbol and 7) from implanted philosophy. Freud taught us that child sexuality is "polymorphously perverted", meaning that all kinds of sexuality is present at least potentially with the little child; and in dreams consciousness often go back to the earlier stages of development, potentially causing all kinds of sexual dreams and fantasies, which can come up in therapy and look like real memories. The therapist working with psychodynamic psychotherapy, clinical holistic medicine, psychiatry, and emotionally oriented bodywork, should be aware of the danger of implanting philosophy and memories. Implanted memories and implanted philosophy must be carefully handled and de-learned before ending the therapy. In conclusion "clinical holistic medicine" has developed a strategy for avoiding implanting memories. PMID:17891319

Ventegodt, Søren; Kandel, Isack; Merrick, Joav

2007-01-01

301

Strategies for therapeutic hypometabothermia  

PubMed Central

Although therapeutic hypothermia and metabolic suppression have shown robust neuroprotection in experimental brain ischemia, systemic complications have limited their use in treating acute stroke patients. The core temperature and basic metabolic rate are tightly regulated and maintained in a very stable level in mammals. Simply lowering body temperature or metabolic rate is actually a brutal therapy that may cause more systemic as well as regional problems other than providing protection. These problems are commonly seen in hypothermia and barbiturate coma. The main innovative concept of this review is to propose thermogenically optimal and synergistic reduction of core temperature and metabolic rate in therapeutic hypometabothermia using novel and clinically practical approaches. When metabolism and body temperature are reduced in a systematically synergistic manner, the outcome will be maximal protection and safe recovery, which happen in natural process, such as in hibernation, daily torpor and estivation. PMID:24179563

Liu, Shimin; Chen, Jiang-Fan

2013-01-01

302

Therapeutic Hypothermia for Neuroprotection  

PubMed Central

The earliest recorded application of therapeutic hypothermia in medicine spans about 5000 years; however, its use has become widespread since 2002, following the demonstration of both safety and efficacy of regimens requiring only a mild (32°C-35°C) degree of cooling after cardiac arrest. We review the mechanisms by which hypothermia confers neuroprotection as well as its physiological effects by body system and its associated risks. With regard to clinical applications, we present evidence on the role of hypothermia in traumatic brain injury, intracranial pressure elevation, stroke, subarachnoid hemorrhage, spinal cord injury, hepatic encephalopathy, and neonatal peripartum encephalopathy. Based on the current knowledge and areas undergoing or in need of further exploration, we feel that therapeutic hypothermia holds promise in the treatment of patients with various forms of neurologic injury; however, additional quality studies are needed before its true role is fully known. PMID:24982721

Karnatovskaia, Lioudmila V.; Wartenberg, Katja E.

2014-01-01

303

Complement-targeted therapeutics  

PubMed Central

The complement system is a central component of innate immunity and bridges the innate to the adaptive immune response. However, it can also turn its destructive capabilities against host cells and is involved in numerous diseases and pathological conditions. Modulation of the complement system has been recognized as a promising strategy in drug discovery, and a large number of therapeutic modalities have been developed. However, successful marketing of complement-targeted drugs has proved to be more difficult than initially expected, and many strategies have been discontinued. The US Food and Drug Administration’s approval of the first complement-specific drug, an antibody against complement component C5 (eculizumab; Soliris), in March 2007, was a long-awaited breakthrough in the field. Approval of eculizumab validates the complement system as therapeutic target and might facilitate clinical development of other promising drug candidates. PMID:17989689

Ricklin, Daniel; Lambris, John D

2010-01-01

304

Therapeutic advances in immunosuppression.  

PubMed Central

Immunosuppressive therapy is appropriate for the prevention or reversal of allograft rejection, and for the treatment of autoimmune disorders and allergic disease. Recent advances in our understanding of the cellular and molecular mechanisms that regulate immune responses have paralleled elucidation of the modes of action of a variety of therapeutic immunosuppressive agents, both 'old' and new. These developments have identified potential targets for more refined and specific intervention strategies that are now being tested in the clinic. PMID:7994898

Thomson, A W; Forrester, J V

1994-01-01

305

Mitochondrial Diseases: Therapeutic Approaches  

Microsoft Academic Search

Therapy of mitochondrial encephalomyopathies (defined restrictively as defects of the mitochondrial respiratory chain) is\\u000a woefully inadequate, despite great progress in our understanding of the molecular bases of these disorders. In this review,\\u000a we consider sequentially several different therapeutic approaches. Palliative therapy is dictated by good medical practice\\u000a and includes anticonvulsant medication, control of endocrine dysfunction, and surgical procedures. Removal of

Salvatore DiMauro; Michelangelo Mancuso

2007-01-01

306

Assessment of Therapeutic Response  

Microsoft Academic Search

Bone is the most common site of metastasis in cancer patients. Bone metastases are associated with increased morbidity as\\u000a reflected through pain, reduced quality of life and so called skeletal related events (SREs) as well as worsening patient\\u000a mortality reflected through decreased survival. This chapter will review the most up-to-date knowledge regarding the assessment\\u000a of therapeutic response in patients with

Orit Freedman; Mark Clemons; Vassilios Vassiliou; Dimitrios Kardamakis; Christine Simmons; Mateya Trinkaus; Edward Chow

307

Nanomaterial-mediated CNS Delivery of Diagnostic and Therapeutic Agents  

PubMed Central

Research into the diagnosis and treatment of central nervous system (CNS) diseases has been enhanced by rapid advances in nanotechnology and an expansion in the library of nanostructured carriers. This review discusses the latest applications of nanomaterials in the CNS with an emphasis on brain tumors. Novel administration routes and transport mechanisms for nanomaterial-mediated CNS delivery of diagnostic and therapeutic agents to bypass or cross the blood brain barrier (BBB) are also discussed. These include temporary disruption of the BBB, use of impregnated polymers (polymer wafers), convection-enhanced delivery (CED), and intranasal delivery. Moreover, an in vitro BBB model capable of mimicking geometrical, cellular and rheological features of the human cerebrovasculature has been developed. This is a useful tool that can be used for screening CNS nanoparticles or therapeutics prior to in vivo and clinical investigation. A discussion of this novel model is included. PMID:22178615

Biddlestone-Thorpe, Laura; Marchi, Nicola; Guo, Kathy; Ghosh, Chaitali; Janigro, Damir; Valerie, Kristoffer; Yang, Hu

2011-01-01

308

Visual Memory and Imagery Visual Memory  

E-print Network

Procedural ­ general knowledge of general skills Episodic ­ information about experiences #12;22 Visual;35 Sleep Tarnow's theory ­ LTM is stored in dream format Doesn't matter how we learned information. How does sleep affect our memory? #12;36 Sleep = better memory? Sleep benefits memory retention

Majumder, Aditi

309

Memory Retrieval and Interference: Working Memory Issues  

ERIC Educational Resources Information Center

Working memory capacity has been suggested as a factor that is involved in long-term memory retrieval, particularly when that retrieval involves a need to overcome some sort of interference (Bunting, Conway, & Heitz, 2004; Cantor & Engle, 1993). Previous work has suggested that working memory is related to the acquisition of information during…

Radvansky, Gabriel A.; Copeland, David E.

2006-01-01

310

Neuroradiology therapeutic workstation  

NASA Astrophysics Data System (ADS)

Two types of workstation are being developed at UCLA for neuroradiology a display workstation and a therapeutic workstation. The display station is used for review of images derived from neuroradiology examinations whereas the therapeutic station is for image analysis. The therapeutic workstation will be used to compare angiograms with CT and MR images and to calculate quantitative information from image sets. Parameters obtained by image analysis will be useful for planning and evaluation of interventional procedures. Current emphasis is on development of analysis tools for digital subtraction angiography. Digital densitometry and parametric imaging routines are being developed for analysis of DSA images of blood flow (with contrast injection) taken with a GE Digital Flouricon 5000 system. These routines include determination of vessel geometry regional blood volume flow rate and velocity. The starting point for software development is the CALIPSO (CALifornia Image Processing SOftware) package developed at UCLA for the Macintosh II. A Stellar GS2000 graphics mini-supercomputer will ultimately be used to allow rapid manipulation of images. The workstation will be connected to various imaging modalities through an Ethernet network. 1.

Close, Robert A.; Duckwiler, Gary R.; Vinuela, Fernando; Dion, Jacques E.; Abramowitz, Joshua

1990-07-01

311

Therapeutic Recreation Directory  

NSDL National Science Digital Library

The Therapeutic Recreation Directory has an abundance of information for the therapeutic recreation specialist, or those who study and teach in the field. There is an extensive collection of activity ideas, ranging from sports and cookery, for educators to experiment with in the classroom or for professionals to use on the job. This site also hosts inTeRlink, a long-running and constantly updated newsletter about developments in recreational therapy, found by clicking on the �News� link on the left hand side of the home page. All articles from the last ten years are available in the archive. A bulletin board, chat room, and forum keep professionals and students informed about current TR issues, and surveys help to gather and disseminate information and ideas about new developments in TR services. Visitors will also find the �Forms� link very helpful in nearly every aspect of providing recreational therapy to clients, including forms to help assess and treat patients, and guidelines on planning and implementing new therapeutic programs.

Dixon, Charles C.

312

Cell microencapsulation with synthetic polymers  

PubMed Central

The encapsulation of cells into polymeric microspheres or microcapsules has permitted the transplantation of cells into human and animal subjects without the need for immunosuppressants. Cell-based therapies use donor cells to provide sustained release of a therapeutic product, such as insulin, and have shown promise in treating a variety of diseases. Immunoisolation of these cells via microencapsulation is a hotly investigated field, and the preferred material of choice has been alginate, a natural polymer derived from seaweed due to its gelling conditions. Although many natural polymers tend to gel in conditions favorable to mammalian cell encapsulation, there remain challenges such as batch to batch variability and residual components from the original source that can lead to an immune response when implanted into a recipient. Synthetic materials have the potential to avoid these issues; however, historically they have required harsh polymerization conditions that are not favorable to mammalian cells. As research into microencapsulation grows, more investigators are exploring methods to microencapsulate cells into synthetic polymers. This review describes a variety of synthetic polymers used to microencapsulate cells. © 2014 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 103A: 846–859, 2015. PMID:24771675

Olabisi, Ronke M

2015-01-01

313

Phthalocyanine polymers  

NASA Technical Reports Server (NTRS)

A method of forming 4,4',4'',4''' -tetraamino phthalocyanines involves reducing 4,4',4'',4''' -tetranitro phthalocyanines, polymerizing the metal tetraamino phthalocyanines with a tetracarboxylic dianhydride (preferably aromatic) or copolymerizing with a tetracarboxylic dianhydride and a diamine (preferably also aromatic) to produce amic acids which are then dehydrocyclized to imides. Thermally and oxidatively stable polymers result which form tough, flexible films, varnishes, adhesives, and fibers.

Achar, B. N.; Fohlen, G. M.; Parker, J. A. (inventors)

1985-01-01

314

BioMEMS in medicine: diagnostic and therapeutic systems  

Microsoft Academic Search

The applications of bio-microelectromechanical systems (bioMEMS) in medicine can be classified as diagnostic or therapeutic systems. In the laboratory, microfluidic systems for cell analysis and characterization contribute to the development of diagnostic systems. Implantable biomedical microdevices can benefit many patients with neurological conditions or spinal cord injury, and flexible polymer-based microelectrode arrays are key technology in future neuroprosthetic devices. Advances

Karen C. Cheung; Philippe Renaud

2005-01-01

315

Mechanical properties and shape memory effect of short fiber reinforced SMP composite  

Microsoft Academic Search

By adding randomly distributed short fiber into a shape memory polymer (SMP) matrix, both the mechanical properties and the shape memory behavior are improved significantly, overcoming some traditional defects of SMP composite reinforced by long fiber and particles. In this paper, the short fiber reinforced SMP composite are developed for the improvement of the mechanical and thermal properties of styrene-based

Kai Yu; Haibao Lv; Guo Yi; Yanju Liu; Jinsong Leng

2010-01-01

316

In vitro wrinkle formation via shape memory dynamically aligns adherent cells  

E-print Network

In vitro wrinkle formation via shape memory dynamically aligns adherent cells Pine Yang, Richard M elegant approach to fabricating cell culture substrates with highly ordered topographies for investigating cell mechanobiology. In this study we present a tunable shape memory polymer (SMP) bilayer system

Mather, Patrick T.

317

Optical memory  

DOEpatents

Optical memory comprising: a semiconductor wire, a first electrode, a second electrode, a light source, a means for producing a first voltage at the first electrode, a means for producing a second voltage at the second electrode, and a means for determining the presence of an electrical voltage across the first electrode and the second electrode exceeding a predefined voltage. The first voltage, preferably less than 0 volts, different from said second voltage. The semiconductor wire is optically transparent and has a bandgap less than the energy produced by the light source. The light source is optically connected to the semiconductor wire. The first electrode and the second electrode are electrically insulated from each other and said semiconductor wire.

Mao, Samuel S; Zhang, Yanfeng

2013-07-02

318

Therapeutic cloning: The ethical limits  

Microsoft Academic Search

A brief outline of stem cells, stem cell therapy and therapeutic cloning is given. The position of therapeutic cloning with regard to other embryonic manipulations – IVF-based reproduction, embryonic stem formation from IVF embryos and reproductive cloning – is indicated. The main ethically challenging stages in therapeutic cloning are considered to be the nuclear transfer process including the source of

Peter A. Whittaker

2005-01-01

319

Memory Systems Doug Burger  

E-print Network

--at a reasonable cost. The memory hierarchies of modern general-purpose computers generally contain registers) and virtual memory (on a magnetic or optical disk). Figure 1 shows a memory hierarchy typical of today's (1995 of the hierarchy. The memory hierarchy usually reduces bandwidth requirements by intercepting a fraction

Burger, Doug

320

Memory Hierarchy Configuration Analysis  

Microsoft Academic Search

This paper presents an analytical study of speed-cost tradeoffs in memory hierarchy design. It develops an optimization criterion by which average access time, i. e., memory system delay, is minimized under a cost constraint for a hierarchy with given memory sizes and access probabilities. Using a power function assumption relating speed and cost of memory units, it is shown that

Terry A. Welch

1978-01-01

321

Infant Visual Recognition Memory  

ERIC Educational Resources Information Center

Visual recognition memory is a robust form of memory that is evident from early infancy, shows pronounced developmental change, and is influenced by many of the same factors that affect adult memory; it is surprisingly resistant to decay and interference. Infant visual recognition memory shows (a) modest reliability, (b) good discriminant…

Rose, Susan A.; Feldman, Judith F.; Jankowski, Jeffery J.

2004-01-01

322

High-throughput gene expression profiling of memory differentiation in primary human T cells  

E-print Network

Background: The differentiation of naive T and B cells into memory lymphocytes is essential for immunity to pathogens. Therapeutic manipulation of this cellular differentiation program could improve vaccine efficacy and ...

