Showing papers by "Sungkyunkwan University published in 1998"

Unit roots, cointegration, and structural change

Abstract: Time series analysis has undergone many changes in recent years with the advent of unit roots and cointegration. Maddala and Kim present a comprehensive review of these important developments and examine structural change. The volume provides an analysis of unit root tests, problems with unit root testing, estimation of cointegration systems, cointegration tests, and econometric estimation with integrated regressors. The authors also present the Bayesian approach to these problems and bootstrap methods for small-sample inference. The chapters on structural change discuss the problems of unit root tests and cointegration under structural change, outliers and robust methods, the Markov-switching model and Harvey's structural time series model. Unit Roots, Cointegration and Structural Change is a major contribution to Themes in Modern Econometrics, of interest both to specialists and graduate and upper-undergraduate students.

Experimental evidence on the evolution of the meaning of messages in sender-receiver games : An experiment

Abstract: This paper experimentally investigates the evolution of message meanings when talk is cheap. We consider communication between a privately informed sender and a receiver when the sender's message does not affect payoffs directly. Sender-receiver games, introduced by Jerry Green and Nancy Stokey (1980) and Vincent P. Crawford and Joel Sobel (1982), provide the simplest stylized environment in which communication is essential; communication is the only way to link the receiver's action to the sender's private information. In addition, sender-receiver games have been widely used to study communication in accounting, economics, finance, and political science. Intuition strongly suggests that effective communication will evolve when the players' interests are closely aligned. However, there is always a Nash equilibrium in which the sender randomizes uniformly across all messages. Such "babbling equilibria" are proper (Roger B. Myerson, 1978; Blume, 1994), and even strategic stability (Elon Kohlberg and JeanFrancois Mertens, 1986) does not rule out uninformative equilibria in general. In response, a literature developed that formulates equilibrium selection criteria by appealing to the existence of a commonly understood language (Matthew Rabin, 1990; Steven A. Matthews et al., 1991; Joseph Farrell, 1993) that can be used to formulate credible deviations from equilibrium. Unfortunately, the selection criteria from this literature are frequently strong enough to remove all equilibria from consideration. In addition, these arguments are vulnerable to Stiglitz's observation (In-Koo Cho and David M. Kreps, 1987) that successful deviations from equilibrium may induce further deviations, which in turn may undermine the credibility of the original deviations. Both problems can be avoided by a dynamic approach as in Rabin and Sobel (1996). We also adopt a dynamic perspective but do not require messages to have a priori meanings; instead, distinct meanings may emerge endogenously. This is important for communication across cultures and for language change.2 We are guided by recent results of * Blume: Department of Economics, University of Iowa, Iowa City, IA 52242; DeJong: Department of Accounting, University of Iowa, Iowa City, IA 52242; Kim: Department of Economics, Sung Kyun Kwan University, Seoul 110-745, Korea; Sprinkle: Department of Accounting, University of Wisconsin, Madison, WI 53706. We thank Joyce Berg, Vince Crawford, Robert Forsythe, Joel Horowitz, Deirdre McCloskey, Forrest Nelson, Larry Samuelson, Gene Savin, Joel Sobel, and especially two anonymous referees for their advice and suggestions. We benefitted from comments and discussions resulting from presentations at the 1994 summer meetings of the Econometric Society, the 1996 Social Learning Workshop at SUNY-Stony Brook, the IO/ME/GT Workshop at the University of Iowa, the University of Bonn, the University of Bielefeld, the CentER for Economic Research at Tilburg University, Ohio State University, Seoul National University, and Texas A&M University. We are grateful for financial support from the College of Business Administration at the University of Iowa, the Ira B. McGladrey Institute, and the National Science Foundation-

Profiling of differentially expressed genes in human primary cervical cancer by complementary DNA expression array.

