Absorbance Matrix Research Articles

Chemical characteristics of chromophoric dissolved organic matter in rainwater

Proton nuclear magnetic resonance ( 1H-NMR), UV absorbance and excitation-emission matrix (EEM) fluorescence spectroscopy were used to define the chemical characteristics of chromophoric dissolved organic matter (CDOM) in whole and C 18 extracted rainwater. The average total recovery of fluorescence determined from the sum of extract and filtrate fractions relative to the whole was 86% suggesting that 14% of fluorescent CDOM in rainwater is comprised of very hydrophobic material that cannot be eluted from the column. Half the fluorescence of rainwater was recovered in the filtrate fraction which is important because it suggests that 50% of the chromophoric material present in precipitation is relatively hydrophilic. The average spectral slope coefficient was smaller in extracted samples (16.3 ± 9.0 μm −1) relative to whole samples (18.9 ± 2.8 μm −1) suggesting that the extracted material contains larger molecular weight material. Approximately one-third of the total dissolved organic carbon (DOC) in rainwater exists in the extract fraction suggesting that a large percentage of the uncharacterized DOC in rainwater can be accounted for by these hydrophobic macromolecular species. The fluorescence of extracted samples is strongly correlated with total NMR integration and is most sensitive to aromatic protons suggesting that molecules in this region are the most important in controlling the optical properties of rainwater. The lower removal efficiency of CDOM in rainwater relative to surface waters or the water-soluble fraction of aerosols during solid phase extraction (SPE) suggests that rainwater contains significantly more hydrophilic chromophoric compounds which are compositionally different than found in these other aquatic matrices.

An Absorbable Local Anesthetic Matrix Provides Several Days of Functional Sciatic Nerve Blockade

Functional blockade of peripheral nerves is the primary objective of local anesthesia, and it is often desirable to have a persistent blockade, sustained throughout and beyond a surgical procedure. Current local anesthetics give effective analgesia for <8-12 h after a single bolus injection. We report on an implantable, controlled-release drug delivery system intended for use in bone and consisting of a Food and Drug Administration-approved matrix containing lidocaine that is capable of local delivery for several days. Xybrex, an absorbable, controlled-release delivery system containing 16% (w/w) lidocaine, was implanted next to the sciatic nerve of male rats (300-350 gm), at lidocaine doses of 5.3, 10.6, 16, and 32 mg lidocaine per rat. For comparison, a lidocaine HCl solution (0.2 mL, 2% = 4 mg) was injected in close proximity to the sciatic nerve. Rats were assessed behaviorally for analgesia by a forceps pinch of the lateral digits, and for motor block by quantifying the extensor postural thrust. Potential neurotoxicity of sciatic nerves was evaluated histologically at 24 h, 4 days, and 4 wk after implantation. The kinetics of lidocaine's release from the matrix was measured in vitro by ultraviolet detection of lidocaine in samples collected at 2.5, 6.5, 20, and 24.25 h. Xybrex at the highest doses (300 and 600 mg/kg, containing 16 and 32 mg of lidocaine free base, respectively) provided complete analgesia to an intense pinch for 7.0 +/- 2.0 h, 6.9 +/- 1.7 h and partial analgesia for 60.0 +/- 5.4 h, 58.8 +/- 4.2 h, respectively, compared to 0.61 +/- 0.03 h of complete analgesia and 0.96 +/- 0.03 h of partial analgesia by sciatic block from the 2% lidocaine solution (containing 4 mg lidocaine). These same high doses of Xybrex produced complete motor block for 17.0 +/- 3.3 h, 17.6 +/- 3.3 h with full recovery in 352.0 +/- 55.7 h (14.7 +/- 2.3 days), 579.0 +/- 36.1 h (24.1 +/- 1.5 days) respectively. Data are reported as mean +/- SE. P < 0.001 for all Xybrex groups compared to the 2% lidocaine group. Minor local tissue inflammation/pathology, primarily in the connective tissue and muscle 0.1 mm adjacent to the nerve, was observed equally in animals treated with Xybrex and 2% lidocaine solution. There were no behavioral signs of systemic toxicity. The in vitro release followed exponential kinetics and its comparison to the time-course of functional nociceptive deficit implied that the duration of nociception represented the local, immediate interaction of lidocaine between the nerve and the matrix and not a cumulative effect of previously released drug. Xybrex is an absorbable, controlled-release drug delivery system that provides several days of analgesia for rat peripheral nerves without apparent significant local neurotoxicity or systemic toxicity.

