• Archives of Pharmacal Research
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• v.2 no.1
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• pp.49-64
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• 1979

In an atempt to elucidate further physicochemical properties of furosemide-PVP coprecipitates, extensive investigations such as TLC, UV,IR, NMR, X-ray diffraction, TGA and DTA studies were carried out for the furosemide test systems. X-ray diffraction studies revealed that the pure furosemide and the furosemide contained within a physical mixture were crystalline in nature. However, there was no crystallinity evident in the 1:5 furosemide-PVP 40,000 coprecipitate system, even after standing for two years. The various ratio furosemide-PVP 40,000 coprecipitate systems revealed that the coprecipitate containing a greater amount of PVP 40,000 than that of furosemide showed a crystalline state of furosemide and that the minimum amounts of PVP to make amorphous form of furosemide was 1:1 ratio of furosemide to PVP. From the furosemide-PVP coprecipitate systems with PVP of different molecular weights of 10,000, 40,000 and 360,000, all the 1:1 ratio coprecipitates did not exhibit any crystallinity of furosemide, whereas all the 2:1 ratio coprecipitates showed a presence of crystalline furosemide. All the coprecipitated preparations with PEG 4,000 and with PEG 6,000 showed the diffraction peaks indicating the presence of crystalline furosemide. The comparison of infrared spectra of the physical mixture and the coprecipitate showed an interaction such as association between the functional groups of furosemide and PVP in the molecular level, whereas the studies by TLC, UV and NMR showed its dissociation in methanol solution. The weight losses in TGA curves showed all the same patterns. However, a little different transition form in DTA thermograms was shown between the physical mixture and the coprecipitate, indicating the different thermal property.

• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.140.2-140.2
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• 2012

The silicate carbon star IRAS 09425-6040 shows very conspicuous crystalline silicate dust features and excessive emission at far infrared. To investigate properties of dusty envelopes around the object, we use radiative transfer models for axisymmetric and sphericallly symmetric dust distributions. We perform model calculations for various possible combinations of dust shells and disks with various dust species. We compare the model results with the observed spectral energy distributions (SEDs) including the IRAS, ISO, AKARI, MSX and 2MASS data. We find that a model with multiple disks of amorphous and crystalline silicate and multiple spherical shells of carbon dust can reproduce the observed SED fairly well. This supports the scenario for the origin of silicate carbon stars that oxygen-rich material was shed by mass loss when the primary star was an M giant and the O-rich material is stored in a circumbinary disk. Highly (about 75 %) crystallized forsterite dust in the disk can reproduce the conspicuous crystalline features of the ISO observational data. This object looks to have a detached silicate and H2O ice shell with a much higher mass-loss rate. It could be a remnant of the chemical transition phase. The last phase of stellar winds of O-rich materials looks to be a superwind.

• Polymer(Korea)
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• v.33 no.4
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• pp.297-306
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• 2009

A homologous series of side chain liquid crystalline polymers, poly [1-{4-(4'-cyanophenylazo)phenoxyalkyloxy}ethylene]s(CAPETn, where n, the number of methylene units in the spacer, is $2{\sim}10$) were synthesized from poly(vinyl alcohol) and 1-{4-(4'-cyanophenylazo)phenoxy}alkylbromides(CAPBn, n=$2{\sim}10$), and their thermotropic liquid crystalline phase behaviors were investigated. The CAPBn with n of $2{\sim}5$ did not show any liquid crystalline behavior, while those with n of 6 and $7{\sim}10$ showed enantiotropic and monotropic nematic phases, respectively. In contrast, among the CAPETn polymers, only CAPET5 exhibited an enantiotropic nematic phase, while other polymers showed monotropic nematic phases. The isotropic-nematic transition temperatures of CAPETns and their entropy variation at the phase transition that were higher values than those of CAPBns, demonstrated a typical odd-even effect as a function of n. These phase transition behaviors were disscussed in terms of the 'virtual trimer model' by Imrie. The mesophase properties of CAPETns were largely different from those reported for the polymers in which the (cyanophenylazo) phenoxy groups are attached to polyacrylate, polymethacrylate, and polystyrene backbones through polymethylene spacers. The results indicate that the mode of chemical linkage of the side group with the main chain plays an important role in the formation, stabilization, and type of mesophase.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.222.2-222.2
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• 2015

A $Ge_2Sb_2Te_5$ nanowire (GST NW) phase change memory device is investigated with Joule heating electrodes. GST is the most promising phase change materials, thus has been studied for decades but atomic structure transition in the phase-change area of single crystalline phase-change material has not been clearly investigated. We fabricated a phase change memory (PCM) device consisting of GST NWs connected with WN electrodes. The GST NW has switching performance with the reset/set resistance ratio above $10^3$. We directly observed the changes in atomic structure between the ordered hexagonal close packed (HCP) structure and disordered amorphous phase of a reset-stop GST NW with cross-sectional STEM analysis. Amorphous areas are detected at the center of NW and side areas adjacent to heating electrodes. Direct imaging of phase change area verified the atomic structure transition from the migration and disordering of Ge and Sb atoms. Even with the repeated phase transitions, periodic arrangement of Te atoms is not significantly changed, thus acting as a template for recrystallization. This result provides a novel understanding on the phase-change mechanism in single crystalline phase-change materials.

