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Shape Memory Polymer Therapeutic Devices for Stroke  

SciTech Connect

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(usually optically) to take on an expanded conformation, and then used to dislodge and grip the thrombus while it is withdrawn through the catheter.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, T S; Small IV, W; Benett, W J; Bearinger, J P; Maitland, D J



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



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



Nitinol-reinforced shape-memory polymers  

E-print Network

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

Di Leo, Claudio V



Porous Shape Memory Polymers.  


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

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



Multifunctional shape-memory polymers.  


The thermally-induced shape-memory effect (SME) is the capability of a material to change its shape in a predefined way in response to heat. In shape-memory polymers (SMP) this shape change is the entropy-driven recovery of a mechanical deformation, which was obtained before by application of external stress and was temporarily fixed by formation of physical crosslinks. The high technological significance of SMP becomes apparent in many established products (e.g., packaging materials, assembling devices, textiles, and membranes) and the broad SMP development activities in the field of biomedical as well as aerospace applications (e.g., medical devices or morphing structures for aerospace vehicles). Inspired by the complex and diverse requirements of these applications fundamental research is aiming at multifunctional SMP, in which SME is combined with additional functions and is proceeding rapidly. In this review different concepts for the creation of multifunctionality are derived from the various polymer network architectures of thermally-induced SMP. Multimaterial systems, such as nanocomposites, are described as well as one-component polymer systems, in which independent functions are integrated. Future challenges will be to transfer the concept of multifunctionality to other emerging shape-memory technologies like light-sensitive SMP, reversible shape changing effects or triple-shape polymers. PMID:20574951

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



Memory as a new therapeutic target  

PubMed Central

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

Nader, Karim; Hardt, Oliver; Lanius, Ruth



Temperature-memory polymer actuators.  


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



Shape memory polymer actuator and catheter  


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)



Thermomechanical modeling of a shape memory polymer  

E-print Network

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

Ghosh, Pritha B.



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.



How polymers lose memory with age.  


Uniquely in the world of materials, polymers deformed at high temperature and subsequently quenched at low temperature, memorize the temperature at which they have been processed. Polymers can even memorize multiple temperatures. This temperature memory is reflected by a maximum of residual stress restored at the temperature of initial processing. It has been speculated that this capability could arise from the presence of dynamical heterogeneities in glassy domains of polymers. Processing the material at a given temperature would result in the selection of certain heterogeneities that participate in the storage of mechanical stress. Because dynamical heterogeneities are associated with particular relaxation times, the temperature memory of polymers should depend on the time, for example, the glass transition temperature depends on the frequency. The first experimental study of temporal effects on the temperature memory of polymers is presently reported. It is found that aging at high temperature shifts the maximum of residual stress towards greater temperatures. The corresponding loss of memory is explained by the relaxation of dynamical heterogeneities with short characteristic times. The present results clarify the origin of the temperature memory and provide insights into their efficient exploitation in applications. PMID:25294363

Grillard, Fabienne; Zakri, Cécile; Gaillard, Patrice; Korzhenko, Alexander; Néri, Wilfrid; Poulin, Philippe



Guide wire extension for shape memory polymer occlusion removal devices  


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)



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.



Polyalkene-based shape-memory polymers  

NASA Astrophysics Data System (ADS)

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

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



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



Thermomechanical Characterization and Modeling of Shape Memory Polymers  

E-print Network

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

Volk, Brent L.



Medical applications of shape memory polymers.  


Shape memory polymers (SMP) are lightweight, have a high strain/shape recovery ability, are easy to process, and required properties can be tailored for variety of applications. Recently a number of medical applications have been considered and investigated, especially for polyurethane-based SMP. SMP materials were found to be biocompatible, non-toxic and non-mutagenic. The glass transition temperature (T(g)) can be tailored for shape restoration/self-deployment of clinical devices when inserted in the human body. Newly developed SMP foams, together with cold hibernated elastic memory (CHEM) processing, further broaden their potential biomedical applications. Polyurethane-based SMP are described here and major advantages are identified over other medical materials. Some SMP applications are already used in a clinical setting, whereas others are still in development. Lately, several important applications are being considered for CHEM foams as self-deployable vascular and coronary devices. One example is the endovascular treatment of aneurysms. PMID:18458416

Sokolowski, Witold; Metcalfe, Annick; Hayashi, Shunichi; Yahia, L'Hocine; Raymond, Jean



Memristive learning and memory functions in polyvinyl alcohol polymer memristors  

NASA Astrophysics Data System (ADS)

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

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



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.



Temperature memory effect in amorphous shape memory polymers.  


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

Yu, Kai; Qi, H Jerry



Photopolymerized Thiol-Ene Systems as Shape Memory Polymers  

PubMed Central

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

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



Polyurethane Shape-Memory Polymers Demonstrate Functional Biocompatibility  

E-print Network

Polyurethane Shape-Memory Polymers Demonstrate Functional Biocompatibility In Vitro Maricel-vitro cytotoxicity of these resins to be comparable to commercial medical grade polyurethanes.[7,16] The Mitsubishi

Simon, Scott I.


Memory T-cell-specific therapeutics attenuate allograft rejection via mediation of alloreactivity in memory cells.  


Many means in inbred rodent models promoted long-term graft survival or donor-specific tolerance, but less so in nonhuman primates, outbred rodents or human patients. A diverse repertoire of memory T cells, derived from heterologous immunity or prior to exposure to alloantigen, has been believed to be an important part of this barrier. Memory T cells have a unique capacity to generate effector functions quickly upon re-exposure to antigen, and this capacity is achieved by reduced activation thresholds, and expressed high level trafficking and adhesion molecules, which is likely responsible for their exhibiting differential susceptibility to immune therapeutics compared with naïve T cells. This review outlines recent progress on characteristics of memory T cells and focuses on these potential therapies targeting memory T cells which are likely to ameliorate allograft rejection by inducing transplant tolerance. PMID:22902239

Luo, Lei; Sun, Zhaolin; Cheng, Hui; Luo, Guangheng



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



Shape memory polymer foams for endovascular therapies  


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)



Polymers with multishape memory controlled by local glass transition temperature.  


A multishape memory polymer with flexible design capabilities is fabricated by a very simple method. Local glass transition temperatures of a loosely cross-linked polymer film are changed by immersing sections of the film in a cross-linker solution with a different concentration. Each section memorizes a temporary shape, which recovers its permanent shape at a different recovery temperature depending on the local glass transition temperature. As a base polymer, we chose a network polymer prepared by a Diels-Alder reaction between poly(2,5-furandimethylene succinate) (PFS) and 1,8-bis-maleimidotriethyleneglycol (M2). Quintuple shape memory behavior was demonstrated by a PFS/M film with four sections with distinct glass transition temperatures. The number of temporary shapes was determined by the number of different M2 solutions. Furthermore, owing to the reversibility of the Diels-Alder reaction, the permanent shape was rewritable. PMID:24471436

Zeng, Chao; Seino, Hidetake; Ren, Jie; Yoshie, Naoko



Shape memory polymer cellular solid design for medical applications  

Microsoft Academic Search

Shape memory polymers (SMPs) are an emerging class of active materials whose response can be easily tailored via modifications of the molecular parameters and optimization of the transformation processes. In this work, we originally demonstrated that a correct coupling of polymer transformation processes (co-extrusion with chemical blowing agents, salt co-extrusion\\/particulate leaching, solvent casting\\/particulate leaching) and SMPs allows one to obtain

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



Actuation of MAV control surface using conducting shape memory polymer actuator  

Microsoft Academic Search

The current MAVs used servomotors as actuators for the control surfaces, such as elevators and rudders. In this paper, the application possibility of conducting shape memory polymer to smart actuator has been assessed. Our final goal will be to replace the servomotor with a newly developed conducting shape memory polymer actuator. As the first step, a conducting shape memory polymer

Nam S. Goo; Il H. Paik; Kwang J. Yoon; Yong C. Jung; Jae W. Cho



Toward a self-deploying shape memory polymer neuronal electrode.  


The widespread application of neuronal probes for chronic recording of brain activity and functional stimulation has been slow to develop partially due to long-term biocompatibility problems with existing metallic and ceramic probes and the tissue damage caused during probe insertion. Stiff probes are easily inserted into soft brain tissue but cause astrocytic scars that become insulating sheaths between electrodes and neurons. In this communication, we explore the feasibility of a new approach to the composition and implantation of chronic electrode arrays. We demonstrate that softer polymer-based probes can be inserted into the olfactory bulb of a mouse and that slow insertion of the probes reduces astrocytic scarring. We further present the development of a micromachined shape memory polymer probe, which provides a vehicle to self-deploy an electrode at suitably slow rates and which can provide sufficient force to penetrate the brain. The deployment rate and composition of shape memory polymer probes can be tailored by polymer chemistry and actuator design. We conclude that it is feasible to fabricate shape memory polymer-based electrodes that would slowly self-implant compliant conductors into the brain, and both decrease initial trauma resulting from implantation and enhance long-term biocompatibility for long-term neuronal measurement and stimulation. PMID:17124327

Sharp, Andrew A; Panchawagh, Hrishikesh V; Ortega, Alicia; Artale, Ryan; Richardson-Burns, Sarah; Finch, Dudley S; Gall, Ken; Mahajan, Roop L; Restrepo, Diego



Environmental memory of polymer networks under stress.  


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



Biomedical applications of thermally activated shape memory polymers  

PubMed Central

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

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



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



Capacitance-voltage measurement in memory devices using ferroelectric polymer  

NASA Astrophysics Data System (ADS)

Application of thin polymer film as storing mean for non-volatile memory devices is investigated. Capacitance-voltage (C-V) measurement of metal-ferroelectric-metal device using ferroelectric copolymer P(VDF-TrFE) as dielectric layer shows stable 'butter-fly' curve. The two peaks in C-V measurement corresponding to the largest capacitance are coincidental at the coercive voltages that give rise to zero polarization in the polarization hysteresis measurement. By comparing data of C-V and P-E measurement, a correlation between two types of hysteresis is established in which it reveals simultaneous electrical processes occurring inside the device. These processes are caused by the response of irreversible and reversible polarization to the applied electric field that can be used to present a memory window. The memory effect of ferroelectric copolymer is further demonstrated for fabricating polymeric non-volatile memory devices using metal-ferroelectric-insulator-semiconductor structure (MFIS). By applying different sweeping voltages at the gate, bidirectional flat-band voltage shift is observed in the ferroelectric capacitor. The asymmetrical shift after negative sweeping is resulted from charge accumulation at the surface of Si substrate caused by the dipole direction in the polymer layer. The effect is reversed for positive voltage sweeping.

Nguyen, Chien A.; Lee, Pooi See



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



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



Microstructured shape memory polymer surfaces with reversible dry adhesion.  


We present a shape memory polymer (SMP) surface with repeatable, very strong (>18 atm), and extremely reversible (strong to weak adhesion ratio of >1 × 10(4)) dry adhesion to a glass substrate. This was achieved by exploiting bulk material properties of SMP and surface microstructuring. Its exceptional dry adhesive performance is attributed to the SMP's rigidity change in response to temperature and its capabilities of temporary shape locking and permanent shape recovery, which when combined with a microtip surface design enables time-independent control of contact area. PMID:23945078

Eisenhaure, Jeffrey D; Xie, Tao; Varghese, Stephen; Kim, Seok



Comparing techniques for drug loading of shape-memory polymer networks--effect on their functionalities.  


A family of oligo[(epsilon-caprolactone)-co-glycolide]dimethacrylate (oCG-DMA) derived networks of different glycolide contents as well as precursor molecular weights has been synthesized by crosslinking oCG-DMA, providing matrices of different hydrophilicity, network density, and morphology at body temperature. Such networks were loaded with a hydrophilic model drug, ethacridine lactate, either before crosslinking or afterwards by swelling in drug solution. Disadvantageous alterations of the shape-memory functionality and degradation characteristics were observed only in few loaded materials. Loading by swelling generally resulted in low payloads, which slightly increased for more hydrophilic polymer networks, and a substantial burst and fast subsequent release for all investigated materials. Loading before crosslinking gave almost no burst and higher subsequent release rates over longer periods of time. Overall, depending on the needs of a specific application, a material from this polymer family with the desired mechanical properties, shape-memory functionality, and degradation pattern can be selected and combined with drugs when considering that (i) loading by swelling is best suited for applications that require high initial doses and (ii) loading before crosslinking allows easy variation of payloads and low burst release for therapeutics that are non-sensitive to chemical alterations during crosslinking. PMID:20542110

Wischke, Christian; Neffe, Axel T; Steuer, Susi; Lendlein, Andreas



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



The future orientation of constructive memory: an evolutionary perspective on therapeutic hypnosis and brief psychotherapy.  


We explore a new distinction between the future, prospective memory system being investigated in current neuroscience and the past, retrospective memory system, which was the original theoretical foundation of therapeutic hypnosis, classical psychoanalysis, and psychotherapy. We then generalize a current evolutionary theory of sleep and dreaming, which focuses on the future, prospective memory system, to conceptualize a new evolutionary perspective on therapeutic hypnosis and brief psychotherapy. The implication of current neuroscience research is that activity-dependent gene expression and brain plasticity are the psychobiological basis of adaptive behavior, consciousness, and creativity in everyday life as well as psychotherapy. We summarize a case illustrating how this evolutionary perspective can be used to quickly resolve problems with past obstructive procrastination in school to facilitate current and future academic success. PMID:18524301

Rossi, Ernest; Erickson-Klein, Roxanna; Rossi, Kathryn



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

E-print Network

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

Wee, Brian (Brian J.)



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

E-print Network

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

Buckley, Patrick Regan, 1981-



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

E-print Network

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

Buckley, Patrick R.



Bioactive factor delivery strategies from engineered polymer hydrogels for therapeutic medicine  

PubMed Central

Polymer hydrogels have been widely explored as therapeutic delivery matrices because of their ability to present sustained, localized and controlled release of bioactive factors. Bioactive factor delivery from injectable biopolymer hydrogels provides a versatile approach to treat a wide variety of diseases, to direct cell function and to enhance tissue regeneration. The innovative development and modification of both natural-(e.g., alginate (ALG), chitosan, hyaluronic acid (HA), gelatin, heparin (HEP), etc.) and synthetic-(e.g., polyesters, polyethyleneimine (PEI), etc.) based polymers has resulted in a variety of approaches to design drug delivery hydrogel systems from which loaded therapeutics are released. This review presents the state-of-the-art in a wide range of hydrogels that are formed though self-assembly of polymers and peptides, chemical crosslinking, ionic crosslinking and biomolecule recognition. Hydrogel design for bioactive factor delivery is the focus of the first section. The second section then thoroughly discusses release strategies of payloads from hydrogels for therapeutic medicine, such as physical incorporation, covalent tethering, affinity interactions, on demand release and/or use of hybrid polymer scaffolds, with an emphasis on the last 5 years.

Nguyen, Minh Khanh; Alsberg, Eben



Dynamic cell behavior on shape memory polymer substrates Kevin A. Davis a,b  

E-print Network

Dynamic cell behavior on shape memory polymer substrates Kevin A. Davis a,b , Kelly A. Burke b: Cell culture Shape memory Thermally responsive material Surface topography a b s t r a c t Cell culture substrates of defined topography have emerged as powerful tools with which to investigate cell mechanobiology

Mather, Patrick T.


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. PMID:23329002

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



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.



Micro devices using shape memory polymer patches for mated connections  


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

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



Method for loading shape memory polymer gripper mechanisms  


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)



Light-triggered self-healing and shape-memory polymers.  


In this review, we highlight the recent progress made in light-controlled self-healing and shape memory polymers. We analyse the materials design, underlying mechanisms and chemistries involved in the different methods developed for these two types of emerging photoresponsive materials. We show that these two seemingly different groups of functional materials are linked by a number of common approaches enabling their optical control, particularly the approaches based on the photothermal effect and photochemical reactions of photoswitching groups incorporated in polymer structures. Possible future developments and perspectives of using light as a unique trigger for polymer self-healing and shape-memory are also discussed. PMID:23440057

Habault, Damien; Zhang, Hongji; Zhao, Yue



Anomalous Polymer Dynamics Is Non-Markovian: Memory Effects and The Generalized Langevin Equation Formulation  

E-print Network

Any first course on polymer physics teaches that the dynamics of a tagged monomer of a polymer is anomalously subdiffusive, i.e., the mean-square displacement of a tagged monomer increases as $t^\\alpha$ for some $\\alphaClassical examples of anomalous dynamics in polymer physics are single polymeric systems, such as phantom Rouse, self-avoiding Rouse, self-avoiding Zimm, reptation, translocation through a narrow pore in a membrane, and many-polymeric systems such as polymer melts. In this pedagogical paper I report that all these instances of anomalous dynamics in polymeric systems are robustly characterized by power-law memory kernels within a {\\it unified} Generalized Langevin Equation (GLE) scheme, and therefore, are non-Markovian. The exponents of the power-law memory kernels are related to the relaxation response of the polymers to local strains, and are derived from the equilibrium statistical physics of polymers. The anomalous dynamics of a tagged monomer of a polymer in these systems is then reproduced from the power-law memory kernels of the GLE via the fluctuation-dissipation theorem (FDT). Using this GLE formulation I further show that the characteristics of the drifts caused by a (weak) applied field on these polymeric systems are also obtained from the corresponding memory kernels.

Debabrata Panja



3D networked graphene-ferromagnetic hybrids for fast shape memory polymers with enhanced mechanical stiffness and thermal conductivity.  


A novel 3D networked graphene-ferromagnetic hybrid can be easily fabricated using one-step microwave irradiation. By incorporating this hybrid material into shape memory polymers, the synergistic effects of fast speed and the enhancement of thermal conductivity and mechanical stiffness can be achieved. This can be broadly applicable to designing magneto-responsive shape memory polymers for multifunction applications. PMID:24912455

Lee, Sang-Heon; Jung, Jung-Hwan; Oh, Il-Kwon



Constitutive model for a stress- and thermal-induced phase transition in a shape memory polymer  

NASA Astrophysics Data System (ADS)

Recently, increasing applications of shape memory polymers have pushed forward the development of appropriate constitutive models for smart materials such as the shape memory polymer. During the heating process, the phase transition, which is a continuous time-dependent process, happens in the shape memory polymer, and various individual phases will form at different configuration temperatures. In addition, these phases can generally be divided into two parts: the frozen and active phase (Liu Y et al 2006 Int. J. Plast. 22 279-313). During the heating or cooling process, the strain will be stored or released with the occurring phase transition between these two parts. Therefore, a shape memory effect emerges. In this paper, a new type of model was developed to characterize the variation of the volume fraction in a shape memory polymer during the phase transition. In addition to the temperature variation, the applied stress was also taken as a significant influence factor on the phase transition. Based on the experimental results, an exponential equation was proposed to describe the relationship between the stress and phase transition temperature. For the sake of describing the mechanical behaviors of the shape memory polymer, a three-dimensional constitutive model was established. Also, the storage strain, which was the key factor of the shape memory effect, was also discussed in detail. Similar to previous works, we first explored the effect of applied stress on storage strain. Through comparisons with the DMA and the creep experimental results, the rationality and accuracy of the new phase transition and constitutive model were finally verified.

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



Electrical properties and shape-memory behavior of self-assembled carbon nanofiber nanopaper incorporated with shape-memory polymer  

NASA Astrophysics Data System (ADS)

The present paper studies the electrical and shape-memory behavior of self-assembled carbon nanofiber (CNF) nanopaper incorporated with shape-memory polymer (SMP). The morphology and structure of the self-assembled nanopapers were characterized with scanning electron microscopy (SEM). A continuous and compact network was observed from the SEM images, which indicates that the CNF nanopaper could have highly conductive properties. The electrical conductivity of the CNF nanopaper was measured by the four-point probe method and its temperature coefficient effect was studied. Finally, the actuation of SMP was demonstrated by the electrical resistive heating of the CNF nanopaper.

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



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


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

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



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



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. PMID:20375285

Song, Jie



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.



[Diagnostic, forensic and therapeutic-ethical aspects of false memory of sexual abuse induced by psychotherapy].  


This article examines the risk of false memories induced by psychotherapy with special regard to sexual abuse. Current psychological constructs based on depth psychology are reviewed critically. The multitude of psychological disorders connected with sexual abuse in recent time and a subjectivistic misunderstanding of empathy frequently lead sometimes to uncritical acceptance of anamnestic reports about sexual abuse. Thus, the question of what really happened often is risen not before forensic appraisals. It can be shown that the descriptive psychiatric view and depth psychological oriented constructs tend to compete with each other with the consequence of different results in therapeutic practise and forensic appraisal if inappropriately applied. The author shows how to distinct between induced delusional symptoms and dissociative phenomena. Furthermore he draws attention on the ethically doubtful long-term results of a not correctly indicated use of psychological constructs based on depth psychology about extreme traumatization in the psychotherapy of strongly suggestible patients. PMID:10603595

Simmich, T



Bulk heterojunction polymer memory devices with reduced graphene oxide as electrodes.  


A unique device structure with a configuration of reduced graphene oxide (rGO) /P3HT:PCBM/Al has been designed for the polymer nonvolatile memory device. The current-voltage (I-V) characteristics of the fabricated device showed the electrical bistability with a write-once-read-many-times (WORM) memory effect. The memory device exhibits a high ON/OFF ratio (10(4)-10(5)) and low switching threshold voltage (0.5-1.2 V), which are dependent on the sheet resistance of rGO electrode. Our experimental results confirm that the carrier transport mechanisms in the OFF and ON states are dominated by the thermionic emission current and ohmic current, respectively. The polarization of PCBM domains and the localized internal electrical field formed among the adjacent domains are proposed to explain the electrical transition of the memory device. PMID:20540553

Liu, Juqing; Yin, Zongyou; Cao, Xiehong; Zhao, Fei; Lin, Anping; Xie, Linghai; Fan, Quli; Boey, Freddy; Zhang, Hua; Huang, Wei



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

PubMed Central

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

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



Electron Beam Crosslinked Polyurethane Shape Memory Polymers with Tunable Mechanical Properties  

PubMed Central

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

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



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

NASA Astrophysics Data System (ADS)

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.



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


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



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


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



Damage healing ability of a shape-memory-polymer-based particulate composite with small thermoplastic contents  

NASA Astrophysics Data System (ADS)

The purpose of this study is to investigate the potential of a shape-memory-polymer (SMP)-based particulate composite to heal structural-length scale damage with small thermoplastic additive contents through a close-then-heal (CTH) self-healing scheme that was introduced in a previous study (Li and Uppu 2010 Comput. Sci. Technol. 70 1419-27). The idea is to achieve reasonable healing efficiencies with minimal sacrifice in structural load capacity. By first closing cracks, the gap between two crack surfaces is narrowed and a lesser amount of thermoplastic particles is required to achieve healing. The particulate composite was fabricated by dispersing copolyester thermoplastic particles in a shape memory polymer matrix. It is found that, for small thermoplastic contents of less than 10%, the CTH scheme followed in this study heals structural-length scale damage in the SMP particulate composite to a meaningful extent and with less sacrifice of structural capacity.

Nji, Jones; Li, Guoqiang



The tunable bistable and multistable memory effect in polymer nanowires.  


Tunable bistable and multistable resistance switching in conducting polymer nanowires has been reported. These wires show reproducible switching transition under several READ-WRITE-ERASE cycles. The switching is observed at low temperature and the ON/OFF resistance ratio for the voltage biased switching transition was found to be more than 10(3). Current biased measurements show lower ON/OFF ratio and some of the nanowires exhibit a multistable switching transition in current biased measurements. The threshold voltage for switching and the ON/OFF resistance ratio can be tuned by changing doping concentration of the nanowires. PMID:21832588

Rahman, Atikur; Sanyal, Milan K



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



High performance shape memory polymer networks based on rigid nanoparticle cores.  


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 (T(trans)) 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 T(trans), respectively. Both T(trans) 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 T(trans) 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 T(trans) between 42 and 48 degrees C. The materials could stably hold their temporary shapes for > 1 year at room temperature and achieve full shape recovery

Xu, Jianwen; Song, Jie



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


New design of shape memory polymers based on natural rubber crosslinked via oxa-Michael reaction.  


Shape memory polymers (SMPs) based on natural rubber were fabricated by crosslinking epoxidized natural rubber with zinc diacrylate (ZDA) using the oxa-Michael reaction. These SMPs possessed excellent shape fixity and recovery. The glass transition largely accounted for the fixing of the SMPs temporary shape. Increasing the ZDA content allowed the trigger temperature (20-46 °C) and recovery time (14-33 s) of the SMPs to be continuously tuned. Nanosized silica (nanosilica) was incorporated into the neat polymers to further increase the flexibility and tune the recovery stress. The nanosilica-SMPs exhibited exceptionally high strength in a rubbery state (>20 MPa). The nanosilica-SMPs exhibited high transparency, making them suitable in visible heat-shrinkable tubes. PMID:24673791

Lin, Tengfei; Ma, Siwei; Lu, Yang; Guo, Baochun



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



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



Synergistic effect of carbon nanofiber and carbon nanopaper on shape memory polymer composite  

NASA Astrophysics Data System (ADS)

The present work studies the synergistic effect of carbon nanofiber (CNF) and carbon nanopaper on the shape recovery of shape memory polymer (SMP) composite. The combination of CNF and carbon nanopaper was used to improve the thermal and electrical conductivities of the SMP composite. The carbon nanopaper was coated on the surface of the SMP composite in order to achieve the actuation by electrical resistive heating. CNFs were blended with the SMP resin to improve the thermal conductivity to facilitate the heat transfer from the nanopaper to the underlying SMP composite to accelerate the electroactive responses.

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



Femtosecond-laser direct writing in polymers and potential applications in microfluidics and memory devices  

NASA Astrophysics Data System (ADS)

We have investigated femtosecond-laser-induced microstructures (on the surface and within the bulk), gratings, and craters in four different polymers: polymethyl methacrylate, polydimethylsiloxane, polystyrene, and polyvinyl alcohol. The structures were achieved using a Ti:sapphire laser delivering 100-fs pulses at 800 nm with a repetition rate of 1 kHz and a maximum pulse energy of 1 mJ. Local chemical modifications leading to the formation of optical centers and peroxide radicals were studied using ultraviolet-visible absorption and emission, confocal micro-Raman and electron spin resonance spectroscopic techniques. Potential applications of these structures in microfluidics, waveguides, and memory-based devices are demonstrated.

Kallepalli, Lakshmi Narayana Deepak; Soma, Venugopal Rao; Desai, Narayana Rao



Recovery torque modeling of carbon fiber reinforced shape memory polymer nanocomposites  

NASA Astrophysics Data System (ADS)

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

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



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

NASA Astrophysics Data System (ADS)

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

Ahmad, Manzoor; Luo, Jikui; Miraftab, Mohsen



Laser-Activated Shape Memory Polymer Microactuator for Thrombus Removal Following Ischemic Stroke: Preliminary In Vitro Analysis  

SciTech Connect

Due to the narrow (3-hour) treatment window for effective use of the thrombolytic drug recombinant tissue-type plasminogen activator (rt-PA), there is a need to develop alternative treatments for ischemic stroke. We are developing an intravascular device for mechanical thrombus removal using shape memory polymer (SMP). We propose to deliver the SMP microactuator in its secondary straight rod form (length = 4 cm, diameter = 350 {micro}m) through a catheter distal to the vascular occlusion. The microactuator, which is mounted on the end of an optical fiber, is then transformed into its primary corkscrew shape by laser heating (diode laser, {lambda} = 800 nm) above its soft phase glass transition temperature (T{sub gs} = 55 C). Once deployed, the microactuator is retracted and the captured thrombus is removed to restore blood flow. The SMP is doped with indocyanine green (ICG) dye to increase absorption of the laser light. Successful deployment of the microactuator depends on the optical properties of the ICG-doped SMP and the optical coupling efficiency of the interface between the optical fiber and the SMP. Spectrophotometry, thermal imaging, and computer simulation aided the initial design effort and continue to be useful tools for optimization of the dye concentration and laser power. Thermomechanical testing was performed to characterize the elastic modulus of the SMP. We have demonstrated laser-activation of the SMP microactuator in air at room temperature, suggesting this concept is a promising therapeutic alternative to rt-PA.

