275 research outputs found
Synthesis and characterization of novel polycyclic structures, precursors to high performance polymers Humayun Mandal.
No full textOur primary goal in this thesis was to develop convenient methods for the synthesis of oligomeric polycyclics which could be ring-opened at elevated temperatures in the presence of a catalyst to give new classes of thermoset materials.A simple and commercially attractive approach was utilized to synthesize novolac type resins by reacting p-substituted phenols with formaldehyde using a cation exchange resin as catalyst in the presence of chlorobenzene as solvent.Novel oligomeric polycyclic carbonates were prepared by reacting the multifunctional phenol-formaldehyde resin with excess triphosgene under high dilution conditions. When the oligomeric polycyclic carbonates were heated at elevated temperatures using an initiator, a highly cross-linked network was obtained. In addition, the polycyclics were mixed with a commercial BPA polycarbonate and cured at different temperatures in the presence of a catalyst. When the mixture of BPA polycarbonate with 10 wt.% polycyclic carbonate was cured at 350ºC for 30 min. using a catalytic amount of lithium stearate, it gave a highly cross-linked network.Two series of polycyclic phosphonates were synthesized by reacting the oligomeric phenol-formaldehyde resins with phosphonic dichlorides under high dilution conditions in a polar aprotic solvent. The polycyclic phosphonates were similarly subjected to ring-opening polymerization at elevated temperatures in the presence of an initiator. The crosslinked phosphonates exhibited good flame retardance properties.Two classes of oligomeric siloxane resins were also synthesized by reacting the phenol-formaldehyde novolac type resins with dialkyl or diaryl dichloro, silanes under high dilution conditions. The formation of predominantly polycyclic siloxane structures was revealed by MALDI-TOF MS, Gradient HPLC and 1H NMR. Blends of commercial polysiloxane gums with different proportions of polycyclic siloxane resins were subjected to curing at 300ºC in the presence of KOH catalyst. Polysiloxane gums are highly unstable at 300ºC in the presence of a basic catalyst. However, the cross-linked polysiloxane gum at 30 wt.% loading of polycyclic siloxanes, was sufficiently stable at this temperature.A Bisphenol A dimer (o, o' methylene bridged) was synthesized by a single-pot reaction between formaldehyde and excess BPA using cation exchange resin catalyst. A few novel classes of oligomeric polycyclics with low melt viscosities were synthesized from this dimer under high dilution conditions.A series of co-polycarbonates of BPA were synthesized by the reaction of methylene bridged dimer with BPA and triphosgene. An alternative in-situ polymerization method was also developed to synthesize the BPA co-polycarbonates. These co-polymers containing cross-linkable cyclic carbonate moieties on the backbone, gave thermoset materials when cured at elevated temperatures in the presence of a catalyst.Low molecular weight poly(aryl ether sulfone)s end-capped with metallophthalocyanine moieties were prepared by reacting poly(aryl ether sulfone)s containing o-phthalonitrile end-groups with excess phthalonitrile and metals/metal salts in quinoline. These polymers were characterized in detail by using IR, UV-VIS, 1 H NMR and GPC techniques. Annealing studies on the polymers containing PcM end-groups were undertaken in order to investigate the occurrence of stacking of plithalocyanine rings in the melt. This study was conducted by using a Thermo-Gravimettic/Differential Thermal Analysis (TG/DTA) instrument
Constitutional Validity of Implementation of Mandal Commission Recommendations
No full textThe author argues that the Government action on the Mandal Commission is constitutionally valid. It does not in any way violate any of the Fundamental Rights let alone Articles 14, 15 and 16. However, the author concedes, considering the volatile situation at hand and the instability writ large in the political scenario, it is difficult to be certain as to how the Supreme Court will react. The author maintains that it is possible to uphold the Mandal Commission government action by focusing on the Supreme Court’s interpretation of Articles 14, 15 and 16 as three provisions form part of one code, each embodying a different facet of the guarantee of equality. (Editor’s abstract.
Constitutional Validity of Implementation of Mandal Commission Recommendations
No full textThe author argues that the Government action on the Mandal Commission is constitutionally valid. It does not in any way violate any of the Fundamental Rights let alone Articles 14, 15 and 16. However, the author concedes, considering the volatile situation at hand and the instability writ large in the political scenario, it is difficult to be certain as to how the Supreme Court will react. The author maintains that it is possible to uphold the Mandal Commission government action by focusing on the Supreme Court’s interpretation of Articles 14, 15 and 16 as three provisions form part of one code, each embodying a different facet of the guarantee of equality. (Editor’s abstract.