• Journal of the Korean Applied Science and Technology
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• v.16 no.3
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• pp.255-262
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• 1999

The new copolymers which contain flexible spacers in main chain were prepared and their properties were studied. the copolymers were synthesized in the melt polymerization melted from diacetoxynaphthalene isomers, ${\alpha},{\omega}bis(4-carboxyphenoxy)$ alkanes and p-acetoxy benzoic acid in the molar ratio of 1:1:2 and characterized for the effects of structure of naphthalenediol isomer moieties and the spacers on thermal crystalline and liquid crystalline properties of the resulting polymers. Diacetoxy naphthalene isomers were used 1. 5-,1. 6-,2. 6-and 2. 7-disubstituted ones and the spacers was either tetramethylene or decamethylene. The polymer was characterized by elemental and spectropic analysis, differential scanning calorimetry (DSC) on a polaring microscope, wide-angle X-ray diffractometry and thermogravimetry (TGA). There glass transition temperatures (Tg) and melting temperature (Tm) on the structure of the naphthalenediol isomer moieties and the length of the spacers. The presence of spacers was found to the helpful in crystallization of 1. 6-naphthalenediol copolyesters. The presence of amide group in the backbone chain of polymer was found to increase transition temperature, crystallization, thermal stability of polymers but to decreas solubility.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.118-119
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• 2006

In the present work, we investigate the basic physical and thermal properties and electrical resistance change due to phase change in chalcogenide-based $Ge_1Se_1Te_2$ and $Ge_2Se_2Te_5$ thin films. The phase transition from amorphous to crystalline states, and vice versa, of $Ge_1Se_1Te_2$ and $Ge_2Se_2Te_5$ thin films by applying electrical pulses have been studied. The reversible phase transition between the amorphous and crystalline states, which is accompanied by a considerable change in electrical resistivity, is exploited as means to store bits of information.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.151.1-151.1
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• 2016

Complex oxide heterointerfaces have been extensively explored in the past due to the novel phenomenon emerging at such interfaces that differ from their individual bulk counterparts. The integration of a ferromagnetic (FM) material with the superconducting (SC) material leading to proximity effect is one of the commonly studied phenomenon in these heterostructures. In continuation, we have stabilized the FM layer La0.7Ca0.3MnO3 (LCMO) on SC material YBa2Cu3O7-${\delta}$ (YBCO) using pulsed laser deposition technique and explored the structural, magnetic, electrical and magneto-transport properties of this heterostructure. ${\Phi}$-scan measurements confirm the epitaxial nature of LCMO/YBCO heterostructure grown on single crystalline SrTiO3 substrate. The FM transition of LCMO and SC transition of YBCO are observed in the magnetization measurements of the bilayer structure. Through electrical measurements, we understood that the proximity effect leads to lowering of the SC transition of YBCO. The role of interface in the bilayer structure is also realized through electrical transport measurements.

• Journal of the Korean Society of Food Science and Nutrition
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• v.27 no.3
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• pp.518-524
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• 1998

Liposomes have been widely employed as biomembrane-mimetic system and drug-delivery system. In these applications, the low stability of liposomes has been the most serious problem. They have relatively short half-lives and easily lysed through interactions with biological components. This study was performed to investigate the effects of godulbaegi extracts on the fludity of phospholipid liposomes. We used dipalmitoyl phosphatidylcholine(DPPC) liposomes which make most stable liposomes among the other phosphatidylcholines. The thermograms of the DPPC liposomal bilayers incorporated with the hexane extract of godulbaegi(Ixeris sonchifolia H.) were obtained, and the enthalpy changes and the sizes of cooperative unit of the transition were calculated. The incorporation of the Ixeris sonchifolia H. into the liposomal bilayers effectively reduced the transition temperature at which the transition from gel state to liquid-crystalline state occurs, broadened the thermogram peaks, and reduced the ratio of van't Hoff to calorimetric enthalpies. These results indicate indicate that the godulbaegi extracts (Ixeris sonchifolia H.) have significant effects on the fluidity of biological membrance.

• Journal of the Korean Ceramic Society
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• v.34 no.6
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• pp.569-576
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• 1997

Electrically-induced strain and polarization studies of the (1-x)Pb(Mg1/3Nb2/3)O3-PbZrO3 crystalline solutions have been done. Dielectric constants with temperature were investigated for 0$\leq$x$\leq$0.95. With increasing PbZrO3 content the transition maxima were found to move to higher temperature region and DPT (Diffused Phase Transition) properties were decreased for x$\leq$0.60. Phase transition between ferroelectric states and antiferroelectric states was confirmed for 0.93$\times$10-3 for 0.4

• Electrical & Electronic Materials
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• v.10 no.2
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• pp.156-165
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• 1997

D-E hysteresis loops have been measured for the 65/35 mole % copolymer of vinylidene fluoride and trifluoroethylene over wide temperature range. The remanent polarization and the coercive field at room temperature were estimated to be 75 mC/m$^{2}$ and 55 MV/m respectively. D-E hysteresis loops were observed even below the glass transition temperature(-20.deg. C) and the remanent polarization and the coercive field were larger, as the temperature lower. It seems that the remanent polarization and the coercive field depend on the amorphous region as well as crystalline region in this copolymer. And the ferroelectric-to-paraelectric phase transition was observed at 90.deg. C on heating and 80'C on cooling. Double hysteresis loops were observed at the temperature(85.deg. C) of paraelectric phase.