Small, W; Metzger, M F; Wilson, T S; Maitland, D J



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


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

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



Pneumatic artificial rubber muscle using shape-memory polymer sheet with embedded electrical heating wire  

NASA Astrophysics Data System (ADS)

Shape-memory polymer (SMP) can be deformed by applying a small load above its glass transition temperature (Tg). Shape-memory polymer maintains its shape after it has cooled below Tg and returns to a predefined shape when subsequently heated above Tg. The reversible change in the elastic modulus between the glassy and rubbery states of an SMP can be on the order of several hundred times. Based on the change in stiffness of the SMP in relation to the change in temperature, the present study attempts to evaluate the application of the SMP to soft actuators of a robot. In order to control the temperature of the SMP, we developed an SMP sheet with an embedded electrical heating wire. We formed a uniform, thin SMP sheet without air bubbles using a heat press. The SMP sheet with a heating wire can be heated quickly and can be maintained at a constant temperature. Moreover, the effects of the embedded wire on the mechanical properties in bending and tensile tests were small. Then, we applied the SMP sheet with the embedded electrical heating wire to a pneumatic artificial rubber muscle. The enhanced versatility of SMP sheet applications is demonstrated through a series of experiments conducted using a prototype. The initial shape and bending displacement of the pneumatic artificial rubber muscle can be changed by controlling the temperature of the SMP sheet.

Takashima, Kazuto; Sugitani, Kazuhiro; Morimoto, Naohiro; Sakaguchi, Seiya; Noritsugu, Toshiro; Mukai, Toshiharu



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


Analysis of the mechanical behavior of shape memory polymer membranes by nanoindentation, bulging and point membrane deflection tests  

Microsoft Academic Search

The mechanical properties of a thin film of polyurethane shape memory polymer were investigated experimentally. Non-conventional mechanical tests such as nanoindentation, bulging and point membrane deflection are used. The quantitative results obtained by these three experimental investigations are consistent. These tests, performed at room temperature (approx. 35 K below the glass transition temperature Tg), yield a Young's modulus equal to

C. Poilane; P. Delobelle; C. Lexcellent; S. Hayashi; H. Tobushi



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)



IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING, VOL. 53, NO. 10, OCTOBER 2006 2075 Inductively Heated Shape Memory Polymer for the  

E-print Network

IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING, VOL. 53, NO. 10, OCTOBER 2006 2075 Inductively Heated, inductive heating magnetic particle, medical device, shape memory polymer (SMP). I. INTRODUCTION SHAPE heating is presented. Prototype medical devices made from SMP loaded with nickel zinc ferrite


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

SciTech Connect

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

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



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

NASA Astrophysics Data System (ADS)

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

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



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


Ferroelectric polymers are among the most promising materials for flexible electronic devices. Highly ordered arrays of the defect-modified ferroelectric polymer P(VDF-TrFE-CFE) (poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene)) are fabricated by nanoimprint lithography for nonvolatile memory application. The defective CFE units reduce the coercive field to one-fifth of that of the un-modified P(VDF-TrFE), which can help minimize the energy consumption and extend the lifespan of the device. The nanoimprint process leads to preferable orientation of polymer chains and delicately controlled distribution of the defects, and thus a bi-stable polarization that makes the memory nonvolatile, as revealed by the pulsed polarization experiment. PMID:25316324

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



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

NASA Astrophysics Data System (ADS)

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

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



Effect of Biodegradable Shape-Memory Polymers on Proliferation of 3T3 Cells  

NASA Astrophysics Data System (ADS)

This article evaluates the in vitro biocompatibility for biodegradable shape-memory polymers (BSMP) invented by the authors. 3T3 cells (3T3-Swiss albino GNM 9) of primary and passaged cultures were inoculated into two kinds of carriers: the BSMP carrier and the control group carrier. Viability, proliferation, and DNA synthesis (the major biocompatibility parameters), were measured and evaluated for both the BSMP and naked carrier via cell growth curve analysis, MTT colorimetry and addition of 3H-TdR to culture media. The results showed that there was no difference between the BSMP carrier and the control dish in terms of viability, proliferation, and metabolism of the 3T3 cells. Overall, the BSMP carrier provides good biocompatibility and low toxicity to cells in vitro, and could indicate future potential for this medium as a biological material for implants in vivo.

Xu, Shuo-Gui; Zhang, Peng; Zhu, Guang-Ming; Jiang, Ying-Ming



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. PMID:18465981

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



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



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

SciTech Connect

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

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



Effects of sensitizer length on radiation crosslinked shape-memory polymers  

NASA Astrophysics Data System (ADS)

Shape-memory polymers (SMPs) are smart materials that can be designed to retain a metastable state and upon activation, recover a preprogrammed shape. In this study, poly(methyl acrylate) (PMA) is blended with poly(ethylene glycol) diacrylate (PEGDA) of various molecular weights in various concentrations and subsequently exposed to ionizing radiation. PEGDA sensitizes the radiation crosslinking of PMA, lowering the minimum absorbed dose for gelation and increasing the rubbery modulus, after crosslinking. Minimum dose for gelation, as determined by the Charlesby-Pinner equation, decreases from 25.57 kGy for unblended PMA to 2.06 kGy for PMA blended with 10.00 mole% PEGDA. Moreover, increase in the blend concentration of PEGDA increases the crosslinking density of the resulting networks. Sensitizer length, namely Mn of PEGDA, also affects crosslinking and final mechanical properties. Increase in the length of the PEGDA molecule at a constant molar ratio increases the efficacy of the molecule as a radiation sensitizer as determined by the increase in gel fraction and rubbery modulus across doses. However, at a constant weight ratio of PEGDA to PMA, shorter PEGDA chains sensitize more crosslinking because they have more reactive ends per weight fraction. Sensitized samples of PMA with PEGDA were tested for shape-memory properties and showed shape fixity of greater than 99%. Samples had a glass transition temperature near 28 °C and recovered between 97% and 99% of the induced strain when strained to 50%.

Ware, Taylor; Voit, Walter; Gall, Ken



Solution-processable low-voltage and flexible floating-gate memories based on an n-type polymer semiconductor and high-k polymer gate dielectrics.  


High-performance low-voltage flash memories based on organic floating-gate field-effect transistors are prepared by a solution process for the first time. Transistors with a high-mobility n-type polymer semiconductor, poly{[N,N(')-bis(2-octyldodecyl)naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)}, and a high-k polymer gate dielectric, poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (k ? 60), are successfully fabricated on flexible substrates. A thin layer of Au nanoparticles is embedded in the gate dielectric, which can store injected charge from the channel and result in a memory effect. The organic memories demonstrate high carrier mobilities (>0.3 cm(2)/(V s)), low program/erase voltages (±6 V), little degradation after 10(5) program/erase cycles, and good retention after 10(5) s, which suggest great promise in the application of nonvolatile memories in flexible electronics. PMID:25026221

Li, Jinhua; Yan, Feng



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


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


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




ERIC Educational Resources Information Center

Discusses current research (including that involving amnesiacs and snails) into the nature of the memory process, differentiating between and providing examples of "fact" memory and "skill" memory. Suggests that three brain parts (thalamus, fornix, mammilary body) are involved in the memory process. (JN)

McKean, Kevin



Qualitative separation of the effects of carbon nano-powder and moisture on the glass transition temperature of polyurethane shape memory polymer  

Microsoft Academic Search

Based on a series of cyclic differential scanning calorimetry analyses together with thermogravimetric analyses, the effects of carbon nano-powder and moisture on the glass transition temperature of a polyurethane shape memory polymer were separated and qualitatively identified. This approach should be applicable to other polyurethane polymers and their composites.

B. Yang; W. M. Huang; C. Li; L. Li; J. H. Chor



A 3D finite deformation constitutive model for amorphous shape memory polymers: A multi-branch modeling approach for nonequilibrium relaxation processes  

Microsoft Academic Search

Shape memory polymers (SMPs) are materials that can recover a large pre-deformed shape in response to environmental stimuli. For a thermally activated amorphous SMP, the pre-deformation and recovery of the shape require the SMP to traverse its glass transition temperature (Tg) to complete the shape memory (SM) cycle. As a result, the recovery behavior of SMPs shows strong dependency on

Kristofer K. Westbrook; Philip H. Kao; Francisco Castro; Yifu Ding; H. Jerry Qi



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

NASA Astrophysics Data System (ADS)

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 SMP can be activated by the electrical resistive heating. It is shown that sub-micro filamentary nickel-coated nanostrands significantly improved the electrical conductivity to facilitate the actuation of the SMP nanocomposite despite the low nanostrand volume content and low electrical voltage. Also the CNFs are blended with the SMP resin to facilitate the dispersion of nanostrands and improve the thermal conductivity to accelerate the electro- and thermo-active responses.

Lu, Haibao; Gou, Jihua; Leng, Jinsong; Du, Shanyi



Forming-free resistive switching memory based on LiFePO4 nano-particle embedded in conjugated polymer  

NASA Astrophysics Data System (ADS)

In this paper, we report the resistive switching characteristics of organic-inorgainc nanocomposite layer of LiFePO4 nano-particle (NP) embedded in conjugated polymer P3HT (P3HT:LiFePO4-NP). Memory devices with Al/P3HT/P3HT:LiFeP4-NP/ITO structure exhibit forming-free bipolar resistive switching behavior under bias voltage sweeping. Our devices achieved low set (??1.2 V) and reset voltage (??0.7 V), excellent data retention, high memory margin of more than 105 on/off resistance ratio and data endurance >100 times, indicating their great potential for memory application. The resistive switching mechanism was investigated by c-AFM measurement and temperature-current dependence results based on conductive filament model. It is deduced that the metallic filament was formed by diffusion and redox of Li+ ion under bias.

Liang, Jun; Su, YanTao; Lin, Qinxian; Zhou, Hang; Zhang, ShengDong; Pei, Yanli; Hu, RuiQin



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


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



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.



Development of a McKibben artificial muscle using a shape-memory polymer  

NASA Astrophysics Data System (ADS)

When McKibben artificial muscle actuators are applied to robotic joints, the joints are driven by pairs of actuators located antagonistically to increase the joint stiffness. However, the force for shape fixity is not large. Therefore, the objective of this study is to develop a McKibben artificial muscle using a shape-memory polymer (SMP). SMPs can be deformed above their glass transition temperature (Tg) by applying a small load. They maintain their shape after they have been cooled to below Tg. They then return to the predefined shape when heated above Tg. Exploiting these characteristics, we coated the braided mesh shell of a commercial McKibben artificial muscle and made a prototype of the actuator using the SMP. When this new actuator is warmed above Tg, the SMP deforms. Then, when the internal bladder is pressurized, the actuator shortens and/or produces a load. After the actuator becomes the desirable length, the actuator is cooled to below Tg and the SMP is fixed in a rigid state even without the air supply. Consequently, this actuator can maintain its length more rigidly and accurately. The experimental results conducted on this prototype confirm the feasibility of this new actuator.

Takashima, Kazuto; Rossiter, Jonathan; Mukai, Toshiharu



A self-healing 3D woven fabric reinforced shape memory polymer composite for impact mitigation  

NASA Astrophysics Data System (ADS)

In this paper, a three-dimensional (3D) woven fabric reinforced shape memory polymer composite for impact mitigation was proposed, fabricated, programmed using a three-step strain-controlled thermomechanical cycle at a pre-strain level of 5% and machined to two groups of specimens (G1 and G2) with dimensions 152.4 mm × 101.6 mm × 12.7 mm. The specimens were impact tested, transversely, centrally and repeatedly with 32 and 42 J of energy. G1 specimens were healed after each impact until perforation occurred. G2 specimens were not healed after each impact and served as controls. At 32 J impact energy, G2 specimens were perforated at the 9th impact while G1 specimens lasted until the 15th impact; at 42 J impact energy, G2 specimens were perforated at the 5th impact while G1 specimens were perforated at the 7th impact. Visual inspection, C-scan, and scanning electron microscopy techniques were used to evaluate damage, failure modes, and healing efficiency.

Nji, Jones; Li, Guoqiang



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

PubMed Central

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

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



Thermoresponsive semicrystalline poly(?-caprolactone) networks: exploiting cross-linking with cinnamoyl moieties to design polymers with tunable shape memory.  


The overall goal of this study was to synthesize semicrystalline poly(?-caprolactone) (PCL) copolymer networks with stimuli-responsive shape memory behavior. Herein, we investigate the influence of a cinnamoyl moiety to design shape memory polymer networks with tunable transition temperatures. The effect of various copolymer architectures (random or ABA triblock), the molecular weight of the crystalline domains, PCL diol, (M(w) 1250 or 2000 g mol(-1)) and its composition in the triblock (50 or 80 mol %) were also investigated. The polymer microstructures were confirmed by NMR, DSC, WAXS and UV-vis spectroscopic techniques. The thermal and mechanical properties and the cross-linking density of the networks were characterized by DSC, tensile testing and solvent swelling, respectively. Detailed thermomechanical investigations conducted using DMA showed that shape memory behavior was obtained only in the ABA triblock copolymers. The best shape memory fixity, R(f) of ~99% and shape recovery, R(r) of ~99% was obtained when PCL diol with M(w) 2000 g mol(-1) was incorporated in the triblock copolymer at a concentration of 50 mol %. The series of triblock copolymers with PCL at 50 mol % also showed mechanical properties with tunable shape memory transition temperatures, ranging from 54 °C to close to body temperature. Our work establishes a general design concept for inducing a shape memory effect into any semicrystalline polyester network. More specifically, it can be applied to systems which have the highest transition temperature closest to the application temperature. An advantage of our novel copolymers is their ability to be cross-linked with UV radiation without any initiator or chemical cross-linker. Possible applications are envisioned in the area of endovascular treatment of ischemic stroke and cerebrovascular aneurysms, and for femoral stents. PMID:22252722

Garle, Amit; Kong, Sany; Ojha, Umaprassana; Budhlall, Bridgette M



Anomalous polymer dynamics is non-Markovian: memory effects and the generalized Langevin equation formulation  

Microsoft Academic Search

Any first course on polymer physics teaches that the dynamics of a tagged monomer of a polymer is anomalously subdiffusive, i.e., the mean-square displacement of a tagged monomer increases as talpha for some alpha < 1 until the terminal relaxation time tau of the polymer. Beyond time tau the motion of the tagged monomer becomes diffusive. Classical examples of anomalous

Debabrata Panja



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

NASA Astrophysics Data System (ADS)

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

Huang, Jinying; Ma, Dongge



The flexible non-volatile memory devices using oxide semiconductors and ferroelectric polymer poly(vinylidene fluoride-trifluoroethylene)  

NASA Astrophysics Data System (ADS)

We demonstrated flexible ferroelectric gate thin-film transistors (Fe-TFTs) with ferroelectric polymer poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] and amorphous indium gallium zinc oxide (a-IGZO) channel on the polyethylene-naphthalate (PEN) substrate. First, we confirm basic ferroelectric properties of the P(VDF-TrFE) film on the PEN substrate with various bending radius. Next, we fabricated Fe-TFTs with Al/120 nm-P(VDF-TrFE)/40 nm-IGZO top gate structure. Excellent electrical characteristics are demonstrated and nonvolatile memory function was confirmed with a memory window of 8.4 V. A subthreshold voltage swing of 400 mV/decade, Ion/Ioff ratio of more than 107 and the field-effect mobility of ˜1 cm2/Vs were obtained.

Lee, Gwang-Geun; Tokumitsu, Eisuke; Yoon, Sung-Min; Fujisaki, Yoshihisa; Yoon, Joo-Won; Ishiwara, Hiroshi



Biodegradable Silicon-Containing Elastomers for Tissue Engineering Scaffolds and Shape Memory Polymers  

E-print Network

and inorganic polymer components in a block copolymer system: poly(e-caprolactone) (PCL) and poly(dimethylsiloxane) (PDMS), respectively. A block structure maintains the distinct properties of the PCL and PDMS components. These elastomers may be useful...

Schoener, Cody A.



Transparent photostable ZnO nonvolatile memory transistor with ferroelectric polymer and sputter-deposited oxide gate  

NASA Astrophysics Data System (ADS)

We report on the fabrication of transparent top-gate ZnO nonvolatile memory thin-film transistors (NVM-TFTs) with 200 nm thick poly(vinylidene fluoride/trifluoroethylene) ferroelectric layer; semitransparent 10 nm thin AgOx and transparent 130 nm thick indium-zinc oxide (IZO) were deposited on the ferroelectric polymer as gate electrode by rf sputtering. Our semitransparent NVM-TFT with AgOx gate operates under low voltage write-erase (WR-ER) pulse of ±20 V, but shows some degradation in retention property. In contrast, our transparent IZO-gated device displays very good retention properties but requires anomalously higher pulse of ±70 V for WR and ER states. Both devices stably operated under visible illuminations.

Park, C. H.; Im, Seongil; Yun, Jungheum; Lee, Gun Hwan; Lee, Byoung H.; Sung, Myung M.



Transparent photostable ZnO nonvolatile memory transistor with ferroelectric polymer and sputter-deposited oxide gate  

SciTech Connect

We report on the fabrication of transparent top-gate ZnO nonvolatile memory thin-film transistors (NVM-TFTs) with 200 nm thick poly(vinylidene fluoride/trifluoroethylene) ferroelectric layer; semitransparent 10 nm thin AgO{sub x} and transparent 130 nm thick indium-zinc oxide (IZO) were deposited on the ferroelectric polymer as gate electrode by rf sputtering. Our semitransparent NVM-TFT with AgO{sub x} gate operates under low voltage write-erase (WR-ER) pulse of {+-}20 V, but shows some degradation in retention property. In contrast, our transparent IZO-gated device displays very good retention properties but requires anomalously higher pulse of {+-}70 V for WR and ER states. Both devices stably operated under visible illuminations.

Park, C. H.; Im, Seongil [Institute of Physics and Applied Physics, Yonsei University, Seoul 120-749 (Korea, Republic of); Yun, Jungheum; Lee, Gun Hwan [Department of Surface Technology, Korea Institute of Material Science, Changwon, Gyeongnam 641-831 (Korea, Republic of); Lee, Byoung H.; Sung, Myung M. [Department of Chemistry, Hanyang University, Seoul 133-791 (Korea, Republic of)




ERIC Educational Resources Information Center

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

Brand, Judith, Ed.



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



On modeling shape memory polymers as thermoelastic two-phase composite materials  

E-print Network

. Diani Laboratoire Procédés et Ingénierie en Mécanique et Matériaux, Arts et Métiers ParisTech, CNRS, 151 behavior, without strain rate effects, and assumes essentially that the polymer can be considered as a two a uniform stress hypothesis was used in the original formulation, with an inconsistency when thermal

Paris-Sud XI, Université de



NSDL National Science Digital Library

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



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:; 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)



Revealing the respective effect of aging and cyclic deformation through the memory effect in glassy polymers  

NASA Astrophysics Data System (ADS)

It has been known for 40 years that the state of a glass cannot be characterized by a single parameter such as its density and depends on its whole thermal history in a complex way. This phenomenon, known as the memory effect, reveals that the spatial distribution of the dynamics in a glass is deeply heterogeneous. Among the various memory effects, we will focus on the following one. After an annealing at a temperature T, a glassy system will exhibit a specific signature of susceptibility—around the temperature T of annealing. This effect shows that relaxations during annealing occur only in some domains of specific dynamics. This has been observed in a variety of glasses, with different techniques. The memory effect, here, is observed for the first time through the dynamical elastic modulus. We show that the dynamical elastic modulus can be described by the simple phenomenological so-called Tool Narayanaswamy Moynhian (TNM) model. We evidence the competition between plastic deformation and annealing by applying cyclic strain during the annealing. As a result, we establish that deformation exhibits an effect that is opposite to thermal annealing and less selective in temperature.

Bodiguel, H.; Lequeux, F.; Montes, H.



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 PMID:22778531

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



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

NASA Astrophysics Data System (ADS)

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

Yang, Qianxi; Li, Guoqiang



A bioactive "self-fitting" shape memory polymer scaffold with potential to treat cranio-maxillo facial bone defects.  


While tissue engineering is a promising alternative for treating critical-sized cranio-maxillofacial bone defects, improvements in scaffold design are needed. In particular, scaffolds that can precisely match the irregular boundaries of bone defects as well as exhibit an interconnected pore morphology and bioactivity would enhance tissue regeneration. In this study, a shape memory polymer (SMP) scaffold was developed exhibiting an open porous structure and the capacity to conformally "self-fit" into irregular defects. The SMP scaffold was prepared via photocrosslinking of poly(?-caprolactone) (PCL) diacrylate using a SCPL method, which included a fused salt template. A bioactive polydopamine coating was applied to coat the pore walls. Following exposure to warm saline at T>Ttrans (Ttrans=Tm of PCL), the scaffold became malleable and could be pressed into an irregular model defect. Cooling caused the scaffold to lock in its temporary shape within the defect. The polydopamine coating did not alter the physical properties of the scaffold. However, polydopamine-coated scaffolds exhibited superior bioactivity (i.e. formation of hydroxyapatite in vitro), osteoblast adhesion, proliferation, osteogenic gene expression and extracellular matrix deposition. PMID:25063999

Zhang, Dawei; George, Olivia J; Petersen, Keri M; Jimenez-Vergara, Andrea C; Hahn, Mariah S; Grunlan, Melissa A



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

PubMed Central

Purpose: The objective of this study was to determine to what extent the diagnostic and therapeutic procedures taught in the undergraduate program used for patients with lumbopelvic conditions are expected to be utilized by students during their clinical internship program at Canadian Memorial Chiropractic College or are being used by the clinical faculty. Methods: A confidential survey was distributed to clinical faculty at the college. It consisted of a list of diagnostic and therapeutic procedures used for lumbopelvic conditions taught at that college. Clinicians were asked to indicate the frequency with which they performed or they required students to perform each item. Results: Seventeen of 23 clinicians responded. The following procedures were most likely required to be performed by clinicians: posture; ranges of motion; lower limb sensory, motor, and reflex testing; and core orthopedic tests. The following were less likely to be required to be performed: Waddell testing, Schober's test, Gillet tests, and abdominal palpation. Students were expected to perform (or clinicians performed) most of the mobilization (in particular, iliocostal, iliotransverse, and iliofemoral) and spinal manipulative therapies (in particular, the procedures referred to as the lumbar roll, lumbar pull/hook, and upper sacroiliac) taught at the college. Conclusion: This study suggests that there was considerable, but not complete, vertical integration between the undergraduate and clinical education program at this college. PMID:20480014

Vermet, Shannon; McGinnis, Karen; Boodham, Melissa; Gleberzon, Brian J.



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

PubMed Central

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

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



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.


Probing molecular interactions of poly(styrene-co-maleic acid) with lipid matrix models to interpret the therapeutic potential of the co-polymer.  


To understand and maximize the therapeutic potential of poly(styrene-co-maleic acid) (SMA), a synthetic, pharmacologically-active co-polymer, its effect on conformation, phase behavior and stability of lipid matrix models of cell membranes were investigated. The modes of interaction between SMA and lipid molecules were also studied. While, attenuated total reflection-Fourier-transform infrared (ATR-FTIR) and static (31)P nuclear magnetic resonance (NMR) experiments detected SMA-induced conformational changes in the headgroup region, differential scanning calorimetry (DSC) studies revealed thermotropic phase behavior changes of the membranes. (1)H NMR results indicated weak immobilization of SMA within the bilayers. Molecular interpretation of the results indicated the role of hydrogen-bond formation and hydrophobic forces between SMA and zwitterionic phospholipid bilayers. The extent of membrane fluidization and generation of isotropic phases were affected by the surface charge of the liposomes, and hence suggested the role of electrostatic interactions between SMA and charged lipid headgroups. SMA was thus found to directly affect the structural integrity of model membranes. PMID:22197504

Banerjee, Shubhadeep; Pal, Tapan K; Guha, Sujoy K



Laser-Induced Nondestructive Patterning of a Thin Ferroelectric Polymer Film with Controlled Crystals using Ge8Sb2Te11 Alloy Layer for Nonvolatile Memory.  


We present a simple but robust nondestructive process for fabricating micropatterns of thin ferroelectric polymer films with controlled crystals. Our method is based on utilization of localized heat arising from thin Ge8Sb2Te11 (GST) alloy layer upon exposure of 650 nm laser. The heat was generated on GST layer within a few hundred of nanosecond exposure and subsequently transferred to a thin poly(vinylidene fluoride-co-trifluoroethylene) film deposited on GST layer. By controlling exposure time and power of the scanned laser, ferroelectric patterns of one or two microns in size are fabricated with various shape. In the micropatterned regions, ferroelectric polymer crystals were efficiently controlled in both degree of the crystallinity and the molecular orientations. Nonvolatile memory devices with laser scanned ferroelectric polymer layers exhibited excellent device performance of large remnant polarization, ON/OFF current ratio and data retention. The results are comparable with devices containing ferroelectric films thermally annealed at least for 2 h, making our process extremely efficient for saving time. Furthermore, our approach can be conveniently combined with a number of other functional organic materials for the future electronic applications. PMID:25127181

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



Bistable electrical switching and electronic memory effect in a solution-processable graphene oxide-donor polymer complex  

NASA Astrophysics Data System (ADS)

A solution-processable and electroactive complex of poly(N-vinylcarbazole)-derivatized graphene oxide (GO-PVK) was prepared via amidation of end-functionalized PVK, from reversible addition fragmentation chain transfer polymerization, with tolylene-2,5-diisocyanate-functionalized graphene oxide. The Al/GO-PVK/ITO device exhibits bistable electrical conductivity switching and nonvolatile rewritable memory effects. Both the OFF and ON states of the memory device are stable under a constant voltage stress of -1 V for up to 3 h, or under a pulse voltage stress of -1 V for up to 108 read cycles, with an ON/OFF state current ratio in excess of 103.

Liu, Gang; Zhuang, Xiaodong; Chen, Yu; Zhang, Bin; Zhu, Jinhui; Zhu, Chun-Xiang; Neoh, Koon-Gee; Kang, En-Tang



n-Channel Organic Thin-Film Transistors based on Naphthalene-Bis(dicarboximide) Polymer for Organic Transistor Memory Using Hole-Acceptor Layer  

NASA Astrophysics Data System (ADS)

An investigation of threshold voltage shifts in organic thin-film transistors (OTFTs) based on poly[N,N '-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene) [P(NDI2OD-T2)] with additional poly(3-hexylthiophene) (P3HT) films on a poly(methyl methacrylate) (PMMA) organic dielectric layer is reported. With a top source-drain contact structure, the device exhibited a unipolar property with n-channel characteristics similar to those of the P(NDI2OD-T2)-only device. Furthermore, the existence of P3HT films as hole acceptor-like storage layers resulted in reversible Vth shift upon the application of external gate bias (Vbias) for a certain bias time (Tbias). Hence, the P(NDI2OD-T2)/P3HT-OTFTs exhibited a large memory window (?Vth = 10.7 V) for write and erase electrically without major degradation in saturation mobility [µsat = (1.8-2.8) ×10-4 cm2 V-1 s-1]. These results clearly indicate the utility of the naphthalene-bis(dicarboximide) (NDI)-based polymer-hole acceptor layer in the development of n-channel organic transistor memories.

