Cefuroxime-impregnated calcium phosphates as an implantable delivery system in experimental osteomyelitis

The study aimed to investigate the effectiveness of porous calcium phosphates viz., hydroxyapatite (HAp) and a bi-phasic calcium phosphate (BCP) with predominately β-tricalcium phosphate (β-TCP) prepared by aqueous solution combustion method impregnated with cefuroxime axetil for the treatment of experimental osteomyelitis and compared with parenteral treatment. In vitro release of the drug was tested for its sustained elution characteristics for 21 days in PBS (pH 7.2) and measured by HPLC. In the in vivo study, bone infection was induced in tibia of rabbits by inoculation of 1 ml (3 × 10⁶) CFU Staphylococcus aureus. On the 21st day, after the development of osteomyelitis, six animals were treated by filling the cavity with cefuroxime-impregnated HAp blocks (Group II), six animals with the same drug-impregnated β-TCP (Group III) and in six others, only cefuroxime (15 mg/kg twice daily) was injected parenterally 6 weeks (Group IV). Group I with six animals was kept untreated. Histologically, the signs of infection were found to subside by 3 and 6 weeks. Radiological evaluation with cefuroxime-impregnated HAp and β-TCP pointed out the disappearance of sequestrum and existence of newly formed bony specules. Concentration of cefuroxime in bone and serum as estimated by HPLC showed highest value on day 21 itself which reduced marginally by day 42 in both the groups and these values were higher than minimum inhibitory concentration (MIC) against S. aureus. Our findings suggest that bi-phasic calcium phosphates with predominately β-TCP content is a very efficient carrier material for antibiotic compounds even for refractory infections by S. aureus.     

Evaluating extent and causes of overbreak in tunnels

Damage or overbreak not only endangers safety of structure but also increases cost of construction and time of completion. Drilling and blasting being cost-effective for excavation of any underground structure should strictly adhere into specialized controlled blasting pattern to minimize the unacceptable impact on peripheral in situ rock mass. The paper reveals that in addition to geo-technical properties of rock mass, in situ stress condition plays an important role in enhancing the magnitude of overbreak. Implementation of same blast pattern throughout the length of tunnel results into different magnitudes of overbreak and the magnitude increases in highly stressed zone. Furthermore, implementation of same controlled perimeter blast pattern along the tunnel cross-section may result into different magnitudes of overbreak. Different magnitude of overbreak along the tunnel cross-section i.e., in left and right wall and crown has been observed even with implementation of same controlled blast pattern throughout the tunnel cross-section. Feasibility and compatibility of drilling equipment with respect to tunnel cross-section also adds to the quality and magnitude of overbreak. Undersize drilling equipment leads to angular drilling on either walls or crown and enhances the magnitude of overbreak. The paper with the help of statistical and graphical analysis revealed that blast pattern for peripheral rock mass should consider geo-technical properties and in situ stress condition of rock mass to minimize the magnitude of overbreak. The authors also emphasized that to contain magnitude of overbreak within allowable limit; the implemented blast pattern should be different for different sections viz., right wall, left wall and crown of tunnel. Furthermore, in poor rock mass condition or in highly stressed zone, drivage of tunnel should be carried out in small sections and in different phases until the excavation reaches the required excavation profile in that area. Excavation in small sections and in different phases would lead to proper excavated profile and minimize overbreak and damage of peripheral rock mass.     

Effect of environmental pollutants on the C-reactive protein of a freshwater major carp, Catla catla

C-reactive proteins (CRP) have been affinity purified to electrophoretic homogeneity from the sera of major carp, Catla catla before and after exposure to environmental pollutants. Exposure to these pollutants elevate the levels of circulating CRPs to 2.8-3.5 times the normal values. Kinetic studies of metal intoxication indicate that a unique molecular variant of CRP is present in the serum at the peak level of acute phase induction, and this variant coexists with normal CRPs. Carbohydrate analysis and lectin binding reveals that these CRPs are glycoproteins differing significantly in total carbohydrate contents. Their electrophoretic mobilities in native gel are different but become identical on desialylation and deglycosylation implying that the molecular variants vary in the glycan parts. All these forms of CRP contain two nonidentical subunits of Mr 22 and 29 kDa. Examination of their immunological crossreactivity demonstrate their similarity in overall molecular topology but their differences in the quantitative extent of binding are reflected.     

Neutron diffraction structural study of 1201 superconductor (Hg0.7Cr0.3)Sr2CuOδ

Rietveld analysis of powder neutron diffraction pattern recorded on Sr-based 1201-phase superconductor (T _c =53 K), (Hg_0.7Cr_0.3)Sr₂CuO_4+δ shows that the oxygen atoms at O(3) site are disordered atx=y=0.3712. This fourfold split site has a total combined occupancy of ～80% and is the only occupied site in the (Hg, Cr)O plane.     