Absorption and fluorescence properties of rainwater during the cold season at a town in Western Portugal

This study aims at evaluating the variability of the optical properties of chromophoric dissolved organic matter (CDOM) of rainwater during the cold season, specifically between Autumn and Winter periods. The spectroscopic characteristics of rainwater samples collected at a town (Aveiro) in western Portugal were assessed by UV-Vis absorbance and three-dimensional excitation-emission matrix (EEM) fluorescence spectroscopies. Rainwater samples showed similar characteristics to those of natural humic substances when analysed by UV-Vis absorbance spectroscopy, but a significant difference was observed in the volume weight average (VWA) of absorbances between Autumn and Winter. In general, the EEM fluorescence spectra of the Autumn and Winter samples disclosed the presence of six fluorophores with different VWA specific fluorescence intensities: three humic-like (λexcitation/λemission ≈ 230/415 nm; 290/415 nm; and 340/415 nm) and three protein-like (λexcitation/λemission ≈ 230/350 nm; 280/340 nm; and 225/300 nm), but one of the humic-like peaks (≈340/415 nm) does not always appear in the EEM fluorescence spectra of the Winter samples. During the cold season, chromophoric compounds are important constituents of rainwater dissolved organic matter and the presence of these highly absorbing and fluorescing compounds may exert a determining effect in atmospheric absorption of solar radiation.

Mandibular reconstruction after gunshot trauma in a dog by use of recombinant human bone morphogenetic protein-2

A 6-year-old German Shorthaired Pointer was evaluated for possible reconstruction of a mandibular defect resulting from gunshot trauma. A 5-cm defect of the right mandibular body was evident. A segment of the mandibular body was removed 9 weeks earlier because of severe contamination and comminution associated with gunshot trauma. Subsequent right-sided mandibular drift resulted in malocclusion in which the left mandibular canine tooth caused trauma to mucosa of the hard palate medial to the left maxillary canine tooth. The right maxillary canine tooth caused trauma to gingiva lingual to the right mandibular canine tooth. The right mandible was stabilized with a 2.0-mm maxillofacial miniplate positioned along the lateral alveolar margin and a 2.4-mm locking mandibular reconstruction plate placed along the ventrolateral mandible. An absorbable compression-resistant matrix containing collagen, hydroxyapatite, and tricalcium phosphate was soaked in recombinant human bone morphogenetic protein-2 (rhBMP-2; 7.2 mL of a 0.5 mg/mL solution for a dose of 3.6 mg) and placed in the defect. By 4 weeks after surgery, an exuberant callus was evident at the site of the defect. By 7 months after surgery, the callus had remodeled, resulting in normal appearance, normal occlusion, and excellent function of the jaw. Mandibular defects resulting from gunshot trauma can be treated by removal of contaminated tissue and comminuted bone fragments, followed by staged reconstruction. The combination of rhBMP-2 and compression-resistant matrix was effective in a staged mandibular reconstruction in a dog with a severe traumatic mandibular defect.