Anuar Mohamad, Khairul; Yousuke, Kakuta; Uesugi, Katsuhiro; Fukuda, Hisashi



n-Channel Organic Thin-Film Transistors based on Naphthalene--Bis(dicarboximide) Polymer for Organic Transistor Memory Using Hole-Acceptor Layer  

NASA Astrophysics Data System (ADS)

An investigation of threshold voltage shifts in organic thin-film transistors (OTFTs) based on poly{[N,N\\aku '-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl]-alt-5,5'-(2,2'-bithiophene)} [P(NDI2OD-T2)] with additional poly(3-hexylthiophene) (P3HT) films on a poly(methyl methacrylate) (PMMA) organic dielectric layer is reported. With a top source-drain contact structure, the device exhibited a unipolar property with n-channel characteristics similar to those of the P(NDI2OD-T2)-only device. Furthermore, the existence of P3HT films as hole acceptor-like storage layers resulted in reversible Vth shift upon the application of external gate bias (Vbias) for a certain bias time (Tbias). Hence, the P(NDI2OD-T2)/P3HT-OTFTs exhibited a large memory window (? Vth = 10.7 V) for write and erase electrically without major degradation in saturation mobility [?sat = (1.8{--}2.8) × 10-4 cm2 V-1 s-1]. These results clearly indicate the utility of the naphthalene--bis(dicarboximide) (NDI)-based polymer--hole acceptor layer in the development of n-channel organic transistor memories.

Mohamad, Khairul Anuar; Yousuke, Kakuta; Uesugi, Katsuhiro; Fukuda, Hisashi



The flexible non-volatile memory devices using oxide semiconductors and ferroelectric polymer poly(vinylidene fluoride-trifluoroethylene)  

Microsoft Academic Search

We demonstrated flexible ferroelectric gate thin-film transistors (Fe-TFTs) with ferroelectric polymer poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] and amorphous indium gallium zinc oxide (a-IGZO) channel on the polyethylene-naphthalate (PEN) substrate. First, we confirm basic ferroelectric properties of the P(VDF-TrFE) film on the PEN substrate with various bending radius. Next, we fabricated Fe-TFTs with Al\\/120 nm-P(VDF-TrFE)\\/40 nm-IGZO top gate structure. Excellent electrical characteristics are

Gwang-Geun Lee; Eisuke Tokumitsu; Sung-Min Yoon; Yoshihisa Fujisaki; Joo-Won Yoon; Hiroshi Ishiwara



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


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

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



Building a Better Hormone Therapy?: How Understanding The Rapid Effects of Sex Steroid Hormones Could Lead to New Therapeutics for Age-Related Memory Decline  

Microsoft Academic Search

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.

Karyn M. Frick



"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



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

PubMed Central

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



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


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

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



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

E-print Network

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

Srivastava, Vikas



Mechanical memory  


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)



Mechanical memory  


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)



Therapeutic mammaplasty.  


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



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


Longevity pathways and memory aging  

PubMed Central

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

Gkikas, Ilias; Petratou, Dionysia; Tavernarakis, Nektarios



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



Annealing effect upon chain orientation, crystalline morphology, and polarizability of ultra-thin P(VDF-TrFE) film for nonvolatile polymer memory device  

Microsoft Academic Search

The ferroelectric behavior of spin-cast ultra-thin P(VDF-TrFE) (72-28) film is highly influenced by sample preparation methods including thermal annealing. The effect of sample preparation methods on the surface morphology, chain and dipole orientation, ferroelectric properties, and nonvolatile memory characteristics were studied using FTIR-grazing incident reflection absorption spectroscopy (GIRAS), grazing incident wide angle X-ray diffraction (GIWAXD), atomic force microscope (AFM), dynamic

Jong Soon Lee; Arun Anand Prabu; Kap Jin Kim




PubMed Central

Our memories are not all created equally strong: Some experiences are well remembered while others are remembered poorly, if at all. Research on memory modulation investigates the neurobiological processes and systems that contribute to such differences in the strength of our memories. Extensive evidence from both animal and human research indicates that emotionally significant experiences activate hormonal and brain systems that regulate the consolidation of newly acquired memories. These effects are integrated through noradrenergic activation of the basolateral amygdala which regulates memory consolidation via interactions with many other brain regions involved in consolidating memories of recent experiences. Modulatory systems not only influence neurobiological processes underlying the consolidation of new information, but also affect other mnemonic processes, including memory extinction, memory recall and working memory. In contrast to their enhancing effects on consolidation, adrenal stress hormones impair memory retrieval and working memory. Such effects, as with memory consolidation, require noradrenergic activation of the basolateral amygdala and interactions with other brain regions. PMID:22122145

Roozendaal, Benno; McGaugh, James L.



Coordination polymers  

Microsoft Academic Search

This paper is a review of the metal complex forming coordination polymers. A polymer–metal complex is composed of synthetic polymer and metal ions bound to the polymer ligand by a coordinate bond. A polymer ligand contains anchoring sites like nitrogen, oxygen or sulphur obtained either by the polymerization of monomer possessing the coordinating site or by a chemical reaction between

T. Kaliyappan; P. Kannan



Polymers Presentation  

NSDL National Science Digital Library

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



Cognitive memory.  


Regarding the workings of the human mind, memory and pattern recognition seem to be intertwined. You generally do not have one without the other. Taking inspiration from life experience, a new form of computer memory has been devised. Certain conjectures about human memory are keys to the central idea. The design of a practical and useful "cognitive" memory system is contemplated, a memory system that may also serve as a model for many aspects of human memory. The new memory does not function like a computer memory where specific data is stored in specific numbered registers and retrieval is done by reading the contents of the specified memory register, or done by matching key words as with a document search. Incoming sensory data would be stored at the next available empty memory location, and indeed could be stored redundantly at several empty locations. The stored sensory data would neither have key words nor would it be located in known or specified memory locations. Sensory inputs concerning a single object or subject are stored together as patterns in a single "file folder" or "memory folder". When the contents of the folder are retrieved, sights, sounds, tactile feel, smell, etc., are obtained all at the same time. Retrieval would be initiated by a query or a prompt signal from a current set of sensory inputs or patterns. A search through the memory would be made to locate stored data that correlates with or relates to the prompt input. The search would be done by a retrieval system whose first stage makes use of autoassociative artificial neural networks and whose second stage relies on exhaustive search. Applications of cognitive memory systems have been made to visual aircraft identification, aircraft navigation, and human facial recognition. Concerning human memory, reasons are given why it is unlikely that long-term memory is stored in the synapses of the brain's neural networks. Reasons are given suggesting that long-term memory is stored in DNA or RNA. Neural networks are an important component of the human memory system, and their purpose is for information retrieval, not for information storage. The brain's neural networks are analog devices, subject to drift and unplanned change. Only with constant training is reliable action possible. Good training time is during sleep and while awake and making use of one's memory. A cognitive memory is a learning system. Learning involves storage of patterns or data in a cognitive memory. The learning process for cognitive memory is unsupervised, i.e. autonomous. PMID:23453302

Widrow, Bernard; Aragon, Juan Carlos



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



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



Frequency of use of diagnostic and manual therapeutic procedures of the spine currently taught at the Canadian Memorial Chiropractic College: A preliminary survey of Ontario chiropractors. Part 2 - procedure usage rates  

PubMed Central

Objective: The purpose of this study was to determine which diagnostic and therapeutic procedures of the spine are most commonly utilized by chiropractors practicing in Ontario, based on a list of currently taught procedures at CMCC. In Part 1 of this study (published previously), the demographics and practice patterns of the respondents were presented. Part 2 of this study (presented here) reports on the utilization rates of spinal diagnostic and therapeutic procedures by the respondents. Methods: The study consisted of a paper-based survey that was sent to 500 randomly selected Ontario chiropractors who responded confidentially. Survey questions inquired into demographic and practice style characteristics as well as the frequency with which spinal diagnostic and therapeutic procedures were performed. Results: There were 108 respondents to the survey, giving a response rate of 22.4%. Frequency of use of diagnostic procedures fell into three broad categories: (i) those tests that are almost always performed, (ii) those tests that are almost always performed by two-thirds to one-half of patients, and (iii) those tests that are virtually never used. By comparison, respondents utilized the same therapeutic procedures for patients care less consistently. Conclusions: Despite a low response rate, respondents reported mostly relying on static and motion palpation, joint play, neurological tests, and ranges of motion when assessing their patients. Due to a low response rate, the results of this study may not be generalizable to all Ontario chiropractors. PMID:23754862

Gleberzon, Brian; Stuber, Kent



Emerging memories  

NASA Astrophysics Data System (ADS)

Memory is a key component of any data processing system. Following the classical Turing machine approach, memories hold both the data to be processed and the rules for processing them. In the history of microelectronics, the distinction has been rather between working memory, which is exemplified by DRAM, and storage memory, exemplified by NAND. These two types of memory devices now represent 90% of all memory market and 25% of the total semiconductor market, and have been the technology drivers in the last decades. Even if radically different in characteristics, they are however based on the same storage mechanism: charge storage, and this mechanism seems to be near to reaching its physical limits. The search for new alternative memory approaches, based on more scalable mechanisms, has therefore gained new momentum. The status of incumbent memory technologies and their scaling limitations will be discussed. Emerging memory technologies will be analyzed, starting from the ones that are already present for niche applications, and which are getting new attention, thanks to recent technology breakthroughs. Maturity level, physical limitations and potential for scaling will be compared to existing memories. At the end the possible future composition of memory systems will be discussed.

Baldi, Livio; Bez, Roberto; Sandhu, Gurtej



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. PMID:24795583

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



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



Virtual memory  

NASA Technical Reports Server (NTRS)

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

Denning, P. J.



Polymer Transfected Primary Myoblasts- Mediated Angiogenic Gene Therapy for Ischemic Heart Disease.  

E-print Network

??Polymer transfected primary myoblasts-mediated angiogenic gene therapy is proposed as a new therapeutic regime for ischemic heart disease. The conventional drug therapy and surgical treatment… (more)

Ou, Mei



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



Organic Memory Device Fabricated Through Solution Processing  

Microsoft Academic Search

Novel organic memory devices including nonvolatile and write-once-read-many-times memory devices are reported. These devices were fabricated through a simple solution processing technique. Programmable electrical bistability was observed on a device made from a polymer film containing metal nanoparticles capped with saturated alkanethiol and small conjugated organic compounds sandwiched between two metal electrodes. The pristine device, which was in a low-conductivity

Jianyong Ouyang; Chih-Wei Chu; Ricky Jia-Hung Tseng; ANKITA PRAKASH; Yang Yang



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



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.



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



Are recovered memories accurate?  

E-print Network

Research in our laboratory has demonstrated blocked and recovered memories within the context of a controlled experiment. The comparative memory paradigm allows for comparisons of recovered memories, continuous memories, and false memories...

Gerkens, David



Polymer adsorption  

NASA Astrophysics Data System (ADS)

The aim of this talk is to review Pierre-Gilles deGennes' work on polymer adsorption and the impact that it has now in our understanding of this problem. We will first present the self-consistent mean-field theory and its applications to adsorption and depletion. De Gennes most important contribution is probably the derivation of the self-similar power law density profile for adsorbed polymer layers that we will present next, emphasizing the differences between the tail sections and the loop sections of the adsorbed polymers. We will then discuss the kinetics of polymer adsorption and the penetration of a new polymer chain in an adsobed layer that DeGennes described very elegantly in analogy with a quantum tunneling problem. Finally, we will discuss the role of polymer adsorption for colloid stabilization.

Joanny, Jean-Francois



Natural Polymers  

NSDL National Science Digital Library

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

Teegarden, David



Polymer carpets.  


The fabrication of defined polymer objects of reduced dimensions such as polymer-coated nanoparticles (zero-dimensional (0D)), cylindrical brushes (1D), and polymer membranes (2D), is currently the subject of intense research. In particular, ultrathin polymer membranes with high aspect ratios are being discussed as novel materials for miniaturized sensors because they would provide extraordinary sensitivity and dynamic range when sufficient mechanical stability can be combined with flexibility and chemical functionality. Unlike current approaches that rely on crosslinking of polymer layers for stabilization, this report presents the preparation of a new class of polymer material, so-called "polymer carpets," a freestanding polymer brush grown by surface-initiated polymerization on a crosslinked 1-nm-thick monolayer. The solid-supported, as well as freestanding, polymer carpets are found to be mechanically robust and to react instantaneously and reversibly to external stimuli by buckling. The carpet mechanics and the dramatic changes of the film properties (optical, wetting) upon chemical stimuli are investigated in detail as they allow the development of completely new integrated micro-/nanotechnology devices. PMID:20635346

Amin, Ihsan; Steenackers, Marin; Zhang, Ning; Beyer, André; Zhang, Xianghui; Pirzer, Tobias; Hugel, Thorsten; Jordan, Rainer; Gölzhäuser, Armin



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.



Frequency of use of diagnostic and manual therapeutic procedures of the spine taught at the Canadian Memorial Chiropractic College: A preliminary survey of Ontario chiropractors. Part 1 - practice characteristics and demographic profiles  

PubMed Central

Background: Students learn a plethora of physical examination and manual therapy procedures over the course of their chiropractic education. However, it is uncertain to what extent they continue to use these procedures in practice after graduation. Objective: The purpose of this study was to determine which diagnostic and therapeutic procedures of the spine are most commonly utilized by chiropractors practicing in Ontario. In Part 1 of this study (presented here), the demographics and practice patterns of the respondents are presented. Part 2 of this study will present the results of the utilization rates of diagnostic and therapeutic procedures used by respondents. Methods: The study consisted of a paper-based survey that was sent to 500 pseudo-randomly selected Ontario chiropractors who responded confidentially. Survey questions inquired into demographic and practice style characteristics. Results: There were 108 respondents to the survey, giving a response rate of 22.4%. Many chiropractors self-identified themselves with more than one practice style characteristic such as 72.4% of the self-described pain-based chiropractors who also described themselves as evidence-based, compared with 51.9% of subluxation-based chiropractors who also described themselves as evidence-based. Diversified technique was the most commonly employed technique used by 90.7% of respondents, followed by trigger point therapy indicated by 57.4% of respondents. Conclusions: Despite a low response rate, respondents reported practice characteristics in this study that were similar to practice characteristics previously published, particularly in terms of professional demographics and techniques employed. While Diversified was the most commonly used technique, respondents reported higher levels of use of proprietary soft tissue techniques systems and upper cervical techniques than have been previously reported. PMID:23482716

Gleberzon, Brian; Stuber, Kent



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.



Electroluminescent polymers  

Microsoft Academic Search

Electroluminescent polymers are reviewed in terms of synthesis and relationships between structure and light emission properties.The main concepts, problems and ideas related to the subject as a whole and to each class of electroluminescence (EL) polymer, have been systematically addressed. The elements of device architecture were considered, such as electrode characteristics and transport layers. The main mechanisms for light emission

Leni Akcelrud



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



Polymers Guide  

NSDL National Science Digital Library

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



Polymer flooding  

Microsoft Academic Search

This book covers all aspects of polymer flooding, an enhanced oil recovery method using water soluble polymers to increase the viscosity of flood water, for the displacement of crude oil from porous reservoir rocks. Although this method is becoming increasingly important, there is very little literature available for the engineer wishing to embark on such a project. In the past,




Fullerene Embedded Shape Memory Nanolens Array  

NASA Astrophysics Data System (ADS)

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

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



Fullerene Embedded Shape Memory Nanolens Array  

PubMed Central

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

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



Learning, Memory, & Attention Instructor  

E-print Network

1 COGS 101B: Learning, Memory, & Attention · Welcome! · Instructor ­ Dr. Coulson ­ Email: coulson Attention ­ Divided Attention ­ Automaticity ­ Attentional Capture · Immediate Memory ­ Sensory Memory ­ Short-Term Memory ­ Working Memory · Long-Term Memory ­ Levels of Processing ­ Memory Systems

Coulson, Seana


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



Memorial Sloan-Kettering Cancer Center

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.


On memories of childhood abuse: a phenomenological study  

Microsoft Academic Search

Objective: To explore the phenomenon of memories and reported recovered memories of childhood abuse, and to examine ways in which clients and therapists assess the veridicality of such memories.Method: Qualitative methodology utilizing phenomenological inquiry. Within the context of a wider study exploring perceptions of helpful and unhelpful factors in the therapeutic process, a sub-sample of 36 in-depth interviews with clients,

Peter Dale; John Allen



Branched Polymers  

E-print Network

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

Richard Kenyon; Peter Winkler



Polymer Synthesis  

NSDL National Science Digital Library

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

Teegarden, David



Noradrenergic modulation of cognition: therapeutic implications.  


The noradrenaline (norepinephrine) system exerts profound influences on cognition via ascending projections to the forebrain, mostly originating from the locus coeruleus. This paper provides an overview of available infrahuman and healthy human studies, exploring the effects of specific noradrenergic manipulations on dissociable cognitive functions, including attention, working memory, cognitive flexibility, response inhibition and emotional memory. Remarkable parallels across species have been reported which may account for the mechanisms by which noradrenergic medications exert their beneficial effects in disorders such as depression and attention-deficit hyperactivity disorder (ADHD). The literature is discussed in relation to prevailing models of noradrenergic influences over cognition and novel therapeutic directions, including in relation to investigating the effects of noradrenergic manipulations on other disorders characterized by impulsivity, and dementias. Unanswered questions are also highlighted, along with key avenues for future research, both proof-of-concept and clinical. PMID:23518815

Chamberlain, Samuel R; Robbins, Trevor W



Nitric Oxide Release Part II. Therapeutic Applications  

PubMed Central

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

Carpenter, Alexis W.; Schoenfisch, Mark H.



Reactivating personal memory 1 RUNNING HEAD: Reactivating personal memory  

E-print Network

Reactivating personal memory 1 RUNNING HEAD: Reactivating personal memory Modifying memory: Selectively enhancing and updating personal memories for a museum; Reactivating personal memory 2 Abstract Memory can be modified when reactivated

Schacter, Daniel


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



Milestoning with coarse memory.  


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

Hawk, Alexander T



Non-Alzheimer's disease--related memory impairment and dementia  

PubMed Central

Although Alzheimer's disease (AD) is a common cause of memory impairment and dementia in the elderly disturbed memory function is a widespread subjective and/or objective symptom in a variety of medical conditions. The early detection and correct distinction of AD from non-AD memory impairment is critically important to detect possibly treatable and reversible underlying causes. In the context of clinical research, it is crucial to correctly distinguish between AD or non-AD memory impairment in order to build homogenous study populations for the assessment of new therapeutic possibilities. The distinction of AD from non-AD memory impairment may be difficult, especially in mildly affected patients, due to an overlap of clinical symptoms and biomarker alterations between AD and certain non-AD conditions. This review aims to describe recent aspects of the differential diagnosis of AD and non-AD related memory impairment and how these may be considered in the presence of memory deficits. PMID:24459413

Arlt, Sonke



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

PubMed Central

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

Kandel, E R; Pittenger, C



Spatial memory, recognition memory, and the hippocampus  

E-print Network

Spatial memory, recognition memory, and the hippocampus Nicola J. Broadbent*, Larry R. Squire. Squire, August 27, 2004 There is wide agreement that spatial memory is dependent on the integrity recognition memory is not as clear. We examined the relationship between hippocampal lesion size and both

Squire, Larry R.


Memory systems (cont.) Interactions among memory systems  

E-print Network

of evidence would help resolve this? Implanting memories · Researchers have asked whether memories can be implanted? ­ If a false memory can be implanted, that would make us more skeptical about reports forgotten in the intirim · It is easy to implant false memories ­ Some therapists have been sued

Pillow, Jonathan


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



Memory Technologies Vivek Asthana  

E-print Network

Memory Technologies Vivek Asthana 13th Mar 2013 #12;13-Mar-13 2 Memory Usage (2025) #12;13-Mar-13 3 Outline What is a Memory Current Memory technologies · SRAM · DRAM · Flash Upcoming Memory technologies · MRAM · PCRAM · FeRAM · ... #12;13-Mar-13 4 What is a Memory Memory cell: Binary data storage element

Kumar, M. Jagadesh


Injectable preformed scaffolds with shape-memory properties  

PubMed Central

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

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



Ferroelectric polymers  

Microsoft Academic Search

In the early 1970s it became clear that the polymer polyvinylidene fluoride is ferroelectric. There have been extensive studies of its properties and of the properties of copolymers of vinylidene fluoride with tri- or tetra-fluoroethylene. This work has led to a fairly complete understanding of the ferroelectric and related properties of these materials. The emphasis in this review is on

R. G. Kepler; R. A. Anderson



Polymer solutions  


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

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



Treatment for traumatic memories: review and recommendations.  


The aim of this article is to provide recommendations concerning the use of exposure-based therapy for reduction of emotional responding to traumatic memories. Background for these recommendations consists of a summary of the literature on traumatic stress and symptoms of posttraumatic stress disorder (PTSD); an overview of biological, cognitive, and behavioral models for traumatic memory; and a selective review of evidence for the effectiveness of therapeutic exposure as a treatment for trauma memories and PTSD. The recommendations themselves demonstrate how clinical decision making during the course of treatment might be informed by empirical evidence and theoretical models concerning human memory, as well as ethical and legal considerations that mark this topic. PMID:9885771

Leskin, G A; Kaloupek, D G; Keane, T M



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. PMID:24222916

Nakagami, Hironori; Kaneda, Yasufumi; Morishita, Ryuichi



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. PMID:20392284

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.



Imprinted polymers assisting protein crystallization.  


Molecularly imprinted polymers (MIPs) are 'smart materials' polymerised in the presence of a template molecule, of which they retain a chemical 'memory'. When the template molecule is extracted from the polymer, it leaves behind cavities that are complementary to it, thus making the material capable of rebinding that molecule with high affinity and selectivity. Such materials, imprinted both with small molecule and with protein templates, have been used in chromatographic, chemical, and biological sensing applications. Here, we review a variety of uses for MIPs, focusing on their recently discovered role as nucleation inducing substances for protein crystals. This discovery makes them useful tailor-made 'nucleants' to be used both for optimisation of protein crystal growth and for discovering new crystallization conditions. PMID:23764007

Saridakis, Emmanuel; Chayen, Naomi E



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. PMID:21227404

Ehlers, Anke; Mauchnik, Jana; Handley, Rachel



Solid Tumor-Targeting Theranostic Polymer Nanoparticle in Nuclear Medicinal Fields  

PubMed Central

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

Makino, Akira; Kimura, Shunsaku



Predictors of sustained therapeutic change  

Microsoft Academic Search

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

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



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



Therapeutic Recombinant Monoclonal Antibodies  

ERIC Educational Resources Information Center

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

Bakhtiar, Ray



Complement-targeted therapeutics  

Microsoft Academic Search

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

Daniel Ricklin; John D Lambris



Processing the therapeutic relationship  

Microsoft Academic Search

The authors propose that if therapists and clients process their therapeutic relationship (i.e., directly address in the here and now feelings about each other and about the inevitable problems that emerge in the therapy relationship), feelings will be expressed and accepted, problems will be resolved, the relationship will be enhanced, and clients will transfer their learning to other relationships outside

Clara E. Hill; Sarah Knox



Memory Coalescing Techniques 1 Accessing Global and Shared Memory  

E-print Network

Memory Coalescing Techniques 1 Accessing Global and Shared Memory memory coalescing to global memory avoiding bank conflicts in shared memory 2 Memory Coalescing Techniques accessing global memory for a matrix using shared memory for coalescing 3 Avoiding Bank Conflicts computing consecutive powers MCS 572

Verschelde, Jan


What is memory for? Short term memory (STM)  

E-print Network

1 Memory · What is memory for? · Short term memory (STM) · Characteristics of STM Who has a better with an examination of visual memory. STM and LTM · And now for some jargon ­ Short term memory (STM) ­ Long term memory (LTM) · Today, we focus on short term memory. Short-term memory · You know many things ­ Facts

Pillow, Jonathan


How Memory Works  


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 ...


Memory Slips and Dementia  


... the lower right-hand corner of the player. Memory Slips and Dementia HealthDay September 26, 2014 Related MedlinePlus Pages Dementia Memory Seniors' Health Transcript Little memory slips as you ...


Types of Memory  


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


Transient behaviour of a polymer dragged through a viscoelastic medium  

E-print Network

We study the dynamics of a polymer that is pulled by a constant force through a viscoelastic medium. This is a model for a polymer being pulled through a cell by an external force, or for an active biopolymer moving due to a self generated force. Using a Rouse model with a memory dependent drag force, we find that the center of mass of the polymer follows a subballistic motion. We determine the time evolution of the length and the shape of the polymer. Through an analysis of the velocity of the monomers, we investigate how the tension propagates through the polymer. We discuss how polymers can be used as a probe of the properties of a viscoelastic medium.

Hans Vandebroek; Carlo Vanderzande



Transient behaviour of a polymer dragged through a viscoelastic medium  

NASA Astrophysics Data System (ADS)

We study the dynamics of a polymer that is pulled by a constant force through a viscoelastic medium. This is a model for a polymer being pulled through a cell by an external force, or for an active biopolymer moving due to a self-generated force. Using the Rouse model with a memory dependent drag force, we find that the center of mass of the polymer follows a subballistic motion. We determine the time evolution of the length and the shape of the polymer. Through an analysis of the velocity of the monomers, we investigate how the tension propagates through the polymer. We discuss how polymers can be used to probe the properties of a viscoelastic medium.

Vandebroek, Hans; Vanderzande, Carlo



Transient behaviour of a polymer dragged through a viscoelastic medium.  


We study the dynamics of a polymer that is pulled by a constant force through a viscoelastic medium. This is a model for a polymer being pulled through a cell by an external force, or for an active biopolymer moving due to a self-generated force. Using the Rouse model with a memory dependent drag force, we find that the center of mass of the polymer follows a subballistic motion. We determine the time evolution of the length and the shape of the polymer. Through an analysis of the velocity of the monomers, we investigate how the tension propagates through the polymer. We discuss how polymers can be used to probe the properties of a viscoelastic medium. PMID:25240375

Vandebroek, Hans; Vanderzande, Carlo



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.



Polyphenols: Multipotent Therapeutic Agents in Neurodegenerative Diseases  

PubMed Central

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

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



Periodic Polymers  

NASA Astrophysics Data System (ADS)

Periodic polymers can be made by self assembly, directed self assembly and by photolithography. Such materials provide a versatile platform for 1, 2 and 3D periodic nano-micro scale composites with either dielectric or impedance contrast or both, and these can serve for example, as photonic and or phononic crystals for electromagnetic and elastic waves as well as mechanical frames/trusses. Compared to electromagnetic waves, elastic waves are both less complex (longitudinal modes in fluids) and more complex (longitudinal, transverse in-plane and transverse out-of-plane modes in solids). Engineering of the dispersion relation between wave frequency w and wave vector, k enables the opening of band gaps in the density of modes and detailed shaping of w(k). Band gaps can be opened by Bragg scattering, anti-crossing of bands and discrete shape resonances. Current interest is in our group focuses using design - modeling, fabrication and measurement of polymer-based periodic materials for applications as tunable optics and control of phonon flow. Several examples will be described including the design of structures for multispectral band gaps for elastic waves to alter the phonon density of states, the creation of block polymer and bicontinuous metal-carbon nanoframes for structures that are robust against ballistic projectiles and quasi-crystalline solid/fluid structures that can steer shock waves.