Angelosanto, Jill

323

Inhibition and enhancement of contextual fear memory destabilization  

PubMed Central

The reactivation of a memory can result in its destabilization, necessitating a process of memory reconsolidation to maintain its persistence. Here we show that the destabilization of a contextual fear memory is potentiated by the cannabinoid CB1 receptor agonist Arachidonyl-2-chloroethylamide (ACEA). Co-infusion of ACEA and the IkappaB kinase (IKK) inhibitor sulfasalazine (Sulf) into the dorsal hippocampus impaired contextual fear memory reconsolidation. This observation was achieved under behavioral conditions that, by themselves, did not result in a reconsolidation impairment by Sulf alone. Moreover, we show that the destabilization of a contextual fear memory is dependent upon neuronal activity in the dorsal hippocampus, but not memory expression per se. The effect on contextual fear memory destabilization of intra-hippocampal ACEA was replicated by systemic injections, allowing an amnestic effect of MK-801. These results indicate that memory expression and destabilization, while being independent from one another, are both dependent upon memory reactivation. Moreover, memory destabilization can be enhanced pharmacologically, which may be of therapeutic potential. PMID:24808841

Lee, Jonathan L. C.; Flavell, Charlotte R.

2014-01-01

324

Polymer Electronics: Power from Polymers  

SciTech Connect

We review polymer-based electronics and photovoltaics to provide the reader with a sense of how the field has developed, where we stand at present, and what possibilities are looming in the future. Expertise in areas ranging from synthesis to morphology to device design was sought to achieve this end. While these reviews cannot be exhaustive, they do provide a snapshot of the field at present and give some sense of where the key impediments are.

Venkataraman, D.; Russell, Thomas P.

2012-01-01

325

Amphetamine increases errors during episodic memory retrieval.  

PubMed

Moderate doses of stimulant drugs are known to enhance memory encoding and consolidation, but their effects on memory retrieval have not been explored in depth. In laboratory animals, stimulants seem to improve retrieval of emotional memories, but comparable studies have not been carried out in humans. In the present study, we examined the effects of dextroamphetamine (AMP) on retrieval of emotional and unemotional stimuli in healthy young adults, using doses that enhanced memory formation when administered before encoding in our previous study. During 3 sessions, healthy volunteers (n = 31) received 2 doses of AMP (10 and 20 mg) and placebo in counterbalanced order under double-blind conditions. During each session, they first viewed emotional and unemotional pictures and words in a drug-free state, and then 2 days later their memory was tested, 1 hour after AMP or placebo administration. Dextroamphetamine did not affect the number of emotional or unemotional stimuli remembered, but both doses increased recall intrusions and false recognition. Dextroamphetamine (20 mg) also increased the number of positively rated picture descriptions and words generated during free recall. These data provide the first evidence that therapeutic range doses of stimulant drugs can increase memory retrieval errors. The ability of AMP to positively bias recollection of prior events could contribute to its potential for abuse. PMID:24135845

Ballard, Michael Edward; Gallo, David A; de Wit, Harriet

2014-02-01

326

[Value of memory functions in implantable prostheses].  

PubMed

The development of memory functions with memorised electrogrammes is one of the most important technical advances in cardiac pacemakers and defibrillators. These memory functions are very useful in the management of patients with implanted prostheses. In the case of defibrillators, the memory allows evaluation and validation of appropriate treatments (shock or asymptomatic antitachycardia stimulation) or inappropriate function. The memory can also help assess the efficacy of complementary antiarrhythmic therapy or radiofrequency ablation. The incorporation of memory functions in pacemakers is more recent but no less useful. The latest generation of pacemakers have not only a therapeutic but also a diagnostic role with respect to atrial and ventricular arrhythmias. They can lead to the prescription of an antiarrhythmic or anticoagulant drug in cases of sustained atrial fibrillation confirmed by the memorised electrogrammes. The memory function is also a great aid in reprogramming stimulators in cases of overdetection (V-A cross talk). They may also be activated by the patient in cases of sporadic paroxysmal symptoms. The latest development is that of a purely diagnostic prosthesis: the implantable Holter, whose main indication is in the investigation of unexplained syncope. PMID:15609919

Defaye, P; Dechaux, D; Machecourt, J

2004-11-01

327

Amphetamine Increases Errors During Episodic Memory Retrieval  

PubMed Central

Moderate doses of stimulant drugs are known to enhance memory encoding and consolidation, but their effects on memory retrieval have not been explored in depth. In laboratory animals, stimulants seem to improve retrieval of emotional memories, but comparable studies have not been carried out in humans. In the present study, we examined the effects of dextroamphetamine (AMP) on retrieval of emotional and unemotional stimuli in healthy young adults, using doses that enhanced memory formation when administered before encoding in our previous study. During 3 sessions, healthy volunteers (n = 31) received 2 doses of AMP (10 and 20 mg) and placebo in counter-balanced order under double-blind conditions. During each session, they first viewed emotional and unemotional pictures and words in a drug-free state, and then 2 days later their memory was tested, 1 hour after AMP or placebo administration. Dextroamphetamine did not affect the number of emotional or unemotional stimuli remembered, but both doses increased recall intrusions and false recognition. Dextroamphetamine (20 mg) also increased the number of positively rated picture descriptions and words generated during free recall. These data provide the first evidence that therapeutic range doses of stimulant drugs can increase memory retrieval errors. The ability of AMP to positively bias recollection of prior events could contribute to its potential for abuse. PMID:24135845

Ballard, Michael Edward; Gallo, David A.; de Wit, Harriet

2014-01-01

328

Cystic Fibrosis Therapeutics  

PubMed Central

A great deal of excitement and hope has followed the successful trials and US Food and Drug Administration approval of the drug ivacaftor (Kalydeco), the first therapy available that targets the underlying defect that causes cystic fibrosis (CF). Although this drug has currently demonstrated a clinical benefit for a small minority of the CF population, the developmental pathway established by ivacaftor paves the way for other CF transmembrane conductance regulator (CFTR) modulators that may benefit many more patients. In addition to investigating CFTR modulators, researchers are actively developing numerous other innovative CF therapies. In this review, we use the catalog of treatments currently under evaluation with the support of the Cystic Fibrosis Foundation, known as the Cystic Fibrosis Foundation Therapeutics Pipeline, as a platform to discuss the variety of candidate treatments for CF lung disease that promise to improve CF care. Many of these approaches target the individual components of the relentless cycle of airway obstruction, inflammation, and infection characteristic of lung disease in CF, whereas others are aimed directly at the gene defect, or the resulting dysfunctional protein, that instigates this cycle. We discuss how new findings from the laboratory have informed not only the development of novel therapeutics, but also the rationales for their use and the outcomes used to measure their effects. By reviewing the breadth of candidate treatments currently in development, as well as the recent progress in CF therapies reflected by the evolution of the therapeutics pipeline over the past few years, we hope to build upon the optimism and anticipation generated by the recent success of Kalydeco. PMID:23276843

Ramsey, Bonnie W.

2013-01-01

329

Revitalizing Psychiatric Therapeutics  

PubMed Central

Despite high prevalence and enormous unmet medical need, the pharmaceutical industry has recently de-emphasized neuropsychiatric disorders as ‘too difficult' a challenge to warrant major investment. Here I describe major obstacles to drug discovery and development including a lack of new molecular targets, shortcomings of current animal models, and the lack of biomarkers for clinical trials. My major focus, however, is on new technologies and scientific approaches to neuropsychiatric disorders that give promise for revitalizing therapeutics and may thus answer industry's concerns. PMID:24317307

Hyman, Steven E

2014-01-01

330

The Therapeutic Roller Coaster  

PubMed Central

Survivors of severe childhood abuse often encounter profound difficulties. In addition to posttraumatic and dissociative symptomatology, abuse survivors frequently have characterologic problems, particularly regarding self-care and maintaining relationships. Backgrounds of abuse, abandonment, and betrayal are often recapitulated and reenacted in therapy, making the therapeutic experience arduous and confusing for therapists and patients. Efforts must be directed at building an adequate psychotherapeutic foundation before undertaking exploration and abreaction of past traumatic experiences. This discussion sets out a model for treatment of childhood abuse survivors, describing stages of treatment and suggesting interventions. Common treatment dilemmas or "traps" are discussed, with recommendations for their resolution. PMID:22700116

CHU, JAMES A.

1992-01-01

331

A Comparison of Three Types of Autobiographical Memories in Old-Old Age: First Memories, Pivotal Memories and Traumatic Memories  

Microsoft Academic Search

Background: Autobiographical memory enables us to construct a personal narrative through which we identify ourselves. Especially important are memories of formative events. Objective: This study describes autobiographical memories of people who have reached old-old age (85 years and above), studying 3 types of memories of particular impact on identity and adaptation: first memories, pivotal memories and traumatic memories. In this

Jiska Cohen-Mansfield; Dov Shmotkin; Nitza Eyal; Yael Reichental; Haim Hazan

2010-01-01

332

Silk constructs for delivery of muskuloskeletal therapeutics  

PubMed Central

Silk fibroin (SF) is a biopolymer with distinguishing features from many other bio- as well as synthetic polymers. From a biomechanical and drug delivery perspective, SF combines remarkable versatility for scaffolding (solid implants, hydrogels, threads, solutions), with advanced mechanical properties and good stabilization and controlled delivery of entrapped protein and small molecule drugs, respectively. It is this combination of mechanical and pharmaceutical features which render SF so exciting for biomedical applications. his pattern along with the versatility of this biopolymer have been translated into progress for musculoskeletal applications. We review the use and potential of silk fibroin for systemic and localized delivery of therapeutics in diseases affecting the musculoskeletal system. We also present future directions for this biopolymer as well as the necessary research and development steps for their achievement. PMID:22522139

Meinel, Lorenz; Kaplan, David L.

2012-01-01

333

AMUM LECTURE: Therapeutic ultrasound  

NASA Astrophysics Data System (ADS)

The use of ultrasound in medicine is now quite commonplace, especially with the recent introduction of small, portable and relatively inexpensive, hand-held diagnostic imaging devices. Moreover, ultrasound has expanded beyond the imaging realm, with methods and applications extending to novel therapeutic and surgical uses. These applications broadly include: tissue ablation, acoustocautery, lipoplasty, site-specific and ultrasound mediated drug activity, extracorporeal lithotripsy, and the enhancement of natural physiological functions such as wound healing and tissue regeneration. A particularly attractive aspect of this technology is that diagnostic and therapeutic systems can be combined to produce totally non-invasive, imageguided therapy. This general lecture will review a number of these exciting new applications of ultrasound and address some of the basic scientific questions and future challenges in developing these methods and technologies for general use in our society. We shall particularly emphasize the use of High Intensity Focused Ultrasound (HIFU) in the treatment of benign and malignant tumors as well as the introduction of acoustic hemostasis, especially in organs which are difficult to treat using conventional medical and surgical techniques.

Crum, Lawrence A.

2004-01-01

334

Nitrones as Therapeutics  

PubMed Central

Nitrones have the general chemical formula X-CH=NO-Y. They were first used to trap free radicals in chemical systems and then subsequently in biochemical systems. More recently several nitrones including PBN (?-phenyl-tert-butylnitrone) have been shown to have potent biological activity in many experimental animal models. Many diseases of aging including stroke, cancer development, Parkinson’s disease and Alzheimer’s disease are known to have enhanced levels of free radicals and oxidative stress. Some derivatives of PBN are significantly more potent than PBN and have undergone extensive commercial development in stroke. Recent research has shown that PBN-related nitrones also have anti-cancer activity in several experimental cancer models and have potential as therapeutics in some cancers. Also in recent observations nitrones have been shown to act synergistically in combination with antioxidants in the prevention of acute acoustic noise induced hearing loss. The mechanistic basis of the potent biological activity of PBN-related nitrones is not known. Even though PBN-related nitrones do decrease oxidative stress and oxidative damage, their potent biological anti-inflammatory activity and their ability to alter cellular signaling processes can not readily be explained by conventional notions of free radical trapping biochemistry. This review is focused on our observations and others where the use of selected nitrones as novel therapeutics have been evaluated in experimental models in the context of free radical biochemical and cellular processes considered important in pathologic conditions and age-related diseases. PMID:18793715

Floyd, Robert A.; Kopke, Richard D.; Choi, Chul-Hee; Foster, Steven B.; Doblas, Sabrina; Towner, Rheal A.

2008-01-01

335

Influenza antiviral therapeutics.  

PubMed

In this review we conducted a landscaping study of the therapeutic anti-influenza agents, limiting the scope by exclusion of vaccines. The resulting 2800 patent publications were classified into 23 distinct technological sectors. The mechanism of action, the promise and drawbacks of the corresponding technological sectors were explored on comparative basis. A set of quantitative parameters was defined based on landscaping procedure that appears to correlate with the practical success of a given class of therapeutics. Thus, the sectors not considered promising from the mechanistic side were also displaying low value of the classifying parameters. The parameters were combined into a probabilistic Marketing Prediction Score, assessing a likelihood of a given sector to produce a marketable product. The proposed analytical methodology may be useful for automatic search and assessment of technologies for the goals of acquisition, investment and competitive bidding. While not being a substitute for an expert evaluation, it provides an initial assessment suitable for implementation with large-scale automated landscaping. PMID:19929841

Mayburd, Anatoly L

2010-01-01

336

[Choledocholithiasis--therapeutic splitting].  

PubMed

Despite new developments like chemolitholysis and extracorporeal shock wave lithotripsy, conventional cholecystectomy was the "gold standard" in the treatment of gallstones. The range of indications and the operative strategy were well standardized, although the management of common bile duct stones in gallstone disease was still under debate. For high-risk and elder patients endoscopic retrograde cholangio-pancreatography (ERCP), papillotomy and stone extraction was established, in younger patients the best management was questionable. According to better and more accurate preoperative tests like ultrasound and the ample evidence of the function of the papilla after endoscopic papillotomy the trend seemed to be the preoperative endoscopic bile duct clearance in all patients, just when the "bushfire" of laparoscopic cholecystectomy arised and until then praised standards were thrown overboard because of technical difficulties. Routine intraoperative cholangiography (IOC) was replaced by indicated selective IOC due to the lack of talent of many surgeons. Only the therapeutic concept of the removal of the stone-bearing gallbladder survived all new concepts and the debate of whether to perform routine IOC and whether to clear the bile ducts--pre-, intra- or postoperatively or primarily or secondarily convert to open cholecystectomy and bile duct revision. In the eye of a new "gold standard" and according to the literature and our own results we should standardize our management especially in the era of laparoscopic cholecystectomy as "therapeutical splitting" with indicated and selective preoperative ERCP and bile duct clearance offers the best results and facilitates minimally invasive surgery. PMID:8050295

Boeckl, O; Sungler, P; Heinerman, P M; Lexer, G

1994-05-01

337

Multilayered Polymer Coated Carbon Nanotubes to Deliver Dasatinib  

PubMed Central

Multilayered, multifunctional polymer coatings were grafted onto carbon nanotubes (CNT) using a one-pot, ring-opening polymerization in order to control the release kinetic and therapeutic efficacy of dasatinib. Biocompatible, biodegradable multilayered coatings composed of poly(glycolide) (PGA), and poly(lactide) (PLA) were polymerized directly onto hydroxyl-functionalized CNT surfaces. Sequential addition of monomers into the reaction vessel enabled multilayered coatings of PLA-PGA, or PGA-PLA. Poly(ethylene glycol) capped the polymer chain ends, resulting in a multifunctional amphiphilic coating. Multilayer polymer coatings on CNTs enabled control of anticancer dasatinib’s release kinetics and enhanced the in vitro therapeutic efficacy against U-87 glioblastoma compared to monolayer polymer coatings. PMID:24294824

Moore, Thomas L.; Grimes, Stuart W.; Lewis, Robert L.; Alexis, Frank

2014-01-01

338

Episodic memory and executive functioning in currently depressed patients compared to healthy controls.  

