Physicochemical characterisation and biological evaluation of polyvinylpyrrolidone-iodine engineered polyurethane (Tecoflex<Superscript>®</Superscript>)

Bacterial adhesion and encrustation are the known causes for obstruction or blockage of urethral catheters and ureteral stents, which often hinders their effective use within the urinary tract. In this in vitro study, polyvinylpyrrolidone-iodine (PVP-I) complex modified polyurethane (Tecoflex^®) systems were created by physically entrapping the modifying species during the reversible swelling of the polymer surface region. The presence of the PVP-I molecules on this surfaces were verified by ATR-FTIR, AFM and SEM-EDAX analysis, while wettability of the films was investigated by water contact angle measurements. The modified surfaces were investigated for its suitability as a urinary tract biomaterial by comparing its lubricity and ability to resist bacterial adherence and encrustation with that of base polyurethane. The PVP-I modified polyurethane showed a nanopatterned surface topography and was highly hydrophilic and more lubricious than control polyurethane. Adherence of both the gram positive Staphylococcus aureus (by 86%; **P < 0.01) and gram-negative Pseudomonas aeruginosa (by 80%; *P < 0.05) was significantly reduced on the modified surfaces. The deposition of struvite and hydroxyapatite the major components of urinary tract encrustations were significantly less on PVP-I modified polyurethane as compared to base polyurethane, especially reduction in hydroxyapatite encrustation was particularly marked. These results demonstrated that the PVP-I entrapment process can be applied on polyurethane in order to reduce/lower complications associated with bacterial adhesion and deposition of encrustation on polyurethanes.     

Synthesis and photoluminescence characterization of Ce<Superscript>3 + </Superscript> and Dy<Superscript>3 + </Superscript> activated ALa(WO<Subscript>4</Subscript>)<Subscript>2</Subscript>(A = Na and Li) novel phosphors

In this paper, we report the synthesis of Ce^3 + and Dy^3 + activated alkali lanthanide tungstates, ALa(WO₄)₂(where A = Na and Li), prepared by solid state reaction method. The prepared phosphors were characterized by X-ray diffraction and photoluminescence techniques. The NaLa(WO₄)₂:Dy^3 + and LiLa(WO₄)₂:Dy^3 + phosphors show two emission peaks at around 574 and 486 nm (λ_exc = 354 nm). NaLa(WO₄)₂:Ce^3 + and LiLa(WO₄)₂:Ce^3 + show two emission peaks at around 378 and 425 nm (λ_exc = 350 nm). Excitation wavelengths of Ce^3 + and Dy^3 + activated alkali lanthanide tungstates are in near UV region i.e. Hg free excitation. These characterizations of phosphors are applicable for solid state lighting. Accordingly, Ce^3 + and Dy^3 + activated NaLa(WO₄)₂ and LiLa(WO₄)₂ may be the promising materials for solid state lighting applications.     

Effect of the high doze of N<Superscript>+</Superscript>(10<Superscript>18</Superscript> cm<Superscript>–2</Superscript>) ions implantation into the (TiHfZrVNbTa)N nanostructured coating on its microstructure,elemental and phase compositions,and physico-mechanical properties

Structure and properties of (TiHfZrVNbTa)N nanostructured multicomponent coatings implanted with a very high (10¹⁸ cm^–2) dose of N⁺ions have been studied. As a result of the implantation a multilayer structure has been formed in the surface layer of the coating. The structure is composed of amorphous, nanocrystalline (disperse) and nanostructured (with the initial sizes) nanolayers. In the depth of the coating two phases (with the fcc and hcp structures) having a small volume content are formed. The nitrogen concentration near the surface attains 90 at % and then decreases with the depth. In the initial state after the deposition the coating nanohardness values are from 27 to 34 GPa depending on the conditions of the deposition. As a result of the implantation the hardness is decreased approximately by the depth of the projective ions range, i.e., to 12 GPa and then increases with the depth to 23 GPa. The investigations were conducted using the Rutherford backscattering, scanning electron microscopy with the microanalysis, high resolution electron microscopy (with local microanalysis), X-ray diffraction, nanoindentation, and wear tests.     

