The Role of Molecular Weight in Controlling the Structure and Properties of High-Speed Melt Spun Nylon-6 Filaments

A comprehensive study of the structure development during high speed melt spinning of nylon-6 was performed. The major emphasis of the research was on the effect of molecular weight in the structure development of high speed melt spun nylon-6 filaments. The various measurements done on the filaments to determine their morphology included diameter, tensions in spin-line, density as well as x-ray diffraction and birefringence measurements. The effects of mass throughputs were also studied. Tensile properties of conditioned fibers were measured and related to the spinning variables and molecular weight. The spin-line stresses measured increased rapidly with take-up velocity and molecular weight. The increase with molecular weight was more rapid at higher take-up velocities than at lower take-up velocities. The wide angle x-ray diffraction pattern indicated a significant level of crystallinity, and a high y-phase content at high take-up velocities in low molecular weight samples. The chain axis crystalline orientation function increased rapidly at the beginning with take-up velocity and then started to level off after reaching an attainable maximum at higher take-up velocities. Increase in spin-line stresses increased crystalline orientation but not independent of molecular weight. Increased molecular weights resulted in increased crystalline orientation functions at low take-up speeds and they decreased at higher take-up speeds. Birefringence measurements showed increases with take-up speeds and molecular weights and decreases with increased mass throughputs. The tensile strength and modulus of the conditioned filaments increased, but the elongation at break decreased with increasing take-up velocity and spin-line stress. Modulus and tensile strength increased with molecular weight. The increase in modulus with molecular weight was rapid at high take-up speeds, producing very high modulus fibers at high speeds and high molecular weight. The tensile properties correlated with spin-line stress and birefringence, but not independent of mass throughput and molecular weight

Visual perception based bit allocation for low bitrate video coding

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1996.Includes bibliographical references (leaves 45-47).by Rajesh Suryadevara.M.S

The Socio‐Political Implications of the 20th Century Narratives on Indian Dances

From mentions of dance in treatises as old as 2nd century to regional variations around 13th century to the 20th century ‐ dance has travelled, traversedand evolved. When the agenda of Nationalism was in vogue during pre and post‐independence periods, there was a necessity to produce somethingunique to the nation and make a point about its rich heritage. Dance was one effective medium that served as a cultural symbol. This very notion modifiedthe course of dance, its form and structure. The ancient practices were modified and tailor‐made to suit agendas of the time and popular choices. This paper attempts to understand this phenomenon of how the socio‐political ideologies have affected the Indian classical dances. The focus would be on the political affiliations specific to the Kūcipūḍi form of dance

Molecular Magnetic Architectures: From Mononuclear to Polynuclear complexes

The broad field of molecular magnetic materials has potential applications in the storage and processing of the information. Despite of the enormous applications of these materials, till now, there are no suitable candidates ready for the real application. So, over the decades, plenty of research has been progressing to develop suitable candidates in the field of Spin-crossover (SCO) and single molecule magnetism (SMM). In SCO, there are several reports with large hysteresis but found to be not suitable for applications since they do not satisfy many other criteria, which include the stability of the hysteresis that should be around room temperature. At the same time, for the development of the molecular devices, the bottom-up fabrication of these functional molecules is needed. Even though most of the SCO complexes are mononuclear, significant progress has been seen towards polynuclear complexes due to their tunable properties. Molecular chirality is an additional concept that plays a key role in magnetism, particularly in spintronic applications. So introducing the concept of chirality into these polynuclear SCO complexes may result in novel magneto-optical hybrid complexes. On the other hand, in the field of SMMs, lanthanide complexes have risen as attractive materials due to extremely large anisotropy in lanthanide ions. However, most of these complexes show characteristic SMM behaviour at liquid helium temperatures; there is a need for designing newer SMMs with higher blocking temperatures. In the present thesis, in the first chapter, a brief introduction to fields - SCO and SMM, and their importance to the present technological world is provided. Moreover, the methods for characterization used for these complexes are presented. The second chapter deals with the studies of bis(pyrazolyl)pyridine (bpp) derivatives in bulk and surface. The ligand (bpp-COOH) was deposited on Ag(111) surface and was found to form a Kagome lattice structure on annealing, and the ligand showing two types of coordination modes with Fe on Ag(111). STM and XPS were used to study the self-assembled structures formed on the surface. On the other hand, the bulk SCO Fe(II) complexes were prepared using a derivative of bpp ligand by varying the counter anions. The structural and SCO properties of the complexes were investigated by various techniques like X-ray diffraction (XRD), Superconducting Quantum Interference Device (SQUID) magnetometry, and differential scanning calorimetry (DSC). Interestingly, our magnetic studies on the complex synthesized with perchlorate anion showed a stable hysteresis of 60 K around room temperature. The third chapter deals with the chiral resolution of tetra-nuclear Fe(II) SCO grid complexes. For this deconvolution of grid complexes, we designed and synthesized a novel chiral ligand. The complexation of these ligands with Fe(II) resulted in enantiomerically pure grid complexes which were elucidated by XRD and Circular Dichroism (CD) studies. These enantiomeric complexes showed gradual SCO and photo-induced SCO properties. The CD spectra calculated using TDDFT showed good agreement with experimental results obtained from Mössbauer spectroscopy and SQUID magnetometry. The fourth chapter deals with mononuclear, binuclear and tri-nuclear Tb-sandwich SMM complexes. We explored and characterized the series of complexes of mixed porphyrin and phthalocyanine mono Tb SMM sandwich complexes by tuning the periphery of porphyrin ligand and redox properties. Moreover, a series of binuclear complexes were synthesized by varying the length of the linker, and their magnetic properties were characterized. Besides, preliminary electron paramagnetic resonance (EPR) studies were performed in the neutral complexes to study the radical. In summary, various kinds of molecular magnetic architectures were synthesized and characterized in this thesis as below - (i) surface and bulk studies of bpp based Fe(II) complexes, (ii) tetranuclear enantiomeric Fe(II) SCO grid complexes, and (iii) mononuclear, binuclear and trinuclear Tb- SMM complexes based on porphyrins and phthalocyanine. Such design and studies of these magnetic materials are key for future devices based on a bottom-up approach

