bluuebunny/crossref_metadata_2025 huggingface dataset:
Hepatitis C virus infection as a risk factor for non‐alcoholic liver cirrhosis in taiwan
Authors: Tsai Jung‐Fa , Chang Wen‐Yu , Jeng Jen‐Eing , Ho Mei‐Shang , Wang Liang‐Yen , Hsieh Ming‐Yuh , Chen Shinn‐Chern , Chuang Wan‐Long , Lin Zu‐Yau , Tsai Juei‐Hsiung
Published: March 2007

To assess whether hepatitis C virus infection was a risk factor for the development of non‐alcoholic liver cirrhosis, antibody to hepatitis C virus (anti‐HCV; detected by a second generation HCV enzyme immunoassay), hepatitis B surface antigen (HBsAg; detected by radioimmunoassay) were tested in 150 cirrhotics and 150 sex‐matched and age‐matched healthy controls. The prevalence of anti‐HCV and HBsAg in cirrhotics was higher than in controls (22.0%, 73.3% vs. 2%, 18.7%; P = 0.001). The prevalence of anti‐HCV in HBsAgnegative cirrhotics (45.0%) was higher than that in HBsAg‐positive patients (13.6%; P =0.001). Both the anti‐HCV and carriage of HBsAg were associated significantly with liver cirrhosis, showing odds ratio of 12.0 for HBsAg carriers and 13.8 for patients with anti‐HCV. Compared with those without HBsAg and anti‐HCV, there was a significantly positive linear trend for developing cirrhosis with the presence of HBsAg alone (odds ratio = 19.9), anti‐HCV alone (odds ratio = 49.0), and those positive for HBsAg and anti‐HCV (odds ratio = 81.8) (P = 0.00001). The population‐attributable risk for developing liver cirrhosis was estimated as 10.8% for anti‐HCV alone, 55.2% for HBsAg alone, and 9.4% for both anti‐HCV and HBsAg in southern Taiwan. In conclusion, this study shows that hepatitis B and C virus infection act independently and synergistically in the development of non‐alcoholic liver cirrhosis among Chinese in Taiwan.
Seroepidemiology of human herpesvirus 7 in healthy children and adults in Japan
Authors: Yoshikawa Tetsushi , Asano Yoshizo , Kobayashi Ikuko , Nakashima Toshihiko , Yazaki Takehiko , Suga Sadao , Ozaki Takao , Wyatt Linda S. , Frenkel Niza
Published: March 2007

The isolation of human herpesvirus 7 (HHV‐7) from saliva and blood, and the prevalence of antibodies to the virus in healthy individuals were investigated in Japan. By cocultivating samples with phytohemagglutinin‐P‐stimulated cord blood mononuclear cells, HHV‐7 was isolated from the saliva of 1 of 20 children and from 4 of 38 adults but not from their blood. The isolates were confirmed as closely related to RK strain of HHV‐7, but not to U1102 (human herpesvirus 6, HHV‐6 type A) or Z29 (HHV‐6 type B) strains by restriction cleavage patterns of the DNA. The virus antibody of 330 healthy children and adults was measured with an indirect immunofluorescence assay, using one of our isolates (FG7‐6). The positivity rate of antibody was 40% in the first 2 months of life, declined during the first 6 months, then gradually increased and was 45% at 1‐4 years of age. It reached the highest level (60%) at 11‐13 years of age and was maintained until the end of the third decade, then decreased thereafter. Additionally, no simultaneous rise in the antibody titers was observed in 7 virologically confirmed exanthem subitum patients.
Rapid detection of hepatitis C virus RNA by direct capture from blood
Authors: van Doom Leen‐Jan , Kleter Bernhard , Voermans Jolanda , Maertens Geert , Brouwer Hans , Heijtink Ruud , Quint Wim
Published: March 2007

A new diagnostic assay for hepatitis C virus RNA detection is described. HCV genomic RNA is captured onto streptavidin‐coated magnetic beads by solution hybridization with biotinylated complementary oligonucleotides. The specificity of the capture assay is confirmed using different capture oligonucleotides as well as sera representing different types of HCV. Sensitivity was determined by testing serial dilutions of a HCV infected plasma. A panel of 50 sera was tested for anti‐HCV by a Line Immunoassay and for HCV‐RNA by both a conventional guanidinium extraction method and the new capture assay. The specificity of the capture assay was 95.8% and the sensitivity was 92.3% compared to the standard protocol. This method provides a rapid and simple alternative for HCV‐RNA detection in blood samples. © 1994 Wiiey‐Liss, Inc.
Virus‐induced autoimmunity in hepatitis C virus infections: A rare event
Authors: McFarlane Barbara M. , Bridger Cynthia , Tibbs C. J. , Saleh M. G. , Fuzio Antonella , Verucchi Gabriella , Attard L. , Boschi A. , Chiodo F. , McFarlane I. G. , Williams Roger
Published: March 2007

