bluuebunny/crossref_metadata_2025 huggingface dataset:
Hyponatremia in cirrhosis: Pathogenesis, clinical significance, and management
Authors: Ginès Pere , Guevara Mónica
Published: May 2008

Hyponatremia is a frequent complication of advanced cirrhosis related to an impairment in the renal capacity to eliminate solute-free water that causes a retention of water that is disproportionate to the retention of sodium, thus causing a reduction in serum sodium concentration and hypo-osmolality. The main pathogenic factor responsible for hyponatremia is a nonosmotic hypersecretion of arginine vasopressin (or antidiuretic hormone) from the neurohypophysis related to circulatory dysfunction. Hyponatremia in cirrhosis is associated with increased morbidity and mortality. There is evidence suggesting that hyponatremia may affect brain function and predispose to hepatic encephalopathy. Hyponatremia also represents a risk factor for liver transplantation as it is associated with increased frequency of complications and impaired short-term survival after transplantation. The current standard of care based on fluid restriction is unsatisfactory. Currently, a new family of drugs, known as vaptans, which act by antagonizing specifically the effects of arginine vasopressin on the V2 receptors located in the kidney tubules, is being evaluated for their role in the management of hyponatremia. The short-term treatment with vaptans is associated with a marked increase in renal solute–free water excretion and improvement of hyponatremia. Long-term administration of vaptans seems to be effective in maintaining the improvement of serum sodium concentration, but the available information is still limited. Treatment with vaptans represents a novel approach to improving serum sodium concentration in cirrhosis. (Hepatology 2008.)
Programmed death 1 expression during antiviral treatment of chronic hepatitis B: Impact of hepatitis B e-antigen seroconversion
Authors: Evans Alexander , Riva Antonio , Cooksley Helen , Phillips Sandra , Puranik Smrithi , Nathwani Amit , Brett Sara , Chokshi Shilpa , Naoumov Nikolai V.
Published: May 2008

Hyperexpression of the programmed death 1 (PD-1) molecule is a hallmark of exhausted T-cells, having a negative impact on T-cell activation and function. We studied longitudinally 18 hepatitis B e antigen (HBeAg)–positive patients undergoing treatment with direct antivirals (telbivudine or lamivudine) to determine the relationship between treatment-induced viremia reduction and HBeAg seroconversion with respect to PD-1 levels and T-cell reactivity. PD-1 expression was assessed by (1) flow cytometry and (2) quantitative real-time polymerase chain reaction; hepatitis B virus (HBV)–specific CD8+ T-cells were quantitated by pentamer staining; T-cell reactivity to HBV antigens was determined by interferon gamma (IFNγ) and interleukin 10 (IL-10) enzyme-linked immunosorbent spot (ELISPOT) assays; and central/effector memory phenotypes were defined by phenotypic markers. PD-1 expression correlated closely with viremia levels. On therapy, PD-1 decreased significantly on total CD8+ T-cells, HBV-specific CD8+ T-cells, and CD3+/CD8− T-cells both as the percentage of positive cells (

P

< 0.01) and as the mean fluorescent intensity (

P

< 0.05), and this was paralleled by a marked reduction of PD-1 messenger RNA levels (

P

= 0.001). HBeAg serocoversion (in 6/18 patients) resulted in a further PD-1 decrease with a 50% reduction in the frequency of PD-1+/CD8+ T-cells, which was not observed in patients remaining HBeAg-positive. The decrease in PD-1 expression was associated with increased frequencies of IFNγ-producing T-cells and decreased frequencies of IL-10 producing T-cells. At baseline, PD-1 expression correlated directly with the frequency of hepatitis B core antigen (HBcAg) central and effector memory phenotypes, whereas an inverse correlation was observed between PD-1 expression and HBcAg-specific effector phenotypes.

Conclusion:

These results demonstrate that in chronic HBV infection, both viremia levels and HBeAg drive PD-1 expression and resulting T-cell impairment. Treatment-induced suppression of HBV replication reduces PD-1 expression; however, additional immunotherapeutic interventions are needed for restoration of T-cell functions. (Hepatology 2008.)
Paraben esters: review of recent studies of endocrine toxicity, absorption, esterase and human exposure, and discussion of potential human health risks
Authors: Darbre Philippa D. , Harvey Philip W.
Published: May 2008

This toxicology update reviews research over the past four years since publication in 2004 of the first measurement of intact esters ofp‐hydroxybenzoic acid (parabens) in human breast cancer tissues, and the suggestion that their presence in the human body might originate from topical application of bodycare cosmetics. The presence of intact paraben esters in human body tissues has now been confirmed by independent measurements in human urine, and the ability of parabens to penetrate human skin intact without breakdown by esterases and to be absorbed systemically has been demonstrated through studies not onlyin vitrobut alsoin vivousing healthy human subjects. Using a wide variety of assay systemsin vitroandin vivo, the oestrogen agonist properties of parabens together with their common metabolite (p‐hydroxybenzoic acid) have been extensively documented, and, in addition, the parabens have now also been shown to possess androgen antagonist activity, to act as inhibitors of sulfotransferase enzymes and to possess genotoxic activity. With the continued use of parabens in the majority of bodycare cosmetics, there is a need to carry out detailed evaluation of the potential for parabens, together with other oestrogenic and genotoxic co‐formulants of bodycare cosmetics, to increase female breast cancer incidence, to interfere with male reproductive functions and to influence development of malignant melanoma which has also recently been shown to be influenced by oestrogenic stimulation. Copyright © 2008 John Wiley & Sons, Ltd.
CH/π hydrogen bonds determine the selectivity of the Src homology 2 domain to tyrosine phosphotyrosyl peptides: An ab initio fragment molecular orbital study
Authors: Ozawa Tomonaga , Okazaki Kosuke
Published: May 2008