PREPARATION AND EVALUATION OF METOLAZONE SOLID DISPERSIONS AND FAST DISSOLVING TABLETS USING STERCULIA FOETIDA SEED STARCH AND PLASDONE K-29/32 AS SUPERDISINTEGRANTS

Objective: The objective of the current study is to improve the solubility of the Biopharmaceutical Classification System (BCS) Class-II drug, Metolazone, using various superdisintegrants. Methods: Starches were extracted from Sterculia foetida seed powder by water and alkali techniques i.e., sodium hydroxide at 0.1%, 0.25% and 0.5% concentrations. Several phytochemical and physicochemical parameters were evaluated on the extracted starches. Solid dispersions of Metolazone were prepared by the solvent evaporation technique using plasdone K-29/32 alone and by mixing plasdone K-29/32 with Sterculia foetida seed starch. Various physical parameters were evaluated for the prepared solid dispersions. Tablets were prepared using Metolazone solid dispersions and varying concentrations of Sterculia foetida seed starch by direct compression technique. Pre and post-compression parameters were evaluated along with in vitro drug release studies, characterization using Scanning Electron Microscopy (SEM) and stability studies. Results: Phytochemical tests showed the presence of starch in all extracts. Starch prepared from 0.1% sodium hydroxide (SFS2) showed best physicochemical properties. In vitro dissolution studies revealed that solid dispersion MS4 containing Metolazone and plasdone K-29/32 in 1:3 ratios showed better drug release. Formulation MPT6 containing MS5 solid dispersion with 15% w/w of SFS2 showed enhanced drug release. SEM studies revealed no major interactions between drugs and excipients. Accelerated stability studies showed that all tablets were stable. Conclusion: Sterculia foetida seed starch and plasdone K-29/32 have enhanced the solubility of Metolazone

Method for one-to-one polishing of silicon nitride and silicon oxide

The present invention provides a method of removing silicon nitride at about the same removal rate as silicon dioxide by CMP. The method utilizes a polishing slurry that includes colloidal silica abrasive particles dispersed in water and additives that modulate the silicon dioxide and silicon nitride removal rates such that they are about the same. In one embodiment of the invention, the additive is lysine or lysine mono hydrochloride in combination with picolinic acid, which is effective at a pH of about 8. In another embodiment of the invention, the additive is arginine in combination with picolinic acid, which is effective at a pH of about 10

Item analysis to identify quality multiple choice questions/items in an assessment in Pharmacology of II MBBS students in Guntur Medical College of Andhra Pradesh, India

Background: In medical education, multiple choice questions/Items are the more frequently used assessment tools to assess the knowledge abilities and skills of medical students, for being their objectivity, wide coverage in less time. However only the Quality Items gives a valid and reliable assessment. The quality of an Item is determined by difficulty index (DIF I), Discrimination Index (DI) and Distractor efficiency (DE). Aim of the study was to know the quality of Items in pharmacology by Item analysis and to develop a MCQs bank with quality Items.Methods: The present study was conducted on 150 II MBBS students of Guntur Medical College, AP, India. A class test containing 50 Items with 150 distractors from topic chemotherapy was conducted. Item with the correct choice/response was awarded with one mark and with the wrong choice zero marks, no negative marks. Each test Item was analysed with DIF I, DI and DE and the results were tabulated and tested statistically, with unpaired "t" test.Results: Mean DIF I, DI, DE values with standard deviations in the present study are 44.72+17.63%, 0.30+0.12%, 84.48+24.65 respectively. DIF I of 32 (64%) items was good to excellent range (31%-60%) 9 (18%) Items were easy (>61%) and 9(18%) Items were difficult (>30%). DI of 10 (20%) Items was good (0.15 to 0.24.) 29 (58%) Items were excellent with DI > 0.25 and 11 (22%) Items were poor with DI <0.15. Among 150 distractors, 127 (85%) were functional distractors (FDs) and 23 (15%) were non-functional distractors (NFDs). DE of 33 (66%) items with nil NFDs was 100%, for 12 (24%) Items with one NFD, was 66.6%, for 4 (8%) items with 2 NFDs was 33.3% and for 1 (2%) Item with 3NFDs DE was 0%. When unpaired "t" test was applied to the means of "difficult" and "easy" Items, 96.22+11.33% SD, 51.44+29.31% SD respectively, the p-value obtained was 0.00058, which was highly significant.Conclusions: The study showed that Item analysis is a valid tool to identify quality Items, which assess, the students’ knowledge abilities and discriminate different levels of performance abilities of students effectively