Tissue reactions to bioabsorbable ciprofloxacin-releasing polylactide-polyglycolide 80/20 screws in rabbits’ cranial bone

The aim of this study was to assess tissue reactions to bioabsorbable self-reinforced ciprofloxacin-releasing polylactide/polyglycolide (SR-PLGA) 80/20 screws in rabbits' cranial bone. Two screws were implanted in each rabbit, one screw on either side of the sagittal suture (n = 28 rabbits). Animals were sacrificed after 2, 4, 8, 16, 24, 54 and 72 weeks, four animals per group. On histological examination the number of macrophages, giant cells, active osteoblasts and fibrous tissue layers were assessed and degradation of the screws was evaluated. At 2 weeks, the highest number of macrophages and giant cells were seen near the heads of the screws. After 4 and 8 weeks, the number of giant cells decreased but that of macrophages decreased from 16 weeks and on. Screws were surrounded by fibrous tissue capsule that progressively was growing in thickness by time. Active osteoblasts were seen around the shaft of the screws with the highest number seen at 4 weeks postoperatively. At 16 weeks, compact fragmentation of the screw heads was seen with macrophages seen inside the screw matrices. After 24 weeks, no polarization of the screws was seen. After one year, PLGA screws had been replaced by adipose tissue, fibrous tissue and "foamy macrophages" which had PLGA particles inside them. After 1(1/2) years, the amount of biomaterial remaining had decreased remarkably. The particles of biomaterial were inside "foamy macrophages." Ciprofloxacin-releasing SR-PLGA 80/20 screws elicited a mild inflammatory reaction but did not interfere with osteoblast activity. No complications were seen when implanted in cranial bone of rabbit.     

Material and knot properties of braided polyester (Ticron®) and bioabsorbable poly-L/D-lactide (PLDLA) 96/4 sutures

The purpose of the present study was to investigate in vitro the biomechanical material and knot properties and histomorphometrical knot properties of 3-0 braided polyester suture (Ticron) and bioabsorbable poly-L/D-lactide (PLDLA) 96/4 suture. In Ticron five throws are needed to form a secure knot, and the 1 = 1 = 1 = 1 = 1 and the 2 = 1 = 1 = 1 configurations are recommended. For PLDLA several granny and square knots formed a secure knot, but the 1 = 1 and 1 = 1 = 1 knots were the best. These PLDLA knots had lower yield force and strain at yield point, but higher stiffness than the recommended Ticron knots. The ultimate force values did not differ, but PLDLA knots had significantly higher strain at ultimate point. In the histomorphometrical analysis of the recommended knots, the PLDLA knots had a significantly smaller knot surface area than the Ticron knots. According to these results, PLDLA suture proved to be suitable for flexor tendon repair.     

The specific heat of samarium metal (80–400 K)

We have measured the specific heat of several high purity polycrystalline specimens of samarium metal over the temperature range 80 K to 400 K. A broad peak is observed at T_Nh ~106K, the temperature at which antiferromagnetic ordering first sets in with ordering of the moments on hexagonal sites. This behaviour contrasts with the sharp peak observed by previous workers on samarium samples of lower purity.     

Alfred Swaine Taylor (1801–80)

