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Applicator conspicuity in ultrasound-guided brachytherapy procedures is commonly impaired by imaging artifacts or non-ideal imaging geometry, which can slow down applicator position digitization and increase the geometric uncertainty of the delivered dose distribution.The purpose of this study was to improve the conspicuity of high-dose rate (HDR) brachytherapy needles under B-mode ultrasound imaging by applying an echogenic surface coating. Our hypothesis was that an echogenic coating would reduce artifacts and improve needle visualization within regions of signal degradation.In this study, 17-gauge, 25-cm long titanium HDR brachytherapy needles were coated with acoustically reflective microspheres over a 2.5 cm region starting from the needle tip. Three coating thicknesses (27 μm, 40 μm, 64 μm) were compared against an uncoated control needle. The coated and uncoated needles were imaged using B-mode ultrasound in a tissue-equivalent prostate phantom and in a cadaverous male pelvis using a transrectal probe. Needle conspicuity was assessed under multiple conditions: a single needle implant, an implant with multiple needles between the probe and the needle of interest, and an angled needle implant. All images were assessed qualitatively for needle conspicuity and the presence of artifacts and quantitatively using gray-scale image intensity values.The 64 μm echogenic coating reduced the magnitude of reverberation artifacts by 31 ± 14% and comet tail artifacts by 40-70%. The echogenic coating also improved needle contrast, measured by the relative differences in signal intensity compared with the adjacent environment, when needles were angled up to 30An echogenic surface coating reduced imaging artifacts and improved needle conspicuity under realistic clinical conditions for ultrasound-based prostate or gynecological brachytherapy. The improved conspicuity has the potential to improve the efficiency of needle placement and the accuracy of needle position digitization during brachytherapy procedures. This article is protected by copyright. All rights reserved.

OBJECTIVES—: To quantify the bias of shear wave speed (SWS) measurements between different commercial ultrasonic shear elasticity systems and a magnetic resonance elastography (MRE) system in elastic and viscoelastic phantoms. METHODS—: Two elastic phantoms, representing healthy through fibrotic liver, were measured with 5 different ultrasound platforms, and 3 viscoelastic phantoms, representing healthy through fibrotic liver tissue, were measured with 12 different ultrasound platforms. Measurements were performed with different systems at different sites, at 3 focal depths, and with different appraisers. The SWS bias across the systems was quantified as a function of the system, site, focal depth, and appraiser. A single MRE research system was also used to characterize these phantoms using discrete frequencies from 60 to 500 Hz. RESULTS—: The SWS from different systems had mean difference 95% confidence intervals of ±0.145 m/s (±9.6%) across both elastic phantoms and ± 0.340 m/s (±15.3%) across the viscoelastic phantoms. The focal depth and appraiser were less significant sources of SWS variability than the system and site. Magnetic resonance elastography best matched the ultrasonic SWS in the viscoelastic phantoms using a 140 Hz source but had a − 0.27 ± 0.027-m/s (−12.2% ± 1.2%) bias when using the clinically implemented 60-Hz vibration source. CONCLUSIONS—: Shear wave speed reconstruction across different manufacturer systems is more consistent in elastic than viscoelastic phantoms, with a mean difference bias of < ±10% in all cases. Magnetic resonance elastographic measurements in the elastic and viscoelastic phantoms best match the ultrasound systems with a 140-Hz excitation but have a significant negative bias operating at 60 Hz. This study establishes a foundation for meaningful comparison of SWS measurements made with different platforms.

Electrically accelerated self-healable poly(ionic liquids) copolymers that exhibit resistor-capacitor (RC) circuit properties are developed. At low alternating current (AC) frequencies these materials behave as a resistor (R), whereas at higher frequencies as a capacitor (C). These properties are attributed to a combination of dipolar and electrostatic interactions in (1-[(2-methacryloyloxy)ethyl]-3-butylimidazolium bis(trifluoromethyl-sulfonyl)imide) copolymerized with methyl methacrylate (MMA) monomers to form p(MEBIm-TSFI/MMA)] copolymers. When the monomer molar ratio (MEBIm-TSFI:MMA) is 40/60, these copolymers are capable of undergoing multiple damage-repair cycles and self-healing is accelerated by the application of alternating 1.0-4.0 V electric field (EF). Self-healing in the absence of EFs is facilitated by van der Waals (vdW) interactions, but the application of AC EF induces back and forth movement of charges against the opposing force that result in dithering of electrostatic dipoles giving rise to interchain physical crosslinks. Electrostatic inter- and intrachain interactions facilitated by copolymerization of ionic liquid monomers with typically dielectric acrylic-based monomers result in enhanced cohesive energy densities that accelerate the recovery of vdW forces facilitating self-healing. Incorporating ionic liquids into commodity polymers offers promising uses as green conducting solid polyelectrolytes in self-healable energy storage, energy-harvesting devices, and many other applications.

Although dipolar forces between copolymer chains are relatively weak, they result in ubiquitous inter‐ and/or intramolecular interactions which are particularly critical in achieving the mechanical integrity of polymeric materials. In this study, a route is developed to obtain self‐healable properties in thermoplastic copolymers that rely on noncovalent dipolar interactions present in essentially all macromolecules and particularly fluorine‐containing copolymers. The combination of dipolar interactions between C─F and C═O bonds as well as CH2/CH3 entities facilitates self‐healing without external intervention. The presence of dipole‐dipole, dipole‐induced dipole, and induced‐dipole induced dipole interactions leads to a viscoelastic response that controls macroscopic autonomous multicycle self‐healing of fluorinated copolymers under ambient conditions. Energetically favorable dipolar forces attributed to monomer sequence and monomer molar ratios induces desirable copolymer tacticities, enabling entropic energy recovery stored during mechanical damage. The use of dipolar forces instead of chemical or physical modifications not only eliminates additional alternations enabling multiple damage‐repair cycles but also provides further opportunity for designing self‐healable commodity thermoplastics. These materials may offer numerous applications, ranging from the use in electronics, ion batteries, H2 fuel dispense hoses to self‐healable pet toys, packaging, paints and coatings, and many others., Fluorine‐containing acrylic‐based copolymers that rely on noncovalent dipolar interactions between CH2/CH3 entities as well as C─F and C═O bonds result in a viscoelastic response leading to macroscopic autonomous self‐healing. The presence of favorable dipolar forces is attributed to monomer sequences and monomer molar ratios facilitating desirable copolymer tacticity, enabling entropic energy storage, and recovery during multiple damage‐repair cycles.

