Improving the performance of an active carbon-nitrogen adsorption cryocooler by thermal regeneration

Thermodynamic analysis was done on single and two stage active carbon nitrogen adsorption cryocoolers to study the effect of thermal regeneration on the performance. Heat regeneration within compressors operating in the same temperature range is considered. From the analysis done on 80 K cooler and 117.5 K cooler, it is found that dramatic efficiency improvement is possible with the use of compressor heat regeneration techniques.     

Natural rubber–isotactic polypropylene thermoplastic blends

Thermoplastic elastomers, prepared by melt blending of natural rubber (NR) and isotactic polypropylene (PP) through a dynamic vulcanization technique, were developed during the later 1970s. However, they have certain drawbacks due to thermal degradation and higher molecular weight of NR. In the study reported here, NR was masticated to different levels prior its addition to isotactic polypropylene to improve the flow properties and to reduce the incompatibility resulting from molecular weight mismatch of NR/PP thermoplastic blends. Mixing energy curves of uncrosslinked blends and those of dynamically vulcanized blends crosslinked using different cure systems were compared. The mixing energy curves of blends containing NR of different molecular weight (M _n) and two grades of PP (injection and film grades) were also compared. Technological and processing properties of the dynamically vulcanized (sulphur and peroxide cure systems) and unvulcanized blends were compared with those of the samples containing unmasticated NR. The results indicated that a number average molecular weight in the range 4 × 10⁵ for NR increased the procoessability without significantly affecting the technological properties of NR/PP thermoplastic blends. Among the three cure systems studied Luperox 101 and dicumyl peroxide gave better technological properties than the sulphur‐cured samples. Two antioxidants, viz. quinoline (TDQ) and imidazole (MBI) type, were tried in NR/PP blends. It was found that TDQ imparts better aging resistance compared to MBI. The improvement in processability due to the reduction in molecular weight of natural rubber by mastication is more noticeable in the case of peroxide vulcanized blends compared to sulphur vulcanized samples. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2063–2068, 2004     

Analysis of unsteady flow of blood conveying iron oxide nanoparticles on melting surface due to free convection using Casson model

Iron oxide nanoparticles have great importance in future biomedical applications because of their intrinsic properties, such as low toxicity, colloidal stability, and surface engineering capability. So, blood containing iron oxide nanoparticles are used in biomedical sciences as contrast agents following intravenous administration. The current problem deals with an analysis of the melting heat transfer of blood consisting iron nanoparticles in the existence of free convection. The principal equations of the problem are extremely nonlinear partial differential equations which transmute into a set of nonlinear ordinary differential equations by applying proper similarity transformations. The acquired similarity equalities are then solved numerically by Runge‐Kutta Felhsberg 45th‐order method. The results acquired are on the same level with past available results. Some noteworthy findings of the study are: the rate of heat transfer increases as the Casson parameter increases and also found that the temperature of the blood can be controlled by increasing or decreasing the Prandtl number. Hence, we conclude that flow and heat transfer of blood have significant clinical importance during the stages where the blood flow needs to be checked (surgery) and the heat transfer rate must be controlled (therapy).     

Investigations on Forced Convection in Compact Passages With Surface Irregularities

Two-dimensional, fully developed, convective heat transfer in compact passages is investigated numerically, incorporating the effects of the surface irregularities, to analyze the influence of these irregularities on fluid flow and heat transfer. This analysis helps to bring out the differences in the performance evaluation if regular cross sections are assumed in analyzing compact and mini channels. Forced convection in compact passages with an apparent rectangular shape is analyzed using a finite-difference method. The calculation is validated experimentally using Michelson interferometry. The numerical results for the channel, incorporating surface irregularities, are compared with those assuming a regular cross-sectional geometry. The results indicate that the coefficient of friction and the Nusselt number calculated for channels, considering the irregular cross section, are less than those predicted using an assumption of regular geometry. The results provide some insight into the reasons for the observed deviations in the comparisons. The observations are attributed to the influence of the surface irregularities on the relative dominance of the surface area to the cross-sectional area, which gets pronounced in compact passages. The findings suggest that some of the observed deviations in the performance of compact passages, compared to theoretical results, may be due to the use of regular geometries to define domain shapes while performing theoretical analysis.     