Abstract

After a period in decline the Portobello Road market in London has enjoyed a revival in the past two or three years. There are at least three dealers in historic photographs within fifty yards of an East Anglian couple who regularly bring good quality decorative antiques and other curios to sell on Saturday mornings. I stopped at their showcase, looked in, walked on, and then returned to take a second look at a scrapbook, so often a source of good printed ephemera. It was open at a page showing a comic drawing of a wagon done up as an itinerant photographer's studio. I was told how much the scrapbook was and spent the next ten minutes looking through it. I decided on balance that I could ‘just about see the price in it’ ignoring the four photographs, which I believed must be of little or no value. On reaching my car I had another look through the album. A negative image of a leaf (figure 1) looked interesting, for a few months earlier I had been to Lacock and now remembered Talbot's photogenic drawings. Examination of the engravings and lithographs showed that they started in the 1820s and ended in 1853. This was undoubtedly a girl's scrapbook begun when she was quite small and probably continued until her early teens when the enthusiasm for pasting was bound to wane. I settled on a probable year of birth of 1840 for the girl but most careful combing discovered no name or initials in the book. There were, however, some postcards celebrating a pageant in 1907 at Bury St Edmunds, Suffolk, and one had been posted to a Mrs F. Methold at an address in Bury, but how she was connected with the book remained to be disovered. I looked once more through the printed ephemera and spotted that two cards with heavily embossed borders had small hand-coloured lithographs pasted on to them. My suspicion that these were early Victorian invitations proved to be correct. Removing the little pictures revealed that they were invitations from the Pharmaceutical Society to Alfred S. Taylor, FRS, to attend two dinners dated May 1848 and July 1849. I did not think that it was straining common sense to conclude that father had given his daughter these old invitations for her scrapbook.     

Characterization of microstructure and mechanical properties of Al–Cu–Mg–Ag–(Mn/Zr) alloy with high Cu:Mg

This study examines the effects of the addition of Mn or Zr on the microstructure and mechanical properties of Al–Cu–Mg–Ag alloy using optical microscopy, scanning electron microscopy, X-ray diffraction, differential scanning calorimetry, transmission electron microscopy, tensile test, and tear test. The results showed that the alloy with Zr exhibited the highest strength and the lowest fracture toughness, which may be attributed to the segregation of the secondary phases containing the Zr element on the recrystallization grain boundaries. The alloy with Mn exhibited strength that is roughly equal to the Al–Cu–Mg–Ag alloy and the highest fracture toughness, which may be due to the formation of secondary phases containing Mn and Fe elements. Mn or Zr addition also has no remarkable influence on the characteristics of the precipitates. The Ω phase and a small quantity of θ′ phases dominated the microstructure of the three alloys after aging.     

Effect of manganese content on hot deformation behaviour of Fe–(20/27)Mn–4Al–0.3C non-magnetic steels

The influence of Mn content on flow behaviour and constitutive equations of Fe–(20/27)Mn–4Al–0.3C austenitic steels was investigated by uniaxial hot compression tests. The recrystallisation fraction was also measured using electron backscattered diffraction. Although dynamic recrystallisation is slightly delayed by the increased Mn content, the peak stress still has a pronounced decline especially during the deformation at relatively low temperature. The reason should be ascribed to the enhanced stacking fault energy, by which workhardening rate before the onset of dynamic recrystallisation is diminished significantly with the reinforced cross-slip process. The hot deformation activation energy is decreased under the condition of higher Mn addition, while the strain rate sensitivity of flow stress almost remains unchanged.     

Adherence of alumina scale formed on Fe–20Cr–4Al alloys with noble metals (Pd,Pt)

Abstract

Adherence of oxide scale formed on Fe–20Cr–4Al (standard: 4 ppmS), Fe–20Cr–4Al (FZ: <1 ppmS) purified by floating zone melting, and Fe–20Cr–4Al–(0.05, 0.1, 0.3, 0.5)–Pd(Pt) alloys was studied in oxygen for 18 ks at 1373–1673 K, by mass gain measurements, X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). Spalling of oxide scale on the standard alloy occurred along the alloy grain boundaries after oxidation at 1373 K, and was found to spall over the entire surface after oxidation at 1473 and 1573 K. However, the standard alloy showed good oxide adherence after oxidation at 1673 K. The other alloys showed good oxide adherence after oxidation at any temperature. Mass gain of the FZ and noble metal-containing alloys increased with increasing temperature of oxidation, and showed almost the same values at each temperature. Oxide scale on the standard alloy showed wavy morphology after oxidation at 1373 and 1473 K, and changed to planar morphology after oxidation at 1573 and 1673 K. On the other hand, oxide scale on the other alloys showed almost planar morphology after oxidation at any temperature. Oxide scale formed on all the alloys was only found to be α-Al₂O₃ after oxidation at any temperature.     