Serial serum samples from 16 Italian patients presenting with acute hepatitis C virus (HCV) infections (which progressed to chronic hepatitis in six) were screened for the non‐organ‐specific autoantibodies most frequently associated with autoimmune hepatitis (AIH), as well as for antibodies against the hepatic asialoglycoprotein receptor (ASGP‐R) and against the GOR peptide. One patient had low titres (1:10–1:80) of liver‐kidney microsomal (LKM‐1) antibodies during the recovery phase and three others had transient low titres of anti‐smooth muscle (IgM class, 1:10) or anti‐ASGP‐R (1:150–1:300). Anti‐GOR was detected in 43 (65%) of 66 sera from 13 of these patients. There was no correlation between any of these findings and progression to chronicity. By comparison, 18 patients with AIH studied concurrently before institution of immunosuppressive therapy all had antinuclear and/or smooth muscle antibodies, or LKM‐1, at 1:40–1:640 and anti‐ASGP‐R at 1:300–1:2, 100. None of these 18 had evidence of HCV infection and all were seronegative for anti‐GOR. The findings indicate that the autoantibodies usually associated with AIH are rare in HCV infections but the virus can very occasionally induce a transient autoimmune response. Anti‐GOR appears to be an antibody specifically related to HCV infection and is probably not a marker of induced autoimmunity, and it does not predict progression to chronic hepatitis. © 1994 Wiiey‐Liss, Inc.
Intrafamilial transmission of hepatitis C virus: The important role of inapparent transmission
Authors: Chang Ting‐Tsung , Liou Tai‐Cherng , Young Kung‐Chia , Lin Xi‐Zhang , Lin Ching‐Yih , Shin Jeng‐Shiann , Wu Hua‐Lin
Published: March 2007

To evaluate the intrafamilial transmission of hepatitis C virus (HCV) 104 index patients with type C chronic liver disease and their 307 family contacts were interviewed. After a questionnaire on the risk factors of parenteral exposure, blood samples were obtained and tested for liver biochemistry and anti‐HCV antibody by enzyme‐linked immunosorbent assay (Abbott II). Overall, 52 family contacts (17%) were positive for anti‐HCV, indicating a higher anti‐HCV prevalence among family contacts than among the general population in Taiwan. The anti‐HCV prevalences in parents, spouses, children, and other contacts of the patients were 54% (14/26), 28% (25/91), 6.9% (10/143), and 6.4% (3/47), respectively. The contacts of index patients had increasingly greater risk of HCV infection when they became older and had lived longer with index patients. All family contacts were divided into two groups categorized by whether the index patients had or did not have a history of parenteral exposure. Among 126 family contacts of the 42 patients without parenteral exposure, blood transfusion and surgery were the factors significantly associated with HCV infection in these family contacts (odds ratio = 7.26, 95% confidence interval = 2.32–32.67; odds ratio = 3.95, 95% CI = 1.29–12.11, respectively). Risk factors were not significantly associated with HCV infection among 181 family contacts of the 62 index patients with parenteral exposure. It is concluded that the index patients without parenteral exposure appeared to have acquired the disease from HCV‐infected family members with risk factors. Most of the index patients had a history of parenteral exposure and in turn served as the source of the disease for family members. © 1994 Wiiey‐Liss, Inc.
Detection of the negative strand of hepatitis e virus rna in the livers of experimentally infected rhesus Monkeys: Evidence for viral replication
Authors: Nanda Santosh Kumar , Panda Subrat Kumar , Durgapal Hemlata , Jameel Shahid
Published: March 2007

Hepatitis E virus (HEV), the causative agent of enteric non‐A, non‐B hepatitis, is a positive‐stranded RNA virus. Because of the virus's inability to grow in culture, several nonhuman primates have been used for the propagation of HEV. Using strand‐specific reverse transcription‐polymerase chain reaction (RT‐PCR), we demonstrate the presence of negative‐stranded HEV RNA replicative intermediates in the livers of infected animals. This constitutes the first direct evidence of HEV replication in the liver of the infected animals and reinforces the validity of such a model to study HEV infection, disease pathogenesis, and immunity. © 1994 Wiley‐Liss, Inc.
Radioimmunoprecipitation in the diagnosis of chronic active epstein‐barr virus infection
Authors: Beauparlant Pierre , Alfieri Caroline , Joncas Jean‐Harry
Published: March 2007

Chronic active Epstein‐Barr virus (EBV) infection occurs sporadically in a small fraction of individuals infected with EBV. A clear definition of the disease and an unambiguous diagnostic test are still lacking. In an attempt to identify a serologic marker to facilitate the diagnosis, immunoblot and radioimmunoprecipitation assay (RIPA) were compared with standard immunofluorescence on 39 available sera. Results by RIPA revealed that antibodies to a 120 kDa viral protein correlated with the presence of chronic active EBV infection; these antibodies were not detected in sera from other EBV‐seropositive individuals, with the exception of one of two patients with ataxia telangiectasia. Also, RIPA was the most sensitive technique for detecting EBV antibodies in sera weakly or doubtfully positive for antibody to EB viral capsid antigen by indirect immunofluorescence. All these sera had antibodies to the 150 kDa protein, also known as p160, the major viral capsid antigen. © 1994 Wiley‐Liss, Inc.
Suppression of simian immunodeficiency virus replication in primary peripheral mononuclear cells by antisense RNA
Authors: Tung Frank Y. T.
Published: March 2007

It has been demonstrated that human immunodeficiency virus (HIV) replication can be effectively blocked by an antisense sequence that was introduced into the lymphoid cell line through retroviral‐mediated gene transfer. In this study, it is demonstrated that antisense RNA can also inhibit simian immunodeficiency virus (SIV) replication in the peripheral blood mononuclear cells (MNCs) of healthy donors. MNCs were transduced with amphotropic recombinant virus encoding either sense or antisense constructs of SIV DNA fragments. After challenge with SIV, the viral replication was suppressed in the an‐tisense‐recombinant virus‐transduced MNCs compared to sense‐recombinant virus‐transduced and untransduced MNCs. These data indicate that amphotropic retroviral vectors can be used to introduce antiviral factors (antisense sequence) into human primary MNCs and render them resistant to viral replication. © 1994 Wiley‐Liss, Inc.
Changes in antibody titers to hepatitis C virus following interferon therapy for chronic infection
Authors: Urushihara Akihiko , Sodeyama Takeshi , Matsumoto Akihiro , Tanaka Eiji
Published: March 2007

