bluuebunny/crossref_metadata_2025 huggingface dataset:
Cloning and expression of three aquaporin homologues from the European eel (Anguilla anguilla): effects of seawater acclimation and cortisol treatment on renal expression
Authors: Martinez Anne‐Sophie , Cutler Christopher P. , Wilson Gillian D. , Phillips Claire , Hazon Neil , Cramb Gordon
Published: July 2005

Background information. The European eel (Anguilla anguilla) is able to osmoregulate over a wide range of environmental salinities from FW (freshwater) to hyperconcentrated SW (seawater). Successful acclimation is associated with strict regulation of ion and water transport pathways within key osmoregulatory epithelia to enable animals to survive the dehydrating or oedematous conditions. These observations suggested that homologues of the AQP (aquaporin) water channel family were expressed in the eel and that these proteins may contribute to the water transport and osmoregulation in all euryhaline teleosts.

Results. Complementary DNAs encoding a homologue of the mammalian aquaglyceroporins (termed AQPe) and two homologues of mammalian aquaporin‐1 [termed AQP1 and AQP1dup (aquaporin‐1 duplicate)] were isolated from the European eel. Northern‐blot analysis revealed (i) two AQP1 transcripts exhibiting a wide tissue distribution, (ii) a single AQP1dup mRNA transcript found in the kidney and the oesophagus, and (iii) a single AQPe mRNA detectable mainly in the kidney and the intestine. The relative expression of isoforms within the kidney was AQP1dup>AQPe>AQP1. SW acclimation significantly reduced the abundance of AQP1, AQP1dup and AQPe transcripts in the kidney of yellow eels by approx. 72, 66 and 34$ respectively, whereas the expression levels in silver eels were independent of salinity and equivalent to those observed in yellow SW‐acclimated fish. AQP1 protein expression was primarily located within the vascular endothelium in yellow eels and the epithelial apical brush border in some renal tubules in silver eels. Infusion of cortisol into FW eels had no effect on AQPe mRNA expression, but induced significant decreases in AQP1 and AQP1dup mRNA levels in the kidney of yellow eels. Cortisol infusion had no effect on the expression of any isoform in the silver eels.

Conclusions. These results suggest that SW‐acclimation or cortisol infusion induces a down‐regulation of renal AQP expression in yellow eels. However, the lower levels of aquaporin expression found within the silver eel kidney were not further reduced by salinity transfer or steroid infusion. These differences in mRNA expression were accompanied by changes in the cellular distribution of the AQP1 protein between vascular endothelial and tubular epithelial cells.
Expression pattern of the Brachyury and Tbx2 homologues from the sponge Suberites domuncula
Authors: Adell Teresa , Müller Werner E.G.
Published: July 2005

Background information. T‐box transcription factors are a large family of transcriptional regulators involved in many aspects of embryonic development. In a previous report, we described the isolation and genomic characterization of two T‐box genes from the siliceous sponge Suberites domuncula: a Brachyury homologue, Sd‐Bra, and a Tbx2 homologue, Sd‐Tbx2. Elucidation of the genomic structure of Sd‐Bra allowed us to demonstrate the existence of two different isoforms, resulting from alternative splicing. Moreover, we demonstrated that the shorter isoform exists in two different glycosylation states.

Results. In the present study, we demonstrate a differential subcellular localization of the three Sd‐Bra isoforms, suggesting that its differential nuclear import could be an important mechanism for its functional regulation. Furthermore, we demonstrate that Sd‐Tbx2 exists only in one isoform, which is mainly localized in the nucleus. The pattern of expression of Sd‐Bra and Sd‐Tbx2 genes is analysed in sponge tissue, in gemmules and in cultured cells.

Conclusion. These results suggest a conserved role for Sd‐Bra in the control of morphogenetic movements through the regulation of cell‐adhesion properties and the involvement of Sd‐Tbx2 in the determination of cell identity in the early stages of differentiation, reminiscent of the function of Tbx2‐3‐4‐5 in vertebrates during limb specification. Also, the fact that a Brachyury and a Tbx2 homologue exist in S. domuncula suggests that the first divergence from the ancestral Brachyury‐like gene might be a Tbx2‐like gene and not a Tbrain‐like gene as had been previously suggested [Adell, Grebenjuk, Wiens and Müller (2003) Dev. Genes Evol. 213, 421–434].
Yeast Ypt11 is targeted to recycling endosomes in mammalian cells
Authors: Kail Mark , Hollinshead Mike , Kaufmann Miriam , Boettcher Jens , Vaux David , Barnekow Angelika
Published: July 2005

Background information. In yeast, Ypt11 or Ypt32 along with the highly homologous Ypt8 or Ypt31 has been reported to be an essential component of intra‐Golgi trafficking and has been implicated in the budding of vesicles from the most distal Golgi compartment.