Thomas, Edwin



Complement-targeted therapeutics  

PubMed Central

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

Ricklin, Daniel; Lambris, John D



Memory Retrieval and Interference: Working Memory Issues  

ERIC Educational Resources Information Center

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

Radvansky, Gabriel A.; Copeland, David E.



Therapeutic targets for neuroblastomas  

PubMed Central

Introduction Neuroblastoma (NB) is the most common and deadly solid tumor in children. Despite recent improvements, the long-term outlook for high-risk NB is still < 50%. Further, there is considerable short- and long-term toxicity. More effective, less toxic therapy is needed, and the development of targeted therapies offers great promise. Areas covered Relevant literature was reviewed to identify current and future therapeutic targets that are critical to malignant transformation and progression of NB. The potential or actual NB therapeutic targets are classified into four categories: i) genes activated by amplification, mutation, translocation or autocrine overexpression; ii) genes inactivated by deletion, mutation or epigenetic silencing; iii) membrane-associated genes expressed on most NBs but few other tissues; or iv) common target genes relevant to NB as well as other tumors. Expert opinion Therapeutic approaches have been developed to some of these targets, but many remain untargeted at the present time. It is unlikely that single targeted agents will be sufficient for long-term cure, at least for high-risk NBs. The challenge will be how to integrate targeted agents with each other and with conventional therapy to enhance their efficacy, while simultaneously reducing systemic toxicity. PMID:24387342

Brodeur, Garrett M; lIyer, Radhika; Croucher, Jamie L; Zhuang, Tiangang; Higashi, Mayumi; Kolla, Venkatadri



Mitochondria-directed therapeutics.  


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



Connection in therapeutic communities.  


The success of therapeutic community treatment is based on trust. Trust underlies the willingness of residents to endorse and profit from confrontations of their denial. Lack of trust can be seen to underlie the high dropout rate of many therapeutic communities. Social learning theory, which is usually cited as a theoretical foundation for therapeutic communities, does not explain the role of trust. Instead, we need an explanation of trust based on a logic of emotion rather than the cognitive, calculating logic of social learning. This logic can be found in the process of connection. Trust, in the theoretical orientation of connection, grows out of the resident's perception that community members care. This caring is revealed in their empathy for the resident, their willingness to take responsibility for helping the resident, and their nurturance. The resident's level of trust determines his (her) willingness to be open and responsive to the community. The implications of the connection process for the development of trust between new residents and old residents and between residents and staff are developed. PMID:8188445

Bell, D C



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.



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


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



In vitro wrinkle formation via shape memory dynamically aligns adherent cells  

E-print Network

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

Mather, Patrick T.


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



Polymeric memory device with dual electrical and optical reading modes  

NASA Astrophysics Data System (ADS)

We report a write-once-read-many polymeric memory device that can be read by both electrical and optical methods. The device consists of two layers of conjugated polymer blends sandwiched between a metal electrode and a transparent electrode. One of the polymer blends functions as an ion-trapping, electrochromic layer, while the other polymer blend functions as a light-emitting electrochemical cell. Recording is facilitated by applying a negative writing voltage on the device. Reading can be performed by either probing with a low positive voltage, probing with a laser beam, or by measuring the light emission intensity from the device.

Deng, Xian-Yu; Wong, King Y.



Memory Hard Drive Peripherals  

E-print Network

1! CSI3131 Topics CPU Memory Hard Drive Peripherals Computing Systems OS Overview StructureDeadlocks M em ory M anagem ent Basic Memory Managermtn Virtual Memory Storage and I/O File Systems Hard Drive Management Swap I/O Management 2 Module 7: Memory Management Reading: Chapter 8 § To provide a detailed

Stojmenovic, Ivan


Memories of Things Unseen  

Microsoft Academic Search

New findings reveal more about the malleability of memory. Not only is it possible to change details of memories for previously experienced events, but one can sometimes also plant entirely false memories into the minds of unsuspecting individuals, even if the events would be highly implausible or even impossible. False memories might differ statistically from true ones, in terms of

Elizabeth F. Loftus



Female Memory in Narrative  

Microsoft Academic Search

The author searches past ages to trace the development of a specific women’s memory. She attempts to show how this memory is made up, describing the female memory in the Bible, in Greek and Roman history and mythology, and its hidden trajectory behind the scenes of conventional (male) history. She suggests that social exile made female memory a matrix from

Nélida Piñon



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



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

E-print Network

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

Angelosanto, Jill


Alzheimer's disease pathogenesis and therapeutic interventions.  


Alzheimer's disease (AD) is a neurodegenerative disorder of the central nervous system associated with progressive cognitive and memory loss. Molecular hallmarks of the disease are characterized by extracellular deposition of the amyloid beta peptide (Abeta) in senile plaques, the appearance of intracellular neurofibrillary tangles (NFT), cholinergic deficit, extensive neuronal loss and synaptic changes in the cerebral cortex and hippocampus and other areas of brain essential for cognitive and memory functions. Abeta deposition causes neuronal death via a number of possible mechanisms including oxidative stress, excitotoxicity, energy depletion, inflammation and apoptosis. Despite their multifactorial etiopathogenesis, genetics plays a primary role in progression of disease. To date genetic studies have revealed four genes that may be linked to autosomal dominant or familial early onset AD (FAD). These four genes include: amyloid precursor protein (APP), presenilin 1 (PS1), presenilin 2 (PS2) and apolipoprotein E (ApoE). Plaques are formed mostly from the deposition of Abeta, a peptide derived from APP. The main factors responsible for Abeta formation are mutation of APP or PS1 and PS2 genes or ApoE gene. All mutations associated with APP and PS proteins can lead to an increase in the production of Abeta peptides, specifically the more amyloidogenic form, Abeta42. In addition to genetic influences on amyloid plaque and intracellular tangle formation, environmental factors (e.g., cytokines, neurotoxins, etc.) may also play important role in the development and progression of AD. A direct understanding of the molecular mechanism of protein aggregation and its effects on neuronal cell death could open new therapeutic approaches. Some of the therapeutic approaches that have progressed to the clinical arena are the use of acetylcholinesterase inhibitors, nerve growth factors, nonsteroidal inflammatory drugs, estrogen and the compounds such as antioxidants, neuronal calcium channel blockers or antiapoptotic agents. Inhibition of secretase activity and blocking the formation of beta-amyloid oligomers and fibrils which may inhibit fibrilization and fibrilization-dependent neurotoxicity are the most promising therapeutic strategy against the accumulation of beta-amyloid fibrils associated with AD. Furthermore, development of immunotherapy could be an evolving promising therapeutic approach for the treatment of AD. PMID:15177383

Parihar, M S; Hemnani, Taruna



Amphetamine Increases Errors During Episodic Memory Retrieval  

PubMed Central

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

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



Amphetamine increases errors during episodic memory retrieval.  


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

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



Polymer microphotonics  

NASA Astrophysics Data System (ADS)

We report on a polymer-based planar lightwave circuit platform that enables high levels of integration. The materials used represent the state of the art in optical polymers, and include properties such as ultra-low loss (0.1 dB/cm in single-mode waveguides at 1550 nm), widely tunable refractive index contrast (0-35%), and large thermo-optic coefficient (-3.2×10-4/°C). The large index contrast values enable compact photonic microcircuits. The circuits are produced photolithographically, and can have a variety of inorganic materials integrated in them (e.g., by insertion in slots or by flip-chip mounting), resulting in a platform that can support functions that span the range of the building blocks needed in optical circuitry, while using the highest-performance material for each function. In this manuscript, we focus on the polymeric microcircuits, which provide interconnects, static routing elements such as couplers, taps, and multi/demultiplexers, as well as thermo-optically dynamic elements such as tunable couplers, switches, variable optical attenuators, and tunable notch filters. We demonstrate complex-functionality polymeric photonic microcircuits based on this technology, including fully reconfigurable optical add/drop multiplexing subsystems on a chip that perform channel switching, power monitoring, load balancing, and wavelength shuffling.

Eldada, Louay A.



Silk constructs for delivery of muskuloskeletal therapeutics  

PubMed Central

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

Meinel, Lorenz; Kaplan, David L.



Unique Properties of Reversibly Associating Polymer Networks  

NASA Astrophysics Data System (ADS)

Reversibly associating functional groups offer the polymer physicist with a new tool to develop stimuli-responsive polymers. Our focus has been to attach reversibly associating groups onto rubbery network polymers. Free radical copolymerization was used to synthesize a series of crosslinked poly(n-butylacrylate)s containing quadruple H-bonding ureidopyrimidinone (UPy) side-groups. Resulting elastomeric networks contain both covalent and dynamic non-covalent crosslinks, and this unique architecture is shown to affect viscoelastic behavior and mass-transport properties. Shape-memory effects are studied quantitatively using thermomechanical techniques. Experiments show how reversible interactions, such as hydrogen bonding, are capable of stabilizing mechanically strained states. Unlike conventional shape-memory polymers, these dynamic networks lack a well-defined shape recovery temperature. Instead, their shape recovery rate depends on temperature. To further study the dynamics and temperature dependence of mechanical relaxation, isothermal creep experiments and dynamic mechanical analysis were performed. Creep data, acquired at several different temperatures, are fit to a simple viscoelastic model. Fit viscosities exhibit Arrhenius-like temperature dependence with activation energies of ˜90 kJ/mol, which is in rough agreement with H-bond dissociation barriers. Molecular transport through dynamic networks is studied using gravimetric sorption and dye-diffusion techniques. Diffusion depends on temperature, network architecture, solute size, and the interaction between the solute and the network. Membranes with high temperature-sensitive diffusion properties may be useful in applications such as transdermal drug delivery, microfluidics, or liquid chemical separation processes.

Anthamatten, Mitchell



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


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



Small diameter active catheter using shape memory alloy  

Microsoft Academic Search

Three kinds of active catheters whose outside diameters are less than 2 mm were fabricated. One uses polymer links, the other two are linkless active catheters using adhesive. Distributed shape memory alloy (SMA) coil were used as actuators for the active motion. There are endoskeletal type and exoskeletal type in the linkless active catheters. We have applied the endoskeletal type

Y. Hagal; Y. Tanahashi; M. Esashi



Memory Metals  

NASA Technical Reports Server (NTRS)

Under contract to NASA during preparations for the space station, Memry Technologies Inc. investigated shape memory effect (SME). SME is a characteristic of certain metal alloys that can change shape in response to temperature variations. In the late 1980s and early 1990s, Memry used its NASA-acquired expertise to produce a line of home and industrial safety products, and refined the technology in the mid-1990s. Among the new products they developed are three MemrySafe units which prevent scalding from faucets. Each system contains a small valve that reacts to temperature, not pressure. When the water reaches dangerous temperatures, the unit reduces the flow to a trickle; when the scalding temperature subsides, the unit restores normal flow. Other products are the FIRECHEK 2 and 4, heat-activated shutoff valves for industrial process lines, which sense excessive heat and cut off pneumatic pressure. The newest of these products is Memry's Demand Management Water Heater which shifts the electricity requirement from peak to off-peak demands, conserving energy and money.



Intelligent manufacturing of polymers  

Microsoft Academic Search

Integrated multivariable process control can have a significant strategic impact on polymer plant operability and economics. Polymer manufacturers face increasing pressures for production cost reductions and more stringent “polymer quality” requirements. The main goals in operating a polymer reactor (e.g. high yield, better product quality and safe operation) are very difficult, if not impossible, to achieve without efficient and reliable

C. Kiparissides; J. Morris



Bidirectional changes to hippocampal theta-gamma comodulation predict memory for recent spatial episodes  

PubMed Central

Episodic memory requires the hippocampus, which is thought to bind cortical inputs into conjunctive codes. Local field potentials (LFPs) reflect dendritic and synaptic oscillations whose temporal structure may coordinate cellular mechanisms of plasticity and memory. We now report that single-trial spatial memory performance in rats was predicted by the power comodulation of theta (4–10 Hz) and low gamma (30–50 Hz) rhythms in the hippocampus. Theta–gamma comodulation (TGC) was prominent during successful memory retrieval but was weak when memory failed or was unavailable during spatial exploration in sample trials. Muscimol infusion into medial septum reduced the probability of TGC and successful memory retrieval. In contrast, patterned electrical stimulation of the fimbria-fornix increased TGC in amnestic animals and partially rescued memory performance in the water maze. The results suggest that TGC accompanies memory retrieval in the hippocampus and that patterned brain stimulation may inform therapeutic strategies for cognitive disorders. PMID:20351262

Shirvalkar, Prasad R.; Rapp, Peter R.; Shapiro, Matthew L.



Shared Memory Parallel Programming with Entry Consistency for Distributed Memory  

E-print Network

Midway: Shared Memory Parallel Programming with Entry Consistency for Distributed Memory memory multiprocessing offers a cost­effective and scalable solution for a large class of scientific and numeric applications. Unfortunately, the performance of current distributed memory programming


Addiction: A drug-induced disorder of memory reconsolidation  

PubMed Central

Persistent maladaptive memories that maintain drug seeking and are resistant to extinction are a hallmark of addiction. As such, disruption of memory reconsolidation after retrieval has received attention for its therapeutic potential. Unrestrained reconsolidation may have the opposite effect, leading to reiterative and cumulative strengthening of memory over long periods of time. Here we review the molecular mechanisms underlying reconsolidation of appetitive and drug-rewarded memories, and discuss how these findings contribute to our understanding of the nature of this process. Finally, we suggest that drug-induced alterations to signal transduction might lead to dysregulation of reconsolidation, causing enhancements of drug-related memory after retrieval, and significantly contribute to the compulsive drug seeking that is a core component of addiction. PMID:23415831

Tronson, Natalie C; Taylor, Jane R.



Neural and Cellular Mechanisms of Fear and Extinction Memory Formation  

PubMed Central

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

Orsini, Caitlin A.; Maren, Stephen



[Therapeutic education didactic techniques].  


This article includes an introduction to the role of Therapeutic Education for Diabetes treatment according to the recommendations of the American Diabetes Association (ADA), the Diabetes Education Study Group (DESG) of the "European Association for Study of Diabetes (EASD) and the clinical Practice Guidelines (CPG) of the Spanish Ministry of Health. We analyze theoretical models and the differences between teaching vs. learning as well as current trends (including Internet), that can facilitate meaningful learning of people with diabetes and their families and relatives. We analyze the differences, similarities, advantages and disadvantages of individual and group education. Finally, we describe different educational techniques (metaplan, case method, brainstorming, role playing, games, seminars, autobiography, forums, chats,..) applicable to individual, group or virtual education and its application depending on the learning objective. PMID:23157069

Valverde, Maite; Vidal, Mercè; Jansa, Margarida



Antimicrobial peptides: therapeutic potentials.  


The increasing appearance of multidrug-resistant pathogens has created an urgent need for suitable alternatives to current antibiotics. Antimicrobial peptides (AMPs), which act as defensive weapons against microbes, have received great attention because of broad-spectrum activities, unique action mechanisms and rare antibiotic-resistant variants. Despite desirable characteristics, they have shown limitations in pharmaceutical development due to toxicity, stability and manufacturing costs. Because of these drawbacks, only a few AMPs have been tested in Phase III clinical trials and no AMPs have been approved by the US FDA yet. However, these obstacles could be overcome by well-known methods such as changing physicochemical characteristics and introducing nonnatural amino acids, acetylation or amidation, as well as modern techniques like molecular targeted AMPs, liposomal formulations and drug delivery systems. Thus, the current challenge in this field is to develop therapeutic AMPs at a reasonable cost as well as to overcome the limitations. PMID:25371141

Kang, Su-Jin; Park, Sung Jean; Mishig-Ochir, Tsogbadrakh; Lee, Bong-Jin



[Humanized antibodies as therapeutics].  


Since 1997, nine humanized antibodies received the approval of the FDA to be used as drugs for the treatment of various diseases including transplant rejections, metastatic breast and colon cancers, leukaemia, non-Hodgkin lymphomas, allergic conditions or multiple sclerosis. This review describes techniques used to engineer these antibodies and presents the recent evolutions of these techniques : SDRs grafting or < abbreviated > CDRs grafting. Based on the illustrative examples of several antibodies, Mylotarg, Herceptin or Xolair, the therapeutic effectiveness of humanized antibodies are underlined and, with the example of Tysabri, the sometimes dramatic adverse effects associated with their clinical use is stressed. In a second part, this review presents some future and realistic avenues to improve the effectiveness of the humanized antibodies, to decrease their immunogenicity and to reduce their cost. PMID:16324646

Bellet, Dominique; Dangles-Marie, Virginie



Polymer and nano-technology applications for repair and reconstruction of the central nervous system  

Microsoft Academic Search

The hydrophilic polymer PEG and its related derivatives, have served as therapeutic agents to reconstruct the phospholipid bilayers of damaged cell membranes by erasing defects in the plasmalemma. The special attributes of hydrophilic polymers when in contact with cell membranes have been used for several decades since these well-known properties have been exploited in the manufacture of monoclonal antibodies. However,

Youngnam Cho; Richard Ben Borgens



E-print Network

a witness to history being made, a notion present in the concept of memory and the processes of remembering · (Post)memory and (post)trauma · Memory theatre and resonant spaces · Theatre as / and memorial

Sankoff, David


Memory abstractions for parallel programming  

E-print Network

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

Lee, I-Ting Angelina



Practical Memory Checking with Dr. Memory Derek Bruening  

E-print Network

Practical Memory Checking with Dr. Memory Derek Bruening Google Qin Zhao Massachusetts Institute of Technology qin Abstract--Memory corruption, reading uninitialized memory, using freed memory, and other memory-related errors are among the most difficult programming bugs

Tomkins, Andrew


Chronic caffeine consumption prevents memory disturbance in different animal models of memory decline.  


Caffeine, the most widely consumed psychoactive drug, enhances attention/vigilance, stabilizes mood, and might also independently enhance cognitive performance. Notably, caffeine displays clearer and more robust beneficial effects on memory performance when memory is perturbed by stressful or noxious stimuli either in human or animal studies. Thus, caffeine restores memory performance in sleep-deprived or aged human individuals, a finding replicated in rodent animal models. Likewise, in animal models of Alzheimer's disease (AD), caffeine alleviates memory dysfunction, which is in accordance with the tentative inverse correlation between caffeine intake and the incidence of AD in different (but not all) cohorts. Caffeine also affords beneficial effects in animal models of conditions expected to impair memory performance such as Parkinson's disease, chronic stress, type 2 diabetes, attention deficit and hyperactivity disorder, early life convulsions, or alcohol-induced amnesia. Thus, caffeine should not be viewed as a cognitive enhancer but instead as a cognitive normalizer. Interestingly, these beneficial effects of caffeine on stress-induced memory disturbance are mimicked by antagonists of adenosine A2A receptors. This prominent role of A2A receptors in preventing memory deterioration is probably related to the synaptic localization of this receptor in limbic areas and its ability to control glutamatergic transmission, especially NMDA receptor-dependent plasticity, and to control apoptosis, brain metabolism, and the burden of neuroinflammation. This opens the real and exciting possibility that caffeine consumption might be a prophylactic strategy and A2A receptor antagonists may be a novel therapeutic option to manage memory dysfunction both in AD and in other chronic neurodegenerative disorders where memory deficits occur. PMID:20182043

Cunha, Rodrigo A; Agostinho, Paula M



Therapeutic cloning: The ethical limits  

SciTech Connect

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

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



Therapeutic ritual. Helping families grow.  


1. Family development can be inhibited by lack of social or family rituals to facilitate life cycle transitions. Therapeutic rituals can be used to help families mobilize their resources for healing, growth, and change. 2. A therapeutic ritual can help a family to resolve conflicts and resentments, to negotiate new roles and relational boundaries, and to develop new shared meanings among its members about their ongoing life together. 3. The success of a therapeutic intervention is influenced by the nurse-therapist's understanding of the family's culture, values, and needs, as well as familiarity with the directive nature of strategic therapy concepts on which therapeutic rituals are based. PMID:2283598

Bright, M A



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

E-print Network

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

Kamat, Vineet R.


Memory-mapped transactions  

E-print Network

Memory-mapped transactions combine the advantages of both memory mapping and transactions to provide a programming interface for concurrently accessing data on disk without explicit I/O or locking operations. This interface ...

Sukha, Jim



Drifting absence :: drafting memory  

E-print Network

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

Kuhn, Marlene Eva



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,...



[Memory and cognitivism].  


The goal of this article is to explore the notion of cognitive memory. For that reason we would study the implicit and explicit memory. We would also study the notion of childhood amnesia and trauma. PMID:11780154

Spinetto, M



Recoverable distributed shared memory  

E-print Network

Distributed Shared Memory (DSM) is a model for interprocess communication, implemented on top of message passing systems. In this model, processes running on separate hosts can access a shared, coherent memory address space, provided...

Kanthadai, Sundarrajan S



Coping with Memory Loss  


... Loss? Anything that affects cognition—the process of thinking, learning, and remembering—can affect memory. Doctors use ... increasing impairment of memory and other aspects of thinking that are sufficiently severe to impair day-to- ...


Medications for Memory Loss  


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 ...


Memory and Aging  


... that require medical and psychological attention. Memory and Aging What Brain Changes Are Normal for Older Adults? Although new ... Your Memory Here is good news about our aging brains. Scientists have identified ways to minimize age-related ...


Cocoa Flavanols and Memory  

MedlinePLUS Videos and Cool Tools

... brain imaging and took a 20-minute memory test to start. The study relied on a process, ... After three-months, new brain imaging and memory tests were done. The researchers compared the scans looking ...


Understanding Memory Loss  


... 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: ...


Memory Correspondence to Author:  

E-print Network

INTRODUCTION: Nootropics also referred to as smart drugs, memory enhancers, and cognitive enhancers, are drugs, supplements, nutraceuticals, and functional foods that are purported to improve mental functions such as cognition, memory, intelligence, motivation,

Preksha Dwivedi; Richa Singh; Mohd. Tabish Malik; Talha Jawaid; Talha Jawaid


Cognitive Neuroscience Learning and Memory  

E-print Network

1 Slide 1 Cognitive Neuroscience PSYC 685 Learning and Memory Raja Parasuraman WorkingWorking MemoryMemory SelectiveSelective AttentionAttention Slide 2 Overview Short term, working, and long-term memory The medial temporal lobe/prefrontal cortex memory system Amnesia Implicit memory Slide 3

Parasuraman, Raja


Exercise and Memory  

NSDL National Science Digital Library

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

Twin Cities Public Television, Inc.



Memory Loss Chapter 6  

E-print Network

Part II Memory Loss 129 #12;#12;Chapter 6 Generalized Conditionalization Up to this point we have to help CLF model two types of certainty-loss stories: stories in- volving memory loss and stories-sensitivity, (PEP) does almost no work in modeling stories involving memory loss. So we will proceed in stages: We

Fitelson, Branden


Memory distortion in hypnosis  

Microsoft Academic Search

This paper presents data from a programmatic series of studies that varied the range of conditions affecting potential increase of recall, memory distortions, and distortions of confidence during and following hypnosis. All the studies used a paradigm that exposed Ss to misleading information some time before memory was tested and applied procedures in the hypnotic setting to analyze memory performance

Peter W. Sheehan



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



SENSING MEMORY Festival Directors  

E-print Network

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

Miranda, Eduardo Reck


Carbon Based Resistive Memory  

Microsoft Academic Search

We propose carbon as new resistive memory material for non-volatile memories and compare three allotropes of carbon, namely carbon nanotubes, graphene-like conductive carbon and insulating carbon for their possible application as resistance-change material in high density non-volatile memories. Repetitive high-speed switching and the potential for multi-level programming have been successfully demonstrated.

Franz Kreupl; Rainer Bruchhaus; Petra Majewski; Jan B. Philipp; Ralf Symanczyk; Thomas Happ; Christian Arndt; Mirko Vogt; Roy Zimmermann; Axel Buerke; Andrew P. Graham; Michael Kund



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.


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.


Lipid-absorbing Polymers  

NASA Technical Reports Server (NTRS)

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

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



Polyketal microparticles for therapeutic delivery to the lung  

PubMed Central

Inflammation in the setting of interstitial lung disease (ILD) occurs in the distal alveolar spaces of the lung, which presents significant challenges for therapeutic delivery. The development of aerosolizable microparticles from non-immunogenic polymers is needed to enable the clinical translation of numerous experimental therapeutics that require localization to the deep lung and repeated delivery for optimal efficacy. Polyketals (PK), a family of polymers, have several unique properties that make them ideal for lung delivery, specifically their hydrolysis into non-acidic, membrane-permeable compounds and their capacity to form microparticles with the aerodynamic properties needed for aerosolization. In this study, we tested the lung biocompatibility of microparticles created from a polyketal polymer, termed PK3, following intratracheal instillation in comparison to commonly used PLGA microparticles. We furthermore tested the initial efficacy of PK3 microparticles to encapsulate and effectively deliver active superoxide dismutase (SOD), a free radical scavenging enzyme, in a model of lung fibrosis. Our findings indicate that PK3 microparticles display no detectable level of alveolar or airway inflammation, whereas PLGA induced a small inflammatory response. Furthermore, SOD loaded into PK3 microparticles maintained its activity upon release and, when delivered via PK3 microparticles, inhibited the extent of lung fibrosis. PMID:19846216

Fiore, Vincent F.; Lofton, Megan C.; Roser-Page, Susanne; Yang, Stephen C.; Roman, Jesse; Murthy, Niren; Barker, Thomas H.



Phytonutrients as therapeutic agents.  


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

Gupta, Charu; Prakash, Dhan



Plasmids encoding therapeutic agents  


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

Keener, William K. (Idaho Falls, ID)



Therapeutic cloning: promises and issues  

Microsoft Academic Search

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

Charlotte Kfoury



Language Patterns and Therapeutic Change.  

ERIC Educational Resources Information Center

Noting that the mental health practitioner needs highly developed linguistic and communicative skills in order to precipitate therapeutic changes, this paper discusses the nature of the contexts of therapeutic interaction. It examines verb tense as a linguistic context marker and shows how various schools of therapy can use it. In addition, it…

Phoenix, Valdemar G.; Lindeman, Mary L.


The sodium ion-assisted memory behaviour of a silicon nanowire partial composite field-effect transistor.  


A partial composite consisting of rough silicon nanowires and a polymer dielectric layer with sufficient Na(+) ions was used to create a field-effect transistor based memory device. Addition of Na(+) ions helped compensate for water molecule trapped charges leading to narrow hysteresis characteristics and stable memory retention stability of the resulting device. PMID:24622941

Moon, Kyeong-Ju; Lee, Tae Il; Lee, Sang-Hoon; Myoung, Jae-Min



Transdermal delivery of therapeutic agent  

NASA Technical Reports Server (NTRS)

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

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



Smart polymers for implantable electronics  

NASA Astrophysics Data System (ADS)

Neural interfaces have been heavily investigated due to their unique ability to tap into the communication system of the body. Substrates compatible with microelectronics processing are planar and 5-7 orders of magnitude stiffer than the tissue with which they interact. This work enables fabrication of devices by photolithography that are stiff enough to penetrate soft tissue, change in stiffness to more closely match the modulus of tissue after implantation and adopt shapes to conform to tissue. Several classes of physiologically-responsive, amorphous polymer networks with the onset of the glass transition above 37 °C are synthesized and thermomechanically characterized. These glassy networks exhibit an isothermal reduction in modulus due to plasticization in the presence of aqueous fluids. Modulus after plasticization can be tuned by the dry glass transition temperature, degree of plasticization and crosslink density. Acrylic shape memory polymer based intracortical probes, which can change in modulus from above 1 GPa to less than 1 MPa, are fabricated through a transfer process that shields the substrate from processing and enhances adhesion to the microelectronics. Substrates capable of withstanding the conditions of photolithography are fabricated "thiol-ene" and "thiol-epoxy" substrates. These materials provide processing windows that rival engineering thermoplastics, swell less than 6% in water, and exhibit a controllable reduction in modulus from above 1 GPa to between 5 and 150 MPa. Substrates, planar for processing, that subsequently recover 3D shapes are synthesized by the formation of post-gelation crosslinks either covalent or supramolecular in nature. Acrylics with varied supramolecular, based on ureidopyrimidone moieties, and covalent crosslink density demonstrate triple-shape memory behavior. Post-gelation covalent crosslinks are established to permanently fix 3D shapes in thiol-ene networks. Devices fabricated include intracortical and nerve cuff electrodes. Neuronal viability and device performance suggest these materials may be suitable for the design of chronically-viable neural interfaces.