The use of quantitative assays for hepatitis C virus specific antibodies (anti‐HCV) as a prognostic marker was evaluated in 31 patients with chronic hepatitis C treated with interferon (IFN). Changes in titers of serum HCV‐RNA and anti‐HCV antibodies; anti‐C11 (anti‐core), anti‐C100 (anti‐NS3), and anti‐C7 (anti‐NS3) were investigated. Recombinant IFN‐α 2a was administered and the patients were followed for more than 1 year. The patients were classified into three groups according to their responses to IFN: 11 sustained responders with continuous normalizations of serum alanine aminotransferase (ALT) levels; 14 transient responders with transient decreases in ALT; and six nonresponders who had no changes in ALT levels. Ten of 11 sustained responders had a continuous decrease in anti‐C11 titers after completion of treatment, decreasing to less than half of pretreatment titers. No patients in the other two groups had a continuous decrease in anti‐C11 titers. Although sustained responders had decreases in anti‐C100 and anti‐C7 titers after IFN therapy, these titers also decreased in some patients in the other two groups. HCV‐RNA was not detected in the sera of 10 of 11 sustained responders following IFN therapy. In contrast, while 9 of 10 transient and nonresponders had a decrease or disappearance of HCV‐RNA at the completion of therapy, they had increased levels thereafter. These results indicate that anti‐HCV‐core (anti‐C11) titers most closely reflect the status of HCV replication. A quantitative assay for anti‐HCV‐core antibody can be used as a predictive marker of remission in IFN‐treated patients with chronic hepatitis C. © 1994 Wiley‐Liss, Inc.
Ribozyme mediated destruction of influenza A virus in vitro and in vivo
Authors: Tang Xiao‐Bo , Hobom Gerd , Luo Dong
Published: March 2007

Short catalytic RNAs with inherent, specific endoribonuclease activity, called ribozymes, have recently been shown to exist in nature. According to the structural models artificial ribozymes have been designed that can potentially hydrolyse any chosen target RNA sequence in trans at a specific site. We have constructed and characterized in vitro hammerhead and hairpin ribozymes designed to cleave viral RNA segment 5 of influenza A virus. Both ribozymes were functional under optimal in vitro conditions, but quantitative measurements indicate that the hammerhead ribozyme is considerably more efficient at this target site than the hairpin ribozyme. Mg2+ dependent hammerhead ribozyme‐mediated cleavage reactions were enhanced at higher temperature and in presence of spermidine, but catalytic activities were retained also in cellular extract S‐100 or nuclear extracts at physiological temperatures.

Recombinant plasmids derived from transfection vector pSV2‐neo were engineered to allow the expression of specific ribozymes under the control of SV40 early promoter or SV40 early+ late promoters. These plasmids were introduced by transfection into COS cells, and their expression and enzymatic activities were analyzed in stable cell lines after selection of neomycin‐re‐sistance. Several permanent ribozyme‐express‐ing clones were established and characterized: ribozyme coding DNA sequences and synthesis of ribozyme RNA molecules in the transfected cells were determined and monitored by polymerase chain reactions. It was found that the highest levels (up to 70‐80%) of resistance to influenza A virus strain X‐31 super‐infection was observed in COS cells transfected with plasmids containing SV40 early or SV40 early+late promoters coinciding with relatively high and constitutive rates of ribozyme expression. These results suggest the feasibility of developing ribozymes designed against influenza virus to achieve therapeutic value. © 1994 Wiley‐Liss, inc.
Detection of HIV‐1 sequences in children using radioactive and colorimetric polymerase chain reactions
Authors: Giri Adriana A. , Lillo Flavia B. , McDermott Jennifer L. , Jannuzzi Clotilde , Risso Stefania , Fornia Gianluce , Concedi Donatella R. , Varnier Oliviero E.
Published: March 2007

The detection of HIV‐1 proviral DMA in children born to seropositive mothers was studied using the polymerase chain reaction with either a radioactive electrophoretic method or a novel procedure that employs colorimetric microwell visualization.

Peripheral blood mononuclear cell lysates from 18 HIV‐1 infected children and 28 uninfected subjects were assayed for a 142 bp fragment of DNA from the gag region of HIV‐1 using the primer pair SK145‐431. Detection of amplified DNA was carried out by hybridization with a radiolabeled SK102 probe, or with a tagged SK102 probe permitting colorimetric detection.

The radioactive detection procedure demonstrated 100% specificity and correlated with the serological results. The assay was more sensitive than the p24 antigen test, but two false negative results were obtained. One was from a sample taken at 2 weeks, an age at which unde‐tectable provirus levels were reported in almost all HIV‐1 infected newborns. The second was probably due to a low copy number of proviral DNA, as positive results were obtained in all other (6) samples from this child.

Comparative analysis in a limited number of specimens of radioactive and colorimetric detection following PCR revealed 100% specificity and comparable sensitivity with 4 discordant results.