Stem/progenitor cell transplantation delivery of astrocytes is a potentially powerful strategy for spinal cord injury (SCI). Axon extension into SCI lesions that occur spontaneously or in response to experimental manipulations is often observed along endogenous astrocyte "bridges," suggesting that augmenting this response via astrocyte lineage transplantation can enhance axon regrowth. Given the importance of respiratory dysfunction post-SCI, we transplanted glial-restricted precursors (GRPs)-a class of lineage-restricted astrocyte progenitors-into the C2 hemisection model and evaluated effects on diaphragm function and the growth response of descending rostral ventral respiratory group (rVRG) axons that innervate phrenic motor neurons (PhMNs). GRPs survived long term and efficiently differentiated into astrocytes in injured spinal cord. GRPs promoted significant recovery of diaphragm electromyography amplitudes and stimulated robust regeneration of injured rVRG axons. Although rVRG fibers extended across the lesion, no regrowing axons re-entered caudal spinal cord to reinnervate PhMNs, suggesting that this regeneration response-although impressive-was not responsible for recovery. Within ipsilateral C3-5 ventral horn (PhMN location), GRPs induced substantial sprouting of spared fibers originating in contralateral rVRG and 5-HT axons that are important for regulating PhMN excitability; this sprouting was likely involved in functional effects of GRPs. Finally, GRPs reduced the macrophage response (which plays a key role in inducing axon retraction and limiting regrowth) both within the hemisection and at intact caudal spinal cord surrounding PhMNs. These findings demonstrate that astrocyte progenitor transplantation promotes significant plasticity of rVRG-PhMN circuitry and restoration of diaphragm function and suggest that these effects may be in part through immunomodulation., National Institute of Neurological Disorders and Stroke. Grant Number: 2R01NS079702‐06 (to A.C.L.) Paralyzed Veterans of America Research Foundation. Grant Numbers: Grant 476686 (to A.C.L), 476686 NINDS. Grant Number: 2R01NS079702‐06

Known for their adaptability to surroundings, capability of transport control of molecules, or the ability of converting one type of energy to another as a result of external or internal stimuli, responsive polymers play a significant role in advancing scientific discoveries that may lead to an array of diverge applications. This review outlines recent advances in the developments of selected commodity polymers equipped with stimuli-responsiveness to temperature, pH, ionic strength, enzyme or glucose levels, carbon dioxide, water, redox agents, electromagnetic radiation, or electric and magnetic fields. Utilized diverse applications ranging from drug delivery to biosensing, dynamic structural components to color-changing coatings, this review focuses on commodity acrylics, epoxies, esters, carbonates, urethanes, and siloxane-based polymers containing responsive elements built into their architecture. In the context of stimuli-responsive chemistries, current technological advances as well as a critical outline of future opportunities and applications are also tackled.

Objectives The purpose of this study was to systematically investigate the feasible echocardiographic views for human transthoracic cardiac shear wave elastography (SWE) and the impact of myocardial anisotropy on myocardial stiffness measurements. Methods A novel cardiac SWE technique using pulse inversion harmonic imaging and time-aligned sequential tracking was developed for this study. The technique can measure the quantitative local myocardial stiffness noninvasively. Ten healthy volunteers were recruited and scanned by the proposed technique 3 times on 3 different days. Results Seven combinations of echocardiographic views and left ventricular (LV) segments were found to be feasible for LV diastolic stiffness measurements: basal interventricular septum under parasternal short- and long-axis views; mid interventricular septum under parasternal short- and long-axis views; anterior LV free wall under parasternal short- and long-axis views; and posterior LV free wall under a parasternal short-axis view. Statistical analyses showed good repeatability of LV diastolic stiffness measurements among 3 different days from 70% of the participants for the basal interventricular septum and posterior LV free wall short-axis views. On the same LV segment, the mean diastolic shear wave speed measurements from the short-axis view were statistically different from the long-axis measurements: 1.82 versus 1.29 m/s for the basal interventricular septum; 1.81 versus 1.45 m/s for mid interventricular septum; and 1.96 versus 1.77 m/s for the anterior LV free wall, indicating that myocardial anisotropy plays a substantial role in LV diastolic stiffness measurements. Conclusions These results establish the preliminary normal range of LV diastolic stiffness under different scan views and provide important guidance for future clinical studies using cardiac SWE.

Objectives To investigate the correlation between 2-dimensional (2D) ultrasound shear wave elastography (SWE) and magnetic resonance elastography (MRE) in liver stiffness measurement and the diagnostic performance of 2D SWE for liver fibrosis when imaging from different intercostal spaces and using MRE as the reference standard. Methods Two-dimensional SWE was performed on 47 patients. One patient was excluded from the study. Each of the remaining 46 patients underwent same-day MRE for clinical purposes. The study was compliant with the Health Insurance Portability and Accountability Act and approved by the Institutional Review Board. Informed consent was obtained from each patient. Two-dimensional SWE measurements were acquired from the ninth, eighth, and seventh intercostal spaces. The correlation with MRE was calculated at each intercostal space and multiple intercostal spaces combined. The performance of 2D SWE in diagnosing liver fibrosis was evaluated by receiver operating characteristic curve analysis using MRE as the standard. Results The 47 patients who initially underwent 2D SWE included 22 female and 25 male patients (age range, 19-77 years). The highest correlation between 2D SWE and MRE was from the eighth and seventh intercostal spaces (r = 0.68-0.76). The ranges of the areas under the receiver operating characteristic curves for separating normal or inflamed livers from fibrotic livers using MRE as the clinical reference were 0.84 to 0.92 when using the eighth and seventh intercostal spaces individually and 0.89 to 0.90 when combined. Conclusions The results suggest that 2D SWE and MRE are well correlated when SWE is performed at the eighth and seventh intercostal spaces. The ninth intercostal space is less reliable for diagnosing fibrosis with 2D SWE. Combining measurements from multiple intercostal spaces does not significantly improve the performance of 2D SWE for detection of fibrosis.

