bluuebunny/crossref_metadata_2025_split huggingface dataset:
Third Order Nonlinear Optical Susceptibility of Trans-(CH)x: A Degenerate Ground State Conjugated Polymer
Authors: Sinclair M. , Moses D. , Akagi K. , Heeger A. J. 
Published: March 2011

ABSTRACTThe promise of conducting polymers as fast response nonlinear optical materials has been recently emphasized [1,3]. Polymers such as polyacetylene, polythiophene and the soluble (and processible) poly(3-alkylthienylenes) contain a high density of x-electrons, and they are known to exhibit photoinduced absorption and photoinduced bleaching, indicating major shifts of oscillator strength upon photoexcitation [2,4]. For polyacetylene, these nonlinear effects have been studied in detail in the picosecond [5a,b] and sub-picosecond [5c] time regime and correlated with the photoproduction of charge carriers through fast photoconductivity measurements [6]. The data have demonstrated ultra-fast response with nonlinear shifts in oscillator strength occurring at times of the order of 10-13 seconds. These resonant nonlinear optical properties are intrinsic; they originate from the nonlinearity of the self-localized photoexcitations [7] which characterize this class of polymers: solitons, polarons and bipolarons [4].
Rational Construction of Polymeric Nonlinear Optical Materials. Properties of Chromophore-Functionalized Polystyrenes
Authors: Ye C. , Minami N. , Marks T. J. , Yang J. , Wong G. K. 
Published: March 2011

ABSTRACTProcessable polymeric nonlinear optical materials can be synthesized by functionalizing a glassy macromolecule with chromophores having large quadratic hyperpolarizabilities, followed by poling in an electric field. In the present case, the functionalization of polystyrene with 4- (4-nitrophenylaza)(N-ethyl)(2-hydroxyethyl))aniline, 4-(4-N,N-dimethylaminostyryl) pyridine, and N-(4-nitrophenyl)-L-prolinol is described. Particularly noteworthy is the high level of chromophore units that can be incorporated into transparent films of these materials, the high second harmonic coefficients that can be achieved (as high as d33 – 11 × 10-9 esu at 1064 nm), and the long-term temporal stability of the second harmonic generation capacity.
A New Intramolecular Charge Transfer Material for Nonlinear Optics: Piperonal Derivatives
Authors: Mori Y. , Okamoto M. , Wada T. , Sasabe H. 
Published: March 2011

ABSTRACTThis paper describes a new organic nonlinear material, piperoniridene ethyl cyano acetate which shows short cut-off wavelength, good nonlinearity (better than POM in powder) and good crystallinity. These features of this compound encourage its application in second harmonic generation (SHG) coupled with semiconductor laser.
An Optically Detected Magnetic Resonance Study of Recombination Mechanisms in Polythiophene
Authors: Hess B. C. , Shinar J. , Vardeny Z. , Ehrenfreund E. , Wudl F. 
Published: March 2011

ABSTRACTFrom detailed optically detected magnetic resonance measurements in polythiophene, we show that the g=2.003 signal is luminescence enhancing, and that the signal comes from a broad photoluminescence band peaking near 1.65 eV. This band is tentatively assigned to Phe radiative recombination of polarons, with lifetimes between 10-8 and 5×10-5sec.
An Efficient Second-Harmonic Generating Crystal: 4-(Aminobenzophenone)
Authors: Guha S. , Frazier C. C. , Chauchard E. , Chen W. P. , Cockerham M. P. 
Published: March 2011

ABSTRACTEfficient, phase-matched second-harmonic generation of 1.064 µm radiation has been observed with single crystals of 4-aminobenzophenone (ABP). These crystals are tr nsparent from 420–2000 nm and have damage thresholds exceeding 30 GW/cm2 (for a 30-picosecond laser pulse).
Implementation of Neural Networks: Optical Architectures and Devices
Authors: Malloy Kevin J. , Giles C. Lee 
Published: March 2011

ABSTRACTWe introduce neural networks as a new basis for computation. The role optics can play In implementing neural networks is discussed in terms of the requirements for optical systems and devices. A conclusion is drawn that the rapidly evolving knowledge of neural network models argues for a flexible and adaptable device technology. Such a technology is described using the self electro-optic effect device as an example.
In vitro Study of the Rheological Effect of Mixtures of Perfluorotributylamine (FC-43) and Stroma Free Hemoglobin (SFH) On Sickled Erythrocytes
Authors: Reindorf Carl A. , Thompson Novelette E. 
Published: March 2011