The results show that PCR is the best method for early diagnosis of HIV‐1 infection in pediatric subjects. The study also demonstrated the value of a colorimetric detection method for PCR products. This colorimetric microwell plate procedure may prove a useful technique in routine diagnosis of HIV‐1 infection in children. © 1994 Wiley‐Liss, Inc.
Antibodies and viremia in acute post‐transfusion hepatitis C: A prospective study
Authors: Peters T. , Mohr L. , Scheiffele F. , Schlayer H.‐J. , Preisler S. , Berthold H. , Gerok W. , Rasenack J.
Published: March 2007

Fourteen patients who developed acute post‐transfusion hepatitis C after open‐heart surgery were studied for seroconversion, viremia, and aminotransferases. Anti‐HCV antibodies were measured by first and second generation ELISA and became positive between one week and more than 6 months after infection. Seroconversion in four patients and passively transfused antibodies were only found by the second generation assay, indicating its significantly higher sensitivity. Viremia was detected by reverse transcription and the polymerase chain reaction within the first 4 weeks of infection in 13 patients and persisted for more than 2 years in all of them. One patient died of cardiac cause. Viral strains were heterogeneous between the different patients, but showed no significant variation within one patient during the course of hepatitis deduced from the results with different sets of oligonucleotides. Viremia preceded hepatitis by 4 weeks, seroconversion determined by ELISA II followed after an 8 week interval, and anti‐C‐100 antibodies appeared 26 weeks later. Aminotrans‐ferase activities returned to normal values in 10 patients. © 1994 Wiley‐Liss, Inc.
Rapid differentiation between Hantaan and Seoul viruses by polymerase chain reaction and restriction enzyme analysis
Authors: Kim Eui Chong , Kim Ik Sang , Choi Yong , Kim Suhng Gwon , Lee Jung Sang
Published: March 2007

The majority of causative strains of hemorrhagic fever with renal syndrome (HFRS) are known as Hantaan and Seoul viruses in Korea. The clinical manifestations may be indistinguishable between both viruses, although the clinical course of Hantaan virus infection is more severe than that of the Seoul virus. Therefore, the differentiation of Hantaan or Seoul virus may be important for predicting the prognosis.

The primers were selected from the published sequences of the S segments of Hantaan virus strain 76–118 and Seoul virus strain SR‐11, which made it possible to obtain the same size of 403 bp amplified product by reverse transcriptase polymerase chain reaction (RT‐PCR) and nested PCR from both viral strains. The differentiation of the amplified products was carried out by restriction enzyme digestion. With HindIII, the 403 bp amplified product from Hantaan virus strain 76–118 was cleaved into two segments of 175 bp and 228 bp. By contrast, the 403 bp product from Seoul virus strain SR‐11 was not cut by HindIII. With HinfI, the 403 bp amplified product from Hantaan virus strain 76–118 was divided into two bands of 280 bp and 60 bp on the electrophoresis. In the case of the digestion of 403 bp PCR product from Seoul virus strain SR‐11 with HinfI, more than four bands (155 bp, 115 bp, 60 bp, and 32/29 bp) were observed on the 2% agarose gel electrophoresis. This rapid technique may be useful for the differential diagnosis of Asian HFRS in Korea. © 1994 Wiley‐Liss, Inc.
Sequence similarity of human caliciviruses and small round structured viruses
Authors: Cubitt W. D. , Jiang X. J. , Wang J. , Estes M. K.
Published: March 2007

The application of reverse transcription‐polymerase chain reaction (RT‐PCR) using primers directed to the RNA dependent RNA polymerase region within ORF1 of Norwalk virus (NV) showed that 31 percent of morphologically typical human caliciviruses (HuCV) and 57% of small round structured viruses (SRSVs) produced a product of 470 bp similar to the NV control, NV 8Flla/68/US. Alignment of the amino acid sequences of morphologically typical HuCVs with previously published sequences for SRSVs, NV, and Snow Mountain agent (SMA) showed a high degree of homology (90–92%) with SMA and a lesser extent of homology with NV (60–61%). The amino acid sequence of two strains of HuCV, HuCV/3C/92/UK, and HuCV/5C/92/UK differed by only one or two amino acids respectively in the RNA dependent RNA polymerase region from that of two strains of SRSV obtained from children in the United Kingdom, SRSV/4S/90/UK and Japan, SRSV/OTH‐25/89/J which were found to have identical amino acid sequences. The use of an EIA for detection of NV antigen employing antisera raised to recombinant NV protein indicated that HuCVs and SRSVs obtained from children and adults in the United Kingdom were antigenically distinct from the prototype Norwalk Virus, NV/8flla/68/US. © 1994 Wiley‐Liss, Inc.
Different genotypes of hepatitis C virus are associated with different severity of chronic liver disease
Authors: Pozzato Gabriele , Kaneko Suichi , Moretti Michéle , Croce Lory Saveria , Franzin Francesco , Unoura Masashi , Bercich Luisa , Tiribelli Claudio , Crovatto Marina , Santini Gianfranco , Kobayashi Kenichi
Published: March 2007