Abstract: The profiling of differentially expressed genes from primary tumor samples using cDNA expression array can reveal new tumor markers as well as target genes for therapeutic intervention Using cDNA expression array technology, we produced an expression profile of genes that are associated with human cervical cancer Hybridization of the cDNA blotting membrane (588 genes on a single membrane) was performed with 32P-labeled cDNA probes synthesized from RNA isolated from either normal cervix or cervical cancer Parallel analyses of the hybridized signals enabled us to profile genes that were differentially expressed in cervical cancer In each experiment, the extent of hybridization of each gene was evaluated by comparison with the most abundant mRNAs in the human cervix These include myc proto-oncogene, 40S ribosomal protein S19, heat shock proteins, leukosialin S (CD43), integrin alphaL (CD11A), calgranulin (A), and CDK4 inhibitor (p16ink4) No detectable changes were observed in the expression levels of these genes Several mRNAs, such as those encoding guanine nucleotide-binding protein Gs (alpha subunit), leukocyte adhesion protein (LFA1-beta), nuclear factor NF45, homeobox protein Hox-A1, and beta-catenin were detected in increased levels in cervical cancer Genes that showed decreased expression in cervical cancer tissue were a group of apoptosis-related proteins, cell adhesion molecules, nuclear transcription factors, and a homeobox protein (Hox7) For example, the expression levels of Smad1 and Hox7 were consistently decreased in all tumor tissues tested Northern analysis of Smad1 and Hox7 RNA in primary cervical tumor tissues and cervical carcinoma cell lines indicated that, in general, the mRNA levels of these genes were decreased in human cervical cancer The precise relationship between the altered expression of these genes and cervical tumorigenesis is a matter of further investigation

Survey of Klebsiella pneumoniae Strains Producing Extended-Spectrum β-Lactamases: Prevalence of SHV-12 and SHV-2a in Korea

Abstract: Fifty-three clinical isolates of extended-spectrum β-lactamase (ESBL)-producing Klebsiella pneumoniae collected from three hospitals in Korea were investigated for phenotypical and genotypical characterizations. Among these, 39 strains (74%) were shown by isoelectric focusing to carry SHV-type β-lactamases: 27 strains showed the pI 8.2 β-lactamase, and another 12 strains showed the pI 7.6 β-lactamase. The SHV gene of each of these strains was amplified by PCR, followed by nucleotide sequencing analysis. The gene of the pI 8.2 β-lactamase was found to be identical to the sequences encoding SHV-12, and the gene of the pI 7.6 β-lactamase was identical to the sequences encoding SHV-2a. A total of eight cefoxitin-resistant strains were found to have the plasmid-mediated AmpC-type β-lactamase, with a pI of 8.0, and this was confirmed to be CMY-1 β-lactamase by PCR and hybridization analysis. Noteworthy in this study is the fact that SHV-12 and SHV-2a have been the most commonly identified SHV-type ESBLs in Korea.

On the Choice of Insurance Distribution Systems

Abstract: This article examines insurers' choice between independent and exclusive agents. We assume that alternative distribution systems are efficient mechanisms for controlling contracting problems among policyholders, insurers, and agents. Because the use of independent agents helps control potential expropriative behavior by the insurer, the independent agency system should be more valuable for ownership structures where such problems are more severe. Thus, ownership structures and distribution systems are strategic complements. We test this theory by analyzing the association between distribution-system choice and the firm's ownership structure, lines of insurance, advertising policy, size, geographic concentration, and cost structure among property-liabi lity insurers.

A new joint algorithm of symbol timing recovery and sampling clock adjustment for OFDM systems

Abstract: This paper discusses the effects of time synchronization errors on OFDM (orthogonal frequency division multiplexing) digital communications. Time synchronization consists of symbol timing recovery and sampling clock adjustment. In general, symbol timing recovery is carried out before sampling clock adjustment. The main problem with time synchronization errors is that the sample rob/stuff phenomenon due to sampling clock frequency offset leads to adding the symbol timing offset. Thus a more efficient synchronization algorithm is required. This paper introduces a new joint algorithm between symbol timing recovery and sampling clock adjustment using the difference of phase changes between the pilot carriers. The performance of the proposed algorithm is carried out under AWGN and multipath fading channel.

Vascular leiomyoma of an extremity: MR imaging-pathology correlation.