PubMed

At present, little is still known about the link between depression, memory and executive functioning. This study examined whether there are memory-related impairments in depressed patients and whether the size of such deficits depends on the age group and on specific types of cognitive measures. Memory performances of 215 clinically depressed patients were compared to the data of a matched control sample. Regression analyses were performed to determine the extent to which executive dysfunctions contributed to episodic memory impairments. When compared with healthy controls, significantly lower episodic memory and executive functioning performances were found for depressed patients of all age groups. Effect sizes appeared to vary across different memory and executive functioning measures. The extent to which executive dysfunctions could explain episodic memory impairments varied depending on the type of measure examined. These findings emphasise the need to consider memory-related functioning of depressed patients in the context of therapeutic treatments. PMID:24828417

Pauls, Franz; Petermann, Franz; Lepach, Anja Christina

2015-04-01

339

Virginia Memory  

NSDL National Science Digital Library

The Virginia Memory initiative is part of the online presence of the Library of Virginia and it represents a magnificent effort to bring together thousands of documents that tell the story of this very unique place. The sections of the site include Digital Collections, Reading Rooms, Exhibitions, and the Online Classroom. First-time visitors may wish to start with the This Day in Virginia History section. Here they can learn about key moments in the state's history via primary documents tied to each calendar date, such as May 6, 1776, when the House of Burgesses met for the last time. The Exhibitions area contains interactive exhibits like You Have No Right: Law & Justice in Virginia. There are over two dozen past exhibits to look over on the site as well. The Digital Collections area is quite a remarkable one, featuring over 50 exhibits, including the 1939 World's Fair Photograph Collection, Revolutionary War Virginia State Pensions, and the tremendous Richmond Esthetic Survey/Historic Building Survey. To complement these materials, the Online Classrooms area contains an educator's guide, a document-based activity titled "Shaping the Constitution," and other resources. [KMG

340

Polymer Spheulites  

NASA Astrophysics Data System (ADS)

The growth and/or structural features that determine lamellar shape in polymer spherulites and therefore their structure and properties have been debated for many years. The spectacular twisting of lamellae in optically banded spherulites has been explained by the existence of unbalanced stresses in opposite fold surfaces of the lamellae. This mechanical origin implying the folds explains also the demonstrated absence of correlation between lamellar twist sense and molecular chirality of chiral polymers. Unbalanced surface stresses may also generate spherulites made of scrolled lamellae, with the scroll axis radial. This original morphology was first observed in spherulites of poly(vinylidene fluoride) in its ? phase. It arises from a chemical disparity of folds formed on opposite fold surfaces, the volumes of which differ by 10å*3. Similar chemical disparities have been suggested to explain the formation of highly unusual scrolled single crystals of polyamide 66 obtained from solution under specific annealing and crystallization conditions. Related thermal histories lead to the formation, in the bulk, of unusual optically negative spherulites of polyamide 66 that were first observed in the 1940s. These still poorly understood negative spherulites may well display a similar scrolled lamellar morphology. The analysis of unbalanced surface stresses requires to evaluate the interplay and mutual impact of crystal and fold structures. The stresses associated with different fold structures are locally small perturbations but are cumulative and are exerted on thin, flexible lamellae. The latter non-planar morphologies reveal these stresses and help reach sub-moleculr insights on the fold structures.

Lotz, Bernard

2013-03-01

341

Making Art From Memories: Honoring Deceased Loved Ones Through a Scrapbooking Bereavement Group  

Microsoft Academic Search

When loved ones die, family and friends treasure memories with photographs and mementos. Creating a memory book from these treasures provides a tangible means for healing from loss, celebrating life events, and preserving family stories and legacies. This article describes the history and current popularity of scrapbooking, and its therapeutic benefits in an art therapy bereavement group for grieving adults

Mary Kohut

2011-01-01

342

Advanced subcompartmentalized microreactors: polymer hydrogel carriers encapsulating polymer capsules and liposomes.  

PubMed

The design of compartmentalized carriers for advanced drug delivery systems or artificial cells and organelles is of interest for biomedical applications. Herein, a polymer carrier microreactor that contains two different classes of subcompartments, multilayered polymer capsules and liposomes, is presented. 50 nm-diameter liposomes and 300 nm-diameter polymer capsules are encapsulated into a larger polymer carrier capsule, demonstrating control over the spatial positioning of the subcompartments, which are either 'membrane-associated' or 'free-floating' in the aqueous interior. Selective and spatially dependent degradation of the 300 nm-diameter subcompartments (without destroying the structural integrity of the enzyme-loaded liposomes) is also shown, by performing an encapsulated enzymatic reaction using the liposomal subcompartments. These findings cover several important aspects toward the development of engineered compartmentalized carrier vessels for the creation of artificial cell mimics or advanced therapeutic delivery systems. PMID:23606518

Hosta-Rigau, Leticia; Shimoni, Olga; Städler, Brigitte; Caruso, Frank

2013-11-11

343

Memory beyond expression.  

PubMed

The idea that memories are not invariable after the consolidation process has led to new perspectives about several mnemonic processes. In this framework, we review our studies on the modulation of memory expression during reconsolidation. We propose that during both memory consolidation and reconsolidation, neuromodulators can determine the probability of the memory trace to guide behavior, i.e. they can either increase or decrease its behavioral expressibility without affecting the potential of persistent memories to be activated and become labile. Our hypothesis is based on the findings that positive modulation of memory expression during reconsolidation occurs even if memories are behaviorally unexpressed. This review discusses the original approach taken in the studies of the crab Neohelice (Chasmagnathus) granulata, which was then successfully applied to test the hypothesis in rodent fear memory. Data presented offers a new way of thinking about both weak trainings and experimental amnesia: memory retrieval can be dissociated from memory expression. Furthermore, the strategy presented here allowed us to show in human declarative memory that the periods in which long-term memory can be activated and become labile during reconsolidation exceeds the periods in which that memory is expressed, providing direct evidence that conscious access to memory is not needed for reconsolidation. Specific controls based on the constraints of reminders to trigger reconsolidation allow us to distinguish between obliterated and unexpressed but activated long-term memories after amnesic treatments, weak trainings and forgetting. In the hypothesis discussed, memory expressibility--the outcome of experience-dependent changes in the potential to behave--is considered as a flexible and modulable attribute of long-term memories. Expression seems to be just one of the possible fates of re-activated memories. PMID:25102126

Delorenzi, A; Maza, F J; Suárez, L D; Barreiro, K; Molina, V A; Stehberg, J

2014-01-01

344

74. AERIAL VIEW OF MEMORIAL BRIDGE AND MEMORIAL AVENUE LOOKING ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

74. AERIAL VIEW OF MEMORIAL BRIDGE AND MEMORIAL AVENUE LOOKING EAST AT LINCOLN MEMORIAL. - George Washington Memorial Parkway, Along Potomac River from McLean to Mount Vernon, VA, Mount Vernon, Fairfax County, VA

345

Reactivating personal memory 1 RUNNING HEAD: Reactivating personal memory  

E-print Network

Reactivating personal memory 1 RUNNING HEAD: Reactivating personal memory Modifying memory: Selectively enhancing and updating personal memories for a museum Department of Psychology, Harvard University, Cambridge, MA, 02138, USA Center

Schacter, Daniel

346

Storage Techniques in Flash Memories and Phase-change Memories  

E-print Network

Non-volatile memories are an emerging storage technology with wide applica- tions in many important areas. This study focuses on new storage techniques for flash memories and phase-change memories. Flash memories are currently the most widely used...

Li, Hao

2010-10-12

347

Neural and Cellular Mechanisms of Fear and Extinction Memory Formation  

PubMed Central

Over the course of natural history, countless animal species have evolved adaptive behavioral systems to cope with dangerous situations and promote survival. Emotional memories are central to these defense systems because they are rapidly acquired and prepare organisms for future threat. Unfortunately, the persistence and intrusion of memories of fearful experiences are quite common and can lead to pathogenic conditions, such as anxiety and phobias. Over the course of the last thirty years, neuroscientists and psychologists alike have attempted to understand the mechanisms by which the brain encodes and maintains these aversive memories. Of equal interest, though, is the neurobiology of extinction memory formation as this may shape current therapeutic techniques. Here we review the extant literature on the neurobiology of fear and extinction memory formation, with a strong focus on the cellular and molecular mechanisms underlying these processes. PMID:22230704

Orsini, Caitlin A.; Maren, Stephen

2012-01-01

348

Therapeutic applications of melatonin.  

PubMed

Melatonin is a methoxyindole synthesized within the pineal gland. The hormone is secreted during the night and appears to play multiple roles within the human organism. The hormone contributes to the regulation of biological rhythms, may induce sleep, has strong antioxidant action and appears to contribute to the protection of the organism from carcinogenesis and neurodegenerative disorders. At a therapeutic level as well as in prevention, melatonin is used for the management of sleep disorders and jet lag, for the resynchronization of circadian rhythms in situations such as blindness and shift work, for its preventive action in the development of cancer, as additive therapy in cancer and as therapy for preventing the progression of Alzheimer's disease and other neurodegenerative disorders. PMID:23515203

Kostoglou-Athanassiou, Ifigenia

2013-02-01

349

Therapeutic applications of melatonin  

PubMed Central

Melatonin is a methoxyindole synthesized within the pineal gland. The hormone is secreted during the night and appears to play multiple roles within the human organism. The hormone contributes to the regulation of biological rhythms, may induce sleep, has strong antioxidant action and appears to contribute to the protection of the organism from carcinogenesis and neurodegenerative disorders. At a therapeutic level as well as in prevention, melatonin is used for the management of sleep disorders and jet lag, for the resynchronization of circadian rhythms in situations such as blindness and shift work, for its preventive action in the development of cancer, as additive therapy in cancer and as therapy for preventing the progression of Alzheimer’s disease and other neurodegenerative disorders. PMID:23515203

2013-01-01

350

Polymers in Small-Interfering RNA Delivery  

PubMed Central

This review will cover the current strategies that are being adopted to efficiently deliver small interfering RNA using nonviral vectors, including the use of polymers such as polyethylenimine, poly(lactic-co-glycolic acid), polypeptides, chitosan, cyclodextrin, dendrimers, and polymers-containing different nanoparticles. The article will provide a brief and concise account of underlying principle of these polymeric vectors and their structural and functional modifications which were intended to serve different purposes to affect efficient therapeutic outcome of small-interfering RNA delivery. The modifications of these polymeric vectors will be discussed with reference to stimuli-responsiveness, target specific delivery, and incorporation of nanoconstructs such as carbon nanotubes, gold nanoparticles, and silica nanoparticles. The emergence of small-interfering RNA as the potential therapeutic agent and its mode of action will also be mentioned in a nutshell. PMID:21749290

Singha, Kaushik; Namgung, Ran

2011-01-01

351

Antioxidant therapeutics: Pandora's box.  

PubMed

Evolution has favored the utilization of dioxygen (O2) in the development of complex multicellular organisms. O2 is actually a toxic mutagenic gas that is highly oxidizing and combustible. It is thought that plants are largely to blame for polluting the earth's atmosphere with O2 owing to the development of photosynthesis by blue-green algae over 2 billion years ago. The rise of the plants and atmospheric O2 levels placed evolutionary stress on organisms to adapt or become extinct. This implies that all the surviving creatures on our planet are mutants that have adapted to the "abnormal biology" of O2. Much of the adaptation to the presence of O2 in biological systems comes from well-coordinated antioxidant and repair systems that focus on converting O2 to its most reduced form, water (H2O), and the repair and replacement of damaged cellular macromolecules. Biological systems have also harnessed O2's reactive properties for energy production, xenobiotic metabolism, and host defense and as a signaling messenger and redox modulator of a number of cell signaling pathways. Many of these systems involve electron transport systems and offer many different mechanisms by which antioxidant therapeutics can alternatively produce an antioxidant effect without directly scavenging oxygen-derived reactive species. It is likely that each agent will have a different set of mechanisms that may change depending on the model of oxidative stress, organ system, or disease state. An important point is that all biological processes of aerobes have coevolved with O2 and this creates a Pandora's box for trying to understand the mechanism(s) of action of antioxidants being developed as therapeutic agents. PMID:23856377

Day, Brian J

2014-01-01

352

GTI-2040. Lorus Therapeutics.  

PubMed

Loris Therapeutics (formerly GeneSense Therapeutics) is developing the antisense oligonucleotide GTI-2040, directed against the R2 component of ribonucleotide reductase, for the potential treatment of cancer [348194]. It is in phase I/II trials [353796] and Lorus had anticipated phase II trials would be initiated in July 2001. By August 2001, GTI-2040 was undergoing a phase II trial as a monotherapy for the potential treatment of renal cell carcinoma, and was about to enter a phase II combination study for this indication with capecitabine (Hoffmann-La Roche). At this time, the company was also planning a phase II trial to study the drug's potential in the treatment of colorectal cancer [418739]. GTI-2040 has been tested in nine different tumor models, including tumors derived from colon, liver, lung, breast, kidney and ovary. Depending on the tumor model, significant inhibition of tumor growth, disease stabilization and dramatic tumor regressions was observed [347683]. Lorus filed an IND to commence phase I/II trials with GTI-2040 in the US in November 1999 [347683], and received approval for the trials in December 1999 [349623]. As of January 2000, these trials had commenced at the University of Chicago Cancer Research Center; it was reported in February 2000 that dosing to date had been well tolerated with no apparent safety concerns [357449]. Lorus has entered into a strategic supply alliance with Proligo to provide the higher volumes of drug product required for the planned multiple phase II trials [385976]. In February 1998, Genesense (now Lorus) received patent WO-09805769. Loris also received a patent (subsequently identified as WO-00047733) from the USPTO in January 2000, entitled 'Antitumor antisense sequences directed against components of ribonucleotide reductase' covering the design and use of unique antisense anticancer drugs, including GTI-2040 and GTI-2501 [353538]. PMID:11890366

Orr, R M

2001-10-01

353

Chelating polymeric beads as potential therapeutics for Wilson's disease.  