The CH/π hydrogen bond is a weak molecular force occurring between CH groups (soft acids) and π‐systems (soft bases), and has been recognized to be important in the interaction of proteins with their specific ligands. For instance, it is well known that Src homology‐2 protein (SH2) recognizes its specific pTyr peptide in two key regions, pTyr‐binding region and specificity‐determining region, by the use of attractive molecular forces, including the CH/π hydrogen bond. We hypothesized that the CH/π hydrogen bond plays a key role in determining the selectivity of SH2 proteins, and studied this issue by the ab initio fragment molecular orbital (FMO) method. The FMO calculations were carried out, at the HF/6‐31G* and MP2/6‐31G* level, for SH2 domains of Src, Grb2, P85α(N), Syk, and SAP, in complex with corresponding pTyr peptides. CH/π hydrogen bonds have in fact been found to be important in stabilizing the structure of the complexes. We conclude that the CH/π hydrogen bond plays an indispensable role in the recognition of SH2 domains with their specific pTyr peptides, thus playing a vital role in the signal transduction system. © 2008 Wiley Periodicals, Inc. J Comput Chem 2008
Polarizable continuum model with the fragment molecular orbital‐based time‐dependent density functional theory
Authors: Chiba Mahito , Fedorov Dmitri G. , Kitaura Kazuo
Published: May 2008

The polarizable continuum model (PCM) for describing the solvent effect was combined with the fragment molecular orbital‐based time‐dependent density functional theory (TDDFT). Several levels of the many‐body expansion were implemented, and the importance of the many‐body contributions to the singlet‐excited states was discussed. To calibrate the accuracy, we performed a number of the model calculations using our method and the regular TDDFT in solution, applying them to phenol and polypeptides at the long‐range corrected BLYP/6‐31G* level. It was found that for systems up to 192 atoms the largest error in the excitation energy was 0.006 eV (vs. the regular TDDFT/PCM of the full system). The solvent shifts and the conformer effects were discussed, and the scaling was found to be nearly linear. Finally, we applied our method to the lowest singlet excitation of the photoactive yellow protein (PYP) in aqueous solution and determined the excitation energy to be in reasonable agreement with experiment. The excitation energy analysis provided the contributions of individual residues, and the main factors as well as their solvent shifts were determined. © 2008 Wiley Periodicals, Inc. J Comput Chem 2008
Effects of cryopreservation on CD4+ CD25+ T cells of HIV‐1 infected individuals
Authors: Seale Anna C. , de Jong Bouke C. , Zaidi Irfan , Duvall Melody , Whittle Hilton , Rowland‐Jones Sarah , Jaye Assan
Published: May 2008

The role of T regulatory cells (Tregs) in human immunodeficiency virus (HIV)‐1 infection, although not entirely clear, has recently been highlighted. Despite their lack of specificity, fluorochrome‐labeled CD4 and CD25 antibodies are common flow cytometric reagents used to identify these cells with immunosuppressive potential. Cryopreservation has previously been shown to alter the proportions of lymphocytes with certain phenotypes expressed in peripheral blood mononuclear cells (PBMCs). The aim of this study was to assess the effect of cryopreservation on CD4+ CD25+ T cells in PBMCs from HIV‐1+ individuals to guide the design of future studies on Tregs. We recruited 30 HIV‐1+ individuals and nine healthy controls. CD25 expression in CD4+ T cells was compared between fresh and frozen/thawed PBMC samples from the same time point. In this study, cryopreservation significantly decreased the proportion of CD4+ CD25+ T cells in PBMC samples from HIV‐1 infected subjects. This finding suggests that studies of CD4+ CD25+ T cells should be carried out on fresh samples to avoid bias introduced by cryopreservation. J. Clin. Lab. Anal. 22:153–158, 2008. © 2008 Wiley‐Liss, Inc.
Elevated serum level and gene polymorphisms of TGF‐β1 in gastric cancer
Authors: Li Xue , Yue Zhi‐Chao , Zhang Yun‐Yan , Bai Jing , Meng Xiang‐ning , Geng Jing‐Shu , Fu Song‐Bin
Published: May 2008

Transforming growth factor (TGF)‐β1, as a candidate tumor marker, is currently of interest. In this study, serum TGF‐β1 levels in gastric cancer (GC) patients and healthy volunteers were measured using enzyme‐linked immunosorbent assay (ELISA). In addition, single nucleotide polymorphisms (SNPs) of the TGF‐β1 gene at codon 10 and codon 25 were identified by means of amplification refractory mutation system–polymerase chain reaction (ARMS‐PCR) and sequence analysis. Our results indicated that serum concentrations of TGF‐β1 in GC patients were significantly higher than those in the control, and positively correlated with tumor mass, invasion, metastasis, and clinical stage. The serum TGF‐β1 levels of patients recovering from radical resection were markedly lower than those before surgery. Meanwhile, no deoxyribonucleic acid (DNA) sequence variation at codon 25 of the TGF‐β1 gene was found and a TGF‐β1 gene polymorphism at codon 10 did not show obvious correlations with either TGF‐β1 expression or clinicopathological parameters of GC. Our evidence suggested that serum concentration of TGF‐β1 might be a novel tumor marker for GC and the polymorphisms of TGF‐β1 gene did not play a role as a determinant of serum TGF‐β1 concentration or as a genetic risk factor in the gastric carcinogenesis and progression. J. Clin. Lab. Anal. 22:164–171, 2008. © 2008 Wiley‐Liss, Inc.
Performance characteristics of a new rapid immunochromatographic test for the detection of antibodies to human immunodeficiency virus (HIV) types 1 and 2
Authors: Syed Iqbal H. , Balakrishnan P. , Murugavel K.G. , Suniti Solomon
Published: May 2008