Sugar moieties were incorporated into cross-linked polyurethane (PUR) networks in an effort to achieve self-repairing in the presence of atmospheric carbon dioxide (CO2) and water (H2O). When methyl-α-D-glucopyranoside (MGP) molecules are reacted with hexamethylene diisocyanate trimer (HDI) and polyethylene glycol (PEG) to form cross-linked MGP-polyurethane (PUR) networks, these materials are capable of self-repairing in air. This process requires atmospheric amounts of CO2 and H2O, thus resembling plant behavior of carbon fixation during the photosynthesis cycle. Molecular processes responsible for this unique self-repair process involve physical diffusion of cleaved network segments as well as the formation of carbonate and urethane linkages. Unlike plants, MGP-PUR networks require no photo-initiated reactions, and they are thus capable of repair in darkness under atmospheric conditions.

Preface SYNTHETIC AND PHYSICOCHEMICAL ASPECTS OF ADVANCED STIMULI-RESPONSIVE POLYMERS Introduction Controlled Free Radical Polymerization of Stimuli-Responsive Polymers Synthesis of Stimuli-Responsive Colloidal Dispersions Summary BIOLOGICAL- AND FIELD-RESPONSIVE POLYMERS: EXPANDING POTENTIAL IN SMART MATERIALS Introduction Biologically Responsive Polymer Systems Field-Responsive Polymers Conclusions SELF-OSCILLATING GELS AS STIMULI-RESPONSIVE MATERIALS Introduction Methodology Results and Discussions Conclusions SELF-REPAIRING POLYMERIC MATERIALS Introduction Damage and Repair Mechanisms in Polymers Summary STIMULI-DRIVEN ASSEMBLY OF CHROMOGENIC DYE MOLECULES: A VERSATILE APPROACH FOR THE DESIGN OF RESPONSIVE POLYMERS Introduction Excimer-Forming Sensor Molecules Fluorescent Mechanochromic Sensors Thermochromic Sensors Chemical Sensing with Excimer-Forming Dyes Summary and Outlook SWITCHABLE SURFACE APPROACHES Introduction Electroactive Materials Photoresponsive Materials pH-Responsive Materials Thermoresponsive Materials Switchable Surfaces Based on Supramolecular Shuttles Switchable Surfaces Comprising DNA and Peptide Monolayers Summary LAYER-BY-LAYER SELF-ASSEMBLED MULTILAYER STIMULI-RESPONSIVE POLYMERIC FILMS Introduction Fabrication of Multilayer Polymer Coatings Response of Multilayer Polymer Coatings to External Stimuli Conclusion and Outlook PHOTOREFRACTIVE POLYMERS Introduction The Photorefractive Effect in Polymers The Two-Beam Coupling Effect High-Performance Photorefractive Polymers Experimental Techniques Conclusions PHOTOCHROMIC RESONSES IN POLYMER MATRICES Introduction Photochromic Polymeric Systems Photochromic Systems Outlook of Photochromic Materials COVALENT BONDING OF FUNCTIONAL COATINGS ON CONDUCTIVE MATERIALS: THE ELECTROCHEMICAL APPROACH Introduction Electrodeposited Coatings Electrografted Coatings Compounds Requiring an Anodic Process Compounds Requiring a Cathodic Process Conclusions

Although the technological and scientific importance of functional polymers has been well established over the last few decades, currently much attention has been focused on stimuli-responsive polymers. This group of materials is of particular interest owing to their ability to respond to internal and/or external chemicophysical stimuli that is often manifested by the large macroscopic responses [1]. Stimuli-responsive polymers are also referred to as smart, sensitive, or intelligent polymers [2, 3], just to name a few. These terms are loosely used under the same stimuli-responsiveness umbrella attributed to selective polymer segments or the entire polymer backbones that exhibit stimuli-responsive characteristics. Notwithstanding the scientific challenges of designing stimuli-responsive polymers, the main technological interest is in the numerous applications ranging from reactive surfaces [4] to drug-delivery and separation systems [5], or from chemomechanical actuators [6] to other applications that have been extensively explored [7, 8]. In contrast to traditional polymers, in order to incorporate responsive components, it is necessary to copolymerize responsive blocks into a polymer or copolymer backbone [8]. For this reason, the preparation of well-defined block copolymers with different architectures is essential: for example, grafting amphiphilic blocks to a hydrophobic polymer backbone [9]. Using living anionic [10] and cationic polymerizations [11] as well as controlled radical polymerizations (CRPs) techniques [12], wide ranges of block copolymers were synthesized. However, the development of the CRP based on the concept of reversible chain termination minimizes the disadvantage of the free-radical polymerization, thus permitting the synthesis of well-defined block copolymer structures [13]. The growing demand for well-defined and functional soft materials in a nanoscale range has led to a significant increase of procedures that combine architectural control with the flexibility of incorporating functional groups. In view of these considerations, there has been a significant quest for elucidating a variety of controlled polymerization strategies, which resulted in nitroxide-mediated radical polymerization (NMRP) [14–16], atom transfer

