Synthesis and crystal structure of (η5-C5H5)2Ti(NH(2,4-(C$${\equiv}$$CSiMe3)2C6H3))2

The crystal structure of the bis-amido complex of Ti(IV) (η⁵-C₅H₅)₂Ti(NH(2,4-(C CSiMe₃)₂C₆H₃))₂ is reported. This complex was prepared in 52% yield from the reaction of (η⁵-C₅H₅)₂TiCl₂ with two equivalents of LiNH(2,4-(C CSiMe₃)₂C₆H₃) (prepared in situ in THF at −78^∘C). The substituted aniline H₂N(2,4-(C CSiMe₃)₂C₆H₃) was prepared in 70% yield from the reaction of 2,4-dibromoaniline with Me₃SiC CH using conventional Pd/Cu coupling methodology. The molecular structure of (η⁵-C₅H₅)₂Ti(NH(2,4-(C CSiMe₃)₂C₆H₃))₂ (monoclinic, space group C2/c, Z = 4, a = 29.7523(5) Å, b = 9.5339(2) Å, c = 15.8864(3) Å, β = 93.022(1)^∘ features a titanium (IV) center with a distorted tetrahedral geometry which lies on a crystallographic twofold axis. The amido units are arranged so that steric interactions are minimized. The Ti– N distance is 2.016(2) Å.     

Determination of trace impurities in nickel-based alloy using neutron activation analysis

A radiochemical neutron activation analysis procedure has been applied to investigate 40 major, minor, and trace impurities in nickel-based alloy. The extensive use of these alloys in the electronic industry, telecommunications, manufacturing of aircraft engine turbine blades and chemical equipments desires for their precise characterization. The concentration of nickel in the nickel-based alloy was found to be 56.8%, whereas Fe, Cr, Ca, Mg, Ce, Mn, Na and V were the major components of the alloy, which constituted to more than 26%. The rest of the elements was present in minor or trace levels. Most of the rare earth elements except Ce were also present in trace amounts. Neutron activation analysis technique was preferably used because of its good sensitivity and multielement determination capabilities for the characterization of high purity materials. The comparison of RNAA and INAA indicated improvement in the detection limits utilizing radiochemical separation procedures developed in the present work.     

Validation of INAA and AAS analysis protocols for whole blood: A study on cardiovascular and malignant hypertensive patients

Instrumental neutron activation analysis (INAA) and atomic absorption spectrophotometry (AAS) were used to verify the protocols for the quantification of zinc and magnesium in human whole blood. A study was conducted on group of volunteers consisting of 131 patients having cardiovascular diseases (CVD) and 23 malignant hypertension (MH) patients along with 432 control subjects with 218 male and 214 females. The elemental data of these elements has been exploited to establish the base line values in control subjects. The possibility of any relationship between blood Mg and Zn levels with CVD and MH has also been investigated. The mean blood Mg and Zn levels were found to be depleted in both CVD and MH patients as compared to normal subjects. In our findings Mg and Zn were found to have an inverse relation with systolic and diastolic pressure. The reliability of the methods was checked by the concurrent analysis of the IAEA reference material (RM) employing the optimized INAA and AAS protocols. The determined values by both techniques were found to be in good agreement with the IAEA reference values. The elemental data in whole blood samples of normal volunteers has also been compared with Mg and Zn contents reported by other countries.     

Melting heat transfer effects on stagnation point flow of micropolar fluid saturated in porous medium with internal heat generation （absorption）

The effect of melting heat transfer on the two dimensional boundary layer flow of a micropolar fluid near a stagnation point embedded in a porous medium in the presence of internal heat generation/absorption is investigated. The governing non-linear partial differential equations describing the problem are reduced to a system of non-linear ordinary differential equations using similarity transformations solved numerically using the Chebyshev spectral method. Numerical results for velocity, angular velocity and temperature profiles are shown graphically and discussed for different values of the inverse Darcy number, the heat generation/absorption parameter, and the melting parameter. The effects of the pertinent parameters on the local skin-friction coefficient, the wall couple stress, and the local Nusselt number are tabulated and discussed. The results show that the inverse Darcy number has the effect of enhancing both velocity and temperature and suppressing angular velocity. It is also found that the local skin-friction coefficient decreases, while the local Nusselt number increases as the melting parameter increases.     

Cosmic acceleration and Brans-Dicke theory

We study the accelerated expansion of the universe by exploring the Brans-Dicke parameter in different eras. For this, we take the FRW universe model with a viscous fluid (without potential) and the Bianchi type-I universe model with a barotropic fluid (with and without a potential). We evaluate the deceleration parameter and the Brans-Dicke parameter to explore cosmic acceleration. It is concluded that accelerated expansion of the universe can also be achieved for higher values of the Brans-Dicke parameter in some cases.     