Ware, Taylor H.


Quantum random access memory  

E-print Network

A random access memory (RAM) uses n bits to randomly address N=2^n distinct memory cells. A quantum random access memory (qRAM) uses n qubits to address any quantum superposition of N memory cells. We present an architecture that exponentially reduces the requirements for a memory call: O(log N) switches need be thrown instead of the N used in conventional (classical or quantum) RAM designs. This yields a more robust qRAM algorithm, as it in general requires entanglement among exponentially less gates, and leads to an exponential decrease in the power needed for addressing. A quantum optical implementation is presented.

Vittorio Giovannetti; Seth Lloyd; Lorenzo Maccone



Degradability of Polymers for Implantable Biomedical Devices  

PubMed Central

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

Lyu, SuPing; Untereker, Darrel



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

PubMed Central

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

Ahmed, Eilaf; Morton, Stephen W.



The Therapeutic Implications of Plasticity of the Cancer Stem Cell Phenotype  

E-print Network

States of America, 2 Cancer Biology and Genetics Program, Department of Neurosurgery, Memorial SloanThe Therapeutic Implications of Plasticity of the Cancer Stem Cell Phenotype Kevin Leder1 , Eric C. Holland2 , Franziska Michor1 * 1 Department of Biostatistics and Computational Biology, Dana-Farber Cancer


Therapeutic Devices for Epilepsy  

PubMed Central

Therapeutic devices provide new options for treating drug-resistant epilepsy. These devices act by a variety of mechanisms to modulate neuronal activity. Only vagus nerve stimulation, which continues to develop new technology, is approved for use in the United States. Deep brain stimulation (DBS) of anterior thalamus for partial epilepsy recently was approved in Europe and several other countries. Responsive neurostimulation, which delivers stimuli to one or two seizure foci in response to a detected seizure, recently completed a successful multicenter trial. Several other trials of brain stimulation are in planning or underway. Transcutaneous magnetic stimulation (TMS) may provide a noninvasive method to stimulate cortex. Controlled studies of TMS split on efficacy, and may depend on whether a seizure focus is near a possible region for stimulation. Seizure detection devices in the form of “shake” detectors via portable accelerometers can provide notification of an ongoing tonic-clonic seizure, or peace of mind in the absence of notification. Prediction of seizures from various aspects of EEG is in early stages. Prediction appears to be possible in a subpopulation of people with refractory seizures and a clinical trial of an implantable prediction device is underway. Cooling of neocortex or hippocampus reversibly can attenuate epileptiform EEG activity and seizures, but engineering problems remain in its implementation. Optogenetics is a new technique that can control excitability of specific populations of neurons with light. Inhibition of epileptiform activity has been demonstrated in hippocampal slices, but use in humans will require more work. In general, devices provide useful palliation for otherwise uncontrollable seizures, but with a different risk profile than with most drugs. Optimizing the place of devices in therapy for epilepsy will require further development and clinical experience. PMID:22367987

Fisher, Robert S.



Polymer composites containing nanotubes  

NASA Technical Reports Server (NTRS)

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

Bley, Richard A. (Inventor)



Engineering Polymer Informatics  

E-print Network

Engineering Polymer Informatics Nico Adams, Jen Ryder, Nicholas England, David Jessop, Peter Corbett, Peter Murray-Rust Our mission is to develop an informatics toolbox, which will take into account the special computational needs of polymers...

Adams, Nico; Ryder, Jennifer; Jessop, David M; Corbett, Peter; Murray-Rust, Peter



Stiff Quantum Polymers  

E-print Network

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

H. Kleinert



Polymer Fluid Dynamics.  

ERIC Educational Resources Information Center

Problems in polymer fluid dynamics are described, including development of constitutive equations, rheometry, kinetic theory, flow visualization, heat transfer studies, flows with phase change, two-phase flow, polymer unit operations, and drag reduction. (JN)

Bird, R. Byron



Flexible Kernel Memory  

PubMed Central

This paper introduces a new model of associative memory, capable of both binary and continuous-valued inputs. Based on kernel theory, the memory model is on one hand a generalization of Radial Basis Function networks and, on the other, is in feature space, analogous to a Hopfield network. Attractors can be added, deleted, and updated on-line simply, without harming existing memories, and the number of attractors is independent of input dimension. Input vectors do not have to adhere to a fixed or bounded dimensionality; they can increase and decrease it without relearning previous memories. A memory consolidation process enables the network to generalize concepts and form clusters of input data, which outperforms many unsupervised clustering techniques; this process is demonstrated on handwritten digits from MNIST. Another process, reminiscent of memory reconsolidation is introduced, in which existing memories are refreshed and tuned with new inputs; this process is demonstrated on series of morphed faces. PMID:20552013

Nowicki, Dimitri; Siegelmann, Hava



Flexible kernel memory.  


This paper introduces a new model of associative memory, capable of both binary and continuous-valued inputs. Based on kernel theory, the memory model is on one hand a generalization of Radial Basis Function networks and, on the other, is in feature space, analogous to a Hopfield network. Attractors can be added, deleted, and updated on-line simply, without harming existing memories, and the number of attractors is independent of input dimension. Input vectors do not have to adhere to a fixed or bounded dimensionality; they can increase and decrease it without relearning previous memories. A memory consolidation process enables the network to generalize concepts and form clusters of input data, which outperforms many unsupervised clustering techniques; this process is demonstrated on handwritten digits from MNIST. Another process, reminiscent of memory reconsolidation is introduced, in which existing memories are refreshed and tuned with new inputs; this process is demonstrated on series of morphed faces. PMID:20552013

Nowicki, Dimitri; Siegelmann, Hava



Immunological memory is associative  

SciTech Connect

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

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



Synthetic polymer delivery system  

Microsoft Academic Search

A synthetic delivery system based on the copolymer ethylene vinyl-acetate (from now on EVA-polymer) and the carrier, bovine serum albumin (from now on BSA) were prepared by polymer dissolution in the presence of persulfate. This system acted as a long-term polymer release device, cleaning aqueous solutions containing Orange II under visible light irradiation. The polymer and the carrier used were

M. R. Dhananjeyan; E. Fine; J. Kiwi



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



Pulling Knotted Polymers  

E-print Network

We compare Monte Carlo simulations of knotted and unknotted polymers whose ends are connected to two parallel walls. The force $f$ exerted on the polymer is measured as a function of the separation $R$ between the walls. For unknotted polymers of several monomer numbers $N$, the product $fN^\

Oded Farago; Yacov Kantor; Mehran Kardar



Blue light emitting polymers  

Microsoft Academic Search

Polymer light emitting diodes have a good chance to become the main display system in the near future since diodes have many advantages concerning preparation and operation over other display systems. This review focuses on blue light emitting polymers introduced in the literature during the last 10 years. The characteristics of the photoluminescence and electroluminescence of these polymers is reviewed.

D. Y Kim; H. N Cho; C. Y Kim



Polymer Hydrogels: A Review  

Microsoft Academic Search

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

Waham Ashaier Laftah; Shahrir Hashim; Akos N. Ibrahim



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

NASA Astrophysics Data System (ADS)

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 ultraviolet photoelectron spectroscopy (UPS), which give information about the atomic and chemical composition, workfunction, and ionization potential of materials, are used to study these interfaces. In studying metal-polymer interfaces, it is shown that the interface between the conjugated polymer fully sulfonated polyaniline (NSPAN) and an aluminum alloy is an active interface, in which copper is extracted by the polymer from the aluminum alloy. This results in the aluminum alloy becoming more resistant to corrosion in a salty environment. The interface between aluminum and NSPAN, as it is found in some light emitting devices (LEDS), is also studied. It is concluded that negative charge is transferred from the aluminum to the polymer, resulting in a thin layer of oxidized aluminum and a more reduced form of the polymer at the interface. In studying polymer-polymer interfaces, it is proposed that NSPAN protonates a pyridine containing polymer at an interface which is also found in some LEDs. This is proposed to be responsible for color variation found in some LEDs. A model system was studied, and protonation at the polymer-polymer interface was directly observed, supporting the earlier proposals. Polymer-polymer interfaces found in SCALE devices, which are LEDs made with three polymer layers, are studied by UPS to determine the band structure of these devices. It is concluded that the EB layers decrease the hole barrier and increase the electron barrier, which leads to better charge balance and a better device. The EB layers also create a symmetric device, which enables it to emit light under both forward and reverse bias. Finally, a new type of all polymer transistor device is studied, with an emphasis on how modifying the charge on the polymer surface affects device performance.

Smallfield, Julie Anne Osladil


Multiscale Simulation of History Dependent Flow in Polymer Melt  

E-print Network

We have developed a new multiscale simulation technique to investigate history-dependent flow behavior of entangled polymer melt, using a smoothed particle hydrodynamics simulation with microscopic simulators that account for the dynamics of entangled polymers acting on each fluid element. The multiscale simulation technique is applied to entangled polymer melt flow around a circular obstacle in a two-dimensional periodic system. It is found that the strain-rate history-dependent stress of the entangled polymer melt affects its flow behavior, and the memory in the stress causes nonlinear behavior even in the regions where ${\\rm Wi} \\le 1$. The spatial distribution of the entanglements $$ is also investigated. The slightly low entanglement region is observed around the obstacle and is found to be broaden in the downstream region.

Takahiro Murashima; Takashi Taniguchi



March 29, 2008 Operating Systems: Main Memory 1 Main Memory  

E-print Network

March 29, 2008 Operating Systems: Main Memory 1 Main Memory Chapter 8 #12;March 29, 2008 Operating Systems: Main Memory 2 Chapter Outline Background Contiguous Memory Allocation Paging Structure of the Page Table Segmentation #12;March 29, 2008 Operating Systems: Main Memory 3 Objectives To provide

Adam, Salah


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

E-print Network

Memory of myself: Autobiographical memory and identity in Alzheimer's disease Donna Rose Addis autobiographical memory and identity. To test this we assessed the status of autobiographical memory and identity degree of autobiographical memory impairment was associated with changes in identity. Two tests

Addis, Donna Rose



Microsoft Academic Search

In the debate on memories of traumatic events (especially childhood abuse), traumatic memories and dissociative amnesia are central topics. These phenomena are frequently described as dissociative memory problems. The aim of the present article is to assess to what extent memory mechanisms as identified in experimental research (such as encoding, storage, and retrieval factors) are adequate in explaining memories of

Philip Spinhoven; Ellert R. S. Nijenhuis; Richard Van Dyck



Reconsolidation of drug memories.  


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. PMID:22342780

Sorg, Barbara A



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

PubMed Central

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

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



Modifications of Glycans: Biological Significance and Therapeutic Opportunities  

PubMed Central

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

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



RNAi and small interfering RNAs in human disease therapeutic applications  

PubMed Central

Small interfering RNAs (siRNAs) have shown to effectively down-regulate gene expression in human cells, giving them potential to eradicate disease. Prospects for clinical applications are discussed in this review, along with an overview of recent history and our current understanding of siRNAs used for therapeutic application in human diseases, such as cancer and viral infections. Over recent years, progress has been made in lipids, ligands, nanoparticles, polymers and viral vectors as delivery agents and for gene-based expression of siRNA to enhance the efficacy and specificity of these methods while at the same time reducing toxicity. It has become apparent that given the recent advances in chemistry and delivery, RNAi will soon prove to be an important and widely used therapeutic modality. PMID:20833440

Lares, Monica R.; Rossi, John J.; Ouellet, Dominique L.



Targeted nanotherapy for induction of therapeutic immune responses.  


Nanotechnology permits the design of therapeutic devices with defined structure and molecular composition. Modular designs employing surface-bound ligands provide specific homing devices for loaded cargo, and biocompatible and biodegradable constructs provide surrogate temporary microenvironments. We first present a case for developing 'smart' modular constructs as immunogenic vaccines to prime immune memory against specific pathogens where current vaccines fail. Second, we argue that nanotherapeutic intervention can harness pivotal molecular pathways recently discovered to regulate lineage development between pathogenic TH17 cells associated with autoimmune disease, versus tolerogenic regulatory T cells (Treg). Underpinned by molecular mechanisms that enable exquisitely specific responses in adaptive immunity, targeted nanodevices designed to stimulate either immune aggression or immune tolerance signify the birth of a new era in therapeutics. PMID:22172276

Metcalfe, Su M; Fahmy, Tarek M



DCTD — Developmental Therapeutics Program (DTP)

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


Broad-Spectrum Antiviral Therapeutics  

E-print Network

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

Rider, Todd H.


DCTD — Developmental Therapeutics Program (DTP)

For researchers who hold a valid radioactive materials license, there are roughly 90 radiolabeled drugs available from DTP’s Radiolabeled Materials Repository. Radiolabeled compounds are instrumental in noninvasive studies of biodistribution and in target pharmacokinetics of therapeutics.


A generalized memory test algorithm  

NASA Technical Reports Server (NTRS)

A general algorithm for testing digital computer memory is presented. The test checks that (1) every bit can be cleared and set in each memory work, and (2) bits are not erroneously cleared and/or set elsewhere in memory at the same time. The algorithm can be applied to any size memory block and any size memory word. It is concise and efficient, requiring the very few cycles through memory. For example, a test of 16-bit-word-size memory requries only 384 cycles through memory. Approximately 15 seconds were required to test a 32K block of such memory, using a microcomputer having a cycle time of 133 nanoseconds.

Milner, E. J.



Examining object location and object recognition memory in mice.  


This unit is designed to provide sufficient instruction for the setup and execution of tests for object location and object recognition in adult mice. This task is ideally suited for the study of a variety of mouse models that examine disease mechanisms and novel therapeutic targets. By altering several key parameters, the experimenter can investigate short-term or long-term memory and look for either memory impairments or enhancements. Object location and object recognition memory tasks rely on a rodent's innate preference for novelty, and can be conducted sequentially in the same cohort of animals. These two tasks avoid the inherent stress induced with other common measures of rodent memory such as fear conditioning and the Morris water maze. This protocol covers detailed instructions on conducting both tasks, as well as key points concerning data collection, analysis, and interpretation. Curr. Protoc. Neurosci. 69:8.31.1-8.31.17. © 2014 by John Wiley & Sons, Inc. PMID:25297693

Vogel-Ciernia, Annie; Wood, Marcelo A



DCTD — Developmental Therapeutics Program (DTP)

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


Fluphenazine pharmacokinetics and therapeutic response  

Microsoft Academic Search

We conducted a double-blind study of therapeutic outcome versus mean steady-state levels in 29 newly admitted schizophrenic and schizoaffective patients who were treated with a constant dose of fluphenazine HCl over a 2-week period. Both an upper and lower end of the therapeutic window were suggested by three nonresponders whose plasma levels were above 2.8 ng per ml and by

Maurice W. Dysken; Javaid I. Javaid; Sidney S. Chang; Charles Schaffer; Agha Shahid; John M. Davis



Therapeutic Vaccines for Chronic Infections  

NASA Astrophysics Data System (ADS)

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

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



Mechanics of light-activated network polymers  

NASA Astrophysics Data System (ADS)

Mechanically responsive, environmentally activated polymers can undergo large, complex deformation in response to external stimuli such as thermal, luminous, and chemical changes to the environment. Light as a stimulus provides unique application potential because it allows for remote, rapid, and isothermal activation of the material with precise spatial control via existing optical technologies. While certain systems have received considerable attention, the state of the art of most light-activated polymers is limited to basic characterization and demonstrations. To make such materials available to the engineering and scientific communities, physically based theoretical and computational tools are required to guide experimental and design efforts that capitalize on their complex photo-mechanical couplings. The central objective of this thesis is to develop a multi-physics constitutive modeling framework to simulate the continuum scale, photo mechanical behavior of light-activated polymers and implement it into a finite element analysis setting. This framework is independent of specific underlying photo-stimulation mechanisms and is discussed in the context of photo-activated shape memory polymers and network rearranging polymers. Next, the framework is applied to the light-activated network rearranging polymer system, which is relaxed of stress upon irradiation with UV light, and a suite of characterization and application oriented experiments are carried out to calibrate and validate the model's predictive capabilities. The calibrated model is used to investigate several applications such as photo-activated stress relaxation of notched specimens, bending actuation, creep, the buckling of equi-biaxially deformed and irradiated films, and photomechanically formed 1D channels and ridges. Modeling creep involves additional complexity through simultaneous deformation and irradiation, and so the model framework is extended to cover such scenarios. Experiments, finite element analyses, and analytic solutions are developed to explore the phase space available to the experimentalist and design engineer for these different problems.

Long, Kevin Nicholas


21 CFR 890.5975 - Therapeutic vibrator.  

...2014-04-01 2014-04-01 false Therapeutic vibrator. 890.5975 Section 890...SERVICES (CONTINUED) MEDICAL DEVICES PHYSICAL MEDICINE DEVICES Physical Medicine Therapeutic Devices § 890.5975 Therapeutic...



21 CFR 890.5975 - Therapeutic vibrator.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Therapeutic vibrator. 890.5975 Section 890...SERVICES (CONTINUED) MEDICAL DEVICES PHYSICAL MEDICINE DEVICES Physical Medicine Therapeutic Devices § 890.5975 Therapeutic...



21 CFR 890.5660 - Therapeutic massager.  

...2014-04-01 2014-04-01 false Therapeutic massager. 890.5660 Section 890...SERVICES (CONTINUED) MEDICAL DEVICES PHYSICAL MEDICINE DEVICES Physical Medicine Therapeutic Devices § 890.5660 Therapeutic...



21 CFR 890.5975 - Therapeutic vibrator.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 2011-04-01 false Therapeutic vibrator. 890.5975 Section 890...SERVICES (CONTINUED) MEDICAL DEVICES PHYSICAL MEDICINE DEVICES Physical Medicine Therapeutic Devices § 890.5975 Therapeutic...



21 CFR 890.5975 - Therapeutic vibrator.  

Code of Federal Regulations, 2012 CFR

...2012-04-01 2012-04-01 false Therapeutic vibrator. 890.5975 Section 890...SERVICES (CONTINUED) MEDICAL DEVICES PHYSICAL MEDICINE DEVICES Physical Medicine Therapeutic Devices § 890.5975 Therapeutic...



21 CFR 890.5660 - Therapeutic massager.  

Code of Federal Regulations, 2011 CFR

...2011-04-01 2011-04-01 false Therapeutic massager. 890.5660 Section 890...SERVICES (CONTINUED) MEDICAL DEVICES PHYSICAL MEDICINE DEVICES Physical Medicine Therapeutic Devices § 890.5660 Therapeutic...



21 CFR 890.5660 - Therapeutic massager.  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Therapeutic massager. 890.5660 Section 890...SERVICES (CONTINUED) MEDICAL DEVICES PHYSICAL MEDICINE DEVICES Physical Medicine Therapeutic Devices § 890.5660 Therapeutic...



21 CFR 890.5660 - Therapeutic massager.  

Code of Federal Regulations, 2012 CFR

...2012-04-01 2012-04-01 false Therapeutic massager. 890.5660 Section 890...SERVICES (CONTINUED) MEDICAL DEVICES PHYSICAL MEDICINE DEVICES Physical Medicine Therapeutic Devices § 890.5660 Therapeutic...



Nanomaterials for photo-based diagnostic and therapeutic applications.  


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

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



Reversal of cognitive decline: A novel therapeutic program.  


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

Bredesen, Dale E



Reversal of cognitive decline: A novel therapeutic program  

PubMed Central

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

Bredesen, Dale E.



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.



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



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.



Using Cyclic Memory Allocation to Eliminate Memory Leaks  

E-print Network

We present and evaluate a new memory management technique for eliminating memory leaks in programs with dynamic memory allocation. This technique observes the execution of the program on a sequence of training inputs to ...

Nguyen, Huu Hai


The future of memory  

NASA Astrophysics Data System (ADS)

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

Marinella, M.


Building synthetic memory  

PubMed Central

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

Inniss, Mara C.; Silver, Pamela A.



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




Microsoft Academic Search

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

Steven H. Zarit; Dolores Gallagher; Nan Kramer



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



Wechsler Memory Scale, Rivermead Behavioral Memory Test, and Everyday Memory Questionnaire in Healthy Adults and Alzheimer Patients  

Microsoft Academic Search

The Wechsler Memory Scale (WMS) is a laboratory-based memory test that has been criticized for its lack of ecological validity and for not testing long-term memory. A more recent memory test, which aims at testing everyday memory, is the Rivermead Behavioral Memory Test (RBMT); it tests prospective memory and other forms of memory not tapped by WMS. However, even this

Anastasia Efklides; Efterpi Yiultsi; Theopisti Kangellidou; Fotini Kounti; Fotini Dina; Magda Tsolaki



Mechanics of amorphous polymers and polymer gels  

E-print Network

Many applications of amorphous polymers require a thermo-mechanically coupled large-deformation elasto-viscoplasticity theory which models the strain rate and temperature dependent response of amorphous polymeric materials ...

Chester, Shawn Alexander



Mark A. Wyatt Memorial Scholarship  

E-print Network

and a passion for research The Wyatt Scholarship is a memorial to Mark Wyatt, a pre- med Biological SciencesMark A. Wyatt Memorial Scholarship Application Due: March 30, 2012 The Mark A. Wyatt Memorial

Ben-Arie, Jezekiel


Neural Protein Synthesis during Aging: Effects on Plasticity and Memory  

PubMed Central

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

Schimanski, Lesley A.; Barnes, Carol A.



Large energy absorption in Ni-Mn-Ga/polymer composites  

SciTech Connect

Ferromagnetic shape memory alloys can respond to a magnetic field or applied stress by the motion of twin boundaries and hence they show large hysteresis or energy loss. Ni-Mn-Ga particles made by spark erosion have been dispersed and oriented in a polymer matrix to form pseudo 3:1 composites which are studied under applied stress. Loss ratios have been determined from the stress-strain data. The loss ratios of the composites range from 63% to 67% compared to only about 17% for the pure, unfilled polymer samples.

Feuchtwanger, Jorge; Richard, Marc L.; Tang, Yun J.; Berkowitz, Ami E.; O'Handley, Robert C.; Allen, Samuel M. [Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); University of California, San Diego, La Joya, California 92093 (United States); Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)



Low-power write-once-read-many-times memory devices  

NASA Astrophysics Data System (ADS)

We introduce low-power write-once-read-many-times memory devices fabricated from solution. These devices are based on an electron-only structure using colloidal ZnO semiconductor nanoparticles and the doped conjugated polymer polyethylenedioxythiophene doped with polystyrene sulfonic acid (PEDOT:PSS). The conductive p-doped conjugated polymer is permanently dedoped by injected electrons, producing an insulating state. This demonstration provides a class of memory devices with the potential for extremely low-cost, low-power-consumption applications, such as radio-frequency identification tags.

Wang, Jianpu; Gao, Feng; Greenham, Neil C.



Polymer microdisk and microring lasers  

NASA Astrophysics Data System (ADS)

Dye-doped polymer microlasers have been fabricated by photolithography and self-assembly. Microdisk lasers 5 to 30 mu m in diameter were photolithographically patterned on thin planar polymer waveguides. We formed polymer microring lasers on thinned silica fibers by dipping the fibers in polymers and allowing the polymer droplets to cure.

Kuwata-Gonokami, M.; Jordan, R. H.; Dodabalapur, A.; Katz, H. E.; Schilling, M. L.; Slusher, R. E.; Ozawa, S.



Polymer-peptide delivery platforms: effect of oligopeptide orientation on polymer-based DNA delivery.  


The success of nonviral transfection using polymers hinges on efficient nuclear uptake of nucleic acid cargo and overcoming intra- and extracellular barriers. By incorporating PKKKRKV heptapeptide pendent groups as nuclear localization signals (NLS) on a polymer backbone, we demonstrate protein expression levels higher than those obtained from JetPEI and Lipofectamine 2000, the latter being notorious for coupling high transfection efficiency with cytotoxicity. The orientation of the NLS peptide grafts markedly affected transfection performance. Polymers with the sequence attached to the backbone from the valine residue achieved a level of nuclear translocation higher than the levels of those having the NLS groups attached in the opposite orientation. The differences in nuclear localization and DNA complexation strength between the two orientations correlated with a striking difference in protein expression, both in cell culture and in vivo. Polyplexes formed from these comb polymer structures exhibited transfection efficiencies superior to those of Lipofectamine 2000 but with greatly reduced toxicity. Moreover, these novel polymers, when administered by intramuscular ultrasound-mediated delivery, allowed a high level of reporter gene expression in mice, demonstrating their therapeutic promise in vivo. PMID:24606402

Parelkar, Sangram S; Letteri, Rachel; Chan-Seng, Delphine; Zolochevska, Olga; Ellis, Jayne; Figueiredo, Marxa; Emrick, Todd



P(VDF-TrFE) ferroelectrics: Integration in hybrid and thin-film memories  

Microsoft Academic Search

Poly(vinylidene fluoride-trifluoroethylene) P(VDF-TrFE) is a promising ferroelectric polymer with potential application for both high density hybrid and printable low-cost memory. This talk will review the structural, polarization, and electrical properties of this polymer ferroelectric, identifying the key challenges and opportunities at the system level from both processing and architectural standpoints. The unique hysteresis and time-response properties permit fabrication of large

Michael O. Thompson; Connie Lew; Johan Carlsson; Per Brahms



Prototype Fabrication and Preliminary In Vitro Testing of a Shape Memory Endovascular Thrombectomy Device  

Microsoft Academic Search

An electromechanical microactuator comprised of shape memory polymer (SMP) and shape memory nickel-titanium alloy (nitinol) was developed and used in an endovascular thrombectomy device prototype. The microactuator maintains a straight rod shape until an applied current induces electro-resistive (Joule) heating, causing the microactuator to transform into a corkscrew shape. The straight-to-corkscrew transformation geometry was chosen to permit endovascular delivery through

Ward Small; Thomas S. Wilson; Patrick R. Buckley; William J. Benett; Jeffrey M. Loge; Jonathan Hartman; Duncan J. Maitland



Polymer Solutions and Dispersions  

NSDL National Science Digital Library

So far, we have spent a considerable amount of time discussing the strength of polymers and their unique physical and mechanical properties. However, some applications take excellent advantage of the interesting properties polymers bring to solutions. Examples include paints, motor oils, and some of the products we put on our hair. In addition, as we saw in the last chapter, some polymers are synthesized in solution. In this chapter, we will present some of the important properties of polymer solutions and develop a basic understanding of their origin. Some polymers would "like" to dissolve but can't. We'll try to understand why, and see how to take advantage of this. And, finally, we'll investigate some uses for polymers that are not actually dissolved in a solvent but rather are dispersed in a liquid.