Diagnostic kits for the detection of human immunodeficiency virus (HIV) antibodies have reached an unprecedented number. But choice of an ideal, cost‐effective, and rapid test for HIV infection is of immense value for use in developing countries like India, where resources are limited. In this study we have evaluated the performance characteristics of the rapid immunochromatographic HIV test kit First Response HIV 1‐2.O. First, the laboratory archived 450 characterized plasma/serum specimens, which were tested on First Response HIV 1‐2.O. Second, a total of 134 consecutive voluntary counseling and testing (VCT) specimens were also tested and positive specimens were further confirmed with HIV TRI‐DOT. All these VCT specimens were cross‐checked with HIV double‐enzyme‐linked immunosorbent assay (ELISA) (Murex and Vironostika), and the results were matched. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and efficiency of First Response HIV 1‐2.O with the 450 characterized specimens was 100% for HIV‐1 with reference assay. The results in the VCT algorithm were correlating with double‐ELISA. In the HIV‐2 analysis, five HIV‐2‐positive specimens in First Response HIV 1‐2.O were found to be HIV‐2‐indeterminate on Western blot. HIV TRI‐DOT was unable to pick up two HIV‐2 Western blot–positive specimens. First Response HIV 1‐2.O has several advantages: low‐cost (U.S. $0.70); only 10 µL of specimen; involves only two steps; room temperature storage; ability to differentiate HIV‐1 and 2; and use of whole blood specimen. Hence this test kit could be suitable for initial screening in the HIV testing algorithm in resource‐limited settings. J. Clin. Lab. Anal. 22:178–185, 2008. © 2008 Wiley‐Liss, Inc.
Alcohol dehydrogenase (ADH) isoenzymes and aldehyde dehydrogenase (ALDH) activity in the sera of patients with liver cancer
Authors: Jelski Wojciech , Zalewski Bogdan , Szmitkowski Maciej
Published: May 2008

The principal enzymes catalyzing the conversion of ethanol to acetate are alcohol dehydrogenase (ADH) and aldehyde dehydrogenase (ALDH). The activities of these enzymes are elevated in the serum during the course of alcoholism or cirrhosis. In previous investigations we have found elevated levels of ADH, ALDH, and class I ADH activity in liver cancer cells. It can suggest that these changes may be reflected by enzyme activity in the serum. In this work, the activity of ADH isoenzymes, and ALDH in the sera of patients with liver cancer was measured. Serum samples were taken from 64 patients (28 drinkers, 36 nondrinkers), with liver cancer. 25 patients had primary and 39 metastatic liver tumors. Total ADH activity was measured by photometric method with p‐nitrosodimethylaniline (NDMA) as a substrate and ALDH activity by the fluorimetric method with 6‐methoxy‐2‐naphtaldehyde as a substrate. For the measurement of the activity of class I and II isoenzymes we employed the fluorimetric methods, with class‐specific fluorogenic substrates. The activity of class III ADH was measured by the photometric method with formaldehyde and class IV with m‐nitrobenzaldehyde as a substrate. A statistically significant increase of class I ADH isoenzymes was found in the sera of cancer patients. The median activity of this class isoenzyme in the total cancer group increased about 51% (2.94 mU/L) in the comparison to the control level (1.43 mU/L). The activity of the class I ADH isoenzyme was significantly higher in the sera of patients with metastatic tumors than with primary cancers. The activity of this class in the sera of drinkers and group of moderate drinkers was significantly higher in comparison to the control group and higher in the sera of heavy drinkers when compared with moderate drinking patients. The total ADH activity was significantly higher (44%) among patients with cancer than healthy ones. The activity of class I ADH isoenzymes was elevated only in the serum of patients with metastatic liver cancer. This increase of activity seems to be caused by the enzyme released from liver cancer cells and primary tumors originating in other organs. J. Clin. Lab. Anal. 22:204–209, 2008. © 2008 Wiley‐Liss, Inc.
Protein oxidation markers in the serum and synovial fluid of psoriatic arthritis patients
Authors: Firuzi Omidreza , Spadaro Antonio , Spadaro Chiara , Riccieri Valeria , Petrucci Rita , Marrosu Giancarlo , Saso Luciano
Published: May 2008

The role of oxidative stress has been studied in rheumatoid arthritis (RA) and other inflammatory joint diseases to some extent, but its importance in psoriatic arthritis (PsA) has rarely been investigated. The aim of this study was to analyze the levels of protein oxidation markers, sulfhydryl (SH) and carbonyl (CO) groups, in the synovial fluid (SF) and serum of PsA patients and compare them with the findings in RA and osteoarthritis (OA) patients. A total of 49 subjects with a knee‐joint effusion including 16  PsA, 18  RA, and 15 OA patients were studied. In all patients, the levels of SH groups measured in the serum and SF inversely correlated with the number of white blood cells (WBC) (P<0.05) and the percentage of polymorphonuclear leukocytes (PMN) (P<0.01) in SF. Serum SH levels inversely correlated with serum erythrocyte sedimentation rate (ESR) (P<0.02) and C‐reactive protein (CRP) (P<0.05) values. The SH levels in SF were significantly lower in patients affected by PsA and RA compared to OA cases (P<0.02). The serum SH levels in PsA were lower than OA (P<0.001) and higher than RA patients (P<0.05). The serum and synovial levels of CO groups in PsA, RA, and OA patients were similar. Our study provides novel evidence on the involvement of protein oxidation in PsA and confirms the important role of oxidative stress in the pathogenesis of RA. These data suggest that antioxidant agents can potentially be a useful addition to the conventional therapy in the management of these diseases. J. Clin. Lab. Anal. 22:210–215, 2008. © 2008 Wiley‐Liss, Inc.
Viral loads of cerebrospinal fluid in infants with enterovirus meningitis
Authors: Kawashima Hisashi , Ioi Hiroaki , Ishii Chiako , Hasegawa Yuka , Amaha Masahiro , Kashiwagi Yasuyo , Takekuma Kouji , Hoshika Akinori , Watanabe Yasuo
Published: May 2008