Results and conclusions. In the present study, we show that, in human cells, after heterologous expression of GFP—Ypt11 (where GFP stands for green fluorescent protein), the protein is targeted to transferrin‐positive recycling endosomes. This compartment has been shown to form extensive tubular networks on applying the drug Brefeldin A. We also show, by confocal fluorescent microscopy, that these networks also contain Rab11 in cells expressing CFP—Rab11a (where CFP stands for cyan fluorescent protein) fusion protein and that these structures are identical with those targeted by GFP—Ypt11.
p38 mitogen‐activated protein kinase (MAPK) first regulates filamentous actin at the 8–16‐cell stage during preimplantation development
Authors: Paliga Andrew J.M. , Natale David R. , Watson Andrew J.
Published: July 2005

Background information. The MAPK (mitogen‐activated protein kinase) superfamily of proteins consists of four separate signalling cascades: the c‐Jun N‐terminal kinase or stress‐activated protein kinases (JNK/SAPK); the ERKs (extracellular‐signal‐regulated kinases); the ERK5 or big MAPK1; and the p38 MAPK group of protein kinases, all of which are highly conserved. To date, our studies have focused on defining the role of the p38 MAPK pathway during preimplantation development. p38 MAPK regulates actin filament formation through the downstream kinases MAPKAPK2/3 (MAPK‐activated protein kinase 2/3) or MAPKAPK5 [PRAK (p38 regulated/activated kinase)] and subsequently through HSP25/27 (heat‐shock protein 25/27). We recently reported that 2‐cell‐stage murine embryos treated with cytokine‐suppressive anti‐inflammatory drugs (CSAID™; SB203580 and SB220025) display a reversible blockade of development at the 8–16‐cell stage, indicating that p38 (MAPK) activity is required to complete murine preimplantation development. In the present study, we have investigated the stage‐specific action and role of p38 MAPK in regulating filamentous actin during murine preimplantation development.

Results. Treatment of 8‐cell‐stage embryos with SB203580 and SB220025 (CSAID™) resulted in a blockade of preimplantation development, loss of rhodamine phalloidin fluorescence, MK‐p (phosphorylated MAPKAPK2/3), HSP‐p (phosphorylated HSP25/27) and a redistribution of α‐catenin immunofluorescence by 12 h of treatment. In contrast, treatment of 2‐ and 4‐cell‐stage embryos with CSAID™ drugs resulted in a loss of MK‐p and HSP‐p, but did not result in a loss of rhodamine phalloidin fluorescence. All these effects of p38 MAPK inhibition were reversed upon removal of the inhibitor, and development resumed in a delayed but normal manner to the blastocyst stage. Treatment of 8‐cell embryos with PD098059 (ERK pathway inhibitor) did not affect development or fluorescence of MK‐p, HSP‐p or rhodamine phalloidin.

Conclusion. Murine preimplantation development becomes dependent on p38 MAPK at the 8–16‐cell stage, which corresponds to the stage when p38 MAPK first regulates filamentous actin during early development.
Pulse wave analysis during supine rest may identify subjects with recurrent vasovagal syncope
Authors: Simek Jan , Wichterle Dan , Melenovsky Vojtech , Malik Jan , Svobodova Jaroslava , Svacina Stepan
Published: July 2005

In the present study, we studied whether analysis of the FAP (finger arterial pressure) waveform during supine rest discriminates subjects with recurrent VVS (vasovagal syncope) from healthy controls. Signal-averaged FAP waveforms (Finapres) were obtained in 32 head-up tilt-test-positive subjects with recurrent VVS (35±13 years) and in 32 sex- and age-matched healthy controls. The DT (time delay) between the systolic and diastolic peaks of the FAP waveform was measured and large artery SI (stiffness index) was calculated as a ratio of body height and DT. VVS patients had significantly shorter DT compared with controls (303±31 compared with 329±18 ms; P<0.001) and higher SI (5.79±0.70 compared with 5.20±0.36 m/s; P<0.001). The differences were independent of heart rate and blood pressure. SI >5.45 m/s identified subjects with syncope with a sensitivity of 72% and a specificity of 84%. Age-corrected DT (cDT=DT+age−350) identified subjects with syncope with a sensitivity of 75% and a specificity of 84%. Combined use of cDT <0 ms and SI >5.45 m/s increased sensitivity and specificity to 81% and 96% respectively. The discriminative power of FAP descriptors improved further when younger subjects were excluded. In subjects aged >30 years (median age), the combination of cDT and SI identified subjects with syncope with a sensitivity of 93% and a specificity of 100%. These results suggest that FAP descriptors during supine rest might be useful in the diagnosis of VVS in middle-aged subjects.
Cardiovascular risk parameters in men with ankylosing spondylitis in comparison with non-inflammatory control subjects: relevance of systemic inflammation
Authors: Divecha Hiren , Sattar Naveed , Rumley Ann , Cherry Lynne , Lowe Gordon D. O. , Sturrock Roger
Published: July 2005

Men with AS (ankylosing spondylitis) are at elevated risk for CHD (coronary heart disease) but information on risk factors is sparse. We compared a range of conventional and novel risk factors in men with AS in comparison with healthy controls and, in particular, determined the influence of systemic inflammation. Twenty-seven men with confirmed AS and 19 controls matched for age were recruited. None of the men was taking lipid-lowering therapy. Risk factors inclusive of plasma lipids, IL-6 (interleukin-6), CRP (C-reactive protein), vWF (von Willebrand factor), fibrin D-dimer, ICAM-1 (intercellular cell-adhesion molecule-1) and fibrinogen were measured, and blood pressure and BMI (body mass index) were determined by standard techniques. A high proportion (70%) of men with AS were smokers compared with 37% of controls (P=0.024). The AS patients also had a higher BMI. In analyses adjusted for BMI and smoking, men with AS had significantly higher IL-6 and CRP (approx. 9- and 6-fold elevated respectively; P<0.001), fibrinogen (P=0.013) and vWF (P=0.008). Total cholesterol and HDL-C (high-density lipoprotein cholesterol) were lower (P<0.05 and P=0.073 respectively) in AS and thus the ratio was not different. Pulse pressure was also significantly higher in AS (P=0.007). Notably, adjustment for IL-6 and CRP levels rendered all case-control risk factor differences, except pulse pressure, non-significant. In accordance with this finding, IL-6 correlated positively (r=0.74, P<0.001) with fibrinogen, but negatively (r=−0.46, P=0.016) with total cholesterol concentration. In conclusion, men with AS have perturbances in several CHD risk factors, which appear to be driven principally by systemic inflammatory mediators. Inflammation-driven atherogenesis potentially contributes to the excess CHD risk in AS.
Increased uterine arterial pressure and contractility of perfused swine uterus after treatment with serum from pre-eclamptic women and endothelin-1
Authors: Maltaris Theodoros , Scalera Fortunato , Schlembach Dietmar , Hoffmann Inge , Mueller Andreas , Binder Helge , Goecke Tamme , Hothorn Torsten , Schild Ralf L. , Beckmann Matthias W. , Dittrich Ralf
Published: July 2005