Size-fractionated airborne particulate matter characterization of a residential area near Islamabad airport by IBA methods

Size fractionated PM_2.5 and PM_2.5?C10 airborne particulates collected from the airport housing society site in Rawalpindi were characterized using the non destructive ion beam analysis method. Proton induced X-ray emission and Proton induced gamma ray emission were employed to quantify 28 trace elements in fine and coarse filter samples. The average PM_2.5 and PM_2.5?C10 masses were found to be 15.7 and 144???g/m³, respectively which, when combined exceed the Pakistani limit for PM₁₀ of 100???g/m³. The average black carbon (BC) content was found to be 3.49 and 5.95???g/m³ corresponding to 23.8 and 4.30% of the fine and coarse masses, respectively. The reconstructed mass (RCM) was calculated for both particle modes using 5 pseudo sources, namely soil, sulfate, smoke, sea salt and BC. It was found that 5 sources could account for 80.6 and 49.0% of the fine and coarse masses, respectively. The low value of RCM for the coarse mode may imply a much higher organic content. The major sources contributing to the fine mode were soil, sulfate and BC. Similarly for the coarse mass fraction it was found that soil was the major source whereas the sulfate and BC sources did not contribute as much.     

Ion-Pair Formation in Pharmaceutical Analysis. Conductimetric Determination of Promazine, Chlorpromazine, Promethazine, Imipramine and Ciprofloxacin Hydrochlorides in Pure Form, Drug Formulations and Urine

 Potassium ferricyanide and sodium tetraphenylborate were used as titrants for the conductimetric determination of promazine HCl, chlorpromazine HCl, promethazine HCl, imipramine HCl and ciprofloxacin HCl through ion-associate complex formation. The molar combining ratio, effects of dilution of titrant, temperature and solvent were studied. The accuracy of the method is indicated by excellent recovery (99.50–99.96%). The sensitivity of the proposed method is discussed and the results are compared with the pharmacopoeial or the official methods. The suggested method has been applied for the analysis of the mentioned compounds in their pharmaceutical formulations and urine. Received March 1, 1998. Revision May 31, 1999.     

Trace element evaluation of rice and husk by INAA

An instrumental neutron activation analysis technique has been utilized to study the prevailing levels of certain inorganic trace elements in different varieties of rice produced in Pakistan. The data have been compared with those of other countries. The elemental ratios within rice and rice to husk have been computed to evaluate indirectly the impact of soil and environment on the rice crops. The dietary spectum for the inhabitants of Rawalpindi/Islamabad areas has been evaluated by estimating the daily intake and comparing with allowances suggested in the literature.     

Applicability Evaluation of Bright Green‐Emitting Carbon Dots in the Solid State for White Light‐Emitting Diodes

Self‐quenching‐resistant and bright green‐emitting carbon dots (CDs) in the solid state were synthesized via a facile hydrothermal method. Their structure, optical properties together with their thermal and photostabilities, as well as their applicability in white LEDs were investigated. The obtained CDs have nearly spherical shape with a size around 4–5 nm. The resulting powder CDs show excitation‐independent emission behavior, and can be excited over a broad range from 300–450 nm. Under optimal excitation at 400 nm, the resultant powder CDs yield bright and broad green emission around 505 nm with full width at half maximum (FWHM) of about 110 nm and under 360 nm excitation with lifetime of 15.8 ns. A potential application of the green‐emitting CDs was evaluated by constructing a white light‐emitting diode lamp. The fabricated white LED lamp emitted bright, warm white light with excellent color rendering properties (a color rendering index of 86.9 and a correlated color temperature of 3863 K).     

Proficiency test exercise on the determination of natural levels of radionuclides in mushroom reference material

The results from a proficiency test exercise for the determination of natural levels of radionuclides in mushroom reference material carried out by laboratories in six different countries are discussed. These laboratories submitted data on seven radionuclides, namely ¹³⁴Cs, ¹³⁷Cs, ⁴⁰K, ⁹⁰Sr, ²⁴¹Am, ²²⁶Ra, and ²¹⁰Po. However, only the data received for three of these radionuclides could be statistically evaluated to obtain consensus mean values and confidence intervals (at a significance level of 0.05). The contents of ¹³⁴Cs, ¹³⁷Cs and ⁴⁰K were quantified as 4.4, 2,899 and 1,136 Bq/kg, respectively.