PubMed

Wilson's disease is a genetic disorder caused by a malfunction of ATPase 7B that leads to high accumulation of copper in the organism and consequent toxic effects. We propose a gentle therapy to eliminate the excessive copper content with oral administration of insoluble non-resorbable polymer sorbents containing selective chelating groups for copper(II). Polymeric beads with the chelating agents triethylenetetramine, N,N-di(2-pyridylmethyl)amine, and 8-hydroxyquinoline (8HQB) were investigated. In a preliminary copper uptake experiment, we found that 8HQB significantly reduced copper uptake (using copper-64 as a radiotracer) after oral administration in Wistar rats. Furthermore, we measured organ radioactivity in rats to demonstrate that 8HQB radiolabelled with iodine-125 is not absorbed from the gastrointestinal tract after oral administration. Non-resorbability and the blockade of copper uptake were also confirmed with small animal imaging (PET/CT) in mice. In a long-term experiment with Wistar rats fed a diet containing the polymers, we have found that there were no signs of polymer toxicity and the addition of polymers to the diet led to a significant reduction in the copper contents in the kidneys, brains, and livers of the rats. We have shown that polymers containing specific ligands could potentially be novel therapeutics for Wilson's disease. PMID:24815561

Mattová, Jana; Pou?ková, Pavla; Ku?ka, Jan; Skodová, Michaela; Vetrík, Miroslav; St?pánek, Petr; Urbánek, Petr; Pet?ík, Miloš; Nový, Zbyn?k; Hrubý, Martin

2014-10-01

354

The quintuple-shape memory effect in electrospun nanofiber membranes  

NASA Astrophysics Data System (ADS)

Shape memory fibrous membranes (SMFMs) are an emerging class of active polymers, which are capable of switching from a temporary shape to their permanent shape upon appropriate stimulation. Quintuple-shape memory membranes based on the thermoplastic polymer Nafion, with a stable fibrous structure, are achieved via electrospinning technology, and possess a broad transition temperature. The recovery of multiple temporary shapes of electrospun membranes can be triggered by heat in a single triple-, quadruple-, quintuple-shape memory cycle, respectively. The fiber morphology and nanometer size provide unprecedented design flexibility for the adjustable morphing effect. SMFMs enable complex deformations at need, having a wide potential application field including smart textiles, artificial intelligence robots, bio-medical engineering, aerospace technologies, etc in the future.

Zhang, Fenghua; Zhang, Zhichun; Liu, Yanju; Lu, Haibao; Leng, Jinsong

2013-08-01

355

From Commodity Polymers to Functional Polymers  

NASA Astrophysics Data System (ADS)

Functional polymers bear specified chemical groups, and have specified physical, chemical, biological, pharmacological, or other uses. To adjust the properties while keeping material usage low, a method for direct synthesis of functional polymers is indispensable. Here we show that various functional polymers can be synthesized by in situ cross-linked polymerization/copolymerization. We demonstrate that the polymers synthesized by the facile method using different functional monomers own outstanding pH-sensitivity and pH-reversibility, antifouling property, antibacterial, and anticoagulant property. Our study opens a route for the functionalization of commodity polymers, which lead to important advances in polymeric materials applications.

Xiang, Tao; Wang, Ling-Ren; Ma, Lang; Han, Zhi-Yuan; Wang, Rui; Cheng, Chong; Xia, Yi; Qin, Hui; Zhao, Chang-Sheng

2014-04-01

356

From commodity polymers to functional polymers.  

PubMed

Functional polymers bear specified chemical groups, and have specified physical, chemical, biological, pharmacological, or other uses. To adjust the properties while keeping material usage low, a method for direct synthesis of functional polymers is indispensable. Here we show that various functional polymers can be synthesized by in situ cross-linked polymerization/copolymerization. We demonstrate that the polymers synthesized by the facile method using different functional monomers own outstanding pH-sensitivity and pH-reversibility, antifouling property, antibacterial, and anticoagulant property. Our study opens a route for the functionalization of commodity polymers, which lead to important advances in polymeric materials applications. PMID:24710333

Xiang, Tao; Wang, Ling-Ren; Ma, Lang; Han, Zhi-Yuan; Wang, Rui; Cheng, Chong; Xia, Yi; Qin, Hui; Zhao, Chang-Sheng

2014-01-01

357

Antioxidant Stabilisation of Polymers  

Microsoft Academic Search

Physicochemical aspects of the stabilisation of polymers are discussed. Attention is paid mainly to the aging and stabilisation of polymers under processing conditions. Topics considered are the kinetics and mechanism of the high-temperature oxidation of polymers, critical phenomena in the inhibited oxidation of polymers, the theory of synergism and antagonism among antioxidants, the reasons for differences in efficiency of antioxidants,

Yurii A Shlyapnikov

1981-01-01

358

Microstructured polymer optical fibre  

Microsoft Academic Search

The first microstructured polymer optical fibre is described. Both experimental and theoretical evidence is presented to establish that the fibre is effectively single moded at optical wavelengths. Polymer-based microstructured optical fibres offer key advantages over both conventional polymer optical fibres and glass microstructured fibres. The low-cost manufacturability and the chemical flexibility of the polymers provide great potential for applications in

Martijn van Eijkelenborg; Maryanne Large; Alexander Argyros; Joseph Zagari; Steven Manos; Nader A. Issa; Ian M. Bassett; Simon C. Fleming; Ross C. McPhedran; C. Martijn de Sterke; Nicolae A. P. Nicorovici

2001-01-01

359

Memory abstractions for parallel programming  

E-print Network

A memory abstraction is an abstraction layer between the program execution and the memory that provides a different "view" of a memory location depending on the execution context in which the memory access is made. Properly ...

Lee, I-Ting Angelina

2012-01-01

360

Device Memories and Matrix Multiplication 1 Device Memories  

E-print Network

Device Memories and Matrix Multiplication 1 Device Memories global, constant, and shared memories Verschelde, 2 April 2014 Introduction to Supercomputing (MCS 572) Device Memories & Matrix Multiplication L-31 2 April 2014 1 / 28 #12;Device Memories and Matrix Multiplication 1 Device Memories global

Verschelde, Jan

361

Memory of myself: Autobiographical memory and identity in Alzheimer's disease  

E-print Network

, 1990). Personal incident memory MEMORY, 2004, 12 (1), 56±74 # 2004 Psychology Press Ltd httpMemory of myself: Autobiographical memory and identity in Alzheimer's disease Donna Rose Addis autobiographical memory and identity. To test this we assessed the status of autobiographical memory and identity

Addis, Donna Rose

362

Nanoreplication in polymers using hot embossing and injection molding  

Microsoft Academic Search

With polymer molding techniques, it is possible to fabricate nanostructures with a replication fidelity of 25 nanometers. Both hot embossing and injection molding can be used, and cycle times of down to 4 sec can be achieved in a CD injection molding process. The resolution is far below the structure size found today in compact disc memory media. The master

H. Schift; C. David; M. Gabriel; J. Gobrecht; L. J. Heyderman; W. Kaiser; S. Koeppel; L. Scandella

2000-01-01

363

Introduction to Therapeutic Recreation Services  

MedlinePLUS

... Health Professionals Teachers Submit Home About Goals Articles Directories Videos Resources Contact Home About Goals Articles Directories Videos Resources Contact Therapeutic Recreation Services Home » Article ...

364

Therapeutic cloning: The ethical limits  

SciTech Connect

A brief outline of stem cells, stem cell therapy and therapeutic cloning is given. The position of therapeutic cloning with regard to other embryonic manipulations - IVF-based reproduction, embryonic stem formation from IVF embryos and reproductive cloning - is indicated. The main ethically challenging stages in therapeutic cloning are considered to be the nuclear transfer process including the source of eggs for this and the destruction of an embryo to provide stem cells for therapeutic use. The extremely polarised nature of the debate regarding the status of an early human embryo is noted, and some potential alternative strategies for preparing immunocompatible pluripotent stem cells are indicated.

Whittaker, Peter A. [ESRC Centre for Economic and Social Aspects of Genomics, Lancaster University, Furness College, Lancaster LA1 4YG (United Kingdom)]. E-mail: p.whittaker@lancaster.ac.uk

2005-09-01

365

Thermal conductivity and multiferroics of electroactive polymers and polymer composites  

NASA Astrophysics Data System (ADS)

Electronically conducting polymers and electromechanical polymers are the two important branches of the cutting-edge electroactive polymers. They have shown significant impact on many modern technologies such as flat panel display, energy transport, energy conversion, sensors and actuators. To utilize conducting polymers in microelectronics, optoelectronics and thermoelectrics, it is necessary to have a comprehensive study of their thermal conductivity since thermal conductivity is a fundamental materials property that is particularly important and sometimes a determining factor of the device performance. For electromechanical polymers, larger piezoelectric effect will contribute to the improvement of magnetoelectric (ME) coupling efficiency in their multiferroic composites. This dissertation is devoted to characterizing electronically conducting polymers for their electrical and thermal conductivity, and developing new classes of electromechanical polymers and strain-mediated electromechanical polymer-based multiferroic ME composites. Conducting polymers opened up new possibilities for devices combining novel electrical and thermal properties, but there has been limited understanding of the length-scale effect of the electrical and thermal conductivity, and the mechanism underlying the electricity and heat transport behavior. In this dissertation, the analytical model and experimental technique are presented to measure the in-plane thermal conductivity of polyaniline thin films. For camphorsulfonic acid doped polyaniline patterned on silicon oxide/silicon substrate using photolithography and reactive ion etching, the thermal conductivity of the film with thickness of 20 nm is measured to be 0.0406 W/m?K, which significantly deviates from their bulk (> 0.26 W/m?K). The size effect on thermal conductivity at this scale is attributed to the significant phonon boundary scattering. When the film goes up to 130 nm thick, the thermal conductivity increases to 0.166 W/m?K, greatly affected by the phonon-phonon scattering and phonon boundary scattering. When the films are thicker than 130 nm, heat capacity also plays an important role in thermal conduction in polyaniline. The same technique is extended to measure the electrical and thermal conductivity of 55 nm thick polyaniline thin films doped with different levels of camphorsulfonic acid. Results indicate that the effect of the doping level (camphorsulfonic acid/polyaniline ratio) is more pronounced on electrical conductivity than on thermal conductivity, thereby greatly affecting their ratio that determines the thermoelectric efficiency. At the 60% doping level, polyaniline thin film exhibits the maximum electrical and thermal conductivity due to the formation of mostly delocalized polaron structures. It is suggested that polarons are the charge carriers responsible for the electrical conduction, while phonons play a dominant role in the heat conduction in doped polyaniline thin films. Multiferroic materials combine unusual elastic, magnetic and electric properties, and have promising applications in many areas, such as sensors, transducers and read/write memory devices. For strain-mediated multiferroic ME composites, their ME effect are generated as a product property of the piezoelectric phase and magnetostrictive phase. In this dissertation, new multiferroic composites are developed and presented. One of them is based on chain-end cross-linked ferroelectric poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE). With a low dc bias magnetic field, the ME coefficient of this composite is 17.7 V/cm Oe at non-resonance and 383 V/cm Oe at resonance, well above the reported ME voltage coefficient of polymer based ME composite in current literature. ME composite based on poly(vinylidene fluoride-co-hexafluoropropylene) P(VDF-HFP) are also developed in this dissertation. Crystalline beta phase structure in P(VDF-HFP) is produced by uniaxially stretching of pre-melted and quenched films. ME voltage coefficient as a function of dc magnetic field at different poling field

Jin, Jiezhu

366

Photomechanics of light-activated polymers  

NASA Astrophysics Data System (ADS)

Light-activated polymers are an exciting class of modern materials that respond mechanically when irradiated by light at particular wavelengths. While details of the mechanisms that connect the optical excitation to mechanical behavior are complex and differ from material to material, there is sufficient commonality among them to permit the development of a generalized modeling framework to describe the photomechanics. The features shared by light-activated polymers involve light interacting with the material, which triggers photochemical reactions that alter the structure of the crosslinked polymer network. Many such structural alterations result in an evolution of the polymer network, and subsequent macroscopic deformation. When this process is appropriately executed it can enable a photomechanical shape-memory effect. In this paper, we develop a three-dimensional finite-deformation modeling framework to describe the photomechanical response of light-activated polymer systems. This framework integrates four coupled phenomena that contribute to macroscopic photomechanical behavior: photophysics, photochemistry, chemomechanical coupling, and mechanical deformation. The chemomechanical coupling consists of chemically induced structural alterations of the crosslinked network that result in subsequent deformation. We describe this behavior through a decomposition of the crosslinked network into two components consisting of an original network and a photochemically altered network; both evolve during photomechanical deformation. The modeling framework presented in this paper is sufficiently general that it is applicable to light-activated polymer systems that operate with various mechanisms in each of the four areas. Using this modeling approach, we develop constitutive models for two recently developed light-activated polymer systems [Lendlein, A., Hongyan, J., Junger, O., Langer, R., 2005. Light-induced shape-memory polymers. Nature 434 (7035) 879; Scott, T.F., Schneider, A.D., Cook, W.D., Bowman, C.N., 2005. Photoinduced plasticity in crosslinked polymers. Science 308 (5728) 1615]. For the material developed by Scott and his co-workers we validate our model by measuring and numerically simulating photo-induced stress relaxation and bending deformation and obtain good agreement between measurements and predictions. Finally, we use the model to study the effects of photomechanical parameters (applied strain magnitude, irradiation time and intensity, and photoabsorber concentration) and the behavior of the network evolution rule on the material response.

Long, Kevin N.; Scott, Timothy F.; Jerry Qi, H.; Bowman, Christopher N.; Dunn, Martin L.

2009-07-01

367

Silicon nanocrystal memories  

Microsoft Academic Search

In this paper, we present an overview of memory structures fabricated by our group by using silicon nanocrystals as storage nodes. These devices show promising characteristics as candidates for future deep-submicron non-volatile memories.

S. Lombardo; B. De Salvo; C. Gerardi; T. Baron

2004-01-01

368

Drifting absence :: drafting memory  

E-print Network

The emotive power of a memorial derives from its ability to engage the viewer in active remembrance. The project considers the limitations of a monumentality which embraces a distinct division between viewer and memorial. ...

Kuhn, Marlene Eva

2006-01-01

369

Memory and Aging  

MedlinePLUS

Memory and Aging Losing keys, misplacing a wallet, or forgetting someone’s name are common experiences. But for people nearing or over ... that require medical and psychological attention. Memory and Aging What Brain Changes Are Normal for Older Adults? ...