The present study was designed to examine the effects of ET-1 (endothelin-1) and serum from PE (pre-eclamptic), HP (healthy pregnant) and HNP (healthy non-pregnant) women on uterine arterial perfusion pressure and uterine contractility. Swine uteri (n=25) were perfused for a period of up to 11 h, with the aim being to preserve a viable organ. Various concentrations of ET-1 as well as serum from PE, HP and HNP women (n=10 per group) were administered to the perfused swine uteri and IUP (intrauterine pressure) and IAP (intra-arterial pressure) were recorded. ET-1 produced dose-dependent increases in IUP and IAP. The ET-1 concentration in serum was higher in serum from PE women than in HP and HNP women (P>0.05). Administration of all serum samples had a contractile effect on the swine uterus, with the greatest effect being seen in HNP women (12.8±5.3 mmHg), followed by PE (9.06±4.2 mmHg) and HP (6.1±4.1 mmHg) women. Statistically significant differences were observed between HNP and PE women (P=0.048), and PE and HP women (P=0.021). Increases in IAP following administration of serum from PE women (48.8±20.0 mmHg) were significantly higher (P=0.024) compared with the effect of serum from HP women (28.4±13.7 mmHg). In conclusion, the findings show that serum from PE women has significant vasoconstrictive and oxytocic effects compared with serum from HP women. In pre-eclampsia, the balance between vasorelaxing and vasoactive substances is disturbed.
Specific effect of arachidonic acid on inducible nitric oxide synthase mRNA expression in human osteoblastic cells
Authors: Priante Giovanna , Musacchio Estella , Pagnin Elisa , Calò Lorenzo A. , Baggio Bruno
Published: July 2005

A specific modulatory effect of PUFAs (polyunsaturated fatty acids) on gene expression of some cytokines involved in bone remodelling has been reported previously. In particular, although a direct action of AA (arachidonic acid) on bone cytokine gene expression has been shown in human osteoblastic cells, OA (oleic acid) and EPA (eicosapentaenoic acid) were ineffective. Since the NO (nitric oxide) system has also been shown to have an important modulatory activity on osteoblasts, osteoclasts and bone metabolism, in the present study we have investigated the effects of PUFAs on iNOS (inducible NO synthase) gene expression in a human osteoblast-like cell line. AA induced a significant increase in iNOS mRNA expression, whereas EPA and OA had no stimulatory effects but instead caused a significant inhibition of AA-induced iNOS gene expression. Blocking of the COX (cyclo-oxygenase) pathway did not inhibit AA-induced iNOS expression. AA action was inhibited instead by the addition of calphostin C and genistein, inhibitors of PKC (protein kinase C) and tyrosine kinases respectively. Experiments performed with specific anti-cytokine antibodies showed a significant decrease in iNOS expression in AA-treated osteoblastic cells, suggesting that both cytokine-dependent and -independent mechanisms account for the effects of AA on iNOS gene expression. In conclusion, our investigation clearly shows specific effects of PUFAs on iNOS expression in human osteoblast-like cells with a cytokine-dependent and -independent mechanism. These results might have clinical relevance and are of interest for understanding the reported beneficial effects of dietary PUFA manipulation on the prevention and/or treatment of primary and secondary bone disease.
Vascular complications in diabetes mellitus: the role of endothelial dysfunction
Authors: Schalkwijk Casper G. , Stehouwer Coen D. A.
Published: July 2005

The endothelium is a complex organ with a multitude of properties essential for control of vascular functions. Dysfunction of the vascular endothelium is regarded as an important factor in the pathogenesis of diabetic micro- and macro-angiopathy. Endothelial dysfunction in Type I and II diabetes complicated by micro- or macro-albuminuria is generalized in that it affects many aspects of endothelial function and occurs not only in the kidney. The close linkage between microalbuminuria and endothelial dysfunction in diabetes is an attractive explanation for the fact that microalbuminuria is a risk marker for atherothrombosis. In Type I diabetes, endothelial dysfunction precedes and may cause diabetic microangiopathy, but it is not clear whether endothelial dysfunction is a feature of the diabetic state itself. In Type II diabetes, endothelial function is impaired from the onset of the disease and is strongly related to adverse outcomes. It is not clear whether impaired endothelial function is caused by hyperglycaemia or by other factors. Impaired endothelial function is closely associated with and may contribute to insulin resistance regardless of the presence of diabetes. Endothelial dysfunction in diabetes originates from three main sources. Hyperglycaemia and its immediate biochemical sequelae directly alter endothelial function or influence endothelial cell functioning indirectly by the synthesis of growth factors, cytokines and vasoactive agents in other cells. Finally, the components of the metabolic syndrome can impair endothelial function.
ATP-binding cassette transporter G8 M429V polymorphism as a novel genetic marker of higher cholesterol absorption in hypercholesterolaemic Japanese subjects
Authors: Miwa Kenji , Inazu Akihiro , Kobayashi Junji , Higashikata Toshinori , Nohara Atsushi , Kawashiri Masaaki , Katsuda Shoji , Takata Mutsuko , Koizumi Junji , Mabuchi Hiroshi
Published: July 2005