Cilia are wavy hair-like structures that extend outward from surfaces of various organisms. They are classified into two general categories, primary cilia, which exhibit sensing attributes, and motile cilia, which exert mechanical forces. A new poly(2-(N,N-dimethylamino)ethyl methacrylate-co-n-butyl acrylate-co-N,N-(dimethylamino) azobenzene acrylamide) (p(DMAEMA/nBA/ DMAAZOAm) copolymer is prepared using colloidal synthesis, which, upon coalescence, form films capable of generating surfaces with cilia-like features. While film morphological features allow the formation of wavy whiskers, the chemical composition ofthe copolymer facilitates chemical, thermal, and electromagnetic responses manifested by simultaneous shape and color changes as well as excitation wavelength dependent fluorescence. These studies demonstrate that synthetically produced polymeric films can exhibit combined thermal, chemical, and electromagnetic sensing leading to locomotive and color responses, which may find numerous applications in sensing devices, intelligent actuators, defensive mechanisms, and others.

Repair of physically separated thermoplastic polymers containing γ-Fe2 O3 nanoparticles without sacrificing their mechanical properties is achieved by applying an oscillating magnetic field. As γ-Fe2 O3 nanoparticles oscillate at the frequency of the magnetic field, localized amorphous flow occur, and a permanent repair of physically separated polymeric films is achieved.

Recent advances in developments of anticoagulant, antifouling, and antimicrobial polymeric surfaces with the focus on surface modifications of polymeric materials as well as the influence of nanosize materials on interactions with biological systems are discussed. Controllable surface modifications using microwave plasma reactions in the presence of maleic anhydride provides a platform for attaching acid groups to inert polymeric surfaces which serves as a reactive anchor for further reactions. To effectively attach bioactive species inhibiting interactions with biological systems it is often necessary to attach a molecular spacer that facilitates mobility to terminal bioactive species.

Amphiphilic copolymer networks were prepared from hyperbranched fluoropolymer (HBFP*, Mn = 38 kDa, by atom transfer radical-self condensing vinyl copolymerization) and linear diamine-terminated poly(ethylene glycol) (DA-PEG, Mn = 1,630 Da). Model studies found that the crosslinking mechanism occurred at ambient temperature as a result of reaction between DA-PEG and the benzylic chlorides of HBFP*. These networks underwent covalent attachment to glass microscope slides derivatized with 3-aminopropyltriethoxysilane, whereupon gel percent studies at various weight percentages of DA-PEG to HBFP* found that curing could be achieved at lower temperatures and shortened time periods relative to the previously reported parent HBFP–PEG system. Thermogravimetric analysis revealed that the crosslinked materials gave no evident mass loss up to 250 °C. Differential scanning calorimetry of the complex amphiphilic networks showed a suppressed glass transition temperature, relative to that observed for neat HBFP*, and multiple melting DA-PEG endotherm(s) near 30 °C. The films possessed a topographically-complex surface with features that increased in tandem with an increase in the ratio of DA-PEG to HBFP*, as detected by atomic force microscopy and quantified by increased rms roughness values. Internal reflection infrared imaging revealed a heterogeneous surface composition and confirmed that the domain sizes increased as the weight percent of DA-PEG increased. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4782–4794, 2006

BACKGROUND It has been shown that spinal reflexes such as the H-reflex predict motor responses to painful stimuli better than cortical parameters derived from the EEG. The precise concentration-dependence of H-reflex suppression by anaesthetics, however, is not known. Here we investigated this concentration-response relationship and the equilibration between the alveolar and the effect compartment for sevoflurane. METHODS In 26 patients, the H-reflex was recorded at a frequency of 0.1 Hz while anaesthesia was induced and maintained with sevoflurane at increasing and decreasing concentrations. Population pharmacodynamic modelling was performed using the NONMEM software package, yielding population mean parameters as well as indicators of interindividual variability. RESULTS Suppression of H-reflex amplitude occurred at lower concentrations (mean EC(50) 1.04 +/- 0.10 vol%, SE of NONMEM estimate) than the effect on either BIS or SEF(95) of the EEG (mean EC(50) 1.55 +/- 0.08 and 1.72 +/- 0.18 vol%, respectively), and exhibited a higher interindividual variability. The concentration-response function for the H-reflex was also steeper (mean e 2.83 +/- 0.25). In addition, the equilibration between alveolar and effect compartment was slower for the H-reflex (mean k(e0) 0.15 +/- 0.01 min(-1)) than for BIS or SEF(95) (mean k(e0) 0.22 +/- 0.02 and 0.41 +/- 0.05 min(-1)). CONCLUSION The differences in EC(50) and slope of the concentration-response relationships for H-reflex suppression and the EEG parameters point to different underlying mechanisms. In addition, the differences in time constant for equilibration between alveolar and effect compartment confirm the notion that immobility is caused at a different anatomic site than suppression of the EEG.

Fourier transform infrared spectroscopy was used to study the kinetics of noncatalyzed and catalyzed polyurethanes. These studies show that for noncatalyzed acrylic polyol–hexamethylene diisocyanate (HDI) trimer reactions, the reactions between OH and NCO of HDI exhibit second-order kinetics, with first-order kinetics with respect to NCO and OH. On the other hand, when dibutyltin dilaurate (DBTDL) is used as a catalyst in acrylic polyol–HDI trimer reactions, the reaction rate is first order with respect to NCO and 0.5 order in OH and DBTDL concentrations. A mechanism for the catalyzed acrylic polyol–HDI trimer crosslinking reactions is proposed and it appears that an equilibrium involving associations between OH and DBTDL exists, resulting in the formation of an active anion, which interacts with NCO to generate polyurethanes. To further verify this mechanism, the influence of acidity on the reaction rate constant was investigated. When the acidity of the system is increased, retardation of urethane formation occurs. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 2322–2329, 2002