370

Memorial prize winner named.  

PubMed

The Queen's Nursing Institute (QNI) has announced the first recipient of the Philip Goodeve-Docker Memorial Prize, named in memory of a young man who died while raising funds for the charity. PMID:25408015

2014-11-25

371

The Cellular Engineering & Nano-Therapeutics Laboratory (CENT LAB) Our research program focuses on the development of bio-inspired drug delivery systems that enhance  

E-print Network

Science and Engineering Program, the Pharmaceutical Engineering Program, the UM Comprehensive CancerThe Cellular Engineering & Nano-Therapeutics Laboratory (CENT LAB) Our research program focuses research approach combining molecular engineering, synthetic polymer chemistry, and cellular and molecular

Kamat, Vineet R.

372

Uniform Memory Hierarchies  

Microsoft Academic Search

The authors introduce a model, called the uniform memory hierarchy (UMH) model, which reflects the hierarchical nature of computer memory more accurately than the RAM (random-access-machine) model, which assumes that any item in memory can be accessed with unit cost. In the model memory occurs as a sequence of increasingly large levels. Data are transferred between levels in fixed-size blocks

Bowen Alpern; Larry Carter; Ephraim Feig

1990-01-01

373

T Cell Memory  

Microsoft Academic Search

T cell memory induced by prior infection or vaccination provides enhanced protection against subsequent microbial infections.\\u000a The processes involved in generating and maintaining T cell memory are becoming better understood due to recent technological\\u000a advances in identifying memory T cells and monitoring their behavior and function in vivo. Memory T cells develop in response\\u000a to a progressive set of cues—starting

J. Tan; C. Surh

374

Exercise and Memory  

NSDL National Science Digital Library

This activity (on page 2 of the PDF) is a full inquiry investigation into the effects of exercise on short term memory. Groups of learners will set a baseline score with an initial memory test. Then they split into two teams, one participating in physical exercise while the other remains sedentary. After ten minutes, both teams take another memory test to tabulate and graph score changes. Relates to linked video, DragonflyTV: Exercise and Memory.

Twin Cities Public Television, Inc.

2005-01-01

375

Phytonutrients as therapeutic agents.  

PubMed

Nutrients present in various foods plays an important role in maintaining the normal functions of the human body. The major nutrients present in foods include carbohydrates, proteins, lipids, vitamins, and minerals. Besides these, there are some bioactive food components known as "phytonutrients" that play an important role in human health. They have tremendous impact on the health care system and may provide medical health benefits including the prevention and/or treatment of disease and various physiological disorders. Phytonutrients play a positive role by maintaining and modulating immune function to prevent specific diseases. Being natural products, they hold a great promise in clinical therapy as they possess no side effects that are usually associated with chemotherapy or radiotherapy. They are also comparatively cheap and thus significantly reduce health care cost. Phytonutrients are the plant nutrients with specific biological activities that support human health. Some of the important bioactive phytonutrients include polyphenols, terpenoids, resveratrol, flavonoids, isoflavonoids, carotenoids, limonoids, glucosinolates, phytoestrogens, phytosterols, anthocyanins, ?-3 fatty acids, and probiotics. They play specific pharmacological effects in human health such as anti-microbial, anti-oxidants, anti-inflammatory, antiallergic, anti-spasmodic, anti-cancer, anti-aging, hepatoprotective, hypolipidemic, neuroprotective, hypotensive, diabetes, osteoporosis, CNS stimulant, analgesic, protection from UVB-induced carcinogenesis, immuno-modulator, and carminative. This mini-review attempts to summarize the major important types of phytonutrients and their role in promoting human health and as therapeutic agents along with the current market trend and commercialization. PMID:25051278

Gupta, Charu; Prakash, Dhan

2014-09-01

376

Plasmids encoding therapeutic agents  

DOEpatents

Plasmids encoding anti-HIV and anti-anthrax therapeutic agents are disclosed. Plasmid pWKK-500 encodes a fusion protein containing DP178 as a targeting moiety, the ricin A chain, an HIV protease cleavable linker, and a truncated ricin B chain. N-terminal extensions of the fusion protein include the maltose binding protein and a Factor Xa protease site. C-terminal extensions include a hydrophobic linker, an L domain motif peptide, a KDEL ER retention signal, another Factor Xa protease site, an out-of-frame buforin II coding sequence, the lacZ.alpha. peptide, and a polyhistidine tag. More than twenty derivatives of plasmid pWKK-500 are described. Plasmids pWKK-700 and pWKK-800 are similar to pWKK-500 wherein the DP178-encoding sequence is substituted by RANTES- and SDF-1-encoding sequences, respectively. Plasmid pWKK-900 is similar to pWKK-500 wherein the HIV protease cleavable linker is substituted by a lethal factor (LF) peptide-cleavable linker.

Keener, William K. (Idaho Falls, ID)

2007-08-07

377

Associative Memory Acceptors.  

ERIC Educational Resources Information Center

The properties of an associative memory are examined in this paper from the viewpoint of automata theory. A device called an associative memory acceptor is studied under real-time operation. The family "L" of languages accepted by real-time associative memory acceptors is shown to properly contain the family of languages accepted by one-tape,…

Card, Roger

378

SENSING MEMORY Festival Directors  

E-print Network

SENSING MEMORY Festival Directors: Simon Ible, Director of Music, Peninsula Arts, Plymouth University Eduardo R. Miranda, Professor of Computer Music, Plymouth University Sensing Memory As well as creating a platform for music emerging from research, this year's festival will explore the theme of memory

Miranda, Eduardo Reck

379

Memory Consolidation in Sleep  

Microsoft Academic Search

We discuss several lines of evidence refuting the hypothesis that procedural or declarative memories are processed\\/consolidated in sleep. One of the strongest arguments against a role for sleep in declarative memory involves the demonstration that the marked suppression or elimination of REM sleep in subjects on antidepressant drugs or with brainstem lesions produces no detrimental effects on cognition. Procedural memory,

Robert P. Vertes

2004-01-01

380

Stephenson Memorial Concert Series  

E-print Network

Stephenson Memorial Concert Series 1997-1998 #12;Stephenson Memorial Concert Series Dorian Wind Stokes Auditorium The Stephenson Memorial Concert fund was established in 1987 by the late Louis B life. Following his death a few months after his retirement, the concerts also honored their son, John

Baltisberger, Jay H.

381

Numerical Memory Explanation  

NSDL National Science Digital Library

This Numerical Memory experiment employs a similar format to Digit Span tasks found in assessment instruments, comparing an individual's short-term memory for digits presented in an auditory vs. visual format. This page provides information about the memory task and how it can be used in the classroom.

382

Numerical Memory Experiment  

NSDL National Science Digital Library

This is the entry page for the Numerical Memory Experiment. This Numerical Memory experiment employs a similar format to Digit Span tasks found in assessment instruments, comparing the individual's short-term memory for digits presented in an auditory vs. visual format.

383

Origins of Autobiographical Memory.  

ERIC Educational Resources Information Center

Tested predictions of infantile amnesia theory compared with social-interactionist account of autobiographical memory. Found maternal reminiscing style and self-recognition when child was 19 months old uniquely predicted children's shared memory reports across time, even with children's initial language and nonverbal memory factored out.…

Harley, Keryn; Reese, Elaine

1999-01-01

384

Drawings as a therapeutic medium  

Microsoft Academic Search

This paper describes a 4-year-old boy whose presenting problem was anxiety. The treatment used is of particular interest because of the graphic exposition of the development of the therapeutic alliance, the immediacy of the Oedipal issues, and the usefulness of the child's drawings as a therapeutic medium. The phases of therapy are reflected in the drawings, as is identification with

Joseph B. LeRoy; Andre Derdeyn

1976-01-01

385

Therapeutic cloning: promises and issues  

Microsoft Academic Search

Advances in biotechnology necessitate both an understanding of scientific principles and ethical implications to be clinically applicable in medicine. In this regard, therapeutic cloning offers significant potential in regenerative medicine by circumventing immunorejection, and in the cure of genetic disorders when used in conjunction with gene therapy. Therapeutic cloning in the context of cell replacement therapy holds a huge potential

Charlotte Kfoury

2007-01-01

386

DCTD — Developmental Therapeutics Program (DTP)  

Cancer.gov

In 2009, NCI consolidated its anticancer drug discovery and development resources in support of a robust, balanced, goal-driven therapeutics pipeline--the NCI Experimental Therapeutics (NExT) Program. For more information about this new initiative, including how to submit an application, please visit the NExT website.

387

Transdermal delivery of therapeutic agent  

NASA Technical Reports Server (NTRS)

A device for the transdermal delivery of a therapeutic agent to a biological subject that includes a first electrode comprising a first array of electrically conductive microprojections for providing electrical communication through a skin portion of the subject to a second electrode comprising a second array of electrically conductive microprojections. Additionally, a reservoir for holding the therapeutic agent surrounding the first electrode and a pulse generator for providing an exponential decay pulse between the first and second electrodes may be provided. A method includes the steps of piercing a stratum corneum layer of skin with two arrays of conductive microprojections, encapsulating the therapeutic agent into biocompatible charged carriers, surrounding the conductive microprojections with the therapeutic agent, generating an exponential decay pulse between the two arrays of conductive microprojections to create a non-uniform electrical field and electrokinetically driving the therapeutic agent through the stratum corneum layer of skin.

Kwiatkowski, Krzysztof C. (Inventor); Hayes, Ryan T. (Inventor); Magnuson, James W. (Inventor); Giletto, Anthony (Inventor)

2008-01-01

388

CRIB (NGF delivery) Cyto Therapeutics Inc.  

PubMed

Cellular Replacement by Immunoisolatory Biocapsule (CRIB) is a technology under development by Cyto-Therapeutics for the delivery of therapeutic substances to the central nervous system (CNS). Preclinical studies with implants are underway for the potential treatment of Alzheimer's disease, Huntington's chorea and other neurodegenerative diseases [180367]. Theses implants contain cells that have been genetically engineered to secrete human nerve growth factor. Development of the CRIB implant is in collaboration with Genentech. CRIB consists of product-secreting cells encapsulated in a semipermeable polymer membrane. The device is surgically implanted into the target area of the brain, thus bypassing the blood-brain barrier, whilst isolating the foreign cells from the patient's immune system [180367]. CRIB implants secreting nerve growth factor (NGF) were effective in preventing nerve degeneration in a monkey model of Alzheimer's disease. The devices contained baby hamster kidney fibroblasts (genetically modified to secrete human NGF) and were implanted into brain ventricles of elderly rhesus monkeys whose cholinergic neurons had been cut. The monkeys treated with non-NGF secreting implants showed a decrease in the number of cholinergic neurons, while those treated with NGF-secreting implants showed a smaller loss of neurons and sprouting of cholinergic nerve fibres [200261]. CytoTherapeutics is working towards clinical trials with these implants in patients with Alzheimer's disease [168581]. Trials of NGF-secreting implants have also been carried out in animal models of Huntington's disease. The company demonstrated that in rodents whose brains had been lesioned with quinolinic acid to approximate the neuronal death which occurs in the disease, NGF-releasing implants protected many striatal neurons that would normally have died. In addition, it was shown that behaviors normally lost as a result of striatal neuron damage could be significantly attenuated. Further investigations are scheduled for the potential use of CRIB/NGF technology in Huntington's disease [180367]. The CRIB technology was originally developed at Brown University (Rhode Island, USA) which owns several patents that cover the technology. CytoTherapeutics has entered into collaborative agreements with the university for the use of the technology [199903] as well as with NeuroSpheres, Canada, for the use of their neural stem cells [199898]. PMID:18465562

Cockett, M I

1998-07-01

389

Therapeutics in Huntington's Disease.  

PubMed

OPINION STATEMENT: There is no specific treatment for Huntington's disease (HD). Its many symptoms of motor, psychiatric, and cognitive deterioration are managed with symptomatic relief, rehabilitation, and support. The only drug approved by the US Food and Drug Administration (FDA) for the treatment of HD is an antichoreic agent, tetrabenazine, but this drug is used sparingly because of uneasiness regarding its propensity to cause depression and suicidality in this population, which is already at risk for these complications. Neuroleptics are still first-line treatments for chorea accompanied by comorbid depression and/or behavioral or psychotic symptoms, as is often the case. Psychiatric features, which have a significant impact on a patient's professional and personal life, often become the major focus of management. In addition to neuroleptics, commonly used medications include antidepressants, mood stabilizers, anxiolytics, and psychostimulants. In contrast, few treatment options are available for cognitive impairment in HD; this remains an important and largely unmet therapeutic need. HD patients typically lack insight into their disease manifestations, failing to recognize their need for treatment, and possibly even arguing against it. Multipurpose medications are employed advantageously to simplify the medication regimen, so as to facilitate compliance and not overwhelm the patient. For example, haloperidol can be prescribed for a patient with chorea, agitation, and anorexia, rather than targeting each symptom with a different drug. This approach also limits the potential for adverse effects, which can be difficult to distinguish from the features of the disease itself. With HD's complexity, it is best managed with a multidisciplinary approach that includes a movement disorders specialist, a genetic counselor, a mental health professional, a physical therapist, and a social worker for support and coordination of services. As the disease progresses, there may be need for other specialists, such as a speech and occupational therapist, a nutritionist for weight loss, and ultimately, a palliative care specialist. PMID:22314929

Killoran, Annie; Biglan, Kevin M

2012-02-01

390

DOI: 10.1002/adfm.200500692 Self-Assembled Shape-Memory Fibers of Triblock Liquid-Crystal  

E-print Network

DOI: 10.1002/adfm.200500692 Self-Assembled Shape-Memory Fibers of Triblock Liquid-Crystal Polymers of fibers. However, although the alignment of drawn polymer fibers is easily and commonly achieved** By Samit V. Ahir, Ali Reza Tajbakhsh, and Eugene M. Terentjev* 1. Introduction Liquid

Terentjev, Eugene

391

Immunological memory is associative  

SciTech Connect

The purpose of this paper is to show that immunological memory is an associative and robust memory that belongs to the class of sparse distributed memories. This class of memories derives its associative and robust nature by sparsely sampling the input space and distributing the data among many independent agents. Other members of this class include a model of the cerebellar cortex and Sparse Distributed Memory (SDM). First we present a simplified account of the immune response and immunological memory. Next we present SDM, and then we show the correlations between immunological memory and SDM. Finally, we show how associative recall in the immune response can be both beneficial and detrimental to the fitness of an individual.

Smith, D.J.; Forrest, S. [New Mexico Univ., Albuquerque, NM (United States). Dept. of Computer Science; Perelson, A.S. [Los Alamos National Lab., NM (United States)

1996-12-31

392

Origins of autobiographical memory.  