The ratio of serum plant sterols to cholesterol is positively correlated with the fractional cholesterol absorption, whereas serum precursors of cholesterol synthesis are positively correlated with cholesterol synthesis. Recently, two ABC (ATP-binding cassette) transporters, ABCG5 and ABCG8, have been described as playing an important role in the absorption and excretion of sterols. In the present study, we tested the hypothesis that genetic variation in ABCG5/ABCG8 influences the levels of serum plant sterol (sitosterol) and cholesterol precursor (lathosterol) in Japanese primary hypercholesterolaemic patients (n=100). We identified a novel mutation [859T/C (C287R)] and a novel polymorphism [1285A/G (M429V)] at the ABCG5/ABCG8 loci, as well as four polymorphisms reported previously [1810C/G (Q604E), 161G/A (C54Y), 1199C/A (T400K) and 1895C/T (A632V)]. In carriers of the novel M429V variant, the serum level of sitosterol and the sitosterol/cholesterol ratio were significantly higher than those in non-carriers (3.64 compared with 2.56 μg/ml, and 1.45 μg/mg compared with 1.00 μg/mg respectively; P<0.01 for both), and serum lathosterol tended to be lower (1.95 μg/ml compared with 3.03 μg/ml; P=0.08), whereas no significant difference was observed in other lipid profiles. These four polymorphisms (1810C/G, 161G/A, 1199C/A and 1285A/G) generated six haplotypes, and the C/G/C/G haplotype was significantly associated with a higher sitosterol level and sitosterol/cholesterol ratio compared with the other five haplotypes (P<0.05 for both). We conclude that, in 8% of patients with hypercholesterolaemia, the novel ABCG8 M429V variant was associated with higher cholesterol absorption efficiency. Future studies should investigate whether these findings have implications for the optimal cholesterol-lowering drug treatment in hypercholesterolaemic patients.
Changes in the expression of genes related to bile acid synthesis and transport by the rat liver during hepatocarcinogenesis
Authors: Monte Maria J. , Fernandez-Tagarro Maria , Macias Rocio I. R. , Jimenez Felipe , Gonzalez-San Martin Francisco , Marin Jose J. G.
Published: July 2005

The relationship between BA (bile acid) secretion (measured by GC–MS) and the expression of genes (measured by reverse transcription real-time PCR) involved in liver BA transport and metabolism was investigated at 20 and 32 weeks during rat hepatocarcinogenesis. A progressive loss of mRNA for transporters (more marked for Ntcp, Bsep and Mrp2 than for Oatp1/Oatp1a1, Oatp2/Oatp1a4 and Oatp4/Oatp1b2) was found. The mRNA levels of Cyp7a1 and the nuclear receptors FXR (farnesoid X receptor), SHP (small heterodimer partner) and FTF (α-fetoprotein transcription factor) were not modified, whereas those of Cyp8b1 were enhanced and those of Cyp27 were reduced. Biliary secretion of CA (cholic acid) remained unchanged, whereas that of CDCA (chenodeoxycholic acid) and other non-C12-hydroxylated BAs was diminished. The re-appearance of ‘flat-BAs’ (mainly allo-BAs at 20 weeks and Δ4-unsaturated-BAs at 32 weeks) probably reflects the progressive decrease observed in the expression of 3-oxo-Δ4-steroid 5β-reductase, together with the maintenance of steroid 5α-reductase type I. A significant correlation between the 5α-reductase/5β-reductase ratio and bile output of ‘flat-BAs’ was found. In conclusion, during rat hepatocarcinogenesis, the expression of transporters/enzymes responsible for BA homoeostasis is changed due to mechanisms other than those controlled by FXR/SHP/FTF. These modifications result in the re-appearance of ‘flat-BAs’, together with an increased CA/CDCA ratio in bile.
TNF-α as a promising therapeutic target in chronic asthma: a lesson from rheumatoid arthritis
Authors: Russo Cristina , Polosa Riccardo
Published: July 2005

TNF-α (tumour necrosis factor-α) is known to play a critical role in the pathogenic mechanisms of a number of chronic inflammatory diseases, including RA (rheumatoid arthritis), Crohn's disease and psoriasis. The notion that TNF-α is released in allergic responses from both mast cells and macrophages via IgE-dependent mechanisms, the demonstration that elevated levels of TNF-α are frequently observed in bronchoalveolar fluid of asthmatic subjects undergoing allergen challenge and the results from exposure studies of TNF-α in vivo showing increases in airway responsiveness in both normal and asthmatic subjects emphasize the importance of TNF-α in the initiation of allergic asthmatic airway inflammation and the generation of airway hyper-responsiveness. Drugs targeting TNF-α have been developed to neutralize the deleterious effects of this inflammatory cytokine and have proved to be safe and effective in the treatment of patients with RA, Crohn's disease and psoriasis refractory to conventional treatments. Biological therapies blocking TNF-α are likely to constitute a considerable advance in the management of those difficult cases of asthma that are particularly resistant to typical treatment modalities. In this review article, we intend to address the potential role of TNF-α in asthma and to put forward the idea that drugs that have been developed to neutralize the deleterious effects of TNF-α may also be useful in the management of chronic severe asthma.
Paraoxonase-1 (PON-1) genotype and activity and in vivo oxidized plasma low-density lipoprotein in Type II diabetes
Authors: Sampson Mike J. , Braschi Simon , Willis Gavin , Astley Sian B.
Published: July 2005