The presence of the “Japanese type” NS4 region was investigated in two series of patients (53 from Italy and 58 from Japan) with hepatitis C virus (HCV)‐related chronic liver disease. The two populations were homogeneous as regard to age, male/female ratio, histological diagnosis, and serum aminotransferase activities. Genomic amplification was carried out by “nested” poly‐merase chain reaction (PCR) with a pair of primers synthesized according to the sequence of JK‐1 isolated in Japan. The presence of viral replication was confirmed further by PCR amplification of the 5′NC region. The NS4 region of the Japanese strain was detected in 24 sera (45%) from Italy and in 44 (71%) from Japan. NS4‐posi‐tive patients were significantly older and showed an ALT serum level significantly lower (P < 0.01) than NS4 negative cases in each group. Cirrhosis was significantly (P < 0.0007) more common in NS4‐positive than in NS4‐negative patients. The HCV genotype was subsequently obtained according to Okamoto. All the NS4‐positive patients were infected by Type II, whereas in NS4‐negative patients all four genotypes were present though Type II still constituted the majority. Cirrhosis was associated exclusively with Type II both in NS4‐positive and ‐negative subjects. These data indicate that, although the pos‐itivity for NS4 “Japanese” region seems to be associated with a more aggressive liver disease, the most prevalent Type II predicts more specifically those who are likely to develop cirrhosis. Since the same findings were obtained in two population from different areas of the world, the genotype of HCV appears to be one of the major determinants of the progression of chronic active hepatitis to cirrhosis. © 1994 Wiiey‐Liss, Inc.
Assessment of the matrix effect on the headspace solid‐phase microextraction (HS‐SPME) analysis of chlorophenols in wines
Authors: Insa Sara , Besalú Emili , Salvadó Victòria , Anticó Enriqueta
Published: March 2007

In this paper, we propose a comparative study to check the matrix effect on the extraction of three chlorophenols, 2,4,6‐trichlorophenol (TCP), 2,3,4,6‐tetrachlorophenol and pentachlorophenol, direct precursors of 2,4,6‐trichloroanisole, in synthetic and commercial wines (white and red wines). A rapid, simple and sensitive methodology based on solid‐phase microextraction (SPME) and GC with electron capture detection (GC‐ECD) and mass spectrometric detection (GC‐MS) was developed and the variables affecting the extraction process (temperature, time and salt content) were examined employing a factorial design at two levels. Since GC‐ECD does not allow the clear identification of target analytes in white wine, owing to overlapped interferences, GC‐MS/MS was used for subsequent examinations. Calibration curves were constructed in synthetic, white and red wine. Significant differences between the slopes of synthetic and red wine, with the exception of TCP, were observed. Analytical parameters were evaluated and satisfactory results were obtained, showing the usefulness of the headspace SPME (HS‐SPME) method for determining chlorophenolic compounds in wines.
HPLC retention behavior on hydride‐based stationary phases
Authors: Pesek Joseph J. , Matyska Maria T. , Larrabee Susan
Published: March 2007

Two stationary phases attached to a silica hydride surface, cholesterol and bidentate C18, are investigated with a number of pharmaceutically related compounds in order to illustrate the various retention mechanisms that are possible for these bonded materials. The test solutes range from hydrophilic to hydrophobic based on log P (octanol/water partition coefficient) and pKa values. The mobile phases consist of acidified (formic and perchloric acid) water/methanol or water/ACN mixtures. Of particular interest are the high organic content mobile phase compositions where the retention would increase if the bonded material was operating in the aqueous normal phase (ANP) mode. Plots of retention factor (k) versus mobile phase composition are used to elucidate the retention mechanism. A number of examples are presented where solutes are retained based on RP, ANP, or dual retention mechanisms. The silica hydride‐based stationary phases can also retain compounds in the organic normal phase.
On the long‐time stability of the Crank–Nicolson scheme for the 2D Navier–Stokes equations
Authors: Tone Florentina
Published: March 2007

In this article we study the stability for all positive time of the Crank–Nicolson scheme for the two‐dimensional Navier–Stokes equations. More precisely, we consider the Crank–Nicolson time discretization together with a general spatial discretization, and with the aid of the discrete Gronwall lemma and of the discrete uniform Gronwall lemma we prove that the numerical scheme is stable, provided a CFL‐type condition is satisfied. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2007
Performance and numerical behavior of the second‐order scheme of precise time‐step integration for transient dynamic analysis
Authors: Ma Hang , Yin Feng , Qin Qing‐Hua
Published: March 2007

Spurious high‐frequency responses resulting from spatial discretization in time‐step algorithms for structural dynamic analysis have long been an issue of concern in the framework of traditional finite difference methods. Such algorithms should be not only numerically dissipative in a controllable manner, but also unconditionally stable so that the time‐step size can be governed solely by the accuracy requirement. In this article, the issue is considered in the framework of the second‐order scheme of the precise integration method (PIM). Taking the Newmark‐β method as a reference, the performance and numerical behavior of the second‐order PIM for elasto‐dynamic impact‐response problems are studied in detail. In this analysis, the differential quadrature method is used for spatial discretization. The effects of spatial discretization, numerical damping, and time step on solution accuracy are explored by analyzing longitudinal vibrations of a shock‐excited rod with rectangular, half‐triangular, and Heaviside step impact. Both the analysis and numerical tests show that under the framework of the PIM, the spatial discretization used here can provide a reasonable number of model types for any given error tolerance. In the analysis of dynamic response, an appropriate spatial discretization scheme for a given structure is usually required in order to obtain an accurate and meaningful numerical solution, especially for describing the fine details of traction responses with sharp changes. Under the framework of the PIM, the numerical damping that is often required in traditional integration schemes is found to be unnecessary, and there is no restriction on the size of time steps, because the PIM can usually produce results with machine‐like precision and is an unconditionally stable explicit method. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2007
Spline methods for the solution of hyperbolic equation with variable coefficients
Authors: Rashidinia J. , Mohammadi R. , Jalilian R.
Published: March 2007