Royal Assemblies and Imperial Libraries: Polygonal Pavilions and Their Functions in Mughal and Safavid Architecture
No full textThis article examines the architectural form and potential functions of two royal buildings: the Sher Mandal and the Guldasta pavilion. An octagonal tower located in the Purana Qila in Delhi, the Sher Mandal was in all likelihood the library (kitab-khana) built by the Mughal emperor Humayun (r. 1530-56). Erected during the reign of the Safavid ruler Shah Abbas I (r. 1587-1629), the now-vanished Guldasta pavilion was located south of the palace complex in Isfahan and can be studied through drawings and photographs. A close examination of the formal structure of the two buildings reveals that they belong to a distinct type of polygonal pavilion that first emerged in the late fifteenth century in the works of architecture sponsored by the Timurid dynasty (c. 1370-1405). Moreover, this comparative study opens up new venues for investigating the physical setting of the royal kitab-khana in Mughal and Safavid contexts
Correlations between meteorological parameters and prostate cancer
No full textAbstract Background There exists a north-south pattern to the distribution of prostate cancer in the U.S., with the north having higher rates than the south. The current hypothesis for the spatial pattern of this disease is low vitamin D levels in individuals living at northerly latitudes; however, this explanation only partially explains the spatial distribution in the incidence of this cancer. Using a U.S. county-level ecological study design, we provide evidence that other meteorological parameters further explain the variation in prostate cancer across the U.S. Results In general, the colder the temperature and the drier the climate in a county, the higher the incidence of prostate cancer, even after controlling for shortwave radiation, age, race, snowfall, premature mortality from heart disease, unemployment rate, and pesticide use. Further, in counties with high average annual snowfall (>75 cm/yr) the amount of land used to grow crops (a proxy for pesticide use) was positively correlated with the incidence of prostate cancer. Conclusion The trends found in this USA study suggest prostate cancer may be partially correlated with meteorological factors. The patterns observed were consistent with what we would expect given the effects of climate on the deposition, absorption, and degradation of persistent organic pollutants including pesticides. Some of these pollutants are known endocrine disruptors and have been associated with prostate cancer.</p
Dielectric and infrared studies of radio frequency processes in some alcohols
No full textIn this thesis, the results of dielectric studies on a number of aliphatic
alcohol molecules with variable chain lengths are presented. This investigation was
complemented by infrared and viscosity measurements. Dielectric studies were
confined to the radio frequency range using an H.P. 419lA RF Inpedance Analyzer.
The experimental data, as a function of frequency and temperature, were subjected to
analysis by a series of computer programs written in APL language. The activation
energy barriers for the dielectric relaxation were obtained by application of the
Eyring rate equation.
Initially, a number of pure liquid alcohol molecules were studied with
increasing chain length in a wide temperature and frequency range. The effect of
size on the relaxation parameters could then be revealed. In all cases a Debye type
process was observed which is in accordance with the literature report
A few of these alcohols were also studied in a variety of solvents ranging
from inert to strongly interacting. The experimental relaxation times were compared
with the theoretical ones obtained using Higasi's theory of the dielectric relaxation
mechanism. Furthermore, the relaxation parameters were analysed in terms of
solute-solute and solute-solvent interactions.
The importance of chain length on the associative equilibria was examined.
Methanol, which has no chain length and no intramolecular motion within the
experimental temperature and frequency ranges, was selected for this purpose. A
detailed dielectric study for this alcohol was carried out in different media.
An attempt was made to gain insight into the impact of steric hindrance on
the relaxation times and energy parameters. Small alcohols were substituted by larger alcohol molecules in three component systems. The position of the dipole
was varied for different alcohols in two component systems. These studies
constitute the latter part of this thesis
Jane Austen and the popular novel: the determined author
No full textJane Austen and the Popular Novel: The Determined Author offers a provocative reinterpretation of one of the most cherished authors in the English literary canon. Austen criticism has traditionally fixed her oeuvre within the ideological locus of the 1790s, ignoring the more topical elements displayed by her novels. Such accounts have consequently neglected the complex interactions that took place between Austen's works and newer forms of popular fiction, such as the Evangelical tale, the national romance, and historical novel. By situating Austen in the 1810s - the immediate literary period within which she published - this book argues for the inherently intertextual nature of her novels, positing that her 'innovation' lies not in her uniqueness, but in her polyvalent negotiations with other literary models. Jane Austen and the Popular Novel demonstrates the extent to which Austen was not only a determined author, but also an author determined by the literary marketplace itself
Supporting Data for “Why So Slow? Mechanistic Insights from Studies of a Poor Catalyst for Polymerization of ε-Caprolactone”
No full textThese files contain data along with associated output from instrumentation supporting all results reported in Stasiw, D. E.; Mandal, M.; Neisen, B. D.; Mitchell, L. A.; Cramer, C. J.; Tolman, W. B. Why so slow? Mechanistic insights from studies of a poor catalyst for polymerization of ε-caprolactone. Inorg. Chem., 2016, 56, 725–728. Polymerization of ε-caprolactone (CL) using an aluminum alkoxide catalyst (1) designed to prevent unproductive trans binding was monitored at 110 °C in toluene-d8 by 1H NMR and the concentration versus time data fit to a first-order rate expression. A comparison of t1/2 for 1 to values for many other aluminum alkyl and alkoxide complexes shows much lower activity of 1 toward polymerization of CL. Density functional theory calculations were used to understand the basis for the slow kinetics. The optimized geometry of the ligand framework of 1 was found indeed to make CL trans binding difficult: no trans-bound intermediate could be identified as a local minimum. Nor were local minima for cis-bound precomplexes found, suggesting a concerted coordination–insertion for polymer initiation and propagation. The sluggish performance of 1 is attributed to a high-framework distortion energy required to deform the “resting” ligand geometry to that providing optimal catalysis in the corresponding transition-state structure geometry, thus suggesting a need to incorporate ligand flexibility in the design of efficient polymerization catalysts..