The HDL (high-density lipoprotein)-associated enzyme PON (paraoxonase)-1 protects LDL (low-density lipoprotein) from oxidative modification in vitro, although it is unknown if this anti-atherogenic action occurs in vivo. In a cross-sectional study of 58 Type II diabetic subjects and 50 controls, we examined the fasting plasma LDL basal conjugated diene concentration [a direct measurement of circulating oxLDL (oxidatively modified LDL)], lipoprotein particle size by NMR spectroscopy, PON-1 polymorphisms (coding region polymorphisms Q192R and L55M, and gene promoter polymorphisms −108C/T and −162G/A), PON activity (with paraoxon or phenyl acetate as the substrates) and dietary antioxidant intake. Plasma oxLDL concentrations were higher in Type II diabetic patients (males, P=0.048; females, P=0.009) and unrelated to NMR lipoprotein size, PON-1 polymorphisms or PON activity (with paraoxon as the substrate) in any group. In men with Type II diabetes, however, there was a direct relationship between oxLDL concentrations and PON activity (with phenyl acetate as the substrate; r=0.611, P=0.0001) and an atherogenic NMR lipid profile in those who were PON-1 55LL homozygotes. Circulating oxLDL concentrations in vivo were unrelated to PON-1 genotypes or activity, except in male Type II diabetics where there was a direct association between PON activity (with phenyl acetate as the substrate) and oxLDL levels. These in vivo data contrast with in vitro data, and may be due to confounding by dietary fat intake. Male Type II diabetic subjects with PON-1 55LL homozygosity have an atherogenic NMR lipid profile independent of LDL oxidation. These data do not support an in vivo action of PON on LDL oxidation.
Can we diagnose, treat or even understand neurally mediated syncope?
Authors: Raj Satish R. , Diedrich André , Biaggioni Italo
Published: July 2005

There are significant gaps in our understanding of the pathophysiology, diagnosis and treatment of NMS (neurally mediated syncope). Contributions in this area will be welcomed by patients and physicians taking care of them alike. In this issue of Clinical Science, Simek and co-workers report a novel non-invasive physiological measurement that does not require head-up tilt to diagnose NMS. However, validation studies applied to an unselected patient population are needed before we can judge how useful this test will be in the diagnosis of NMS.
Effects of strain relaxation on the electronic properties of epitaxial Sr2FeMoO6 grown by pulsed laser deposition on SrTiO3 (001)
Authors: Fix T. , Stoeffler D. , Colis S. , Ulhaq C. , Versini G. , Vola J. P. , Huber F. , Dinia A.
Published: July 2005

Thin films of Sr2FeMoO6 (SFMO) are grown epitaxially on (001) SrTiO3 substrates by pulsed laser deposition. The in-plane and out-of-plane SFMO lattice parameters are determined for different thicknesses, from 13 to 600 nm. Samples below a critical thickness of around 34 nm are fully strained, samples between 34 and 80 nm are relaxing, and samples between 80 and 600 nm are fully relaxed. Transmission electron microscopy reveals that the relaxation is done by stacking the faults perpendicular to the substrate. Ab initio calculations show first that the variation of SFMO lattice parameters due to strain has a limited impact on the magnetization, which is also observed experimentally. Second, ab initio calculations indicate that SFMO is half metallic only for thicknesses above 44 nm.
Defects and morphological changes in nanothin Cu films on polycrystalline Mo analyzed by thermal helium desorption spectrometry
Authors: Venugopal V. , Seijbel L. J. , Thijsse B. J.
Published: July 2005

Thermal helium desorption spectrometry (THDS) has been used for the investigation of defects and thermal stability of thin Cu films (5–200Å) deposited on a polycrystalline Mo substrate in ultrahigh vacuum. These films are metastable at room temperature. On heating, the films transform into islands, giving rise to a relatively broad peak in the helium desorption spectra. The temperature of this island formation is dependent on film thickness, being 417K for 10Å and 1100K for a 200Å film. The activation energy for island formation was found to be 0.3±0.1eV for 75Å film. Grain boundaries have a strong effect on island formation. The defect concentration in the as-deposited films is ∼5×10−4, for films thicker than 50Å and more for thinner films. Helium release from monovacancies was identified in the case of a 200Å film. Helium release was also seen during sublimation of the Cu film (∼1350K). Overlayer experiments were used to identify helium trapped close to the film surface. An increase of the substrate temperature during deposition resulted in a film that had already formed islands. Argon-ion assistance (250eV) during film deposition with an ion/atom ratio of ∼0.1 resulted in a significant enhancement of helium trapping in the films. The argon concentration in the films was found to be 10−3. The temperature of island formation was increased due to argon-ion assistance. The helium and argon desorption spectra are found to be similar, which is due to most of the helium becoming trapped in the defects created by the argon beam. The role of the Mo surface in affecting the defects at the film-substrate interface is investigated. The effect of variation of helium fluence and helium implantation energy is also considered. The present THDS results of Cu/poly-Mo are compared to those of Cu∕Mo(100) and Cu∕Mo(100) reported earlier.
Correlation dimension and integral do not predict epileptic seizures
Authors: Harrison Mary Ann F. , Osorio Ivan , Frei Mark G. , Asuri Srividhya , Lai Ying-Cheng
Published: July 2005