There is increasing evidence that stimuli-responsive nanomaterials have become significantly critical components of modern materials design and technological developments. Recent advances in synthesis and fabrication of stimuli-responsive polymeric nanoparticles with built-in stimuli-responsive components (Part A) and surface modifications of functional nanoparticles that facilitate responsiveness (Part B) are outlined here. The synthesis and construction of stimuli-responsive spherical, core-shell, concentric, hollow, Janus, gibbous/inverse gibbous, and cocklebur morphologies are discussed in Part A, with the focus on shape, color, or size changes resulting from external stimuli. Although inorganic/metallic nanoparticles exhibit many useful properties, including thermal or electrical conductivity, catalytic activity, or magnetic properties, their assemblies and formation of higher order constructs are often enhanced by surface modifications. Section B focuses on selected surface reactions that lead to responsiveness achieved by decorating nanoparticles with stimuli-responsive polymers. Although grafting-to and grafting-from dominate these synthetic efforts, there are opportunities for developing novel synthetic approaches facilitating controllable recognition, signaling, or sequential responses. Many nanotechnologies utilize a combination of organic and inorganic phases to produce ceramic or metallic nanoparticles. One can envision the development of new properties by combining inorganic (metals, metal oxides) and organic (polymer) phases into one nanoparticle designated as "ceramers" (inorganics) and "metamers" (metallic).

1. Fundamental to the understanding of CNS function is the question of how individual neurons integrate multiple synaptic inputs into an output consisting of a sequence of action potentials carrying information coded as spike frequency. The availability for activation of neuronal Na(+) channels is critical for this process and is regulated both by fast and slow inactivation processes. Here, we have investigated slow inactivation processes in detail in hippocampal neurons. 2. Slow inactivation was induced by prolonged (10-300 s) step depolarisations to -10 mV at room temperature. In isolated hippocampal dentate granule cells (DGCs), recovery from this inactivation was biexponential, with time constants for the two phases of slow inactivation tau(slow,1) and tau(slow,2) ranging from 1 to 10 s and 20 to 50 s, respectively. Both (slow,1) and tau(slow,2) were related to the duration of prior depolarisation by a power law function of the form tau(t) = a (t/a)b, where t is the duration of the depolarisation, a is a constant kinetic setpoint and b is a scaling power. This analysis yielded values of a = 0.034 s and b = 0.62 for tau(slow,1) and a = 24 s and b = 0.30 for tau(slow,2) in the rat. 3. When a train of action potential-like depolarisations of different frequencies (50, 100, 200 Hz) was used to induce inactivation, a similar relationship was found between the frequency of depolarisation and both tau(slow,1) and tau(slow,2) (a = 0.58 s, b = 0.39 for tau(slow,1) and a = 3.77 s and b = 0.42 for tau(slow,2)). 4. Using nucleated patches from rat hippocampal slices, we have addressed possible cell specific differences in slow inactivation. In fast-spiking basket cells a similar scaling relationship can be found (a = 3.54 s and b = 0.39) as in nucleated patches from DGCs (a = 2.3 s and b = 0.48) and non-fast-spiking hilar neurons (a = 2.57 s and b = 0.49). 5. Likewise, comparison of human and rat granule cells showed that properties of ultra-slow recovery from inactivation are conserved across species. In both species ultra-slow recovery was biexponential with both tau(slow,1) and tau(slow,2) being related to the duration of depolarisation t, with a = 0.63 s and b = 0.44 for tau(slow,1) and a = 25 s and b = 0.37 for tau(slow,2) for the human subject. 6. In summary, we describe in detail how the biophysical properties of Na(+) channels result in a complex interrelationship between availability of sodium channels and membrane potential or action potential frequency that may contribute to temporal integration on a time scale of seconds to minutes in different types of hippocampal neurons.

Unique shape-memory transitions manifested by directional extension and subsequent retraction in polymers are attributed to stored conformational entropy. This behavior is quantified in terms of stored (ΔS S ) entropic energy density, the maximum strain (emax ), and stress (σSF at emax ). This concept allows quantitative assessments of the shape-memory effect (SME) and can be utilized in any material that exhibits a glass-transition temperature (T g ) and a rubbery plateau.

Crosslinking reactions and stratification processes in polyurethane films were investigated using attenuated total reflectance (ATR) FTIR spectroscopy. The HDI trimer levels near the film–substrate (F–S) interface appear to increase at the early stages of reactions, and after reaching a maximum, decrease. This is attributed to solvent depletion and subsequent film shrinkage, thus causing local NCO concentration changes. At the later stages of crosslinking reactions, stratification of the 1,6-hexamethylene diisocyanate (HDI) trimer occurs, with higher concentration levels at shallower penetration depths from the F–S interface. At the same time, NCO-containing groups assume preferentially parallel orientation to the F–S interface. On the other hand, H-bonded carbonyl groups tend to orient themselves in a perpendicular direction. Quantitative analysis indicates that at extended reaction times the amount of H-bonded CO groups at shallower penetration depths increases and their orientation tends to be more random, which is correlated with migration toward the F–S interface. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2045–2054, 2001

Behavior of macromolecules near surfaces and interfaces of polymeric thin films and coatings may play a vital role in numerous applications. Therefore, understanding of molecular level processes responsible for durability, adhesion, and many other macroscopic processes is of a particular importance. This presentation will focus on stratification processes in multi-component polymeric films, with particular emphasis to polymer-surfactant interactions in latexes, responsiveness of individual components during coalescence of water-borne polyurethanes, and behavior of thermoplastic olefins (TPO). The presence of macromolecular arrange-ments and interactions among various components near the film-air (F-A) and the film-substrate (F-S) interfaces can be effectively monitored using attenuated total reflectance (ATR) and step-scan photoacoustic (SSPA) Fourier transform infrared (FT-IR) spectroscopy. Both approaches are capable of obtaining infonnation from various surface depths and complement each other if one seeks molecular level infonnation from 0 -150 μm into the film. If one combines ATR and PA information with IR and/or Raman surface imaging, it is possible to obtain a 3-dimensional representation of polymeric films.

