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1

Shape memory polymer therapeutic devices for stroke  

NASA Astrophysics Data System (ADS)

Shape memory polymers (SMPs) are attracting a great deal of interest in the scientific community for their use in applications ranging from light weight structures in space to micro-actuators in MEMS devices. These relatively new materials can be formed into a primary shape, reformed into a stable secondary shape, and then controllably actuated to recover their primary shape. The first part of this presentation will be a brief review of the types of polymeric structures which give rise to shape memory behavior in the context of new shape memory polymers with highly regular network structures recently developed at LLNL for biomedical devices. These new urethane SMPs have improved optical and physical properties relative to commercial SMPs, including improved clarity, high actuation force, and sharper actuation transition. In the second part of the presentation we discuss the development of SMP based devices for mechanically removing neurovascular occlusions which result in ischemic stroke. These devices are delivered to the site of the occlusion in compressed form, are pushed through the occlusion, actuated (usually optically) to take on an expanded conformation, and then used to dislodge and grip the thrombus while it is withdrawn through the catheter.

Wilson, Thomas S.; Small, Ward, IV; Benett, William J.; Bearinger, Jane P.; Maitland, Duncan J.

2005-11-01

2

Shape-Memory Polymers  

Microsoft Academic Search

Material scientists predict a prominent role in the future for self-repairing and intelligent materials. Throughout the last few years, this concept has found growing interest as a result of the rise of a new class of polymers. These so- called shape-memory polymers by far surpass well-known metallic shape- memory alloys in their shape-memory properties. As a consequence of the relatively

Andreas Lendlein; Steffen Kelch

2002-01-01

3

Bioactive and Therapeutic ROMP Polymers  

Microsoft Academic Search

This review summarizes the developments in the area of ROMP?based polymer carriers as well as side?chain and main?chain polymer therapeutics during the period of 1993–2007. The promising emergence of ROMP?derived amphiphilic block copolymers containing therapeutic agents, their assembly into polymer nanoparticles, together with their modification for the targeting group attachment is outlined. Recent application of ROMP?based side?chain polymer therapeutics as

DeeDee Smith; Emily B. Pentzer; SonBinh T. Nguyen

2007-01-01

4

Shape memory polymer medical device  

DOEpatents

A system for removing matter from a conduit. The system includes the steps of passing a transport vehicle and a shape memory polymer material through the conduit, transmitting energy to the shape memory polymer material for moving the shape memory polymer material from a first shape to a second and different shape, and withdrawing the transport vehicle and the shape memory polymer material through the conduit carrying the matter.

Maitland, Duncan (Pleasant Hill, CA) [Pleasant Hill, CA; Benett, William J. (Livermore, CA) [Livermore, CA; Bearinger, Jane P. (Livermore, CA) [Livermore, CA; Wilson, Thomas S. (San Leandro, CA) [San Leandro, CA; Small, IV, Ward (Livermore, CA); Schumann, Daniel L. (Concord, CA) [Concord, CA; Jensen, Wayne A. (Livermore, CA) [Livermore, CA; Ortega, Jason M. (Pacifica, CA) [Pacifica, CA; Marion, III, John E. (Livermore, CA); Loge, Jeffrey M. (Stockton, CA) [Stockton, CA

2010-06-29

5

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.

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

2013-01-01

6

TARGETING POLYMER THERAPEUTICS TO BONE  

PubMed Central

An aging population in the developing world has led to an increase in musculoskeletal diseases such as osteoporosis and bone metastases. Left untreated many bone diseases cause debilitating pain and in the case of cancer, death. Many potential drugs are effective in treating diseases but result in side effects preventing their efficacy in the clinic. Bone, however, provides an unique environment of inorganic solids, which can be exploited in order to effectively target drugs to diseased tissue. By integration of bone targeting moieties to drug-carrying water-soluble polymers, the payload to diseased area can be increased while side effects decreased. The realization of clinically relevant bone targeted polymer therapeutics depends on (1) understanding bone targeting moiety interactions, (2) development of controlled drug delivery systems, as well as (3) understanding drug interactions. The latter makes it possible to develop bone targeted synergistic drug delivery systems.

Low, Stewart; Kopecek, Jindrich

2012-01-01

7

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.

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

2013-01-01

8

Temperature-memory polymer actuators.  

PubMed

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 (?T(m)) 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 T(act)s 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 T(sep) in a nearly linear correlation. The temperature T(sep) divides ?T(m) into an upper T(m) range (T > T(sep)) forming a reshapeable actuation geometry that determines the skeleton and a lower T(m) range (T < T(sep)) 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

2013-07-30

9

Shape memory polymer networks from styrene copolymer  

Microsoft Academic Search

This paper is concerned about the synthesis of shape memory styrene copolymer and the investigation of the influence of cross-linking degree on its shape memory effect. As one of novel actuators in smart materials, shape memory polymers (SMPs) have been investigated intensively. Styrene copolymer with proper cross-linking degree can exhibit shape memory effect (SME). In this paper, the influence of

Dawei Zhang; Xiaoguang Wang; Wuyi Zhang; Yanju Liu; Jinsong Leng

2007-01-01

10

Thermomechanics of shape memory polymer nanocomposites  

Microsoft Academic Search

Shape memory polymers (SMPs) have the capacity to recover large strains when pre-deformed at an elevated temperature, cooled to a lower temperature, and reheated. The thermomechanical behavior of SMPs can be tailored by modifying the molecular structure of the polymer, or by using the polymer as a matrix for multiphase composites. Here we study the thermomechanics of a SMP polymer

Yiping Liu; Ken Gall; Martin L Dunn; Patrick McCluskey

2004-01-01

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. (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

12

Characterization Methods for Shape-Memory Polymers  

Microsoft Academic Search

\\u000a Shape-memory polymers (SMPs) are able to fix a temporary deformed shape and recover their original permanent shape upon application\\u000a of an external stimulus such as heat or light. A shape-memory functionalization can be realized for polymer based materials\\u000a with an appropriate morphology by application of a specific shape-memory creation procedure (SMCP). Specific characterization\\u000a methods have been tailored to explore the

Wolfgang Wagermaier; Karl Kratz; Matthias Heuchel; Andreas Lendlein

2010-01-01

13

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

14

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

15

Nanoindentation of shape memory polymer networks  

Microsoft Academic Search

This work examines the small-scale deformation and thermally induced recovery behavior of shape memory polymer networks as a function of crosslinking structure. Copolymer shape memory materials based on diethylene glycol dimethacrylate and polyethylene glycol dimethacrylate with a molecular weight of 550 crosslinkers and a tert-butyl acrylate linear chain monomer were synthesized with varying weight percentages of crosslinker from 0 to

Edem Wornyo; Ken Gall; Fuzheng Yang; William King

2007-01-01

16

Constitutive modeling of glassy shape memory polymers  

NASA Astrophysics Data System (ADS)

The aim of this research is to develop constitutive models for non-linear materials. Here, issues related for developing constitutive model for glassy shape memory polymers are addressed in detail. Shape memory polymers are novel material that can be easily formed into complex shapes, retaining memory of their original shape even after undergoing large deformations. The temporary shape is stable and return to the original shape is triggered by a suitable mechanism such heating the polymer above a transition temperature. Glassy shape memory polymers are called glassy because the temporary shape is fixed by the formation of a glassy solid, while return to the original shape is due to the melting of this glassy phase. The constitutive model has been developed to capture the thermo-mechanical behavior of glassy shape memory polymers using elements of nonlinear mechanics and polymer physics. The key feature of this framework is that a body can exist stress free in numerous natural configurations, the underlying natural configuration of the body changing during the process, with the response of the body being elastic from these evolving natural configurations. The aim of this research is to formulate a constitutive model for glassy shape memory polymers (GSMP) which takes in to account the fact that the stress-strain response depends on thermal expansion of polymers. The model developed is for the original amorphous phase, the temporary glassy phase and transition between these phases. The glass transition process has been modeled using a framework that was developed recently for studying crystallization in polymers and is based on the theory of multiple natural configurations. Using the same frame work, the melting of the glassy phase to capture the return of the polymer to its original shape is also modeled. The effect of nanoreinforcement on the response of shape memory polymers (GSMP) is studied and a model is developed. In addition to modeling and solving boundary value problems for GSMP's, problems of importance for CSMP, specifically a shape memory cycle (Torsion of a Cylinder) is solved using the developed crystallizable shape memory polymer model. To solve complex boundary value problems in realistic geometries a user material subroutine (UMAT) for GSMP model has been developed for use in conjunction with the commercial finite element software ABAQUS. The accuracy of the UMAT has been verified by testing it against problems for which the results are known.

Khanolkar, Mahesh

17

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

18

Guide wire extension for shape memory polymer occlusion removal devices  

DOEpatents

A flexible extension for a shape memory polymer occlusion removal device. A shape memory polymer instrument is transported through a vessel via a catheter. A flexible elongated unit is operatively connected to the distal end of the shape memory polymer instrument to enhance maneuverability through tortuous paths en route to the occlusion.

Maitland, Duncan J. (Pleasant Hill, CA); Small, IV, Ward (Livermore, CA); Hartman, Jonathan (Sacramento, CA)

2009-11-03

19

Shape memory polymer networks from styrene copolymer  

NASA Astrophysics Data System (ADS)

This paper is concerned about the synthesis of shape memory styrene copolymer and the investigation of the influence of cross-linking degree on its shape memory effect. As one of novel actuators in smart materials, shape memory polymers (SMPs) have been investigated intensively. Styrene copolymer with proper cross-linking degree can exhibit shape memory effect (SME). In this paper, the influence of cross-linking degree on shape memory effect of styrene copolymer was investigated through altering the dosage of cross-linking agent. The cross-linking degree of styrene copolymer was determined by measuring the gel content. The glass transition temperature (T g) of styrene copolymer, which is determined the cross-linking degree, was measured by Dynamic Mechanical Analysis (DMA). The shape memory performance of styrene copolymer with different cross-linking degrees was also evaluated. Results indicated that the shape memory polymer (SMP) was synthesized successfully. The T g increased from 35°C to 55°C followed by increasing the gel content from 0% to 35% through increasing the dosage of cross-linking agent from 0% to 1%. Moreover, the SMP experienced good SME and the largest reversible strain of the SMP reached as high as 150%. When heating above T g+30°C (different copolymers performed different T g), the shape recovery speed of the copolymers increased with increasing the gel content. However, the recovery speed decreased with increasing the gel content at the same temperature of 80°C.

Zhang, Dawei; Wang, Xiaoguang; Zhang, Wuyi; Liu, Yanju; Leng, Jinsong

2007-10-01

20

Temperature and electrical memory of polymer fibers  

NASA Astrophysics Data System (ADS)

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

2014-05-01

21

Polymer memory device based on conjugated polymer and gold nanoparticles  

Microsoft Academic Search

Electrical bistability is demonstrated in a polymer memory device with an active layer consisting of conjugated poly(3-hexylthiophene) and gold nanoparticles capped with 1-dodecanethiol sandwiched between two metal electrodes. The device was fabricated through a simple solution processing technique and exhibited a remarkable electrical bistable behavior. Above a threshold voltage the pristine device, which was in a low conductivity state, exhibited

Ankita Prakash; Jianyong Ouyang; Jen-Lien Lin; Yang Yang

2006-01-01

22

Laser-activated shape memory polymer intravascular thrombectomy device  

NASA Astrophysics Data System (ADS)

A blood clot (thrombus) that becomes lodged in the arterial network supplying the brain can cause an ischemic stroke, depriving the brain of oxygen and often resulting in permanent disability. As an alternative to conventional clot-dissolving drug treatment, we are developing an intravascular laser-activated therapeutic device using shape memory polymer (SMP) to mechanically retrieve the thrombus and restore blood flow to the brain. Thermal imaging and computer simulation were used to characterize the optical and photothermal behavior of the SMP microactuator. Deployment of the SMP device in an in vitro thrombotic vascular occlusion model demonstrated the clinical treatment concept.

Small, Ward, IV; Wilson, Thomas S.; Benett, William J.; Loge, Jeffrey M.; Maitland, Duncan J.

2005-10-01

23

Single polymer-based ternary electronic memory material and device.  

PubMed

A ternary polymer memory device based on a single polymer with on-chain Ir(III) complexes is fabricated by combining multiple memory mechanisms into one system. Excellent ternary memory performances-low reading, writing, and erasing voltages and good stability for all three states-are achieved. PMID:22539455

Liu, Shu-Juan; Wang, Peng; Zhao, Qiang; Yang, Hui-Ying; Wong, Jenlt; Sun, Hui-Bin; Dong, Xiao-Chen; Lin, Wen-Peng; Huang, Wei

2012-06-01

24

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

25

Polymer-based resistive memory materials and devices.  

PubMed

Due to the advantages of good scalability, flexibility, low cost, ease of processing, 3D-stacking capability, and large capacity for data storage, polymer-based resistive memories have been a promising alternative or supplementary devices to conventional inorganic semiconductor-based memory technology, and attracted significant scientific interest as a new and promising research field. In this review, we first introduced the general characteristics of the device structures and fabrication, memory effects, switching mechanisms, and effects of electrodes on memory properties associated with polymer-based resistive memory devices. Subsequently, the research progress concerning the use of single polymers or polymer composites as active materials for resistive memory devices has been summarized and discussed. In particular, we consider a rational approach to their design and discuss how to realize the excellent memory devices and understand the memory mechanisms. Finally, the current challenges and several possible future research directions in this field have also been discussed. PMID:24339246

Lin, Wen-Peng; Liu, Shu-Juan; Gong, Tao; Zhao, Qiang; Huang, Wei

2014-01-01

26

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

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

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

29

Aging effects of epoxy shape memory polymers  

NASA Astrophysics Data System (ADS)

In this paper, experimental results are reported to study the influence of high-temperature aging on the thermo-mechanical behavior of a commercially-available, thermo-responsive shape memory polymer (SMP), Veri ex-E™ (glass transition temperature, Tg = 90-105 °C). To achieve a shape memory effect in high Tg SMPs such as this, high temperature cycles are required that can result in macromolecular scission and/or crosslinking, which we term thermo-mechanical aging (or chemo-rheological degradation). This process results in mechanical property changes and possible permanent set of the material that can limit the useful life of SMPs in practice. We compare experimental results of shape memory recovery with and without aging. Similar to the approach originated by Tobolsky in the 1950's, a combination of uniaxial constant stress and intermittent stretch experiments are also used in high temperature creep-recovery experiments to deduce the kinetics of scission of the original macromolecular network and the generation of newly formed networks having different reference configurations. The macroscopic effects of thermo-mechanical aging, in terms of the evolution of residual strains and change in elastic response, are quantified.

Dasharathi, Kannan; Shaw, John A.

2013-04-01

30

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

31

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.

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

2010-01-01

32

Fabrication and characterization of shape memory polymers at small-scales  

Microsoft Academic Search

The objective of this research is to thoroughly investigate the shape memory effect in polymers, characterize, and optimize these polymers for applications in information storage systems. Previous research effort in this field concentrated on shape memory metals for biomedical applications such as stents. Minimal work has been done on shape memory polymers; and the available work on shape memory polymers

Edem Wornyo

2008-01-01

33

A novel type of shape memory polymer blend and the shape memory mechanism  

Microsoft Academic Search

A novel styrene–butadiene–styrene tri-block copolymer (SBS) and poly(?-caprolactone) (PCL) blend were introduced for its shape memory properties. Compared to the reported shape memory polymers (SMPs), this novel elastomer and switch polymer blend not only simplified the fabrication process but also offer a controllable approach for the study of mechanisms and the optimization of shape memory performances. Microstructures of this blend

Heng Zhang; Haitao Wang; Wei Zhong; Qiangguo Du

2009-01-01

34

Shape memory polymers for active cell culture.  

PubMed

Shape memory polymers (SMPs) are a class of "smart" materials that have the ability to change from a fixed, temporary shape to a pre-determined permanent shape upon the application of a stimulus such as heat(1-5). In a typical shape memory cycle, the SMP is first deformed at an elevated temperature that is higher than its transition temperature, T(trans;) [either the melting temperature (T(m;)) or the glass transition temperature (T(g;))]. The deformation is elastic in nature and mainly leads to a reduction in conformational entropy of the constituent network chains (following the rubber elasticity theory). The deformed SMP is then cooled to a temperature below its T(trans;) while maintaining the external strain or stress constant. During cooling, the material transitions to a more rigid state (semi-crystalline or glassy), which kinetically traps or "freezes" the material in this low-entropy state leading to macroscopic shape fixing. Shape recovery is triggered by continuously heating the material through T(trans;) under a stress-free (unconstrained) condition. By allowing the network chains (with regained mobility) to relax to their thermodynamically favored, maximal-entropy state, the material changes from the temporary shape to the permanent shape. Cells are capable of surveying the mechanical properties of their surrounding environment(6). The mechanisms through which mechanical interactions between cells and their physical environment control cell behavior are areas of active research. Substrates of defined topography have emerged as powerful tools in the investigation of these mechanisms. Mesoscale, microscale, and nanoscale patterns of substrate topography have been shown to direct cell alignment, cell adhesion, and cell traction forces(7-14). These findings have underscored the potential for substrate topography to control and assay the mechanical interactions between cells and their physical environment during cell culture, but the substrates used to date have generally been passive and could not be programmed to change significantly during culture. This physical stasis has limited the potential of topographic substrates to control cells in culture. Here, active cell culture (ACC) SMP substrates are introduced that employ surface shape memory to provide programmed control of substrate topography and deformation. These substrates demonstrate the ability to transition from a temporary grooved topography to a second, nearly flat memorized topography. This change in topography can be used to control cell behavior under standard cell culture conditions. PMID:21750496

Davis, Kevin A; Luo, Xiaofan; Mather, Patrick T; Henderson, James H

2011-01-01

35

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.

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

2013-01-01

36

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

37

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

38

Shape memory properties of ionic polymer-metal composites  

NASA Astrophysics Data System (ADS)

The shape memory properties of hydrated Nafion ionic polymer-metal composite (IPMC) actuators under combined thermal cycling and electrical shape fixing are presented and experimentally demonstrated. By exploiting these new properties the utility of such ionic actuators can be greatly enhanced to include bistability, multi-modal operation and increased actuation range. Shape memory effects were shown when the IPMC was deformed during programming by either an external force or by voltage-induced actuation. Comparison is made to the shape memory effects in hydrated raw Nafion membrane. It was observed that shape memory effects undergo slow decay, with different programming methods and subsequent electrical excitation exhibiting different decay profiles.

Rossiter, Jonathan; Takashima, Kazuto; Mukai, Toshiharu

2012-11-01

39

Recent Development in Polymer Ferroelectric Field Effect Transistor Memory  

Microsoft Academic Search

The article presents the recent research development in polymer ferroelectric non-volatile memory. A brief overview is given of the history of ferroelectric memory and device architectures based on inorganic ferroelectric materials. Particular emphasis is made on device elements such as metal\\/ferroelectric\\/metal type capacitor, metal- ferroelectric-insulator-semiconductor (MFIS) and ferroelectric field effect transistor (FeFET) with ferroelectric poly(vinylidene fluoride) (PVDF) and its copolymers

Youn Jung Park; Hee June Jeong; Jiyoun Chang; Seok Ju Kang

2008-01-01

40

Recent advances in shape memory polymers and composites: a review  

Microsoft Academic Search

Shape memory polymers (SMPs) belong to a class of smart polymers, which have drawn considerable research interest in last\\u000a few years because of their applications in microelectromechanical systems, actuators, for self healing and health monitoring\\u000a purposes, and in biomedical devices. Like in other fields of applications, SMP materials have been proved to be suitable substitutes\\u000a to metallic ones because of

Debdatta Ratna; J. Karger-Kocsis

2008-01-01

41

Thermomechanical Constitutive Modeling in Shape Memory Polymer of Polyurethane Series  

Microsoft Academic Search

In order to describe the thermomechanical properties in shape memory polymer of polyurethane series, a thermomechanical constitutive model was developed by modifying a standard linear viscoelastic model. The model involved a slip element due to internal friction and took account of thermal expansion. In order to describe the variation in mechanical properties due to the glass transition, coefficients in the

H. Tobushi; T. Hashimoto; S. Hayashi; E. Yamada

1997-01-01

42

Biodegradable, Elastic Shape-Memory Polymers for Potential Biomedical Applications  

Microsoft Academic Search

The introduction of biodegradable implant materials as well as minimally invasive surgical procedures in medicine has substantially improved health care within the past few decades. This report describes a group of degradable thermoplastic polymers that are able to change their shape after an increase in temperature. Their shape-memory capability enables bulky implants to be placed in the body through small

Andreas Lendlein; Robert Langer

2002-01-01

43

Reversible bidirectional shape-memory polymers.  

PubMed

Free-standing copolymer network samples with two types of crystallizable domains are capable of a fully reversible bidirectional shape-memory effect. One set of crystallizable domains determines the shape-shifting geometry while the other provides the thermally controlled actuation capability. PMID:23765645

Behl, Marc; Kratz, Karl; Zotzmann, Jörg; Nöchel, Ulrich; Lendlein, Andreas

2013-08-27

44

Environmental Memory of Polymer Networks under Stress.  

PubMed

Generally reversible stimuli-responsive materials do not memorize the stimulus. In this study we describe an example in which stretched and constrained semi-crystalline polymer networks respond to solvent gases with stress and simultaneously memorize the concentration and the chemical nature of the solvent itself in their microstructure. This written solvent signature can even be deleted by temperature. PMID:24633757

Quitmann, Dominik; Gushterov, Nikola; Sadowski, Gabriele; Katzenberg, Frank; Tiller, Joerg C

2014-06-01

45

Infrared laser-activated shape memory polymer  

Microsoft Academic Search

This paper is concerned about the drive of shape memory styrene copolymer through an infrared optical fiber carrying infrared laser. The infrared laser was chosen to drive the SMP through the optical fiber embedded into the SMP. The working frequency of infrared laser was installed in 3-4mum, the working band of optical fiber was 1-6mum. An optical fiber was embedded

Dawei Zhang; Yanju Liu; Jinsong Leng

2008-01-01

46

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.

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

2011-01-01

47

Characterization and recovery of shape memory polymers filled with carbon nanofibers  

Microsoft Academic Search

The microstructure and shape memory properties of polymers utilizing two different shape memory processes reinforced with vapor grown carbon nanofibers (CNFs) were investigated by thermal and thermomechanical techniques. The first shape memory polymer (SMP) was a thermoplastic polyurethane elastomer (Irogran) that used strain-induced crystallization for locking in the deformation. Shape recovery occurred through the melting temperature of the crystallites and

Daniel Stephen Powers

2008-01-01

48

Strong, Tailored, Biocompatible Shape-Memory Polymer Networks**  

PubMed Central

Shape-memory polymers are a class of smart materials that have recently been used in intelligent biomedical devices and industrial applications for their ability to change shape under a predetermined stimulus. In this study, photopolymerized thermoset shape-memory networks with tailored thermomechanics are evaluated to link polymer structure to recovery behavior. Methyl methacrylate (MMA) and poly(ethylene glycol) dimethacrylate (PEGDMA) are copolymerized to create networks with independently adjusted glass transition temperatures (Tg) and rubbery modulus values ranging from 56 to 92 °C and 9.3 to 23.0 MPa, respectively. Free-strain recovery under isothermal and transient temperature conditions is highly influenced by the Tg of the networks, while the rubbery moduli of the networks has a negligible effect on this response. The magnitude of stress generation of fixed-strain recovery correlates with network rubbery moduli, while fixed-strain recovery under isothermal conditions shows a complex evolution for varying Tg. The results are intended to help aid in future shape-memory device design and the MMA-co-PEGDMA network is presented as a possible high strength shape-memory biomaterial.

Shandas, Robin; Safranski, David; Ortega, Alicia M.; Sassaman, Katie; Gall, Ken

2009-01-01

49

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

50

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

51

Shape memory polymer sensors for tracking cumulative environmental exposure  

NASA Astrophysics Data System (ADS)

Cornerstone Research Group Inc. (CRG) has developed environmental exposure tracking (EET) sensors using shape memory polymers (SMP) to monitor the degradation of perishable items, such as munitions, foods and beverages, or medicines, by measuring the cumulative exposure to temperature and moisture. SMPs are polymers whose qualities have been altered to give them dynamic shape "memory" properties. Under thermal or moisture stimuli, the SMP exhibits a radical change from a rigid thermoset to a highly flexible, elastomeric state. The dynamic response of the SMP can be tailored to match the degradation profile of the perishable item. SMP-based EET sensors require no digital memory or internal power supply and provide the capability of inexpensive, long-term life cycle monitoring of thermal and moisture exposure over time. This technology was developed through Phase I and Phase II SBIR efforts with the Navy. The emphasis of current research centers on transitioning SMP materials from the lab bench to a production environment. Here, CRG presents the commercialization progress of thermally-activated EET sensors, focusing on fabrication scale-up, process refinements, and quality control. In addition, progress on the development of vapor pressure-responsive SMP (VPR-SMP) will be discussed.

Snyder, Ryan; Rauscher, Michael; Vining, Ben; Havens, Ernie; Havens, Teresa; McFerran, Jace

2010-03-01

52

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

53

Polymer-ultrathin graphite sheet-polymer composite structured flexible nonvolatile bistable organic memory devices  

NASA Astrophysics Data System (ADS)

We present data, which were obtained before bending and after bending, for the electrical bistabilities, memory stabilities, and memory mechanisms of three-layer structured flexible bistable organic memory (BOM) devices, which were fabricated utilizing the ultrathin graphite sheets (UGS) sandwiched between insulating poly(methylmethacrylate) (PMMA) polymer layers. The UGS were formed by transferring UGS (about 30 layers) and using a simple spin-coating technique. Transmission electron microscopy (TEM) measurements were performed to investigate the microstructural properties of the PMMA/UGS/PMMA films. Current-voltage (I-V) measurements were carried out to investigate the electrical properties of the BOM devices containing the UGS embedded in the PMMA polymer. Current-time (I-t) and current-cycle measurements under flat and bent conditions were performed to investigate the memory stabilities of the BOM devices. The memory characteristics of the BOM maintained similar device efficiencies after bending and were stable during repeated bendings of the BOM devices. The mechanisms for these characteristics of the fabricated BOM are described on the basis of the I-V results.

Ick Son, Dong; Shim, Jae Ho; Park, Dong Hee; Jung, Jae Hun; Lee, Jung Min; Park, Won Il; Kim, Tae Whan; Choi, Won Kook

2011-07-01

54

Reduced time as a unified parameter determining fixity and free recovery of shape memory polymers  

NASA Astrophysics Data System (ADS)

Shape memory polymers are at the forefront of recent materials research. Although the basic concept has been known for decades, recent advances in the research of shape memory polymers demand a unified approach to predict the shape memory performance under different thermo-temporal conditions. Here we report such an approach to predict the shape fixity and free recovery of thermo-rheologically simple shape memory polymers. The results show that the influence of programming conditions to free recovery can be unified by a reduced programming time that uniquely determines shape fixity, which consequently uniquely determines the shape recovery with a reduced recovery time. Furthermore, using the time-temperature superposition principle, shape recoveries under different thermo-temporal conditions can be extracted from the shape recovery under the reduced recovery time. Finally, a shape memory performance map is constructed based on a few simple standard polymer rheology tests to characterize the shape memory performance of the polymer.

Yu, Kai; Ge, Qi; Qi, H. Jerry

2014-01-01

55

Investigation of mechanical behavior of epoxy shape memory polymers  

NASA Astrophysics Data System (ADS)

Shape memory polymer (SMP) is a new class of smart material which attracts great interest in recent years. In this paper, in addition to the synthesizing of three types of epoxy SMPs with various linear epoxy monomer contents, their mechanical properties are focused on. Structure characteristic, dynamic mechanical property and quasi-static tension property and shape memory behavior of the epoxy SMPs are presented. Results indicate that glass transition temperature determined by dynamic mechanical analysis (loss modulus) varies from 69 to 113 °C for the epoxy SMPs. And it should be noted that the linear monomer has no effect on storage modulus in glass state but decrease the storage modulus in rubber state for the polymers. From tensile test, it is found that the content of linear monomer has significant effect on the tensile deformation behavior which varies from a brittle response to elastomeric response at room temperature. And the strength varies from 15 to 62MPa with the corresponding elastic modulus ranging from 2.5 to 1.7GPa for the epoxy system. Characterization of the shape memory effect in epoxy SMP suggests a high (above 99%) shape recovery ratio at 100 °C, besides, the epoxy SMP with higher linear monomer content shows a quicker shape recovery speed. Moreover, effect of linear monomer content on glass transition temperature and thermo-mechanical property is also investigated. Results indicate that, epoxy SMP fabricated in this study possess not only unique shape memory effect but also excellent mechanical properties, which will be the leading candidate for applications in engineering fields.

Wu, Xuelian; Liu, Yanju; Leng, Jinsong

2009-03-01

56

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.

57

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

58

Post-Polymerization Crosslinked Polyurethane Shape-Memory Polymers  

PubMed Central

Novel urethane shape-memory polymers (SMPs) of significant industrial relevance have been synthesized and characterized. Chemically crosslinked SMPs have traditionally been made in a one-step polymerization of monomers and crosslinking agents. However, these new post-polymerization crosslinked SMPs can be processed into complex shapes by thermoplastic manufacturing methods and later crosslinked by heat exposure or by electron beam irradiation. Several series of linear, olefinic urethane polymers were made from 2-butene-1,4-diol, other saturated diols, and various aliphatic diisocyanates. These thermoplastics were melt-processed into desired geometries and thermally crosslinked at 200°C or radiation crosslinked at 50 kGy. The SMPs were characterized by solvent swelling and extraction, differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), tensile testing, and qualitative shape-recovery analysis. Swelling and DMA results provided concrete evidence of chemical crosslinking, and further characterization revealed that the urethanes had outstanding mechanical properties. Key properties include tailorable transitions between 25 and 80°C, tailorable rubbery moduli between 0.2 and 4.2 MPa, recoverable strains approaching 100%, failure strains of over 500% at Tg, and qualitative shape-recovery times of less than 12 seconds at body temperature (37°C). Because of its outstanding thermo-mechanical properties, one polyurethane was selected for implementation in the design of a complex medical device. These post-polymerization crosslinked urethane SMPs are an industrially relevant class of highly processable shape-memory materials.

Hearon, K.; Gall, K.; Ware, T.; Maitland, D. J.; Bearinger, J. P.; Wilson, T. S.

2011-01-01

59

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

60

Finite deformation thermo-mechanical behavior of thermally induced shape memory polymers  

Microsoft Academic Search

Shape memory polymers (SMPs) are polymers that can demonstrate programmable shape memory effects. Typically, an SMP is pre-deformed from an initial shape to a deformed shape by applying a mechanical load at the temperature TH>Tg. It will maintain this deformed shape after subsequently lowering the temperature to TLmemory effect is activated

H. Jerry Qi; Thao D. Nguyen; Francisco Castro; Christopher M. Yakacki; Robin Shandas

2008-01-01

61

Polymer therapeutics-prospects for 21st century: the end of the beginning.  