Reports in the literature have indicated potential value of the correlation integral and dimension for prediction of epileptic seizures up to several minutes before electrographic onset. We apply these measures to over 2000 total hours of continuous electrocortiogram, taken from 20 patients with epilepsy, examine their sensitivity to quantifiable properties such as the signal amplitude and autocorrelation, and investigate the influence of embedding and filtering strategies on their performance. The results are compared against those obtained from surrogate time series. Our conclusion is that neither the correlation dimension nor the correlation integral has predictive power for seizures.
Aminomethanol water elimination: Theoretical examination
Authors: Feldmann Michael T. , Widicus Susanna L. , Blake Geoffrey A. , Kent David R. , Goddard William A.
Published: July 2005

The mechanism for the formation of hexamethylenetetraamine predicts the formation of aminomethanol from the addition of ammonia to formaldehyde. This molecule subsequently undergoes unimolecular decomposition to form methanimine and water. Aminomethanol is the predicted precursor to interstellar glycine, and is therefore of great interest for laboratory spectroscopic study, which would serve as the basis for observational searches. The height of the water loss barrier is therefore useful in the determination of an appropriate experimental approach for spectroscopic characterization of aminomethanol. We have determined the height of this barrier to be 55kcal∕mol at ambient temperatures. In addition, we have determined the infinite-pressure Rice–Ramsperger–Kassel–Marcus unimolecular decomposition rate to be <10−25s−1 at 300K, indicating gas-phase kinetic stability for typical laboratory and hot core temperatures. Therefore, spectroscopic characterization of and observational searches for this molecule should be straightforward provided an efficient formation mechanism can be found.
Atomic spin-orbit pseudopotential definition and its relation to the different relativistic approximations
Authors: Fromager Emmanuel , Teichteil Christian , Maron Laurent
Published: July 2005

A critical analysis of usual shape-consistent spin-orbit pseudopotential extraction procedures is presented, considering the basic requirements of the atomic pseudopotentials. It is based on a perturbative analysis of both reference all-electron Dirac–Coulomb and pseudopotential calculations by means of the formalism developed by Lindgren and Morrisson. In the light of this analysis, we propose a new hybrid extraction of spin-orbit pseudopotentials, taking advantage of both shape-consistent and energy-consistent procedures. These new pseudopotentials are extracted and checked for the P2 ground state of the halogens.
Dynamics of end-linked star-polymer structures
Authors: Satmarel C. , von Ferber C. , Blumen A.
Published: July 2005

In this work we focus on the dynamics of macromolecular networks formed by end-linking identical polymer stars. The resulting macromolecular network can then be viewed as consisting of spacers which connect branching points (the cores of the stars). We succeed in analyzing exactly, in the framework of the generalized Gaussian model, the eigenvalue spectrum of such networks. As applications we focus on several topologies, such as regular networks and dendrimers; furthermore, we compare the results to those found for regular hyperbranched structures. In so doing, we also consider situations in which the beads of the cores differ from the beads of the spacers. The analytical procedure which we use involves an exact real-space renormalization, which allows to relate the star network to a (much simpler) network, in which each star is reduced to its core. It turns out that the eigenvalue spectrum of the star-polymer structure consists of two parts: one follows in terms of polynomial equations from the relaxation spectrum of the corresponding renormalized structure, while the second part involves the motion of the spacer chains themselves. Finally, we show exemplarily the situation for copolymeric dendrimers, calculate their spectra, and from them their storage and the loss moduli.
Pattern formation induced by ion-selective surfaces: Models and simulations
Authors: Horvát Szabolcs , Hantz Péter
Published: July 2005

Simple inorganic reactions in gels, such as NaOH+CuCl2, NaOH+AgNO3, and CuCl2+K3[Fe(CN)6], can yield to various precipitation patterns. The first compound penetrates in a hydrogel by diffusion, and reacts with the second compound homogenized in the gel. The precipitate patterns formed in these reactions have got two kinds of bordering surfaces. Recent experimental results suggested that one of these surfaces has an ion-selective (semipermeable) character: It restrains the diffusion of the reacting ion contained by the reactant that diffuses into the gel. In this paper, we built the above experimental observation into a reaction-diffusion cellular-automata model of the pattern formation. Computer simulations showed that the model is able to reproduce the basic building elements of the patterns.
Molecular dynamics simulations of side chain liquid crystal polymer molecules in isotropic and liquid-crystalline melts
Authors: Stimson Lorna M. , Wilson Mark R.
Published: July 2005

A detailed molecular dynamics simulation study is described for a polysiloxane side chain liquid crystal polymer (SCLCP). The simulations use a coarse-grained model composed of a combination of isotropic and anisotropic interaction sites. On cooling from a fully isotropic polymer melt, we see spontaneous microphase separation into polymer-rich and mesogen-rich regions. Upon application of a small aligning potential during cooling, the structures that form on microphase separation anneal to produce a smectic-A phase in which the polymer backbone is largely confined between the smectic layers. Several independent quenches from the melt are described that vary in the strength of the aligning potential and the degree of cooling. In each quench, defects were found where the backbone chains hop from one backbone-rich region to the next by tunneling through the mesogenic layers. As expected, the number of such defects is found to depend strongly on the rate of cooling. In the vicinity of such a defect, the smectic-A structure of the mesogen-rich layers is disrupted to give nematiclike ordering. Additionally, several extensive annealing runs of approximately 40 ns duration have been carried out at the point of microphase separation. During annealing the polymer backbone is seen to be slowly excluded from the mesogenic layers and lie perpendicular to the smectic-A director. These observations agree with previous assumptions about the structure of a SCLCP and with interpretations of x-ray diffraction and small angle neutron scattering data. The flexible alkyl spacers, which link the backbone to the mesogens, are found to form sublayers around the backbone layer.
Monte Carlo simulations of oppositely charged macroions in solution
Authors: Rydén Jens , Ullner Magnus , Linse Per
Published: July 2005