Crystal structure of compounds CsA<Superscript>V</Superscript>A′<Superscript>VI</Superscript>O<Subscript>6</Subscript> (A<Superscript>V</Superscript> = Sb,Ta; A′<Superscript>VI</Superscript> = W,U)

Compounds CsA^VA′^VIO₆ (A^V = Sb, Ta; A′^VI = W, U) were synthesized by high-temperature solidphase reactions. The crystal structures of the compounds were refined by the Rietveld method (space group Fd \(\bar 3\) m).     

Spectroscopic properties of Nd<Superscript>3+</Superscript>, Yb<Superscript>3+</Superscript>-doped and Nd<Superscript>3+</Superscript>–Yb<Superscript>3+</Superscript>-codoped high silica glass

The Nd³⁺, Yb³⁺-doped and Nd³⁺–Yb³⁺-codoped high silica glasses (HSGs) were fabricated by sintering porous glasses impregnated with Nd³⁺ and Yb³⁺ ions solutions. The Judd–Ofelt theory was used to study the spectroscopic properties of Nd³⁺-doped HSGs. Large parameter Ω₂ of Nd³⁺-doped HSGs suggests a lower centrosymmetric coordination environment around the Nd³⁺ in HSG. The spontaneous emission probability and emission cross-section (σ_em) of Yb³⁺-doped HSGs are obtained. A broad emission band from 950 to 1,100 nm was detected when the Nd³⁺–Yb³⁺-codoped HSG was excited by 808 nm LD. The energy transfer process from Nd³⁺ to Yb³⁺ in HSG was described in this paper.     

Comparison of an experimental bone cement with surgical Simplex<Superscript>®</Superscript> P,Spineplex<Superscript>®</Superscript> and Cortoss<Superscript>®</Superscript>

Conventional polymethylmethacrylate (PMMA) cements and more recently Bisphenol-a-glycidyl dimethacrylate (BIS-GMA) composite cements are employed in procedures such as vertebroplasty. Unfortunately, such materials have inherent drawbacks including, a high curing exotherm, the incorporation of toxic components in their formulations, and critically, exhibit a modulus mismatch between cement and bone. The literature suggests that aluminium free, zinc based glass polyalkenoate cements (Zn-GPC) may be suitable alternative materials for consideration in such applications as vertebroplasty. This paper, examines one formulation of Zn-GPC and compares its strengths, modulus, and biocompatibility with three commercially available bone cements, Spineplex, Simplex P and Cortoss. The setting times indicate that the current formulation of Zn-GPC sets in a time unsuitable for clinical deployment. However during setting, the peak exotherm was recorded to be 33 degrees C, the lowest of all cements examined, and well below the threshold level for tissue necrosis to occur. The data obtained from mechanical testing shows the Zn-GPC has strengths of 63 MPa in compression and 30 MPa in biaxial flexure. Importantly these strengths remain stable with maturation; similar long term stability was exhibited by both Spineplex and Simplex P. Conversely, the strengths of Cortoss were observed to rapidly diminish with time, a cause for clinical concern. In addition to strengths, the modulus of each material was determined. Only the Zn-GPC exhibited a modulus similar to vertebral trabecular bone, with all commercial materials exhibiting excessively high moduli. Such data indicates that the use of Zn-GPC may reduce adjacent fractures. The final investigation used the well established simulated body fluid (SBF) method to examine the ability of each material to bond with bone. The results indicate that the Zn-GPC is capable of producing a bone like apatite layer at its surface within 24 h which increased in coverage and density up to 7 days. Conversely, Spineplex, and Simplex P exhibit no apatite layer formation, while Cortoss exhibits only minimal formation of an apatite layer after 7 days incubation in SBF. This paper shows that Zn-GPC, with optimised setting times, are suitable candidate materials for further development as bone cements.     

Controllable synthesis and luminescence of YPO<Subscript>4</Subscript>:Ln<Superscript>3+</Superscript> (Ln = Eu and Sm) nanotubes

YPO₄:Ln³⁺ (Ln = Eu and Sm) nanotubes were synthesized by a precipitation process in the presence of SDS. The XRD results showed that all samples have a xenotime type tetragonal structure, indicating that doped rare earth ions have no influence on the phase. The SEM and TEM images showed that all samples are nanotubes. On basis of the morphology of samples and the properties of SDS, the possible formation mechanism was speculated. YPO₄:Eu³⁺ and YPO₄:Sm³⁺ nanotubes showed characteristic emission bands of Eu³⁺ and Sm³⁺ ions, respectively. For YPO₄:Eu³⁺/Sm³⁺ nanotubes, the codoping Sm³⁺ ions can enhance the emission intensity of Eu³⁺ ions.     