For a better understanding of the role of the viral load, free radicals, and cytokines in viral meningitis, we surveyed cerebrospinal fluid (CSF) obtained from patients below 1 year of age who showed positive for enterovirus. In their first examinations interleukin (IL)‐6 and free radicals increased whereas pleocytosis was rarely observed. IL‐6 decreased within the short period. Viral loads and free radicals increased simultaneously. IL‐6 and free radicals of CSF are helpful for diagnosis and treatment of viral meningitis at an early stage. J. Clin. Lab. Anal. 22:216–219, 2008. © 2008 Wiley‐Liss, Inc.
Study of serum argininosuccinate lyase determination for diagnosis of liver diseases
Authors: Feng Jia‐fu , Chen Ting‐mei , Wen Yang‐an , Wang Jian , Tu Zhi‐guang
Published: May 2008

The objectives of this research were to establish an automatic analysis method for the determination of serum argininosuccinate lyase (ASL) and to investigate the value of serum ASL test in the diagnosis of various liver disorders. According to the chemical reaction catalyzed by ASL, an enzyme‐coupled reaction system was designed, and a methodology evaluation of this method was performed. A total of 291 patients with various liver diseases, 247 patients with nonliver disease and 32 healthy controls, were recruited, their serum levels of ASL and traditional hepatopathy markers, including alanine aminotransferase (ALT), aspartate aminotransferase (AST), γ‐glutamyltransferase (GGT), lactate dehydrogenase (LDH), alkaline phosphatase (ALP), and total bilirubin (TBil), were all determined, and their diagnostic values in liver diseases were analyzed and compared. Liver biopsy and the score of histopathological inflammation grading were performed in 31 patients with hepatopathy to explore the correlation between serum ASL level and hepatic histopathological change. A continuous monitoring assay method of serum ASL activity was established, which could be performed with automatic biochemistry analyzer. Methodological evaluation exhibited that the precision of this method was good indicated by the 4.0% intraassay coefficient of variation (CV), and 5.9% interassay CV. The mean recovery was 100.5%, linear range was from 0 to 167.7 U/L, and the lowest detection limit was approximately 0 U/L. All of the tested hepatopathy markers listed above were significantly increased in the liver disease group. However, levels of traditional markers of hepatopathy were all significantly increased at different degrees (all P<0.001) in patients with nonliver diseases; in contrast, there were no significantly increased ASL levels in all nonhepatopathy groups (P=0.335). The receiver operating characteristic (ROC) curve showed that the sensitivity and specificity of ASL were 100% and 91.1% (cutoff value=8 U/L), respectively, in the assessment of liver diseases. In contrast, ALT levels were 97.6% and 24.7%, and AST levels were 83.8% and 28.3% (both cutoff values=40.0 U/L), respectively. A positive correlation (r=0.417, P=0.019) was observed between serum ASL levels (86.9±26.5) and scores of histopathological inflammation grading (SHIG) (9.83±3.36). The sensitivity and specificity of ALS is much higher than that of ALT and AST for the diagnosis of liver diseases. ASL may be a more valuable marker for estimating hepatopathy. J. Clin. Lab. Anal. 22:220–227, 2008. © 2008 Wiley‐Liss, Inc.
Transplantation of urokinase‐type plasminogen activator gene‐modified bone marrow‐derived liver stem cells reduces liver fibrosis in rats
Authors: Sun Chao , Li Ding‐Guo , Chen Yuan‐Wen , Chen Ying‐Wei , Wang Bao‐Can , Sun Qiao‐Ling , Lu Han‐Ming
Published: May 2008

Background

Bone marrow‐derived liver stem cells (BDLSCs) are very robust cells that can differentiate into liver epithelial cells. These stem cells are promising targets for gene therapy treatment of liver diseases. Liver fibrosis results from chronic liver damage characterized by an accumulation of extracellular matrix (ECM) and levels of urokinase‐type plasminogen activator (uPA) play an important role in ECM degradation. In the present study, we investigated the therapeutic effects of uPA gene‐modified BDLSC transplantation on carbon tetrachloride (CCl4)‐induced liver fibrosis in rats.

Methods

BDLSCs were obtained from the bone marrow of cholestatic rats. These stem cells were selected and proliferated in medium containing 5% cholestatic serum. BDLSCs transfected with adenovirus‐mediated human urokinase‐plasminogen activator were transplanted into rats with CCl4‐induced hepatic fibrosis. Liver function and the area of hepatic fibrosis were correlated with the development and prognosis of hepatic fibrosis.