PubMed

This study tested the predictions of M. L. Howe and M. L. Courage's (1993, 1997) theory of infantile amnesia compared with a social-interactionist account of autobiographical memory development (R. Fivush & E. Reese, 1992; K. Nelson, 1993b). Fifty-eight mother-child dyads were assessed for maternal styles of talking about the past and for children's self-recognition, language production, and nonverbal memory when the children were 19 months old. Children's shared and independent memory reports were then assessed from 19 to 32 months. Maternal reminiscing style and self-recognition uniquely predicted children's shared memory reports across time, even with children's initial language and nonverbal memory factored out. Self-recognition skills also predicted children's later independent memory. These results support a pluralistic account of the origins of autobiographical memory. PMID:10493658

Harley, K; Reese, E

1999-09-01

393

Lipid-absorbing Polymers  

NASA Technical Reports Server (NTRS)

The removal of bile acids and cholesterol by polymeric absorption is discussed in terms of micelle-polymer interaction. The results obtained with a polymer composed of 75 parts PEO and 25 parts PB plus curing ingredients show an absorption of 305 to 309%, based on original polymer weight. Particle size effects on absorption rate are analyzed. It is concluded that crosslinked polyethylene oxide polymers will absorb water, crosslinked polybutadiene polymers will absorb lipids; neither polymer will absorb appreciable amounts of lipids from micellar solutions of lipids in water.

Marsh, H. E., Jr.; Wallace, C. J.

1973-01-01

394

Isomeric Trisaryloxycyclotriphosphazene Polymer Precursors  

NASA Technical Reports Server (NTRS)

Substances useful for making heat-and fire-resistant polymers. Cyclotriphosphazene-based monomers and polymer precursors led to development of high-temperature materials. Cyclotriphosphazene-derived monomers, polymer precursors, and polymers becoming important from both industrial and scientific points of view. Presence of phosphazene moiety in cyclotriphosphazene-based monomers and polymer precursors expected to impact special properties in desired high-performance materials containing inorganic backbones for aerospace applications. Useful for obtaining heat-and fire-resistant polymers for composites, adhesives, molding powders, and coating laminates. Also used in structures (e.g. secondary structures in aircraft), in construction of spacecraft, and in electronics and computer industries.

St. Clair, Terry L.; Kumar, Devendra

1990-01-01

395

Memory access in shared virtual memory  

SciTech Connect

Shared virtual memory (SVM) is a virtual memory layer with a single address space on top of a distributed real memory on parallel computers. We examine the behavior and performance of SVM running a parallel program with medium-grained, loop-level parallelism on top of it. A simulator for the underlying parallel architecture can be used to examine the behavior of SVM more deeply. The influence of several parameters, such as the number of processors, page size, cold or warm start, and restricted page replication, is studied.

Berrendorf, R. [Zentralinstitut fuer Angewandte Mathematik Forschungszentrum Juelich, KFA (FRG)

1992-09-01

396

Memory access in shared virtual memory  

SciTech Connect

Shared virtual memory (SVM) is a virtual memory layer with a single address space on top of a distributed real memory on parallel computers. We examine the behavior and performance of SVM running a parallel program with medium-grained, loop-level parallelism on top of it. A simulator for the underlying parallel architecture can be used to examine the behavior of SVM more deeply. The influence of several parameters, such as the number of processors, page size, cold or warm start, and restricted page replication, is studied.

Berrendorf, R. (Zentralinstitut fuer Angewandte Mathematik Forschungszentrum Juelich, KFA (FRG))

1992-01-01

397

Stimuli-responsive supramolecular polymers in aqueous solution.  

PubMed

CONSPECTUS: Aiming to construct various novel supramolecular polymeric structures in aqueous solution beyond small supramolecular self-assembly molecules and develop functional supramolecular polymeric materials, research interest on functional supramolecular polymers has been prevailing in recent years. Supramolecular polymers are formed by bridging monomers or components together via highly directional noncovalent interactions such as hydrogen bonding, hydrophobic interaction, ?-? interaction, metal-ligand coordination, electrostatic interaction, and so forth. They can be easily functionalized by employing diverse building components with specific functions besides the traditional polymeric properties, a number of which are responsive to such external stimuli as pH variance, photoirradiation, chemically or electrochemically redox with the controllable conformation or construction switching, polymerization building and rebuilding, and function adjustment reversibly owing to the reversibility of noncovalent interactions. Supramolecular polymers are "soft matters" and can be functionalized with specific properties such as morphology adjustment, controllable luminescence, shape memory, self-healing, and so forth. Supramolecular polymers constructed based on macrocycle recognition and interlocked structures represent one typical branch of the supramolecular polymer family. Cyclodextrin (CD), cucurbituril (CB), and hydrophilic calixarene derivatives are usually employed to construct hydrophilic supramolecular polymers in aqueous solution. Stimuli-responsive hydrophilic supramolecular polymers, constructed in aqueous solution particularly, can be promising candidates for mimicking biocompatible or vital functional materials. This Account mainly focuses on the recent stimuli-responsive supramolecular polymers based on the host-guest interaction in aqueous solution. We describe the hydrophilic supramolecular polymers constructed via hydrophobic effects, electrostatic interaction, metal-ligand coordination, and multiple combinations of the above noncovalent interactions. The disparate ways to engender stimuli-responsive supramolecular polymers via the hydrophobic effects of ?-CD, ?-CD, and ?-CD macrocycles are illustrated and discussed. Some recent works on CD-based photoresponsive functional supramolecular polymers are summarized. CB (especially CB[8]) based supramolecular polymers and their pH-responsive and photoresponsive properties are introduced. Hydrophilic calixarene derivative (bis(p-sulfonatocalix[4]arene) typically) based supramolecular polymers via electrostatic interactions are reviewed, and their redox-responsive association/disassociation elaborated in detail. More complicate supramolecular polymers based on multiple noncovalent interactions are illustrated including hydrophobic effect, metal-ligand coordination, and electrostatic interactions and their functional stimuli-responsiveness elaborated as well. Finally, we give perspectives on the strength of these diverse noncovalent interactions to form supramolecular polymers in aqueous solution, on the advantage, disadvantage, efficiency, and reversibility of using certain stimuli in constructing supramolecular polymers and prospect the future function improvement of these polymers as functional materials. PMID:24669851

Ma, Xiang; Tian, He

2014-07-15

398

Thermomechanical behavior of shape memory elastomeric composites  

NASA Astrophysics Data System (ADS)

Shape memory polymers (SMPs) can fix a temporary shape and recover their permanent shape in response to environmental stimuli such as heat, electricity, or irradiation. Most thermally activated SMPs use the macromolecular chain mobility change around the glass transition temperature ( Tg) to achieve the shape memory (SM) effects. During this process, the stiffness of the material typically changes by three orders of magnitude. Recently, a composite materials approach was developed to achieve thermally activated shape memory effect where the material exhibits elastomeric response in both the temporary and the recovered configurations. These shape memory elastomeric composites (SMECs) consist of an elastomeric matrix reinforced by a semicrystalline polymer fiber network. The matrix provides background rubber elasticity while the fiber network can transform between solid crystals and melt phases over the operative temperature range. As such it serves as a reversible "switching phase" that enables shape fixing and recovery. Shape memory elastomeric composites provide a new paradigm for the development of a wide array of active polymer composites that utilize the melt-crystal transition to achieve the shape memory effect. This potentially allows for material systems with much simpler chemistries than most shape memory polymers and thus can facilitate more rapid material development and insertion. It is therefore important to understand the thermomechanical behavior and to develop corresponding material models. In this paper, a 3D finite-deformation constitutive modeling framework was developed to describe the thermomechanical behavior of SMEC. The model is phenomenological, although inspired by micromechanical considerations of load transfer between the matrix and fiber phases of a composite system. It treats the matrix as an elastomer and the fibers as a complex solid that itself is an aggregate of melt and crystal phases that evolve from one to the other during a temperature change. As such, the composite consists of an elastomer reinforced by a soft liquid at high temperature and a stiff solid at low temperature. The model includes a kinetic description of the non-isothermal crystallization and melting of the fibers during a temperature change. As the fibers transform from melt to crystal during cooling it is assumed that new crystals are formed in an undeformed state, which requires careful tracking of the kinematics of the evolving phases which comes at a significant computational cost. In order to improve the computational efficiency, an effective phase model (EPM) is adopted to treat the evolving crystal phases as an effective medium. A suite of careful thermomechanical experiments with a SMEC was carried out to calibrate various model parameters, and then to demonstrate the ability of the model to accurately capture the shape memory behavior of the SMEC system during complex thermomechanical loading scenarios. The model also identifies the effects of microstructural design parameters such as the fiber volume fraction.

Ge, Qi; Luo, Xiaofan; Rodriguez, Erika D.; Zhang, Xiao; Mather, Patrick T.; Dunn, Martin L.; Qi, H. Jerry

2012-01-01

399

Fluorescent Multiblock ?-Conjugated Polymer Nanoparticles for In Vivo Tumor Targeting  

PubMed Central

Highly fluorescent multiblock conjugated polymer nanoparticles with folic acid surface ligands are highly effective for bioimaging and in vivo tumor targeting. The targeted nanoparticles were preferentially localized in tumor cells in vivo, thereby illustrating their potential for diagnostic and therapeutic applications. PMID:23794490

Ahmed, Eilaf; Morton, Stephen W.

2014-01-01

400

Photo-mechanical patterning with light activated polymers.  

SciTech Connect

Light activated polymers, which are capable of mechanically responding to light, promise to offer exciting, innovative, and unique material capabilities. Such materials include: photo-radical mediated cleavage and reformation of the polymer backbone in cross-linked elastomers that results in local stress relaxation; photo-switching cross-links in shape memory polymers; and photo-isomerization of azobenzene groups contained in liquid crystal elastomers. In this paper, using our recent material model that couples multiphysical processes involved in light-activated polymers, we demonstrate that a variety of patterns can be created on light activated polymer thin films when coupling mechanical deformation with light irradiation. Here, the polymer thin film is first stretched uniaxially or biaxially. Light is then irradiated on the surface of the thin film. After light irradiation, removal external load partially recovers the initial stretching of the polymer thin film and induces patterns. The variation of the geometry of the patterns can be controlled by a variety of parameters such as initial stretching, light intensity, etc. Photo-patterning with light activated polymer therefore offers a novel way to create surface patterns.

Long, Kevin N.; Qi, H. Jerry (University of Colorado, Boulder, CO); Dunn, Martin L. (University of Colorado, Boulder, CO)

2010-11-01

401

Degradability of Polymers for Implantable Biomedical Devices  

PubMed Central

Many key components of implantable medical devices are made from polymeric materials. The functions of these materials include structural support, electrical insulation, protection of other materials from the environment of the body, and biocompatibility, as well as other things such as delivery of a therapeutic drug. In such roles, the stability and integrity of the polymer, over what can be a very long period of time, is very important. For most of these functions, stability over time is desired, but in other cases, the opposite–the degradation and disappearance of the polymer over time is required. In either case, it is important to understand both the chemistry that can lead to the degradation of polymers as well as the kinetics that controls these reactions. Hydrolysis and oxidation are the two classes of reactions that lead to the breaking down of polymers. Both are discussed in detail in the context of the environmental factors that impact the utility of various polymers for medical device applications. Understanding the chemistry and kinetics allows prediction of stability as well as explanations for observations such as porosity and the unexpected behavior of polymeric composite materials in some situations. In the last part, physical degradation such interfacial delamination in composites is discussed. PMID:19865531

Lyu, SuPing; Untereker, Darrel

2009-01-01

402

Cache Basics Cache Performance Memory Organization Virtual Memory Engineering 9859  

E-print Network

-- Computer Architecture Memory Hierarchy Design Dennis Peters1 Fall 2007 1 Based on notes from Dr. R;Cache Basics Cache Performance Memory Organization Virtual Memory Memory hierarchy ­ Why and How slower (due to high decoding time and other reasons). · Therefore, hierarchy of memory: · locate small

Peters, Dennis

403

Young and old Pavlovian fear memories can be modified with extinction training during reconsolidation in humans  

PubMed Central

Extinction training during reconsolidation has been shown to persistently diminish conditioned fear responses across species. We investigated in humans if older fear memories can benefit similarly. Using a Pavlovian fear conditioning paradigm we compared standard extinction and extinction after memory reactivation 1 d or 7 d following acquisition. Participants who underwent extinction during reconsolidation showed no evidence of fear recovery, whereas fear responses returned in participants who underwent standard extinction. We observed this effect in young and old fear memories. Extending the beneficial use of reconsolidation to older fear memories in humans is promising for therapeutic applications. PMID:24934333

Steinfurth, Elisa C.K.; Kanen, Jonathan W.; Raio, Candace M.; Clem, Roger L.; Huganir, Richard L.; Phelps, Elizabeth A.

2014-01-01

404

Young and old Pavlovian fear memories can be modified with extinction training during reconsolidation in humans.  

PubMed

Extinction training during reconsolidation has been shown to persistently diminish conditioned fear responses across species. We investigated in humans if older fear memories can benefit similarly. Using a Pavlovian fear conditioning paradigm we compared standard extinction and extinction after memory reactivation 1 d or 7 d following acquisition. Participants who underwent extinction during reconsolidation showed no evidence of fear recovery, whereas fear responses returned in participants who underwent standard extinction. We observed this effect in young and old fear memories. Extending the beneficial use of reconsolidation to older fear memories in humans is promising for therapeutic applications. PMID:24934333

Steinfurth, Elisa C K; Kanen, Jonathan W; Raio, Candace M; Clem, Roger L; Huganir, Richard L; Phelps, Elizabeth A

2014-07-01

405

Memory bistable mechanisms of organic memory devices  

NASA Astrophysics Data System (ADS)

To investigate the memory bistable mechanisms of organic memory devices, the structure of [top Au anode/9,10-di(2-naphthyl)anthracene (ADN) active layer/bottom Au cathode] was deposited using a thermal deposition system. The Au atoms migrated into the ADN active layer was observed from the secondary ion mass spectrometry. The density of 9.6×1016 cm-3 and energy level of 0.553 eV of the induced trapping centers caused by the migrated Au atoms in the ADN active layer were calculated. The induced trapping centers did not influence the carrier injection barrier height between Au and ADN active layer. Therefore, the memory bistable behaviors of the organic memory devices were attributed to the induced trapping centers. The energy diagram was established to verify the mechanisms.

Lee, Ching-Ting; Yu, Li-Zhen; Chen, Hung-Chun

2010-07-01

406

Playing with Polymers.  

ERIC Educational Resources Information Center

Presents an activity that enables students to gain a better understanding of the importance of polymers. Students perform an experiment in which polymer chains of polyvinyl acetate form crosslinks. Includes background information and discussion questions. (DDR)

Chemecology, 1997

1997-01-01

407

Stiff Quantum Polymers  

E-print Network

At ultralow temperatures, polymers exhibit quantum behavior, which is calculated here for the moments and of the end-to-end distribution in the large-stiffness regime. The result should be measurable for polymers in wide optical traps.