Summary: Purpose: Carbamazepine (CBZ) is a well-established drug in the therapy of temporal lobe epilepsy (TLE). The anticonvulsant action of CBZ has been explained mainly by use-dependent effects on voltage-dependent Na+ channels in various nonhuman cell types. However, it is unclear whether Na+ currents in neurons within the focal epileptogenic area of patients with medically intractable TLE show similar characteristics. Methods: Therefore we used the whole-cell patch-clamp technique to investigate the effects of CBZ on voltage-dependent Na+ currents in 23 acutely isolated dentate granule cells (DGCs) from the resected hippocampus of eight patients with medically intractable TLE. Results: As in findings in animal preparations, CBZ significantly reduced the amplitude of the Na+ current and significantly shifted the current-voltage dependence of the steady-state inactivation in the hyperpolarizing direction. In contrast, the rapid component of the recovery from inactivation of the Na+ currents was not affected by CBZ. In addition, the reduction of the Na+ current amplitude observed during repetitive stimulation with depolarizing pulses was not significantly altered by CBZ. Conclusions: In summary, CBZ strongly affects the voltage-dependent steady-state inactivation, with no effects on the removal of inactivation in Na+ currents of human DGCs. In spite of the lack of suitable control material, the CBZ insensitivity of the removal of inactivation may be an interesting concept to explain the medically intractable TLE in these patients.

Although there are various forms of energy available for conducting surface and interfacial reactions, microwave plasma energy is an attractive means for surface modifications because it is fast and it usually does not alter bulk properties. In this study, a closed-system microwave plasma reactor was used to react imidazole molecules to poly(vinyl chloride) (PVC) surfaces. Newly created surfaces were analyzed using attenuated total reflectance (ATR) Fourier-transformed infrared (FTIR) spectroscopy. These studies show that surface reactions on PVC are heavily dependent upon a prior thermal history of the PVC substrate. It appears that the plasma reactions on hot-pressed PVC not only result in the development of CH2 linkages, but a significant increase of crystallinity in the hot-pressed PVC inhibits the reactivity of imidazole to the PVC surface. On the other hand, for a solvent-cast PVC with a significantly lower surface crystalline phase content, imidazole reacts to the PVC surface through CC bond opening. The amount of imidazole reacted to the PVC surface changes with the depth from the surface. Using quantitative ATR FTIR spectroscopy, imidazole content can be quantified, and its concentrations are in the 10−6 mol/cm2 range at about 0.8–1.2 μm for the PVC surface. A mechanism of the PVC–imidazole reactions is also proposed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 1–6, 1999

Surfactant-latex molecular level interactions as well as transient effects during latex film formation play an important role in latex technology. This review article focuses on the siloxane effects on anionic sodium dioctylsulfosuccinate (SDOSS) surfactant exudation during latex coalescence and quantitative analysis of SDOSS distribution at the both film-air (F-A) and film-substrate (F-S) interfaces. Attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy was utilized for characterization of the interactions between SDOSS and styrene-butyl acrylate latex copolymers. In addition, studies of SDOSS stratification along with depth-profiling analysis during latex film formation utilizing step-scan photoacoustic (S 2 -PAS) FTIR spectroscopy illustrate that SDOSS content is enriched at the F-A interface and decreases as the penetration depth increases across the latex film thickness.

1 Properties of voltage-dependent Na+ currents were investigated in forty-two dentate granule cells (DGCs) acutely isolated from the resected hippocampus of twenty patients with therapy-refractory temporal lobe epilepsy (TLE) using the whole-cell patch-clamp technique. 2 Depolarizing voltage commands elicited large, rapidly activating and inactivating Na+ currents (140 pS μm−2; 163 mm extracellular Na+) that were reduced in amplitude by lowering the Na+ gradient (43 mm extracellular Na+). At low temperatures (8-12 °C), the time course of Na+ currents slowed and could be well described by the model of Hodgkin & Huxley. 3 Na+ currents were reversibly blocked by tetrodotoxin (TTX) and saxitoxin (STX) with a half-maximal block of 4.7 and 2.6 nm, respectively. In order to reduce series resistance errors, the Na+ current was partially blocked by low toxin concentrations (10-15 nm) in the experiments described below. Under these conditions, Na+ currents showed a threshold of activation of about -50 mV, and the voltages of half-maximal activation and inactivation were -29 and -55 mV, respectively. 4 The time course of recovery from inactivation could be described with a double-exponential function (time constants, 3-20 and 60-200 ms). The rapid and slow time constants showed a distinct voltage dependence with maximal values around -55 and -80 mV, respectively. These properties contributed to a reduction of the Na+ currents during repetitive stimulation that was more pronounced with higher stimulation frequencies and also showed a dependence on the holding potential. 5 In summary, the most striking features of DGC Na+ currents were the large current density and the presence of a current component showing a slow recovery from inactivation. Our data provide a basis for comparison with properties of Na+ currents in animal models of epilepsy, and for the study of drug actions in therapy-refractory epilepsy.

Human CNS sodium channels provide a protein model system for our continuing study of anaesthetic drug interactions at the molecular level. The impact of ethanol, an alcohol with general anaesthetic properties, on sodium channel function and their significance for the overall anaesthetic effect was quantified. Sodium channels from human brain cortex tissue were incorporated into voltage-clamped planar lipid bilayers in the presence of batrachotoxin and studied at various ethanol concentrations (0.085 – 0.84 M). Ethanol caused a concentration-dependent and membrane potential independent reduction of the single channel amplitude (major effect) and of the fractional channel open-time (minor effect) with no effect on channel steady-state activation. Severe membrane perturbing effects at the highest ethanol levels terminated the measurements. The weighted computer fit of the concentration-response curve with an estimate of a maximal conductance block of 40% yielded an EC50 of 1.03 M. The EC50 for the 100% maximal theoretical block was calculated to be 3.3 M. These effects occurred at levels far beyond toxic human serum levels (0.1 M; 0.5%). Thus, the human CNS sodium channel is not a main target site for the clinical effects of ethanol and other, more sensitive central receptors are involved in ethanol's mechanism of action. © 1997 John Wiley & Sons, Ltd.