In this study, we developed the methods based on nonpolynomial cubic spline for numerical solution of second‐order nonhomogeneous hyperbolic partial differential equation. Using nonpolynomial cubic spline in space and finite difference in time directions, we obtained the implicit three level methods of O(k2 + h2) and O(k2 + h4). The proposed methods are applicable to the problems having singularity at x = 0, too. Stability analysis of the presented methods have been carried out. The presented methods are applied to the nonhomogeneous examples of different types. Numerical comparison with Mohanty's method (Mohanty, Appl Math Comput, 165 (2005), 229–236) shows the superiority of our presented schemes. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2007
A practical approach to control of nonlinear discrete‐time state‐delay systems
Authors: Boukas El‐Kébir , Mahmoud Magdi S.
Published: March 2007

The robust feedback stabilization of a class of nonlinear discrete‐time systems with unknown constant state‐delay and uncertain function of nonlinear perturbations is considered based on linear matrix inequality (LMI)‐based analysis and design procedures. In both cases of nominal and resilient feedback designs, the trade‐off between the size of the controller gains and the bounding factors is illuminated and incorporated into the design formalism. A dynamic output feedback controller is then designed for this class of systems. Seeking computational convenience, all the developed results are cast in the format of LMIs and several numerical examples are presented throughout the paper to demonstrate the advantages of the design methods. Copyright
© 2007 John Wiley & Sons, Ltd.
Deficiency of the autoimmune regulator AIRE in thymomas is insufficient to elicit autoimmune polyendocrinopathy syndrome type 1 (APS‐1)
Authors: Ströbel P , Murumägi A , Klein R , Luster M , Lahti M , Krohn K , Schalke B , Nix W , Gold R , Rieckmann P , Toyka K , Burek C , Rosenwald A , Müller‐Hermelink HK , Pujoll‐Borrell R , Meager A , Willcox N , Peterson P , Marx A
Published: March 2007

Thymomas are thymic epithelial neoplasms, associated with a variety of autoimmune disorders (especially myasthenia gravis), that apparently result from aberrant intra‐tumourous thymopoiesis and export of inefficiently tolerized T‐cells to the periphery. The autoimmune regulator (AIRE) drives the expression of self‐antigens in the thymic medulla and plays an essential role in ‘central’ tolerance in both humans and mice. However, while inactivating AIRE mutations result in the ‘autoimmune polyendocrinopathy syndrome type 1’ (APS‐1), its major features are not well reproduced in AIRE‐knock‐out mice. Therefore, alternative human disease scenarios with concomitant AIRE deficiency may be valuable tools to test conclusions drawn from mouse models. Here we show, in a large series, that ∼95% of thymoma patients are ‘chimeric’; expression of AIRE and major AIRE‐related autoantigens (eg insulin) were undetectable in their tumours but maintained in their remnant thymic tissue and lymph nodes. Notably, despite the AIRE‐deficient thymopoiesis in thymomas, disorders and autoantibodies typical of APS‐1 were distinctly uncommon in these patients. The one striking similarity was in the recently observed neutralizing anti‐type I interferon (IFN) antibodies, which are found at diagnosis in 100% of patients with APS‐1 and in ∼60% of patients with thymomas, as we show here. We conclude that APS‐1 type autoantigens must be protected from autoimmunity by mechanisms that do not extend to the muscle autoantigens so frequently targeted in thymoma patients but so rarely recognized in APS‐1. Thus our findings argue strongly for a tolerogenic function of AIRE beyond its role in negative T‐cell selection in human thymopoiesis, and/or for specific autoimmunization against muscle in thymomas. Copyright © 2007 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Packaging of prions into exosomes is associated with a novel pathway of PrP processing
Authors: Vella LJ , Sharples RA , Lawson VA , Masters CL , Cappai R , Hill AF
Published: March 2007

Prion diseases are fatal, transmissible neurodegenerative disorders associated with conversion of the host‐encoded prion protein (PrPC) into an abnormal pathogenic isoform (PrPSc). Following exposure to the infectious agent (PrPSc) in acquired disease, infection is propagated in lymphoid tissues prior to neuroinvasion and spread within the central nervous system. The mechanism of prion dissemination is perplexing due to the lack of plausible PrPSc‐containing mobile cells that could account for prion spread between infected and uninfected tissues. Evidence exists to demonstrate that the culture media of prion‐infected neuronal cells contain PrPSc and infectivity but the nature of the infectivity remains unknown. In this study we have identified PrPC and PrPSc in association with endogenously expressing PrP neuronal cell‐derived exosomes. The exosomes from our prion‐infected neuronal cell line were efficient initiators of prion propagation in uninfected recipient cells and to non‐neuronal cells. Moreover, our neuronal cell line was susceptible to infection by non‐neuronal cell‐derived exosome PrPSc. Importantly, these exosomes produced prion disease when inoculated into mice. Exosome‐associated PrP is packaged via a novel processing pathway that involves the N‐terminal modification of PrP and selection of distinct PrP glycoforms for incorporation into these vesicles. These data extend our understanding of the relationship between PrP and exosomes by showing that exosomes can establish infection in both neighbouring and distant cell types and highlight the potential contribution of differentially processed forms of PrP in disease distribution. These data suggest that exosomes represent a potent pool of prion infectivity and provide a mechanism for studying prion spread and PrP processing in cells endogenously expressing PrP. Copyright © 2007 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Synthesis, photophysical properties, and electron paramagnetic resonance studies of new poly(bisbenzothiazole)s containing bulky pendant groups
Authors: Huang Wei , Yin Jie
Published: March 2007