PubMed

The term "polymer therapeutics" was coined to describe polymeric drugs, polymer conjugates of proteins, drugs and aptamers, together with those block copolymer micelles and multicomponent non-viral vectors which contain covalent linkages. These often complex, multicomponent constructs are actually "drugs" and "macromolecular prodrugs" in contrast to drug delivery systems that simply entrap (non-covalently) therapeutic agents. They have also been described as nanomedicines. First polymer-protein conjugates entered routine clinical use in 1990 and a growing number of polymeric drugs/sequestrants and PEGylated proteins/aptamers have since come into the market. Valuable lessons have been learnt over >3 decades of clinical development, especially in relation to critical product attributes governing safety and efficacy, the validated methods needed for product characterisation. Not least there has been improved understanding of polymer therapeutic-specific biomarkers that will in future enable improved selection of patients for therapy. Advances in synthetic polymer chemistry (including control of 3D architecture), the move towards greater use of biodegradable polymers, polymers delivering combination therapy, increased understanding of polymer therapeutic critical product attributes to guide pharmaceutical development, and advances in understanding of endocytosis and intracellular trafficking pathways in health and disease are opening new opportunities for design and clinical use of polymer-based therapeutics in the decades to come. PMID:22981753

Duncan, Ruth; Vicent, María J

2013-01-01

62

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

63

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

64

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

65

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

66

Polymers with dual light-triggered functions of shape memory and healing using gold nanoparticles.  

PubMed

Shape-memory and stimuli-healable polymers (SMP and SHP) are two types of emerging smart materials. Among the many stimuli that can be used to control SMP and SHP, light is unique because of its unparalleled remote activation and spatial control. Generally, light-triggered shape memory and optically healable polymers are different polymers and it is challenging to endow the same polymer with the two light-triggered functions because of their structural incompatibility. In this paper, we describe a general polymer design that allows a single material to exhibit both light-controlled shape memory and optical healing capabilities. We show that by chemically cross-linking a crystalline polymer and loading it with a small amount of gold nanoparticles (AuNPs), the polymer displays optically controllable shape memory and fast optical healing based on the same localized heating effect arising from the surface plasmon resonance of AuNPs. The photothermal effect controls, on the one hand, the shape memory process by tuning the temperature with respect to Tm of the crystalline phase and, on the other hand, activates the damage healing through crystal melting and recrystallization. Moreover, we show that these two features can be triggered separately in a sequential manner. PMID:24308556

Zhang, Hongji; Zhao, Yue

2013-12-26

67

Active repair of self-healing polymers with shape memory alloy wires  

Microsoft Academic Search

We report the first measurements of self-healing polymers with embedded shape memory alloy (SMA) wires. Improvements of healed peak loads by up to a factor of two are observed, approaching the performance of the virgin material. Moreover, the repairs can be effected with reduced amounts of healing agent. The improvements in performance of self-healing polymers with SMA wires are due

Eva L. Kirkby; Joseph D. Rule; Véronique J. Michaud; Nancy R. Sottos; Scott R. White; Jan-Anders E. Månson

2007-01-01

68

Experimental Evaluation of the Rheological Properties of Veriflex Shape Memory Polymer  

Microsoft Academic Search

Shape memory polymers (SMPs) are materials with a great potential for future use in smart materials and structures. When heated from cold state (below the transformation temperature, which can either be the glass transition temperature or the melting temperature of the polymer) to hot state (above the transformation temperature) they undergo transformation which can be compared with martensitic transformation of

Jan Klesa; Vincent Placet; Emmanuel Foltete; Manuel Collet

2009-01-01

69

Laser-activated shape memory polymer microactuators for treating stroke  

NASA Astrophysics Data System (ADS)

In this paper the photothermal engineering issues of novel shape memory polymer (SMP) microactuators for treating stroke are presented. The engineering issues for using lasers to heat and subsequently actuate these SMP devices are presented in order to provide design criteria and guidelines for intravascular, laser activated SMP devices. The optical properties of SMP, methods for coupling laser light into SMP, heating distributions in the SMP devices and the impact of operating the thermally activated material in a blood vessel are presented. A total of three devices will be presented: two interventional ischemic stroke devices and one device for releasing embolic coils. The optical properties of SMP, methods for coupling laser light into SMP, heating distributions in the SMP devices and the impact of operating the thermally activated material in a blood vessel are presented. Actuating the devices requires device temperatures in the range of 65 degrees C - 85 degrees C. Attaining these temperatures under flow conditions requires critical engineering of the SMP optical properties, optical coupling into the SMP, and device geometries. Laser- activated SMP devices are a unique combination of laser- tissue and biomaterial technologies. Successful deployment of the microactuator requires well-engineered coupling of the light form the diffusing fiber through the blood into the SMP.

Maitland, Duncan J.; Wilson, Thomas; Metzger, Melodie; Schumann, Daniel L.

2002-06-01

70

Virtual Treatment of Basilar Aneurysms Using Shape Memory Polymer Foam  

PubMed Central

Numerical simulations are performed on patient-specific basilar aneurysms that are treated with shape memory polymer (SMP) foam. In order to assess the post-treatment hemodynamics, two modeling approaches are employed. In the first, the foam geometry is obtained from a micro-CT scan and the pulsatile blood flow within the foam is simulated for both Newtonian and non-Newtonian viscosity models. In the second, the foam is represented as a porous media continuum, which has permeability properties that are determined by computing the pressure gradient through the foam geometry over a range of flow speeds comparable to those of in vivo conditions. Virtual angiography and additional post-processing demonstrate that the SMP foam significantly reduces the blood flow speed within the treated aneurysms, while eliminating the high-frequency velocity fluctuations that are present within the pre-treatment aneurysms. An estimation of the initial locations of thrombus formation throughout the SMP foam is obtained by means of a low fidelity thrombosis model that is based upon the residence time and shear rate of blood. The Newtonian viscosity model and the porous media model capture similar qualitative trends, though both yield a smaller volume of thrombus within the SMP foam.

Ortega, J.M.; Hartman, J.; Rodriguez, J.N.; Maitland, D.J.

2013-01-01

71

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

72

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

73

Fabrication and characterization of shape memory polymers at small-scales  

NASA Astrophysics Data System (ADS)

The objective of this research is to thoroughly investigate the shape memory effect in polymers, characterize, and optimize these polymers for applications in information storage systems. Previous research effort in this field concentrated on shape memory metals for biomedical applications such as stents. Minimal work has been done on shape memory polymers; and the available work on shape memory polymers has not characterized the behaviors of this category of polymers fully. Copolymer shape memory materials based on diethylene glycol dimethacrylate (DEGDMA) crosslinker, and tert butyl acrylate (tBA) monomer are designed. The design encompasses a careful control of the backbone chemistry of the materials. Characterization methods such as dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC); and novel nanoscale techniques such as atomic force microscopy (AFM), and nanoindentation are applied to this system of materials. Designed experiments are conducted on the materials to optimize spin coating conditions for thin films. Furthermore, the recovery, a key for the use of these polymeric materials for information storage, is examined in detail with respect to temperature. In sum, the overarching objectives of the proposed research are to: (i) Design shape memory polymers based on polyethylene glycol dimethacrylate (PEGDMA) and diethylene glycol dimethacrylate (DEGDMA) crosslinkers, 2-hydroxyethyl methacrylate (HEMA) and tert-butyl acrylate monomer (tBA). (ii) Utilize dynamic mechanical analysis (DMA) to comprehend the thermomechanical properties of shape memory polymers based on DEGDMA and tBA. (iii) Utilize nanoindentation and atomic force microscopy (AFM) to understand the nanoscale behavior of these SMPs, and explore the strain storage and recovery of the polymers from a deformed state. (iv) Study spin coating conditions on thin film quality with designed experiments. (iv) Apply neural networks and genetic algorithms to optimize these systems.

Wornyo, Edem

74

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

NASA Astrophysics Data System (ADS)

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 (TFX) and a biodegradable multiblock copolymer (PDC) with poly(p-dioxanone) as hard segment and poly(-caprolactone) as soft segment were investigated as matrix component. Nanoparticles consisting of an iron(III)oxide core in a silica matrix could be processed into both polymers. A homogeneous particle distribution in TFX could be shown. Compounds have suitable elastic and thermal properties for the shape-memory functionalization. Temporary shapes of TFX compounds were obtained by elongating at increased temperature and subsequent cooling under constant stress. Cold-drawing of PDC compounds at 25°C resulted in temporary fixation of the mechanical deformation by 50-60%. The shape-memory effect of both composite systems could be induced by inductive heating in an alternating magnetic field (f = 258 kHz; H = 30 kA·m-1). The maximum temperatures achievable by inductive heating in a specific magnetic field depend on sample geometry and nanoparticle content. Shape recovery rates of composites resulting from magnetic triggering are comparable to those obtained by increasing the environmental temperature. nanocomposite | shape-memory polymer | stimuli-sensitive polymer


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

2006-03-01

75

Constitutive modeling of shape memory polymer based self-healing syntactic foam  

Microsoft Academic Search

In a previous study, it was found that the shape memory functionality of a shape memory polymer based syntactic foam can be utilized to self-seal impact damage repeatedly, efficiently, and almost autonomously [Li G., John M., 2008. A self-healing smart syntactic foam under multiple impacts. Comp. Sci. Technol. 68(15–16), 3337–3343]. The purpose of this study is to develop a thermodynamics

We Xu; Guoqiang Li

2010-01-01

76

Magnetic memory effects in nickel ferrite/polymer nanocomposites  

NASA Astrophysics Data System (ADS)

Memory effects are reported in the field cooled (FC) magnetization of pure nickel ferrite powders and nickel ferrite nanocomposites prepared by the solution casting method. Studies carried out at different concentrations of the nanocomposite indicate that memory effects are suppressed with increasing concentration of the magnetic component in the nanocomposite. This is linked to the increase in the dipolar interaction strength in the nanocomposites, which increase with increasing concentration, as confirmed by the Henkel plots. Model simulations of the FC magnetization carried out on an interacting array of monodispersed magnetic nanoparticles indicate that growing cluster sizes inhibit memory effects.

Malik, Rakesh; Sehdev, Neeru; Lamba, Subhalakshmi; Sharma, Parmanand; Makino, Akihiro; Annapoorni, Subramanian

2014-03-01

77

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

78

Shape Fixity and Shape Recovery in a Film of Shape Memory Polymer of Polyurethane Series  

Microsoft Academic Search

The shape fixity and recovery in a film of shape memory polymer of polyurethane series were investigated by the thermomechanical cycling tests with loading at various temperatures. The results are summarized as follows: (1) Strain is recovered at temperatures in the vicinity of the glass transition temperature Tg for loading above Tg, but it is recovered at temperatures in the

H. Tobushi; T. Hashimoto; N. Ito; S. Hayashi; E. Yamada

1998-01-01

79

Shape Memory Polymer Based Self-Healing Sealant for Expansion Joint.  

National Technical Information Service (NTIS)

Failure of expansion joints is a leading cause of damage to bridge superstructures and concrete pavements. Failure of sealant material facilitates decay of the structure beneath it. The objective of this study is to develop a novel shape memory polymer (S...

G. Li

2012-01-01

80

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

Microsoft Academic Search

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

Haibao Lv; Jinsong Leng; Shanyi Du

2008-01-01

81

Active disassembly using shape memory polymers for the mobile phone industry  

Microsoft Academic Search

This paper reports results the application of shape memory polymer (SMP) technology to the active disassembly of modern mobile phones. The smart material SMP of polyurethane (PU) composition was employed. Two different types of SMP fasteners were created for these experiments. With these smart material devices, it is possible for products to disassemble themselves at specific triggering temperatures at EoL.

J. D. Chiodo; E. H. Billett; D. J. Harrison

1999-01-01

82

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

Microsoft Academic Search

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 of a safe and effective method of thermally actuating various device geometries in vivo. A novel scheme of actuation by Curie-thermoregulated inductive heating is presented. Prototype medical

Patrick R. Buckley; Gareth H. McKinley; Thomas S. Wilson; Ward Small; William J. Benett; Jane P. Bearinger; Michael W. McElfresh; Duncan J. Maitland

2006-01-01

83

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

Microsoft Academic Search

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

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

2006-01-01

84

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

Microsoft Academic Search

A deployable, shape memory polymer adapter is investigated for reducing the hemodynamic stress caused by dialysis needle flow impingement 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. Preliminary in vitro flow visualization measurements are made within a graft model

Jason M. Ortega; Ward Small; Thomas S. Wilson; William J. Benett; Jeffrey M. Loge; Duncan J. Maitland

2007-01-01

85

High performance shape memory polymer networks based on rigid nanoparticle cores  

PubMed Central

Smart materials that can respond to external stimuli are of widespread interest in biomedical science. Thermal-responsive shape memory polymers, a class of intelligent materials that can be fixed at a temporary shape below their transition temperature (Ttrans) and thermally triggered to resume their original shapes on demand, hold great potential as minimally invasive self-fitting tissue scaffolds or implants. The intrinsic mechanism for shape memory behavior of polymers is the freezing and activation of the long-range motion of polymer chain segments below and above Ttrans, respectively. Both Ttrans and the extent of polymer chain participation in effective elastic deformation and recovery are determined by the network composition and structure, which are also defining factors for their mechanical properties, degradability, and bioactivities. Such complexity has made it extremely challenging to achieve the ideal combination of a Ttrans slightly above physiological temperature, rapid and complete recovery, and suitable mechanical and biological properties for clinical applications. Here we report a shape memory polymer network constructed from a polyhedral oligomeric silsesquioxane nanoparticle core functionalized with eight polyester arms. The cross-linked networks comprising this macromer possessed a gigapascal-storage modulus at body temperature and a Ttrans between 42 and 48?°C. The materials could stably hold their temporary shapes for > 1 year at room temperature and achieve full shape recovery ? 51 °C in a matter of seconds. Their versatile structures allowed for tunable biodegradability and biofunctionalizability. These materials have tremendous promise for tissue engineering applications.

Song, Jie

2010-01-01

86

Shape Memory as a Process: Optimizing Polymer Design for Shape Recovery  

NASA Astrophysics Data System (ADS)

Shape memory is a process that enables the reversible storage and recovery of mechanical energy through a change in shape. Polymers provide a unique alternative to kinematic designs and other materials (e.g. metallic alloys) for applications requiring large deformation and novel control options. The effect control of storage and relaxation of strain energy associated with chain deformation depends on the nonlinear visco-elasitc behavior and glassy dynamics of the polymer network. Considering the molecular understanding of rubbery elasticity, chain entanglements in concentrated polymer liquids, affine deformation of networks, and glass fragility, heuristic guidelines can be formulated to optimize the molecular design of a polymer for shape memory. These are applied to the development of a polymer system for shape memory processes at high-temperature (200^oC). The low-crosslink density polyimide exhibits very rapid shape recovery, excellent fixity, high creep resistance, and good cyclability. Furthermore, the molecular design affords a very narrow temperature range for programming and triggering shape change that can also be accessed by photo-isomerization of the cross-link nodes.

Vaia, Richard; Koerner, Hilmar; Lee, Kyungmin; Strong, Robert; Smith, Mattew; Wang, Huabin; White, Tim; Tan, Loon-Seng

2012-02-01

87

A thermomechanical constitutive model for an epoxy based shape memory polymer and its parameter identifications  

NASA Astrophysics Data System (ADS)

This paper presents a three-dimensional (3D) finite deformation thermomechanical model to study the glass transition and shape memory behaviors of an epoxy based shape memory polymer (SMP) (Veriflex E) and a systematic material parameter identification scheme from a set of experiments. The model was described by viscoelastic elements placed in parallel to represent different active relaxation mechanisms around glass transition temperature in the polymer. A set of standard material tests was proposed and conducted to identify the model parameter values, which consequently enable the model to reproduce the experimentally observed shape memory (SM) behaviors. The parameter identification procedure proposed in this paper can be used as an effective tool to assist the construction and application of such 3D multi-branch model for general SMP materials.

Yu, Kai; McClung, Amber J. W.; Tandon, Gyaneshwar P.; Baur, Jeffrey W.; Jerry Qi, H.

2014-04-01

88

A thermomechanical constitutive model for an epoxy based shape memory polymer and its parameter identifications  

NASA Astrophysics Data System (ADS)

This paper presents a three-dimensional (3D) finite deformation thermomechanical model to study the glass transition and shape memory behaviors of an epoxy based shape memory polymer (SMP) (Veriflex E) and a systematic material parameter identification scheme from a set of experiments. The model was described by viscoelastic elements placed in parallel to represent different active relaxation mechanisms around glass transition temperature in the polymer. A set of standard material tests was proposed and conducted to identify the model parameter values, which consequently enable the model to reproduce the experimentally observed shape memory (SM) behaviors. The parameter identification procedure proposed in this paper can be used as an effective tool to assist the construction and application of such 3D multi-branch model for general SMP materials.

Yu, Kai; McClung, Amber J. W.; Tandon, Gyaneshwar P.; Baur, Jeffrey W.; Jerry Qi, H.

2014-05-01

89

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

90

A polymer/semiconductor write-once read-many-times memory  

NASA Astrophysics Data System (ADS)

Organic devices promise to revolutionize the extent of, and access to, electronics by providing extremely inexpensive, lightweight and capable ubiquitous components that are printed onto plastic, glass or metal foils. One key component of an electronic circuit that has thus far received surprisingly little attention is an organic electronic memory. Here we report an architecture for a write-once read-many-times (WORM) memory, based on the hybrid integration of an electrochromic polymer with a thin-film silicon diode deposited onto a flexible metal foil substrate. WORM memories are desirable for ultralow-cost permanent storage of digital images, eliminating the need for slow, bulky and expensive mechanical drives used in conventional magnetic and optical memories. Our results indicate that the hybrid organic/inorganic memory device is a reliable means for achieving rapid, large-scale archival data storage. The WORM memory pixel exploits a mechanism of current-controlled, thermally activated un-doping of a two-component electrochromic conducting polymer.

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

2003-11-01

91

PGSE-NMR and SANS studies of the interaction of model polymer therapeutics with mucin.  

PubMed

The viscous mucus coating that adheres to the epithelial surfaces of mammalian organs provides protection for the underlying tissues and is an efficient barrier to drug delivery. Pulsed-gradient spin-echo NMR and small-angle neutron scattering have been used to study the aqueous solution interaction of various model polymer therapeutics with mucin, the principle organic component within mucus. Nonionic polymers such as linear and star-branched poly(ethylene oxide) (PEO) and dextrin showed no appreciable interaction with mucin but suffered a moderate retardation in their rate of diffusion through the mucin solution. A strong interaction with mucin was observed for a series of polyamidoamine (PAMAM) dendrimers and hyperbranched poly(ethylene imine) (PEI), which displayed a characteristic pH-dependent profile and led to significant reductions in their rates of diffusion. These observations have implications for the design of optimized polymer therapeutic structures being adopted for the delivery of therapeutic moieties through mucin-rich environments. PMID:19950890

Griffiths, Peter Charles; Occhipinti, Paola; Morris, Christopher; Heenan, Richard K; King, Stephen Michael; Gumbleton, Mark

2010-01-11

92

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

93

Fabrication of Bistable Switching Memory Devices Utilizing Polymer-ZnO Nanocomposites  

NASA Astrophysics Data System (ADS)

This work reports fabrication of bistable memory switching devices employing wet-chemically synthesized ZnO nanoparticles with polymethyl methacrylate and poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] polymers. ZnO nanoparticle-embedded polymer layers were coated on conducting indium tin oxide (ITO) glasses using the spin-coating technique. Synthesized ZnO nanoparticles were characterized by scanning electron microscopy, transmission electron microscopy, x-ray diffraction, energy-dispersive x-ray, and photoluminescence studies. These ZnO particles are 20 nm to 30 nm in size with hexagonal structure. Switching and memory effects of the devices fabricated employing the ZnO nanoparticle-polymer composite films were investigated using current-voltage ( I- V) characteristics. The I- V measurements of both polymer devices showed electrical bistability. The ON to OFF current ratio of the bistable device was found to be ˜103. The observed current-time response showed good memory retention behavior of the fabricated devices. The carrier transport mechanism of the devices has been described on the basis of I- V experimental results and electronic structure.

Kathalingam, A.; Rhee, Jin-Koo

2012-08-01

94

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

2014-04-01

95

Active repair of self-healing polymers with shape memory alloy wires  

NASA Astrophysics Data System (ADS)

We report the first measurements of self-healing polymers with embedded shape memory alloy (SMA) wires. Improvements of healed peak loads by up to a factor of two are observed, approaching the performance of the virgin material. Moreover, the repairs can be effected with reduced amounts of healing agent. The improvements in performance of self-healing polymers with SMA wires are due to three effects: i) crack closure, which reduces the crack volume, ii) heating of the curing agent during polymerisation, which improves the cross-linking, and iii) mechanical registration of the two crack faces, which results in a reduced crack volume on closure.

Kirkby, Eva L.; Rule, Joseph D.; Michaud, Véronique J.; Sottos, Nancy R.; White, Scott R.; Månson, Jan-Anders E.

2007-04-01

96

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

PubMed

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 cm(2)V(-1)s(-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

97

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.

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

2014-01-01

98

Relaxation based modeling of tunable shape recovery kinetics observed under isothermal conditions for amorphous shape-memory polymers  

Microsoft Academic Search

Polymers, which allow the adjustment of shape-memory properties by variation of physical parameters during programming, are advantageous to their counterparts requiring synthesis of a new material.Here we explored the stress relaxation behaviour of polyurethane (PEU) based shape-memory polymers at temperatures from 0°C to 80°C and different strain values from 100% to 250%. The obtained relaxation curves could be well described

M. Heuchel; J. Cui; K. Kratz; H. Kosmella; A. Lendlein

2010-01-01

99

Thermoreversibly crosslinked poly(?-caprolactone) as recyclable shape-memory polymer network.  

PubMed

A new concept to build shape memory polymers (SMP) combining outstanding fixity and recovery ratios (both above 99% after only one training cycle) typical of chemically crosslinked SMPs with reprocessability restricted to physically crosslinked SMPs is demonstrated by covalently bonding, through thermoreversible Diels-Alder (DA) adducts, star-shaped poly(?-caprolactones) (PCL) end-functionalized by furan and maleimide moieties. A PCL network is easily prepared by melt-blending complementary end-functional star polymers in retro DA regime, then by curing at lower temperature to favour the DA cycloaddition. Such covalent network can be reprocessed when heated again at the retro DA temperature. The resulting SMP shows still excellent shape memory properties attesting for its good recyclability. PMID:21692124

Defize, Thomas; Riva, Raphaël; Raquez, Jean-Marie; Dubois, Philippe; Jérôme, Christine; Alexandre, Michaël

2011-08-17

100

Characterization and recovery of shape memory polymers filled with carbon nanofibers  

NASA Astrophysics Data System (ADS)

The microstructure and shape memory properties of polymers utilizing two different shape memory processes reinforced with vapor grown carbon nanofibers (CNFs) were investigated by thermal and thermomechanical techniques. The first shape memory polymer (SMP) was a thermoplastic polyurethane elastomer (Irogran) that used strain-induced crystallization for locking in the deformation. Shape recovery occurred through the melting temperature of the crystallites and demonstrated relatively good shape memory properties. Both shape fixity (ability to lock in the deformation) and recovery time (how fast the material recovered back to its original shape) improved with carbon nanofiber loading; however, the percent recovery (ability to return back to its original shape) decreased with CNF loading. Initial studies verified the role of strain-induced crystallization. Solid-state proton nuclear magnetic resonance (NMR) was used to investigate the impact of CNFs on the structure and dynamics of the crystallites in this thermoplastic polyurethane elastomer (TPE). The introduction of CNFs led to a shifting and broadening of the spectra, where the magnitude of the induced shifts and line broadening increased with CNF concentration. The spin-lattice and spin-spin relaxation times were not significantly changed with the introduction of CNFs. This demonstrated that the line broadening was inhomogeneous and a consequence of the magnetic susceptibility of the CNFs and not a reduction in segment mobility due to the proximity of the CNF surface. Spin diffusion experiments provided additional insight into the strain induced structure of the TPE/CNF composites. The second SMP was a thermoset epoxy (TEMBO DP5.1) reinforced with CNFs. This SMP used vitrification through the glass transition temperature for locking in the deformation and demonstrated excellent shape memory properties. The morphology of the CNFs throughout the epoxy polymer matrix, along with the recovery times of the nanocomposites was investigated. The incorporation of CNFs throughout the polymer matrix did not show an improvement in the shape fixity, shape recovery, or recovery times. Since the CNFs did not interact with the polymer matrix, there was no enhancement of the shape memory properties.

Powers, Daniel Stephen

101

Thermomechanical properties in a thin film of shape memory polymer of polyurethane series  

Microsoft Academic Search

The thermomechanical properties of a thin film of shape memory polymer of polyurethane series were investigated experimentally. Based on the experimental results, the dynamic mechanical properties, cyclic deformation properties at high temperature, thermomechanical cycling properties, creep and stress relaxation are discussed. The shape fixity with loading above the glass transition temperature 0964-1726\\/5\\/4\\/012\\/img7 followed by unloading below 0964-1726\\/5\\/4\\/012\\/img7 does not change

Hisaaki Tobushi; Hisashi Hara; Etsuko Yamada; Shunichi Hayashi

1996-01-01

102

Regular arrays of highly ordered ferroelectric polymer nanostructures for non-volatile low-voltage memories  

Microsoft Academic Search

Ferroelectric nanostructures are attracting tremendous interest because they offer a promising route to novel integrated electronic devices such as non-volatile memories and probe-based mass data storage. Here, we demonstrate that high-density arrays of nanostructures of a ferroelectric polymer can be easily fabricated by a simple nano-embossing protocol, with integration densities larger than 33Gbitsinch-2. The orientation of the polarization axis, about

Zhijun Hu; Mingwen Tian; Bernard Nysten; Alain M. Jonas

2009-01-01

103

Electromagnetic interference shielding effect of nanocomposites with carbon nanotube and shape memory polymer  

Microsoft Academic Search

The nanocomposites with carbon nanotubes (CNTs) and shape memory polymer (SMP) were developed for electrical applications. The specimens with different CNTs weight fractions were prepared. Their electrical resistivities and electromagnetic interference (EMI) shielding effectiveness (SE) were investigated. The electrical resistivity was examined by four-probe method at different testing temperatures of 25,35,45,55 and 65°C around glass transfer temperature (Tg). As a

Chun-Sheng Zhang; Qing-Qing Ni; Shao-Yun Fu; Ken Kurashiki

2007-01-01

104

Self-healing of sandwich structures with a grid stiffened shape memory polymer syntactic foam core  

Microsoft Academic Search

In this paper, a new sandwich with an orthogrid stiffened shape memory polymer (SMP) based syntactic foam core was proposed, fabricated, programmed, impacted, healed (sealed), and compression tested, for the purposes of healing impact damage repeatedly and almost autonomously. Two prestrain levels (3% and 20%), two impact energy levels (30.0 and 53.3 J), and two recovery (healing) conditions (2D confined

Manu John; Guoqiang Li

2010-01-01

105

Triple-Shape Memory Polymers Based on Self-Complementary Hydrogen Bonding  

PubMed Central

Triple shape memory polymers (TSMPs) are a growing subset of a class of smart materials known as shape memory polymers, which are capable of changing shape and stiffness in response to a stimulus. A TSMP can change shapes twice and can fix two metastable shapes in addition to its permanent shape. In this work, a novel TSMP system comprised of both permanent covalent cross-links and supramolecular hydrogen bonding cross-links has been synthesized via a one-pot method. Triple shape properties arise from the combination of the glass transition of (meth)acrylate copolymers and the dissociation of self-complementary hydrogen bonding moieties, enabling broad and independent control of both glass transition temperature (Tg) and cross-link density. Specifically, ureidopyrimidone methacrylate and a novel monomer, ureidopyrimidone acrylate, were copolymerized with various alkyl acrylates and bisphenol A ethoxylate diacrylate. Control of Tg from 0 to 60 °C is demonstrated: concentration of hydrogen bonding moieties is varied from 0 to 40 wt %; concentration of the diacrylate is varied from 0 to 30 wt %. Toughness ranges from 0.06 to 0.14 MPa and is found to peak near 20 wt % of the supramolecular cross-linker. A widely tunable class of amorphous triple-shape memory polymers has been developed and characterized through dynamic and quasi-static thermomechanical testing to gain insights into the dynamics of supramolecular networks.

Ware, Taylor; Hearon, Keith; Lonnecker, Alexander; Wooley, Karen L.; Maitland, Duncan J.; Voit, Walter

2012-01-01

106

Finite deformation thermo-mechanical behavior of thermally induced shape memory polymers  

NASA Astrophysics Data System (ADS)

Shape memory polymers (SMPs) are polymers that can demonstrate programmable shape memory effects. Typically, an SMP is pre-deformed from an initial shape to a deformed shape by applying a mechanical load at the temperature TH> Tg. It will maintain this deformed shape after subsequently lowering the temperature to TL< Tg and removing the externally mechanical load. The shape memory effect is activated by increasing the temperature to TD> Tg, where the initial shape is recovered. In this paper, the finite deformation thermo-mechanical behaviors of amorphous SMPs are experimentally investigated. Based on the experimental observations and an understanding of the underlying physical mechanism of the shape memory behavior, a three-dimensional (3D) constitutive model is developed to describe the finite deformation thermo-mechanical response of SMPs. The model in this paper has been implemented into an ABAQUS user material subroutine (UMAT) for finite element analysis, and numerical simulations of the thermo-mechanical experiments verify the efficiency of the model. This model will serve as a modeling tool for the design of more complicated SMP-based structures and devices.

Qi, H. Jerry; Nguyen, Thao D.; Castro, Francisco; Yakacki, Christopher M.; Shandas, Robin

107

Investigation of buckling behavior of carbon nanotube/shape memory polymer composite shell  

NASA Astrophysics Data System (ADS)

Shape memory polymer(SMP) is a class of smart materials used in intelligent biomedical devices and industrial application as sensors or actuators for their ability to change shape under a predetermined stimulus. Carbon nanotube (CNT)/shape memory polymer (SMP) composites demonstrate good mechanical properties and shape memory effect. In this work, a model of CNT/SMP composite shell with a vaulted cross-section was established. This composite shell structure could further elevate the recovery stress of CNT/SMP composites. The folding properties of CNT/SMP composite shell structure were analyzed by finite element method and the influence of structural parameters on the buckling behavior of the shell was studied using the energy conservation principle. The results indicate that vaulted cross-section shell had unique mechanical properties. The structural parameters, such as the vaulted radius and the total length have a great impact on buckling moment of the shell. This shell structure is expected to achieve effective control of buckling and deploying process, relying on the special shape memory property of SMP and high elastic modulus CNTs. Moreover, it could also largely avoid the vibration problem during the deploying process.

Shi, Guanghui; Yang, Qingsheng; Zhang, Qiang

2011-11-01

108

Synergistic effect of carbon nanofiber and sub-micro filamentary nickel nanostrand on the shape memory polymer nanocomposite  

Microsoft Academic Search

This work studies the synergistic effect of carbon nanofiber (CNF) and sub-micro filamentary nickel nanostrand on the thermal and electrical properties, as well as the electro-active shape memory behavior, of a shape memory polymer (SMP) nanocomposite. The combination of electrical CNF and electromagnetic nickel nanostrand is used to render insulating thermo-responsive SMPs conductive. Subsequently, the shape memory behavior of the

Haibao Lu; Jihua Gou; Jinsong Leng; Shanyi Du

2011-01-01

109

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

110

Nanoscale indent formation in shape memory polymers using a heated probe tip  

NASA Astrophysics Data System (ADS)

This paper presents experimental investigation of nanoscale indentation formation in shape memory polymers. The polymers were synthesized by photopolymerizing a tert-butyl acrylate (tBA) monomer with a poly(ethylene glycol dimethacrylate) (PEGDMA) crosslinker. The concentration and the molecular weight of the crosslinker were varied to produce five polymers with tailored properties. Nanoscale indentations were formed on the polymer surfaces by using a heated atomic force microscope (AFM) cantilever at various temperatures near or above the glass transition (between 84 and 215 °C) and a range of heating durations from 100 µs to 8 ms. The images of the indents were obtained with the same probe tip at room temperature. The contact pressure, a measure of transient hardness, was derived from the indentation height data as a function of time and temperature for different polymers. With increasing crosslinker molecular weight and decreasing crosslinker concentration, the contact pressures decreased at a fixed maximum load due to increased crosslink spacing in the polymer system. The results provide insight into the nanoscale response of these novel materials.