Abstract: OBJECTIVE: The objective of our study was to analyze MR images of vascular leiomyoma of the extremity and to compare these images with histopathologic findings to determine if a correlation exists. CONCLUSION: T2-weighted MR images of vascular leiomyoma of an extremity showed a mass with mixed areas that were both hyper- and isointense to skeletal muscle and also revealed a hypointense rim; these images correlate with histopathologic findings of smooth muscle, vessels, fibrous tissue, an intravascular thrombus, and a fibrous capsule.

Catalytic Asymmetric Allenylation: Regulation of the Equilibrium between Propargyl- and Allenylstannanes during the Catalytic Process.

Abstract: Achiral substrates 1 and 2 can be regioselectively converted into chiral allenyl alcohols 3 through the title reaction [Eq. (1)] with the synergetic reagent iPrSBEt2 and a chiral TiIV catalyst. The dramatic regioselectivity originates from the regulation of the equilibrium between propargyl- and allenylstannanes during the catalytic process.

Weyl's theorem for operator matrices

Abstract: “Weyl's theorem holds” for an operator when the complement in the spectrum of the “Weyl” spectrum” coincides with the isolated points of the spectrum which are eigenvalues of finite multiplicity By comparison “Browder's theorem holds” for an operator when the complement in the spectrum of the Weyl spectrum coincides with Riesz points Weyl's theorem and Browder's theorem are liable to fail for 2×2 operator matrices In this paper we explore how Weyl's theorem and Browder's theorem survive for 2×2 operator matrices on the Hilbert space

Differential effects and transport kinetics of ascorbate derivatives in leukemic cell lines.

Abstract: In order to investigate the differential effects of ascorbate derivatives on leukemic cell growth, we examined their stabilities and transmembrane transport efficiencies. The growth of HL-60 and U937 cells was dose-dependently inhibited by ascorbic acid and sodium ascorbate, but not by dehydroascorbic acid and magnesium ascorbyl 2-phosphate up to 200 microM. The growth-suppression by ascorbic acid was dependent on its redox state, showing a complete or partial reversion by ascorbate oxidase or FeCl3 addition, respectively. Three different patterns of intracellular ascorbic acid accumulation were observed by HPLC according to the species of ascorbate derivative applied for the incubation. Compared with the reduced form of ascorbic acid, the oxidized forms (dehydroascorbic acid, ascorbic acid plus ascorbate oxidase or FeCl3) were rapidly transported into cells and readily degraded, while magnesium ascorbyl 2-phosphate, a stable derivative of ascorbic acid, slowly elevated the intracellular level of ascorbic acid, reaching a plateau at 24 hours. We also measured the differential kinetics of ascorbic acid levels In culture supernatants following the addition of ascorbate derivatives. Ascorbic acid at 40, 10, or 1 microM was observed 3 hours following treatment with 100 microM of ascorbic acid, ascorbic acid plus FeCl3, or magnesium ascorbyl 2-phosphate, respectively. No ascorbic acid was found in the culture supernatant treated with dehydroascorbic acid. This order of ascorbic acid concentrations in culture supernatant reflects their growth-inhibitory effects. Thus the growth inhibitory effect of ascorbic acid appears to be dependent on its concentration in culture medium rather than its intracellular concentration. In conclusion, the results in this study indicate that the differential effects of ascorbate derivatives appear to be due to the actual concentration differences of the reduced form of ascorbic acid in culture medium following their addition, which is determined by their stability and efficiency of cellular uptake.

Imprint failures and asymmetric electrical properties induced by thermal processes in epitaxial Bi4Ti3O12 thin films

Abstract: Epitaxial Bi4Ti3O12 (BTO) thin films were deposited on MgO(001) substrates using Pt layers as top and bottom electrodes. In spite of the apparently symmetric capacitor structure, polarization–voltage measurements revealed strong imprint failures and current–voltage measurements showed rectifying behaviors. Imprint pulse tests with a 5 V dc bias and post-annealing treatments suggested that the asymmetric behaviors should be due to interfacial states induced by thermal processes. To probe the interfacial states, capacitance–voltage (C–V) measurements were performed. By fitting the C–V data with a model which describes the Pt/BTO/Pt structure as a series circuit composed of three capacitors, built-in voltages at the top and the bottom interfaces could be determined. Difference in the built-in voltages could explain the imprint failures and the rectifying behaviors. The interfacial states in the BTO capacitors were controlled by varying electrode materials.

