Comparative study of spectroscopic techniques for the estimation of iron in apple and vegetables

Iron has been determined in apple and vegetables spectrophotometrically, by complexing it with xylenol orange. 1:1 complex formed in a highly acidic medium is measured for its absorbance at its λ_max of 585 nm. The results have been compared by employing atomic absorption technique. Apples and vegetable samples were collected from local markets of Pakistan. Statistical manipulations, t-test and F-test, were performed and it was found that the results from the two techniques have an excellent agreement.     

A bis-bithiophene from Tridax procumbens L. (Asteraceae)

The ethyl acetate soluble part of hexane extract of Tridax procumbens yielded a new bis-bithiophene named tridbisbithiophene along with four known terpenoids: taraxasteryl acetate, beta-amyrenone, lupeol and oleanolic acid, which have never been reported so far from Tridax procumbens. The structures of all the isolated constituents were elucidated with the aid of 1D-NMR spectroscopy whereas, the structure of new constituent tridbisbithiophene was confirmed via COSY and HMBC interactions.     

Dramatic 5'-residue effect on conformer distribution of short oligonucleotide retro models of the cisplatin-DNA cross-link: implications for the Lippard and cross-link distorted base pair steps present in cisplatin-DNA duplex adducts

The cisplatin anticancer drug preferentially attacks the GG sequence of DNA duplexes. Virtually all DNAs containing the key G*G* lesion (G* = N7 platinated G) have large distortions in the cross-link (G*G*) base pair (bp) step and also in the adjacent Lippard (XG*) bp step, making the adducts very different from B-form DNA in the XG*G* region. The XG*G* strand in duplexes also differs in several ways from single-strand (ss) models with G*G* and XG*G* sequences. In the duplex, the X residue has an N sugar, the 5'-G* and 3'-G* bases have slight "R" canting (3'-G* H8 atom toward the 5'-G* base), and there is no or weak H-bonding by the NH3 ligands. In most XG*G* ss models, X has an S sugar, the 5'-G* base normally cants strongly toward the 3'-G* base (L canting), and the NH3 forms an H-bond. Well-defined ss models exist in the solid state, but dynamic motion obscures the properties of the ss models in solution. In this work, we employ retro models (better defined, less dynamic ss models) to understand the differences between duplex and ss models. The retro models in this study lack carrier ligand NH's, thus eliminating H-bonding. To correlate previous ss solid-state models with our solution work, we constructed hybrid molecules by overlaying parts of known structures. The combined model and experimental information indicates that the X N-pucker is not favorable in L-canted ss models, that X residue steric effects (not H-bonding) favor L canting in ss models, that X N-pucker is needed for favorable WC hydrogen bonding and stacking interactions in duplexes, and that X N-pucker minimizes X base clashes with bases in the complementary strand in duplexes. The R canting minimizing clashes between the X and G* residues of the Lippard bp step (independent of X pucker) and the repositioning of the X residue base caused by the change from S-pucker to N-pucker together lead to the unusual features of the Lippard bp step in the duplex.     

Inelastic deformations of stainless steel leaf springs-experiment and nonlinear analysis

A stainless steel leaf spring is designed and constructed followed by its performance evaluation by experiment and non-linear analysis so that an insight into the optimum use of material can be made. Cantilever beams of uniform strength, popularly termed as leaf springs, undergo much larger deflections in comparison to a beam of constant cross-section; that needs inclusions of geometric non-linearity for rigorous analysis. This study deals with such a cantilever beam, but takes into account the material non-linearity as well. Experiments were conducted for such a cantilever beam, with highly non-linear stress-strain curves. In addition to the experiment, a computer code in ‘C’ has been developed using the Runge-Kutta technique for the purpose of simulation. Effective modulus-curvature relations are obtained from the non-linear stress-strain relations for different sections of the beam and used for the analysis. It is seen that non-linear stress-strain curve governs the bending of the beam. Importantly, non-linear analysis shows the stresses are not so high as predicted by the linear theory without end-shortening. Moreover, the tensile and compressive stresses are different in magnitude and both decrease along the span. Experimental load-deflection curves are found to be initially concave upward but, non-linear and convex upward at a high load. Comparison of the numerical results with the available experimental results from another research group and theory shows excellent agreement verifying the soundness of the entire numerical simulation scheme.     

Experimental investigation and optimization of loop heat pipe performance with nanofluids

Journal of Thermal Analysis and Calorimetry - High heat generation from electronic devices needs to cool down properly to prevent overheating. Loop heat pipe (LHP) is one of the excellent cooling...     

Computational study on the effects of variable viscosity of micropolar liquids on heat transfer in a channel

Journal of Thermal Analysis and Calorimetry - A numerical model is developed to study the effects of temperature-dependent viscosity on heat transfer in magnetohydrodynamic flow of micropolar fluid...     

On model for Darcy–Forchheimer 3D nanofluid flow subject to heat flux boundary condition

Journal of Thermal Analysis and Calorimetry - This paper provides a theoretical study of 3D nanofluid flow with zero nanoparticles mass and constant heat fluxes conditions. An incompressible...     

Hybrid nanofluids

Journal of Thermal Analysis and Calorimetry -     

Properties of Ozone-Oxidized Tapioca Starch and Its Use in Coating of Fried Peanuts

Oxidation of tapioca via ozone oxidation was carried out under different conditions in comparison with H₂O₂. The impact of ozonation on physicochemical properties of tapioca was studied and fried peanuts coated with different tapioca were characterized. Different ozone oxidation times (10, 20, and 30 min) and various pH values (5, 7, and 9) were used for tapioca modification. Tapioca oxidized by ozone for 20 min at pH 7 had higher swelling power (SP), water holding capacity (WHC), oil holding capacity (OHC), and viscosity than the native counterpart (P < 0.05). This coincided with the higher carbonyl and carboxyl contents (P < 0.05). The highest frying expansion (FE) with the lowest hardness was attained for fried peanut coated with tapioca oxidized under the aforementioned condition. Therefore, oxidation of tapioca using ozone under optimal conditions could be a potential means to improve frying expansion as well as the crispiness of the fried coated peanuts.     

On-line spectrophotometric determination of scandium after preconcentration on XAD-4 resin impregnated with nalidixic acid

An on-line scandium preconcentration and determination method was developed with spectrophotometer associated with flow injection. Scandium from aqueous sample solution of pH 4.5 was selectively retained in the minicolumn containing XAD-4 resin impregnated with nalidixic acid at a flow rate of 11.8 mL min^?1 as scandium–nalidixic acid complex. The scandium complex was desorbed from the resin by 0.1 mol L^?1 HCl at a flow rate of 3.2 mL min^?1 and mixed with arsenazo-III solution (0.05 % solution in 0.1 mol L^?1 HCl, 3.2 mL min^?1) and taken to the flow through cell of spectrophotometer where its absorbance was measured at 640 nm. The preconcentration factors obtained were 35 and 155; detection limits of 1.4 and 0.32 μg L^?1 and sample throughputs of 40 and 11 were obtained for preconcentration time of 60 and 300 s, respectively. The tolerance limits of many interfering cations like Th(IV), U (VI), rare-earths and anions like tartrate, citrate, oxalate and fluoride were improved. The method was successfully applied to the determination of scandium from mock seawater samples and good recovery was obtained. The method was also validated on certified reference material IAEA-SL-1 (lake sediment) and the result was in good agreement with the reported value.