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Home > Eff Ect of Compa Atibilit Enha Ty Anceme Ent on Structu S Ure, Mo Orphol Logy an the Rmo-M Echani Nd Ical Proper P Rties of Polyi F Imide/S Silica N Nanoco Omposi Tes

Eff Ect of Compa Atibilit Enha Ty Anceme Ent on Structu S Ure, Mo Orphol Logy an the Rmo-M Echani Nd Ical Proper P Rties of Polyi F Imide/S Silica N Nanoco Omposi Tes

Thesis Info

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Author

Saeed, Shaukat

Program

PhD

Institute

Pakistan Institute of Engineering and Applied Sciences

City

Islamabad

Province

Islamabad

Country

Pakistan

Thesis Completing Year

2009

Thesis Completion Status

Completed

Subject

Applied Sciences

Language

English

Link

http://prr.hec.gov.pk/jspui/handle/123456789/1538

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676725945987

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Polyimide/silica (PI/silica) and poly(hydroxyl imide)/silica (PHI/silica) nanocomposites containing pure as well as organically modified silica network structures have been prepared through the sol-gel process from solution mixtures of poly(amic acid) (PAA) and alkoxysilanes. Two types of PAAs were employed. The first was obtained from the reaction of pyromellitic dianhydride (PMDA) with oxydianiline (ODA) in dimethylacetamide as a solvent. The second was prepared from the reaction of PMDA with a mixture of 3,3′- diamino-4,4′-dihydroxybiphenyl and ODA. The hybrid films obtained by solvent elution technique were thermally cured to carry out the imidization process and the silica network formation. The effect of compatibility enhancement achieved through the modification of polymer backbone as well as through the use of non-silane and silane-terminated imide coupling oligomers on structure and properties of hybrids was studied and compared with the systems where reinforcement of the matrix was achieved using pure silica. The presence of pendant hydroxyl groups on polymer backbone played an important role in dictating the morphology of the PHI/silica hybrids. A model namely “Retain and React” based on two-step process has been proposed to explain the formation of polymer- modified silica clusters composed of co-continuous nano-domains with diffused boundaries as the previously proposed models failed to explain the observed morphology. The introduction of coupling oligomers in hybrid systems impeded the agglomeration of nano- sized silica domains and promoted the formation of novel fibril structures connecting the organic and inorganic phases together. Significant reduction in the roughness of the surfaces in the hybrid materials having modified matrix and silica networks has also been attributed to effect of enhanced coupling. A large shift in the glass transition temperature (Tg) of the hybrid material to higher temperatures confirmed the restricted segmental motion of polymer backbone due to increased interfacial interaction. The high surface-area of the interconnected silica domains stabilized the materials and shifted the decomposition profiles to higher temperatures by providing barriers to heat and mass transport in the hybrid material and thus slowing down the diffusion of oxygen in the matrix. The enhanced polarity coupled with organically modified silica offer an opportunity for improving Tg, reducing the coefficient of thermal expansion and increasing thermal-oxidative stability of polyimide/silica hybrids. The co-continuous and interpenetrating network structure thus produced also improves mechanical properties. Key words: Organic/inorganic hybrids; nanocomposites; polyimide; silica; sol-gel process; compatibilization; morphology; visco-elastic and thermal properties
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ہک واری تاں پھیرا پا

ہک واری تاں پھیرا پا
درشن اپنا آپ کرا
ناں تاں ساڈا سن لیندا اے
بھانویں یار ہے بے وفا
جیہڑی چنگیر تیری وچ روٹی
پڑھ بسم اللہ اوہنوں کھا
لگدا اس دی منگنی ہو گئی
ٹردی پئی چنی لٹکا
ملنا خوشی غمی تے چاہیدا
دنیا دا ہے رکھ رکھا
جو گدا بوہے تے آوے
خیر خوشی نال اوہنوں پا
ساری عمر گناہیں گزری
ہن تاں در توبہ دے آ

Study of Pragmatic Losses in the English Translation of Surah Al Ikhlas: A Comparative Pragma-Linguistic Analysis

The comprehension of the message of the Holy Qur’ān is obligatory for the whole of humanity which is revealed in the Arabic language. Scholars all over the world, Muslims as well as non-Muslims have devoted their best efforts to translate the word of Allah Almighty in different languages of the world, although absolute translation is not possible. These translations from Arabic to other languages of the world result into pragmatic losses. Small wonder, these pragmatic losses cause problems in the process of understanding the actual message of the Holy Qur’ān enshrined in the source text. This study was conducted to analyze the pragmatic losses in the English translations of Sūrah Ikhlāṣ (chapter 112) through a comparative pragma-linguistic analysis. Three different translations have been selected for the study. A comparative and critical study of these translations has established the presence of certain pragmatic losses which are likely to bear upon the comprehension of the reader in more than one way. To the researchers, the presence of these losses calls for the greater sensitivity towards and understanding of the pragmatic aspects of interlingual translation, specifically for a text which in its primordial form was intended to be a Speech (Kalām). To retain the pragmatic value and meaning of the source text become all the more paramount when the text translated is sacred one with its own canonical conventions and discursive norms.

Studies on Biochemical and Hematological Parameters in Workers of Iron and Steel Industries Exposed to Heat Stress

In the present work, 203 iron and steel industrial units located in and around Lahore were surveyed to gather information regarding physical parameters, processes involved, product types, raw materials used, fuel types, mode of employment, working conditions and use of PPEs in these units. General health and socio-economic status, disease history and anthropometric measurements of 656 workers from different work points were measured. Total serum proteins, albumin, ALT, AST and ALP were photometrically analyzed. Haematological parameters i.e., TLC, DLC, RBC, Hgb, Hct%, MCV, MCH, MCHC and platelet counts were made on automated haematology analyzer. Data was statistically analyzed on the basis of work points, job duration and worker’s age using ANOVA and students t-test at SPSS 13.0 version. Survey results revealed that the working conditions in these units are not satisfactory. Workers are exposed to variety of hazards. Socio-economic status of the workers also portrayed a dismal condition. Biochemical analysis showed general trend of increased concentration of total serum proteins, albumin and globulins, suggesting dehydration and non-specific infections as probable cause. Old workers working at comparatively higher temperature point showed more evident changes in total protein contents as compared to the young workers at the same points. ALT and AST, although within normal reference range, were evidently towards the higher limits in almost all categories of the workers. Younger and oldest workers with shortest and longest job duration presented higher value for ALT and AST as compared to the middle aged workers and with medium job duration. ALP is found significantly higher in all categories of workers depicting the obvious response to environmental stress. Physical activity along with the temperature appeared to be the contributory to enhance ALP activity. Although the haematological parameters did not show any direct correlation with the job duration or worker’s age but increased WBCs in circulation along with the complementary increase in lymphocytes number reflects the elicitation of immune response in these subjects. Hemoglobin, RBCs, Hct%, MCV, MCH, MCHC and platelets are found to show alteration, in general indicating a stress on the hematopoietic system to cope with the stress of hypoxic conditions and enhanced demand of energy due to heavy physical exertion. The results suggest that work point temperature along with heavy physical activity probably causes effects on liver physiology and also the hematopoietic system as apart of compensatory response. The results suggest more detailed studies with reference to heat stress and protein profile with special emphasis of the role of Hsps. Along with the detailed haematological investigations; studies on liver and kidney physiology are also recommended to understand the effect on hormones and electrolytes under hyperthermic conditions. Strict monitoring and enforcement of rules for the workers health and safety are strongly recommended.