Teegarden, David



Introduction to flash memory  

Microsoft Academic Search

This paper mainly focuses on the development of the NOR flash memory technology, with the aim of describing both the basic functionality of the memory cell used so far and the main cell architecture consolidated today. The NOR cell is basically a floating-gate MOS transistor, programmed by channel hot electron and erased by Fowler-Nordheim tunneling. The main reliability issues, such




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



Eavesdropping without quantum memory  

E-print Network

In quantum cryptography the optimal eavesdropping strategy requires that the eavesdropper uses quantum memories in order to optimize her information. What happens if the eavesdropper has no quantum memory? It is shown that the best strategy is actually to adopt the simple intercept/resend strategy.

H. Bechmann-Pasquinucci



Memory's Role in Catechesis.  

ERIC Educational Resources Information Center

The aim of this dissertation is to explicate memory's role in catechesis. Catechesis is a term that early Christians chose to describe their " of teaching the gospel mean 'instruction given by word of mouth.'" A brief historical overview confirms the continuity between catechesis and memory from apostolic to present times. Selected…

Williams, Robert Bryan


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.



Trading Memory for Randomness.  

National Technical Information Service (NTIS)

Strategies in repeated games can be classified as to whether or not they use memory and/or randomization. We consider Markov decision processes and 2-player graph games, both of the deterministic and probabilistic varieties. We characterize when memory an...

K. Chatterjee, L. de Alfaro, T. A. Henzinger



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



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.



Working memory and attitudes  

Microsoft Academic Search

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 leads to more positive

Eun Sook Jung; Norman Reid



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.



Research Report Mismaking Memories  

E-print Network

, car, turn, tire, axle, round, circle, roll) are studied and, in a subsequent memory test, a critical; Schacter et al., 1996). Like the snapshot of a photo-finish horse race, neurophysiological recordings made as memory illusions occur provide objective measurements of an elusive event but do not reveal how the race

Kutas, Marta



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




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.



The Psychology of Memory  

Microsoft Academic Search

In this chapter I will try to provide a brief overview of the concepts and techniques that are most widely used in the psychology of memory. Although it may not appear to be the case from sampling the literature, there is in fact a great deal of agreement as to what constitutes the psychology of memory, much of it developed

Alan D. Baddeley



Programmable memory BIST  

Microsoft Academic Search

In modern SoCs embedded memories include the large majority of defects. In addition defect types are becoming more complex and diverse and may escape detection during fabrication test. As a matter of fact memories have to be tested by test algorithms achieving very high fault coverage. Fixing the test algorithm during the design phase may not be compatible with this

Slimane Boutobza; Michael Nicolaidis; Kheiredine M. Lamara; Andrea Costa



Major memory for microblogs.  


Online social networking is vastly popular and permits its members to post their thoughts as microblogs, an opportunity that people exploit, on Facebook alone, over 30 million times an hour. Such trivial ephemera, one might think, should vanish quickly from memory; conversely, they may comprise the sort of information that our memories are tuned to recognize, if that which we readily generate, we also readily store. In the first two experiments, participants' memory for Facebook posts was found to be strikingly stronger than their memory for human faces or sentences from books-a magnitude comparable to the difference in memory strength between amnesics and healthy controls. The second experiment suggested that this difference is not due to Facebook posts spontaneously generating social elaboration, because memory for posts is enhanced as much by adding social elaboration as is memory for book sentences. Our final experiment, using headlines, sentences, and reader comments from articles, suggested that the remarkable memory for microblogs is also not due to their completeness or simply their topic, but may be a more general phenomenon of their being the largely spontaneous and natural emanations of the human mind. PMID:23315488

Mickes, Laura; Darby, Ryan S; Hwe, Vivian; Bajic, Daniel; Warker, Jill A; Harris, Christine R; Christenfeld, Nicholas J S



Retrieval of Emotional Memories  

ERIC Educational Resources Information Center

Long-term memories are influenced by the emotion experienced during learning as well as by the emotion experienced during memory retrieval. The present article reviews the literature addressing the effects of emotion on retrieval, focusing on the cognitive and neurological mechanisms that have been revealed. The reviewed research suggests that the…

Buchanan, Tony W.



Resistive Random Access Memories (RRAMs) Based on Metal Nanoparticles  

Microsoft Academic Search

\\u000a It is demonstrated that planar structures based on silver nanoparticles hosted in a polymer matrix show reliable and reproducible\\u000a switching properties attractive for non-volatile memory applications. These systems can be programmed between a low conductance\\u000a (off-state) and high conductance (on-state) with an on\\/off ratio of 3 orders of magnitude, large retention times and good\\u000a cycle endurance. The planar structure design

Asal Kiazadeh; Paulo R. Rocha; Qian Chen; Henrique L. Gomes



Polymer solar cells  

Microsoft Academic Search

Recent progress in the development of polymer solar cells has improved power-conversion efficiencies from 3% to almost 9%. Based on semiconducting polymers, these solar cells are fabricated from solution-processing techniques and have unique prospects for achieving low-cost solar energy harvesting, owing to their material and manufacturing advantages. The potential applications of polymer solar cells are broad, ranging from flexible solar

Gang Li; Rui Zhu; Yang Yang



RNAi Therapeutics in Autoimmune Disease  

PubMed Central

Since the discovery of RNA interference (RNAi), excitement has grown over its potential therapeutic uses. Targeting RNAi pathways provides a powerful tool to change biological processes post-transcriptionally in various health conditions such as cancer or autoimmune diseases. Optimum design of shRNA, siRNA, and miRNA enhances stability and specificity of RNAi-based approaches whereas it has to reduce or prevent undesirable immune responses or off-target effects. Recent advances in understanding pathogenesis of autoimmune diseases have allowed application of these tools in vitro as well as in vivo with some degree of success. Further research on the design and delivery of effectors of RNAi pathway and underlying molecular basis of RNAi would warrant practical use of RNAi-based therapeutics in human applications. This review will focus on the approaches used for current therapeutics and their applications in autoimmune diseases, including rheumatoid arthritis and Sjögren’s syndrome. PMID:24276020

Pauley, Kaleb M.; Cha, Seunghee



Improving chemoradiotherapy with nanoparticle therapeutics  

PubMed Central

Chemoradiotherapy has been a key treatment paradigm in cancer management. One of the main research objectives in cancer research has been to identify agents and strategies to improve the therapeutic index of chemoradiation. Recent development of nanoparticle (NP)-based chemotherapeutics offers a unique opportunity to improve the delivery of chemotherapy, which can in turn improve chemoradiotherapy’s efficacy while lowering toxicity. NP-based chemotherapeutics also possess several characteristics that are well suited for chemoradiotherapy. Therefore, NP chemotherapeutics hold high potential in improving the therapeutic index of chemoradiotherapy. This manuscript reviews the NP properties that are favorable for chemoradiation and the rationale to utilize nanotherapeutics in chemoradiation. This review also discusses the preclinical and clinical data on using NP therapeutics in chemoradiotherapy.

Eblan, Michael Joseph; Wang, Andrew Zhuang



Targeting caspases in cancer therapeutics  

PubMed Central

The identification of the fundamental role of apoptosis in the growth balance and normal homeostasis against cell proliferation led to the recognition of its loss contributing to tumorigenesis. The mechanistic significance of reinstating apoptosis signaling towards selective targeting of malignant cells heavily exploits the caspase family of death-inducing molecules as a powerful therapeutic platform for the development of potent anticancer strategies. Some apoptosis inhibitors induce caspase expression and activity in preclinical models and clinical trials by targeting both the intrinsic and extrinsic apoptotic pathways and restoring the apoptotic capacity in human tumors. Furthermore, up-regulation of caspases emerges as a sensitizing mechanism for tumors exhibiting therapeutic resistance to radiation and adjuvant chemotherapy. This review provides a comprehensive discussion of the functional involvement of caspases in apoptosis control and the current understanding of reactivating caspase-mediated apoptosis signaling towards effective therapeutic modalities in cancer treatment. PMID:23509217

Hensley, Patrick; Mishra, Murli; Kyprianou, Natasha



Novel therapeutic strategies for cardioprotection.  


The morbidity and mortality from ischemic heart disease (IHD) remain significant worldwide. The treatment for acute myocardial infarction has improved over the past decades, including early reperfusion of occluded coronary arteries. Although it is essential to re-open the artery as soon as possible, paradoxically this leads to additional myocardial injury, called acute ischemia-reperfusion injury (IRI), for which currently no effective therapy is available. Therefore, novel therapeutic strategies are required to protect the heart from acute IRI in order to reduce myocardial infarction size, preserve cardiac function and improve clinical outcomes in patients with IHD. In this review article, we will first outline the pathophysiology of acute IRI and review promising therapeutic strategies for cardioprotection. These include novel aspects of mitochondrial function, epigenetics, circadian clocks, the immune system, microvesicles, growth factors, stem cell therapy and gene therapy. We discuss the therapeutic potential of these novel cardioprotective strategies in terms of pharmacological targeting and clinical application. PMID:24837132

Sluijter, Joost P G; Condorelli, Gianluigi; Davidson, Sean M; Engel, Felix B; Ferdinandy, Peter; Hausenloy, Derek J; Lecour, Sandrine; Madonna, Rosalinda; Ovize, Michel; Ruiz-Meana, Marisol; Schulz, Rainer; Van Laake, Linda W



Therapeutic cloning and reproductive liberty.  


Concern for "reproductive liberty" suggests that decisions about embryos should normally be made by the persons who would be the genetic parents of the child that would be brought into existence if the embryo were brought to term. Therapeutic cloning would involve creating and destroying an embryo, which, if brought to term, would be the offspring of the genetic parents of the person undergoing therapy. I argue that central arguments in debates about parenthood and genetics therefore suggest that therapeutic cloning would be prima facie unethical unless it occurred with the consent of the parents of the person being cloned. Alternatively, if therapeutic cloning is thought to be legitimate, this undermines the case for some uses of reproductive cloning by implying that the genetic relation it establishes between clones and DNA donors does not carry the same moral weight as it does in cases of normal reproduction. PMID:19240247

Sparrow, Robert



Oligonucleotide conjugates for therapeutic applications  

PubMed Central

Insufficient pharmacokinetic properties and poor cellular uptake are the main hurdles for successful therapeutic development of oligonucleotide agents. The covalent attachment of various ligands designed to influence the biodistribution and cellular uptake or for targeting specific tissues is an attractive possibility to advance therapeutic applications and to expand development options. In contrast to advanced formulations, which often consist of multiple reagents and are sensitive to a variety of preparation conditions, oligonucleotide conjugates are defined molecules, enabling structure-based analytics and quality control techniques. This review gives an overview of current developments of oligonucleotide conjugates for therapeutic applications. Attached ligands comprise peptides, proteins, carbohydrates, aptamers and small molecules, including cholesterol, tocopherol and folic acid. Important linkage types and conjugation methods are summarized. The distinct ligands directly influence biochemical parameters, uptake machanisms and pharmacokinetic properties. PMID:23883124

Winkler, Johannes



Optical quantum memory  

E-print Network

Quantum memory is important to quantum information processing in many ways: a synchronization device to match various processes within a quantum computer, an identity quantum gate that leaves any state unchanged, and a tool to convert heralded photons to photons-on-demand. In addition to quantum computing, quantum memory would be instrumental for the implementation of long-distance quantum communication using quantum repeaters. The importance of this basic quantum gate is exemplified by the multitude of optical quantum memory mechanisms being studied: optical delay lines, cavities, electromagnetically-induced transparency, photon-echo, and off-resonant Faraday interaction. Here we report on the state-of-the-art in the field of optical quantum memory, including criteria for successful quantum memory and current performance levels.

A. I. Lvovsky; B. C. Sanders; W. Tittel



Computer memory management system  


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)



Making Memories Matter  

PubMed Central

This article reviews some of the neuroendocrine bases by which emotional events regulate brain mechanisms of learning and memory. In laboratory rodents, there is extensive evidence that epinephrine influences memory processing through an inverted-U relationship, at which moderate levels enhance and high levels impair memory. These effects are, in large part, mediated by increases in blood glucose levels subsequent to epinephrine release, which then provide support for the brain processes engaged by learning and memory. These brain processes include augmentation of neurotransmitter release and of energy metabolism, the latter apparently including a key role for astrocytic glycogen. In addition to up- and down-regulation of learning and memory in general, physiological concomitants of emotion and arousal can also switch the neural system that controls learning at a particular time, at once improving some attributes of learning and impairing others in a manner that results in a change in the strategy used to solve a problem. PMID:23264764

Gold, Paul E.; Korol, Donna L.



Memory: Pandora's hippocampus?  


Greater knowledge of the human brain has enabled us to begin devising therapies to rescue or modify memory for the afflicted, such as Alzheimer's patients or post-traumatic stress disorder victims. This same knowledge could also allow us to alter how normal, healthy memory operates; we may become able to enhance memory and learning through biological intervention. But the brain consists of complex, interactive networks, and unintended consequences could easily occur. Moreover, memory is woven into our individuality. Altering our memory processes therefore risks altering us fundamentally. We may not be able to resist opening this neuroscientific Pandora's Box, John Gabrieli writes, but we must proceed with all the wisdom we can muster. PMID:15986534

Gabrieli, John D E



Polymers and People  

NSDL National Science Digital Library

Each Tuesday during the fall of 2002, teams of high school students from three South Carolina countries conducted a four-hour polymer institute for their peers at the local public library. In less than two months, over 300 students visited the exhibit and explored DNA, nylon, rubber, gluep, and other polymers. Visiting students also viewed the Chemical Heritage Foundation (CHF) exhibit, Polymers and People, which catalyzed this collaboration between the library, various teachers, and local industry. In the end, however, teams of students, not adults, brought the exhibit to life and generated a vibrant excitement as student teams led their peers in polymer experiments and investigations.

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



Proteins and polymers  

E-print Network

Proteins, chain molecules of amino acids, behave in ways which are similar to each other yet quite distinct from standard compact polymers. We demonstrate that the Flory theorem, derived for polymer melts, holds for compact protein native state structures and is not incompatible with the existence of structured building blocks such as $\\alpha$-helices and $\\beta$-strands. We present a discussion on how the notion of the thickness of a polymer chain, besides being useful in describing a chain molecule in the continuum limit, plays a vital role in interpolating between conventional polymer physics and the phase of matter associated with protein structures.

Jayanth R. Banavar; Trinh Xuan Hoang; Amos Maritan



Therapeutic target database update 2014: a resource for targeted therapeutics  

PubMed Central

Here we describe an update of the Therapeutic Target Database ( for better serving the bench-to-clinic communities and for enabling more convenient data access, processing and exchange. Extensive efforts from the research, industry, clinical, regulatory and management communities have been collectively directed at the discovery, investigation, application, monitoring and management of targeted therapeutics. Increasing efforts have been directed at the development of stratified and personalized medicines. These efforts may be facilitated by the knowledge of the efficacy targets and biomarkers of targeted therapeutics. Therefore, we added search tools for using the International Classification of Disease ICD-10-CM and ICD-9-CM codes to retrieve the target, biomarker and drug information (currently enabling the search of almost 900 targets, 1800 biomarkers and 6000 drugs related to 900 disease conditions). We added information of almost 1800 biomarkers for 300 disease conditions and 200 drug scaffolds for 700 drugs. We significantly expanded Therapeutic Target Database data contents to cover >2300 targets (388 successful and 461 clinical trial targets), 20 600 drugs (2003 approved and 3147 clinical trial drugs), 20 000 multitarget agents against almost 400 target-pairs and the activity data of 1400 agents against 300 cell lines. PMID:24265219

Qin, Chu; Zhang, Cheng; Zhu, Feng; Xu, Feng; Chen, Shang Ying; Zhang, Peng; Li, Ying Hong; Yang, Sheng Yong; Wei, Yu Quan; Tao, Lin; Chen, Yu Zong



Preparation and characterization of triple shape memory composite foams.  


Foams prepared from shape memory polymers (SMPs) offer the potential for low density materials that can be triggered to deploy with a large volume change, unlike their solid counterparts that do so at near-constant volume. While examples of shape memory foams have been reported in the past, they have been limited to dual SMPs: those polymers featuring one switching transition between an arbitrarily programmed shape and a single permanent shape established by constituent crosslinks. Meanwhile, advances by SMP researchers have led to several approaches toward triple- or multi-shape polymers that feature more than one switching phase and thus a multitude of temporary shapes allowing for a complex sequence of shape deployments. Here, we report the design, preparation, and characterization of a triple shape memory polymeric foam that is open cell in nature and features a two phase, crosslinked SMP with a glass transition temperature of one phase at a temperature lower than a melting transition of the second phase. The soft materials were observed to feature high fidelity, repeatable triple shape behavior, characterized in compression and demonstrated for complex deployment by fixing a combination of foam compression and bending. We further explored the wettability of the foams, revealing composition-dependent behavior favorable for future work in biomedical investigations. PMID:25170743

Nejad, Hossein Birjandi; Baker, Richard M; Mather, Patrick T



Challenges and opportunities in polymer technology applied to veterinary medicine.  


An important frontier in the administration of therapeutic drugs to veterinary species is the use of different polymers as drug delivery platforms. The usefulness of polymers as platforms for the administration of pharmaceutical and agricultural agents has been clearly recognized in the recent decades. The chemical versatility of polymers and the wide range of developed controlled-release strategies enhance the possibilities for the formulation of active molecules. In particular, the veterinary area offers opportunities for the development of novel controlled-release drug delivery technologies adapted to livestock or companion animal health needs. In some cases, it also allows to improve profitability in meat production or to meet the safety criteria related to drug residues. A number of factors affect the selection of polymers and subsequent properties of the controlled-release drug delivery system. However, their selection also dictates the release kinetics of the drug from the delivery system. Such choices are therefore crucial as they affect the success and potential of the delivery system for achieving the therapeutic goals of the veterinarian. It is the intention of this review to give an overview of the most relevant polymers, which are used or have been tested as drug delivery release rate modifiers in the veterinary field. The article highlights some recent developments focusing on their advantages and applications and analyzes the future direction of the scientific and technological advancements in this area. PMID:23980692

Bermudez, J M; Cid, A G; Ramírez-Rigo, M V; Quinteros, D; Simonazzi, A; Sánchez Bruni, S; Palma, S



Systemic Inhibition of Mammalian Target of Rapamycin Inhibits Fear Memory Reconsolidation  

PubMed Central

Background Established traumatic memories have a selective vulnerability to pharmacologic interventions following their reactivation that can decrease subsequent memory recall. This vulnerable period following memory reactivation is termed reconsolidation. The pharmacology of traumatic memory reconsolidation has not been fully characterized despite its potential as a therapeutic target for established, acquired anxiety disorders, including posttraumatic stress disorder (PTSD). The mammalian target of rapamycin (mTOR) kinase is a critical regulator of mRNA translation and is known to be involved in various forms of synaptic plasticity and memory consolidation. We have examined the role of mTOR in traumatic memory reconsolidation. Methods Male C57BL/6 mice were injected systemically with the mTOR inhibitor rapamycin (1 – 40 mg/kg), at various time points relative to contextual fear conditioning training or fear memory retrieval, and compared to vehicle or anisomycin-treated groups (N = 10–12 in each group). Results Inhibition of mTOR via systemic administration of rapamycin blocks reconsolidation of an established fear memory in a lasting manner. This effect is specific to reconsolidation as a series of additional experiments make an effect on memory extinction unlikely. Conclusions Systemic rapamycin, in conjunction with therapeutic traumatic memory reactivation, can decrease the emotional strength of an established traumatic memory. This finding not only establishes mTOR regulation of protein translation in the reconsolidation phase of traumatic memory, but also implicates a novel, FDA-approved drug treatment for patients suffering from acquired anxiety disorders such as PTSD and specific phobia. PMID:18316213

Blundell, Jacqueline; Kouser, Mehreen; Powell, Craig M.



A biodegradable shape-memory nanocomposite with excellent magnetism sensitivity  

NASA Astrophysics Data System (ADS)

This paper reports a kind of biodegradable nanocomposite which can show an excellent shape-memory property in hot water or in an alternating magnetic field with f = 20 kH and H = 6.8 kA m-1. The nanocomposite is composed of crosslinked poly(?-caprolactone) (c-PCL) and Fe3O4 nanoparticles. The crosslinking reaction in PCL with linear molecular structure was realized using benzoyl peroxide (BPO) as an initiator. The biocompatible Fe3O4 magnetite nanoparticles with an average size of 10 nm were synthesized according to a chemical coprecipitation method. The initial results from c-PCL showed crosslinking modification had brought about a large enhancement in shape-memory effect for PCL. Then a series of composites made of Fe3O4 nanoparticles and c-PCL were prepared and their morphological properties, mechanical properties, thermodynamic properties and shape-memory effect were investigated in succession. Significantly, the photos of the shape-memory process confirmed the anticipatory magnetically responsive shape-recovery effect of the nanocomposites because inductive heat from Fe3O4 can be utilized to actuate the c-PCL vivification from their frozen temporary shape. All the results imply a very feasible method to fabricate shape-memory PCL-based nanocomposites since just a simple modification is required. Additionally, this modification would endow an excellent shape-memory effect to all other kinds of polymers so that they could broadly serve in various fields, especially in medicine.

Yu, Xiongjun; Zhou, Shaobing; Zheng, Xiaotong; Guo, Tao; Xiao, Yu; Song, Botao



Noradrenergic modulation of working memory and emotional memory in humans  

Microsoft Academic Search

Rationale  Noradrenaline (NA) is implicated in arousal. Working memory is dependent upon prefrontal cortex, and moderate levels of NA are thought to facilitate working memory whereas higher levels during extreme stress may impair working memory and engage more posterior cortical and sub-cortical circuitry. The NA system also influences emotional memory via modulation of the amygdalae and related mediotemporal structures. NA dysfunction

Samuel R. Chamberlain; Ulrich Müller; Andrew D. Blackwell; Trevor W. Robbins; Barbara J. Sahakian



Sleep & Memory/Review Memory reactivation and consolidation during sleep  

E-print Network

Sleep & Memory/Review Memory reactivation and consolidation during sleep Ken A. Paller1 and Joel L, Illinois 60208-2710, USA Do our memories remain static during sleep, or do they change? We argue here that memory change is not only a natural result of sleep cognition, but further, that such change constitutes

Paller, Ken


Aging Memories: Differential Decay of Episodic Memory Components  

ERIC Educational Resources Information Center

Some memories about events can persist for decades, even a lifetime. However, recent memories incorporate rich sensory information, including knowledge on the spatial and temporal ordering of event features, while old memories typically lack this "filmic" quality. We suggest that this apparent change in the nature of memories may reflect a…

Talamini, Lucia M.; Gorree, Eva



Effects of aging and working memory demands on prospective memory  

Microsoft Academic Search

The current study used event-related brain potentials (ERPs) to examine the effects of aging, increasing the working memory demands of the ongoing activity, and a prospective memory load on the neural correlates of prospective remembering and target recognition. The behavioral data revealed that the success of prospective memory was sensitive to working memory load in younger, but not older, adults

Robert West; Ritvij Bowry



Memory Processing Memory Processing includes tests of  

E-print Network

biologic parents having lived to age 70 or beyond without having developed dementia Thanks to our wonderful the Study Coordinator at: 314-286-2683 Adult Children Study Memory and Aging Project Alzheimer's Disease Adult Children Study Alzheimer's Disease Research Center Department of Neurology Washington University


Encapsulation of Semiconducting Polymers in Vault Protein Cages  

SciTech Connect

We demonstrate that a semiconducting polymer [poly(2-methoxy-5-propyloxy sulfonate phenylene vinylene), MPS-PPV] can be encapsulated inside recombinant, self-assembling protein nanocapsules called 'vaults'. Polymer incorporation into these nanosized protein cages, found naturally at {approx}10,000 copies per human cell, was confirmed by fluorescence spectroscopy and small-angle X-ray scattering. Although vault cellular functions and gating mechanisms remain unknown, their large internal volume and natural prevalence within the human body suggests they could be used as carriers for therapeutics and medical imaging reagents. This study provides the groundwork for the use of vaults in encapsulation and delivery applications.

Ng, B.C.; Yu, M.; Gopal, A.; Rome, L.H.; Monbouquette, H.G.; Tolbert, S.H.



Reconciliation and the Therapeutic State  

Microsoft Academic Search

National reconciliation emerged as a key strategy for conflict management and national reconstruction in political transitions to democracy in the 1980s and 1990s. More recently, reconciliation and human rights discourse has been applied to international humanitarian intervention in states in crisis and in the ‘new wars’. In both cases the focus on the victims of violence is a therapeutic strategy

Michael Humphrey



Therapeutics To Treat Ocular Diseases

The National Eye Institute's Section on Epithelial and Retinal Physiology and Disease (SERPD) is seeking statements of capability or interest from parties interested in collaborative research to further develop, evaluate, or commercialize therapeutics for ocular diseases caused by accumulation of sub-retinal fluid.



Microsoft Academic Search

Inflammation is the physiological response to infection and tissue injury. It is characterized by release of proteins called cytokines and other mediators produced by cells of the immune system. Sepsis, the systemic inflammatory response to infection, is a public health issue because of its high incidence, mortality and economical cost. Experimental paradigms and therapeutic strategies designed to harness systemic inflammation

Masayoshi Kubo; Mauricio Rosas


Therapeutic arterial embolization in trauma.  


Use of therapeutic arterial embolization (TAE) in the traumatized patient can achieve rapid control of hemorrhage and obviate the need for immediate surgery on poor-risk patients or in high-risk areas of the body. The techniques of embolization, its risks, and complications are discussed in light of the authors' experience, and a review of recent literature is presented. PMID:513174

Ben-Menachem, Y; Handel, S F; Thaggard, A; Carnovale, R L; Katragadda, C; Glass, T F



Pathologically activated therapeutics for neuroprotection  

Microsoft Academic Search

Many drugs that have been developed to treat neurodegenerative diseases fail to gain approval for clinical use because they are not well tolerated in humans. In this article, I describe a series of strategies for the development of neuroprotective therapeutics that are both effective and well tolerated. These strategies are based on the principle that drugs should be activated by

Stuart A. Lipton



Faculty Position Therapeutic Medical Physics  

E-print Network

at the assistant or associate professor level in the area of Therapeutic Medical Physics. ERHS of the ERHS department, located at the Veterinary Teaching Hospital. This program provides radiation therapy for companion animals utilizing a VarianTM Trilogy accelerator, EclipseTM treatment planning and AriaTM record


Radioluminescent polymer lights  

Microsoft Academic Search

The preparation of radioluminescent light sources where the tritium is located on the aryl-ring in a polymer has been demonstrated with deuterium\\/tritium substitution. This report discusses tests, results, and future applications of radioluminescent polymers. 10 refs. (FI)

G. A. Jensen; D. A. Nelson; P. M. Molton



Microstructured Polymer Optical Fibers  

Microsoft Academic Search

The fabrication, materials, properties and applications of microstructured polymer optical fibers are reviewed. Microstructured polymer optical fibers formed the basis of extensive work on the physics of microstructured fibers, and an outline of the contribution to the wider field of microstructured fibers is also presented.

Alexander Argyros



Polymer optical fibers  

Microsoft Academic Search

The progress of the GRIN polymer optical fiber (GI POF) for high-speed telecommunication is reviewed. Gigabit data transmission for several hundred meters from visible to 1.3-?m wavelength was experimentally enabled by the low-loss perfluorinated (PF) polymer base GI POF. We describe an improvement in the thermal stability and long-term reliability of the GI POF

Y. Koike; T. Ishigure; M. Sato; E. Nihei



Graphene\\/Polymer Nanocomposites  

Microsoft Academic Search

Graphite has attracted large attention as a reinforcement for polymers due to its ability to modify electrical conductivity, mechanical and gas barrier properties of host polymers and its potentially lower cost than carbon nanotubes. If graphite can be exfoliated into atomically thin graphene sheets, it is possible to achieve the highest property enhancements at the lowest loading. However, small spacing

Chris Macosko; Ahmed A. Abdala



Stiff quantum polymers  

E-print Network

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

H. Kleinert



Polymers that Conduct Electricity.  