Results

Hepatocyte‐like colony‐forming units were formed by bone marrow cells after 2 weeks in culture. In the uPA gene‐modified BDLSC group, the areas of hepatic fibrosis were smaller and liver function was markedly ameliorated compared to controls. The expression of α‐smooth muscle actin protein, transforming growth factor‐β1 protein and collagen types I and III mRNA were downregulated. By contrast, the levels of matrix metalloproteinases‐2, ‐3 and ‐9 mRNA, hepatic growth factor mRNA and proliferating cell nuclear antigen protein increased.

Conclusions

Transplantation of uPA gene‐modified BDLSCs may suppress hepatic fibrosis and ameliorate liver function. Copyright © 2008 John Wiley & Sons, Ltd.
Raman spectroscopic evaluation of the influence of Pseudomonas bacteria on aflatoxin B1 in the BioArena complex bioautographic system
Authors: Móricz Á. M. , Horváth E. , Ott P. G. , Tyihák E.
Published: May 2008

The mechanism of the antibacterial‐toxic effect of aflatoxin B1 (AFB1) was investigated in the BioArena complex bioautographic system that consists of planar liquid chromatographic development and biological detection. In this system, the killing‐inhibiting activity of AFB1 against Pseudomonas savastanoi (Psm) bacterial cells was visualised. The role of formaldehyde (HCHO) was suggested in the antibacterial‐toxic action of AFB1. Raman spectroscopy (RS) was used to investigate whether the excess HCHO found earlier in the AFB1 spot (comparing with background) originated partly from the demethylation of the toxin, or only from the enhanced demethylation of the normal cell ingredients because of the stress situation. Fourier transform (FT) Raman and surface‐enhanced FT‐Raman spectra were obtained in situ about the AFB1 chromatographic and background spots in bacteria‐free and inoculated thin layer chromatography (TLC) layers, and ex situ about their dried methanolic extract. The reduction of the δ CH3 band of AFB1 (1386 cm−1) in the presence of Psm can indicate the demethylation of aflatoxin at its methoxy‐group in BioArena. It seems from the Raman spectra that, apart from demethylation, aflatoxin does not suffer other structural changes. However, Psm can reduce the Raman activity of νCO bond of the pyran ring of AFB1, causing lower intensity and a broader band (1747 and 1754 cm−1). Psm can also disrupt the strong interactions between the AFB1 and the adsorbent layer through the νCO bond of the cyclopentene ring causing a blue‐shift (1667 → 1686 cm−1).

The very reactive HCHO that originated from exogenous sources, e.g. from the demethylation of AFB1, has no determined biochemical pathway, so it means higher risk. Copyright © 2008 John Wiley & Sons, Ltd.
Photoinduced second harmonic generation studies on Tris(thiourea)copper(I) perchlorate Cu(SC(NH2)2)3(ClO4)
Authors: Krishnakumar V. , Kalyanaraman S. , Piasecki M. , Kityk I. V. , Bragiel P.
Published: May 2008

We have established a possibility to obtain the photoinduced optical second harmonic generation in the initially centrosymmetric single crystals of tris(thiourea)copper(I) perchlorate crystallized in the monoclinic system with the space group P21/c. The second‐order susceptibility of the investigated crystal was measured by inducing the crystal by external laser field. The results obtained are interesting and discussed in detail. We have established that the optical second harmonic generation achieves its maximum (about 0.84 pm/V) at photoinducing power density about 1430 kW/cm2 for the fundamental wavelength 1064 nm. The maximal output second harmonic generation (SHG) was achieved at an angle of about 35° between the pumping and fundamental power beam's polarizations. Such maximum may be a consequence of a competition between the so formed anharmonic photothermal expansions and the thermal destruction that occurred because of the heating of the crystal surfaces. Our independent verifications have shown that the photoinduced surfaces were heated up to 8–12° C. This may cause occurrence of photothermal relaxation processes. The output SHG exists only immediately after the act of photoinduction. The obtained dependences are caused by specific features of the Raman spectra of the investigated crystals. Copyright © 2008 John Wiley & Sons, Ltd.
Polyhedral Oligomeric Silsesquioxane‐ and Fullerene‐End‐Capped Poly(ε‐caprolactone)
Authors: Kai Weihua , Hua Lei , Dong Tungalag , Pan Pengju , Zhu Bo , Inoue Yoshio
Published: May 2008

Novel fullerene‐ and polyhedral oligomeric silsesquioxane‐ (POSS) double end‐capped poly(ε‐caprolactone) (PCL) were successfully synthesized. The crystallization behavior of the fullerene‐ and POSS‐ double end‐capped PCL and the effect of aggregation of the POSS and fullerene moieties on the crystallization of PCL were thoroughly studied. The aggregation of the fullerene moieties has much larger confinement effect on the crystallization of PCL than that of POSS. The successful incorporation of two nano‐sized objects, that is, fullerene and POSS, into the PCL matrix may introduce their merits, so that PCL can attain multi‐functional properties.

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Poly(p‐phenylene vinylene) Derivatives with Different Contents of cis‐Olefins and their Effect on the Optical Properties
Authors: Wang Fangfang , He Feng , Xie Zeng Qi , Li Yu Peng , Hanif Muddasir , Li Mao , Ma Yuguang
Published: May 2008

Soluble poly[(2,5‐dihexyloxy‐1,4‐phenylene vinylene)‐alt‐(2,5‐diphenyl‐1,4‐phenylene vinylene)] (DPO‐PPV) with a majority of cis‐vinylenes (>87%) has been synthesized by the Wittig reaction. A series of DPO‐PPV derivatives with different contents of cis‐olefins from approximately 0.05% to 87% was successfully prepared using the photoisomerization technique. On the basis of 1H NMR, Fourier transform IR (FTIR), ultraviolet (UV), and photoluminescence (PL) spectroscopy, as well as fluorescence quantum efficiency measurements, the effect of cis‐olefins on the optical properties of the polymer in solution and in film was systemically studied. The results indicate that with a cis‐configuration above 75%, the luminescence of DPO‐PPV is decayed due to cis‐trans isomerization with rotational motions of the double bonds; however, the luminescence is dramatically improved on increasing of the trans‐configuration.