Corresponding author for experimental data is William B. Tolman ([email protected]).
Corresponding author for computational data is Christopher J. Cramer ([email protected]).Funding for this project was provided by the Center for Sustainable Polymers at the University of Minnesota, a National Science Foundation (NSF)-supported Center for Chemical Innovation (Grant CHE-1413862). The X-ray diffraction experiments were performed using a crystal diffractometer acquired through NSF-MRI Award CHE-1229400. The authors acknowledge the MSI at the University of Minnesota for providing resources that contributed to the research results.Tolman, William, B; Cramer, Christopher, J; Stasiw, Daniel E; Mandal, Mukunda; Neisen, Benjamin D; Mitchell, Lauren A. (2017). Supporting Data for “Why So Slow? Mechanistic Insights from Studies of a Poor Catalyst for Polymerization of ε-Caprolactone”. Retrieved from the University Digital Conservancy, https://doi.org/10.13020/D6F60H
Zero Energy States for Commensurate Hopping Modulation of a Generalized Su-Schrieffer-Heeger Chain in the Presence of a Domain Wall
No full textWe study the effect of domain wall (DW) on zero-energy states (ZESs) in the Su-Schrieffer-Heeger (SSH) chain. The chain features two fractional ZESs in the presence of such DW, one of which is localized at the edge and the other bound at the location of DW. This zero-energy DW state exhibits interesting modifications when hopping modulation is tuned periodically. We studied the energy spectra for commensurate frequencies and . Following the recent study by the author of this paper [S. Mandal, S. Kar, Phys. Rev. B 109, 195124 (2024)], we showed numerically, along with physical intuition, that one ZES can bound at the DW position only for commensurate frequency for zero or an integer values, while for with nonzero or an integer value they appear only at the edges of the chain. We verify our numerical results by using exact analytical techniques. Both analyses indicate the realization of the Jackiw-Rebbi modes for our model only with . Moreover, the localization of zero-energy edge and DW states are investigated which reveals their localized (extended) nature for smaller (larger) (amplitude of DW). The localization of topological DW states is suppressed as the width of DW () increases (typically scaled as ) while the edge state shows an extended behavior only for the large limit.10 pages, 9 figure
Retraction note: Autophagy-independent induction of LC3B through oxidative stress reveals its non-canonical role in anoikis of ovarian cancer cells (Cell Death & Disease, (2018), 9, 10, (934), 10.1038/s41419-018-0989-8)
No full text\ua9 The Author(s) 2024. Retraction Note to: Cell Death and Diseasehttps://doi.org/10.1038/s41419-018-0989-8, published online 17 September 2018 The Editors have retracted this article because there appear to be anomalies in three of the figures. Specifically Duplication of GADPH bands between Figs. 1d and 4g. Partial overlap of the first and fourth panels in Fig. 3i. Repeated regions in the third panel of Fig. 2e. Duplication of the Atg12 band in Fig. 2i with the beta-actin band in Fig. 4d. Duplication of the Bax band in Fig. 3n with the Slug band in Fig. 4g after flipping horizontally. Duplication of GADPH bands between Figs. 1d and 4g. Partial overlap of the first and fourth panels in Fig. 3i. Repeated regions in the third panel of Fig. 2e. Duplication of the Atg12 band in Fig. 2i with the beta-actin band in Fig. 4d. Duplication of the Bax band in Fig. 3n with the Slug band in Fig. 4g after flipping horizontally. The Editors, therefore, no longer have confidence in the results and conclusions presented. Eswara Murali Satyavarapu, Ranjita Das, Chandan Mandal, and Chitra Mandal have not responded to correspondence from the Publisher about this retraction. The Publisher was not able to find a current email address for Asima Mukhodhyay
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