Yang, F.; Wornyo, E.; Gall, K.; King, W. P.

2007-07-01

111

Shape-Memory Polymers Based on Fatty Acid-Filled Elastomeric Ionomers  

NASA Astrophysics Data System (ADS)

Shape memory polymers (SMPs) have applications as medical devices, actuators, sensors, artificial muscles, switches, smart textiles, and self-deployable structures. All previous design of SMPs has involved synthesizing new polymers or modifying existing polymers. This paper describes a new type of SMP based on blends of an elastomeric ionomer and low molar mass fatty acids or their salts (FAS). Shape memory elastomers were prepared from mixtures of a sulfonated EPDM ionomer and various amounts of a FAS (e.g., zinc stearate, zinc oleate, and various aliphalic acids). Nanophase separation of the metal sulfonate groups provided the ``permanent'' crosslinks, while sub-microscopic crystals of the low molecular weight FAS provided a physical crosslink needed for the temporary shape. The material was deformed above the melting point of the FAS and the new shape was fixed by cooling the material while under stress to below the melting point of the FAS. Polar interactions between the ionomer and the FAS stabilized the dispersion of the FAS in the polymer and provided the continuity between the phases that allowed the crystals of the FAS to provide a second network of physical crosslinks. The temporary shape was erased and the material returned to the primary shape by heating above the melting point of the FAS.

Izzo, Elise; Weiss, Robert

2009-03-01

112

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

113

Nonvolatile polymer memory with nanoconfinement of ferroelectric crystals.  

PubMed

We demonstrate significantly improved performance of a nonvolatile polymeric ferroelectric field effect transistor (FeFET) memory using nanoscopic confinement of poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) within self-assembled organosilicate (OS) lamellae. Periodic OS lamellae with 30 nm in width and 50 nm in periodicity were templated using block copolymer self-assembly. Confined crystallization of PVDF-TrFE not only significantly reduces gate leakage current but also facilitates ferroelectric polarization switching. These benefits are due to the elimination of structural defects and the development of an effective PVDF-TrFE crystal orientation through nanoconfinement. A bottom gate FeFET fabricated using a single-crystalline triisopropylsilylethynyl pentacene channel and PVDF-TrFE/OS hybrid gate insulator shows characteristic source-drain current hysteresis that is fully saturated at a programming voltage of ±8 V with an ON/OFF current ratio and a data retention time of approximately 10(2) and 2 h, respectively. PMID:21114332

Kang, Seok Ju; Bae, Insung; Shin, Yu Jin; Park, Youn Jung; Huh, June; Park, Sang-Min; Kim, Ho-Cheol; Park, Cheolmin

2011-01-12

114

Metal-free, single-polymer device exhibits resistive memory effect.  

PubMed

All-polymer, write-once-read-many times resistive memory devices have been fabricated on flexible substrates using a single polymer, poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS). Spin-cast or inkjet-printed films of solvent-modified PEDOT:PSS are used as electrodes, while the unmodified or as-is PEDOT:PSS is used as the semiconducting active layer. The all-polymer devices exhibit an irreversible but stable transition from a low resistance state (ON) to a high resistance state (OFF) at low voltages caused by an electric-field-induced morphological rearrangement of PEDOT and PSS at the electrode interface. However, in the metal-PEDOT:PSS-metal devices, we have shown a metal filament formation switching the device from an initial high resistance state (OFF) to the low resistance state (ON). The all-PEDOT:PSS memory device has low write voltages (<3 V), high ON/OFF ratio (>10(3)), good retention characteristics (>10,000 s), and stability in ambient storage (>3 months). PMID:24206048

Bhansali, Unnat S; Khan, Mohd A; Cha, Dongkyu; AlMadhoun, Mahmoud N; Li, Ruipeng; Chen, Long; Amassian, Aram; Odeh, Ihab N; Alshareef, Husam N

2013-12-23

115

Isothermal recovery response and constitutive model of thermoset shape memory polymers  

NASA Astrophysics Data System (ADS)

Deformation recovery capability is one of the important indexes to examination shape memory effect of the shape memory polymers (SMPs). And the shape memory characteristic of SMPs is closely related to different phase states and mechanical properties above and below the glass transition temperature (Tg). In this paper, we investigated the strain recovery response of a thermoset shape memory epoxy resin modified by polyurethane (PU) through uniaxial compression experiments under various isothermal conditions and strain rates and developed a "three-phase" constitutive model based on phase transition concept, which including stationary phase, active phase and frozen phase. This model established the mutual transformation relationships between frozen phase and active phase of SMPs by introducing temperature switch function, which presents the stain storage and release process of SMPs under loading and changing temperature environment. Besides, the proposed model represents the SMPs deformation process of viscous hysteresis response by employing the rheological elements description of the three phases. The numerical results agree very well with experiment results of stress-strain response curve of isothermal compression/unloading test, which validated this model can predict the finite deformation behavior of SMPs.

Tan, Huifeng; Zhou, Tao; Liu, Yuyan; Lan, Lan

2011-11-01

116

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

117

Flexible low voltage nonvolatile memory transistors with pentacene channel and ferroelectric polymer  

NASA Astrophysics Data System (ADS)

We report on the fabrication of pentacene-based nonvolatile memory thin-film transistors (NVM-TFTs) with thin poly(vinylidene fluoride/trifluoroethylene) ferroelectric gate insulators. Our NVM-TFT adopts flexible polyethersulfone substrate and operates under the low voltage write-erase (WR-ER) pulses of +/-13~+/-20 V with field effect mobilities of 0.1-0.18 cm2/V s, depending on the ferroelectric polymer thickness. Our NVM-TFT displays good memory window (?V) of 2.5-8 V and also exhibits WR-ER current ratio of 20-40. The retention properties persist over ~10 000 s and the dynamic response for WR-ER pulses demonstrates clear distinction of WR-ER states under the short switching pulse of 50 ms.

Lee, Kwang H.; Lee, Gyubaek; Lee, Kimoon; Oh, Min Suk; Im, Seongil

2009-03-01

118

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

119

Memory  

NSDL National Science Digital Library

Our memory must b exercised in order for it to function properly. Click on Memory Exhibition, then click on droodles and common cents. Memory Exhibition Now play the memory game Memory game Take this test Short Term Memory Test Play Simon Says Play Simon Says 2 ...

Hirschi, Mrs.

2005-10-25

120

Improving the in vivo therapeutic index of siRNA polymer conjugates through increasing pH responsiveness.  

PubMed

Polymer based carriers that aid in endosomal escape have proven to be efficacious siRNA delivery agents in vitro and in vivo; however, most suffer from cytotoxicity due in part to a lack of selectivity for endosomal versus cell membrane lysis. For polymer based carriers to move beyond the laboratory and into the clinic, it is critical to find carriers that are not only efficacious, but also have margins that are clinically relevant. In this paper we report three distinct categories of polymer conjugates that improve the selectivity of endosomal membrane lysis by relying on the change in pH associated with endosomal trafficking, including incorporation of low pKa heterocycles, acid cleavable amino side chains, or carboxylic acid pH sensitive charge switches. Additionally, we determine the therapeutic index of our polymer conjugates in vivo and demonstrate that the incorporation of pH responsive elements dramatically expands the therapeutic index to 10-15, beyond that of the therapeutic index (less than 3), for polymer conjugates previously reported. PMID:24409989

Guidry, Erin N; Farand, Julie; Soheili, Arash; Parish, Craig A; Kevin, Nancy J; Pipik, Brenda; Calati, Kathleen B; Ikemoto, Nori; Waldman, Jacob H; Latham, Andrew H; Howell, Bonnie J; Leone, Anthony; Garbaccio, Robert M; Barrett, Stephanie E; Parmar, Rubina Giare; Truong, Quang T; Mao, Bing; Davies, Ian W; Colletti, Steven L; Sepp-Lorenzino, Laura

2014-02-19

121

A stress-induced phase transition model for semi-crystallize shape memory polymer  

NASA Astrophysics Data System (ADS)

The developments of constitutive models for shape memory polymer (SMP) have been motivated by its increasing applications. During cooling or heating process, the phase transition which is a continuous time-dependent process happens in semi-crystallize SMP and the various individual phases form at different temperature and in different configuration. Then, the transformation between these phases occurred and shape memory effect will emerge. In addition, stress applied on SMP is an important factor for crystal melting during phase transition. In this theory, an ideal phase transition model considering stress or pre-strain is the key to describe the behaviors of shape memory effect. So a normal distributed model was established in this research to characterize the volume fraction of each phase in SMP during phase transition. Generally, the experiment results are partly backward (in heating process) or forward (in cooling process) compared with the ideal situation considering delay effect during phase transition. So, a correction on the normal distributed model is needed. Furthermore, a nonlinear relationship between stress and phase transition temperature Tg is also taken into account for establishing an accurately normal distributed phase transition model. Finally, the constitutive model which taking the stress as an influence factor on phase transition was also established. Compared with the other expressions, this new-type model possesses less parameter and is more accurate. For the sake of verifying the rationality and accuracy of new phase transition and constitutive model, the comparisons between the simulated and experimental results were carried out.

Guo, Xiaogang; Zhou, Bo; Liu, Liwu; Liu, Yanju; Leng, Jinsong

2014-03-01

122

Biodegradable shape-memory block co-polymers for fast self-expandable stents.  

PubMed

Block co-polymers PCTBVs (M(n) of 36,300-65,300 g/mol, T(m) of 39-40 and 142 degrees C) containing hyperbranched three-arm poly(epsilon-caprolactone) (PCL) as switching segment and microbial polyester PHBV as crystallizable hard segment were designed as biodegradable shape-memory polymer (SMP) for fast self-expandable stent and synthesized in 96% yield by the reaction of three-arm PCL-triol (M(n) of 4200 g/mol, T(m) of 47 degrees C) with methylene diphenyl 4,4'-diisocyanate isocynate (MDI) to form the hyperbrached MDI-linked PCL (PTCM; M(n) of 25,400 g/mol and a T(m) of 38 degrees C), followed by further polymerization with PHBV-diol (M(n) of 2200 g/mol, T(m) of 137 and 148 degrees C). The polymers were characterized by (1)H NMR, GPC, DSC, tensile test, and cyclic thermomechanical tensile test. PCTBVs showed desired thermal properties, mechanical properties, and ductile nature. PCTBV containing 25 wt% PHBV (PCTBV-25) demonstrated excellent shape-memory property at 40 degrees C, with R(f) of 94%, R(r) of 98%, and shape recovery within 25s. PCTBV-25 was also shown as a safe material with good biocompatibility by cytotoxicity tests and cell growth experiments. The stent made from PCTBV-25 film showed nearly complete self-expansion at 37 degrees C within only 25 s, which is much better and faster than the best known self-expandable stents. PMID:20723973

Xue, Liang; Dai, Shiyao; Li, Zhi

2010-11-01

123

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

124

Method for preparation, programming, and characterization of miniaturized particulate shape-memory polymer matrices.  

PubMed

Their capability to change their shape on demand has created significant interest for shape-memory polymers (SMPs) in minimally invasive surgery. To evaluate the miniaturization of SMP matrices for small-sized implants or controlled release systems, a strategy to prepare and evaluate microsized SMP model particles is required. This methodological study reports the emulsion-based preparation of ~30 ?m microparticles (MPs) from a phase-segregated SMP, poly(?-caprolactone) [PCL] and poly(?-pentadecalactone) [PPDL], with a particular focus on the effects of process parameters such as polymer solvents or stabilizer type/concentration on formation and size distribution of SMP MPs. Processes for the preparation of SMP MP-loaded water-soluble polymer films with tailored mechanical properties were developed and applied for programming the SMP MP to a temporary ellipsoid shape by film stretching. For the functional evaluation of shape recovery of MPs, a light microscopy-based setup with temperature control is proposed by which the stimuli-induced switching of the microsized SMP matrices could be confirmed. Overall, by applying this methodological strategy to various thermoplastic SMPs, a routine to identify and characterize the microscale functionality of SMPs in miniaturized applications will be broadly accessible. PMID:24564390

Wischke, Christian; Lendlein, Andreas

2014-03-18

125

Ferroelectric polymer thin films for solid-state non-volatile random access memory applications  

NASA Astrophysics Data System (ADS)

Electronic polymers offer significant advantages towards ubiquitous computing due to their low-cost, flexibility and benign fabrication conditions. In this research, ferroelectric polymers were investigated for usage in non-volatile memory applications. The work is focused on the fabrication and ferroelectricity of Polyvinylidene-trifluoroethylene and Polyamide-11 (Nylon-11) thin films. Polyvinylidene fluoride (PVDF) and its copolymers were the first class of ferroelectric polymers discovered. Although the processes and properties of PVDF and copolymers have been extensively studied, most of the reports have been on polymers in the bulk form. This work focuses on thin films of PVDF-TrFE (75:25) copolymer fabricated by solution spin-casting. Remnant polarization, Pr, of the thin films was measured to be 6 muC/cm 2 with a coercive field, Ec, of 60 MV/m. The thin film properties are highly dependent on the temperature of crystallization and is attributed to the amount of all-trans beta-phase and crystallinity. Fatigue, defined as polarization loss with repeated switching, was studied and a model based on space charge formation was proposed as the fatigue mechanism. Space charge formation was proposed to be caused by electrochemical reaction of ions (F-) at electrodes and accumulations of detrapped ions at grain boundaries. Incorporating a F- scavenger and forming small crystallites was both observed to decrease fatigue. Nylon-11 and other odd-nylons are the only other class of polymers that have been reported to exhibit ferroelectric D-E hysteresis. The published work has almost exclusively been reported on melt-quenched and cold-drawn bulk polymers and consequently there is no literature on ferroelectricity in thin film odd-nylons. The present work developed a process for the fabrication of ferroelectric thin films of nylon-11 by spin-casting. Among the solvents tested, only a solution with m-cresol was observed to result in ferroelectricity in spun films and could be correlated to the crystal structure of the films. A polarization response, Pr, of 5muC/cm 2 with a coercive field, Ec, of 50MV/m was observed. The processing conditions and their effect on crystal structure were investigated to achieve optimal polarization response. In conclusion, PVDF-TrFE copolymers were fabricated in thin film form and process conditions developed to improve ferroelectric properties. Nylon-11 thin films were successfully fabricated for the first time with a polarization response equivalent to that in bulk polymers.

Kaza, Swaroop

126

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

127

Switching Device Based on a Thin Film of an Azo-Containing Polymer for Application in Memory Cells  

Microsoft Academic Search

Results obtained on a conductive multilevel device realized with a 100 nm azo-polymer film are reported. The capability to switch between three different conductance states makes the device versatile both for Write Once Read Many and Write Many Read Many memory cell application. The analysis of the - curves indicates that the hysteretic conductance change with the external voltage can

Domenico Attianese; Mario Petrosino; Paolo Vacca; Simona Concilio; Pio Iannelli; Alfredo Rubino; Salvatore Bellone

2008-01-01

128

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

129

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.

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

2011-01-01

130

Fabrication and characterization of cylindrical light diffusers comprised of shape memory polymer  

PubMed Central

We 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. The devices are 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 are characterized for various blasting pressures, nozzle-to-sample distances, and nozzle translation speeds. The diffusers are generally strongly forward-directed and consistently withstand over 8 W of incident IR laser light without suffering damage when immersed in water. These devices are suitable for various endoluminal and interstitial biomedical applications.

Small, Ward; Buckley, Patrick R.; Wilson, Thomas S.; Loge, Jeffrey M.; Maitland, Kristen D.; Maitland, Duncan J.

2009-01-01

131

TECHNICAL NOTE: The formation of micro-protrusions atop a thermo-responsive shape memory polymer  

NASA Astrophysics Data System (ADS)

We present an experimental investigation on a novel approach to produce micro-sized protrusive features atop a thermo-responsive shape memory polymer (SMP). This approach includes three steps, namely, indenting atop an SMP sample (using a Berkovich indenter in this study), polishing and then heating it for full shape recovery. Apart from ordinary samples, some SMP samples are pre-stretched in the in-plane direction or pre-compressed in the out-of-plane direction. The relationships between the height/shape of protrusion and the depth of indent are obtained for all indents in samples with/without pre-straining. Intrinsic relationships among the indentation depth, polishing depth and height/shape of protrusion are further revealed quantitatively in a dimensionless manner. The influence of pre-straining is discussed.

Liu, N.; Huang, W. M.; Phee, S. J.; Tong, T. H.

2008-10-01

132

Thermomechanical properties, collapse pressure, and expansion of shape memory polymer neurovascular stent prototypes.  

PubMed

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 degrees 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

2009-07-01

133

Monitoring static shape memory polymers using a fiber Bragg grating as a vector-bending sensor  

NASA Astrophysics Data System (ADS)

We propose and demonstrate a technique for monitoring the recovery deformation of the shape-memory polymers (SMP) using a surface-attached fiber Bragg grating (FBG) as a vector-bending sensor. The proposed sensing scheme could monitor the pure bending deformation for the SMP sample. When the SMP sample undergoes concave or convex bending, the resonance wavelength of the FBG will have red-shift or blue-shift according to the tensile or compressive stress gradient along the FBG. As the results show, the bending sensitivity is around 4.07 nm/cm-1. The experimental results clearly indicate that the deformation of such an SMP sample can be effectively monitored by the attached FBG not just for the bending curvature but also the bending direction.

Li, Peng; Yan, Zhijun; Zhou, Kaiming; Zhang, Lin; Leng, Jinsong

2013-01-01

134

Self-healing of sandwich structures with a grid stiffened shape memory polymer syntactic foam core  

NASA Astrophysics Data System (ADS)

In this paper, a new sandwich with an orthogrid stiffened shape memory polymer (SMP) based syntactic foam core was proposed, fabricated, programmed, impacted, healed (sealed), and compression tested, for the purposes of healing impact damage repeatedly and almost autonomously. Two prestrain levels (3% and 20%), two impact energy levels (30.0 and 53.3 J), and two recovery (healing) conditions (2D confined and 3D confined) were employed in this paper. Up to seven impact-healing cycles were conducted. Macroscopic and microscopic damage-healing observation and analysis were implemented. Residual strength was evaluated using an anti-buckling compression test fixture. It was found that the healing efficiency was over 100% for almost all the impact-healing cycles; programming using 20% prestrain led to higher residual strength than that with 3% prestrain; 3D confined recovery resulted in higher residual strength than 2D confined recovery; and as the impact energy increased, the healing efficiency slightly decreased.

John, Manu; Li, Guoqiang

2010-07-01

135

PCL-based Shape Memory Polymers with Variable PDMS Soft Segment Lengths  

PubMed Central

Thermoresponsive shape memory polymers (SMPs) are stimuli-responsive materials that return to their permanent shape from a temporary shape in response to heating. The design of new SMPs which obtain a broader range of properties including mechanical behavior is critical to realize their potential in biomedical as well as industrial and aerospace applications. To tailor the properties of SMPs, “AB networks” comprised of two distinct polymer components have been investigated but are overwhelmingly limited to those in which both components are organic. In this present work, we prepared inorganic-organic SMPs comprised of inorganic polydimethyl-siloxane (PDMS) segments of varying lengths and organic poly(?-caprolactone) (PCL) segments. PDMS has a particularly low Tg (?125 °C) which makes it a particularly effective soft segment to tailor the mechanical properties of PCL-based SMPs. The SMPs were prepared via the rapid photocure of solutions of diacrylated PCL40-block-PDMSm-block-PCL40 macromers (m = 20, 37, 66 and 130). The resulting inorganic-organic SMP networks exhibited excellent shape fixity and recovery. By changing the PDMS segment length, the thermal, mechanical, and surface properties were systematically altered.

Zhang, Dawei; Giese, Melissa L.; Prukop, Stacy L.; Grunlan, Melissa A.

2012-01-01

136

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.

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

2011-01-01

137

Nonvolatile memory effects in an orthoconic smectic liquid crystal mixture doped with polymer-capped gold nanoparticles.  

PubMed

Promising applications of liquid crystal nanocomposites have driven extensive efforts to achieve non-volatile memory effects for the realization of electronic storage devices. In this context, non-volatile memory effects in an orthoconic smectic liquid crystal mixture, with and without polymer capped gold nanoparticles, were investigated. The dielectric spectroscopy technique was performed by applying a d.c. bias during the measurement or a d.c. potential before the start of the measurement in order to obtain pre-conditioning of the sample. Both techniques showed the presence of non-volatile memory effects in the pure orthoconic smectic liquid crystal mixture similar to the doped one. The results demonstrate that the addition of gold nanoparticles enhances the memory effect making it permanent. Our experimental evidence underlines the importance of the structure of the host liquid crystal and clearly suggests that the prolonged time memory effect, observed in the doped liquid crystal, is due to the electric field inducing charge transfer from the liquid crystal molecules to the gold nanoparticles, thanks to the polymer-capping which acts as an ionic charge trapper. Such an ionic trap effect is also responsible for strong reduction of total conductivity of the doped system. PMID:24727831

Marino, L; Marino, S; Wang, D; Bruno, E; Scaramuzza, N

2014-06-01

138

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

139

Memory effect in the chain-collapse process in a dilute polymer solution  

NASA Astrophysics Data System (ADS)

The effect of temperature perturbation on a single-chain-collapse process was studied for poly(methyl methacrylate) with the molecular weight Mw=1.05×107 in the mixed solvent of tert-butyl alcohol+water (2.5 vol %). In the chain-collapse process after a quench from the ? temperature to a temperature T1, the temperature was changed from T1 to T2 at the time t1 after the quench and returned to T1 at the time t1+t2. In the three stages at T1, T2, and T1, measurements of the mean-square radius of gyration of polymer chains were carried out by static light scattering and the chain-collapse process was represented by the expansion factor as a function of time. An effect of chain aggregation on the measurements was negligibly small because of the very slow phase separation. For the negative temperature perturbation (T1>T2), the chain-collapse processes observed in the first and third stages were connected smoothly and agreed with the collapse process due to a single-stage quench to T1. A memory of the chain collapse in the first stage at T1 was found to persist into the third stage at the same temperature T1 without being affected by the temperature perturbation of T2 during t2. The memory effect was observed irrespective of the time period of t2. The positive temperature perturbation (T1

Maki, Yasuyuki; Sasaki, Naoki; Nakata, Mitsuo

2004-12-01

140

NEW OPTICAL MEMORY EFFECTS IN POLYMER-STABILIZED CHOLESTERIC LIQUID CRYSTALS DUE TO PITCH CHANGES DURING THE UV-CURING  

Microsoft Academic Search

A Polymer-Stabilized Cholesteric Liquid Crystal (PSCLC) is elaborated by combining the UV-curing with a thermally-induced pitch variation. We intend investigating possible memory effects into the characteristics of the reflection band of the PSCLC when the material comes back to the room temperature. Different thermal processes are studied when the curing occurs at one or two temperatures (with the role of

Emmanuelle Nouvet; Michel Mitov

2004-01-01

141

Therapeutic Effect of Caffeine Treatment Immediately Following Neonatal Hypoxic-Ischemic Injury on Spatial Memory in Male Rats  

PubMed Central

Hypoxia Ischemia (HI) refers to the disruption of blood and/or oxygen delivery to the brain. Term infants suffering perinatal complications that result in decreased blood flow and/or oxygen delivery to the brain are at risk for HI. Among a variety of developmental delays in this population, HI injured infants demonstrate subsequent memory deficits. The Rice-Vannucci rodent HI model can be used to explore behavioral deficits following early HI events, as well as possible therapeutic agents to help reduce deleterious outcomes. Caffeine is an adenosine receptor antagonist that has recently shown promising results as a therapeutic agent following HI injury. The current study sought to investigate the therapeutic benefit of caffeine following early HI injury in male rats. On post-natal day (P) 7, HI injury was induced (cauterization of the right common carotid artery, followed by two hours of 8% oxygen). Male sham animals received only a midline incision with no manipulation of the artery followed by room air exposure for two hours. Subsets of HI and sham animals then received either an intraperitoneal (i.p.) injection of caffeine (10 mg/kg), or vehicle (sterile saline) immediately following hypoxia. All animals later underwent testing on the Morris Water Maze (MWM) from P90 to P95. Results show that HI injured animals (with no caffeine treatment) displayed significant deficits on the MWM task relative to shams. These deficits were attenuated by caffeine treatment when given immediately following the induction of HI. We also found a reduction in right cortical volume (ipsilateral to injury) in HI saline animals as compared to shams, while right cortical volume in the HI caffeine treated animals was intermediate. These findings suggest that caffeine is a potential therapeutic agent that could be used in HI injured infants to reduce brain injury and preserve subsequent cognitive function.

Alexander, Michelle; Smith, Amanda L.; Rosenkrantz, Ted S.; Fitch, R. Holly

2013-01-01

142

Memory  

NSDL National Science Digital Library

This is a description for a learning module from Maricopa Advanced Technology Education Center. This PDF describes the module; access may be purchased by visiting the MATEC website. PC memory is one of the most critical and rapidly advancing assemblies within modern microcomputers. The challenge of developing learners' knowledge of PC memory and keeping it current and directly applicable to today's microcomputer industry is addressed by this module. The three major topics included in this module are ROM/Flash, System Memory, and Cache Systems. Hands-on practice and final skill assessment verify learners' readiness for working with memory in an Intel-based PC system.

2012-12-07

143

The mesoscopic approach to the dynamics of polymer melts: consequences for the constitutive equation 1 Dedicated to the memory of Professor Gianni Astarita. 1  

Microsoft Academic Search

The mesoscopic approach in the dynamics of polymer melts is based on the equation of the dynamics of a single macromolecule in the entangled system. The general linear form of the dynamic equation of a macromolecule allows different hypotheses about the decay law of memory function to be tested. To obtain consistency with experimental evidence for strongly entangled polymer melts,

V. N. Pokrovskii; Yu. A. Altukhov; G. V. Pyshnograi

1998-01-01

144

The effect of moisture absorption on the physical properties of polyurethane shape memory polymer foams  

NASA Astrophysics Data System (ADS)

The effect of moisture absorption on the glass transition temperature (Tg) and the stress/strain behavior of network polyurethane shape memory polymer (SMP) foams has been investigated. With our ultimate goal of engineering polyurethane SMP foams for use in blood-contacting environments, we have investigated the effects of moisture exposure on the physical properties of polyurethane foams. To the best of our knowledge, this study is the first to investigate the effects of moisture absorption at varying humidity levels (non-immersion and immersion) on the physical properties of polyurethane SMP foams. The SMP foams were exposed to differing humidity levels for varying lengths of time, and they exhibited a maximum water uptake of 8.0% (by mass) after exposure to 100% relative humidity for 96 h. Differential scanning calorimetry results demonstrated that water absorption significantly decreased the Tg of the foam, with a maximum water uptake shifting the Tg from 67 to 5 °C. Samples that were immersed in water for 96 h and immediately subjected to tensile testing exhibited 100% increases in failure strains and 500% decreases in failure stresses; however, in all cases of time and humidity exposure, the plasticization effect was reversible upon placing moisture-saturated samples in 40% humidity environments for 24 h.

Yu, Ya-Jen; Hearon, Keith; Wilson, Thomas S.; Maitland, Duncan J.

2011-08-01

145

Characterizing and modeling the free recovery and constrained recovery behavior of a polyurethane shape memory polymer  

NASA Astrophysics Data System (ADS)

In this work, tensile tests and one-dimensional constitutive modeling were performed on a high recovery force polyurethane shape memory polymer that is being considered for biomedical applications. The tensile tests investigated the free recovery (zero load) response as well as the constrained displacement recovery (stress recovery) response at extension values up to 25%, and two consecutive cycles were performed during each test. The material was observed to recover 100% of the applied deformation when heated at zero load in the second thermomechanical cycle, and a stress recovery of 1.5-4.2 MPa was observed for the constrained displacement recovery experiments. After the experiments were performed, the Chen and Lagoudas model was used to simulate and predict the experimental results. The material properties used in the constitutive model—namely the coefficients of thermal expansion, shear moduli, and frozen volume fraction—were calibrated from a single 10% extension free recovery experiment. The model was then used to predict the material response for the remaining free recovery and constrained displacement recovery experiments. The model predictions match well with the experimental data.

Volk, Brent L.; Lagoudas, Dimitris C.; Maitland, Duncan J.

2011-09-01

146

Fabrication and in vitro deployment of a laser-activated shape memory polymer vascular stent  

PubMed Central

Background 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. Methods 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. Results 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 ~8 W. Conclusion 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, Geraldine M; Small, Ward; Wilson, Thomas S; Benett, William J; Matthews, Dennis L; Hartman, Jonathan; Maitland, Duncan J

2007-01-01

147

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

148

The effect of moisture absorption on the physical properties of polyurethane shape memory polymer foams.  

PubMed

The effect of moisture absorption on the glass transition temperature (T(g)) and stress/strain behavior of network polyurethane shape memory polymer (SMP) foams has been investigated. With our ultimate goal of engineering polyurethane SMP foams for use in blood contacting environments, we have investigated the effects of moisture exposure on the physical properties of polyurethane foams. To our best knowledge, this study is the first to investigate the effects of moisture absorption at varying humidity levels (non-immersion and immersion) on the physical properties of polyurethane SMP foams. The SMP foams were exposed to differing humidity levels for varying lengths of time, and they exhibited a maximum water uptake of 8.0% (by mass) after exposure to 100% relative humidity for 96 h. Differential scanning calorimetry results demonstrated that water absorption significantly decreased the T(g) of the foam, with a maximum water uptake shifting the T(g) from 67 °C to 5 °C. Samples that were immersed in water for 96 h and immediately subjected to tensile testing exhibited 100% increases in failure strains and 500% decreases in failure stresses; however, in all cases of time and humidity exposure, the plasticization effect was reversible upon placing moisture-saturated samples in 40% humidity environments for 24 h. PMID:21949469

Yu, Ya-Jen; Hearon, Keith; Wilson, Thomas S; Maitland, Duncan J

2011-08-01

149

Memory  

Microsoft Academic Search

.  Progress towards amelioration and eventual cure of human cognitive disorders requires understanding the molecular signaling\\u000a mechanisms that normally govern learning and memory. The fly Drosophila melanogaster has been instrumental in the identification of molecules and signaling pathways essential for learning and memory, because\\u000a genetic screens have produced mutants in these processes and the system facilitates integrated genetic, molecular, histological\\u000a and

E. M. C. Skoulakis; S. Grammenoudi

2006-01-01

150

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

151

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

152

Qualitative separation of the effect of the solubility parameter on the recovery behavior of shape-memory polymer  

NASA Astrophysics Data System (ADS)

For the thermal response of shape-memory polymer (SMP) it has been experimentally demonstrated that the actuation can be achieved using interactive solvent. In this paper, the effect of the solubility parameter of the interactive solvent on the shape recovery behavior and glass transition temperature of polystyrene SMP was investigated experimentally. The effect of the solubility parameter on the activation energy was separated and qualitatively identified, as expected from the relaxation theory and Eyring equation. This approach should be applicable to other SMPs and their composites and many extension applications and achievements could be based on this outcome.

