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At least 631 records · Page 35Linked to original sources
PubMed1998

Combined modality treatment of bone metastases: response of the rhabdomyosarcoma R1H of the rat to postoperative irradiation combined with local release of daunorubicin from acrylic cement.

Reconstruction techniques for pathological fractures caused by bone metastases often include acrylic cement to stabilise defects. The aim of this study was to test in a rodent model, whether outcome could be improved by local chemotherapy from an anticancer drug added to the acrylic cement. Tumour excision 17 days after transplantation into the femur was followed by fractionated irradiation. Supplementation of acrylic cement with daunorubicin led to a considerable reduction of TCD37% from 72.9 Gy (62.2-82.8) to 29.3 Gy (21.8-37.5) (P = 0.0007). Local chemotherapy diffusing from bone cement combined with postoperative radiotherapy was highly effective in the experimental system studied.

Animals↗
PubMed1997

Reoperative aortic root surgery late after use of histo-acryl.

Cardiovascular reoperations after the use of histo-acryl are extremely rare. A patient is described, who underwent an aortic root replacement according to Bentall's technique, for a postdissectional aneurysm. At that time, to achieve hemostasis, histo-acryl adhesive was applied and a Cabrol's fistula was created. Fourteen years later, a recurrent 'false', aneurysm had developed and the fistula had a hemodynamically significant left-right shunt. At reoperation, the composite graft was replaced by a cryopreserved aortic root allograft with long coronary arteries. To our knowledge, this is the first report of a cardiovascular reoperation after previous use of histo-acryl. This patient also merits attention as to the fact that it illustrates a failure of a modified Cabrol's procedure.

Adult↗
PubMed2001

Initial experience with use of tris-acryl gelatin microspheres for uterine artery embolization for leiomyomata.

PURPOSE: To assess the safety and effectiveness of tris-acryl gelatin microspheres (Embospheres) in the treatment of leiomyomata by uterine artery embolization. MATERIALS AND METHODS: This was a Phase I study of 30 patients with symptomatic leiomyomata. Each patient underwent ultrasound imaging and completed questionnaires regarding symptoms and health status at baseline and 3 and 6 months after treatment. Bilateral embolization was performed with use of tris-acryl gelatin microspheres. Summary statistics were used to characterize the demographic and procedure data. Paired t-tests were used to assess change in the severity of menstrual bleeding and health-related quality of life. RESULTS: Bilateral embolization was technically successful in all patients. Three months after treatment, menstrual bleeding was markedly improved as assessed by menorrhagia questionnaire (P <.0001) and menstrual calendar (P <.0001). Pelvic pain and discomfort was improved in 92% of cases. Physical component summary scores of the SF-12 also increased from baseline at 3 months (P =.02) and at 6 months (P =.01). Minor complications occurred in nine patients; there were no major complications. CONCLUSION: Although limited, this initial experience suggests that tris-acryl gelatin microspheres are an effective and safe embolic agent for the treatment of uterine leiomyomata.

Adult↗
PubMed2001

Intracluster anionic oligomerization of acrylic ester molecules initiated by electron transfer from an alkali metal atom.

Stabilities and intracluster reactions have been investigated by photoionization mass spectrometry for clusters composed of an alkali metal atom (M; Na and K) and acrylic ester molecules, CH(2)=CHCO(2)R, such as methyl acrylate (MA; R = CH(3)) and ethyl acrylate (EA; R = C(2)H(5)). The following two features are commonly observed in the photoionization mass spectra of M(CH(2)=CHCO(2)R)(n): (1) The ion with n = 3 is clearly observed as a magic number. (2) Fragmented cluster ions with the loss of ROH, [M(CH(2)=CHCO(2)R)(n) - ROH] are detected only for n = 3. These features are both explained by an intracluster oligomerization reaction initiated by electron transfer from the metal atoms. The magic number trimer is concluded to have the stable structure of cyclohexane derivatives as a result of oligomerization. The fragmentation reaction is explained by Dieckmann cyclization after anionic oligomerization to produce another isomer of the trimer. The intracluster electron transfer is also supported by theoretical calculation for Na(MA) based on density functional theory.