H. Kleinert

2007-05-01

408

Mechanical Properties of Polymers.  

ERIC Educational Resources Information Center

Mechanical properties (stress-strain relationships) of polymers are reviewed, taking into account both time and temperature factors. Topics include modulus-temperature behavior of polymers, time dependence, time-temperature correspondence, and mechanical models. (JN)

Aklonis, J. J.

1981-01-01

409

Introduction to Polymer Chemistry.  

ERIC Educational Resources Information Center

Reviews the physical and chemical properties of polymers and the two major methods of polymer synthesis: addition (chain, chain-growth, or chain-reaction), and condensation (step-growth or step-reaction) polymerization. (JN)

Harris, Frank W.

1981-01-01

410

Polymer composites containing nanotubes  

NASA Technical Reports Server (NTRS)

The present invention relates to polymer composite materials containing carbon nanotubes, particularly to those containing singled-walled nanotubes. The invention provides a polymer composite comprising one or more base polymers, one or more functionalized m-phenylenevinylene-2,5-disubstituted-p-phenylenevinylene polymers and carbon nanotubes. The invention also relates to functionalized m-phenylenevinylene-2,5-disubstituted-p-phenylenevinylene polymers, particularly to m-phenylenevinylene-2,5-disubstituted-p-phenylenevinylene polymers having side chain functionalization, and more particularly to m-phenylenevinylene-2,5-disubstituted-p-phenylenevinylene polymers having olefin side chains and alkyl epoxy side chains. The invention further relates to methods of making polymer composites comprising carbon nanotubes.

Bley, Richard A. (Inventor)

2008-01-01

411

Modifications of Glycans: Biological Significance and Therapeutic Opportunities  

PubMed Central

Carbohydrates play a central role in a wide range of biological processes. As with nucleic acids and proteins, modifications of specific sites within the glycan chain can modulate a carbohydrate’s overall biological function. For example, acylation, methylation, sulfation, epimerization, and phosphorylation can occur at various positions within a carbohydrate to modulate bioactivity. Therefore, there is significant interest in identifying discrete carbohydrate modifications and understanding their biological effects. Additionally, enzymes that catalyze those modifications and proteins that bind modified glycans provide numerous targets for therapeutic intervention. This review will focus on modifications of glycans that occur after the oligomer/polymer has been assembled, generally referred to as postglycosylational modifications. PMID:22195988

Muthana, Saddam M.; Campbell, Christopher; Gildersleeve, Jeffrey C.

2012-01-01

412

DCTD — Developmental Therapeutics Program (DTP)  

Cancer.gov

Skip to Content Click here to view the Site Map Home | Sitemap | Contact DCTD Search this site Developmental Therapeutics Program (DTP) Introduction Major Ongoing Initiatives Current Funding Opportunities Tools and Resources Scientific Advances DCTD

413

Broad-Spectrum Antiviral Therapeutics  

E-print Network

Currently there are relatively few antiviral therapeutics, and most which do exist are highly pathogen-specific or have other disadvantages. We have developed a new broad-spectrum antiviral approach, dubbed Double-stranded ...

Rider, Todd H.

414

Bispecific antibody conjugates in therapeutics  

Microsoft Academic Search

Bispecific monoclonal antibodies have drawn considerable attention from the research community due to their unique structure against two different antigens. The two-arm structure of bsMAb allows researchers to place a therapeutic agent on one arm while allowing the other to specifically target the disease site. The therapeutic agent can be a drug, toxin, enzyme, DNA, radionuclide, etc. Furthermore, bsMAb may

Ying Cao; Laura Lam

2003-01-01

415

Therapeutic Vaccines for Chronic Infections  

NASA Astrophysics Data System (ADS)

Therapeutic vaccines aim to prevent severe complications of a chronic infection by reinforcing host defenses when some immune control, albeit insufficient, can already be demonstrated and when a conventional antimicrobial therapy either is not available or has limited efficacy. We focus on the rationale and challenges behind this still controversial strategy and provide examples from three major chronic infectious diseases-human immunodeficiency virus, hepatitis B virus, and human papillomavirus-for which the efficacy of therapeutic vaccines is currently being evaluated.

Autran, Brigitte; Carcelain, Guislaine; Combadiere, Béhazine; Debre, Patrice

2004-07-01

416

DCTD — Developmental Therapeutics Program (DTP)  

Cancer.gov

To address the mechanistic gap that occurs because of difficulties in determining the effect of a therapeutic intervention on its putative site of action in patients, in 2005, the DTP Toxicology and Pharmacology Branch was expanded to include NCTVL. This laboratory will elucidate novel methodologies in target tissues specifically applicable to human cancer clinical trials. These methodologies will demonstrate the therapeutic effects of small molecule anticancer agents on specific cellular pathways of interest.

417

Thermosetting Phthalocyanine Polymers  

NASA Technical Reports Server (NTRS)

Group of phthalocyanine polymers resist thermal degradation. Polymers expected semiconducting. Principal applications probably in molded or laminated parts that have to withstand high temperatures. Polymers made from either of two classes of monomer: Bisphthalonitriles with imide linkages or Bisphthalonitriles with ester-imide linkages.

Fohlen, G.; Parker, J.; Achar, B.

1985-01-01

418

Polymer Hydrogels: A Review  

Microsoft Academic Search

This review encompasses definitions, classification, main properties, and application of polymer hydrogels. Raw materials and preparation techniques of polymer hydrogels were described. The factors that affect absorption capacity and swelling properties of polymer hydrogels were reviewed. PHG materials are defined as a viscoelastic network structure, swellable and not soluble in water with high absorbent capacity, which may reach 1000 g\\/g of

Waham Ashaier Laftah; Shahrir Hashim; Akos N. Ibrahim

2011-01-01

419

Therapeutic education of diabetic patients.  

PubMed

Therapeutic patient education is a patient-centred approach, focussed on patients' needs, resources, values and strategies. It allows patients to improve their knowledge and skills not only concerning their illness but also their treatment. It brings a better quality of life, a greater therapeutic compliance and a reduction in complications. The most difficult part of therapeutic patient education occurs when patients must change their behaviour. Motivational interviewing and cognitive-behavioural approaches contribute greatly here and allow both the preparation and support of patients during progressive 'step by step' change. The work on resistance to change is fundamental, and ambivalence when faced with the choice of a new way of life must be measured, discussed and negotiated. Patients become partners and we become 'coaches'. The negotiation of objectives must allow patients to choose their own strategies, which normally should cost them the least possible, psychologically, and bring them the maximum benefit. The efficiency of therapeutic patient education no longer needs to be proved: 80% less amputations over 10 years in diabetic patients; 50% maintenance of weight loss over 5 years, etc. In conclusion, therapeutic education is part of a humanistic medical approach centred on patients; it allows them to be active participants in their own treatment with the aim of improving their quality of life and therapeutic compliance, as well as reducing potential complications. Thus, health care professionals teach, inform, train, negotiate with, motivate and accompany patients in the long-term follow-up of their illness. PMID:18229887

Golay, A; Lagger, G; Chambouleyron, M; Carrard, I; Lasserre-Moutet, A

2008-01-01

420

Reversal of cognitive decline: A novel therapeutic program  

PubMed Central

This report describes a novel, comprehensive, and personalized therapeutic program that is based on the underlying pathogenesis of Alzheimer's disease, and which involves multiple modalities designed to achieve metabolic enhancement for neurodegeneration (MEND). The first 10 patients who have utilized this program include patients with memory loss associated with Alzheimer's disease (AD), amnestic mild cognitive impairment (aMCI), or subjective cognitive impairment (SCI). Nine of the 10 displayed subjective or objective improvement in cognition beginning within 3-6 months, with the one failure being a patient with very late stage AD. Six of the patients had had to discontinue working or were struggling with their jobs at the time of presentation, and all were able to return to work or continue working with improved performance. Improvements have been sustained, and at this time the longest patient follow-up is two and one-half years from initial treatment, with sustained and marked improvement. These results suggest that a larger, more extensive trial of this therapeutic program is warranted. The results also suggest that, at least early in the course, cognitive decline may be driven in large part by metabolic processes. Furthermore, given the failure of monotherapeutics in AD to date, the results raise the possibility that such a therapeutic system may be useful as a platform on which drugs that would fail as monotherapeutics may succeed as key components of a therapeutic system. PMID:25324467

Bredesen, Dale E.

2014-01-01

421

Vegetable-oil-based polymers as future polymeric biomaterials.  

PubMed

Vegetable oils are one of the most important classes of bio-resources for producing polymeric materials. The main components of vegetable oils are triglycerides - esters of glycerol with three fatty acids. Several highly reactive sites including double bonds, allylic positions and the ester groups are present in triglycerides from which a great variety of polymers with different structures and functionalities can be prepared. Vegetable-oil-based polyurethane, polyester, polyether and polyolefin are the four most important classes of polymers, many of which have excellent biocompatibilities and unique properties including shape memory. In view of these characteristics, vegetable-oil-based polymers play an important role in biomaterials and have attracted increasing attention from the polymer community. Here we comprehensively review recent developments in the preparation of vegetable-oil-based polyurethane, polyester, polyether and polyolefin, all of which have potential applications as biomaterials. PMID:24012607

Miao, Shida; Wang, Ping; Su, Zhiguo; Zhang, Songping

2014-04-01

422

Optical mass memories  

NASA Technical Reports Server (NTRS)

Optical and magnetic variants in the design of trillion-bit read/write memories are compared and tabulated. Components and materials suitable for a random access read/write nonmoving memory system are examined, with preference given to holography and photoplastic materials. Advantages and deficiencies of photoplastics are reviewed. Holographic page composer design, essential features of an optical memory with no moving parts, fiche-oriented random access memory design, and materials suitable for an efficient photoplastic fiche are considered. The optical variants offer advantages in lower volume and weight at data transfer rates near 1 Mbit/sec, but power drain is of the same order as for the magnetic variants (tape memory, disk memory). The mechanical properties of photoplastic film materials still leave much to be desired.

Bailey, G. A.

1976-01-01

423

Nanomaterials for Photo-Based Diagnostic and Therapeutic Applications  

PubMed Central

Photo-based diagnosis and treatment methods are gaining prominence due to increased spatial imaging resolution, minimally invasive modalities involved as well as localized treatment. Recently, nanoparticles (NPs) have been developed and used in photo-based therapeutic applications. While some nanomaterials have inherent photo-based imaging capabilities, others including polymeric NPs act as nanocarriers to deliver various fluorescent dyes or photosensitizers for photoimaging and therapeutic applications. These applications can vary from Magnetic Resonance Imaging (MRI) and optical imaging to photothermal therapy (PTT) and chemotherapy. Materials commonly used for development of photo-based NPs ranges from metal-based (gold, silver and silica) to polymer-based (chitosan, dextran, poly ethylene glycol (PEG) and poly lactic-co-glycolic acid (PLGA)). Recent research has paved the way for multi-modal 'theranostic' (a combination of therapy and diagnosis) nano-carriers capable of active targeting using cell-specific ligands and carrying multiple therapeutic and imaging agents for accurate diagnosis and controlled drug delivery. This review summarizes the different materials used today to synthesize photo-based NPs, their diagnostic and therapeutic applications as well as the current challenges faced in bringing these novel nano-carriers into clinical practices. PMID:23471164

Menon, Jyothi U.; Jadeja, Parth; Tambe, Pranjali; Vu, Khanh; Yuan, Baohong; Nguyen, Kytai T.

2013-01-01

424

1. GENERAL VIEW SHOWING EVERGREEN SCREEN BEHIND MEMORIAL (MEMORIAL NOT ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

1. GENERAL VIEW SHOWING EVERGREEN SCREEN BEHIND MEMORIAL (MEMORIAL NOT VISIBLE) - Adams Memorial, Rock Creek Cemetery, Section E, entrance at Webster Street & Rock Creek Church Road Northwest, Washington, District of Columbia, DC

425

Nanoparticle-polymer and polymer-polymer blend composite photovoltaics  

NASA Astrophysics Data System (ADS)

The main factors inhibiting higher conversion efficiencies in plain polymer layer sandwich photovoltaic devices are the low exciton dissociation efficiency and the low carrier mobilities in the polymer. We consider two different blend approaches for increasing these qualities. NiO (or LiNiO) hole transporting nanoparticles are blended into the photoactive polymer MEH-DOO-PPV in an attempt to increase hole mobility across the device. Improvements to device performance were not significant at these blend concentrations. Devices made using blends of hole and electron transporting polymers M3EH-PPV and CN-ether-PPV showed increased dissociation efficiency and gave power conversion efficiencies of up to 0.6% with stable electrodes.

Breeze, Alison J.; Schlesinger, Zack; Carter, Sue A.; Hoerhold, Hans-Heinrich; Tillmann, Hartwig; Ginley, David S.; Brock, Phillip J.

2001-02-01

426

Astronaut Memorial Space Mirror  

NASA Technical Reports Server (NTRS)

A view of the Astronaut Memorial Space Mirror at the Kennedy Space Center Visitor Complex. The memorial is a national tribute to the 17 American astronauts who gave their lives in the quest to explore space. The memorial has received added attention since the loss of the Columbia crew on February 1, 2003, when they perished in an explosion as they were returning to Earth from mission STS-107. For more information on STS-107, please see GRIN Columbia General Explanation

2003-01-01

427

Memory Golf Clubs  

NASA Technical Reports Server (NTRS)

Memory Corporation's investigation of shape memory effect, stemming from Marshall Space Flight Center contracts to study materials for the space station, has aided in the development of Zeemet, a proprietary, high-damping shape memory alloy for the golf industry. The Nicklaus Golf Company has created a new line of golf clubs using Zeemet inserts. Its superelastic and high damping attributes translate into more spin on the ball, greater control, and a solid feel.

1997-01-01

428

21 CFR 890.5975 - Therapeutic vibrator.  

Code of Federal Regulations, 2012 CFR

...AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES PHYSICAL MEDICINE DEVICES Physical Medicine Therapeutic Devices § 890.5975 Therapeutic vibrator. (a) Identification. A...

2012-04-01

429

21 CFR 890.5660 - Therapeutic massager.  

Code of Federal Regulations, 2013 CFR

...AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES PHYSICAL MEDICINE DEVICES Physical Medicine Therapeutic Devices § 890.5660 Therapeutic massager. (a) Identification. A...

2013-04-01

430

21 CFR 890.5975 - Therapeutic vibrator.  

Code of Federal Regulations, 2010 CFR

...AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES PHYSICAL MEDICINE DEVICES Physical Medicine Therapeutic Devices § 890.5975 Therapeutic vibrator. (a) Identification. A...

2010-04-01

431

21 CFR 890.5660 - Therapeutic massager.  

Code of Federal Regulations, 2010 CFR

...AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES PHYSICAL MEDICINE DEVICES Physical Medicine Therapeutic Devices § 890.5660 Therapeutic massager. (a) Identification. A...