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Novel Zirconocene Hydride Complexes in Homogeneous and in SiO2‐Supported Olefin‐Polymerization Catalysts Modified with Diisobutylaluminum Hydride or Triisobutylaluminum
Authors: Babushkin Dmitrii E. , Panchenko Valentina N. , Timofeeva Maria N. , Zakharov Vladimir A. , Brintzinger Hans H.
Published: May 2008

Reactive species in SiO2‐supported, zirconocene‐based olefin‐polymerization catalysts have been characterized by comparison of their UV‐vis spectra with those of related, NMR‐spectroscopically identified catalyst species in homogeneous solution. Neutral zirconocene dihydride complexes are found to arise in hydrocarbon solutions as well as on SiO2 supports when catalyst systems that contain rac‐Me2Si(ind)2ZrCl2 and methylaluminoxane (MAO) are modified by addition of diisobutylaluminum hydride or triisobutylaluminum. These complexes, tentatively formulated as adducts with Lewis‐acidic alkylaluminum species AlR2X, rac‐Me2Si(ind)2ZrH2 · {nAlR2X}, are reconverted into the initial reactive zirconocene cations upon addition of isobutene to these reaction systems.

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An Improved Non‐Isothermal Kinetic Model for Prediction of Extent of Transesterification Reaction and Degree of Randomness in PET/PEN Blends
Authors: Golriz Mahdi , Khonakdar Hossein Ali , Jafari Seyed Hassan , Oromiehie Abdolrasoul , Abedini Hossein
Published: May 2008

An improved non‐isothermal kinetic model was developed based on mass balance and Arrhenius laws using a second‐order reversible reaction capable of predicting the extent of transesterification reaction (X) and the degree of randomness (RD) in poly(ethylene terephthalate) (PET)/poly(ethylene naphthalene‐2,6‐dicarboxylate) (PEN) blends prepared by a twin screw micro‐compounder over a full composition range under different processing conditions. The experimental values of X and RD were determined by 1H‐NMR and a direct relationship between them developed. The model constants were tuned by an optimization method using half of the experimental data, with the other half used for verification. Good agreement was found between the experimental and theoretical data in the verification stage and, therefore, it was concluded that the model is capable of predicting the extent of transesterification reaction with a high level of confidence for a wide range of processing conditions. Similarly to the experimental results, the model showed that, among all parameters affecting the extent of transesterification reaction, the time and temperature play the major role, whereas the blend composition does not have a significant role.

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Phase Transitions in Melts of Alternating Rodlike Copolymers: Monte Carlo Simulation by the Wang‐Landau Approach
Authors: Berezkin Anatoly V.
Published: May 2008

A lattice model of a melt of rigid copolymeric molecules is proposed. The density of states is calculated for alternating AB‐copolymers with block lengthslAandlB. The system under consideration exhibits behavior similar to the two‐dimension Ising model. In the case oflA = lB ≤ 2 there is a second‐order order‐disorder phase transition in the system. Copolymers with longer blocks demonstrate two second‐order phase transitions, or a single first‐order phase transition. The critical temperatures of these transitions are found in analytical form.

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Equilibration and Deformation of Amorphous Polystyrene: Scale‐jumping Simulational Approach
Authors: Mulder Tim , Harmandaris Vagelis A. , Lyulin Alexey V. , van der Vegt Nico F. A. , Vorselaars Bart , Michels Matthias A. J.
Published: May 2008

A polymer sample‐preparation method (extended‐chain condensation, ECC) based solely on molecular‐dynamics simulations has been compared to a connectivity‐altering Monte Carlo method (coarse‐grained end‐bridging, CGEB). Since the characteristic ratio for the CGEB samples is closer to the experimental value, ECC results in polymer structures that are too compact. The stress–strain relations are different in the strain‐hardening regime. For CGEB samples, a stronger strain hardening is observed and the strain‐hardening modulus is more realistic; for the CGEB polystyrene (PS) sample GR = 9 ± 1 MPa is found versus GR = 4 ± 2 MPa for the ECC samples. These differences have to be attributed to a steeper increase in the contributions to the total stress from bond‐ and dihedral angles for CGEB than for ECC samples.

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A two‐scale model for liquid‐phase epitaxy
Authors: Eck Ch. , Emmerich H.
Published: May 2008

We study a model for liquid‐phase epitaxy that is based on a continuum description of the transport processes in the liquid and a Burton–Cabrera–Frank (BCF) model for the growth of the solid by epitaxy. In order to develop a model that is capable to incorporate structures of a very small scale in the solid phase within a computation for a technically relevant macroscopic length scale, we apply homogenization methods. The result of the homogenization procedure is a two‐scale model that consists of macroscopic equations for fluid flow and solute diffusion in the fluid volume, coupled to microscopic BCF models for the evolution of the microstructure in the solid phase. The obtained two‐scale model is justified by an estimate for the model error that is valid under appropriate assumptions on the regularity of the solutions. This estimate is proved for a phase field approximation of the BCF model. Copyright © 2008 John Wiley & Sons, Ltd.
Behaviour of the Landau–Lifschitz equation in a ferromagnetic wire
Authors: Sanchez David
Published: May 2008