High-temperature tensile-hold crack-growth behavior of HASTELLOY<Superscript>®</Superscript> X alloy compared to HAYNES<Superscript>®</Superscript> 188 and HAYNES<Superscript>®</Superscript> 230<Superscript>®</Superscript> alloys

The creep–fatigue crack-growth tests of HASTELLOY^® X alloy were carried out at the temperatures of 649°C, 816°C, and 927°C in laboratory air. The experiments were conducted under a constant stress-intensity-factor-range (ΔK) control mode with a R-ratio of 0.05. In the constant ΔK tests, a ΔK of 27.5 MPa\(\sqrt{\mathrm{m}}\) and a triangular waveform with a frequency of 0.333 Hz were used. Various tensile hold times at the maximum load were imposed to study fatigue and creep–fatigue interactions. Crack lengths were measured by a direct current potential drop method. In this paper, effects of hold time and temperature on the crack-growth rates are discussed. Furthermore, the crack-growth rates of the HASTELLOY^® X alloy are compared to those of the HAYNES^® 188 and HAYNES^® 230^® superalloys.     

Effects of nano-sized α<Superscript>2</Superscript> (Ti<Superscript>3</Superscript>Al) particles on quasi-static and dynamic deformation behavior of Ti-6Al-4V alloy with bimodal microstructure

A bimodal microstructure containing very fine α²(Ti³Al) particles was produced by over-aging a Ti-6Al-4V alloy. The effects of α² precipitation on quasi-static and dynamic deformation behavior were investigated in comparison with an unaged bimodal microstructure. Quasi-static and dynamic torsional tests were conducted on them using a torsional Kolsky bar. The quasi-static torsional test data indicated that the over-aged bimodal microstructure showed higher fracture shear strain than the unaged bimodal microstructure, while their maximum shear stresses were similar. Under dynamic torsional loading, both maximum shear stress and maximum shear strain of the over-aged microstructure were higher than those of the unaged microstructure. The possibility of the adiabatic shear band formation under dynamic loading was quantitatively analyzed by introducing concepts of critical shear strain, absorbed deformation energy, and void initiation. In the over-aged microstructure, the energy required for forming adiabatic shear bands was higher than that in the unaged microstructure, thereby lowering the possibility of the adiabatic shear band formation. The α² precipitation in the over-aged microstructure was effective in both the improvement of quasi-static and dynamic torsional properties and the reduction in the adiabatic shear banding, which suggested a new approach to improve ballistic performance of Ti alloy armor plates.     

Use of a nanostructured material for separation of <Superscript>238</Superscript>U and <Superscript>237</Superscript>U produced by the photonuclear reaction <Superscript>238</Superscript>U(γ, <Emphasis Type="Italic">n</Emphasis>)<Superscript>237</Superscript>U

²³⁷U was produced by the reaction ²³⁸U(γ, n) on an electron accelerator, MT-25 microtron, at the Flerov Laboratory of Nuclear Reactions. For the separation of ²³⁷U and [²³⁸U, the recoil nuclei were collected by a nanostructured material, hydrated manganese dioxide (of the cryptomelane type), in the solid-solid system. From fission products, ²³⁷U was separated by ion exchange. The specific activity of the resulting ²³⁷U was 4.5 × 10⁹ Bq (mg ²³⁸U)^-1, with the content of radioactive impurities of ≤10^-6 Bq Bq^-1. The chemical yield of ²³⁷U was 80%.     