The structure and phase behavior of oppositely charged macroions in solution have been studied with Monte Carlo simulations using the primitive model where the macroions and small ions are described as charged hard spheres. Size and charge symmetric, size asymmetric, and charge asymmetric macroions at different electrostatic coupling strengths are considered, and the properties of the solutions have been examined using cluster size distribution functions, structure factors, and radial distribution functions. At increasing electrostatic coupling, the macroions form clusters and eventually the system displays a phase instability, in analogy to that of simple electrolyte solutions. The relation to the similar cluster formation and phase instability occurring in solutions containing oppositely charged polymers is also discussed.
Free energy of solvation of simple ions: Molecular-dynamics study of solvation of Cl− and Na+ in the ice/water interface
Authors: Smith E. J. , Bryk T. , Haymet A. D. J.
Published: July 2005

Molecular-dynamics simulations of Cl− and Na+ ions are performed to calculate ionic solvation free energies in both bulk simple point-charge/extended water and ice 1h at several different temperatures, and at the basal ice 1h∕water interface. For the interface we calculate the free energy of “transfer” of the ions across the ice/water interface. For the ions in bulk water in the NPT ensemble at 298K and 1atm, results are found to be in good agreement with experiments, and with other simulation results. Simulations performed in the NVT ensemble are shown to give equivalent solvation free energies, and this ensemble is used for the interfacial simulations. Solvation free energies of Cl− and Na+ ions in ice at 150K are found to be ∼30 and ∼20kcalmol−1, respectively, less favorable than for water at room temperature. Near the melting point of the model the solvation of the ions in water is the same (within statistical error) as that measured at room temperature, and in the ice is equivalent and ∼10kcalmol−1 less favorable than the liquid. The free energy of transfer for each ion across ice/water interface is calculated and is in good agreement with the bulk observations for the Cl− ion. However, for the model of Na+ the long-range electrostatic contribution to the free energy was more negative in the ice than the liquid, in contrast with the results observed in the bulk calculations.
On the scaling of avaloids and turbulence with the average density approaching the density limit
Authors: Antar G. Y. , Counsell G. , Ahn J.-W.
Published: July 2005

This article is dedicated to the characterization of turbulent transport in the scrape-off layer of the Mega Ampère Spherical Tokamak [A. Sykes et al., Phys. Plasmas 8, 2101 (2001)] as a function of the average density (nL). The aim is to answer a renewed interest in this subject since the bursty character of turbulence in the scrape-off layer was shown to be caused by large-scale events with high radial velocity reaching about 1∕10th of the sound speed called avaloids [G. Antar et al., Phys. Rev. Lett 87, 065001 (2001)]. With increasing density, turbulence and transport increase nonlinearly at the midplane while remaining almost unchanged in the target region. Using various and complementary statistical analyses, the existence of a “critical” density, at nL∕nG≃0.35 is emphasized; nG is the Greenwald density. Both above and below this density, intermittency decreases and avaloids play a decreasing role in the particle radial transport. This is interpreted as caused by the interplay between avaloids and the surrounding turbulent structures which mix them more efficiently with increasing density as the level of the background turbulence increases. The scaling of the different quantities with respect to the normalized density is obtained. It reveals that not only the level of turbulence and transport increase, but also the radial velocity and length scales. This increases the coupling between the hot plasma edge and the cold scrape-off layer that may explain the disruptive instability occurring at high densities.
Study of structural-, compositional-, and thickness-dependent thermoelectric and electrical properties of Bi93Sb7 alloy thin films
Authors: Mallik Ramesh Chandra , Das V. Damodara
Published: July 2005

We have used the melt-quenching technique to prepare the bulk material and vapor-quenching technique to prepare the thin films of Bi93Sb7 alloy. The Bi93Sb7 alloy thin films of different thicknesses were grown onto well-cleaned glass and silicon substrates. The films were annealed at 150 ° C for 4 h in a vacuum of the order of 10−6torr in order to remove the defects and to increase the grain size. The bulk and thin-film x-ray diffraction results agree with the transmission electron microscopy results and the compositional analysis of bulk by particle-induced x-ray emission and of thin films by Rutherford backscattering. The thickness and temperature dependences of thermoelectric power and electrical resistivity have been analyzed. The negative temperature coefficient of resistivity confirmed that the material is semiconducting in nature. The negative thermoelectric power confirmed that the present bismuth-rich material is a n type. In this paper we have made an attempt to study the thermoelectric properties of bulk as well as thin films of Bi93Sb7, maintaining the same composition. The scattering index parameter was calculated from the experimental data and was compared with the theoretical predictions of the size effect theory.
On the heat-capacity change of pairwise hydrophobic interactions
Authors: Graziano Giuseppe
Published: July 2005