Multifragmentation of the remnant produced in the reaction of 1A GeV gold with carbon

Abstract: A high-statistics exclusive study of the multifragmentation of 1A GeV gold on carbon has been performed. Particles with Z{le}2 show evidence of emission in a first prompt stage as well as in a second equilibrium stage whereas fragments with Z{ge}3 appear to be emitted essentially only in the second stage. Two methods for the separation of the Z{le}2 particles into the two stages are given and they are in agreement. The yields for each stage are determined as a function of the event charged particle multiplicity m. The mass, nuclear charge, excitation energy per nucleon, and temperature of the remnant left after the first stage and their fluctuations have been determined as a function of m. The expansion of the remnant to fragment freeze-out is examined. The freeze-out temperature is determined from double isotope ratios as a function of m and isentropic trajectories are obtained in the temperature-density plane. The caloric curve shows a monotonic increase with excitation energy. Some of the energy is in the form of radial flow. Overall, the results are consistent with a previous statistical analysis of the data which suggests that, over a certain range of excitation energies, multifragmentation involves a continuous phase transition. {copyright}more » {ital 1998} {ital The American Physical Society}« less

Blood eosinophils and serum IgE as predictors for prognosis of interferon-gamma therapy in atopic dermatitis.

Abstract: Background Interferon-gamma (IFN-gamma) therapy has been reported to be effective in atopic dermatitis. However, IFN-gamma therapy in atopic dermatitis has not yet been well established. In this study, immunologic variables were evaluated as predictors for the prognosis of IFN-gamma therapy in atopic dermatitis. Methods Sixty-eight atopic dermatitis patients were each treated 18 times with 2 x 10(6) units/m2 IFN-gamma. Blood IgE level, eosinophil percentage, eosinophil count, and levels of IFN-gamma, interleukin-4 (IL-4), IL-5, and IL-10 were investigated. According to clinical responses, patients were classified into three groups: patients with improved clinical severity scores of over 20% were included in group A; those with improved scores of 20% or less in group B; and those with no improvement in group C. Results Serum IgE levels and blood eosinophil percentages were the lowest in group A. Most atopic dermatitis patients with an eosinophil percentage over 9% and IgE level over 1500 IU/ml did not respond to IFN-gamma therapy. Initial IL-10 levels were the highest in group A. IL-4 levels in group A, and IL-5 and IL-10 levels in all groups were significantly decreased by IFN-gamma therapy. Conclusions IFN-gamma therapy may be recommended for atopic dermatitis patients with blood eosinophil percentages less than 9% and serum IgE levels less than 1500 IU/ml.

Stenting therapy for stenosing airway disease.

Abstract: Stenosing airway disease is classified as intraluminal obstruction, extrinsic compression, and malacia by the anatomical site of the lesion. Stenting therapy is indicated for symptomatic relief of life-threatening dyspnea caused by the last two types. Airway stents are made with metal mesh and/or silicone rubber, and currently more than 20 kinds of stent are available. The metal stent (e.g. Gianturco stent, Wallstent) is easy to insert, may not need general anesthesia, and has wider internal lumen. Because it is very hard to reposition or remove, it is mainly used in malignant airway obstruction. Among many kinds of silicone stent, the Dumon stent is most widely used for benign and malignant airway stenoses, but general anesthesia and rigid bronchoscopy are needed for insertion. It can be removed when the stenosing airway disease subsides completely. In many clinical studies, most patients (85-90%) improved immediately after stenting, and procedure-related mortality is low (< 3%) in experienced centers. Stent displacement, mucus impaction, and granulation tissue formation are potential complications. Stenting is one of many effective therapeutic modalities for stenosing central airway disease. Careful patient selection, experiences, and continuous development of new technology will bring better results.