Shigella and the fluorinated quinolones

An 8-year-old girl presented with marked shortening of the right forearm due to destruction of both the radius and ulna secondary to neonatal osteomyelitis. A one-bone forearm operation was performed to achieve a stable forearm. Two years later, the one-bone forearm was lengthened for 6 months by callus distraction (callotasis) achieving 12 cm of extra length. The patient was last followed up at the age of 16. The appearance and functional outcome of the right upper limb had been improved and she was independent in all activities of daily living.     

Scanning electron microscopy studies on tensile,tear and abrasion failure of thermoplastic elastomers

The tensile strength, tear resistance and abrasion resistance of four different types of commercial thermoplastic elastomers have been studied and their fracture surfaces examined by scanning electron microscopy. Thermoplastic polyurethane (TPU) showed elastic deformation under tensile fracture, whereas in 1,2 polybutadiene (1,2 PB) the fracture was initiated by craze formation and propagated by tear failure. Styrene-isoprene-styrene block copolymer (K1107) showed ductile type failure whereas in styrene-butadiene-styrene block copolymer containing a higher proportion of styrene and silica filler (K5152), the fracture occurred by shearing action. The tear failure surfaces of the thermoplastic elastomers showed different fracture patterns which could be correlated with the tear strength of the materials. The tear fracture surface of 1,2 PB showed stick-slip tear lines and that of TPU had a broad tear path with vertical striations. The fracture surfaces of K5152 and K1107 had the characteristics of laminar tearing and uninterrupted continuous tearing processes, respectively. The abrasion resistance of the samples was in the order TPU>1,2 PB>K5152, which was manifested through the type of ridge patterns formed on the abraded surfaces. Abraded surfaces of TPU, 1,2 PB and K5152 showed closely spaced stable ridges, widely spaced ridges bridged by elongated fibrils and highly deformed ridges, respectively.     

Scanning electron microscopy studies on tensile failure of thermoplastic elastomers from polypropylene-natural rubber blends

The tensile properties of thermoplastic polypropylene [pp]-natural rubber [NR]blends have been evaluated with special reference to the effect of blend ratios and dynamic cross-linking of the elastomer phase. The effects of silica filler and silane coupling agent on the tensile properties of the 30:70 PP:NR blend have also been studied. Analysis of the stress-strain curves and scanning electron microscopic examination of the tensile fracture surfaces of the blends have been used to correlate the test results on tensile properties.     

Insights into the Interaction of LVV-Hemorphin-7 with Angiotensin II Type 1 Receptor

Hemorphins are known for their role in the control of blood pressure. Recently, we revealed the positive modulation of the angiotensin II (AngII) type 1 receptor (AT1R) by LVV-hemorphin-7 (LVV-H7) in human embryonic kidney (HEK293) cells. Here, we examined the molecular binding behavior of LVV-H7 on AT1R and its effect on AngII binding using a nanoluciferase-based bioluminescence resonance energy transfer (NanoBRET) assay in HEK293FT cells, as well as molecular docking and molecular dynamics (MD) studies. Saturation and real-time kinetics supported the positive effect of LVV-H7 on the binding of AngII. While the competitive antagonist olmesartan competed with AngII binding, LVV-H7 slightly, but significantly, decreased AngII’s k_D by 2.6 fold with no effect on its B_max. Molecular docking and MD simulations indicated that the binding of LVV-H7 in the intracellular region of AT1R allosterically potentiates AngII binding. LVV-H7 targets residues on intracellular loops 2 and 3 of AT1R, which are known binding sites of allosteric modulators in other GPCRs. Our data demonstrate the allosteric effect of LVV-H7 on AngII binding, which is consistent with the positive modulation of AT1R activity and signaling previously reported. This further supports the pharmacological targeting of AT1R by hemorphins, with implications in vascular and renal physiology.