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

2009-08-01

153

Self-assembled regular arrays of carbon nanotube and the route toward actuation of shape memory polymer  

NASA Astrophysics Data System (ADS)

The synthesis of massive arrays of monodispersed carbon nanotubes that are self-assembled on hydrophilic polycarbonate membrane is reported. This approach involves individual carbon nanotube manufacturing by non-ionic surfactant to aid in dispersion and nanotubes self-assembled for three-dimensional orientation by high press filtration. The inherent capability of carbon nanotube and microstructure of well-packed arrays predominate excellent conductive properties of massive arrays. These potential applications of nanometer-sized sensor, probe and energy resistor have been characterized in this study. Furthermore, the route toward application of self-assembled regular arrays, as heat transmission intermedium, has been carried out by activating shape-memory polymer. The electrical conductivity of insulating polymer is significantly improved by assembled carbon nanotubes, resulting in shape recovery behavior of nanocomposite being driven by electrical resistive heating.

Lu, Haibao; Wu, Chunxia; Liu, Yanju; Gou, Jan; Leng, Jinsong

2010-03-01

154

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

155

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.

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

2012-01-01

156

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

157

Partial erasing of temporal memory by using picosecond accumulated photon echoes in dye doped polymer film  

Microsoft Academic Search

The stimulated photon echo memory using persistent hole-burning materials has been attracting much attention as a possible candidate for high-density data storage. Most studies have been related to the writing and reading processes and little attention has been paid for a partial erasing. We demonstrate for the first time that partial erasing of photon echo memory can be accomplished by

R. Yano; N. Uesugi

1999-01-01

158

Modeling of the drug delivery from a hydrophilic transdermal therapeutic system across polymer membrane  

Microsoft Academic Search

A mathematical simulation is presented which describes the in vitro drug delivery kinetics from hydrophilic adhesive water-soluble poly-N-vinylpyrrolidone (PVP) –polyethylene glycol (PEG) matrices of transdermal therapeutic systems (TTS) across skin-imitating hydrophobic Carbosil membranes. Propranolol is employed as the test drug. The contributions of the following physicochemical determinants to drug delivery rate control have been estimated: the drug diffusion coefficients both

Alexei L. Iordanskii; Mikhail M. Feldstein; Valery S. Markin; Jonathan Hadgraft; Nicolai A. Plate

2000-01-01

159

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

160

Determination of recovery energy densities of shape memory polymers via closed-loop, force-controlled recovery cycling  

NASA Astrophysics Data System (ADS)

Shape memory polymers offer semi-active properties, which can be used for actuation. Possible applications are deployment or release mechanisms in spacecraft, or the shape readjustment of high precision composite parts. For these kinds of applications, especially the recovered energy density, which is the product of recovered strain and recovered stress, is an important figure of merit. The present study shows the experimental procedure for the determination of recovery energy densities for tension and compression samples. To ensure simultaneous recording of loaded recovered strain and stress, closed-loop, force-controlled recovery cycles are performed using an Instron tensile testing machine and a thermal chamber. More-dimensional working fields of a polystyrene-based shape memory polymer are determined, using the introduced experimental technique. The resulting more-dimensional working fields show the nonlinear relationships between recovery ratio, maximum strain and recovery stress. It was discovered that the optimal working points of the tension and compression mode are complementary, which leads to an extended working range of SMP actuators if both modes are considered. As an application example for SMP energy recovery, a finite element simulation of the shape readjustment of a high precision composite part is shown.

Rapp, S.; Baier, H.

2010-04-01

161

A phenomenological model for the chemo-responsive shape memory effect in amorphous polymers undergoing viscoelastic transition  

NASA Astrophysics Data System (ADS)

We present a phenomenological approach to study the viscoelastic transition and working mechanism of the chemo-responsive shape memory effect (SME) in amorphous shape memory polymers (SMPs). Both the copolymerization viscosity model and Doolittle equation are initially applied to quantitatively identify the influential factors behind the chemo-responsive SME in the SMPs exposure to a right solvent. After this, the Williams-Landel-Ferry (WLF) equation is employed to couple the viscosity (?), time-temperature shift factor (??) and glass transition temperature (Tg) in amorphous polymers. By means of combining the WLF and Arrhenius equations together, the inductively decreased transition temperature is confirmed as the driving force for the chemo-responsive SME. Finally, a phenomenological viscoelastic model is proposed and then verified by the available experimental data reported in the literature and then compared with the simulation results of a semi-empirical model. This phenomenological model is expected to provide a powerful simulation tool for theoretical prediction and experimental substantiation of the chemo-responsive SME in amorphous SMPs by viscoelastic transition.

Lu, Haibao; Huang, Wei Min

2013-11-01

162

Strain rate- and temperature-dependent tensile properties of an epoxy-based, thermosetting, shape memory polymer (Veriflex-E)  

NASA Astrophysics Data System (ADS)

In this study, the inelastic deformation behavior of an epoxy-based, thermally triggered shape memory polymer resin, known as Veriflex-E, was investigated. The experimental program was designed to explore the influence of strain rate on monotonic loading at various temperatures which is needed to establish the design space of SMPs in load bearing applications. Thermally actuated shape memory polymers can be thought of as having two phases separated by the glass transition temperature ( T g ). At temperatures below the T g , Veriflex-E exhibits a high elastic modulus and positive, non-linear strain rate sensitivity in monotonic loading. The Poisson's ratio at room temperature is independent of the strain rate, but dependent upon the strain magnitude. As the temperature is increased, the strain rate sensitivity in monotonic loading decreases. Well above the T g , the elastic modulus drops by several orders of magnitude. In this high temperature region, the material achieves strain levels well above 100% and Poisson's ratio is constant at 0.5 regardless of strain rate or strain magnitude.

McClung, Amber J. W.; Tandon, Gyaneshwar P.; Baur, Jeffery W.

2012-05-01

163

Incorporation of Benzocyclobutene Cross-Linkable Moieties in Poly(Methyl Acrylate): A Novel Approach to Shape-Memory Polymers Accompanied with Microphase Separation  

Microsoft Academic Search

Benzocyclobutene (BCB) moieties were incorporated into a typical polyolefin, poly(methyl acrylate), by free radical copolymerization of benzocyclobutene-4-yl acrylate and methyl acrylate. The subsequent cross-linking of the generated copolymers by ring-opening reaction of BCB gave rise to shape-memory polymers. This new cross-linking process did not require cross-linker and yielded small molecules. Most importantly, submicron-sized particles within the cross-linked polymers, which were

Junxiao Yang; Liqin Xie; Fanghua Zhu; Haibo Sui; Huiling Li; Yawen Huang

2011-01-01

164

Incorporation of Benzocyclobutene Cross-linkable Moieties in Poly (methyl acrylate): A Novel Approach to Shape-memory Polymers Accompanied with Microphase Separation  

Microsoft Academic Search

Benzocyclobutene moieties were incorporated into a typical polyolefin, poly (methyl acrylate), by free radical copolymerization of benzocyclobutene-4-yl acrylate and methyl acrylate. The subsequent cross-linking of the generated copolymers by ring-opening reaction of benzocyclobutene gave rise to shape-memory polymers. This new cross-linking process did not require cross-linker and yield small molecules. Most importantly, submicron-sized particles within the cross-linked polymers, which were

Junxiao Yang; Liqin Xie; Fanghua Zhu; Haibo Sui; Huiling Li; Yawen Huang

2011-01-01

165

Surface modification of medical implant materials with hydrophilic polymers for enhanced biocompatibility and delivery of therapeutic agents  

NASA Astrophysics Data System (ADS)

In the research reported here, the surface modification of medical grade poly(dimethyl siloxane), polyetherurethane, and stainless steel through gamma-radiation grafting of hydrophilic polymers was investigated. Emphasis was placed on developing improved and simplified surface modification methods that produce more stable and more bioacceptible hydrophilic graft surfaces. As a result of this research, new surface modification techniques were developed that yield significantly improved surface stability unachievable using previous surface modification techniques. The surface modification of poly(dimethyl siloxane) with hydrophilic polymers was carried out using gamma radiation initiated graft polymerization. The addition of alkali metal hydroxides afforded a unique way to enhance the grafting of N-vinyl-2 pyrrolidone, dimethylacryamide, 2-methacryloyloxyethyl phosphoryl choline, N,N-dimethyl-N-(methacryloyloxyethyl)-N-(3-sulfopropyl)-ammonium-betaine, N,N-dimethyl-N-(methacrylamidopropyl)-N-(3-sulfopropyl)-ammonium-betaine, and copolymers thereof to silicones. Ethanolamine was found to further enhance the grafting of some hydrophilic polymers to silicone. The resulting hydrophilic surface grafts were resistant to hydrophobic surface rearrangement. This process overcomes previous problems inherent in silicone surface modification. The technique was also found to moderately enhance the grafting of hydrophilic monomers to polyetherurethane and to 316-L stainless steel. The surface modification of 316-L stainless steel was further enhanced by treating the substrates with a chromium III methacrylate bonding agent prior to irradiation. The coatings were evaluated for their potential use as depots for delivering therapeutic agents. The release of ofloxacin from surface-modified poly(dimethyl siloxane) and dexamethasone from surface-modified 316-L stainless steel was evaluated by in-vitro experiments. Therapeutic levels of drugs were released from surface-modified specimens via a burst effect. Improved surface characterization methods were another aspect of this research. New nanomechanical testing techniques were developed and used to evaluate the viscoelastic surface mechanical properties of low modulus surface-modified specimens. Dynamic nanoindentation characterization techniques were designed to measure the storage modulus and loss modulus of compliant viscoelastic substrate surfaces. The results of these experiments were compared with modulus data obtained by conventional dynamic mechanical spectroscopy. Nanoscratch testing methods were also developed that qualitatively compared the abrasion resistance of surface-modified substrates. (Abstract shortened by UMI.)

Urbaniak, Daniel J.

2004-11-01

166

Multi-layer metal/shape memory polymer roll-up wing structures for fitment-constrained air vehicles  

US Patent & Trademark Office Database

A laminated wing structure includes at least one layer of metal material and at least one layer of a shape memory polymer (SMP) material. The SMP is heated to a temperature in its glass transition band Tg to roll the wing around the air vehicle into a stored position. The metal layer(s) must be thin enough to remain below its yield point when rolled up. In preparation for launch, the SMP material is thermally activated allowing the strain energy stored in the layer of metal material to return the wing to its deployed position at launch. Once deployed, the SMP cools to its glassy state. The SMP material may be reinforced with fiber to form a polymer matrix composite (PMC). SMP may be used to provide shear strain relief for multiple metal layers. By offloading the motive force required to return the wing to its original deployed position from the SMP to the metal, the polymer does not acquire a permanent set and the wing may be deployed accurately.

2013-09-10

167

Modeling of the drug delivery from a hydrophilic transdermal therapeutic system across polymer membrane.  

PubMed

A mathematical simulation is presented which describes the in vitro drug delivery kinetics from hydrophilic adhesive water-soluble poly-N-vinylpyrrolidone (PVP)-polyethylene glycol (PEG) matrices of transdermal therapeutic systems (TTS) across skin-imitating hydrophobic Carbosil membranes. Propranolol is employed as the test drug. The contributions of the following physicochemical determinants to drug delivery rate control have been estimated: the drug diffusion coefficients both in the matrix and the membrane; the membrane-matrix drug partition coefficient: the drug concentration in the matrix and the membrane thickness. Drug transfer from the hydrophilic matrix across the membrane is shown to be controlled by the drug partitioning from the matrix into the membrane. The best correlation between simulation data and experimental results is obtained when the effect of membrane hydration is taken into consideration during in vitro drug release. PMID:10799821

Iordanskii, A L; Feldstein, M M; Markin, V S; Hadgraft, J; Plate, N A

2000-05-01

168

A biocompatible oxidation-triggered carrier polymer with potential in therapeutics.  

PubMed

Dextran, a water-soluble, biocompatible polymer of glucose, was modified at its hydroxyls with arylboronic esters to make it soluble in common organic solvents, allowing for the facile preparation of oxidation-sensitive dextran (Oxi-DEX) carrier microparticles. These particles were found to release their payload with a half-life of 36 min at 1 mM H2O2, which can be compared with a half-life of greater than 1 week in the absence of H2O2. When used in a model vaccine application, Oxi-DEX particles loaded with ovalbumin (OVA) increased the presentation to CD8+ T-cells 27-fold relative to OVA encapsulated in a classical vehicle not sensitive to oxidation. No presentation was observed from cells incubated with unencapsulated OVA. Additionally, Oxi-DEX was found to be nontoxic in preliminary in vitro cytotoxicity assays. Because it is easy to prepare, sensitive to biological oxidation, and biocompatible, this material may represent an attractive new platform for selective delivery applications. PMID:21171594

Broaders, Kyle E; Grandhe, Sirisha; Fréchet, Jean M J

2011-02-01

169

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

170

Investigating siRNA delivery to chronic myeloid leukemia K562 cells with lipophilic polymers for therapeutic BCR-ABL down-regulation.  

PubMed

RNAi represents a new alternative for treatment of chronic myeloid leukemia (CML) to overcome the difficulties of current drug treatments such as the acquired resistance. However, potent carriers that can overcome delivery barriers to RNAi agents and have therapeutic efficacy especially in difficult-to-transfect CML cells are needed. Here, we explored the use of lipid-modified polyethylenimines (PEI) of low molecular weights (0.6, 1.2 and 2.0kDa) in K562 cells and showed that the delivery efficiency was dependent on the type of lipid used for polymer modification, degree of lipid substitution and polymer molecular weight. Among the lipid-substituted polymers investigated, palmitic acid (PA)-substituted 1.2kDa PEI (~2 lipids/PEI) has proven to be highly efficient in delivering siRNA and silencing of the reporter gene green fluorescent protein (GFP). The silencing efficacy achieved with this polymer was found to be higher than the 25kDa PEI and is similar to commercial reagent Lipofectamine™ 2000. Moreover, when BCR-ABL protein was targeted in K562 cells, a reduction in the corresponding mRNA levels was observed, as well as an induction of early and late stage apoptosis. The results of this study demonstrated that PA-substitutions on low MW polymers could be useful for siRNA delivery in CML cells for therapeutic purposes. PMID:23726887

Valencia-Serna, Juliana; Gul-Uluda?, Hilal; Mahdipoor, Parvin; Jiang, Xiaoyan; Uluda?, Hasan

2013-12-10

171

Therapeutic use of H2O2-responsive anti-oxidant polymer nanoparticles for doxorubicin-induced cardiomyopathy.  

PubMed

Doxorubicin (DOX) is a commonly used anti-neoplastic agent but its clinical use is limited due to serious hepatic and cardiac side effects. DOX-induced toxicity is mainly associated with overproduction of reactive species oxygen (ROS) such as hydrogen peroxide (H2O2). We have recently developed H2O2-responsive anti-oxidant polymer, polyoxalate containing vanillyl alcohol (PVAX), which is designed to rapidly scavenge H2O2 and release vanillyl alcohol with anti-oxidant, anti-inflammatory and anti-apoptotic properties. In this study, we report that PVAX nanoparticles are novel therapeutic agents for treating DOX-induced cardiac and hepatic toxicity. Intraperitoneal injection of PVAX nanoparticles (4 mg/kg/day) resulted in significant inhibition in apoptosis in liver and heart of DOX-treated mice by suppressing the activation of poly (ADP ribose) polymerase 1 (PARP-1) and caspase-3. PVAX treatment also prevented DOX-induced cardiac dysfunction. Furthermore, survival rate (vehicle = 35% vs. PVAX = 75%; p < 0.05) was significantly improved in a PVAX nanoparticles-treated group compared with vehicle treated groups. Taken together, we anticipate that PVAX nanoparticles could be a highly specific and potent treatment modality in DOX-induced cardiac and hepatic toxicity. PMID:24767791

Park, Seunggyu; Yoon, Jooheung; Bae, Soochan; Park, Minhyung; Kang, Changsun; Ke, Qingen; Lee, Dongwon; Kang, Peter M

2014-07-01

172

Phase transformation behavior of thin shape memory alloy wires embedded in a polymer matrix composite  

Microsoft Academic Search

Shape memory alloy composites (SMA-composites) are adaptive materials, whose external shape or mechanical properties can be controlled by the activation of embedded SMA actuators. While considerable information is now available on the structural, mechanical and functional behavior of plain SMAs, nearly nothing is known about embedded SMAs. However, the characteristics of the matrix, and its viscoelastic properties in particular, can

J.-E. BIDAUX; L. BATAILLARD; R. GO' ITHARDT; R. GOTTHARDT

1993-01-01

173

Flexible non-volatile ferroelectric polymer memory with gate-controlled multilevel operation.  

PubMed

A flexible field-effect transistor with a poly(3-hexylthiophene) (P3HT) active channel and a ferroelectric poly(vinlyidene fluoride-co-trifluoro ethylene) (PVDF-TrFE) insulator exhibits gate-voltage-controllable multilevel non-volatile memory characteristics with highly reliable data retention and endurance. PMID:22887686

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

2012-11-20

174

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

175

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

176

Small-angle neutron scattering from polymer hydrogels with memory effect for medicine immobilization  

SciTech Connect

Hydrogels synthesized based on cross-linked copolymers of 2-hydroxyethyl methacrylate and functional monomers (acrylic acid or dimethylaminoethyl methacrylate), having a memory effect with respect to target medicine (cefazolin), have been investigated by small-angle neutron scattering. The hydrogels are found to have a two-level structural organization: large (up to 100 nm) aggregates filled with network cells (4-7 nm in size). The structural differences in the anionic, cationic, and amphiphilic hydrogels and the relationship between their structure and the ability of hydrogels to absorb moisture are shown. A relationship between the memory effect during cefazolin immobilization and the internal structure of hydrogels, depending on their composition and type of functional groups, is established.

Kulvelis, Yu. V., E-mail: kulvelis@pnpi.spb.ru; Lebedev, V. T.; Trunov, V. A. [Russian Academy of Sciences, Orlova roshcha, Konstantinov Nuclear Physics Institute (Russian Federation); Pavlyuchenko, V. N. [Kirov Military Medical Academy (Russian Federation); Ivanchev, S. S.; Primachenko, O. N.; Khaikin, S. Ya. [Boreskov Institute of Catalysis, St. Petersburg Branch (Russian Federation)

2011-12-15

177

A general approach towards thermoplastic multishape-memory polymers via sequence structure design.  

PubMed

The chain sequence of a poly(styrene-co-methyl acrylate) copolymer is designed to form a V-shaped gradient sequence via controlled/living radical emulsion copolymerization. This specially designed chain sequence gives this common copolymer the capacity of multishape memory. The copolymer can sequentially recover to its permanent shape from three or more previously programmed temporary shapes with the stimulus of temperature. PMID:23108904

Luo, Yingwu; Guo, Yunlong; Gao, Xiang; Li, Bo-Geng; Xie, Tao

2013-02-01

178

Deformation Behavior of NiTi\\/Polymer Shape Memory Alloy Composites – Experimental Verifications  

Microsoft Academic Search

Composites containing NiTi shape memory alloy (SMA) long-fiber, short-fibers or Ti long-fiber in a Polycarbonate (PC) matrix have been fabricated by the injection molding technique. Also, prestrained SMA long-fiber\\/Epoxy matrix composites have been fabricated. The fracture behavior and thermo-mechanical deformation behavior are examined; (1) Fracture behavior – uniaxial tensile tests up to fracture for SMA long-fiber and short-fiber composite (SMAC).

Go Murasawa; Keiichiro Tohgo; Hitoshi Ishii

2004-01-01

179

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

180

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

NASA Astrophysics Data System (ADS)

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.

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

2008-05-01

181

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

182

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

183

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

NASA Astrophysics Data System (ADS)

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 the 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 5 h or to 125 °C for up to 24 h if stabilized with 10,000 ppm BQ and could also be heated to 125 °C for up to 5 h 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.

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

2013-02-01

184

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

185

Memory effect in the current-voltage characteristic of a low-band gap conjugated polymer  

NASA Astrophysics Data System (ADS)

Diodes formed by electrodeposition of the low-band gap polymer poly(4-dicyano methylene-4H-cyclopenta[2,1-b:3,4-b']dithiophene), onto glass slides coated with indium tin oxide (ITO) and furnished with evaporated aluminum counterelectrodes exhibit a reversible bistability in their current-voltage (I-V) characteristics. Applying +5 V to the ITO electrode induces a ``high'' conductance state while applying -5 V induces a ``low'' conductance state. The effect is identical in most respects to recent observations in diodes formed from thin films of chromium-doped SrZrO3 sandwiched between SrRuO3 and gold electrodes. A number of mechanisms are discussed but the evidence points to the controlling influence of an interfacial depletion layer at the ITO-polymer interface. It is also shown that the high capacitances associated with such layers can lead to higher than expected displacement currents being generated during the automated collection of I-V data. The presence of such currents distorts the I-V characteristics in the low-bias low-current regime.

Taylor, D. M.; Mills, C. A.

2001-07-01

186

Degree of Vertical Integration Between the Undergraduate Program and Clinical Internship With Respect to Cervical and Cranial Diagnostic and Therapeutic Procedures Taught at the Canadian Memorial Chiropractic College  

PubMed Central

Objective: The purpose of this study was to determine if diagnostic and therapeutic procedures for the cervical and cranial spine taught to students during the undergraduate program at Canadian Memorial Chiropractic College are required to be used during their internship by their supervising clinicians and, if so, to what extent these procedures are used. Methods: Course manuals and course syllabi from the Applied Chiropractic and Clinical Diagnosis faculty of the undergraduate chiropractic program for the academic year 2009–2010 were consulted and a list of all diagnostic and therapeutic procedures for the cranial and cervical spine was compiled. This survey asked clinicians to indicate if they themselves used or if they required the students they were supervising to use each procedure listed and, if so, to what extent each procedure was used. Demographic information of each clinician was also obtained. Results: In general, most diagnostic procedures of the head and neck were seldom used, with the exception of postural observation and palpation. By contrast, most cervical orthopaedic tests were often used, with the exception of tests for vertigo. Most therapeutic procedures were used frequently with the exception of prone cervical and “muscle” adjustments. Conclusion: There was a low degree of vertical integration for cranial procedures as compared to a much higher degree of vertical integration for cervical procedures between the undergraduate and clinical internship programs taught. Vertical integration is an important element of curricular planning and these results may be helpful to aid educators to more appropriately allocate classroom instruction

Leppington, Charmody; Gleberzon, Brian; Fortunato, Lisa; Doucet, Nicolea; Vandervalk, Kyle

2012-01-01

187

Conductance quantization in a Ag filament-based polymer resistive memory.  

PubMed

Resistive switching and conductance quantization are systematically studied in a Ag/poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester/indium-tin oxide sandwich structure. The observed bipolar switching behavior can be attributed to the formation and dissolution of Ag filaments during positive and negative voltage sweeps, respectively. More importantly, conductance quantization with both integer and half integer multiples of single atomic point contact can be realized by slowing down the voltage sweep speed as well as by pulse measurement. The former may reflect the formed Ag filaments with different atomic point contacts, while the latter probably originates from the interaction between the Ag filaments and the elemental hydrogen provided by the organic storage medium. With appropriate current compliances, low resistance states with desired quantized conductance values are successfully achieved, thus showing the potential for ultrahigh density memory applications. Besides, 100 successive switching cycles with densely distributed resistance values of each resistance state and extrapolated retention properties over ten years are also demonstrated. PMID:23893907

Gao, Shuang; Zeng, Fei; Chen, Chao; Tang, Guangsheng; Lin, Yisong; Zheng, Zifeng; Song, Cheng; Pan, Feng

2013-08-23

188

Conductance quantization in a Ag filament-based polymer resistive memory  

NASA Astrophysics Data System (ADS)

Resistive switching and conductance quantization are systematically studied in a Ag/poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester/indium-tin oxide sandwich structure. The observed bipolar switching behavior can be attributed to the formation and dissolution of Ag filaments during positive and negative voltage sweeps, respectively. More importantly, conductance quantization with both integer and half integer multiples of single atomic point contact can be realized by slowing down the voltage sweep speed as well as by pulse measurement. The former may reflect the formed Ag filaments with different atomic point contacts, while the latter probably originates from the interaction between the Ag filaments and the elemental hydrogen provided by the organic storage medium. With appropriate current compliances, low resistance states with desired quantized conductance values are successfully achieved, thus showing the potential for ultrahigh density memory applications. Besides, 100 successive switching cycles with densely distributed resistance values of each resistance state and extrapolated retention properties over ten years are also demonstrated.

Gao, Shuang; Zeng, Fei; Chen, Chao; Tang, Guangsheng; Lin, Yisong; Zheng, Zifeng; Song, Cheng; Pan, Feng

2013-08-01

189

Treatment with targeted vesicular stomatitis virus generates therapeutic multifunctional anti-tumor memory CD4 T cells  

Microsoft Academic Search

A generally applicable, easy-to-use method of focusing a patient's immune system to eradicate or prevent cancer has been elusive. We are attempting to develop a targeted virus to accomplish these aims. We previously created a recombinant replicating vesicular stomatitis virus (VSV) that preferentially infected Her2\\/neu expressing breast cancer cells and showed therapeutic efficacy in an implanted Balb\\/c mouse tumor model.

Y Gao; P Whitaker-Dowling; J A Griffin; I Bergman

2012-01-01

190

Facile fabrication of uniaxial nanopatterns on shape memory polymer substrates using a complete bottom-up approach  

NASA Astrophysics Data System (ADS)

In earlier work, we have demonstrated an assisted self-assembly fabrication method for unidirectional submicron patterns using pre-programmed shape memory polymers (SMP) as the substrate in an organic/inorganic bilayer structure. In this paper, we propose a complete bottom-up method for fabrication of uniaxial wrinkles whose wavelength is below 300 nm. The method starts with using the aforementioned self-assembled bi-layer wrinkled surface as the template to make a replica of surface wrinkles on a PDMS layer which is spin-coated on a pre-programmed SMP substrate. When the shape recovery of the substrate is triggered by heating it to its transition temperature, the substrate has been programmed in such a way that it shrinks uniaxially to return to its permanent shape. Consequently, the wrinkle wavelength on PDMS reduces accordingly. A subsequent contact molding process is carried out on the PDMS layer spin-coated on another pre-programmed SMP substrate, but using the wrinkled PDMS surface obtained in the previous step as the master. By activating the shape recovery of the substrate, the wrinkle wavelength is further reduced a second time in a similar fashion. Our experiments showed that the starting wavelength of 640 nm decreased to 290 nm after two cycles of recursive molding. We discuss the advantages and limitations of our recursive molding approach compared to the prevalent top-down fabrication methods represented by lithography. The present study is expected to o er a simple and cost-e ective fabrication method of nano-scale uniaxial wrinkle patterns with the potential for large-scale mass-production.

Chen, Zhongbi; Krishnaswamy, Sridhar

2014-03-01

191

A low switching voltage organic-on-inorganic heterojunction memory element utilizing a conductive polymer fuse on a doped silicon substrate  

NASA Astrophysics Data System (ADS)

We present a simple, nonvolatile, write-once-read-many-times (WORM) memory device utilizing an organic-on-inorganic heterojunction (OI-HJ) diode with a conductive polymer fuse consisting of polyethylene dioxythiophene:polysterene sulfonic acid (PEDOT:PSS) forming one side of the rectifying junction. Current transients are used to change the fuse from a conducting to a nonconducting state to record a logical ``1'' or ``0'', while the nonlinearity of the OI-HJ allows for passive matrix memory addressing. The device switches at 2 and 4 V for 50 nm thick PEDOT:PSS films on p-type Si and n-type Si, respectively. This is significantly lower than the switching voltage used in PEDOT:PSS/p-i-n Si memory elements [J. Appl Phys. 94, 7811 (2003)]. The switching results in a permanent reduction of forward-bias current by approximately five orders of magnitude. These results suggest that the OI-HJ structure has potential for use in low-cost passive matrix WORM memories for archival storage applications.

Smith, Shawn; Forrest, Stephen R.

2004-06-01

192

Fabrication and characterization of a foamed polylactic acid (PLA)/ thermoplastic polyurethane (TPU) shape memory polymer (SMP) blend for biomedical and clinical applications  

NASA Astrophysics Data System (ADS)

Shape memory polymers (SMP) are a class of stimuli-responsive materials that are able to respond to external stimulus such as heat by altering their shape. Bio-compatible SMPs have a number of advantages over static materials and are being studied extensively for biomedical and clinical applications (such as tissue stents and scaffolds). A previous study has demonstrated that the bio-compatible polymer blend of polylactic acid (PLA)/ thermoplastic polyurethane (TPU) (50/50 and 70/30) exhibit good shape memory properties. In this study, the mechanical and thermo-mechanical (shape memory) properties of TPU/PLA SMP blends were characterized; the compositions studied were 80/20, 65/35, and 50/50 TPU/PLA. In addition, porous TPU/PLA SMP blends were fabricated with a gas-foaming technique; and the morphology of the porous structure of these SMPs foams were characterized with scanning electron microscopy (SEM). The TPU/PLA bio-compatible SMP blend was fabricated with melt-blending and compression molding. The glass transition temperature (Tg) of the SMP blends was determined with a differential scanning calorimeter (DSC). The mechanical properties studied were the stress-strain behavior, tensile strength, and elastic modulus; and the thermomechanical (or shape memory) properties studied were the shape fixity rate (Rf), shape recovery rate (Rr), response time, and the effect of recovery temperature on Rr. The porous 80/20 PLA/TPU SMP blend was found to have the highest tensile strength, toughness and percentage extension, as well as the lowest density and uniform pore structure in the micron and submicron scale. The porous 80/20 TPU/PLA SMP blend may be further developed for specific biomedical and clinical applications where a combination of tensile strength, toughness, and low density are required.

Song, Janice J.; Srivastava, Ijya; Kowalski, Jennifer; Naguib, Hani E.

2014-03-01

193

Shape-memory behavior of poly (methyl methacrylate-co –N-vinyl-2-pyrrolidone) \\/ poly (ethylene glycol) semi-interpenetrating polymer networks based on hydrogen bonding  

Microsoft Academic Search

Based on hydrogen bonding interactions, Poly(methyl methacrylate-co-N-vinyl-2-pynolidone) (P(MMA-co-VP)) networks and linear\\u000a poly(ethylene glycol) (PEG) can form semi-interpenetrating polymer networks (semi-IPNs), i.e. P(MMA-co-VP)\\/PEG semi-IPNs,\\u000a which has shape memory behaviour; its maximum storage modulus ratio can be more than 400, and its shape recovery ratio could\\u000a reach 99%. The morphology, thermal behaviors and dynamic mechanical properties of P(MMA-co-VP)\\/PEG semi-IPNs were studied\\u000a by

Guoqin Liu; Weichun He; Yuxing Peng; Hesheng Xia

194

Randomly addressable read\\/write\\/erase holographic memory system based on a dye-polymer recording medium  

Microsoft Academic Search

With a potential of up to 1012 bits\\/cm3, storage medium based on volume holographic memory can be the next generation of optical memory systems. However, any storage media for holographic memory must have large reflective index modulation, large available volume material while simultaneously preserving high response speed and low crosstalk. Photorefractive crystals, such as LiNbO3, SBN, and BaTiO3, are the

Shudong Wu; Jenkin C. Chen; Peter W. Low; Freddie S. Lin

1992-01-01

195

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.