SurgiSIS vs. Autologous Fascia Myringoplasty in Children

Objective SurgiSIS is a new bioactive material derived from porcine small intestinal mucosa (SIS). This acellular, easily absorbable collagen matrix promotes early and new vessel growth, and provides scaffolding for the remodeling tissues. This is an inexpensive and ready-to-use alternative to autologous grafts. We evaluated the efficacy, safety, and surgery time of SIS myringoplasty, and compared clinical outcomes with patient's temporalis fascia (PTF) repair in children. Methods Prospective, 2-group (SIS, and PTF) randomized, blinded study in a tertiary-care pediatric institution. 82 children for whom tympanic membrane (TM) repair was indicated were randomly assigned to receive either SIS or PTF myringoplasty. Patients and examining physician were blinded to surgical modality. Primary outcomes were the healing of the TM and surgical time; secondary outcome was presence of any reaction or inflammation of the TM. 2-year follow-up was obtained in all enrolled children. Results A total of 82 TM (43 in the SIS and 39 in the ATF groups) perforations were treated. There were 42 stable TM closures in the SIS (97.6%) and 37 (94.8%) in the PTF arm. TM closure was higher in the SIS arm, but results were not statistically significant (OR=04, 95% CI 0.12–1.41). SIS myringoplasty yielded reduced surgical time. No clinical evidence of reaction to SIS was encountered. Conclusions SIS myringoplasty is a safe and effective method for TM closure in children, with reduced surgical time. As compared with PTF, the SIS myringoplasty is not associated with significant decrease in the incidence of residual perforations.

Zero degree Cherenkov calorimeters for the ALICE experiment

The collision centrality in the ALICE experiment will be determined by the Zero Degree Calorimeters (ZDCs) that will measure the spectator nucleons energy in heavy ion collisions. The ZDCs detect the Cherenkov light produced by the fast particles in the shower that cross the quartz fibers, acting as the active material embedded in a dense absorber matrix. Test beam results of the calorimeters are presented.

Repair of a Large Furcation Perforation: A Four-Year Follow-Up

This case report describes the management of a large furcation perforation in a maxillary first molar. Although the majority of the pulpal floor was destroyed and the mesiobuccal root was damaged, an attempt was made to repair the defect and restore the tooth. An absorbable gelatin sponge matrix was placed, and the defect was repaired with gray ProRoot mineral trioxide aggregate. Subsequently the endodontic treatment was completed; the tooth was restored and was later used as a fixed partial denture abutment. A 55-month recall showed no evidence of periodontal breakdown, no symptoms, and complete healing of all periradicular lesions.

Biosorption of Zn(II) on the different Ca-alginate beads from aqueous solution

The performance of a new biosorbent system, consisting of a fungal biomass immobilized within an orange peel cellulose absorbent matrix, for the removal of Zn 2+ heavy metal ions from an aqueous solution was tested. The amount of Zn(II) ion sorption by the beads was as follows; orange peel cellulose with Phanerochaete chrysosporium immobilized Ca-alginate beads (OPCFCA) (168.61 mg/g) > orange peel cellulose immobilized Ca-alginate beads (OPCCA) (147.06 mg/g) > P. chrysosporium (F) (125.0 mg/g) > orange peel cellulose (OPC) (108.70 mg/g) > plain Ca-alginate bead (PCA) (98.26 mg/g). The Zn 2+ concentration was 100 to 1000 mg/L. The widely used Langmuir and Freundlich isotherm models were utilized to describe the biosorption equilibrium process. The isotherm parameters were estimated using linear and non-linear regression analysis. The Box–Behnken model was found to be in close agreement with the experimental values, as indicated by the correlation coefficient value of 0.9999.

Study of Complex Formation between 4-(2-Pyridylazo) Resorcinol and Al3+, Fe3+, Zn2+, and Cd2+ Ions in an Aqueous Solution at 0.1 M Ionic Strength

The complexation reactions between 4-(2-pyridylazo)resorcinol (PAR) and Al3+, Fe3+, Zn2+, and Cd2+ ions at 25 °C and 0.1 M ionic strength are performed spectrophotometrically. A critical comparison of the various PCA methods on the absorbance matrix data concerning the number of light-absorbing species has been made. Knowing the number of light-absorbing species is a critical step for subsequent quantitative and qualitative solution equilibria studies. Therefore, the nine selected index functions for the prediction of the number of light-absorbing components which contribute to a set of spectra are critically tested using the algorithms implemented in INDICES software. Behind the number of various complexes formed the stability constants of species ML and MLH, type log β110 and log β111, for the system of PAR (ligand L) with Zn2+ and Cd2+ ions and the stability constants of species MLH and ML2H, type log β111 and log β121, for the system of PAR (ligand L) with Al3+ and Fe3+ ions at 25 °C and 0.1 M ionic s...