Immunoblot analysis of a 10 kDa antigen in cyst fluid of Taenia solium metacestodes

Abstract: The diagnostic value of a 10 kDa subunit of 150 kDa protein in cyst fluid (CF) of Taenia solium metacestodes was evaluated. Immunoblot analysis revealed that most sera from patients with neurocysticercosis recognized the 10 kDa subunit strongly (209/217 cases, 84.6%), while a few sera from individuals with other parasitic diseases including alveolar echinococcosis (AE, 2/20, 10%) and cystic echinococcosis (CE, 2/25, 8%) showed faint reactions. Sera of cases with other parasitic diseases, especially AE and CE, exhibited cross reactions against other bands in CF. Both differential immunoblot and immunoprecipitation analyses showed that the 10 kDa subunit was the most specific to cysticercosis and highly antigenic, whereas other components at 20–40, 64, 95 and 106 kDa in CF were cross-reactive. IgG subclass ELISA and immunoblot demonstrated that both IgG4 and IgG1 reactions were predominant in neurocysticercosis and recognized the 10 kDa.

Polymorphism of the CYP1A1 and glutathione-S-transferase genes in Korean lung cancer patients

Abstract: The levels of expressions and catalytic activities of cytochrome P450 (CYP1A1) and glutathione-S-transferase class mu (GSTM1) enzymes in lungs and their metabolic balance may be an important determinant host factor underlying lung cancer. Genetic differences in metabolism, MspI restriction sites, Ile-Val polymorphism of CYP1A1 gene, and the null genotype of GSTM1 have been reported to be associated with susceptibility to lung cancer. The present studies were undertaken to establish frequencies of the polymorphic genotypes of CYP1A1 and GSTM1 in Koreans, and to evaluate linkage disequilibrium of the genotypes associated with higher lung cancer risks among Koreans. GSTM1(-) genotype was found in 52% of control subjects, whereas it was found in 55% of lung cancer patients. The allelic variants in CYP1A1 were distributed differently in lung cancer patients and controls. The heterozygous genotype frequency of the MspI site in lung cancer patients (53%) was higher than in controls (49%). The frequency of Ile/Val genotype of CYP1A1 was low in lung cancer patients, which are mostly squamous cell carcinoma.

Effect of lanthanide ions on the magnetotransport properties in layered Sr 1.6 R 1.4 Mn 2 O 7 ( R = L a , P r , N d , G d )

Abstract: The magnetoresistances (MR's) and magnetic properties of layered manganese oxides, ${\mathrm{Sr}}_{1.6}{R}_{1.4}{\mathrm{Mn}}_{2}{\mathrm{O}}_{7}$ ($R=\mathrm{L}\mathrm{a},\phantom{\rule{0ex}{0ex}}\mathrm{P}\mathrm{r},\phantom{\rule{0ex}{0ex}}\mathrm{N}\mathrm{d},\phantom{\rule{0ex}{0ex}}\mathrm{G}\mathrm{d}$; $R$-327), have been investigated. The La-, Pr-, and Nd-substituted compounds show metal insulator transitions below 150 K, whereas isostructural Gd-327 compound is semiconducting and paramagnetic. For La-327, the transition temperature corresponds well to the onset of ferromagnetic ordering and the MR ratio is fairly large compared with perovskite-type $A{\mathrm{MnO}}_{3}$ oxides. The Pr and Nd analogs show negative MR's, but both compounds display other anomalous transitions to semiconductors below 50 K. Neither material shows a transition to a ferromagnetic state below 350 K. The observation of colossal magnetoresistance in the absence of bulk ferromagnetism suggests that the double-exchange interaction alone is not sufficient to explain the resistivity of $R$-327 near ${T}_{c}.$

Pediatric pineal tumors: need for a direct surgical approach and complications of the occipital transtentorial approach.