196

Therapeutic and Prognostic Value of Modal Number of Chromosomes at the Blastic Phase of Philadelphia-Chromosome-Positive Chronic Myeloid Leukemia: Comparison Based on the Same Criteria between Nagasaki University and Roswell Park Memorial Institute  

Microsoft Academic Search

In a comparison of 47 patients with Philadelphia-chromosome (Ph)-positive chronic myeloid leukemia (CML) in the Nagasaki University School of Medicine and 64 patients with the same disease in the Roswell Park Memorial Institute, the correlation between the modal number of chromosomes and the therapeutic response and\\/or survival after the onset of the blastic phase (BP) was evaluated. The patients were

Naoki Sadamori; Ei-ichi Yao; Mariko Mine; Seiji Tokunaga; Masako Matsunaga; Hideo Nakamura; Ippei Sasagawa; Takahiro Itoyama; Toshihisa Hayashibara; Avery A. Sandberg

1992-01-01

197

Stress-induced melting of crystals in natural rubber: a new way to tailor the transition temperature of shape memory polymers.  

PubMed

Lightly cross-linked natural rubber (NR, cis-1,4-polyisoprene) was found to be an exceptional cold programmable shape memory polymer (SMP) with strain storage of up to 1000%. These networks are stabilized by strain-induced crystals. Here, we explore the influence of mechanical stress applied perpendicular to the elongation direction of the network on the stability of these crystals. We found that the material recovers its original shape at a critical transverse stress. It could be shown that this is due to a disruption of the strain-stabilizing crystals, which represents a completely new trigger for SMPs. The variation of transverse stress allows tuning of the trigger temperature T(trig) (?) in a range of 45 to 0 °C, which is the first example of manipulating the transition of a crystal-stabilized SMP after programming. PMID:22760997

Heuwers, Benjamin; Quitmann, Dominik; Katzenberg, Frank; Tiller, Joerg C

2012-09-26

198

Physical ageing of a PU-based shape memory polymer: Influence on their applicability to the development of medical devices  

Microsoft Academic Search

The variation in the properties of polymeric materials through ageing has considerable implications, since it affects the performance of any associated devices. Specially in the case of implantable devices with shape memory, any change in the switching temperature can give rise to problems in the thermal activation of the geometrical changes necessary to treat certain pathologies.This paper presents a study

V. Lorenzo; A. Díaz-Lantada; P. Lafont; H. Lorenzo-Yustos; C. Fonseca; J. Acosta

2009-01-01

199

Memory effect of a polymer thin-film transistor with self-assembled gold nanoparticles in the gate dielectric  

Microsoft Academic Search

A self-assembled film of gold nanoparticles is integrated into the gate dielectric of an organic thin-film transistor to produce memory effects. The transistor is fabricated on a heavily doped n-type silicon (n+-Si) substrate with a thermally grown oxide layer of 100 nm thick. n+-Si serves as the gate electrode while the oxide layer functions as the gate dielectric. Gold nanoparticles

Zhengchun Liu; Fengliang Xue; Y. Su; Y. M. Lvov; K. Varahramyan

2006-01-01

200

Chemical reversability of the electrical dedoping of conducting polymers: An organic chemically erasable programmable read-only memory  

Microsoft Academic Search

The loss of electronic conductivity of p-doped poly(3,4-ethylenedioxythiophene) at high electrical bias is shown to be chemically reversible upon redoping with iodine vapor. This provides further confirmation that the initial loss of conductivity arises from the injection-induced dedoping mechanism. Repeat “write-erase” cycles are possible, which gives a rudimentary organic chemically erasable programmable read-only memory. Transient measurements show that the write

Perq-Jon Chia; Yee-Chia Yeo; Jeremy H. Burroughes; Richard H. Friend; Peter K.-H. Ho

2008-01-01

201

Chemical reversability of the electrical dedoping of conducting polymers: An organic chemically erasable programmable read-only memory  

Microsoft Academic Search

The loss of electronic conductivity of p-doped poly(3,4-ethylenedioxythiophene) at high electrical bias is shown to be chemically reversible upon redoping with iodine vapor. This provides further confirmation that the initial loss of conductivity arises from the injection-induced dedoping mechanism. Repeat ``write-erase'' cycles are possible, which gives a rudimentary organic chemically erasable programmable read-only memory. Transient measurements show that the write

Perq-Jon Chia; Yee-Chia Yeo; Jeremy H. Burroughes; Richard H. Friend; Peter K.-H. Ho

2008-01-01

202

Nitrogen-doped, boron-doped and undoped multiwalled carbon nanotube/polymer composites in WORM memory devices  

NASA Astrophysics Data System (ADS)

We report the preparation of write-once-read-many times memory devices using composites of carbon nanotubes and poly(vinyl phenol) sandwiched between Al electrodes. Three types of nanotubes (undoped multiwalled carbon nanotubes, nitrogen-doped multiwalled carbon nanotubes and boron-doped multiwalled carbon nanotubes) are investigated for this application. The OFF to ON state switching threshold is only slightly dependent on nanotube type, but the ON/OFF current ratio depends on both nanotube type and concentration and varies up to 106, decreasing for nanotube concentrations larger than 0.50 wt% in the composite.

Mamo, Messai A.; Sustaita, Alan O.; Tetana, Zikhona N.; Coville, Neil J.; Hümmelgen, Ivo A.

2013-03-01

203

Building a better hormone therapy?: How understanding the rapid effects of sex steroid hormones could lead to new therapeutics for age-related memory decline  

PubMed Central

A wealth of data collected in recent decades has demonstrated that ovarian sex-steroid hormones, particularly 17?-estradiol (E2), are important trophic factors that regulate the function of cognitive regions of the brain such as the hippocampus. The loss of hormone cycling at menopause is associated with cognitive decline and dementia in women, and the onset of memory decline in animal models. However, hormone therapy is not currently recommended to prevent or treat cognitive decline, in part because of its detrimental side effects. In this article, it is proposed that investigations of the rapid effects of E2 on hippocampal function be used to further the design of new drugs that mimic the beneficial effects of E2 on memory without the side effects of current therapies. A conceptual model is presented for elucidating the molecular and biochemical mechanisms through which sex-steroid hormones modulate memory, and a specific hypothesis is proposed to account for the rapid memory-enhancing effects of E2. Empirical support for this hypothesis is discussed as a means of stimulating the consideration of new directions for the development of hormone-based therapies to preserve memory function in menopausal women.

Frick, Karyn M.

2012-01-01

204

Exploration of use of SenseCam to support autobiographical memory retrieval within a cognitive-behavioural therapeutic intervention following acquired brain injury.  

PubMed

Delivering effective psychotherapy to address the significant emotional consequences of acquired brain injury (ABI) is challenged by the presence of acquired cognitive impairments, especially retrieval of detailed autobiographical memories of emotional trigger events. Initial studies using a wearable camera (SenseCam) suggest long-term improvements in autobiographical retrieval of recorded events. In this study a single-case experimental design was implemented to explore the use of SenseCam as a memory aid for a man with a specific anxiety disorder and memory and executive difficulties following ABI. We predicted that SenseCam supported rehearsal of memories of events that trigger high levels of anxiety would yield improved retrieval of both factual detail and internal state information (thoughts and feelings) compared with a conventional psychotherapy aid (automatic thought record sheets, ATRs) and no strategy. The findings indicated SenseCam supported retrieval of anxiety trigger events was superior to ATRs or no strategy in terms of both detail and internal state information, with 94% of the information being recalled in the SenseCam condition, compared to 39% for the "no strategy" and 22% for the ATR conditions. It is concluded that SenseCam may be of use as a compensatory aid in psychotherapies relying on retrieval of emotionally salient trigger events. PMID:20635299

Brindley, Rob; Bateman, Andrew; Gracey, Fergus

2011-10-01

205

Psychotherapy and Memories of Childhood Sexual Abuse.  

ERIC Educational Resources Information Center

This conference address examines the question of whether "memory work"--using therapeutic techniques to help clients recover suspected hidden memories of childhood sexual abuse--has led some clients to develop illusory memories or false beliefs. Prospective research on memory for childhood trauma indicates that the gist of traumatic childhood…

Lindsay, D. Stephen

206

Integrating a novel shape memory polymer into surgical meshes decreases placement time in laparoscopic surgery: an in vitro and acute in vivo study.  

PubMed

About 600,000 hernia repair surgeries are performed each year; recently, 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 study, 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. Results indicate surgical mesh modified with SMP is capable of laparoscopic deployment in vivo, activated by body temperature. This suggests a reduction in surgical operating time and improved mesh placement characteristics is possible with SMP-integrated surgical meshes. PMID:23412974

Zimkowski, Michael M; Rentschler, Mark E; Schoen, Jonathan; Rech, Bryan A; Mandava, Nageswara; Shandas, Robin

2013-09-01

207

"Only Connect"--A Sexually Abused Girl's Rediscovery of Memory and Meaning as She Works towards the Transition from a Therapeutic Community to a Foster-Family  

ERIC Educational Resources Information Center

This paper looks at the role of individual psychotherapy with a severely sexually abused girl in a therapeutic community, and the place of this work as she makes the transition into foster-care. It emphasizes the importance, not only of the individual work, but also of the drawing together of the work around the child, particularly at such a…

Cant, Diana

2005-01-01

208

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

209

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

210

Learning and memory.  

PubMed

Learning and memory functions are crucial in the interaction of an individual with the environment and involve the interplay of large, distributed brain networks. Recent advances in technologies to explore neurobiological correlates of neuropsychological paradigms have increased our knowledge about human learning and memory. In this chapter we first review and define memory and learning processes from a neuropsychological perspective. Then we provide some illustrations of how noninvasive brain stimulation can play a major role in the investigation of memory functions, as it can be used to identify cause-effect relationships and chronometric properties of neural processes underlying cognitive steps. In clinical medicine, transcranial magnetic stimulation may be used as a diagnostic tool to understand memory and learning deficits in various patient populations. Furthermore, noninvasive brain stimulation is also being applied to enhance cognitive functions, offering exciting translational therapeutic opportunities in neurology and psychiatry. PMID:24112934

Brem, Anna-Katharine; Ran, Kathy; Pascual-Leone, Alvaro

2013-01-01

211

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 30min 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

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

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.

Gkikas, Ilias; Petratou, Dionysia; Tavernarakis, Nektarios

2014-01-01

214

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

215

[Memory systems and memory disorders].  

PubMed

Recent cognitive models suggest that memory has a complex structure, composed of several independent systems (working memory, and four long-term memory systems: episodic memory, semantic memory, perceptual representation system, and procedural memory). Furthermore, neuropsychological studies show that a brain lesion can selectively impair some systems or some particular process in a system, while others are spared. In this theoretical context, the objective of assessment is to detect the impaired memory systems and processes as well as those, which remain intact. To do this, the clinician has to use various-tests specifically designed to assess the integrity of each memory system and process. PMID:12708274

Van der Linden, Martial; Juillerat, Anne-Claude

2003-02-15

216

Augmentation of therapeutic efficacy in drug-resistant tumor models using ceramide coadministration in temporal-controlled polymer-blend nanoparticle delivery systems.  

PubMed

The development of multidrug resistance (MDR) is a major hindrance to cancer eradication as it renders tumors unresponsive to most chemotherapeutic treatments and is associated with cancer resurgence. This study describes a novel mechanism to overcome MDR through a polymer-blend nanoparticle platform that delivers a combination therapy of C6-ceramide (CER), a synthetic analog of an endogenously occurring apoptotic modulator, together with the chemotherapeutic drug paclitaxel (PTX), in a single formulation. The PTX/CER combination therapy circumvents another cellular mechanism whereby MDR develops, by lowering the threshold for apoptotic signaling. In vivo studies in a resistant subcutaneous SKOV3 human ovarian and in an orthotopic MCF7 human breast adenocarcinoma xenograft showed that the PTX and CER nanoparticle combination therapy reduced the final tumor volume at least twofold over treatment with the standard PTX therapy alone. The study also revealed that the cotherapy accomplished this enhanced efficacy by generating an enhancement in apoptotic signaling in both tumor types. Additionally, acute evaluation of safety with the combination therapy did not show significant changes in body weight, white blood cell counts, or liver enzyme levels. The temporal-controlled nanoparticle delivery system presented in this study allows for a simultaneous delivery of PTX + CER in breast and ovarian tumor model drug, leading to a modulation of the apoptotic threshold. This strategy has tremendous potential for effective treatment of refractory disease in cancer patients. PMID:20143195

van Vlerken, Lilian E; Duan, Zhenfeng; Little, Steven R; Seiden, Michael V; Amiji, Mansoor M

2010-06-01

217

Therapeutic cells via functional modification: influence of molecular properties of polymer grafts on in vivo circulation, clearance, immunogenicity, and antigen protection.  

PubMed

Modulation of cell surface properties via functional modification is of great interest in cell-based therapies, drug delivery, and in transfusion. We study the in vivo circulation, immuogenicity, and mechanism of clearance of hyperbranched polyglycerol (HPG)-modified red blood cells (RBCs) as a function of molecular properties of HPGs. The circulation half-life of modified cells can be modulated by controlling the polymer graft concentration on RBCs; low graft concentrations (0.25 and 0.5 mM) showed normal circulation as that of control RBCs. Molecular weight of HPG did not affect the circulation of modified RBCs. HPG grafting on RBCs reduced CD47 self-protein accessibility in a graft concentration-dependent fashion. HPG-grafted RBCs are not immunogenic, as is evident from their similar circulation profile upon repeated administration in mice and monitoring over 100 days. Histological examination of the spleen, liver, and kidneys of the mice injected with modified RBCs revealed distinct differences, such as elevated iron deposits and an increase in the number of CD45 expressing cells at high graft concentration of HPGs (1.5 mM); no changes were seen at low graft concentration. The absence of iron deposits in the white pulp region of the spleen and its presence in the red pulp region indicates that the clearance of functional RBCs occurs in the venous sinuses mechanical filtering system, similar to the clearance of unmodified senescent RBCs. HPG modification at grafting concentrations that yield long circulation in mice produced camouflage of a large number of minor blood group antigens on human RBCs, demonstrating its utility in chronic transfusion. The normal circulation, nonimmunogenic nature, and the potential to modulate the circulation time of modified cells without toxicity make this HPG-based cell surface modification approach attractive for drug delivery and other cell-based therapies. PMID:23713758

Chapanian, Rafi; Constantinescu, Iren; Medvedev, Nadia; Scott, Mark D; Brooks, Donald E; Kizhakkedathu, Jayachandran N

2013-06-10

218

Environmental Enrichment: Aging and Memory  

PubMed Central

A decline in learning and memory is a feature of the normal aging process and associated with neurodegenerative diseases such as dementia and Alzheimer’s disease. Moreover, certain forms of dementia and memory loss are inevitable due to the normal aging process. The unavoidable effect of age on memory is an ongoing study, as the findings assist in identifying cortical functions of the brain. Histone acetylation is a mechanism in synaptic plasticity and a key function in learning and memory because changes within the process alter gene transcription and the quantity of synthesized proteins. Similar to histone acetylation, environmental enrichment has also been found to improve memory formation by stimulating synaptic plasticity. Through understanding the mechanisms by which environmental enrichment and histone acetylation interact in the brain and affect learning and memory, novel applications can be developed for therapeutic interventions to neurodegenerative diseases and aging.

Patel, Toral Rohit

2012-01-01

219

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

220

Polymer Concretes.  

National Technical Information Service (NTIS)

A review of the uses of polmers in concretes was carried out, including: polymer concretes such as impregnated composites, premixed polymer concretes and polymer bound aggregates; concretes which have solid, water soluble or dispersed polymers added to th...

1975-01-01

221

Rewritable holographic memory card system  

Microsoft Academic Search

The new rewritable holographic memory card (HMC) of Optilink provides a novel solution for high density optical storage of personal data. In contrast to most holographic storage systems using highly multiplexed transmissive volume holograms in bulk materials, our approach is adapted to the card format using a polymer thin film holographic storage material, operating in reflection mode, allowing writing and

E. Lorincz; P. Koppa; F. Ujhelyi; P. I. Richter; G. Szarvas; Gabor Erdei; P. S. Ramanujam

2000-01-01

222

Working Memory  

Microsoft Academic Search

The term working memory refers to a brain system that provides temporary storage and manipulation of the information necessary for such complex cognitive tasks as language comprehension, learning, and reasoning. This definition has evolved from the concept of a unitary short-term memory system. Working memory has been found to require the simultaneous storage and processing of information. It can be

Alan Baddeley

1992-01-01

223

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

224

Present and Future of PLA Polymers  

Microsoft Academic Search

Lactic acid-based aliphatic polyesters (PLAs) are well known biocompatible bioresorbable polymers which are being increasingly used as biomaterials for temporary therapeutic applications. Because of their sensitivity to water and the formation of degradation by-products which can be easily metabolized by microorganisms, this type of polymers also has potential to replace commodity polymers in packagings or as mulch films. From an

M. Vert; G. Schwarch; J. Coudane

1995-01-01

225

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

226

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

227

THERAPEUTIC PERSPECTIVE  

PubMed Central

Unless proper perspective is maintained in medical therapeutics, a physician in his earnest desire to cure disease may often use measures which may ultimately cause more damage than the disease being treated. In order to avoid loss of perspective, it is necessary to balance the known consequences of the disease against the expected benefits of the treatment minus the known hazards of the treatment.

Scholtz, Jud R.; Williamson, Craig

1951-01-01

228

Glycobiology: drifting toward polymer perfection.  

PubMed

The addition of polysialic acid to proteins and cells is emerging as a promising therapeutic strategy. Polysialyltransferases synthesize polymers of widely varying lengths not optimal for therapeutic reagents, but the development of enzyme variants using neutral genetic drift offers a new way to overcome this problem. PMID:24727902

Colley, Karen J

2014-06-01

229

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

230

Influence of cross-linking degree on shape memory effect of styrene copolymer  

Microsoft Academic Search

This paper is concerned about the synthesis of shape memory styrene copolymer and the investigation of the influence of cross-linking degree on its shape memory effect. As one of novel actuators in smart materials, shape memory polymers (SMPs) have been investigated intensively. Styrene copolymer with proper cross-linking degree can exhibit shape memory effect (SME). In this paper, the influence of

Dawei Zhang; Xin Lan; Yanju Liu; Jinsong Leng

2007-01-01

231

Cholinesterase inhibitors and memory.  

PubMed

A consensus exists that cholinesterase inhibitors (ChEIs) are efficacious for mild to moderate Alzheimer's Disease (AD). Unfortunately, the number of non-responders is large and the therapeutic effect is usually short-lasting. In experimental animals, ChEIs exert three main actions: inhibit cholinesterase (ChE), increase extracellular levels of brain acetylcholine (ACh), improve cognitive processes, particularly when disrupted in models of AD. In this overview we shall deal with the cognitive processes that are improved by ChEI treatment because they depend on the integrity of brain cholinergic pathways and their activation. The role of cholinergic system in cognition can be investigated using different approaches. Microdialysis experiments demonstrate the involvement of the cholinergic system in attention, working, spatial and explicit memory, information encoding, sensory-motor gating, skill learning. No involvement in long-term memory has yet been demonstrated. Conversely, memory consolidation is facilitated by low cholinergic activity. Experiments on healthy human subjects, notwithstanding caveats concerning age, dose, and different memory tests, confirm the findings of animal experiments and demonstrate that stimulation of the cholinergic system facilitates attention, stimulus detection, perceptual processing and information encoding. It is not clear whether information retrieval may be improved but memory consolidation is reduced by cholinergic activation. ChEI effects in AD patients have been extensively investigated using rating scales that assess cognitive and behavioural responses. Few attempts have been made to identify which scale items respond better to ChEIs and therefore, presumably, depend on the activity of the cholinergic system. Improvement in attention and executive functions, communication, expressive language and mood stability have been reported. Memory consolidation and retrieval may be impaired by high ACh levels. Therefore, considering that in AD the degeneration of the cholinergic system is associated with alteration of other neurotransmitter systems and a diffuse synaptic loss, a limited efficacy of ChEIs on memory processes should be expected. PMID:19941841

Pepeu, Giancarlo; Giovannini, Maria Grazia

2010-09-01

232

Poor working memory predicts false memories  

Microsoft Academic Search

Two studies investigated whether individual differences in simple span verbal working memory and complex working memory capacity are related to memory accuracy and susceptibility to false memory development. In Study 1, undergraduate students (N=60) were given two simple span working memory tests: forward and backward digit span. They also underwent a memory task that is known to elicit false memories

Maarten J. V. Peters; Marko Jelicic; Hilde Verbeek; Harald Merckelbach

2007-01-01

233

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

234

Neurocognitive correlates of therapeutic alliance in schizophrenia.  

PubMed

Although therapeutic alliance in schizophrenia has been linked with treatment adherence and outcome, less is known about its clinical correlates. This study explored neurocognition as a possible predictor of perceived therapeutic alliance among people with schizophrenia in cognitive behavior therapy. Twenty-four participants with schizophrenia spectrum disorders and their therapists were administered the Working Alliance Inventory, Short Form after 3 months of therapy. Totals for clients and therapists were correlated with measures of verbal memory, premorbid intelligence, visual spatial reasoning, executive function, and attention, all obtained before beginning therapy. Poorer performance on verbal memory was significantly related to client report of stronger alliance, whereas better performance on visual spatial reasoning was significantly related to therapist report of stronger alliance. Client and therapist ratings of therapeutic alliance were significantly and positively related. Clients' abilities may differentially affect therapist and client perception of therapeutic alliance in schizophrenia. PMID:15232322

Davis, Louanne W; Lysaker, Paul H

2004-07-01

235

Episodic Memories in Anxiety Disorders: Clinical Implications  

PubMed Central

The aim of this review is to summarize research on the emerging role of episodic memories in the context of anxiety disorders (AD). The available literature on explicit, autobiographical, and episodic memory function in AD including neuroimaging studies is critically discussed. We describe the methodological diversity of episodic memory research in AD and discuss the need for novel tests to measure episodic memory in a clinical setting. We argue that alterations in episodic memory functions might contribute to the etiology of AD. We further explain why future research on the interplay between episodic memory function and emotional disorders as well as its neuroanatomical foundations offers the promise to increase the effectiveness of modern psychological treatments. We conclude that one major task is to develop methods and training programs that might help patients suffering from AD to better understand, interpret, and possibly actively use their episodic memories in a way that would support therapeutic interventions and counteract the occurrence of symptoms.

Zlomuzica, Armin; Dere, Dorothea; Machulska, Alla; Adolph, Dirk; Dere, Ekrem; Margraf, Jurgen

2014-01-01

236

Epigenetic memory: the Lamarckian brain.  

PubMed

Recent data support the view that epigenetic processes play a role in memory consolidation and help to transmit acquired memories even across generations in a Lamarckian manner. Drugs that target the epigenetic machinery were found to enhance memory function in rodents and ameliorate disease phenotypes in models for brain diseases such as Alzheimer's disease, Chorea Huntington, Depression or Schizophrenia. In this review, I will give an overview on the current knowledge of epigenetic processes in memory function and brain disease with a focus on Morbus Alzheimer as the most common neurodegenerative disease. I will address the question whether an epigenetic therapy could indeed be a suitable therapeutic avenue to treat brain diseases and discuss the necessary steps that should help to take neuroepigenetic research to the next level. PMID:24719207

Fischer, Andre

2014-05-01

237

Memory Makers  

Microsoft Academic Search

When predicting application performance, allocating re- sources, and scheduling jobs, an accurate estimate of the required resources is essential. Although CPU and disk performance is relatively well understood, memory perfor- mance is often ignored or considered constant. Our re- search shows that memory bandwidth can vary by up to two orders of magnitude depending upon access pattern, read\\/write ratio, and

Tim Kaldewey; Andrea Di Blas; Jeff Hagen; Eric Sedlar; Scott Brandt

1998-01-01

238

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

239

Distributed Memory.  

National Technical Information Service (NTIS)

A brief account is given of how a neural network can store a distributed content addressable memory. Some of the properties of such a network as well as a possible site of storage of long and short term memory are discussed.

L. N. Cooper

1985-01-01

240

Memory Magic.  

ERIC Educational Resources Information Center

This paper outlines several "tricks" that aid students in improving their memories. The distinctions between operational and figural thought processes are noted. Operational memory is described as something that allows adults to make generalizations about numbers and the rules by which they may be combined, thus leading to easier memorization.…

Hartman, Thomas G.; Nowak, Norman

241

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

242

False Memories  

NSDL National Science Digital Library

Use this activity (10th on the page) to help learners explore memory and how sometimes your brain makes up its own memories. Learners will read and try to remember the words in list #1. Five minutes later, learners will try to remember which words on list #2 they remember from list #1. Learners will be surprised to find out that their brains can be easily tricked. This activity guide includes two word challenges. Learners can make up their own lists to see if they can create false memories.

Chudler, Eric H.

2010-01-01

243

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

244

Advanced Polymers  

Microsoft Academic Search

Polymer science gains its power from the infinite versatility of synthetic polymers. Not only the bulk materials but also their basic constituents, polymer molecules, are tailor-made. The polymer molecule is built from smaller molecular units known as monomers, repeated hundreds or thousands of times in a chainlike structure. The choice of monomers and the way they are assembled shape the

Eric Baer

1986-01-01

245

Memory loss  

MedlinePLUS

... to brain tissue or nerve cells, such as Parkinson disease , Huntington disease , or multiple sclerosis Low levels of ... suspected (such as low vitamin B12 or thyroid disease) Cerebral ... Lumbar puncture Treatment depends on the cause of memory loss.

246

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

247

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

248

Frontiers in Alzheimer's Disease Therapeutics  

PubMed Central

Alzheimer's disease (AD) is a progressive neurodegenerative disease which begins with insidious deterioration of higher cognition and progresses to severe dementia. Clinical symptoms typically involve impairment of memory and at least one other cognitive domain. Owing to the exponential increase in the incidence of AD with age, the aging population across the world has seen a congruous increase in AD, emphasizing the importance of disease-altering therapy. Current therapeutics on the market, including cholinesterase inhibitors and N-methyl-D-aspartate receptor antagonists, provide symptomatic relief but do not alter progression of the disease. Therefore, progress in the areas of prevention and disease modification may be of critical interest. In this review, we summarize novel AD therapeutics that are currently being explored, and also mechanisms of action of specific drugs within the context of current knowledge of AD pathologic pathways.

Stone, Jeremy G.; Casadesus, Gemma; Gustaw-Rothenberg, Kasia; Siedlak, Sandra L.; Wang, Xinglong; Zhu, Xiongwei; Perry, George; Castellani, Rudy J.; Smith, Mark A.

2011-01-01

249

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.

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

2013-01-01

250

Frozen Topology: Entanglements Control Nucleation and Crystallization in Polymers  

NASA Astrophysics Data System (ADS)

Polymer chains form lamellar structures during crystallization which display a memory of thermal history. Using molecular dynamics simulations and primitive path analysis, we show a direct dependence of both density and crystalline stem length on the local entanglement length. The slow relaxation of the entanglement state after a change of external conditions can directly explain the role of thermal history for polymer crystallization, in particular memory effects. The analysis of the local entanglement state can be used to predict the occurrence of nucleation events. Our results present a fresh insight of the nonequilibrium properties of polymer crystals which might be identified as "frozen topology" of polymer melts.

Luo, Chuanfu; Sommer, Jens-Uwe

2014-05-01

251

Organosilane Polymers.  

National Technical Information Service (NTIS)

Purified dialkyldichlorosilane monomers were reacted with alkali metals in organic solvent solutions to form linear diorganosilane homopolymers and copolymers. The organosilane polymers were characterized by spectrometric and thermal analysis. Polymer sol...

J. P. Wesson T. C. Williams

1976-01-01

252

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.

2002-01-01

253

Data storage on holographic memory card  

Microsoft Academic Search

Our goal is to develop a re-writable holographic memory card system based on thin film polymer media on credit card size plastic carriers. Data is stored in our system in form of polarization holograms that present high efficiency and excellent suppression of higher orders even for thin material. Data is written on the card in a parallel way using spatial

Pal Koppa; Gabor Erdei; Ferenc Ujhelyi; Peter Varhegyi; T. Ujvari; Emoeke Loerincz; Gabor Szarvas; Soeren Hvilsted; P. S. Ramanujam; Peter I. Richter

2000-01-01

254

Zoetic polymers  

Microsoft Academic Search

Conditions mediating the formation of biological polymers in situ are reviewed, and terminology suggested to differentiate polymers found in living cells from synthetic materials and polymers derived from biological sources that are modified or studied in a way that obscures their biological function. Methods currently used to characterize the mechanical properties of biopolymer networks in cells are briefly discussed.

Ralph Nossal

2004-01-01

255

Memory Loss  

ERIC Educational Resources Information Center

In four decades of teaching college English, the author has watched many good teaching jobs morph into second-class ones. Worse, she has seen the memory and then the expectation of teaching jobs with decent status, security, and salary depart along with principles and collegiality. To help reverse this downward spiral, she contends that what is…

Cassebaum, Anne

2011-01-01

256

Ferroelectric Memories.  

National Technical Information Service (NTIS)

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 dens...

J. F. Scott C. A. Paz De Arujo

1989-01-01

257

Memory slicing  

Microsoft Academic Search

Traditional dynamic program slicing techniques are code-centric, meaning dependences are introduced between executed statement instances, which gives rise to various problems such as space requirement is decided by execution length; dependence graphs are highly redundant so that inspecting them is labor intensive. In this paper, we propose a data-centric dynamic slicing technique, in which dependences are introduced between memory locations.

Bin Xin; Xiangyu Zhang

2009-01-01

258

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

259

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.

Text, Word

2001-01-01

260

Retracing Memories  

ERIC Educational Resources Information Center

There are plenty of paths to poetry but few are as accessible as retracing ones own memories. When students are asked to write about something they remember, they are given them the gift of choosing from events that are important enough to recall. They remember because what happened was funny or scary or embarrassing or heartbreaking or silly.…

Harrison, David L.

2005-01-01

261

Painting memory  

Microsoft Academic Search

This article develops the Victorian fascination with the ways in which one visualizes, in the mind's eye, what is in fact invisible.†† In particular, it explores what happens when one exercises the faculty of memory.†† It argues that developments in painting during the period – especially the shift from an emphasis on realism to styles which invoke a spectator's subjective

Kate Flint

2003-01-01

262

Memory Matters  

MedlinePLUS

... a blockage in the pathway or because a blood vessel (which carries the blood) bursts. Continue Brain Injuries Affect Memory At any age, an injury ... by a severe hit to the head. Traumatic brain injuries can happen in a lot of ways and can be ... accidents, bike accidents, and falls can cause TBIs. If ...

263

Semantic Memory.  

National Technical Information Service (NTIS)

The report describes a model for the general structure of human long term memory. In this model, information about such things as the meanings of words is stored in a complex network, which then displays some of the desirable properties of a human's seman...

M. R. Quinlan

1966-01-01

264

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.

265

Early Memories as a Guide to Client Movement through Life.  

ERIC Educational Resources Information Center

Outlines the theory of the significance of early memories used as a projective tool by Adlerian psychologists. Describes a procedure for elicitation and interpretation of early memories and provides several examples of their use in an encouraging therapeutic context. Attempts to show effectiveness of this technique in assessing client issues and…

Slavik, Steve

1991-01-01

266

Optical polymer materials with photocontrolled fluorescence  

NASA Astrophysics Data System (ADS)

The results of the development of optical fluorescent solid film materials for applications as recording media for two-photon three-dimension bitwise optical memory with nondestructive fluorescent readout are presented. It was shown that photochromic diarylethenes in combination with organic fluorophore phenalenone or inorganic quantum dots CdSe/ZnS provide preparation of multilayer optical disks for working optical memory. Polymer layers based on irreversible light - sensitive chromones are acceptable for making optical disks of the archival type.