Number of species in complexation equilibria of o-, m- and p-CAPAZOXS with Cd 2+, Co 2+, Ni 2+, Pb 2+ and Zn 2+ ions by PCA of UV–vis spectra

A critical comparison of the selected derivative principal component analysis (PCA) methods on the absorbance matrix data concerning the complexation equilibria between o-CAPAZOXS and Cd 2+, Pb 2+ and Zn 2+ or m-CAPAZOXS and Cd 2+, Co 2+, Ni 2+ and Zn 2+ or p-CAPAZOXS and Cd 2+ and Zn 2+ at 25 °C is provided. As the number of complex species in a complex-forming equilibria mixture is an important step in spectral data treatment, the nine selected index functions for the prediction of the number of light-absorbing species that contribute to a set of spectra is critically tested by the PCA. An improved identification with the second SD(AE) or third derivative TD(AE) and derivative ratio function ROD(AE) for the average error criterion AE is preferred. After the number of various complexes formed the stability constants of species ML, ML 2 (and ML 3, respectively) type log β 11, log β 12 (and log β 13, respectively) for the system of o-CAPAZOXS (ligand L) with the metals (the standard deviation s(log β pq ) of the last valid digits is given in brackets) Cd 2+ (6.39(5) and 11.51(9)), Pb 2+ (4.24(2) and 9.01(2)) and Zn 2+ (5.18(7) and 9.06(10)) and for the system of m-CAPAZOXS with Cd 2+ (6.59(20) and 11.51(32)), Co 2+ (7.19(6) and 12.19(8)), Ni 2+ (7.64(7) and 13.39(12)) and Zn 2+ (4.83(3) and 9.57(3)) and for the system of p-CAPAZOXS with Cd 2+ (6.44(5), 10.99(10) and 14.57(25)) and Zn 2+ (6.84(16), 13.05(29) and 18.74(43)) at 25 °C are estimated using SQUAD(84) nonlinear regression of the mole-ratio spectrophotometric data. The computational strategy is presented with goodness-of-fit tests and various regression diagnostics capable of proving the reliability of the chemical model proposed.

Number of species in complexation equilibria of SNAZOXS or Naphtylazoxine 6S and Cd 2+, Co 2+, Cu 2+, Ni 2+, Pb 2+ and Zn 2+ ions by PCA of UV–vis spectra

A critical comparison of the various PCA methods on the absorbance matrix data concerning the complexation equilibria between SNAZOXS and Cd 2+, Co 2+, Cu 2+, Ni 2+, Pb 2+ and Zn 2+ or Naphtylazoxine 6S and Cd 2+, Cu 2+, Ni 2+ and Zn 2+ at 25 °C is performed. The number of complex species in a complex-forming equilibria mixture is the first important step for further qualitative and quantitative analysis in all forms of spectral data treatment. Therefore, the accuracy of the nine selected index functions for the prediction of the number of light-absorbing components that contribute to a set of spectra is critically tested using the principal component PCA algorithm INDICES in S-Plus software. Four precise methods based upon a knowledge of the experimental error of the absorbance data and five approximate methods requiring no such knowledge are discussed. Precise methods always predict the correct number of components even a presence of the minor species in mixture. Due to the large variations in the index values and even at logarithmic scale they do not reach an obvious point where the slope changes. An improved identification with the second or third derivative and derivative ratio function for some indices is preferred. Behind the number of various complexes formed the stability constants of species ML, ML 2, (and ML 3, respectively) type log β 11, log β 12, (and log β 13, respectively) for the system of SNAZOXS (ligand L) with six metals (the standard deviation s(log β pq ) of the last valid digits are in brackets) Cd 2+ (4.50(3), 8.36(7)), Co 2+ (5.75(6), 9.79(9), 13.05(2)), Cu 2+ (6.69(6), 11.40(7)), Ni 2+ (6.44(8), 10.91(11), 15.07(10)), Pb 2+ (5.63(5), 9.97(9)) and Zn 2+ (5.11(3), 8.84(5)) and for system of Naphtylazoxine 6S with Cd 2+ (6.08(4), 11.44(7), 16.06(11)), Cu 2+ (7.80(8), 13.41(14)), Ni 2+ (6.35(12), 11.43(19), 16.68(24)) and Zn 2+ (7.01(8), 12.65(15)) at 25 °C are estimated with SQUAD(84) nonlinear regression of the mole-ratio spectrophotometric data. The proposed strategy of an efficient experimentation in a stability constants determination, followed by a computational strategy, is presented with goodness-of-fit tests and various regression diagnostics able to prove the reliability of the chemical model proposed.