CALPHAD simulation of the Mg–(Mn,Zr)–Fe system and experimental comparison with as-cast alloy microstructures as relevant to impurity driven corrosion of Mg-alloys

Four Mg alloys with variations in the ratio of Mn, Zr and Fe additions were cast and their microstructures analysed via electron microscopy. Thermodynamic calculations of the expected phases using PANDAT were evaluated with actual as-cast microstructures. Some of the as-cast alloys did appear to form phases similar to those anticipated from the PANDAT calculations. Furthermore, there was a new Mn–Fe particle interaction observed that was not predicted, but which is posited to be responsible for the increase in corrosion resistance among Mn containing Mg alloys with Fe impurities. The experimental work herein has been shown to be invaluable in the understanding of this practically important system with sparingly soluble Fe and its potential influence on the corrosion of Mg alloys.     

Nano-mechanical characterization of synthetic calcium–silicate–hydrate (C–S–H) with varying CaO/SiO2 mixture ratios

Synthetic calcium silicate hydrate (C–S–H) made with calcium to silicate (C/S) mixture ratios of 0.9, 1.2 and 1.5 respectively is characterized. C–S–H was produced by extracting calcium oxide (CaO) from calcium carbonate (CaCO₃) and then mixing it with micro-silica (SiO₂) and deionized water to make slurry. The slurry was continuously mixed for 7 days, then the excess water was removed and thermo gravimetric analysis (TGA) was conducted. The drying method was equilibrated to 11% relative humidity (RH). The stoichiometric formula of the synthetic C–S–H were approximated as C_0.7SH_0.6, C_1.0SH_0.8 and C_1.2SH_2.4 for C/S mixture ratios of 0.9, 1.2 and 1.5 respectively. The dried powders were characterized using X-ray diffraction analysis (XRDA), and ²⁹Si magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. The powders were also compacted with 95 MPa pressure and nanoindentation of the compacted specimens were then undergone to mechanically characterize the synthetic C–S–H. The experiments provide insight on the nanoscale mechanical characteristics of C–S–H.     

Applicability of the polymeric precursor method to the synthesis of nanometric single- and multi-layers of Zn1?xMnxO (x?=?0–0.3)

Polymeric precursor method (Pechini) was employed to fabricate single- and multilayers of Zn_1−x Mn _x O (x = 0–0.3) on glass substrates. X-ray diffraction measurements revealed that crystal structure of Zn_1−x Mn _x O multilayers is the typical hexagonal würzite structure of pristine ZnO. A reduced peak intensity and widened full width half maximum (FWHM) value of prominent peaks suggested that the Mn²⁺ ions have substituted the Zn²⁺ ion without changing the würzite structure of pristine ZnO up to Mn concentrations x ≤ 0.2. A distinct redshift of the absorption edge was observed as the Mn concentration x was increased. Additionally, the absorption edge was less sharp due, probably, to s–d and p–d interactions, which give rise to band gap bowing. Nevertheless, amorphous states appearing in the band gap as a consequence of reduced crystallinity may also be responsible for the shrinking of the band gap in this material. Interestingly, the field dependence of the magnetization showed typical paramagnetic behavior for all the chosen Mn concentrations with no evidence of ferromagnetic ordering. Probably, the absence of ferromagnetism in the studied Zn_1−x Mn _x O films is strongly related to defects (say Mn impurities at the interface between nano-crystallites) in ZnO due to partial substitution of host Zn ions by Mn ions.     