Barachevsky, V. A.; Kobeleva, O. I.; Ayt, A. O.; Gorelik, A. M.; Valova, T. M.; Krayushkin, M. M.; Yarovenko, V. N.; Levchenko, K. S.; Kiyko, V. V.; Vasilyuk, G. T.

2013-08-01

267

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

268

Memory coherence in shared virtual memory systems  

Microsoft Academic Search

This paper studies the memory coherence problem in designing and implementing a shared virtual memory on looselycoupled multiprocessors. Two classes of algorithms for solving the problem are presented. A prototype shared virtual memory on an Apollo ring has been implemented based on these algorithms. Both theoretical and practical results show that the memory coherence problem can indeed be solved efficiently

Kai Li; Paul Hudak

1986-01-01

269

Radio Memories  

NSDL National Science Digital Library

The "Golden Age of Radio" that arguably lasted until the early 1950s may be hard to imagine today in an era of swirling iPod playlists and other genre-bending devices and technologies, but during this time the radio reigned supreme. People tuned in every week to hear the exploits of Flash Gordon, Sam Spade, and Amos n' Andy. Thanks to the Radio Memories website, many of these memories can be relived, or just experienced for the first time. Started in May 2005, the site contains a host of compelling programs, including episodes from the Interplanetary Adventures of Flash Gordon and a number of original episodes of the fabled Radio Detective Story Hour. If those types of programs fail to pique the interest of the casual visitor, the site also contains archived shows that explore the world of radio soap operas from the 1940s and the musical worlds of such stars as Tommy Dorsey and Harry James.

270

Memory Cards  

Microsoft Academic Search

Before we go into detail with the theme of this chapter it is appropriate to introduce some terms that will be used in the\\u000a rest of the chapter. For this purpose we will define the field of application and the environment of the Flash memory card,\\u000a and some useful notions to better understand its basic architecture and use.

M. Iaculo; M. Picca; F. Tiziani; S. Ghezzi; P. Baggi

271

Disposable polymer \\  

Microsoft Academic Search

The recent development of an innovative disposable polymer smart lab-on-a-chip, which includes smart passive microfluidics, embedded on-chip power sources, and integrated biosensor array, has opened a new era for the point-of-care testing in clinical diagnostics. Several challenging issues in the development of the disposable polymer smart lab-on-a-chip have been explored and addressed in this work. A new disposable polymer \\

Chong H. Ahn

2005-01-01

272

Polymer Network Volume Stabilized Ferroelectric Liquid Crystal Displays  

Microsoft Academic Search

A ferroelectric liquid crystal (FLC) cell for flat panel displays with volume stabilized bistable states is described. Volume stabilization is achieved by the FLC\\/polymer gel dispersion which is prepared by polymerizing a FLC\\/polymer precursor solution in a suitably aligned FLC display cell. The volume stabilized LC cell gives mechanical stability to FLC displays with internal memory and provides for high

J. Pirš; R. Blinc; B. Marin; S. Pirs; J. W. Doane

1995-01-01

273

Organizational emotional memory  

Microsoft Academic Search

Purpose – As a fascinating concept, the term of organizational memory attracted many researchers from a variety of disciplines. In particular, the content of organizational memory, which involves declarative and procedural memory, found broad research interest in the management literature. Nevertheless, there is sparse research in the management literature on the emotional content aspect of organizational memory. Emotional memory is

Ali E. Akgün; Halit Keskin; John Byrne

2012-01-01

274

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.

Kandel, E R; Pittenger, C

1999-01-01

275

Polymer Electrolytes  

NASA Astrophysics Data System (ADS)

This review article covers applications in which polymer electrolytes are used: lithium batteries, fuel cells, and water desalination. The ideas of electrochemical potential, salt activity, and ion transport are presented in the context of these applications. Potential is defined, and we show how a cell potential measurement can be used to ascertain salt activity. The transport parameters needed to fully specify a binary electrolyte (salt + solvent) are presented. We define five fundamentally different types of homogeneous electrolytes: type I (classical liquid electrolytes), type II (gel electrolytes), type III (dry polymer electrolytes), type IV (dry single-ion-conducting polymer electrolytes), and type V (solvated single-ion-conducting polymer electrolytes). Typical values of transport parameters are provided for all types of electrolytes. Comparison among the values provides insight into the transport mechanisms occurring in polymer electrolytes. It is desirable to decouple the mechanical properties of polymer electrolyte membranes from the ionic conductivity. One way to accomplish this is through the development of microphase-separated polymers, wherein one of the microphases conducts ions while the other enhances the mechanical rigidity of the heterogeneous polymer electrolyte. We cover all three types of conducting polymer electrolyte phases (types III, IV, and V). We present a simple framework that relates the transport parameters of heterogeneous electrolytes to homogeneous analogs. We conclude by discussing electrochemical stability of electrolytes and the effects of water contamination because of their relevance to applications such as lithium ion batteries.

Hallinan, Daniel T.; Balsara, Nitash P.

2013-07-01

276

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

277

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 ...

278

Studies of Perceptual Memory.  

National Technical Information Service (NTIS)

Perceptual memory refers to experience-induced changes in perceptual processing of particular objects or scenes. Part 1 of this report summarizes the results of 8 studies of the role of perceptual memory in recognition memory. The hypothesis was confirmed...

J. M. Farnham K. J. Hawley W. A. Johnston

1992-01-01

279

Barrier Polymers  

Microsoft Academic Search

The general theory of permeation of a gas or liquid through a polymer matrix [1] states that permeation is the product of a diffusion term and a solubility constant of the permeant in the polymer matrix, both of which are often independent of each other. The process of permeation through a polymeric barrier involves four steps: absorption of the permeating

M. Salame; S. Steingiser

1977-01-01

280

Disordered polymers  

Microsoft Academic Search

A single polymer macromolecule is considered with disorder types such as branches, knots, and heterogeneous sequences of chemical units. In all cases, simple theoretical approaches are employed to gain useful physical insights. For branched polymers, a simple Flory-type theory is described by means of which the difference between the universality classes for molecules with quenched and annealed branches is demonstrated.

Aleksandr Yu Grosberg

1997-01-01

281

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

282

Antimocrobial Polymer  

Microsoft Academic Search

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

William F. McDonald; Zhi-Heng Huang; Stacy C. Wright

2005-01-01

283

Antimicrobial Polymer  

Microsoft Academic Search

A polymeric composition having antimicrobial properties and a process for rendering the surface of a substrate antimicrobial are disclosed. The polymeric 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 metals, metal alloys, metal salts, metal complexes and mixtures thereof, and (iii)

William F. McDonald; Stacy C. Wright; Andrew C. Taylor

2004-01-01

284

A Beginner's Guide to Memory.  

ERIC Educational Resources Information Center

This article is designed to equip the reader with the information needed to deal with questions of computer memory. Discussed are core memory; semiconductor memory; size of memory; expanding memory; charge-coupled device memories; magnetic bubble memory; and read-only and read-mostly memories. (KC)

Hughes, Elizabeth M.

1981-01-01

285

Polymer sensorised microgrippers using SMA actuation  

Microsoft Academic Search

In this paper a polymer sensorised microgripping tool for micromanipulation is presented. The gripper structure is made by moulding of polyurethane in silicon moulds by the technique of shape deposition manufacturing (SDM), in which the force sensing elements and part of the actuator (in this case, microstrain gauges and SMA (shape memory alloy) wire, respectively) are embedded into the microgripper

Keith Houston; Clemens Eder; Arne Sieber; Arianna Menciassi; Maria Chiara Carrozza; Paolo Dario

2007-01-01

286

Reducing unwanted trauma memories by imaginal exposure or autobiographical memory elaboration: An analogue study of memory processes  

PubMed Central

Unwanted memories of traumatic events are a core symptom of post-traumatic stress disorder. A range of interventions including imaginal exposure and elaboration of the trauma memory in its autobiographical context are effective in reducing such unwanted memories. This study explored whether priming for stimuli that occur in the context of trauma and evaluative conditioning may play a role in the therapeutic effects of these procedures. Healthy volunteers (N = 122) watched analogue traumatic and neutral picture stories. They were then randomly allocated to 20 min of either imaginal exposure, autobiographical memory elaboration, or a control condition designed to prevent further processing of the picture stories. A blurred picture identification task showed that neutral objects that preceded traumatic pictures in the stories were subsequently more readily identified than those that had preceded neutral stories, indicating enhanced priming. There was also an evaluative conditioning effect in that participants disliked neutral objects that had preceded traumatic pictures more. Autobiographical memory elaboration reduced the enhanced priming effect. Both interventions reduced the evaluative conditioning effect. Imaginal exposure and autobiographical memory elaboration both reduced the frequency of subsequent unwanted memories of the picture stories.

Ehlers, Anke; Mauchnik, Jana; Handley, Rachel

2012-01-01

287

Kansas Memory  

NSDL National Science Digital Library

You can travel from Cheyenne County in the northwestern corner of Kansas all the way down to Cherokee County in the southeast with a just couple of clicks on the Kansas Memory site. It's a trip filled with compelling historical artifacts, photographs, and other ephemera, and it's an engaging way to learn about the Sunflower State's history. Created by the Kansas State Historical Society, Kansas Memory helps to fulfill the Society's mission "to identify collect, preserve, interpret, and disseminate materials and information pertaining to Kansas history." First-time visitors can explore the "Item of the Week" on the homepage, create their own profiles to save materials for future visits, and take a look at the "Special Exhibits" area. On the left-hand side of the homepage, visitors will find thematic headings that allow them to browse materials dealing with the subjects including the built environment, business, and agriculture. With over 17,000 items available on the site, it's safe to say that several visits will be in order for anyone with even the faintest interest in Kansas history.

2012-01-27

288

Polymer nanolithography  

NASA Astrophysics Data System (ADS)

Nanolithography involves making patterns of materials with at least one dimension less than 100 nanometers. Surprisingly, writable CDs can provide polymer nanostructures for pennies a piece. Building on work previously done in the Drain lab, with an inherited home-built oven press, this research will explore the relationships between polymer chemical reactivity, polymer printing, and material surface energies. In addition, a relatively inexpensive entry point into high school and undergraduate education in nanolithography is presented. The ability to pattern cheaply at the nanoscale and microscale is necessary and attractive for many technologies towards biosensors, organic light emitting diodes, identification tags, layered devices, and transistors.

Vance, Jennifer M.

289

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

290

Atomic memory  

NASA Astrophysics Data System (ADS)

The fundamental principles of atomic-memory effects related to the Loschmidt paradox in the second law of thermodynamics are introduced and illustrated with simple analogies, photographs, and diagrams; and the results of RF and laser experiments are summarized. Nuclear-spin echoes in response to RF pulses and the NMR free-induction decay phenomenon are described, and the extension of these concepts to the visible spectrum in laser-frequency-switching and multipulsed-laser experiments is examined with an emphasis on studies of free-induction decay in LaF3 crystals containing Pr impurities (DeVoe and Brewster). The laser-induced phenomena can be applied to studies of intramolecular and intermolecular interactions, and an improved understanding of the RF effects is needed to enhance the performance of medical NMR imaging systems.

Brewer, R. G.; Hahn, E. L.

1984-12-01

291

Memory formation and memory alterations: 5-HT6 and 5-HT7 receptors, novel alternative.  

PubMed

Abstract Agonists and antagonists of the 5-hydroxytryptamine (serotonin) receptor6 (5-HT6) or receptor7 (5-HT7) might improve memory and/or reverse amnesia, although the mechanisms involved are poorly understood. Hence, the current work summarizes recent reviews and findings involving these receptors. Evidence indicates that diverse 5-HT6 receptor antagonists produce promnesic and/or antiamnesic effect in conditions, such as memory formation, age-related cognitive impairments and memory deficit in preclinical studies, as well as in diseases such as schizophrenia, Parkinson's, and Alzheimer's disease (AD). Memory, aging, and AD modify 5-HT6 receptors and signaling cascades; likewise, the modulation of 5-HT6 drugs on memory seems to be accompanied with neural changes. Moreover, 5-HT7 receptors are localized in brain areas mediating memory, including the cortex, hippocampus (e.g., Zola-Morgan and Squire, 1993) and raphe nuclei; however, the role of these receptors on memory has yet to be fully explored. Hence, findings and reviews are summarized in this work. Evidence suggests that both 5-HT7 receptor agonists and antagonists might have promnesic and anti-amnesic effects. These effects seem to be dependent on the basal level of performance, i.e., normal or impaired. Available evidence suggests that a potential utility of 5-HT6 and 5-HT7 receptor in mild-to-moderate AD patients and other memory dysfunctions as therapeutic targets. PMID:24698823

Meneses, Alfredo

2014-01-01

292

Extending Mondrian Memory Protection  

Microsoft Academic Search

Most modern operating systems implement some sort of memory protection scheme for user processes. These schemes make it is possible to set access permissions that determine whether a region of memory allocated for a process can be read, written, or executed by this process. Mondrian memory protection is a technique that extends the traditional memory protection scheme and allows fine-grain

Clemens Kolbitsch; Christopher Kruegel; Engin Kirda

293

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

294

Errors in autobiographical memory  

Microsoft Academic Search

Memory is always constructive. People create the past based on the information that remains in memory, their general knowledge, and the social demands of the retrieval situation. Thus, memories will often contain some small errors and occasionally some large errors. In this article, we describe several different types of memory errors and consider how these errors may influence therapy.

Ira E. Hyman; Elizabeth F. Loftus

1998-01-01

295

Problems of neural memory  

Microsoft Academic Search

The paper considers the neural memory of the human brain from the viewpoint of visual information processing. A model that explains the principle of data recording and storing, memory relaxation, associative remembering and other memory functions is offered. The model of associative memory is based on the methods of holography, \\

Andrei L. Mikaelian

2005-01-01

296

Targeted drug delivery by thermally responsive polymers  

Microsoft Academic Search

This review article summarizes recent results on the development of macromolecular carriers for thermal targeting of therapeutics to solid tumors. This approach employs thermally responsive polymers in conjunction with targeted heating of the tumor. The two thermally responsive polymers that are discussed in this article, poly(N-isopropylacrylamide-co-acrylamide) (poly(NIPAAm)) and an artificial elastin-like polypeptide (ELP), were designed to exhibit a soluble–insoluble lower

Ashutosh Chilkoti; Matthew R Dreher; Dan E Meyer; Drazen Raucher

2002-01-01

297

Drug Delivery Systems Based On Mucoadhesive Polymers  

Microsoft Academic Search

\\u000a Transmucosal delivery of therapeutic agents is a non-invasive approach that utilizes human entry paths such as the nasal,\\u000a buccal, rectal and vaginal routs. Mucoadhesive polymers have the ability to adhere to the mucus layer covering those surfaces\\u000a and by that promote drug release, targeting and absorption. Mucoadhesive polymers commonly interact with mucus through non-covalent\\u000a bonds such as hydrogen bonds, ionic

Maya Davidovich-Pinhas; Havazelet Bianco-Peled

298

Electrical bistability in a composite of polymer and barium titanate nanoparticles.  

PubMed

Growth in the use of organic materials in the fabrication of electronic devices is on the rise. Recently, some attempts have been undertaken to manufacture polymer memory devices. Such devices are fabricated by depositing a blend (an admixture of organic polymer, small organic molecules and nanoparticles) between two metal electrodes. These devices show two electrical conductivity states ('high' and 'low') when a voltage is applied, thus rendering the structures suitable for data retention. In this paper, we describe an attempt to fabricate memory devices using ferroelectric nanoparticles embedded in an organic polymer. This paper also discusses issues related to the observed memory effect. PMID:19770146

Salaoru, I; Paul, S

2009-10-28

299

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

300

Invasion percolation with memory  

NASA Astrophysics Data System (ADS)

Motivated by the problem of finding the minimum threshold path (MTP) in a lattice of elements with random thresholds ?i, we propose a new class of invasion processes, in which the front advances by minimizing or maximizing the measure Sn=?i?ni for real n. This rule assigns long-time memory to the invasion process. If the rule minimizes Sn (case of minimum penalty), the fronts are stable and connected to invasion percolation in a gradient [J. P. Hulin, E. Clement, C. Baudet, J. F. Gouyet, and M. Rosso, Phys. Rev. Lett. 61, 333 (1988)] but in a correlated lattice, with invasion percolation [D. Wilkinson and J. F. Willemsen, J. Phys. A 16, 3365 (1983)] recovered in the limit \\|n\\|=?. For small n, the MTP is shown to be related to the optimal path of the directed polymer in random media (DPRM) problem [T. Halpin-Healy and Y.-C. Zhang, Phys. Rep. 254, 215 (1995)]. In the large n limit, however, it reduces to the backbone of a mixed site-bond percolation cluster. The algorithm allows for various properties of the MTP and the DPRM to be studied. In the unstable case (case of maximum gain), the front is a self-avoiding random walk.

Kharabaf, Hooshang; Yortsos, Yanis C.

1997-06-01

301

Inhibition and enhancement of contextual fear memory destabilization.  

PubMed

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

302

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.

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

2014-01-01

303

Linkage effect on the memory behavior of sulfonyl-containing aromatic polyether, polyester, polyamide, and polyimide.  

PubMed

Sulfonyl-containing aromatic polymers DSPE, DSPET, DSPA, and DSPI consisting of a triphenylamine moiety were synthesized and the memory behavior was investigated. By choosing the suitable linkage between the electron donor and acceptor, tunable memory properties (from insulator to different retention time SRAM) could be achieved. PMID:23423191

Chen, Chih-Jung; Hu, Yi-Cheng; Liou, Guey-Sheng

2013-03-28

304

Polymer–drug conjugation, recent achievements and general strategies  

Microsoft Academic Search

The field of drug delivery is fast expanding and its potentials have already been proved by the many products in the market. Among all approaches, polymer conjugation is a well known and widely exploited technique useful to improve therapeutic properties of peptides, proteins, small molecules or oligonucleotides. Polymer-conjugated drugs generally exhibit prolonged half-life, higher stability, water solubility, lower immunogenicity and

G. Pasut; F. M. Veronese

2007-01-01

305

Polymers Technical Activities, 1996.  

National Technical Information Service (NTIS)

Technical activities for the Polymers Division, 854, for the 1996 fiscal year are described. The report is organized by programs: Electronic Packaging and Interconnections, Polymer Blends and Processing, Polymer Composites, Polymer Characterization, Denta...

B. M. Fanconi L. E. Smith

1996-01-01

306

Cannabis: its therapeutic use.  

PubMed

This article provides an overview of the issues surrounding the use of cannabis for therapeutic purposes. Examples of some of the ethical issues related to professional practice are discussed. The authors do not advocate legalising cannabis for all, but the therapeutic advantages and disadvantages of using cannabis are highlighted. PMID:11975210

Wall, J; Davis, S; Ridgway, S

307

Chicanoizing the Therapeutic Community  

ERIC Educational Resources Information Center

Focusing on the drug addiction problem and its antecedent conditions in a Chicano population, the article examines several therapeutic interventions suggested by these conditions and indicates how they might be incorporated into a drug addiction Therapeutic Community treatment program designed to meet the needs of Chicano drug addicts. (Author/NQ)

Aron, William S.; And Others

1974-01-01

308

Study of Memory Alignment of Nematic Liquid Crystals on Polyvinyl Alcohol Coatings  

NASA Astrophysics Data System (ADS)

Polymer layers can cause memory alignment of nematic liquid crystals. We describe an experimental method to characterize this effect. We studied the temperature dependence of the memory alignment on polyvinyl alcohol coatings. We also investigated the influence of the time span during which the memory alignment is generated. We propose an adsorption-desorption mechanism by which we can explain our observations in a reasonable way.

Vetter, Peter; Ohmura, Yoshinori; Uchida, Tatsuo

1993-09-01

309

Glutamate-based therapeutic approaches: ampakines.  

PubMed

Ampakines are a structurally diverse family of small molecules that positively modulate alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)-type glutamate receptors, and thereby enhance fast, excitatory transmission throughout the brain. Surprisingly, ampakines have discrete effects on brain activity and behavior. Because their excitatory synaptic targets mediate communication between cortical regions, serve as sites of memory encoding, and regulate the production of growth factors, ampakines have a broad range of potential therapeutic applications. Several of these possibilities have been tested with positive results in preclinical models; preliminary clinical work has also been encouraging. PMID:16361116

Lynch, Gary

2006-02-01

310

Antimicrobial Polymer  

DOEpatents

A polymeric composition having antimicrobial properties and a process for rendering the surface of a substrate antimicrobial are disclosed. The polymeric 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 metals, metal alloys, metal salts, metal complexes and mixtures thereof, and (iii) a crosslinking agent containing functional groups capable of reacting with the amino groups. In one example 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).sub.3 P wherein A is hydroxyalkyl; and the metallic antimicrobial agent is selected from chelated silver ions, silver metal, chelated copper ions, copper metal, chelated zinc ions, zinc metal and mixtures thereof.

McDonald, William F. (Utica, OH); Wright, Stacy C. (Flint, MI); Taylor, Andrew C. (Ann Arbor, MI)

2004-09-28

311

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

312

Problems of neural memory  

NASA Astrophysics Data System (ADS)

The paper considers the neural memory of the human brain from the viewpoint of visual information processing. A model that explains the principle of data recording and storing, memory relaxation, associative remembering and other memory functions is offered. The model of associative memory is based on the methods of holography, "wave biochemistry" and autowaves. Brief consideration is given to the associative properties of holographic neural structures and the memory architecture using running chemical reactions. The paper also outlines the problem of developing artificial memory elements for restoring the brain functions and possible interface devices for coupling neurons to electronic systems.

Mikaelian, Andrei L.

2005-01-01

313

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); Jacobs, Steve

2004-01-01

314

Understanding Memory Loss  

MedlinePLUS

... National Alzheimer's Project Act (NAPA) About ADEAR Understanding Memory Loss: What To Do When You Have Trouble ... home may be signs of a more serious memory problem. This booklet will help you learn about: ...

315

Medications for Memory Loss  

MedlinePLUS

Medications for Memory Loss Tweet Although current medications cannot cure Alzheimer’s or stop it from progressing, they may help lessen symptoms, such as memory loss and confusion, for a limited time. Types ...

316

Memory and Aging  

MedlinePLUS

Memory and Aging Losing keys, misplacing a wallet, or forgetting someone’s name are common experiences. But for ... from those that require medical and psychological attention. Memory and Aging What Brain Changes Are Normal for ...

317

GDM: Global Distributed Memory.  

National Technical Information Service (NTIS)

Global Distributed Memory (GDM) is a distributed memory system in the spirit of Linda. Its distinctive features are multiple object spaces and efficient write-invalidate caching of frequently accessed objects. The report describes the GDM model and the Tr...

A. Gustafsson H. Aronsson H. Suonsivu

1991-01-01

318

Sparse Distributed Memory.  

National Technical Information Service (NTIS)

Sparse distributed memory was proposed be Pentti Kanerva as a realizable architecture that could store large patterns and retrieve them based on partial matches with patterns representing current sensory inputs. This memory exhibits behaviors, both in the...

P. J. Denning

1989-01-01

319

Memory Technology Survey.  

National Technical Information Service (NTIS)

The current status of semiconductor, magnetic, and optical memory technologies is described. Projections based on these research activities planned for the shot term are presented. Conceptual designs of specific memory buffer pplications employing bipola,...

1981-01-01

320

The Harris Data Memory.  

ERIC Educational Resources Information Center

A description of the commercially produced Harris Data Memory is presented. Operation instructions, memory capabilities, data storage, and applications are included. Usefulness of the instrument to instruction in all of the sciences is considered. (SA)

Muir, D. H. T.; Elwell, M. J.

1979-01-01

321

Electroconductive Polymers.  

PubMed

Polymers of a new type with an unusual combination of properties have been synthesized. They are of high molecular weight, they are soluble in organic solvents, and they can be cast as films. Their electrical conduction is electronic in the solid state and can be controlled up to a conductivity of 10(-2) ohm(-1) cm(-1). PMID:17832400

Lupinski, J H; Kopple, K D

1964-11-20

322

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) [Bremen, DE; Miller, Kevin Michael (West Dundee, IL) [West Dundee, IL

2011-07-26

323

Enhancing the therapeutic efficacy of adenovirus in combination with biomaterials  

PubMed Central

With the reason that systemically administered adenovirus (Ad) is rapidly extinguished by innate/adaptive immune responses and accumulation in liver, in vivo application of the Ad vector is strictly restricted. For achieving to develop successful Ad vector systems for cancer therapy, the chemical or physical modification of Ad vectors with polymers has been generally used as a promising strategy to overcome the obstacles. With polyethylene glycol (PEG) first in order, a variety of polymers have been developed to shield the surface of therapeutic Ad vectors and well accomplished to extend circulation time in blood and reduce liver toxicity. However, although polymer-coated Ads can successfully evacuate from a series of guarding systems in vivo and locate within tumors by enhanced permeability and retention (EPR) effect, the possibility to entering into the target cell is few and far between. To endow targeting moiety to polymer-coated Ad vectors, a diversity of ligands such as tumor-homing peptides, growth factors or antibodies, have been introduced with avoiding unwanted transduction and enhancing therapeutic efficacy. Here, we will describe and classify the characteristics of the published polymers with respect to Ad vectors. Furthermore, we will also compare the properties of variable targeting ligands, which are being utilized for addressing polymer-coated Ad vectors actively.

Kim, Jaesung; Kim, Pyung-Hwan; Kim, Sung Wan; Yun, Chae-Ok

2011-01-01

324

Emotional Memory Persists Longer than Event Memory  

ERIC Educational Resources Information Center

The interaction between amygdala-driven and hippocampus-driven activities is expected to explain why emotion enhances episodic memory recognition. However, overwhelming behavioral evidence regarding the emotion-induced enhancement of immediate and delayed episodic memory recognition has not been obtained in humans. We found that the recognition…

Kuriyama, Kenichi; Soshi, Takahiro; Fujii, Takeshi; Kim, Yoshiharu

2010-01-01

325

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

326

Imagery and memory illusions  

Microsoft Academic Search

This article provides a summary of current knowledge about memory illusions. The memory illusions described here focus on\\u000a the recall of imagined events that have never actually occurred. The purpose is to review theoretical ideas and empirical\\u000a evidence about the reality-monitoring processes involved in memory illusions. Reality monitoring means deciding whether the\\u000a memory has been perceptually derived or been self-generated

Frédérique Robin

2010-01-01

327

SECM study of defect repair in self-healing polymer coatings on metals  

Microsoft Academic Search

In this paper the local healing efficiency of shape-memory polymers as a new alternative for the protection against corrosion of damaged coated metals is studied by scanning electrochemical microscopy (SECM). These measurements allowed us to evaluate the local corrosion activity at a damaged self-healing polymer coating on an aluminum alloy before and after the thermally healing process of the shape-memory

Y. González-García; J. M. C Mol; T. Muselle; I. De Graeve; G. Van Assche; G. Scheltjens; B. Van Mele; H. Terryn

2011-01-01

328

Testing eyewitness memory  

Microsoft Academic Search

This study identifies a memory-testing procedure that is relatively resistant to the documented effects of suggestibility on eyewitness memory. Most studies on suggestibility have used averbal recognition memory test in which the alternative test items are sentences, each to be verified as true or false regarding an originally viewedvisual sequence. In this study, participants were tested with either the verbal

Kathy Pezdek; Joelle Greener

1993-01-01

329

Suggesting a Memory Screening  

MedlinePLUS

Suggesting a Memory Screening... Text Size: Email This Post Print This Post Suggesting a Memory Screening By Kevin Gault It can be a ... cognitive abilities, want to suggest screening for possible memory deficit, but aren’t sure how to go ...

330

Memories (Children's Books).  

ERIC Educational Resources Information Center

Presents brief annotations of 46 children's books that explore memories of childhood, memories of love, keepsakes that capture those memories, memorable tales from long ago, memorable journeys, times that are painful to remember, and heroes and heroines who have provided hope and change in a troubled world. (SR)

McKinley, Carol; Peters, Donna; Semer, Susie; White, W. Quinn; Scharer, Patricia L.

1998-01-01

331

Generation and Context Memory  

ERIC Educational Resources Information Center

Generation enhances memory for occurrence but may not enhance other aspects of memory. The present study further delineates the negative generation effect in context memory reported in N. W. Mulligan (2004). First, the negative generation effect occurred for perceptual attributes of the target item (its color and font) but not for extratarget…

Mulligan, Neil W.; Lozito, Jeffrey P.; Rosner, Zachary A.

2006-01-01

332

Organizing Corporate Memories 1  

Microsoft Academic Search

This paper presents some preliminary thoughts on how corporate memories should be organized in such a way that they maximally contribute to the competitiveness of an organization. We argue that a corporate memory should support three types of organizational learning, which are described. Then we formulate functional requirements and present an architecture for corporate memories that would satisfy these requirements.

Rob van der Spek; Eelco Kruizinga; Gertjan van Heijst

1996-01-01

333

Music, memory and emotion  

Microsoft Academic Search

Because emotions enhance memory processes and music evokes strong emotions, music could be involved in forming memories, either\\u000a about pieces of music or about episodes and information associated with particular music. A recent study in BMC Neuroscience has given new insights into the role of emotion in musical memory.

Lutz Jäncke

2008-01-01

334

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.

335

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.

336

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.

Orsini, Caitlin A.; Maren, Stephen

2012-01-01

337

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.

338

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.

Abu Dayyeh, Barham K.

2012-01-01

339

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

340

New shape memory effects in semicrystalline polymeric networks  

NASA Astrophysics Data System (ADS)

Shape memory polymers (SMPs) have attracted much research interest as a type of smart material that possesses the capacity to undergo rapid changes of their shape and size under a specific or tailored environment. Herein, we prepared semicrystalline polymers-based networks such as poly (cyclooctene) (PCO), poly (e-caprolactone) (PCL) and poly (ethylene glycol) (PEG) networks in order to explore their shape memory effects and thermomechanical properties as well as the possibilities for their applications. Interestingly, besides so-called one-shape memory effect that can be manipulated and fixed to a temporary shape under specific conditions of temperature and stress, and subsequently relax to the original shape on heating, the semicrystalline polymer networks exhibit a reversible two-way shape memory effect, revealing crystallization-induced elongation on cooling and melting-induced contraction on heating. These thermally induced reversible two-way shape memory effects were systematically explored with respect to the crosslinking density of networks and the applied stress. In order to develop a shape memory network with temperature sensing capability, we incorporated appropriately tailored chromogenic cyano-OPVs into cross-linked PCO via guest-diffusion to create phase-separated blends in which the dye's emission properties are dominated by excimer fluorescence. Heatng to the temperature above melting temperature and cooling below the crystallization temperature of PCO led to reversible optical changes through dissolution or agregation of the dye molecules. These optical changes happened in conjuction with shape changes of PCO networks. For an application of shape memory network in bone tissue engineering, we fabricated novel shape memory nanocomposite scaffolds base on PCL and nano-hydroxyapatite (nano-HAP) using thiol-ene photopolymerization and salt leaching technique. The shape memory property, morphologies and biomineralization of the scaffolds were characterized. In addition, the effect of biomineralization on shape recovery of the deformed PCL-HAP scaffolds was studied. These results suggest the possibility that these shape memory scaffolds can be tailored to fit bone defects and can maintain the tailored shape as well as achieve bioactive properties by apatite growth on the surface. We anticipate that the shape memory network systems studied for this dissertation will have the potential for many technological applications in various fields where shape memory effects are needed.