ERIC Educational Resources Information Center

Although polymers are regarded as electrical insulators, it was discovered that they can be made to conduct electricity. This discovery has opened vast new practical and theoretical areas for exploration by physicists and chemists. Research studies with these conducting polymers and charge-transfer salts as well as possible applications are…

Edelson, Edward



Imine Oligomers and Polymers  

Microsoft Academic Search

In the last few years, polymers with highly conjugated chains have attracted much attention because of their wide variety of applications in the field of electronics, opto?electronics, and photonics. Polyimines (PIs) (polymeric Schiff bases) is a class of polymer family, which has been less reviewed. In this paper, we focus on the synthesis methods of PIs by polycondensation, using diamines

Mircea Grigoras; Carmen Otilia Catanescu



Radioluminescent polymer lights  

SciTech Connect

The preparation of radioluminescent light sources where the tritium is located on the aryl-ring in a polymer has been demonstrated with deuterium/tritium substitution. This report discusses tests, results, and future applications of radioluminescent polymers. 10 refs. (FI)

Jensen, G.A.; Nelson, D.A.; Molton, P.M.



Polymer based tunneling sensor  

NASA Technical Reports Server (NTRS)

A process for fabricating a polymer based circuit by the following steps. A mold of a design is formed through a lithography process. The design is transferred to a polymer substrate through a hot embossing process. A metal layer is then deposited over at least part of said design and at least one electrical lead is connected to said metal layer.

Cui, Tianhong (Inventor); Wang, Jing (Inventor); Zhao, Yongjun (Inventor)



Memory distortion: an adaptive perspective  

E-print Network

Memory distortion: an adaptive perspective Daniel L. Schacter, Scott A. Guerin* and Peggy L. St. Jacques* Department of Psychology, Harvard University, Cambridge, MA 02138, USA Memory is prone that several types of memory distortions ­ imagination inflation, gist-based and associative memory errors

Schacter, Daniel


Sleep-dependent memory consolidation  

Microsoft Academic Search

The concept of `sleeping on a problem' is familiar to most of us. But with myriad stages of sleep, forms of memory and processes of memory encoding and consolidation, sorting out how sleep contributes to memory has been anything but straightforward. Nevertheless, converging evidence, from the molecular to the phenomenological, leaves little doubt that offline memory reprocessing during sleep is

Robert Stickgold



Recovered Memories of Child Abuse  

Microsoft Academic Search

In this paper we exemplify the ongoing and inconclusive nature of empirical research examining the validity of adults' recovered memories of childhood abuse. In view of increasing evidence that the processes underlying traumatic memories differ in fundamental ways from those underlying memories for nontraumatic events, experimental studies of everyday memory processes are likely to have little relevance for our understanding

Connie M. Kristiansen; Kathleen A. Felton; Wendy E. Hovdestad



Encoding [quiet memories  

E-print Network

visual archetypes of memories. Feelings and emotions are preserved and travel with me through time, affecting and enriching my life. Reminiscences make up a complex network that includes very specific memories and more general and abstract moments from..., and together tell the story of who I am. When we encode, we transform what we feel, think or see at a particular point in our life, into memories. I use a variety of materials and processes to transform these personal feelings and sensations into reminiscences...

Brebenel, Elena



Memory clinics in context  

PubMed Central

The growing number of older people in all parts of the world raises the question of how best to respond to their health needs, including those associated with memory impairment. Specialist Memory Clinics have a role to play, complementing community services which reach out to older people with mental health problems and encompassing younger people who become forgetful. Dementia is the most common syndrome seen, but there are other important treatable conditions which present with subjective or objective dysmnesia. Memory Clinics provide a high quality, devoted focus for early intervention, treatment, support and research. PMID:21416022

Jolley, David; Moniz-Cook, Esme



Plated wire memory subsystem  

NASA Technical Reports Server (NTRS)

The design, construction, and test history of a 4096 word by 18 bit random access NDRO Plated Wire Memory for use in conjunction with a spacecraft input/output and central processing unit is reported. A technical and functional description is given along with diagrams illustrating layout and systems operation. Test data is shown on the procedures and results of system level and memory stack testing, and hybrid circuit screening. A comparison of the most significant physical and performance characteristics of the memory unit versus the specified requirements is also included.

Carpenter, K. H.



Polymer infrared proximity sensor  

NASA Astrophysics Data System (ADS)

A proximity sensor that combines a polymer light-emitting diode and a polymer photodiode is presented. The operation wavelength is in the near infrared from 700to850nm. The infrared emission is obtained by adding a color conversion film of polyvinylpyrrolidone polymer matrix blended with infrared dye 1,1-diethyl-2,2-dicarbocyanine iodide to a red polymer light-emitting diode. The photodetector relies on the direct charge-transfer exciton generation in a donor-acceptor polymer blend of poly(3-hexylthiophene) and (6,6)-phenyl-C61-butyric acid methyl ester. The detection distance is up to 19cm for objects with various colors and roughness under ambient indoor lighting.

Chen, En-Chen; Tseng, Shin-Rong; Ju, Jia-Hong; Yang, Chia-Ming; Meng, Hsin-Fei; Horng, Sheng-Fu; Shu, Ching-Fong



Fabrication and Characterization of Carbon Nanofiber Reinforced Shape Memory Epoxy (CNFR-SME) Composites  

NASA Astrophysics Data System (ADS)

Shape memory polymers have a wide range of applications due to their ability to mechanically change shapes upon external stimulus, while their achievable composite counterparts prove even more versatile. An overview of literature on shape memory materials, fillers and composites was provided to pave a foundation for the materials used in the current study and their inherent benefits. This study details carbon nanofiber and composite fabrication and contrasts their material properties. In the first section, the morphology and surface chemistry of electrospun-poly(acrylonitrile)-based carbon nanofiber webs were tailored through various fabrication methods and impregnated with a shape memory epoxy. The morphologies, chemical compositions, thermal stabilities and electrical resistivities of the carbon nanofibers and composites were then characterized. In the second section, an overview of thermal, mechanical and shape memory characterization techniques for shape memory polymers and their composites was provided. Thermal and mechanical properties in addition to the kinetic and dynamic shape memory performances of neat epoxy and carbon nanofiber/epoxy composites were characterized. The various carbon nanofiber web modifications proved to have notable influence on their respective composite performances. The results from these two sections lead to an enhanced understanding of these carbon nanofiber reinforced shape memory epoxy composites and provided insight for future studies to tune these composites at will.

Wang, Jiuyang


The Relationships of Working Memory, Secondary Memory, and General Fluid Intelligence: Working Memory Is Special  

Microsoft Academic Search

Recent efforts have been made to elucidate the commonly observed link between working memory and reasoning ability. The results have been inconsistent, with some work suggesting that the emphasis placed on retrieval from secondary memory by working memory tests is the driving force behind this association (Mogle, Lovett, Stawski, & Sliwinski, 2008), whereas other research suggests retrieval from secondary memory

Jill Talley Shelton; Emily M. Elliott; Russell A. Matthews; B. D. Hill; Wm. Drew Gouvier



Hardware Transactional Memory  

E-print Network

This work shows how hardware transactional memory (HTM) can be implemented to support transactions of arbitrarily large size, while ensuring that small transactions run efficiently. Our implementation handles small ...

Lie, Sean


Modelling Immunological Memory  

E-print Network

Accurate immunological models offer the possibility of performing highthroughput experiments in silico that can predict, or at least suggest, in vivo phenomena. In this chapter, we compare various models of immunological memory. We first validate an experimental immunological simulator, developed by the authors, by simulating several theories of immunological memory with known results. We then use the same system to evaluate the predicted effects of a theory of immunological memory. The resulting model has not been explored before in artificial immune systems research, and we compare the simulated in silico output with in vivo measurements. Although the theory appears valid, we suggest that there are a common set of reasons why immunological memory models are a useful support tool; not conclusive in themselves.

Garret, Simon; Walker, Joanne; Wilson, William; Aickelin, Uwe



Warship : memorial in antithesis  

E-print Network

This thesis is divided into three distinct yet related parts. The first consists of observations and reflections on some of New York City's many war memorials, ranging from one commemorating the Revolutionary War to one ...

Tchelistcheff, Andre Victor



Emotional Memory Mara Mather  

E-print Network

enhance memory a week later for what happened right beforehand (Knight & Mather, 2009). How does arousal background, they were able to remember more of the salient dark grey letters and fewer of the light grey

Mather, Mara


Mondriaan memory protection  

E-print Network

Reliability and security are quickly becoming users' biggest concern due to the increasing reliance on computers in all areas of society. Hardware-enforced, fine-grained memory protection can increase the reliability and ...

Witchel, Emmett Jethro, 1970-



Object Location Memory Explanation  

NSDL National Science Digital Library

Silverman and Eals (1992) developed a task to measure object location memory. This page describes the classic object location task and offers suggestions for investigating gender differences related to the task.


Phase change memory technology  

Microsoft Academic Search

We survey the current state of phase change memory (PCM), a non-volatile solid-state memory technology built around the large electrical contrast between the highly-resistive amorphous and highly-conductive crystalline states in so-called phase change materials. PCM technology has made rapid progress in a short time, having passed older technologies in terms of both sophisticated demonstrations of scaling to small device dimensions,

Geoffrey W. Burr; Matthew J. Breitwisch; Michele Franceschini; Davide Garetto; Kailash Gopalakrishnan; Bryan Jackson; Bulent Kurdi; Chung Lam; Luis A. Lastras; Alvaro Padilla; Bipin Rajendran; Simone Raoux; Rohit S. Shenoy



Photonic crystal optical memory  

NASA Astrophysics Data System (ADS)

After several decades pushing the technology and the development of the world, the electronics is giving space for technologies that use light. We propose and analyze an optical memory embedded in a nonlinear photonic crystal (PhC), whose system of writing and reading data is controlled by an external command signal. This optical memory is based on optical directional couplers connected to a shared optical ring. Such a device can work over the C-Band of ITU (International Telecommunication Union).

Lima, A. Wirth; Sombra, A. S. B.



Iwo Jima Memorial  

Microsoft Academic Search

The Marine Corps War Memorial stands as a symbol of this grateful Nation's esteem for the honored dead of the U.S. Marine Corps. While the statue depicts one of the most famous incidents of World War II, the memorial is dedicated to all Marines who have given their lives in the defense of the United States since 1775. The 32-foot-high

Chet Smolski



Pitch Memory Experiment  

NSDL National Science Digital Library

This is the entry page for the Pitch Memory Experiment. The pitch memory task is patterned after Deutsch (1979). On each trial, a target tone and a test tone are presented with five distracter tones between them. Participants will be asked to judge whether the target and test tones are the same or different. There are 38 trials when the tones are the same and 38 when they are different.


Verification of Embedded Memory Systems using Efficient Memory Modeling  

E-print Network

We describe verification techniques for embedded memory systems using efficient memory modeling (EMM), without explicitly modeling each memory bit. We extend our previously proposed approach of EMM in Bounded Model Checking (BMC) for a single read/write port single memory system, to more commonly occurring systems with multiple memories, having multiple read and write ports. More importantly, we augment such EMM to providing correctness proofs, in addition to finding real bugs as before. The novelties of our verification approach are in a) combining EMM with proof-based abstraction that preserves the correctness of a property up to a certain analysis depth of SAT-based BMC, and b) modeling arbitrary initial memory state precisely and thereby, providing inductive proofs using SAT-based BMC for embedded memory systems. Similar to the previous approach, we construct a verification model by eliminating memory arrays, but retaining the memory interface signals with their control logic and adding constraints on tho...

Ganai, Malay K; Ashar, Pranav



Quantum Channels with Memory  

E-print Network

We present a general model for quantum channels with memory, and show that it is sufficiently general to encompass all causal automata: any quantum process in which outputs up to some time t do not depend on inputs at times t' > t can be decomposed into a concatenated memory channel. We then examine and present different physical setups in which channels with memory may be operated for the transfer of (private) classical and quantum information. These include setups in which either the receiver or a malicious third party have control of the initializing memory. We introduce classical and quantum channel capacities for these settings, and give several examples to show that they may or may not coincide. Entropic upper bounds on the various channel capacities are given. For forgetful quantum channels, in which the effect of the initializing memory dies out as time increases, coding theorems are presented to show that these bounds may be saturated. Forgetful quantum channels are shown to be open and dense in the set of quantum memory channels.

Dennis Kretschmann; Reinhard F. Werner



Mechanisms of memory enhancement.  


The ongoing quest for memory enhancement is one that grows necessary as the global population increasingly ages. The extraordinary progress that has been made in the past few decades elucidating the underlying mechanisms of how long-term memories are formed has provided insight into how memories might also be enhanced. Capitalizing on this knowledge, it has been postulated that targeting many of the same mechanisms, including CREB activation, AMPA/NMDA receptor trafficking, neuromodulation (e.g., via dopamine, adrenaline, cortisol, or acetylcholine) and metabolic processes (e.g., via glucose and insulin) may all lead to the enhancement of memory. These and other mechanisms and/or approaches have been tested via genetic or pharmacological methods in animal models, and several have been investigated in humans as well. In addition, a number of behavioral methods, including exercise and reconsolidation, may also serve to strengthen and enhance memories. By utilizing this information and continuing to investigate these promising avenues, memory enhancement may indeed be achieved in the future. PMID:23151999

Stern, Sarah A; Alberini, Cristina M



False memories and confabulation.  


Memory distortions range from the benign (thinking you mailed a check that you only thought about mailing), to the serious (confusing what you heard after a crime with what you actually saw), to the fantastic (claiming you piloted a spaceship). We review theoretical ideas and empirical evidence about the source monitoring processes underlying both true and false memories. Neuropsychological studies show that certain forms of brain damage (such as combined frontal and medial-temporal lesions) might result in profound source confusions, called confabulations. Neuroimaging techniques provide new evidence regarding more specific links between underlying brain mechanisms and the normal cognitive processes involved in evaluating memories. One hypothesis is that the right prefrontal cortex (PFC) subserves heuristic judgments based on easily assessed qualities (such as familiarity or perceptual detail) and the left PFC (or the right and left PFC together) subserves more systematic judgments requiring more careful analysis of memorial qualities or retrieval and evaluation of additional supporting or disconfirming information. Such heuristic and systematic processes can be disrupted not only by brain damage but also, for example, by hypnosis, social demands and motivational factors, suggesting caution in the methods used by `memory exploring' professions (therapists, police officers, lawyers, etc.) in order to avoid inducing false memories. PMID:21227110

Johnson, M K; Raye, C L



Sustained gastrointestinal activity of dendronized polymer-enzyme conjugates  

NASA Astrophysics Data System (ADS)

Methods to stabilize and retain enzyme activity in the gastrointestinal tract are investigated rarely because of the difficulty of protecting proteins from an environment that has evolved to promote their digestion. Preventing the degradation of enzymes under these conditions, however, is critical for the development of new protein-based oral therapies. Here we show that covalent conjugation to polymers can stabilize orally administered therapeutic enzymes at different locations in the gastrointestinal tract. Architecturally and functionally diverse polymers are used to protect enzymes sterically from inactivation and to promote interactions with mucin on the stomach wall. Using this approach the in vivo activity of enzymes can be sustained for several hours in the stomach and/or in the small intestine. These findings provide new insight and a firm basis for the development of new therapeutic and imaging strategies based on orally administered proteins using a simple and accessible technology.

Fuhrmann, Gregor; Grotzky, Andrea; Luki?, Ružica; Matoori, Simon; Luciani, Paola; Yu, Hao; Zhang, Baozhong; Walde, Peter; Schlüter, A. Dieter; Gauthier, Marc A.; Leroux, Jean-Christophe



Therapeutic hypothermia after cardiac arrest.  


Prognosis following out-of-hospital cardiac arrest is generally poor, which is mostly due to the severity of neuronal damage. Recently, the use of therapeutic hypothermia has gradually occupied an important role in managing neuronal injuries in some cases of cardiac arrests. Some of the clinical trials conducted in comatose post-resuscitation cardiac arrest patients within the last decade have shown induced hypothermia to be effective in facilitating neuronal function recovery. This method has since been adopted in a number of guidelines and protocols as the standard method of treatment in carefully selected patient groups. Patient inclusion criteria ensure that hypothermia-associated complications are kept to a minimum while at the same time maximizing the treatment benefits. In the present work, we have examined different aspects in the use of therapeutic hypothermia as a means of managing comatose patients following cardiac arrest. PMID:25281626

Alshimemeri, Abdullah



Liquid crystalline conducting polymers  

SciTech Connect

Recently we developed side chain liquid crystalline polyacetylene derivatives and achieved a substantial enhancement of electrical conductivity through magnetically forced alignment of the side chain of the polymer. When an electric field is employed as an alternative external force instead of the magnetic force, a ferroelectric liquid crystal should the more favorable than usual liquid crystals. This is because the former can respond more smoothly to the electric field owing to its spontaneous polarization than the latter. Here, in order to develop a novel liquid crystalline conducting polymer, we have synthesized a chiroptical liquid crystalline polyacetylene derivative. The liquid crystalline side chain of the polymer consists of a chiral alkyl moiety as a terminal group and a biphenyl moiety as a mesogenic core and a trimethylene segment as a spacer. The polymerization was carried out using a metathesis catalyst of MoCl{sub 5}-SnPh{sub 4}. Both the monomer and polymer showed the same signs in CD (circular dichroism) bands, indicating that the chirality of the monomer is maintained in the polymer. Measurements of DSC (differential scanning calorimeter) and polarizing microscope indicated that the polymer has a chiral smectic C (S{sub m} C*) phase assignable to the ferroelectric liquid crystal. Electrical and chemical properties of the polymer, including dielectric constant, electrical conductivity upon iodine doping and morphological alignment under an external force, are to be presented.

Akagi, K.; Goto, H.; Shirakawa, H. [Univ. of Tsukuba, Ibaraki (Japan)



Fabrication of a light-emitting shape memory polymeric web containing indocyanine green  

E-print Network

Fabrication of a light-emitting shape memory polymeric web containing indocyanine green Amir H Library ( DOI: 10.1002/jbm.b.33107 Abstract: Dye-containing polymers are highly, and drug delivery. In par- ticular, dyes that emit light in the NIR region of the electro- magnetic

Mather, Patrick T.


An earthworm-like micro robot using shape memory alloy actuator  

Microsoft Academic Search

A novel bio-mimetic micro robot with wireless control and wireless power supply using shape memory alloy (SMA) actuator is developed. There have been many kinds of mobile micro robot using the micro actuators such as ionic polymer metal composite (IPMC), micro motors and piezo actuators. These actuators generally require electric cable for power supply, which might highly influence the mobility

Byungkyu Kim; Moon Gu Lee; Young Pyo Lee; YongIn Kim; GeunHo Lee




E-print Network

be embedded in a host matrix to induce active shape control, alter the stiffness, or change the modal response transfer behavior of a one-way SMA ribbon in a room temperature cured polymer matrix was quantified usingLOCAL DISPLACEMENTS AND LOAD TRANSFER OF SHAPE MEMORY ALLOYS IN POLYMERIC MATRICES BY KRISHNA D

Sottos, Nancy R.


Antibody Engineering and Therapeutics Conference  

PubMed Central

The Antibody Engineering and Therapeutics conference, which serves as the annual meeting of The Antibody Society, will be held in Huntington Beach, CA from Sunday December 8 through Thursday December 12, 2013. The scientific program will cover the full spectrum of challenges in antibody research and development, and provide updates on recent progress in areas from basic science through approval of antibody therapeutics. Keynote presentations will be given by Leroy Hood (Institute of System Biology), who will discuss a systems approach for studying disease that is enabled by emerging technology; Douglas Lauffenburger (Massachusetts Institute of Technology), who will discuss systems analysis of cell communication network dynamics for therapeutic biologics design; David Baker (University of Washington), who will describe computer-based design of smart protein therapeutics; and William Schief (The Scripps Research Institute), who will discuss epitope-focused immunogen design.   In this preview of the conference, the workshop and session chairs share their thoughts on what conference participants may learn in sessions on: (1) three-dimensional structure antibody modeling; (2) identifying clonal lineages from next-generation data sets of expressed VH gene sequences; (3) antibodies in cardiometabolic medicine; (4) the effects of antibody gene variation and usage on the antibody response; (5) directed evolution; (6) antibody pharmacokinetics, distribution and off-target toxicity; (7) use of knowledge-based design to guide development of complementarity-determining regions and epitopes to engineer or elicit the desired antibody; (8) optimizing antibody formats for immunotherapy; (9) antibodies in a complex environment; (10) polyclonal, oligoclonal and bispecific antibodies; (11) antibodies to watch in 2014; and (12) polyreactive antibodies and polyspecificity.

Almagro, Juan Carlos; Gilliland, Gary L; Scott, Jamie; Larrick, James W; Pluckthun, Andreas; Veldman, Trudi; Adams, Gregory P; Parren, Paul WHI; Chester, Kerry A; Bradbury, Andrew; Reichert, Janice M; Huston, James S



DNA molecules and human therapeutics  

Microsoft Academic Search

Nucleic acid molecules are championing a new generation of reverse engineered biopharmaceuticals. In terms of potential application in gene medicine, plasmid DNA (pDNA) vectors have exceptional therapeutic and immunological profiles as they are free from safety concerns associated with viral vectors, display non-toxicity and are simpler to develop. This review addresses the potential applications of pDNA molecules in vaccine design\\/development

Michael K. Danquah; Jenny Ho; Shan Liu; Gareth M. Forde


Photoacoustic thermometry for therapeutic hyperthermia  

Microsoft Academic Search

Local hyperthermia is widely studied as a treatment option for small tumors. This study investigates the feasibility of exploiting the photoacoustic (PA) effect to monitor the in situ temperature rise during high-intensity focused ultrasound (HIFU) exposures for therapeutic hyperthermia. Polyacrylamide phantoms with a cylindrical inclusion (3 ?? 20 mm) of graphite (0.01 g\\/ml) were heated using 30 s exposures from

Parag V. Chitnis; Jonathan Mamou; J. McLaughlan; T. Murray; R. A. Roy



Avian Diagnostic and Therapeutic Antibodies  

SciTech Connect

A number of infectious agents have the potential of causing significant clinical symptomology and even death, but dispite this, the number of incidence remain below the level that supports producing a vaccine. Therapeutic antibodies provide a viable treatment option for many of these diseases. We proposed that antibodies derived from West Nile Virus (WNV) immunized geese would be able to treat WNV infection in mammals and potential humans. We demonstrated that WNV specific goose antibodies are indeed successful in treating WNV infection both prophylactically and therapeutically in a golden hamster model. We demonstrated that the goose derived antibodies are non-reactogenic, i.e. do not cause an inflammatory response with multiple exposures in mammals. We also developed both a specific pathogen free facility to house the geese during the antibody production phase and a patent-pending purification process to purify the antibodies to greater than 99% purity. Therefore, the success of these study will allow a cost effective rapidly producible therapeutic toward clinical testing with the necessary infrastructure and processes developed and in place.

Bradley, David Sherman [UND SMHS] [UND SMHS



Therapeutic Strategies in Huntington's Disease.  


This article provides an overview of the therapeutic strategies, from ordinary classical drugs to the modern molecular strategy at experimental level, for Huntington's disease. The disease is characterized by choreic movements, psychiatric disorders, striatal atrophy with selective small neuronal loss, and autosomal dominant inheritance. The genetic abnormality is CAG expansion in huntingtin gene. Mutant huntingtin with abnormally long glutamine stretch aggregates and forms intranuclear inclusions. In this review, I summarize the results of previous trials from the following aspects; 1. symptomatic/palliative therapies including drugs, stereotaxic surgery and repetitive transcranial magnetic stimulation, 2. anti-degenerative therapies including anti-excitotoxicity, reversal of mitochondrial dysfunction and anti-apoptosis, 3. restorative/reparative therapies including neural trophic factors and tissue or stem cell transplantation, and 4. molecular targets in specific and radical therapies including inhibition of truncation of huntingtin, inhibition of aggregate formation, normalization of transcriptional dysregulation, enhancement of autophagic clearance of mutant huntingtin, and specific inhibition of huntingtin expression by sRNAi. Although the strategies mentioned in the latter two categories are mostly at laboratory level at present, we are pleased that one can discuss such "therapeutic strategies", a matter absolutely impossible before the causal gene of Huntington's disease was identified more than 10 years ago. It is also true, however, that some of the "therapeutic strategies" mentioned here would be found difficult to implement and abandoned in the future. PMID:20396523

Kanazawa, Ichiro



Memory Distortion in Alzheimer's Disease: Deficient Monitoring of Short-and Long-Term Memory  

E-print Network

Memory Distortion in Alzheimer's Disease: Deficient Monitoring of Short- and Long-Term Memory Objective: This study measured distortions of memory during short-term memory (STM) and long-term memory: Alzheimer's disease, false memory, short-term memory, long-term memory, semantic mem- ory Distortion


Towards Polymer-Based Capsules with Drastically Reduced Controlled Permeability  

NASA Astrophysics Data System (ADS)

Small molecules (dyes, therapeutics, etc.) could be easily handled, stored, delivered, and released by polyelectrolyte capsules. To make the polyelectrolyte capsule more efficient for small molecule encapsulation, capsule permeability should be significantly decreased. Here, we demonstrate the possibility to entrap water-soluble molecular species into polyelectrolyte capsules modified by a low permeable dense polymer (polypyrrole). Possible future areas in PE capsule application as carriers for gases and volatiles in the pharmaceutical, food, and gases industry, agriculture and cosmetology are discussed.

Andreeva, Daria V.; Sukhorukov, Gleb B.


Polymer thin films embedded with in situ grown metal nanoparticles.  


Metal nanoparticle-polymer composites are versatile materials which not only combine the unique characteristics of the components, but also manifest mutualistic effects between the two. Embedding inside polymer thin films facilitates immobilization and organization of the metal nanoparticles and tuning of their electronic and optical responses by the dielectric environment. The embedded metal nanoparticles in turn can impact upon the various material attributes of the polymer matrix. Some of the most convenient and attractive routes to the fabrication of metal nanoparticle-embedded polymer thin films involve in situ generation of the nanoparticles through reduction or decomposition of appropriate precursors inside the solid film. In this tutorial review we present an overview of the different methodologies developed using this general concept and describe the environment-friendly protocol we have optimized for the fabrication of noble metal nanostructures inside polymer thin films, using aqueous media for the synthesis and deploying the polymer itself as the reducing as well as stabilizing agent. A variety of techniques that have been exploited to characterize the precursor to product transformation inside the polymer film are discussed. The unique control provided by the in situ fabrication route on the size, shape and distribution of the nanostructures, and application of the polymer thin films with the in situ generated metal nanoparticles in areas such as nonlinear optics, surface enhanced Raman scattering, e-beam lithography, microwave absorption, non-volatile memory devices and random lasers, illustrate the versatility of these materials. A brief appraisal of the avenues for future developments in this area is presented. PMID:19690744

Ramesh, G V; Porel, S; Radhakrishnan, T P



A Silly Polymer  

NSDL National Science Digital Library

The Materials Science and Technology Teacher's Workshop (MAST) provides this lesson plan for students learning about polymers. The class will create a material similar to silly putty using cross linking polymers. The module will allow students to observe the changes in physical properties when a polymer is cross linked, as well as the changes in properties at varying temperatures. The procedure should take about 20-25 minutes of class time. Discussion questions, teacher notes and a link to a video clip are included.