Abstract: In an investigation of the benefits and risks of direct surgical approaches to pediatric pineal tumors, the need for such approaches, the feasibility of surgical removal and operative complications were evaluated in 25 histologically proven cases. Five tumors were germinomas (GEs) or GE-predominant mixed germ cell tumors (GCTs), in which stereotactic biopsy can be adequate. Twenty of the 25 pineal tumors (80%) were teratomas (TEs), TE-predominant mixed GCTs or other tumors that need direct surgical approaches. Among the 21 tumors resected by the occipital transtentorial (OTT) approach, 13 were removed radically (>95%) and 6 others, subtotally (>75%). Complications of using the OTT approach included homonymous hemianopsia (7), Parinaud's syndrome (6), other eyeball movement limitation (7), seizure (5), and new hydrocephalus (3). The majority of these were transient, resolving within a few days or months, or easily controlled. The results showed that 80% of pediatric pineal tumors needed direct surgical approaches and that the majority were successfully removed by OTT surgery with an acceptable level of risk.

Korean Nationwide Surveillance of Antimicrobial Resistance of bacteria in 1997

Abstract: Antimicrobial-resistant bacteria are known to be prevalent in tertiary-care hospitals in Korea. Twenty hospitals participated to this surveillance to determine the nationwide prevalence of resistance bacteria in 1997. Seven per cent and 26% of Escherichia coli and Klebsiella pneumoniae were resistant to 3rd-generation cephalosporin. Increased resistance rates, 19% of Acinetobacter baumannii to ampicillin/sulbactam, and 17% of Pseudomonas aeruginoa to imipenem, were noted. The resistance rate to fluoroquinolone rose to 24% in E. coli, 56% in A. baumannii and 42% in P. aeruginosa. Mean resistance rates were similar in all hospital groups: about 17% of P. aeruginosa to imipenem, 50% of Haemophilus influenzae to ampicillin, 70% of Staphylococcus aureus to methicillin, and 70% of pneumococci to penicillin. In conclusion, nosocomial pathogens and problem resistant organisms are prevalent in smaller hospitals too, indicating nosocomial spread is a significant cause of the increasing prevalence of resistant bacteria in Korea.

Ca2+ influx through carbachol-activated non-selective cation channels in guinea-pig gastric myocytes.

Abstract: 1. Ca2+ microfluorometry (100 microM K5 fura-2) and the voltage-clamp technique were combined to study the effect of carbachol (CCh, 50 microM) in inducing currents (ICCh) through non-selective cation channels (NSCCCh) and increments in global cytosolic Ca2+ concentration (Delta[Ca2+]c). 2. In Na+-containing bath solution, ICCh fell from an initial phasic to a subsequent small (5 %) tonic component; Delta[Ca2+]c fell to zero. Tonic ICCh and [Ca2+]c became prominent after substitution of extracellular 140 mM Na+ by 140 mM Cs+. Tonic ICCh and Delta[Ca2+]c were insensitive to intracellular heparin (3 mg ml-1) and ryanodine (4 microM), i.e. they did not depend on Ca2+ release from sarcoplasmic reticulum (SR). 3. Single channel currents of NSCCCh could be resolved in whole-cell recordings. Substitution of Na+ by Cs+ increased NSCCCh activity by one order of magnitude and slope conductance from 22 to 30 pS. Extracellular quinidine (3 microM) reversibly blocked the NSCCCh activity. 4. Both tonic ICCh and tonic Delta[Ca2+]c (a) followed a similar time course of activation, desensitization and facilitation, (b) were reversibly blocked by 3 microM quinidine, and (c) persisted upon block of SR Ca2+ release. 5. A Ca2+ fractional current of tonic ICCh (fCa) of 0.009 was calculated by comparing the ratio Delta[Ca2+]c (corrected for simultaneous Ca2+ redistribution) over ICCh with depolarization-induced *Delta[Ca2+]c (Delta[Ca2+]c calculated from ICa induced by a 400 ms depolarization from -60 to 0 mV at 2 mM [Ca2+]o, 145 mM [Cs+]o) over ICa. fCa was 0.023 at [Ca2+]o = 4 mM. 6. With 110 mM extracellular CaCl2 and 145 mM intracellular CsCl, ICCh reversed at +19.5 mV suggesting a permeability ratio PCa/PCs of 2.8. 7. We conclude that Ca2+ influx through NSCCCh under physiological [Ca2+]o could induce Delta[Ca2+]c. The fCa was, however, much smaller than the one calculated from the reversal potential.