Chung, Taekwoong

341

Are therapeutic communities therapeutic for women?  

PubMed Central

This paper addresses the growing phenomena of therapeutic community (TC) treatment approaches for women in correctional settings. Although rapidly increasing in number across the country, there is very little empirical research to support the effectiveness of TC treatment for women. Therefore, the literature on the efficacy and effectiveness of TC treatment for women is reviewed in relation to the literature on women's treatment issues. The literature review highlights the gaps where TC treatment ignores or exacerbates issues that are common to addicted women, or uses methods that may be contradictory to women's recovery.

Eliason, Michele J

2006-01-01

342

Botulism and memory.  

PubMed

Although botulinum toxin is thought not to affect the human CNS, previous studies have not examined those behaviors, such as memory, that have been shown to be dependent on central acetylcholine transmission. In eight patients with type A botulism, subjective analysis, bedside memory testing, and formal memory testing with Hebb's verbal sequencing test, Corsi's nonverbal sequencing test, and Buschke's verbal serial list learning test failed to demonstrate impairment in immediate and recent memory. Botulism severe enough to block peripheral nicotinic and muscarinic cholinergic transmission does not block those central cholinergic synapses involved in memory. PMID:7425889

Haaland, K Y; Davis, L E

1980-10-01

343

AIT-082 NeoTherapeutics Inc.  

PubMed

AIT-082 (an analog of hypoxanthine) is an orally-active nerve growth factor (NGF) agonist under development by NeoTherapeutics as a potential treatment for Alzheimer's disease (AD), stroke and motor neuron disease. A phase II safety and efficacy trial in AD, originally scheduled to begin in the summer of 1997 [283677], began in May 1998 [286975,285562]. The study will enroll more than 60 AD patients [286975]. In February 1998, NeoTherapeutics began a phase I multiple-dose pharmacokinetic study of AIT-082 in 24 healthy elderly volunteers. Subjects of the phase I study will be administered AIT-082 once a day for 7 consecutive days at doses of 100 to 2000 mg per dose [279422]. A limited double-blind, placebo-controlled phase I/II trial in 10 AD patients commenced in Canada in the first quarter of 1997. Treatment with 4000 mg improved memory in 60% of the patients within 3 h, as determined by the word recall test. A decrease in memory was observed in 80% of placebo-treated patients [257132]. A phase I US trial, conducted by the Alzheimer's Disease Cooperative Study, with funding from the National Institute of Aging, began in July 1997. AIT-082 was administered to eight healthy, elderly volunteers as part of an escalating single-dose study. Oral administration of AIT-082 was well-tolerated at high doses [284325] AIT-082 also enhanced memory function in both young adult and aged mice within 2 h of oral administration. Prophylactic treatment prevented or delayed the onset of age-induced memory deficits in mice when administered in drinking water. When memory impairment was produced by brain lesions, the drug restored memory performance and increased the genetic expression of neurotrophin-3 (NT-3), a natural protein growth factor associated with nerve cell function [284325]. AIT-082 appears to have at least three effects on the growth of PC-12 cells in culture. Firstly, it stimulates outgrowth of neurites, secondly it potentiates the growth effects of neurotrophin, and thirdly, it stimulates the synthesis of certain neurotrophins (nerve growth factor, neurotrophin-3 and fibroblast growth factor) and pleiotrophins by astrocytes. These progrowth mechanisms are thought to form the basis of the ability of AIT-082 to restore and prevent age-related working memory deficits in mice [195438]. In October 1997, further preclinical results were presented, demonstrating that treatment with AIT-082 produced an increase in neurotrophic factors following spinal cord injury in rats. This study was conducted at NeoTherapeutics and McMaster University, and was partially funded by the Amyotrophic Lateral Sclerosis Society of Canada. After 7 days of treatment, rats with spinal cord injuries showed an increase in the levels of CNTF and BDNF, naturally occurring growth factors in the spinal cord [267514]. PMID:18465624

Geerts, H

1998-10-01

344

Advanced Polymer  

NASA Technical Reports Server (NTRS)

In the mid-1980's, Langley developed a polyimide sulfone, combining desirable properties of two classes of polymers. Composites and other products made from polyimide sulfone can be used with solvents and corrosive fluids, are light weight, low cost and can be easily fabricated for a wide range of industrial uses. High Technology Systems, Inc. obtained a license for the polymer and was awarded a Small Business Innovation Research (SBIR) contract for development in a powder form. Although its principal use is as a matrix resin for composites, the material can also be used as a high temperature structural adhesive for aircraft structures and as a coating for protection from heat and radiation for electronic components.

1992-01-01

345

Child maltreatment and memory.  

PubMed

Exposure to childhood trauma, especially child maltreatment, has important implications for memory of emotionally distressing experiences. These implications stem from cognitive, socio-emotional, mental health, and neurobiological consequences of maltreatment and can be at least partially explained by current theories concerning the effects of childhood trauma. In this review, two main hypotheses are advanced: (a) Maltreatment in childhood is associated with especially robust memory for emotionally distressing material in many individuals, but (b) maltreatment can impair memory for such material in individuals who defensively avoid it. Support for these hypotheses comes from research on child abuse victims' memory and suggestibility regarding distressing but nonabusive events, memory for child abuse itself, and autobiographical memory. However, more direct investigations are needed to test precisely when and how childhood trauma affects memory for emotionally significant, distressing experiences. Legal implications and future directions are discussed. PMID:19575622

Goodman, Gail S; Quas, Jodi A; Ogle, Christin M

2010-01-01

346

Emulsion Polymers  

NASA Astrophysics Data System (ADS)

The symposium "Emulsion Polymers" was held at the 217th American Chemical Society (ACS) Meeting in Anaheim, CA in March 1999. Topic areas presented included novel concepts in emulsion and miniemulsion homo- and copolymerization, the role of polymeric stabilizers in emulsion polymerization, particle morphology and film formation, and applications of latex systems. The papers in this volume of Macromolecular Symposia cover a broad range of topics characteristic of the symposium.

El-Aasser, Mohamed S.; Smith, Carrington D.; Meisel, I.; Spiegel, S.; Kniep, C. S.

2000-08-01

347

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

348

Memory-effects of magnetic nanocomposites.  

PubMed

The thermally induced shape memory effect (SME) is the capability of a material to fix a temporary (deformed) shape and recover a 'memorized' permanent shape in response to heat. SMEs in polymers have enabled a variety of applications including deployable space structures, biomedical devices, adaptive optical devices, smart dry adhesives and fasteners. By the incorporation of magnetic nanoparticles (mNP) into shape-memory polymer (SMP), a magnetically controlled SME has been realized. Magnetic actuation of nanocomposites enables remotely controlled devices based on SMP, which might be useful in medical technology, e.g. remotely controlled catheters or drug delivery systems. Here, an overview of the recent advances in the field of magnetic actuation of SMP is presented. Special emphasis is given on the magnetically controlled recovery of SMP with one switching temperature T(sw) (dual-shape effect) or with two T(sw)s (triple-shape effect). The use of magnetic field to change the apparent switching temperature (T(sw,app)) of the dual or triple-shape nanocomposites is described. Finally, the capability of magnetic nanocomposites to remember the magnetic field strength (H) initially used to deform the sample (magnetic-memory effect) is addressed. The distinguished advantages of magnetic heating over conventional heating methods make these multifunctional nanocomposites attractive candidates for in vivo applications. PMID:22941347

Razzaq, Muhammad Yasar; Behl, Marc; Lendlein, Andreas

2012-10-21

349

Memory-effects of magnetic nanocomposites  

NASA Astrophysics Data System (ADS)

The thermally induced shape memory effect (SME) is the capability of a material to fix a temporary (deformed) shape and recover a `memorized' permanent shape in response to heat. SMEs in polymers have enabled a variety of applications including deployable space structures, biomedical devices, adaptive optical devices, smart dry adhesives and fasteners. By the incorporation of magnetic nanoparticles (mNP) into shape-memory polymer (SMP), a magnetically controlled SME has been realized. Magnetic actuation of nanocomposites enables remotely controlled devices based on SMP, which might be useful in medical technology, e.g. remotely controlled catheters or drug delivery systems. Here, an overview of the recent advances in the field of magnetic actuation of SMP is presented. Special emphasis is given on the magnetically controlled recovery of SMP with one switching temperature Tsw (dual-shape effect) or with two Tsws (triple-shape effect). The use of magnetic field to change the apparent switching temperature (Tsw,app) of the dual or triple-shape nanocomposites is described. Finally, the capability of magnetic nanocomposites to remember the magnetic field strength (H) initially used to deform the sample (magnetic-memory effect) is addressed. The distinguished advantages of magnetic heating over conventional heating methods make these multifunctional nanocomposites attractive candidates for in vivo applications.

Razzaq, Muhammad Yasar; Behl, Marc; Lendlein, Andreas

2012-09-01

350

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

351

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

352

Nanoporous organic polymer networks  

Microsoft Academic Search

Nanoporous organic polymer networks are a class of materials consisting solely of the lighter elements in the periodic table. These materials have potential uses in areas such as storage, separation, and catalysis. Here, we review the different classes of nanoporous polymer networks including covalent organic frameworks, hypercrosslinked polymers, conjugated microporous polymers, and polymers of intrinsic microporosity. The growing variety in

Robert Dawson; Andrew I. Cooper; Dave J. Adams

353

Nanoimprint lithography for functional polymer patterning  

NASA Astrophysics Data System (ADS)

Organic semiconductors have generated huge interested in recent years for low-cost and flexible electronics. Current and future device applications for semiconducting polymers include light-emitting diodes, thin-film transistors, photovoltaic cells, photodetectors, lasers, and memories. The performance of conjugated polymer devices depends on two major factors: the chain conformation in polymer film and the device architecture. Highly ordered chain structure usually leads to much improved performance by enhancing interchain interaction to facilitate carrier transport. The goal of this research is to improve the performance of organic devices with the nanoimprint lithography. The work begins with the controlling of polymer chain orientation in patterned nanostructures through nanoimprint mold design and process parameter manipulation, and studying the effect of chain ordering on material properties. Then, step-and-repeat thermal nanoimprint technique for large-scale continuous manufacturing of conjugated polymer nanostructures is developed. After that, Systematic investigation of polymer chain configuration by Raman spectroscopy is carried out to understand how nanoimprint process parameters, such as mold pattern size, temperature, and polymer molecular weight, affects polymer chain configuration. The results indicate that chain orientation in nanoimprinted polymer micro- and nanostructures is highly related to the nanoimprint temperature and the dimensions of the mold structures. The ability to create nanoscale polymer micro- and nanostructures and manipulate their internal chain conformation establishes an original experimental platform that enables studying the properties of functional polymers at the micro- and nanoscale and understanding their fundamental structure-property relationships. In addition to the impact on basic research, the techniques developed in this work are important in applied research and development. Large-area conjugated polymer micro- and nanostructures can be easily fabricated by thermal step-and-repeat nanoimprint for organic flat-panel displays, organic circuits and organic solar panels. The ability to manipulate chain orientation through nanoimprint presents a new route to fine-tune the electrical and photophysical properties of conjugated polymers, which can lead to improved performance for all organic electronics. The techniques developed here also allow for easy incorporation of other micro- and nanoscale soft functional polymers in miniaturized devices and systems for new applications in electronics, photonics, sensors and bioengineering.

Cui, Dehu

354

Orientational photorefractive properties in polymer-dispersed liquid crystals with different polymer matrixes  

NASA Astrophysics Data System (ADS)

We report orientational photorefractive effects observed in photoconductive liquid crystals (LCs) contained with three kinds of polymer, i.e., poly(methyl methacrylate) (PMMA), poly(vinyl alcohol) (PVA) and a side-chain liquid crystalline polymer (SLCP1). The morphology of the photorefractive composites depended on the kind of polymer strongly. In both PMMA and PVA cases, LC and polymer were phase-separated and the composite showed memory effects. In SLCP1 case, the phase-separation in the composite dose not occur and the high resolution could be achieved. In this case, the photorefractive Bragg gratings were generated and a high two-beam coupling gain coefficient with a low applied field of 4 V/micrometers was observed.

Ono, Hiroshi; Saito, Isao; Kawatsuki, Nobuhiro

1998-10-01

355

Molecularly imprinted polymers: a new approach to the preparation of functional materials  

Microsoft Academic Search

Molecular imprinting is a method for creating specific cavitie s in synthetic polymer matrices with memory for the template molecules. To date molecularly imprinted polymers (MIPs) have obtained a strong position in materials science and technology, expanding significantly the list of functional materials. This article provides a short review of the molecular imprinting technique with special attention paid to electrosynthesized

Andres Öpik; Anna Menaker; Jekaterina Reut; Vitali Syritski

2009-01-01

356

Memory for Speech and Speech for Memory  

ERIC Educational Resources Information Center

Thirty kindergarteners, 15 who substituted /w/ for /r/ and 15 with correct articulation received two perception tests and a memory test that included /w/ and /r/ in minimally contrastive syllables. (Author)

Locke, John L.; Kutz, Kathryn J.

1975-01-01

357

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

Microsoft Academic Search

A number of theories posit a relationship between autobiographical memory and identity. To test this we assessed the status of autobiographical memory and identity in 20 individuals with Alzheimer's disease (AD) and 20 age?matched controls, and investigated whether degree of autobiographical memory impairment was associated with changes in identity. Two tests of autobiographical memory (Autobiographical Memory Interview, autobiographical fluency) and

Donna Rose Addis; Lynette Tippett

2004-01-01

358

Memory Demands and the Development of Young Children's Memory.  

ERIC Educational Resources Information Center

Investigates the nature of and changes in early memory demands and assesses the relationship between memory demands and memory performance among 10 children 30 and 42 months old and their mothers. Results suggested that mothers' memory demands have an impact on children's memory performance--providing at least partial support for Vygotsky's…

Ratner, Hilary Horn

1984-01-01

359

Psychophysiology of prospective memory.  

PubMed

Prospective memory involves the self-initiated retrieval of an intention upon an appropriate retrieval cue. Cue identification can be considered as an orienting reaction and may thus trigger a psychophysiological response. Here we present two experiments in which skin conductance responses (SCRs) elicited by prospective memory cues were compared to SCRs elicited by aversive stimuli to test whether a single prospective memory cue triggers a similar SCR as an aversive stimulus. In Experiment 2 we also assessed whether cue specificity had a differential influence on prospective memory performance and on SCRs. We found that detecting a single prospective memory cue is as likely to elicit a SCR as an aversive stimulus. Missed prospective memory cues also elicited SCRs. On a behavioural level, specific intentions led to better prospective memory performance. However, on a psychophysiological level specificity had no influence. More generally, the results indicate reliable SCRs for prospective memory cues and point to psychophysiological measures as valuable approach, which offers a new way to study one-off prospective memory tasks. Moreover, the findings are consistent with a theory that posits multiple prospective memory retrieval stages. PMID:24138288

Rothen, Nicolas; Meier, Beat

2014-10-01

360

Reconsolidation of drug memories  

PubMed Central

Persistent, unwanted memories are believed to be key contributors to drug addiction and the chronic relapse problem over the lifetime of the addict. Contrary to the long-held idea that memories are static and fixed, new studies in the last decade have shown that memories are dynamic and changeable. However, they are changeable only under specific conditions. When a memory is retrieved (reactivated), it becomes labile for a period of minutes to hours and then is reconsolidated to maintain long-term memory. Recent findings indicate that even well-established long-term memories may be susceptible to disruption by interfering with reconsolidation through delivery of certain amnestic agents during memory retrieval. Here I review the growing literature on memory reconsolidation in animal models of addiction, including sensitization, conditioned place preference and self-administration. I also discuss (a) several issues that need to be considered in interpreting the findings from reconsolidation studies and (b) future challenges and directions for memory reconsolidation studies in the field of addiction. The findings indicate promise for using this approach as a therapy for disrupting the long-lasting memories that can trigger relapse.

Sorg, Barbara A.

2012-01-01

361

Helicobacter pylori: therapeutic targets.  

PubMed Central

Helicobacter pylori is now considered a major pathogen of the upper gastrointestinal tract. It is seen as an important cause of peptic ulceration not associated with NSAID use. It is also increasingly linked to other diseases of the GI tract, although the relationship between the organism and conditions such as gastric cancer, non-ulcer dyspepsia and gastroesophageal reflux disease is not as clear as is the case in peptic ulcer disease. This is probably because of a lack of well-performed, statistically powerful, prospective therapeutic trials that indicate that H. pylori eradication is of benefit in these diseases. The high infection rate without overt disease seen in many populations, especially from developing countries, probably contributes to this "credibility gap." While we have excellent therapeutic regimens available at this time, rational targeting requires that the objective evidence in favor of therapeutic intervention in upper GI disease, as well as the local H. pylori epidemiology, needs to be considered.

Louw, J. A.; Marks, I. N.

1998-01-01

362

Therapeutic antioxidant medical gas.  

PubMed

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

363

Therapeutics for cognitive aging  

PubMed Central

This review summarizes the scientific talks presented at the conference “Therapeutics for Cognitive Aging,” hosted by the New York Academy of Sciences and the Alzheimer’s Drug Discovery Foundation on May 15, 2009. Attended by scientists from industry and academia, as well as by a number of lay people—approximately 200 in all—the conference specifically tackled the many aspects of developing therapeutic interventions for cognitive impairment. Discussion also focused on how to define cognitive aging and whether it should be considered a treatable, tractable disease.

Shineman, Diana W.; Salthouse, Timothy A.; Launer, Lenore J.; Hof, Patrick R.; Bartzokis, George; Kleiman, Robin; Luine, Victoria; Buccafusco, Jerry J.; Small, Gary W.; Aisen, Paul S.; Lowe, David A.; Fillit, Howard M.

2011-01-01

364

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.

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

2009-01-01

365

Lymphedema and Therapeutic Lymphangiogenesis  

PubMed Central

Lymphedema is a disorder of the lymphatic vascular system characterized by impaired lymphatic return and swelling of the extremities. Lymphedema is divided into primary and secondary forms based on the underlying etiology. Despite substantial advances in both surgical and conservative techniques, therapeutic options for the management of lymphedema are limited. Although rarely lethal, lymphedema is a disfiguring and disabling condition with an associated decrease in the quality of life. The recent impressive expansion of knowledge on the molecular mechanisms governing lymphangiogenesis provides new possibilities for the treatment of lymphedema. This review highlights the lymphatic biology, the pathophysiology of lymphedema, and the therapeutic lymphangiogenesis using hepatocyte growth factor.

Nakagami, Hironori; Kaneda, Yasufumi; Morishita, Ryuichi

2013-01-01

366

Novel biomimetic polymersomes as polymer therapeutics for drug delivery.  

PubMed

Novel amphiphilic diblock copolymers, cholesterol-end-capped poly(2-methacryloyloxyethyl phosphorylcholine) (CMPC), which have poly(2-methacryloyloxyethyl phosphorylcholine) (poly(MPC)) as hydrophilic segment and cholesterol as hydrophobic segment, was specially designed as drug delivery systems. Fluorescence probe technique and transmission electron microscope (TEM) characterizations indicated that this novel amphiphilic copolymer formed micelles structure in water and the critical micelle concentration (CMC) was determined to be 1.57 x 10(-7) mol/l. A commercial obtained polymeric amphiphiles, Cholesterol end capped PEO (CPEO), which had a similar structure with CMPC, was used as a control in the cytotoxicity test. While CPEO showed obvious cytotoxicity, cytotoxicity of this novel amphiphiles was not observed as indicated by cell culture. Anti-cancer drug adriamycin (ADR) was incorporated into the micelles by oil-in-water method. The size of the drug-containing micelles was less than 200 nm, and the size distribution of the drug-containing micelles showed a narrow and monodisperse unimodal pattern. The release rate of ADR from the nanosphere was slow and the release continued over 7 days and the release rate decreased with the increase of molecular weights of the copolymer and the amount of the drug entrapped. These experimental results suggested that the nanoparticles prepared from CMPC block copolymers could be a good candidate for injectable drug delivery carrier. PMID:16154659

Xu, Jian-Ping; Ji, Jian; Chen, Wei-Dong; Shen, Jia-Cong

2005-10-20

367

PPAR? AGONISTS AS THERAPEUTICS FOR THE TREATMENT OF ALZHEIMER'S DISEASE  

PubMed Central

Alzheimer’s Disease is characterized by the deposition of ?-amyloid within the brain parenchyma and is accompanied by the impairment of neuronal metabolism and function, leading to extensive neuronal loss. The disease involves the perturbation of synaptic function, energy and lipid metabolism. The development of amyloid plaques results in the induction of microglial-mediated inflammatory response. The nuclear receptor PPAR? is a ligand-activated transcription factor whose biological actions are to regulate glucose and lipid metabolism and suppress inflammatory gene expression. Thus, agonists of this receptor represent an attractive therapeutic target for AD. There is now an extensive body of evidence that has demonstrated the efficacy of PPAR? agonists in ameliorating disease–related pathology and improved learning and memory in animal models of AD. Recent clinical trials of the PPAR? agonist rosiglitazone have shown significant improvement in memory and cognition in AD patients. Thus, PPAR? represents an important new therapeutic target in treating AD.

Landreth, Gary; Jiang, Qingguang; Mandrekar, Shweta; Heneka, Michael

2008-01-01

368

Metal-polymer and polymer-polymer interfaces: Application to conjugated polymer electronic devices  

Microsoft Academic Search

The study of metal-polymer and polymer-polymer interfaces is applied to conjugated polymer electronic devices. Conjugated polymers are a class of organic materials which have metallic or semiconducting properties which are being investigated as alternatives to traditional semiconducting materials. When conjugated polymers are used in devices, the interfaces are found to be critical to device performance. X-ray photoelectron spectroscopy (XPS) and

Julie Anne Osladil Smallfield

2002-01-01

369

Children's Memory for Early Experience.  

ERIC Educational Resources Information Center

This introduction reviews recent trends in childhood memory research, focusing on closer relations between the study of memory development and the study of cognitive and neurological development, new relations between the study of memory development and the study of adult memory, and new relations between the study of memory development and…

Newcombe, Nora; And Others

1995-01-01

370

Practical Memory Concerns in Adulthood  

ERIC Educational Resources Information Center

In this article, we focus on practical memory concerns in adulthood. Young, middle-aged, and community-dwelling older adults responded to seven open-ended questions covering the topics of memory self-efficacy, memory management, memory remediation, and fears about memory aging in adulthood. The results revealed several similarities among the age…

Reese, Celinda M.; Cherry, Katie E.

2004-01-01

371

Does fascia hold memories?  

PubMed

The idea that tissues may possess some sort of memory is a controversial topic in manual medicine, calling for research and clinical exploration. Many bodyworkers, at some point in their practice, have experienced phenomena that may be interpreted as representing a release of memory traces when working on dysfunctional tissues. This feeling may have been accompanied by some type of sensory experience, for the therapist and/or the patient. In some cases, early traumatic experiences may be recalled. When this happens, the potency of the memory may be erased or eased, along with restoration of tissue function. Hence the questions: can memories be held in the fascia? And: are these memories accessible during manual fascial work? Modern research has proposed a variety of different interpretations as to how memory might be stored in soft tissues, possibly involving other forms of information storage not exclusively processed neurologically (Box 1). PMID:24725795

Tozzi, Paolo

2014-04-01

372

Lincoln Memorial Interactive  

NSDL National Science Digital Library

It is hard not be moved by the Lincoln Memorial in Washington, D.C., and this engaging and interactive exhibit captures the essence of this moving tribute to the nation's 16th president. The site is divided into two areas, "Reflections" and "Memorial". In the "Reflections" area, visitors can listen and watch park rangers talk about their own memories and remembrances of this august and somber place. There are seven separate profiles here, and it's a good idea to start with Kawther Elmi's thoughts on her childhood in East Africa. The "Memorial" area includes dramatic and multi-perspective views of the Lincoln statue and the Memorial grounds. Visitors may also use the "Downloads" area to download audio files of the ranger's talks, along with images of the Memorial.

373

Emotional Memory in Schizophrenia  

PubMed Central

Emotional memories play an important role in our day-to-day experience, informing many of our minute-to-minute decisions (eg, where to go for dinner, what are the likely consequences of not attending a meeting), as well as our long-term goal setting. Individuals with schizophrenia appear to be impaired in memory for emotional experiences, particularly over longer delay periods, which may contribute to deficits in goal-related behavior and symptoms of amotivation and anhedonia. This article reviews factors that are known to influence emotional memory in healthy subjects, applies these factors to results from emotional memory studies with individuals with schizophrenia, and then uses extant neurobiological models of emotional memory formation to develop hypotheses about biological processes that might particularly contribute to emotional memory impairment in schizophrenia.

Herbener, Ellen S.

2008-01-01

374

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

375

Effect of Different Shape-Memory Processing Methods on the Thermomechanical Cyclic Properties of a Shape-Memory Polyurethane  

NASA Astrophysics Data System (ADS)

Shape-memory polymers are materials that are capable of changing their shape when an external stimulus is applied. This effect is called the shape-memory effect (SME) and takes place by means of a thermomechanical cycle called programming. The SME depends on the thermomechanical conditions at which programming is performed, and the influence of these conditions differs depending on whether the programming is performed with a strain- or stress-controlled protocol. This study focuses on finding the thermomechanical cycling conditions in stress-controlled programming (T prog and ?m) that stabilize the material in the fewest cycles while obtaining the best mechanical and shape-memory properties over the highest number of cycles. Using a T prog above or below, the glass transition temperature makes a big difference in terms of shape recovery and the maximum stress is a key factor in the stabilization of shape-memory properties.

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

2014-04-01

376

Sparse distributed memory  

SciTech Connect

Theoretical models of the human brain and proposed neural-network computers are developed analytically. Chapters are devoted to the mathematical foundations, background material from computer science, the theory of idealized neurons, neurons as address decoders, and the search of memory for the best match. Consideration is given to sparse memory, distributed storage, the storage and retrieval of sequences, the construction of distributed memory, and the organization of an autonomous learning system. 63 refs.

Kanerva, P.

1988-01-01

377

Sparse distributed memory  

NASA Technical Reports Server (NTRS)

Theoretical models of the human brain and proposed neural-network computers are developed analytically. Chapters are devoted to the mathematical foundations, background material from computer science, the theory of idealized neurons, neurons as address decoders, and the search of memory for the best match. Consideration is given to sparse memory, distributed storage, the storage and retrieval of sequences, the construction of distributed memory, and the organization of an autonomous learning system.

Kanerva, Pentti

1988-01-01

378

Schemas and Memory Consolidation  

Microsoft Academic Search

Memory encoding occurs rapidly, but the consolidation of memory in the neocortex has long been held to be a more gradual process. We now report, however, that systems consolidation can occur extremely quickly if an associative ``schema'' into which new information is incorporated has previously been created. In experiments using a hippocampal-dependent paired-associate task for rats, the memory of flavor-place

Dorothy Tse; Rosamund F. Langston; Masaki Kakeyama; Ingrid Bethus; Patrick A. Spooner; Emma R. Wood; Menno P. Witter; Richard G. M. Morris

2007-01-01

379

Removing pathogenic memories  

Microsoft Academic Search

Experimental research examining the neural bases of nondeclarative memory has offered intriguing insight into how functional\\u000a and dysfunctional implicit learning affects the brain. Long-term modifications of synaptic transmission, in particular, are\\u000a currently considered the most plausible mechanism underlying memory trace encoding and compulsions, addiction, anxiety, and\\u000a phobias. Therefore, an effective psychotherapy must be directed to erase maladaptive implicit memories and

Diego Centonze; Alberto Siracusano; Paolo Calabresi; Giorgio Bernardi

2005-01-01

380

Testing Shared Memories  

Microsoft Academic Search

. Sequential consistency is the most-widely used correctness condition for multiprocessormemory systems. This paper studies the problem of testing shared memory multiprocessors todetermine if they are indeed providing a sequentially consistent memory. It presents the first formalstudy of this problem, which has applications to testing new memory system designs and realizations,providing run-time fault tolerance, and detecting bugs in parallel programs.A

Phillip B. Gibbons; Ephraim Korach

1997-01-01

381

The Memory Management Reference  

NSDL National Science Digital Library

The Memory Management Reference is a useful compilation of memory management resources. The site offers a range of information including a handy, hyperlinked dictionary of terms, an introduction to memory management, a detailed bibliography which includes abstracts, FAQs, links to other resources, and more. It is both a good reference point for current garbage collection research, as well as a nice introduction to the subject for the novice.

2001-01-01

382

Thinking and Memory  

Microsoft Academic Search

\\u000a Remembering the past is crucially important for cognitive functions, such as anticipating and planning future activities or\\u000a thinking about one’s own self. In Tulving’s hierarchy of long-term memory systems, episodic memory is the highest one that\\u000a is most likely uniquely human. One of the characteristics of episodic memory is the ability to mentally travel into the past\\u000a and the future.

Matthias Brand; Hans J. Markowitsch

383

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

384

Memory Load and Dump  

NASA Astrophysics Data System (ADS)

This proposal is a test and verification of the STIS dump of memory capability.Areas of Control Section {CS} to dump include: EDAC RAM, EEPROM, and CS PROM {with the CS in Operate}. Areas of MIE memory to dump include: MIE RAM and MIE PROM {with the MIE in Operate}. Note that the MIE memory must first be copied to CS buffer RAM as images, which are then dumped.Supports Activity STIS-02;

Welty, Alan

2008-07-01

385

Measuring Therapeutic Effectiveness.  

ERIC Educational Resources Information Center

In the recent past, there has been a great deal of effort directed toward developing techniques for documenting therapeutic outcome. Funding sources and the general public seem to be demanding more meaningful data which indicate, in a clear manner, whether or not the services they are paying for are of value. Mental health centers, like other…

Callister, Sheldon L.

386

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

387

Aptamers as therapeutics  

Microsoft Academic Search

Nucleic acid aptamers can be selected from pools of random-sequence oligonucleotides to bind a wide range of biomedically relevant proteins with affinities and specificities that are comparable to antibodies. Aptamers exhibit significant advantages relative to protein therapeutics in terms of size, synthetic accessibility and modification by medicinal chemistry. Despite these properties, aptamers have been slow to reach the marketplace, with

Anthony D. Keefe; Supriya Pai; Andrew Ellington

2010-01-01

388

Developing Therapeutic Listening  

ERIC Educational Resources Information Center

We present an experience-near account of the development of therapeutic listening in first year counselling students. A phenomenological approach was employed to articulate the trainees' lived experiences of their learning. Six students who had just completed a one-year postgraduate certificate in counselling skills were interviewed and the…

Lee, Billy; Prior, Seamus

2013-01-01

389

Plasmids Encoding Therapeutic Agents.  

National Technical Information Service (NTIS)

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 ...

W. K. Keener

2004-01-01

390

Interpretations of Polymer-Polymer Miscibility.  

ERIC Educational Resources Information Center

Discusses various aspects of polymeric mixtures, mixtures of structurally different homopolymers, copolymers, terpolymers, and the like. Defines concepts of polymer-polymer miscibility from practical and theoretical viewpoints, and ways of predicting such miscibility. (JN)

Olabisi, Olagoke

1981-01-01

391

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

392

Memory on time.  