Journal Article↗
PubMed2005

Ruthenium-complex-catalyzed regio- and stereoselective linear codimerization of 2-norbornenes with acrylic compounds.

A linear codimerization of 2-norbornenes with acrylic compounds such as acrylates and an acrylamide proceeded efficiently by ruthenium catalyst systems, RuCl3(tpy)/Zn (tpy = 2,2':6',2' '-terpyridine) or [RuCl2(C6H6)]2/Zn in a primary or secondary alcoholic solvent, to afford the corresponding exo-trans-2-norbornylacrylates as major products regio- and stereoselectively along with a small amount of cis isomers. The reaction of 2,5-norbornadiene with methyl acrylate also gave the linear exo-trans codimer, which was effectively catalyzed by the addition of triarylphosphines to the RuCl3(tpy)/Zn catalyst system.

Journal Article↗
PubMed2005

The effect of positive ion energy on plasma polymerization: a comparison between acrylic and propionic acids.

Using a novel RF biasing technique, the energy of positive ions at a depositing substrate is controlled, independently of other parameters. Under bias conditions which gave the maximum and minimum ion energies, plasmas of propionic and acrylic acid were investigated using mass spectrometry, an ion flux probe, quartz crystal microbalance, and X-ray photoelectron spectroscopy (XPS). For both compounds investigated, the ion energy affects the deposition rate but leaves the neutral gas-phase chemistry and positive ion fluxes unchanged. The chemistry of the polymer deposit for acrylic acid is unaffected by the change in ion energy, but the chemistry of the propionic acid plasma polymer changes markedly. We argue that the results presented are consistent with the hypothesis that, under the plasma conditions explored, the carbon-carbon double bond present in acrylic acid plays a significant role in the formation of the polymer. Conversely, the absence of this bond in propionic acid leads us to conclude that positive ions contribute significantly to film formation for this compound.

Journal Article↗
PubMed2005

Roles of surface Te, Nb, and Sb oxides in propane oxidation to acrylic acid over bulk orthorhombic Mo-V-O phase.

The outermost surfaces and subsurface layers of the orthorhombic (M1) Mo-V-O catalysts promoted with Te, Nb, and Sb oxide species at submonolayer surface coverage were examined by low-energy ion scattering (LEIS). This study indicated that the Nb oxide species was preferentially located at the topmost surface, while the subsurface Te and Sb concentrations declined gradually into the bulk. Although the original Mo-V-O catalyst was essentially unselective in propane oxidation to acrylic acid, significant improvement in the selectivity to acrylic acid was observed when Te, Nb, and Sb oxides were present as the surface species at submonolayer coverage. These findings further suggested that the formation of the surface V-O-M bonds (M = Nb, Te, or Sb) was highly beneficial for both the activity and selectivity of the orthorhombic Mo-V-O catalysts in propane oxidation to acrylic acid. The highest selectivity was observed when both Nb and Te (or Sb) oxide species were present at the surface. The selectivity trends established for the surface-promoted Mo-V-O catalyst parallel those found previously for the corresponding bulk Mo-V-M-O catalysts. These results further indicated that the introduction of surface metal oxide species is a highly promising method to prepare well-defined model catalysts for studies of the structure-activity/selectivity relationships as well as optimize the catalytic performance of the bulk mixed Mo-V-M-O catalysts for selective (amm)oxidation of propane.

Journal Article↗
PubMed2004

Polystyrene-b-poly(acrylic acid) vesicle size control using solution properties and hydrophilic block length.