This study addresses the effect of particle structure and composition on the mobility and orientation of sodium dioctyl sulfosuccinate (SDOSS) surfactant molecules in polybutyl acrylate/polystyrene core/shell-type latex films near the film-air (F-A) and film-substrate (F-S) interfaces. In an effort to determine how the surface tension of the substrate influences the migration and orientation of the SDOSS surfactant molecules, polytetrafluoroethylene (PTFE) and liquid Hg substrates were used. It appears that, as the concentration of styrene monomer in the latex increases, SDOSS migrates toward the F-A and F-S interfaces. As the surface tension of the substrate changes from 18 mN/m in PTFE to 400 mN/m for liquid Hg, the surfactant also migrates toward the two interfaces. For the latex particles composed of 50%/50% styrene/n-butyl acrylate (Sty/n-BA) latex copolymer, the hydrophilic SO−3Na+ groups of SDOSS surfactant are present primarily near the F-A interface, and they appear to be mostly parallel to the surface for the films cast on the PTFE surface. For the latex films cast on the liquid Hg surface, the SDOSS hydrophilic surfactant groups are found to be preferentially parallel near the F-A interface and perpendicular near the F-S interface. These studies indicate that the surfactant concentration and its orientation throughout the latex film change as a function of the initial monomer composition and the surface tension of the substrate. Furthermore, the SDOSS concentration appears to vary with depth into the latex interfaces. © 1996 John Wiley & Sons, Inc.

This study focuses on the behavior of sodium dioctylsulfosuccinate (SDOSS) in 50/50 w/w % polystyrene/poly(butyl acrylate) (p-Sty/p-BA) latex films. Specifically, mobility and orientation are examined in the context of the film formation by the use of dynamic mechanical thermal analysis and attenuated total reflectance (ATR) Fourier transform infrared (FT-IR) spectroscopy. While for the homopolymer blends of p-Sty and p-BA, two T g values resulting from a phase separation of p-Sty and p-BA phases are observed, only a single T g is detected for a copolymer of the same mixture, indicating a single phase within the film. ATR FTIR spectroscopic data indicate that the phase separation of p-Sty and p-BA blends does not occur uniformly across the film. After coalescence, p-Sty particles produce a significant degree of stratification at approximately 1.6 μm from the film surface. At this depth, the polystyrene rings assume preferentially parallel orientation to the film surface. At the same time, the hydrophilic groups of SDOSS surfactant (SO 3 - Na + ) are oriented preferentiallyparallel to the surface. Under high relative humidity conditions, water is able to diffuse into the film and swells the surface layers, thus causing them to expand. As a result, the top, predominately poly-n-BA surface becomes thicker, and p-Sty phase appears to be near 2.3 μm from the surface. The polystyrene rings maintain their preferential parallel orientation to the surface, but the hydrophilic groups of SDOSS are able to diffuse into the film with the water uptake and are thus not present at the film-air interface.

Migration and concentration levels of sodium dioctylsulfosuccinate (SDOSS) surfactant molecules in 50%/50% styrene/butyl acrylate latex were detected at the film-substrate (F-S) and film-air (F-A) interfaces in mono- and double-layered films. For the purpose of quantitative analysis, absorption coefficients of the 1,056 and 1,046 cm -1 bands attributed to the SO 3 - Na + ... HOOC and SO 3 - Na + ... H 2 O associations, respectively, were determined. Using group theory formalism, local geometries of the SO 3 - Na + hydrophilic groups of SDOSS can be predicted. The analysis is extended to the 1,261 and 1,209 cm -1 bands resulting from the S - O asymmetric stretching vibrations, due to the same SO 3 - Na + ... HOOC and SO 3 - Na + ... H 2 O associations, and to the 1,290 and 1,236 cm -1 bands, due to asymmetric stretching modes of hydrophobic tails of the SDOSS. By the use of polarization attenuated total reflectance Fourier transform infrared (ATR FT-IR) experiments, these studies show that hydrophilic SO 3 - Na + ends on SDOSS are preferentially parallel to the film surface. At the same time, hydrophobic tails are perpendicular to the surface. The assessment of the amounts of SDOSS at the F-S and F-A interfaces was obtained by quantitative ATR FTIR analysis, which was extended to the silicone-modified double-layer latex films. In this case, the concentration of SDOSS molecules decreases as the depth of penetration increases. The highest concentrations of SDOSS molecules are detected at the shallowest depths near the surface of the top layer and the interfacial regions between the latex layers.

These studies examine how various latex copolymer compositions, ranging from 100% n-BA to 50%/50% Sty/n-BA, may influence sodium dioctylsulfosuccinate (SDOSS) mobility, diffusion, and orientation near the film–air (F–A) and film–substrate (F–S) interfaces. Polarized attenuated total reflection Fourier transform infrared spectroscopy is utilized to examine the surfactant behavior in Sty/n–BA latexes at the F–A and F–S interfaces. Based on the analysis developed for the purpose of these studies, the highest concentration of SDOSS is detected near the F–A interface for 50%/50% Sty/n-BA compositions. However, when the content of styrene in Sty/n-BA compositions. However, when the content of styrene in Sty/n-BA copolymer is diminished, the highest content of SDOSS is detected near the F–S interface. This behavior is particularly evident for 100% poly(n-BA) latexes. When SDOSS molecules are near the F–A and F–S interfaces, the SO3−Na+ hydrophilic ends are preferentially parallel to the surface, whereas hydrophobic tails are perpendicular. © 1996 John Wiley & Sons, Inc.