PubMed

Considerable recent work has shown that the hippocampus is critical for remembering the order of events in distinct experiences, a defining feature of episodic memory. Correspondingly, hippocampal neuronal activity can 'replay' sequential events in memories and hippocampal neuronal ensembles represent a gradually changing temporal context signal. Most strikingly, single hippocampal neurons - called time cells - encode moments in temporally structured experiences much as the well-known place cells encode locations in spatially structured experiences. These observations bridge largely disconnected literatures on the role of the hippocampus in episodic memory and spatial mapping, and suggest that the fundamental function of the hippocampus is to establish spatio-temporal frameworks for organizing memories. PMID:23318095

Eichenbaum, Howard

2013-02-01

393

Memory on time  

PubMed Central

Considerable recent work has shown that the hippocampus is critical for remembering the order of events in distinct experiences, a defining feature of episodic memory. Correspondingly, hippocampal neuronal activity can ‘replay’ sequential events in memories and hippocampal neuronal ensembles represent a gradually changing temporal context signal. Most strikingly, single hippocampal neurons – called time cells – encode moments in temporally structured experiences much as the well-known place cells encode locations in spatially structured experiences. These observations bridge largely disconnected literatures on the role of the hippocampus in episodic memory and spatial mapping, and suggest that the fundamental function of the hippocampus is to establish spatio-temporal frameworks for organizing memories.

Eichenbaum, Howard

2013-01-01

394

Distinguishing short-term memory from working memory  

Microsoft Academic Search

The aim of the present research was to determine whether short-term memory and working memory could be distinguished. In two\\u000a studies, 7- to 13-year-olds (N = 155,N = 132) were administered tasks thought to assess short-term memory as well as tasks thought to assess working memory. Both\\u000a exploratory and confirmatory factor analyses distinguished short-term memory tasks from working memory tasks.

Robert Kail; Lynda K. Hall

2001-01-01

395

Memory-to-memory connection structures in FPGAs with embedded memory arrays  

Microsoft Academic Search

This paper shows that the speed of FPGAs with large embedded memory arrays can be improved by adding direct programmable connections between the memories. Nets that connect to multiple memory arrays are often difficult to route, and are often part of the critical path of circuit implementations. The memory-to-memory connection structure proposed in this paper allows for the efficient implementation

Steven J. E. Wilton; Jonathan Rose; Zvonko G. Vranesic

1997-01-01

396

Polymer--drug conjugates as nano-sized medicines.  

PubMed

Polymer Therapeutics have enormously evolved in the past decades. Several polymeric drugs as well as polymer-protein conjugates have been in the market since the 90s, but although polymer-drug conjugates are already in clinical trials they still need to reach this final goal. There are four main convergent strategies to move this platform technology further. First, exploitation of new molecular targets in cancer therapy and design of polymer-drug conjugates as treatments for other diseases. Second, the development of combination therapy. Third, attempts to improve polymer chemistry, including the use of new well-defined architectures and the optimization of the advanced characterization techniques essential to transform a promising conjugate into a candidate for clinical evaluation. Finally, increased understanding of polymer conjugate features that govern clinical risk-benefit is leading to an appreciation of clinical biomarkers that will open new possibilities for personalized therapy. PMID:21724381

Canal, Fabiana; Sanchis, Joaquin; Vicent, María J

2011-12-01

397

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

398

Molecularly imprinted polymers in the drug discovery process  

Microsoft Academic Search

Since molecularly imprinted polymers (MIPs) are designed to have a memory for their molecular templates it is easy to draw parallels with the affinity between biological receptors and their substrates. Could MIPs take the place of natural receptors in the selection of potential drug molecules from synthetic compound libraries? To answer that question this review discusses the results of MIP

Daniel L. Rathbone

2005-01-01

399

Design strategies for therapeutic ultrasound phased arrays  

NASA Astrophysics Data System (ADS)

High-intensity focused ultrasound is used in many therapeutic applications such as drug activation/drug delivery, hyperthermia, cancer therapy, ultrasound surgery and myocardial ablation. Various ultrasonic systems have been proposed for these therapeutic applications. While many applicators produce adequate power levels, multiple element ultrasound phased arrays adjust for phase aberrations, focus around obstructions such as bone and/or air spaces (lungs), and follow, in real time, a moving target. Since large aperture arrays with several hundred elements are required, design compromises keep the element count and fabrication cost at a reasonable level. These trade-offs, which optimize the array aperture with respect to element count, often result in a non-ideal aspect ratio (element width to thickness), leading to lateral mode vibrations which reduce the electrical to acoustical efficiency to about 10 - 20%. These vibrations are easily observed with a laser interferometer system. Piezo composite technology, which eliminates the non-ideal aspect ratio by dividing the individual array elements into long, thin rods, provides a solution to this problem. The spaces between the rods are filled with a polymer to provide structural support and allow deposition of electrode layers to interconnect individual rods and to outline array elements. Several piezo composite transducers have been tested, and initial results show a greatly improved beam pattern and increased efficiency. Power handling capability of composites has recently improved allowing outputs in excess of 10 watts/cm2 with efficiencies greater than 60%. This is sufficient for many therapeutic applications.

Kluiwstra, Jan-Ulco A.; McGough, Robert J.; Hamilton, James D.; O'Donnell, Matthew; Cain, Charles A.

1997-04-01

400

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.

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

2014-01-01

401

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

402

Synthetic circuits integrating logic and memory in living cells.  

PubMed

Logic and memory are essential functions of circuits that generate complex, state-dependent responses. Here we describe a strategy for efficiently assembling synthetic genetic circuits that use recombinases to implement Boolean logic functions with stable DNA-encoded memory of events. Application of this strategy allowed us to create all 16 two-input Boolean logic functions in living Escherichia coli cells without requiring cascades comprising multiple logic gates. We demonstrate long-term maintenance of memory for at least 90 cell generations and the ability to interrogate the states of these synthetic devices with fluorescent reporters and PCR. Using this approach we created two-bit digital-to-analog converters, which should be useful in biotechnology applications for encoding multiple stable gene expression outputs using transient inputs of inducers. We envision that this integrated logic and memory system will enable the implementation of complex cellular state machines, behaviors and pathways for therapeutic, diagnostic and basic science applications. PMID:23396014

Siuti, Piro; Yazbek, John; Lu, Timothy K

2013-05-01

403

Early genomics of learning and memory: a review.  

PubMed

The characterization of the molecular mechanisms whereby our brain codes, stores and retrieves memories remains a fundamental puzzle in neuroscience. Despite the knowledge that memory storage involves gene induction, the identification and characterization of the effector genes has remained elusive. The completion of the Human Genome Project and a variety of new technologies are revolutionizing the way these mechanisms can be explored. This review will examine how a genomic approach can be used to dissect and analyze the complex dynamic interactions involved in gene regulation during learning and memory. This innovative approach is providing information on a new class of genes associated with learning and memory in health and disease and is elucidating new molecular targets and pathways whose pharmacological modulation may allow new therapeutic approaches for improving cognition. PMID:16594975

Paratore, S; Alessi, E; Coffa, S; Torrisi, A; Mastrobuono, F; Cavallaro, S

2006-04-01

404

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

405

From Commodity Polymers to Functional Polymers  

PubMed Central

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

2014-01-01

406

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

407

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.

Karnatovskaia, Lioudmila V.; Wartenberg, Katja E.

2014-01-01

408

Therapeutic antibodies against cancer  

PubMed Central

Antibody-based therapeutics against cancer are highly successful in clinic and currently enjoy unprecedented recognition of their potential; 13 monoclonal antibodies (mAbs) have been approved for clinical use in the European Union and in the United States (one, mylotarg, was withdrawn from market in 2010). Three of the mAbs (bevacizumab, rituximab, trastuzumab) are in the top six selling protein therapeutics with sales in 2010 of more than $5 bln each. Hundreds of mAbs including bispecific mAbs and multispecific fusion proteins, mAbs conjugated with small molecule drugs and mAbs with optimized pharmacokinetics are in clinical trials. However, challenges remain and it appears that deeper understanding of mechanisms is needed to overcome major problems including resistance to therapy, access to targets, complexity of biological systems and individual variations.

Adler, Mark J.; Dimitrov, Dimiter S.

2012-01-01

409

Complement-targeted therapeutics.  

PubMed

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

2007-11-01

410

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.

Ricklin, Daniel; Lambris, John D

2010-01-01

411

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.

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

2011-01-01

412

Memory Metals (Marchon Eyewear)  

NASA Technical Reports Server (NTRS)

Another commercial application of memory metal technology is found in a "smart" eyeglass frame that remembers its shape and its wearer's fit. A patented "memory encoding process" makes this possible. Heat is not required to return the glasses to shape. A large commercial market is anticipated.

1991-01-01

413

Shape Memory Alloys  

Microsoft Academic Search

This special issue on shape memory alloys (SMA) is an encore to a special issue on the same topic edited by us six years ago (Smart Mater. Struct.9 (5) October 2000). A total of 19 papers is offered in this issue, organized into the three broad categories of modeling, characterization and applications. In addition to thermally activated shape memory alloys,

Abhijit Bhattacharyya; Dimitris C Lagoudas

2007-01-01

414

Working Memory and Attitudes  

ERIC Educational Resources Information Center

Working memory capacity has been shown to be an important factor in controlling understanding in the sciences. Attitudes related to studies in the sciences are also known to be important in relation to success in learning. It might be argued that if working memory capacity is a rate controlling feature of learning and success in understanding…

Jung, Eun Sook; Reid, Norman

2009-01-01

415

Learning & Memory Online  

NSDL National Science Digital Library

Cold Spring Harbor Laboratory Press has placed online the journal Learning & Memory, an interdisciplinary journal dedicated to research on the neurobiology of learning and memory. Online full-text content begins with the May/June 1998 issue; abstracts begin with the September/October, 1995 issue. The journal is produced in conjunction with Stanford University's HighWire Press.

1998-01-01

416

The Biology of Memory  

ERIC Educational Resources Information Center

Discusses the conflicting evidence and points of view presented by scientists involved in research on the nature of memory. The research of one group supports a chemical basis for memory, while the other group presents evidence supporting an electro-physiological basis. (JR)

Arehart-Treichel, Joan

1973-01-01

417

Memory technology survey  

NASA Technical Reports Server (NTRS)

The current status of semiconductor, magnetic, and optical memory technologies is described. Projections based on these research activities planned for the shot term are presented. Conceptual designs of specific memory buffer pplications employing bipola, CMOS, GaAs, and Magnetic Bubble devices are discussed.

1981-01-01

418

Eavesdropping without quantum memory  

SciTech Connect

In quantum cryptography the optimal eavesdropping strategy requires that the eavesdropper uses ancillas and quantum memories in order to optimize her information. What happens if the eavesdropper has no quantum memory? It is shown that in this case the eavesdropper obtains a better information/disturbance trade-off by adopting the simple intercept/resend strategy.

Bechmann-Pasquinucci, H. [Dipartimento di Fisica 'A. Volta', University of Pavia, via Bassi 6, I-27100 Pavia, Italy and UCCI.IT, via Olmo 26, I-23888 Rovagnate (Italy)

2006-04-15

419

Memory and Resilience  

Microsoft Academic Search

This study reviews the memories of 40 Holocaust survivors who reflected on their lives more than 60 years after liberation. The participants were randomly selected from the larger group of Holocaust survivors in the “Forgiveness, Resiliency, and Survivorship Among Holocaust Survivors” study funded by the John Templeton Foundation. Data collected from open-end questions about their memories were analyzed. The findings

Harriet L. Cohen; Katie Meek; Mary Lieberman

2010-01-01

420

Human Learning and Memory  

ERIC Educational Resources Information Center

This innovative textbook is the first to integrate learning and memory, behaviour, and cognition. It focuses on fascinating human research in both memory and learning (while also bringing in important animal studies) and brings the reader up to date with the latest developments in the subject. Students are encouraged to think critically: key…

Lieberman, David A.

2012-01-01

421

MEMORY AND CONSCIOUSNESS  

Microsoft Academic Search

Speculations supported by empirical observations are offered concerning different memory systems (procedural, semantic, and episodic) and corresponding varieties of consciousness (anoetic, noetic, and autonoetic), with special emphasis on episodic memory and autonoetic consciousness as its necessary correlate. Evidence relevant to these speculations is derived from a case study of an amnesic patient who is conscious in some ways but not

ENDEL TULVING

1985-01-01

422

Composable memory transactions  

Microsoft Academic Search

Writing concurrent programs is notoriously difficult, and is of increasing practical importance. A particular source of concern is that even correctly-implemented concurrency abstractions cannot be composed together to form larger abstractions. In this paper we present a new concurrency model, based on transactional memory, that offers far richer composition. All the usual benefits of transactional memory are present (e.g. freedom

Tim Harris; Simon Marlow; Simon Peyton-Jones; Maurice Herlihy

2005-01-01

423

Extending Mondrian Memory Protection.  

National Technical Information Service (NTIS)

Most modern operating systems implement some sort of memory protection scheme for user processes. These schemes make it is possible to set access permissions that determine whether a region of memory allocated for a process can be read, written, or execut...

C. Kolbitsch C. Kruegel E. Kirda

2010-01-01

424

Human Memory: The Basics  

ERIC Educational Resources Information Center

The human mind has two types of memory: short-term and long-term. In all types of learning, it is best to use that structure rather than to fight against it. One way to do that is to ensure that learners can fit new information into patterns that can be stored in and more easily retrieved from long-term memory.

Martinez, Michael E.

2010-01-01

425

Predicting Reasoning from Memory  

ERIC Educational Resources Information Center

In an effort to assess the relations between reasoning and memory, in 8 experiments, the authors examined how well responses on an inductive reasoning task are predicted from responses on a recognition memory task for the same picture stimuli. Across several experimental manipulations, such as varying study time, presentation frequency, and the…

Heit, Evan; Hayes, Brett K.

2011-01-01

426

Regret as Autobiographical Memory  

ERIC Educational Resources Information Center

We apply an autobiographical memory framework to the study of regret. Focusing on the distinction between regrets for specific and general events we argue that the temporal profile of regret, usually explained in terms of the action-inaction distinction, is predicted by models of autobiographical memory. In two studies involving participants in…

Davison, Ian M.; Feeney, Aidan

2008-01-01

427

Reading, Memory, and Metacognition.  

ERIC Educational Resources Information Center

This study was designed to explore relations among reading skills, metareading, memory, and metamemory. Interactions among these skills were investigated as related to reading ability, operativity, and grade level. The effects of experience, operativity, and metacognition on reading and memory skills were discussed. (Author/DWH)

Byrd, Diana M.; Gholson, Barry

1985-01-01

428

When forgetting preserves memory.  

PubMed

There has been a resurgence of interest in defining the circumstances leading to memory modifications. Studies have shown that reactivating a supposedly stable memory re-introduces a time-limited window of plasticity during which presentation of interfering material can cause long-term memory changes. The present study asks whether such memory changes can be prevented if people are instructed to forget the memory before the new material is encoded. Participants learned a set of objects. After 48?h, they were reminded of this learning episode, and learned another set of objects. Again 48?h later, they recalled the first (Exp. 1) or second set (Exp. 3). As shown previously, a reminder caused intrusions from the second set into recall of the first set. Here I show that the instruction to forget the first set significantly diminished intrusions from the second set, especially when the instruction was given before the new set was encoded in the second session. Experiment 2 suggests that the reduced intrusions were due to list segregation/isolation, rather than temporarily inhibited access to Set 1. Taken together, the study shows that the attempt to forget a memory can immunize it such that the presentation of interfering material has limited effects, and the memory can be recalled unchanged in the future. This is important when veridical memory is essential, such as in eyewitness testimonies. PMID:23382724

Hupbach, Almut

2013-01-01

429

Linux Physical Memory Analysis  

Microsoft Academic Search

We present a tool suite for analysis of physical memory usage within the Linux kernel environment. This tool suite can be used to collect and analyze how the physi- cal memory within a Linux environment is being used. Embedded subsystems are common in today's computer systems. These embedded subsystems range from the very simple to the very complex. In such

Paul Movall; Ward Nelson; Shaun Wetzstein

2005-01-01

430

Computer Associative Memory Study.  

National Technical Information Service (NTIS)

Work done in the Computer Associative Memory Study Program is described. The object was to determine whether use of an Associative Memory would be of value in spaceborne computing problems. The results of the study are that a class of spaceborne problems ...

1964-01-01

431

Distributed memory. Technical report  

SciTech Connect

A brief account is given of how a neural network can store a distributed content addressable memory. Some of the properties of such a network as well as a possible site of storage of long and short-term memory are discussed.

Cooper, L.N.

1985-03-13

432

Types of Memory  

MedlinePLUS

... remember until you pass it on. Long-term memory stores information that your brain retains because it is important to you. Basic information remembered includes names of family and friends, your address, as ... Long-term memory can be further divided into explicit, implicit and ...

433

Age and prospective memory  

Microsoft Academic Search

This paper reports an investigation into the effects of age, intelligence, and retrospective memory on performance in a prospective memory task in which subjects aged between 52 and 95 were required to telephone once a day either between two times or at an exact time. The most important influence on performance was how subjects chose to remember to make the

Elizabeth A. Maylor

1990-01-01

434

When Forgetting Preserves Memory  

PubMed Central

There has been a resurgence of interest in defining the circumstances leading to memory modifications. Studies have shown that reactivating a supposedly stable memory re-introduces a time-limited window of plasticity during which presentation of interfering material can cause long-term memory changes. The present study asks whether such memory changes can be prevented if people are instructed to forget the memory before the new material is encoded. Participants learned a set of objects. After 48?h, they were reminded of this learning episode, and learned another set of objects. Again 48?h later, they recalled the first (Exp. 1) or second set (Exp. 3). As shown previously, a reminder caused intrusions from the second set into recall of the first set. Here I show that the instruction to forget the first set significantly diminished intrusions from the second set, especially when the instruction was given before the new set was encoded in the second session. Experiment 2 suggests that the reduced intrusions were due to list segregation/isolation, rather than temporarily inhibited access to Set 1. Taken together, the study shows that the attempt to forget a memory can immunize it such that the presentation of interfering material has limited effects, and the memory can be recalled unchanged in the future. This is important when veridical memory is essential, such as in eyewitness testimonies.

Hupbach, Almut

2013-01-01

435

High Density Memory Device.  

National Technical Information Service (NTIS)

This invention provides novel high density memory devices that are electrically addressable permitting effective reading and writing, that provide a high memory density (e.g., 10.sup.15 bits/cm.sup.3), that provide a high degree of fault tolerance, and th...

D. E. Bocian D. T. Gryko J. Lindsey P. C. Clausen W. G. Kuhr

2005-01-01

436

Holographic Random Access Memory.  

National Technical Information Service (NTIS)

We designed and demonstrated a fully working, large-scale random-access holographic memory. The recording medium is a Fe-doped LiNb03 photorefractive crystal. The storage capacity of the memory is limited by the dynamic range and geometric limitation. The...

D. Psaltis

1997-01-01

437

Toxicology of antisense therapeutics.  

PubMed

Targeting unique mRNA molecules using antisense approaches, based on sequence specificity of double-stranded nucleic acid interactions should, in theory, allow for design of drugs with high specificity for intended targets. Antisense-induced degradation or inhibition of translation of a target mRNA is potentially capable of inhibiting the expression of any target protein. In fact, a large number of proteins of widely varied character have been successfully downregulated using an assortment of antisense-based approaches. The most prevalent approach has been to use antisense oligonucleotides (ASOs), which have progressed through the preclinical development stages including pharmacokinetics and toxicological studies. A small number of ASOs are currently in human clinical trials. These trials have highlighted several toxicities that are attributable to the chemical structure of the ASOs, and not to the particular ASO or target mRNA sequence. These include mild thrombocytopenia and hyperglycemia, activation of the complement and coagulation cascades, and hypotension. Dose-limiting toxicities have been related to hepatocellular degeneration leading to decreased levels of albumin and cholesterol. Despite these toxicities, which are generally mild and readily treatable with available standard medications, the clinical trials have clearly shown that ASOs can be safely administered to patients. Alternative chemistries of ASOs are also being pursued by many investigators to improve specificity and antisense efficacy and to reduce toxicity. In the design of ASOs for anticancer therapeutics in particular, the goal is often to enhance the cytotoxicity of traditional drugs toward cancer cells or to reduce the toxicity to normal cells to improve the therapeutic index of existing clinically relevant cancer chemotherapy drugs. We predict that use of antisense ASOs in combination with small molecule therapeutics against the target protein encoded by the antisense-targeted mRNA, or an alternate target in the same or a connected biological pathway, will likely be the most beneficial application of this emerging class of therapeutic agent. PMID:15519609

Jason, Tracey L H; Koropatnick, James; Berg, Randal W

2004-11-15

438

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

439

“Enabling Technology” Polymers  

Microsoft Academic Search

An area of polymer science that is of current and growing industrial importance is where the polymer is the enabling technology that makes a component, system, or process work. Without the special polymer, the technology simply does not operate in a useful manner.The characteristics of this arena are very different from high volume commodity or engineering polymers. Performance is the

Joseph G. Wirth

1997-01-01

440

Mitochondria-directed therapeutics.  

PubMed

Mitochondria are key regulators of cell life and death and play an important role in a wide range of diseases, including cancer, diabetes, cardiovascular disease, and the age-related neurodegenerative diseases. The unique structural and functional characteristics of mitochondria enable the selective targeting of drugs designed to modulate the function of this organelle for therapeutic gain. This forum discusses (a) potential new mitochondrial targets for therapeutic intervention, including components of the electron transport chain, the permeability transition, and the membrane dynamics protein mitofusin-2; (b) the role of mitochondria-targeted antioxidants including MitoQ and SS peptides in modulating reactive oxygen and chlorine species induced mitochondrial permeabilization and cell death; and (c) the potential use of SS peptides in ischemia and reperfusion tissue injury. In the future, mitochondrial drug-targeting strategies will be expected to open up avenues for manipulating mitochondrial functions and allow for selective protection or eradication of cells for therapeutic gain in a variety of diseases. PMID:18092938

Armstrong, Jeffrey S

2008-03-01

441

Polycyclic peptide therapeutics.  

PubMed

Owing to their excellent binding properties, high stability, and low off-target toxicity, polycyclic peptides are an attractive molecule format for the development of therapeutics. Currently, only a handful of polycyclic peptides are used in the clinic; examples include the antibiotic vancomycin, the anticancer drugs actinomycin D and romidepsin, and the analgesic agent ziconotide. All clinically used polycyclic peptide drugs are derived from natural sources, such as soil bacteria in the case of vancomycin, actinomycin D and romidepsin, or the venom of a fish-hunting coil snail in the case of ziconotide. Unfortunately, nature provides peptide macrocyclic ligands for only a small fraction of therapeutic targets. For the generation of ligands of targets of choice, researchers have inserted artificial binding sites into natural polycyclic peptide scaffolds, such as cystine knot proteins, using rational design or directed evolution approaches. More recently, large combinatorial libraries of genetically encoded bicyclic peptides have been generated de novo and screened by phage display. In this Minireview, the properties of existing polycyclic peptide drugs are discussed and related to their interesting molecular architectures. Furthermore, technologies that allow the development of unnatural polycyclic peptide ligands are discussed. Recent application of these technologies has generated promising results, suggesting that polycyclic peptide therapeutics could potentially be developed for a broad range of diseases. PMID:23355488

Baeriswyl, Vanessa; Heinis, Christian

2013-03-01

442

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.

2007-02-05

443

Therapeutic AIDS vaccines.  

PubMed

Therapeutic HIV vaccines represent promising strategy as an adjunct or alternative to current antiretroviral treatment options for HIV. Unlike prophylactic AIDS vaccines designed to prevent HIV infection, therapeutic vaccines are given to already infected individuals to help fight the disease by modulating their immune response. The first immunotherapeutic trial in AIDS patients was conducted in 1983. Since then several dozen conventional therapeutic vaccine trials have been carried out. Unfortunately, the results have consistently shown that while HIV-specific immune responses were evident as a result of vaccination, the clinical improvement has been seldom observed. The instances of the apparent clinical benefit were invariably associated with unconventional vaccines that acted in accord with the principles of alloimmunization and/or autologous vaccination. All such vaccines were derived from the blood of HIV carriers or a cell culture and thus they inherently contained allo- or self-antigens unrelated to HIV. This intriguing observation raises the issue whether this clinically successful approach has been unduly neglected. The current strategy biased toward vaccines, which have shown little evidence of clinical efficacy, needs to be diversified and supplemented with research on alternative vaccine approaches geared toward immune tolerance induction. PMID:16787245

Bourinbaiar, A S; Root-Bernstein, R S; Abulafia-Lapid, R; Rytik, P G; Kanev, A N; Jirathitikal, V; Orlovsky, V G

2006-01-01

444

Therapeutic antibody engineering  

PubMed Central

It is an important event in any knowledge area when an authority in the field decides that it is time to share all accumulated knowledge and learnings by writing a text book. This does not occur often in the biopharmaceutical industry, likely due to both the highly dynamic environment with tight timelines and policies and procedures at many pharmaceutical companies that hamper knowledge sharing. To take on a task like this successfully, a strong drive combined with a desire and talent to teach, but also an accommodating and stimulating environment is required. Luckily for those interested in therapeutic monoclonal antibodies, Dr. William R. Strohl decided about two years ago that the time was right to write a book about the past, present and future of these fascinating molecules. Dr. Strohl’s great expertise and passion for biotechnology is evident from his life story and his strong academic and industry track record. Dr. Strohl pioneered natural product biotechnology, first in academia as a full professor of microbiology and biochemistry at Ohio State University in Columbus, Ohio and later in industry while at Merck. Despite his notable advances in recombinant natural products, industry interest in this area waned and in 2001 Dr. Strohl sought new opportunities by entering the field of antibody therapeutics. He initiated antibody discovery through phage display at Merck, and then moved to Centocor Research and Development Inc. (now Janssen Biotech, Inc.) in 2008 to head Biologics Research, where he now directs the discovery of innovative therapeutic antibody candidates.

Parren, Paul W.H.I.; Lugovskoy, Alexey A.

2013-01-01

445

Schemas and memory consolidation.  

PubMed

Memory encoding occurs rapidly, but the consolidation of memory in the neocortex has long been held to be a more gradual process. We now report, however, that systems consolidation can occur extremely quickly if an associative "schema" into which new information is incorporated has previously been created. In experiments using a hippocampal-dependent paired-associate task for rats, the memory of flavor-place associations became persistent over time as a putative neocortical schema gradually developed. New traces, trained for only one trial, then became assimilated and rapidly hippocampal-independent. Schemas also played a causal role in the creation of lasting associative memory representations during one-trial learning. The concept of neocortical schemas may unite psychological accounts of knowledge structures with neurobiological theories of systems memory consolidation. PMID:17412951

Tse, Dorothy; Langston, Rosamund F; Kakeyama, Masaki; Bethus, Ingrid; Spooner, Patrick A; Wood, Emma R; Witter, Menno P; Morris, Richard G M

2007-04-01

446

Computer memory management system  

DOEpatents

A computer memory management system utilizing a memory structure system of "intelligent" pointers in which information related to the use status of the memory structure is designed into the pointer. Through this pointer system, The present invention provides essentially automatic memory management (often referred to as garbage collection) by allowing relationships between objects to have definite memory management behavior by use of coding protocol which describes when relationships should be maintained and when the relationships should be broken. In one aspect, the present invention system allows automatic breaking of strong links to facilitate object garbage collection, coupled with relationship adjectives which define deletion of associated objects. In another aspect, The present invention includes simple-to-use infinite undo/redo functionality in that it has the capability, through a simple function call, to undo all of the changes made to a data model since the previous `valid state` was noted.

Kirk, III, Whitson John (Greenwood, MO)

2002-01-01

447

Memory Event Clocks  

NASA Astrophysics Data System (ADS)

We introduce logics and automata based on memory event clocks. A memory clock is not really reset: instead, a new clock is created, while the old one is still accessible by indexing. We can thus constrain not only the time since the last reset (which was the main limitation in event clocks), but also since previous resets. When we introduce these clocks in the linear temporal logic of the reals, we create Recursive Memory Event Clocks Temporal Logic (RMECTL). It turns out to have the same expressiveness as the Temporal Logic with Counting (TLC) of Hirshfeld and Rabinovich. We then examine automata with recursive memory event clocks (RMECA). Recursive event clocks are reset by simpler RMECA, hence the name "recursive". In contrast, we show that for RMECA, memory clocks do not add expressiveness, but only concision. The original RECA define thus a fully decidable, robust and expressive level of real-time expressiveness.

Jerson Ortiz, James; Legay, Axel; Schobbens, Pierre-Yves

448

Graphene flash memory.  

PubMed

Graphene's single atomic layer of sp(2) carbon has recently garnered much attention for its potential use in electronic applications. Here, we report a memory application for graphene, which we call graphene flash memory (GFM). GFM has the potential to exceed the performance of current flash memory technology by utilizing the intrinsic properties of graphene, such as high density of states, high work function, and low dimensionality. To this end, we have grown large-area graphene sheets by chemical vapor deposition and integrated them into a floating gate structure. GFM displays a wide memory window of ?6 V at significantly low program/erase voltages of ±7 V. GFM also shows a long retention time of more than 10 years at room temperature. Additionally, simulations suggest that GFM suffers very little from cell-to-cell interference, potentially enabling scaling down far beyond current state-of-the-art flash memory devices. PMID:21854056

Hong, Augustin J; Song, Emil B; Yu, Hyung Suk; Allen, Matthew J; Kim, Jiyoung; Fowler, Jesse D; Wassei, Jonathan K; Park, Youngju; Wang, Yong; Zou, Jin; Kaner, Richard B; Weiller, Bruce H; Wang, Kang L

2011-10-25

449

Polymer-drug conjugates: recent progress on administration routes.  

PubMed

Introduction: Polymer-drug conjugates are an important part of polymer therapeutics. Recently, they have been used as an appealing platform for drug delivery. As a delivery vector, the route of administration performs a serious impact on the accessibility of drug molecules to their respective target site and therapeutic index. Furthermore, the physicochemical and biological properties of conjugates also correlate distinctly with the route of administration. Areas covered: This article reviews the recent advances of polymer-drug conjugates as drug delivery systems through parenteral, enteral and topical routes. In particular, it mainly focuses on the classical and emerging routes such as injection, oral, transdermal, pulmonary and ocular routes using polymer-drug conjugates as delivery systems. Expert opinion: Although polymer-conjugated drug delivery systems reported so far face severe shortcoming of being incomplete methodology and limited routes for administration (mostly concentrated in injection), some polymer carriers like poly(amidoamine) and hyaluronic acid still offer an appealing platform to deliver drug. Acquiring the particular characteristics of each polymer carrier, exploiting novel biodegradable polymer, expanding classical drug administration ways by emerging routes and developing a rational and systematic methodology to design administration routes will be the promising directions. PMID:24758250

Pang, Xin; Yang, Xiaoye; Zhai, Guangxi

2014-07-01

450

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

451

Polymer-Drug Conjugates: Recent Development in Clinical Oncology  

PubMed Central

Targeted drug delivery aims to increase the therapeutic index by making more drug molecules available at the diseased sites while reducing systemic drug exposure. In this update, we provide an overview of polymer-drug conjugates that have advanced into the clinical trials. These systems use synthetic water-soluble polymers as the drug carriers. The preclinical pharmacology and recent data in clinical trials with poly(L-glutamic acid)-paclitaxel (PG-TXL) are discussed first. This is followed by a summary of conjugates of a variety of polymeric conjugates with chemotherapeutic agents. Results from early clinical trials of these polymer-drug conjugates have demonstrated several advantages over the corresponding parent drugs, including fewer side effects, enhanced therapeutic efficacy, ease of drug administration, and improved patient compliance. Collectively, these data warrant further clinical development of polymer-drug conjugates as a new class of anticancer agents.

Li, Chun; Wallace, Sidney

2008-01-01

452

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