Cyclic loading and fracture mechanics of Ductal<Superscript>®</Superscript> concrete

Reactive Powder Concrete (RPC) is a special type of ultra high strength, superplasticized, silica fume concrete, often fibre-reinforced, with improved homogeneity because the traditional coarse and fine aggregate are replaced by fine sand with particle sizes in the range of 100–400 μm [4–16 thousandths of an inch]. RPC properties are attractive because compressive strengths up to 800 MPa [116 ksi] have been recorded, but more typically in excess of 200 MPa [29 ksi]. Flexural strengths up to 141 MPa [20.4 ksi] and fracture energy of 40 kJ/m²[kJ/in.²] have been reported—the latter achieved when steel or stainless steel fibres were included in the mix (Baché (1998) Proceedings of the 2nd international conference on superplasticizers in concrete, Ottawa, pp 35–41; Coppola et al. L’Industria Ital Cemento 707:112–125 (1996); Blais and Couture PCI J 44(5):60–71 (1999); Richard and Cheyrezy (1994) Proceedings of V. Mohan Malhotra symposium on concrete technology: past, present, and future (SP 144). American Concrete Institute, Detroit, pp 507–518; Richard and Cheyrezy Cement Concrete Res 25(7):1501–1511 (1995)). Ductal^®, a commercial RPC, has a compressive strength of approximately 150 MPa [22 ksi] with metallic or organic fibres. All tests described here were performed on 40 × 40 × 160 mm [1.6 × 1.6 × 6.3 in.] (Width (b) × Depth (d) × length (L)) prisms with Poly Vinyl Alcohol (PVA) fibres. Ductal^® is a family of RPC and micro-defect-free concretes containing micro silica, silica fume, cement, Quartz sand, superplasticizer, and PVA fibres. Mechanical and fracture parameters were investigated using four point bending. Low and high cyclic fatigue tests were conducted in three stages, starting from low to high strain cycles. Cracks generated by cyclic fatigue tests were monitored periodically in order to evaluate the rate of crack propagation. Cracks were also investigated using a high magnification microscope. Three pairs of specimens were tested, notched and un-notched to evaluate fracture parameters. Four point bending was used again because determination of the J-Integral (J _IC ) requires the application of pure bending over a portion of the beam. Load was applied at the third points over a span (S) of 120 mm [4.7 in.], providing a span to depth ratio (S/d) of 3.0. Specimens were notched using a 1 mm [0.04 in.] thick diamond saw. The crack tip generated was circular and the crack length (s) was approximately 10 mm [0.4 in.]. Tests on the notched specimens included measurement of the crack mouth opening displacement (CMOD). Closed-loop testing was developed using a feed back signal from the (CMOD) clip gauge attached to the notched specimens and from strain gauges attached to the un-notched specimens. The weight (w) of each specimen was obtained prior to testing. Fracture parameters were calculated from the load–deflection curves obtained from the notched and un-notched specimens.     

Synthesis and characterization of the M<Superscript>II</Superscript>U<Subscript>3</Subscript>O<Subscript>10</Subscript> · 6H<Subscript>2</Subscript>O (M<Superscript>II</Superscript> = Ni,Zn) triuranates

We have developed a process for the synthesis of Ni(II) and Zn(II) triuranates with the general formula M^IIU₃O₁₀ · 6H₂O through reaction of schoepite, UO₃ · 2.25H₂O, with aqueous solutions of nickel and zinc nitrates under hydrothermal conditions. Using chemical analysis, X-ray diffraction, IR spectroscopy, and thermal analysis, we have determined the composition and structure of the triuranates and investigated their dehydration and thermal decomposition.     

Synthesis of Yb<Superscript>3+</Superscript>, Ho<Superscript>3+</Superscript> and Tm<Superscript>3+</Superscript> co-doped β-NaYF<Subscript>4</Subscript> nanoparticles by sol–gel method and the multi-color upconversion luminescence properties

Well-crystalline β-NaYF₄:Yb³⁺, Ho³⁺, Tm³⁺ nanoparticles were synthesized by sol–gel method using isopropyl alcohol [(CH₃)₂CHOH] as a complexing agent. The samples were characterized by X-ray diffraction, scanning electron microscopic analysis and fluorescence spectrum analysis methods. Under the excitation of 980 nm laser diode (LD), the samples displayed bright upconversion luminescence (UCL), which was generated from the energy level transition of Ho³⁺ and Tm³⁺ ions. With the increase of Tm³⁺, Ho³⁺ and Yb³⁺-doping concentration, the UCL intensity of blue, green and red light emission of the samples varied. Calculation of the CIE color coordinate of the β-NaYF₄:Yb³⁺, Ho³⁺, Tm³⁺ nanoparticles revealed that with the adjustment of Tm³⁺, Ho³⁺ and Yb³⁺ doping concentration and the excitation power of 980 nm LD, the multi-color UCL can be realized. Approximately single red light output with the CIE color coordinate of x?=?0.545, y?=?0.306 and white light output with the CIE color coordinate of x?=?0.325, y?=?0.320 can be obtained in the synthesized β-NaYF₄: Yb³⁺, Ho³⁺, Tm³⁺ nanoparticles.     