Stranski–Krastanov growth of (Si)Ge/Si(001): transmission electron microscopy compared with segregation theory

ABSTRACT

We performed transmission electron microscopy of SiGe/Si(001) and Ge/Si(001) samples that undergo the Stranski–Krastanov transition from flat layer to island growth. With the help of quantitative X-ray maps of those layers, we have determined the total amount of deposited germanium at which islanding commences. The maximum amount of Ge buried in a flat layer amounts to 2.3 monolayers. We show by modelling that it is the strain due to the total amount of Ge atoms deposited that drives the islanding process. At 600°C [400°C], 1.62 [1.74] monolayers of Ge are expected from simulations to segregate towards the surface, the strain of which is sufficient to trigger plastic relaxation by islanding, in agreement with our electron microscope observations.

This is part of a thematic issue on Nanoscale Materials Characterisation and Modeling by Advances Microscopy Methods - EUROMAT.     

Scientometric study of biochemical literature of Nigeria, 1970–1984: Application of Lotka's law and the 80/20-Rule

A bibliography of biochemical literature of Nigeria for the period, 1970–1984 containing a total of 500 items, was analysed to test the applicability of Lotka's law and 80/20-rule to the author productivity distribution patterns. Four different files were created out of the data on author productivity: one for the publication of all the authors, second for the publications by first authors only, third for single authors and fourth for the contributions of only coauthors. Lotka's law could apply in all the four cases with different values of . The Kolmogorov-Smirnov test was applied to test the applicability of Lotka's law at 0.01 level of significance. Egghe's theory and formula were used to test 80/20-rule and it was found that the rule did not apply to any of the four data sets.     

Decomposition of Fe–(6–20) at.% Mo alloys

Binary iron alloys containing 6, 10, 15 and 20 at.% Mo were investigated. It was found that the “ordering–phase separation” transition is a time depending process: at the beginning of isothermal aging at 550 °C, a modulated structure is formed in the solid solution as a result of the tendency toward phase separation; with time, Fe₂Mo particles precipitate in the modulated structure dissolving as a result of the tendency toward ordering. Further aging at 550 °C leads to the complete dissolution of the modulated structure and Fe₂Mo particles remain the only phase precipitated in the solid solution.     

Fe_(80)B_(20)、Fe_(80)Si_6B_(14)金属玻璃中近邻原子间的相互作用

由过渡金属-类金属形成的金属玻璃的结构的研究有不少的报导。其中某些结构模型的研究,表明类金属原子周围的近邻结构具有一定的特性。因此,深入研究这类金属玻璃中近邻原子,特别是金属-类金属原子间的相互作用是很重要的。     

Structure and micro-nanomechanical characterization of synthetic calcium–silicate–hydrate with Poly(Vinyl Alcohol)

The principal phase of hardened Portland cement pastes is calcium silicate hydrate (C–S–H), which influences the physical and mechanical properties of construction materials. In this work calcium silicate hydrate (C–S–H) was synthesized, with the addition of Poly(Vinyl Alcohol) (PVA), for the development of C–S–H/polymer nanocomposites. Among the polymers available, PVA is indicated by the literature as one of the most viable for producing C–S–H/polymer complexes. However, no consensus exists regarding the kind of interaction. The resulting compounds were characterized by XRD, FT-IR, TGA, carbon content (CHN), TEM, SEM and elastic modulus and hardness were measured by instrumented indentation. The set of results presented do not confirm the intercalation of PVA in the interlayer space of C–S–H, but presented evidence of the potential for intercalation, since changes in the structure clearly occurred. A significant change in the micro-nanomechanical properties of C–S–H occurred in the presence of PVA.     

Turbidity removal of fine coal–water suspension by flocculation using Taguchi (L16) experimental design

Taguchi method is rather practical way for setting the best combination of different variables for various parameters in such phenomenon requiring excessive number of experiments. In this study, a series of flocculation experiments were performed using Taguchi (L₁₆) experimental design to determine the optimum conditions for the turbidity removal from fine coal suspensions. The effects of some controllable factors on the turbidity removal were evaluated by effective flocculation recovery via analysis of mean statistical approach and the percentage contributions of each parameters were also defined using analysis of variance statistical approach. The most influential factor was determined as the polymer concentration with a contribution of 47.831%. The optimum conditions were ascertained as pH?=?7, stirring speed of 500?rpm, polymer concentration of 2?mg/L, flocculation time of 3?min, and polymer type of 934SH.     