Chemical speciation of Ag in galena by EPR spectroscopy

Electron paramagnetic resonance (EPR) spectroscopy has been used to study the valence state of silver in “argentiferous” galena samples from the Apuane Alps (Tuscany, Italy) mining district. This method was used to reveal primary metallic silver (Ag0) in galena. Both thermodynamic data and experimental studies suggest that galena and native silver can stably coexist, but have not been reported as a primary (hypogene) assemblage in natural samples. EPR spectroscopy proved to be a suitable tool to solve this problem, because this technique is capable of detecting paramagnetic species down to the ppb level, even in a highly absorbent matrix such as galena. A detailed SEM-EDS investigation could not detect metallic silver (or gold) in galena samples, but did reveal small (few micrometers) inclusions of Ag-bearing phases, in which silver has a formal valence of +1. On the other hand, EPR spectra indicated the presence in galena of pairs and clusters of elemental silver atoms, which may be associated with pairs of metallic gold, or with silver-gold hetero-atomic pairs. Therefore, SEM/EDS and EPR are complementary techniques, revealing the presence of both Ag + and Ag 0 . The Ag(Au) metallic species were apparently deposited on the galena surface during its growth from mineralizing fluids. Their scarcity, and the presence of larger amounts of Ag 1+ phases, suggest that the assemblage galena-metallic silver was stable only under peculiar physical and chemical conditions. The formation of Ag 0 was presumably linked to local and rare chemical fluctuations of the hydrothermal environment, characterized by low activities of S, Sb, Bi (Cu…) and high activity of Ag in the fluids. The occurrence of both homo- and hetero-atomic pairs suggests either different kinetics of pair formation, or possible fluctuations in the composition of the hydrothermal fluids, which alternatively carried Ag or Au species, or both

Simultaneous spectrophotometric determination of cyproterone acetate and estradiol valerate in pharmaceutical preparations by ratio spectra derivative and chemometric methods

Ratio spectra derivative spectrophotometry and two chemometric methods (classical least squares, CLS and inverse least squares, ILS, were proposed for the simultaneous quantitative analysis of a binary mixture consists of cyproterone acetate (CA) and estradiol valerate (EV) in the commercial pharmaceutical preparations. In the ratio spectra derivative method, linear regression equations for both drugs were obtained by measuring the analytical signals at the wavelenghts corresponding to either maximums and minimums in the first derivative spectra of the ratio spectra. In the chemometric techniques, the concentration matrix was prepared by using the synthetic mixtures containing these drugs. The absorbance matrix corresponding to the concentration matrix was obtained by measuring the absorbances at 14 wavelengths in the range 220–290 nm for the zero-order spectra. Two chemometric calibrations were constructed by using the absorbance matrix and concentration matrix for the prediction of the unknown concentrations of CA and EV in their mixture. The numerical values were calculated by using ‘ maple v’ software. The accuracy and the precision of the methods have been determined and they have been validated by analyzing synthetic mixtures containing these two drugs. The proposed methods were successfully applied to a pharmaceutical formulation, sugar-coated tablet, and the results were compared with each other.

Correction of inner filter effect in mirror coating cells for trace level fluorescence measurements.