Polarized attenuated total reflection Fourier transform infrared spectroscopy was used to assess the mobility and orientation of sodium dioctylsulfosuccinate surfactant molecules at the film-air (F-A) and film-substrate (F-S) interfaces in electrodeposited latex films. Copolymer compositions ranging from 100% poly(n-BA) to 50%/50% Sty/n-BA were examined. When particle diameters are 50 and 100 nm, it appears that the 1046 cm -1 band is detected at the F-A and F-S interfaces. However, the 1056 cm -1 band is detected only for 50%/50% Sty/n-BA at the F-A interface with an average particle diameter of 100 nm. These studies allow us to determine that at the F-A interface, SDOSS surfactant molecules are preferentially parallel to the surface. Utilizing electrodeposition of latex particles, it is possible to slow the coalescence process, which ultimately allows us to follow diffusion and mobility of low-molecular-weight SDOSS surfactant molecules.

Exudation of sodium dioctylsulfosuccinate (SDOSS) surfactant molecules to the film–substrate (F–S) and film–air (F–A) interfaces in styrene/n-butyl acrylate (Sty/n-BA) latex films in the presence of trimethoxysilyl propylmethacrylate (MSMA) molecules was examined by polarized attenuated total reflection Fourier transform infrared (ATR FTIR) spectroscopy. It appears that SDOSS molecules are present at the F–A interface but are not detected at the F–S interface due to their displacement by MSMA. When the second layer of latex is deposited on the previously coalesced latex film with the same composition, SDOSS molecules are detected at the F–A of the top overlayer and the interfacial regions between both films. While the top film contains SDOSS surfactant molecules in their free or COOH hydrogen-bonded forms, the interfacial regions between the films exhibit arrays of SDOSS molecules preferentially parallel to the film surface. © 1996 John Wiley & Sons, Inc.

In an effort to establish to what extent transient effects prior to coalescence may influence mobility, distribution, and orientation of surfactant molecules after coalescence, poly(n-butyl acrylate) (n-BA) and polystyrene (Sty) were polymerized independently and mixed in a 5 : 1 ratio. It appears that if a mixture of the n-BA and Sty latex particles is allowed to stabilize prior to coalescence, the time of stabilization may have a significant effect not only on the distribution of SDOSS surfactant molecules across the coalesced film, but also on their orientation changes depending upon the stage of coalescence and the water front moving toward the surface. The coalescence of latex films was conducted under gaseous nitrogen and at 60% relative humidity. While the water front moves from the film-substrate upward, during this process, various segments of the surfactant molecule change their orientation. Near the F–A interface, hydrophobic segments are being reoriented from parallel to perpendicular, whereas preferentially parallel orientation exhibit hydrophylic SO−3 Na+ segments. When water molecules, however, diffuse out of the film, the surfactant molecules have no preferred orientation. © 1995 John Wiley & Sons, Inc.

The effects of homopolymer and copolymer compositions and structures in styrene/n-butyl acrylate (Sty/BA) latices on sodium dioctyl sulfosuccinate (SDOSS) surfactant mobility and its preferential concentration at the film-air (F-A) and film-substrate (F-S) interfaces were examined using attenuated total reflectance Fourier transform infrared (ATR FTIR) spectroscopy. It appears that the SDOSS concentration at the F-S interface is highest when the Sty/BA feed ratio is 50/50, and excess of Sty results in migration of SDOSS surfactant to the F-A interface. This behavior is attributed to the increased glass transition temperature and diminished compability between surfactant molecules and copolymer latex. This study also shows that the primary factors that influence exudation to either F-A or F-S interfaces are surface tension of the substrate, glass transition temperature, water flux during coalescence, and compatibility between latex components

A careful analysis of experimental data for a CO laser plasma shows a considerable depletion of the vibrational distribution of the electronic ground state in the energy range of the first excited electronic state a 3 Π. If the transferred population would reappear completely, the corresponding concentration of CO in the a 3 Π state should be observable by the most sensitive Faraday laser magnetic resonance technique. From the fact that no signal could be found, we deduce an upper concentration for CO a 3 Π which is then compared to a new refined model. This model takes into account both VE transfer rates between the ground state and the a 3 Π and a relaxation rate for the triplet state

This article, part VII in a series of latex studies, focuses on the effect of ethyl acrylate/methacrylic acid (EA/MAA) latex stability on the exudation of sodium dioctyl sulfosuccinate (SDOSS) surfactant molecules after coalescence. It is found that “aging” of the latex aqueous suspension causes excessive exudation of the surfactant molecules to the film-air interface. Upon exudation to the surface, the surfactant SO Na+ hydrophilic heads assemble in preferentially normal-to-the-surface directions, whereas hydrophobic aliphatic tails are randomly burred in the latex surface. ATR FT–IR spectroscopy and a particle size analysis are utilized to elucidate the effects of flocculation and coalescence on the surfactant mobility in latex films. It appears that flocculation, prior to coalescence, enhances exudation and mobility of the surfactant molecules. © 1993 John Wiley & Sons, Inc.

Polarized attenuated total reflection Fourier transform infrared (ATR FT–IR) spectroscopy was used to identify the mobility and surfactant exudation of sodium dioctyl sulfocuccinate (SDOSS) surfactant molecules to the film–air (F–A) and film–substrate (F–S) interfaces in styrene/n-butyl acrylate (Sty/n-BA) latex films. It was found that, depending upon the latex particle composition, the surfactant molecules could be driven to the F–A or F–S interfaces. The primary factors that governed the direction of exudation were the compatibility of the latex components, interfacial film-substrate surface tension, and the chemical composition of the latex particles. Concentration, as well as orientation, of the hydrophilic SONa+ surfactant ends changed as a function of depth and the latex particle composition. © 1993 John Wiley & Sons, Inc.