Synthesis and luminescence properties of RMgPO<Subscript>4</Subscript>:Mn<Superscript>2+</Superscript> (R = Li,Na, and K) red phosphor

RMgPO₄:Mn²⁺ (R?=?Li, Na, and K) phosphors are synthesized by a solid-state reaction method in air. The crystal structures and luminescence properties are investigated. A broad emission band peaking at 638 nm of RMgPO₄:Mn²⁺ (R?=?Li and Na) phosphors with excitation 408 nm is observed in the range of 550–800 nm owing to the ⁴T₁(G) → ⁶A₁ transition of the Mn²⁺ ion. KMgPO₄:Mn²⁺ phosphor with excitation 416 nm shows a broad emission band peaking at 658 nm in the range of 550–800 nm owing to the ⁴T₁(G) → ⁶A₁ transition of the Mn²⁺ ion. The optimal Mn²⁺ ion concentration in RMgPO₄:Mn²⁺ (R?=?Li, Na, and K) phosphors is about 5 mol%. The lifetimes of RMg_0.95PO₄:0.05Mn²⁺ (R?=?Li, Na, and K) phosphors is ~6.21, 6.03, and 6.28 ms, respectively. The luminous mechanism is explained by Tanabe-Sugano diagram of Mn²⁺ ion.     

The reaction Pu(VI) + Fe(CN)<Stack><Subscript>6</Subscript><Superscript>3−</Superscript></Stack> ⇄ Pu(VII) + Fe(CN)<Stack><Subscript>6</Subscript><Superscript>4−</Superscript></Stack> in NaOH solutions

A spectrophotometric study showed that, in 5 M NaOH, Pu(VII) prepared by ozonation of Pu(VI) is reduced with excess K₄Fe(CN)₆. The Pu(VII) content can be estimated from the amount of the Fe(CN)₆³⁻ formed. In NaOH solutions of concentration exceeding 8 M, the Fe(CN)₆³⁻ ion oxidizes Pu(VI). In 10.3 M NaOH, the tenfold excess of K₃Fe(CN)₆ fully converts 1 mM Pu(VI) to the heptavalent state within 4 min (rate constant 1.3 l mol⁻¹ s⁻¹ at 20°C). With an increase in the NaOH concentration, the oxidation rate increases, and smaller excess of K₃Fe(CN)₆ is required. This oxidant is consumed not only for Pu(VI) oxidation but also in reactions with H₂O and OH⁻ ions. Pu(VII) is unstable and is slowly reduced with water and with products of decomposition of iron complexes.     

Geometric and Disorder-Type Magnetic Frustration in Ferrimagnetic “114” Ferrites: Role of Diamagnetic Li<Superscript>+</Superscript> and Zn<Superscript>2+</Superscript> Cation Substitution

The comparative study of the substitution of zinc and lithium for iron in the “114” ferrites, YBaFe₄O₇ and CaBaFe₄O₇, shows that these diamagnetic cations play a major role in tuning the competition between ferrimagnetism and magnetic frustration in these oxides. The substitution of Li or Zn for Fe in the cubic phase YBaFe₄O₇ leads to a structural transition to a hexagonal phase YBaFe_4−x M _x O₇, for M = Li (0.30≤x≤0.75) and for M = Zn (0.40≤x≤1.50). It is seen that for low doping values, i.e. x=0.30 (for Li) and x=0.40 (for Zn), these diamagnetic cations induce a strong ferrimagnetic component in the samples, in contrast to the spin-glass behavior of the cubic phase. In all the hexagonal phases, YBaFe_4−x M _x O₇ and CaBaFe_4−x M _x O₇ with M = Li and Zn, it is seen that in the low-doping regime (x∼0.3 to 0.5), the competition between ferrimagnetism and 2D magnetic frustration is dominated by the average valency of iron. In contrast, in the high-doping regime (x∼1.5), the emergence of a spin glass is controlled by the high degree of cationic disorder, irrespective of the iron valency.     