The sensitivity of the spectrofluorometric technique can be improved by a factor of about 3.6 using a mirror coating cell. In the case of a large working range, the nonlinear relationship due to the absorbance of solutions between concentration of the analyte of interest and fluorescence intensity (called inner filter effect) must be corrected. This paper suggests a universal inner filter correction equation based on the physical absorbance phenomenon of a mirror coating cell that only depends on the solution absorbance spectra and the cell parameters. These parameters are determined with rhodamine b standard solutions and a simplex method-based mathematical fitting. The methodology has been successfully applied to the correction of classical and synchronous spectra in absorbent media. The partial least squares (PLS) quantification of a mixture of trace levels (approximately 1-10 microg L(-1)) of six polycyclic aromatic hydrocarbons (PAHs) by synchronous fluorescence is possible, even in an absorbent matrix. This simple method allows extension of the analytical field of fluorescence quantification to a large working range in absorbent solutions.

Extracting Experimental Information from Large Matrices. 2. Model-Free Resolution of Absorbance Matrices: M3

We present a new method for the decomposition of an experimental absorbance matrix into concentration and molar absorption coefficient matrices. The decomposition in general is not unambiguous; the...

低栄養塩濃度条件下におけるＭｉｃｒｏｃｙｓｔｉｓ ａｅｒｕｇｉｎｏｓａ産生有機物のＳＵＶＡ及び励起蛍光マトリクスによる特性評価

The analyses of specific ultraviolet absorbance (SUVA) and excitation emission matrix (EEM) were applied to characterize algogenic organic matter (AOM) produced by Microcystis aeruginosa at low nutrient concentrations and at three different N/P ratios. The production of dissolved organic carbon (DOC) during stationary phase was 3.6-5.8 times as much as that during exponential phase at any N/P ratios, while the components with ultraviolet absorbance at 260nm (E260) were remarkably released during the exponential phase at N/P=20. The ΔE260/ΔDOC value during the exponential phase at N/P=20 was 5.1 l·Abs·mgC-1·m-1, which was significantly higher than the reported values for AOMs. Six peaks of fluorescence intensity on EEM maps were identified and one of them (called “Pα” at 230 nm/430 nm (excitation/emission)) had never been reported as a fluorescence peak before. Peak profiles of AOMs on EEM maps were characterized by 1) the presence of Pα, 2) the absence of P3, 3) the relatively high fluorescence intensities at P1 and P2, and 4) the higher fluorescence intensity at P4 than at P6. EEM maps were divided into four zones according to the position of important peaks. The presence of unidentified peaks was discussed based on the relationship between fluorescence peak intensity and the integral value of fluorescence within each zone.

Time resolved fluorescence spectroscopy of quercetin and morin complexes with Al 3+

The association process of Al 3+ with quercetin and morin in methanol was studied by electronic absorption and emission spectroscopies. The number of species in solution with different absorption spectra were determined by the method of Rank analysis of the absorbance matrix, and the stoichiometries of the complexes were evaluated using the Job method. The number of fluorescent species in solution were calculated from the Rank analysis method of the time resolved emission spectra (TRES), and compared with a global analysis of the decay surface using a proper multi-exponential decay model. The association of Al 3+ with morin gives rise to two complexes with 1:1 and 2:1 (morin: Al 3+) stoichiometries, but in both species the association of the cation involves the carbonyl and 3-hydroxyl groups of the pyrone ring. The fluorescence decay surface of this system is biexponential and the lifetimes of the 1:1 and 2:1 complexes are 4.3 and 2.0 ns, respectively. The association of Al 3+ with quercetin forms preferentially two complexes with 1:1 and 1:2 (quercetin: Al 3+) stoichiometries where the first cation binds to the site of the pyrone ring but the second one is bound to the cathecol group of the molecule. However, the multichelation character of the quercetin ligand allows larger aggregates to be formed, thereby the species Al 2Q 3 is also detected in methanol. The lifetime of the 1:1 complex is about 2.7 ns, while for 1:2 and 3:2 complexes the lifetimes measured are 3.5 and 1.8 ns, respectively.

Preliminary in vivo studies on the osteogenic potential of bone morphogenetic proteins delivered from an absorbable puttylike polymer matrix.