AbstractStroma Free Hemoglobin (SFH) and Perfluorotributylamine (FC-43) have been extensively studied as oxygen carriers. Therefore, capitalizing on the role of oxygen reversing sickling, and thus decreasing resistance, this study was undertaken to investigate possible differences in the rheological effects of mixtures of FC-43 and SFH at different ratios. We used the positive pressure cell filtration system (PPCFS) of Lessin and Kurantsin- Mills. FC-43 was purchased from Alpha Therapeutics Corporation, and SFH was prepared by the method of Rabiner et al. The FC-43/SFH mixtures were made on a volume basis in ratios of 1:1 and 1:2. Fresh sickle cell anemia (HbSS) blood was used to prepare 0.2% cell suspensions which were deoxygenated, by bubbling with moist N2 for one hour. Studies of the rheological effects of FC-43/SFH mixtures on sickled erythrocytes were determined by obtaining filtration measurements on the following:- 1. sickle cells in ambient air; 2. deoxygenated sickle cells; 3. deoxygenated sickle cells + oxygenated FC-43/SFH (1:1 v/v); 4. deoxygenated sickle cells + oxygenated FC - 43/SFH (1:2 v/v). The results showed that treatment of deoxygenated sickle erythrocytes with oxygenated SFH/FC-43 mixtures decreased the flow resistance of the deoxygenated cells. Secondly, the SFH/FC-43 (1:2 v/v) mixture caused greater decrease in flow resistance than the 1:1 mixture.Therefore it is reasonable to conclude that the mixtures of SFH/FC-43 (1:2 v/v) ratio appear to have a additive effect in reducing the flow resistance i.e. increasing the filterability of sickled erythrocytes.
Comparison of Dense Versus Porous Hydroxylapatite (HA) Particles for Rat Mandibular Defect Repair
Authors: Fredette Stephen A. , Hanker Jacob S. , Terry Bill C. , Giammara Beverly L. 
Published: March 2011

AbstractRepair was compared in 4.4mm experimental rat mandibular ramus defects implanted with dense or porous HA particles with or without a plaster binder. Animals were sacrificed 6 months postimplantation. Specimens underwent gross, radiographic, histochemical and X-ray microanalytical examination. Gross and radiographic examinations showed good particle containment or retention only in defects filled with implants containing plaster. Only porous HA/plaster filled defects showed bone formation throughout the implant when examined histochemically by the PATS reaction and by X-ray microanalysis. They also showed greater radiographic opacity compared to dense HA/plaster implants. Only porous HA/plaster implants showed macroscopic bone formation. Examination of defects filled with porous HA/plaster or porous HA alone by the PATS reaction showed new cancellous bone around, and through the pores of, retained particles. The dense HA/plaster implants showed some new bone around the rims of the defects with only occasional bony incorporation of an HA particle. Dense particles in other areas showed only soft tissue encapsulation. Defects implanted with dense HA without plaster showed no new bone formation but retained particles were incorporated by fibrovascular tissue.
Osteogenesis in Cat Cranioplasty with Composite Hydroxylapatite/Plaster
Authors: Hanker Jacob S. , Yates Peggy E. , Giammara Beverly L. , Rawlings Charles E. , Ovelmen-Levitt Janice , Georgiade Nicholas G. , Wilkins Robert F. 
Published: March 2011