The genetics of vitiligo in Korean patients.

Abstract: Background Vitiligo is a common disorder whose exact cause is unknown, but genetic factors are thought to be involved. We analyzed 120 Korean proband families to clarify which genetic factors are involved in the pathogenesis of vitiligo in Korean patients. Methods The genetics of vitiligo were analyzed in 120 Korean proband families out of 1030 vitiligo patients. Each family was analyzed through a proband afflicted with vitiligo. Results In 51 (42.5%) of 120 proband families, at least one first-degree relative of the proband had vitiligo. The incidence of those affected among 1755 relatives (first-, second-, and third-degree) was found to be 8.0 ± 0.6%. There was a statistically significant departure for segregation analysis which was inconsistent with inheritance as an autosomal or X-linked locus model. On the basis of our results, the inheritance pattern of vitiligo is more likely to tend toward the model of multifactorial inheritance. The threshold trait among first-degree relatives (7.2%) appeared to tend more toward the square root of the frequency in the general population (10%) than towards those of dominant (50%) or recessive (25%) models. Conclusions These results indicate that there are certain genetic factors involved in the etiology of vitiligo, and that vitiligo seems to have a polygenic nature.

Effect of composition and molecular structure on the LC phase of PHB-PEN-PET ternary blend

Abstract: Poly(p-hydroxybenzoic acid) (PHB)-poly(ethylene terephthalate) (PET) 8/2 thermotropic liquid crystalline copolyester, poly(ethylene 2,6-naphthalate) (PEN), and PET were mechanically blended to pursue the liquid crystalline (LC) phase of ternary blends. The torque values of blends with increasing PHB content abruptly decreased above 40 wt % of PHB content because the melt viscosity of ternary blends dropped. Glass transition temperature and melting temperature of blends increased with increasing PHB content. The tensile strength and initial modulus of blends were low at 10 and 20 wt % PHB. However, the blends containing above 30 wt % PHB were improved with increasing PHB content due to the formation of fibrous structure. The blend of 20 wt % PHB formed irregularly dispersed spherical domains, and the blends of 30-40 wt % PHB showed LCP ellipsoidal domains and fibrils. In the polarized optical photographs, the blends of 40 wt % PHB showed pseudo LC phases. The degree of transesterification and randomness of blends were increased with blending time.

A second look at the embryotoxicity of hydrosalpingeal fluid: an in-vitro assessment in a murine model.

Abstract: The purpose of this study was to evaluate whether hydrosalpingeal fluid (HSF) is toxic to the mouse embryo as assessed by the blastocyst development rate (BDR) and by cell counting in vitro. HSF was collected from nine patients undergoing salpingoneostomy to correct hydrosalpinx. Two-cell embryos were obtained from superovulated ICR mice. T6 medium and T6 + 0.4% bovine serum albumin (BSA) were used as control media. T6 medium containing 10% or 50% HSF and 100% HSF from each patient were used as test media. Nine to 15 embryos were cultured in microdrops prepared from each of these media. The BDR was examined after 72 h of culture in these media. To assess the total cell number within each blastocyst, the blastocysts were fixed and stained with Hoechst 33342 to facilitate cell counting. The BDR was affected adversely only by 100% HSF and not in media containing 10% or 50% HSF. The mean BDR using T6 medium and T6 + BSA were 88.7% and 85.3%, respectively. The mean BDR using media containing 10% HSF or 50% HSF were 90.0% and 89.4%, respectively. Mean BDR using 100% HSF was 75.2% (P < 0.05). The overall mean cell counts (+/- SEM) using T6 medium and T6 + BSA were 86.9+/-3.2 and 91.0+/-3.8 respectively. Mean cells counts were decreased significantly only in blastocysts cultured in 100% HSF (63.3+/-4.6; P < 0.01) but not in blastocysts cultured in 10% or 50% HSF (90.8+/-4.2 and 81.9+/-6.1 respectively). Thus, it is concluded that HSF has no embryotoxic effect but has a mildly negative effect on embryonic growth and development.