Rechargeable solid polymer electrolyte battery cell  


A rechargeable battery cell comprising first and second electrodes sandwiching a solid polymer electrolyte comprising a layer of a polymer blend of a highly conductive polymer and a solid polymer electrolyte adjacent said polymer blend and a layer of dry solid polymer electrolyte adjacent said layer of polymer blend and said second electrode.

Skotheim, Terji (East Patchoque, NY)



Acetyl l-carnitine (ALCAR) prevents hypobaric hypoxia–induced spatial memory impairment through extracellular related kinase–mediated nuclear factor erythroid 2-related factor 2 phosphorylation  

Microsoft Academic Search

Exposure to hypobaric hypoxia, a condition involving decreased availability of oxygen is known to be associated with oxidative stress, neurodegeneration and memory impairment. The multifactorial response of the brain and the complex signaling pathways involved therewith limits the therapeutic efficacy of several antioxidants in ameliorating hypobaric hypoxia–induced memory impairment. The present study was therefore aimed at investigating the potential of

K. Barhwal; S. K. Hota; V. Jain; D. Prasad; S. B. Singh; G. Ilavazhagan



Fast Domain Wall Switching in a Thin Ferroelectric Polymer Jong Yeog Son,a  

E-print Network

Fast Domain Wall Switching in a Thin Ferroelectric Polymer Layer Jong Yeog Son,a Yun-Sok Shin such as nonvolatile memories.8 Meanwhile, scanning probe microscopy SPM on ferroelectric domains has exhibited to switch ferroelectric domains and the readout.10-14 In detail, the EFM and KFM methods can map surface

Lee, EokKyun


Polymer carriers for anticancer drugs targeted to EGF receptor.  


A novel actively targeted polymer carrier for anticancer drugs based on an N-(2-hydroxypropyl)methacrylamide copolymer (PHPMA) is proposed. An oligopeptide sequence GE7, attached to the polymer, is a specific ligand for the EGF receptor overexpressed on most tumor cells. Co-attachment of selected chemotherapeutics will therefore lead to formation of tumor-specific polymer therapeutics, further enhanced by the EPR effect. FACS measurements prove elevated binding activity of the fluorescently labeled PHPMA/GE7 conjugate in EGFR-rich cells (FaDu, MCF-7), compared to conjugates of scrambled peptides. Cell lines with low EGFR level (SW620, B16F10) bind the GE7 conjugate significantly less. PMID:23077133

Studenovsky, Martin; Pola, Robert; Pechar, Michal; Etrych, Tomas; Ulbrich, Karel; Kovar, Lubomir; Kabesova, Martina; Rihova, Blanka



Sulfonated polyphenylene polymers  


Improved sulfonated polyphenylene compositions, improved polymer electrolyte membranes and nanocomposites formed there from for use in fuel cells are described herein. The improved compositions, membranes and nanocomposites formed there from overcome limitations of Nafion.RTM. membranes.

Cornelius, Christopher J. (Albuquerque, NM); Fujimoto, Cy H. (Albuquerque, NM); Hickner, Michael A. (Albuquerque, NM)



Heavily fluorinated electronic polymers  

E-print Network

Building blocks, containing majority fluorine content by weight, for PPEs and PPVs have been synthesized. Some of the monomers were shown to give exclusively fluorous-phase soluble polymers, the syntheses of which were ...

Lim, Jeewoo



Primordial polymer perturbations  

NASA Astrophysics Data System (ADS)

We study the generation of primordial fluctuations in pure de Sitter inflation where the quantum scalar field dynamics are governed by polymer (not Schrödinger) quantization. This quantization scheme is related to, but distinct from, the structures employed in Loop Quantum Gravity; and it modifies standard results above a polymer energy scale Mstar. We recover the scale invariant Harrison Zel'dovich spectrum for modes that have wavelengths bigger than Mstar-1 at the start of inflation. The primordial spectrum for modes with initial wavelengths smaller than Mstar-1 exhibits oscillations superimposed on the standard result. The amplitude of these oscillations is proportional to the ratio of the inflationary Hubble parameter H to the polymer energy scale. For reasonable choices of Mstar, we find that polymer effects are likely unobservable in CMB angular power spectra due to cosmic variance uncertainty, but future probes of baryon acoustic oscillations may be able to directly constrain the ratio H/Mstar.

Seahra, Sanjeev S.; Brown, Iain A.; Mortuza Hossain, Golam; Husain, Viqar



Knots in Charged Polymers  

E-print Network

The interplay of topological constraints and Coulomb interactions in static and dynamic properties of charged polymers is investigated by numerical simulations and scaling arguments. In the absence of screening, the long-range interaction localizes irreducible topological constraints into tight molecular knots, while composite constraints are factored and separated. Even when the forces are screened, tight knots may survive as local (or even global) equilibria, as long as the overall rigidity of the polymer is dominated by the Coulomb interactions. As entanglements involving tight knots are not easy to eliminate, their presence greatly influences the relaxation times of the system. In particular, we find that tight knots in open polymers are removed by diffusion along the chain, rather than by opening up. The knot diffusion coefficient actually decreases with its charge density, and for highly charged polymers the knot's position appears frozen.

Paul G. Dommersnes; Yacov Kantor; Mehran Kardar



Polymer Modified Road Bitumens.  

National Technical Information Service (NTIS)

The present thesis is based on six publications, including a literature review (Paper I) and experimental studies (Papers II - VI) on polymer modified bitumens. In the literature review, basic aspects of bitumen chemistry and rheology and characteristics ...

X. Lu



Lipases in polymer chemistry.  


Lipases are highly active in the polymerization of a range of monomers. Both ring-opening polymerization of cyclic monomers such as lactones and carbonates as well as polycondensation reactions have been investigated in great detail. Moreover, in combination with other (chemical) polymerization techniques, lipase-catalyzed polymerization has been employed to synthesize a variety of polymer materials. Major advantages of enzymatic catalysts are the often-observed excellent regio-, chemo- and enantioselectivity that allows for the direct preparation of functional materials. In particular, the application of techniques such as Dynamic Kinetic Resolution (DKR) in the lipase-catalyzed polymerization of racemic monomers is a new development in enzymatic polymerization. This paper reviews selected examples of the application of lipases in polymer chemistry covering the synthesis of linear polymers, chemoenzymatic polymerization and applications of enantioselective techniques for the synthesis and modification of polymers. PMID:20859733

Yeniad, Bahar; Naik, Hemantkumar; Heise, Andreas



Demixing Problems in Polymers.  

National Technical Information Service (NTIS)

Phase transitions in polymers were studied in four chapters: Flory-Huggins theory and experiment, critical demixing properties, effects of polydispersion, and two-dimensional systems. (ERA citation 05:019162)

J. F. Joanny



Polymers and Liquid Crystals  

NSDL National Science Digital Library

This newly enhanced site is the result of a cooperative effort between the Department of Physics and the Department of Macromolecular Science and Engineering at Case Western Reserve University in conjunction with the Center for Advanced Liquid Crystalline Optical Materials (ALCOM) at Kent State University. The project aims to demonstrate the potential of the hypertext multimedia medium for instructional use, and is still under development (occasionally users will come across an "under construction" notice). Topics covered include polymers, liquid crystals, polymer liquid crystals, polymer dispersed liquid crystals, polymer stabilized cholesterics, and liquid crystal displays. The previous version, which debuted in January 1996, has been enhanced with more video and audio, frames, and a glossary. Throughout the text, users are invited to enter the Virtual Laboratory, in which browser applets allow control of experiments demonstrating the principles under discussion. A CD-ROM version of the textbook is planned.



Memory function and supportive technology  

PubMed Central

Episodic and working memory processes show pronounced age-related decline, with other memory processes such as semantic, procedural, and metamemory less affected. Older adults tend to complain the most about prospective and retrospective memory failures. We introduce a framework for deciding how to mitigate memory decline using augmentation and substitution and discuss techniques that change the user, through mnemonics training, and change the tool or environment, by providing environmental support. We provide examples of low-tech and high-tech memory supports and discuss constraints on the utility of high-tech systems including effectiveness of devices, attitudes toward memory aids, and reliability of systems. PMID:24379752

Charness, Neil; Best, Ryan; Souders, Dustin



Polymer Nanowires and Nanofibers  

Microsoft Academic Search

\\u000a As is well known, all matter is made up of atoms. The term molecule is used to describe groups of atoms that tend to exist together in a stable form. As the term implies, macromolecule (or polymer) refers to a molecule of the extraordinarily large size (typically, >1,000 in molecular weight). Although polymer\\u000a molecules are large, they can be defined

Liming Dai; Darrell H. Reneker


Dilatant aqueous polymer solutions  

Microsoft Academic Search

A dilatant aqueous solution of minor amounts of a high molecular weight polymer of ethylene oxide and petroleum sulfonate is useful in enhanced oil recovery. The polymer, having an average molecular weight of about 600,000 or greater, is employed with a concentration between about 0.02 and 1.5 percent by weight. A molecular weight in the range of about 400 to




Cylodextrin Polymer Nitrate  

NASA Technical Reports Server (NTRS)

The development of the use of cyclodextrin nitrates as possible components of insensitive, high-energy energetics is outlined over a time period of 12 years. Four different types of cyclodextrin polymers were synthesized, nitrated, and evaluated regarding their potential use for the military and aerospace community. The synthesis of these novel cyclodextrin polymers and different nitration techniques are shown and the potential of these new materials is discussed.

Kosowski, Bernard; Ruebner, Anja; Statton, Gary; Robitelle, Danielle; Meyers, Curtis



Crystallization of Polymers  

Microsoft Academic Search

This new edition of Volume 2 of Leo Mandelkern's self-contained work is an up-to-date, authoritative account of the kinetics and mechanisms of polymer crystallization. Progressing from the equilibrium concepts presented in volume 1, it provides a comprehensive treatment of the surrounding theories and experimental results from simple to complex polymer systems. The volume will be an invaluable reference work for

Leo Mandelkern



Using Cyclic Memory Allocation to Eliminate Memory Leaks  

E-print Network

We present and evaluate a new memory management technique foreliminating memory leaks in programs with dynamic memoryallocation. This technique observes the execution of the program on asequence of training inputsto find ...

Nguyen, Huu Hai



Tapestry of memory.  


In this essay, I have elaborated on the ideas and experiments that have guided my research career. First, I present my early research history and my involvement in determining the neurobiological basis of the consolidation process based primarily on the consolidation paradigm. Based on a series of experiments and a new interest in cognitive psychology, I then developed a cognitive and neurobiologically based model of memory. This model represents a comprehensive view of memory organization based on multiple processes and multiple forms of memory representation and is based on the neurobiology of a multiple attribute, multiple process, tripartite system model of memory. I present some detailed evidence in terms of the neural foundations, specific attributes, and processes of operation for the event-based, knowledge-based, and rule-based memory systems. In addition, I present a set of experiments to demonstrate that there might be parallel processing of mnemonic information in rats and humans. Finally, I recognize that ideas can be generated by reading the extant literature, interaction with colleagues at meetings, and exchange of ideas with students to design and execute hopefully meaningful experiments. PMID:19170425

Kesner, Raymond P



Australian War Memorial  

NSDL National Science Digital Library

The online presence of the Australian War Memorial, located in Canberra, Australia, this site contains dozens of valuable resources for those with a penchant either for Australian military history or merely for finding the military unit in which a relative may have served during the past 100 years. With numerous sectional headings, the Web site has an effective long-form essay that serves as a good introduction to the subject, detailing the highlights of Australian military involvement from the Boer War to the Vietnam Conflict. There are numerous databases that can be searched on this site, including Australian military unit rosters and the Memorial's vast collection of papers and recorded ephemera relating to Australian military history. There is also an exhaustive section about the actual War Memorial building and grounds, detailing the inspiration for the Memorial building (completed in 1941) and a few notes by the director of the Memorial, Steve Gower, on some of his favorite selections in their holdings. All in all, the site is a wonderful resource for those with an interest in Australian military history and, more broadly, is a way of reminding the public that the contributions of Australians to world military conflicts is quite significant.


Polymer and composite polymer slot waveguides  

NASA Astrophysics Data System (ADS)

A fully polymer slot Young interferometer operating at 633 nm wavelength was fabricated by using nanoimprint molding method. The phase response of the interference pattern was measured with several concentrations of glucose-water solutions, utilizing both TE and TM polarization states. The sensor was experimentally found to detect a bulk refractive index change of 6.4×10-6 RIU. Temperature dependency of silicon slot waveguide has been demonstrated to be reduced with composite slot waveguide structure. The slot filled with thermally stable polymer having negative thermo-optic coefficient showed nearly an athermal operation of silicon slot waveguide. Experimental results show that the slot waveguide geometry covered with Ormocomp has thermo-optical coefficient of 6 pm/K.

Hiltunen, Marianne; Fegadolli, William S.; Lira, Hugo L. R.; Vahimaa, Pasi; Hiltunen, Jussi; Aikio, Sanna; Almeida, Vilson R.; Karioja, Pentti



[Therapeutic update in cystic fibrosis].  


We present the recent therapeutic advances in the cystic fibrosis care. It concerns improvements in symptomatic treatment with the development of dry powder inhaled antibiotics that improved quality of life, and innovative treatments namely the modulators of the cystic fibrosis transmembrane protein conductance regulator (CFTR), molecules which act specifically at the level of the defective mechanisms implied in the disease. The life expectancy of cystic fibrosis patients born after 2000, is estimated now to be about 50 years. This improvement of survival was obtained with the organization of the care within the specialized centers for cystic fibrosis (Centre de ressource et de compétences de la mucoviscidose) and remains still based on heavy symptomatic treatments. Dry powder inhaled antibiotics constitute a significant time saving for patients to whom all the care can achieve two hours daily. Since 2012, the modulators of CFTR, molecules allowing a pharmacological approach targeted according to the type of the mutations, allows a more specific approach of the disease. Ivacaftor (Kalydeco(®)) which potentialises the function of the CFTR protein expressed on the cellular surface is now available for patients with the G551D mutation. Lumacaftor is going to be tested in association with ivacaftor in patients with the F508del mutation, that is present in at least 75% of the patients. The ataluren which allows the production of a functional protein CFTR in patients with a no sense mutation is the third representing of this new therapeutic class. We presently have numerous symptomatic treatments for the cystic fibrosis care. The development of CFTR modulators, today available to a restricted number of patients treated with ivacaftor represents a very promising therapeutic avenue. It will represent probably the first step to a personalized treatment according to CFTR genotype. PMID:24309546

Durupt, S; Nove Josserand, R; Durieu, I



[Therapeutic perspectives in heart failure  


Many different diseases may lead to heart failure. Nevertheless, the symptoms and pathophysiological changes in heart failure are uniform as are the basic principles of treatment. Although significant progress has been achieved in understanding the biology of heart failure and the therapeutic options, the quality of life of heart failure patients and their survival are often poor. Since cardiac transplantation as a final therapeutic option is limited by the availability of donor organs, new strategies and technologies need to be explored to treat the failing heart effectively. Approaches to improve the medical therapy of heart failure mainly focus on strategies to escape the vicious circle of decreased contractility and neurohumoral activation. Substances with promising experimental and clinical results include neutral endopeptidase inhibitors, endothelin antagonists or cytokine inhibitors, e.g. TNF antagonists. Mechanical and electrical devices are under development such as left ventricular assist devices (LVADs), biventricular pacemakers and artificial hearts, which may become valuable alternative therapies. Gene therapy approaches aim to improve the vascularization of the heart, the Ca-homeostasis of the myocytes or the survival of cardiac cells in disease. Finally, cellular cardiomyoplasty is a relatively novel approach to replace or support the cardiomyocytes of the diseased heart by implanting new ones. Which cell type under which conditions will turn out to be the most suitable is still unknown and subject to debate. Ongoing clinical studies will only help to demonstrate the safety and feasibility of this technique but not determine its long-term efficacy. It is highly desirable that one of these new therapeutic strategies or a combination of them will have a significant impact on the future management of heart failure. Currently, our main clinical focus must be to treat as many patients as possible with drugs that are known to improve symptoms and survival, like ACE inhibitors, beta-blockers, cardiac glycosides, diuretics and spironolactone. PMID:12806818

Müller-Ehmsen, Jochen; Schwinger, Robert H



[Therapeutic possibilities after traumatic experiences].  


Acute stress disorder (ASD) and posttraumatic stress disorder (PTSD) are frequent, but not obligatory psychological sequelae following trauma. A major subgroup of patients face a chronic course of illness associated with an increased psychiatric comorbidity and significant impairments in psychosocial adaptation. The typical psychopathological symptoms of ASD and PTSD are best described within a multifactorial model integrating both neurobiological and psychosocial influences. The complex etiopathogenesis of acute and posttraumatic stress disorder favours multimodal approaches in the treatment. Differential psychotherapeutic and pharmacological strategies are available. In a critical survey on empirical studies, psychological debriefing cannot be considered as a positive approach to be recommended as general preventive measure during the immediate posttraumatic phase. Positive effects of cognitive-behavioral interventions can be established for ASD. Psychodynamic psychotherapy, cognitive-behavioral therapy and EMDR show promising results in the treatment of PTSD. Major clinical restrictions of patient sampling within special research facilities, however, do not allow an unconditional generalization of these data to psychiatric routine care. In an empirical analysis the SSRIs are the most and best studied medications for ASD and PTSD. In comparison to tricyclic antidepressants SSRIs demonstrate a broader spectrum of therapeutic effects and are better tolerated. The substance classes of SSNRI, DAS, SARI and NaSSA are to be considered as drugs of second choice. They promise a therapeutic efficacy equivalent to the SSRIs, being investigated so far only in open studies. MAO-inhibitors may dispose of a positive therapeutic potential, their profile of side effects must be respected, however. Mood stabilizers and atypical neuroleptics may be used first and foremost in add-on strategies. Benzodiazepines should be used only with increased caution for a short time in states of acute crisis. In early interventions, substances blocking the norepinephric hyperactivity seem to be promising alternatives. Stress doses of hydrocortisone may be considered as an experimental pharmacological strategy so far. PMID:19011595

Kapfhammer, Hans-Peter



Memory on the beach: an Australian memory (and hypnosis) laboratory  

Microsoft Academic Search

The memory (and hypnosis) lab at the University of New South Wales investigates a broad range of memory topics. We try to\\u000a find innovative methods from cognitive and clinical psychology to address theoretical and empirical questions about memory.\\u000a We aso use hypnosis as one major methodological tool in our investigations of memory (as well as other cognitive processes).\\u000a In this

Amanda J. Barnier; Richard A. Bryant; Leah Campbell; Rochelle Cox; Celia Harris; Lynette Hung; Fiona Maccallum; Stefanie J. Sharman



Polymer-enhanced delivery increases adenoviral gene expression in an orthotopic model of bladder cancer.  


Gene therapy has garnered significant attention as a therapeutic approach for bladder cancer but efficient delivery and gene expression remain major hurdles. The goal of this study was to determine if cationic polymers can enhance adenoviral gene expression in cells that are difficult to transduce in vitro and to subsequently investigate lead candidates for their capacity to increase adenoviral gene expression in an orthotopic in vivo model of bladder cancer. In vitro screening of linear polyamine-based and aminoglycoside-based polymer libraries identified several candidates that enhanced adenoviral reporter gene expression in vitro. The polyamine-based polymer NPGDE-1,4 Bis significantly enhanced adenoviral gene expression in the orthotopic model of bladder cancer but unfortunately further use of this polymer was limited by toxicity. In contrast, the aminoglycoside-based polymer paromomycin-BGDE, enhanced adenoviral gene expression within the bladder without adverse events. Our study demonstrates for the first time that cationic polymers can enhance adenoviral gene expression in an orthotopic model of bladder cancer, thereby providing the foundation for future studies to determine therapeutic benefits of polymer-adenovirus combination in bladder cancer gene therapy. PMID:24370892

Gosnell, Helen; Kasman, Laura M; Potta, Thrimoorthy; Vu, Lucas; Garrett-Mayer, Elizabeth; Rege, Kaushal; Voelkel-Johnson, Christina



DCTD — Developmental Therapeutics Program (DTP)

Sipuleucel-T is a therapeutic vaccine developed to treat prostate cancer. A patient’s dendritic cells are isolated and pulsed with a peptide (PAP-GM-CSF fusion protein) derived from prostatic acid phosphatase. Then the modified dendritic cells are administered back to the patient. This vaccine was considered first-in-class as it was created to treat prostate cancer, whereas most vaccines are developed to build immunity to prevent disease. In the case of sipuleucel-T, the immune system is stimulated to attack the tumor and thereby prolong survival.


Liposarcoma: Molecular Genetics and Therapeutics  

PubMed Central

Sarcomas are a group of heterogeneous tumours with varying genetic basis. Cytogenetic abnormalities range from distinct genomic rearrangements such as pathognomonic translocation events and common chromosomal amplification or loss, to more complex rearrangements involving multiple chromosomes. The different subtypes of liposarcoma are spread across this spectrum and constitute an interesting tumour type for molecular review. This paper will outline molecular pathogenesis of the three main subtypes of liposarcoma: well-differentiated/dedifferentiated, myxoid/round cell, and pleomorphic liposarcoma. Both the molecular basis and future avenues for therapeutic intervention will be discussed. PMID:21253554

Conyers, Rachel; Young, Sophie; Thomas, David M.



Neonatal lung function and therapeutics.  


Abstract Respiratory diseases are increasingly recognized as having their origins during perinatal and early postnatal lung development, a time of significant adaptation to large changes in redox conditions as well as to mechanical forces. This Forum of the journal presents a Forum highlighting studies of the interplay between reactive oxygen/nitrogen species and the systems that have evolved to degrade them or exploit them, as well as the cellular repair processes which respond to early life redox stress in the lung. This group of authors suggests new understandings of these events that may point the way to improved therapeutic approaches. Antioxid. Redox Signal. 21, 1819-1822. PMID:25111369

Auten, Richard L; Farrow, Kathryn N



Exploring breast with therapeutic ductoscopy  

PubMed Central

Breast lesions are thought to arise mostly from the epithelium of ductal lining. Conventional imaging could only show indirect images of suspected lesions which are confirmed by percutaneous biopsies. However, ductoscopy provides direct images of the ductal epithelium which is the source of most malignant and papillary lesions. As an advance of current ductoscopy systems, pathologic nipple discharge (PND) could be treated ductoscopically by miniaturized endo-baskets or wires. Our goal is to discuss current intraductal technology which enables diagnostic and therapeutic advance for breast lesions that cause nipple discharge. PMID:25083507

Feldman, Sheldon Marc



Structurally Based Therapeutic Evaluation: A Therapeutic and Practical Approach to Teaching Medicinal Chemistry.  

ERIC Educational Resources Information Center

Explains structurally based therapeutic evaluation of drugs, which uses seven therapeutic criteria in translating chemical and structural knowledge into therapeutic decision making in pharmaceutical care. In a Creighton University (Nebraska) medicinal chemistry course, students apply the approach to solve patient-related therapeutic problems in…

Alsharif, Naser Z.; And Others



A users' guide to understanding therapeutic substitutions.  


Therapeutic substitutions are common at the level of ministries of health, clinicians, and pharmacy dispensaries. Guidance in determining whether drugs offer similar risk-benefit profiles is limited. Those making decisions on therapeutic substitutions should be aware of potential biases that make differentiating therapeutic agents difficult. Readers should consider whether the biological mechanisms and doses are similar across agents, whether the evidence is sufficiently valid across agents, and whether the safety and therapeutic effects of each drug are similar. This article uses a problem-based format to address the biological mechanism, validity, and results of a scenario in which therapeutic substitutions may be considered. PMID:24291506

Mills, Edward J; Gardner, David; Thorlund, Kristian; Briel, Matthias; Bryan, Stirling; Hutton, Brian; Guyatt, Gordon H



Flow-History-Dependent Behavior in Entangled Polymer Melt Flow with Multiscale Simulation  

E-print Network

Polymer melts represent the flow-history-dependent behavior. To clearly show this behavior, we have investigated flow behavior of an entangled polymer melt around two cylinders placed in tandem along the flow direction in a two dimensional periodic system. In this system, the polymer states around a cylinder in downstream side are different from the ones around another cylinder in upstream side because the former ones have a memory of a strain experienced when passing around the cylinder in upstream side but the latter ones do not have the memory. Therefore, the shear stress distributions around two cylinders are found to be different from each other. Moreover, we have found that the averaged flow velocity decreases accordingly with increasing the distance between two cylinders while the applied external force is constant. While this behavior is consistent with that of the Newtonian fluid, the flow-history-dependent behavior enhances the reduction of the flow resistance.

Takahiro Murashima; Takashi Taniguchi



Flexible Memory Networks  

E-print Network

Networks of neurons in some brain areas are flexible enough to encode new memories quickly. Using a standard firing rate model of recurrent networks, we develop a theory of flexible memory networks. Our main results characterize networks having the maximal number of flexible memory patterns, given a constraint graph on the network's connectivity matrix. Modulo a mild topological condition, we find a close connection between maximally flexible networks and rank 1 matrices. The topological condition is H_1(X;Z)=0, where X is the clique complex associated to the network's constraint graph; this condition is generically satisfied for large random networks that are not overly sparse. In order to prove our main results, we develop some matrix-theoretic tools and present them in a self-contained section independent of the neuroscience context.

Curto, Carina; Itskov, Vladimir



Vietnam Veterans Memorial  

NSDL National Science Digital Library

Visiting the Vietnam Veterans Memorial in Washington, DC can be an emotional experience, and it has garnered substantial acclaim since it was unveiled in 1982. The people behind the Footnote historical records site recently crafted this interactive version of the Vietnam Veterans Memorial, and it's well worth a look. The interactive image was assembled from 6301 images photographed by Peter Krogh and stitched together by Darren Higgins. Visitors can type in names to the search engine at the top of the homepage, browse names by category, and also look up names by military branch. Additionally, visitors can leave a tribute, a story, or a photograph about any of the 58,256 veterans listed on the Memorial.


Memory in viral quasispecies.  


Biological adaptive systems share some common features: variation among their constituent elements and continuity of core information. Some of them, such as the immune system, are endowed with memory of past events. In this study we provide direct evidence that evolving viral quasispecies possess a molecular memory in the form of minority components that populate their mutant spectra. The experiments have involved foot-and-mouth disease virus populations with known evolutionary histories. The composition and behavior of the viral population in response to a selective constraint were influenced by past evolutionary history in a way that could not be predicted from examination of consensus nucleotide sequences of the viral populations. The molecular memory of the viral quasispecies influenced both the nature and the intensity of the response of the virus to a selective constraint. PMID:10729128

Ruiz-Jarabo, C M; Arias, A; Baranowski, E; Escarmís, C; Domingo, E



Emotion and autobiographical memory  

NASA Astrophysics Data System (ADS)

Autobiographical memory encompasses our recollections of specific, personal events. In this article, we review the interactions between emotion and autobiographical memory, focusing on two broad ways in which these interactions occur. First, the emotional content of an experience can influence the way in which the event is remembered. Second, emotions and emotional goals experienced at the time of autobiographical retrieval can influence the information recalled. We discuss the behavioral manifestations of each of these types of interactions and describe the neural mechanisms that may support those interactions. We discuss how findings from the clinical literature (e.g., regarding depression) and the social psychology literature (e.g., on emotion regulation) might inform future investigations of the interplay between the emotions experienced at the time of retrieval and the memories recalled, and we present ideas for future research in this domain.

Holland, Alisha C.; Kensinger, Elizabeth A.



Public memorializing in postmodernity: The Vietnam veterans memorial as prototype  

Microsoft Academic Search

This essay argues for a reading of the Vietnam Veterans Memorial as a postmo