سر ائزک بیلی بالفور
سر ائزک بیلی بالفور کی موت علمی دنیا کا حادثہ سمجھا جاتا ہے۔ سرمذکور ۳۴ سال تک اڈنبرا یونیورسٹی کے علم نباتات کے اعلیٰ پروفیسر رہے ہیں۔ (فروری ۱۹۲۳ء)
Since the creation of this world, there have been disagreements in different matters among mankind. Technically, difference in opinion is of two kinds. One is Invalid or unpleasant disagreement; which has no valid reasoning and it bases on other evil objectives. While the other one is valid or pleasant disagreement; which bases on valid reasoning. The second one is also known as healthy disagreement. The disagreements among Islamic Scholars, ‘Ulamā and fuqahā relates to the second kind; valid disagreements, because they are established on valid reasons and evidences. They are also considered as a blessing for mankind. That is why these scholarly and fiqhī disagreements are always deeply admired. An important book scholarly written on the subject matter is ‘Kitāb al Tajrīd’ by Imām Qudūrī. This article is an introduction to his book ‘Kitāb al Tajrīd’ and its style. It is a distinct and excellent book of its kind. The features of the book motivate to discuss about it.
Laser ablation is a versatile technique used for the investigations of technological advanced and industrially important materials. In this technique, the interaction of a short and intense laser pulse forms a plasma plume. The laser produced plasma plume consists of radiation which arises due to transitions of electrons from the excited states of atoms and ions. The aim of this thesis is the fabrication of the laser ablation time of flight mass spectrometer (LA-TOF-MS) with an improved resolution and to compare the compositional results of mass spectra from LA-TOF-MS with the emission spectra obtained from laser induced breakdown spectroscopy (LIBS). The compositional analysis using calibration free (CF-LIBS) techniques is based on the observed emission spectra of the laser produced plasma plume whereas, the elemental composition analysis using laser ablation time of flight mass spectrometer (LA TOFMS) is based on the mass spectra of the ions produced by laser ablation. We have successfully designed and locally fabricated an improved version of the laser ablation time-of-flight mass spectrometer (LA-TOF-MS) for isotope mass analysis and elemental analysis of materials. This system is coupled with a Q-switched Nd: YAG laser, which is capable of delivering the energy of about 850 mJ at 1064 nm and 500 mJ at 532 nm. The resolution of system has been improved by adjusting spatial and space focusing, and optimizing other parameters. The capability of the system has been exploited by the isotopic analysis and compositional analysis of different alloy samples, having certified composition. The laser ablation time of flight mass spectrometer complementary with Laser induced breakdown spectroscopy has xxi been used for the quantitative determination of constituents of certified samples; different Karats of gold (18K, 19K, 20K, 22K, 24K), Brass alloy (Cu 62%, Zn 38%) and Cu-Ni Alloy (75% Cu, 25% Ni). Moreover, the samples with the unknown compositions such as different brands of the cigarette available in Pakistan have also been investigated using LIBS and LA-TOF-MS techniques. Initially five Karats of gold alloys, 18K, 19K, 20K, 22K and 24K having certified composition of gold as 75%, 79%, 85%, 93% and 99.99% were selected and their precise elemental compositions were determined by LIBS and LA-TOF-MS. Here internal reference line self-absorption correction laser induce breakdown spectroscopy (IRSAC-LIBS) technique have been utilized for the quantitative determination of constituents present in different Karats. Elemental compositions of these gold alloys were also determined using a Laser Ablation time of flight mass spectrometer (LA-TOF-MS). The quantitative analysis of brass alloy has been studied using Laser Induced Breakdown Spectroscopy (LIBS), Energy Dispersive X-ray Spectroscopy (EDX) and Laser Ablation Time of Flight Mass Spectrometry (LA-TOF-MS). The emission lines of copper (Cu I) and zinc (Zn I) are used to calculate the plasma parameters. Here we have compared the elemental composition obtained by SCF-LIBS and IRSAC-LIBS with LA-TOF-MS and EDX. After utilizing SCF-LIBS and IRSAC-LIBS for quantitative analysis, we have compared the composition for Cu-Ni alloy using three calibration free LIBS techniques other than IRSAC-LIBS, and also compared the results with laser ablation LA-TOF-MS. For the quantitative determination of constituents of Cu-Ni Alloy (Pakistani five rupee coin of year 2004) of known composition (Cu 75%, Ni 25%), we have utilized one line calibrations-free (OL-CF xxii LIBS), self-calibration free (SCF-LIBS), and algorithm based calibration free (AB-CF LIBS) techniques. Results obtained by these LIBS based techniques have also been compared with LA-TOF-MS. The samples of fourteen different brands of cigarettes available in Pakistan have also been analyzed using the above mentioned techniques. We have also performed compositional analysis of the trace elements in different brands of tobacco available in Pakistan using one line calibration free (OLCF-LIBS) and Laser ablation Time of Flight Mass Spectrometer (LA-TOFMS). The results obtained by (CF-LIBS) are comparable with (LA-TOF-MS). The compositional results obtained by OL-CF-LIBS, SCF-LIBS, IRSAC-LIBS and algorithm based AB-CF LIBS are in agreement with that of LA-TOF-MS and other standard techniques. The analysis of different industrial important alloys and different brands of cigarettes demonstrates that LIBS complemented with LA-TOF-MS are powerful techniques for the elemental analysis of the major and trace elements in any solid samples.