2010-04-01

432

21 CFR 890.5660 - Therapeutic massager.  

Code of Federal Regulations, 2012 CFR

...AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES PHYSICAL MEDICINE DEVICES Physical Medicine Therapeutic Devices § 890.5660 Therapeutic massager. (a) Identification. A...

2012-04-01

433

Building synthetic memory  

PubMed Central

Synopsis Cellular memory – conversion of a transient signal into a sustained response – is a common feature of biological systems. Synthetic biologists aim to understand and reengineer such systems in a reliable and predictable manner. Synthetic memory circuits have been designed and built in vitro and in vivo based on diverse mechanisms such as oligonucleotide hybridization, recombination, transcription, phosphorylation, and RNA editing. Thus far, building these circuits has helped us explore the basic principles required for stable memory and ask novel biological questions. Here we discuss strategies for building synthetic memory circuits, their use as research tools, and future applications of these devices in medicine and industry. PMID:24028965

Inniss, Mara C.; Silver, Pamela A.

2013-01-01

434

New Gravitational Memories  

E-print Network

The conventional gravitational memory effect is a relative displacement in the position of two detectors induced by radiative energy flux. We find a new type of gravitational `spin memory' in which beams on clockwise and counterclockwise orbits acquire a relative delay induced by radiative angular momentum flux. It has recently been shown that the displacement memory formula is a Fourier transform in time of Weinberg's soft graviton theorem. Here we see that the spin memory formula is a Fourier transform in time of the recently-discovered subleading soft graviton theorem.

Pasterski, Sabrina; Zhiboedov, Alexander

2015-01-01

435

New Gravitational Memories  

E-print Network

The conventional gravitational memory effect is a relative displacement in the position of two detectors induced by radiative energy flux. We find a new type of gravitational `spin memory' in which beams on clockwise and counterclockwise orbits acquire a relative delay induced by radiative angular momentum flux. It has recently been shown that the displacement memory formula is a Fourier transform in time of Weinberg's soft graviton theorem. Here we see that the spin memory formula is a Fourier transform in time of the recently-discovered subleading soft graviton theorem.

Sabrina Pasterski; Andrew Strominger; Alexander Zhiboedov

2015-02-21

436

The future of memory  

NASA Astrophysics Data System (ADS)

In the not too distant future, the traditional memory and storage hierarchy of may be replaced by a single Storage Class Memory (SCM) device integrated on or near the logic processor. Traditional magnetic hard drives, NAND flash, DRAM, and higher level caches (L2 and up) will be replaced with a single high performance memory device. The Storage Class Memory paradigm will require high speed (< 100 ns read/write), excellent endurance (> 1012), nonvolatility (retention > 10 years), and low switching energies (< 10 pJ per switch). The International Technology Roadmap for Semiconductors (ITRS) has recently evaluated several potential candidates SCM technologies, including Resistive (or Redox) RAM, Spin Torque Transfer RAM (STT-MRAM), and phase change memory (PCM). All of these devices show potential well beyond that of current flash technologies and research efforts are underway to improve the endurance, write speeds, and scalabilities to be on-par with DRAM. This progress has interesting implications for space electronics: each of these emerging device technologies show excellent resistance to the types of radiation typically found in space applications. Commercially developed, high density storage class memory-based systems may include a memory that is physically radiation hard, and suitable for space applications without major shielding efforts. This paper reviews the Storage Class Memory concept, emerging memory devices, and possible applicability to radiation hardened electronics for space.

Marinella, M.

437

Sparse distributed memory overview  

NASA Technical Reports Server (NTRS)

The Sparse Distributed Memory (SDM) project is investigating the theory and applications of massively parallel computing architecture, called sparse distributed memory, that will support the storage and retrieval of sensory and motor patterns characteristic of autonomous systems. The immediate objectives of the project are centered in studies of the memory itself and in the use of the memory to solve problems in speech, vision, and robotics. Investigation of methods for encoding sensory data is an important part of the research. Examples of NASA missions that may benefit from this work are Space Station, planetary rovers, and solar exploration. Sparse distributed memory offers promising technology for systems that must learn through experience and be capable of adapting to new circumstances, and for operating any large complex system requiring automatic monitoring and control. Sparse distributed memory is a massively parallel architecture motivated by efforts to understand how the human brain works. Sparse distributed memory is an associative memory, able to retrieve information from cues that only partially match patterns stored in the memory. It is able to store long temporal sequences derived from the behavior of a complex system, such as progressive records of the system's sensory data and correlated records of the system's motor controls.

Raugh, Mike

1990-01-01

438

Fire-safe polymers and polymer composites  

NASA Astrophysics Data System (ADS)

The intrinsic relationships between polymer structure, composition and fire behavior have been explored to develop new fire-safe polymeric materials. Different experimental techniques, especially three milligram-scale methods---pyrolysis-combustion flow calorimetry (PCFC), simultaneous thermal analysis (STA) and pyrolysis GC/MS---have been combined to fully characterize the thermal decomposition and flammability of polymers and polymer composites. Thermal stability, mass loss rate, char yield and properties of decomposition volatiles were found to be the most important parameters in determining polymer flammability. Most polymers decompose by either an unzipping or a random chain scission mechanism with an endothermic decomposition of 100--900 J/g. Aromatic or heteroaromatic rings, conjugated double or triple bonds and heteroatoms such as halogens, N, O, S, P and Si are the basic structural units for fire-resistant polymers. The flammability of polymers can also be successfully estimated by combining pyrolysis GC/MS results or chemical structures with TGA results. The thermal decomposition and flammability of two groups of inherently fire-resistant polymers---poly(hydroxyamide) (PHA) and its derivatives, and bisphenol C (BPC II) polyarylates---have been systematically studied. PHA and most of its derivatives have extremely low heat release rates and very high char yields upon combustion. PHA and its halogen derivatives can completely cyclize into quasi-polybenzoxazole (PBO) structures at low temperatures. However, the methoxy and phosphate derivatives show a very different behavior during decomposition and combustion. Molecular modeling shows that the formation of an enol intermediate is the rate-determining step in the thermal cyclization of PHA. BPC II-polyarylate is another extremely flame-resistant polymer. It can be used as an efficient flame-retardant agent in copolymers and blends. From PCFC results, the total heat of combustion of these copolymers or blends changes linearly with composition, but the change of maximum heat release rates also depends on the chemical structure of the components. The flammability of various polymers and polymer composites measured by PCFC, cone calorimeter ASTM E1354 and Ohio State University (OSU) calorimeter ASTM E906 were also compared. For pure polymers, there is a relatively good correlation between different methods. However, for polymer composites with inert fillers or flame-retardant additives, OSU and cone calorimetries are more suitable evaluation methods.

Zhang, Huiqing

439

Nanoporous polymer electrolyte  

DOEpatents

A nanoporous polymer electrolyte and methods for making the polymer electrolyte are disclosed. The polymer electrolyte comprises a crosslinked self-assembly of a polymerizable salt surfactant, wherein the crosslinked self-assembly includes nanopores and wherein the crosslinked self-assembly has a conductivity of at least 1.0.times.10.sup.-6 S/cm at 25.degree. C. The method of making a polymer electrolyte comprises providing a polymerizable salt surfactant. The method further comprises crosslinking the polymerizable salt surfactant to form a nanoporous polymer electrolyte.

Elliott, Brian (Wheat Ridge, CO); Nguyen, Vinh (Wheat Ridge, CO)

2012-04-24

440

MEMORY TRAINING IN THE COMMUNITY AGED: EFFECTS ON DEPRESSION, MEMORY COMPLAINT, AND MEMORY PERFORMANCE  

Microsoft Academic Search

This study compares the effects of two types of training programs on memory complaints, memory performance, and affective status in the community elderly. Prior research has suggested that although there are some age differences in memory, the memory complaints of older persons are related to depression and not to actual memory performance. In the present project subjects were randomly assigned

Steven H. Zarit; Dolores Gallagher; Nan Kramer

1981-01-01

441

Physical chemistry of supramolecular polymer networks.  

PubMed

Supramolecular polymer networks are three-dimensional structures of crosslinked macromolecules connected by transient, non-covalent bonds; they are a fascinating class of soft materials, exhibiting properties such as stimuli-responsiveness, self-healing, and shape-memory. This critical review summarizes the current state of the art in the physical-chemical characterization of supramolecular networks and relates this knowledge to that about classical, covalently jointed and crosslinked networks. We present a separate focus on the formation, the structure, the dynamics, and the mechanics of both permanent chemical and transient supramolecular networks. Particular emphasis is placed on features such as the formation and the effect of network inhomogeneities, the manifestation of the crosslink relaxation dynamics in the macroscopic sample behavior, and the applicability of concepts developed for classical polymer melts, solutions, and networks such as the reptation model and the principle of time-temperature superposition (263 references). PMID:21909565

Seiffert, Sebastian; Sprakel, Joris

2012-01-21

442

Ion conducting organic/inorganic hybrid polymers  

NASA Technical Reports Server (NTRS)

This invention relates to a series of organic/inorganic hybrid polymers that are easy to fabricate into dimensionally stable films with good ion-conductivity over a wide range of temperatures for use in a variety of applications. The polymers are prepared by the reaction of amines, preferably diamines and mixtures thereof with monoamines with epoxy-functionalized alkoxysilanes. The products of the reaction are polymerized by hydrolysis of the alkoxysilane groups to produce an organic-containing silica network. Suitable functionality introduced into the amine and alkoxysilane groups produce solid polymeric membranes which conduct ions for use in fuel cells, high-performance solid state batteries, chemical sensors, electrochemical capacitors, electro-chromic windows or displays, analog memory devices and the like.

Meador, Maryann B. (Inventor); Kinder, James D. (Inventor)

2010-01-01

443

Neural Protein Synthesis during Aging: Effects on Plasticity and Memory  

PubMed Central

During aging, many experience a decline in cognitive function that includes memory loss. The encoding of long-term memories depends on new protein synthesis, and this is also reduced during aging. Thus, it is possible that changes in the regulation of protein synthesis contribute to the memory impairments observed in older animals. Several lines of evidence support this hypothesis. For instance, protein synthesis is required for a longer period following learning to establish long-term memory in aged rodents. Also, under some conditions, synaptic activity or pharmacological activation can induce de novo protein synthesis and lasting changes in synaptic transmission in aged, but not young, rodents; the opposite results can be observed in other conditions. These changes in plasticity likely play a role in manifesting the altered place field properties observed in awake and behaving aged rats. The collective evidence suggests a link between memory loss and the regulation of protein synthesis in senescence. In fact, pharmaceuticals that target the signaling pathways required for induction of protein synthesis have improved memory, synaptic plasticity, and place cell properties in aged animals. We suggest that a better understanding of the mechanisms that lead to different protein expression patterns in the neural circuits that change as a function of age will enable the development of more effective therapeutic treatments for memory loss. PMID:20802800

Schimanski, Lesley A.; Barnes, Carol A.

2010-01-01

444

RON MINER MEMORIAL BIOENGINEERING SCHOLARSHIP The Ron Miner Memorial Scholarship honors the memory of J. Ronald Miner, an  

E-print Network

RON MINER MEMORIAL BIOENGINEERING SCHOLARSHIP The Ron Miner Memorial Scholarship honors the memory from the Ron Miner Memorial Scholarship which resides with the OSU Foundation. The name & Ecological Engineering. DONOR Ron Miner Memorial Bioengineering Scholarship Fund ELIGIBILITY REQUIREMENTS

Tullos, Desiree

445

Regulating critical period plasticity: insight from the visual system to fear circuitry for therapeutic interventions.  

PubMed

Early temporary windows of heightened brain plasticity called critical periods developmentally sculpt neural circuits and contribute to adult behavior. Regulatory mechanisms of visual cortex development - the preeminent model of experience-dependent critical period plasticity-actively limit adult plasticity and have proved fruitful therapeutic targets to reopen plasticity and rewire faulty visual system connections later in life. Interestingly, these molecular mechanisms have been implicated in the regulation of plasticity in other functions beyond vision. Applying mechanistic understandings of critical period plasticity in the visual cortex to fear circuitry may provide a conceptual framework for developing novel therapeutic tools to mitigate aberrant fear responses in post traumatic stress disorder. In this review, we turn to the model of experience-dependent visual plasticity to provide novel insights for the mechanisms regulating plasticity in the fear system. Fear circuitry, particularly fear memory erasure, also undergoes age-related changes in experience-dependent plasticity. We consider the contributions of molecular brakes that halt visual critical period plasticity to circuitry underlying fear memory erasure. A major molecular brake in the visual cortex, perineuronal net formation, recently has been identified in the development of fear systems that are resilient to fear memory erasure. The roles of other molecular brakes, myelin-related Nogo receptor signaling and Lynx family proteins - endogenous inhibitors for nicotinic acetylcholine receptor, are explored in the context of fear memory plasticity. Such fear plasticity regulators, including epigenetic effects, provide promising targets for therapeutic interventions. PMID:24273519

Nabel, Elisa M; Morishita, Hirofumi

2013-01-01

446

Electrospun nanofiber membranes for electrically activated shape memory nanocomposites  

NASA Astrophysics Data System (ADS)

A novel shape memory nanocomposite system, consisting of a thermoplastic Nafion polymer and ultrathin electrospun polyacrylonitrile (PAN)-based carbonization nanofiber membranes, is successfully synthesized. PAN-based carbonization nanofiber networks that offer responses to deformations are considered to be an excellent actuation source. Significant improvement in the electrical conductivity of carbon nanofiber membranes is found by adjusting the applied voltage power in the electrospinning PAN process varying from 7.85 to 12.30 S cm-1. The porous structure of the carbon nanofiber membranes provides a large specific surface area and interfacial contact area when combined with the polymer matrix. Shape memory Nafion nanocomposites filled with interpenetrating non-woven electrospun PAN carbonization membranes can be actuated by applying 14 V electrical voltage within 5 s. The results, as demonstrated through morphology, electrical and thermal measurements and a shape recovery test, suggest a valuable route to producing soft nanocomposites.

Zhang, Fenghua; Zhang, Zhichun; Liu, Yanju; Leng, Jinsong

2014-06-01

447

A Review of Monte Carlo Simulations of Polymers with PERM  

NASA Astrophysics Data System (ADS)

In this review, we describe applications of the pruned-enriched Rosenbluth method (PERM), a sequential Monte Carlo algorithm with resampling, to various problems in polymer physics. PERM produces samples according to any given prescribed weight distribution, by growing configurations step by step with controlled bias, and correcting "bad" configurations by "population control". The latter is implemented, in contrast to other population based algorithms like e.g. genetic algorithms, by depth-first recursion which avoids storing all members of the population at the same time in computer memory. The problems we discuss all concern single polymers (with one exception), but under various conditions: Homo