Computer simulations [S. Shimizu and H. S. Chan, J. Am. Chem. Soc. 123, 2083 (2001); D. Paschek, J. Chem. Phys. 120, 10605 (2004)] have demonstrated that the heat-capacity change associated with the interaction of two nonpolar spherical particles, at room temperature, shows a complex behavior with a significant maximum at the distance corresponding to the desolvation barrier configuration and a small minimum at the distance corresponding to the contact configuration. Taking advantage of the detailed analysis performed by Paschek, the two-state model of Muller is applied to estimate the energetic strength and the intactness of the H bonds in the hydration shell of a xenon atom and in the concave part of the joint Xe–Xe hydration shell. In both hydration shell regions the H bonds are energetically stronger but more broken than those in bulk water. In addition, those in the concave part of the joint Xe–Xe hydration shell are, in absolute, stronger and more broken. These thermodynamic features coupled to simple geometric arguments allow the calculation of heat-capacity values that are in agreement with those provided by computer simulations for the pairwise Xe–Xe interaction.
Intermodulation response of superconducting filters
Authors: Salkola M. I.
Published: July 2005

Superconducting technology is ideal for producing selective and sensitive base-station receive filters for wireless communications. Although superconducting filters improve the performance of wireless communications systems, filter nonlinearities limit their potential applications under real-world operating conditions that involve high-power interfering signals. These limitations are examined numerically and experimentally. The intermodulation response of a minimum-phase filter is found to be largely independent of its topology, and to depend on the bandwidth and the steepness of the amplitude response at the band edge. The effect of the small-signal frequency response on the intermodulation response can be separated from those that depend on resonator geometry and material properties. As a result, the intermodulation performance is quantified by a set of figures of merit that measure the quality of a filter design and the material and resonator properties.
Effects of annealing temperature on the degree of inhomogeneity of nickel-silicide/SiC Schottky barrier
Authors: Calcagno L. , Ruggiero A. , Roccaforte F. , La Via F.
Published: July 2005

The electrical characteristics of nickel-silicide Schottky contacts on silicon carbide have been measured by using current-voltage technique in the temperature range of 120–700K. Thermal annealing at 873K formed the nickel silicide. The electrical behavior of the contact showed a deviation from linearity at low temperatures. Annealing at high temperature (1223K) produces deep modifications in the electrical characteristics at low bias and low temperatures, which are consistent with the formation of an inhomogeneous barrier. The description of the experimental results by using Tung’s model [R. T. Tung, Phys. Rev. B 45, 13509 (1992)] allowed us to determine the values of the average barrier height of 1.62 and 1.14eV for the diode annealed at 873 and 1223K, respectively.
A new derivation of the CPT and spin-statistics theorems in noncommutative field theories
Authors: Franco Daniel H. T. , Polito Caio M. M.
Published: July 2005

We propose an alternative axiomatic description for noncommutative field theories (NCFT) based on some ideas by Soloviev to nonlocal quantum fields. The local commutativity axiom is replaced by the weaker condition that the fields commute at sufficiently large spatial separations, called asymptotic commutativity, formulated in terms of the theory of analytic functionals. The question of a possible violation of the CPT and spin-statistics theorems caused by nonlocality of the commutation relations [x̂μ,x̂ν]=iθμν is investigated. In spite of this inherent nonlocality, we show that the modification aforementioned is sufficient to ensure the validity of these theorems for NCFT. We restrict ourselves to the simplest model of a scalar field in the case of only space–space noncommutativity.
Microstructure and electrical properties of Ho-doped BaTiO3-sputtered films
Authors: Wu C. H. , Chu J. P. , Wang S. F.
Published: July 2005

The holmium-doped 200-nm-thick BaTiO3 (BT) thin films were prepared by rf magnetron sputtering. The effects of postannealing temperature and dopant concentration on microstructure and electrical properties were studied. Compositions of thin films studied are BT1 (Ba∕Ti=0.8543), BT (Ba∕Ti=0.9681), BT–0.05Ho, BT–1.1Ho, and BT–1.8Ho, and BT–2.9Ho where Ho content is in at %. For all films studied, the dielectric constant increases with increasing annealing temperature up to 700 °C due to better crystallinity and large grain sizes. The BT1 film annealed at 700 °C shows a high dielectric constant of 287 measured at 100 kHz and the Ho-doped film exhibited a dielectric constant of 135 for BT–1.1Ho annealed at 700 °C. A significant role of the Ho on the reduction of leakage current density is observed for the 700 °C annealed samples because of the smooth surface roughness. The BT–2.9Ho film shows the low leakage current density of 1.27×10−8A∕cm2 at an electric field of 100kV∕cm.
Influence of substrate temperature on growth of nanocrystalline silicon carbide by reactive magnetron sputtering
Authors: Colder H. , Rizk R. , Morales M. , Marie P. , Vicens J. , Vickridge I.
Published: July 2005

Hydrogenated nanocrystalline silicon carbide were grown at various deposition temperatures Td from 200to600°C by means of reactive magnetron sputtering in a plasma of 80% H2 and 20% Ar mixture. A detailed investigation of the structural, compositional, phase nature, and morphology was carried out by complementary sophisticated techniques, such as Fourier transform infrared spectroscopy, x-ray diffraction (XRD), Rutherford backscattering, nuclear reaction, and elastic recoil detection analysis techniques, in addition to conventional and high-resolution transmission electron microscopy (HRTEM) observations. A crystallization onset with a fraction of 35% was observed for Td=300°C, which improved to 80% for Td=600°C, reflected by an increasing density of the SiC nanocrystals which kept an average size of about 5nm. The observed fiber textures present ⟨102⟩ and ⟨11ℓ⟩ texture components, with ℓ larger than 2, while SiC nanocrystals elongated along the [111] direction are also evidenced. These latter are supported by the careful analyses of the HRTEM images which show evidence of faulted growing cubic SiC, as the origin of the very close hexagonal 6H–SiC structure taken into account in the XRD refinement. These various features were found quite consistent with the optical properties of the layers, and, in particular, the evolutions of both optical gap and static refractive index.