Following a suggestion from A. Thiaville and J. Miltat, whose work and experiments are about ferromagnetic thin layers and nanowires, we study in this paper the behaviour of the Landau–Lifschitz equation in a straight ferromagnetic wire. As the diameter of the domain and the exchange coefficient in the equation simultaneously tend to zero, we perform an asymptotic expansion to precise the solution for well‐prepared initial conditions and are led to consider 2D exterior problems. Copyright © 2008 John Wiley & Sons, Ltd.
Boundary derivatives of the phases of inner and outer functions and applications
Authors: Qian Tao
Published: May 2008

We prove that boundary derivatives of the phases of inner functions exist and are positive almost everywhere, but those of outer functions, on the other hand, have zero mean on the boundary. The concepts and results have definitive applications to the definitions of instantaneous frequency and mono‐components complying with requirements in physics and contemporary study of analytic signals. Copyright © 2008 John Wiley & Sons, Ltd.
The effect of carbon nanotube agglomeration on the thermal and mechanical properties of polyethylene oxide
Authors: Narh Kwabena A. , Jallo Laila , Rhee Kyong Y.
Published: May 2008

The effects of agglomerated versus deagglomerated multiwalled carbon nanotubes on the thermal and mechanical characteristics of polyethylene oxide were studied. The specimens were prepared via solution‐sonication method, using two procedures. In the first procedure, CNT‐PEO solutions were prepared with as‐received MWCNTs, before sonication using an ultrasonic bath; in the second procedure, aggregated MWCNTs were first deagglomerated using high‐intensity ultrasonic processor, before mixing with the PEO. The two solution preparation procedures did result in significant thermal property differences such as increased transition temperature and crystallinity, but only one mechanical property can be conclusively associated with the sample preparation method—the breaking strain which was marginally higher for nanocomposites containing deagglomerated CNTs, although in all cases the breaking strains were much lower for nanocomposites than for unfilled polymer. However, the overall results confirm the effectiveness of CNTs both as nucleation agents for semicrystalline polymers, and as fillers for enhancement of mechanical properties of the matrix polymer. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers
Influence of interfacial phenomena on the mechanical properties of particulate composite membranes
Authors: Pal Rajinder
Published: May 2008

New models are proposed to describe the mechanical behavior of particulate composite membranes. The mechanical properties of particulate composite membranes are strongly influenced by interfacial phenomena. When adhesion between the filler particles and matrix is poor, the mechanical properties of composite membranes deteriorate with the addition of filler to the matrix. The addition of filler particles to the matrix has a reinforcement effect when adhesion between the particles and matrix is good. The presence of interphase (interfacial shell) around the particles can strongly influence the mechanical properties of particulate composite membranes. Some of the key factors affecting the mechanical properties of composite membranes are interphase‐to‐matrix moduli ratio, core‐to‐shell moduli ratio, and shell‐to‐core radii ratio. Theproposed models are verified using 15 sets of experimental data on the mechanical properties of particulate composites. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Enabling controlled dispersion in polyethylene nanocomposites using small‐angle scattering
Authors: Xiao Zhicheng , Li Ying , Akpalu Yvonne A.
Published: May 2008

In this article, we present some key results that demonstrate the useful application of light scattering to characterize the dispersion of nanoparticles in polymer matrix, using polyethylene nanocomposite as an example. Our results show that the dispersions of nanoparticles in polyethylene nanocomposite, that influence the thermomechanical properties of polyethylene nanocomposites, can be characterized by using small angle light scattering. This proposition is motivated by recent synthetic and morphological characterization progress towards achieving ideally dispersed polyethylene nanocomposites. Our results are significant because it is shown that using light, size and shape features that correlate well with the scanning electron microscopy observations of nanoparticle dispersion can be obtained using our unique vertical light scattering set‐up. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Electrochemical copolymerization and stability of crosslinked bis[1,2‐(pyrrol)ethoxy]ethane with pyrrole
Authors: Wang Min , Zhang Hanchang , Bai Ruke , Ge Xueping
Published: May 2008

The copolymers, pyrrole‐co‐bis[1,2‐(pyrrol)ethoxy]ethane (PEE), were produced by electropolymerization in acetonitrile (containing 0.1 mol L−1lithium perchlorate). The properties and morphology of these polymers were investigated by cyclic voltammetry, UV–vis absorption spectra and scanning electron microscopy (SEM), respectively. The results exhibit that the cyclic voltammograms and rates of electropolymerization of the prepared copolymers were significantly affected by PEE concentration in water and acetonitrile solution. Higher applied potential was required for the polymerization with decreasing the ratio of pyrrole/PEE. This was ascribed to the steric hindrance of high concentration of N‐substituted groups. The SEM images of the poly(pyrrole‐co‐PEE) and PPEE films show more compact and more smooth morphology compared with that of PPy and cyclic voltammogram of the poly(pyrrole‐co‐PEE) films, which display good electrochemical stability in the mixed solution, indicating that the modification of crosslinked structure was effective for the stabilization of the redox cycles. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers
Ferromagnetic nanoparticles embedded in self‐arranged matrices
Authors: Rumpf K. , Granitzer P. , Pölt P. , Šimić S. , Krenn H.
Published: May 2008