AbstractComposite hydroxylapatite (HA)/plaster alloplasts were studied for frontal and parietal cranioplasty. The experimental defects were created in 61 anesthetized cats. They were filled with a moist 2:1 mixture of durapatite/plaster or Interpore/plaster containing 0.85% potassium sulfate. After setting, the implant site was sutured. The filled defects were very firm by physical examination and showed little particle scatter by radiography. At the time this report was prepared only 43 of the cat skulls were available for examination. After sacrifice, postmortem visual examination (VE) of the skulls suggested that new bone had formed over some implants. In most implants, however, VE could not determine whether new bone had formed between the HA particles. Probing examination (PE) of the parietal implants with a periodontal explorer gave a better indication; the presence of new bone rather than soft tissue between the HA particles was confirmed by x-ray microanalysis. The ventral surfaces (VS) of the parietal implants showed greater degrees of bone formation by PE; only 12 of 43 parietal implants showed a high degree of bone formation on the dorsal surfaces (DS) by PE whereas 34 of 43 showed this on the VS. The highly significant difference (^3X) in the amount of bone formation on the VS compared with the DS suggests that this osteogenesis, like that observed in cranial trauma, may be stimulated by the dura which acts as a periosteum by supplying blood vessels to the implant.
Effects of Compression During Formation on the Mechanical Strengths and Physical Properties of Composite Hydroxylapatite/Plaster Implants for Bone Reconstruction
Authors: Cowden K. , Giammara B. , Georgiade N. , Noecker R. , Hanker J. 
Published: March 2011

AbstractComposite hydroxylapatite/plaster of Paris implants, preformed or formed during the surgical implantation procedure, are undergoing study for the surgical reconstruction of craniofacial bones. It is frequently necessary to accelerate setting times of the hydroxylapatite/plaster (HA/PP) mixtures by the addition of potassium sulfate; in many of these cases rapid delivery of the moistened implant mixture to the surgical site may be achieved by employing a non-tapered syringe with a plunger. This device can facilitate implantation of quick-setting moistened mixtures through soft tissue tunnels or small incisions, and can result in a less invasive surgical procedure. During experimental surgery it was found beneficial to effect maximum compression of the moistened HA/PP mixture against a sterile glass plate prior to its extrusion from the cylinder. This resulted in elimination of excess water from the mixture. Discs formed from compressed mixtures showed greater mechanical or breaking strengths after setting than discs formed without prior compression when evaluated with a Stokes Hardness-Tester. Examination by light and scanning electron microscopy confirmed the greater compactness of the compressed mixtures.
Critical Evaluation of an in Vitro Model for Evaluation of Platelet Reactivity of Biomaterials
Authors: Connolly Raymond , Shoenfeld Norman , Ramberg Karen , Callow Allan D. 
Published: March 2011

AbstractAn in vitro model for measuring platelet reactivity to a variety of biomaterial candidates for vascular grafts is described. A model consisting of a standard area of test material exposed to freshly labeled In platelets in plasma was evaluated. The platelets were isolated from ACD anticoagulated blood and resuspended in ACD plasma. It has been previously demonstrated that platelets so treated circulate in the body and will deposit on biomaterials exposed to the blood in vivo. The in vitro test consisted of an incubation of the platelets and materials at 37°C for one hour. At the end of the incubation, the platelet rich plasma was removed and the materials washed and removed for gamma counting. Platelet reactivity was normalized as a percentage of the counts on the material to counts in an aliquot of the platelet-plasma incubation media. The maximum uptake of platelets occurred within one hour. Platelets from three species, human, baboon, and dog were tested. Platelet uptake by Dacron and PTFE were in the range of 30–40% and 1–5% respectively. This is in accord with the known reactivity of these two vascular graft materials in vivo.A second series of studies were conducted with physically and pharmacologically inactivated platelets and inert particles. Those studies suggest that the initial results do not represent a biologic event but may reflect the porosity of the materials. This emphasizes the necessity of adequately defining an in vitro model against known in vivo activity.
Various Forms of Crosslinked Dextran Gel as Surface Wound Covering Materials
Authors: Wang Paul Y. 
Published: March 2011