Polymeric vesicles have attracted considerable attention in recent years, since they are a model for biological membranes and have versatile structures with several practical applications. In this study, we prepare vesicles from polystyrene-b-poly(acrylic acid) block copolymer in dioxane/water and dioxane/THF/water mixtures. We then examine the ability of additives (such as NaCl, HCl, or NaOH), solvent composition, and hydrophilic block length to control vesicle size. Using turbidity measurements and transmission electron microscopy (TEM) we show that larger vesicles can be prepared from a given copolymer by adding NaCl or HCl, while adding NaOH yields smaller vesicles. The solvent composition (ratio of dioxane to THF, as well as the water content) can also determine the vesicle size. From a given copolymer, smaller vesicles can be prepared by increasing the THF content in the THF/dioxane solvent mixture. In a given solvent mixture, vesicle size increases with water content, but such an increase is most pronounced when dioxane is used as the solvent. In THF-rich solutions, on the other hand, vesicle size changes only slightly with the water concentration. As to the effect of the acrylic acid block length, the results show that block copolymers with shorter hydrophilic blocks assemble into larger vesicles. The effect of additives and solvent composition on vesicle size is related to their influence on chain repulsion and aggregation number, whereas the effect of acrylic acid block length occurs because of the relationship among the block length, the width of the molecular weight distribution, and the stabilization of the vesicle curvature.

Journal Article↗
PubMed2004

Aggregation states and surface wettability in films of poly(styrene-block-2-perfluorooctyl ethyl acrylate) diblock copolymers synthesized by atom transfer radical polymerization.

Well-defined poly(styrene-block-2-perfluorooctyl ethyl acrylate) [P(St-b-PFA)] copolymers with various chemical compositions were synthesized by atom transfer radical polymerization. Films of P(St-b-PFA) were structurally characterized, from bulk to surface, on the basis of transmittance electron microscopic observation and small-angle X-ray scattering, X-ray photoelectron spectroscopic, and contact angle measurements. For a comparison, poly(styrene-random-2-perfluorooctyl ethyl acrylate) [P(St-ran-PFA)] copolymers were also synthesized by conventional free radical polymerization. While P(St-b-PFA) with the 2-perfluorooctyl ethyl acrylate (PFA) content higher than 18.7 mol % formed a typical phase-separated cylinder structure, P(St-b-PFA) with a lower PFA content and P(St-ran-PFA) were in a miscible state. Since the perfluoroalkyl groups possess extremely low surface energy, they were preferentially segregated at the film surface, resulting in the formation of the PFA surface layer. This was the case for all P(St-b-PFA) films examined, although the aggregation state at the surface was strongly dependent on the PFA content. In the case of the P(St-b-PFA) with the PFA content higher than 18.7 mol %, both advancing and receding contact angles for water were 120 degrees and even larger with almost no hysteresis. In addition, extremely excellent oil-repellent surface properties such as advancing and receding contact angles for dodecane of 76 degrees and 75 degrees were also observed. However, these intriguing liquid-repellent properties were not observed for the films of miscible P(St-b-PFA) and P(St-ran-PFA). Therefore, it can be concluded that the internal structure beneath the surface as well as the surface itself should be deeply considered to design excellent and stable liquid-repellent materials.

Journal Article↗
PubMed2006

Efficient Heck arylations of cyclic and acyclic acrylate derivatives using arenediazonium tetrafluoroborates. A new synthesis of the antidepressant drug (+/-)-paroxetine.

[reaction: see text] The Heck arylation of acyclic- and cyclic-substituted acrylates using several arenediazonium tetrafluoroborates was investigated. Arylations were carried out under aerobic, ligand-free conditions to provide the corresponding substituted acrylates in moderate to high isolated yields. Heck arylations were usually completed in less than 2 h in refluxing methanol. The aza-endocyclic acrylate derivative 11a was converted into the antidepressant drug (+/-)-paroxetine in a concise new route in good overall yield.

Antidepressive Agents↗
PubMed2002

Curing characteristics of acrylic bone cement.

Commercial acrylic bone cements are supplied as two components, a polymer powder and a liquid monomer. Mixing of the two components is followed by a progressive polymerization of the liquid monomer to yield a solid mass, a high level of heat being generated during this exothermic reaction. The exposure of bone to high temperatures has led to incidences of bone necrosis and tissue damage, ultimately resulting in failure of the prosthetic fixation. The aim of this study was to determine the thermal properties of two acrylic bone cements as they progress through their polymerization cycles. It was also felt that there was a need to quantify the variations in the curing characteristics as a function of preparing bone cement by different techniques, hand mixing and vacuum mixing. A number of parameters were calculated using the data gathered from the investigation: peak temperature, cure temperature, cure time, and the cumulative thermal necrosis damage index. The results show the temperature profile recorded during polymerization was lowest when the cement was prepared using the Howmedica Mix-Kit I system: 36 degrees C for Palacos R and 41 degrees C for CMW3 respectively. When the acrylic cements were prepared in any vacuum mixing system there was evidence of an increase in the cure temperature. The main factor that contributed to this rise in temperature was an imbalance in the polymer powder : liquid monomer ratio, there was a high incidence of unmixed powder visible in the mixing barrel of some contemporary vacuum mixing devices. Observing the thermal characteristics of the polymethyl methacrylate (PMMA) bone cements assessed, it was found that particular formulations of bone cements are suited to certain mixing methodologies. It is vital that a full investigation is conducted on a cement mixing/delivery system prior to its introduction into the orthopaedic market.