Thermal properties of aqueous solutions of polyvinylpyrrolidone in the temperature range 20–80°C

The thermal properties (thermal diffusivity a, thermal conductivity , and volumetric heat capacity C _p) of aqueous solutions of polyvinylpyrrolidone (PVP) were measured in the temperature range 20–80°C. The measurements were carried out using the hot-wire (strip) technique. Three different average molecular weights of PVP were used [M = 10,000 (PVP-10), M = 24,500 (PVP-24.5), and M = 40,000 (PVP-40)], i.e., the average degrees of polymerization are 90, 220, and 360, respectively. The results show that the values of the thermal properties depend on the temperature and the concentration of PVP in the medium. The mechanism of heat transfer was discussed. The role of convection and radiation were taken into consideration.     

Physical and electrical attributes of sintered Ag80–Al20 high temperature die attach material with different organic additives content

In this work, the primary focus was to establish a relationship between the post-sintered physical attributes of the high temperature Ag₈₀–Al₂₀ die attach material and its electrical performance. The post-sintered Ag₈₀–Al₂₀ die attach material depicted the formation of Ag₂Al and Ag₃Al compounds. The melting point and maximum operational temperature for the Ag₈₀–Al₂₀ die attach material was determined to be 518 ± 1 °C and approximately 400 °C respectively, whereby the maximum operational temperature was based on a homologue temperature ratio of 0.85. The die attach material also demonstrated good electrical properties, i.e., an electrical conductivity value of 1.005 × 10⁵ (ohm–cm)^?1, which is higher than or equal to that of most solder systems. By varying the nanoparticle versus organics content between 83.3 and 87.0 %, it was seen that the surface morphology of the die attach material changed and the root-mean-square roughness values reduced to 175.1 nm. A similar observation was seen as the sintering temperature increased between 100 and 380 °C. This reduction in surface roughness proved that there was grain growth and particle coalescence within the die attach material. This translated to a reduction in electrical resistivity. Die attach area and thickness simulations found that smaller and thinner die attach areas are preferred for the Ag₈₀–Al₂₀ die attach material, whereby the highest recorded electrical conductivity value was 1.006 × 10⁵ (ohm–cm)^?1 for an area of 0.2 × 0.2 cm² and thickness of 25.4 μm.     

溅射工艺对Cu/SiO_2/Ni_(80)Fe_(20)复合结构丝形貌及磁性能影响

利用射频磁控溅射方法在自旋的Cu上制备了Cu/SiO2和Cu/SiO2/Ni80Fe20两个系列复合结构丝。利用扫描电镜、阻抗分析仪分析了溅射SiO2时基底丝旋转速率对复合结构丝的表面微观结构和巨磁阻抗效应的影响。实验结果表明,镀层表面颗粒大小随着制备SiO2时转速的增加先减小后增大,Cu/SiO2/Ni80Fe20复合结构丝的巨磁阻抗效应则随着转速的增加先增大后减小。     

Unusual photoluminescence of Cu–ZnO and its correlation with photocatalytic reduction of Cr(VI)

Cu–ZnO was synthesized by sol–gel route with a varied copper concentration of 1, 2 and 3 mol%. The synthesized materials were structurally characterized with powder X-ray diffraction and Raman spectroscopy, morphologically using a field emission scanning electron microscope, and electronic properties were studied with UV–visible spectroscopy and photoluminescence spectroscopy. Variation in Cu doping showed enhancement/quenching in photoluminescence of ZnO. This special characteristic is reflected in photocatalytic reduction of Cr(VI).