A new series of poly(bisbenzothiazole)s containing bulky pendant cyclohexylidene or 4‐tert‐butylcyclohexylidene group was synthesized. Their structures were characterized by NMR (1H, 13C), FTIR, and EA. These polymers exhibited good solubility, thermal stability, and an amorphous nature. The photophysical properties of them were investigated in detail by UV absorption spectroscopy and photoluminescence spectroscopy. Compared with poly(p‐phenylene benzobisthiazole), the absorption maxima of these polymers were all blue shifted, and their optical bandgaps were increased. The emission peaks, having different intensity, were also blue shifted. They both changed in shape and position gradually with the increasing concentration, which showed the evidence of aggregate formation. In addition, the degree of aggregation was decreased with the increasing size of bulky pendant group and the PL quantum yield could be improved by the introduction of bulky pendant group. The result of electron paramagnetic resonance studies showed the intrinsic paramagnetic defects in this class of polymers. A new soliton–antisoliton model was constructed to interpret these intrinsic paramagnetic signals. POLYM. ENG. SCI., 47:429–438, 2007. © 2007 Society of Plastics Engineers.
Effect of diisocyanate structures on the properties of liquid crystalline polyurethanes
Authors: Lee Mooyoung , Hong Sung Chul , Lee Sang‐Won
Published: March 2007

Thermotropic liquid crystalline polyurethanes (LCPUs) were synthesized through the polyaddition reaction of 2,4‐toluene diisocyanate (2,4‐TDI), 4,4′‐diphenylmethane diisocyanate (MDI), or o‐toluidine diisocyanate (ODI) with 4,4′‐bis(6‐hydroxyhexoxy)biphenyl, and the effect of the structures of the diisocyanates on the properties of LCPUs were investigated. Intrinsic viscosities of the polymers were in the range of 0.23–0.30 dL/g. Mesomorphic behavior of the polyurethanes were investigated by differential scanning calorimetry, polarized optical microscopy, and wide‐angle X‐ray scattering. Different mesomorphic behaviors were observed according to the different structural characteristics of diisocyanates. Polyurethanes employing 2,4‐TDI and MDI exhibited monotropic behaviors, while that with ODI showed enantiotropic behavior. POLYM. ENG. SCI., 47:439–446, 2007. © 2007 Society of Plastics Engineers.
Rheology studies of foam flow during injection mold filling
Authors: Qin X. , Thompson M.R. , Hrymak A.N.
Published: March 2007

This work studies the flow behavior of a developing two‐phase gas‐polymer suspension during injection into the instrumented mold cavity of an injection molding machine. In the experiments, blowing agent type and concentration were varied along with processing conditions, to generate controlled cell structures in two different polymers, low density polyethylene and thermoplastic polyolefin. Experimental results indicate that the rheological properties of two phase gas‐polymer suspensions were sensitive to shear rate, blowing agent concentration, melt temperature, and mold temperature. The viscosity of all gas‐polymer suspensions revealed a reduction compared with neat polymer melt in the presence of gas bubbles, because of the reduced volume fraction of polymer matrix. A two‐phase rheological model has been used for fitting with our experimental results for estimating the shear viscosity of two‐phase flow in the mold cavity of the injection molding machine. POLYM. ENG. SCI., 47:522–529, 2007. © 2007 Society of Plastics Engineers.
External and internal plasticization of cellulose acetate with caprolactone: Structure and properties
Authors: Vidéki Bianka , Klébert Szilvia , Pukánszky Béla
Published: March 2007

Cellulose acetate was modified with caprolactone in an internal mixer at temperatures between 120 and 220 °C, and reaction times between 5 and 45 min in the presence of tinoctoate catalyst. The effect of plasticization on the properties of the polymer was studied by dynamic mechanical analysis and tensile testing. The dynamic mechanical spectrum of cellulose acetate exhibits three main relaxation transitions. These can be assigned to segments (α), to smaller structural units of the main chain, probably individual glucose rings (β), and to hydroxyl or hydroxylmethyl groups (γ). Plasticization by caprolactone leads to the decrease of the glass transition temperature of CA, but also to the breakdown of relatively large segments to smaller structural units. Free hydroxyl groups interact with the plasticizer forming larger units with higher transition temperature. Grafting decreases the intensity of the γ‐transition peak. External plasticization creates a larger number of small structural units, but the external plasticizer is less efficient in the decrease of stiffness than grafted polycaprolactone chains. Internal plasticization is more advantageous because it leads to higher flexibility at larger strength than external plasticization, and the migration of the plasticizer is prevented at the same time. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 873–883, 2007
A new implicit solvent model for protein–ligand docking
Authors: Morreale Antonio , Gil‐Redondo Rubén , Ortiz Ángel R.
Published: March 2007