Journal Article↗
PubMed2003

Head-to-tail dimerization of acrylates catalyzed by iridium complexes.

Head-to-tail dimerizations of acrylates and vinyl ketone were successfully performed by the use of iridium complexes in good yields. An iridium hydride complex generated in situ from [IrCl(cod)]2 and alcohols in the presence of Na2CO3 and (MeO)3P was found to be an active species promoting the head-to-tail dimerization of acrylates. Thus, butyl acrylate afforded the corresponding head-to-tail dimer in 86% yield.

Journal Article↗
PubMed2004

The mutual diffusion coefficient for (meth)acrylate monomers as determined with a nuclear microprobe.

The value of the mutual diffusion coefficient DV of two acrylic monomers is determined with nuclear microprobe measurements on a set of polymer films. These films have been prepared by allowing the monomers to diffuse into each other for a certain time and subsequently applying fast ultraviolet photo-polymerization, which freezes the concentration profile. The monomer diffusion profiles are studied with a scanning 2.1 MeV proton microprobe. Each monomer contains a marker element, e.g., Cl and Si, which are easily detected with proton induced x-ray emission. From the diffusion profiles, it is possible to determine the mutual diffusion coefficient. The mutual diffusion coefficient is dependent of concentration, which is concluded from the asymmetry in the Cl- and Si-profiles. A linear dependence of the mutual diffusion coefficient on the composition is used as a first order approximation. The best fits are obtained for a value of b=(0.38+/-0.15), which is the ratio of the diffusion coefficient of 1,3-bis(3-methacryloxypropyl)-1, 1,3,3-tetramethyldisiloxane in pure 2-chloroethyl acrylate and the diffusion coefficient of 2-chloroethyl acrylate in pure 1,3-bis(3-methacryloxypropyl)-1,1,3,3-tetramethyldisiloxane. Under the assumption of a linear dependence of the mutual diffusion coefficient DV on monomer composition, it follows that DV = (2.9+/-0.6)10(-10) m(2)/s at a 1:1 monomer ratio. With Flory-Huggins expressions for the monomer chemical potentials, one can derive approximate values for the individual monomer diffusion coefficients.

Journal Article↗
PubMed1999

Period-doubling behavior in frontal polymerization of multifunctional acrylates.

Front dynamics in the frontal polymerization of two multifunctional acrylate monomers, 1,6-hexanediol diacrylate (HDDA) and trimethylolpropane ethoxylate triacrylate (TMPTA), with Lupersol 231 [1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane] as the initiator, are studied. In most frontal polymerization systems, the dynamics are associated with a planar front propagating through the sample. However, in some cases, front behavior can be altered: the front becomes nonplanar characterized by complex patterns like spin modes and pulsations. To determine how these periodic and aperiodic modes arise, reactant solutions consisting of HDDA diluted with diethyl phthalate (DEP) and TMPTA diluted with dimethyl sulfoxide (DMSO) were used in the study. In the study we reveal frontal behavior characteristic of period-doubling behavior, a doubling of spin heads that degenerate into an apparently chaotic mode. Also, a pulsating symmetric mode has been observed. These observations have a striking similarity to observations made in studies of self-propagating high-temperature synthesis (SHS) in which the addition of an inert diluent afforded a rich variety of dynamical behavior. The degree of cross-linking has also been found to be a bifurcation parameter. The energy of activation of multifunctional acrylate polymerization is a strong function of the degree of polymerization. By adding a monoacrylate (benzyl acrylate: BzAc), such that the front temperature was invariant, we observed a period-doubling bifurcation sequence through changes in the energy of activation, which has not been previously reported. (c) 1999 American Institute of Physics.