AbstractDextran and its crosslinked beads have many biomedical applications. If stirring to maintain the epichlorohydrin emulsion is stopped in about 7 minutes, crosslinked dextran gel sheets can be prepared. The elastic sheet obtained after washing in water, followed by treatment with propylene glycol containing 15% isopropanol is suitable as a covering on rodent skin wound. Antibacterial agents can be dispersed into the sheet or admixed in the paste form of the gel.In standard tests, a 4 cm × 4 cm surface wound on the back of a 400-g Wistar rat was covered with the dextran gel material. The evaporation loss was found to reduce immediately from 94 mg H20/cm2/hr to 1/2 of this value which became 12.5 mg H20/cm2hr in 18 hours. Such a covered wound healed in 10–17 days with 10–15% distortion, while the controls were delayed to 25 ± 7 days with >65% wound contraction.Another modification of the gel material involves the surface attachment of the positively charged 2-diethylaminoethyl function (DEAE). Although up to 2.41 mM DEAE groups/g gel can be introduced, only <10% is on the gel surface. Tests with mouse 3T3 fibroblists showed 5 that it was possible to increase the cell binding from 9 × 103 to 2 × 105 cells/cm2. Therefore, the gel material may have potential as a substrate for dermal cells as well for later transfer.
Hydrotheral Synthesis of Hydroxyapatite Powders with Zirconia Dispersion
Authors: Ioku Koji , Yoshimura Masahiro , Sōmiya Shigeyuki 
Published: March 2011

AbstractHydroxyapatite (HAp) fine powders dispersed with zirconia were prepared by hydrothermal techniques at 200°C, under 2 MPa for 10 h. The transmission electron microscopy (TEM) showed the homogeneous mixtures of HAp and zirconia.The HAp powders were stoichiometric fine single crystals of about 90 nm × 25 nm in size and the zirconia powders were also fine single crystals of about 10 nm in size. The reactivity between HAp and zirconia was examined. According to the X-ray diffractometry (XRD), decomposition of HAp to B-tricalcium phosphate (β-TCP) was observed above 800°C then β-TCP was transformed into α-TCP at about 1200°C.
Comparison of Osteoconduction in Porous Implants of Co-Cr-Mo, Vitreous Carbon, Silicone Rubber and Hydroxyapatite in Rabbit Bone Defects
Authors: Shors Edwin C. , White Gene W. , Kopchok George 
Published: March 2011

AbstractThere is a need for new materials which attach to bone. Attachment can occur through bioactive surfaces or porosity. The Replamineform process can be used to produce polymers, metals and ceramics with these properties. In this study, porous implants were manufactured in cobalt-chromemolybdenum (Co-Cr-Mo) vitreous carbon and silicone rubber. The pores were 200 pm in diameter and fully interconnected. The biocompatibility and osteoconduction of these materials was compared to porous hydroxyapatite (Interpore 200 HA). In 10 rabbits, blocks (2mm×3mm×5mm) of each material were implanted subperiosteally onto the femur, or rods (5mm D×10 L) were press-fit into unicortical defects of the proximal tibia. Explants were harvested at 1–6 months, sectioned midsagitally and embedded in plastic for histomorphometry using SEM or bright field microscopy. Bone grew up to and into all implants by two months. However, implants of porous Co-Cr-Mo, vitreous carbon and silicone rubber had less bone than implants of hydroxyapatite. Also, bone formed in direct apposition to hydroxyapatite, but secondly incorporated the other materials. Moreover, implants containing hydroxyapatite in the pores of the Co-Cr-Mo induced more complete and intimate bone ingrowth. This study demonstrates the potential for bone ingrowth and bonding into a range of biocompatible materials with interconnected porosity and the superior osteconduction of porous hydroxyapatite.
Mini Short-Rod Fracture Toughness Testing of Bone Cements Exhibitng Elastic-Plastic Behaviour
Authors: Wang C. T. , Pilliar R. M. 
Published: March 2011

AbstractFracture of bone cement is considered to be a major factor contributing to total joint replacement failures because of implant loosening. While plane-strain fracture toughness (Klc) provides a parameter for assessing fracture resistance, the standard methods for testing (ASTM E399) require (1) the use of specimens greater than a certain minimum size (for bone cement this minimum size is greater than that found in clinical applications) and (2) fatigue precracking of specimens prior to testing. The short-rod fracture toughness test proposed by Barker offers a method of testing not requiring fatigue precracking and furthermore, it appears that a valid fracture toughness value can be determined using a modified miniature test specimen that we have proposed. Our mini short-rod specimen size approaches the actual dimensions of bone cement as used clinically. In this study mini short-rod fracture toughness test specimens were used to assess fracture toughness for two commercial brands of bone cement (Simplex-P and Zimmer LVC). An elastic-plastic fracture mechanics (EPFM) analysis was used to obtain experimental results with a plasticity correction factor being introduced. The cements were assessed as a function of method of preparation (hand mixed versus centrifuged) and aging conditions (3 days in air versus 7 days in distilled water at 37° C). The results indicated that (1) true fracture toughness values could be obtained only using an EPFM analysis for these specimens, (2) centrifugation did not significantly affect fracture toughness and (3) a significant difference in the plasticity correction factor due to water aging at 37° C was indicated for only the hand-mixed Zimmer LVC cement. There was, however, no significant change in fracture toughness due to water aging.
Complex Dielectric Properties of Tooth Constituents
Authors: Masi James V. , Masi Louis C. 
Published: March 2011