A new implicit solvent model for computing the electrostatics binding free energy in protein–ligand docking is proposed. The new method is based on an adaptation of the screening coulombic potentials proposed originally by Hassan et al. (J Phys Chem B 2000;104:6490–6498). In essence, it relies on two basic assumptions; (i) solvent screening can be accounted for by means of radially dependent sigmoidal dielectric functions and; (ii) the effective atom Born radii can be expressed only as a function of the exposed atom surface. Parameters of the model other than radii and charges are generic. These were optimized for a dataset of 826 protein–ligand complexes, comprising both X‐ray complexes for 23 receptors as well as decoys generated by docking computations. We show that the new model provides satisfactory results when benchmarked against reference values based on the numerical solution of the Poisson equation, with a root mean square error of 4.2 kcal/mol over a range of ∼40 kcal/mol in electrostatics binding free energies, a cross‐validated r2 of 0.81, a slope of 0.97, and an intercept of 1.06 kcal/mol. We show that the model is appropriate for ligands of different sizes, polarities, overall charge, and chemical composition. Furthermore, not only the total value of the electrostatic contribution to the binding free energy, but also its components (coulombic term, receptor desolvation, and ligand desolvation) are reasonably well reproduced. Computation times of ∼0.030 s per pose are obtained on a single processor desktop workstation. Proteins 2007. © 2007 Wiley‐Liss, Inc.
Optical and electronic conduction behavior in germanium ferrite additive with transition metal
Authors: Fayek S. A. , Balboul M. R. , El‐Ocker M.
Published: March 2007

The effects of adding transition metals (Ni and Co) on the optical and electrical properties of four thin films Ni1.25Fe1.5Ge0.25O4, Ni1.5Fe1Ge0.5O4, Co1Fe1Ge0.5O4 and Co1.25Fe1.5Ge0.25O4 are reported. X‐ray diffraction was used to ascertain the amorphization nature of the deposited films. The optical absorption behavior of these films was studied from the transmission and reflection in the range 200–1100 nm. It was found that the optical band gap increases on increasing GeO2 and arises from direct forbidden transitions. The opposite trend was found with the band tail width of the localized state. Optical constant parameters such as refractive index and absorption index were obtained for the films. The results for the alternating‐current (ac) conductivity and the dielectric constant of the four films are presented over the temperature range 277–357 K and the frequency range 0.1 to 1000 kHz. The ac conductivity increases with temperature and frequency and decreases with the increase in Ni2+ or Co2+ content. The effect of composition and temperature on the dielectric constant was also studied. The frequency variation of the dielectric constant does not have a peak, unlike many semiconductor glasses. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nanoscale surface characterization of GaN nanowires correlated with metal contact characteristics
Authors: Koley G. , Lakshmanan L. , Wu H. , Cha Ho‐Young
Published: March 2007

Surface electronic properties of GaN nanowires have been investigated using scanning probe microscopy and correlated with metal/nanowire contact characteristics. Surface current map of the nanowire was observed to be highly nonuniform, resulting from a large variation in surface barrier of the nanowire, on the order of a few tenths of an eV. The surface barrier non‐uniformity, which most likely determines the formation of an ohmic or Schottky contact, is increased dramatically with the nanowire surface deformation. Current–voltage characteristics and scanning gate microscopy of the nanowires also indicate significant carrier trapping at the nanowire and silicon dioxide surface. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Some aspects of ion implantation technique in nanostructured materials
Authors: Mazzoldi P. , Mattei G.
Published: March 2007

The paper will discuss the synthesis of metal nanoclusters (NCs) composites, in silica matrix, in which the cluster concentration is below the percolation limit (dispersed clusters). Some case studies will be presented in which ion‐beam‐based techniques are exploited either for the synthesis, but also for the structural or compositional modification of composites. As regards the technological properties of the studied systems, some results will be presented about the nonlinear properties and energy transfer mechanisms in silica containing Erbium ions and molecular‐like metal structures. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Transport in defective ionic materials: from bulk to nanocrystals
Authors: Chadwick A. V.
Published: March 2007

This contribution reviews the current state of knowledge of atomic transport in ionic materials, a dominant theme of the EURODIM Conference series for nearly four decades. The early history of the subject is briefly reviewed followed by the important developments that occurred in the early post‐WWII period. That work was mainly based on studies of relatively simple binary ionic systems in the form of single crystals and laid the foundation for much of the current knowledge. An overview is given of more recent work on fast‐ion conductors where the materials are generally more complex and the aim is to produce good ionic conductors for applications as electrolyte membranes in batteries and fuel cells. This includes the development of computer simulation techniques that are now an almost essential part of any investigation of ionic transport. Finally, a brief summary is given of transport in nanocrystalline ionic materials (nanoionics) where enhanced ionic conduction has been reported with the potential for significantly improved devices. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Defects and photorefraction: A relation with mutual benefit
Authors: Imlau M.
Published: March 2007

Intrinsic and extrinsic defects are at the origin of photorefraction. Donor and acceptor defects define the properties of the photorefractive response in particular its dispersive behavior. This enables, e.g., targeted material design by incorporation of extrinsic defects in photorefractive media. Vice versa, defect physics benefits from photorefraction, i.e., photorefraction is successfully applied in defect studies and material analysis. Concepts for investigations make use of the great variety of nonlinear photorefractive phenomena. These include the appearance of a transient light‐induced absorption, two‐wave mixing at one‐dimensional photonic gratings, photo‐assisted self‐assembly of photonic gratings and space‐charge waves originating from oscillating photonic gratings. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Defect based real‐time diagnostics of ferroelectric domain wall motion
Authors: Dierolf V. , Sandmann C. , Capek P.
Published: March 2007

We investigated the static and dynamic interaction of defect dipoles and ferroelectric domain walls in lithium niobate. Using a home‐built confocal microscope with high spatial and temporal resolution we are able to image both the static domain wall region and the domain wall regions associated with a moving domain wall by monitoring the emission from rare earth ions. We find that the extent of perturbation induced by the presence of a domain wall is increasing with the speed of the domain wall motion. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)