Magnetic and Electrical Properties of Al<Superscript>3+</Superscript> Implanted Co–ZnO

Co-doped ZnO ceramic samples sintered at four different temperatures were prepared by solid-state reaction method and implanted by Al ions subsequently. The microstructural, defect, magnetic and electrical properties of the samples were systematically investigated by x-ray diffraction, micro-Raman spectroscope, vibrating sample magnetometer and Hall measurement, respectively. The results show that all the samples exhibit room-temperature ferromagnetism with a saturation magnetization of 0.02–0.03 emu g^?1, the value of which is affected by the sintering temperature. The origin of room-temperature ferromagnetism is considered as the formation of Co²⁺– V _O–Co²⁺ bound magnetic polarons. Even though the implantation of Al³⁺ slightly reduces the saturation magnetization because of the lattice damage, less V _O and larger lattice spacing, however, an appropriate amount of Al³⁺ implantation and a proper sintering temperature can remarkably improve the electrical properties with the mobility of 200 ～300 cm² Vs^?1 and the resistivity of 20 ～40 Ω cm. In general, samples sintered at 1200^°C present more excellent comprehensive performances.     

Microstructure and wear properties of LENS<Superscript>® </Superscript>deposited medical grade CoCrMo

There is a growing interest in metal-on-metal bearing surfaces for orthopedic implants. Although some success has been achieved in applications like hip implants which involve a large contact area, non-conforming joints, such as knees, have proved more difficult. The current work examines the applicability of a novel additive manufacturing process, Laser Engineered Net Shaping (LENS), the registered trademark and service mark of Sandia National Laboratories and Sandia Corporation), for producing CoCrMo implants. A series of experiments were conducted to determine the optimum parameters for deposition of CoCrMo. Microstructural studies, hardness tests, and dry sand/rubber wheel abrasive wear tests were conducted on the LENS deposits. The results showed that metallurgically sound deposits can be produced using the LENS process under optimized conditions. The hardness of the LENS deposited CoCrMo was found to be comparable to that of standard CoCrMo wrought material; however, wear tests indicated that LENS deposits were considerably less resistant to abrasive wear than wrought CoCrMo. The reasons for this behaviour are discussed based on microstructural observations.     

Luminescent properties of single-phase Ba<Subscript>2</Subscript>P<Subscript>2</Subscript>O<Subscript>7</Subscript>:Tb<Superscript>3+</Superscript>, R (R = Eu<Superscript>2+</Superscript>, Ce<Superscript>3+</Superscript>) phosphors for white LED

The Ba₂P₂O₇:Tb³⁺, R (R?=?Eu²⁺, Ce³⁺) phosphors were synthesized by use of a co-precipitation method. Crystal phase, excitation and emission spectra of sample phosphors are analyzed by means of XRD and FL, respectively. The emission spectra of Ba₂P₂O₇:Ce³⁺, Tb³⁺ phosphors exhibit four linear peaks attributed to the ⁵D₄?→?⁷F_J (J?=?6–3) transition of Tb³⁺ while four broad emission bands are observed in the emission spectra of Ba₂P₂O₇:Eu²⁺, Tb³⁺ phosphors. The effects of Eu²⁺ concentration on the luminescent properties of Ba₂P₂O₇:Tb³⁺, R (R?=?Eu²⁺, Ce³⁺) are studied. Ce³⁺ affects the luminescent properties of Ba₂P₂O₇:Ce³⁺, Tb³⁺ phosphors just as the sensitizer. However, Eu²⁺ is considered both as the sensitizer and the activator in Ba₂P₂O₇:Eu²⁺, Tb³⁺ phosphors. The chromaticity coordinates of Eu²⁺ and Tb³⁺ co-doped phosphors gather around the white light field with the CCT approximate to 5000 K, indicating that the luminescent property of Ba₂P₂O₇:Eu²⁺, Tb³⁺ phosphors may approach to a desired level needed for white LED application.