AbstractDue to the recently indicated causal relationship between the piezoelectric properties of teeth and the formation of root caries, a study was undertaken to further classify the dielectric properties of the actual tooth constituents. The properties considered are the real and imaginary components of the complex dielectric constant, including the electrical conductivity, for human teeth in vitro, both dry and saline solution saturated. The frequency range covered is from 1 Hz to 1.35 GHz. An attempt has been made to present the data for the two most prominent constituents, namely, enamel and dentin. Ways in which the dielectric properties can aid physiological studies and an understanding of the caries process are also described. Some possible explanations for the biological and physiological processes in the dielectric properties of tooth constituents are given. Pathological variations among teeth are noted. Some hypotheses for causal relationships between caries and electrical properties of natural dental constituents are proposed.
Adhesion and Electrical Insulation of Thin Polymeric Coatings Under Saline Exposure
Authors: Leyden R. N. , Basiulis D. I. 
Published: March 2011

AbstractA study was made of the adhesion of insulating polymer coatings under long term exposure to electrical bias. Since a common mode of failure in implanted devices is the penetration of water into poorly adhering insulation/conductor interfaces followed by electrolytic degradation, development of processes, primers, and insulators with good adhesion that resist the effects of water were sought. Polyimide coatings were tested for their ion barrier properties by immersion of insulated comb patterns in saline with 9 V D.C. bias between the comb fingers. Leakage currents, measured over three years exposure, increased from several picoamps initially to several nanoamps in surviving specimens. Subsequent studies showed that dramatic improvements in the moisture durability of the adhesion could be obtained using Hitachi's aluminum chelate type primer. Whereas the peel strength of polyimide on unprimed platinum fell more than 90% after several hours of boiling saline exposure, the peel strength of polyimide coatings on primed surfaces remained at over 80% of their initial values. ESCA analysis of the peel interfaces showed that both aluminum oxide and polyimide remain on the substrate after peeling back the polyimide. This suggests a combination of cohesive and adhesive failure at the primer/polyimide interface. The effects of exposure of the polymer/substrate interfaces (edges) to saline and electrochemical stress were examined by patterning circular openings in the polyimide. A 10 V anodic potential was found to damage adhesion to titanium as far as 75 microns away from the edge. Pulsing at 500 Hz, 1 V peak to peak was found to have no measurable effect in the short term.
Softenable, Shape-Memory Thermoplastic for Use in Biomedical Devices
Authors: White Kathleen A. , Ward Robert S. 
Published: March 2011

AbstractMany implantable biomedical devices could benefit from a material with a strongly temperature-dependent modulus. Catheters made from such a material could be inserted as a stiff plastic, and upon reaching body temperature, would soften dramatically to minimize erosion of adjacent tissue. Sutures could be stiff during placement in an incision, heated slightly to form a shape to hold the suture in place, and then cooled. A new family of materials known as softenable, shape-memory thermoplastics have a distinct and adjustable thermal transition that produces a dramatic change in modulus at a predetermined temperature (range)
The Role of Fibrinogen in Platelet Interaction with Methacrylate Polymers
Authors: Lindon Jack N. , Shiba Eiichi , Kushner Leslie , Salzman Edwin W. 
Published: March 2011

AbstractWhen blood comes in contact with a foreign surface, protein adsorption occurs within seconds and precedes the arrival of blood cells. Since a layer of plasma proteins is laid down on any surface in contact with blood before the platelets arrive, differences in platelet reactivity with different surfaces must result from variations in the nature of the protein-surface interactions. These interactions may vary in terms of which proteins bind to the surfaces, the amounts bound, and the various changes in protein conformation induced by surface contact.