The investigated nanoscopic system, consisting of a non magnetic host material and precipitated ferromagnetic nanostructures shows a magnetic behaviour correlated to the size and shape of the deposited particles but also to their spatial distribution within the template which modifies the magnetic interactions between them. The nanostructures are deposited electrochemically into an etched silicon wafer exhibiting an array of channels of a few ten nanometers in diameter and a length up to 50 µm. The self‐assembled grown templates offer the opportunity of tuning the magnetic properties by varying the geometrical characteristics of the membrane which can be loaded with different metals like Ni or Co with variable metal distribution. Magnetic characteristics like coercivity, magnetic anisotropy and temperature dependent magnetization give a survey about the structure and the magnetic interactions of the nanocomposite. This achieved ferromagnetic nanocomposite system is not only of interest for basic research but also gives rise to applications in magneto‐optics, spintronics and sensor application. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermal oxidation of few‐layer graphite plates: an SPM study
Authors: Osváth Z. , Nemes‐Incze P. , Tapasztó L. , Horváth Z. E. , Biró L. P.
Published: May 2008

Commercial few‐layer graphite platelets were characterized by atomic force microscopy (AFM). Successive oxidation of the graphite platelets was carried out at 450–550 °C in air, and AFM measurements were performed after each oxidation step. The measurements showed that the applied thermal oxidation reduced the dimensions of the platelets. We have also observed the spontaneous assembly of the few‐layers thick platelets into a macroscopic, free‐standing film. Portions of this free‐standing graphite film were investigated by AFM and scanning tunneling microscopy (STM). (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The case for MR‐compatible robotics: a review of the state of the art
Authors: Elhawary Haytham , Tse Zion Tsz Ho , Hamed Abbi , Rea Marc , Davies Brian L. , Lamperth Michael U.
Published: May 2008

Background

The numerous imaging capabilities of magnetic resonance imaging (MRI) coupled with its lack of ionizing radiation has made it a desirable modality for real‐time guidance of interventional procedures. The combination of these abilities with the advantages granted by robotic systems to perform accurate and precise positioning of tools has driven the recent development of MR‐compatible interventional and assistive devices.

Methods

The challenges in this field are presented, including the selection of suitable materials, actuators and sensors in the intense magnetic fields of the MR environment.

Results

Only a small number of developed systems have made it to the clinical level (only two have become commercial ventures), showing that the field has not yet reached maturity.

Conclusions

A brief overview of the current state of the art is given, along with a description of the main opportunities, possibilities and challenges that the future will bring to this exciting and promising field. Copyright © 2008 John Wiley & Sons, Ltd.
An interregional system dynamics model of animal disease control: applications to foot‐and‐mouth disease in the Southern Cone of South America
Authors: Rich Karl M.
Published: May 2008

Foot‐and‐mouth disease (FMD) is costly for meat producers, given its ability to rapidly spread over space, with control efforts in one region crucially depending on the control efforts undertaken in other regions. This paper presents a model of FMD control that applies system dynamics to the spatial spread of disease among South American countries with traditionally different control regimes and assesses the impact of alternative control strategies. Model results demonstrate that preventative vaccination led to shorter outbreaks (by over 2 weeks) than other strategies, though the resources required to implement this may be difficult to mobilize. The model also shows that a combination of region‐specific policies often controls disease better than uniform region‐wide approaches, suggesting the need for improved multinational coordination of disease control. Copyright © 2008 John Wiley & Sons, Ltd.
Steering without Circe: attending to reinforcing loops in social systems
Authors: Lane David C. , Husemann Elke
Published: May 2008

Relating system dynamics to the broad systems movement, the key notion is that reinforcing loops deserve no less attention than balancing loops. Three specific propositions follow. First, since reinforcing loops arise in surprising places, investigations of complex systems must consider their possible existence and potential impact. Second, because the strength of reinforcing loops can be misinferred—we include an example from the field of servomechanisms—computer simulation can be essential. Be it project management, corporate growth or inventory oscillation, simulation helps to assess consequences of reinforcing loops and options for interventions. Third, in social systems the consequences of reinforcing loops are not inevitable. Examples concerning “globalization” illustrate how difficult it might be to challenge such assumptions. However, system dynamics and ideas from contemporary social theory help to show that even the most complex social systems are, in principle, subject to human influence. In conclusion, by employing these ideas, by attending to reinforcing as well as balancing loops, system dynamics work can improve the understanding of social systems and illuminate our choices when attempting to steer them. Copyright © 2008 John Wiley & Sons, Ltd.
High‐rate preparation of thin Si films by atmospheric‐pressure plasma enhanced chemical transport
Authors: Kamada Daiki , Kishimoto Kazuya , Kakiuchi Hiroaki , Yasutake Kiyoshi , Ohmi Hiromasa
Published: May 2008

Polycrystalline Si films were prepared by chemical transport using near‐atmospheric‐pressure pure hydrogen plasma (6.7 × 10−3 to 5.3 × 10−2 MPa). Substrate temperatures were varied from 200 to 600 °C and solid Si source was used as the feedstock to generate SiHx species. To generate high‐density stable glow hydrogen plasma at near atmospheric pressure, 150 MHz very high frequency (VHF) power was used. The dependence of deposition rate on various preparation parameters, such as VHF input power, hydrogen pressure, and substrate temperature, was investigated. The deposition rate increased with increasing VHF power density and substrate temperature. The attained deposition rate on glass substrates was 15 nm/s at 400 °C. Prepared Si films exhibited columnar structures along the growth direction. The maximum lateral grain size was 5 µm at the film thickness of 15 µm. It was found by Raman spectroscopy that the crystalline fraction of prepared Si film would not be influenced with increasing deposition rate (Rd). Copyright © 2008 John Wiley & Sons, Ltd.