This article describes preliminary in vivo studies evaluating the osteogeneic potential of bone morphogenetic proteins (BMPs) delivered from an absorbable puttylike polymer matrix. In the first study, bovine-derived bone morphogenetic proteins were incorporated in an polymer matrix consisting of 50:50 poly(DL-lactide-co-glycolide) dissolved in N-methyl-2-pyrrolidone. The matrix was implanted in an 8 mm critical-size calvarial defect created in the skull of adult Sprague-Dawley rats (n = 5 per treatment group). After 28 days, the implant sites were removed and examined for new bone formation, polymer degradation, and tissue reaction. Gamma-irradiated polymer matrices appeared to give more bone formation than nonirradiated samples (histological analysis; 2. 76 + 1.34 mm(2) of bone versus 1.30 + 0.90 mm(2) of bone, respectively and x-ray analysis; 27.2 + 15.9 mm(2) of bone versus 20. 7 + 16.7 mm(2) of bone, respectively) and less residual polymer (0.0 + 0.0 versus 0.2 + 0.4, respectively). The polymer implants with bone morphogenetic protein also gave less inflammatory response than the polymer controls (gamma irradiated polymer/BMP = 1.8 + 0.4 and nonirradiated polymer/BMP = 1.2 + 0.4 versus polymer only = 3.0 + 1. 2, respectively). However, despite trends in both the x-ray and histological data there was no statistical difference in the amount of new bone formed among the four treatment groups (P > 0.05). This was most likely due to the large variance in the data scatter and the small number of animals per group. In the second animal study, bovine-derived BMPs and the polymeric carrier were gamma irradiated separately, at doses of 1.5 or 2.5 Mrad, and their ability to form bone in a rat skull onlay model was evaluated using Sprague-Dawley rats (n = 5 per treatment group). Histomorphometry of skull caps harvested 28 days after implantation showed no significant differences as compared to non-irradiated samples, in implant area, new bone area, and percent new bone (P > 0.05). These results suggest gamma irradiation may be useful in sterilization of the bovine-derived BMPs and the polymeric carrier for potential bone repair and/or regeneration applications.

Phase behavior of a two-dimensional quenched–annealed lattice gas with nearest-neighbor attraction. Grand canonical Monte Carlo simulation

We performed Monte Carlo simulation of the phase diagram of a two-dimensional lattice with the nearest-neighbor attraction on a hexagonal lattice. A fraction of sites is rigidly fixed in a disordered configuration in order to mimic quenched absorbent (matrix). It is shown that the phase diagram of this partly quenched system is essentially narrower and the critical temperature is lower, compared with the bulk system, i.e. without matrix. Moreover, a liquid-like branch of the coexistence envelope has a specific shape. It is shown that different, thermodynamically equivalent, matrix configurations result in a slightly different gas-liquid critical temperature. We have analyzed profoundly thermodynamic behavior of a fluid in each copy of the matrix realization. In particular, the behavior of the heat capacity, of the fourth Binder cumulant, compressibility of a fluid along coexistence are analyzed. The pair distribution function of fluid species and its blocking term, due to correlations of fluid particles via matrix subsystem, have been obtained. The blocking distribution function appears to be more long ranged than the total fluid–fluid distribution function. The fluctuations of the blocking effects may serve as a measure of the number of matrix realizations necessary to involve in obtaining adequate statistical averages in the partly quenched systems.

Low-Cost MR Fluid Sponge Devices

A variety of robust, high-strength, MR fluids and devices that enable the benefits of controllable fluid technology are now commercially available. Commercial, mass-produced devices include rotary brakes for use in exercise equipment, real-time controllable vibration dampers for truck seats and adjustable linear shock absorbers for racing cars. Recently, a new way of using MR fluids in which the fluid is contained in an absorbent matrix has been developed. Such MR fluid sponge devices enable the benefits of controllable MR fluids to be realized in cost sensitive applications. Most of the high-cost components normally associated with a fluid filled device can be eliminated with this approach. Low-cost, controllable MR fluid sponge dampers are particularly appropriate for moderate-force vibration control problems where a high degree of control authority is desired such as a new generation of high-performance, home washing machines now being developed.