Journal Article↗
PubMed1983

Changes in cardiac output and systemic arterial pressure after insertion of acrylic cement during trimetaphan, sodium nitroprusside and glycerol trinitrate-induced hypotension. A comparison with changes during normotension.

The effects of implantation of acrylic monomer on the cardiovascular response were studied in 37 patients undergoing hip arthroplasty and receiving high-dose fentanyl anaesthesia, under normotensive conditions or during hypotension induced by trimetaphan (TMP), sodium nitroprusside or nitroglycerine. Heart rate, mean arterial pressure (MAP), the ventricular stroke volume (SV) and the cardiac output (CO) were monitored before, and at 1, 2, 4, 6, and 8-min intervals after the insertion of the acrylic cement into the acetabulum or the neck of femur. There was a moderate decrease in MAP after insertion into the acetabulum under normotensive conditions and TMP-induced hypotension, while the reduction in pressure was significant after the cement's application in the femur. Heart rate did not change on insertion of the monomer in any of the patients. Moderate decreases in SV and CO were observed during normotension or TMP-induced hypotension. There were no significant changes in the cardiovascular haemodynamics on the insertion of the acrylic material under hypotension induced by nitroprusside or nitroglycerine.

Acetabulum↗
PubMed1988

Porous acrylic cement: evaluation of a novel implant material.

The preparation and some properties of in situ curing porous acrylic cement, a modification of the traditional bone cement, are described. Through numerous animal experiments, the behavior of the porous cement in a biological environment has been studied. The histological evaluation reveals that hard and soft tissues readily grow into the pores of the cement, thus anchoring the implant to the host tissues. Some inflammatory foci, decreasing in number with residence time, together with varying numbers of multinucleated giant cells were found occasionally in the tissues in and around implants. When implanted in soft tissues, the porous cement behaved favorably with respect to solid acrylic implants because of the immobility of the implants and the absence of ectopic hard tissue formation. The biocompatibility of porous acrylic cement is judged to justify clinical trials in plastic and reconstructive surgery.

Animals↗
PubMed1996

Persistence of bacteria on antibiotic loaded acrylic depots. A reason for caution.

Bacterial growth on the surface of antibiotic loaded acrylic cement was examined in an in vitro model. Tobramycin or vancomycin impregnated discs were incubated in broth containing either Staphylococcus epidermidis or Staphylococcus aureus organisms. At 24, 48, and 96 hours, the broth and the surface of the acrylic discs were examined for viable organisms. In the broth, only 6% (8 of 136) of samples contained viable organisms at 24 hours, and all samples were sterile by 96 hours. This is in contrast to the surface of the discs, which revealed the presence of viable organisms at all study time periods. Growth was noted in 99% and 30% of the Staphylococcus epidermidis and Staphylococcus aureus discs, respectively, at 24 hours. Viable organisms were found on both types of discs through 96 hours (20% of Staphylococcus epidermidis and 15% of Staphylococcus aureus). The surface of bone cement is therefore a suitable substrate for bacterial growth, even in the presence of antibiotics. In clinical practice, antibiotic loaded acrylic cement should therefore be used with caution and clear indications.

Anti-Bacterial Agents↗
PubMed1998

Porosity reduction in acrylic cement is clinically irrelevant.

Evidence from studies on migration raises serious doubts regarding the part played by fatigue failure of acrylic bone cement in the genesis of aseptic loosening of the components of total hip arthroplasties. Moreover, the viscoelastic properties of cement raise serious doubts concerning the relevance of conventional laboratory fatigue studies to the in vivo behavior of acrylic cement. It is not surprising that there is considerable clinical evidence that reduction of porosity in acrylic cement is of no relevance to the long term outcomes of total hip arthroplasty. These matters remain controversial, and randomized prospective trials would be necessary to settle the issues. For various reasons, such trials are unlikely to be performed.

Arthroplasty, Replacement, Hip↗