Synthesis of DNA-polypyrrole nanocapsule

A template synthesis technique of encapsulating DNA molecules inside polypyrrole (PPy) nanotubes, termed as DNA-PPy nanocapsule, has been described here. The insertion of DNA molecules inside polypyrrole nanotubes is spontaneous in nature. The structural characterizations and possible applications of DNA-PPy nanocapsule in bio-sensing devices have been discussed.     

Low-Power CMOS Rectifier Design for RFID Applications

We investigate theoretical and practical aspects of the design of far-field RF power extraction systems consisting of antennas, impedance matching networks and rectifiers. Fundamental physical relationships that link the operating bandwidth and range are related to technology dependent quantities like threshold voltage and parasitic capacitances. This allows us to design efficient planar antennas, coupled resonator impedance matching networks and low-power rectifiers in standard CMOS technologies (0.5-mum and 0.18-mum) and accurately predict their performance. Experimental results from a prototype power extraction system that operates around 950 MHz and integrates these components together are presented. Our measured RF power-up threshold (in 0.18-mum, at 1 muW load) was 6 muWplusmn10%, closely matching the predicted value of 5.2 muW.     

Surface wave propagation in sandy layer overlying a liquid saturated porous half-space and lying under a uniform liquid layer

Dispersion of Rayleigh-type surface waves is studied in a sandy layer under a uniform layer of homogeneous liquid lying over liquid-saturated porous solid half-space. The frequency equation in the form of a ninth-order determinant is obtained and evaluated. Special cases have been deduced and dispersion curves for the phase velocity and wave number have been plotted for a particular model.     

Effect of the compatibilizer,on the engineering properties of TPV based on Hypalon® and PP prepared by dynamic vulcanization

Elastomeric Chlorosulfonated polyethylene (Hypalon^®) and thermoplastic Polypropylene (PP) based thermoplastic vulcanizates (TPVs) were prepared in presence of different doses of compatibilizer, maleic anhydride grafted PP (PP‐g‐MA) by employing dynamic vulcanization technique. The effect of incorporation in different proportions of compatibilizer on mechanical, spectral, morphological, thermal, and rheological properties of such TPVs was studied and the same were compared to that of virgin PP and amongst themselves. The mechanical analysis of the prepared TPVs exhibited significant improvements in stress at 25% modulus, ultimate tensile strength (UTS), and hardness values. FTIR studies revealed that a chemical interaction had taken place between Hypalon^® and functionalized compatibilizer during the process of dynamic vulcanization which led to an enhancement of interfacial adhesion between them. The two‐phase morphologies were clearly observed by scanning electron microscopic studies. The T_g values of Hypalon^® was modified in the TPVs as exhibited by differential scanning calorimetric studies. TGA studies indicated the increase in thermal stability of all TPVs with respect to the elastomeric Hypalon^®. Rheological properties showed that the compatibilizer reduces the melt viscosity of TPVs and thus facilitates the processibility of such TPVs. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40312.     

Simulation studies on the nature of fractal dimensions of glass-ceramics at percolation threshold

We simulate the fractal dimensions (D) of glass-ceramics resulting from different glass microstructures, at their percolation thresholds. We consider only crystallisation in glasses resulting from phase separation by nucleation. Phase separation may occur at a lower temperature or at the same temperature at which crystallisation takes place. We have studied both cases. The structure-property relationship of such glass-ceramics is dictated by the evolution of the structure of crystalline phase percolation cluster. At the percolation threshold the structure of the percolation path may be quantified by its fractal dimensionality (D). The value of D displays universal behaviour for a system in the thermodynamic limit. However, it deviates owing to finite size effects. Our simulations suggest that these deviations for a given system size depend on the nature of the glass microstructure. As the value of D reaches Euclidean dimension, the system attains more compact percolation cluster. This has invariably occurred in the present investigation for fine crystalline phase microstructure.     

A Three-Phase AC-to-DC Power Transistor Converter-Controlled DC Motor Drive

A three-phase ac-to-dc power transistor converter that is suitable for speed control of a dc motor and for a variable dc power supply is investigated. The availability of power transistors of fairly high power rating has made the task of ac-to-dc conversion relatively easy due to simplification of the converter circuit configuration. The external performance characteristics of the power transistor converter-controlled separately excited dc motor are obtained by employing the equal pulsewidth modulation (EPWM) control technique with 18 pulses per half-cycle of the supply voltage and are verified experimentally. There is good agreement between experimental and theoretical results. The external performance is also evaluated under constant torque operation. The use of inductance-capacitance (LC) filters for reducing the effect of predominant supply harmonics is briefly discussed. Experimental oscillograms of some typical waveforms are illustrated to verify the basic principles of operation.